US2641573A - Production of motor fuels from petroleum oils - Google Patents

Description

J. wElKART 2,641,573

PRODUCTION OF' MOTOR FUELS FROM PETROLEUM OILS June 9, 1953 Filed Nov. 50, 1950 Patented June 9, 1953 PRODUCTION OF MOTOR FUELS-FROM f l PETROLEUM OILS John Weikart, Cranford, N.'J., assignor 'to Standard Oil Development Company, a corporation of Delaware 'Applieation November' so, 195o, serial No. 198,252

11 Claims.

The present invention relates to improvements in the production of motor fuels and other valuable hydrocarbon products from petroleum oils by a process involving catalytic cracking of relatively high-boiling oils and naphtha reforming.

More specifically, the invention pertains to a combination cracking and reforming treatment wherein virgin petroleum oils boiling above the gasoline boiling range are catalytically cracked in dense phase fluid operation to produce cracked gasoline and higher boiling oils, and virgin naphtha mixed with at least a portion of the higher boiling oils formed in the catalytic cracking stage is reformed in the presence of a cracking catalyst suspended in the oil vapors subjected to reforming.

In conventional petroleum refining the crude petroleum is first distilled to produce various virgin distillate fractions which may be converted into motor fuels by suitable rening processes. Of these, catalytic cracking is the most important because it permits the conversion of most of the virgin distillate fractions boiling substantially above the motor fuel range into high octane number gasoline. Catalytic cracking involves an endothermic reaction in the course of which carbon is deposited on the catalyst whereby the activity of the catalyst is rapidly reduced. It is necessary, therefore, to supply substantial amounts of heat to the cracking reaction and to maintain catalyst activity high by carbon removal. These requirements have been met in the most efcient manner by the development of the so-called fluid catalyst technique wherein finely divided catalyst is continuously circulated between a cracking zone and a combustion-regeneration zone. In these two Zones the catalyst is maintained in the form of dense highly turbulent solid masses iiuidized by upwardly flowing gases and/or vapors to resemble boiling liquids. In the regeneration Zone the catalyst is regenerated by carbon combustion and simultaneously heated to a temperature above cracking temperature so that a substantial portion of the heat required in the cracking zone may be supplied as sensible heat of `hot regenerated catalyst continuously circulating from the regenerator to the reactor. It will be appreciated from the above that the production capacity of any given ud catalytic cracking plant is limited by its carbon burning capacity. rI his means that only as much feed stock may be cracked as will yield an amount of carbon not in excess of that which may be burned in a regenerator of given design. It also follows that the production capacity of suchv a plant is partly a function of the carbon-forming tendency of the feed stock, the production capacity being the lower, the stronger thecoking tendency of the feed. In the case of fluid type catalytic cracking, this situation vis further aggravated by the fact that excessive 4carbon build-up on the catalyst detrimentally affects the fluidization characteristics of the catalyst.

For these and other reasons, reduction of carbon formation is onerci the strongest desiderata in fluid catalytic cracking. One factor complicating the control of carbon formation within desirably low limits is closely connected with the fact that the cracking reaction yields,` in addition to motor fuel range and lighter products, substantial proportions of up to about 30-50% based on cracking feed, of higher boiling fractions such as gas oils and hea-vier materials boiling above 450 F. and up to 800 F. or higher. Most of these materials are of a considerably lower value than motor fuels. Their extensivefurther conversion into motor fuels is indispensable for a sound economical balance of the process. Recycle of most of these materials to the catalytic cracking stage has, therefore, been widely practiced. However, these relatively heavy cracked products generally called cycle oils constitute a cracking feed stock far inferior to virgin gas oils particularly with respect to carbon-forming tendencies, the latter beig the stronger, generally, the higher the boiling range of 'the cycle oil. The permissible amount of oil recycle is, therefore, limited again Furthermore, the capacity of the system for virgin gas oil rapidly decreases as the amount and boiling range of oil recycled increase.

In spite of these unfavorable aspects, extensive recycle even of the relatively heavy and most marginal cycle stocks has been considered indispensable in most commercial operations as the best and most economic method known for disposing of these materials without excessive losses in valuable motor fuels. It will be readily appreciated that any efcient method permitting a full utilization of the potential motor fuel value of these cycle oils, other than their recycle to the catalytic cracking stage, would greatly increase the virgin gas oil capacity of the system and would thus represent a substantial improvement. In some of its aspects the present invention pertains to an improvement of thistype.

It is, thereforefone lof the principal .objects of the invention to provide means for converting into valuable motor fuels cycle oils obtained ingp fluid-type catalytic cracking without recycling Other and more specific objects and advantages will appear from the description lhereafter 4in .Y

which reference will be made `fto the accompany@ ing drawing, the single figure of which is a fiow diagram illustrating a preferred .modification of I.

the invention.

