CA1145700A - Sulfur oxides control in cracking catalyst regeneration - Google Patents
Sulfur oxides control in cracking catalyst regenerationInfo
- Publication number
- CA1145700A CA1145700A CA000359354A CA359354A CA1145700A CA 1145700 A CA1145700 A CA 1145700A CA 000359354 A CA000359354 A CA 000359354A CA 359354 A CA359354 A CA 359354A CA 1145700 A CA1145700 A CA 1145700A
- Authority
- CA
- Canada
- Prior art keywords
- alumina
- cracking
- weight percent
- catalyst
- particulate solid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/14—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts
- C10G11/18—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils with preheated moving solid catalysts according to the "fluidised-bed" technique
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/90—Regeneration or reactivation
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
- C10G11/04—Oxides
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G11/00—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils
- C10G11/02—Catalytic cracking, in the absence of hydrogen, of hydrocarbon oils characterised by the catalyst used
- C10G11/04—Oxides
- C10G11/05—Crystalline alumino-silicates, e.g. molecular sieves
Abstract
ABSTRACT OF THE DISCLOSURE
In removing sulfur oxides from flue gas in a cracking catalyst regenerator in the presence of a silica-containing particulate catalyst by reacting the sulfur oxides with alumina in a particulate solid other than the catalyst, activity loss in the alumina as a result of migration of silica from the catalyst particles to the alumina-containing particles is decreased by using alumina-containing particles which contain sodium, manganese or phosphorus.
In removing sulfur oxides from flue gas in a cracking catalyst regenerator in the presence of a silica-containing particulate catalyst by reacting the sulfur oxides with alumina in a particulate solid other than the catalyst, activity loss in the alumina as a result of migration of silica from the catalyst particles to the alumina-containing particles is decreased by using alumina-containing particles which contain sodium, manganese or phosphorus.
Description
003 The present invention relates to a method for 004 reducing pollutant gas levels in flue gases generated in 005 catalyst regenerators in hydrocarbon catalytic cracking 006 systems.
007 Modern hydrocarbon catalytic cracking systems use a 008 moving bed or fluidized bed of a particulate catalyst.
009 Catalytic cracking is carried out in the absence of externally 010 supplied molecular hydrogen, and is thereby distinguished from 011 hydrocracking, in which hydrogen is added. In catalytic crack-012 ing, catalyst is subjected to a continuous cyclic cracking 013 reaction and catalyst regeneration procedure. In a fluidized 014 catalytic cracking ~FCC) system, a stream of hydrocarbon feed 015 is contacted with fluidized catalyst particles in a hydrocarbon 016 cracking zone, or reactor, usually at a temperature of about 017 427-600C. The reactions of hydrocarbons in the hydrocarbon 018 stream at this temperature result in deposition of carbonaceous 019 coke on the catalyst particles. The resulting fluid products 020 are thereafter separated from the coked catalyst and are with-021 drawn from the cracking zone. The coked catalyst is stripped 022 of volatiles, usually with steam, and is cycled to a catalyst 023 regeneration zone. In the catalyst regenerator, the coked 024 catalyst is contacted with a gas, such as air, which contains a 025 predetermined concentration of molecular oxygen to burn off a 026 desired portion of the coke from the catalyst and simul-027 taneously to heat the catalyst to a high temperature desired 028 when the catalyst is again contacted with the hydrocarbon 029 stream in the cracking zone. After regeneration, the catalyst 030 is cycled to the cracking zone, where it is used to vaporize 031 the hydrocarbons and to catalyze hydrocarbon cracking. The 032 flue gas formed by combustion of coke in the catalyst 033 regenerator is removed from the regenerator. It may be treated 034 to remove particulates and carbon monoxide from it, after which 035 it is normally passed into the atmosphere. Concern with the 036 emission of pollutants in flue gas, such as sulfur oxides, has 037 resulted in a search for improved methods for controlling such 038 pollutants.
11457~0 002 The amount of conversion obtained in an FCC cracking 003 operation is the volume percent of fresh hydrocarbon feed 004 changed to gasoline and lighter products during the conversion 005 step. The end boiling point of gasoline for the purpose of 006 determining conversion is conventionally defined as 221C.
007 Conversion is often used as a measure of the severity of a 008 commercial FCC operation. At a given set of operating 009 conditions, a more active catalyst gives a greater conversion 010 than does a less active catalyst. The ability to provide 011 higher conversion in a given FCC unit is desirable in that it 012 allows the FCC unit to be operated in a more flexible manner.
013 Feed throughput in the unit can be increased, or alternatively 014 a higher degree of conversion can be maintained with a constant 015 feed throughput rate. The type of conversion, i.e., selec-016 tivity, is also important in that poor selectivity results in 017 less naphtha, the desired cracked product~ and higher gas and 018 coke makes.
019 The hydrocarbon feeds processed in commercial FCC
020 units normally contain sulfur, usually termed "feed sulfur".
021 It has been found that about 2-10% or more of the feed sulfur 022 in a hydrocarbon feedstream processed in an FCC system is 023 invariably transferred from the feed to the catalyst particles 024 as a part of the coke formed on the catalyst particles during 025 cracking. The sulfur deposited on the catalyst, herein termed 026 "coke sulfur", is passed from the cracking zone on the coked 027 catalyst into the catalyst regenerator. About 2-10% or more of 028 the feed sulfur is continuously passed from the cracking zone 029 into the catalyst regeneration zone in the coked catalyst. In 030 an FCC catalyst regenerator, sulfur contained in the coke is 031 burned along with the coke carbon and hydrogen, forming gaseous 032 sulfur dioxide and sulfur trioxide, which are conventionally 033 removed from the regenerator in the flue gas.
034 Most of the feed sulfur does not become coke sulfur 035 in the cracking reactor. Instead, it is converted either to 036 normally gaseous sulfur compounds such as hydrogen sulfide and 037 carbon oxysulfide, or to normally liquid organic sulfur . 11457~)0 001 ~ _3_ 002 compounds. All these sulfur compounds are carried along with 003 the vapor cracked hydrocarbon products recovered from the 004 cracking reactor. About 90% or more of the feed sulfur is 005 continuously removed from the cracking reactor in the stream of 006 processed, cracked hydrocarbons, with about 40-60~ of this 007 sulfur being in the form of hydrogen sulfide. Provisions are 008 conventionally made to recover hydrogen sulfide from the 009 effluent from the cracking reactor. Typically, a 010 very-low-molecular-weight off-gas vapor stream is separated 011 from the C3+ liquid hydrocarbons in a gas recovery unit, and 012 the off-gas is treated, as by scrubbing it with an amine 013 solution, to remove the hydrogen sulfide. Removal of sulfur 014 compounds such as hydrogen sulfide from the fluid effluent from OlS an FCC cracking reactor, e.g., by amine scrubbing, is rela-016 tively simple and inexpensive, relative to removal of sulfur 017 oxides from an FCC regenerator flue gas by conventional 018 methods. Moreover, if all the sulfur which must be removed 019 from streams in an FCC operation could be recovered in a single 020 operation performed on the reactor off-gas, the use of plural 021 sulfur recovery operations in an FCC unit could be obviated, 022 reducing expense.
023 It has been suggested to diminish the amount of 024 sulfur oxides in FCC regenerator flue gas by desulfurizing a 025 hydrocarbon feed in a separate desulfurization unit prior to 026 cracking or to desulfurize the regenerator flue gas itself, by 027 a conventional flue gas desulfurization procedure, after its 028 removal from the FCC regenerator. Clearly, either of the 029 foregoing alternatives requires an elaborate, extraneous 030 processing operation and entails large capital and utilities 031 expenses.
032 If sulfur normally removed from the FCC unit as sul-033 fur oxides in the regenerator flue gas is instead removed from 034 the cracking reactor as hydrogen sulfide along with the 035 processed cracked hydrocarbons, the sulfur thus shifted from 036 the regenerator flue gas to the reactor effluent constitutes 037 simply a small increment to the large amount of hydrogen ~14S7~)0 001 ~4~
002 sulfide and organic sulfur invariably present in the reactor 003 effluent. The small added expense, if any, of removing even as 004 much as 5-15% more hydrogen sulfide from an FCC reactor off-gas 005 by available means is substantially less than the expense of 006 reducing the flue gas sulfur oxides level by separate feed 007 desulfurization. Present commercial facilities for removing 008 hydrogen sulfide from reactor off-gas can, in most if not all 009 cases, handle any additional hydrogen sulfide which would be 010 added to the off-gas if the sulfur normally discharged in the 011 regenerator flue gas were substantially all shifted to form 012 hydrogen sulfide in the FCC reactor off-gas. It is accordingly 013 desirable to direct substantially all feed sulfur into the 014 fluid cracked products removal pathway from the cracking 015 reactor and thereby reduce the amount of sulfur oxides in the 016 regenerator flue gas.
017 It has been suggested, e.g., in U.S. Patent 018 3,699,037, to reduce the amount of sulfur oxides in FCC
019 regenerator flue gas by adding particles of Group IIA metal 020 oxides and/or carbonates, such as dolomite, MgO or CaCO3, to 021 the circulating catalyst in an FCC unit. The Group IIA metals 022 react with sulfur oxides in the flue gas to form solid sulfur-023 containing compounds. The Group IIA metal oxides lack physical 024 strength. Regardless of the size of the particles introduced, 025 they are rapidly reduced to fines by attrition and rapidly pass 026 out of the FCC unit with the catalyst fines. Thus, addition of 027 dolomite and the like Group IIA materials is essentially a 028 once-through process, and relatively large amounts of material 029 must be continuously added in order to reduce the level of flue 030 gas sulfur oxides.
