U.S. patent application number 17/016271 was filed with the patent office on 2021-01-07 for catalyst for ethylbenzene conversion in a xylene isomerization process.
The applicant listed for this patent is BP Corporation North America Inc.. Invention is credited to Jeffrey Amelse, Philip Nubel.
Application Number | 20210001312 17/016271 |
Document ID | / |
Family ID | |
Filed Date | 2021-01-07 |
United States Patent
Application |
20210001312 |
Kind Code |
A1 |
Nubel; Philip ; et
al. |
January 7, 2021 |
Catalyst for Ethylbenzene Conversion in a Xylene Isomerization
Process
Abstract
The present invention relates to a method for converting a feed
mixture comprising an aromatic C8 mixture of xylenes and
ethylbenzene in which the para-xylene content of the xylene portion
of the feed is less than equilibrium to produce a product mixture
of reduced ethylbenzene content and a greater amount of
para-xylene, which method comprises contacting the feed mixture at
conversion conditions with a first catalyst having activity for the
conversion of ethylbenzene, and with a second catalyst having
activity for the isomerization of a xylene.
Inventors: |
Nubel; Philip; (Naperville,
IL) ; Amelse; Jeffrey; (Batavia, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BP Corporation North America Inc. |
Houston |
TX |
US |
|
|
Appl. No.: |
17/016271 |
Filed: |
September 9, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15771529 |
Apr 27, 2018 |
10799852 |
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PCT/US2016/059115 |
Oct 27, 2016 |
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17016271 |
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62247371 |
Oct 28, 2015 |
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Current U.S.
Class: |
1/1 |
International
Class: |
B01J 29/48 20060101
B01J029/48; B01J 29/40 20060101 B01J029/40; C07C 5/27 20060101
C07C005/27; B01J 21/08 20060101 B01J021/08; B01J 35/00 20060101
B01J035/00 |
Claims
1-8. (canceled)
9. A catalyst composition comprising a ZSM-5 aluminosilicate
zeolite comprising 0.7+/-0.05 weight percent aluminum, wherein the
catalyst composition comprises a hydrogenation metal, wherein the
catalyst composition has activity for the conversion of
ethylbenzene, and wherein crystals of the catalyst composition have
an average particle size of at least about 1 micron.
10. The catalyst composition of claim 9, wherein the
aluminiosilicate molecular sieve comprises about 0.7 weight percent
aluminum.
11. The catalyst composition of claim 9, wherein crystals of the
catalyst composition have an average length between about 5 microns
and 25 microns.
12. The catalyst composition of claim 9, wherein crystals of the
catalyst composition have an average width between about 1 micron
and 10 microns, and an average thickness between about 1 micron and
10 microns.
13. The catalyst composition of claim 9, wherein the
aluminosilicate molecular sieve is on a support.
14. The catalyst composition of claim 13, wherein the support
comprises silica.
15. (canceled)
16. The catalyst composition of claim 9, wherein crystals of the
catalyst composition have an average length in the range of about 5
to about 25 microns, an average width in the range of about 1 to
about 10 microns, and an average thickness in the range of about 1
to about 10 microns.
17. The catalyst composition of claim 9, wherein the hydrogenation
metal is selected from metals of groups VI and VIII.
18. The catalyst composition of claim 9, wherein the hydrogenation
metal includes one or more of molybdenum, platinum, palladium,
rhodium, and ruthenium.
19. The catalyst composition of claim 9, wherein crystals of the
catalyst composition have an average length in the range of about 5
to about 25 microns, an average width in the range of about 1 to
about 10 microns, and an average thickness in the range of about 1
to about 10 microns; and the hydrogenation metal includes one or
more of molybdenum, platinum, palladium, rhodium, and
ruthenium.