It has been pointed out above that, of the distillates, only those boiling substantially in excess of about 450 F. are suitable lfor catalytic cracking. The virgin .motor fuel range jportion such as lightand heavy naphthas boiling Within the approximate range of 150450 F. are too refractory .to undergo appreciable-conversion at the conditions of catalytic .gas .o'il cracking. .As a matter of fact, 4care must be taken to exclude the `presence `of -these .low -octane .naphtha .fractions in the catalytic cracking .feed vas completely as practically feasible. NAny-:amount of such virgin .naphtha passing through the catalytic crack-ingstage .merelyfactsas a di-luent of .the Ihigh octane naphtha -produced by cracking, with respect to the octane rating of the total gasoline recovered from the cracking stage.l However, the virgin naphthas likewise require upgrading, particularly with respect to their octane rating to become useful as motor fuels .for .modern high compression engines. It is, therefore, common practice to subject Ythe virgin naphthasbo'iling within the approximate range of 15T-450 F. to a so-called thermal reforming treatment at relatively high temperatures of about`1000-'1'200 F., relatively high pressures of about v200`1,000 p. s. i. g., and relatively high throughputs 'of about 3-30 volumes of liquid feed per lvolume of reactor space per hour (v./v./hr.`).

It has now been found that the upgrading of virgin naphthas maybe combined with thedisposal of catalytic cycle 'stock ina 4highly `efficient manner 'so as to reduce or practically eliminate the oil recycle `requirements of fluid rcatalytic cracking 'processes without any loss in total highoctane lgasoline yield based on VYcrude and With a substantial increase in the 'virgin v'gas `o'il cracking capacity ofthe Ycatalytic cracking stage. .'In accordance with 'the present invention, fvirgin gas oil is 'subjected to fluid `catalytic cracking 'to produce-cracked naphtha and cycle"oils,a;t .least a portion of the .latter :is mixed `with virgin naphtha and suitable mixtures of -virgin naphtha with catalytic cycle stock, lso obtained, are subjected `substantially in the vapor phaseand in the presence of a .finely .divided cracking catalyst suspended ,in the Vvaporized oil mixtulie to a2 simultaneous naphtha reforming and cycle stock cracking treatment at temperatures of about 10001200 F., pressures of about 3D0-600 p. s. i. g. and throughputs of about 5-20 v./v./hr. Suitable proportions of naphtha and cycle oil in the mixtures subjected to this treatment fall Within the approximate ranges of 20-80 volume percent of naphtha and -20 volume percent of catalytic cycle stock, the naphtha concentration of the mixture being the higher, Within the range specified, the higher the boiling range of the catalytic cycle stock used. Steam may be added in amounts ranging from about 0 to about 80 mol percent in either stage of the invention, to improve product distribution and octane number of the gasoline. The amount of catalyst which may ."lrave :a particle size of v,about '10D-400 mesh or fsmaller may vvary from 4about 2 to about 30 lbs. of catalyst per liquid barrel of mixed feed.

While all fluid catalytic cracking products boiling above .themotor fuel range may be used `together with virgin naphtha in the combina- 4tion naphtha reforming-cycle oil cracking stage lof the invention, Athe' benefits derived from the fprocess .are the greater the less valuable the cycle oil for fluid catalytic cracking or for other purposes, i. e., the higher the boiling range of the cycle oil used in the combination reforming and cracking stage. For example, cracked products boiling between the motor fuel range and about 620 F. have normally -susbtantial value 'as :heating -.oil while the vscr-called light cycle oi1 boil` ing between about 620 and '700 may ybe recycled -to `the uid catalytic Cracking stage to fair advantage. However, the higher -lboiling products such as so-ca-lled :heavy rcycle -oils "are so Arich .in high molecular Tweight condensed aromatic's as to nbe :merely Aof vmarginal utility as a cycle stock for fluid catalytic cracking .operations. These -oils which may boil vbetween about 700 and `1100" F. are, therefore, .particularly suitable for the purposes of the invention. .Regarding the virgin naphtha, it is noted that the light cuts boiling up vto about 200 or 250 vvare not as readily susceptible to .improvements o'f their octane rating by reforming treatments of the type 'here involved, :as are the heavier cuts boilingffrom Aabout 200 or 250 F. up 'to about 450" F. Therefore, a 'preferred embodiment 'of theinvention provides for 'the use of mixtures of heavy naphtha boiling 'within lthe approximate range of .200450 F. 4with heavy iiuid catalytic cycle stock y'boiling `above about 700' F., in 'the combination naphtha reforming and cycle 'oil cracking 'stage of the invention. Preferred mixtures for this type of operation `contain 'aboutZO- 30 volume percent of -heavy cycle stock and 'Z0-80 volume percent of heavy naphtha. This ratio corresponds approximately to that 'at 'which heavy virgin naphtha and heavy vcycle stock are normally rproduced in .commercial .combination crude distillation and Viiuid 'catalytic cracking plants.

