Catalyst and Process for Conversion of Hydrocarbons

This invention relates to the conversion of hydrocarbons and more particularly to the chemical conversion of hydrocarbons, preferably sulfur-containing hydrocarbon feedstocks, 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. Although free molecular hydrogen may be added to the reaction zone, 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 with a solid catalytic material in at least one reaction zone 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 at least one reaction zone in the presence of free oxygen. During the catalyst regeneration carbon monoxide and carbon dioxide are often produced as gaseous combustion products, the relative amounts of each depending upon the efficiency of the oxidation step. If the hydrocarbon feedstock contains sulfur, the carbonaceous deposit material will often also contain sulfur. During catalyst regeneration, at least a portion of the sulfur in the carbonaceous deposit material may combust or oxidize, e.g., to SO.sub.2 and SO.sub.3, and exits with the flue gases from the regeneration zone.

Recent federal and local air pollution control legislation has made it necessary to eliminate or drastically reduce the amount of carbon monoxide and/or sulfur (or sulfur oxides) being discharged into the atmosphere. The amount of carbon monoxide as a gaseous by-product from hydrocarbon conversion processes using a regenerative catalyst can be reduced by using a catalyst which contains a promoter, usually a metal or metal compound, for the conversion of carbon monoxide to carbon dioxide. U.S. Pat. No. 2,647,860 describes a hydrocarbon cracking process using a synthetic silica-alumina catalyst which is capable of regeneration, and which contains 0.01% to 1% by weight of chromic oxide to promote the oxidation of carbon monoxide in the catalyst regenerator. This patent acknowledges the fact that the chromic acid adversely affects the cracking reaction. U.S. Pat. No. 3,140,249 describes the preparation and use of crystalline aluminosilicate compositions containing small amount of metals such as vanadium and manganese in hydrocarbon cracking processes. U.S. Pat. No. 3,140,253 discloses the preparation and use of crystalline aluminosilicates in hydrocarbon conversion processes. This patent states that metal promoters such as chromium, cobalt and platinum may be present in the catalyst in amounts of 5% to 40% by weight. U.S. Pat. No. 3,173,854 describes a process for the hydrocracking of hydrocarbon oils using a crystalline aluminosilicate containing, as a hydrogenation component, 0.01% to 25% by weight of a metal selected from Groups VI and VIII of the Periodic Table. U.S. Pat. No. 3,650,990 discloses the preparation of a crystalline aluminosilicate useful for the conversion of hydrocarbons containing a metal promoter selected from Groups IVB, VB, VIB, VIIB AND VIII of the Periodic Chart. The metal is incorporated into the crystalline aluminosilicate prior to or during its formation and may vary from 0.001% to 5% by weight. U.S. Pat. No. 3,788,977 describes hydrocarbon cracking using a platinum-impregnated inorganic oxide-crystalline aluminosilicate-containing catalyst. The platinum, which is present in amounts of at least 100 ppm based on the amount of inorganic oxide, increases the yield of aromatic product.

U.S. Pat. No. 3,364,136 describes hydrocarbon conversion using a catalyst comprised of a first component consisting of solid particles containing a crystalline aluminosilicate which is active for the conversion of the hydrocarbon, and a second component consisting of solid particles containing a crystalline aluminosilicate which is inert with respect to the hydrocarbon conversion reaction because its pores are too small to admit the hydrocarbon reactant, but which is effective to promote the oxidation of carbon monoxide to carbon dioxide. The latter component contains from less than 0.01% up to 20% by weight of a metal, metal oxide or metal sulfide from Groups IB, IIB, VIB, VIIB or VIII of the Periodic Chart. Belgain Pat. No. 820,181 describes a process of cracking hydrocarbons with a cracking catalyst material which contains less than the 100 ppm. of a metal chosen from Periods 5 and 6 of Group VIII of the Periodic Chart or rhenium. This patent teaches that the metal may be applied uniformly over all of the catalyst or it may be applied at a higher concentration on a portion of the catalyst and blended with unmodified catalyst provided that the total metal content of the final catalyst mixture does not exceed 100 ppm.

Such carbon monoxide oxidation catalyst systems have met with varying degrees of success. One problem which has become apparent is the tendency of such oxidation catalysts to rapidly deactivate. The tendency is especially apparent when the oxidation catalyst comprises a Group VIII, platinum group metal component. Thus, carbon monoxide oxidation catalysts which are satisfactory, e.g., reduce carbon monoxide emissions to meet or approach govermental standards, in the virgin state, have been found to lose a substantial amount of carbon monoxide oxidation activity after a relatively short time in hydrocarbon conversion-catalyst regeneration service.

Accordingly, one object of this invention is to provide an improved process for hydrocarbon conversion.

Another object of the invention is to provide an improved process for hydrocarbon conversion in the substantial absence of added free molecular hydrogen.

Another object of this invention is to provide an improved process for hydrocarbon conversion in a two-step chemical conversion-catalyst regeneration process.

A still further object of this invention is to reduce the amount of carbon monoxide produced during the regeneration of a hydrocarbon conversion catalyst.

