US3649526A - Multiple-stage production of fuel oil - Google Patents

Abstract

A HYDROCARBONACEOUS BLACK OIL IS CONVERTED TO FUEL OIL IN A PLURALITY OF CATALYTIC CONVERSION ZONES. THE FIRST ZONE, CONTAINING A CTALYTIC COMPOSITE OF AN ALUMINA-CONTAINING CARRIER MATERIAL, A BISMUTH COMPONENT AND A GROUP VI-B COMPONENT, FUNCTIONS TO PRODUCE A HYDROCARBON STREAM CONTAINING FROM 1.0% TO ABOUT 2.0% BY WEIHT OF SULFUR, AND PREFERABLY FROM ABOUT 1.30% TO ABOUT 1.70% BY WEIGHT. THE SUBSEQUENT CONVERSION ZONE, CONTAINING A CATALYTIC COMPOSITE OF A SILICEOUS CARIER MATERIAL, A GROUP VIII METAL COMPONENT AND A GROUP VI-B METAL COMPONENT, EFFECTS FURTHER DESULFURIZATION TO A LEVEL OF ABOUT 1.0% BY WEIGHT, OR LESS, THE LIMITATION CURRENTLY PLACED ON HYDROCARBONACEOUS MATERIAL UTILIZED AS FUEL OIL.

Description

United States US. Cl. 208210 6 Claims ABSTRACT OF THE DISCLOSURE A hydrocarbonaceous black oil is converted to fuel oil in a plurality of catalytic conversion zones. The first zone, containing a catalytic composite of an alumina-containing carrier material, a bismuth component and a Group VI-B component, functions to produce a hydrocarbon stream containing from 1.0% to about 2.0% by weight of sulfur, and preferably from about 1.30% to about 1.70% by weight. The subsequent conversion zone, containing a catalytic composite of a siliceous carrier material, a Group VIII metal component and a Group VIB metal component, effects further desulfurization to a level of about 1.0% by weight, or less, the limitation currently placed on hydrocarbonaceous material utilized as fuel oil.

APPLICABILITY OF INVENTION Desulfurization is a process well known and thoroughly described in petroleum technology, the literature relating thereto being replete with references directed toward suitable desulfurization catalysts, methods and techniques of catalyst manufacture and the various operating techniques employed while effecting the desulfurization process. Although desulfurization connotes the destructive removal of sulfurous compounds, through conversion thereof to hydrogen sulfide and hydrocarbons, it is often included in the broad term hydrorefining. Hydrorefining processes are effected at operating conditions which promote denitrification and desulfurization primarily, and asphaltene conversion, non-distillable hydrocarbon conversion, hydrogenation and hydrocracking to a somewhat lesser extent. In other words, the terms hydrorefining and desulfurization are generally employed synonymously to allude to a process wherein a hydrocarbonaceous feed stock is cleaned-up in order to prepare a charge stock suitable for utilization in subsequent hydrocarbon conversion, or to result in a product having an immediate utility. For example, the combination process of my invention can be beneficially utilized to produce a fuel oil containing less than about 1.0% by weight of sulfur. Hydrorefining is further characterized in that some conversion into lower-boiling hydrocarbon products is effected.

A perusal of the prior art relating to desulfurization processes reveals that catalytic composites which are intended to be used, particularly with respect to residual stocks or black oils, traditionally contain an element selected from the Iron-group metals, especially nickel or cobalt, in combination with a metal component from the metals of Group VI-B, particularly molybdenum or tungsten. In general, preferred metal components are nickel and molybdenum, or nickel and tungsten, and these components are generally combined with a porous carrier material which is either amorphous, or zeolitic in nature. Ample evidence may be found in the literature to indicate that the nickel component, or cobalt component, although present in a significantly lower concentration than the molybdenum or tungsten, materially contributes to the activity of these hydrorefining catalysts. Notwithstanding the fact that these catalysts exhibit an acceptable high iniatent tial activity with respect to the conversion of sulfurous compounds into hydrogen sulfide and hydrocarbons, they also promote the dehydrogenation of heavy hydrocarbons, and the high molecular weight species in black oils are easily subjected to dehydrogenation which inherently leads to rapid excessive coke formation. Most black oils contain sulfurous compounds in amounts of 2.5% to 6.0% by weight, as sulfur, and dehydrogenation of the high molecular weight species is favored by the equilibrium existing at the operating conditions required to result in a product having an acceptable sulfur level, generally considered to be 1.0% by weight, or less.

