US3502572A - Single-stage hydrocracking for varied product distribution - Google Patents

Description

United States Patent 3,502,571 CATALYTIC CONVERSION OF HYDROCAR- BONACEOUS BLACK OIL Frank Stolfa, Park Ridge, Ill., assignor to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Filed Dec. 27, 1967, Ser. No. 693,925 Int. Cl. Cg 13/02 US. Cl. 208-408 10 Claims ABSTRACT OF THE DISCLOSURE The use of a metal phthalocyanine catalyst for the conversion of hydrocarbonaceous black oil into lowerboiling, normally liquid hydrocarbon products. The thermally stable phthalocyanine catalyst is employed in an amount within the range of about 250 p.p.m. to about 5000 p.p.m., based upon the weight of the black oil; preferred metal phthalocyanine catalysts are selected from Groups V, VI and VIII, and especially those containing cobalt, nickel, platinum, vanadium and molybdenum. A phthalocyanine-containing residuum fraction is recycled to combine with the black oil, necessitating only a minor quantity of additional metal phthalocyanine catalyst in order to maintain the desired concentration thereof within the reaction chamber.

APPLICABILITY OF INVENTION The invention described herein is adaptable to a process for the conversion of petroleum crude oil, as well as the heavier fractions derived therefrom, into lower-boiling hydrocarbon products. More specifically, the present invention is directed toward a process for converting atmospheric tower bottoms products, vacuum tower bottoms products, crude oil residuum, coal oil extracts, topped crude oils, tar sand oil extracts, etc., all of which are referred to in the art as black oils.

Crude oils, particularly the heavy oils extracted from tar sands, vacuum residuum, that resulting from the liquefaction of coal, etc., generally contain high molecular weight sulfurous compounds in exceedingly large quantities. In addition, these black oils contain excessive quantities of nitrogenous compounds, high molecular weight organo-metallic complexes, comprising nickel and vanadium, and asphaltic material. At the present time, an abundant supply of such hydrocarbonaceous material exists, most of which has a gravity less than 200 API, and a significant proportion of which has a gravity less than about 100 API. This material is generally further characterized by a boiling range which indicates that 10.0% or more, by volume, boils at temperatures above about 1050" F. The conversion of at least a portion of the heavier boiling material into distillable hydrocarbonsi.e. those boiling below a temperature of about 1050 F. has hitherto been considered economically non-feasible. However, the abundant supply thereof virtually demands conversion for the purpose of satisfying the ever-increasing need for greater quantities of lower-boiling distillables.

Exemplary of those charge stocks, to which the present invention is particularly adaptable, include a vacuum tower bottoms product having a gravity of 7.1 API and containing 4.1% 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, and containing 10.1% by weight of asphaltics and 5.2% by weight of sulfur; and, a vacuum residuum having a gravity of 8.6 API, containing 3.0% by weight of sulfur and more than 4000 p.p.m. of nitrogen, having a 20.0% volumetric distillation temperature of 1055 F. The principal difficulties, accompanying the conversion of black oils, arise primarily from the presence of the asphaltic material. This 3,502,571 Patented Mar. 24, 1970 ice asphaltic material consists of extremely high molecular weight, nondistillable coke precursors, insoluble in light hydrocarbons such as pentane or heptane, which are often found to be complexed with hetero compounds including nitrogen, metals and sulfur.

PRIOR ART While it must be acknowledged that the literature is replete with descriptions of processes of various types, designed to effect the conversion of black oils into lowerboiling hydrocarbons, a perusal of the art reveals little with respect to the non-fixed bed method of catalytic processing. For example, many literature references and/or publications might be found which disclose deasphalting followed by crack-ing of the resulting normally liquid product, desalting followed by halogen hydride treatment to coagulate the metallic-containing asphaltics, etc. It is significant that previously described processing schemes for the catalytic conversion of black oils appear to favor a slurry-type process wherein a solid catalytic composite, in finely divided, .powdery form, is intimately admixed with the liquid charge, the resulting slurry being brought to reaction conditions in a reaction chamber. With these techniques, great expense is incurred in the recovery of spent catalyst from the reaction chamber eflluent, accompanied by extensive regeneration facilities necessary to permit re-use of the catalyst. With respect to the ,so-called unsupported" catalytic slurry-type processes, in which a compound is employed as the catalyst, the compound generally undergoes transformation into a non-catalytic form. This subsequently not only must be removed from the various product effluent streams, but must necessarily be converted into the catalytic form originally employed.

