EP0732389A2

EP0732389A2 - Complete catalytic hydroconversion process for heavy petroleum feedstocks

Info

Publication number: EP0732389A2
Application number: EP96103874A
Authority: EP
Inventors: James J. Colyar; James B. Macarthur
Original assignee: IFP Energies Nouvelles IFPEN
Current assignee: IFP Energies Nouvelles IFPEN
Priority date: 1995-03-16
Filing date: 1996-03-12
Publication date: 1996-09-18
Anticipated expiration: 2016-03-12
Also published as: EP0732389B1; JPH08325580A; EP0732389A3; ZA961830B; CA2171894C; JP3864319B2; DE69614165T2; DE69614165D1; CA2171894A1

Abstract

A process for high catalytic hydroconversion of heavy liquid hydrocarbon feedstocks, such as petroleum resid containing at least about 40 vol% material boiling above 975°F⁺, using two-staged catalytic reactors operated at elevated temperature and pressure conditions so as to produce increased yields of lower boiling hydrocarbon liquids and gas products. In the process, the feedstock is reacted with hydrogen in a first stage catalytic ebullated bed reactor operated at 820-875°F temperature, 1500-3500 hydrogen partial pressure, and 0.30-1.0 V_f/Hr/V_r space velocity. The first stage reactor effluent liquid portion is fed into a second stage catalytic reactor maintained at lower temperature of 700-800°F, 0.10-0.80 V_f/hr/V_r space velocity. The particulate catalyst material used in each stage reactor contains 2-25 wt.% active metals, and has 0.30-1.50 cm²/gm total pore volume and 100-400 m²/gm surface area. From the second stage reactor effluent, a vacuum bottoms fraction normally boiling above about 850°F and preferably above 900°F is removed and recycled back to the first stage reactor, so as to provide a recycle volume ratio to fresh feedstock of 0.2-1.5/1 and achieve increased hydroconversion to produce lower boiling liquid products. If desired, used catalyst withdrawn from the second stage reactor can be treated and passed back to the first stage catalytic reactor for further use therein before being discarded, so as to provide for matched reaction conditions and catalytic activity in each stage reactor.

Description

BACKGROUND OF INVENTION

This invention pertains to a catalytic two-stage hydroconversion process for achieving essentially complete hydroconversion of heavy petroleum-based feedstocks to produce lower-boiling hydrocarbon liquid products. It pertains particularly to such a process utilizing a high temperature first stage ebullated bed catalytic reactor and lower temperature second stage ebullated bed catalytic reactor, with extinction recycle of all distilled vacuum bottoms material back to the first stage reactor to provide 90-100 vol% hydroconversion of the feedstocks.
For H-Oil® catalytic hydroconversion processes for heavy petroleum feedstocks, effective use of the catalyst, poor product quality and disposition of unconverted residue material have been concerns for potential users. The catalytic hydroconversion of petroleum residua in a single-stage ebullated bed catalytic reactor with recycle of a vacuum bottoms fraction to the reactor is well known, having been previously disclosed in U.S. Patents No. 2,987,465 to Johanson and U.S. 3,412,010 to Alpert, et al. Also, U.S. Patent No. 3,322,665 to Chervenak et al discloses a process for catalytic treatment of heavy gas oil, in which a fractionator bottoms material is recycled to the reactor for further extinction reactions therein. U.S. No. 3,549,517 to Lehman discloses a single stage catalytic process in which a vacuum distillation side stream is recycled to the reactor. U.S. Patent No. 3,184,402 to Kozlowski, et al discloses a two-stage catalytic hydrocracking process with intermediate fractionation and some recycle of a distillation bottoms fraction to either a first or second catalytic cracking zone. U.S. Patent No. 3,254,017 to Arey, Jr. et al discloses a two-stage process for hydrocracking heavy oils utilizing small pore zeolite catalyst in the second stage reactor. U.S. No. 3,775,293 to Watkins, discloses a two-stage catalytic desulfurization process with recycle of some heavy oil fraction boiling above diesel fuel oil to a second stage fixed bed type reactor. U.S. No. 4,457,831 to Gendler discloses a two-stage catalytic hydroconversion process in which vacuum bottoms residue material is recycled to the second stage reactor for further hydroconversion reactions. Also. U.S. No. 4,576,710 to Nongbri et al discloses a two-stage catalytic desulfurization process for petroleum residua feedstocks utilizing catalyst regeneration.
However, further process improvements are needed to achieve higher hydroconversion of heavy high boiling hydrocarbon liquid feedstocks, such as petroleum residua normally boiling above about 800°F, to produce desired low-boiling hydrocarbon liquid products. The present invention advantageously overcomes the concerns of potential users and provides a desirable improvement over the known prior art hydroconversion processes for heavy petroleum feedstocks.