The present invention is directed toward a combination process for effecting the desulfurization of petroleum crude oils, atmospheric tower bottoms products, vacuum tower bottoms products, heavy cycle stocks, crude oil residuum, topped crude oils, the heavy hydrocarbonaceous oils extracted from tar sands, etc. Petroleum crude oils, and the heavier hydrocarbon fractions and/or distillates obtained therefrom, contain nitrogenous and sulfurous compounds in exceedingly large quantities, the latter often exceeding about 3.0% by weight. In addition, such heavy hydrocarbon fractions, commonly referred to as black oils contain large quantities of organo-metallic contaminants, principally comprising nickel and vanadium, and heptane-insoluble asphaltenes. Specific examples of black oils, illustrative of those to which the present invention is applicable, include a vacuum tower bottoms product having a gravity of 7.1 API, containing 4.05% by weight of sulfur and 23.7% by weight of asphaltics; a topped Middle-East Kuwait crude oil, having a gravity of 11.0 API, containing 10.1% by weight of asphaltenes and 5.20% by weight of sulfur; and, a vacuum residuum having a gravity of about 8.8 API, containing 3.0% by weight of sulfur, 4,300 p.p.m. by weight of nitrogen and having a 20.0% volumetric distillation temperature of about 1055 F.

OBJECTS AND EMBODIMENTS A principal object of the present invention is to provide a process for effecting the desulfurization of hydrocarbonaceous material. A corollary objective resides in a multiple-stage process for desulfurizing hydrocarbonaceous material characterized as black oil in order to produce an acceptable fuel oil.

Another object is to provide a desulfurization process which improves the stability of the traditional catalysts containing nickel and molybdenum, or cobalt and molybdenum.

Therefore, in one embodiment, the present invention involves a combination process for producing fuel oil, containing less than about 1.0% by weight of sulfur, from a higher-boiling, sulfurous charge stock, containing more than about 2.5% by weight of sulfur, which process comprises the steps of: (a) reacting said charge stock and hydrogen, at a first set of desulfurizing conditions selected to convert sulfurous compounds into hydrogen sulfide and a first hydrocarbon stream containing from 1.0% to about 2.0% by weight of sulfur, and in contact with a first desulfurizing catalyst of a composite of an aluminacontaining carrier material, a Group VI-B metal component and a bismuth component; and, (b) reacting at least a portion of the resulting product efiluent and hydrogen, at a second set of desulfurizing conditions selected to convert sulfurous compounds into hydrogen sulfide and a second hydrocarbon stream containing less than about 1.0% by weight of sulfur, and in contact with a second desulfurizing catalyst of a composite of a siliceous carrier material, a Group VIII metal component and a Group VI-B metal component.

Other objects and embodiments of my invention relate to additional details regarding the preferred catalytic ingredients, the concentration of components within the catalytic composite, preferred processing techniques and similar particulars which are hereinafter given in the following, more detailed summary. One such embodiment relates to preferred operating conditions wherein the first set of desulfurizing conditions includes a maximum catalyst bed temperature in the range of about 600 F. to about 900 F., while said second set of desulfurizing conditions includes a maximum catalyst bed temperature in the range of about 550 F. to about 850 F.

SUMMARY OF THE INVENTION Investigations in the field of desulfurization, in regard to catalyst activity and stability, particularly with respect to black oils, have confirmed the known effect induced by a. nickel component, or cobalt component when used in combination with a molybdenum component. With respect to activity, defined as the maximum catalyst bed temperature (all other conditions being equal) required to achieve initially a product sulfur level of 1.0% by weight, a nickel-molybdenum catalyst is slightly more active than a cobalt-molybdenum catalyst, both of which indicate a greater degree of activity than a catalyst containing only molybdenum. While processing a black oil at a pressure of 2,000 p.s.i.g., the nickel-molybdenum catalyst required a maximum catalyst bed temperature of 718 F., the cobalt-molybdenum catalyst required a temperature of 722 F., whereas the molybdenum catalyst required a temperature of 784 F. At a pressure of 1,500 p.s.i.g., the maximum catalyst bed temperatures are 729 F., 723 F. and 777 F., respectively. With respect to catalyst stability, however, the order reverses itself, with a molybdenum catalyst being significantly more stable than either a cobalt-molybdenum, or nickel-molybdenum catalyst. With catalyst stability being defined as the temperature increase, "Q R, per barrel of fresh feed processed per pound of catalyst disposed in the reaction zone, F./b.p.p., virtually no deactivation, at 2,000 p.s.i.g., is observed with the molybdenum catalyst. For the cobalt-molybdenum and nickel-molybdenum catalysts, the deactivation rates were 19 F. per barrel per pound and 25 F. per barrel per pound, respectively. At 1,500 p.s.i.g., the corresponding deactivation rates were 7 F., 13 F. and 50 F. per barrel per pound, respectively. Additional investigations, instituted as a result of the fact that the most active hydro-refining catalyst possessed the lowest degree of stability, indicated that the stability, as hereinabove defined, of the nickel-molybdenum catalyst, for example, was significantly improved when processing hydrocarbon charge stocks, containing not more than 2.0% by weight of sulfur, to a target sulfur level of 1.0% by weight. Furthermore, substantially no deactivation of the nickel molybdenum catalyst was observed at charge stock sulfur concentrations of about 1.5% by weight. That is, the stability of a nickel-molybdenum catalyst is greatly improved when effecting a sulfur decrease of from 0.5% to about 1.0% i.e. from 2.0% down to 1.0%, or from 1.5% down to 1.0% by weight.

