CA1048009A

CA1048009A - Catalytic cracking with catalyst regeneration and co emission control

Info

Publication number: CA1048009A
Application number: CA220,983A
Authority: CA
Inventors: Ralph J. Bertolacini; William L. Forsythe (Jr.)
Original assignee: Standard Oil Co
Current assignee: Standard Oil Co
Priority date: 1974-03-04
Filing date: 1975-02-28
Publication date: 1979-02-06
Also published as: DD116258A5; DE2507343C2; DE2507343A1; AU7817675A; BE826266A; NL7501695A; FR2263033A1; CS227651B2; GB1499682A; FR2263033B1; JPS5722617B2; JPS50124893A

Abstract

Abstract of the Disclosure An improved fluid catalytic cracking process comprises a method for the regeneration of the fluidizable hydrocarbon conversion catalyst, particularly of the molecular sieve type, which has been deactivated with coke deposits while employed in a hydrocarbon catalytic cracking process, in which the coke-containing hydrocarbon conversion catalyst is contacted with an oxygen-containing gas to burn the coke from the catalyst under conditions supporting substantially complete combustion of carbon monoxide. In the regenerator, the hydrocarbon conversion catalyst is primarily in physical (rather than chemical) association with an oxidation catalyst which promotes the combustion of carbon monoxide to carbon dioxide. Evolved heat is recovered by direct heat transfer to the catalyst, for example within a dilute or dense phase zone in the regenerator vessel. The gaseous effluent from the regener-ator has a low content of carbon monoxide and may be discharged directly to the atmosphere with little discernible effect upon ambient air quality. The regenerated hydrocarbon conversion catalyst may have less than about 0.05 weight percent coke thereon.

Description

ll 104~9 This lnvention relates to an improved fluid catalytic conversion process, including an improved process for the regeneration of catalyst employed in fluid catalytic converslon of hydrocarbon feedstocks wherein the cataly~t i8 deactivated by the depositlon of coke bn the catalyst surfaces. By the process of this invention, regeneration of conversion catalysts, particularly fluid cracking catalysts, may be sustained over a long period of operation while enabling the coke level on the regener-ated catalyst to be maintained at beneficially low levels. The regener-ation process of this invention may frequently provide a flue gas stream having an extremely low carbon monoxide content.
In accordance with the proce~s of this invention, the catalyst6 for the fluld catalytlc conversion operation, particularly catalysts of the molecular sieve type, are in a well-disper6ed, pri~arily physical a~sociation, rather than chemical association, with a finely-divided o~idation catalyst when the mixed catalyst undergoes regeneration. The oxidation catalyst exhibits an act:Lvity for promoting the oxidation of carbon monoxide to carbon dioxide in the presence of molecular oxygen, and frequently has little, if any, adverse effect on the catalytic conversion operation. The regeneration of the fluid catalyst may be conducted by passing an oxygen-containing regeneration gas stream into contact with the catalyst wherein the amount of oxygen supplied to the catalyst is at least that stoichiometrically sufficient for complete oxidation of the coke deposited on the catalyst at a temperature of a~ ~ ,l7 least that required to maintain sustained catalytic oxidation of carbon 2s mo~oxide by oxidation of coke on the catalyst. The gaseous effluent from the regeneration of the catalyst may be very low in carbon monoxide content, thereby reducing the emission of this highly toxic material to the atmosphere, or eliminating or reducing the necess~ty ~o treat the effluent from the catalyst regeneration unit to convert carbon monoxide to relatively innocuous carbon dioxide.

lo~oa The process of thls inv~ntion contemplates the contacting of a deactivated fluid conversion catalyst, such as a fluidizable molecular sieve-type hydrocarbon-cracking catalyst deactivated by the deposition t~ereon of carbonaceoua deposits or coke and stripped ~ith steam, with an oxygen-containing regeneration gas to burn coke from the catalyst.
The conditions employed effect sub6tantially complete combustion of the coke and re6ulting carbon monoxide, and provision is made f~r re-covery of the mn~or amount of eyolvPd heat by transfer directly to the catalyst, for example, within a dilute or dense phase zone in the regenerator ves~el.
The process of this lnventlon provides a regenerated, hydrocarbon co~version cataly~t having a very low coke content, desirably le~ than about 0 05 weight percent and preferably within ~he range from about 0.01 to 0.03 weight percent, by control of the ~ubstantially complete ls combustion of coke therefrom, together with substantially complete combustion of carbon monoxide gas present or formed during regenera-tion of the catalyst. The process is characterized by having an oxi-dation catalyst in physical association with the hydrocarbon conversion catalyst, and the oxidation catalyst may be in the form of a solid

2~ metal oxide-containing material. The process employ6 regeneration temperatures which are sufficiently high to activate the solid metal oxide catalyst ~o promote oxidation of carbon monoxide and for the substantially complete combustion of the coke deposit on the conver-~ion catalyst. The temperatures are not so high that the conversion 2s catalyst particle~ become thermally deactivated or that the regenera-tion vessel and its internals become unsafe or inoperative. The re-generation temperatures may advantageously range from about 1000 to about 1500F., de~irably from about 1050 to about 1400F. These com-bu~tion temperatures are achieved by the use of the oxidation cataly6ts, 30 l re f~lly doNcrlbed beloa 1C14~ 9 In one aspect of this invention there is provided a process for the continuous cyclic catalytic cracking of hydro~
carbons wherein a fluidizable cracking catalyst which has been deactivated with coke deposits is withdrawn from a cracking zone, stripped of volatile materiall passed to a regeneration zone and recycled to the cracking zone. The regeneration stage in the regeneration zone comprises the ~ollowing six steps:
(a) fluidizing the deactivated catalyst particles in physical association with a carbon monoxide oxidation promoter, within the regeneration zone, with a molecular oxygen containing regeneration gas, to provide molecular oxygen in excess of the amount re~uired for complete conversion of the coke to carbon dioxide and burniny substantially all of the coke from said cracking catalyst, wherein the oxidation promoter comprises one or more metals having an atomic number of at least 20 and selected from the ~roups IB, IIB, and III to VIII of the Periodic Table, and wherein said oxidation promoter is present in a minor amount which is effective to enhance the oxidation of carbon monoxide withi~ the regeneration zone;
(b) initiating and sustaining, within the regeneration ; zone, the combustion of carbon monoxide produced by said burning through contact with the molecular oxygen containing gas in the regeneration zone while in contact with the cracking catalyst in physical association with said oxidation promoter, so that substantially all of the carbon monoxide is burned to carbon dioxide and most of the heat so produced is absorbed by the cracking catalyst;
(c~ maintaining the temperature of the regeneration zone in the range from 1000 to 1500~F;

3~

~ - 3~a) -(~

~04~0~9 (d) withdrawing from the regeneration zone an effluent gas stream ha~ing no more than l.0 vol. % of carbon monoxide;
(e) withdrawing from the regeneration zone oxidation promoter associated with regenerated catalyst particles contain-ing said absorbed heat and having no more than 0.10 wt. % of residual coke; and (f) recycling said oxidation promoter and regenerated catalyst particles containing said absorbed heat to the ~racking zone. The regeneration zone is preferably maintained at a temperature in the range from 1050 to 1400F.
In a preferred embodiment the regeneration zone com-prises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with the oxidation promoting catalyst. Substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase.
In another preferred embodiment the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with the oxidation promoting catalyst. Coke is burned from the catalyst in the dense phase. The combustion of the carbon monoxide is completed in the dilute phase~ and the temperature of the dilute phase is at least 50 higher than that of the dense phase.

- 3 Ib) . ~

.. .. .... ~ . . ~ , ~048009 ¦ An outstanding advantage of this invention lies in providing a ¦ regenerated catalyst generally possessing enhanced activity and selec-¦ tivity characteristics more closely approaching those of fresh conver-¦ sion catalyst, particularly for use in conversions effected at very I short contact times in riser reactors. Accordingly~ higher conversions ¦ of feedstock and higher yields of desirable conversion products may be ¦ achieved. The oxidation catalyst assists in stabilizing regenerator ¦ control by controlling the oxidation of carbon monoxide. Moreover, the ¦ risk of extinguishing the oxidation of the carbon monoxide through drop lo ¦ in temperature, increase in gas velocity which may cause blowout, or ¦ reduction in carbon monoxide content, i8 substantially abated since ¦ the oxidation of the carbon monoxide may be conducted catalytically.
¦ In those rege=eratlon processes using a lower dense phase zone and an upper dilute phase zone in the regener&tor, the oxidation of the carbon ¦ monoxide to carbon dioxide may be accomplished to a ma~or extent, often ¦ at least about 60 percent, and frequently about 65 to 95 percent or more, to completion in the dense catslyst phase of the fluid catalyst regenerator. The oxidation of carbon monoxide to carbon dioxide in the dense phase provides heat to aid in sustaining the combustion of ~he coke deposits from the fluid catalyst. Furthermore, with a sub-stantial portion of the carbon monoxide being oxidized in the densephase, a lesser amount of carbon monoxide is present for combustion in the upper phase of the fluid catalyst in the regenerator, and thus "afterburning" and high temperatures due to uncontrolled excessive carbon monoxide combustion in the upper portion of the fluidized cata-lyst in the regenerator which may deleteriously affect materials em-ployed to construct the reac~or, waste gas flue, the collectors for any particulate materials in the waste gas, e.g., cyclones, and which may impair catalyst activity, may be substantially reduced or avoided.