SUMMARY OF INVENTION

This invention provides a catalytic two-stage ebullated bed hydroconversion process for heavy petroleum, residual oil and bitumen feedstocks, which process effectively hydroconverts essentially all of the high boiling residue material in the feedstock to desirable high quality lower boiling hydrocarbon liquid products. The process is particularly useful for those feedstocks containing 40-100 vol% 975°F⁺ petroleum resid and 10-50 wt% Conradson carbon residue (CCR), and containing up to 1000 wppm total metals (V+Ni). Preferred feedstocks should contain 75-100 vol% 975°F⁺ residual material with 15-40 wt% CCR, and 100-600 wppm total metals (V+Ni). Such feedstocks may include but are not limited to heavy crudes, atmospheric bottoms and vacuum resid materials from Alaska, Athabasca, Bachaquero, Cold Lake, Lloydminster, Orinoco and Saudi Arabia.
In the process, the fresh feedstock is introduced together with hydrogen into a first stage catalytic ebullated bed type reactor, which is essentially a high temperature hydroconversion reactor utilizing a particulate supported hydroconversion catalyst. The reactor is maintained at operating conditions of 820-875°F temperature, 1500-3500 psig hydrogen partial pressure, and space velocity of 0.30-1.0 volume feed per hour per volume of reactor (V_f/hr/V_r). The catalyst replacement rate should be 0.15-0.90 pound catalyst/barrel of fresh oil feed. The first stage reactor hydroconverts 70-95 vol.% of the fresh feed material and recycled residue material to form lower boiling hydrocarbon materials.
The first stage reactor effluent material is phase separated, a gas fraction is removed and the resulting liquid fraction is passed together with additional hydrogen on to a second stage catalytic ebullated bed type reactor containing a particulate high activity catalyst and which is maintained at lower temperature conditions of 700-800°F temperature and 0.10-0.80 V_f/hr/V_f, space velocity, so as to effectively hydrogenate the unconverted residue material therein. The second stage reactor catalyst replacement rate should be 0.15-0.90 pound catalyst/barrel feed to the second stage, which hydroconverts 10-50 vol% of the second stage feed material to lower boiling hydrocarbon materials.
The second stage reactor effluent material is passed to gas/liquid separation and distillation steps, from which hydrocarbon liquid product and distillation vacuum bottoms fraction materials are removed. The vacuum bottoms material boiling above at least 850°F temperature and preferably above 900°F is recycled back to the first stage catalytic reactor inlet at a volume ratio to the fresh feedstock of 0.2-1.5/1, and preferably at 0.5-1.0/1 recycle ratio for further hydroconversion extinction reactions therein.
Particulate catalyst materials which are useful in this petroleum hydroconversion process may contain 2-25 wt. percent total active metals selected from the group consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin, tungsten, and mixtures thereof deposited on a support material selected from the group of alumina, silica and combinations thereof. Also, catalysts having the same characteristics may be used in both the first stage and second stage reactors.
The particulate catalyst will usually be in the form of extrudates or spheres and have the following useful and preferred characteristics:
Catalysts having unimodal, bimodal and trimodal pore size distribution are useful in this process. Preferred catalysts should contain 5-20 wt.% total active metals consisting of combinations of cobalt, molybdenum and nickel deposited on alumina support material.
