US2434000A - Production of motor fuel - Google Patents

Description

Jah. 6, 1948. M, P, MATUSZAK 2,434,000

PRODUCTION OF MOTOR FUEL Filed Jan. 25, 1946 Patented Jan. 6, 1948 L2,434,000 PRODUCTION oF Mo'roR'FUEL Maryan P. .Matuszain Bartlesville, ,0k1a., .assignor .to PhillipsPetroleum Company, a corporation ,of 4Delaware Application 'ianuaryas, 194e; serial No.f64s',222. 4 Claims. CL 2260-6834) This application is a ycontinuationfinepart of my. copending applicationSerial No. igfilfiled December 4, 1942, which is .now Patent..-2',39.9,368, grantedAprilBO, 1946. The inventionLrepresen'ts an improvement. over .conventional lprocesses -fo'f producing motor-fuel .hydrocarbons .by :hydroiiuoric acid alkylation. of .isoparaiins witholefins and/ oralkyl zfluorides, vWhiclrhave.been described in the prior art. .Itris distinguished lfrornithese processes in that theaikylation vis-eifected .with a .l-olen .in substantially .prehydrofluorinated Iform,.with any: other olenrbein-g: utilized: as. such, without first being ',prehydroiiuorinated. It ,is based in part upon the surprising.andunexpected `discovery that a positive` .advantageresides in: hydrofluorinating 4a ll-olei'ln .prior to f. utilization for 4alkylating an isoparafm in vthat .the Vresulting alkylate-is superior .in .octane ratingfto 4thatobtainedby directalkylation Withthe 1-olefin1as such; Whereas substantially only .disadvantages reside .in .similar prehydrofluorination of .olens other than-l-olens. In one specific embodiment, the invention is animproved process ofmanufacturingA motor-fuel` parafns 'frombutanea .whereby normal butane is dehydrogenated,. thepresul'ting butene-l is isolatediand isusedinxsubstantially hydroluorinated form to alkylate isobutanein the .presencebf hydroiiuoric acid, the butene;2 ,resulting from the dehydrogenationissimultaneously used substantiallyv as such to alkyl'ategisobutane, and the resulting alkylates are Withdrawn together as a motor-fuel product of .high octane lrating.

An object of thisinvention is torproducezparafn .hydrocarbons boiling ,in the ,motor fuel :rangetand Viofhigh Voctane number.

Another object of my invention-iste produce paraffin hydrocarbons of high octane number from a mixture of low-boiling olen hydrocarbons.

Still another object of my invention is toproduce paraiiin hydrocarbonsfroma mixture ofvlowyboiling alpha and beta olens.

Further objects and advantages of my invention will become apparent, to oneskilled in the art, from the accompanying disclosureand discussion.

One specific embodiment, which may serve as an `illustrative example of the invention, is depicted by the drawing, which is a schematic iioW-dial having more carbonatomsper molecule maybe utilizedl similarly,

yA mixture of :butanes brought into lthe system by inlet Iis,fractionatedin'fractionator.2 into an overhead fraction :richinii'sobutane and into abottom fraction v,rich ininormal lontane. The isobutane vfraction is vpassed into `conduit f3, Abeing controllably augmentedroridiminished, as. may be desired, through valve 4v ina vconnection With.k an outside storage of Aisobutane7 vnot shown. The

Anormal butanefraction .is .passed through 'conduit 5 -to :dehydrogenator 16, being .controllably augmented ordiminished, asLm'ay be desired, vthrough valve 1 vinria vconnection-With an outside :source of normal butane, ,notgshown .In-'dehydrogenator 6,'y normalV butaner is catalytically dehydrogenated substantially into normal butylenes, preferably-by the action of a dehydrogenation catalyst comprising chromium oxide. .Inasmuchas catalytic.dehydrogenating of parafns is well known, it need not be described indetail. In presentindustrial practice, such dehydrogenation converts approximately 25 to/40per :cent pf :the :normal .butane .per pass, Ayieldingfnor- ,mal-butylenes with a selectivity of. approximately .7 Oito 85; per cent -The resulting :dehydrogenation vmixture is passed through conduit .8 :to l'separation .means Vrepresented i bjy -f-ractionator :19, Awhich in vpractice generallycomprises'several:fractional-distillation and/'or extractive-:distillation columns. Lowboiling gaseous by-products are withdrawn, Vas '.throughoutlet t0. :Butadienepreferably also is Withdrawn, :as through outlet ll. Undehydrol,genatednormal butan'e is recycled through confduit i2fto ,.'dehydrogenator 6. .Butene-z 4is .passed intoiconduit' I3. .-Butene-l is ,passed through conduit'Iditohydrouorinator I5.