,, I!

~OQ80~)D
The carbon monoxide content of the flue gas from this novel re-generation process may be maintained at less than about 0.2 volume ¦percent, for example, about 500 to 1000 parts per million by volume ¦ (ppmv). Advantageously, the content is even lower, for example, within ¦the range from 0 to about 500 ppmv. This low concentration of carbon ¦monoxide in the flue-gas stream permits the direct release of effluent ¦gases to the atmosphere while meeting ambient air quality standards.
¦This advantage of the invention additionally permits the elimination ¦of capital expenditures otherwise required for installation of carbon 0 ¦monoxide boilers and associated turbine-type devices or other means ¦for partial recovery of energy produced by the subsequent oxidation ¦of the carbon monoxide.
¦ The novel regeneration process of this invention is advantageously ¦ practiced as a step in the fluid catalytic cracking process, especially 1s ¦where at least a substantial portion of the conversion is effected in a ¦ dilute-phase transfer line or riser reactor system utilizing very active ¦ catalysts employed at relatlvely high space velocities. The low coke ¦ level on the regenerated catalyst is especially preferred when em-ploying fluid cracking catalysts containing catalytically active, ¦ crystalline aluminosilicates, otherwise known as zeolites or "molecular ¦ sieves". The cracking activity of sieve-containing catalysts and their ¦ selectivity for converting hydrocarbon feeds to desired products are both dramatically affected in a favorable direction by the increased ~5 ¦ elimination of residual carbon or coke on the catalyst during regener-ation. A particularly suitable hydrocarbon conversion process for the practice of this invention comprises the fluid c~talytic cracking pro-cess for the conversion of gas oils and heavier hydrocarbon stocks to lower boiling hydrocarbon components suitable for blending into fuels for automotive engines, ~et power plants, domestic and industrial furnaces, and the like.

1~141~009 ¦ Catalytic cracking of heavy mineral oil fractions is one of the ¦ major refining operations employed in the conversion of crude oils to desirable fuel produc~s such as high-octane gasoline fuels used in I spark-ignited, internal combustion engines. Illustrative of "fluid"
¦ catalytic conversion processes i8 the fluid catalytic cracking process ¦ wherein high molecular weight hydrocarbon liquids or vapors are con-¦ tacted with hot, finely-divided, solid catalyst particles, either in a I fluidized bed reactor or in an elongated riser reactor, and the cata-¦ lyst-hydrocarbon mixture is maintained at an elevated temperature in a o ¦ fluidized or dispersed state for a period of time sufficient to effect I the desired degree of cracking to lower molecular wei~ht hydrocarbons ¦ typically present in motor gasolines and distillate fuels. Suitable ¦ hydrocarbon feeds boil generally above the gasoline boiling range~ e.g., ¦ within the range from about 400 to about 1200F., and are usually I
I~ cracked at temperatures ranging from about 850 to 1050~F.
¦ In the catalytic process some non-volatile carbonaceous material, or "coke", is deposited on the catalyst particles. Coke comprises ¦ highly condensed aromatic hydrocarbons which generally contain a minor I amount of hydrogen, say about 4 to 10 weight percent. As coke builds ¦ up on the catalyst, the activity of the catalyst for cracking and the ¦ selectivity of the catalyst for producing gasoline blending stocks ¦ diminish. The catalyst particles may recover a major proportion of their original capabilities by removal of most of the coke therefrom in a suitable regeneration process.
2s ¦ Càtalyst regeneration is accomplished by bur~ing the coke deposits from the catalyst surface with a molecular oxygen-containing gas, such as air. Many regeneratlon techniques are practiced commercially whereby a significant restoration of catalyst activity is achieved in response to the degree of coke removal. As coke is progressively removed from ¦ the catalyst, removal of the remaining coke becomes most difficult and, in practice, an intermediate level of restored catalyst activity is ¦ accepted as an economic compromise.
¦ The burning of coke deposits from the catalyst requires a large ¦ volume of oxygen or ~ir. Oxidation of coke may be characterized in a ¦ simplified manner as the oxidation of carbon and represented by the ¦ following chemical equations:

(a) C + 2 C2 (b) 2C + 2 2CO
(c) 2CO + 2 2CO2 ¦ Reactions (a) and (b) both occur under typical catalyst regeneration ¦ conditions wherein the catalyst temperature may range from about 1050 ¦ to about 1300F. and are exemplary of gas-solid chemical interactions ¦ when regenerating catalyst at temperatures within this range. The ¦ effect of any increase in temperature is reflected in an increased ¦ rate of combustion of carbon and a more complete removal of carbon, or ¦ coke, from the catalyst particles. As the increased rate of combustion ¦ is accompanied by an increased evolution of heat, whenever sufficient ¦ ree or molecular oxygen is present, the gas-phase reaction (c) may ¦ occur. This latter reaction is initiated and propagated by free radi-cals.
A major problem often encountered and sought to be avoided in the practice, particularly of fluid catalyst regeneration, is the phenome-non known as "afterburning", described, for example, in Hengstebeck, etroleum Processin~, McGraw-Hill Book Co., 1959, at pages 160 and 175 aad discussed in Oil and Gas Journal, Volume 53 (No. 3), 1955, at pages 93-94. This term is descriptive of the further combustion of CO

to CO2, as represen~ed by reaction (c) above~ which is highly exo-l thermic. Afterburning has been vigorously avolded in catalyst regen-¦ eration processes because it could lead to very high temperatures i -7-I

104~009 ¦which may damage equipment and cause permanent deactivation of catalyst particles. Many fluid catalyst regenerator operations have experienced a~terburning, and a very substantial body of art has developed around ¦numerous means for controlling regeneration techniques so as to avoid 5 ¦afterburning. More recently, it has been sought to raise regenerator ¦temperatures for various reasons; elaborate arrangements have also been ¦developed for cqntrol of regenerator temperatures at the point of inci-~pient afterburning by suitable means for control of the oxygen supply to the regenerator vessel as set forth, for example, in U.S. Patents ¦Nos. 3,161,583 and 3,206,393, as well as in U.S. Patent No. 3,513,087.
¦In typical contemporary practice, accordingly, with avoidance of after-¦burning, the flue gas from catalyst regenerators usually contains very ¦little oxygen and a substantial quantity of carbon monoxide and carbon ¦dioxide in nearly equimolar amounts.
Further combustion of carbon monoxide to carbon dioxide is an attractive source of heat energy because reaction (c) is highly exo-¦ thermic. Afterburning can proceed at temperatures above about 1100F.
I and liberates approximately 4350 BTU per pound of carbon monoxide oxi-dized. This typically represents about one-fourth of the total heat ¦ evolution realizable by combustion of coke. The combustion of carbon ¦ monoxide can be performed controllably 1n a separate zone or carbon ¦ monoxide boiler, after separation of effluent gas from catalyst, as ¦ described in, for example, U.S. Patent No. 2,753,925, with the released heat energy being em210yed in various refinery operations such as the ¦ generation of high pressure steam. Other uses of such heat energy have been described in U.S. Patents Nos. 3,012,962 and 3,137,133 (turbine drive) and U.S. Patent No. 3,363,993 (preheating of petroleum feedstock). Such heat recovery processes require separate and elaborate equipment but do serve to minimi~e the discharge of carbon monoxide into the atmosphere as a component of effluent gases, and hence, serve to avoid a potentially serious pollution ha~ard.
Silica-alumina catalysts, employed conventionally for many years in various processes for the cracking of petroleum hydrocarbons, are not particularly sensitive to the level of residual coke on catalyst provided that the coke level be no greater than about 0.5 weight percent. However, silica-alumina catalysts have largely been supplanted by catalysts additionally incorporating a crystalline aluminosilicate component and known as ~eolites or "molecular sieves". The molecular sieve-containing catalysts are much more sensitive to the residual coke level, being greatly affected both with regard to catalyst activity and to catalyst selectivity for conversion of feed to the desired product or products. Due to the difficulties encountered in conventional catalyst regeneration techniques for removal of the last increments of residual carbon, the practical coke level usually corresponds to a residual coke content on regenerated catalyst within the range from about 0.2 to about 0.3 weight percent.
Since enhanced activity and selectivity are achievable with sieve-type cracking catalysts at low coke levels, an attractive incentive is provided for discovering a means for reducing residual coke levels still furtherO Coke levels below about 0.05 weight percent are greatly desired but usually cannot be achieved by commercially practicable means.
Considerations such as larger regeneration vessels, greater catalyst inventory, greater heat losses, and the like, all serve to discourage attainment of such ideal equilibrium catalyst activity levels.
Canadian Patent 983,877 issued February 17, 1976, which corresponds to West German Offenlegungschrift No. 2,256,276 published June 14, 1973, is directed to an improved catalytic cracking process, including an improved process for the regeneration of catalysts employed in fluid catalytic conversion of hydrocarbon feedstocks wherein the catalyst is deactivated by the depo-sition of coke on the catalytic surfaces. The process enables the coke level on regenerated catalyst to be maintained at an extremely low level while simultaneously maintaining a favorable heat balance in the conversion unit and providing a flue gas stream having an extremely low carbon monoxide content. In one embodiment of the process of that application, the combustion of carbon monoxide to carbon dioxide is carried substantially to completion within the regeneration vessel in a relatively dilute secondary catalyst regeneration zone advantageously 0 at a temperature between about 1200 and 1500F., desirably between about 1250 and 1450~. The temperature of the secondary zone is ~sually at least about 50 or 100F. higher than that of the first re-generation zone. Partially regenerated catalyst from a relatively dense primary catalyst rege~eration zone can be controllably flowed through the secondary zone in an amount and at a rate sufficient to absorb sub-stantially all of the heat released by the combustion occurring in the secondary zone, Although st of the coke is burned from the catalyst in the primary zone, additional coke is burned from the partially re-generated catalyst while present in the secondary zone, and catalyst substantially free of coke may be recovered for recycle to the hydro-carbon conversion zone. Heat from the combustion of carbon monoxide and sbsorbed by the regenerated catalyst provides part of the process heat required in the hydrocarbon conversion zone. Additionally, the -~
flue-gas stream released from the secondary regeneration zone is sub-2s stantially free of carbon monoxide. In a second embodiment of the process of that application substantially all of the combustion, in-cluding both the ox$dation of coke or carbon on the catalyst and the oxidation of carbon monoxide, occurs within a single, relatively dense phase regeneration zone in response to the proper control of principally the regeneration temperature and gas velocity.

