WO2008014150A2

WO2008014150A2 - Hydrocracking process

Info

Publication number: WO2008014150A2
Application number: PCT/US2007/073708
Authority: WO
Inventors: Laura E. Leonard; Peter Kokayeff
Original assignee: Uop Llc
Priority date: 2006-07-27
Filing date: 2007-07-17
Publication date: 2008-01-31
Also published as: BRPI0715107A2; US20080023372A1; CN101517042B; MX2009000941A; DE112007001743T5; RU2405024C2; CN101517042A; RU2009106855A; WO2008014150A3

Abstract

A catalytic hydrocracking process wherein a liquid phase stream comprising a hydrocarbonaceous feedstock (1), a liquid phase effluent from a hydrocracking zone (16), and hydrogen in a sufficiently low hydrogen concentration to maintain a liquid phase continuous system is fed into a hydrotreating zone (4) to produce a first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen. The resulting hydrocarbons having a reduced level of sulfur and nitrogen are introduced into a hydrocracking zone (13) with a sufficiently low hydrogen concentration to maintain a liquid phase continuous system to produce a hydrocracking zone effluent (16) which provides lower boiling range hydrocarbons.

Description

HYDROCRACKING PROCESS

FIELD OF THE INVENTION

[0001] The field of art to which this invention pertains is the catalytic conversion of hydrocarbons to useful hydrocarbon products. More particularly, the invention relates to catalytic hydrocracking.

BACKGROUND OF THE INVENTION

[0002] The present invention pertains to the hydrocracking of a hydro-carbonaceous feedstock. Petroleum refiners often produce desirable products such as turbine fuel, diesel fuel and other products known as middle distillates as well as lower boiling hydrocarbonaceous liquids such as naphtha and gasoline by hydrocracking a hydrocarbon feedstock derived from crude oil or heavy fractions thereof. Feedstocks most often subjected to hydrocracking are gas oils and heavy gas oils recovered from crude oil by distillation. A typical heavy gas oil comprises a substantial portion of hydrocarbon components boiling above 371°C (700⁰F), usually at least 50 percent by weight boiling above 371°C (700⁰F). A typical vacuum gas oil normally has a boiling point range between 315°C (600⁰F) and 565°C (1050⁰F).

[0003] Hydrocracking is generally accomplished by contacting in a hydro-cracking reaction vessel or zone the gas oil or other feedstock to be treated with a suitable hydrocracking catalyst under conditions of elevated temperature and pressure in the presence of hydrogen as a separate phase in a two-phase reaction zone so as to yield a product containing a distribution of hydrocarbon products desired by the refiner. The operating conditions and the hydrocracking catalysts within a hydrocracking reactor influence the yield of the hydrocracked products.

[0004] Traditionally, the fresh feedstock for a hydrocracking process is first introduced into a denitrification and desulfurization zone having hydrogen in a gaseous phase and particularly suited for the removal of sulfur and nitrogen contaminants and subsequently introduced into a hydrocracking zone containing hydrocracking catalyst and having hydrogen in a gaseous phase. Another method of hydrocracking a fresh feedstock is to introduce the fresh feedstock and the effluent from the hydrocracking zone into the denitrification and desulfurization zone. The resulting effluent from the hydrocracking zone is separated to produce desired hydrocracked products and unconverted feedstock which is then introduced into the hydrocracking zone. Previously, at least a major portion of the hydrogen present in reaction zones was present in a gaseous phase. This method or technique is commonly referred to as "trickle bed" wherein the continuous phase is gaseous and not liquid. [0005] Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial activities, there is always a demand for new hydrocracking methods which provide lower costs, ease of construction, higher liquid product yields and higher quality products.