,.In;hydro`fluor.inator x l5, 4butenelis substantially fhydroiiuorinated to butyl ,uoride Great care must b e :exercised in #the hydro'iiuorination .to V.minimize consumption di cbutene-,l to products other than :butyl viiuoride, and certain specific yfeatures vof this invention :are concerned primarily -withith'is fact. .Itis-essential for optimum results .tc avoidnhavingfpresent in .the hydrouorination vzone -a distinct .liquid phase rich in hydroiluoric acid, inasmuchas a'. liquid hydrofluoric acid phase acts'catalytically to promote such'undesired side reactionsas polymerization of the butene-l and alkylation of isoparafns, Whenpresent. These reactions,-ifiinitiated'by a 'trace of liquid hydroiiuoric acid phase, have a -pronounced tendency to pyramid or run away because they yliberate additional hydrouoric 'acid from butyl iiuoride already formed, therebyaugmenting the amount of undesirably catalytically .active liquid hydrojfluoriccacidphasepresent. "When run-away side reactions occur,'introducton 0f hydrofluoric acid into the hydroluorination zone must be discontinued, until al1 liquid hydroiiuoric acid phase has disappeared by reaction and by dissolution in the hydrocarbon phase. Inasmuch as uniformity of ultimate product and minimization of process changes or controls to compensate for operational' difliculties are highly advantageous and desirable, it is clear that run-away side reactions in the hydrouorination are strongly disadvantageous and are not lightly to be tolerated.

Although the occurrence of run-away side reactions in the hydrofluorination zone can be substantially avoided by conducting the hydrouorination in gaseous phase, and although gas-phase hydrofluorination is not to be considered as being excluded from the broadest scope of this invention, it is usually relatively economically advantageous to employ liquid-phase hydrofluorination, in View of the smaller size of equipment that is then adequate for maintaining a desired throughput. To achieve this objective without any possibility of a liquid hydroiluoric acid phase being present, it is an advantageous specic feature of this invention to introduce the hydrolluoric acid into hydrofluorinator l5 in the form of a saturated solution in the isoparafn that is subsequently to be alkylated. In addition to serving as a carf rier or solvent for the hydrofiuoric acid, the iscparain dilutes the butene-l in the hydrouorination zone, thereby preferentially disfavoring polymerization, inasmuch as the rate of polymerization is proportional to the second power of the hydrous, hydrofluoric acid is introduced into` saturator 22 through inlet 23. In saturator 22, the isobutane -becomes saturated with the hydrouoric acid. Various means of contacting or mixing to achieve this objective can be used;

they need not be described in detail, inasmuch as they can be readily provided by those skilled in the art. However, it may be mentioned that the isobutane is introduced into saturator 22 at a somewhat elevated temperature, in order to increase the solubility of hydrofluoric acid in it; the most satisfactory temperature range is approximately 120 to 180 F., which may be obtained directly, without heat exchange, in the isobutane fraction from fractionator 2. At the middle temperature of this range, 150 F., which is preferred, the solubility of anhydrous hydrofluoric acid in isobutane appears to be approximately 2.1 per cent by weight; however, the solubility of hydrofluoric acid of the purity ordinarily available at present for commercial alkylation may be appreciably less than this value, apparently chiefly because of a small content of water, so that at times the solubility may be so low as approximately 1.5 per cent, especially when the solubility is somewhat decreased by the presence of normal butane in the isobutane. The value of 2.1 per cent corresponds to a mol ratioof isobutane to hydrogen fluoride of approximately 16:1. If desired, the temperature of the influent isobutane may be adjusted so that approximately this preferred ratio is maintained; however, other ratios are operative and may be used, especially the higher "ratios obtained at lower temperatures,

thereby disfavoring polymerization and favoring alkylation in the subsequent alkylation step.

