Method for catalytic cracking of residual oils

Abstract

A method and system for the fluid catalytic cracking of residual and lower boiling oil streams is described which relies upon the residual oil as a quench medium for limiting the conversion of a recycle oil product thereof in a riser conversion zone. The overall combination is enhanced by using a dual component cracking catalyst of large and small pore size. Other virgin feeds requiring limited conversion residence time may be used in the combination to obtain restricted conversion of the residual oil feed.

Description

BACKGROUND OF THE INVENTION

It has been known for a long time that high octane gasoline product can be obtained from various selected hydrocarbon oils by catalytic cracking. However heavy oils such as residual oils have a large percentage of very refractory components such as polycyclic aromatics which are difficult to crack and cause an excessive amount of coke to be deposited on the catalyst. Furthermore, metal contaminants in the heavy oil feed poison or inactivate the catalyst. Therefore it has been necessary in the prior art to drastically reduce these components by different techniques such as hydrogenation, thermal cracking and adsorption on particle material of little or no cracking activity prior to disposal of the particle material. Thus, mild thermal cracking and visbreaking operations to produce more suitable feed materials for a catalytic cracking operation has been the trend of the prior art processing combinations.

Residual oil is a distress stock in the petroleum industry. A substantial amount of residual oil is sold as fuel oil or thermally processed to obtain lighter components and coke. Residual oils contain large quantities of components having coke forming tendencies and also metal components which exert adverse effects on the stability and activity of cracking catalysts. For example, residual oils contain carbon residue in excess of 0.6% by weight and this characteristic, producing high additive coke in a cracking operation, will operate to rapidly deactivate crystalline zeolite cracking catalysts.

SUMMARY OF THE INVENTION

The present invention relates to an improved method for the catalytic upgrading of residual oil. In a more particular aspect the present invention is concerned with the catalytic upgrading of residual oils in the presence of crystalline zeolite catalytic materials to obtain gasoline, lower and higher boiling components thereof.

A particular expedient of the processing concepts of the present invention is concerned with providing a short contact time residual oil catalytic conversion operation or operations at reasonable cracking temperatures by effecting the cracking conversion operation in the presence of a crystalline aluminosilicate conversion catalyst. The process concepts of the present invention are considerably different from present day fluid catalytic cracking (FCC) operations in that feeds used in the operation will be relatively cold (in the range of 100.degree. to about 350.degree.F.) and used in combination with a relatively high catalyst to oil ratio as well as high catalyst circulation rates. Furthermore since coke make will be in excess of that normally required for a heat balanced operation, it will be expedient to remove heat from the regenerators. The process concepts of the present invention include using a recycle oil product stream of cracking as the fresh feed for initially contacting suspended hot highly active regenerated catalyst at an elevated temperature of at least 950.degree.F. in a dispersed phase catalytic conversion zone and thereafter injecting a heavy oil feed such as a residual oil into a downstream portion of the dispersed phase suspension to quench the cracking reaction initiated with the recycle oil. Thus the fresh residual oil feed will be in contact with the regenerated catalyst for only a limited residence time in the range of 0.5 to 6 seconds at temperature conditions herein identified and particularly promoting the conversion thereof to lighter oil components thereof before separation of the catalyst from hydrocarbon material as by cyclonic separation means.

The method of converting residual oils and other hydrocarbon feed materials contemplated by the present invention relies upon the combination of initially forming a suspension of regenerated catalyst with a low boiling hydrocarbon feed such as a recycle oil product of cracking or other low boiling virgin feed herein identified to provide a suspension at a temperature preferably in the range of 1,000.degree. to about 1,300.degree.F. and a catalyst to oil ratio in the range of 5 to 40. The suspension thus formed is moved rapidly through a reaction zone such as a riser reaction zone for a hydrocarbon residence time selected from within the range of about 0.5 to about 4 seconds before the cracking reaction is quenched at least 100.degree. and to a temperature in the range of 900.degree.F. to about 1,200.degree.F. by the injection of a heavier hydrocarbon material such as the residual oil feed material. To facilitate dispersion, the residual oil may be combined with a diluent such as steam, low boiling gasiform hydrocarbons or other suitable diluent material. The suspension formed comprising catalysts, recycle oil conversion product and injected residual oil is then separated after an additional residence time in the range of 0.5 to about 6 seconds by cyclonic means or by discharging into an upper dispersed catalyst phase for gravity separation above a dense fluid bed of catalysts. The separated hydrocarbon material is passed to a fractionation zone for the separation recovery of various product fractions of the conversion operation. The separated catalyst is collected in a dense fluid bed of catalyst particles being stripped with stripping gas or used for other conversion purposes. The thus separated catalyst may be mixed with hot regenerated catalyst and thereafter moved generally downwardly to and through a catalyst stripping zone as provided below.

