CA2195306A1 - Shape selective hydrocarbon conversion - Google Patents
Shape selective hydrocarbon conversionInfo
- Publication number
- CA2195306A1 CA2195306A1 CA002195306A CA2195306A CA2195306A1 CA 2195306 A1 CA2195306 A1 CA 2195306A1 CA 002195306 A CA002195306 A CA 002195306A CA 2195306 A CA2195306 A CA 2195306A CA 2195306 A1 CA2195306 A1 CA 2195306A1
- Authority
- CA
- Canada
- Prior art keywords
- catalyst
- xylene
- molecular sieve
- toluene
- mixture
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
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Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/0272—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing elements other than those covered by B01J31/0201 - B01J31/0255
- B01J31/0274—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing elements other than those covered by B01J31/0201 - B01J31/0255 containing silicon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J31/00—Catalysts comprising hydrides, coordination complexes or organic compounds
- B01J31/02—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides
- B01J31/12—Catalysts comprising hydrides, coordination complexes or organic compounds containing organic compounds or metal hydrides containing organo-metallic compounds or metal hydrides
- B01J31/123—Organometallic polymers, e.g. comprising C-Si bonds in the main chain or in subunits grafted to the main chain
- B01J31/124—Silicones or siloxanes or comprising such units
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C6/00—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions
- C07C6/08—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond
- C07C6/12—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond of exclusively hydrocarbons containing a six-membered aromatic ring
- C07C6/123—Preparation of hydrocarbons from hydrocarbons containing a different number of carbon atoms by redistribution reactions by conversion at a saturated carbon-to-carbon bond of exclusively hydrocarbons containing a six-membered aromatic ring of only one hydrocarbon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/12—After treatment, characterised by the effect to be obtained to alter the outside of the crystallites, e.g. selectivation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/32—Reaction with silicon compounds, e.g. TEOS, siliconfluoride
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/42—Addition of matrix or binder particles
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/52—Improvements relating to the production of bulk chemicals using catalysts, e.g. selective catalysts
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
- Catalysts (AREA)
- Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)
- Soft Magnetic Materials (AREA)
- Diaphragms For Electromechanical Transducers (AREA)
- Analysing Materials By The Use Of Radiation (AREA)
Abstract
A process for a shape selective hydrocarbon conversion such as toluene disproportionation, involves contacting a reaction stream under conversion conditions with a catalytic molecular sieve which has been preselectivated by agglomerating with an organosilicon compound.
Description
W096l03360 2 i ~ 5 3 0 6 PCT~S94/08239 8HAPE 8BLECTIVE ~yn~r~R~N C~..~K~N
The present invention is directed to shape selective hydrocarbon conversion such as the selective production of para-substituted aromatic ~ '- and in particular the selective diD~L~y~LLionation of toluene to produce para-xylene.
The term shape-selectiVe catalysis describes nn~Yr~cted catalytic selectiVities in zeolites. The principles behind shape selective catalysis have been reviewed extensively, e.g. by N-Y- Chen, W.E. Garwood and F.G. Dwyer, "Shape SelectiVe Catalysis in Industrial Applications, 36, Marcel Dekker, Inc- (1989). Within a zeolite pore, hydrocarbon conversion reactions such as paraffin isomerization, olefin skeletal or double bond isomerization, oligomerization and aromatic diD~l~uLLionation, alkylation or transalkylation reactions are g~v~L..ed by constraints imposed by the channel size.
Reactant selectivity occurs when a fraction of the feedstock is too large to enter the zeolite pores to react;
while product selectivity occurs when some of the products cannot leave the zeolite rh~nn~l c. Product distributions can also be altered by transition state selectivity in which certain reactions cannot occur because the reaction transition state is too large to form within the zeolite pores or cages. Another type of selectivity results from configurational diffusion where the ~ ;r,nc of the molecule approach that of the zeolite pore system. A small change in ~ irnC of the molecule or the zeolite pore can result in large diffusion changes leading to different product distributions. This type of shape selective catalysis is ~ LL~ted, for example, in selective toluene di~L~olLionation to p-xylene.
Para-xylene may be pL~uc~d by methylation of toluene with - -n~l as described by Chen et al., J. Amer. Chem.
Sec. 1~2, 101, 6783, and by toluene d~ ~oLLionation, as described by Pines in "The Chemistry of Catalytic W096/03360 2 1 q 5 3 a ~ PCT~S94/08239 Hydrocarbon Conversions", Academic Press, N.Y., 1981, p.
72. Such methods typically result in the production of a mixture inrll-~;ng para-xylene, ortho-xylene, and meta-xylene. D~p~n~i ng upon the para-selectivity of the catalyst and the reaction conditions, different percentages of para-xylene are obtained. The yield, i.e., the amount of feedstock actually converted to xylene, is also affected by the catalyst and the reaction conditions.
Previously known toluene methylation reactions typically provide many by-products such as those indicated in the ~ollowing formula:
T~h~ YI~m;c E~];libria for Toluene Conversion to th~ Products Tn~i cated Non-MTPX
184.27 g (2 moles Toluene) 82.92 g 101J~35 g C ~ ~ Ç Ç Et Et Et Et ~ 55~ ~ + ~ + ~ + ~ ~ + ~ + ~ +
C C
g= 52.59 9.64 21.45 10.05 3.00 1.22 1.90 0.70 Yield = Selectivity x Conversion=lOOx9.64 x 0.55 ~ 5.23 wt%
101.35 p-Xylene Yield = 100 x 9.64 = 5.23 wt%
184.27 p-Xylene Purity (p-Xylene/all C~'5) = 21.45 wt%
One method for increasing para-selectivity of zeolite catalysts is to modify the catalyst by ~.~ai -nt with "selectivating agents". Various silicon ~ ~ have been used to modify catalysts to improve selectivity in 1IYdLO~LU1I conversion processes. For example, U.S. Patent W096/03360 2 1 ~ 5 3 Q 6 PCT~S94/08239 ~ -3-hydrocarbon conversion processes. For example, U.S. Patent Nos. 4,145,315, 4,127,616, and 4,090,981 describe the use of a silic~n~ .d dissolved in an organic solvent to treat a zeolite. U.S. Patent Nos. 4,465,886 and 4,477,583 describe the use of an aqueous ~ n of a silicone to treat a zeolite. U.S. Patent Nos. 4,950,835 and 4,927,979 describe the use of alkoxysilanes carried by gases or organic solvents to treat a zeolite. U.S. Patent Nos.
4,100,215 and 3,698,157 describe the use of silanes in hydrocArhon~, e.g., pyridine, ethers, to treat a zeolite.
Such modification methods are known in the art to be carried out after agglomeration of the zeolite.
Some of these catalyst modification procedures, for example, U.S. Patent Nos. 4,477,583 and 4,127,616 have been successful in obtaining para-selectivity, i.e., para-xylene/all xylenes, of greater than about 90% but with commercially unacceptable toluene conversions of only about 10%, resulting in a yield of not greater than about 9%, i.e., 10% x 90%. Such plocesses also produce significant quantities of ortho-xylene and meta-xylene thereby necessitating expensive separation ~locesses in order to separate the para-xylene from the other isomers.