20. The catalyst composition of claim 9, wherein crystals of the
catalyst composition have an average length in the range of about 5
to about 25 microns, an average width in the range of about 1 to
about 10 microns, and an average thickness in the range of about 1
to about 10 microns; and the hydrogenation metal is molybdenum.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a catalyst composition, its
preparation, and its use in ethylbenzene dealkylation.
BACKGROUND OF THE INVENTION
[0002] Hydrocarbon mixtures containing C.sub.8+ aromatics are
by-products of certain oil refinery processes including, but not
limited to, catalytic reforming processes. These hydrocarbon
mixtures typically contain up to about 30 weight percent (wt. %)
C.sub.9+ aromatics, up to about 10 wt. % non-aromatics, up to about
50 wt. % ethylbenzene, the balance (e.g., up to about 100 wt. %)
being a mixture of xylene isomers. Most commonly present among the
C.sub.8 aromatics are ethylbenzene ("EB"), and xylene isomers,
including meta-xylene ("mX"), ortho-xylene ("oX"), and para-xylene
("pX"). Typically, when present among the C.sub.8 aromatics,
ethylbenzene is present in a concentration of up to about 20 wt. %
based on the total weight of the C.sub.8 aromatics. The three
xylene isomers typically comprise the remainder of the C.sub.8
aromatics, and are present at an equilibrium weight ratio of about
1:2:1 (oX:mX:pX).
[0003] The separation of xylene isomers has been of particular
interest because of the usefulness of para-xylene in the
manufacture of terephthalic acid which is used in the manufacture
of polyester fabric. However, because the boiling points of
ethylbenzene (EB), ortho-xylene (oX), meta-xylene (mX) and
para-xylene (collectively referred to as "C.sub.8 aromatics") are
close, they are difficult to separate by fractional distillation.
Ethylbenzene can be converted to other products, which can be
removed from the C.sub.8 aromatics by fractional distillation.
[0004] For example the para-xylene production unit may contain a
catalyst reactor for pretreatment of a C.sub.8 aromatic feed to
reduce the amount of ethylbenzene in the feed by ethylbenzene
conversion. The ethylbenzene may be selectively eliminated from the
C.sub.8 aromatics via dealkylation to provide benzene and
ethane.
[0005] In ethylbenzene dealkylation it is a primary concern to
ensure not just a high degree of conversion to benzene but also to
avoid xylene loss. Xylenes may typically be lost due to
transalkylation, e.g. between benzene and xylene to give toluene,
or by addition of hydrogen to form, for example, alkenes or
alkanes.
[0006] It is therefore the aim of the present invention to provide
a catalyst that will convert ethylbenzene to benzene with a high
selectivity without xylene loss.
SUMMARY OF THE INVENTION
[0007] The present invention relates to a catalyst system suitable
for the isomerization of xylene and conversion of ethylbenzene in a
feed containing xylene and ethylbenzene comprising a first catalyst
having activity for the conversion of ethylbenzene, a second
catalyst having activity for the isomerization of xylene.
[0008] The present invention also relates to a method for
converting a feed mixture comprising an aromatic C.sub.8 mixture of
xylenes and ethylbenzene in which the para-xylene content of the
xylene portion of the feed is less than equilibrium to produce a
product mixture of reduced ethylbenzene content and a greater
amount of para-xylene, which method comprises contacting the feed
mixture at conversion conditions with a first catalyst having
activity for the conversion of ethylbenzene, and with a second
catalyst having activity for the isomerization of a xylene.
[0009] The present invention provides a two component catalyst
system for isomerizing a feed containing an aromatic C.sub.8
mixture of ethylbenzene and xylene in which the para-xylene is less
than at thermal equilibrium which comprises a first catalyst having
activity for the conversion of ethylbenzene, and a second catalyst
having activity for the isomerization of a xylene.
