CA1182769A

CA1182769A - Two-bed catalytic hydroprocessing for heavy hydrocarbon feedstocks

Info

Publication number: CA1182769A
Application number: CA000370431A
Authority: CA
Inventors: Ronald S. Tolberg; Susan Bradrick
Original assignee: Chevron Research and Technology Co
Current assignee: Chevron USA Inc
Priority date: 1980-04-10
Filing date: 1981-02-09
Publication date: 1985-02-19
Also published as: GB2073770A; GB2073770B; JPH0435519B2; DE3114210A1; DE3114210C2; NL8101650A; AU6759581A; JPS56161494A; AU540482B2

Abstract

ABSTRACT OF THE DISCLOSURE
Heavy hydrocarbon feedstocks are hydroprocessed using a synergistic two-stage catalyst combination. The first stage catalyst comprises at least one group VIb or group VIII metal, metal oxide, or metal sulfide on a porous support and has an average pore diameter of 60-150 .ANG..
The second stage catalyst comprises at least one group VIb or VIII metal, metal oxide, or metal sulfide on a porous catalyst support and has an average pore diameter of 30-70 .ANG.. Preferably the first stage catalyst has at least 40% pore volume present as pores having diameters greater than 80 .ANG. and the second porous catalyst has at least 50%
pore volume present as pores having diameters smaller than 80 .ANG..

