Note: Descriptions are shown in the official language in which they were submitted.
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CATALYST SELECTIVATION
FIELD OF THE INVENTION
The present invention relates to methods for modifying zeolite
catalysts and catalysts so modified, and more particularly relates, in one
embodiment, to methods for modifying zeolite catalysts to make them
more selective to the synthesis of para-substituted dialkylbenzenes
relative to other dialkylbenzene isomers, as well as useful in other
reactions, and catalysts so modified.
BACKGROUND OF THE INVENTION
Of the para-substituted dialkylbenzenes, para-xylene (PX) is of
particular value as a large volume chemical intermediate in a number of
applications being useful in the manufacture of terephthalates which are
intermediates for the manufacture of polyethylene terephthalate (PET).
One source of feedstocks for manufacturing PX is by disproportionation of
toluene into xylenes. One of the disadvantages of this process is that large
quantities of benzene are also produced. Another source of feedstocks
used to obtain PX involves the isomerization of a feedstream that contains
non-equilibrium quantities of mixed ortho- and meta-xylene isomers (OX
and MX, respectively) and is lean with respect to PX content. A
disadvantage of this process is that the separation of the PX from the
other isomers is expensive.
Zeolites are known to catalyze the reaction of toluene with other
reactants to make xylenes. Some zeolites are silicate based materials
which are comprised of a silica lattice and, optionally, alumina combined
with exchangeable cations such as alkali or alkaline earth metal ions.
Although the term "zeolites" includes materials containing silica and
optionally alumina, it is recognized that the silica and alumina portions
may be replaced in whole or in part with other oxides. For example,
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germanium oxide, tin oxide, phosphorus oxide, and mixtures thereof can
replace the silica portion. Boron oxide, iron oxide, gallium oxide, indium
oxide, and mixtures thereof can replace the alumina portion. Accordingly,
the terms "zeolite", "zeolites" and "zeolite material", as used therein, shall
mean not only materials containing silicon and, optionally, aluminum
atoms in the crystalline lattice structure thereof, but also materials which
contain suitable replacement atoms for such silicon and aluminum, such
as gallosilicates, borosilicates, ferrosilicates, and the like.
The term "zeolite, "zeolites", and "zeolite materials" as used herein,
besides encompassing the materials discussed above, shall also include
aluminophosphate-based materials. Aluminophosphate zeolites are made
of alternating A104 and P04 tetrahedra. Aluminophosphate-based
materials have lower acidity compared to aluminosilicates. The lower
acidity eliminates many side reactions, raises reactants' utilization, and
extends catalyst life. Aluminophosphate-based zeolites are often
abbreviated as ALPO. Substitution of silicon for P and/or a P-AI pair
produces silicoaluminophosphate zeolites, abbreviated as SAPO.
Processes have been proposed for the production of xylenes by the
methylation of toluene using a zeolite catalyst. For instance, U.S. Pat. No.
3,965,207 involves the methylation of toluene using a zeolite catalyst such
as a ZSM-5. U.S. Pat. No. 4,670,616 involves the production of xylenes by
the methylation of toluene with methanol using a borosilicate zeolite which
is bound by a binder such as alumina, silica, or alumina-silica. One of the
disadvantages of such processes is that catalysts deactivate rapidly due
to build up of carbonaceous material and heavy by-products. Another
disadvantage is that methanol selectivity to para-xylene, the desirable
product, has been low, in the range of 50 to 60%. The balance is wasted
on the production of coke and other undesirable compounds.
It has been further demonstrated that alkylaromatic compounds can
be synthesized by reacting an aromatic compound such as toluene with a
mixture of carbon dioxide (C02), and carbon monoxide (CO) and hydrogen
(H2) (synthesis gas) at alkylation conditions in the presence of a catalyst
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system, which comprises (1 ) a composite of oxides of zinc, copper,
chromium, and/or cadmium; and (2) an aluminosilicate material, either
crystalline or amorphous, such as zeolites or clays; as disclosed in U.S.
Pat. Nos. 4,487,984 and 4,665,238. Such catalyst systems, however, are
not capable of producing greater than equilibrium concentrations of para-
xylene (PX) in the xylene-fraction product. Typically, the xylene-fraction
product contains a mixture of xylene isomers at or near the equilibrium
concentration, i.e., 24% PX, 54% MX, and 22% OX. The lack of para-
xylene selectivity in alkylation of toluene with syngas can be caused by (1 )
the acidic sites on the surface outside the zeolite channels, and/or (2) the
channel structure not being able to differentiate para-xylene from its
isomers. It would be desirable for the toluene alkylation to be more para-
selective due to the much higher value of PX compared to that of MX and
OX. Furthermore, such processes suffer from catalyst deactivation as well.
In addition, the prior art disclosed neither syngas alkylation to alkyl
aromatic compounds nor syngas selective alkylation to high purity PX
using aluminophosphate-based materials.
It has been recognized that certain zeolites can be modified to
enhance their molecular-sieving or shape-selective capability. Such
modification treatments are usually called zeolite selectivation.
Selectivated zeolites can more accurately differentiate molecules on the
basis of molecular dimension or steric characteristics than the
unselectivated precursors. For example, silanized ZSM-5 zeolites
adsorbed PX much more preferentially over MX than untreated ZSM-5. It
is believed that the deposition of silicon oxide onto zeolite surfaces from
the silanization treatment has (1 ) passivated the active sites on the
external surface of zeolite crystals, and (2) narrowed zeolitic pores to
facilitate the passage of the smaller PX molecules and prevent the bigger
MX and OX molecules from entering or exiting the pores. In this
application, the term "para-alkyl selectivation" refers to modifying a
catalyst or catalytic reaction system so that it preferentially forms more
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pare-substituted dialkylbenzenes than the expected equilibrium proportions
relative to the other isomers.
Zeolite selectivation can be accomplished using many techniques.
Reports of using compounds of silicon, phosphorous, boron, antimony,
coke, magnesium, etc. for selectivation have been documented.
Unfortunately many, if not most of the zeolites used in the prior art have
undesirably short active lifetimes before they deactivate and have to be
reactivated or replaced.
U.S. Pat. No. 4,034,053 discusses a catalytic process for the
selective production of pare-xylene by contacting, under conversion
conditions, a charge stock containing, as a major reactant, at least one
hydrocarbon selected from the group consisting of toluene, a C3-Coo olefin,
and mixtures of the foregoing with a catalyst. The catalyst is a crystalline
aluminosilicate zeolite having a silica to alumina ratio of at least about 12,
a constraint index within the approximate range of 1 to 12 and which has
combined therewith magnesium in an amount of at least about 0.5 percent
by weight.
WPI Abstract AN 2000-114955 of RU-C-2119470 mentions
increased selectivity in respect to dimethylnaphthalenes, andlor p-xylene
and p-ethyltoluene when a toluenel2-methylnaphthalenelsynthesis gas
mixture is brought into contact with a catalyst in the gas phase. The
catalyst may be a zeolite of ZSM-5 type or ZSM-5 modified by silicon and
magnesium compounds and metal oxide component containing 65-70%
zinc oxide, 29-34% chromium oxide, and 1 % tungsten at a zeolite/metal
oxide ratio of 30-70:70-30.
