U.S. patent application number 11/550831 was filed with the patent office on 2007-04-19 for alumina guard bed for aromatics transalkylation process.
Invention is credited to Edwin P. Boldingh, Antoine Negiz, Sergio A. Pischek.
Application Number | 20070086933 11/550831 |
Document ID | / |
Family ID | 37569441 |
Filed Date | 2007-04-19 |
United States Patent
Application |
20070086933 |
Kind Code |
A1 |
Negiz; Antoine ; et
al. |
April 19, 2007 |
Alumina Guard Bed for Aromatics Transalkylation Process
Abstract
A transalkylation process for reacting carbon number nine
aromatics with toluene to form carbon number eight aromatics such
as para-xylene is herein disclosed. The process is based on the
discovery that deactivating contaminants present in typical
hydrocarbon feeds, such as chlorides, can be removed with an
alumina guard bed prior to contacting with a transalkylation
catalyst. Effective transalkylation catalysts have a solid-acid
component such as mordenite, and a metal component such as rhenium.
The invention is embodied in a process, a catalyst system, and an
apparatus. The invention provides for longer catalyst cycle life
when processing aromatics under commercial transalkylation
conditions.
Inventors: |
Negiz; Antoine; (Wilmette,
IL) ; Boldingh; Edwin P.; (Arlington Heights, IL)
; Pischek; Sergio A.; (Westmont, IL) |
Correspondence
Address: |
HONEYWELL INTELLECTUAL PROPERTY INC;PATENT SERVICES
101 COLUMBIA DRIVE
P O BOX 2245 MAIL STOP AB/2B
MORRISTOWN
NJ
07962
US
|
Family ID: |
37569441 |
Appl. No.: |
11/550831 |
Filed: |
October 19, 2006 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10946948 |
Sep 22, 2004 |
7154014 |
|
|
11550831 |
Oct 19, 2006 |
|
|
|
Current U.S.
Class: |
422/600 |
Current CPC
Class: |
C07C 2529/85 20130101;
C07C 2523/36 20130101; C07C 2523/14 20130101; C07C 2529/18
20130101; C07C 2521/12 20130101; C07C 2529/70 20130101; C07C
2523/75 20130101; C07C 2523/755 20130101; C07C 2523/745 20130101;
C07C 6/126 20130101; C07C 2521/04 20130101; C07C 2523/40 20130101;
C07C 2523/08 20130101 |
Class at
Publication: |
422/190 ;
422/191; 422/192 |
International
Class: |
B01J 8/00 20060101
B01J008/00 |
Claims
1. A transalkylation apparatus comprising a first zone for
containing an alumina guard bed in fluid communication with a
second zone for containing a transalkylation catalyst.
2. The apparatus of claim 1 wherein the first zone comprises a
first vessel and the second zone comprises at least one reactor
connected to the first vessel with piping suitable for hydrocarbon
stream transfer.
3. The apparatus of claim 1 wherein the first zone and the second
zone are placed in a single vessel comprising an entrance conduit
and an exit conduit such that said first zone is located near the
entrance conduit and said second zone if located near the exit
conduit.
4. The apparatus of claim 3 further comprising inert support
material disposed before and after the first zone.
5. The apparatus of claim 3 wherein the vessel is a radial flow
reactor.
6. The apparatus of claim 3 wherein the vessel is a cylindrical
down-flow reactor.
7. The apparatus of claim 6 wherein the first zone is disposed in a
layer on top of the second zone.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a Division of copending application Ser.
No. 10/946,948 filed Sep. 22, 2004, the contents of which are
hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates to catalytic hydrocarbon conversion,
and more specifically to the use of an activated alumina guard bed
for extending the life of a transalkylation catalyst used in
reacting aromatic C.sub.9.sup.+ compounds with toluene to produce
xylenes. By decomposing contaminant species present in
transalkylation feed aromatics, such as chlorides, the guard bed
reduces coke formation on the transalkylation catalyst.
BACKGROUND OF THE INVENTION
[0003] Xylene isomers, para-xylene, meta-xylene and ortho-xylene,
are important intermediates which find wide and varied application
in chemical syntheses. Para-xylene upon oxidation yields
terephthalic acid, which is used in the manufacture of synthetic
textile fibers and resins. Meta-xylene is used in the manufacture
of plasticizers, azo dyes, wood preservers, etc. Ortho-xylene is
feedstock for phthalic anhydride production.
