U.S. patent application number 10/122769 was filed with the patent office on 2002-12-26 for continuous process for the preparation of diaminodicyclohexylmethane.
Invention is credited to Bunnenberg, Rolf, Groschl, Andreas, Holzbrecher, Michael, Tilling, Andreas Schulze.
Application Number | 20020198409 10/122769 |
Document ID | / |
Family ID | 7681937 |
Filed Date | 2002-12-26 |
United States Patent
Application |
20020198409 |
Kind Code |
A1 |
Bunnenberg, Rolf ; et
al. |
December 26, 2002 |
Continuous process for the preparation of
diaminodicyclohexylmethane
Abstract
The invention relates to a process for the preparation of
diaminodicyclohexylmethane ("PACM") with a proportion of
trans,trans-4,4'-diaminodicyclohexylmethane of from 17 to 24% by
hydrogenation of diaminodiphenylmethane ("MDA") in the presence of
a pulverulent catalyst in a continuously operated suspension
reactor at a conversion of MDA of at least 95%, based on the amount
of MDA used.
Inventors: |
Bunnenberg, Rolf;
(Leichlingen, DE) ; Groschl, Andreas; (Leverkusen,
DE) ; Holzbrecher, Michael; (Engelskirchen, DE)
; Tilling, Andreas Schulze; (League City, TX) |
Correspondence
Address: |
BAYER CORPORATION
PATENT DEPARTMENT
100 BAYER ROAD
PITTSBURGH
PA
15205
US
|
Family ID: |
7681937 |
Appl. No.: |
10/122769 |
Filed: |
April 15, 2002 |
Current U.S.
Class: |
564/451 |
Current CPC
Class: |
C07C 211/36 20130101;
C07C 209/72 20130101; C07C 209/72 20130101; C07C 2601/14
20170501 |
Class at
Publication: |
564/451 |
International
Class: |
C07C 29/52 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 19, 2001 |
DE |
10119135.9 |
Claims
What is claimed is:
1. A process for the preparation of diaminodicyclohexylmethane with
a proportion of trans,trans-4,4'-diaminodicyclohexylmethane of from
17 to 24% comprising hydrogenating diaminodiphenylmethane in the
presence of a pulverulent catalyst in a continuously operated
suspension reactor at a conversion of diaminodiphenylmethane of at
least 95%, based on the amount of diaminodiphenylmethane.
2. A process according to claim 1 wherein the continuously operated
suspension reactor is a cascade of two or more serially connected
suspension reactors.
3. A process according to claim 2 wherein the cascade of two or
more serially connected suspension reactors is a cascade of
stirred-tank reactors.
4. A process according to claim 2 wherein the cascade of two or
more serially connected suspension reactors is a cascade of
bubble-columns.
5. A process according to claim 1 wherein the pulverulent catalyst
comprises 1 to 10% by weight of ruthenium.
6. A process according to claim 5 wherein the ruthenium is applied
to a support material and is distributed over the entire cross
section of the support material.
7. A process according to claim 1 wherein the catalyst is used as a
powder with an average diameter of from 5 to 150 .mu.m.
8. A process according to claim 1 carried out at a temperature of
from 130 to 200.degree. C.
9. A process according to claim 1 carried out at a pressure of from
50 to 400 bar is used.
10. A process according to claim 1 carried out in the presence of
an alcohol as solvent.
11. A process according to claim 1 wherein the proportion of water
in the reaction mixture is less than 1% by weight.
12. A process according to claim 1 wherein the
diaminodiphenylmethane additionally comprises higher molecular
weight aromatic amines.
13. A process according to claim 1 wherein the pulverulent catalyst
is suspended in the diaminodiphenylmethane and the resultant
mixture is brought to the reaction temperature before being fed
into the continuously operated suspension reactor.
14. A process according to claim 1 wherein the
diaminodicyclohexylmethane is separated from the catalyst and the
separated catalyst is washed with a solvent.
15. A process according to claim 1 wherein the
diaminodicyclohexylmethane is separated from the catalyst and the
separated catalyst is reused.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a continuous process for
the preparation of diaminodicyclohexylmethane ("PACM") by
hydrogenation of diaminodiphenylmethane ("MDA") in the presence of
a pulverulent catalyst.
