US2369523A

US2369523A - Catalytic conversion of hydrocarbons

Info

Publication number: US2369523A
Application number: US418005A
Authority: US
Inventors: Belchetz Arnold
Original assignee: MW Kellogg Co
Current assignee: MW Kellogg Co
Priority date: 1941-11-06
Filing date: 1941-11-06
Publication date: 1945-02-13
Anticipated expiration: 1962-02-13

Description

Feb. 13, 1945. A .BELQHEWl 2,369,523

CATALYTIC CONVERSION OF HYDROCARBONS ATTORNEYS Feb. 13, 1945. A. BELCHETZ CATALYTIO CONVERSION OF HYDROCARBONS 4 Sheds-Sheet 2 Filed NOV. 6, 1941 Feb. 13, 1945.

A. BELCHETZ CATALYTIC CONVERSION OF HYDROCARBONS Filed Nov. 6, 1941 4 Sheets-Sheet 3 FIG. 3

ARNO/.0 BELCHETZ INVENTOR Feb. 13, 1945.

A. BELCHETZ CATALYTIC CONVERSION OF HYDROCARBONS Filed Nov. 6, 1941 4 Sheets-Sheecl 4 ARNOLD BELCHETZ INVENTOR ATTORNE Patcnted Feb. l3,- A1,945 l UNITED STATES PATENT OFFICE mais wenn, new Gardens. N. r., anni tu The M. W. Kellogg Company, Jersey City, N. J., a corporation of Delaware Claims.

l'heupresentinvention in its speciilc aspectsl relates to'the catalytic conversion of hydrocarbons into lighter-hydrocarbons of lower-boiling point orshydrocarbons. otherwise altered in structure.

oertain'of' itsv aspectsV the invention is particularlyconcerned with hydrocarbon conversionsl -plates particularly an improved process involving a conversion stage wherein vapors of the hydrocarbons undergoing treatment are contacted in-a conversion zone with particles of a suitable catalyst: anda regeneration step wherein the used catalyst particles, after separation from the gaseous'conversion products, are contacted with an oxygen-containing gas in a regeneration zone under suitable conditions to regenerate them by burning olf deposited carbonaceous material.

This method of catalytically converting hydrocarbons has certain advantages arising particu Application November 6, 1941, Serial No. 418,605

larly out of the relative intimacy of contact which Y taining the temperature of the regeneration rey action within desired limits and in 'such manner as to eliminate the carbonaceous deposit on the catalyst to the desired extent without overheating of the catalyst.

The present application is a continuation-inpart of my copending application Ser. No. 343,222, illed'- June 29, 1940. and the latter application in turn being a continuation-impart of my copending application, Serial No. 274,670 led May 20, 1939, now U. S. Patent 2,253,486.- In the latter application, I have disclosed several modiilcations of'processes for controllingthe temperature of the catalyst regeneration zone within desired limits by the charging of catalyst to the regeneration zone in a predetermined and controlledre1ationship with respect'to certain of the variable operating conditions involved including the quantity of feed charged to the conversion zone. The present application is directed particularly to the modifications disclosed in said copen'dins application involving the additional feature of controlling the temperature of the re.. generation zone by cooling a portion of the catalyst withdrawn from the regeneration zone in a zone distinct from the conversion zone and returning the cooled catalyst tothe regeneration zone for the purpose of temperature control therein.

The foregoing and various other features and advantages of the invention will be apparent from the follow' ng detailed description thereofv given with vreference to the appended drawings which illustrate suitable process flow and arrangement of apparatus for its practice.

Fig. 1 illustrates a suitable arrangement of ap'- paratus and process flow involving the feature of introducing cooled regenerated catalyst to the regeneration zone for temperature control therein asapplied to the catalytic conversion of high boiling hydrocarbons to low boiling hydrocarbons within the motor fuel boiling range.

Fig. 2 is a modified embodiment generally similar to Fig. 1 and involving the additional feature. of recycling used catalyst to the conversion zone.`

Fig. 3 is a modified form of process flow involving the feature of recycling cooled regenerated catalyst in a plurality of streams.

Fig. 4 is a modified embodiment generally similar to Fig. l and involving the feature of maintaining the velocity of vapor ilow within certain preferred ranges.

Referring to Fig. 1, a suitable feed, for example a cracking stock such as avaporized petroleum gas oil heated to a suitable temperature, is introduced through transfer line I2 leading from a. conventional pipe still or other suitable source not illusl, trated. The feed vapors in transfer line I2 may. be advantageously combined with a recycle oil fraction introduced through line I4, the combined streams passing to the conversion stage through line I 5. The oil passes through line I5 into pipe I6 constituting an extension of the conversion reactor I1. Hot preheated catalyst is supplied from collecting or surge drum I8 by helical feeder I9 and mixed with the oil in pipe I 6. I'he upper surface of the body of catalyst in drum I8 is indicated by dotted line 60. Suflicient steam or other suitable gas to initially disperse the catalyst as dischargedfrom feeder I9 is preferably introduced through line 20. Steam or other suitable gas may be supplied in greater quantities through line 2l when required. Operating conditions such as the ratio by weight of the catalyst to fresh feed stock may be maintained and regulated as set forth in detail hereinafter. 'I'he gaseous mixture of feed stock, catalyst and steam fiows upwardly Vthrough reactor Il during which flow conversion or cracking of the oil to the de sired extent occurs.