WPI Abstract AN 1987-305992 of SU-A-1301485 discusses a
catalyst that contains, in wt.%: Lanthanum 0.1-2.0 and decationised high
silica-zeolite 98.0-99.9. The catalyst is prepared as follows: first the
zeolite
containing, in wt.%: AI203 3.1, SiOZ 91.2 and Na20 1.59 at SiOz/A1203
ratio equals 50.0; or AI203.3.65, Si02 90.4 and NazO 3.32, at SiOZ/A1203
ratio of 42.1, is subjected to two stage (first catalyst) or three-stage
~o isr~,v~rt. ~:'~~.~_~;~:o.i!E.t: :~:~
AMENDED SHEET
Cmnf,~vnsni~ Q Inni 1~~~Q
.08-06-2001 l 07:42A DLM-Madan Mossman& Sriram 915 392 8805 ~JS 00001300
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4a
(second catalyst) ion-exchange treatment with 1 N solution of ammonium
chloride 96 ml NH;CI per 1 g of zeolite), to produce NH4 form of zeolite.
The obtained zeofite is washed with distilled water, dried and impregnated
with a solution of lanthanum nitrate containing 0.0312 g La(N03)3.9H20 in
10 ml water for 1 day, dried in air.over 24 hours., then at 100°C for 2
hours and calcined at 500°C. Tests show that the proposed catalyst
increases xylene conversion to 45% and selectivity of the process to
100%, as compared to 42 and 90% for the known catalyst containing no
lanthanum.
Further, WO-A-90 09845 describes a mordenite-based cataiyzer for
the isomerization of an aromatic C8 fraction characterized in that said
mordenite contains at least one metal from the Ila, IVb, Ilb or IVa groups
and is such that: its global atomic ratio SilAl is between 6 and 15, its
sodium content by weight in relation to the dry mordenite weight is less
than 2,000 ppm, its basic grain size volume is between 2,725 nm, its n-
hexane adsorption capacity is above 0.065 cm~ liquid/gram, its isooctane
adsorption capacity is less than 0.068 cm3 liquid/gram. The publication
also concerns the preparation of mordenite by grafting on an H-shaped
mordenite at least one organometallic composition of said metal.
A catalyst composition, a process for producing the catalyst
composition, and a hydrocarbon conversion process for converting a fluid
stream comprising at least one saturated hydrocarbon to C6 to C8 aromatic
hydrocarbons such as benzene, toluene, and xylenes are disclosed in U.S.
Pat. No. 5,990,032. The catalyst composition comprises a zeolite and a
promoter. The process for. producing the composition comprises the steps
of: (1) combining a zeolite with a complexing ligand and a promoter
compound under a condition sufficient to produce a modified zeolite; and
(2) heating the modified zeolite to produce a promoted zelite. The
hydrocarbon conversion process comprises contacting a fluid stream with
the catalyst composition under a condition sufficient to effect the
conversion of a saturated hydrocarbon to a C6 to Cs aromatic hydrocarbon.
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AMENDED SHEET
FmnfanRe~ait R..Inni lS;dR
08-Ufi-2UU1 1 07:42A DLM-Madan Mossman& Srirarn 915 392 8805 US 00001300:
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There remains a need for still further improved processes for
catalytic PX synthesis which minimizes or avoids the disadvantages of
prior systems, which include low PX selectivity, low methanol selectivity,
rapid catalyst deactivation, and the like.
SUMMARY Ot~ THE II~,IEINTION
It is an object of the present invention to provide a method for
producing a modified catalyst capable of being more selective to para-
substituted dialkyl benzenes in the synthesis of dialkylbenzenes.
Accordingly, it is another object of the present invention to provide a
modified catalyst useful in a method for synthesizing para-substituted
dialkyl benzenes in high product concentration via alkylation of toluene
andlor benzene with a mixture of gases including H2, and CO andlor C02
andlor methanol.
In canying out these and other objects of the invention, there is
provided, in one form, a method for modifying catalysts involving
contacting first component, such as crystalline or amorphous
aluminosilicates, substituted aluminosilicates, substituted silicates,
crystalline or amorphous alurninophosphates, zeolite-bound zeolites,
substituted aluminophosphates, and mixtures thereof with an agent which
may be compounds of elements selected from Groups 1 through 16, and
mixtures thereof.
Sl.!EiSri-!'UTF S~f=~~'';i~~tl.;i..::. . ,
AMENDED SHEET
Cmnfonpovci+ Q liini 1~~AQ
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DETAILED DESCRIPTION OF THE INVENTION
It has been discovered that catalysts, particularly zeolite catalysts,
may be modified using organometallic compounds in such a way to
5 enhance selectivity to para-substituted alkyl benzenes in the synthesis of
alkyl benzenes. It will be appreciated that the modified catalysts of this
invention will find utility in catalyzing other reactions.
The improvement in para-substituted selectivity is achieved by
treating the catalysts with proper chemical compounds of elements
selected from Groups 1-16, and mixtures thereof, to (1 ) inhibit the external
acidic sites to minimize aromatic alkylation on the non-para positions,
and/or the isomerization of the para-substituted compounds, and/or (2)
impose more restrictions on the channel structure to facilitate the
formation and transport of para-substituted aromatic compounds, in one
non-limiting explanation of the mechanism of the invention. It must be
understood that such treatment may be performed on aluminophosphate
catalyst reaction systems of this invention, but that some
aluminophosphate catalyst reaction systems do not require this para-
substituted selectivation treatment to be effective at para-substituent
selectivation.
The catalytic reaction systems suitable for this invention include (1 )
a first component of one or more than one silicate-based materials,
including but not necessarily limited to, crystalline or amorphous
aluminosilicates, substituted aluminosilicates, substituted silicates, zeolite-
bound zeolites, and/or crystalline or amorphous aluminophosphates,
and/or substituted aluminophosphates and mixtures thereof, and,
optionally (2) a second component of one or more than one of the metals
or oxides of the metals selected from Groups 1, 2, 3, 4, 5, 6, 7, 8, 9, 10,
11, 12, 13, 14, 15, and 16 (new IUPAC notation, e.g. zinc, copper,
chromium, cadmium, palladium, ruthenium, manganese, etc.). The first
and second components may be chemically mixed, physically mixed, and
combinations thereof, as will be described.
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The composition of the proposed catalyst reaction systems may
range from 95 wt.% silicate-based material or aluminophosphate-based
material first component/5 wt.% metals or metal oxides second
component, if present, to 5 wt.% silicate-based material or
aluminophosphate-based material first component/95 wt.% metals or
metal oxides second component, if present.
It will be understood that the selectivation techniques of this
invention may be practiced before or after the silicate-based materials or
aluminophosphate-based materials are mixed with or combined chemically
or physically with metals or metal oxides, if used. That is, in some
embodiments, the silicate-based materials and aluminophosphate-based
materials may be selectivated before combination with metals or metal
oxides. In other embodiments, silicate-based materials and
aluminophosphate-based materials may be selectivated after combination
with metals or metal oxides. The former process might be termed "pre-
selectivation", while the latter process may be termed "post-selectivation".