The method of the present invention contemplates combining freshly regenerated catalyst with the catalyst separated from the riser conversion zone to adjust the temperature thereof before further contact with a light hydrocarbon feed material or by a stripping gas. To accomplish this end, freshly regenerated catalyst may be lifted through a separate riser reactor with relatively inert lift gas or light hydrocarbons such as virgin naphtha or low severity reformates may be used to convey the regenerated catalyst at an elevated temperature of at least about 1,000.degree.F. into a bed of catalyst separated from the heavier oil feed riser cracking operation above discussed.

As provided herein the processing concepts of the present invention contemplate varying the reaction residence time of the various hydrocarbon components over a range of from a fraction of a second up to several seconds and controlling this reaction residence time by catalyst oil ratio and temperature through the concept of multipoint quench oil injection in the riser and/or the addition of regenerated catalyst to a downstream portion of the riser.

The processing concepts of the present invention lend themselves to many different apparatus variations, two of which are specifically discussed hereinafter. In one arrangement a side by side reactor-regenerator system is employed which permits the use of freshly regenerated cracking catalyst alone and in combination with used catalyst to perform the various conversion reaction desired under particularly selected temperature and catalyst to oil (C/O) ratio reaction conditions. In yet another arrangement, a stacked system is relied upon to accomplish the multiple hydrocarbon conversion reactions desired which reactions are controlled primarily as a function of temperature and hydrocarbon residence time.

In the methods and systems of this invention, it is contemplated using a relatively large diameter riser reactor for conversion of the recycle oil and a smaller diameter riser reactor for converting lower boiling hydrocarbon charge materials such as reformates, heavy virgin or cracked naphtha and light virgin gas oils. Furthermore, it is contemplated injecting the heavy quench oil in the downstream portion of the recycle oil riser reactor at one or more spaced intervals promoting the optimum desired conversion of the recycle oil. Also the heavy quench oil injected in the light hydrocarbon conversion riser reactor may be introduced at one or more spaced intervals promoting the optimum upgrading of the light hydrocarbon feed. Generally the recycle oil feed will require a longer hydrocarbon conversion residence time.

The stacked regenerator-riser reactor system herein referred to also lends itself to a regenerator system which improves upon the recovery of available heat by effectively improving upon a first stage of riser regeneration and a clean up stage of dense bed catalyst regeneration by promoting the conversion of carbon monoxide and the recovery of heat therefrom by the catalyst passed to the first and second stages of catalyst regeneration. A better understanding of the regeneration concepts of this invention will be had by referring to the specific embodiments hereinafter discussed.

The processing combination of the present invention contemplates the use of catalyst compositions varying considerably in activity and selectivity characteristics. That is, it is contemplated employing as one of the catalyst compositions, a crystalline zeolite of the X and Y faujasite type along or as the major catalyst component with the other of said catalyst compositions being an amorphous type cracking component of lower cracking activity. On the other hand, the faujasite cracking component may be combined with a smaller pore size crystalline zeolite having a maximum pore opening not substantially in excess of about 9 Angstroms or smaller than about 4 Angstroms. It is contemplated using with the large pore faujasite type crystalline zeolite cracking catalyst and prepared from either X or Y type zeolites, a crystalline zeolite of the erionite or offertite crystal structure or preferably a crystalline aluminosilicate of the ZSM-5 type may be employed with the larger pore crystalline zeolites. On the other hand, the catalyst may be a mordenite type zeolite cracking catalyst in combination with a ZSM-5 type of crystalline zeolite. The ZSM-5 type component of the catalyst may be retained as a separate particle in a support matrix material in combination with separate particles of the larger pore size cracking component. Furthermore the weight percent of ZSM-5 component may be less than or equal to the other crystalline cracking component of the dual component catalyst. The dual component catalyst disclosed in copending application Ser. No. 135,783, filed Apr. 20, 1971, now U.S. Pat. No. 3,748,251, may be employed with preference in the process of the present invention.