The catalysts used in the uid catalytic 'cracking stage 4and the combination virgin .naphtha reforming-recycle stock cracking stage of the invention'quite generally may be those known in thexart as crackingcatalystssuch as various synthetic Ior activated natural clays, particularly various composites of silica gel with alumina and/or magnesia, vwhich may contain certain activating constituents .such 'as boria or certain heavy metal oxides. An excellent 'catalyst for both process stages of .the reaction is a plural Synthetic. silica-alumina, gel combination of about 85-89 wt. percent of SiOz and 11-15 wt. percent of A1203. A catalyst of comparable quality consists of, say, 20-40 wt. percent MgO gel, vthe remainder being SiOz gel.

When operating in accordance with the present invention substantial improvements are secured over conventional recycling of cycle stock to uid catalytic cracking and over separate virgin naphtha reforming and catalytic cycle stock cracking under similar conditions, as willA appear from the experiments reported below.v

A heavy cycle stock obtained in a commercial uid catalytic cracking plant and virgin heavy naphtha were subjected to several upgrading treatments including once-through uid catalytic cracking of the cycle stock, high temperature,

high pressure, short contact time catalytic cracky ing, i. e., suspensoid cracking of the cycle stock alone, thermal and catalytic reforming of naphtha alone, and mixed feed suspensoid reforming and cracking of a cycle stock-naphtha mixture in accordance with the invention.

The heavy cycle stock was produced by uid catalytic cracking of an AEast Texas wide cut gas oil (5U-85% on crude) at 900 F. over natural clay catalyst at an average conversion to 430 F. end point gasoline of 49%. This heavy cycle stock which was used in the experiments had the following inspections:

Gravity, API 27 Aniline point, F. 178 Initial boiling point, F 544 End point, F. 874 Sulfur, Wt. percent 0.31 Carbon, wt. percent 0.13 Viscosity (Say. Univ. at 100 F.) sec. 63.0

The catalyst employed in all experiments was a commercial synthetic mixed gel SiOz-AlzOs catalyst consisting of about 87% SiOz and 13% A1203 brought to equilibrium activity by previous extensive use in a commercial fluid catalytic cracking plant. It was adjusted to a content of 80+ microns particles of about 30%.

The essential operating conditions and results 0f the catalytic cracking experiments carried out with heavy catalytic cycle stock alone are summarized in Table I below:

TABLE I Catalytic cracking of catalytic heavy cycle stock Once- Once-Through Plocess suspensoid b Operating Conditions:

Temperature, F al, 052 al, 075 975 Pressure, p. s. i. g 200 360 10 Steam, Vol. Percent 0 5 21. 9 Catalyst/Oil Ratio, lbs/bbl 10 10 9,300 Throughput 9 9 '31. 4 Product Distribution: Y

Gasoline (10 lbs. RVP, 430 F.

Vapor Temp), Vol. Percent 31.4 39. 6 31.2 Gas Oil (430660 F.) Vol. Percent 27. 0 17. 8 10. 8 Tal' (660 F.+), V01. Percent 3l. 1 24.6 23.0 Gas, Wt. Percent 10.0 15. 9 13. 8 Carbon, Wt. Percent 0. 5 0. 7 11. 9 Gasoline Inspection:

ASTM Motor O. N., Clear 67. l 70. 1 83. 5 CFR Research O. N., Clear 76. 4 79. 6 96. 3

l Maximum severity limited by cokin'g.

b Conditions for maximum gasoline yield.v

Volumes of cold oil per hour per volume of coil section maintained above 800 F.

d Pounds of 011 per hour per pound of catalyst:y

The above data show that once-through fluid cracking ofthe cycle stock at severe conditions suitable for maximum gasoline yield gives about the samefamount of gasoline as suspensoid cracking in the absence of steam, but less than suspensoid cracking in the presence of steam. The octane ratingsof the gasoline obtained by fluid cracking `is substantially greater than that obtained by suspensoid cracking. However, the excessive carbon formation of the fluid operation makes this method unattractive for commercial application.

Operating conditions and results of thermal and suspensoid catalytic naphtha reforming experiments are summarized in Table II. The naphtha used in these experiments was a Mid- C'ontinent-Louden mixed naphtha (150-400 F. boiling range).

