US3696024A

US3696024A - Petroleum crude oil conversion process

Info

Publication number: US3696024A
Application number: US58480A
Authority: US
Inventors: Laurence O Stine
Original assignee: Universal Oil Products Co
Current assignee: Honeywell UOP LLC; Universal Oil Products Co
Priority date: 1970-07-27
Filing date: 1970-07-27
Publication date: 1972-10-03
Anticipated expiration: 1989-10-03

Abstract

A HEAVY HYDROCARBON FEEDSTOCK IS CONVERTED INTO MORE VALUABLE HYDROCARBON PRODUCT BY A COMBINATION EXTRACTION AND HYDROREFINING PROCESS WHICH INCLUDES THE CONTACTING OF THE FEEDSTOCK IN A LIQUID-LIQUID CONTACTING ZONE WITH A LIGHT HYDROCARBON SOLVENT UNDER CONITIONS SUFFICIENT TO PRODUCE A LOW DENSITY LIQUID PHASE COMPRISING SOLVENT AND A LOW BOILING FRACTION OF THE FEEDSTOCK, AND A HIGH DENSITY LIQUID PHASE COMPRISING SOLVENT AND A HIGH BOILING FRACTION OF THE FEEDSTOCK. THE LOW DENSITY PHASE IS PASSED TO A HYDROREFINING REACTION ZONE AND THE RESULTING EFFLUENT CONTAINS HYDROREFINED HYDROCARBON AND SOLVENT. THE EFFLUENT AND THE HIGH DENSITY PHASE ARE PASSED TO A FRACTIONATION ZONE WHEREIN THE HIGH BOILING FRACTION OF

THE FEEDSTOCK IS RECOVERED, HYDROREFINED PRODUCT IS RECOVERED, AND LIGHT HYDROCARBON SOLVENT IS RECOVERED FOR RECYCLE TO THE CONTACTING ZONE. THE LIGHT HYDROCARBON SOL VENT CONTAINS HYDROCARBONS HAVING FROM THREE TO TEN CARBON ATOMS PER MOLECULE, AND PREFERABLY FROM FIVE TO EIGHT CARBON ATOMS PER MOLECULE. THE PROCESS HAS PARTICULAR APPLICATION TO HYDROTREATING AND HYDROCRACKING HEAVY FEEDSTOCKS CONTAINING A SIGNIFICANT QUANTITY OF ASPHALTIC MATERIALS, ORGANO-METALLIC COMPLEXES, SULFUR COMPOUNDS, AND NITROGEN COMPOUNDS, WHEREIN AT LEAST ABOUT 10% BY VOLUME OF THE FEEDSTOCK BOILS AT A TEMPERATURE IN EXCESS OF ABOUT 1050*F.

Description

Oct. 3, 1972 l.. o. s'rlNE PETROLEUM CRUDE OIL CONVERSION PROCESS Filed July 27, 1970 QQQGS Q United States Patent Office Patented Oct. 3, 1972 U.S. Cl. 208-87 16 Claims lABSTRACT OF THE DISCLOSURE A heavy hydrocarbon feedstock is converted into more valuable hydrocarbon product by a combination extraction and hydrorefining process which includes the contacting of the feedstock in a liquid-liquid contacting zone with a light hydrocarbon solvent under conditions sufficient to produce a low density liquid phase comprising solvent and a low boiling fraction of the feedstock, and a high density liquid phase comprising solvent and a high boiling fraction of the feedstock. The low density phase is passed to a hydrorefining reaction zone and the resulting etiiuent contains hydrorefined hydrocarbon and solvent. The eiiuent and the high density phase are passed to a fractionation zone wherein the high boiling fraction of the feedstock is recovered, hydroreiined product is recovered, and light hydrocarbon solvent is recovered for recycle to the contacting zone. The light hydrocarbon solvent contains hydrocarbons having from three to ten carbon atoms per molecule, and preferably from five to eight carbon atoms per molecule. The process has particular application to hydrotreating and hydrocracking heavy feedstocks containing a significant quantity of asphaltic materials, organo-metallic complexes, sulfur compounds, and nitrogen compounds, wherein at least about by volume of the feedstock boils at a temperature in excess of about 1050" F.

CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part application based upon copending application Ser. No. 758,217, filed on Sept. 9, 1968, now Patent No. 3,544,450, Dec. l, 1970.

BACKGRO'U ND OF THE INVENTION The present invention relates to a hydrorefining process wherein apetroleum crude oil feedstock is converted into more valuable hydrocarbon product. More particularly, the present invention relates to an improved combination process for hydrorefining a heavy hydrocarbon feedstock, wherein the feedstock is contacted with a light hydrocarbon solvent in a contacting zone to produce a low boiling fraction of the feedstock and a high boiling fraction of the feedstock.

As used herein, the terms petroleum crude oil feedstock and heavy hydrocarbon feedstock are meant to include heavy oils extracted from tar sands, topped or reduced crudes, vacuum residuum (vacuum tower bottoms products), and especially those petroleum crude oils referred to as black oils, which contain a significant quantity of asphaltic materials and high concentrations of sulfur, as well as large quantities of nitrogenous compounds and high molecular weight organo-metallic complexes, principally comprising nickel and vanadium. These black oils include those hydrocarbon charge stoc-ks wherein at least about 10% by volume boils above a temperature of about 1050 F. These black oils usually have an ABI gravity at 60 F. of less than 20.0, and the sulfur concentrations of these feedstocks are usually more than 1% and often in excess of 3% by weight.

In brief, the present invention provides a method for converting such petroleum crude oils, and especially black oils, to more valuable products inasmuch as the inventive process sharply reduces the metallic content and asphaltic content of the charge passing to the hydrorefining reaction zone so that a significant proportion of the charge can be more easily converted into distillable hydrocarbons boiling below about 1050 F. The hydrorefining reaction zone may be classified as a hydrogen consuming reaction zone in which processing techniques dictate the recycle of a hydrogen-rich gaseous phase and, in many instances, the recycle of at least a portion of the normally liquid fraction of the reaction zone efiiuent. Such hydrogen consuming processes include the hydrotreating processes wherein gasoline or naphtha fractions, kerosine fractions, middle-distillate fractions, light and heavy vacuum gas oils, light and heavy cycle stocks, etc. are treated with hydrogen for the primary purpose of reducing the concentration of various chemical contaminants contained therein.

Another typical hydrogen consuming hydrocarbon conversion process is known in the petroleum refining art as hydrocracking, which may be defined more particularly as the destructive hydrogenation of petroleum. Basically, hydrocracking techniques are utilized to convert relatively heavy hydrocarbonaceous material into lower boiling hydrocarbon products such as gasoline, fuel oil, light cycle oils, etc. In other instances the desired end result of hydrocracking is the production of liquefied petroleum gas.

Relatively recent developments in the area of petroleum technology have indicated that the hydrotreating reactions and the hydrocracking reactions can be applied successfully to residual stocks, or so called black oils. Typical examples of hydrocarbons classified as black oils are atmospheric tower bottoms products, vacuum tower bottoms (vacuum residum), crude oil residum, topped crude oils, crude oils extracted from tar sands, etc. Such typical black oils have been further characterized hereinabove relative to their analytical characteristics.

