DEHYDROGENATION CATALYST COMPOSITION

Abstract: This invention relates to a new catalyst for converting hydrocarbons. The catalyst comprises a platinum group component, a Group IVA component, especially tin, an alkali or alkaline earth component, more than 0.2 weight %, calculated on an elemental basis, of a halogen component and a porous carrier material, wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is more than 10. The catalyst is particularly useful for dehydrogenating paraffins having from 2 to 5 or more carbon atoms to the corresponding mono-olefins, or for dehydrogenating mono-olefins having from 3 to 5 or more carbon atoms to the corresponding di-olefins.

Description: "DEHYDROGENATION CATALYST COMPOSITION" BACKGROUND OF THE INVENTION (1) Field of the Invention This invention pertains to the conversion of hydrocarbons, especially the dehydrogenation of dehydrogenatable hydrocarbons, in the presence of a catalyst composite. This invention alsopertains to a new catalyst composite and a method of raking it. Dehydrogenating hydrocarbons is an important commercial hydrocarbon conversion process because of the great demand for dehydro genated hydrocarbons for the manufacture of various chemical products such as detergents, high octane gasolines, pharmaceutical products, plastics, synthetic rubbers, and other products well-known to those skilled in the art. One example of this process is dehydrogenating isobutane to produce isobutylene which can be polymerized to provide tackifying agents for adhesives, viscosity-index additives for motor oils and impart-resistant and anti-oxidant additives for plastics. (2) Description of the Prior Art It is well-known to catalyze the conversion of hydrocarbons with solid catalysts comprising platinum group metals. For example, U.S. Patents Nos. 2,479,109 and 2,479,110 disclose a catalyst compris - ing platinum on alumina with combined halogen for catalyzing reforming, hydrogenating, hydrocracking, oxidizing and dehydrogenating reactions. The ter "reforming" in these patents means simultaneously dehydrogenating, isomerizing, cyclizing and cracking a gasoline feedstock. The combined halogen component of this catalyst contributes to a controlled type of cracking activity. The halogen content is preferably maintained below about 8 weight vr: of the alumina to avoid excessive side reactions, including cracking reactions, which result in excessive oas formation and low liquid volume yield of reformed products. These patents do not disclose utilizing an alkali'or alkaline earth component. U.S. Patent No. 2,602,772 discloses convert hydrocarbons, especially reforming and hydrocracking hydrocarbons, with a catalyst comprising platinum, not more than 1 weight ; of an oxide of an alkaline earth metal or magnesium and from about 0.1 to about 8 weight % combined halogen on alumina. According to this patent catalysts containing an alkaline earth metal or magnesium oxide produced less carbon, or coke, after 3 days of reforming operations. The halogen content for catalysts of this patent is from 0.3 to 3 weight , preferably between 0.6 and 2.3 weight *. This patent does not disclose utilizing a Group IVA component. U.S. Patent No. 2,930,763 discloses a two-step process for reforming hydrocarbons. In the first step a hydrocarbon fraction containing unsaturated compounds and/or nitro, sulfur or oxygen compounds is contacted with hydrogen in the presence of a catalyst comprising platinum and an alkali metal component on alumina to hy- drogenate and saturate the unsaturated compounds and/or reduce the nitrogen, sulfur or oxygen content of the hydrocarbon fraction. In the second step of this process the treated hydrocarbon¯fraction from the first step is contacted at reforming conditions with a conventional reforming catalyst comprising platinum and combined halogen on alumina. Optionally the catalyst utilized in the first step may contain halogen. A catalyst consisting essentially of alumina, from about O.Olck to about 1 by weight of platinum, from about 0.1 to about 1 by weight of combined halogen, and from about 0.01 to about 1° by weight of an alkali metal is recited in Claim 2 of this patent. This patent also does not disclose utilizing a Group IVA component. U.S. Patent No. 3,531,543 discloses dehydrogenating hydrocarbons with a catalyst comprising platinum, tin and neutralized metal oxide carrier. The preferred carriers are oxide materials whose intrinsic acidity is substantially neutralized by an alkali or alkaline earth metal component. Pure alumina, for example, has such intrinsic acidity. (cf. Pines and Haag, Journal of the America Chemical Society, 82, 2471 (1960)). For example, alumina catalyzed the skeletal isomerization of olefins, dehydrates alcohols and strongly chemisorbs amines. Also, with increasing amounts of alkali present there is a parallel decrease in these acidic alumina properties. Preferably the carrier of this patent is a non-acidic lithiated alumina. Preferably, the catalysts of this patent are prepared from halogen-free compounds. Compounds containing halogen may be used to rrnufacture the catalyst provided the halogen residue is efficiently removed from the final catalyst composite. U.S. Patent No. 3,745,112 discloses a catalyst for reform- ing hydrocarbons which comprises a platinum group component, a tin component and a halogen component with a porous carrier material. This patent discloses also that a platinum-tin-alkali or alkaline earth composite is a particularly effective catalyst for dehydrogenating hydrocarbons. In the dehydrogenation catalyst composite of this paten; wherein the alkali or alkaline earth component is added the amount of halogen, if not entirely eliminated, is minimized in order to minimize or neutralize the acidic functions of the alumina and halogen components which tend to promote hydrocarbon cracking and isomerization side reactions which are not desired in commercial dehvdrogenation processes. U.S. Patent No. 3,892,657 discloses that indium is a goodS prompter for platinum group-containing catalysts when the atomic ratio of indium to platinum is from about 0.1:1 to about 1:1. This patent discloses also that a Group IVA component selected frorn the group of germanium, tin, and lead can be added to the acidic forw of the