US3654133A - Dewaxed lubricating oil production - Google Patents

Abstract

A MULTIPLE-STAGE PROCESS FOR PRODUCING DEWAXED LUBRICATING OIL BASE STOCKS HAVING VISCOSITY INDICES GREATER THAN ABOUT 100. THE HYDROCARBONACEOUS CHARGE STOCK IS INITIALLY PROCESSED IN A HYDROCRACKING ZON E SELECTIVELY CONDENSED-RING HYDROCARBONS TO A RELATIVELY HIGH VISCOSITY INDEX PRODUCT. THE PRODUCT EFFLUENT FROM THIS FIRST ZONE IS SEPARATED, AT SUBSTANTIALLY THE SAME TEMPERATURE AND PRESSURE, PRODUCING A PRINCIPALLY LIQUID PHASE CONTAINING THE HEAVIER WAXY COMPONENTS. THIS WAXY DISTILLATE SERVES AS A CHARGE STOCK TO THE SECOND REACTION ZONE WHICH IS SELECTIVELY CONTROLLED TO CONVERT THE WAXY CONSTITUENTS, BY WAY OF BOTH HYDROCRACKING AND HYDROISOMERIZATION, INTO LOWER-BOILING HYDROCARBON PRODUCTS.

Description

April 4, 1972 R. K. oLsoN DEWAXED LUBRICATING OIL PRODUCTION Filed June 23, 1970 United States Patent U.S. Cl. 208-59 7 Claims ABSTRACT OF THE DISCLOSURE A multiple-stage process for producing dewaxed lubricating oil base stocks having viscosity indices greater than about 100. The hydrocarbonaceous charge stock is initially processed in a hydrocracking zone selectively controlled to convert relatively low viscosity index, condensed-ring hydrocarbons to a relatively high viscosity index product. The product etliuent from this lirst zone is separated, atsubstantially the same temperature and pressure, producing a principally liquid phase containing the heavier waxy components. This -waxy distillate serves as a charge stock to the second reaction zone which is selectively controlled to convert the waxy constituents, by way of both hydrocracking and hydroisomerization, into lower-boiling hydrocarbon products.

APPLICABILITY OF INVENTION The inventive concept described herein is directed towar-d the catalytic conversion of hydrocarbons in a multiple-stage process. More particularly, the present invention is directed toward the production of dewaXed lubricating oil -base stocks having viscosity indices above about 100. A lubricating oil base stock is synonymously referred to in the art as a neutral oil, the base oil contains both neutral and bright stock with the neutral oils being of lower viscosity, and is, in eifect, a dewaxed hydrocarbon mixture boiling in the lubbricating oil boiling range which does not contain viscosity improvers or other additives. That is, a lubricating oil denotes in the art a dewaxed lube oil base stock containing various additives. Through the utilization of the present invention, there is produced a dewaxed lubricating oil base stock having a viscosity index above about 100. Contrary to the standard prior art technique, the present invention involves catalytic dewaxing whereby the waxy constituents are converted, by way of hydrocracking and hydroisomerization, into lowerboiling products including gasoline and lubricating oils. The ultimate product of the present process is readily separated for the recovery of the desirable neutral oil for use in the subbsequent production of multi-graded lubricating oils.

The prior art is replete with references to crude oils containing hydrocarbonaceous components suitably adaptable for use as lubricating oils. In general, those lubricating oils which are derived from highly parainic crude stocks are utilized in the production of high quality motor oils, aviation and turbine oils. This type of lubricating oil is characterized `by a relatively high viscosity index (V.I.), although it is actually a blend of relatively low and relatively high viscosity index components. Lubricating oil base stocks derived from highly naphthenic crudes are employed in the production of lubricating oils having exceptionally desired properties with respect to heavy duty use such as that found in diesel engines. Desirable components of lubricating oil base stocks, or neutral oils, are isoparains and molecules containing single rings, whether naphthenic or aromatic. Essentially all heavy hydrocarbonaceous fractions derived from petroleum crude oils, contain condensed-ring as well as straight-chain hydrocarbons, in addition to waxy components 'which generally 3,654,133 Patented Apr. 4, 1972 are parainic in nature and characterized by an exceptionally long straight-chain. Characteristically, condensed-ring hydrocarbons have low viscosity indices and relatively poor resistance to oxidation. Therefore, they are undesirable as components of various types of lubricating oils.