The processing concepts of this invention are concerned with adjusting and optimizing the temperature of the various catalyst streams employed and particularly that separated from the residual oil contact step and collected as a dense fluid bed of catalyst. Thus as discussed above, provision is made for adding high temperature regenerated catalyst to the dense fluid bed of catalyst. In addition a light hydrocarbon gasiform fluid material may be added to the bed of catalyst for conversion thereof by the small pore crystalline aluminosilicate compound of the catalyst. Thus depending upon the extent of quench effected with the residual oil feed and the temperature desired in the collected dense fluid bed of catalyst, the small pore crystalline zeolite, such as a ZSM-5 type material, may be maintained at substantially any temperature within the range of 300.degree.F. up to 1,000.degree.F., it being preferred to select temperatures, which upgrade the light hydrocarbons to useful products by the ZSM-5 catalyst component. Preferred temperatures will be in the range of 500.degree.F. to about 950.degree.F.

The dense fluid bed of catalyst collected and temperature adjusted as above described is stripped of entrained vaporous hydrocarbon material before passing thereof to a catalyst regeneration zone. The processing combinations herein identified will be a producer carbonaceous deposits on the catalyst which will generate in many cases an excess amount of heat during combustion thereof in the regeneration zone. Therefore it is proposed when required to provide steam coils or other means in combination with the regeneration operation to develop process steam or a source of process heat for use in the process or in other adjacent operations of the refinery.

In pursuing the processing concepts of this invention it is contemplated restricting conversion of the residual oil injected to relatively low levels so that a relatively mild cracking of the residual oil will be effected and produce a gas oil product considerably less contaminated with metal contaminants and additive carbon components.

Thus conversion of the residual oil may be restricted to less than about 45 volume percent (vol.%) of 400.degree.F. ASTM boiling point material and lighter but conversion may go as high as 70 vol. percent. The cycle stock product thereof will be subjected to temperatures, catalyst to oil ratios and space velocity conditions in an initial portion of the riser reactor commensurate with obtaining significant conversion thereof to a lighter oil product boiling in the range of 90.degree. to 700.degree.F. Thus conversion of recycle oil to gasoline boiling range products will normally be restricted not to exceed about 50%.

It is contemplated injecting gaseous materials into the dense fluid bed of catalyst collected as above identified as well as with the recycle feed and/or the residual oil feed passed to the hydrocarbon conversion zone. Gaseous materials which may be used with the heavy hydrocarbon feed to suppress the adverse effects of metal contaminants and additive coke characteristics of the feed on the catalyst in the conversion zone include hydrogen, gaseous hydrocarbon products of more severe gas oil cracking operations, mixtures of paraffin and olefin, C.sub.1 -C.sub.3 hydrocarbons, with or without hydrogen combined therewith. It is also contemplated as suggested above of lifting hot regenerated catalyst from the regeneration zone into the collected dense fluid bed of catalyst with straight run or other low octane naphtha boiling range products including reformate to obtain a high temperature zeolite cracking catalyst octane improvement thereof before discharge into the dense fluid bed of catalyst. This of course can be used as a means for controlling the temperature of the catalyst thus employed. Thus by the use of diluent materials as above identified with the heavy residual oil and recycle oil feeds, the effects of hydrocarbon partial pressure on the conversion operation can be considerably altered.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. I shows diagrammatically in elevation a side-by-side arrangement of vessels with interconnecting transfer conduits for effecting regeneration of a hydrocarbon conversion catalyst, conversion of hydrocarbons and the transfer of catalyst particles within the system.