Description

7~i~

003 HEAVY ~IYDROCARBON FEEDSTOCKS

Q05 BACKG~OUND_OF _THE INVENTION
Q06 This invention relates to catalytic hydroprocessing C07 of heavy hydrocarbon feedstocks such as crude oil, topped 008 crude, reduced crude, a~mosphexic residual oil, vacuum residual 009 oil, deasphalted atmospheric or vacuum residua, vacuum gas oil, 010 coal liquefaction product fractions such as solvent refined 011 coal (SRC) and liquid solvent refined coal (SRC II), shale oil, 012 oil from tar sands, and other heavy hydrocarbonaceous 013 materials. Heavy hydrocarbon feedstocks suitable for pro-014 cessing according to this invention include those feedstocks 015 containing significant quantities, e.g. at least about 95~ by 016 weight materials boiling above 200C and particularly those 017feedstocks containing at least 25%, 50%, or 75~ material 015boiling above 300C or above 450C. The hydroprocessing pro-019 cess of the present invention can perform hydrodemetalation 020 hydrodesulfurization, hydrodenitrlfication, hydrocracking, 021 and/or hydrogenation of olefinic and aromatic hydrocarbons.
022 The process is particularly useful for the hydrocracking of 023 heavy feedstocks containing nitrogen and sulfur prior to fluid 024 catalytic cracking.
025DESCRIPTION C)~ THE PRIt:)R ART
026A number of workers have described hydroprocessing of 027 heavy hydrocarbons by sequential catalytic steps. Some cata-028 lyst arrangements provide high metals capacity in a first 02~ catalyst bed to reduce fouling of subse~uent catalysts. Other 030 systems employ successive catalytic zones individually 031 optimized for demetalation, desulfurization and denitrlflca-032tion. U.S. Patents 4,019,976 and 3,159,568 describe the use of 033 two catalyst beds wherein the second bed contains a rnore active 034catalyst than the first. U.S. Patent 3,437,588 describes the 035 use of a mixture of hydrogenation catalysts on supports having 03620-lC0 A pores~ U.S. Patents 3,977,961 and 3,977,962 describe 037 two-stage catalyst systems containing 100-275 ~ pores in the 002 irst stage and 100-200 A pores in the second stage. ~.S.
003 Patent 3,696,027 describes hydrodesulfurization using a cata-004 lyst having graded macroporosity (pores greater than 500A).
005 The graded catalyst is packed in a downflow reactor with pore 006 volume varying from greater than 30~ macropores in the upper 007 section to less than 5~ macropores in the lower sections. U.S.
008 Patents 3,254,017 and 3,535,225 describe t~o-stage hydro-009 cracking using a first stage large pore catalyst and second 010 stage zeolites. U.S. Patent 3,385,731 suygests two-stage hydro-011 cracking using a large pore zeolite having 10 to 13 A pores in 012 the first stage and a small pore zeolite having 4 to 6 A pores 013 in the second stage. Two-stage catalyst beds wherein the pores 014 of the second stage catalyst are larger than those of the first 015 stage catalyst are depicted in U.S. Patents 3,730,879, 016 3,766,058, and 4,048,0600 018 It is an object of this invention to provide a two-019 stage catalyst system capable of effectively hydrocracking, 020 hydrodenitrifying and hydrodesulfurizing heavy hydrocarbon feed--021 stocks. It is a further object to provide such a catalyst 022 system useful in a single reactor under hydroprocesslng condi-023 tions without the need for separation of reaction products 024 between catalyst stages. It is a further object to prov1de 025 such a catalyst system having enhanced hydrocracking, hydrodeni-0~6 trification, and~'or hydrodesulfuri3ation activity. Another 027 object is to provide a two-stage catalyst system having 028 enhanced fouling resistance for hydrocracking, hydrodenitrifica-029 tion and/or hydrodesulfurization relative to elther of the 030 catalyst stages alone. A further object is to provide such a 031 catalyst configuration which ls capable of providing feedstock 032 of reduced metals, sulfur, and nitrogen content for subsequent 033 fluid catalytic cracking.
034 These and other objects are provided according to the 035 present invention in a process for hydroprocessing a heavy 036 hydrocarbon feedstock comprising the steps of:
037 (a) contacting said hydrocarbon feedstock with hydrogen under hydroprocessing conditions in the presence of a Eirs-t hydroprocessing catalyst comprising refractory suppor-t material and at least one metal, metal oxide or metal sulfide of groups VIb and VIII elements, said first hydroprocessing catalyst having an average pore diameter in -the range of 60-lS0 ~;
(b) contacting at least a por-tion of -the hydrocarbon pro-duct from said step (a) under hydroprocessing conditions with a second hydroprocessing catalyst comprising refractory support material and at least one metal, metal oxide or metal sulfide of groups VIb and VIII elements, said second hydroprocessing catalyst having an average pore diameter of 30-70 ~ and smaller than the average pore diameter of said first hydroprocessing catalyst, said first and second hydroprocessing catalysts con-stituting a synergistic hydroprocessing combination wherein said hydroprocessing conditions include a temperature at which at least one of the hydrocracking activity, the hydrodesulfuriza-tion activity, and the hydrodenitrification activity of said synergistic hydroprocessing combination exceeds the correspond-ing activity of said first hydroprocessing catalyst and said second hydroprocessing catalyst alone. Preferably the first stage catalyst has at least 40% and more preferably 50% pore volume in pores >80~. The second stage catalyst preferably has at least 50% and more preferably at least 90% pore volume present as pores having diameters smaller than 80A. The feed to the second contacting step can be the entire liquid hydrocarbon product of the first contacting step, or the entire product of the first contacting step, including reaction products of hydro-desulfurization (e.g. H2S) or hydrodenitrification (e.g. NH3).
The process of this invention is particularly applicable to -3a-hydroprocessing heavy hydrocarbon feedstocks containing above about 1 weight percent sulfur and abou-t 0.1 weight percent nitrogen. The first catalyst refractory suppor-t material preferably consists essentially of alumina, the second catalyst refractory support material preferably consists essen-tially of alumina and 10 to 70 weight % silica. It is preferred tha-t the hydrocarbonaceous feed contain less than about 5 weight %
asphaltenes such as a deasphalted atmospheric residuum, deasphal-ted vacuum residuum, vacuum gas oil, or mixtures thereof.
FIG. 1 is a graphical representation of the hydro-cracking activity of the catalyst combination of the invention compared to single catalysts.

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001 -4~

002 FIG. 2 is a graphical representation of the hydrode-003 sulfurization activity of the catalyst combination of this 004 invention compared to single catalysts.
005 FIG. 3 is a graphical representation of the hydrode-006 nitrification activities of the catalyst combination of this 007 invention compared to single catalysts.

