U.S. patent application number 10/586470 was filed with the patent office on 2008-11-13 for method for producing linear pentenenitrile.
This patent application is currently assigned to BASF AKTIENGESELLSCHAFT. Invention is credited to Tobias Aechtner, Michael Bartsch, Peter Bassler, Robert Baumann, Petra Deckert, Gerd Haderlein, Tim Jungkamp, Hermann Luyken, Peter Pfab, Jens Scheidel, Wolfgang Siegel.
Application Number | 20080281120 10/586470 |
Document ID | / |
Family ID | 34830756 |
Filed Date | 2008-11-13 |
United States Patent
Application |
20080281120 |
Kind Code |
A1 |
Jungkamp; Tim ; et
al. |
November 13, 2008 |
Method for Producing Linear Pentenenitrile
Abstract
A process is described for preparing 3-pentenenitrile,
characterized by the following process steps: (a) isomerizing a
reactant stream which comprises 2-methyl-3-butenenitrile over at
least one dissolved or dispersed isomerization catalyst to give a
stream 1 which comprises the at least one isomerization catalyst,
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, (b) distilling stream 1 to obtain a
stream 2 as the top product which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product
which comprises the at least one isomerization catalyst, (c)
distilling stream 2 to obtain a stream 4 as the top product which,
compared to stream 2, is enriched in (Z)-2-methyl-2-butenenitrile,
based on the sum of all pentenenitriles in stream 2, and a stream 5
as the bottom product which, compared to stream 2, is enriched in
3-pentenenitrile and 2-methyl-3-butenenitrile, based on the sum of
all pentenenitriles in stream 2, (d) distilling stream 5 to obtain
a stream 6 as the bottom product which comprises 3-pentenenitrile
and a stream 7 as the top product which comprises
2-methyl-3-butenenitrile.
Inventors: |
Jungkamp; Tim; (Kapellen,
BE) ; Baumann; Robert; (Mannheim, DE) ;
Bartsch; Michael; (Neustadt, DE) ; Haderlein;
Gerd; (Grunstadt, DE) ; Luyken; Hermann;
(Ludwigshafen, DE) ; Scheidel; Jens; (Hirschberg,
DE) ; Aechtner; Tobias; (Mannheim, DE) ; Pfab;
Peter; (Neustadt, DE) ; Deckert; Petra;
(Bammental, DE) ; Siegel; Wolfgang; (Limburgerhof,
DE) ; Bassler; Peter; (Viernheim, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
1875 EYE STREET, N.W., SUITE 1100
WASHINGTON
DC
20006
US
|
Assignee: |
BASF AKTIENGESELLSCHAFT
LUDWIGSHAFEN
DE
|
Family ID: |
34830756 |
Appl. No.: |
10/586470 |
Filed: |
January 27, 2005 |
PCT Filed: |
January 27, 2005 |
PCT NO: |
PCT/EP05/00781 |
371 Date: |
July 18, 2006 |
Current U.S.
Class: |
558/355 |
Current CPC
Class: |
Y02P 20/582 20151101;
C07C 253/30 20130101; C07C 253/10 20130101; C07C 253/10 20130101;
C07C 255/07 20130101 |
Class at
Publication: |
558/355 |
International
Class: |
C07C 255/00 20060101
C07C255/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 29, 2004 |
DE |
10-2004-004-671.9 |
Sep 2, 2004 |
DE |
102-004-042-949.9 |
Dec 23, 2004 |
DE |
10-2004-063.381.9 |
Claims
1. A process for preparing 3-pentenenitrile, comprising the
following process steps: (a) isomerizing a reactant stream which
comprises 2-methyl-3-butenenitrile over at least one dissolved or
dispersed isomerization catalyst to give a stream 1 which comprises
the at least one isomerization catalyst, 2-methyl-3-butenenitrile,
3-pentenenitrile and (Z)-2-methyl-2-butenenitrile, (b) distilling
stream 1 to obtain a stream 2 as the top product which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product
which comprises the at least one isomerization catalyst, (c)
distilling stream 2 to obtain a stream 4 as the top product which,
compared to stream 2, is enriched in (Z)-2-methyl-2-butenenitrile,
based on the sum of all pentenenitriles in stream 2, and a stream 5
as the bottom product which, compared to stream 2, is enriched in
3-pentenenitrile and 2-methyl-3-butenenitrile, based on the sum of
all pentenenitriles in stream 2, (d) distilling stream 5 to obtain
a stream 6 as the bottom product which comprises 3-pentenenitrile
and a stream 7 as the top product which comprises
2-methyl-3-butenenitrile, the (Z)-2-methyl-2-butenenitrile-depleted
2-methyl-3-butenenitrile being recycled.
2. The process according to claim 1, wherein the reactant stream is
obtained by the following process steps: (e) hydrocyanating
1,3-butadiene over at least one hydrocyanation catalyst using
hydrogen cyanide to obtain a stream 8 which comprises the at least
one hydrocyanation catalyst, 3-pentenenitrile,
2-methyl-3-butenenitrile, 1,3-butadiene and residues of hydrogen
cyanide, (f) distilling stream 8 one or more times to obtain a
stream 9 which comprises 1,3-butadiene, a stream 10 which comprises
the at least one hydrocyanation catalyst, and a stream 11 which
comprises 3-pentenenitrile and 2-methyl-3-butenenitrile, (g)
distilling stream 11 to obtain a stream 12 as the bottom product
which comprises 3-pentenenitrile, and a stream 13 as the top
product which comprises 2-methyl-3-butenenitrile.
3. The process according to claim 2, wherein process step (d) and
(g) are carried out in the same distillation apparatus, in which
case streams 6 and 12 and streams 7 and 13 coincide.
4. The process according to claim 2, wherein process steps (c) and
(g) are carried out in a common distillation column, in which case
process step (d) is dispensed with, stream 2 from process step (b)
and stream 11 from process step (f) are directed to process step
(g), and, in process step (g), stream 4 is obtained as the top
product comprising (Z)-2-methyl-2-butenenitrile, stream 12 as the
bottom product comprising 3-pentenenitrile and stream 13 as a side
draw stream comprising 2-methyl-3-butenenitrile.
5. The process according to claim 1, wherein the at least one
isomerization catalyst obtained in stream 3 in process step (b) is
recycled into process step (a).
6. The process according to claim 1, wherein process steps (b) and
(c) are carried out together in one distillation apparatus, in
which case stream 3 which comprises the at least one isomerization
catalyst is obtained as the bottom product, stream 4 which
comprises (Z)-2-methyl-2-butenenitrile as the top product, and
stream 5 which comprises 3-pentenenitrile and
2-methyl-3-butenenitrile at a side draw of the column.
7. The process according to claim 1, wherein process steps (a), (b)
and (c) are carried out together in one distillation apparatus, in
which case stream 4 which comprises (Z)-2-methyl-2-butenenitrile is
obtained as the top product, and stream 5 which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile at a side draw of the
distillation apparatus, and the isomerization catalyst remains in
the bottom of the distillation column.
8. The process according to claim 1, wherein the isomerization
catalyst contains nickel(0), a trivalent phosphorus-containing
compound which complexes nickel(0) as a ligand and, optionally, a
Lewis acid.
9. The process according to claim 1, wherein pressure and
temperature in process step (b) are set so that the isomerization
catalyst is less active than in process step (a) or is
inactive.
10. The process according to claim 2, wherein the hydrocyanation
catalyst and the isomerization catalyst are identical.
11. A process for preparing 3-pentenenitrile, comprising the
following process steps: (a*) isomerizing a reactant stream which
comprises 2-methyl-3-butenenitrile over at least one dissolved or
dispersed isomerization catalyst to give a stream 1 which comprises
the at least one isomerization catalyst, 2-methyl-3-butenenitrile,
3-pentenenitrile and (Z)-2-methyl-2-butenenitrile, (b*) distilling
stream 1 to obtain a stream 2 as the top product which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product
which comprises the at least one isomerization catalyst, (c*)
distilling stream 2 to obtain a stream 4 as the top product which,
compared to stream 2, is enriched in (Z)-2-methyl-2-butenenitrile,
based on the sum of all pentenenitriles in stream 2, and a stream 5
as the bottom product which, compared to stream 2, is enriched in
3-pentenenitrile and 2-methyl-3-butenenitrile, based on the sum of
all pentenenitriles in stream 2, (d*) distilling stream 5 to obtain
a stream 6 as the bottom product which comprises 3-pentenenitrile
and a stream 7 as the top product which comprises
2-methyl-3-butenenitrile, (h*) catalyst regeneration to replenish
the nickel(0) content of substream 14 from stream 3 and substream
16 from stream 10 to generate a stream 18, (i*) optionally adding a
diluent F to the stream 18 to generate stream 19, (j*) extracting
the stream 18, with regard to the catalyst components and/or
disruptive component(s) by adding a dinitrile stream 20 and
hydrocarbon stream 21 to generate two nonmiscible phases 22 and 23,
stream 22 comprising the predominant proportion of the catalyst
components and stream 23 the predominant proportion of the
disruptive component, (k*) distillatively removing the hydrocarbon
from the catalyst components from the stream 22 to generate a
stream 25 which comprises the predominant proportion of the
catalyst components and, optionally, partly or fully recycling the
stream 25 into process steps (a*) or (e*), (e*) hydrocyanating
1,3-butadiene over at least one hydrocyanation catalyst using
hydrogen cyanide to obtain a stream 8 which comprises the at least
one hydrocyanation catalyst, 3-pentenenitrile,
2-methyl-3-butenenitrile, 1,3-butadiene and residues of hydrogen
cyanide, (f*) distilling the stream 8 one or more times to obtain a
stream 9 which comprises 1,3-butadiene, a stream 10 which comprises
the at least one hydrocyanation catalyst, and a stream 11 which
comprises 3-pentenenitrile and 2-methyl-3-butenenitrile, and (g*)
distilling the stream 11 to obtain a stream 12 as the bottom
product which comprises 3-pentenenitrile, and a stream 13 as the
top product which comprises 2-methyl-3-butenenitrile.
12. The process according to claim 11, wherein the replenishment of
the nickel(0) catalyst content is carried out in process stage h*)
by reductive catalyst regeneration.
13. The process according to claim 11, wherein the catalyst system
is operated as two separate catalyst circuits, one of the circuits
including the stages e*) and f*) and the other circuit the stages
a*), b*) and c*).
14. The process according to claim 11, wherein
stabilizer-containing butadiene is used as the feed stream to
e*).
15. The process according to claim 11, wherein the catalysts
comprise phosphite ligands of the formula Ib
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(O--R.sup.4).sub.p
(Ib) where R.sup.1: aromatic radical having a
C.sub.1-C.sub.18-alkyl substituent in the o-position to the oxygen
atom which joins the phosphorus atom to the aromatic system, or
having an aromatic substituent in the o-position to the oxygen atom
which joins the phosphorus atom to the aromatic system, or having a
fused aromatic system in the o-position to the oxygen atom which
joins the phosphorus atom to the aromatic system, R.sup.2: aromatic
radical having a C.sub.1-C.sub.18-alkyl substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having an aromatic substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having a fused aromatic system in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, the aromatic radical bearing a hydrogen atom
in the o-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, R.sup.3: aromatic radical having a
C.sub.1-C.sub.18-alkyl substituent in the p-position to the oxygen
atom which joins the phosphorus atom to the aromatic system, or
having an aromatic substituent in the p-position to the oxygen atom
which joins the phosphorus atom to the aromatic system, the
aromatic radical bearing a hydrogen atom in the o-position to the
oxygen atom which joins the phosphorus atom to the aromatic system,
R.sup.4: aromatic radical which bears substituents other than those
defined for R.sup.1, R.sup.2 and R.sup.3 in the o-, m- and
p-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, the aromatic radical bearing a hydrogen atom
in the o-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, x: 1 or 2, y, z, p: each independently
0, 1 or 2, with the proviso that x+y+z+p=3.
16. The process according to claim 11, wherein the catalysts
comprise phosphite ligands of formula Ib
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(O--R.sup.4).sub.p
(Ib) where R.sup.1, R.sup.2 and R.sup.3 are each independently
selected from o-isopropylphenyl, m-tolyl and p-tolyl, R.sup.4 is
phenyl; x is 1 or 2, and y, z, p are each independently 0, 1 or 2,
with the proviso that x+y+z+p=3; and mixtures thereof.
Description
[0001] The present invention relates to a process for preparing
3-pentenenitrile by isomerizing streams comprising
2-methyl-3-butenenitrile.
[0002] In the preparation of adiponitrile, an important
intermediate in nylon production, 1,3-butadiene is initially
reacted with hydrogen cyanide in the presence of nickel(0) which is
stabilized with phosphorus ligands to give pentenenitriles. In
addition to the main products of the hydrocyanation,
3-pentenenitrile and 2-methyl-3-butenenitrile, numerous secondary
components are also obtained. Examples thereof are
2-pentenenitriles, 2-methyl-2-butenenitrites, C.sub.9-nitriles and
methylglutaronitrile. 2-methyl-3-butenenitrile is formed in
significant amounts. Depending on the catalyst used, the molar
ratio of 2-methyl-3-butenenitrile formed to 3-pentenenitrile may be
up to 2:1.
[0003] In a second hydrocyanation, 3-pentenenitrile is subsequently
reacted with hydrogen cyanide to give adiponitrile over the same
nickel catalyst with addition of a Lewis acid. For the second
hydrocyanation, it is essential that the 3-pentenenitrile is
substantially free of 2-methyl-3-butenenitrile. A hydrocyanation of
2-methyl-3-butenenitrile would lead to methylglutaronitrile which
constitutes an undesired by-product. Accordingly, in an economic
process for preparing adiponitrile, there has to be a separation of
3-pentenenitrile and 2-methyl-3-butenenitrile.
[0004] In order to likewise be able to utilize
2-methyl-3-butenenitrile for the preparation of adiponitrile,
processes have been proposed for isomerizing
2-methyl-3-butenenitrile to linear pentenenitrile, especially
3-pentenenitrile.
[0005] For instance, U.S. Pat. No. 3,676,481 describes the
discontinuous, batchwise isomerization of 2-methyl-3-butenenitrile
in the presence of Ni(0), a phosphite ligand and certain Lewis
acids. After the isomerization, the resulting product mixture is
distilled off from the catalyst system. A disadvantage in this
process is that of the high residence times during the
isomerization, the high thermal stress on the thermally sensitive
catalyst during the isomerization and during the subsequent
distillation. The high thermal stress on the catalyst leads to
undesired degradation of the catalyst.
[0006] The German patent application DE 103 11 119.0 to BASF AG,
which has an earlier priority date but was unpublished at the
priority date of the present application, describes a process for
isomerizing 2-methyl-3-butenenitrile to linear pentenenitrile in
the presence of a system comprising Ni(0) catalysts and Lewis
acids. In this case, a mixture comprising 2-methyl-3-butenenitrile
and linear pentenenitrile is withdrawn distillatively from the
reaction mixture during the isomerization. A disadvantage in this
process is that the product stream withdrawn still contains
distinct amounts of unconverted 2-methyl-3-butenenitrile.
[0007] It is common to all known processes for isomerizing
2-methyl-3-butenenitrile that 2-methyl-3-butenenitrile cannot be
fully converted to 3-pentenenitrile owing to the position of the
thermodynamic equilibrium. Unconverted 2-methyl-3-butenenitrile has
to be fed to the isomerization step for economic performance of the
process. However, in the isomerization of 2-methyl-3-butenenitrile,
(Z)-2-methyl-2-butenenitrile is obtained as a by-product and would
accumulate in the cycle stream in the case of recycling of
2-methyl-3-butenenitrile, since, in the course of the removal of
3-pentenenitrile from the isomerization product stream by
distillation, it would distill over together with the
2-methyl-3-butenenitrile owing to the very similar vapor
pressures.
[0008] U.S. Pat. No. 3,865,865 describes the removal of
2-methyl-2-butenenitrile from a mixture with
2-methyl-3-butenenitrile. The removal is carried out by treating
the mixture of the nitrites with an aqueous solution which consists
of sulfite and bisulfite ions. This forms the bisulfite adduct of
2-methyl-2-butenenitrile which transfers to the aqueous phase. The
resulting organic phase is depleted to 50% of the original content
of 2-methyl-2-butenenitrile. The process of U.S. Pat. No. 3,865,865
is laborious, since a phase separation of an organic from an
aqueous phase is required. Furthermore, this separation can only be
integrated with difficulty into an overall process for preparing
adiponitrile. An additional disadvantage in this process is that
the resulting organic phase first has to be fully freed of water
before further use in hydrocyanation reactions using nickel(0)
catalysts with phosphorus(III) ligands, since the phosphorus(III)
ligands are otherwise irreversibly hydrolyzed and thus inactivated.
Another disadvantage in this process is that the resulting
bisulfite adducts, for the purpose of reuse of the conjugated
nitriles, as described in U.S. Pat. No. 3,865,865, can only be
dissociated under drastic conditions and only with moderate
yield.
[0009] It is thus an object of the present invention to provide a
process for preparing 3-pentenenitrile by isomerizing
2-methyl-3-butenenitrile, wherein the catalyst for isomerization
can be removed from the reaction mixture in a simple manner and
recycled, and both the removal of (Z)-2-methyl-2-butenenitrile from
2-methyl-3-butenenitrile and the recycling of the
2-methyl-3-butenenitrile depleted in (Z)-2-methyl-2-butenenitrile
are enabled. The process should preferably be simple and economic
to carry out and be incorporable into an overall process for
preparing adiponitrile.
[0010] This object is achieved in accordance with the invention by
a process for preparing 3-pentenenitrile.
EMBODIMENT I
[0011] In one embodiment I, the process is characterized by the
following process steps: [0012] (a) isomerizing a reactant stream
which comprises 2-methyl-3-butenenitrile over at least one
dissolved or dispersed isomerization catalyst to give a stream 1
which comprises the at least one isomerization catalyst,
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, [0013] (b) distilling stream 1 to
obtain a stream 2 as the top product which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product
which comprises the at least one isomerization catalyst, [0014] (c)
distilling stream 2 to obtain a stream 4 as the top product which,
compared to stream 2, is enriched in (Z)-2-methyl-2-butenenitrile,
based on the sum of all pentenenitriles in stream 2, and a stream 5
as the bottom product which, compared to stream 2, is enriched in
3-pentenenitrile and 2-methyl-3-butenenitrile, based on the sum of
all pentenenitriles in stream 2, [0015] (d) distilling stream 5 to
obtain a stream 6 as the bottom product which comprises
3-pentenenitrile and a stream 7 as the top product which comprises
2-methyl-3-butenenitrile.
Reactant Stream
[0016] In process step (a), an isomerization of a reactant stream
which comprises 2-methyl-3-butenenitrile takes place over at least
one isomerization catalyst.
[0017] In a particular embodiment of the process according to the
invention, the reactant stream is obtainable by the following
process steps: [0018] (e) hydrocyanating 1,3-butadiene over at
least one hydrocyanation catalyst using hydrogen cyanide to obtain
a stream 8 which comprises the at least one hydrocyanation
catalyst, 3-pentenenitrile, 2-methyl-3-butenenitrile, 1,3-butadiene
and residues of hydrogen cyanide, [0019] (f) distilling stream 8
once or more than once to obtain a stream 9 which comprises
1,3-butadiene, a stream 10 which comprises the at least one
hydrocyanation catalyst, and a stream 11 which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile, [0020] (g)
distilling stream 11 to obtain a stream 12 as the bottom product
which comprises 3-pentenenitrile, and a stream 13 as the top
product which comprises 2-methyl-3-butenenitrile.
[0021] In process step (e), the reactant stream is prepared by a
hydrocyanation of 1,3-butadiene initially taking place over at
least one hydrocyanation catalyst using hydrogen cyanide to obtain
a stream 8 which comprises the at least one hydrocyanation
catalyst, 3-pentenenitrile, 2-methyl-3-butenenitrile and
unconverted 1,3-butadiene.
[0022] The hydrocyanation catalyst used is preferably a homogeneous
nickel(0) catalyst which is stabilized with phosphorus ligands.
[0023] The phosphorus ligands of the nickel(0) complexes and the
free phosphorus ligands are preferably selected from mono- or
bidentate phosphines, phosphites, phosphinites and
phosphonites.
[0024] These phosphorus ligands preferably have the formula I
P(X.sup.1R.sup.1)(X.sup.2R.sup.2)(X.sup.3R.sup.3) (I)
[0025] In the context of the present invention, compound I is a
single compound or a mixture of different compounds of the
aforementioned formula.
[0026] According to the invention, X.sup.1, X.sup.2, X.sup.3 each
independently are oxygen or a single bond. When all of the X.sup.1,
X.sup.2 and X.sup.3 groups are single bonds, compound I is a
phosphine of the formula P(R.sup.1R.sup.2R.sup.3) with the
definitions of R.sup.1, R.sup.2 and R.sup.3 specified in this
description.
[0027] When two of the X.sup.1, X.sup.2 and X.sup.3 groups are
single bonds and one is oxygen, compound I is a phosphinite of the
formula P(OR.sup.1)(R.sup.2)(R.sup.3) or
P(R.sup.1)(OR.sup.2)(R.sup.3) or P(R.sup.1)(R.sup.2)(OR.sup.3) with
the definitions of R.sup.1, R.sup.2 and R.sup.3 specified
below.
[0028] When one of the X.sup.1, X.sup.2 and X.sup.3 groups is a
single bond and two are oxygen, compound I is a phosphonite of the
formula P(OR.sup.1)(OR.sup.2)(R.sup.3) or
P(R.sup.1)(OR.sup.2)(OR.sup.3) or P(OR.sup.1)(R.sup.2)(OR.sup.3)
with the definitions of R.sup.1, R.sup.2 and R.sup.3 specified in
this description.
[0029] In a preferred embodiment, all X.sup.1, X.sup.2 and X.sup.3
groups should be oxygen, so that compound I is advantageously a
phosphite of the formula P(OR.sup.1)(OR.sup.2)(OR.sup.3) with the
definitions of R.sup.1, R.sup.2 and R.sup.3 specified below.
[0030] According to the invention, R.sup.1, R.sup.2, R.sup.3 are
each independently identical or different organic radicals.
R.sup.1, R.sup.2 and R.sup.3 are each independently alkyl radicals
preferably having from 1 to 10 carbon atoms, such as methyl, ethyl,
n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, aryl groups
such as phenyl, o-tolyl, m-tolyl, p-tolyl, 1-naphthyl, 2-naphthyl,
or hydrocarbyl, preferably having from 1 to 20 carbon atoms, such
as 1,1'-biphenol, 1,1'-binaphthol. The R.sup.1, R.sup.2 and R.sup.3
groups may be bonded together directly, i.e. not solely via the
central phosphorus atom. Preference is given to the R.sup.1,
R.sup.2 and R.sup.3 groups not being bonded together directly.
[0031] In a preferred embodiment, R.sup.1, R.sup.2 and R.sup.3
groups are radicals selected from the group consisting of phenyl,
o-tolyl, m-tolyl and p-tolyl. In a particularly preferred
embodiment, a maximum of two of the R.sup.1, R.sup.2 and R.sup.3
groups should be phenyl groups.
[0032] In another preferred embodiment, a maximum of two of the
R.sup.1, R.sup.2 and R.sup.3 groups should be o-tolyl groups.
[0033] Particularly preferred compounds I which may be used are
those of the formula Ia
(o-tolyl-O--).sub.w(m-tolyl-O--).sub.x(p-tolyl-O--).sub.y(phenyl-O--).su-
b.zP (Ia)
where w, x, y, z are each a natural number, and the following
conditions apply: w+x+y+z=3 and w, z.ltoreq.2.
[0034] Such compounds Ia are, for example,
(p-tolyl-O--)(phenyl-O--).sub.2P, (m-tolyl-O--)(phenyl-O--).sub.2P,
(o-tolyl-O--)(phenyl-O--).sub.2P, (p-tolyl-O--).sub.2(phenyl-O--)P,
(m-tolyl-O--).sub.2(phenyl-O--)P, (o-tolyl-O--).sub.2(phenyl-O--)P,
(m-tolyl-O--)(p-tolyl-O--)(phenyl-O--)P,
(o-tolyl-O--)(p-tolyl-O--)(phenyl-O--)P,
(o-tolyl-O--)(m-tolyl-O--)(phenyl-O--)P, (p-tolyl-O--).sub.3P,
(m-tolyl-O--)(p-tolyl-O--).sub.2P,
(o-tolyl-O--)(p-tolyl-O--).sub.2P,
(m-tolyl-O--).sub.2(p-tolyl-O--)P,
(o-tolyl-O--).sub.2(p-tolyl-O--)P,
(o-tolyl-O--)(m-tolyl-O--)(p-tolyl-O--)P, (m-tolyl-O--).sub.3P,
(o-tolyl-O--)(m-tolyl-O--).sub.2P(O-tolyl-O--).sub.2(m-tolyl-O--)P
or mixtures of such compounds.
[0035] Mixtures comprising (m-tolyl-O--).sub.3P,
(m-tolyl-O--).sub.2(p-tolyl-O--)P,
(m-tolyl-O--)(p-tolyl-O--).sub.2P and (p-tolyl-O--).sub.3P may be
obtained, for example, by reacting a mixture comprising m-cresol
and p-cresol, in particular in a molar ratio of 2:1, as obtained in
the distillative workup of crude oil, with a phosphorus trihalide,
such as phosphorus trichloride.
[0036] In another, likewise preferred embodiment, the phosphorus
ligands are the phosphites, described in detail in DE-A 199 53 058,
of the formula Ib:
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(O--R.sup.4).sub.-
p (Ib)
where [0037] R.sup.1: aromatic radical having a
C.sub.1-C.sub.18-alkyl substituent in the o-position to the oxygen
atom which joins the phosphorus atom to the aromatic system, or
having an aromatic substituent in the o-position to the oxygen atom
which joins the phosphorus atom to the aromatic system, or having a
fused aromatic system in the o-position to the oxygen atom which
joins the phosphorus atom to the aromatic system, [0038] R.sup.2:
aromatic radical having a C.sub.1-C.sub.18-alkyl substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having an aromatic substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having a fused aromatic system in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, the aromatic radical bearing a hydrogen atom
in the o-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, [0039] R.sup.3: aromatic radical
having a C.sub.1-C.sub.18-alkyl substituent in the p-position to
the oxygen atom which joins the phosphorus atom to the aromatic
system, or having an aromatic substituent in the p-position to the
oxygen atom which joins the phosphorus atom to the aromatic system,
the aromatic radical bearing a hydrogen atom in the o-position to
the oxygen atom which joins the phosphorus atom to the aromatic
system, [0040] R.sup.4: aromatic radical which bears substituents
other than those defined for R.sup.1, R.sup.2 and R.sup.3 in the
o-, m- and p-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, the aromatic radical bearing a
hydrogen atom in the o-position to the oxygen atom which joins the
phosphorus atom to the aromatic system, [0041] x: 1 or 2, [0042] y,
z, p: each independently 0, 1 or 2, with the proviso that
x+y+z+p=3.
[0043] Preferred phosphites of the formula Ib can be taken from
DE-A 199 53 058. The R.sup.1 radical may advantageously be o-tolyl,
o-ethylphenyl, o-n-propylphenyl, o-isopropylphenyl,
o-n-butylphenyl, o-sec-butylphenyl, o-tert-butylphenyl,
(o-phenyl)phenyl or 1-naphthyl groups.
[0044] Preferred R.sup.2 radicals are m-tolyl, m-ethylphenyl,
m-n-propylphenyl, m-isopropylphenyl, m-n-butylphenyl,
m-sec-butylphenyl, m-tert-butylphenyl, (m-phenyl)phenyl or
2-naphthyl groups.
[0045] Advantageous R.sup.3 radicals are p-tolyl, p-ethylphenyl,
p-n-propylphenyl, p-isopropylphenyl, p-n-butylphenyl,
p-sec-butylphenyl, p-tert-butylphenyl or (p-phenyl)phenyl
groups.
[0046] The R.sup.4 radical is preferably phenyl. p is preferably
zero. For the indices x, y, z and p in compound Ib, there are the
following possibilities:
TABLE-US-00001 x y z p 1 0 0 2 1 0 1 1 1 1 0 1 2 0 0 1 1 0 2 0 1 1
1 0 1 2 0 0 2 0 1 0 2 1 0 0
[0047] Preferred phosphites of the formula Ib are those in which p
is zero, and R.sup.1, R.sup.2 and R.sup.3 are each independently
selected from o-isopropylphenyl, m-tolyl and p-tolyl, and R.sup.4
is phenyl.