indium-containing catalysts for reforming applications. The acidic form of this catalyst, then, comprises a platinum group cor:- ponent, a Group IVA component, an indium component, a halogen compo- nent and a porous carrier mterial. The acidic catalyst contains up to about 3.5 weight g halogen for reforming applications and up to about 10 weight e halogen for isomerization and cracking applications. In the dehydrogenation catalyst of this patent wherein the alkali or alkaline earth component is added, however, the halogen content is maintained at the lowest possible value (about 0. weight ). U.S. Patent No. 3,9g9,451 discloses a new method for mak- ing e dehydrogenation catalyst comprising a platinum component, a tin component and an alkali or alkaline earth component. In Exam- ple V this patent discloses a platinum, tin and potassium composition comprising less than 0.2 weight % combined chloride. U.S. Patent Nos. 4,329,258 and 4,363,721 disclose a catalyst comprising a platinum group metal, tin, an alkali or alkaline earth metal and combined halogen element with a refractory oxidemineral carrier. The atomic ratio Gr alkali or alkaline earth met- al to. platinum group metal for catalysts of these patents is from 0.2 to 10. The patentees discovered that parts-per-million quantities of alkali or alkaline earth component added to catalyst containing a platinum group metal, tin and halogen helped increase the C5+ yield in a reforming process. British Patent 1 499 297 discloses a dehydrogenation cat; lyst comprising platinum, at least one of the elements gallium, indium and thallium, and an alkali metal, especially lithium: or po- potassium, with alumina as the carrier material. The catalysts of this patent also contain a halogen in an amount of from 0.01 to 0.1 weight . The halogen content is purposely reduced to within this low weight range in order to increase the selectivity and stability of the catalyst. In the prior art dehydrogenation catalysts acknowledged above comprising a platinum group component, a Group IVA component and an alkali or alkaline earth component wherein the atomic-ratio of the alkali or alkaline earth component to the platinum group component is more than 10, then, the halogen component has been eliminated completely or otherwise maintained at the lowest possible level, generally less than 0.1 weight , and always less than 0.2 weight , calculated on an elemental basis. Surprisingly, we discovered that incorporating more halogen component than was previously present in these types of dehydrogenation catalysts provided catalysts with improved activity and selectivity characteristics. SUMMARY OF THE INVENTION This invention relates to a new catalyst for converting hydrocarbons, especially for dehydrogenating hydrocarbon. The cata lyst comprises é platinum group component, a Group IVA component, an alkali or alkaline earth component, more than 0.2 weight ', calculated qn an elemental basis, of a halogen component and a porous carrier material, wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is more than 10. The catalyst is particularly useful for dehydrogenating paraffins havino from 2 to 5 or more carbon atoms to the corresponding mono-olefins or for dehydrogenating mono-olefins having from 3 to 5 or more carbon atoms to the corresponding di-olefins. BRIEF DESCRIPTION OF THE DRAWINGS Figures 1-6 illustrate results from tests with catalysts of this invention, namely catalysts "A", "C" and "E" compared with results fro tests with prior art catalysts "B", "0" and "F", respectively. DETAILED DESCRIPTION DF THE INVENTION Heterogeneous catalysis practice, that is, catalyzing reactions of liquid or gaseous reactants with solid catalysts, is itr portant to industry. For many years persons skilled in the art of hydrocarbon conversion, for example, have endeavored to discover and develop new hydrocarbon conversion catalysts with improved performince characteristics. Many of these persons are highly trained in one or more of a wide variety of disciplines including, for example, organic and inorganic chemistry, solid state and surface physics, ceramics, metallurgy and chemical engineering. Notwithstanding this high level of skill in the art, hydrocarbon conversion catalysis, like other fields of heterogeneous catalysis, continues to be "a vast-and confusing-field replete with-an enormous quantity of perhaps significant but empirical facts intermixed with perhaps useful theories." (C. N. Satterfield, Heteroceneous Catalvsis in Practice, preface (19by)). Ccnse2uently, significant contributions to the art of het- erogenous hydrocarbon conversion catalysis have generally resulted from empirical discoveries and developments rather than from theoretical extrapolations. Our contribution to this field of art is that we have discovered a new catalyst for dehydrogenating hydrocarbons. The catalyst comprises a platinum group component, a Group IVA component, an alkali or alkaline earth component, more than 0.2 weight %, calculated on an elemental basis, of a halogen component and a porous carrier ma- serial, wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is more than 10. The platinum. group component is preferably present in the final composite in an amount, calculated on an elemental basis, of about 0.01 to 5 weight %; the Group IVA component is preferably present in an amount of about 0.01 to 5 weight C; the alkali or alkaline earth component is preferably present in an amount of about 0.01 to 15 weight C; ; and the halogen component is present preferably in an amount of about 0.2 to 15 weight . Dehydrogenation conditions include a temperature of from about 4000 to 900 C, a pressure of from about 0.01 to 10 atmospheres (1 to 1000 kPa) and a liquid hourly space velocity (LHSV - calculated on the basis of the volume amount, as a liquid at standard conditions, of hydrocarbon charged to the dehydrogenation zone per hour divided by the volume of the catalyst bed utilized in the dehydrogenation zone) of from about 0.1 to 109 her. 1 The hydrocarbons to be dehydrogenated are dehydrogenatable hydrocarbons having from 2 to 30 or more carbon atoms including paraffins, alkylaromatics, naphthenes and olefins. One group of hydrocarbons which can be dehydrogenated with the catalyst is the group of normal paraffins having