~0~8~10~
The present invention is directed to the discovery that the pro-cesses described in Canadian Patent 983,877, cited above, employing a cracking catalyst, particularly of the molecular sieve type, when additionally employing an oxidation-promoting catalyst is very advantageous in providing regenerated catalyst having a very low coke content and in producing useful heat. The low catalyst coke levels achieved are less that about 0.05 weight percent and preferably from about 0.01 to about 0.03 weight percent. The process includes the use of a cracking catalyst in primarily physical, rather than chemical, association with an oxidation-promoting catalyst in a system which supports substantially complete combustion of carbon monoxide. This process can result in flue gas having carbon monoxide levels of less than about 0.2 volume percent, for example about 500 to 1000 ppm, and as low as from about 0 to 500 ppm. The process also includes provision for recovery of evolved heat by transfer directly to the conversion catalyst, particularly within the regeneration vessel.
All embodiments of the process described in Canadian Patent 983,877 are useful in carrying out the process of the present invenion, and the embodiment directed to substantially complete combustion within a single relatively dense phase is particularly advantageous.
Suitable cracking catalysts for this process include those containing silica and/or alumina, including the acidic type, and the catalysts may contain other refractory metal oxides such as magnesia or zirconia. Preferred cracking catalysts are those containing crystalline aluminosilicates known as zeolites or molecular sieves in an amount sufficient to materially increase the cracking activity of the catalyst.
The crystalline aluminosilicates usually have silica to alumina mole ratios of at least about 2:1, for instance about 2 to 12:1, preferably about 4 to 6:10 The crystalline aluminosilicates are usually available or made in sodium form and this component can be 104~009 ¦ reduced, for instance to les~ than about 4, or even less than about 1, weight percent, through ion exchange with hydrogen ions, hydrogen-pre-¦ cursors such as ammonium ions, or polyvalent metal ions. Suitable ¦ polyvalent metals include calcium, strontium, barium, and the rare ¦ earths such as cerium, lanthanum, neodyminium, and naturally-occurring ¦ rare eartXs and their mixtures. The useable crystalline materials are ¦ able to maintain their pore structure under the high temperature con-¦ ditlons of catalyst manufacture, hydrocarbon processing and catalyst ¦ regeneration. The crystalline aluminosilicates often have a uniform o ¦ pore 3tructure Df exceedingly small size. The cross-section diameter ¦ of the pores being in a size range of about 6 to 20 angstroms, prefer-¦ ably about 10 to 15 angstroms~ Silica-based crscking catalysts having ¦ a ma~or proportion of silica, e.g., about 60 to 90 weight percent silica ¦ and about 10 to 40 weight percent aiumina, are suitable bases.
¦ The catalyst particles are finely-divided, for $nstance, they ¦ may have an average particle size in the range of about 20 microns or ¦ leas to about 150 microns, such that they are in a form suitable for ¦ fluidization. The fluidizing gas in the dense zone o~ the regenerator ¦ ~ay have a velocity, for example, in the range of from about 0.~ to 4 ; 20 ~ feet per second, desirably about 0.5 to 3 feet per second. The regen-~ ¦ eration gas serving to fluidize the dense-bed contains free or molecular ; ¦ oxygen, and the oxygen is preferably charged to the regenerator in an ¦ amount somewhat in excess of that required for complete combustion of ¦ coke (carbon and hydrogen) to carbon dioxide and steam. The amount of ¦ oxygen in excess of that required for complete combustion of the coke ¦ may vary from about 0.1 to about 25 or more percent of the theoretical stoichiometric oxygen requirement for complete combustion of the coke, but advantageously need not be greater than about 10 percent. For example, when air is employed as the regeneration gas a 10 percent 1 ~80~1 1 excess of air provides only about 2 volume percent oxygen in the efflu-¦ ent spent gas stream. Advantageously, the concentration of molecular ¦ or free oxygen and carbon monoxide at any point within the regenerator ¦ is maintained outside of the explosive range at those conditions, pre-ferably the concentration of carbon monoxide is below the explosive range at those conditions, to eliminate any ris~ of detonation.
~ he regenera~ion gas, in addition to free or molecular oxygenl m~
contain inert, or diluent, gas such as nitrogen, steam, etc., recycle 10 8as from the regenerator effluent, and the like. Frequently the oxygen concentratio~ of the regeneration gas at the inlet to the regenerator is ; from about 2 to 30 volume percent, preferably about S to 25 volume per-cent. Since air i6 conveniently employed as a source of oxygen, a major portion of the inert gas may be nitrogen. The inert gas may cerve to dissipate excessive heat fro= the combustion of coke from the catalyst. A source of hot, inert gag ig the effluent from the regener-ator, and a portion of this Ba~ may be recycled to the regenerator and, for instance, combined with sufficient incoming air or other oxygen-containlng gas, includlng essentially pure oxygen, to provide the desired oxygen content. Thus, the recycle gas may be employed in direct heat exchange to increase the temperature of the regeneration gas to provide even further heat economies in the system.
In accordance with the present invention, the hydrocarbon cracking catalyst and the solid oxidation-promoting catalyst are employed in the 2s regenerator vessel. The solid oxidation catalyst may be impregnated on the hydrocarbon cracking catalyst s~ructure, or may be introduced into the catalyst matrix durlng the catalyst manufacture. Alternatively, the solid oxidation catalyst may be in a finely divided form, such as a powder, separate from the hydrocarbon cracking catalyst, or it may be supported on another substrate, and admixed with the hydrocarbon crack-ing catalyst. In all such methods lon exchange of the essential oxida-tion catalyst component with the zeolite is avoided. The support for 1 ~11;)48~9 1the oxidation catalyst, if one be present, may be less catalytically-¦active or even inert, to the oxidation and hydrocarbon conversion re-1 actions; and may, for instance, be ceramic in nature. Desirably, the support is porous and frequently has a surface area, including the area 1f the pores on the surface, of at least about lO, preferably at least ¦about 50, square meters per gram. Illustrative of the supports are ¦ silica, alumina, silica-alumina, and the like.
1 The solid oxidation catalysts used in this invention may be the ¦ types used or generally known in the art to promote the oxidation of carbon monoxide in the presence of molecular oxygen. These catalysts ¦ generally contain a catalytic metal which promotes the oxidation, and l the metal may be in a combined form, such as an oxide, rather than ¦ being in the elemental state. Frequently, the catalytically-active ¦ metals are in the heavy metal groups of the periodic chart of the elements, and in Groups IB) IIB, or III to VIII and having atomic num-¦ bers above about 20. Generally, the more active oxidation catalysts are ¦ the platinum group metals, such as platinum, palladium and rhodium;
¦ or the metals of Groups IB, IIB, V, VI, such as Mo and W, VII, the iron 1 1 series of Group VIII, e.g., Cu, Cr, Ni, Nn~ Co, V, Fe, and the like, the rare earths such as cerlum and ytterbium, and uranium and the like.
1 Advantageously, the solid oxidation catalyst may comprise two or more ¦ catalytlcally-active metal3 either physically or chemically combined.
l By a chemical combination of metals, there are included bi or poly-¦ metallic salts such as an oxide, e.g., tungstocerate, tungstoborate, tungstoaluminate, tungstoferrate, tungstogermanate, molybdoferrate, ` ¦ molybdocerate, molybdogermanate, and the like. Illustrative of combina-; ¦ tions of catalytically-active metals which may promote oxidation of ¦ carbon monoxide without unduly adversely affecting the hydrocarbon ¦ cracking operation are the oxides of iron and manganese, iron and rhenium, iron and-cerium, and the like.