009 According to this invention, the heavy hydrocarbon 010 feedstock is contacted under hydrprocessing conditions with at 011 least two catalyst beds to cause hydrodesulfurization, hydro-012 denitrification and/or hydrocracking of the feedstock. The 013 precise hydroprocessing conditions depend primarily upon the 014 extent of reaction needed. Hydroprocessing conditions include 015 temperatures in the range of 250 to 600C, preferably 350 to 016 500~C and most preferably 400 to 450C; total pressures in the 017 range of 30 to Z00 atmospheres, preferably 100 to 170 atmo-018 spheres and more preferably 120 to 150 atmosph`eres; hydrogen 019 partial pressures in the range of 25 to 190 atmospheres, prefer-020 ably 90 to 160 atmospheres and most preferably 110 to 140 atmo-021 spheres, and space velocities (LHSV) of 0.1 to 10, preEerably 022 0.3 to 5 and most preferably 0.5 to 3 hours 1, The catalyst of 023 each stage is comprised of a refractory ceramic support 024 material such as alumina, silica, magnesia, zirconia, or 025 mixtures thereof. The catalysts contain as a hydrogenation com-02.6 ponent one or more metals, metal oxides or metal sulfides, 027 selected from elements of group VIb and group VIII of the 028 Periodic Table of the Elements as set forth in Handbook of 029 Chemistry and Physics, 45th Ed~ Chesnical Rubber Company, 030 Cleveland, Ohio, 1964. It is preferred that each catalyst 031 contain at least one metal, metal oxide, or metal sulfide from 03~ group VIb and one metal, metal oxide or metal sulfide from 033 group VIII, for example, Co/~o, Ni/~o, Ni/~, etc. The metals 034 should typically be present in quantities of 5 to 25 weight %
035 of group VIb and 1 to 20 weight ~ of group VIII, as metals, 036 based upon total weight of catalyst, as is typical for hydropro-037 cessing catalysts. Promoters, such as phosphorus or titanium 002 as metals, oxides or sulfides, can be added, if desired. The 003 hydrogenation and promoter metals or metal compounds can be 004 included in the catalyst by any of the well known methods of im~
005 pregnation of a refractory shaped support, coprecipitating 006 comulling, cogelling, etc.
007 The catalyst supports of the first and second stage 008 differ in the pore size distribution. Catalyst for the fi.rst 009 bed, i.e., the bed which first encounters the heavy hydrocarbon 010 feedstock, has an average pore diameter within the range of 011 60-150, preferably 80-120A. The pore volume distribution is 012 such that at least 40%, preferably at least ~5%, and most 013 preferably at least 50~ of its pore volume is present in pores 014 having diameters larger than 80A. The catalyst for the second 015 bed is characterized by an average pore diameter within the 01~ range of 30-70, and preferably 40-60A. The pore volume distri~
017 bution is such that at least 50%, preferably at least 75~ and 018 most preferably at least 90% of its pore volume is present in 019 pores smaller than 80A in diameter. It has been found that a 020 combination of hydroprocessing catalysts having such pore 021 structures illustrates excellent hydrocracking, hydrodenitri-022 fication and hydrodesulfuri~ation activities as well as 023 enhanced fouling resistance relative to either catalyst alone.
024 Consequently, the two-bed catalyst configuration of this inven-025 tion can provide synergistic hydrodenitrification, hydrodesul-026 furization, and/or hydrocracking activities.
027 When heavy feeds are hydroprocessed in order to pro-028 duce lighter components, i.e~ hydrocracking, the second stage 029 catàlyst should have higher acidity, hence increased hydro-030 cracking activity, than the ~irst stage catalyst. The first 031 stage catalyst reduces the nitrogen content of the feedstock 03~ before it contacts the second stage catalyst thereby preserving 033 the acidity of the second stage. For example, the first stage 034 catalyst support material can be alumina and the second stage 035 catalyst support material can be alumina containing 10 to 70 036 weight % silica, more preferably ~0-60 weight ~ silica.
037 Activated forms of alumina such as beta, gamma, etc. can be 002 used in either stage if desired. Either catalyst can contain 003 zeolitic components; however, little improvement in hydro-004 cracking is obtained unless temperatures above about 430C are OOS used. Consequently, the process oE this invention operates 006 satisfactorily when one or both the first and second stage 007 catalysts are free of zeolitic components.
008 The hydroprocessing conditions of the first and 009 second catalyst beds can be the same or different. For 010 particularly heavy feedstocks, hydrogenation conditions should 011 be more severe in the first catalyst bed. It is believed that 012 the first catalyst bed results in some hydrocracking of heavy 013 materials to molecules more able to diffuse into the second 014 stage catalyst pores.
015 The first and second catalyst stages can be operated 016 as fluidized beds, moving beds, or fixed beds. When both beds 017 are operated as fixed beds, they can be disposed in fluid 01~ communication in a single reactor or reaction zone. No other 019 group VIb or VIII metal-containing catalytic material need be 020 present between the two catalyst stages, e.g. the stages can be 021 unseparated or separated only b~ porous support material or 022 reactor internals. It may be desirable, however, to include 023 inexpensive support catalysts between the beds, such as alumina 024 impregnated with less than 10 weight percent total metals, as 025 metals.
0~6 The catalysts in the fixed beds can be irregular 027 particulates or any of the other conven~ional catalyst shapes 028 and sizes. The catalysts are preferably in the form of 029 extrudate, spheres, pellets, trilobes, etc. having diameters of 030 1/8 inch or less.
031 In order to preserve the catalytic activity of the 032 catalyst beds, the feedstock entering the first catalyst bed 033 should contain no more than about 25 ppmw, total V, Ni, and Fe 034 as metals. Ine~pensive guard catalysts such as red mud, etc.
035 can be employed to demetalize the feed to the required metals`
036 level. Due to the small pore size of the first stage catalyst, 037 the feedstock should be substantially free of large asphaltene molecules. The feed preferably contains less than 5 weight % asphaltenes, more preferably less than 0.02 weight % asphaltenes. Asphaltenes are defined as hydrocarbonaceous materials which are soluble in benzene but not in n-}leptane.
~xamples of such low asphaltene feedstocks are solvent (e.g. liquefied propane) deasphalted atmospheric or vacuum residual oils, and vacuum gas oils, etc. from the fractionation of crude oil, shale oil, oil from tar sand, dissolved coal or other coal liquefaction products. The relative amounts of first and second stage catalyst in the process can range from 1:10 to 10:1, depellding upon the feedstock. Feedstocks higher in metals and heavy components generally require a greater proportion of first stage catalyst.
Catalysts useful in the first and second stages according to this invention can be obtained commercially, either as supports which can be impregnated or as catalysts containing the desired level of metals, metal oxides, or metal sulfides. Catalysts suitable for use in the first stage and second stage reactors can be prepared in the following manner. All percentages are by weight.
First Stage Catalyst Preparation Hydrated Kaiser alumina is peptized with concentrated IINO3. The resulting solution is back-titrated with concentrated Nl~ OH to a pll of 5. The mixture is extruded at a consistency of about 50% volatiles. The extrudate is surface-dried at 120C for 2 llours and at 200C for 2 hours. The dried extrudates are calcined at 750C for one hour in dry air. An impregnant is prepared by mixing 50 ml of crude phosphomolybdic acid (a mixture of 20 parts MoO3, 2 parts H3PO4 and 48 parts water and containing 2.5 weight % P, and 20.1 weight % Mo) with 0.8 ml of 85% 113PO4, followed by heating to 45C. 7 ml of an aqueous NiCO3, containing 62.8% NiO is added. After the solution becomes clear, it is cooled to 25C and diluted wilh water to a volume of 55cc per 100 grams of catalyst to be produced. The resulting impregnant solution is sprayed onto the extrudate under vacuum. The sprayed extrudate is allowed 7~