[0048] Particularly preferred phosphites of the formula Ib are
those in which R.sup.1 is the o-isopropylphenyl radical, R.sup.2 is
the m-tolyl radical and R.sup.3 is the p-tolyl radical with the
indices specified in the table above; also those in which R.sup.1
is the o-tolyl radical, R.sup.2 is the m-tolyl radical and R.sup.3
is the p-tolyl radical with the indices specified in the table;
additionally those in which R.sup.1 is the 1-naphthyl radical,
R.sup.2 is the m-tolyl radical and R.sup.3 is the p-tolyl radical
with the indices specified in the table; also those in which
R.sup.1 is the o-tolyl radical, R.sup.2 is the 2-naphthyl radical
and R.sup.3 is the p-tolyl radical with the indices specified in
the table; and finally those in which R.sup.1 is the
o-isopropylphenyl radical, R.sup.2 is the 2-naphthyl radical and
R.sup.3 is the p-tolyl radical with the indices specified in the
table; and also mixtures of these phosphites.
[0049] Phosphites of the formula Ib may be obtained by [0050] a)
reacting a phosphorus trihalide with an alcohol selected from the
group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and R.sup.4OH
or mixtures thereof to obtain a dihalophosphorous monoester, [0051]
b) reacting the dihalophosphorous monoester mentioned with an
alcohol selected from the group consisting of R.sup.1OH, R.sup.2OH,
R.sup.3OH and R.sup.4OH or mixtures thereof to obtain a
monohalophosphorous diester and [0052] c) reacting the
monohalophosphorous diester mentioned with an alcohol selected from
the group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and
R.sup.4OH or mixtures thereof to obtain a phosphite of the formula
Ib.
[0053] The reaction may be carried out in three separate steps.
Equally, two of the three steps may be combined, i.e. a) with b) or
b) with c). Alternatively, all of steps a), b) and c) may be
combined together.
[0054] Suitable parameters and amounts of the alcohols selected
from the group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and
R.sup.4OH or mixtures thereof may be determined readily by a few
simple preliminary experiments.
[0055] Useful phosphorus trihalides are in principle all phosphorus
trihalides, preferably those in which the halide used is Cl, Br, I,
in particular Cl, and mixtures thereof. It is also possible to use
mixtures of various identically or differently halogen-substituted
phosphines as the phosphorus trihalide. Particular preference is
given to PCl.sub.3. Further details on the reaction conditions in
the preparation of the phosphites Ib and for the workup can be
taken from DE-A 199 53 058.
[0056] The phosphites Ib may also be used in the form of a mixture
of different phosphites Ib as a ligand. Such a mixture may be
obtained, for example, in the preparation of the phosphites Ib.
[0057] However, preference is given to the phosphorus ligand being
multidentate, in particular bidentate. The ligand used therefore
preferably has the formula II
##STR00001##
where [0058] X.sup.11, X.sup.12, X.sup.13, X.sup.21, X.sup.22,
X.sup.23 are each independently oxygen or a single bond [0059]
R.sup.11, R.sup.12 are each independently identical or different,
separate or bridged organic radicals [0060] R.sup.21, R.sup.22 are
each independently identical or different, separate or bridged
organic radicals, [0061] Y is a bridging group.
[0062] In the context of the present invention, compound II is a
single compound or a mixture of different compounds of the
aforementioned formula.
[0063] In a preferred embodiment, X.sup.11, X.sup.12, X.sup.13,
X.sup.21, X.sup.22, X.sup.23 may each be oxygen. In such a case,
the bridging group Y is bonded to phosphite groups.
[0064] In another preferred embodiment, X.sup.11 and X.sup.12 may
each be oxygen and X.sup.13 a single bond, or X.sup.11 and X.sup.13
each oxygen and X.sup.12 a single bond, so that the phosphorus atom
surrounded by X.sup.11, X.sup.12 and X.sup.13 is the central atom
of a phosphonite. In such a case, X.sup.21, X.sup.22 and X.sup.23
may each be oxygen, or X.sup.21 and X.sup.22 may each be oxygen and
X.sup.23 a single bond, or X.sup.21 and X.sup.23 may each be oxygen
and X.sup.22 a single bond, or X.sup.23 may be oxygen and X.sup.21
and X.sup.22 each a single bond, or X.sup.21 may be oxygen and
X.sup.22 and X.sup.23 each a single bond, or X.sup.21, X.sup.22 and
X.sup.23 may each be a single bond, so that the phosphorus atom
surrounded by X.sup.21, X.sup.22 and X.sup.23 may be the central
atom of a phosphite, phosphonite, phosphinite or phosphine,
preferably a phosphonite.
[0065] In another preferred embodiment, X.sup.13 may be oxygen and
X.sup.11 and X.sup.12 each a single bond, or X.sup.11 may be oxygen
and X.sup.12 and X.sup.13 each a single bond, so that the
phosphorus atom surrounded by X.sup.11, X.sup.12 and X.sup.13 is
the central atom of a phosphonite.
[0066] In such a case, X.sup.21, X.sup.22 and X.sup.23 may each be
oxygen, or X.sup.23 may be oxygen and X.sup.21 and X.sup.22 each a
single bond, or X.sup.21 may be oxygen and X.sup.22 and X.sup.23
each a single bond, or X.sup.21, X.sup.22 and X.sup.23 may each be
a single bond, so that the phosphorus atom surrounded by X.sup.21,
X.sup.22 and X.sup.23 may be the central atom of a phosphite,
phosphinite or phosphine, preferably a phosphinite.
[0067] In another preferred embodiment, X.sup.11, X.sup.12 and
X.sup.13 may each be a single bond, so that the phosphorus atom
surrounded by X.sup.11, X.sup.12 and X.sup.13 is the central atom
of a phosphine. In such a case, X.sup.21, X.sup.22 and X.sup.23 may
each be oxygen, or X.sup.21, X.sup.22 and X.sup.23 may each be a
single bond, so that the phosphorus atom surrounded by X.sup.21,
X.sup.22 and X.sup.23 may be the central atom of a phosphite or
phosphine, preferably a phosphine.
[0068] The bridging group Y is preferably an aryl group which is
substituted, for example by C.sub.1-C.sub.4-alkyl, halogen, such as
fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or is unsubstituted,
preferably a group having from 6 to 20 carbon atoms in the aromatic
system, in particular pyrocatechol, bis(phenol) or
bis(naphthol).
[0069] The R.sup.11 and R.sup.12 radicals may each independently be
identical or different organic radicals. Advantageous R.sup.11 and
R.sup.12 radicals are aryl radicals, preferably those having from 6
to 10 carbon atoms, which may be unsubstituted or mono- or
polysubstituted, in particular by C.sub.1-C.sub.4-alkyl, halogen,
such as fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl
groups.
[0070] The R.sup.21 and R.sup.22 radicals may each independently be
the same or different organic radicals. Advantageous R.sup.21 and
R.sup.22 radicals are aryl radicals, preferably those having from 6
to 10 carbon atoms, which may be unsubstituted or mono- or
polysubstituted, in particular by C.sub.1-C.sub.4-alkyl, halogen,
such as fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl
groups.
[0071] The R.sup.11 and R.sup.12 radicals may each be separate or
bridged. The R.sup.21 and R.sup.22 radicals may also each be
separate or bridged. The R.sup.11, R.sup.12, R.sup.21 and R.sup.22
radicals may each be separate, two may be bridged and two separate,
or all four may be bridged, in the manner described.
[0072] In a particularly preferred embodiment, useful compounds are
those of the formula I, II, III, IV and V specified in U.S. Pat.
No. 5,723,641. In a particularly preferred embodiment, useful
compounds are those of the formula I, II, III, IV, V, VI and VII
specified in U.S. Pat. No. 5,512,696, in particular the compounds
used there in examples 1 to 31. In a particularly preferred
embodiment, useful compounds are those of the formula I, II, III,
IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV and XV specified in
U.S. Pat. No. 5,821,378, in particular the compounds used there in
examples 1 to 73.
[0073] In a particularly preferred embodiment, useful compounds are
those of the formula I, II, III, IV, V and VI specified in U.S.
Pat. No. 5,512,695, in particular the compounds used there in
examples 1 to 6. In a particularly preferred embodiment, useful
compounds are those of the formula I, II, III, IV, V, VI, VII,
VIII, IX, X, XI, XII, XIII and XIV specified in U.S. Pat. No.
5,981,772, in particular the compounds used there in examples 1 to
66.
[0074] In a particularly preferred embodiment, useful compounds are
those specified in U.S. Pat. No. 6,127,567 and the compounds used
there in examples 1 to 29. In a particularly preferred embodiment,
useful compounds are those of the formula I, II, III, IV, V, VI,
VII, VIII, IX and X specified in U.S. Pat. No. 6,020,516, in
particular the compounds used there in examples 1 to 33. In a
particularly preferred embodiment, useful compounds are those
specified in U.S. Pat. No. 5,959,135, and the compounds used there
in examples 1 to 13.
[0075] In a particularly preferred embodiment, useful compounds are
those of the formula I, II and III specified in U.S. Pat. No.
5,847,191. In a particularly preferred embodiment, useful compounds
are those specified in U.S. Pat. No. 5,523,453, in particular the
compounds illustrated there in formula 1, 2, 3, 4, 5, 6, 7, 8, 9,
10, 11, 12, 13, 14, 15, 16, 17, 18, 19, and 21. In a particularly
preferred embodiment, useful compounds are those specified in WO
01/14392, preferably the compounds illustrated there in formula V,
VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII, XXI, XXII,
XXIII.
[0076] In a particularly preferred embodiment, useful compounds are
those specified in WO 98/27054. In a particularly preferred
embodiment, useful compounds are those specified in WO 99/13983. In
a particularly preferred embodiment, useful compounds are those
specified in WO 99/64155.
[0077] In a particularly preferred embodiment, useful compounds are
those specified in the German patent application DE 100 380 37. In
a particularly preferred embodiment, useful compounds are those
specified in the German patent application DE 100 460 25. In a
particularly preferred embodiment, useful compounds are those
specified in the German patent application DE 101 502 85.
[0078] In a particularly preferred embodiment, useful compounds are
those specified in the German patent application DE 101 502 86. In
a particularly preferred embodiment, useful compounds are those
specified in the German patent application DE 102 071 65. In a
further particularly preferred embodiment of the present invention,
useful phosphorus chelate ligands are those specified in US
2003/0100442 A1.
[0079] In a further particularly preferred embodiment of the
present invention, useful phosphorus chelate ligands are those
specified in the German patent application reference number DE 103
50 999.2 of Oct. 30, 2003 which has an earlier priority date but
had not been published at the priority date of the present
application.
[0080] The compounds I, Ia, Ib and II described and their
preparation are known per se. Phosphorus ligands used may also be a
mixture comprising at least two of the compounds I, Ia, Ib and
II.
[0081] In a particularly preferred embodiment of the process
according to the invention, the phosphorus ligand of the nickel(0)
complex and/or the free phosphorus ligand is selected from tritolyl
phosphite, bidentate phosphorus chelate ligands and the phosphites
of the formula Ib
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(O--R.sup.4).sub.-
p (Ib)
where R.sup.1, R.sup.2 and R.sup.3 are each independently selected
from o-isopropylphenyl, m-tolyl and p-tolyl, R.sup.4 is phenyl; x
is 1 or 2, and y, z, p are each independently 0, 1 or 2 with the
proviso that x+y+z+p=3; and mixtures thereof.
[0082] Process step (e) may be carried out in any suitable
apparatus known to those skilled in the art. Useful apparatus for
the reaction is thus customary apparatus, as described, for
example, in: Kirk-Othmer, Encyclopedia of Chemical Technology, 4th
ed., Vol. 20, John Wiley & Sons, New York, 1996, pages 1040 to
1055, such as stirred tank reactors, loop reactors, gas circulation
reactors, bubble columns or tubular reactors, in each case, if
appropriate, with apparatus to remove heat of reaction. The
reaction may be carried out in a plurality of, such as two or
three, apparatuses.
[0083] In a preferred embodiment of the process according to the
invention, advantageous reactors have been found to be reactors
having backmixing characteristics or batteries of reactors having
backmixing characteristics. It has been found that batteries of
reactors having backmixing characteristics which are operated in
crossflow mode with regard to the metering of hydrogen cyanide are
particularly advantageous.
[0084] The hydrocyanation may be carried out in the presence or in
the absence of a solvent. When a solvent is used, the solvent
should be liquid at the given reaction temperature and the given
reaction pressure and inert toward the unsaturated compounds and
the at least one catalyst. In general, the solvents used are
hydrocarbons, for example benzene or xylene, or nitrites, for
example acetonitrile or benzonitrile. However, preference is given
to using a ligand as the solvent.
[0085] The reaction may be carried out in batch mode, continuously
or in semibatch operation.
[0086] The hydrocyanation reaction may be carried out by charging
the apparatus with all reactants. However, it is preferred when the
apparatus is filled with the catalyst, the unsaturated organic
compound and, if appropriate, the solvent. The gaseous hydrogen
cyanide preferably floats over the surface of the reaction mixture
or is passed through the reaction mixture. A further procedure for
charging the apparatus is the filling of the apparatus with the
catalyst, hydrogen cyanide and, if appropriate, the solvent, and
slowly metering the unsaturated compound into the reaction mixture.
Alternatively, it is also possible that the reactants are
introduced into the reactor and the reaction mixture is brought to
the reaction temperature at which the hydrogen cyanide is added to
the mixture in liquid form. In addition, the hydrogen cyanide may
also be added before heating to reaction temperature. The reaction
is carried out under conventional hydrocyanation conditions for
temperature, atmosphere, reaction time, etc.
[0087] Preference is given to carrying out the hydrocyanation
continuously in one or more stirred process steps. When a multitude
of process steps is used, preference is given to the process steps
being connected in series. In this case, the product is transferred
from one process step directly into the next process step. The
hydrogen cyanide may be fed directly into the first process step or
between the individual process steps.
[0088] When the process according to the invention is carried out
in semibatch operation, preference is given to initially charging
the catalyst components and 1,3-butadiene in the reactor, while
hydrogen cyanide is metered into the reaction mixture over the
reaction time.
[0089] The reaction is preferably carried out at absolute pressures
of from 0.1 to 500 MPa, more preferably from 0.5 to 50 MPa, in
particular from 1 to 5 MPa. The reaction is preferably carried out
at temperatures of from 273 to 473 K, more preferably from 313 to
423 K, in particular from 333 to 393 K. Advantageous average mean
residence times of the liquid reactor phase have been found to be
in the range from 0.001 to 100 hours, preferably from 0.05 to 20
hours, more preferably from 0.1 to 5 hours, in each case per
reactor.
[0090] In one embodiment, the reaction may be performed in the
liquid phase in the presence of a gas phase and, if appropriate, of
a solid suspended phase. The starting materials, hydrogen cyanide
and 1,3-butadiene, may each be metered in liquid or gaseous
form.
[0091] In a further embodiment, the reaction may be carried out in
liquid phase, in which case the pressure in the reactor is such
that all feedstocks such as 1,3-butadiene, hydrogen cyanide and the
at least one catalyst are metered in liquid form and are in the
liquid phase in the reaction mixture. A solid suspended phase may
be present in the reaction mixture and may also be metered in
together with the at least one catalyst, for example consisting of
degradation products of the catalyst system comprising nickel(II)
compounds inter alia.
[0092] In process step (e), a stream 8 which comprises
3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one
catalyst and unconverted 1,3-butadiene is obtained.
[0093] Stream 8 which comprises 3-pentenenitrile,
2-methyl-3-butenenitrile, the at least one catalyst and unconverted
1,3-butadiene is subsequently transferred in process step (f) to a
distillation apparatus. In this distillation apparatus, stream 8 is
distilled once or more than once to obtain a stream 9 which
comprises 1,3-butadiene, a stream 10 which comprises the at least
one hydrocyanation catalyst, and a stream 11 which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile.
[0094] The distillation of process step (f) may be effected in two
stages, as described in DE-A-102 004 004 720, process steps (b) and
(c). The distillation of process step (f) may also be effected
according to DE-A-102 004 004 729, process steps (b) and (c).
[0095] The distillation(s) of process step (f) may be carried out
in any suitable apparatus known to those skilled in the art.
Suitable apparatus for distillation is described, for example, in:
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th ed., Vol. 8,
John Wiley & Sons, New York, 1996, pages 334-348, such as sieve
tray columns, bubble-cap tray columns, columns having structured
packing or random packing, which may also be operated as dividing
wall columns. These distillation units are each equipped with
suitable apparatus for evaporating, such as falling-film
evaporators, thin-film evaporators, multiphase helical-tube
evaporators, natural-circulation evaporators or forced-circulation
flash evaporators, and also with apparatus for condensation of the
vapor stream. The individual distillations can each be carried out
in a plurality of, such as two or three, apparatuses,
advantageously in a single apparatus in each case.
[0096] The distillation(s) may additionally each be effected in one
stage in the case of a partial evaporation of the feed stream.
[0097] The pressure in process step (f) is preferably from 0.001 to
10 bar, more preferably from 0.010 to 1 bar, in particular from
0.02 to 0.5 bar. The distillation(s) is/are carried out in such a
way that the temperature(s) in the bottom of the distillation
apparatus(es) is/are preferably from 30 to 200.degree. C., more
preferably from 50 to 150.degree. C., in particular from 60 to
120.degree. C. The distillation(s) is/are carried out in such a way
that the condensation temperatures at the top of the distillation
apparatus are preferably from -50 to 150.degree. C., more
preferably from -15 to 60.degree. C., in particular from 5 to
45.degree. C. In a particularly preferred embodiment of the process
according to the invention, the aforementioned temperature ranges
are maintained both at the top and in the bottom of the
distillation apparatus(es).
[0098] Stream 11 is subsequently subjected to a distillation in a
further process step (g). This distillation may be carried out in
any suitable apparatus known to those skilled in the art. Suitable
apparatus for distillation is described, for example, in:
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th ed., Vol. 8,
John Wiley & Sons, New York, 1996, pages 334-348, such as sieve
tray columns, bubble-cap tray columns, columns having structured
packing or random packing, which may also be operated as dividing
wall columns. These distillation units are each equipped with
suitable apparatus for evaporating, such as falling-film
evaporators, thin-film evaporators, multiphase helical-tube
evaporators, natural-circulation evaporators or forced-circulation
flash evaporators, and also with apparatus for condensation of the
vapor stream. The distillation can be carried out in a plurality
of, such as two or three, apparatuses, advantageously in a single
apparatus. The distillation may additionally be effected in one
stage in the case of a partial evaporation of the feed stream.
[0099] The pressure in process step (g) is preferably from 0.001 to
100 bar, more preferably from 0.01 to 20 bar, in particular from
0.05 to 2 bar. The distillation is carried out in such a way that
the temperature in the bottom of the distillation apparatus is
preferably from 30 to 250.degree. C., more preferably from 50 to
200.degree. C., in particular from 60 to 180.degree. C. The
distillation is carried out in such a way that the condensation
temperature at the top of the distillation apparatus is preferably
from -50 to 250.degree. C., more preferably from 0 to 180.degree.
C., in particular from 15 to 160.degree. C. In a particularly
preferred embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0100] In process step (g), a stream 12 is obtained as the bottom
product which comprises 1,3-pentenenitrile, and stream 13 as the
top product which comprises 2-methyl-3-butenenitrile. Stream 13 is
preferably used as the reactant stream in the process according to
the invention for preparing 3-pentenenitrile.
[0101] In further preferred embodiments of the process according to
the invention, stream 8 obtained in process step (e) is transferred
directly to process step (g). In this process step (g), a stream is
then obtained via the bottom and comprises substantially
3-pentenenitrile and the at least one hydrocyanation catalyst. In
addition, a stream is obtained overhead which comprises
substantially 2-methyl-3-butenenitrile and 1,3-butadiene. This
2-methyl-3-butenenitrile- and 1,3-butadiene-rich stream may
likewise be used as the reactant stream in the process according to
the invention for preparing 3-pentenenitrile. If this reactant
stream is used in the process according to the invention, the
content of 2-methyl-3-butenenitrile in this stream is preferably
from 10 to 90% by weight, more preferably from 20 to 85% by weight,
in particular from 30 to 80% by weight, based in each case on the
stream.
[0102] Alternatively, it is also possible to deplete stream 8
obtained in process step (e) only in 1,3-butadiene in process step
(f). Via the bottom of process step (f) is then obtained a stream
11a which comprises substantially 3-pentenenitrile,
2-methyl-3-butenenitrile and the at least one hydrocyanation
catalyst. In that case, this stream 11a is subsequently worked up
further in process step (g) with removal of 3-pentenenitrile and
the at least one hydrocyanation catalyst on the one hand, and also
of 2-methyl-3-butenenitrile on the other. Stream 13a stemming from
process step (g) at the top of the distillation comprises
substantially 2-methyl-3-butenenitrile. This stream 13a may
likewise be used as the reactant stream in the process according to
the invention for preparing 3-pentenenitrile.
[0103] In a further embodiment, stream 8 from process step (e) is
depleted only in 1,3-butadiene in process step (f) and transferred
to process step (g), where a stream 12 comprising 3-pentenenitrile
and the hydrocyanation catalyst is obtained in the bottom.
[0104] In a further embodiment of the present invention, a reactant
stream is used which stems from a hydrocyanation of process step
(e) and a subsequent workup in process step (f), in which case, if
appropriate, only a depletion in 1,3-butadiene is undertaken in
process step (f). The stream 11b resulting therefrom is
subsequently transferred into process step (a) of the process
according to the invention. The hydrocyanation catalyst present in
this stream 11b is then preferably used as the at least one
isomerization catalyst in process step (a) of the process according
to the invention. It is possible to additionally add a suitable
Lewis acid, as described, for example, in DE-A-102 004 004 696.
[0105] In a further embodiment of the present invention, it is
possible that the reactant stream used in the inventive process
step (a) corresponds to stream 11 of process step (f), so that a
separation of stream 11 in process step (g) is dispensed with.
[0106] In a further embodiment of the process according to the
invention, the reactant stream used is stream 8 which stems from
process step (e). In this case, process steps (f) and (g) are thus
dispensed with in the preparation of the reactant stream for the
process according to the invention.
Process Step (a)
[0107] In process step (a), an isomerization of the reactant stream
which comprises 2-methyl-3-butenenitrile takes place over at least
one isomerization catalyst. This gives a stream 1 which comprises
the isomerization catalyst, unconverted 2-methyl-3-butenenitrile,
3-pentenenitrile and (Z)-2-methyl-2-butenenitrile.
[0108] According to the invention, the isomerization is carried out
in the presence of a system comprising [0109] a) nickel(0), [0110]
b) a compound which contains trivalent phosphorus and complexes
nickel(0) as a ligand and, if appropriate, [0111] c) a Lewis
acid.
[0112] Nickel(0)-containing catalyst systems can be prepared by
processes known per se.
[0113] The ligands for the isomerization catalyst may be the same
phosphorus ligands as used for the hydrocyanation catalyst used in
process step (e). The hydrocyanation catalyst may thus be identical
to the isomerization catalyst. However, the selection of the
ligands for the reactions in process steps (a) and (e) does not
necessarily have to be the same.
[0114] In addition, the system, if appropriate, comprises a Lewis
acid.
[0115] In the context of the present invention, a Lewis acid refers
to a single Lewis acid or a mixture of a plurality of, such as two,
three or four, Lewis acids.
[0116] Useful Lewis acids are inorganic or organic metal compounds
in which the cation is selected from the group consisting of
scandium, titanium, vanadium, chromium, manganese, iron, cobalt,
copper, zinc, boron, aluminum, yttrium, zirconium, niobium,
molybdenum, cadmium, rhenium and tin. Examples include ZnBr.sub.2,
ZnI.sub.2, ZnCl.sub.2, ZnSO.sub.4, CuCl.sub.2, CuCl,
Cu(O.sub.3SCF.sub.3).sub.2, CoCl.sub.2, CoI.sub.2, FeI.sub.2,
FeCl.sub.3, FeCl.sub.2, FeCl.sub.2(THF).sub.2,
TiCl.sub.4(THF).sub.2, TiCl.sub.4, TiCl.sub.3,
ClTi(O-i-propyl).sub.3, MnCl.sub.2, ScCl.sub.3, AlCl.sub.3,
(C.sub.8H.sub.17)AlCl.sub.2, (C.sub.8H.sub.17).sub.2AlCl,
(i-C.sub.4H.sub.9).sub.2AlCl, (C.sub.6H.sub.5).sub.2AlCl,
(C.sub.6H.sub.5)AlCl.sub.2, ReCl.sub.5, ZrCl.sub.4, NbCl.sub.5,
VCl.sub.3, CrCl.sub.2, MoCl.sub.5, YCl.sub.3, CdCl.sub.2,
LaCl.sub.3, Er(O.sub.3SCF.sub.3).sub.3, Yb(O.sub.2CCF.sub.3).sub.3,
SmCl.sub.3, B(C.sub.6H.sub.5).sub.3, TaCl.sub.5, as described, for
example, in U.S. Pat. No. 6,127,567, U.S. Pat. No. 6,171,996 and
U.S. Pat. No. 6,380,421. Also useful are metal salts such as
ZnCl.sub.2, CoI.sub.2 and SnCl.sub.2, and organometallic compounds
such as RAlCl.sub.2, R.sub.2AlCl, RSnO.sub.3SCF.sub.3 and R.sub.3B,
where R is an alkyl or aryl group, as described, for example, in
U.S. Pat. No. 3,496,217, U.S. Pat. No. 3,496,218 and U.S. Pat. No.
4,774,353. According to U.S. Pat. No. 3,773,809, the promoter used
may be a metal in cationic form which is selected from the group
consisting of zinc, cadmium, beryllium, aluminum, gallium, indium,
thallium, titanium, zirconium, hafnium, erbium, germanium, tin,
vanadium, niobium, scandium, chromium, molybdenum, tungsten,
manganese, rhenium, palladium, thorium, iron and cobalt, preferably
zinc, cadmium, titanium, tin, chromium, iron and cobalt, and the
anionic moiety of the compound may be selected from the group
consisting of halides such as fluoride, chloride, bromide and
iodide, anions of lower fatty acids having from 2 to 7 carbon
atoms, HPO.sub.3.sup.2-, H.sub.3PO.sup.2-, CF.sub.3COO.sup.-,
C.sub.7H.sub.15OSO.sub.2.sup.- or SO.sub.4.sup.2-. Further suitable
promoters, disclosed by U.S. Pat. No. 3,773,809, are borohydrides,
organoborohydrides and boric esters of the formula R.sub.3B and
B(OR).sub.3, where R is selected from the group consisting of
hydrogen, aryl radicals having from 6 to 18 carbon atoms, aryl
radicals substituted by alkyl groups having from 1 to 7 carbon
atoms and aryl radicals substituted by cyano-substituted alkyl
groups having from 1 to 7 carbon atoms, advantageously
triphenylboron. Moreover, as described in U.S. Pat. No. 4,874,884,
it is possible to use synergistically active combinations of Lewis
acids, in order to increase the activity of the catalyst system.
Suitable promoters may, for example, be selected from the group
consisting of CdCl.sub.2, FeCl.sub.2, ZnCl.sub.2,
B(C.sub.6H.sub.5).sub.3 and (C.sub.6H.sub.5).sub.3SnX, where
X.dbd.CF.sub.3SO.sub.3, CH.sub.3C.sub.6H.sub.4SO.sub.3 or
(C.sub.6H.sub.5).sub.3BCN, and the preferred ratio specified of
promoter to nickel is from about 1:16 to about 50:1.
[0117] In the context of the present invention, the term Lewis acid
also includes the promoters specified in U.S. Pat. No. 3,496,217,
U.S. Pat. No. 3,496,218, U.S. Pat. No. 4,774,353, U.S. Pat. No.
4,874,884, U.S. Pat. No. 6,127,567, U.S. Pat. No. 6,171,996 and
U.S. Pat. No. 6,380,421.
[0118] Particularly preferred Lewis acids among those mentioned are
in particular metal salts, more preferably metal halides, such as
fluorides, chlorides, bromides, iodides, in particular chlorides,
of which particular preference is given to zinc chloride, iron(II)
chloride and iron(III) chloride.
[0119] The isomerization may be carried out in the presence of a
liquid diluent, [0120] for example a hydrocarbon such as hexane,
heptane, octane, cyclohexane, methylcyclohexane, benzene,
decahydronaphthalene [0121] for example an ether such as diethyl
ether, tetrahydrofuran, dioxane, glycol dimethyl ether, anisole,
[0122] for example an ester such as ethyl acetate, methyl benzoate,
or [0123] for example a nitrile such as acetonitrile, benzonitrile,
or [0124] mixtures of such diluents.
[0125] In a particularly preferred embodiment, a useful
isomerization is in the absence of such a liquid diluent.
[0126] Moreover, it has been found to be advantageous when the
isomerization in process step (a) is carried out in an unoxidizing
atmosphere, for example under a protective gas atmosphere composed
of nitrogen or a noble gas such as argon.
[0127] Process step (a) may be carried out in any suitable
apparatus known to those skilled in the art. Useful apparatus for
this reaction is customary apparatus as described, for example, in:
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th ed., Vol. 20,
John Wiley & Sons, New York, 1996, pages 1040 to 1055, such as
stirred tank reactors, loop reactors, gas circulation reactors,
bubble column reactors or tubular reactors. The reaction may be
carried out in a plurality of, such as two or three,
apparatuses.
