US2466334A - Method of producing synthetic fuel - Google Patents

Description

April 5, 1949. w. E. SKELTN METHOD OF PRODUGNG SYNTHETIC FUEL 2 Sheets-Sheet l Filed Aug. l0, 1944 April 5, 1949. w. E. sKELToN METHODAOF PRODUCING SYNTHETIC FUEL Filed Aug. l0, 1944 2 Sheets-Sheet 2 Patented Apr. 5, 1949 VWilliam E.-.Skelton, yBeacomll. X.,vassignor to A.The .Texas Company, .N .ew York,N. Y.,a .corporation .of Delaware Application IAugust 10, 1944, Serial No. 548,870

s Claims. .1

.This :invention relates Lto the vmanufacture rof motor -fuel and jmore particularly aviation .ga-soline, and 'is particularly directed :to the production of high octane `aviation igascline -jof the type .classed V:as super-,fueL

It is conventional practice to prepare so-:called i100 .octane .aviation :gasoline by :blending @a .suitable .base stock, such .as .straight-run .orwcatalytireally. cracked :naphtha -of :high octane, Withvarious :synthetic :fuel components :or `additives such .as @C4 alkylate and :hydrogenated `polymer fgasoline, :together -.withisopentane .and :amanti-knock compound of thecharacter of .tetraethyl lead. Where .aviation gasoline of still .higher performance values is required, las determined by .the 'fwe'll `known AFD-LC :and AFD-.3C vknock:rating tests, Yit has 'been .necessary to include .larger proportions up to substantially 100% of the synthetic fuels, thereby reducing the :proportion :of `the ibase fuel permissible in the blend, and also .include `:aromatic additives of the .character off /cumene v.to improve :the .rich `mixture performance .in .supercharged engines 'as determined by the AFD-.3C test. .It `has been vfound that lrisobut-aneethylene alkylate, prepared under certain critical f f xconditions with .an :aluminum lhalide acatalyst, produces a high yield 4.of v2,3-diniethylbntane, which latter :has exceptional properties `iior mproving 'the vAFD-3C erich mixture .rating While at the Sametime avoiding'the normal deterioration of the AFDelC rating `encountered with .the .aromatic additives vheretofore employed. 'While ythe total C2 alkylate can .be :employed as :such :an .aviation gasoline :additive with .good results, it is preferred to utilize a .fraction :boiling upto vabout 265 F., or even a yC5-C26 cut or a ,hexane `cut Which is highly concentrated in the fdesired2,3 fdimethylbutane.

One of the `chief diiiculties heretofore encountered in the ldesign .of a plant to manufacture thesaid C2 alkylate additive A'as .a bomponent .of high grade aviation .gasoline tor super-fuel, has been lthe high installation and operating :expense involved in the preparation of Ya satisfactory ethylene .feed :stock .t or the C2 aalkylation unit. .It

:is .desirable that the lethylene feed stock .should contain vat least about A3.0% `by weight :of ethylene, Yand `preferably .about :4D-:50%, :and :should .be comparatively free from propylene .or .at least 'have not lmore than .about 10% by wete-ht of ipropylene based on tthe yWeight -of the :ethylene in the charge. Also, :the feed stock should contain less than .about 30%, and `prefer-ably.less than .25 by lWeight of lixed :gases .lighter Vthan G2, namely .methane and hydrogen. While .re-

.I2 iinery ,gases from fboth thermal Land `catalytic fcrac'leingoperartions `are vavailable in Alarge i quantities, the `ethylene -icontent of these vgases `is comparatively low, and the expense of `low-.temperature :high-pressure fractionation to separate between -ethy-lene .and methane and .form a desired ethylene fchfa-rge :stock yhas been Econsidered eco- .nomicall y -vunattractive `with the equipment `and metho ds available.

.It has heretofore been Asuggested that Tan fethane-,propane .feed Astock be .thermal-1y convented under temperature and flow pressure conditions to ,pro-duce .-a .resultant fconversion ,product enrichedfinfethylene, which can be subsequently treated by fractionation .and selective polymerization .to yremove ipropylene, to thereby produce fan ethylenecharge for the C2 alkylation .Thisfprocess involvesexpensive fractionation, and the Ca polymer .resulting from ,the selective .polymerization is .of llower grade, suitable for motor -iuel `ibut not yfor `high -g-rade 4aviation gasoline. :Even in -this case, the ethylene charge is diluted 'with .a large Vproportion oi eth-ane, methane land :hydrogen and the'dilu'ent gases-in large proportion Irender the charge Adiiiicult to handle in the C2 alkylationfstep, and result in substantial .losses -of un-reactedethylene and ireduction 4in the 'yield ci the C2 alkylate. Y

@ne of :the principal `objects yof the present invention is to provide .la unitary process lfor producing Yaviation gasoline yor super-fuel including .C2 alky-Iate as a component thereof., `and wherein -a .puried and concentrated ethylene yfeed stock izor the alkylationstepris obtained 'as acomponent par-t of the `unitary process rand in a simple and economical manner without having to fractionate lbetween ethylene ran-d methane.

lAnother object of the present invention is `-to provide -an improved .method of preparing 4a concentrated ethylene feed :stock by a combination xof ,petroleum oil cracking, thermal vconversion -of a C3 .and lighter condensate fraction of the .selectively from gases llighter than "C2, :and a rcracking gases `from the cracking step, an absorptionfoperation-for treating'uncondensed products of -the thermal conversion vto 'absorb Cz of .catalytic Vcracking under conditions to give high gas yields and form `a :high .grade `aviation base stock, thermal conversion -of Ca :and lighter condensate gases from the catalytic cracking, recovery of a purified and concentrated ethylene feed stock low in fixed gas content from the products of thermal conversion, alkylation of the resultant ethylene feed stock to produce the 2,3- dimethylbutane additive, and catalytic conversion of C4 constituents of the gases from catalytic cracking by alkylation or co-polymerization and hydrogenation or both, and blending of the resultant high grade products.

Another object of the invention is to provide an improved recovery and recycling system for an aluminum chloride and HC1 alkylation unit, whereby both HCl and isobutane are recovered in substantial amount from the offgases in a simple and inexpensive manner for recycling to the unit.

A further object of the present invention is to provide an aviation super-fuel and an improved method of producing the same, including a blend of aviation base stock, C2 alkylate, hydrocodimer or mixtures of hydrocodimer with C4 alkylate, and an anti-knock agent, such as tetraethyl lead.

Other objects and advantages of the present invention will be apparent from the following description when taken in conjunction with the attached drawing and the appended claims.