031 It has also been suggested, e.g., in U.S. Patent 032 3,835,031, to reduce the amount of sulfur oxides in an FCC
033 regenerator flue gas by impregnating a Group IIA metal oxide 034 onto a conventional silica-alumina cracking catalyst. The 035 attrition problem encountered when using unsupported Group IIA
036 metals is thereby reduced. However, it has been found that ~14S7~0 001 - ~5~
002 Group IIA metal oxides, such as ma~nesia, when used as a compo-003 nent of cracking catalysts, have a rather pronounced 004 undesirable effect on the activity and selectivity of the 005 cracking catalysts. The addition of a Group IIA metal to a 006 cracking catalyst results in two particularly noticeable 007 adverse consequences relative to the results obtained in 008 cracking without the presence of the Group IIA metals: (1) the 009 yield of the liquid hydrocarbon fraction is substantially 010 reduced, typically by greater than 1 volume percent of the feed 011 volume; and (2) the octane rating of the gasoline or naphtha 012 fraction (24-221C boiling range) is substantially reduced.
013 Both of the above-noted adverse consequences are seriously 014 detrimental to the economic viability of an FCC cracking opera-015 tion, so that even complete removal of sulfur oxides from 016 regenerator flue gas would not normally compensate for the 017 simultaneous losses in yield and octane which result from 018 adding Group IIA metals to an FCC catalyst.
019 Alumina has been a component of many FCC and 020 moving-bed cracking catalysts, but normally in intimate 021 chemical combination with at least 40 weight percent silica.
022 Alumina itself has low acidity and has generally been 023 considered to be undesirable for use as a cracking catalyst.
024 The art taught that alumina is not selective, i.e., the cracked 025 hydrocarbon products recovered from an FCC or other cracking 026 unit using an alumina catalyst would not be desired valuable 027 products, but would include, for example, relatively large 028 amounts of C2 and lighter hydrocarbon gases.
029 U.S. Patent 4,071,436 discloses the use of alumina 030 for reducing the amount of sulfur oxides in the flue gas formed 031 during cracking catalyst regeneration. The alumina can be used 032 in the form of a particulate solid mixed with cracking catalyst 033 particles. In some cases, alumina contained in the cracking 034 catalyst particles is also suitable; however, alumina contained 035 in conventional cracking catalysts is usually not very active, 036 since it is intimately mixed with a large fraction of silica.
037 U.S. Patents 4,115,250 and 4l115,251 disclose the 11457~0 002 synergistic use of oxidation-promoting metals for carbon 003 monoxide burning in combination with the use of alumina for 004 reducing the amount of sulfur oxides in cracking catalyst 005 regenerator flue gas. When alumina and highly active 006 oxidation-promoting metals are both included in the same 007 particle, alumina in the particle is ineffective for removing 008 sulfur oxides from the regenerator flue gas, especially in the 009 presence of even a small amount of carbon monoxide. On the 010 other hand, when the alumina and combustion-promoting metal are 011 used on separate particles circulated together in a cracking 012 system in physical admixture, the ability of the alumina to 013 reduce the level of sulfur oxides in the flue gas can be consid-014 erably enhanced.
015 In reducing the level of sulfur ox ~es in catalyst 016 regenerator flue gas using alumina, as disclosed in U.S.
017 Patents No. 4,017,436, No. 4,115,250 and No. 4,115,251, in a 018 catalytic cracking system under commerci~al operating conditions 019 it has now been noted that silicon and silicon compounds, espe-020 cially silica, in the particulate catalyst used in a catalytic 021 cracking system, can exert an unexpected detrimental effect on 022 the activity and stability of alumina contained in particles 023 other than the catalyst particles in the particulate inventory, 024 with respect to the capacity and rate of reaction of the alu-025 mina in forming sulfur-containing solids in a catalyst regene-026 rator. Silicon contained in æeolitic crystalline alumino-027 silicates apparently does not migrate to any substantial 028 extent, and therefore does not cause alumina deactivation. Pre-029 viously, it was known that contamination of alumina by silica 030 presented a problem when the silica was chemically combined 031 with alumina prior to introduction into the circulating 032 particulate solids inventory, or, more generally, when the 033 silica was already present in the same particles as the 034 alumina. It has now been found that under the conditions found 035 in commercial catalytic cracking and regeneration systems, 036 silica can migrate from particles of higher silica concen-037 tration to particles of lower or zero silica concentration 1~457~0 002 during circulation of a mixture of such particles in a cracking 003 system. Silica which is subject to such migration may be 004 termed "amorphous" or "non-crystalline" silica, to distinguish 005 it from silica in the form of zeolitic crystalline aluminosili-006 cates, which is relatively stable and is subject to little or 007 no migration between particles under commercial FCC operating 008 conditions. It is believed that the silicon is carried between 009 particles in the hot gases, such as steam, which are present in 010 catalytic cracking systems. The present invention is directed, 011 in part, to overcoming the problem of deactivation of alumina 012 resulting from silica migration from high-silica-content parti-013 cles to alumina-containing particles in the particulate solids 014 inventory in a catalytic cracking system.
015 SUMMARY OF ~H~ IN~ENTION
016 In an embodiment of the present invention, an 017 improvement is provided in a process for cracking a sulfur-018 containing hydrocarbon stream in the absence of externally 019 supplied molecular hydrogen including the steps of (a) cycling 020 an inventory of particulate solids involving acidic cracking 021 catalyst particles between a cracking zone and a catalyst 022 regeneration zone; (b) cracking the sulfur-containing hydro-023 carbon stream in the cracking zone in contact with the cracking 024 catalyst particles, the catalyst particles containing at least 025 20 weight persent of a silicon component, calculated as silica 026 and excluding silicon in the form of zeolitic crystalline 027 aluminosilicate, in a cracking zone at cracking conditions 028 including a temperature in the range from 425C to 700C, where-029 by sulfur-containing coke is deposited on the catalyst parti-030 cles, and removing the hydrocarbon stream from the cracking 031 zone; (c) passing coke-containing catalyst particles from the 032 cracking zone and an oxygen-containing gas into the catalyst 033 regeneration zone, burning the sulfur-containing coke therein 034 at a temperature in the range from 538C to 816C to form a 035 flue gas containing sulfur oxides, and removing the flue gas 036 from the catalyst regeneration zone; (d) forming a sulfur-con-037 taining solid in the regeneration zone by reacting the sulfur 11457~0 002 oxides with alumina in at least one particulate solid in the 003 particulate solids inventory other than the catalyst particles, 004 the particulate solid containing less than 20 weight percent 005 silicon, calculated as silica; (e) returning the resulting coke-006 depleted catalyst particles from the catalyst regeneration zone 007 to contact with the hydrocarbon stream in the cracking zone;
008 and (f) forming hydrogen sulfide in the cracking zone by 009 contacting the sulfur-containing solid with the hydrocarbon 010 stream; the method for reducing poisoning of alumina in the 011 particulate solid for reaction with sulfur oxides caused by 012 migration of silicon or a silicon compound from the catalyst 013 particles onto the particulate solid, comprising:
014 employing in the particulate solid from 100 parts per 015 million by weight to 1.0 weight percent, relative to the amount 016 of alumina in the particulate solid and calculated on an elemen-017 tal basis, of a promoter comprising at least one element or com-018 pound of an element selected from sodium, manganese and 019 phosphorus.
020 Sulfur oxides can be removed from the regenerator 021 flue gas by reaction with high-surface-area alumina present in 022 particles other than the catalyst, circulated in physical 023 mixture with siliceous catalyst particles in a cracking system.
024 Silicon and/or silicon compounds such as silica migrate from 025 the catalyst particles to the alumina particles, especially in 026 a steam-containing atmosphere such as a catalyst stripper or 027 regenerator. Poisoning of the active alumina component by con-028 tamination with silica migrating from the catalyst particles is 029 reduced, according to the invention, by employing alumina-030 containing particles including at least one element or compound 031 of an element selected from sodium, manganese and phosphorus.
032 It has been found that active alumina loses at least part of 033 its capacity to react with sulfur oxides when contaminated with 034 migrating silica. The loss of activity can be substantially 035 lessened by including at least one of the above-mentioned 036 elements, or a compound ~hereof, in the alumina-containing 037 particles.
1~457~0 003 The present invention is used in connection with a 004 fluid catalyst cracking process for cracking hydrocarbon feeds.
005 The same hydrocarbon feeds normally processed in commercial ~CC
00~ systems may be processed in a cracking system employing the 007 present invention. Suitable feedstocks include, for example, 008 petroleum distillates or residuals, either virgin or partially 009 refined. Synthetic feeds such as coal oils and shale oils are 010 also suitable.
011 Suitable feedstocks normally boil in the range from 012 about 200-~00CC or higher~ A suitable feed may include recy-013 cled hydrocarbons which have already been subjected to 014 cracking.
015 The cracking catalysts with which the present inven-016 tion finds utility are those which include a substantial concen-017 tration of silica and which are recognized by those skilled in 018 the art to be suitably acidic and active for catalyzing 019 cracking of hydrocarbons in the absence of externally supplied 020 molecular hydrogen. The invention is most useful in connection 021 with catalysts containing at least 20 weight percent silica, 022 especially at least 30 weight percent silica, excluding silica 023 in the form of zeolitic crystalline aluminosilicates. Silica 024 is generally included in commercially used cracking catalysts 025 in combination with one or more other inorganic oxides such as 02~ alumina, magnesia, et:c. Many commercial catalysts presently 027 include a zeolite component associated with a non-crystalline 028 silica-alumina or silica-containing clay matrix. Non-zeolite-029 type catalysts including silica, such as amorphous silica-030 aluminas, silica-magnesias, clays, etc., are also within the 031 scope of the invention, however. Particularly suitable 032 cracking components are the acidic, zeolitic crystalline 033 aluminosilicates such as X-type and Y-type faujasites, 034 preferably in the hydrogen form, the rare earth form, or other 035 equally stable form. Zeolitic crystalline aluminosilicates are 03~ preferred acidic cracking components in that silicon included 037 in zeolites is not particularly subject to migration between 038 particles during use in catalytic cracking, and thus do not 1~457~0 .