FIG. II shows diagrammatically in elevation a stacked arrangement of vessels with interconnecting transfer conduits for effecting the catalytic conversion of different hydrocarbon feed materials and regeneration of catalyst particles used for that purpose.

DISCUSSION OF SPECIFIC EMBODIMENTS

Referring now to FIG. I by way of example, there is shown a side-by-side reactor-regenerator system with product fractionator for converting different hydrocarbon feed materials in the presence of catalyst compositions comprising crystalline aluminosilicate conversion catalysts. In the arrangement of FIG. I, a regenerator 2 containing a bed of finely divided catalyst particles in maintained in a fluidized condition by regeneration gas introduced to the bottom portion of the fluid bed by conduit 6 and communicating with a regeneration gas distributor grid 8. Coils 10 for generating process steam are provided in the regeneration zone. Cyclone separators 12 with diplegs 14 are provided in the upper portion of the regenerator for separating and returning to the catalyst bed entrained catalyst fines from regeneration flue gas. The separated flue gases pass into plenum chamber 16 and are withdrawn therefrom by conduit 18. During regeneration of the catalyst in fluid bed 4, carbonaceous material deposits on the catalyst are removed by burning in the presence of oxygen containing regeneration gas thereby raising the temperature of the catalyst about 1,000.degree.F. and more usually to a temperature in the range of 1,200.degree.F. up to about 1,400.degree.F. Regeneration of the catalyst may be accomplished in many different processing systems, it being important to select a system which will accomplish a desired heating of the catalyst during burning removal of carbonaceous deposits in an efficient manner.

Regenerated catalyst obtained at an elevated temperature of about 1,300.degree.F. is withdrawn from bed 4 by withdrawal conduit 20 provided with a catalyst flow control valve 22 for passage to the inlet of riser 24. Lift gasiform material which may be inert or a hydrocarbon reactant is introduced to the bottom of riser 24 by conduit 26. In riser 24 a suspension is formed comprising catalyst and lift gasiform material which is conveyed under elevated temperature conditions upwardly therethrough for deposit in a dense fluid bed of catalyst 28 obtained as hereinafter described. As indicated herein before the light gasiform material used in riser 24 may be relatively inert or it may be a reactant material which undergoes elevated temperature conversion reactions during contact with the hot catalyst transferred through the riser. Thus the gasiform material used may comprise C.sub.1 -C.sub.3 hydrocarbons which are converted by the ZSM-5 component of the catalyst mixture; a naphtha boiling range material may be used which is then provided with a high temperature octane boost primarily by the faujasite component of the catalyst; or a relatively inert gaseous material may be used to convey the catalyst. Other materials identified above may be used.

Regenerated catalyst is also withdrawn from bed 4 by withdrawal conduit 30 provided with catalyst flow control valve 32 for passage to the inlet of riser reactor 34.

The processing concepts of the present invention are particularly concerned with the relationship of conditions for converting distress stocks of high coke producing characteristics and comprising metal contaminates known as residual oils. Generally residual oils are high boiling hydrocarbon materials having an initial boiling point in excess of about 950.degree.F. and more usually at least about 1,000.degree.F. Thus to accomplish the catalytic conversion of such residual oil distress stocks, the present invention employs the procedure of initially contacting freshly regenerated catalyst at an elevated temperature of at least 900.degree.F. with a recycle oil product fraction of the cracking step introduced by conduit 36 to riser 34 to provide a recycle oil reaction residence time in the presence of suspended catalyst passing up the riser in the range of 1 to 5 seconds and thereafter injecting a residual oil in a downstream portion of riser 34 by conduit 38 connected to a plurality of separate spaced apart injection conduit 38. The residual oil at a temperature in the range of 100.degree. to 300.degree.F. is used as a quench fluid to the catalyst oil suspension and products formed with the recycle feed. The introduction of residual oil is sufficient to quench the suspension to a temperature within the range of 850.degree. to 1,000.degree.F. before separation thereof preferably by cyclonic means in separators 40 provided. The suspension is separated in separators 40 into a hydrocarbon phase and a catalyst phase. The hydrocarbon phase is withdrawn from the separators by conduit 42 and then passed by conduit 44 to a product fractionator 46 wherein products of conversion are separated into a bottom fraction withdrawn by conduit 48, a heavy oil recycle fraction withdrawn by conduit 50, a light oil recycle fraction withdrawn by conduit 52, a heavy gasoline fraction withdrawn by conduit 54 and materials boiling below the separated gasoline fraction withdrawn by conduit 56. The vaporous material withdrawn by conduit 56 is passed to a condenser wherein reflux material is separated for return to the tower as reflux by conduit 58.