The present invention is founded upon the discovery that a catalyst containing a bismuth component and a Group VI-B component, for example molybdenum, experiences little activity decline when processing high sulfur-containing black oils to a sulfur concentration below about 2.0% by weight, and preferably at conditions which result in a liquid product containing from 1.30% to about 1.70%--e.g. about 1.5% by weight. Therefore, the traditional nickel-molybdenum, or cobait-molybdenum, can be utilized in the second stage of the two-stage process wherein the bismuth-molybdenum catalyst is employed in the first conversion zone to decrease the sulfur concentration to a level below about 2.0% by weight. With respect to the first conversion zone, a preferred target sulfur level is in the range of about 1.30% to about 1.70% by weight.

There is some indication that the addition of the bismuth component to a catalyst containing both nickel and molybdenum, nickel and tungsten, cobalt and molybdenum, or cobalt and tungsten, results in improved desulfurization stability. However, it appears advantageous to avoid the dehydrogenation effect of either nickel, or cobalt, and the direct substitution of bismuth therefor is preferred. The slight sacrifice made with respect to the initial catalyst activity, in the first conversion zone, is clearly overshadowed by the benefits accruing with respect to stability. Furthermore, catalyst stability comparisons at the higher sulfur level of black oils indicate that the maximum catalyst bed temperature of a nickel-molybdenum catalyst very rapidly increases to the initial maximum catalyst temperature of the bismuth-molybdenum catalyst. I

The catalyst disposed in the first reaction zone, intended for the initial processing of a black oil, contains from about 1.0% to about 10.0% by weight of a bismuth component and from 4.0% to about 30.0% by weight of a. molybdenum, or tungsten component, calculated as the elemental metals. These metallic components are combined with a porous carrier material, containing alumina, which may be either amorphous, or zeolitic in nature. The second stage catalyst contains from about 1.0% to about 10.0% by weight of a nickel, or cobalt component, and from about 4.0% to about 30.0% by weight of a molybdenum, or tungsten component, again calculated as if existing as the elemental metals. The second stage active components are also combined with a porous carrier material, preferably containing silica, and which may also be either amorphous, or zeolitic. Since neither the method of catalyst preparation, nor the ultimate form of the catalyst particles, with respect to either conversion zone, is an essential feature of my invention, further discussion thereof is not believed necessary herein. However, one suitable method of catalyst preparation involves impregnating a preformed carrier material, for example spherical particles, with an aqueous solution of suitable soluble salts of the desired metal. Such suitable salts include molybdic acid, ammonium molybdate, tungstic acid, ammonium tungstate, nickel chloride, cobaltous chloride, nickel nitrate hexahydrate, cobalt nitrate hexahydrate, etc. With respect to the bismuth component, the impregnation solution can comprise a hydrochloric acid solution of bismuth bromide, an ether solution of bismuth bromide, an acidic solution of bismuth carbonate, an acetone solution of bismuth trichloride, a nitric acid solution of bismuth nitrate, an acidic solution of bismuth trioxide, etc.

