. 17; 1946. J. c. MUNDAY TREATING H/YDROCARBON FLUIDS Filed Oct. 14, 1943 2,412,645 Patented Dec. 17, 1946 2,412,645 UNITED STATES PATENT oFElcE 2,412,645 TREATING mmRocAaBoN FLUms John C. Monday, Cranford,-N. J., assigner to Standard Oil Development Company, a corpo ration oi' Delaware Application October 14, 1943, Serial No. 506,169 1 Claim. (Cl. 20o-683.4) 1 . _ This invention relates to the production of aviation gasoline. In the catalytic cracking of hydrocarbon oils, naphthas are produced which have a relatively high octane number, but as ordinarily produced, they are not of high enough quality for aviation gasoline. Various methods have been suggested for treating catalytically cracked gasoline or v naphtha to produce aviation gasoline. My pres 2 -_ « - der to maintaincatalyst activity. The. yield of aviation alkylate was 125% of the 60-150° F. fraction and the A. S. T. M. octane number was ' 87.5. The aviation octane number-|-4 cc. llead per gallon was equivalent to iso-octane+0.24_ cc. lead per gallon. - Example 1A y. A 60-200° F. fraction from the same gasoline ent invention is an improvement over such other 10 containing 8.8% aromatics when alkylated under the same conditions required an acid replace processes. y ment rate of Y1.5-1.8 pounds per gallon of al According to my invention, a relatively heavy kylate in order to maintain activity. The yield hydrocarbon, such as gas oil, is cracked in the of alkylate was 118% and` thel A. S. T. M. octane presence'of a catalyst at a relatively high tem number was 85. Y perature and from the cracked products are sep arated a light naphtha fraction, a heavy naphtha fraction, and a heavier oil'fraction. The light naphtha fraction is alkylated with isobutane, and Example 1B If a 400° F. end point naphtha is subjected to alkylation. the yield is very low and the octane 'the heavy naphtha fraction is 'subjected to 'a number of the product may actually be lower catalytic recracking operation. The products 20 than that of the `feed stock as a result of the from these steps are then fractionated to sepa rate light hydrocarbon fractions boiling in the ~ absorption of aromatics by the catalyst and the alkylation of aromatics thus forming compounds boiling above the gasoline range. In the alkylation step, the oleiins react With of high stability, high octane number, high sus 25 isobutane to form saturated hydrocarbons of ceptibility to tetraethyl lead and high rich mix high clear octane number, high octane number ture performance. Furthermore, the ethylene appreciation on the addition of tetraethyl lead,and butylenes produced in the cracking and re high blending octane number, and high per cracking steps may also. be subjected to alkyla formance when employing rich fuel/air ratios aviation gasoline range, and the fractions are blended to produce a finished aviation gasoline tion with isobutane since the product alkylate is 30 as in take-oil or under heavy loads as measured of high quality and augments the yield of avia by the AFD-3C test method. Each of these fac tion gasoline. tors is of prime importance in the production The light fraction of the catalytically cracked of large quantities of aviation gasoline having naphtha which is fed to the alkylation step octane numbers of 100 or above. Removal or should be substantially free of aromatics. The 35 conversion of the ole?lns in the naphtha is nec end p-oint should be chosen to exclude benzene, essary to achieve this end, and the alkylation ofl if an appreciable amount is formed in the crack the light catalytic naphtha originally contain ing step. For example, the end point may be ing about 40% oleñns lowers the bromine num 165 or 170° F. In some cases wherein the amount ber from about 82 ogs/gm. to less than l. of benzene is very small the end point may be In the catalytic recracking step, also, oleñns 200° or somewhat higher, but it should be borne are converted. so that the blend of alkylated in mind that the presence of even small amounts of aromatics in the alkylation feed stock re sults in rapid degradation of alkylation cata ‘ lysts, as well as in lower yields and lower oc . tane number products. This will be evident from the following Examples 1, 1A and 1B, Example 1 showin-g my preferred alkylation step and EX amples 1A and 1B showing poorer results when selecting improper fractions. . Example 1 A Sil-150° F. fraction containing