Hydrogen treatment of contaminated hydrocarbon charge stocks is well-known in the art of hydrocarbon processing, and a typical method is shown in U.S. Patent No. 2,878,180. Hydrogen treatment, or hydrotreating, saturates the olefinic constituents of the stock and removes sulfur, nitrogen, chlorine, and other inorganic contaminants by hydrogenation. Hydrotreating also serves to remove trace quantities of arsenic, lead, copper, nickel, vanadium, tungsten, and other metals which may be present in untreated hydrocarbon fractions and which may be detrimental in subsequent processing operations or in final product use. The purification is effected by passing the hydrocarbon charge in admixture with hydrogen into the presence of a suitable catalyst at a pressure of from about p.s.i.g. t0 about 4000 p.s.i.g., the operating pressure being dependent upon the composition or type of charge stock being processed. The hydrogen not only serves as a reactant in effecting the purification of the hydrocarbons but it also affords a method for protecting the catalyst against excessive carbonization Iby providing a thermal sink for the exothermic heat of reaction. Hydrogen is, therefore, normally present at a concentration of from about 100 standard cubic feet per barrel (s.c.f.b.) of hydrocarbon charge to about 10,000 s.c.f.b., the amount again being dependent upon the type of charge stock being processed. The temperature of the hydrogen treating zone is maintained in the range from about 350 F. to about 900 F. The actual temperature required will necessarily vary in accordance with the degree of contamination, the type of stock being processed, and with the activity level of the catalyst. The hydrocarbon is normally processed at a liquid hourly space velocity in the range of from about 1.0 to about 10.0. A suitable catalyst for such hydrogen treating of hydrocarbons comprises alumina, silica, and a Group VIII metal or a Group VI-B metal or any combination of metals thereof. The metals of Groups VI-B and VIII are intended to include those indicated in the Periodic Chart of the Elements, Fisher Scientitic Company, 1953. A preferred hydrotreating catalyst is comprised of alumina, silica, nickel, molybdenum, and cobalt wherein the metals may be specifically present as the oxides or sulfides.

As previously noted hereinabove hydrocracking is also commonly referred to as destructive hydrogenation and is thereby distinguished from hydrotreating. In hydrotreating there is simple addition of hydrogen to unsaturated bonds between the carbon atoms and simple substitution of hydrogen for inorganic atoms bonded to the carbon atoms. Hydrocracking effects a more definite charge in the molecular structure of the hydrocarbons being processed, however, in that it breaks carbon-tocarbon bonds in the molecules of the hydrocarbon charge to produce lower boiling products. Hydrocracking processes are most commonly employed for the conversion of various hydrocarbon products boiling above the gasoline or naphtha boiling range, for the primary purpose of producing substantial yields of lower boiling saturated products. Although many hydrocracking reactions may be conducted on a thermal basis, the preferred processing technique involves utilization of a catalytic composite possessing a very high degree of hydrocracking activity. In virtually all hydrocracking processes, whether thermal or catalytic, controlled or selective cracking is highly desirable from the standpoint of producing increasing yields of liquid products boiling within the desired boiling ranges.

Selective hydrocracking is of particular importance when processing hydrocarbons and mixtures of hydrocarbons which boil at temperatures above the gasoline and the middle-distillate boiling range, that is, hydrocarbons and mixtures of hydrocarbons having a boiling range indicating an initial boiling point greater than 400 F. and an end boiling point as high as 1000 F. or more. Recent developments in hydrocracking technology have now indicated that the hydrocracking of residual oils or black oils having substantial quantities of hydrocarbonaceous material boiling at about 1200 F. or more may be undertaken. Selective hydrocracking of such hydrocarbon fractions results in greater yields of hydrocarbons boiling within the gasoline and middle-distillate boiling range, that is, hydrocarbons Iboiling below a temperature of 650 F. to 700 F. The practice of the present invention has particularly significant application to the selective hydrocracking of such heavy hydrocarbon stocks.

The hydrocracking of hydrocarbon charge stocks not only provides cracking of high molecular weight materials but it also saturates olenic constituents of the stock and removes sulfur, nitrogen, chlorine, and other inorganic contaminants by hydrogenation. The hydrocracking reaction, thus, also serves to remove trace quantities or arsenic, lead, copper, nickel, vanadium, tungsten, and other metals which may be present in the hydrocarbon fractions.

The hydrocracking reaction is effected by passing the hydrocarbon charge in admixture with hydrogen in the presence of a suitable catalyst at a pressure of from about 100 p.s.i.g. to about 4000 p.s.i.g. or more, the operating pressure being dependent upon the composition or type of charge-stock being processed and the catalyst being utilized. The hydrogen not only serves as reactant in effecting the cracking and the purification of the hydrocarbon, but again affords a method for protecting the catalyst against excessive carbonization. Hydrogen is, therefore, normally present at a concentration from about 100 s.c.f.b. of hydrocarbon charge to about 20,000 s.c.f.b. the amount again being dependent upon the type of chargestock being processed. The temperature of the hydrocracking reaction zone is maintained in the range of about 500 to 1000 F. or more. The actual temperature required will necessarily vary in accordance with the degree of contamination of the stock, the boiling range of the stock, the activity level of the catalyst, and the type of ultimate products which it is desired to produce. The hydrocarbon s normally processed at a liquid hourly space velocity in the range of from about 0.5 to about 10. A typical catalyst for such hydrocracking of hydrocarbons comprises alumina, silica, and Group VIII metal or a Group VI-B metal or any combination of metals thereof.

It is well known by those skilled in the art that the catalyst composites which are typically utilized within the catalytic hydrorefining reaction zones to the type hercinabove described, are subjected to conditions which promote deterioration of catalytic activity due to the accumulation of extraeous deposits upon the catalyst particles contained within the reaction zone. The activity of the catalyst declines with the continued accumulation of carbon, metals, and heavy hydrocarbonaceous materials of metallic or non-metallic character which are deposited upon the surfaces of the catalyst particles with continued operation. The rate of deposition of the interfering contaminants upon the catalyst depends not only upon the amount of contaminating constituents within the feedstock, but also on the type of contaminants contained within the feedstock. In particular, as the end boiling point of the feedstock is increased for a given operation, the amount of heavy hydrocarbon of asphaltic character is increased, and such increase promotes the premature deterioration of the catalyst due to carbon deposition. In addition, the catalyst life becomes foreshortened with higher boiling feedstocks since the amount of metallic contaminants within the feedstock is increased. When hydrotreating or hydrocracking a feedstock which contains organometallic complexes, the metallic elemments thereof are totally deposited upon the catalyst surface during normal operation. However, when processing a feedstock containing asphaltic materials, only a portion of the asphaltic material produces deposition of carbon or tarry hydrocarbonaceous material upon the catalyst since the asphaltic constituents, to the greater extent, will be readily hydrocracked to produce lower boiling constituents which are of a less viscous and more liquid character.

SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an improved process for the conversion of a petroleum crude oil feedstock into a more valuable hydrocarbon product.

