US3891539A

US3891539A - Hydrocracking process for converting heavy hydrocarbon into low sulfur gasoline

Info

Publication number: US3891539A
Application number: US445365A
Authority: US
Inventors: Gerald Verdell Nelson; Glenn Cooper Wray
Original assignee: Texaco Inc
Current assignee: Texaco Inc
Priority date: 1971-12-27
Filing date: 1974-02-25
Publication date: 1975-06-24
Anticipated expiration: 1992-06-24
Also published as: CA984324A; DE2255321A1; IT972915B; BE793384A; JPS4880603A; NL7217483A; JPS5139882B2; GB1378829A

Abstract

A hydrocracking process wherein heavy hydrocarbon oils having from about 10 to 50 percent boiling above 1,000*F. and containing appreciable amounts of sulfur, nitrogen, and metal-containing compounds as well as asphaltenes are converted into a minor fraction of low sulfur residual fuel oil and a major fraction of low sulfur gasoline. The process comprises hydrocracking the heavy oil with molecular hydrogen, at a temperature of about 700*-850*F. in the presence of a sulfur and nitrogen resistant hydrocracking catalyst comprising a hydrogenating component supported upon an amorphous inorganic oxide cracking base to convert the heavy hydrocarbon oil into a gas-oil fraction and a low sulfur residual fraction; separating the gas-oil fraction from the residual fraction; hydrocracking the gas-oil fraction with molecular hydrogen, at a temperature of 700*-780*F., in the presence of a sulfur and nitrogen resistant hydrocracking catalyst comprising a hydrogenation component supported upon a cation exchanged crystalline silica-alumina zeolitic molecular sieve cracking base to yield low sulfur, low nitrogen gasoline.

Description

United States Patent 1191 Nelson et a1.

m1 3,891,539 ['45] June 24, 1975 HYDROCRACKING PROCESS FOR CONVERTING HEAVY HYDROCARBON INTO LOW SULFUR GASOLINE [75] Inventors: Gerald Verdell Nelson, Nederland.

Tex.; Glenn Cooper Wray, Dyersburg, Tenn. [73] Assignee: Texaco Inc., New York, NY. [22] Filed: Feb. 25, 1974 [21] Appl. No.: 445,365

Related US. Application Data [63] Continuation-impart of Ser. No. 212,565. Dec. 27.

1971. abandoned.

[52] US. Cl. 208/59; 208/D1G. 2; 208/52 CT; 208/77; 208/102; 208/215; 208/251 H; 252/455 R; 208/254 H [51] Int. Cl. B0lj 11/82; ClOg 13/02 [58] Field of Search 208/59 [56] References Cited UNITED STATES PATENTS 3.360.457 12/1967 Peck et a1 208/59 3.540.997 11/1970 Hahn et a1. 208/69 3,551,323 12/1970 Hamblin 208/58 3.562.144 2/1971 Child et a1. 208/59 3,583,902 6/1971 Masologites et a1. 208/59 3.617.501 11/1971 Eng 208/89 3.623.974 11/1971 Mounce ct a1... 208/97 3.640.817 2/1972 O'Hara 208/59 3.684.688 8/1972 Rose1ius.... 208/50 3.723.296 3/1973 Hahn 208/89 3,773,653 11/1973 Nongbri et a1 208/50 C. G. Ries;

[ 57] ABSTRACT A hydrocracking process wherein heavy hydrocarbon oils having from about 10 to 50 percent boiling above 1,000F. and containing appreciable amounts of su1- fur. nitrogen, and metal-containing compounds as well as asphaltenes are converted into a minor fraction of low sulfur residual fuel oil and a major fraction of low sulfur gasoline. The process comprises hydrocracking the heavy oil with molecular hydrogen. at a temperature of about 700-850F. in the presence of a sulfur and nitrogen resistant hydrocracking catalyst comprising a hydrogenating component supported upon an amorphous inorganic oxide cracking base to convert the heavy hydrocarbon oil into a gas-oil fraction and a low sulfur residual fraction; separating the gas-oil fraction from the residual fraction; hydrocracking the gasoil fraction with molecular hydrogen. at a temperature of 700-780F.. in the presence of a sulfur and nitrogen resistant hydrocracking catalyst comprising a hydrogenation component supported upon a cation exchanged crystalline silica-alumina zeolitic molecular sieve cracking base to yield low sulfur. low nitrogen gasoline.

13 Claims, 1 Drawing Figure IIYDROCRACKING PROCESS FOR CONVERTING HEAVY HYDROCARBON INTO LOW SULFUR GASOLINE RELATED APPLICATIONS This application is a continuation-in-part of copending application Ser. No. 2l2,565 filed Dec. 27, 1971, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the hydrocracking of heavy hydrocarbon oils. Particularly, it relates to hydrocracking heavy hydrocarbon oils having from about 10 to 50 volume percent boiling above IOF. and containing appreciable amounts of sulfur, nitrogen, and metalcontaining compounds as well as asphaltenes and other coke forming hydrocarbons. By the process of this invention such heavy hydrocarbon oils are converted into a minor fraction of heavy residual fuel oil and a major fraction of low sulfur gasoline. Such gasoline product is suitable for further processing, such as catalytic reforming or the like, to upgrade the quality and octane number. More particularly, the process comprises a two-stage catalytic hydrocracking process wherein heavy oil charge is contacted with molecular hydrogen in a first reaction zone in the presence ofa hydrocrack ing catalyst comprising a hydrogenation component selected from the group consisting of Group VI metals, Group VIII metals, their oxides, their sulfides, and combinations thereof supported upon an amorphous refractory oxide cracking base, at a temperature in the range of 700-850F., for conversion of from 50 to 90 volume percent of the heavy hydrocarbon oil into a sulfur and nitrogen containing gas-oil having very low metals content without any substantial production of gasoline; separating the effluent from the first hydrocracking zone into a gas-oil fraction and a residual fuel fraction; and hydrocracking the gas-oil fraction in a second hydrocracking zone with molecular hydrogen in the presence of a catalyst comprising a hydrogenation component selected from the group consisting of Group VI metals, Group VIII metals, their oxides, their sulfides, and combinations thereof supported upon a refractory metal oxide cracking base such as alumina, silica-alumina, zirconia, titania, cation exchanged crystalline silica-alumina zeolites, etc., at a temperature in the range of 700-780F. for conversion of the sulfur and nitrogen containing gas-oil fraction into a low sulfur and nitrogen containing gasoline.

Within the present specification and claims, the term gas-oil fraction" is meant to include hydrocarbon fractions derived from crude petroleum, shale oil and the like, or from a hydrocarbon conversion process such as hydrocracking; catalytic cracking, thermal cracking, coking, etc., which fraction boils within the range of from about 430F. to about 1000F. The term gas-oil" as used herein is meant to include the light, medium, and heavy gas-oils as those terms are commonly employed in the art. The term gasoline" is meant to include the hydrocarbon fraction boiling in the range of from about 55F. to 430F., or, as it is sometimes expressed, C /430F.". The term dry gas refers to a fraction comprising methane, ethane, and propane when such fraction is separated from normally liquid, higher boiling hydrocarbons.

