IL34833A - Hydrocarbon conversion process and catalyst therefor - Google Patents

Description

The subject of the present invention is a novel 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 cracking function. More precisely, the present invention involves a novel dual-function 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 provided by the use of a catalytic composite comprising a platinum group component, a rhenium component,, and a germanium 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 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 utilized as the support or carrier for a heavy metal component, such as the metals or compounds of metals of Group V through VIII of the Periodic Table, to which is 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, alkylation, polymerization, cracking and hydroisomerization. In many cases, the commercial applications of these catalysts are in processes where more than one of these reactions is 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, hydro-cracking 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 an relatively rich in straight-chain paraffin components is contacted 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, selectivityj 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'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 hydrogen, (2) selectivity refers to the amount of desired product or products obtained relative to the amount of reactants converted; (3) stability refers to the. rate of. change with time of the activity and selectivity parameters — the smaller rate implying the more stable catalyst. In a reforming process, for example, activity commonly refers to the amount of conversion of a given charge stock at a specified severity level and is typically measured relatively rich in straight-chain paraffin components is contacted 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'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 hydrogen, (2) selectivity refers to the amount of desired product or products obtained relative to the amount of reactants converted; (3) stability refers to the. rate of change with time of the activity and selectivity parameters — the smaller rate implying the more stable ca"talyst. In a reforming process, for example, activity commonly refers to the amount of conversion of a given charge stock at a specified severity level and is typically measured to the amount of C5+ yield that is obtained at the particular severity level; and stability refers to the rate of change with time of activity,, as measured by octane number of C5+ product, and of selectivityff as measured by C5+ yield.

Generally a continuous reforming process is run to produce a constant octane C5+ product with severity level being continuously adjusted to attain this result. 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 used in a hydrocarbon conversion reaction is that coke forms on the surface of the catalyst. 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 coats the surface of the catalyst and 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 on the surface of the catalyst. Accordingly, 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 C5+ yield-octane relationship —■ yield being representative of selectivity and octane being proportional to activity.

The present invention provides a dual-function catalytic composite which possesses improved activity, selectivity, and stability when employed for the conversion of hydrocarbons in processes for isomerization, hydroisomeri-zation, dehydrogenation, desulfurization, denitrogenization, hydrogenation, alkylation, dealkylation, hydrodealkylation, transalkylation, cyclization, dehydrocyclization, cracking, hydrocracking, reforming, and the like,, In particular, a composite comprising a platinum group component, a rhenium component, and a germanium component with a porous refractory carrier material enables the performance of hydrocarbon conversion processes utilizing dual-function catalysts to be substantially improved. Moreover, a catalytic composite comprising catalytically effective amounts of a platinum component, a germanium component,, a rhenium component/ and a halogen component with an, alumina carrier material can be utilized to substantially improve the performance of a reforming process which operates on a gasoline-boiling-range fraction to produce a high-octane reformate. In the case of a reforming process, the principal advantage associated with the use of the novel catalyst of the present invention involves the capability to operate in a stable manner in a high severity operation; for example, a low pressure reforming process designed to produce a C5+ reformate having an octane of about 100 F-l clear. As indicated,, the present invention involves the discovery that the addition of a germanium component and a rhenium component to a dual-function hydrocarbon conversion catalyst containing a platinum group component enables the performance characteristics of the catalyst to be sharply and materially improved,^ It is, accordingly, one object of the present invention to provide a hydrocarbon conversion process utilizing a novel catalyst having superior performance characteristics.

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 e /nsureji the achievement and maintenance of its properties. having superior activity, selectivity, and stability. Yet another object is to provide a dual-function hydrocarbon conversion catalyst which utilizes a combination of a relatively inexpensive component, germanium, and a relatively expensive component, rhenium, to promote a platinum metal component.

Accordingly, the present invention provides a process for the conversion of a hydrocarbon, which comprises subjecting said hydrocarbon to contact at hydrocarbon conversion conditions with a catalytic composite comprising a platinum group component, a rhenium component, and a germanium component with a porous carrier material. The porous carrier material is a porous, refractory material cuoh as a rofraotory inorganic oxide, and the germanium component, the rhenium component, and the platinum group component are usually utilized in relatively small amounts which are effective to promote the desired hydrocarbon conversion reaction.

The invention further provides a catalytic composite comprising a platinum component, a rhenium component, and a germanium component, with an alumina carrier material. These components are preferably present in the composite in the following amounts, on an elemental basis; from about 0.01 to about 2 wt % platinum, from about 0.01 to about 2 wt % rhenium, and from about 0.01 to about 5 wt % germanium.

The composite may also contain a halogen component the range from about 0.1 to about 3.5 wt % (elemental basis).