Reaction products pass from the top of reactor I'I to a suitable separator system to separatethe catalyst from the vaporous reaction products. That shown comprises a settling tank 2i in which the maior proportion of the suspended catalyst is separated, the separated catalyst owing by gravity from the bottom of tank2i through conduit 22 to the top of a steam stripper tower 23 and the vapors containing a relatively small fraction of ilne catalytic material are withdrawn at the top through line 24. These vapors pass through line 24 to a suitable separator such as a cyclone type of dust collector 2l wherein most of the remaining suspended catalyst is separated and then passed to tower 2l by gravity flow from the bottom of the separator through line 2l.

Tower 2l serves to displace hydrocarbon vapors contained in the voids between the particles oi' catalyst and is suitably provided with bailles 2I to effectively expose the catalyst passing downwardly therethrough to the displacing action of a countercurrently flowing current of steam introduced at the basel of the tower through line 2l. Steam containing the oil. vapors displaced from the .catalyst is withdrawn from the top of the tower through line 29 and combined with the vapor stream vfrom tank 2|. Used catalyst falls from the bottom of tower 23 into a surge drum 3l. The gaseous suspension withdrawn from separator 2l containing the gaseous conversion products, steam and a small residual amount of used catalyst, is passed through line 2| to `a, suitable type of fractionator l2k wherein a low-boiling fraction such as gasoline and fixed gases may be separated from the high-boiling products such as light and heavy cycle gas oils. In the fractionator l2 the conversion products may, for example, be fractionated into a lowboiling fraction including gasoline and fixed gases withdrawn as overhead product from the fractionator through line J3, an intermediate product such as light gas oil withdrawn as a side cut through line 34, and a residual high-boiling fraction such as heavy recycle gas oil withdrawn through line 35, cooled in cooling coil 8|, and pumped to storage through line Il.

In the bottom of fractionator l2 suitable means may be provided for separating residual catalyst present in the vapors introduced through line 3i. As shown, these means comprise a line 31 through which a portion of the high-boiling fraction withdrawn through line 3l is returned to the fractionator over baiiies I6 which dei'iect the vapors from line 3| into intimate contact with the returned fraction which consequently adsorbs or scrubs out residual catalyst present in the vapor. After passing over baiiies 3l the scrubbing liquid with the residual catalyst suspended therein collects in the bottom of fractionator 32 from which it is withdrawn through line Il and pumped by pump 4I into line I4 for utilization as a recycle oil, as previously described.

Used catalyst is fed from drum I0, in which the upper surface of the catalyst mass is indicated by dotted line 42, by screw feeder 4I to pipe 42. A further stream of catalystv is introduced into line 42 from line 8l, the latter stream consisting of cooled and previously regenerated catalyst, the quantity thus introduced being preferably regulated as hereinafter described. A suitable quantity of air is introduced to line 42 through line 43 supplementedV if desired by steam introduced through line 45,l The mixture of used and recycled catalyst-is vcarried through line 42 ance with the embodiment shown in Fig. 1, the

stream of regeneration gas carrying the regenerated catalyst upon leaving the regeneration zone 44 is split into two streams, one portion being by-passed through valve Ii to line 10, and the other portion passing through valve 80 to separator 48. In `separator' or settling tank l4B most of the catalyst present in the stream introduced thereto is separated and flows downwardly therefrom through conduit 4'I to surge drum I8. The separated gases containing a small residual amount of catalyst fines leave separator 48 at the topthrough line 4B and pass to a cyclone type of dust collector 49, wherein substantially complete separation of the catalyst is effected. Thevseparated catalyst from collector 49 then ilows downwardly through line 50 and is combined with the initiallyl separated catalyst in drum i8 from which it is fed to the conversion stage by feeder I9. Drum I8 and feeder I9 may be suitably provided with heat insulation material to obviate loss of heat by the regenerated catalyst in its passage therethrough.

40 In the practice of m'y invention lthe quantity and temperature of regenerated catalyst recycled to the regeneration zone through line III may be suitably determined by the application of a generalized formula. `In fixing the ratio (r), by

a weight, of the total catalyst charged to the regeneration zone relative to the fresh gas cil charged to the conversion zone for any particular oil and extent of conversion required, this ratio is determined under the other given or fixed operating conditions concerned in a manner adapt ed to assure the presence of the cool recycled catalyst in sufficient amount to absorb a, definite minimum amount of the heat of regeneration by the application of the following formula:

In this formula r represents the catalyst-to-oil weight ratio as defined above; the symbol C, the fraction of the gas oil or other hydrocarbon charged,.converted to coke or carbonaceous material and deposited on the catalyst during the conversion; H, the heat of combustion of the coke liefe entering the regeneration zone represented by the weighted average temperature of used catalyst and cooled recycled catalyst-'entering the regeneration zone; and K, a coeilicient having a lower limit determined by the extent to which expedients otherl than the heat absorption capacity of the catalyst may be employed to dissipatethe heat of regeneration.

The quantity of catalyst recycled to the regeneration zone and the temperature thereof is preferably controlled in such manner that the value' of K in the above equation is in excess of 0.2 and preferably in excess of 0.5, and may suitably be about 0.8 or even higher.

