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uC .A 2 3, u _.W w œ w G. N . 2,404,452 N PRODUCTION OF AVIATION GASOLINE Filed March 27, 1944 «o„îmm4%. . mcrnowù.+En mm NN coIudL InvenTor'. lIvcn* G. Nixon Bg his A’H'or'neHLÈ .___ 2,404,452 Patented July 23, 1946 AUNITED sTATEs PATENT OFFICE, PRODUCTION OF AVIATION GASOLINE Ivor G. Nixon, Ewell, England, assigner to Shell Development Company, San Francisco, Calif.,` a _ corporation of Delaware Application March 27, 1944, Serial No. 528,290 . , 1 f2 . . ¢ . This invention relates to the manufacture of when conducted by'iconventional methods, us _. aviation gasoline base stocks by the cracking and re-cracking of selected hydrocarbon .distillatea ally cause the formation of large amounts of ole iins. For this reason, thermally cracked naph-i thas have not generally been used in aviationV and especially to the art of re-forming low oc tane naphthas to increase their rich mixture rat ings in blends in super-charged aviation engines. in gasolines, It is also known that for a given hydrocarbon feed, a practical limit is placed on the attainable vseverity of cracking conditions because Vof coke deposition. There is a certain severity of crack These ratings are expressed inV “index numbers” which are obtained by calculation. fromv blends tested at their detonation limited power outputs, Research .Committee ing above whichcoking becomes very rapid, and. (C. F. R.) super-charged 3-C engine.4 The test was carried out according to the Coordinating Research Council method designated CRC-F-4~ ybelow which it `is very slow. .This critical value may to some extent depend upon'the de‘sígnof »143, and described in the report of August Vv2, but for a given furnace it isa function of the nature of the feed.` Sinceaçfurnace must be shut in a Cooperative Fuel the furnace inwhich the cracking is conducted, » 1943 of the subcommittee on Blending Octane' Numbers of the Aviation GasolineA-dvisory Conn , down and cleaned as'soonyas deposition `of'coke - - begins to plug it, it is obvious >that only processes mittee to the Petroleum Administrator for War. Index numbers areapproximately equal to the in which coking is relativelypslow are economi cally practical. However, more severe cracking. percent of power that the fuel can produce as compared with the power produced by iso-octane 20 conditions can be maintained without objection- f underthe same conditions. able coking by any one or more of the following ' ' methods:v (1) introducing into the cracking zone, together withV the naphtha, flow" boiling hydro»Y ` `carbonscontaining from“ 1 to'about 5 vcarbonat “Index number” differs from “octane number” in that the lformer is a >measure of the allowable output of a super-charged aviation engine under take-off and climb conditions while octane num 25 oms per molecule; (2) reducing the amount of Y oleñns present in theïnaphthaLto-be cracked ;-'a’nd ' b_erv is a measure of the detonation tendency of the fuel in a nOn-Super-Charged'engine under Y » (3) l.increasing-the aroma-tic content of the -frac cruising conditions. Thus octane numbersand index numbers referto very diiferent fuel prop erties. , Y _; . ‘ ` tionto be cracked.y . .. ì l , . naphtha ,fractionsV having'ilow olefin content are cracked and recracked under certain- conditions, ‘ It is well known that naphthas used inthe blending of high grade motor fuels,` >and partic-> ‘ a relatively high boiling fraction may be obtainedv .that has a high concentration of aromatics, a low ularly aviation gasoline, must have a high anti knock value, must be free of gumeforming com ponents, and must maintain their anti-knockv properties under severe engine conditions, i. e.V high temperature, high compression and rich mix ture. A _ It has been discovered'that-if certain selected concentration of oleñns and a greatly increased index number. ‘ . It is an object of the present invention to pro vide an improved methodV for making aviation " blending stockhaving a high rich mixture rating For these reasons naphthasV rich in aro in supercharged engines, that is, a blending stock matic hydrocarbons and substantially’free from olefins are preferred. Aromatics are known to 40 having a‘high index number. Itis another ob ject to produce naphtha having superior anti have excellent anti-knock properties which dol `knock andy storage properties.' ‘ Another object is not decrease under severe operating conditions to provide a cracking process capable of» produc and have' no tendency to form gums“ or to de teriorate otherwise during storage.` Olefins, on ing a naphtha having high aromatic content and » the contrary, frequently oxidize and‘polymerize fr unusually low olefin content from which ,purei during storage, forming gums, and thus render a motor «fuel less desirable »for airplane engines.. It is well. known that by suitable thermal treat- Y ments 4Which may involve carbon-carbon scission . , and dehydrogenation or isomerization or poly merization or a com-bination of these reactions, it is possible 'to increase the octane number andthe aromatic content of hydrocarbon oils without substantially changing their boiling range. At the same time, however, such thermal operations, aromatica' particularly toluene, may be obtained, if desired. Still another object is to produce a maximum amount of aromatics and high index 'I number components from 'a >naphtha fraction‘ with a minimum amount of re-forming capac ity. ‘ - . . " ' . The process of this invention comprises the lfollowing essential steps: « 1. Thermally cracking a'straight run naphtha 55 having a selected boiling range; ` ` 2,404,452 s _ 4 . 