CA1184522A - Process for reducing coke formation in heavy feed catalytic cracking - Google Patents
Process for reducing coke formation in heavy feed catalytic crackingInfo
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- CA1184522A CA1184522A CA000378365A CA378365A CA1184522A CA 1184522 A CA1184522 A CA 1184522A CA 000378365 A CA000378365 A CA 000378365A CA 378365 A CA378365 A CA 378365A CA 1184522 A CA1184522 A CA 1184522A
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Abstract
ABSTRACT OF THE DISCLOSURE
A method for decreasing the amount of coke produced during the cracking of hydrocarbon feedstock to lower molecular weight products in a reaction zone (10) is disclosed, where the feedstock contains at least two metal contaminants selected from the class consisting of nickel, vanadium and iron, and where these contaminants become deposited on the catalyst. The method comprises passing the catalyst from reaction zone (10) through a reduction zone (70) maintained at an elevated temperature for a time sufficient to at least partially passivate the catalyst. The amount of coke may be decreased still further by the addition to reaction zone (10) of a hydrogen donor material.
A method for decreasing the amount of coke produced during the cracking of hydrocarbon feedstock to lower molecular weight products in a reaction zone (10) is disclosed, where the feedstock contains at least two metal contaminants selected from the class consisting of nickel, vanadium and iron, and where these contaminants become deposited on the catalyst. The method comprises passing the catalyst from reaction zone (10) through a reduction zone (70) maintained at an elevated temperature for a time sufficient to at least partially passivate the catalyst. The amount of coke may be decreased still further by the addition to reaction zone (10) of a hydrogen donor material.
Description
BACKGROUND OF THE INVENTION
2This invention relates to a ~nethod for 3decreasing the catalytic activity of metal contam-4inants on cracking catalysts and for decreasing the 5hydrogen and coke formation on cracking catalysts~
6More specifically, this invention is directed to a 7method for reducing the coke and hydrogen formation 8caused by metal contaminantsl such as nickel, vana-gdium and/or iron, which have become deposited upon cracking catalysts from feedstock containing sameO
11 In the catalytic cracking of hydrocarbon 12 feedstocks, particularly heavy feedstocks, vanadium, 13 nickel and/or iron present in the feedstock becomes 14 deposited on the cracking catalyst promoting exces-sive hydrogen and coke makes. These metal contamin-16 ants are not removed during conventional catalyst 17 regeneration operations during which coke deposits on 18 the catalyst are converted to C0 and C02. As used 19 hereinafter the term "passivation" is defined as a method for decreasing the detrimental cataly.ic 21 effects of metal contaminants such as nickel, vana-22 dium and iron which become deposited on catalyst.
23 U.S. Patent Nos. 3,711,422; 4,025,545;
24 ~,031,002; 4,111,8~5; 4,141,858; 4,1~8,712; 4,148,714 ~5 and 4,166,806 al] are directed to the contacting of 26 the cracking catalyst with antimony compounds to 27 passivate the catalytic ac~ivity of the ironf nickel 28 and vanadium contaminants deposited on the catalyst.
29 However, antimony compounds, alone, may not passivate the metal contaminants to sufficiently low levels 31 particularly where the metal contaminant concentra-32 tion on the catalys~ is relatively high. U.S~
33 Patent No. 4,176,084 is directed to the passivation 34 o metals contaminated catalyst in a regeneration ~iB~522 1 zone operated for incomplete combustion of the coke
2This invention relates to a ~nethod for 3decreasing the catalytic activity of metal contam-4inants on cracking catalysts and for decreasing the 5hydrogen and coke formation on cracking catalysts~
6More specifically, this invention is directed to a 7method for reducing the coke and hydrogen formation 8caused by metal contaminantsl such as nickel, vana-gdium and/or iron, which have become deposited upon cracking catalysts from feedstock containing sameO
11 In the catalytic cracking of hydrocarbon 12 feedstocks, particularly heavy feedstocks, vanadium, 13 nickel and/or iron present in the feedstock becomes 14 deposited on the cracking catalyst promoting exces-sive hydrogen and coke makes. These metal contamin-16 ants are not removed during conventional catalyst 17 regeneration operations during which coke deposits on 18 the catalyst are converted to C0 and C02. As used 19 hereinafter the term "passivation" is defined as a method for decreasing the detrimental cataly.ic 21 effects of metal contaminants such as nickel, vana-22 dium and iron which become deposited on catalyst.
23 U.S. Patent Nos. 3,711,422; 4,025,545;
24 ~,031,002; 4,111,8~5; 4,141,858; 4,1~8,712; 4,148,714 ~5 and 4,166,806 al] are directed to the contacting of 26 the cracking catalyst with antimony compounds to 27 passivate the catalytic ac~ivity of the ironf nickel 28 and vanadium contaminants deposited on the catalyst.
29 However, antimony compounds, alone, may not passivate the metal contaminants to sufficiently low levels 31 particularly where the metal contaminant concentra-32 tion on the catalys~ is relatively high. U.S~
33 Patent No. 4,176,084 is directed to the passivation 34 o metals contaminated catalyst in a regeneration ~iB~522 1 zone operated for incomplete combustion of the coke
2 to CO2 by periodically increasing the oxygen con-
3 centration above that required for complete combus-
4 tion of the coke and by maintaining the temperature above 1300F~ This patent does no~ disclose a 6 method for passivating metals-contaminated catalyst 7 in a system where the regeneration zone is routinely 8 operated for complete combustion of the coke.
9 U.S. Patent No. 4,162,213 is directed at decreasing the catalytic ac~ivity of metal contamin-11 ants present in cracking catalyst by regenerating the 12 catalyst at temperatures of 1300-1400F in such a 13 manner as to leave less than 0.10 wt. % residual 14 carbon on the catalyst.
lS Cimbalo, Foster and Wachtel in an article 16 entitled "Deposited Metals Poison FCC Catalyst"
17 published at pp 112~122 of the May 15, 1972 issue of 18 Oil and Gas Journal disclose that the catalytic 19 activit~ of metal contaminants decrease with repeated oxidation and reduction cycles.
21 U.S. Patent No. 3,718,553 is directed at 22 the use of a cracking catalyst impregnated with 23 100~1000 parts per million by weight (WPPM~ of iron, 2~ nickel or vanadium or a combination of these metals to increase the octane number of the cracked hydro-26 carbon products. This reference does not recognize 27 that use of certain of these metals may adversely 28 affect the catalyst selectivity or activity.
29 U.S. Patent Nos. 3,479,279 and 4,035,285 disclose hydrotreating of catalytic cracker produc~
31 cuts and recirculating this product to the catalytic 32 cracker. Related U~S. Patent Nos. 3,413,212 and 33 3,533,936 disclose the use of hydrogen donor mate-34 rials for decreasing the rate of coke formation on cracking catalystO These patents each disclose in i;2~
1 Table V that hydrotreating a fraction from a cata-2 lytic cracking zone and returning the hydrotreated 3 material with the cat cracker feed decreases the coke 4 make in the catalytic cracking zone. These patents also disclose that the hydrotreated material prefer-6 ably is a hydrogen donor material which releases 7 hydrogen to unsaturated olefinic hydrocarbons in a 8 cracking zone without dehydrogenative action. Suit-g able materials disclosed are hydroaromatic, naphthene aromatic and naphthenic compounds. Preferred mate-11 rials are compounds having at leas~ one and prefer-12 ably 2, 3 or 4 aromatic nuclei, partially hydro-13 genated and containing olefinic bondsO The hydrogen 14 donor ~aterial was hydrogenated by contacting the donor material with hydrogen over a suitable hydro-1~ genation catalyst at hydrogenation conditions~
17 The subject invention is directed at the ~8 addition of hydrogen donor material to a catalytic 19 cracking zone in which the metals contaminated cracking catalyst has been passivated by passing the 21 catalyst thro~gh a reduction zone maintained at 22 an elevated temperature. The addition of hydrogen 23 donor material and passivation of the cracking catalyst operate to decrease the coke makes on the cracking catalyst.
27 This invention is direc~ed at a method for 28 reducing the rate of coke produc~ion from a hydro-~9 carbon feedstock cracked to lower molecular weigh~
products in a reaction zone containing cracking 31 catalyst where the feedstock contains at least ~
32 ~16 selected from the class consisting of nickel, 33 vanadium and iron and where at least some of the ~ ~r/~at~ 7a~ t hecon-~s 34 metal ~Ym~s}~-be4~e deposited on the catalyst.
The method comprises passing the catalyst after -- 4 ~
1 regeneration from the reaction zone through a 2 reduction zone maintained at an elevated temperature 3 for a time sufficient to at least partially passivate O~ 7~a~
the metal ~}rrn~ on the catalyst, a reducing environ~ent maintained in the reduction zone by the 6 addition to the reduction zone of a material selected 7 from tne class consisting of hydrogen, carbon monox-~ ide and mixtures thereof, said passivated ca~alyst 9 thereafter passing to the reaction zone without further processing. The metal ~ may be 11 further passivated by the addi~ion to the reaction 12 zone of a hydrogen donor material which transfers 13 hydrogen ~o the hydrocarbon feedstock and/or to the 14 cracked lower molecular weight products. The metal ~aJ~a~"~"-t _CQ~;w~ ~ may be passivated still further by 16 monitoring the concentration of each metal con-17 taminant on the catalyst and adding predetermined ~8 amounts of selected metal contaminants to the system.
lg The catalyst may be still further passivated by the addition of known passivation agents to the system~
21 The temperature of the reduction zone preferably is 22 maintained above about 600C. The hydrogen donor 23 material added to the reaction zone preferably has a 24 boiling point between about 200C and about 500C~
2$ In a preferred embodiment, the hydrogen donor 26 material is obtained by fractionating the cracked 2.7 molecular products Erom the reaction zone, passing 28 the desired fraction through a hydrogenation zone and 29 then recirculating the material to the reaction zone.
~ . ... . . .... _ _ 32 The Figure is a flow diagram of a fluidized 33 catalytic cracking unit employing the subject inven-34 tion.
2;~
DETAILED DESCRIPTION O~ THE INVENTION
. .