Ther preferred quantity and temperature of recycled catalyst may be expressed directly by a modiaction of the above basic equation as follows, f

CHKRS(T1- Tal In the above equation'the symbol R represents the ratio by weight of the regenerated catalyst charged to the conversion zone to the weight ol oil charged to the same zone; T3, the temperathrough which a cooling medium is circulated through lines 13 and 1,4. The cooled suspension of ue gas and catalyst then passes through line 15 into a separating zone 16 wherein ilue gas is taken overhead through line 18 and separated catalyst is collected in the lower portion as indicated by line 11. Any catalyst remaining in the I iue gas withdrawn overhead may be sepa-v rated by a cyclone separator 19 or similardevice and returned through line 8| to zone 16.' Catalyst is fed from zone 16 by means of a screw conveyor 82 and suspended in air supplied through line 84, and carried through line 83 to transfer line 42 wherein its is mixed with used catalyst supplied by screw conveyor 4 I Any type of catalyst suitable for effecting the desired conversion may be employed in the practice of my invention.- For the conversion or cracking of high-boiling fractions such as gas oil to low-boiling fractions such as gasoline, I re-l gard cracking catalysts of the alumina-silica" type as especially suitablepthis term being inclusive of cracking catalysts such ascertain types of activated clays or synthetically produced mixtures'or compounds of aluminal and silica. The circulated catalyst may'be composed entirely of the active catalyticvrnaterial and is ypreferably "predominantly composed thereof.4 Howeventhe active catalystmay be associated withk supports,

of the catalyst relative traten m Fig. 2, uns is similar to that of mg. 1 in that it involves the recyling of cooled regenerated catalyst to the regeneration zone, but also involves additional novel featuresincluding the ,recyling of catalyst to the conversion zone without intervening regeneration thereof.

Regeneration gas containing regenerated catalyst suspended therein is withdrawn from regenerator 44' through line 88 and split into two streams. one stream passing through recycle line 10' controlled by valve 1| and the other stream passing to the conversion side of the system by line 81 controlled by valve 80'.. The recycled catalyst passing through line 1.0 as in the case of the embodiment shown in Fig. l, is returned to the initial part of the regeneration zone after cooling and separation from the flue gas carrier by means similar to those shown in Fig. 1 and designated by corresponding lprimed reference numerals. A

The iluid suspension of regenerated catalyst passing through line 81 may be passed directly to 4settling drum 88through valve 89 and line 90, o1' allora portion thereof may be by-passed through valve 9| and line 92 through a suitable cooler or heat exchanger 93 through which a suitable cooling or heating fluid is circulated through lines 94 and 95. In passing through exchanger 93 the temperature of the catalyst is brought to that most suitable for the particular conversion reaction concerned. The fluid suspension passes from line 90 into settling drum 88 wherein most of the catalyst is separated from the flue gasy and settles into the bottom of the drum. Flue gas bearing a residual amount of suspended catalyst passes overhead from drum 88 through .line 9B into a suitable separator such as cyclone separator 91 wherein substantially complete separation of the residual catalyst is elected and the separated catalyst returned from the bottom of the cyclone through line 98 to drum 88. l

. From drum 88 the regenerated catalyst is fed into a stripping tower 99 by suitable feeding means |00. In tower 99, the catalyst flows downwardly over baffles |0 countercurrentlyto a current of steam introduced through line |02. The stripping steam bearing with it any oxygen-containing gases previously entrained with the regenerated catalyst passes overhead through line |03 into cyclone |04 wherein any catalyst particles entrained with the steam are separated and pass from the bottom of the cyclone to an accumulator drum |05 and are then returned to the bottom of tower 99 by suitable feeding means |06. The stripping operation serves to remove any oxygencontaining gases present in the regenerated cata# lyst which might be detrimental in the subsequent conversion reaction. f

Stripped catalyst is fed from the bottom of tower 99 by suitable feeding means |01 into line |08 wherein it is suspended in the vapors of the feed stock yundergoing treatment and the suspension introduced into the conversion reactor |09. Additional catalyst may be added at this point by means of feeding means |0. Reaction products are withdrawn from the top of reactorv ,|09 through line andpassed to a ysuitable `settling drum |"|2vwherein mostofthe suspended catalyst drops out of suspension 'into 'the bottom of the drum. The conversion product slpass overhead from drum ||2 through line |3and residualcatalyst ,is separated therefrom injcyclone [I 4: from whence vit is' returned to drum 1`| 2` through line |5.A The hydrocarbon yconversion products are line |50 and passed to a suitable fractionating system such as that indicated on Figure 1. From drum |I2 a portion of the used catalyst may be recycled to the conversion zone by feeding means I I without 'any intervening stripping operation, the proportionsintroduced into the reaction zone of regenerated catalyst from feeding means |01 and recycled catalyst from means ||0 being ad- `iusted to provide any desired activity of catalyst in the reactor. y

Used catalyst is fed from the bottom of drum I|2 into a suitable stripping system by feeding means i I5 at the same rate that regenerated catalyst is fed to the reactor by feeding means |01. The stripping system is similar to that described in connection with the stripping tower 99 and includes a stripping tower II'I and a fines recov ery system including cyclone |I8, accumulator drum 9 and return feeding means |20. In

`passing through tower II'I the used catalyst is stripped of hydrocarbons entrained therewith which pass out from the system with the steam by line |2|, and may be recovered therefrom by any suitable recovery means. Stripped used catalyst is fed from the bottom `of tower ||1 by suitable feeding means |22 and suspended in regeneration air introduced through line |23 and the suspen- `sion then passed through line |24 into the regenerator 44'.A Recycled catalyst may be introduced into the regeneration zone by means 82', the regeneration steps thereafter being similar to those described in connection with Fig. 1.