2. Fractionating the resulting cracked products to obtain a'selected naphtha fraction; ' y ing stocks or which yield such aromatics in the subsequent cracking steps of the process. Ii’ the cracking stock is very rich in oleñns, then the product of re-cracking, that is the aviation blend~ Y 3. Rea-cracking said second fraction, preferably Vin the presence of a light feed; ' Y 4. Fractionating the resulting re-crackedprmi-V ing stock, will also be relatively rich in oleñns. ' . `uctsto produce light aviation blending stock and a relatively heavy ,Y fraction boiling essentially Also more coke formation will be encounteredY within about 140° and 225° C.; caribe obtained in the process. ’,That this must be which will, in part, limit the index number that » . 5. Further re-cracking said heavy fraction,r Vpreferably in the presence of a lightieed; and avoided has -been pointed out before. ' Thus the boiling range of this starting material Y ,_ 6. Fractionating the Yresulting cracked heavy'Y “lies in a range essentially within about 96°. and Vfraction to produce a heavy Yf,aviatio_nY¿bleriding--> Y stockof high index number. " ' 230° C; If the boiling range is high, say essen-k tially within about 150° and 236° C., an increase ' be inserted between'steps'4 >and 5' a treating stepY wherein both Ythe lightandheavy fractions are in the, yield of the heavy aviation blending stock Y `is obtained/.at the expense of a decrease in the c ,yield of the light aviation blending stock which v treated vto »remove small.V "quantities 'ci .olefins , maybe removed between steps ‘l and 5, men- f ' .r 'In addition to these essentialv steps, there'may f Which’maybe present before they Yare' separated. . . f, Further, Ithe iinalheavyraviation base stoc’k‘may be fractionated andtreated to improve its avia~VVV ti-onblending characteristicsz‘ ' 1 i " ï> Y, » «-.»‘ÍTl`iermalf’~’=V `rcracking vmeansV non-catalytic cracking. o'rïcracking in the.A absence-oi"~ a catalyst "asun'derstood in theV conventional> sense, in »aocordance with the accepted usage in the prior art tioned above. For example, if .the initial boilingpoint ofthe starting material is above theV boiling point of toluene, say at about 1l9° C., then the yield of vthe heavy aviation blending stock al most twice that compared` to the yield- obtainedk ` ' from a starting material having an‘initial- boilingVVV . Y point at §5° Cland includingïtoluene, While the total yieldofrrlight and heavy aviation ’fraction ’ as exemplified. by the deñnition found onY page?! , remains about the same. of‘fThe, Chemistry ofV Petroleum DerivatiJzes’Í-‘by , y In the» ñrstrstep of thisV process, the selected Carlton Ellis, publishedin 193s. The .success oiìrtheV present*k invention, and! par-_ ` ticularly ofx'the re-cracking, ¿dependsy onîV the ~. properl selection ofrthefstraight run'v andr the.' crackedénaphtha fractions. 'It is only` when alli 1 three' ofgthesefractions are-properly chosen crackedrunder the proper.conditionsfthat the full beneñts of ¿this inventionareï obtained.. ’ - lfllhe. natureVV of 'the .invention willV be better un- t . r 1 ‘~ ' . ` " straight run»_` naphtha fraction .is introduced» throughline l tintov a cracking zone sucha'sïa crackingcoiliä whereinrit is cracked in a pseudo , liquid phase,l (that is,"l~cra`ckedl above the critical Y temperature and pressure 'of-. the naphtha-frac-ï tion) ¿under conditionsvas severe as ispractical withoutexcessive‘ coking.> Il» desired, the time off vcracking may be extended andg'controlledi with theuaid or” a reaction> or soakingY chammr notiV derstoodefroin thedfolloivingdetailed description, »v shown.Y Forrinstance, these crack-ing conditions ~ , taken. together with the' drawing: forming` apart ~ Y Qfllthis. specification., .This ‘drawing presentsY ar of. a `preferred embodi Y simplified. flowdiagram ' mentofthe;invention.- ‘ . „ . . For; simplicity/riY the.“ drawing . doesßfnot show», . pumps, vheat:.exchangers> valveabyëpasses, vents, » have been> found` to- correspond- to lcrackim'g »tem peratures'between-.about 5409 C.V andë580° and; v inlet pressures between# about 54€) and Yi100; Lrg/sq. crn. Y ' Y Y ln >the secondV step, the resulting cracked prod- kj ~ @ucts froml'zone ¿Klare Wíthdrawnthrough line,- 53'2 and» are quenched` and fractionallydistilled in the ‘ reboilers, '"condensers, and 'otherÁauxiliariea Ythe proper ,placement- of.; which ,willvv at=-fonce .be evi 45 distillation column Zi‘lto separate therefrom those dent tdthoselskilledin theart.' products boiling aboveabout 230° C. and preferl- ' Y 11:? Therst‘raight runchydrocarbonl ¿napht a. which' > forms the starting material of thepresent process ably above Zûû‘îf C. whichY are Withdrawn from thev ' bottomof the column 2li through line 2 l. The maycoriginateïi‘rom, anyçcrudaßthoughÍaromatic remaining lighter portion of the products »is With- ' Floriinstance, a. 4straight run: 'naphtha‘ fraction having.' a _U.„;O. lE...characterizatio'ni.factor Vbelof-.xz tion column or naphthenic.' oils are :preferred=.to.p‘arañir1icones.' 50 drawn from the top of the column through line? 22- K ' ~ Y1.1;6 . andi preferably. below, 171.4; is.' preferred. ,ì The andfintroduced into another fractional distiller-_ wherein- the, products boiling Vbef low about $0", Grand-»preferably belowY about-¿193°l U. O. l?. characterization. factor is Aacm'easureloi`the parafûnicity of an oil. A highly paraiiinicjoil 55 of. columnlrZä.V rThe remainingfraction,` which; hasa, factor„of,=l2.5_ and aA highly aromatic and; has a boiling range.essentially-within aboutQGîTC; ' naphthenic Yoil has a> lovverf‘actor .approaching li) and< 230€’. C. ’will be -referred to hereinafter» as thel asça, minimum. i See. “Characterization of. l’petrvoe'f ` “second naphtha fraction,” and is?