TABLE II Reforming of naphtha alone Process Thermal Suspensoid Operating Conditions:

Temperature, F l, 050 1, 070 1, 050 1, 085 Pressure. p. s. i. g 800 8 8 800 Steam, Vol. Percent Catalyst/Oil Ratio 10 Throughput, v./v./hr 9. 5 10. 4 10. 4 9. 0 Product Distillation:

Gasoline (l0 lbs. RVP, 430 F.

V. T.), Vol. Percent 69. 3 73. 4 72. 6 66. Gas, Wt. Percent 19.1 18. 2 15.4 21. Carbon, Wt. `Percent 0.8 1. Gasoline Inspection:

ASTM Motor O. N., Clear 74. 0 72. 9 72. 4 75. CFR Research O. N., Olear 83. 6 81. 7 80. 0 85.

The data of Table II demonstrate that catalytic suspensoid reforming of naphtha affords no appreciable advantages over thermal naphtha reforming with` respect to gasoline yield and quality.

In the remaining experiments oil mixtures con- Gravity, APL. 4.9.5

Annine Point, F 119 Initial boiling point, oF 228 Final boiling point 397 Reid Vapor Pressure, p. s. i 0.2 ASTM Motor O. N., clear 41.0

CFR Research O; N., clear 42.2

Thev cycle stock was that used to obtain the data ofl Table I. The conditions and results of these experiments are summarized in column C of Table III below. The results obtained are compared with the total overall results for yields and gasoline qualitycalculated from segregated operations on l.the individual stocks as summarized in colums A and B of Table III. The

conditions of naphtha reforming of the segregated runs in columns A and B are typical for present daycommercial operation. The conditions used for segregated cycle stock cracking are those required for maximum gasolineiylelds.

TABLE III Processing of cycle stock:` and naphtha by various methods Prnce A B C segregated Thersegregated Thermal Naphtha Remal Naphtha Reforming and Susforming and Fluid pensoid Cycle. Cycle Stock Mixed Feed Suspenscid Stock Cracking' Cracking Naphtha Reformmg and Cycle Stock Crack- C l C l ing N aphtha yc e Naphtha. yc e Reform- Stocl Reform- Stock Crack Cracking ing mg ng Process Conditions: y

Temperature, F 1, 050 1,075 1,050 975 1, 055 1, 077 1, 096 Pressure, p. S i g-- 750 360 750 l() 350 350 350 Steam, Vol. Percent.. 21.9 T- Catalyst/Oil Ratio, lb bbl. 9, 300 10 10 l0 Throughput, v./v./hr 10 9 l0 1 1. 4 9 9 9 Product Distribution (Yields based on feed to process indicated): L

Gasoline (10 lbs. RVP, 430F. V. T.)

Vol. Per Cent....l 4,8- 7 48. 7 42.4 42. 4 48. 2 52. 7 44. 1 Bottoms (430 F. V. TJ, V01. Per Cent--- 32.9 32. 9 26. 4 26. 4 37. 3 31.7 32. 6 Gas, Wt. Per Cent 15.8 15. 8 14.1 14. 1 12. 5 14. 0 18.4 Carbon, Wt. Percent 0. 5 0.5 9. 2 9. 2 0. 6 0.6 0. 6 Gasoline Inspection:

ASTM Motor O. N'., 72. 6 72. 6 80. 4 80. 4 69. 8 72.2 74. 4 CFR Research O. N., Clear 83.2 B3- 2 93.4 93.4 79.2 81.8 84. 6

From the data of column C of Table III it appears that the gasoline yield passes through a maximum at about 1077 F. A further increase in temperature merely cracked gasoline to gas without affecting the yield of product boiling above 430 F. A temperature range of about 10701085 F. is, therefore, preferred for this stage of the invention. When operating at these intermediate temperatures, gasoline yields of 'or exceeding 53 vol. per cent may be obtained at a Research Octane number level of about '82. This result is clearly superior to that of the best segregated process including suspensoid cracking of cycle stock alone even in the presence of steam as is shown in column A of Table III. The reasons for this improvement in results are not fully understood. It can not be explained by the effect of the catalyst on the naphtha because thermal and s'uspensoid catalytic naphtha reforming give equivalent gasoline yield/octane relationships as shown by the experiments of Table II. However. it is possible that the naphthenic hydrocarbons in the naphtha may donate hydrogen by means of hydrogen transfer reactions to the high boiling condensed heavy hydrocarbons of the cycle stock and promote cracking to `gasoline range compounds.

The segregated process `involving fluid cycle stock cracking (column B) enjoys a marked advantage with respect to gasoline octane rating. However, gasoline yields are lower than those shown in column C for the process of the invention. This drawback, in combination with the excessive carbon formation, out-weighs the octane advantage in commercial operation.