Referring to Fig. 3, this illustrates a modification of the regeneration system shown in Fig. 2, the distinctive feature being the recycling of cooled regenerative catalyst to the regeneration zone in a plurality of streams at spaced points in said zone. As in the case of Fig. 1 the regeneration gas bearing the regenerated catalyst is split into two streams, one passing through line I3| to the converslon'systein and the other through a recycle line |32, the quantity of suspension in each stream being controlled by valves |33 and |34, respectively. The suspension of regenerated catalyst passes through recycle line |32 into settling drum |35 `wherein most of the catalyst settles out into the bottom of the drum, and any residual catalyst carried out overhead from the drum by the flue gas is separated in a suitable cyclone separator |36 and returned to drum |35. Used catalyst from the conversion stage is supplied to the regeneration stage by suitable feeding means |38 and is suspended in part of the total air required for regeneration supplied through line |39, the quantity of air supplied at this point being controlled so that the combustion which occurs in zone A will bring the catalyst to a temperature approximating the maximum safe regeneration temperature when it reaches the point at which cool recycled catalyst is rst introduced. A plurality of streams of recycled regenerated catalyst is returned from drum |35 to the regenerator by means of piunps |40, |4I and |42 through lines |43, |44 and |45, respectively. Air is injected at the outlet of each of these pumps to convey the regenerated catalyst through coolers |46, |41 and |43, respectively. Using a plurality of streams as shown, theerecycled catalyst is injected into the regenerator at a series of spaced points so that each injection of the cooled catalyst will drop the temperature in the regenerator by only a relatively small amount. Air is preferably introduced with each stream of recycled catalyst in amount such that the catalyst will be approximately at the maximum safe regeneration temperature when it reaches the next catalyst injection point. By this means the burning of the coke is accomplished at a high temperature level approaching the maximum safe regeneration temperature throughout the regenerator, and with the result that the time required for coke combustion is decreased.v 'I'he diameter of the regenerator may be enlarged after any catalyst injection point as shown to increase its volume by an amount corresponding to air added at this point, thereby maintaining uniform velocity of flow. In addition to the flexibility of temperature control, this systemA has the added advantage that the injection of the cooled recycle catalyst will not drop the temperature in the regenerator to a point Where combustion of coke on the partially regeneratedcatalyst may cease.

In the practice of my invention, the upward velocity of the regeneration gas through the regenerator may be varied over a wide range with attainment of reasonably satisfactory results. For a given quantity of gas introduced, this gas velocity will be dependent upon the cross sectional area of the regenerator and varies inversely therewith. A range of gas velocity from about 1 to 25 feet persecond is regarded as satisfactory in most instances. At the higher order of velocities the catalyst particles are carried along with the gas at a speed somewhat lower but approximating that of the gas, and accordingly the period during which the catalyst particles are in the regenerator is approximately the same but somewhat greater than the period of contact of the gas molecules with the catalyst. Also, under such c0ndition the direction of movement of the catalyst particles upward through the regenerator is largely linear, as in the process flow of Fig. 3. Certain distinctive advantages are obtained by the prac tice of my invention under conditions wherein a relatively low upward velocity of the regeneration gas through the regeneration zone is maintained. for example, a. velocity of about l ft. per second, and generally velocities in the range of about 0.5 to 6 ft. per second and preferably within the range 0.5 to 3 ft. per second. These velocity ranges are especially desirable with powdered catalyst consisting of small particles indiscriminately sized and smaller than about microns. With widely different sized particles variation in these Velocity ranges may be desirable. The conditions and advantages of the invention as thus practiced .are illustrated by the process flow shown in FigA.

Referring to Fig. 4, catalyst particles such as a powdered cracking catalyst are introduced through the valve |89 of a catalyst standpipe IBI into a stream of the feed vapors traveling at a relatively high velocity through the reactor inlet line |52. Both the catalyst and vapors are heated v prior to their mixture in line |52 to a temperature suitable for the subsequent conversion. Vaporized feed may be supplied to line |52 by a transfer line |53 leading from a pipe still heater or other suitable source of hot vaporized feed stock. In certain instances, the hydrocarbon feed may be introduced through line |53 entirely or partially in the liquid phase and the necessary vaporization produced upon the mixture of hot catalyst therewith. Catalyst thus introduced is Picked up by the vapors and carried therewith through line |52 into a conical inlet I 55 in the lower part of reactor |56. Reactor |56 is a vessel in the form of a cylinder or other suitable shape, having a relatively great escasas 5 cross-sectional area compared with the crosssectional area of the vapor inlet line |52, and these relative proportions cause a corresponding reduction in the velocity of the vapors after their passage from inlet line |52 into the reactor |56. The velocity of the vapors in reactor |56 is preferably maintained relatively low and within such limits a8 previously given so as to produce a concentrated dense turbulent phase of the catalyst 10 mixture passing through pipe |56.

in this zone which state may conveniently be designated as uidized. This fluidized" condltion, in general, is'characterized by the relatively high concentration of catalyst measured in This condition is further characterized by the extensive turbulence or internal recycling" oi the catalyst particles throughout the reaction 'zone so that the temperature of the zone. regardless of whether the reaction involved is endothermic or exothermic tends towards uniformity throughout the zone and hence is characterized by the absence of a substantial temperature gradient. Also due to this extensive turbulence the particles tend to reach a'n average composition with respect to their carbon content throughout the zone regardless or Whether the reaction concerned is one involving deposition of carbonaceous. material or its removal. The level of the relatively dense iluidiz'ed phase is preferably maintained at the upper portion of the reaction zone as indicated by line |90.