According to a further feature of the invention, the composite is reduced with hydrogen under substantially water-free conditions prior to use thereof in the conversion of hydrocarbons. The pre-reduced catalytic composite may be combined with a sulfur component in an amount which incorporates therein from about 0.05 to about 0.5 wt % sulfur, calculated on an elemental basis „ A preferred embodiment of the invention provides a process for reforming a gasoline fraction which comprises contacting the gasoline fraction and hydrogen with the catalytic composite described above at reforming conditions selected to produce a high-octane reformate„ As indicated above, the catalyst of the present invention comprises a porous carrier material or support having combined therewith catalytically effective amounts of a platinum group component, a rhenium component, a germanium component, and in the preferred case 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 2 having a surface area of about 25 to about 500 m /gm. 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 < 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's earth, kaolin, and kieselguhr; (3) ceramics, porcelain,, crushed firebrick, bauxite; (4) refractory inorganic oxides such as alumina, titanium dioxide, zirconium dioxide, chromium oxide, zinc oxide, magnesia, thoria, boria, silica-alumina, silica-magnesia, chromia-alumina , alumina-boria, and silica-zirconia ; (5) crystalline 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; and, (6) combinations 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 alumina materials are the crystalline aluminas known as the gamma-, eta-, and theta-aluminas with gamma-or eta-alumina giving best results. In addition, in some embodimentp the alumina carrier material may contain minor proportions of other well known refractory inorganic oxides such as silica, zirconia, and magnesia; 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 0.7 gm/cc and surface area characteristics such that the average pore diameter is about 20 to about 300 Angstroms, the pore volume is about 0.1 to about 1 ml/gm and the surface area is about 100 to about 500 m /gm. Excellent results are obtained with a gamma-alumina carrier material which is used in the form of spherical particles having a relatively small diameter, for example, about 106 mm (1/16 inch), an apparent bulk density of about 0=5 gm/cc, a pore volume of about 0.4 ml/gm, and a surface area of about 175 m /gm.

The preferred alumina carrier material 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, or steaming, and it may be in a form known as activated alumina, activated alumina of commerce, porous alumina, or alumina gel. 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 or aluminum nitrate, 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, or granules, and utilized in any desired size. For the purpose of the present invention a particularly preferred form of alumina is the sphere.

Alumina spheres may be continuously manufactured by the well known oil drop method, which comprises forming an alumina hydrosol, combining the hydrosol with a suitable gelling agent and dropping the resultant mixture into an oil bath maintained at elevated temperatures. The droplets remain in the oil bath until they set and form hydrogel spheres. The spheres are then washed, dried and calcined. The final spheres are crystalline gamma-alumina.

One essential constituent of the catalyst of the present invention is a germanium component. This component may be present as elemental metal or as a chemical compound such as the oxide, sulfide, halide, oxychloride, or aluminate. Although it is not intended to restrict the present invention by this explanation, it .is believed that best results are obtained when the germanium component is present in the composite in an oxidation state above that of the elemental metal „ Best results are obtained when the composite contains from about 0.05 to about 2 wt % germanium. The germanium component may be incorporated in the catalytic composite in any suitable manner such as by coprecipitation or cogellation with the porous carrier material, ion exchange with the gelled carrier material, or impregnation with the carrier material either after or before it is dried and calcined. Any conventional method for incorporating the germanium component in a catalytic composite may be used. The particular method used method involves coprecipita ting the germanium component with the preferred carrier material, alumina. This method involves the addition of a soluble germanium compound such as germanium tetrachloride to the alumina hydrosol, combining the hydrosol with a suitable gelling agent and then dropping the resulting mixture into an oil bath, aging, washing, drying and calcining as explained in detail hereinbefore. The resulting catalytic composite contains an intimate combination of alumina and germanium oxide. A preferred method of incorporating the germanium component into the catalytic composite involves using a soluble, decomposable compound of germanium 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 germanium compound and is preferably an aqueous, acidic solution. Thus, the germanium component may be added to the carrier material by commingling the latter with an aqueous, acidic solution of suitable germanium salt or suitable compound of germanium such as germanium tetrachloride, germanium difluoride, germanium tetrafluoride, germanium di-iodide, germanium monosulfide, or the like compounds. A particularly preferred impregnation solution comprises nascent germanium metal dissolved in chlorine water to yield germanium monoxide. The germanium component may be impregnated either prior to, simultaneously with, or after the other metallic components are added to the carrier material.

Excellent results are obtained when the germanium component is impregnated simultaneously with the other metallic components. A preferred impregnation solution contains chloro-platinic acid, hydrogen chloride, perrhenic acid and germanous oxide dissolved in chlorine water. Following the impregnation step, the resulting composite is dried and calcined as explained hereinafter.

It is preferred that the germanium component be uniformly distributed throughout the carrier material, and this is achieved by maintaining the pH of the impregnation solution in a range of about 1 to about 7 and by diluting the impregnation solution to a volume which is substantially in excess of the volume of the carrier material which is to be impregnated. It is preferred to use a volume ratio of impregnation solution to carrier material of at least 1.5:1 and preferably from about 2:1 to about 10:1 or more. Similarly, it is preferred to use a relatively long contact time during the impregnation step, ranging from about 1/4 hour up to about 1/2 hour or more, before drying to remove excess solvent. This insures a high dispersion of the germanium component on the carrier material. The carrier material is preferably constantly agitated during this preferred impregnation step.