to stand at room temperature for one hour and is then surface-dried at 120C
for one hour. The dried catalyst is then calcined in 570 liters/hr of dry air for 6 hours at 95C, 4 hours at 230C, ~ hours at 400C and 4 hours at 510 C and allowed to coo]. The pore diameter can be varied, if desired, by conventional techniques, such as varying the back titration of the extrusion mix as described in United States 4,082,697.
Second Sta~e Catalyst Preparation (100 gram basis) A first solution is prepared by combining 407cc of H20, 66 grams of a 21.5% aqueous AlC13 solution, 57 grams of 30.7% aqueous NiC12 solution and 369 grams of an aqueous solution containing 5.15% TiC14, 81.3% AlC13, and 13.5% acetic acid. The heat of solvation produces a final temperature of about 40C for the first solution. A second solution is prepared by mixing 94 grams of a 28.7% aqueous SiO2 with 283cc H20. The second solution is added slowly to the first solution, with mixing. The pH is increased to 4.5 with aqueous N~140H (8.0%) whereupon a gel is formed. After a pH of 4.5 is obtained, 281 grams aqueous ammonium paratungstate [(N~l4)6W7024-6H20]
solution, containing 6~97%W, is added and the pH is raised to 7.5 by adding 8.0% NH40H, whereupon gellation is completed and coprecipitation occurs.
IE an aluminosilicate zeolite (e.g. ultrastable Y-type) component is desired, the necessary amount of a 25% aqueous zeolite slurry is added.
The catalyst gel is aged at 75 C Eor one hour and filtered. The filter cake is surface-dried and twice extruded. The extrudates are washed and calcined in air for 4 hours at 200C and 5 hours at 510C. Those familiar with the art of preparing cogelled catalyst supports can vary the pore size distribution, if desired, using conventional techniques such as adding a detergent as described in IJnited States Patent 3,657,151.
EXPERI~ENTAL
Several catalyst configurations were tested in a fixed bed pilot plant reactor. The feed was a mixture of Alaskan North Slope solvent deasphalted vacuum residuum and 27~