from 2 to 30 or more carbon atoms. The catalyst is particularly useful for dehydrogenat- ing paraffins having from 2 to 5 or more carbon atoms to the corresponding mono-olefins or for dehydrogenating mono-olefins having from 3 to 5 or more carbon atoms to the corresponding di-olefins. Our invention, then, is a new catalyst composition which comprises a platinum group component, a Group IVA component, an al ka0i or alkaline earth component, more than 0.2 weight, calculated on an elemental basis, of a halogen component and a porous carrier material, wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is more than 10. To be commercially successful a dehydrogenation catalyst must satisfy three requirements, namely high activity, high selectivity and good stability. Activity is a measure of the catalyst's ability to help convert reactants into products at a specified severity level where severity level means the reaction conditions used - that is, the temperature, pressure, contact time and presence of diluents such as hydrogen if any. For dehydrogenation catalyst activity we measured the conversion, or disappearance, of paraffins in percent relative to the amount of paraffins in the feedstock. Selectivity is a measure of the catalyst's ability to help convert reactants into desired product or products relative to the amount of reactants charged or converted. For catalyst selectivity we measured the amount of olefins in the product, in mol percent, relative to the total mols of the paraffins converted. Stability is a measure of the rate of change with time.on stream of the activity and selectivity parameters - the smaller rates implying the more stable catalysts. Since dehydrogenation of hydrocarbons is an endothermic reaction and conversion levels are limited by chemical equilibrium, it is desirable in order to achieve high conversion to operate at high temperatures and low hydrogen partial pressures. At such severe conditions it is difficult to maintain high activity and selectivity for long periods of time because undesirable side reactions such as aromatizatiDn, cracking, isomerization and coke formation increase. Therefore, there is a considerable demand for a new hydrocarbon dehydrogenation catalyst with improved activity, selectivity and stability characteristics. The catalyst of our invention, that is, a dehydrogenation catalyst comprising a platinum group component, a Group IVA component, an alkali or alkaline earth component, more than 0.2 weight , calculated on an elemental basis, of a halogen component and a porous carrier material wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is more than 10, will answer to such a demand. Regarding the platinum group component of our catalyst composite, it may be selected from the group of platinum or palladium or iridiumi or rhodium or osmium or ruthenium or mixtures thereof. Platinum, however, is the preferred platinum group component. We believe that substantially all of the platinum group component exists within the catalyst in the elemental metallic state. Preferably the platinum group component is well dispersed throughout the catalyst. The platinum group component generally will comprise about 0.01 to 5 weight , calculated on an elemental basis, of the final catalytic composite. Preferably the catalyst comprises about 0.1 to 1 weight * platinum. The platinum group component may be incorporated in the catalytic composite in any suitable manner such as, for-example, by coprecipitation or cogelation, ion exchange or impregnation, or deposition fro a vapor phase or from an atomic source or by like procedures either before, while or after other catalytic components are incorporated. The preferred method of incorporating the platinum group component is to impregnate the carrier material with a solution or suspension of a decomposable compound of platinum group metal. For example, platinum may be added to the support by commingling the latter with an aqueous solution of chioroplatinic acid. Another acid, for example, nitric acid or other optional components may be added to the impregnating solution to further assist in dispersing or fixing the platinum group component in the final catalyst composite. Regarding the Group IVA component, it may be selected from the group of gerranium or tin or lead or mixtures thereof. Tin, however, is the preferred Group IVA component. We believe the Group IVA component exists within the catalyst in an oxidation state above that of the elemental metal. The Group IVA component may be present as a compound such as the oxide, for example, or combined with the carrier material or with the other catalytic components. Preferably the Group IVA component is well dispersed throughout the catalyst. The Group IVA component generally will comprise about Q.01 to 5 weight , calculated on an elemental basis, of the final catalyst composite. Preferably the catalyst comprises about 0.2 to 2 weight ° tin. The Group IVA component nay be incorporated in the catalytic composite in any suitable manner such as, for example, by coprecipitation or cogelation, ion exchange or impregnation or by like procedures either before, while or after other catalytic components are incorporated. A preferred method of incorporating the tin component is cogelling it during preparation of the porous carrier material. For example, tin may be incorporated in an alumina carrier material by mixing a soluble tin compound such as stannous or stannic chloride with an alumina hydrosol, adding a gelling agent such as hexamethylenetetramine and dropping the mixture into an oil bath to form spheres containing alumina and tin. h preferred method of incorporating the gerrrianium component is to impregnate the carrier material with a solution or suspension of a decomposable compound of germanium such as germanium tetrachlorde dissolved in an alcohol. Likewise, the lead component may be impregnated frorr a solution of lead nitrate in water. Regarding the alkali or alkaline earth component, it may be selected from the group of cesium, rubidium, potassium, sodium and lithium or from the group of barium, strontium, calcium and magnesium or mixtures of components from either or both of these groups. Lithium, sodium, potassium, cesium and magnesium, however, are the preferred alkali