` withdrawn leum f_ractions’.’ by Watsonghlelson:Murphy fromV the bottom of` column 25 through vline Z-‘llï ,oi/U, O. P,.,'I¿nd, 'and Eng.` Chem., vol..2"!', l§lo„~l2, eo lTheY ,'gases.V and 'light hydrocarbons Withdrawn `‘135.14.60...) i' ' ; Furthermore, this 'starting `material` orfiirst naphthafraction should p_l‘eferably have an *AQ S. Y ` from the topfof. column 2,5,throughilinel2ä mayv 4'be separated rand employed in other processes’. For example, the C5 and lighter hydrocarbons ‘may Í Y 'Il-'_fl‘v/Luinitial boílingpointpf, not below Soi C. and --preierably notbelow 190,? C. „ its end boiling. point line, or, any C5 orhigher hydrocarbons. maygbe distillatiûïi Shouldbe below about employedas a blending. stock formotorífgas'olines if desired. The C4, hydrocarbons mayV becohvertedl ¿and preferably belowy about 290° C'. The reasonsforthese limitationsare asY follows: h_rst,V most of therihyvdrocarbons boiling youtside »these be alkylated to producea blending stock for. gaso-V » into octylenes, cracked to produce.- butadiene, 'on Valkylated to produce aviation blending stocks. limitstend upon craclfnng to4 produce' relatively 70 The C3 hydrocarbons may be. chemically treated'A large amounts of oleñns boiling within the boiling ' toproduce. acetone; and the. C1y and (lajhydro-k range of, the cracked naphtha> selected.;for.` the carbons maybe employed. as'fuel. Still further, _ 'subsequent cracking steps andïsecond, that this thehydrooarbons having `from 3.to»5.carbon atoms fraction contains most. of ythe'.ar.ornatic hydrocar per moleculemay beemployed again inl this proc. v bons which are valuable for.l aviation'fuel blend 75 essasthe light feed that is preferably introduced 2,404,452 5 into the next two cracking steps as described be low. ' . . , Y, . This sec ndy naphtha fraction usually hasan octane number of at least 74 or '75, and can be used Vwith advantage as a motor fuel, but not as aviation fuel. It is characterized by a relatively the second operation. In the third cracking op eration, the change in boiling range is less sige niflcant because of its `relatively high aromatic content. , ' Another way of determining the severity of cracking includes methods of determining the aromatic content of the cracked product. Some highlcontent of monocyclic aromatics and naph of the ways of measuring this aromatic content thenes, asV opposed to naphthas boiling above 'are as follows: v about 230° C., which contain a relatively large One method is by measuring the change in amount of polycyclic aromatics and naphthenes. 10 These latter compounds should not be included in the selective fraction because upon cracking under severe conditions they tend to promote coke for octane rating of the fraction after it is cracked. In general, the octane rating is determined for a debutanized fraction having an end point of 200° mation and lower the quality of the final product. Moreover, as pointed out before, relatively high boiling hydrocarbons tend to form large amounts of oleiins upon cracking, which boil within gaso produced in the process of this invention should. preferably have an octane number of vbetween .74 line boiling range. . Y Y _ By further treating this second vnaphtha frac C. For example, the second naphtha fraction and 78 by the C. F. R. motor method. ` Y Another method is by measuring the aromatic content by percent by weight of the cracked prod tion as described below, its octane number can be 20 uct which is extractable in 98% sulfuric acid. aviation fuel. This method is not very accurate, because >the strong acid tends to polymerize some of the ole ñns, causing them to remain in the oil phase. However, if the bromine number of the cracked through lineY 3|, wherein it isre-cracked under aromatics present in the cracked product. greatly improved, its aromatic content increased, and itsparaflin, naphthene, and particularly ole iin content decreased so that it can be used for " AIn the third step, the second naphtha fraction 25 product is below about l0, the weight percent extractable is within about 5% of the amount of is introduced into a second cracking coil 30 A more accurate method is by means of the conditions similar to those maintained in crack specific dispersion which is a measure of the ing zone I0. It is desirable, although not neces sary, to add to this second naphtha fraction, 30 percentage of aromatics inthe resulting product (see Ind. and Eng. Chem., vol. 29, No. 3, March, through valved line 32 before it enters zone 30, 1937, .p11 319-325). For example, a fraction a minor amount of light hydrocarbon feed con which has a specific dispersion of about 135 con sisting essentially of atleast one hydrocarbon tains at least about 50% aromatics. ' Thus, the having from l to 5 and preferably from 3 to 5 selected third naphtha fraction obtained from carbon atoms per molecule. The amount of the the products `of zone 30 should havea specific light feed employed as previously indicated is dispersion of at least about 135 and preferably merely sufficient to reduce the speed of coking for economical purposes, and otherwise has no ma terial effect on the properties of the selected ‘cracked naphtha fractions. This amount mayv rvary between about 