US2415998A - Combination process for the cracking and destructive hydrogenation of hydrocarbons - Google Patents

Description

Feb. 18, 1947.`

A. L. FOSTER COMBINATION PROCESS FOR THE CRACKING AND DESTRUOTIV'E HYDROGENATION OF HYDROCARBONS sheets-snelst 1 INVENTOR A L. FOSTER BY j ATTOR Feb. 18, 1947.

A. L. FOSTER 2,415,998

COMBINATION PROCESS FOR THE CRACKING AND DESTRUCTIVE HYDROGENATION OF HYDROCARBONS Filed May`l7, 1945 3 Sheets-Sheet 2 AL. FOSTER ATTO Feb. 18, 1947. A. FOSTER 2,415,998

COMBINATION PROCESS FOR THE CRACKING AND DESTRUCTIVE I HYDROGENATION 0F HYDROCARBONS Filed May 17, 1945 :s sheets-sheet :s

R TERMAl. CRACK-GAS REvERsmN/ |52 '53/|+\HEAv|Es FLASH CHAMBE INVENTOR I m A.| FOSTER Il BY EYS W JU ATTO Patented Feb. 18, 1947 COMBINATION PROCESS FOR THE CRACK- ING AND DESTRUCTIV E HYDROGENATION OF HYDROCARBONS Arch L. Foster, Tulsa, Okla., assignor to Phillips Petroleum Company, a corporation of Dela- Ware i Application May 17, 1943, Serial No. 487,364

1 Claim. 1

This invention relates to the treatment of ipetroleum hydrocarbons for the purpose of converting crude materials into finished products. More specifically it relates to the conversion of hydrocarbons by catalytic and non-catalytic means and to the intercorrelation of particular treatments of definite fractions of crude petroleum to give improved yields of high octane number motor fuel stock.

Modern refinery technology requires that crude petroleum, before being processed further, shall be divided into various fractions suitable for different purposes which may be processed in different ways to yield similar or different products. Furthermore, during the processing of these different fractions, intermediate materials are formed which are ordinarily considered by-products or waste materials, unprocessible formaking the main product from the given reaction which, however, may be processed further in a different manner to yield marketable products. In some cases such intermediate or by-products from two or more processes may be combined in such manner as to yield another product. otherwise not made, converting a low-grade or waste material into valuable products to improve the efficiency of the process.

A primary object of my invention is to produce high yields of valuable hydrocarbons suitab-le for use as motor fuel. Another object is to provide increased yields of motor fuel from heavy components of crude oil. Another` object is to combine and correlate certain processes and materials in such manner as to produce new materials therefrom, to utilize all waste products to the highest advantage, and to produce large yields of the most valuable products. A further object is to treat together gaseous and heavy residual products obtained by distillation of crude petroleum and from certain catalytic and noncatalytic hydrocarbon conversion processes in such manner as to give optimum yields of high octane number motor fuel stock. Yet another object is to provide a method for the production of motor fuel hydrocarbons from heavier hydrocarbons which are not ordinarily treated to give motor fuel hydrocarbons. Further objects and advantages of the invention will be apparent from the accompanying disclosure and discussion.

In a preferred .practice of my invention, a crude petroleum is separated by fractionation into a number of fractions comprising at least (a) pentanes and lighter, (b) gasoline or naphtha, (c) gas oil, and (d) residuum. Fraction (a) is passed to a second fractionator in admixture with satiii) vurated and unsaturated C5 and lighter hydrocarbons and usually some hydrogen from other conversion steps described below, and the admixture therein separated into fractions including a C3 and lighter gas. The fourand iive-carbon-atom hydrocarbons are recovered together or separately from said fractionator, a portion thereof catalytically dehydrogenated followed by separation of hydrogen and olefins, and said hydrocarbons including said olefins subjected to controlled alkylation which will be described more fully hereinafter. The C3 and lighter gas mentioned above is heated and admiXed with the residuum (d) and the mixture flashed, with separation of gas and liquid phases. The gas phase is maintained under reaction conditions such as to effect a non-catalytic gas reversion type of conversion producing light gases, motor fuel, and heavier hydrocarbons.

The liquid phase is admixed with hydrogen from the aforementioned catalytic dehydrogenation and subjected to destructive hydrogenation whereby it is converted in large part to motor fuel and hydrocarbons amenable to catalytic cracking. Said hydrocarbons, in admixture with heavier hydrocarbons from said gas reversion and with virgin gas-oil separated from the crude petroleum as fraction (c), are subjected to catalytic cracking to give high yields of motor fuel. Light gases produced as by-products are passed to the aforementioned second fractionator. Fraction or fractions (b) are subjected'to catalytic reforming to give higher octane number motor fuel, and any light gases passed to said second fractionator. Additional features include the non-catalytic cracking of cycle stocks separated from catalytic cracking.