[0004] Xylene isomers from catalytic reforming or other sources
generally do not match demand proportions as chemical
intermediates, and further comprise ethylbenzene, which is
difficult to separate or to convert. Para-xylene in particular is a
major chemical intermediate with rapidly growing demand, but
amounts to only 20 to 25% of a typical C.sub.8 aromatics stream.
Among the aromatic hydrocarbons, the overall importance of the
xylenes rivals that of benzene as a feedstock for industrial
chemicals. Neither the xylenes nor benzene are produced from
petroleum by the reforming of naphtha in sufficient volume to meet
demand, and conversion of other hydrocarbons is necessary to
increase the yield of xylenes and benzene. Often toluene (C.sub.7)
is dealkylated to produce benzene (C.sub.6) or selectively
disproportionated to yield benzene and C.sub.8 aromatics from which
the individual xylene isomers are recovered.
[0005] A current objective of many aromatics complexes is to
increase the yield of xylenes and to de-emphasize benzene
production. Demand is growing faster for xylene derivatives than
for benzene derivatives. Refinery modifications are being effected
to reduce the benzene content of gasoline in industrialized
countries, which will increase the supply of benzene available to
meet demand. A higher yield of xylenes at the expense of benzene
thus is a favorable objective, and processes to transalkylate
C.sub.9 and heavier aromatics with benzene and toluene have been
commercialized to obtain high xylene yields.
[0006] U.S. Pat. No. 4,857,666 discloses a transalkylation process
over mordenite and incorporating a metal modifier into the
catalyst.
[0007] U.S. Pat. No. 5,763,720 discloses a transalkylation process
for conversion of C.sub.9.sup.+ into mixed xylenes and
C.sub.10.sup.+ aromatics over a catalyst containing zeolites
including amorphous silica-alumina, MCM-22, ZSM-12, and zeolite
beta, where the catalyst further contains a Group VIII metal such
as platinum.
[0008] U.S. Pat. No. 6,060,417 discloses a transalkylation process
using a catalyst based on mordenite with a particular zeolitic
particle diameter and having a feed stream limited to a specific
amount of ethyl containing heavy aromatics. The catalyst contains
nickel or rhenium metal.
[0009] U.S. Pat. No. 6,486,372 B1 discloses a transalkylation
process using a catalyst based on dealuminated mordenite with a
high silica to alumina ratio that also contains at least one metal
component.
[0010] U.S. Pat. No. 6,613,709 B1 discloses a catalyst for
transalkylation comprising zeolite structure type NES and metals
such as rhenium, indium, or tin.
[0011] U.S. Pat. No. 6,740,788 B1 discloses an integrated process
for aromatics production enabled by a stabilized transalkylation
catalyst having a metal function.
[0012] Many types of supports and elements have been disclosed for
use as catalysts in processes to transalkylate various types of
aromatics into xylenes, but there exists a problem presented by
transalkylation aromatics feed stream contaminants, whereby such
contaminants reduce the useful catalyst cycle life. Applicants have
found a solution with the application of a contaminant removal
guard bed that extends catalyst life, resulting in a more stable
aromatics transalkylation process that will be more profitable over
the catalyst life cycle by requiring less frequent down time for
regeneration to remove deactivating coke deposits.
SUMMARY OF THE INVENTION
[0013] A principal object of the present invention is to provide a
process of using a guard bed in front of a transalkylation
catalyst, the guard bed catalyst system itself, and a reactor
configuration for the transalkylation of alkylaromatic hydrocarbons
into xylenes. More specifically, the present invention is directed
to improved conversion of aromatic hydrocarbons by removal of feed
contaminants. This invention is based on the discovery that feed
contaminants removed in a guard bed prior to contacting the feed
with a transalkylation catalyst demonstrates a process showing
increased stability of xylene production under transalkylation
conditions.
[0014] Accordingly, a broad embodiment of the present invention is
a process for contacting an aromatics stream containing a
contaminant material with a guard bed and then with a catalyst
suitable for transalkylation of the aromatics into xylenes. In
another embodiment, the present invention is a catalyst system
combining guard bed material with catalyst material. In yet another
embodiment, the present invention is a reactor configuration
providing an apparatus for situating a guard bed before a catalyst
bed.
