GB1585507A - Catalyst and process for conversion of hydrocarbons - Google Patents

Description

PATENT SPECIFICATION

L ( 21) Application No 42599/79 ( 22) Filed 25 April 1977 ( 62) Divided out of No 1 585 505 ( 31) Convention Application No 681 657 ok ( 32) Filed 29 April 1976 el' ( 31) Convention Application No 699 005 _ 1 ( 32) Filed 21 June 1976 in ( 33) United States of America (US) ( 44) Complete Specification published 4 March 1981 ( 51) INT CL 3 B Ol D 53/36; BO 1 J 21/20, 29/38 ( 52) Index at acceptance Bl E 1121 1122 1124 1125 1193 1203 1205 1206 1207 1213 1285 1315 1611 1617 1631 1701 1705 1714 1723 1738 1739 1811 1812 G ( 54) CATALYST AND PROCESS FOR CONVERSION OF HYDROCARBONS ( 71) We, ATLANTIC RICHFIELD

COMPANY, a Corporation organised and existing under the laws of the State of Pennsylvania, United States of America, of Arco Plaza, 515 Flower Street, Los Angeles, California, 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 and by the following statement: -

This invention relates to the conversion of hydrocarbons and more particularly to the chemical conversion of hydrocarbon promoted by catalyst which is periodically regenerated to remove carbonaceous deposits.

The terms "hydrocarbon conversion" and "hydrocarbon chemical conversion" as used herein, in general, refer to those chemical reactions for improving the octane number of gasoline or converting heavy hydrocarbons to light, low boiling hydrocarbons, or converting one or more hydrocarbons to one or more different hydrocarbon products Hence, among those reactions included in such terms are isomerization, cracking, polymerization, alkylation, dealkylation, disproportionation and the like Each of these "hydrocarbon conversions" is preferably carried out in the substantial absence of added free molecular hydrogen.

Each such "hydrocarbon conversion" is often carried out commercially by contacting a hydrocarbon feedstock in a reaction zone with solid particles of catalytic material at conditions at which the desired hydrocarbon chemical conversion takes place However, such conditions also allow formation of carbonaceous material, such as coke, which deposits on the catalyst These deposits are periodically removed as they tend to inactivate the catalyst.

The catalyst may be regenerated by burning or combusting at least a portion of such carbonaceous deposit material from the catalyst in a regeneration zone in the presence of free oxygen.

Fresh hydrocarbon feedstocks, e g petroleum derived gas oils, often contain sulfur as a contaminant, e g in an amount of 0 01 % to % or more and generally in an amount of 0.1 to 3 % by weight The carbonaceous deposits formed on the catalyst during the conversion of such sulfur-containing hydrocarbon feedstocks will also contain sulfur and during the above-described regeneration of the catalyst by contact with an oxygen-containing gaseous stream, at least a portion of this sulfur is oxidised and, ordinarily, leaves the system with the combustion flue gases.

The present invention provides a means whereby the sulfur oxide emissions from the regenerator zone flue gases may be reduced.

Thus, in acordance with one aspect of the present invention, there is provided a process for converting a sulfur-containing hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles capable of promoting the conversion of said feedstock at hydrocarbon conversion conditions to produce at least one hydrocarbon product and to cause deactivating sulfur-containing carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; ( 2) contacting said deposit-containing particles in at least one regeneration zone with an oxygen-containing vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a portion of the hydrocarbon conversion catalytic activity of said solid particles and to form a regeneration zone flue gas containing at least one sulfur-containing carbonaceous deposit material combustion product; and ( 3) repeating steps ( 1) and ( 2) periodically, and in which the amount of sulfur in said regeneration zone flue gas is ( 11) 1 585 507 2,8,0 reduced by circulating said solid particles between said reaction zone and said regeneration zone in intimate admixture with a minor amount of discrete entities which comprise a major amount by weight of support and a minor, catalytically effective, amount by weight of at least one metal-containing component disposed, preferably substantially uniformly disposed, on the support, the metalcontaining component being capable of promoting the oxidation of carbon monoxide to carbon dioxide at carbon oxidising conditions, said discrete entities also being more attrition resistant than the solid particles and capable of promoting the oxidation of sulfur dioxide to sulfur trioxide at the conditions of step ( 2), associating with sulfur trioxide at the conditions of step ( 2) and disassociating from sulfur trioxide at the conditions of step ( 1), thereby associating at least a portion of said sulfur-containing combustion product with said discrete entities in said regeneration zone and disassociating at least a portion of said sulfur-containing combustion product from said discrete entities in said reaction zone to form H 2 S which exits said reaction zone with said hydrocarbon product.

Suitable metals for inclusion in the metalcontaining components are selected from the group consisting of Group IB, IIB, VIB, VIIB, and VIII of the Periodic Table, vanadium and mixtures thereof Platinum group metal components which are also capable of promoting the oxidation of sulfur dioxide to sulfur trioxide in the regeneration zone; i e under the conditions of step ( 2), provide preferred examples of metal-containing components.

Aluminas are examples of support materials which are capable of associating with sulfur trioxide at the conditions of step ( 2) and disassociating from sulfur trioxide at the conditions of step ( 1).