R~ferring to the Figure, ~he present invention is shownas applied to a typical fluid catalytic cracking process~ Various items such as pumps, compressors, steam lines, instrumentation and other process equipmen~ ha~ been omitted to simplify the drawing.
Reaction or cracking zone 10 is shown containing a fluidized catalys~ ~ed 12 having a level at 14 in which a hydrocarbon feed-stock is in-troduced into the fluidized bed through lines 16 and 94 for catalytic cracking. The hydrocarbon feedstock may comprise nAphthas, light gas oils, heavy gas oils, residual fractions, reduced rude oils t cycle oils derived from any of these, as well as suitable fractions derived from shale oil kerogen, tar sands, bitumen processing, synthetic oils, coal hydrogenation, and the like. Such feedstocks may be employed singly, separately in paxallel reaction zones, or in any desired combination. Typically, these feedstocks will contain metal contaminants such as nickel, vanadium and/or iron. Heavy feedstocks typically contain rela-tively high concentrations of vanadium and/or nickel as well as coke precursors, such as Conradson carbon materials. The deter-mination of the amount of Conradson carbon material present maybe cletermined by ASTM test D189-65 Hydrocarborl gas and vapors p~ing through fluidized bed 12 maintain the bed in a dense tur-bulent fluidized condition. Preferably hydrogen donor material pas.ses through line 92 for preblending with cat cracker feedstock in l:Lne 16 prlor to entering fluidized catalyst bed 12 through line ~4. Alternatively the hydrogen donor material may be added clirectly to reaction zone 10 in close proximity 1 to the point where the cat cracker feedstock enters 2 reaction zone 10~ Typically, the hydrogen donor 3 material will comprise between about 5 and about 100 4 wt. ~ of the hydrocarbon feedstock to be cracked.
In reaction zone 10, the cracking catalyst 6 becomes spent during contact with the hydrocarbon 7~ ~eedstock due to the deposition of coke thereon.
8 Thus, the terms "spentl' or l'coke contaminated"
9 catalyst as used herein generally refer to catalyst which has passed through a reaction zone and which 11 contains a sufficient quantity of coke thereon to 12 cause activity loss, thereby requiring regenerationO
13 Generally, the coke content of spent catalyst can 14 vary anywhere from about 0.5 to about 5 wt~ ~ or more~ Typically, spent catalyst coke contents vary 16 from about 0.5 to about 1.5 wt. %.
17 Prior to actual regeneration, the spent 18 catalyst is usually passed from reaction zone 10 into 19 a stripping zone 13 and contacted therein with a stripping gas, which is introduced into the lower 21 portion of zone 18 via line 20. The stripping gas, 22 which is usually introduced at a pressure of from 23 about 10 tG about 50 psig, serves to remove most of 24 the volatlle hydrocarbons from the spent catalyst. A
preferred stripping gas is steam~ although nitrogen, 26 other inert gase.s or flue gas may be employed.
27 Normally, the stripping zone is maintained at essen-28 tially the same temperature as the reaction zone, 29 i.eO from about 450C to about 600C. Stripped spent catalyst from which most of the volatile 31 hydrocarbons have been removed, is then passed from 32 the bottom of stripping zone 18, through U-bend 22 33 and into a connecting vertical riser 24 which extends 34 into the lower portion of regeneration zone 26. Air 52,~:
1 i5 added to riser 24 via line 28 in an amount suffic-2 ient to reduce the density of the catalyst flowing 3 therein, thus causing the catalyst to flow upward 4 into regeneration zone 26 by simple hydraulic balance In the particular configuration shown, the 6 regeneration zone is a separate vessel (arranged at 7 approximately the same level as reaction zone 10) 8 containing a dense phase catalyst bed 30 having a 9 level indicated at 32, which is undergoing regenera-tion to burn-off coke deposits formed in the reaction 11 zone during the cracking reaction, above which is a 12 dilute catalyst phase 34. An oxygen-containing 13 regeneration gas enters the lower portion of regener-14 ation zone 26 via line 36 and passes up through a grid 38 and the dense phase catalyst bed 30, main-16 taining said bed in a turbulent fluidized condition L7 similar to that present in reaction zone 10. Oxygen-18 contalning regeneration gases which may be employed 19 in the process of the present invention are those gases which contain molecular oxygen in admixture 21 with a sub~tantial portion of an inert diluent gasO
22 Air is a particularly suitable; regeneration gas. ~n 23 additional gas which may be employed is air enriched 24 with oxygen. Additionally, i desired, steam may be added to the dense phase bed along with the 26 regeneration gas or separately therefrom to provide 27 additional inert diluents and/or fluidization gas.
28 Typically, the specific vapor velocity of the regen 29 eration gas will be in the range of from about 0.8 to about 6.0 feet/sec., preferably from about 1.5 to 31 about 4 feet/sec.
32 Regenerated catalyst from the dense phase 33 catalyst bed 30 in the regeneration zone 25 flows 34 downward through standpipe 42 and passes through 1 U-bend 44r and line 80 into reduction zone 70 main-2 tained at a temperature above 500C preferably 3 above about 600C having a reducing agent such as 4 hydrogen or carbon monoxide, entering through line 72 to maintain a reducing environment in the reduction 6 zone to passivate the contaminants as described in 7 more detail hereinafter. The regenerated and passi-8 vated catalyst then passes from reduction zone 70 9 through line 82 and U-bend 84 into the reaction zone 10 by way of transfer line 46 which joins U-bend 84 11 near the level of the oil injection line 16 and 12 hydrogen donor line ~2.
13 By regenerated catalyst is meant catalyst 14 leaving the regeneration zone which has contacted an oxygen-containing gas causing at least a portion, 16 preferably a substantial portion, of the coke present 17 on t:he catalyst to be removed. More specifically, 18 the carbon content of the regenerated catalyst can 19 vary anywhere from about 0~01 to about 0.2 wt. %, but preferably is from about 0.01 to about 0.1 wt. %.
21 Predetermined quantities of selected metals or con-22 ventional passivation promoters may be added to 23 the hydrocar~on feedstock through lines 16 and/or 94, 24 if desired~ as described more fully hereinafter. The hydrocarbon feedstock for the cracking process, 26 containing minor amounts of iron, nickel and/or 27 vanadium contaminants is injected into line 46 28 through line 94 to form an oil and catalyst mixture 29 which is passed into fluid bed 12 within reaction zone 10. The metal contaminants and the passivation 31 promoter, if any, become deposited on the cracking 32 catalyst. Product vapors containing entrained 33 catalyst particles pass overhead from fluid bed 12 34 into a gas-solid separation means 48 wherein the entrained catalyst particles are separated therefrom
9 U.S. Patent No. 4,162,213 is directed at decreasing the catalytic ac~ivity of metal contamin-11 ants present in cracking catalyst by regenerating the 12 catalyst at temperatures of 1300-1400F in such a 13 manner as to leave less than 0.10 wt. % residual 14 carbon on the catalyst.
lS Cimbalo, Foster and Wachtel in an article 16 entitled "Deposited Metals Poison FCC Catalyst"
17 published at pp 112~122 of the May 15, 1972 issue of 18 Oil and Gas Journal disclose that the catalytic 19 activit~ of metal contaminants decrease with repeated oxidation and reduction cycles.
21 U.S. Patent No. 3,718,553 is directed at 22 the use of a cracking catalyst impregnated with 23 100~1000 parts per million by weight (WPPM~ of iron, 2~ nickel or vanadium or a combination of these metals to increase the octane number of the cracked hydro-26 carbon products. This reference does not recognize 27 that use of certain of these metals may adversely 28 affect the catalyst selectivity or activity.
29 U.S. Patent Nos. 3,479,279 and 4,035,285 disclose hydrotreating of catalytic cracker produc~
31 cuts and recirculating this product to the catalytic 32 cracker. Related U~S. Patent Nos. 3,413,212 and 33 3,533,936 disclose the use of hydrogen donor mate-34 rials for decreasing the rate of coke formation on cracking catalystO These patents each disclose in i;2~
1 Table V that hydrotreating a fraction from a cata-2 lytic cracking zone and returning the hydrotreated 3 material with the cat cracker feed decreases the coke 4 make in the catalytic cracking zone. These patents also disclose that the hydrotreated material prefer-6 ably is a hydrogen donor material which releases 7 hydrogen to unsaturated olefinic hydrocarbons in a 8 cracking zone without dehydrogenative action. Suit-g able materials disclosed are hydroaromatic, naphthene aromatic and naphthenic compounds. Preferred mate-11 rials are compounds having at leas~ one and prefer-12 ably 2, 3 or 4 aromatic nuclei, partially hydro-13 genated and containing olefinic bondsO The hydrogen 14 donor ~aterial was hydrogenated by contacting the donor material with hydrogen over a suitable hydro-1~ genation catalyst at hydrogenation conditions~
17 The subject invention is directed at the ~8 addition of hydrogen donor material to a catalytic 19 cracking zone in which the metals contaminated cracking catalyst has been passivated by passing the 21 catalyst thro~gh a reduction zone maintained at 22 an elevated temperature. The addition of hydrogen 23 donor material and passivation of the cracking catalyst operate to decrease the coke makes on the cracking catalyst.
27 This invention is direc~ed at a method for 28 reducing the rate of coke produc~ion from a hydro-~9 carbon feedstock cracked to lower molecular weigh~
products in a reaction zone containing cracking 31 catalyst where the feedstock contains at least ~
32 ~16 selected from the class consisting of nickel, 33 vanadium and iron and where at least some of the ~ ~r/~at~ 7a~ t hecon-~s 34 metal ~Ym~s}~-be4~e deposited on the catalyst.