Thus for the present process, the heavy petroleum feedstock is first catalytically hydroconverted in the first stage catalytic higher temperature reactor, and the remaining resid fraction is catalytically hydrogenated in the second stage catalytic lower temperature reactor, after which a vacuum distilled 850°F⁺ fraction is recycled back to the first stage reactor for further hydrocracking reactions at the higher temperature maintained therein. Passing the first stage reactor liquid phase effluent material to the second stage reactor operated at lower temperature and space velocity conditions concentrates unconverted residue material, minimizes any gas velocity related problems in the second stage reactor, and reduces contaminant partial pressures (H₂S, NH₃, H₂O). The second stage catalytic reactions increase the hydrogen/carbon ratio of the residue being processed therein, thereby decreasing aromaticity and increasing the hydrogen donor capability of the residue, so that by its recycle back to the first stage reactor the hydrogenated residue can donate hydrogen to the fresh feedstock and the hydrogenated residue can also be more readily hydroconverted to desirable lower boiling fractions. This approach is more selective to producing high yields of desirable hydrocarbon liquid fuel products, i.e. reduced hydrocarbon gas contributes to high conversion operations. This catalytic hydroconversion process can also be further improved by selectively feeding fresh hydrogen to the second stage reactor and recycling hydrogen gas to the first stage reactor, so as to maximize hydrogen partial pressure in the more catalytic second stage hydrogenation reactor.
Also if desired, used catalyst in the second stage ebullated bed reactor can be withdrawn, treated to remove undesired fines, etc., and introduced into the first stage ebullated bed reactor for further use therein, before the used catalyst is withdrawn from the first stage reactor and discarded. Because of the presence of metal contaminants in the fresh heavy feedstock and the more thermal nature of the first stage reactions, utilizing used second stage catalyst material in the first stage reactor is appropriate and beneficial, because use of fresh, high activity catalyst in the higher temperature mainly thermal type reactor would not provide substantially improved catalytic activity therein. Also, by providing complete extinction of the feedstock resid fraction, any disposition problems usually related to an unconverted bottoms fraction material are eliminated.
This process advantageously provides for improved matching of the reaction conditions and the catalytic activity needed in each stage reactor, by providing higher reaction temperature and lower catalyst activity in the first stage reactor and lower temperature and higher catalyst activity in the second stage reactor, so as to achieve a more complete hydroconversion of the feedstock and effective use of the catalyst. This combination of the two staged reaction conditions is unexpectedly beneficial and results in essentially complete hydroconversion of heavy petroleum feedstocks to produce desirable lower boiling hydrocarbon liquid products, without substantially increasing reactor volume over the single stage approach to achieving high hydroconversion of the feedstock.
Other advantages of this catalytic two stage hydroconversion process for heavy petroleum feedstocks include complete destruction of the feedstock heavy residue fraction utilizing the selected catalytic reaction conditions, without producing undesired cokes, sediment or other such carbonaceous material in the reactors. The process also provides effective use of the catalyst by cascading used catalyst from the second stage ebullated bed reactor back to the first stage higher temperature ebullated bed reactor for further use therein. Optimal selection of reactor operating conditions and reactor volumes minimizes gas production and hydrogen consumption. After achieving effective hydrogenation of the unconverted residue in the second stage reactor, recycle of the hydrogenated residue material back to the first stage reactor provides effective hydroconversion with minimal gas and light ends production and with minimal additional hydrogen consumption. Passing the first stage reactor effluent liquid fraction to the second stage reactor concentrates liquid residue in the second stage reactor, and minimizes any operating problems therein due to incompatibility (light end fractions already being removed) and due to excessive gas velocity. Distillate (700-975°F) product quality is superior relative to that obtained from typical high conversion single stage H-Oil process operations due to the selective hydrogenation of the feedstock resid fractions in the second stage reactor.