From saturator 22, the mixture of isobutane and hydroiiuoric acid is passed through conduit 24 to separator 25, in which it is separated into two liquid phases. The lower, hydrouoric acidrich phase is recycled through conduit 26 to saturator 22. The upper, isobutane-rich phase vis passed through conduit 21 to hydrofluorinator I5.

-In hydrofluorinator l5, this isobutane phase, which is substantially saturated with hydrofiuoric acid, is intimately mixed with butene-l from conduit ill, whereupon substantial hydrofluorination of thebutene-l is effected. The proportion of butene-I introduced into the hydrouorination zone is preferably such that the mol ratio of ingoing hydrouoric acid to ingoing butene-l is approximately 1:1, Although advantageously higher values for this ratio are desirable, especially those in the range of 1.311 to 1.6:1, inasmuch as the rate of hydrofluorination is directly proportional to the concentration of hydrofluoric acid, this particular ratio has been found to represent the approximate optimum compromise among the several reaction-affecting factors or variables involved; however, lower Values, down to approximately O.5:1, are also usefully operative, though the hydroluorination then proceeds somewhat relatively slowly and is necessarily relatively less nearly complete. Inasmuch as the Yrate of hydrofluorination increases with increase in temperature, the temperature is preferably somewhat elevated, but it should not be so high as to interfere by substantially lowering the thermodynamic ceiling. The temperature established by the influent isobutane, which is at approximately 120 to 180 F., is advantageously convenient, so that no special heat-exchange means for hydrofluorinator l5 need be provided; this temperature is somewhat increased, by approximately 10 F, or so, by liberation of the heat of hydrouorination. The reaction time, or time of residence of the reaction mixture in hydrofluorinator i5, may vary considerably, depending on the temperature and the reactant concentrations; times in the range of 4 to 40 minutes have been used with satisfaction, and ordinarily sumcient hydrofluorination occurs under the preferred conditions in 5 to 10 minutes. understood that the hydrofluorination of butene- 1 need not proceed to completion, or to the thermodynamic equilibrium, and that only the substantial hydrofluorination that occurs within an industrially feasible reaction time is desirably eifected.

From hydrofiuorinator I5, the effluent reaction mixture is passed through conduit 30 to alkylator 5i l. Preferably, this mixture is cooled, as in cooler 32, to a temperature of to 110 F., inasmuch as the subsequent alkylation is exothermic. However, cooler 32 is not always necessary, as when adequate cooling for the subsequent alkylation is provided in alkylator 3l, which in present commercial practice is ordinarily designed for the somewhat relatively more highly exothermic alkylation with olefins.

Although, in some modiiications of this invention, the alkylation taking place in alkylator 3l, may be substantially-limited to the isobutane, the butyl iiuoride, and the unhydrofluorinated butene-l in the efliuent from hydrofluorinator l5, in most preferred modifications the butene-2 in conduit i3 is simultaneously introduced into alkylator 3i. Ordinarily, such butene-Z, which It will be QABOD if desired may have associated with it an appreciable proportion of isobutylene added as through inlet 33 to enhance the octane rating of the ulti nator I5,such-zas, for example, isobutylene and/or .,butene-.Zpismndesirable and .disadvantageous, in-

asmuch as no correspondingly additional enhancement in ,octane rating of the ultimate al- Y kylate is thereby obtained; inasmuch as they disavor hydroiiuorination of the 1olefin,.as by decreasing :the concentration of hydroiuoric acid in -this zone; and intsmuch Vas `they undergo poly- `rnerization relatively more easily :than butene-d, :so thatsubjecting them to prehydrouorination results in a net decrease in the yield of the ltialkylation catalyst is introduced through inlet' 3,5. f