As indicated above, a second essential component of the catalyst of the invention is the platinum group component. The platinum group component preferably will be platinum, but ruthenium, osmium, or iridium. The platinum group component may exist within the final catalytic composite as a compound such as an oxide, sulfide, halide, or as an elemental metal. Generally, the amount of the platinum group component present in the final catalyst composite is small compared to the quantities of the other components combined therewith. Generally it will comprise from 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 the platinum group metal.

The platinum group component may be incorporated in the catalytic composite in any suitable manner such as co-precipitation or cogellation with the preferred carrier material, ion-exchange, or impregnation. The preferred method involves the utilization of a soluble, decomposable compound of a platinum group metal to impregnate the carrier material.

Thus, the platinum group component may be added to the support by commingling the latter with an aqueous solution of chloro-platinic acid. Other water-soluble compounds of platinum may be employed, such as ammonium chloroplatinate, bromoplatinic acid, platinum dichloride, platinum tetrachloride hydrate, platinum dichlorocarbonyl dichloride, or dinitrodiamino platinum. A platinum chloride compound, such as chloro-platinic acid, is preferred since it facilitates the incorporation of both the platinum component and at least a minor Hydrogen chloride is also generally added to the impregnation solution to further facilitate the incorporation of the halogen component. It is generally preferred to impregnate the carrier material after it has been calcined, to minimize the risk of washing away the valuable platinum metal compounds. However, in some cases it may be advantageous to impregnate the carrier material when it is in a gelled state. Following the impregnation, the impregnated support is dried and subjected to a high temperature calcination or oxidation technique.

Another essential component of the catalyst of the present invention is the rhenium component. This component may be present as elemental metal, as a chemical compound such as the oxide, sulfide or halide, or as a physical or chemical combination with the porous carrier material and/or other components of the catalytic composite. The rhenium component is preferably utilized in an amount which provides in the final catalytic composite from about 0,01 to about 2 wt % rhenium, calculated on an elemental basis, with best results obtained at a level of about 0.05 to about 1 wt % rhenium. The rhenium component may be incorporated in the catalytic composite in any suitable manner and at any stage in the preparation of the catalyst. It is generally advisable to incorporate the rhenium component in an impregnation step after the porous carrier material has been formed in order that the expensive metal will not be lost due to washing carrier material during the course of its production. Although any suitable method can be utilized to incorporate the rhenium component, the preferred procedure involves impregnation of the porous carrier material. The impregnation solution may, in general, be a solution of a decomposable rhenium salt such as ammonium perrhenate, sodium perrhenate, potassium perrhenate, and the like salts. Alternatively, solutions of rhenium halides, such as rhenium chloride, may be used. The preferred impregnation solution is an aqueous solution of perr-henic acid. The porous carrier material may be impregnated with the rhenium component either prior to, simultaneously withj, or after the other components mentioned herein are combined therewith. Best results are ordinarily achieved when the rhenium component is impregnated simultaneously with the other metallic components. In fact, excellent results have been obtained with a one step, impregnation · procedure utilizing as an impregnation solution, an aqueous solution of chloroplatinic acid, perrhenic acid, hydrochloric acid„ and germanous oxide dissolved in chlorine water.

Although not essential, it is generally preferred to incorporate a halogen component into the catalytic composite of the present invention. The precise chemistry of the association of the halogen component with the carrier material is not entirely known. It is customary that the halogen component is combined with the carrier material or halogen may be either fluorine, chlorine, iodine, bromine, or mixtures thereof. Fluorine, and particularly chlorine, are preferred. The halogen may be added to the carrier material 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 the calcined carrier material, as an aqueous solution of an acid such as hydrogen fluoride, hydrogen chloride, hydrogen bromide or the like. The halogen component or a portion thereof may be composited with the carrier material during the impregnation of the latter with the platinum group component; for example, by using a mixture of chloroplatinic acid and hydrogen chloride. The alumina hydrosol utilized to form the preferred alumina carrier material may also contain halogen and thus contribute at least a portion of the halogen component to the final composite. For reforming, the halogen is combined with the carrier material in an amount which yields a final composite containing from about 0.1 to about 3.5 wt % and preferably about 0.5 to about 1.5 wt % of halogen, calculated on an elemental basis. For utilization as isomeri- zation or hydrocracking catalyst, it is generally preferred to utilize relatively larger amounts of halogen, — ranging up to about 10 wt % halogen calculated on an elemental basis, and more preferably about 1 to about 5 wt % Regarding the amounts of the various metallic com component as a function of the amount of the platinum group component. On this basis, the amount of the rhenium component is selected so that the atomic ratio of rhenium to the platinum group metal contained in the composite is from about 0.1:1 to about 3:1. Similarly, the amount of the germanium component is selected to produce a composite containing an atomic ratio of germanium to platinum group metal of about 0.25:1 to about 6:1.

Another significant parameter for the subject catalyst is the "total metals content" which is the sum of the platinum group component, the rhenium component, and the germanium component, calculated on an elemental metal 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 achieved at a metals loading of about 0.3 to about 2 wt %.

