Patent Publication Number: US-3875049-A

Title: Platinum-tin catalyst regeneration

Description:
United States Patent 1191 1111 3,875,049 Kluksdahl *Apr. 1, 1975 [5 PLATINUM-TIN CATALYST 3.531.543 9/1970 Clippinger et al. 260/6833 REGENERATION glippinger et al. ox n e Harris Kluksdahl, San Rafael. 3,700,588 10/1972 Weisang et al. 208/139 Cahf. 3,725,304 4/l973 Wilhelm 208/l39 3,740,328 6/l973 Rausch 208/139 [73] Asslgnee: &#39;f&#39;&#34; Cmnlmy, 3,745,112 7/1973 Rausch 208/139 Francisco, callf- 3,764,557 10/1973 Kluksdahl 208/139 [*1 Notice: The portion of the term of Hayes patent subsequent to Oct. 9, 1990, D has been disdaimed Prunary E.\&#39;am1r 1erDelbert E. Gantz Amman: Examiner-James W. Hellwege Filed: P 1 1973 Attorney, Agent, or Firm-G. F. Magdeburger; R. H. [211 App]. No: 355,607 Dav1es; .l. J. De Young Related US. Application Data 57 ABSTRACT co 9 1 8 1 [970, bwhich Hydroconversion of hydrocarbons particularly reg; &#39;g 0 8659)! formlng of naphthas, is conducted 1n the presence of a an one hydrogen with a catalyst comprising a platinum group component in an amount of from 0.0l to 5 weight per- [52] Cl 547 472 cent, a tin component in an amount of from 0.01 to 5 l Cl 6 &#34;/14 weight percent and a halogen in an amount of from g i 140 0.1 to 3 weight percent in association with a porous 252/441, 442, 466 PT, 416 mm came [56] References Cited 4 Claims, 6 Drawing Figures C LIQUID PRODUCT, VOL. AVERAGE CATALYST TEMPERATURE, F  
 PATEIIIED 3. 875.049  
 SHEET 1 [IF 2 96o PLATINUM CATALYST 900 PLATINUM TIN CATALYST I l I I I I l l l I I I O 5 IO I5 3O 4O 5O HOURS ON STREAM FIG. I  
  [PLATINUM TIN CATALYST 86 82 PLATINUM CATALYST 7 I l 1 1 1 l l O 5 IO I5 20 25 3O 35 4O 45 5O 55 60 HOURS ON STREAM FIG. 2  
 INVENTOR HARRIS E. KLUKSDAHL L ATTORNEYS 1 PLATINUM-TIN CATALYST REGENERATION CROSS REFERENCE This is continuaton, of application Ser. No. 8,663. filed Feb. 4, I970 which is a continuation-in-part of copending application Ser. No. 865,010 filed Oct. 9, 1969, now abandoned.  
 BACKGROUND OF THE INVENTION l. Field The present invention is directed to hydrocarbon hydroconversion processes, and more particularly to reforming processes. Still more particularly, the present invention is concerned with a catalytic composition and a process for the hydroconversion of hydrocarbon in the presence of the catalytic composition. The catalyst comprises a platinum group component and a tin component in accociation with a porous solid carrier.  
 2. Prior Art Hydrocarbon hydroconversion processes, such as hydrocracking, hydrogenation, hydrofining, isomerization, alkylation, desulfurization and reforming, are of special importance in the petroleum industry as a means for improving the quality and usefulness of hydrocarbons. The requirement for a diversity of hydro carbon products, including, for example, high quality gasoline, has led to the development of many catalysts and procedures for converting hydrocarbons in the presence of hydrogen to useful products. A particularly important hydrocarbon hydroconversion process is reforming. Although many features of the present invention are discussed in terms of reforming, it is to be understood that the present invention relates to other bydrocarbon hydroconversion processes as well.  