[0010] The present invention includes a process for isomerizing a
feed containing an aromatic C.sub.8 mixture of ethylbenzene and
xylene in which the para-xylene is less than at thermal equilibrium
which comprises contacting the feed under isomerization conditions
with a two component catalyst system including component (1) and
component (2), wherein component (1) comprises a catalyst having
activity for the conversion of ethylbenzene, and component (2)
comprises a catalyst having activity for the isomerization of a
xylene and wherein the component (2) is located in the system below
component (1) relative to a flow of the ethylbenzene/xylene feed
through the catalyst system.
[0011] Preferably, the first catalyst having activity for the
conversion of ethylbenzene is, an acidic molecular sieve which is
characterized by a constraint index in the approximate range of
about 1 to about 12, more preferably it is a zeolite, preferably a
crystalline aluminosilicate zeolite having a particle size of at
least about 1 micron. In one embodiment of the invention, the EB
conversion catalyst may contain a hydrogenation metal selected from
metals of groups VI and VIII of the Periodic Table of Elements.
[0012] The second catalyst having activity for the isomerization of
xylene is preferably, an acidic molecular sieve which is
characterized by a constraint index in the approximate range of
about 1 to about 12. Preferred molecular sieves are borosilicate
molecular sieves or ZSM-type zeolite molecular sieves. The
molecular sieve used is preferably dispersed on alumina, silica or
another suitable matrix. In one embodiment of the invention, the
xylene isomerization catalyst may contain a hydrogenation metal
selected from metals of groups VI and VIII of the Periodic Table of
Elements.
[0013] In one embodiment what is provided is a process for
isomerizing a feed stream comprising xylenes and ethylbenzene, the
process comprising:
[0014] contacting the feed stream with a first catalyst in a
dual-bed catalyst system to produce a first effluent stream;
and
[0015] contacting the first effluent stream with a second catalyst
in the dual-bed catalyst system to produce a second effluent
stream,
[0016] wherein the first catalyst comprises an aluminosilicate
molecular sieve with up to 0.8 weight percent aluminum,
[0017] wherein the first catalyst has activity for the conversion
of ethylbenzene,
[0018] wherein about 20 percent or more of the ethylbenzene in the
feed stream is converted to hydrocarbons other than ethylbenzene,
and
[0019] wherein EBC/Xylene Loss is at least 45 when about 30 percent
of the ethylbenzene is converted
[0020] The aluminosilicate molecular sieve comprises about
0.7+/-0.05 weight percent aluminum. About 33 percent of the
ethylbenzene in the feed stream is converted to hydrocarbons other
than ethylbenzene. The aluminosilicate molecular sieve is on a
support, wherein the support comprises silica. In one embodiment
the support comprises at least 50% silica. In one embodiment the
aluminosilicate molecular sieve is ZSM-5 aluminosilicate zeolite.
In one embodiment, the second catalyst has activity for
isomerization of xylenes.
[0021] In another embodiment, what is provided is a catalyst
composition comprising an aluminosilicate molecular sieve with MFI
framework with up to 0.8 weight percent aluminum,
[0022] wherein the catalyst composition has activity for the
conversion of ethylbenzene, and wherein crystals of the catalyst
composition have average lengths in the range of about 5 to about
25 microns and average widths in the range of about 1 to about 10
microns and average thickness in the range of about 1 to about 10
microns.
[0023] In one embodiment, the aluminosilicate molecular sieve
comprises about 0.5 to 0.8 wt % Al, more preferably 0.7+/-0.05
weight percent Al, and most preferably 0.7 wt % Al. In one
embodiment, the crystals of the catalyst composition have average
lengths between about 5 microns and 25 microns, and have average
widths and thicknesses of between about 1 micron and 10 microns. In
one embodiment, the aluminosilicate molecular sieve is on a
support, wherein the support comprises silica. In one embodiment,
the aluminosilicate molecular sieve is ZSM-5 aluminosilicate
zeolite.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The first catalyst component of the dual-bed catalyst system
is a large-particle aluminosilicate molecular sieve with 0.5-0.8 wt
% Al, more preferably 0.7+/-0.05 wt % Al, and most preferably 0.7
wt % Al content on a predominantly silica support. The first
catalyst comprises about 10% to about 90%, and more preferably from
about 40% to about 80% of the dual-bed catalyst system and is
designed to hydrodeethylate ethylbenzene to ethane and benzene
ahead of the second catalyst.