A particularly preferred catalytic composite comprises a platinum component, a rhenium component, a germanium component, and a halogen component with an alumina carrier material, in amounts which provide a composite containing about 0.5 to about 1.5 wt % halogen, about 0.05 to about 1 wt % platinum, about 0.05 to about 1 wt % rhenium, and about 0.05 to about 2 wt % germanium. Accordingly, specific examples of especially preferred catalytic composites are tabulated below, the concentrations indicated being on an elemental basis: Catalyst Wt % Wt % Wt % No. Germanium Rhenium Platinum 1 0.5 0.5 0.75 2 0.1 0.1 0.1 3 0.375 0.375 0.375 4 0.2 0.1 0.5 0.5 0.25 0.25 6 1.0 0.5 0.5 For all of the above mentioned composites the preferred carrier material comprises alumina and the composite contains from about 0.5 to about 1.5 wt % halogen, on an elemental basis .

The final catalyst generally is dried at a temperature of about 93°C (200°F) to about 316°C (600°F) for a period of from about 2 to about 24 hours or more, and finally calcined at a temperature of about 371°C (700°F) to about 593°C (1100°F) in an air atmosphere for a period of about 0.5 to about 10 hours to convert the metallic components substantially to the oxide form. In the case where a halogen component is utilized in the catalyst, best results are generally obtained when the halogen content of the catalyst is adjusted during the calcination step by including a halogen or a halogen-containing compound in the air atmosphere utilized. In particular, when the halogen component of the H20 to HC1 of about 20:1 to about 100:1 during at least a portion of the calcination step in order to adjust the final chlorine content of the catalyst to a range of about 0.5 to about 1.5 t % It is preferred that the resultant calcined catalytic composite be subjected to a substantially water-free reduction step prior to its use in the conversion of hydrocarbons. This step is designed to insure a uniform and finely divided dispersion of the metallic components throughout the carrier material. Preferably, substantially pure and dry halogen containing less than 20 vol ppm H2O is used as the reducing agent. The reducing agent is contacted with the calcined catalyst at a temperature of about 427°C (800°F) to about 649°C (1200°F) and for a period of time of about 0.5 to 10 hours or more, effective to substantially reduce the platinum and rhenium components to their elemental state. This reduction treatment may be performed in situ as part of a start-up sequence if precautions are taken to pre-dry the plant to a substantially water-free state and if substantially water-free hydrogen is used.

The resulting reduced catalytic composite may, in some cases, be beneficially subjected to a presulfiding operation designed to incorporate in the catalytic composite from about 0.05 to about 0.5 wt % sulfur calculated on an elemental basis. Preferably, this, presulfiding treatment takes place in the presence of hydrogen and a suitable sulfur-containing compound such as hydrogen sulfide, lower molecular weight mercaptans,. or organic sulfides. This procedure comprises treating the reduced catalyst with a sulfiding gas, such as a mixture of hydrogen and hydrogen sulfide having about 10 moles of hydrogen per mole of hydrogen sulfide, at conditions which effect. the desired incorporation of sulfur, generally including a temperature ranging from about 10°C (50°F) up to about 593°C (1100°F) . It is generally a good practice to perform this presulfiding step under substantially water-free conditions.

According to the present invention, a hydrocarbon charge stock and hydrogen are contacted with a catalyst of the type described above 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. In this system, a hydrogen -rich gas and the charge stock are preheated to the desired reaction temperature and passed into a conversion zone containing a fixed bed of the aforementioned catalyst. The conversion zone may comprise one or more separate reactors with suitable means therebetween to insure that the desired conversion temperature is maintained at the entrance to each reactor. The reactants may be contacted with the catalyst bed in either upward, downward, or radial flow fashion with the latter being preferred. 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.

When the catalyst of the present invention is used in a reforming operation, the reforming system will comprise one or more separate reactors containing fixed beds of catalyst with suitable heating means therebetween to compensate for the endothermic nature of the reaction that takes place in each catalyst bed. The hydrocarbon feed to the reforming system will comprise hydrocarbon fractions containing naph-thenes and paraffins boiling within the gasoline range. The preferred charge stocks are those consisting essentially of naphthenes and paraffins, although aromatics may also be present. This preferred class includes straight run gasolines, natural gasolines, synthetic gasolines, as well as thermally or catalytically cracked gasolines or higher boiling fractions thereof, or mixtures of these. The gasoline charge stock may be a full boiling gasoline having an initial boiling point of from about 10°C (50°F) to abput 66°C (150°F) and an end boiling point within the range of from about 163°C (325°F) to about 219°C (425°F) , or may be a selected fraction thereof referred to as a heavy naphtha — for example,, a naphtha boiling in the range of C-, to 204°C (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„ hydrotrea ting, or hydrodesulfurization„ to remove substantially all sulfurous, nitrogenous and water-yielding contaminants and to saturate any olefins present.