An additional object of this invention is to reduce the emission of carbon monoxide into the atmosphere from a hydrocarbon conversion process using a catalyst which is periodically regenerated to combust carbonaceous deposit material from the catalyst.

Another object of the present invention is to reduce the emission of sulfur into the atmosphere from a hydrocarbon conversion process using a catalyst which is periodically regenerated to combust sulfur-containing carbonaceous deposit material from the catalyst.

Another object of the invention is to provide an improved hydrocarbon conversion catalyst. A further object of the invention is to provide an improved carbon monoxide oxidation catalyst. A still further object of the invention is to provide an improved sulfur dioxide oxidation catalyst. These and other objects of the invention will become apparent from the following description and examples.

In accordance with the invention, the hydrocarbon conversion process is carried out using a mixture of solid particles comprised of (1) a major amount of solid particles capable of promoting the desired hydrocarbon chemical conversion at hydrocarbon conversion conditions and which are, preferably, substantially free of Group VIII, platinum group metal component or components and (2) a minor amount of discrete entities comprising (A) a major amount of weight of alumina and (B) a minor, catalytically effective amount of at least one Group VIII, platinum group metal component disposed, preferably substantially uniformly disposed, on the alumina, this metal component being capable of promoting the oxidation of carbon monoxide to carbon dioxide at carbon monoxide oxidizing conditions. The Group VIII, platinum group metals include 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 entities are about 80 to about 99 parts and about 1 to about 20 parts by weight, respectively. This catalyst system is especially effective for the catalytic cracking of a hydrocarbon feedstock to lighter, lower boiling products. The present catalyst system has improved carbon monoxide oxidation catalytic activity stability.

In accordance with another aspect of the present invention, the hydrocarbon conversion process is carried out in at least one chemical reaction zone and at least one regeneration zone with a sulfur-containing hydrocarbon feedstock using a mixture of solid particles comprising (1) a major amount of solid particles capable of promoting the desired hydrocarbon chemical conversion at hydrocarbon conversion conditions and, which are, preferably, substantially free of Group VIII, platinum group metal component or components and (2) a minor amount of discrete entities comprising a major amount of alumina capable of associating with sulfur trioxide in the regeneration zone and disassociating with sulfur trioxide in the chemical reaction zone. In one preferred embodiment, the discrete entities further comprise a minor amount of at least one metal, e.g., platinum group metal, component capable of promoting the oxidation of sulfur dioxide to sulfur trioxide at the conditions in the regeneration zone.

The improvement of this invention can be used to advantage with the catalyst being disposed in any conventional reactor-regenerator system, e.g., in a fixed catalyst bed conversion-regeneration system, in ebullating catalyst bed systems, in systems which involve continuously conveying or circulating catalyst between reaction zone and regeneration zone and the like. Circulating catalyst systems are preferred. Typical of the circulating catalyst bed systems are the conventional moving bed and fluidized bed reactor-regenerator systems. Both of these circulating bed systems are conventionally used in hydrocarbon conversion, e.g., hydrocarbon cracking, operations with the fluidized catalyst bed reactor-regenerator systems being preferred.

The catalyst system used in accordance with certain embodiments of the invention is comprised of a mixture of two types of solid particles.

Although the presently useful solid particles and discrete entities may be used as a physical admixture of separate particles, in one preferred embodiment, the discrete entities are combined as part of the solid particles. That is, the discrete entities, e.g., comprising calcined alumina microspheres, are combined with the solid particles, e.g., during the manufacture of the solid particles, to form combined particles which function as both the presently useful solid particles and discrete entities. In this embodiment, the alumina of the discrete entities is preferably a separate and distinct phase, and is substantially accessible to the carbon monoxide, carbon dioxide and/or sulfur dioxide, sulfur trioxide present in the regeneration zone and, preferably, to the hydrocarbon feedstock in the reaction zone. By "accessible" is meant that the alumina has physical properties, e.g., porosity, pore volume, surface area and the like, which allow at least a major portion by weight of the hydrocarbon feedstock and the carbon and sulfur oxides noted above to come into intimate, e.g., molecular, contact with the alumina of the discrete entities contained in the combined particles. One preferred method for providing the combined particles with substantially accessible alumina is to calcine the discrete entities prior to incorporating the discrete entities into the combined particles. When the discrete entities comprise substantially accessible alumina a major amount of such alumina is preferably extractable by contacting the discrete entities or the combined particles containing the discrete entities, with 0.2N HCl at about 165.degree.-170.degree. F. for four (4) hours. This indication of substantially accessible alumina finds particular applicability when the discrete entities comprise gamma alumina, e.g., alumina derived from hydrous alumina predominating in alumina monohydrate, alumina derived from hydrous alumina predominating in amorphorous hydrous alumina, and mixtures thereof.