One type of the zeolite materials would be silicate-based zeolites
such as faujasites, morden~ites, pentasils, etc.
Zeolite materials suitable for this invention include silicate-based
zeolites and amorphous compounds. Silicate-based zeolites are made of
alternating Si02 and MOX tetrahedra, where in the formula M is an element
selected from the Groups 1 through 16 of the Periodic Table (new IUPAC).
These types of zeolites have 8-, 10-, or 12-membered oxygen ring
channels. Silicate-based materials are generally acidic. The more
preferred zeolites of this invention include 10- and 12-membered ring
zeolites, such as ZSM-5, ZSM-11, ZSM-22, ZSM-48, ZSM-57, etc.
One of the disadvantages to the use of many unselectivated
silicate-based materials for such para-substituted synthesis systems is the
lack of product selectivity (i.e. an undesirably broad product distribution
results). The acidity of many aluminosilicates are sufficiently high that they
often promote many undesirable side reactions (e.g. dealkylation, multi-
alkylation, oligomerization, and condensation) which deactivate the
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catalysts and lower the product value. It follows that silicate-based
materials are typically not capable of delivering the shape selectivity for
increasing the yield for high-value products such as para-xylene (PX).
Some of the silicate-based materials have one-dimensional channel
structures, which are capable of generating higher-than-equilibrium PX
selectivity. These materials may optionally be para-substituent
selectivated. Other silicate-based materials having two- or three-
dimensional channel structures are preferably para- substituent
selectivated or modified to be more selective through the use of certain
chemical compounds, as will be described, such as organometallic
compounds and compounds of elements selected from Groups 1-16. In
one embodiment, the selectivation of the zeolite materials including the
silicate-based materials can be accomplished using compounds including,
but not necessarily limited to silicon, phosphorus, boron, antimony,
magnesium compounds, coke, and the like, and mixtures thereof.
Other silicate-based materials suitable for the second component
include zeolite bound zeolites as described in WO 97/45387. Zeolite
bound zeolite catalysts useful in the present invention concern first
crystals of an acidic intermediate pore size first zeolite and a binder
comprising second crystals of a second zeolite. Unlike zeolites bound with
amorphous material such as silica or alumina to enhance the mechanical
strength of the zeolite, the zeolite bound zeolite catalyst suitable for use
in
the present process does not contain significant amounts of non-zeolitic
binders.
The first zeolite used in the zeolite bound zeolite catalyst is an
intermediate pore size zeolite. Intermediate pore size zeolites have a pore
size from about 5 to about 7 A and include, for example, AEL, MFI, MEL,
MFS, MEI, MTW, EUO, MTT, HEU, FER, and TON structure type zeolites.
These zeolites are described in Atlas of Zeolite Structure Types, eds. W.
H. Meier and D. H. Olson, Butterworth-Heineman, Third Edition, 1992.
Examples of specific intermediate pore size zeolites include, but are not
limited to, ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-34, ZSM-35,
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ZSM-38, ZSM-48, ZSM-50, and ZSM-57. Preferred first zeolites are
galliumsilicate zeolites having an MFI structure and aluminosilicate
zeolites having an MFR structure.
The second zeolite will usually have an intermediate pore size and
have less activity than the first zeolite. Preferably, the second zeolite will
be substantially non-acidic and will have the same structure type as the
first zeolite. The preferred second zeolites are aluminosilicate zeolites
having a silica to alumina mole ratio greater than 100 such as low acidity
ZSM-5. If the second zeolite is an aluminosilicate zeolite, the second
zeolite will generally have a silica to alumina mole ratio greater than 200:1,
e.g., 500:1; 1,000:1, etc., and in some applications will contain no more
than trace amounts of alumina. The second zeolite can also be silicalite,
i.e., a MFI type substantially free of alumina, or silicalite 2, a MEL type
substantially free of alumina. The second zeolite is usually present in the
zeolite bound zeolite catalyst in an amount in the range of from about 10%
to 60% by weight based on the weight of the first zeolite and, more
preferably, from about 20% to about 50% by weight.
The second zeolite crystals preferably have a smaller size than the
first zeolite crystals and more preferably will have an average particle size
from about 0.1 to about 0.5 microns. The second zeolite crystals, in
addition to binding the first zeolite particles and maximizing the
performance of the catalyst will preferably intergrow and form an over-
growth which coats or partially coats the first zeolite crystals. Preferably,
the crystals will be resistant to attrition.
The zeolite bound zeolite catalyst suitable for the process of the
present invention is preferably prepared by a three step procedure. The
first step involves the synthesis of the first zeolite crystals prior to
converting it to the zeolite bound zeolite catalyst. Next, a silica-bound
aluminosilicate zeolite can be prepared preferably by mixing a mixture
comprising the aluminosilicate crystals, a silica gel or sol, water and
optionally an extrusion aid and, optionally, the metal component until a
homogeneous composition in the form of an extrudable paste develops.
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The final step is the conversion of the silica present in the silica-bound
catalyst to a second zeolite which serves to bind the first zeolite crystals
together.
As noted, aluminophosphate-based materials may be used in
conjunction with metal oxides for aromatic alkylation with syngas.
Aluminophosphate-based materials usually have lower acidity compared
to silicate-based materials. The lower acidity eliminates many side
reactions, raises reactants' utilization, and extends catalyst life.
Further catalytic reaction systems suitable for this invention include
aluminophosphate-based materials and amorphous compounds.
Aluminophosphate-based materials are made of alternating A104 and P04
tetrahedra. Members of this family have 8- (e.g. AIP04-12, -17, -21, -25, -
34, -42, etc.), 10- (e.g. AIP04-11, 41, etc.), or 12- (AIP04-5, -31, etc.)
membered oxygen ring channels. Although AIP04s are neutral,
substitution of AI and/or P by cations with lower charge introduces a
negative charge in the framework, which is countered by cations imparting
acidity.
By turn, substitution of silicon for P and/or a P-AI pair turns the
neutral binary composition (i.e. AI, P) into a series of acidic-ternary-
composition (Si, AI, P) based SAPO molecular sieves, such as SAPO-5, -
11, -14, -17, -18, -20, -31, -34, -41, -46, etc. Acidic ternary compositions
can also be created by substituting divalent metal ions for aluminum,
generating the MeAPO materials. Me is a metal ion which can be selected
from the group consisting of, but not limited to, Mg, Co, Fe, Zn and the
like. Acidic materials such as MgAPO (magnesium substituted), CoAPO
(cobalt substituted), FeAPO (iron substituted), MnAPO (manganese
substituted), ZnAPO (zinc substituted) etc. belong to this category.
