U.S. patent application number 11/931134 was filed with the patent office on 2008-10-23 for hydrogenation and dehydrogenation processes and catalysts therefor.
This patent application is currently assigned to Total Petrochemicals Research Feluy. Invention is credited to Jean-Pierre Dath, Walter Vermeiren.
Application Number | 20080257784 11/931134 |
Document ID | / |
Family ID | 8180652 |
Filed Date | 2008-10-23 |
United States Patent
Application |
20080257784 |
Kind Code |
A1 |
Dath; Jean-Pierre ; et
al. |
October 23, 2008 |
HYDROGENATION AND DEHYDROGENATION PROCESSES AND CATALYSTS
THEREFOR
Abstract
A process for hydrogenating unsaturations in petrochemical
feedstocks, the process comprising contacting the petrochemical
feedstock, including at least one component having unsaturations,
and hydrogen with a catalyst comprising at least one Group Ia, Ib,
IIb, VIb, VIIb or VIII metal on a support of an alkaline earth
metal silicate having a surface area of at least 30 m.sup.2/g at a
temperature of from 0 to 250.degree. C. and a pressure of from 3 to
50 barg.
Inventors: |
Dath; Jean-Pierre; (Beloeil,
BE) ; Vermeiren; Walter; (Houthalen, BE) |
Correspondence
Address: |
FINA TECHNOLOGY INC
PO BOX 674412
HOUSTON
TX
77267-4412
US
|
Assignee: |
Total Petrochemicals Research
Feluy
Seneffe (Feluy)
BE
|
Family ID: |
8180652 |
Appl. No.: |
11/931134 |
Filed: |
October 31, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10484417 |
Jul 6, 2004 |
7294604 |
|
|
PCT/EP02/07947 |
Jul 16, 2002 |
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11931134 |
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Current U.S.
Class: |
208/134 ;
208/143; 502/439 |
Current CPC
Class: |
B01J 35/108 20130101;
B01J 23/58 20130101; B01J 23/44 20130101; B01J 23/40 20130101; B01J
23/74 20130101; C10G 45/46 20130101; B01J 23/02 20130101; B01J
35/1014 20130101; C10G 45/34 20130101; B01J 35/08 20130101; B01J
21/16 20130101 |
Class at
Publication: |
208/134 ;
208/143; 502/439 |
International
Class: |
C10G 35/06 20060101
C10G035/06; C10G 45/34 20060101 C10G045/34; B01J 32/00 20060101
B01J032/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2001 |
EP |
01 202 732.2 |
Claims
1. A process for hydrogenating unsaturations in a petrochemical
feedstock, the process comprising contacting the petrochemical
feedstock, including at least one component having unsaturations,
and hydrogen with a catalyst comprising at least one Group Ia, Ib,
IIb, VIb, VIb or VIII metal impregnated on a support of a
crystalline calcium silicate having a surface area of at least 30
m.sup.2/g, the support being in the form of substantially spherical
particles having a mean diameter of from 10 to 200 microns and
comprising pores in the particles having a diameter of from 100 to
2000 Angstroms, at a temperature of from 0 to 550.degree. C. and a
pressure of from 3 to 150 barg.
2. A process according to claim 1 wherein the calcium silicate has
the chemical composition Ca.sub.6Si.sub.6O.sub.17(OH).sub.2.
3. A process according to claim 1 wherein the support has a
basicity corresponding to a pH of greater than 7.5.
4. A process according to claim 1 wherein said catalyst comprises
palladium impregnated onto the support in an amount of from 0.01 to
10 wt. % based on a weight of the supported catalyst.
5. A process according to claim 1 wherein the petrochemical
feedstock is passed over the catalyst at a liquid hourly space
velocity of from 0.1 to 100 h.sup.-1.
6. A process according to claim 1 wherein the molar ratio of
hydrogen to the at least one component having unsaturations which
is hydrogenated is from 0.7 to 200.
7. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises
butadiene in a C4 stream.
8. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises at
least one of vinyl acetylene and ethyl acetylene in a C4
stream.
9. (canceled)
10. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises at
least one of methyl acetylene and propadiene in a C3 stream.
11. (canceled)
12. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises at
least one of a diolefin and an unsaturated aromatic in pyrolysis
gasoline.
13. (canceled)
14. (canceled)
15. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises
phenyl acetylene in a styrene stream.
16. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated comprises
olefins in an aromatic rich fraction.
17. (canceled)
18. (canceled)
19. A process according to claim 1 wherein the support is in the
form of substantially spherical particles having a mean diameter of
from 10 to 200 microns and comprising pores in the particles having
a diameter of from 100 to 2000 Angstroms.
20. (canceled)
21. A process according to claim 1 wherein the support has a
surface area of from 30 to 200 m.sup.2/g.
22. (canceled)
23. A process according to claim 1 wherein the petrochemical
feedstock is passed over the catalyst at a liquid hourly space
velocity of from 1 to 100 h.sup.-1, an inlet temperature of from 0
to 250.degree. C. and a pressure of from 3 to 50 barg.