Having set forth its objects 'and general nature, the invention in its practica1 aspects will be .best understood from the subsequent more detailed description read with reference to the drawing.

Referring now to the drawing, the system illustrated therein essentially comprises a crude distillation section 1, 2I, a fluid catalytic cracking section 40, 50 and a suspensoid processing section 84, the functions and coaction of which will be presently described using the production of motor fuels from a West Texas crude oil as an example. It should be understood, however, that the system may be employed for the conversion of other types of crude oil in a substantially analogous manner.

In operation, a typical West Texas crude oil supplied through line I is heated in fur-nace 3 to about 500-800 F. and supplied through line 5 to a crude still 'I operated substantially at atmospheric pressure. The crude may be fractionated in still 'I into several fractions comprising a normally gaseous fraction (about 1 wt. per cent on crude) withdrawn as overhead through line 9; a light naphtha having an end boiling point of about 200250 F. (about 8-13 vol. per cent on crude) withdrawn via line II, a heavy naphtha having a boiling range of -about 200 or 250-430 F. (23-18 vol. per cent on crude) withdrawn via line I3, a heating oil boiling between about 430 and 620 F. (about 21 vol. per cent on crude) recovered via line I5, and a reduced crude containing all constituents boiling above -about 620 F. (about 48 vol. per cent on crude) withdrawn through line II. The light products recovered Via lines 9 and II may be further treated by alkylation and other refining treatments to produce high quality motor fuels or blending stock in any conventional manner. rThe heating oil recovered via line I5 may be finished in a conventional manner and then passed to storage.

The reduced crude withdrawn through line I1 may be passed via line I 9 to a conventional vacuum still 2I to be separated therein into pitch (about 14% on crude) recovered through line 23 and gas oil of about 620-1100 F'. boiling range (about 34 vol. per cent on crude) taken overhead via line 25 to be passed Via line 21 by means of pump 28 to the uid catalytic cracking stage as virgin gas oil feed for this stage. Instead of using a vacuum still in the manner just described, atmospheric pressure still 'I may be so operated that in addition to the fractions withdrawn through lines 9, I I, I3 and I5 a gas Ioil boiling within the approximate range vof 620-950 F. (25 vol. per cent on crude) is withdrawn via line 29 and vpassed to line 21 while the bottoms withdrawn via line I'I (about 22 vol. per cent on crude) may contain all constituents boiling above 950 F. and serve as. a .fuel Oil 0r a feed stock for conventional coking or visbreaking operations. In any case, the virgin gas oil in line 21 andthe virgin heavy naphtha in line I3 will be treated in accordance with the invention as follows.

The gas oil substantially at the temperature at Which it is produced in still 1 or vacuum still 2l is passed from line 21 into line 33 wherein it is mixed with hot regenerated cracking catalyst supplied from regenerator standpipe 35 as will appear more clearly hereinafter. The catalyst which may be a silica-alumina gel composite (87% SiO2-13% A1203) having a iluidizable'particle size distribution averaging about 40-70 microns may be supplied from standpipe 35 at a temperature of about 10001200 F. in amounts of `about -35 lbs. per 1b. of gas oil flowing in line 33. If desired, about 5-20 lbs. of steam per lb.'o`f gas oil may be added from line 31 to line 33.

lThe dilute suspension of catalyst in gas oil vapors passes upwardly through line 33 into a conical distributing device 39 arranged in the bottom portion of reactor 40. entering reactor 40 at a suitable cracking temperature of about 800l000 F. forms therein a highly turbulent solids mass M40 resembling a boiling liquid having an apparent 'density of about 2li-40 lbs. per cu. ft. separated by an interface L40 from a superimposed dilute phase. Linear superficial vapor velocities in mass M40 of about 0.3-3 ft. per second are suitable for this purpose. Cracking may take place in mass M40 at about 900-1000 F., 0-20 p. s. i. g. pressure and oil throughputs of about .3-5 lbs. of gas oil per hour per pound of catalyst in mass M40.

vlSpent catalyst passes continuously frommass M40 into the annular space between cone 39 and the walls of reactor 40 and thence into reactor standpipe 42 substantially at the rate of catalyst supply via line 33. Steam, flue gas or other inert gas may be admitted through a plurality of taps t to strip and aerate the catalyst withdrawnl from mass M40. Standpipe 42 feeds into gas line 44 wherein the spent catalyst is picked up by air` or other oxidizing gas containing sufficient oxygen to remove, in the form of carbon oxides, substantially all the carbon deposited on the catalyst in reactor 40. Y y