The form, i.e., particle size, of the present catalyst particles, e.g., both solid particles and discrete entities as well as the combined particles, is not critical to the present invention and may vary depending, for example, on the type of reaction-regeneration system employed. Such catalyst particles may be into any desired shape such as pills, cakes, extrudates, powders, granules, spheres and the like using conventional methods. Where, for example, the final catalyst is designed for use in hydrocarbon conversion operations employing a fixed bed of catalyst, the catalyst may preferably be formed into particles having a minimum dimension of at least about 0.01 inch and a maximum dimension up to about one-half inch or one inch or more. Spherical particles having a diameter of about 0.03 inch to about 0.25 inch, preferably about 0.03 inch to about 0.15 inch, are often useful, especially in fixed catalyst bed or 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 about 10 microns to about 250 microns, more preferably about 20 microns to about 150 microns.

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

In one aspect of the present invention, the second solid particles, i.e., discrete entities, comprise (A) a major amount, i.e., at least 50%, by weight of alumina and (B) a minor amount of at least one platinum group metal component disposed on the alumina 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 oxygen-containing gaseous medium to combust at least a portion of the carbonaceous deposit material from the first solid particles. In another aspect of the present invention, the discrete entities, whether present as a separate and distinct particle and/or combined with the solid particles in a single, preferably substantially uniform, mass of combined particles comprise a major amount of alumina capable of associating and disassociating with sulfur trioxide in the regeneration zone and the reaction zone, respectively, and preferably further comprise a minor amount of at least one metal, e.g., platinum group metal, component capable of promoting the oxidation of sulfur dioxide at the conditions in the regeneration zone.

The composition of the solid particles useful in the present invention is not critical, provided that such particles are capable of promoting the desired hydrocarbon conversion. Particles having widely varying compositions are conventionally used as catalysts in such hydrocarbon conversion processes, the particular composition chosen being dependent, for example, on the type of hydrocarbon chemical conversion desired. Thus, the solid particles suitable for use in the present invention include at least one of the natural or synthetic materials which are capable or promoting the desired hydrocarbon chemical conversion. For example, when the desired hydrocarbon conversion involves one or more of hydrocarbon cracking, disproportionation, isomerization, polymerization, alkylation and dealkylation, such suitable materials include acid-treated natural clays such as montmorillonite, kaolin and bentonite clays; natural or synthetic amorphous materials, such as amorphous silica-alumina, silicamagnesia and silica-zirconia composites; crystalline aluminosilicates often referred to as zeolites or molecular sieves and the like. In certain instances, e.g., hydrocarbon cracking and disproportionation, the solid particles preferably include such crystalline aluminosilicates to increase catalytic activity. Methods for preparing such solid particles and the combined solid particles-discrete entities particles are conventional and well known in the art. For example, crystalline aluminosilicate compositions can be made from alkali metal silicates and alkali metal aluminates so that they initially contain significant concentrations of alkali metal. Sodium tends to reduce the catalyst activity of the composition for hydrocarbon conversion reactions such as hydrocarbon cracking and disproportionation. Accordingly, most or all of the sodium in the crystalline aluminosilicate is removed or replaced, e.g., with other metal cations such as calcium or aluminum ions or ions of the rare earths. This can be accomplished by contacting the crystalline aluminosilicate with a source of hydrogen ions such as acids, or hydrogen precursors such as ammonium compounds. These procedures are thoroughly described in U.S. Pat. Nos. 3,140,253 and Re. 27,639.

Compositions of the solid particles which are particularly useful in the present invention are those in which the crystalline aluminosilicate is incorporated in an amount effective to promote the desired hydrocarbon conversion, e.g., a catalytically effective amount, into a porous matrix which comprises, for example, amorphous material which may or may not be itself capable of promoting such hydrocarbon conversion. Included among such matrix materials are clays and amorphous compositions of silica-alumina, magnesia, zirconia, mixtures of these and the like. The crystalline aluminosilicate is preferably incorporated into the matrix material in amounts within the range of about 1% to about 75% more preferably about 2% to about 50%, by weight of the total solid particles. The preparation of crystalline aluminosilicate-amorphous matrix catalytic materials is described in the above-mentioned patents. Catalytically active crystalline aluminosilicates which are formed during and/or as part of the method of manufacturing the solid particles, discrete entities and/or combined particles are within the scope of the present invention.

As indicated above, in one aspect the discrete entities utilized in the present invention comprise a major amount of alumina and a minor amount of at least one platinum group metal component disposed on the alumina and present in an amount sufficient to promote the oxidation of carbon monoxide to carbon dioxide. In another aspect, the present discrete entities comprise a major amount of alumina capable of associating and disassociating with sulfur trioxide and, preferably, a minor amount of at least one metal, e.g., platinum group metal, component capable of promoting sulfur dioxide oxidation. It is essential that the discrete entities include at least one separate alumina phase, e.g., on which the platinum group metal is disposed. It is preferred that the discrete entities comprise a major amount of alumina having a surface area of from about 25 m..sup.2 /gm. to about 600 m..sup.2 /gm. or more. The alumina comprises a major amount, preferably at least about 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 theta-alumina are preferred, while gamma- and eta-alumina are more preferred and gamma-alumina is still more preferred. Minor, substantially non-interferring 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-interferring" is meant amounts of other materials which do not have a substantial deleterious effect on the present catalyst system or hydrocarbon conversion process. The inclusion of minor amount of such materials such as silica, zirconia, magnesia and the like into the present discrete entities may act to improve the one or more of the functions of the discrete entities. In one preferred embodiment, the present discrete entities further comprise a minor amount of at least one aluminosilicate capable of promoting the desired hydrocarbon conversion. Typical aluminosilicates have been described above. Preferably, such aluminosilicates comprise about 1% to about 20%, more preferably about 1% to about 10%, 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, steaming and the like. Thus, for instance, hydrated alumina in the form of a hydrogel can be precipitated from an aqueous solution of a soluble aluminum salt such as aluminum chloride. Ammonium hydroxide is a useful agent for effecting the precipitation. Control of the pH to maintain it within the value of about 7 to about 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, spheres, and the like using conventional methods. The size selected for the particles can be dependent upon the intended environment in which the final discrete entities are to be used--as, for example, whether in a fixed catalyst bed or circulating catalyst bed reaction system or whether as a separate particle or as part of a mass of combined particles.