24. (canceled)
25. A process according to claim 1 wherein the at least one
component having unsaturations which is hydrogenated is selected
fi-n the group consisting of butadiene in a C4 stream; at least one
of methyl acetylene and propadiene in a C3 stream; at least one of
a diolefin and an unsaturated aromatic in pyrolysis gasoline; at
least one of a diene and an alkyne in pyrolysis gasoline; phenyl
acetylene in a styrene stream; and an alpha-olefin in an aromatic
rich fraction.
26-29. (canceled)
30. (canceled)
31. A process for dehydrogenating or reforming a hydrocarbon
feedstock comprising contacting the catalyst of claim 1 with said
feedstock under conditions effective to dehydrogenate or reform
said feedstock.
32-33. (canceled)
34. A catalyst support comprising a crystalline calcium silicate of
molecular formula 6CaO.6SiO.sub.2.H.sub.2O having a surface area of
at least 30 m.sup.2/g, the Support being in the form of
substantially spherical particles having a mean diameter of from 10
to 200 microns and pores in the particles having a diameter of from
100 to 2000 Angstroms, wherein a catalyst is produced by
impregnating at least one Group Ia, Ib, IIb, VIb, VIIb or VIII
metal on the calcium silicate support.
35. (canceled)
36. (canceled)
37. (canceled)
38. (canceled)
39. (canceled)
40. The process according to claim 1 wherein the at least one
component comprises at least one vinyl acetylene and an ethyl
acetylene in a C.sub.4 stream.
41. The process according to claim 1 wherein the C.sub.4 stream is
from a FCC unit, a visbreaker, a coker, or a steam cracker.
42. (canceled)
43. The process according to claim 25 wherein the C.sub.3 stream is
from a steam cracking unit.
44. (canceled)
45. (canceled)
46. The process according to claim 12 wherein the pyrolysis
gasoline is from a steam cracking unit, a coker unit, a visbreaker,
or comprises a light cracked naphtha from a FCC unit.
47. (canceled)
48. The process according to claim 36 wherein the at least one
component comprises an olefin in an aromatic rich fraction.
49. (canceled)
50. (canceled)
51. (canceled)
52. (canceled)
53. (canceled)
54. (canceled)
55. A process for dehydrogenating or reforming a hydrocarbon
feedstock using the catalyst of claim 1 comprising contacting said
catalyst with said feedstock under conditions effective to
dehydrogenate or reform said feedstock.
Description
[0001] The present invention relates to a process for hydrogenating
unsaturated petrochemical feedstocks, in particular a process for
the selective hydrogenation of such feedstocks. The present
invention also relates to a process for dehydrogenating
petrochemical feedstocks. The present invention also relates to a
catalyst, in particular a catalyst for use in such a process.
[0002] There are a number of known processes for the hydrogenation
of unsaturated hydrocarbons. For most applications, the
hydrogenation must be carried out in a selective manner, i.e. some
unsaturated hydrocarbons have to be hydrogenated while other
unsaturated hydrocarbons may not be hydrogenated. Among the pure
hydrocarbons, three kinds of unsaturated hydrocarbons can be
considered: (1) multiple unsaturated hydrocarbons are alkynes with
triple bonds, diolefins with two double bonds or even multiple
olefins with more double bonds; (2) unsaturated hydrocarbons with
only one double bond; and (3) aromatic unsaturated hydrocarbons,
having an aromatic nucleus. Selective hydrogenation means that only
one or two of the three unsaturates are reduced. Very important
industrial applications of hydrogenation are: (1) removal of
impurities from steam cracker product streams, for example
selective hydrogenation of multiple unsaturated hydrocarbons in
olefin rich streams, or selective hydrogenation of multiple
unsaturates and unsaturated hydrocarbons from aromatic rich
streams, and (2) hydrogenation of macromolecules, for example
hydrocarbon solvents and base oils, polyalpha-olefins and even
resins, polymers and copolymers.
[0003] Heterogeneous hydrogenation catalysts contain an active
metal compound on a carrier.
[0004] Among the active metal compounds are Group IIb, VIb, VIIb
and VIII element compounds. They can be in the metallic state, in
an oxidic state, in a partially reduced oxide state or even in a
sulphided or partially sulphided state. Also metallic Group Ia
metals are known to be active hydrogenation catalysts. The most
preferred metals or metal compounds are those of Pd, Pt, Ni, Rh,
Co, Fe, Cu, Ir, Ru, Os, W, Mo and Na or K. All these active
hydrogenation catalysts can also exhibit isomerisation activity to
some extent. It is known that in particular Na, K, Fe, Pd and Ni
metals catalyse double bond migration, while Pt and Cu are much
less active isomerisation catalysts. Activity and selectivity of
selective hydrogenation catalysts can still further be improved by
employing bimetallics or bimetallic compounds. Typical examples are
CoMo, NiW and NiMo sulphided catalysts used for hydrotreatment.