The suspension of catalyst in oxidizing gasis passed from line 44 through the conical bottom Y portion 46 of regenerator 50, if desired, through a The suspension most ofthe carbon is burned off at substantially atmospheric pressure. Flue gases pass overhead from level L50, preferably through a gas-solids separator such as cyclone 52 to be removed via line 54 for any desired purpose. Separated catalyst may be returned via dip-pipe 56 to massMo or discarded via line 58. Make-up catalyst may be supplied via line 31, suspended in steam. In order to prevent catalyst overheating, particularly in thecase of excessive carbon formation in reactor 40, suitable cooling devices (not shown); may be imbedded in mass M50 or catalystfrom" mass Msu'may be ycontinuously circulated through a suitable'separate cooling device (not shown)l and returned to mass M50 at a lower temperature, all in a manner known per se. catalyst leaves mass M50 through standpipe 35 to enter line 33 as'descri'bed above. Small amounts Regenerated A 62.' Cracked products of reduced solids content arev passed Avia line 64 to fractionator 66 which may be operated as follows. An overhead fraction` containing about 10-25 vol. per cent on crude of motor fuel range hydrocarbons and about 1-4 v wt. per cent on crude of hydrocarbon gases may be recoveredgvia line Gte be passed to conventional nishing equipment (not shown). Product heating oil having a boiling range of about 4302620" F. and amounting to about 5-10 vol. per cent on crude may be withdrawn through line 10 and passed to storage. The products boiling above about 6 20 F. and amounting to about 5-.10 vol. per cent on cruderep-resent cycle oils. They may berecovered from fractionator 66 in three conventional fractions including a light cycle oil having a boiling range of about 620-700 F. (about 1;-3 vol. per cent on crude) withdrawn via line 12, a heavy cycle oil boiling between about 700 and 900 F. (about 3-5 vol. per cent on crude) withdrawn through line 14 and bottoms boiling above 900 F. (about 3-5 vol. per cent on crude) withdrawn via line'16.

At least the total bottoms fraction in line 16 and most of the heavy cycle oilin line 14, being cycle stock of highly marginal quality, are passed to line 18 for further treatment in accordance with the invention. Any desired portion of the light cycle oil inline 12, say about l0-100%, may be recycled to reactor 4I) via lines 80, 82 and 33, by means of pump 83'. Any remainder, or if desired, the total light cycle oil in line 12, may be likewise added to line 18 for further treatment as will be presently described. That portion of the heavy cycleoilin line 'I4 which is not passed to line 18may be recycled via line 82. The fractionator bottoms in line 1B contain as a Sludge the entire catalyst carried out of cyclone 60 with the oil vapors. This catalyst, which normally has a particle size'of less vthan 40 microns and and which may amount to about .1-1 lb. per gallon, maybeused to full advantage in the subsequent' suspensoid treating stage of the invention.

,The combined cycley Ioils containing suspended cracking catalyst are passed by means of pump 19 through line 18 wherein they are mixed preferably `with the heavy virgin naphtha fraction produced in still 1 and supplied through line i3 f by means of pump I4. Since the virgin naphtha requirement for the suspensoid stage of the invention decreases as the volatility of the catalytic cycle oil increases, the amount of virgin naphtha available in line I3 will be sufficient for the purposes of the invention no matter what proportion of the light cycle voils in lines 12 and I4 is passed on through line 18.

The mixture of recycle stock and virgin heavy naphtha, containing about 20-80 v'ollpercent of the latter,- depending on the disposition of the cycle oils, is passed to suspensoid Vreactor coil 84 arranged in furnace 86. If desired, additional silica-alumina cracking catalyst of about -400 mesh or liner may be added through line 88, preferably suspended in steam amounting to about 0.5-5 vol. percent of steam on total oil in line 18V so. as to maintaina Ycatalyst/oil ratio, in reactor f liliv of about 2-30 lbs., preferably about5-15. lbs. per bbl. of oil supplied thereto.. Reaction. conditions in coil reactor 84 may include temperatures of about 1000-12'00F., preferably wwf-1085 F., pressures of 100-600 p. s. i. g., Preferably 300- 600 p. s. i. g. and throughputs of about 5-20 v./v./hr., preferably about '7-12 v./v./hr.

The reaction products are withdrawn froml reactor 84 through line 90 and may be passed to a cyclone separator 92 from which mostof the catalyst may be recovered via line S4 for reuse in the system, if desired, after regeneration. The` product vapors leaving cyclone 92 va 1ine96, may be expanded to a pressure of about 100 p. s. i. g, or lower by means of valve 9.1 and quenched to a temperature of about 600-800 F. by a cold gas. oil (4304'7'00" F.) introduced via line 98.