It is an additional object of the present invention to provide an improved process for converting a heavy hydrocarbon feedstock containing asphaltic constituents and organo-metallic contaminants to a more valuable hydrocarbon product in a catalytic hydrorelining reaction zone.

It is a further object of the present invention to provide an improved process for converting a heavy hydrocarbon feedstock containing asphaltic constituents and organometallic contaminants to a more valuable hydrocarbon product in a catalytic hydrorefning reaction zone, by passing to said reaction zone a selected feedstock fraction having reduced concentration of organic-metallic contaminants.

It is a still further object of the present invention to provide an improved combination process for conversion of such a heavy hydrocarbon feedstock, wherein the irnprovement resides in contacting the feedstock with a light hydrocarbon solvent to prepare a selected feedstock fraction containing solvent, and in charging the solvent-containing fraction to the hydrorelining reaction zone.

These and other objects of the present invention, as well as the advantages thereof, will become more readily apparent as the inventive process is set forth hereinafter in light of the accompanying drawing which setsforth a simplified schematc representation of one particularly preferred embodiment of the inventive process.

As set forth hereinabove, the present invention relates to an improved combination process for hydrorening a heavy hydrocarbon feedstock wherein the feedstock is initially contacted with a light hydrocarbon solvent in a liquid-liquid contacting zone to produce a low boiling fraction of the feedstock and a high boiling fraction of the feedstock. This initial liquid-liquid contacting step is broadly similar to the conventional deasphalting procedures employing light parain to precipitate the asphaltic and other more highly aromatic portions of the feed. In contacting the heavy hydrocarbon feedstock or black oil with the light hydrocarbon solvent, the highly aromatic asphaltic constituents of the black oil are separated out as a distinct high density rainate liquid phase while the lower boiling constituents of the feedstock are dissolved within the light hydrocarbon solvent to produce an extract liquid phase of lower density. In conventional deasphalting procedures, the two liquid phases are separately withdrawn from the contacting zone and individually distilled or stripped for the removal of the light hydrocarbon solvent.

In the practice of the present invention, however, the low density liquid phase comprising the light hydrocarbon solvent and a low boiling fraction of the feedstock, is passed directly into the hydrorefining reaction zone, preferably, with no intervening separation step for the removal of light hydrocarbon solvent. The resulting hydrorefined hydrocarbon eiliuent will then comprise light hydrocarbon solvent and hydroreined hydrocarbon products. The reactor efuent accordingly is passed into a fractional distillation zone simultaneously with the high density liquid phase from the contacting zone. The high density liquid phase of the contacting zone typically will comprise the high boiling fraction of the heavy hydrocarbon feedstock containing a portion of the low boiling light hydrocarbon solvent. The fractional distillation zone accordingly is utilized to fractionally distill the reaction zone eiuent and to fractionally distill the high boiling fraction of the contacting zone in order to recover the light hydrocarbon solvent and the desired hydrorefned product in a single fractional distillation zone. Recovered light hydrocrabon solvent is then returned to the liquid-liquid contacting zone for further processing.

In summary then, the present invention may be characterized as a process for hydroreining a heavy hydrocarbon feedstock which comprises, (a) contacting the feedstock with a light hydrocarbon solvent in a liquidliquid contacting zone maintained under conditions sufficient to produce a high density liquid phase comprising light hydrocarbon solvent and high boiling constituents of the feedstock, and a low density liquid phase cornprising light hydrocarbon solvent and low boiling constituents of the feedstock; (b) passing a reactor charge stream comprising the low boiling constituents in liquid solution with light hydrocarbon solvent, from the contacting zone into a hydroreiining reaction zone maintained under conditions suflicient to convert at least a portion of the low boiling constituents into hydroretined hydrocarbon product; (c) passing a reactor efliuent comprising light hydrocarbon solvent and hydrorened hydrocarbon product from the reaction zone into a fractional distillation zone maintained under fractionation conditions (d) passing a heavy fractionator feed stream comprising the high boiling constituents in liquid solution with light hydrocarbon solvent, from the contacting zone into the fractionation zone; (e) withdrawing from the fractionation zone, a bottoms fraction comprising the high boiling constituents having substantial freedom from light hydrocarbon solvent; (f) withdrawing light hydrocarbon solvent from the `fractionation zone, and passing at least a portion thereof into the contacting zone; and, (g) recovering hydrorefned hydrocarbon product from the fractionation zone.

A further embodiment of the present invention may be characterized as the broad embodiment defined hereinabove wherein the low density liquid phase is passed into the reaction zone as the reactor charge stream, directly from the contacting zone without intervening component separation.

A further broad embodiment of the present invention may be characterized as the broad embodiment defined hereinabove wherein the high density liquid phase is passed into the fractionation zone as the heavy fractionator feedstream, directly from the contacting zone without intervening component separation.

As pointed out hereinabove, it has been determined that the most deleterious contaminant in the typical black oil feedstock are the metallic constituents of the feedstock. The asphaltic constituents of the heavy hydrocarbon feed will be readily hydrotreated or hydrocracked within the typical catalytic hydrorening zone and thereby provide an increased yield of more valuable hydrocarbon products. In contrast, however, the organometallic contaminants of the black oil feedstock will be hydrocracked to produce hydrocarbon products with the concomitant result that the metallic portion of the contaminant will be deposited upon the catalyst and thereby lead to premature catalyst deactivation.

Therefore, it is an object of the present invention to contact the heavy hydrocarbon feedstock with a light hydrocarbon solvent which is selective for removal of a substantial portion of the asphaltic material into the desired reactor charge stream while selectively rejecting a substantial portion of the metallic constituents of the feedstock into the higher boiling fraction which is not passed to the reaction zone. In order to achieve this objective, it is desirable to use light hydrocarbon solvent which contains molecular species having from about three to about ten carbon atoms per molecule, with the light hydrocarbon solvent predominating in the heavier hydrocarbons of this definition. In particular, it is desired to use as a light hydrocarbon solvent, hydrocarbon species having from about ve to about eight carbon atoms per molecule. Although a light hydrocarbon solvent predominating in propane could be utilized within the practice of the present invention, propane is extremely selective for heavy asphaltic material and a considerable portion of such heavy aromatic constituents which could otherwise be hydrotreated or hydrocracked in the hydrorening zone, will be rejected into the high density liquid phase in the contacting zone by using propane.

In the practice of the present invention it is preferred to use a light hydrocarbon solvent comprising pentane or heavier hydrocarbons since these hydrocarbon solvents will reject the metallic constituents of the feedstock while retaining a substantial portion of the asphaltic materials in the low density liquid phase which is then passed to the reactor. In addition, use of the heavier hydrocarbon species hereinabove defined, affords the ability to contact the feedstock with a ratio of solvent to feedstock which is lower than that normally practiced in propane or butane deasphalting operations. Accordingly then, since the heavier hydrocarbon species having from five to ten carbon atoms per molecule are preferred for use by the practice of the present invention, the low density liquid phase produced within the contacting zone may be passed directly into the hydrorening reaction zone without separating out light hydrocarbon solvent, since the amount of solvent then contained in the reactor charge stock is substantially reduced below what is normally experienced in propane deasphalting operations.