INFORMATION DISCLOSURE

[0006] US 5,720,872 (Gupta) discloses a process for hydroprocessing liquid feedstocks in two or more hydroprocessing stages which are in separate reaction vessels and wherein each reaction stage contains a bed of hydroprocessing catalyst. The liquid product from the first reaction stage is sent to a low pressure stripping stage and stripped of hydrogen sulfide, ammonia and other dissolved gases. The stripped product stream is then sent to the next downstream reaction stage, the product from which is also stripped of dissolved gases and sent to the next downstream reaction stage until the last reaction stage, the liquid product of which is stripped of dissolved gases and collected or passed on for further processing. The flow of treat gas is in a direction opposite the direction in which the reaction stages are staged for the flow of liquid. Each stripping stage is a separate stage, but all stages are contained in the same stripper vessel.

[0007] US 3,328,290 (Hengstebeck) discloses a two-stage process for the hydrocracking of hydrocarbons in which the feed is pretreated in the first stage.

[0008] US 5,403,469 (Vauk et al) discloses a parallel hydrotreating and hydrocracking process. Effluent from the two processes are combined in the same separation vessel and separated into a vapor comprising hydrogen and a hydrocarbon-containing liquid. The hydrogen is shown to be supplied as part of the feed streams to both the hydrocracking and the hydrotreater.

[0009] US 5,980,729 (Kalnes et al) discloses a hydrocracking process wherein a hydrocarbonaceous feedstock and a hot hydrocracking zone effluent containing hydrogen is passed to a denitrification and desulfurization reaction zone to produce hydrogen sulfide and ammonia to thereby clean up the fresh feedstock. The resulting hot, uncooled effluent from the denitrification and desulfurization zone is hydrogen stripped in a stripping zone maintained at essentially the same pressure as the preceding reaction zone with a hydrogen- rich gaseous stream to produce a vapor stream comprising hydrogen, hydrocarbonaceous compounds boiling at a temperature below the boiling range of the fresh feedstock, hydrogen sulfide and ammonia, and a liquid hydro-carbonaceous stream containing unconverted feedstock. This liquid hydrocarbonaceous stream is introduced into a hydrocracking zone to produce a hydrocracking zone effluent which then joins the fresh feedstock as described hereinabove and is subsequently introduced into the denitrification and desulfurization zone. [0010] US 6,106,694 (Kalnes et al) discloses a hydrocracking process wherein a hydrocarbonaceous feedstock and a hot hydrocracking zone effluent is passed to a denitrification and desulfurization reaction zone to produce hydrogen sulfide and ammonia to thereby clean up the fresh feedstock. The resulting hot, uncooled effluent from the denitrification and desulfurization zone is hydrogen stripped in a stripping zone maintained at essentially the same pressure as the preceding reaction zone with a hydrogen-rich gaseous stream to produce a vapor stream comprising hydrogen, hydrocarbonaceous compounds boiling at a temperature below the boiling range of the fresh feedstock, hydrogen sulfide and ammonia, and a liquid hydrocarbonaceous stream containing unconverted feedstock. This liquid hydrocarbonaceous stream is subsequently introduced into the hydrocracking zone to produce an effluent which is subsequently introduced into the denitrification and desulfurization reaction zone as described hereinabove.

[0011] US 6,123,835 (Ackerson et al.) and US 6,428,686 (Ackerson et al.) disclose a hydro process where the need to circulate hydrogen through the catalyst is eliminated by mixing the hydrogen and the oil feedstock in the presence of a diluent in which the hydrogen solubility is high relative to the feedstock. The oil/diluent/ hydrogen solution can then be fed to a plug flow reactor containing catalyst.