[0015] These, as well as other objects and embodiments will become
evident from the following detailed description of the
invention.
BRIEF DESCRIPTION OF THE DRAWING
[0016] The Figure shows the effect of guard bed addition upon
catalyst activity for transalkylation of C.sub.7, C.sub.9, and
C.sub.10 aromatics at a level of about 50 wt-% conversion while
producing C.sub.8 aromatics. The slope of the weighted average
catalyst bed temperature (WABT) is proportional to stability, with
a flatter slope representing greater stability.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The feed stream to the present process generally comprises
alkylaromatic hydrocarbons of the general formula
C.sub.6H.sub.(6-n)R.sub.n, where n is an integer from 0 to 6 and R
is CH.sub.3, C.sub.2H.sub.5, C.sub.3H.sub.7, or C.sub.4H.sub.9, in
any combination. Suitable alkylaromatic hydrocarbons include, for
example but without so limiting the invention, benzene, toluene,
ethylbenzene, ethyltoluenes, propylbenzenes, tetramethylbenzenes,
ethyl-dimethylbenzenes, diethylbenzenes, methylpropylbenzenes,
ethylpropylbenzenes, triethylbenzenes, di-isopropylbenzenes, and
mixtures thereof. The feed stream may comprise lower levels of
ortho-xylene, meta-xylene, and para-xylene that are the desired
products of the present process.
[0018] The feed stream also may comprise naphthalene and other
C.sub.10 and C.sub.11 aromatics and suitably is derived from one or
a variety of sources. Polycyclic aromatics such as the bi-cyclic
components including naphthalene, methylnaphthalene, are permitted
in the feed stream of the present invention. Indane, which is also
referred to as indan or indene, is meant to define a carbon number
nine aromatic species with one carbon six ring and one carbon five
ring wherein two carbon atoms are shared. Naphthalene is meant to
define a carbon number ten aromatic species with two carbon six
rings wherein two carbon atoms are shared. Polycyclic aromatics may
also be present, even in substantial amounts such as greater than
about 0.5 wt-% of the feed stream.
[0019] Feed components may be produced synthetically, for example,
from naphtha by catalytic reforming or by pyrolysis followed by
hydrotreating to yield an aromatics-rich product. The feed stream
may be derived from such product with suitable purity by extraction
of aromatic hydrocarbons from a mixture of aromatic and nonaromatic
hydrocarbons and fractionation of the extract. For instance,
aromatics may be recovered from reformate. Reformate may be
produced by any of the processes known in the art. The aromatics
then may be recovered from reformate with the use of a selective
solvent, such as one of the sulfolane type, in a liquid-liquid
extraction zone. The recovered aromatics may then be separated into
streams having the desired carbon number range by fractionation.
When the severity of reforming or pyrolysis is sufficiently high,
extraction may be unnecessary and fractionation may be sufficient
to prepare the feed stream. Such fractionation typically includes
at least one separation column to control feed end point.
[0020] The feed heavy-aromatics stream, characterized by
C.sub.9.sup.+ aromatics (or A.sub.9.sup.+), permits effective
transalkylation of light aromatics such as benzene and toluene with
the heavier C.sub.9.sup.+ aromatics to yield additional C.sub.8
aromatics that are preferably xylenes. The heavy-aromatics stream
preferably comprises at least about 90 wt-% total aromatics; and
may be derived from the same or different known refinery and
petrochemical processes as the benzene and toluene, and/or may be
recycled from the separation of the product from transalkylation.
When the feed is predominantly heavy-aromatics then de-alkylation
or hydrocracking of the heavy aromatics to lighter aromatics may
also occur and provide additional intermediate feed components that
may further convert to benzene, toluene or xylene.
[0021] Feed contaminants may be present in small amounts, such as
amounts less than 100 wt-ppm, and more generally are present in
amounts less than 10 wt-ppm. Feed contaminants include, but are not
limited to, oxygen, chloride, sulfur, and nitrogen species.
[0022] According to the process of the present invention, the feed
mixture of heavy A.sub.9.sup.+, toluene, and feed contaminants is
contacted with an alumina guard bed and then with a transalkylation
catalyst of the type hereinafter described in a two zone system.