As a preferred and specific embodiment, the process of the present invention involves catalytic cracking, particularly ilulid catalyst cracking, of a suitable petroleum oil feed stock such as gas oil, depropanization of the resulting naphtha and lighter cracked hydrocarbon condensation products after removal of the tail gas, thermal conversion of the overhead from the depropanizing step to substantially increase the ethylene content thereof while materially reducing the C3 content, compressing and refrigerating the compressed stream from thermal conversion to Yeffect partial condensation with separation of uncondensed vapors from resulting condensate,

passing the uncondensed vapors in contact with a Cri-C4 absorption oil produced in a subsequent step of the process to absorb most of the ethylene and eifect a separation from methane and hydrogen, passing the rich absorption oil together with the above-mentioned condensate to a fractionating step where a Cz and lighter fraction containing atleast 30 weight per cent of ethylene and less than 30 weight per cent of methane and lighter is taken overhead and thus separated from a Ca-Ci bottoms, the major portion of the latter being returned to the absorption step to serve as the absorption oil, alkyiating the resulting C2 and lighter fraction with isobutane under conditions to produce a C2 alkylate consisting mainly of 2,3-dimethylbutane, debutanizing the depropanized products of catalytic cracking to separate a C4 fraction from a stabilized cracked naphtha, subjecting the C4 fraction to catalytic alkylation and/or co-polymerization and hydrogenation to produce C4 alkylate or hydrocodimer or preferably both, and blending an aviation fraction of the stabilized cracked naphtha with said C2 alkylate, said C4 alkylate or hydrocodimer or preferably both, and with a suitable antiknock agent, such as tetraethyl lead, to produce a resultant aviation super-fuel.

The invention is more particularly illustrated in the attached drawing which shows a preferred embodiment thereof, and wherein Fig. 1 is a diagrammatic view of a portion of the apparatus for carrying out the method of the present invention; and

Fig'. 2 is a continuation of Fig. 1 and is a dia- 4 grammatic view of the balance of the apparatus. Referring to Fig. 1 of the drawing, a gas oil charge stock is introduced by the line I0 to the heating coil II, where the temperature is raised to about E50-900 F. The heated oil then passes -by line I2 to the catalytic cracking unit I3, where 'it is cracked in the presence of a suitable active cracking catalyst, such as a synthetic silicaalumina. It is to be understood that any conventional type of catalytic cracking can be employed, such as xed bed, fluid catalyst, etc., although fluid catalyst cracking is preferred. It will be appreciated that the gases from catalytic cracking are more unsaturated than the corresponding gases from thermal cracking, and catalytic cracking is therefore preferred for the present process. Where the object is to produce a high grade aviation gasoline or super-fuel, the cracking step is carried out under more severe conditions to produce higher gas yields and proportionately lower motor fuel or naphtha yields, thereby forming increased quantities of ethylene and C4 olefins which are subsequently converted to the high grade motor fuel additives. For this purpose, the fluid catalyst cracking is generally carried out at the higher temperatures of about 950-1000 F. and low pressures of the order of 5-10 pounds gauge, with a severity factor determined by the catalyst to oil ratio and the weight of oil per hour per weight of catalyst held up in the reactor to provide a conversion of (5U-80% of the gas oil charged, as is well understood in this art. This will produce roughly about 15-25% by weight of total C4 of which approximately half is butylene, about 10-15% of C3 and lighter with the ethylene running around one-third or more of the C2 content, and about 3545% of 400 F. E. P. naphtha.

The resulting cracked products pass by line I4 to fractionator I5, where cycle gas oil is removed as a side stream I6, and heavier material, together with remaining suspended catalyst, is removed as bottoms by line I'I leading to a suitable filter or thickener for the recovery of the catalyst in conventional manner. It will be understood that the fluid catalyst cracking unit is merely illustrated diagrammatically, and any suitable conventional unit can be employed for this step. Moreover, it will be appreciated that the heating coil II need not be provided, since the oil can be heated to the desired cracking temperature by direct contact with the hot catalyst from the regenerator, as is conventional practice in certain of the iiuid catalyst cracking units.

The resulting cracked naphtha together with the crackingrv gases pass by line I8 to condenser and cooler I9 and thence to accumulator 20, Where uncondensed gas passes 01T by line 2l. This gas is picked up by compressor Illa and forced under high pressure of the order of 200 pounds per square inch through line I la to a conventional absorption and stripping unit indicated by I2a. Here the gas is cooled and contacted with a suitable absorption oil, such as a 3438 gravity gas oil, to absorb a substantial proportion of the condensable gases. Unabsorbed gas, including a substantial proportion of the Vfixed gases, namely methane and hydrogen, and

termed tail gas, is discharged from the top of the absorber by line I3a to the refinery fuel lines. The rich absorption oil containing the absorbed gases then passes to a stripper, Where the absorbed gases are stripped out of the remaining lean oil, which latter is then recycled to the absorber after being cooled. The overhead gases :cracking of jpropa-ne and propylena .are chilled and Icondonsed to -form lthe iso-called ""absorption condensate? which 51s returned lsto "the system "by pump Ma-and line 15a.

`While the tail gas of course contains vvsom-'e un- :condensed ethylene, it is found that vthis separation 'is highly desirable `'in order `to remove a large part of the methane and substantially .all Aof the hydrogen from the system. This iis limhportant-,since Athe and lighter feed stock ultirnately supplied to the thermal conversion un'it should befrelatively low vin inert or xed Jgases ('C1 and H2) and 'preferably should run below-'2.0 `volume1: erc'ent'of such -xed gases. By ut'ilizing only the gas condensate ifrom the cracking 'operation and discharging the tail gas, expensive low tempera-ture fractionation to remove methane Iand hydrogen from the gas charge to the thermal 4'cor-lversion is avoided, -thereby effecting fan `economical advantage in spite oi someloss `of ethylene in the tail gas.

The 'condensate from accumulator '218 iis then forced by pump 22a through line l22, where it -is mixed with the absorption condensate fromv line 15a, -and the mixture passed into the prestabilizmoved overhead by line v24. A portion of the overhead stream sucient for reflux is diverted by line '-25 through condenser 26 to accumulator v2l "and returned by pump 28 and line 29 to the 'top of tow-er 2-3. 'The balance of the voverhead gas which may be under line pressure of about -200 pounds 'per square inch at atemp'erature `of about 100 F. is passed through a pressure reducing valve Bill, where the pressure lis -lowered if necessary to provide an outlet pressure 'from the thermal conversion coil `3`| of 0-50 pounds per square inch gauge. vIt will be vappreciated that 'the coil inlet pressure for this Vcondition will be dependent upon the coil design and the Icharge rate. 'Thecharge -gas is heated to a temperature of about '1400" to eiect crackin-g in the coil, yand the'cracked products are then rapidly cooled wlthoutallowing appreciable soaking time to precent any substantial polymerization with the formation of normally liquid products.