As indicated above the discrete entities utilized in the present invention preferably also contain at least one metal, e.g., platinum group metal, component disposed on the alumina. The metal components are capable of promoting the oxidation of carbon monoxide and/or the oxidation of sulfur dioxide to sulfur trioxide at the conditions present in the regenerator. Such metal components are selected from the group consisting of Group IB, IIB, VIB, VIIB, VIII of the Periodic Table, vanadium and mixtures thereof and may be incorporated onto the alumina of the discrete entities in any suitable manner. The metal, e.g., platinum group metal, such as platinum, may exist within the final discrete entities at least in part as a compound such as an oxide, sulfide, halide and the like, or in the elemental state. Generally, the amount of the platinum group metal component present in the final discrete entities is small compared to the quantity of the alumina. The platinum group metal component preferably comprises from about 0.05 parts-per-million (ppm.) to about 1%, more preferably about 0.05 ppm. to about 1,000 ppm., and still more preferably about 0.5 ppm. to about 500 ppm., by weight of the discrete entities, calculated on an elemental basis. Excellent results are obtained when the discrete entities contain about 50 ppm. to about 200 ppm., and in particular about 50 ppm. to about 90 ppm., by weight of at least one platinum group metal component.

The metal, e.g., platinum group metal, component may be incorporated in the alumina based composition in any suitable manner, such as by coprecipitation or cogellation with the alumina, ion-exchange with the alumina and/or alumina hydrogel, or by the impregnation of the alumina and/or alumina hydrogel at any stage in its preparation and either after or before calcination of the alumina hydrogel. Preferably, the platinum group metal component is substantially uniformly disposed on the alumina of the present discrete entities. One preferred method for adding the platinum group metal to the alumina involves the utilization of a water soluble compound of the platinum group metal to impregnate the alumina prior to calcination. For example, platinum may be added to the alumina by comingling the uncalcined alumina with an aqueous solution of chloroplatinic acid. Other water-soluble compounds of platinum may be employed as impregnation solutions, including, for example, ammonium chloroplatinate and platinum chloride.

Both inorganic and organic compounds of the platinum group metals are useful for incorporating the platinum group metal component into the present discrete entities. Typically, such inorganic compounds include ruthenium nitrate, ruthenium chloride, rhodium trichloride, ammonium palladium hexachloride, palladium chloride, diamminedichloropalladium, diamminedinitropalladium, tetraamminepalladium chloride, tetraaminepalladium hydroxide, palladium nitrate, palladium acetate, osmium tetroxide, ammonium platinum hexachloride, diamminodichloroplatinum, diamminedinitroplatinum, tetraammineplatinous hydroxide and the like. Platinum group metal compounds, such as chloroplatinic acid and palladium chloride are preferred.

Representative organic metal-containing compounds which can be used to incorporate the platinum group metal component into the discrete entities include ruthenocene, tricarbonyltris (triphenylphosphino) ruthenium, palladium acetylacetonate, tetrakis (triphenylphosphino) palladium, dichloro(ethylene) palladium (II) dimer, .pi.-cyclopentadinyldicarbonylosmium (I) dimer, platinum acetylacetonate, dichlorodicarbonylplatinum (II), trimethylplatinum chloride, dichlorotetracarbonyldirhodium (I), chlorocarbonylbis (tri-phenylphosphino)rhodium (I), triiodotricarbonyliridium (III), trichlorobis (trichlorophosphino) iridium (III) and the like.

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 segregation.

As noted above, the presently useful solid particles and discrete entities can be employed in a mass of combined particles which function as both the solid particles, e.g., promotes hydrocarbon conversion, and the alumina-based discrete entities, e.g., promotes oxidation of carbon monoxide and/or associates-disassociates with sulfur-containing combustion products. Such combined particles may be produced in any suitable manner, certain of which methods are conventional and known in the art.