no aromatics from catalytically cracked gasoline was alkylat light naphtha and èatalytically r'ecracked heavy naphtha has a low bromine number and low acid heat and easily passes speciñcations. Since in the recracking of the heavy naphtha lower boil ingoleñns are produced, in a preferred modiii cation of my process the light naphtha pro duced in the recracking step is passed‘to the al kylation unit along with the light naphtha pro 50 duced in the catalytic cracking. In this manner there is produced an aviation gasoline of quite low oleñn content and very high quality. Apparently the oleiin content is reduced in the catalytic recracking step partly by polymeriza ed With isobutane at 45° F. employing a 10/1 55 tion and partly by hydrogenation through hydro isobutane/olefin ratio andI sulfuric acid catalyst in 'a 1/1 acid/hydrocarbonV ratio for 30 minutes gen exchange with naphthene hydrocarbons. The recracking causes a sharp reduction in the .amounts of naphthenes and parañlns present, contact time in a continuous run of 103 hours particularly in the high boiling portions which duration. An acid replacement Arate of 0.5 to 0.7 pound per gallon of alkylate'was required in or 60 are very high in aromatic content. 2,412,845 - 3 and this- base stock has an aviation octane number-+4 cc. lead of 98.2. Blending of the The heavy fractionof the catalytically cracked naphtha which is subjected to catalytic recrack alkylate and recracked aviation base stock gives ing must likewise be a selected fraction if high ' a yield oi _83% of aviation gasoline based on the 410° F. end point catalytic gasoline in addition to the pentane produced in recracking, and the aviation gasoline+4 cc'. lead per gallon has an aviation octane number of 100 and a rich mix ture performance ' equivalent to about iso yields of high octane number aviation gasoline are to be realized, as shown by the following ex amples. Example 2C shows improved yields ob tained when catalytically recracking a selected _ heavy naphtha fraction, _whereas Examples 2,12A and 2B show that best results are not obtained 10 octane+1.8 cc. lead per gallon by the AFD-3C with improperly selected fractions. Example 2 As pointed out'above, the yield and quality ofthe aviation gasoline maybe augmentedÍ by A 'l0-410° F. naphtha produced by catalytic method. cracking at a temperature lin , the . ‘ ‘ ‘ alkylation of the ethylene and butylenes produced range by cracking and recracking with the isobutane 925-975° F. with powdered synthetic silica produced by cracking and recracking. In view of the requirements of norm‘al butene and iso alumina gel was recracked at 900° F. with the same catalyst and the product was fractionated. butylene as feedstocks 4in synthetic rubber pro duction, it may be desirable vto`-`alkylate only the ' The yield of 335° F. end point aviation base stock. exclusive of pentane was 46.8% and the yield of ethylene at the present time.V The ethylene pentane was 25.9%. The aviation octane num 20 should be alkylated with isobutane in a separate ` ber+4 cc. tetraethyl lead per gallon of the feed. unit not in the presence of sulfuric. acid catalyst stock to recracking was 88.7 while that of the but in the presence ofïa halide catalyst, such depentanized aviation base product was 94.2. as aluminum chloride or bromide, employing Example 2A about 3/1v to. 5/1 isobutane-ethylene ratio at A 11o-220? F. fraction of the same gasoline as 25 100-150° F. and 250-350 lbs./sq. in. pressure. The product contains 'I0-85% of Ce hydrocarbons, predominantly v2,3-dimethyl butane'which has a employed in Example 2 was recracked under the same' conditions. The yield of aviation gasoline very high rich mixturerating on the AFD-3C y base exclusive of pentane was 58% and the yield of pentane was 14%, while aviation octane 30 The ethylene alkylate, or only the Cs fraction numbers+4 cc. lead of the >feedand ofthe de scale. . . therefrom, is blended with the aviation fractions produced by alkylation of the light catalytic naphtha and by recracking the'heavy fraction of thecatalytic naphtha. When operating sol as pentanized aviation base product were‘86.4 and y 92.6, respectively. ' ` V A' Example 2B i a' _, ' A 11G-289° F. fraction of the same gasolineas' to alkylate ethylene and C4l oleiins as well as _ theïlight catalytic naphtha, the yield of finished high quality aviation gasoline'is more than 100% based on' the