BRIEF DESCRIPTION OF DRAWING

Fig. 1 is a schematic flow diagram of a catalytic two-stage hydroconversion process for processing heavy petroleum feedstocks to produce lower-boiling liquid and gas products according to the invention.

DESCRIPTION OF INVENTION

This invention will now be described in greater detail for a catalytic two-stage ebullated bed reaction process and system which is adapted for achieving substantially complete hydroconversion and destruction of residue material (975°F⁺ fraction) contained in heavy petroleum oil, residual oil, or bitumen feedstocks, and for producing desirable low-boiling hydrocarbon liquid products. As shown by Fig. 1, a pressurized heavy petroleum feedstock such as Cold Lake vacuum resid is provided at 10, combined with hydrogen at 12 and mixed with recycled hydrogenated heavy vacuum bottoms material at 13, and the combined stream 14 is fed upwardly through flow distributor 15 in first stage catalytic ebullated bed upflow reactor 16 containing catalyst ebullated bed 18. The total feedstock consists of the fresh hydrocarbon feed material at 10 plus the recycled vacuum bottoms material at 13. The recycle rate for the vacuum bottoms material at 13 to the first stage reactor 16 is selected so as to completely destroy or extinct this residue material in two staged catalytic reactors, with the recycle volume ratio of the vacuum bottoms material to the fresh oil feedstock being in the range of 0.2-1.5/1, and preferably 0.50-1.0/1 recycle ratio.
In the first stage reactor 16, the hydrocracking reactions are primarily thermal type as the reactor is maintained at a relatively high temperature of 820-875°F, at 1,500-3,500 psig hydrogen partial pressure, and liquid hourly space velocity of 0.30-1.0 volume feed/hr/volume of reactor (V_f/hr/V_r). The feedstock hydroconversion achieved therein is typically 70-95 vol %, with about 75-90 vol. % conversion usually being preferred. Preferred first stage reaction conditions are 825-850°F temperature, 2000-3000 psig, hydrogen partial pressure, and 0.40-0.80 V_f/hr/V_r space velocity. The catalyst bed 18 in first stage reactor 16 is expanded by the upflowing gas and reactor liquid to 30-60% above its settled height and is ebullated as described in more detail in U.S. Patent No. 3,322,665 which is incorporated herein by reference to the extent needed to describe operation of the reactor ebullated catalyst beds.
From first stage reactor 16, overhead effluent stream 19 is withdrawn and passed to phase separator 20. A liquid stream is withdrawn from the separator 20 through downcomer conduit 22, and is recirculated through conduit 24 by ebullating or recycle pump 25 back to the reactor 16. For the first stage reactor 16, the particulate catalyst material added at 17 is preferably used extrudate catalyst withdrawn at 36 from second stage reactor 30, and usually treated at zone 38 as desired to remove particulate fines, etc. at 37. Fresh make-up catalyst can be added as needed at 17a, and spent catalyst is withdrawn at connection 17b from catalyst bed 18.
From the phase separator 20, gaseous material at 21 is passed to a gas purification section 42, which is described further herein below. Also from the separator 20, a liquid portion 26 from the liquid stream 22 provides the liquid feed (∼700°F⁺) material upwardly through flow distributor 27 into the second stage catalytic ebullated bed reactor 30.
In the second stage catalytic reactor 30, which preferably has larger volume and provides lower space velocity than for the first-stage reactor 16, less hydroconversion and more catalytic hydrogenation type reactions occur. The second stage reactor 30 contains ebullated catalyst bed 28 and is operated at conditions of 700-800°F temperature 1,500-3,500 psig hydrogen partial pressure, and 0.10-0.80 V_f/hr/V_r space velocity, and thereby maximizes resid hydrogenation reactions which occur therein. Preferred second stage reaction conditions are 730-780°F temperature, and 0.20-0.60 V_f/hr/V_r space velocity. Additional fresh hydrogen is provided at 32 to the second stage reactor 30, so that a high level of hydrogen partial pressure is maintained in the reactor.
The catalyst bed 28 is expanded by 30-60% above its settled height by the upflowing gas and liquid therein. Reactor liquid is withdrawn from an internal phase separator 33 through downcomer conduit 34 to recycle pump 35, and is reintroduced upwardly through the flow distributor 27 into the ebullated bed 28. Used particulate catalyst is withdrawn at 36 from the second stage reactor bed 28 and fresh catalyst is added at 36 a as needed to maintain the desired catalyst volume and catalytic activity therein. This used catalyst withdrawn, which is relatively low in metal contaminant concentration, is passed to a treatment unit 38 where it is washed, and screened to remove undesired fines at 37, and the recovered catalyst at 39 provides the used catalyst addition at 17 to the first stage reactor bed 18, together with any fresh make-up catalyst added at connection 17a as needed.
The catalyst particles in ebullated beds 18 and 28 usually have a relatively narrow size range for uniform bed expansion under controlled upward liquid and gas flow conditions. While the useful catalyst size range is between 6 and 60 mesh (U.S. Sieve Series), the catalyst size is preferably particles between 8 and 40 mesh size including beads, extrudates, or spheres of approximately 0.020-0.100 inch effective diameter. In the reactor, the density of the catalyst particles, the liquid upward flow rate, and the lifting effect of the upflowing hydrogen gas are important factors in the desired expansion and operation of the catalyst bed.
From the second stage reactor 30, an effluent stream is withdrawn at 31 and passed to a phase separator 40. From this separator 40, a hydrogen-containing gas stream 41 is passed to the purification section 42 for removal of contaminants such as CO₂, H₂S, and NH₃ at 43. Purified hydrogen at 44 is recycled back to each reactor 16 and 30 as desired as the H₂ streams 12 and 32, respectively, while fresh hydrogen is added at 45 as needed.
Also from separator 40, a liquid fraction 46 is withdrawn, pressure-reduced at 47 to 0-100 psig, and is introduced into fractionation unit 48. A gaseous product stream is withdrawn at 49 and a light hydrocarbon liquid product normally boiling between 400-850°F are withdrawn at 50. A bottoms 850°F⁺ fraction is withdrawn at 52, reheated at heater 53, and passed to vacuum distillation step at 54. A vacuum gas oil liquid product is withdrawn overhead at 55. Vacuum bottoms stream 56, which has been hydrogenated in the second stage catalyst reactor 30, is completely recycled back to the first stage catalytic reactor 16 for predominantly thermal hydrocracking reactions therein using the low activity catalyst provided at 17. The recycle volume ratio for vacuum bottoms stream 56 to fresh feed 10 should be 0.2-1.5/1, and preferably should be 0.50-1.0/1. It is pointed out that by utilizing this two stage catalytic hydroconversion process, the thermal reactions and catalytic activity in each stage reactor are effectively matched, so that there is essentially no net 975°F⁺ hydrocarbon material produced from the process.
The process of the present invention will be further described by use of the following examples, which are illustrative only and should not be construed as limiting the scope of the invention.