5 and 30% and preferably be tween 5'and 15% by volume of the feed to zone ‘30. ' ' at least about 140. ' ' It is essential that each cracking operation de scribed in this process be carried out as a sep arate step. If it were attempted to maintain cracking conditions sufficiently severe to produce the desired result in one operation without inter mediate separation of light and heavy compo The re-cracking operation in zone 30 should be conducted under the most severe conditions which 45 nents, heavy and tarry components produced in the initial stages would cause rapid coking in the can be tolerated without excessive coking. These `first cracking zone I because many components subsequent stages. Moreover, the light unsatu rated components formed at the beginning would resulting . recracked products are withdrawn v through line 33, quenched, and fractionated as de are removed through bottom line 4| and the re conditions may be more severe than those in the be present in a large concentration, would poly of the original fuel, which tend to decompose readily, and cause coking, have been cracked in 60 merize to form oleñns boiling within the naphtha range, and thus would produce finally a more the ñrst cracking step and eliminated in the frac unsaturated naphtha, which is not desired. tional distillation columns 20 and 25. The con In the fourth step, the cracked product from Vditions correspond, for example, to temperatures line 33 is introduced into the fractional distilla ranging between about 540°-580° C. and pressures ranging between about 40 and 100 kgs/cm?. The 55 tion column 40 wherein the products boiling above about 230° C., and preferably above 200° C., maining portion is withdrawn through top line scribed in the second. step. 42 into the fractionating column 45, wherein the The severity of the cracking may be defined either by the crackingV conditions, or by the 60 lighter hydrocarbons boiling below about 90° C., and preferably below 100° C., are> withdrawn changes brought about by these cracking con through Vapor line 46 to produce the “third nap-y ditions in the properties of the hydrocarbon tha fraction” which is withdrawn through bottom and particularly in its boiling range. The line 41. latter method is particularly applicable when This third naphtha fraction has an olefin con the feed stock has a relatively narrow boil 65 tent much lower and an aromatic content much ing range, because in such a case, portions whose boiling ranges are changed are most likely to boil outside the boiling limits of the higher than that of the corresponding fraction obtained from the products of the first cracking zone l0. This third fraction should have an oc feed. When deñned according'tothis method, 'the cracking conditions which, for this process, 70 tane number, by theV C. F. R. motor method, at least 5 points higher than the second naphtha 'are such that a cracked fraction having the same fraction present in line 21, and preferably should boiling range as the naphtha feed amounts to have an octane number between about 80 and 85. about 50% to 90% of the cracked products in It should be between about 50 and '75% by weight 'each cracking operation, and preferably about „70% in the first operation and about 60% in 75 extractable with strong sulfuric acid and ~s'lioi'ild 2,404,452 .7 Y , haveaspecific'dispersion of atleast 140 and 'Vpref- - f A portion of the third'naphtha fraction (treated or untreated, and/or containing toluene or not) AIn a preferred, although not »essential embodi may, however, be removed from Ythe system ment of this process, the third naphtha fraction through valved line 59 and employedras an avia ' is subjeeted'to a refining treatment. Thus, as Cl tion blending stock, in that it now‘h'as an' octane illustrated yin. `the drawing, thev third naphtha number between about 80 and 85 and an index erably lï50Íorabove. a - ` ‘_ ’ fraction from the bottom' of îcolumn 45 is passed through lines >«il and’5l to a treating unit'äû. number, in a blend with 4 cc. of tetra ethyl lead/gallon, between about 125 and 135. The type of treatment employed depends large~ ly upon the properties of the third naphtha frac tion. For instance, if `this fraction 'should con Continuing the operation ofthe process of'this invention, the untreated, or preferably the treated tain'considerable amounts of oleiins, a treatment ating column 60 Vthrough -v‘alved line 6l, `where inïit is separated into a light aviation base stock thirdna'phtha fraction i'spassed into the fraction V‘adapted to'remove ithe ’major part'of the oleñns is preferred. ' Such a‘treatment, for example, is , a light sulfuric acid treatment. and `a heavy fraction. The’ out point for this separation may range 'essentially> within about 140° and 155"y C., but preferably whereinthe Although a sul furie acid 'treatment is known ordinarily to re duce the octane number of cracked gasoline, it does, on. the contrary, further raise the octane number of the third naphtha fraction prepared xylenes 'and eumene which have high index núm bers, pass overhead into the light aviation baseV stock (for'instance, at about 150 or 152° C.) . This according to this invention. 'A suitable sulfuric acid ~treatment lmay involve the contact of the light aviation base `stock is withdrawn through vapor line 62 and if desired may >be .further treated or may be blended directly into aviation - fraction with between about 1 and 5% by volume of a "95 'to 98% sulfuric'acid. The acid employed in theztreati'ng may be fresh 'or V‘may be spent or yother motor fuels. ' . Y The light aviation base stock should have an ' Other treatments which may be employed in 25 octane number by the C. F. R.