One particularly preferred method for manufacturing the presently useful combined particles has special application for providing combined particles useful in a conventional fluidized bed reaction zone-regenerator system. A major portion by weight of such combined particles preferably have diameters in the range of about 10 microns to about 250 microns. This improved method comprises:

1. forming a mixture of a minor amount, preferably about 1% to about 40%, more preferably about 1% to about 20% and still more preferably about 1% to about 10%, by weight of calcined alumina-based discrete entities and a major amount, preferably about 60% to about 99%, more preferably about 80% to about 99% and still more preferably about 90% to about 99%, by weight of a binder, as hereinafter defined, in a hydrous state, the weight proportions being based on the proportions present in the combined particles hereinafter described, the binder, after calcination, having substantially the same properties and composition as the presently useful solid particles, described previously, at least a portion of the hydrous binder preferably being able to wet the external surface of discrete entities; and

2. drying and forming the mixture and thereby producing from the mixture combined particles which when calcined are of a size suitable for use as a catalyst in a fluidized bed reactor-regenerator system.

The average size, i.e., in diameter, of the calcined alumina-based discrete entities may be in the range of about 1 micron to about 135 microns, preferably about 1 micron to about 70 microns.

The calcined alumina-based discrete entities may be produced in any suitable manner. One particularly preferred method of manufacturing these entities comprises forming an aqueous slurry of hydrous alumina, drying and calcining at least a portion of the hydrous alumina thereby forming properly sized discrete entities. The aqueous slurry preferably contains about 5 to about 16, more preferably about 8 to about 14, weight percent of alumina (calculated as Al.sub.2 O.sub.3). The metal, e.g., platinum group metal, component or components may be added to the alumina-based discrete entities at one or more of various stages in the manufacture of such entities.

Step (2) of the present improvement may involve spray drying. Equipment which is conventionally used to produce catalyst particles suitable for use in fluidized bed reactors may be utilized in the practice of the present invention. For example, this equipment may involve at least one restriction or high pressure nozzle having a diameter in the range from about 0.01 in. to about 0.2 in., preferably from about 0.013 in. to about 0.15 in. The pressure upstream of this high pressure nozzle may range from about 400 psig. to about 10,000 psig., preferably from about 400 psig. to about 7000 psig. The material to be dried is sent through the nozzle system into a space or chamber. The pressure in the space or chamber downstream from the nozzle system is lower than that immediately upstream of the nozzle and is typically in the range from about 0 psig. to about 100 psig., preferably from about 0 psig. to about 20 psig. Once through the nozzle, the material to be dried is contacted for a relatively short time, e.g., from about 0.1 seconds to about 20 seconds with a gas stream which is at a temperature of from about 200.degree. F. to about 1500.degree. F., preferably from about 200.degree. F. to about 750.degree. F. The gas stream which may be, for example, air or the flue gases from an inline burner (used to provide a gas stream having the proper temperature) or a substantially oxygen-free gas, may flow co-current, counter-current or a combination of the two relative to the direction of flow of the material to be dried. The spray drying conditions, such as temperatures, pressures and the like, may be adjusted because, for example, of varying the composition of the material to be dried to obtain optimum results. However, this optimization may be achieved through routine experimentation.

An alternative to the high pressure nozzle described above is the "two-fluid" nozzle in which the material to be dried is dispersed by a stream of gas, typically air. The two fluid nozzle has the advantage of low operating pressure, e.g., from about 0 psig. to about 60 psig. for the material to be dried and from about 10 psig. to about 100 psig. for the dispersing gas. The dispersing gas may also function as at least a portion of the drying gas stream. The various operating parameters noted above may be varied in order to achieve the correct or desired combined particle size.

In order to minimize contact between the chamber walls and wet material, the chamber downstream from the nozzle system is large in size, e.g., from about 4 to about 30 feet in diameter and from about 7 to about 30 feet long, often with an additional conical shaped portion for convenient withdrawal of the dried material. The spray drying apparatus may also include separation means, e.g., cyclone separators, in the outlet gas line to recover at least a portion of the dried material entrained in this stream. If the dried material collected in the outlet gas separation means is not of the proper size to be of value as a fluid bed catalyst, this material may be recycled back to step (1) thus providing for optimum utilization of the catalyst materials.

The solid particles, alumina-based discrete entities and bound particles are often used in the reaction zone-regenerator system in the calcined state. Calcination may occur as part of the method of manufacturing and/or may occur in situ, i.e., during use in the reaction zone-regenerator system.

Calcination often involves treating the catalyst particles at high temperatures, e.g., from about 600.degree. F. to about 1700.degree. F. or more, for a period of time, e.g., about 4 hours, to release at least a portion of the water of hydration from the particles and catalytically activate the particles. Calcination may occur in an inert, oxidizing or reducing environment. Preferred calcination conditions include a temperature in the range of about 700.degree. F. to about 1600.degree. F., more preferably about 800.degree. F. to about 1500.degree. F., for a period of time in the range of about 0.1 hours to 48 hours, more preferably about 0.5 hours to about 20 hours.