[0128] In a preferred embodiment of the process according to the
invention, the isomerization is carried out in a compartmented
tubular reactor.
[0129] In a further preferred embodiment of the process according
to the invention, the isomerization is carried out in at least two
reactors connected in series, in which case the first reactor has
substantially stirred tank characteristics and the second reactor
is designed in such a way that it has substantially tubular
characteristics.
[0130] In a particularly preferred embodiment of the process
according to the invention, the isomerization is carried out in a
reactor, the reactor having the characteristics of a stirred tank
battery which corresponds to from 2 to 20 stirred tanks, in
particular from 3 to 10 stirred tanks.
[0131] In one embodiment of the process according to the invention,
the reaction may be carried out in one distillation apparatus, in
which case the isomerization reaction takes place at least in the
bottom region of the distillation apparatus. Any distillation
apparatus known to those skilled in the art is suitable, as
described, for example, in: Kirk-Othmer, Encyclopedia of Chemical
Technology, 4th ed., Vol. 8, John Wiley & Sons, New York, 1996,
pages 334-348, such as sieve tray columns, bubble-cap tray columns,
columns having structured packing or random packing, which may also
be operated as dividing wall columns. These distillation units are
each equipped with suitable apparatus for evaporation, such as
falling-film evaporators, thin-film evaporators, multiphase
helical-tube evaporators, natural-circulation evaporators or
forced-circulation flash evaporators, and also with apparatus for
condensing the vapor stream. The distillation with simultaneous
reaction can be carried out in a plurality of, such as two or
three, apparatuses, advantageously in a single apparatus. The
distillation may additionally be effected in one stage in the case
of a partial evaporation of the feed stream.
[0132] Process step (a) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 16 bar, in particular
from 10 mbar to 6 bar. The temperature in process step (a) is
preferably from 25 to 250.degree. C., more preferably from 30 to
180.degree. C., in particular from 40 to 140.degree. C.
[0133] The composition of the stream withdrawn, with regard to the
molar ratio of 2-methyl-3-butenenitrile to linear pentenenitrile
and thus the degree of conversion of 2-methyl-3-butenenitrile used,
may be adjusted, depending on the composition of the feed stream,
in a technically simple manner by the temperature, the catalyst
concentration, the residence time and the configuration of the
reactor. In a preferred embodiment of the process according to the
invention, the degree of conversion is adjusted with the aid of
these measures to values in the range from 10 to 99%, more
preferably from 30 to 95%, in particular from 60 to 90%.
Process Step (b)
[0134] In process step (b), the stream 1 obtained in process step
(a) is distilled. This gives a stream 2 which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile as the top product. In addition, a
stream 3 is obtained in process step (b) as the bottom product
which comprises the at least one isomerization catalyst.
[0135] Process step (b) of the process according to the invention
may be carried out in any suitable distillation apparatus known to
those skilled in the art. Suitable apparatus for distillation is
described, for example, in: Kirk-Othmer, Encyclopedia of Chemical
Technology, 4th ed., Vol. 8, John Wiley & Sons, New York, 1996,
pages 334-348, such as sieve tray columns, bubble-cap tray columns,
columns having structured packing or random packing, which may also
be operated as dividing wall columns. These distillation units are
each equipped with suitable apparatus for evaporating, such as
falling-film evaporators, thin-film evaporators, multiphase
helical-tube evaporators, natural-circulation evaporators or
forced-circulation flash evaporators, and also with apparatus for
condensation of the vapor stream. The distillation can be carried
out in a plurality of, such as two or three, apparatuses,
advantageously in a single apparatus. The distillation may
additionally be effected in one stage in the case of a partial
evaporation of the feed stream.
[0136] Process step (b) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 6 bar, in particular
from 10 mbar to 500 mbar. The distillation is carried out in such a
way that the temperature in the bottom of the distillation
apparatus is preferably from 25 to 250.degree. C., more preferably
from 40 to 180.degree. C., in particular from 60 to 140.degree. C.
The distillation is carried out in such a way that the temperature
at the top of the distillation apparatus is preferably from -15 to
200.degree. C., more preferably from 5 to 150.degree. C., in
particular from 10 to 100.degree. C. In a particularly preferred
embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0137] In a particularly preferred embodiment of the present
invention, the distillation, carried out in process step (b), of
stream 1 takes place under pressure and temperature conditions
under which the isomerization catalyst present in the mixture is
less active than in process step (a) or is inactive.
[0138] In a preferred embodiment of the present invention, stream
3, obtained in process step (b), which comprises the at least one
isomerization catalyst is recycled at least partly into process
step (a).
[0139] In a further embodiment of the process according to the
invention, process steps (a) and (b) take place in the same
apparatus. It is also possible that stream 3 which comprises the at
least one isomerization catalyst is not withdrawn from process step
(b) and resides in the common apparatus of process steps (a) and
(b).
[0140] Alternatively, it is also possible that stream 3, stemming
from process step (b), which comprises the at least one
isomerization catalyst is used at least partly to prepare the
reactant stream used in accordance with the invention in process
step (e). In process step (e), this at-least one isomerization
catalyst then functions as a hydrocyanation catalyst.
Process Step (c)
[0141] In process step (c), a distillation of stream 2 takes place.
This gives a stream 4 as the top product which, compared to stream
2, is enriched in (Z)-2-methyl-2-butenenitrile in relation to the
sum of all pentenenitriles present in stream 2. In addition, a
stream 5 is obtained as the bottom product which, compared to
stream 2, is depleted in (Z)-2-methyl-2-butenenitrile in relation
to the sum of all pentenenitriles present in stream 2.
[0142] Process step (c) may be carried out in any suitable
apparatus known to those skilled in the art. Suitable apparatus for
distillation is described, for example, in: Kirk-Othmer,
Encyclopedia of Chemical Technology, 4th ed., Vol. 8, John Wiley
& Sons, New York, 1996, pages 334-348, such as sieve tray
columns, bubble-cap tray columns, columns having structured packing
or random packing, which may also be operated as dividing wall
columns. These distillation units are each equipped with suitable
apparatus for evaporating, such as falling-film evaporators,
thin-film evaporators, multiphase helical-tube evaporators,
natural-circulation evaporators or forced-circulation flash
evaporators, and also with apparatus for condensation of the vapor
stream. The distillation can be carried out in a plurality of, such
as two or three, apparatuses, advantageously in a single apparatus.
The distillation may additionally be effected in one stage in the
case of a partial evaporation of the feed stream.
[0143] Process step (c) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 6 bar, in particular
from 10 mbar to 500 mbar. The distillation is carried out in such a
way that the temperature in the bottom of the distillation
apparatus is preferably from 25 to 250.degree. C., more preferably
from 40 to 180.degree. C., in particular from 60 to 140.degree. C.
The distillation is carried out in such a way that the temperature
at the top of the distillation apparatus is preferably from -15 to
200.degree. C., more preferably from 5 to 150.degree. C., in
particular from 10 to 100.degree. C. In a particularly preferred
embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0144] In a particularly preferred embodiment of the process
according to the invention, process steps (b) and (c) are carried
out together in one distillation apparatus, in which case stream 3
which comprises the at least one isomerization catalyst is obtained
as the bottom product, stream 4 which comprises
(Z)-2-methyl-2-butenenitrile as the top product, and stream 5 which
comprises 3-pentenenitrile and 2-methyl-3-butenenitrile at a side
draw of the column.
[0145] In a further preferred embodiment of the process according
to the invention, process steps (a), (b) and (c) are carried out
together in one distillation apparatus. In this case, stream 4
which comprises (Z)-2-methyl-2-butenenitrile is obtained as the top
product. Stream 5 which comprises 3-pentenenitrile and
2-methyl-3-butenenitrile is obtained at a side draw of the
distillation column. In this embodiment, the isomerization catalyst
remains preferably in the bottom of the distillation column.
Process Step (d)
[0146] Stream 5, obtained in process step (c), which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile is subsequently
transferred to a further distillation apparatus. In this
distillation apparatus, stream 5 is separated into a
3-pentenenitrile stream which is withdrawn as the bottom product,
and a 2-methyl-3-butenenitrile stream which is withdrawn at the
top.
[0147] Process step (d) may be carried out in any suitable
apparatus known to those skilled in the art. Suitable apparatus for
distillation is described, for example, in: Kirk-Othmer,
Encyclopedia of Chemical Technology, 4th ed., Vol. 8, John Wiley
& Sons, New York, 1996, pages 334-348, such as sieve tray
columns, bubble-cap tray columns, columns having structured packing
or random packing, which may also be operated as dividing wall
columns. These distillation units are each equipped with suitable
apparatus for evaporating, such as falling-film evaporators,
thin-film evaporators, multiphase helical-tube evaporators,
natural-circulation evaporators or forced-circulation flash
evaporators, and also with apparatus for condensation of the vapor
stream. The distillation can be carried out in a plurality of, such
as two or three, apparatuses, advantageously in a single apparatus.
The distillation may additionally be effected in one stage in the
case of a partial evaporation of the feed stream.
[0148] The absolute pressure in process step (d) is preferably from
0.001 to 100 bar, more preferably from 0.01 to 20 bar, in
particular from 0.05 to 2 bar. The distillation is carried out in
such a way that the temperature in the bottom of the distillation
apparatus is preferably from 30 to 250.degree. C., more preferably
from 50 to 200.degree. C., in particular from 60 to 180.degree. C.
The distillation is carried out in such a way that the condensation
temperature at the top of the distillation apparatus is preferably
from -50 to 250.degree. C., more preferably from 0 to 180.degree.
C., in particular from 15 to 160.degree. C.
[0149] In a particularly preferred embodiment of the process
according to the invention, the aforementioned temperature ranges
are maintained both at the top and in the bottom of the
distillation apparatus.
[0150] In a particularly preferred embodiment of the process
according to the invention, process step (d) and process step (g)
are carried out in the same distillation apparatus. In this case,
streams 6 and 12, and also 7 and 13, coincide. In addition, in this
preferred embodiment, stream 5 is conducted directly into the
common apparatus of process steps (d) and (g). In this case, the
inlet points of streams 5 and 11, in the case of a distillation
column as the distillation apparatus, may be the same or
different.
[0151] In a further embodiment of the process according to the
invention, process steps (c) and (g) are carried out in a common
distillation column, in which case process step (d) is dispensed
with, stream 2 from process step (b) and stream 11 from process
step (f) are conducted into process step (g), and, in process step
(g), stream 4 is obtained as the top product comprising
(Z)-2-methyl-2-butenenitrile, stream 12 as the bottom product
comprising 3-pentenenitrile and stream 13 as a side draw stream
comprising 2-methyl-3-butenenitrile.
[0152] In the process according to the invention of embodiment I,
it is possible that stream 2 is recycled directly into process step
(g) and the reactant stream is conducted directly into process step
(c), in which case a stream 5a from process step (c) is recycled
into the isomerization of process step (a).
[0153] Alternatively, it is also possible to recycle stream 2
directly into process step (g) and conduct the reactant stream into
process step (c), in which case stream 5 from process step (c) is
recycled into process step (f).
[0154] Alternatively, it is also possible that stream 2 is recycled
directly into process step (g) and the reactant stream is conducted
into process step (c), and stream 5 from process step (c) is
recycled into process step (e).
EMBODIMENT II
[0155] The present invention further provides a process for
preparing 3-pentenenitrile according to an embodiment II, which is
characterized by the following process steps: [0156] (a')
isomerizing a reactant stream which comprises
2-methyl-3-butenenitrile over at least one dissolved or dispersed
isomerization catalyst to give a stream 1' which comprises
3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one
isomerization catalyst and (Z)-2-methyl-2-butenenitrile, [0157]
(b') distilling stream 1' to obtain a stream 2' which comprises
(Z)-2-methyl-2-butenenitrile, 2-methyl-3-butenenitrile, and
recycling it into the isomerization step (a'), a stream 3' as the
bottom product which comprises the at least one isomerization
catalyst and recycling it into the isomerization step (a'), and a
stream 4' which comprises 3-pentenenitrile at a side draw of the
distillation column.
[0158] The reactant stream which is used in process step (a') of
the process according to the invention according to embodiment II
may be obtained by the above-described process for preparing the
reactant stream for the process according to the invention
according to embodiment I.
[0159] For process step (a') according to embodiment II, the same
conditions apply as for process step (a) according to embodiment I,
especially with regard to the catalyst complex used and the free
ligand.
[0160] The absolute pressure in process step (b') is preferably
from 0.001 to 100 bar, more preferably from 0.01 to 20 bar, in
particular from 0.1 to 2 bar. The distillation is carried out in
such a way that the temperature in the bottom of the distillation
apparatus is preferably from 25 to 250.degree. C., more preferably
from 40 to 180.degree. C., in particular from 60 to 140.degree. C.
The distillation is carried out in such a way that the condensation
temperature at the top of the distillation apparatus is preferably
from -50 to 250.degree. C., more preferably from 0 to 150.degree.
C., in particular from 10 to 100.degree. C.
[0161] A partial discharge of stream 2' is in some cases
appropriate in order to prevent accumulation of
(Z)-2-methyl-2-butenenitrile. The residual stream is recycled in
step (a').
[0162] In one variant of the present process according to
embodiment II, the reactant stream is conducted into process step
(b') instead of into process step (a').
[0163] Stream 2' which leaves process step (b') in the process
according to the invention according to embodiment II may, if
appropriate, in a further optional process step (c') be subjected
to a distillation. This preferably forms a
(Z)-2-methyl-2-butenenitrile-enriched stream 5' and a
(Z)-2-methyl-2-butenenitrile-depleted stream 6', and stream 5' is
preferably recycled into process step (a').
[0164] Process step (c') to be carried out if appropriate may also
be carried out in the apparatus of process step (a'), in which case
a distillation apparatus is then used in process step (a') in whose
bottom the isomerization reaction takes place, stream 1' is drawn
off via the bottom of the distillation apparatus, and the
(Z)-2-methyl-2-butenenitrile-rich stream 6' is drawn off via the
top of the distillation apparatus.
[0165] According to the invention, in the processes according to
embodiment I and II, 3-pentenenitrile is obtained. In the context
of the present invention, the term 3-pentenenitrile refers to a
single isomer of 3-pentenenitrile or a mixture of two, three, four
or five different such isomers. Isomers include
cis-2-pentenenitrile, trans-2-pentenenitrile, cis-3-pentenenitrile,
trans-3-pentenenitrile, 4-pentenenitrile or mixtures thereof,
preferably cis-3-pentenenitrile, trans-3-pentenenitrile,
4-pentenenitrile or mixtures thereof, which are referred to in the
context of the present invention, both in each case individually
and as a mixture, as 3-pentenenitrile.
[0166] The process according to the invention is associated with
advantages. For instance, in an integrated process for preparing
adiponitrile, for example, the recycling of unconverted
2-methyl-3-butenenitrile from the isomerization is economically
necessary, because the degree of conversion of
2-methyl-3-butenenitrile to 3-pentenenitrile is restricted by the
thermodynamic equilibrium. The recycling entails the removal of
(Z)-2-methyl-2-butenenitrile which accumulates in the
2-methyl-3-butenenitrile circuit. In the process according to the
invention, the removal is effected by distillation to separate
2-methyl-3-butenenitrile and (Z)-2-methyl-2-butenenitrile
preferably only after step (a) has been carried out, in step (c),
in order to minimize losses of products of value in a controlled
manner.
[0167] The process according to the invention according to a
preferred version of embodiment I is illustrated in detail with
reference to FIG. 1:
[0168] In a reactor R1, hydrogen cyanide and 1,3-butadiene are fed
in the presence of a nickel(0) catalyst. In the reactor,
hydrocyanation takes place to form a stream 8. This stream 8
comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the
hydrocyanation catalyst and unconverted 1,3-butadiene.
Subsequently, stream 8 is transferred to a distillation column K1
in which 1,3-butadiene (stream 9) is removed from stream 8
overhead. In the bottom of the distillation column K1, a stream 10
is obtained which comprises the hydrocyanation catalyst. At the
side draw of the distillation column K1, a stream 11 is obtained
which comprises 3-pentenenitrile and 2-methyl-3-butenenitrile. This
stream 11 is subsequently transferred to a distillation column
K2.
[0169] In the distillation column K2, stream 11 is separated into a
stream 12 which comprises 3-pentenenitrile, and a stream 13 which
comprises 2-methyl-3-butenenitrile.
[0170] Stream 13 is subsequently transferred to an isomerization
apparatus R2. In this isomerization apparatus R2, the
2-methyl-3-butenenitrile which is present in stream 13 is
isomerized over an isomerization catalyst. The stream 1 stemming
from this isomerization comprises 3-pentenenitrile,
2-methyl-3-butenenitrile, (Z)-2-methyl-2-butenenitrile, and also
the isomerization catalyst.
[0171] This stream 1 is subsequently separated in a distillation
apparatus K3. This forms stream 3 which comprises the isomerization
catalyst (bottoms). At the top of the distillation apparatus K3,
stream 2 is withdrawn. This stream 2 comprises 3-pentenenitrile,
(Z)-2-methyl-2-butenenitrile and 2-methyl-3-butenenitrile. This
stream 2 is subsequently transferred to a distillation column
K4.
[0172] In this distillation column K4, stream 2 is separated into
(Z)-2-methyl-2-butenenitrile which has been formed during the
isomerization (stream 4). In addition, stream 5 is obtained in the
bottom of the distillation column K4 and comprises 3-pentenenitrile
and 2-methyl-3-butenenitrile. This stream 5 is transferred to the
distillation column K2, and the 3-pentenenitrile is obtained from
stream 5 in the distillation column.
[0173] Streams 9 and 10 may be partly or fully recycled into the
reactor R1, or not recycled into it at all. The same applies to
stream 3 in the direction of reactor R2. These variants are not
shown in FIG. 1.
[0174] The process according to the invention according to a
preferred version of embodiment II is illustrated in detail with
reference to FIG. 2:
[0175] In a reactor R1, hydrogen cyanide and 1,3-butadiene are fed
in the presence of a nickel(0) catalyst. In the reactor,
hydrocyanation takes place to form a stream 8. This stream 8
comprises 3-pentenenitrile, 2-methyl-3-butenenitrile, the
hydrocyanation catalyst and unconverted 1,3-butadiene.
Subsequently, stream 8 is transferred to a distillation column K1
in which 1,3-butadiene (stream 9) is removed from stream 8
overhead. In the bottom of the distillation column K1, a stream 10
is obtained which comprises the hydrocyanation catalyst. At the
side draw of the distillation column K1, a stream 11 is obtained
which comprises 3-pentenenitrile and 2-methyl-3-butenenitrile. This
stream 11 is subsequently transferred to an isomerization apparatus
R2.
[0176] In the isomerization apparatus R2, isomerization catalyst
(stream 3') and 2-methyl-3-butenenitrile (stream 2'), each stemming
from the distillation column K2, are additionally introduced. In
the isomerization apparatus R2, an isomerization takes place. The
stream 1' resulting therefrom is subsequently transferred to the
distillation apparatus K2 in which stream 1' is separated into a
stream 2' (2-methyl-3-butenenitrile) which is recycled into R2, a
stream 3' (isomerization catalyst) which is recycled into R2, and
into a stream 4' which comprises 3-pentenenitrile.
[0177] Feeding of a stream comprising isomerization catalyst to
R.sup.2 allows any necessary discharges from stream 3' to be
compensated, so that the Ni(0) content in R2 remains constant.
[0178] Streams 9 and 10 may be recycled fully or partly into the
reactor R1, or not recycled into it at all.
[0179] These recycling and discharge variants are not shown in FIG.
2.
EMBODIMENT III
[0180] In embodiment III, hydrocyanation and isomerization Ni(0)
catalysts of those ligands which catalyze process steps a*) and e*)
are used.
[0181] The nickel(.phi.) complexes used with preference as a
catalyst, which contain phosphorus ligands and/or free phosphorus
ligands, are preferably homogeneously dissolved nickel(.phi.)
complexes.
[0182] The phosphorus ligands of the nickel(0) complexes and the
free phosphorus ligands are preferably selected from the group of
the mono- or bidentate phosphines, phosphites, phosphinites and
phosphonites, preferably of the mono- or bidentate phosphites,
phosphinites and phosphonites, more preferably of the mono- or
bidentate phosphites and phosphonites, in particular of the
monodentate phosphites, phosphinites and phosphonites, most
preferably of the monodentate phosphites and phosphonites.
[0183] These phosphorus ligands preferably have the formula I
P(X.sup.1R.sup.1)(X.sup.2R.sup.2)(X.sup.3R.sup.3) (1)
[0184] In the context of the present invention, compound I is a
single compound or a mixture of different compounds of the
aforementioned formula.
[0185] According to the invention, X.sup.1, X.sup.2, X.sup.3 each
independently are oxygen or a single bond. When all of the X.sup.1,
X.sup.2 and X.sup.3 groups are single bonds, compound I is a
phosphine of the formula P(R.sup.1R.sup.2, R.sup.3) with the
definitions of R.sup.1, R.sup.2 and R.sup.3 specified in this
description.
[0186] When two of the X.sup.1, X.sup.2 and X.sup.3 groups are
single bonds and one is oxygen, compound I is a phosphinite of the
formula P(OR.sup.1)(R.sup.2)(R.sup.3) or
P(R.sup.1)(OR.sup.2)(R.sup.3) or P(R.sup.1)(R.sup.2)(OR.sup.3) with
the definitions of R.sup.1, R.sup.2 and R.sup.3 specified
below.
[0187] When one of the X.sup.1, X.sup.2 and X.sup.3 groups is a
single bond and two are oxygen, compound I is a phosphonite of the
formula P(OR.sup.1)(OR.sup.2)(R.sup.3) or
P(OR.sup.1)(OR.sup.2)(OR.sup.3) or P(OR.sup.1)(R.sup.2)(OR.sup.3)
with the definitions of R.sup.1, R.sup.2 and R.sup.3 specified in
this description.
[0188] In one embodiment, all X.sup.1, X.sup.2 and X.sup.3 groups
should be oxygen, so that compound I is a phosphite of the formula
P(OR.sup.1)(OR.sup.2)(OR.sup.3) with the definitions of R.sup.1,
R.sup.2 and R.sup.3 specified below.
[0189] According to the invention, R.sup.1, R.sup.2, R.sup.3 are
each independently identical or different organic radicals.
R.sup.1, R.sup.2 and R.sup.3 are each independently alkyl radicals
preferably having from 1 to 10 carbon atoms, such as methyl, ethyl,
n-propyl, i-propyl, n-butyl, i-butyl, s-butyl, t-butyl, aryl groups
such as phenyl, o-tolyl, m-tolyl, p-tolyl, 1-naphthyl, 2-naphthyl,
or hydrocarbyl, preferably having from 1 to 20 carbon atoms, such
as 1,1'-biphenol, 1,1'-binaphthol. The R.sup.1, R.sup.2 and R.sup.3
groups may be bonded together directly, i.e. not solely via the
central phosphorus atom. Preference is given to the R.sup.1,
R.sup.2 and R.sup.3 groups not being bonded together directly.
[0190] In one embodiment, R.sup.1, R.sup.2 and R.sup.3 groups are
radicals selected from the group consisting of phenyl, o-tolyl,
m-tolyl and p-tolyl. In one embodiment, a maximum of two of the
R.sup.1, R.sup.2 and R.sup.3 groups should be phenyl groups.
[0191] In another embodiment, a maximum of two of the R.sup.1,
R.sup.2 and R.sup.3 groups should be o-tolyl groups.
[0192] Compounds I which may be used are those of the formula
Ia
(o-tolyl-O--).sub.w(m-tolyl-O--).sub.x(p-tolyl-O--).sub.y(phenyl-O--).su-
b.zP (Ia)
where w, x, y and z are each a natural number and the following
conditions apply: w+x+y+z=3 and w, z.ltoreq.2.
[0193] Such compounds Ia are, for example,
(p-tolyl-O--)(phenyl-O--).sub.2P, (m-tolyl-O--)(phenyl-O--).sub.2P,
(o-tolyl-O--)(phenyl-O--).sub.2P, (p-tolyl-O--).sub.2(phenyl-O--)P,
(m-tolyl-O--).sub.2(phenyl-O--)P, (o-tolyl-O--).sub.2(phenyl-O--)P,
(m-tolyl-O--)(p-tolyl-O--)(phenyl-O--)P,
(o-tolyl-O--)(p-tolyl-O--)(phenyl-O--)P,
(o-tolyl-O--)(m-tolyl-O--)(phenyl-O--)P, (p-tolyl-O--).sub.3P,
(m-tolyl-O--)(p-tolyl-O--).sub.2P,
(o-tolyl-O--)(p-tolyl-O--).sub.2P,
(m-tolyl-O--).sub.2(p-tolyl-O--)P,
(o-tolyl-O--).sub.2(p-tolyl-O--)P,
(o-tolyl-O--)(m-tolyl-O--)(p-tolyl-O--)P, (m-tolyl-O--).sub.3P,
(o-tolyl-O--)(m-tolyl-O--).sub.2P (o-tolyl-O--).sub.2(m-tolyl-O--)P
or mixtures of such compounds.
[0194] Mixtures comprising (m-tolyl-O--).sub.3P,
(m-tolyl-O--).sub.2(p-tolyl-O--)P,
(m-tolyl-O--)(p-tolyl-O--).sub.2P and (p-tolyl-O--).sub.3P may be
obtained, for example, by reacting a mixture comprising m-cresol
and p-cresol, in particular in a molar ratio of 2:1, as obtained in
the distillative workup of crude oil, with a phosphorus trihalide,
such as phosphorus trichloride.
[0195] In one embodiment, the phosphorus ligands are the
phosphites, described in detail in DE-A 199 53 058, of the formula
Ib:
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(o-R.sup.4).sub.p
(Ib)
where [0196] R.sup.1: aromatic radical having a
C.sub.1-C.sub.18-alkyl substituent in the o-position to the oxygen
atom which joins the phosphorus atom to the aromatic system, or
having an aromatic substituent in the o-position to the oxygen atom
which joins the phosphorus atom to the aromatic system, or having a
fused aromatic system in the o-position to the oxygen atom which
joins the phosphorus atom to the aromatic system, [0197] R.sup.2:
aromatic radical having a C.sub.1-C.sub.18-alkyl substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having an aromatic substituent in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, or having a fused aromatic system in the
m-position to the oxygen atom which joins the phosphorus atom to
the aromatic system, the aromatic radical bearing a hydrogen atom
in the o-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, [0198] R.sup.3: aromatic radical
having a C.sub.1-C.sub.18-alkyl substituent in the p-position to
the oxygen atom which joins the phosphorus atom to the aromatic
system, or having an aromatic substituent in the p-position to the
oxygen atom which joins the phosphorus atom to the aromatic system,
the aromatic radical bearing a hydrogen atom in the o-position to
the oxygen atom which joins the phosphorus atom to the aromatic
system, [0199] R.sup.4: aromatic radical which bears substituents
other than those defined for R.sup.1, R.sup.2 and R.sup.3 in the
o-, m- and p-position to the oxygen atom which joins the phosphorus
atom to the aromatic system, the aromatic radical bearing a
hydrogen atom in the o-position to the oxygen atom which joins the
phosphorus atom to the aromatic system, [0200] x: 1 or 2, [0201] y,
z, p: each independently 0, 1 or 2, with the proviso that
x+y+z+p=3.
[0202] Preferred phosphites of the formula Ib can be taken from
DE-A 199 53 058. The R.sup.1 radical may advantageously be o-tolyl,
o-ethylphenyl, o-n-propylphenyl, o-isopropylphenyl,
o-n-butylphenyl, o-sec-butylphenyl, o-tert-butylphenyl,
(o-phenyl)phenyl or 1-naphthyl groups.
[0203] Preferred R.sup.2 radicals are m-tolyl, m-ethylphenyl,
m-n-propylphenyl, m-isopropylphenyl, m-n-butylphenyl,
m-sec-butylphenyl, m-tert-butylphenyl, (m-phenyl)phenyl or
2-naphthyl groups.
[0204] Advantageous R.sup.3 radicals are p-tolyl, p-ethylphenyl,
p-n-propylphenyl, p-isopropylphenyl, p-n-butylphenyl,
p-sec-butylphenyl, p-tert-butylphenyl or (p-phenyl)phenyl
groups.
[0205] The R.sup.4 radical is preferably phenyl. p is preferably
zero. For the indices x, y, z and p in compound Ib, there are the
following possibilities:
TABLE-US-00002 x y z p 1 0 0 2 1 0 1 1 1 1 0 1 2 0 0 1 1 0 2 0 1 1
1 0 1 2 0 0 2 0 1 0 2 1 0 0
[0206] Preferred phosphites of the formula Ib are those in which p
is zero, and R.sup.1, R.sup.2 and R.sup.3 are each independently
selected from o-isopropylphenyl, m-tolyl and p-tolyl, and R.sup.4
is phenyl.