002 vacuum gas oil (3:2 vol. ratio). The properties of the feed 003 are shown in Table I.

006 Specific Gravity 0.95 007 S, wt. % 1.6 008 N, ~t. ~ 0.4 009 Ni/V/Fe, ppmw 8/7/4 010 Ramsbottom carbon, wt. ~ 3.0 011 Distillation, ASTM D1160 012 Start 258C

017 End Point ~90 018 % Recovery 73 019 The feed was passed through the pilot plant reactor 020 containing fixed beds of catalystsO The liquid hourly space 021 velocity was 1.0, total pressure was 135 atmospheres and 022 hydrogen pressure was 110 atmospheres. The temperature was 023 varied in order to measure the reaction constant. The hydro~
024 processing reactor atmosphere was provided by recycle gas from 02S the reactor at 890 cubic meters per cubic meter of feedstock.
026 The properties of catalysts tested are shown in Table 027 II. Catalyst C contained an ultrastable Y zeolite component.

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002 Table 3 sets forth the pore size distribution of the 003 catalysts. The pore distribution was obtained by nitrogen 004 adsorption technique, using a Digisorb 2500, Micrometrics 005 Instrument Corporation. The average pore diameter, as used 006 herein, is obtained by dividing the measured pore volume, in 007 cc/gm by the measured surface area, in m2/gm and multiplying 008 the result by 40,000.

011 Catalyst A B C D E

014 Pore Volume, cc/gm .40 .38 .40 .49 .40 015 Avg. pore O
016 diameter, A 10745 48 86 60 017 ~ volume present 018 as pores having 019 diameters, A
020 <30 ~
021 30-60 10appr.10098 15 85 022 60-80 40 - appr.2 50 15 024 90-100 15 - - appr.12 025 100-150 10 - - apprO 3 ~26 028 The catalysts were tested individually and in beds con-029 taining various combinations of two catalysts in equal volumes, 030 with a layer of the first catalyst directly over a layer of the 031 second catalyst. Reaction constants KHCR (hydrocracklng), KHDS
032 (hydrodesulfurization) and KHDN (hydrodenitrification) were 033 computed for the plant runs. These reaction constants are 034 plotted as a func~ion of catalyst temperature for single cata-035 lyst and 50/50 volume catalyst mixtures in Figures 1, 2 and 3.
036 ~HCR is equal to LHSV ln l-Xo 037 l-x OOl ~12 00~ where 003 x = liquid volume percent oE product boiling below 343C
004 and XO = liquid volume percent of feed material boiling 005 below 343C.
006 KHDS = (LEISV) 7 ln S~ where Sf = % sul~ur in the feeds~)c~
007 Sp 008 and Sp = ~ sulfur in the product 009 KHDN = LHSV ln Nf where Nf = ~ nitrogen in the feedstock 010 Np 011 and Np = % nitrogen in the product.
012 Because the ordinate has a logarithmic scale, the slope of the 013 straight lines is equal to dlog K/dT, which is a measure o~ the 014 activation energy or the reaction. FIGS. 1, 2 and 3 demon-015 strate that the combinations of catalysts A and B and A and C
OlG are synergistic in that the combinations have greater activa-017 tion energies (greater slopes) than either of the catalysts 018 alone. Because the reaction constants for the combined cata-019 lysts increase more rapidly with temperature than do the 020 -- reaction constants of either catalyst alone, there will 021 necessarily be a temperature above which the combination cata-022 lyst is more active for the particular reaction than either 023 catalyst alone. This corresponds to the intersection of the 024 appropriate lines connecting the calculated K values. Conse-025 quently, catalyst combinations for which the slope of ln K vsO
026 T, for at least one of hydrocracklng, hydrodesulfurization, and 027 hydrodenitrification, is greater than for either catalyst 028 component alone are defined as synergistic hydroprocessing 029 combinations. FIG. 1 demonstrates that at temperatures above 030 about 410C, the combination catalysts A/B and A/C have greater 031 hydrocracking activity than catalysts A or B alone. Catalyst 032 D/C would demonstrate greater activity than catalyst D above 033 about 427C. FIG. 2 shows that above about 415C and 421C
034 catalysts A/B and A/C, respectively, have greater desulfuriza-035 tion activity than either catalyst A or B. Catalyst D/C, on 036 the other hand, will not surpass catalyst D in 037 hydrodesulfurization temperature until much higher temperatures 038 are employed.