[0002] PACM is prepared industrially by hydrogenating MDA. PACM is
used, for example, for the preparation of surface coatings,
primarily as a precursor for the surface-coating raw material
diisocyanatodicyclohexyl-m- ethane. The isomer ratio is of
particular importance for a number of applications.
[0003] EP 639,403 A2 discloses a catalyst for the preparation of
PACM with a low proportion of trans,trans isomer by hydrogenating
MDA. This catalyst has a thin ruthenium- or rhodium-containing
layer on a special support, namely a calcined or superficially
rehydrated transition alumina, particularly hydragillite or
bayerite.
[0004] EP 639,403 A2 describes the deactivation of the catalyst by
higher molecular weight constituents of the reaction mixture and
the adjustment of a low proportion of trans,trans isomer in the
product as a problem in the industrial preparation of PACM. The use
of special catalysts is intended to solve these problems. However,
the special catalyst is primarily suitable for use in reactors with
a fixed catalyst bed in which the catalyst cannot be exchanged
during operation. In addition, a large part of the reactor volume
is occupied by the inactive core of the coated catalyst used and is
no longer available as reaction volume.
[0005] Hydrogenations in discontinuously operated suspension
reactors have already been described. This procedure has the
disadvantage that in the case of a rapid reaction, the reaction
cannot be terminated quickly enough at the end-point of the
reaction, i.e., upon complete conversion and simultaneously
specified content of trans,trans isomer. There is therefore always
the risk that incomplete conversion or product with an undesirably
high proportion of trans,trans isomer is obtained. For this
reaction procedure, it is thus necessary to generally use catalysts
with a lower activity or to work at low temperatures, which leads
to long reaction times and a low space-time yield.
[0006] An object of the invention was therefore to provide a
continuously operable process for the preparation of PACM with a
low proportion of trans,trans-4,4'-diaminodicyclohexylmethane
characterized by a high space-time yield and a high catalyst
service life.
[0007] Surprisingly, it has been found that the object can be
achieved by carrying out the hydrogenation of MDA to PACM in a
continuously operated suspension reactor.
SUMMARY OF THE INVENTION
[0008] The invention provides a process for the preparation of
diaminodicyclohexylmethane ("PACM") with a proportion of
trans,trans-4,4'-diaminodicyclohexylmethane of from 17 to 24%
comprising hydrogenating diaminodiphenylmethane ("MDA") in the
presence of a pulverulent catalyst in a continuously operated
suspension reactor at a conversion of MDA of at least 95%, based on
the amount of MDA.
DETAILED DESCRIPTION OF THE INVENTION
[0009] The conversion of MDA is preferably at least 99%, based on
the amount of MDA used. The conversion can be influenced by
measures known to the person skilled in the art, for example, by
adjusting the residence time in the continuously operated
suspension reactor.
[0010] It is particularly advantageous to use a cascade of two or
more serially connected suspension reactors, for example, a cascade
of stirred-tank reactors or a cascade of bubble-columns. Preference
is given to using a cascade of two or more serially connected
suspension reactors consisting of at least three serially connected
reactors.
[0011] The MDA starting material is mixed with the pulverulent
catalyst and the hydrogen required for the hydrogenation when using
stirred-tank reactors as the suspension reactors by means of a
stirrer and when using bubble-columns as suspension reactors by
introducing hydrogen at high speed and generating a turbulent flow
within the reactor.
[0012] The pulverulent catalyst to be used according to the
invention preferably comprises ruthenium, preferably 1 to 10% by
weight (particularly preferably 4 to 8% by weight) of
ruthenium.
[0013] The ruthenium is preferably applied to a support in fine
distribution in order to ensure good catalyst service life and good
filterability. Suitable supports are, for example, aluminum
oxides.
[0014] In a particular embodiment, the ruthenium is distributed
largely homogeneously over the cross section of the support
particles. This ensures that, upon mechanical stress within the
reactor, no ruthenium particles are detached from the support,
which is readily possible in the case of coated catalysts.
Mechanical loading within the reactor sometimes results in breakage
of the catalyst particles. In contrast to a coated catalyst, a
homogeneously impregnated catalyst does not produce a
ruthenium-free surface but instead a fresh active
ruthenium-containing catalyst surface.