Thus, according to another aspect of the invention, there is provided a process for converting a sulfur-containing hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles capable of promoting the conversion of said feedstock at hydrocarbon conversion conditions to produce at least one hydrocarbon product and to cause deactivating sulfur-containing carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; ( 2) contacting said deposit-containing particles in at least one regeneration zone with an oxygen-containing vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a portion of the hydrocarbon conversion catalytic activity of said solid particles and to form a regeneration zone flue gas containing at least one sulfur-containing carbonaceous deposit material combustion product; and ( 3) repeating steps ( 1) and ( 2) periodically, and in which the amount of sulfur in said regeneration zone flue gas is reduced by circulating said solid particles between said reaction zone and said regeneration zone in intimate admixture with a minor 70 amount of discrete entities whose composition differs from that of the solid particles and which comprise alumina and a catalytically effective amount of at least one platinum group metal component disposed on the alu 75 mina, said discrete entities being capable of associating with sulfur trioxide at the conditions of step ( 2) and capable of disassociating from sulfur trioxide at the conditions of step ( 1), thereby associating at least a portion 80 of said sulfur-containing combustion product with said discrete entities in said regeneration zone and disassociating at least a portion of said sulfur-containing combustion product from said discrete entities in said reaction zone 85 to form HS which exits said reaction zone with said hydrocarbon product The said discrete entities are preferably more attrition resistant than are the solid particles.

By "attrition resistant" or "attrition resist 90 ance" is meant the measure of a material's ability to resist the formation of fines by physical breakage, abrasion and the like Such discrete entities thus have a reduced tendency to produce fines relative to the solid particles 95 of the present catalyst system.

In one preferred embodiment, the discrete entities comprise a major amount by weight of alumina and a minor, catalytically effective, amount of at least one platinum group metal 100 component disposed on the alumina, this metal component being capable of promoting also the oxidation of carbon monoxide to carbon dioxide at carbon monoxide oxidising conditions The platinum group metals include 105 platinum, palladium, osmium, iridium, ruthenium, and rhodium The preferred platinum group metals are palladium and platinum, most preferably platinum The preferred relative amounts of the solid particles and discrete 110 entities are 80 to 99 parts and 1 part to 20 parts by weight, respectively This catalyst system is especially effective for the catalytic cracking of a hydrocarbon feedstock to lighter, lower boiling products and has improved car 115 bon monoxide oxidation catalytic activity stability.

Typical of reactor-regenerator arrangements having circulating catalyst bed systems are the conventional moving bed reactor-regenerator 120 system and the fluidized catalyst bed reactorregenerator system Both of these circulating bed systems are conventionally used in hydrocarbon conversion, e g hydrocarbon cracking, operations 125 The catalyst system used in the process of the present invention comprises a mixture of two types of solid particles The form, i e.

particle size, of the present catalyst, e g both solid particles and discrete entities, is not 130 1,585,507 1,585,507 3 critical provided it is such that the catalyst can be circulated between the reaction zone and the regeneration zone, and may vary depending, for example, on the type of reactionregeneration system employed Such catalyst particles may be formed into any desired shape such as pills, cakes, extrudates, powders, granules and spheres using conventional methods For example, spherical particles having a diameter of 0 03 inch to 0 25 inch, preferably 0 03 inch to 0 15 inch, are often useful in moving catalyst bed operations With regard to fluidized catalyst bed systems, it is preferred that the major amount by weight of the present catalyst particles have a diameter in the range of 10 microns to 250 microns, more preferably 20 microns to 150 microns.

The first solid particles are capable of promoting the desired hydrocarbon conversion and are substantially free of added platinum group metal components.

The second solid particles, i e, discrete entities, suitably comprise (A) a major amount, i.e, at least 50 % by weight, of a support, e g.

alumina, and (B) a minor amount of at least one metal, preferably a platinum group metal, component disposed on the support and capable of promoting the conversion of carbon monoxide to carbon dioxide at carbon monoxide oxidizing conditions, e g, conditions existing during contacting the deposit-containing first solid particles with an oxygencontaining gaseous medium to combust at least a portion of the carbonaceous deposit material from the first solid particles.

The discrete entities utilized in the present invention may conveniently comprise a major amount of alumina and a minor amount of at least one metal, preferably a platinum group metal component disposed on the support and present in an amount sufficient to promote the oxidation of carbon monoxide to carbon dioxide It is preferred that the discrete entities comprise a major amount of alumina having a surface area of from 25 m 2/g to 600 m 2 g or more The alumina comprises preferably at least 70 %, and more preferably at least 90 %, by weight of the discrete entities Suitable aluminas for use in the discrete entities are those aluminas derived from hydrous alumina predominating in alumina trihydrate, alumina monohydrate, amorphous hydrous alumina and mixtures thereof Alumina in the form of chi-, gamma-, delta-, eta-, kappa-, and thetaalumina is preferred, while gamma-and etaalumina are more preferred Minor, substantially non-interfering proportions of other well known refractory materials, e g, inorganic oxides such as silica, zirconia, magnesia and the like may be included in the present discrete entities By "substantially non-interfering" is meant amounts of other materials which do not have a substantial deleterious effect on the present catalyst system or hydrocarbon conversion process In another preferred embodiment, the present discrete entities further comprise a minor amount of at least one alumino-silicate capable of promoting the desired hydrocarbon conversion.