The reactant vapors travel upwardly through the reactor in contact with the fluidized catalyst and during this period of contact undergo the desired conversion. Operating conditions in the reactor determined by variables such as the dimensions of the reactor, and the temperatures and rates at which reactant vapors and catalyst are supplied thereto, are maintained within such limits asto bring about the desired quality and extent of conversion.

The vaporous reaction products are withdrawn of the reactor into the conical outlet |51 of de-` creasing cross-sectional area wherein their velocity is progressively increased and then into an outlet pipe |68 of relatively restricted cross-sectional area compared with that of the reactor.

The vaporous conversion products mixed with spent catalyst -pass through the outlet pipe I 56 at a relatively high velocity into a settling chamber or collecting hopper |59- of such cross-sectional area that the velocity of the vapors therein is preferably of about the same order of magnitude but may be more or less than the vapor velocity in reactor |56. A baille |60 is preferably interposed directly in the path of the vapor mixture passing from pipe |56 whereby the mixture is directed laterally and downwardly thus functionving to propel catalyst particles present in the mixture out of the path of the vapor ow into a quiescent collecting zone deiined by the outer walls of the outlet cone |51 and outlet pipe |56 and the lower inner w'alls of the settling or collecting hopper |59. Catalyst thus separated is withdrawn through suitable means such as cataof the collecting zone. 'A `quantityoi catalyst is preferably left at all times insaid mue to maintain va level or catalyst therein at a substantial distance above the spent catalyst out 5 let opening as indicated by dotted line |62.

Vaporous conversion products are withdrawn from the upper part of the collecting hopper through line |63 mixed with a relatively small portion of the catalyst originally present in the Residual catalyst left in the vaporous conversion products leaving through line |61 is separated in a suitable recovery system such as cyclone separators or the like, and' may befreturned to the spent catalyst separated in chamber |59 through line |56.

-A surname stripping mediumswn as steam isA introduced through a line V|65 having suitable -vapor distributing means |66, in the bottom of theymass of catalyst in the collecting zone to strip'or .displace hydrocarbon vapors. absorbed A thereon or entrained therewith and to maintain the mass in an aerated flowable condition. While only one suchv line |65 for introduction of the stripping medium is shown, it is to be understood that any suitable number may be employed and be so distributed throughout the collecting chamber as to assure the required stripping and areating eilects. The quantity of stripping steam is preferably such that its velocity in the collectconversion products.

As illustrative of operating conditions suitably maintained in the conversion zone |56 in the cracking of high boiling hydrocarbons to gasoline, reference is made to the data-tabulated in o the following Table 1 which sets forth conditions suitable for -a large scale commercial unit for a given type of charging stock and capacity.

Table 1 4 Gas 011 feed (31.1 A. P. 1. -bb1./day- 10,000 Steam feed, lbs/hr 13,380 Reactor dimensions (a) ht.ft 28 Reactor dimensions (b) dia.ft. 15 Feed weight ratio of regenerated catalystto-oilin line 152 (R) .5 Reactor temperature, inlet cone 155- F.- 933 Reactor temperature (substantially throughout) F 900 Reactor pressure, inlet cone -l'vS--lbs/sli...

in. 13 Reactor pressure, outlet cone A15'llbs.,/ 'f

sq. in. Vapor velocity, inlet, ft./sec. 1.48 on Vapor velocity, outlet, ftJsec. 2.45 Ratio of weight of oil fed/hr. to weight of catalyst in reactor (w/lirJw) 2.6 Oil vapor, lcontact time- .-seconds .13.8 Catalyst time-seconds 290 Catalyst concentration. lbs/cu. It.; l f

(a) Inlet line 152 0.96 (b) Reactor 18 (c) Reactor outlet, line 15B 0.6

In conveying the spent catalyst from'the spent 7o ycatalyst collecting zone` to the 'regeneration zone lyst standpipe |6| opening into the lower' part 75 regeneration zone than the pressure maintained in the collecting zone, and a head of suitably aerated or iluldized catalyst is preferably maintained in the outlet standpipe |8| of a sumcient magnitude to balance or exceed this differential pressure. For this purpose spent catalyst flowing through standpipe |8| is maintained in a oondition in which it has the ilow'characteristics of a liquid by introducing in suitably regulated amounts an aerating medium such as steam through lines |61 at the bottom of and at othersuitably spaced points along the length of pipe IBI.

From the bottom of standpipe |8| spent catalyst is fed under the iniluence of the pressure head maintained therein and the pressure head provided by the mass of'- aerated catalyst in chamber |58 through a suitable feeding means such as a valve |68 into the regeneratox'` inlet line |69.

Spent catalyst thus introduced is mixed with air or other suitable carrying medium such as steam introduced into pipe |68 by line |18'. In case air isemployed, the quantity introduced is so controlled that the combustion of the spent catalyst in line |88 is not sumcient to raise the temperature of the catalyst beyond the maximum safe regeneration temperature.

