Hydrocarbon conversion with an acidic multimetallic catalytic composite
The subject of the present invention is a novel acidic multimetallic catalytic composite which has exceptional activity and resistance to deactivation when employed in a hydrocarbon conversion process that requires a catalyst having both a hydrogenation-dehydrogenation function and a controllable cracking function. More precisely, the present invention involves a novel dual-function acidic multimetallic catalytic composite which, quite surprisingly, enables substantial improvements in hydrocarbon conversion processes that have traditionally used a dual-function catalyst. In another aspect, the present invention comprehends the improved processes that are produced by the use of an acidic catalytic composite comprising a combination of catalytically effective amounts of a platinum or palladium component, a rhodium component, an indium component, and a halogen component with a porous carrier material; specifically, an improved reforming process which utilizes the subject catalyst to improve activity, selectivity, and stability characteristics. 
     Composites having a hydrogenation-dehydrogenation function and a controllable cracking function are widely used today as catalysts in many industries, such as the petroleum and petrochemical industry, to accelerate a wide spectrum of hydrocarbon conversion reactions. Generally, the cracking function is thought to be associated with an acid-acting material of the porous, adsorptive, refractory oxide type which is typically utilized as the support or carrier for a heavy metal component such as the metals or compounds of metals of Groups V through VIII of the Periodic Table to which are generally attributed the hydrogenation-dehydrogenation function. 
     These catalytic composites are used to accelerate a wide variety of hydrocarbon conversion reactions such as hydrocracking, isomerization, dehydrogenation, hydrogenation, desulfurization, cyclization, polymerization, alkylation, cracking, hydroisomerization, etc. In many cases, the commercial applications of these catalysts are in processes where more than one of the reactions are proceeding simultaneously. An example of this type of process is reforming wherein a hydrocarbon feed stream containing paraffins and naphthenes is subjected to conditions which promote dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraffins to aromatics, isomerization of paraffins and naphthenes, hydrocracking of naphthenes and paraffins and the like reactions, to produce an octane-rich or aromatic-rich product stream. Another example is a hydrocracking process wherein catalysts of this type are utilized to effect selective hydrogenation and cracking of high molecular weight unsaturated materials, selective hydrocracking of high molecular weight materials, and other like reactions, to produce a generally lower boiling, more valuable output stream. Yet another example is a hydroisomerization process wherein a hydrocarbon fraction which is relatively rich in straight-chain paraffin compounds is contacted in the presence of hydrogen with a dual-function catalyst to produce an output stream rich in isoparaffin compounds. 
     Regardless of the reaction involved or the particular process involved, it is of critical importance that the dual-function catalyst exhibit not only the capability to initially perform its specified functions, but also that it has the capability to perform them satisfactorily for prolonged periods of time. The analytical terms used in the art to measure how well a particular catalyst performs its intended functions in a particular hydrocarbon reaction environment are activity, selectivity, and stability. And for purposes of discussion here, these terms are conveniently defined for a given charge stock as follows: (1) activity is a measure of the catalyst&#39;s ability to convert hydrocarbon reactants into products at a specified severity level where severity level means the conditions used--that is, the temperature, pressure, contact time, and presence of diluents such as H 2  ; (2) selectivity refers to the amount of desired product or products obtained relative to the amount of reactants charged or converted; (3) stability refers to the rate of change with time of the activity and selectivity parameters--obviously, the smaller rate implying the more stable catalyst. In a reforming process, for example, activity commonly refers to the amount of conversion that takes place for a given charge stock at a specified severity level and is typically measured by octane number of the C 5  + product stream; selectivity refers to the amount of C 5  + yield, relative to the amount of the charge, that is obtained at the particular activity or severity level; and stability is typically equated to the rate of change with time of activity, as measured by octane number of C 5  + product, and of selectivity as measured by C 5  + yield. Actually, the last statement is not strictly correct because generally a continuous reforming process is run to produce a constant octane C 5  + product with severity level being continuously adjusted to attain this result; and furthermore, the severity level is for this process usually varied by adjusting the conversion temperature in the reaction zone so that, in point of fact, the rate of change of activity finds response in the rate of change of conversion temperatures and changes in this last parameter are customarily taken as indicative of activity stability. 
     As is well known to those skilled in the art, the principal cause of observed deactivation or instability of a dual-function catalyst when it is used in a hydrocarbon conversion reaction is associated with the fact that coke forms on the surface of the catalyst during the course of the reaction. More specifically, in these hydrocarbon conversion processes, the conditions utilized typically result in the formation of heavy, high molecular weight, black, solid or semi-solid, carbonaceous material which is a hydrogen-deficient polymeric substance having properties akin to both polynuclear aromatics and graphite. This material coats the surface of the catalyst and thus reduces its activity by shielding its active sites from the reactants. In other words, the performance of this dual-function catalyst is sensitive to the presence of carbonaceous deposits or coke on the surface of the catalyst. Accordingly, the major problem facing workers in this area of the art is the development of more active and selective catalytic composites that are not as sensitive to the presence of these carbonaceous materials and/or have the capability to suppress the rate of the formation of these carbonaceous materials on the catalyst. Viewed in terms of performance parameters, the problem is to develop a dual-function catalyst having superior activity, selectivity, and stability. In particular, for a reforming process the problem is typically expressed in terms of shifting and stabilizing the C 5  + yield-octane relationship at the lowest possible severity level--C 5  + yield being representative of selectivity and octane being proportional to activity. 
     I have now found a dual-function acidic multimetallic catalyst composite which possesses improved activity, selectivity, and stability characteristics when it is employed in a process for the conversion of hydrocarbons of the type which have heretofore utilized dual-function acidic catalytic composites such as processes for isomerization, hydroisomerization, dehydrogenation, desulfurization, denitrogenization, hydrogenation, alkylation, dealkylation, disproportionation, polymerization, hydrodealkylation, transalkylation, cyclization, dehydrocyclization, cracking, hydrocracking, halogenation, reforming, and the like processes. In particular, I have ascertained that an acidic catalyst, comprising a combination of catalytically effective amounts of a platinum or palladium component, a rhodium component, an indium component, and a halogen component with a porous refractory carrier material, can enable the performance of hydrocarbon conversion processes utilizing dual-function catalysts to be substantially improved if the active sites induced by the metallic components are uniformly dispersed throughout the carrier material and if the oxidation states of the metallic components are controlled to be in the states hereinafter specified. Moreover, I have determined that an acidic catalytic composite, comprising a combination of catalytically effective amounts of a platinum or palladium component, a rhodium component, an indium component, and a chloride component with an alumina carrier material, can be utilized to substantially improve the performance of a reforming process which operates on a low-octane gasoline fraction to produce a high-octane aromatic-rich reformate if the active sites induced by the metallic components are uniformly dispersed throughout the alumina carrier material, and if the oxidation states of the metallic components are fixed in the states hereinafter specified. In the case of a reforming process, the principal advantage associated with the use of the present invention involves the acquisition of the capability to operate in a stable manner in a high severity operation, for example, a low pressure reforming process designed to produce a C 5  + reformate having an octane of about 100 F-1 clear. As indicated, the present invention essentially involves the finding that the addition of a combination of an indium component and a rhodium component to a dual-function acidic hydrocarbon conversion catalyst containing a platinum or palladium component can enable the performance characteristics of the catalyst to be sharply and materially improved, if the hereinafter specified limitations on amounts of ingredients, oxidation states of metals, and distribution of metallic components in the support are met. 