Typical aluminosilicates have been described above Preferably, such aluminosilicates comprise 1 % to 20 %, more preferably 1 % to %, by weight of the discrete entities The presence of such aluminosilicates in the present discrete entities acts to increase the overall catalytic activity of the solid particles-discrete entities mixture for promoting the desired hydrocarbon conversion.

The alumina may be synthetically prepared in any suitable manner and may be processed prior to use by one or more treatments including drying, calcination and steaming.

Thus, for instance, hydrated alumina in the form of a hydrogel can be precipitated from an aqueous solution of a soluble aluminium salt such as aluminium chloride Ammonium hydroxide is a useful agent for effecting the precipitation Control of the p H to maintain it within the values of 7 to 10 during the precipitation is desirable for obtaining a good rate of conversion Extraneous ions, such as halide ions, which are introduced in preparing the hydrogel, can, if desired, be removed by filtering the alumina hydrogel from its mother liquor and washing the filter cake with water.

Also, if desired, the hydrogel can be aged, say for a period of several days The effect of such aging is to build up the concentration of alumina trihydrate in the hydrogel Such trihydrate formation can also be enhanced by seeding an aqueous slurry of the hydrogel with alumina trihydrate crystallites, for example, gibbsite.

The alumina-based composition may be formed into particles of any desired shape such as pills, cakes, extrudates, powders, granules and spheres using conventional methods.

The size selected for the particles can be dependent upon the intended environment in which the final discrete entities is to be used.

In a further preferred embodiment, the support of the discrete entities has substantially the same chemical composition as the catalyst useful in promoting the desired hydrocarbon conversion, e g, the present solid particles, as described above Thus, the support of the discrete entities can provide additional hydrocarbon conversion catalytic activity.

As indicated above, the discrete entities utilized in the present invention may also contain at least one of certain metal, preferably platinum group metal, components disposed on the support The metal, such as platinum, may exist within the final discrete entities at least in part as a compound such as an oxide, sulfide or halide, or in the elemental state.

Generally, the amount of the metal component present in the final discrete entities is small compared to the quantity of the support In general, it is desirable to incorporate into the 1,585,507 1,585,507 discrete entities 0 05 parts per million (ppm) to 10 % and preferably 0 5 ppm to 1 %, by weight of the metal, based on the total weight of the discrete entities The platinum group metal component preferably comprises from 0.05 ppm to 1 %, more preferably 0 05 ppm.

to 1,000 ppm, and still more preferably 0 5 ppm to 500 ppm, by weight of the discrete entities, calculated on an elemental basis.

Excellent results are obtained when the discrete entities contain 50 ppm to 200 ppm, by weight of at least one platinum group metal component.

The metal component may be incorporated in the discrete entities in any suitable manner, such as by co-precipitation or co-gellation with the support, ion-exchange with the support, or by the impregnation of the support at any stage in its preparation and either after or before calcination of the support Preferably, the metal component is substantially uniformly disposed on the support of the present discrete entities One preferred method for adding the metal to the support involves the utilization of a water soluble compound of the metal to impregnate the support For example, platinum may be added to an alumina support by co-mingling the uncalcined alumina with an aqueous solution of chloroplatinic acid.

Other water-soluble components of platinum may be employed as impregnation solutions, including, for example, ammonium chloroplatinate and platinum chloride.

Both inorganic and organic compounds of the metals are useful for incorporating the metal component into the present discrete entities Typical inorganic compounds for incorporation into the second solid particles include copper nitrate, copper chloride, silver nitrate, chromic acid, chromium nitrate, ammonium molybdate, ammonium tungstate, manganous nitrate, ammonium perrhenate, perrhenic acid, ferric chloride, ferride nitrate, ferrous ammonium sulfate, cobalt chloride, cobalt nitrate, nickel nitrate, nickel chloride, ruthenium nitrate, ruthenium chloride, rhodium trichloride, ammonium palladium hexachloride, palladium chloride, diamminedichloropalladium, diamminedinitropalladium, tetraamminepalladium chloride, tetraamminepalladium hydroxide, palladium nitrate, palladium acetate, osmium tetroxide, ammonium platinum hexachloride, chloroplatinic acid, diamminodichloroplatinum, diamminedinitroplatinum, tetraammineplatinous hydroxide, pentachloromolybdenum, hexacarbonylmolybdenum, tetrachloromolybdenum, tetrachloroxytungsten (VI), hexachlorotungsten (VI), nitrosyl tricarbonyl cobalt (I), dichlorodicarbonyl platinum (II), dichlorotetracarbonyl dirhodium (I), triiodotricarbonyl iridium (III) and trichlorobis(trichlorophosphino)iridium (III) As mentioned above, platinum series compounds, such as chloroplatinic acid, palladium chloride and osmium tetroxide are preferred because of their greater catalytic activity.