BRIEF SUMMARY OF THE INVENTION

[0012] The present invention is a catalytic hydrocracking process, in one embodiment, wherein a liquid phase stream comprising a hydrocarbonaceous feedstock, a liquid phase effluent from a hydrocracking zone, and a sufficiently low hydrogen concentration to maintain a liquid phase continuous system is fed into a hydrotreating zone to produce hydrogen sulfide and ammonia and provide a first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen. The hydrocarbons having a reduced level of sulfur and nitrogen are introduced into a hydrocracking zone with a sufficiently low hydrogen concentration to maintain a liquid phase continuous system to produce a hydrocracking zone effluent which provides lower boiling range hydrocarbons. In preferred embodiments, the first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen is separated in a high pressure product stripper or by conventional distillation to provide the hydrocarbons having a reduced level of sulfur and nitrogen which are subsequently introduced into the hydrocracking zone. [0013] In a second embodiment, the present invention is a catalytic hydrocracking process wherein a liquid phase stream comprising a hydrocarbonaceous feedstock, a liquid phase effluent from a hydrocracking zone, and a sufficiently low hydrogen concentration to maintain a liquid phase continuous system is fed into a hydrotreating zone to produce hydrogen sulfide and ammonia, and provide a first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen. The first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen is introduced into a hydrocracking zone with a sufficiently low hydrogen concentration to maintain a liquid phase continuous system to produce a hydrocracking zone effluent. The hydrocracking zone effluent is introduced into a separation zone which in one embodiment is preferably a high pressure product stripper to produce a second hydrocarbonaceous stream containing lower boiling hydrocarbons and a liquid phase hydrocarbonaceous stream comprising unconverted hydrocarbons which is introduced into the hydrotreating zone as hereinabove described. Hydrocracked hydrocarbons boiling at a temperature range lower than the hydrocarbonaceous feedstock are recovered.

[0014] Conventional hydroprocessing operations utilize trickle bed technology. This technology necessitates the use of large amounts of hydrogen relative to the hydrocarbon feedstock, sometimes exceeding 1685 nm³/m³ (10,000 SCF/B), and requires the use of costly recycle gas compression. The large amounts of hydrogen relative to the hydrocarbon feedstock in conventional hydroprocessing operations renders this type of operation a gas phase continuous system. It has been discovered that it is neither economical nor necessary to have this large excess of hydrogen to effect the desired conversion. The desired conversion can be effected with much less hydrogen, and can be economically and efficiently performed with only sufficient hydrogen to ensure a liquid phase continuous system. A liquid phase continuous system would exist at one extreme with only sufficient hydrogen to fully saturate the hydrocarbon feedstock and at the other extreme where sufficient hydrogen is added to transition to a gas phase continuous system. The amount of hydrogen that is added between these two extremes is dictated by economic considerations. Operation with a liquid phase continuous system avoids the high costs associated with a recycle gas compressor. [0015] Other embodiments of the present invention encompass further details such as types and descriptions of feedstocks, hydrocracking catalysts, hydrotreating catalysts, and preferred operating conditions including temperatures and pressures, all of which are hereinafter disclosed in the following discussion of each of these facets of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are simplified process flow diagrams of preferred embodiments of the present invention. The drawings are intended to be schematically illustrative of the present invention and not be a limitation thereof. While the drawings depict the process as operating in a downflow mode it is presented for illustrative purposes and is not intended to exclude an upflow mode of operation.

DETAILED DESCRIPTION OF THE INVENTION

[0017] The process of the present invention is particularly useful for hydrocracking a hydrocarbon oil containing hydrocarbons and/or other organic materials to produce a product containing hydrocarbons and/or other organic materials of lower average boiling point and lower average molecular weight. The hydrocarbon feedstocks that may be subjected to hydrocracking by the method of the invention include all mineral oils and synthetic oils (e.g., shale oil, tar sand products, etc.) and fractions thereof. Illustrative hydrocarbon feedstocks include those containing components boiling above 288°C (550⁰F), such as atmospheric gas oils, vacuum gas oils, deasphalted, vacuum, and atmospheric residua, hydrotreated or mildly hydrocracked residual oils, coker distillates, straight run distillates, solvent-deasphalted oils, pyrolysis-derived oils, high boiling synthetic oils, cycle oils and cat cracker distillates. A preferred hydrocracking feedstock is a gas oil or other hydrocarbon fraction having at least 50% by weight, and most usually at least 75% by weight, of its components boiling at a temperature above 371⁰C (700⁰F). One of the most preferred gas oil feedstocks will contain hydrocarbon components which boil above 288°C (550⁰F) with best results being achieved with feeds containing at least 25 percent by volume of the components boiling between 315°C (600⁰F) and 565°C (1050⁰F).