     It is, accordingly, one object of the present invention to provide an acidic multimetallic hydrocarbon conversion catalyst having superior performance characteristics when utilized in a hydrocarbon conversion process. A second object is to provide a catalyst having dual-function hydrocarbon conversion performance characteristics that are relatively insensitive to the deposition of hydrocarbonaceous material thereon. A third object is to provide preferred methods of preparation of this catalytic composite which insures the achievement and maintenance of its properties. Another object is to provide an improved hydrocarbon reforming catalyst having superior activity, selectivity, and stability attributes. Yet another object is to provide a dual-function hydrocarbon conversion catalyst which utilizes a combination of carefully selected amounts of an indium component and a rhodium component under specified circumstances to promote an acidic catalyst containing a platinum or palladium component. 
     In brief summary, the present invention is, in one embodiment, an acidic catalytic composite comprising a porous carrier material containing, on an elemental basis, about 0.01 to about 2 wt. % platinum or palladium metal, about 0.01 to about 2 wt. % rhodium metal, about 0.01 to about 1 wt. % indium, and about 0.1 to about 3.5 wt. % halogen; wherein the platinum or palladium, indium, and rhodium are uniformly dispersed throughout the porous carrier material; wherein substantially all of the platinum or palladium and rhodium are present in the elemental metallic state; and wherein substantially all of the indium is present in an oxidation state above that of the elemental metal. 
     A second embodiment relates to an acidic catalytic composite comprising a porous carrier material containing, on an elemental basis, about 0.01 to about 1 wt. % platinum metal, about 0.05 to about 1 wt. % rhodium metal, about 0.01 to about 0.25 wt. % indium, and about 0.5 to about 1.5 wt. % halogen; wherein the platinum, indium, and rhodium are uniformly dispersed throughout the porous carrier material; wherein substantially all of the platinum and rhodium are present in the elemental metallic state; and wherein substantially all of the indium is present in an oxidation state above that of the elemental metal. 
     Another embodiment relates to a sulfided acidic catalytic composite comprising a combination of the catalytic composite described in the first or second embodiment with a sulfur component in an amount sufficient to incorporate about 0.01 to about 1 wt. % sulfur, calculated on an elemental basis. 
     Yet another embodiment relates to a process for the conversion of a hydrocarbon comprising contacting the hydrocarbon and hydrogen with the catalytic composite described above in the first or second or third embodiment at hydrocarbon conversion conditions. 
     A preferred embodiment relates to a process for reforiming a gasoline fraction which comprises contacting the gasoline fraction and hydrogen with the catalytic composite described above in the first or second or third embodiment at reforming conditions selected to produce a high-octane reformate. 
     Other objects and embodiments of the present invention relate to additional details regarding essential, preferred and optional catalytic ingredients, preferred amounts of ingredients, suitable methods of composite preparation, operating conditions for use in the hydrocarbon conversion processes, and the like particulars. These are hereinafter given in the following detailed discussion of each of these facets of the present invention. 
     The acidic multimetallic catalyst of the present invention comprises a porous carrier material or support having combined therewith catalytically effective amounts of a platinum or palladium component, a rhodium component, an indium component, and a halogen component. 
     Considering first the porous carrier material utilized in the present invention, it is preferred that the material be a porous, adsorptive, high-surface area support having a surface area of about 25 to about 500 m 2  /g. The porous carrier material should be relatively refractory to the conditions utilized in the hydrocarbon conversion process, and it is intended to include within the scope of the present invention carrier materials which have traditionally been utilized in dual-function hydrocarbon conversion catalysts such as: (1) activated carbon, coke, or charcoal; (2) silica or silica gel, silicon carbide, clays, and silicates including those synthetically prepared and naturally occurring, which may or may not be acid treated, for example, attapulgus clay, china clay, diatomaceous earth, fuller&#39;s earth, kaolin, kieselguhr, etc.; (3) ceramics, porcelain, crushed firebrick, bauxite; (4) refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, beryllium oxide, vanadium oxide, cesium oxide, hafnium oxide, zinc oxide, magnesia, boria, thoria, silica-alumina, silica-magnesia, chromia-alumina, alumina-boria, silica-zirconia, etc.; (5) crystalline zeolitic aluminosilicates such as naturally occurring or synthetically prepared mordenite and/or faujasite, either in the hydrogen form or in a form which has been treated with multivalent cations; (6) spinels such as MgAl 2  O 4 , FeAl 2  O 4 , ZnAl 2  O 4 , MnAl 2  O 4 , CaAl 2  O 4 , and other like compounds having the formula MO.Al 2  O 3  where M is a metal having a valence of 2; and, (7) combinations of elements from one or more of these groups. The preferred porous carrier materials for use in the present invention are refractory inorganic oxides, with best results obtained with an alumina carrier material. Suitable materials are the crystalline aluminas known as gamma-, eta-, and theta-alumina, with gamma- or eta-alumina giving best results. In addition, in some embodiments the alumina carrier material may contain minor proportions of other well-known refractory inorganic oxides such as silica, zirconia, magnesia, etc.; however, the preferred support is substantially pure gamma- or eta-alumina. Preferred carrier materials have an apparent bulk density of about 0.3 to about 0.8 g/cc and surface area characteristics such that the average pore diameter is about 20 to 300 Angstroms, the pore volume is about 0.1 to about 1 cc/g, and the surface area is about 100 to about 500 m 2  /g. In general, best results are typically obtained with a gamma-alumina carrier material which is used in the form of spherical particles havng: a relatively small diameter (i.e. typically about 1/16 inch), an apparent bulk density of about 0.3 to about 0.8 g/cc, a pore volume of about 0.4 cc/g, and a surface area of about 150 to about 250 m 2  /g. 
     The preferred alumina carrier material may be prepared in any suitable manner and may be synthetically prepared or natural occurring. Whatever type of alumina is employed, it may be activated prior to use by one or more treatments including drying, calcination, steaming, etc., and it may be in a form known as activated alumina, activated alumina of commerce, porous alumina, alumina gel, etc. For example, the alumina carrier may be prepared by adding a suitable alkaline reagent, such as ammonium hydroxide, to a salt of aluminum such as aluminum chloride, aluminum nitrate, etc., in an amount to form an aluminum hydroxide gel which upon drying and calcining is converted to alumina. The alumina carrier may be formed in any desired shape such as spheres, pills, cakes, extrudates, powders, granules, tablets, etc., and utilized in any desired size. For the purpose of the present invention a particularly preferred form of alumina is the sphere; and alumina spheres may be continuously manufactured by the well-known oil drop method which comprises: forming an alumina hydrosol by any of the techniques taught in the art and preferably by reacting aluminum metal with hydrochloric acid, combining the resultant hydrosol with a suitable gelling agent and dropping the resultant mixture into an oil bath maintained at elevated temperatures. The droplets of the mixture remain in the oil bath until they set and form hydrogel spheres. The spheres are then continuously withdrawn from the oil bath and typically subjected to specific aging treatments in oil and an ammoniacal solution to further improve their physical characteristics. The resulting aged and gelled particles are then washed and dried at a relatively low temperature of about 300° F. to about 400° F. and subjected to a calcination procedure at a temperature of about 850° F. to about 1300° F. for a period of about 1 to about 20 hours. This treatment effects conversion of the alumina hydrogel to the corresponding crystalline gamma-alumina. See the teachings of U.S. Pat. No. 2,620,314 for additional details. 