002 contribute to poisoning of alumina activity for sulfur oxides 003 removal from flue gas. Preferably, the particulate solids 004 inventory used in a system in an embodiment of the invention 005 includes at least 75 weight percent of particles containing 006 from 5 to 30 weight percent of a zeolitic crystalline alumino-007 silicate. On the other hand, acidic, non-crystalline catalyst 008 such as silica-aluminas can be used. For example, it may be 009 desirable, for economic reasons, to use a mixture of cracking 010 catalysts, one of which contains a zeolitic cracking component, 011 while the other contains only relatively inexpensive amorphous 012 silica-alumina, e.g., in systems where catalyst must be added 013 frequently as a result of high feed metals levels or the like.
014 A zeolite-containing cracking catalyst component may 015 be formed by treatment of kaolin clay, as by slurrying the 016 clay, sizing and spray drying, followed by treatment with 017 caustic at elevated temperature for a time sufficient to 018 generate a fraction of the desired zeolite in the treated clay, 019 with the clay acting as the matrix. The zeolite component in 020 the particles can then be converted to the ammonium and/or rare 021 earth form by ion-exchange, if desired. Of course, there is 022 usually still a substantial non-crystalline silica content in 023 catalysts manufactured in this manner. The zeolite can also be 024 manufactured separately and added to the desired matrix or 025 binder material. Conventional binders such as clays, acid-026 treated clays, synthetic silica-alumina cogels, etc., can be 027 used as the binder, or as a component of the binder.
028 Cracking conditions employed in the cracking or 029 conversion step in an FCC system are frequently provided in 030 part by pre-heating or heat-exchanging hydrocarbon feeds to 031 bring them to a temperature of about 315-400C before 032 introducing them into the cracking zone; however, pre-heating 033 of the feed is not essential. Cracking conditions usually 034 include a catalyst/hydrocarbon weight ratio of about 3-10. A
035 hydrocarbon weight space velocity in the cracking zone of about 036 5-50 per hour is preferably used. The average amount of coke 037 contained in the catalyst after contact with the hydrocarbons ~14S7~o 002 in the cracking zone, when the catalyst is passed to the 003 regenerator, is preferably between about 0.5 weight percent and 004 about 2.5 weight percent, depending in part on the carbon 005 content of regenerated catalyst in the particular system, as 006 well as the heat balance of the particular system.
007 The catalyst regeneration zone used in an FCC system 008 employing an embodiment of the present invention may be of 009 conventional design. Preferably, the total pressure in the 010 regeneration zone is maintained at at least 20 psig. The 011 gaseous atmosphere within the regeneration zone normally 012 includes a mixture of gases in concentrations which vary 013 according to the locus within the regenerator. The 014 concentrations of gases also vary according to the coke 015 concentration on catalyst particles entering the regenerator 016 and according to the amount of molecular oxygen and steam 017 passed into the regenerator. Generally, the gaseous atmosphere 018 in a regenerator contains 5-25~ steam, varying amounts of 019 oxygen, carbon monoxide, carbon dioxide and nitrogen. The 020 present invention is applicable in cases in which an oxygen-021 containing and nitrogen-containing gas, such as air, is 022 employed for combustion of coke in the catalyst regenerator.
023 As will be appreciated by those skilled in the art, air is 024 essentially invariably employed to provide the oxygen needed 025 for combustion in FCC regenerators.
026 Sulfur oxides are removed from the flue gas in a cata-027 lyst regeneration zone by reacting sulfur oxides, e.g., sulfur 02~ trioxide, with alumina in the regeneration zone. The alumina 029 active for reaction with sulfur oxides usually has a surface 030 area of at least 50 m2/g, e.g., gamma- or eta-alumina.
031 Suitable alumina must not be in intimate combination with more 032 than 20 weight percent silica, based on the alumina and silica 033 concentrations in a given particle, and preferably the alumina-034 containing particles used are substantially free from admixture 035 with silica. Alumina from any source is suitable for use in 036 the present method if it contains an average of about 0.1 to 037 lO0 weight percent of "reactive alumina", as determined by 1~457~0 002 treating particles containing the alumina by the following 003 steps:
004 (1) passing a stream of a gas mixture containing, by 005 volume, 10% water, 1% hydrogen sulfide, 10% hydrogen and 79%
006 nitrogen over the solid particle continuously at a temperature 007 of 650C and atmospheric pressure until the weight of the solid 008 particle is substantially constant;
009 (2) passing a stream of a gas mixture containing, by 010 volume, 10~ water, 15% carbon dioxide, 2% oxygen and 73%
011 nitrogen over the solid particle resulting from step (1) at a 012 temperature of 650C and atmospheric pressure until the weight 01~ of the solid particle is substantially constant, the weight of 014 the particle at this time being designated "Wa''; and 015 (3) passing a stream of a gas mixture containing, by 016 volume, 0.0S% sulfur dioxide, and, in addition, the same gases 017 in the same proportions as used in step (2), over the solid 018 particle resulting from step (2) at a temperature of 650C and 019 atmospheric pressure until the weight of the solid particle is 020 substantially constant, the weight of the solid particle at 021 this time being designated "Wsl'.
022 The weight fraction of reactive alumina in the solid 023 particle, designated "Xa", is determined by the formula Xa Ws-Wa x Molecular Wt. Alumina 8~5 Wa 3 x Molecular Wt. Sulfur Trioxide 028 The alumina used in embodiments of the present inven-029 tion is included in particulate solids, other than catalyst 030 particles, which are physically suitable for circulation in the 031 cracking system. Suitable particles normally have an alumina 032 content of at least 80 weight percent and, preferably, the 033 alumina content of such particles is 90 weight percent or more.
034 In a particularly preferred embodiment, the alumina-containing 035 particles consist of gamma-alumina. Alumina can be formed into 036 particles of suitable size for circulation with FCC catalyst in 037 an FCC system by spray-drying, crushing larger particles, etc.
038 In carrying out the invention, alumina-containing 039 particles are introduced into a cracking system and circulated 1~457~0 002 in physical mixture with silica-containing cracking catalyst.
003 The amount of separate, alumina-containing particles employed 004 in the particulate solids inventory is preferably 25 weight 005 percent, or less, of the total particulate solids inventory 006 circulating in the cracking system. The addition of an amount 007 of alumina between 1.0 and 25 weight percent of the total 008 particulate solids inventory is particularly preferred. The 009 size, shape and density of separate, alumina-containing parti-010 cles circulated in admixture with catalyst particles is pref-011 erably such that the alumina-containing particles circulate in 012 substantially the same manner as conventional catalyst 013 particles in the particular cracking system, e.g., beads are 014 used in a moving-bed, bead~catalyst unit, whereas 50-100 micron 015 diameter particles are quite suitable in an FCC unit. Alumina 016 reacts with sulfur trioxide or sulfur dioxide and oxygen in the 017 cracking catalyst regenerator to form at least one sulfur-con-018 taining solid, such as a sulfate of aluminum. In this way, sul-019 fur oxides are removed from the regenerator atmosphere and are 020 not discharged from the regenerator in the flue gas.
021 Particles containing the solid aluminum- and sulfur-022 containing material are passed to the cracking zone along with 023 the other particulate solids, such as regenerated catalyst. In 024 the cracking zone, alumina is regenerated and hydrogen sulfide 025 is formed by reaction of sulfur in the sulfur-containing solid 026 by contacting the sulfur-containing solid with the stream of 027 hydrocarbon being treated in the cracker. In addition to 028 forming hydrogen sulfide, the reaction between the sulfur- and 029 aluminum-containing solid and the hydrocarbon feed may produce 030 some other sulfur~compounds such as carbon oxysulfide, organic 031 sulfides, etc., which are vapor-phase at cracking conditions.
032 The resulting hydrogen sulfide and other vapor-phase sulfur 033 compounds exit the cracking zone as a part of the stream of 034 cracked hydrocarbons, along with a much larger amount of 035 vapor-phase sulfur compounds formed directly from sulfur in the 036 hydrocarbon feed during the cracking reactions. Off-gas subse-037 quently separated from the cracked hydrocarbon stream thus ~457~0 .
002 includes hydrogen sulfide formed directly from the feed sulfur 003 and hydrogen sulfide formed by reaction of the sulfur- and 004 aluminum-containing solid with the hydrocarbon stream in the 005 cracking zone.
006 I have found that, by including at least one of 007 sodium, manganese or phosphorus in the alumina-containing 008 particles employed to react with sulfur oxides, deactivation of 00g the alumina for reaction with SOx, caused by silica migration, 010 can be substantially reduced. Although sodium, manganese and 011 phosphorus, or compounds thereof, are the most useful materials 012 for addition to alumina to prevent deactivation by migrating 013 silica, several other materials can have a positive effect in 014 many cases. These include lithium, potassium, nickel, 015 lanthanum, tin and iron. On the other hand, these last-016 mentioned Inaterials do not appear to be as effective as sodium, 017 manganese or phosphorus, judging from data presently available.
018 The sodium, manganese or phosphorus component can be 019 combined with the alumina in any convenient manner. For 020 example, a water-soluble compound can be introduced into parti-021 cles containing alumina by aqueous impregnation. The desired 022 material can be mixed with alumina prior to shaping, as by dry-023 mixing, comulling, or the like. The amount of sodium, 024 manganese or phosphorus added, on an elemental basis, is 025 usually at least 100 parts per million, by weight, of the 026 alumina. The maximum amount added is 1.0 weight percent. Pref-027 erably, not more than 0.5 weight percent of the promoter is 028 included with the alumina, on an elemental basis. The concen-029 trations of promoter are based on the alumina content of the 030 alumina-containing particulate solid. Those skilled in the art 031 will recognize that the alumina may be combined as a mixture, 032 particle pack, or the like, with other materials, such as other 033 porous inorganic oxides, such as chromia, magnesia, titania, 034 etc.
035 Surprisingly, I have found that concentrations of 036 sodium, manganese or phosphorus in alumina of 0.1 weight per-037 cent are more effective in preventing silica-deactivation 1~4S7~0 .
002 of the alumina than are higher concentrations such as 0.5 003 weight percent or more.
005 Samples of particulate alumina impregnated with water-006 soluble salts of various promoters were prepared. The alumina 007 employed was Reynolds RH-30, a commercially available material.