[0025] The present invention provides a novel means for stabilizing
the xylene isomerization activity of a dual bed xylene
isomerization catalyst system. This invention is useful for
isomerizing a feed containing an aromatic C.sub.8 mixture of
xylenes and ethylbenzene (EB) in which the para xylene content of
the xylene-containing portion of the feed is less than the
equilibrium content, to produce a product stream of reduced
ethylbenzene content and a greater amount of desired para xylene.
Para-xylene is an important hydrocarbon feed material for the
manufacture of terephthalic acid. In the present invention, a novel
ethylbenzene conversion catalyst is provided having higher
ethylbenzene conversion activity.
[0026] The ethylbenzene conversion catalyst is a catalyst that
selectively catalyzes the conversion of ethylbenzene in the feed
mixture to another compound or compounds that can easily be removed
from the product mixture. For example, within the scope of the
invention, ethylbenzene conversion can occur by a deethylation
reaction, whereby the ethylbenzene is catalytically converted to
benzene and a mixture of ethylene and ethane.
[0027] In processes for the manufacture of pure para-xylene, the
para-xylene is separated from a C.sub.8 feed mixture of xylenes and
ethylbenzene using standard methods such as crystallization or
adsorption. After removal of the para-xylene, the mother liquor or
raffinate is recycled and subjected to isomerization to reestablish
a near equilibrium mixture of xylenes. In this isomerization,
process, meta-xylene and ortho-xylene are converted to para-xylene.
However, it is very difficult to separate ethylbenzene from the
xylenes prior to recycle using ordinary separation techniques.
[0028] If the ethylbenzene is not removed, it accumulates in the
process stream to unacceptable levels. Rather than separate
ethylbenzene, most processes for preparing pure para-xylene employ
a means to convert ethylbenzene to compounds that can be removed by
ordinary separation processes, such as, for example, distillation.
The ethylbenzene conversion catalysts described herein serve to
affect such conversion reactions.
[0029] The xylene isomerization catalyst is a catalyst that will
catalyze the conversion of one xylene, such as meta-xylene or
ortho-xylene, to another xylene, such as para-xylene. In
particular, effective xylene isomerization catalysts will isomerize
a mixture of xylenes where the xylenes are present in
non-equilibrium amounts to a mixture containing, or very nearly
containing, the xylenes in equilibrium amounts at the temperature
used for the isomerization reaction. For example, a mixture of
xylenes containing ortho-xylene, meta-xylene and para-xylene, where
the para-xylene is present in less than the equilibrium amount, can
be converted by an effective xylene isomerization catalyst to a
mixture of xylenes where the ortho-, meta- and para-xylenes are
present at or very near their equilibrium amounts.
[0030] This invention is a catalyst system suitable for the
isomerization of a xylene and conversion of ethylbenzene in a feed
containing xylene and ethylbenzene comprising a novel first
catalyst having activity for the conversion of ethylbenzene, and a
second catalyst having activity for the isomerization of a xylene
where the second catalyst is located in the system below the first
catalysts relative to a flow of feed mixture through the catalyst
system.
[0031] This invention is also a method for converting a feed
mixture comprising an aromatic C.sub.8 mixture of xylenes and
ethylbenzene in which the para-xylene content of the xylene portion
of the feed is less than equilibrium to produce a product mixture
of reduced ethylbenzene content and a greater amount of
para-xylene, which method comprises contacting the feed mixture at
conversion conditions with a first catalyst having activity for the
conversion of ethylbenzene, and with a second catalyst having
activity for the isomerization of a xylene, wherein the second
catalyst is positioned below the first catalyst relative to the
flow of the feed mixture through the catalysts.