Typical organic compounds include bis(ethyl acetoacetato) copper (II), copper acetylacetonate, silver palmitate, w-cyclopentadienyltricarbonylmanganese (I), bis( 7 r-cyclopentadienyl)-tricarbonylrhenium (II), trichloro(tetrahydrufuran)iron (III), tricarbonyl(cyclooctatetraene) iron, tetracarbonyl-triphenylphosphinoiron, 7 r-cyclopentadienyldicarbonylcobalt (I), ruthenocene, tricarbonyltris(triphenylphosphino)ruthenium, palladium acetylacetonate, tetrakis(triphenylphosphino)palladium, dichloro(ethylene)palladium (II) dimer, 7 r-cyclopentadienyldicarbonylosmium (I) dimer, platinum acetylacetonate, trimethylplatinum chloride and chlorocarbonylbis(triphenylphosphino) rhodium (I) As above, the platinum series organic series are preferred.

It may be desirable to be able to separate the discrete entities from the solid particles, for example, when it is desired to use the solid particles alone for hydrocarbon conversion or where it is desired to recover the discrete entities for other uses or for platinum group metal recovery This can be conveniently accomplished by preparing the second solid particles in a manner such that they have a different size than the first solid particles The separation of the first and second solid particles can then be easily effected by screening or other means of size segragation.

The improved attrition resistance of the discrete entities may be obtained in any suitable manner For example, the fully composited discrete entities may be contacted in a reducing, inert or oxidizing atmosphere at elevated temperatures, preferably in the range of 1200 F to 3000 F and more preferably, 1600 F, to 2500 F, for a time sufficient to increase the attrition resistance of the discrete entities Such time is preferably in the range of 1/2 hour to 48 hours or more, more preferably 1 hour to 16 hours In a preferred embodiment, the support of the discrete entities is contacted at elevated temperatures to improve attrition resistance After such contacting, the catalytically active metal components are incorporated into the support using suitable techniques described above.

Such discrete entities have been found to exhibit increased attrition resistance.

An additional means for improving the attrition resistance of the discrete entities, particularly such entities which are larger than 500 microns in diameter and include an amount of silica in the support, involves the use of glazing components Thus, the fully composited discrete entities are contacted with a minor amount, preferably 0 01 % to 2 % by weight of the total discrete entities, of at least one material selected from the group consisting of compounds of alkali metals, alkaline earth metals and boron at temperatures above 1000 F sufficiently high as to in1,8,0 5 duce "fusion" between the added composition and adjacent portions of the discrete entity surface.

The following compounds are representative of those which can be used either singly, or in any desired combination, to form the glazing composition for application to the discrete entities: Na Cl, Na 2 CO 3, KCI, K 2 C 03, Li F, Li 2 SO,, Cs 2 CO 3, Rb 2 CO,, Na 45 i O 4, Na 2 Si 2 O, Na 2 Si Ol, Ca Si O 2, Be F 2, Be Cl, Be O, Be CO,, Mg O, Mg C 12, Mg SO 4, Mg CO, Ca O, Ca:;(PO 4)2, Ca F 2, Ca COQ, Ca oleate, Ca naphthenate, Mg oxalate, Ca sulfonate, Na oleate, Sr O, Sr CO, Sr F 2, Ba CI,, Ba CO,, Ba O, Ba naphthenate, B 20,, HBOA, Na BIOT 10 H 2 O Ca(B 02)2, Ca B 407 and Mg,(B 11), Particularly good results have been obtained with Ca CO,, B 203, Na 2 B 4 07 (including hydrates), HBO,, Ba CO, and compositions containing 1-25 % Mg O, 30-75 % Ca CO, and 25-50 % Ca 3 (PO 4)J, by weight In this preferred grouping, it is intended that carbonates may be replaced in whole or in part by the equivalent oxides, since the latter are formed at glazing temperatures, in any event In glazing discrete entities for employment in peroleum hydrocarbon cracking operations, it is preferred not to utilize halides or alkali metal salts in the glazing composition For further details of such glazing procedures, see U S.

Patents 3,030,300 and 3,030,314 When glazing discrete entities which do not contain silica, the glazing composition preferably comprises at least one metal salt, e g, silicate, capable of decomposing to form silica at the elevated temperatures noted above.

In certain instances, e g, where the solid particles have been equilibrated at severe hydrocarbon conversion conditions and/or over a lengthy period of time, a minor amount of the solid particles may have attrition resistance equal to or greater than the discrete entities However, in the preferred embodiment of the present invention employing discrete entities which have improved attrition resistance, the reference to improved attrition resistance is relative to the co-mingled solid particles taken as a whole, or, in other words, relative to the average of the solid particles.

Preferably, the discrete entities are at least % and more preferably, at least 20 % more attrition resistant than the average of the solid particles with which they are co-mingled The attrition resistant discrete entities of the present invention have a longer average service life in conventional hydrocarbon conversion reactor-regenerator systems than the co-mingled solid particles The present discrete entities reduce losses of valuable carbon monoxide oxidation promoters while providing effective carbon monoxide oxidation and not unduly detrimentally affecting the desired hydrocarbon conversion.