> motorvmethod between> about 80 and 85 and should havean the treating `unit include for example passing index number in a blend with 4 cc. of tetra ethyl the fraction over adsorption agents such as clay, alkylationacid. , w. '- ' , lead of between aboutl 130 and 140. bauxite, fuller’s earth, diatomaceous earth, sili Between ca.- gel, etc., vat elevated temperatures below in about 50` and 75% of the light aviation base stock of suitable concentration toV produce a sludge con tainingthe undesirable constituents which can and it should have a, specific dispersion above cipient cracking; contacting with phosphoric acid 30 should be extractable with strong sulfuric acid, about 140 and preferably above 150. The boilf ing range of this base stock may lie between about 90 and 155c C. and preferably between 100 and . be separated; selective hydrogenation in the pres ence of a-suitable hydrogenation catalyst, suchl as l5ü° C., although its end boilingr point‘may be Vfinely divided nickel, chromium oxide, molybde num or tungsten sulfide or a combination of as low as 140° C. these, etc.; treatment with catalyst of the clay The heavy naphth'a fraction Withdrawn from the bottom of column 6U, which hasa boiling range essentially within about 140 and '230° C. and preferably essentially Within about 150 and '200° C., usually has an octane number by the C. F. R. motor method within about 80 and`85, type'under conditions which do not cause sub~ stantial cracking; destruction or removal of harmful sulfur compound by -doctor treatment, extraction with alkaline Vsolution in the presence 40 of a solutizer for mercaptans, lor oxidation -in the presence of copper catalysts, etc. The specific conditions involved in the treat obtained from the book, “Chemical Refining of tween about 1-10 and V125. this book are descriptions of processes for the Chapter II), with alkaline reagents (see Chapter IV), sweetening processes (see Chapter V), re ñning by adsorption (see Chapter VI) and relin aviation base stock, in that it has/a specific dis _persion of-at least 15€) and preferably aboveand it is between 65 and 95% extractable with strong , ' ,much lighter than treatments which would have to'b’e applied to conventionally cracked naphthas lor to the naphtha obtained in the iirs't cracking 60 Y desirable, but not necessary, t0 introduce Ywithr the'heavy fraction in line 63 a light hydrocarbôn between about 5 and ~30% by volume, and pref erably between about 5 'and 15% by voluineof ’the 'bottoms from the rfa-distillation are usually high.Y If desired, the untreated third naphtha frac feed'to cracking zone 170. tion, or the treated andre-distilled naphtha frac tion may be withdrawn through Valved lines y¿il or 5I and 52 to the toluene recovery plant 53, where in toluene is extracted and withdrawn through ¿Valved line 54. The remaining non-toluene por . tion of the third naphtha fraction is .returned 4to the process "through >valved line 58. „ „ r3 t‘o 5 carbon atoms per molecule. The -amount These 65 -of this added light hydrocarbon should range -ly aromatic and may beblended into fuel oils. . , In the ñfth essential step, the heavy fraction withdrawn from the bottom of columneûû »through through valve line "i2 consisting essentiallyiof at least one hydrocarbon having preferably from The treated naphtha may be'redistilledin col umn 55 to remove higher boiling constituents formed during the treating operations which are withdrawn through "bottom line 56. sulfuric acid. lines 63 and 'H is introducedrinto a third'crack ing coil lû. As in cracking Zone 30, it i's'also step of this process, in order to obtain a product having the same color, stability, low degree of The aromatic-con tentof this heavy fraction from >the bottom of column 60 is much higherthan that of the light treatment of hydrocarbons with sulfuric acid (see unsaturation and low mercaptan content. , top of column 6B. Thisheavy aviation `base-stock usually has an index number ranging only be-V In These treatments may be relatively light, i.‘e. . but its index number in a blend with 4 cc. of tetra Petroleum,” vKalicl'ievsky and' Stagner, published Ving with a solvent (see -Chapter VII). ` ethyl lead is usually much lower than «that of the light aviationfbase stock withdrawn from the ing processes as above mentioned may be readily ' by Reinhold Publishing Corporation, 1942. , 70 ' , ' It is possible, 'but not preferred economically, -to employ the treated third naphtha fraction from :line el as the feed to cracking zone Tllby >by-jpassingthe column `60 >through line 13. The cracking in zone ‘lil is generally'carried l‘out 'under substantially the same coi-idi'tionsy as ‘those -employed 'in Àzones H1 and 30, although v , 9 _ f Y _ 12,404,452 . the pressure may be higher, if desired, ranging etc. Many of these blending agentsmaybe ob tained or produced from the -icy-products o'f'this between about 40 and 95 k'g./sq. cm. In the sixth essential step, the resulting cracked heavy fraction Vis introduced intoV a fractionating process. ._ __ » It may be noted that the described process pro' vides for the manufacture of a'superior aviation column 80 through line 8| from cracking zone 10, wherein the products boiling above about 200° base stock and valuable products from naphtha C; and preferably above about 180° C; are with fractions of relatively little value. ' drawn through bottom line 82. The lower