A perusal of the prior art procedures and techniques, for producing lubricating oil base stocks, indicates that relatively high viscosity index lubricating oils may be produced through the use of a combination of solvent extraction techniques and clay-treating, acid-treating, etc. Some heavy duty lubricating oils are obtained through a combination of vacuum distillation followed by alkali-treating for the removal of naphthenic acids. The complex nature of high viscosity index lubricating oil production presents a challenge to a petroleum industry in the form of processing problems which are not easily solved through the use of present-day operating techniques. For example, solvent extraction of the undesirable components is inefiicient in view of the fact that available solvents are not highly selective for the components Which must be removed from the lubricating oil base stock. Furthermore, immense, complicated equipment is required in contacting the lubricating oil with the solvent and in recovering the solvent in order that the process becomes economically attractive. With respect to acid-treating and clay-treating techniques, major diculties involve disposal of clay and loss of hydrocarbon yield, as well as an acidic sludge disposal problem when strong acids, such as sulfuric acid, are employed. In brief summation, it might be said that the prior art schemes are severely hampered in their capability to produce lhigh yields of pure lubricating oils having high viscosity indices, and are tedious and expensive to operate in an acceptably eiicient manner.

Certain prior art techniques are required if satisfactory lubricating oils are to be produced. For example, it is necessary to subject a petroleum crude oil to one or more distillation techniques in order to provide a crude oil bottoms product concentrated in lubricating oil components. Another prior art scheme involves a preliminary processing step in the form of a deasphalting process. Crude oil bottoms, containing asphaltenic constituents, is intimately admixed with a light hydrocarbon solvent such as propane, pentane or heptane at conditions of temperature and pressure under which the asphaltenic constituents are precipitated. In view of the fact that the preliminary processing techniques of distillation and deasphalting are well known to those skilled in the art of petroleum refining technology, and further form no essential part of my invention, additional description thereof is not believed required herein.

The prior art also indicates that another technique is necessary to produce a suitable lubricating oil base stock. Waxy constituents must be removed to improve the overall quality of the ultimate lubricating oil. In the prior art, the dewaxing technique is accomplished by a method which generally employs a suitable solvent such as methyl-ethyl ketone, toluene, etc. The waxy lubricating oil base stock and solvent are heated to a temperature sufficiently high to render the solvent and base stock substantially miscible. The resulting mixture is then chilled in order to precipitate the wax from the solution. In practicing the dewaxing technique of the prior art, a wax concentrate in an amount of about 10.0% to about 20.0% by weight of the fresh hydrocarbonaceous charge stock is produced. With exceptionally heavy charge stocks, the quantity of paratiinic Wax resulting from the dewaxing technique can be as high as about 25.0% to about 30.0%.

In accordance with the present process, dewaxing is effected catalytically. The heavier portion of the product eiuent resulting from the initial conversion of the fresh charge stock, containing the waxy constituents, is subjected to additional conversion in a second reaction zone wherein hydrocracking and hydroisomerization reactions predominate. The waxy constituents are converted into naptha boiling range hydrocarbons, and isoparafns boiling within the lubricating oil boiling range, Without excessive yield loss to light, normally gaseous materials such as methane, ethane and propane. Not only is the tedious solvent dewaxing technique eliminated, but increased conversion to more valuable normally liquid hydrocarbon products is attained.

OBJECTS AND EMBODIMENTS A principal object of the present invention resides in the production of a maximum yield of lubricating oil base stocks. A corollary objective is to -produce a dewaxed lube oil base stock having a viscosity index above 100.

Another object of my invention is to produce dewaxed lubricating oil base stocks, all of which have viscosity indices above about 100, from different fractions of a petroleum crude oil.

Before describing the various embodiments of the present invention, brief reference will be made to the accompanying drawing in conjunction with the terms ernployed in the embodiments and in the appended claims. This will facilitate a clear understanding of my invention. Therefore, referring briefly to the drawing:

(l) The first hydrocracking zone is reaction zone 5.

-(2) The first separation zone is hot separator 7.

(3) The second hydrocracking zone is designated in the drawing as dewaxing zone 13.