A more clear understanding of the present invention may now be obtained by discussing the inventive process in light of the accompanying drawing. As noted hereinabove, the accompanying drawing provides a simplified schematic flow diagram of the process of the present invention. While of necessity certain limitations must be present in such a schematic description, no intention is meant thereby to limit the generally broad scope of this invention.

DESCRIPTION OF THE DRAWING As stated hereinabove, the initial step of the process of the present invention comprises contacting a petroleum crude oil or other heavw hydrocarbon feedstock with a light hydrocarbon solvent comprising hydrocarbon species having from about three to about ten carbon atoms per molecule, said contacting occurring in a liquid-liquid contacting zone maintained under contacting conditions wherein a heavy fraction of the feedstock is separated from a light fraction of the feedstock. In reference to the drawing, this first step is represented as taking place in contacting zone 4. The contacting zone is supplied with the petroleum crude oil or other heavy hydrocarbon feedstock entering the process via line 3, and with a light hydrocarbon solvent entering the process via line 2. In the drawing which illustrates a preferred embodiment of the present invention there is also provided a line 1 for `passage of a reaction gas, such as make-up hydrogen, to

admix with the light hydrocarbon solvent stream flowing in line 2. The resulting mixture of hydrogen and light hydrocarbon solvent enters line 3 via line 2, wherein it is combined with the petroleum crude oil or other heavy hydrocarbon feedstock passing via line 3 into contacting zone 4.

Contacting zone 4 may be equipped with heat exchanger means, mixing means, and the like, and is usually maintained under liquid-liquid contacting conditions including a temperature of from about 100 F. to about 500 F., and, preferably, the temperature is maintained in the range of from about 200 F. to about 400 F. The contacting zone is maintained at a pressure sufficient to maintain the light hydrocarbon solvent in the liquid phase. Accordingly the pressure within the contacting zone 4 will normally be in the range of from about atmospheric pressure to about 25 atmospheres, but preferably in the range of from about ten to about twenty atmospheres. As noted hereinabove, make-up hydrogen for the hydrorening reaction zone, to be described hereinafter, is introduced into the process via line 1. This hydrogen gas phase is introduced into the contacting zone 4 in admixture with the light hydrocarbon solvent and the heavy hydrocarbon feedstock in order to provide a method of agitation within the contacting zone 4 for the intimate mixing of feedstock in solvent. Because of the elevated temperature at which the contacting is conducted, a portion of the hydrogen will dissolve within the liquid and thereby be pumped via line 6 into the reaction zone 7, hereinafter described. Any hydrogen which is not dissolved is compressed by means not shown, and is discharged from contacting zone 4 via line 6 into the reaction zone 7.

The light hydrocarbon solvent is contacted in the contacting zone with the heavy hydrocarbon feedstock at a volumetric ratio of solvent to feedstock which is in the range of from about 0.5 to about 5.0 and preferably at a ratio of 2.0 or less. The contacting conditions produce a heavy hydrocarbon fraction of the feedstock as a distinct high density liquid phase containing a portion of the light hydrocarbon solvent. In addition, the contacting conditions produce a low density liquid phase which comprises the greatest portion of the light hydrocarbon solvent and a lower boiling fraction of the hydrocarbon feedstock. By proper selection of the type of light hydrocarbon solvent utilized in the contacting zone 4, it is possible to produce a low density liquid fraction which contains a substantial amount of asphaltic constituents and lower boiling hydrocarbon portions of the feedstock, while at the same time having a greatly reduced concentration of the organo-metallic complexes of the feedstock.

In addition, these conditions and the proper selection of light hydrocarbon solvent, produce a high density liquid phase within contacting zone 4, which will contain the substantially greater portion of the organo-metallic complexes of the feedstock and only a smaller portion of the asphaltic constituents thereof.

The high density liquid phase containing the heavy hydrocarbon fraction of the feedstock is withdrawn from a. phase separating section of the contacting zone 4, and passed via line 5 into a fractionation line 12, hereinafter to be described, which is maintained under distillation conditions. The low density liquid phase separating section of zone 4 via line 6 and passed into the catalytic hydrorefining reaction zone 7, entering zone 7 in admixture with a hydrogen-containing gas stream which enters line 6 via line 10 from a source hereinafter described. As noted hereinabove, the fluid flowing within line 6 contains at least a portion of the make-up hydrogen which is required at the hydrorening reaction zone 7, and which is introduced into the process via line 1 prior to the contacting zone 4.

The catalytic reaction zone 7 is maintained under hydrocarbon conversion conditions wherein the low boiling fraction of the feedstock is at least partially converted into more valuable products. In a preferred embodiment the process of this invention is particularly applicable to the hydrorening of the petroleum crude oil feedstocks, black oils, or other heavy hydrocarbon feedstock of the type hereinabove defined. Reaction zone 7 is of the conventional type of hydrorefining reaction zone, having one or more beds of conversion catalyst disposed therein. The reaction zone is equipped with heat transfer means, catalyst support trays, heating means, etc. The reaction zone is preferably of the adiabatic or semi-adiabatic type, and the feed to the reaction zone will, therefore, be provided with the requisite amount of heat prior to passage thereof into the bed or beds of conversion catalyst. The actual operation of the reaction zone may be upflow, downow, or radial flow through the catalyst beds.

A preferred hydrorening catalyst which may be utilized in the process of the present invention can be characterized a s a hydrotreating or a hydrocracking catalyst of the type well known in the art, comprising a metallic component possessing hydrogenation activity, which is composited with a refractory inorganic oxide carrier material which may be of either synthetic or natural origin. The precise composition and method of manufacture for the catalyst composite is not considered to be an essential element of the present process. Typical catalysts utilized within the reaction zone 7 have been previously described hereinabove and when utilizing such hydrorefining catalysts, the reaction zone 7 is maintained under hydroretining conversion conditions which include a temperature of from about 600 F. to about 1,000 F. as normally measured at the inlet to each fixed catalyst bed which is contained within reaction zone 7. The reaction zone eiuent is discharged from reaction zone 7 via line 8 normally at a temperature which is substantially elevated above that of the reactor inlet due to the exothermic nature of the hydrogenation reaction which is being effected within the catalyst bed. Suicient hydrogen is circulated through reaction zone 7 via lines 10 and 6, as hereinafter described, in order to maintain the proper degree of temperature control within the catalyst bed. The hydrogen circulation rate is maintained at an amount which is usually less than about 10,000 standard cubic feet per barrel, and the operating pressure preferably maintained within reaction zone 7, is in the range of from about 1,000 to about 4,000 p.s.i.g. The liquid hourly space velocity, as measured by volume of liquid hydrocarbon charge per hour per volume of catalyst disposed within the reaction zone 7, is preferably maintained in the range of from about 0.25 to about 4.0.