boil ing fraction withdrawn through line 83 is dis _ ~~ _. The'follo’wing comparative examples illustrate- tilledin fractionating column 85 to produce a 10 hydrocarbon 4fraction boiling below about 100° C. and preferably _120° C.l withdrawn through top 'A straight _run naphtha fraction having ythe the . .invention: Example > . I _ - ' , _ vapor line 86, andan intermediate fraction with properties `disclosed in the table lbelow lwas drawn 4through bottom line 81. This Vbottom cracked in a iirst cracking zone having atransfer _ product is a vheavy aviation base stock usuallyV V15 temperature »of about 548° C. and an inlet pres having an octane number above about 80 and an sure of about 51 kg./sq. cm. to produce a cracked product which was fractionated to obtain a sec index number in a' blend- containing l‘1_-cc. of tetra ethyl lead/gallon,»between about 150 and 165. The index number range is considerably ond naphtha fraction having the properties 4dis closed in ¿the table below. This second naphtha higher than the index number of the light avia 20 fraction and a mixture of C3 to C5 cut amounting 'tionîbase'sto'ck removed from the _top of column to about _14% of the feed was then cracked'in a >(il), orthe third‘ naphtha fractionfremoved from line 59 or the heavy fraction in line 63. 'second cracking furnace having a transfer tem perature of about 5419 C. and an inlet `pressure of about 63 lig/sq. cm. to produce a re-cracked , vThe lighter hydrocarbon withdrawn through lines-’46 and`86 _of columns 45>`and 85 may be ïiìoinedfwith those> _from the top -of ‘column 25 in Y product which was fractionated to- obtain a third V'line 26 and separated for use in the same manner . in the table below. 'This third naphtha fraction Was then acid treated with about 2% by weight of 98% sulfuric acid and re-distilled to remove A‘a's‘ï those described from line 26. ` " naphtha fraction having the properties disclosed ' '_ ¥~ The heavier fractions withdrawn from vlines 2 I, - 4l »and r8i of columns 2U, .'40 and 80, respectively, 30 lanyA high polymers formed during the acid treat _are highly aromatic and may be blended, if de ment. This treated fractionwas then further si'red,_'i_nto fuel oils or used for any other suitable fractionated into a lightl aviation Vbase stock and purposes. _ Y _i a heavy fraction having the properties disclosed The heavy aviation base stock maybe With in the table below. The resulting heavy fraction drawn from the _system through valve line 88 or and aV mixture of C3 and C5 gases amounting to it may be _subjected to treatment similar `to that , about _11% of the feed was-_then passed through described for treating unit 50. If the heavy a third cracking furnace vhavinga transfertem ibase stock is treated, it is passed through valve perature of about 545° Q. and an inlet pressure "line 89_ into thetreating unit 90 and then passed . of about 76 kg./sq. cm. to produce a cracked vinto the re-run column' ¿95 _similar to column 55. 40 product which was fractionated to obtain a heavy. Thistreatmentof the base` stock does not ma aviation base stock having the properties dis teriallychangeits octane number orits index closed in the table below.A Straight . ' I Light Heavy rltiln!1 nssf’gää‘lia n'äääga avliation tHezìvy aviation fralîztion traction fraction stock , _ stock na " ‘ ' ‘ l f .Speciñc gravity ____________________________ __ . C t a 0. 786 A. S. T. M.: f ' I. B. ’F. B. P _ _ _ _ _ _ _ 120 77 _-°C__ ._°O_-°C__ 134 157 210 , 123 146 209 _ _ _ _ _ _ _ _ ._°C__ __________________ -_ 'Bromine number;- ______________________ __ ._ (Reed.) vapor pressure ________________ _. Octane number (clear, A. S. T. M \ . Y 0. 824 0.805 0. 844 110 97 146 _ 130 121 139 . 166 108 117 138 154 160 170 148 157% 169% 152 179 180 ` 25.4 6 18 49 60 .8 V1. 2 75.8 81.5 80.5 _ y 6% 5 53 69 , ` motor method)- __________________________ _.. Index number (in blends containing 4 cc. llnarblend. y _ . 0 0.858 _ ' 129 180 4 __ 86 - 0. 3 . 52.6 ` TEL.) ..... ..`-'. .......... __f_'.' ________________________________ _- . niimbergfrom what it; ase ~ --°O-_ `>Percent byw.extractablew h98% HzSO4 ~` ‘ ^ rac lon P34. ` 10%50%. 90% ____ ._ ‘ 0.807 ase » ' 0. 4 83.5 ‘90 119 157 ` 136 . as before the Ltreatment. 60 f__f ‘__fI_'h__e_ _treated vproduct may- be withdrawn _from fthe top of vcolumn l95. throughyalve line `9_6 ,or .it `'may be _passed _throught valve line _9,1 `into a blend "ing- plant _^ I_.ûßiwhere?itLisi mixed with _other base _stocks to produce _a finished aviation gasoline.` is materially above that of the third naphtha fraction or even thelight aviation base stock. Furthermore, it may berseen that the high boil f >ing range of the heavy aviation base stock lends jSome suitable Vblending yagents ` toV `produce >a 7iinished aviationggasoline include light straight run gaso1ines,_`isopentane, cyclopentane, neo itself well forÁblending with iso-pentane andfsirn ._ ilar volatile blending stocks. _ ' „ i Example II ' hexane, '2, Bedimethyl butano, di-isoprop-yl ether, triptane, iso-octane, alkylationgasoline produced From the above tame, it may Vte' yseen that the index_number of thel heavy aviation base. stock Y 70 Another sample of a heavy fraction which had " by reacting isobutane with" C5 and lower oleñns, been cracked, fractionated, re-’cracked and fur _ etc._ These blendingagents give the proper boil ther fractionated as described in Example I had the properties shown in the table lbelow. A feed ing range tothe final blend and _its octane num ‘jbe'r may be ¿further improved by the