008 Two samples of alumina containing each promoter were prepared, 009 one containing 0.1 weight percent promoter and the other con-010 taining 0.5 weight percent. All samples were prepared by 011 aqueous impregnation with a water-soluble salt. Each sample 012 was calcined at 593C in dry air for 4 hours.
014 An 0.5-gram portion of each sample prepared as 015 described in Example I was physically mixed with 4.5 grams of 016 an equilibrium zeolite-containing FCC catalyst of commercially 017 available type, containing about 37 weight percent silica, ex-018 cluding silica in the form of zeolitic crystalline alumino-019 silicate. Each of the catalyst-alumina particle mixtures was 020 then steamed for 96 hours at 650C to induce silica migration 021 from the catalyst particles to the alumina particles. The 022 rates of reaction of the steamed samples of alumina were then 023 determined by thermogravimetric analysis by the following 024 procedure: (1) a portion of each steamed catalyst-alumina 025 mixture was heated to 650C in a flowing atmosphere containing, 026 by volume, 2% 2' 15% CO2 and 10% H2O in N2 until the weight of 027 the sample was constant; (2) the atmosphere composition was 028 changed to 10% H2 and 10% H2O in N2 and maintained until the 029 weight of the sample was constant; (3) the atmosphere was 030 returned to the composition used in step (1) and maintained 031 until the sample weight was constant; and (4) 0.2% SO2 was 032 added to the atmosphere and the weight gained during 6 minutes 033 of exposure to SO2 was measured. The rate of reaction for the 034 samples is defined as the average weight gain per minute for 035 the first 6 minutes divided by the total weight of the sample 036 after step (3). The results for each promoted alumina, for a 037 control sample of unpromoted alumina, and for a sample of ~1457~0 002 catalyst without alumina particles are shown in Table I.
003 Referring to Table I, it can be seen that sodium, manganese 004 and phosphorus promoters provide a substantially higher 005 activity for reaction with Sx after a sample has been sub-006 jected to silica migration than do the other promoters tested, 007 particularly in the samples containing 0.1 weight percent of 008 the promoters.
010 Promoter Rate (ppm/minute) 011 0.1 wt.% 0.5 wt.%
012 Phosphorus 77 66 013 Manganese 71 63 014 Sodium 74 68 015 Nickel 69 61 016 Lanthanum 64 64 017 Tin 60 62 018 Iron 64 67 019 Copper 66 61 020 Vanadium 62 43 021 Titanium 63 51 022 Magnesium 60 56 023 Cerium 59 54 024 Lead 52 59 025 Boron 53 46 026 Molybdenum 46 50 027 Arsenic 57 52 028 None 54 54 029 Catalyst alone 51 51 031 For purposes of comparison with the alumina particles 032 used in the improvement of the invention, particles of silica 033 gel were impregnated with sodium or manganese. The silica gel 034 used was Davison Grade 70 gel screened to 100-325 mesh. Four 035 samples of silica gel were impregnated with an aqueous solution 036 of either sodium nitrate or manganese nitrate in amounts 11457~0 002 sufficient to provide a sample containing 0.1 weight percent 003 sodium, 0.S weight percent sodium, 0.1 weight percent manganese 004 and 0.5 weight percent manganese.
006 A 0.5 gram sample of the plain gel was mixed with 4.5 007 grams of the same equilibrium zeolite-containing FCC catalyst 008 used in the test of Example II. Four mixtures were made up 009 each containing 4.5 grams of the FCC catalyst and 0.5 grams of 010 the silica gel containing either 0.1 weight percent Na, 0.5 011 weight percent Na, 0.1 weight percent Mn or 0.5 weight percent 012 Mn. The five mixtures prepared as described were each steamed 013 for 96 hours at 650C. The rate of reaction, if any, for 014 reaction with sulfur oxides was then measured by the same 015 procedure described in Example II. The results for the unmixed 016 catalyst and each of the five mixtures are shown in Table II.
019 Rate (ppm/minute) 020 Promoter ~ 1 5 wt.%
022 Unmixed Catalyst 51 51 024 Catalyst with Plain 025 Silica Gel 29 29 027 Manganese Impregnated 40 37 029 Sodium Impregnated 31 27 032 Referring to Table II, it is apparent that all the 033 silica gel mixtures are substantially poorer for reacting with 034 sulfur oxides than is the FCC catalyst alone.
035 ILLUSTRATIVE EM~ODIMENT
036 A conventional, commercial FCC processing system 037 having a capacity of 22,000 barrels per day is employed. The 038 feed used is a mixture of hydrocarbons having a boiling range 039 of 3Q4-593C with a sulfur content of 0.85 weight percent. The 040 cracking reactor employs a combination of riser and dense-bed ` 11457~0 002 cracking. Cracking conditions employed include a reactor 003 average temperature of about 495C, a hydrocarbon weight hourly 004 space velocity of about 5 per hour and a conversion rate (feed 005 converted to 220C-) of about 85%. Catalyst is circulated at 006 the rate of about 8 metric tons per minute with a total inven-007 tory of about 154 metric tons. The catalyst used contains Y-008 type zeolitic crystalline aluminosilicate dispersed in a non-009 crystalline silica-alumina matrix. A separate combustion pro-010 moter is used to get complete combustion in the regenerator.
011 The silica concentration in the catalyst, excluding silica in 012 the form of zeolite, is about 40 weight percent. The spent 013 catalyst contains about 0.8 weight percent coke, and the coke 014 contains about 0.7 weight percent sulfur. Regeneration condi-015 tions include a temperature of about 670C. After regene-016 ration, the catalyst contains about 0.2 weight percent coke.
l? Prior to the introduction of alumina into the circulating inven-018 tory to react with SOx, the flue gas removed from the catalyst 019 regenerator contains about 300 parts per million, by volume, of 020 SOx, calculated as SO2. For purposes of comparison, an un-021 treated particulate gamma-alumina is first used to remove Sx 022 from the regenerator flue gas. Sufficient alumina is intro-023 duced and circulated to provide 10 weight percent of the 024 particulate solids inventory. The amount of Sx initially 025 removed from the flue gas is relatively high, but over a period 026 of 5 days of operation it is observed that migration of silica 027 from the cracking catalyst particles reduces the activity of 028 the alumina, so that the amount of Sx in the flue gas 029 increases to about 220 ppm (volume). According to the inven-030 tion, the unpromoted alumina is withdrawn from the FCC system, 031 and particles of alumina promoted with 0.1 weight percent phos-032 phorus are introduced in an amount sufficient to provide 10 033 weight percent of the particulate solids inventory in the FCC
034 system. The promoted alumina has been prepared by spray-drying 035 the alumina and subsequent aqueous impregnation with ammonium 036 phosphate solution. After introduction of the phosphorus-037 promoted alumina, the amount of Sx initially removed from 1 ~1457a~
002 the regenerator flue gas is again found to be relatively high.
003 After 5 days of operation, substantially less silica migration 004 deactivation of the phosphorus-promoted alumina is observed 005 than was found using the unpromoted alumina, resulting in a 006 flue gas Sx of only 140 ppm (volume).
007 The foregoing detailed description of the invention, 008 examples, and illustrative embodiment illustrate a preferred 009 mode of carrying out the invention. It will be clear to those 010 skilled in the art that other embodiments and obvious modifi-011 cations, equivalents and variations of the invention can be 012 employed and adapted to a variety of catalytic cracking 013 systems. Such modifications, alterations and adaptations are 014 intended to be included within the scope of the appended 015 claims.
007 Modern hydrocarbon catalytic cracking systems use a 008 moving bed or fluidized bed of a particulate catalyst.
009 Catalytic cracking is carried out in the absence of externally 010 supplied molecular hydrogen, and is thereby distinguished from 011 hydrocracking, in which hydrogen is added. In catalytic crack-012 ing, catalyst is subjected to a continuous cyclic cracking 013 reaction and catalyst regeneration procedure. In a fluidized 014 catalytic cracking ~FCC) system, a stream of hydrocarbon feed 015 is contacted with fluidized catalyst particles in a hydrocarbon 016 cracking zone, or reactor, usually at a temperature of about 017 427-600C. The reactions of hydrocarbons in the hydrocarbon 018 stream at this temperature result in deposition of carbonaceous 019 coke on the catalyst particles. The resulting fluid products 020 are thereafter separated from the coked catalyst and are with-021 drawn from the cracking zone. The coked catalyst is stripped 022 of volatiles, usually with steam, and is cycled to a catalyst 023 regeneration zone. In the catalyst regenerator, the coked 024 catalyst is contacted with a gas, such as air, which contains a 025 predetermined concentration of molecular oxygen to burn off a 026 desired portion of the coke from the catalyst and simul-027 taneously to heat the catalyst to a high temperature desired 028 when the catalyst is again contacted with the hydrocarbon 029 stream in the cracking zone. After regeneration, the catalyst 030 is cycled to the cracking zone, where it is used to vaporize 031 the hydrocarbons and to catalyze hydrocarbon cracking. The 032 flue gas formed by combustion of coke in the catalyst 033 regenerator is removed from the regenerator. It may be treated 034 to remove particulates and carbon monoxide from it, after which 035 it is normally passed into the atmosphere. Concern with the 036 emission of pollutants in flue gas, such as sulfur oxides, has 037 resulted in a search for improved methods for controlling such 038 pollutants.
11457~0 002 The amount of conversion obtained in an FCC cracking 003 operation is the volume percent of fresh hydrocarbon feed 004 changed to gasoline and lighter products during the conversion 005 step. The end boiling point of gasoline for the purpose of 006 determining conversion is conventionally defined as 221C.
007 Conversion is often used as a measure of the severity of a 008 commercial FCC operation. At a given set of operating 009 conditions, a more active catalyst gives a greater conversion 010 than does a less active catalyst. The ability to provide 011 higher conversion in a given FCC unit is desirable in that it 012 allows the FCC unit to be operated in a more flexible manner.
