US3365389A - Residuum conversion process - Google Patents

Description

1958' B. e. SPARS ETAL 89 RES IDUUM CONVERSION PROCESS Filed June 1, 1966 BYRON a. SPARS ROBERT H. KOZLOWS/(l E q "3 D 3 N Q i v N 7) LIJ II 3 2 im y E INVENTORS HIGH-METALS I A RESIDUUM/ United States Patent 3,365,389 RESIDUUM CONVERSKON PROCESS Byron G. Spars, Mill Valley, and Robert H. Kozlowski,

Berkeley, Calif., assignors to Chevron Research Company, San Francisco, Calif., a corporation of Delaware Continuation-impart of application Ser. No. 372,448, June 4, 1964. This application June 1, 1966, Ser. No. 554,423 5 Claims. (Cl. 208-59) This application is a continuation-in-part of copending application Ser. No. 372,448 entitled, Residuum Conversion Process, filed June 4, 1964, now abandoned.

This invention relates to processes for converting the highest boiling portions of crude petroleum and like hydrocarbonaceous materials to lower boiling distillate oils. More particularly, the invention relates to processes for converting high boiling oils to lower boiling oils by the combined actions of hydrogen and elevated temperature.

Since crude petroleum (and similar oils derived from carbonaceous deposits of ancient origin) are composed primarily of materials boiling above about 700 F., but the hydrocarbon materials boiling below about 700 F. have greatest economic value, many processes have been devised and proposed for converting the higher boiling materials to lower boiling materials. Many methods are available for converting the distillate portion, i.e., materials boiling up to an end point of about 1000 F., to lower boiling distillates, but the problem remains what to do with the asphaltic residuum or remainder boiling above about 1000 F. This residuum generally contains asphaltenes, metal compounds, and other nonhydrocarbon contaminants. Solvent decarbonizing processes such as propane deasphalting can be used to separate nonasphaltic oil from the asphaltic residuum, but there is thereby produced a more asphaltic residuum, which is not readily disposed of. Some of the asphaltic residuum can be used in the production of asphalt, but the residuum from most crude oils is not of suitable quality. Consequently, most of the asphaltic residuum ends up being burned as low value fuel.

A portion of the residuum can be converted to distillates by thermal cracking, but excessive production of coke limits conversion to fairly low levels of below about 60 volume percent. The addition of hydrogen donor diluent materials, such as saturated hydrocarbon ring compounds, to the residuum in thermal cracking effects some improvement, but the conversion still cannot be increased above about 60% without excessive coke formation, Even when hydrogen itself is added to the residuum in thermal cracking, to effect what is termed herein thermal hydrocracking, coke production is still excessive if it is attempted to obtain high conversions, e.g., above about 60 volume percent, even at very high pressures. The same holds true if the residuum and hydrogen are contacted with an active hydrocracking catalyst.

By taking a low per-pass conversion in thermal hydrocracking, and recycling unconverted residuum in a high ratio to net feed, coke formation in the reaction zone can be made small, but coke forms later, from precursors of benzene insolubles which are formed during thermal hydrocracking. That is, precursors of benzene insolubles apparently form at thermal hydrocracking conditions when the conditions are severe enough to give more than about 60% conversion of net residuum feed to distillates. These precursors actually form benzene insolubles (which includes coke) rather slowly. This formation of benzene insolubles frequently causes clogging in lines and equipment downstream of the thermal hydrocracking zone and gives rise to the formation of unstable and incompatible fuels.

In the aforementioned prior application it was proposed to hydrocrack residua using fixed beds of active hydrogenation catalysts at thermal hydrocracking reaction conditions leading to the conversion of at least of the residuum boiling above 900 F. to distillates boiling below 900 F. At the high conversion levels in the presence of the hydrogenation catalysts, benzene insolubles were prevented from forming. It is found, however, that when processing a metal contaminated residuum, the catalyst beds become plugged with metal deposits. Guard chambers were provided to take out the metal compounds, but it is found that the metals cannot be removed completely without using conditions causing such a high conversion of the residuum to distillates that benzene insolubles form in the guard bed, causing plugging by coke deposits.