The accompanying drawing, along with the description thereof, is provided to aid in the understanding of the various aspects and intercorrelations of my invention, and exemplifies a preferred modification thereof. It will, of course, be understood that the invention is not limited to the exact arrangement shown, since various other modifications are indicated herein or willv be obvious to one skilled in the art in ,view of the disclosure herein. The drawing shows diagrammatically an arrangement ofV apparatus, not necessarily drawn to scale, suitable for carrying out treatment of hydrocarbons in accordance with my invention. The single drawing, for the sake of clarity, comprises three sheets, numbered Figures 1A, 1B, and 1C, with lines interconnecting between the sheets as shown. v

Raw crude oil or other charge of Wide boiling range, heated to the desired temperature in any convenient manner not shown in the drawing, enters through line I and is flashed in crude fractionator 2. By methods well known to the art the charge is divided into a plurality of overhead, side, and bottom streams, such as the six shown in the figure: line ||2| carries pentanes and lighter hydrocarbons, line |02 carries a light gasoline fraction of up to 275-300 F. end point, line |03 carries a heavy naphtha boiling up to 450 F. or higher, line |04 carries a kerosene-light gas oil fraction with, for example, a E50-600 F. end point, line |05 carries a heavy gas oil fraction, and line |06 carries a medium or heavy residuum of any desired specifications. The crudeorother charge may be sub-dividedinto 'any desired combination of fractions to meet the requirements oi the operations without departing from the principles of the invention.

The C5 and lighter stream passes from fractionator 2 via line lill into an ecient fractionator 3, 3

4 .to .further use as will be explained later. Any

portion not required for such usemay be withdrawn through line 'i0 foruse .asfuel A portion of the C3 and lighter `strearn may rlie-,continuously bled off, as by line 'Ill or line lut, to avoid pyramiding of hydrogen and/or methane in the system. VIt may sometimes be desirable to` separate a .lightest fraction comprising Vhydrogen and which also may comprise methane, via `lines 9.9 and `||l|i,.a portion of whichmay ybe passedto line 4 if desired, with another .fraction comprising C2 and C3, and also .methane if desired, Ybeing separated via ylines .98 and 4. The ,kettle product from fractionator 3 is passed via line |98 to fractionatorli, wherein C4-s.are separated from Css The butane-butene fractionis carried overhead through .line 5 into fractionator 1 wherein isobutane `and at least part, and preferably substantially --all, of the isobutylene and butene-l, are separated as an overhead .product which is carried through line 8 to alkylation unit 9. The normal butane together with .butenes-,Z and any other butenes .not taken voi overhead are withdrawn as kettle product from column 1 via line I3 and passed to a catalytic dehydrogenation system indicated diagrammatically at .i This` system comprises the usual furnaces, catalyst chambers, catalyst regeneration means, and other equipment wellknown to the art, which need not be recited here in detail. fThe dehydrogenation may be carried .out without Vtheaid of catalysts, but this is generallyless desirable, inthat agreater variety of products and poorer eiiiciency isob- .tained AThe hydrocarbons to 'be dehydrogenated are preferably passed 'at theidesired temperature, generallyinthe range of.,'950.to `1150" and ow rate, suchas space velocities from 50t0 2000, over aneicient dehydrogenation catalyst, such as one of the chromia-alumina catalysts now widely used for this purpose, and the .dehydrogenation'products areintroduced ,via .line .|98 into fractionating systemr lill, from which V.hydrogen is separatedvialine |22 to be used in the destructive hydrogenation step of the process' as .described below. System .fl It `ordinarily Acomprises a singleor multiple-stage scrubbing, combined With'fraction- 4 ation in one or more conventional columns. The butenes formed in the dehydrogenation, plus any butenes fed thereto, are passed from unit IU via line i3 to alkylator 9. These butenes may be separated in unit I@ from any undehydrogenated normal butane which is recycled to the dehydrogenation unit Ordinarily, however, this is not done, the entire C4 hydrocarbon content of the dehydrogenation eiliuents being passed to the alkylation step, wherein the normal butane may take part in the alkylation reaction, although kmore often, and preferably, it acts merely as a desirable or at least innocuous diluent.