With respect to catalytic processing of hydrocarbonaceous black oils, two principal approaches have been advanced: liquid-phase hydrogenation and vapor-phase hydrocracking. In the former, liquid-phase oil is passed (generally upwardly), in admixture with hydrogen, into a fixedfluidized bed of catalyst particles. Although perhaps effective in converting at least a portion of the oil-insoluble metallic complexes, this type process is relatively ineffective with respect to asphaltics dispersed in the charge, since the probability of effecting simultaneous contact between the catalyst particle and the asphaltic molecule is at best remote. Furthermore, since hydrogenation reactions are generally conducted at elevated temperatures of at least 500 C. (932 F.), the retention of unconverted asphaltics, suspended in a free liquid-phase oil, for an extended period of time results in further flocculation and agglomeration, adding to the difiiculty of effecting conversion. Vapor-phase hydrocracking of black oil charge stocks containing substantial quantities of asphalitcs is, for all practical purposes, virtually ineffective. The high molecular weight asphaltic material tends to migrate immediately to the catalytically active centers and surfaces of the catalytic composite, thereby rendering the same ineffectual.

Briefly, the process of the present invention makes use of a class of compounds which function as true catalysts; that is, they remain substantially unchanged while promoting the desired reactions. As hereinafter set forth, two principal advantages attendant the use of metallic phthalocyanine compounds reside in thermal stability up to temperatures as high as 1500 F., and the fact that they are Vii A principal object of the present invention is, therefore, to provide a catalytic process for the conversion of hydrocarbon residuals, or black oils, to minimum bottoms.

United States Patent 3,502,572 SINGLE-STAGE HYDROCRACKING FOR VARIED PRODUCT DISTRIBUTION Charles H. Watkins, Arlington Heights, and Laurence O.

Stine, Western Springs, lll., Leslie C. Hardison, Norwalk, Conn., and Robert A. Lengemann, Arlington Heights, 111., assignors to Universal Oil Products Company, Des Plaines, Ill., a corporation of Delaware Filed Oct. 18, 1967, Ser. No. 676,232 Int. Cl. Cg 13/02 US. Cl. 208-111 4 Claims ABSTRACT OF THE DISCLOSURE A single-stage hydrocracking process for maximizing the production of gasoline and middle-distillate boiling range hydrocarbons. Charge stocks are generally those contaminated fractions having an initial boiling point about 650 F. The charge stock is introduced into the reaction zone at a locus intermediate thereof, and preferably about one-third from the top of the catalyst bed therein. Catalytic composites include Groups VI-B and VIII metals combined with a siliceous carrier material.

APPLICABILITY OF INVENTION The invention encompassed by this application relates to a single-stage process for the conversion of hydrocarbonaceous material into lower-boiling hydrocarbon products, providing flexibility to an overall petroleum refining operation by affording varied product distribution. More specifically, the present invention involves a conversion process for decontaminating nitrogen-containing, heavy hydrocarbon mixtures, accompanied by simultaneous hydrocracking for the production of hydrocarbons boiling within the gasoline and middle-distillate boiling ranges. The present process is particularly adaptable for effecting the conversion of hydrocarbon fractions and/or distillates boiling above a temperature of about 550 F.

Hydrocracking, also commonly referred to as destructive hydrogenation, or catalytic cracking in the presence of hydrogen, effects a definite change in the molecular structure of the hydrocarbons being processed, and is often described as cracking under hydrogenation conditions. Hydrocracking reactions are most commonly employed for the conversion of a wide variety of coals, tars, and heavy residual oils, in order to produce lower-boiling, saturated products; to some extent, intermediates, including jet fuel, diesel and/or domestic fuels, and heavier gas oil fractions are also produced. Although many of the current cracking processes may be, and are, conducted thermally, the preferred refinery processing technique involves the utilization of a catalytic composite having a high degree of selective hydrocracking activity. This affords a measure of control by which the cracking reactions being effected become more selective from the standpoint of producing an increased yield of normally liquid product having improved chemical and physical characteristics.

