CA1090315A - Process for producing p-dialkyl substituted benzenes and catalyst therefor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A new class of catalysts is described comprising crystalline aluminosilicate zeolites having an activity, alpha, of 2 to 5000, a xylene sorption capacity greater than lg./100g. zeolite and an orthoxylene sorption time for 30 percent of said capacity greater than 10 minutes, said sorption capacity and sorption time being measured at 120°C
and 4.5 ? 0.8 mm. Hg. These catalysts have the capacity to convert diverse feeds to pedialkyl benzenes with remarkable selectivity.

Description

PROCESS FOR PRODUCING P-DIALKYL SUBSTITUTED
BENZENES AND CATALYST THEREFOR

This invention relates to a catalyst suitable for the selective production of para dialkyl substituted benzenes and to a process for converting certain hydrocarbons in high yield to para dialkyl substituted benzenes using that catalyst.
The disproportionation of aromatic hydrocarbons in the presence of zeolite catalysts has been described by Grandio et. al.
in Oil and Gas Journal, Vol.69, No.48 (1971). U.S.Patents 3,126,422;
3,413,374; 3,598,878; 3,598,879 and 3,607,961 show vapor-phase disproportionation of toluene over various catalysts. In these processes the ~Ylenes produced exhibit equilibrium composition, namely approximately 24 percent para, 54 percent meta and 22 percent ortho.
Of the xylene isomers meta-xylene is the least desired, pàra-xylene being of particular value in the manufacture of tere-phthalic acid which is an intermediate in manufacture of synthetic fibers. Mixtures of xylene isomers, either alone or together with ethylbenzene, generally containing the equilibrium concentration of para-xylene, have previously been separated by expensive super-fractionation and multistage refrigeration step~.
We have now identified a catalyst which has the capacity to convert many available feedstocks to para-dialkyl benzenes with gratifying selectivity. According to the present invention such a composition comprises a crystalline aluminosilicate zeolite having an activity, alpha, of 2 to 5000, a xylene sorption capacity ~.~
:

`

~9Q315 greater than 1 g./100 g. zeolite, and an orthoxylene sorption time for 30 percent of said capacity Breater than 10 minutes, said sorption capacity and sorption time being measured at 120C
and 4.5 + 0.8 mm. Hg. In many embodiments the zeolite has a SiO2/A1203 ratio of 12 to 3000 and a constraint index in the range 1 to 12.
A catalyst which fulfills the prescriptions above set forth, and which is thus capable of participating in conversions which partake of the desired selectivity, can be realised in several different forms of which those set forth below constitute preferred embodiments of the invention. Thus, according to a first embodi-ment the crystal size of the zeolite is a determining factor, at least part of the zeolite being present as crystals from 0.5 to 20 microns in size, preferably 1 to 6 microns.
According to a second embodiment the catalyst achievesits properties by coking, in particular by bearing a deposit of coke in a quantity of 15 to 75 percent by weight of unco~d catalyst, preferably 20 to 40 percent of the weight of uncoked catalyst.
According to a third embodiment the prescribed activity and sorption properties pertain to a zeolite which is intimately associated with from 2 to 30 percent each, by weight of zeolite, of one or more difficulty reducible oxides, particularly by those of antimony, phosphorus, boron, uranium, magnesium, zinc and/or calcium.
In a favoured realisation of this embodiment the zeolite is associated with 0.25 to 25 weight percent of an oxide of phosphorus - \
~315 and of an oxide of magnesi~m the weight percentage of phosphorus oxide being preferably between 0.7 and 15, that of magnesium oxide between 1 and 15.
According to a fourth embodiment the prescribed propertiss are achieved by virtue of the fact that the interior crystalline structure of the zeolite contains from 0.1 to 10 percent, of the weight of the zeolite, of added amorphous silica: preferably the weight percentage of said silica i8 2 to 10. In one of the more convenient methods of preparation the added amorphous silica is the product of decomposition of a silicon compound capable of entering the pores of the zeolite, such as a silicone, siloxane or polysilane or a mono-methyl, -chloro or -fluro derivative thereof.
Particularly uqeful silicon compounds have the formula SiR1R2R3R4, in which R1 and R2 are hydrogen, fluorine, chlorine, methyl, ethyl, amino, methoxy or ethoxy, R3 is hydrogen, fluorine, chlorine, methyl or amino. and R4 is hydrogen or fluorine: other useful silicon compounds are silane, dimethylsilane, dichlorosilane, methyl silane or silicon tetrafluoride.
A fifth embodiment differs, inter alia, from the fourth in that the desired properties are conferred by silica which is not present in the interior crystalline structure. According to this embodiment the external surface of the zeolite bears a coating of silica in a quantity between 0.5 and 30 percent by weight of the zeolite. Again, such silica may be the product of decomposition f a silicone compound incapable of entering the pores of the zeolite, such as one having the formula ~ (R1) (R2) Sio ] , in ~315 which R1 and R2 represent fluorine, hydroxy, alkyl, aralkyl or alkaryl or fluroalkyl, may be the same or different except for the fact that R1 ~only) may be hydrogen, n being 10 to 1000, the number of carbon atoms in R1 or R2 being from 1 to 10. The silicone compound preferably has a molecular weight of 500 to 20,000, pre-ferably 1000 to 10,000, and compounds found particularly effective have been dimethylsilicone, diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydro-gensilicone, methylethylsilicone, phenylethylsilicone, diphenyl-silicone, methyltrifluoropropylsilicone, ethyltrifluoropropyl-silicone, polydimethylsilicone, tetrachlorophenylmethyl silicone, tetrachlorophenylethyl silicone, tetrachlorophenylhydrogen silicone, tetrachlorophenylphenyl silicone, methylvinylsilicone and ethyl-vinylsilicone.
The preferred zeolites employed in the catalysts according to the invention are zeolites ZSM-5, ZSM-11, ZSM-12, ZSM-35 or ZSM-38: it is usually of advantage to employ them in a form characterized by the presence of hydrogen cations. The preferred cataly3ts, furthermore, are those in which the zeolite has an activity, alpha, in the range 5 to 200.
The catalyst certainly does not have to consist of zeolite:
it may ~ust as well comprise a composite of a zeolite as aforesaid with a binder, for example a naturally-occurring or synthetic refractory oxide. Suitable naturally-occurring oxides are mont-morillonite or kaolin clay, suitable synthetic oxides silica, alumina, magnesia, zieconia, thoria, beryllia and/or titania. When used, the binder comprises 1 to 99, preferably 20 to 95, weight percent of catalyst, a particularly successful proportion being 30 to 40 weight percent.
According to another aspect of the invention a process for selectively producing para-dialkyl benzenes, in which each alkyl group contains 1 to 4 carbon atoms, comprises contacting a C1 ~ C4 monoalkyl benzene, a C2-C15 olefin and/or a C3-C44 paraffin, or a mixture of any of the foregoing with benzene, under conversion conditions, with a catalyst as hereinabove set forth. The pre-ferred conditions comprise a temperature of 250 to 750C, a pressure between 0.1 atmosphere and 100 atmospheres and a weight hourly space velocity between 0.1 and 2000.
When operating at a temperature of 400 to 700C, a pressureof 1 to 100 atmospheres and a space velocity is 0.1 to 100, toluene may be disproportionated, or alkylated with an alkylating agent having from 1 to 4 carbon atoms, with highly beneficial results.
A preferred space velocity for those two conversions is 1 to 50.
The same conditions are also conduclve to the use as feed of C3-C44 paraffins. Operating at a temperature of 300 to 700C, a pressure of 1 to 100 atmospheres and a space velocity of 1 to 1000 C3-C15 olefins may be contacted with the catalyst to yield the desired p-dialkyl benzenes.
The more useful products obtainable according to the invention comprise p-xylene, p-diethyl benzene or p-ethyl toluene; under some circumstances their yield may be increased if the reaction is conducted in the presence of hydrogen, the mole ratio of hydrogen to hydrocarbon feed being suitably from 2 to 20.

33iS

The above catalyst is particularly applicable for the selective production of para dialkyl substituted benzenes contain-ing alkyl groups of 1 to 4 carbon atoms by contacting a hydrocarbon precursor, such as mono alkyl-substituted benzenes having 1-4 carbon atoms in the alkyl substituent, C2-C15 olefins or a C3-C44 paraffin or mixture thereof, under conversion conditions with such catalyst.
In a preferred embodiment, the present process comprises conversion of the specified precursors to yield xylenes in which the proportion of para-xylene is substantially in excess of its normal equilibrium concentration and preferably in excess of 40 weight percent of the xylene product produced in the presence of the specified catalyst at a temperature between about 250 and about 750C. at a pressure between about 0.1 and about 100 atmospheres utilizing a feed weight hourly space velocity (WHSV) between about 0.1 and about 2000. The latter WHSV is ba3ed upon the weight of catalyst compositions, i.e. total weight of active catalyst and binder therefor. The effluent is separated and distilled to remove the desired product, e.g. para-xylene and unreacted product is recycled for further reaction.
Figure 1 of the drawings shows change in paraxylene selec-tivity with variation in ortho-xylene sorption time for 30 percent of xylene sorption capacity of the zeolite catalytst used.
Figure 2 shows a comparison of the para-xylene selectivity achieved with small and large crystal crystalline aluminosilicate zeolite catalyst.
Figure 3 shows the changed in toluene conversion and para-xylene selectivity occurring with time on stream utilizing a co-feed of toluene and hydrogen.

~IS(~315 The hydrocarbon precursor charge utilized in the process of this invention may be a mono-alkyl substituted benzene having 1-4 carbon atoms in the alkyl substituent, such as toluene; a C2-C15 olefin such as ethylene, propylene, butenes, pentenes,hexenes, heptenes, octenes, nonenes, decenes, pentadecenes, or mixtures-thereof with one another or a C3-C44 paraffin such as butane, hexane, octane, dodecane, eicosane, dotriacontane, tetracontane, or mixtures thereof with one another. Preferably, such paraffins are straight chain or only slightly branched.
Typical of the processes contemplated herein are dis-proportionation of toluene to benzene and xylene, wherein the pro-portion of para-xylene obtained is greatly in excess of its normal equilibrium concentration. Such process is effectively carried out at a temperature of between about 400C. and about 700-C at a pressure , 10!~315 between about 1 atmosphere and about 100 atmospheres utilizing a weight hourly space velocity of between about 1 and about 50.
Another charge stock suitable for use in the process of the invention is a stream high in C2-C15 olefin content. Thus, ethylene, propylene, butenes, pentenes, hexenes, dienes such as butadiene, pentadienes, cycloolefins such as cyclopentene and cyclo-hexene, alkyl-substituted cycloolefins such as ethyl cyclopentene, cyclopentadiene and cyclohexadiene can be effectively converted to a high yield of para dialkyl substituted benzenes utilising the hereinabove described catalyst. Conversion utilizing such olefin feed is carried out at a temperature within the approximate range of 300 to 700C, a pressure between atmospheric and 100 atmos-pheres employing a weight hourly space velocity between about 1 and about 1000. As sources of the olefin reaction either sub-stantially pure streams of the C2-C15 olefin may be employed or refinery or Chemical streams high in such reactant, i.e. generally more than 25 volume percent may be used.
A still further charge stock which can be effectively used in the present invention to selectively produce para dialkyl substituted benzenes containing alkyl group of 1 to 4 carbon atoms includes paraffinic hydrocarbons ha~ing between 3 and 44 carbon atoms.
Representative of such paraffins are butane~, pentanes, hexanes, heptanes, octanes, dodecanes, eiconsane, dotriacontane, tetra-contane and alkyl-substituted derivatives of these paraffins.
Utilizing such paraffinic charge, reaction conditions include contact with the above-described crystalline aluminosilicate zeolite catalyst at a temperature of between about 400 to 700~C., a , .

~90315 pressure between about atmospheric and about 100 atmospheres and a weight hourly space velocity between about 0.1 and about 100.
The use of mixed aromatics as feed is also feasible.
For example, a mixture of ethylbenzene and toluene is converted selectively to a mixture rich in p-diethylbenzene and p-ethyltoluene, the latter predominating at high toluene to ethylbenzene ratios in the feed.
Reaction of benzene, toluene, ethylbenzene, propyl-benzene or butylbenzene with C2-C20 olefines o~ C5-C25~paraffins at 250 to 500C yields p-dialkyl benzenes. This reaction'is preferably carried out under pressure greater than 200 psig.
For example, benzene and ethylene at a mole ratio of 1:2 to 10:1 yield p-diethylbenzene besides ethylbenzene (p=400 psig), Temp. = 800F); toluene and l-octene yield p-ethyltoluene and a mixture of n- and isopropyl toluene rich in p-isomer.
In the absence of added aromatics, C2-C15 olefines and C3-C44 paraffins each yield a mixture of aromatics rich in p-di-alkylbenzenes. The olefins and the higher paraffins are more reactive and require lower severity of operation, e.g., a tempera-ture of 250-600C and preferably 300-550C, while the lower paraf-fins, e.g. C3-C5 paraffins yield aromatics at a practical rate only above 400C. The aromatization can be carried out a atmos-pheric pressure or at elevated pressure; low pressure hydrogen can be used to retard catalyst aging, but high hydrogen partial pressure above 200 psig diminishes aromatics' formation. Production of p-dialkylated benzenes containing alkyl groups greater than C1 is favored by higher pressure and lower temperature; for example, p-ethyltoluene is formed from either dodecane or 1-butene at 400C, whereas p-xylene is the preferred dialkybenzene formed at higher temperature.

Methylation of toluene in the presence of the above-described catalyst, particularly that bearing a deposit of coke, is effected by contact of the toluene with a methylating agent, preferably methanol, at a tempature between about 300 and about 750 C and prefeEably~between abont 400 and about 700C.
At the higher temperatures, the ~eolites of high silicalalumina ratio are preferred. For example, ZSM-5 of 300 SiO2/A1203 ratio and upwards is very stable at high temperatures. The reaction generally takes place at atmospheric pressure, but the pressure may be within the approximate range of 1 atmosphere to 1000 psig.
A weight hourly space velocity of between about 1 and about 2000 is employed. The molar ratio of methylating agent to toluene is generally between about .05 and about 5. When methanol is employed as the methylating agent a suitable molar ratio of methanol to toluene has been found to be approximately 0.1 to 8 moles of methanol per mole of toluene. With the use of other methylating agents, such as methylchloride, methylbromide, dimethylether or dimethylsulfide, the molar ratio of methylating agent to toluene may vary within the aforenoted range. Reaction is suitable accomplished utilizing a weight hourly space velocity of between about 1 and about 2000 and preferably between about 5 and about 1500 weight of charge per weight of catalyst per hour. The reaction product consisting predominantly of para-xylene, together with comparatively smaller amounts of meta-xylene and ortho-xylene may be separated by any suitable means, such as by passing the same through a water condenser and subsequently passing the organic phase through a column in which chromatographic separation of the xylene isomers is accomplished.