The present invention is directed to a type of processing disclosed in the aforesaid prior application, wherein an active hydrocracking catalyst is used to promote conversion of the residuum at lower temperatures than could be used with the hydrogenation catalysts of low hydrocracking activity. In the present invention a fixed bed of active hydrocracking catalyst is used to promote conversion of residuum to distillates at lower temperature conditions where bed-plugging metal deposits do not form. This becomes possible because the plugging metal compounds are first removed in a guard bed employing porous solid contact particles at conditions limiting the conversion by thermal hydrocracking to below the point at which benzene insolubles form.

As mentioned, nearly all crude residua contain metal compounds, but the amounts and types of metals may vary considerably depending on the geographic and geological origin of the oil. Certain South American crudes, for example, contain large amounts of vanadium but only small amounts of other metals. Other crudes, for example Middle Eastern, contain a broad spectrum of metals in only moderate concentrations, mostly metals such as nickel and vanadium with smaller amounts of such metals as iron, sodium, and calcium. Still other crudes, for example California crudes, contain large amounts of many metals, including large amounts of iron, sodium, and calcium.

It has been found that when residuum is passed through a bed of solid porous contact particles at elevated temperature and hydrogen pressure, some of the metal compounds present in the residuum will form metalliferous deposits on and between the contact particles in the bed, whereas other metal compounds in the residuum form metalliferous deposits within the pores of the contact particles, It is found that the first-mentioned class of metal compounds, forming deposits on and between the particles, includes such metals as iron, sodium, calcium, and some of the vanadium compounds. The second-mentioned class of metal compounds, forming deposits within the pores, includes such metals as nickel and most of the vanadium compounds.

Metal compounds in the first-mentioned class generally tend to decompose to form deposits more readily under the influence of heat and hydrogen than metal compounds in the second-mentioned class, but there does not appear to be a clear line of demarcation in this respect. After residuum has been passed through a bed of porous contact particles at elevated temperature and hydrogen pressure effective to decompose metal compounds in the residuum, metalliferous deposits of both types are found throughout the bed. The amount of each type of deposit is greatest near the inlet end of the bed, decreasing toward the outlet end of the bed with respect to the direction of oil flow. The deposits of the class including iron, sodium, and calcium present a special problem in that, because the deposits form on and between the particles, the bed may become clogged with deposits restricting oil flow therethrough. The deposits of nickel and vanadium which form within the pores of the particles could build up to substantial concentrations without restricting oil flow through the bed and, in many cases, without too adversely affecting catalytic activity in a situation where, for example, hydrogenation or hydrocracking catalyst particles are used as the porous contact particles.

The present invention provides a process for hydrocracking a hydrocarbon residuum feed containing above about 50 parts per million metals in metal compounds, including metal compounds which form metalliferous deposits on and between solid particles when decomposed by hydrogenation in contact with such particles. The concentration level of 50 ppm. is about the point at which the resulting metal deposits become particularly troublesome in ordinary processing. In accordance with the invention, the residuum and hydrogen are passed through a first reaction zone comprising a bed of solid porous contact particles at thermal hydrocracking reaction conditions including a temperature of at least 820 F. elevated pressure, and space velocity effective to remove most of those metal compounds present in the residuum which form metalliferous deposits on and between the contact particles, with the proviso that no more than 50% of that portion of the residuum which boils above 900 F. is to be converted to distillates boiling below 900 F. in said zone. The residuum effluent of the first reaction zone is cooled to a temperature between about 730 F. and 800 F., and the cooled residuum and hydrogen are passed through a second reaction zone comprising at least one bed of solid active hydrocracking catalyst particles. The average temperature in the second zone is maintained below 800" F. at elevated pressure and space velocity effective to convert overall at least 80% of the residuum feed to distillates boiling below 900 F. and such that the concentration of benzene insolubles in the liquid oil efliuent of said second reaction zone does not exceed 0.1 weight percent. The porous contact particles have no more than slight hydrocracking activity such that the conversion to distillates occurring in the first reaction zone is substantially that which would occur at the conditions used in the absence of any catalyst. The hydrocracking catalyst particles have initially high activity such that the conversion to distillates in the second reaction zone is substantially greater than would occur in the absence of any catalyst.