     One essential constituent of the acidic multimetallic catalyst of the present invention is an indium component. This component may be present in the instant catalytic composite in any form wherein substantially all of the indium moiety is in an oxidation state above that of the corresponding elemental metal such as a chemical compound like the oxide, hydroxide, halide, oxyhalide, aluminate, or in chemical combination with one or more of the other ingredients of the catalyst. Although it is not intended to restrict the present invention by this explanation, it is believed that best results are obtained when the indium component is present in the composite in the form of the corresponding indium oxide and the subsequently described oxidation and reduction steps that are preferably used in the preparation of the instant catalytic composite are specifically designed to achieve this end. This indium component can be used in any amount which is catalytically effective, with good results obtained, on an elemental basis, with about 0.01 to about 1 wt. % indium in the catalyst. Best results are ordinarily achieved with about 0.01 to about 0.25 wt. % indium, calculated on an elemental basis. 
     This indium component may be incorporated in the catalytic composite in any suitable manner known to the art to results in a relatively uniform dispersion of the indium moiety in the carrier material, such as by coprecipitation or cogelation with the porous carrier material, ion exchange with the gelled carrier material, or impregnation with the carrier material either after, before, or during the period when it is dried and calcined. It is to be noted that it is intended to include within the scope of the present invention all conventional methods for incorporating and simultaneously uniformly distributing a metallic component in a catalytic composite and the particular method of incorporation used is not deemed to be an essential feature of the present invention. One method of incorporating the indium component into the catalytic composite involves coprecipitating the indium component in the form of the corresponding hydrous oxide during the preparation of the preferred carrier material, alumina. This method typically involves the addition of a suitable soluble indium compound such as indium trichloride, indium nitrate, and the like to the alumina hydrosol and then combining the hydrosol with a suitable gelling agent and dropping the resulting mixture into an oil bath, etc., as explained in detail hereinbefore. Alternatively, the indium compound can be added to the gelling agent. After drying and calcining the resulting gelled carrier material in air there is obtained an intimate combination of alumina and indium oxide. A preferred method of incorporating the indium component into the catalytic composite involves utilization of a soluble, decomposable compound of indium to impregnate the porous carrier material. In general, the solvent used in this impregnation step is selected on the basis of the capability to dissolve the desired indium compound and is preferably an aqueous, acidic solution. Thus, the indium component may be added to the carrier material by commingling the latter with an aqueous acidic solution of suitable indium salt or suitable compound of indium such as indium tribromide, indium perchlorate, indium trichloride, indium trifluoride, indium nitrate, and the like compounds. A particularly preferred impregnation solution comprises an acidic solution of indium trichloride in water. Suitable acids for use in the impregnation solution are: inorganic acids such as hydrochloric acid, nitric acid, and the like, and strongly acidic organic acids such as oxalic acid, malonic acid, citric acid, and the like. In general, the indium component can be impregnated either prior to, simultaneously with, or after the other ingredients are added to the carrier material. However, excellent results are obtained when the indium component is impregnated simultaneously with the platinum or palladium and rhodium components. In fact, a preferred impregnation solution is an aqueous solution of chloroplatinic acid, hydrochloric acid, indium trichloride, and rhodium trichloride hydrate. 
     Regardless of which indium compound is used in the preferred impregnation step, it is important that the indium component be uniformly distributed throughout the crrier material. In order to achieve this objective, it is necessary to maintain the pH of the impregnation solution in a range of about 7 to about 1 or less, with a preferred range of about 3 to 1, and to dilute the impregnation solution to a volume which is at least equal to the volume of the carrier material which is impregnated. Similarly, it is preferred to use a relatively long contact time during the impregnation step ranging from about 0.25 up to about 1 hour or more before drying to remove excess solvent in order to insure a high dispersion of the indium component on the carrier material. The mixture of solution and carrier material is, likewise, preferably constantly agitated during this preferred impregnation step. 
     A second essential ingredient of the subject catalyst is the platinum or palladium component. That is, it is intended to cover the use of platinum or palladium or mixtures thereof as a second component of the present composite. It is an essential feature of the present invention that substantially all of this platinum or palladium component exists within the final catalytic composite in the elemental metallic state. Generally, the amount of this component present in the final catalytic composite is small compared to the quantities of the other components combined therewith. In fact, the platinum or palladium component generally will comprise about 0.01 to about 2 wt. % of the final catalytic composite, calculated on an elemental basis. Excellent results are obtained when the catalyst contains about 0.05 to about 1 wt. % of platinum or palladium metal. 
     This platinum or palladium component may be incorporated in the catalytic composite in any suitable manner known to result in a relatively uniform distribution of this component in the carrier material such as coprecipitation or cogelation, ion exchange or impregnation. The preferred method of preparing the catalyst involves the utilization of a soluble, decomposable compound of platinum or palladium to impregnate the carrier material in a relatively uniform manner. For example, this component may be added to the support by commingling the latter with an aqueous solution of chloroplatinic or chloropalladic acid. Other water-soluble compounds of platinum or palladium may be employed in impregnation solutions and include ammonium chloroplatinate, bromoplatinic acid, platinum trichloride, platinum tetrachloride hydrate, platinum dichlorocarbonyl dichloride, dinitrodiaminoplatinum, sodium tetranitroplatinate (II), palladium chloride, palladium nitrate, palladium sulfate, diamminepalladium (II) hydroxide, tetramminepalladium (II) chloride, etc. The utilization of a platinum or palladium chloride compound, such as chloroplatinic or choropalladic acid, is preferred since it facilitates the incorporation of both the platinum or palladium component and at least a minor quantity of the halogen component in a single step. Hydrogen chloride or the like acid is also generally added to the impregnation solution in order to further facilitate the incorporation of the halogen component and the uniform distribution of the metallic components throughout the carrier material. In addition, it is generally preferred to impregnate the carrier material after it has been calcined in order to minimize the risk of washing away the valuable platinum or palladium compounds; however, in some cases it may be advantageous to impregnate the carrier material when it is in a gelled state. 
     Yet another essential ingredient of the present catalytic composite is a rhodium component. It is of fundamental importance that substantially all of the rhodium component exists within the catalytic composite of the present invention in the elemental metallic state or in a state such as the corresponding oxide or sulfide which is reducible to the metallic state under hydrocarbon conversion conditions or in a mixture of these states. The rhodium component may be utilized in the composite in any amount which is catalytically effective, with the preferred amount being about 0.01 to about 2 wt. % thereof, calculated on an elemental basis. Typically, best results are obtained with about 0.01 to about 1 wt. % rhodium. It is additionally preferred to select the specified amount of rhodium from within this broad weight range as a function of the amount of the platinum or palladium component, on an atomic basis, as is explained hereinafter. 