EXAMPLE 1

A typical heavy vacuum resid feedstock such as Cold Lake vacuum resid is processed by using the catalytic two-stage hydroconversion process with vacuum bottoms recycle arrangement of the present invention. This Cold Lake vacuum resid feedstock contains 90 vol % 975°F⁺ material, 5.1 wt.% sulfur, 19 wt.% CCR, and 350 wppm metals (V+Ni), with the vacuum bottoms fraction normally boiling above 975°F being recycled back to the first stage catalytic reactor of the two-reactor system for further hydroconversion reactions and extinction recycle therein. The reaction conditions used and overall conversion results are summarized in Table 1 below.

Table 1

Hydroconversion of Cold Lake Vacuum Resid Feedstock
Catalyst Used	16-20 wt.% Cobalt-moly on alumina
Hydroconversion, Vol%	up to 100%

	Reactor 1	Reactor 2	Overall
Reaction Temperature, °F	827	760	--
H₂ Partial Pressure, psig	2,000	2,000	--
Reactor Space velocity, V_f/hr/V_r	0.40	0.20	--
H₂ Consumption, SCF/Bbl Feed	--	--	2570
Recycle Ratio	0.75	--	--
Catalyst Repl. Rate, Lb/Bbl Feed	0.435 (from 2nd reactor)	0.40 (fresh catalyst)	0.40
Residue (975°F⁺) Conversion, V%	76	26	99.6
Hydrodesulfurization, W%	80	58	93.5
Hydrodemetallization, W%	84	57	99
Hydrodenitrogenation, W%	35	20	67

Product Yields, % of Fresh Feed
C₁-C₃ Gas, W%	--	--	3.9
C₄-350°F, Naphtha, V%	--	--	21.0
350-650°F Mid Distillate, V%	--	--	52.2
650-975°F Gas Oil, V%	--	--	39.1
975°F⁺ Residue, V%	--	--	0.4
C₄-975°F Distillate, V%	--	--	112.3

As seen from the Table 1 results, by using the selected operating conditions and matching catalyst activity for the two staged reactors, the overall hydroconversion of the feedstock obtained by recycling the vacuum bottoms fraction back to the first stage reactor is 99.6 vol%, along with high percentage demetallization and desulfurization of the feedstock. A comparable improvement is also shown for the distillate product yields, with the total yield of the 975°F⁺ material being only 0.4% by volume.
Although this invention has been described broadly and in terms of preferred embodiments, it will be understood that modifications and variations of the process can be made all within the spirit and scope of the invention, which is defined by the following claims.