Hydrocracking processes for the conversion of heavy hydrocarbon oils into lower boiling fractions are well known. Examples of such hydrocracking processes may be found in such sources as US. Pat. Nos. 3,640,817; 3,617,50l; 3,583,902; 3,562,144; 3,551,323; 3,540,997; 3,360,457; and 3,254,017. In such hydrocracking processes, it is recognized that when a heavy hydrocarbon oil with a substantial volume boiling above IOOOF., and containing substantial amounts of asphaltenes, sulfur, nitrogen, and metal-containing organic compounds, is treated in the presence ofa hydrocracking catalyst, such compounds act as catalyst poisons. In addition, compounds of such metals as vana dium, iron, nickel, sulfur, etc., which generally are present in such hydrocarbon oils tend to deposit ash and metals upon the hydrocracking catalyst which increases the rate of coke formation and deposition, thereby interfering with catalytic activity by covering the active catalytic sites.

Efforts have been made to minimize the poisoning effects and catalyst deactivating effects of such sulfur, nitrogen, and metal compounds. For instance, U.S. Pat. No. 3,254,017 describes a hydrocracking process wherein a heavy hydrocarbon oil is sequentially treated in two hydrocracking zones. In the first hydrocracking zone, the heavy hydrocarbon oil is partially hydrocracked to gas-oil and is partially desulfurized and denitrogenated with molecular hydrogen in the presence of a selected catalyst. The catalyst selected for the first hydrocracking zone comprises a hydrogenation component selected from Group VI metals, Group VIII metals, their oxides, their sulfides and mixtures thereof supported upon an amorphous refractory oxide cracking base having large pore openings in the range of at least 20 up to 200 angstrom units and preferably larger, such base being selected from alumina, silica-alumina, zirconia, titania, etc. Such a large pore, amorphous cracking base has a capacity for adsorbing or otherwise collecting substantial quantities of ash and metals such as vanadium, nickel, iron and copper without destroying the hydrocracking activity of such catalyst. Effluent from such a first hydrocracking zone, comprising a gasoil fraction and unconverted residual fraction, is then treated in a second hydrocracking zone under conditions such that a substantial portion of the gas-oil fraction is hydrocracked into lower boiling fractions such as gasoline but with a limitation upon operating conditions such that not more than a strict upper limit of 30 volume percent of the unconverted residual fraction is hydrocracked into lower boiling fractions. To obtain the desired hydrocracking of the gas-oil fraction without substantial hydrocracking of the residual fraction, a second selected hydrocracking catalyst is employed in the second hydrocracking zone. Such second catalyst comprises a hydrogenation component selected from Group V] metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof, supported upon a cracking base comprising a cation exchanged crystalline silica-alumina zeolite containing cations selected from hydrogen, ammonia, divalent metals such as calcium, magnesium and zinc, and rare earth metals, and containing less than about 5 percent sodium. Such second selected catalyst has uniform pore openings in the limited range of 5-20 angstroms such that hydrocarbon molecules contained in the residual fraction will not enter the catalyst pores to be hydrocracked. By limiting the access of the residual fraction hydrocarbons, the

accumulation of coke, ash, and metal within the second hydrocracking catalyst is reduced such that the hydrocracking activity of the second catalyst is not severely affected by such accumulation. Effluent from the second hydrocracking zone is separated into desired product fractions such as dry gas, gasoline, and heavy fuel oil. Unconverted residual fraction may be recycled to the first reaction zone and unconverted gas-oil may be recycled to the second hydrocracking zone. Thus, while recognizing the deleterious effect of metals and coke accumulation upon a gas-oil hydrocracking catalyst, the method of US. Pat. No. 3,254,017 attempts to prevent such metal and ash deposition by strictly limiting conversion in the second hydrocracking zone. Consequently, high yields of gasoline are difficult or impossible to obtain by hydrocracking heavy hydrocarbon oils according to this procedure.

In US. Pat. No. 3,562,!44 a process is taught wherein heavy hydrocarbon oil, containing nitrogen, sulfur, and 1 percent or more Conradson Carbon is hydrocracked in a first hydrocracking zone to yield substantial amounts of gasoline; and wherein fractions of the first reaction zone effluent boiling above gasoline are hydrocracked in a second reaction zone to yield substantial amounts of high quality jet fuel. A hydrocracking catalyst comprising sulfided nickel and tungsten upon a zeolitic refractory metal oxide cracking base is employed in the first reaction zone, and in the second hydrocracking zone a catalyst comprising noble metal (platinum or palladium) upon a refractory metal oxide cracking base is employed. Since platinum and palladium are very sensitive to sulfur and nitrogen, reaction conditions in the first reaction zone must be sufficiently severe to remove a substantial portion of the sulfur and nitrogen contained in the hydrocarbon oil charge. No account is taken, in US. Pat. No. 3,562,144, of the effect of metals and ash upon the activity of the catalyst in the first hydrocracking zone. Metals and ash deposited upon the catalyst cause increased production of coke, and under the severe reaction conditions of the first hydrocracking zone coke production is substantial, causing rapid catalyst deactivation.

A combined hydretreating-hydrocracking process for whole crude oil is disclosed in US. Pat. No. 3,6l7,50l. In one embodiment, whole crude oil is hydrotreated for removal of sulfur and nitrogen compounds in a hydrotreating zone; hydrotreating effluent is fractionated into light product fractions, a heavy gas oil fraction and, a low sulfur fuel oil fraction; and the heavy gas oil is hydrocracked into additional light products. By following the disclosed process a very substantial portion of the gas-oil component of the crude oil can be converted to gasoline, however the residual fraction of the crude oil, boiling above lOF. remains substantially unconverted, and is recovered from the process as a low value fuel oil product.

It has been observed in the hydrocracking of heavy hydrocarbon oils containing sulfur, nitrogen and compounds of metals such as nickel, vanadium and iron, that, although the hydrocracking activity may be maintained by properly selecting a first hydrocracking zone catalyst, such catalyst rapidly loses its activity to convert sulfur and nitrogen compounds. Particularly, it has been noted that at temperatures of about 790F. and higher desulfurization and denitrogenation activity of such catalyst undergoes a very rapid decline with increased temperature. It has also been noted that at temperatures of about 790F. up to about 850F. the activity of such catalyst to hydrocrack heavy oils into lower boiling gas oil fractions is not substantially effected. The decline in desulfurization activity has been observed to be greater for lower molecular weight sulfur compounds than for higher molecular weight sulfur compounds. Consequently, we have discovered that cffluent from the first hydrocracking zone may be separated into a relatively low sulfur residual fraction and a sulfur and nitrogen containing gas-oil fraction. Substantial amounts of metals are removed in the first hydrocracking zone, such that the gas-oil fraction contains only minor amounts of metals even though the residual fraction may still contain an appreciable concentration of metals. If the entire liquid effluent from a first hydrocracking zone is passed into a second hydrocracking zone, the metals, ash, coke, asphaltenes, etc. contained in the residual fraction will accumulate upon the second reaction zone catalyst thereby requiring increased temperatures to maintain the desired hydrocracking activity for the conversion of gas-oil. However, as above noted, as the reaction temperature exceeds about 790F., the desulfurization and denitrogenation activity of hydrocracking catalyst declines very rapidly, without a concomitant decline in the hydrocracking activity of such catalyst. Consequently, even though a relatively efficient conversion of heavy hydrocarbon oils into gasoline may be obtained by employing two hydrocracking zones in sequential alignment, the gasoline product from such a process may contain substantial amounts of sulfur and nitrogen compounds, particularly when the catalyst has been in service for a period such that the reaction temperature of the second hydrocracking zone has been increased to a temperature above about 790F. in order to maintain the hydrocracking activity of the second hydrocracking catalyst.