The method comprises passing the catalyst after -- 4 ~
1 regeneration from the reaction zone through a 2 reduction zone maintained at an elevated temperature 3 for a time sufficient to at least partially passivate O~ 7~a~
the metal ~}rrn~ on the catalyst, a reducing environ~ent maintained in the reduction zone by the 6 addition to the reduction zone of a material selected 7 from tne class consisting of hydrogen, carbon monox-~ ide and mixtures thereof, said passivated ca~alyst 9 thereafter passing to the reaction zone without further processing. The metal ~ may be 11 further passivated by the addi~ion to the reaction 12 zone of a hydrogen donor material which transfers 13 hydrogen ~o the hydrocarbon feedstock and/or to the 14 cracked lower molecular weight products. The metal ~aJ~a~"~"-t _CQ~;w~ ~ may be passivated still further by 16 monitoring the concentration of each metal con-17 taminant on the catalyst and adding predetermined ~8 amounts of selected metal contaminants to the system.
lg The catalyst may be still further passivated by the addition of known passivation agents to the system~
21 The temperature of the reduction zone preferably is 22 maintained above about 600C. The hydrogen donor 23 material added to the reaction zone preferably has a 24 boiling point between about 200C and about 500C~
2$ In a preferred embodiment, the hydrogen donor 26 material is obtained by fractionating the cracked 2.7 molecular products Erom the reaction zone, passing 28 the desired fraction through a hydrogenation zone and 29 then recirculating the material to the reaction zone.
~ . ... . . .... _ _ 32 The Figure is a flow diagram of a fluidized 33 catalytic cracking unit employing the subject inven-34 tion.
2;~
DETAILED DESCRIPTION O~ THE INVENTION
. .
R~ferring to the Figure, ~he present invention is shownas applied to a typical fluid catalytic cracking process~ Various items such as pumps, compressors, steam lines, instrumentation and other process equipmen~ ha~ been omitted to simplify the drawing.
Reaction or cracking zone 10 is shown containing a fluidized catalys~ ~ed 12 having a level at 14 in which a hydrocarbon feed-stock is in-troduced into the fluidized bed through lines 16 and 94 for catalytic cracking. The hydrocarbon feedstock may comprise nAphthas, light gas oils, heavy gas oils, residual fractions, reduced rude oils t cycle oils derived from any of these, as well as suitable fractions derived from shale oil kerogen, tar sands, bitumen processing, synthetic oils, coal hydrogenation, and the like. Such feedstocks may be employed singly, separately in paxallel reaction zones, or in any desired combination. Typically, these feedstocks will contain metal contaminants such as nickel, vanadium and/or iron. Heavy feedstocks typically contain rela-tively high concentrations of vanadium and/or nickel as well as coke precursors, such as Conradson carbon materials. The deter-mination of the amount of Conradson carbon material present maybe cletermined by ASTM test D189-65 Hydrocarborl gas and vapors p~ing through fluidized bed 12 maintain the bed in a dense tur-bulent fluidized condition. Preferably hydrogen donor material pas.ses through line 92 for preblending with cat cracker feedstock in l:Lne 16 prlor to entering fluidized catalyst bed 12 through line ~4. Alternatively the hydrogen donor material may be added clirectly to reaction zone 10 in close proximity 1 to the point where the cat cracker feedstock enters 2 reaction zone 10~ Typically, the hydrogen donor 3 material will comprise between about 5 and about 100 4 wt. ~ of the hydrocarbon feedstock to be cracked.
In reaction zone 10, the cracking catalyst 6 becomes spent during contact with the hydrocarbon 7~ ~eedstock due to the deposition of coke thereon.
8 Thus, the terms "spentl' or l'coke contaminated"
9 catalyst as used herein generally refer to catalyst which has passed through a reaction zone and which 11 contains a sufficient quantity of coke thereon to 12 cause activity loss, thereby requiring regenerationO
13 Generally, the coke content of spent catalyst can 14 vary anywhere from about 0.5 to about 5 wt~ ~ or more~ Typically, spent catalyst coke contents vary 16 from about 0.5 to about 1.5 wt. %.
17 Prior to actual regeneration, the spent 18 catalyst is usually passed from reaction zone 10 into 19 a stripping zone 13 and contacted therein with a stripping gas, which is introduced into the lower 21 portion of zone 18 via line 20. The stripping gas, 22 which is usually introduced at a pressure of from 23 about 10 tG about 50 psig, serves to remove most of 24 the volatlle hydrocarbons from the spent catalyst. A
preferred stripping gas is steam~ although nitrogen, 26 other inert gase.s or flue gas may be employed.
27 Normally, the stripping zone is maintained at essen-28 tially the same temperature as the reaction zone, 29 i.eO from about 450C to about 600C. Stripped spent catalyst from which most of the volatile 31 hydrocarbons have been removed, is then passed from 32 the bottom of stripping zone 18, through U-bend 22 33 and into a connecting vertical riser 24 which extends 34 into the lower portion of regeneration zone 26. Air 52,~:
1 i5 added to riser 24 via line 28 in an amount suffic-2 ient to reduce the density of the catalyst flowing 3 therein, thus causing the catalyst to flow upward 4 into regeneration zone 26 by simple hydraulic balance In the particular configuration shown, the 6 regeneration zone is a separate vessel (arranged at 7 approximately the same level as reaction zone 10) 8 containing a dense phase catalyst bed 30 having a 9 level indicated at 32, which is undergoing regenera-tion to burn-off coke deposits formed in the reaction 11 zone during the cracking reaction, above which is a 12 dilute catalyst phase 34. An oxygen-containing 13 regeneration gas enters the lower portion of regener-14 ation zone 26 via line 36 and passes up through a grid 38 and the dense phase catalyst bed 30, main-16 taining said bed in a turbulent fluidized condition L7 similar to that present in reaction zone 10. Oxygen-18 contalning regeneration gases which may be employed 19 in the process of the present invention are those gases which contain molecular oxygen in admixture 21 with a sub~tantial portion of an inert diluent gasO
22 Air is a particularly suitable; regeneration gas. ~n 23 additional gas which may be employed is air enriched 24 with oxygen. Additionally, i desired, steam may be added to the dense phase bed along with the 26 regeneration gas or separately therefrom to provide 27 additional inert diluents and/or fluidization gas.
28 Typically, the specific vapor velocity of the regen 29 eration gas will be in the range of from about 0.8 to about 6.0 feet/sec., preferably from about 1.5 to 31 about 4 feet/sec.
32 Regenerated catalyst from the dense phase 33 catalyst bed 30 in the regeneration zone 25 flows 34 downward through standpipe 42 and passes through 1 U-bend 44r and line 80 into reduction zone 70 main-2 tained at a temperature above 500C preferably 3 above about 600C having a reducing agent such as 4 hydrogen or carbon monoxide, entering through line 72 to maintain a reducing environment in the reduction 6 zone to passivate the contaminants as described in 7 more detail hereinafter. The regenerated and passi-8 vated catalyst then passes from reduction zone 70 9 through line 82 and U-bend 84 into the reaction zone 10 by way of transfer line 46 which joins U-bend 84 11 near the level of the oil injection line 16 and 12 hydrogen donor line ~2.
13 By regenerated catalyst is meant catalyst 14 leaving the regeneration zone which has contacted an oxygen-containing gas causing at least a portion, 16 preferably a substantial portion, of the coke present 17 on t:he catalyst to be removed. More specifically, 18 the carbon content of the regenerated catalyst can 19 vary anywhere from about 0~01 to about 0.2 wt. %, but preferably is from about 0.01 to about 0.1 wt. %.
21 Predetermined quantities of selected metals or con-22 ventional passivation promoters may be added to 23 the hydrocar~on feedstock through lines 16 and/or 94, 24 if desired~ as described more fully hereinafter. The hydrocarbon feedstock for the cracking process, 26 containing minor amounts of iron, nickel and/or 27 vanadium contaminants is injected into line 46 28 through line 94 to form an oil and catalyst mixture 29 which is passed into fluid bed 12 within reaction zone 10. The metal contaminants and the passivation 31 promoter, if any, become deposited on the cracking 32 catalyst. Product vapors containing entrained 33 catalyst particles pass overhead from fluid bed 12 34 into a gas-solid separation means 48 wherein the entrained catalyst particles are separated therefrom
5~
and returned through diplegs 50 leading back into fluid hed 12.
The product vapors are then conveyed through line 52 and condenser 102 into fractionation zone 100, wherein the product stream is separated into two or more fractions. Fractiona~ion zone 100 may comprise any means for separating the product into fractions having different boiling ranges. Typically, zone 100 may comprise a plate or packed column of conventional design. In the embodi-ment shown the product is separa~ed into an overhead stream exitiny through line 104, comprising light boiling materials, i.e.
compounds ~oiling below about 200C, a middle cut boiling in the range of about 200 to 370C exiting through line 106 and a bottoms stream boiling above about 370C exiting through line 108. At least a fraction of the product in line 106, preferably a major fraction, passes into hydrogenation zone 110 maintained under hydrogenating conditions where the product contacts hydrogen enterin~ zone 110 through line 112~ A gaseous stream may pass from æone 110 through line 114 for removal of any undesired by-products. Zone 110 typically will contain a conventional hydxo-genating catalyst as, for example, a molybdenum salt such as moly-bdenum oxide or molybdenum sulfide, and a nickel or cobalt salt,suah as nickel or cobalt oxides and/or sulfides. These salts ~ypically are deposited on a support material such as alumina and/or silica stabilized alumina. Hydrogenation catalysts which are particularly suitable are described in U.S. Patent No.
3,509,0~4. Zone 110 will be maintained at a temperature ranging between about 350 and 400C and a pressure ranging between about 600 and 3000 psi. A vapor stream exits zone 110 for ..,.~...
:~8~
1 recycling and a further processing (not shown)O
2 The at least partially hydrogenated stream exiting 3 zone 110, also referred to as the hydrogen donor 4 material, is recycled to the reaction zone through line 92.
and returned through diplegs 50 leading back into fluid hed 12.
The product vapors are then conveyed through line 52 and condenser 102 into fractionation zone 100, wherein the product stream is separated into two or more fractions. Fractiona~ion zone 100 may comprise any means for separating the product into fractions having different boiling ranges. Typically, zone 100 may comprise a plate or packed column of conventional design. In the embodi-ment shown the product is separa~ed into an overhead stream exitiny through line 104, comprising light boiling materials, i.e.
compounds ~oiling below about 200C, a middle cut boiling in the range of about 200 to 370C exiting through line 106 and a bottoms stream boiling above about 370C exiting through line 108. At least a fraction of the product in line 106, preferably a major fraction, passes into hydrogenation zone 110 maintained under hydrogenating conditions where the product contacts hydrogen enterin~ zone 110 through line 112~ A gaseous stream may pass from æone 110 through line 114 for removal of any undesired by-products. Zone 110 typically will contain a conventional hydxo-genating catalyst as, for example, a molybdenum salt such as moly-bdenum oxide or molybdenum sulfide, and a nickel or cobalt salt,suah as nickel or cobalt oxides and/or sulfides. These salts ~ypically are deposited on a support material such as alumina and/or silica stabilized alumina. Hydrogenation catalysts which are particularly suitable are described in U.S. Patent No.