Claims

A process for catalytic two-stage hydroconversion of heavy petroleum-based feedstocks to provide high hydroconversion of the feed and produce lower-boiling hydrocarbon liquids and gases, said process comprising:
(a) feeding a heavy hydrocarbon liquid feedstock containing at least 40 vol, % normally boiling above 975°F together with hydrogen into a first stage catalytic ebullated bed reactor containing a bed of particulate catalyst, said catalyst containing active 2-25 wt.% total metal oxides selected from the group consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin, tungsten and mixtures thereof deposited on a support material selected from the group of alumina, silica and combinations thereof, said reactor being maintained at 820-875°F temperature, 1500-3500 psig hydrogen partial pressure, and 0.30-1.0 volume feed/hr/volume reactor (V_f/hr/V_r) overall space velocity, and catalyst replacement rate of 0.15-0.90 pound catalyst per barrel of fresh feedstock, for partially hydroconverting the feedstock and producing an effluent material containing gaseous and liquid fractions;

(b) phase separating said partially hydroconverted effluent material, withdrawing the gaseous fraction and passing the liquid fraction on to a second stage catalytic ebullated bed reactor containing a bed of particulate catalyst, said catalyst containing 2-25 wt.% total active metal oxides selected from the group consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin, tungsten and mixtures thereof deposited on a support material selected from the group of alumina, silica and combinations thereof, said reactor being maintained at 700-800°F temperature, 1500-3500 psi hydrogen partial pressure, and 0.10-0.80 volume feed/hr/volume reactor (V_f/hr/V_r) space velocity, and catalyst replacement rate of 0.15-0.90 pound catalyst per barrel of the feedstock for maximizing catalytic hydrogenation reactions and further hydroconverting the liquid fraction therein to produce hydrocarbon gases and lower boiling liquid fractions;

(c) removing said hydrocarbon gases and liquid fractions from said second stage reactor, separating the hydrocarbon gases from said liquid fractions and withdrawing the liquid fractions;

(d) distilling said liquid fractions to produce a medium boiling hydrocarbon liquid product having normal boiling range of 400-850°F and a vacuum bottoms material having a normal boiling point above about 850°F; and