Considering first the porous carrier material, it is preferred that it be an adsorptive, high-surface area support. With respect to the first conversion zone, a preferred carrier material contains alumina, and with respect to the second conversion zone, a preferred carrier material contalns silica. Suitable carrier materials are selected from the group of alumina-containing amorphous refractory inorganic oxides including alumina, in and of itself, and in admixture with titania, zirconia, chromia, silica, magnesia, boria, such as, for example, alumina-silica, aluminasilica-zirconia, alumina-silica-boron phosphate, etc. When the carrier material constitutes a combination of alumina and silica, the concentration of the latter is in the range of about 10. 0% to about 90.0% by weight, and preferably from about 30.0% to about 70.0%. In many applications of the present invention, the carrier material will consist, at least in part, of a crystalline aluminosilicate. This may be naturally-occurring, or synthetically-prepared, and includes mordenite, faujasite, Type A or Type U molecular sieves, etc. One common method of preparing a crystalline aluminosilicate constitutes mixing solutions of sodium silicate, or colloidal silica, and sodium aluminate, permitting the solutions to react to form a solid crystalline aluminosilicate. Another method is to contact a solid inorganic oxide from the group of silica, alumina and mix tures thereof with an aqueous treating solution containing alkali metal cations (preferably sodium) and anions selected from the group of hydroxyl, silicate and aluminate, and permit the solid-liquid mixture to react until the desired crystalline aluminosilicate has been formed. In addition to the foregoing, the carrier material may comprise a combination in which the zeolitic material is dispersed within an amorphous matrix, the latter being alumina, silica, or silica-alumina.

Following the formation of the catalytic composite, by whatever means desired, it will generally be dried at a temperature in the range of about 200 F. to about 600 F., for a period of from /2 hour to about 24 hours, and finally calcined at a temperature of about 700 F. to about 1200 F., in an atmosphere of air, for a period of about 0.5 to about hours. When the carrier material comprises a crystalline aluminosilicate, it is preferred to limit the calcination temperature to a maximum of 1000 F.

Investigations respecting the bismuth-molybdenum catalyst, for use in the first stage of the combination process, have not been exhaustive. However, there are indications that the use of a co-extruded catalyst particle further improves the results obtained. The particles are prepared by commingling the pre-formed carrier material, whether amorphous or zeolitic in nature, in talc-like powdered form, with salts of the metallic components, for example, bismuth nitrate and molybdenum trioxide. The extrudable mass results from commingling the solid mixture with l'lltl'lC acid by way of mulling, and aging the mulled matenal for a period of about fifteen minutes to about two hours.

While not essential to successful desulfurization, a halogen component may be combined with the other components of the mtalytic composite. Although the precise form of the chemistry of association of the halogen component with the carrier material and metallic components is not accurately known, it is customary in the an t refer to the halogen component as being combined with the carrier material or with the other ingredients of the catalyst. It is commonly referred to therefore as combined halogen. The halogen may be either fluorine, chlorine iodine, bromine or mixtures thereof with fluorine and chlorine being particularly preferred. The quantity of halogen such that the final composite contains about 0.1% to about 3.5% by weight and preferably from about 0.5% to about 1.5% by Weight, calculated on the basis of the elemental halogen.

Prior to its use in the desulfurization of hydrocarbons, the resultant catalytic composite may be subjected to a substantially water-free reduction technique. Substantially pure and dry hydrogen (less than about 30.0 vol. ppm. of water) is employed as the reducing agent. The calcined composite is contacted at a temperature of about 800 F. to about 1200 F., and for a period of about 0.5 to about 10 hours. This reduction may be performed in situ prior to introducing the charge stock.

Additional improvements are generally obtained when the reduced composite is subjected to a pre-sulfiding operation for the purpose of incorporating therewith from about 0.05% to about 0.5% by weight of sulfur, on an elemental basis. The pre-sulfiding treatment may be effected in the presence of hydrogen at a suitable sulfurcontaining compound such as hydrogen sulfide, low molecular weight mercaptans, various organic sulfides, carbon disulfide, etc. One technique involves treating the reduced catalyst with a sulfiding gas, such as a mixture of hydrogen and hydrogen sulfide having about 10 mols of hydrogen per mol of hydrogen sulfide, at conditions selected to effect the desired incorporation of sulfur. Pre-sulfiding is preferably effected in situ by way of charging a relatively lowboiling hydrocarbon feed containing sulfurous compounds.

In the present combination process, the hydrocarbon charge stock and hydrogen are contacted with a catalyst of the type described above in a hydrocarbon conversion zone. The 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. In view of the risk of attrition loss of the catalyst, it is preferred to use a fixed-bed system. In this type of system, a hydrogen-rich vaporous phase and the charge stock are preheated by any suitable heating means to the desired initial reaction temperature, the mixture being passed into the conversion zone containing the fixed-bed of the catalytic composite. It is understood, of course, that the hydrocarbon conversion zone may consist of one or more separate reactors having suitable means therebetween to insure that the desired conversion temperature is maintained at the entrance to one or more catalyst beds. The reactants may be contacted with the catalyst in either upward, downward, or radial flow fashion, with a downward/radial flow being preferred.

