US3161582A

US3161582A - Two-stage hydrocarbon conversion process

Info

Publication number: US3161582A
Application number: US218210A
Authority: US
Inventors: Henry P Wickham
Original assignee: Pullman Inc
Current assignee: Pullman Inc
Priority date: 1962-08-15
Filing date: 1962-08-15
Publication date: 1964-12-15
Anticipated expiration: 1981-12-15

Description

Dec. 15, 1964 H. P. WICKHAM TWO-STAGE HYDROCARBON CONVERSION PROCESS Filed Aug. 15, 1962 I4 STEAM- 24 -REc. GAS

HYC. FEED 8 INVENTOR.

HENRY P. WlCKHAM BY 636W ATTORNEY MM? AGENT United States Patent C) 3,161,582 TWO-STAGE HYDROCAREON (IONVERSEQN PRQCESS Henry ll Wickham, Glen Head, NY, assignor, by inesne assignments, to Pullman incorporated, a corporation of Delaware Filed Aug. 15, N62, Ser. No. 218,210 '7 Claims, (Cl. Edd-74) oils with a minimum formation of carbonaceous material.

To eifect the desired conversions, the depth of cracking of the oil during the cracking operations depends primarily upon the so-called conversion or severity factor which in any given system with a given catalyst is primarily a function of the temperature and space velocity and secondarily a function of the activity of the catalyst. Numerous investigations and experience in practice have shown that the practical temperature range in many fluid catalytic cracking processes lies within the range of for example about 900 to 950 F. Using such temperatures the space velocity has been adjusted to give a conversion corresponding to the optimum gasoline yield. However, during such conversions the coke production rises slowly at first and then more steeply as the depth of conversion is increased. Since the advent of fluidized solid cracking systems for conversion of a hydrocarbon reactant the engineers have employed every technique within their skill to develop simple and effective methods as Well as apparatus for utilizing this principle. In addition, to achieve their objectives, the engineers have been constantly striving to develop simplified systems of high thermal eificiency which would enable them to obtain an optimum product distribution of the feed undergoing conversion. This has been accomplished in a varying degree in a large variety of hydrocarbon conversion systems. For instance, it is known that certain hydrocarbon feed materials and certain fractions of a given feed are best treated under somewhat diiferent processing conditions depending on the product desired in order to achieve the optimum conversion thereto. Various suggested methods have been proposed wherein dilferent feed stocks or fractions thereof are separately cracked. This procedure, which is practical in certain cases, but very expensive to carry out, has been extended to cracking of a cycle stock under relatively more drastic conditions in a separate vessel. It has also been suggested to effect the catalytic cracking with numerous modified methods of operation for handling the powdered catalyst and/or oil to be cracked. While many of these suggested procedures have resulted in a marked improvement over prior art systems and were commercially utilized, nevertheless these too have not been completely satisfactory to the engineer or refiner par ticularly from the standpoint of eificiency of operation, the cost of the apparatus or conversion equipment to install and maintain, as well as product distribution.

As a result of an extensive investigation many of the difficulties inherent in prior art designs have been overcome by the process and apparatus of the present invention and consequently an improved method and apparatus for the conversion of hydrocarbons into desired products is now available to the producer for commercial use.

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An object of this invention, therefore, is to provide an improved process and apparatus for converting hydrocarbons to desired products in the presence of finely divided contact material.

Another object of this invention is to provide an improved process and apparatus for handling finely divided contact material for converting high-boiling hydrocarbons to desired lower boiling hydrocarbons.

A further object of this invention is to provide an improved method and means for obtaining desired conversion of high-boiling hydrocarbons to gasoline and other desired products.

A still further object of this invention is to provide an improved apparatus design for handling finely divided contact material in a two-stage conversion system.

Other objects and advantages of this invention will become apparent from the following description.

Accordingly, the present invention provides a process for the catalytic cracking of hydrocarbon oil feed materials boiling essentially above gasoline boiling range products into desired gasoline and lower boiling products by the process which comprises passing a fresh hydrocarbon feed material to be cracked upwardly through a first high temperature, high velocity reaction zone in substantially the vapor phase, passing simultaneously through said high velocity reaction zone in contact with said oil feed a freshly re enerated finely divided solid conversion catalyst at a rate sufficient to form a relatively dilute suspension of catalyst in the oil vapors and at a rate such that the contact time between the vapors and the catalyst in said first reaction zone is held within a desired range to eifect the desired degree of conversion of the hydrocarbon feed, the linear velocity in said zone being above the highest linear velocity at which the catalyst can separate into a dense pseudo-liquid phase condition and the temperature in said high velocity reaction zone being above the temperature employed in a second reaction zone, passing the suspension comprising conversion products, insufficiently converted hydrocarbons and finely divided catalyst from the upper portion of said first reaction zone into a dense fluidized bed of catalyst in a second conversion zone substantially above the bottom thereof to separate entrained catalyst from the hydrocarbon-catalyst suspension discharged from the first conversion zone and cool said hydrocarbons to a desired temperature prior to passing the hydrocarbons into the dilute catalyst phase above the dense catalyst phase in the second conversion zone, the catalyst passed from said first reaction zone into the dense fluidized bed of catalyst in the second reaction zone being at a temperature sufficiently elevated to provide the major portion of the heat requirements of said fluid bed of catalyst in said second reaction zone, passing a hydrocarbon feed more refractory than the feed to said first conversion zone into the lower portion of and upwardly through said second conversion zone in contact with said dense fluidized bed of catalyst at a velocity sufficient to maintain the catalyst in a dense fluidized condition in said second conversion zone, removing hydrocarbon conversion products of the first and second conversion zones from the upper portion of the dense phase of catalyst in said second conversion zone, separating entrained finely divided catalyst from said products, removing hydrocarbon conversion products of said first and secondreaction zones from the upper portion of said second conversion zone substantially free of entrained catalyst, pas's'- ing contaminated catalyst from the dense catalyst phase in said second conversion zone to an adjacent stripping zone, stripping catalyst in said stripping zone, passing stripped catalyst to a regeneration zone and passing regenerated catalyst to the inlet of said first conversion zone.

