US 3894935 A
The fluid catalytic cracking of a gas oil and a C3-C4 rich fraction in separate conversion zones in the presence of a faujasite conversion catalyst is described wherein freshly regenerated catalyst may be employed in each separate conversion zone or it may be cascaded from the gas oil conversion zone to the conversion zone for the C3-C4 rich feed.
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Description (OCR text may contain errors)
O United States Patent 1191 1111 3,894,935 Owen July 15, 1975  CONVERSION OF HYDROCARBONS WITH 3,406,! 12 IO/ 1968 Bowles 208/ 153 Y FAUJASITE TYPE CATALYSTS 3,679,576 7/1972 McDonald 208/74 3,776,838 l2/l973 Youngblood et a1. 208/74 75] Inventor: Ha tley e e e Mead. NJ 3,784,463 1/1974 Reynolds et al. 208/74  Assignee: Mobil Oil Corporation, New York,
NY. Primary Examiner-Delbert E. Gantz Assistant Examiner-G. E. Schmitkons  filed: 1973 Attorney, Agent, or Firm-Charles A. Huggett; Carl D. 211 App]. No.: 417,002 Famswoflh  US. Cl. 208/78; 23/288 8; 208/74;  ABSTRACT 203 120; 20 5 20 5 2 5 The fluid catalytic cracking of a gas 0|] and a C -C 208/164; 0 7 rich fraction in separate conversion zones in the pres 51 m. Cl C10 37 02; m 11/13;B01j9/20 ence of a faujasite conversion catalyst is described  Field of Search 208/78. 71. 62 wherein freshly regenerated Catalyst y be employed in each separate conversion zone or it may be cas- 5 References Cited caded from the gas oil conversion zone to the conver- UNITED STATES PATENTS sion zone for the C -C rich feed.
2.427.820 9/1947 Thomas 208/57 6 Claims, 2 ing g s CONVERSION OF HYDROCARBONS WITH Y" F AUJ ASITE-TYPE CATALYSTS BACKGROUND OF THE INVENTION The field of catalytic cracking and particularly the operations related to dense and dilute fluid phase catalytic operations have been undergoing progressive development since early 1940. As new experience was gained in operating and design parameters. new cata lyst compositions were developed which prompted a further refinement in known operating technology. With the development of high activity crystalline zeolite catalyst, the industry found a further need to im prove upon its operating parameters to take advantage of the new catalysts activity, selectivity and operating sensitivity. The present invention is thus concerned with an improved method of cracking or catalytic operation which relates the catalyst activity and selectivity to processing parameters in a manner mutually contributing to improving the conversion of available refinery feed materials.
SUMMARY OF THE INVENTION The present invention is directed to the conversion of hydrocarbons in the presence of a relatively large pore crystalline material of the faujasite type of crystalline zeolite. In a more particular aspect, the present invention is concerned with more completely utilizing the activity and selectivity characteristics of X and Y" faujasite crystalline aluminosilicate conversion catalyst to upgrade gas oil feed materials and normally gaseous C and lower boiling hydrocarbon products such as those obtained in a petroleum refinery operation. In yet another aspect the present invention is concerned with using a large pore faujasite cracking catalyst either freshly regenerated or as separated from a gas oil hydrocarbon conversion zone to upgrade particularly C and C rich hydrocarbon gaseous material to higher boiling gasoline boiling material. The C -C rich gaseous material may be the product of a high temperature hydrocarbon cracking operation or the gaseous hydrocarbons may be a combination thereof with other comparable material recovered from other available refinery sources. More particularly, the present invention is concerned with the cracking of heavy hydrocarbons such as gas oil, hydrogenated gas oil, residual material and hydrogenated residual material. Thus, gas oils and higher boiling range hydrocarbon feed materials are cracked with faujasite cracking catalyst under elevated temperature cracking conditions selected from within the range of about 950F. to about 1200F. but more usually less than about ll50F. at a hydrocarbon