Substitution can also create acidic quaternary-composition based
materials such as the MeAPSO series, including FeAPSO (Fe, AI, P, and
Si), MgAPSO (Mg, AI, P, Si), MnAPSO, CoAPSO, ZnAPSO (Zn, AI, P, Si),
etc. Other substituted aluminophosphate-based materials include EIAPO
and EIAPSO (where EI = B, As, Be, Ga, Ge, Li, Ti, etc.) As mentioned
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above, these materials have the appropriate acidic strength for
syngas/aromatic alkylation. Some preferred aluminophosphate-based
materials of this invention include 10- and 12-membered ring molecular
sieves (SAPO-11, -31, -41; MeAPO-11, -31, -41; MeAPSO-11, -31, 41;
5 EIAPO-11, -31, -41; EIAPSO-11, -31, -41, etc.) which already have
significant shape selectivity due to their narrow channel structure.
These aluminophosphates may be para-alkyl selectivated or
modified to be more selective through the use of certain chemical
compounds, as will be described, such as organometallic compounds and
10 compounds of elements selected from Groups 1-16. In one embodiment,
the para-alkyl selectivation of the zeolite materials including the
aluminophosphate-based materials can be accomplished using
compounds including, but not necessarily limited to silicon, phosphorus,
boron, antimony, magnesium compounds, coke, and the like, and mixtures
thereof.
The preparation of the catalytic reaction systems can be
accomplished with several techniques known to those skilled in the art.
Some examples are given below.
Para-selectivation involves the treatment of the above mentioned
catalytic reaction system materials with proper chemical compounds of
elements selected from Groups 1-16, and mixtures thereof. The
composition of the selectivated catalyst may range from 1 wt.% of the
selectivating elements/99 wt.% of the first component to 99 wt.% of the
selectivating elements/1 wt.% of the first component. By "selectivating
elements" is meant the elemental portion of the elemental form or
elemental oxide form of the selectivating chemical compounds.
Some para-substituent selectivation treatments are known, e.g.
using silicon compounds. Other compounds that may be used include, but
are not limited to compounds of phosphorus, boron, antimony,
magnesium, and the like, and coke, and the like. Para-substituent
selectivation treatments of the materials of the above catalytic reaction
systems can be carried out either prior to the selective formation of PX (ex
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situ) or during the PX formation (in situ), to use PX formation as a non-
limiting example. In the in situ embodiment, the selectivating agents are
added with the feed to the reactor containing a catalytic reaction system.
In more detail, in one non-limiting embodiment, the technique for
selectivating the materials according to the method of this invention is
based on the consideration that by depositing on a silicate-based material
or aluminophosphate-based material one or more than one of the
organometallic compounds which are too bulky to enter the channels (or
other selectivating agent), one should be able to modify only the external
surface and regions around channel mouth. The fact that the selectivation
agent does not enter the channels preserves the active sites inside the
channels. Since the channel active sites account for more the majority of
the total active sites, their remaining active prevents any significant loss
of
reactivity or conversion.
One type of the bulky organometallic compounds suitable for
selectivating 10-member-ring zeolites, such the ZSM family (e.g. ZSM-5, -
11, -22, -48, etc.), mordenite, etc., is the salts of large organic anions and
metallic cations. The organic anions can be selected from molecules
containing carboxylic and/or phenolic functional groups, including but not
limited to phthalate, ethylenediaminetetraacetic acid (EDTA), vitamin B-5,
trihydroxy benzoic acid, pyrogallate, salicylate, sulfosalicylate, citrate,
naphthalene dicarboxylate, anthradiolate, camphorate, and others. The
metallic cations can be selected from the elements) of Groups 1, 2, 3, 4,
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, and 16 (new IUPAC notation). Other
compounds for selectivating the silicate-based and aluminophosphate-
based materials include, but are not necessarily limited to silicon,
phosphorus, boron, antimony, magnesium compounds, coke, and the like,
and mixtures thereof.
Selectivation of silicate-based materials and aluminophosphate-
based materials with the above-mentioned organometallic salts can be
accomplished by various means. For example, one can use impregnation
of a solution of an organometallic salt onto a silicate-based material or
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aluminophosphate-based material. Either water or any suitable organic
solvent can be used. Addition of non-metallic salts and/or adjustments of
pH to facilitate the treatment are optional. Heat will be provided to drive
off
the solvent, leaving behind a material coated homogeneously with the
organometallic salt. Drying and calcination of the coated zeolite or
aluminophosphate-based material at appropriate temperatures will turn
the salt into metal oxide form or elemental metal form (agent derivative).
Alternatively, one can use a dry-mix technique, which involves mixing
directly a zeolite in the form of powder or particles with an organometallic
salt also in the form of powder or particles without the use of any solvent.
The mixture will then be subjected to heat treatment, which facilitates the
dispersion of the salt over the material and eventually turns the salt into
elemental form or metal oxide form (agent derivative).
Known techniques for ex situ and in situ catalytic reaction system
modification can be incorporated into producing the para-alkyl selectivated
catalytic reaction systems of the present invention in addition to those
herewith, such as those seen in U.S. Pat. Nos. 5,476,823 and 5,675,047.
In one embodiment, the same elemental metals and/or metal oxide
second components used in the catalytic reaction system can be used
alone or together to selectivate the silicate-based material or
aluminophosphate-based material components.
The catalytic reaction systems can be prepared by adding solutions
of elemental metal salts either in series to or as a mixture with the fine
powder or particles such as extrudates, spheres, etc. of the unselectivated
silicate-based materials having one dimensional channel structures, or
optionally ex situ selectivated silicate-based materials, unselectivated
aluminophosphate-based materials, or optionally ex situ selectivated
aluminophosphate-based materials, until incipient wetness is reached. The
solvent (water or other solvents) can be evacuated under heat or vacuum
using typical equipment such as a rotary evaporator. The final product is
dried, calcined, and pelletized, if necessary.
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Alternatively, solutions of metal salts and the ex situ selectivated
fine powder or particles such as extrudates, spheres, etc. of silicate-based
and aluminophosphate-based materials are thoroughly mixed. A dilute
basic solution (e.g. ammonia, sodium carbonate, potassium hydroxide,
etc.) is used to adjust the pH value of the mixture to facilitate the
precipitation of metal hydroxides and zeolites. The precipitate is filtered
and washed thoroughly with water. The final product is dried, calcined,
and pelletized, if necessary.
The catalytic reaction systems can also be prepared using physical
mixing. Finely divided powders of metals) or metal oxide(s), or powders of
metals) or metal oxides) supported on any inert materials, are mixed
thoroughly with finely divided powder of the ex situ selectivated silicate-
based materials, unselectivated aluminophosphate-based materials, or
optionally ex situ selectivated aluminophosphate-based materials in a
blending machine or a grinding mortar. The mixture is optionally pelletized
before use.
If the catalytic reaction system is mixed with a binder, such as silica
gel or sol or the like, an extrudable paste may be formed. The resulting
paste can be molded, e.g. extruded, and cut into small strands which can
then be dried and calcined.
The catalytic reaction system can also be prepared by mixing
physically the particles of silicate-based material or aluminophosphate-
based materials components and the particles of the metal and/or metal
oxide second components, if present. The same metals and/or metal
oxides can also be used alone or together to selectivate catalytic reaction
systems and thus simultaneously catalyze syngas and/or other reactions.