  In the development of catalysts for catalytic hydroconversion processes, it is important that the catalyst exhibit not only the capability to initially perform the specified functions but also that it has the capability to perform satisfactorily for prolonged periods of time. Thus, in the development of new catalysts, attention must be directed to the activity, selectivity and stability characteristics of the catalyst. The activity of a catalyst is a measure of the catalysts ability to convert hydrocarbon reactants to products at a specified severity level, i.e., at a particular temperature, pressure. hydrogen to hydrocarbon mole ratio, etc. The selectivity of the catalyst refers to the ability of the catalyst to produce high yields of desirable products, and accordingly low yields of undesirable products. The stability of a catalyst is a measure of the ability of the catalyst to maintain the activity and selectivity characteristics over a specified period of time. Thus, for example, a catalyst for successful reforming must possess good selectivity, i.e., be able to produce high yields of high octane number gasoline products and accordingly low yields of light hydrocarbon gases. The catalyst should also possess good activity in order that the temperature required to produce a certain quality product need not be too high. Also, the stability should be such that the activity and selectivity characteristics can be retained during prolonged periods of reforming operation. Thus, the temperature stability, which is generally measured as the fouling rate of the catalyst, should be such that the temperature need not be raised at an excessively high rate in order to maintain conversion of the feed to a constant octane product. Also, the yield stability of the catalyst should be such that the production of valuable C gasoline products does not decrease appreciably during prolonged operation at a constant conversion.  
  As indicated above, the present invention is particularly concerned with catalytic reforming, that is, the treatment of naphtha fractions or feeds to improve the octane rating. Most catalytic reforming operations are characterized by employing catalysts comprising dehydrogenation-promoting metal components associated with porous solid carriers, which catalysts selectively promote such hydrocarbon reactions as dehydrogenation of naphthenes to aromatics, dehydrocyclization of paraffms to naphthenes and aromatics, isomerization of normal paraffins to isoparaffins, and hydrocracking of relatively long-chained paraffins. Most catalysts used in reforming processes comprise platinum group components, particularly platinum, in association with porous solid carriers, for example, alumina. Research efforts have been expended to seek substitutes for platinum and/or to seek catalytic promoters to use with platinum catalysts to increase their activity, stability. and selectivity characteristics.  
 SUMMARY OF THE INVENTION In accordance with the present invention, an improved hydroconversion process can be conducted in the presence of a catalyst comprising a platinum group component, a tin component, and a halogen associated with a porous solid carrier. The platinum group component is present in an amount of from 0.01 to 5 weight percent based on the finished catalyst; preferably the platinum group component is platinum. Preferably the tin component is present in an amount of from 0.01 to 5 weight percent and the halogen in an amount of from 0.l to 3 weight percent, based on the finished catalyst. The hydrocarbon hydroconversion process is preferably the reforming of naphtha or gasoline fractions to produce high octane products.  
  Also, in accordance with the present invention, a novel catalytic composition of matter has been discovered comprising a porous solid carrier, preferably a porous inorganic oxide carrier, having associated therewith from 0.0] to 5 weight percent of a platinum group component, 0.01 to 5 weight percent of a tin component, and 0.] to 3 weight percent ofa halogen. The catalytic composition is preferably in a reduced state. The novel catalyst of the present invention is found to be highly active and stable for the reforming of naphtha and gasoline boiling range hydrocarbons and, in fact, is superior to commercial reforming catalysts containing only a platinum group component.  
  Another of the several advantages of the present invention is that the catalyst does not require presulfldin g to reduce initial formation of low molecular weight hydrocarbons during startup of the reforming process, in contrast to other reforming catalysts which often re quire such pretreatment for such purpose.  
 BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be better understood and will be further explained hereinafter by reference to the Figures.  
  The graphs in FIGS. 1 and 2 show for comparison purposes data from simulated life tests indicating the reforming activity and stability of a conventional catalyst comprising platinum and chloride on an alumina support and a catalyst comprising platinum, tin, and chloride on an alumina support. Conditions of opera tion were more severe than normally used in reforming operations in order to simulate the response of the catalysts to much longer tests (life tests). The graph in FIG. 1 shows the average catalyst temperature as a function of the length ofthe test or hours onstream re quired to maintain a 99 F-l clear octane for each of the two catalysts. The graph in FIG. 2 shows as a function of the time onstream the yield of C,-,+ liquid product or gasoline having 99 Fl clear octane rating produced during the reforming of each of the two catalysts. From FIG. 2 it is seen that the process using the platinum-tin catalyst yields significantly higher amounts of 99 F] clear octane product than the process using the plati num catalyst without tin.  