In accordance with the improved process of the present invention, a suspension of hydrocarbon vapors and cat- 3 alyst at a temperature in the range of from about 900 F. to about 1050 F., preferably from about 975 F. to about 1000 F., is passed upwardly through a first transfer line high velocity catalytic reaction zone. The suspension of catalyst and reaction products is discharged directly from the upper portion of said first reaction zone into a dense fluidized catalyst bed substantially above the bottom thereof maintained in the second reaction zone, the point of discharge being sufiiciently below the upper level of the dense catalyst phase in the second reaction zone to not only reduce the temperature of the vaporous products discharged from the first reaction zone to a temperature below about 1000 F., usually from about 900 F. to about 950 F., prior to entering the dilute catalyst phase above the dense catalyst phase, but also to separate entrained catalyst from the hydrocarbons discharged from the first reaction zone. The separation of catalyst is facilitated by changing the vertical velocity components of the suspension in the first conversion to substantially a horizontal or downwardly sloping component as the suspension is discharged from the first reaction zone into the dense bed of catalyst maintained in the second reaction zone. As previously stated, the point of discharge should be sufiiciently below the upper meniscus of the dense bed to effect the desired cooling, which point will vary depending upon the reaction temperatures employed in the first reaction zone. This may be controlled by varying the height of the dense catalyst bed in the second conversion zone. The cooling of reaction products discharged from the first high temperature high velocity cracking stage reduces the temperature of the products suificiently to prevent overcracking and at the same time substantially reduces excessive temperatures in the dilute catalyst phase above the dense catalyst phase attributed to the reaction products of the first cracking stage. Accordingly applicants method of operation has at least a three-fold improvement in that overcracking of the products of the first conversion zone is minimized, separation of catalyst from the products of the first conversion zone is greatly facilitated, high temperature reaction products are cooled to a desired temperature level prior to entering the dilute catalyst phase to avoid damage to the reactor vessel and heat recovery is maintained at a high desired level, thereby increasing the etficiency of the process. Controlling the reaction product temperature is particularly important where unlined reactor vessels and cyclones are employed. This, of course, amounts to a substantial savings in the initial costs of construction, as well as maintenance of the reactor. Catalysts contaminated with carbonaceous material and vaporous reaction products from the first and second cracking stages are removed from the second cracking stage and passed to a suitable stripping zone, the upper end of the stripping zone being in open communication with the upper portion of the second reaction zone. While the stripping zone has been shown to be confined within the vessel or second reaction zone, it may also be outside of the vessel, if desired. The contaminated catalyst is passed downwardly through the stripping zone in a relatively dense pseudo-liquid con dition, usually more dense than that employed in the second reaction zone, countercurrent to a suitable stripping gas such as steam, hydrogen, methane, ethane, propane or mixtures thereof introduced near the bottom of the stripping zone which strips entrained vaporous hydrocarbon products from the catalyst. The temperatures employed in the stripping zone may be the same as, above or below the temperature employed in the second reaction zone. The stripped catalyst is passed downwardly from the bottom of the s ripping zone as an elongated confined relatively dense stream through a catalyst standpipe to a dense fluidized catalyst bed maintained in the regeneration zone positioned beneath the second reaction zone and encompassing the lower portion of said first reaction zone. In the regeneration zone carbonaceous material contaminating the catalyst as a result of the bydrocarbon conversion reactions is removed by burning in the presence of an oxygen-containing gas under suitable controlled conditions of the order of from about 1050 F. to about 1150 F. to regenerate and heat the catalyst to an elevated temperature of from about 1050 F. to about 1150 F., preferably about 1100 F. The hot regenerated catalyst is then passed to a suitable stripping zone within the lower portion of the regeneration zone for removal of regeneration gases. The freshly regenerated catalyst is passed from the regenerated catalyst stripping zone to the inlet of the first reaction zone for recirculation through the process as hereinbefore described.