Under the conditions specified above, 'the :charge gas fed to the thermal conversion unit will gene-rally `contain about-'304119 -by vivtngg'lfift of C2-*of which at least half is ethylene, about 40-55 lby weight of C3, less than l@ weight per -cent of methane with substantially no hydrogen, and a small `percentage of C4. It lis Vdesirable that this charge gas be as high in `ethylene content as practicable, `since the yethylene appears fto A`pass `through the cracking coil substantially unchanged. Therefore, 'the vdepropanizer overhead Afrom the catalytic cracking condensate represents 1a very 'suitable charge stock 1.to the gas "conversion step, since it is higher in initial ethylene icontent than the Ycomparable vfCs and lighter 'fr-action :obtained 'from the condensate `ol? `tl'ierxn-al cracking, and `is vmuch higher in ethylene :content vand much lower 1in methane and hydrogen content than the C3 and lighter -gases from either v'catalytic yor thermal cracking vtrom. which the gas has not been separated. The propane-propylene ratio of the charge gas appears :relatively unimportant, since :both of these constituents are :susceptible to cracking 'to ethylene iequa-l degree. Some :ofthe ethane of the .charge Igas .of :course breaks down with the lcnrnalti-on of .ethylene and lighter; but *additional ethan-eis v,formed fin the .gas conversion istep .from -the Conso' vquently, the .ethane content of lthe products of --zstant'ally decrease the Cs content :of the charge `gas, while at the same tune increasing the ethyllfenfe, methane, and hydrogen :content thereof with .little ior no increase .of the fethane content. Also, there :is fa very smallbLuld-up to 'C4 and heavier. The :ineuiftablebreakdown to Vmethane and :hydrogen under these conditions is not objectionable since the :charge :gas .had :been 4lair-,rely denuded of .these yconstituents and the resultant products of `conversion will therefore :contain `.less than about 25% by Weight of methane and hydrogen. .This proportion fof the lighter or `i'ixed :gases can readily be tolerated in the subse quent absorption step `without objectionable .loss of ethylene. Such isinot the lcase where the xed gas content of the products of conversion is higher, :since the :sweeping ieffect -of higher :proportions of these Li'lxed gases acts to entrain ethylene in the olegas from Ithe absorption :step with @correspondingly .greater `loss of the vdesirable ethylene.

lThe conversion products from :cracking @coil 23:1 4are passed by line .32 to exchanger 33 `icontaining heating coil M connected `to waste rheat bo'ler r35. 'Boiler feed water :is supplied by line fsand passes vthrough :the vneat exchange coi-l 2311, whereby the waste heat of the conversion prodfuchs is `used to generate high pressure steam, such as steam tof :150 `,pounds per isqua-re linch gauge, :and the conversion :products are `llherc'eby "rapidly cooled below Aa reaction temperature. The -resulting :gaseous products of thermal :.converson, whichana-y `thereby ;be cooled from 1400" to around 4660 `thencefrpass by .line 3l `.through Water cooler 3B Where Athey :are vfurther @cooled to about 110" The gases .are ythen lfed 4byline 39 :to :a compressorlw, where they are compressed to about #500 pounds per-:square inch, and thence are supplied to 'exchanger 41 where they are refrigerated to yabout 0" F. with refrigerant supiplied 'byjlirrefl iatabiout -20 The resultant compressed Vand refrigerated kproductszare `then introduced by vline 4.3 into accumulator 44,` where vapor-liquid `separation .is rinade. This condensa.- :tion substantially .reduces `the load on the abfsorber fand 'materially improves the :ethylene rre- .covery in the :absorption rstep.

'The :llncorndensed'zzgases from accumulator 44 pass -by :overheadvapor line 45 to absorber Mi, which latter .is supplied `with la lean absorption `oil `by line 41.. Asfwi-llrbe more particularly described hereinafter, the Vabsorption .oil :is Aprefer-ably `-a Csech'bottoms :obtained,fromme-conversion prodnots, land -therefore'supplied by the sys-tern. yThe heat ol' absorption is continuously removed-lay circulating condensate from fan `intermediate tray of the fa'bsorber'by line l48 through 'exch-anger '49 supplied with refrigerant atabout-20" Fr-.byli-ne 59 and :returned loy'guump 5| :and line -52 rizo a 'flow'er trayI fofl the absorber. `By fthe use lof this 75, tweenthe ethylene fand-:ethane on l:tlie @one hand;

.ntercoole1:, the tempera,ture :of 'the ,absorbergis end Lmetlume.undv hydrogen .on Ythe othen whereby -a substantial proportion of the methane and most of the hydrogen can be removed by overhead lline 54 through pressure release valve 55 as tail gas which can be sent to the gas fuel lines. The net result is a recovery of a C2 and lighter product gas in the absorber containing about 40 weight per cent of ethylene for an overall recovery of about 94% of the ethylene in the gas supplied to the absorber by line 45. By somewhat reducing the percentage of overall ethylene recovery down to say '85%, a product gas will be absorbed containing as high as 50 weight per cent or more of ethylene in the C2 and lighter portion.

The rich absorption oil passes from absorber 46 by bottom line 51 and is mixed with a stream of condensate passing from the bottom of accumulator 44 by line 58. The mixed stream then flows through pressure reducing valve 59 where the pressure is reduced to about 400 pounds per square inch, and is introduced into fractionator 62, and to which high pressure steam is supplied from the waste heat boiler 35 by line 63 and branch line 64.

The C2 and lighter overhead from fractionator 60 passes by line 65 through exchanger 66 supplied with refrigerant at about 20 F. by line 61, the chilled overhead then flowing by line 68 to accumulator 69 where suflicient liquid is .condensed to supply vthe reiiux requirements of tower 60, said reux being returned to the tower by pump 10 and line 1|.

Lean oil accumulating in the bottom of fractionator 60, and which consists essentially of Cri-C4 hydrocarbons with the C3 amounting to at least about 80% by weight thereof, is discharged by line 12. A major proportion thereof is recirculated by pump 13- and line 14 through water cooler 15 and then through exchanger 16 supplied with refrigerant at about F. by line 11, and the refrigerated lean oil then passes by line 41 to the top of the absorber to serve as the absorption oil therein; It is thus seen that the bottoms heavier than C2 from the gas conversion unit 3| is utilizadas the absorption oil, so that absorption oil from an extraneous source is not required. Moreover, sufiicient makeup Ca-Ci is continuously formed and supplied from the conversion unit 3|, so that the absorption oil in the system is continuously replenished, while some excess is continuously discharged from the system. This excess hows through line 18, and all or any portion thereof may be recycled by line 19 to the inlet of the conversion coil 3| for recracking.

Since the high temperature employed in the rconversion unit 3| produces a small amount of aromatics, a portion ofthe excess bottoms is continuously or intermittently diverted by line 80 'through heater 8|, where the temperature is' raised to about 40G-500 F. The heated (J3-C4.

'..polymerized to form Vpolymergasoline for motor fuel. Products of polymerization are passed by line 83 to depropanizer 84, where C3 and any lighter is removed overhead and returned by line 85 to the recycle line 19 for return of this material to the thermal conversion unit 3|. In this manner, heavier aromatics are removed from the absorption-stripping system to prevent build-up therein, while at the same time a yield of polymer gasoline for motor fuel is obtained and unpoly merized paraiiin gases recovered and recycled to the thermal conversion unit. Thedepropanized polymer gasoline is discharged from tower 04 by line 86 leading to a suitable stabilizer and thence to storage (not shown).