Selective hydrocracking is of particular importance when processing hydrocarbons and mixtures of hydrocarbons having normal boiling points at temperatures above the gasoline and middle-distillate boiling ranges; that is, hydrocarbons and various mixtures of hydrocarbons, as well as hydrocarbon fractions and distillates, having a boiling range which indicates an initial boiling point of from about 550 F. to about 700 F., and an end boiling point which may be as high as 1000 F., or more. Selective hydrocracking of such hydrocarbon fractions results in greater yields of hydrocarbons boiling within "ice the gasoline and middle-distillate boiling ranges; that is, hydrocarbons and hydrocarbon fractions boiling below about 650 F. to about 700 F. As a result of the availability of control with respect to the hydrocracking of such heavier hydrocarbon fractions, there is produced a substantially increased yield of middle-distillate boiling range hydrocarbons; that is, those hydrocarbons and hydro-carbon fractions having a boiling range indicating an initial boiling point of about 350 F. to about 450 F., and an end boiling point of about 550 F. to about 700 F. Selectivity is required in order to avoid the usually experienced excessive decomposition of normally liquid gasoline and middle-distillate boiling range hydrocarbons substantially or completely into normally gaseous hydrocarbons, the latter generally considered to be waste products. Non-selective cracking, when unabated, will result in the decomposition of normally liquid hydrocarbons into normally gaseous hydrocarbons; for example, the continuous demethylation of normal heptane produces seven methyl groups which are converted to seven molecules of methane. Another disadvantage of non-selective hydrocracking is the resulting rapid formation of increased quantities of coke and heavy hydrocarbonaceous material which becomes deposited within the process hardware and upon the catalyst, and decreases, or destroys, the activity thereof to catalyze the desired reactions in an acceptable controlled manner. A shorter acceptable processing cycle results, accompanied by the necessity of more frequent regeneration of catalyst, or total replacement thereof with fresh catalyst. Furthermore, the deactivation of the catalyst appears to inhibit the hydrogenation activity thereof to the extent that a significant proportion of the gasoline and middle-distillate boiling range products consists of unsaturated hydrocarbons, whereby the same are not especially suitable for immediate utilization, or for subsequent direct processing by catalytic reforming. Through the utilization of the hydrocracking process of the present invention, a hydrocarbon charge stock, consisting entirly of hydrocarbons boiling above the middle-distillate boiling range, is converted in a virtual 100.0% yield by weight, into hydrocarbons boiling within the gasoline and middle-distillate boiling ranges. As hereinafter set forth in greater detail, the process of the present invention, unlike present-day processes, affords the economic advantage of being capable of high yields of lower-boiling products while utilizing a single reaction zone, notwithstanding severe contamination of the charge stock by sulfurous and nitrogenous compounds.

PRIOR ART Investigations into catalytic hydrocracking of hydrocarbons boiling at temperatures above the middle-distillate boiling range, or at temperatures above about 550 F., have indicated that the presence of nitrogencontaining compounds, and sulfur-containing compounds within the hydrocracking charge stock, regardless of the exact boiling range thereof, results in the relatively rapid deactivation of the catalytically active metallic components, as well as the solid carrier material generally employed to serve as the acidic-hydrocracking component. The deactivation of the catalyst appears to result from the reaction of the nitrogenous and sulfurous compounds with the various catalytic components, the extent of such deactivation increasing as the process continues, and as the charge stock further contaminates the catalyst through contact therewith. It further appears that the deactivation, resulting from the presence of excessive quantities of nitrogenous and sulfurous compounds, is not a simple reversible phenomenon, which may be easily rectified by the relatively simple expediency of heating the catalyst in a suitable atmosphere continues through line 31 as a drag stream. The remainder thereof is diverted through line 3, is admixed with the #hydrogenated diluent in line 27 and continues to combine with the fresh hydrocarbon charge stock in line 1. To compensate for the quantity of phthalocyanine catalyst removed from the system via the drag stream in time 31, additional catalyst is introduced by way of line 32. As hereinbefore set forth, design considerations for any given commercially-scaled installation will dictate various fractionation/ separation schemes to handle the reactor chamber efiluent in line 7. For example, in a situation where a portion of the hydrogenated middle-distillate is not utilized as a diluent in line 27, it will generally be necessary to divert a portion of the heavy vacuum gas oil in line 30 to combine with the fresh hydrocarbon charge stock in order to maintain the combined feed ratio to reaction chamber 6 at the selected level. Therefore, it is understood that the schematic flow diagram presented in the accompanying drawing is for illustrative purposes only.

EXAMPLE The following example is presented for the purpose of further illustrating the process of the present invention and the benefits aiforded through the utilization thereof in maximizing the production of distillable hydrocarbons from hydrocarbonaceous black oils. The charge stock was a vacuum column bottoms fraction having a 20.0% volumetric distillation temperature of 1055 F. Other pertinent charge stock properties include a gravity of 8.6 API 3.0% by weight of sulfur, about 4200 p.p.m. of nitrogen, a UGP K-factor of 11.2 and a Conradson Carbon Residue of 17.7 Weight percent.

Two operations were efiected at a heater transfer temperature of about 740 F., resulting in a reaction chamber peak temperature of about 840 F. The reaction chamber was maintained under an imposed pressure of 3000 p.s.i.g., and the hydrogen concentration was 10,000 standard cubic feet per barrel, based upon the fresh hydrocarbon charge stock. The combined feed ratio of the reaction chamber was 2.0, the combined feed consisting of the vacuum bottoms charge stock, 25.0% of a hydrogenated diluent and 75.0% of a substantially gasoline-free cracked hydrocarbon stream having an end boiling point of about 1050 F.