[0015] A catalyst in which the ruthenium is distributed largely
homogeneously over the cross section of the support particles can
be prepared, for example, by first allowing an aqueous solution of
a ruthenium salt (e.g., ruthenium chloride or ruthenium nitrosilyl
nitrate) to act upon an aluminum oxide powder and then
precipitating out the ruthenium by adding a base (e.g., NaOH).
[0016] The catalyst is preferably used as a powder with an average
diameter of the catalyst particles of from 5 to 150 .mu.m,
particularly preferably 10 to 120 .mu.m, particularly preferably 30
to 100 .mu.m. The catalyst can be used, for example, in an amount
of from 1 to 10% by weight (preferably 3 to 8% by weight), based on
the reaction mixture.
[0017] The process according to the invention is carried out, for
example, at a temperature of from 130 to 200.degree. C., preferably
from 140 to 190.degree. C., particularly preferably from 150 to
180.degree. C.
[0018] When using a cascade reactor, the temperatures of the
individual reactors can be different. It is advantageous to choose
a temperature in the first reactor that is higher than that in the
last reactor. For a cascade of three reactors, the first reactor
can be operated at 180.degree. C., the second at 170.degree. C.,
and the third at 150.degree. C., for example.
[0019] The hydrogen pressure is, for example, from 50 to 400 bar,
preferably from 100 to 200 bar.
[0020] Hydrogen is advantageously added in an excess of from 5 to
200%, preferably from 20 to 100%, of theory.
[0021] The process according to the invention can be carried out
with or without the addition of organic solvents. Examples of
suitable solvents are alcohols, preferably secondary alcohols
(e.g., isobutanol, cyclohexanol, or methylcyclohexanol) or tertiary
alcohols (e.g., tert-butanol), particularly preferably tertiary
alcohols.
[0022] After the catalyst has been separated off, the solvent can
be separated from the product by distillation and returned to the
hydrogenation process.
[0023] It is advantageous to keep the content of water in the
reaction mixture low since water results in deactivation of the
catalyst. The proportion of water in the reaction mixture is
preferably kept lower than 1% by weight, particularly preferably
lower than 0.5% by weight.
[0024] In the process according to the invention, it is possible to
use diaminodiphenylmethane ("MDA") which, in addition to MDA,
comprises possible higher molecular weight aromatic amines.
[0025] In order to achieve an optimum space-time yield, it is
advantageous to bring the reaction mixture to the reaction
temperature before it is fed into the continuously operated
suspension reactor.
[0026] The parameters catalyst concentration, temperature, and
residence time in the reactor can be used to adjust the content of
trans,trans isomer in the product. In this way, products with a low
proportion of trans,trans isomer, particularly with a proportion
between 17 and 24%, can be achieved. For example, at a given
temperature and catalyst concentration, the proportion of
trans,trans isomer in the product can be adjusted by adapting the
residence time of the reaction mixture in the reactor.
[0027] In the process according to the invention, the catalyst can
be conveyed through the reactor or the reactor cascade together
with the reaction mixture. The product mixture is then usually
cooled, the excess hydrogen is removed, and the catalyst is
filtered off. Preferably, after the product solution has been
separated off, the catalyst is reused.
[0028] With regard to catalyst activity and service life, it is
advantageous to wash the catalyst with a solvent after the product
solution has been separated off, which enables the catalyst surface
to be freed from deposits of higher molecular weight reaction
products.
[0029] If the catalyst activity decreases after a relatively long
period of operation, some of the catalyst can be removed from the
system and replaced by fresh catalyst, meaning that a plant for
carrying out the process according to the invention can be operated
with constant average catalyst activity and constant
throughput.
[0030] The invention is illustrated in more detail below by
reference to examples. The examples represent individual
embodiments of the invention, but the invention is not limited to
the examples. Those skilled in the art will readily understand that
known variations of the conditions of the following procedures can
be used. Unless otherwise noted, all temperatures are degrees
Celsius and all percentages are percentages by weight.
EXAMPLES
Example 1
[0031] The experiment was carried out in a continuously operated
stirred tank reactor having a reaction volume of 330 ml. A
pulverulent catalyst containing 5% by weight of ruthenium on an
Al.sub.2O.sub.3 support in a catalyst concentration of 5% by weight
was introduced into the stirred-tank reactor. MDA was used in
technical-grade quality (so-called MDA 90/10) with a proportion of
about 10% of higher molecular weight components as a 33% strength
by weight solution in isobutanol. The MDA 90/10-isobutanol mixture
was metered into the reactor from a storage container. The reaction
pressure was kept constant at 150 bar by continually replenishing
hydrogen, and a temperature of 150.degree. C. was set.