Uncondensed C2 and lighter is removed from accumulator 69 by line 81 together with any excess condensate over that required as reiiux for tower 60 and which is removed by liquid line 88. The resulting concentrated and purified ethylene charge then passes through pressure reducirlar valve 89, where the pressure is reduced to about Z50-300 pounds per square inch as desired for passage through the C2 alkylation unit hereinafter described. The charge then passes by line 90 through product heater 9| supplied with high pressure steam from waste heat boiler 35 by line 63 and branch line 92 to compensate for the heat of expansion and to raise the temperature of the charge to about 1l0-130 F. The puriiied ethylene charge at the proper pressure and temperature then passes by line 93 to the C2 alkylation unit as more particularly described in connection with Fig. 2.

Referring again to the depropanizer 23, the catalytically cracked naphtha bottoms from that tower is passed by line 95 to the debutanizer 96 which is operated to remove C4 overhead by line 91. The stabilized cracked naphtha then passes by line 98 to the fractionator 99 where the desired aviation fraction is removed overhead by line |00 through condenser |0| to accumulator |02. Aviation naphtha base stock is then drawn from this accumulator and passed by line |03 to theblending tank for the preparation of finished l aviation gasoline, as more particularly described hereinafter in connection with Fig. 2. The heavy naphtha bottoms from fractionator 99 are withdrawn by line |04 to storage for motor fuel.

The overhead C4 fraction from line 91, which contains a high proportion of butylenes in addition to isobutane and normal butane, is passed all or in part by line |05 to the C4 alkylation unit |06, where the butylenes are alkylated in conventional manner with isobutane introduced by line |01 in the presence of a suitable alkylation catalyst, preferably strong sulfuric acid or hydrouoric acid, introduced by line |08. As the conditions for butylene alkylation are well-known and any conventional type of alkylation unit, such as the pump and time tank, jet reactor or impeller reactor, together with customary neutralizing, washing and fractionating equipment, can be employed, no further description of this step is required. A debutanized 311 to 350 F. end point fraction of the C4 alkylate is passed by line |09 to the blending tank described in connection with Fig. 2.

On the other hand, all or any part of the C?. fraction from line 91 may be passed by branch line 0 to the C4 copolymerization unit l I, where isobutylene and normal butylene are copolymerized in conventional and well-known manner. The resulting codimer or fraction thereof boiling up to about 265 F. is then passed by line ||2 to a hydrogenation unit ||3 to saturate the product and form hydrocodimer inconyentional manner'. The resulting hydroc'dinnis fsuppliediby l'in ll'l to the blending tank described in connectioniwith Fig. 2.

The proportions 'of fthe 'Ci :faeti'on from `1ine'9'l supplied to C4 alkylation and to hydro'odimer production `respectively depend upon the Ai'solii-'1t'alle and butylene balance of the particular refinery as well as up'on the ultimate grade `o"f iai/lation gasoline desired. Botnthe ci -lkylation andthe C4 alk'ylati'on :require substantial 'amounts Adf "iso-'- butan'e. Where the is'obutane s'upply is limiting, and there is an 'oversilpply of butyl'en'es fin relai tion to isohutane yrequired 'for `Ci alkylation and C4 alkyl'ation, then a part o'i fall of the Ci-niy She passed to hydrooo'diifnfer production, with .povi sion for the recovery of 'the isbutane in the charge supplied thereto by line rijn, so that this isobtane 'can b'e used forCg aflikylaitoh. lVV-hefte there vis a plentiful supply :of isobutane `"and ma# oapacity of 'aviatiohalkylate fis desi-riedjthn' all or Substantially Aall 'f the C11 frein VYliie 9-1 Will be passed to C4 alkylatio'n. However, where the object is to produce a high grade "s'uioe'i'i-ieli, A'and quality rather than 'quantity 'of the aviation :glas-1 olih'e is controlling, the' G4 charge 'will generally be split between the el alkyl'ation unit and the hydrocodimer unit to v'provide b 'o'th types 'of high grade aviation oripoilet's 'foi' blending Withvth C2 alkyl-ate and the ca aiyti'cally cracked base stok in the manner her after dsiibed.-

Refeir'gfto Fig; l2, 't e pil e'd 'd trated ethylene hae fro ii'lle 93 passs" by line IIS together with fresh feed isobutane from line IIT and recyolei'sob'uitah'e from l-iln'e 'I'BM'tthe surge tank |'|9. FiOln-iir'eytn una 'ie' passs byline lat and either of Vvalve controlled 'tranen lines |2| and |22 to one bf a' pair b'f de u ation tanks |23 andl |24. These tanks nlleu with activated aljiiiiiiinabr other dita-ble dehydiatin' agent which "serves 'to' m'dv i ture from the hydrocarbon b alkylaton unit. The d'hyia il e` flows by either of brauen lines '|25 'and |26 line rzl, which in tui-fiy cbnnebts with lin-ej |29 leading to th alkylati ate'r-l l tanks I 23 and |24 are operated'alt being on- St'lea'in for' drying? the4 h', e Whil" other is being fea-buvait 'i sir 'supplied' by line- |30 containing steainbe |31 and connected by vali/e' ebntijollci bib elles |32 andv l|33` with tanks '|23 and |14 r by either of branch-lines |34 "nu ls'etb line |36 containing water c'oler |31, and l'adin to water settler |331. Water ieiiibved freni tneiclsliyurj j ing bed by the ratjj ating? gas is separated from that gas in las and uisbliarg'uby line |39V to suitable disposal, while the' rea V then passed hy line |40 to asil'itablholder? f ultimate retu'ln to line |'3'0 and rertlfilla'i'ilig i`n theV system.

The C2 alllylation reactor |42i ispreff" the tower type as desorifbedand -elairnefd' ln pending application of Louis Clarke,v Se 535,261, filed' May 142;'- 1`94l5; new Pali 2,.1.C|",137YV dated September 3; lgllywttfil: tions of' the reaction as described application. For example; weer 14a may be is feet in diameter and 7 0 vfeet' in" height and lly nearly toe the top withV a alu4 sin hydrocarbon-commend ti' ed dition-ofd'ispersd aluminum hlonde: Th co ples liquidi may be' "pared-by neati""g herbs e,

napbtna. or alkyl @blends steli teit being mainly etnan-e and riii-etnane. and u ii'gfV i ene' tlijeenarg' gas can' butyl chloride; with aluminum `c hlrid'e until liquid p'rcidl'lct -is r4formed as the -result 'of fafcoml binatin vkoi' complexing of the 'aluminum chloride with the hydrocarbon o'r alkyl chloride; Ker# serr isfgenrally used -to initially form'the co'mpleii liquid for 'starting lip `the plant, and thereafter the' ndessary `makeup vooinplex 'liquid -is .supplied ih 'si-til. by Taon b f al-kyla-te with dispersed aluminum 'chloride To the preformed complet liquid there is added a quantity of anhydrous aluminum 4chloride which 'is dispersed in 'the 'coniplei: liquid and aiotiyat'es the same. Duringr conitinuacef the Aprocess; additional aluminum chloride is added :by line |43 to maintain the aci tivity of the catalyst; as generally controlled by measurement of "rthe heat vof hydrolysis which shuld be maintained above about r320 Calories per grani Av activated Complex' liquid.