I .
I

~4~ 9 One method of preparlng the solld oxidat~on catalyst for use in the present invention iB by impregnation of a suitable support with a water or organic solvent-soluble salt of the catalytically-active metal.
The impregnation may be practiced in any way which will not destroy the structure of the substrate. Preferably, water-soluble nitrate salts are employed in the impregnating solution since residue from the thermal decomposition of nitrate salts is relatively innocuous to the activity of the hydrocarbon cracking catalyst. The halogen and sulfate salts of the metal to be impregnated may be employed; however, since halogen or sulfide may be evolved during thermal degradation of the salt which maJ be deleterious to the activity of the hydrocarbon cracking catalyst, these methodæ of impregnation are most often employed when depositing the oxidation catalyst on a separate substrate which does not signlfi-cantly adversely affect the hydrocarbon cracking reaction. Thus, the catalyst may be deposited on a support inert to the hydrocarbon crack-ing or be impregnated into a minor portion of the hydrocarbon cracking catalyst~ Impregnation differs from, for instance, cation-exchange, in that the metal is in the anionic part of a water or organic solvent-soluble compound. Impregnation results in greater deposition on the surface of the catalyst while ion exchange resul~s in greater diffu-sion and therefore less surface deposition. In the impregnation, themetal is deposited and no significant ion exchange occurs between the metal and the substrate. In impregnating a substrate, the metal which promotes the oxidation of carbon monoxide can be present as a water-soluble or organic solvent-soluble salt in solution in an amount suf-ficient to contain the quantity of metal desired on the substrate, andthe substrate is contacted therewith. The composite may be dried to remove the solvent, leaving the metal deposited on the substrate.

Further heating may in some instances be required to convert the metal ~048009 ¦to its active state, such as calcining or heatlng in hydrogen or other reactive or inert atmospheres. Alternatively, some or all of the Irequired activation may be effected in the regeneration vessel during ¦regeneration. Generally, in order to effect the best distribution of ¦the metal compound on the catalyst, the solution of the metal compound ¦should be as concentrated as practical.
¦ Another method of depositing catalytically-active metal on a sub-¦~trate, particularly porous substrates such as crystal?ine alumino-¦sillcates, is by adsorptlon of a fluid decomposable compound of the lo ¦metal by the substrate followed by thermal or chemical decomposition of Ithe metal compound. The substrate may be activated by heating to re-¦move any adsorbed water and then contac~ed with a fluid decomposable ¦ compound of metal thereby adsorbing the compound into the substrate.
¦ Typical of such compounds are the metal carbonyls, metal alkyls, vola-¦ tile metal halides and the like. The adsorbed compound may then be ¦ reduced thermally or chemically to its elemental metal thus leaving ¦ uniformly dispersed on the substrate an active metal for promoting oxidation of carbon monoxide to carbon dioxide. Thermal reduction may ¦ be effeceed in the regeneration vessel durin~ the regeneration process.
¦ A further method of incorporation into a support a ca~alytically-¦ active metal which promotes the oxidation of carbon monoxide comprises ¦ admixing the active metal component with a substrate precursor, for ¦ instance a silica gel or silica-alumina gel, prior to spray drying or ¦ other physical formation process, and drying the precursor to prepare ~s ¦ the oxidation catalyst. The resultant substrate body may be calcined ¦ to form the catalytically-active material. Alternatively, heat treat-¦ ment may be effected in the catalyst regenerator o the cracking system.
¦ The substrate for the solid oxidation catalyst may be the hydro-~ carbon cracking catalyst, or portion thereof, or msy be different 104~:009 therefrom, for example, it may be a non-catalytic, porous, solid sub-st~ate. When the hydrocarbon cracking catalyst serves as the substrate, care should be taken in selection of the deposition process such that the cracking activity and selectivity of the catalyst iæ not adversely affected. It is preferred that if the hydrocarbon cracking catalyst is of tbe type having ion-exchanged sites, the ion-exchange be completed prior to deposition of the oxidation ca~alyst. The amount of oxidation-promoting metal employed for promotion of the oxidation of carbon monoxide may be in a minor amount effective to enhance the desired 0 1 oxidatlon, frequently about 0.01 to 5, preferably about 0.05 to 1, per-cent by weight ba~ed on the hydrocarbon cracking cataly6t employed.
Rather than depositin~ the oxidation catalyst on a support, the solld oxidation catalyst may be a powdered, catalytically-active metal oxide which is admixed with the hydrocarbon cracking ca~alyat. Gener-al b , the powdered, metal ox~de, o~Ldation catalyst is advantageous inthat the catalyst is relatively inexpensive and is easy to charge to and handle in a fluidized catalyst reactor-regenerator system. The particle size of the powdered oxidation catalyst should be selected so as to avoid segregation of the particles at the fluidizing veloci-ties. Desirably, the metal oxide particles are not~so minute that problem3 occur such as excessive emission with the gases from the bed as entrained particulate matter; however, filters, cyclones, precipi-tators, and the li~e are usually employed in con~unction with fluldized catalyst operations to recover most of the entrained particulate matter and return it to the system to abate losses. The metal oxide powder should be sufficiently ~trong that excessive attrition and degrada-tion of the sized powder may be avoided. Frequently, the average parti-cle size of the powcLered metal oxide catalyst is from about 0.5 or 1 to 100, preferably less than about 50, microns in diameter. It has ~0~801)9 been noted that micro6ized particles, that i8, having an average particle size of less than about l micron, for instance, about O.Ol to 0.5 micron, may tend to form aggregates of larger size which may beneficially be employed in the process of this invention. Illustrative of powdered metal oxides which may be employed to promote oxidation of carbon monoxide are ferric oxide, ferrous oxide, ferric and zinc oxide, manganese dioxide, cerium oxide and the like.
The attached drawings, Figures l and 2, provide elevational views, partly in section, of embodiments of apparatus suitable for catalyst 0 regeneration according to the process of this invention. Regeneration of spent cataly~t, especially the molecular sieve type, in various suitable hydrocarbon cracking processes, when the catalyst is in physi-cal association with oxidation promoting catalysts as described can be effected in an improved manner i~ accordance with this invention.
Indeed, this improved process may be employed beneficially in many existing petroleum hydrocarbon crac~ing process units, particularly fluid catalytic cracking units having a variety of spatial arrange-ments of cracking, stripping and regeneration sections thereo~.

Figure 1 is il~ustrative of one e~bodiment of the regeneration of this invention employing bottom entry of strlpped, spent catalyst passing from the cracking reactor (not shown) to the regenerator.
Spent catalys~ from a stripp~ng zone associated with the catalyst exit from the reactor, enters from the bottom regeneration vessel l, and is in physical association with an oxidation promoting catalyst.
2s The catalyst flows upwardly through inlet lines 2 and 3 and discharges into the dense catalyst bed through discharge hands 4 and 5. The dense-phase catalyst bed is maintsined within the lower section 6 of the regenerator vessel and extends upwardly to the catalyst phase interface 7. Catalyst within th~ dense-phase bed is fluidized by the lU48DO9 flow of combustion air through line 8, valve 9 and line 10 to alr ring 11. Substantailly bglanced air flow patterns through the regener-ation zones may be achieved by the use of additional air rings, not sho~n1 as required. Combustion of coke contain~d on the spent catalyst with air is initiated within the dense-phase bed. Higher temperatures may be achieved by temporarily burning a stream of torch oil, for e~-ample a decanted oil, within the bed. Torch oil may be added by pas-sage through line 12, valve 13 and line 14 which terminates in a nozzle located above the air ring 11. Fluidizing air velocities continuously carry some of the catalyst particles upwardly into the dilute-phase zone wh~ch occupie~ the upper section 15 of the regenerator vessel;
i.e. 9 the section above the catalyst phase interface 7. Combustion of coke continues in the dilute-phase zone and the largely spent com-bustion gas together with entrained catalyst i8 withdrawn in~o first-stage cyclone separators 20 and 21. Most of the catalyst par~iclesare separated in the firs~-~tage cyclones and discharged downwardly through dip-legs 22 and 23 into the dense-phase zone. Gases and re-maining catalyst particles are passed through interstage cyclone lines 24 and 25 to second~stage cyclone s~p~rstors 26 and 27 where substan-tially all of the remaining catalyst is separated and passed downwardly through dip-legs 28 and 29 into the denAe-phase bed~ Substantially spent combustion gas then passes through llnes 30 and 31 into plenum 32 and finally is discharged from the regenerator vessel through line 2s 33. This effluent m8y be suitably heat exchanged, not shown, with re-finery stream or for production of process s~ream. Regenerated cata-ly~t from the dense bed is withdrawn through standpipes 34 and 35, fitted with collector heads 36 and 37, for return to the cracking reactor.