The mixture` of hot spent catalyst and carrying medium flows through line |88 into an inlet cone |10 at the bottom of the regenerator I1| where aseasas suitable means H11 and "annular tcpipe m and distribuwr im, are provided in the lower portion of hopper I1! to introduce a suitable medium such as steam to strip and displace-'nue gas absorbed or entrained with the regenerated catalyst and maintain the separated catalystin an aerated owable state. As in the case ofjthe reactor a level of separated catalyst indicated by dotted line` |18 is preferably maintained lata substantial distance /above the catalyst outlet lines.

'Regenerated catalyst is withdrawn` from separator |14 in a split stream, a portion' being sent through regenerated catalyst recycle'line Ill, and .another portion through regenerated catalyst line |8| leading to the conversion or reaction system. Both catalyst outlet lines .|88

it meets and mixes with a stream of relatively Y cool recycled regenerated catalyst and air from cooler |12 and passes therewith upwardly through the regeneration chamber |1|. Operating conditions in the regeneration chamber or zone |1| are suitably maintained to provide a condition similar to that maintained in the reaction zone with respect to a fluidized condition of the catalyst. This condition similar to that maintained in the reactor is characterized by the relatively large concentration of catalyst and low gas velocity maintained in the regeneration zone. Also, as in the case of the conversion zone, a high degree of turbulence and "internal recycling vmay be maintained in the iluidized mass whereby its temperature and the average carbon content of the catalyst is substantially uniform throughout the reactor. The level of the relatively dense uidized phase is preferably maintained at the upper portion of the reaction zone as indicated by line |8|. During the course of the passageofthe spent catalyst through regeneration chamber |1| combustionof the carbonaceous deposit thereon is effected to the required extent at an elevated temperature maintained below the safe maximum regeneration temperature by means of the cooled recycled catalyst.

Gaseous regeneration products (flue gas) and regenerated catalyst pass from the upper part of the regenerator through an outlet |18 and into a. separator |14 similar in design and mode of operation to separator |58 described in connection with the reactor. The major portion oi' the regenerated catalyst is separated and collectedl in a. collecting zone'at the bottom portion of the regenerated catalyst collecting hopper |14, and the gaseous combustion products together with a relatively small amount of regenerated catalyst pass out overhead from chamber |14 through line |15 to a suitable recovery system. Catalyst recovered from the flue gas leaving through line |15 may suitably be returned to hopper |1I through line |16. V

vand |8|k are suitably pressure standpipes similar to standpipe |8| in that they are provided with means for introducing an aerating medium at suitable points along their length so as to maintain the catalyst flowing therethrough in a condition wherein it has the ow characteristics of a liquid, such means being lines |82 leading into recycle line |88 and lines |83 leading to catalyst outlet line |8|. The quantity of catalyst withdrawn/ and recycled through line |80 and the cooling thereof is controlled so asto maintain the temperature in regeneration zone |1| within required limits as may be determined by the application of the mathematical formulae pre viously Elven. l I

Regenerated recycle catalyst, is fed from the bottom of standpipe lll through a suitable' feeding means such as a slide valve |84 into an inlet line |88 leading to a heat exchanger or catalyst recycle cooler |12. Regenerated catalyst thus ilitrodueed is picked up by air introduced into line |85 through line |88, the quantity of air thus introdueed being sumeient together with any anintroduced through line |18' to effect combustion to the required extent in the regenerator |1I. From line |88 the mixture of air and regenerated catalyst passes through exchanger or cooler |12 wherein the temperature of the recycled catalyst is lowered to the required degree by indirect heat exchange with a cooling medium -circulated through the exchanger by lines |81 Table 2 I Spent catalystlbs./hr 632,840 Cooled recycled catalyst lbs./hr 1,750,000

Feed Weight ratio (R4-Ri) of Otal fed to revalues for the symbols utilized in the above ex-k.

generation zone-to-oil (r) 18.85 f

H, the heat of combustion of the carbonaceous deposit ln B. t. u.s 16,400

S, the specific heat of powdered alumina-silica cracking catalyst 0.22

Inlet temperature to regenerator by line |69 Temperature, Weighted average of mixture recycled and spent catalyst, F. through lines |80 and |69 (T2) 850 Temperature, regeneration chamber '(substantially throughout), F. and catalyst withdrawn through lines |8| and |80 (T1) 1,000 Regeneration dimensions: v

(a) Height, ft; 50 (b) Dia., ft 18 Regeneration velocity:

(a) Base 1.62 (b) Top 2.59 Air feed, lbs/hr 88,350 Catalyst concentration regenerator, lbs/cu. ft 20 Weight percent of coke based on oil feed (100 C.) 4.85 Coke percent by weight on spent catalyst 1.3 Carbon percent by Weight on regenerated catalyst (lines |80 and |8|) 0.7 Catalyst contact time, seconds 352 Pressure in regenerator, lbs/sq. in.:

(a) Inlet cone 16 (b) Outlet cone 9 Value of symbol K 0.75

about 1.3% to about 0.7% by weight ofthe catalyst.

In the above example it is to be noted that the value of K is maintained in excess of 0.5 and consequently exemplies the practice of the invention in accordance with the preferred range for this value. It willbe further apparent that the quantity and temperature of regenerated catalyst recycled to the' regeneration zone through line |80 pursuant to the above example conforms to the appli-cation of either of the two generalized equations given in the foregoing.