[0032] The overflow of the reaction mixture passed into another
container from which samples were taken for analysis. The samples
were analyzed using gas chromatography. By varying the discharge
capacity of the dosing pump, various average residence times were
set. For comparison, the residence time was set in one case so that
the conversion of MDA, based on the amount of MDA used, was only
91.5%. In this case, the proportion of trans,trans isomer of the
resulting PACM was below the desired range.
[0033] The contents of MDA, [H.sub.6]-MDA (i.e.,
4-aminocyclohexyl-4-amino- -phenylmethane), PACM and the proportion
of trans,trans-PACM (t,t proportion) are given in Table 1.
1 TABLE 1 Single-stage Single-stage Single-stage stirred-tank
stirred-tank stirred-tank reactor reactor reactor (comparison)
Temperature [.degree. C.] 150 150 150 Residence time 61 29 12 [min]
Throughput [g of 247 494 715 PACM per l and h] PACM [%] 88 81 48 tt
proportion [%] 24 17 14 [H.sub.6]-MDA [%] 1.5 8.2 34 MDA [%] 0.1
0.1 8.5 Higher molecular 10 10 10 weight components [%]
Example 2
[0034] The experiment was carried out under the same conditions as
in Example 1, but the residence time was shortened so that
conversion was only partial. The product was then conveyed through
the reactor two more times. The product corresponds to the product
obtained in a cascade of three stirred-tank reactors.
[0035] The contents of MDA, [H.sub.6]-MDA, and PACM and the
proportion of trans,trans-PACM (t,t proportion) are given in Table
2.
2 TABLE 2 Single-stage stirred-tank Three-stage stirred- reactor
tank reactor Temperature [.degree. C.] 150 150 Residence time 51 45
[min] Throughput [g of 247 330 PACM per l and h] PACM [%] 88 89 tt
proportion [%] 24 19 [H.sub.6]-MDA [%] 1.5 0.9 MDA [%] 0.1 0.1
Higher 10 10 molecular weight components [%]
[0036] The experiment shows that when a cascade of three reactors
is used, a very high conversion of MDA and a trans,trans proportion
in the region of 20% can be simultaneously achieved and a high
space-time yield is also achieved.
Comparative Example
[0037] Discontinuously operated stirred-tank reactor The experiment
was carried out in a discontinuously operated stirred-tank reactor
having a reaction volume of 330 ml. A pulverulent catalyst
comprising 5% by weight of ruthenium on an Al.sub.2O.sub.3 support
in a catalyst concentration of 5% by weight was introduced into the
stirred-tank reactor. MDA was used in a technical-grade quality
(so-called MDA 90/10) with a proportion of about 10% of higher
molecular weight components as a 33% strength by weight solution in
isobutanol. 330 ml of the MDA 90/10-isobutanol mixture were metered
into the reactor from a storage container. The reactor pressure was
kept constant at 150 bar by continually replenishing hydrogen, and
a temperature of 150.degree. C. was set.
[0038] Samples were taken for analysis from the reaction mixture
after various residence times of the reaction mixture in the
reactor. The samples taken were analyzed using gas chromatography.
The contents of MDA, [H.sub.6]-MDA, and PACM and the proportion of
trans,trans-PACM (t,t proportion) are given in Table 3.
3 TABLE 3 Discontinuous Discontinuous Discontinuous stirred-tank
stirred-tank stirred-tank reactor reactor reactor Temperature
[.degree. C.] 150 150 150 Residence time 51 111 171 [min]
Throughput [g of 282 131 81 PACM per l and h] PACM [%] 84 85 81 tt
proportion [%] 14 24 37 [H.sub.6]-MDA [%] 3.1 0.2 0.3 MDA [%] 0.5
0.1 0 Higher molecular 12 14 18 weight components [%]
[0039] The experiment shows that a product with a proportion of 20%
trans,trans isomer can be obtained at a significantly lower
space-time yield than for continuous hydrogenation in a cascade of
three reactors.
* * * * *