The operating conditions imposed upon the reaction zone, or zones, are primarily dependent upon the charge stock properties and the desired end result. However, these conditions will include a maximum catalyst bed temperature, with respect to the catalyst disposed within the first reaction zone, in the range of about 600 F. to about 900 F. With respect to the second reaction zone, the maximum catalyst bed temperature will be in the range of about 550 F. to about 850 F., and about 50 F. lower than the temperature of the catalyst in the first reaction zone. Other operating variables include a pressure of from about 400 to about 5,000 p.s.i.g., an LHSV of about 0.1 to about 10.0 and a hydrogen concentration of about 1,000 to about 50,000 s.c.f./bbl. Desulfurization reactions are exothermic in nature, and an increasing temperature gradient will be experienced as the hydrogen and feed stock traverse the catalyst bed. In order to insure that the catalyst bed temperature does not exceed the maximum allowed, conventional quench streams, either normally liquid or normally gaseous, may be introduced at one or more intermediate loci of the catalyst bed. In some situations, a heavy hydrocarbonaceous material is intended for hydrorefining, accompanied by the partial conversion into lower-boiling hydrocarbon products. A portion of the normally liquid product effluent boiling above the desired end boiling point of the product will generally be recycled to combine either with the fresh feed charge stock, or with the treated charge stock to the second stage of the process, or in part to both. A preferred technique is to recycle the heavier material to combine with the fresh feed charge stocck to the first reaction zone, whereby the combined liquid feed ratio will be within the range of about 1.1 to about 6.0.

ILLUSTRATIVE EXAMPLE Specific operating conditions, processing techniques, particular catalytic composites and other individual processing details will be given in the following description of my invention. In presenting this illustration, it is not intended that the present invention be limited to the specifics, nor is it intended that a given process be limited to the particular operating conditions, catalytic composite, processing techniques, charge stock, etc. Therefore, it is understood that the present invention is merely illustrated by the specifics hereinafter set forth.

A traditional desulfurization catalyst was prepared by impregnating calcined alumina-silica spheres, containing about 88.0% by weight of alumina, with nickel nitrate hexahydrate and molybdic acid (85.0% molybdenum trioxide) in amounts to result in a final composite containing about 1.8% by weight of nickel and 16.0% by weight of molybdenum, calculated as the elements.

This catalyst was employed to process a reduced crude oil having a gravity of 13.1 API, an initial boiling point of 650 F., a 30.0% volumetric distillation temperature of 818 F., a 50.0% volumetric distillation temperature of 914 F. and a 70.0% volumetric distillation temperature of 1038 F. At a temperature of 1060 F., 73.0% by volume was distillable. The sulfur concentration was 3.80% by weight, the heptane-insoluble fraction was 7.11% by Weight, and the reduced crude contained 102 p.p.m. by weight of nickel and vanadium and 4,200 ppm. by weight of nitrogen.

At a pressure of 3,000 p.s.i.g., a hydrogen concentration of 5,000 s.c.f./bbl. and an LHSV of 1.0, a 224-hour operation indicated a deactivation rate of 24 F./b.p.p. The entire operation was very erratic with sulfur levels immediately increasing as the maximum catalyst bed temperature was increased. Under similar conditions, with the exception of a lower pressure of 2,000 p.s.i.g., the deactivation rate was 32 F./b.p.p.

Previous investigations had indicated some stability improvement with the nickel-molybdenum catalyst with a decrease in space velocity. At 0.5 LHSV, a pressure of 3,000 p.s.i.g. and 5,000 s.c.f./bbl. of hydrogen, the deactivation rate was again calculated to be 24 F./b.p.p. At 2,000 p.s.i.g., 5,000 s.c.f./bbl. of hydrogen and a lower LHSV of 0.5, the deactivation rate was 18 F./'b.p.p.