In accordance with the first generalizedr equation the feed Weight ratio (r) of the totalcatalyst charged to the regeneration zone relative to the oil charged to the conversion zone is determined by the following equation y ":Sw-Tal Substituting in the above equation for the symbols the numerical values utilized in the above example (the value given for T2 beingapproxv imated) gives the following:

sii/eh; .yf applying-:thelfcllovina 1,.

,-Substitutin thelabove eouation the numerical ample gives the following:

It is to be noted that regeneration is effected pursuant to the above example without employing the conventional expedients for controlling the temperature of the catalyst during regeneration such as the provision of cooling surfaces within the regeneration zone or dilution of the regeneration air with large quantities of an inert gas.

The maintenance of a definite minimum concentration of carbonaceous material on the catalyst as exempliiled by the above example, has important and distinctive advantages. It assists in the regeneration reaction since the rate of combustion is accelerated and more readily controlled by the presence of an amount of carbonaceous material in excess of that which is to be removed by combustion. The retention of residual carbonaceous material also makes it possible to discharge the regeneration combustion gas with a relatively low percentage or in some cases, entirely free of oxygen, and the gas is thus better adapted for use for various purposes. Also, in certain instances, particularly in catalytic cracking in the presence of alumina-silica type of cracking catalyst such as Super-Filtrol, the conversion reaction is facilitated by the presence of a small amount of residual carbon and in most instances the advantages obtained in regeneration `by the maintenance of a residual carbon concentration will outweigh the disadvantages if any, resulting in the conversion stage. The residual carbon concentration maintained may depart somewhat from that given in the foregoing example wherein a Super-Filtrol type of alumina-silica cracking catalyst was employed. Preferably, this permissible rangeis confined to about 0.5% to 2.0%, by Weight of the catalyst.

As an alternative, the process iiow shown in Fig. 4 may be modified to the extent of having line and/or line |8| connect directly with the regeneration zone at a point below the level |9| of the dense catalyst phase. By this arrangement all but a small portion of the regenerated catalyst is Withdrawn directly from the regeneration zone and only a relatively smallfquantity withdrawn overhead With the flue gas passing through line |15. In this alternative arrangement the high velocity outlet cone |13 may be omitted.

Although my invention is especially well exemplied and advantageous as applied to the catalytic cracking of high boiling hydrocarbons to lower boiling hydrocarbons within the gasoline boiling range, it may be applied with advantage to gas-solid contact processes generally and to other hydrocarbon conversions such as the catalytic reforming of naphtha fractions and to catalytic hydrocarbonv conversion reactions generally, as will be apparent to those skilled in .the art.

Fromthe foregoing it will, be apparent that the process therein described accomplishes the objects of my invention, and that various features thereof may be utilized to advantage either c onjointlyv or separately. i It-will further bereadily apparent to those skilledin the art vthat while the invention has been illustrated and described `Withrespect-to a: preferred operation and examples, and with reference` `to suitable.; apparatus for its. practice, the4 vinvention isynot- 4limited to. such exemplifications but may .variously be practiced and embodied within the scope of the claims hereafter made.

I claim:

1. A continuous process for the catalytic cracking of high-boiling hydrocarbons to low-boiling hydrocarbons within the gasoline boiling range which comprises contacting high-boiling hydrocarbons with a preheated powdered regenerated cracking catalyst at an elevated temperature in a catalytic cracking zone, continuously separating the used hot catalyst particles contaminated with carbonaceous material from the vaporous cracked products and introducing said particles while still at an elevated temperature to a regeneration zone, maintaining in said regeneration zone inan upwardly flowing stream of an oxygen-containing combustion-supporting gas an intimate dispersion including two components (l) the hot used catalyst particles thus intro duced and (2) other catalyst particles previously circulated through said regeneration zone and an extraneous cooling zone other than the cracking zone, in such proportions as to maintain the temperature in said zone within limits adapted to cause combustion of the carbonaceous deposit without undue impairment of the activity of the catalyst and at a substantially higher average temperature level than that maintained in the cracking zone, continually withdrawing regenerated catalyst particles and gaseous combustion products from said regeneration zone, commingling a portion of the withdrawn regenerated catalyst with said high-boiling hydrocarbons undergoing cracking thereby supplying said preheated catalyst, continually conveying a further portion of the withdrawn regenerated catalyst through a cooling zone other than the cracking zone and then injecting it into the regeneration zone to supply said (2) component whereby `the mixing of said components is effected in the presence of the oxygen-containing combustion-supporting gas, and maintaining the weight ratio (R1) of the (2) component thus cooled and returned to the regeneration zone tothe high--y boiling hydrocarbons fed to the cracking zone in conformity with the following equation wherein the symbol C represents the fraction of the high-boiling hydrocarbons feedconverted to produce the carbonaceous deposit on the catalyst during conversion; H, the heat of combustion of the carbonaceous deposit expressed in B. t. u.s per pound; K, a numerical coei`l`cient maintained at a value in excess of 0.2; R, the weight ratio of the regenerated catalyst introduced to the cracking zone to the high-boiling hydrocarbons fed to said zone; S, the speciilc heat of the catalyst; T1, the temperature of catalyst upon withdrawal from the regeneration zone; T3, the temperature of the used catalyst upon introduction to the regeneration zone; Ti, the temperature of the (2) catalyst component upon introduction to the regeneration zone.

