GB1574523A

GB1574523A - Process for producing p-diakyl substituted benzenes and catalyst therefor

Info

Publication number: GB1574523A
Application number: GB12642/77A
Authority: GB
Inventors: Chin-Chiun Chu; Werner Otto Haag; David Harold Olson; Paul Gerhard Rodewald
Original assignee: Mobil Oil Corp
Current assignee: ExxonMobil Oil Corp
Priority date: 1976-03-31
Filing date: 1977-03-25
Publication date: 1980-09-10
Also published as: JPS6247854B2; BE852865A; NO149492C; NO149492B; SE438606B; NL187424C; JPS52120292A; IT1075368B; FR2357303A1; NL7703484A; CS218565B2; JPH01199920A; DE2760479C2; NZ183608A; DE2714239C2; FR2357303B1; DE2760481C2; DE2714239A1; PL115528B1; JPH0567613B1

Description

(54) PROCESS FOR PRODUCING p-DIALKYL SUBSTITUTED BENZENES AND CATALYST THEREFOR (71) We, MOBIL OIL CORPORATION, a Corporation organised under the laws of the State of New York, United States of America, of 150 East 42nd Street, New York, New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in any by the following statement:- 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 disporportionation of toluene over various catalysts. In these processes the xylenes 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, para-xylene being of particular value in the manufacture of terephthalic 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 steps.

We have now identified a catalyst which has the capacity to convert many available feedstocks to para-dialkylbenzenes with gratifying selectivity. According to the present invention a catalyst composition comprises a crystalline aluminosilicate zeolite having an activity, alpha, of 2 to 5000, a xylene sorption capacity greater than 1 g./100 g. zeolite, an orthoxylene sorption time for 30 percent of said capacity greater than 10 minutes, said sorption capacity and sorption time being measured at 1200C and 4.5+0.8 mm. Hg, and a SiO2/AI203 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 cpnversions 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 embodiment 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 achieves its properties by coking, in particular by bearing a deposit of coke in a quantity of 15 to 75 percent by weight of uncoked 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 and of an oxide of magnesium, 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 properties 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 is 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 -fluoro derivative thereof. Particularly useful silicon compounds have the formula SiRtR2R3R4, in which R, and R2 are hydrogen, fluorine, chlorine, methyl, ethyl, amino, methoxy or ethoxy, RJ is hydrogen, fluorine, chlorine, methyl or amino, and R4 is hydrogen or fluorine: other useful silicon compounds are silane, dimethylsilane, dichlorosilane, methylsilane 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 of a silicone compound incapable of entering the pores of the zeolite, such as one having the formula [(Rt) (R2) SiO ]n, in which R1 and R2 represent fluorine, hydroxy, alkyl, aralkyl or alkaryl of fluoroalkyl, 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, preferably 1000 to 10,000, and compounds found particularly effective have been diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethylsilicone, phenylethylsilicone, diphenylsilicone, methyltrifluoropropylsilicone, ethyltrifluoropropylsilicone, polydimethylsilicone, tetrachlorophenylmethylsilicone, tetrachlorophenylethylsilicone, tetrachlorophenylhydrogensilicone, tetrachlorophenylphenylsilicone, methylvinylsilicone and ethylvinylsilicone.

The preferred zeolites employed in the catalysts according to the invention are zeolites ZSM-5, ZSM-l 1, ZSM12, 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 catalysts, 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 just 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 montmorillonite or kaolin clay, suitable synthetic oxides silica, alumina, magnesia, zirconia, 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-dialkylbenzenes, in which each alkyl group contains 1 to 4 carbon atoms, comprises contacting a C1-C4 monoalkylbenzene, a C2-C15 olefin and/or a C3C44 paraffin, or a mixture of any of the foregoing with benzene, under conversion conditions, with a catalyst as hereinabove set forth. The preferred conditions comprise a temperature of 250 to 7500C, 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 7000 C, a pressure of I to 100 atmospheres and a space velocity of 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 I to 50.

The same conditions are also conducive to the use as feed of C3-C44 paraffins.

Operating at a temperature of 300 to 7000 C, 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-dialkylbenzenes.

The more useful products obtainable according to the invention comprise pxylene, p-diethylbenzene or p-ethyltoluene; 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.

The above catalyst is particularly applicable for the selective production of para dialkyl substituted benzenes containing alkyl groups of 1 to 4 carbon atoms by contacting a hydrocarbon precursor, such as mono alkyl-substituted benzenes having 14 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 250 and 750"C. at a pressure between 0.1 and 100 atmospheres utilizing a feed weight hourly space velocity (WHSV) between 0.1 and 2000. The latter WHSV is based 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 selectivity with variation in ortho-xylene sorption time for 30 percent of xylene sorption capacity of the zeolite catalyst 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 changes in toluene conversion and para-xylene selectivity occurring with time on stream utilizing a co-feed of toluene and hydrogen.

The hydrogen 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-C4 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 disproportionation of toluene to benzene and xylene, wherein the proportion of para-xylene obtained is greatly in excess of its normal equilibrium concentration. Such process is effectively carried out at a temperature of between 4000 C. and 700"C at a pressure between 1 atmosphere and 100 atmospheres utilizing a weight hourly space velocity of between 1 and 50.

Another charge stock suitable for use in the process of the invention is a stream high in C2C,5 olefin content. Thus, ethylene, propylene, butenes, pentenes, hexenes, dienes such as butadiene, pentadienes, cycloolefins such as cyclopentene and cyclohexene, alkyl-substituted cycloolefins such as ethyl cyclopentene, cyclopentadiene and cyclohexadiene can be effectively converted to a high yield of para dialkyl substituted benzenes utilizing the hereinabove described catalyst. Conversion utilizing such olefin feed is carried out at a temperature within the range of 300 to 7000 C, a pressure between atmospheric and 100 atmospheres employing a weight hourly space velocity between 1 and 1000. As sources of the olefin reactant either substantially pure streams of the C2C15 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 groups of 1 to 4 carbon atoms includes paraffinic hydrocarbons having between 3 and 44 carbon atoms. Representative of such paraffins are butanes, pentanes, hexanes, heptanes, octanes, dodecanes, eicosane, dotriacontane, tetracontane 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 400 to 7000 C., a pressure between atmospheric and 100 atmospheres and a weight hourly space velocity between 0.1 and 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 pdiethylbenzene and p-ethyltoluene, the latter predominating at high toluene to ethylbenzene ratios in the feed.

Reaction of benzene, toluene, ethylbenzene, propylbenzene or butylbenzene with C2-C20 olefins or C5-C25 paraffins at 250 to 5000C yieldsp-dialkylbenzenes.

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 pdiethylbenzene besides ethylbenzene (p=400 psig, Temp.=8000F); toluene and 1octene yield p-ethyltoluene and a mixture of n- and iso-propyltoluene rich in pisomer.

In the absence of added aromatics, C2-C15 olefins and C3C44 paraffins each yield a mixture of aromatics rich in p-dialkylbenzenes. The olefins and the higher paraffins are more reactive and require lower severity of operation, e.g., a temperature of 2506000C and preferably 300550 C, while the lower paraffins, e.g. C3-C5 paraffins yield aromatics at a practical rate only above 400"C. The aromatization can be carried out at atmospheric 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 pdialkylated benzenes containing alkyl groups greater than C, is favored by higher pressure and lower temperature; for example, p-ethyltoluene is formed from either dodecane or l-butene at 4000C, whereas p-xylene is the preferred dialkylbenzene 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 temperature between 3000 and 750"C and preferably between 400 and 700"C. At the higher temperatures, the zeolites of high silica/alumina 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 range of 1 atmosphere to 1000 psig. A weight hourly space velocity of between 1 and 2000 is employed. The molar ratio of methylating agent to toluene is generally between 0.05 and 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 methyl chloride, methyl bromide, dimethyl ether or dimethyl sulfide, 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 1 and 2000 and preferably between 5 and 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.

