US2347317A - Treatment of mixtures of hydrocarbons and hydrofluoric acid - Google Patents

Description

prilvzs, 1944. J, D. GIBSON 2,347,317

TREATMENT OF MIXTURES OF HYDROCARBONS AND HYDROFLUORC ACID Filed April 6, 1942 47 I IGI-IT GASES 26 77 62' 63 46 f ISOBUTANE CONDENSER I I9 i 74 l I 46 /44 l Y l C F Z 'I 2| n: t 0 O. g -4- E 73 67 2o 26 A}27 ..71 25 I 5 6 L3 72 /IQ A22/70 75 76 33 23\ BUTANE MINORI-1% I H 6I I I6 ISOBIJTANE 66l 42 LZ Ooi 3i 63 62 F2 E A,/ 43 z fr OD I Q oLEI-'IN 36 *QH 56| 32 C y-T-r-ALKYLATOR U 35 34 37 g LL -A "\24 65 e|\ 64 HYDROFLUORIG AGID 38 t 3o 29 5l 5 39 .jo l d *7 t AI.KYI ATE\ 50 l 4| eo 53 54 i LIJ Y E i I- 55 v 3 I I ,5 I I I 0i Z I z I I4 I PQ E 1 I- 3 O U I3 I o I2 II 3 ISOMERIZATION REAGTOR LID "f il Q CI:

J 56 56 82 I y I MOTOR FUEI.

INVENTOR JAMES D. GIBSON ATTORNEYS Patented Apr. VV, 1944 TREATMENT OF MIXTURES OF HYDROCAR- BONS AND HYDROFLUORIC ACID James D. Gibson, Bartlesville,

Phillips Petroleum Company,

Delaware Okla., assigner to a corporation of Application April s, 1942, serial No. 437.898

4 claims. (ci.

This invention relates to the treatment of mixtures which comprise hydrouoric acid and hydrocarbons. More particularly it relates to the production of hydrocarbon-hydrofluoric acid mixtures of desired proportions. It relates iurther to the production of liquid paraiiins from low-boiling normal paraiiins. l

Inprocesses in which hydrouoric acid is used as a catalyst .or reagent, such as alkylation of hydrocarbons to produce motor fuel and reconstruction of hydrocarbons -to produce other hydrocarbons having achemical structure different from that o'the feed material, there is frequently produced, at some stage in the process', a mixture which comprises hydrouoric acid and one or more saturated hydrocarbons. Often,

acid-soluble materials such as unsaturated hydrocarbons andfluorinated organic compounds are also present. At times it is desired to separate such mixtures into several fractions,'among which may be a fraction containing hydrofiuoric acid and one or more specic hydrocarbons, such as isobutane or normaliy butane, in desired proportion for use in a subsequent step.

In feeds to a process such as the alkylation of isobutane in the presence of hydrofiuoric acid as catalyst, it is desirable to have a mixture of hy-A droiluoric acid and isobutane that comprises more than 25 per cent hydrofluoric acid by weight; for example, acid-to-isobutane ratios of 0.421 to 4:1 or more are ordinarily needed in alkylating steps. l

An object of this invention is to provide an improved process for converting relatively lowboiling hydrocarbons to motor fuel hydrocarbons in the presence of hydrofluoric acid as a catalyst.

Another object is to produce by distillation, from a two-liquid-phase mixture comprising hydroiluoric acid and one or more hydrocarbons,

a fraction comprising hydrofiuoric acid and isobutane in controlled proportions and suitable for use as feed to an alkylating step.

Another object is to produce by distillation, from a two-liquid-phase mixture comprising hydrouoric acid and one or more hydrocarbons, a fraction comprising hydrofiuoric acid and normal butane in controlled proportions and suitable for use as feed in a reconstructing or isomerizing step.

Other objects and advantages of this invention will become apparent from the accompanying disclosure and discussion.

In accordance with one aspect of this invention, a mixture comprising isobutane, normal the isobutane is treated.A to produce a mixture' consisting, of hydrouoric acid and isobutane in desired proportions by distilling the mixture while retaining the normal butane in the kettle, cooling andseparating the overhead distillate into two liquidphases, withdrawing substantially all of the lower or hydrouoric acid phase and a desired limited proportion only of the upper or -isobutane phase, and returning the remainder of the upper phase as reflux to the distillation co1- umn. This procedure is especially advantageous in a combination isomerization-alkylation process in which normal butane is isomerized to isobutane in the presence of hydroiluoric acid; the resulting reaction mixture is distilled; and the distilled hydroiluoric acid and isobutane, in any desiredV proportion whereby the acid-to-isobutane ratio is greater than that in a corresponding azeotropic mixture, are passed to'an alkylating zone.