In the preferred apparatus of the present invention the reactor and regeneration chambers are so positioned and interconnected within a unitary vessel as to provide substantially vertical transfer of catalytic material through conduits of minimum length. This is also particularly advantageous since it provides a system of desired heat retention or high thermal efiiciency and permits circulation of catalyst within the vessel at desired pre-selected temperature levels and at a rate sufiiciently high to provide the desired catalyst to oil ratio in each contact zone. In general, the cracking reactions for which this invention is particularly applicable permits transporting the hot freshly regenerated catalyst material at a temperature of from about 900 F. to about 1050 F., preferably about 975 F. at a superficial linear velocity of from about 30 to about 60 feet per second upwardly through said first transfer conduit reaction zone. At such velocities, provisions for decelerating the catalyst suspension discharged from the first cracking zone and separation of conversion products therefrom is provided by the present invention, as Well as to sufficiently reduce the temperature of the products discharged from the first stage cracking prior to coming in contact with the vessel walls or cyclones employed in the dilute catalyst phase separation zone. By discharging the hydrocarbon catalyst suspension from the first cracking stage into the dense fluidized bed of catalyst maintained in the second reaction zone below the upper meniscus thereof the temperature of the reaction products of the first conversion stage is reduced below 1000 F., prior to passing the products into the dilute catalyst phase. In addition, separation of the cat alyst from the conversion products of the first stage isgreatly enhanced by deflecting the catalyst outwardly and downwardly from the horizontal into the dense phase catalyst bed. This is accomplished 'to a large extent by employing what is commonly referred to as a bird cage or a deflecting bafile positioned at the outlet of the first cracking zone. The bird cage consists of a capped or closed end conduit being a plurality of elongated vertical slots approximately 1 /2 feet long, positioned around the periphery of the discharge end of the transfer line cracking conduit. The capped end of the conduit prevents the suspension from passing vertically upwardly through the dense fluidized bed of catalyst above the discharge outlet. The deflecting battle when used is placed above the open discharge end of the transfer line cracking zone or conduit and is usually spaced apart thereupon equal to about 1 /2 times, but may be from 1 to 3 times, the cross sectional area of the transfer line cracking conduit. Although this defleeting baffle may be of any shape which will change the direction of flow of the suspension to an outward direction or substantially a horizontal direction, the preferred shape of the bafile in cross-section is a gull-winged shape. These arrangements for deflecting the suspension have a particular advantage in that the catalyst vertical velocity component is transferred to a substantially horizontal component which in effect ejects the catalyst into the dense fluidized bed of catalyst maintained in the second reaction zone, surrounding the discharge outlet of the transfer line cracking zone and also prevents excessive attrition of the catalyst in the system. Furthermore, this facilitates reducing the velocity of the catalyst for its separation from the hydrocarbon products of the first cracking stage. By operating in this manner the catalytic material from the first cracking stage may be discharged into the dense fluidized catalyst bed wherein hydrocarbon reactant or vapor superficial linear velocity of from about 0.5 to about 3.0 feet per second, preferably from about 1 to about 2.5 feet per second are employed.

As previously indicated herein, discharging the hot catalyst from the first cracking stage into the dense bed of catalyst in the second cracking stage below the upper level or meniscus thereof, but above the bottom thereof is particularly advantageous for recovering available heat for use in the dense phase catalyst bed of the second conversion zone. The second cracking stage or conversion zone containing a dense fluidized bed of catalytic material is generally operated at a temperature lower than that employed in the first reaction zone which will be optimum for the particular feed being treated. This, however, may be varied over rather wide ranges depending upon the degree of severity desired and may be of the order of from about 50 to about 100 degrees less than that employed in the first reaction zone. By virtue of the fact that a much larger quantity of catalytic material is utilized at a lower temperature, the time of contact of the hydrocarbon feed with the catalyst in the second conversion zone is of much longer duration than employed in the first reaction zone (about 1 to 2 second) and usually is from about to about seconds longer. Accordingly the catalyst residence time in the second conversion zone is much longer and this may be referred to as a soaking type of catalytic cracking. That is to say, under the conditions employed in the second cracking stage a more refractory feed is desirably converted under lower temperature conditions for a longer time of contact than employed in the first cracking stage. The products of reaction for the first cracking stage and those from the second cracking stage are combined, entrained catalytic material is separated from the combined reaction products in the dilute catalyst phase of the second reaction zone and removed at a desired low temperature in the range of from about 850 to about 950 F. The catalyst which becomes contaminated with carbonaceous material and volatile reaction products in both cracking steps is withdrawn from the dense catalyst phase and passed into a stripping zone, preferably confined within the vessel or second reaction zone and separated from the second reaction zone by a substantially vertical transverse partition having a plurality of catalyst transfer slots located in the baffie below the outlet of the first cracking zone. The upper end of the stripping zone is in open communication with the dilute phase of catalyst in the second reaction zone for passage of stripped products and stripping gas into the dilute phase.

The improved process and operating technique employed in the present invention desirably provides a system in which the quantity of catalyst in the conversion zone is substantially less than that maintained in the regeneration zone. This is of particular importance wherein it is desired to maintain a catalyst of substanitally high activity in order to carry out the selective cracking as practiced in accordance with the present invention. Consequently and because of the method of operating the respective conversion zones, the zones may be of reduced cross-sectional area with respect to the regeneration zone. In general, it is desirable to operate the process of the present invention such that the regenerator contains from about 1.5 to about 6 times as much catalyst on a weight basis than the catalyst contained in the conversion zones and preferably from about 2 to 3 times on the same basis.

The apparatus to be used for the purpose of this invention contains in addition to the conversion chambers and regeneration chamber as hereinbefore discussed, suitable conduit means for withdrawal of the catalyst from the dense fluidized bed in the regeneration zone. For

this purpose a suitable well or stripping chamber, generally cylindrical in shape and open at its upper end is provided in the lower portion of the regeneration chamber extending upwardly from the bottom thereof to which regenerated catalyst is passed prior to introduction to the inlet of the first transfer line cracking conduit. The stripping well employed in the regeneration chamber provides many advantages in the operation of the system in that the well not only prevents passing contaminated catalyst to the inlet of the first cracking conduit before it has been properly regenerated, but also precludes by virtue of the catalytic pressure head developed within the well, the passage of regeneration gases to the inlet of the cracking conduit or passage of hydrocarbon feed material into the regeneration chamber. Generally this Well may be from about 2 to about 10 feet in height or from about 10 to about percent of the total height of the regenera'tor chamber. Another preferred aspect of the apparatus design of the present invention is in positioning the regenerated catalyst withdrawal well in the central portion of coaXially within the regenerator chamber. This location of the withdrawal well is particularly advantageous in not only providing better circulation of the catalyst within the catalyst bed, but it also provides for a more uniform withdrawal of regenerated catalyst from the catalytic bed.