Other examples used for selective hydrogenation are: Cu--Pd,
Cu--Ni, Cu--Co, Cu--Pt, Fe--Pd, Co--Pd, Ni--Pd, Pt--Pd, Ag--Pd,
Fe--Pt, Ni--Pt, Pt--Sn, Pt--Pb, Pd--Sn, Pd--Pb, Au--Pd and many
others.
[0005] It is known that activity and selectivity can also be
influenced by the characteristics of the carrier for the metal
compound. The carrier can influence the dispersion of the metal or
metal compound, the particle size of the metal of metal compound
and the electronic properties of the metal or metal compound.
[0006] Known carriers include carbon, alumina, silica, titania,
zirconia, salts of alkaline earth metals and zeolites or molecular
sieves. The acid-base properties of the carrier can be very
important for several reasons. The carrier properties can influence
the dispersion of the metal or metal compound, its electronic
properties and hence its activity and selectively. Moreover, when
the carrier is not completely covered with metal or metal compound,
the remaining acid and/or basic sites may influence the catalytic
behaviour of the catalyst. When highly unsaturated hydrocarbons are
to be hydrogenated, they will interact strongly with acidic
carriers whereas they will interact little with basic carriers.
Even when hydrogenation needs high temperature, site reactions such
as acid catalysed isomerisation or cracking can occur. It is known
that addition of basic compounds during hydrogenation or adding
basic metal compounds on the carrier do increase catalytic
performance. Known basic carriers are salts of alkaline earth
metals. However, they develop only very low surface areas.
[0007] A number of catalysts for selective hydrogenation of
unsaturated hydrocarbons are available commercially. Such catalysts
comprise, for example palladium on an alumina support, palladium on
an activated carbon support, nickel tungsten on an alumina support
and palladium on a barium sulphate support.
[0008] In complete contrast to the hydrogenation process, it is
also known to dehydrogenate hydrocarbons. For example, it is known
in the art that dehydrogenation catalysts for the dehydrogenation
of light paraffins such as propane and butane primarily employ
supported platinum, nickel or chromium. In such supported platinum
catalysts, the platinum is present as a metal and is often promoted
with tin. Chromium-based catalysts contain chromium oxide as the
active phase. The nickel-based catalysts mainly employ nickel in
the form of sulphide which is present on the support. For these
three catalyst types it is known in the art that the carrier of the
active phase has a very important effect on catalyst
performance--the activity, the selectivity and the stability are
all influenced by the support. Often, these three kinds of
catalysts are supported on alumina-type carriers which have been
modified by the addition of one or more alkali metal or alkaline
earth metal compounds, which tend to moderate the acidity of the
alumina in the carrier and hence increase the selectivity and the
potential lifetime of the catalyst. On the other hand, the active
metal compound may be supported on a spinel-like carrier such as
MgAl.sub.2O.sub.4 or ZrO.sub.2 which are less acidic than
alumina-type carriers and which exhibit a high thermal stability.
The property of high thermal stability is very important, since
dehydrogenation reactions typically require a temperature of from
500 to 630.degree. C.
[0009] Another catalytic dehydrogenation process is reforming which
is a very important refinery application, in which the main goal is
to dehydrogenate alkyl cycloparaffins into aromatics with
co-production of hydrogen. Conventional reforming catalysts
typically comprise platinum supported on an acidified alumina
carrier. The acidic function is required when isomerisation and
dehydrocyclisation are desired to convert additional paraffins into
isomers and aromatics. There is an interest in the art to convert
only paraffins with at least 6 carbon atoms into aromatic compounds
with co-production of hydrogen. It is known in the art that this
may be done over a catalyst comprising a basic zeolite carrier
impregnated with platinum. Since there are no acidic sites
associated with the basic zeolite carrier, competing reactions such
as isomerisation and hydrocracking are suppressed, resulting in a
very high selectivity for the production of aromatic compounds.
[0010] However, there is a need in the art for improved
dehydrogenation catalysts, and in particular carriers for such
dehydrogenation catalysts.
[0011] A huge variety of naturally occurring and synthetically
produced silicates are known in the art.
[0012] U.S. Pat. No. 3,806,585 discloses the production of a
hydrous calcium silicate composed preponderantly of xonotlite in
the shape of rod crystals which is described as having outstanding
refractory properties, whereby moulded bodies comprised primarily
of xonotlite provide strength unattained by other inorganic
materials. The specification discloses that hydrous calcium
silicate of the xonotlite type has use in construction as a fire
proof coating material, as a fire proof moisture retaining material
and as a potential filler for plastics and rubber products.
[0013] U.S. Pat. No. 3,804,652 discloses a method of producing
calcium silicate products, such as drain pipes and insulating
material, to form tobermorite having the empirical formula
5CaO.6SiO.sub.2.5H.sub.2O.
[0014] U.S. Pat. No. 3,928,539 discloses a method of producing
hydrous calcium silicates such as xonotlite, tobermorite and the
like.
[0015] U.S. Pat. No.3,915,725 discloses a process for producing
hollow spherical aggregates of xonotlite, which aggregates are
employed to form shaped articles.