When catalyst of the present invention is used to promote isomerization, the charge stock can be„ for example, a paraffinic stock rich in C4 to Cg normal paraffins, n-butane-rich stock,, n-alkyl aromatic hydrocarbons, such as hexane-rich stock,, a mixture of xylene isomers, or naphthenic hydrocarbon. In hydrocracking embodiments the charge stock will be typically a gas oil or heavy cracked cycle oil.

Likewise, pure hydrocarbons or substantially pure hydrocarbons can be converted to more valuable products by using the catalyst of the present invention in any of the hydrocarbon conversion processes known to the art that use a dual-function catalyst.

In the case of reforming it is sometimes preferred that the novel catalytic composite be utilized in a sub in the reforming zone requires control of the water content of the charge stock and of the hydrogen stream charged to the conversion zone. Best results are obtained when the total amount of water (expressed as weight of equivalent water in the charge stock) entering the conversion zone from any source is less than 50 and preferably less than wt ppm. The charge stock can be dried by using any conventional solid adsorbent selective 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 suita 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 less than 20 ppm of water. In general, it is preferred to dry the hydrogen stream entering the hydrocarbon conversion zone to 10 vol ppm of water or less. This can be conveniently accomplished by contacting the hydrogen stream with a suitable desiccant such as those mentioned above.

In the reforming embodiment, an effluent stream is withdrawn from the reforming zone and passed through cooling means to a separation zone, typically maintained at about -4°C (25°F) to 66°C (150°F), wherein hydrogen-rich gas is separated from high octane liquid product,, commonly called unstabilized reformate. Preferably, at least a portion of this hydrogen-rich gas is withdrawn from the separating zone and passed over an adsorbent selective for water. The resultant substantially water-free hydrogen stream is then recycled to the reforming zone. The liquid phase from the separating zone is then withdrawn and treated in a fractionati system to adjust the butane concentration and 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 to be effected,, For instance alkylaromatic and paraffin isomerization conditions include: a temperature of about 0°C (32°F) to about 538°C (1000°F) and preferably about 24°C (75°F) to about 316°C (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 a liquid hourly space velocity (LHSV) (calculated on the basis of equivalent liquid volume per hour of the charge stock contacted with the catalyst divided by the volume of catalyst) of about 0„2 to 10„ Dehydrogenation conditions include: a temperature of about 371°C (700°F) to about 677°C (1250°F) , a pressure of about 0.1 to about 10 atmos / hydrocarbon mole ratio of about lsl to about 20:1. Hydro-cracking conditions include: a pressure of about 35 atm (500 psig) to about 205 atm (3000 psig) ; a temperature of about 204°C (400PF) to about 482°C (900°F); an LHSV of about 0»1 to about 10? and hydrogen circulation rates of about 178 to 1780 standard cubic meters per cubic meter (cm/cm) of liquid charge (corresponding to from 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 atmospheric of about 69 atm (1000 psig) . With the preferred pressure range being about 4.4 atm (50 psig) to about 24.8 atm (350 psig) . Particularly good results are obtained at low pressure? namely„ a pressure of from about 6.1 to about 14.6 a atm (75 to 200 psig) . In fact, it is/singular advantage of the present invention that it allows stable operation at lower pressures than have heretofore been possible in so-called "continuous" reforming systems (i.e., reforming for periods of about 5„2 to about 70 cubic meters of charge per Kg of catalyst without regeneration) . In other words,- the catalyst of the present invention allows the operation of a continuous reforming system to be conducted at lower pressure for about the same or better catalyst life as has been heretofore realizi with conventional catalysts at higher pressures (i.e., 28 „ 2 to 41 „ 8 atms) .

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 catalyst of the present invention for the octane-upgrading reactions that are preferably induced in a typical reforming operation.

The initial selection of the temperature is made primarily as a function of the desired octane of the product reformate. Ordinarily, the temperature is slowly increased during the run to compensate for the inevitable deactivation that occurs to provide a constant octane product. Therefore, it an advantage of the catalyst of the present invention that the rate of temperature increase required to maintain a constant octane product is substantially less than for reforming catalys manufactured in exactly the same manner except for the exclusion of the germanium and rhenium component. Moreover, when using the catalyst of the present invention, the yield loss for a given temperature increase is substantially lower than for reforming catalysts of the prior art. In addition, hydrogen production is substantially higher.

The reforming embodiment of the present invention utilizes sufficient hydrogen to provide from about 1 to about 20 moles of hydrogen per mole of hydrocarbon entering the reforming zone, with excellent results being obtained when mole of hydrocarbon., The LHSV used is within the range of about 0ol to about 10, with a value in the range of about 1 to about 5 being preferred. In fact, it is a further advantage of the present invention that it allows operations to be conducted at higher LHSV than normally can be achieved in a stable, continuous reforming process with a high quality reforming catalyst of the prior art. This is of immense economic significance because it allows a continuous reforming process to operate at increased throughput with the same catalyst inventory.

The following examples are given to illustrate further the preparation of the catalytic composite of the present invention and the use thereof in the conversion of hydrocarbons. It is understood that the examples are given for the sole purpose of illustration and are not to be considered to limit the generally broad scope and spirit of the appended claims „ EXAMPLE I This example demonstrates a particularly good method of preparing the preferred catalytic composite of the present invention.