SUMMARY OF THE INVENTION Now according to the method of the present invention, we have discovered an improved process for the conversion into gasoline of a heavy hydrocarbon oil comprising from 10 to 50 volume percent hydrocarbon boiling above l000F. and containing at least 1 percent Conradson Carbon, asphaltenes, about 0.1 to 8 percent sulfur, about I00 to over 1000 ppm nitrogen, as well as nickel, vanadium and iron compounds. According to the process of the invention, such a hydrocarbon oil charge is hydrocracked in a first hydrocracking zone to yield a major portion of a low metals content, sulfur and nitrogen containing gas-oil fraction, and a partially desulfurized residual fraction boiling above I00OF. under hydrocracking conditions wherein no more than percent of the hydrocarbon oil charge residual fraction boiling above l000F. is converted to gas-oil and wherein 5 percent or less hydrocracked gasoline is produced; and wherein the gas-oil fraction is hydrocracked in a second hydrocracking zone with molecular hydrogen at a temperature of from about 700-780F. in the presence of a sulfur and nitrogen resistant hydrocracking catalyst to yield low sulfur, low nitrogen content gasoline.

Catalyst selected for the first hydrocracking zone comprises a hydrogenation component selected from Group VI metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof supported upon an amorphous inorganic oxide cracking base. Such cracking base is selected such that it has pore openings of from at least about to 200 angstroms and preferably larger. so a substantial portion of metal contaminants which may be present in the heavy hydrocarbon oil charge, may be adsorbed within such cracking base without severely affecting the hydrocracking activity of the first hydrocracking catalyst.

By separating the first hydrocracking reaction zone effluent into a gas-oil fraction and residual oil fraction, a portion of the residual oil may be recirculated to the first reaction zone for conversion into additional gas-oil fraction. However, we have discovered that the conversion of heavy hydrocarbon oil charge residual fraction boiling above IOOOF. into gas-oil fraction boiling below 1000F. should be limited to a maximum of about 90 volume percent, and preferably no more than 80 volume percent. In the event that conversion of the residual fraction of the heavy hydrocarbon oil charge is carried out to more than about 90 volume percent, asphaltenes and other heavy hydrocarbon materials contained in the hydrocarbon oil charge tend to precipitate onto the first cracking catalyst, thereby preventing access of convertible hydrocarbons to the active catalytic sites. Also, we have discovered that controlling hydrocracking severity in the first hydrocracking zone to a severity such that no more than 5 percent, and preferably less gasoline is produced therein, improves desulfurization of residual fuel oil, lengthens catalyst life, and reduces the rate of coke deposition upon the first zone hydrocracking catalyst. Additionally, any gasoline produced in the first hydrocracking zone will contain substantial amounts of undesirable nitrogen and sulfur compounds such that reduction of gasoline production from the first hydrocracking zone substantially improves the quality of gasoline recovered from this process.

The gas-oil fraction, recovered from the effluent of the first hydrocracking reaction zone, contains sulfur and nitrogen compounds, but is relatively free of metal compounds, such as the compounds of nickel, vanadium and iron. Therefore, the gas-oil fraction may be rather severely hydrocracked and simultaneously desulfurized and denitrogenated in the second hydrocracking zone to form desulfurized and denitrogenated gasoline, by employing a second hydrocracking catalyst which maintains its activity in the presence of sulfur and nitrogen compounds and employing temperatures in the range of 700780F. Such second hydrocracking catalyst is comprised of a hydrogenation component selected from the Group V] metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof, supported upon a refractory metal oxide cracking base. The cracking base may be in the amorphous form, such as alumina, silica-alumina, zirconia, silica-zirconia, silica-titania, etc., or the cracking base may comprise a crystalline silica-alumina zeolite wherein the sodium cations have been exchanged for cations selected from hydrogen, ammonia, calcium, magnesium, zinc, etc.

By maintaining the reaction temperature, within the second hydrocracking zone, in the range of 700-780F. the gas-oil fraction may be hydrocracked into gasoline and simultaneously desulfurized and denitrogenated. At temperatures above about 780F., the desulfurization and denitrogenation activity of the preferred second hydrocracking catalyst declines rapidly.

By following the method of the present invention. a heavy hydrocarbon oil containing sulfur, nitrogen, and metal compounds may be converted into gasoline which is low in sulfur and nitrogen content and which is essentially free of metal contaminants. Such gasoline is suitable for further treatment, such as in a catalytic reforming unit, to improve the quality and octane number thereof.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing is a schematic representation of a process for carrying out the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Heavy hydrocarbon oil charge stocks within the contemplation of the present invention include those hydrocarbon oils comprising from [0 to 50 volume percent of a residual fraction boiling above 1,000F. and containing at least about I weight percent Conradson Carbon, from 0.1 to 8 percent sulfur, and from 100 to 1000 ppm or more nitrogen. Examples of such heavy hydrocarbon oils include total crudes, atmospheric and vacuum residuum, shale oils, tar sand oils, petroleum residues, coal tar, heavy coker distillates, heavy catalytically cracked recycle stocks, etc. Such hydrocarbon oils may contain substantial amounts, from 50 to 1000 ppm and more, metal compounds such as organometallic compounds of vanadium, nickel, iron, copper, etc. Such heavy hydrocarbon oils may also contain substantial amounts of refractory hydrocarbons such as asphaltenes and other high molecular weight hydrocarbons which may lead to the deposition of coke upon the hydrocracking catalyst.

The hydrogen which is employed with such heavy hydrocarbon oils in the first hydrocracking zone and the gas-oil fraction in the second hydrocracking zone need not be I00 percent pure. Conveniently, hydrogen from the reaction zones is recirculated within the process to conserve the consumption of hydrogen, and only sufficient fresh hydrogen is vented from the process to maintain hydrogen purity in the range of about percent or higher. Sources of hydrogen commonly available within a refinery such as catalytic reformer hydrogen with a purity of about percent or higher are suitable as sources of makeup hydrogen for the process to replace the hydrogen consumed in the reactions and that which is vented.

According to this invention, in the first hydrocracking zone, a major portion of the heavy hydrocarbon charge is hydrocracked into a gas-oil fraction without substantial production of lighter hydrocarbons such as gasoline and dry gas. An effective temperature range for this conversion is from about 700F. to about 850F. In order to limit coke deposition upon the catalyst in the first hydrocracking zone, it is desirable to maintain a sufficient hydrogen partial pressure to saturate a large percentage of the unsaturated hydrocarbons which result from cracking high boiling hdrocarbons into lower boiling hydrocarbons. The desired hydrogen partial pressure may be maintained by utilizing hydrogen to hydrocarbon ratios in the range of from about L000 to about 15,000 standard cubic feed per barrel and operating pressures of from about 500 to about 3,000 psig. Liquid hourly space velocity (LHSV), expressed as volumes of oil per hour per volume of catalyst (Vo/Hr/Vc) of from about 0.1 to about l may be utilized. Preferably, LHSVs in the range of 0.3 to 5.0 are employed to obtain a relatively long reac tion period before the catalyst must be regenerated.