In alkylation unit 9, the isobutane is alkylated by the butenesin any manner known to the art, to give a very high octane number substantially saturated motor fuel blending stock. Preferably 'a liquid catalyst such as sulfuric acid, or especiallyhydrouoric acid, is used, at atmospheric or near-atmospheric temperatures, and with suicient pressure to maintain the entire .reaction mixture in iiquidphase. .The ratio of isoparain to olelinis kept at a value well above 1:'1, and frequently as high as :1 or even higher, depending upon the particular method of contacting hydrocarbons with acid and upon other characteristics of the alkylation system. Theart ci alkylation is now Vwell developed .and accordingly the various details for 4carrying'out the alkylation itself need not be discussed further. Hydrocarbons effluent from .the .alkylation are passed via line to fracti'onator I4, wherein a separation is made between the alkylate product, comprising C5 and heavier, whichleavesthrough line H2, and C4 hydrocarbons, :generally vconsisting entirely of isoand normal butane, which are recycled by means of line I3 to one or more desired points in the fractionation and alkylation system just described. According to the composition of the stream in line ||3 and of the other streams, a portion or all may be reintroduced throughline H4 for introduction to alkylator 9, line H5 for dehydrogenation in unit Il, or line H for separation into isoand normal components in fractionator 1, from which it again is passed Yalong with other hydrocarbons for dehydrogenation and/or alkylation as described.

It is to be understood that throughout the process disclosed herein various auxiliary steps of intermediate or secondary -fractionations or separations other vthan thosedescribed may be employed, such as settling and Vrecycling of mobile catalyst, separation of catalyst from hydrocarbons, 'separating reacted product from unreactcd material which may be recycled, separating by-products from `other desired products, and other ysimilar steps which may be required in practice to promote yefficiency and increase yields of primary products. All of rsuch steps lare `not shown herein, their use being indicated by, or being Yobvious to one skilled in the art in View of, the disclosure herein,

A pentan'e-pentene fraction is obtained as bottom product from fractionator 5 through vline 22,

" andis subjected'to the same Vtype ofptreatment as thatjust described for the butane-butene fraction obtained as top product from iraetionator 5, but under conditions chosen as optimum jfor the particular C5 hydrocarbons being treated, jwhich are generally different from the optimum `conditions for the same operations on C4 hydrocarbons` Material Hows from line 22 into fractionatorv23f, iso-C5s, particularly isopentane, are `taken ofi overhead via line 24 ,and passed toalkylator 2 5,

, higher boiling Css, particularly normalvpentane,

tenes, preferably through the aid of a suitable alkylation catalyst as described above with reference to theC4 alkylation step, and eiuent hydrocarbons are then passed via line |22 to fractionator 29. The alkylate, a high octane number saturatedxmotor fuel stock particularly suited for -use in aviation fuels, is withdrawn via line 3|.

All or a part of the unreacted Cas, which are usually substantially free from olefins, may be lwithdrawn as part of the alkylate to give a desired volatility thereto, and/or may be separated overhead, as by line 30, for recycle in a manner similar to the C4 recycle from line ||3 as heretofore explained. For this purpose lines |23, |24, and |25 are provided, leading from line 30 to alkylator 25, dehydrogenator 21, and fractionator 23, respectively.

Frequently it is desirable to separate out a substantially pure isopentane fraction for use as a blending agent for aviation fuels inasmuch as isopentane has a high octane number and at the same time is highly volatile. Such a fraction may be separated' out via line 26. When the pentene content of the feed to fractionator 23 issuficiently low, or such that pure, olefin-free isopentane can be separated therefrom, such isopentane may be taken oil! overhead through line 24, with part being diverted to line 26 for the purpose stated. More often, however, such olefin-free isopentane blending stock is best obtained from the alkylation effluents by fractionation in column 29, the alkylation thus serving to remove pentenes from admixture with the isopentane.

lIn this instance, isopentane may be taken as a top product through line 3U, with part or all passing via line |21 to line 26, while normal pentane is separated from fractionation system 29 via. line |28 and recycled via line 30 to one or more desired points either alone or in admixture with some isopentane. The relative amounts of isopentane used up in the alkylation step or separated as blending agent will of course depend upon the available supply thereof from the crude oil or other charge stock and from the various conversions soon to be described, as well upon the properties desired of the finished motor fuel blend or blends produced by my invention.