Catalyst particles separated from hydrocarbon vapors in cyclone separators 40 are conveyed by diplegs 60 to a collected dense fluid bed of catalyst 28 therebelow.

The catalyst employed in the processing sequence of the present invention is a dual cracking component catalyst comprising a ZSM-5 type of crystalline aluminosilicate as one of the cracking components. The other cracking component of the composition is preferably a faujasite type of zeolite with the Y type being preferred. To take full advantage of the conversion potential of the ZSM-5 type of crystalline zeolite in the catalyst mixture, a light hydrocarbon feed is introduced by conduit 62 to a lower portion of the dense fluid bed of catalyst 28 and above the catalyst entrance to a catalyst stripping zone therebelow. The light hydrocarbon feed may be a mixture of C.sub.1 -C.sub.3 hydrocarbons alone or in combination with a light naphtha boiling range material. In the dense fluid bed 28 and riser 24, utilization of the ZSM-5 type catalyst component is particularly promoted and this is enhanced by maintaining the catalyst bed, for example, at a temperature in the range of from about 500.degree.F. up to about 900.degree.F. The fluid bed of catalyst 28 is caused to move generally downwardly into and through a catalyst stripping zone in countercurrent contact with stripping gas such as steam introduced to a lower portion thereof by conduit 64. Stripped hydrocarbon products and stripping gas are removed from the upper portion of fluid bed 28 and pass through one or more cyclone separators represented by separator 66. Separated catalyst is returned to the catalyst bed as by dipleg 68 with the separated vaporous material passing into a plenum chamber 70 from which the vapors are withdrawn by conduit 44.

Stripped catalyst obtained as above defined is then passed by conduit 72 provided with catalyst flow control valve 74 to a bed of catalyst 4 in the regeneration zone, thus completing the primary circulation of catalyst through and between the regeneration zone and the hydrocarbon conversion zones. However, as shown in the drawing, additional catalyst may be withdrawn from regenerator catalyst bed 4 as by conduit 80 containing flow control valve 82 for admixture with the suspension passing upwardly through riser 34 in a region for residual oil injection.

Provision is made for adding a diluent material with the recycle oil as by conduit 76. An injection conduit 78 is also provided in the lower portion of riser 34 for introducing recycle hydrocarbon material initially or in addition to for admixture with catalyst particles flowing upwardly through the riser. For example, it is contemplated initially lifting the catalyst introduced to the bottom of riser 34 with gasiform material alone as identified hereinbefore to form a suspension which is contacted with recycle oil feed introduced by conduit 78. On the other hand the recycle feed may be split so that a portion is introduced by conduit 36 with or without gasiform materials with another portion of the recycle oil feed being introduced by conduit 78. In any of these arrangements, the conversion of the recycle oil feed may be controlled as by catalyst to oil ratio employed to maximize production of gasoline boiling range product or be restricted in favor of producing product boiling above gasoline. Also the conversion of the residual oil feed may be restricted over a relatively wide range, depending upon the conversion conditions selected for converting the recycle oil in the riser beneath the residual oil injection point. In addition, the processing concepts of this invention may be enhanced by subjecting the recycle oil feed to a prehydrogenation treatment prior to the cracking thereof in riser 34. Prehydrogenation of the recycle oil will operate to reduce the coke forming characteristics of the oil charge by hydrogenating polycyclic aromatics in the charge. Also the prehydrogenation of the oil feed will reduce to a considerable extent metal contaminants in the oil feed.