As set forth hereinabove, the reactor charge stock passing into the reaction zone 7 via line 6, preferably cornprises the low density liquid phase withdrawn from the liquid-liquid contacting zone 4. Accordingly, the reactor charge stock comprises the low boiling constituents of the heavy hydrocarbon feedstock of line 3 and light hydrocarbon solvent. Since the light hydrocarbon solvent comprises hydrocarbon having from about three to about ten carbon atoms per molecule, the greater portion of the light hydrocarbon solvent will pass through the reaction zone 7 without being catalytically reacted, particularly when reaction zone 7 is a hydrotreating reaction zone. However, as is well known to those skilled in the art, where reaction zone 7 is a hydrocracking zone a portion of the light hydrocarbon solvent typically will be hydrocracked within reaction zone 7. However, the low boiling fraction of the original feedstock is hydrocracked into more valuable lower boiling hydrocarbon product within reaction zone 7, and such hydroreiined hydrocarbon product will contain a substantial amount of light hydrocarbon constituents which are of a hydrocarbon type and amount sufficient to replace any portion of the original light hydrocarbon solvent which is otherwise lost through hydrocracking occuring within zone 7.

The resulting effluent from reaction zone 7 is passed via line 8 into a separation zone 9. This effluent stream typically contains normally gaseous inorganic components such as hydrogen and hydrogen sufide, normally gaseous hydrocarbons, and normally liquid hydrocarbons which are separated into liquid and vapor phases in separation zone 9. Separation zone 9 is a typical reactor efuent separation zone of conventional prior art conliguration, which is operated under phase separation conditions. Separation zone 9 may comprise a series of high pressure and low temperature separation vessels from which a net hydrogenrich vapor or gas stream is withdrawn via line 10 and recycled via lines 10 and 6 to reaction zone 7, while a net hydrocarbon-containing liquid stream is passed via line 11 from separation zone 9 to fractionation zone 12. It is also contemplated within the scope of this invention, that any number of hot ash and/or cold ash systems may be utilized in conjunction with a series of hot and/ or cold separators, maintained in series flow or parallel flow or a combination of both flows within separation zone 9. Separation zone 9, accordingly, may contain a number of heat exchangers and phase separators maintained at different temperatures and pressures.

Fractionation zone 12 may be of a conventional type which is utilized for obtaining the desired fractionated hydrorened hydrocarbon product and for the recovery of light hydrocarbon solvent for return to the contacting zone 4. While fractionation zone 12 is illustrated within the drawing as a single fractional distillation column, those skilled in the art will realize that more than one fractional distillation column may be employed in order to effect the desired fractional separation of the reaction zone effluent entering via line 11 and of the high density liquid phase entering fractionation column 12 via line 5. Normally, at least two fractional distillation columns will be utilized, and very often more than two columns will be utilized. Fractionation zone 12, Whether a single distillation column or a plurality of columns, will be operated at conditions of temperature and pressure selected so that the desired hydrocarbon fractions can be recovered therefrom While meeting predetermined product specifications.

Referring to the drawing, an overhead vapor fraction containing normally gaseous constituents is removed from fractionation zone i12 via line 14. The normally gaseous stream will typically contain some hydrogen but will predominate in hydrogen sulfide and the lower boiling normally gaseous hydrocarbon components having from one to about four, or even ve carbon atoms per molecule. A first liquid fraction is withdrawn from fractionation zone 12 via line 15, normally comprising liquefied petroleum gas (LPG)` predominating in propane and butane, but containing trace amounts of ethane and pentane. A light hydrocarbon solvent fraction is withdrawn from zone 12 via line 13. As noted hereinabove, there are conditions of hydrorelining within reaction zone 7, which are suiiicient to produce additional light hydrocarbon constituents of the type utilized as the light hydrocarbon solvent. Accordingly, a net light hydrocarbon product is withdrawn from line 13y via line 17. The remainder of the light hydrocarbon fraction Withdrawn from fractionator 12 is returned to line 2 in order to provide a continuing cycle of light hydrocarbon solvent passing into the contacting zone 4 in admixture with the heavy hydrocarbon feedstock of line 3. A stabilized gasoline fraction is, typically withdrawn from fractionation zone 12 via line 118 and a diesel oil fraction may be withdrawn from fractionation zone 12 via line 19.

A net bo-ttoms fraction is also withdrawn from zone 12 via line 16. This net bottoms fraction comprises heavy hydrocarbon constituents of the hydrocarbon feedstock which passed into the reaction zone 7 via line 6 within the low density liquid phase of the contacting zone 4, but which were not converted into lower boiling hydrocarbon constituents within reaction zone 7. In addition, the bottoms fraction of line 16 will contain the heavy hydrocarbon fraction of the feedstock which Was separated out as the high density liquid phase in zone 4 and passed from zone 4 into fractionator i12 via line 5. Therefore, the bottoms fraction of line 16 will contain a substantial amount of organo-metallic complexes. While the bottoms fraction may be discarded or burned as fuel, typically, the amount of this liquid is of such a high volume that it is preferable to pass it to additional processing to produce desired more valuable hydrocarbon products.

The effectiveness of the present invention may now be more readily understood by the following example which provides an adaptation of the inventive process for commercial exploration to process a typical petroleum crude oil, black oil, or heavy hydrocarbon feedstock to produce more valuable hydrocarbon products with improved hydrorefining catalyst life.

ILLUSTRATIVE EXAMPLE It is desired to hydrorefine a vacuum bottoms fraction obtained from a South American crude oil in order to produce more valuable hydrocarbon products having substantial freedom from inorganic contaminants and oleiinic hydrocarbons. The vacuum bottoms fraction has a gravity at 60 F. of 10.1 API and contains 186 ppm. of elemental metal present as organo-metallic constituents. The con carbon residue of the vacuum bottoms feedstock is 15.8 weight percent, the C, insolubles fraction is 5.2 weight percent, and the total sulfur of the feedstock is 3.08 weight percent.

Referring now to the attached drawing, this vacuum bottoms feedstock enters the process of the present invention via line 3 at a rate of 30,000 barrels per stream day (b.p.s.d.). A light hydrocarbon solvent is combined with the feedstock in line 3 by introduction of 53,000 b.p.s.d. of solvent entering line 3 via line 2. This light hydrocarbon solvent comprises pentane containing trace amounts of butane and hexane. The combined mixture of vacuum bottoms feedstock and light hydrocarbon sol vent enters the contacting zone 4 at a total rate of 83,000l b.p.s.d.

Contacting zone 4 is maintained under conditions suflicient to provide for the liquid-liquid contacting of the vacuum bottoms feedstock with the light hydrocarbon solvent in order to produce a low density liquid phase comprising lower boiling constituents of the vacuums lbottoms feedstock dissolved within light hydrocarbon solvent, and to provide a high density liquid phase comprising a minor portion of light hydrocarbon solvent dissolved within the heavier boiling constituents of the vacuum bottoms feedstock. These contacting conditions rwithin zone 4 comprise a temperature of about 300 degrecs F. and a pressure of about 175 p.s.i.g.