The first reaction zone acts as a fixed bed guard chamber for the second reaction zone, which is a fixed bed hydrocracker. Deposits of the class exemplified by iron, sodium, and calcium are collected in the first reaction zone, being mostly removed from the residuum so that bed-plugging amounts of these metals do not reach the second reaction zone. To remove most of the metal compounds, thermal hydrocracking conditions have to be used. If the residuum contains large amounts of such metals as iron, sodium, and calcium, conditions in the first zone may have to be sufficiently severe as to remove also a substantial portion of the nickel and vanadium. Desirably, as much as possible of both classes of metal compounds is removed in the first reaction zone. However, conditions in the first reaction zone must not be so severe as to result in conversion of more than 50% of that portion of the residuum which boils above 900 F. to distillates boiling below 900 F., unless the particles comprise active hydrogenation catalysts, because otherwise the bed may then be plugged by coke or the benzene insolubles in oil passed to the second zone may increase, causing plugging there. The feasibility of operating in the above described manner, removing most of both classes of metals, thus depends on the amounts and relative amounts of metals in the different classes present in the residuum feed. Accordingly, it is within the contemplation of the invention to permit substantial passage of metal compounds of the class nickel and vanadium to the second reaction zone. When a lower temperature is used in the second, hydrocracking, reaction zone, the nickel and vanadium compounds can largely pass through unconverted, i.e. without forming deposits therein. The iron, sodium, and calcium would not do this because they form deposits more readily, i.e. at a lower temperature, and thus must always be removed in the first reaction zone. Thus, the first reaction zone is always operated in the previously described manner, using thermal hydrocracking conditions including a temperature of at least 820 F. The operation of the second reaction zone may later be changed by gradually increasing the average temperature therein as needed to maintain the desired conversion, as the catalysts hydrocracking activity declines with time, until in the range of about 820 F. To achieve continuous operation for a still longer time, residua can continue to be converted to distillates in the second reaction zone at thermal hydrocracking reaction conditions of 8209S0 F., whereby hydrocracking catalyst replacement or regeneration in the second reaction zone are not needed during a total run length of at least 2000 hours. In such a case, the porous contact particles containing collected metals in the first reaction zone would be replaced with fresh contact particles at least once during said run length. In the first reaction zone residuum and hydrogen are passed through a reaction chamber containing porous solid contact particles in at least one fixed bed through which the residuum and hydrogen pass, at thermal hydrocracking conditions including temperature of 820950 F. and pressure of 1000-5000 p.s.i.g., until most of the metal compounds present in the residuum which form metalliferous deposits on and between the contact particles are converted to such metalliferous deposits. Space velocities of 0.2-20 LHSV are used, providing a sufficiently short contact time such that no more than about of that portion of the residuum boiling above 900 F. is converted to distillate oil boiling below 900 F., so that the concentration of benzene insolubles in the liquid oil effluent of the first reaction zone does not exceed 0.1 weight percent. If the conversion to distillates is permitted to reach about weight percent, benzene insolubles are formed and the reaction chamber is in danger of plugging with coke. The porous solid contact particles employed have low activity for cracking at the conditions used such that the conversion occurs at a rate which is substantially that which would occur in the absence of any catalyst. Thus, suitable materials include alumina, silica-alumina composites, and various mixed oxides comprising mixtures or cogels of one of more of silica, alumina, magnesia, titania, zirconia, boria, and similar inorganic refractory oxides. Alundum is also usable, but it is much preferred that the contact particles have substantial surface area and porosity to increase their capacity for removing and retaining metal deposits. Active hydrogenation catalysts comprising refractory inorganic oxide carriers such as previously described promoted with sulfactive hydrogenation promoting metals and metal compounds, such as the metals, oxides, and sulfides of Group VI and Group VIII metals, are also operable, but their use cannot generally be justified. As disclosed in the aforementioned copending application, active hydrogenation catalysts can be employed at high conversions of about and above of residuum to distillates boiling below 900 F., but such high conversion is not desired and is to be avoided in the practice of the present invention. At the lower conversions of below about 50% specified herein, the relatively expensive active hydrogenation catalysts provide no particiular advantage over the inexpensive unpromoted refractory oxides which have substantially no catalytic hydrogenation activity.

Whether a particular porous solid contact material is suitable for use in the first reaction zone, or is too active for hydrocracking, can readily be determined by comparing the conversion of residuum to distillates obtained using the material with the conversion at the same conditions without any solid contact particles, at 800 F. or

higher. Conversion with a suitable porous contact will 5 not be significantly higher than with no catalyst or contact material present.