In accordance with the present invention the above described feed precursors are brought into contact, under conversion conditions, with a bed comprising particle-form catalyst containing a crystalline aluminosilicate zeolite having: (1) an activity, in terms of alpha value, of between 2 and 5000, (2) a xylene sorption capacity greater than I gram/100 grams of zeolite (3) an ortho-xylene sorption time for 30 percent of said capacity of greater than 10 minutes, where the sorption capacity and sorption time are measured at 1200C and a xylene pressure of 4.5+0.8 mm of mercury, and a SiO2/AI203 ratio of 12 to 3000 and a constraint index in the range 1 to 12.

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 1000"F.

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 1000"F. Catalytic activity of the catalysts are expressed as multiple of this standard, i.e. the silica-alumina standard. The silicaalumina reference catalyst contains about 10 weight percent Al203 and remainder SiO2. This method of determining alpha, modified as described above, is more fully decribed 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 equilibrium 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 1200C and a xylene pressure of 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 substituted benzenes.

It has been found that zeolites exhibiting very high selectivity for paradialkylbenzene 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 50 sorption: two*3 = F.t005 Percent of sorption capacity Factor (F) to Estimate 30% Sorption Time 5 36 10 9 20 2.2 In assessment of zeolite crystal size, conventional scanning electron microscopy (SEM) 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 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 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 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 of 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 thereafter controlled within the above-noted range of 15 to 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 precoked catalyst for effecting the desired reaction for a period of time such that the activity of the catalyst declines to a point where further use becomes uneconomical, it can be readily regenerated by burning off excess coke in an oxygen-containing atmosphere, e.g. air, at a temperature, generally within the range of 400 to 7000 C. 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 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 I weight percent and generally between 2 and 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 tendencies, such as alumina, coke content of the total catalyst is in the 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.

Prior modification of the zeolite may also be suitably effected by combining therewith a small amount, generally in the range of 2 to 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 contacting the zeolite with a solution of an appropriate compound of the element to be introduced, followed by drying and calcining to convert the compound to its oxide form.

In an advantageous embodiment of the foregoing modification the difficult reducible oxides are those of phorphorus 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 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, RPX2, R2PX, R3P, X3PO, (XO3)PO, (XO)3P, R3P=O, R3P=S, RPO2, PPS2, RP(O) (OX)2, RP(S) (SX)2, R2P(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 is 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 butylphosphine; the tertiary 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 phosphonate, (RO)2P(O)H, dialkyl alkylphosphonates, (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 alkylphosphonite, (RO)2PR esters.

Corresponding 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)PR, and (RS)2PR. Examples of phosphite esters include trimethyl phosphite, triethyl phosphite, diisopropyl phosphite, butyl phosphite; and pyrophosphites such as tetraethyl pyrophosphite. The alkyl groups in the mentioned compounds contain one to four carbon atoms Other suitable phosphorus-containing compounds include the phosphorus halides such as phosphorus trichloride, bromide, and iodide, alkyl phosphorodichloridites, (RO)PCl2, dialkyl phosphorochloridites, (RO)2PX, dialkylphosphinochloridites, R2PCI, alkyl alkylphosphonochloridates, (RO)(R)P(O)CI, dialkyl phosphinochloridates, R2P(O)Cl and RP(O)Cl2. Applicable corresponding sulfur derivatives include (RS)PCl2, (RS)2PX, (RS)(R)P(S)CI and R2P(S)CI.

Preferred phosphorus-containing compounds include diphenylphosphine chloride, trimethyl phosphite and phosphorus trichloride, phosphoric acid, phenylphosphine oxychloride, trimethyl phosphate, diphenylphosphinous acid, diphenylphosphinic acid, diethylchlorothiophosphate, methyl acid phosphate and other alcohol-P2O5 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 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 compound and the zeolite may be employed. Suitable solvents include water and aliphatic, aromatic or alcoholic liquids. Where the phosphoruscontaining compound is, for example, trimethyl phosphite or liquid phosphorus trichloride, 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 compound 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 such 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 subsequent to preparation and prior to use is also preferred. The heating can be carried out in the presence of oxygen, for example air. Heating can be at a temperature of about 150"C.

However, higher temperatures, i.e., up to 5000 C. are preferred. Heating is generally carried out for 1-5 hours but may be extended to 24 hours or longer.

While heating temperatures above 500"C. can be employed, they are not necessary. At temperatures of 1000"C., 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 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 150"C. However, higher temperatures, i.e. up to 5000C. are preferred. Heating is generally carried out for 1-5 hours but may be extended to 24 hours or longer.

While heating temperatures above 500"C. may be employed, they are generally not necessary. At temperatures of 10000C., the crystal structure of the zeolite tends to deteriorate. After heating in air at elevated 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 0.25 percent by weight. However, it is preferred that the amount of magnesium oxide in the zeolite be at least 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 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 is between 1 and 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 magnesium 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 conditions 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 disproportionation 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 Bronsted acids, e.g. by contact with an aqueous solution of hydrochloric acid; followed by calcination in air at a temperature between 300 and 7000 C. 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 1.5 weight percent alkali metal and preferably having at least a portion of 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:

where R, 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 decasiloxanes and poly-silanes, such as di-silanes, tri-silanes and higher 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 necessarily, saturated 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 between 300 and 700"C. for I 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 300"C. but below a temperature at which the crystallinity of the zeolite after contact of the same with the treating compound and the amount not volatilize before undergoing oxidation of silica.

The silicone compound utilized to effect the silica coating is characterized by the general formula:

where R, is hydrogen, fluorine, hydroxy, alkyl, aralkyl, alkaryl or fluoro-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 at 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 500 and 20,000 and preferably within the approximate range of 1000 to 10,000.

Representative silicone compounds include dimethylsilicone, diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethylsilicone, phenylethylsilicone, diphenylsilicone, methyltrifluoropropylsilicone, ethyltrifluoropropylsilicone, polydimethylsilicone, tetrachlorophenylmethylsilicone, tetrachlorophenylethylsilicone, tetrachlorophenylhydrogensilicone, tetrachlorophenylphenylsilicone, methylvinylsilicone and ethylvinylsilicone.

The silicone compound dissolved in a suitable solvent therefor, e.g., n-hexane, pentane, heptane, benzene, toluene, chloroform, carbon tetrachloride, is contacted with the above-described zeolite at a temperature between 10 C. and 100"C. for a period of time sufficient to deposit the ultimately desired amount of silicone thereon. Time of contact will generally be within the range of 0.2 to 5 hours, during which time the mixture is desirably subjected to evaporation. The resulting residue is then calcined in an oxygen-containing atmosphere, preferably air, at a rate of 0.2 to 5 C./minute to a temperature greater than 300"C. but below a temperature at which the crystallinity of the zeolite is adversely affected. Generally, such temperature will be below 600"C. Preferably the temperature of calcination is within the range of 350 to 5500 C. The product is maintained at the calcination temperature usually for I to 24 hours to yield a silica-coated zeolite containing between 0.5 and 30 weight percent and preferably between 1 and 15 weight percent silica.

Zeolites such as ZSM--4, faujasite, mordenite, ferrierite and offretite which satisfy the aforenoted activity and sorption characteristics and have a silica to alumina ratio of 12 to 3000 and a constraint index within the range of 1 to 12 are within the confines of this invention. These zeolites induce profound transformations of aliphatic hydrocarbons to aromatic hydrocarbons in commercially desirable yields and are generally highly effective in conversion reactions involving aromatic hydrocarbons. Although they have unusually low alumina contents, i.e. high silica to alumina ratios, they are very active even when the silica to alumina ratio exceeds 30. The activity is surprising since catalytic activity is generally attributed to framework aluminium atoms and cations associated with these aluminium atoms. These zeolites retain their crystallinity for long periods in spite of the presence of steam at high temperature which induces irreversible collapse of the framework of other zeolites, e.g. of the X and A type.

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, conducive 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 virtue of having a pore dimension greater than 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 making up the anionic framework of the crystalline aluminosilicate, the oxygen atoms themselves being bonded to the silicon or aluminium atoms at the centers of the tetrahedra.

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 aluminium in the 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 30. Such zeolites, after activation, acquire an intracrystalline sorption capacity for normal hexane which is greater than that for water, i.e. they exhibit "hydrophobic" properties. It is believed that this hydrophobic character is advantageous in the present invention.