[0016] U.S. Pat. No.4,298,386 discloses the production of globular
secondary particles of the woolastonite group of calcium silicate
crystals, including woolastonite and xonotlite.
[0017] U.S. Pat. No.4,689,315 discloses the production of
amorphous, approximately spherical silica particles obtained by the
acidic hydrolysis of an approximately spherical synthetic calcium
silicate. The resultant silica particles, obtained by such acid
hydrolysis, are disclosed as being particularly suitable for use as
catalyst support. The starting material may comprise spherical
synthetic calcium silicates such as xonotlite, tobermorite and/or
calcium silicate hydrate, which are then treated with an aqueous
acid having a pH of from 0.6 to 3 to produce the resultant silica
particles for use as a catalyst support.
[0018] U.S. Pat. No.4,849,195 discloses synthetic substantially
spherical crystal aggregates of xonotlite. The aggregates can be
mixed with inert particles, for example to produce thermal
insulation products. Alternatively, as for U.S. Pat. No.4,689,315
described above, the aggregates of xonotlite can be used as
starting material for acid extraction of calcium atoms in order to
obtain silica.
[0019] The present invention in one preferred aspect aims to
provide an improved method of selectively hydrogenating unsaturated
petrochemical feedstocks.
[0020] Accordingly, the present invention provides a process for
hydrogenating unsaturations in petrochemical feedstocks, the
process comprising contacting the petrochemical feedstock,
including at least one component having unsaturations, and hydrogen
with a catalyst comprising at least one Group Ia, Ib, IIb, VIb,
VIIb or VIII metal on a support of an alkaline earth metal silicate
having a surface area of at least 30 m.sup.2/g at a temperature of
from 0 to 550.degree. C. and a pressure of from 3 to 150 barg.
[0021] Preferably, the at least one petrochemical feedstock is
passed-over the catalyst at an LHSV of from 1 to 100 h.sup.-1.
[0022] The molar ratio of hydrogen to the at least one component
having unsaturations to be selectively hydrogenated may be from 0.7
to 200.
[0023] The present invention also provides a process for
hydrogenating unsaturations in petrochemical feedstocks, the
process comprising contacting the petrochemical feedstock,
including at least one component having unsaturations, and hydrogen
with a catalyst comprising at least one Group Ia, Ib, IIb, VIb,
VIIb or VIII metal on a support of a crystalline calcium silicate
having the chemical composition
Ca.sub.6Si.sub.6O.sub.17(OH).sub.2.
[0024] The present invention further provides a catalyst comprising
at least one Group Ia, Ib, IIb, VIb, VIIb or VIII metal on a
crystalline calcium silicate support having a surface area of at
least 30 m.sup.2/g, the support being in the form of substantially
spherical particles and pores in the particles having a diameter of
from 100 to 2000 Angstroms.
[0025] Preferably, the particles have a mean diameter of from 10 to
200 microns.
[0026] The catalyst may be used, in accordance with the invention,
in a process for hydrogenating an unsaturated hydrocarbon feedstock
or in a process for dehydrogenating or reforming a hydrocarbon
feedstock.
[0027] The present invention yet further provides a catalyst
comprising a metal on a support comprising a crystalline calcium
silicate of molecular formula 6CaO.6SiO.sub.2.H.sub.2O.
[0028] Preferably, the metal comprises at least one metal selected
from Groups Ia, Ib, IIb, VIb, VIIb and VIII of the periodic
table.
[0029] The present invention still further provides the use of a
crystalline calcium silicate of molecular formula
6CaO.6SiO.sub.2.H.sub.2O as a catalyst support.
[0030] The present invention is at least partly predicated on the
surprising discovery that a basic hydrated crystalline calcium
silicate when used as a catalyst support can yield hydrogenation
catalysts for selective hydrogenation of petrochemical feedstocks
having high activity and selectivity. This is all the more
surprising since xonotlite-type materials have been known for a
number of years but to the applicant's knowledge there has been no
disclosure or suggestion in the prior art of using xonotlite-type
materials as catalysts or catalyst carriers. Rather, as disclosed
in for example U.S. Pat. No. 4,689,315 as discussed above,
xonotlite has been proposed in the prior art for use as a starting
material for the production of silica, where the chemical
composition and structure of the xonotlite is destroyed in the
preparation of the silica particles by acid hydrolysis.
[0031] The present invention is also at least partly predicated on
the surprising discovery that a basic hydrated crystalline calcium
silicate comprising xonotlite is a is a suitable carrier for
dehydrogenation and reforming reactions because at temperatures of
up to 650.degree. C., such a basic carrier has high temperature
stability, in that the carrier retains its crystallinity and
substantially retains its pore volume and surface area.
[0032] Preferred embodiments of the present invention will now be
described in greater detail by way of example only.
[0033] The catalyst of the present invention preferably comprises a
supported noble metal catalyst.
[0034] The catalyst of the present invention comprises at least one
Group Ia, Ib, IIb, VIb, VIIb or VIII metal, such as Pd, Co, Rh, Ru,
Ni, Mo, W, Fe, Cu, Na or K or a combination thereof with palladium
being particularly preferred.