or alkaline earth components. We believe that the alkali or alkaline earth component exists in the final catalytic composite in an oxidation state above that of the elemental metal. The alkali or alkaline earth component may be present as a compound such as the oxide, for example, or combined with the carrier material or with the other catalytic components. Preferably the alkali or alkaline earth component is well dispersed throughout the catalytic composite. The alkali or alkaline earth component generally will comprise about 0.01 to 15 weight , calculated on an elemental basis, of the final catalytic composite. Preferably the catalyst comprises about 1 to 3 weight tr potassium. The alkali or alkaline earth component may be¯incorporated in the catalytic composite in any suitable manner such as, for example, by coprecipitation or cogelation, by ion exchange or impregnation, or by like procedures either before, while or after other catalytic components are incorporated. A preferred method of incorporating the potassium component is to impregnate the carrier material with a solution of potassium nitrate. In contradistinction to reforming or isomerization catalysts of the prior art, the catalyst of our invention comprises an atomic ratio of alkali or alkaline earth component to platinum group component of more than 10. In the prior art catalysts comprising a platinum group component and an alkali or alkaline earth component, on the other hand, the amount of the alkali or alkaline earth component was purposely maintained below this level. This is because addition of the alkali or alkaline earth component tends to decrease the acidity of these catalysts, which acidity is responsible for acceler atinc isomerization and cracking reactions. For reforming and isomer iztion catalysts it is desired to maintain some substantial amount of catalyst acidity, so the atomic ratio of alkali or alkaline earth component to platinum group component for these catalysts has been rintained at less than or equal to 10. For our catalyst, however, the atomic ratio of the alkali or alkaline earth component to the platinum group component is preferably from about 15 to about 25. Regarding the porous carrier material, it is preferably a porous,absorptive support with high surface area of from about 25 to about 500 mê/g. The propous carrier material should be relatively refractory to the conditions utilized in the hydrocarbon conversion process. It is intended to include within the scope of our invention the use of carrier materials which have traditionally been utilized in hydrocarbon conversion catalysts such as', for -example; (1-) activated carbon, coke, or charcoal; (2) silica or silica gel, silicon carbide, clays, and silicates, including synthetically prepared and naturally occurring ones, which may or may not be acid treated, for example, attapulgus clay, china clay. diatomaceous earth, fuller's earth, kaolin, kieselguhr, etc.; (3) ceramics, procelain, crushed firebrick, bauxite; (4) refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide, cerium oxide, hafnium oxide, zinc oxide, magnesia, boric, thoria, silica-alurrna, silica-magnesia, chromie- alumina, alumina-boria, silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such as naturally occurring or synthetically prepared mardenite and/or faujasite, for example, either in the hydrogen form or in a form which has been exchanged wit metal cations; (6) sDinels such as MgAl2O4, FeA1204, 2nAl204, CaAl2O4, and other like compounds having the formula MO-A1203 where M is a metal having a valence of 2; and (7) combinations of materials from one or more of these groups. The preferred carrier material for our catalyst is alumina, especially gamma- or eta-alumina. The preferred alumina carrier material may be prepared in any suitable manner from synthetic or naturally occurring raw materials. The carrier may be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, etc., and it may be utilized in any particle size. A preferred shape of alumina is the sphere. -A preferred particle size is about 1/16 inch (1.60 mm) in diameter, though particles as small as about 1/32 inch (0.80 mm), and smaller, may also be utilized. To make alumina spheres aluminum metal is converted into an alumina sol by reacting it with a suitable peptizing acid and water, and then dropping a mixture of the resulting sol and a gelling agent into an oil bath to form spherical particles of an a allumina gel which are easily converted into the preferred gamma- or eta-alumina carrier material by known methods including aging, drying and cal cinin . To rke alu-::ina cylinders, an alumina powder is mixed with water and enough of a suitable peptizing agent such as nitric acid, for example, until an extrudable dough is formed. The dough is then extrude through a suitably-sized die and cut to form extrudate particles Other shapes of the alumina carrier material may also be prepared by conventional methods. After the alumina particles are shaped generally they are dried and calcined. The alumina carrier may be subjected to intermediate treatments during its preparation, includinc.washing with water or a solution of ammonium hydrox idle, for example, which treatments are well-known in the art. The catalytic composite of our invention also contains a halogen component. The halogen component may be either fluorine, chlorine, brorine or iodine or mixtures thereof. Chlorine and bromine are the preferred halogen components. The halogen component is generally present, we believe, in a combined state with the porous carrier traterial. Preferably the halogen component is well dispersed throughout the catalytic composite. The halogen component will comprise from more than 0.2 weight % to about 15 weight %, calculated on an elemental basis, of the final catalytic composite. Preferably the catalyst comprises about 1-to 3 weight % chlorine. The halogen component may be incorporated in the catalytic composite in any suitable manner, either during the preparation of the carrier material or before, while or after other catalytic components are incorporated. For example, the alumina sol utilized to form the preferred aluminum carrier material may contain halogen and thus contribute at l-east some portion-of the balogen content in tht final