Typical separation P1OCedUL~S comprise costly fractional crystallization and adsorptive separation of para-xylene from other xylene isomers which are customarily recycled. Xylene isomerization units are then required for additional conversion of the recycled xylene isomers into an e~lilihrium mixture comprising para-xylene.
Those skilled in the art appreciate that the expense of the separation process is proportional to the degree of separation required. Therefore, significant cost savings are achieved by increasing selectivity to the para-isomer ~ while maintaining ~ially acceptable conversion levels.
It is, therefore, highly desirable to provide a highly selective process for the production of para-xylene from w096l03360 2 ~ 9 5 ~ ~6 PCT~S94/08239 toluene while maintaining commercially acceptable toluene conversion levels. It i5 al80 highly desirable to provide an efficient and economical method for selectivating the catalyst employed.
Accordingly, the invention resides in one aspect in a catalyst comprising a crystalline molecular sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising crystalline molecular sieve and an org~n~ci7 icnn ~ , _ ' and then calcining the resultant agglomerate.
In a further aspect, the invention resides in a process for shape selective hydrocarbon conversion, such as the para-selective di~Lu~uLLionation of toluene, comprising contacting a hydrocarbon feedstock with a catalyst comprising a crystalline ~~lecnlAr sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising crystalline molecular sieve and an org~n~c;l;c~n _ ' and then calcining the resultant nggl~ ~te.
The present invention is useful in shape selective hydrocarbon conversion processes such as in converting various aromatics of C6l2 e.g., toluene and benzene, to commercially useful pa~ L~Lituted b~n~oneF, such as para-xylene.
Molecular sieves to be used in the process of the invention include int~ ~';ate pore zeolites. Such medium pore zeolites have a Constraint Index from 1 to 12. The method by which Constraint Index is determ;ned is described fully in U.S. Patent No. 4,016,218. Molecular sieves which conform to the specified values of Constraint Index for int~ te pore zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, MCM-2Z, and Zeolite Beta which are described, for example, in U.s. Patent Noc.
3,702,886 and Re. No. 29,949, 3,709,979, 3,832,449, 4,556,447, 4,07s,842, 4,016,245, 4,397,827, 4,650,655, 3,308,069, Re. 28,341 and EP 127,399. These zeolites may W096l03360 2 1 9 5 3 0 6 PCT~S94108~g be ~Luduced with differing silica:alumina ratios ranging from 12:1 upwards. Preferred molecular sieves include ZSM-5, ZSM-ll, ZSM-12, ZSN-35 and MCM-22. Particularly preferred is ZSM-5.
In the invention, the catalyst preferably has a silica-alumina ratio less than 100, preferably 20 - 80 and an alpha value greater than 100, for example 150 - 2000.
Alpha Value is an indication of the catalytic cracking activity of the catalyst compared to a standard catalyst and gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time.) It is based on the activity of an amorphous silica-alumina cracking catalyst taken as an Alpha of 1 (Rate Constant =
0.016 sec~l). The Alpha Test is described in U.S. Patent 3,354,078 and in The Journal of Catalvsis, Vol. 4, pp. 522-529 (August 1965): Vol. 6, p. 278 (1966); and Vol. 61, p.
395 (1980).
In the synthesis of zeolites, a reaction mixture is prepared generally containing an oxide of silicon, optionally an aluminum source, a templating agent which i5 normally an organic nitrogen containing ', and an Alki~l in~ aqueous medium.
The silicon oxide can be sl~pplj~d from known sources such as silicates, silica hydrosol, precipitated silica hydrosol, precipitated silica, e.g. Hi-Sil, silica gel, silicic acid. The aluminum oxide may be provided as only an impurity in another reactant, e.g., the silica source.
The sources of organic niLLv~n uullLaining cations, ~p~n~;n~ of cour5e, on the particular zeolite product to result from crystallization from the reaction mixture, may be primary, ~ecnnr3i~ry or tertiary amines or quaternary ;llm _ '-. Non-limiting examples of quaternary ;nm ~ '- include salts of teLL thyli ;llm, tetraethylammonium, t~LL~pL~yl~ ;llm~
tetrabuty3 D ; um, diethyli inm, triethyli inm~
dibenzyli inm, dibenzyl~i- Lhylammonium, WO 96/03360 ~ I q ~ 3- 6 PCT~US94108239 dibenzyldiethylammonium, benzyltrimethylammonium and chlorine. Non-limiting examples of amines useful herein include the : a_ of trimethylamine, triethylamine, tripropylamine ~ ethylpnprali~minp~ propAn Pali A minP~
butAnP~ mine, pentAne~a;Am;nP, hPYAn~;Am;nP, methylamine, ethylamine, propylamine, butylamine, ~ hylamine, diethylamine, dipropylamine, benzylamine, aniline, pyridine, piperidine and pyrrolidine.
The sources of alkali or AlkAlinP earth metal oxide may be, for example, sodium, lithium, calcium, m~7nPcil.m, cesium or potassium hydroxides, halides (e.g. chlorides, and bL i~a~pc)~ sulfates, nitrates, acetates, silicates, aluminates, phosphates and salts of carboxylic acids.
After crystallization of the zeolite, the organic cations are generally removed by calcination or other methods known in the art, and alkali or AlkAl~nP earth metals are generally removed, often by intP ~;Ate formation of inm ion P~rhAnqe and calcination of the ;mm form to yield the hyd-o~n form.
After crystallization, zeolite crystals to be used in commercial p~vceP~es are generally formed into agglomerates for i u~d strength and resistance to attrition. Various methods are used to agglomerate zeolite crystals. These methods include, for example, extrusion into pellets or beads, spray-drying into f~ l7~hle microspheres, or by hot pressing the zeolite crystals into aggl~ -~ates.
In the present invention a silivv~ ied zeolite molecular sieve catalyst is ~Lepa~ed by mixing zeolite crystals with an organosilicon _ and optionally a binder material, and agglomerating the mixture, followed by calcination of the agglomerate. Calcination is convenienty effected in an oxygen-containing atmosphere, preferably air, at a rate of 0.2- to 5~C/minute to a temperature greater 300- C but below a temperature at which the crystallinity of the zeolite is adversely affected.
Generally! such t ~LaLu,a will be below 600-C.
W096l03360 2 i q 5 3 0 6 PCT~S9410~239 Preferably the temperature of calcination is within the approximate range of 350- to 550-C. The product is maintained at the calcination temperature usually for 1 to 24 hours.
Zeolite crystals may be inLLoduced into the mixture in ~n LyllLi~pci 7~ form, and the organic template and alkali or ~lk~l in~ earth metal ions r~ ining in the zeolite structure from the crystallization reaction mixture may be removed by methods known in the art after the crystals are agglomerated.
The organosilicon ~ ~ ' is added to the mixture in an aqueous form, for example, as an : lci~n which may be surfactant stabilized, as a solution, or as an aerosol.
Useful surfactants include, for example, ethers of polyoxyethyl~l,e o~ylrh~nnlc.
The org~nn~ilicnn ~ include silanes such as alkyl ci 1 ~nn~, aryl ~ n~c, alkyarylsilanes, alkoxysilanes, aryloxysilanes, oxyethylenesilanes, alkyaryloxysilanes, siloxanes and polysiloxanes with alkyl and/or aryl and/or glycol groups. AlXyl is int~n~d to include 1 to 12 carbons. Aryl is intpn~d to include 6 to 10 carbons. The org~no&1licon _ _ '- also include the silicone ~-described below which may also be used in trim selectivation. Preferred are &i 1 ny~nec such as phenyl-methylpolysiloxane.