013 Feed throughput in the unit can be increased, or alternatively 014 a higher degree of conversion can be maintained with a constant 015 feed throughput rate. The type of conversion, i.e., selec-016 tivity, is also important in that poor selectivity results in 017 less naphtha, the desired cracked product~ and higher gas and 018 coke makes.
019 The hydrocarbon feeds processed in commercial FCC
020 units normally contain sulfur, usually termed "feed sulfur".
021 It has been found that about 2-10% or more of the feed sulfur 022 in a hydrocarbon feedstream processed in an FCC system is 023 invariably transferred from the feed to the catalyst particles 024 as a part of the coke formed on the catalyst particles during 025 cracking. The sulfur deposited on the catalyst, herein termed 026 "coke sulfur", is passed from the cracking zone on the coked 027 catalyst into the catalyst regenerator. About 2-10% or more of 028 the feed sulfur is continuously passed from the cracking zone 029 into the catalyst regeneration zone in the coked catalyst. In 030 an FCC catalyst regenerator, sulfur contained in the coke is 031 burned along with the coke carbon and hydrogen, forming gaseous 032 sulfur dioxide and sulfur trioxide, which are conventionally 033 removed from the regenerator in the flue gas.
034 Most of the feed sulfur does not become coke sulfur 035 in the cracking reactor. Instead, it is converted either to 036 normally gaseous sulfur compounds such as hydrogen sulfide and 037 carbon oxysulfide, or to normally liquid organic sulfur . 11457~)0 001 ~ _3_ 002 compounds. All these sulfur compounds are carried along with 003 the vapor cracked hydrocarbon products recovered from the 004 cracking reactor. About 90% or more of the feed sulfur is 005 continuously removed from the cracking reactor in the stream of 006 processed, cracked hydrocarbons, with about 40-60~ of this 007 sulfur being in the form of hydrogen sulfide. Provisions are 008 conventionally made to recover hydrogen sulfide from the 009 effluent from the cracking reactor. Typically, a 010 very-low-molecular-weight off-gas vapor stream is separated 011 from the C3+ liquid hydrocarbons in a gas recovery unit, and 012 the off-gas is treated, as by scrubbing it with an amine 013 solution, to remove the hydrogen sulfide. Removal of sulfur 014 compounds such as hydrogen sulfide from the fluid effluent from OlS an FCC cracking reactor, e.g., by amine scrubbing, is rela-016 tively simple and inexpensive, relative to removal of sulfur 017 oxides from an FCC regenerator flue gas by conventional 018 methods. Moreover, if all the sulfur which must be removed 019 from streams in an FCC operation could be recovered in a single 020 operation performed on the reactor off-gas, the use of plural 021 sulfur recovery operations in an FCC unit could be obviated, 022 reducing expense.
023 It has been suggested to diminish the amount of 024 sulfur oxides in FCC regenerator flue gas by desulfurizing a 025 hydrocarbon feed in a separate desulfurization unit prior to 026 cracking or to desulfurize the regenerator flue gas itself, by 027 a conventional flue gas desulfurization procedure, after its 028 removal from the FCC regenerator. Clearly, either of the 029 foregoing alternatives requires an elaborate, extraneous 030 processing operation and entails large capital and utilities 031 expenses.
032 If sulfur normally removed from the FCC unit as sul-033 fur oxides in the regenerator flue gas is instead removed from 034 the cracking reactor as hydrogen sulfide along with the 035 processed cracked hydrocarbons, the sulfur thus shifted from 036 the regenerator flue gas to the reactor effluent constitutes 037 simply a small increment to the large amount of hydrogen ~14S7~)0 001 ~4~
002 sulfide and organic sulfur invariably present in the reactor 003 effluent. The small added expense, if any, of removing even as 004 much as 5-15% more hydrogen sulfide from an FCC reactor off-gas 005 by available means is substantially less than the expense of 006 reducing the flue gas sulfur oxides level by separate feed 007 desulfurization. Present commercial facilities for removing 008 hydrogen sulfide from reactor off-gas can, in most if not all 009 cases, handle any additional hydrogen sulfide which would be 010 added to the off-gas if the sulfur normally discharged in the 011 regenerator flue gas were substantially all shifted to form 012 hydrogen sulfide in the FCC reactor off-gas. It is accordingly 013 desirable to direct substantially all feed sulfur into the 014 fluid cracked products removal pathway from the cracking 015 reactor and thereby reduce the amount of sulfur oxides in the 016 regenerator flue gas.
017 It has been suggested, e.g., in U.S. Patent 018 3,699,037, to reduce the amount of sulfur oxides in FCC
019 regenerator flue gas by adding particles of Group IIA metal 020 oxides and/or carbonates, such as dolomite, MgO or CaCO3, to 021 the circulating catalyst in an FCC unit. The Group IIA metals 022 react with sulfur oxides in the flue gas to form solid sulfur-023 containing compounds. The Group IIA metal oxides lack physical 024 strength. Regardless of the size of the particles introduced, 025 they are rapidly reduced to fines by attrition and rapidly pass 026 out of the FCC unit with the catalyst fines. Thus, addition of 027 dolomite and the like Group IIA materials is essentially a 028 once-through process, and relatively large amounts of material 029 must be continuously added in order to reduce the level of flue 030 gas sulfur oxides.
031 It has also been suggested, e.g., in U.S. Patent 032 3,835,031, to reduce the amount of sulfur oxides in an FCC
033 regenerator flue gas by impregnating a Group IIA metal oxide 034 onto a conventional silica-alumina cracking catalyst. The 035 attrition problem encountered when using unsupported Group IIA
036 metals is thereby reduced. However, it has been found that ~14S7~0 001 - ~5~
002 Group IIA metal oxides, such as ma~nesia, when used as a compo-003 nent of cracking catalysts, have a rather pronounced 004 undesirable effect on the activity and selectivity of the 005 cracking catalysts. The addition of a Group IIA metal to a 006 cracking catalyst results in two particularly noticeable 007 adverse consequences relative to the results obtained in 008 cracking without the presence of the Group IIA metals: (1) the 009 yield of the liquid hydrocarbon fraction is substantially 010 reduced, typically by greater than 1 volume percent of the feed 011 volume; and (2) the octane rating of the gasoline or naphtha 012 fraction (24-221C boiling range) is substantially reduced.
013 Both of the above-noted adverse consequences are seriously 014 detrimental to the economic viability of an FCC cracking opera-015 tion, so that even complete removal of sulfur oxides from 016 regenerator flue gas would not normally compensate for the 017 simultaneous losses in yield and octane which result from 018 adding Group IIA metals to an FCC catalyst.
019 Alumina has been a component of many FCC and 020 moving-bed cracking catalysts, but normally in intimate 021 chemical combination with at least 40 weight percent silica.
022 Alumina itself has low acidity and has generally been 023 considered to be undesirable for use as a cracking catalyst.
024 The art taught that alumina is not selective, i.e., the cracked 025 hydrocarbon products recovered from an FCC or other cracking 026 unit using an alumina catalyst would not be desired valuable 027 products, but would include, for example, relatively large 028 amounts of C2 and lighter hydrocarbon gases.
029 U.S. Patent 4,071,436 discloses the use of alumina 030 for reducing the amount of sulfur oxides in the flue gas formed 031 during cracking catalyst regeneration. The alumina can be used 032 in the form of a particulate solid mixed with cracking catalyst 033 particles. In some cases, alumina contained in the cracking 034 catalyst particles is also suitable; however, alumina contained 035 in conventional cracking catalysts is usually not very active, 036 since it is intimately mixed with a large fraction of silica.
037 U.S. Patents 4,115,250 and 4l115,251 disclose the 11457~0 002 synergistic use of oxidation-promoting metals for carbon 003 monoxide burning in combination with the use of alumina for 004 reducing the amount of sulfur oxides in cracking catalyst 005 regenerator flue gas. When alumina and highly active 006 oxidation-promoting metals are both included in the same 007 particle, alumina in the particle is ineffective for removing 008 sulfur oxides from the regenerator flue gas, especially in the 009 presence of even a small amount of carbon monoxide. On the 010 other hand, when the alumina and combustion-promoting metal are 011 used on separate particles circulated together in a cracking 012 system in physical admixture, the ability of the alumina to 013 reduce the level of sulfur oxides in the flue gas can be consid-014 erably enhanced.
015 In reducing the level of sulfur ox ~es in catalyst 016 regenerator flue gas using alumina, as disclosed in U.S.
017 Patents No. 4,017,436, No. 4,115,250 and No. 4,115,251, in a 018 catalytic cracking system under commerci~al operating conditions 019 it has now been noted that silicon and silicon compounds, espe-020 cially silica, in the particulate catalyst used in a catalytic 021 cracking system, can exert an unexpected detrimental effect on 022 the activity and stability of alumina contained in particles 023 other than the catalyst particles in the particulate inventory, 024 with respect to the capacity and rate of reaction of the alu-025 mina in forming sulfur-containing solids in a catalyst regene-026 rator. Silicon contained in æeolitic crystalline alumino-027 silicates apparently does not migrate to any substantial 028 extent, and therefore does not cause alumina deactivation. Pre-029 viously, it was known that contamination of alumina by silica 030 presented a problem when the silica was chemically combined 031 with alumina prior to introduction into the circulating 032 particulate solids inventory, or, more generally, when the 033 silica was already present in the same particles as the 034 alumina. It has now been found that under the conditions found 035 in commercial catalytic cracking and regeneration systems, 036 silica can migrate from particles of higher silica concen-037 tration to particles of lower or zero silica concentration 1~457~0 002 during circulation of a mixture of such particles in a cracking 003 system. Silica which is subject to such migration may be 004 termed "amorphous" or "non-crystalline" silica, to distinguish 005 it from silica in the form of zeolitic crystalline aluminosili-006 cates, which is relatively stable and is subject to little or 007 no migration between particles under commercial FCC operating 008 conditions. It is believed that the silicon is carried between 009 particles in the hot gases, such as steam, which are present in 010 catalytic cracking systems. The present invention is directed, 011 in part, to overcoming the problem of deactivation of alumina 012 resulting from silica migration from high-silica-content parti-013 cles to alumina-containing particles in the particulate solids 014 inventory in a catalytic cracking system.