[0207] Particularly preferred phosphites of the formula Ib are
those in which R.sup.1 is the o-isopropylphenyl radical, R.sup.2 is
the m-tolyl radical and R.sup.3 is the p-tolyl radical with the
indices specified in the table above; also those in which R.sup.1
is the o-tolyl radical, R.sup.2 is the m-tolyl radical and R.sup.3
is the p-tolyl radical with the indices specified in the table;
additionally those in which R.sup.1 is the 1-naphthyl radical,
R.sup.2 is the m-tolyl radical and R.sup.3 is the p-tolyl radical
with the indices specified in the table; also those in which
R.sup.1 is the o-tolyl radical, R.sup.2 is the 2-naphthyl radical
and R.sup.3 is the p-tolyl radical with the indices specified in
the table; and finally those in which R.sup.1 is the
o-isopropylphenyl radical, R.sup.2 is the 2-naphthyl radical and
R.sup.3 is the p-tolyl radical with the indices specified in the
table; and also mixtures of these phosphites.
[0208] Phosphites of the formula Ib may be obtained by [0209] a)
reacting a phosphorus trihalide with an alcohol selected from the
group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and R.sup.4OH
or mixtures thereof to obtain a dihalophosphorous monoester, [0210]
b) reacting the dihalophosphorous monoester mentioned with an
alcohol selected from the group consisting of R.sup.1OH, R.sup.2OH,
R.sup.3OH and R.sup.4OH or mixtures thereof to obtain a
monohalophosphorous diester and [0211] c) reacting the
monohalophosphorous diester mentioned with an alcohol selected from
the group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and
R.sup.4OH or mixtures thereof to obtain a phosphite of the formula
Ib.
[0212] The reaction may be carried out in three separate steps.
Equally, two of the three steps may be combined, i.e. a) with b) or
b) with c). Alternatively, all of steps a), b) and c) may be
combined together.
[0213] Suitable parameters and amounts of the alcohols selected
from the group consisting of R.sup.1OH, R.sup.2OH, R.sup.3OH and
R.sup.4OH or mixtures thereof may be determined readily by a few
simple preliminary experiments.
[0214] Useful phosphorus trihalides are in principle all phosphorus
trihalides, preferably those in which the halide used is Cl, Br, I,
in particular Cl, and mixtures thereof. It is also possible to use
mixtures of various identically or differently halogen-substituted
phosphines as the phosphorus trihalide. Particular preference is
given to PCl.sub.3. Further details on the reaction conditions in
the preparation of the phosphites Ib and for the workup can be
taken from DE-A 199 53 058.
[0215] The phosphites Ib may also be used in the form of a mixture
of different phosphites Ib as a ligand. Such a mixture may be
obtained, for example, in the preparation of the phosphites Ib.
[0216] It is likewise possible for the phosphorus ligand to be
multidentate, in particular bidentate. The ligand used then has,
for example, the formula II
##STR00002##
where [0217] X.sup.11, X.sup.12, X.sup.13, X.sup.21, X.sup.22,
X.sup.23 are each independently oxygen or a single bond [0218]
R.sup.11, R.sup.12 are each independently identical or different,
separate or bridged organic radicals [0219] R.sup.21, R.sup.22 are
each independently identical or different, separate or bridged
organic radicals, [0220] Y is a bridging group.
[0221] In the context of the present invention, compound II is a
single compound or a mixture of different compounds of the
aforementioned formula.
[0222] In one embodiment, X.sup.1, X.sup.12, X.sup.13, X.sup.21,
X.sup.22, X.sup.23 may each be oxygen. In such a case, the bridging
group Y is bonded to phosphite groups.
[0223] In another embodiment, X.sup.11 and X.sup.12 may each be
oxygen and X.sup.13 a single bond, or X.sup.11 and X.sup.13 each
oxygen and X.sup.12 a single bond, so that the phosphorus atom
surrounded by X.sup.11, X.sup.12 and X.sup.13 is the central atom
of a phosphonite. In such a case, X.sup.21, X.sup.22 and X.sup.23
may each be oxygen, or X.sup.21 and X.sup.22 may each be oxygen and
X.sup.23 a single bond, or X.sup.21 and X.sup.23 may each be oxygen
and X.sup.22 a single bond, or X.sup.23 may be oxygen and X.sup.21
and X.sup.22 each a single bond, or X.sup.21 may be oxygen and
X.sup.22 and X.sup.23 each a single bond, or X.sup.21, X.sup.22 and
X.sup.23 may each be a single bond, so that the phosphorus atom
surrounded by X.sup.21, X.sup.22 and X.sup.23 may be the central
atom of a phosphite, phosphonite, phosphinite or phosphine,
preferably a phosphonite.
[0224] In another embodiment, X.sup.13 may be oxygen and X.sup.11
and X.sup.12 each a single bond, or X.sup.11 may be oxygen and
X.sup.12 and X.sup.13 each a single bond, so that the phosphorus
atom surrounded by X.sup.11, X.sup.12 and X.sup.13 is the central
atom of a phosphonite. In such a case, X.sup.21, X.sup.22 and
X.sup.23 may each be oxygen, or X.sup.23 may be oxygen and X.sup.21
and X.sup.22 each a single bond, or X.sup.25 may be oxygen and
X.sup.22 and X.sup.23 each a single bond, or X.sup.21, X.sup.22 and
X.sup.23 may each be a single bond, so that the phosphorus atom
surrounded by X.sup.21, X.sup.22 and X.sup.23 may be the central
atom of a phosphite, phosphinite or phosphine, preferably a
phosphinite.
[0225] In another embodiment, X.sup.11, X.sup.12 and X.sup.13 may
each be a single bond, so that the phosphorus atom surrounded by
X.sup.11, X.sup.12 and X.sup.13 is the central atom of a phosphine.
In such a case, X.sup.21, X.sup.22 and X.sup.23 may each be oxygen,
or X.sup.21, X.sup.22 and X.sup.23 may each be a single bond, so
that the phosphorus atom surrounded by X.sup.21, X.sup.22 and
X.sup.23 may be the central atom of a phosphite or phosphine,
preferably a phosphine.
[0226] The bridging group Y is preferably an aryl group which is
substituted, for example by C.sub.1-C.sub.4-alkyl, halogen, such as
fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or is unsubstituted,
preferably a group having from 6 to 20 carbon atoms in the aromatic
system, in particular pyrocatechol, bis(phenol) or
bis(naphthol).
[0227] The R.sup.11 and R.sup.12 radicals may each independently be
identical or different organic radicals. Advantageous R.sup.11 and
R.sup.12 radicals are aryl radicals, preferably those having from 6
to 10 carbon atoms, which may be unsubstituted or mono- or
polysubstituted, in particular by C.sub.1-C.sub.4-alkyl, halogen,
such as fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl
groups.
[0228] The R.sup.21 and R.sup.22 radicals may each independently be
the same or different organic radicals. Advantageous R.sup.21 and
R.sup.22 radicals are aryl radicals, preferably those having from 6
to 10 carbon atoms, which may be unsubstituted or mono- or
polysubstituted, in particular by C.sub.1-C.sub.4-alkyl, halogen,
such as fluorine, chlorine, bromine, halogenated alkyl, such as
trifluoromethyl, aryl, such as phenyl, or unsubstituted aryl
groups.
[0229] The R.sup.11 and R.sup.12 radicals may each be separate or
bridged. The R.sup.21 and R.sup.22 radicals too may each be
separate or bridged. The R.sup.11, R.sup.12, R.sup.21 and R.sup.22
radicals may each be separate, two may be bridged and two separate,
or all four may be bridged, in the manner described.
[0230] In one embodiment, useful compounds are those of the formula
I, II, III, IV and V specified in U.S. Pat. No. 5,723,641. In one
embodiment, useful compounds are those of the formula I, II, III,
IV, V, VI and VII specified in U.S. Pat. No. 5,512,696, in
particular the compounds used there in examples 1 to 31. In one
embodiment, useful compounds are those of the formula I, II, III,
IV, V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV and XV specified in
U.S. Pat. No. 5,821,378, in particular the compounds used there in
examples 1 to 73.
[0231] In one embodiment, useful compounds are those of the formula
I, II, III, IV, V and VI specified in U.S. Pat. No. 5,512,695, in
particular the compounds used there in examples 1 to 6.
[0232] In one embodiment, useful compounds are those of the formula
I, II, III, IV, V, VI, VII, VIII, IX, X, XI, XII, XIII and XIV
specified in U.S. Pat. No. 5,981,772, in particular the compounds
used there in examples 1 to 66.
[0233] In one embodiment, useful compounds are those specified in
U.S. Pat. No. 6,127,567 and the compounds used there in examples 1
to 29. In one embodiment, useful compounds are those of the formula
I, II, III, IV, V, VI, VII, VIII, IX and X specified in U.S. Pat.
No. 6,020,516, in particular the compounds used there in examples 1
to 33. In one embodiment, useful compounds are those specified in
U.S. Pat. No. 5,959,135 and the compounds used there in examples 1
to 13.
[0234] In one embodiment, useful compounds are those of the formula
I, II and III specified in U.S. Pat. No. 5,847,191. In one
embodiment, useful compounds are those specified in U.S. Pat. No.
5,523,453, in particular the compounds illustrated there in formula
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20 and 21. In one embodiment, useful compounds are those specified
in WO 01/14392, in particular the compounds illustrated there in
formula V, VI, VII, VIII, IX, X, XI, XII, XIII, XIV, XV, XVI, XVII,
XXI, XXII, XXIII.
[0235] In one embodiment, useful compounds are those specified in
WO 98/27054. In one embodiment, useful compounds are those
specified in WO 99/13983. In one embodiment, useful compounds are
those specified in WO 99/64155.
[0236] In one embodiment, useful compounds are those specified in
the German patent application DE 100 380 37. In one embodiment,
useful compounds are those specified in the German patent
application DE 100 460 25. In one embodiment, useful compounds are
those specified in the German patent application DE 101 502 85.
[0237] In one embodiment, useful compounds are those specified in
the German patent application DE 101 502 86. In one embodiment,
useful compounds are those specified in the German patent
application DE 102 071 65. In a further embodiment of the present
invention, useful phosphorus chelate ligands are those specified in
US 2003/0100442 A1.
[0238] In a further embodiment of the present invention, useful
phosphorus chelate ligands are those specified in the German patent
application reference number DE 103 50 999.2 of Oct. 30, 2003 which
has an earlier priority date but had not been published at the
priority date of the present application.
[0239] The compounds I, Ia, Ib and II described and their
preparation are known per se. Phosphorus ligands used may also be a
mixture comprising at least two of the compounds I, Ia, Ib and
II.
[0240] In a particularly preferred embodiment of the process
according to the invention, the phosphorus ligand of the nickel(0)
complex and/or the free phosphorus ligand is selected from the
phosphites of the formula Ib
P(O--R.sup.1).sub.x(O--R.sup.2).sub.y(O--R.sup.3).sub.z(O--R.sup.4).sub.-
p (Ib)
where R.sup.1, R.sup.2 and R.sup.3 are each independently selected
from o-isopropylphenyl, m-tolyl and p-tolyl, R.sup.4 is phenyl; x
is 1 or 2, and y, z, p are each independently 0, 1 or 2, with the
proviso that x+y+z+p=3; and mixtures thereof, i.e. mixtures of 2 or
more, preferably from 2 to 10, more preferably from 2 to 6, of the
compounds of the formula Ib.
[0241] In one embodiment III, the process is characterized by the
following process steps: [0242] (a*) isomerizing a reactant stream
which comprises 2-methyl-3-butenenitrile over at least one
dissolved or dispersed isomerization catalyst to give a stream 1
which comprises the at least one isomerization catalyst,
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, [0243] (b*) distilling stream 1 to
obtain a stream 2 as the top product which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile, and a stream 3 as the bottom product
which comprises the at least one isomerization catalyst, [0244]
(c*) distilling stream 2 to obtain a stream 4 as the top product
which, compared to stream 2, is enriched in
(Z)-2-methyl-2-butenenitrile, based on the sum of all
pentenenitriles in stream 2, and a stream 5 as the bottom product
which, compared to stream 2, is enriched in 3-pentenenitrile and
2-methyl-3-butenenitrile, based on the sum of all pentenenitriles
in stream 2, [0245] (d*) distilling stream 5 to obtain a stream 6
as the bottom product which comprises 3-pentenenitrile and a stream
7 as the top product which comprises 2-methyl-3-butenenitrile,
[0246] (h*) catalyst regeneration to replenish the nickel(0)
content of the substreams 14 from stream 3 and 16 from stream 10 to
generate a stream 18, [0247] (i*) if appropriate with addition of a
diluent F to stream 18 to generate stream 19, [0248] (j*)
extracting stream 18, if appropriate stream 19, with regard to the
catalyst components and/or disruptive component(s) by adding a
dinitrile stream 20 and hydrocarbon stream 21 to generate two
nonmiscible phases 22 and 23, stream 22 comprising the predominant
proportion of the catalyst components and stream 23 the predominant
proportion of the disruptive component(s), [0249] (k*)
distillatively removing the hydrocarbon from the catalyst
components from stream 22 to generate a stream 25 which comprises
the predominant proportion of the catalyst components and, if
appropriate, partly or fully recycling stream 25 into process steps
(a*) or (e*).
Reactant Stream
[0250] In process step (a*) an isomerization of a reactant stream
which comprises 2-methyl-3-butenenitrile over at least one
isomerization catalyst takes place.
[0251] In a particular embodiment of the process according to the
invention, the reactant stream is obtainable by the following
process steps: [0252] (e*) hydrocyanating 1,3-butadiene over at
least one hydrocyanation catalyst using hydrogen cyanide to obtain
a stream 8 which comprises the at least one hydrocyanation
catalyst, 3-pentenenitrile, 2-methyl-3-butenenitrile, 1,3-butadiene
and residues of hydrogen cyanide, [0253] (f*) distilling stream 8
once or more than once to obtain a stream 9 which comprises
1,3-butadiene, a stream 10 which comprises the at least one
hydrocyanation catalyst, and a stream 11 which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile, [0254] (g*)
distilling stream 11 to obtain a stream 12 as the bottom product
which comprises 3-pentenenitrile, and a stream 13 as the top
product which comprises 2-methyl-3-butenenitrile.
Process Step e*)
[0255] In process step (e*), to prepare the reactant stream, a
hydrocyanation of 1,3-butadiene initially takes place over at least
one hydrocyanation catalyst with hydrogen cyanide to obtain a
stream 8 which comprises the at least one hydrocyanation catalyst,
3-pentenenitrile, 2-methyl-3-butenenitrile and unconverted
1,3-butadiene.
[0256] Process step (e*) may be carried out in any suitable
apparatus known to those skilled in the art. Useful apparatus for
the reaction is thus customary apparatus, as described, for
example, in: Kirk-Othmer, Encyclopedia of Chemical Technology, 4th
ed., Vol. 20, John Wiley & Sons, New York, 1996, pages 1040 to
1055, such as stirred tank reactors, loop reactors, gas circulation
reactors, bubble column or tubular reactors, in each case, if
appropriate, with apparatus to remove heat of reaction. The
reaction may be carried out in a plurality of, such as two or
three, apparatuses.
[0257] In a preferred embodiment of the process according to the
invention, advantageous reactors have been found to be reactors
having backmixing characteristics or batteries of reactors having
backmixing characteristics. It has been found that batteries of
reactors having backmixing characteristics which are operated in
crossflow mode with regard to the metering of hydrogen cyanide are
particularly advantageous.
[0258] The hydrocyanation may be carried out in the presence or in
the absence of a solvent. When a solvent is used, the solvent
should be liquid at the given reaction temperature and the given
reaction pressure and inert toward the unsaturated compounds and
the at least one catalyst. In general, the solvents used are
hydrocarbons, for example benzene or xylene, or nitrites, for
example acetonitrile or benzonitrile. However, preference is given
to using a ligand as the solvent.
[0259] The reaction may be carried out in batchwise mode,
continuously or in semibatchwise operation.
[0260] The hydrocyanation reaction may be carried out by charging
the apparatus with all reactants. However, it is preferred when the
apparatus is filled with the catalyst, the unsaturated organic
compound and, if appropriate, the solvent. The gaseous hydrogen
cyanide preferably floats over the surface of the reaction mixture
or is passed through the reaction mixture. A further procedure for
charging the apparatus is the filling of the apparatus with the
catalyst, hydrogen cyanide and, if appropriate, the solvent, and
slowly metering the unsaturated compound into the reaction mixture.
Alternatively, it is also possible that the reactants are
introduced into the reactor and the reaction mixture is brought to
the reaction temperature at which the hydrogen cyanide is added to
the mixture in liquid form. In addition, the hydrogen cyanide may
also be added before heating to reaction temperature. The reaction
is carried out under conventional hydrocyanation conditions for
temperature, atmosphere, reaction time, etc.
[0261] Preference is given to carrying out the hydrocyanation
continuously in one or more stirred process steps. When a multitude
of process steps is used, preference is given to the process steps
being connected in series. In this case, the product is transferred
from one process step directly into the next process step. The
hydrogen cyanide may be fed directly into the first process step or
between the individual process steps.
[0262] When the process according to the invention is carried out
in semibatchwise operation, preference is given to initially
charging the catalyst components and 1,3-butadiene in the reactor,
while hydrogen cyanide is metered into the reaction mixture over
the reaction time.
[0263] The reaction is preferably carried out at absolute pressures
of from 0.1 to 500 MPa, more preferably from 0.5 to 50 MPa, in
particular from 1 to 5 MPa. The reaction is preferably carried out
at temperatures of from 273 to 473 K, more preferably from 313 to
423 K, in particular from 333 to 393 K. Advantageous average mean
residence times of the liquid reactor phase have been found to be
in the range from 0.001 to 100 hours, preferably from 0.05 to 20
hours, more preferably from 0.1 to 5 hours, in each case per
reactor.
[0264] In one embodiment, the reaction may be performed in the
liquid phase in the presence of a gas phase and, if appropriate, of
a solid suspended phase. The starting materials, hydrogen cyanide
and 1,3-butadiene, may each be metered in liquid or gaseous
form.
[0265] In a further embodiment, the reaction may be carried out in
liquid phase, in which case the pressure in the reactor is such
that all feedstocks such as 1,3-butadiene, hydrogen cyanide and the
at least one catalyst are metered in liquid form and are in the
liquid phase in the reaction mixture. A solid suspended phase may
be present in the reaction mixture and may also be metered in
together with the at least one catalyst, for example consisting of
degradation products of the catalyst system comprising nickel(II)
compounds inter alia.
[0266] In process step (e*), a stream 8 which comprises
3-pentenenitrile, 2-methyl-3-butenenitrile, the at least one
catalyst and unconverted 1,3-butadiene is obtained.
Process Step (f*)
[0267] Stream 8 which comprises 3-pentenenitrile,
2-methyl-3-butenenitrile, the at least one catalyst and unconverted
1,3-butadiene is subsequently transferred in process step (f*) to a
distillation apparatus. In this distillation apparatus, stream 8 is
distilled once or more than once to obtain a stream 9 which
comprises 1,3-butadiene, a stream 10 which comprises the at least
one hydrocyanation catalyst, and a stream 11 which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile.
[0268] The distillation of process step (f*) may be effected in two
stages, as described in DE-A-102 004 004 720, process steps (b*)
and (c*). The distillation of process step (f*) may also be
effected according to DE-A-102 004 004 729, process steps (b*) and
(c*).
[0269] The distillation(s) of process step (f*) may be carried out
in any suitable apparatus known to those skilled in the art.
Suitable apparatus for distillation is described, for example, in:
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th ed., Vol. 8,
John Wiley & Sons, New York, 1996, pages 334-348, such as sieve
tray columns, bubble-cap tray columns, columns having structured
packing or random packing, which may also be operated as dividing
wall columns. These distillation units are each equipped with
suitable apparatus for evaporating, such as falling-film
evaporators, thin-film evaporators, multiphase helical-tube
evaporators, natural-circulation evaporators or forced-circulation
flash evaporators, and also with apparatus for condensation of the
vapor stream. The individual distillations can each be carried out
in a plurality of, such as two or three, apparatuses,
advantageously in a single apparatus in each case.
[0270] The distillation(s) may additionally each be effected in one
stage in the case of a partial evaporation of the feed stream.
[0271] The pressure in process step (f*) is preferably from 0.001
to 10 bar, more preferably from 0.010 to 1 bar, in particular from
0.02 to 0.5 bar. The distillation(s) is/are carried out in such a
way that the temperature(s) in the bottom of the distillation
apparatus(es) is/are preferably from 30 to 200.degree. C., more
preferably from 50 to 150.degree. C., in particular from 60 to
120.degree. C. The distillation(s) is/are carried out in such a way
that the condensation temperatures at the top of the distillation
apparatus are preferably from -50 to 150.degree. C., more
preferably from -15 to 60.degree. C., in particular from 5 to
45.degree. C. In a particularly preferred embodiment of the process
according to the invention, the aforementioned temperature ranges
are maintained both at the top and in the bottom of the
distillation apparatus(es).
[0272] Stream 11 is subsequently subjected to a distillation in a
further process step (g*). This distillation may be carried out in
any suitable apparatus known to those skilled in the art. Suitable
apparatus for distillation is described, for example, in:
Kirk-Othmer, Encyclopedia of Chemical Technology, 4th ed., Vol. 8,
John Wiley & Sons, New York, 1996, pages 334-348, such as sieve
tray columns, bubble-cap tray columns, columns having structured
packing or random packing, which may also be operated as dividing
wall columns. These distillation units are each equipped with
suitable apparatus for evaporating, such as falling-film
evaporators, thin-film evaporators, multiphase helical-tube
evaporators, natural-circulation evaporators or forced-circulation
flash evaporators, and also with apparatus for condensation of the
vapor stream. The distillation can be carried out in a plurality
of, such as two or three, apparatuses, advantageously in a single
apparatus. The distillation may additionally be effected in one
stage in the case of a partial evaporation of the feed stream.
[0273] The pressure in process step (g*) is preferably from 0.001
to 100 bar, more preferably from 0.01 to 20 bar, in particular from
0.05 to 2 bar. The distillation is carried out in such a way that
the temperature in the bottom of the distillation apparatus is
preferably from 30 to 250.degree. C., more preferably from 50 to
200.degree. C., in particular from 60 to 180.degree. C. The
distillation is carried out in such a way that the condensation
temperature at the top of the distillation apparatus is preferably
from -50 to 250.degree. C., more preferably from 0 to 180.degree.
C., in particular from 15 to 160.degree. C. In a particularly
preferred embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0274] In process step (g*), a stream 12 is obtained as the bottom
product which comprises 1,3-pentenenitrile, and stream 13 as the
top product which comprises 2-methyl-3-butenenitrile. Stream 13 is
preferably used as the reactant stream in the process according to
the invention for preparing 3-pentenenitrile.
[0275] In a further embodiment of the present invention, it is
possible that the reactant stream used in the inventive process
step (a*) corresponds to stream 11 of process step (f*), so that a
separation of stream 11 in process step (g*) is dispensed with.
Process Step (a*)
[0276] In process step (a*), an isomerization of the reactant
stream which comprises 2-methyl-3-butenenitrile takes place over at
least one isomerization catalyst. This gives a stream 1 which
comprises the isomerization catalyst, unconverted
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile.
[0277] According to the invention, the isomerization is carried out
in the presence of a system comprising [0278] nickel(0) and [0279]
a compound which contains trivalent phosphorus and complexes
nickel(0) as a ligand.
[0280] Nickel(0)-containing catalyst systems can be prepared by
processes known per se.
[0281] The ligands for the isomerization catalyst may be the same
phosphorus ligands as used for the hydrocyanation catalyst used in
process step (e*). The hydrocyanation catalyst is thus identical to
the isomerization catalyst.
[0282] The catalyst in process steps (a*) and (e*) is substantially
Lewis acid-free, i.e. no Lewis acid is added to the catalyst at any
time, and the catalyst preferably does not contain any Lewis
acid.
[0283] Lewis acid refers in this context to inorganic or organic
metal compounds in which the cation is selected from the group
consisting of scandium, titanium, vanadium, chromium, manganese,
iron, cobalt, copper, zinc, boron, aluminum, yttrium, zirconium,
niobium, molybdenum, cadmium, rhenium and tin. Examples include
ZnBr.sub.2, ZnI.sub.2, ZnCl.sub.2, ZnSO.sub.4, CuCl.sub.2, CuCl,
Cu(O.sub.3SCF.sub.3).sub.2, CoCl.sub.2, CoI.sub.2, FeI.sub.2,
FeCl.sub.3, FeCl.sub.2, FeCl.sub.2(THF).sub.2,
TiCl.sub.4(THF).sub.2, TiCl.sub.4, TiCl.sub.3,
ClTi(O-i-propyl).sub.3, MnCl.sub.2, ScCl.sub.3, AlCl.sub.3,
(C.sub.8H.sub.17)AlCl.sub.2, (C.sub.8H.sub.17).sub.2AlCl,
(i-C.sub.4H.sub.9).sub.2AlCl, (C.sub.6H.sub.5).sub.2AlCl,
(C.sub.6H.sub.5)AlCl.sub.2, ReCl.sub.5, ZrCl.sub.4, NbCl.sub.5,
VCl.sub.3, CrCl.sub.2, MoCl.sub.5, YCl.sub.3, CdCl.sub.2,
LaCl.sub.3, Er(O.sub.3SCF.sub.3).sub.3, Yb(O.sub.2CCF.sub.3).sub.3,
SmCl.sub.3, B(C.sub.6H.sub.5).sub.3, TaCl.sub.5, RAlCl.sub.2,
R.sub.2AlCl, RSnO.sub.3SCF.sub.3 and R.sub.3B, where R is an alkyl
or aryl group, B(C.sub.6H.sub.5).sub.3 and
(C.sub.6H.sub.5).sub.3SnX, where X.dbd.CF.sub.3SO.sub.3,
CH.sub.3C.sub.6H.sub.4SO.sub.3 or (C.sub.6H.sub.5).sub.3BCN, as
described, for example, in U.S. Pat. No. 6,127,567, U.S. Pat. No.
6,171,996, U.S. Pat. No. 6,380,421, U.S. Pat. No. 3,496,217, U.S.
Pat. No. 3,496,218, U.S. Pat. No. 4,774,353, U.S. Pat. No.
3,773,809, U.S. Pat. No. 3,496,217 and U.S. Pat. No. 4,874,884.
[0284] The isomerization may be carried out in the presence of a
liquid diluent, [0285] for example a hydrocarbon such as hexane,
heptane, octane, cyclohexane, methylcyclohexane, benzene,
decahydronaphthalene [0286] for example an ether such as diethyl
ether, tetrahydrofuran, dioxane, glycol dimethyl ether, anisole,
[0287] for example an ester such as ethyl acetate, methyl benzoate,
or [0288] for example a nitrile such as acetonitrile, benzonitrile,
or [0289] mixtures of such diluents.
[0290] In a particularly preferred embodiment, a useful
isomerization is in the absence of such a liquid diluent.
[0291] Moreover, it has been found to be advantageous when the
isomerization in process step (a*) is carried out in a nonoxidizing
atmosphere, for example under a protective gas atmosphere composed
of nitrogen or a noble gas such as argon.
[0292] Process step (a*) may be carried out in any suitable
apparatus known to those skilled in the art. Useful apparatus for
the reaction is customary apparatus for this purpose, as described,
for example, in: Kirk-Othmer, Encyclopedia of Chemical Technology,
4th ed., Vol. 20, John Wiley & Sons, New York, 1996, pages 1040
to 1055, such as stirred tank reactors, loop reactors, gas
circulation reactors, bubble column reactors or tubular reactors.
The reaction may be carried out in a plurality of, such as two or
three, apparatuses.
[0293] In a preferred embodiment of the process according to the
invention, the isomerization is carried out in a compartmented
tubular reactor.
[0294] In a further preferred embodiment of the process according
to the invention, the isomerization is carried out in at least two
reactors connected in series, in which case the first reactor has
substantially stirred tank characteristics and the second reactor
is designed in such a way that it has substantially tubular
characteristics.
[0295] In a particularly preferred embodiment of the process
according to the invention, the isomerization is carried out in a
reactor, the reactor having the characteristics of a stirred tank
battery which corresponds to from 2 to 20 stirred tanks, in
particular from 3 to 10 stirred tanks.