002 FIG. 3 shows that above about 410C and 416C, catalysts A/3 003 and ~/C have higher hydrodenitrification activitles than either 004 catalysts A or B alone. Again, nnuch higher temperatures will 005 be required before catalyst D/C becomes more active than 006 catalyst D. In order to best achieve the objects o~ this 007 invention, the catalyst components of the two-stage catalyst 008 should be selected so that enhanced hydrocracking, hydro-009 desulfurization, and/or hydrodenitrification activities are 010 achieved at the desired hydroprocessing temperature, e.g. most011 preferably in the 350 to 500C range. Table 4 sets forth the 012 product distribution and the precise reaction conditions of the 013 various runs. As seen, the combination of catalysts A and B
014 and C and D produce significantly higher naphtha (C5-205C) and 015 diesel (205 to 343C) fractions than do the individual catalyst 016 components.
017 Additional pilot plant runs were made to determine the 018 fouling rate of the combination bed of this invention relatlve 019 to larger pored catalyst, which would ordinarily be expected to 020 be the more resistant to fouling. The feedstock was an Alaskan 021 North Slope deasphalted oil having the composition set ~orth in 022 Table 5. In each case the feed was passed downwardly through a 023 bed having an impregnated A1203 guard catalyst compeising 40%
024 of the bed volume and situated above the catalyst sample 025 tested. The guard catalyst was a commercially low density 02~ catalyst containing about 2~ Co and 4~ ~lo present as oxides, 027 and having a pore volume of 0.67 cc/gm and an average pore 028 diameter of 80-lOOA.

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o o o o o o o o o o o o o ~ o o o o o o o o o 004 Specific Gravity .955 005 S, wt. ~ 1.4 006 N, wt. % 0.5 007 Ni/V/Fe, ppmw 10/5/3 008 Ramsbottom carbon, wt. ~ 3.8 010 Distillation, ASTM D1160 011 Start 385C

016 End Point 591 017 % Recovery 55 019 Table 6 sets forth the results of these fouling 020 tests. The hydrocracking fouling of the combination catalyst 021 charge proceeded at about the same rate as the single charge, 022 while the hydrodesulurization and hydrodenitrification fouling 023 rates of the combination catalyst A/B were approximately half 024 the ouling rates of catalyst A alone.

7~

004 FO~LING TEST

007 1.0 LHSV
008 105 atmospheres H2 011 Catalyst Charge, Vol. % 40~ Guard A12O3 40% Guard A12O3 012 60% A 30~ A
013 , 30~ B
015 ~HCR (Hr 016 SORl0.25, 22 LV% <343C 0.25, 22 LV% <343C
017 1600 Hr0.19, 17 LV% <343C 0.20, 18 LV~ <343C
018 HCR Fouling Rate 1C/Hr) 0.003 0.003 020 RHDS ~Hr 021 SORl 4.5, 150 ppm S 4.5, 150 ppm S
022 1600 Hr 3.2, 560 ppm S 3.7, 340 ppm S
024 HDS Fouling Rate (C/Hr) 0.0077 0.0044 .
026 KHDN (Hr 027 SORl 1.9, 700 ppm N 1.8, 780 ppm N
028 1600 Hr 1.0, 1730 ppm N 1.3, 1280 ppm N
030 HDN Fouling Rate (F/Hr) 0.023 0.011 oo323 1 Start of Run ~8~7~i~