(4) 'Ihe second separation zone is cold separator 1S.

(5) The third separation zone is cold separator 10.

In achieving the foregoing objects, my invention provides a process for producing a dewaxed lubricating oil base stock which comprises steps of: (a) reacting a hydrocarbonaceous charge stock and hydrogen in a first hydrocracking reaction zone, at hydrocracking conditions, in contact with a first hydrocracking catalyst; (b) separating the resulting first zone efliuent at substantially the same pressure and temperature, in a first separation zone, to provide a first vaporous phase and a first liquid phase containing waxy components; (c) reacting said first liquid phase and hydrogen, in a second hydrocracking reaction zone, in contact with a, second hydrocracking catalyst, at hydrocracking conditions including a lower pressure than that imposed upon said first hydrocracking reaction zone; (d) separating the resulting second zone efliuent and a second separation zone, at substantially the same pressure and a temperature in the range of 60 F. to about 140 F., to provide a second liquid phase and hydrogen-rich second vaporous phase; (e) separating said first vaporous phase, in a third separation zone, at substantially the same pressure and a temperature in the range of 60 F. to about 140 F., to provide a third liquid phase and hydrogen-rich third vaporous phase; and, (f) separating said second and third liquid phases to recover said dewaxed lubricating oil base stock.

In another embodiment, said second and third hydrogen rich vaporous phases are recycled, at least in part, to said first and second hydrocracking reaction zones.

Other objects and embodiments of my invention involve particularly preferred operating conditions and techniques as Well as preferred catalytic composites for utilization within the hydrocracking reaction zones. One such embodiment involves lower-severity operating conditions Within the second hydrocracking reaction zone. Particularly included are a lower maximum catalyst bed temperature, a higher liquid hourly space velocity, or both. In most applications of my invention, such lowerseverity operating conditions will also include a lower pressure. These, as Well as other objects and embodiments of my invention, will become evident from the following summary of the present dewaxed lubricating oil base stock producing process.

SUMMARY OF INVENTION The hydrocarbon charge stocks, suitable for use in the present multiple-stage process, are conventional and well known in petroleum refining technology. Such suitable charge stocks include vacuum gas oils, propane deasphalted oils, reduced crude stocks, mixtures thereof, etc. One illustrative feed stock is a propane deasphalted oil having a gravity of 18.8 API and an initial boiling point of about 1013 F. The deasphalted oil contains about 3.23% by weight of sulfur and about 1,450 ppm. by weight of nitrogen, and has a viscosity index of about 85 and a pour point of about 80 F. Another illustrative charge stock is a topped vacuum gas oil, derived from an Illinois crude, having a gravity of 22.3 API, an initial boiling point of about 750 F., a 50.0% of volumetric distillation temperature of 905 F. and an end boiling point of about 1050 F. This vacuum gas oil contains about 1630 p.p.m. by weight of nitrogen and 0.44% by Weight of sulfur.

The multiple-stage process of the present invention is a catalytic process wherein the catalytic composites are disposed as fixed-beds in the hydrocracking and dewaxing reaction zones. Although the precise composition of the catalyst need not necessarily be identical in both stages, the catalytically active components of the various composites are generally selected from the metals of Groups VI- B and VIII of the Periodic Table, and often from Groups V-B and VII-B. These metallic components are composited with a porous carrier material, and, in many applications, the catalytic composites will also contain a halogen component, generally from the group of chlorine, tluorine and mixtures thereof. Of necessity, the porous carrier material is highly refractory with respect to the operating conditions employed in the hydrocracking reaction zones, and it is intended to include those carrier materials which have traditionally been utilized to effect the hydrocracking of hydrocarbonaceous material. In particular, suitable carrier materials are selected from the group of amorphous refractory inorganic Oxides including alumina, silica, titania, zirconia, magnesia, alumina-silica, silicamagnesia, alumina-silca-boron phosphate, silica-zirconia, etc. When of the amorphous type, one preferred carrier material for utilization in the first hydrocracking reaction zone constitutes a composite of alumina and silica, the latter being present in an amount of about 10.0% to about 90.0% by Weight. The carrier material may consist of a crystalline aluminosilicate, particularly with respect to the catalytic composite disposed within the dewaxing zone; the zeolitic material may be naturally-occurring or synthetically-prepared, including mordenite, faujasite, Type- A or Type-U molecular sieves, mordenite and/or faujasite disposed within an amorphous matrix, etc. When utilized as a carrier, the zeolitic material may be in the hydrogen form or in a form which results from treatment with multi-valent cations. No particular refractory inorganic oxide carrier is essential to the present invention, and it is intended to include within the scope of my invention all conventional carrier materials, as Well as the wide variety of methods for the preparation thereof.