  The graphs in FIGS. 3 and 4 show, as a function of the onstream time, the average catalyst temperature and the C gasoline yield produced, respectively, for an accelerated test (as defined in Example 2) reforming process conducted in accordance with the present invention using a freshly prepared platinum-tin chloride catalyst. The graphs in FIGS. 5 and 6 show the same information using a catalyst that was regenerated and activated as later described after being used in a pilot plant test. The reforming conditions included an average reactor pressure of 125 psig, a hydrogen-tohydrocarbon molar ratio of 3. and a liquid hourly space velocity of 3. The catalyst temperature was adjusted as fouling occurred to maintain production of a I F-l clear octane product. The catalyst responded well to regeneration and the yield of C product remained high over the entire run length. Furthermore, the reforming periods, both with fresh and regenerated and activated catalyst, were of substantial duration, i.e., around to hours. This is significant considering the low pressure and accelerated nature of the tests.  
 DESCRIPTION OF THE INVENTION The porous solid carrier or support which is employed in the preparation of the catalyst of the present invention can be any of a large number of materials upon which catalytically active amounts of a platinum group component, a tin component, and a halogen component can be included. The porous solid carrier can be, for example, charcoal, or carbon. preferably, the porous solid carrier is an inorganic oxide. A high surface area inorganic oxide carrier is particularly preferred, e.g., an inorganic oxide having a surface area of greater than 50 m /gm and preferably greater than about 150 m lgm. Generally, the porous inorganic oxides which are useful as catalyst supports for the present invention have surface areas of from about 50 to 750 m lgm. Natural or syhthetically produced inorganic oxides or combinations thereof can be used. Typical acidic inorganic oxide supports which can be used are the naturally occurring aluminum silicates, particularly when acid treated to increase the activity, and the synthetically produced cracking supports, such as silica-alumina, silica-zirconia, silica-alumina-zirconia, silica-magnesia, silica-alumina-magnesia, and crystalline zeolitic aluminosilieates. For hydrocracking processes it is generally preferred that the carrier comprises a siliceous oxide. Generally, preferred hydrocracking catalysts contain silica-alumina, particularly silica-alumina having a silica content in the range of to 99 weight percent.  
  For reforming processes, it is generally preferred that the catalyst has low cracking activity, that is, has limited acidity. It is preferred for reforming processes to use inorganic oxide carriers such as magnesia and alumina. Alumina is particularly preferred for purposes of this invention. Any of the forms of alumina suitable as a support for reforming catalysts can be used, e.g., gamma alumina, eta alumina, etc. Gamma alumina is particularly preferred. Furthermore, alumina can be prepared by a variety of methods satisfactory for the purposes of this invention. Thus, the alumina may be prepared by adding a suitable alkaline agent such as ammonium hydroxide to a salt of aluminum, such as aluminum chloride, aluminum nitrate, etc., in an amount to form aluminum hydroxide which on drying and calcining is converted to alumina. Alumina may also be prepared by the reaction of sodium aluminate with a suitable reagent to cause precipitation thereof with the resulting formation of aluminum hydroxide gel. Also alumina may be prepared by the reaction of metallic aluminum with hydrochloric acid, acetic acid, etc., in order to form a hydrosol which can be gelled with a suitable precipitating agent, such as ammonium hydroxide, followed by drying and calcination.  
  The catalyst of the present invention comprises a platinum group component, a tin component, and a halogen in association with a porous solid carrier, particularly a porous inorganic oxide carrier. The platinum group component should be present in an amount of from 0.01 to 5 weight percent, preferably from 0.01 to 3 weight percent, based on the finished catalyst. The platinum group component embraces all the members of Group VIII of the Periodic Table having an atomic weight greater than 100, i.e., ruthenium, rhodium, palladium, osmium, iridium, and platinum, as well as compounds and mixtures of any of these. Thus, the platinum group components are the Group VIII noble metals or compounds thereof. Platinum is preferred because of its better performance in reforming and other hydroconversion reactions. When platinum is used, particularly in reforming processes, the preferred amount is from 0.01 to 3, more preferably 0.1 to 2 weight percent, and still more preferably 0.] to 0.9 weight percent. Regardless of the form in which the platinum group component exists on the carrier, whether as metal or compound, e.g., as an oxide, halide, sulfide, or the like, the weight percent is calculated as the metal. Reference to platinum,&#34; platinum group component,&#34; etc., is meant to refer to both the metal and the compound form.  