     This rhodium component may be incorporated into the catalytic composite in any suitable manner known to those skilled in the catalyst formulation art which results in a relatively uniform distribution of rhodium in the carrier material. In addition, it may be added at any stage of the preparation of the composition--either during preparation of the carrier material or thereafter--and the precise method of incorporation used is not deemed to be critical. However, best results are obtained when the rhodium component is relatively uniformly distributed throughout the carrier material, and the preferred procedures are the ones known to result in a composite having this relatively uniform distribution. One acceptable procedure for incorporating this component into the composite involves cogelling or coprecipitating the rhodium component during the preparation of the preferred carrier material, alumina. This procedure usually comprehends the addition of a soluble, decomposable compound of rhodium such as rhodium trichloride hydrate or rhodium nitrate to the alumina hydrosol before it is gelled. The resulting mixture is then finished by conventional gelling, aging, drying, and calcination steps as explained hereinbefore. A preferred way of incorporating this component is an impregnation step wherein the porous carrier material is impregnated with a suitable rhodium-containing solution either before, during, or after the carrier material is calcined. Preferred impregnation solutions are aqueous solutions of water soluble, decomposable rhodium compounds or complexes such as hexamminerhodium (III) chloride, rhodium carbonylchloride, rhodium trichloride hydrate, rhodium nitrate, sodium hexachlororhodate (III), sodium hexanitrorhodate (III), rhodium sulfate, and the like complexes of compounds. Best results are ordinarily obtained when the impregnation solution is an aqueous solution of rhodium trichloride hydrate or rhodium nitrate. This component can be added to the carrier material either prior to, simultaneously with, or after the other metallic components are combined therewith. Best results are usually achieved when this component is added simultaneously with the other metallic components. In fact, excellent results are obtained, as reported in the examples, with a one step impregnation procedure using an aqueous solution comprising chloroplatinic or chloropalladium acid, rhodium trichloride hydrate, hydrochloric acid, and indium trichloride. 
     It is essential to incorporate a halogen component into the multimetallic catalyst composite of the present invention. Although the precise form of the chemistry of the association of the halogen component with the carrier material is not entirely known, it is customary in the art to refer to the halogen component as being combined with the carrier material, or with the other ingredients of the catalyst in the form of the halide (e.g. as the chloride). This combined halogen may be either fluorine, chlorine, iodine, bromine, or mixtures thereof. Of these, fluorine and, particularly, chlorine are preferred for the purposes of the present invention. The halogen may be added to the carrier material in any suitable manner, either during preparation of the support or before or after the addition of the other components. For example, the halogen may be added, at any stage of the preparation of the carrier material or to the calcined carrier material, as an aqueous solution of a suitable, decomposable halogen-containing compound such as hydrogen fluoride, hydrogen chloride, hydrogen bromide, ammonium chloride, etc. The halogen component or a portion thereof, may be combined with the carrier material during the impregnation of the latter with the platinum or palladium, indium, or rhodium component; for example, through the utilization of a mixture of chloroplatinic acid and hydrogen chloride. In another situation, the alumina hydrosol which is typically utilized to form the preferred alumina carrier material may contain halogen and thus contribute at least a portion of the halogen component to the final composite. For reforming, the halogen will be typically combined with the carrier material in an amount sufficient to result in a final composite that contains about 0.1 to about 3.5%, and preferably about 0.5 to about 1.5%, by weight, of halogen, calculated on an elemental basis. In isomerization or hydrocracking embodiments, it is generally preferred to utilize relatively larger amounts of halogen in the catalyst--typically ranging up to about 10 wt. % halogen calculated on an elemental basis, and more preferably about 1 to about 5 wt. %. It is to be understood that the specified level of halogen component in the instant catalyst can be achieved or maintained during use in the conversion of hydrocarbons by continuously or periodically adding to the reaction zone a decomposable halogen-containing compound such as an organic chloride (e.g. ethylene dichloride, carbon tetrachloride, t-butyl chloride) in an amount of about 1 to 100 wt. ppm. of the hydrocarbon feed, and preferably about 1 to 10 wt. ppm. 
     Regarding the preferred amounts of the various metallic components of the subject catalyst, I have found it to be a good practice to specify the amounts, expressed on an atomic basis, of the rhodium and indium components as a function of the amount of the platinum or palladium component. On this basis, the amount of the rhodium component is ordinarily selected so that the atomic ratio of rhodium to platinum or palladium metal contained in the composite is about 0.1:1 to about 10:1, with the preferred range being about 0.1:1 to about 3:1. Similarly, the amount of the indium component is ordinarily selected to produce a composite having an atomic ratio of indium to platinum or palladium metal of about 0.05:1 to about 1:1, with the preferred range being about 0.1:1 to about 0.5:1. In the same manner, it is a very good idea to select the amounts of rhodium and indium so that the atomic ratio of indium to rhodium for the instant catalyst is about 0.05:1 to about 0.8:1, with best results obtained in a range of about 0.1:1 to about 0.6:1. 
     Another significant parameter for the instant catalyst is the &#34;total metals content&#34; which is defined to be the sum of the platinum or palladium component, the rhodium component, and the indium component, calculated on an elemental basis. Good results are ordinarily obtained with the subject catalyst when this parameter is fixed at a value of about 0.15 to about 4 wt. % with best results ordinarily achieved at a metals loading of about 0.3 to about 3 wt. %. 
     In embodiments of the present invention wherein the instant multimetallic catalyst composite is used for the dehydrogenation of dehydrogenatable hydrocarbons or for the hydrogenation of hydrogenatable hydrocarbons, it is ordinarily a preferred practice to include an alkali or alkaline earth metal component in the composite and to minimize or eliminate the halogen component therefrom. More precisely, this optional ingredient is selected from the group consisting of the compounds of the alkali metals--cesium, rubidium, potassium, sodium, and lithium--and the compounds of the alkaline earth metals--calcium, strontium, barium, and magnesium. Generally, good results are obtained in these embodiments when this component constitutes about 0.1 to about 5 wt. % of the composite, calculated on an elemental basis. This optional alkali or alkaline earth metal component can be incorporated in the composite in any of the known ways, with impregnation with an aqueous solution of a suitable water-soluble, decomposable compound being preferred. 
     An optional ingredient for the multimetallic catalyst of the present invention is a Friedel-Crafts metal halide component. This ingredient is particularly useful in hydrocarbon conversion embodiments of the present invention wherein it is preferred that the catalyst utilized has a strong acid or cracking function associated therewith--for example, an embodiment wherein hydrocarbons are to be hydrocracked or isomerized with the catalyst of the present invention. Suitable metal halides of the Friedel-Crafts type include aluminum chloride, aluminum bromide, ferric chloride, ferric bromide, zinc chloride, and the like compounds, with the aluminum halides and particularly aluminum chloride ordinarily yielding best results. Generally, this optional ingredient can be incorporated into the composite of the present invention by any of the conventional methods for adding metallic halides of this type; however, best results are ordinarily obtained when the metallic halide is sublimed onto the surface of the carrier material according to the preferred method disclosed in U.S. Pat. No. 2,999,074. The component can generally be utilized in any amount which is catalytically effective, with a value selected from the range of about 1 to about 100 wt. % of the carrier material generally being preferred. 