For the shape selective hydrocarbon conversion processof this invention, the suitable molecular sieve may be aggl~ ~ted or extruded in combination with a support or binder material such as, for example, a porous inorganic oxide support or a clay binder. While the preferred binder is silica, other non-limiting ~ l~s of such binder materials include alumina, zirconia, magnesia, thoria, ~ titania, boria and combinations thereof, generally in the form of dried inorganic oxide gels or gelatinous precipitates. Suitable clay materials include, by way of example, bentonite and kieselguhr. The relative proportion W096l03360 2 ~ q 5 ~ ~ 6 PCT~S94/08239 ~
of suitable crystalline molecular sieve to the total composition of catalyst and binder or support may be 30 to 90 percent by weight and is preferably about 50-80 percent by weight of the composition. The composition may be in the form of an extrudate, beads, pellets (tablets) or flll;rl;7slhle miuLua~lleles.
Sha~e Selective ~onversion Molecular sieves which are selectivation agglomerated in accordance with the invention are generally useful as catalysts in shape selective hydrocarbon conversion yLocesses including cracking r~actinn~ involving dewaxing of hydrocarbon feedstocks; isomerization of ~lkylaromatics;
oligomerization of olefins to form gasoline, distillate, lube oils or rhr~ir~lR; transalkylation Or aromatics;
alkylation of aromatics; conversion of oxygenates to hydror~rhon~, rearr~ , L of u~y~nates~ and conversion of light paraffins and olefins to aromatics.
In general, catalytic conversion conditions over a catalyst comprising the ---';fi~d zeolite include a t~ ~Lu.a of lOO-C to 760 C, a yL~S~UL~ of 10 to 20,000 kPa (0.1 aL , -re (bar) to 200 a, - ~ res), a weight hourly space velocity of 0.08 hr~l to 2000 hr~l and a hydlùg~n/organic, e.g. hydrocarbon - _ ~ of 0 to 100.
The catalyst of the invention is particularly intended for use in the transalkylation or di~y~ UpUL Lionation of toluene to produce para-xylene and this process will now be described as a 1~yL~s~..L~tive example of shape selective conversion over the present catalyst.
Toluene Di~u~LLionation Reaction conditions in the toluene diayLuyoLLionation contemplated herein include temperatures ranging from 350-C
to 540-C, preferabiy greater than 400 C; pressures ranging from 100 to 34,500 kPa (0 to 5000 psig), preferably from 790 to 7000 kPa (100 to 1000 psig); a mole ratio of W096/03360 2 1 9 5 3 0 6 PCT~S94108239 ~ _g_ I.ydL~gen to hydron~rhnnc from 0.1 to 20, preferably from 2 to 4; at a weight hourly space velocity (WHSV) from O.l to 20 hr~l, preferably from 2 to 4 hr~l.
The toluene feedstock preferably includes 50~ to 100%
toluene, more preferably at least about 80% toluene in the toluene feedstock. Other _ ~- such as benzene, xylenes, and trimethylhpn7pn~ may also be present in the toluene feedstock without adversely affecting the present invention. The toluene feedstock may also be dried, if desired, in a manner which will minimize moisture entering the reaction zone. Methods known in the art suitable for drying the toluene charge for the present process are ~ u~. These methods include percolation through any suitable ~pcic~nt~ for example, silica gel, activated alumina, molecular sieves or other suitable substances, or the use of liquid charge dryers.
Normally a single pass conversion of a toluene stream results in a product stream which includes dimethylbenzenes having alkyl groups at all locations, i.e., ortho-, meta-, and para-xylenes. Furth ~, the xylenes are known to proceed in a reaction which produces unwanted ethylbenzenes (EB) by the following reaction:
CH3 CH2CHy CHy Previously, the purity of p-xylene with respect to all of the CD products in a single pass has been limited to less than 90% when isomerization is permitted. This efficiency is reduced somewhat by the production of ethylbenzene.
The present invention, however, provides high efficiency conversion which reduces production of ortho-and meta-isomers to the benefit of the desired para-isomer.
The resulting product stream contains greater than a 90%
The present invention is directed to shape selective hydrocarbon conversion such as the selective production of para-substituted aromatic ~ '- and in particular the selective diD~L~y~LLionation of toluene to produce para-xylene.
The term shape-selectiVe catalysis describes nn~Yr~cted catalytic selectiVities in zeolites. The principles behind shape selective catalysis have been reviewed extensively, e.g. by N-Y- Chen, W.E. Garwood and F.G. Dwyer, "Shape SelectiVe Catalysis in Industrial Applications, 36, Marcel Dekker, Inc- (1989). Within a zeolite pore, hydrocarbon conversion reactions such as paraffin isomerization, olefin skeletal or double bond isomerization, oligomerization and aromatic diD~l~uLLionation, alkylation or transalkylation reactions are g~v~L..ed by constraints imposed by the channel size.
Reactant selectivity occurs when a fraction of the feedstock is too large to enter the zeolite pores to react;
while product selectivity occurs when some of the products cannot leave the zeolite rh~nn~l c. Product distributions can also be altered by transition state selectivity in which certain reactions cannot occur because the reaction transition state is too large to form within the zeolite pores or cages. Another type of selectivity results from configurational diffusion where the ~ ;r,nc of the molecule approach that of the zeolite pore system. A small change in ~ irnC of the molecule or the zeolite pore can result in large diffusion changes leading to different product distributions. This type of shape selective catalysis is ~ LL~ted, for example, in selective toluene di~L~olLionation to p-xylene.
Para-xylene may be pL~uc~d by methylation of toluene with - -n~l as described by Chen et al., J. Amer. Chem.
Sec. 1~2, 101, 6783, and by toluene d~ ~oLLionation, as described by Pines in "The Chemistry of Catalytic W096/03360 2 1 q 5 3 a ~ PCT~S94/08239 Hydrocarbon Conversions", Academic Press, N.Y., 1981, p.
72. Such methods typically result in the production of a mixture inrll-~;ng para-xylene, ortho-xylene, and meta-xylene. D~p~n~i ng upon the para-selectivity of the catalyst and the reaction conditions, different percentages of para-xylene are obtained. The yield, i.e., the amount of feedstock actually converted to xylene, is also affected by the catalyst and the reaction conditions.