A modification of the alkylation steps just discussed which is sometimes preferred because of the relative amounts of the various hydrocarbons available, other uses to which certain of the hydrocarbons may be put, or certain properties of `valkylate which it is desired to obtain, involves the alkylation of isobutane with pentenes and/or this modification may be taken advantage of is when butenes are needed for another use, such as a dehydrogenation feed for the production of butadiene to be used in producing a synthetic rubber or the like, and when isopentane is more valuable as an aviation fuel blending stock than as alkylation feed. In this case, only alkylation unit 9 is operated, on a butane-pentene feed, while butenes and isopentane are sent to their respective utilizations instead of being subjected to alkylation. Furthermore, when one or the other of the two alkylation systems is overloaded or underloaded due to a particular mannerpin which the various conversions-are being operated, a portion of fresh charge or recycle charge or both, comprising parafns and/or oleiins, may be diverted through lines shown and/or by means not shown, from one system to the alkylation unitl of the other system, and the two charges may thus be at least partially comingled with the production of a mixed alkylate. This type of operation may be utilized over a wide range of concentrations without departing from the limits of the invention as described and claimed, and allows a very desirable flexibility in carrying out the over-all operations. When any of these varous modifications are practiced it may be desirable to recycle streams of unconverted hydrocarbons containing both 4- and 5-carbon atom hydrocarbons back to fractionator 5 for separation into the two families of C4 and C5 hydrocarbons prior to further treatment, and for this purpose lines ||1 and |26 are provided.

While I have referred primarily to alkylation of isoparaillns, it should be understood that IA may also alkylate normal paraiiins under some circumstances, by either catalytic or non-catalytic means known to the art. Conditions necessary are usually more severe than with isoparaflin alkylation, and the choice will depend upon the relative availability of the various C4 and C5 hydrocarbons. Furthermore, While I have shown specific steps for separation of paraflin's from' olefins and the like, other steps, includingv those such as selective solvent extraction and the like as Well as conventional fractionation, may be utilized, depending again upon the relative proportions of the various hydrocarbons, and on the particular fractions Vit may be desired to separate out for a certain alkylation or other conversion or utilization. In some cases a portion of the C3 hydrocarbons comprising propylene may be passed to alkylation along with butenes and/or pentenes. The extent t'o which dehydrogenation will be used to provide olefin feed for the alkylations is indirectly at least a function of the conversions of heavier hydrocarbons effected in other portions of the system. Generally these conversions are such that, although highly olefinic gases are formed, there is still an excess of paraiiins available for alkylation feed stock, thus making possible the use of catalytic dehydrogenation of the same to increase the ultimate yield of alkylate. Turning now to the hydrocarbons in the crude oil having more than five carbon atoms to the molecule, it will be seen fromthe drawing that each of the fractions |02, |03, |04, and-|05fis treated separately in a catalytic conversion step to produce optimum yields of desired hydrocarbons, usually those boiling .-in the motor fuel range. Much higher ultimate yields of desired products are obtainablethrough catalytictreatr ment of these fractionsthan` would be vobtain.,-

vable if .they vwere treated by non-catalytic eonvversion processes exclusively.

The .light gasoline fraction separated from'still 2 via .line `|02 is heated by lmeans not shownto a reforming temperature such as 900 to 1050 F., and passed into unit |29 atailow rate preferably in the range of 10 to 20 barrels of liquid charge peiahour per ton of catalyst over a suitable reforming catalyst such as bauxite, alumina `having Aa small proportion of chromium oxide associated therewith, or others such'as those well-known to vthe art, whereby an appreciable improvement in octane number of the gasoline maybe obtained while suffering comparativelysmall loss inl -yield of `|gasoline. Reforming v.eiliu-ents -are passed `via line |--to-stabilizer |3'| wherein light gases, primarily hydrogen, are separated overhead Via line .|32 for passage to line Ill-|- and thence to fractionator `3, while-'the'reformed gasoline 'product is takenvialine- |33 for vblending with other gasoline products produced elsewhere vin the system. Ordinarily no appreciable amount of material heavier 4than gasoline is formedand thus no prolvisions need be made for separating out such material. D

The heavy naphtha fraction obtained through line L|03 is ,subjected in known manner to catalytict-rea-tment in unit 35, conditions preferably being'suchl l.that `an effect 'somewhat intermediate simple non-destructive reforming and-.cracking is obtained. The catalyst may be primarily a reforming ycatalyst similar to that used in unit |29, or it may bezprimar-ily a cracking catalyst vsirnilarto -that `used in units 4l and/or 55 to be described, vor it! may be a mixture of such catal-ysts or any other catalyst composition producing the desired results, the choice being Within the skillof the art in view ofthe instant disclosure. The reaction maybe such as to yproduce a desirable quantity of aromatic hydrocarbons.`

Reaction effluents vpass from unit 35 via line 36 into separator Y3i, ordinarily a single fractionator, wherefrommaterial boiling below a desired motor fuel yend point, such as 325 to425 F., is taken cverheadvia lline 30 to fractionator 39,

vwhile heavier material is passed via line 42 to unit 6| for non-catalytic ypyrolytic treatment, since this material is more amenable to such non-catalytic treatment than it is to a recycling operation to the catalyst over whichl ithas already been passed. A reformed or 'cracked gasoline is separated from column 39 via line 4|, whilelight gases, comprising/C4 or C5 and lighter hydrocarbons, .generally along with some hydrogen, are passed Vvia line to line |01 and 'fractionator 3. v