     Regardless of the details of how the components of the catalyst are combined with the porous carrier material, the final catalyst generally will be dried at a temperature of about 200 to about 600° F. for a period of at least about 2 to about 24 hours or more, and finally calcined or oxidized at a temperature of about 700° F. to about 1100° F. in an air or oxygen atmosphere for a period of about 0.5 to about 10 hours in order to convert substantially all of the metallic components to the corresponding oxide forms. Because a halogen component is utilized in the catalyst, best results are generally obtained when the halogen content of the catalyst is adjusted during this oxidation step by including a halogen or a halogen-containing compound such as HCl or an HCl-producing substance in the air or oxygen atmosphere utilized. In particular, when the halogen component of the cataylst is chlorine, it is preferred to use a mole ratio of H 2  O to HCl of about 5:1 to about 100:1  during at least a portion of the oxidation step in order to adjust the final chlorine content of the catalyst to a range of about 0.1 to about 3.5 wt. %. Preferably, the duration of this halogenation step is about 1 to 5 hours. 
     It is an essential feature of the present invention that the resultant oxidized catalyst composite is subjected to a substantially water-free reduction step prior to its use in the conversion of hydrocarbons. This step is designed to selectively reduce the platinum or palladium and rhodium components to the corresponding metals and to insure a uniform and finely divided dispersion of these metallic components throughout the carrier material, while maintaining the indium component in a positive oxidation state. Preferably, a substantially pure and dry hydrogen stream (i.e. less than 20 vol. ppm. H 2  O) is used as the reducing agent in this step. The reducing agent is contacted with the oxidized catalyst at conditions including a temperature of about 400° F. to about 1200° F. and a period of time of about 0.5 to 10 or more hours effective to reduce substantially all of the platinum or palladium and rhodium to the elemental metallic state, while maintaining the indium component in a positive oxidation state. This reduction treatment may be performed in situ as part of a start-up sequence if precautions are taken to predry the plant to a substantially water-free state and if a substantially water-free hydrogen stream is used. 
     The resulting selectively reduced catalytic composite may, in some cases, be beneficially subjected to a presulfiding operation designed to incorporate in the catalytic composite from about 0.01 to about 1 wt. % sulfur, and preferably about 0.05 to about 0.5 wt. %, calculated on an elemental basis. This treatment typically takes place in the presence of hydrogen and a suitable sulfur-containing sulfiding reagent such as hydrogen sulfide, lower molecular weight mercaptans, organic sulfides, etc. Typically, this procedure comprises treating the selectively reduced catalyst with a sulfiding gas such as a mixture of hydrogen and hydrogen sulfide or a hydrogen sulfide-producing compound having about 10 moles of hydrogen per mole of hydrogen sulfide at conditions sufficient to effect the desired incorporation of sulfur, generally including a temperature ranging from about 50° F. up to about 1100° F. or more. It is generally a good practice to perform this presulfiding step under substantially water-free conditions. It is within the scope of the present invention to maintain or achieve the sulfided state of the instant catalyst during use in the conversion of hydrocarbons by continuously or periodically adding a decomposable sulfur-containing compound, such as the sulfiding reagents previously mentioned, to the reactor containing the catalyst in an amount sufficient to provide about 1 to 500 wt. ppm., preferably 1 to 20 wt. ppm. of sulfur based on hydrocarbon charge. 
     According to the present invention, a hydrocarbon charge stock and hydrogen are contacted with the instant acidic multimetallic catalyst in a hydrocarbon conversion zone. This contacting may be accomplished by using the catalyst in a fixed bed system, a moving bed system, a fluidized bed system, or in a batch type operation; however, in view of the danger of attrition losses of the valuable catalyst and of well-known operational advantages, it is preferred to use a fixed bed system or a dense-phase moving bed system such as is shown in U.S. Pat. No. 3,725,429. It is also contemplated that the contacting step can be performed in the presence of a physical mixture of particles of the catalyst of the present invention and particles of a conventional dual-function catalyst of the prior art. In the fixed bed system, a hydrogen-rich gas and the charge stock are preheated by any suitable heating means to the desired reaction temperature and then are passed into a conversion zone containing a fixed bed to the catalyst type previously characterized. It is, of course, understood that the conversion zone may be one or more separate reactors with suitable means therebetween to insure that the desired conversion temperature is maintained at the entrance to each reactor. It is also important to note that the reactants may be contacted with the catalyst bed in either upward, downward, or radical flow fashion with the latter being preferred. In addition, the reactants may be in the liquid phase, a mixed liquid-vapor phase, or a vapor phase when they contact the catalyst, with best results obtained in the vapor phase. 
     In the case where the acidic multimetallic catalyst of the present invention is used in a reforming operation, the reforming system will comprise a reforming zone containing one or more fixed beds or dense-phase moving beds of the catalyst type previously characterized. In a multiple bed system it is of course within the scope of the present invention to use the present catalyst in less than all of the beds, with a conventional dual-function catalyst being used in the remainder of the beds. This reforming zone may be one or more separate reactors with suitable heating means therebetween to compensate for the endothermic nature of the reactions that take place in each catalyst bed. The hydrocarbon feed stream that is charged to this reforming system will comprise hydrocarbon fractions containing naphthenes and paraffins that boil within the gasoline range. The preferred charge stocks are those consisting essentially of naphthenes and paraffins, although in some cases aromatics and/or olefins may also be present. This preferred class includes straight run gasolines, natural gasolines, synthetic gasolines, partially reformed gasolines, and the like. On the other hand, it is frequently advantageous to charge thermally or catalytically cracked gasolines or higher boiling fractions thereof. Mixtures of straight run and cracked gasolines can also be used to advantage. The gasoline charge stock may be a full boiling gasoline having an initial boiling point of from about 50° F. to about 150° F. and an end boiling point within the range of from about 325° F. to about 425° F., or may be a selected fraction thereof which generally will be a higher boiling fraction commonly referred to as a heavy naphtha--for example, a naphtha boiling in the range of C 7  to 400° F. In some cases, it is also advantageous to charge pure hydrocarbons or mixtures of hydrocarbons that have been extracted from hydrocarbon distillates--for example, straight-chain paraffins--which are to be converted to aromatics. It is preferred that these charge stocks be treated by conventional catalytic pretreatment methods such as hydrorefining, hydrotreating, hydrodesulfurization, etc., to remove substantially all sulfurous, nitrogenous, and water-yielding contaminants therefrom and to saturate any olefins that may be contained therein. 