015 SUMMARY OF ~H~ IN~ENTION
016 In an embodiment of the present invention, an 017 improvement is provided in a process for cracking a sulfur-018 containing hydrocarbon stream in the absence of externally 019 supplied molecular hydrogen including the steps of (a) cycling 020 an inventory of particulate solids involving acidic cracking 021 catalyst particles between a cracking zone and a catalyst 022 regeneration zone; (b) cracking the sulfur-containing hydro-023 carbon stream in the cracking zone in contact with the cracking 024 catalyst particles, the catalyst particles containing at least 025 20 weight persent of a silicon component, calculated as silica 026 and excluding silicon in the form of zeolitic crystalline 027 aluminosilicate, in a cracking zone at cracking conditions 028 including a temperature in the range from 425C to 700C, where-029 by sulfur-containing coke is deposited on the catalyst parti-030 cles, and removing the hydrocarbon stream from the cracking 031 zone; (c) passing coke-containing catalyst particles from the 032 cracking zone and an oxygen-containing gas into the catalyst 033 regeneration zone, burning the sulfur-containing coke therein 034 at a temperature in the range from 538C to 816C to form a 035 flue gas containing sulfur oxides, and removing the flue gas 036 from the catalyst regeneration zone; (d) forming a sulfur-con-037 taining solid in the regeneration zone by reacting the sulfur 11457~0 002 oxides with alumina in at least one particulate solid in the 003 particulate solids inventory other than the catalyst particles, 004 the particulate solid containing less than 20 weight percent 005 silicon, calculated as silica; (e) returning the resulting coke-006 depleted catalyst particles from the catalyst regeneration zone 007 to contact with the hydrocarbon stream in the cracking zone;
008 and (f) forming hydrogen sulfide in the cracking zone by 009 contacting the sulfur-containing solid with the hydrocarbon 010 stream; the method for reducing poisoning of alumina in the 011 particulate solid for reaction with sulfur oxides caused by 012 migration of silicon or a silicon compound from the catalyst 013 particles onto the particulate solid, comprising:
014 employing in the particulate solid from 100 parts per 015 million by weight to 1.0 weight percent, relative to the amount 016 of alumina in the particulate solid and calculated on an elemen-017 tal basis, of a promoter comprising at least one element or com-018 pound of an element selected from sodium, manganese and 019 phosphorus.
020 Sulfur oxides can be removed from the regenerator 021 flue gas by reaction with high-surface-area alumina present in 022 particles other than the catalyst, circulated in physical 023 mixture with siliceous catalyst particles in a cracking system.
024 Silicon and/or silicon compounds such as silica migrate from 025 the catalyst particles to the alumina particles, especially in 026 a steam-containing atmosphere such as a catalyst stripper or 027 regenerator. Poisoning of the active alumina component by con-028 tamination with silica migrating from the catalyst particles is 029 reduced, according to the invention, by employing alumina-030 containing particles including at least one element or compound 031 of an element selected from sodium, manganese and phosphorus.
032 It has been found that active alumina loses at least part of 033 its capacity to react with sulfur oxides when contaminated with 034 migrating silica. The loss of activity can be substantially 035 lessened by including at least one of the above-mentioned 036 elements, or a compound ~hereof, in the alumina-containing 037 particles.
1~457~0 003 The present invention is used in connection with a 004 fluid catalyst cracking process for cracking hydrocarbon feeds.
005 The same hydrocarbon feeds normally processed in commercial ~CC
00~ systems may be processed in a cracking system employing the 007 present invention. Suitable feedstocks include, for example, 008 petroleum distillates or residuals, either virgin or partially 009 refined. Synthetic feeds such as coal oils and shale oils are 010 also suitable.
011 Suitable feedstocks normally boil in the range from 012 about 200-~00CC or higher~ A suitable feed may include recy-013 cled hydrocarbons which have already been subjected to 014 cracking.
015 The cracking catalysts with which the present inven-016 tion finds utility are those which include a substantial concen-017 tration of silica and which are recognized by those skilled in 018 the art to be suitably acidic and active for catalyzing 019 cracking of hydrocarbons in the absence of externally supplied 020 molecular hydrogen. The invention is most useful in connection 021 with catalysts containing at least 20 weight percent silica, 022 especially at least 30 weight percent silica, excluding silica 023 in the form of zeolitic crystalline aluminosilicates. Silica 024 is generally included in commercially used cracking catalysts 025 in combination with one or more other inorganic oxides such as 02~ alumina, magnesia, et:c. Many commercial catalysts presently 027 include a zeolite component associated with a non-crystalline 028 silica-alumina or silica-containing clay matrix. Non-zeolite-029 type catalysts including silica, such as amorphous silica-030 aluminas, silica-magnesias, clays, etc., are also within the 031 scope of the invention, however. Particularly suitable 032 cracking components are the acidic, zeolitic crystalline 033 aluminosilicates such as X-type and Y-type faujasites, 034 preferably in the hydrogen form, the rare earth form, or other 035 equally stable form. Zeolitic crystalline aluminosilicates are 03~ preferred acidic cracking components in that silicon included 037 in zeolites is not particularly subject to migration between 038 particles during use in catalytic cracking, and thus do not 1~457~0 .
002 contribute to poisoning of alumina activity for sulfur oxides 003 removal from flue gas. Preferably, the particulate solids 004 inventory used in a system in an embodiment of the invention 005 includes at least 75 weight percent of particles containing 006 from 5 to 30 weight percent of a zeolitic crystalline alumino-007 silicate. On the other hand, acidic, non-crystalline catalyst 008 such as silica-aluminas can be used. For example, it may be 009 desirable, for economic reasons, to use a mixture of cracking 010 catalysts, one of which contains a zeolitic cracking component, 011 while the other contains only relatively inexpensive amorphous 012 silica-alumina, e.g., in systems where catalyst must be added 013 frequently as a result of high feed metals levels or the like.
014 A zeolite-containing cracking catalyst component may 015 be formed by treatment of kaolin clay, as by slurrying the 016 clay, sizing and spray drying, followed by treatment with 017 caustic at elevated temperature for a time sufficient to 018 generate a fraction of the desired zeolite in the treated clay, 019 with the clay acting as the matrix. The zeolite component in 020 the particles can then be converted to the ammonium and/or rare 021 earth form by ion-exchange, if desired. Of course, there is 022 usually still a substantial non-crystalline silica content in 023 catalysts manufactured in this manner. The zeolite can also be 024 manufactured separately and added to the desired matrix or 025 binder material. Conventional binders such as clays, acid-026 treated clays, synthetic silica-alumina cogels, etc., can be 027 used as the binder, or as a component of the binder.
028 Cracking conditions employed in the cracking or 029 conversion step in an FCC system are frequently provided in 030 part by pre-heating or heat-exchanging hydrocarbon feeds to 031 bring them to a temperature of about 315-400C before 032 introducing them into the cracking zone; however, pre-heating 033 of the feed is not essential. Cracking conditions usually 034 include a catalyst/hydrocarbon weight ratio of about 3-10. A
035 hydrocarbon weight space velocity in the cracking zone of about 036 5-50 per hour is preferably used. The average amount of coke 037 contained in the catalyst after contact with the hydrocarbons ~14S7~o 002 in the cracking zone, when the catalyst is passed to the 003 regenerator, is preferably between about 0.5 weight percent and 004 about 2.5 weight percent, depending in part on the carbon 005 content of regenerated catalyst in the particular system, as 006 well as the heat balance of the particular system.
007 The catalyst regeneration zone used in an FCC system 008 employing an embodiment of the present invention may be of 009 conventional design. Preferably, the total pressure in the 010 regeneration zone is maintained at at least 20 psig. The 011 gaseous atmosphere within the regeneration zone normally 012 includes a mixture of gases in concentrations which vary 013 according to the locus within the regenerator. The 014 concentrations of gases also vary according to the coke 015 concentration on catalyst particles entering the regenerator 016 and according to the amount of molecular oxygen and steam 017 passed into the regenerator. Generally, the gaseous atmosphere 018 in a regenerator contains 5-25~ steam, varying amounts of 019 oxygen, carbon monoxide, carbon dioxide and nitrogen. The 020 present invention is applicable in cases in which an oxygen-021 containing and nitrogen-containing gas, such as air, is 022 employed for combustion of coke in the catalyst regenerator.
023 As will be appreciated by those skilled in the art, air is 024 essentially invariably employed to provide the oxygen needed 025 for combustion in FCC regenerators.
026 Sulfur oxides are removed from the flue gas in a cata-027 lyst regeneration zone by reacting sulfur oxides, e.g., sulfur 02~ trioxide, with alumina in the regeneration zone. The alumina 029 active for reaction with sulfur oxides usually has a surface 030 area of at least 50 m2/g, e.g., gamma- or eta-alumina.
031 Suitable alumina must not be in intimate combination with more 032 than 20 weight percent silica, based on the alumina and silica 033 concentrations in a given particle, and preferably the alumina-034 containing particles used are substantially free from admixture 035 with silica. Alumina from any source is suitable for use in 036 the present method if it contains an average of about 0.1 to 037 lO0 weight percent of "reactive alumina", as determined by 1~457~0 002 treating particles containing the alumina by the following 003 steps:
004 (1) passing a stream of a gas mixture containing, by 005 volume, 10% water, 1% hydrogen sulfide, 10% hydrogen and 79%
006 nitrogen over the solid particle continuously at a temperature 007 of 650C and atmospheric pressure until the weight of the solid 008 particle is substantially constant;
009 (2) passing a stream of a gas mixture containing, by 010 volume, 10~ water, 15% carbon dioxide, 2% oxygen and 73%
011 nitrogen over the solid particle resulting from step (1) at a 012 temperature of 650C and atmospheric pressure until the weight 01~ of the solid particle is substantially constant, the weight of 014 the particle at this time being designated "Wa''; and 015 (3) passing a stream of a gas mixture containing, by 016 volume, 0.0S% sulfur dioxide, and, in addition, the same gases 017 in the same proportions as used in step (2), over the solid 018 particle resulting from step (2) at a temperature of 650C and 019 atmospheric pressure until the weight of the solid particle is 020 substantially constant, the weight of the solid particle at 021 this time being designated "Wsl'.