The first zone is the guard bed zone, while the second zone is the
transalkylation zone. The guard bed may be contained in a separate
vessel from the transalkylation reactor of the types hereinafter
described, or it may be contained within the same reactor vessel as
the transalkylation catalyst. Better flow distribution is achieved
when catalyst support materials, for example inert ceramic objects,
are placed in upstream and downstream positions from the alumina
guard bed material. Therefore, when the two zones are placed in
separate vessels appropriate piping is used to serially connect
them together. When the two zones are in the same vessel, then the
zones are generally layered on top or next to each other such that
contacting with hydrocarbons occurs sequentially and under the same
conditions. Alternatively, the zones may be intermixed, such that
physical mixtures of guard bed and transalkylation particles are
combined together on a bulk basis where separate particles are
intermingled, or on a particulate basis where effective guard bed
material is directly composited alongside catalyst material.
Finally, such zones are herein described as in fluid communication
with each other by being present in the same vessel, or connected
in series with separate vessels and piping there between for
transference of the alumina guard bed product to the
transalkylation reactor.
[0023] The hydrocarbon feed is passed through an alumina guard bed
and produces an alumina guard bed product stream. The alumina guard
bed product stream is then preferably transalkylated in the vapor
phase and in the presence of hydrogen. If transalkylated in the
liquid phase, then the presence of hydrogen is optional. If
present, free hydrogen is associated with the feed stream and
recycled hydrocarbons in an amount of from about 0.1 moles per mole
of alkylaromatics up to 10 moles per mole of alkylaromatic. This
ratio of hydrogen to alkylaromatic is also referred to as hydrogen
to hydrocarbon ratio. The transalkylation reaction preferably
yields a product having increased xylene content.
[0024] The feed to alumina guard bed zone usually first is heated
by indirect heat exchange against the effluent of the
transalkylation reaction zone and then is heated to reaction
temperature by exchange with a warmer stream, steam or a furnace.
The feed then is passed through the guard bed zone and then through
a reaction zone, which may comprise one or more individual
reactors. The use of a single transalkylation reaction vessel
having a fixed cylindrical bed of catalyst is preferred, but other
reaction configurations utilizing moving beds of catalyst or
radial-flow reactors may be employed if desired. Passage of the
combined feed through the reaction zone effects the production of
an effluent stream comprising unconverted feed and product
hydrocarbons including C.sub.8 aromatic compounds. This effluent is
normally cooled by indirect heat exchange against the stream
entering the reaction zone and then further cooled through the use
of air or cooling water. The effluent may be passed into a
stripping column in which substantially all C.sub.5 and lighter
hydrocarbons present in the effluent are concentrated into an
overhead stream and removed from the process. An aromatics-rich
stream is recovered as net stripper bottoms, which is referred to
herein as the transalkylation effluent.
[0025] To effect a transalkylation reaction, the present invention
incorporates a transalkylation catalyst in at least one zone, but
no limitation is intended in regard to a specific catalyst other
than such catalyst must possess a solid-acid component and a metal
component. Conditions employed in the transalkylation zone normally
include a temperature of from about 200.degree. to about
540.degree. C. The transalkylation zone is operated at moderately
elevated pressures broadly ranging from about 100 kPa to about 6
MPa absolute. The transalkylation reaction can be effected over a
wide range of space velocities. Weight hourly space velocity (WHSV)
generally is in the range of from about 0.1 to about 20 hr.sup.-1.
Such transalkylation conditions are similar to the alumina guard
bed conditions.
[0026] The transalkylation effluent is separated into a light
recycle stream, a mixed C.sub.8 aromatics product and a heavy
recycle stream. The mixed C.sub.8 aromatics product can be sent for
recovery of para-xylene and other valuable isomers. The light
recycle stream may be diverted to other uses such as to benzene and
toluene recovery, but alternatively is recycled partially to the
transalkylation zone or the alumina guard bed zone. The heavy
recycle stream contains substantially all of the C.sub.9 and
heavier aromatics and may be partially or totally recycled to the
transalkylation reaction zone or the alumina guard bed zone as
well.