     In other hydrocarbon conversion embodiments, the charge stock will be of the conventional type customarily used for the particular kind of hydrocarbon conversion being effected. For example, in a typical isomerization embodiment the charge stock can be a paraffinic stock rich in C 4  to C 8  normal paraffins, or a normal butane-rich stock, or a n-hexane-rich stock, or a mixture of xylene isomers, or an olefin-containing stock, etc. In a dehydrogenation embodiment, the charge stock can be any of the known dehydrogenatable hydrocarbons such as an aliphatic compound containing 2 to 30 carbon atoms per molecule, a C 4  to C 30  normal paraffin, a C 8  to C 12  alkylaromatic, a naphthene, and the like. In hydrocracking embodiments, the charge stock will be typically a gas oil, heavy cracked cyclic oil, etc. In addition alkylaromatic, olefins, and naphthenes can be conveniently isomerized by using the catalyst of the present invention. Likewise, pure hydrocarbons or substantially pure hydrocarbons can be converted to more valuable products by using the acidic multimetallic catalyst of the present invention in any of the hydrocarbon conversion processes, known to the art, that use a dual-function catalyst. 
     In a reforming embodiment, it is generally preferred to utilize the novel multimetallic catalytic composite in a substantially water-free environment. Essential to the achievement of this condition in the reforming zone is the control of the water level present in the charge stock and the hydrogen stream which is being charged to the zone. Best results are ordinarily obtained when the total amount of water entering the conversion zone from any source is held to a level less than 50 ppm. and preferably less than 20 ppm. expressed as weight of equivalent water in the charge stock. In general, this can be accomplished by careful control of the water present in the charge stock and in the hydrogen stream. The charge stock can be dried by using any suitable drying means known to the art, such as a conventional solid adsorbent having a high selectivity for water, for instance, sodium or calcium crystalline aluminosilicates, silica gel, activated alumina, molecular sieves, anhydrous calcium sulfate, high surface area sodium, and the like adsorbents. Similarly, the water content of the charge stock may be adjusted by suitable stripping operations in a fractionation column or like device. And in some cases, a combination of adsorbent drying and distillation drying may be used advantageously to effect almost complete removal of water from the charge stock. Preferably, the charge stock is dried to a level corresponding to less than 20 ppm. of H 2  O equivalent. In general, it is preferred to maintain the hydrogen stream entering the hydrocarbon conversion zone at a level of about 10 vol. ppm. of water or less. If the water level in the hydrogen stream is too high, drying of same can be conveniently accomplished by contacting the hydrogen stream with a suitable disiccant such as those mentioned above. 
     In the reforming embodiment, an effluent stream is withdrawn from the reforming zone and passed through a cooling means to a separation zone, typically maintained at about 25° to 150° F., wherein a hydrogen-rich gas is separated from a high octane liquid product, commonly called an unstabilized reformate. When a super-dry operation is desired, at least a portion of this hydrogen-rich gas is withdrawn from the separating zone and passed through an adsorption zone containing an adsorbent selective for water. The resultant substantially water-free hydrogen stream can then be recycled through suitable compressing means back to the reforming zone. The liquid phase from the separating zone is typically withdrawn and commoly treated in a fractionating system in order to adjust the butane concentration, thereby controlling front-end volatility of the resulting reformate. 
     The conditions utilized in the numerous hydrocarbon conversion embodiments of the present invention are those customarily used in the art for the particular reaction, or combination of reactions, that is to be effected. For instance, alkylaromatic, olefin and paraffin isomerization conditions include: a temperature of about 32° F. to about 1000° F. and preferably from about 75° to about 600° F.; a pressure of atmospheric to about 100 atmospheres, a hydrogen to hydrocarbon mole ratio of about 0.5:1 to about 20:1, and an LHSV (calculated on the basis of equivalent liquid volume of the charge stock contacted with the catalyst per hour divided by the volume of conversion zone containing catalyst) of about 0.2 hr. -1  to 10 hr. -1 . Dehydrogenation conditions include: a temperature of about 700° to about 1250° F., a pressure of about 0.1 to about 10 atmospheres, a liquid hourly space velocity of about 1 to 40 hr. -1 , and a hydrogen to hydrocarbon mole ratio of about 1:1 to 20:1. Likewise, typically hydrocracking conditions include: a pressure of about 500 psig. to about 3000 psig., a temperature of about 400° F. to about 900° F., an LHSV of about 0.1 hr. -1  to about 10 hr. -1 , and hydrogen circulation rates of about 1000 to 10,000 SCF per barrel of charge. 
     In the reforming embodiment of the present invention, the pressure utilized is selected from the range of about 0 psig. to about 1000 psig., with the preferred pressure being about 50 psig. to about 600 psig. Particularly good results are obtained at low pressure; namely, a pressure of about 50 to 350 psig. In fact, it is a singular advantage of the present invention that it allows stable operation at lower pressure than have heretofore been successfully utilized in so-called &#34;continuous&#34; reforming systems (i.e. reforming for periods of about 15 to about 200 or more barrels of charge per pound of catalyst without regeneration) with all platinum monometallic catalyst. In other words, the acidic multimetallic catalyst of the present invention allows the operation of a continuous reforming system to be conducted at lower pressure (i.e. 100 to about 350 psig.) for about the same or better catalyst life before regeneration as has been heretofore realized with conventional monometallic catalysts at higher pressures (i.e. 400 to 600 psig.). On the other hand, the stability feature of the present invention enables reforming operations conducted at pressures of 400 to 600 psig. to achieve substantially increased catalyst life before regeneration. 
     Similarly, the temperature required for reforming is generally lower than that required for a similar reforming operation using a high quality catalyst of the prior art. This significant and desirable feature of the present invention is a consequence of the selectivity of the acidic multimetallic catalyst of the present invention for the octane-upgrading reactions that are preferably induced in a typical reforming operation. Hence, the present invention requires a temperature in the range of from about 800° F. to about 1100° F. and preferably about 900° F. to about 1050° F. As is well known to those skilled in the continuous reforming art, the initial selection of the temperature within this broad range is made primarily as a function of the desired octane of the product reformate considering the characteristics of the charge stock and of the catalyst. Ordinarily, the temperature then is thereafter slowly increased during the run to compensate for the inevitable deactivation that occurs to provide a constant octane product. Therefore, it is a feature of the present invention that the rate at which the temperature is increased in order to maintain a constant octane product is substantially lower for the catalyst of the present invention than for a high quality reforming catalyst which is manufactured in exactly the same manner as the catalyst of the present invention except for the inclusion of the rhodium and indium components. Moreover, for the catalyst of the present invention, the C 5  + yield loss for a given temperature increase is substantially lower than for a high quality reforming catalyst of the prior art. 
     The reforming embodiment of the present invention also typically utilizes sufficient hydrogen to provide an amount of about 1 to about 20 moles of hydrogen per mole of hydrocarbon entering the reforming zone, with excellent results being obtained when about 5 to about 10 moles of hydrogen are used per mole of hydrocarbon. Likewise, the liquid hourly space velocity (LHSV) used in reforming is selected from the range of about 0.1 to about 10 hr. -1 , with a value in the range of about 1 to about 5 hr. -1  being preferred. In fact, it is a feature of the present invention that it allows operations to be conducted at higher LHSV than normally can be stably achieved in a continuous reforming process with a high quality reforming catalyst of the prior art. This last feature is of immense economic significance because it allows a continuous reforming process to operate at the same throughput level with less catalyst inventory than that heretofore used with conventional reforming catalysts at no sacrifice in catalyst life before regeneration. 