  The tin component is present on the catalyst in an amount of from 0.01 to 5 weight percent and preferably from 0.01 to 3 weight percent and more preferably from 0.l to 1.5 weight percent, based on the finished catalyst. The tin component can exist on the carrier in the metallic form or as a compound, e.g., as an oxide, sulfide, or the like. Reference to tin&#34; is meant to refer to both the metal and the compound form of tin. Regardless of the form in which tin exists on the carrier, whether as the metal or compound form, the weight percent is calculated as the metal.  
  The platinum group component and tin component can be intimately associated with the porous solid car rier by suitable techniques such as ion exchange, precipitation, coprecipitation, etc. Preferably, however, the components are associated with the porous solid carrier by impregnation. Furthermore, one of the components can be associated with the carrier by one procedure, e.g., ion exchange, and the other component associated with the carrier by another procedure, e.g., impregnation. As indicated, however, the components are preferably associated with the carrier by impregna tion The catalyst can be prepared by either coimpregnation of the platinum group component and tin component or by sequential impregnation.  
  The platinum group component is preferably associated with the porous solid carrier by impregnation of water soluble compounds of the platinum group metals. For example, platinum may be added to the support by impregnation from an aqueous solution of chloroplatinic acid. Other water soluble compounds of platinum which may be incorporated as part of the impregnation solution are, for example, ammonium chloroplatinates, platinum chloride, polyammine platinum salts, etc. Compounds of the other platinum group components may be used as, for example, palladium chloride, rhodium chloride, etc. lmpregnation solutions using organic solvents may also be used.  
  The tin component is preferably associated with the porous solid carrier suitably by impregnation. impregnation can be accomplished using an aqueous solution of a suitable compound. However, when using an aqueous tin impregnating procedure, the resulting catalytic composition of matter is preferably activated in order to obtain optimum catalytic activity. The preferred activation process comprises reacting the catalytic composition with an activating gas including oxygen at a temperature from 500F. to 1300F. for at least 0.5 hours to calcine it. A halogenating component, for example, carbon tetrachloride, chloroform, t-butyl chloride, t-butyl fluoride or the like, may preferably be added during the activation. The activating gas may be slightly moist. The use of a slightly moist activating gas is preferred if a halogenating component is included with said activating gas.  
  As another embodiment, the tin component is impregnated on the carrier, which has previously been im pregnated with a decomposable compound of a plati&#39; num group component and calcined, from an organic solution. Thus, a tin compound dissolved in ether or alcohol or other suitable organic solvent may be used as the impregnation solution. Care should be exercised after impregnation that the organic material is completely evaporated or removed from the catalyst prior to heating of the catalyst in the presence of a reducing atmosphere, for example, hydrogen. Thus, careful drying or calcination should follow impregnation using an organic solvent in order to thoroughly rid the catalyst of hydrocarbon molecules. The presence of hydrocarbons on the catalyst during contact with a hydrogen atmosphere appears to detrimentally affect the performance of the catalyst during hydroconversion reactions as, for example, reforming. The organic solution is preferably substantially anhydrous. If it is not substantially anhydrous, then the catalytic composition should preferably be activated as described above to insure that it has substantially optimum activity. In general, if the catalytic composition is contacted with a substantial amount of moisture during or after impregnation with a tin component, it is desirable to activate the composite as disclosed above to insure that it has substantially optimum activity.  
  Suitable tin compounds which can be used for impregnation are the chlorides, nitrates, sulfates, acetates and ammine complexes. Also, useful tin compounds include the organic tin compounds, such as the tetraalkyl compounds (tetra, butyl, phenyl, ethyl, propyl, octyl, decyl, tin and the like), and the tetra-alkoxide compounds (tin tetraethoxides, etc.). Other useful compounds are the stannates. The particular compound chosen will depend somewhat on the solvent chosen, whether water, or an organic solvent. The tin can be in the stannous or stannic oxidation state. It is particularly preferred to use the chloride or halide compounds of tin inasmuch as the impregnation not only distributes the tin component but also the halide component, which is beneficial to most hydroconver&#39; sion reactions.  