[0035] The metal or metals may be in the metallic state, in an
oxidic state, in a partially reduced oxide state, or in a sulphided
or partially sulphided state. Optionally, bi-metallic metals or
bi-metallic compounds may be incorporated into the hydrogenation
catalyst, such as CoMo, NiW, and NiMo sulphided catalyst for
hydro-treatment and, for selective hydrogenation, Cu--Pd, Cu--Ni,
Cu--Co, Cu--Pt, Fe--Pd, Co--Pd, Ni--Pd, Pt--Pd, Ag--Pd, Fe--Pt,
Ni--Pt, Pt--Sn, Pt--Pb, Pd--Sn, Pd--Pb and Au--Pd.
[0036] The preferred catalyst support is a basic alkaline earth
metal silicate with a very open and accessible pore structure. A
most preferred catalyst support comprises a synthetic crystalline
hydrated calcium silicate having a chemical composition of
Ca.sub.6Si.sub.6O.sub.17(OH).sub.2 which corresponds to the known
mineral xonotlite (having a molecular formula
6CaO.6SiO.sub.2.H.sub.2). The catalyst support preferably has a
spherical morphology with a mean diameter of the spherical
particles being from 10 to 200 .mu.m. The support has a very open
structure comprising an outer shell with a very close-crystal
structure surrounding an open inner structure. This may be referred
to as an egg shell like structure. The outer shell is formed of
interlocked ribbon-shaped crystals yielding regular and homogeneous
surface properties. The outer shell is provided with pore openings
up to 2000 Angstroms, more preferably from 100 to 1000 Angstroms,
in diameter, This provides a good pore structure with high pore
volume.
[0037] Preferably, the support has a specific surface area well
above 10 m.sup.2/g, ranging from 30 to 200 m.sup.2/g, more
preferably from 40 to 90 m.sup.2/g.
[0038] The support material is preferably pH basic. More
preferably, the support material has a minimum basicity
corresponding to a pH of greater than 7.5. The pH may be measured
when 4 wt % of the support material is immersed in water.
[0039] Generally, a synthetic hydrated calcium silicate is
synthesised hydrothermally under autogeneous pressure. A
particularly preferred synthetic hydrated calcium silicate is
available in commerce from the company Promat of Ratingen in
Germany under the trade name Promaxon D. This material exhibits
some basicity due to the presence of calcium, and in a 4% by weight
dispersion in water, the pH reaches a value of around 10. The
specific composition of the preferred synthetic hydrated calcium
silicate is specified in Table 1.
[0040] In order to demonstrate the thermal stability of xonotlite,
and therefore the applicability of xonotlite as a carrier for
dehydrogenation and reforming reactions, commercial xonotlite Bold
under the trade name Promaxon D was calcined in ambient air at a
relative humidity of about 50% at two different temperatures,
namely 650.degree. C. and 750.degree. C., each for a period of 24
hours. The initial xonotlite had a crystalline phase
Ca.sub.6Si.sub.6O.sub.17(OH).sub.2 with a BET surface area of 51
m.sup.2/gram and a pore volume (of less than 100 nanometers) of
0.35 ml/gram. After calcination at 650.degree. C., the carrier
retained its crystallinity which corresponds to that of xonotlite.
Thus after a 24 hour calcination at 650.degree. C., the crystalline
phase still comprised xonotlite
(Ca.sub.6Si.sub.6O.sub.17(OH).sub.2) with a BET surface area of
47.4 m.sup.2/gram and a pore volume (less than 100 nanometers) of
0.30 ml/gram. After the calcination at 750.degree. C., the carrier
was transformed into wollastonite (having the crystalline phase
CaSiO.sub.3) by losing one water molecule. This made the carrier
less basic. Furthermore, as a result of calcination at 750.degree.
C. the carrier lost much of its pore volume, being reduced to 0.09
ml/gram (for pore sizes of less than 100 nanometers) and the BET
surface area was correspondingly reduced to 38 m.sup.2/gram.
[0041] These results show that xonotlite has utility as a basic
carrier for high temperature reactions in the range of from 500 to
650.degree. C., more particularly from 500 to 630.degree. C., the
typical temperature range for dehydrogenation and reforming
reactions. In these temperature ranges the xonotlite retains its
basicity, resulting in the carrier being suitable for incorporation
in a catalyst for use in reforming reactions.
[0042] The at least one Group Ia, Ib, IIb, VIb, VIIb or VIII metal
is preferably present in an amount of from 0.01 to 10 wt %, more
preferably about 0.5 wt %, based on the weight of the supported
catalyst.