Preferred catalytic composites contain at least one metallic component from the metals of Group VI-B and VIII as indicated in the Periodic Table of the Elements, E. H. Sargent & Company, 1964; it is understood that equivalent results are not achieved through the indiscriminant selection of the metallic components. That is to say, a mixture of chromium and cobalt components will not yield results which are equivalent to those obtained through the use of molybdenum and nickel components. Suitable metallic components include chromium, molybdenum, tungsten, iron, nickel and cobalt, as well as the noble metals of Group VIII, ruthenium, rhodium, palladium, osmium, iridium and platinum. The Group VIII noble metal components generally comprise about 0.1% to about 2.0% by weight of the final composite, calculated on an elemental basis. The noble metal components may :be incorporated within the catalytic composites in any suitable manner including coprecipitation or cogellation, ion-exchange or impregnation. When utilized as a component of the catalytic composite, the metals of Group VI-B, chromium, molybdenum and tungsten are utilized in an amount of from about 4.0% to about 30.0% by weight. The iron group metal components, iron, cobalt and nickel, will be employed in an amount within the range of about 1.0% to about 10.0% by weight. These metallic components may also be composited with the carrier material in any suitable manner described within the prior art. In a particularly preferred embodiment, the catalytic composite disposed within the initial hydrocracking reaction zone contains a metal component from Group VI-B and a metal component from the iron group--i.e. nickel and molybdenum. In this preferred embodiment, the dewaxing reaction zone will have disposed therein a noble metal component-platinum or palladium-composited with a crystalline aluminosilicate, preferably mordenite, or mordenite within an alumina, or silica-alumina matrix.

The process of the present invention eliminates the necessity of both an initial extraction operation and a final solvent dewaxing technique while producing a suitable dewaxed lubricating oil base stock. While solvent extraction removes those components having a low viscosity index without chemical reactions being effected, hydrocracking simultaneously converts the components of low viscosity index into high quality naphthas and distillates, while converting the components of high viscosity index to a lesser extent, whereby the same continue to :be within the boiling range of lubricating oils. Catalytic dewaxing, as contrasting to solvent dewaxing, results in additional yields of normally liquid hydrocarbon products falling Within the gasoline, kerosene, and lubricating oil boiling ranges.

During the hydrocracking of heavy distillates for the production of lubricating oil bas'e stocks, the viscosity index prole, herein dened as being the viscosity indices of 10.0% by volume fractions of the total lubricating oil, plotted as a function of the volume distilled, indicates low viscosity indices at the front end, and high viscosity indices on the heavier end. Thus, the viscosity index profile of the total waxy lubricating oil :base stock typically indicates from about 10.0% to about 30.0% by volume or more as having a viscosity index below about 100. The viscosity indices of the remaining 10.0% fractions increase to values above 100, and often into the 130 to 140 range. With respect to a dewaxed lubricating oil base stock, it is very desirable to have the viscosity indices of all the 10.0 vol. percent fractions about 100.