catalyst composite. Also, the halogen component or a portion thereof tnay be added to the catalyst composite during the incorporation of the carrier material with other catalyst components, for ex apple, by usinc chloroplatinic acic to impregnate the platinum com- ponent. Alsc, the haloc-er component or portion thereof may be added to the catalyst composite by contacting the catalyst with the halogen or a compound, solution, suspension or dispersion containing the halogen before or after other catalyst components are incorporated with the carrier material. Suitable compounds containing the halogen include acids containing the halogen, for exar:.ple,hydro- chloric acid. Or, the halogen component or a portion thereof may be incorporated by contacting the catalyst with G compound, solution. suspension or dispersion containing the helogen in a subsequent catalyst regeneration step. In the regeneration step carbon depos- ited on the catalyst as coke during use of the catalyst in hydrocarbon conversion process is burned off the catalyst and the platinum group component on the catalyst is redistributed to provide a regenerated catalyst with performance characteristics much like the fresh catalyst. The halogen component may be added during the car bo burn step or during the platinum group component redistribution step, for example, by contacting the catalyst with a hydrogen chloride gas. Also, the halogen component may be added to the catalyst composite by adding the halogen or a compound, solution, suspension or dispersion containing the halogen, such as propylene dichloride, for example, to the hydrocarbon feed stream or to the recycle gas during operation of the hydrocarbon conversion process. In contradistinction to the dehydrogenation catalysts of the prior art, the catalyst composite of our invention comprises more than 0.2 weight hs calculated on an elemental basis, of a halogen component. -In the prior art dehy-drogenationcatalysts com-- prising a platinum group component and an alkali or alkaline earth component wherein the atomic ratio of the alkali or alkaline earth component to te platinum croup component is more than 1D, on the other hand, the halogen component was purposely eliminated entirely or otherwise maintained at the lowest possible level. This was accomplished generally by treating the catalyst with a stream of high temperature ste or a mixture of steaw. and a diluent suc as air or hydrogen or ri.ropen to remove the halogen component. In any event, the prior art dehydrogenation catalysts maintained the halogen component at less than 0.2 weight % of the catalyst compos- ite, calculated on an elemental basis. Tie halogen component in the catalyst of our invention is an active catalyst component. The active halogen component helps improve the activity of our catalyst for dehydrogenating hydrocarbons. Also, the active halogen component helps suppress carbon formation on our catalyst durinc its use in a dehydrogenation process. These advantages are obtained with our catalyst without increesed undesirable isomerization or cracking side reactions taking place, that is, the selectivity of our catalyst is about the same as for prior art dehydrogenation catalysts. Optionally the catalyst of our invention may also contain -a sulfur component. Generally the sulfur component will comprise about 0.01 to 10 weight , calculated on an elemental basis, of the final catalytic composite The sulfur component may be incorporated intc the catalytic composite in any suitable manner. Preferably sulfur or 2 compounc' containing sulfur such as hydrogen sulfide or a lower molecular weight mercaptan, for example, is contacted with the catalyst composite in the presence of hydrogen at - hydrogen tlo sulfur ratio of about 100 and a temperature of from about low to about SEO'C, preferably under water-free conditions, to incorporate the sulfur component. Optionally, the catalyst may also contain other, additional components or mixtures thereof which act alone or in concert as catalyst modifiers to improve catalyst activity, selectivity or stability. Some well-known catalyst modifiers include antimony, arsenic, beryllium, bismuth, cadmium, calcium, chromium, cobalt, copper, gallium, gold, indium, iron, lithium, manganese, mDlybdenum, nickel, rhenium, scandium, silver, tantalur, thalliur, titanium, tungsten, uranium, zinc, and zirconium. These additional components may be added in any suitable manner to the carrier material during or after its preparation, or they may be added in any suitable manner to the catalytic composite either before, while or after other catalytic components are incorporated. Preferably the catalyst of our invention is nonacidic. "Nonacidic" in this context means that the catalyst has very little skele tl isomerization activity, that is, the catalyst converts less than 30 mol % of butene-l to isobutylene when tested at dehydrogenation conditions and; preferably, converts less than 1 mol . The acidity of the catalyst can be decreased if necessary to make the catalyst nonacidic by increasing the amount of the alkali or alkaline earth component within our claimed range, or by treating the catalyst with steam to remove some of the halogen component within our claimed range. After the catalyst components have been combined with the porous carrier material, the resulting catalyst composite will gener- ally be dried at a temperature-of from about-100C to about 320 C for a period of typically about 1 to 24 hours or more and thereafter calcined at a temperature of about 320C to about 6DD C for a period of bout 9.5 to about 10 or more hours. Finally the calcined catalyst composite is typically subjected to a reduction step betore use in the hydrocarbon conversion process. This reduction ste; is effected at 2 temperature of about 230 C to about 650 C for a period of about 0. to about 10 or more hours in 2 reducing environment, preferably dry hydrogen, the temperature and time beino selected to be long and not enough to reduce substantially all of the platinum group component to the elemental metallic state. A cording to one process of our invention dehydrogen- stable hydrocarbons are contacted with the catalytic composite of our ir''ention in a dehydrogenation zone maintained at dehydrogen- ratio conditions. This contacting may be accomplished in a fixed catalyst bed system, e moving catalyst bed system, a fluidized bed syster, etc., or in 2 batch-type operation. A fixed bed system. is preferrec. In this fixed bed system the hydrocarbon feed stream is preheated tc the desired reaction temperature and then passed into tr,e dehydrogenation zone containing a fixed bed of the catalyst. Tne dehydrogenation zone ry itself comprise one or mDre separate reaction zones with heating means therebetween to ensure that the desire reaction temperature can be maintained at the entrance to each reaction zone. The hydrocarbon may be contacted with the cata- lyst bed in either upward, downward or radial flow fashion. Radial from of the hydrocarbon through the catalyst bed is preferred for comr.