[0027] Several types of alumina guard bed materials may be used in
the present invention including gamma alumina, theta alumina, and
other alumina phase materials having high surface areas generally
greater than about 25 m.sup.2/g, with gamma phase alumina being
preferred. Alpha phase alumina generally has a low surface area is
not generally suitable for the present invention. Gamma phase
alumina is obtained by aging and calcining aluminum trihydroxides
[Al (OH).sub.3], aluminum oxyhydroxides [AlOOH], transition
aluminas derived from Al (OH).sub.3 and AlOOH, and, optionally
metal promoters with any combination thereof. Generally, alumina
will be precipitated from an aqueous solution containing Al+3 ions.
Such precipitate is aged, filtered, washed and dried. During these
operations alumina passes through various phases. Typically, the
initial precipitation leads to a gel with minute crystals of
boehmite. The gel can be aged at a temperature of about 80.degree.
C. into crystalline boehmite that forms gamma-phase alumina upon a
calcination temperature of about 600.degree. C. Gamma phase alumina
has a high surface area, generally between 100 and 300 m.sup.2/g.
Upon heating to higher temperatures of about 1100.degree. C. or
more, the alumina moves through theta or delta phases to becomes
alpha phase and has a low surface area less than 25 m.sup.2/g and
commonly less than 1 m.sup.2/g.
[0028] Several types of transalkylation catalysts that may be used
in the present invention are based on a solid-acid material
combined with an optional metal component. Suitable solid-acid
materials include all forms and types of mordenite, mazzite (omega
zeolite), beta zeolite, ZSM-11, ZSM-12, ZSM-22, ZSM-23, MFI type
zeolite, NES type zeolite, EU-1, MAPO-36, MAPSO-31, SAPO-5,
SAPO-11, SAPO-41, and silica-alumina or ion exchanged versions of
such solid-acids. For example, in U.S. Pat. No. 3,849,340 a
catalytic composite is described comprising a mordenite component
having a SiO.sub.2/Al.sub.2O.sub.3 mole ratio of at least 40:1
prepared by acid extracting Al.sub.2O.sub.3 from mordenite prepared
with an initial SiO.sub.2/Al.sub.2O.sub.3 mole ratio of less than
30:1 and a metal component selected from copper, silver and
zirconium. Refractory inorganic oxides, combined with the
above-mentioned and other known catalytic materials, have been
found useful in transalkylation operations. For instance,
silica-alumina is described in U.S. Pat. No. 5,763,720. Crystalline
aluminosilicates have also been employed in the art as
transalkylation catalysts. ZSM-12 is more particularly described in
U.S. Pat. No. 3,832,449. Zeolite beta is more particularly
described in Re. 28,341 (of original U.S. Pat. No. 3,308,069). A
favored form of zeolite beta is described in U.S. Pat. No.
5,723,710, which is incorporated herein by reference. The
preparation of MFI topology zeolite is also well known in the art.
In one method, the zeolite is prepared by crystallizing a mixture
containing an alumina source, a silica source, an alkali metal
source, water and an alkyl ammonium compound or its precursor.
Further descriptions are in U.S. Pat. No. 4,159,282, U.S. Pat. No.
4,163,018, and U.S. Pat. No. 4,278,565. The synthesis of the
Zeolite Omega is described in U.S. Pat. No. 4,241,036. ZSM
intermediate pore size zeolites useful in this invention include
ZSM-5 (U.S. Pat. No. 3,702,886); ZSM-11 (U.S. Pat. No. 3,709,979);
ZSM-12 (U.S. Pat. No. 3,832,449); ZSM-22 (U.S. Pat. No. 4,556,477);
ZSM-23 (U.S. Pat. No. 4,076,842). European Patent EP 0378916 B1
describes NES type zeolite and a method for preparing NU-87. The
EUO structural-type EU-1 zeolite is described in U.S. Pat. No.
4,537,754. MAPO-36 is described in U.S. Pat. No. 4,567,029.
MAPSO-31 is described in U.S. Pat. No. 5,296,208 and typical SAPO
compositions are described in U.S. Pat. No. 4,440,871 including
SAPO-5, SAPO-11 and SAPO-41. Typically, the solid-acid component
will be present in the catalyst in an amount from about 1 to about
99 wt-%.