[0296] In one embodiment of the process according to the invention,
the reaction may be carried out in one distillation apparatus, in
which case the isomerization reaction takes place at least in the
bottom region of the distillation apparatus. Any distillation
apparatus known to those skilled in the art is suitable, as
described, for example, in: Kirk-Othmer, Encyclopedia of Chemical
Technology, 4th ed., Vol. 8, John Wiley & Sons, New York, 1996,
pages 334-348, such as sieve tray columns, bubble-cap tray columns,
columns having structured packing or random packing, which may also
be operated as dividing wall columns. These distillation units are
each equipped with suitable apparatus for evaporation, such as
falling-film evaporators, thin-film evaporators, multiphase
helical-tube evaporators, natural-circulation evaporators or
forced-circulation flash evaporators, and also with apparatus for
condensing the vapor stream. The distillation with simultaneous
reaction can be carried out in a plurality of, such as two or
three, apparatuses, advantageously in a single apparatus. The
distillation may additionally be effected in one stage in the case
of a partial evaporation of the feed stream.
[0297] Process step (a*) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 16 bar, in particular
from 10 mbar to 6 bar. The temperature in process step (a*) is
preferably from 25 to 250.degree. C., more preferably from 30 to
180.degree. C., in particular from 40 to 140.degree. C.
[0298] The composition of the stream withdrawn, with regard to the
molar ratio of 2-methyl-3-butenenitrile to linear pentenenitrile
and thus the degree of conversion of 2-methyl-3-butenenitrile used,
may be adjusted, depending on the composition of the feed stream,
in a technically simple manner by the temperature, the catalyst
concentration, the residence time and the configuration of the
reactor. In a preferred embodiment of the process according to the
invention, the degree of conversion is adjusted with the aid of
these measures to values in the range from 10 to 99%, more
preferably from 30 to 95%, in particular from 60 to 90%.
Process Step (b*)
[0299] In process step (b*), the stream 1 obtained in process step
(a*) is distilled. This gives a stream 2 which comprises
2-methyl-3-butenenitrile, 3-pentenenitrile and
(Z)-2-methyl-2-butenenitrile as the top product. In addition, a
stream 3 is obtained in process step (b*) as the bottom product
which comprises the at least one isomerization catalyst.
[0300] Process step (b*) of the process according to the invention
may be carried out in any suitable distillation apparatus known to
those skilled in the art. Suitable apparatus for distillation is
described, for example, in: Kirk-Othmer, Encyclopedia of Chemical
Technology, 4th ed., Vol. 8, John Wiley & Sons, New York, 1996,
pages 334-348, such as sieve tray columns, bubble-cap tray columns,
columns having structured packing or random packing, which may also
be operated as dividing wall columns. These distillation units are
each equipped with suitable apparatus for evaporating, such as
failing-film evaporators, thin-film evaporators, multiphase
helical-tube evaporators, natural-circulation evaporators or
forced-circulation flash evaporators, and also with apparatus for
condensation of the vapor stream. The distillation can be carried
out in a plurality of, such as two or three, apparatuses,
advantageously in a single apparatus. The distillation may
additionally be effected in one stage in the case of a partial
evaporation of the feed stream.
[0301] Process step (b*) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 6 bar, in particular
from 10 mbar to 500 mbar. The distillation is carried out in such a
way that the temperature in the bottom of the distillation
apparatus is preferably from 25 to 250.degree. C., more preferably
from 40 to 180.degree. C., in particular from 60 to 140.degree. C.
The distillation is carried out in such a way that the temperature
at the top of the distillation apparatus is preferably from -15 to
200.degree. C., more preferably from 5 to 150.degree. C., in
particular from 10 to 100.degree. C. In a particularly preferred
embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0302] In a particularly preferred embodiment of the present
invention, the distillation, carried out in process step (b*), of
stream 1 takes place under pressure and temperature conditions
under which the isomerization catalyst present in the mixture is
less active than in process step (a*) or is inactive.
[0303] In a preferred embodiment of the present invention, stream
3, obtained in process step (b*), which comprises the at least one
isomerization catalyst is recycled at least partly into process
step (a*).
[0304] In a further embodiment of the process according to the
invention, process steps (a*) and (b*) take place in the same
apparatus. It is also possible that stream 3 which comprises the at
least one isomerization catalyst is not withdrawn from process step
(b*) and resides in the common apparatus of process steps (a*) and
(b*).
Process Step (c*)
[0305] In process step (c*), a distillation of stream 2 takes
place. This gives a stream 4 as the top product which, compared to
stream 2, is enriched in (Z)-2-methyl-2-butenenitrile in relation
to the sum of all pentenenitriles present in stream 2. In addition,
a stream 5 is obtained as the bottom product which, compared to
stream 2, is depleted in (Z)-2-methyl-2-butenenitrile in relation
to the sum of all pentenenitriles present in stream 2.
[0306] Process step (c*) may be carried out in any suitable
apparatus known to those skilled in the art. Suitable apparatus for
distillation is described, for example, in: Kirk-Othmer,
Encyclopedia of Chemical Technology, 4th ed., Vol. 8, John Wiley
& Sons, New York, 1996, pages 334-348, such as sieve tray
columns, bubble-cap tray columns, columns having structured packing
or random packing, which may also be operated as dividing wall
columns. These distillation units are each equipped with suitable
apparatus for evaporating, such as falling-film evaporators,
thin-film evaporators, multiphase helical-tube evaporators,
natural-circulation evaporators or forced-circulation flash
evaporators, and also with apparatus for condensation of the vapor
stream. The distillation can be carried out in a plurality of, such
as two or three, apparatuses, advantageously in a single apparatus.
The distillation may additionally be effected in one stage in the
case of a partial evaporation of the feed stream.
[0307] Process step (c*) of the process according to the invention
is preferably carried out at an absolute pressure of from 0.1 mbar
to 100 bar, more preferably from 1 mbar to 6 bar, in particular
from 10 mbar to 500 mbar. The distillation is carried out in such a
way that the temperature in the bottom of the distillation
apparatus is preferably from 25 to 250.degree. C., more preferably
from 40 to 180.degree. C., in particular from 60 to 140.degree. C.
The distillation is carried out in such a way that the temperature
at the top of the distillation apparatus is preferably from -15 to
200.degree. C., more preferably from 5 to 150.degree. C., in
particular from 10 to 100.degree. C. In a particularly preferred
embodiment of the process according to the invention, the
aforementioned temperature ranges are maintained both at the top
and in the bottom of the distillation apparatus.
[0308] In a particularly preferred embodiment of the process
according to the invention, process steps (b*) and (c*) are carried
out together in one distillation apparatus, in which case stream 3
which comprises the at least one isomerization catalyst is obtained
as the bottom product, stream 4 which comprises
(Z)-2-methyl-2-butenenitrile as the top product, and stream 5 which
comprises 3-pentenenitrile and 2-methyl-3-butenenitrile at a side
draw of the column.
[0309] In a further preferred embodiment of the process according
to the invention, process steps (a*), (b*) and (c*) are carried out
together in one distillation apparatus. In this case, stream 4
which comprises (Z)-2-methyl-2-butenenitrile is obtained as the top
product. Stream 5 which comprises 3-pentenenitrile and
2-methyl-3-butenenitrile is obtained at a side draw of the
distillation column. In this embodiment, the isomerization catalyst
remains preferably in the bottom of the distillation column.
Process Step (d*)
[0310] Stream 5, obtained in process step (c*), which comprises
3-pentenenitrile and 2-methyl-3-butenenitrile is subsequently
transferred to a further distillation apparatus. In this
distillation apparatus, stream 5 is separated into a
3-pentenenitrile stream which is withdrawn as the bottom product,
and a 2-methyl-3-butenenitrile stream which is withdrawn at the
top.
[0311] Process step (d*) may be carried out in any suitable
apparatus known to those skilled in the art. Suitable apparatus for
distillation is described, for example, in: Kirk-Othmer,
Encyclopedia of Chemical Technology, 4th ed., Vol. 8, John Wiley
& Sons, New York, 1996, pages 334-348, such as sieve tray
columns, bubble-cap tray columns, columns having structured packing
or random packing, which may also be operated as dividing wall
columns. These distillation units are each equipped with suitable
apparatus for evaporating, such as falling-film evaporators,
thin-film evaporators, multiphase helical-tube evaporators,
natural-circulation evaporators or forced-circulation flash
evaporators, and also with apparatus for condensation of the vapor
stream. The distillation can be carried out in a plurality of, such
as two or three, apparatuses, advantageously in a single apparatus.
The distillation may additionally be effected in one stage in the
case of a partial evaporation of the feed stream.
[0312] The absolute pressure in process step (d*) is preferably
from 0.001 to 100 bar, more preferably from 0.01 to 20 bar, in
particular from 0.05 to 2 bar. The distillation is carried out in
such a way that the temperature in the bottom of the distillation
apparatus is preferably from 30 to 250.degree. C., more preferably
from 50 to 200.degree. C., in particular from 60 to 180.degree. C.
The distillation is carried out in such a way that the condensation
temperature at the top of the distillation apparatus is preferably
from -50 to 250.degree. C., more preferably from 0 to 180.degree.
C., in particular from 15 to 160.degree. C.
[0313] In a particularly preferred embodiment of the process
according to the invention, the aforementioned temperature ranges
are maintained both at the top and in the bottom of the
distillation apparatus.
[0314] In a particularly preferred embodiment of the process
according to the invention, process step (d*) and process step (g*)
are carried out in the same distillation apparatus. In this case,
streams 6 and 12, and also 7 and 13, coincide. In addition, in this
preferred embodiment, stream 5 is conducted directly into the
common apparatus of process steps (d*) and (g*). In this case, the
inlet points of streams 5 and 11, in the case of a distillation
column as the distillation apparatus, may be the same or
different.
[0315] In a further embodiment of the process according to the
invention, process steps (c*) and (g*) are carried out in a common
distillation column, in which case process step (d*) is dispensed
with, stream 2 from process step (b*) and stream 11 from process
step (f*) are conducted into process step (g*), and, in process
step (g*), stream 4 is obtained as the top product comprising
(Z)-2-methyl-2-butenenitrile, stream 12 as the bottom product
comprising 3-pentenenitrile and stream 13 as a side draw stream
comprising 2-methyl-3-butenenitrile.
[0316] In the process according to the invention of embodiment III,
it is possible that stream 2 is recycled directly into process step
(g*) and the reactant stream is conducted directly into process
step (c*), in which case a stream 5a from process step (c*) is
recycled into the isomerization of process step (a*).
[0317] Alternatively, it is also possible to recycle stream 2
directly into process step (g*) and conduct the reactant stream
into process step (c*), in which case stream 5 from process step
(c*) is recycled into process step (f*).
[0318] Alternatively, it is also possible that stream 2 is recycled
directly into process step (g*) and the reactant stream is
conducted into process step (c*), and stream 5 from process step
(c*) is recycled into process step (e*).
Process Step h*):
[0319] Process step h*) comprises a process for preparing
nickel(0)-phosphorus ligand complexes containing at least one
nickel(0) central atom and at least one phosphorus ligand.
[0320] In the following, the terms reductive catalyst
synthesis/regeneration and redox catalyst synthesis/regeneration
are synonymous.
Process Step h.sub.1*):
[0321] In a preferred embodiment of process step h*), referred to
here as process step h.sub.1*), an aqueous nickel(II) halide dried
by azeotropic distillation (previously aqueous but of course dry
after azeotropic distillation) is reduced in the presence of at
least one phosphorus ligand.
Azeotropic Distillation
[0322] In the azeotropic distillation, an aqueous nickel(II) halide
is used. Aqueous nickel(II) halide is a nickel halide which is
selected from the group of nickel chloride, nickel bromide and
nickel iodide which contains at least 2% by weight of water.
Examples thereof are nickel chloride dihydrate, nickel chloride
hexahydrate, an aqueous solution of nickel chloride, nickel bromide
trihydrate, an aqueous solution of nickel bromide, nickel iodide
hydrates or an aqueous solution of nickel iodide. In the case of
nickel chloride, preference is given to using nickel chloride
hexahydrate or an aqueous solution of nickel chloride. In the case
of nickel bromide and nickel iodide, preference is given to using
the aqueous solutions. Particular preference is given to an aqueous
solution of nickel chloride.
[0323] In the case of an aqueous solution, the concentration of the
nickel(II) halide in water is not critical per se. An advantageous
proportion of the nickel(II) halide in the total weight of
nickel(II) halide and water has been found to be at least 0.01% by
weight, preferably at least 0.1% by weight, more preferably at
least 0.25% by weight, especially preferably at least 0.5% by
weight. An advantageous proportion of the nickel(II) halide in the
total weight of nickel(II) halide and water has been found to be in
the region of at most 80% by weight, preferably at most 60% by
weight, more preferably at most 40% by weight. For practical
reasons, it is advantageous not to exceed a proportion of nickel
halide in the mixture of nickel halide and water which results in a
solution under the given temperature and pressure conditions. In
the case of an aqueous solution of nickel chloride, it is therefore
advantageous for practical reasons to select at room temperature a
proportion of nickel halide in the total weight of nickel chloride
and water of at most 31% % by weight. At higher temperatures,
higher concentrations may correspondingly be selected which result
from the solubility of nickel chloride in water.
[0324] The aqueous nickel(II) halide is dried before the reduction
by an azeotropic distillation. In a preferred embodiment of the
present invention, the azeotropic distillation is a process for
removing water from the corresponding aqueous nickel(II) halide, in
which it is admixed with a diluent whose boiling point, in the case
that the diluent does not form an azeotrope with water, under the
pressure conditions of the distillation mentioned below, is higher
than the boiling point of water and which is present in liquid form
at this boiling point of water or which forms an azeotrope or
heteroazeotrope with water under the pressure and temperature
conditions of the distillation mentioned below, and the mixture
comprising the aqueous nickel(II) halide and the diluent is
distilled to remove water or the azeotrope mentioned or the
heteroazeotrope mentioned from this mixture to obtain an aqueous
mixture comprising nickel(II) halide and said diluent.
[0325] In addition to the aqueous nickel(II) halide, the starting
mixture may comprise further constituents such as ionic or
nonionic, organic or inorganic compounds, especially those which
are homogeneously and monophasically miscible with the starting
mixture or are soluble in the starting mixture.
[0326] According to the invention, the aqueous nickel(II) halide is
admixed with a diluent whose boiling point under the pressure
conditions of the distillation is higher than the boiling point of
water and which is liquid at this boiling point of water.
[0327] The pressure conditions for the subsequent distillation are
not critical per se. Advantageous pressures have been found to be
at least 10.sup.-4 MPa, preferably at least 10.sup.-3 MPa, in
particular at least 5*10.sup.3 MPa. Advantageous pressures have
been found to be at most 1 MPa, preferably at most 5*10.sup.-1 MPa,
in particular at most 1.5*10.sup.-1 MPa.
[0328] Depending on the pressure conditions and the composition of
the mixture to be distilled, the distillation temperature is then
established. At this temperature, the diluent is preferably in
liquid form. In the context of the present invention, the term
diluent refers either to an individual diluent or to a mixture of
diluents, in which case the physical properties mentioned in the
present invention relate to such a mixture.
[0329] In addition, the diluent preferably has a boiling point
under these pressure and temperature conditions which, in the case
that the diluent does not form an azeotrope with water, is higher
than that of water, preferably by at least 5.degree. C., in
particular at least 20.degree. C., and preferably at most
200.degree. C., in particular at most 100.degree. C.
[0330] In a preferred embodiment, diluents may be used which form
an azeotrope or heteroazeotrope with water. The amount of diluent
compared to the amount of water in the mixture is not critical per
se. Advantageously, more liquid diluent should be used than
corresponds to the amounts to be distilled off by the azeotropes,
so that excess diluent remains as the bottom product.
[0331] When a diluent is used which does not form an azeotrope with
water, the amount of diluent compared to the amount of water in the
mixture is not critical per se.
[0332] The diluent used is selected in particular from the group
consisting of organic nitrites, aromatic hydrocarbons, aliphatic
hydrocarbons and mixtures of the aforementioned solvents. With
regard to the organic nitrites, preference is given to using
acetonitrile, propionitrile, n-butyronitrile, n-valeronitrile,
cyanocyclopropane, acrylonitrile, crotonitrile, allyl cyanide,
cis-2-pentenenitrile, trans-2-pentenenitrile, cis-3-pentenenitrile,
trans-3-pentenenitrile, 4-pentenenitrile, 2-methyl-3-butenenitrile,
Z-2-methyl-2-butenenitrile, E-2-methyl-2-butenenitrile,
ethylsuccinonitrile, adiponitrile, methylglutaronitrile or mixtures
thereof. With regard to the aromatic hydrocarbons, benzene,
toluene, o-xylene, m-xylene, p-xylene or mixtures thereof may
preferably be used. Aliphatic hydrocarbons may preferably be
selected from the group of the linear or branched aliphatic
hydrocarbons, more preferably from the group of the
cycloaliphatics, such as cyclohexane or methylcyclohexane, or
mixtures thereof. Particular preference is given to using
cis-3-pentenenitrile, trans-3-pentenenitrile, adiponitrile,
methylglutaronitrile or mixtures thereof as the solvent.
[0333] When the diluent used is an organic nitrile or mixtures
comprising at least one organic nitrile, it has been found to be
advantageous to select the amount of diluent in such a way that the
proportion of nickel(II) halide in the total weight of nickel(II)
halide and diluent in the finished mixture is at least 0.05% by
weight, preferably at least 0.5% by weight, more preferably at
least 1% by weight.
[0334] When the diluent used is an organic nitrile or mixtures
comprising at least one organic nitrile, it has been found to be
advantageous to select the amount of diluent in such a way that the
proportion of nickel(II) halide in the total weight of nickel(II)
halide and diluent in the finished mixture is at most 50% by
weight, preferably at most 30% by weight, more preferably at most
20% by weight.
[0335] According to the invention, the mixture comprising the
aqueous nickel(II) halide and the diluent is distilled to remove
water from this mixture to obtain an anhydrous mixture comprising
nickel(II) halide and said diluent. In a preferred embodiment, the
mixture is initially prepared and subsequently distilled. In
another preferred embodiment, the aqueous nickel halide, more
preferably the aqueous solution of the nickel halide, is added
gradually to the boiling diluent during the distillation. This
allows the formation of a greasy solid which is difficult to handle
from a process technology point of view to be substantially
prevented.
[0336] In the case of pentenenitrile as the diluent, the
distillation can advantageously at a pressure of at most 1
megapascal, preferably 0.5 megapascal.
[0337] In the case of pentenenitrile as diluent, the distillation
can be carried out preferably at a pressure of at least 1 kPa,
preferably at least 5 kPa, more preferably at least 10 kPa.
[0338] The distillation may advantageously be effected by
single-stage evaporation, preferably by fractional distillation in
one or more, such as 2 or 3, distillation apparatuses. Useful
apparatus for the distillation is customary apparatus for this
purpose, as described, for example, in: Kirk-Othmer, Encyclopedia
of Chemical Technology, 3rd ed., Vol. 7, John Wiley & Sons, New
York, 1979, pages 870-881, such as sieve tray columns, bubble-cap
tray columns, columns having structured packing or random packing,
columns having side draws or dividing wall columns.
[0339] The distillation may be carried out batchwise or
continuously.
Reduction
[0340] The process for preparing nickel(0) phosphorus ligand
complexes containing at least one nickel(0) central atom and at
least one phosphorus ligand by reduction is preferably carried out
in the presence of a solvent. The solvent is in particular selected
from the group consisting of organic nitrites, aromatic
hydrocarbons, aliphatic hydrocarbons and mixtures of the
aforementioned solvents. With regard to the organic nitrites,
preference is given to using acetonitrile, propionitrile,
n-butyronitrile, n-valeronitrile, cyanocyclopropane, acrylonitrile,
crotonitrile, allyl cyanide, cis-2-pentenenitrile,
trans-2-pentenenitrile, cis-3-pentenenitrile,
trans-3-pentenenitrile, 4-pentenenitrile, 2-methyl-3-butenenitrile,
Z-2-methyl-2-butenenitrile, E-2-methyl-2-butenenitrile,
ethylsuccinonitrile, adiponitrile, methylglutaronitrile or mixtures
thereof. With regard to the aromatic hydrocarbons, benzene,
toluene, o-xylene, m-xylene, p-xylene or mixtures thereof may
preferably be used. Aliphatic hydrocarbons may preferably be
selected from the group of the linear or branched aliphatic
hydrocarbons, more preferably from the group of the cycloaliphatics
such as cyclohexane or methylcyclohexane, or mixtures thereof.
Particular preference is given to using cis-3-pentenenitrile,
trans-3-pentenenitrile, adiponitrile, methylglutaronitrile or
mixtures thereof as a solvent.
[0341] Preference is given to using an inert solvent.
[0342] The concentration of the solvent is preferably from 10 to
90% by mass, more preferably from 20 to 70% by mass, in particular
from 30 to 60% by mass, based in each case on the finished reaction
mixture.
[0343] In a particular embodiment of the present invention, the
solvent is identical to the diluent which is used in the
above-described inventive process for preparing the anhydrous
mixture comprising the nickel(II) halide and the diluent.
[0344] In the process according to the invention, the concentration
of the ligand in the solvent is preferably from 1 to 90% by weight,
more preferably from 5 to 80% by weight, in particular from 50 to
80% by weight.
[0345] The reducing agent used in the process according to the
invention is preferably selected from the group consisting of
metals which are more electropositive than nickel, metal alkyls,
electrical current, complex hydrides and hydrogen.
[0346] When the reducing agent used in the process according to the
invention is a metal which is more electropositive than nickel,
this metal is preferably selected from the group consisting of
sodium, lithium, potassium, magnesium, calcium, barium, strontium,
titanium, vanadium, iron, cobalt, copper, zinc, cadmium, aluminum,
gallium, indium, tin, lead and thorium. Particular preference is
given in this context to iron and zinc. When the reducing agent
used is aluminum, it is advantageous when it is preactivated by
reaction with a catalytic amount of mercury(II) salt or metal
alkyl. For the preactivation, preference is given to using
triethylaluminum in an amount of preferably from 0.05 to 50 mol %,
more preferably from 0.5 to 10 mol %. The reduction metal is
preferably finely divided, the term "finely divided" a meaning that
the metal is used in a particle size of less than 10 mesh, more
preferably less than 20 mesh.
[0347] When the reducing agent used in the process according to the
invention is a metal which is more electropositive than nickel, the
amount of metal is preferably from 0.1 to 50% by weight, based on
the reaction mixture.
[0348] When the reducing agent used in the process according to the
invention comprises metal alkyls, they are preferably lithium
alkyls, sodium alkyls, magnesium alkyls, in particular Grignard
reagents, zinc alkyls or aluminum alkyls. Particular preference is
given to aluminum alkyls such as trimethylaluminum,
triethylaluminum, triisopropylaluminum or mixtures thereof, in
particular triethylaluminum. The metal alkyls may be used in
substance or dissolved in an inert organic solvent such as hexane,
heptane or toluene.
[0349] When the reducing agent used in the process according to the
invention comprises complex hydrides, preference is given to using
metal aluminum hydrides such as lithium aluminum hydride, or metal
borohydrides such as sodium borohydride.
[0350] The molar ratio of the redox equivalents between the
nickel(II) source and the reducing agent is preferably from 1:1 to
1:100, more preferably from 1:1 to 1:50, in particular from 1:1 to
1:5.
[0351] In the process according to the invention, the ligand to be
used may also be present in a ligand solution which has already
been used as a catalyst solution in hydrocyanation reactions, for
example step e*), or isomerization reactions, for example step a*),
and has been depleted in nickel(0). Such streams are streams 3 and
10 respectively, either partly or in each case independently
selected substreams 14 (from substream 3) and substream 16 (from
substream 10) respectively in stage h*) and the following stages,
if appropriate i*), j*) and k*) conducted are. Any remaining
substreams 15 (from stream 3) and 17 (from stream 10) are not
conducted through h*), i*), j*) and k*), but rather recycled
directly into stage a*) or e*). This "return catalyst solution"
generally has the following composition:
[0352] from 2 to 60% by weight, in particular from 10 to 40% by
weight, of pentenenitriles,
[0353] from 0 to 60% by weight, in particular from 0 to 40% by
weight, of adiponitrile,
[0354] from 0 to 10% by weight, in particular from 0 to 5% by
weight, of other nitriles,
[0355] from 10 to 90% by weight, in particular from 50 to 90% by
weight of phosphorus ligand and
[0356] from 0 to 2% by weight, in particular from 0 to 1% by
weight, of nickel(0).
[0357] The free ligand present in the return catalyst solution may
thus be converted again to a nickel(0) complex in the process
according to the invention.
[0358] In a particular embodiment of the present invention, the
ratio of the nickel(II) source to phosphorus ligand is from 1:1 to
1:100. Further preferred ratios of nickel(II) source to phosphorus
ligand are from 1:1 to 1:3, in particular from 1:1 to 1:2.
[0359] The process according to the invention may be carried out at
any pressure. For practical reasons, preference is given to
pressures between 0.1 bara and 5 bara, preferably 0.5 bara and 1.5
bara.
[0360] The process according to the invention may be carried out in
batchwise mode or continuously.
[0361] In the process according to the invention, it is possible to
work without an excess of nickel(II) halide or reducing agent, for
example zinc, so that there is no need to remove them after the
nickel(0) complex formation.
[0362] In a particular embodiment of the present invention, the
process according to the invention comprises the following process
steps: [0363] (1) drying an aqueous nickel(II) halide by azeotropic
distillation, [0364] (2) precomplexing the azeotropically dried
nickel(II) halide in a solvent in the presence of a phosphorus
ligand, [0365] (3) adding at least one reducing agent to the
solution or suspension stemming from process step (2) at an
addition temperature of from 20 to 120.degree. C., [0366] (4)
stirring the suspension or solution stemming from process step (3)
for at a reaction temperature of from 20 to 120.degree. C.
[0367] The precomplexation temperatures, addition temperatures and
reaction temperatures may each independently be from 20.degree. C.
to 120.degree. C. Particular preference is given in the
precomplexation, addition and reaction to temperatures of from
30.degree. C. to 80.degree. C.
[0368] The precomplexation times, addition times and reaction times
may each independently be from 1 minute to 24 hours. The
precomplexation time is in particular from 1 minute to 3 hours. The
addition time is preferably from 1 minute to 30 minutes. The
reaction time is preferably from 20 minutes to 5 hours.
Process Step h.sub.2*):
[0369] A further preferred embodiment of process step h*),
described here as process step h.sub.2*), comprises the
replenishment of the nickel(0) content of the streams 14 or 16, for
example, by stirring in nickel powder. When this is done, free
phosphorus ligand in the streams 14 or 16 is used as a complex
formation partner or fresh ligand is added.
[0370] The catalyst compounds may be prepared from nickel powder
with a suitable halide source as an initiator, for example a halide
or an alkyl-substituted halide of phosphorus, arsenic or antimony,
such as CH.sub.3PCl.sub.2, CH.sub.3AsCl.sub.2 or
CH.sub.3SbCl.sub.2, or a suitable metal halide, elemental halogen
such as chlorine, bromine or iodine, or the corresponding hydrogen
halides or thionyl halide. Metal halides to be used in accordance
with the invention are the halides of Cr, Ni, Ti, Cu, Co, Fe, Hg,
Sn, Li, K, Ca, Ba, Sc, Ce, V, Mn, Be, Ru, Rh, Pd, Zn, Cd, Al, Th,
Zr and Hf. The halide may be chloride, bromide or iodide.
Particularly suitable halide sources are PX.sub.3, TiX.sub.4,
ZrX.sub.4, HfX.sub.4 or HX, where X is chloride, bromide or iodide.
When the inventive reaction is carried out, mixtures of 2 or more
initiators or catalysts may also be used.
[0371] The catalyst regeneration may be carried out batchwise, for
example in batch mode analogously to U.S. Pat. No. 3,903,120, or
continuously analogously to U.S. Pat. No. 4,416,825, at
temperatures of from 0 to 200.degree. C., preferably from 25 to
145.degree. C., more preferably from 50 to 100.degree. C. The
residence time of the catalyst may be varied within wide limits and
is generally between 15 minutes and 10 h, preferably 20 minutes and
5 h, more preferably 30 minutes and 2 h.
[0372] When process step h.sub.2*) is carried out instead of
process step h.sub.1*), the process steps i*), j*) and k*) may if
appropriate be dispensed with fully or partly.
Process Step i*):
[0373] If necessary, stream 18 may be concentrated before step i)
by distillation, for example at pressures of from 0.1 to 5000 mbar
(abs.), preferably from 0.5 to 1000 mbar (abs.) and in particular
from 1 to 200 mbar (abs.), and temperatures of from 10 to
150.degree. C., preferably from 40 to 100.degree. C.--or other
suitable measures--for example to from 50 to 95%, preferably from
60 to 90%, of its original volume. In a particularly preferred
embodiment, this stream contains after the concentration up to 10%
by weight, i.e. from 0 to 10% by weight, preferably from 0.01 to 8%
by weight, of pentenenitriles.
Step i*): Addition of the Nonpolar Aprotic Liquid L
[0374] In step i*), a nonpolar aprotic liquid L is added to the
stream 18 to obtain a stream 19. In this context, liquid means that
the compound L is present in liquid form under the pressure and
temperature conditions in step i*); under other pressure and
temperature conditions, L may also be solid or gaseous.