-crcial scale reactors. The hydrocarbon may be in the liquid phase, é ixed vapor-liquid phase or the vapor phase when it contacts the catalyst. Preferably it is in the vapor phase. Conditions in the dehydrogenation zone include a tempera- ture of from about 400 to about 900 C, a pressure of from about 0.01 to 10 atmpospheres (1 to 1000 kPa) and a liquid hourly space velocity (LHSV) of fror about 0.1 to 100 hr. . Genera'ly for normal parrafins tne lower the molecular weight the higher the temperature required for com- parable conversion. The pressure in the dehydrogenation zone is maintained as low as practicable, consistent with equipment limitations, to maxirize the chemical equilibrium advantages. The effluent stream fro the dehydrogenation zone cenerally will contein unconverted dehydrogenatable hydrocarbons, hvdro- aen and the products of dehydrogenation reactions. This effluent stream is typically cooled and passed to 2 hydrogen separation zone to separate a hydrogen-ricr' vapor phase fror. e hydrocarbon-rich liquid phase. Generally, the hydrocarbon-rich liquid phase is further separated by means of either a suitable selective adsorbent, a selective solvent, a selective reaction or reactions or by means of a suitable fractionation scheme. Unconverted dehydrogenation hydrocarbons are recovered and may be recycled to the dehydrogenation zone. Products of the dehydrogenation reactions are recovered as final products or as intermediate products in the preparation of other compounds. The dehydrogenatable hydrocarbons may be admixed with a diluent material before, while or after being passed to the dehydrogenat-ion zone. The diluent material may be hydrogen, steam, methane, ethane, carbon dioxide and the like. Hydrogen is the preferred diluent. Ordinarily, when hydrogen is utilized as the diluent it is utilized in amounts sufficient to ensure a hydrogen to hydrocarbon mol ratio of about 0.1:1 to about 40:1, with best results being obtained when the mol ratio range is about 1:1 to about 10:1. The diluent stream passed to the dehydrogenation zone will typically be recycled hydrogen separated frorr the effluent from he dehydrogenation zone in the hydrogen separatior zone. Water or a material which decomposes at dehydrogenation conditions to form water such as an alcohol, aldehyde, ether or ketone, for example, may be added to the dehydrogenation zone, either continuously or intermittently, in an amount to provide, calculated on the basis of equivalent water, about 1 to about 20,000 weight ppm of the hydrocarbon feed stream. AbDut 1 to about IO,ODO weight ppm of water addition gives best results when dehydrogenating paraffins having from 6 to 30 more carbon atoms. The following worked Examples are introduced to describe further the catalyst of our invention and to teach one skilled in the art how to wake it and how to use it in the hydrocarbon conversion process of our invention. These Examples represent several specific embodiments of our invention and are intended to be illustrative only and not restrictive. EXAMPLE I k catalyst composite, hereinafter catalyst t was prepared to represent a catalyst according to our invention. It com- prised about 0.8 weight % platinum, about 0.5 weight % tin, about 2.7 weight t potassium and about 1.3 weight ; chlorine on a carrier of gamrra-alumina-. The atomic ratio of potassium to platinum for= this catalyst was about 16.8. The catalyst was prepared by dissolving substantially pure aluminum pellets in a hydrochloric acid solution, thereafter dissolving in this sol an amount of stannic chloride calculated to provide a final composite containing about 0.5 weight % tin, and then stirring the sol vigorously to distribute the tin evenly throughout it. Hexamethylenetetramine was then added to the sol and the resulting mixture was dropped into an oil bath in a manner tc for spherical particles having an average particle diameter of about 1/1E inch (1.60 rr). Thereafter the spheres were aged and washed with an ammoniacal solution, then dried and calcined to form a spherical gamma-alumina carrier material containing about 0.5 weight % tin in the form of tin oxide. More details about this method of preparing the preferred alumina carrier material are disclosed in U.S. Patent No. 2,620,314. Then, 333 9 (600 cc) of the tin-containing alumina carrier was contracted with 600 cc of a deionized water solution containinc chloroplatinic acid equivalent the specified weight % of platinum and hydrochloric acid equivalent to 2 weight % of the alumina ir, e rotary drier for 15 minutes et roo temperature. Then steam was passed to the jacket of the drier and the water was driven off under a nitrogen purge for 2-3 hours, leaving the platinum component and some chlorine component incorporated with the tin-containing alumina carrier. The chlorine component present was then removed by treatinc the platinum, tin and halogen-containing composite et 550 C with 300 hr.-1 gas hourly space velocity (GHSV) of a 50/50 air 800C steam mixture for 6 hours. After this treatment with steam the composite contained less than 0.1 weight C; chlorine. Then, the plati nut. and tin-containing composite was contacted with a deionized water solution containing potassium nitrate equivalent to the specified weight % of potassium and dried to incorporate the potassium component. Then, 220 cc of the platinum, tin and potassium-containing composite was heated to 110 C in 1000 hr. -1 GHSV of dry air for 1/2 hour, the temperature was raised to 525 C and 12 cc per hour of 0.9 M hydrochloric acid was added with 300 hr.