[0043] The catalyst is produced by impregnating the at least one
Group Ia, Ib, IIb, VIb, VIIb or VIII metal on the alkaline earth
metal silicate support. Preferably, an incipient wetness
impregnation technique is employed where the pores of the support
are filled with a volume of solution containing the metal. In this
technique, the dried catalyst is impregnated with a solution of a
salt of the at least one Group Ia, Ib, IIb, VIb, VIIb or VIII
metal, for example a halide of the metal, in particular the Group
VIII metal chloride. The amount of the metal salt is calculated to
provide a desired metal content on the support, for example a metal
content of from 0.01 to 10 wt % based on the weight of the
supported catalyst, most preferably about 0.5 wt % based on the
weight of the supported catalyst. The impregnated solid is dried
first under vacuum and subsequently at elevated temperature.
Finally, the product is calcined, for example at a temperature of
about 250.degree. C. for a period of about 3 hours.
[0044] Alternatively an excess of solution is used during the
impregnation step and the solvent is removed by evaporation.
Depending on the properties of the impregnation solution and the
carrier the active metal phase can have different locations: (1)
the metal or metal compound is concentrated in a thin layer close
to the external surface, this may be referred to as an "egg-shell
mode", (2) the metal or metal compound is concentrated in a thin
layer below the surface, but not penetrating to the centre, this
may be referred to as an "egg-white mode", (3) the metal or metal
compound is concentrated in a small zone near the centre of the
particle carrier, this may be referred to as an "egg-yolk mode",
and (4) the metal or metal compound is uniformly distributed
throughout the particle carrier. The way that the metal precursor
will interact with the carrier depends on the isoelectric point
(IEP) which is the pH at which the particle of the carrier in an
aqueous solution has no net charge. At pH's above the IEP, cations
will be adsorbed, because the surface carries a negative charge;
below the IEP, only anions will be adsorbed, because the surface
carries a positive charge. During the contact of the impregnating
solution and the carrier, ion exchange can also occur. The
impregnating solution may be altered by adding complexing agents,
which can change the charge of the metal precursor. In another
technique, competing ions may be added to improve the spreading of
the metal precursor over the carrier.
[0045] In alternative embodiments of the catalyst production
process, the metal may be deposited on the support by ion exchange
or vapour phase deposition.
[0046] The catalyst of the present invention is a heterogeneous
catalyst which may be used in a batch wise or continuous process.
Preferably, the catalyst is used in a fixed bed reactor. A most
preferred process employs a continuously operated fixed bed
reactor.
[0047] In the hydrogenation process, the petrochemical feedstock is
contacted batch-wise or continuously passed over the catalyst at a
selected temperature and pressure. The temperature is preferably
from 0 to 250.degree. C. The total pressure is preferably from 3 to
50 bar. The petrochemical feedstock is preferably contacted with
the catalyst at a liquid hourly space velocity (LHSV) of from 0.1
to 100 h.sup.-1, more preferably from 1 to 100 h.sup.-1.
[0048] The hydrogenation conditions vary dependent on the nature of
the petrochemical feedstock and the process of the invention may be
employed for hydrogenating a variety of different unsaturated
petrochemical feedstocks. Fundamentally, the feedstocks are those
to be selectively hydrogenated where one of two unsaturates is
reduced or one or two of three unsaturates are reduced, the
unsaturates being selected from multiple unsaturated hydrocarbons
such as alkynes with triple bonds, diolefins with two double bonds
or multiple olefins with more double bonds; unsaturated
hydrocarbons with only one double bond; and aromatic unsaturated
hydrocarbons having an aromatic nucleus.
[0049] In a first preferred aspect, the process is used for
selective hydrogenation of butadiene to butenes in crude C4
streams.
[0050] The C4 streams may come from an FCC unit, a visbreaker or a
coker, or may comprise a C4 stream from a steam cracker or a C4
fraction of an ethylene plant. The C4 fraction of an ethylene plant
contains high concentrations of butadiene (typically 25 to 75 wt
%). It is desirable to hydrogenate such butadiene into butenes for
further processing. Moreover, a C4 fraction from which the
butadiene has been removed by conversion or extraction may still
contain residual butadiene. Typically, in this preferred process
the C4 stream containing butadiene is fed over the catalyst
together with hydrogen so as to have a hydrogen/butadiene molar
ratio of from 1 to 10, under process conditions comprising an inlet
temperature of from 20 to 200.degree. C., a total pressure of from
5 to 50 barg and an LHSV of from 1 to 40 h.sup.-1. The reactor
effluent may be recycled in order to control the outlet
temperature. Optionally, several reactors in series may be used
with intermittent cooling and/or injection of hydrogen for improved
control of the hydrogen content in the feedstock.
[0051] In a second preferred aspect of the invention the process
may be employed for selective hydrogenation of vinyl-and ethyl
acetylenes in crude C4 streams. The C4 streams typically come from
steam crackers. The C4 fraction from an ethylene plant contains,
beside the butadiene discussed hereinabove, varying amounts of
vinyl acetylene and ethyl acetylene. These have to be removed
before further processing, such as by extraction or conversion. The
feedstock is fed together with hydrogen over the catalyst, there
being a hydrogen/butadiene molar ratio of from 1 to 10 under
process parameters having an inlet temperature of from 0 to
100.degree. C., a total pressure of from 3 to 35 barg and an LHSV
of from 1 to 40 h.sup.-1. Again, the reactor effluent may be
recycled in order to control the outlet temperature and optionally
several reactors in series may be used with intermittent cooling
and/or injection of hydrogen for improved control of the hydrogen
content in the feed.