residence time in a once through conversion zone restricted to within the range of about 1 to about seconds. Catalyst to oil ratios may be selected from within the range of4 to about 20. Generally, it is preferred to accomplish cracking of gas oil and/or higher boiling residual material in an upflowing riser conversion zone discharging into an enlarged separation zone or cyclonic separating means housed in a larger zone such as an upper portion of an enlarged catalyst separation and collection vessel wherein products of such cracking are separated from the catalyst used. The gas oil catalyst suspension in the riser may be discharged directly into cyclonic separating means. The catalyst separated from hydrocarbon conversion products is collected in the lower portion of a vessel comprising or communicating with a stripping zone therebelow wherein the catalyst is stripped with countercurrent flowing stripping gas such as steam. The stripped products and products of cracking separated from the catalyst after discharge from the riser conversion zone are combined and passed to one or more down-stream product recovery separation zones. In the arrangement and system of this invention a second separate riser reactor discharging into a catalyst separation zone such as one or more cyclonic separators is provided wherein catalyst particles are separated from hydrocarbon vapors and therafter stripped in the same or a different stripping zone than that used for stripping catalyst separated from the gas oil riser conversion operation. In accordance with this invention the stripped catalyst separated from each riser conversion zone may be passed to a common regeneration zone or all or a portion of the catalyst separated from the gas oil riser con version zone may be cascaded to the second separate riser reactor wherein it is contacted with a gaseous stream rich in C -C hydrocarbons. In this arrangement the catalyst separated from the gas oil conversion step generally at an elevated temperature of at least 900F. is available for flow upwardly through a second separate riser conversion zone suspended in normally gaseous C and lower boiling feed material. In this invention. a C;,-C rich hydrocarbon mixture or an isobutylene rich feed material is combined with freshly regenerated Y" faujasite conversion catalyst or that separated and cascaded from the gas oil conversion zone under conditions to provide a catalyst to hydrocarbon feed ratio in the range of 5 to about 40 at an elevated hydrocarbon feed temperature sufficient to form a suspension at a temperature in the range of about 900F. to about llO0F. The normally gaseous hydrocarboncatalyst suspension passes upwardly through the second riser conversion zone under conditions providing a hydrocarbon residence time within the range of l to about 10 seconds before separation of the suspension. During this operation, the *Y" faujasite catalyst comprising hydrogen transfer activity and cyclization selectivity converts the C -C hydrocarbons to aromatics; alkyl aromatics and low boiling gaseous material.
Catalyst particles separated from the conversion zones herein defined are caused to flow downwardly to and through one or more stripping zones countercurrent to rising stripping gas such as steam. The stripped catalyst is then transferred as above provided or to a catalyst regeneration zone not shown for the removal of deposited carbonaceous material thereby heating the catalyst to an elevated temperature.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a diagrammatic sketch in elevation of an arrangement of first and second hydrocarbon conversion zones for catalytically converting selected hydrocarbon feeds with freshly regenerated faujasite fluid conversion catalyst.
FIG. II is a diagrammatic sketch in elevation of a ves sel arrangement for separately stripping catalyst recovered from separate riser conversion zone. for cascading catalyst from one zone to the other and for effecting the conversion of a gas oil feed separately from gaseous C and lower boiling material with faujasite conversion catalysts.