Hydrocracking catalysts which may be employed in the first hydrocracking zone comprise those hydrocracking catalysts which are sulfur and nitrogen resistant, and which can maintain hydrocracking activity in the presence of relatively large amounts of metal compounds such as are commonly found in heavy hydrocarbon oils. Such a first hydrocracking catalyst comprises a hydrogenation component supported upon a refractory metal oxide cracking base. The hydrogenation component may be selected from Group Vl metals, Group VIII metals, their oxides, their sulfides, and

mixtures thereof. Preferably, the hydrogenation component comprises a Group Vl metal oxide or sulfide in combination with a Group VIII metal oxide or sulfide. Examples of particularly preferred hydrogenation components include cobalt-molybdenum sulfide mixtures, nickel-cobalt-molybdenum sulfide mixtures, and nickel-molybdenum sulfide mixtures. Examples of other combinations which may be effectively employed include nickel-cobalt mixtures, nickel oxide-cobalt oxide mixtures, nickel oxide-cobalt oxide-molybdenum oxide mixtures, and nickel cobalt-molybdenum mixtures. When a Group V] metal or its oxide or sulfide is employed as a hydrogenation component, it is preferable that such metal be present in an amount of from about 5.0 to about 25.0 weight percent of the total catalyst. When a Group VIII metal, or its oxide or sulfide, is employed as the hydrogenation component, it is preferable that such metal be present in an amount from about 0.3 to about 8.0 weight percent of the total catalyst. When Group V] and Group VIII metals, their oxides, or their sulfides are employed in combination, it is preferred that the Group V! metal be present in an amount from about 5.0 to about 25.0 weight percent and the Group Vlll metal be present in an amount from about 1.0 to about 8.0 weight percent of the total catalyst.

The refractory metal oxide cracking bases which may be employed in the first hydrocracking zone include those amorphous oxides having cracking activity and which have relatively large pore openings in the range of to 200 angstroms and larger suitable for adsorption of substantial amounts of metal compounds and coke from the hydrocarbon charge oil without substantially affecting the hydrocracking activity. Examples of such amorphous cracking bases include alumina, silicaalumina, silica-zirconia, silica-titania, mixtures thereof, etc. At the temperatures and space velocities specified herein, such amorphous cracking bases having good cracking activity are useful for converting a major portion of the hydrocarbon oil charge boiling above about 1000F. into gas-oil boiling in the range of 430F.-l000F. without substantial production of gasoline and dry gas. Under such operating conditions, coke production is substantially decreased over more severe conditions, thus extending the useful life of the first hy drocracking catalyst.

By employing such selected catalyst in the first hydrocracking zone, the gas-oil conversion product of the heavy hydrocarbon charge is substantially demetalized. However, with accumulation of metals and coke upon the catalyst, it is necessary to increase the reaction zone temperature incrementally in order to maintain the desired hydrocracking of the heavier fraction of the hydrocarbon charge oil into gas-oil fraction. As the hydrocracking reaction temperature exceeds about 790F., desulfurization and denitrogenation activity of the first selected hydrocracking catalyst decreases rapidly. It has been noted that such decline in desulfurization activity is proportionally greater for oils boiling in the gas-oil range than for residual fractions. Therefore, even though desulfurization activity of the first hydrocracking catalyst declines at temperatures above 790F., the residual fraction effluent from the first hydrocracking reaction zone is still substantially desulfurized and may be recovered, if desired, as a relatively low sulfur content heavy fuel oil containing from about 1 percent or less sulfur. Hydrocracking reaction temperatures below 700F. are not preferred, as conversion of heavy hydrocarbon oils into the desired gas-oil fraction is not substantial, thus requiring recycle of large volumes of unconverted residual fraction to the first reaction zone. Reaction temperatures above about 850F. are not desirable because, at these temperatures, substantial amounts of the heavy hydrocarbon oil are converted into low quality sulfur containing gasoline and dry gas.

It has been found that conversion of the residual fraction of a hydrocarbon charge oil greater than about 90 volume percent into gas-oil fraction boiling below l000F. is undesirable. At conversions of about 90 percent or greater, asphaltenes and other high molecular weight hydrocarbon components of the heavy hydrocarbon charge oil precipitate in the reaction zone and collect upon the surface of the first hydrocracking catalyst. The precipitated asphaltenes and high molecular weight hydrocarbons form tarry films and coke upon the surface of the hydrocracking catalyst, effectively blinding the reactive catalytic sites, such that reactant hydrocarbons may not contact such active sites. Therefore, it is within the contemplation of the present invention that conversion of the residual fraction of heavy hydrocarbon charge oil into gas-oil range hydrocarbons boiling below l000F. not exceed about 90 volume percent and preferably, such conversion be maintained at not more than about 80 percent of the heavy hydrocarbon charge.

A portion of the unconverted residual recycle fraction boiling above I000F. may be withdrawn from the process to maintain conversion of the heavy hydrocarbon charge within the desired range. Such residual recycle fractions may be employed as a heavy fuel oil, and since the desulfurization activity of the first hydrocracking catalyst remains more effective for the recycle fraction than for the gas-oil fraction at temperatures above 790F., the residual recycle fraction which is yielded from the process is relatively low in sulfur content, containing about one percent or less sulfur.

Efi'luent from the first hydrocracking zone may be separated, in a high pressure separation zone, into a first gas fraction comprising hydrogen and a liquid fraction. The hydrogen containing gas fraction may be recirculated to the inlet of the first hydrocracking reaction zone for contact with additional amounts of heavy hydrocarbon oil charge. A portion of the recycle gas may be vented to remove hydrogen sulfide, ammonia, and low boiling hydrocarbons in order to maintain the recycle gas hydrogen concentration at the desired value of about percent or higher. Additional hydrogen may be added to the recycle gas to replace that consumed in the reaction and that vented from the process.

Liquid from the first high pressure separator, comprising residual fraction, gas-oil fraction, and a small amount of gasoline and dry gas is passed into a fractionation zone. In the fractionation zone, the residual frac' tion, the gas-oil fraction, the gasoline and dry gas are separated. A portion of the residual fraction may be recycled from the fractionation zone to the inlet of the first hydrocracking zone for conversion into additional amounts of gas-oil fraction. An amount of the residual oil fraction is recovered from the fractionation zone such that the conversion of the residual fraction of the heavy hydrocarbon oil charge to gas-oil fraction boiling below l000F. is not greater than about 90 volume percent, and preferably not greater than about 80 volume percent.

The gas-oil fraction from the fractionation zone contains substantial amounts of sulfur and nitrogen compounds and only very small or trace amounts of metal contaminants. Such gas-oil fraction is passed from the fractionation zone to the second hydrocracking zone for conversion into gasoline. If the heavy hydrocarbon charge oil is particularly heavy, containing from about 30 to about 50 percent residual hydrocarbons boiling above lO0F., it is desirable to recycle a small portion of the gas-oil fraction to the inlet of the first hydrocracking zone as a viscosity cutting oil for the heavy hydrocarbon charge. Such gas-oil fraction used as viscosity cutting oil in the first reaction zone serves also as a wash oil, and helps prevent accumulation of coke, tar and other high molecular weight hydrocarbons upon the surface of the first hydrocracking catalyst.