The second operation, designated in the following Table as Run B, was effected with the addition of cobalt phthalocyanine to the fresh hydrocarbon charge stock in an amount of 1000 p.p.m. by weight thereof. A comparison of the two oeprations is presented in the following table:

TABLE-COMPARATIVE RESULTS I claim as my invention:

1. A process for the conversion by hydrocracking of hydrocarbonaceous black oil into lower-boiling hydrocarbon products which comprises reacting said black oil with hydrogen in admixture with a metal phthalocyanine catalyst at conversion conditions including a temperature above about 500 F. and a pressure greater than about 500 p.s.i.g., and recovering lower-boiling hydrocarbons from the resulting conversion efiluent.

2. The process of claim 1 further characterized in that said phthalocyanine catalyst contains a metal selected from the group consisting of the metals of Groups V, VI and VIII of the Periodic Table.

3. The prcess of claim 2 further characterized in that said catalyst is vanadium phthalocyanine.

4. The process of claim 2 further characterized in that said catalyst is moiybdenum phthalocyanine.

5. The process of claim 2 further characterized in that said catalyst is cobalt phthalocyanine.

6. The process of claim 2 further characterized in that said catalyst is platinum phthalocyanine.

7. The process of claim 2 further characterized in that said catalyst is nickel phthalocyanine.

8. A process for the conversion by hydrocracking of hydrocarbonaceous black oil into lower-boiling hydrocarbon products which comprises the steps of:

(a) reacting said black oil with hydrogen in admixture with a metal phthalocyanine catalyst at conversion conditions including a temperature above about 500 F. and a pressure greater than about 500 p.s.i.g.;

(b) separating the resulting conversion efiluent to provide (I): a hydrogen-rich vapor phase, (2) a middledistillate boiling range fraction, and (3) a metal phthalocyanine-containing residuum fraction;

(c) recycling said hydrogen-rich vapor phase and at least a portion of said metal phthalocyanine-containing residuum fraction to combine with said black oil;

(d) hydrogenating at least a portion of said middledistillate fraction and recycling the hydrogenated product to combine with said black oil; and

(e) recovering lower-boiling hydrocarbons as products of the process.

9. The process of claim 8 further characterized in that said black oil is reacted with hydrogen in admixture with from about 250 p.p.m. to 5000 p.p.m. of a metal phthalocyanine catalyst.

10. The process of claim 8 further characterized in that said conversion eflluent is further separated to provide a It should be noted that the method of the present invention resulted in 10.0 volume percent additional distillable hydrocarbons, accompanied by the production of only 0.4% by Weight of additional normally gaseous material (C -C Of further interest is the fact that a greater degree of hydrodesulfurization was effected. Design considerations indicate further that the continuous addition of metal phthalocyanine, to replenish the system for that removed in the drag stream, is only from about 150 p.p.m. to about 400 p.p.m. per barrel of fresh hydrocarbon charge.

The foregoing specification and example indicate the means by which the present process is effected and the benefits afforded through the utilization thereof.

heavy vacuum gas oil fraction, at least a portion of which is recycled to combine with said black oil.

References Cited DELBERT E. GANTZ, Primary Examiner A. RIMENS, Assistant Examiner US. Cl. X.R.

propensity for the destructive removal of the nitrogenous and sulfurous compounds as the case may be. As hereinafter set forth in greater detail, the process of the present invention preferably utilizes a catalytic composite consisting of at least four components in particular concentrations. The precise boiling range of any particular fraction depends, of course, on the overall desired end result. In any event, the process of the present invention affords a great degree of flexibility with respect to the final product distribution.

Regardless of the precise composition of the catalytic composite, it is prepared through the use of a suitable carrier material which may be either naturally-occurring or synthetically-prepared. Suitable naturally-occurring carrier materials include various aluminum silicates, especially when acid-treated to increase the activity thereof, various alumina-containing clays, sands, ores, earths and the like, while the preferred synthetically-prepared cracking catalyst components are selected from the refractory inorganic oxides and include at least a portion of both silica and alumina. Other suitable refractory inorganic oxides which may be combined as an integral portion of the hydrocracking catalyst, in particular instances, and for the purpose of imparting certain desired characteristics to the catalyst, include zirconia, magnesia, titania thoria, strontia, hafnia, boria, etc., the preferred cracking catalyst component comprising a composite of silica and alumina, containing from about 20.0% to about 50.0% by weight of silica.