DISCUSSION OF SPECIFIC EMBODIMENTS Referring now to FIG. I, there is shown a riser conversion zone 2 supplied with hot regenerated catalyst by conduit 4 provided with a catalyst flow control valve 6. Steam is introduced to the bottom of riser 2 by one or more steam inlet conduits 8 and about a gas oil inlet conduit 10 which projects upwardly into the bottom portion of riser 2. A suspension of hot freshly regenerated catalyst in upflowing gas oil and steam provides a mix temperature of at least 950F. which is passed upwardly through the riser 2 under velocity conditions selected to provide a hydrocarbon residence time within the range of 2 to about 10 seconds. The upflowing suspension in riser 2 is discharged from the end thereof into a separation zone, shown in the drawing, to house one or more cyclonic separation zones. On the other hand. riser 2 may discharge directly into one or more cyclonic separating means, as shown in FIG. I] discussed below. for separating fluid catalyst particles from hydrocarbon vapors. In the arrangement of FIG. I the suspension in riser 2 is discharged through slotted openings at the riser outlet into an enlarged settling zone of reduced fluid stream velocity or vessel 12 wherein separation of catalyst from hydrocarbon vapors is encouraged by a substantial reduction in the suspension velocity. Hydrocarbon vapors then pass through cyclonic separation means 14 for removal of entrained fines before the hydrocarbon vapors pass into a plenum chamber 16 and removal from the vessel by conduit 18. Catalyst separated from hydrocarbon vapors by settling and in cyclonic means 14 pass to a fluid bed of catalyst 22 maintained in the lower portion of vessel 12. The fluid bed of catalyst 22 is in open communication with a stripping zone 24 therebelow through which the fluid bed of catalyst moves countercurrent to rising stripping gas introduced by conduit 26. Stripped catalyst is removed from a bottom portion of the stripping zone by conduit 28 for transfer to a catalyst regeneration zone not shown. The fluid bed of catalyst 22 separated from the riser conversion zone 2 is at an elevated temperature in the range of about 800F. to about lOOOF. In accordance with this invention, a second separate riser conversion zone 30 is provided in parallel arrangement with riser 2 which also discharges into an upper portion of vessel 12. Risers 2 and 30 are preferably positioned within vessel 12 at least at their discharge end so that a suspension of catalyst and hydrocarbon vapors is discharged substantially adjacent the inlet of cyclonic separation means within the vessel. A gaseous hydrocarbon feed such as a mixture of C -C hydrocarbons or a C rich fraction is introduced to the bottom inlet conduit 32 of riser 30 for admixture with hot regenerated catalyst particles in conduit 34 to form a mixture or suspension at a temperature within the range of 700 to about i IF. The suspension formed in a catalyst/oil ratio in the range of to about 40 is passed upwardly through riser 30 under conditions to provide a hydrocarbon residence time within the range of l to about seconds. The upwardly flowing suspension in riser 30 is discharged in the specific arrangement of FIG. I from the upper end thereof through slots provided into the enlarged settling section of vessel 12. The discharged suspension is separated by catalyst settling induced by a drop in the suspension velocity and by the aid of cyclonic separation means such as cyclonic means 14. The separated catalyst is returned to the fluid bed of catalyst 22. The discharge end of riser 30 may also be provided with one or more cyclonic separation means so that the suspension passed upwardly through the riser will pass directly into the cyclonic separators rather than pass first into the enlarged settling zone and then through cyclonic separation means.
The method and system of FIG. 1 above described may be modified to some considerable extent without departing from the concepts of the present invention. FIG. II is one example of such a modification. In the arrangement of FIG. I] a gas oil conversion riser is charged in a bottom portion thereof with gas oil by conduit 42, steam by conduit 44 and hot freshly regenerated catalyst by conduit 46 to form a suspension at an elevated cracking temperature of at least about I00OF. The suspension formed is passed through the riser under conditions to provide a hydrocarbon residence time in the range of 2 to 10 or more seconds be discharged from the riser directly into a cyclonic separation zone 48. Catalyst particles separated from hydrocarbon vapors in zone 48 are passed by dipleg S0 to a bed of catalyst 52 in a stripping zone therebelow. Hydrocarbon vapors separated from catalyst in zone 48 are conveyed to a collecting zone 54 or plenum chamber in the upper portion of vessel 56 before removal therefrom by conduit 58.