002 DESCRIPTION OF T~E PREFERRED CONFIG[~RATION
003 A solvent-deasphalted vacuum gas oil having character-004 istics as shown in Table 5 is introduced with a hydrogen-con-005 taining gas into the upper portion of a downflow, fixed bed 006 catalytic reactor having at least 3 layers of catalyst 007 material The first, or upper, layer is a bed of guard cata-008 lyst such as alumina particles about 5 mm. in diameter having a 009 pore volume of about 0.7 cc/gram and an average pore diameter 010 of about 80 to 100 A. The second catalyst layer is comprised 011 of 2.5 mm~ particles of alumina impregnated with nickel, 012 molybdenum, and phosphorous compounds and calcined to provide a 013 catalyst containing about 2-5 wt. % Ni as NiO, 8-15 wt. ~ Mo as 014 MoO3 and 1-4 wt. ~ P as P2O5. The catalyst of the second layer 015 has a pore volume of about 0.4 cc/gram, an average pore 016 diameter of 80-120 A, and at least 50% pore volume in pores of 017 80 to 150 A diameter. The third catalyst layer is comprised of 018 1/10 inch particles of cogelled SiO2/A12O3 particles having a 019 SiO2/A12O3 ratio of about one-to-one and containing about O-9 020 wt. % Ni as NiO~ 4-25 wt.~ W--as WO3 and about 4 wt. ~ Ti as 021 TiO2. The third stage catalyst has a pore volume of about 0.4 022 cc/g and at least 90% pore volume in pores of 30 to 80 A. The Q23 first catalyst occupies about 40~ of the volume of the beds in 024 the reactor. The second and third beds are of equal volumeO
025 Additional catalys'cs such as alumina containing no more than 026 about 5-10% group VIb or VIII metals as metals can be used as 027 support catalysts between the beds or elsewhere in the reactor.
028 The reactor is operated at a liquid hourly space velocity, 029 based on the second and third bed volumes of 1.7. The total 030 pressure is 140 atmospheres with a 100-atmosphere E12 pressure.
031 The H2 flow rate is 140,000 liters/min. and the reactor 032 temperature is 425C. The product leaves the reactor below the 033 third catalyst layer and is fractionated at atmospheric 034 pressure. H2 is recovered from the vapor fracticn and recycled 035 to the reactor. Intermediate cuts of naphtha (C5-200C) and `
036 diesel (200-350C), are recovered. The 350C+ bottom fraction, 037 having significantly reduced nitrogen and sulfur contents, is 038 passed as feed to a conventional fluld catalytic cracking unit.

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002 The examples and embodiments herein are provided to 003 illustrate the invention and are not intended to b~ exhaustive 004 or limiting, the scope of the invention being limited only by 005 the claimsO

,

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for the hydroprocessing of a heavy hydrocarbon feedstock comprising the steps of:
(a) contacting said hydrocarbon feedstock with hydrogen under hydro-processing conditions in the presence of a first hydroprocessing catalyst comprising refractory support material consisting essentially of low-temperature alumina and at least one metal, metal oxide, or metal sulfide of Groups VIb and VIII elements, said first hydroprocessing catalyst having an average pore diameter within the range of 60-150.ANG., and (b) contacting at least a portion of the hydrocarbon product from said step (a) under hydroprocessing conditions with a second hydroprocessing catalyst comprising refractory support material and at least one metal, metal oxide, or metal sulfide of Groups VIb and VIII elements, said second hydroprocessing catalyst having an average pore diameter within the range of 30-70.ANG. and smaller than the average pore diameter of said first hydroprocessing catalyst, said first and second hydroprocessing catalysts constituting a synergistic hydro-processing combination, wherein said hydroprocessing conditions include a temperature at which at least one of the hydrocracking activity, the hydro-desulfurization activity, and the hydrodenitrification activity of said syner-gistic hydroprocessing combination exceeds the corresponding activity of said first hydroprocessing catalyst and said second hydroprocessing catalyst alone.