addition of »tetra-#ethyl lead, aromatic mono-cyclic amines, consisting of this heavy fraction contained 13% j by volume of a light hydrocarbon feed consisting ' _ Öl predominantly of propane ._andnpropylene, vbut j î ,also including soniei'C'i; and> Cs' hydrocarbons, was Y f 12 Y l fingf ¿the resulting ¿re-.cracked .product ¿bye itself :to 1 produce a heavy fraction-boilingfessentiallyiwitl'lin ì `ture* of ab.outv540°_C. and an inlet ¿pressure Vof 76 :midrange _oiabout `.140° «,C.l:and.r230°:.C.,;turther -non-catalytically crackingsaidheavy'v fractionziin Y; thenfractio-nated toob'tain a heavy'aviation gas Vconsisting >essentially o1" at: least k:oneghyfdrcc'arbon î further cracked in a cracking coil ata tempera- i ¿1kg/sq. cin. ' The resulting 'cracked ‘product »was ,5 fthe'fpre'sence of `a minor amount iof: a light’ffeed havingA from §13 ltori 5» lcarbon-zatorns Vper finolecule, i >oline base stock having> the ,improved properties .separating thegresu'ltingi further ci‘ackedmrodguet ' It shouldV be .g noted ' Y l ¿shown inthe table below. byitself to produce: an aviation¿'¿basexstockiboil~ ing; essentially ywithinf the -range `of ¿about ¿100°` that the index number of the- heavyY aviation f ' i base stock is better than iso-.octane containing î4 4 cc. tetra ethyl lead. The resulting cracked'p'rod- " l yuct wasthen fractionated to obtain a heavy avia-V ` .-tion gasoline lb_ase .stock having` the ’improved "fpropjertiesshown Yinthe 'table below.V ' Y Heavy '„gaand100kg/saam. . - . 'i .A „i . .. ¿volumegoflthe îfraction being-cracked. _ avlationf .fractlonr . f 6. >TIT-he process of ìclaim-5,` wherein theiamount Heavy _ ~ «and 200710.., each ofcsaidcracking operations-being. yconducted ,iatgartemperature'r between. about; 540° base stock n .'7. 'The> 'processoffclaim’ì whereinîfsaidi-light Y `feed is between about 5%1-anri'l5%.byf:vclumeïzof Speciñc'gravity _____________________ _ _ Y » 1504 ___________ __ __- ; l0. 8,47 0. 858 »149 133 155 1,6 148 l5 174. 5 186 170. 5 184 14. 7 8. 5 68 87.0 ` y20 Octane numbericlear, A. S. 4T.,M.-vC. F.-R. motor method)____ 'index number (in blends, c Y `'l"EL)K_______._. _._‘__ ’ ~83. 5 t ming 4 , - . in the range of ~about"90°C„;»and 230°„-C_.,¿non-catalytically Vre-cr.acl«:ir~1g said y*second '.naphtha Above‘l54 separating the resulting re-cracked'. 13o fraction, product by itself to produce awthird naphth'affrac i `I claimas my invention: -tion boiling essentially withinthefrangeof about ._1. Aprocess forîproducing anaviation gasoline i 100° C. and 200° C., further separating said third ,naphtha fraction `vby itself «into» aY light îaviation basestock.l from la straight-run naphtha having a ‘ boiling range; essentiallywithin about 90° C; and ' ¿ ' , second naphtha‘ fraction boiling essentially 'With- ' 91:3 Y .___.__-., ____________ ._ 1 lytically cracking said naphtha, sepa-rating'the resulting crackedp-roduct by itself- to‘pro'duceîf'a v25 Y _ à~8. ,A ’process for producing.¿anfaviationfgaso line base stock from a- straight runinaphtha »hav ing a boilingrangelessentiallyfwithin about 90° C. and=230° C., comprising theqsteps of none-cata `(Reed.) Avapor pressure___; ________ __, ........... _____ ....., ...... __ i the ~vfractionfbeing cracked. Y Y `35 230°.C;, comprising _thestepsof ncnfcatalytically base rstock boiling -essentially vwithintheY range ; .cracking saidnaphtha, >separatir-ig the resulting> . of about 90°C. and l,155° C. anda heavy fraction boiling essentially within the range of about,1v40° l ~cracked Íproduct by itself >to produce .a second ï -naphtha fraction boiling essentially :within‘_:t‘neV f C. and 200° C.; furtherlnon-catalytically cracking /said heavy fractionfseparating the resulting ,-fur- 'V Q rrangeofiabout90° C. 'and 230° C., nonscatalyti 1 ¿cally 17e-cracking said .second naphtha fraction,` .i0L ther crackedproduct by »itself _to .produce .an Y"separat-ing _the resulting :re-*cracked product-,by . aviation base «stock lboilingïV esentialli7 _within lthe Y Y mangent about .100° C..fand 200°fC.,¿each¿of.îsaid ' ‘ >about 140° c_and abouezßo" _0., furtnernoßncata- Y ' „cracking Aoperations „being conducted at a tem- ¿ perature between about 540° C. and 580° C. and at Y lytically cracking said heavy fraction and separat- ` Aing i the resulting «,further~gcracked 1product by it» 45V a pressure between about 40 and 100 kg./sq. cm. ` itself to produce a heavyfraction boilinggbetween self to produce 9. A process for producing an aviation gasolineV aviation base stockkgb‘oiling hasezstcckrfrcm astraieht run 'naphtha having> essentially within .the vrange ._ofabcut _1.00° _Q. i and a boiling range v.essentially within about 90° C. conducted at a temperature between about §540° " and 230° C., comprising the steps of non-catalyti gC. and i5180° C. ¿and at a pressurebetween about 50 vcallycrackingsaidnaphtha, separating the re ',sulting cracked product- by itself to produce a ¿40 and 100 kg./sq. cm. ' ‘ .20.0° C.,._each.of.said cracking-practices being second naphtha .fraction boiling essentially with ‘2. The process of ¿claim 1,-wherein the `firsty cracking operation is conductedunder »conditions in the range of about'90°'C. and 230° C., non-cata v@lytically¿refcracking `.said second naphtha frac to yieldazgacoline having an octane number above: . about El7_4: _and said second crackingroperation -is Ation('inlthe.presenceof -a minor amount of a light ffeedV consisting V.essentially of at least one hydro , conducted to yield agasoline having ‘an octane Y *numberßabove about 80. _ Y ` ,Y carbon >havingfromvß to 5 carbon atoms per " molecule, »separating »the resulting Y1re-cracked >3. The .process of claim.lfwhereingthe.naphtha - _. Vproduct by itself to produce a third naphtha frac-V` fractions boil essentially within the range of f ‘ "about.100°`C.