  it is necessary to promote the catalyst for hydrocar bon hydroconversion reactions by the addition of com bined halogens (halides), particularly fluorine or chlorine. Bromine may also be used. The catalyst promoted with halogen usually contains from 0.] to 10 weight percent, preferably 0.1 to 3 weight percent, total halogen content. When the halogen is chlorine, it even more preferably contains 0.5 to 2.0 weight percent and still more preferably 0.8 to 1.6 weight percent, total chlorine content. The preferred amounts are particularly desirable in reforming. The halogens may be incorporated onto the catalyst at any suitable stage of catalyst manufacture, e.g., prior to or following incorporation of the platinum group component and tin component. Generally, the halogens can be combined with the catalyst by contacting suitable compounds such as hydrogen fluoride, ammonium fluoride, hydrogen chloride, and ammonium chloride, either in the gaseous form or in the water soluble form with the catalyst. Preferably the fluorine or chlorine is incorporated with the catalyst from an aqueous solution containing the halogen. Often halogen is incorporated with the catalyst by impregnating with a solution of a halogen compound of a platinum group metal or tin. Thus, for example, impregnation with chloroplatinic acid normally results in chlorine addition to the catalyst. Halogen may also be incorporated during the activation process previously described.  
  Following incorporation of the porous solid carrier with the platinum group component, the tin component, and the halogen, the resulting composite is usu ally treated by heating at a temperature of, for example, no greater than 500F and preferably at 200 to 400F. Thereafter the composite can be calcined at an elevated temperature as, for example, up to l,300F., if desired. In the case of sequential deposition of the metal components onto the porous solid carrier, it may be desirable to dry and calcine the catalyst after the introduction of one of the metal components and prior to introduction of the other.  
  Following calcination, the catalyst containing a platinum group component and a tin component is preferably heated at an elevated temperature in a hydrogen containing atmosphere, preferably dry hydrogen to produce the catalyst in reduced form. It is particularly preferred that this treatment with hydrogen be accomplished at a range of 600 to l,300F and preferably from 600 to 1000F. The heating in the presence of hydrogen preferably continues until the partial pressure of hydrogen substantially stabilizes. This will usually take 5 minutes or longer. The treatment in the presence of hydrogen should be accomplished in a hydrocarbon-free environment. Thus, any hydrocarbon on the catalyst should be removed prior to contact with the hydrogen. The environment should also be substantially free of carbon oxides. By reduced form it is not meant to imply that the entire catalyst or even all of the platinum group component and tin component are reduced to a zero valence state, although the great major ity of the platinum group component is believed to be reduced to the metal (zero valence). The reduction of the catalytic composition as described above to form a reduced catalytic composition enhances the usefulness of the catalytic composition in, for example. reforming processes.  
  The novel catalytic composition of the present invention finds utility for various hydrocarbon hydroconversion reactions including hydrofining, hydrogenation, reforming. alkylation, dehydrocyclization, isomerization, and hydrocracking. The catalyst composition of the present invention is most advantageously used for reforming. The hydrocarbon feeds employed and the reaction conditions used will depend on the particular hydrocarbon hydroconversion process involved and are generally well known in the petroleum art. The conditions of temperature. pressure, hydrogen flow rate, and liquid hourly space velocity in the reaction zone can be correlated and adjusted depending on the particular feedstock utilized, the particular hydrocarbon hydroconversion process, and the products desired. For example, hydrocracking operations are generally accomplished at a temperature of from about 450 to 900F and a pressure between about 500 to 10,000 psig. Preferably pressures between 1200 to 1600 psig are used. The hydrogen flow rate into the reactor is maintained between lOOO to 20,000 SCF/bbl of feed and preferably in the range 4000 to 10,000 SCF/bbl. The liquid hourly space velocity (LHSV) will generally be in the range of from 0.l to 10 and preferably from 0.3 to 5.  
  As indicated above. the catalyst of the present The is preferably employed in reforming. the feedstock desirably used for reforming is a light hydrocarbon oil, e.g., a naphtha fraction. Generally, the naphtha will boil in the range falling within the limits of from 70 to 550F and preferably from 150 to 450F. The feedstock can be, for example, either a straight-run naphtha or a thermally-cracked or catalytically-cracked naphtha or blends thereof. The feedstock can preferably be low in sulfur, i.e., preferably contain less than 10 ppm sulfur and more preferably less than 5 ppm sulfur. In the case of a feedstock which is not already low in sulfur, acceptable levels can be reached by hydrogenating the feedstock in a presaturation zone where the naphtha is contacted with a hydrogenation catalyst which is resistant to sulfur poisoning. A suitable catalyst for this bydrodesulfurization process is, for example, an aluminacontaining support with a minor proportion of molybdenum oxide and cobalt oxide. Hydrodesulfurization is ordinarily conducted at a temperature of from 700 to 850F, a pressure of from 200 to 2000 psig, and a liquid hourly space velocity of from 1 to 5. The sulfur contained in the naphtha is converted to hydrogen sulfide which can be removed prior to reforming by suitable conventional processes.  