The light virgin gas oil separated Afrom other constituents of the crude oil is passed by way of line VHM into catalyticcrackingfunit 4l, wherein it is contacted with a suitable cracking catalyst at an elevated temper-ature generally in the range of '750 .to 11.00 F., at a low superatmospherc pressure ranging" up to or 100 pounds per square inch gage, `and at a flow rate andother reaction conditions usually chosen for optimum production of motor fuel hydrocarbons. The catalyst -is preferably one of the so-called silicaalumina type, either synthetic or natural, characterized by the presence of silica alongwith usu ally' relatively minor amounts of alumina, zirconia, and/or other metal oxides, and typified by silica'g'el activated'with adsorbed alumina on the one hand and acid-washedv bentonite clay,v lsuch as Super-Filtrol, on the other. 'If-the productionof more `isoparaiiinsa'nd less olen's' is de'- sired, a .metal halide cracking'catalyst .such 'as aluminum chloride :may be used in'this and/or other cracking units.

It may be mentioned here that the catalytic re- 5 forming and/ or cracking units |29, 35, 4l, and 55, are merely illustrated diagrammatically inthe drawing, and that in general any of these Yunits .may be of the fixed catalyst bed type, of .thefmoving catalyst bed type,fas typified lby the so-called TCC process, or of the powdered catalyst ,type typified by the so-ca1led fluid catalyst systems, or of'any other designwhich the leconomics of a particular situation indicate to be lmost desirable. While' the results obtained from .these various typesof systems on a given charging stock :may vary to a limited extent, it --may be said vthat .a given general result-may be obtained from anyvof these systems, yandthe preciseoperating details Afor any such-catalytic system'will be readily supplied by one skilled in the art, vbased on the diS- jclosures herein of the materials treated andthe results desired. It -is to be further understood that all of the necessary equipment'for effecting catalyst reactivation, as by burning with air 0r other oxygen-containing gas, is included inthe diagrammatic representation, ysince `such equipment and the operation thereof are now well understood, and accordingly do not of themselves form part of the present invention. To show such Aequipment further would merely .complicatethe drawing without contributing appreciably to, the teachings of this disclosure. I l l Returning to the catalytic cracking system 41, reaction products, including unconverted gas oil, pass via line |34 to fractionator'48, from the kettle of which is drawn cycle oil which is passedin whole or in part via line 5| into line 42 for treatment in unit 6|. Cracked products are `taken overhead through line |35 into fractionator 449 from which a ycracked gasoline product of high antiknock value is `removed through line 50 while light gases, comprising predominantly oleins and isoparainns of five and/or four carbon' atoms and lighter oleiins, and usually very minor quan- I tities of hydrogen and/or methane, are sent via lines |36 and |0'| to fractionator `3 -for separation yinto components and-utilization as specied--else where herein. l y t Heavy virgin gas oil is vpassed via -line |05, vin 50 admixture lwith material from .lines-6B, 19,-and

S3 lprepared as hereinafter described, into catalytic unit-55, wherein cracking is effected to produce motor fuel stock of good ant-iknock value. The catalyst in this 'case is again preferably -of the -silica-alumina'type, and will generally be derived from anatural clay rather than4 being syn,- theticall-y produced, since the life :of the catalyst in this step fis 'frequently not so long as in the other cracking units shown, and thecost of synthetic catalyst is likely to exceed its 'value 'in obtaining any increased -eiliciency Reaction con ditions` are similar 'to those used in unitJH. `Ordinarily, with catalyst -of equal activity, 'a-lower temperature maywv be utilized in cracking -the heavier hydrocarbons. Howeverfwith afless active catalyst the temperature in unit-55fmay beas high as, or even higher than, `that in"unit 41. Cracked and unconverted hydrocarbons pass via line |31' into fractionation system 5B wherein residue higher boiling `than gasoline is separated as kettle bottoms and passed lvia'lin'edi rto 'line-T42 Where it is intermin'gled with other charge :stock passing to non-catalytic'unit- 6|, while gasoline and lighter fractions are taken' overhead fromi56 via une ras wfracuonatoriei;familienaam fractionator, the desired high octane number motor fuel stock is obtained as kettle product, which is withdrawn through line 50, and light gases somewhat similar in composition to those obtained from fractionator 49 are taken through line 58 to line |01 for admixture and subsequent separation and treatment with other light gases.