original catalytic naphtha. employed in Example 2 was recrackedunder-the same conditions, . and. yields `of 61% vof dac-'. pentanized aviation' base and 11.3%_of 'pentane were obtained. The feed had‘an aviation octane '40 In contrast to ethylene alkylation, either the Vnormal butenes or -isobutylene or both can be number-F4 cc. lead of 88, while that of the de alkylated with isobutane in-‘the presence of sul pentanizeal aviation b_ase product was 92.5. furic acidcatalyst with good results, and it is Example Í2C ' preferred 'to do this»¢simultaneously and in the A 220-410° F. fraction4 of the gasoline employed f45 same unit as employed in the alkylation of the - in Example 2 was recracke'd'under the >same con light naphtha fractions. In the drawing, the figure represents one form ditions. ’ The feed' stock .contained 38.2% ,of material boiling in the .aviation gasoline range ¿ of apparatus which may be used to practice my below» 3_35" F. The yield ci depentanized’aviation process.> ’ " base was 5,8%; the pentaneyield being 4.4%, and vReferring now to the drawing, the reference the yield of C4 hydrocarbons being 5.5%. Where 50 character'lll designates aline _through which the as .the aviation octane .number-’r4 cc. leadof the hydrocarbon oilfeed stock is introduced to the feedstock was 87, that lof the depentanized avia system. For example, the feed` may comprise gas .oil vapors4 or votherrelativelyheavy vapor- v tion It base has product Abeen found‘that was' 98.2.' ~ _` ,the fraction«of~ » » a catalytically _ cracked gasoline boilingï- between 55 about 160° or 170°v F. and-"about 220° F. has va low 'octane number, for»y example, ` about- 84 - aviation+4 cc. lead, and that» recracking im »ized petroleum stock.v When4 using powdered catalyst, it is also possible to startv with> a partly 1 preheated liquid stock andto supply the heat of vaporization and conversion by contact with a suilicient quantity of hot catalyst. The hydro proves ‘it lonly slightly, for example,-to about _88. carbons> are cracked at atmospheric pressure or It is generally preferred >to discard this'fraction, 60 thereab'outs at'a temperature of about 900° F. to , which may amount to 10 or 12% of the catalytic 1000°. F., preferably about-975° F. when cracking gasoline, and to use it in automotive fuels. When 'a a relatively heavy gas oil having an A. P. I. ~ discarding this fraction the charge'to the alkyla gravityof 25430"v and a mid-boiling point of tion unit is about.48% of the catalytic gasoline - exclusive >of C4 hydrocarbons, and the 220-410° F. 65 fraction charged to the recracking step amounts to about 40% of the catalytic gasoline. t As shown in VExample 1, the yield Vfrom alkyla ` about 60G-750° F. Thecatalyst may be 'any suitable cracking catalyst, such as synthetic silica alumina gel, syn thetic silica magnesia- gel, acid-treated bentonites, etc. For the preparation of aviation gasoline tion is 125%.of the charge„or 60% based on- the catalytic gasoline, and this alkylate has an avia 70 and relatively large amounts of oleiins, it is pre ferred to use the synthetic silica alumina gel. tion octane number-i4 cc. lead greaterthan 100 The preparation of such a catalyst is well known (iso-octane+0.24 cc. lead) . As shown in Ex and is ,not described here.l Instead of vusing ample 2C, the yield of depentanized aviation base powdered catalyst, it is within the contempla stock from the recracking step -is 58% of the tion of my invention> to use larger particles of charge, or 23% based on the` catalytic gasoline. 75 _amaca ’ catalyst in a moving bed or to use larger particles tower 32 through line-38 and are subjected _to l ' catalyst has a size o_f about 200 to 400 standard arate fractions rich in ethylene and in C4 hydro carbons. These operations, which are well known 'in iixed bed operation.