Catalyst bed 52 is confined within a stripping section in the lower portion of vessel 56 and is adjacent to a second bed of catalyst 60 but separated therefrom by a substantially vertical baffle 62. Baffle 62 is provided in an upper portion thereof with a plurality of catalyst transfer slots 64 for transferring catalyst from bed 52 to bed 60 as more fully discussed below. The catalyst in bed 52 at an elevated temperature in the range of about 900F. to about l00UF. may be further temperature elevated by adding hot regenerated catalyst directly to the bed Catalyst bed 52 moves generally downward and countercurrent to rising stripping gas introduced by conduit 66. Stripped catalyst at an elevated temperature in the range of 850F. to about I000F. is removed by conduit 68 and passed to the bottom portion of a second riser conversion zone 70. Steam is introduced to a bottom portion of riser 70 by conduit 72 and normally gaseous hydrocarbons comprising C and lighter hydrocarbons are introduced by conduit 74. A suspension of catalyst in normally gaseous hydrocarbons and steam is formed which then moves upwardly through riser conversion zone 70 at a temperature within the range of 800F. to about l(lF. under velocity conditions providing a hydrocarbon residence time in the range of 5 to 15 seconds. The suspension passing through riser 70 is discharged in this arrangement directly into a cyclonic separation zone 76 wherein hydrocarbon vapors are separated from catalyst particles. The hydrocarbon vapors and steam pass overhead to plenum chamber 54 for admixture with hydrocarbon products of gas oil cracking. Catalyst separated in zone 76 is conveyed by dipleg 78 to fluid catalyst bed 60. Catalyst bed will normally be at a lower temperature than bed 52 but this can be remedied to some extent by conveying catalyst particles through slots 64 in baffle 62 from bed 52 to bed 60. Also, it is contemplated adding hot freshly regenerated catalyst to bed 60 to adjust the temperature thereof to a desired elevated temperature of at least 850F. and preferably at least 950F. Catalyst bed 60 moves generally downward through its stripping section countercurrent to stripping gas introduced by conduit 80. Stripped catalyst removed from the bottom of bed 60 is then conveyed by conduit 82 to a regeneration zone not shown.
Stripped products and stripping gas separated from the upper surface of beds 52 and 60 pass through cyclonic separating means represented by 84. Gasiform material comprising stripping gas separated from entrained catalyst fines pass from separator 84 to plenum 54. Separated catalyst fines are passed by dipleg 86 to bed 60.
It is to be understood that cyclonic separating zones 48, 76 and 84 may each be a plurality of interconnected separation zones preferably arranged in sequence to provide more than one stage of cyclonic separation in the recovery of catalyst fines from vaporous hydrocarbon material and stripping gas.
In yet another embodiment, it is contemplated modifying the arrangement of either FIG. I or I] to use low boiling gaseous hydrocarbons such as isobutylene or a mixture of C and lower boiling hydrocarbons as a fluidizing gas instead of steam introduced to the bottom portion of the gas oil riser conversion zone as by conduits 8 and 44. On the other hand, steam is a desirable fluidizing medium for use in riser conversion zones 30 and 70 since it may be used to alter or adjust the catalyst/hydrocarbon ratio in these transfer conversion zones using the C -C hydrocarbon stream as the primary feed.
DISCUSSION OF SPECIFIC EXAMPLE A series of conversion runs with an isobutylene rich feed were made under selected temperature and hydrocarbon residence time conditions which support the combination operations contemplated by the present invention and variations thereon. A catalyst comprising percent REY was contacted under the conditions identified in the table below which produced the results identified. It was observed upon examination of the product that a considerable amount of hydrogen transfer occurred along with the production of a significant amount of liquid product. The liquid product was identified as consisting chiefly of toluene, Xylenes, trimethylbenzenes and naphthalenes. Runs were made at a temperature of lO50F. and 850F. using a wide spread in hydrocarbon residence time.
gases and to coke is much reduced. However, at total conversion levels of 82.6, 67.8 and 90.9 percent of the isobutylene, losses to undesirable products are l2.2l percent and the ratios of isobutane to butylene plus propylene range from l.l5 to 3.25.