Although this invention is useful in many hydrocarbon chemical conversions, the present catalyst, i.e., mixture comprising solid particles and discrete entities, and process find particular applicability in systems for the catalytic cracking of hydrocarbons and the regeneration of catalyst so employed. Such catalytic hydrocarbon cracking 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, 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, coal and the like. Such feedstock may comprise a mixture of straight run, e.g., virgin, gas oil. Such gas oil fractions often boil primarily in the range of about 400.degree. F. to about 1000.degree. F. Other substantially hydrocarbon feedstocks, e.g., other high boiling or heavy fractions of petroleum, shale oil, tar sand oil, coal and the like may be cracked using the apparatus and method of the present invention. Such substantially hydrocarbon feedstock often contain minor amounts of contaminants, e.g., sulfur, nitrogen and the like. In one aspect, the present invention involves converting a hydrocarbon feedstock containing sulfur and/or sulfur chemically combined with the molecules of hydrocarbon feedstock. The present invention is particularly useful when the amount of sulfur in such hydrocarbon feedstock is in the range of about 0.01% to about 5%, preferably about 0.1% to about 3%, by weight of the total feedstock.

Hydrocarbon cracking conditions are well known and often include temperatures in the range of about 850.degree. F. to about 1100.degree. F., preferably about 900.degree. F. to about 1050.degree. F. Other reaction conditions usually include pressures of up to about 100 psig; catalyst to oil ratios of about 1 to 5 to about 25 to 1; and weight hourly space velocities (WHSV) of from about 3 to about 60. These hydrocarbon cracking conditions are not critical to the present invention and may be varied depending, for example, on the feedstock and solid particles or combined particles being used and the product or products wanted.

In addition, the catalytic hydrocarbon cracking system includes a regeneration zone for restoring the catalytic activity of the solid particles or combined particles of catalyst previously used to promote hydrocarbon cracking. Carbonaceous, in particular sulfur-containing carbonaceous, deposit-containing catalyst particles from the reaction zone are 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 particles. When the carbonaceous deposit material contains sulfur, at least one sulfur-containing combustion product is produced in the regeneration zone and may leave the zone with the regenerator flue gas. The conditions at which such free oxygen-containing gas 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 about 900.degree. F. to about 1500.degree. F., preferably about 900.degree. F. to about 1300.degree. F. and more preferably about 1100.degree. F. to about 1300.degree. F. Other conditions within such regeneration zone include, for example, pressures up to about 100 psig., average catalyst contact times within the range of about 3 minutes to about 120 minutes, preferably from about 3 minutes to about 75 minutes. Sufficient oxygen is preferably present in the regeneration zone to completely combust the carbon and hydrogen of the carbonaceous deposit material, for example, to carbon dioxide and water. The amount of carbonaceous material deposited on the catalyst in the reaction zone is preferably in the range of about 0.005% to about 15%, more preferably about 0.1% to about 10%, by weight of the catalyst. The amount of sulfur, if any, contained in the carbonaceous deposit material depends, for example, on the amount of sulfur in the hydrocarbon feedstock. This deposit material may contain about 0.01% to about 10% or more by weight of sulfur. 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 silica-alumina and at least one crystalline aluminosilicate having pore diameters of about 8A to about 15A 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 promotors such as the rare earth metals, in particular, cerium.

The catalyst, i.e., mixture comprising solid particles and discrete entities and/or combined particles, 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 about 3 to about 20 carbon atoms per molecule and aromatic hydrocarbons containing one or two rings and from 7 to about 18 carbon atoms per molecule. The process of the invention is particularly useful for the disproportionation of methyl benzenes containing 7 to about 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 to xylenes can be increased by introducing higher methyl-benzenes with the toluene feed. These higher methyl-benzenes 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.sub.9 + 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.sub.9 + stream, the extent to which the C.sub.9 + 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.sub.9 + 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 toluene 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 about 5 to 60, preferably about 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 vapor phase is disproportionated in a moving catalyst bed reactor in which the catalyst comprises a mixture of about 80 to 99% by weight of solid particles which contain about 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 about 1% to about 20% of discrete entities comprising about 1% to about 20% by weight of a crystalline aluminosilicate of substantially the same pore size as the crystalline aluminosilicate included in the solid particles, at least about 80% by weight of alumina and about 0.05 ppm. to about 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 about 70.degree. F. to about 1200.degree. F. and more preferably about 800.degree. F. to about 1000.degree. F. and preferably at approximately atmospheric pressures such as about 0 psig. to about 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 about 6 to about 240 and more preferably about 12 to about 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 about 800.degree. F. to about 1500.degree. F. and more preferably about 900.degree. F. to about 1200.degree. 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 examples clearly illustrate the present invention. However, these examples are not to be interpreted as specific limitations on the invention.

This example illustrates certain of the advantages of the present invention.

A quantity of alumina-based particles of substantially pure gamma alumina, which is derived from a mixture of alumina monohydrate and amorphous hydrous alumina, in the shape of spheres having a diameter of about 1/16-1/4 inch is charged into a vessel equipped with means for evacuating the vessel. These spheres can be obtained, for example, by the conventional oil-drop method. 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.degree. F. for one hour.

Example I is repeated except that substantially all of the alumina based particles have diameters in the range of about 50 microns to about 100 microns. Such particles can be obtained by conventional spray drying techniques. As in Example I, the final discrete entities contain about 100 ppm. of platinum, by weight of the total discrete entities, calculated as elemental platinum. Also, as in Example I, the platinum is substantially uniformly distributed in the discrete entities.