In the present invention, there is employed in the second reaction zone a catalyst which promotes hydrocracking. Thus, in a comparison test such as just described, the catalyst employed in the second reaction zone will accomplish substantially greater conversion of the portion of residuum boiling above 900 F. to distillates boiling below 900 F. Suitable catalytic materials comprise hydrogenation components such as metals or compounds of metals of Group VI and Group VIII distended or dispersed in or on a porous retfractory oxide carrier, having at least moderate hydrocracking activity. It will be understood that the hydrocracking activity referred to is that of the entire composite catalyst, rather than merely that of the support or carrier alone, Preferred hydrogenation components comprise molybdenum or tungsten, their oxides or sulfides, together with an iron group metal, oxide or sulfide, such as cobalt or nickel. Nickel sulfide in combination with molybdenum sulfide and/or tungsten sulfide is particularly preferred. To provide the catalyst in the form of particles suitable for use in a fixed bed, the hydrogenation components are attached to or incorporated in a refractory oxide carrier, for example by impregnation of a preformed carrier or by coprecipitation or cogellation with the carrier. The conventional hydrofining catalysts, such as cobalt-moly'bdenum-alumina, nickel-molybdenumalumina, unsupported cobalt-molybdate, and unsupported nickel-tungsten sulfide, do not appear to have sufficient hydrocracking activity for use in the second reaction zone of the present invention.

To provide sufficent hydrocracking activity there is preferably employed as the carrier a mixed oxide carrier such as silica-alumina, silica-magnesia, silica-titania, silicazirconia-alumina, and similar combinations. When promoted with hydrogenation promoting metals, the catalysts may act similarly to sulfactive hydrogenation catalysts at low temperature conditions ordinarily used for hydrofining. At temperatures above about 730 F., however, the hydrocracking activity of the preferred catalysts becomes appreciable. Such catalysts cannot be used for any appreciable length of time to treat residuum at the high temperature conditions used in the first reaction zone, because it is found that conversion is so rapid that the unit soon becomes plugged with coke. Accordingly, in the invention the effluent of the first reaction zone must be cooled to a lower temperature in the range 730 F.-800' F. for passage through the second reaction zone. Also, the average temperature in the second reaction zone is maintained below about 800 F for example by adding cold quenching medium such as hydrogen part-way through the second reaction zone. Elevated pressures of 1000-5000 p.s.i.g. and space velocities of 02-10 LHSV are employed effective to convert overall in the process at least 80% of the residuum feed to distillates boiling below 900 F. When the lower temperature conditions are employed in the second reaction zone, the concentration of benzene insolubles in the liquid oil effiuent thereof does not exceed 0.1 weight percent.

Referring noW to the single figure in the attached drawing, there is shown diagrammatically a suitable and preferred method of carrying out the process of the invention. As shown in the drawing, a heavy oil comprising residual components not removable by distillation and containing metal compounds of the class iron, sodium, and calcium, is passed via line 11, with hydrogenrich gas added from line 12, through line 13, furnace 14, and line containing valve 16 into first stage reaction zone 17. Reaction zone 17 contains high surface area porous contacting materials such as granules or particles of silica alumina or alumina. Reaction conditions employed in zone 17 include temperatures in the range 820 950 F., pressures of 1000-5000 p.s.i.g., and flow rate of oil relative to contact particles in the range 0.2- LHSV. The throughput of hydrogen relative to oil ranges 6 from about 2,000 to about 20,000 standard cubic feet per barrel. At suitable conditions within the named ranges, entrained solid trash is collected and organic metal compounds comprising metals of the class iron, sodium, and calcium are mostly converted to insoluble inorganic metal compounds which deposit on and around the porous contact particles. In addition, a portion of the organic nickel and vanadium compounds in the residuum feed are converted to metalliferous deposits which collect in the pores of the contact material. Conversion of the residual portion of the oil feed to distillates boiling below 900 F. is limited to less than 50%.