-1 GHSV of a 50/50 air/80 C steam mixture for 3 hours to incorporate the halogen compo- nent. Finally, the platinum, tin, potassium and chlorine-containing composite was dried at 525 C and 1000 hr.-1 GHSV of dry air for 1/ hour. This catalyst "A" represents one preferred embodiment D; our catalyst composite. A different catalyst, hereinafter catalyst "B" was prepared to represent the dehydrogenation catalysts of the prior art herein the halogen content was maintained at less than 0.2 weight % Teis catalyst comprised about 0.8 weight % platinum, about 0.5 weight % tin, about 2.7 weight % potassium and about 0.0 weight % chlorine on e carrier of gamma alumina. Catalyst "B" was prepared in the same manner as catalyst "A" above, except the chlorine component from the hydrochloric acid, required at inore than 0.2 weight % for the catalyst "A" of our invention was not added to catalyst "B". Catalysts "A" and "B" both contained a small amount of sulfur component which was incorporated in a sulfiding step at 6250C and 1 atmosphere pressure from a 1% mixture of hydrogen sulfide in hydrogen gas at 850 hr. -1 gas hourly space velocity (GHSV) for 7 hours After the sulfiding step these catalysts contained approximately 1 weight % sulfur, calculated on an elemental basis. These catalysts were also reduced in a reduction step prior to being tested. Reduction conditions were; 6250C and 1 atmo- sphere (100 -kPa) pressure in hydroqen oas at 700 hr.-1 GHSV fnr 1 hour These catalysts were then tested for dehydrogenation acti pity, selectivity and stability in a laboratory scale dehydrogenation plant comprising a reactor, a hydrogen separation zone, and heaters, coolers, pumps, compressors, and the like conventional equipment for handling hydrocarbons. In this plant, the feed stream containing the dehydrogenatable hydrocarbon is combinated with a hydrogen gas stream and the resulting mixture is heated to the desired conversion temperature which is measured at the inlet to the dehydrogenation reactcr. The heated r..xture then contacts the fixed bed of catalyst in aDwn flow fashion. The pressures reported here in are measured at the outlet fro the reactor. An effluent stream is withdrawn from the reactor and cooled. A portion of the effluent stream is collected and analyzed to treasure the amount of conversion, or activity, and the relative amount of desired dehydrogenated hy drocarbons, or selectivity, for the catalyst composite being tested. Conversion numbers reported herein are calculated on the basis of disappearance of isobutane, expressed in weight %, of the feed stream. Similarly, selectivity numbers retorted are calculated or. the basis of desired isobutylene produced, expressed in mol ', of the isobutane converted. The same isobutane feed stream. was used in both tests. It comprised in weight %; isobutane 99.85 normal butane 0.10 propane 0.05 Reaction conditions were the same for both tests. They were: 625 C, 2 atmospheres (200 kPa), 2 hydrogen to hydrocarbon mol ratio and 1 hr. I LHSV. Results from the tests are presented in Figures i and 2. Figure 1 clearly shows that the catalyst of our invention, catalyst "A" comprising a platinum group component, an alkali or alka line earth component, more than 0.2 weight , calculated on an ele mental basis, of a halogen component and a porous carrier material, has more activity, represented by the higher weight % isobutane conversion, than the catalyst of the pio'r art, catalyst "B" compris ing the same components except less than 0.2 weight X of the halogen component. Figure 2 shows that the selectivity of oWr catalyst "A' is comparable to that of prior art catalyst 11B'. Also, after 97 hours on strear. the catalysts in this Ex apple were removed from. the reactor and analyzed for carbon tD measure the amount of coke which had been deposited on catalyst during the test. Catalyst "A" of our invention contained 0.11 weight % carbon, calculated on an elemental basis. Catalyst "B" of the prior art, on the other hand, contained 0.39 weight carbon, more than 3 times as much carbon as catalyst "A". So, the catalyst of our invention also helps to suppress coke deposition, which is one of the major causes of dehydrogenation catalyst deactivation, and loner catalyst life and less regeneration time are expected for our catalyst compared to the prior art catalysts. EXAMPLE II A catalyst composite, hereinafter catalyst "C", was prepared to represent also one catalyst of our invention. It comprised about 0.7 weight z platinum, about 0.5 weight % tin, about 2.8 weight g potassium and about 2.5 weight % chlorine on a carrier of ganrria-alur.ina. The atomic ratio of potassium to platinum for this catalyst was about 2-0.0 The catalyst wes prepared in substantially the same manner as catalyst "A" in Example I above. This catalyst "C" represents another preferred embodiment of our catalyst composite. Another different catalyst, hereinafter catalyst "D" was prepared also to represent the dehydrogenation catalysts of the prior art wherein the halogen content was maintained at less than 0.2 weight %. This catalyst comprised about 0.7 weight % platinum, about 0.5 weight 9 tin, about 2.9 weight C; potassium and about 0.1 weight X chlorine on a carrier of gamma-alumina. Catalyst "D" was prepared in substantially the sare manner as catalyst "B' in Example I above, and the amount of the chlorine component, required at more than 0.2 weight '; for the catalyst "C" of our invention, was maintained at about 0.1 weight S. Catalysts "C" and "D" were both tested for dehydrogenation of ethane to ethylene in a laboratory plant like the plant in Example I. Reaction conditions for both tests were about fro 680 to 72DCC, 1.3 atmospheres (132 kPa), 1 hydrogen to hydrocarbon mol ratio and 5.0 hr.