Except for the differences ralready indicated hereinbefore the alkylation and productfrecovery steps may be along substantially conventional lines. Briefly, alkylati-on of isobutane with 'butyl lfluori-deand'butylenes occurs in alkylator -3 lun- 'der-conditi'cnssubstantiallylike those well known vin "the art, with liberation 'of yhydrofluoric acid Ifrom the vrbutyl fluoride. 'The resulting eliluent reaction mixture is passed ythrough conduit '-365 `to-separator 31. The separated used-acid'or catallyst phase-is recycled in Vpart'through conduit 38 'to alkylator 31| and is passed in part through Aconduit 339 -to acid lfractionatorf'dl |for purification, with tar or acid-soluble oil lbeing removed through outlet 4| and with purified hydrouoric acid and a minor proportion of isobutane being passed to saturator 22 through conduit '42, `When the hydrofluoric acid in the alkylatorv builds up too much, part ofthe used acid maybe passed to saturator 22, throughconduitEJ. The hydro- 'carbon phaseirom separator 31 is passed through conduit 43 to fractionator 44, 'usually a system rof fractional-distillation columns, from which a :major fraction comprising isobutane and a minor proportion of hydrofluoric lacid is returned Lthroughconduit i515 to saturator 22. It Yis'worthy for note that :the recovered hydrofluoric acid and the recovered unalkylated isobutane, in conduits 42 and 45, are passed to saturator 22 instead of :to alkylator :3|, in conformity with the'over-all :requirements of the process; however, if desired, 'means,-not shown, may be readily provided E-for :passing spartfof either or both of these'materials fto alkylator 3l. Tar or heavy alkylate is withdrawn .through outlet 46, andmotor fuel is withdrawnfasthe principal product through outlet 41.

The resulting motor fuel .is substantially su- ;perior in octane rating to Vthat obtainable withtout the improvements provided by this invention.

It willbeunderstood that various conformably applicable known means for improving alkylation in gener-a1, or similarly for improving the alkylate, .such as, for example, a deiiuorination step to decrease .traces of organic fluorine-containing byproducts, may be -iutilized in connection with the process of the present invention; for example, :the defluorination means described in Frey lPatfent 2,347,945, Vor in my copending application ,Serial No. 602,247, filed June 29, 1945, may be applied tothe material in conduit 43. The gist of thepresent .invention resides in one or more of :the steps and conditions vherein set forth for obtaining an alkylate of enhanced octane rating by virtue of substantial prehydrofluorination of substantially only a l-olefin, which in most instances fis specically butene-l but in other instances may comprise pentene-l or even propylene. The presence of otherolens in the prehyyturbo-mixer.

`mate alkylate. Consequently, althoughthe ultimate alkylate in many cases may contain, inthe form of va blend or composite mixture, -alkylation products ffrom 4these .or vother .olensiother Athan 1-olens that may be formed in a Vcommonalkylationzon'e or alternativelyandordinarilyrelatively less economically in analkylation zone `different from that in which the prehydroluorinated 1- olen vis used, prehydrofluorination in yaccordance Withtheprinciples of the present invention ismost advantageously applied to 'only l-olens, 'inasmuch as thereby `the Ycontribution ofthe i1- olefin to the quality of the ultimate alkylate lenhancedI tothe fullest .possible extent consistent Withthe other conditions of manufacture. "The actual octane rating of the ultimtae alkyl-ate -vdepends to a considerable degree onjthe proportions .of the various olens going'into `-its l'manufa'ctur'e; for example, the relative octane rating of the hydrofluoric acid alkylate from isobutane Aand isobutylene is largest, from isobutane and butene-2 is intermediate, and from isobutane and `butene1 is smallest. By way of comparison, it

may be said that, by the practice of this invention, the octane'rating-for the alkylate from isobutane and butene-1 is increased substantially to 'the intermediate -value characteristic for that .from isobutane and butene-2, The mechanism or theoretical -explanation of this effect is not completely understood at present, but it may be significant that both butene-l and butene-Z un- -dergo hydrouorination to substantially the same principal product, secondary butyl uoride. From a `theoretical `point of view, therefore, a particular advantage of excluding butene-2 from the hydroluorination vof butene-l, in addition to the general advantages already indicated hereinbefore, appears to'be one of avoiding an unnecessarily highconcentra'tion of this butyl fluoride, inasmuch as, `in laccordance with the principle of mass action, the :presence of this butyl iluoride militates againstvunion of the butene-l with the hydrofluoric Jacid.