The entire effluent of zone 17 passes through line 18 containing valve 19 and is mixed with cold hydrogen-rich gas supplied via line 20 before passing through line 21 into second stage reaction zone 22. Reaction zone 22 contains particles of sulfactive hydrocracking catalysts in at least one fixed bed through which the at least partiallydemetallized residuum and hydrogen pass at reaction conditions including temperatures in the range 730-800 F., pressures of 1000-5000 p.s.i.g, desirably substantially the same as the pressure in reaction zone 17, and flow rate of oil relative to catalyst in the range 0.2-10 LHSV. The throughput of hydrogen relative to oil will range from 2,000 to 20,000 standard cubic feet per barrel. To prevent the average temperature in zone 22 exceeding 800 F., and to limit conversion of residuum to distillates being excessively high, cold hydrogen-rich quench gas may be introduced between catalyst beds in zone 22 via line 24. At suitable conditions within the named ranges, and with a suitable catalyst, the con-version of the residual portion of the oil feed to distillates boiling below 900 F. can be controlled so as to obtain virtually complete conversion of the fresh feed to distillate oil. As mentioned, preferably the conversion is overall at least to dis tillates. Because metal compounds of the class comprising iron, sodium, and calcium have been mostly eliminated lfrom the resid-um feed, the catalyst in reaction zone 22 does not tend to become plugged by metal deposits. Metal compounds are of the class comprising nickel and vanadium may still be present in the oil passed to zone 22, and these compounds will be converted to metalliferous deposits which, however, deposit in the catalyst pores rather than externally on the surfaces of the particles. Accordingly, there can also be added to the feed entering zone 22 a low metals content residuum from another source through line 23, the low metals content being with reference to metals of the class iron, sodium, and calcium and not excluding the possibility of nickel and vanadium being present.

The effluent of reaction zone 22 passes through line 25 to separation zone 26 wherein it is separated into a vapor portion in line 28 and a liquid portion in line 30 at substantially the temperature and pressure of reaction zone 22. To aid in vaporization of the distillate portion of the reaction zone efiluent a stripping medium such as hot hydrogen-rich gas or superheated steam may be introduced into the separator via line 27. The vaporized mixture in line 28 is cooled in heat exchanger 25? and passed to separation drum 31. Condensed liquid oils are withdrawn from drum 31 through line 32 and passed to distillation facilities, not shown, for recovery of distillate fractions. If superheated steam is used in separation zone 26, the condensed water is withdrawn from drum 3]. through line 33. A portion of light gases may be withdrawn through line 34 to maintain a high hydrogen partial pressure, and a substantially larger quantity of hydrogen-rich recycle gas is withdrawn through line 35 containing recycle gas compressor 36. As indicated, a portion of the hydrogen-rich recycle gas may be used as quench through line 24., but the major essential portion passes through line 37 for admixture with makeup hydrogen added through line 38, and is then mixed with the residuum feed via line 12. As described, a portion may be used to quench the material entering reactor 22 by passing through line 20.

The unvaporizable portion of oil withdrawn from separator 26 through line 30 contains the unconverted residual oil boiling above 900 F. and some distillates which may not have been separated therefrom. Preferably a small portion of this oil, amounting to no more than 20% of the net residuum feed, is withdrawn as a bleed stream which can be blended into fuel oil or used as a feedstock for the production of hydrogen. Any remaining portion may be recycled to reaction zone 22 as the low metals residuum of line 23.

Depending on the concentration of metals in the residuum feed, the porous contact solids in reaction zone 17 will sooner or later become heavily coated with a deposit of metal compounds of the class iron, sodium, and calcium. Before the preliminary contacting zone is saturated with such metal deposits and metals begin to deposit in the hydrocracking reaction zone 22, reaction zone 17 is taken out of service, and the oil and hydrogen are instead passed through another chamber containing porous solid contact material free of metal deposits. For example, as illustrated, there is provided another reaction chamber 17, which is shown as having the fixed bed of porous contact particles 40 being withdrawn therefrom, by means of crane 41, for treatment elsewhere to recover the metal deposits. A new bed of metal-free porous contact material is then placed in reactor 17, top head 39 is reinstalled on the reactor, and reaction chamber 17 can then be taken out of service by closing valves 16 and 19. Flow of preheated residuum and hydrogen is then through line containing valve 16, through chamber 17, and into reaction chamber 22 via line 18' containing valve 19'. The frequency with which a guard bed chamher is taken out of service in the above-described manner will be determined primarily by pressure drop increasing to restrictive levels as metal deposits collect therein. The entire bed need not be replaced each time fiow is switched to the other first-stage reaction chamber, as it is found that most of the plugging deposits are on the uppermost contact particles. For example, using bauxite, the top upstream 20% of a guard bed operated as specified herein contained five times as much deposited calcium, and nearly three times as much deposited iron, as the bottom downstream 20%. Accordingly, it is only necessary to scrape off and replace the top layer of particles. Ultimately, of course, downstream deposits build up to the point where all the particles should be renewed.