An alumina carrier material comprising 1.6 mm (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 hexamethyl- solution by dropping it into an oil bath to form spherical particles of an aluminum 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 carrier material are given in the teachings of U.S.

Patent No. 2,620,314.

A measured amount of germanium dioxide crystals was placed in a porcelain boat and subjected to a reduction treatment with substantially pure hydrogen at a temperature of about 650°C for about 2 hours. The resulting grayish-black solid material was dissolved in chlorine water to form an aqueous solution of germanium monoxide. An aqueous solution containing chloroplatinic acid, perrhenic acid, and hydrogen chloride was then prepared. The two solutions were then intimately admixed and used to impregnate the gamma-alumina particles in amounts which produced a final composite containing 0.1 wt ¾ Re, 0.2 wt % Ge, and 0.5 wt % Pt. To insure uniform distribution of the metallic components throughout the carrier material, this impregnation step was performed by adding the carrier material particles to the impregnation mixture with constant agitation. The volume of the solution was double 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 hour at a temperature of about 21°C (70°F) . Thereafter, the temperature of the impregnation mixture was raised to about 107°C (225°F) and the excess solution was evaporated in a period of about 1 hour.

The resulting dried particles were then subjected to a calcination in an air. atmosphere at a temperature of about 496°C (925°F) for about 1 hour. The calcined spheres were then contacted with an air stream containing H2O and HCl in a mole ratio of about 40:1 for about 4 hours at 524°C (975°F) to adjust the halogen content of the catalyst particles.

The resulting catalyst particles were analyzed and found to contain, on an elemental basis, about 0.5 wt % platinum, about 0„2 wt % germanium, about 0„1 wt % rhenium, and about 0.85 wt % chloride.

Thereafter, the catalyst particles were subjected to a dry pre-reduction treatment by contacting them with a substantially pure hydrogen stream containing less than vol ppm H20 at a temperature of about 538°C (1000°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 (volume per hour of gas/ volume of catalyst) of about 720. The duration of this prereduction step was about 1 hour.

EXAMPLE II A portion of the spherical particles produced by model of a continuous, fixed-bed reforming plant of conventional design. In this plant a heavy Kuwait naphtha and hydrogen are continuously contacted at the following conditions: an LHSV of 1.5, a pressure of 7.8 atm (100 psig) , a hydrogen-to-hydrocarbon mole ratio of 8:1, and a temperature sufficient to continuously produce a C5+ reformate of 102 F-l clear. These are exceptionally severe conditions.

The heavy Kuwait naphtha has a specific gravity of 0.7374 (15.6°C/15.6°C) (API gravity at 60°F of 60.4), an initial boiling point of 84°C (184°F) , a 50%-dis tilled boiling point of 125°C (256°F), and an end boiling point of 182°C (360°F) . In addition, it contains about 8 liq. vol % aromatics, 71 liq. vol % paraffins, 21 liq vol % naphthenes, 0.5 wt ppm sulfur, and 5 to 8 wt ppm water. The F-l clear octane number of the raw stock is 40.0.

The fixed bed reforming plant is made up of a catalyst-containing reactor, a hydrogen separation zone, a debutanizer column, and suitable heating, pumping, cooling, and controlling means. In this plant, a hydrogen recycle stream and the charge stock are commingled and heated to the desired temperature. The resultant mixture is then passed downwardly through a reactor containing the catalyst as a fixed bed. An effluent stream is then withdrawn from the bottom of the reactor, cooled to about 13°C (55°F) and passed to a separating zone wherein a hydrogen-rich gaseous phase separates from a liquid hydrocarbon phase. A portion of the gaseous phase is passed through a high surface area sodium scrubber and the resulting sulfur-free hydrogen stream is recycled to the reactor in order to supply hydrogen thereto, and the excess hydrogen over that needed to maintain plant pressure is recovered as excess separator gas. The liquid hydrocarbon phase from the hydrogen separating zone is with¬ drawn therefrom and passed to a debutanizer column of conventional design wherein light ends are taken overhead as debutanizer gas and a C5+ reformate stream is recovered as bottoms .

The test run is continued for a catalyst life of about 7 cubic meters of liquid charge per Kg of catalyst (20 barrels per pound) utilized, and it is determined that the activity, selectivity, and stability of the subject catalyst are vastly superior to conventional commercial reforming catalysts utilized in a similar test. More speci¬ fically, the results obtained using the catalyst of the invention are superior to the platinum metal-containing cat-alyst of the prior art in respect of hydrogen production, C + yield at a given octane, average rate of. temperature increase necessary to maintain octane, and yield-decline rate.

EXAMPLE III In order to compare the catalyst of the present in a manner designed to bring out the interaction between the germanium component and the platinum and rhenium components, a comparison test was made. A catalyst was prepared according to the method given in Example I, with the exclusion of the germanium component, resulting in a reforming catalyst comprising a combination of 0.5 wt % platinum, 0.1 wt % rhenium, and 0.85 wt % chloride with an alumina carrier material.