(e) recycling said vacuum bottoms material directly to said first stage catalytic ebullated bed reactor to provide a recycle volume ratio of vacuum bottoms material to fresh feedstock of 0.2-1.5/1, so as to achieve at least about 75 vol % conversion of the 975°F⁺ fraction in the feed to lower boiling hydrocarbon material and produce increased yields of said medium boiling hydrocarbon liquid product.
A hydroconversion process according to claim 1, wherein said first stage reaction conditions are 825-850°F temperature, 2000-3000 psig hydrogen partial pressure, and 0.40-0.80 V_f/Hr/V_r space velocity.
A hydroconversion process according to claim 1, wherein said second stage reaction conditions are 730-780°F temperature, 2000-3000 psig hydrogen partial pressure, and 0.20-0.60 V_f/Hr/V_r space velocity.
A hydroconversion process according to claim 1, wherein said recycled vacuum bottoms material has a normal boiling point above about 900°F.
A hydroconversion process according to claim 1, wherein the volume ratio of vacuum bottoms material recycled to said first stage reactor to the fresh feedstock fed to said first stage reactor is about 0.5-1.0/1.
A hydroconversion process according to claim 1, wherein the catalyst used in said first stage and second stage reactors contains 5-20 wt.% total active metals and have total pore volume of 0.30-1.50 cc/gm, total surface area of 100-400 m²/gm and average pore diameter of at least 50 angstrom units.
A hydroconversion process according to claim 1, wherein the catalyst used in the first stage and second stage reactors has total pore volume of 0.50-1.20 cc/gm, total surface area of 150-350 m²/gm and average pore diameter of 100-250 angstrom units.
A hydroconversion process according to claim 1, wherein the catalyst used in said second stage catalytic reactor contains 5-20 wt.% cobalt-molybdenum on alumina support material.
A hydroconversion process according to claim 1, wherein the catalyst used in said second stage catalytic reactor contains 5-20 wt.% nickel-molybdenum on alumina support material.
A hydroconversion process according to claim 1, wherein used catalyst is withdrawn from said second stage catalytic reactor and passed to said first stage catalytic reactor as the catalyst addition therein and catalyst replacement rate is 0.20-0.80 pound catalyst per barrel of the fresh feedstock to said first stage reactor.
A hydroconversion process according to claim 1, wherein the feedstock is petroleum residua material having 75-100 vol % normally boiling above 975°F and containing 10-50 wt.% Conradson Carbon Residue (CCR) and up to 1,000 wppm total metals.
A hydroconversion process according to claim 1, wherein the feedstock is bitumen derived from tar sands.
A hydroconversion process according to claim 9, wherein the feedstock contains 15-40 wt.% Conradson Carbon Residue (CCR) and 100-600 wppm total metals (Va + Ni).
A process for catalytic two-stage hydroconversion of heavy petroleum feedstocks to provide high hydroconversion of the feed and produce increased yields of lower boiling hydrocarbon liquids and gases, said process comprising:
(a) feeding a petroleum resid feedstock having 40-90 vol % boiling above 975°F and containing 15-40 wt.% Conradson Carbon Residue (CCR) and 100-600 wppm total metals (Va + Ni) together with hydrogen into a first stage catalytic reactor containing an ebullated bed of particulate catalyst, said catalyst containing 5-20 wt.% total active metal oxides selected from the group consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin, tungsten, and mixtures thereof deposited on a support material selected from the group of alumina, silica and combinations thereof, said catalyst having 0.30-1.50 cc/gm total pore volume and 100-400 m²/gm surface area, said reactor being maintained at 825-850°F temperature, 2000-3000 psig hydrogen partial pressure, and 0.40-0.80 volume feed per hour per volume of reactor (V_f/Hr/V_r) overall space velocity for partially hydroconverting the feedstock to produce an effluent material containing gaseous and liquid fractions;

(b) phase separating said partially hydroconverted effluent material, withdrawing the gaseous fraction and passing the liquid fraction on to a second stage catalytic ebullated bed reactor containing a bed of particulate catalyst, said catalyst containing 5-20 wt.% total active metal oxides selected from the group consisting of cadmium, chromium, cobalt, iron, molybdenum, nickel, tin, tungsten, and mixtures thereof deposited on a support material selected from the group of alumina, silica and combinations thereof, said catalyst having 0.30-1.50 cc/gm total pore volume and 100-400 m²/gm surface area, said reactor being maintained at 730-780°F temperature, 2000-3000 psig hydrogen partial pressure, and 0.20-0.60 V_f/Hr/V_r overall space velocity, and catalyst replacement rate of 0.15-0.90 pound fresh catalyst per barrel of the feedstock for maximizing catalytic hydrogenation reactions and further hydroconverting the liquid material therein to produce hydrocarbon gases and lower boiling liquid fractions;

(c) removing said hydrocarbon gas and liquid fractions from said second stage reactor, separating said hydrocarbon gases from said liquid fractions, and withdrawing the liquid fractions;

(d) distilling said liquid fractions to produce a medium boiling hydrocarbon liquid product having a normal boiling range of 400-900°F and also a vacuum bottoms material having a normal boiling point above 900°F; and

(e) recycling said vacuum bottoms material directly back to said first stage catalytic ebullated bed reactor to provide a recycle volume ratio of recycled vacuum bottoms material to fresh feedstock of about 0.5-1.0/1, and withdrawing used catalyst from said second stage catalytic reactor and passing it to said first stage catalytic reactor as catalyst addition therein at a catalyst replacement rate of 0.15-0.90 pounds catalyst per barrel of feedstock, so as to achieve substantially complete overall conversion of the 975°F⁺ fraction to lower boiling hydrocarbon material and produce increased yields of said medium boiling hydrocarbon liquid product.