As the catalyst in reaction chamber 22 declines in hydrocracking activity, either due to the gradual accumulation in the pores of metal deposits of the class nickel and vanadium or simply due to prolonged exposure to the residuum at elevated temperature, the inlet and/ or average temperature therein can be gradually increased by decreasing the amount of cold hydrogen-rich quench gas added through line 20 and/ or through line 24. Conditions in reaction chamber 22 thus gradually approach thermal hydrocracking conditions. When such conditions are reached, namely a temperature above 820 F., the hydrocracking can still be continued at thermal hydrocracking conditions although the catalyst in zone 22 will no longer contribute substantially to the conversion achieved. In this way, however, a much longer run length can be achieved than if reaction zone 22 were always operated at thermal hydrocracking conditions with a nonhydrocracking catalyst having hydrogenation activity only, or with a porous contact material, in which latter case a much shorter run length would be obtained due to formation of benzene insolubles. A longer run length is attainable than with nonhydrocracking hydrogenation catalyst because of the long period of operation at low temperatures with the hydrocracking catalyst. The preferred catalysts used in reaction chamber 22 retain substantial hydrogenation activity even after the hydrocracking activity has been largely lost due to protracted usage.

The following examples illustrate operation of the process of the invention, show the importance of controlling certain of the process variables in the ranges disclosed herein, and present comparison with results obtained by processing outside the scope of the invention. The feedstock treated in Examples 13 was an atmospheric residuum of California crude oil having the following inspections:

Gravity, API 11.6 Sulfur, wt. percent 1.18 Total N, wt. percent 0.88 Oxygen, wt. percent 0.70 Rams. carbon, Wt. percent 7.8 Metals, p.p.m.:

Fe 60 Ni V 44 Na l6 Distillation (ASTM D-1l60):

St. F. 639 5 730 10 767 30 824 50 962 EP (at 55% overhead) 980 Sed. by ext, wt. percent 0.04 Vis., SSU: at 130 F 17,000 at 210 F. 703

Example 1.Operali0n 0f the first reaction zone The residuum and hydrogen were passed through a bed of particles of nickel-molybdenum-alumina sulfactive hydrogenation catalyst at 840 F., 2000 p.s.i.g., 2.5 LHSV, using 5,000 standard cubic feet of hydrogen per barrel. Conversion to distillates boiling below 900 F. was 35 This treatment removed of the iron, 70% of the sodium, but only 45-55% each of the nickel and vanadium. The space velocity was lowered to 1.25 LHSV to prolong the contact time in an effort to increase the metal removal. Conversion of the residuum to distillates increased to about 58%, and the iron and sodium content of the product began to vary erratically as coke evidently began to form in the reactor. When the space velocity was increased back to 2.5 LHSV, removal of nickel and vanadium was only about 40%, and only about 60% of the iron and less than 50% of the sodium were removed, showing that the catalyst was badly coked.

In another run at the same conditions, bauxite was used as the porous contact material. The results obtained were essentially the same as those using the nickel-molybdenum-alumina catalyst. Conversion was about 35% and nearly all of the iron and sodium were removed, with much less complete removal of nickel and vanadium, showing that it is not necessary to use an active hydrogenation catalyst in the first reaction zone.

At temperatures below about 820 F. less than half of the iron and sodium and very little of the nickel and vanadium are removed, with either the bauxite or the nickelmolybdenum-alumina catalyst. Other materials which it was found gave results essentially equivalent to the above included alumina and silica-alumina composites containing various proportions of silica and alumina, unpromoted with any hydrogenating metal components.

Example 2.-0perati0n of the second reaction zone Residuum and hydrogen were passed through a bed of nickel-molybdenum-silica-alumina sulfactive hydrocracking catalyst at an inlet and average bed temperature of 780 F. The reactor effluent was stripped with 10,000 standard cubic feet of hydrogen per barrel at reaction temperature and pressure, 2900 p.s.i.g., and the unvaporized portion was returned to the reactor inlet in about a 1:1 ratio with the feed. Space velocity was 1.0 LHSV. A bottom bleed stream amounting to about 13% Stripper Bottoms Overhead Gravity, API 28. 6 8 7 E-P Bed. by Ext, Wt. Percent 0. 08

1 At 42% overhead.

It is to be noted that the bottoms stream contained essentially no iron, but approximately the same concentration of nickel and vanadium as the feed.