Previously known toluene methylation reactions typically provide many by-products such as those indicated in the ~ollowing formula:
T~h~ YI~m;c E~];libria for Toluene Conversion to th~ Products Tn~i cated Non-MTPX
184.27 g (2 moles Toluene) 82.92 g 101J~35 g C ~ ~ Ç Ç Et Et Et Et ~ 55~ ~ + ~ + ~ + ~ ~ + ~ + ~ +
C C
g= 52.59 9.64 21.45 10.05 3.00 1.22 1.90 0.70 Yield = Selectivity x Conversion=lOOx9.64 x 0.55 ~ 5.23 wt%
101.35 p-Xylene Yield = 100 x 9.64 = 5.23 wt%
184.27 p-Xylene Purity (p-Xylene/all C~'5) = 21.45 wt%
One method for increasing para-selectivity of zeolite catalysts is to modify the catalyst by ~.~ai -nt with "selectivating agents". Various silicon ~ ~ have been used to modify catalysts to improve selectivity in 1IYdLO~LU1I conversion processes. For example, U.S. Patent W096/03360 2 1 ~ 5 3 Q 6 PCT~S94/08239 ~ -3-hydrocarbon conversion processes. For example, U.S. Patent Nos. 4,145,315, 4,127,616, and 4,090,981 describe the use of a silic~n~ .d dissolved in an organic solvent to treat a zeolite. U.S. Patent Nos. 4,465,886 and 4,477,583 describe the use of an aqueous ~ n of a silicone to treat a zeolite. U.S. Patent Nos. 4,950,835 and 4,927,979 describe the use of alkoxysilanes carried by gases or organic solvents to treat a zeolite. U.S. Patent Nos.
4,100,215 and 3,698,157 describe the use of silanes in hydrocArhon~, e.g., pyridine, ethers, to treat a zeolite.
Such modification methods are known in the art to be carried out after agglomeration of the zeolite.
Some of these catalyst modification procedures, for example, U.S. Patent Nos. 4,477,583 and 4,127,616 have been successful in obtaining para-selectivity, i.e., para-xylene/all xylenes, of greater than about 90% but with commercially unacceptable toluene conversions of only about 10%, resulting in a yield of not greater than about 9%, i.e., 10% x 90%. Such plocesses also produce significant quantities of ortho-xylene and meta-xylene thereby necessitating expensive separation ~locesses in order to separate the para-xylene from the other isomers.
Typical separation P1OCedUL~S comprise costly fractional crystallization and adsorptive separation of para-xylene from other xylene isomers which are customarily recycled. Xylene isomerization units are then required for additional conversion of the recycled xylene isomers into an e~lilihrium mixture comprising para-xylene.
Those skilled in the art appreciate that the expense of the separation process is proportional to the degree of separation required. Therefore, significant cost savings are achieved by increasing selectivity to the para-isomer ~ while maintaining ~ially acceptable conversion levels.
It is, therefore, highly desirable to provide a highly selective process for the production of para-xylene from w096l03360 2 ~ 9 5 ~ ~6 PCT~S94/08239 toluene while maintaining commercially acceptable toluene conversion levels. It i5 al80 highly desirable to provide an efficient and economical method for selectivating the catalyst employed.
Accordingly, the invention resides in one aspect in a catalyst comprising a crystalline molecular sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising crystalline molecular sieve and an org~n~ci7 icnn ~ , _ ' and then calcining the resultant agglomerate.
In a further aspect, the invention resides in a process for shape selective hydrocarbon conversion, such as the para-selective di~Lu~uLLionation of toluene, comprising contacting a hydrocarbon feedstock with a catalyst comprising a crystalline ~~lecnlAr sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising crystalline molecular sieve and an org~n~c;l;c~n _ ' and then calcining the resultant nggl~ ~te.
The present invention is useful in shape selective hydrocarbon conversion processes such as in converting various aromatics of C6l2 e.g., toluene and benzene, to commercially useful pa~ L~Lituted b~n~oneF, such as para-xylene.
Molecular sieves to be used in the process of the invention include int~ ~';ate pore zeolites. Such medium pore zeolites have a Constraint Index from 1 to 12. The method by which Constraint Index is determ;ned is described fully in U.S. Patent No. 4,016,218. Molecular sieves which conform to the specified values of Constraint Index for int~ te pore zeolites include ZSM-5, ZSM-11, ZSM-12, ZSM-22, ZSM-23, ZSM-35, ZSM-48, ZSM-50, MCM-2Z, and Zeolite Beta which are described, for example, in U.s. Patent Noc.
3,702,886 and Re. No. 29,949, 3,709,979, 3,832,449, 4,556,447, 4,07s,842, 4,016,245, 4,397,827, 4,650,655, 3,308,069, Re. 28,341 and EP 127,399. These zeolites may W096l03360 2 1 9 5 3 0 6 PCT~S94108~g be ~Luduced with differing silica:alumina ratios ranging from 12:1 upwards. Preferred molecular sieves include ZSM-5, ZSM-ll, ZSM-12, ZSN-35 and MCM-22. Particularly preferred is ZSM-5.
In the invention, the catalyst preferably has a silica-alumina ratio less than 100, preferably 20 - 80 and an alpha value greater than 100, for example 150 - 2000.
Alpha Value is an indication of the catalytic cracking activity of the catalyst compared to a standard catalyst and gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time.) It is based on the activity of an amorphous silica-alumina cracking catalyst taken as an Alpha of 1 (Rate Constant =
0.016 sec~l). The Alpha Test is described in U.S. Patent 3,354,078 and in The Journal of Catalvsis, Vol. 4, pp. 522-529 (August 1965): Vol. 6, p. 278 (1966); and Vol. 61, p.
395 (1980).
In the synthesis of zeolites, a reaction mixture is prepared generally containing an oxide of silicon, optionally an aluminum source, a templating agent which i5 normally an organic nitrogen containing ', and an Alki~l in~ aqueous medium.
The silicon oxide can be sl~pplj~d from known sources such as silicates, silica hydrosol, precipitated silica hydrosol, precipitated silica, e.g. Hi-Sil, silica gel, silicic acid. The aluminum oxide may be provided as only an impurity in another reactant, e.g., the silica source.
The sources of organic niLLv~n uullLaining cations, ~p~n~;n~ of cour5e, on the particular zeolite product to result from crystallization from the reaction mixture, may be primary, ~ecnnr3i~ry or tertiary amines or quaternary ;llm _ '-. Non-limiting examples of quaternary ;nm ~ '- include salts of teLL thyli ;llm, tetraethylammonium, t~LL~pL~yl~ ;llm~
tetrabuty3 D ; um, diethyli inm, triethyli inm~
dibenzyli inm, dibenzyl~i- Lhylammonium, WO 96/03360 ~ I q ~ 3- 6 PCT~US94108239 dibenzyldiethylammonium, benzyltrimethylammonium and chlorine. Non-limiting examples of amines useful herein include the : a_ of trimethylamine, triethylamine, tripropylamine ~ ethylpnprali~minp~ propAn Pali A minP~
butAnP~ mine, pentAne~a;Am;nP, hPYAn~;Am;nP, methylamine, ethylamine, propylamine, butylamine, ~ hylamine, diethylamine, dipropylamine, benzylamine, aniline, pyridine, piperidine and pyrrolidine.
The sources of alkali or AlkAlinP earth metal oxide may be, for example, sodium, lithium, calcium, m~7nPcil.m, cesium or potassium hydroxides, halides (e.g. chlorides, and bL i~a~pc)~ sulfates, nitrates, acetates, silicates, aluminates, phosphates and salts of carboxylic acids.
After crystallization of the zeolite, the organic cations are generally removed by calcination or other methods known in the art, and alkali or AlkAl~nP earth metals are generally removed, often by intP ~;Ate formation of inm ion P~rhAnqe and calcination of the ;mm form to yield the hyd-o~n form.