- Preferably the .powdered ' ‘ fractionating and/or scrubbing operations to sep mesh or finer. , The hydrocarbon feed stock is passed through » line I0 into the bottom portion of a reaction vessel I8 which contains dry powdered catalyst and need not be described in detail here, are in - dicated on thedrawing by numeral 43. Light ' gases pass overhead through line 44. A C3 frac at reaction temperature. The velocity of the î tion is withdrawn through line 45. -The sep 4arated C4 fraction withdrawn through' line 45 vapors passing throughreaction vessel I8 is con trolled so that the catalyst -particles remain in 10 contains isobutylen‘e which is useful in the pro- ‘ duction of synthetic'rubber and the isobutylene the vessel for a much longer period of time than may be recovered by scrubbing with acid. The the vapors, and preferably such that a relatively acid used is preferably sulfuric acid having a densev layer of catalyst is present in the lowerconcentration of about „65% by weight. The C4> portion ofthe vessel. - Suitable velocities lie in_ the range from 0.5 to 10, preferablyvl to 3, linear 15 fraction is introduced into the bottom portion feet per'second when employing 200-400 mesh catalyst having a density when freely settled of of an acid scrubbing vessel 48, the acid is intro relatively dense catalyst phase is aerated by the from the`acid by treating with steam, thus rais ing the temperature to about 250° F. and lowering the acid concentration to Ll0-45%. Isobutylene duced at the top through line 52, and the acid extract is removed through line 53. In the scrub from 35 to 60 lbs/cu. ft.' Under these condi bing vessel 48 the temperature of the sulfuric tions the relatively dense catalyst phase has a density of the order of 10 to 30 lbs./cu. ft. The 20 acid is about 75° F. The isobutylene is recovered rising vapors and has the appearance of a violent ly boiling liquid, and possesses properties of and di-isobutylene are ñashed overhead and the static pressure and a level or meniscusY which is 25 latter is cracked to form isobutylene. If iso liquids such as fluidity, the ability to exert hydro _ butylene is not desired for synthetic rubber, the especially noticeable when low vapor velocities entire C4 cut is by-passed around acidv scrubber are employed. Also, when employing relatively 48 through line 54 to line 56 leading to alkylation low velocities, such as from 0.5 to 2 ft. per second, unit 51. ' the carry-over of catalyst by the cracked prod uots is very small, of the order of 0.003-0.01 30 , 'I'he rest _of the C4 fraction containing isobutane and butenes leaves scrubber 48 through the line lbs/cu. ft. of vapors. 55 and is mixed with a light naphtha fraction The cracked products leave the top of the re introduced through line 58. This light naphtha action vessel I8 through line 22, after lpassing fraction is withdrawn from the upper part of - through cyclone separator 24 where entrained powdered catalyst is separated therefrom. » Cy 35 fractionating tower 32 wherein the catalytically clone separator 24 is preferably located inside cracked products ~are fractionated. The light naphtha fraction collects on trap-out tray- 62 in the fractionating tower 32 and is passed through separating means may be used. Separated line 58 by pump 64. The light naphtha fraction catalyst is returned to the reaction zone proper through linie 25. During the conversion oper 40 contains oleñns and para?lins, but as mentioned above, should be substantially free of aromatics. ation the powdered catalyst becomes contami The light naphtha fraction has a boiling range nated with coke or carbonaceous material and of about 60° to about 170° F. or 200° F. .l lt is necessary to regenerate the catalyst in any The mixture of the light cracked naphtha and known manner,l preferably by burning with air or oxygen-containing gas at about 1000--1l00"l F. 45 the C4 fraction is passed through line 58 to the alkylation unit or reactor 51 wherein the oleñns toV remove the carbonaceous deposit. Catalyst are alkylated with isobutane to transform the for regeneration is withdrawn from reaction the upper portion of vessel I8. Other forms of » vessel I8 through line 26 in a ?luidized condition and is passed to a regenerator (not shown) Ywhich may be similar in construction to vessel i8. Hot regenerated-catalyst is returned to line I0 and to the reactor through line 28 at a suiii olefins to branched parafñns. Any suitable al kylation -catalyst is used, such as sulfuric acid, boron fluoride-water, hydrogen fluoride, etc. Where sulfuric acid is used, the titratable acidity of the acid is maintained above about 82%, pref cient rate to maintain reactor` temperature and ‘ erably at about 85~90%, by continuous .replace ment with 94-98% acid. The temperature dur catalyst activity at the desired levels, vand if liquid feed stock is being supplied to the re 55 ing alkylation is preferably in the range li5-`-80"` action, to absorb or vaporize the liquid