-1 LHSV. The tests consisted of 4 consecutive 25 hour periods; period 1.) at 680 C, period 2.) at 700 C, period 3.) at 720 C and period 4.) at 680 C again. From Figure 4 it can be seen that in all periods of the tests selectivity for both catalysts was more than OD mol . Generally, however, selectivity for our catalyst "C", at more than 98% for all the periods, was slightly higher than for prior art catalyst "D". From Figure 3 it can be seen thet in periods 1 and 2 these catalysts exhibited similar activity at about 15 and 19 average mol r conversion, respectively, and they exhibited similar activity stability throughout these periods. In period 3, however, at about-- 24 mol % conversion, activity stability for prior art catalyst "D" became notably worse than for our catalyst "C", and by the end of the period activity for catalyst "D", at about 20 mol % conversion, was notably worse also. Activity for catalyst "C" on the other hand, was stable at about 23 mol % conversion throughout the period. These trends continued in period 4 where activity for our catalyst "C" was stable at about 13 mol C; conversion, and activity for prior art catalyst "D" fell from about 11 to about 8 mol % conversion. These tests suggest that in a commercial dehydrogena tion process catalyst "C" of our invention will be more stable than catalyst "D" of the prior art. Also, after 97 hours on streak the catalysts in this Example were removed fron. the realtor and analyzed for carbon. Cata- lyst "C" of our invention contained E.7 weight % carbon, calculated on an elemental basis. Catalyst "D" of the prior art, on the other hand, contained 25.6 weight f carbon, nearly three times as much carbon as catalyst "C". This data suggests that in a commercial dehydrogenation process catalyst "C" of our invention will be more quickly and easily regenerated than catalyst "D" of the prior art. EXAMPLE III A catalyst composite, hereinafter catalyst "E", was prepared to represent also one catalyst of our invention. It comprised about 0.75 weight Vr; platinum, about 0.5 weight % tin, about 2.8 weight % potassium and about 3.2 weight % chlorine on a carrier of gamma-alumina. The atomic ratio of potassium to platinum for this catalyst was about 18.6. The catalyst was prepared in substantially the same manner as catalyst "A" in Example I above. This catalyst "E" represents another-preferred embodiment of our catalyst composite. Another different catalyst, hereinafter catalyst "F" was prepared to represent the catalysts of the prior art wherein the atomic ratio of the alkali or alkaline earth component was maintained at less than or equal to 10. This catalyst comprised about 0.75 weight % platinum, about 0.5 weight X tin, about 1.4 weight % po- tassium and about ?.-o 'weight chlorine on a carrier of gamma-alu- mina. The atomic ratio of potassium to platinum for this catalyst was about 9.3. Catalyst "F" was prepared in substantially the same manner as catalyst "E" except the amount of potassium added to catalyst "F" was maintained at the lower level to ensure an atomic ratio of potassium to platinum for this catalyst of less than or equal to 10. Catalysts "E" and "F" were tested for dehydrogenation of isobutane to isobutylene in a laboratory plant like the plant in Example I. Reaction conditions were about 695"C, 2.S atmosphere. (200 kPa), 1.5 hydrogen to hydrocarbon mol ratio and 5.0 hr. 1 LHSV. Results from the tests are presented in Figures 5 and ±. In Figure 5 it can be seen that the dehydrogenation activity stability for our catalyst "E" is much greater than for prior art catalyst "F", represented by the much smaller change with time of the Cg isobutane conversion throughout the test for our catalyst "E". Also, in Figure 6 it can be seen that the undesirable isom- erization activity for our catalyst "E" is much less than for prior art catalyst "F", represented by the lower total butene-1 and butene-2 selectivity throughout the test for our catalyst "E". These tests suggest that in a commercial dehydrogenation process our catalyst "E" will be more stable and more selective than prior art catalyst "F".

Claims: What We Claim is: 1. A catalyst composition comprising a platinum group component, a Group IVA component, an alkali or alkaline earth component, more than 0.2 weight %, calculated on an elemental basis, of a halogen component and a porous carrier material, wherein the atomic ratio of the alkali or alkaline earth component to the platinum group is more than 10. 2. The composition of Claim 1 wherein said platinum group component comprises platinum. 3. The composition of Claim 1 wherein said Group IVA component comprises tin. 4. The composition of Claim 1 wherein said alkali or alkaline earth component comprises potassium. 5. The composition of Claim 1 wherein said halogen component comprises chlorine. 6. The composition of Claim 1 wherein said porous carrier material comprises alumina. 7. The composition of Claim 1 wherein the atomic ratio of the alkali or alkaline earth component to the platinum group component is from about 15 to about 25. 8. The composition of Claim 1 which comprises a platinum component, a tin component, a potassium component and a chlorine component with alumina or a platinum component, a tin component, a lithium component and'a chlorine component with alumina or a platinum coniponent, a lithium component, a cesium component and a chlorine component with alu maria or a platinum component, a tin component, an indium component, a lithium component and a chlorine component with alumina. 9. The composition of Claim 1 which also comprises a sulfur component. 10. A process for converting hydrocarbons which comprises contacting them at hydrocarbon conversion conditions with a catalyst--co,npr-ising a -platinum group -component,--- a Group IVA component, an alkali or alkaline earth component, more than 0.2 weight %, calculated on an elemental basis, of a halogen component and a porous carrier material, where in the atomic ratio of the alkali or alkaline earth component to the platinum component is more than 10. 11. The process of Claim 13 wherein said hydrocarbons are dehydrogenatable hydrocarbons including paraffins, alkylaromatics, naphthenes and olefins having from 2 to 30 or more carbon atoms, especially paraffins having from 2 to 5 or more carbon atoms. 12. The process of Claim 13 wherein the hydrocarbons are dehydrogenated at conditions which include a temperature of from about 400" to 9000 C, a pressure of from about 0.01 to 10 atmospheres (1 to 1000 kPa) and a liquid hourly space velocity (LHSV) of from about 0.1 to 100 hr. .

Inventors: HUNG, CHI-WEN, IMAI, TAMOTSU
Applicants: UOP INC.
Application year: 1984
Main classification: B01J23
IPC codes: C07B35, C07B61, C07B31, C07C67, B01J23, C07C5, B01J27, C07C1, C07C11