Thus run 195 effected at a high temperature and short residence time supports the concept of the present invention where the hot freshly regenerated catalysts contact the C -C rich feed initially in either a separate riser reactor or in an initial portion of a riser reactor followed by gas oil cracking. On the other hand, run 196 supports that portion of the concept of this invention where previously used catalyst is contacted in a separate riser reactor or in a down-stream portion of a single riser reactor with a C -C rich gaseous hydrocarbon feed material or a feed rich in isobutylene. Thus in any of these arrangements, a faujasite conversion catalyst and particularly a Y" faujasite conversion catalyst has activity and selectivity for hydrogen transfer reaction and olefin cyclization reaction leading to the production of significant quantities of isobutane and aromatics.
Having thus generally described the method and means of the present invention and discussed specific embodiments related thereto, it is to be understood that no undue restrictions are to be imposed by reason thereof except as defined by the following claims.
1. In a process for converting hydrocarbons in the presence ofa faujasite catalyst, the improvement which comprises passing a fluid particle size faujasite conversion catalyst at an elevated conversion temperature to the lower portion of each of two separate riser conver sion zones,
passing a high boiling gas oil hydrocarbon fraction as feed to the lower portion of one of said riser conversion zones under conditions to form a catalyst- /oil suspension in the range of 4-20/1 at a temperature of at least 950F. which is passed through said riser conversion zone,
passing a low boiling hydrocarbon fraction rich in C and C hydrocarbons to the other of said riser conversion zones under conditions to form a catalyst- /hydrocarbon suspension at a temperature in the range of 700F. to 1100F. which is then passed through the second riser conversion zone at a hydrocarbon residence time within the range of l to TABLE Uni! Hopper (dense bed) Riser (dilute phase. steady state) Run No. ISOC- 193 194 l95 I96 I97 Temp., "F 1050 1050 1050 850 850 1' gas, sec. 46 22 7 8 l7 Cat/gas (wt/wt) 29 41 40 40 Conversion (NLB):
Unconv. butylene 5.4 8.7 17.4} 29.3 27.4] 3 I .7 9i |4.6
Propylene 3.3 4.] l 1.9 4.3 5.5
lsobutane 19.9 23.7 34.1 42.0 47.4
C,,+ gaso. 3.3* 4.3 l9.8 |3.8 17.3
Other C -gases 39.1 32.4 2.0 l6.8 2.5} 12.5 6.5} 20.6
Coke 29.0 26.8 8.8 10.0 14.1
No liquid trap used It will be observed from these data, that at the shorter 15 seconds,
residence time used for the riser conversion runs, cracking of isobutylene to lower molecular weight discharging a catalyst/hydrocarbon suspension from each riser conversion zone and separating the sus- 7 pensions into a relatively dense fluid catalyst phase and a hydrocarbon phase.
recovering the hydrocarbon phase separated from each conversion zone as a combined phase of hydrocarbons, and
stripping the dense fluid catalyst phase separated from each conversion zone.
2. The process of claim I wherein freshly regenerated faujasite type zeolite catalyst is passed to each riser conversion zone.
3. The process of claim 1 wherein freshly regenerated catalyst passed to the hydrocarbon conversion zone processing a gas oil boiling hydrocarbon fraction is then cascaded at a temperature within the range of 850F. to 1OS0F. after stripping to said conversion zone processing a low boiling C -C hydrocarbon fraction.
4. The process of claim 1 wherein catalyst particles separated from the conversion zone processing the high boiling hydrocarbon fraction are cascaded in part to a separate adjacent stripping zone provided for stripping a separate bed of catalyst separated from the low boiling hydrocarbon conversion zone before regeneration thereof.
5. The process of claim 3 wherein the catalyst separated from the high boiling hydrocarbon conversion zone is stripped in a separate stripping zone at an elevated temperature before use thereof in the low boiling hydrocarbon conversion zone at a catalyst to hydrocarbon ratio in the range of 5-40/1 at a temperature selected from within the range of 800F. to about l050F. for a hydrocarbon residence time in the range of 5 to 15 seconds and catalyst separated from the low boiling hydrocarbon conversion zone is stripped in a separate stripping zone at an elevated temperature before passage to catalyst regeneration.
6. The process of claim 1 wherein the catalyst separated from each conversion zone is passed to a common stripping zone before passage to catalyst regeneratlol'l.