In the second hydrocracking zone, the gas-oil fraction is treated with molecular hydrogen in a hydrogen to hydrocarbon ratio of from about 1,000 to about 10,000 standard cubic feet per barrel (scf/b) at a temperature of from about 700780F., a pressure of from about 500 to about 2,500 psig, in the presence ofa sulfur resistant hydrocracking catalyst at a liquid hourly space velocity of from about 0.5 to about 8.0 Vo/Hr/Vc for conversion of said gas-oil fraction into a desulfurized and denitrogenated gasoline fraction boiling in the range of 55F. to 430F.

Temperatures in the range of from about 700-780F. are preferred in the gas-oil hydrocracking reaction because at temperatures below about 700F. the rate of hydrocracking and desulfurization of the gas-oil fraction is too low to be economical and at temperatures of about 790F. and higher the desulfurization and denitrogenation activity of hydrocracking catalysts declines rapidly. The hydrogen to hydrocarbon ratio and pressure are maintained within the described limits in order to provide a hydrogen partial pressure sufficient to promote hydrogenation of cracked hydrocarbons and promote desulfurization and denitrogenation of the gasoline fraction.

Catalysts useful within the second hydrocracking zone have hydrocracking activity and are resistant to sulfur and nitrogen poisoning. Such hydrocracking catalysts comprise a hydrogenation component selected from Group V! metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof. When Group Vl metals, their oxides or their sulfides are employed, such metals are preferably present in an amount from about 5.0 to about 25.0 weight percent of the total catalyst. When Group VIII metals are employed as hydrogenation components, such metals are preferably present in an amount from about 0.3 to about 8.0 weight percent of the total catalyst. When Group VI and Group VIII metals, or their compounds are used in combination, Group Vl metals are preferably present from about 5.0 to 25.0 weight percent of the catalyst and Group VIII metals are present in an amount of from about 1.0 to 8.0 weight percent of the catalyst. Examples of hydrogenation components which are effective in the second hydrocracking zone include a nickel-tungsten combination, a nickel-oxide-tungsten oxide combination, a nickel-sulfide-tungsten sulfide combination, a cobalt sulfide-molybdenum sulfide combination, and a nickel sulfide-cobalt sulfide-molybdenum sulfide combination. Such hydrogenation components are supported upon a refractory metal oxide cracking base. Such cracking base may be selected from amorphous metal oxides such as alumina, silica-alumina, silica-zirconia, silica-titania, etc.; from cation exchanged crystalline silica-alumina, zeolitic molecular sieves; and from mixtures thereof. Preferably, for the zeolitic molecular sieves, cations such as hydrogen, ammonia, calcium, magnesium, zinc, etc. have been exchanged therein until the sodium ion content is less than 5 percent and preferably less than I percent. A particularly effective hydrogenation component for the second hydrocracking catalyst comprises a mixture of about 4.0-8.0 weight percent nickel sulfide and about 9.0-25.0 weight percent tungsten sulfide supported upon a cracking base. A particularly effective cracking base comprises 40 to 85 percent amorphous silica-alumina having a silica/alumina ratio of from about 2:1 to about 9: l and about [5 to 60 percent ofa hydrogen or amm onia exchanged, type Y crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 to about 20 angstrom units, and having less than 1 percent sodium content.

Effluent from the second hydrocracking zone is separated into a second gas fraction comprising hydrogen and a liquid fraction in a second high pressure separation zone. The second gas fraction may be recycled to the inlet of the second hydrocracking zone in order to conserve hydrogen. When the second gas fraction is recycled, a portion may be vented to remove hydrogen sulfide, ammonia, and low molecular weight hydrocarbons from the system thereby maintaining hydrogen purity within the desired range of about percent or higher. Makeup hydrogen may be added to the recycle gas to replace hydrogen consumed in the second hydrocracking zone and that vented.

The liquid component of the second hydrocracking reaction zone effluent comprises unreacted gas-oil fraction, gasoline and dry gas. The gasoline is desulfurized and denitrogenated and is suitable for further processing, such as catalytic reforming, to improve the quality and octane number thereof. The gasoline is separated from the liquid fraction and unconverted gas-oil may then be recycled to the second hydrocracking zone, along with gas-oil fraction from the first hydrocracking zone, for conversion into additional amounts of gasoline. It is contemplated that the unconverted gas-oil fraction may be recycled to the second hydrocracking zone to extinction, such that the entire gas-oil fraction charged from the first hydrocracking zone to the second hydrocracking zone is completely converted into gasoline and dry gas.

Conveniently, liquid effluent from the second hydro cracking zone may be charged to the fractionation zone for separation into its component fractions. [n such a case, liquid effluent from the first hydrocracking zone and liquid effluent from the second hydrocracking zone are charged to the fractionation zone wherein they are separated into a residual fraction, a gasoil fraction, dry gas and gasoline. A portion of the residual fraction is yielded to limit conversion of heavy hydrocarbon charge to 90 volume percent or less, and the remaining residual fraction may be recycled to the first hydrocracking zone for conversion into additional gas-oil fraction. The gas-oil fraction from the fractionation zone is charged to the second hydrocracking zone. The gasoline and dry gas are recovered as products from the fractionation zone.

The process of the present invention may be further understood by reference to the attached drawing, which is a schematic diagram of a preferred embodiment of the invention. For clarity, many elements commonly found in a commercial process such as pumps, valves, instrumentation, etc. not necessary for a proper description of the present invention have been omitted. It is to be understood that such drawing is intended to demonstrate the invention only and is not intended to limit such invention in any manner.

Referring now to the drawing, a residuum hydrocarbon containing up to about weight percent sulfur, 1 weight percent nitrogen, 600 ppm vanadium, 100 ppm nickel and 200 ppm iron, charged at a rate of about 1000 barrels per hour (B/H) in Line 1 is mixed with 400 B/H of residual fraction recycle from Line 2, a gasoil fraction wash stream from Line 3 and a recirculating hydrogen gas stream from Line 4 to form a first reaction mixture, at a pressure of about 2,000 psig, a hydrogen to hydrocarbon ratio of about 10,000 scf/b, and a temperature of about 780F., which is contacted with a first hydrocracking catalyst comprising about 2.0 weight percent cobalt and about 10.0 weight percent molybdenum supported upon an amorphous silicaalumina base having pore openings of from about to about 1,000 angstroms. The reaction mixture contacts the hydrocracking catalyst at a LHSV of about 0.5 vo/hr/vc.