_ 10 ---~gU31S

In accordance with the present invention the above described feed precursors are brought into contact, under conve~-sion conditions, with a bed comprising particle-form catalyst con-taining a crystalline aluminosilicate having: (1) an activity, in terms of alpha value, of between about 2 and about 5000, (2) a xylene sorption capacity greater than 1 gram/100 grams of zeolite and (3) an ortho-xylene sorption time for 30 percent of said capacity of Breater than 10 minutes, where the sorption capacity and sorption time are measured at 120 C and a xylene pressure of 4.5 + 0.8 mm - of mercury.
The alpha value reflects the relative activity of the catalyst with respect to a high activity silica-alumina cracking catalyst. To determine the alpha value as such term is used herein, n-hexane conversion is determined at about 1000F. Conversion is varied by variation in space velocity such that a conversion level of 10 to 60 percent of n-hexane is obtained and converted to a rate constant per unit volume of zeolite and compared with that of silica-alumina catalyst which is normalized to a reference activity of 1000F. Catalytic activity of the catalysts are expressed as multiple of this standard, i.e. the silica-alumina standard. The silica-alumina reference catalyst contains about 10 weight percent A1203 and remainder SiO2. This method of determining alpha, modified as described above, is more fully described in the Journal of Catalysis, Vol. VI, Pages 278-287, 1966.
The measurements of hydrocarbon sorption capacities and rates are conveniently carried out gravimetrically in a thermal balance. In particular, it has been found that an equil-ibrium sorption capacity of xylene, which can be either para, meta, ortho or a mixture thereof, preferably para-xylene since this isomer reaches equilibrium within the shortest time of at least 1 gram per 100 grams of zeolite measured at 120C and a xylene pressure of _ 11 _ 4.5 + 0.8 mm of mercury and an orthoxylene sorption time for 30 percent of said capacity of greater than 10 minutes (at the same conditions of temperature and pressure) are required in order to achieve the desired selective production of para dialkyl substi-tuted benzenes.
It has been found that zeolites exhibiting very highselectivity for para-dialkybenzene production require a very long time up to and exceeding a thousand minutes to sorb o-xylene in an amount of 30% of total xYlene sorption capacity. For those materials it is more convenient to determine the sorption time for a lower extent of sorption, such as 5%, 10% or 20% of capacity, and to estimate the 30% sorption time by applying the following multiplication factors F as illustrated for 5% sorption:

t = F.t 0.3 0.05 15Percent of sorption capacityFactor (F) to Estimate 30%
Sorption Time

2.2 In assessment of zsolite crystal size, conventional scanning electron microscopy tSEM) techniques can be used, the minimum crystal dimension of a given crystal being taken as the dimension of reference. The crystalline aluminosilicate zeolites used in the present invention in substantial proportion are essentially characterized by a crystal size of greater than about 0.5 micron.
It is contemplated that the amount of zeolite of such crystal size will be such as to exert a directive influence in the desired lQ~Q315 selective production of paradialkyl substituted benzenes.
Generally, the amount of zeolite of such crystal size will be present in predominate proportion, i.e. in an amount exceeding 50 weight percent, and preferably may constitute up to 100 weight percent of the total zeolite employed.
In addition to the use of scanning electron microscopy as a tool in the selection of an effective crystalline aluminosilicate zeolite for use in the catalyst employed herein, the measurement of hydrocarbon sorption capacities and rates have been useful in 1C characterizing such catalyst. Such measurements are conveniently carried out gravimetrically in a thermal balance.
The deposition on the catalyst of the carbonaceous coating commonly referred to as "coke", resulting from the decomposition of hydrocarbons, is generally effected under conditions of high temperature, in the presence of the specified catalyst during the course of a reaction such as the methylation o~-toluene. Generally, precoking of the catalyst will be accomplished by initially utilizing the uncoked catalyst in the reaction of interest, during which coke is deposited on the catalyst surface and there-after controlled within the above-noted range of about 15 to about 75 weight percent by periodic regeneration by exposure to an oxygen-containing atmosphere at an elevated temperature.
Indeed, one advantage of utilizing the catalyst described herein is its ease of regenerability. Thus, after use of the pre-coked catalyst for effecting the desired reaction for a period oftime such that the activity of the catalyst declines to a point where further use becomes uneconomical, it can be readily regenerated .

10~(~315 by burning off excess coke in an oxygen-contain~ng atmosphere, e.g. air, at a temperature, generally within the approximate range of 400 to 700C. The catalyst may thereby be rendered substantially free of coke, necessitating subjecting the catalyst to a precoking step. Alternatively, the catalyst may be partially freed of coke during the combustion regeneration step to leave a residual deposition of coke on the surface of the catalyst, the amount of which is within the approximate range of 15 to 75 weight percent coke. The thus regenerated catalyst can then be employed for further use in achieving the desired selective production of para-xylene.
In a preferred embodiment, the crystalline aluminosilicate zeolites employed may have undergone modification prior to use by selective precoking thereof to deposit at least about 1 weight percent and generally between about 2 and about 40 weight percent of coke thereon, based on the weight of total catalyst. If zeolite is employed in substantially pure form or in combination with a low coking binder, such as silica, then the weight percent of coke is generally in the range of 2 to 10 weight percent. When the zeolite is combined with a binder of high coking tendencie~, such as alumina coke~ content of the total catalyst is in the approximate range of 10 to 40 weight percent. Precoking can be accomplished by contacting the catalyst with a hydrocarbon charge e.g. toluene, under high severity conditions or alternatively at a reduced hydrogen to hydrocarbon concentration, i.e. 0 to 1 mole ratio of hydrogen to hydrocarbon for a sufficient time to deposit the desired amount of coke thereon.

l~S0315 Prior modification of the zeolite may also be suitably effected by combining therewith a small amount, generally in the range of about 2 to about 30 weight percent, of a difficulty reducible oxide, such as oxides of antimony, phosphorus, boron, magnesium, uranium, zinc and/or calcium. Combination of the desired oxide with the zeolite can readily be effected by contact-ing the zeolite with a solution of an appropriate compound of the element to be introduced, followed by drying the calcining to convert the compound to its oxide form.
In an advantageous embodiment of the foregoing modification the difficultly reducible oxides are those of phosphorus and magnesium, present simultaneously. Preparation of the catalyst (which is particularly effective in toluene disproportionation) is accomplished in two stages, the crystals of zeolite in a form substantially free of alkali metal, i.e. containing less than about 1.5 weight percent alkali metal and preferably having at least a portion of the original cations associated therewith replaced by hydrogen, being first contacted with a phosphorus compound.
Representative phosphorus-containing compounds include derivatives of groups represented by PX3, RPX~, R2PX, R3P, X3P0, (X03)P0, (X0)3P, R3P=0, R3P=S, RP02, PPS2, RP(0) (OX)2, RP(S) (SX)2, 1~(~315 R P(O)OX, R2P(S)SX, RP(OX)2, RP(SX)2, ROP(OX?2, RSP(SX)2, (RS)2PSP(SR)2, and (RO)2POP(OR)2, where R i9 an alkyl or aryl, such as a phenyl radical and X is hydrogen, R, or halide.
These compounds include primary, RPH2, secondary, R2PH and tertiary, R3P, phosphines such as butyl phosphine; the teriary phosphine oxides R3PO, such as tributylphosphine oxide, the tertiary phosphine sulfides, R3PS, the primary, RP(O)(OX)2, and secondary, R2P(O)OX, phosphonic acids such as benzene phosphonic acid; the corresponding sulfur derivatives such as RP(S)(SX)2 and R2P(S)SX, the esters of the phosphonic acids such as diethyl phosphon~te, ~RO)2P~O~E, dialkyl alkyl-~pho;s-phonates, (RO)2P(O)R, and alkyl dialkylphosphinates, (RO)P(O)R2;
phosphinous acids, R2POX, such as diethylphosphinous acid.
primary, (RO)P(OX)2, secondary, (RO)2POX, and tertiary, (RO)3P, phosphites; and esters thereof such as the monopropyl ester, alkyl dialkylphosphinites (RO)PR2, and dialkyl alkylphospho-nite, (RO)2PR esters. Correspondlng sulfur derivatives may also be employed including (RS)2P(S)H, (RS)2P(S)R, (RS)P(S)R2, R2PSX, (RS)P(SX)2, (RS)2PSX, (RS)3P, (RS)PR2 and (RS)2PR. Ex- -amples of phosphite esters include trimethylphosphite, tri-ethylphosphite, diisopropylphosphite, butylphosphite; and pyro-phosphites such as tetraethylpyrophosphite. The alkyl groups in the mentioned compounds contain one to four carbon atoms.
Other suitable phosphorus-con~aining~compounds include the phosphorus halides such as phosphorus trichloride, bromide, and iodide, alkyl phosphorodichloridites, (RO)PC12, dialkyl phosphorochloridites, (RO)2PX, dialkylphosphionochloridites, R2PC1, alkyl alkylphosphonochloridates, (RO)(R)P(O)C1, dialkyl phosphinochloridates, R2P(O)C1 and RP(O)C12. Applicable corres-ponding sulfur derivatives include (RS)PC12, (RS)2PX,(RS)(R)P(S)C1 and R2P(S)C1.

l~g~3~5 Preferred iphosp~orus-containing compounds include diphenyl phosphine chloride, trimethylphosphite and phosphorus trichloride, phosphoric acid, phenyl phosphine oxychloride, trimethylphosphate, diphenyl phosphinous acid, diphenyl phosphinic acid, diethylchloro thiophosphate, methyl acid phosphate and other alcohol-P205 reaction products.
Reaction of the zeolite with the phosphorus compound is effected by contacting the zeolite with such compound.
Where the treating phosphorus compound is a liquid, such com-pound can be in solution in a solvent at the time contact with the zeolite i9 effected. Any solvent relatively inert with respect to the treating compound and the zeolite may be employed.
Suitable solvents include water and aliphatic, aromatic or alcoholic liquids. Where the phosphorus-containing compound is, for example, trimethylphosphite or liquid phosphorus tri-chloride, a hydrocarbon solvent such as n-octane may be employed.
The phosphorus-containing compound may be used without a solvent.
i.e., may be used as a neat liquid. Where the phosphorus-containing compound is in the gaseous phase, such as where gaseous phosphorus trichloride is employed, the treating com-pound can be used by itself or can be used in admixture with a gaseous diluent relatively inert to the phosphorus-containing compound and the zeolite ~uch as air or nitrogen or with an organic solvent, such as octane or toluene.
Prior to reacting the zeolite with the phosphorus-containing compound, the zeolite may be dried. Drying can be effected in the presence of air. Elevated temperatures may be employed. However, the temperature should not be such that the crystal structure of the zeolite is destroyed.
Heating of the phosphorus-containing catalyst sub-sequent to preparation and prior to use is also preferred.
The heating can be carried out in the presence of oxygen, for

3~5 example air. Heating can be at a temperature of about 150C.
However, higher temperatures, i.e., up to about 500C. are preferred. Heating is generally carried out for 1-5 hours but may be extended to 24 hours or longer. While heating temperatures above about 500C. can be employed, they are not necessary. At pemperatures of about 1000C., the crystal structure of the zeolite tends to deteriorate. After heating in air at elevated temperatures, phosphorus is present in oxide form.
The amount of phosphorus oxide incorporated with the zeolite should be at least about 0.25 percent by weight. How-ever, it is preferred that the amount of phosphorus oxide in the zeolite be at least about 2 percent by weight, particularly when the same is combined with a binder, e.g. 35 weight percent of alumina. The amount of phosphorus oxide can be as high as about 25 percent by weight or more depending on the amount and type of binder present. Preferably the amount of phosphor~s oxide added to the zeolite is between about 0.7 and about 15 percent by weight.
The amount of phosphorus oxide incorporated with the zeolite by reaction with elemental phosphorus or phosphorus-containing compound will depend upon several factors. One of these is the reaction time, i.e., the time that the zeolite and the phosphorus-containing source are maintained in contact with each other. With greater reaction times, all other factors being equal, a greater amount of phosphorus is incorporated with the zeolite. Other factors upon which the amount of phos-phorus incorporated with the zeolite is dependent include re-action temperature, concentration of the treating compound in the reaction mixture, the degree to which the zeolite has been dried prior to reaction with the phosphorus-containing compound, the conditions of drying of the zeolite after reaction of the - 18 _ ~090315 zeolite with the treating compound, and the amount and type of binder incorporated with the zeolite.
T~ zeolite containing phosphorus oxide is then further combined with magnesium oxide by contact with a suit-able compound of magnesium. Representative magnesium-containing compounds include magnesium acetate, magnesium nitrate, magnesium benzoate, magnesium proprionate, magnesium 2-ethylhexoate, magnesium carbonate, magnesium formate, magnesium oxylate, magnesium amide, magnesium bromide, magnesium hydride, magnesium lactate, magnesium laurate, magnesium oleate, magnesium palmitate, magnesium silicylate, magnesium stearate and magnesium sulfide.
Reaction of the zeolite with the treating magnesium compound i8 effected by contacting the zeolite with such com-pound. Where the treating compound is a liquid, such compound can be in solution in a solvent at the time contact with the zeolite is effected. Any solvent relatively inert with respect to the treating magnesium compound and the zeolite may be em-ployed. Suitable solvents include water and aliphatic, aromatic or alcoholic liquid. The treating compound may also be used without a solvent, i.e. may be used as a neat liquid. Where the treating compound is in the gaseous phase, it can be used by itself or can be used in admixture with a gaseous diluent rela-tively inert to the treating compound and the zeolite such as helium or nitrogen or with an organic solvent, such as octane or toluene.
Heating of the magnesium compound impregnated cata-lyst subsequent to preparation and prior to use is preferred.
The heating can be carried out in the presence of oxygen, for example, air. Heating can be at a temperature of about 150C.
However, higher temperatures, i.e. up to about 500C. are pre-ferred. Heating is generally carried out for 1-5 hours but may be extended to 24 hours or longer. While heating temperatures _ 19 _ 1~}0315 above about 500DC. may be employed, they are generally not necessary. At temperatures of about 1000C., the crystal structure of the zeolite tends to deteriorate. After heating in air at el~vated temperatures, the oxide form of magnesium is present.
The amount of magnesium oxide incorporated in the calcined phosphorus oxide-containing zeolite should be at least about 0.25 percent by weight. However, it is preferred that the amount of magnesium oxide in the zeolite be at least about 1 percent by weight, particularly when the same is combined with a binder, e.g. 35 weight percent of alumina. The amount of magnesium oxide can be as high as about 25 percent by weight or more depending on the amount and type of binder present.
Preferably, the amount of magnesium oxide added to the zeolite between about 1 and about 15 percent by weight.
The amount of magnesium oxide incorporated with the zeolite by reaction with the treating solution and subsequent calcination in air will depend on several factors. One of these is the reaction time, i.e. the time that the zeolite and the magnesium-containing source are maintained in contact with each other. With greater reaction times, all other factors being equal, a greater amount of magnesium oxide is incorporated with the zeolite. Other factors upon which the amount of magne-sium oxide incorporated with the zeolite is dependent include reaction temperature, concentration of the treating compound in the reaction mixture, the degree to which the zeolite has been dried prior to reaction with the treating compound, the condi-tions of drying of the zeolite after reaction of the zeolite with the magnesium compound and the amount and type of binder incorporated with the zeolite.
After contact of the phosphorus oxide-containing zeolite with the magnesium reagent, the resulting composite is dried and heated in a manner similar to that used in preparing the phosphorus oxide-containing zeolite.