[0052] In a third preferred aspect of the invention the process may
be employed for selective hydrogenation of methyl acetylene and
propadiene to propylene in C3 streams. The feedstock typically
comprises a C3 cut from a steam cracking unit, which most typically
is a C3 fraction with high propylene content which is obtained from
an ethylene plant. This fraction contains methyl acetylene and
propadiene. These compounds have to be removed for further
processing of the propylene. In this aspect of the process, the
feedstocks is fed together with hydrogen, at a hydrogen/MAPD molar
ratio of from 0.7 to 5 (MAPD being the total molar content of
methyl acetylene and propadiene) under process parameters
comprising an inlet temperature of from 0 to 100.degree. C., a
total pressure of from 10 to 50 barg and an LHSV of from 10 to 50
h.sup.-1. The reaction may be carried out in a multi-tubular
pseudo-isothermal reactor or in an adiabatic reactor. As for the
other preferred aspects, the reactor effluent may be recycled in
order to control the outlet temperature and optionally several
reactors in series may be used with intermittent cooling and/or
injection of hydrogen in order to provide better control of the
hydrogen content in the feedstock.
[0053] In accordance with a fourth preferred aspect of the
invention, the process of the invention may be employed for the
selective hydrogenation of pyrolysis gasoline, which may also be
known in the art as "first stage" hydrogenation of the pyrolysis
gasoline. The feedstock comprises pyrolysis gasoline from steam
cracking units, coker units or visbreakers. In accordance with this
aspect, diolefins and unsaturated aromatics are converted into the
corresponding olefins and aromatics. The hydrogenated product can
be used as a stable gasoline blending feed or can be further
hydrotreated for the recovery of aromatics. The feedstock is passed
over the catalyst together with hydrogen to provide a
hydrogen/diene molar ratio of from 1 to 10 under the process
parameters of an inlet temperature of from 20 to 200.degree. C., a
total pressure of from 5 to 50 barg and an LHSV of 1 to 20
h.sup.-1. Again, as for the other aspects, the reactor effluent may
be recycled in order to control the outlet temperature and
optionally several reactors in series may be used with intermittent
cooling and/or injection of hydrogen in order to achieve better
control of the hydrogen content in the feedstock.
[0054] In a yet fifth preferred aspect of the invention the process
of the invention is employed for selective hydrogenation of
gasoline fractions. The feedstock may comprise fractions from
pyrolysis gasoline originating from steam cracking units, coker
units or visbreakers and light cracked naphthas from FCC units. In
this aspect, dienes and acetylenes in the gasoline fractions are
selectively removed for the preparation of ethers. The feedstock is
passed over the catalyst together with hydrogen to provide a
hydrogen/diene molar ratio of from 1 to 20, and the process
parameters are an inlet temperature of from 20 to 250.degree. C., a
total pressure of from 5 to 50 barg and an LHSV of from 1 to 20
h.sup.-1.
[0055] In a sixth preferred aspect of the invention, the process of
the invention may be employed for selective hydrogenation of phenyl
acetylene in crude styrene streams. The feedstock comprises crude
styrene. Crude styrene production by dehydrogenation of ethyl
benzene or recovery from pyrolysis gasoline tends to yield styrene
containing small amounts of phenyl acetylene which has to be
removed before further processing. The styrene is fed together with
hydrogen to yield a hydrogen/phenyl acetylene molar ratio of from 1
to 20 over the catalyst at an inlet temperature of from 10 to
150.degree. C., a total pressure of from 5 to 50 barg and an LHSV
of from 10 to 100 h.sup.-1.
[0056] In a seventh preferred aspect of the invention, the process
of the invention is for selective hydrogenation of olefins in
aromatic rich fractions. The feedstocks may comprise aromatic rich
fractions from reforming units, from cokers or from steam cracking
units. Such aromatic rich fractions need to be treated to extract
the aromatics. Before the extraction of the aromatics, the residual
bromine index (which reflects the olefin content) has to be very
low. Any process to reduce the olefin content by hydrogenation
needs to minimize the conversion of the aromatics. Also, a further
reduction of the bromine index in almost pure aromatic fractions
may require a further hydrogenation step which can replace
conventional clay treatment. The feedstock is passed together with
hydrogen over the catalyst at a hydrogen/olefins molar ratio of
from 5 to 100 under process parameters comprising an inlet
temperature of from 5 to 250.degree. C., a total pressure of from 5
to 50 barg and an LHSV of from 5 to 50 h.sup.-1.
[0057] In an eight preferred aspect or the present invention, the
process of the invention may be employed for selective
hydrogenation of petrochemical feedstocks in conjunction with a
reforming process.