The catalytic reaction system can also be formed by packing the
first and the second components, if present, in a stacked-bed manner with
some of the first component in front of the physical or chemical mixture of
the first and second components.
Prior to exposing the catalysts to the feed components of toluene
and/or benzene, H2, CO, and/or C02 and/or methanol, the catalyst
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reaction systems can optionally be activated under a reducing
environment (e.g. 1-80% H2 in N2) at 150-500°C, and 1-200 atm (1.01 x
105 - 2.03 x 10' Pa) for 2-48 hours.
The average crystal size of the crystals in the silicate-based
material or aluminophosphate-based materials is preferably from above
0.1 micron to about 100 microns, more preferably from about 1 micron to
about 100 microns.
Procedures to determine crystal size are known to persons skilled
in the art. For instance, crystal size may be determined directly by taking a
suitable scanning electron microscope (SEM) picture of a representative
sample of the crystals.
The catalysts of this invention may be used in a methylation
process which can be carried out as a batch type, semi-continuous or
continuous operation utilizing a fixed or moving bed catalyst system.
Multiple injection of the methylating agent may be employed. The
methylating agent includes CO, C02 and H2 and/or CH30H and
derivatives thereof. The methylating agent reacts with benzene to form
toluene. Toluene reacts with the methylating agent to form a xylene,
preferably PX in this invention.
Toluene and/or benzene and the methylating agents) are usually
premixed and fed together into the reaction vessel to maintain the desired
ratio between them with no local concentration of either reactant to disrupt
reaction kinetics. Individual feeds can be employed, however, if care is
taken to insure good mixing of the reactant vapors in the reaction vessel.
Optionally, instantaneous concentration of methylating agent can be kept
low by staged additions thereof. By staged additions, the ratios of toluene
and/or benzene to methylating agent concentrations can be maintained at
optimum levels to give good toluene conversions. Hydrogen gas can also
serve as an anticoking agent and diluent.
The method of this invention, particularly when using para-
substituent selectivated catalytic reaction systems, stabilizes catalytic
reaction system performance and increases catalytic reaction system life.
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That is, catalytic reaction system deactivation is slowed and even
prevented. With properly para- substituent selectivated catalytic reaction
systems, it is expected that the catalytic reaction system may not have to
be regenerated at all. This is in part due to the silicate-based materials
5 and aluminophosphate-based materials being para- substituent
selectivated. With production selective to PX, in one non-limiting instance,
less by-products, such as heavy aromatics, are formed which would
deactivate the catalytic reaction systems. This characteristic is not shown
or taught by the prior art.
10 Further, in one non-limiting embodiment of the invention, there is a
belief that the catalytic reaction systems of this invention have the
capability of preventing or reducing the side reactions of the methylating
agents with themselves, and in particular that the para- substituent
selectivated catalytic reaction systems function to catalyze more than one
15 reaction, that is, that a syngas reaction is catalyzed to form methylating
agents which react with benzene and/or toluene to produce PX, e.g.
However, because the methylating agent is produced on a local,
molecular scale, its concentrations are very low (as contrasted with
feeding a methylating agent as a co-reactant). It has been demonstrated
that feeding a blend of methylating agent and toluene to make PX
increases coke build-up and hence catalytic reaction system deactivation.
In one non-limiting embodiment of the invention, the catalyst activity
decrease is less than 0.5% toluene and/or benzene conversion per day,
preferably less than 0.1 %,
In carrying out the PX synthesis process, the feed mixtures can be
co-fed into a reactor containing one of the above mentioned catalytic
reaction systems. The catalytic reaction system and reactants can be
heated to reaction temperatures separately or together. Reaction can be
carried out at a temperature from about 100-700°C, preferably from
about
200-600°C; at a pressure from about 1-300 atm (1.01 x 105-3.04 x 10'
Pa), preferably from about 1-200 atm (1.01 x 105-2.03 x 10' Pa); and at a
flow rate from about 0.01-100 h-' LHSV, preferably from about 1-50 h-'
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LHSV on a liquid feed basis. The composition of the feed, i.e. the mole
ratio of H2/CO(and/or C02)/aromatic can be from of about 0.01-10/0.01-
10/0.01-10, preferably from about 0.1-10/0.1-10/0.1-10.
As noted, typical methylating agents include or are formed from, but
are not necessarily limited to hydrogen together with carbon monoxide
and/or carbon monoxide, and/or methanol, but also dimethylether,
methylchloride, methylbromide, and dimethylsulfide.
It is conceivable that in the scenarios described above, the toluene
can be pure, or in a mixture with benzene. The benzene may alkylate to
toluene, and/or ultimately to PX, with or without recycle. The presence of
benzene may also enhance heat and/or selectivity control.
The PX method is expected to tolerate many different kinds of feed.
Unextracted toluene, which is a mixture of toluene and similar boiling
range olefins and paraffins, is preferred in one embodiment. For example,
premium extracted toluene, essentially pure toluene, and extracted
aromatics, essentially a relatively pure mixture of toluene and benzene,
may also be used. Unextracted toluene and benzene which contains
toluene, benzene, and olefins and paraffins that boil in a similar range to
that of toluene or benzene, may also be employed. When unextracted
feedstocks are used, it is important to crack the paraffins and olefins into
lighter products that can be easily distilled. For example, the feed may
contain one or more paraffins and/or olefins having at least 4 carbon
atoms; the catalytic reaction systems have the dual function to crack the
paraffins and/or olefins and methylate benzene or toluene to selectively
produce PX.
Indeed, some of the catalytic reaction systems of this invention may
be multifunctional in some embodiments, catalyzing a reaction or
reactions of CO, H2, and/or C02 and/or methanol to produce a methylating
agent, catalyzing the selective methylation of toluene and/or benzene to
produce PX, and catalyzing the cracking of paraffins and olefins into
relatively lighter products.
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The PX method is capable of producing mixtures of xylenes where
PX comprises at least 30 wt.% of the mixture, preferably at least 36 wt.%,
and most preferably at least 48 wt.%. The method of this invention is also
capable of converting at least 5 wt.% of the aromatic compound to a
mixture of xylenes, preferably greater than 15 wt.%.
The following examples will serve to illustrate processes and some
merits of the present invention. It is to be understood that these examples
are merely illustrative in nature and that the present process is not
necessarily limited thereto.
COMPARATIVE EXAMPLE I
This example illustrates the lack of para-selectivity from an
untreated ZSM-5 for toluene methylation with methanol. The ZSM-5
zeolite had a Si02/AI203 ratio of 38. It was tested at the conditions of
450°C, 1 atmospheric pressure (1.01 x 105 Pa), 7 WHSV (weight hourly
space velocity), and a toluene to methanol molar ratio of 1. Test results
indicated that one hour after cutting in the toluene/methanol feed, toluene
conversion was at 46% and the PX concentration in the xylene-fraction
product was at the equilibrium value of 24%, indicating the lack of
selectivity toward PX.