Referring now to FIG. II there is shown a stacked fluid cracking system employing a plurality of riser reactors to effect conversion of a recycle oil product of residual oil conversion and lower boiling hydrocarbon straight run feed materials. In the arrangement of FIG. II, a first riser reactor 1 is provided with hot regenerated catalyst in the lower portion thereof by conduit 3 containing flow control valve 5. A hydrocarbon feed material such as a recycle oil product of cracking a residual oil is introduced to the riser by conduit 7 to form a suspension with the introduced catalyst. A suspension of desired catalyst to oil ratio is formed having a preselected conversion temperature designed to accomplish conversion primarily to gasoline boiling products or to products boiling above gasoline. The suspension formed as above identified then passes upwardly through riser 1 under velocity conditions providing a hydrocarbon reaction residence time within the range herein identified. In a downstream portion of riser 1 provisions are made for introducing a heavy hydrocarbon material such as a residual oil in an amount to effect quenching of the conversion of the recycle oil feed and its products of reaction. The heavy hydrocarbon is introduced by conduit 9 to a manifold 11 providing the plurality of spaced apart injection points for the quench oil. Thus the residual quench oil may be introduced throughout the length of riser 1 to provide the recycle oil with reaction conversion residence time in the range of 1 to 6 seconds. The suspension comprising catalyst and hydrocarbon material in riser 1 is discharged directly into cyclonic separation means 13 positioned in the upper portion of a vessel 15. Vessel 15 is primarily a catalyst collection and stripping hopper within which cyclone separation means are retained. Catalyst separated in 13 is withdrawn by dipleg 17 and passed to a dense fluid bed of catalyst particles 19 therebelow. Hydrocarbon material separated from the catalyst is withdrawn from separator 13 by conduit 21 and conveyed to chamber 23 from whence it is withdrawn by conduit 25 for passage to a product fractionator not shown.

A riser reactor 27 supplied with hot regenerated catalyst in a lower portion thereof by conduit 29 containing flow control valve 31 is provided. A hydrocarbon feed is introduced to the lower portion of riser 27 by conduit 33. The hydrocarbon feed introduced by conduit 33 is preferably either a heavy virgin naphtha or a light virgin gas oil. The feed thus introduced is combined with introduced catalyst to form a suspension at a temperature in the range of 1,000.degree.F. to about 1,200.degree.F. of desired catalyst to oil ratio. The suspension then passes upwardly through riser 27 under velocity conditions designed to achieve high temperature octane improvement of the virgin naphtha and in the case of light virgin gas oil a conversion thereof to gasoline boiling range products. To control these conversions within the limits desired, provision is made for introducing a heavy hydrocarbon such as a residual oil to that portion of the riser as quench to secure the desired conversion result. For example, quench fluid is introduced by conduit 35 to a manifold provided with a plurality of spaced apart injection conduits 37. Thus it will be seen that conversion of the naphtha or light gas oil may be obtained under very short reaction residence time before the quench fluid is introduced and itself converted under the limited conversion conditions as herein defined. The suspension thus obtained is caused to move through riser 27 to a cyclone separator 39 positioned in the upper portion of vessel 15. Catalyst separated in separator is conveyed by dipleg 41 to catalyst bed 19 and hydrocarbon vaporous material is conveyed by conduit 43 to chamber 23. The risers used in the arrangement of FIG. II may be of the same diameter or of different diameter. For example, riser 1 used for converting the recycle oil feed may be of a larger diameter than riser 27 used for converting the much lighter virgin feed materials.

The catalyst collected in bed 19 is caused to move generally downward through a stripping zone and countercurrent to stripping gas introduced by conduit 45. A plurality of baffles 47 are provided in the stripping zone comprising the lower portion of vessel 15. The stripped catalyst is withdrawn by standpipe 49 and conveyed to the lower portion of a riser regeneration zone. In this embodiment the bottom open end of the standpipe is in matching engagement with an adjustable plug valve 51 provided with stem 53 for adjusting the vertical height of the plug valve and thus the rate of discharge of catalyst from standpipe 49.