The high density liquid phase is withdrawn from the contacting zone 4 via line 5 at a rate of 4,700 b.p.s.d., and is passed into the fractionation zone 12 as a heavy fractionator feedstock. This high density liquid phase or heavy fractionator feed comprises 800 b.p.s.d. of light hydrocarbon solvent in solution with 3,900 b.p.s.d. of the heavy fraction of the original vacuum bottoms feedstock. Analysis of this heavy fraction of the original vacuum bottoms feedstock (solvent free basis) indicates a specific gravity of 1.147, a con carbon residue of 44.9 weight percent, and a sulfur content of 5.60 weight percent. Fractionation zone 12 is operated under conditions sufficient to separate the light hydrocarbon solvent from this heavy fraction of the vacuum bottoms feedstock in a manner which shall be disclosed hereinafter.

The low density liquid phase produced within contacting zone 4 is Withdrawn therefrom via line 6 and passed directly into a hydrocracking reaction zone 7 as a reactor charge stock. This reactor charge stock enters reaction Zone 7 at a rate of 78,300 b.p.s.d. comprising 26,100 b.p.s.d. of a light fraction of the vacuum bottoms feedstock dissolved within 52,200 b.p.s.d. of the light hydrocarbon solvent. The light fraction of the original vacuum bottoms feedstock of line 3 provides an anlysis which indicates a gravity of 13.3 API at `60 F., a metals content of 47 p.p.m., a con carbon residue of 10.7 weight percent, a C7 insolubles content of 1.05 weight percent, and a sulfur content of 2.63 weight percent.

Hydrocracking reaction zone 7 contains a typical hydrocracking catalyst and is operated under conditions sufficient to provide that the llight hydrocarbon solvent will pass therethrough substantially free of hydrocracking while the light hydrocarbon fraction of the original vacuum bottoms feedstock is hydrocracked in order to produce more valuable hydrocarbon products having substantial freedom from inorganic contaminants and olefinic constituents. These conditions include a reaction zone inlet temperature of 700 F., a reaction zone pressure of 2,650 p.s.i.g., and a liquid hourly space velocity of 0.5 based upon the hydrocarbon feedstock measured on a solvent free basis. In addition, these reaction zone conditions include the presence of hydrogen in the reaction zone in an amount equivalent to 7,500 standard cubic feet of hydrogen per barrel of hydrocarbon feedstock as measured on a solvent free basis. This hydrogen requirement is provided by introducing a circulating hydrogen stream into reaction zone 7 via lines 10 and 6.

A net reaction zone effluent is withdrawn from hydrocracking reaction zone 7 via line 8, and is passed thereafter into a separation zone 9. Separation zone 9 is operated under conditions sufficient to separate the hydrogen-rich vapor phase from the normally liquid hydrocarbon constituents. A net vapor phase is withdrawn from separation zone 9 via line 10 and recycled back to reaction zone 7 via line 6 as hereinabove noted. This withdrawn vapor phase is a hydrogen-rich vapor phase containing normally vaporous hydrocarbon species and hydrogen sulfide. A net reaction zone liquid effluent stream containing hydrogen, hydrogen sulfide, normally gaseous hydrocarbon vapors, and normally liquid hydrocarbons is withdrawn from separation zone 9 and passed into the fractionation zone 12 via line 11.

Fractionation zone 12 comprises two fractionating columns operated under conditions sufficient to separate the reaction zone liquid efliuent of line 11 and the heavy fractionator feed of line into more valuable hydrorefined hydrocarbon products and a heavy fraction of the original vacuum bottoms feedstock. The first fractionation column receives the liquid efiiuent of line 11 and the heavy fractionator feed of line 5 and produces therefrom a bottoms fraction which is drawn from the bottom of the first column and from fractionation zone 12 via line 16 at a rate of 21,094 b.p.s.d. This bottoms fraction has a boiling range of from 650 F. to an end boiling point in excess of 1200 F., and it contains the 3,900 b.p.s.d. of

the original vacuum bottoms feedstock of line 3 which was separated out in contacting zone 4. The heavy oil or bottoms fraction of line 16 is sent to storage, and is, preferably, thereafter sent to a vacuum column for the production of a vacuum gas oil and pitch.

A diesel oil cut is Withdrawn from the first column of fractionation zone 12 via line 19 at a rate of 4917 b.p.s.d. This diesel fuel has an initial boiling point of about 350 F. and an end boiling point of about 650 F. This diesel fuel product is sent to storage, but it may thereafter be sent to further fractionation for separation into a jet fuel fraction and a heavy diesel oil fraction.

An unstabilized gasoline fraction and all lower boiling constituents of the reaction zone eiuent are passed to the second column of zone 12 from the first column. The second column produces a stabilized gasoline product which then leaves fractionation zone 12 via line 18 at a rate of 1062 b.p.s.d. This depentanized gasoline fraction has an end boiling point of about 350 F., and it is sent to storage via line 18. The gasoline fraction has a research octane number of 63 clear, and, therefore, is sent thereafter to further processing for octane enhancement.

A pentane fraction is withdrawn from the second column and discharged from fractionation zone 12 via line 13. This pentane fraction contains a trace of butane and a trace of pentane, but it is essentially free of other contaminants such as hydrogen sulfide. This pentane product in line 13 comprises the light hydrocarbon solvent which was contained within the heavy fractionator feed entering fractionation zone 12 via line 5. This pentane fraction additionally includes the light hydrocarbon solvent entering zone 12 via line 11, which was contained in the reactor charge stock passing into reaction zone 7 from the contacting zone 4 via line 6, as well as additional pentane constituents which were produced by hydrocracking the light fraction of the vacuum bottoms feedstock within reaction zone 7. Accordingly, the pentane fraction is withdrawn from fractionation zone 12 via line 13 at a rate of 53,154 b.p.s.d., and a net light hydrocarbon product is withdrawn from line 13 at a rate of 154 b.p.s.d. as a net pentane product which is sent to storage. The remaining 53,000 b.p.s.d. of this pentane stream is returned via line 13 and line 2 to the contacting zone 4 as the light hydrocarbon solvent contacting the vacuum bottoms feedstock of line 3.

A net liquid petroleum gas fraction is withdrawn from the second column and from fractionation zone 12 via line 15 at a rate of 248 b.p.s.d., comprising propane and butane but containing hydrogen sulfide. Fractionation zone 12 also produces a net hydrocarbon vapor stream which is withdrawn from the second column and from zone 12 via line 14 at a rate of 3.810 mm. s.c.f.d. of total gas. This total Vapor stream comprises 2.088 mm. s.c.f.d. of hydrogen sulfide and 1.722 mm. s.c.f.d. of butane and lighter vaporized hydrocarbon constituents. Accordingly, the hydrocarbon vapor of line 14 and the liquefied petroleum gas of line 15 are sent to additional processing for recovery of elemental sulfur and for the recovery of purified liquefied petroleum gas product.

In processing the above defined vacuum bottoms feedstock of line 3 in accordance with the foregoing example, a catalyst service of 18 barrels per pound is obtained for the hydrocracking catalyst utilized within the reaction zone 7. In contrast, prior experience indicates that if the vacuum column bottoms feedstock of line 3 is passed directly into the reaction zone 7, a catalyst life of only 2 barrels per pound is obtained, primarily due to the high metals content of the original vacuum bottoms feedstock.

PREFERRED EMBODIMENTS From the foregoing discussion, the method of operation of the present invention as well as the advantages thereof Will be readily apparent to those skilled in the art.