After crystallization, zeolite crystals to be used in commercial p~vceP~es are generally formed into agglomerates for i u~d strength and resistance to attrition. Various methods are used to agglomerate zeolite crystals. These methods include, for example, extrusion into pellets or beads, spray-drying into f~ l7~hle microspheres, or by hot pressing the zeolite crystals into aggl~ -~ates.
In the present invention a silivv~ ied zeolite molecular sieve catalyst is ~Lepa~ed by mixing zeolite crystals with an organosilicon _ and optionally a binder material, and agglomerating the mixture, followed by calcination of the agglomerate. Calcination is convenienty effected in an oxygen-containing atmosphere, preferably air, at a rate of 0.2- to 5~C/minute to a temperature greater 300- C but below a temperature at which the crystallinity of the zeolite is adversely affected.
Generally! such t ~LaLu,a will be below 600-C.
W096l03360 2 i q 5 3 0 6 PCT~S9410~239 Preferably the temperature of calcination is within the approximate range of 350- to 550-C. The product is maintained at the calcination temperature usually for 1 to 24 hours.
Zeolite crystals may be inLLoduced into the mixture in ~n LyllLi~pci 7~ form, and the organic template and alkali or ~lk~l in~ earth metal ions r~ ining in the zeolite structure from the crystallization reaction mixture may be removed by methods known in the art after the crystals are agglomerated.
The organosilicon ~ ~ ' is added to the mixture in an aqueous form, for example, as an : lci~n which may be surfactant stabilized, as a solution, or as an aerosol.
Useful surfactants include, for example, ethers of polyoxyethyl~l,e o~ylrh~nnlc.
The org~nn~ilicnn ~ include silanes such as alkyl ci 1 ~nn~, aryl ~ n~c, alkyarylsilanes, alkoxysilanes, aryloxysilanes, oxyethylenesilanes, alkyaryloxysilanes, siloxanes and polysiloxanes with alkyl and/or aryl and/or glycol groups. AlXyl is int~n~d to include 1 to 12 carbons. Aryl is intpn~d to include 6 to 10 carbons. The org~no&1licon _ _ '- also include the silicone ~-described below which may also be used in trim selectivation. Preferred are &i 1 ny~nec such as phenyl-methylpolysiloxane.
For the shape selective hydrocarbon conversion processof this invention, the suitable molecular sieve may be aggl~ ~ted or extruded in combination with a support or binder material such as, for example, a porous inorganic oxide support or a clay binder. While the preferred binder is silica, other non-limiting ~ l~s of such binder materials include alumina, zirconia, magnesia, thoria, ~ titania, boria and combinations thereof, generally in the form of dried inorganic oxide gels or gelatinous precipitates. Suitable clay materials include, by way of example, bentonite and kieselguhr. The relative proportion W096l03360 2 ~ q 5 ~ ~ 6 PCT~S94/08239 ~
of suitable crystalline molecular sieve to the total composition of catalyst and binder or support may be 30 to 90 percent by weight and is preferably about 50-80 percent by weight of the composition. The composition may be in the form of an extrudate, beads, pellets (tablets) or flll;rl;7slhle miuLua~lleles.
Sha~e Selective ~onversion Molecular sieves which are selectivation agglomerated in accordance with the invention are generally useful as catalysts in shape selective hydrocarbon conversion yLocesses including cracking r~actinn~ involving dewaxing of hydrocarbon feedstocks; isomerization of ~lkylaromatics;
oligomerization of olefins to form gasoline, distillate, lube oils or rhr~ir~lR; transalkylation Or aromatics;
alkylation of aromatics; conversion of oxygenates to hydror~rhon~, rearr~ , L of u~y~nates~ and conversion of light paraffins and olefins to aromatics.
In general, catalytic conversion conditions over a catalyst comprising the ---';fi~d zeolite include a t~ ~Lu.a of lOO-C to 760 C, a yL~S~UL~ of 10 to 20,000 kPa (0.1 aL , -re (bar) to 200 a, - ~ res), a weight hourly space velocity of 0.08 hr~l to 2000 hr~l and a hydlùg~n/organic, e.g. hydrocarbon - _ ~ of 0 to 100.
The catalyst of the invention is particularly intended for use in the transalkylation or di~y~ UpUL Lionation of toluene to produce para-xylene and this process will now be described as a 1~yL~s~..L~tive example of shape selective conversion over the present catalyst.
Toluene Di~u~LLionation Reaction conditions in the toluene diayLuyoLLionation contemplated herein include temperatures ranging from 350-C
to 540-C, preferabiy greater than 400 C; pressures ranging from 100 to 34,500 kPa (0 to 5000 psig), preferably from 790 to 7000 kPa (100 to 1000 psig); a mole ratio of W096/03360 2 1 9 5 3 0 6 PCT~S94108239 ~ _g_ I.ydL~gen to hydron~rhnnc from 0.1 to 20, preferably from 2 to 4; at a weight hourly space velocity (WHSV) from O.l to 20 hr~l, preferably from 2 to 4 hr~l.
The toluene feedstock preferably includes 50~ to 100%
toluene, more preferably at least about 80% toluene in the toluene feedstock. Other _ ~- such as benzene, xylenes, and trimethylhpn7pn~ may also be present in the toluene feedstock without adversely affecting the present invention. The toluene feedstock may also be dried, if desired, in a manner which will minimize moisture entering the reaction zone. Methods known in the art suitable for drying the toluene charge for the present process are ~ u~. These methods include percolation through any suitable ~pcic~nt~ for example, silica gel, activated alumina, molecular sieves or other suitable substances, or the use of liquid charge dryers.
Normally a single pass conversion of a toluene stream results in a product stream which includes dimethylbenzenes having alkyl groups at all locations, i.e., ortho-, meta-, and para-xylenes. Furth ~, the xylenes are known to proceed in a reaction which produces unwanted ethylbenzenes (EB) by the following reaction:
CH3 CH2CHy CHy Previously, the purity of p-xylene with respect to all of the CD products in a single pass has been limited to less than 90% when isomerization is permitted. This efficiency is reduced somewhat by the production of ethylbenzene.
The present invention, however, provides high efficiency conversion which reduces production of ortho-and meta-isomers to the benefit of the desired para-isomer.
The resulting product stream contains greater than a 90%
2 ~ 9 ~ 3 0~ PCT/11594/08239 purity of para-xylene. For example, the ortho-xylene isomer can be reduced to not more than about 0.5% of the total xylenes content while the meta-xylene isomer can be reduced to less than about 5% of the total xylene content.
llo~uveI, when the reaction system is properly treated, such as by deposition of platinum on the molecular sieve, the presence of ethyl h~n7~n~ can be reduced to less than about 0.3% of the C~ product.
As ~Ypl~;n~ in greater detail herein, the present invention provides a method for obtaining para-xylene at conversion rates of at least about 15~, preferably at least about 20-25%, and with para-xylene purity of greater than 90%, preferably at least 95%, and most preferably about 99% .
Therefore higher para-xylene purity can be attained at commercially acceptable conversion rates than with previously ~i~nlose~ pLucesses. The present invention thus allows for a significant r~ tion in process costs previously associated with the separation of unwanted by-products. Toluene di~u~uLLionation p~ucesses of the prior art typically require expensive secondary and tertiary treatment ~luceduL~s in order to obtain these efficiencies.