A bismuth-molybdenum catalyst was prepared via a double impregnation technique using 110 grams of spherical silica-alumina (88.0% by weight of alumina). The carrier was first impregnated in a rotary drier with 23.32 grams of molybdic acid (85.0% molybdenum trioxide) dissolved in 175 cc. of 3.3% by weight ammonia. Following impregnation and drying at 225 F., the composite was calcined for one hour at 1100 F. The calcined catalyst was reintroduced into the rotary drier with 13.49 grams of bismuth nitrate pentahydrate dissolved in 60 cc. of water and eight drops of concentrated nitric acid. The composite, after drying, was again calcined at 1100 F. for a one-hour period. Analyses indicated an apparent bulk density of 0.85 gram/cc., and the composite contained 4.6% by weight of bismuth and 10.5% by weight of molybdenum.

The reduced crude above described was processed over the bismuth-molybdenum catalyst at a pressure of 2,000 p.s.i.g., an LHSV of 1.0 and a hydrogen concentration of 10,000 s.c.f./bb1. The object was to determine (1) the temperature at which the product efiluent contained about 1.5% by weight of sulfur, (2) catalyst stability at 1.5 sulfur level, and (3) capability of achieving a product sulfur level of 1.0% by weight. The results are given in the following Table I.

TABLE I.STABILITY OF BISMUTH-MOLYBDENUM CATALYST Although the bismuth-containing catalyst was not successful in attaining the target sulfur level of 1.0%, it should be noted that unusual stability is indicated at about 1.5 during the 310-654 hour period. This catalyst is, therefore, well-suited for use in the first stage of the present combination process.

A second operation was effected, using the bismuthmolybdenum catalyst, with the target sulfur level being 1.5% by weight. Five separate product blends were obtained, and again a stable operation was achieved at a pressure of 2,000 p.s.i.g., an LHSV of 1.0, a hydrogen rate of 5,000 s.c.f./bbl. and a maximum catalyst temperature of about 740 F. Pertinent analyses of the five blends are given in the following Table II.

These blends were then processed over a catalyst of 1.8% nickel and 16.0% molybdenum, combined with 88.0% alumina and 12.0% silica. The processing conditions were a pressure of 2,000 p.s.i.g., an LHSV of 1.0 and a hydrogen concentration of 5,000 s.c.f./bb1. The results are presented in the following Table TABLE III.SECOND-STAGE DESULFURIZATION Catalyst Sulfur, Deaotlvat-ion Oil-stream temp. weight, rate, F hours F.) percent b.p.p.

The foregoing specification, and especially the illustrative example, clearly indicates the benefits afforded through the utilization of the present combination process.

1 claim as my invention:

1. A combination process for producing fuel oil, containing less than about 1.0% by weight of sulfur, from a black oil charge stock, containing more than about 2.5% by weight of sulfur, which process comprises the steps of:

(a) reacting said charge stock with hydrogen, in a first reaction zone, at a temperature in the range of 600 F. to about 900 F. selected to convert sulfur compounds into hydrogen sulfide and a first hydrocarbon stream containing from 1.0% to about 2.0% by weight of sulfur, and in contact with a first desulfurizing catalyst composite comprising an alumina carrier, a Group VI-B metal component and a bismuth component; and,

(b) reacting said first hydrocarbon stream with hydrogen, in a second reaction zone, at a temperature in the range of 550 F. to about 850 F. selected to convert additional sulfur compounds into hydrogen sulfide and a second hydrocarbon stream as said fuel oil containing less than about 1.0% by weight of sulfur, and in contact with a second desulfurizing catalyst composite comprising a silica carrier, a Group VIII metal component and a Group VI-B metal component.

2. The process of claim 1 further characterized in that said first desulfurizing catalyst is a composite of an amorphous alumina carrier, from about 4.0% to about 30.0% by weight of a molybdenum, or a tungsten component and from about 1.0% to about 10.0% by weight of a bismuth component.

3. The process of claim 1 further characterized in that said second desulfurizing catalyst is a composite of a porous alumina-silica carrier containing 10.0% to about by weight of silica, from 4.0% to about 30.0% by weight of a molybdenum, or a tungsten component and from 1.0% to about 10.0% by weight of a nickel, or a cobalt component.

10 4. The process of claim 3 further characterized in that References Cited said porous carrier material is an amorphous composite UNITED STATES PATENTS 1,932,174 10/1933 Gaus et a1. 208-216 5. The process of claim 3 further characterlzed in that 3,055,823 9/1962 Mason et said porous carrier material includes a crystalline alumino- 5 silicate. DELBERT E. GANTZ, Primary Examiner 6. The process of claim 1 further characterized in that CRASANAKIS Assistant tExaminer the maximum temperature in said second reaction zone is at least about 50 F. lower than the maximum temper- 10 US. Cl. X.R.

ature in said first reaction zone. 208216; 252464