In particular, it is to be noted that by having the heavy fraction of the heavy hydrocarbon feedstock which is rseparated within contacting zone 4, completely bypass the hydrorefining reaction zone 7, the greater portion of the organo-metallic complexes and a substantial portion of the asphalt and other carbon residue precursors do Vachieved when processing the light fraction of the heavy oil feedstock within reaction zone 7 under conditions which include a substantial reduction of the organometallic complexes and carbon residue precursors. The reduction in the amount of these heavy contaminants in the feed to the hydroreiining reaction zone allows the light fraction of the heavy oil feedstock to be hydrogenated at a lower catalytic severity, thereby enhancing catalyst selectivity as well as catalyst life.

Furthermore, in hydroreining the light fraction of the heavy hydrocarbon feedstock of line 3 in accordance with the inventive process, the light fraction will not only be more easily desulfurized, denitrogenated, and saturated, but the resulting hydrorefmed effluent will typically contain a substantial quantity of light hydrocarbon species suitable for use as light hydrocarbon solvent. Thus, the process of the present invention not only minimizes the loss of light hydrocarbon solvent but it is also capable of producing light solvent species sufficient to compensate for any extraneous loss of light hydrocarbon solvent from the process.

In addition, it must be noted that a substantial savings in capital costs is obtained by passing the low density liquid phase from zone 4 directly into the hydrorefining reaction zone 7 without intervening fractional distillation for recovery of the light hydrocarbon solvent. The distillation facilities which are included in a typical deasphalting operation are eliminated since the light hydrocarbon solvent is easily recovered in the fractionation facilities which are necessary for the separation of the reaction zone eiuent into the desired more valuable hydrorened hydrocarbon product fractions. Although such operation requires that the equipment of reaction zone 7, separation zone 9, and fractionation zone 12 be increased in size to accommodate the increased loading due to the presence of solvent, the elimination of duplicate fractionation facilities at contacting zone 4 still results in a net capital savings for the overall combination processing unit.

As previously noted hereinabove, the light solvent which is utilized in the contacting zone of the inventive process is a hydrocarbon solvent containing hydrocarbon species having from 'about three carbon atoms per molecule to about ten carbon atoms per molecule. It is particularly preferred that the light hydrocarbon solvent be selected from the group consisting of pentane and heavier hydrocarbons. 'Ihe reason for this preference is that in the process of the present invention, the objective is not to completely deasphalt the heavy oil feedstock to produce the lighter boiling fraction for reaction in the hydro- `zone 7. As noted hereinabove, the asphaltic materials of the heavy oilmay be readily hydrocracked within the reaction zone 7, but the metallic constituents of the heavy oil feedstock will be deposited on the catalyst as elemental metals or organo-metallic carbonaceous deposits. Accordingly, it is one primary objective of the inventive process to reduce the metals content of the hydrocarbon passing into reaction zone 7 and to maximize the amount of asphalt passing into reaction zone 7.

For this vpurposeit is therefore preferred to use the higher paranic solvents such as pentane, hexane, heptane, and octane or mixtures thereof. These light hydrocarbon solvents may comprise substantially pure components or mixtures thereof, such as those derived from parainic gasoline fractions such as straight run gasoline or alkylate gasoline. Indeed, there is some evidence that branch chained parainic hydrocarbons are more eicient in rejecting metallic contaminants from the low density liquid phase which is subsequently passed into the hydroreiining reaction zone, and accordingly, the branch chained paraffins of an alkylate gasoline fraction may be preferably employed. Light hydrocarbon solvents having five or more carbon atoms per molecule are to be preferred over the propane or butane solvents since the selectivity which is acquired with propane and butane is not necessary and, in fact, is not desired in the process of the present invention.

However, it is within the scope of the present invention to employ mixtures of hydrocarbon species as the light hydrocarbon solvent, wherein pentane and heavier para'iuic constituents predominate but a minor portion of propane or butane may be present. By using various mixtures of such hydrocarbon species to provide the desired light hydrocarbon solvent, it is possible to obtain the desired degree of solvency and selectivity for any given heavy hydrocarbon feedstock or black oil passing into the process of the present invention. As noted hereinabove, the objective of the present invention is to produce a feedstock for the hydror'efining reaction zone which has a reduced content of organo-metallic complexes While at the same time having a substantial amount of asphaltic material contained therein, so that the propane and butane should not predominate in the solvent mixture. Since the presence of propane and butane within the light hydrocarbon solvent will introduce high vapor pressure hydrocarbon constituents into the reaction zone, it may be desirable in such embodiments to pass the low density liquid phase from the contacting zone 4 into a simple single stage iiash phase separation zone wherein the high vapor pressure propane or butane constituents ma'y be withdrawn, while the reactor charge stock is passed to the reaction zone as a solution containing only the higher boiling hydrocarbon species of the solvent.

As noted hereinabove, the heavy hydrocarbon feedstock is contacted with the light hydrocarbon solvent in contacting zone 4 under conditions which include a ternperature in the range of from about F. to about 500 F. A pressure in the range of from about atmospheric pressure to about 25 atmospheres, and a volumetric ratio of solvent to heavy hydrocarbon feedstock in the range of from about 0.5 :1.0 to about 5.01:l.0. The actual conditions which will be selected for the contacting zone 4 will depend upon the specific heavy hydrocarbon feedstock being contacted and upon the hydrocarbon species contained in the solvent. The temperature must be selected judiciously since higher temperatures will normally result in dissolving a larger amount of the organo-metallic contaminants into the low density phase which is passed into the reaction zone. Similarly, excessive temperatures may cause a single phase condition to result in the contacting zone, and thereby produce a condition in which no separation whatsoever can occur. The pressure selected within contacting zone 4 normally will be that pressure which is sullicient to retain all hydrocarbon species in a liquid phase, and the solvent to feedstock ratio will be set to produce the desired degree of separation between the light liquid phase and the heavy liquid phase obtained within the contacting zone.

Those skilled in the art are readily capable of judiciously selecting those operating conditions necessary to achieve the required objectives of the present invention when utilizing any given heavy hydrocarbon feedstock and any selected solvent composition. However, it must be pointed out that it is a preferred embodiment of the present invention to select conditions which Will produce a light hydrocarbon fraction of the feedstock passing into the reaction zone in solution with the light hydrocarbon solvent, wherein the light hydrocarbon fraction has a metals content of 50 p.p.m. or less on a solvent free basis. These conditions preferably will include a temperature of from about 200 to about 400 F., a pressure of from about atmospheric pressure to atmospheres, a volumetric ratio of light hydrocarbon solvent to heavy oil feedstock of 2.0 or less, and a light hydrocarbon solvent predominating in pentane and heavier hydrocarbon species.