3,509,0~4. Zone 110 will be maintained at a temperature ranging between about 350 and 400C and a pressure ranging between about 600 and 3000 psi. A vapor stream exits zone 110 for ..,.~...
:~8~
1 recycling and a further processing (not shown)O
2 The at least partially hydrogenated stream exiting 3 zone 110, also referred to as the hydrogen donor 4 material, is recycled to the reaction zone through line 92.
6 In regeneration zone 26, flue gases formed
7 during regeneration of the spent ca~alyst pass from
8 the dense phase catalyst bed 30 into the dilute
9 catalyst phase 34 along with entrained catalyst particles. The catalyst particles are separated from 11 the flue gas by a suitable gas-solid separation means 12 54 and returned to the dense phase catalyst bed 30 13 via diplegs 56~ The substantially catalyst-free flue 14 gas then passes into a plenum chamber 58 prior to discharge ~rom the regeneration zone 26 through line 16 60. Where the regeneration zone is operated for 17 substantially complete combustion of the coke, the 18 flue gas typically will contain less than abou~ 0.2, 19 preferably less than 0.1 and more preferably less than 0.05 volume % carbon monoxide The oxygen 21 content usually will vary from about 0.4 to about 7 22 vol. %, preferably from about 0.8 to about 5 vol~ %, 23 more pre~erably from about 1 to about 3 vol~ %, most 24 preferably from about loO to about 2 vol. %~
Reduction zone 70 may be any vessel provid 26 ing suitable contacting of the catalyst with a reduc-27 ing environment at elevated temperatures. The shape 28 of reduction zone 70 is not cri~ical~ In the embodi-29 ment shown, reduction zone 70 comprises a treater vescel having a shape generally similar to that of 31 regeneration zone 26, with the reducing environment 32 maintained, and catalyst fluidized by, reducing agent 33 entering through line 72 and exiting through line 78.
34 The volume of dense phase 74 having a level at 76 is dependent on the required residence time. The 1 residence time of the catalyst in reduction zone 70 2 i5 not critical as long as it is sufficient to effect 3 the passivation. The residence time will range from 4 about 5 sec. to about 30 min., typically from about 2 to 5 minutes. The pressure in this zone is not 6 critical and generally will be a function of the 7 location of reduction zone 70 in the system and the 8 pressure in the adjacent regeneration and reaction 9 zones. In the embodiment shown, the pressure in zone 70 will be maintained in the range of about 5 to 50 11 psia, although the reduction zone preferably should 12 be designed to withstand pressures of 100 psia. The 13 temperature in reduction zone 70 should be above 14 about 500C preferably above 600C, but below the temperature at which the catalyst sinters or de-16 gradesO A preferred temperature range is about 17 600-850C, with the more preferred temperature ran~e 18 being 650-750C. The reduction zone 70 can be 19 located either before or after regeneration zone 26, with the preferred location being after the 21 regeneration zoner so that the heat irnparted to the 22 catalyst by the regeneration obviates or minimizes ~3 the need for additional catalyst heating~ The 24 reducing agent utilized in the reduction zone 70 is not critical, although hydrogen and carbon monoxide 26 are the preferred reducing agents. Other reducing 27 agents including light hydrocarbons, such as C3 28 hydrocarbons, may also be satisfactory.
29 Reduction zone 70 can be constructed of any chemically resistant material sufficiently able to 31 withstand the relatively high temperatures involved 32 and the high attrition conditions which are inherent 33 in systems wherein fluidized catalyst is transported.
34 Specifically, metals are contemplated which may or may not be lined. More specifically, ceramic liners 36 are contemplated within any and all portions of the - 12 ~
1 reduction zone together with alloy use and structural 2 designs in order to withstand the maximum contem-3 plated operating temperatures~
4 The reducing agent utilized in all but one of the following tests was high purity grade hydrogen, 6 comprising 99.9% hydrogenO In the remaining test, 7 shown in Table VIII a reducing agent comprising 99.3%
8 CO was utilized. It is expected that commercial 9 grade hydrogen, commercial grade CO, and process gas streams containing H2 and/or CO can be utilizedn 11 Examples include cat cracker tail gas, catalytic 12 reformer off gas, spent hydrogen streams from cata-13 lytic hydroprocessing, synthesis gas~ and flue 14 gases. The rate of consumption of the reducing agent in reducing zone 70 will, of course, be dependent on 16 the amount of reducible material entering the 17 reducing zoneO In a typical fluidized catalytic 18 cracking unit it is anticipated that about 10 to 100 19 scf of hydrogen or about 10 to 100 scf of CO gas would be required for each ton of catalyst passed 21 through reduction zone 70.
22 If the reducing agent entering through line 23 72 is circulated through reduction zone 70 and thence 24 into other units, a gas-solids separation means may be required for use in connection with the reduction 26 zone. If the reducing agent exiting from zone 70 is 27 circulated back into the reduction zone, a gas-solids 28 separation means may not be necessary. Preferred 29 separation means for zones 10, 26 and 70 will be cyclone separators, multiclones or the like whose 31 design and construction are well known in the art.
32 In the case of cyclone separators, a single cyclone 33 may be used, but preferably, more than one cyclone 34 will be used in parallel or in series flow to effect the desired degree of separa~ion~
l The construction of regeneration zone 26 2 can be made with any material sufficiently able to 3 withstand the relatively high temperatures involved 4 when afterburning is encountered within the vessel and ~he high attrition conditions which are inherent 6 in systems wherein fluidized catalyst is regenerated 7 and transported. Specifically/ metals are contem-~ plated which may or may not be lined. More specif g ically, ceramic liners are contemplated within any and all portions of the regeneration zone ll together with alloy use and structural designs in 12 order to withstand temperatures of about 76QC and, 13 for rea50nably short periods of time, temperatures 14 which may be as high as 1000C.
The pressure in the regeneration zone is 16 usually maintained in a range from about atmospheric 17 to about 50 psig., preferably from about 10 to 50 18 psig. It is preferred, however, to design the 19 regeneration zone to withstand pressures of up to about 100 psig. Operation of the regeneration zone 21 at increased pressure has the effect of promoting the 22 conversion of carbon monoxide to carbon dioxide and 23 redllcing the temperature level within the dense bed 24 phase at which the substantially comp]ete combustion Of carbon monoxide can be accomplished. The higher 26 pressure also lowers the equilibrium level of carbon 27 on regenerated catalyst at a given regeneration 23 temperatureO
29 The residence time of the spent catalyst in the regeneration zone is not critical so long as the 31 carbon on the catalyst is reduced to an acceptable 32 level. In general, it can vary from about l to 33 30 minutes. The contact time or residence time of 34 the flue gas in the dilute catalyst phase establishes the extent to which the combustion reaction can reach 1 equilibrium. The residence time of the flue gas may 2 vary from about 10 to abou~ 60 seconds in the regen-3 eration zone and from about 2 to about 30 seconds in 4 the dense bed phase. Preferably, the residence time of the flue gas varies from about 15 to about 20 6 seconds in the dense bed.
7 The present invention may be applied ~ beneficially to any type of fluid cat cracking unit g without limitation as to the spatial arrangement of the reaction, stripping, and regeneration zones, with 11 only the addition of reduction zone 70 and related 12 elementsO In general, any commercial catalytic 13 cracking catalyst designed for high thermal stability 14 could be suitably employed in the present invention.
Such catalysts include those containing silica and/or 16 alumina. Catalysts containing combustion promoters 17 such a3 platinum can be used~ Other refractory metal 18 oxides such as magnesia or zirconia may be employed 19 and are limited only by their ability to be effec-tively regenerated under the selected conditions.
21 With particular regard to catalytic cracking, pre-22 ferred catalysts include the combinations of silica 23 and alumina, containing 10 to 50 wt. ~ alumina, and 29 particularly their admixtures with molecular sieves or crystalline alumino~ilicates. Suitable molecular 26 sieves include both naturally occurring and synthetic 27 aluminosilicate materials, such as faujasite, cha-28 bazite, X-type and Y-type aluminosilicate materials 29 and ultra stable, large pore crystalline alumino-silicate materials. When admixed with, for example, 31 silica-alumina to provide a petroleum cracking 32 catalyst, the molecular sieve content of the fresh 33 finished catalyst particles is suitably within 3~ the range from 5 35 wto ~, preferably 8-20 wt. ~. An equilibrium molecular sieve cracking catalyst may 2~
1 cor.tain as little as about 1 wt. % crystalline 2 material. Admixtures of clay-extended aluminas may 3 also be employed. Such catalysts may be prepared in 4 any suitable method such as by impregnation, milling, co~gelling, and the like, subject only to the provi-6 sion that the finished catalyst be in a physical 7 form capable of fluidization. In the following tests 8 a commercially available silica alumina zeolite g catalyst sold under the tradename CBZ-l, manufactured by Davison Division, W. R. Grace & Company was used 11 after steaming to simulate the approximate equilib-12 rium activity of the catalyst.
13 Fractionation zone 100, of conventional 14 design, typically is maintained at a top pressure ranging between about 10 and 20 psi and a bottoms 16 temperature ranging up to about 400C. The specific 17 conditions will he a function of many variables 13 including inlet product composition, inlet feed rates 19 and desired compositions in the overhead, middle cut and bottoms. The middle cut fed to hydrogena~ion 2L zone 110 preferably has a boiling range of about 200 22 to about 370C and is frequently referred to as a ~3 light cat cycle oil. The feed to the hydrogenation 24 zone, preferably light ca~ cycle oil, should include compounds which will accept hydrogen in zone llO and 26 readily release the hydrogen in reaction zone 1O
27 without dehydrogenative action. Preferred hydrogen 28 donor compounds include two ring naphthenic compounds 29 such as decahydronaphthalene (decalin) and two ring hydroaromatic compounds such as tetrahydronaphthalene 31 (tetralin).