[0032] Xylene isomerization feeds, processed in accordance with the
invention are any aromatic C.sub.8 mixture containing ethylbenzene
and xylene(s). Generally, such a mixture will have an ethylbenzene
content in the approximate range of about 5 to about 60 weight %,
an ortho-xylene content in the approximate range of about 0 to
about 35 weight %, a meta-xylene content in the approximate range
of about 20 to about 95 weight %, and a para-xylene content in the
approximate range of about 0 to about 15 weight %. The feed in
addition to the above aromatic C.sub.8 mixture can contain
non-aromatic hydrocarbons, such as paraffins and naphthenes. The
paraffins and naphthenes will generally comprise about 0 to about
20 weight % of the feed; generally, the paraffins and naphthenes
will comprise C.sub.8-C.sub.10 paraffins and naphthenes.
[0033] The catalyst system used in accordance with the invention is
multicomponent. The function of the first catalyst component is to
effect conversion of ethylbenzene and C.sub.8-C.sub.10 paraffins
and naphthenes to byproducts which are easily separated from the
C.sub.8 aromatics stream. The function of the second catalyst
component is to effect isomerization of the xylene components in
the feed to thermal equilibrium.
[0034] This invention can be used for, but is not limited to, vapor
phase isomerization of a mixture of xylenes with a
transalkylation-type (i.e., wherein EB is primarily converted via
transalkylation to diethylbenzenes) dual bed catalyst for
stabilizing the xylene isomerization activity of the xylene
isomerization catalyst. The reaction conditions for the method of
this invention are suitably a temperature of about 480.degree. F.
(248.8.degree. C.) to about 1000.degree. F. (537.8.degree. C.),
preferably about 500.degree. F. (260.degree. C.) to about
850.degree. F. (454.4.degree. C.), and more preferably about
600.degree. F. (315.6.degree. C.) to about 800.degree. F.
(426.7.degree. C.); a pressure of about 0 to about 1000 psig,
preferably about 50 to about 600 psig, more preferably about 100 to
about 400 psig, and most preferably about 150 to about 300 psig; a
hydrogen-to-total hydrocarbon mole ratio of from about 0.5:1 to
about 10:1, preferably from about 1:1 to about 10:1, more
preferably from about 1:1 to about 6:1, and most preferably from
about 1:1 to about 3:1. The Weight Hourly Space Velocity (WHSV) may
be in the range of from about 0.5 to about 100, preferably about 2
to about 50, more preferably about 3 to about 20, and most
preferably about 4 to about 14. Hydrogen is typically included to
hydrogenate coke precursors and hence minimize catalyst
deactivation.
[0035] In the present invention, either or both of the EB
conversion and xylene isomerization components may additionally
contain a hydrogenation metal. Such hydrogenation metal may
include, but is not limited to, one or more of molybdenum,
platinum, palladium, rhodium, or ruthenium.
[0036] Even where the EB conversion catalyst component and/or the
xylene isomerization catalyst component additionally contain a
hydrogenation metal, it is expected that a hydrogenation bed, for
example, a molybdenum on alumina catalyst, would still hydrogenate
olefins not hydrogenated over the first catalyst bed, and therefore
reduce the deactivation of the xylene isomerization component, thus
extending its useable life. In general, the xylene isomerization
reaction is carried out in a fixed bed flow reactor containing the
catalyst system described above. In a preferred embodiment the feed
is cascaded over the catalyst system disposed in the reactor in at
least two sequential beds, i.e., the EB conversion catalyst bed,
and then the xylene isomerization catalyst bed. The conversion
process of the invention could also be carried out in separate
sequential reactors wherein the feed would first be contacted with
the EB conversion catalyst in a reactor and the resulting effluent
stream would then be contacted with the xylene isomerization
catalyst in a second reactor.