  The feedstock can preferably be low in moisture i.e., preferably contain less than 50 ppm water (by weight) and more preferably less than ppm moisture. This limits the amount of moisture that contacts the catalyst and thereby serves to keep the activity of the catalyst high for longer periods of time.  
  Reforming conditions will depend in large measure on the feed used, whether highly aromatic, paraffinic or naphthenic, and upon the desired octane rating of the product. The temperature in the reforming process will generally be in the range of about 600 to l l00F and preferably about 700 to l050F. The pressure in the reforming reaction zone can be atmospheric or superatmospheric. The pressure will generally lie within the range of from 25 to 1000 psig and preferably from about 50 to 750 psig. The temperature and pressure can be correlated with the liquid hourly space velocity (LHSV) to favor any particularly desirable reforming reaction as, for example, dehydrocyclization, or isomerization. Generally, the liquid hourly space velocity will be from 0.1 to 10, and preferably from I to 5.  
  Reforming of a naphtha is accomplished by contacting the naphtha at reforming conditions and in the presence of hydrogen with the desired catalyst. Reforming generally results in the production of hydrogen. The hydrogen produced during the reforming process is generally recovered from the reaction products and preferably at least part of said hydrogen is recycled to the reaction zone. Preferably, the recycle hydrogen is substantially dried, as by being contacted with an adsorbent material such as a molecular sieve, prior to being recycled to the reaction zone. Thus, excess or make-up hydrogen need not necessarily be added to the reforming process, although it is sometimes preferred to introduce excess hydrogen at some stage of the operation, for example, during startup. Hydrogen, either as recycle or make-up hydrogen, can be added to the feed prior to contact with the catalyst or can be contacted simultaneously with the introduction of feed to the reaction zone. Generally, during startup of the process, hydrogen is recirculated over the catalyst prior to contact of the feed with the catalyst. Hydrogen is preferably introduced into the reforming reaction zone at a rate of from about 0.5 to 20 moles of hydrogen per mole of feed. The hydrogen can be in admixture with light gaseous hydrocarbons.  
  Although, as previously pointed out, it is not necessary, it may be desirable in some instances to presulfide the catalyst prior to use in catalytic hydroconversion reactions, for example, reforming. The presulfiding can be done in situ or ex situ by passing a sulfur-containing gas, e.g., H 8, and hydrogen through the catalyst bed. A temperature of from 25 to ll00F or more can be used for the presulfiding. Other presulfiding treatments are known in the prior art. It may also be desirable on startup of the reforming process to use a small amount of sulfur, e.g., H S or dimethyl disulfide. The sulfur compound is added to the reforming zone in the presence of the flowing hydrogen. The sulfur can be introduced into the reaction zone in any convenient manner and at any convenient location. It can be contained in the liquid hydrocarbon feed, the hydrogenrich gas, the recycle liquid stream or a recycle gas stream or any combination.  
  After a period of operation when the catalyst becomes deactivated by the presence of carbonaceous deposits, the catalyst can be regenerated, for example, by passing an oxygen-containing gas having no more than about 2 percent oxygen, into contact with the catalyst at an elevated temperature in order to burn carbonaceous deposits from the catalyst. The method of regenerating the catalyst will depend on whether there is a fixed bed. moving bed, or fluidized bed operation.  
  It may be desirable to activate the catalyst after if has been regenerated by reacting it with an activating gas including oxygen. The activating technique is that disclosed above for increasing the activity of a catalyst where tin has been included by an aqueous impregnating procedure. It is generally preferred to include a halogenating component with the activating gas when activating a deactivated and regenerated catalyst. The reason for this is that the deactivated and regenerated catalyst may have lost some halogen content during its use in a hydrocarbon hydroconversion process. The catalyst may be analyzed for halide content to determine whether a halogenating component should be included with the activating gas.  