The mixture may then be discharged via line I G into fractionator |05 wherein it may befractionated to yield final products as follows. A combined light ends and motor fuel fraction boiling up to about 430 F. (about 20-30 vol. percent on crude) may be recovered through line w8 to be treated as described with referencey to the overhead of fractionator 66 in line 68. Heat-- ing. oil. boiling withinv the range of 430-620 F. may be recovered through line- H0 and. may be combined with the productsl recovered through lines Iv and/or 10. Bottoms boiling above 620 F. (about 3 8 vol. percenton crude) may be recovered via line I I2 freed ofY any suspended catalyst by filtration or the like and used for any desired purpose, for example asfuel oil or a speciality product (for carbon black manufac ture).

The system illustrated in the drawing permits of various modications. For example, frac-` tionators 66 and |115v may bel so operated Athat separate streams of normally gaseous, productsv and motor fuel range. hydrocarbons are recovered. Instead of removing three separatestreams of cycle oils from fractionator 6.6:, the .products boiling above 620 F. may be removed in ay single. bottoms stream or in more than three fractions, depending on the character of thexcrude oil fed to the system. Similarly, fractionator i05- may: be operated to yield more than one fraction of the products boiling above 620 F. In, place of. coil reactor liliv other types. of reactorsl known in.

oilcracking may be used, such astube andv tank ,arrangements in which theoil isY heated' inA a fired coil and discharged into a tank, conversion taking place in either the coil or theA tank, or both.

The above descriptionand exemplaryopera-y tions have served to illustrate specific: embodi ments of the invention but are not intended to be limiting in scope.

What is claimedis:

1. In the process of producing motor fuels from crude petroleum which comprises subject-` ing crude petroleum to distillation to produce a heavy virgin naphtha fraction boiling between about 200 and 450L3 F. and agasoil fraction, sub jecting said gas oil fraction to catalytic: cracking in a cracking Zone in the presence of a dense turbulent fluidized. mass ofv subdivided cracking: catalyst at motor fuel producing conditions, withdrawing catalyst f-rom. said mass, regenerating said withdrawn. catalyst in a regeneration. zone by a combustion reaction to remove carbonaceous deposits and reheat the catalyst, returningv hot regenerated catalyst from saidregeneration zonet to saidmass, withdrawing cracked pfroductszfronr said cracking zone, fractionatingsaid, cracked.

pro-ducts in ya fractionation. zone,v withdrawing. from. said fractionation zone a fraction contain* ing motor fuels and a cycle oil fraction. boiling` above about 700 F., the improvement which consists of combining at least a major portion of said cycle oil fraction with at least a portion; of said heavy Virgin naphtha fraction to produce a mixture containing about- 20-80 vol. percent of virgin naphtha, passingl said mixture substantially inthe vapor phase through a narrowly con,- ned path at temperatures of about 1000l200` F., pressures of about 300-600 p. s. i. g. and resi-,- dence times corresponding to throughputs of about 5-20 v./v./hr. in the presence of finely divided cracking catalystsuspended in said mixture in a proportion of about 2 to 30 pounds ofv catalyst per liquid barrel of mixed feed, withdrawing reaction products from said path andre--Y covering motor fuels from said reaction products.

2l. The process of claim 1- in which said mixf, ture consists of about 20-30 v oLpercent of said cycle oil fraction and of about 70-80 vol. percent of said naphtha fraction.

3. The process of claim 1 in which av fraction boiling within the approximate rangey of 6209-- 700" F. is withdrawn from said fractionation zoney and recycled to said cracking zone.

4. In the process of producing motor fuels from crude petroleum which comprises `subjecting crude petroleum to distillation to produce a light vir-- gin naphtha. -fraction, a heavy virgin naphtha fractionboiling between 200 and 450 F.', and a gas oil fraction, subjecting. said gas oil fraction. to catalytic cracking in a cracking zone inthe pres,- en'ce of a dense turbulent fluidized mass of` subdivided. silica-alumina cracking catalyst at. motor fuel producing conditions, withdrawing catalyst from said. mass, regenerating said withdrawn catalyst in a regeneration zone by a combustion reaction to remove carbonaceous deposits and reheat the catalyst, returning hot regenerated catalyst from said regeneration zone to said mass withdrawing from said cracking zone a dilute,

suspension of fines of said cracking catalyst in cracked product vapors, passing said suspension.

to a-r fractionation zone, withdrawing from said fractionation zone a motor fuel fraction,y acycle oil fraction boiling between aboutf620 and 706 anda bottoms. fraction boiling-between about 700* and 1100 F., and containing, said catalyst iines, the improvement which consists of combining at least a portion of said fines-containing bottoms fraction with at least a portion of said heavy virgin naphtha fraction to produce a mixture icon,- taining about 20 to 80 volumek percent of said heavy virgin naphtha and about 2 to 30 pounds of catalyst per barrelof mixed liquid feed, passing the mixture so obtained substantially in the vapor phase through a narrowly confined path.

yat temperatures of` about 10'70'6-1085" F., pres.-

sures of about 3004500 p. s. i. g. and' residence times corresponding to throughputs of about 5-20 v./v./hr. in the presence of said catalyst fines suspended in said mixture; withdrawing reaction products from said path and recovering motor fuels from said reaction products'.