[0375] Suitable nonpolar (or apolar) aprotic liquids L are all
compounds liquid under the conditions of step i*) which chemically
or physically alter the catalyst, for example the Ni(0) complex
with phosphorus ligands and/or the free phosphorus ligands, only
insignificantly, if at all. Compounds suitable as the liquid L do
not contain any ionizable proton in the molecule and generally have
low relative dielectric constants (.epsilon..sub.r<15) and low
electrical dipole moments (.mu.<2.5 Debye).
[0376] Especially suitable are hydrocarbons which may, for example,
be unhalogenated or halogenated, and also amines, especially
tertiary amines, and carbon disulfide.
[0377] In a preferred embodiment, the liquid L is a hydrocarbon H*.
Suitable hydrocarbons H* are aliphatic, cycloaliphatic or aromatic.
Suitable aliphatic hydrocarbons are, for example, linear or
branched alkanes or alkenes having from 5 to 30, preferably from 5
to 16 carbon atoms, in particular pentane, hexane, heptane, octane,
nonane, decane, undecane and dodecane (in each case all
isomers).
[0378] Suitable cycloaliphatic hydrocarbons have, for example, from
5 to 10 carbon atoms, such as cyclopentane, cyclohexane,
cycloheptane, cyclooctane, cyclononane and cyclodecane.
Substituted, in particular C.sub.1-10-alkyl-substituted,
cycloaliphatics such as methylcyclohexane are also suitable.
Suitable aromatic hydrocarbons are preferably those having from 6
to 20 carbon atoms, in particular benzene, toluene, o-, m- and
p-xylene, naphthalene and anthracene. It is also possible to use
substituted, preferably C.sub.1-10-alkyl-substituted aromatics such
as ethylbenzene.
[0379] The hydrocarbon H* is more preferably selected from the
compounds mentioned below for the hydrocarbon H. Very particular
preference is given to the hydrocarbon H* being identical to the
hydrocarbon H, i.e. the same hydrocarbon is used for the extraction
in step j*) and as the liquid L.
Configuration of the Addition of the Liquid
[0380] The nonpolar aprotic liquid L may be added to stream 18 in
customary mixing apparatus. Because it is particularly simple from
a process technology point of view, preference is given to mixing
the nonpolar aprotic liquid L with stream 18 in step i*) in a
stirred vessel or a pumped circulation system.
[0381] Preference is given to intimately mixing the nonpolar
aprotic liquid with stream 18. Suitable stirred vessels are
customary liquid mixers which may be provided with intensively
mixing mixer elements and/or static or mobile internals.
[0382] Preference is likewise given to the use of a pumped
circulation system. It is typically operated in such a way that the
ratio of amount in pumped circulation to output from the pumped
circulation system is from 0.1:1 to 1000:1, preferably from 1:1 to
100:1 and more preferably from 2:1 to 25:1. Suitable circulation
pumps are, for example, gear pumps or other customary pumps. The
circulation pump preferably works against an overflow valve which
opens at a defined pressure of, for example, from 3 to 10 bar
(abs.).
[0383] When the same hydrocarbon is used in step i*) and j*), it is
possible in both steps to use fresh hydrocarbon in each case. It is
equally possible to reuse the hydrocarbon used in step i*) in step
j*), or recycle the hydrocarbon used in step j*) after step i*) and
reuse it there.
[0384] In a very particularly preferred embodiment, the liquid L is
a substream of stream 22 (hydrocarbon H enriched with catalyst, see
below) which is obtained in step j*). This means that a portion of
stream 22 is branched off in step j*) and the branched-off portion
is added to stream 18 in step i*). In this embodiment, a portion of
stream 22 is accordingly circulated.
[0385] In another, likewise preferred embodiment, the nonpolar
aprotic liquid L is metered directly into a delay zone (see below),
for example at the start thereof.
[0386] The liquid L is added generally at temperatures of from 0 to
150.degree. C., preferably from 10 to 100.degree. C. and in
particular from 20 to 80.degree. C., and pressures of from 0.01 to
100 bar (abs.), preferably from 0.1 to 10 bar (abs.) and in
particular from 0.5 to 5 bar (abs.).
[0387] The amount of liquid L required may vary within wide limits.
It is generally lower than the amount of hydrocarbon H used with
which extraction is effected in step j*), but may also be greater.
The amount of liquid L is preferably from 0.1 to 200% by volume, in
particular from 1 to 50% by volume and more preferably from 5 to
30% by volume, based on the amount of the hydrocarbon H used for
extraction in step j*).
Optional treatment with ammonia or amine
[0388] When step h*) comprises a redox regeneration, it is possible
if appropriate to add ammonia or a primary, secondary or tertiary,
aromatic or aliphatic amine to stream 18 or stream 19, or during
step i*) or during step j*) itself. Aromatic includes
alkylaromatic, and aliphatic includes cycloaliphatic.
[0389] It has been found that this ammonia or amine treatment can
reduce the content of catalyst, in particular of nickel(0) complex
or ligand in the extraction (step j*)) in the second phase enriched
with dinitriles (stream 23), i.e. in the extraction, the
distribution of the Ni(0) complex or the ligands between the two
phases is shifted in favor of the first phase (stream 22). The
ammonia or amine treatment improves the catalyst enrichment in
stream 22; this means smaller catalyst losses in the catalyst
circuit and improves the economic viability of the
hydrocyanation.
[0390] Accordingly, in this embodiment, the extraction is preceded
by a treatment of stream 18 or of stream 19 with ammonia or an
amine, or it is effected during the extraction. Treatment during
the extraction is less preferred.
[0391] Particular preference is given to adding the ammonia or the
amine together with the nonpolar aprotic liquid L. In particular,
the liquid L and the ammonia or amine are added in the same mixing
apparatus.
[0392] The amines used are monoamines, diamines, triamines or more
highly functional amines (polyamines). The monoamines typically
have alkyl radicals, aryl radicals or arylalkyl radicals having
from 1 to 30 carbon atoms; suitable monoamines are, for example,
primary amines, e.g. monoalkylamines, secondary or tertiary amines,
e.g. dialkylamines. Suitable primary monoamines are, for example,
butylamine, cyclohexylamine, 2-methylcyclohexylamine,
3-methylcyclohexylamine, 4-methylcyclohexylamine, benzylamine,
tetrahydrofurfurylamine and furfurylamine. Useful secondary
monoamines are, for example, diethylamine, dibutylamine,
di-n-propylamine and N-methylbenzylamine. Suitable tertiary amines
are, for example, trialkylamines having C.sub.1-10-alkyl radicals,
such as trimethylamine, triethylamine or tributylamine.
[0393] Suitable diamines are, for example, those of the formula
R.sup.1--NH--R.sup.2--NH--R.sup.3, where R.sup.1, R.sup.2 and
R.sup.3 are each independently hydrogen or an alkyl radical, aryl
radical or arylalkyl radical having from 1 to 20 carbon atoms. The
alkyl radical may be linear or, especially for R.sup.2, also be
cyclic. Suitable diamines are, for example, ethylenediamine, the
propylenediamines (1,2-diaminopropane and 1,3-diaminopropane),
N-methyl-ethylenediamine, piperazine, tetramethylenediamine
(1,4-diaminobutane), N,N'-dimethylethylenediamine,
N-ethylethylenediamine, 1,5-diaminopentane,
1,3-diamino-2,2-diethylpropane, 1,3-bis(methylamino)propane,
hexamethylenediamine (1,6-diaminohexane),
1,5-diamino-2-methylpentane, 3-(propylamino)propylamine,
N,N'-bis-(3-aminopropyl)piperazine,
N,N'-bis(3-aminopropyl)piperazine and isophoronediamine (IPDA).
[0394] Suitable triamines, tetramines or more highly functional
amines are, for example, tris(2-aminoethyl)amine,
tris(2-aminopropyl)amine, diethylenetriamine (DETA),
triethylenetetramine (TETA), tetraethylenepentamine (TEPA),
isopropylenetriamine, dipropylenetriamine and
N,N'-bis(3-aminopropylethylenediamine). Aminobenzylamines and
aminohydrazides having 2 or more amino groups are likewise
suitable.
[0395] Of course, it is also possible to use mixtures of ammonia
with one or more amines, or mixtures of a plurality of amines.
[0396] Preference is given to using ammonia or aliphatic amines, in
particular trialkylamines having from 1 to 10 carbon atoms in the
alkyl radical, e.g. trimethylamine, triethylamine or tributylamine,
and also diamines such as ethylenediamine, hexamethylenediamine or
1,5-diamino-2-methylpentane.
[0397] Particular preference is given to ammonia alone, i.e.
particular preference is given to using no amine in addition to
ammonia. Anhydrous ammonia is very particularly preferred; in this
context, anhydrous means a water content below 1% by weight,
preferably below 1000 ppm by weight and in particular below 100 ppm
by weight.
[0398] The molar ratio of amine to ammonia may be varied within
wide limits, and is generally from 10 000:1 to 1:10 000.
[0399] Factors determining the amount of ammonia or amine used
include the type and amount of catalyst, for example of the
nickel(0) catalyst, and/or of the ligands, and, where used, the
type and amount of Lewis acid which is used as a promoter in the
hydrocyanation. Typically, the molar ratio of ammonia or amine to
Lewis acid is at least 1:1. The upper limit of this molar ratio is
generally uncritical and is, for example, 100:1, but the excess of
ammonia or amine should not be so great that the Ni(0) complex or
ligands thereof decompose. The molar ratio of ammonia or amine to
Lewis acid is preferably from 1:1 to 10:1, more preferably from
1.5:1 to 5:1, and in particular about 2:1. Where a mixture of
ammonia and amine is used, these molar ratios apply to the sum of
ammonia and amine.
[0400] The temperature in the treatment with ammonia or amine is
typically not critical and is, for example, from 10 to 140.degree.
C., preferably from 20 to 100.degree. C. and in particular from 20
to 90.degree. C. The pressure is generally also not critical.
[0401] The ammonia or the amine may be added to stream 18 in
gaseous, liquid (under pressure) or dissolved form in a solvent.
Suitable solvents are, for example, nitriles, especially those
which are present in the hydrocyanation, and also aliphatic,
cycloaliphatic or aromatic hydrocarbons, as are used as extractants
in the process according to the invention, for example cyclohexane,
methylcyclohexane, n-heptane or n-octane.
[0402] The ammonia or amine is added in customary apparatus, for
example those for gas introduction or in liquid mixers. The solid
which precipitates in many cases may either remain in stream 18,
i.e. a suspension is fed to the extraction, or be removed as
described below.
Optional Removal of Solids
[0403] In a preferred embodiment, solids which precipitate out in
step i*) of the process are removed from stream 19 before the
extraction (step j*)).
[0404] In many cases, this allows the extraction performance of the
process according to the invention to be improved further, since
solids which occur often reduce the separating performance of the
extraction apparatus. It has also been found that a solids removal
before the extraction in many cases once again distinctly reduces
or fully suppresses the undesired formation of rag.
[0405] Preference is given to configuring the solids removal in
such a way that solid particles having a hydraulic diameter greater
than 5 .mu.m, in particular greater than 1 .mu.m and more
preferably greater than 100 nm are removed.
[0406] For the solids removal, customary processes may be used, for
example filtration, crossflow filtration, centrifugation,
sedimentation, classification or preferably decanting, for which
common apparatus such as filters, centrifuges or decanters may be
used.
[0407] Temperature and pressure in the solids removal are typically
not critical. For example, it is possible to work in the
temperature and pressure ranges mentioned above or below.
[0408] The solids removal may be carried out before, during or
after the optional treatment of stream 18 or of stream 19 with
ammonia or amine. Preference is given to removal during or after
the ammonia or amine treatment, and particular preference to
removal after it.
[0409] When the solids are removed during or after the ammonia or
amine treatment, the solids are usually compounds of ammonia or
amine with the Lewis acid used or the promoter which are sparingly
soluble in stream 18. When, for example, ZnCl.sub.2 is used,
substantially sparingly soluble ZnCl.sub.2.2NH.sub.3 precipitates
out in the ammonia treatment.
[0410] When the solids are removed before the ammonia or amine
treatment, or if there is no treatment at all with ammonia or
amine, the solids are generally nickel compounds in the +II
oxidation state, for example nickel(II) cyanide or similar
cyanide-containing nickel(II) compounds, or are Lewis acids or
compounds thereof. The compounds mentioned may precipitate out, for
example, because their solubility has been reduced, for example, by
temperature change.
Optional Delay Zone
[0411] Stream 19 as the effluent from step i*) may be transferred
directly into step j*), for example through a pipeline. Directly
means that the average residence time of stream 19 in the pipeline
is less than 1 min.
[0412] However, in a preferred embodiment of the process according
to the invention, stream 19 is conducted through a delay zone after
step i*) and before step j*). The delay zone is consequently
downstream of the addition of the liquid L and upstream of the
extraction.
[0413] Suitable delay zones are, for example, pipelines, static
mixers, stirred or unstirred vessels or vessel batteries, and
combinations of these elements. The delay zone is preferably
configured in such a way that the average residence time of stream
19 in the delay zone is at least 1 min, preferably at least 5
min.
[0414] The optional solids removal described above may also be
effected in the delay zone. In this case, the delay zone serves as
a calming zone in which the solids can settle. In this way, the
delay zone functions like a decanter or crossflow filter. It may be
provided with apparatus for conveying and/or for the discharge of
solids.
[0415] As mentioned, in a preferred embodiment, the nonpolar
aprotic liquid L is metered directly into the delay zone, for
example at the start thereof. In this embodiment, particular
preference is given to selecting a delay zone which ensures
intimate mixing of stream 18 and liquid L. As likewise already
described, the delay zone may bring about a phase separation of
stream 19.
[0416] The delay zone is generally operated at temperatures of from
0 to 200.degree. C., preferably from 10 to 150.degree. C. and in
particular from 20 to 100.degree. C., and pressures of from 0.01 to
100 bar (abs.), preferably from 0.1 to 10 bar (abs.) and in
particular from 0.5 to 5 bar (abs.).
[0417] In a preferred embodiment of the invention, the flow rate of
stream 19 in all of the pipelines used in the process according to
the invention is at least 0.5 m/s, in particular at least 1 m/s and
more preferably at least 2 m/s.
[0418] The stream 19 obtained in step a) is, if appropriate after
the treatment with ammonia or amines, and/or after the solids
removal and/or after passing through the delay zone, extracted in
step j*).
Process Step j*):
Process Principle
[0419] The process according to the invention is suitable for the
extractive purification of Ni(0) complexes which contain phosphorus
ligands and/or free phosphorus ligands in stream 19 or, if
appropriate, stream 18 when step i*) is not performed, by adding a
C6-dinitrile such as adiponitrile (ADN), 2-methylglutaronitrile
(MGN) or 2-ethylsuccinonitrile (ESN) with regard to the disruptive
component(s) which induce increased formation of C5 mononitriles
not amenable to hydrocyanation, such as E-2-methyl-2-butenenitrile
and/or Z-2-methyl-2-butenenitrile.
[0420] In addition, the catalyst losses are reduced in the
extraction by introducing a hydrocarbon H in stream 21 at an inlet
point which is closer to the outlet point of the extract than to
the inlet point of feed stream 18 or 19. The inlet point of the
dinitrile (stream 20) is closer to the outlet point of the
raffinate than the inlet point of feed stream 18 or 19. In this
context, closer should be understood in the sense of the number of
theoretical plates between two points. Between the inlet points of
streams 18 or 19 and 21 there are generally from 0 to 10,
preferably from 1 to 7, theoretical extraction (separation) stages
(re-extraction zone for the catalyst); between the inlet points of
streams 18 or 19 and 20 there are generally from 1 to 10,
preferably from 1 to 5, theoretical extraction (separation) stages
(purification zone with regard to disruptive component(s)).
[0421] In general, a first phase [raffinate; stream 22] is formed
at a temperature T (in .degree. C.) and is enriched in the Ni(0)
complexes or ligands mentioned compared to stream 18, and a second
phase [extract; stream 23; enriched disruptive component(s)], which
is enriched in dinitriles compared to stream 18. Usually, the first
phase is the lighter phase, i.e. the upper phase, and the second
phase the heavier phase, i.e. the lower phase.
[0422] After the phase separation, the upper phase contains
preferably between 50 and 99% by weight, more preferably between 60
and 97% by weight, in particular between 80 and 95% by weight, of
the hydrocarbon used for the extraction.
[0423] The Lewis acid which is in some cases (specifically when the
redox catalyst regeneration is implemented in process step hi*))
present in the inlet stream of the extraction remains preferably
for the most part and more preferably fully in the lower phase.
Here, fully means that the residual concentration of the Lewis acid
in the upper phase is preferably less than 1% by weight, more
preferably less than 0.5% by weight, in particular less than 500
ppm by weight.
[0424] The discharge of the disruptive component(s) improves the
process selectivity, since fewer C5 mononitriles not amenable to
hydrocyanation are formed (reduction of incorrect
isomerizations).
[0425] A particular advantage of embodiment III is that dinitriles
such as ADN, MGN, ESN, which form in small amounts in process step
e*) and thus accumulate in stream 10, are discharged at least
partly with the lower phase of the extraction.
[0426] A further particular advantage of the employment of process
step j*) is that the reactant used in process step e*) may be
stabilizer-containing butadiene. Such a stabilizer may be, for
example, tert-butylpyrocatechol. This stabilizer is discharged via
the lower phase of the extraction. Thus, no catalyst-damaging
concentrations of the stabilizer can be accumulated in the catalyst
circuit.
[0427] A further particular advantage is that a redox regeneration
of the catalyst for the replenishment of the Ni(0) value according
to h.sub.1*) can be undertaken in process step h*), since the Lewis
acid formed in this way is discharged via the lower phase of the
extraction. This Lewis acid would otherwise lead to increased
dinitrile formation in the first hydrocyanation (process step
e*)).
[0428] The lower phase of the extraction may suitably be worked up,
so that the dinitriles present therein may be used again as a feed
to the extraction. Such a workup may be effected, for example, by
distillation (DE-A-10 2004 004683; stream 7 from step c)).
Configuration of the Extraction
[0429] The extractive tasks may preferably be achieved by using a
countercurrent extraction column having a re-extraction zone.
However, identically functioning combinations of any suitable
apparatus known to those skilled in the art, such as countercurrent
extraction columns, mixer-settler units or combinations of
mixer-settler units with columns, for example a series connection
of two countercurrent extraction columns (for example one for the
purification with regard to disruptive component(s), the other for
the re-extraction of the catalyst) are also. Particular preference
is given to the use of countercurrent extraction columns which are
in particular equipped with sheet metal packings as dispersing
elements. In a further particularly preferred embodiment, the
extraction is performed in countercurrent in compartmented, stirred
extraction columns.
[0430] With regard to the direction of dispersion, in a preferred
embodiment of the process, the hydrocarbon is used as the
continuous phase and stream 18 of the hydrocyanation as the
disperse phase. This generally shortens the phase separation time
and reduces the formation of rag. However, the reverse direction of
dispersion is also possible, i.e. stream 18 as the continuous and
hydrocarbon as the disperse phase. The latter is especially true
when the rag formation is reduced or fully suppressed by preceding
solids removal (see below), higher temperature in the extraction or
phase separation or use of a suitable hydrocarbon. Typically, the
direction of dispersion more favorable for the separating
performance of the extraction apparatus is selected.
[0431] In the extraction, the following ratios of the feeds are
set:
[0432] Stream 20 to the sum of stream 18 or 19 and stream 21 in the
range from 0.01 to 10 kg/kg, preferably from 0.05 to 5 kg/kg.
Stream 21 to stream 20 in the range from 0.05 to 20 kg/kg,
preferably from 1 to 10 kg/kg. Stream 21 to stream 18 or 19 in the
range from 0.05 to 20 kg/kg, preferably from 0.5 to 8 kg/kg.
[0433] The absolute pressure during the extraction is preferably
from 10 kPa to 1 MPa, more preferably from 50 kPa to 0.5 MPa, in
particular from 75 kPa to 0.25 MPa (absolute).
[0434] The extraction is preferably carried out at a temperature
from -15 to 120.degree. C., in particular from 20 to 100.degree. C.
and more preferably from 30 to 800.degree. C. It has been found
that the rag formation is lower at higher temperature of the
extraction.
Configuration of the Phase Separation
[0435] Depending upon the apparatus configuration, the phase
separation may also be viewed in spatial and temporal terms as the
last part of the extraction. For the phase separation, a wide
pressure, concentration and temperature range may typically be
selected, and the optimal parameters for the particular composition
of the reaction mixture may be determined readily by a few simple
preliminary experiments.
[0436] The temperature T in the phase separation is typically at
least 0.degree. C., preferably at least 10.degree. C., more
preferably at least 20.degree. C. Typically, it is at most
120.degree. C., preferably at most 100.degree. C., more preferably
at most 950.degree. C. For example, the phase separation is carried
out at from 0 to 100.degree. C., preferably from 60 to 95.degree.
C. It has been found that the rag formation is lower at higher
temperature of the phase separation.
[0437] The pressure in the phase separation is generally at least 1
kPa, preferably at least 10 kPa, more preferably 20 kPa. In
general, it is at most 2 MPa, preferably at most 1 MPa, more
preferably at most 0.5 MPa.
[0438] The phase separation time, i.e. the time from the mixing of
stream 18 with the hydrocarbon (extractant) to the formation of a
uniform upper phase and a uniform lower phase, may vary within wide
limits. The phase separation time is generally from 0.1 to 60 min,
preferably from 1 to 30 min and in particular from 2 to 10 min.
When the process according to the invention is carried out on the
industrial scale, a phase separation time of not more than 15 min,
in particular not more than 10 min, is typically technically and
economically viable.
[0439] It has been found that the phase separation time is reduced
in an advantageous manner especially when long-chain aliphatic
alkanes such as n-heptane or n-octane are used as the hydrocarbon
H.
[0440] The phase separation may be carried out in one or more
apparatuses known to those skilled in the art for such phase
separations. In an advantageous embodiment, the phase separation
may be carried out in the extraction apparatus, for example in one
or more mixer-settler combinations, or by equipping an extraction
column with a calming zone.
[0441] In the phase separation, two liquid phases are obtained, of
which one phase has a higher proportion of the nickel(0) complex
with phosphorus ligands and/or free phosphorus ligands, based on
the total weight of this phase, than the other phase or other
phases. The other phase is enriched in the disruptive
component(s).
Dinitrile
[0442] Stream 20 which is conducted to the extraction as a feed
stream comprises predominantly dinitriles, preferably C6
dinitriles, especially preferably adiponitrile (ADN),
2-methylglutaronitrile (MGN), 2-ethylsuccinonitrile (ESN) or
mixtures thereof. The content in this stream of dinitriles is
preferably greater than 50% by weight, more preferably greater than
70% by weight, especially preferably greater than 90% by weight.
Processes for preparing dinitriles, in particular C6 dinitriles,
are known per se. One possible such process is described in DE-A-10
2004 004683. Streams of C6 dinitriles prepared in this way, in
particular streams 15, 16 and 17 from process step h) of DE-A-10
2004 004683, are generally suitable to be used here as stream
20.
[0443] Dinitriles are added preferably to the extent that a phase
separation is effected in the extraction stage k*).
Hydrocarbon
[0444] The hydrocarbon is the extractant. It preferably has a
boiling point of at least 300.degree. C., more preferably at least
60.degree. C., in particular at least 90.degree. C., and preferably
at most 140.degree. C., more preferably at most 135.degree. C., in
particular at most 130.degree. C., in each case at a pressure of
10.sup.5 Pa absolute.
[0445] A hydrocarbon, this referring in the context of the present
invention to an individual hydrocarbon or to a mixture of such
hydrocarbons, may more preferably be used for the removal,
especially by extraction, of adiponitrile from a mixture comprising
adiponitrile and the Ni(0)-containing catalyst, said hydrocarbon
having a boiling point in the range between 90.degree. C. and
140.degree. C. From the mixture obtained by this process after the
removal, the adiponitrile may be obtained advantageously by
distillative removal of the hydrocarbon, the use of a hydrocarbon
having a boiling point in the range mentioned permitting a
particularly economically viable and technically simple removal by
virtue of the possibility of condensing the hydrocarbon distilled
off with river water.
[0446] Suitable hydrocarbons are described, for example, in U.S.
Pat. No. 3,773,809, column 3, line 50-62. Useful hydrocarbons are
preferably selected from cyclohexane, methylcyclohexane,
cycloheptane, n-hexane, n-heptane, isomeric heptanes, n-octane,
isooctane, isomeric octanes such as 2,2,4-trimethylpentane, cis-
and trans-decalin or mixtures thereof, in particular of
cyclohexane, methylcyclohexane, n-heptane, isomeric heptanes,
n-octane, isomeric octanes such as 2,2,4-trimethylpentane, or
mixtures thereof. Particular preference is given to using
cyclohexane, methylcyclohexane, n-heptane or n-octane.
[0447] Very particular preference is given to n-heptane or
n-octane. In the case of these hydrocarbons, the undesired rag
formation is particularly low. Rag refers to a region of incomplete
phase separation between upper and lower phase, usually a
liquid/liquid mixture, in which solids may also be dispersed.
Excessive rag formation is undesired, since it hinders the
extraction and the extraction apparatus can under some
circumstances be flooded by rag, as a result of which it can no
longer fulfill its separating task.
[0448] The hydrocarbon used is preferably anhydrous, anhydrous
meaning a water content of below 100 ppm by weight, preferably
below 50 ppm by weight, in particular below 10 ppm by weight. The
hydrocarbon may be dried by suitable processes known to those
skilled in the art, for example by adsorption or azeotropic
distillation. The drying may be effected in a step preceding the
process according to the invention.
Process Step k*):
[0449] In process step (k*), a distillation of stream 22 to obtain
a stream 25 comprising the at least one catalyst and a stream 24
comprising the extractant takes place.
[0450] This process step serves substantially to recover the
catalyst and the extractant.
[0451] Process step (k*) may be carried out in any suitable
apparatus known to those skilled in the art. The distillation of
process step k*) takes place preferably in one or more evaporation
stages, or else rectification columns/distillation columns.
[0452] The internals used for the rectification
columns/distillation columns are preferably structured sheet metal
packing, structured fabric packing, bubble-cap trays, dual-flow
trays or beds of random packings or combinations of two or more of
these classes of separating internals. The rectification
column/distillation column of process step k*) may be configured
with one or more liquid or gaseous side draws. The rectification
column/distillation column from process step k*) may be configured
as a dividing wall column having one or more gaseous or liquid side
draws present.
[0453] The one or more evaporator stages or the rectification
column/distillation column of process step k*) may in particular be
equipped with falling-film evaporators, thin-film evaporators,
natural-circulation evaporators, forced-circulation flash
evaporators and multiphase helical-tube evaporators.
[0454] In a further embodiment of the process according to the
invention, at least one of the evaporator units of process step k*)
is operated with a divided column bottom, in which case the
circulation stream, generally large in relation to the bottom draw
stream, is conducted from a first column bottom of the evaporator
stage in question to the evaporator, but the liquid output stream
from the evaporator is not returned directly into the column
bottom, but rather collected in a second column bottom which is
separate from the first column bottom, the bottom draw stream is
obtained from the second column bottom and the remaining excess
from the evaporator circulation stream is allowed to overflow into
the first column bottom to obtain, as the bottom draw stream from
the second column bottom, a mixture which is depleted in low
boilers compared to the draw from the first column bottom.
[0455] The absolute pressure in process step k*) is preferably from
0.001 to 2 bar(a), more preferably from 0.01 to 0.5 bar(a), in
particular from 0.09 to 0.12 bar(a). The distillation is carried
out in such a way that the temperature in the bottom of the
distillation apparatus is preferably from 40 to 150.degree. C.,
more preferably from 70 to 120.degree. C., in particular from 80 to
100.degree. C. The distillation is carried out in such a way that
the temperature at the top of the distillation apparatus is
preferably from -15 to 100.degree. C., more preferably from 0 to
60.degree. C., in particular from 20 to 50.degree. C. In a
particularly preferred embodiment of the process according to the
invention, the aforementioned temperature ranges are maintained
both at the top and in the bottom.
[0456] In the removal of the extractant to recover the catalyst in
process step k*), 3-pentenenitrile may be added if appropriate to
the distillation as an intermediate boiler. This solvent change in
some cases has the advantage that an effective depletion of the
extractant from the high-boiling catalyst stream becomes possible
at evaporator temperatures which are low enough not to thermally
damage the nickel catalyst used in each case, especially when
chelate ligands are used, and to thermally conserve it when
monodentate ligands are used, the pressure still being high enough
in order still to be able to condense the extractant, comparatively
low-boiling in comparison to the catalyst constituents, at the top
of the evaporator stage or distillation column at customary cooling
water temperatures of from 25 to 50.degree. C. The solvent change
additionally in some cases has the advantage that the flowability
and the monophasicity of the catalyst solution is ensured, since,
depending on the temperature and residual content of
extractants--without the addition of 3-pentenenitrile--catalyst
constituents can in some cases crystallize out. In this case,
3-pentenenitrile which, for example, depending on the pressure
conditions, can be removed from the cyclohexane or
methylcyclohexane or heptane or n-heptane extractants only with
difficulty or cannot be removed completely at all owing to minimum
vapor pressure azeotrope formation does not have a disruptive
effect on the process according to the invention at a content of
preferably up to 10% by weight, more preferably up to 5% by weight,
in particular up to 1% by weight, based on the total amount of the
extractant inlet stream to the extraction column in process step
j*).