Still another important apparatus feature of this invention resides in the location of the stripping chamber adjacent to and within the second conversion chamber. This location of the stripping chamber which exists as a segmental well within the second conversion chamber is formed by means of a substantially vertical transverse bafile member. Such construction is not only simple, efiicient and effective, but lends itself to substantially uniform Withdrawal of the contaminated catalyst from the second conversion chamber, thereby minimizing the danger of forming a stagnant portion of contaminated catalyst in the second conversion chamber. The contaminated catalyst as hereinbefore described is withdrawn through suitable withdrawal slots provided in the bafiie with the slots in the battle member positioned at least six inches below the outlet of the first cracking conduit, but substantially above the hydrocarbon inlet to the second cracking chamber. The contaminated catalyst withdrawal slots in the bafile member should be located at a point such that there is not less than about two feet of the dense fluidized bed of catalyst above the slots. In addition to these withdrawal slots, a suitable withdrawal means which may be opened or closed as desired is provided at the lower end of the battle for use in Withdrawing catalyst from the second conversion chamber, particularly when the unit is shut-down.

A standpipe or substantially vertical conduit extends downwardly from the bottom of the stripping chamber to the lower portion of the regeneration chamber having a suitable plug valve control for transfer of contaminated catalyst to the regeneration chamber.

The present invention is particularly applicable for catalytically cracking high-boiling hydrocarbons either of the same or different boiling range, for example, residual oils, reduced crudes, gas oils, cycle oils, etc. The present invention is particularly adaptable for contacting fresh feed in the first transfer line conversion stage or relatively dilute phase cracking stage and a recycle stock in the second or dense fluidized catalytic conversion stage. The amount of recycle stock returned to the reactor, together with any slurry material returned thereto, may be substantially equal to the amount of fresh feed. Accordingly, the cooling effect of the recycle feed is generally of the same order as the cooling effect of the fresh feed stream so far as the catalyst is concerned. Therefore, with the regcnerator operating at about 1120 F. and supplying catalyst at this temperature to the first cracking step, the mixture of fresh feed and regenerated catalyst will be of the order of about 1060 F. when the body of the catalyst in the second cracking step is about 900 F. or even 930 F., when contacting the catalyst with recycle stock. It is to be understood, however, that these temperatures may be considerably varied depending upon the rate of catalyst circulation, feed preheat and ratio of catalyst to oil employed in each reaction stage. The temperature Spread between stages is effected particularly by the amount of recycle used with respect to the amount of fresh feed. The cracking of fresh feed is etiected at an appreciably higher temperature than the cracking of cycle oil in the second stage and this higher temperature cracking step is particularly desirable because there is generally high-boiling material to be cracked in the fresh feed which would not vaporize upon contact with the catalyst at lower temperatures and would, therefore, cause additional load on the regeneration system. The cycle oil, on the other hand, has been vaporized before and is more suitably cracked at reduced temperatures over a longer period of time. The cracking in the dilute phase or first conversion zone will take place with catalyst of relatively higher activity than the catalyst in the second conversion zone and for a shorter time of contact. The contact time between the hydrocarbon reactant and catalyst in the first cracking step will be of the order of from about 1 to about 2 seconds, whereas the contact time in the second conversion zone under less severe temperature conditions will be appreciably longer, of the order of about 3 to about 20 seconds, preferably from about 5 to about seconds. The catalyst employed in the process and apparatus of the present invention may be selected from a wide variety of catalytic cracking material either naturally occurring or synthetically prepared and is usually of a siliceous nature which contains from about 75 to about 99 percent silica with the remainder selected from one or more than one of the following suitable promoters, such as alumina, boria, magnesium, zirconia or combination thereof. However, it is also within the scope of the present invention to employ a catalytic material consisting primarily of alumina with lesser percentages of activating material to obtain a selective cracking of different feed material which may be introduced thereto. Generally the cracking reactions effected in the process of this invention are carried out at a temperature of from about 700 to about 1050 F., more usually from about 850 to about 1000" F. That is to say the conversion temperature employed in the first conversion zone is usually at a temperature of about 100 degrees higher than the temperature in the second conversion zone. Applicants process is particularly important not only from the standpoint of controlling the severity of cracking, but also in controlling the carbon deposition on the catalyst within predetermined desired limits for optimum effectiveness in each cracking stage. This, however, does not mean that the temperature employed in each cracking stage may not be considerably varied since this will depend upon the type of feed to be treated in each conversion zone, feed preheat and the product desired. The process of the present invention is particularly advantageous since it enables one to carry out a high temperature cracking step in low temperature designed apparatus. Generally the apparatus of this invention is designed to handle temperatures less than about 950 F. in the second hydrocarbon conversion chamber to eliminate use of expensive heat resistant liners in this chamber. This also reduces the costs of the cyclone separators employed in the second conversion chamber. This is of particular advantage to the consumer since it results in a substantial saving in initial apparatus cost as well as maintenance thereof throughout extended use.

The pressures employed within the vessel are selected to facilitate transfer of catalytic material from one zone to the other. The pressure employed may vary from about 1 atmosphere to about 50 p.s.i.g more usually from about 5 to about 25 p.s.i.g. The weight space velocity measured as pounds of oil charged to each reaction zone per pound of catalyst present therein is usually of the order of about 0.25 to about 100, depending upon the particular reaction stage being considered. It is preferred in the first reaction stage, to maintain the weight space velocity Within the range of from about 3 to about 15, whereas in the dense fluidized catalyst stage it is preferred to maintain the weight space velocity in the range of from about 0.5 to about 10. The relative ratio of catalyst to oil on a weight basis may vary from about 1 to about 30, generally the catalyst to oil ratio is about 5 to about 20.