32 Hydrogenation zone 110 may be of conven-33 tional design. Typical hydrogenation catalysts 34 include molybdenum salts and nickel and/or cobalt salts deposited on a support material~ The residence ,5~
time of the middle cut from zone 100 in the hydrogenation zone may range from about 10 to about 240 minutes, depending on the hydrogen donor, hydrogenation catalyst, operating conditions and the desired degree of hydrogenation.
As shown by the data in Tables I-~X the incorporatiOn of a reduction zone 70 is not effective for passivating a metal contaminated catalyst unless a temperature in excess of about 500C is used.
The data in Table X shows that use of a hydrogen donor also decreases hydrogen and coke makes. When the use of a hydrogen donor is combined with the previously described passi-vation process, this results in still lower coke malces.
Unless otherwise noted the following test conditions were used. The CBZ-l catalyst utilized was first steamed at 760C for 16 hours after which the catalyst was contaminated with the indicated metals by laboratory impregnation followed by calcining in air at about 540C for four hours~ The catalyst was then subjected to the indicated number of redox cycles. Each cycle consisted of a five-minute residence in a hydrogen atmos-phere, a ~ive-minute nitrogen flush and then a five-minute re~.idence in an air atmosphere at the indicated temperatures.
Followiny the redox cycles the catalyst was utilized in a micro-catalytic cracking (MCC) unit. The MCC unit comprises a capti~e fluidized bed of catalyst kept at a cracking zone temperature of 500 C. Tests were run by passiny a vacuum gas oil haviny a minimum boiling point of about 340 C
. . ..
"~ I
~4~5~
1 and a maximum boiling poin~ of about 565C through 2 the reactor for two minutes and analyzing for hydro-3 gen and coke production. In Table I data is pre-4 sented illustrating that the incorporation of a reduction step followed by an oxidation step (redox) 6 significantly decreased the hydrogen and coke makesO
7 TABL,E I
8 Treatment 9 Wt. ~ Metal Prior to on Ca _ yst Cracking Yields Wt. ~ on Feed 11 Ni V Fe H2 Coke ~a lc ~n t cl 120.16 0.18 -43~ 0.8~ 7.82 130.16 0.18 Redox 650C0.62 6.04 140.12 0.12 Calcined 0.53 5.49 150.12 0~12 Redox 650C0.34 4.15 160.15 0.190.35 Calcined 1.1610.61 170.15 0.190.35 Redox 650C0.79 7.48 18 Table II illustrates that hydrogen and coke make 19 reductions similar to that shown in Table I also were obtained vn a metals contaminated catalyst wherein 21 tho metals had been deposited by the processing of 22 heavy metal containing feeds rather than by labora-23 tory impregnation.
2 Wt~ % Metal 3 on Catalyst Yields Wto % on Feed 4 Ni V Fe Treatment H2 Coke 5 0.28 0.31 0.57 510C 1~13 9~11 6 Cracking 8 Regen.
9 (Many cycles) 100.28 0.31 0O57 Redox 650C 0.75 5.41 11 4 cycles 120.26 0.29 0.36 510C Cracking0.73 6.05 13 707C Regen.
14 (Many cycles) 150.26 0.29 0.36 Redox 650~C 0.53 3.94 16 4 cy~les 17 Table III illustrates that the degree of passivation 1~ is a function of the reduction zone temperatureO It 19 can be seen that the adverse catalytic effects of the metal contaminants are only slightly reduced over 21 that of untreated catalyst, where the temperature in 22 reduction zone 70 is only 500C. As the reduction ~3 zone temperature is increased, it can be seen that z~ the degree of passivation increases.
TABLE III
26 Yields Wt. %
27 Wt. ~ Metal Redox On Feed 28 on Catalyst Treat~ent Temp. C H2 Cokë
29 0.28Ni, 0.31V9 0.57Fe No Redox Treatment 1.13 9.11 500 1.10 8.55 31 600 0.g9 7.9~
32 625 0.98 7.33 33 650 0.75 5.41 3~ 700 0.59 4.80 750 0.50 4.11 1 Based on this data, it is believed that the reduction 2 step decreases the hydrogen and coke makes and that 3 the reduction must be performed at a temperature in 4 excess of 500C.
Table IV, illustrates that where only one 6 of the metal contaminants is present, the redox step 7 at 650C is not~ effective in reducing the hydrogen 8 and coke makes.
g TABLE IV
Reduction zone 70 may be any vessel provid 26 ing suitable contacting of the catalyst with a reduc-27 ing environment at elevated temperatures. The shape 28 of reduction zone 70 is not cri~ical~ In the embodi-29 ment shown, reduction zone 70 comprises a treater vescel having a shape generally similar to that of 31 regeneration zone 26, with the reducing environment 32 maintained, and catalyst fluidized by, reducing agent 33 entering through line 72 and exiting through line 78.
34 The volume of dense phase 74 having a level at 76 is dependent on the required residence time. The 1 residence time of the catalyst in reduction zone 70 2 i5 not critical as long as it is sufficient to effect 3 the passivation. The residence time will range from 4 about 5 sec. to about 30 min., typically from about 2 to 5 minutes. The pressure in this zone is not 6 critical and generally will be a function of the 7 location of reduction zone 70 in the system and the 8 pressure in the adjacent regeneration and reaction 9 zones. In the embodiment shown, the pressure in zone 70 will be maintained in the range of about 5 to 50 11 psia, although the reduction zone preferably should 12 be designed to withstand pressures of 100 psia. The 13 temperature in reduction zone 70 should be above 14 about 500C preferably above 600C, but below the temperature at which the catalyst sinters or de-16 gradesO A preferred temperature range is about 17 600-850C, with the more preferred temperature ran~e 18 being 650-750C. The reduction zone 70 can be 19 located either before or after regeneration zone 26, with the preferred location being after the 21 regeneration zoner so that the heat irnparted to the 22 catalyst by the regeneration obviates or minimizes ~3 the need for additional catalyst heating~ The 24 reducing agent utilized in the reduction zone 70 is not critical, although hydrogen and carbon monoxide 26 are the preferred reducing agents. Other reducing 27 agents including light hydrocarbons, such as C3 28 hydrocarbons, may also be satisfactory.
29 Reduction zone 70 can be constructed of any chemically resistant material sufficiently able to 31 withstand the relatively high temperatures involved 32 and the high attrition conditions which are inherent 33 in systems wherein fluidized catalyst is transported.
34 Specifically, metals are contemplated which may or may not be lined. More specifically, ceramic liners 36 are contemplated within any and all portions of the - 12 ~
1 reduction zone together with alloy use and structural 2 designs in order to withstand the maximum contem-3 plated operating temperatures~
4 The reducing agent utilized in all but one of the following tests was high purity grade hydrogen, 6 comprising 99.9% hydrogenO In the remaining test, 7 shown in Table VIII a reducing agent comprising 99.3%
8 CO was utilized. It is expected that commercial 9 grade hydrogen, commercial grade CO, and process gas streams containing H2 and/or CO can be utilizedn 11 Examples include cat cracker tail gas, catalytic 12 reformer off gas, spent hydrogen streams from cata-13 lytic hydroprocessing, synthesis gas~ and flue 14 gases. The rate of consumption of the reducing agent in reducing zone 70 will, of course, be dependent on 16 the amount of reducible material entering the 17 reducing zoneO In a typical fluidized catalytic 18 cracking unit it is anticipated that about 10 to 100 19 scf of hydrogen or about 10 to 100 scf of CO gas would be required for each ton of catalyst passed 21 through reduction zone 70.
22 If the reducing agent entering through line 23 72 is circulated through reduction zone 70 and thence 24 into other units, a gas-solids separation means may be required for use in connection with the reduction 26 zone. If the reducing agent exiting from zone 70 is 27 circulated back into the reduction zone, a gas-solids 28 separation means may not be necessary. Preferred 29 separation means for zones 10, 26 and 70 will be cyclone separators, multiclones or the like whose 31 design and construction are well known in the art.
32 In the case of cyclone separators, a single cyclone 33 may be used, but preferably, more than one cyclone 34 will be used in parallel or in series flow to effect the desired degree of separa~ion~
l The construction of regeneration zone 26 2 can be made with any material sufficiently able to 3 withstand the relatively high temperatures involved 4 when afterburning is encountered within the vessel and ~he high attrition conditions which are inherent 6 in systems wherein fluidized catalyst is regenerated 7 and transported. Specifically/ metals are contem-~ plated which may or may not be lined. More specif g ically, ceramic liners are contemplated within any and all portions of the regeneration zone ll together with alloy use and structural designs in 12 order to withstand temperatures of about 76QC and, 13 for rea50nably short periods of time, temperatures 14 which may be as high as 1000C.
The pressure in the regeneration zone is 16 usually maintained in a range from about atmospheric 17 to about 50 psig., preferably from about 10 to 50 18 psig. It is preferred, however, to design the 19 regeneration zone to withstand pressures of up to about 100 psig. Operation of the regeneration zone 21 at increased pressure has the effect of promoting the 22 conversion of carbon monoxide to carbon dioxide and 23 redllcing the temperature level within the dense bed 24 phase at which the substantially comp]ete combustion Of carbon monoxide can be accomplished. The higher 26 pressure also lowers the equilibrium level of carbon 27 on regenerated catalyst at a given regeneration 23 temperatureO
29 The residence time of the spent catalyst in the regeneration zone is not critical so long as the 31 carbon on the catalyst is reduced to an acceptable 32 level. In general, it can vary from about l to 33 30 minutes. The contact time or residence time of 34 the flue gas in the dilute catalyst phase establishes the extent to which the combustion reaction can reach 1 equilibrium. The residence time of the flue gas may 2 vary from about 10 to abou~ 60 seconds in the regen-3 eration zone and from about 2 to about 30 seconds in 4 the dense bed phase. Preferably, the residence time of the flue gas varies from about 15 to about 20 6 seconds in the dense bed.