Example 3.-Catalyst of low hydrocracking activity in the second reaction zone For comparison with the above Example 2, the residuum and hydrogen were passed through a bed of nickelmolybdenum-alumina catalyst of the type used in the first reaction zone in Example 1, at 830 F. As in Example 2, the effluent was stripped with hydrogen and a bottoms bleed stream was withdrawn, the remainder being recycled to the second zone, there being obtained essentially the same percentage conversion to distillates as in Example 2. No problem of coke plugging arose, but the bottoms bleed stream contained 0.05 weight percent benzene insoluble. The nitrogen content of the distillates produced was nearly five times as high as was obtained using the hydrocracking catalyst. At 1200 hours onstream the bottoms product contained 0.08 weight percent benzene insoluble. Lower conversions and even less purification of the residuum are obtained at temperatures below about 820 F. Other catalysts found to behave in essentially the same way as the nickel-molybdenum-alumina catalyst included conventional cobaltmolybdenum-alumiua hydrofining catalysts, nickel-molybdenum-alumina catalysts containing lower metal contents, and bauxite promoted with nickel and molybdenum.

Example 4.-Imprtance of the hydrocracking temperature In catalyst screening runs, a heavy crude oil mixture having a gravity of 14 API was introduced into a bed of nickel-tungsten-silica-magnesia sulfactive hydrocracking catalyst at 840 F., 1200 p.s.i.g., and 0.5 LHSV using 5,000 standard cubic feet of hydrogen per barrel. Conversion to distillates was high, but the reactor plugged with coke in about 60 hours. The nickel-tungsten-silicamagnesia catalyst has about the same hydrocracking activity as the nickel-molybdenum-silica-alumina catalyst used in Example 2, and the latter catalyst will likewise coke rapidly if started out at this high a temperature. Thus, it is essential to cool the effluent of the first reaction zone before passing the effluent to the second reaction zone, and it is important to control the average temperature in the second reaction zone below about 800 F. until the catalysts hydrocracking activity has substantially declined.

As disclosed in the aforementioned copending application Ser. No. 372,448, the eflluent of the second reaction zone may be worked up into distillate and residual fractions, including recycled unconverted residua, by a variety of flash separation, stripping at high temperature and pressure, and distillation techniques, and such disclosures are considered incorporated by reference herein.

As indicated, the feedstocks treated in the process of the invention are residual oils containing materials of such high molecular weight that they cannot be distilled overhead even under vacuum without the use of conditions resulting in their decomposition. In general, therefore, the feed will include a substantial portion of materials boiling above 1100 F. Included within the feeds, therefore, are topped crude oil, atmospheric reduced crude residum, vacuum reduced crude residum, and residual portions thereof such as may be obtained by solvent extraction of residua. The process is particularly advantageous for use in converting short residua, i.e., vacuum residum of high initial boiling point, substantially entirely to distillate oils. Thus, it is particularly desirable to remove from the feed by distillation and other conventional methods the distillable portion boiling up to about 900 F., whereby the maximum upgrading is obtained of the material boiling above 900 F. by means of the present invention.

We claim: 1. In a process for hydrocracking a hydrocarbon residuum feed containing above 50 p.p.m. metals in metal compounds, including metal compounds which form metalliferous deposits on and between solid particles when decomposed by hydrogenation in contact with such particles, said process comprising passing the residuum and hydrogen through a first reaction zone containing solid contact particles at elevated temperature and pressure and space velocity effective to remove metal compounds present in the residuum by hydrogenation, and passing the residuum and hydrogen effiuent of said first reaction zone through a second reaction zone containing solid catalyst particles at elevated temperature and pressure and space velocity effective to convert a portion of the residuum feed to distillates boiling below 900 F., the improvement which comprises: providing in said first reaction zone a bed of solid porous contact particles having no more than slight hydrocracking activity such that the conversion to distillates occurring in said first reaction zone is substantially that which would occur at the conditions used in the absence of any catalyst,

maintaining in said first reaction zone a temperature of at least 820 F. and space velocity effective to remove most of those metal compounds present in the residum which form metalliferous deposits on and between the contact particles, with the proviso that no more than 50 percent of that portion of the residuum which boils above 900 F. is to be converted to distillates boiling below 900 F. in said zone;