COMPARATIVE EXAMPLE II
This example illustrates the loss of zeolite activity or conversion
from conventional selectivation techniques that use compounds which are
small enough to enter the zeolite channels. An aqueous solution of
magnesium nitrate was prepared by mixing magnesium nitrate
hexahydrate and water on the basis of 0.71 gram per gram of water. The
solution was used to impregnate a ZSM-5 (Si02/A1203 = 38) zeolite
powder at a ratio of 1.35 cc solution to 1.50 g of zeolite. The mixture was
heated at 75°C to evaporate the water. It was then dried at
120°C for 6
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hours, at 250°C for 1/2 hour, and at 300°C for 1/2 hour, and
then calcined
at 500°C for 3 hours. Analysis of the zeolite sample indicated that
0.06
gram of magnesium oxide per gram of zeolite was deposited on the
zeolite.
A portion of the treated zeolite was tested for toluene methylation
with methanol. The test was carried out at the same conditions as in
Example I. Test results indicated that one hour after cutting in the feed,
toluene conversion was 29% and PX concentration in the xylene-fraction
product was 58%.
The selectivation treatment was repeated on the remaining of the
treated zeolite. This second treatment raised the Mg0 on zeolite from 0.06
g/g to 0.12 g/g. Toluene methylation results on this double-treated zeolite
showed a toluene conversion of 18% and a PX concentration in the
xylene-fraction product of 90%. Comparing Example II to Example I, it is
apparent that an increase of PX selectivity from 24% to 90% lowered the
conversion from 46% to 18%.
INVENTIVE EXAMPLE III
This example illustrates the use of bulky organometallic salts for
zeolite selectivation. An aqueous solution of lanthanum nitrate was
prepared by dissolving 18.0 gram of La(N03)3~6H20 in 80.0 cc of water. 60
cc of 25% ammonia solution was added to the lanthanum solution with
stirring. The addition was completed in a period of 10 minutes. The
precipitate of La(OH)3 was filtered and suspended into 300 cc of water.
13.7 gram of ethylenediaminetetraacetic acid (EDTA) was added to the
suspension with stirring to obtain a solution, which was boiled and
concentrated to obtain a La-EDTA solution with a concentration of 0.02
gram La per cc of solution.
11.4 cc of the La solution was used to impregnate 2.0 gram of
ZSM-5 zeolite (Si02/AI203 = 38). The mixture was heated at 75°C to
evaporate the water. It was then dried at 120°C overnight, and calcined
at
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500°C for 6 hours. Analysis of the zeolite sample indicated that 0.14
gram
of La203 per gram of zeolite was deposited on the zeolite.
The La-treated zeolite was tested for toluene methylation with
methanol at the same conditions as that in Examples I and II. Test results
indicated a toluene conversion of 38% and a PX selectivity of 81 %.
Apparently, selectivation using a bulky organometallic salt such as La-
EDTA was able to increase para-selectivity significantly with only small
loss in zeolite activity.
INVENTIVE EXAMPLE IV
This example illustrates the use of another bulky organometallic salt
for zeolite selectivation. An aqueous solution of Mg(N03)2 was prepared
by mixing 128.35 g of Mg(N03)2~6H20 in 300 cc water. 60 cc of 25%
ammonia solution was added to the Mg(N03)2 solution with stirring in a 10
minutes period. The Mg(OH)2 precipitate was filtered and suspended in
500 cc water. 66.36 g phthalic acid was deeded to the suspension with
stirring and heating to obtain a clear solution, which was boiled and
concentrated to 300 cc. It was cooled to room temperature and filtered to
obtain a Mg-phthalate filtrate having a concentration of 0.017g Mg per cc
of filtrate.
2.05 cc of the Mg-phthalate solution was used to impregnate 2.01 g
ZSM-5 zeolite (Si02/AI203 = 38). The mixture was heated at 75°C to
evaporate the water. It was then dried at 120°C for 6 hours and
calcined at
500°C for 8 hours. This procedure was repeated twice to obtain a 3-time
selectivated zeolite sample containing 0.075 g Mg0 per gram of zeolite.
Results of toluene methylation test showed a toluene conversion of 39%
and a PX selectivity of 84%, indicating again the effectiveness of bulky
organometallic salts for zeolite selectivation.
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COMPARATIVE EXAMPLE V
This example illustrates one of the methods in preparing a catalyst.
The catalyst comprises (1 ) Cr and Zn mixed metal oxides; and (2) H-ZSM-
5 5 zeolite with a Si02/AI203 molar ratio of 30 (obtained from PQ
Corporation, Valley Forge, PA). The Cr and Zn mixed metal oxides were
prepared by co-precipitation of Cr(N03)3 and Zn(N03)2 with NH40H. 7.22
grams of Cr(N03)3 and 13.41 grams of Zn(N03)2 were dissolved in 100 ml
distilled water separately. The two solutions were then mixed together.
10 NH40H was slowly added into the mixed solution with stirring until the pH
value of the solution reached about 8. The precipitate was filtered and
recovered. This precipitate was dried at a temperature of 120°C for 12
hours, and then calcined in air at 500°C for 6 hours. These Cr/Zn mixed
metal oxides were ground into powders.
15 The catalytic reaction system was prepared by physically mixing
powders of a composition of 50% (w/w) Cr/Zn mixed metal oxides and
50% (w/w) H-ZSM-5 zeolite. Powders of 2.0 grams of Cr/Zn mixed metal
oxides and 2.0 grams of H-ZSM-5 zeolite were mixed thoroughly in a
grinding mortar. The mixed catalytic reaction system powders were
20 pelletized and screened to 8-12 mesh (0.89-0.73 cm) particles.
COMPARATIVE EXAMPLE VI
This example shows that the synthesis of xylenes with syngas
alkylation of toluene can be achieved in a catalytic process as disclosed in
a prior process. However, this example indicates that this process cannot
achieve high para-xylene selectivity when the aluminosilicate component
in the catalytic reaction system is not modified for shape selectivity. The
catalytic reaction system was prepared as in Example V. The catalyst was
reduced at 350°C under 5% H2 (balanced with 95% N2) for 16 hours at 1
atm prior to reaction.
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The catalytic reaction system was evaluated with co-feed of syngas
(CO and H2) and toluene with a composition of H2/CO/toluene of 2/1/0.5
(molar ratio), a temperature of about 450°C, and a pressure of about 18
atm (i.e., 250 psig, 2.53 x 10' Pa). The WHSV (Weight Hourly Space
Velocity) was about 3 h~' for toluene with respect to the catalyst. Test
results are given in Table 1. Similar to prior art reported, the selectivity
of
para-xylene in xylenes is about 25%, which is close to equilibrium, with
toluene conversion of 28.6% and xylene selectivity of 71.1 %.
TABLE 1
Synthesis of PX using Zeolite not Selectivated
CO conv. % H2 conv. % Toluene conv. % Xylene select. PX select.