Further, in a process in which a mixture comprising normal butano, hydrocarbons boiling portion, greater than zero and less than-100 per cent, of the upperor hydrocarbon phase and returning the remainder of the upper' phase as reiiux to the distillation column. This procedure is especially advantageous ina combination isomerization-alkylationprocess lin which normal butane is isomerized to isobutane in the presence of hydroiluoric acid as a catalyst: the resulting reaction mixture is cooled and separated into two liquid phases, of which the heavier or hydrofiuoric acid phase is passed as catalyst to an alkylating zone, and of which thel lighter or hydrocarbon phase is passed together with the total eiliuent from the alkylating zone to a fractionator; from this fractionator an overhead azeotropic mixture of isobutane and hydrofluoric acid is passed (after depropanization if necessary) to the alkylating zone, and a kettle fraction comprising normal butane, hydrocarbons boiling above normal butane, and hydroiiuoric acid in;t

excess of that required to form an ,azeotropicf mixture with all the normal butane, is passed to a distillation column; and the distilled hydrofiuoric acid and normal butane, in any desired proportion'whereby the acid-to-outane ratio is greater than that in a corresponding azeotropic mixture, are passed to an isomerizing zone.

An understanding of' some aspects of my lnvention may be aided by reference to the accompanying drawing, which is a schematic iiowdiagram of one arrangement for practicing my invention in a combination isomerizaton-alkylation process for producing motor fuel hydrocarbons. By omitting part of the equipment shown and making other minor changes, as will be described hereinafter, the process may be operated as an allgvlation process without an isomerizlng sten In the arrangement shown, a mixture of a suitable hydrocarbon, for example, normal butano, and hydrofluoric acid is admitted through inlet il, valve i2, pump I3, and heating coil I4 to reactor iii, wherein a substantial proportion of the normal butane is converted to insobutane, and'. to some extent, to higher-boiling hydrocarbons, such as pentanes and hexanes.

In reactor I5, the ratio of hydroiluoric acid to hydrocarbon is preferably in the range from about 0.2:1 to irl or more by weight; usually, operating with an, acid-to-hydrocarbon ratio within this range will effect the maximum conversion of normal paramns to isoparains. Preferably most of the acid comes from other steps (to be described hereinafterL and only enough fresh or make-up acid is introduced through inlet il to maintain a desired quantity in temperature may vary from about 250 to 1000 F. A temperature in the range 30o to 900 F. is usually preferred; at low temperatures, the rate ci reaction is low, and at high temperatures, some cracking and carbon formation occurs. The pressure may be within the range of about atmospheric to 5000 pounds per square inch or more; usually, it is preferred, for reasons of economy in equipment and operating costs, to use a pressure in the range of 250 to 2000 pounds per square inch. The reaction time may vary from about 1 to about 300 minutes, depending chiefly upon the temperature. The time required decreases with increase in temperature. If the reaction time is very short, such as 1 to 5 minutes, the reaction can be completed in heating coil I4 or in an extension thereof; whereupon reactor I5 may be by-passed or removed from the system. Preferably the reaction zone is packed with a. contact mass, such as steel turnings, alumina, bauxite, or other material resistant to destruction by hydroiiuoric acid and suitable for aiding the reaction and/or heat transfer.

The resulting mixture of hydroiiuoric acid and hydrocarbons is passed from reactor I5 through valve i6 and conduit Il to distillation column I8, wherein it is subjected to distillation in accordance with this invention to produce, as an overhead product, a mixture of iluoric acid in which the proportion of hydroiiuoric acid is greater than that in an azeotropic mixture and which is suitable for use as feed to an alkylating'step. An overhead mixture of hydrofluoric acid and isobutane (some propane may also be present at times) from the top of column I 8 is cooled, liquefied, and separated into two liquid phases, as by passing it through cooling coil I S and valve 25 to separator 2l. This will be substantially an azeotropic mixture. Substanthe system. The reaction isobutane and hydro-- junctures or polymerization reactions.

tially all of the lower or acid phase is passed through valve 22 and conduit 23 to alkylator 24, together with any desired proportion, less than per cent and greater than zero, of the upper or hydrocarbon phase (mostly isobutane), which is passed through valve 25, the resultant mixture passing through conduit 23 being the aforesaid overhead product. The remainder of the hydrocarbon phase is returned through valve 25 and conduit 2l as reflux to the top of column I8. If desired part of the effluent .from cooling coil i5 may be recycled through valve 28 and conduit 2l for use as additional reflux in column I8, or a part may be passed directly to the alkylatlon step through conduit 69 and valve 70.

The kettle fraction from column I8 comprises normal butano, motor-fuel-range hydrocarbons, small proportions of higher-boiling hydrocarbons, and acid-soluble materials; in some cases, when not all the hydrouoric acid is distilled overhead hydrofluoric acid will also be present. This fraction is preferably passed through conduit 29 and valve 30 to fractionator 3l for producing an overhead fraction comprising normal butane, which is passed through conduit 32 and valve 33 to pump I3.