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 the same approximate size as the discrete entities from Example I, is combined with the discrete entities of Example I 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 commercial moving-bed hydrocarbon conversion service.

The mixture of solid particles and discrete entities is loaded to a conventional TCC moving catalyst bed reaction-catalyst regeneration system. Briefly, this system causes catalyst particles to flow by gravity from supply hopper through a reaction zone, where the catalyst is contacted with hydrocarbon feedstock at hydrocarbon conversion conditions and the desired hydrocarbon chemical conversion takes place. The catalyst then flows to a catalyst regeneration zone where the catalyst is contacted with an oxygen-containing gaseous medium to combust at least a portion of the catalyst carbonaceous deposits which are formed in the reaction zone. The regenerated catalyst leaves the regeneration zone and is air lifted back to the supply hopper and the cycle is repeated.

Toluene is disproportionated in this moving catalyst bed reactor system loaded with the catalyst mixture. The catalyst is advanced through at a rate such that each particle has an averge residence time in the reaction zone of about 50 minutes. With equilibrium conditions achieved the reaction zone temperature is maintained at about 955.degree. F. and a reaction zone pressure of between about 5 psig. and about 20 psig. is maintained. Toluene is fed into the reactor at a weight hourly space velocity (WHSV) of about 1.3. Air is fed to the catalyst regeneration zone which is maintained at conditions to combust at least a portion of the carbonaceous catalyst deposit material, e.g., temperature of about 1000.degree. F. to 1100.degree. F. and average catalyst residence time of about 50 minutes.

After a period of time in operation, it is determined that the catalyst mixture according to the present invention is effective both to promote toluene disproportionation in the reaction zone and to promote the oxidation of carbon monoxide to carbon dioxide in the regeneration zone. The catalyst mixture of this invention is found to provide improved results, e.g., improved carbon monoxide oxidation catalytic activity stability while having substantially no deleterious effect on the hydrocarbon conversion in the reaction zone.

Example I is repeated, except that the alumina-based spheres include about 7% by weight of a crystalline aluminosilicate known to be catalytically active to promote hydrocarbon conversion.

Example III is repeated except that the discrete entities produced in Example I are replaced by the discrete entities of Example IV. After a period of time in toluene disproportionation-catalyst regeneration service, this catalyst mixture is shown to be effective to promote both toluene disproportionation in the reaction zone and carbon monoxide oxidation in the regeneration zone.

Examples III and V are repeated except that the catalyst mixtures are used to crack a petroleum derived gas oil fraction, a combined fresh feed and recycle stream, in the moving catalyst bed reaction-regeneration system. The fresh gas oil fraction boils in the range of about 400.degree. F. to about 1000.degree. F. and is substantially hydrocarbon in nature, containing minor amounts of sulfur and nitrogen as contaminants. Conventional hydrocarbon cracking and catalyst regeneration conditions are employed in the reaction zone and regeneration zone, respectively.

The catalyst mixtures are found to be effective to promote hydrocarbon cracking and to promote carbon monoxide oxidation. Such hydrocarbon cracking operation provides improved results, e.g., prolonged carbon monoxide oxidation catalytic activity while providing for effective hydrocarbon cracking catalytic activity.

The discrete entities produced in Example II are intimately comingled with solid particles of commercially available hydrocarbon cracking catalyst similar to that used in Example III except that the substantially all, by weight, of the particles have diameters in the range of about 20 microns to about 150 microns. The hydrocarbon cracking catalytic activity of such particles is equilibrated by service in a conventional commercial fluid-bed catalyst cracking (FCC) unit. The resulting catalyst mixture includes 5 parts by weight of discrete entities and 95 parts by weight of the solid particles.

This catalyst mixture is used to crack a petroleum derived gas oil stream, similar to that described in Examples VI and VII, to lower boiling hydrocarbons in a conventional FCC unit.

Briefly, such 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 with the reaction zone include:

Temperature, .degree. F.: 930

Pressure, psig.: 8

WHSV: 15

Such conditions result in about 70% by volume conversion of the gas oil feedstock to products boiling at 400.degree. 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, 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 the regeneration zone. Conditions within the regeneration zone include:

Temperature, .degree. F.: 1150

Pressure, psig.: 8

Average Catalyst Residence Time, min.: 12

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 zone.

One additional feature of the present invention illustrated by the above Example involves the processing of sulfur contaminated hydrocarbon feedstock. For example, fresh hydrocarbon feedstocks, e.g., petroleum derived gas oils, often contain about 0.01% to about 5% or more, preferably from about 0.1% to about 3%, by weight of sulfur. Such feedstocks form carbonaceous deposits on the catalyst which also contain sulfur. During regeneration of such catalyst by contacting with an oxygen-containing gaseous stream, at least a portion of this deposit sulfur is oxidized to sulfur dioxide and, ordinarily, leaves the system with combustion flue gases. It is now found that the presence of at least one platinum group metal component in the catalyst regeneration zone acts to promote the further oxidation of sulfur and sulfur-containing compounds to SO.sub.3. The SO.sub.3 thus formed, associates with the alumina of the discrete entities, until such entities are placed in a hydrocarbon chemical conversion reaction zone environment. Under such reaction zone conditions, at least a portion of this sulfur trioxide is converted to H.sub.2 S which is removed from the reaction zone with the hydrocarbon conversion products. Thus, in this embodiment, i.e., when processing a sulfur contaminated hydrocarbon feedstock, the present catalyst and process provide for reduced sulfur dioxide emissions from the regenerator zone combustion flue gases.