[0018] The selected hydrocarbonaceous feedstock and hydrogen are introduced into a hydrotreating reaction zone at hydrotreating reaction conditions. In addition, the resulting effluent from a hereinafter described hydrocracking reaction zone is also introduced into the hydrotreating reaction zone. Preferred hydrotreating reaction conditions include a temperature from 204⁰C (400⁰F) to 482°C (900⁰F), a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig), a liquid hourly space velocity of the fresh hydrocarbonaceous feedstock from 0.1 hr^"1 to 10 hr^"1 with a hydrotreating catalyst or a combination of hydrotreating catalysts. Only enough hydrogen is introduced into the hydrotreating reaction zone to maintain a liquid phase continuous system. This means that in contrast to conventional hydroprocessing processes which operate in trickle bed mode in which it is the gas phase that is continuous, the present invention operates in a liquid phase continuous system.

[0019] The term "hydrotreating" as used herein refers to a process wherein a hydrogen- containing treat gas absorbed in the liquid hydrocarbon is used in the presence of suitable catalysts which are primarily active for the removal of heteroatoms, such as sulfur and nitrogen from the hydrocarbon feedstock. Suitable hydrotreating catalysts for use in the present invention are any known conventional hydrotreating catalysts and include those which are comprised of at least one Group VIII metal, preferably iron, cobalt and nickel, more preferably cobalt and/or nickel and at least one Group VI metal, preferably molybdenum and tungsten, on a high surface area support material, preferably alumina. Other suitable hydrotreating catalysts include zeolitic catalysts, as well as noble metal catalysts where the noble metal is selected from palladium and platinum. It is within the scope of the present invention that more than one type of hydrotreating catalyst be used in the same reaction vessel. The Group VIII metal is typically present in an amount ranging from 2 to 20 weight percent, preferably from 4 to 12 weight percent. The Group VI metal will typically be present in an amount ranging from 1 to 25 weight percent, preferably from 2 to 25 weight percent. [0020] In one embodiment of the present invention, the resulting effluent from the hydrotreating reaction zone is directly introduced into a hydrocracking reaction zone to provide lower boiling hydrocarbons. In another embodiment of the present invention, the resulting effluent is introduced into a separation zone which is preferably a high pressure product stripper or a conventional fractionation zone to recover lower boiling hydrocarbons and to provide a hydrocarbonaceous stream containing hydrocarbons boiling in the range of the fresh feedstock which is subsequently introduced into a hydrocracking zone. The high pressure product stripper is preferably operated at a temperature from 204⁰C (400⁰F) to 482°C (900⁰F) and a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig). [0021] In a preferred embodiment where the hydrotreating zone effluent is directly introduced into the hydrocracking zone, the effluent from the hydrocracking reaction zone is preferably introduced into a high pressure stripper preferably operated at a temperature from 204⁰C (400⁰F) to 482°C (900⁰F) and a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig) to produce a vaporous hydrocarbonaceous stream and a liquid hydrocarbonaceous stream containing hydrocarbons boiling in the range of the fresh feedstock which is introduced into the hydrotreating zone. In a preferred embodiment where the hydrotreating zone effluent is separated between the hydrotreating zone and the hydrocracking zone, the effluent from the hydrocracking zone is directly introduced into the hydrotreating zone. [0022] In any event, the feed is introduced into the hydrocracking zone along with the added hydrogen in an amount sufficiently low to maintain a liquid phase continuous system. The hydrocracking zone may contain one or more beds of the same or different catalyst. In one embodiment, when the preferred products are middle distillates, the preferred hydrocracking catalysts utilize amorphous bases or low-level zeolite bases combined with one or more Group VIII or Group VIB metal hydrogenating components. In another embodiment, when the preferred products are in the gasoline boiling range, the hydrocracking zone contains a catalyst which comprises, in general, any crystalline zeolite cracking base upon which is deposited a minor proportion of a Group VIII metal hydrogenating component. Additional hydrogenating components may be selected from Group VIB for incorporation with the zeolite base. The zeolite cracking bases are sometimes referred to in the art as molecular sieves and are usually composed of silica, alumina and one or more exchangeable cations such as sodium, magnesium, calcium, rare earth metals, etc. They are further characterized by crystal pores of relatively uniform diameter between 4 and 14 angstroms (1(T¹⁰ meters). It is preferred to employ zeolites having a relatively high silica/alumina mole ratio between 3 and 12. Suitable zeolites found in nature include, for example, mordenite, stilbite, heulandite, ferrierite, dachiardite, chabazite, erionite and faujasite. Suitable synthetic zeolites include, for example, the B, X, Y and L crystal types, e.g., synthetic faujasite and mordenite. The preferred zeolites are those having crystal pore diameters between 8 and 12 angstroms (1(X¹⁰ meters), wherein the silica/alumina mole ratio is 4 to 6. A prime example of a zeolite falling in the preferred group is synthetic Y molecular sieve. [0023] The natural occurring zeolites are normally found in a sodium form, an alkaline earth metal form, or mixed forms. The synthetic zeolites are nearly always prepared first in the sodium form. In any case, for use as a cracking base it is preferred that most or all of the original zeolitic monovalent metals be ion-exchanged with a polyvalent metal and/or with an ammonium salt followed by heating to decompose the ammonium ions associated with the zeolite, leaving in their place hydrogen ions and/or exchange sites which have actually been decationized by further removal of water. Hydrogen or "decationized" Y zeolites of this nature are more particularly described in US 3,130,006.