As hereinabove discussed, the catalyst as a result of the cracking reactions becomes contaminated with carbonaceous material which must be periodically removed by regeneration with an oxygen containing gas, for example, air at a temperature which may vary from about 1050 F. to about 1200 F., and at a pressure in the order of about 1 atmosphere to about p.s.i.g. In order to effect regeneration of the catalyst, air or a suitable oxygencontaining gas is passed upwardly through the bed under carefully controlled temperature conditions of about 1150 F. to remove the carbonaceous material by burning, thereby heating the catalyst. The thus heated catalyst is then employed in the process to supply a large part or the major portion of the heat for the endothermic cracking reactions to be effected therein.

As can be seen by referring to the drawing, the contact chambers for effecting applicants improved process are confined within a single substantially vertical vessel with the chambers so positioned within the vessel that the catalyst may be transferred within the apparatus substantially vertically through suitable transfer conduits. This unitary apparatus not only minimizes the length of catalyst transfer conduits and reactor chamber size, but also provides a system of high thermal efiiciency as a result thereof. Furthermore, the particular apparatus arrangement minimizes catalyst attrition as well as erosion of equipment due to the substantially vertical movement of finely divided catalyst within the vessel.

In order to more clearly define applicants process and apparatus by way of example, reference is now had to the accompanying drawing which is a diagrammatic illustration in elevation of an arrangement of apparatus used to practice the present invention.

Referring to the drawing, a unitary vessel 2 is provided with an upper reaction zone 4 containing a dense fluidized bed of finely divided catalytic material having an upper level 60 and a lower regeneration zone 6 containing a dense fluidized bed of finely divided catalytic material having an upper level or meniscus 28, there being a dilute catalyst phase above each of the dense catalyst beds. Adjacent to the reaction zone 4 and confined within the vessel is a stripping zone 8 separated from said reaction zone by a substantially vertical batfie or partition member 10 having a plurality of catalyst transfer slots 12 therein for transfer of contaminated or spent catalyst from the reaction zone 4 to the stripping zone. The finely divided catalytic material contaminated with carbonaceous deposits and vaporous reaction products as a result of the conversion reactions is stripped of reaction products in the stripping zone at a temperature of about 900 F. by contact with a suitable stripping gas such as steam introduced to the lower portion of the stripping zone by conduit 14 through a stripping gas distributor ring 16. The stripping gas passes upwardly countercurrent to the downwardly moving relatively dense bed of catalyst to remove reaction products, which products and stripping gas pass into the dilute catalyst phase. The stripped finely divided catalytic material is then passed substantially vertically downwardly as an elongated confined relatively dense column of catalyst through conduit 18 to the lower portion of the regeneration zone 6. The stripped catalyst is discharged from the bottom of conduit 18 through a discharge outlet 20, the rate of catalyst discharged controlled by plug valve 22. The vertically movable plug valve which extends upwardly into and coaxially aligned with 9 the outlet 20 of conduit 18 is controllable in order that the quantity of catalyst discharged from standpipe 18 may be varied over a desired range. Regeneration gas such as air is introduced by conduit 24 to the lower portion of the regeneration zone and passes upwardly through a distributing grid or perforated bathe 26 into the dense fluidized bed of catalyst to maintain the catalyst in a relatively dense fluidized condition and regenerate the catalytic material by burning carbonaceous contaminants thereof, thereby heating the catalyst to a temperature of about 115 F. Positioned above the dense fluidized catalyst bed in the regeneration zone is a relatively dilute phase of catalyst wherein catalyst entrained in the flue gas is separated by settling and thereafter the flue gas is passed to a suitable cyclone separator 39 for removal of additional entrained catalyst fines from the flue gases prior to removal of flue gas by conduit 34. The finely divided catalytic material separated from the flue gas in the cyclone separator is returned to the dense bed of catalytic material in the regeneration zone by dipleg 36. Regenerated catalytic material at a temperature of about 1150 F. is passed from the dense catalyst phase downwardly into a circular well 40 defined by wall 42. It is to be noted that the wall of the well adjacent to the outlet of conduit 18 is extended above the outlet a substantial distance in order to minimize the tendency of the contaminated catalyst discharged from conduit 18 and not sufliciently regenerated from passing into the well. The regenerated catalyst is passed downwardly in the well 4-0 countercurrent to stripping gas such as steam introduced to the bottom of the well by conduit 44 through stripping gas distributor rings 46. The fluidized catalytic material in the well by virtue of its pressure head causes finely divided catalyst to pass to the inlet of the catalyst riser conduit for conversion of hydrocarbon therein as hereindescribed. The stripping gas employed in the stripper well removes regeneration gases from the catalyst before passing to the inlet of the riser identified as 56 and also prevents hydrocarbon feed from bypassing the riser and into the regeneration zone. The riser 56 of the present invention functions not only as a means of transferring hot regenerated catalyst from the lower portion of the regeneration zone to the upper conversion zone 5, but it is also used as the first stage transfer line high temperature cracking zone. A hydrocarbon feed preheated to about 600 F. in a preheater not shown is introduced by conduit 48 to a hollow stem vertically movable plug valve 52. Steam may be admixed with the hydrocarbon feed, if desired, by conduit 50. In any event, the hydrocarbon feed with or without steam introduced to plug valve 52 which extends into and is substantially in concentric alignment with the inlet 54 of riser 56 picks up finely divided regenerated catalyst at substantially the temperature employed in the regeneration zone and the mixture is passed upwardly as a relatively dilute catalyst phase suspended in oil vapors at a temperature of about 975 F. through the reactor riser 56 at relatively severe cracking conditions and discharged into the dense fluidized catalyst bed below the upper meniscus thereof maintained in the second cracking zone 4 positioned above the regeneration zone. Suflicient dense fluidized catalyst is maintained above the discharge outlet 58 of the riser to reduce the temperature of the reaction products of the first cracking stage to a temperature not exceeding about 950 F. and separate catalyst from hydrocarbon products. Thereafter the hydrocarbon products pass into the dilute phase of catalyst existing above the dense catalyst bed phase. The conversion products and entrained catalyst from the first stage cracking zone are deflected outwardly into the dense catalyst bed through slots 58 positioned around the periphery of the discharge end of the first cracking stage or riser 56. The products of reaction of the first cracking stage are separated from entrained catalyst as hereinbefore discussed, and the products pass upwardly into the dilute catalyst phase prior to entering a cyclone separator 62 for removal of entrained catalyst fines. The reaction products substantially free of finely divided catalytic material are then removed from the upper portion of the reactor by conduit 64 and passed to suitable recovery equipment (not shown). The separated finely divided catalyst collected in cyclone separator 62 is returned by dipleg 66 to the dense catalyst phase in reaction zone 4. In conversion zone 4 a preheated cycle oil feed material is introduced to the lower portion of the dense fluidized catalyst bed at a temperature of about 600 F. by conduit 68 to distributor nozzles '70. The cycle oil hydrocarbon feed, which may be a liquid or partially vaporized is passed upwardly through the dense fluidized catalyst bed under less severe cracking conditions at a temperature of about 900 F. to convert the feed to desirable reaction products. Provisions are also made for introducing steam by conduit 72 and distributor rings 74 to the lower portion of the dense fluidized catalyst bed beneath the hydrocarbon feed inlet to prevent defluidization of catalyst material below the hydrocarbon feed inlet to the reactor. Products of this second conversion stage pass upwardly through the dense fluidized catalyst bed, are commingled and recovered with the products of the first cracking stage.