The types of zeolites useful in this invention freely sorb normal hexane and have a pore dimension greater than 5 Angstroms. In addition, the structure must provide constrained access to larger molecules. It is sometimes possible to judge trom 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 molecules 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 puckering 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.

Rather than attempt to judge from crystal structure whether or not a zeolite possesses the necessary constrained access, a simple determination of the "constraint index" may be made by passing continuously a mixture of an equal weight of normal hexane and 3-methylpentane over a small sample, approximately I 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 10000F for at least 15 minutes.

The zeolite is then flushed with helium and the temperature adjusted between 550 F and 950 F to give an overall conversion between 10% and 60%. The mixture of hydrocarbons is passed at I liquid hourly space velocity (i.e., I volume of liquid hydrocarbon 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 chromatography, to determine the fraction remaining unchanged for each of the two hydrocarbons.

The "constraint index" is calculated as follows: Constraint Index = log10 (fraction of n-hexane remaining) logrO (fraction of 3-methylpentane remaining) The constraint index approximates the ratio of the cracking rate constants for the two hydrocarbons. Zeolites suitable for the present invention are those having a constraint index in the range of I to 12. Constraint Index (CI) values for some typical zeolites are: CAS C.I.

ZSM-5 8.3 ZSM-l I 8.7 ZSM--12 2 ZSM-38 2 ZSM-35 4.5 TMA Offretite 3.7 Beta 0.6 ZSM " 0.5 H-Zeolon 0.4 REY 0.4 Amorphous Silica-Alumina 0.6 Erionite 38 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 5500F to 9500 F, with accompanying conversion between 10% and 60%, the constraint index may vary within the indicated 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 affect 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 550 F to 9500 F, the constraint index will have a value for any given zeolite of interest herein within the range of 1 to 12.

The class of zeolites defined herein is exemplified by ZSM-5, ZSM-l 1, ZSM-l2, ZSM-35, ZSM-38, and other similar materials. U.S. Patent 3,702,886 describes ZSM-5.

ZSM-l 1 is more particularly described in U.S. Patent 3,709,979.

ZSM--12 is more particularly described in U.S. Patent 3,832,449.

ZSM-38 can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.3-2.5)R2O:(0-0.8)M2O:Al2O3: > 8 SiO2 wherein R is an organic nitrogen-containing cation derived from a 2 (hydroxyalkyl)trialkylammonium compound 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: (0.4-2.5)R2O:(0-0.6)M2O:Al2O3:xSiO2 wherein R is an organic nitrogen-containing cation derived from a 2 (hydroxyalkyl)trialkylammonium compound, wherein alkyl is methyl, ethyl or a combination thereof, M is an alkali metal, especially sodium, and Xis from greater than 8 to 50.

The synthetic ZSM-38 zeolite possesses 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 pattern (significant lines) is similar to that of natural ferrierite with a notable exception being that natural ferrierite patterns exhibit a significant line at 11.33 A.

TABLE I. d( ) I/Io 9.8 # 0.20 Strong 9.1 +0.19 Medium 8.0 +0.16 Weak 7.1 +0.14 Medium 6.7 -10.14 Medium 6.0 +0.12 Weak 4.37 + 0.09 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 A further characteristic of ZSM-38 is 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 calcination of an ammonium exchanged form. The characteristic sorption ratio n-hexane/2-methylpentane for ZS M-38 (after calcination at 6000 C.) 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 preparing a solution containing sources of an alkali metal oxide, preferably sodium oxide, an organic nitrogencontaining 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 0.3O.9 OH-/SiO2 0.05--0.5 0.07O.49 H2O/OH- 41.500 100-250 SiO2/Al2O3 8.8-200 1260 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 crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from 90 C. to 400 C. for a period of time of from 6 hours to 100 days. A more preferred temperature range is from 150 C. to 400 C. with the amount of time at a temperature in such range being from 6 hours to 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 thereafter dried, e.g. at 2300 F. for from 8 to 24 hours.

ZSM-35 can be identified, in terms of mole ratios of oxides and in the anhydrous state, as follows: (0.3-2.5)R2 : ((.8)M2O: Al203: > 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: (0.4-2.5)R2O : (0.0.6) M2O : Al203: xSiO2 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 50.

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 11.33 A. Close examination of some individual samples of ZSM-35 may show a very weak line at 11.3-11.5 A. 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 z 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 z 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 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 600"C.) 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, preferably sodium oxide, an organic nitrogencontaining 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 0.30.9 OH/SiO2 0.05--0.5 0.07--0.49 H2OOH- 41-500 100250 SiO2/Al2O3 8.8-200 1260 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 contribution). Thereafter, the crystals are separated from the liquid and recovered. Typical reaction conditions consist of heating the foregoing reaction mixture to a temperature of from about 90"C. to about 400"C. for a period of time of from about 6 hours to about 100 days.

A more preferred temperature range is from about 150"C. to about 400"C. 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 230"F., 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 10000 F. for one hour, for example, followed by base exchange with ammonium salts followed by calcination at 10000F. 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 desirable to activate this type of catalyst by base exchange with ammonium salts followed by calcination in air at about 1000"F. for from 15 minutes to 24 hours.

Natural zeolites may sometimes be converted to this type of 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 clinoptilolite. The preferred crystalline aluminosilicate zeolites are ZSM-5, ZSM-l 1, ZSM-l2, ZSM-38 and ZSM-35, with ZSM-5 particularly preferred.

In a preferred aspect of this invention, the zeolites are selected as those having a crystal framework density, in the dry hydrogen form, of not substantially below 1.6 grams per cubic centimeter. Therefore, the preferred zeolites of this invention have not only a constraint index as defined above of 1 to about 12 and a silica to alumina ratio of at least 12 but also a dried crystal density of not less than 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 hydrocarbon products. 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, the entire contents of which are incorporated herein by reference, 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 framework density of not less than 1.6 grams per cubic centimeter. This high density, of course, must be associated with a relatively small amount of free space within the crystal, which might be expected to result in more stable structures. This free space, however, is important as 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 0.28 1.7 ZSM--5, --11 0.29 1.79 Dachiardite 0.32 1.72 L 0.32 1.61 Clinoptilolite 0.34 1.71 Laumontite 0.34 1.77 ZSM4 (Omega) 0.38 1.65 Heulandite 0.39 1.69 P 0.41 1.57 Offretite 0.40 1.55 Levynite 0.40 1.54 Erionite 0.35 1.51 Gmelinite 0.44 1.46 Chabazite 0.47 1.45 A 0.5 1.3 Y 0.48 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 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 earth metals.

In practising 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 occurring or in the form of gelatinous precipitates of 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 subbentonites 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 used in the raw state as originally mined or initially subjected to calcination, acid treatment 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, silicamagnesia, silica-zirconia, silica-thoria, silica-berylia, silica-titania as well as ternary compositions, such as silica-alumina-thoria, silica-alumina-zirconia, silica-aluminamagnesia and silica-magnesia-zirconia. The matrix may be in the form of a cogel.

The relative proportions of zeolite component and inorganic oxide gel matrix may vary widely with the zeolite content ranging from between I to 99 percent by weight and more usually in the range of 5 to 80 percent by weight of the composite.

The conversion 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 wherein 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 2 and 20, with hydrogen pressure extending from I atmosphere up to 100 atmospheres. 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 reference to selective production of para dimethyl substituted benzenes typified by para-xylene, it is contemplated that other para dialkyl substituted benzenes, wherein the alkyl group contains from I to 4 carbon atoms may similarly be selectively produced. Thus, utilizing the technique described herein, it is contemplated that with selection of suitable precursor, mixtures of ethylbenzenes and toluene may be selectively converted to para-ethyltoluene; likewise para-ethyltoluene is formed from dodecane or l-butene, in addition to para-xylene; ethylbenzene may be selectively converted to diethylbenzene, propylbenzene may be converted to dipropylbenzene, and butylbenzene may be selectively converted to dibutylbenzene.

The following examples will serve to illustrate the catalyst and process of the invention without limiting the same. In all Examples except those marked "Comparative" the zeolite meets the criteria of the invention claimed.