[0024] Mixed polyvalent metal -hydrogen zeolites may be prepared by ion-exchanging first with an ammonium salt, then partially back exchanging with a polyvalent metal salt and then calcining. In some cases, as in the case of synthetic mordenite, the hydrogen forms can be prepared by direct acid treatment of the alkali metal zeolites. The preferred cracking bases are those which are at least 10 percent, and preferably at least 20 percent, metal-cation- deficient, based on the initial ion-exchange capacity. A specifically desirable and stable class of zeolites are those wherein at least 20 percent of the ion exchange capacity is satisfied by hydrogen ions.

[0025] The active metals employed in the preferred hydrocracking catalysts of the present invention as hydrogenation components are those of Group VIII, i.e., iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium and platinum. In addition to these metals, other promoters may also be employed in conjunction therewith, including the metals of Group VLB, e.g., molybdenum and tungsten. The amount of hydrogenating metal in the catalyst can vary within wide ranges. Broadly speaking, any amount between 0.05 percent and 30 percent by weight may be used. In the case of the noble metals, it is normally preferred to use 0.05 to 2 weight percent. The preferred method for incorporating the hydrogenating metal is to contact the zeolite base material with an aqueous solution of a suitable compound of the desired metal wherein the metal is present in a cationic form. Following addition of the selected hydrogenating metal or metals, the resulting catalyst powder is then filtered, dried, pelleted with added lubricants, binders or the like if desired, and calcined in air at temperatures of, e.g., 371°-648°C (700°-1200°F) in order to activate the catalyst and decompose ammonium ions. Alternatively, the zeolite component may first be pelleted, followed by the addition of the hydrogenating component and activation by calcining. The foregoing catalysts may be employed in undiluted form, or the powdered zeolite catalyst may be mixed and copelleted with other relatively less active catalysts, diluents or binders such as alumina, silica gel, silica-alumina cogels, activated clays and the like in proportions ranging between 5 and 90 weight percent. These diluents may be employed as such or they may contain a minor proportion of an added hydrogenating metal such as a Group VIB and/or Group VIII metal.

[0026] Additional metal promoted hydrocracking catalysts may also be utilized in the process of the present invention which comprises, for example, aluminophosphate molecular sieves, crystalline chromosilicates and other crystalline silicates. Crystalline chromosilicates are more fully described in US 4,363,718 (Klotz).