A further embodiment of the catalyst of the invention, which again has particular utility in the selective disproportiona-tion of toluene to p-xylene, is that in which the zeolite contains interdispersed within its interior crystalline structure amorphous silica added to the crystalline zeolite subsequent to the latter's formation in an amount of at least about 0.1 weight percent and generally in the approximate range of 2 to 10 weight percent.
It has been found that such catalyst is suitably prepared by sorption of a silicon-containing compound, generally a silane, into the pores of a crystalline aluminosilicate zeolite having the above-specified silica/alumina ratio and constraint index characteristics. The molecular dimensions of the silicon compound employed are such that it is readily sorbed into the pores of the crystalline aluminosilicate zeolite. The sorbed silicon compound contained in the pores of the crystalline aluminosilicate is subjected to catalyzed hydrolysis, either by base catalyzed hydrolysis, e.g. by contact with a solution of aqueous ammonia or by acid catalyzed hydrolysis in the presence of Lewis or ~ronsted _..
acids, e.g. by contact with an aqueous solution of hydrochloric acid; followed by calcination in air at a temperature between about 300 and about 700C. to yield amorphous silica within the pores of the crystalline aluminosilicate zeolite.
In a preferred preparative technique the crystals of zeolite in a form substantially free of alkali metal, i.e. containing less than about 1.5 weight percent alkali metal and preferably having at least a portion o~ the original cations associated therewith replaced by hydrogen, are then contacted with a silicon-containing compound of molecular dimensions such that it is readily sorbed into the pores of the zeolite. Generally, the silicon-containing compound employed is a silane having the following formula:

R4 li R2 where R1 and R2 are hydrogen, fluorine, chlorine, methyl, ethyl, amino, methoxy or ethoxy; R3 is hydrogen, fluorine, chlorine, methyl, amino or methoxy; and R4 is hydrogen or fluorine. Other suitable silicon-containing compounds include siloxanes such as di-siloxanes, tri-siloxanes and higher siloxanes up to deca-siloxanes and poly-silanes, such as di-silanes, tri-silanes and hi~her silanes, up to deca-silanes. It is also contemplated to use derivatives of the aforenoted siloxanes and poly-silanes having methyl, chloro or fluoro substituents, where such silicon atom contains no more than one of such substituents.
The silicon compound employed may be either in the form of a liquid or a gas under the conditions of contact with the zeolite.
The pores of the latter are preferably, but not neces~arily, sa-turated with the liquid or gaseous silicon compound. Thereafter, the silicon compound undergoes catalyzed hydrolysis as described above, e.g. by contacting the zeolite containing the sorbed silicon compound with a suitable acid or base for a period of time sufficient to effect the desired hydrolysis with evolution of hydrogen. The resulting product is then calcined in an oxygen-containing atmosphere, such as air, at a temperature of betweeen . .
~ .

l~gO315 about 300 and about 700C. for 1 to 24 hours to yield a catalyst of the specified crystalline aluminosilicate zeolite having silica contained within its interior structure.
The amount of silica incorporated with the zeolite will depend on several factors. One of these is the time that the zeolite and the silicon-containing source are maintained in contact with each other. With greater contact times, all other factors being equal, a greater amount of silica is incorporated with the zeolite. Other factors upon which the amount of silica incorporated with the zeolite is dependent include temperature, concentration of the treating compound in the contacting media, the degree to which the zeolite has been dried prior to contact with the silicon-containing compound, the conditions of hydrolysis and calcination of the zeolite after contact of the same with the treating compound and the amount and type of binder incorporated with the zeolite.
In an alternative embodiment the zeolite has a coating of silica deposited on its external surface. Such coating extensively covers the external surface of the zeolite and resides substantially completely on the external surface, although it will be appreciated that a number of factors affect the ultimate location of the silica. The coating of silica is deposited on the surface of the zeolite by contacting the latter with a silicone compound of molecular size incapable of entering the pores of the zeolite and subsequently heating in an oxygen-containing atmosphere, such as air, to a temperature above 300C. but below a temperature at which the crystallinity of the zeolite is adversely affected at a 1~190315 rate such that the silicone compound does not volatilize before udergoing oxidation of silica.
The silicone compound utilized to effect the silica coating is characterized by the general formula:

- ~ Si-0 ~ _ _ R2 _ where Rl i9 hydrogen, fluorine, hydroxy, alkyl, aralkyl, alkaryl or fluor~-alkyl. The hydrocarbon substituents generally contain from 1 to 10 carbon atoms and preferably are methyl or ethyl groups. R2 is selected from the same group as R1, other than hydrogen and n is an integer of at least 10 and generally in the range of 10 to 1000. The molecular weight of the silicone compound employed is generally between about 500 and about 20,000 and preferably within the approximate range of 1000 and 10,000.

l~Q315 Representative silicone compounds include dimethylsilicone, diethylsilicone. phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethyl-silicone, phenylethylsilicone, diphenylsilicone, methyltri-fluoropropylsilicone, ethyltrifluoropropylsilicone, polydi-methylsilicone, tetrachlorophenylmethyl silicone, tetrachloro-phenylethyl silicone, tetrachlorophenylhydrogen silicone, tetrachlorophenylphenyl silicone, methylvinylsilicone and ethylvinylsilicone.
The silicone compound dissolved in a suitable solvent therefort e.g., n-hexane, pentane, heptane, benzene, toluene, chloroform, carbon tetrachloride, is contacted with the above-described zeolite at a temperature between about 10C. and about 100C. for a period of time sufficient to deposit the ultimately desired amount of silicone thereon. Time of contact will gener-ally be within the range of 0.2 to 5 hours, during which time the mixture is desirably subjected to evaporation. The re-sulting residue i9 then calcined in an oxygen-containing atmos-phere, preferably air, at a rate of 0.2 to 5C./minute to a temperature greater than 300C. but below a temperature at which the crystallinity of the zeolite is adversely affected.
Generally, such temperature will be below 600C. Preferably the temperature of calcination is within the approximate range of 350 to 550C. The product is maintained at the calcination temperature usually for 1 to 24 hours to yield a silica-coated zeolite containing between about 0.5 and about 30 weight percent and preferably between about 1 and 15 weight percent silica.

Zeolites such as zeolite X, zeolite Y, ZSM-4, faujasite, mordenite, ferrierite and offretite which satisfy the aforenoted activity and sorption characteristics are within the confined of this invention. Particularly preferred are those zeolites having a silica to alumina ratio at least about 12 and a constraint index within the approximate range of 1 to 12. These zeolites in-duce profound transformations of aliphatic hydrocarbons to aromatic hydrocarbons in commercially desirable yields and are generally highly effective in conversion reactions involving aromatic hydro-carbons. Although they have unusually low alumina contents, i.e.

~W~315 high silica to alumina ratios', they are very active even when the silica to alumina ratio exceeds 30. The activity is sur-prising since catalytic activity is generally attributed to framework aluminum atoms and cations associated with these aluminum atoms. These zeolites retain their crystallinity for long periods in spite of the presence of steam at high tempera-ture which induces irreversible collapse of the framework of other zeolites, e.g. of the X and A typeO Furthermore, carbonaceous deposits, when formed, may be removed by burning at higher than usual temperatures to restore activity. In many environments the zeolites of this class exhibit very low coke forming capability, conductive to very long times on stream between burning regenerations.
An important characteristic of the crystal structure of this class of zeolites is that it provides constrained access to, and egress from the intracrystalline free space by virtu~ of having a pore dimension greater than about 5 Angstroms and pore windows of about a size such as would be provided by 10-membered rings of oxygen atoms. It is to be understood, of course, that these rings are those formed by the regular disposition of the tetrahedra makinB up the anionic framework of the crystalline aluminosilicate, the oxygen atoms themselves being bonded to the silicon or aluminum atoms at the centers of the tetrahedra. Brief-ly, the preferred type zeolites useful in this invention possess, in combination: a silica to alumina mole ratio of at least about 12; and a structure providing constrained access to the crystalline free space.
The silica to alumina ratio referred to may be determined by conventional analysis. This ratio is meant to represent, as closely as possible, the ratio in the rigid anionic framework of the zeolite crystal and to exclude aluminum in the 1~03~5 binder or in cationic or other form within the channels. Although zeolites with a silica to alumina ratio of at least 12 are useful, it is preferred to use zeolites having higher ratios of at least about 30. Such zeolites, after activation, acquire an intracrystal-line sorption capacity for normal hexane which is greater than that for water, i.e. they exhibit "hydrophobic" properties. It is be-lieved that this hydrophobic character is advantageous in the pre-sent invention.
The type zeolites useful in this invention freely sorb normal hexane and have a pore dimension greater than about 5 Angstroms. In addition, the structure must provide constrained access to larger molecules. It is sometimes possible to judge from a known crystal structure whether such constrained access exists. For example, if the only pore windows in a crystal are formed by 8-membered rings of oxygen atoms, then access by mole-cules of larger cross-section than normal hexane is excluded and the zeolite is not of the desired type. Windows of 10-membered rings are preferred, although, in some instances, excessive pucker-ing or pore blockage may render these zeolites ineffective.
Twelve-membered rings do not generally appear to offer sufficient constraint to produce the advantageous conversions, although puckered structures exist such as TMA offretite which is a known effective zeolite. Also, structures can be conceived, due to pore blockage or other cause, that may be operative.
~ather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained ac-cess, a simple determination of the "constraint index" may be made by passing continuously a mixture of an equal weight of normal - ~8 -~9~15 hexane and 3-methylpentane over a small sample, approximately 1 gram or less, of catalyst at atmospheric pressure according to the following procedure. A sample of the zeolite, in the form of pellets or extrudate, is crushed to a particle size about that of coarse sand and mounted in a glass tube. Prior to testing, the zeolite is treated with a stream of air at 100CF for at least 15 minutes. The zeolite is then flushed with helium and the tempera-ture adjusted between 550F and 950F to give an overall conver-sion between 10% and 60%. The mixture of hydrocarbons is passed at 1 liquid hourly space velocity (i.e., 1 vo~ume of liquid hydro-carbon per volume of zeolite per hour) over the zeolite with a helium dilution to give a helium to total hydrocarbon mole ratio of 4:1. After 20 minutes on stream, a sample of the effluent is taken and analyzed, most conveniently by gas chromotography, to determine the fraction remaining unchanged for each of the two hydrocarbons.
The "constraint index" is calculated as follows:

Constraint Index = lg10 (fraction of n-hexane remaining) lg10 fraction of 3-methylpentane remaining) The oonstraint index approximates the ratio of the cracking rate constants for the two hydrocarbons. Zeolites suit-able for the present invention are those having a constraint index in the approximate range of 1 to 12. Constraint Index (CI) values for some typical zeolites are:

CAS C.I.
ZSM-5 8.3 ZSM-11 8.7 ZSM-35 4.5 TMA Offretite 3.7 Beta 0.6 ZSM-4 0.5 H-Zeolon 0.4 REY 0.4 Amorphous Silica-Alumina 0.6 ~rionite 38 "` 1~9(~315 It is to be realized that the above constraint index values typically characterize the specified zeolites but that such are the cumulative result of several variables used in determination and calculation thereof.
Thus, for a given zeolite depending on the temperature - --employed within the aforenoted range of 550F to 950DF, with accompanying conversion between 10% and 60%, the constraint index may vary within the indicated approximate range of 1 to 12. Likewise, other variables such as the crystal size of the zeolite, the presence of possible occluded contaminants and binders intimately combined with the zeolite may afect the constraint index. It will accordingly be understood by those skilled in the art that the constraint index, as utilized herein, while affording a highly useful means for characterizing the zeolites of interest is approximate, taking into consideration the manner of its determination, with probability, in some instances of compounding variable extremes. However, in all instances, at a temperature within the above-specified range of 550F to 950F, the constraint index will have a -value for any given zeolite of interest herein within the approximate range of 1 to 12.
The class of zeolites defined herein is exemplified by ZSM-5, ZSM-ll, ZSM-12, ZSM-35, ZSM-38, and other similar materials. U.S. Patent 3,702,886 describes and claims ZSM-5. ZSM-ll is more particularly described in U.S. Patent 3,709,979, while ZSM-12 is more particularly described in U.S. Patent 3,832,449.

--.,~

l~S031S

ZSM-38 can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows:

(0.3-2.5)R20 : (0-0.8)M2o : A1203 : > 8 SiO2 wherein R is an organic nitrogen-containing cation derived from a 2-(hydroxyalkyl) trialkylammonium compound and M i3 an alkaki metal cation, and is characterized by a specified X-ray powder diffraction pattern.
In a preferred synthesized form, the zeolite has a formula, in terms of mole ratios of oxides and in the anhydrous state, as follows:

(0.4-2.5)R20 : (o-0.6)M20 : A12 3 2 wherein R is an organic nitrogen -containing cation derived from a 2-~ydroxyalkyl) trialkylammonium compound, wherein alkyl is methyl, ethyl or a combination thereof, M i9 an alkali metal, especially sodium, and x is from greater than 8 to about 50.
The synthetic ZSM-38 zeolite po3sesses a definite distinguishing crystalline structure whose X-ray diffraction pattern shows substantially the significant lines set forth in Table I. It is observed that this X-ray diffraction pat-tern (significant lines) is similar to that of natural fer-rierite with a notable exception being that natural ferrierite patterns exhibit a significant line at 11.33A.

-: - :

lOg~`3~S

TABLE I

d (A) I/Io 9.8 + 0.20 Strong 9.1 + 0.19 Medium 8.0 + 0.16 Weak 7 1 + o 14 Medium 6.7 + 0.14 Medium 6.0 + 0.12 Weak

4.37 + o.~g Weak 4.23 + 0.09 Weak 4.01 + 0.08 Very Strong 3.81 + 0.08 Very Strong 3.69 + 0.07 Medium 3.57 + 0.07 Very Strong 3.51 + 0.07 Very Strong 3.34 + 0.07 Medium 3.17 + 0.06 Strong 3.08 + 0.06 Medium 3.00 + 0.06 Weak 2.92 + 0.06 Medium 2.73 + 0.06 Weak 2.66 + 0.05 Weak 2.60 + 0.05 Weak 2.49 + 0~05 Weak ~0315 A further characteristic of ZSM-38 i9 its sorptive capacity providing said zeolite to have increased capacity for 2-methylpentane (with respect to n-hexane sorption by the ratio n-hexane/2-methyl-pentane) when compared with a hydrogen form of natural ferrierite resulting from calcina-tion of an ammonium exchanged form. The characteristic sorption ratio n-hexane/2-methylpentane for ZSM-38 (after calcination at 600C.) is less than 10, whereas that ratio for the natural ferrierite is substantially greater than 10, for example, as high as 34 or higher.
Zeolite ZSM-38 can be suitably prepared by pre-paring a solution containing sources of an alkali metal oxide, preferably sodium oxide, an organic nitrogen-containing oxide, an oxide of aluminum, an oxide of silicon and water and having a composition. in terms of mole ratios of oxides, falling within the following ranges:

R+ Broad Preferred R+ + M+ 0.2-1.0 0.3-0.9 OH-/SiO2 0.05-0.5 0.07-0.49 SiO2/A1203 8.8-200 12-60 wherein R is an organic nitrogen-containing cation derived from a 2-(hydroxyalkyl) trialkylammonium compound and M is an alkali metal ion, and maintaining the mixture until crystals of the zeolite are formed. (The quantity of OH

is calculated only from the inorganic sources of alkali without any organic base contribution). Thereafter, the t315 crystals are separated from the liquid and recovered.
Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from about 90C. to about 400C. for a period of time of from about 6 hours to about 100 days. A more preferred temperature range is from about 150C. to about 400C. with the amount of time at a temperature in such range being from about 6 hours to about 80 days.
The digestion of the gel partic~es is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering and water washing. The crystalline product is thereafter dried, e.g. at 230F. for from about 8 to 24 hours.
15. ZSM-35 can be identified, in terms of mole ratios of oxides and in the anhydrous state, a~ follows:

(0.3-2.5)R20 : (0-0.8)M20 : A1203: > 8 SiO2 wherein R is an organic nitrogen-containing cation derived from ethylenediamine or pyrrolidine and M is an~alkali metal cation, and is characterized by a specified X-ray powder diffraction pattern.
In a preferred synthesized form the zeolite has a formula~ in terms of mole ratios of oxides and in the anhydrous state, as follows:
(o.4-2.5)R2o : (o-o.6)M 0 : A1 0 : ~ xSiO
wherein R is an organic nitrogen containing cation derived from ethylenediamine or pyrrolidine, M is an alkali metal, especially sodium, and x is from greater than 8 to about 50.

-` ~ --~90315 The synthetic ZSM-35 zeolite possesses a definite distinguishing crystalline structure whose X-ray diffraction pattern shows substantially the significant lines set forth in Table II. It is observed that this X-ray diffraction pattern (with respect to significant lines) is similar to that of natural ferrierite with a notable exception being that natural ferrierite patterns exhibit a significant line at 11.33A. Close examination of some individual samples of ZSM-35 may show a very 10 weak line at 11.3-11.5A. This very weak line, however, is determined not to be a significant line for ZSM-35.