Were an attempt made to process the entire fresh feed charge stock at an operating severity such that the viscosity index of the front end is at least say 105, the overall yield of lubricating oil base stock would be decreased from about 5.0% to about 15.0% by volume, based upon fresh feed. It must be remembered, as hereinbefore set forth, an additional 10.0% to about 20.0%, by weight of fresh feed is withdrawn as wax during the solvent dewaxing technique. In accordance with the present invention, the fresh feed charge stock is initially converted at hydrocracking conditions including a maximum catalyst ternperature of from 700 F. to about 900 F., a liquid hourly space velocity of about 0.2 to about 3.0, a pressure in the range of about 1,500 to about 5,000- p.s.i.g. and a hydrogen concentration in the range of about 1,500 to about 15,000 s.c.f./bbL Under these conditions, and in contact with a catalytic composite of the type previously described, the hydrocracking reaction is selectively controlled to convert the low viscosity index condensed-ring hydrocarbons to relatively high viscosity index products. The total product eluent from this inital reaction zone is separated in a hot separator at substantially the same pressure and temperature to provide a principally vaporous phase containing some hydrocarbons boiling above about 850 F. to about 900 F. The heavier portion of the product eflluent, containing the waxy components, becomes the charge stock to the dewaxing reaction zone wherein hydrocracking and hydroisomerization combine to produce naphtha boiling range products and additional lubricating oil base stock. With respect to this second hydrocracking reaction zone, the operating conditions include a lower maximum catalyst bed temperature of from 600 F. to about 860 F., a higher liquid hourly space velocity of about 0.5 to about 4.0, a lower pressure in the range of about 300 to about 1,500 p.s.i.g. and a hydrogen circulation rate of about 1,500 to about 15,000 s.c.f./bbL A series of separation techniques are utilized to concentrate and recover the dewaxed lubricating oil base stock as the product of the process, lighter normally liquid hydrocarbons boiling within the naphtha and kerosene boiling range and, where desired, a high viscosity index bright stock. Recovery of the latter permits backblending with various neutral oils, derived from the dewaxed lubricating oil base stock, in order to produce lubricating oils having intermediate Viscosity indices. Where desired, the bright stock may be recycled either to the rst or the second hydrocracking reaction zone in order to achieve additional conversion thereof into the lower-boiling lubricating oil components.

The hydrocarbonaceous charge stock and hydrogen are contacted with a catalyst of the type hereinabove described in the hydrocracking zones. The particular catalyst selected is primarily dependent upon the characteristics of the charge stock as well as the desired end result. Although the catalytic composite may be the same in both hydrocracking reaction zones, many situations arise where enhanced results are achieved through the use of different catalytic composites. The contacting may be accomplished in fixed-bed systems, moving-bed systems, uidized-bed systems, or in batch-type operations. However, in view of the risk of attrition loss of the catalyst, it is preferred to use a fixed-bed system. Furthermore, it is well known that a fixed-bed catalytic system offers many operational advantages. In such a system, the reactants may be contacted with the catalyst in either upward, downward, or radial flow fashion, with a downward ow being preferred. Additionally, the reactants may be in the liquid phase, a mixed liquid-vapor phase or a vapor phase when they contact the catalyst. In view of the fact that hydrocracking reactions are exothermic in nature, an increasing temperature gradient will be experienced as the hydrogen and charge stock traverse the catalyst bed. It is preferred that the maximum catalyst bed temperature in the first hydrocracking reaction zone be maintained in the range of 700 F. to about 900 F. while that within the second hydrocracking reaction zone will be in the lower range of from 600 F. to about 860 F. In order to assure that the catalyst bed temperatures do not exceed the maximum allowed levels, conventional quench streams, either normally liquid or normally gaseous, introduced at one or more intermediate loci of the catalyst bed may be utilized.

In the present specification and appended claims, a pressure substantially the same as, or temperature substantally the same as, is intended to connote that the pressure or temperature under which a downstream vessel is maintained is the same, allowing only for the normal pressure drop due to fluid flow and the normal temperature loss due to transfer of materials from one zone to another. Thus, Where the rst hydrocracking zone is at a pressure of about 2,650 p.s.i.g., and the temperature of the effluent is about 875 F. the iirst separation zone will function at a pressure of 2,550 p.s.i.g. and a temperature about 50 F. lower.

In further describing the process encompassed by my inventive concept, reference will be made to the accompanying drawing which illustrates one embodiment. For the purpose of demonstrating the illustrating embodiment; the drawing will be described in connection with a commercially-scaled unit having a fresh feed charge rate of about 28,000 barrels per day. It is understood that the charge stock, stream compositions, operating conditions, vessel designs, separators, catalysts and the like, are exemplary only, and may be varied widely without departure from my invention, the scope and spirit of which is defined by the appended claims. While the embodiment illustrated in the drawing indicates that the dewaxing zone follows the hydrocracking zone, as the second stage, it is understood that beneficial results might be obtained by reversing the procedure. Thus, dewaxing at lower severity can precede the hydrocracking at higher severity. The preferred scheme, for reasons which will be readily apparent to those skilled in the art, is that which is illustrated.