activated aluminum chlorideehydrocaboh complex liquid is maintained as the oontinuo'us phase in the tower and -the isobutarie-ethylen'e charge together with a smallproportion `of HC1 in"V` trod'uce'd by line' IMA in va, pro'portio'n' t .provide less than 0;1% lby .Weight on the Weight -(if the hydroearbon charge; are passed through line' FM and dispersed through a plurality of nozzles or orifices fl i5 into the liquid `catalyst body adjt'loe'nt the base of the tower. As 'heretofore described, the `pressure -n the tower is maintained at around 225 pounds per square inch so that the isobltan', which is usedy substantial v'molar excess "of the ethylene', 'is liquid "phase: ethylene feed however may be in gas phase, being effectively rise upwardly through the catalyst liquid dueto dilrere'no'fe in gravity therebetween and without sufdient agitation' to-v frm anv e'rnul's n; until they reach the upp'r surface thereof, when the Y liquid hydrocarbon constituents' o'alsce" t frny alsupsrpbseu'hydrocarbon layer attire top '6i tli tower;

witnanfetnyiertnarge gassosi-aiding atleast abut :3o weight vper cent etnyiene-,` the b" with "ai suitable absorption oil;` suh as a" 36:538" soil, byline |55'. The absorber -i"s"'cnoled by recirculation from intermediate' tray th'" iirlflflinev |57 passing'throgh Watercooler |58 an t ned-by line- |59 to* Icwe tr y. Th'

ets ana'- of the iso'butane from the gas, which latter is` discharged by overhead line |60 to fuel, or may be recycled to the inlet of the conversion heater 3| as illustrated in Fig. 1. It will be understood that the above described recovery and recycling process is generally applicable to any isoparaiin alkylation process employing aluminum chloride and HC1 as the catalyst, and particularly a mixed phase process where both HC1 and isobutane are present in oigases from the alkylation unit.

The enriched absorption oil passes by line |62 through steam heater |63 into the upper portion of stripper |64. Live steam is introduced into the bottom of the stripper by line |65 and serves to strip out the absorbed isobutane. The lean absorption oil is returned from the `bottom of the stripper by pump |66 through Water cooler |61 and thence by line |56 to the absorber |55. Overhead vapors of water and isobutane pass from stripper |64 by line |68 through water cooled condenserl 69 to separator |10, where separate layers of condensed Water and isobutane form. The lower Water layer is discharged to ditch by line |1|. The upper isobutane layer is returned by line |12, pump |13 and line ||8 to form a portion of the recycle isobutane for the C2 alkylation unit. As this recycle isobutane is mixed with the ethylene charge in advance of ,the dehydration unit, any remaining water is thereby effectively removed.

When it is desired to recover the HCl in the off-gas of line |50 for recycling to the aikylation unit, an alternative procedure is employed in scrubber |5|. In place of supplying an alkaline solution to the scrubber by line |52, a constant boiling mixture of water and HC1 is substituted,

containing approximately 11 mol per cent HCl and 89 mol per cent H2O. Contact of this constant boiling mixture with the vapors in scrubber |5| dissolves or absorbs the HC1. HC1 solution discharged by bottom line |53 is then passed by line |50a to a distillation tower |5|a containing a closed coil heater |52a. The excess HCl is removed overhead by line 53a, dried in a suitable sulfuric acid or alumina drier |54a, and recycled by line |55a to line |44. Theconstant boiling mixture of HCl and water-.dis-m charged as bottoms by line |56a from the distillation unit is passed through a suitable cooler |`51a and then recycled by line |58a and line |52 to the scrubber |5|. Depending upon the percentage of HC1 employed' in the hydrocarbon charge to the alkylation unit, the expense of recovering and recycling the HCl may be less than the expense of the fresh HCl and neutralizingagent required in the first described procedure, in'which event the HC1 recovery system is used. Ordinarily, where proportions of HCl less than about 0.05% by weight of the hydrocarbon charge are employed, the HC1 recovery system is not economically justied and the neutralization procedure is used.

The hydrocarbon liquid layer in gas separator |49, in which some of the complex catalyst-may beentrained, passes by line |15 to settler |16 Where the liquid complex catalyst immediately drops out and is returned by gravity through line |'|1,to the continuous catalyst phase within tower-v |42. Excess complex liquid formed in situ in the tower |42 during continuance of the process is discharged intermittently or continuously at a low rate by bottom line |18. This also serves to prevent the thickening or increase in viscosity of. the complex liquid which would otherwise occur during long periods of continuous operation,

The enriched.

` liquid by line thereof is diverted to line |8| through water cooler |82, and thence recycled by line |41 and pump |83 for mixing with the fresh hydrocarbon charge from line |21 and recycle isobutane from line |46, the mixture passing through line |28 to the :dispersion nozzles |45 in the base of tower |42 as `previously described. This hydrocarbon recycle :thus serves to maintain the proper reaction temperature within the alkylation tower, as well asv to supply a substantial volume of liquid for mixing with the gas phase of the hydrocarbon charge, thereby producing more eiective dispersion and reaction of the ethylene in the mixed phase operation. A minor proportion of the hydrocarbon product from line |80 is discharged by line |85 to the deisobutanizer |86 equipped with reboiler |81 and operated under conditions to. remove overhead an isobutane-rich stream containing up to 95% or more of isobutane. This isobutane stream passes through condenser |88 and line |89 to accumulator |80, from which pump |9| returns a portion thereof through line |82 to serve as reflux for the tower, the balance being recycled by line |46 to the alkylation charge line |28 as heretofore described.

-line |99 to accumulator 200, from which pump `through a heating coil 201 where the temperature is raised to about 300 to 650 F. and preferably about 500 F. The heated alkylate then flows by line 208 through either of valve controlled branch lines 209 and 2|0 into one of the clay treating chambers 2| and 2|2. These chambers are filled with a suitable percolation clay, such as fullers earth, which serves to remove combined chlorine from the heated alkylate. This chloride removal materially improves the lead susceptibility and other desirable properties of the alkylate.

VThe resulting chloride-free alkylate then passes by one of valve controlled branch lines 2|3 and' 2|4 to line 2 I5, which latter introduces the same into alkylate fractionator 2|6. The percolation -clay chambers are employed alternately, so that jdimethylbutanemay run about 'Z5-85 volume pery aie-casas cent, with the 4C5 content :being .less than 5 fvnhnne per cent, and the 'Cn-eCs content running about 10-,15 volume per cent. The bottoms 'boiling above 265 F. Awill also :generally Irun vless Athan about 5 volume lper cent. Consequently, the debutanized 265 F. end point ial-kylate fraction constitutes a very satisfactory aviation tfuel additive to provide the rich mixture `performance and other desirable characteristics of .2,3-dimethylbutane. If desired, the cut point yon the fractionator 2 I S can be at the .initial boiling point of the C7 fraction to take overhead a Gis-Cs Inaterial; and the .latter can be further fractionated to separate a total hexane cut or a material consisting almost entirely of 2,3-dimethylbutane.