TABLE II

d (A) ~

9.6 + 0.20 Very Strong-Very Very Strong 7.10 + 0.15 Medium 6.98 + 0.14 Medium 6.64 + 0.14 Medium

5.78 + 0.12 Weak 5.68 + 0.12 Weak 4.97 + 0.10 Weak 4.58 + 0.09 Weak 3.99 + 0.08 Strong 3.94 + 0.08 Medium Strong 3.85 + 0.08 Medium 3.78 + 0.08 Strong 3.74 + 0.08 . Weak 3.66 + 0.07 Medium 3.54 + 0.07 Very Strong 3.48 + 0.07 Very Strong 3.39 + 0.07 Weak 3.32 + 0.07 Weak Medium 3.14 + 0.06 Weak Medium 2.90 + 0.06 Weak 2.85 + 0.06 Weak 2.71 + 0.05 Weak 2.65 + 0.05 Weak 2.62 + 0.05 Weak 2.58 + 0.05 Weak 2.54 + 0.05 Weak 2.48 + 0.05 Weak l~g~315 A further characteristic of ZSM-35 is its sorptive capacity proving said zeolite to have increased capacity for 2-methylpentane (with respect to n-hexane sorption by the ratio n-hexane/2-methylpentane) when compared with a hydrogen form of natural ferrierite resulting from calcination of an ammonium exchanged form. The characteristic sorption ratio n-hexane/2-methylpentane for ZSM-35 (after calcination at 600C.) is less than 10, whereas that ratio for the natural ferrierite is substantially greater than 10, for example, as high as 34 or higher.
Zeolite ZSM-35 can be suitably prepared by preparing a solution containing sources of an alkali metal oxide, pre-ferably sodium oxide, an organic nitrogen-containing oxide, an oxide of aluminum, an oxide of silicon and water and having a composition, in terms of mole ratios of oxides, falling within the following ranges: -R+ Broad Preferred R+ + M+ 0.2-1.0 0.3-0.9 OH-/SiO2 0.05-0.5 0.07-0.49 Sio2/A12o3 8.8-200 12-60 wherein R is an organic nitrogen-containing cation derived from pyrrolidine or ethylenediamine and M is an alkali metal ion, and maintaining the mixture until crystals of the zeolite are formed. (The quantity of OH is calculated only from the inorganic sources of alkali without any organic base contri-bution). Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of 3~5 from about 90C. to about 400C. for a period Or time of from about 6 hours to about 100 days. A more preferred temperature range is from about 150C. to about 400C. with the amount of time at a temperature in such range being from about 6 hours to about 80 days.
The digestion of the gel particles is carried out until crystals form. The solid product is separated from the reaction medium, as by cooling the whole to room temperature, filtering and water washing. The crystalline product is dried, e.g. at 230F., for from about 8 to 24 hours.
The specific zeolites described, when prepared in the presence of organic cations, are catalytically inactive, possible because the intracrystalline free space is occupied by organic cations from the forming solution. They may be activated by heating in an inert atmosphere at 1000~F. for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 1000F. in air. The presence of organic cations in the forming solution may not be absolutely essential to the formation of this type zeolite; however, the presence of these cations does appear to favor the formation of this special type of zeolite. More generally, it is desi-rable to activate this type catalyst by base exchange with ammonium salts followed by calcination in air at about 1000F.
for from about 15 minutes to about 24 hours.
Natural zeolites may ~ometimes be converted to this type zeolite catalyst by various activation procedures and other treatments such as base exchange, steaming, alumina extraction and calcination, in combinations. Natural minerals which may be so treated include ferrierite, brewsterite, stilbite, dachiardite, epistilbite, heulandite, and -~ 109~315 clinoptilolite. The preferred crystallaine aluminosilicates are ZSM-5, ZSM-ll, ZSM-12, ZSM-38 and ZSM-35, with ZSM-5 particularly preferred.
In a preferred aspect of this invention, the zeolites hereof are selected as those having a crystal framework density, in the dry hydrogen form, of not substantially below about 1.6 grams per cubic centimeter.
It has been found that zeolites which satisfy all three of these criteria are most desired because they tend to maximize the production of gasoline boiling range hydro-carbon products. Therefore, the preferred zeolites of this invention are those having a constraint index as defined above of about 1 to about 12, a silica to alumina ratio of at least about 12 and a dried crystal density of not less than about 1.6 grams per cubic centimeter. The dry density for known structures may be calculated from the number of silicon plus aluminum atoms per 1000 cubic Angstroms, as -~
given, e.g., on page 19 of the article on Zeolite Structure by W. M. Meier. This paper is included in "Proceedings of the Conference on Molecular Sieves, London, April 1967,"
published by the Society of Chemical Industry, London, 1968. When the crystal structure is unknown, the crystal ~-framework density may be determined by classical pyknometer techniques. For example, it may be determined by immersing --the dry hydrogen form of the zeolite in an organic solvent which is not sorbed by the crystal. It is possible that the unusual sustained activity and stability of this class of zeolites is associated with its high crystal anionic frame-work density of not less than about 1.6 grams per cubic centimeter. This high density, of course, must be associated with a relatively small amount f ~

1~ 315 of free space within the crystal, which might be expected to result in more stable structures. This free space, however, is important a~ the locus of catalytic activity.
Crystal framework densities of some typical zeolites are:

Void Framework Zeolite Volume Density Ferrierite 0.28 cc~cc 1.76 g/cc Mordenite .28 1.7 ZSM-5, -11 .29 1.79 Dachiardite .32 1.72 L .32 1.61 Clinoptilolite .34 1.71 Laumontite .34 1-77 ZSM-4 (Omega) .38 1.65 Heulandite .39 1.69 p .41 1.57 Offretite .40 1.55 Levynite .40 1.54 Erionite .~5 1.51 Gmelinite .44 1.46 Chabazite .47 1.45 A .5 1.3 Y .48 1.27 When synthesized in the alkali metal form, the zeolite is conveniently converted to the hydrogen form, generally by intermediate formation of the ammonium form as a result of ammonium ion exchange and calcination of the ammonium form to yield the hydrogen form. In addition to the hydrogen form, other forms of the zeolite wherein the original alkali metal has been reduced to less than about 1.5 percent by weight may be used. Thus, the original alkali metal of the zeolite may be replaced by ion exchange with other suitable ions of Groups IB to VIII of the Periodic Table, including, by way of example, nickel copper, zinc, palladium, calcium or rare earths metals.

l~Q315 In practicing the desired conversion process, it may be desirable to incorporate the above described crystalline aluminosilicate zeolite in another material resistant to the temperature and other conditions employed in the process.
Such matrix materials include synthetic or naturally occurring substances as well as inorganic materials such as clay, silica and/or metal oxides. The latter may be either naturally occurr-ing or in the form of gelatinous precipitates or gels including mixtures of silica and metal oxides. Naturally occurring clays which can be composited with the zeolite include those of the montmorillonite and kaolin families, which families include the sub-bentonites and the kaolins commonly known as Dixie, McNamee-Georgia and Florida clays or others in which the main mineral constituent is halloysite, kaolinite, dickite, nacrite or anauxite. Such clays can be usd in the raw state as orig-inally mined or initially subjected to calcination, acid treat-ment or chemical modification.
In addition to the foregoing materials, the zeolites employed herein may be composited with a porous matrix material, such as alumina, silica-alumina, silica-magnesia, silica-zirconia, silica-thoria, silica-berylia, silica-titania as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, silica-alumina-magnesia and silica-magnesia-zirconia. The matrix may be in the form of a cogel.
The relative proportions of aeolite component and inorganic oxide gel matrix may vary widely with the zeolite content ranging from between about 1 to about 99 percent by weight and more usually in the range of about 5 to about 80 percent by weight of the composite.

1~9(~3~5 The con~ersion process described herein may be carried out as a batch type, semi-continuous or continuous operation utilizing a fixed or moving bed catalyst system. The catalyst after use is conducted to a regeneration zone whereln coke is burned from the catalyst in an oxygen-containing atmosphere, e.g.
air, at an elevated temperature, after which the regenerated catalyst is recycled to the conversion zone for further contact with the charge stock. It is particularly feasible to conduct the desired conversion in the presence of hydrogen utilizing a hydrogen-precursor mole ratio of between about 2 and about 20, with hydrogen pressure extending from 1 atmosphere up to 100 atmos-pheres. The presence of hydrogen in the reaction zone has been found to very substantially reduce the aging rate of the catalyst.
While the above process has been described with refer-ence to selective production of para dimethyl substituted benzenestypified by para-xylene, it is contemplated that other para dialkyl substituted benzenes, wherein the alkyl group contains from 1 to 4 carbon atoms may similarly be selectively produced. Thus, utilizing the technique described herein, it is contemplated that with selec-tion of suitable precursor, mixture of ethyl benzene and toluenemay be selectively converted to para ethyl toluene; likewise para ethyl toluene is formed from dodecane or l-butene, in addition to para-xylene; ethyl benzene may be ~electively converted to diethyl benzene, propyl benzene may be converted to dipropyl benzene, and butyl benzene may be selectively converted to dibutylbenzene.

- 42 _ l~g~315 The following examples will serve to illustrate the catalyst and process of the invention without limiting the same:
Example 1 42.2 pounds of Q-Brand sodium silicate were mixed with 52.8 pounds of water. The resulting solution was designated Solution A. 1.35 pounds of commercial grade aluminum sulfate ~A12(S04)3 14H20], 15.84 pounds of commercial grade NaC1 and 3.52 pounds of H2S04 (96.5 wt.% H2S04) were mixed with 72.2 pound~
of water. The resulting solution was designated Solution B. 2.6 pounds of water were added to an autoclave equipped with agitation.
Solution A and Solution B were mixed simultaneously in a nozzle and sprayed into the autoclave. The resulting gel was mixed in the autoclave at ambient temperature for one hour. 2.84 pounds of tri-n-propylamine and 2.44 pounds of n-propyl bromide were added to the contents of the autoclave. The mixture was reacted at 320F. with agitation. After twenty hours at 320F., the autoclave contents were sampled and the solid product was found to be 100% ZSM-5 by X-ray diffraction. After a total reaction time of 28.7 hours at 320F., the autoclave contents were cooled. The resulting solid product was washed by decantation with deionized water containing 3500 ppm Primafloc~C-7 (polyammonium bisulfate) until the decant water was chloride-free. The solid product was filtered and dried at 250F.
Five hundred (500) grams of the dried filter coke product were calcined in nitrogen for three hours at 1000F. 444 grams of the calcined product were mixed with 2220 cc of 1 N NH4N03 solution for one hour at ambient temperature. The mixture was 1~9~315 vacuum filtered. The ion exchange procedure was repeated.
The filter coke was washed with 1776 cc of water and the solid product was dried at 250F. The sodium content of the final product was less than 0.01%.
The resulting catalyst had a crystal size of 1-2 microns, an alpha activity of 162, a para-xylene sorption capacity of

6.5 weight percent and an ortho-xylene sorption time for 30 percent of said capacity of 92 minutes. Both of the latter measurements were made at 120C. For the para-xylene sorption, the hydrocarbon partial pressure was 5.1 mm. of mercury.
For ortho xylene sorption time the hydrocarbon partial pressure was 3.8 mm. of mercury.
Example 2 Toluene was passed over the catalyst of Example 1 at 1022F. at 390 psig, at a weight hourly space velocity of 50 and a hydrogen to hydrocarbon ratio of 6. The toluene conversion was 20.1 weight percent and the para-xylene yield, as percent of xylene, was 30 percent.
Example 3 The catalyst of Example 1 was treated with toluene for five hour~ at 640C., at a weight hourly space velocity of 50 and one atmosphere pressure to deposit about 4 weight percent coke thereon. The treated catalyst sorbed 6.1 grams of para-xylene per 100 grams of zeolite at 120C. and a para-xylene pressure f 5 1 mm. of mercury. At 120C. and on ortho-xylene pressure of 3.8 mm. of mercury, the time for sorption of 30 percent of xylene capacity was 6000 minutes. The catalyst had an alpha value of 281.

~315 The catalyst which contained approximately 4 weight percent of coke was contacted with toluene at 550C., a pressure of 600 psig, a weight hourly space velocity of 40 and a hydrogen to hydrocarbon mole ratio of 10. The liquid product contained ôO.7 weight percent toluene (19.3 percent conversion) and 9.6 weight percent xylenes in addition to benzene. The xylene fraction contained 82 percent of para-xylene.
Example 4 Three grams of the catalyst of Example 1 were contacted with a solution consisting of 1.02 grams of magnesium acetate tetrahydrate in 4 cc. of water. The resulting slurry was evaporated to dryness over a 24 hour period and then air calcined for 10 hours at 1000F. to yield a product of HZSM-5 containing 6 weight percent of MgO. The catalyst sorbed 6.3 grams of para-xylene per 100 grams of zeolite at 120C. and a para-xylene pressure of 5.1 mm. of mercury. At 120C. and an ortho-xylene pressure of 3.8 mm of mercury, the time for sorption of 30 percent of xylene capacity was 583 minutes. The catalyst had an alpha value of 129.
Example 5 The catalyst of Example 4 was contacted with toluene at 550C., a pressure of 600 psig, a weight hourly space velocity of 40 and a hydrogen to hydrocarbon ratio of 4.
Toluene conversion was 29.4 percent; the liquid product contained 15.3 weight percent xylene, which consisted of 53 percent of the para isomer.

Example 6 HZSM-5 having a crystallite size of about 0.03 micron was prepared as ~ollows:
a) Solution Preparation Silicate Solution 90.9 lb. Q-Brand Sodium Silicate 52.6 lb. H20 118 g. Daxa 7 Dispersant (sodium salt o~
polymerized substituted benzenoid alkyl sulfonic acid combined with a suspending agent) Acid Solution 1430 g. A12(S04)3.xH20 (M.W.=595) 3440 g- H2S4 4890 g. NaC1 54 lb. H20 Add'l_Solids 2840 g. NAC1 2390 g. n-propyl bromide 4590 g. methyl-ethyl ketone Add'l Liquid 1180 g. H20 b) Procedure The silicate solution and acid solution were mixed in a mixing nozzle to form a gel which was discharged intc a 30 gallon autoclave to which 1180 grams of H20 had been previously added.

The gel was whipped by agitation and 2840 grams of NaC1 was added and thoroughly blended. The agitation was stopped and the organics solution was added as a layer on top of the gel. The autoclave was sealed and heated to about 220F without agitation and held there for 14-15 hours to prereact the organics. At the end of the prereaction period the agitation was commenced to start the initial crystallization period. After about 75-80 hours the temperature was raised to 320 and held there for about three hours to complete crystallization. The excess or unreacted organics were flashed off and the contents of the autoclave were cooled and discharged. The product was analyzed by x-ray diffraction and shown to be 100% crystallinity ZSM-5. Chemical analysis of the thoroughly washed crystalline product was:
% Wt.Mole Ratio _ A1203 2.21 1.0 Si2 94 9 72.8 Na , 0.81 Na20 - 0.82 N 0.67 2.48 C 8.2 35.6 After thorough washing and drying at about 250F. the zeolite was transformed into the catalytic form by the following steps:
a) Precalcination in a 100% N2 atmosphere for three hours at 1000F, atmospheric pressure employing a programmed heat-up rate of 5F/min to 1000F from ambient.

1~315 b) Ion exchange with lN NH4N03 at room temperature for one hour using 5 cc of exchange solution per gram of dry zeolite.
c) Washed with four volumes of water.
d) Repeat steps (b) and (c) and dry at 250F in air.
The exchanged zeolite was analyzed and was found to contain 0.01 wt % sodium and to have an alpha value of 162.
It was characterized by an ortho-xylene sorption capacity of 5.6 weight percent and an ortho xylene sorption time for 30 percent of said capacity of less than 1.3 minutes. Both of the latter measurements were made at 120C and a hydrocarbon partial pressure of about 3.8 mm. of mercury.
Example 7 Toluene was passed over the microcrystalline HZSM-5 catalyst of Example 6 at 1 atmosphere pressure, 1112F, and a weight hourly space velocity of 50. The toluene conversion was 15 weight percent and the p-xylene yield, as percent of xylene~, was 25 percent, i.e. approximately the normal equilibrium concentration of p-xylene.
Example 8 Cataly~t prepared as in Example 6 was combined with alumina to produce an extruded catalyst consiting of 65 weight percent zeolite and 35 weight percent alumina. Following use for toluene disproportionation under a variety of conditions and regeneration, toluene was passed over this catalyst at 885-970F, WHSV = 5-6.3, pressure = 450 psig and a hydrogen to hydrocarbon ratio of 0.5 for 38 days.