    
    
     The following examples are given to illustrate further the preparation of the acidic multimetallic catalytic composite of the present invention and the use thereof in the conversion of hydrocarbons. It is understood that the examples are intended to be illustrative rather than restrictive. 
     EXAMPLE I 
     An alumina carrier material comprising 1/16 inch spheres was prepared by: forming an aluminum hydroxyl chloride sol by dissolving substantially pure aluminum pellets in a hydrochloric acid solution, adding hexamethylenetetramine to the resulting alumina sol, gelling the resulting solution by dropping it into an oil bath to form spherical particles of an aluminum-containing hydrogel, aging and washing the resulting particles, and finally drying and calcining the aged and washed particles to form spherical particles of gamma-alumina containing about 0.3 wt. % combined chloride. Additional details as to this method of preparing the preferred gamma-alumina carrier material are given in the teachings of U.S. Pat. No. 2,620,314. 
     An aqueous acidic impregnation solution comprising indium trichloride, chloroplatinic acid, rhodium trichloride hydrate, and hydrogen chloride was then prepared. The gamma-alumina carrier material was thereafter admixed with the impregnation solution. The amounts of the reagents contained in this impregnation solution were calculated to result in a final composite containing, on an elemental basis, 0.30 wt. % platinum, 0.05 wt. % indium, and 0.15 wt. % rhodium. In order to insure uniform dispersion of the metallic components throughout the carrier material, the amount of hydrochloric acid used was about 2 wt. % of the alumina particles. This impregnation step was performed by adding the carrier material particles to the impregnation mixture with constant agitation. In addition, the volume of the solution was approximately the same as the volume of the carrier material particles. The impregnation mixture was maintained in contact with the carrier material particles for a period of about 1/2 to about 3 hours at a temperature of about 70° F. Thereafter, the temperature of the impregnation mixture was raised to about 225° F. and the excess solution was evaporated in a period of about 1 hour. The resulting dried impregnated particles were then subjected to an oxidation treatment in a dry and sulfur-free air stream at a temperature of about 975° F. and a GHSV of about 500 hr. -1  for about 1/2 hour. This oxidation step was designed to convert substantially all of the metallic ingredients to the corresponding oxide forms. The resulting oxidized spheres were subsequently contacted in a halogen-treating step with a sulfur-free air stream containing H 2  O and HCl in a mole ratio of about 30:1 for about 2 hours at 975° F. and a GHSV of about 500 hr. -1  in order to adjust the halogen content of the catalyst particles to a value of about 0.9 wt. %. The halogen-treated spheres were thereafter subjected to a second oxidation step with a dry and sulfur-free air stream at 975° F. and a GHSV of 500 hr. -1  for an additional period of about 1/2 hour. 
     The oxidized and halogen-treated catalyst particles were then subjected to a dry selective reduction treatment, designed to reduce the platinum and rhodium components to the elemental state while maintaining the indium component in a positive oxidation state. This was accomplished by contacting the particles for about 1 hour with a substantially hydrocarbon-free and sulfur-free dry hydrogen stream containing less than 5 vol. ppm. H 2  O at a temperature of about 1050° F., a pressure slightly above atmospheric, and a flow rate of the hydrogen stream through the catalyst particles corresponding to a gas hourly space velocity of about 400 hr. -1 . At the completion of this prereduction step, it is believed that substantially all of the platinum and rhodium components have been reduced to the elemental state, whereas substantially all of the indium component remains in the indium oxide state. 
     A sample of the resulting selectively reduced catalyst particles was analyzed and found to contain, on an elemental basis, about 0.30 wt. % platinum, about 0.15 wt. % rhodium, about 0.05 wt. % indium, and about 0.9 wt. % chloride. This corresponds to an atomic ratio of indium to platinum of 0.283:1, an atomic ratio of rhodium to platinum of 0.95:1 and an atomic ratio of indium to rhodium of 0.3:1. The resulting acidic selectively reduced multimetallic catalyst is hereinafter referred to as catalyst &#34;A&#34;. 
     EXAMPLE II 
     In order to compare the novel acidic multimetallic catalytic composite of the present invention with catalytic composites of the prior art it a manner calculated to bring out the beneficial interaction of a combination of an indium component and a rhodium component on a platinum-containing acidic catalyst, a comparison test was made between the acidic multimetallic catalyst of the present invention which was prepared in Example I (i.e. catalyst &#34;A&#34;) and two control catalysts: the first was a bimetallic reforming catalyst of the prior art which contained a combination of platinum and rhodium as its hydrogenation-dehydrogenation component and the second was a monometallic reforming containing only platinum as its dehydrogenation-hydrogenation component. The first control catalyst was a combination of platinum component, a rhodium component, and a chloride component with a gamma-alumina carrier material in amounts sufficient to result in the final catalyst containing about 0.3 wt. % platinum, about 0.15 wt. % rhodium and about 0.9 wt. % chloride. The first control catalyst is hereinafter referred to as catalyst &#34;B&#34;. The second control catalyst, hereinafter called catalyst &#34;C&#34;, was a combination of a platinum component and a chloride component with a gamma-alumina carrier material in amounts sufficient to result in the final catalyst containing 0.3 wt. % platinum and 0.94 wt. % chloride. Catalysts &#34;B&#34;  and &#34;C&#34; were prepared by methods analogous to that set forth in Example I with appropriate modifications to result in the specified composition. 
     These catalysts were then separately subjected to a high stress accelerated catalytic reforming evaluation test designed to determine in a relatively short period of time their relative activity, selectivity, and stability characteristics in a process for reforming a relatively low-octane gasoline fraction. In all tests the same charge stock was utilized and its pertinent characteristics are set forth in Table I. It is to be noted that all runs were performed under substantially sulfur-free conditions with the only sulfur input into the plant being the 0.1  ppm. sulfur contained in the charge stock. The runs with catalysts &#34;A&#34; and &#34;B&#34; were performed with a high surface area sodium feed dryer so that the amount of water present in the feed for these runs was less than about 1 wt. ppm. 
     
                       TABLE I                                                     
______________________________________                                    
Analysis of Charge Stock                                                  
Gravity, ° API at 60° F.                                    
                        59.7                                              
Distillation Profile, ° F.                                         
 Initial Boiling Point  178                                               
  5% Boiling Point      199                                               
 10% Boiling Point      210                                               
 30% Boiling Point      232                                               
 50% Boiling Point      244                                               
 70% Boiling Point      286                                               
 90% Boiling Point      320                                               
 95% Boiling Point      336                                               
 End Boiling Point      376                                               
Chloride, wt. ppm.      0.35                                              
Nitrogen, wt. ppm.      0.2                                               
Sulfur, wt. ppm.        0.1                                               
Water, wt. ppm.         14-18                                             
Octane Number, F-1 clear                                                  
                        41.0                                              
Paraffins, vol. %       67                                                
Naphthenes, vol. %      21.2                                              
Aromatics, vol. %       11.8                                              
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     This accelerated reforming test was specifically designed to determine in a very short period of time whether the catalyst being evaluated has superior characteristics for use in a high severity reforming operation. Each run consisted of a series of evaluation periods of 24 hours, each of these periods comprised a 12 hour line-out period followed by a 12 hour test period during which the C 5  + product reformate from the plant was collected and analyzed. All test runs were performed at identical conditions which comprised a liquid hourly space velocity (LHSV) of 3.0 hr. -1 , a pressure of 300 psig., a 10:1 recycle gas to oil ratio, and an inlet reactor temperature which was continuously adjusted throughout the test in order to achieve and maintain a C 5  + target octane of 100 F-1 clear. 