[0037] Catalyst components one and two (i.e., the EB conversion and
xylene isomerization catalysts, respectively) contain an acidic
molecular sieve which is characterized by a constraint index in the
approximate range of about 1 to about 12. Molecular sieves having
such a constraint index are often grouped as members of the class
of molecular sieves referred to as shape selective. Although an
MFI-type of molecular sieve was used in the EB conversion and
xylene isomerization components of the dual bed catalyst system in
the embodiment of this invention described in the Examples, other
types of molecular sieve catalysts can also be used (e.g., ZSM-11,
ZSM-12, ZSM-35, ZSM-38 and other similar materials).
[0038] The amount of catalysts and the relative amount of catalysts
used in the catalyst system and process of this invention are the
amounts that provide for the desired ethylbenzene conversion and
xylene isomerization at the reaction conditions that are
employed.
[0039] When a molecular sieve is used as a component of the
isomerization or ethylbenzene conversion catalyst, the amount of
molecular sieve can be about 1% to about 100% by weight, more
preferably about 10 to about 70% by weight, with the remainder
preferably being support matrix material such as alumina or silica.
Preferably the support material is silica. The weight ratio of
ethylbenzene conversion catalyst to isomerization catalyst is
suitably about 1:1 to about 6:1. The weight ratio of ethylbenzene
catalyst to hydrogenation catalyst is suitably about 1:1 to about
5:1.
[0040] Ethylbenzene conversion catalysts suitable for use in the
present invention include but are not limited to AI-MFI molecular
sieve dispersed on silica and large particle size molecular sieves,
particularly a ZSM-5-type of molecular sieve having a particle size
of at least about 1 micron, dispersed on silica, alumina,
silica/alumina or other suitable support. The support material is
preferably silica. Suitable catalysts based on a ZSM-type molecular
sieve, for example, ZSM-5 molecular sieves, are described in U.S.
Pat. No. Re. 31,782, which is incorporated herein by reference in
its entirety.
[0041] In one embodiment what is provided is a process for
isomerizing a feed stream comprising xylenes and ethylbenzene, the
process comprising:
[0042] contacting the feed stream with a first catalyst in a
dual-bed catalyst system to produce a first effluent stream;
and
[0043] contacting the first effluent stream with a second catalyst
in the dual-bed catalyst system to produce a second effluent
stream,
[0044] wherein the first catalyst comprises an aluminosilicate
molecular sieve with up to 0.8 weight percent aluminum,
[0045] wherein the first catalyst has activity for the conversion
of ethylbenzene,
[0046] wherein about 20 percent or more of the ethylbenzene in the
feed stream is converted to hydrocarbons other than ethylbenzene,
and
[0047] wherein EBC/Xylene Loss is at least 45 when about 30 percent
of the ethylbenzene is converted.
[0048] The aluminosilicate molecular sieve comprises about
0.7+/-0.05 weight percent aluminum. About 33 percent of the
ethylbenzene in the feed stream is converted to hydrocarbons other
than ethylbenzene. The aluminosilicate molecular sieve is on a
support, wherein the support comprises silica. In one embodiment
the support comprises at least 50% silica. In one embodiment the
aluminosilicate molecular sieve is ZSM-5 aluminosilicate zeolite.
In one embodiment, the second catalyst has activity for
isomerization of xylenes.
[0049] In another embodiment, what is provided is a catalyst
composition comprising an aluminosilicate molecular sieve with MFI
framework with up to 0.8 weight percent aluminum,
[0050] wherein the catalyst composition has activity for the
conversion of ethylbenzene, and
[0051] wherein crystals of the catalyst composition have average
lengths in the range of about 5 to about 25 microns and average
widths in the range of about 1 to about 10 microns and average
thickness in the range of about 1 to about 10 microns.