The catalyst discharged from standpipe 49 is combined with hot regenerated catalyst as more fully discussed below in an amount to raise the temperature of the spent catalyst and promote the combustion of carbonaceous deposits on the catalyst. Regeneration gas such as air introduced by conduit 55 is passed to separate air distributor means 57 and 59 for admixture with the catalyst in zone 61 and the conveyance thereof as a suspension upwardly through an annular regeneration zone 63. The suspension in zone 63 may be varied in density considerably by adjustment of air rates and/or catalyst feed rate to zone 61. It is contemplated passing the suspension upwardly through zone 63 as a relatively dilute catalyst phase suspended in regeneration gas under catalyst regeneration conditions of at least 1,000.degree.F. The suspension may also be considerably more dense depending upon the amount of recycled regenerated catalyst combined with the spent catalyst passed upwardly through the annular regeneration zone. The suspension discharged from the upper end of the annular regeneration zone is separated into a catalyst phase and a combustion gas or flue gas phase. Separation is effected by gravity and cyclonic means with cyclonic separation being particularly relied upon when high velocities are used in zone 63 for regenerating a relatively dilute catalyst phase. Cyclonic separation is effected in a plurality of suitable separators 65 provided with a dipleg 67. The catalyst particles separated by cyclonic means and by gravity are collected in an annular bed of catalyst 69 maintained in a relatively dense fluid phase condition. Regeneration gas is introduced to the lower portion of bed 69 by conduits 71 and 73. Regenerated catalyst is withdrawn from the bottom of catalyst bed 69 by conduits 75 and 77 provided with flow control valves 79 and 81. Thus catalyst mix zone 61 is provided with hot regenerated catalyst by conduits 75 and 77 in an amount sufficient to raise the temperature of the spent catalyst discharged from standpipe 49 up to a catalyst regeneration temperature of at least 1,000.degree.F. Regeneration of the catalyst is completed in fluid bed 69 with flue gases discharged from the upper portion thereof mixing with catalyst and flue gas discharged from the upper end of the annular riser regeneration zone. Thus in the dispersed catalyst phase of the regenerator between the riser outlet and the inlet to the cyclone separators 65, the conversion of carbon monoxide (CO) to carbon dioxide (CO.sub.2) is promoted thereby heating the flue gases to an elevated temperature and providing heat exchange with catalyst particles in direct contact therewith before and during cyclonic separation in separators 65. Thus the regeneration combination of steps lends itself to the type of operation providing a relative rapid circulation of catalyst through the riser regeneration stage, the cyclonic separation stage, the dense fluid bed catalyst regeneration stand and recycle of regenerated catalyst therefrom to the riser regeneration step.

The combination of the present invention lends itself to the processing of various hydrocarbon feed materials in addition to those disclosed above to improve the product composition and/or the product material for conversion to more desired products. For example, in the arrangement of FIG. I it is contemplated initially cracking a heavy catalytic naphtha in the lower portion of riser 78 before quench of the conversion reaction. On the other hand, conversion of heavy naphtha may be accomplished alone in riser 24. In the arrangement of FIG. II, heavy catalytic naphtha may be subjected to a high temperature short contact recracking in either riser 1 or riser 27 or in both risers before quench of the conversion reaction with a heavier hydrocarbon feed material. Cracking of such heavy naphtha product of cracking will provide an octane improvement, a reduction in the product sulfur level, a reduction in olefin content and generally improve the volatility of the gasoline product.

On the other hand, a light hydrocarbon feed material in the C.sub.3 to C.sub.4 boiling range may be initially converted under selected high temperature short contact time conversion conditions in the riser reactors comprising 1, 27, 34 and 24 to form light olefins, free radicals and aromatics. The light olefins and free radicals that do not combine to form aromatics in the presence of the ZSM-5 catalyst component may undergo reaction with the heavier hydrocarbon material charged to a downstream portion of the riser and conversion products thereof.