     All test runs were performed in a pilot plant scale reforming unit comprising a reactor containing a fixed bed of the catalyst undergoing evaluation, a hydrogen separation zone, a debutanizer column, and suitable heating means, pumping means, condensing means, compressing means, and the like conventional equipment. The flow scheme utilized in this plant involves commingling a hydrogen recycle stream with the charge stock and heating the resulting mixture to the desired conversion temperature. The heated mixture is then passed downflow into a reactor containing the catalyst undergoing evaluation as a stationary bed. An effluent stream is then withdrawn from the bottom of the reactor, cooled to about 55° F. and passed to a gas-liquid separation zone wherein a hydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. A portion of the gaseous phase is then continuously passed through a high surface area sodium scrubber and the resulting substantially water-free and sulfur-free hydrogen stream is returned to the reactor in order to supply the hydrogen-containing recycle gas stream. The excess gaseous phase from the separation zone is recovered as the hydrogen-containing product stream (commonly called &#34;excess recycle gas&#34;). The liquid phase from the separation zone is withdrawn therefrom and passed to a debutanizer column wherein light ends (i.e. C 1  to C 4 ) are taken overhead as debutanizer gas and a C 5  + reformate stream recovered as the principal bottom product. 
     The results of the separate tests performed on the catalyst of the present invention, catalyst &#34;A&#34;, and the control catalysts, catalysts &#34;B&#34; and &#34;C&#34;, are presented for each test period in Table II in terms of inlet temperature to the reactor in ° F. necessary to achieve the target octane level and the amount of C 5  + reformate recovered expressed as liquid vol. % (LV%) of the charge stock. It is to be noted that the run with catalyst &#34;B&#34; was shut down prematurely because of acute instability and inability to make octane that developed during period No. 5. 
     
                       TABLE II                                                    
______________________________________                                    
Results of Accelerted Reforming Test                                      
CATALYST &#34;A&#34;   CATALYST &#34;B&#34; CATALYST &#34;C&#34;                                  
               C.sub.5 +,     C.sub.5 +,   C.sub.5 +,                     
Period                                                                    
      T. ° F.                                                      
               LV%     T. ° F.                                     
                              LV%   T. ° F.                        
                                           LV%                            
______________________________________                                    
1     954.0    --      926.0  --    1002.5 70.23                          
2     957.0    66.58   933.0  64.87 1012.5 --                             
3     952.0    64.67   940.5  64.35 1020.0 --                             
4     964.0    62.87   963.5  63.30 1025.5 65.93                          
5     971.0    --       985+  --    1030.5 --                             
6     968.5    63.54   --     --    1040.0 59.78                          
______________________________________                                    
 
    
     Referring now to the results of the comparison test presented in Table II, it is evident that the principal effect of the conjoint use of rhodium and indium on a platinum-containing catalyst is to selectively promote and stabilize same and to enable catalyst &#34;A&#34; to substantially outperform catalysts &#34;B&#34; and &#34;C&#34;, particularly, in the areas of activity-stability and selectivity-stability. That is, the data presented in Table II clearly indicates that the acidic multimetallic catalyst of the present invention is superior to both control catalysts in a high severity reforming process. As was pointed out in detail hereinbefore, a good measure of activity for a reforming catalyst is the inlet temperature to the reactor which is required to make target octane and the data presented in Table II on this variable clearly shows the catalyst &#34;A&#34; was extraordinarily more active than catalyst &#34;C&#34;. A comparison of the results for catalyst &#34;A&#34; with those for catalyst &#34;B&#34; demonstrates a marked superiority in average activity over the duration of the test for the acidic multimetallic catalyst of the present invention inasmuch as catalyst &#34;B&#34; was unable to finish the six period test. The activity advantage that catalyst &#34;A&#34; manifests relative to catalyst &#34;C&#34; is consistently better than about 50° F. in inlet reactor temperature and is truly outstanding when one realizes that as a rule of thumb, the rate of a reaction ordinarily doubles for every 18° to 20° F. increase in reactor temperature. Thus, a 50° F. activity advantage means that the catalyst of the present invention is approximately four to six times as active as the control catalyst. A specific example of this activity advantage can be obtained by looking at the data for period 6 of the test (i.e. 144 hours into the test), at this point, catalyst &#34;A&#34; required an inlet temperature of 968.5° F. in order to make octane which stands in sharp contrast to the 1040.0° F. requirement of catalyst &#34;C&#34; at the same point in the run. This 71.5° F. difference in temperature requirement for octane vis-a-vis catalyst &#34;C&#34; is impressive evidence of the ability of the catalyst of the present invention to materially accelerate the rate of the involved reforming reaction without materially changing the C 5  + yield. The difference between the activity results for catalysts &#34;A&#34; and &#34;B&#34; is not as startling as that between &#34;A&#34; and &#34;C&#34; for the first five periods of the test, but is nonetheless quite impressive in view of the fact that the run with catalyst &#34;B&#34; had to be aborted after period five because of onset of severe instability which was manifest in dramatically increased light gas make and coke make. Thus, the data clearly shows that the composite of the present invention was extraordinarily more active than catalyst &#34;C&#34; for the six periods of the test and was clearly more active on the average for the duration of the test than catalyst &#34;B&#34; because of the fact that catalyst &#34;B&#34; was unable to complete the six period test. However, activity is only one of the necessary attributes needed in order for a catalyst to demonstrate superiority. Good activity characteristics must be coupled with superior selectivity and stability characteristics in order to demonstrate improved performance. Selectivity is measured directly by C 5  + yield and the data presented in Table II clearly indicates that catalyst &#34;A&#34; produced an average C 5  + yield which was equivalent or better than those for catalysts &#34;B&#34; and &#34;C&#34;. (It is to be noted that the dashes in Table II represent periods where the relevant analyses of the product streams were not made.) On the other hand, good stability characteristics are shown by the rate of change of the activity and selectivity parameters as was explained hereinbefore, and on this basis the incremental changes in temperature required to maintain octane and in C 5  + yield exhibited in Table II clearly shows excellent and singular stability for the catalysts of the present invention relative to the performances of catalysts &#34;B&#34; and &#34;C&#34;. 
     In summary, it is clear from the data presented in Table II that the combination of an indium component and a rhodium component provides an efficient and effective promoter for a platinum-containing acidic reforming catalyst in a high severity reforming operation. 
     It is intended to cover by the following claims, all changes and modifications of the above disclosure of the present invention which would be self-evident to a man of ordinary skill in the hydrocarbon conversion art or the catalyst formulation art.