Although this invention is useful in many hydrocarbon chemical conversions where the hydrocarbon feedstock contains sulfur, the present process finds particular applicability in systems for the catalytic cracking of hydrocarbons and the regeneration of catalysts so employed Such catalytic hydrocarbon crack 70 ing often involves converting, i e, cracking, heavier or higher boiling hydrocarbons to gasoline and other lower boiling components, such as hexane, hexene, pentane, pentene, butane, butylene, propane, propylene, ethane, 75 ethylene, methane and mixtures thereof Often, the substantially hydrocarbon feedstock comprises a gas oil fraction, e g, derived from petroleum, shale oil, tar sand oil or coal Such feedstock may comprise a mixture of straight 80 run, e g, virgin, gas oil Such gas oil fractions often boil primarily in the range of 400 F to 1000 F Other substantially hydrocarbon feedstocks, e g, other high boiling or heavy fractions of petroleum, shale oil, tar sand oil and 85 coal, may be cracked using the apparatus and method of the present invention Such substantially hydrocarbon feedstocks often contain minor amounts of contaminants, not only of sulfur but also of nitrogen 90 Hydrocarbon cracking conditions are well known and often include temperatures in the range of 850 F to 1100 F, preferably 900 F.

to 1050 F Other reaction conditions usually include pressures of up to 100 psig; catalyst 95 to oil ratios of 1 to 5 to 25 to 1; and weight hourly space velocities (WHSV) of from 3 to These hydrocarbon cracking conditions are not critical to the present invention and may be varied depending, for example, on the feed 100 stock and solid particles being used and the product or products wanted.

In the process of the invention, the catalyst is cyclal between the reaction zone where the hydrocarbon conversion takes place and a re 105 generation zone for restoring the catalytic activity of the solid particles of catalyst previously used to promote the hydrocarbon cracking Carbonaceous deposit-containing catalyst particles from the reaction zone are 110 contacted with free oxygen-containing gas in the regeneration zone at conditions to restore or maintain the activity of the catalyst by removing, i e, combusting, at least a portion of the carbonaceous material from the catalyst 115 particles The conditions at which such contacting takes place are not critical to the present invention The temperature in the catalyst regeneration zone of a hydrocarbon cracking system is often in the range of 900 F to 120 1500 F, preferably 900 F to 1300 F and more preferably 11000 F to 13000 F Other conditions within such regeneration zone include, for example, pressures up to 100 psig, average catalyst contact times within the range 125 of 3 minutes to 120 minutes, preferably from 3 minutes to 75 minutes Sufficient oxygen is preferably present in the regeneration zone to completely combust the carbonaceous deposit material, for example, to carbon dioxide and 130 1,585,507 1,585,507 water The amount of carbonaceous material deposited on the catalyst in the reaction zone is preferably in the range of 0 005 % to 15 %, more preferably 0 1 % to 10 %, by weight of the catalyst At least a portion of the regenerated catalyst is often returned to the hydrocarbon cracking reaction zone.

The solid particles useful in the catalytic hydrocarbon cracking embodiment of the present invention may be any conventional catalyst capable of promoting hydrocarbon cracking at the conditions present in the reaction zone, i e, hydrocarbon cracking conditions Similarly, the catalytic activity of such solid particles is restored at the conditions present in the regeneration zone Typical among these conventional catalysts are those which comprise amorphous silicaalumina and at least one crystalline aluminosilicate having pore diameters of 8 A to 15 A and mixtures thereof When the solid particles and/or discrete entities to be used in the hydrocarbon cracking embodiment of the present invention contain crystalline aluminosilicate, the compositions may also include minor amounts of conventional metal pro-moters such as the rare earth metals, in particular, cerium.

The catalyst, i e, mixture comprising solid particles and discrete entities, and process of the invention can be beneficially used for the disproportionation of paraffinic or aromatic hydrocarbons For example, the present invention is well adaptable to the disproportionation of paraffinic hydrocarbons containing 3 to carbon atoms per molecule and aromatic hydrocarbons containing one or two rings and from 7 to 18 carbon atoms per molecule The process of the invention is particularly useful for the disproportionation of methylbenzenes containing 7 to 10 carbon atoms per molecule and is especially useful for the disproportionation of toluene to mixed xylenes and benzene.

When disproportionating specific hydrocarbons it is often desirable to add a higher molecular weight hydrocarbon to the feedstock for the purpose of increasing the yield of a desired product For example, when disproportionating toluene to benzene and mixed xylenes the yield of xylenes can be increased by introducing higher methyl-benzenes with the toluene feed These higher methylbenzenes usually have 9 to 10 carbon atoms and 1 to 4 methyl groups, and thus other alkyl groups such as ethyl or propyl groups may be present Thus, the aromatic streams available as a source of methyl groups for alkylation of toluene frequently do not consist only of methylaromatics For example, the C,+ product obtained from a xylene isomerization process normally contains substantial ethyl (and possibly higher alkyl) ring substituents.

Ethyl or higher alkylaromatic substituents tend to crack more readily than methyl groups to form olefins and the parent aromatic ring.