TABLE I Fluid Catalytic Cracking, Virgin Gas Oil [55.0 vol. percent conversion, 900 F., 8.13. 100 catalyst] Fresh Dry (3 Light Heavy Deeant Feed Coke Gas Butanes Gaso.* Gas Gas Oil Oil Oil Vol. percent 12. 5 43. 6 20. 5 19. 0 3. 0 B.p.s.d 2, 000 6, 970 3, 280 3, 040 480 API 59. 0 28. 0 26.0 10. 0 LbJGal. 4. 09 6.184 7. 387 7. 481 8. 328 G3,l /H1 3, 500 12, 198 .5, 740 5, 320 840 Lb. /Hr 17, 140 75, 430 42, 400 39, 800 7, 000 Wt. percent Analysis of total C4s Analysis of Inert-Free Dry Gas Comp 0411 1041110 nOiHm Total Comp. Wt. LbJHr.

' percent Vol. percent 53. 0 36. 0 11 0 100. 0 H2 1. 2 160 1, 060 720 220 2, 000 CH4... 15.0 1, 960 5. 04 4. 4. 87 4. 90 (12114.- 8. 5 1, 1, 855 1, 260 385 3, 500 02115.. 13. 3. 1, 740 9, 350 5, 920 1, 870 17, C3H6 37. 2 4, 870 03:58 24. 8 3, 240

Total HG 100. 0 13, 080

*Approximately 430 F. ASTM End Point Gasoline.

TABLE II Fresh Dry 05+ Light Heavy Decant Feed Coke Gas Butanes Gaso.* Gas Gas Oil Oil Oil Vol. percent 46. 1 21. 7 13.6 3.0 B.p.s 7, 382 3, 472 2,176 480 e. 27. 5 5.0 10. 6. 184 7. 410 7. 529 8. 328 12, 918 6, 076 3, 808 840 Lb./Hr 79, 300 45, 020 28,670 7, 000 Wt. percent Analysis of total Cis Analysis of Inert-Free Dry Gas Comp 04H; iCiHm nGiH Total Comp. Wt. Lb./Hr.

percent Vol. percent 56. 0 33. 2 10. 8 100.0 1.1 180 691 225 2, 080 15. 3 2, 510 4. 70 4. 87 4. 91 9. 5 1, 560 1, 209 394 3, 640 13. 1 2,150 5, 680 1, 920 17, 870 38. 7 6, 340 22. 3 3, 660

Total HG 100.0 16, 400

*Approximatcly 430 F. ASTM End Point Gasoline.

Table I above presents the results obtained when practicing catalytic cracking in a typical dense fluidized catalyst bed reaction zone employing a temperature of about 910 F., wherein all of the feed to be converted is introduced to the lower portion of the catalyst bed.

Table II above presents the results obtained when practicing the improved method of the present invention, wherein a temperature of about 975 F. is employed in the riser or first high temperature cracking stage and a temperature of about 900 F. is employed in the dense fluidized catalyst bed or second cracking stage.

It can be seen when comparing the data presented above that Table 11 gives a higher conversion of the feed to gasoline products than obtained in Table I. Furthermore, not only is the gasoline yield higher at the same coke yield, but also quite unexpectedly, applicant obtained a higher yield of butylene and propylene than that obtained in a typical prior art system of Table I. This is of particular interest to the refiner sincei these products are desired as feeds in such processes as polymerization, alkylation and the production of butadiene.