  After regeneration, or regeneration and activation if the catalyst is activated, the catalyst is preferably heated at an elevated temperature in a hydrogen containing atmosphere to reduce it. Preferably the heating is performed in the presence of a substantially hydrocarbon-free, hydrogen containing gas that is preferably substantially dry at a temperature from 600F. to 1,300F., and more preferably from 600F. to 1000F. The substantially hydrocarbon-free hydrogencontaining gas is preferably also free of carbon oxides and water.  
  The process of the present invention will be more readily understood by reference to the following Exam ples.  
 EXAMPLE 1 A catalyst comprising platinum, tin, and chlorine in association with alumina was prepared as follows: Stannic tetrachloride (anhydrous) in an amount of 0.5 ml was diluted to 65 mls by the addition of absolute ethanol. The stannic tetrachloride-ethanol solution was then contacted with 125 grams ofa commercially available 0.3 weight percent platinum-0.6 weight percent chlorine-alumina catalyst. The impregnated composite was then left for 2 hours in a closed vessel at room temperature. Thereafter the composite was dried in a vac uum oven for approximately 16 hours at about 250F. The catalyst was then calcined in flowing air for about 2 hours at 900F and then reduced in one atmosphere of hydrogen for 1 hour at 900F. The resulting catalyst contained about 0.5 weight percent tin and about 1.0 weight percent chlorine.  
  The catalyst was tested for reforming of a naphtha feed having a boiling range of 1 to 428F comprising 23.4 volume percent aromatics, 36.5 volume percent paraffins, and 40.1 volume percent naphthenes. The feed was essentially sulfur free. Reforming conditions included a pressure of 125 psig, a liquid hourly space velocity of 3 and hydrogen to hydrocarbon mole ratio of 3; once-through hydrogen was used. The temperature was adjusted to maintain conversion to 99 F-l clear octane product.  
  For comparison purposes, the commercially avail able 0.3 weight percent platinum-0.6 weight percent chlorine-alumina catalyst was also tested for reforming at the same reaction conditions and with the same feed as that described above for the platinum-tin catalyst.  
  The reforming processes were conducted under con ditions to simulate an accelerated life test for the cata lyst. These conditions were not necessarily maintained at levels used in a commercial reforming process but,  
 in general, were much more severe to test in a relatively few hours how well the catalyst would perform. The increase in temperature necessary to maintain conversion to 99 F-l clear octane product was measured for each catalyst to give an indication of the activity and temperature stability of each catalyst. The results are shown in the graph in FIG. I. The change in yield of C gasoline product over the period of the run was measured for each catalyst to give an indication of the yield stability of each catalyst. The C gasoline yield product having an octane rating of 99 F-l clear is shown in FIG. 2.  
  The response of the platinum-containing catalyst to the simulated life test was very poor compared to the performance of the platinum-tin catalyst. As seen in FIG. 1, it was necessary to increase the temperature very rapidly for the process using the platinum catalyst without tin in order to maintain a 99 Fl clear octane. Moreover, the yield of C liquid product having the desired octane rating decreased significantly for the process using the platinum catalyst without tin as shown in FIG. 2. On the other hand, the catalyst comprising platinum and tin performed remarkably well during the reforming test. From FIG. 1 it can be seen that the reforming temperature required to maintain a 99 Fl clear octane product increased much slower as compared to the temperature increase when reforming with the platinum catalyst without tin. Also, from FIG. 2 the catalyst comprising platinum and tin displayed remarkable stability during the reforming process. Thus, the C product remained very high during the reforming test compared to the C yield when reforming with the platinum catalyst without tin. As another advantage of the platinum-tin catalyst, it is noted that the initial startup temperature for the process using the platinumtin catalyst was significantly lower than that of the pro cess using the platinum catalyst without tin. Also, production of low molecular weight hydrocarbons was low even though the platinum-tin catalyst was not sulfided.  