¦ Although the supply of combu~tion alr normally provides an excess ¦ of oxygen over the amount required to effect complete combustion of 1 the coke on the catalyst particle~ to stesm and carbon dioxide, combus-¦ tion of coke may not be completed in the dense-phase bed in one embodi-¦ ment of this invention. In this situation, the combustion gases rising 1 from the dense bed zone thus contain a substantial quantity of carbon ¦ monoxide as well &~ carbon dioxide and oxygen. The remaining coke on ¦ cataly~t and the carbon monoxide are substantially co~pletely burned in ¦ the dilute phase zone with evolution of much heat. When carbon monox-ide burns in the dilute phase a hlgh temperature zone will usually be ¦ present throughout much of ~he dilute phase zone and particularly at ¦ approximately the locatio~ indicated by X and can readily be viewed ¦ through a window, not shown, at tha~ horizontal plane. Control of regeneration temperature within the dilute phase zone is effected in 5~ ¦~ part through absorptlon of heat by the mass of catalyst particles ¦ either carried upwardly by the rising combustion gas stream or educted ¦ upwardly from the dense-bed through eductor tube 40 and catalyst dis-¦ tributor head 41 where a rain, or fountain~ of catalyst particles dis-perses into the dilute phase zone. Catalyst can be ed ted by means of air, steam or other inert gas entering through line 42, valve 43 snd ~et tube 44 which extends a short distance into the lower end of eductor tube 40. Excessive temperature levels in the top section of the regenerator may be further controlled by distribution of steam, 2s for example through lines 45 and 46, valve 47 and line 48 to steam pod 49. Temperatures in the vicinity of the plenum may also be controlled with steam fed through line 50, valve 51 and line 52 to steam ring 53 which surrounds plenum 32, Additional cooling if desired may be pro-vided by use of a water spray, not shown, whlch may advantageously be directed within the region of interstage cyclone lines 24 and 25.

~048~9 Figure 2 is illu3trati~e of another embodiment of this invention employing side entry of stripped, spent catalyst in physical association with an oxidation promoting catalyst from the cracking reactor to the regenerator. Spent catalyst enters regeneration ve6sel 101 flowing downwardly through inlet line 102 located on the side of the regenera-tion vessel to provide entry into the dense-pha~e catalyst bed main-tained within bottom section 106 a short di~tance below catalyst phase interface 107. Fluidization of the catalyst is effected by combustion air passing through line 108, valve lOg and line 110 to air ring 111.
lo Additional air r1ngs, not shown, may be employed as desired for further balancing of air flow patterns through the regeneration zones. As described in Figure 1, combustion of coke on the spent catalyst parti-cles i5 initiated within the dense-phase zone where higher temperatures as desired may be achieved by temporary burning of a torch oil s~ream within the zone. Such tcrch oil may be added through line 112, valve 113 and line 114 terminating in a nozzle.
Fluidizlng air velocity may be controlled to continuously carry catalyst particles upwardly for purposes of heat absorption into the dilute-phase zone which occupies the upper section 115 of the regener-ator ve~sel; i.e., the section above the catalyst phase interface 107.
Combustion of coke as well as of carbon monoxide may continue in the dilute-phase zone and the largely spent combustion gas together with the entrained portion of catalyst particles is withdrswn into first-2~ stage cyclone separators 120 and 121. Most of these catalyst particles are separated in the first-stage cyclones and discharged downwardly through dip-legs 122 and 123 into the den~e-phase zone. Gases and re-maining catalyst particles subsequently pass through interstage cyclone lines 124 and 125 to second-stage cyclone separators 126 and 127 where substantially all of the remaining catalyst is separated and passed downwardly through dip-legs 128 and 129 into the dense-phase bed. Sub-~t&ntially spent combustion gas then passes through lines 130 and 131 into plenum 132 and flnally is discharged Erom the regenerator vessel through line 133. Regenersted catalyst from the dense bed is withdrawn through standplpes 134 and 135, fitted with collector heads 136 and 137, for return to the catalytlc cracking reactor.
As described for the embodiment of Figure 1, carbon monoxide burns in the dilute-phase providing a high temperature zone throughout much of the dllute-phase zone and particularly at approximately the location lo indicated by X. Control of regeneration temperature within the dilute-phase zone is effected largely through absorption of heat by the mass of catalyst partlclec carried upwardly by the rlsing combustion gas stream. Temperature~ in the vicinity of the plenum, cyclone and connect-ing lines may, as required, be reduced with steam fed through line 150, valve 151 and llne 152 to steam ring 153 which surrounds plenum 132.
Water ~pray means, not shown, may similarly be employed.
In another, particularly preferred embodiment of this invention, the apparatus shown in Figure 2 is employed with a significant change ln operating parameters as compared to the above descrlbed embodlment.
In thls embodiment gas velocity and catàlyst partlcle input are adjusted so that essentlally complete combustlon of coke and carbon monoxide is completed withln the dense phase and the heat is dispersed throughout the bed. The stabillzation of the combustlon reaction is particularly enhanced by the employment of the oxidation-promoting catalyst and the regenerator is thereby able to be operated at lower temperatures or to combust greater quantities of carbon monoxide and thus regenerate more catalyst at the same temperature.
Suitable hydrocarbon feedstocks for the cracking process include various mineral oil fractions boiling above the gasoline range such a~

~LO~Oal9 light gas oils, heavy gas oils, wide-cut gas oils, vacuum gas oils, kerosenes~ decanted oils, residual fractions, reduced crude oils and cycle oils derived from any of these, as well as suitable fractions derlved from shale oil, tar sands processing, synthetic oils, coal hydrogenation and the like. Such fractions may be~employed singly or in any desired combination.
Beneficially, the process of the present invention enables con-siderable coke and carbon monoxide to be combusted in the dense-phase zone wherein a substantially increa~ed amount of catalyst particles as co~pared to the dilute-phase zone, is present to disperse the heat evolved therefrom. As the portion of combustion occurring in the dense-phase zone is increased, the evolution of heat in the dilute-phase zone is substantially reduced, hence, the need to provide rapid catalyst turnover in tbe dilute-phase zone to absorb the evolved heat is reduced or eliminated.
A particularly desirable use of the process of this invention is an integral part of the fluid cracking unit employing a fluidizable cracking catalyst, as described above, in a transport, or "riser", re-actor with attendant provislon for stripping of spent, coke cstalysts,followed by regeneration of the spent catalyst according to the process of this invention. Preferably, cracking occurs essentially exclusively in the riser reactor and a following dense catalyst bed i8 not employed for cracking. In a typical case where rise cracking is employed for convers~on of a gas oil~ the throughput ratio, or volume ratio of total 2s feed to fresh feed, may vary from about l to 2. The conver~ion level may vary from 40 to about lO0 weight percent, and advantageously is maintained above about 60 weight percent, for exa~ple, between about 60 and 90 weight percent. By conversion, it is meant the percentage reduction by weight of hydrocarbons boiling above about 430F. at atmospheric pressure by the formation of lighter ma~erials or coke. The 1~ ~L04~00:1 l weight ratio of catalyst to oil ln ~he riser reactor may vary within the range from about 2 to 10 in order that the fluidi~ed dispersion will have a density within the range from about 1 to 5 pounds per cubic foot.
Desirably, the catalyst oil ratio is maintained at no greater than about 5 and preferably within the range from about 3 to 5. The fluidizing veloci~y in the riser reactor may range from about 20 to 60 feet per second. The riser reactor should preferably be substantially vertical, having a ratio of length to average dlameter of at least about 25. For production of a typical nsphtha product, the bottom section mixing temperature within the riser reactor i9 advantageously maintained at about 1000F. for substantially complete vaporization of the oil feed, and so that the top section exit temperature will be about 950F. Under these conditions, including provision for a rapid separation of spent catalyst from effluent oil vapor, a v~ry short period of contact between catalyst and oil will be establlshed. Contact time within the riser reactor will generally be within the range from about 3 to 10 seconds, and preferably within the range from about 3 to 7 seconds. Shorter contact times are preferred because most of the hydrocarbon cracking occurs during the initial increment of contac~ time, and the undesirable secondary reactions are avoided. This is especially important if higher product yield and selectivity, including lesser coke production9 are to be realized.
Short coneact time between catalyst particles and oil vapors may be achieved by various means. For example, catalysts may be injected at one or more points along the length of a lower, or bottom, section of the riser. Similarly, oil feed may be in~ected at all the points along the length of the lower section of the riser reactor and a dlfferent injection point may be employed for fresh and recycle feed streams. The lower section of the riser reactor may, for this purpose, include up to about 80 percent of the total riser length in order to provide ex~remely short effective contact times inducive to optimum conversion ~L~481C~1~9 of petroleum feeds. Where a following dense catalyst bed is employed, provision may also be made for in~ection of catalyst particles and/or oil feed directly into the dense-bed zone. Although the conversion conditions set forth above are directed to the production of gasoline as fuel for spark-ignition internal co~bustion engines, the process-ing scheme may be suitably varied to permit maximum production of heavier hydrocarbon products such as jet fuel, diesel fuel, and heating oil.