7 The present invention may be applied ~ beneficially to any type of fluid cat cracking unit g without limitation as to the spatial arrangement of the reaction, stripping, and regeneration zones, with 11 only the addition of reduction zone 70 and related 12 elementsO In general, any commercial catalytic 13 cracking catalyst designed for high thermal stability 14 could be suitably employed in the present invention.
Such catalysts include those containing silica and/or 16 alumina. Catalysts containing combustion promoters 17 such a3 platinum can be used~ Other refractory metal 18 oxides such as magnesia or zirconia may be employed 19 and are limited only by their ability to be effec-tively regenerated under the selected conditions.
21 With particular regard to catalytic cracking, pre-22 ferred catalysts include the combinations of silica 23 and alumina, containing 10 to 50 wt. ~ alumina, and 29 particularly their admixtures with molecular sieves or crystalline alumino~ilicates. Suitable molecular 26 sieves include both naturally occurring and synthetic 27 aluminosilicate materials, such as faujasite, cha-28 bazite, X-type and Y-type aluminosilicate materials 29 and ultra stable, large pore crystalline alumino-silicate materials. When admixed with, for example, 31 silica-alumina to provide a petroleum cracking 32 catalyst, the molecular sieve content of the fresh 33 finished catalyst particles is suitably within 3~ the range from 5 35 wto ~, preferably 8-20 wt. ~. An equilibrium molecular sieve cracking catalyst may 2~
1 cor.tain as little as about 1 wt. % crystalline 2 material. Admixtures of clay-extended aluminas may 3 also be employed. Such catalysts may be prepared in 4 any suitable method such as by impregnation, milling, co~gelling, and the like, subject only to the provi-6 sion that the finished catalyst be in a physical 7 form capable of fluidization. In the following tests 8 a commercially available silica alumina zeolite g catalyst sold under the tradename CBZ-l, manufactured by Davison Division, W. R. Grace & Company was used 11 after steaming to simulate the approximate equilib-12 rium activity of the catalyst.
13 Fractionation zone 100, of conventional 14 design, typically is maintained at a top pressure ranging between about 10 and 20 psi and a bottoms 16 temperature ranging up to about 400C. The specific 17 conditions will he a function of many variables 13 including inlet product composition, inlet feed rates 19 and desired compositions in the overhead, middle cut and bottoms. The middle cut fed to hydrogena~ion 2L zone 110 preferably has a boiling range of about 200 22 to about 370C and is frequently referred to as a ~3 light cat cycle oil. The feed to the hydrogenation 24 zone, preferably light ca~ cycle oil, should include compounds which will accept hydrogen in zone llO and 26 readily release the hydrogen in reaction zone 1O
27 without dehydrogenative action. Preferred hydrogen 28 donor compounds include two ring naphthenic compounds 29 such as decahydronaphthalene (decalin) and two ring hydroaromatic compounds such as tetrahydronaphthalene 31 (tetralin).
32 Hydrogenation zone 110 may be of conven-33 tional design. Typical hydrogenation catalysts 34 include molybdenum salts and nickel and/or cobalt salts deposited on a support material~ The residence ,5~
time of the middle cut from zone 100 in the hydrogenation zone may range from about 10 to about 240 minutes, depending on the hydrogen donor, hydrogenation catalyst, operating conditions and the desired degree of hydrogenation.
As shown by the data in Tables I-~X the incorporatiOn of a reduction zone 70 is not effective for passivating a metal contaminated catalyst unless a temperature in excess of about 500C is used.
The data in Table X shows that use of a hydrogen donor also decreases hydrogen and coke makes. When the use of a hydrogen donor is combined with the previously described passi-vation process, this results in still lower coke malces.
Unless otherwise noted the following test conditions were used. The CBZ-l catalyst utilized was first steamed at 760C for 16 hours after which the catalyst was contaminated with the indicated metals by laboratory impregnation followed by calcining in air at about 540C for four hours~ The catalyst was then subjected to the indicated number of redox cycles. Each cycle consisted of a five-minute residence in a hydrogen atmos-phere, a ~ive-minute nitrogen flush and then a five-minute re~.idence in an air atmosphere at the indicated temperatures.
Followiny the redox cycles the catalyst was utilized in a micro-catalytic cracking (MCC) unit. The MCC unit comprises a capti~e fluidized bed of catalyst kept at a cracking zone temperature of 500 C. Tests were run by passiny a vacuum gas oil haviny a minimum boiling point of about 340 C
. . ..
"~ I
~4~5~
1 and a maximum boiling poin~ of about 565C through 2 the reactor for two minutes and analyzing for hydro-3 gen and coke production. In Table I data is pre-4 sented illustrating that the incorporation of a reduction step followed by an oxidation step (redox) 6 significantly decreased the hydrogen and coke makesO
7 TABL,E I
8 Treatment 9 Wt. ~ Metal Prior to on Ca _ yst Cracking Yields Wt. ~ on Feed 11 Ni V Fe H2 Coke ~a lc ~n t cl 120.16 0.18 -43~ 0.8~ 7.82 130.16 0.18 Redox 650C0.62 6.04 140.12 0.12 Calcined 0.53 5.49 150.12 0~12 Redox 650C0.34 4.15 160.15 0.190.35 Calcined 1.1610.61 170.15 0.190.35 Redox 650C0.79 7.48 18 Table II illustrates that hydrogen and coke make 19 reductions similar to that shown in Table I also were obtained vn a metals contaminated catalyst wherein 21 tho metals had been deposited by the processing of 22 heavy metal containing feeds rather than by labora-23 tory impregnation.
2 Wt~ % Metal 3 on Catalyst Yields Wto % on Feed 4 Ni V Fe Treatment H2 Coke 5 0.28 0.31 0.57 510C 1~13 9~11 6 Cracking 8 Regen.
9 (Many cycles) 100.28 0.31 0O57 Redox 650C 0.75 5.41 11 4 cycles 120.26 0.29 0.36 510C Cracking0.73 6.05 13 707C Regen.
14 (Many cycles) 150.26 0.29 0.36 Redox 650~C 0.53 3.94 16 4 cy~les 17 Table III illustrates that the degree of passivation 1~ is a function of the reduction zone temperatureO It 19 can be seen that the adverse catalytic effects of the metal contaminants are only slightly reduced over 21 that of untreated catalyst, where the temperature in 22 reduction zone 70 is only 500C. As the reduction ~3 zone temperature is increased, it can be seen that z~ the degree of passivation increases.
TABLE III
26 Yields Wt. %
27 Wt. ~ Metal Redox On Feed 28 on Catalyst Treat~ent Temp. C H2 Cokë
29 0.28Ni, 0.31V9 0.57Fe No Redox Treatment 1.13 9.11 500 1.10 8.55 31 600 0.g9 7.9~
32 625 0.98 7.33 33 650 0.75 5.41 3~ 700 0.59 4.80 750 0.50 4.11 1 Based on this data, it is believed that the reduction 2 step decreases the hydrogen and coke makes and that 3 the reduction must be performed at a temperature in 4 excess of 500C.
Table IV, illustrates that where only one 6 of the metal contaminants is present, the redox step 7 at 650C is not~ effective in reducing the hydrogen 8 and coke makes.
g TABLE IV
10 Treatment Yields, Wt. %
11 Prior To on Feed
12 Wt. % Me~al on Catalyst Cracking_ _ Cok
13 0~21 Ni Calcined 0.80 8~10
14 0.21 Ni Redox 650C 0.72 7.96 4 cycles 16 0.29 V Calcined 0.38 3.88 17 Q.29 V Redox 650C 0.36 4.20 18 4 cycles 19 Thus, to passivate the metal contaminants on a catalyst, where a~ least a major portion i.e~, 21 at least 50 wt~ % of the total of the metal contamin-22 ants comprises nickel, vanadium or iron, it may be 23 necessary to add predetermined quantities of either 24 o~ the other two contaminants. Typically, crude oil 1V-'/y will not contain -~4~ ~e high concentrations of 26 iron~ Vanadium and r-ickel, however, typically are ~7 found in many crudes, with the relative amounts 2~ varying with the type of crude. For example, cer-29 tain Venezuelan crudes have relatively high vanadium and relatively low nickel concentrations, while the 31 converse is true for certain domestic crudes. In 32 addition, certain hydrotreated residual oils and 33 hydrotreated gas oils may have relatively high nickel .SZ~
and relatively low vanadium concentrations, since hydrotreating removes vanadium more effective]y than nickel. A catalyst could have substantial iron depositions where the iron oxide scale on process equipment upstream of the catalyst breaks off and is transported through the system by the feestock. The relative catalytic activity of the individual metal contaminants nickel, vanadium and iron for the formation of hydrogen and coke are approximately 10:2.5: 1. Based on this, iron preferably should be added to passivate catalyst contaminated only with nickel, or vanadium. Table V illustrates ~he passivation that is achieved by adding quantities of iron to catalyst comprising only vanadium or only nickel.
TABLE V
Treatment Yield, Wt. %
Prior to on Feed Wt- ~ e~ bYSt Cracking H Coke 0.17 Ni Calcined 0~76 7O30 0.17 Ni, 0.23 Fe Redox 650C 0.51 5.27 4 cycles 0.29 V Calcined 0.38 3.88 0.29 V, 0.13 Fe Redox 650C 0.30 3.72 4 cycles Table VI illustrates the passivation achieved by adding var~in~ weights of vanadium to catalyst comprising only the nickel contarninant. ~tten~ion i~ directed to the fact that the addition of 0.02 wt. % vanadium followed by redox passivated the catalyst to a lower level than ~hat achieved by redox alone.
Combination of the nickel contaminated catalyst with 0.12 wt.
vanadium followed by redox further passivated the catalyst.
However, combination of the nickel contaminated . .
1 catalyst with 0O50 wt. ~ vanadium resulted in an 2 increase in undesired catalytic activity over that of 3 the catalyst containing only 0.12 wt. % nickel.