2. The process of Claim 1 wherein said first hydroprocessing catalyst has at least 40% pore volume present as pores having diameters greater than 80.ANG. and said second hydroprocessing catalyst has at least 50% pore volume present as pores having diameters smaller than 80.ANG..

3. The process of Claim 1 wherein said first hydroprocessing catalyst has at least 50% pore volume present as pores having diameters greater than 80.ANG. and said second hydroprocessing catalyst has at least 90% pore volume present as pores having diameters smaller than 80.ANG..

4. The process of Claim 1 in which substantially the entire hydrocarbon product of step (a) is fed to step (b).

5. The process of Claim 1 wherein said heavy hydrocarbon feedstock contains at least 1 weight percent sulfur, at least 0.1 weight percent nitrogen, less then 25 ppmw total V, Ni, and Fe, as metals, and less than 5 weight percent asphaltenes.

6. The process of Claim 1 wherein the refractory support material of said second hydroprocessing catalyst consists essentially of alumina and 10-70 weight percent silica.

7. The process of Claim 1 in which steps (a) and (b) are conducted in a single reaction zone containing a fixed bed of said first hydroprocessing catalyst and a fixed bed of said second hydroprocessing catalyst.

8. The process of Claim 1 in which said hydroprocessing conditions include a temperature of 350 to 500°C, a hydrogen pressure from 90 to 170 atmospheres and a liquid hourly space velocity of 0.3 to 5 hours-1.

9. The process of Claim 1 wherein said heavy hydrocarbon feedstock is a deasphalted vacuum residuum, a vacuum gas oil, or mixtures thereof.

10. The process of Claim 1 further comprising prior to said contacting step (a), contacting said heavy hydrocarbon feedstock with a bed of guard catalyst to reduce the total V, Ni, Fe content of said hydrocarbon feedstock to less than 25 ppmw as metals.

11. The process of Claim 1 wherein said first hydroprocessing catalyst comprises Ni and Mo as metals, oxides, or sulfides and refractory support material consisting essentially of low-temperature alumina and said second hydroprocessing catalyst comprises Ni, W, and Ti as metals, oxides or sulfides and refractory support material consisting essentially of alumina and 10 to 70 weight percent silica.

12. A process for the hydroprocessing of a heavy hydrocarbon feedstock containing less than 5 weight percent asphaltenes, less than 25 ppmw total V, Ni, and Fe as metals, at least 1 weight percent S, and at least 0.1 weight percent N, comprising the steps of:
(a) contacting said hydrocarbon feedstock with hydrogen under hydro-processing conditions in the presence of a first hydroprocessing catalyst comprising refractory support material consisting essentially of low-temperature alumina, said first hydroprocessing catalyst containing 1 to 20 weight percent as metal Ni, and 5 to 25 weight percent as metal Mo, as metals, oxides, or sulfides, said first hydroprocessing catalyst having an average pore diameter in the range of 60-150.ANG. and at least 40% of its pore volume present in pores having diameters greater than 80.ANG., and (b) contacting at least a portion of the hydrocarbon product from said step (a) under hydroprocessing conditions with a second hydroprocessing catalyst comprising a refractory support material consisting essentially of alumina and silica, said second hydroprocessing catalyst containing 1 to 20 weight percent as metal Ni and 5 to 25 weight percent as metal W, as metals, oxides, or sulfides, said second hydroprocessing catalyst having an average pore diameter in the range of 30-70.ANG. and at least 50% of its pore volume present in pores smaller than 80.ANG., said first and second hydroprocessing catalyst constituting a synergistic hydroprocessing combination, wherein said hydroprocessing conditions include a temperature at which at least one of the hydrocracking activity, the hydrodesulfurization activity, and the hydrodentrification activity of said synergistic hydroprocessing combination exceeds the correspond-ing activity of said first hydroprocessing catalyst and said second hydro-processing catalyst alone.

13. A process of Claim 12 in which said contacting steps (a) and (b) are carried out in a single reaction zone under the same hydroprocessing conditions, such that substantially the entire hydrocarbon product of said contacting step (a) is a feed for said contacting step (b).