From the first hydrocracking zone, an effluent stream is withdrawn via line 6 and passes into a first high pressure separation zone 7 wherein a first gas fraction comprising hydrogen is separated from a first liquid fraction. A portion of the first gas fraction is vented from the first high pressure separation zone via line 8 to maintain the concentration of hydrogen within the first gas fraction at about 75 volume percent or higher. The remainder of the first gas fraction passes from the high pressure separator 7 via line 9 to compressor 10. From compressor 10 the first gas fraction is recycled via line 4 for combination with additional amounts of residuum charge to form a reaction mixture for charge to the first hydrocracking zone 5, as hereinabove described. Makeup hydrogen of about 85 percent purity or higher is added to the recycle gas in line 4 via line 11 to make up for the amount of hydrogen consumed in the first hydrocracking zone and for the amount of hydrogen vented via line 8. From the first high pressure separation zone a first liquid fraction is transferred via line 12 and is combined with a second hydrocracking zone liquid effluent (as will hereinafter be further described) from line 13. The combined hydrocracking zone liquid effluents pass via line 14 into fractionation zone 15 wherein they are separated into a residual fraction, a gas-oil fraction, gasoline and dry gas. From fractionation zone 15, residual fraction is withdrawn via line 16 and a portion of the residual fraction, at a rate of about 400 B/H is recycled via line 2 for combination with additional amounts of residuum as hereinbefore described. The remainder of the residual fraction at a rate of about 200 B/H is withdrawn from the process via line 17 as a heavy fuel oil, containing about 1.0 weight percent sulfur. Such residual fraction is withdrawn as fuel oil at such a rate to maintain the overall conversion of hydrocarbon oil charge boiling above I000F. into gasoil boiling below 1000F. to about volume percent or less.

The gas-oil fraction, containing about 0.5 weight percent sulfur and about ppm nitrogen, is withdrawn from fractionator 15 via line 18. A small portion ofgasoil fraction at a rate of about 50 B/H is transferred from line 18 via line 3 to the inlet of the first hydrocracking zone as a wash-oil stream as has hereinabove been described. The remainder of the gas-oil fraction is mixed with the second recirculating gas stream from line 19 to form a second reaction mixture and is passed into second hydrocracking zone 20. In second hydrocracking zone 20, the second reaction mixture at a temperature of about 750F., a pressure of about 1,500 psig, a hydrogen to hydrocarbon ratio of about 7,500 scf/b contacts a second hydrocracking catalyst comprising about 6.0 weight percent nickel sulfide and about 19 weight percent tungsten sulfide hydrogenation component supported upon a hydrogen exchanged crystalline silica-alumina zeolitic molecular sieve having pore openings of from about 5 to about 20 angstrom units, at an LHSV of about 1.5 vo/hr/vc to desulfurize, denitrogenate, and convert said gas-oil fraction into gasoline. Effluent from the second hydrogenation zone 20 is passed via line 21 into a second high pressure separator 22 wherein the effluent is separated into a second gaseous fraction and a second liquid fraction. A portion of the second gaseous fraction is vented via line 23 to remove hydrogen sulfide, ammonia, and low boiling hydrocarbons from the system and the remainder of the second gaseous fraction passes via line 24 into compressor 25. From compressor 25 the second gaseous fraction passes as second recycle gas into line 19 for combination with additional gas-oil fraction as hereinabove described. Makeup hydrogen to replace the hydrogen consumed in the second hydrocracking zone and the hydrogen vented via line 23 is added via line 26 to the second recycle gas stream in line 19.

Liquid component of the second hydrocracking zone effluent passes from the second high pressure separator 22 via line 13 for admixture with first hydrocracking zone liquid effluent in line 14 as hereinabove described. [n the fractionation zone 15 a dry gas comprising methane, ethane, and propane is separated and removed at a rate of about 250,000 scf/h via line 27. A gasoline stream is separated in fractionation zone 15 for recovery as a product. Such gasoline, at a rate of 825 Elf! and containing about 20 ppm sulfur and 2 ppm nitrogen, is recovered via line 28. The gasoline product has an octane rating of 65 research octane clear, and is suitable for use as a charge stock to an octane improving process such as, for example, catalytic reforming.

Thus, the present invention provides a novel method for treating a hydrocarbon oil, containing substantial amounts of sulfur, nitrogen, and metal compounds, to produce a low sulfur gasoline product and a low sulfur heavy fuel oil product. Obviously. many variations and modifications which may be made without departing from the spirit and scope of the present invention will occur to those skilled in the art. Therefore, no limitations to the present invention are intended except such limitations as are embodied in the appended claims.

We claim:

1. A hydrocracking process wherein heavy hydrocarbon oil charge containing 0.1 to 8 percent sulfur, l to 1000 ppm and more nitrogen, and I00 ppm and more compounds of nickel, vanadium, iron, and copper, and comprising from about 10 to 50 volume percent residual fraction boiling above l000F. are converted into a major portion of gasoline containing less than 100 ppm sulfur and nitrogen, and a minor portion of residual fuel oil containing about 1 percent or less sulfur; which process comprises:

a. hydrocracking heavy hydrocarbon oil charge, in a first hydrocracking zone, with molecular hydrogen at a temperature in the range of from about 700850F. in the presence of a sulfur and nitrogen resistant hydrocracking catalyst comprising a hydrogenation component supported upon a cracking base consisting of an amorphous inorganic oxide having pore size distribution in the range of at least 20-200 angstrom units for conversion of said heavy hydrocarbon oil charge into not more than about percent gasoline fraction, a major portion of gas-oil fraction boiling in the range of 430l000F., and at least about percent residual oil fraction boiling above l00OF. containing about 1 percent or less sulfur;

b. separating, in a separation zone, the gas-oil fraction from the residual oil fraction;

c. recovering at least a portion of said residual fraction as low sulfur heavy fuel oil product; and

d. hydrocracking the gas-oil fraction in a second hydrocracking zone with molecular hydrogen at a temperature in the range of about 700F. to about 780F., in the presence of a sulfur and nitrogen resistant hydrocracking catalyst to produce gasoline boiling in the range of 55430F. and containing I00 ppm or less sulfur and nitrogen.

2. The process of claim 1 wherein a portion of the residual fraction is recycled from the separation zone to the first hydrocracking zone for conversion into additional gas-oil fraction, and wherein residual fuel oil yield from the separation zone is equivalent to at least l0 percent of the residual fraction boiling above [000F. contained in the heavy hydrocarbon oil charge.

3. The process ofclaim 2 wherein the residual fuel oil product is equivalent to at least percent of the residual fraction boiling above lO00F. contained in the heavy hydrocarbon oil charge.

4. The process of claim 3 wherein the gas-oil fraction is partially converted to gasoline in the second hydrocracking zone, wherein unconverted gas-oil fraction is separated from gasoline and wherein said unconverted gas-oil fraction is recycled to the second hydrocracking zone for conversion into additional gasoline.

5. The process of claim 4 wherein liquid effluent from the second hydrocracking zone, comprising gasoline, dry gas and unconverted gas-oil fraction is charged along with liquid effluent from the first hydrocracking zone comprising gas-oil fraction, residual fraction, and a small amount of gasoline and dry gas, to

the separation zone, wherein said first and second hydrocracking zone liquid effluent is separated into a dry gas fraction, gasoline, a gas-oil fraction, and a residual fraction.

6. The process of claim 5 wherein the hydrocracking catalyst in the first hydrocracking zone comprises a sulfur and nitrogen resistant hydrogenation component selected from the group consisting of Group Vl metals, Group Vlll metals, their oxides, their sulfides, and mixtures thereof, supported upon an amorphous metal oxide cracking base selected from the group consisting of alumina, silica-alumina, silica-zirconia, silica-titania, and mixtures thereof.