These tri-metallic and bi-metallic catalysts were then separately subjected to a high-stress evaluations test designed to determine their relative activity and selectivity for the reforming of a gasoline charge stock. In all tests the same charge stock was utilized, its characteristics being given in Table I. This test was conducted under substantially water-free conditions, the only significant source of water being the 5.9 wt ppm water in the charge stock.

TABLE I — ANALYSIS OF HEAVY KUWAIT NAPHTHA Specific gravity (15.6 °C/15.6°C) 0.7374 Initial boiling point, °C ' 85 % boiling point, °C 96 50% boiling point, °C 124 90% boiling point, °C 161 End boiling point, °C 182 Sulfur, wt ppm 0.5 Nitrogen, wt ppm 0.1 Aromatics, vol % 8 Paraffins vol % 71 Naphthenes, vol 21 Water, ppm 5.9 Octane no., F-l clear 40.0 This test was specifically designed to determine evaluated has superior characteristics for the reforming process. It consists of 6 periods comprising a 6 hour line-out period followed by a 10 hour test period run at a constant temperature during which time a C5+ product reformate is collected. It was performed in a laboratory-scale reforming plant comprising a reactor containing the catalyst, hydrogen separation zone, a debutanizer column, suitable heating, pumping, and condensing means, and other equipment.

A hydrogen recycle stream and the charge stock are commingled and heated, then passed downflow through a reactor containing the catalyst as a fixed bed. An effluent stream is withdrawn from the bottom of the reactor, cooled to about 13°C (55°F) and passed to the separating zone wherein a hydrogen-rich gaseous phase separates from a liquid phase„ A portion of the gaseous phase is passed through a high surface area sodium scrubber and the resulting substantially water-free hydrogen stream recycled to the reactor. The excess oyer that needed to maintain plant pressure is recovered as excess separator gas. The liquid phase from the separating zone is withdrawn therefrom and passed to the debutanizer column wherein light ends are taken overhead and a C_+ reformate stream recovered as bottoms, Conditions utilized in this test are: a constant temperature of about 517°C (963°F) for the first three periods followed by a constant temperature of about 536°C (997°F) for the last three periods, an LHSV of 3.0, a reactor outlet pressure of 7.8 atm (100 psig) „ and a mole ratio of hydrogen to hydrocarbon at the reactor inlet of 10:1. This two-temperature test is designed to quickly and efficiently yield two points on the yield-octane curve for the particular catalysts. The conditions utilized are selected on the basis of experience to yield the maximum amount of information on the capability of the catalyst being tested to respond to a high severity operation.

The results of the separate tests performed on the catalyst of the present invention and the control catalyst ar presented for each test period in Table II in terms of inlet temperature to the reactor, net excess separator gas, debutanizer overhead gas production, and the ratio of debutanizer overhead gas to the sum of separator gas and debutanizer gas, and F-l clear octane number. Temperatures are given in °C, and gas productions are given as cubic meters of gas per cubi meter of liquid charge.

TABLE II — RESULTS OF ACCELERATED REFORMING TESTS Tri-metallic catalyst (with 0.2 wt% germanium) Clear Reactor Inlet Separator Gas Debut„ gas Debut, gas: Octane Test °C cm/cm cm/cm Total gas F-l 1 517 283 10 .033 97.2 2 517 280 9 .033 97.2 4 536 311 11 .034 99.8 536 310 11 .035 99.4 6 536 303 11 .035 99.1 Bi-metallic catalyst (No germanium) 1 517 281 12 .042 97.1 2 517 260 12 .045 95„3 3 517 250 13 .049 94.1 4 536 279 15 .050 98 „0 536 274 15 .051 97.3 6 536 266 16 .055 96.6 Referring now to the results given in Table II of the separate tests performed on these catalysts, it is evident that the effect of the germanium component on the catalyst is to substantially promote the platinum-rhenium catalyst. That is, the catalyst of the present invention is sharply superior to the control catalyst in both activity and selectivity. As was pointed out hereinbefore, a good measure of activity for a reforming catalyst is octane number of reformate produced at the same conditions; on this basis, the catalyst of the present invention was more active than the control catalyst at both temperature conditions. However, activity is only half of the story: activity must be coupled with selectivity to demonstrate superiority. Selectivity is measured directly by reference to C5+ yield and indirectly by reference to separator gas. production which, is roughly proportional to net hydrogen production which, in turn, is a product of the preferred upgrading reactions,, Debutanizer gas production is a rough measure of undesired hydrocracking, which should be minimized by a highly selective catalyst. Referring again to the data presented in the table and using the selectivity criteria, it is manifest that the catalyst of the present invention beside having superior activity, is materially more selective than the control catalyst„ 34833/2

Claims (6)

CLAIMS ■t'

1. A process for the conversion of a hydrocarbon, which comprises subjecting said hydrocarbon to contact at hydrocarbon conversion conditions with a catalytic composite comprising a platinum group component, a rhenium component and a germanium component with a porous carrier material comprising a refractory inorganic oxide.