The present invention involves a process for producing hydrocarbons which boil within the gasoline and middledistillate boiling range from those hydrocarbons which boil at a temperature in excess of the gasoline boiling range, and especially those hydrocarbons boiling entirely at temperatures above the middle-distillate boiling range. The process of the present invention utilizes a single reaction zone to accomplish the two-fold object of hydrorefining accompanied by simultaneous hydrocracking, which object heretofore required a minimum of two distinctly separate reaction zones, with intervening separation and fractionation techniques. Suitable charge stocks include kerosene fractions, gas-oil fractions, lubricating oil and white oil stocks, cycle oil stocks, black oil stocks, topped crude oils, reduced crude oils and other sources of hydrocarbons which have a depreciated market demand due to the high boiling points of those hydrocarbons and the presence of asphaltic and other heavy hydrocarbonaceous residue. Generally, all of the sources of feed stock contain high-boiling nitrogenous compounds and sulfurous compounds as contaminants; the nitrogenous compounds will be present in quantities as high as 8000 ppm. Through the utilization of the process and the nitrogen-insensitive catalyst of the present invention, heavy hydrocarbon charge stocks may be subjected to conversion notwithstanding the fact that they are contaminated by sulfurous compounds in an amount as high as about 8.0% by weight of sulfur, and nitrogenous compounds in amounts as high as 8000 p.p.m., and without prior treatment in an individually separated hydrorefining reaction zone.

The present invention may be more clearly understood through reference to the accompanying drawing which illustrates one particular embodiment thereof. It is not intended, however, that the process of the present invention be unduly limited to the particular embodiment so illustrated. In the drawing, various flow valves, control valves, coolers, condensers, overhead reflux condensers, pumps, compressors, knock-out pots, etc., have either been eliminated, or greatly reduced in number as not being essential to the complete understanding of the present process. The use of such miscellaneous appurtenances are well within the purview of one having skill in the art of petroleum processing.

With reference now to the drawing, the hydrocarbon charge stock, for example a heavy vacuum gas oil, having a boiling range of from 566 F. to about 940 F., and

containing about 3,200 ppm. of nitrogen and approximately 2.6% by weight of sulfur, enters the process via line 1, and is introduced into heater 2. In a commercial installation, the charge would first be heated by Way of heat-exchange with the hot reactor effluent (line 6). Heater 2 increases the temperature to a level in the range of about 600 F. to 850 F., the heated charge continuing through line 17 into reactor 4 by way of an intermediate locus. As indicated, line 17 terminates, within reactor 4, in a suitable distribution means 3, for example a spray head. In accordance with our invention, the locus at which the fresh charge is introduced is within the upper one-third of said reactor. That is, with respect to the first 10.0% to to about 33.0% of the catalyst disposed in the reactor, contact thereof is made only by a recycled liquid stream, the source of which vis hereafter described.

The recycled liquid stream in line 5 consists primarily of those normally liquid hydrocarbons which have normal boiling points above the middle-distillate boiling rangei.e. above about 650 F. This heavy hydrocarbon fraction, separated from the total reactor efiluent, is admixed with a hydrogen-rich recycled gaseous phase in line 8, and the mixture is passed into heater 2. The heated stream, at a temperature of from about 600 F. to about 850 F., passes via line 18 into reactor 4, being introduced therein at a point upstream of the locus at which the fresh charge stock is introduced via line 17. In commercially-sized installations, common practice provides asuitable distribution head at the top of the reactor, and upstream of the top of the catalyst bed. Likewise, the bottom of the reactor is designed to provide a type of disengaging zone below the bottom of the catalyst bed. For purposes of describing the present inventive concept, it is presumed that the reactor is filled with catalyst, and the locus at which the fresh charge is introduced is situate such that at least about two-thirds of the catalyst is downstream. Thus, the upper portion of the catalyst is reserved for hydrocracking of the contaminant-free recycled material. As hereinafter indicated by a specific example, such an arrangement induces more effective use of the entire catalyst bed.

Since the reactions are principally exothermic, a temperature rise is experienced within the catalyst bed, and the outlet temperature is considerably higher than that at the inlet. Generally, the inlet temperature is controlled such that the maximum catalyst bed temperature does not exceed about 950 F. In any event, the hot product efliuent is withdrawn from reactor 4 via line 6, and, following service as a heat-exchange medium, is condensed and passed into a cold (60 F. to about F.) highpressure separator 7. Separator 7 serves to provide a hydrogen-rich gaseous phase which is withdrawn through line 8 via compressive means not illustrated, and combined with the heavy recycle stream in line 5, prior to being heated in heater 2. A principally normally liquid hydrocarbon stream is withdrawn through line 9, and is introduced into stripping column 10 which is maintained at conditions necessary to remove hydrogen sulfide and light gaseous hydrocarbons via line 13. A substantially hydrogen sulfide-free hydrocarbon mixture is recovered as a bottoms stream in line 11, and is introduced thereby into product fractionator 12.