7. The method of claim 6 wherein the hydrocracking catalyst employed in the second hydrocracking zone comprises a hydrogenation component selected from the group consisting of Group Vl metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof, and an inorganic oxide cracking base selected from the group consisting of alumina, silica-alumina, silica-zirconia, silica-titania, a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 angstroms to about 20 angstroms, and mixtures thereof.

8. The process of claim 7 wherein the hydrocracking catalyst contained in the first hydrocracking zone comprises a hydrogenation component selected from the group consisting of a cobalt-molybdenum mixture, a cobalt oxide-molybdenum oxide mixture, a cobalt sulfide-molybdenum sulfide mixture, a nickel-cobaltmolybdenum mixture, a nickel oxide-cobalt oxidemolybdenum oxide mixture, and a nickel sulfide-cobalt sulfide-molybdenum sulfide mixture, and wherein the amorphous metal oxide cracking base is selected from the group consisting of alumina and silica-alumina.

9. The process of claim 8 wherein the hydrogenation component of the hydrocracking catalyst contained in the second hydrocracking zone is selected from the group consisting of a nickel-tungsten mixture, a nickel oxide-tungsten oxide mixture, a nickel sulfide-tungsten sulfide mixture, a cobalt sulfide-molybdenum sulfide mixture, and a nickel sulfide-cobalt sulfidemolybdenum sulfide mixture and wherein the inorganic oxide cracking base is selected from the group consisting of alumina, silica-alumina, and a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 angstroms to about 20 angstroms, and mixtures thereof.

10. The process of claim 9 wherein the exchanged cations of the zeolitic molecular sieve are selected from the group consisting of hydrogen, ammonia, calcium, magnesium, zinc, and mixtures thereof, and wherein said zeolitic molecular sieve contains from about 0 to about 5 percent weight sodium cations.

11. The method of claim 10 wherein a small portion of the gas-oil fraction is recycled to the first hydrocracking zone as a wash oil.

12. A hydrocracking process for the conversion of a heavy hydrocarbon charge oil containing 0. l-4 percent sulfur, -1000 ppm or more nitrogen, and 100 ppm or more compounds of nickel, vanadium, iron and copper, and comprising from about I0 to 50 volume percent residual fraction boiling above l000F. into residual fuel oil containing 0-l percent sulfur and gasoline containing -l00 ppm sulfur and nitrogen; which proto about 10,000 scf/b, a pressure of from about 500 cess comprises: to about 2,500 psig, a liquid hourly space velocity at. treating said heavy hydrocarbon oil, in a first hyof from about 0.5 to about 8.0 volumes of oil per drocracking Zone. with m lecular hy oge in a hour per volume of catalyst, at temperature of from hydrogen to hydrocarbon of about L SCf/b about 700 to about 790F., in the presence ofa byabout 15,000 at Pressure of from about drocracking catalyst comprising a hydrogenation 500 to about 3,000 p liquid hourly Space component selected from the group consisting of a locity of from about 0.1 to about 10.0 volumes of charge per hour per volume of catalyst, a temperature of from about 700-850F. in the presence of 10 a hydrocracking catalyst consisting of a hydrogenation component selected from the group consisting of cobalt, molybdenum, nickel, their oxides, their sulfides, and mixtures thereof, and an amorphous metal oxide cracking base selected from the group consisting of alumina, silica-alumina, silicazirconia, silica-titania, and mixtures thereof, to partially convert said heavy hydrocarbon oil into 0-5 percent gasoline boiling in the range 55-430F; a

. ()100 ppm sulfur and nitrogen. ma or portion of gas 01' boiling in the range of 4300 IOOOOF and at least 10 volume percent 13. The method of claim 12 wherein effluent from Sidual oil boiling above 100001;; the second hydrocracking reaction zone comprises unb. separating effluent from the first hydrocracking convefted low sulfur gasolme and zone into a gas-oil fraction and a residual fraction; wherein emufmt from f first lllydroc'jackmg zone c. recycling a first portion of the separated residual comprlses resfldual fracnon, fracuon, and 0 5 fraction to the first hydrocracking zone for conver' percent gasoline and dry gas, wherein effluent from the Sion into additional first hydrocracking zone and from the second hydrod. yielding a second portion of the separated residual cracking Zone are separated in a separation Zone into fraction sufficient to limit the conversion of the redry gas, gasoline, fraction and a residual frac- 5idua| fractio ili above |0OOF f the heavy tion, wherein the gas-oil fraction from the separation hydrocarbon oil charge into gas-oil fraction to Zone, comprising 8 from the first hydrocracking about 80 volume percent as heavy fuel oil containzone and unconverted gas-oil from the second hydroing 0-1 percent sulfur; and cracking zone is charged to the second hydrocracking e. contacting separated gas-oil, in a second hydrozone for conversion into gasoline and wherein gasoline cracking zone, with molecular hydrogen in a hy- 35 from the separation zone is recovered as product. drogen to hydrocarbon ratio of from about 1,000

cobalt oxide-molybdenum oxide mixture, a cobalt sulfide-molybdenum sulfide mixture, a nickel sulfide-tungsten sulfide mixture, a nickel oxidetungsten oxide mixture, and a nickel-tungsten mixture, and an inorganic cracking base selected from the group consisting of alumina, silicaalumina, a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 to about 20 angstrom units, and mixtures thereof, to convert said separated gas-oil fraction into gasoline containing

Claims

1. A HYDROTREATING PROCESS WHEREIN HEAVY HYDROCARBON OIL CHARGE CONTAINING 0.1 TO 8 PERCENT SULFUR, 100 TO 1000 PPM AND MORE NITROGEN, AND 100PPM AND MORE COMPOUNDS OF NICKEL, VANADIUM, IRON AND COPPER, AND COMPRISING FROM BOUT 10 TO 50 VOLUME PERCENT RESIDUAL FRACTION BOILING ABOVE 1000*F ARE CONVERTED INTO A MAJOR PORTIOON OF GASLINE CONTAINING LESS THAN 100PPM SULFUR AND NITROGEN, AND A MINOR PORTION OF RESIDUAL FUEL OIL CONTANING ABOUT 1 PERCENT OR LESS SULFUR; WHICH PROCESS COMPRISES: A. HYDROCRACKING HEAVY HYDROCARBON OIL CHARGE, IN A FIRST HYDROCRACKING ZONE, WITH MOLECULAR HYDROGEN AT A TEMPERATURE IN THE RANGE OF FROM ABOUT 700*-850*F IN THE PRESENCE OF A SULFUR AND NITROGEN RESISTANT HYDROCRACKING CATALYST COMPRISING A HYDROGENATION COMPONENT SUPPORTED UPON A CRACKING BASE CONSISTING OF AN AMORPHOUS OF AT EAST 20-200 ANGSTROM UNITS FOR CONVERSION OF SAID INORGANIC OXIDE HAVING PORE SIZE DISTRUBITION IN THE RANGE HEAVY HYDROCARBON OIL CHARGE INTO NOT MORE THAN ABOUT 5 PERCENT GASOLINE FRACTION, A MAJOR PORTION OF GAS-OIL FRACTION BOILING IN THE RANGE OF 430*-1000*F, AND AT LEAST ABOUT 10 PERCENT RESIDUAL OIL FRACTION BOILING ABOVE 1000*F. CONTAINING ABOUT 1 PERCENT OR LESS SULFUR; B. SEPARATING, IN A SEPARATION ZONE, THE GAS-OIL FRACTION FROM THE RESIDUAL OIL FRACTION; C. RECOVERING AT LEAST A PORTION OF SAID RESIDUAL FRACTION AS LOW SULFUR HEAVY FUEL OIL PRODUCT; AND D. HYDROCRACKING THE GAS-OIL FRACTION IN A SECOND HYDROCRACKING ZONE WITH MOLECULAR HYDROGEN AT A TEMPERATURE IN THE RANGE OF ABOUT 700*F TO ABOUT 780*F IN THE PRESENCE OF A SULFUR AND NITROGEN RESISTANT HYDROCRACKING CATALYST TO PRODUCE GASOLINE BOILING IN THE RANGE OF 55*-430*F AND CONTAINING 100PPM OR LESS SULFUR AND NITROGEN.