~W(~315 The coke level was 45 grams per 100 grams of catalyst.
The p-xylene sorption capacity, measured at a p-xylene pressure of 5.1 mm of mercury, was 2 grams per 100 grams of zeolite and the o-xylene sorption time for 30% of xylene sorption capacity was 2900 minutes; this measurement was at an o-xylene pressure of 3.8 mm of mercury. The catalyst had an alpha value of 20.
Toluene was passed over the catalyst at 970F, 450 psig, WHSV =
6.3 and a hydrogen to hydrocarbon ratio of 0.5. The toluene conversion was 37 weight percent and the p-xylene yield, as 0 percent of xylenes pro~uced, was 43.
Example 9 A catalyst was prepared by adding 3 grams of the catalyst of Example 1 to a solution made from 0.3 grams of magnesium nitrate hexahydrate 2.2 ml of water. The slurry was mixed thoroughly and air calcined by heating 3F per minute to 1000F
followed by 10 hours at 1000F. The resultant catalyst contained 2.4 weight percent magnesium. It sorbed 5.2 grams of p-xylene per 100 grams of zeolite at 120C and a p-xylene pressure of 5.1 mm of mercury. At 120C and a o-xylene pressure of 3.8 mm of mercury, the time for sorption of 30 percent of xylene capacity was 2600 minutes. The catalyst had an alpha value of 36.

-1''~9~)3~5 Example 10 Toluene was passed over the catalyst of Example 9 at 1022F, 600 psig, hydrogen to hydrocarbon ratio of 4 and a WHSV of 10. The toluene conversion was 20 weight percent and the p-xylene yield, as percent of xylenes, was 45.
Example 11 A five gram sample of the HZSM-5 catalyst of the type described in Example 6 was placed in a glass tube fitted with a fritted glass disc. Dimethylsilane was passed through the bed of HZSM-5 at a rate of 40 cc/minute. After 15 minutes, the HZSM-5 had sorbed 0.60 gram of dimethylsilane. The product was added to 200 cc of 15 percent aqueous ammonia to hydrolyze the silane. Hydrogen was evolved rapidly. After one hour, the product was filtered and calcined at 1C/minute to 538C and held at this temperature for 6 hours.
The above procedure was repeated a total of three times to yield a silica-loaded HZSM-5 containing 5 weight percent of added silica.
The catalyqt sorbed 4.1 grams of o-xylene per 100 grams of zeolite at 120C and a o-xylene pressure of 3.8 mm of mercury.
The sorption reached 30 percent of capacity in 2.7 minutes.
The catalyst had an alpha value of 75.

l~g~315 Example 12 Toluene was passed over the catalyst of Example 11 at 1112F, one atmosphere pressure, WHSV = 40 and a hydrogen to hydrocarbon ratio of 2. The toluene conversion was 2 weight percent and the p-xylene yield, as percent of xylenes, was 62.
At more realistic toluene conversion, e.g. 20 percent, the selectivity to para-xylene was only 27 percent, i.e.
substantially the same as equilibrium, indicating that the sorption time to reach 30 percent of capacity of only 2.7 minutes was too low.
Example 13 Twenty grams of NH4-ZSM-5 of 0.03 micron crystal size was suspended in a solution of 5.35 grams of ortho boric acid in 40 ml of water at a temperature of 80C. After standing overnight (16.5 hours) at 90C the contents were poured into a 30 x 50 mm crystallizing dish and placed in an oven at 110C. The contents were stirred frequently until a uniform dry powder was formed. The temperature was gradually increased to 200C and the catalyst allowed to stand for 1-2 hours. It was then transferred to a furnace at 500C, in air, in the same open crystallizing dish for a period of 17.5 hours. The theoretical amount of boron, present as the oxide, was 4.06 wt % B. The powder was pressed into wafers, crushed and screened to 14-20 mesh size for use.
This catalyst sorbed 3.1 grams of p-xylene at 120C
and a p-xylene pressure of 5.1 mm of mercury. At 120C and an o-xylene pressure of 3.8 mm of mercury, the time for sorbing 30 percent of capacity was 270 minutes. The catalyst had an alpha value of 3.8.

1~315 Example 14 Toluene was passed over 5 grams of the catalyst of Example 13 at 1112F, one atmosphere pressure, and a WHSV = 4.5.
The toluene conversion was 11.9 weight percent and the p-xylene yield, as percent of xylenes, was 74.
Example 15 Ten (10.0) grams of zeolite of the type described in Example 6 was mixed with 6.5 grams of antimony trimethoxide and 75 cc of p-xylene. This slurry was refluxed over nitrogen gas for 17 hours. The solids were then washed with 100 cc of toluene, then 100 cc of methanol followed by 100 cc of n-hexane.
The product was air dried then placed in a vacuum oven at 100C
for 3 hours. It was then air calcined for 10 hours at 1000F.
The product contained 24 weight percent antimony.
The catalyst sorbed 3.5 grams of p-xylene per 100 grams of zeolite at 120C and a p-xylene pressure of 5.1 mm of mercury.
At 120C and a o-xylene pressure of 3.8 mm of mercury, the time for sorption of 30 percent of xylene capacity was 89 minutes.
The catalyst had an alpha value of 8.
Example 16 10 grams of the ammonium form of ZSM-5 was suspended in a solution of 5 grams of uranium dioxide dinitrate hexahydrate in 20 cc of water. The slurry was heated to a temperature of 73C and allowed to stand overnight. The entire contents of the flask were then poured into a crystallizing dish and placed in oven at 130C. The catalyst was stirred every 30 minutes.

-After about 2 hours, the catalyst had a dry appearance. It was then placed in an oven at 500C and allowed to stand overnight. The final weight of the calcined catalyst was 12.17 grams. The catalyst had a xylene sorption capacity at 120C and a xylene pressure of 4.5 + 0.8 mm. mercury of 6.3 grams xylene per 100 grams of zeolite. The time to sorb ortho-xylene at 120C and 3.8 mm. pressure to an extent of 30 percent of the capacity was 4.8 minutes. The catalyst had an alpha value of 83.
Example 17 Toluene was passed over the catalyst of Example 16 at 1022F, one atmosphere pressure, and a WHSV of 3.5 The toluene conversion was 46 weight percent and the p-xylene yield, as percent of xylenes, was 24.
Example 18 11.6 grams of magnesium acetate tetrahydrate were dissolved in 25 ml of water. To this was added 10 grams of 1/8 pellets of the ammonium form of ZSM-5 zeolite crystal. After soaking for a few minutes, the excess liquid was withdrawn and held.
The catalyst was placed in an oven to drive off the water. After cooling, the dry catalyst was placed in the remaining solution of magnesium acetate. Excess liquid was withdrawn and the wet catalyst placed in an over to dry. This procedure was repeated until all of the liquid had been absorbed by the catalyst.
Finally, the catalyst was placed in a furnace at 500C over-night. The weight of the final catalyst was 11.56 grams. The catalyst had a xylene sorption capacity of 120C and a xylene pressure of 4.5 + 0.8 mm mercury of 4.2 grams xylene per 100 grams ~315 of zeolite. The time to sorb ortho-xylene at 120C and 3.8 mm pressure to an extent of 30 percent of the capacity was 7.5 minutes. The catalyst had an alpha value of 21.
Example 19 Toluene was passed over the catalyst of Example 18 at 1022F, one atmosohere pressure, and a WHSV of 3.5. Toluene conversion was 12 weight percent and the p-xylene yield, as percent of xylenes, was 25.
Example 20 10 grams of ammonium ZSM-5 were added to a solution of

7.28 grams of zinc nitrate hexahydrate in 20 ml of water.
Suspension was heated to approximately 90C and allowed to stand overnight. The entire contents of the flask were then poured into a crystallizing dish and placed in an ove~r at about 130C. After about 2 hours, the catalyst was placed in a furnaoe at 500C and allowed to stand for about 8 hours.
Final weight of the oatalyst after calcination was 11.21 grams.
The catalyst had a xylene &orption capacity of 120C and a xylene pressure of 4.5 1 0.8 mm mercury of 4.9 grams of xylene per 100 grams of zeolite. The time to sorb ortho-xylene at 120C and 3.8 mm pressure to an extent of 30 percent of the capacity was 38 minutes. The catalyst had an alpha value of 504.
Example 21 Toluene was passed over the catalyst of Example 20 at 1022 F, one atmosphere pressure, and a WHSV of 3.5. The toluene conversion was 20 weight percent and the p-xylene yield, as percent of xylenes, was 28.

1~3~5 Example 22 10 grams of the acid form of ZSM-5 were suspended in a solution of 12.9 grams of calcium nitrate tetrahydrate in 25 ml of water. The slurry was heated to 88C and allowed to stand overnight. The entire contents were then poured into a crystallizing dish and placed in an oven at 100-130C.
After about 4 hours the temperature was raised to 200C for approximately 2 hours. The catalyst was then placed in a furnace at 500C overnight. Final weight of the oatalyst after calcination is 12.80 grams. The catalyst had a xylene sorption capacity of 120C and a xylene pressure of 4.5 + 0.8 mm mercury of 1.2 grams of xylene per 100 grams of zeolite.
The time to sorb ortho-xylene at 120C and 3.8 mm pressure to an extent of 30 percent of the capacity was 116 minutes.
The catalyst had an alpha value of 0.9.
Example 23 Toluene was pas~ed over the catalyst of Example 22 at 1022F, one atmosphere pressure, and a WHSV of 3.5. Toluene conversion wa~ 0.4 weight percent and the p-xylene yield, as percent of xylenes, was 67.
Example 24 10 gram~ of the ammomium form of powdered ZSM-5 were placed in a solution of 11.6 grams of magnesium acetate tetrahydrate in 25 ml of water. The suspension was heated to a temperature of 95C and allowed to stand overnight.
The entire contents of the flask were then poured into a crystallizing di~h and placed in an oven at 56C. The 109~315 temperature was then turned up to 100-120C. The slurry was stirred frequently until the catalyst developed a dry appearance.
Temperature was then gradually raised to 200C and held for about 1 hour. The catalyst was then placed in a furnace at 500C overnight. The final weight of the catalyst was 11.37 grams.
The catalyst had a xylene sorption capacitY at 120C and a xylene pressure of 4.5 + O.ô mm mercury of 4.4 grams of xylene per 100 grams -of zeolite. The time to sorb ortho-xylene at 120C and 3.8 mm pressure to an extent of 30 percent of the capacity was 655 minutes. The catalyst had an alpha value of 24.
Example 25 Toluene was passed over the catalyst of Example 24 at 1022DF, one atmosphere pressure, and a WHSV of 4.5. The toluene conversion was 16 weight percent and the p-xylene yield, as percent of xylenes, was 59.
Example 26 A boron-containing ZSM-5 catalyst was prepared according to the procedure of Example 13, except that 0.22 grams of ortho boric acid was used per gram of ammonium-ZSM-5. The finished catalyst is calculated to contain 3.34 weight % B, probably present as the oxide.
Propylene was passed over the above catalyst at ~HSV =
2.6 at 400C. The conversion was 94%. The aromatics produced (25 wt.%) contained 31% xylenes. The p-xylene content of the xylene fraction was 56%.

Example 27 A sample of HZSM-5 was mixed with reagent Sb203 in a ratio of 0.43 g Sb203 per gram of HZSM-5. After pressing and screening to 8/14 mesh, about one gram was charged to a micro glass reactor of 15-20 cm length x 14-18 mm diameter. A 4-6 mm thermowell was located in the catalyst bed. The catalyst was heated to 525C during one hour in 50 cc/min flowing nitrogen, holding in nitrogen for three hours at 500-525, followed by air (50 cc/min) for 0.5 hours. The resultant catalyst contained 30% Sb203.
Example ?8 A sample of 30% Sb203/HZSM-5, prepared according to Example 27 was placed in a vertical flow reactor; propylene was passed over the catalyst at 400C at WHSV = 3Ø Propylene conversion was 90.3%. Aromatics were produced in 14.8% selectivity, containing benzene, toluene, xylenes and ethyltoluene as major components. The largest fraction (34%) was xylene which contained 91% of the para isomer.
Example 29 Another sample of 30% Sb203/HZSM-5 ofExample 27 was used for selective toluene disproportionation. Toluene was passed over the catalyst in a vertical fixed-bed flow reactor at 550C and atmospheric pressure at a WHSV = 1Ø After 6 hours on stream, the conversion of toluene was 20%. Products were benzene and xylenes. The xylenes contained 81% of the para isomer.

Example 30 Another sample of Sb203-ZSM-5 was prepared following the procedure of Example 27 except that 0.33 g Sb203 was used per gram of HZSM-5. The resultant catalyst contained nominally 25% Sb203.
Example 31 The catalyst prepared in Example 30 was used in toluene disproportionation to benzene and xylene at atmospheric pressure, 550C and 1 WHSV. After 6 hours on stream, toluene conversion was 9.5%. The xylene fraction contained 83% p-xylene.
The catalyst sorbed 1. 39 grams of p-xylene per 100 gram of zeolite at 120C and a p-xylene pressure of 5.1 mm Hg.
At 120C and an o-xylene pressure of 3.8 mm Hg, the time for sorption of 30% of xylene capacity, to~3~ exceeded 300 minutes.
Example 32 The catalyst of Example 1 was contacted with 1-butane at 400C. at a weight hourly space velocity of 4 and 1 atmosphere pressure. The liquid product which was 89 percent of the weight of charge contained 13.4 weight percent xylene and 3.9 weight percent ethyl toluene. The xylene fraction contained 37 percent p-xylene and the ethyl toluene fraction was 43 percent para ethyl toluene. Equilibrium values of these para isomers are 24 and 32 percent respectively.
Example 33 The catalyst of Example 1 was contacted with do-decane at 400C. at a weight hourly space velocity of 10 and 1 atmosphere pressure. The liquid product which was 41 weight percent of the charge consisted of 12.6 weight percent xylene and 4.3 weight percent ethyl toluene. The xylene fraction was 63 percent para-xylene and the ethyl toluene fraction was 58 percent para-ethyltoluene.
Example 34 This example illustrates the production of p-diethyl-benzene with catalyst of Example 1 pretreated with toluene as in Example 3 to deposit approximately 4 weight percent of coke.
A mixture of benzene and ethylene at a mole ratio of 1:2 (fresh feed) is mixed with a recycle stream containing benzene and ethylbenzene and passed over the catalyst at a temperature of 825-850F, a pressure of 300 psig and a WHSV of 2, based on 1b.
ethylene per hour per lb. catalyst. The reactor effluent is distilled to yield an overhead fraction trecycle stream) con-sisting of benzene, ehtylbenzene and unreacted ethylene which is recycled to the reactor and a bottom fraction containing the desired product, p-diethylbenzene.
The specific para-dialkylaromatic selectivity obtainable with the catalysts described herein depends on the particular feed and the operating conditions. In toluene disproportionation, the para-xylene content of the xylenes produced is highest at low toluene conversion. In addition, the catalysts of this invention have been found to exhibit a very surprising and unusual phenomenon, namely, at a given percent toluene conversion, the para-xylene selectivity is increased as the temperature is increased over the approximate range of 400 to 700C.