[0052] In one embodiment, the aluminosilicate molecular sieve
comprises about 0.5 to 0.8 wt % Al, more preferably 0.7+/-0.05
weight percent Al, and most preferably 0.7 wt % Al. In one
embodiment, the crystals of the catalyst composition have average
lengths between about 5 microns and 25 microns, and have average
widths and thicknesses of between about 1 micron and 10 microns. In
one embodiment, the aluminosilicate molecular sieve is on a
support, wherein the support comprises silica. In one embodiment,
the aluminosilicate molecular sieve is ZSM-5 aluminosilicate
zeolite.
[0053] The present invention will now be illustrated by the
following Examples.
EXAMPLES
Example 1
[0054] Five small-scale ZSM-5 zeolite syntheses were performed
using 125-cc Teflon-lined autoclave reactors. The following
reagents were mixed at room temperature: 36-38 grams deionized
water, 0.2-0.4 g sodium aluminum oxide (Alfa Aesar, 28.4 wt % Al),
ethylenediamine (6.25 grams), tetrapropylammonium bromide (2.88
grams), and Nalco 2327 colloidal silica sol (27 grams). The amount
of sodium aluminum oxide was varied (0.20 g, 0.30 g, 0.35 g, or
0.40 g) to obtain different aluminum levels in the ZSM-5 zeolite
product (0.5 wt %, 0.75 wt %, 0.88 wt %, and 1.0 wt %,
respectively). A small amount of aqueous sulfuric acid solution was
added to each mixture to adjust pH to 11.2-11.4. The mixtures were
then charged into an autoclave and heated with agitation by
rotational tumbling inside an oven for 72 hours at 170.degree. C.
After cooling, solid products were collected by filtration, washed
with deionized water, dried and calcined in air for 4 hours at
538.degree. C. The calcined ZSM-5 products were characterized by
ICP (inductively coupled plasma spectroscopy) for elemental
composition and XRD (X-ray diffraction) for measuring % ZSM-5
crystallinity relative to a reference ZSM-5. Preparation and
analytical data are given in Table I.
[0055] Ten ZSM-5 zeolites with varying aluminum content were
prepared on a larger scale using 1-liter stainless steel autoclaves
equipped with internal agitators. The procedure was the same as
above using the same relative amounts of reagents but at
approximately 10-fold larger scale. The ten zeolite preparations
were identical except for the amount of sodium aluminum oxide
employed which was varied to obtain different aluminum contents in
the ZSM-5 products. The mixtures were charged into a 1-liter
autoclave and heated with agitation for 72 hours at 170.degree. C.
After cooling, solid products were collected by filtration, washed
with deionized water, dried and calcined in air for 4 hours at
510.degree. C. Silica-supported catalysts containing molybdenum
(Mo) were prepared from each calcined ZSM-5 using Cabot
CAB-O-SIL.RTM. HS-5 fumed silica powder in a mass ratio of 60:40
ZSM-5/silica. ZSM-5 powder (30 g) was dry-mixed with fumed silica
powder (20 g). Deionized water (65-85 g) was added and the mixture
stirred to form an aqueous slurry, after which ammonium
heptamolybdate tetrahydrate (2.15 g in 9 g deionized water) was
added and mixed in. This slurry was dried at 165.degree. C. and
calcined at 510.degree. C. for 4 hours. The calcined catalysts were
ground and sieved to 18-40 mesh size for catalytic testing.
Characterization data for the larger-scale ZSM-5 zeolite and
catalysts are given in Table II. The ZSM-5 zeolites are numbered
1-10 and the Mo-ZSM-5/silica catalysts prepared from them are
designated with a letter "C" after the respective ZSM-5 zeolite
number.
[0056] Fixed-bed reactor pilot plant tests of the Mo-ZSM-5/silica
catalysts were performed at initial conditions of 700.degree. F.,
220 psig, 1.7 mole H.sub.2/HC mole ratio, and 15.9 h.sup.-1 WHSV HC
(hydrocarbon) feed rate. The HC feed contained 9 wt % ethylbenzene
(EB), 10 wt % p-xylene (pX), 53 wt % m-xylene (mX), 25 wt %
(o-xylene (oX), 1 wt % toluene, 0.5 wt % benzene. The catalysts
were tested at the above conditions for 1 day. If EB conversions
were not .about.30%, the HC and H.sub.2 feed rates were adjusted to
obtain EB conversions of .about.30% (27-33%) and the tests were
continued for 1-2 additional days. Results of these tests are given
in Table III.