The spent catalyst from the petroleum conversion reactor is pre-ferably stripped prior to entering the regenerator. The stripping vessel for use in a fluidized bed catalytic cracking unit may suitably be maintained essentially at conversion reactor temperature in the range from about 850 to 1050F. and desirably will be maintained at about 95~F. Preferred stripping gas iB steam although nitrogen, other inert gas or flue gas may be employed, introduced at a pressure, usually in the range from 10 to 35 p.s.i.g., suitable to effect substantially com-plete removal of volatile compounds from the spent conversion catalyst.
Stripped spent catalyst particles may enter the dense-bed section of the regenerator vessel through suitable lines and valving from the stripping vessel. Entry may be from the bottom or from the side, de-sirably near the top of the dense-bed fluidized zone. Entry may also be from the top of the regenerator where catalyst has first been con-tacted with substantially ~pent regeneration gas in a restricted dilute-phase zone.
Catalyst particles, with the oxidation promoting catalyst, withinthe dilute-phase may partially be carried into the separation zone, usually comprising cyclone separators in a plurality of ~tages, from which catalyst can be returned directly through dip-legs to the dense-bed zone, and spent regeneration and combustion gases are collected in ~L048009 a plenum and finally discharged for suitable recovery of heat energycontained therein. Recovery processes for heat from flue gas include steam regeneration, spent catalyst stripping, indirect heat exchange with various refinery streams, and particularly with feed to the par-ticular conversion process, the employment in vari~s drying or evapor-ation arrangements.
When the system is operated according to either of the first two sbove-described embodiments, recovery of the heat relea~ed by the essentially complete co~bustion of coke and C0 is by absorption in lo catalyst particles in both phases, and return of the catalyst to the dense-phaae serves also to secure maintenance of the ~uitably high temperature within the dense-phase 20ne. The returned catalyst parti-cles may carry with them additional heat to serve to raise the tempera-ture of the dense-phase zone to a te~perature which favors additional remQval of coke deposits thereon such that the combustion of the final increments of coke becomes substantially complete. When the system i~ operated 80 that essentially all conbustion is completed within the dense catalyst phase, and the heat is dispersed throughout the phase as it is absorbed by the fluidized particles and final increments of coke are combusted. Accordingly, in all embodiments, the regenerated catalyst passing from the regenerator back to the cracking reactor suitably contains from about 0.01 to about 0.10 weight percent, de-sirably 0.01 to 0.05 weight percent and preferably about 0.01 to about 0.03 weight percent carbon or coke, and can be withdrawn from the re-generator at an advantageous temperature for use in the cracking re-actor.
The regenerated catalyst particles having unusually low residualcoke content, are recovered from the dense-phase and passed at the substantially dense-bed temperature through a standpipe to the cracking ~ 8~
reactor for contacting with fresh hydrocarbon feed or mixture thereof with recycle hydrocarbon fractions. Since the catalytic oxidation of the carbon monoxide evolved from the combustion of the coke deposits on the catalyst may occur to a ma~or extent ln the dense-phase and in the preferred e~bodiments essentially completely occurs in the dense phase, the regenerated catalyst can be returned to the cracklng reactor at a much higher temperature as well as a higher activity than hereto-` fore conventional operations.

Many fluid cracking units are operated on the "heat balance" princi-lo pal, depending upon combustion of coke for the evolution of heat require in the process. Such units, however, have not been able to fully uti-lize the benefits of the cracking catalysts, particularly zeolite cata-lysts, which can especially be achieved in a riser reactor where contact times between catalysts and oil vapors may be estremely short. The type of operation which affords high conversion coupled with high selec-tivlty, favors a low ratio of catalyst to oil in the riser reactor which leats to less coke being available to generate heat by combustion in the regenerator. Accordingly, an external heat source such as a feed-preheat furnace, ~ay frequently be added to increase the tempera-o ~ure of the catalyst or, alternstively, the unit may be operated at alrwer temperature of fresh feed. Such undesirable features may be avoided or minimized by the process of this invention which permits efficient recovery of additional heat by regenerated catalyst particles for transfer to the riser reactor. The heat of combustion of coke in conventional operations is about 12,000 BTU per pound. The process of this invention may increase available heat by combustion of the coke to about 17,000 or re BTU's per pound. This higher heat of combustion tends to raise the regenerator temperature, lower the level of coke on the regenerated catalyst, and lower the catalyst circulation rate while providing improved yields at a given conversion level.

~04~009 A further benefit from the regeneration processes of this inven-¦ tion relates to the unusually low carbon monoxide content in the efflu-¦ ent gas stream from the regenerator which may be obtained. Whereas ¦ flue gas from conventional regeneration of cracking catalysts usually ¦ contains from about ~ to 10 percent carbon monoxide, a similar amount ¦ of carbon dioxide and very little oxygen, the flue gas from regeneration in accordance with this invention generally contains less than about ¦ 0.2 percent, and often no more than about 5 to 500 parts per million ¦ carbon monoxide. The oxygen content of the flue gas is, of course, not ~o ¦ of primary importance from an ecological point of view and may vary ¦ from about 0.1 to about 10 percent, advantageously being within the ¦ range from about 1 to about 3 percent and preferably no more than about ¦ 2 percent in order to restrict the amount of flue gas and conserve heat ¦ with~n the regeneration reactor system. If required, any remainin8 carbon monoxide may suitably be burned in the exhaust from the regener-¦ ator flue gas stack. From a process point of view, heat recovery by ¦ downstream combustion of carbon monoxide in a carbon monoxide boiler I or after~urner arrangement may be avoided employing the process of this ¦ invention, with consequent substantial savings in process equipment ¦ and operational costs while still meeting the existing standards for ¦ ambient air quality for carbon monoxide emissions.
¦ The following examples are illustrative of the process of this in-¦ vention. All parts and percentages referred to are by weight unless ¦ otherwise indicated.
¦ EXAMPLE I
¦ 200 grams of a calcined, equilibrium commercial cracking catalyst ¦ containing 5.3% of hydrogen and rare ear~h ion-exchanged, Y-type crys-talline aluminosilicate and silica-alumina (30% total A1203) are impreg-nated with 3.90 grams of a fifty percent manganese nitrate solution and 210 millillters of water. About 80% of the catalyst is in the 20 to ¦ 75 micron range in size. The impregnated catalyst particles are re-covered and dried at 250F. followed by calcination for 3 hours at ¦ 1250F. The resultant catalyst has 0.3 percent manganese deposited ¦ thereupon.
I EXAMPLE II
I _ ¦ Example I is repeated except the impregnation is conducted employ-¦ i~g 1.265 gr2ms of uranyl nitrate dissolved in 210 milliliters of water.
¦ The impregnated catalyst is dried at 250F., and thsn calcined for 3 lo ¦ hours at 1200F. The catalyst has 0.3 percent uranium thereon.
¦ EXAMPLE III
¦ Example I i8 repeated except employing 0.82 ~,rams of ammonium ¦ metatungstate dissolved in 210 milliliters of water as the impregnating ¦ solution. The catalyet is dried at 250F., then calcined for 3 hours at ¦ 1200E. The resultant catalyst has 0.3 weight percent tungsten thereon.
I EXAMPLE IV
I __ ¦ Rxample I i8 repeated except employing 2.35 grams of ceric ammonium~
¦ nitrate dissolved in 200 milliliters of water as tha impregnating ~olu-¦ tion. The catalyst is dried and calcined as in Example I and is found ¦ to contain 0.3 percent cerium.
¦ EXANPLE V
¦ Example I is repeated except using 2.73 grams of zinc nitrate hexa-¦ hydrate dissolved in 200 milliliters of water as the impregnating solu-¦ tion. The catalyst is dried and calcined as in E~ample I and is found 2s ¦ to contain 0.3 weight percent zinc.
_XAMPLE VI
Example I is repeated except employing 4.35 gram~ of ferric nitrate dissolved in 200 milliliters of water as the impregnating solution. The impregnated cataly~t is dried and calcined as in Example I and the cata-lyst is found to have 0.3 percent iron thereon.