2. Process according to Claim 1 , wherein the refractory inorganic oxide is alumina.

3. Process according to Claim 1 or 2, herein the hydrocarbon is subjected to contact with the catalytic composite in the presence of hydrogen.

4. Process according to any of the Claims 1 to 3» wherein the catalytic composite contains, on an elemental basis, about 0.01 to about 2 wt $ of the platinum group component, about 0.01 to about 2 wt of rhenium, and about 0.01 to about 5 wt of germanium.

5. Process according to Claim 4, wherein the catalytic composite contains on an elemental basis, about 0.05 to 1 wt % of the platinum group component, about 0.05 to 1 wt % rhenium, and about 0.05 to 2 wt $ germanium.

6. Process according to any of Claims 1 to 5» wherein the platinum group component comprises platinum or a compound of platinum. 7· Process according to any of Claims 1 to 6, wherein the catalytic composite also contains a halogen component. 8; Process according to Claim 7, wherein the halogen component is present in a concentration within the range from 0.1 to 3.5 wt o, on an elemental basis. 34833/2 ^

9. Process according to Claim 8, wherein the halogen component is present in a concentration within the range from 0.5 to 1 .5 wt .

10. Process according to any of Claims 7 to 9 » wherein the halogen component is chlorine or a compound of chlorine. 1 1 . Process according to any of Claims 3 to 10 , wherein a gasoline fraction is subjected to contact with the catalytic composite at gasoline reforming conditions, and a reformed gasoline is recovered as product of the process, 1 2. Process according to Claim 1 1 , wherein the gasoline fraction is reformed at a temperature of about 427° to 593°C, a pressure of about atmospheric to about 69 atmospheres, a liquid hourly space velocity of about 0. 1 to about 1 0 , and a mole ratio of hydrogen to hydrocarbon of about 1 to 20. 1 3 · Process according to Claim 1 2 , wherein the gasoline fraction is reformed at a pressure of about 4.4 to about 24.8 atmospheres . 1 4. Process according to any of Claims 1 1 to 1 3 t wherein the gasoline fraction is reformed in a substantially waters-free environment. 1 · Process according to any of Claims 1 to 1 , wherein the catalytic composite also contains a sulfur component in a concentration of about 0.05 to 0.5 wt % on an elemental basis. 1 6. Process according to any of Claims 1 to 10 , wherein an isomerizable hydrocarbon selected from the alkylaromatic and paraffin hydrocarbons is subjected to contact with the catalytic composite at a temperature of about 0° to about 538°C, a pressure of about 1 to TOO atmospheres, an LHSV of about 0.2 34833/2 Λ . 0.5 to 20, and an isomerized hydrocarbon is recovered from the process.

17. Process according to any of the Claims 1 to 10, wherein a charge stock selected from the gas oils and heavy cracked cyc'le oils is subjected to, contact with the catalytic composite at a temperature of about 204° to .482°C, a pressure of about 35 to 205 atmSj an LHSV of about 0.1 to 10 and a hydrogen circulation rate within the range of about 178 to 1780 cubic meters per cubic meter of charge, and a hydrocracked product is recovered from the prooess.

18. A catalytic composite for the conversion of a hydrocarbon, which comprises a platinum group component, a rhenium component, and a germanium component with a porous carrier material comprising a refractory inorganic oxide. 19· A catalytic com osite as defined in Claim 18, wherein t e platinum group component comprises platinum or a compound of platinum.

20. A catalytic composite as d efined in Claim 18 or 19, where in the refractory inorganic oxide is alumina.

21. A catalytic composite a3 defined in any of the Claims 18 to 20, wherein the composite contains on an elemental basis, from about 0.01 to about 2 wt platinum group component from about 0.01 to about 2 wt # rhenium, and from about 0.01 to about 5 wt germanium.

22. A catalytic composite as defined in any of Claims 18 to 21 wherein the atomic ratio of rhenium to platinum group metal is within themnge of from about 0.1:1 to about 3:1 and the atomic 34833/2 ratio of germanium to platinum group metal is within the range of from about 0.25:1 to about 6:1.

23. A catalytic composite as defined in any of the Claims 18 to 22, wherein the composite contains a halogen component within the aange of from about 0,1 to about 10 wt on an elemental basis,

24. A catalytic composite as d efined in any of the Clains 18 to 23» wherein the halogen component comprises chlorine or compounds of chlorine.

25. A catalytic composite as defined in Claim 24» -wherein the composite contains from a bout 0.5 to 1.5 wt $ chlorine on an elemental basis.

26. A catalytic composite as defined in any of the Claims 18 to 21, wherein the composite contains from about 0.05 to about 0.5 wt > sulfur on an elemental basis.

27. A catalytic composite as defined in any of the Claims 18 to 26, wherein the composite is treated with hydrogen at a temperature of from about 427°C to about 649°C whereby to reduce the platinum and rhenium components to their elemental state.

28. A catalytic composite substantially as hereinbefore described.