1~90315 For purposes of comparing the para-selectivity of different catalysts, it is therefore desirable to compare them at the same operating temperature, e.g. 550C and the same percent toluene conversion, e.g. 20%, by adjusting the toluene feed rate. Para-selectivity may be obtained for these re~erence conditions directly or by extrapolation from other actual operating conditions.
Para-xylene selectivities (% p-xylene in total xylenes) for the above standard conditions (20% toluene conversion at 550C and ortho-xylene sorption times, to.3 (3~ of capacity at 120C) are shown in the following table:

1~9~315 TABLE III
Ortho-Xylene Catalyst ofSorption time, Para-xylene Selectivity ++
Exampleto.3 tmin) Selectivity Factor 6 < 1.3 24 0 11 2.7 27 3.7 16 4.8 25 1.3 18 7.5 24 0 38 28 5.4

8 2900 69 59 + From toluene, 550C, 20% toluene conversion.
24% p-xylene represents the equilibrium composition and hence no unusual selectivity.
+ Selectivity factor = ( ~ ) O

1~90315 The above data are presented graphically in the attached Figure where the para-xylene selectivity factor is plotted against the ortho-xylene sorption time for 30 percent of capacity. By reference to this Figure, it can be readily seen that catalys~ having a xylene sorption time for 30 percent of xylene sorption capacity of greater than 10 minutes are para-xylene selective.

:1~)9U3~5 42.2 pounds of Q-Brand sodium silicate were mixed with 52.8 pounds of water. The resulting solution was desig-nated Solution A. 1.35 pounds of commercial grade aluminum sulfate (A12(S04)3.14 H20)), 15.84 pounds of commercial grade NaC1, and 3.52 pounds of H2S04 (96.06 wt. % H2S04) were mixed with 72.2 pounds of water. The resulting solution was desig-nated Solution B. Solution A and Solution B were mixedsimultaneously in a nozzle and sprayed into an autoclave equipped with a paddle agitator. 2.84 pounds of tri-n-propylamine and 2.44 pounds of n-propyl bromide were added to the contents of the autoclave. The mixture was reacted at 316F with 121 rpm agitation. After 14.1 hours at 316F, the solid product was analyzed by X-ray diffraction and found to be 100% ZSM-5, having a SiO2/A1203 ratio of 70.
A 10 gram sample of the above ZSM-5 was contacted with 500 ml. of 1N NH4C1 solution. Three ion exchange steps were carried out, the first at 100C for 2 hours, the second at room temperature for 18 hours and the third at 100C for 3 hours. The exchanged product was thereafter calcined 1C/
minute to a temperature of 1000F and held at such temperature for 10 hours. The resulting HZSM-5 had a crystallite size of 1-2 microns. It was further characterized by a paraxylene sorption capacity of 6 weight percent and an ortho xylene sorption time for 30 percent of said capacity of 116 minutes. Both of the latter mea-surements were made at 120C. For the para-xylene sorption the hydro-carbon partial pressure was 5.1 mm of mercury. For ortho xylene sorp-tion time the hydrocarbon partial pressure was 3.8 mm of mercury.

Toluene was passed over the large crystal HZSM-5 catalyst of Example 1 at 1 atmosphere pressure and at temperatures between about 400 and about 650C at a weight hourly space velocity between 5 and 100. The reaction conditions and results offered in weight percent are set forth in Table IV below:

~ 64 -C O 1~ O ~ O ~0 O N ~ ~ ~ L~ `D co 0 ~
O ~rl O~ t-- ~ ~ O ~ Ln O O t~J t\l ~ Cl~ Ir~ I~ O

+t~oooooooooooooooo ~1 N O ~ ~ ~ 11~ ) ~ ~ -- N 0 u~ a~
O
E~ . .~
C
_ _ ~ ~ ~ ~ ~ ~ ~ ~ ~
OD O O ~ O ~O ~ ~ ~ ~ ~ ~ ~ ~ O ~ O~ ~ ~ ~ 00 ~O ~D OD U~ ~ ~ O ê-- ~
O ~ C5~ 0 ~ J ~ O ~D 1~ ~ ~ 1--~Y) O~ . ~ ~ 'D O ~ O ~t O ~ O t-- ~ O --~ ~ ~ Q) ~ , , , ~ , ~ ~_ , ~ ~ . ~ ~ ~ _ C

C
O~ O t -- t~J ~D ~7 0 ~ O Ir) t--~ ) o~ J t~l LO O
~3 1$~ ~ O u~ O O O ~ ~ O C~ O
t t 1~
' S
Pl ~ C
~ OD 0~ OD --0~ ~ ~ ~ O ~ 0~ o o~ ~ c~ -- ~ c~ ~ U~ ~ ~ 0 ~ ~
E~ ~ tr~ _ _ J ~ o~ o ~ ~o tU ~I Ll) O~ J O J ~--O ~ O J O t~ I ~
~ ~1 OJ J ~ I J t~

OD O ~ OD ~n t-- -- ~o -- --ot) ~ co o~ ~ ~ X
:1 J O ~ J CJ~ I J J -- (~ -- -- N
O C o ~ ~ ~ J O~ O J J O~ O
E~ ~> 0 o~ 0 ~

I ~D ~ ~ ~ a~ ~ ~D ~O O ~ cr~ D
C C tr~ r- o ~ ~ OD 11~ . O ~ IS~ ~ ~ -- O I
O a~ CD t~i O -- ~) ~O ~ O O O ~1 0 ~-- J
m N
~
u~ I O o o o u~ o o o o u~ u~ o o o o o a~
N 10 -- O ~ I m O

~ J ~ ~ c~ J o OD-- ~ -- O ) ~1 E3 C~ t\l ~ ~J O N ~ O O 0~ O ~ J o~
o ~ ~ ~ 3 ~~ S
C

S ~ ~ ~ o ~ cD~1 ~ N ~1 O o ~ C
~_ ~ -- cC) (~ O J 0 -- J 0 0 o~ ~ In ~ 0 ~,~
-- N ~ ~ U~ ~ ~ ~~ 3 3 1 ~ C) ~ 0 ~ o --t~ ~ S
*

From the above results, it will be evident that para-xylene was selectively produced in an amount over the thermodynamic equilibrium concentration thereof in the total xylenes produced.
It will further be seen that increasing the temperature within the range of 400 to 650C served to increase para-xylene selectivity substantially.

HZSM-5 having a crystallite size of about 0.03 micron was prepared as follows:
a) Solution Preparation Silicate Solution 90.9 lb. Q-Brand Sodium Silicate 52.6 lb. H20 118 g. Daxad~27 (dispersant) Acid Solution 1430 g- A12(S04)3 xH20 (M.W. = 595) 3440 g- H2S4 4890 g. NaCl 54 lb. H20 Add'l Solids 2840 g. NaCl 2390 g. n-propyl bromide 4590 g. MEK
Add'l Liquid 1180 g. H20 b) Procedure The silicate solution and acid solution were mixed in a mixing nozzle to form a gel which was discharged into a 30 gallon autoclave to which 1180 grams of H20 had been previously added.

9(~315 The gel was whipped by agitation and 2840 grams of NaC1 was added and thoroughly blended. The agitation was stopped and the organics solution was added as a layer on top of the gel. The autoclave was sealed and heated to about 220F without agitation and held there for 14-15 hours to prereact the organics. At the end of the prereaction period the agitation was commenced at 90 RPM to start the initial crystallization period. After about 75-80 hours the temperature was raised to 320 and held there for about three hours to eomplete crystallization. The excess or unreacted organics were flashed off and the contents of the autoclave were cooled and discharged. The product was analyzed by x-ray diffraction and shown to be 100% crystallinity ZSM-5 based upon a standard sample.
Chemical analysis of the thoroughly washed crystalline product was: -% Wt. Mole Ratio A1203 2.21 1.0 SiO2 94.9 72.8 Na 0.81 Na20 - 0.82 N 0.67 2.48 C 8.2 35.6 After thorough washing and drying at about 250F the zeolite was transformed into the catalytic form by the following steps:
a~ Precalcination in a 100% N2 atmosphere for three hours at 1000F, atmospheric pressure employing a programmed heat-up rate of 5F/min to 1000F from ambient.

~ \
109(i 31S

b) Ion exchange with lN NH4N03 at room temperature for one hour using 5 cc exchange solution per gram of dry zeolite.
c) Washed with four volumes of water.
d) Pepeat steps (b) and (c) and dry at 250~F in air.
The exchanged zeolite was analyzed and was found to contain 0.01 wt % Na. It was characterized by an ortho-xylene sorption capacity of 5.6 weight percent and an ortho xylene sorption time for 30 percent of said capacity of less than 1.3 minutes. Both of the latter measurements were made at 120C and a hydrocarbon partial pressure of about 3.8 mm. of mercury.

Toluene was passed over the microcrystalline HZSM-5 catalyst of Example 3 at 1 atmosphere pressure and at tempera-tures of 600-650C at a weight hourly space velocity between 20 and 100. The reaction conditions and results expressed in weight percent are set forth in Table 5 below:

. ~ . , ......... ~

.

l~g0315 L
C g ~ O J
O ,1 l~ 0 o + o~l C~ o o o ~ 0 E~ I ~ J In ~ .
ta o~ a~ o ~ -l 00 0~ ~ C
O --~ O ~
t~J N -- .-1 *
G~ _l ~' ~1 N
x e ~ ~ N - ~`J - O
U~
U~ .,1 ¦ ~ O 'n ~ ~0 ~q E~ ~-- ~ -- ~ -- O~

~ .
U~ O -- ~
3 0 0 ~ O
O C J
E~ ~ 0 ~ 0 C

~D ~D 0 I a~ ~ 0 c ~: r~

I O O O
O O

., O O O
~ ~) O O U~ 5:

E~ C
C~.
~ 0 ~ ,.
o ~ ~ oq ~ . . . a~
~1-- -- N 3 ol _ (~ s From the above results, it will be seen that the amount of para-xylene in the total xylenes produced was essentially the thermodynamic equilibrium concentration.
Figure 2 of the drawing shows a comparison of the para-xylene selectivity of the small, i.e. about 0.03 micron and large, i.e. about 1 micron crystal HZSM-5. It will be seen that para-xylene selectivity was greatly improved by use of the large crystal material Thus, at 10 percent toluene con-version, use of the large crystals showed a 48 percent para-xylene selectivity as compared with 27 percent para-xylene selec-tivity with use of the small crystals.

A sample of the large crystal HZSM-5 catalyst of Example 35 was steamed for 2 hours at 560C in one atmosphere steam.

Toluene was passed over the large crystal HZSM-5 catalyst of Example 39 at 1 atmosphere pressure and at a temperature of approximately 650C at a weight hourly space velocity of 20. The reaction conditions and results are set forth in Table 6 below:

.
.
:, . ., : -l~g0315 ~ o N 11~ c~
O~-l CC~
~ Oi + I O O
~) I
a _1 In N 0~ ct~
O --~ N ~ OLf~ ~ -E-~~ Ir ~ C

~1 -- O N OD O
N -- CD O ~ ~ O ~ ~ -- ~D O O O O
_ ~17 0 _ O O 0 00 0 15~ O t'~7 0 0 0 0 ~It ~ , ~ ~ S
0~ C
C ~D ~0~ ~'` ~r~'` ~ '~
~3 l~t ~ N O~ `J 1~ ~ N ~ ~O O t-- O~ O O E3 ~: :~C tr) o t~ O <~J O ~ O O In C
,~
o ~ ~ ~~ ~ ~ _ ~ O
`O ~ N ~ `D ~ :~J ~ ~ ~ ~) o~ _ o J~
J 1~ O C

~
~ 3 ~ N O t--co 3 _i ~ 0 L~J 0~ O~ O O N,~
O C -- J~O ~ OD O ~ t~

N (~N
m o 0~ 3 ~
O~
V~
O O O O O O O O ~

;~

C
O O O O O O~ ~ ~
E~ ~ .

_~ OD N ~1 Lt~
Ei In O t- ~ O 1~ 0 0 *
E-' O ---- N ~1 t~

.

109C~315 It will again be evident that with the use of laree crystal HZSM-5 the amount of para-xylene produced was substan-tially greater than its equilibrium concentration, approaching 100 percent after 5-6 hours on stream.

Toluene was co-fed along with hydrogen at a molar ratio of hydrogen to hydrocarbon of 2, over the large crystal HZSM-5 catalyst of Example 39 at 1 atmosphere pressure and at a temperature of approximately 650C at a weight hourly space velocity of 10. The reaction conditions and results are set forth in Table 7 below:

1~90315 ~ o . . ~o .- o ~o o ~ L~
C~ oq _ _ :~ =t + I o o o o o o ~, I o o o o o o c ~ ~ , u~ o~ a~ ~ ~ ) ~ a~ OD ~ ~ U~ ~ ~
EO~ ~ ~ ~ ~ ~ ~ C

x 00 N ~) ~ t-- =t O
O O N CJ~ ~0 a~ 0:)CD ~ CD 11 11~ -- N O -- O -- O _ O _ O , oq ,~
. ~ C -- ~ N N
l ~ ~ u- ~- o u~ o ~ a) ~ ~ ~o 1~ ~0 Irl ~C ~ o~ N c~ N ~D N u~
E~
C

I ~ ~ o^ ~^ ~
O. N N 0~ 0 N 0~ t-- ~ ~ O
~ a~ ~ ~ C
._ --' ~ O

N ~ 15~ ~0 ~ _ , 3 O C ~ ~ u~ In ~ ~D.,~
c~

N ~ 11~ 0 o~ O C
~n 1~ ~ o~ J
S~ C
~ ~ ~O ~O ~O ~O ~O ~O
a~ N t~l I t~ ~
_ . _ _ _ -- C

Q, a~ o o o o o E~ ~

,_ ~:
O. o a~ o o ~ ~ O O - O. O O *
E~ -- N 3 ~O 0 1~315 Comparing the results o~ Tables 6 and 7, it will be seen that the presence of hydrogen, even at one atmosphere total pressure, greatly reduces the catalyst aging rate and thus significantly enhances the effective life of the catalyst while reducing the need for frequent regeneration.

Toluene was passed over a sample of the large crystal HZSM-5 catalyst of Example 39 at about 625C. at a weight hourly space velocity (WHSV) of 20 and a pressure of 375 psig in the presence of hydrogen, the molar ratio of hydrogen to hydrocarbon being 6.
Initial conver~ion was 24.8 weight percent with a para-xylene selectivity (as percent of xylenes) of 45 percent.
After a period of 14 days, conversion and para-xylene selec-tivity were 12 percent and 82 percent respectively.
The changes in toluene conversion and para-xylene selectivity occuring during the course of the 14 day run are shown in Figure 3. Referring more particularly to this Figure, it will be seen that the aging rate was modest, amounting to a 1.2 percent relative conversion loss per day. It will also be seen that during this period, para-xylene selectivity (as percent of xylenes) increased 2.9 percent per day.

`-` 1~0315 A catalyst was prepared by heating 8.5 grams of ZSM-5 consisting of about 10 percent twinned crystals having up to 3 microns minimum dimension and about 90 percent of 5 5 to 10 microns polycrystalline spheroids for 5 hours at 1000F. in air followed by three ion exchanges, at room temperature, with 500 ml. of 1 N NH4C1 solution for 15.3 hours, 3.8 hours and 3.0 hours respectively. This material was then air calcined for 10 hours at 1000F. The resulting product was characterized by a para-xylene sorption capacity of 6.2 weight percent and an ortho-xylene sorption time for 30 percent of said capacity of 43 minutes. Both of the latter measurements were made at 120C. For the para-xylene sorption the hydrocarbon partial pressure was 5.1 mm of mercury. For 15 ortho xylene sorption time the hydrcarbon partial pressure was 3.8 mm of mercury.
Toluene was passed over the catalyst of Example 43 at 600C. at a ~leight hourly space velocity of 50 and one atmosphere pressure. Toluene conversion was 10.6 weight per-20 cent. The product consisted of 5.1 weight percent benzene,89.4 weight percent toluene and 5.5 weight percent xylenes.
The xylene fraction contained 35. 2 percent para-xylene.