 EXAMPLE 2 A catalyst (Catalyst A) comprising 0.3 weight percent platinum, O.6 weight percent tin, and about 0.9 weight percent chlorine supported on an alumina car rier was used in reforming a hydrofmed, catalytically cracked naphtha under accelerated conditions. The catalyst was reduced prior to use. The process was conducted at reforming conditions including an average reactor pressure of 125 psig, a hydrogen-tohydrocarbon molar ratio of 3.0 and a liquid hourly space velocity of 3. The temperature ofthe catalyst was adjusted throughout the run to maintain production of a F-l clear octane product. The run was made using oncethrough hydrogen. The hydrofined, catalytically cracked naphtha had an initial boiling boint of 151F, an end boiling point of 428F, and a 50 percent boiling point of 307F. The research octane number of the feed, without antiknock additives (Fl clear), was 64.6. The naphtha contained less than 0.1 ppm nitrogen and less than 0.1 ppm sulfur. The feed was specifically chosen because of its severe deactivating effect upon reforming catalysts. Using this feed and the above reaction conditions, tests of reforming catalysts can be accelerated, i.e., performed in a fraction of the time needed with a less severely deactivating feed and less severe conditions.  
  The results of reforming the naphtha at the acceler ated conditions specified. using Catalyst A, are shown in FIGS. 3 and 4. The graph in FIG. 3 shows the average catalyst temperature in degrees Farenheit as a function of the run length. The graph in FIG. 4 shows the C yield decline as a function of the run length.  
  A catalyst (Catalyst B) comprising 0.3 weight percent platinum. 0.6 weight percent tin, and about L35 weight percent chlorine supported on an alumina carrier was used in reforming the same hydrofined, catalytically cracked naphtha under the same accelerated conditions as was Catalyst A. Catalyst B was a regener ated and activated catalyst that had previously become deactivated by use in a pilot plant run.  
  The regeneration of Catalyst B was accomplished by passing a gas comprising nitrogemoxygen, the oxygen being present in about 0.5 volume percent, through a bed ofthe catalyst at a temperature of 750F. The temperature in the bed increased to about 800F as the combustion flame travelled through the bed. The temperature of the bed was then increased to about 850F and a small amount of additional burning off of coke occurred.  
  The catalyst was contacted with an air-nitrogencarbon tetrachloride mixture having about 5 percent oxygen at a temperature of about 950F to activate it. The air-nitrogen-carbon tetrachloride mixture contained about 0.3 percent moisture. The catalyst was then flushed of air. moisture. nitrogen, and carbon tetrachloride, heated in pure dry hydrogen at 900F to reduce it, and then contacted with the feed at reforming conditions.  
  The results of reforming the naphtha at the conditions specified with Catalyst B are shown in FIGS. 5 and 6. The graph in FIG. 6 shows the average catalyst temperature in degrees Farenheit as a function of run length. The graph in FIG. 6 shows the C yield decline as a function of run length.  
  As can be seen from FIGS. 36, regeneration and activation ofa platinum-tin-chlorine catalyst results in the restoration ofsubstantially the initial activity of the catalyst, i.e., initial catalyst temperature of Catalyst B was within a few degrees Farenheit of the initial catalyst temperature of Catalyst A. It is noted that a run length of approximately equal time can be obtained after regeneration and activation.  
  The graphs in FIGS. 4 and 6 show the C,-,+ liquid yield produced during the reforming process as a function of run length. It can be seen that the yield remained at least about volume percent throughout the runs with both Catalyst A (fresh) and Catalyst B (regenerated and activated).  
  The foregoing disclosure of this invention is not to be considered as limiting since many variations can be made by those skilled in the art without departing from the scope or spirit of the appended claims. Thus, the catalyst of the present invention can be used for isomerization of alkyl aromatics, e.g., the isomerization of xylenes to other xylene isomers.  
 I claim:  
  1. A regenerative process for the hydroconversion of hydrocarbons. which comprises (1 contacting the hydrocarbons at hydroconversion conditions in the presence of hydrogen with a catalyst comprising a platinum group component in an amount from 0.0l to 5 weight percent, a tin component in an amount from 0.01 to 5 weight percent, and a halogen in an amount from (H to 3 weight percent in association with a porous solid carrier. until said catalyst has become deactivated by carbonaceous deposits. and (2] contacting the deactivated catalyst with an activating gas containing oxygen at elevated temperatures for a time sufficient to activate the catalytic composition.  
  2. A process as in claim 1 wherein the porous solid carrier is alumina.  
  3. The process of claim 1, wherein said activating gas also contains a halogen component.  
  4. The process of claim 1, wherein the catalyst is reduced in the presence of hydrogen after contact with said activating gas.