EXAMPLE VII
Example I is repeated except employing 1.1 grams of a D nium molyb-date as in a 210 milliliter aqueous solution for impregnation. The imr pregnated catalyst ls dried at 250F. for three hours, and then calcined at 1200F. for three hours. The resultant catalys~ has 0.3 weight per-cent lybdenum thereon.
EXANPLE VIII
Example I is repeated except using 1.4 grams of bismuth nitrate dissolved in 200 milliliters of a dilute nitric acid solution as the impregnating solution. The dilute nitric acid solution is prepared by adding 5 milliliters of concentrated nitric acid to the 1.4 grams of bismuth nitrate, and then diluting the ~olution with water to make volume. The catalyst is dried at 250F. for 3 hours and then calcined for 3 hours at 1200F. The catalyst contains 0.3 weight percent bismuth.
EXAMPLE IX

Example I is repeated ~xcept using as an impregnating solution a composition comprised o 5.0 gramg of titanium sulfate dissolved in 25 milliliters of an aqueous 30 percent solution of hydrogen peroxide which iB diluted to 200 milliliters with water. The solution was heated until the titanium salt was fully dissolved. The catalyst i8 dried at 250F.

and then calcined for 3 hours at 1200F. The resultant catalyst has 0.3 weight percent titanium thereon.
EXAMPLE X

2s Example I is repeated except using 1.2 grams of chromic oxide dis-solved in 200 milliliters of water 8S the impregnating solution. The impregnated catalyst is dried for 3 hours at 250F. and then calcined for 3 hours at 1200F. The resultant catalyst has 0.6 we~ght percent chromium thereon.

10480(3a EXAXPLE XI
Example I is repeated except employing 2.12 grams of zirconyl chloride dissolved in 200 milliliters of water as the impregnating solution. The impregnated catalyst is dried at 250F. for 3 hours then calcined for 3 hours at 1200F. The resultan~ catalyst has 0.3 weight percent zirconium thereon.
EXAMPLE XII
Example I is repeated except using 0.2506 gram of a 50 percent manganese nitrate solution and 200 ~illili~ers of water as the ; 10 impregnating solution. The impregnated catalyst is dried at 250F. for 3 hours and the calcined for 3 hours at 1200F. The resultant catalyst has 0.02 weight percent manganese thereon.
EXAMPLE XIII
Example 2II is repeated except using 1.253 gram of a 50 percent 1s solution of manganese nitrate in 210 milliliters of water as the imr pregnating solutlon. The resultant catalyst has 0.1 percent manganese thereon.
EXAMPIE XIV
:
In this example, a bench-scale regeneration unit comprised of 2a ~ycor glass having a 1-3/8" inside diameter by 6" fluidization section, and a 1-3~4" inside diameter by 5" disengaging section. A synthetic flue gas mixture containiDg 4 percent by volume carbon monoxide, 4 percent oxygen, 4 percent water vapor, and 88 percent nltrogen is passed through the fluidized bed of ~he catalyst with a superficial gas velo-city of about 0.2 feet per second. The regeneration unit is surrounded by a furnace to maintain the temperature at the desired level. The temperature of the fluidi~ed bed is measured by thermocouples. A
first-stage cyclone is proYided to separate entrained catalyst which may exlt the regeneration unit. A second-stage cyclone is provided downstream from the fir~t-stage cyclone to remove additional catalyst 10~009 ¦ particle~ which still may be entrained in the exit gas. The catalyst ¦ separated by the first-stage cyclone is recycled to the catalyst bed by ¦ the use of a dip-leg. The outlet gas from the second-stage cyclone is ¦ further filtered using glass wool, and is analyzed with a gas chroma-s ¦ tograph for oxygen, nitrogen, carbon monoxide, and carbon dioxide.
¦ Operating time of the bench-scale regeneration unit at a given set of ¦ conditions ranges from a minimum of 40 minutes to about 90 minutes.
I This range of residence times is sufficient to establish the oxidation ¦ state relevant to a particular promoter in an actual fluid cracking ¦ unit operation.
¦ In this example, the catalysts of Examples I, IV, V, VI and XI are ¦ individually used in the bench-scale regeneration unit which is opera-¦ tlng-at 1200F. to determine the volume percent carbon monoxide conver-¦ sion effected by the catalyst. The results are provided in Table I.
ls ¦ TABLE I

¦ Oxidation Weight % Based On ¦ Promoter - Total Catal~stCO Conversion, Vol. %
I Manganese 0.3 65 ¦ Cerium 0.3 72 20 ¦ Zinc 0.3 55 ¦ Iron 0 3 ¦ Zirconium 0.3 65 ¦ Untreated --- 31 Several of the above catalysts were tested according to standard z5 uniform test methods used in the industry in a micro-fluidi~ed cata-lytic unit to determine the desired selectivity or catalytic cracklng.
As a basi~, the catalyst without metal promoter has a relative micro-activity of 154, a coke factor of 1.0, and a hydro~en to methanemol percent ratio of 0.64. The catalyst of Example I, in comparison, 1 4~009 shows a relatlve micro-activity of 147, a coke factor of 1.1, and a hydrogen to methane mol percent ratio of about 1.1 to 1.2. The catalyst of Example IV demonstrates a relative micro-activity of 150, a coke factor of 1.1, and a hydrogen to methane mol percent ratio of 0.9 to 1.1. The catalyst of Example VI i8 found to have a relative activity of 134, a coke fac~or of 2.0, and a hydrogen to methane mol percent ra~io of 6.5.
EXAMPLE XV

Example XIV is repeated using several of the catalysts having 0.3 wei~ht percent metal contained thereon, at different temperatures to determine carbon monoxide conversion at those temperatures. The cata-lysts employed are the manganese-promoted catalyst of Example I, the cerium-pro ted catalyst of Example IV, the iron-promoted catalyst of ~xample VI, and the zirconium-promoted catalyst of Example XI. The results are provided in Table II.

TABLE II

Oxidstion Amount of Metal CO Conversion, Vol. %
Promoter Impregnated Metal Weight, Percent 1100~F. 1200F. 1250P.

Man~snese 0.3 32 -- 50 Cerium 0.3 31 45 --Iron 0.3 38 45 55 Zirconlum 0.3 -- -- 50 Untreated --- 15 25 40 No Catalyst In Bed --- -- 20 50-60 -EXAMPLE XVI
Example XIV is repeated, using the same regeneration temperature of 1200F., except employing powdered metal oxide as the oxidation pro-motor in admixture with the cracking catalyst used in Example I. Theresults are provided in Table III.

104~009 TABLE III
Metal Oxide Weight % Based Oxidation On Total Pro ter CatalystCO Conversion, Vol. %
M~nganese 5Dioxide l.O 46 Manganese Dioxide 2.0 51 Iron Oxide 0.3 About 34 Iron Oxide 1.0 About 35 No oxidation IOPromoter --- 28 The sdded oxide powders used in this Example are about 5 microns and finer. For example, the iron oxides have an average particle size of le}~ than 1 micron.
; EXAMPLE XVII
Example XVI is repeated except using the folloT~ing metal oxide oxidation promoters in the followi~g concentrations at a 1200F. bed temperature. The results are provided in Table IV.
TABLE IV

Added Oxide RunCO Conversion~ Vol. %
20Powdcr, Wt. % 0 0.1 0.4 1 2 4 ide Type:
Fe2O3 (Reagent) 1 33 91 Iron Oxide~
(Inland) 1 33 About 33 2S(~lsconsin) 1 30 63 90 Rare Earth Oxides (Davison) 1 33 50 62 (Kerr-McGee) 1 33 65 Manganese Dioxide 30(Re~gent) 1 27 41 51 ~ 8~)09 EXAMPLE XVIII
Example XVII is repeated except using an 1150F. bed temperature with the added metal oxlde powder being as set forth in the Table V.
TABLE V

CO Conversion, Vol. ~
With and Without Powder Added Oxide Powder, Wt. % Metal 0 0.3 Added as:
Fe203 (Rea~ent) 49 95-100 FeO (Reagent) 52 90-100 MnO2 (Technical) 51 75-80 NgO (Reagent) 58 About 70 EXAMPLE XIX
Mld-continent gas oil (23.4API~ having a boiling ran8e from 650 to 1050F. is cracked in a fluidized transport-type reactor at an average cracking tempe.rature of 960F. The throughput ratio (weight total feed/weigbt fresh feed) is 1.34 and the total feed rate is 36,000 bbl/day The cs~alyst particles comprise those described iD Example I above im-pregn~ted with the oxidation catalyst and are circulated at a rate of 19.6 tons/minute. The weight of ratio of catsly6t to oil in the crack-ing zone is 3.7.
Effluent from the riser reactor is passed to a separation zone and fed into a cyclone separator. ~ydrocarbon products are removed and ~pent catalyst is psssed downwardly through the cyclone dip-leg into a Ytripping`zone maintained at 950F. The settled catalyst is stripped wlth steam to remove remaining volatile material prior to regeneration.
Str~pped spent catalyst, contain~ng 0.9 wt. ~ coke on catalyst, is fed into the bottom section of a regenerator vessel of the type ~hown ln Figure 2 where it is fluidized with air in a dense-phase catalyst bed ~ 3009 maintained at 1250~1275F. (average temperature i 1260DF.) by combus-tion of coke and occasional combustion of torch oil as requlred. The air rate i8 set at about 290,000 lbs./hr. to provide approximately 14.0 lbs. air per lb. coke on spent catalyst. Catalyst is entrained in the rising air stream and carried into the dilute-phase catalyst zone in the upper portion of the regenerator vessel about the interface with the dense bed. Combustion of carbon monox$de ie completed within the dilute-phase zone at a temperature of about 1400F. Gases and entrained cstalyet were passed from the dilute~phase zone into a series of cyclone ~eparator~ with catalyst being returned directly to the dense-phase zone.