The conditions of temperature and pressure, at which fractionator 12 functions, will, of course, be dependent upon the product distribution and select fractions which are desired. One such product distribution consists of a C -C hydrocarbon concentrate, a C to 400 F. end point or gasoline fraction and a 400 F. to 650 F. middle-distillate. These are withdrawn from fractionator 12 via lines 14, 15 and 16 respectively. Since these streams are substantially, completely free from contaminating influences, they are well suited either for direct use-the C -C fraction may be employed as a gasoline blending agentor for direct, subsequent processingthe C to 400 F. hydrocarbon fraction may be processed directly in a catalytic reforming unit in order to enhance its anti-knock characteristics. The 400 F.650 F. middle-distillate fraction can be employed directly as a fuel oil, or further processed via hydrocracking to produce additional gasoline components. The particular utilization of these various fractions will be dependent upon the current marketing considerations, as well as the overall refinery operations and economic aspects.

Those hydrocarbon components of the product eflluent which have normal boiling points above the end boiling point of the middle-distillate fraction, in this instance 650 F., are removed from fractionator 12 as a bottoms stream through line 5. This heavy fraction is combined with the hydrogen-rich gaseous phase in line 8, and the mixture raised to the desired temperature in heater 2. The hydrogen concentration in reactor 4, with respect to the fresh hydrocarbonaceous charge stock in line 1, is in the range of from about 2,000 to about 25,000 s.c.f./ bbl. Since hydrogen is consumed by the reactions being effected, supplemental hydrogen is added from any suitable external sourcei.e. a hydrogen-producing process such as catalytic reforming. The liquid hourly space velocity, based upon fresh charge stock, is generally from about 0.5 to about 10.0.

From the foregoing description of the various embodiments, it is readily ascertained that the present process is, in effect, a process for producing hydrocarbons boiling within the middle-distillate and gasoline boiling ranges, possessing the inherent flexibility of maximizing the yield of middle-distillate boiling range hydrocarbons or select fractions thereof. Both the gasoline and middledistillate hydrocarbon streams are produced substantially completely free from nitrogenous and sulfurous compounds, and other contaminating influences. The gasoline boiling range hydrocarbons are, therefore, extremely well suited for immediate direct processing by way of catalytic reforming, the middle-distillate hydro-carbons being adaptable for utilizaiton as a light lubricating or fuel oil. As hereinbefore stated, a kerosene fraction boiling up to about a temperature of 500 F., and substantially free from contaminating nitrogenous and sulfurous compounds may be produced; also, a jet fuel blending component, and a diesel fuel can be produced where economic considerations so dictate. Various modifications may be made to the illustrated embodiment by those possessing skill within the art of petroleum processing, and it is not intended that such modifications remove the process from the scope and spirit of the appended claims. For example, the separating means indicated by separator 7 may be equipped with a dip-leg to remove water injected into line 6 for the purpose of absorbing the ammonia resulting from the conversion of nitrogenous compounds.

The preferred four component catalyst, comprising alumina, silica, molybdenum and a metal from the iron group, preferably nickel, may be manufactured by any suitable means; a particularly convenient method utilizes impregnating techniques. The impregnating method of preparation involves initially forming an aqueous solution of water-soluble compounds of nickel and molybdenum, such as nickel nitrate, nickel carbonate, ammonium molybdate, molybdic acid, etc. The alumina-silica carrier material particles are commingled with the aforementioned aqueous solutions, and subsequently dried at a temperature of about 200 F. The dried composite is thereafter subjected to high temperature calcination in an atmosphere of air, at a temperature of from about 1100 F. to about 1700 F. The molybdenum and nickel, after being composited with the alumina-silica carrier material, may be caused to exist therein in any desired form, and either as the element or as some compound thereof. Thus, the calcined composite may be further treated for the purpose of providing a catalyst in which the molybdenum and nickel exist as sulfides, nitrates, oxides, or in their most reduced state. It is, however, understood that, for the purposes of defining the scope of the present invention, the concentrations of molybdenum and nickel, as stated in the specification and the appended claims, refer to the concentrations of molybdenum and nickel, as stated in the specification and the appended claims, refer to the concentrations calculated as the elements thereof, and are based upon the weight of the alumina-silica carrier material. That is, a catalyst comprising 16.0% by weight of molybdenum contains that percentage of the element whetherexisting as the oxide, the sulfide, or in some other combined form.

Synthetically prepared carrier materials, whether amorphous or crystalline, are preferred, since they facilitate creating a tailor-made composite, and may be manufactured in any suitable manner including, separate, successive, or coprecipitation methods. For example, an alumina-silica carrier material, comprising from about 20.0% to about 50.0% by weight of silica, may be prepared by the method wherein the oxides are precipitated separately and then mixed, preferably in the wet state.