[0457] In a preferred embodiment of the process according to the
invention, the stream 24 obtained in process step k*), comprising
the extractant, is recycled at least partly into the extraction
step j*). The recycled stream 24 is dried if appropriate before the
extraction step j*), so that the water content in this stream is
preferably less than 100 ppm by weight, more preferably less than
50 ppm by weight, in particular less than 10 ppm by weight.
[0458] In a further preferred embodiment of the process according
to the invention, the stream obtained in process step k*),
comprising the catalyst, is recycled at least partly into the
hydrocyanation of process step e*) or into the isomerization of
process step a*). In a preferred embodiment of the process
according to the invention, the proportion of extractant in stream
25 is preferably less than 10% by weight, more preferably less than
5% by weight, in particular less than 1% by weight, based on the
total amount of stream 25.
[0459] Preferred embodiments of the catalyst flow control through
process stages a*) to k*) are described hereinbelow with reference
to schemes 1 to 5. Process step i*) is not present in schemes 1 to
5, but can in each case be carried out between h*) and j*). In
schemes 1 to 5, process step h*) is described by way of example in
the embodiment as process step h.sub.1*). Alternatively, the
embodiment may also be carried out as process step h.sub.2*). In
these cases, the nickel(II) chlorides would be replaced by nickel
powder, and there is no reducing agent (red.), nor is there any
Lewis acid (LA). ADN synonymously represents dinitrile streams;
heptane synonymously represents hydrocarbons as the extractant.
Cat. in each case means catalyst complexes plus free ligand. The
dashed lines in schemes 1 to 5 denote optional bypass substreams of
the catalyst streams.
[0460] A particular embodiment of the process with regard to the
catalyst flow control is shown in scheme 1. In this scheme, the
catalyst-conducting stages are combined in a single catalyst
circuit. The sequence of the process stages starting from the first
hydrocyanation is e*), f*), a*), b*), c*), h*), if appropriate i*),
j*), k*), before being fed back to e*). If appropriate, a substream
of the catalyst may be recycled past stages h*), i*), j*) and k*),
and directly into e*). Process stage a*) is fed here with
unseparated mixture of 2-methyl-3-butenenitrile and
3-pentenenitrile, i.e. d*) or g*) is performed after a*).
[0461] A further particular embodiment of the process with regard
to the catalyst flow control is shown in scheme 2. In this scheme,
the catalyst-conducting stages are combined in a single catalyst
circuit. Starting from the first hydrocyanation, the sequence of
the process stages is e*), f*), a*), b*), c*), h*), if appropriate
i*), j*), k*), before being fed back to e*). If appropriate, a
substream of the catalyst may be recycled past stages h*), i*), j*)
and k*), and directly into e*). Process stage a*) is fed here with
2-methyl-3-butenenitrile depleted in 3-pentenenitrile, i.e. d*) or
g*) is performed before a*).
[0462] A further particular embodiment of the process with regard
to the catalyst flow control is shown in scheme 3. In this scheme,
a catalyst stream is circulated through stages e*) and f*). From
this stream, a substream is discharged and used as catalyst feed
for stage a*). Subsequently, this stream is fully, if appropriate
partly, fed through stages b*), c*), h*), Hf appropriate i*), j*)
and k*), back into e*). The isomerization stage a*) is fed with
2-methyl-3-butenenitrile depleted in 3-pentenenitrile, i.e. d*) or
g*) is performed before a*). Equally, d* or g* may also be
performed after a*.
[0463] A further particular embodiment of the process with regard
to the catalyst flow control is shown in scheme 4. In this scheme,
two catalyst circuits are formed. Catalyst circuit 1 comprises the
stages e*) and f*), catalyst circuit 2 the stages a*), b*), c*).
From both streams, substreams, if appropriate also the particular
overall catalyst streams, are conducted via stages h*), if
appropriate i*), j*) and k*), in order to purify the catalyst of
disruptive component(s) and/or to replenish the Ni(0) content. The
proportion from catalyst circuit 2 conducted through the extraction
is preferably greater than that from catalyst circuit 1. If
appropriate, the entire stream from catalyst circuit 2 is conducted
through the extraction. The two catalyst circuits are coupled to
one another only via stages h*), if appropriate i*), j*) and k*).
The division of the stream from k*) for feeding of a*) or e*)
corresponds generally to the ratio of the feed streams to h*) from
a*) and e*). The isomerization stage a*) is fed with
2-methyl-3-butenenitrile depleted in 3-pentenenitrile, i.e. d*) or
g*) is performed before a*). Equally, d* or g* may also be
performed after a*.
[0464] A further particular embodiment of the process with regard
to the catalyst flow control is shown in scheme 5. According to
this, a catalyst circuit is operated via stages a*), b*), c*), h*),
if appropriate i*), j*) and k*). From this catalyst circuit, a
substream is drawn off before h*) and the first hydrocyanation e*)
is operated with it. The stream is recycled to h*) via f*). If
appropriate, the recycling may also be directly to a*). A substream
of the isomerization catalyst circuit may also be recycled from c*)
directly into a*). The isomerization stage a*) is fed with
2-methyl-3-butenenitrile depleted in 3-pentenenitrile, i.e. d*) or
g*) is performed before a*). Equally, d* or g* may also be
performed after a*.
[0465] The present invention is illustrated in detail with
reference to the examples detailed hereinbelow.
WORKING EXAMPLES
[0466] In the examples, the following abbreviations are used:
hydrogen cyanide: hydrogen cyanide T3PN: trans-3-pentenenitrile
C3PN: cis-3-pentenenitrile 4PN: 4-pentenenitrile E2M2BN:
(E)-2-methyl-2-butenenitrile T2PN: trans-2-pentenenitrile C2PN:
cis-2-pentenenitrile ADN: adiponitrile MGN: methylglutaronitrile
VAN: valeronitrile VCH: 4-vinylcyclohexene BD: 1,3-butadiene TBP:
tert-butylpyrocatechol C2BU: cis-2-butene LA: Lewis acid
[0467] In the examples, the process steps are reported in a
chronological sequence and thus deviate from the designation in the
description and in the claims. Data in % or ppm which is not
characterized in detail are % by weight and ppm by weight
respectively.
Example 1
[0468] Example 1 is illustrated with reference to FIG. 3.
[0469] In Example 1, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the hydrocyanation of
butadiene. The ligand mixture for the hydrocyanation contains
approx. 60 mol % of tri(m/p-tolyl) phosphite and 40 mol % of the
chelate phosphonite 1:
##STR00003##
[0470] In a step (1), the following streams are conducted into a
loop reactor R1 of capacity 25 l which is equipped with a nozzle,
impulse exchange tube, external pumped circulation system and in a
heat exchanger disposed in the pumped circulation system for
removing the energy of reaction and is heated to 357 K: [0471] (1)
10 kg/h of liquid unstabilized hydrogen cyanide freed of water by
distillation, [0472] (2) 22 kg/h of commercial BD containing 0.25%
C2BU which has been treated by contact with alumina in order to
remove water and TBP stabilizer, [0473] (3) 8 kg/h of recycled BD
from K2a in step (2) (stream 9), so that the entire BD feed to the
reactor R1 which is obtained is a stream of 30 kg/h containing 90%
BD, 5% C2BU and 5% 1-butene, [0474] (4) 21 kg/h of nickel(0)
catalyst solution, obtained as described below in this example, as
stream 10a from column K2b.
[0475] The stream 8 withdrawn from the reactor R1 (63 kg/h)
contains a total of 11% BD and C2BU, corresponding to a conversion
of 79% BD, and also a total of 63% pentenenitriles, 31% T3PN, 29%
2M3BN and small amounts of Z2M2BN and E2M2BN, and further
pentenenitrile isomers (T2PN, C2PN, C3PN, 4PN), and also the
catalyst constituents and catalyst degradation products and
MGN.
[0476] Stream 8 is fed in a step (2) to a distillation column K2a
which is operated with rectifying section and stripping section and
is equipped with a falling-film evaporator and separated bottom,
and also column internals having structured packing which generate
10 theoretical plates. Column K2a is operated at the top with a
direct condenser which consists of a column section equipped with
structured packing and having a total collecting cup, pumped
circulation system and external heat exchanger. The column K2a is
operated at an absolute top pressure of 2.0 bar, top temperature
288 K and bottom draw temperature 363 K.
[0477] Via the top of column K2a is obtained stream 9 which, as
described at the outset, is metered into the reactor R1 as a
recycle stream. The reflux ratio at the top of the column K2a is
adjusted in such a way that stream 9 contains approx. 100 ppm of
2M3BN.
[0478] Via the bottom of the column K2a are obtained 59 kg/h of a
stream 1b which contains 2.9% BD, 4.6% C2BU, 67% pentenenitriles,
and also additionally the catalyst constituents. In relation to BD,
C2BU is distinctly enriched compared to the feed.
[0479] Within step (2), stream 1b is conducted into a distillation
column K2b which is operated in stripping mode and is equipped with
falling-film evaporator, top condenser with postcondenser and also
column internals having structured packing which generate 10
theoretical plates. The column is operated at an absolute top
pressure of 150 mbar, top temperature 329 K and bottom draw
temperature 373 K. The vapor stream of the column is partly
condensed at 308 K and treated with a postcondenser at 263 K. The
BD stream 2c, thus depleted of 2M3BN and other pentenenitriles, is
compressed in a compressor V2 to an absolute pressure of 1.2 bar.
The compressed gas stream is to a great extent condensed at 279 K
to obtain a stream 2e (5 kg/h), and a substream 2d (47 l (STP)/h,
containing 44% C2BU) is disposed of in gaseous form. Stream 2e is
recycled in liquid form into the condensate collecting vessel of
the column K2a.
[0480] In a gaseous side draw of the column K2b, stream 11 is
obtained (40 kg/h) and contains approx. 100 ppm of BD, 46% 2M3BN
and 48% T3PN, and also, to a smaller extent, E2M2BN and Z2M2BN in
addition to other pentenenitrile isomers. The position of the side
draw is selected in such a way that the component 2M3BN in the
stream 10 obtained via the bottom is depleted in relation to T3PN
in a stripping section below the side draw.
[0481] Into column K2b are conducted 13 kg/h of a catalyst stream
which is obtained as described in Example 1 of the German patent
application having the title "Preparation of dinitriles" to BASF AG
(B03/0525) as the side draw of the column K4 from step (4),
containing a total of 73% pentenenitriles, 0.5% Ni(0), 18% ligand
mixture and approx. 5% ADN.
[0482] Via the bottom of the column K2b is obtained the catalyst
stream 10 containing 0.5% Ni(0), approx. 100 ppm of 2M3BN and 73%
remaining pentenenitriles. Stream 10 is split into substream 10a
(21 kg/h) which is recycled into the reactor R1. The other portion
(10b) (5.4 kg/h) is fed to a regeneration according to DE-A-103 51
002, in order, after regeneration, to be used, for example, in the
hydrocyanation of 3-pentenenitrile as described in Example 1 of
DE-A-102 004 004 683.
[0483] In a step (3), stream 11 is conducted to a distillation
column K3 which is equipped with circulation evaporator and top
condenser, and also with structured packing which generate 30
theoretical plates. The column K3 is operated at an absolute top
pressure of 180 mbar, top temperature 345 K and bottom draw
temperature 363 K.
[0484] Into the column K3 are conducted 39 kg/h of recycle stream 5
from column K5 in step (5), containing 54% T3PN, 23% 2M3BN and 16%
Z2M2BN, and also, in small amounts, further pentenenitrile
isomers.
[0485] Via the top of column K3 are obtained 40 kg/h of a stream 13
containing 10% T3PN, 68% 2M3BN, 16% Z2M2BN, and also a total of
0.1% BD and C2BU and small amounts of other pentenenitrile isomers
(T2PN, C2PN, C3PN, 4PN).
[0486] Via the bottom of column K3 are obtained 39 kg/h of stream
12 containing 97% in total of T3PN, C3PN and 4PN, and small amounts
of other pentenenitrile isomers (T2PN, C2PN), and also approx. 100
ppm of 2M3BN and approx. 1% E2M2BN.
[0487] In Example 1, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the isomerization of 2M3BN to
T3PN. The ligand mixture for the isomerization (referred to
hereinbelow as isomerization ligand) comprises mixed phosphite
ligands of the P(OR)(OR')(OR'') class having randomly distributed
R, R', R'' from the group of m-tolyl, p-tolyl, o-isopropylphenyl,
and approx. 40 mol % of the sum of the R, R', R'' radicals are
o-isopropylphenyl radicals. Such ligand mixtures are obtained in
the reaction of a mixture of m- and p-cresol having a ratio of 2:1
of m-cresol compared to p-cresol and a stoichiometrically matched
amount of o-isopropylphenol with a phosphorus trihalide.
[0488] In a step (4), stream 13 is conducted, together with a
catalyst recycle stream 3a and a catalyst supplementation stream,
into a reactor R2, designed as a tubular reactor, which is heated
to 393 K. As the sum of recycled catalyst and fresh catalyst, 56
kg/h of a mixture having 20% T3PN, 5% 2M3BN and other
pentenenitrile isomers, 55% isomerization ligand and 0.5%
nickel(0), and also a small content of catalyst degradation
products, are conducted into reactor R2.
[0489] As the product from reactor R2, 96 kg/h of stream 1 are
obtained, containing 34% T3PN, 12.3% 2M3BN and small amounts of
other pentenenitrile isomers (T2PN, C2PN, C3PN, 4PN), corresponding
to a conversion of 60% 2M3BN.
[0490] In a step (5), stream 1 is conducted into a distillation
column K5 which is operated as a rectifying column and is equipped
with a falling-film evaporator, top condenser, reflux divider,
gaseous side draw in the bottom region of the column, and also
column internals with structured packing which generate 30
theoretical plates. The column is operated at an absolute top
pressure of 250 mbar, top temperature 353 K and bottom draw
temperature 373 K.
[0491] In column K5, the recovered catalyst stream 3 (56 kg/h) is
obtained via the bottom, containing 20% T3PN in addition to other
pentenenitriles, approx. 5% MGN and also 0.5% Ni(0) and 54%
isomerization ligand. A small portion of stream 3 is discharged as
stream 3b to restrict the accumulation of catalyst deactivation
components and MGN. To supplement the amount of catalyst
discharged, sufficient fresh catalyst containing 15% T3PN in
addition to other pentenenitrile isomers, 1% Ni(0) and 80%
isomerization ligand is metered in so that the Ni(0) content in the
catalyst feed to reactor R2 is kept at 0.5%.
[0492] In column K5, a stream 4 is obtained via the top (0.8 kg/h),
containing a total of 0.5% BD and C2BU, 50% 2M3BN, 41% Z2M2BN, and
also small amounts of vinylcyclohexene (VCH) which is firstly
present in traces in the BD starting material and secondly formed
in small amounts in the hydrocyanation of butadiene, and ultimately
accumulates in the 2M3BN cycle of the isomerization and has to be
discharged together with 2M3BN, since the vapor pressures of 2M3BN
and VCH are so close to one another that a separation by
conventional distillation is not possible. The reflux ratio of
column K5 is adjusted in such a way that 10 ppm of T3PN are present
in stream 4. The draw rate of stream 4 from the top of column K5 is
adjusted in such a way that a total of 20% Z2M2BN and VCH are
present in the top draw stream 13 of distillation column K3.
[0493] In column K5, a stream 5 is obtained via the gaseous side
draw (39 kg/h) which, in addition to 3-pentenenitriles, comprises
substantially the 2M3BN unconverted in the isomerization and, after
condensation, is recycled in liquid form into column K3 as
described above.
Example 2
[0494] Example 2 is illustrated with reference to FIG. 4.
[0495] In Example 2, a catalyst system based on nickel(0) complexes
with chelate phosphite 2 as a ligand is used for the hydrocyanation
of BD:
##STR00004##
[0496] In a step (1), the following streams are conducted into a
system composed of two reactors, R1a and R1b, each of capacity 12
l, each of which is equipped with a nozzle, impulse exchange tube,
external pumped circulation system and in a heat exchanger disposed
in the pumped circulation system to remove the energy of reaction,
and are heated to 363 K: [0497] (1) 6 kg/h of liquid, unstabilized
hydrogen cyanide freed of water by distillation to R1a, [0498] (2)
6 kg/h of liquid, unstabilized hydrogen cyanide freed of water by
distillation to R1b, [0499] (3) 25 kg/h of BD to R1a, containing
0.25% C2BU, which has been treated by contact with alumina in order
to remove water and TBP stabilizer, [0500] (4) 2 kg/h of recycled
BD from column K2a in step (2) to R1a (stream 9), so that the
entire BD feed to reactor R1 obtained is a stream of 27 kg/h
containing 98% BD and a total of 2% C2BU and 1-butene, [0501] (5)
14 kg/h of nickel(0) catalyst solution to R1a, obtained as
described below in this example as stream 10a from column K2b.
[0502] The stream 8 drawn off from reactor R1b (54 kg/h) contains a
total of 4% BD and C2BU, corresponding to a conversion of 94% BD,
and also a total of 74% pentenenitriles, of which 33% is T3PN, 37%
2M3BN and small amounts of Z2M2BN and E2M2BN, in addition to other
pentenenitrile isomers, and also the catalyst constituents and
catalyst degradation products and MGN.
[0503] In a step (2), stream 8 is fed to a distillation column K2a
which is operated as a rectifying column and is equipped with a
falling-film evaporator, and also column internals having
structured packing which generate 4 theoretical plates. Column K2a
is operated at the top with a direct condenser which consists of a
column section charged with random packing and having total
collecting cup, pumped circulation system and external heat
exchanger. Column K2a is operated at an absolute top pressure of
0.8 bar, top temperature 263 K and bottom draw temperature 393
K.
[0504] Via the top of column K2a is obtained stream 9 which is
metered into the reactor R1a as a recycle stream as described at
the outset. The reflux ratio at the top of column K2a is adjusted
in such a way that stream 9 contains 0.1% 2M3BN.
[0505] Via the bottom of column K2a are obtained 52 kg/h of a
stream 1b which contains 0.3% BD, 0.1% C2BU, 76% pentenenitriles
and also additionally the catalyst constituents.
[0506] Within step (2), stream 1b is conducted into a distillation
column K2b which is operated in stripping mode and is equipped with
a falling-film evaporator, top condenser with postcondenser, and
also column internals having structured packing which generate 4
theoretical plates. The column is operated at an absolute top
pressure of 70 mbar, top temperature 333 K and bottom draw
temperature 373 K.
[0507] At the gaseous top draw of column K2b, stream 11 is obtained
(40 kg/h), containing 0.4% BD, 54% 2M3BN and 42% T3PN, and also, to
a lesser extent, E2M2BN and Z2M2BN in addition to other
pentenenitrile isomers.
[0508] Into column K2b are conducted 3 kg/h of a catalyst stream,
containing a total of 45% pentenenitriles, 1.5% Ni(0) and the
chelate ligand, obtained, for example, by reacting
nickel(0)(cyclooctadienyl).sub.2 complex with the chelate phosphite
2.
[0509] Via the bottom of column K2b is obtained the catalyst stream
10, containing 1.2% Ni(0), 0.3% 2M3BN and 17% residual
pentenenitriles. Stream 10 is partly recycled into reactor R1 (14
kg/h) (stream 10a). Another portion (stream 10b) (3.8 kg/h) is fed
to a regeneration according to DE-A-103 51 002, in order to be used
in the hydrocyanation of 3-pentenenitrile according to DE-A-102 004
004 683, or, if appropriate, recycled into the hydrocyanation of BD
according to the process according to the invention.
[0510] In a step (3), stream 11 is conducted to a distillation
column K3 which is equipped with circulation evaporator and top
condenser, and also with structured packing which generate 45
theoretical plates. Column K3 is operated at an absolute top
pressure of 1.0 bar, top temperature 395 K and bottom draw
temperature 416 K.
[0511] In step (5), 24 kg/h of recycle stream 5 from column K5 are
conducted into column K3, containing 70% T3PN, 14% 2M3BN and 7%
Z2M2BN, and also small amounts of further pentenenitrile
isomers.
[0512] Via the top of column K3 are obtained 30 kg/h of a stream 13
containing 1% T3PN, 85% 2M3BN, 8% Z2M2BN, and also a total of 3% BD
and C2BU in addition to other pentenenitrile isomers and VCH. The
reflux ratio of column K3 is adjusted in such a way that 1% T3PN is
obtained overhead.
[0513] Via the bottom of column K3 are obtained 38 kg/h of stream
12 containing a total of 97% T3PN, C3PN and 4PN, and also approx.
10 ppm of 2M3BN and approx. 2% E2M2BN, and small amounts of MGN and
also other pentenenitrile isomers.
[0514] In Example 2, the catalyst used for the isomerization is the
chelate phosphite-based nickel(0) complex, as described for the
hydrocyanation of BD in this example.
[0515] In a step (4), stream 13 is conducted, together with a
catalyst recycle stream 3a and a catalyst supplementation stream,
into a reactor R2, designed as a compartmented reactor having
tubular characteristics and equipped with a preheater, by which the
reaction mixture is heated to 383 K. As the sum of recycled
catalyst and fresh catalyst, 12 kg/h of a mixture having 20% T3PN,
3% 2M3BN and other pentenenitrile isomers, 71% ligand mixture and
0.6% nickel(0), and also a small content of catalyst degradation
products, are conducted into reactor R2.
[0516] As the product from reactor R2, 43 kg/h of stream 1 are
obtained, containing 53% T3PN, 12% 2M3BN, corresponding to a
conversion of 80% 2M3BN.
[0517] In a step (5), stream 1 is conducted into a distillation
column K5 which is equipped with a falling-film evaporator, top
condenser, reflux divider, gaseous side draw in the bottom region
of the column, and also column internals which generate 30
theoretical plates. The column is operated at an absolute top
pressure of 377 mbar, top temperature 355 K and bottom draw
temperature 368 K.
[0518] In column K5, the recovered catalyst stream 3 (11 kg/h) is
obtained via the bottom, containing 20% T3PN in addition to other
pentenenitriles, approx. 1% MGN, and also 0.6% Ni(0) and 54%
ligand. A small portion (stream 3b) is discharged to restrict the
accumulation of catalyst deactivation components and MGN. To
replace the amount of catalyst discharged, sufficient fresh
catalyst containing 40% pentenenitrile isomers, 1.2% Ni(0) and 55%
ligand mixture is metered in so that the Ni(0) content in the
catalyst feed to reactor R2 is kept at 0.6%.
[0519] In column K5, a stream 4 is obtained overhead (1.4 kg/h),
containing a total of 18% BD and C2BU, 45% 2M3BN, 28% Z2M2BN, and
also small amounts of vinylcyclohexene (VCH). The reflux ratio of
column K5 is adjusted in such a way that 10 ppm of T3PN are present
in stream 4. The draw rate of stream 4 from the top of column K8 is
adjusted in such a way that 10% Z2M2BN and VCH are present in the
top draw stream 13 of distillation column K3.
[0520] In column K5, a stream 5 is obtained via the gaseous side
draw (24 kg/h) which, in addition to 3-pentenenitriles, comprises
substantially the 2M3BN unconverted in the isomerization and, after
condensation, is recycled in liquid form into column K3 as
described above.
Example 3
[0521] Example 3 is illustrated with reference to FIG. 5.
[0522] In Example 3, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the hydrocyanation of
butadiene. The ligand mixture for the hydrocyanation contains
approx. 60 mol % of tri(m/p-tolyl) phosphite and 40 mol % of the
chelate phosphite 2.
[0523] In a step (1), the following streams are conducted into a
system composed of two reactors, R1a and R1b, each of capacity 12
l, each of which is equipped with a nozzle, impulse exchange tube,
external pumped circulation system and in a heat exchanger disposed
in the pumped circulation system to remove the energy of reaction,
and are heated to 363 K: [0524] (1) 6 kg/h of liquid, unstabilized
hydrogen cyanide freed of water by distillation to R1a, [0525] (2)
6 kg/h of liquid, unstabilized hydrogen cyanide freed of water by
distillation to R1b, [0526] (3) 25 kg/h of commercial BD to R1a,
containing 0.25% C2BU, which has been treated by contact with
alumina in order to remove water and TBP stabilizer, [0527] (4) 2
kg/h of recycled BD from column K2a in step (2) to R1a (stream 9),
so that the entire BD feed to reactor R1 obtained is a stream of 27
kg/h containing 98% BD and a total of 2% C2BU and 1-butene, [0528]
(5) 14 kg/h of nickel(0) catalyst solution to R1a, obtained as
described below in this example as stream 10a from column K2b.
[0529] The stream 8 drawn off from reactor R1b (54 kg/h) contains a
total of 4% BD and C2BU, corresponding to a conversion of 94% BD,
and also a total of 74% pentenenitriles, of which 33% is T3PN, 37%
2M3BN and small amounts of Z2M2BN and E2M2BN, other pentenenitrile
isomers, and also the catalyst constituents and catalyst
degradation products and MGN.
[0530] In a step (2), stream 8 is fed to a distillation column K2a
which is operated as a rectifying column and is equipped with a
falling-film evaporator, and also comprises column internals having
structured packing which generate 4 theoretical plates. Column K2a
is operated at the top with a direct condenser which consists of a
column section charged with random packing and having total
collecting cup, pumped circulation system and external heat
exchanger. Column K2a is operated at an absolute top pressure of
0.8 bar, top temperature 263 K and bottom draw temperature 393
K.
[0531] Via the top of column K2a is obtained stream 9 which is
metered into the reactor R1a as a recycle stream as described at
the outset. The reflux ratio at the top of column K2a is adjusted
in such a way that stream 9 contains 0.1% 2M3BN.
[0532] Via the bottom of column K2a are obtained 52 kg/h of a
stream 1b which contains 0.3% BD, 0.1% C2BU, 76% pentenenitriles
and also additionally the catalyst constituents.
[0533] Within step (2), stream 1b is conducted into a distillation
column K2b which is operated in stripping mode and is equipped with
a falling-film evaporator, top condenser with postcondenser, and
also column internals having structured packing which generate 4
theoretical plates. The column is operated at an absolute top
pressure of 70 mbar, top temperature 333 K and bottom draw
temperature 373 K.
[0534] At the gaseous top draw of column K2b, stream 11 is obtained
(40 kg/h), containing 0.4% BD, 54% 2M3BN and 42% T3PN, and also, to
a lesser extent, E2M2BN and Z2M2BN in addition to other
pentenenitrile isomers.
[0535] Into column K2b are conducted 5 kg/h of a catalyst stream
which is obtained as described in Example 1 of DE-A-102004004683 as
the bottom draw of column K4 from step (4) of Example 2, containing
a total of 45% pentenenitriles, 1.1% Ni(0), 38% ligand mixture and
approx. 12% ADN.
[0536] Via the bottom of column K2b is obtained catalyst stream 10
containing 1.2% Ni(0), 0.3% 2M3BN and 17% residual pentenenitriles.
Stream 10 is recycled partly into reactor R1 (14 kg/h) (stream
10a). Another portion (stream 10b) (3.8 kg/h) is fed to a
regeneration according to DE-A-103 51 002, in order to be used in
the hydrocyanation of 3-pentenenitrile according to DE-A-102 004
004 683.
[0537] In a step (3), stream 11 is conducted to a distillation
column K3 which is equipped with circulation evaporator and top
condenser, and also with structured packing which generate 45
theoretical plates. Column K3 is operated at an absolute top
pressure of 1.0 bar, top temperature 395 K and bottom draw
temperature 416 K.
[0538] In step (6), 28 kg/h of recycle stream 5 from column K6 are
conducted into column K3, containing. 72% T3PN, 15% 2M3BN and 8%
Z2M2BN, and also small amounts of further pentenenitrile
isomers.
[0539] Via the top of column K3 are obtained 30 kg/h of a stream 13
containing 1% T3PN, 85% 2M3BN, 8% Z2M2BN, and also a total of 3% BD
and C2BU, and further pentenenitrile isomers. The reflux ratio of
column K3 is adjusted in such a way that 1% 3PN is obtained
overhead.
[0540] Via the bottom of column K3 are obtained 38 kg/h of stream
12 containing a total of 97% T3PN, C3PN and 4PN, and also approx.
10 ppm of 2M3BN and approx. 2% E2M2BN, and small amounts of MGN and
further pentenenitrile isomers.