Example VIII is repeated except that the discrete entities employed include about 7% by weight of a crystalline aluminosilicate known to be catalytically active to promote hydrocarbon cracking.

The present catalyst and process provide improved properties and results. For example, the present alumina-based discrete entities have outstanding carbon monoxide oxidation catalytic activity stability. That is, the time rate decline of carbon monoxide oxidation catalytic activity of the present catalyst is reduced. Clearly, the present catalyst and process provide for improved hydrocarbon chemical conversion.

A mass of combined particles is prepared as follows:

The alumina-based discrete entities are prepared by forming an aqueous slurry of alumina hydrate so that the alumina concentration, calculated as Al.sub.2 O.sub.3, is about 9% by weight. The composition of the alumina hydrate is established by X-ray diffraction to be about 56% by weight boehmite, and 44% by weight amorphous alumina hydrate. The average boehmite crystallite size is about 56A units. This slurry is stirred for about 1 hour to insure uniformity and then spray dried at a temperature less than that required to eliminate a substantial portion of the water of hydration to form discrete entities. These discrete entities are calcined in an electric muffle furnace using a programmed timer to increase the temperature 300.degree. F. per hour to 1050.degree. F. and maintain this temperature for 3 hours.

Essentially all the calcined discrete entities have a maximum dimension of less than about 200 microns. Micromesh analysis of these calcined discrete entities is as follows:

The discrete entities larger than 60 microns are discarded.

The solid particles-binder material is prepared by adding 6000 parts by weight of a solution containing Philadelphia Quartz Company "E" brand sodium silicate solution diluted with an equal weight of water to 3000 parts by weight of dilute (density--1.234) H.sub.2 SO.sub.4. After these two solutions are thoroughly mixed, 4000 parts by weight of a solution containing 1200 parts by weight of Al.sub.2 (SO.sub.4).sub.3.18H.sub.2 O is added. Sufficient crystalline alumino-silicate, known to be effective to promote hydrocarbon cracking, is added to the mixture so that the final solid particles-binder material contains, on a dry weight basis, about 10% of such crystalline aluminosilicate. The resulting mixture is let stand to gel. The resulting hydrogel is cut into about 3/4" cubes and covered with concentrated NH.sub.4 OH diluted with an equal volume of water. This material is let stand overnight and has a final pH of 11. The material is then washed by percolation until free of Na.sup.+ and SO.sub.4 =ion.

500 parts (on a dry weight basis) of the washed hydrogel and 80 parts (on a dry weight basis) of the remaining calcined discrete entities and 10,000 parts by weight of water are throughly mulled, ground and mixed with agitation. The resulting slurry is dried in a spray drier. This drier is equipped with a two-fluid nozzle system which uses air at about 20 psig. to disperse the slurry into the drying chamber. The drying gas, i.e., flue gas from an inline burner, enters the drying chamber at about 705.degree. F. and exits the chamber at a temperature which ranges from about 305.degree. F. to 315.degree. F. This drying gas is introduced into the top of the drying chamber while the slurry is dispersed upward from near the bottom of the chamber. In this way, the material to be dried is exposed to both counter-current flow (during assent from the nozzle system) and co-current flow (during gravity dissent) relative to the downward drying gas flow. The resulting dried particles are calcined in a manner similar to the calcination of the alumina based discrete entities described above. The resulting combined particles are screened to provide particles properly sized for use in a fluidized catalytic bed reaction zone-regenerator hydrocarbon cracking system.

Example X is repeated except that the alumina-based discrete entities are impregnated with platinum as in Examples I and II prior to being incorporated into the combined particles. The discrete entities contain about 100 ppm by weight of platinum, calculated as elemental platinum, substantially uniformily distributed in the discrete entities.

Example VIII is repeated except that the physical mixture of discrete entities and catalyst particles used in Example VIII are replaced by the combined particles produced in Example X and the hydrocarbon feed contains about 0.5% by weight of sulfur. After a period of time, these combined particles are shown to remain effective to promote both hydrocarbon cracking in the reaction zone and to reduce the amount of sulfur atmospheric emissions in the regeneration zone flue gases.

Example XII is repeated using the combined particles produced in Example XI as catalysts. Over a period of time, these combined particles remain effective to promote hydrocarbon cracking in the reaction zone, reduce the amount of sulfur atmospheric emissions in the regeneration zone flue gases and, also, promote the oxidation of carbon monoxide in the regeneration zone.

While this invention has been described with respect to various specific examples and embodiments, it is to be understood that the invention is not limited thereto and that it can be variously practiced within the scope of the following claims.