.The overhead aviation cut from fractionator 216 passes through condenser '2.18 and line 219 to accumulator 220 from which lpump 22| returns a portion as reflux to 'tower 216 by line '222. The bottoms from tower 2|6 are passed .by pump 223 through cooler 224 and line 225 to storage for motor fuel.

The desired proportion of the aviation fraction of the C2 alkylate isy withdrawn from :accumulator 220 by pump 226 and passed by line 221 to blending tank 228. Suitable proportions of .the C4 alkylate, catalytically cracked base stock 'andA hydrocodimer, produced as described in connection with Fig. 1,'may also be introduced into the blending tank 228 by lines |09, H13 and H4 re spectively. In some cases, a high octane straight run aviation naphtha introduced by line 229 may be used in conjunction with or in substitution for the catalytically cracked base stock. In addition, the desired amount of anti-knock agent such as tetraethyl lead may be added by line 230, and commercial isopentane may be added by line 231. The resulting blended aviation vgasoline is discharged by line 232 to suitable storage. It will be understood that the aviation base stock, either catalytically cracked or straight run, orcertain selected fractions thereof, lcan be acid treated or subjected to catalytic rerunning in conventional manner prior to introduction vinto, blending tank 228. It will also be understood that a gum inhibitor may be added to the blend, particularly one made from the catalytically cracked base stock; and any other agents, such as dyes, color stabilizers, etc. included in well known manner.

The following specific example is given as illustratory of the present invention, but it is to be understood that the invention is not limited thereto.

A 81.7 gravity paraffinic gas oil having a 50% evaporated point at 675 F. was subjected to :fluid catalyst cracking with a synthetic silica-alumina cracking catalyst, resulting in a 65% conversion under the following conditions:

Temperature, F. 975 Pressure pounds per square inch gauge 5-10 Catalyst/oil weight ratio 4.5 'Weight of oil per hour per weight, of catalyst held up in reactor 1.0

The conversion products resulting from this operationv analyzed as follows, based on the gas oil charged:

Per cent vCa and. lighter dry gas weight-- 11.05. Coke dok3.0

i Total C4 volume 2.2.0. C54O0 F. end point naphtha do- 40rd Cycle gas oil do- 35.0v

The depropanizer overhead 'resulting from de- 14 propanization rot' :the combined cataitytlcally cracked naphtha condensateiand :the absorption condensate in depropanizer 23 (Fig. 1.), andsupplied as feed stock to the gas conversion unit '31.; has the following typical analysis:

A typical analysis of ythe vconversion @products e from unit 3|, obtained with the feed `'seit fo'xf'th immediately above, is the .tollowingz Weight per cent Hydrogen 0.5 Methane 21.9 Ethylene 30.0 Ethane 26.6 Propylene 9.0 Propane 7.3 C4 plus 4.7

With an overall recovery of 94% of the ethylene in the absorber-fractionator system I6-60, the product gas supplied by line 93 to the C2 alkylation unit analyzes as follows:

Weight per cent Hydrogen 0.2 Methane 21.9 Ethylene 41.5 Ethane 35.9 C3 0.5

The following tabulation is a -summaryofthe utilities required for'producing 110,000 pounds of ethylene per stream day:

Fuel

Power Btn/nf.

. KWB/Hr.

Heater Gas Compressor.`

W a s t e H e a t Boiler C r a c k e d G a s Cooler Refrigeration.. v Pumping, Reboiler Product Heater-.-

Net Total..

The 8,060 pounds of steam per hour enclosed in parenthesis in the above table represents a. net production in the waste heat` boiler 35,which substantially supplies the steam requirements of the plant, leaving only a net total of 520 pounds per hour to be furnished from an exterior source. The fuel requirements are readily met by the tail gas and other gases discharged to the fuelflines. TheV major requirement for cooling water is readily obtained at low cost, and' they actualrefrigeration requirements are low. It is therefore seen that the operating expense of the present method is extremely low in comparison with the utilities required for conventional low-temperature high-pressure fractionation, anda' very economical system is thereby presented.

The conditions of the C2 alkylationoperation and the results obtained, utilizing the concejo-1 15 trated and purified ethylene charge gas set forth above, are listed in the following table:

based on total hydr o c a r b o n charge minimum Alkylate yield weight per cent :ethylene reacted 262 Ethylene reacted, weight per cent of ethylene charged 81 ene mol ratio in thereactor, with a 67 volume per cent`conversion to codimer based on the butylenes converted, and with a 93% total butylene conversion. The polymerization products were fractionated to separate a codimer fraction boiling up to about 270 F. This fraction was then hydrogenated in the hydrogenation unit l I3 in conventional manner in the presence of Raney nickel at a temperature of about 450 F. and a pressure of about 1000 pounds per square inch to saturate the codimer and produce the so-called hydrocodimer. y

Typical tests on the resulting C2 alkylate, C4 alkylate, hydrocodimer and the catalytically cracked base stock produced as described above, together with the same tests on a straight run aviation base stock `supplied from an exterior source, are set forth `in the following table:

C; alkylate C atayt- Smigh o approxi- C Ik 1 H M ica y t mately 75% 4 a y ycracked run base aa-dimethyt a comme has@ stock butano stock Gr., API 81.0 70.0 66. 4 54. 3 62. 0 RVP, p. s. i 7.6 3.0 2. 7 6. 5 6.7 ASTM Distillation:

Init 132 160 169 114 110 137 190 220 134 144 144 222 23D 213 195 197 250 238 311 238 273 319 265 340 305 Allrylate composition: Per cent by volume 3 On the basis of 1000 barrels per stream day of alkylate, the isobutane and ethylene requirements are:

Isobutane consumed in alkylation reaction BPSD-- 730 Ethylene charged to reactor lbs./SD 109,830 Ethylene consumed lbs/SD-- 88,962

The C4 olenic feed charged by line |05 to the C4 alkylation unit 106 was alkylated under conventional conditions in a pump and time tank reactor at a temperature of around 50 F., utilizing a 5/1 isobutane to butylene feed ratio, a 150/1 isobutane to olen contact ratio in the reactor due to emulsion recycle, a 60% isobutane concentration in the reacted mix, a contact time of minutes, a pressure -of about 50 pounds to maintain the reactants in liquid phase, and makeup fresh feed .of sulfuric acid of 98% strength to maintain a titratable acidity within the reactor system of about B9-9.0% HzSOfl.l The resulting alkylation products were neutralized, washed, and fractionated in conventional manner, and a 310 F. end point aviation alkylate fraction separated.

The portion of the C4 feed supplied by line I I0 to the C4 copolymerization unit lli was treated under conventional conditions at a temperature of about :S20-345 F. in the presence of a xed bed phosphoric acid catalyst, utilizing recycle to maintain about a 2: 1 normal butylene. to isobutylwhich is classed as a superfuel.