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 aluminium sulfate [Al2(SO4)3. 14H2O], 15.84 pounds of commercial grade NaCI and 3.52 pounds of H2SO4 (96.5 wt.% H2SO4) were mixed with 72.2 pounds 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-npropylamine and 2.44 pounds of n-propyl bromide were added to the contents of the autoclave. The mixture was reacted at 3200 F. with agitation. After twenty hours at 320"F., the autoclave contents were sampled and the solid product was found to be 100e, ZSM-5 by X-ray diffraction. After a total reaction time of 28.7 hours at 3200 F., the autoclave contents were cooled. The resulting solid product was washed by decantation with deionized water containing by weight 3500 ppm "Primafloc" C-7 (polyammonium bisulfate) until the decant water was chloridefree. The solid product was filtered and dried at 2500 F. "Primafloc" is a registered Trade Mark.

Five hundred (500) grams of the dried filter cake product were calcined in nitrogen for three hours at 10000 F. 444 grams of the calcined product were mixed with 2220 cc of I N NH4NO3 solution for one hour at ambient temperature. The mixture was vacuum filtered. The ion exchange procedure was repeated. The filter cake was washed with 1776 cc of water and the solid product was dried at 2500 F.

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 1200 C. 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 10220F. 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 hours at 6400 C., 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 or para-xylene per 100 grams of zeolite at 1200C. and a para-xylene pressure of 5.1 mm. of mercury. At 1200C. 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.

The catalyst which contained approximately 4 weight percent of coke was contacted with toluene at 5500 C., 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 80.7 weight percent toluene (19.3 weight 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 10000 F. 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 1200C. and a para-xylene pressure of 5.1 mm. of mercury. At 1200C. 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 5500 C., 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 (Comparative).

HZSM-5 having a crystalline size of about 0.03 micron was prepared as follows: a) Solution Preparation Silicate Solution 90.9 Ib. Q-Brand Sodium Silicate 52.6 Ib. H2O 118 g. Diaxad 27 Dispersant (sodium salt of polymerized substituted benzenoid alkylsulfonic acid combined with a suspending agent) Acid Solution 1430 g. Al2(SO4)3.xH2O (M.W.=595) 3400 g. H2SO4 4890 g. NaCI 54 lb. H2O Add'l Solids 2840 g. NaCI 2390 g. n-propyl bromide 4590 g. methylethyl ketone Add'l Liquid 1180 g. H2O 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 H2O had been previously added.

The gel was whipped by agitation and 2840 grams of NaCI 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 220"F without agitation and held there for 1415 hours to prereact the organics.

At the end of the prereaction period the agitation was commenced to start the initial crystallization period. After 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 Al203 2.21 1.0 SiO2 94.9 72.8 Na 0.81 Na2O 0.82 N 0.67 - 2.48 C 8.2 35.6 After thorough washing and drying at about 250"F the zeolite was transformed into the catalytic form by the following steps: a) Precalcination in a 100% N2 atmosphere for three hours at 1000"F, atmospheric pressure employing a programmed heat-up rate of 5 F/min to 10000F from ambient. b) Ion exchange with IN NH4NO3 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 2500F 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 1200C and a hydrocarbon partial pressure of about 3.8 mm. of mercury.

Example 7 (Comparative).

Toluene was passed over the microcrystalline HZSM-5 catalyst of Example 6 at 1 atmosphere pressure, 1112"F, and a weight hourly space velocity of 50. The toluene conversion was 15 weight percent and the p-xylene yield, as percent of xylenes, was 25 percent, i.e. approximately the normal equilibrium concentration of p-xylene.

Example 8.

Catalyst prepared as in Example 6 was combined with alumina to produce an extruded catalyst consisting 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 885-9700r, WHSV=5--6.3, pressure=450 psig and a hydrogen to hydrocarbon ratio of 0.5 for 38 days.

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 ano-xylene pressure of 3.8 mm of mercury. The catalyst had an alpha value of 20. Toluene was passed over the catalyst at 9700 F, 450 psig, WHSV=6.3 and a hydrogen to hydrocarbon ratio of 0.5.

The toluene conversion was 37 weight percent and thep-xylene yield, as percent of xylenes produced, 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 3"F per minute to 1000 F followed by 10 hours at 10000F. The resultant catalyst contained 2.4 weight percent magnesium. It sorbed 5.2 grams of p-xylene per 100 grams of zeolite at 120"C and a p-xylene pressure of 5.1 mm of mercury. At 1200C and 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.

Example 10.

Toluene was passed over the catalyst of Example 9 at 10220F 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 (Comparative).

A five gram sample of the HZSM-5 zeolite 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 1OC/minute to 538"C and held at this temperature for 6 hours.

The above procedure was repeated a total of three times to yield a silicaloaded HZSM-5 containing 5 weight percent of added silica.

This catalyst sorbed 4.1 grams of o-xylene per 100 grams of zeolite at 1200C 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.

Example 12 (Comparative).

Toluene was passed over the catalyst of Example 11 at 11 120 F, 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 of 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 ot 5.35 grams of orthoboric acid in 40 ml of water at a temperature of 80"C. After standing overnight (16.5 hours) at 900C the contents were poured into a 30 x 50 mm crystallizing dish and P!aced in an oven at 110"C. The contents were stirred frequently until a uniform dry powder was formed. The temperature was gradually increased to 2000C and the catalyst allowed to stand for 1-2 hours. It was then transferred to a furnace at 5000 C, 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 1420 mesh size (U.S. standard) for use.

The catalyst sorbed 3.1 grams of p-xylene at 1200C and ap-xylene pressure of 5.1 mm of mercury. At 120"C 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.

Example 14.

Toluene was passed over 5 grams of the catalyst of Example 13 at 11120 F, 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 1000C for 3 hours. It was then air calcined for 10 hours at 10000 F. The product contained 24 weight percent antimony.

The catalyst sorbed 3.5 grams of p-xylene per 100 grams of zeolite at 120"C and ap-xylene pressure of 5.1 mm of mercury. At 120"C 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 (Comparative).

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 73"C and allowed to stand overnight. The entire contents of the flask were then poured into a crystallizing dish and placed in oven at 1300C. 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 5000C and allowed to stand overnight. The final weight of the calcined catalyst was 12.17 grams. The catalyst had a xylene sorption capacity at 1200C 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 orthoxylene at 1 200C 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 (Comparative).

Toluene was passed over the catalyst of Example 16 at 10220F, 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 (Comparative).

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 oven 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 5000C overnight. The weight of the final catalyst was 11.56 grams. The catalyst had a xylene sorption capacity of 1200C and a xylene pressure of 4.5 + 0.8 mm mercury of 4.2 grams xylene per 100 grams of zeolite. The time to sorb ortho-xylene at 120"C 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 (Comparative).

Toluene was passed over the catalyst of Example 18 at 10220F, one atmosphere 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 90"C and allowed to stand overnight. The entire contents of the flask were then poured into a crystallizing dish and placed in an oven at about 130"C. After about 2 hours, the catalyst was placed in a furnace at 5000C and allowed to stand for about 8 hours. Final weight of the catalyst after calcination was 11.21 grams. The catalyst had a xylene sorption capacity of 120"C and a xylene pressure of 4.5 * 0.8 mm mercury of 4.9 grams of xylene per 100 grams of zeolite. The time to sorb orthoxylene at 120"C 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 10220F, 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.

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 88"C and allowed to stand overnight. The entire contents were then poured into a crystallizing dish and placed in an oven at 100--1300C. After about 4 hours the temperature was raised to 2000C for approximately 2 hours. The catalyst was then placed in a furnace at 5000C overnight. Final weight of the catalyst after calcination is 12.80 grams. The catalyst had a xylene sorption capacity, at 1200C 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 1200C 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 passed over the catalyst of Example 22 at 10220F, one atmosphere pressure; and a WHSV of 3.5. Toluene conversion was 0.4 weight percent and the p-xylene yield, as percent of xylenes, was 67.

Example 24.

10 grams of the ammonium 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 95 C and allowed to stand overnight.

The entire contents of the flask were then poured into a crystallizing dish and placed in an oven at 560C. The temperature was then turned up to 100--1200C.

The slurry was stirred frequently until the catalyst developed a dry appearance.