„and_200°C.. tion boilingessentially .within the rangeïof-about ' _ l. _4, 'Theîprocess of claim Lev/herein,saidgstraight-È " _run A naphtha fraction has , ar U. .0. „ Pjcharacter- § ` _iz?ltiongfactor below 11,6.4 ~ i l. ` Y _100° „C. v and 200° C.,.furtherseparatingßsaid third l ¿fraction ioy-îitseifA _into a. iight aviation base stock: 1 l i'V _15. l._A process for producing an _aviation gasoline.: "boiling »essentiallyiwithin the range .of ` about 100 base stockrfromastraight run naphtha .havínslaî boiling range Ywithin ,about .90° _C. A_and 230°_„C.,' tiauywithin 'thefrange of about v150° aandzoo‘? i . fraction'boiling essentially within the range *of> 70 molecule,-and separating the >resulting further C., further non-catalytically- cracking ysaid :heavy „ comprising the steps >of‘nonecatalyticrally cracking.:V - Afraction in thepresence -of a minoramount gof'a saidv naphtha, separating the resulting cracked light feed consisting .essentially of at ¿least one product by itself :to'produce a second-naphtha `hydrocarbonhaving from 3 tov 5 carbonatoms per about A90° C. and :23.0° C.; non-catalytically lre cracking saidsecond naphthafraction in the pres crackedproduct by itself to produce a heavy avia ‘ » ence of vaininoramount of a light‘feed consist- 4 Ytion base stock boiling `essentially within ¿the range` of about„l00°»C. Vand 200° C., .each of said -ing essentially of atleast one hydrocarbon having .from 3 to 5 carbonratoms -per.molecule, separat ature between about 540° .C- and 580° C... and at cracking operationsbeing conducted at a temper 2,404,452 f ~ 14 13 14. A process for producing an aviation gaso a pressure between about 40 and 100 kg./sq. cm. 10. A process for producing an aviation gaso line base stock from a straight run naphtha hav ing a boiling range essentially within about 90° C, and 230° C., comp-rising the steps of non-cata line base stock from a straight run naphtha hav ing a boiling range essentially within about 100° C. and 200° C., comprising the steps of non-cata lytically cracking said naphtha, separating the resulting cracked product by itselfk to produce a second naphtha fraction boiling essentially Within lytically cracking said naphtha, separating the resulting cracked product by itself to produce a second naphtha fraction boiling essentially with the range of about 100° C. and 200° C., re-crack ing said second naphtha fraction in the presence of between about 5% and 30% Vby volume of a light feed consisting essentially of at least one hydrocarbon having from 3 to 5 carbon atoms per in the range of about 90° C. and 230° C., non-cata lytically re-cracking said second naphtha frac tion, separating the resulting re-cracked prod uct by itself to produce a third naphtha fraction boiling essentially within the range of about 100° C. and 200° C., treating said third naphtha frac tion to remove a major portion of oleñns therein, further separating said third fraction by itself into a light aviation' base stock boiling essentially within the range of about 100° C. and 150° C., and a heavy fraction boiling essentially within the range of about 150° C. and 200° C., further molecule, separating the resulting re-cracked product by itself to produce a third naphtha frac tion boiling essentially within the range of about 100° C. and 200° C., treating said third naphtha y fraction to remove a major portion of the oleñns therein, furtherfseparating said treated third naphtha fraction by itself into alight aviation ' base stock boiling essentially Within the range of about 100° C. and 150° C., and a heavy fraction boiling essentially within the range of about~150° C. and 200° C., further non-catalytically cracking non-catalytically cracking said heavy fraction, separating the resulting further cracked prod uct by itself to produce a heavy aviation base stock boiling essentially within the range of about 100° C. and 200° C., each of said cracking oper ations being conducted at a temperature between said heavy fraction in the presence of between about 5% and 30% by volume of a light feed con sisting essentially of at least one'light hydrocar bon having from 3 to 5 carbon atoms per molecule,l about 540° C. and 580° C. and at a pressure be tween about 40 and 100 kg./sq. cm. separating the resulting further cracked product ' by itself to produce a heavy aviation base stock boiling essentially Within the vrange of about 120° C. and 190° C., treating said heavy aviation base stock to remove a major portion of the oleñns by volume of concentrated sulfuric acid and re therein and blending the resulting treated heavy distilling the acid treated fraction to remove any aviation base stock to produce an aviation fuel, polymers formed by the acid. . 12. The process of claim 10, wherein said heavy 35 each of said cracking operations being conducted at a temperature between about 540° C. and 580° aviation base stock has a boiling range between ' C. and at a pressure between about 40 and 100 about 120 and 180° C. kg./sq, cm. y » 13. The process of claim 10, wherein said heavy IVOR G. NIXON. aviation base stock is also treated to remove a 11. The process of claim 10, wherein the said treating step comprises contacting said third naphtha fraction with between about 1% and 5% 30 major portion of oleñns therein. 40 '