The invention is further illustrated in the following table showing typical blends of the stocks listed above, together with commercial isopentane, to produce a 150 grade aviation fuel, The 12C/150 refers to Army and Navy performance numbers, the 120 performance number being a 1C rating of isooctane plus 0.69 ml. TEL per gallon or a 1C index number of 106; and the performance number of being a 3C rating equivalent to S reference fuel 3.55 m1. TEL/gal. or a 3C index number of 152. The table is based on the preparation of 100 barrels of this grade of aviation fuel containing 4 cc, TEL/gal.

.The aviation base stock set forth in the above table can be either the catalytically cracked base stock or the straight run base stock listed in the preceding table, since the properties of the two base stocks are similar except for 3C octane and the proportions used are small, with the result that little diierence occurs in the calculations for the above blends with either base stock. The above table demonstrates that the smallest isobutane requirement for the production of this superfuel is in the blend of C2 alkylate with hydrocodimer. The largest isobutane requirement is in the blend of C2 alkylate and C4 alkylate, but in this case arhigher proportion of. the base stock :agradecer is permissible. Consequently, where isobutane is available, while isopentane is limited, this represents a desirable blend. For maximum production of this grade of aviationfuel with a relatively small but intermediate isobutane requirement and a minimum amount of Cz alkylate, the blend containing both C4 alkylate and hydrocodimer with the C2 alkylate is preferred.

It is obvious that various grades of aviation super-fuel can be produced by the method of the present invention, the above examples being merely illustratory. Furthermore, while certain specific temperature and pressure conditions have been set forth above for the C3 and lighter thermal conversion, it is to be understood that these conditions can be varied from the specifiedA preferred operating conditions. For example, temperatures of about 1250 to 1500 F. lcan be employed with pressures ranging from about atmospheric up to about 500 pounds per square inch or somewhat higher. Also the specified conditions for the absorption and stripping operations for recovering the ethylene feed stock to the C2 alkylation unit are merely the Vpreferred conditions for economical operation, and the temperature and pressure conditions can be varied from those shown and coordinated to give similar results as will be well understood in this art.

While an activated aluminum chloride-hydrocarbon complex catalyst has been described above as being preferred for the C2 alkylation, it is to be understood that other aluminum halide catalysts can be employed for this purpose. For example, other aluminum halide, such as aluminum bromide, complex liquids activated by the addition of aluminum halide may be used. Likewise, a fixed bed operation with lump aluminum chloride, or a bed of inert contact'material impregnated with aluminum halide may be employed. Likewise, in the C4 alkylation, while sulfuric acid or hydrofluoric acid are preferred as catalysts, other wellknown catalysts for this reaction can be used, such as BFa-water complex, chlorosulfonic acid and the like. The copolymer can also be produced with other conventional catalysts such as sulfuric acid, phosphoric acid and the like, as is well understood; and the hydrogenation ofthe copolymer can be carried out in well-known manner with other conventional hydrogenation catalysts including metal sulfides and oxides.

As set forth above, condensate from catalytic cracking is preferred because of the higher olenic content. Moreover, catalytic cracking is capable of producing a high grade aviation base stock, which is not the case with the naphtha produced by thermal cracking. However, wherea suicient supply of high grade straight run aviation base stock is available, thermal cracking condensate including absorption condensate, from which tail gas has been separated, can be utilized as a, part or all of the charge to the thermal conversion unit in accordance with the present invention. In such case the thermal conversion may be carried out under somewhat more severe conditionsl to increase the ethylene content, and the absorption step is generally operated with a lower net ethylene recovery so as to effect the desired separation of methane and hydrogen and obtain a Cz charge for alkylation which is sufliciently concentrated in ethylene. The present invention thus .enables such thermal crackingV condensate to be utilized as a charge for the process with somewhat lower alkylate yield on the basis of the gas condensate handled. This is feasible for a refinery which is not provided with catalytic cracking facilities but hasa suilicient supply of cracked gases from thermal conversion operations and also a source of supply of straight run aviation base stock.

Further, it is to be understood that a portion of thermal cracking condensate can be mixed with catalytic cracking condensate for purposes of the present invention. This is particularly suitable in those cases where the catalytic cracking produces an excess of aviation base stock over the required amount of C2 and C4 alkylates as well as hydrocodimer. By mixing a portion of the thermal cracking condensates with the catalytic cracking condensate, the supply of ethylene and butylenes can be increased to provide a renery balance, and thus utilize the products produced by 'the present process to the best advantage in the production of maximum quantities of the aviation superfuel.

Obviously many modifications and variations .of the invention, as hereinbefore set forth, may Nbe made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. The method in the manufacture of high octane aviation gasoline which comprises recovering from the products of cracking of hydrocarbon oil a C4 fraction containing butylenes and a v.C3 and lighter condensate fraction containing a Vsubstantial proportion ofethylene and some methane, subjecting the said C3 and lighter condensate fraction to thermal conversion at high temperature and low pressure to substantially in- 3,5crease the ethylene content thereof while ma- `terially reducing the C3 content, recovering from the products of thermal conversion by condensation and absorption most of the ethylene content of said Iconversion products in a refrigerated con- 40T,densate, fractionating said last-mentioned condensate at a pressure substantially below that required to fractionate between ethylene and methane to separate a C2 and lighter fraction containing at least 30% by volume of ethylene and v,less than 25% by volume of methane and hydrogen, alkylating isobutane with ethylene ofthe said C2 and lighter fraction in the presence of an aluminum halide catalyst under alkylating conditions to produce a C2 alkylate consisting mainly of 2,3-dimethyl-butane, dividing said C4 fraction into two portions, subjecting one portion of said C4 fraction to polymerization and hydrogenation to form hydrocodilmer from the butylene content thereof, alkylating isobutane with the other portion of said C4 fraction in the presence of an acid alkylation catalyst to produce C4 alkylate, and blending an aviation base stock with said Cz alkylate, said hydrocodimer, said C4 alkylate and isopentane to form high octane aviation gasoline.

2. The method in the recovery from the products of cracking of hydrocarbon oil of a fraction lighter than C3 containing a high proportion of ethylene, which comprises subjecting the cracked hydrocarbon oil products to cooling and condensation to form a condensate consisting of cracked naphtha together with lighter normally gaseous hydrocarbons, separating uncondensed normally gaseous hydrocarbons from said condensate, subjecting said separate normally gaseous hydrocarn bons to absorption with an absorption oil to absorb a portion of the said gases while the remainder passes off as tail gas, stripping the rich absorption oil to remove the absorbed normally gaseous hydrocarbons and cooling the latter to recover an absorption condensate, combining the nrst -mentionedcracked naphtha condensate with said absorption condensate from which tail gas has been separated, depropanizing said combined condensates to separate a C3 and lighter fraction containing a substantial proportion of ethylene and some methane, subjecting said C3 and lighter fraction to thermal conversion at high temperature and W pressure to substantially increase the ethylene content thereof While materially reducing the C3 content, cooling and compressing the products of said thermal conversion and then refrigerating the compressed products to effect partial condensation thereof, separating uncondensed vapors from the resulting condensate, passing the uncondensed vapors in contact with a Ca--CJt absorption oil produced in a subsequent step of the process to absorb most of the ethylene and separate the same from unabsorbed methane and hydrogen, passing the rich absorption oil together with last-mentioned condensate to a fractionating zone, separating a Cri-C4 bottoms from said fractionating zone, refrigerating and recycling at least a portion of said C3-C4 bottoms to the absorption step to serve as the aforesaid absorption oil therein, and recovering as an overhead from said fractionating zone a C2 and lighter fraction containing at least 30% by volume of ethylene and less than 30% by volume of methane and hydrogen.