022 The weight fraction of reactive alumina in the solid 023 particle, designated "Xa", is determined by the formula Xa Ws-Wa x Molecular Wt. Alumina 8~5 Wa 3 x Molecular Wt. Sulfur Trioxide 028 The alumina used in embodiments of the present inven-029 tion is included in particulate solids, other than catalyst 030 particles, which are physically suitable for circulation in the 031 cracking system. Suitable particles normally have an alumina 032 content of at least 80 weight percent and, preferably, the 033 alumina content of such particles is 90 weight percent or more.
034 In a particularly preferred embodiment, the alumina-containing 035 particles consist of gamma-alumina. Alumina can be formed into 036 particles of suitable size for circulation with FCC catalyst in 037 an FCC system by spray-drying, crushing larger particles, etc.
038 In carrying out the invention, alumina-containing 039 particles are introduced into a cracking system and circulated 1~457~0 002 in physical mixture with silica-containing cracking catalyst.
003 The amount of separate, alumina-containing particles employed 004 in the particulate solids inventory is preferably 25 weight 005 percent, or less, of the total particulate solids inventory 006 circulating in the cracking system. The addition of an amount 007 of alumina between 1.0 and 25 weight percent of the total 008 particulate solids inventory is particularly preferred. The 009 size, shape and density of separate, alumina-containing parti-010 cles circulated in admixture with catalyst particles is pref-011 erably such that the alumina-containing particles circulate in 012 substantially the same manner as conventional catalyst 013 particles in the particular cracking system, e.g., beads are 014 used in a moving-bed, bead~catalyst unit, whereas 50-100 micron 015 diameter particles are quite suitable in an FCC unit. Alumina 016 reacts with sulfur trioxide or sulfur dioxide and oxygen in the 017 cracking catalyst regenerator to form at least one sulfur-con-018 taining solid, such as a sulfate of aluminum. In this way, sul-019 fur oxides are removed from the regenerator atmosphere and are 020 not discharged from the regenerator in the flue gas.
021 Particles containing the solid aluminum- and sulfur-022 containing material are passed to the cracking zone along with 023 the other particulate solids, such as regenerated catalyst. In 024 the cracking zone, alumina is regenerated and hydrogen sulfide 025 is formed by reaction of sulfur in the sulfur-containing solid 026 by contacting the sulfur-containing solid with the stream of 027 hydrocarbon being treated in the cracker. In addition to 028 forming hydrogen sulfide, the reaction between the sulfur- and 029 aluminum-containing solid and the hydrocarbon feed may produce 030 some other sulfur~compounds such as carbon oxysulfide, organic 031 sulfides, etc., which are vapor-phase at cracking conditions.
032 The resulting hydrogen sulfide and other vapor-phase sulfur 033 compounds exit the cracking zone as a part of the stream of 034 cracked hydrocarbons, along with a much larger amount of 035 vapor-phase sulfur compounds formed directly from sulfur in the 036 hydrocarbon feed during the cracking reactions. Off-gas subse-037 quently separated from the cracked hydrocarbon stream thus ~457~0 .
002 includes hydrogen sulfide formed directly from the feed sulfur 003 and hydrogen sulfide formed by reaction of the sulfur- and 004 aluminum-containing solid with the hydrocarbon stream in the 005 cracking zone.
006 I have found that, by including at least one of 007 sodium, manganese or phosphorus in the alumina-containing 008 particles employed to react with sulfur oxides, deactivation of 00g the alumina for reaction with SOx, caused by silica migration, 010 can be substantially reduced. Although sodium, manganese and 011 phosphorus, or compounds thereof, are the most useful materials 012 for addition to alumina to prevent deactivation by migrating 013 silica, several other materials can have a positive effect in 014 many cases. These include lithium, potassium, nickel, 015 lanthanum, tin and iron. On the other hand, these last-016 mentioned Inaterials do not appear to be as effective as sodium, 017 manganese or phosphorus, judging from data presently available.
018 The sodium, manganese or phosphorus component can be 019 combined with the alumina in any convenient manner. For 020 example, a water-soluble compound can be introduced into parti-021 cles containing alumina by aqueous impregnation. The desired 022 material can be mixed with alumina prior to shaping, as by dry-023 mixing, comulling, or the like. The amount of sodium, 024 manganese or phosphorus added, on an elemental basis, is 025 usually at least 100 parts per million, by weight, of the 026 alumina. The maximum amount added is 1.0 weight percent. Pref-027 erably, not more than 0.5 weight percent of the promoter is 028 included with the alumina, on an elemental basis. The concen-029 trations of promoter are based on the alumina content of the 030 alumina-containing particulate solid. Those skilled in the art 031 will recognize that the alumina may be combined as a mixture, 032 particle pack, or the like, with other materials, such as other 033 porous inorganic oxides, such as chromia, magnesia, titania, 034 etc.
035 Surprisingly, I have found that concentrations of 036 sodium, manganese or phosphorus in alumina of 0.1 weight per-037 cent are more effective in preventing silica-deactivation 1~4S7~0 .
002 of the alumina than are higher concentrations such as 0.5 003 weight percent or more.
005 Samples of particulate alumina impregnated with water-006 soluble salts of various promoters were prepared. The alumina 007 employed was Reynolds RH-30, a commercially available material.
008 Two samples of alumina containing each promoter were prepared, 009 one containing 0.1 weight percent promoter and the other con-010 taining 0.5 weight percent. All samples were prepared by 011 aqueous impregnation with a water-soluble salt. Each sample 012 was calcined at 593C in dry air for 4 hours.
014 An 0.5-gram portion of each sample prepared as 015 described in Example I was physically mixed with 4.5 grams of 016 an equilibrium zeolite-containing FCC catalyst of commercially 017 available type, containing about 37 weight percent silica, ex-018 cluding silica in the form of zeolitic crystalline alumino-019 silicate. Each of the catalyst-alumina particle mixtures was 020 then steamed for 96 hours at 650C to induce silica migration 021 from the catalyst particles to the alumina particles. The 022 rates of reaction of the steamed samples of alumina were then 023 determined by thermogravimetric analysis by the following 024 procedure: (1) a portion of each steamed catalyst-alumina 025 mixture was heated to 650C in a flowing atmosphere containing, 026 by volume, 2% 2' 15% CO2 and 10% H2O in N2 until the weight of 027 the sample was constant; (2) the atmosphere composition was 028 changed to 10% H2 and 10% H2O in N2 and maintained until the 029 weight of the sample was constant; (3) the atmosphere was 030 returned to the composition used in step (1) and maintained 031 until the sample weight was constant; and (4) 0.2% SO2 was 032 added to the atmosphere and the weight gained during 6 minutes 033 of exposure to SO2 was measured. The rate of reaction for the 034 samples is defined as the average weight gain per minute for 035 the first 6 minutes divided by the total weight of the sample 036 after step (3). The results for each promoted alumina, for a 037 control sample of unpromoted alumina, and for a sample of ~1457~0 002 catalyst without alumina particles are shown in Table I.
003 Referring to Table I, it can be seen that sodium, manganese 004 and phosphorus promoters provide a substantially higher 005 activity for reaction with Sx after a sample has been sub-006 jected to silica migration than do the other promoters tested, 007 particularly in the samples containing 0.1 weight percent of 008 the promoters.
010 Promoter Rate (ppm/minute) 011 0.1 wt.% 0.5 wt.%
012 Phosphorus 77 66 013 Manganese 71 63 014 Sodium 74 68 015 Nickel 69 61 016 Lanthanum 64 64 017 Tin 60 62 018 Iron 64 67 019 Copper 66 61 020 Vanadium 62 43 021 Titanium 63 51 022 Magnesium 60 56 023 Cerium 59 54 024 Lead 52 59 025 Boron 53 46 026 Molybdenum 46 50 027 Arsenic 57 52 028 None 54 54 029 Catalyst alone 51 51 031 For purposes of comparison with the alumina particles 032 used in the improvement of the invention, particles of silica 033 gel were impregnated with sodium or manganese. The silica gel 034 used was Davison Grade 70 gel screened to 100-325 mesh. Four 035 samples of silica gel were impregnated with an aqueous solution 036 of either sodium nitrate or manganese nitrate in amounts 11457~0 002 sufficient to provide a sample containing 0.1 weight percent 003 sodium, 0.S weight percent sodium, 0.1 weight percent manganese 004 and 0.5 weight percent manganese.
006 A 0.5 gram sample of the plain gel was mixed with 4.5 007 grams of the same equilibrium zeolite-containing FCC catalyst 008 used in the test of Example II. Four mixtures were made up 009 each containing 4.5 grams of the FCC catalyst and 0.5 grams of 010 the silica gel containing either 0.1 weight percent Na, 0.5 011 weight percent Na, 0.1 weight percent Mn or 0.5 weight percent 012 Mn. The five mixtures prepared as described were each steamed 013 for 96 hours at 650C. The rate of reaction, if any, for 014 reaction with sulfur oxides was then measured by the same 015 procedure described in Example II. The results for the unmixed 016 catalyst and each of the five mixtures are shown in Table II.
019 Rate (ppm/minute) 020 Promoter ~ 1 5 wt.%
022 Unmixed Catalyst 51 51 024 Catalyst with Plain 025 Silica Gel 29 29 027 Manganese Impregnated 40 37 029 Sodium Impregnated 31 27 032 Referring to Table II, it is apparent that all the 033 silica gel mixtures are substantially poorer for reacting with 034 sulfur oxides than is the FCC catalyst alone.