42~2 pounds of Q-Brand sodium silicate were mixed with 25 52.8 pounds of water. The resulting solution is designated Solution A. 1.35 pounds of commercial grade aluminium sulfate `` 1~J9(~3~5 (A12(S04)3 . 14H20), 15.84 pounds of commercial grade NaC1.
and 3.52 pound9 of H2S04 (95.5 wt % H2S04) were mixed with 72.2 pounds of water. The resulting solution is designated Solution B. 2.6 pounds of water were added to an autoclave 5 equipped with high shear agitation. Solution A and Solution - -B were mixed simultaneously in a nozzle and sprayed into the autoclave. The resulting gel was mixed in the autoclave at 90 RPM and ambient temperature for one hour. 2.84 pounds of tri-n-propylamine and 2.44 pounds of n-propyl bromide were added to the contents of the autoclave. The mixture was reacted at 320F with 90 RPM agitation. After twenty hours at 320F, the autoclave contents were sampled and the solid product was found to be 100% ZSM-5 by x-ray diffraction. After a total reaction time of 28.7 hours at 320F, the autoclave contents were cooled. The resulting solid product was washed by decanta-tion with deionized water and 3500 ppm Primafloc C-7 (Rohm &
Ha8R) until the decant water was C1 free. The solid product was filtered and dried at 250F.
500 grams of the dried filter cake product were cal-20 cined in N2 for three hours at 1000F.
444 grams of the calcined product were mixed with 22~0 cc of 1 N NH4N03 solution for one hour at ambient temper-ature. The mixture was vacuum filtered. The ion exchange pro-cedure was repeated. The filter cake was washed with 1776 cc of water and the solid product was dried at 250F. The sodium content of the final product was ~ess than 0.01%.

-1~90315 The resulting catalyst had a crystal size of 1-2 microns, a para-xylene sorption capacity of 6.5 weight per-cent and an ortho-xylene sorption time for 30 percent of said capacity of 92 minutes. Both of the latter measurements were made at 120C. For the para-xylene sorption the hydrocarbon partial pressure was 5.1 mm of mercury. For ortho xylene sorption time the hydrocarbon partial pressure was 3.8mm of mercury.

Example 45 The catalyst of Example 11 was contacted with 1-butene at 400C. at a weight hourly space velocity of 4 and 1 atmosphere pressure. The liquid product which was 89 - percent of the weight of charge contained 13.4 weight percent xylene and 3.9 weight percent ethyl toluene. The xylene 15 fraction contained 37 percent p-xylene and ethyl toluene fraction was 43 percent para ethyl toluene. Equilibrium values of these para isomers are 24 and 32 percent respectively.

Example 46 The catalyst of Example 44 was contacted with do-20 decane at 400C. at a weight hourly space velocity of 10 and 1 atmosphere pressure. The liquid product which was 41 weight percent of the charge consisted of 12.6 weight percent xylene and 4.3 weight percent ethyl toluene. The xylene fraction was 63 percent para-xylene and ethyl toluene fraction was 58 25 percent para-ethyltoluene.

:1~9~315 Example 47 The catalyst of Example 44 was contracted with toluene at 550C., at a weight hourly space velocity of 50, a pressure of 375 psig and a hydrogen to hydrocarbon molar ratio of 6. The liquid product which contained 20 weight percent of converted 5 toluene consisted of 12.1 weight percent xylenes in addition to benzene, with the xylene fraction containing 30 percent of para-xylene.

Example 48 The catalyst of Example 44 was treated with toluene for five hours at 640C. at a weight hourly space velocity of 50 and one atmosphere pressure. After this treatment, the catalyst found to contain approximately 4 weight percent of coke was contacted with toluene at 550C., a pressure of 600 psig, a weieht hourly space velocity of 40 and a hydrogen to 15 hydrocarbon mole ratio of 10. The liquid product contained 80.7 weight percent toluene (19.3 percent conversion) and 9.6 weight percent xylenes in addition to benzene. The xylene frac-tion contained 82 percent of para-xylene.

Example 49 Three grams of the catalyst of Example 44 were con-tacted with a solution consiqting of 1.02 grams of magnesium acetate tetrahydrate in 4 cc of water. The resulting slurry was evaporated to dryness over a 24 hour period and then air 1~31S

calcined for 10 hours at 1000F. to yield a product of HZSM-5 containing 6 weight percent of MgO.

Example 50 The catalyst of Example 49 was contacted with toluene at 550C., a pressure of 600 psig, a weight hourly space veloci-ty of 40 and a hydrogen to hydrocarbon ratio of 4. Toluene con-version was 29.4 percent. The liquid product contained 15.03 weight percent xylene, which consisted of 53 percent of the para isomer.
Example 51 This example illustrates the production of p-diethyl-benzene with catalyst of Example 44 pretreated with toluene as in Example 15 to deposit approximately 4 weight percent of coke.
A mixture of benzene and ethylene at a mole ratio of 1:2 (fresh feed) is mixed with a recycle stream containing benzene and ethylbenzene and passed over the catalyst at a temperature of 825-850F, a pressure of 300 psig and a WHSV of 2, based on lb.
ethylene per hour per lb. catalyst. The reactor effluent is distilled to yield an overhead fraction (recycle stream) con-sisting of benzene, ethylbenzene and unreacted ethylene which is recycled to the reactor and a bottom fraction containing thedesired product, p-diethylbenzene .. . ~ .

l~g~315 Example 52 A five gram sample of HZSM-5 of .02-.05 micron crystal size was placed in a glass tube fitted with a fritted glass disc.
Dimethylsilane was passed through the bed of HZSM-5 at a rate of 40 cc/minute. After 15 minutes, the HZSM-5 had sorbed 0.60 gram of dimethylsilane. The product was added to 200 cc of 15 percent aqueous ammonia to hydrolyze the silane. Hydrogen was evolved rapidly. After one hour, the product was filtered and calcined at 1C./minute to 538C. and held at this temperature for 6 hours.
The above procedure was repeated a total of three times to yield a silica-loaded HZSM-5 containing 5 weight percent of added silica.

Example 53 A silica-modified HZSM-5 catalyst was prepared as in Example 52 using 1-2 micron crystal size HZSM-5 in place of the .02-.05 micron HZSM-5.
Toluene (5.2 parts by weight) was contacted with 0.13 part by weight of the above catalyst at a temperature of 600C. and a liquid hourly space velocity of 20. The paraxylene content of the xylene product was observed by gas chromatography to be 79 percent. This figure is considerably higher than the 30 percent xylene content observed using the parent HZSM-5 under comparable reaction conditions.

Example 54 To 1.42 grams of phenylmethylsilicone (molecular) weight 1686) dissolved in 40 cc of n-hexane was added 4 grams of NH4 ZSM-5 having a crystallite size of 1-2 microns. This sample of NH4 ZSM-5 contained 35 percent alumina as a binder.
The mixture was evaporated slowly over a 2-hour period using a rotary evaporator. The residue was calcined in air at 1C./
minute to 538C. and then maintained at this temperature for 7 hours to yield silica-modified HZSM-5, containing 14 weight percent silica.

Example 55 To 0.73 gram of phenylmethylsilicone (molecular weight 1686) dissolved in 40 cc of n-hexane was added 4 grams of NH4 ZSM-5 having a crystalline size of 1-2 microns. The mixture was evaporated over 1/2 hour using a rotary evaporator.
The residue was calcined in air at 1C./minute to 538C. and then maintained at this temperature for 7 hours to yield silica-modified HZSM-5, containing 7.5 weight percent silica.

Example 56 To 0.32 gram of methylhydrogensilicone (molecular weight 3087) dissolved in 40 cc n-hexane was added 4 grams NH4 ZSM-5 having a crystallite size of 1-2 microns. The mix-ture was evaporated over 1/2 hour using a rotary evaporator.
The residue was calcined in air at 1C./minute to 538C. and maintained at this temperature for 7 hours to yield silica-modified HZSM-5, containing 7.5 weight percent silica.

-Example_57 To 0.40 gram dimethylsilicone (molecular weight 4385) dissolved in 40 cc n-hexane was added 4 grams NH4 ZSM-5 having a crystallite size of 1-2 microns. The mixture was evaporated over 1/2 hour using a rotary evaporator. The residue was calcined in air at 1C./minute to 538C. and maintained at this temperature for 7 hours to yield silica-modified HZSM-5, containing 7.5 weight percent silica.

Example 58 A sample of silica-modified HZSM-5 prepared as in Example 57 was pelleted, sized to 14-30 mesh and tested in a flow reactor for toluene disproportionation at atmospheric pressure and with flowing hydrogen, utilizing a hydrogen to hydrocarbon mole ratio of 2. Reaction was carried out at 550-600C. at weight hourly space velocities of 8-22. Results are summarized in Table 8 below.

~315 ..
o o o o o o o o o ~ ~, ~ U~ ~ o o a) O u~

~ o O ~1 O ~ ~ I ~ 0 bO C~
æ

~3 o 0 C ~ ~
~ ~3 . O ~ 01 O 1~ t~J O ~I o m o ~ æ ~ -- ~ ~ ~ . ~
E~ E~ c, a C

I ~:
O~ rl Lr a In a ~q ., a~ :~
æ

- ~'' - -~31S

It will be seen from the above data that selectivity to para-xylene at the same conversion and temperature was significantly higher after modification with silica and that such selectivity remained high after regneration of the cata-lyst by burning carbonaceous deposit therefrom in air at 540C.

Example 59 A sample of silica-modified HZSM-5 prepared as in Example 55 was pelleted, sized to 14-30 mesh and tested for toluene dispropor.tionation-at atmospheric pressure and with flowing hydrogen, utilizing a hydrogen to hydrocarbon mole ratio of 2. Reaction was carried out at a temperature of 550C.
at weight hourly space velocities of 6-25. Results are summa-rized in Table 9 below.

..
~ c~ o o o L~ In P. ~, o o ~ 2 ~ o u~

3 u~

O
o~ C ~
~ ~ ~ .
_l ~ O ~ ~ O ~O O ~O
m ~o g 2 ~ . ~ ~ ~
.~ ~ c~

G~
C ~
O ~r ~ ~ ~o ~x 2 r~ 0 a~ a~ 0 u~ ~ ~
. ~ In x o I ~ C
bO o ~

.
, - \

1~t~315 It will be evident from the foregoing results that the silica modified HZSM-5 catalyst is fully regenerable (in air at 540C.) and shows significantly higher selectivity to para-xylene when compared with the unmodified catalyst at the same conversion and temperature.

Example 60 A silica-modified HZSM-5 catalyst prepared in a manner similar to that to Example 55, but containing 1.9 weight percent silica was tested for toluene disporportionation in a flow reactor at atmospheric pressure and with flowing hydrogen, utilizing a hydrogen to hydrocarbon mole ratio of 2. Reaction was carried out at 550C. at weight hourly space velocities of 5-20. Results are summarized in Table 10 below.

o o U~
E c) u~
~ o IS~ U~
E~

o O
~0 o o U~
bO O
3 v~
l ¢ ¦

C

~ ~ .
o ~ ~ . t~

a~ a C C
_I .
a) CD ~
X X 3 ~ ~ In ,~

.

Example 61 A sample of silica-modified HZSM-5 prepared as in Example 56 was tested for toluene disproportionation as in Example 60. Results are shown in Table 11 below.

1119~13i5 .~
-E C.) O O O
~o L~

L O

3: ~ O O If~
~) c) N
~rl tll ~ V~
,_ ~13 a ~ rl a 0~
3 ~ E~ - O ~
O S: 3 . N N
O

~q .
X ~ CD ~D LO ~ ' a .,, ~9~3iS

Example 62 Toluene disproportionation was carried out with a sample of a silica-modified HZSM-5 catalyst prepared as in Example 54. Reaction was conducted at 500C. and 600 psig.
The hydrogen to hydrocarbon mole ratio was 2 and the weight hourly space velocity was 7. During 18 days time on stream, the toluene conversion decreased slightly from 38 percent to 35 percent while the para-xylene in the xylene increased from 58 percent to 70 percent.

Example 63 Alkylation of toluene with methanol was carried out in the presence of a sample of a silica-modified HZSM-5 pre- -pared as in Example 55. The toluene to methanol mole ratio was 4 utilizing a pelleted catalyst, sized to 14-30 mesh. The reaction was carried out a temperature of 400-500C. and atmospheric pressure at a weight hourly space velocity of 10 with flowing hydrogen, employing a hydrogen to hydrocarbon mole ratio of 2. The results summarized below in Table 12 show high selectivity to para-xylene.

3i5 o o o o E u u~ o ~ o ~ O ~ L~
}~

:~
~, o ~ o 5o o o o o _ r o 3 u~

m ¢

Q) Co C
.
~ O ~ ~O
o 3 co u oq ~ Q) C
~ a _I ~ C~
X ~C 3 OD a~
., _ 91 _ . . ~ , .

Example 64 - ZSM-5 crystals were obtained using the following reactants:
Silicate Solution 42.2 lb. Q-Prand Sodium Silicate (Na20/SiO2 = 3.3) ; 52.8 lb. Water Acid Solution . .
612 grams Aluminum Sulfate 1600 grams Sulfuric Acid 7190 grams Sodium Chloride 72.2 lb. Water Organics ,"', ;, 10 1290 grams Tri-n-propylamine 1110 grams n-Propylbromide The silicate solution and acid solution were nozzle mixed to form a gelatinous precipitate that was charged to a 30 gallon stirred autoclave. When gelation was complete the organics were added and the temperature raised to 315F. with agitation. The reaction mixture was held at 315F. with an agitation rate of 121 RPM for 17 hours. The product at this time was analyzed by X-ray diffraction and was reported to be ZSM-5. The product was then washed free of soluble salts and dried. Analysis of the product gave the following in terms of mole ratios:
A1203 1.0 SiO2 74.4 Na20 0.31 N 2.26 C 21.9 The ZSM-5 so prepared was precalcined in air at 370C. and thereafter ammonium exchanged by contacting twice .

~9C~31S

with 5N NH4C1 solution at 100C. (15 ml per gram zeolite), once for 16 hours, the second time for 4 hours, filtered, washed free of chloride and air dried.

The resulting ammonium form of ZSM-5 was converted to the hydrogen form by calcination in air at 1C./minute to 538C. and then held at 538C. for 10 hours.

A mixture of toluene (1715 grams) and methanol (426 grams) in a molar ratio of 1.4/1 was passed over 5 grams of the so prepared HZSM-5 at 550C. and a weight hourly space velocity of 5 weight of charge/weight of catalyst/hour for a total of 85 hours. Activity of the catalyst decreased from initial conversion of toluene at 70 weight percent to nil at the end of 85 hours. The weight of catalyst was increased by 77 percent, due to coking.
A portion of the coked catalyst was regenerated in air at 550C overnight. Alkylation of toluene with methanol was c~rried out by passing a 1.4:1 molar ratio mixture of toluene and methanol over 0.8 grams of the regenerated catalyst containing about 30 weight percent coke at a temperature of 490C. and a weight hourly space velocity of 11.5 weight of charge per weight of catalyst/hour. Toluene conversion was 60 percent and the para/meta/ortho ratio in the xylene product was 50/33/17.

Example 65 After use in the process of Example 64, the catalyst l~gC31S

was regenerated in alr at 550C. for 16 hours. Alyklation of toluene with methanol was carried out by passing a 1.4:1 molar ratio mixture of toluene and methanol over 0.8 grams of the regenerated catalyst containing about 30 weight percent coke at a temperature of 490C. and a weight hourly space velocity of 18 weight of charge/weight of catalyst/hour. Toluene con-version was 49 percent and the para/meta/ortho ratio was 52/32/16.
Example 66 A catalyst was prepared by blending 5 weight percent HZSM-5 and 95 weight percent silica gel.

Toluene and methanol in a 1:1 molar ratio were passed over this catalyst at a temperature of 550C. at a weight hourly space velocity of 250. Methanol conversion was 11 weight percent. The xylene content in the aromatics product amounted to 50 weight percent. After 32.5 hours on stream, the catalyst had deactivated considerably due to the accumulation of coke thereon and produced 100 percent selectivity to para-xylene at about 1 percent toluene conversion.
Example 67 A catalyst was prepared by blending 5 weight percent HZSM-5 extrudate (containing 65 wt. percent HZSM-5 and 35 wt.
percent A1203 binder) and 95 weight percent silica gel.
Toluene and methanol in a 1:1 molar ratio were passed over this catalyst at a temperature of 550C. at a weight hourly space velocity of 241. Methanol conversion was 10 weight percent. The xylene content in the aromatics product was 100 weight percent. After 4.5 hours on stream the catalyst had deactivated considerably due to the accumulation of coke thereon and gave 100 percent selectivity to para-xylene at about 1 percent toluene conversion.