3. The method according to claim 2, wherein said C3C4 bottoms from the fractionating zone is divided, a minor proportion thereof being passed to a polymerization zone, depropanizing the resulting products of polymerization to separate a polymer bottoms containing the aromatic content from a C3 and lighter overhead fraction, and recycling the said Cx and lighter overhead fraction to thefthermal conversion step.

4. The method in the recovery of a hydrocarbon fraction lighter than C3 Whichis enriched in ethylene from cracked hydrocarbon gas condensate, which comprises separating a C3 and lighter fraction containing a substantial proportion of ethylene and some methane from said condensate, subjecting said Ca and lighter fraction to thermal conversion at high temperature and 10W pressure to substantially increase the ethylene content thereof while materially reducing the C3 content, subjecting the products of thermal conversion to compression and refrigeration to eiect partial condensation thereof, separating uncondensed vapors from the resulting condensate, passing the uncondensed vapors in contact with a Cs-C4 absorption oil produced in a subsequent step of the process to absorb most of the ethylene and separate from unabsorbed methane and hydrogen, passing the rich absorption oil together with the last-mentioned condensate to a fractionating zone, recovering a Ca-Ci bottoms from said fractionating zone, refrigerating and recycling at least a portion of said Cs-Ci bottoms to the absorption step to serve as the aforesaid absorption oil therein, and separating overhead from said fractionating zone a C2 and lighter fraction containing at least 30% by volume of ethylene and less than 30% by volume of methane and hydrogen.

5. The method according to claim 4, wherein the said C3-C4 bottoms from the fractionating zone is divided, a minor proportion being passed to a polymerization step, depropanizing the poly- Inerization products to separate a polymer bottoms containing the aromatic content of said Ca-C-i feed to the polymerization step to thereby prevent aromatic buildup in the absorption system, also separating from said depropanizing step an overhead C3 and lighter fraction, and recycling said overhead C3 and lighter fraction to the thermal conversion step.

6. The method in the recovery of a C2 and lighter fraction enriched in ethylene from a C3 and lighter fraction of cracked gas condensate, which comprises subjecting the said C3 and lighter fraction containing a substantial proportion of ethylene and some methane to thermal conversion at high temperature and low pressure to substantially increase the ethylene content thereof While materially reducing the Cs content, compressing and refrigerating the products of thermal conversion to eect partial condensation thereof, subjecting remaining uncondensed vapors to absorption in a light absorption oil produced in a subsequent step of the process to absorb most of the ethylene thereof and separate from uny`absorbed methane and hydrogen, combining the resulting rich absorption oil with the condensate from said partial condensation step, subjecting the mixture to fractionation to remove a C2 and lighter fraction enriched in ethylene overhead, and refrigerating and recycling a Cs and heavier bottoms from said fractionating step to the said absorption step to serve as the aforesaid absorption oil therein,

7. In the catalytic alkylation of isobutane with methylene to produce an aviation blending alkylate ,wenriched in ethylene and containing less than 2G volume per cent of methane and lighter, subjecting said Cs and lighter absorption condensate to thermal conversion at high temperature and low pressure to substantially increase the ethylene xcontent thereof while materially reducing the C3 content, cooling and compressing the products of said thermal conversion and then refrigerating the compressed products to effect partial condensation thereof, separating uncondensed vapors from the resulting condensate, passing the uncondensed vapors in contact with a C3 and heavier absorption oil produced in a subsequent step of the process to absorb most of the ethylene and separate the same from unabsorbed methane and zhydrogen, combining the resultant rich absorption oil with said last-mentioned condensate, passing the resultant combined mixture to a, fractionating zone, separating a C3 and heavier bottoms from said fractionating zone, refrigerating .and recycling at least a portion of said C3 and A therefor.

8. The method in the manufacture of high octane aviation gasoline which comprises recovering from the products of cracking of hydrocarbon oil a, separate C4 fraction containing butylenes. and a separate Csk and lighter` condensate fraction containing substantial proportions each of propane, propylene,v ethane and ethylene, and some methane, subjecting the said C3 and lighter condensate fraction to thermal conversion at high temperature and low pressure to substantially increase the ethylene content thereof while materially reducing the C3 content, recovering by condensation and absorption most of the ethylene content of said conversion products in a refrigerated condensate, fractionating said last mentioned condensate at a pressure substantially below that required to fractionate between ethylene and methane to separate a C2 and lighter fraction containing in excess of 30% by volume of ethylene and less than 25% by volume of methane and lighter, alkylating isobutane with ethylene of the said C2 and lighter fraction to produce a C2 alkylate consisting mainly of 2,3-dimethyl butane, converting the butylenes of said C4 fraction to high octane saturated parainic hydrocarbons Within the aviation gasoline boiling range, and blending said C2 alkylate and said C4 high octane gasoline hydrocarbons with an aviation base stock and isopentane to produce the said high octane aviation gasoline.

WILLIAM E. SKELTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,421,733 Snelling July 4, 1922 2,154,676 Haeuber et al 1- Apr. 18, 1939 2,181,640 Deanesly NOV. 28, 1939 2,226,467 Hjerpe et a1 Dec. 24, 1940 2,298,383 Ipatiei Oct. 13, 1942 2,307,773 Eglog Jan. 12, 1943 2,309,986 Ruthruff Feb. 2, 1943 2,330,206 Dryer et al Sept. .28, 1943 2,340,600 Lamb et al Feb. 1, 1944 2,360,222 Roetheli Oct. 17, 1944 2,360,585 Ross Oct. 17, 1944 2,361,054 Pevere Oct. 24, 1944 2,385,123 Atkins Sept. 18, 1945 2,389,231 Blumer 1.--- Nov. 20, 1945 2,398,908 Miller Apr. 23, 1946 2,412,645 Munday Dec. 17, 1946 OTHER REFERENCES Oil and Gas Journal, Mar. 19, 1942, pages 18 and 19.

Certificate of Correction Patent No. 2,466,334.

April 5, 1949. WILLIAM E. SKELTON It is hereby certified that errors appear in the printed specification of the `above numbered patent requiring correction as follows:

Column 5, lines 43 and 44, for "preoent read prevent, column 15, hnes 3 4 5 and 6, strike out Reactor temperature, F 4/1 eactor pressure pounds per square inch i 110 so utane/olein mol ratio 275 and insert instead the follo Isobatane/olfyn mol ratio l4/1 r Reactor temperature, "F 110 Reactor pressure pounds per square zack 275 column 16, line 47, for 3.55 m1." read +3.55 ml.; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Office. Signed and sealed this 20th day of September, A. D. 1949.

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