cooling the residuum effluent of said first reaction zone to a temperature between about 730 and 800 F. prior to passing said effluent through said second reaction zone;

providing in said second reaction zone at least one bed of solid active hydrocracking catalyst particles having initially high activity such that the conversion to distillates is substantially greater than would occur in said second reaction zone in the absence of any catalyst,

maintaining in said second zone an average temperature below 810 F. for at least that portion of the catalyst on-stream period up to about the first four hundred 1 1 hours, and space velocity effective to convert overall at least 80 percent of the residuum feed to distillates boiling below 900 F. and such that the concentration of benzene insolubles in the liquid oil efiluent of said second reaction zone does not exceed 0.1 weight percent.

2. Process carried out in accordance with claim 1 until the hydrocracking catalysts activity has substantially declined, thereafter continuing to operate said first reaction zone as aforesaid, and changing the operation of said second reaction zone by gradually increasing the average temperature therein as needed to maintain the desired conversion until in the range of about 820 F.

3. Process carried out in accordance with claim 2, and then continuing converting residua to distillates in said second reaction zone at thermal hydrocracking reaction conditions of 820950 E, whereby hydrocracking catalyst replacement or regeneration in said second reaction zone are not needed during a total run length of at least 2,000 hours.

4. Process in accordance with claim 3 wherein the porous contact particles containing collected metals in said first reaction zone are replaced with fresh contact particles at least once during said run length.

5. A process according to claim 1 wherein the temperature in said second reaction zone is maintained sufficiently below 810 F. such that metal compounds which form metalliferous deposits in the catalyst pores pass through said second reaction zone largely unconverted.

References Cited UNITED STATES PATENTS 1/1963 Oettinger 208-59 1/1966 Frumkin 208-89

Claims (1)

1. IN A PROCESS FOR HYDROCRACKING A HYDROCARBON RESIDUUM FEED CONTAINING ABOVE 50 P.P.M. METALS IN METAL COMPOUNDS, INCLUDING METAL COMPOUNDS WHICH FORM METALLIFEROUS DEPOSITS ON AND BETWEEN SOLID PARTICLES WHEN DECOMPOSED BY HYDROGENATION IN CONTACT WITH SUCH PARTICLES, SAID PROCESS COMPRISING PASSING THE RESIDUUM AND HYDROGEN THROUGH A FIRST REACTION ZONE CONTAINING SOLID CONTACT PARTICLES AT ELEVATED TEMPERATURE AND PRESSURE AND SPACE VELOCITY EFFECTIVE TO REMOVE METAL COMPOUNDS PRESENT IN THE RESIDUUM BY HYDROGENATION, AND PASSING THE RESIDUUM AND HYDROGEN EFFLUENT OF SAID FIRST REACTION ZONE THROUGH A SECOND REACTION ZONE CONTAINING SOLID CATALYST PARTICLES AT ELEVATED TEMPERATURE AND PRESSURE AND SPACE VELOCITY EFFECTIVE TO CONVERT A PORTION OF THE RESIDUUM FEED TO DISTILLATES BOILING BELOW 900*F., THE IMPROVEMENT WHICH COMPRISES: PROVIDING IN SAID FIRST REACTION ZONE A BED OF SOLID POROUS CONTACT PARTICLES HAVING NO MORE THAN SLIGHT HYDROCRACKING ACTIVITY SUCH THAT THE CONVERSION TO DISTILLATES OCCURRING IN SAID FIRST REACTION ZONE IS SUBSTANTIALLY THAT WHICH WOULD OCCUR AT THE CONDITIONS USED IN THE ABSENCE OF ANY CATALYST, MAINTAINING IN SAID FIRST REACTION ZONE A TEMPERATURE OF AT LEAST 820*F. AND SPACE VELOCITY EFFECTIVE TO REMOVE MOST OF THOSE METAL COMPOUNDS PRESENT IN THE RESIDUM WHICH FORM METALLIFEROUS DEPOSITS ON AND BETWEEN THE CONTACT PARTICLES, WITH THE PROVISO THAT NO MORE THAN 50 PERCENT OF THAT PORTION OF THE RESIDUUM WHICH BOILS ABOVE 900*F. IS TO BE CONVERTED TO DISTILLATES BOILING BELOW 900*F. IN SAID ZONE;

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