The ~a3 ~tream leaving the cyclone system is passed first to a plenum area located at the top of the top of the regenerator vessel and then ia discharged at i250DF. Catalyst is withdrawn fro~ the dense phase bed as required through a standpipe at 1250DF. for return to the trans-port reactor.
Analysis of the regenerated catalyst indicates the residual coke content to be only 0.03 wt. %. Analysi~ of the effluent gas indicates the carbon monoxide content to be 0.0 vol. % and the oxy~en content to be 1.9 vol. %. The cracking conversion is 67.7 vol. % on feed. From hest balance calculatlons coke is burned at the rate of 20,700 lbs./hr., liberati~g 17,800 BTU/lb. coke. Of the total heat evolved, over 80% i9 absorbed in the regenerated catalyst and thus kept within the cyclic fluid cracking system.

EXAMPL~ XX
The same system, feedstock and reactor conditions as those of Ex-ample XIX may be employed using the regeneration vessel of Figure 2 but the regeneration gas velocity and particle flow rate may be ad~usted to provide for absorption of the haat from the essentially completè com-bustlon of the coke and C0 by the catalyst in the dense phase bed in ¦ the vessel. Carbon monoxide levels as low as 8 ppm. ~ay be achieved¦ by the process of this invention, while achieving coke removal and heat ¦ recovery similar to that achieved in Example XIX above.
I .
S l

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the continuous cyclic catalytic cracking of hydrocarbons wherein a fluidizable cracking catalyst which has been deactivated with coke deposits is withdrawn from a cracking zone, stripped of volatile material, passed to a regeneration zone and recycled to the cracking zone, in which the regeneration stage in the regeneration zone comprises the steps of:
(a) fluidizing the deactivated catalyst particles in physical association with a carbon monoxide oxidation promoter, within the regeneration zone, with a molecular oxygen containing regeneration gas, to provide molecular oxygen in excess of the amount required for complete conversion of the coke to carbon dioxide and burning substantially all of the coke from said cracking catalyst, wherein the oxidation promoter comprises one or more metals having an atomic number of at least 20 and selected from Groups IB, IIB, and III to VIII of the Periodic Table, and wherein said oxidation promoter is present in a minor amount which is effective to enhance the oxidation of carbon monoxide within the regeneration zone;
(b) initiating and sustaining, within the regeneration zone, the combustion of carbon monoxide produced by said burning through contact with the molecular oxygen containing gas in the regeneration zone while in contact with the cracking catalyst in physical association with said oxidation promoter, so that substantially all of the carbon monoxide is burned to carbon dioxide and most of the heat so produced is absorbed by the cracking catalyst;

(c) maintaining the temperature of the regeneration zone in the range from 1000° to 1500°F;
(d) withdrawing from the regeneration zone an effluent gas stream having no more than 1.0 vol. % of carbon monoxide;
(e) withdrawing from the regeneration zone oxidation promoter associated with regenerated catalyst particles contain ing said absorbed heat and having no more than 0.10 wt. % of residual coke; and (f) recycling said oxidation promoter and regenerated catalyst particles containing said absorbed heat to the cracking zone.

2. The process of Claim 1, wherein the regeneration zone is maintained at a temperature in the range from 1050° to 1400°F.

3. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase.

4. The process of Claim 1, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, coke is burned from the catalyst in the dense phase, the combustion of said carbon monoxide is completed in the dilute phase, and the temperature of the dilute phase is at least 50° higher than that of the dense phase.

5. The process of Claim 4, wherein partially regenerated catalyst particles are circulated from the dense phase to the dilute phase of the regeneration zone and dispersed within the dilute phase at a rate sufficient to absorb substantially all of the heat released by combustion occurring in the dilute phase.

6. The process of Claim 5 wherein additional coke is burned from the partially regenerated catalyst particles while present in the dilute phase.

7. The process of Claim 4, 5 or 6, wherein the temperature within the dense phase is maintained within the range from 1200° to 1300°F, and the temperature within the dilute phase is maintained within the range from 1250° and 1450°F.

8. The process of Claim 1, 2 or 4, wherein the regenerated catalyst particles contain from 0.01 to 0.05% coke.

9. The process of Claim 1, 2 or 4, wherein the regenera-tion gas is air.

10. The process of Claim 1, 2 or 4, wherein the regenera-tion zone effluent gas stream contains from 5 ppm to 500 ppm of carbon monoxide.

11. The process of Claim 1 wherein the cracking catalyst comprises silica, alumina, and a crystalline aluminosilicate.

12. The process of Claim 11, wherein the cracking catalyst comprises between 1 and 15 wt. % crystalline alumino-silicate.

13. The process of Claim 1, 2 or 4, wherein the amount of said oxidation promoting catalyst is from 0.01 to 5 wt. %
based on the weight of the cracking catalyst.

14. The process of Claim 1, 2 or 4, wherein the carbon monoxide oxidation promoting catalyst is supported by a solid ceramic support.

15. The process of Claim 1, 2 or 4, wherein the carbon monoxide oxidation promoting catalyst is supported by a solid support selected from the group consisting of silica, alumina, and mixtures thereof.

16. The process of Claim 1, 2 or 4, wherein the carbon monoxide oxidation promoting catalyst is supported by said cracking catalyst.

17. The process of Claim 1, 2 or 4, wherein said physical association is accomplished by admixture of powdered oxidation promoting catalyst and cracking catalyst.

18. The process of Claim 1, 2 or 4, wherein the amount of excess molecular oxygen is from 0.1 to 25 percent of the theoretical stoichiometric oxygen requirement for complete combustion of the coke.

19. The process of Claim 1, 2 or 4, wherein the metal of said oxidation promoting catalyst is selected from the group consisting of platinum, palladium, rhodium, molybdenum tungsten, copper, chromium, nickel, manganese, cobalt, vanadium, iron, cerium, ytterbium, and uranium.

20. The process of Claim 1, 2 or 4, wherein the metal of said oxidation promoting catalyst is selected from the group consisting of platinum, palladium, and rhodium.

21. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the regenerated catalyst particles contain from 0.01 to 0.05% coke.

22. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the regeneration gas is air.

23. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the regeneration zone effluent gas stream contains from 5 ppm to 500 ppm of carbon monoxide.

24. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase an an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the amount of said oxidation promoting catalyst is from 0.01 to 5 wt. % based on the weight of the cracking catalyst.

25. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with the oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the carbon monoxide oxidation promoting catalyst is supported by a solid ceramic support.

26. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the carbon monoxide oxidation promoting catalyst is supported by a solid support selected from the group consisting of silica, alumina, and mixtures thereof.

27. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the carbon monoxide oxidation promoting catalyst is supported by said cracking catalyst.

28. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and said physical association is accomplished by admixture of powdered oxidation promoting catalyst and cracking catalyst.

29. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the amount of excess molecular oxygen is from 0.1 to 25 percent of the theoretical stoichio-metric oxygen requirement for complete combustion of the coke.

30. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the metal of said oxidation promoting catalyst is selected from the group consisting of platinum, palladium, rhodium, molybdenum, tungsten, copper, chromium, nickel, manganese, cobalt, vanadium, iron, cerium, ytterbium, and uranium.

31. The process of Claim 1 or 2, wherein the regeneration zone comprises a lower dense phase and an upper dilute phase of cracking catalyst particles in physical association with said oxidation promoting catalyst, and wherein substantially all of the coke and carbon monoxide is burned to carbon dioxide in the dense phase and the metal of said oxidation promoting catalyst is selected from the group consisting of platinum, palladium, and rhodium.