[0058] When the crystalline calcium silicate support (such as
xonotlite) is used for a dehydrogenation or reforming catalyst, the
catalyst, as well as the support, comprises at least one Group IIb,
VIb, VIIb or VIII metal such as Pd, Co, Rh, Ru, Ni, Mo, W, Fe, Cu
or a combination thereof. The feedstocks for dehydrogenation may
typically comprise light paraffins, such as propane and butane. The
feedstocks for reforming reactions may typically comprise normal
paraffins and cycloparaffins, such as n-hexane and cyclohexane. The
dehydrogenation and reforming reactions may be carried out at a
temperature of from 500 to 630.degree. C.
[0059] The present invention will now be described with reference
to the following non-limiting Example.
EXAMPLE 1
Catalyst Preparation
[0060] Extrudates of the hydrated crystalline calcium silicate
available in commerce under the Trade name Promaxon D was dried at
a temperature of 500.degree. C. for a period of 3 hours. The dried
support gas then impregnated with a solution of palladium chloride
(PdCl.sub.2) using a wet impregnation technique. In particular,
65.38 g of dried Promaxon D were progressively contacted with 38.23
mol of an aqueous palladium chloride solution, the amount of
solution being selected so as to correspond to the estimated
absorption capacity of the dried Promaxon D. The amount of the
palladium salt was calculated in order to reach a final palladium
content in the resultant catalyst of 0.3 wt %. The impregnated
solid was dried under vacuum for a period of 36 hours at 25.degree.
C. and thereafter dried for a period of 16 hours at a temperature
of 110.degree. C. Finally, the catalyst was calcined at a
temperature of 400.degree. C. for a period of 3 hours.
Selective Hydrogenation of Pyrolysis Gasoline
[0061] An amount of 42.2 g (having a volume of 75 ml) of the
activated catalyst comprising 0.3 wt % Pd on the xonotlite carrier
was transferred under nitrogen into a laboratory scale continuous
trickle bed reactor. The catalyst was then reduced under a flowing
hydrogen stream at 120.degree. C. Thereafter a pyrolysis gasoline
from a steam cracker having the composition and properties
specified in Table 2, was passed through the reactor at an LHSV of
4.92 h.sup.-1 (corresponding to a weight hourly space velocity
(WHSV) of 7.00 h.sup.-1), constituting a mass flow rate of 296 g/h,
together with hydrogen at a flow rate of 40.0 Nl/h. The
hydrogen/diene molar ratio was 4.10. The total pressure was 30 bar
and the inlet temperature was varied from about 45.degree. C. to
about 120.degree. C.
[0062] The composition of the effluent of the reactor was analysed
over the varying inlet temperatures and the results are summarised
in FIG. 1.
[0063] From FIG. 1 it will be seen that for the aromatics content
of the effluent, this was substantially unchanged as compared to
the aromatics content of the feedstock. The olefins content was
increased in the effluent as compared to that in the feedstock.
However, the olefins content tended to decrease with increasing
inlet temperature up to 120.degree. C. For inlet temperatures of
from about 45 to 80.degree. C., the olefins content was about 17 wt
%, decreasing gradually to about 14 wt % at an inlet temperature of
120.degree. C. For the paraffins content, this was increased in the
effluent as compared to the paraffins content of the feedstock. The
paraffins content gradually increased with increasing inlet
temperature. Thus at an inlet temperature of about 45.degree. C.
the paraffins content was about 27 wt %, increasing to a paraffins
content of about 33 wt % at an inlet temperature of about
120.degree. C. Most significantly, the dienes content of the
effluent was significantly reduced as compared to that of the
feedstock, and the dienes content of the effluent tended to
decrease yet further with increasing inlet temperature. Thus at
inlet temperatures of about 45.degree. C., the dienes content was
about 2 wt %, significantly less than the original dienes content
of about 12 wt % and the dienes content of the effluent decreased
to about 0.25 wt % at an inlet temperature of about 120.degree.
C.
[0064] The significant decrease in the dienes content of the
effluent as compared to that of the feedstock, with a corresponding
smaller increase in the paraffins and olefins content, and with the
aromatics content being substantially unchanged, indicates the
effectiveness of the selected hydrogenation catalyst of the present
invention. Thus the catalyst is very active for the hydrogenation
of dienes, and a good selectivity for olefins is maintained.
TABLE-US-00001 TABLE 1 Composition SiO.sub.2 49.0 wt % CaO 42.9 wt
% Al.sub.2O.sub.3 0.2 wt % MgO 0.3 wt % Fe.sub.2O.sub.3 1.1 wt %
Na.sub.2O 0.2 wt % K.sub.2O 0.2 wt % Loss on Ignition 6.1 wt %
Specific area (BET) 50 m.sup.2/g Bulk Density 90 g/l Average
particle size 45 .mu.m
TABLE-US-00002 TABLE 2 Feedstock Composition Paraffins 24.46 wt %
Olefins 10.91 wt % Dienes 12.20 wt % Aromatics 52.43 wt % Diene
Value [gram I.sub.2/100 gram] 18.21 Sulphur 94 wppm Density 0.802
g/ml
* * * * *