Therefore, not only does applicants improved method provide increased yields of desired products, but there is also provided an improved method for the conversion of hydrocarbons whereby product temperatures are reduced to a level that construction and maintenance costs are reduced through elimination of expensive heat resistant liner material.

While the improved process of the present invention has been specifically described with respect to a unitary apparatus having an upper reaction zone and a lower regeneration zone, it is to be understood that it is within the scope of this invention to employ separate zones wherein the regeneration zone may be above, below or adjacent to the reaction zone as in a side-by-side hydrocarbon conversion system.

Having thus described my invention, it is to be understood that the invention is not to be limited necessarily to the specific examples which have been offered merely to illustrate the invention and that modifications may be made thereto without departing from the spirit thereof.

I claim:

1. A method for separating a high temperature suspension of hydrocarbon material and finely divided catalyst which comprises: passing said suspension as a confined stream at an elevated conversion temperature upwardly into the upper portion of a dense fluidized bed of catalyst maintained at a conversion temperature lower than that of said suspension and having a defined upper level, radially discharging said suspension from said confined stream as a plurality of separate streams into the upper portion of said dense fluidized bed of catalyst at a point substantially below the upper level thereof to retain suspended catalyst in said dense bed and to cool the hydrocarbon material separated therefrom in the upper portion of said dense bed, introducing a second hydrocarbon material into the lower portion of said dense fluidized bed of catalyst, and recovering converted hydrocarbon material of reduced temperature from the upper portion of said dense catalyst bed.

2. In a system wherein finely divided solid heat retentive material is continuously circulated through a reaction zone and a regeneration zone, the improved method of operation which comprises continuously withdrawing hot finely divided solids from said regeneration zone at a temperature of at least about 1000 F., mixing a first vaporous hydrocarbon reactant material at an elevated temperature with said hot solids and passing the same under elevated temperature conditions for conversion to desired products as a dilute suspension upwardly as a confined stream into the upper portion of a dense fluidized bed of finely divided solids having an upper meniscus maintained in a second zone at a lower temperature than the finely divided solids in said suspension, radially discharging said suspension into the upper portion of said dense bed and to cool the hydrocarbon material separated streams substantially below the upper meniscus thereof to retain the major portion of said suspended solids in said dense bed and to cool the hydrocarbon material separated from the suspension in the upper portion of the dense bed, introducing a second reactant material into the lower portion of said dense fluidized bed of solids below the point of introduction of said suspension and passing the same upwardly through said bed under lower temperature reaction conditions than employed in said suspension step and withdrawing reaction products from the upper portion of said dense bed of solids at a temperature below the temperature employed in said suspension conversion step.

3. The method of operating a multi-stage catalytic conversion system of the fluid type which comprises: regenerating contaminated catalyst in a regeneration zone thereby heating said catalyst, passing thusly heated catalyst upwardly as a suspension in a hydrocarbon feed material through a first confined conversion zone under conditions such that the temperature of the regenerated catalyst is reduced not more than about 100 F., discharging such suspension of catalyst and products of reaction at an elevated temperature from said first conversion zone into the upper portion of a dense fluidized bed of catalyst maintained at a temperature lower than the temperature of said suspension in a second conversion zone at a point substantially below the upper level thereof to separate catalyst from the reaction products of said first conversion zone and to cool the reaction products of said first conversion zone in the upper portion of said dense catalyst bed, and introducing a cycle oil into the lower portion of said second conversion zone for passage upwardly through said dense catalyst bed under catalytic conversion conditions to desired products.

4. A method for the conversion of hydrocarbons to lower boiling range products which comprises: passing a suspension of finely divided catalytic material and a first hydrocarbon reactant material upwardly through a firs-t confined reaction zone under elevated temperature conditions of about 1000 F. to effect partial conversion of said hydrocarbon reactant to the upper portion of a dense bed of fluidized catalyst maintained at a conversion temperature lower than about 950 F., discharging the suspension into the upper portion of said dense fluidized bed of catalyst at a point substantially below the upper level thereof to separate catalyst from reaction products of said conversion zone and to cool said reaction products in the upper portion of said dense fluidized catalyst bed, passing a second hydrocarbon reactant into the bottom portion of said dense fluidized catalyst bed and withdrawing the combined products of said first and second con version zones at a temperature below about 950 F. from the upper portion of said dense catalyst bed in said second conversion zone.

5. A method for converting hydrocarbon feed material which comprises: contacting freshly regenerated finely divided cracking catalyst with a hydrocarbon oil feed material in a first confined reaction zone maintained at a temperature in the range of about 975 F. and about 1000 F., passing thusly contacted regenerated catalyst and hydrocarbon oil upwardly as a suspension through said confined reaction zone to the upper portion of a dense bed of fluidized catalyst having a defined upper level and maintained at a conversion temperature below about 950 F., discharging such suspension of catalyst and products directly into the upper portion of said dense bed of fluidized catalyst at a point substantially below the defined upper level thereof such that catalyst is separated from reaction produc-tsand the reaction products are cooled to a temperature below about 950 F. in the upper portion of said dense bed before passing into a dilute phase of catalyst maintained above the upper level of said dense fluid bed of catalyst, and introducing a hydrocarbon feed material to the lower portion of said dense fluidized catalyst bed for passage upwardly under catalytic conversion conditions to obtain desired products.