Example 68 Over a fixed bed of extrudate catalyst containing 35 weight percent alumina and 65 weight percent HSZM-5, pre-pared as in Example 1 of U.S. 3,751,506, a feed of toluene was contacted with methyl alcohol in the mole ratio of tol-uene to methyl alcohol of 2: 1. The reactor inlet temperature was 870F. and the reactor pressure was maintained at atmos-phere. The total feed weight hourly space velocity was 4.
The composition of the liquid product was as follows:

Wt. percent Total product Component Toluene 59.6 Xylenes 29.7 Para/Total Xylenes 24.5 Meta/Total Xylenes 52.6 Ortho/Total Xylenes 22. g Benzene 3.2 Cg 6.2 Cg 1.1 Others . 2 Percent Coke on Cata- 3.6 lyst After the Run It will be evident from the results that the amount of coke deposited on the catalyst, i.e. 3.6 weight percent, was insufficient to afford selective production of para-xylene, since the para/meta/ortho xylene concentration was essentially 5 that of the equilibrium mixture.
Example 69-71 An extrudate catalyst similar to that used in Example 68 was pre-coked prior to alkylation. The reaction feed and conditions were the same as in the preceding example. The com-position of the liquid product was as follows:

Example 69 70 71 Percent Coke on Catalyst30 26 27 Toluene 72.972.4 72.8 Xylenes 20.720.6 19.8 Para/Total Xylenes37.830.0 30.7 Meta/Total Xylenes42.348.6 48.1 Ortho/Total Xylenes19.921.4 21.2 Benzene . 2 .5 .4 Cg 5.6 5.9 6.4 Cg+ .5 .5 .5 Others .1 .1 .1 From the above results, it will be seen that with deposition of coke on the catalyst in the range of para-xylene produced was greater than that present in the equilibrium mix-ture, 1.0 para-xylene was selectively produced.

3~5 Examples 72-80 An HZSM-5 catalyst prepared as in Example 64 was em-ployed for methylation of toluene using a 2:1 mole ratio of toluene to methyl alcohol. The reactor inlet temperature was 870F., the pressure was atmospheric and the weight hourly space velocity was 4. The catalyst used in Example 72 was not pre-coked, while the catalysts used in the remaining examples were pre-coked to deposit various amounts of coke on the cata-lyst as indicated. The composition of the liquid products ob-tained in each instance are shown below in Table 13:

1~C~315 * ~ o ~ J o~ ~ o~
O ~ ~ C~ N ~O O It~
c~ 01 ~ ~ ~1~ N

* ~n ~ ~ ` ~ u~ ~ --* ~ ~ ~ ~ ~ In ~ u~
~1~ ~ ~ O ~ O
~_ ~\1 ~ N (~

t~.l ~ N
~O O
t-It~ N 11~ 0 0 0 N
11~ ~ ~ ~
~ ~ N
E~

U~ ~ ~ ~ ~ .
~ ~ o ~ ~ ~
. t-- ~J N 1~ N~O

O ~ ~ ~ ~ U~
~ O ~ ~ ~ t-~ N N 1~
Dq o ~ In ~ 0 ~~ ~ ~
~J ~ ~ O CD ~ N ~r) 1~ ~ C O
N IS~ t~.l 3 ~
-~ 0~

u~

O O ~X X C
_I a> :~ _I ~1 1~1 o 1~1 C~ ~ ~ EO~
~: ~
o .
cr ~ O + S
~O ~ ~ O * *

9C~315 From the above results, it will be seen that a minimum deposit of about 15 weight percent of coke on the catalyst is necessary before selective production of para-xylene is achieved.
Thus, it will be evident from the results of Example 73 that even with an amount of coke deposited on the catalyst exceeding 8 weight percent, the para/meta/ortho xylene concentration was essentially that of the equilibrium mixture.

Example 81 This example serves to illustrate disproportionation of toluene in the presence of a catalyst of HZSM-5 which has not been modified with phosphorus and magnesium.
A catalyst containing 65 weight percent acid ZSM-5 and 35 weight percent alumina was prepared as follows:

_ 99 _ ~ .

~` lt~ 315 A sodium silicate solution was prepared by mixing 8440 lb. of sodium silicate (Q Brand - 28.9 weight percent SiO2, 8.9 weight percent Na20 and 62.2 weight percent H20) and 586 gallons of water. After addition of 24 lb. of a dispersant of a sodium salt of polymerized substituted benzenoid alkyl sulfonic acid combined with an inert inorganic suspending agent (Daxad 27), the solution was cooled to approximately 55~F . An acid alum solution was prepared by dissolving 305 lb. aluminum sulfate (17.2 A1203), 733 lb. sulfuric acid (93%) and 377 lb.
sodium chloride in 602 gallons of water. The solutions were gelled in a mixing nozzle and discharged into a stirred auto-clave. During this mixing operation, 1200 lb. of sodium chloride was added to the gel and thoroughly mixed in the vessel. The resulting gel was thoroughly agitated and heated to 200F. in the closed vessel. After reducing agitation, an organic solu-tion prepared by mixing 568 lb. tri-n-propylamine, 488 lb. n-propyl bromide and 940 lb. methyl ethyl ketone was added to the gel. This mixture was reacted for 14 hours at a temperature of 200-210F. At the end of this period, agitation was increased and these conditions maintained until the crystallinity of the product reached at least 65% ZSM-5 as determined by X-ray dif-fraction. Temperature was then increased to 320F. until crystallization was complete. The residual organics were flashed from the autoclave and the product slurry was cooled.
The product was washed by decantation using a floc-culant of polyammonium bisulfate. The washed product contain-ing less than 1% sodium was filtered and dried. The weight of dried zeolite was approximately 2300 lb.
The dried product was mixed with alpha alumina mono-hydrate and water (65~ zeolite, 35% alumina binder on ignited basis) then extruded to form of 1/16 inch pellet with particle density < O. 98 gram/cc and crush strength of > 20 lb./linear inch.

After drying, the extruded pellets were calcined in nitrogen t700 - 1000 SCFM) for 3 hours at 1000F., cooled and ambient air was passed through the bed for 5 hours. The pellets were then ammonium exchanged for one hour at ambient temperature (240 lb. ammonium nitrate dissolved in approx-imately 800 gallons of deionized water). The exchange was repeated and the pellets washed and dried. Sodium level in the exchanged pellets was less than 0.05 weight percent.
The dried pellets were calcined in a nitrogen-air mixture (10-12.5% air - 90-87.5% nitrogen) for 6 hours at 1000F. and cooled in nitrogen alone.
This catalyst was used for disproportionating toluene by passing the same over 6.0 grams of the catalyst at a weight hourly space velocity of 3.5-3.6 at a temperature between 450C.
and 600C. The conditions and results are summarized in Table 14 below.

C~
.,, o ~ ~ ~ U~ ~ _ X

6ql "~ co a~
~ ~

V~ C
N 1~ ~ O ~
c ~ J' ,.`, m ~ ~ ~ U~, oO C~
1~ 0 ~ O~
EO~

'1 ~ ',' In O O O O

:, :

1~0315 It will be seen from the above results that the unmodified catalyst afforded a xylene product in which the para isomer was present in its normal equilibrium concentra-tion of approximately 24 weight percent of the xylene fraction.
Example 82 To a solution of 8 grams of 85% H3Po4 in 10 ml. of water was added 10 grams of HZSM-5 extrudate which was per-mitted to stand at room temperature overnight. After filtra-tion and drying at 120C. for 3 hours, it was calcined at 500C.
for 3 hours to give 11.5 grams of phosphorus-modified ZSM-5.
Ten grams of the above phosphorus-modified ZSM-5 was then added to a solution of 25 grams of magnesium acetate tetra-hydrate in 20 ml. of water which was permitted to stand at room temperature overnight. After filtration and drying at 120C., it was calcined at 500C. for 3 hours to give 10.6 grams of magnesium-phosphorus-modified ZSM-5. Analysis showed the modi-fier concentrations to be 9.2 weight percent phosphorus and 3.0 weight percent magnesium.
Example 83 Toluene was passed over 5 grams of the catalyst of Example 82 at a weight hourly space velocity of 3.5 (based on total catalyst) at 600C. Conversion of toluene was 24 percent and the concentration of para-xylene in total xylenes was 98-2 percent.
Example &4 Toluene was passed over 5 grams of the catalyst of Example 82 at a weight hourly space velocity of 0.5 (based on total catalyst) at 550C. Conversion of toluene was 32.5 percent and the concentration of para-xylene in total xylenes was 91.2 percent.

1Qg(~315 Example 85 The preparation of Example 82 was repeated except that 7 grams of 85% H3P04 was used. The final catalyst amounted to 10.9 grams. Analysis showed the modifier con-centrations to be 7.4 weight percent phosphorus and 4.2 weightpercent magnesium.
Example 86 Toluene was passed over 5 grams of the catalyst of Example 85 at a weight hourly space velocity of 3.5 (based on total catalyst) at 600C. Conversion of toluene was 27.2 percent and the concentration of para-xylene in total xylenes was 96.6 percent.
Repeating the above run at various temperatures and space velocities, the following results were obtained:

Para-Xylene Temp TolueneConcentration In C WHSVConversionTotal Xylenes 500 0.5 32 85 400 0.1621.9 90.6 20 300 0.08 8 88.2 250 0.084.3 92.8 200 0.082.2 95.7 Example 87 To a solution of 3 grams of 85~ H3P04 in 12 ml. water was added 10 grams HZSM-5 extrudate which was permitted to stand at room temperature overnight. The water was evaporated at 130C.
with occasional stirring and then dried at 200C. for 2 hours.
After calcination at 500C., 11.2 grams were obtained. Analysis showed the phosphorus content to be 7.5 weight percent.

- 104 _ :, , ' :
- ~ -To a solution of 11 grams of Mg (OAc)2.4H2O in 20 ml.
water was added to 10 grams of the above phosphorus-modified ZSM-5 extrudate which was permitted to stand at room temperature overnight. The mixture was evaporated to dryness and was then heated to 200C. It was then calcined at 500C. for 2 hours to give 11.3 grams magnesium-phosphorus-modified ZSM-5. Analysis showed the modifier concentrations to be 5.4 weight percent phosphorus and 8.5 weight percent magnesium.
Example 88 Toluene was passed over 5 grams of the catalyst of Example 87 at a weight hourly space velocity of 3.5 (based on ¦ total catalyst) at 600C. Conversion of toluene was 18.2 ¦ percent and the concentration of para-xylene in total xylenes was 85.5 percent.
¦ 15 Example 89 Toluene was passed over 5 grams of the catalyst of Example 87 at a weight hourly space velocity of 0.4 at 550C.
Conversion of toluene was 30.6 percent and the concentration of para-xylene in total xylenes was 40 percent.
Example 90 The general preparation of Example 82 was repeated to yield a magnesium-phosphorus-modified ZSM-5 catalyst. Analysis showed the modifier concentration to be 10.2 weight percent phosphorus and 4.7 weight percent magnesium.
Example 91 Toluene was passed over 5 grams of the catalyst of ' Example 90 at a weight hourly space velocity of 3.5 (based on ; total catalyst) at 600C. Conversion of toluene was 21.8 .

percent and the concentration of para-xylene in total xylenes was 65.2 percent.
Example 92 Toluene was passed over 5 grams of the catalyst of Example 90 at a weight hourly space velocity of 0.4 (based on total catalyst) at 550C. Conversion of toluene was 35.7 percent and the concentration of para-xylene in total xylenes was 38.4 percent.
From the above results, it will be evident that high selectivities to the para-isomer were obtained in the xylene product utilizing the modified zeolite catalyst described herein. Unmodified catalyst under the same reaction conditions specifie.d for the preceding examples gave para-xylene at an equilibrium ratio of 24 percent.

Claims (28)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A catalyst composition comprising a crystalline aluminosilicate zeolite having an activity, alpha, of 2 to 5000, a xylene sorption capacity greater than 1 g./100 g.
zeolite, and an orthoxylene sorption time for 30 percent of said capacity greater than 10 minutes, said sorption capacity and sorption time being. measured at 120°C and 4.5 ?
0.8 mm. Hg.

2. A catalyst according to Claim 1 wherein the zeolite has a SiO2/Al2O3 ratio of 12 to 3000 and a constraint index in the range 1 to 12.

3. A catalyst according to Claim 1 wherein at least part of the zeolite is present as crystals from 0.5 to 20 microns in size.

4. A catalyst according to Claim 3 wherein the crystal size of the zeolite is in the range 1 to 6 microns.

5. A catalyst according to Claim 1 which bears a deposit of coke in a quantity of 15 to 75 percent by weight of uncoked catalyst.

6. A catalyst according to Claim 5 wherein the quantity of coke is 20 to 40 percent of the weight of uncoked catalyst.

7. A catalyst according to Claim 1 wherein said activity and said sorption properties pertain to a zeolite which is intimately associated with from 2 to 30 percent each, by weight of zeolite, of at least one difficultly reducible oxide.

8. A catalyst according to Claim 7 wherein said oxide comprises an oxide of at least one of antimony, phosphorus, boron, uranium, magnesium, zinc and calcium.

9. A catalyst according to claim 1, 2 or 3 in which the zeolite is zeolite ZSM-5, ZSM-11, ZSM-12, ZSM-35 or ZSM-38.

10. A catalyst according to claim 1, 2 or 3 wherein the zeolite possesses hydrogen cations.

11. A catalyst according to claim 1, 2 or 3 wherein the zeolite has an activity, alpha, in the range 5 to 200.

12. A catalyst according to claim 1 which comprises a composite of a zeolite as aforesaid with a binder.

13. A catalyst according to Claim 12 wherein the binder comprises a naturally-occurring or synthetic refractory oxide.

14. A catalyst according to Claim 13 wherein the naturally-occurring oxide is a montmorillonite or kaolin clay and the synthetic oxide is at least one of silica, alumina, magnesia, zirconia, thoria, beryllia and titania.

15. A catalyst according to Claim 12 of which the binder comprises 1 to 99 weight percent.

16. A catalyst according to Claim 15 of which the binder comprises 30 to 40 weight percent.

17. A process for selectively producing para-dialkyl benzenes in which each alkyl group contains 1 to 4 carbon atoms which comprises contacting a C1-C4 monoalkyl benzene, a C2-C15 olefin and/or a C3-C44 paraffin, or a mixture of any of the foregoing with benzene, under conversion conditions, with a catalyst in accordance with Claim 1.

18. A process according to Claim 17 wherein said conversion conditions comprise a temperature of 250 to 750°C, a pressure between 0.1 atmosphere and 100 atmospheres and a weight hourly space velocity between 0.1 and 2000.

19. A process according to Claim 18 wherein the temperature is 400 to 700°C, the pressure is 1 to 100 atmospheres and the space velocity is 0.1 to 100.

20. A process according to Claim 17, wherein toluene is disproportionated.

21. A process according to Claim 17, wherein toluene is alkylated with an alkylating agent having from 1 to 4 carbon atoms.

22. A process according to Claim 20 or 21 wherein the space velocity is 1 to 50.

23. A process according to Claim 17 wherein one or more C3-C44 paraffins is contacted with said catalyst.

24. A process according to Claim 17 wherein the temperature is 300 to 700°C, the pressure is 1 to 100 atmospheres and the space velocity is 1 to 1000.

25. A process according to Claim 24 wherein one or more C3-C15 olefins is contacted with said catalyst.

26. A process according to Claim 17 wherein the paradialkyl substituted benzene is p-xylene, p-diethyl benzene or p-ethyl toluene.

27. A process according to Claim 17 which is conducted in the presence of a hydrogen.

28. A process according to Claim 27 wherein the mole ratio of hydrogen to hydrocarbon feed is from 2 to 20.