[0541] In Example 3, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the isomerization of 2M3BN to
T3PN. The ligand mixture for isomerization (referred to hereinbelow
as isomerization ligand) comprises mixed phosphite ligands of the
P(OR)(OR')(OR'') class having randomly distributed R, R', R'' from
the group of phenyl, m-tolyl, p-tolyl, o-tolyl, at least 80 mol %
of the sum of the R, R', R'' radicals being m-tolyl and p-tolyl
radicals. Such ligand mixtures are obtained in the reaction of a
mixture of m- and p-cresol (having a mixing ratio of 2:1) of
m-relative to p-cresol with a phosphorus trihalide. The promoter
used for the isomerization reaction is zinc chloride, as described
in U.S. Pat. No. 3,676,481, U.S. Pat. No. 3,852,329 and U.S. Pat.
No. 4,298,546.
[0542] In a step (4), stream 13 is conducted, together with a
catalyst recycle stream 3a and a catalyst supplementation stream,
into a reactor R2, designed as a compartmented reactor having
tubular characteristics and equipped with a preheater, by which the
reaction mixture is heated to 383 K. As the sum of recycled
catalyst and fresh catalyst, 12 kg/h of a mixture having 20% T3PN,
3% 2M3BN and other pentenenitrile isomers, 71% isomerization ligand
and 0.6% nickel(0), and also a small content of catalyst
degradation products, are conducted into reactor R2.
[0543] The product obtained from reactor R2 is 43 kg/h of stream 1
containing 53% T3PN, 12% 2M3BN, corresponding to a conversion of
80% 2M3BN.
[0544] In a step (5), stream 1 is conducted into an evaporator
stage B5 which is equipped with forced-circulation evaporator and
top condenser. The evaporator stage B5 is operated at an absolute
pressure of 510 mbar, bottom draw temperature 403 K and
condensation temperature 366 K.
[0545] In evaporator stage B5, the recovered catalyst stream 3 (11
kg/h) is obtained via the bottom, containing 20% T3PN in addition
to other pentenenitriles, approx. 10% MGN, and also 0.5% Ni(0) and
61% ligand mixture. A small portion (stream 3b) is discharged to
restrict the accumulation of catalyst deactivation components and
MGN. To replace the amount of catalyst discharged, sufficient fresh
catalyst, containing approx. 15% pentenenitrile isomers, approx.
2.0% Ni(0), approx. 70% isomerization ligand and the zinc chloride
promoter in a concentration which corresponds to a molar ratio of
ZnCl.sub.2 to nickel(0) of approx. 5, is metered in so that the
Ni(0) content in the catalyst feed to reactor R2 is kept at
0.6%.
[0546] In the evaporator stage B5, stream 2 is obtained at the top
condenser (25 kg/h), containing 1% BD, 68% T3PN, 16% 2M3BN and
further pentenenitriles, and also small amounts of VCH.
[0547] In a step (6), stream 2 is conducted into distillation
column K6 which is operated as a rectifying column and is equipped
with a circulation evaporator, top condenser, and also column
internals which generate 30 theoretical plates. The column is
operated at an absolute top pressure of 340 mbar, top temperature
357 K, 313 K in the condenser and bottom draw temperature 373
K.
[0548] At the condenser of column K6, the gas phase obtained is
approx. 100 l (STP)/h of a stream which consists substantially of
BD.
[0549] In column K6, the liquid phase obtained at the top condenser
is a stream 4 (1.1 kg/h), containing a total of 5% BD and C2BU, 50%
2M3BN, 30% Z2M2BN, and also small amounts of vinylcyclohexene
(VCH). The reflux ratio of column K6 is adjusted in such a way that
1 ppm of T3PN is present in stream 4. The draw rate of stream 4
from the top of column K6 is adjusted in such a way that a total of
10% Z2M2BN and VCH are present in the feed to reactor R2.
[0550] In column K6, a stream 5 is obtained via the bottom (24
kg/h) which, in addition to 3-pentenenitriles, comprises
substantially the 2M3BN unconverted in the isomerization, and is
recycled into column K3 as described above.
Example 4
[0551] Example 4 is illustrated with reference to FIG. 6.
[0552] In Example 3, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the hydrocyanation of
butadiene. The ligand mixture for the hydrocyanation contains
approx. 80 mol % of tri(m/p-tolyl) phosphite and 20 mol % of the
chelate phosphite 2 (see Example 2).
[0553] In a step (1), the following streams are conducted into a
system composed of three continuous stirred tanks R1a, R1b and R1c
connected in series, each of capacity 10 l, which are heated to 373
K: [0554] (1) 5.2 kg/h of liquid, unstabilized hydrogen cyanide
freed of water by distillation to R1a, [0555] (2) 4.0 kg/h of
liquid, unstabilized hydrogen cyanide freed of water by
distillation to R1b, [0556] (3) 20 kg/h of 1 BD as stream 9 from
the condenser of evaporator B1 in step (2), containing 92% BD, 2%
T3PN, 4% 2M3BN and approx. 2% C2BU to R1a, [0557] (4) 4.1 kg/h of
nickel(0) catalyst solution to R1a, obtained as described below in
this example, as stream 3a from evaporator stage B5 in step (5),
[0558] (5) 3.7 kg/h of nickel(0) catalyst solution to R1a, obtained
as described in Example 3 of the German patent application with the
title "Preparation of dinitriles" to BASF AG (B03/0525) as the
bottom draw of column K4 from step (4) of Example 2, containing a
total of 45% pentenenitriles, 1.1% Ni(0), 38% ligand mixture and
approx. 12% ADN.
[0559] Reactor R1c is operated as a postreactor with the effluent
from reactor R1b at 353 K.
[0560] Stream 8 drawn off from reactor R1c (37 kg/h) contains 1%
BD, corresponding to a conversion of 98% BD, and also a total of
82% pentenenitriles, of which 36% is T3PN, 44% 2M3BN and small
amounts of Z2M2BN and E2M2BN, and also the catalyst constituents
and catalyst degradation products and MGN and further
pentenenitrile isomers.
[0561] In a step (2), stream 8 is fed to an evaporator stage B1
which is equipped with a circulation evaporator. The evaporator
stage B1 is operated at the top with a condenser which is flushed
with condensed material from the reflux vessel. The evaporator
stage B1 is operated at an absolute top pressure of 0.6 bar,
condensation temperature 253 K and bottom draw temperature 363
K.
[0562] In the condensate collecting vessel of evaporator stage B1,
19.5 kg/h of commercial BD containing 0.25% C2BU are metered in,
which has been treated by contact with molecular sieve, the water
content of the BD used having been removed to less than 10 ppm by
weight of water.
[0563] From the condensate collecting vessel of evaporator stage
B1, stream 9 is drawn off as the sum of recycled and freshly
metered butadiene, and recycled to reactor R1a as described
above.
[0564] Via the bottom of evaporator stage B1 are obtained 37 kg/h
of a stream 11b which contains 1% BD, 82% pentenenitriles and also
additionally the catalyst constituents.
[0565] In a step (4), stream 11b is conducted into a reactor R2,
heated to 383 K and designed as a stirred tank with downstream
delay zone, and 2M3BN is isomerized to T3PN in the presence of the
nickel catalyst.
[0566] A pentenenitrile recycle stream 5 is conducted into reactor
R2 (10 kg/h) and is obtained in step (6) in column 6 as the bottom
product containing 60% 2M3BN, a total of 10% T3PN with further
pentenenitrile isomers, and also VCH and small amounts of BD.
[0567] From reactor R2, a stream 1 is obtained (45 kg/h) containing
62% T3PN and 14% 2M3BN, corresponding to a conversion of 70% 2M3BN
to T3PN, and also the catalyst components.
[0568] In a step (5), stream 1 is conducted into an evaporator
stage B5 which is equipped with a failing-film evaporator and
condenser and is operated at an absolute pressure of 50 mbar and
bottom draw temperature 393 K.
[0569] From the condenser of the evaporator stage B5, a stream 2 is
obtained (38 kg/h), containing 91% pentenenitrile isomers and also
approx. 1% BD and, to a lesser extent, E2M2BN, Z2M2BN and VCH.
[0570] Via the bottom of the evaporator stage B5, catalyst stream 3
is obtained (7.2 kg/h), containing 1.2% Ni(0), 0.1% 2M3BN and 15%
residual pentenenitriles. Stream 3 is partly (stream 3a) recycled
into reactor R1 (4.1 kg/h). The remainder (stream 3b) is fed to a
regeneration according to DE-A-103 51 002, and can be used after
the regeneration, for example, in a hydrocyanation of
3-pentenenitrile as in Example 2 of DE-A-102 004 004 683, or used
again as the catalyst in the process according to the invention for
hydrocyanating butadiene, if appropriate after removal of zinc
chloride.
[0571] In a step (3), stream 2 is conducted to a distillation
column K3 which is equipped with a forced-circulation evaporator
and top condenser, and also with column internals which generate 30
theoretical plates. Column K3 is operated at an absolute top
pressure of 120 mbar, top temperature 334 K and bottom draw
temperature 352 K.
[0572] Via the top of column K3 are obtained 10 kg/h of a stream 13
containing 5% T3PN, 60% 2M3BN, 4% Z2M2BN, and also a total of 4% BD
and C2BU, and a remainder of predominantly VCH. The reflux ratio of
column K3 is adjusted in such a way that 5% T3PN are obtained
overhead.
[0573] Via the bottom of column K3 are obtained 27 kg/h of stream
12 containing a total of 98% T3PN, C3PN and 4PN, and also approx.
1000 ppm of 2M3BN and approx. 2% E2M2BN.
[0574] In a step (6), stream 13 is conducted into a distillation
column K6 which is operated as a rectifying column and is equipped
with a forced-circulation evaporator, top condenser, reflux
divider, and also column internals having structured packing which
generate 15 theoretical plates. Column K6 is operated at an
absolute top pressure of 380 mbar, top temperature 361 K and bottom
draw temperature 365 K.
[0575] In column K6, a liquid stream 4 is obtained overhead (0.6
kg/h), containing a total of 4% BD and C2BU, 54% 2M3BN, 38% Z2M2BN,
and also 2.5% vinylcyclohexene (VCH). The draw rate of stream 4
from the top of column K6 is adjusted in such a way that a total of
30% Z2M2BN and VCH are present in the top draw stream 13 of column
K3. In column K6, a gaseous stream is obtained at the top condenser
operated as a partial condenser (195 l (STP)/h) which comprises
substantially BD.
[0576] In column K6, stream 5 is obtained via the bottom (9.4 kg/h)
which, in addition to 3-pentenenitriles, comprises substantially
the 2M3BN unconverted in the isomerization and is recycled into the
isomerization reactor R2.
Example 5
[0577] Example 5 is illustrated with reference to FIG. 7.
[0578] In Example 5, a catalyst system based on nickel(0) complexes
with a mixture of ligands is used for the hydrocyanation of BD. The
ligand mixture for the hydrocyanation contains approx. 80 mol % of
tri(m/p-tolyl) phosphite and 20 mol % of the chelate phosphonite 1
(see Example 1).
[0579] In a step (1), the following streams are conducted into a
system composed of two continuous stirred tanks R1a and R1b
connected in series, each of capacity 50 l, which are heated to 363
K: [0580] (1) 18 kg/h of liquid, unstabilized hydrogen cyanide
freed of water by distillation in equal portions to reactors R1a
and R1b, [0581] (2) 62 kg/h of BD as stream 9 from the top of
evaporator B1 in step (2), containing 87% BD, 3% T3PN, 6% 2M3BN and
approx. 2% C2BU to reactor R1a, [0582] (3) 61 kg/h of nickel(0)
catalyst solution, obtained as described below in this example, as
stream 3a from evaporator stage B5 in step (5) to reactor R1a,
[0583] (4) 6.7 kg/h of nickel(0) catalyst solution to R1a, obtained
as described in Example 1 of the German patent application with the
title "Preparation of dinitriles" to BASF AG (B03/0525) 1, is
obtained as the bottom draw of column K4 from step (4) of Example
2, containing a total of 45% pentenenitriles, 1.1% Ni(0), 38%
ligand mixture, and also approx. 12% ADN to reactor R1a, the
butadiene stream and the catalyst stream being premixed before
contacting with hydrogen cyanide.
[0584] The stream 8 drawn off from reactor R1b (177 kg/h) contains
11% BD, corresponding to a conversion of 66% BD, and also a total
of 64% pentenenitriles, of which 32% is T3PN, 30% 2M3BN and small
amounts of Z2M2BN and E2M2BN and further pentenenitrile isomers,
and also the catalyst constituents and catalyst degradation
products.
[0585] In a step (2), stream 8 is fed to an evaporator stage B1
which is equipped with a falling-film evaporator. The evaporator
stage B1 is operated with a condenser at the top which is flushed
with condensed material from the reflux vessel. The evaporator
stage B1 is operated at an absolute top pressure of 1.3 bar,
condensation temperature 278 K and bottom draw temperature 403
K.
[0586] Into the condensate collecting vessel of the evaporator
stage B1 are metered 37 kg/h of commercial BD containing 0.25% C2BU
which has been treated by contact with molecular sieve, the water
content of the BD used having been removed to less than 5 ppm by
weight of water and the TBP stabilizer present in the BD used
reaching the condensate collecting vessel and condenser flushing
circuit in concentrations on the ppm scale.
[0587] From the condensate collecting vessel of the evaporator
stage B1, stream 9 is drawn off as the sum of recycled and freshly
metered BD and recycled to reactor R1a as described above.
[0588] Via the bottom of evaporator stage B1 are obtained 152 kg/h
of a stream 11b which contains 0.9% BD, 16% 2M3BN, 51% T3PN and
further pentenenitrile isomers, and also additionally the catalyst
constituents. The composition of the bottom effluent of the
evaporator stage allows a degree of conversion of 50% 2M3BN to T3PN
in the bottom of the evaporator B1 to be concluded.
[0589] In a step (5), stream 11b is conducted into an evaporator
stage B5 which is equipped with falling-film evaporator and
condenser and is operated at an absolute pressure of 260 mbar and
bottom draw temperature 383 K.
[0590] From the evaporator stage B5, a stream 2 is obtained in
gaseous form (83 kg/h), containing 93% pentenenitrile isomers, and
also approx. 1% BD and, to a lesser extent, E2M2BN, Z2M2BN and VCH.
Stream 2 is conducted into distillation column K3 in step (3).
[0591] Via the bottom of evaporator stage B5 is obtained the
catalyst stream 3 (69 kg/h), containing 0.6% Ni(0), 2% 2M3BN and
42% residual pentenenitriles. Stream 4 is for the most part
recycled into reactor R1 (61.4 kg/h) (stream 3a). The remainder
(stream 3b) is fed to a regeneration according to DE-A-103 51 002,
and may be used, for example, in the hydrocyanation of
3-pentenenitrile, as described in Example 1 of DE-A-102 004 004
683.
[0592] In a step (3), stream 2 is conducted in gaseous form to a
distillation column K3 which is equipped with a forced-circulation
flash evaporator and top condenser, and also with structured
packing which generate 30 theoretical plates. Column K3 is operated
at an absolute top pressure of 80 mbar, top temperature 375 K and
bottom draw temperature 343 K.
[0593] Via the top of column K3 are obtained 36 kg/h of a stream 13
containing 15% T3PN, 64% 2M3BN, 3% Z2M2BN, and also a total of 4%
BD and C2BU, the remainder comprising predominantly VCH. The reflux
ratio of column K3 is adjusted in such a way that 15% T3PN is
obtained overhead.
[0594] Via the bottom of column K3 are obtained 47 kg/h of stream
12 containing a total of 98% T3PN, C3PN and 4PN, and also 100 ppm
of 2M3BN and approx. 1% E2M2BN.
[0595] In a step (6), stream 13 is conducted into a distillation
column K6 which is operated as a rectifying column and is equipped
with a forced-circulation evaporator, top condenser, reflux
divider, and also column internals having structured packing which
generate 45 theoretical plates. The column is operated at an
absolute top pressure of 320 mbar, condensation temperature 288 K
and bottom draw temperature 363 K.
[0596] In column K6, a liquid stream 4 is obtained via the top (6.8
kg/h) containing a total of 10% BD and C2BU, 80% 2M3BN, 8% Z2M2BN,
and also 0.5% vinylcyclohexene (VCH). The draw rate of stream 4
from the top of column K6 is adjusted in such a way that a total of
15% Z2M2BN and VCH is present in the top draw stream 3 of the
column K3. In column K6, a gaseous stream is obtained at the top
condenser operated as a partial condenser (263 l (STP)/h) which
comprises substantially BD.
[0597] In column K6, stream 5 is obtained via the bottom (28.7
kg/h) which, in addition to 3-pentenenitriles, comprises
substantially the 2M3BN unconverted in the isomerization and is
recycled into the hydrocyanation reactor R1.
Example 6
[0598] Example 6 is illustrated with reference to FIG. 8.
[0599] In Example 8, a catalyst system based on nickel(0) complexes
with chelate phosphonite 1 as the ligand is used for the
hydrocyanation of BD (see Example 1).
[0600] In a step (1), the following streams are conducted into a
continuously operated stirred tank R1 of volume 30 l which is
heated to 363 K: [0601] (1) 16 kg/h of liquid, unstabilized
hydrogen cyanide freed of water by distillation, [0602] (2) 55 kg/h
of BD as stream 9 from the top of evaporator B1 in step (2),
containing 87% BD, 3% T3PN, 6% 2M3BN and approx. 2% C2BU, [0603]
(3) 10 kg/h of nickel(0) catalyst solution, obtained as described
below in this example, as stream 3a from evaporator stage B5 in
step (5), containing a total of 42% pentenenitriles, 23% ligand,
0.9% nickel(0), and also in each case approx. 10% ADN and MGN,
[0604] (4) 4 kg/h of nickel(0) catalyst solution to R1, containing
a total of 45% pentenenitriles, 1.5% Ni(0) and 48% ligand.
[0605] The stream 8 drawn off from reactor R1 (89 kg/h) contains
17% BD, corresponding to a conversion of 71% BD, and also a total
of 73% pentenenitriles, of which 32% is T3PN, 36% 2M3BN and small
amounts of Z2M2BN and E2M2BN, and also the catalyst constituents
and the catalyst degradation products.
[0606] In a step (2), stream 8 is fed to an evaporator stage B1
which is equipped with a falling-film evaporator. The evaporator
stage B1 is operated with a condenser at the top which is flushed
with condensed material from the reflux vessel. The evaporator
stage B1 is operated at an absolute top pressure of 1.3 bar,
condensation temperature 278 K and bottom draw temperature 403
K.
[0607] Into the condensate collecting vessel of evaporator stage B1
are metered 34 kg/h of commercial BD containing 0.25% C2BU which
has been treated by contact with alumina, the water content of BD
used having been reduced to less than 10 ppm by weight of water and
the TBP content to less than 10 ppm.
[0608] From the condensate collecting vessel of the evaporator
stage, stream 9 is drawn off as the sum of recycled and freshly
metered butadiene, and recycled to reactor R1a as described
above.
[0609] Via the bottom of evaporator stage B1 are obtained 76 kg/h
of a stream 5 which contains 0.8% BD, 12% 2M3BN, 69% T3PN and
further pentenenitrile isomers, and also additionally the catalyst
constituents. The composition of the bottom effluent of the
evaporator stage corresponds to a degree of conversion of 75% 2M3BN
to T3PN in the bottom of the evaporator stage B1.
[0610] In a step (5), stream 5 is conducted into an evaporator
stage B5 which is equipped with a falling-film evaporator and
condenser and is operated at an absolute pressure of 220 mbar and
bottom draw temperature 381 K.
[0611] From the evaporator stage B5, a stream 2 is obtained in
gaseous form (58 kg/h) containing 97% pentenenitrile isomers, and
also approx. 1% BD and, to a lesser extent, E2M2BN, Z2M2BN and
VCH.
[0612] Via the bottom of the evaporator stage B5 is obtained the
catalyst stream 3 (17 kg/h) containing 0.9% Ni(0), 0.3% 2M3BN and
42% residual pentenenitriles. Stream 3 is for the most part
recycled into reactor R1 (10 kg/h) (stream 3a). The remainder
(stream 3b) is fed to a regeneration according to US 2003/0100442
and may, after the regeneration, be used in a hydrocyanation of
3-pentenenitrile or recycled into the process according to the
invention, into the step for hydrocyanating. BD.
[0613] Stream 2 is condensed and, in a step (3), conducted in
liquid form to a distillation column K3 which is equipped with a
forced-circulation evaporator and top condenser, and also with
structured packing which generate 50 theoretical plates. Column K3
is operated at an absolute top pressure of 200 mbar, top
temperature 342 K and bottom draw temperature 366 K.
[0614] At the top of column K3, a stream 4 is obtained, containing
10% BD, 18% Z2M2BN, 68% 2M3BN, and also further pentenenitrile
isomers and VCH. The reflux ratio of column K3 is adjusted in such
a way that the top draw stream contains 18% Z2M2BN.
[0615] At a liquid side draw of column K3, 8 kg/h of a stream 13
are obtained, containing 0.5% T3PN, 85% 2M3BN, 5% Z2M2BN, 10% BD.
Stream 13 is recycled into evaporator stage B1.
[0616] Via the bottom of column K3 are obtained 47 kg/h of stream
12 containing a total of 98% T3PN, C3PN and 4PN, and also 100 ppm
of 2M3BN and approx. 1% E2M2BN.
[0617] All experiments below were carried out in a protective gas
atmosphere.
[0618] Nickel(0)[o-isopropylphenyl.sub.0.8 m-/p-tolyl.sub.3.2
phosphite].sub.18, (for short: isopropyl catalyst); corresponds to
a solution of 1.0% by weight of nickel(0) with 19% by weight of 3PN
and 80% by weight of o-isopropylphenyl.sub.0.8 m-/p-tolyl.sub.3.2
phosphite.
Examples of the Continuous Hydrocyanation of BD to 2M3BN/3PN
Example 7 (Comparative)
BD/HCN ratio=1.4:1
[0619] 2.11 mol of moist and stabilized butadiene (100 ppm of
water, 100 ppm of TBP), 1.55 mol of HCN and 14 mmol of Ni in the
form of the isopropyl catalyst are fed per hour into a pressure
reactor (pressure: 15 bar, internal temperature 105.degree. C.,
residence time: approx. 40 min/reactor). According to volumetric
analysis, the HCN conversion is quantitative (Vollhard titration).
The 2M3BN/3PN ratio of the reaction effluent is determined by GC
chromatography (GC area percent). The 2M3BN/3PN ratio was 1.95/1.
The loss of Ni(0) based on product of value formed was: 0.58 kg of
Ni(0)/t of product of value (3PN/2M3BN).
Example 8
BD/HCN ratio=1.4:1
[0620] 2.13 mol of butadiene dried over a bed of 4 .ANG. molecular
sieve, 1.53 mol of HCN and 14 mmol of Ni in the form of the
isopropyl catalyst are fed per hour into a pressure reactor
(pressure: 15 bar, internal temperature 105.degree. C., residence
time: approx. 40 min/reactor). According to volumetric analysis,
the HCN conversion is quantitative (Vollhard titration). The
2M3BN/3PN ratio of the reaction effluent is determined by GC
chromatography (GC area percent). The 2M3BN/3PN ratio was 1.95/1.
The loss of Ni(0) based on product of value formed was: 0.14 kg of
Ni(0)/t of product of value (3PN/2M3BN).
Example 9
BD/HCN ratio=1.2:1
[0621] 2.09 mol of butadiene dried over a bed of alumina, 1.67 mol
of HCN and 14 mmol of Ni in the form of the isopropyl catalyst are
fed per hour into a pressure reactor (pressure: 15 bar, internal
temperature 105.degree. C., residence time: approx. 45
min/reactor). According to volumetric analysis, the HCN conversion
is quantitative (Vollhard titration). The 2M3BN/3PN ratio of the
reaction effluent is determined by GC chromatography (GC area
percent). The 2M3BN/3PN ratio was 1.95/1. The loss of Ni(0) based
on product of value formed was: <0.10 kg of Ni(0)/t of product
of value (3PN/2M3BN).
Examples of the Continuous Isomerization of 2M3BN to 3PN
Example 10
[0622] A hydrocyanation effluent prepared in Example 8 is collected
and freed distillatively of excess BD. The thus obtained mixture is
heated to 130.degree. C. for one hour. After 0 and 30 min and after
1 h, GC samples are taken from the reaction mixture and analyzed by
GC chromatography (GC area percent).
TABLE-US-00003 Time 2M3BN E, Z-2M2BN c, t-2PN 4PN c, t-3PN
3PN/2M3BN 0 h 15.62 0.20 0.50 0.50 38.33 2.45 30 min 10.21 0.21
0.51 0.49 42.36 4.15 1 h 5.69 0.27 0.54 0.51 47.12 8.28
Examples of the Incorrect Isomerization of 2M3BN to 2M2BN by
Recycled Hydrocyanation Catalyst
Example 11
[0623] From a catalyst reservoir, filled with 649 g of fresh
isopropyl catalyst at t=0 h, 100 g of isopropyl catalyst are
withdrawn continuously and fed into a pressure reactor together
with 2.14 mol of butadiene dried over a bed of alumina, and also
1.67 mol of HCN, per hour (pressure: 15 bar, internal temperature
105.degree. C., residence time: approx. 45 min/reactor). According
to volumetric analysis, the HCN conversion is quantitative
(Vollhard titration). The product of value is removed continuously
from the catalyst by means of a Sambay distillation and the thus
obtained return catalyst is recycled into the reservoir. The
reaction is operated for 50 h and the still hydrocyanation-active
catalyst is discharged owing to beginning formation of the 2M2BN
secondary component. The thus obtained catalyst is subjected to
isomerization experiments:
Example 12 (Comparative)
[0624] 10 g of isomerization catalyst are supplemented with 2M3BN
(15 g) and heated at 120.degree. C. for 5 h. At a conversion of 89%
2M3BN (GC area percent), 8.6% incorrect isomers (2M2BN) are
found.
Example 13
[0625] n-Heptane (100 g) and adiponitrile (50 g) are added to the
isomerization catalyst from Example 11 (100 g) and the mixture is
stirred (15 min). After a phase separation (30 min), the lower
phase is discharged. A portion of the upper phase (50 g,
heptane+isomerization catalyst) is concentrated on a rotary
evaporator. The residue (14 g, isomerization catalyst) is
supplemented with 2M3BN (21 g) and heated at 120.degree. C. for 5
h. At a conversion of 95% 2M3BN (GC area percent), 2.0% incorrect
isomers (2M2BN) are found.
Example 14
[0626] The residues of the upper phase from the first extraction
(Example 12) are again admixed with adiponitrile (37.5 g) and
stirred. After the phase separation, a portion of the upper phase
is again concentrated on a rotary evaporator and the residue (9.3
g) is supplemented with 2M3BN (14 g). After 5 h at 120.degree. C.,
a 2M3BN conversion of 94% (GC area percent) and an incorrect
isomerization of 0.7% are found.
Examples of the Incorrect Isomerization of 2M3BN to 2M2BN by
Continuously Used Isomerization Catalyst
Example 15
[0627] A 2 l reactor is charged with 300 g of isopropyl catalyst
which are admixed continuously with 450 g/h of 2M3BN and heated to
130.degree. C. At a residence time of 60 min, reactor contents are
withdrawn and worked up by distillation continuously, and the
isomerization catalyst remaining in the bottom is recycled. The
reaction is operated for 50 h and the still isomerization-active
catalyst is discharged owing to beginning incorrect isomerization
of 2M3BN. The thus obtained catalyst is subjected to isomerization
experiments:
Example 16
[0628] 10 g of isomerization catalyst are supplemented with 2M3BN
(15 g) and heated at 120.degree. C. for 5 h. At a conversion of 90%
2M3BN (GC area percent), 9.8% incorrect isomers (2M2BN) are
found.
Example 17
[0629] n-Heptane (100 g) and adiponitrile (50 g) are added to the
isomerization catalyst from Example 16 (100 g) and the mixture is
stirred (15 min). After a phase separation (30 min), the lower
phase is discharged. A portion of the upper phase (50 g,
heptane+isomerization catalyst) is concentrated on a rotary
evaporator. The residue (14 g, isomerization catalyst) is
supplemented with 2M3BN (21 g) and heated at 120.degree. C. for 5
h. At a conversion of 93% 2M3BN (GC area percent), 2.4% incorrect
isomers (2M2BN) are found.
Example 18
[0630] The residues of the upper phase from the first extraction
(Example 17) are again admixed with adiponitrile (37.5 g) and
stirred. After the phase separation, a portion of the upper phase
is again concentrated on a rotary evaporator and the residue (9.3
g) is supplemented with 2M3BN (14 g). After 5 h at 120.degree. C.,
a 2M3BN conversion of 93% (GC area percent) and an incorrect
isomerization of 0.6% are found.
* * * * *