5f. The process ofr claim 4 in which said catalyst fines have a particle size ofV less than 40 micronsdiameter.

6. The process of claim 4 1 in which said' cracking' catalyst is aV synthetic silica-alumina com. posite; containing about 11-15 wt. per -cent of alumma..

7. The process of claim l inf. which said. mix.-

- turepassingl through. said.path.contains.aboutI 13 volume percent of said heavy virgin naphtha and about 10 lbs. of catalyst per liquid bbl. of mixed feed, and in which the pressure in the confined path is about 350 p. s. i. g. and the throughput about 9 v./v./hr.

8. The process of claim 7 in which extraneous subdivided catalyst is added to said mixture.

9. The process of claim 4 in which said cycle oil fraction boiling between about 620 and 700 F. is withdrawn from said fractionation zone and recycled to said cracking zone.

10. The process of lclaim 4 in which said mixture contains said virgin heavy naphtha and said bottoms in the ratio in which the same are produced in said process.

11. The process of claim 4 in which steam is added to said path.

JOHN WEIKART.

References Cited .in the le of this patent UNITED STATES PATENTS Number Name Date Hemminger June 24, 1941 Straka Apr. 28, 1942 AtWell June .30, 1942 Benedict Oct. 27, 1942 Benedict Nov. 24, 1942 Stratford et al. June 15, 1943 Egloff Mar. 7, 1944 Johnson Apr. 4, 1950 Hepp Apr. 18, 1950

Claims (1)

1. IN THE PROCESS OF PRODUCING MOTOR FUELS FROM CRUDE PETROLEUM WHICH COMPRISES SUBJECTING CRUDE PETROLEUM TO DISTILLATION TO PRODUCE A HEAVY VIRGIN NAPTHA FRACTION BOILING BETWEEN ABOUT 200 AND 450* F. AND A GAS OIL FRACTION, SUBJECTING SAID GAS OIL FRACTION CATALYTIC CRACKING IN A CRACKING ZONE IN THE PRESENCE OF A DENSE TURBULENT FLUIDIZED MASS OF SUBDIVIDED CRACKING CATALYST AT MOTOR FUEL PRODUCING CONDITIONS, WITHDRAWING CATALYST FROM SAID MASS, REGENERATING SAID WITHDRAWN CATALYST IN A REGENERATION ZONE BY A COMBUSTION REACTION TO REMOVE CARBONACEOUS DEPOSITS AND REHEAT THE CATALYST, RETURNING HOT REGENERATED CATALYST FROM SAID REGENERATING ZONE TO SAID MASS, WITHDRAWING CRACKED PRODUCTS FROM SAID CRACKING ZONE, FRACTIONATING SAID CRACKED PRODUCTS IN A FRACTIONATION ZONE, WITHDRAWING FROM SAID FRACTIONATION ZONE AT FRACTION CONTAINING MOTOR FUELS AND A CYCLE OIL FRACTION BOILING ABOVE ABOUT 700* F., THE IMPROVEMENT WHICH CONSISTS OF COMBINING AT LEAST A MAJOR PORTION OF SAID CYCLE OIL FRACTION WITH AT LEAST A PORTION OF SAID HEAVY VIRGIN NAPHTHA FRACTION TO PRODUCE A MIXTURE CONTAINING ABOUT 20-80 VOL. PERCENT OF VIRGIN NAPHTHA, PASSING SAID MIXTURE SUBSTANTIALLY IN THE VAPOR PHASE THROUGH A NARROWLY CONFINED PATH AT TEMPERATURES OF ABOUT 1000*-1200* F., PRESSURES OF ABOUT 300-600 P.S.I.G. AND RESIDENCE TIMES CORRESPONDING TO THROUGHPUTS OF ABOUT 5-20 V./V./HR. IN THE PRESENCE OF FINELY DIVIDED CRACKING CATALYST SUSPENDED IN SAID MIXTURE IN A PROPORTION OF ABOUT 2 TO 30 POUNDS OF CATALYST PER LIQUID BARREL OF MIXED FED, WITHDRAWING REACTION PRODUCTS FROM SAID PATH AND RECOVERING MOTOR FUELS FROM SAID REACTION PRODUCTS.

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