corn pletely. The weight ratio of catalyst to oil. em F. The ratio of isobutane to oleflns in the feed ‘ is generally maintained at 3/1ior higher by re cycling isobutane separated from the products, and the vinstantaneous isoparaiiin/oleñn ratio in While I have shown only one cyclone separator 60 the reactor is maintained considerably higher, for ployed is generally above 3, for example, from 5 to 20. . . ` - on the drawing, it is to be understood that more than one cyclone separator may be used in series example, 30/1 or 100/1 or'greater, by recycling, . products which are low in oleñns to the inlet of to effect a better separation of powdered catalyst I the reactor. ` -' The acid for the alkylation unit is introduced from the vaporous reaction products. The sep arated vaporous reaction products pass overhead 65 through line 'l2 and spent acid sludge is with drawn through line 'M_ The products of alkyla from the separating means 24 through line 22 tion are passed through line 76 into a second and are passed to a fractionating tower 32 for fractionating tower ‘I8 for separating the desired separating desired fractions from the cracked light hydrocarbons boiling in the aviation gaso products. Condensate oil is removed from the bottom of the fractionating tower' 32» through 70 line range from higher boiling constituents. The _ light hydrocarbon constituents lpass overhead line 34 and may be recycled to the reaction. zone through line 82, are partially condensed in con I8 or withdrawn from the system. denser 84, and passed to a separator 86 wherein The light uncondensed constituents comprising gases are separated from liquid. The gases com hydrogen,v methane, ethane, ethylene, C3 and C4 Vhydrocarbons leave the top of the fractionating 75 prising C4 and lighter pass overhead through line ' 'Í r , 9,412,645 boiling above the aviation gasoline range reduces ' I8 ~and are fractionated in equipment (not shown) _their boiling points and thereby increases the yield of aviation naphtha. The'vaporous reaction products pass overhead to -separate isobutane'which is recycled to the alkylatio'n. unit 51. The light aviation naphtha ‘ fraction is withdrawn froml separator 86 as a liquid from reactor ||0 through line |24 to a third through line 82. This light fraction boils up to the end point of the desired aviation gasoline, fractionatingtower |34. During the recracking. of the heavy naphtha fraction additional amounts generally 30D-330° F. and is substantially free of oleñns. Higher boiling constituents are.¿withdrawn from the bottom of the fractionator 18 . of isobutane are formed together with other val uable light oleñnic hydrocarbons. These light hydrocarbons are withdrawn from the top of the through line 94. These higher boiling constitu ents may be addedtogordinary motor gasoline. As mentioned earlier, it is >frequently _desirable to alkylate the ethylene produced in the cracking fractionating tower |34 through line |36 and are .combined withthe gaseous products leaving the ñrst fractionator 32 through line 36. This mix ture is then treated to separate isobutane and olefins from the other gases vfor use in the alkyla and recracking operations with isobutane. To this end the ethylene separated in fractionating and scrubbing equipment 43 and which may have a purity from`25 to 80% is passed through line 85 to an alkylation unit 86 where it isalkylated with isohutanel in the presence of aluminum ch1o-' ride. Isobutane is introduced through line 91. tion units 51 and 86. , _ '_I‘he reaction products in the iractionator |34 `.The isobutane may come from cracked >products are fractionated to separate an aviation naphtha fraction vwhich collects on trap-out tray |40. This‘fraction is relatively heavy, boiling for ,the most__'part-between about 190 and 335° F. and v in my process or froman extraneous source. The - conditions of operation are similar to those em gasoline._ The aromatic content of the naphtha contains high quality constituents for aviation ployed in alkylation unit ä‘lexcept that the tem- . is very high, lparticularly of the 22o-335° F. frac perature- is higher (1D0-150° F.)