Higher temperatures also promote the cracking reaction As a result, the preferred conditions for a particular operation can be dependent on the composition of the C, + stream, the extent to which the C,+ stream is recycled, and the ratio of benzene to xylenes desired in the product In a process involving recycle, the ethyl substituents may also be controlled by fractionating and removing a portion of the stream rich in n-propylbenzenes and ethyltoluenes, or rich in ethylxylenes The C,+ hydrocarbons can be obtained from various sources such as naphtha reformate and coal tar, and in addition, the concentration of aromatics in the hydrocarbon streams can be increased by fractionation or solvent extraction procedures Thus, trimethylbenzenes, for example, those formed as by-products of the disproportionation reaction, can be incorporated in the aluene feed, thus effecting additional xylene production through transalkylation The amount of the higher methylaromatics added to the feed, either from an external supply or by recycling, can be a small amount effective to increase the xylene/benzene ratio in the product, as 5 to 60, preferably 15 to 50, weight percent based on the toluene fed to the reaction zone.

In accordance with a preferred embodiment a hydrocarbon feedstock, such as toluene, which is in the vapour phase is disproportionated in a moving catalyst bed reactor in which the catalyst comprises a mixture of 80 to 99 % by weight of solid particles which contain 5 % to 50 % of a crystalline aluminosilicate having a pore size of at least 5 A disposed in a porous matrix of silica-alumina and 1 % to 20 % of discrete entities comprising 1 % to 20 % by weight of a crystalline aluminosilicate of substantially the same pore size as the crystalline aluminosilicate included in the solid particles, at least 80 % by weight of alumina and 0 05 ppm to 1000 ppm by weight of at least one platinum group metal component disposed substantially uniformly in the alumina The disproportionation reaction zone is preferably operated at a temperature of 700 F to 1200 F and more preferably 800 F to 1000 F and preferably at approximately atmospheric pressures such as 0 psig to 30 psig The catalyst holding time, i e, the average length of time that the catalyst remains in the reaction zone is preferably kept in the range of 6 to 240 and more preferably 12 to 120 minutes.

After the catalyst particles leave the disproportionation reaction zone they enter the catalyst regeneration zone where at least a portion of the carbonaceous substances which were deposited on the catalyst particle surfaces during the disproportionation reaction are removed This is accomplished by contacting the catalyst with an oxygen-containing gas stream, such as air, at temperatures preferably in the range of 800 F to 1500 F and more 1,585,507 preferably 900 'F to 1200 'F The temperature and flow rate of the oxygen-containing gas stream is preferably such that the temperature in the regeneration zone is maintained in the preferred temperature range specified above.

The following Example clearly illustrates the present invention.

EXAMPLE.

PRODUCTION OF DISCRETE ENTITIES A quantity of alumina-based particles of substantially pure gamma alumina, which is derived from a mixture of alumina monohydrate and amorphous hydrous alumina, substantially all of the particles having diameters in the range of 50 microns to 100 microns, such as can be obtained by conventional spray drying techniques, is charged into a vessel equipped with means for evacuating the vessel.

The vessel is evacuated and maintained under a vacuum of about 28 inches Hg for 20 minutes An aqueous solution of chloroplatinic acid is introduced into the vessel and the vessel is agitated sufficiently to effect a substantially uniform distribution of the platinum on the alumina particles The concentration of chloroplatinic acid in the solution is sufficient to impregnate the alumina with about 100 ppm, based on weight, of platinum, calculated as elemental platinum The resulting discrete entities are dried in a hot air stream for three hours and then calcined in an air stream at 1200 'F for one hour.

A quantity of solid particles of a commercially available hydrocarbon conversion catalyst containing about 6 % by weight of crystalline aluminosilicate, about 54 % by weight amorphous silica-alumina and 40 % by weight alpha alumina, and having particle diameters in the range of 20 microns to 150 microns is combined with the above discrete entities so that a mixture of 5 parts by weight of discrete entities and 95 parts by weight of the solid particles results The catalytic activity of the solid particles is equilibrated by using same (prior to combining with the discrete entities) in a conventional commercial fluid bed catalyst cracking (FCC) unit.

This catalyst mixture is used to crack a petroleum derived gas oil stream, a combined fresh feed and recycle stream, to lower boiling hydrocarbons in a conventional FCC unit The fresh gas oil fraction boils in the range 4000 F to 1000 'F and is substantially hydrocarbon in nature, containing minor amounts of sulfur and nitrogen as contaminants.

Briefly, a conventional FCC unit involves two vessels in at least limited fluid communication with each other One vessel serves as a reaction zone Hydrocarbon feedstock and catalyst particles are fed to the reaction zone at hydrocarbon cracking conditions At least a portion of the hydrocarbon cracking occurs in this reaction zone, where the catalyst and hydrocarbon form a fluid phase or bed.

Catalyst and hydrocarbon are continuously drawn from the reaction zone The hydrocarbon is sent for further processing, distillation and the like Catalyst, stripped of hydrocarbon, flows to the other vessel, catalyst regeneration zone, where it is combined with air at proper conditions to combust at least a portion of the carbonaceous deposits from the catalyst formed during the hydrocarbon cracking reaction The catalyst and vapors in the regeneration zone form a fluid phase or bed Catalyst is continuously removed from the regeneration zone and is combined with the hydrocarbon feedstock prior to being fed to the reaction zone.