Temperature was then gradually raised to 2000C and held for about 1 hour. The catalyst was then placed in a furnace at 5000C overnight. The final weight of the catalyst was 11.37 grams. The catalyst had a xylene sorption capacity at 1200C and a xylene pressur eof 4.5 + 0.8 mm mercury of 4.4 grams of xylene per 100 grams of zeolite. The time to sorb ortho-xylene at 1200C 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 10220F, 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 WHSV = 2.6 at 4000 C. 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 Sb2O3 in a ratio of 0.43 g Sb2O3 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 1--18 mm diameter. A 46 mm thermowell was located in the catalyst bed. The catalyst was heated to 5250C during one hour in 50 cc/min flowing nitrogen, holding in nitrogen for three hours at 50C525 , followed by air (50 cc/min) for 0.5 hours. The resultant catalyst contained 30% Sb2O3 based on the weight of zeolite.

Example 28.

A sample of 30% Sb,OdHZSM--5, prepared according to Example 27 was placed in a vertical flow reactor; propylene was passed over the catalyst at 4000C at WHSV = 3.0. 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% Sb2O/HZSM-5 of Example 27 was used for selective toluene disproportionation. Toluene was passed over the catalyst in a vertical fixed-bed flow reactor at 550"C and atmospheric pressure at a WHSV = 1.0. 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 Sb2O3-ZSM-5 was prepared following the procedure of Example 27 except that 0.33 g Sb2O3 was used per gram of HZSM-5. The resultant catalyst contained nominally 25% Sb2O3.

Example 31.

The catalyst prepared in Example 30 was used in toluene disproportionation to benzene and xylene at atmospheric pressure, 550"C 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 1200C and a p-xylene pressure of 5.1 mm Hg. At 120"C and an o-xylene pressure of 3.8 mm Hg, the time for sorption of 30% of xylene capacity exceeded 300 minutes.

Example 32.

The catalyst of Example 1 was contacted with l-butene at 4000C. 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 ethyltoluene. The xylene fraction contained 37 percentp-xylene and the ethyltoluene fra and the same percent toluene conversion, e.g. 20%, by adjusting the toluene feed rate. Para-selectivity may be obtained for these reference 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 5500C) and ortho-xylene sorption times, to.3 (30% of capacity at 1200 C) are shown in the following table: TABLE III Ortho-Xylene Catalyst of Sorption time, Para-xylene Selectivitytt Example to.3 (min) Selectivityt Factor 6* < 1.3 24 0 11* 2.7 27 3.7 16* 4.8 25 1.3 18* 7.5 24 0 20 38 28 5.4 1 92 39 20 22 116 38 18 13 270 48 32 5 583 69 59 24 655 53 38 9 2600 45 28 8 2900 69 59 3 6000 80 73 * Comparative. t From toluene, 550"C, 20% toluene conversion.

24% p-xylene represents the equilibrium composition and hence no unusual selectivity.

%p-xylene in xylenes -24 ##Selectivity factor = # # 100 76 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 catalysts having a xylene sorption time for 30 percent of xylene sorption capacity of greater than 10 minutes are para-xylene selective.

Example 35.

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 aluminium sulfate (Al2(SO4)3 - 14 H2O)), 15.84 pounds of commercial grade NaCI, and 3.52 pounds of H2SO4 (96.06 wt. % H2SO4) were mixed with 72.2 pounds of water. The resulting solution was designated Solution B. Solution A and Solution B were mixed simultaneously 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 316"F with 121 rpm agitation. After 14.1 hours at 3160F, the solid product was analyzed by X-ray diffraction and found to be 100% ZSM-5, having a SiO2/Al2O3 ratio of 70.

A 10 gram sample of the above ZSM-5 was contacted with 500 ml. of 1 N NH4Cl solution. Three ion exchange steps were carried out, the first at 1000C for 2 hours, the second at room temperature for 18 hours and the third at 1000C for 3 hours. The exchanged product was thereafter calcined 1 C/minute to a temperature of 1000 F 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 measurements were made at 1200C. For the para-xylene sorption the hydrocarbon particl pressure was 5.1 mm of mercury. For ortho xylene sorption time the hydrocarbon partial pressure was 3.8 mm of mercury.

Example 36.

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 650 C 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: TABLE IV Xylenes* Run Time (hr) Temp. C WHSV Benzene Toluene p- m- o- Total C9+ Conversion 1 1.28 524 20 8.36 80.48 3.48 5.46 2.18 11.12 0 19.5 (31.29) (49.10) (19.60) 2 2.18 521 50 2.78 93.00 1.76 1.84 0.60 4.20 0 7.0 (34.76) (43.81) (14.29) 3 3.85 523 10 10.05 76.69 3.84 6.72 2.60 13.16 0 23.3 (29.18) (51.06) (19.76) 4 4.27 503 100 1.38 95.98 1.08 1.13 0.43 2.64 0 4.0 (40.91) (42.80) (16.29) 5 5.07 524 5 13.89 69.43 4.48 8.61 3.53 16.61 0 30.6 (26.94) (51.80) (21.26) 6 5.40 525 20 6.87 83.97 2.97 4.55 1.63 9.15 0 16.0 (32.47) (49.67) (17.85) 7 5.87 599 20 16.56 64.81 5.50 9.45 3.62 18.58 0 35.2 (29.63) (50.88) (19.51) 8 6.18 598 50 9.16 79.26 4.69 5.19 1.69 11.57 0 20.7 (40.56) (44.84) (14.60) 9 6.42 602 100 9.00 79.21 4.39 5.42 1.98 11.79 0 20.8 (37.25) (45.95) (16.79) 10 7.83 #400 5 0.62 97.41 0.50 1.00 0.41 1.91 0 2.6 (26.28) (52.49) (21.24) 11 23.02 398 5 0.59 97.48 0.48 0.98 0.48 1.92 0 2.5 (24.68) (50.65) (24.68) 12 23.92 401 10 0.35 98.17 0.41 0.81 0.26 1.48 0 1.8 (27.62) (54.63) (17.76) 13 24.70 524 20 3.97 90.38 2.03 2.64 0.98 5.65 0 9.6 (35.98) (46.77) (17.25) 14 25.50 651 20 18.15 64.18 5.13 8.93 3.61 17.7 0 35.8 (29.05) (50.54) (20.41) 15 25.72 650 50 7.04 84.17 3.32 3.70 1.42 8.4 0 15.8 (39.33) (43.87) (16.81) 16 25.87 648 100 4.56 89.26 2.28 2.81 1.10 6.18 0 10.8 (36.86) (45.37) (17.77) * The values in parenthesis are the weight percent of xylene isomer in the total xylene fraction.

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 6500C served to increase para-xylene selectivity substantially.

Example 37 (Comparative).

HZSM-5 having a crystallite size of about 0.03 micron was prepared as follows: a) Solution Preparation Silicate Solution 90.9 Ib. Q-Brand Sodium Silicate 52.6 lb. H2O 118 g. Daxad 27 (dispersant) Acid Solution 1430 g. Al2(SO4)3 - xH2O (M.W. = 595) 3440 g. H2SO4 4890 g. NaCI 54 lb. H2O Add'l Solids 2840 g. NaCI 2390 g. n-propyl bromide 4590 g. MEK Add'l Liquid 11.80 g. H2O 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 H2O had been previously added. The gel was whipped by agitation and 2840 grams of NaCI 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 2200F without agitation and held there for 1415 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 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 based upon a standard sample. Chemical analysis of the thoroughly washed crystalline product was: % Wt. Mole Ratio Al203 2.21 1.0 SiO2 94.9 72.8 Na 0.81 Na2O 0.82 N 0.67 2.48 C 8.2 35.6 After thorough washing and drying at about 250 F the zeolite was transformed into the catalytic form by the following steps: a) Precalcination in a 100% N2 atmosphere for three hours at 1000 F, atmospheric pressure employing a programmed heat-up rate of 5 F/min to 1000 F from ambient. b) Ion exchange with 1N NH4NO3 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 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 120 C and a hydrocarbon partial pressure of about 3.8 mm. of mercury.

Example 38 (Comparative).