[0027] The hydrocracking of the hydrocarbonaceous feedstock in contact with a hydrocracking catalyst is conducted in the presence of sufficiently low concentrations of hydrogen to maintain a liquid phase continuous system and preferably at hydrocracking reactor conditions which include a temperature from 232°C (450⁰F) to 468°C (875°F), a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig) and a liquid hourly space velocity (LHSV) from 0.1 to 30 hr^"1. In accordance with the present invention, the term "substantial conversion to lower boiling products" is meant to connote the conversion of at least 5 volume percent of the fresh feedstock to products having a lower boiling point than the hydrocarbonaceous feedstock. In a preferred embodiment, the per pass conversion in the hydrocracking zone is in the range from 15% to 75%. More preferably the per pass conversion is in the range from 20% to 60%. Then the ratio of unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock to the hydrocarbonaceous feedstock is from 1:5 to 3:5. The present invention is suitable for the production of naphtha, diesel or any other desired lower boiling hydrocarbons.

[0028] During the conversions or reactions occurring in the hydrotreating and hydrocracking reaction zones, hydrogen is necessarily consumed and must be replaced by one or more hydrogen inlet points located in the reaction zones. The amount of hydrogen added at these locations is controlled to ensure that the system operates as a liquid phase continuous system. The limiting amount of hydrogen that is added is that amount which causes a transition from a liquid phase continuous system to a vapor phase continuous system. [0029] The relative amount of hydrogen required to maintain a liquid phase continuous system in both the hydrotreating and the hydrocracking zones is dependent upon the specific composition of the hydrocarbonaceous feedstock, the level or amount of conversion to lower boiling hydrocarbon compounds, the composition and quantity of the lower boiling hydrocarbons and the reaction zone temperature and pressure. Artisans skilled in the conversion and hydrocracking of hydrocarbons will readily be able to determine the appropriate amount of hydrogen to provide a liquid phase continuous system once all of the above-mentioned variables have been selected.

DETAILED DESCRIPTION OF THE DRAWINGS

[0030] With reference now to the FIG 1, a feedstream comprising vacuum gas oil is introduced into the process via line 1 and admixed with a hereinafter described hydrocracking zone effluent transported via line 16. A hydrogen-rich gaseous stream is introduced via line 2 and also joins the feedstream and the resulting admixture is transported via line 3 and introduced into hydrotreating zone 4. Additional hydrogen-rich gas is introduced via lines 5 and 6 into hydrotreating zone 4 in order to supplement the required hydrogen which is consumed in hydrotreating zone 4. The amount of hydrogen present in hydrotreating zone 4 is sufficiently low to maintain a liquid phase continuous system. The resulting effluent from hydrotreating zone 4 is carried via line 7 and introduced into high pressure product stripper 8. A hydrocarbonaceous vaporous stream comprising hydrogen sulfide, ammonia and hydrocarbons boiling in the range lower than the feedstock is removed from high pressure product stripper 8 via line 9 and recovered. A liquid hydrocarbonaceous stream containing hydrocarbon compounds boiling in the range of the feedstock is removed from high pressure product stripper 8 via line 10 and is joined with a hydrogen-rich stream provided via line 11 and the resulting admixture is transported via line 12 and introduced into hydrocracking zone 13. Additional hydrogen is provided via lines 14 and 15 to hydrocracking zone 13. The hydrogen provided to hydrocracking zone 13 is in an amount sufficiently low to maintain a liquid phase continuous system therein. A resulting hydrocracking zone effluent is removed from hydrocracking zone 13 via line 16 and joins the fresh feedstock provided via line 1 as hereinabove described.