2. A continuous process for the catalytic cracking of high-boiling hydrocarbons to low-boiling hydrocarbons within the gasoline boiling range which comprises contacting high-boiling hydrocarbons with a preheated powdered regenerated cracking catalyst at an elevated temperature in a catalytic cracking zone, continuouslyv separating the used hot catalyst particles contaminated with carbonaceous material from the vaporous cracked products and introducing said particles ina gaseous suspension while still at an elevated temperature to a regeneration zone, maintaining in said regeneration zone in an upwardly flowing stream of an oxygen-containing combustionsupporting gas an intimate dispersion including two components (1) the hot used catalyst particles thus introduced and (2) other catalyst particles previously circulated through said regeneration zone and an extraneous cooling zone other than the cracking zone, in such proportions as to maintain the temperature in said zone within limits adapted to cause combustion of the carbonaceous deposit without undue impairment of the activity of the catalyst, continually withdrawing regenerated catalyst particles and gaseous combustion products from said regeneration zone, commingling a portion of the withdrawn regenerated catalyst with said high-boiling hydrocarbons undergoing cracking, continually conveying a further portion of the withdrawn regenerated catalyst through a cooling zone other than the cracking zone and then injecting it into the regeneration zone to supply said (2) component whereby the mixing of said components is effected in the presence of the oxygen-containing combustion-supporting gas, and maintaining the weight ratio (Ri) of the (2) component thus cooled and returned to the regeneration zone to the high-boiling hydrocarbons fed to the cracking zone in conformity with the (following equation wherein the symbol C represents the fraction of the high-boiling hydrocarbon feed, converted to produce the carbonaceous deposit on the catalyst during conversion; H, the heat of combustion of the carbonaceous deposit expressed in B.t.u.s. iper pound; K, a numerical coeiiicient maintained at a value in excess of 0.2; R, the weight ratio of the regenerated catalyst introduced to the cracking zone to the high-boiling hydrocarbons fed to said zone; S, the specific heat of the catalyst; T1, the temperature of catalyst upon withdrawal from the regeneration zone; T3, the temperature of the used catalyst upon introduction to the regeneration zone; T4, the temperature of the (2) catalyst component; upon introduction to the regeneration zone.

3. A process as defined in claim 2 wherein said coeiiiclent K has a value in excess of 0.5.

4. A continuous cyclic catalytic process for the conversion of hydrocarbons by an endothermic reaction which comprises contacting hydrocarbons undergoing conversion in the vapor phase with a powdered preheated regenerated catalyst at an elevated temperature in a catalytic conversion zone, continuously separating the used hot catalyst particles contaminated with carbonaceous material constituting a by-product of the reaction from the vaporous conversion products, introducing said particles while still at an elevated temperature to a regeneration zone, maintaining in said regeneration zone in a stream of an oxygen-containing combustion-supporting gas as intimate dispersion of suspended catalyst including two components (1) the hot used contaminated catalyst particles thus introduced and (2) other catalyst particles previously circulated through said-regeneration zone and a cooling zcne other than the conversion zone and extraneous to and maintained at a substantially lower temperature than the regeneration zone, the two components being in such proportions as .urea

to maintain the temperature throughout the regeneration zone within limits adapted to cause rapid combustion of the carbonaceous deposit without undue impairment of the activity of the catalyst and at a substantially higher average level than the temperature maintained in the conversion, zone, continually withdrawing regenerated catalyst'particles and gaseous combus. tion products :from said regeneration zone, commingling a portion of the withdrawn hot regenerated catalyst with the hydrocarbons undergoing conversion thereby supplying said preheated catalyst and endothermic heat of reaction, continually conveying a further portion of the withdrawn regenerated catalyst through said cooling zone and then injecting it into the regeneration zone tosupply said (2) component whereby the suspension and mixing of said components is eiected in the presence of the oxygencontaining combustion-supporting gas.

5. A continuous cyclic catalytic process for the conversion of hydrocarbons by an endothermic reaction which comprises contacting hydrocarbons undergoing conversion in the vapor phase with a powdered preheated regenerated catalyst at an elevated temperature in a catalytic conversion zone, continuously separating the used hot catalyst particles contaminated with carbonaceous material constituting a by-product of the reaction from the vaporous conversion products suspending said particles in a gas while still at an elevated temperature and introducing the suspension into a regeneration zone, maintaining in saidv regeneration zone in an upwardly ilowlng stream of an oxygen-containing combustion-supporting gas an intimate dispersion of suspended catalyst including two components (1) the hot used contaminated catalyst particles 'ture throughout theregeneration zone within limits adapted to cause rapid combustonof the carbonaceous deposit without undue impairment of the activity 0l.' the catalyst and at a substantially higher average level than the temperature maintained in the conversion zone, continually withdrawing regenerated catalyst particles and gaseous combustion products from said regeneration zone, commingling a portioniof the with-- drawn hot regenerated catalyst with the hydrocarbons undergoing conversion thereby supplying said preheated catalyst and endothermic heat of reaction, cooling a further portion of the withdrawn regenerated catalyst in said cooling zone and suspending the cooled catalyst in a gas, mixing the suspension of cooled catalyst with said: suspension of used hot contaminated catalyst particles to produce said intimate dispersion in the regeneration zone.

ARNOLD Bmcimrz.