The weight ratio of catalyst particles to total (fresh plus recycle) hydrocarbon feed entering the reaction zone is about 8 to 1.

Other conditions within the reaction zone include:

Temperature, 'F.

Pressure, psig.

WHSV 930 8 Such conditions result in about 70 % by volume conversion of the gas oil feedstock to 90 products boiling at 400 'F and below.

The catalyst particles from the reaction zone include about 1 5 % by weight of carbonaceous deposit material which is at least partially combusted in the regeneration zone Air, 95 in an amount so that amount of oxygen in the regeneration zone is about 1 15 times the amount theoretically required to completely combust this deposit material, is heated to the desired temperature before being admitted to 100 the regeneration zone Conditions within the regeneration zone include:

Temperature, 'F.

Pressure, psig.

Average Catalyst Residence Time, min.

1150 After a period of time, the catalyst is shown to remain effective to promote both hydrocarbon cracking in the reaction zone and carbon monoxide oxidation in the regeneration 110 zone Sulfur present in the feedback causes the carbonaceous deposits formed on the catalyst also to contain sulfur During the regeneration of the catalyst described above at least a portion of this deposit sulfur is oxidised and, 115 ordinarily, would leave the system with combustion flue gases However, in accordance with this invention, SO, produced as a result of the oxidation associates with the alumina of the discrete entities under the conditions of the 120 regeneration zone and remains so associated until such entities are placed in the hydrocarbon chemical reaction zone environment.

Under the reaction zone conditions, at least a portion of this SO 3 is converted to H 2 S which 125 1,585,507 is removed from the reaction zone with the hydrocarbon conversion products The presence of the platinum group metal component in the catalyst regeneration zone acts to promote the formation of SO, from the sulfurcontaining compounds Thus, the sulfur dioxide emissions from the regenerator zone combustion flue gases are reduced.

In our copending Patent Application 17120/77, accepted as No 1,585,505, we describe and claim a process for converting a hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles substantially free of added platinum group metal components and capable of promoting the conversion of said feedstock at hydrocarbon conversion conditions to produce at least one hydrocarbon product and to cause deactivating carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; and ( 2) contacting said deposit-containing particles in at least one regeneration zone with an oxygencontaining vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a portion of the hydrocarbon conversion catalytic activity of said solid particles and to form at least one carbonaceous deposit material combustion product; and ( 3) repeating steps ( 1) and ( 2) periodically, and in which there there are circulated between said reaction zone and said regeneration zone in intimate admixture with said solid particles, a minor amount of discrete entities comprising (A) a major amount by weight of alumina and (B) a minor, catalytically effective amount of at least one platinum group metal component disposed on said alumina, said metal component being capable of promoting the oxidation of carbon monoxide to carbon dioxide at the conditions of step ( 2), thereby promoting the oxidation of carbon monoxide to carbon dioxide in said regeneration zone.

In our copending Patent Application No.

4703/78, accepted as No 1,585,506, we describe and claim a process for converting a hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles capable of promoting the conversion of said feedstock at hydrocarbon conversion conditions to produce at least one hydrocarbon product and to cause deactivating carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; ( 2) contacting said deposit-containing particles in at least one regeneration zone with an oxygen-containing vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a portion of the hydrocarbon conversion catalytic activity of said solid particles and to form at least one carbonaceous deposit material combustion product; and ( 3) repeating steps ( 1) and ( 2) periodically; and in which said solid particles are substantially free of added metal components capable of promoting carbon monoxide oxidation at the conditions of step ( 2) and said particles are circulated between said reaction zone and said regeneration zone in intimate admixture with a minor amount of discrete entities which are more attrition resistant than said solid particles and which comprise (A) a major amount by weight of a support at least a portion of which is capable of promoting hydrocarbon conversion at the conditions of step ( 1) and (B) a minor, catalytically effective, amount of at least one metal component disposed on at least a portion of said support, said metal component being capable of promoting the conversion of carbon monoxide to carbon dioxide at the conditions of step ( 2), thereby promoting the oxidation of carbon monoxide to carbon dioxide in said regeneration zone.

Claims (19)

WHAT WE CLAIM IS:-

1 A process for converting a sulfur 90 containing hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles capable of promoting the conversion of said feedstock at hydrocarbon con 95 version conditions to produce at least one hydrocarbon product and to cause deactivating sulfur-containing carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; ( 2) contacting 100 said deposit-containing particles in at least one regeneration zone with an oxygen-containing vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a por 105 tion of the hydrocarbon conversion catalytic activity of said solid particles and to form a regeneration zone flue gas containing at least one sulfur-containing carbonaceous deposit material combustion product; and ( 3) repeat 110 ing steps ( 1) and ( 2) periodically, and in which the amount of sulfur in said regeneration zone flue gas is reduced by circulating said solid particles between said reaction zone and said regeneration zone in intimate admixture with 115 a minor amount of discrete entities which comprise a major amount by weight of support and a minor, catalytically effective, amount by weight of at least one metal-containing component disposed on the support, the metal 120 containing component being capable of promoting the oxidation of carbon monoxide to carbon dioxide at carbon monoxide oxidising conditions, said discrete entities also being more attrition resistant than the solid particles 125 and capable of promoting the oxidation of sulfur dioxide to sulfur trioxide at the conditions of step ( 2), associating with sulfur trioxide at the conditions of step ( 2) and dis9 1,585,507 9 associating from sulfur trioxide at the conditions of step ( 1), thereby associating at least portion of said sulfur-containing combustion product with said discrete entities in said regeneration zone and disassociating at least a portion of said sulfur-containing combustion product from said discrete entities in said reaction zone to form H 2 S which exits said reaction zone with said hydrocarbon product.