Thus, there appears to be a level of addition of the second metal component, above which the effectivenesS
6 of the passivation decreases. The exact amount of 7 nickel, vanadium or iron which should be added to a 8 metal-contaminated catalyst has not been determined.
g TABLE VI
Wt. % Metal Treatment 11 on Catalyst Prior To Yields, Wt. % on Feed 12 Ni V Cracking H2 Coke 13 0~12 Calcined 0.60 5.65 14 0.12 Redox 650C0~44 4.73 4 cycles 16 0.12 0.02 Redox 650C0~39 4O53 17 4 cycles 18 0.12 0.12 Redox 650C0.34 4.15 19 4 cycles 20 0.12 0.50 Calcined 1.17 11.98 21 0.12 0.50 Redox 650C0.72 6~86 22 4 cycles 23 Table VII illustrates passivation of a 24 catalyst impregnated with equal weight percentages of nickel and vanadium. It should be noted that the 26 redox at 650C resulted in a significant decrease 27 in hydrogen and coke makes, but that) here also, the 28 further addition of passivating metal in the form of 29 iron actually increased the undesired catalytic activity of the metal contaminants slightly.
,s~
2 Wt. % Metal Treatment 3 on Catalyst Prior To ~ields, Wt9 % on Feed 4 Ni_ V Fe Crackin~_ ~2 Coke 0.12 0.12 Calcined 0.53 5O49 6 0.12 0.12 Redox 650C 0.34 4.15 7 4 cycles 8 0.12 0~12 0.26 Redox 650C 0.37 4.50 9 4 cycles Table VIII illustrates that metals-contam-11 inated catalyst also can be passivated by the use of 12 carbon monoxide rather than hydrogen as the reducing 13 agent. In one run CP grade C0 containing 99.3~ C0 by 14 volume was utilized in the previously described passivation process while reagent grade hydrogen was 16 used in ~he comparative run. It can be seen that 17 both reducing agents passivated the catalyst to about 18 the same extent.
Wt. ~ Meta] Treatment 21 on Catalyst Prior To Yields,_Wt. % on Feecl 22 ~i V Fe Cracking H2 Coke 23 0.28 D.31 0.57 Calcined 1.13 9.11 2~ Redox 650C 0.75 5.41 4 cycles, H2 26 Redox 650C 0.73 5083 27 4 cycles, C0 28 As shown by the data of Table IXr ~he 29 addition of iron or antimony followed by high temper-ature redox, reduced the rate of hydrogen and coke 31 formation. The addition of both iron and antimony 32 followed by high temperature redox leads to a still 4~fth~f 33 decrease in hydrogen and coke makes.
Z
~ ~3 -2 Treatment Yields, Wt. %
3 Prior To _ on Feed 4 Wt. g Metal on Catalyst Crackin~ H2 Coke 0.17 Ni Calcined 0076 7.30 6 0.17 Nit 0.23 Fe Redox 650C 0.51 5 27 7 4 cycles 8 0.27 Ni Calcined 0.83 8.40 9 0.27 Ni, 0~52 Sb Redox 650C 0.59 6.03 ~ cycles 11 0~27 Ni, 0v52 Sb, 0.34 Fe Redox 650C 0.54 5.31 12 4 cycles 13 In addition to antimony, it is believed that other 14 known passivation agents such as tin, bismuth and manganese in place of the antimony also would 16 decrease the hydrogen and coke makes.
17 It has been found that one passage through 18 the reaction and regeneration zones reduces the 19 effectiveness of the reduction zone passivationO
Zo Thus, at least a portion of the catalyst preferably 21 is passed through reduction zone 70 on every catalyst ~2 regeneration cycle~
23 The quantity of metal contaminant, cr 2~ passivation promoter, if any, that should be added to the system may be determined preferably by monitoring 26 th~ hydrogen and coke makes in the reaction zone or 27 by analyzing the metal contaminant concentration 28 either in the hydrocarbon feed or on the catalyst.
29 Where additional iron, vanadium or nickel is to be added to the system to reduce the hydrogen and coke 31 makes, it is believed ~hat the additional quantities 32 of these metals should be added to the feed, rather 33 than impregnated onto the catalyst prior to use.
34 Impregnation of an excess of these metals onto the catalyst prior to use in the cracking operation 36 may lead to higher initial hydrogen and coke makes~
.5~
1 Moreover, where passivation promoters having rela-2 tively high vapor pressures, such as antimony, are 3 used, some of the passivation promoter may be lost 4 to the atmosphere if it is impregnated onto the catalyst. It has been found that the passivation 6 efficiency of antimony is higher when the antimony 7 is incorporated into the hydrocarbon feedstock than 8 when it is impregnated onto the catalyst.
9 Table X shows that the addition of a hydrogen donor to the reaction zone reduces the 11 hydrogen and coke makes. When this is combined 12 with the previously described passivation process, 13 still lower coke makes result. In Table X the feed 14 for all tests was 60% vacuum gas oil (VGO), and ~0%
light cat cycle oil (LCCO). The vacuum gas oil had 16 a minimum boiling point of about 340C and a maxi~
17 mum boiling point of about 565C as in the previous 18 tests. The light cat cycle oil had a mini~um boiling 19 point of about 200C and a maximum boiling point of about 325C. In the first test shown in Table X
21 the LCCO was not hydrogenated and the metals contam-22 inated catalyst was not passivated. In the second 23 test the LCCO fraction of the feed was hydrogenated 2~ by passing the LCCO through a hydrogenation zone maintained at a temperature of about 371C and 26 2000 psig, comprising a nickel-molybdenum sulfided 27 catalyst in a carbonaceous matrix to increase the 28 hydrogen content of the LCCO fraction from 10.51 wto 29 % hydrogen to 12~10 wt. ~ hydrogen. The average residence time of the LCCO in the hydrogenation zone 31 was about 180 minutes~ In the third test~ the LCCO
32 fraction of the feed was not hydrogenated, but the 33 catalyst was passivated by subjecting the catalyst to 34 4 redox cycles in a hydrogen atmosphere as previously described. In the fourth test the LCCO fraction of r 1 the feed was hydrogenated as in test 2, and the 2 catalyst was passivated as in test 3. It may be seen 3 that the coke make in test 4 was substantially lower 4 than that in tests 1, 2 or 3, thus demonstrating that use of a hydrogen donor material in the feed 6 combined with catalyst passivation decreases the coke 7 make more than either process alone.
gFeed Composition-40% LCC0:60%VG0 Wt. % Metal Treatment Yields, Wt~ %
11 on Catalyst Test Prior To on Feed 12 Nl V Fe No~ Cracking H2 Coke 13 0.48 0.61 0.61 1 No LCC0 1.1010.10 14 hydrogena-tion. No 16 catalyst 17 passivation 18 2 LCC0 hydro~ 1.02 8.16 19 genated. No catalyst 21 passivation 22 3 No LCC0 0.766.67 23 hydrogena-24 tion.
Catalyst 26 passivated 27 Redox 750C
28 4 cycles, H2 29 4 LCC0 hydro- 0.754.60 genated.
31 Catalyst 32 passivated.
33 Redox 750C
~ cycles, ~2 Although the subject process has been 36 described with reference to a specific embodiment, it 37 will be understood that it is ca`pable of further 38 modification~ Any variations, uses or adaptations of 2~
1 the invention following, in general, the principles 2 of the invention are intended to be covered, includ-3 ing such departures from the present disclosure 4 as come within known or customary practice in ~he art to which the invention pertains and as may be applied 6 to the essential features hereinbefore set forth, and 7 as fall within the scope of the invention.
and relatively low vanadium concentrations, since hydrotreating removes vanadium more effective]y than nickel. A catalyst could have substantial iron depositions where the iron oxide scale on process equipment upstream of the catalyst breaks off and is transported through the system by the feestock. The relative catalytic activity of the individual metal contaminants nickel, vanadium and iron for the formation of hydrogen and coke are approximately 10:2.5: 1. Based on this, iron preferably should be added to passivate catalyst contaminated only with nickel, or vanadium. Table V illustrates ~he passivation that is achieved by adding quantities of iron to catalyst comprising only vanadium or only nickel.
TABLE V
Treatment Yield, Wt. %
Prior to on Feed Wt- ~ e~ bYSt Cracking H Coke 0.17 Ni Calcined 0~76 7O30 0.17 Ni, 0.23 Fe Redox 650C 0.51 5.27 4 cycles 0.29 V Calcined 0.38 3.88 0.29 V, 0.13 Fe Redox 650C 0.30 3.72 4 cycles Table VI illustrates the passivation achieved by adding var~in~ weights of vanadium to catalyst comprising only the nickel contarninant. ~tten~ion i~ directed to the fact that the addition of 0.02 wt. % vanadium followed by redox passivated the catalyst to a lower level than ~hat achieved by redox alone.
Combination of the nickel contaminated catalyst with 0.12 wt.
vanadium followed by redox further passivated the catalyst.
However, combination of the nickel contaminated . .
1 catalyst with 0O50 wt. ~ vanadium resulted in an 2 increase in undesired catalytic activity over that of 3 the catalyst containing only 0.12 wt. % nickel.
Thus, there appears to be a level of addition of the second metal component, above which the effectivenesS
6 of the passivation decreases. The exact amount of 7 nickel, vanadium or iron which should be added to a 8 metal-contaminated catalyst has not been determined.
g TABLE VI
Wt. % Metal Treatment 11 on Catalyst Prior To Yields, Wt. % on Feed 12 Ni V Cracking H2 Coke 13 0~12 Calcined 0.60 5.65 14 0.12 Redox 650C0~44 4.73 4 cycles 16 0.12 0.02 Redox 650C0~39 4O53 17 4 cycles 18 0.12 0.12 Redox 650C0.34 4.15 19 4 cycles 20 0.12 0.50 Calcined 1.17 11.98 21 0.12 0.50 Redox 650C0.72 6~86 22 4 cycles 23 Table VII illustrates passivation of a 24 catalyst impregnated with equal weight percentages of nickel and vanadium. It should be noted that the 26 redox at 650C resulted in a significant decrease 27 in hydrogen and coke makes, but that) here also, the 28 further addition of passivating metal in the form of 29 iron actually increased the undesired catalytic activity of the metal contaminants slightly.