It is also contemplated charging low octane light virgin naphtha, atmospheric gas oil and heavy virgin naphtha to the risers above identified to form alkylate feed material in addition to producing high octane gasoline during high temperature cracking (of at least 1,000.degree.F.) of these feed materials. For example, the high catalyst to oil ratios in combination with high catalyst temperature and relatively short hydrocarbon residence time before introduction of residual oil feed to the riser is particularly suitable for accomplishing the results desired. It is also contemplated charging coker naphtha or low octane reformate material (such as 90 to 95 R+O (Research clear) octane material) to such a high temperature riser cracking zone to raise the octane level thereof in combination with producing alkylate feed material.

Having thus provided a general discussion of the improved methods and systems of the present invention and described specific examples in support thereof, it is to be understood that no undue restrictions are to be imposed by reason thereof except as defined by the following claims.

Claims

I claim:

1. A method for converting residual oils to lower boiling products which comprises,

passing hot crystalline zeolite catalyst particles to the lower portion of an elongated conversion zone, passing a recycle oil product of residual oil cracking to the lower portion of said conversion zone under conditions to form a suspension with said catalyst particles at a temperature of at least 1,000.degree.F., passing said suspension through said conversion zone providing a recycle oil charge residence time in the range of 0.5 to about 4 seconds, combining a residual oil feed with said suspension in said conversion zone in an amount sufficient to quench said recycle oil conversion, passing the suspension comprising said residual oil feed through said conversion zone at lower temperature cracking conditions for an additional hydrocarbon residence time in the range of 0.5 to 6 seconds, cyclonically separating said suspension into a hydrocarbon phase and a catalyst phase and separately recovering said hydrocarbon phase and said catalyst phase.

2. The method of claim 1 wherein the residual oil is introduced to said conversion zone at one or more spaced apart points.

3. The method of claim 1 wherein the catalyst comprises a dual cracking component comprising a large pore crystalline zeolite of the faujasite or mordenite type in combination with a smaller pore crystalline zeolite such as erionite, offertite and ZSM-5 type materials.

4. The method of claim 1 wherein the catalyst to oil ratio of the suspension in the region of residual oil injection is adjusted by adding additional hot catalyst to the suspension.

5. The method of claim 1 wherein the separated and recovered catalyst phase is combined with additional regenerated catalyst before stripping thereof of entrained hydrocarbons.

6. The method of claim 5 wherein the regenerated catalyst combined with the recovered catalyst phase is relied upon to convert a low severity reformate material to higher octane product.

7. The method of claim 1 wherein conversion of the residual oil is restricted not to exceed about 50 volume percent of 400.degree.F. ASTM boiling point material.

8. The method of claim 1 wherein gaseous materials selected from the group comprising hydrogen, gaseous hydrocarbon products of more severe gas oil cracking operations, mixtures of paraffins and olefins and C.sub.1 to C.sub.3 hydrocarbons with or without hydrogen are combined with the residual hydrocarbon feed to suppress the effects of metal contaminants and coking characteristics of the heavy feed.

9. The method of claim 1 wherein a separate second conversion zone is provided for initially converting a heavy virgin naphtha or a light virgin gas oil with suspended catalyst to gasoline boiling product at a temperature of at least 1,000.degree.F. before introducing residual oil to said second conversion zone as quench and conversion thereof by contact with the catalyst suspension provided therein.

10. The method of claim 9 wherein catalyst is separated from each conversion zone and stripped in a common stripping zone, the stripped catalyst is combined with freshly regenerated catalyst and passed upwards through a dispersed phase regeneration zone for discharge into the dispersed catalyst phase above a dense fluid bed of catalyst being regenerated, said discharged catalyst is passed from said dispersed phase into said dense fluid bed of catalyst and dense bed regenerated catalyst is passed to the inlet of each of said conversion zones.

11. The method of claim 1 wherein conversion of the recycle oil feed is restricted not to exceed 50 volume percent.

12. The method of claim 1 wherein conversion of the residual oil feed is restricted to less than 45 volume percent.