2 A process as claimed in claim 1 in which the discrete entities include alumina.

3 A process as claimed in claim 1 or claim 2 in which said at least one metal-containing component comprises at least one platinum group metal component, said component being capable of promoting the oxidation of sulfur and sulfur-containing compounds to SO 3 under the conditions of step ( 2).

4 A process for converting a sulfurcontaining hydrocarbon feedstock which comprises ( 1) contacting said feedstock in at least one reaction zone with a catalyst comprising solid particles capable of promoting the conversion of said feedstock at hydrocarbon conversion conditions to produce at least one hydrocarbon product and to cause deactivating sulfur-containing carbonaceous material to be formed on said solid particles, thereby forming deposit-containing particles; ( 2) contacting said deposit-containing particles in at least one regeneration zone with an oxygen-containing vaporous medium at conditions to combust at least a portion of said carbonaceous deposit material to thereby regenerate at least a portion of the hydrocarbon conversion catalytic activity of said solid particles and to form a regeneration zone flue gas containing at least one sulfur-containing carbonaceous deposit material combustion product; and ( 3) repeating steps ( 1) and ( 2) periodically, and in which the amount of sulfur in said regeneration zone flue gas is reduced by circulating said solid particles between said reaction zone and said regeneration zone in intimate admixture with a minor amount of discrete entities whose composition differs from that of the solid particles and which comprise alumina and a catalytically effective amount of at least one platinum group metal component disposed on the alumina, said discrete entities being capable of associating with sulfur trioxide at the conditions of step ( 2) and capable of disassociating from sulfur trioxide at the conditions of step ( 1), thereby associating at least a portion of said sulfur-containing combustion product with said discrete entities in said regeneration zone and disassociating at least a portion of said sulfur-containing combustion product from said discrete entities in said reaction zone to form H 2 S which exits said reaction zone with said hydrocarbon product.

A process as claimed in claim 4 wherein the discrete entities are more attrition resistant than the solid particles.

6 A process as claimed in claim 4 or claim in which said discrete entities comprise a major amount by weight of alumina and a minor, catalytically effective, amount of at least one platinum group metal component disposed on the alumina 70

7 A process as claimed in any one of claims 2 to 6 wherein said discrete entities contain at least 70 % by weight of alumina.

8 A process as claimed in claim 7 wherein said discrete entities contain at least 90 % by 75 weight of alumina.

9 A process as claimed in any one of claims 2 to 8 wherein said alumina has a surface area of 25 m 2/g to 600 m 2/g.

A process as claimed in any one of 80 claims 2 to 9 wherein said alumina is derived from hydrous alumina predominating in alumina trihydrate, alumina monohydrate, amorphous hydrous alumina and mixtures thereof.

11 A process as claimed in any one of 85 claims 2 to 10 wherein said alumina is gamma alumina.

12 A process as claimed in any one of claims 3 to 11 wherein said at least one platinum group metal component is present 90 in an amount of 0 05 ppm to 1 % by weight of said discrete entities calculated as elemental metal.

13 A process as claimed in any one of claims 3 to 12 wherein said platinum group 95 metal is selected from platinum and/or palladium.

14 A process as claimed in any one of claims 3 to 13 wherein the compositions of said solid particles and said discrete entities 100 minus said platinum group metal component are substantially the same.

A process as claimed in any one of claims 1 to 13 wherein said solid particles comprise at least one aluminosilicate capable 105 of promoting hydrocarbon cracking at the conditions of step ( 1).

16 A process as claimed in any one of claims 1 to 15 wherein said discrete entities further include a minor amount of at least 110 one material selected from silica, zirconia, magnesia and aluminosilicate capable of promoting hydrocarbon cracking at the conditions of step ( 1) and mixtures thereof.

17 A process as claimed in any one of 115 claims 1 to 16 wherein the relative amounts of said solid particles and said discrete entities are in the range of 80 parts to 99 parts and parts to 1 part by weight, respectively.

18 A process as claimed in any one of 120 claims 1 to 17 wherein said hydrocarbon feedstock contains 0 01 to 5 0 % by weight of sulfur.

19 A process as claimed in any one of claims 1 to 18 wherein said hydrocarbon feed 125 stock contains O 1 %_ to 3 % by weight of sulfur.

A process as claimed in any one of claims 1 to 19 wherein said conversion comprises hydrocarbon cracking and said solid particles are fluidizable 130 1,585,507 1,585,507 10 MATHYS & SQUIRE, Chartered Patent Agents, Fleet Street, London EC 4 Y l AY, Agents for the Applicants.

Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981.

Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.