[0029] A refractory binder or matrix is optionally utilized to
facilitate fabrication of the catalyst, provide strength and reduce
fabrication costs. The binder should be uniform in composition and
relatively refractory to the conditions used in the process.
Suitable binders include inorganic oxides such as one or more of
alumina, magnesia, zirconia, chromia, titania, boria, thoria,
phosphate, zinc oxide and silica. Alumina is a preferred binder.
Typically the binder may be present in about 5 to about 95 wt-% of
the catalyst when it is used.
[0030] The catalyst also may contain a metal component. One
preferred metal component is a Group VIII (IUPAC 8-10) metal that
includes nickel, iron, cobalt, and platinum-group metal. Of the
platinum group, i.e., platinum, palladium, rhodium, ruthenium,
osmium and iridium, platinum is especially preferred. Another
preferred metal component is rhenium and it will be used for the
general description that follows. This metal component may exist
within the final catalytic composite as a compound such as an
oxide, sulfide, halide, or oxyhalide, in chemical combination with
one or more of the other ingredients of the composite. The rhenium
metal component may be incorporated in the catalyst in any suitable
manner, such as coprecipitation, ion-exchange, co-mulling or
impregnation. The preferred method of preparing the catalyst
involves the utilization of a soluble, decomposable compound of
rhenium metal to impregnate the carrier material in a relatively
uniform manner. Typical rhenium compounds which may be employed
include ammonium perrhenate, sodium perrhenate, potassium
perrhenate, potassium rhenium oxychloride, potassium
hexachlororhenate (IV), rhenium chloride, rhenium heptoxide,
perrhenic acid, and the like compounds. Preferably, the compound is
ammonium perrhenate or perrhenic acid because no extra steps may be
needed to remove any co-contaminant species. This component may be
present in the final catalyst composite in any amount which is
catalytically effective, generally comprising about 0.01 to about 2
wt-% of the final catalyst calculated on an elemental basis.
[0031] The catalyst may optionally contain additional metal
components along with those metal components discussed above or
include additional metal components instead of those metal
components in their entirety. Additional metal components of the
catalyst include, for example, tin, germanium, lead, and indium and
mixtures thereof. Catalytically effective amounts of such
additional metal components may be incorporated into the catalyst
by any means known in the art. A preferred amount is a range of
about 0.01 to about 2.0 wt-% on an elemental basis.
[0032] One shape of the catalyst of the present invention is a
cylinder. Such cylinders can be formed using extrusion methods
known to the art. Another shape of the catalyst is one having a
trilobal or three-leaf clover type of cross section that can be
formed by extrusion. Another shape is a sphere that can be formed
using oil-dropping methods or other forming methods known to the
art.
[0033] At least one oxidation step may be used in the preparation
of the catalyst. The conditions employed to effect the oxidation
step are selected to convert substantially all of the metallic
components within the catalytic composite to their corresponding
oxide form. The oxidation step typically takes place at a
temperature of from about 370.degree. to about 650.degree. C. An
oxygen atmosphere is employed typically comprising air. Generally,
the oxidation step will be carried out for a period of from about
0.5 to about 10 hours or more, the exact period of time being that
which is required to convert substantially all of the metallic
components to their corresponding oxide form. This time will, of
course, vary with the oxidation temperature employed and the oxygen
content of the atmosphere employed.
[0034] In preparing the catalyst, a reduction step may be employed.
The reduction step is designed to reduce substantially all of the
metal components to the corresponding elemental metallic state and
to ensure a relatively uniform and finely divided dispersion of
this component throughout the catalyst.
[0035] Finally, the catalytic composite is subjected to an optional
sulfur treatment or pre-sulfiding step. The sulfur component may be
incorporated into the catalyst by any known technique. Any one or a
combination of in situ and/or ex situ sulfur treatment methods is
preferred. The resulting catalyst mole ratio of sulfur to rhenium
is preferably from about 0.1 to less than about 1.5.
EXAMPLES
[0036] The following examples are presented only to illustrate
certain specific embodiments of the invention, and should not be
construed to limit the scope of the invention as set forth in the
claims. There are many possible other variations, as those of
ordinary skill in the art will recognize, within the scope of the
invention.