Preferably, the toluene di~,uLu,uoLLionation process of the present invention includes the step of effecting a further in-situ selectivation of the zeolite catalyst, in addition to the ex-situ preselectivation during catalyst agglomeration. This further in-situ selectivation, which is referred to herein as "trim selectivation", involve~
contacting the catalyst simul~lnPo~lcly with toluene, a selectivating agent and hydrogen at reaction conditions until the desired p-xylene selectivity, e.g., 90% or 95%, is attained, whereupon the feed of selectivating agent is ~1~cnntinllnd. The trim selectivating is preferably a sili~ul, ~onLaining ~ ld and more preferably a ~;licnnF ~....l~ining C, ' obeying the general formula:
W096/03360 2 1 9 5 3 0 6 PCT~S94108239 -- si-o --_ Z - n where R1 is hYdLUg~ fluorine, hydroxy, alkyl, aryl, alkylaryl or fluoro-alkyl. The hydrocarbon substituents generally contain from 1 to 10 carbon atoms and preferably are methyl or ethyl groups. Rz is selected from the same group as R1, and n is an integer of at least 2 and generally in the range of 3 to 1000. The molecular weight of the silicone c _ ' employed is generally between 80 and 20,000 and preferably between 150 and 10,000.
Representative ~ cnnP - _ ' include dimethyl~;l;cnnO, diethyl~ onP, phenylmethyl~;l;cone~ methylhydLv~nc;li-cone, ethylhydLùg~llsilicone, phenylh~dLucJ~ il;cnnD, methylethylsilicone, phenylethyl~il;cnno~ diphenyl~ nnP, methyltrifluoLu~Lu~ylsilicone, ethyltriflu<,lu~ru~y~ilicone, polydimethylsilicone, tetrachlorophenylmethyl silicone, tetrachlorophenylethyl ~;licone, tetrachlorophenylhydLuge silicnne, tetrachl~Lu~hellylphenyl silicone, methylvinyl-silicone and ethylviny~ no. The ~ilicnno ,need not be linear but may be cyclic as for example hexamethylcyclotrisiloxane, oui ~ylcyclotetrasiloxane~
hPy~phpnylcyclotrisiloxane and o~ ylcyclotetra-siloxane. Mixtures of these ~ '- may also be used as well as siliconP~ with other functional groups. Other silicu.l cu.,Laining ~ _ ' , such as silanes and siloxanes, may also be utilized.
Preferably, the kinetic ~i~n!~orS of the p-xylene trim selectivating agent and the silicon pre-selectivating ___I.d added during zeolite agglomeration are larger than the zeolite pore diameter, in order to avoid reducing the internal activity of the catalyst.
2 1 9,5~.0,6, W096l03360 i~ : ~ PCT~S94/08239 Reaction conditions for the trim-selectivation step generally include a temperature of 350- - 540-C and a pL~S - UL~ of about 100 to 34500 kPa (~L ~ liC - 5000 psig). The feed is provided to the system at a rate of about 0.1 - 20 W~SV. The hyd g~., is fed at a hydrogen to hydrocarbon molar ratio of about 0.1-20. The trim-selectivating agent is preferably fed in an amount of 0.1~
- 50% of the toluene and, dep~n~;ng upon the percentage of selectivating agent used, the trim selectivation will preferably last for 50-300 hours, most preferably less than 170 hrs.
While not wishing to be bound by theory, it is believed that the adv~llLay~s of the present invention are obtained by rendering acid sites on the external surfaces of the catalyst substantially in~cc~ccible to reactants while increasing catalyst tortuosity. Acid sites existing on the external surface of the catalyst are believed to isomerize the para-xylene exiting the catalyst pores back to an ~ hrium level with the other two isomers thereby reducing the amount of para-xylene in the xylenes to only about 24%. By reducing the availability of these acid sites to the para-xylene exiting the pores of the catalyst, a relatively high level of para-xylene can be maintained.
It is believed that the trim selectivating agents of the present invention block or otherwise render these external acid sites unavailable to the para-xylene by ~h~mic~l ly modifying said sites.
The catalyst may be further modified in order to reduce the amount of undesirable by-products, particularly ethylbenzene. The state of the art is such that the reactor effluent from standard toluene di~lu~u,Lionation typically contains 0.5% ethylbenzene by-product. Upon distillation of the reaction products, the level of ethyl-benzene in the C~ fraction often increases to 3-4 percent.
This level of ethylhpn7en~ is unacceptable for polymer grade p-xylene since ethylh~n7~"~ in the C~ product, if not W096l03360 2 1 ~ 5 3 0 6 PCT~S94/08239 removed, degrades the guality of fibers ultimately ~Luduced from the p-xylene product. C~n~Tl~ntly, ethylbenzene content must be kept low. The specification for ethyl-benzene in the C8 product has been ~tDrm;n~d by industry to be less than 0.3%. Ethylh~n7An~ can be substantially removed by isomerization or by AuyeLr-~ctionation processes. Removal of the ethylh~n~Ane by conventional isomerization would be impractical with the present invention since the xylene stream, which includes greater than 90% para-xylene, would be cu~-uuLLè.lLly isomerized to ~lil;hrium xylenes reducing the amount of para-xylene in this xylene stream to about 24%. It is known in the art that the alternative pIuueduLe of removing the ethylbenzene by ~u~eLLL~ctionation is ë~LL~ -ly expensive.
In order to avoid the need for downstream ethylbenzene removal, the level of ethylbenzene by-product is advantag~ou~ly reduced by inuuL~UL~ting a hydLugenation-dehydLùgel,ation function in the catalyst, such as by addition of a metal - _ ' such as platinum. While platinum is the preferred metal, other metals such as p~ lm, nickel, copper, cobalt, molybdenum, rhodium, ruthenium, silver, gold, mercury, osmium, iron, zinc, ~ cadmium, and mixtures thereof may be utilized. The metal may be added by cation ~Yrh~nge, in amounts of about 0.01 -2%, typically about 0.5%. The metal must be able to enter the pores of the catalyst in order to survive a suhsP~Ant calcination step. For example, a platinum modified catalyst can be prepared by first adding the catalyst to a solution of i ;nm nitrate in order to convert the catalyst to the ammonium form. The catalyst is subse-quently contacted with an aqueous solution of tetraamine platinumtII) nitrate or tetraamine platinum(II) chloride.
The metallic , a advantageously enters the pores of the catalyst. The catalyst can then be filtered, washed with water and calcined at temperatures of about 250- to 500-C.
W096/03360 2 1 q 5 3 0 6 PCT~S9~/08239 ~
The effluent is separated and distilled to remove the desired product, i.e., para-xylone, plus other by-products.
By the present process, toluene can be converted to aromatic concentrates of high value, e.g., about 99% para-xylene based on all C~ products. In a typical ~ Lof the present process, optimum toluene conversion is ~ound to be 20 - 25 weight percent with a para-xylene purity of 90 - 99%.
The following non-limiting ~ 1PC illustrate the invention:
II!Y~MPT.R 1 To 15.57g distilled water in a 150 cc beaker was added 1.01g 50~ sodium hydroxide solution and 2.20g dimethyl silicon modified with oxyethylene groups to render it water soluble to 38C-. To this solution was added a mixture of 10.85g as oyllth~ci ~Q~ ZSN-5 and 5.85g hydrated i ~houO
silica with stirring. The resultant dry paste was extruded using a hand extruder to give well-formed 1.6mm (1/16~ inch e~LLud~te. Drying at 120-C for two hours gave 12.91g product.