31.7 17.1 28.6 71.1 25.0
INVENTIVE EXAMPLE VII
This example illustrates the preparation of para-alkyl selectivated
ZSM-5 zeolite with magnesium oxide as the selectivating agent. 11.68
grams of magnesium hydroxide was mixed with distilled water. To the
solution was added 20.44 grams of ammonium nitrate and 33.54 grams of
phthalic acid in sequence. The mixture was heated to obtain a clear
solution, which was cooled to room temperature before use. 14.80 grams
of the solution was mixed with 7.77 grams of a ZSM-5 zeolite (Si02/A102
of 50). The mixture was heated to evaporate the water solvent. The
remaining solid was dried at 120°C for 12 hours and calcined at
500°C for
8 hours with air purge. The para-alkyl selectivated ZSM-5 zeolite
contained approximately 9 wt.% of magnesium oxide.
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INVENTIVE EXAMPLE VIII
This example illustrates the preparation of another type of the
catalytic reaction system. The catalytic reaction system comprises (1 ) Mn
and Zn mixed metal oxides, and (2) Mg0 modified H-ZSM-5 zeolite with a
Si02/A102 of 38. The same preparation procedures as that given in
Example VII were used. The Mn and Zn mixed metal oxides were
prepared by co-precipitation of Mn(N03)2 and Zn(N03)2 with NH40H. 4.14
grams of Mn(N03)2 and 13.44 grams of Zn(N03)2 were dissolved in 100 ml
distilled water separately. The two solutions were then mixed together.
NH40H was slowly added into the mixed solution with stirring until the pH
value of the solution reached about 7.5. The precipitate was filtered and
recovered. This precipitate was dried at a temperature of 120°C for 12
hours, and then calcined in air at 500°C for 6 hours. These Mn/Zn mixed
metal oxides were ground into powders.
The catalytic reaction system was prepared by physically mixing
powders of a composition of 50% (w/w) Mn/Zn mixed metal oxides and
50% (w/w) Mg0 modified H-ZSM-5 zeolite. Powders of 2.0 grams of
Mn/Zn mixed metal oxides and 2.0 grams of Mg0 modified H-ZSM-5
zeolite were mixed thoroughly in a grinding mortar. The mixed catalytic
reaction system powders were pelletized and screened to 8-12 mesh
(0.89-0.73 cm) particles.
INVENTIVE EXAMPLE IX
This example illustrates that metal oxides other than Cr/Zn mixed
metal oxides are also suitable as one of the components in the catalytic
reaction system used in the xylenes synthesis with syngas alkylation of
toluene. In addition, this example demonstrates that high para-xylene
selectivity can be obtained when the aluminosilicate component in the
catalytic reaction system is modified for shape selectivity. The catalytic
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reaction system was prepared as in Example VIII. The catalytic reaction
system was reduced at 350°C under 5% H2 (balanced with 95% N2) for 16
hours at 1 atm prior to reaction.
The reaction was conducted under similar conditions to those in
Example VI. Test results are given in Table 2. The para-xylene selectivity
in xylenes is about 76.0% with toluene conversion of 10.9% and xylene
selectivity of 85.4%. Compared to Example VI, the para-xylene selectivity
is significantly enhanced when the aluminosilicate component is modified
for shape selectivity.
TABLE 2
Synthesis of PX using Zeolite Modified for Shape Selectivity
CO cony. % H2 cony. % Toluene cony. % Xylene select. % PX select.
11.7 5.6 10.9 85.4 76.0
INVENTIVE EXAMPLE X
This example illustrates that the toluene conversion can be
increased with a similar high para-xylene selectivity when the reaction
operation conditions are optimized. The catalytic reaction system used in
this example was comprised of a composition of (1 ) 50% (w/w) Cr, Zn, and
Mg mixed metal oxides, and (2) 50% (w/w) Mg0 modified H-ZSM-5 zeolite
with a Si02/A102 of 38. The Cr, Zn, and Mg mixed metal oxides were
prepared in a similar method as described in Example V with co-
precipitation of Cr(N03)3, Zn(N03)2, and Mg(N03)2 with NH40H. The
magnesium oxide-modified ZSM zeolite was prepared as described in
Example VIII. The catalytic reaction system was prepared by physical
mixing as described in Example V. The catalytic reaction system was
reduced at 350°C under 5% H2 (balanced with 95% N2) for 16 hours at 1
atm (1.01 x 105 Pa) prior to reaction.
The catalytic reaction system was evaluated with co-feed of syngas
(CO and H2) and toluene with a varied composition of H2/CO/toluene, a
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temperature from 450-490°C, and a pressure in the range of 18-28 atm
(i.e. 250-390 psig, 2.53 x 10'-3.95 x 10' Pa). The WHSV (Weight Hourly
Space Velocity) varied from 1.5-6 h-' for toluene with respect to the
catalytic reaction system. Some of the test results are shown in Table 3.
As shown in Table 3, a toluene conversion of 34% was achieved with a
similar para-xylene selectivity when the reaction was operated at a
temperature of ca. 460°C, a pressure of ca. 28 atm (390 psig.), and a
WHSV of ca. 1.5 h-' for toluene with respect to catalytic reaction system.
TABLE 3
Synthesis of PX using Zeolite e Selectivity
Modified for Shap
Reaction Temperature, C 460 460 460 475
Reaction Pressure, psig 250 390 250 250
Reaction Pressure, Pa 2.53 x 10' 3.95 2.53 x 10' 2.53
x 10' x 10'
Feed Composition, mole ratio 2/1/0.25 2/1/0.252/1/0.5 2/1/0.5
WHSV, h-' (Tol./Catalyst) 1.5 1.5 3 3
CO cony. % 18.4 29.2 17.4 18.1
H2 cony. % 6.6 9.4 7.4 7.6
Toluene cony. % 26.0 34.7 13.6 15.5
Xylene select. % 84.2 80.1 82.4 86.3
PX select. % 74.5 75.2 88.0 85.1
COMPARATIVE EXAMPLE XI
This example illustrates the problems of low methanol selectivity
and fast catalytic reaction system deactivation associated with a low
aromatic/methanol ratio and one-time methanol injection. The catalytic
reaction system was extrudates of SAPO-11 material obtained from UOP.
The extrudates were ground and screened to 8-12 mesh (0.89-0.73 cm)
and calcined at 550°C under air for 16 hours prior to use. The
catalytic
reaction system was evaluated at 350°C, 25 atm (350 psig, 3.55 x 10'
Pa), and 8 h-' WHSV. The feed was a mixture of toluene/methanol with a
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molar ratio of 3.6. Test results are given in Table 4. It is seen that the
methanol selectivity decreased from 70.0% to 55.0 % over a test period of
24 hours. Furthermore, the system was experiencing a severe catalytic
reaction system deactivation as indicated by the decreasing toluene
5 conversion from 18.5% to 15.1 %.