It will be seen from the above discussion that various cuts are separated from the crude petroleum charged to the system, and those cuts ranging from light gasoline to heavy gas oil are separately treated over catalysts to give the desired yields of high octane number motor fuel. This separate treatment makes possible the choice of operating conditions and catalysts optimum for each particular cut. In cracking unit 55 last described, not only is heavy virgin gas oil treated, .but also in admixture therewith products obtained from three other stages in the process, awhich are now to be discussed in detail.

After each of the catalytic treatments referred l to, a separation is made, whereby light gases are separated and sent to a common fractionator 3 in admixture with light material obtained from the crude, motor fuel is taken out, and heavy cycle stock is obtained. These cycle stocks are all shown as passing into line 42 for subsequent treatment in thermal cracking unit 6|. It is to be understood that I may alternatively use a single, common fractionator for separating each of the streams |30, 36, |34, and |31 into the desired light gas, gasoline, and heavier cuts, rather than using the separate fractionators shown in the drawing, and when the catalytic units are each operated on a high conversion per pass, or once-'through type of operation, I prefer to pass the eiiiuents therefrom to a common fractionation system. However, it is sometimes more efficient tocatalytically reform and crack at a relatively low percentage conversion per pass, with recycle of Iat least `a portion of the unconverted material to vther catalyst for additional treatment to obtain a desired overall yield. For this purpose lines |39, |40, I4|, and |42 are provided. When this type offprocedure is used, it is preferable to use the` separate fractionators with each catalytic unitas shown, so that the proper cycle stock for each treatment will be more readily obtained.

VIn all cases, however, I pass at least a portion of the cycle stock, or partly converted or unconverted materials, to unit 6| for further, non-catalytic cracking. Recycle stocks from catalytic cracking operations are rich in relatively saturated types of hydrocarbons, which are more amenable to purely pyrolytic cracking than to further catalytic treatment, and thus the pyrolyticlcracking'of the cycle stocks referred to provides a more efficient operation and higher ultimate yield pof final product than otherwise obtainable. Such cracking is eiected by passing hydrocarbons from line 42 into thermal cracking unit 6|, which is constructed and operated in a manner now well known to the art. Generally thev hydrocarbons are cracked under pressures of above 200 pounds per square inch, ranging on up to 2000 pounds, and at temperatures of the order of 900 to l000 F. on up to as high as 1200 F. as may be desired. Light gases from line 4 may be introduced by means not shown into thecracking coils or reaction zone or elsewhere inthe cracking unit 6| as desired to promote vaporization of the heated charge, to superheat the charge, and/or to promote gas reversion reactions.

Etlluents from 6| are passed via line |43 to fractionator 62, from which gasoline and lighter products are passed overhead via line |44 to column '63, while cycle stock is separated via line |45. This cycle stock may in part be returned via line |46 to unit 6| for further cracking in conventional manner, particularly When a relatively low per pass conversion is being obtained therein. However, since the cycle stock is relatively unsaturated and thus more susceptible to catalytio'than to further thermal cracking, a portion or all is passed via line 66 to catalytic unit 55, and/or units 35 or 41, to be cracked therein with heavy virgin gas oil and other hydrocarbons as previously described. If this recycle of thermaily cracked stock to catalytic cracking, and of catalytically cracked stock to thermal cracking were to be continued indefinitely, the cycle stocks would become more and more refractory due to the build-up of aromatics and other hydrocarbons which are not readily cracked. Accordingly, a, portion of stream |45 is withdrawn from the system through lines |41 and |48. Heavy residues from the non-catalytic cracking are also withdrawn from fractionation system 62 through line |48. From fractiohator 63 light gases, highly oleiinic in character, are taken off overhead through line 65 for passage via line |01 to fractionator 3 in admixture with other light gases, while cracked gasoline product is separated through line 64. This product may be utilized as such, blended with other stocks, or subiected to catalytic aromatizing or other treatment designed to impart particular properties thereto.

Turning now to the residuum from crude iractionator Z, this material passes through line |06 to heater 1| and is heated to such temperature as may be desired, up to that causing some cracking. Light gases separated via line il trom fractionator 3 as heretofore described, and including both paraflinic and oleiinic gases having three and less carbon atoms per molecule, and which also may include some hydrogen, although this is generally not preferred, are introduced via line 12 into a separate coil in heater 1| and/or via line |49 into the liquid charge line |06 prior to entry into a common heating coil. If heated in a separate coil the gases may be brought up to any desired temperature higher or lower than that employed for the liquid reduced crude charge, a'temperature as high as l200 F. being employed in some cases where the maximum vaporization of charge is desired. Both streams, or the streams commingled through use of lines |49 or |50, are ashed in a vaporizing chamber 13, and all vapors pass therefrom via line |51 to the non-catalytic cracking and gas reversion reaction zone 14. The gases serve to superheat the liquid charge before or during hashing, to act as sweeping agent in the vaporization thus giving maximum vaporization of volatile components of the residuum, and to take pai-t in the combined cracking-gas reversion reaction in unit 14. Charge to this unit may be introduced at any desired pressure and temperature, but preferably between about 500 'and 1500 pounds per square inch gage and about 850 to 1000 F. A complex series of reactions takes place which may be regarded as a combination of cracking of heavy constituents and of light saturated constituents, along with polymerization of light olens.