Toluene was passed over the microcrystalline HZSM-5 catalyst of Example 37 at 1 atmosphere pressure and at temperatures of 600-650 C 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: TABLE 5 Xylenes* Run No. Time (hr) Temp. C WHSV Benzene Toluene p@ m@ o@ Total C9+ Conversion 1 1.0 600 50 7.26 84.85 1.97 4.12 1.80 7.89 0.0 15.2 (25.0) (52.2) (22.8) 2 1.5 600 100 3.86 92.00 1.13 2.12 0.89 4.15 0.0 8.0 (27.2) (51.2) (21.5) 3 2.28 650 100 5.18 89.61 1.55 2.65 1.00 5.20 0.0 10.4 (29.8) (51.0) (19.2) * The values in parenthesis are the weight percent of xylene isomer in the total xylene fraction.

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 conversion, use of the large crystals showed a 48 percent para-xylene selectivity as compared with 27 percent paraxylene selectivity with use of the small crystals.

Example 39.

A sample of the large crystal HZSM-5 catalyst of Example 35 was steamed for 2 hours at 5600C in one atmosphere steam.

Example 40.

Toluene was passed over the large crystal HZSM-5 catalyst of Example 39 at I atmosphere pressure and at a temperature of approximately 6500C at a weight hourly space velocity of 20. The reaction conditions and results are set forth in Table 6 below: TABLE 6 Xylenes* Time (hr) Temp. C WHSV Benzene Toluene p- m- o- Total C9+ Conversion 0.58 650 20 8.82 81.83 4.36 3.76 1.22 9.34 0.0 18.2 (46.6) (40.2) (13.1) 1.0 650 20 7.33 84.54 4.25 2.98 0.89 8.13 0.0 15.5 (52.3) (36.7) (11.0) 1.72 650 20 6.62 86.43 3.94 2.30 0.71 6.95 0.0 13.6 (56.7) (33.2) (10.2) 2.33 650 20 5.96 87.82 4.00 1.72 0.50 6.22 0.0 12.2 (64.3) (27.7) (8.0) 3.0 650 20 5.31 88.90 4.24 1.23 0.32 5.79 0.0 11.1 (73.2) (21.3) (5.6) 3.75 649 20 4.85 90.07 4.29 0.61 0.18 5.08 0.0 9.0 (84.4) (12.0) (3.6 5.0 649 20 3.38 93.08 3.47 0.7 0.0 3.54 0.0 6.9 (98.1) (1.9) (0.0) 6.0 649 20 1.45 97.24 1.31 0.0 0.0 1.31 0.0 2.8 (100) (0.0) (0.0) * The values in parenthesis are the weight percent of xylene isomer in the total xylene fraction It will again be evident that with the use of large crystal HZSM-5 the amount of para-xylene produced was substantially greater then its equilibrium concentration, approaching 100 percent after 5-6 hours on stream.

Example 41.

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 650 C at a weight hourly space velocity of 10. The reaction conditions and results are set forth in Table 7 below: TABLE 7 Xylenes* Time (hr) Temp. C WHSV Benzene Toluene p- m- o- Total C9+ Conversion 0.25 649 10 6.32 84.82 4.26 3.51 1.08 8.85 0.0 15.2 (48.2) (39.7) (12.2) 1.00 650 10 6.78 85.34 3.93 3.04 0.92 7.88 0.0 14.7 (49.9) (38.5) (11.6) 2.00 650 10 6.75 85.35 3.94 3.02 0.93 7.89 0.0 14.6 (49.9) (38.3) (11.8) 4.08 650 10 6.80 85.86 3.69 2.82 0.83 7.34 0.0 14.1 (50.2) (38.4) (11.4) 6.00 650 10 6.49 85.97 3.90 2.78 0.87 7.54 0.0 14.0 (51.7) (36.8) (11.5) 8.00 650 10 6.10 86.41 3.97 2.67 0.84 7.48 0.0 12.6 (53.1) (35.7) (11.2) * The values in parenthesis are the weight percent of xylene isomer in the total zylene fraction.

Comparing the results of 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.

Example 42.

Toluene was passed over a sample of the large crystal HZSM-5 catalyst of Example 39 at about 625 C. 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 conversion 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 paraxylene selectivity were 21 percent and 82 percent respectively.

The changes in toluene conversion and para-xylene selectivity occurring 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.

Example 43.

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 to 10 microns polycrystalline spheroids for 5 hours at 1000"F. in air followed by three ion exchanges, at room temperature, with 500 ml. of 1 N NH4Cl solution for 15.3 hours, 3.8 hours and 3.0 hours respectively. This material was then air calcined for 10 hours at 10000F. 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 1200C. 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.

Toluene was passed over the catalyst of Example 43 at 6000 C. at a weight hourly space velocity of 50 and one atmosphere pressure. Toluene conversion was 10.6 weight percent. 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.

Example 44.

42.2 pounds of Q-Brand sodium silicate were mixed with 52.8 pounds of water.

The resulting solution is designated Solution A. 1.35 pounds of commercial grade aluminium sulfate (Al2(SO4)3. 14H2O), 15.84 pounds of commercial grade NaCI, and 3.52 pounds of H2SO4 (96.5 wt % H2SO4) 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 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 3200F with 90 RPM agitation. After twenty hours at 3200 F, 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 3200 F, the autoclave contents were cooled. The resulting solid product was washed by decantation with deionized water and 3500 ppm Primafloc C-7 (Rohm & Haas) until the decant water was Cl- free. The solid product was filtered and dried at 2500 C.

500 grams of the dried filter cake product were calcined in N2 for three hours at 1000 F.

444 grams of the calcined product were mixed with 2220 cc of 1 N NH4NO3 solution for one hour at ambient temperature. The mixture was vacuum filtered.

The ion exchange procedure was repeated. The filter cake was washed with 1776 cc of water and the solid product was dried at 2500 F. The sodium content of the final product was less than 0.01%.

The resulting catalyst had a crystal size of 1-2 microns, 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 1200C.

For the para-xylene sorption the hydrocarbon partial presure was 5.1 mm of mercury. For ortho xylene sorption time the hydrocarbon partial pressure was 3.8 mm of mercury.

Example 45.

The catalyst of Example 44 was contacted with l-butene at 4000C. 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 ethyltoluene. The xylene fraction contained 37 percentp-xylene and the ethyltoluene fraction was 43 percent para-ethyltoluene. Equilibrium values of these para isomers are 24 and 32 percent respectively.

Example 46.

The catalyst of Example 44 was contacted with dodecane at 4000 C. 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 ethyltoluene fraction was 58 percent para-ethyltoluene.

Example 47.

The catalyst of Example 44 was contacted with toluene at 5500C., 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 toluene consisted of 12.1 weight percent xylenes in additon 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 6400 C. at a weight hourly space velocity of 50 and one atmosphere pressure. After this tretment, the catalyst found to contain approximately 4 weight percent of coke was contacted with toluene at 5500C., 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 80.7 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 49.

Three grams of the catalyst of Example 44 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 10000 F. 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 5500 C., 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 15.03 weight percent xylene, which consisted of 53 percent of the para isomer.

Example 51.

This example illustrates the production of p-diethylbenzene with catalyst of Example 44 pretreated with toluene as in Example 48 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--850"F, a pressure of 300 psig and a WHSV of 2, based on lb. ethylene per our per lb. catalyst. The reactor effluent is distilled to yield an overhead fraction (recycle steam) consisting of benzene, ethylbenzene and unreacted ethylene which is recycled to the reactor and a bottom fraction containing the desired product, p-diethylbenzene.

Example 52.

A five gram sample of HZSM-5 of 0.02--0.05 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 5 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 1OC./minute to 5380C. and held at this temperature for 6 hours.

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 0.02--0.05 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 600"C. 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 1 C/minute to 538 C. 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 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 1 C./minute to 5380C. 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 mixture was evaporated over 1/2 hour using a rotary evaporator. The residue was calcined in air at 1 C./minute to 538 C. 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 nhexane was added 4 grams NH4ZSM-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 1 C./minute to 538 C. 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 1430 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 55(6000C. at weight hourly space velocities of 8-22. Results are summarized in Table 8 below.