TABLE-US-00001 TABLE I Small-Scale ZSM-5 Zeolite Preparation and
Analytical Data Targeted Al Actual Al Sodium Aluminum Content in in
ZSM-5 Na in ZSM-5 Oxide used in ZSM-5 Product Product by XRD
preparation Product by ICP ICP Crystallinity* ZSM-5 (grams) (wt %)
(wt %) (ppm) (%) A 0.20 0.5 0.54 162 94 B 0.20 0.5 0.50 145 97 D
0.30 0.75 0.74 682 26 E 0.35 0.88 0.91 834 27 F 0.40 1.0 1.01 251
95 *XRD crystallinity relative to a reference ZSM-5 zeolite
TABLE-US-00002 TABLE II Larger-Scale ZSM-5 Zeolite and Catalyst
Analytical Data Al Na XRD Mo ZSM-5 or Mo-ZSM-5/Silica Catalyst wt %
ppm Cryst* wt % 1 0.61 485 102% -- .sup. 1C 382 58% 2.8 2 0.72 467
102% -- .sup. 2C 363 58% 2.7 3 0.69 433 100% .sup. 3C 388 58% 3.0 4
0.69 399 97% .sup. 4C 363 56% 3.0 5 0.69 301 101% .sup. 5C 285 59%
2.3 6 0.77 215 95% .sup. 6C 203 57% 2.5 7 0.82 244 84% -- .sup. 7C
246 48% 3.2 8 0.88 293 97% -- .sup. 8C 268 53% 3.0 9 0.85 230 97%
-- .sup. 9C 193 57% 2.3 10 1.03 493 103% -- .sup. 10C 405 59% 2.8
*XRD crystallinity relative to a reference ZSM-5 zeolite
TABLE-US-00003 TABLE III Mo-ZSM-5/silica Catalyst Pilot Plant Test
Results Conditions: fixed-bed reactor, 2-4 day runs, 700.degree.
F., 220 psig, 1.7 H.sub.2/HC molar Al EB EBC/ wt % in HC Conv.
Xylene Xylene ZSM-5 Days on WHSV (EBC) Loss Loss Catalyst zeolite
Stream (1/h) (%) (%) Ratio 1C 0.61 0.7 15.9 29.9 0.47 64 1.7 15.9
29.9 0.47 64 2C 0.72 0.7 15.9 30.4 0.44 68 2.4 18.0 27.2 0.37 73
3.4 18.0 27.6 0.37 75 2C (2.sup.nd test) 0.72 0.6 15.9 30.6 0.48 64
1.6 18.5 28.2 0.41 68 2.6 18.5 28.4 0.41 70 3.6 18.5 28.4 0.42 68
3C 0.69 0.7 20 30.4 0.43 71 1.7 19 30.3 0.38 80 2.7 20.6 28.3 0.30
95 4C 0.69 0.7 15.9 32.7 0.59 55 1.7 18.9 28.2 0.44 65 2.7 19.0
28.6 0.43 66 5C 0.69 1.7 18 27.6 0.34 82 2.7 18 28.7 0.35 82 3.7
18.3 28.5 0.36 79 6C 0.77 0.7 15.9 31.9 0.58 55 1.7 19 29.4 0.51 57
2.7 20.5 28.3 0.47 61 7C 0.82 1.8 22.5 27.7 0.97 29 8C 0.88 1.7
22.5 28.4 0.73 39 9C 0.85 1.7 25.0 27.3 0.82 33 10C 1.03 1.7 26.8
30.3 0.75 40 2.0 26.8 30.0 0.72 42
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