I~Y~I''PT.l;! 2 To 15.58g distilled water in a 150cc beaker was added 1.03g 50~ sodium hydroxide solution and a mixture of 4.06g phenylmethylpolycil~Y~n~ and 0.79g iso-Octylphenoxy-polyethoxyethanol surfactant to form an lcinn. To this emulsion was added a mixture of 10.85g as-synthesized ZSN-5 and 5.85g hydrated amorphous silica (HiSil, PPG
Industries, Inc.) with stirring. The resultant dry paste was extruded using a hand extruder to give well-formed 1.6mm (1/16 inch) extrudate. Drying at 120-C ~or two hours gave 13.49g product.
llo~uveI, when the reaction system is properly treated, such as by deposition of platinum on the molecular sieve, the presence of ethyl h~n7~n~ can be reduced to less than about 0.3% of the C~ product.
As ~Ypl~;n~ in greater detail herein, the present invention provides a method for obtaining para-xylene at conversion rates of at least about 15~, preferably at least about 20-25%, and with para-xylene purity of greater than 90%, preferably at least 95%, and most preferably about 99% .
Therefore higher para-xylene purity can be attained at commercially acceptable conversion rates than with previously ~i~nlose~ pLucesses. The present invention thus allows for a significant r~ tion in process costs previously associated with the separation of unwanted by-products. Toluene di~u~uLLionation p~ucesses of the prior art typically require expensive secondary and tertiary treatment ~luceduL~s in order to obtain these efficiencies.
Preferably, the toluene di~,uLu,uoLLionation process of the present invention includes the step of effecting a further in-situ selectivation of the zeolite catalyst, in addition to the ex-situ preselectivation during catalyst agglomeration. This further in-situ selectivation, which is referred to herein as "trim selectivation", involve~
contacting the catalyst simul~lnPo~lcly with toluene, a selectivating agent and hydrogen at reaction conditions until the desired p-xylene selectivity, e.g., 90% or 95%, is attained, whereupon the feed of selectivating agent is ~1~cnntinllnd. The trim selectivating is preferably a sili~ul, ~onLaining ~ ld and more preferably a ~;licnnF ~....l~ining C, ' obeying the general formula:
W096/03360 2 1 9 5 3 0 6 PCT~S94108239 -- si-o --_ Z - n where R1 is hYdLUg~ fluorine, hydroxy, alkyl, aryl, alkylaryl or fluoro-alkyl. The hydrocarbon substituents generally contain from 1 to 10 carbon atoms and preferably are methyl or ethyl groups. Rz is selected from the same group as R1, and n is an integer of at least 2 and generally in the range of 3 to 1000. The molecular weight of the silicone c _ ' employed is generally between 80 and 20,000 and preferably between 150 and 10,000.
Representative ~ cnnP - _ ' include dimethyl~;l;cnnO, diethyl~ onP, phenylmethyl~;l;cone~ methylhydLv~nc;li-cone, ethylhydLùg~llsilicone, phenylh~dLucJ~ il;cnnD, methylethylsilicone, phenylethyl~il;cnno~ diphenyl~ nnP, methyltrifluoLu~Lu~ylsilicone, ethyltriflu<,lu~ru~y~ilicone, polydimethylsilicone, tetrachlorophenylmethyl silicone, tetrachlorophenylethyl ~;licone, tetrachlorophenylhydLuge silicnne, tetrachl~Lu~hellylphenyl silicone, methylvinyl-silicone and ethylviny~ no. The ~ilicnno ,need not be linear but may be cyclic as for example hexamethylcyclotrisiloxane, oui ~ylcyclotetrasiloxane~
hPy~phpnylcyclotrisiloxane and o~ ylcyclotetra-siloxane. Mixtures of these ~ '- may also be used as well as siliconP~ with other functional groups. Other silicu.l cu.,Laining ~ _ ' , such as silanes and siloxanes, may also be utilized.
Preferably, the kinetic ~i~n!~orS of the p-xylene trim selectivating agent and the silicon pre-selectivating ___I.d added during zeolite agglomeration are larger than the zeolite pore diameter, in order to avoid reducing the internal activity of the catalyst.
2 1 9,5~.0,6, W096l03360 i~ : ~ PCT~S94/08239 Reaction conditions for the trim-selectivation step generally include a temperature of 350- - 540-C and a pL~S - UL~ of about 100 to 34500 kPa (~L ~ liC - 5000 psig). The feed is provided to the system at a rate of about 0.1 - 20 W~SV. The hyd g~., is fed at a hydrogen to hydrocarbon molar ratio of about 0.1-20. The trim-selectivating agent is preferably fed in an amount of 0.1~
- 50% of the toluene and, dep~n~;ng upon the percentage of selectivating agent used, the trim selectivation will preferably last for 50-300 hours, most preferably less than 170 hrs.
While not wishing to be bound by theory, it is believed that the adv~llLay~s of the present invention are obtained by rendering acid sites on the external surfaces of the catalyst substantially in~cc~ccible to reactants while increasing catalyst tortuosity. Acid sites existing on the external surface of the catalyst are believed to isomerize the para-xylene exiting the catalyst pores back to an ~ hrium level with the other two isomers thereby reducing the amount of para-xylene in the xylenes to only about 24%. By reducing the availability of these acid sites to the para-xylene exiting the pores of the catalyst, a relatively high level of para-xylene can be maintained.
It is believed that the trim selectivating agents of the present invention block or otherwise render these external acid sites unavailable to the para-xylene by ~h~mic~l ly modifying said sites.
The catalyst may be further modified in order to reduce the amount of undesirable by-products, particularly ethylbenzene. The state of the art is such that the reactor effluent from standard toluene di~lu~u,Lionation typically contains 0.5% ethylbenzene by-product. Upon distillation of the reaction products, the level of ethyl-benzene in the C~ fraction often increases to 3-4 percent.
This level of ethylhpn7en~ is unacceptable for polymer grade p-xylene since ethylh~n7~"~ in the C~ product, if not W096l03360 2 1 ~ 5 3 0 6 PCT~S94/08239 removed, degrades the guality of fibers ultimately ~Luduced from the p-xylene product. C~n~Tl~ntly, ethylbenzene content must be kept low. The specification for ethyl-benzene in the C8 product has been ~tDrm;n~d by industry to be less than 0.3%. Ethylh~n7An~ can be substantially removed by isomerization or by AuyeLr-~ctionation processes. Removal of the ethylh~n~Ane by conventional isomerization would be impractical with the present invention since the xylene stream, which includes greater than 90% para-xylene, would be cu~-uuLLè.lLly isomerized to ~lil;hrium xylenes reducing the amount of para-xylene in this xylene stream to about 24%. It is known in the art that the alternative pIuueduLe of removing the ethylbenzene by ~u~eLLL~ctionation is ë~LL~ -ly expensive.