DESCRIPTION OF DRAWING In the drawing, the embodiment is illustrated by means of a simplified ow diagram in which such details as pumps, instrumentation and controls, pressure-reducing valves, heat-exchange and heat-recovery circuits, start-up lines, compressors, valving and similar hardware have been omitted as not essential to an understanding of the techniques involved. The utilization of such miscellaneous appurtenances, to modify the process, is well within the purview of one skilled in the art of petroleum relining techniques. The fresh feed charge stock is a blend of about 23,400 barrels per day of a vacuum gas oil and 3,750 barrels per day of a propane deasphalted oil. Pertinent properties of the blended charge stock are indicated in the following Table I:

TABLE I Charge stock properties Viscosity index 8l Viscosity, SUS/ 100 F. 718 Viscosity, SUS/210 F. 70.2

In addition, the blend of the vacuum gas oil and propane deasphalted oil indicates an initial boiling point of about 850 F. and 95.0% volumetric distillation temperature of about 1100 F. The intended object is to produce maximum quantities of a dewaxed lubricating oil base stock, a 375 F.-550 F. jet fuel kerosene fraction and a 550 F.600 F. light gas oil fraction, with minimum loss by way of normally gaseous material.

The charge stock, in an amount of about 27,150 barrels per day, enters the process by way of line 1, being admixed with a hydrogen-rich recycle vaporous phase in line 2 in an amount of about 10,000 s.c.f./bbl. Although not illustrated in drawing, about 1,000 scf/bbl. of circulating hydrogen is diverted to quench hydrocracking zone in order to maintain the increasing temperature differential at about 50 F. Following suitable heat-exchange to increase the temperature to about 600 F., the mixture enters heater 3 at a pressure of about 2,150 p.s.i.g., wherein the temperature is increased to a level of about 775 F. as measured at the inlet to the catalyst bed. The heated mixture passes through line 4 at a pressure of about 2,100 p.s.i.g. The liquid hourly space velocity through the catalytic composite disposed within hydrocracking zone 5 is about 0.5. The catalytic composite consists of 1.8% by weight of nickel and 16.0% by weight of molybdenum, combined with an amorphous carrier material of 63.0% by weight of alumina and 37.0% by weight of silica.

The reaction zone eiuent in line 6 is introduced into hot separator 8 at a pressure of about 2,000 p.s.i.g., and a temperature of about 800 F. A principally liquid phase, primarily containing hydrocarbons boiling above about 600 F. is withdrawn from hot separator 7 `by way of line 8, and is introduced thereby into dewaxing zone 13. Prior to entering dewaxing zone 13, the principally liquid phase is utilized as a heat-exchange medium to decrease its temperature to a level such that the maximum catalyst bed temperature in zone 13 is about 750 F., again allowing for a temperature differential of about 50 F. Dewaxing zone 13 is maintained under a pressure of about 1,000 p.s.i.g., and the liquid hourly space velocity is about 0.8. Prior to entering dewaxing zone 13, the principally liquid phase in line 8 containing the wavy components, is admixed with about 10,000 s.c.f./bbl. of hydrogen from line 19. The product eluent from dewaxing zone 13 is introduced by way of line 14 into cold separator 15 at a temperature of about 110 F. Normally liquid hydrocarbons, including pentanes, and some dissolved butanes are withdrawn by way of line 17 for subsequent fractionation to recover the various desired product streams. A hydrogen-rich principally vaporous phase is withdrawn from cold separator 15 by way of line 16 and introduced thereby into compressive zone 18. The rst principally vaporous phase, from hot separator 7, is introduced by way of line 9 into cold separator 10 at a temperature of about F. A hydrogen-rich vaporous phase is withdrawn by way of line 11 and introduced via line 16 into compressive zone 18. Although the principally liquid phase from cold separator 10 may be separately fractionated to recover the desired liquid products, a preferred scheme combines this liquid phase with that from cold separator 1S in line 17, the mixture being subsequently subjected to fractionation. Prior to entering compressive zone 18, the hydrogen-rich vaporous phase from cold separators 10 and 15 may be subjected to treating techniques for the removal of hydrogen-sulfide and normally gaseous material in order to increase the hydrogen concentration. Likewise, make-up hydrogen may be introduced at any suitable point within the process, a preferred locus being directly into compressive zone 18. At least a portion of the hydrogen-rich recycle gaseous phase is withdrawn by w-ay of lines 2 and 19 for introduction thereby into hydrocracking zone 5 and dewaxing zone 13, respectively. Overall product yield and distribution is presented in the following Table II:

TABLE II.-OVERALL PRODUCT YIELD AND DISTRIBUTION Wt. percent Component Vol. percent Ammonia Hydrogen sulfide Methane Ethane. Propane Lube on II 7 Pertinent properties of the 600 F.plus dewaxed lubricating oil base stock are presented in the following Table III:

With respect to the foregoing results, the total hydrogen consumption within both hydrocracking zone 5 and dewaxing zone 13 is 1.95% by weight of the fresh feed charge stock or 1,194 s.c.f./bbl.

The foregoing specification and the example integrated into the description of the accompanying drawing, clearly illustrates the method of effecting the present invention 9 and the benets to be afforded through the utilization thereof.

I claim as my invention:

1. A process for producing a dewaxed lubricating oil base stock which comprises the steps of:

(a) reacting a hydrocarbonaceous charge stock and hydrogen in a first hydrocracking reaction zone, at hydrocracking conditions, in contact with a rst hydrocracking catalyst;

(b) separating the resulting iirst zone eflluent, at substantially the same pressure and temperature, in a iirst separation zone, to provide a rst rvaporous phase and a rst liquid phase containing waxy components;

(c) reacting said first liquid phase and hydrogen, in a second hydrocracking reaction zone, in contact with a second hydrocracking catalyst, at hydrocracking conditions including a lower pressure than that imposed upon said irst hydrocracking reaction zone;

(d) separating the resulting second zone eiuent in a second separation zone, at substantially the same pressure and a temperature in the range of 60 F. to about 140 F., to provide a second liquid phase and a hydrogen-rich second vaporous phase;

(e) separating said rst vaporous phase, in a third separation zone, at substantially the same pressure and a temperature in the range of 60 F. to about 140 F., to provide a third liquid phase and a hydrogenrich third vaporous phase; and

(f) separating said second and third liquid phases to recover said dewaxed lubricating oil base stock.

2. The process of claim 1 further characterized in that said second and third hydrogen-rich vaporous phases are recycled, at least in part, to said first and second reaction zones.

3. The process of claim 1 further characterized in that the hydrocracking conditions, imposed upon said iirst reaction zone, include a maximum catalyst bed temperature of from 700 F. to about 900 F., a liquid hourly space velocity of about 0.2 to about 3.0 and a pressure in the range of 1,500 to about 5,000 p.s.i.g.

4. The process of claim 1 further characterized in that the hydrocracking conditions, imposed upon said second hydrocracking reaction zone, include a lower maximum catalyst bed temperature of from about 600 F. to about 860 F., a higher liquid hourly space velocity of about 0.5 to about 4.0, or a higher liquid hourly space velocity and a lower maximum catalyst bed temperature, and a lower pressure in the range of 300 to about 1,500 p.s.i.g.

5. The process of claim 1 further characterized in that said iirst and second hydrocracking catalysts comprise a composite of at least one metallic component from Groups VI-B and VIII combined with a porous carrier material.

6. The process of claim 5 further characterized in that said first hydrocracking catalyst comprises an amorphous carrier material containing from 10.0% to about 90.0% by weight of silica.

7. The process of claim S further characterized in that said second hydrocracking catalyst comprises a crystalline aluminosilicate carrier material.

References Cited UNITED STATES PATENTS 3,365,390 1/1968 Egan et al. 208-60 3,486,993 12/ 1969 Egan et al. 208-89 3,487,005 12/1'969 Egan et al. 208-59 3,539,498 11/ 1970 Morris et al 208-111 3,544,448 12/ 1970 Jacobs et al. 208-59 3,551,323 12/1970 Hamblin 208-58 DELBERT E. GANTZ, Primary Examiner G. E. SCHMITKONS, Assistant Examiner U.S. Cl. X.R.

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