TABLE 4
Synthesis of PX with Low Methanol Selectivity and Catalyst
Deactivation
Toluene/Methanol (mole) 3.6
Hours on Stream 2 24
Toluene Total Conversion 18.5 % 15.1
Toluene Conversion due to Disproportionation 0 % 0
Toluene Conversion due to Methylation 18.5 % 15.1
Methanol Total Conversion 100 % 97.0
Methanol consumed by mono- and multiple 70.0 % 55.0
methylation of toluene
Methanol consumed by other Reactions 30.0 % 42.0
COMPARATIVE EXAMPLE XII
This example demonstrates the problems of fast catalytic reaction
system deactivation for Mg0 para-alkyl selectivated H-ZSM-5 in toluene
methylation with low toluene/methanol ratio and one-time methanol
injection. The catalytic reaction system was Mg0-para-alkyl selectivated
H-ZSM-5 with a Si02/AIOZ ratio of 38. The same preparation procedure as
that given in Example VIII was used. The catalytic reaction system was
pelletized and screened to 40-60 mesh. The catalytic reaction system was
tested at 460°C, 1 atm, and 14 h-' WHSV. The feed was a mixture of
toluene/methanol with a molar ratio of 1Ø The results presented in Table
5 indicate that although Mg0 para-alkyl selectivation of H-ZSM-5 improves
the para-xylene selectivity, this catalytic reaction system still exhibits
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serious catalytic reaction system deactivation as indicated by the
decreasing toluene conversion from 20.5% to 8.5%.
TABLE 5
Synthesis of PX Showinct Catalytic Reaction System Deactivation
Toluene/Methanol (molar ratio) 1/1
Hours on Stream 0.5 2 2 2.5
Toluene Conversion, % 19.3 19.8 20.5 8.5
Methanol Conversion, % 100 100 100 99.6
Xylene Selectivity, % 76.7 76.4 84.1 86.1
Para-Xylene Selectivity, % 83.3 83.3 86.5 76.3
EXAMPLE XIII
This example demonstrates that the catalytic reaction system would
suffer from deactivation for syngas methylation of toluene if the
aluminosilicate component in the catalytic reaction system is not properly
para-alkyl selectivated. The test was conducted in the same manner as
Example VI. The reaction was monitored as time-on-stream, and the
results are shown in Table 6. The catalytic reaction system displays some
deactivation over a period of 18 hours as indicated by the decreasing
toluene conversion from 35.3% to 28.6%.
08-06-2001 '1 ~'i : '«H uLM-Marian Mossman& sr~ ram 915 392 8805 US 00001300
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28
seen that the catalytic reaction system had a stable activity for toluene
conversion with stable PX selectivity.
TABLE 7
Hiq,.her Activity Mainten ance for -xvlene sis
P~ra Synthe
H2ICO/Toluene (molar ratio) 21110.5
Hours on Stream, h 5.5 24 81.5 120
Toluene Conversion, % 17.0 18.0 17.4 17.1
CO Conversion, l0 20.5 20.7 17.9 17.8
H2 Conversion, % 8.5 9.3 9.1 9.1
Xylene Selectivity, % 76.5 80.2 80.6 80.5
Para-Xylene Selectivity, 63.4 67,0 71.4 75.2
%
In the foregoing specification, the invention has been described with
reference to speck embodiments thereof, and has been demonstrated as
effective in providing methods for modifying catalyst reaction systems, and
the catalyst reaction systems per se, which may be used for directly and
selectively producing PX from benzene andlor toluene and hydrogen
together with CO andlor C02 andlor methanol, and for other reactions.
However, it will be evident that various modifications and changes can be
made thereto without departing from the invention as set forth in the
appended claims. Accordingly, the specification is to be regarded in an
illustrative rather than a restrictive sense. For example, specific
combinations of catalyst components, such as organometallic compounds,
other than those specifically tried, in other proportions or ratios or mixed
in
different ways, falling within the claimed parameters, but.not specifically
identified or tried in a. particular example, are anticipated to be within the
scope of this invention. Further, various combinations of reactants,
catalytic reaction systems, and control techniques not explicitly described
but nonetheless falling within the appended claims are understood to be
included.
':,i3~3~1;'t11~'(.= ;7I~E.::' ::n<:J~.i: ~3~
AMENDED SHEET
Emvfangsteit 8.Juni 15:48
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TABLE 6
Synthesis of PX Showina Catalytic Reaction System Deactivation
CO/Toluene (molar ratio) 2/1/0.5
Hours on Stream 2 9.5 18.2
Toluene Conversion, 35.3 31.1 28.6
%
CO Conversion, % 33.6 31.4 31.7
H2 Conversion, % 17.8 16.4 17.1
Xylene Selectivity, 67.4 69.8 71.1
%
Para-Xylene Selectivity,24.8 24.9 25.0
%
INVENTIVE EXAMPLE XIV
This example illustrates that the process disclosed in this invention
has a much higher activity maintenance for PX synthesis than the
conventional methanol-toluene methylation process.
The catalytic reaction system used in this example comprised (1 )
Cr and Zn mixed metal oxides, and (2) Mg0 modified H-ZSM-5 zeolite
with a Si02/A102 of 38. The Cr and Zn mixed metal oxides were prepared
as described in Example I. The magnesium oxide-modified ZSM zeolite
was prepared as described in Example V. The Cr/Zn mixed metal oxides
were ground into powders. The catalytic reaction system was prepared by
physically mixing powders of a composition of (1 ) 34% (w/w) Cr and Zn
mixed metal oxides, and (2) 66% Mg0 modified H-ZSM-5 zeolite. The
mixed catalytic reaction system powders were pelletized and screened to
8-12 mesh (0.89-0.73 cm) particles. The catalytic reaction system was
reduced at 350°C under 5% H2 (balanced with 95% N2) for 16 hours at 1
atm (1.01 x 105 Pa) prior to reaction. The organometallic modifier was
magnesium phthalate.
The catalytic reaction system was evaluated with similar operation
conditions as those in Example II. Test results are given in Table 7. It is
CA 02371225 2001-12-07
WO 00/74847 PCT/US00/13003
28
seen that the catalytic reaction system had a stable activity for toluene
conversion with stable PX selectivity.
TABLE 7
Higher Activity Maintenance for Para-xylene Synthesis
H2/CO/Toluene (molar ratio) 2/1/0.5
Hours on Stream, h 5.5 24 91.5 120
Toluene Conversion, % 17.0 18.0 17.4 17.1
CO Conversion, % 20.5 20.7 17.9 17.8
H2 Conversion, % 8.5 9.3 9.1 9.1
Xylene Selectivity, % 76.5 80.2 80.6 80.5
Para-Xylene Selectivity, % 63.4 67.0 71.4 75.2
In the foregoing specification, the invention has been described
with reference to specific embodiments thereof, and has been
demonstrated as effective in providing methods for modifying
catalyst
reaction systems, and the catalyst reaction systems per
se, which may be
used for directly and selectively producing PX from benzene
and/or
toluene and hydrogen together with CO and/or C02 and/or methanol,
and
for other reactions. However, it will be evident that various
modifications
and changes can be made thereto without departing from the
broader
spirit or scope of the invention as set forth in the appended
claims.
Accordingly, the specification is to be regarded in an illustrative
rather than
a restrictive sense. For example, specific combinations of
catalyst
components, such as organometallic compounds, other than those
specifically tried, in other proportions or ratios or mixed
in different ways,
falling within the claimed parameters, but not specifically
identified or tried
in a particular example, are anticipated to be within the scope
of this
invention. Further, various combinations of reactants, catalytic
reaction
systems, and control techniques not explicitly described but
nonetheless
falling within the appended claims are understood to be included.