TABLE 8 p-Xylene Toluene in Xylenes Conversion Weight Hourly Catalyst Wt. % Wt. % Space Velocity Temp., OC.

Unmodified 33 20 20 550 HZSM-5 Fresh 65 7 22 550 SiO2/HZSM-S 56 12 11 550 46 20 8 550 Regenerated 71 7 22 550 SiO2/HZSM-5 61 12 11 550 49 20 8 550 79 12 22 600 67 20 11 600 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 regeneration of the catalyst by burning carbonaceous deposit therefrom in air at 5400 C.

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 disproportionation at atmospheric pressure and with flowing hydrogen, utilizing a hydrogen to hydrocarbon mole ratio of 2. Reaction was carried out at a temperature of 550"C. at weight hourly space velocities of 6-25. Results are summarized in Table 9 below.

TABLE 9 ThXyl ene Toluene in Xylenes, Conversion Weight Hourly Catalyst Wt. % Wt. % Space Velocity Temp., OC.

Unmodified 33 20 20 550 HZSM-5 Fresh 92 7 25 550 SiO2/HZSN-S 90 12 13 550 84 20 6 550 Regenerated 94 6 25 550 SiO2/HZSM-5 92 10 13 550 86 16 6 550 It will be evident from the foregoing results that the silica modified HZSM-5 catalyst is fully regenerable (in air at 5400C.) 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 of Example 55, but containing 1.9 weight percent silica was tested toluene disproportionation 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 5500C. at weight hourly space velocities of 5-20. Results are summarized in Table 10 below.

TABLE 10 pxylene Toluene in xylenes, Conversion, Weight Hourly Wt. % Wt. % Space Velocity Temp., OC.

78 7 20 550 68 12 10 550 54 19 5 550 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.

TABLE 11 mxylene Toluene in xylenes, Conversion, Weight Hourly Wt. % Wt. % Space Velocity Temp., OC.

80 11 20 550 66 20 10 550 53 28 5 550 Example 62.

Toluene disproportionation was carried out with a sample of a silica-mofified HZSM-5 catalyst prepared as in Example 54. Reaction was conducted at 500"C. 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 prepared as in Example 55. The toluene to methanol mole ratio was 4 utilizing a pelleted catalyst, sized to 1430 mesh. The reaction was carried out at a temperature of 400 550 C. 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.

TABLE 12 pxylene Toluene in xylenes, Conversion, Weight Hourly Wt. % Wt. % Space Velocity Temp., OC.

88 84 10 550 91 60 10 500 94 44 10 450 95 36 10 400 Example 64.

ZSM-5 crystals were obtained using the following reactants: Silicate Solution 42.2 lb. Q-Band Sodium Silicate (Na2O/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 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 315"F. with agitation. The reaction mixture was held at 3150F. 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: Al203 1.0 SiO2 74.4 Na2O 0.31 N 2.26 C 21.9 The ZSM-5 so prepared was precalculated in air at 3700C and thereafter ammonium exchanged by contacting twice with 5N NH4Cl solution at l000C (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 1OC/minute to 5380C and then held at 5380C 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 5500C and a weight hourly space velocity of 5 weight of charge/weight of cataylst/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 5500C overnight.

Alkylation 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 4900C 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 Examples 64, the catalyst was regenerated in air at 550"C for 16 hours. Alkylation 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 490"C and a weight hourly space velocity of 18 weight of charge/weight of catalyst/hour. Toluene conversion 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 550"C 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 Awl203 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 550"C 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 86 (Comparative).

Over a fixed bed of extrudate catalyst containing 35 weight percent alumina and 65 weight percent HZSM-5, prepared as in Example 1 of U.S. Patent 3,751,506, a feed of toluene was contacted with methyl alcohol in the mole ratio of toluene to methyl alcohol of 2:1. The reactor inlet temperature was 870 F. and the reactor pressure was maintained at atmosphere. The total feed weight hourly space velocity was 4. The composition of the liquid product was as follows: Wt. percent Component Total product Toluene 59.6 Xylenes 29.7 Para/Total Xylenes 24.5 Meta/Total Xylenes 52.6 Ortho/Total Xylenes 22.9 Benzene 3.2 C9 6.2 C9+ 1.1 Others 0.2 Percent Coke on Cata lyst After the Run 3.6 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 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 composition of the liquid product was as follows: Example 69 70 71 Percent Coke on Catalyst 30 26 27 Toluene 72.9 72.4 72.8 Xylenes 20.7 20.6 19.8 Para/Total Xylenes 37.8 30.0 30.7 Meta/Total Xylenes 42.3 48.6 48.1 Ortho/Total Xylenes 19.9 21.4 21.2 Benzene 0.2 0.5 0.4 C9 5.6 5.9 6.4 C9+ 0.5 0.5 0.5 Others 0.1 0.1 0.1 From the above results, it will be seen that with deposition of coke on the catalyst in the range of this Example, the proportion of para-xylene produced was greater than that present in the equilibrium mixture, i.e. para-xylene was selectively produced.

Examples 72-80.

An HZSM-5 catalyst prepared as in Example 64 was employed for methylation of toluene using a 2:1 mole ratio of toluene to methyl alcohol. The reactor inlet temperature was 870 F., 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 catalyst as indicated. The composition of the liquid products obtained in each instance are shown below in Table 13: TABLE 13 Example 72c 73c 74 75 76 77 78** 79** 80** Percent Coke on Catalyst 3.0* 8.1 15 16 20 23 23 27 24 Liquid Products Benzene 4.2 0.7 0.5 0.5 0.4 0.4 0.3 0.3 0.3 Toluene 60.5 70.0 71.7 73.2 75.9 80.1 72.2 74.1 74.0 Xylenes 28.2 21.1 20.3 19.5 17.0 14.7 20.6 19.7 19.4 para/Total Xylenes 24.2 24.3 24.7 25.0 33.9 41.2 27.1 30.9 32.4 meta/Total xylenes 52.8 52.6 52.2 52.0 45.0 39.6 50.4 47.7 46.8 ortho/Total Xylenes 23.0 23.1 23.1 23.0 21.1 19.1 22.5 21.4 20.7 C9 5.6 7.5 6.5 6.2 6.2 4.1 6.2 5.5 5.8 C9+ 1.2 0.6 0.8 0.4 0.3 0.6 0.5 0.4 0.4 Others 0.3 0.1 0.1 0.1 0.2 0.1 0.1 0.1 0.1 * Percent Coke After the Run ** Catalyst Used Was 1/8" Pellets c Comparative 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 (Comparative).

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: A sodium silicate solution was prepared by mixing 8440 lb. of sodium silicate (Q Brand - 28.9 weight percent SiO2, 8.9 weight percent Na2O and 62.2 weight percent H2O) 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 550 F. An acid alum solution was prepared by dissolving 305 lb. aluminum sulfate (17.2 Awl203), 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 autoclave. 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 2000F. in the closed vessel.

After reducing agitation, an organic solution 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 200210 F.

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 diffraction. Temperature was then increased to 3200 F. 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 flocculant of polyammonium bisulfate. The washed product containing 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 monohydrate and water (65% zeolite, 35% alumina binder on ignited basis) then extruded to form of 1/16 inch pellet with particle density < 0.98 gram/cc and crush strength of > 20 Ib./linear inch.

After drying, the extruded pellets were calcined in nitrogen U()(1000 SCFM) for 3 hours at 1000"F., 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 approximately 800 gallons of deionized water). The exchange was repreated 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 (1012.5% air 987.5% nitrogen) for 6 hours at 10000 F. 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 450"C. and 600"C. The conditions and results are summarized in Table 14 below.

TABLE 14 Selectivity, % % Para in Tol. Conv.

Temp., OC WHSV Mole % Benzene Xylenes Xylene Product 450 3.6 7.4 43.5 55.5 24.7 500 3.5 20.5 44.6 53.8 24.5 550 3.5 38.8 48.0 48.8 24.2 600 3.5 49.2 54.4 41.7 24.1 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 concentration of approximately 24 weight percent of the xylene fraction.

Example 82.