035 ILLUSTRATIVE EM~ODIMENT
036 A conventional, commercial FCC processing system 037 having a capacity of 22,000 barrels per day is employed. The 038 feed used is a mixture of hydrocarbons having a boiling range 039 of 3Q4-593C with a sulfur content of 0.85 weight percent. The 040 cracking reactor employs a combination of riser and dense-bed ` 11457~0 002 cracking. Cracking conditions employed include a reactor 003 average temperature of about 495C, a hydrocarbon weight hourly 004 space velocity of about 5 per hour and a conversion rate (feed 005 converted to 220C-) of about 85%. Catalyst is circulated at 006 the rate of about 8 metric tons per minute with a total inven-007 tory of about 154 metric tons. The catalyst used contains Y-008 type zeolitic crystalline aluminosilicate dispersed in a non-009 crystalline silica-alumina matrix. A separate combustion pro-010 moter is used to get complete combustion in the regenerator.
011 The silica concentration in the catalyst, excluding silica in 012 the form of zeolite, is about 40 weight percent. The spent 013 catalyst contains about 0.8 weight percent coke, and the coke 014 contains about 0.7 weight percent sulfur. Regeneration condi-015 tions include a temperature of about 670C. After regene-016 ration, the catalyst contains about 0.2 weight percent coke.
l? Prior to the introduction of alumina into the circulating inven-018 tory to react with SOx, the flue gas removed from the catalyst 019 regenerator contains about 300 parts per million, by volume, of 020 SOx, calculated as SO2. For purposes of comparison, an un-021 treated particulate gamma-alumina is first used to remove Sx 022 from the regenerator flue gas. Sufficient alumina is intro-023 duced and circulated to provide 10 weight percent of the 024 particulate solids inventory. The amount of Sx initially 025 removed from the flue gas is relatively high, but over a period 026 of 5 days of operation it is observed that migration of silica 027 from the cracking catalyst particles reduces the activity of 028 the alumina, so that the amount of Sx in the flue gas 029 increases to about 220 ppm (volume). According to the inven-030 tion, the unpromoted alumina is withdrawn from the FCC system, 031 and particles of alumina promoted with 0.1 weight percent phos-032 phorus are introduced in an amount sufficient to provide 10 033 weight percent of the particulate solids inventory in the FCC
034 system. The promoted alumina has been prepared by spray-drying 035 the alumina and subsequent aqueous impregnation with ammonium 036 phosphate solution. After introduction of the phosphorus-037 promoted alumina, the amount of Sx initially removed from 1 ~1457a~
002 the regenerator flue gas is again found to be relatively high.
003 After 5 days of operation, substantially less silica migration 004 deactivation of the phosphorus-promoted alumina is observed 005 than was found using the unpromoted alumina, resulting in a 006 flue gas Sx of only 140 ppm (volume).
007 The foregoing detailed description of the invention, 008 examples, and illustrative embodiment illustrate a preferred 009 mode of carrying out the invention. It will be clear to those 010 skilled in the art that other embodiments and obvious modifi-011 cations, equivalents and variations of the invention can be 012 employed and adapted to a variety of catalytic cracking 013 systems. Such modifications, alterations and adaptations are 014 intended to be included within the scope of the appended 015 claims.
Claims (8)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a process for cracking a sulfur-containing hydro-carbon stream in the absence of externally supplied molecular hydrogen including the steps of (a) cycling an inventory of particulate solids including acidic cracking catalyst particles between a cracking zone and a catalyst regeneration zone;
(b) cracking said sulfur-containing hydrocarbon stream in said cracking zone in contact with said cracking catalyst particles, said catalyst particles containing at least 20 weight percent of a silicon component, calculated as silica and excluding . silicon in the form of zeolitic crystalline aluminosilicate, in a cracking zone at cracking conditions including a temperature in the range from 425°C to 700°C, whereby sulfur-containing coke is deposited on said catalyst particles, and removing the hydrocarbon stream from said cracking zone; (c) passing coke-containing catalyst particles from said cracking zone and an oxygen-containing gas into said catalyst regeneration zone, burning said sulfur-containing coke therein at a temperature in the range from 538°C to 816°C to form a flue gas containing sulfur oxides, and removing said flue gas from said catalyst regeneration zone; (d) forming a sulfur-containing solid in said regeneration zone by reacting said sulfur oxides with alumina in at least one particulate solid in said particulate solids inventory other than said catalyst particles, said parti-cles containing less than 20 weight percent silicon, calculated as silica; (e) returning the resulting coke-depleted catalyst particles from said catalyst regeneration zone to contact with said hydrocarbon stream in said cracking zone; and (f) forming hydrogen sulfide in said cracking zone by contacting said sulfur-containing solid with said hydrocarbon stream; the method for reducing poisoning of alumina in said particulate solid for reaction with sulfur oxides caused by migration of silicon or a silicon compound from said catalyst particles onto said particulate solid, comprising:
employing in said particulate solid from 100 parts per million, by weight, to 1.0 weight percent, relative to the amount of alumina in said particulate solid and calcu-lated on an elemental basis, of a promoter comprising at least one element or compound of an element selected from sodium, manganese and phosphorus.
(b) cracking said sulfur-containing hydrocarbon stream in said cracking zone in contact with said cracking catalyst particles, said catalyst particles containing at least 20 weight percent of a silicon component, calculated as silica and excluding . silicon in the form of zeolitic crystalline aluminosilicate, in a cracking zone at cracking conditions including a temperature in the range from 425°C to 700°C, whereby sulfur-containing coke is deposited on said catalyst particles, and removing the hydrocarbon stream from said cracking zone; (c) passing coke-containing catalyst particles from said cracking zone and an oxygen-containing gas into said catalyst regeneration zone, burning said sulfur-containing coke therein at a temperature in the range from 538°C to 816°C to form a flue gas containing sulfur oxides, and removing said flue gas from said catalyst regeneration zone; (d) forming a sulfur-containing solid in said regeneration zone by reacting said sulfur oxides with alumina in at least one particulate solid in said particulate solids inventory other than said catalyst particles, said parti-cles containing less than 20 weight percent silicon, calculated as silica; (e) returning the resulting coke-depleted catalyst particles from said catalyst regeneration zone to contact with said hydrocarbon stream in said cracking zone; and (f) forming hydrogen sulfide in said cracking zone by contacting said sulfur-containing solid with said hydrocarbon stream; the method for reducing poisoning of alumina in said particulate solid for reaction with sulfur oxides caused by migration of silicon or a silicon compound from said catalyst particles onto said particulate solid, comprising:
employing in said particulate solid from 100 parts per million, by weight, to 1.0 weight percent, relative to the amount of alumina in said particulate solid and calcu-lated on an elemental basis, of a promoter comprising at least one element or compound of an element selected from sodium, manganese and phosphorus.
2. A method according to Claim 1 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of phosphorus.
3. A method according to Claim 1 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of sodium.
4. A method according to Claim 1 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of manganese.
5. A composition of matter for use in a process for cracking hydrocarbons in the absence of externally supplied molecular hydrogen, comprising:
from 75 to 99 weight percent of an acidic particulate cracking catalyst including at least 20 weight percent of a silicon component, calculated as silica and excluding silicon in the from of zeolitic crystalline alumino-silicate;
from 1 to 25 weight percent of a particulate solid including at least 75 weight percent alumina and from 100 parts per million, by weight, to 1.0 weight percent, relative to the amount of alumina in said particulate solid and calculated on an elemental basis, of a promoter comprising at least one element or compound of an element selected from sodium, manganese and phosphorus, said particulate solid containing less than 20 weight percent silicon, calculated as silica.
from 75 to 99 weight percent of an acidic particulate cracking catalyst including at least 20 weight percent of a silicon component, calculated as silica and excluding silicon in the from of zeolitic crystalline alumino-silicate;
from 1 to 25 weight percent of a particulate solid including at least 75 weight percent alumina and from 100 parts per million, by weight, to 1.0 weight percent, relative to the amount of alumina in said particulate solid and calculated on an elemental basis, of a promoter comprising at least one element or compound of an element selected from sodium, manganese and phosphorus, said particulate solid containing less than 20 weight percent silicon, calculated as silica.
6. A composition as defined in Claim 5 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of phosphorus.
7. A composition as defined in Claim 5 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of sodium.
8. A composition as defined in Claim 5 wherein said alumina-containing particulate solid includes from 100 parts per million, by weight, to 0.5 weight percent, based on alumina in said particulate solid, of manganese.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| BE0/202137A BE885275A (en) | 1980-09-17 | 1980-09-17 | REDUCTION OF THE SULFUR OXIDE CONCENTRATION DURING THE REGENERATION OF A CRACKING CATALYST |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1145700A true CA1145700A (en) | 1983-05-03 |
Family
ID=3843368
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000359354A Expired CA1145700A (en) | 1980-09-17 | 1980-08-29 | Sulfur oxides control in cracking catalyst regeneration |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5753590A (en) |
| CA (1) | CA1145700A (en) |
| DE (1) | DE3033831A1 (en) |
| GB (1) | GB2083835B (en) |
| NL (1) | NL8005244A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2722428B1 (en) * | 1994-07-13 | 1996-09-27 | Rhone Poulenc Chimie | CATALYSTS FOR THE TREATMENT OF GASES CONTAINING SULFUR COMPOUNDS; USE AND METHOD FOR TREATING A GAS CONTAINING SULFUR COMPOUNDS |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4071436A (en) * | 1976-03-11 | 1978-01-31 | Chevron Research Company | Process for removing sulphur from a gas |
-
1980
- 1980-08-29 CA CA000359354A patent/CA1145700A/en not_active Expired
- 1980-09-03 GB GB8028428A patent/GB2083835B/en not_active Expired
- 1980-09-09 DE DE19803033831 patent/DE3033831A1/en not_active Ceased
- 1980-09-12 JP JP12706680A patent/JPS5753590A/en active Granted
- 1980-09-19 NL NL8005244A patent/NL8005244A/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| DE3033831A1 (en) | 1982-04-29 |
| GB2083835A (en) | 1982-03-31 |
| GB2083835B (en) | 1984-01-11 |
| JPS6317314B2 (en) | 1988-04-13 |
| NL8005244A (en) | 1982-04-16 |
| JPS5753590A (en) | 1982-03-30 |
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