Example 1
[0037] A transalkylation catalyst comprising mordenite was prepared
for comparative pilot-plant testing by the forming process called
extrusion. Typically, 2500 g of a powder blend of 25 wt-% alumina
(commercially available under the trade names CATAPAL B and/or
VERSAL 250) and 75 wt-% mordenite (commercially available under the
trade name ZEOLYST CBV-21A) was added to a mixer. A solution was
prepared using 10 g nitric acid (67.5 wt-% HNO.sub.3) with 220 g
deionized water and the solution was stirred. The solution was
added to the powder blend in the mixer, and mulled to make dough
suitable for extrusion. The dough was extruded through a die plate
to form cylindrically shaped (0.08 cm diameter) extrudate
particles. The extrudate particles were calcined at about
565.degree. C. with 15 wt-% steam for 2 hours.
[0038] The catalyst was finished using the extrudate particles and
an evaporative impregnation with rhenium metal by using an aqueous
solution of ammonium perrhenate (NH.sub.4ReO.sub.4). The
impregnated base was calcined in air at 540.degree. C. for 2 hours
and resulted in a metal level of 0.15 wt-% rhenium. Next the
catalyst was reduced for 12 hours in substantially dry hydrogen at
500.degree. C.
Example 2
[0039] The catalyst was tested for aromatics transalkylation
ability in a pilot plant using an aromatics feed blend of C.sub.7,
C.sub.9, and C.sub.10 aromatics to demonstrate effectiveness of
using an alumina guard bed to remove contaminant chlorides when
producing C.sub.8 aromatics. The feed properties are listed in the
table below. TABLE-US-00001 Feed Wt-% Non Aromatics 0.11 Benzene
0.00 Toluene 44.33 Ethylbenzene 0.01 Mixed Xylenes 0.37
Propylbenzene 3.98 Ethyltoluene 20.64 Trimethylbenzene 17.90 DEB +
C10A 3.74 Ethyl Xylenes 5.21 Tetramethylbenzene 1.41 Butylbenzene
0.40 Indane 1.22 C11+ 0.67 Total 100.0
[0040] Methylene chloride was also present in the feed at an amount
of 3.0 wt-ppm.
[0041] The test consisted of loading a vertical down-flow reactor
with 60 cc catalyst located below 240 cc alumina particles. Two
types of alumina particles were loaded in two different tests.
First, a gamma-phase alumina oxide (obtained by calcining
crystalline boehmite at approximately 600.degree. C.) having 185
m.sup.2/g surface area was loaded in Run A. Second, commercially
available corundum, alpha-phase aluminum oxide with 0.83 m.sup.2/g
surface area was loaded in Run B.
[0042] The loaded reactors were contacted with the feed at 2860 kPa
abs (400 psig) under a space velocity (WHSV) of 4 hr.sup.-1 and
hydrogen to hydrocarbon ratio (H.sub.2/HC) of 2. A conversion level
of about 50 wt-% of feed aromatics was achieved during the initial
part of testing. The Figure shows the effect of guard bed addition
upon catalyst activity for transalkylation of C.sub.7, C.sub.9, and
C.sub.10 aromatics at a level of about 50 wt-% conversion while
producing C.sub.8 aromatics. The slope of the weighted average
catalyst bed temperature (WABT) is related to stability where the
flatter slope represents more stable operation and where higher
slope represents less stability and increased catalyst
deactivation. Run B, with the alpha alumina guard bed, also
indicates a time period wherein the hydrogen to hydrocarbon ratio
was increased from 2:1 to 3:1, without approaching the stability of
Run A, with the gamma alumina guard bed.
[0043] The data showed that the addition of a high surface area
gamma phase alumina guard bed improved the stability over a
comparable low surface area alumina phase guard bed. Even under
conditions of increased hydrogen to hydrocarbon ratio, the
stability difference persisted. After testing, the alumina and
catalyst chloride contents were analyzed for each run. Alpha
alumina showed about 0.01 wt-% chloride in front of a catalyst that
showed about 0.25 wt-% chloride. In contrast, gamma alumina showed
approximately 1.2 wt-% chloride in front of a catalyst that showed
about 0.01 wt-% chloride. Accordingly, the gamma alumina guard bed
permitted extended operation of an effective transalkylation
catalyst by removing contaminant feed species.
* * * * *