‘.and»the pressureV 25 tion -which mayfbe v80-90% aromatics or higher. may be 250K-350 'lha/sq. in.1The `products are ' The naphtha fraction is withdrawn from trap _ passed through'1ine’98`into fractionatorJB along :out‘tray |40through line |42 and is mixed with the, »light .alkylate fraction withdrawn through with the products from 'alkylationunit v51. linef92 and the -mixture is Withdrawn through line tionating tower 32, the catalytically crackedprod 30 V| 44 _as 'an aviation gasoline.y The addition of 4 Returning now to the first-mentionedl frac or 4.5`cc.~`_of- tetraethyl lead per gallon andad ucts are further fractionated to separate aheavyf _ naphtha fraction which is .withdrawnv from trap ` justment of 'the vapor pressure by adjustment of ‘out tray |02 through line |04 by pump |06.- _ '_I‘his 1the’isopentane content of the gasoline produces _heavy naphtha fraction has'an initial' _boiling ' -a finished aviation gasoline of high stability and ~ point from about 170° F. to about 4220" F. and may 35 high octane_numberby both the aviation octane have an end point of 350 or -400 lor somewhat number 'and the AFD-3C methods of testing. higher, and contains oleñns, parafilns, aromatics ._A heavier `fraction collects on lower trap-out andnaphthenes. vThe paraflinsand some of the tray |46'in.th_e fractionating tower |34 and this A ality for aviation vgasoline .oleiins are ofr poor fraction is withdrawn through line |48. This and it is> desirable-to'convert them to‘higher heavier fraction may be added to motor gasoline. quality constituents for aviation gasoline. à Also In a preferred modiñcation, a light fraction of Isome of the alkylated aromatics‘have a high boil-l ' ß 'the recrackedproducts, and which contains ole ing point and. it i_s desirable to _break oft'part of the chains of the alkylated aromatics to reduce their boiling point. trapfout Atray |50 and is passed through lines |52 and f_58 toalkylation .unit 51» with isobutane' along ` To improve the quality ofthe heavynaphtha u with the light'ïcracked naphtha of similar boiling range'.~_ In _this 'case only the recracked heavy cracking operation in reactorl'llß. The‘recrack naphtha' fraction is passed directly through line ing unit is` operated in the same manner as the |42¿forgbl_ending'with the alkylated naphtha. fraction, it is passed- through a second catalytic , - cracking unit described earlier, employing vpow.-v .While _I _have shown one form o_f apparatus and dered cracking catalystof thesame or different have'given conditions for carrying out the differ ent steps' lin-niy process, it is to be understood that theseare by _way of example and'changes and modifications may be 'made without depart-‘ _ composition.' Synthetic silica-alumina gel is a` preferred catalyst. The temperature -of opera tion is generally slightly lower than in cracking, V "for example, '700'tof950° F., particularly if the ing' from'the spirit of my invention. cracking unit is `operated toÀ give -high conver II claim: ‘ " ‘ ’ sions. With cracking conversions of the order ` . ¿A methodbt 'producing aviation 'gasoline which of 60-80%, 900° F. is a suitable temperature for comprises. ¿separating a catalytically Acracked 1 _ recracln‘ng. A stream _of catalyst is continuously- . '_ riaphthaintoßa~ fraction having a -Withdrawn from the reactor through line |'|2, re ‘ Í boiling frange o_f_lightlnaphtha about Gti-165° F., an interme generated and _returned through line _| I4. . A cy-i ‘ diate naphthafraction having a boiling range ot . clone separator H6 and return pipe |'l8 ‘are- used.~` about ITG-'220° F.,'and a heavy naphtha fraction _ A common regeneratoris preferably employed for ' G0~ regenerating catalyst'from the` cracking and re cracking operations. .' ~ ' ' _ - During the second cracking‘step paraffins, Lole ñns and naphthenes are cracked, isomerized` and dehydrogenated into isoparañins and aromatics and at least some of the olefìns are removed and . , . ‘ having a boiling range of about 22o-410° F., a1 kylating- the separated light naphtha fraction ` with isobutane to transform oleñns to branched chain hydrocarbons.' discarding the separated in- ' termediate naphtha fraction, catalytically crack ing theheavy naphtha 4fraction to higher avia others are reformedv into higher quality vconstit 70 tion qualityl constituents and combining said al uents for aviation gasoline. `The aromatic con-V stituents originally in the heavy naphtha fraction ` passing to the reaction zone ||0 remain as aro matics, but de-alkylation of alkylated aromatics kylated products Withsaid catalytically cracked heavy'naphtha fraction to produce. aviation gas oline. ‘ , . JOHN C. MUNDAY.