To a solution of 8 grams of 85% H3P04 in 10 ml. of water was added 10 grams of HZSM-5 extrudate which was permitted to stand at room temperature overnight. After filtration and drying at 1200C. for 3 hours, it was calcined at 500"C. for 3 hours to give 11.5 grams of phosphorus-modified to ZSM-5.

Ten grams of the above phosphorus-modified ZSM-5 was then added to a solution of 25 grams of magnesium acetate tetrahydrate in 20 ml. of water which was permitted to stand at room temperature overnight. After filtration and drying at 120"C., it was calcined at 5000C. for 3 hours to give 10.6 grams of magnesiumphosphorus-modified ZSM-5. Analysis showed the modifier 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 6000C. Conversion of toluene was 24 percent and the concentration of para-xylene in total xylenes was 98.2 percent.

Example 84.

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 550"C. Conversion of toluene was 32.5 percent and the concentration of para-xylene in total xylenes was 91.2 percent.

Example 85.

The preparation of Example 82 was repeated except that 7 grams of 85% H3PO4 was used. The final catalyst amounted to 10.9 grams. Analysis showed the modifier concentrations to be 7.4 weight percent phosphorus and 4.2 weight percent 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 6000C. 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. Toluene Concentration In OC WHSV Conversion Total Xylenes 500 0.5 32 85 400 0.16 21.9 90.6 300 0.08 8 88.2 250 0.08 4.3 92.8 200 0.08 2.2 95.7 Example 87.

To a solution of 3 grams of 85% H3PO4 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 1300C. with occasional stirring and then dried at 200"C. for 2 hours. After calcination at 5000C., 11.2 grams were obtained. Analysis showed the phosphorus content to be 7.5 weight percent.

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 2000 C. It was then calcined at 5000 C. 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 6000C. Conversion of toluene was 18.2 percent and the concentration of para-xylene in total xylenes was 85.5 percent.

Example 89.

Toluene was passed over 5 grams of the catalyst of Example 87 at a weight hourly space velocity of 0.4 at 5500 C. 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 magnesiumphosphorus-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 6000C. 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 5500 C. 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 paraisomer were obtained in the xylene product utilizing the modified zeolite catalyst described herein. Unmodified catalyst under the same reaction conditions specified for the preceding examples gave para-xylene at an equilibrium ratio of 24 percent.

Claims

WHAT WE CLAIM IS:

1. A catalyst composition comprising a crystalline aluminosilicate zeolite having an acitivity, alpha, of 2 to 5000, a xylene sorption capacity greater than 1 g/100 g. zeolite, 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, and a SiO/JAI203 ratio of 12 to 3000 and a constraint index in the range 1 to 12.

2. 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.

3. A catalyst according to Claim 2, wherein the crystal size of the zeolite is in the range 1 to 6 microns.

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

5. A catalyst according to Claim 4, wherein the quantity of coke is 20 to 40 percent of the weight of uncoked catalyst.

6. A catalyst according any of Claims I to 3, 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 one or more difficulty reducible oxides.

7. A catalyst according to Claim 6, wherein said oxide comprises an oxide of antimony, phosphorus, boron, uranium, magnesium, zinc and/or calcium.

8. A catalyst according to Claim 6 or Claim 7 wherein the zeolite is associated with 0.25 to 25 weight percent of an oxide of phosphorus and of an oxide of magnesium.

.

9. A catalyst according to Claim 8 wherein the weight percentage of phosphorus oxide is between 0.7 and 15, that of magnesium oxide between 1 and 15.

10. A catalyst according any of Claims I to 3 wherein the interior crystalline structure of the zeolite contains from 0.1 to 10 percent, of the weight of the zeolite, of added amorphous silica.

11. A catalyst according to Claim 10 wherein the weight percentage of said silica is 2 to 10.

12. A catalyst according to Claim 10 or Claim 11 wherein said silica is the product of decomposition of a silicon compound capable of entering the pores of the zeolite.

13. A catalyst according to Claim 12 wherein said silicon compound is a silicone/siloxane or polysilane or a mono-methyl, -chloro or -fluoro derivative thereof.

14. A catalyst according to Claim 12 wherein said silicon compound has the formula SiR,R2R3R4, in which R, 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.

15. A catalyst according to Claim 12 wherein said silicon compound is silane, dimethylsilane, dichlorosilane, methylsilane or silicon tetrafluoride.

16. A catalyst according any of Claims 1 to 3 wherein 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.

17. A catalyst according to Claim 16 wherein said silica is the product of decomposition of-a silicone compound incapable of entering the pores of the zeolite.

18. A catalyst according to Claim 17 wherein the silicone compound has the formula 4(R,) (R2) SiOv, in which R, and R2 represent fluorine, hydroxy, alkyl, aralkyl, alkaryl or fluoroalkyl, may be the same or different except for the fact that R, (only) may be hydrogen, n being 10 to 1000, the number of carbon atoms in R, or R2 being from 1 to 10.

19. A catalyst according to Claim 17 or Claim 18 wherein the silicone compound has a molecular weight of 500 to 20,000, preferably 1000 to 10,000.

20. A catalyst according any of Claims 17 to 19 wherein said silicone, compound is diethylsilicone, phenylmethylsilicone, methylhydrogensilicone, ethylhydrogensilicone, phenylhydrogensilicone, methylethylsilicone, phenylethylsilicone, diphenylsilicone, methyltrifluoropropylsilicone, ethyltriflouropropylsilicone, polydimethylsilicone, tetrachlorophenylmethyl silicone, tetrachlorophenylethyl silicone, tetrachlorophenylhydrogen silicone, tetrachlorophenylphenyl silicone, methylvinylsilicone and ethylvinylsilicone.

21. A catalyst according to any preceding claim in which the zeolite is zeolite ZSM-5, ZSM-l 1, ZSM-12, ZSM-35 or ZSM-38.

22. A catalyst according to any preceding claim wherein the zeolite possesses hydrogen cations.

23. A catalyst according to any preceding claim wherein the zeolite has an activity, alpha, in the range 5 to 200.

24. A catalyst according to any preceding claim which comprises a composite of a zeolite as aforesaid with a binder.

25. A catalyst according to Claim 24 wherein the binder comprises a naturallyoccurring or synthetic refractory oxide.

26. A catalyst according to Claim 25 wherein the naturally-occurring oxide is a montmorillonite or kaolin clay and the synthetic oxide is silica, alumina, magnesia, zirconia, thoria, beryllia and/or titania.

27. A catalyst according any of Claims 24 to 26 of which the binder comprises 1 to 99 weight percent.

28. A catalyst according to Claim 27 of which the binder comprises 30 to 40 weight percent.

29. A process for selectively producing para-dialkylbenzenes in which each alkyl group contains 1 to 4 carbon atoms which comprises contacting a C1-C4 monoalkylbenzene, 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 any of Claims 1 to 28.

30. A process according to Claim 29 wherein said conversion conditions comprise a temperature of 250 to 7500C, a pressure between 0.1 atmosphere and 100 atmospheres and a weight hourly space velocity between 0.1 and 2000.

31. A process according to Claim 30 wherein the temperature is 400 to 7000C, the pressure is 1 to 100 atmospheres and the space velocity is 0.1 to 100.

32. A process according to any of Claims 29 to 31 wherein toluene is disproportionated.

33. A process according to any of Claims 29 to 31 wherein toluene is alkylated with an alkylating agent having from I to 4 carbon atoms.

34. A process according to Claim 32 or 33 wherein the space velocity is I to 50.

35. A process according to any of Claims 29 to 31 wherein one or more C3-C44 paraffins is contacted with said catalyst.

36. A process according to Claim 29 or Claim 30 wherein the temperature is 300 to 7000C, the pressure is 1 to 100 atmospheres and the space velocity is I to 1000.

37. A process according to Claim 36 wherein one or more C3-C15 olefins is contacted with said catalyst.

38. A process according to any of Claims 29 to 37 wherein the paradialkyl substituted benzene is p-xylene, p-diethylbenzene or p-ethyltoluene.

39. A process according to any of Claims 29 to 38 which is conducted in the presence of hydrogen.

40. A process according to Claim 39 wherein the mole ratio of hydrogen to hydrocarbon feed is from 2 to 20.

41. A process according to Claim 29 substantially as described in the foregoing Examples.