[0031] With reference now to FIG 2, a feedstream comprising vacuum gas oil is introduced into the process via line 1 and admixed with a hereinafter described hydrocracking zone effluent transported via line 16. A hydrogen-rich gaseous stream is provided via line 2 and also joins the feedstream and the resulting admixture is transported via line 3 and introduced into hydrotreating zone 4. Additional hydrogen is introduced into hydrotreating zone 4 via lines 5 and 6. The total supply of hydrogen to hydrotreating zone 4 is sufficiently low to maintain a liquid phase continuous system. A resulting effluent stream is removed from hydrotreating zone 4 via line 7 and is joined with a hydrogen-rich gaseous stream provided via line 24 in an amount sufficiently low to maintain a liquid phase continuous system and the resulting admixture is transported via line 25 and introduced into hydrocracking zone 20. Additional hydrogen is provided to hydrocracking zone 20 via lines 26 and 27 in an amount sufficiently low to maintain a liquid phase continuous system therein. A resulting effluent stream is removed from hydrocracking zone 20 via line 17 and is joined with a hydrogen-rich gaseous stream provided via line 18 and the resulting admixture is transported via line 21 and introduced into high pressure product stripper 22. A hydrocarbonaceous vaporous stream containing hydrocarbons boiling in a range below the feed is removed from high pressure product stripper 22 via line 23 and recovered. A liquid stream containing unconverted hydrocarbons is removed from high pressure product stripper via line 16 and joins the feedstream provided via line 1 as hereinabove described. [0032] The foregoing description and drawings clearly illustrate the advantages encompassed by the process of the present invention and the benefits to be afforded with the use thereof.

Claims

CLAIMS:

1. A process for hydrocracking a hydrocarbonaceous feedstock which comprises:

(a) introducing a liquid phase stream (1) comprising a hydrocarbonaceous feedstock, at least a portion of a liquid phase effluent (16) from a hydrocracking zone (13, 20) and hydrogen into a hydrotreating zone to produce hydrogen sulfide and ammonia, and provide a first hydrocarbonaceous stream (7) comprising hydrocarbons having a reduced level of sulfur and nitrogen, said hydrogen present in a sufficiently low concentration to maintain a liquid phase continuous system in said hydrotreating zone;

(b) introducing at least a portion of the first hydrocarbonaceous stream (7) comprising hydrocarbons having a reduced level of sulfur and nitrogen into the hydrocracking zone (13, 20) with hydrogen present in a sufficiently low hydrogen concentration to maintain a liquid phase continuous system in the hydrocracking zone;

(c) separating a hydrocarbonaceous stream selected from the group consisting of the first hydrocarbonaceous stream (7) comprising hydrocarbons having a reduced level of sulfur and nitrogen, and an effluent (17) from the hydrocracking zone in a separation zone (8, 22) to provide hydrocracked hydrocarbons boiling in a temperature range lower than the hydrocarbonaceous feedstock;

(d) recovering the hydrocracked hydrocarbons boiling in a temperature range lower than the hydrocarbonaceous feedstock; and

(e) recycling at least a portion of the effluent (16) from the hydrocracking zone to step (a).

2. The process of claim 1 wherein the hydrocarbonaceous feedstock boils in the range from 315°C (600⁰F) to 565°C (1050⁰F).

3. The process of claim 1 wherein the hydrotreating zone is operated at conditions including a temperature from 204⁰C (400⁰F) to 482°C (900⁰F) and a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig).

4. The process of claim 1 further comprising recovering unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock in a high pressure product stripper.

5. The process of claim 4 wherein the ratio of the unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock to the hydrocarbonaceous feedstock is from 1:5 to 3:5.

6. The process of claim 1 further comprising recovering unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock in a fractionation zone.

7. The process of claim 1 wherein the hydrocracking zone is operated at conditions including a temperature from 232°C (450⁰F) to 468°C (875°F) and a pressure from 3.5 MPa (500 psig) to 17.3 MPa (2500 psig).

8. The process of claim 1 further comprising recovering unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock, hydrogen sulfide and ammonia from the hydrocarbonaceous stream and introducing unconverted hydrocarbons boiling in the range of the hydrocarbonaceous feedstock recovered into the hydrocracking zone (13).

9. The process of claim 1 further comprising introducing the first hydrocarbonaceous stream comprising hydrocarbons having a reduced level of sulfur and nitrogen into a hydrocracking zone (20); introducing the effluent from the hydrocracking zone effluent into a separation zone (22) to produce a second hydrocarbonaceous stream (23) containing lower boiling hydrocarbons and a liquid phase hydrocarbonaceous stream (16) comprising unconverted hydrocarbons; and introducing the liquid phase hydrocarbonaceous stream comprising unconverted hydrocarbons into step (a).

10. The process of claim 9 wherein the separation zone is a high pressure product stripper.