Hot products from unit 14 pass via line |52 to fractionator 16, and vapors boiling in the gasoline range and kbelow pass overhead therefrom through line 11 to stabilizer 18. The stabilized gasoline passes to blending or storage enlaces or for further treatment throughlline tp, While licht overhead ceses ness tiiroiieh line .il .to ir'inle with similar gases Yfrom otbleryunitis inline l''l' ior'passageto 'fractionator 3. The gasoline trius'produced is"hi'ghly"olenic and possessed 'of a' high antiknocl value. In vcase it is desired to produce maximum yields of aviation gasoline stocks; this particular gasoline is 'especially s'uitedfor'use as fedstok'te'a catalytic treatment" which willeffectrng closure and other armatiziiig reactions; whereby' an aromatic 'st/o'ckveryuseful for 'increasing the antiknock value and ricn'niixture performance of aviation fuels is obtained, V Recycle oil and insullciently cracked material, being olefl'nc'to a marked exe tent,are"taken" from' fractionator is "tnrough line' 19 to catalytio'crackin'g fumi 5,5 Where they are 'subjected' tofcatalytic cracking in ardmiggtu're With'heavyvirgin gas oil, ,cycle oil from nonc'e'iolytifi "crociiiis 'finit '61, ,ond .the materiel de rkid aboVe;"'Havy refractory material siii eliicieckiiieiiinnit .5i Wit'iidiolwn es bfc cinsircin fie iciiotcr li tiircofeli. .line .|53 '.scoideci cii'eliffo portion tnereoi'moy so'iiie-tiines.'15en edvoiitoseoosly .recycled i9 line .|05 iiiesi 1111115 i310' 'iick'kili .not .snoivo- Tlienejev'i'f res liolnotctil frein 'the loottom of lfla'sli eliamb -4r .it is teken throne@ .1.' .e 1.5. to iii foei-notion .iiiiitti Wiieiein it 'isy `cciifriiiiirielec viitifiyiiioe'e ircinline 1.2..,"obte1necl herein.- l 're""sli'c1fiecl, 'in ccniect with eiiicient hy,

genetica toVV produce nycirocar: .1.11 eeerectei and oi lower b, line s Dess through line. .Si iectieeeted. in tower. sz

. u f. ne renee ,en

is produced e eosoline. prod. et

. Tee ses. accumulator 1. eieiioiniientlr of hydrogen, may fessee enti 'ietiiroccl tofdestroctive hyf dioeeno'tioi iififiii.L iitiiroiieh. line Iii, while the 1101111 liieisefis taisen'vio llines 1.5i! end lil] to ffii 3 i?? solicitation ond.. subsequent utillzatlon" Wiiiil'eiiie ,invention hes ,been describes. in. some, detil'wiih reference to. ine specific exempte,

111i ietclbi' the drewine. 'it will be eooreiet'ed ny 'fanticos may loe practiced within lient ufheavy virgin 'on in unes igiene lpg respect Vvely'may be treated together in a single catalytic crackingunit'; the samefis Ytrue, of the' light gasoline and heavyV naiohtha'-n lines' H32 and jlI-l respectively, and of'thehea'vy naphtha and lient ygals oiliin lines' Vl 03 and: Hill respectively,V

et?. FurthelIP-Qftlie cycle oils or` otherjprolineY ucts passing tlirjovugli lines iiigf'li and" Snmfafy i-.trlfiil materiel bonnie soci/e me" ih aline 155,. and' alieni ses .fraction Se@ endlessos Violine v1.5i to,