2. The process of claim 1 wherein a portion of the residual fraction is recycled from the separation zone to the first hydrocracking zone for conversion into additional gas-oil fraction, and wherein residual fuel oil yield from the separation zone is equivalent to at least 10 percent of the residual fraction boiling above 1000*F. contained in the heavy hydrocarbon oil charge.

3. The process of claim 2 wherein the residual fuel oil product is equivalent to at least 20 percent of the residual fraction boiling above 1000*F. contained in the heavy hydrOcarbon oil charge.

5. The process of claim 4 wherein liquid effluent from the second hydrocracking zone, comprising gasoline, dry gas and unconverted gas-oil fraction is charged along with liquid effluent from the first hydrocracking zone comprising gas-oil fraction, residual fraction, and a small amount of gasoline and dry gas, to the separation zone, wherein said first and second hydrocracking zone liquid effluent is separated into a dry gas fraction, gasoline, a gas-oil fraction, and a residual fraction.

6. The process of claim 5 wherein the hydrocracking catalyst in the first hydrocracking zone comprises a sulfur and nitrogen resistant hydrogenation component selected from the group consisting of Group VI metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof, supported upon an amorphous metal oxide cracking base selected from the group consisting of alumina, silica-alumina, silica-zirconia, silica-titania, and mixtures thereof.

7. The method of claim 6 wherein the hydrocracking catalyst employed in the second hydrocracking zone comprises a hydrogenation component selected from the group consisting of Group VI metals, Group VIII metals, their oxides, their sulfides, and mixtures thereof, and an inorganic oxide cracking base selected from the group consisting of alumina, silica-alumina, silica-zirconia, silica-titania, a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 angstroms to about 20 angstroms, and mixtures thereof.

8. The process of claim 7 wherein the hydrocracking catalyst contained in the first hydrocracking zone comprises a hydrogenation component selected from the group consisting of a cobalt-molybdenum mixture, a cobalt oxide-molybdenum oxide mixture, a cobalt sulfide-molybdenum sulfide mixture, a nickel-cobalt-molybdenum mixture, a nickel oxide-cobalt oxide-molybdenum oxide mixture, and a nickel sulfide-cobalt sulfide-molybdenum sulfide mixture, and wherein the amorphous metal oxide cracking base is selected from the group consisting of alumina and silica-alumina.

9. The process of claim 8 wherein the hydrogenation component of the hydrocracking catalyst contained in the second hydrocracking zone is selected from the group consisting of a nickel-tungsten mixture, a nickel oxide-tungsten oxide mixture, a nickel sulfide-tungsten sulfide mixture, a cobalt sulfide-molybdenum sulfide mixture, and a nickel sulfide-cobalt sulfide-molybdenum sulfide mixture and wherein the inorganic oxide cracking base is selected from the group consisting of alumina, silica-alumina, and a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 angstroms to about 20 angstroms, and mixtures thereof.

12. A hydrocracking process for the conversion of a heavy hydrocarbon charge oil containing 0.1-4 percent sulfur, 100-1000 ppm or more nitrogen, and 100 ppm or more compounds of nickel, vanadium, iron and copper, and comprising from about 10 to 50 volume percent residual fraction boiling above 1000*F. into residual fuel oil containing 0-1 percent sulfur and gasoline containing 0-100 ppm sulfur and nitrogen; which process comprises: a. treating said heavy hydrocarbon oil, in a first hydrocracking zone, with molecular hydrogen in a hydrogen to hydrocarbon ratio of about 1,000 scf/b to about 15,000 scf/b, at a pressure of from about 500 to about 3,000 psig, a liquid hourly space velocity of from about 0.1 to about 10.0 volumes of charge per hour per volume of catalyst, a temperature of from about 700*-850*F. in the presence of a hydrocracking catalyst consisting of a hydrogenation component selected from the group consisting of cobalt, molybdenum, nickel, their oxides, their sulfides, and mixtures thereof, and an amorphous metal oxide cracking base selected from the group consisting of alumina, silica-alumina, silica-zirconia, silica-titania, and mixtures thereof, to partially convert said heavy hydrocarbon oil into 0-5 percent gasoline boiling in the range 55*-430*F; a major portion of gas oil boiling in the range of 430*-1000*F., and at least 10 volume percent residual oil boiling above 1000*F.; b. separating effluent from the first hydrocracking zone into a gas-oil fraction and a residual fraction; c. recycling a first portion of the separated residual fraction to the first hydrocracking zone for conversion into additional gas-oil; d. yielding a second portion of the separated residual fraction sufficient to limit the conversion of the residual fraction boiling above 1000*F. of the heavy hydrocarbon oil charge into gas-oil fraction to about 80 volume percent as heavy fuel oil containing 0-1 percent sulfur; and e. contacting separated gas-oil, in a second hydrocracking zone, with molecular hydrogen in a hydrogen to hydrocarbon ratio of from about 1,000 to about 10,000 scf/b, a pressure of from about 500 to about 2,500 psig, a liquid hourly space velocity of from about 0.5 to about 8.0 volumes of oil per hour per volume of catalyst, a temperature of from about 700* to about 790*F., in the presence of a hydrocracking catalyst comprising a hydrogenation component selected from the group consisting of a cobalt oxide-molybdenum oxide mixture, a cobalt sulfide-molybdenum sulfide mixture, a nickel sulfide-tungsten sulfide mixture, a nickel oxide-tungsten oxide mixture, and a nickel-tungsten mixture, and an inorganic cracking base selected from the group consisting of alumina, silica-alumina, a cation exchanged crystalline silica-alumina zeolitic molecular sieve having uniform pore openings in the range of from about 5 to about 20 angstrom units, and mixtures thereof, to convert said separated gas-oil fraction into gasoline containing 0-100 ppm sulfur and nitrogen.

13. The method of claim 12 wherein effluent from the second hydrocracking reaction zone comprises unconverted gas-oil, low sulfur gasoline, and dry gas, wherein effluent from the first hydrocracking zone comprises residual fraction, gas-oil fraction, and 0-5 percent gasoline and dry gas, wherein effluent from the first hydrocracking zone and from the second hydrocracking zone are separated in a separation zone into dry gas, gasoline, a gas-oil fraction and a residual fraction, wherein the gas-oil fraction from the separation zone, comprising gas-oil from the first hydrocracking zone and unconverted gas-oil from the second hydrocracking zone is charged to the second hydrocracking zone for conversion into gasoline and wherein gasoline from the separation zone is recovered as product.