The catalytic composite utilized in the hydrocracking reaction zone of the present invention, which composite is specifically designed to effect hydrocracking reactions while simultaneously being relatively immune to the deactivating influence of sulfurous compounds, and especially insensitive to nitrogen, is at least a four-component catalyst comprising alumina, silica, molybdenum, and at least one metallic component from the iron-group of the Periodic Table. With respect to the composite of alumina and silica, the alumina is present in an amount of from about 50.0% to about 80.0%, and at least as great as silica which is present in an amount of from about 20.0% to about 50.0%. The molybdenum component is present in an amount of from about 13.0% to about 20.0% calculated as the element, and not in some combined form, and based upon the weight of the alumina-silica composite. The iron-group component, iron, cobalt, and particularly nickel, is present in an amount less than the molybdenum, and within the range of from about 1.0% to about 6.0% by weight of the alumina-silica composite, and is also calculated as the element.

EXAMPLES The following examples are herein presented for the purpose of further illustrating the present invention, and to indicate the benefits afforded through the utilization thereof. It is not intended that the present invention be limited unduly to the method of preparing the catalyst, the character of the charge stock, or the severity of the operating conditions employed in these examples.

Example I This example is given for the purpose of illustrating the process of the present invention as applied to a hydrocarbon fraction boiling entirely beyond the gasoline boiling range, and virtually completely the middle-distillate boiling range. The hydrocarbon fraction employed was a vacuum gas oil obtained from a blend of Wyoming and West Texas crude oils, the analysis of which is indicated in Table I:

TABLE I.CHARGE STOCK PROPERTIES, VACUUM GAS OIL The catalyst employed was a composite of about 2.0% by weight of nickel and about 20.0% by weight of molybdenum, calculated as the elements thereof. It wasprepared by the method which employs a single impregnat ing technique, and utilized 100 weight parts of alumina spheres (prepared in accordance with the oil-drop method as described in U.S. Patent No. 2,620,314, issued to James Hoekstra), and a single impregnating solution containing nickel nitrate hexahydrate and molybdic acid. This catalyst was disposed in a reaction zone maintained under an imposed pressure of 1500 pounds per square inch, and at an inlet temperature of about 657 F. The fresh liquid charge was passed through the catalyst at a rate of 0.5 liquid hourly space velocity, after having been combined with hydrogen in an amount of 6000 standard cubic feed per barrel. Following a separation, to remove ammonia, hydrogen sulfide and the light paraffinic hydrocarbons (C -C the normally liquid product effiuent, including butanes, was fractionated in a multi-plate distillation column to yield four individual component fractions. These component fractions were a butane to 180 F. fraction, a 180 F. to 400 F. gasoline fraction, a 400 F. to 650 F. middle-distillate fraction, and a bottoms fraction containing those hydrocarbons boiling at temperatures above the middle-distillate boiling range. In regard to the quantity of residual nitrogenous compounds contained within these fractions, the total normally liquid product etfiuent, including butanes, contained 18 parts per million of nitrogen, the gasoline boiling range fraction (180 F. to 400 F.) indicated a nil nitrogen concentration, and that of the middledistillate fraction (400 F. to 650 F.) was less than about 1.0 p.p.m. Other product inspections performed upon the various fraction are indicated in the following Table II.

TABLE IL-PRODUCT INSPECTIONS Light parafiinic hydrocarbon yield, wt. percent 2.2. Yield, butanes, 180 F. fraction, vol. percent 3.0.

As indicated in Table II, the conversion of the vacuum gas oil was of a degree which resulted in 25.6% by volume of gasoline boiling range hydrocarbons, including butanes; there was a 47.0% yield of middle-distillate boiling range hydrocarbons, or a total volumetric yield of 72.6% of hydrocarbons boiling within the gasoline and middle-distillate boiling ranges. In addition, a hydrocarbon-type analysis, performed on the 180 F. 400 F. fraction indicated 41.0% paraffins, 51.0% napthenes, 8.0% aromatics, and nil with respect to olefinic hydrocarbons. The maximum catalyst bed temperature, as measured at the outlet of the catalyst, was about 754 F. It should be noted that this operation was effected once-through without recycle of the 650 F.-plus heavier fraction.

A second operation was conducted in two phases, each of which made use of a catalyst consisting of 1. 8% nickel, 16.0% molybdenum and a carrier of 12.0% by weight of silica and 88.0% by weight of alumina. In both phases, the operating conditions included a pressure of 2,500 p.s.i.g., a liquid hourly space velocity of 0.5 and a hydrogen rate of 10,000 s.c.f./bbl. of fresh charge. In the first phase, the heavy fraction was recycled with the fresh feed and hydrogen to the top of the catalyst bed, whereas the second phase was effected with the fresh feed being introduced into the catalyst bed at a point such that about 30.0% of the catalyst was upstream and contacted only by the heavy recycle and hydrogen. In

both instances, the inlet temperature was adjusted to provide conversion to hydrocarbons below 650 F. of 75.0% by volume, on a once-through basis, exclusive of recycle. The initial inlet temperature was about 620 F., and increased as necessary until the unit lined-out at a temperature which resulted in the 75.0% convers1on.