6. A method for operating a multi-stage catalytic conversion system of the fluid catalyst type which comprises, regenerating catalyst contaminated with carbonaceous deposits obtained as hereinafter described by burning in a rating catalyst from products catalyst of said first conversion zone by discharging the suspension into the upper portion of a dense fluidized bed of catalyst maintained in a second conversion zone at a point substantially below the upper level thereof whereby heat is given up to the dense fluidized catalyst by the separated catalyst and products of said first conversion zone, separating products of said first conversion zone from said dense catalyst bed, passing a second hydrocarbon feed having a different boiling range from the feed employed in said first conversion zone upwardly through substantially the total dense catalyst bed under lower temperature conversion conditions than employed in said first conversion zone to effect conversion to desired products thereby further contaminating the catalyst, combining products of said first and second conversion zones, withdrawing combined products from said second conversion zone and withdrawing contaminated catalyst from said second conversion zone for passage to said regeneration zone.

7. A process for the catayltic cracking of hydrocarbon oil feed materials boiling essentially above gasoline boiling range products into desired gasoline and lower boiling range products which comprises passing a fresh hydrocarbon feed material to be cracked upwardly from the lower portion of a dense fluid bed of catalyst in a regeneration zone through a first high temperature-high velocity reaction zone in vapor phase in contact with freshly regenerated finely divided solid conversion catalyst at a rate suflicient to form a relatively dilute suspension of catalyst in the oil vapors and a time of contact sufiicient to efiect the desired degree of conversion of the hydrocarbon feed, the linear velocity employed in said first conversion zone being above the highest linear velocity at which the catalyst can separate into a dense pseudo liquid phase condition and the temperature of said high velocity reaction zone being above the temperature employed in a second reaction zone, discharging conversion products and finely divided catalyst from the upper portion of said first reaction zone into the upper portion of a relatively dense fluid bed of catalyst in said second reaction zone at a point substantially above the upper level thereof to separate entrained catalyst from the hydrocarbons discharged from said first reaction zone, the catalyst passed from said first reaction zone into the dense fluidized bed of catalyst in the second reaction zone being at a temperature sufficiently elevated to provide the major portion of the heat requirements of said second reaction zone, passing a hydrocarbon feed more refractory than the feed to said first reaction zone into the lower portion of said second reaction zone for cont act with said dense fluidized bed of catalyst at a velocity suflicient to maintain the catalyst in a fluidized condition in said second reaction zone, removing hydrocarbon conversion products of the first and second reaction zones from above the dense fluidized bed of catalyst in said second reaction zone, passing contaminated catalyst from the dense catalyst bed in said second reaction zone to an adjacent stripping zone, stripping catalyst in said stripping zone and passing stripped catalyst substan tially vertically downwardly as a confined stream to said.

fluid bed of catalyst in said regeneration zone.

References Cited in the file of this patent UNITED STATES PATENTS UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3, 161,582 December 15, 1964 Henry F. Wickham It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below Column 5, line 28, for "second" read seconds column 6, line 21, for "of" read or column 8, line 11, for "her'einabove" read hereinbefore column 10, line 45, for "ca talyst" read catalytic same column 10, TABLE I, under the heading "Butanes" line 4 thereof, for "4.09" read 4.90 column 12, line 57, strike out "dense bed and to cool the hydrocarbon material separated" and insert instead dense fluidized bed of solids assa p1ura lity of separate Si ned and ealed this 4th da of Ma 1965. (SEAL) g V b y y Attest:

ERNEST SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

7. A PROCESS FOR THE CATALYTIC CRACING OF HYDROCARBON OIL FEED MATERIALS BOILING ESSENTIALLY ABOVE GASOLINE BOILING RANGE PRODUCTS NTO DESIRED GASOLINE AND LOWER BOILING RANGE PRODUCTS WHICH COMPRISES PASSING A FRESH HYDROCARBON FEED MATERIAL TO BE CRACKED UPWARDLY FROM THE LOWER PORTION OF A DENSE FLUID BED OF CATALYST IN A REGENERATION ZONE THROUGH A FIRST HIGH TEMPERATURE-HIGH VELOCITY REACTION ZONE IN VAPOR PHASE IN CONTACT WITH FRESHLY REGENERATED FINELY DIVIDED SOLID CONVERSION CATALYST AT A RATE SUFFICIENT TO FORM A RELATIVELY DILUTE SUSPENSION OF CATALYST IN THE OIL VAPORS AND A TIME OF CONTACT SUFFICIENT TO EFFECT THE DESIRED DEGREE OF CONVERSION OF THE HYDROCARBON FEED, THE LINEAR VELOCITY EMPLOYED IN SAID FIRST CONVERSION ZONE BEING ABOVE THE HIGHEST LINEAR VELOCITY AT WHICH THE CATALYST CAN SEPARATE INTO A DENSE PSEUDO LIQUID PHASE CONDITION AND THE TEMPERATURE OF SAID HIGH VELOCITY REACTION ZONE BEING ABOVE THE TEMPERATURE EMPLOYED IN A SECOND REACTION ZONE, DISCHARGING CONVERSION PRODUCTS AND FINELY DIVIDED CATALYST FROM THE UPPER PORTIONOF SAID FIRST REACTION ZONE INTO THE UPPER PORTION OF A RELATIVELY DENSE FLUID BED OF CATALYST IN SAID SECOND REACTION ZONE AT A POINT SUBSTANTIALLY ABOVE THE UPPER LEVEL THEREOF TO SEPARATE EN-SUBTRAINED CATALYST FROM THE HYDROCARBONS DISCHARGED FROM SAID FIRST REACTION ZONE, THE CATALYST PASSED FROM SAID FIRST