,s~
2 Wt. % Metal Treatment 3 on Catalyst Prior To ~ields, Wt9 % on Feed 4 Ni_ V Fe Crackin~_ ~2 Coke 0.12 0.12 Calcined 0.53 5O49 6 0.12 0.12 Redox 650C 0.34 4.15 7 4 cycles 8 0.12 0~12 0.26 Redox 650C 0.37 4.50 9 4 cycles Table VIII illustrates that metals-contam-11 inated catalyst also can be passivated by the use of 12 carbon monoxide rather than hydrogen as the reducing 13 agent. In one run CP grade C0 containing 99.3~ C0 by 14 volume was utilized in the previously described passivation process while reagent grade hydrogen was 16 used in ~he comparative run. It can be seen that 17 both reducing agents passivated the catalyst to about 18 the same extent.
Wt. ~ Meta] Treatment 21 on Catalyst Prior To Yields,_Wt. % on Feecl 22 ~i V Fe Cracking H2 Coke 23 0.28 D.31 0.57 Calcined 1.13 9.11 2~ Redox 650C 0.75 5.41 4 cycles, H2 26 Redox 650C 0.73 5083 27 4 cycles, C0 28 As shown by the data of Table IXr ~he 29 addition of iron or antimony followed by high temper-ature redox, reduced the rate of hydrogen and coke 31 formation. The addition of both iron and antimony 32 followed by high temperature redox leads to a still 4~fth~f 33 decrease in hydrogen and coke makes.
Z
~ ~3 -2 Treatment Yields, Wt. %
3 Prior To _ on Feed 4 Wt. g Metal on Catalyst Crackin~ H2 Coke 0.17 Ni Calcined 0076 7.30 6 0.17 Nit 0.23 Fe Redox 650C 0.51 5 27 7 4 cycles 8 0.27 Ni Calcined 0.83 8.40 9 0.27 Ni, 0~52 Sb Redox 650C 0.59 6.03 ~ cycles 11 0~27 Ni, 0v52 Sb, 0.34 Fe Redox 650C 0.54 5.31 12 4 cycles 13 In addition to antimony, it is believed that other 14 known passivation agents such as tin, bismuth and manganese in place of the antimony also would 16 decrease the hydrogen and coke makes.
17 It has been found that one passage through 18 the reaction and regeneration zones reduces the 19 effectiveness of the reduction zone passivationO
Zo Thus, at least a portion of the catalyst preferably 21 is passed through reduction zone 70 on every catalyst ~2 regeneration cycle~
23 The quantity of metal contaminant, cr 2~ passivation promoter, if any, that should be added to the system may be determined preferably by monitoring 26 th~ hydrogen and coke makes in the reaction zone or 27 by analyzing the metal contaminant concentration 28 either in the hydrocarbon feed or on the catalyst.
29 Where additional iron, vanadium or nickel is to be added to the system to reduce the hydrogen and coke 31 makes, it is believed ~hat the additional quantities 32 of these metals should be added to the feed, rather 33 than impregnated onto the catalyst prior to use.
34 Impregnation of an excess of these metals onto the catalyst prior to use in the cracking operation 36 may lead to higher initial hydrogen and coke makes~
.5~
1 Moreover, where passivation promoters having rela-2 tively high vapor pressures, such as antimony, are 3 used, some of the passivation promoter may be lost 4 to the atmosphere if it is impregnated onto the catalyst. It has been found that the passivation 6 efficiency of antimony is higher when the antimony 7 is incorporated into the hydrocarbon feedstock than 8 when it is impregnated onto the catalyst.
9 Table X shows that the addition of a hydrogen donor to the reaction zone reduces the 11 hydrogen and coke makes. When this is combined 12 with the previously described passivation process, 13 still lower coke makes result. In Table X the feed 14 for all tests was 60% vacuum gas oil (VGO), and ~0%
light cat cycle oil (LCCO). The vacuum gas oil had 16 a minimum boiling point of about 340C and a maxi~
17 mum boiling point of about 565C as in the previous 18 tests. The light cat cycle oil had a mini~um boiling 19 point of about 200C and a maximum boiling point of about 325C. In the first test shown in Table X
21 the LCCO was not hydrogenated and the metals contam-22 inated catalyst was not passivated. In the second 23 test the LCCO fraction of the feed was hydrogenated 2~ by passing the LCCO through a hydrogenation zone maintained at a temperature of about 371C and 26 2000 psig, comprising a nickel-molybdenum sulfided 27 catalyst in a carbonaceous matrix to increase the 28 hydrogen content of the LCCO fraction from 10.51 wto 29 % hydrogen to 12~10 wt. ~ hydrogen. The average residence time of the LCCO in the hydrogenation zone 31 was about 180 minutes~ In the third test~ the LCCO
32 fraction of the feed was not hydrogenated, but the 33 catalyst was passivated by subjecting the catalyst to 34 4 redox cycles in a hydrogen atmosphere as previously described. In the fourth test the LCCO fraction of r 1 the feed was hydrogenated as in test 2, and the 2 catalyst was passivated as in test 3. It may be seen 3 that the coke make in test 4 was substantially lower 4 than that in tests 1, 2 or 3, thus demonstrating that use of a hydrogen donor material in the feed 6 combined with catalyst passivation decreases the coke 7 make more than either process alone.
gFeed Composition-40% LCC0:60%VG0 Wt. % Metal Treatment Yields, Wt~ %
11 on Catalyst Test Prior To on Feed 12 Nl V Fe No~ Cracking H2 Coke 13 0.48 0.61 0.61 1 No LCC0 1.1010.10 14 hydrogena-tion. No 16 catalyst 17 passivation 18 2 LCC0 hydro~ 1.02 8.16 19 genated. No catalyst 21 passivation 22 3 No LCC0 0.766.67 23 hydrogena-24 tion.
Catalyst 26 passivated 27 Redox 750C
28 4 cycles, H2 29 4 LCC0 hydro- 0.754.60 genated.
31 Catalyst 32 passivated.
33 Redox 750C
~ cycles, ~2 Although the subject process has been 36 described with reference to a specific embodiment, it 37 will be understood that it is ca`pable of further 38 modification~ Any variations, uses or adaptations of 2~
1 the invention following, in general, the principles 2 of the invention are intended to be covered, includ-3 ing such departures from the present disclosure 4 as come within known or customary practice in ~he art to which the invention pertains and as may be applied 6 to the essential features hereinbefore set forth, and 7 as fall within the scope of the invention.
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method for reducing the rate of coke production from a hydrocarbon feedstock cracked to lower molecular weight products in a reaction zone containing cracking catalyst where the feedstock contains at least one metal selected from the class consisting of nickel, vanadium and iron and where at least some of the metal contaminant becomes deposited on the catalyst, characterized by comprising the step of passing the catalyst after regeneration from the reaction zone through a reduction zone maintained at an elevated temperature of at least about 500°C
for a time sufficient to at least partially passivate the metal contaminant on the catalyst, a reducing environment maintained in the reduction zone by the addition to the reduction zone of a material selected from the class consisting of hydrogen, carbon monoxide and mixtures thereof, said passivated catalyst thereafter passing to the reaction zone without further processing.
for a time sufficient to at least partially passivate the metal contaminant on the catalyst, a reducing environment maintained in the reduction zone by the addition to the reduction zone of a material selected from the class consisting of hydrogen, carbon monoxide and mixtures thereof, said passivated catalyst thereafter passing to the reaction zone without further processing.
2. The method of claim 1 characterized in that the temperature of the reduction zone is maintained above about 600°C
for a time sufficient to at least partially passivate the metal contaminant on the catalyst.
for a time sufficient to at least partially passivate the metal contaminant on the catalyst.
3. The method of claim 1 further characterized in that at least 50 weight percent of the total of said metal contaminants deposited on the catalyst comprises only one of said metal con-taminant.
4. The method of any of claims 1-3 further characterized by:
(a) monitoring the composition of the metal contaminant deposited on the catalyst; and (b) adding an effective amount of one of said metal contaminants not present as the major contaminant on the catalyst.
(a) monitoring the composition of the metal contaminant deposited on the catalyst; and (b) adding an effective amount of one of said metal contaminants not present as the major contaminant on the catalyst.
5. The method of any of claims 1-3 further characterized in that the residence time of the catalyst in the reduction zone ranges between about 10 and about 240 minutes.
6. The method of any of claims 1-3 further characterized in that hydrogen donor material is added to the reaction zone, whereby at least portion of the hydrogen donor material transfers hydrogen to the hydrocarbon feedstock and/or into cracked lower molecular weight products.
7. The method of any of claims 1-3 further characterized in that the hydrogen donor material added to the reaction zone has a boiling point between about 200°C and about 500°C.
8. The method of any of claims 1-3 further characterized in that the hydrogen donor material is obtained by:
(a) fractionating the cracked lower molecular weight products from the reaction zone;
(b) passing a portion of the fractionated product through a hydrogenation zone to at least partially hydrogenate the fractionated product;
and (c) passing the fractionated product from the hydrogenation zone into the reaction zone.
(a) fractionating the cracked lower molecular weight products from the reaction zone;
(b) passing a portion of the fractionated product through a hydrogenation zone to at least partially hydrogenate the fractionated product;
and (c) passing the fractionated product from the hydrogenation zone into the reaction zone.
9. The method of any of claims 1-3 further characterized in that the hydrogen donor material added to the reaction zone ranges between about 5 and about 100 wt. % of the hydrocarbon feedstock to be cracked.
10. The method of any of claims 1-3 further characterized by the addition of a passivation agent selected from the class consisting of antimony, tin, bismuth and manganese to further passivate the catalyst.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/259,830 US4372840A (en) | 1979-12-31 | 1981-05-04 | Process for reducing coke formation in heavy feed catalytic cracking |
| US260,191 | 1981-05-04 | ||
| US06/260,191 US4372841A (en) | 1979-12-31 | 1981-05-04 | Process for reducing coke formation in heavy feed catalytic cracking |
| US259,830 | 1981-05-04 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1184522A true CA1184522A (en) | 1985-03-26 |
Family
ID=26947553
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000378365A Expired CA1184522A (en) | 1981-05-04 | 1981-05-26 | Process for reducing coke formation in heavy feed catalytic cracking |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1184522A (en) |
-
1981
- 1981-05-26 CA CA000378365A patent/CA1184522A/en not_active Expired
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