vIn addition to datasubsequently presented, the

data inTable :Iarepresent some illustrative results obtained in a rpilot-plant investigation directed to determining the optimum conditions for the hydroiiucrination step. The hydrocarbon feed was forcedthrough a silica-gel drier and through a lcopper-coil,pre-'heater into a reactor, which in most'of the-runs vwas a M70-ml. copper-plated steel reactor having a 1'150-R. P. M. 2.5-inch Commercial anhydrous hydroluorio-acid Awas simultaneously forced into the reactor. 'Feed and-eliiuent samples, the latter after being Vfree from dissolved hydroluoric acid by extraction with water, were analyzed by lowtemperature `fractional distillation, supplemented by sulfuric `acid determination of olefin (Matuszak,Ind. and Eng. Chem., Anal, Ed., 10, 354-360 (1938)). Hydrouoric acid in the eluent was determined'byextraction with water and subsequent -titr-ationofthe-extract with standard sodium-hydroxide.

y TABLE I i Data from contmuous pilot -plant hydroftuorinatzon Run-period, l 467-1 l 467-3 476-1 476-2 476-3 476-5 480-2 480-4 Duration, min 60 30 120 60 60 60 120 60 Temperature, F. 82 140 92 90 89 91 59 120 Pressure, p. s.i 127 148 132 134 135 140 130 130 Reaction time, min 19.0 4. 3 19. 1 30. 5 32. 6 31. 0 30 32 Feed compn., wt., per cent: l

`Isobutane 82. 7 82. 7 V83. 0 83.0 83. 0 83. 0 81. 0 81. 0 Btene-l 14.9 14.9 14.6 14. 6 14. 6 14.6 16. 7 16. 7 Normal butane 2. 4 2. 4 2. 4 2. 4 2. 4 2. 4 2.3 2. 3 HF/butene-l (mol.) 1.76 1.17 1.21 1.55 1.51 1.44 1.03 1.35 HF in emuent, wt., per cent 2. 4 5. 2 2. 2 1.3 0.7 1. 4 1. 7 1. 5 Eluent compri., Wt., per cent:

Butaues 85. 7 84. 9 82. 2 1. 6 5. 0 1. 3 11.3 9. 4 11.9 1. 4 0.7 4. 6

2 Determined by weathering 70-80 m1. snap sample.

These data illustrate to a helpful extent the orination of the butene-l. The alkylator was a influences of such operating variables as temperature, reaction time, feed composition, and m01 ratio of hydrouoric acid to butene-l. The phenomenon describable as run-away alkylation occurred in run-periods 476-2 and 476-3, as was evidenced by the large proportion of heavy products formed.

Several continuous pilot-plant runs were made for the hydrouoric acid alkylation of isobutane 5 the prehydrofluorination runs, the total eluent from the hydrofluorinator, which was a 'TO0-ml. brass-lined steel vessel having a 1750-R. P. M. 4- blade impeller, Was passed through a cooling coil directly to the alkylator. The data obtained are `with butene-l, with and Without prehydrofiusummarized in Table II.

TABLE 1I 'Data from continuous pilot-plant alkylatio'n. with and without preh'ydroftuorination of butene-I Run-period 469-1 470-1 473-1 473--3 473-5 473-6 479-1 484-1 Prehydrofluorination Yes Yes Yes No Yes Duration, min 60 415 Temperature, 120 120 122 130 130 135 9. 3 8. 8 9.6

` 27 35o 355 Temperature, 88 92 Pressure, p. 5.1-. 130 130 Reaction time, m 11.1 9.8

81.0 16. 7 Normal butane 2. 3 Titratable HF., Wt. per c .nt 94. 2 90. 3 I-butane/(Butene-1+C4HF) (mo1.) 4. 7 4. 7 IIC/HF (vol.) 1.15 0.92 i-bntane consumed/Butene-l (m01.) 0.96 Eiluent compu wt per cent:

. .2 6 3. 3 2. 9 3. o 67* 4 2. 2 1. 7 3. 1 2. 6 4 27. 5 24. 4 29.0 30.0 Debutanzed alkylate. Yield, Wt. per cent of butene-l 193 193 179 192 195 Compu., v01. per cent- Pentane (-113 F.) 3. 4 0.5 4. 2 3. 9 1. 4 Hexane (11S-167 F.) 3.5 2. 9 3. 7 3.0 5.1 Heptane (IS7-203 F.) 3. 2 3.2 13.3 3.9 6.5 IsoOctane (20S-221 F.) 41.3 34.0 25.1 30.1 36. 5 Other Octane (221257 F.) 37. 3 46. 2 39. 5 43.3 84. 9 Nonane (257-302 F.) 1.2 1.2 1.2 1. 4 3. 2 Decaue (302-347 F.) 1.8 1. 5 3.8 2. 6 3.4 Heavier 347 F.) 8.3 10. 5 9. 2 11.8 9.0 Organic F., wt. per centXlOO 0. 4 0.8 0.5 0.1 0.7 Gravity, API 68. 2 67. 7 67.5 67.8 67.1 Reid vapor pres., 1b 2. 50 1. 95 2. 85 2. 75 2.10 ASTM distn., F.:

First drop 150 148 162 183 10 vol. per cent evap 201 194 203 206 50 vol. per cent evap 223 226 227 227 vol. per cent evap 285 317 293 325 End point 441 438 463 434 ASTM O. N., 0 m1. TEL 90.4 89.4 85.3 90.2

It may be noted that the runs with prehydrouorination of the butene-l yielded alkylates markedly superior to those obtained without prehydrouorination, as is indicated by the relatively high ASTM octane numbers. With one exception, the proportion of isooctane (2,2,4-trimethylpentane) formed in these runs was considerably higher than in the runs without prehydrofluorination, and the consumption of isobutane relative to original butene-l was also higher. In the exceptional run, run 473, run-away alkylation occurred during the prehydrofluorination in period 5, as is indicated by the high content of hydrofluoric acid in the eluent, thereby accounting for the relatively poor alkylate yield, isobutane consumption, isooctane proportion, and octane number, as compared with those obtained in runs 469 and 484. The relatively poor results of this run emphasized the desirability7 of avoiding a liquid hydrouoric acid phase during the prehydrouorination, which as a specific objective is simply and positively attainable in the practice of this invention as set forth hereinbefore, particularly in the discussion of the now-diagram.

It will be appreciated that various modiiications of my invention can be practiced without departing from the spirit or scope of the disclosure and teachings, or without departing from the scope of the claims.

I claim:

l. An improved process for converting a butane mixture into higher-boiling paraffin hydrocarbons, which comprises separating from a butane mixture normal butane and isobutane, saturating `said isobutane as a liquid with hydrogen fluoride,

subjecting said normal butane to dehydrogenation under conditions such as to produce therefrom butene-l and butene-2, separating from efliuents of said dehydrogenation butene-l and butene-2 so produced as separate fractions, admixing said butene-l fraction with said hydrogen uoride-saturated liquid isobutane fraction in an amount such that the mol ratio of hydrogen uoride to added butene-l is between about 1:1 and 1.6:1 and maintaining said admixture at a temperature between about 120 and 180 F. for a. time in the range of about 4 to 40 minutes to react butene-l and hydrogen fluoride, admixing with eiliuents of said treatment said butene-2 and additional liquid concentrated hydrogen fluoride in an amount suiiicient to act as an alkylation catalyst and intimately admixing said materials under alkylation conditions for a time sufficient to effect an alkylation of said isobutane, and recovering from effluents of said alkylation higher-boiling paraiin hydrocarbons so produced.

2. An improved process for converting a mixture of butene-l and butene-2 to higher-boiling paran hydrocarbons, which comprises separating butene-2 from said mixture, converting residual butene-l to butyl fluoride, passing said butene-Z and said butyl fluoride to an alkylation zone and reacting same therein with a low-boiling isoparafn hydrocarbon under alkylation conditions and in the presence of a hydrofluoric acid alkylation catalyst, and recovering as a product of the process a paraffinic hydrocarbon fraction comprising parain hydrocarbons produced by said alkylation.

3. The process of claim 2 wherein said lowboiling isoparain is isobutane.

4. An improved process for converting a mixture of low-boiling normal l-olefin and normal 2- olefn to higher-boiling paraiiin hydrocarbons, which comprises separating said normal 2-o1en from said mixture, converting residual l-olen REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Boedeker et a1. Mar. 26, 1946 OTHER REFERENCES Egloi et al., Isomerization of Pure Hydrocarbons, pages 51453, Reinhold Publishing Corp., 1942.

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