In order to avoid the need for downstream ethylbenzene removal, the level of ethylbenzene by-product is advantag~ou~ly reduced by inuuL~UL~ting a hydLugenation-dehydLùgel,ation function in the catalyst, such as by addition of a metal - _ ' such as platinum. While platinum is the preferred metal, other metals such as p~ lm, nickel, copper, cobalt, molybdenum, rhodium, ruthenium, silver, gold, mercury, osmium, iron, zinc, ~ cadmium, and mixtures thereof may be utilized. The metal may be added by cation ~Yrh~nge, in amounts of about 0.01 -2%, typically about 0.5%. The metal must be able to enter the pores of the catalyst in order to survive a suhsP~Ant calcination step. For example, a platinum modified catalyst can be prepared by first adding the catalyst to a solution of i ;nm nitrate in order to convert the catalyst to the ammonium form. The catalyst is subse-quently contacted with an aqueous solution of tetraamine platinumtII) nitrate or tetraamine platinum(II) chloride.
The metallic , a advantageously enters the pores of the catalyst. The catalyst can then be filtered, washed with water and calcined at temperatures of about 250- to 500-C.
W096/03360 2 1 q 5 3 0 6 PCT~S9~/08239 ~
The effluent is separated and distilled to remove the desired product, i.e., para-xylone, plus other by-products.
By the present process, toluene can be converted to aromatic concentrates of high value, e.g., about 99% para-xylene based on all C~ products. In a typical ~ Lof the present process, optimum toluene conversion is ~ound to be 20 - 25 weight percent with a para-xylene purity of 90 - 99%.
The following non-limiting ~ 1PC illustrate the invention:
II!Y~MPT.R 1 To 15.57g distilled water in a 150 cc beaker was added 1.01g 50~ sodium hydroxide solution and 2.20g dimethyl silicon modified with oxyethylene groups to render it water soluble to 38C-. To this solution was added a mixture of 10.85g as oyllth~ci ~Q~ ZSN-5 and 5.85g hydrated i ~houO
silica with stirring. The resultant dry paste was extruded using a hand extruder to give well-formed 1.6mm (1/16~ inch e~LLud~te. Drying at 120-C for two hours gave 12.91g product.
I~Y~I''PT.l;! 2 To 15.58g distilled water in a 150cc beaker was added 1.03g 50~ sodium hydroxide solution and a mixture of 4.06g phenylmethylpolycil~Y~n~ and 0.79g iso-Octylphenoxy-polyethoxyethanol surfactant to form an lcinn. To this emulsion was added a mixture of 10.85g as-synthesized ZSN-5 and 5.85g hydrated amorphous silica (HiSil, PPG
Industries, Inc.) with stirring. The resultant dry paste was extruded using a hand extruder to give well-formed 1.6mm (1/16 inch) extrudate. Drying at 120-C ~or two hours gave 13.49g product.
Claims (8)
1. A catalyst comprising a crystalline molecular sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising then crystalline molecular sieve and an organosilicon compound and then calcining the resultant agglomerate.
2. A catalyst as claimed in claim 1, wherein the organosilicon compound is selected from silicones, silanes, alkoxysilanes, siloxanes and polysiloxanes.
3. A catalyst as claimed in claim 1 or claim 2, and also including a hydrogenation/dehydrogenation metal.
4. A method for pre-selectivating a catalytic molecular sieve comprising forming a mixture comprising a crystalline molecular sieve material having a Constraint Index of 1 to 12 and an organosilicon compound at a molecular sieve/organosilicon compound weight ratio of 1/10 to 100/1 and agglomerating the mixture.
5. A method as claimed in claim 30 further comprising contacting a pre-selectivated catalytic molecular sieve with a mixture comprising toluene and a second silicon source which is a paraxylene selectivating agent at reaction conditions for converting toluene to xylene for a least one hour to yield a twice modified catalyst.
6. A process for shape selective hydrocarbon conversion comprising contacting the hydrocarbon with a catalyst comprising a crystalline molecular sieve having a Constraint Index of 1-12 which has been preselectivated by agglomerating a mixture comprising then crystalline molecular sieve and an organosilicon compound and then calcining the resultant agglomerate.
7. A process as claimed in claim 5 wherein the shape selective hydrocarbon conversion is selective disproportionation of toluene into para-xylene.
8. A process as claimed in claim 6 wherein the disproportionation is effected at a temperature of 350°C to 540°C, a pressure of 100 to 34500 kPa (atmospheric to 5000 psig), a WHSV of 0.1 to 20, and a hydrogen to hydrocarbon molar ratio of 0.1 to 20.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| PCT/US1994/008239 WO1996003360A1 (en) | 1993-02-25 | 1994-07-21 | Shape selective hydrocarbon conversion |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2195306A1 true CA2195306A1 (en) | 1996-02-08 |
Family
ID=22242769
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002195306A Abandoned CA2195306A1 (en) | 1994-07-21 | 1994-07-21 | Shape selective hydrocarbon conversion |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0804393A4 (en) |
| JP (1) | JPH10503419A (en) |
| KR (1) | KR100248667B1 (en) |
| AU (1) | AU692177B2 (en) |
| CA (1) | CA2195306A1 (en) |
| WO (1) | WO1996003360A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20140100401A1 (en) * | 2011-05-09 | 2014-04-10 | Saudi Basic Industries Corporation | Catalyst for the alkylation of aromatic hydrocarbons |
| WO2017213668A1 (en) | 2016-06-10 | 2017-12-14 | Exxonmobil Research And Engineering Company | Organosilica polymer catalysts and methods of making the same |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4465886A (en) * | 1983-06-09 | 1984-08-14 | Mobil Oil Corporation | Silica-modified catalyst and use for selective production of para-dialkyl substituted benzenes |
| US4594332A (en) * | 1983-10-20 | 1986-06-10 | Basf Aktiengesellschaft | Preparation of hard, fracture-resistant catalysts from zeolite powder |
| US4582815A (en) * | 1984-07-06 | 1986-04-15 | Mobil Oil Corporation | Extrusion of silica-rich solids |
| US4950835A (en) * | 1989-10-24 | 1990-08-21 | Taiwan Styrene Monomer Corporation | Novel silicon-modified catalyst Si/HZSM-5, it's preparation, and a process for synthesizing high purity p-dialkyl benzene from monoalkyl benzene by using said catalyst |
| US5321183A (en) * | 1992-03-12 | 1994-06-14 | Mobil Oil Corp. | Process for the regioselective conversion of aromatics to para-disubstituted benzenes |
-
1994
- 1994-07-21 AU AU76687/94A patent/AU692177B2/en not_active Ceased
- 1994-07-21 KR KR1019970700315A patent/KR100248667B1/en not_active IP Right Cessation
- 1994-07-21 EP EP94927149A patent/EP0804393A4/en not_active Ceased
- 1994-07-21 JP JP8505698A patent/JPH10503419A/en not_active Ceased
- 1994-07-21 CA CA002195306A patent/CA2195306A1/en not_active Abandoned
- 1994-07-21 WO PCT/US1994/008239 patent/WO1996003360A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| KR100248667B1 (en) | 2000-03-15 |
| JPH10503419A (en) | 1998-03-31 |
| AU7668794A (en) | 1996-02-22 |
| KR970704516A (en) | 1997-09-06 |
| WO1996003360A1 (en) | 1996-02-08 |
| EP0804393A1 (en) | 1997-11-05 |
| AU692177B2 (en) | 1998-06-04 |
| EP0804393A4 (en) | 1998-05-20 |
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