Where the 650 F.-plus recycle, hydrogen and fresh charge was introduced into the top of the catalyst bed, the 75.0% conversion level was attained at a maximum catalyst bed temperature of 750 F. In the operation wherein the fresh charge was introduced at an intermediate point, and only the heavy recycle and hydrogen entered at the top of the catalyst bed, the maximum catalyst temperature, required to achieve 75.0% conversion, was 725 F. Itmust be noted that both operations were carried out at a combined feed ratio of 2.0 in order that this processing variable be eliminated as a factor affecting the results.

Example II A second comparative operation was effected utilizing both the conventional reaction zone wherein the total charge thereto, contacts all the catalyst, and the singlestage zone of the present invention wherein the fresh charge stock contacts only the bottom 75.0% of the catalyst. In the conventional operation, the peak or maximum catalyst temperature was 793 R; where the fresh charge stock entered'intermediate the catalyst bed, the maximum temperature was 769 F. Aside from a combined feed ratio of 2.01 versus 2.11, the other operating conditions were identical: the pressure was 2,000 p.s.i.g., the liquid hourly space velocity was about 0.95 (based upon the fresh feed only) and hydrogen was recycled in an amount of about 10,000 s.c.f./bbl. In these operations, the desired object was to maximize the quantity of middle-distillate hydrocarbons having an initial boiling point of 500 F. and en end boiling point of about 675 F. The product yield and distributions are presented in the followingTable III, the conventional system designated as Run A:

TABLE III.-PRODUCT DISTRIBUTION AND YIELD Run No A B Light gases, wt. percent:

Methane 0. 4 0. 2 0. 4 1. 2 0. 2

Liquid components, vol. percent:

utanes 2. 5 0. 4 1. 9 0. 6 1. 9 l. 3 13. 2 16. 0 18. 0 16. 6 500 F.675 F 65. 1 70. 4

While the data in Table III are self-explanatory, several items should be particularly noted. With conventional hydrocracking, twice as much light paraffinic gaseous components were produced: 1.6% by weight as compared to 0.8 Wt. percent. This is reflected in turn by comparing the butane-plus volumetric yield: 102.6% as compared to 105.3%.

The foregoing specification and examples indicate the benefits afforded single-stage hydrocracking through the utilization therein of the present invention.

We claim as our invention:

1. A process for converting a hydrocarbon charge stock, having an initial boiling point above a temperature of about 555 F. and containing contaminants from the group of sulfurous compounds, nitrogenous compounds and mixtures thereof, into lower-boiling hydrocarbon products having a predetermined end boiling point, which process comprises introducing said charge stock into a downflow conversion zone at an intermediate locus in the height thereof, commingling said charge stock therein with a hereinafter specified heavy hydrocarbon fraction boiling above said predetermined end boiling point and hydrogen, said conversion zone containing a hydrocracking catalytic composite and 'being maintained at hydrocracking conditions; withdrawing conversion zone efiiuent from the lower portion of said conversion zone and separating said effluent to provide a hydrogen-rich gaseous phase; fractionating the remaining portion of: said efiluent to recover normally liquid hydrocarbons having,said predetermined end boiling point; and, recycling a heavy hydrocarbon fraction, boiling above said predetermined end boiling point, in admixture with hydrogen, to said conversion zone at a locus substantially above that at which said charge stock is introduced, the points,of introducing said recycled heavy fraction and said charge stock to said conversionizone being vertically spaced apart in relation to the total hydrocracking catalyst contained there'm such that thefirst 103% to about 33.0% of said catalyst is contacted only by said recycled heavy fraction-hydrogen mixture while the remaining 90.0% to about 67.0% of saidcatalyst is contacted by said heavy fraction andsaid charge stock in admixture with hydrogen.

2. The process of claim 1 further characterized in that said charge stock is introduced into said conversion zone ata locus :within the upper one-third of said zone.

3. The process of claim 1 further characterized in that said conversion is effected at hydrocracking conditions including a temperature of from about 600 to about 850 F., a superatrnospheric:pressure: above about 700 p.s.i,g. and a liquid hourly space velocity within the range of from about 0.5 to 10.0. V a W 4. The process of claim 1 further characterized in that said catalytic composite comprises molybdenum, at least one metallic component selected from the iron-group and a siliceous refractory inorganic oxide.

L Regerences ited 77 UNITED STATES PATENTS 3,159,568 l2/1964 Price etj'al. 208-111 DELBERT E GANT Z, Primary Examiner A. RIMENS, Assistant Examiner US. 01 X.R. 208-89, 108

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