is" of litio.iiliiiftion-A iler exemple. tine` 12 orsi :be .seperated .into light Vand neatly fractions, h .are subsequently ,treated .separately as `in 4;? endior ne )lightand neat/yzrespee-Y tit/ely. -Wliile maximum Iyields of 1motor fuel hudrooarbons .are .generally .sought .and :obtained through `use `of frny invention, it gwill flee .seen that other products may Joe .obtained in increased yields .at the .expense .of motor iiuel .production Wheneeononiio .conditions .so .demand The nari.- ous .gasoline and .other products .will 'frequently be .blended together to `sive a final .composite motor fuel lout in ineny Ynoses one 4or more .of tbe products .may be. utilized separately. Alsor many .oi the V,orooliicts and intermediate streams will reoeiye adol' nal treatment, such .as .clay treating, vde.suliuiization, etc., not .described .or shown, ,since .lille application of Ysuch treatment is Wel-l understood in Atne art. .Qbyiously .many auxiliary .and .minor lsteps have been .omitted from this description, .since they .arewell Yknown in the .and simply. ,constitute .good practice known .to .any ...dl/laled y:.o'lesigner. yor operator. Various ,pieces lof equipment, including. .refluxv condensors .and .accumulators, reboilers, valves, pumps, compressors, heating and cooling means, heat exchangers, and the like vhave not been shown in the drawingfor the sake of simplicity, A few Valves lioie'eeeii indicated where ob.- viously alternative flows" might be used, but it will'lbe understood that no' attempt has ,been made to v'snow all pressure reducing Vorv other Valves. V

claim:

A process for the production of motor fuel stool; from heavy conwonentsfci crude Petroleum whichy combrisessenoroiins frein seid crude Petroleum ay virgin 'gasoil anda 'residuum consisting o f l'iydrocarbonjs higher boiling than said gas oil, cash: me' soicl'resicliiiini in edinixtore with e lient. ees comprisingnydrocarbons of more than oneccarfbon'atom 'per moleculefat an elevated. teni'peatliij thereby e eos boese' ispioduced comprising said light `gas and volatile constituents of said i'csidiiim and el liquid phase is' riconosci-coole prising heavier constituents of said'residuum, seid lient ses comprising pereiiinic end; oleiinie gases produced in rst, second, and third conver-` sion stepshereinafter described, separating'said eesoiies'e 'and maintaining the .ccnipcneotlsfihere ci iii'iiist conversion step4 onder elevated tem:

peratu're 'endnressiirc usind for e suilicient timev in' o 'neil-celelytic reaction, Zone to. effect. sub?. stantial production of motor fue] hydrocarbons, separating said motor fuelY hydro carbonsI as," a precinct ci# the 'Processi .senoreltiins'A e 'irectionci hcaviiiydfocorbens so produced endsnbstenf tiallj free fromconstituents boiling inl tlie range ofsaid residuurnand passingthe san-ie in admiX-tu're With seid 'Virei 'feels 01.1 end al hjydr 11-.. solicited materiel 'of siiniiortoiline renee duced as leere.'inafter described in', arse'cond con,-v veision 'step' iii Contact with ecieenegieeelyst at cracking co'nditio'nsl to effect v'substanti@ pro. duction o'fmotor fuel' hydrocarbons, separating saidj'rioto'r` fuelhydrocarbons as` a'prcductof the""`niocess, subjecting seid.. liouiclnliese foro--` duced by said flashing of said residuum and light gasto destructive hydrogepationin efthird con version step inadmijrture with`'hydr@gianY the presence of Ia h'ydrogenatifon catalyst at elevated temperatures andi pressures to produce "stubstan tial quantities oihydroc'arbons lower boiling'tlxan said. residuum, separating motorl fuel hydocarfbons so produced as a product of the processi, andl f subjeQlf/.iiig to cracking as hereinbefore specified 13 14 hydrogenated hydrocarbons so produced higher Number Name Date boiling than said motor fuel hydrocarbons but 2,129,506 Sachs Sept. 6, 1938 lower boiling than said residuum. 2,205,434 Phinney June 25, 1940 ARCH L. FOSTER. 2,319,354 Sperling May 18, 1943 5 2,352,025 Seguy June 20, 1944 REFERENCES CITED 2,256,615 Hederhorst sept. 23, 1941 The following references are of record in the OTHER REFERENCES me of this patent' i Article entitled Technique for Rening War UNITED STATES PATENTS 10 Products Explained, in The Oil and Gas Jour- Number Name Date nal, of March 19, 1942, pgs. 19 and 18. (Copy in 2,222,060 Arveson Nov. 19, 1940 196-49 of Division 3L) 2,257,723 Arveson 0011 7J 1941 Flow Sheet inserted between pgs. 140 and 141 2,300,691 @con N0v 3, 1942 of The Rener, of October 1942, v01. 21, No. 10. 2,303,107 Benedict Nov. 3, 1942 15 C0py in Div. 310 2,312,445 Ruthruff Man 2, 1943 Williams, The Oil and Gas Journal, of Nov.

2,276,171 Ewell Mar. 10, 1942 7, 1935, DgS. 38 and 39. (Copy in Scientific Lib.)

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