In conclusion, therefore, it may now be summarized that a preferred embodiment of the present invention resides in a process for hydrorening a heavy hydrocarbon feedstock containing a rst concentration of asphaltic constituents which comprises, (a) contacting said feedstock with a light hydrocarbon solvent in a liquid-liquid contacting zone maintained under conditions sufficient to provide an extract liquid phase comprising said solvent in solution with a relatively low boiling fraction of said feedstock containing a second concentration of organometallic contaminants below said first concentration, and to provide a raffinate liquid phase comprising said solvent in solution with a relatively high boiling fraction of said feedstock containing a third concentration of organometallic contaminants above said second concentration; (b) passing said low boiling fraction in solution with light hydrocarbon solvent, from said contacting zone into a hydrorening reaction zone maintained under hydrorening reaction conditions, said conditions including the presence of a hydrogen-rich vapor phase and a hydroreiining catalyst; (c) reacting said low boiling fraction in said reaction zone with said hydrogen-rich vapor phase, and thereby producing a hydrorened hydrocarbon fraction, (d) passing a reaction zone effluent comprising said hydrorened hydrocarbon fraction and light hydrocarbon solvent, from said reaction zone into a fractional distillation zone maintained under fractionation conditions; (e) passing said high boiling fraction in solution with light hydrocarbon solvent, from said contacting zone into said fractional distillation zone; (f) withdrawing from said fractional distillation zone, a bottoms fraction comprising said high boiling fraction and having substantial freedom from light hydrocarbon solvent; (g) withdrawing from said fractional distillation zone, a light hydrocarbon solvent fraction, and passing at least a portion thereof into said contacting zone; and, (h) recovering from said fractional distillation zone, hydroreiined hydrocarbon product having substantial freedom from organo-metallic contaminants.

I claim:

1. Proce for hydrorefning a heavy hydrocarbon feedstock which comprises:

(a) contacting said feedstock with a light hydrocarbon solvent in a liquid-liquid contacting zone maintained under conditions sufficient to produce a high density liquid phase comprising light hydrocarbon solvent and high boiling constituents of said feedstock, and a low density liquid phase comprising light hydrocarbon solvent and low boiling constituents of said feedstock;

(b) passing a reactor charge stream comprising said low boiling constituents in liquid solution with light hydrocarbon solvent, from said contacting zone into a catalytic hydrorening reaction zone maintained under conditions sufficient to convert at least a portion of said low boiling constituents into hydrorefined hydrocarbon product;

(c) passing a reactor eiiluent comprising light hydrocarbon solvent and hydrorefined hydrocarbon product from said reaction zone into a fractional distillation zone maintained under fractionation conditions;

(d) passing said high boiling constituents in liquid solution with light hydrocarbon solvent from said contacting zone around said reaction zone into said fractionation zone;

(e) withdrawing from said fractionation zone, a bottoms fraction comprising said high boiling constituents having substantial freedom from light hydrocarbon solvent;

(f) withdrawing light hydrocarbon solvent from said fractionation zone, and passing at least a portion thereof into said contacting zone; and,

(g) recovering said hydroretned hydrocarbon product from said fractionation zone.

2. Process of claim 1 wherein said hydrorelining reaction zone conditions are suicient to convert a portion of said low boiling constituents into light hydrocarbon solvent.

3. Process of claim 1 wherein said low density liquid phase is passed into said reaction zone as said reactor charge stream, directly from said contacting zone without intervening component separation.

4. Process of claim 1 wherein said high density liquid phase is passed into said fractionation zone directly from said contacting zone without intervening component separation.

5. Process of claim 1 wherein said heavy hydrocarbon feedstock has an end boiling point in excess of 1050 F.

6. Process of claim 1 wherein said light hydrocarbon solvent comprises at least one hydrocarbon species having from three to ten carbon atoms per molecule.

7. Process of claim 6 wherein said light hydrocarbon solvent comprises at least one hydrocarbon selected from the group consisting of pentane, hexane, heptane, and octane.

8. Process for hydrorefining a heavy hydrocarbon feedstock containing a first concentration of organometallic contaminants and a rst concentration of asphaltic constituents which comprises:

(a) contacting said feedstock with a light hydrocarbon solvent in a liquid-liquid contacting zone maintained under conditions sufficient to provide an extract liquid phase comprising said solvent in solution with a relatively low boiling fraction of said feedstock containing a second concentration of organo-metallic contaminants below said first concentration, and to provide a raffinate liquid phase comprising said solvent in solution with a relatively high boiling fraction of said feedstock containing a third concentration of organo-metallic contaminants above said second concentration;

(b) passing said low boiling fraction in solution with light hydrocarbon solvent, from said contacting zone into a hydrorefining reaction zone maintained under hydrorening reaction conditions, said conditions ncluding the presence of a hydrogen-rich vapor phase and a hydrorening catalyst;

(c) reacting said low boiling fraction in said reaction zone with said hydrogen-rich vapor phase, and thereby producing a hydrorened hydrocarbon fraction;

.(d) passing a reaction zone efliuent comprising said hydrorefned hydrocarbon fraction and light hydrocarbon solvent, from said reaction zone into a fractional distillation zone maintained under fractionation conditions;

(e) passing said high boiling fraction in solution with light hydrocarbon solvent from said contacting zone around said reaction zone into said fractional distillation zone;

(f) withdrawing from said fractional distillation zone,

a bottoms fraction comprising said high boiling fraction and having substantial freedom from light hydrocarbon solvent;

(g) withdrawing from said fractional distillation zone, a light hydrocarbon solvent fraction, and passing at least a portion thereof into said contacting zone; and,

(h) recovering from said fractional distillation zone, hydrorefned hydrocarbon product having substantial freedom from organo-metalic contaminants.

9. Process of claim 8 wherein said second concentration of organo-metallic contaminants does not exceed 50 p.p.m. by weight of free metal in said low boiling fraction.

10. Process of claim 8 wherein said low boiling fraction contains a second concentration of asphaltic constituents below said irst concentration, said high boiling fraction contains a third concentration of asphaltic constituents above said second concentration, and said hydrorened product has substantial freedom from asphaltic constituents.

11. Process of claim 8 wherein said reaction zone conditions convert a portion of said low boiling fraction into a hydrorefined hydrocarbon fraction comprising light hydrocarbon solvent.

12. Process of claim 8 wherein said extract liquid phase is passed from said contacting zone directly into said reaction zone without intervening component separation.

13. Process of claim 8 wherein said raffinate liquid phase is passed from said contacting zone directly into said fractional distillation zone without intervening component separation.

14. Process of claim 8 wherein said light hydrocarbon solvent comprises atleast one hydrocarbon species having from three to ten carbon atoms per molecule.

15. Process of claim 14 wherein said light hydrocarbon 18 solvent comprises at least one hyrocarbon selected from the group consisting of pentane, hexane, heptane, and octane.

16. Proces of claim 14 wherein said contacting zone is maintained at a temperature in the range of from about 100 F. to about 500 F., at a pressure in the range of from about atmospheric pressure to about 25 atmospheres, and at a solvent-to-feedstock ratio in the range of from about 0.5 1.0 to about 5.0: 1.0.

References Cited UNITED STATES PATENTS 2,606,141 8/ 1952 Meyer 208-211 2,973,313 2/1961 Revere et al. 208-212 3,155,607 11/ 1964 Friess 208-212 3,598,720 8/ 1971 Stolfa 208--57 HERBERT LEVINE, Primary Examiner U.S. Cl. X.R.