Under some conditions of operation, it is advantageous to yremove propane and otheri rela` tively low-boiling inert material from t-he system by passing part of the hydrocarbon phase from the top of separator 2| through valve 44 and conduit 45 to depropanizer 45, from which an overhead fraction comprising mainly material boiling below insobutane is withdrawn through outlet 41 having valve 48, and from which a kettle fraction comprising mainly isobutane is passed via valve t9 and conduit 23 to alkylator 24.

In alkylator 24, the mixture of isobutane and hydrofiuoric acid is mixed under alkylatng' conditions with an alkylating reactant, such es an olefin having from 3 to 5 carbon atoms per molecule, an alkyl compound, such as an alcohol or a halide, or an oleiinic polymer, which is introduced through inlet 34 and valve 35.

In the total feed to alkylator 24, the weight ratio of isobutane to olefin, or other alkylating reactant, is preferably in the range of 2:1 to 20:1 or more, and will generally be even higher in the reaction zone, and the weight ratio of hydrouoric acid to total hydrocarbons is preferably in the range of 0.4:1 to 4:1. 'Ihe olen or other alkylating reactant is preferably introduced into the reaction mixture under conditions of high turbulence and/or in multipointwise fashion, so that it is rapidly mixed with the isobutane. This procedure is advantageous in order to favor the desired olefin-isoparaiiin junctures, or alkylation reactions, and to hinder undesirable olefin-olefin Preferred operating conditions in alkylator 24 are a temperature in the range of 30 to 150 F., a pressure suicient to maintain all components in the liquid phase, and a time of about 1 to 30 or more minutes; however, conditions outside of these ranges may also be used without passing beyond the scope of this invention.

After asuitable reaction time, the resulting mixture passes from alkylator 24 through conduit 36 and valve 3l to separator 38, wherein, as by cooling and gravitational or centrifugal means, it is separated into two liquid phases. Part of the heavier or hydrofluoric acid phase may be recycled through valve 39 and conduit 40 to alkyla tor 24; preferably, however, most of it is passed through conduit 40 and valve 4I to pump I3 for ple, in a combination isomerizatiomalkylation use as catalyst in the isomeriaing step. The

Alighter or hydrocarbon phase from separator 33 is passed through valve @l2 and conduit 43 to column i3, in which, together with the eiiluent from the isomerizing step, it is separated into two frac tions as already described. l

The kettle fraction from ractionator 3 i which comprises mainly branched-chain motor-fuel hydrocarbons or alkylate is passed through valve 50 and conduit 5i to rerun column 52. In this column it is separated into two fractions: (l) `a major motorfuel-range fraction, which is passed through valve 53 and conduit 54 to deiiuorinator l 55; and (2) a bottom fraction comprisnig hydrocarbons boiling above the motor-fuel range. which is withdrawn through outlet 56 having valve al.

Fluorine remover or deiiuorinator 55 comprises a chamber containing a contact mass having hydrogenation and/or dehydrogenation properties, such as bauxite, alumina, or other similar catalyst. Usually suitable operating conditions are a temperature in the range or 75 to 500 F. and a space velocity in the range of. 1 to 50 volumes of liquid hydrocarbon material per volume of catalyst per hour. Under such conditions, which may be particularly selected by trial i'or any particular case, organically combined iiuorine is substantially completely removed from the hydrocarbon material, which then is withdrawn through outlet 58 having Valve 59.

Under some conditions other modications of the foregoing general scheme will be preferable. For example, if the available parainic feed material comprises appreciable proportions of isobutane, it is advantageous to introduce this feed to column i8 through inlet 60 having valve 6i. If auxiliary supplies of isobutane are available, it is advantageous to introduce them directly to alkylator-24 through inlet 62 and valve t3. If

desired, additional or make-up acid may also be introduced to alkylator 24, as through inlet @d and valve 65.

My invention is also applicable to a. simple alkylation process, such as that used if adequate supplies of isobutane are available without isomerization of normal butane, Such a process may also be illustrated by the accompanying drawing, with the following changes in operation:

The isobutane-containing feed material preferably is admitted through inlet 62 having valve t3 50 to alkylator 24. Make-up hydroiiuoric acid is introduced through inlet 64 having valve d5. Part of the total eiiluent from alkyiator 24, preferably at least one-fourth or more, is by-passed around separator 38 directly through valve S6 and conduit 43 to column I8. The amount of alkylation eiiiuent so lay-passed is adjusted or regulated so that the material returning to alkylator 2d through conduit 23 has the desired proportion of hydroiiuoric acid needed for the alkylation and so' that the kettle product from column I8 is free from hydroiiuoric acid. Appropriate valves, such yas valves I6, 33, and 44, abre closed 'to remove from use equipment not necessary to the alkylation step. Normal butane may be withdrawn from the system through outlet 61 having valve 68. Hydroiiuoric acid from the bottom of separator 33 is recycled through valve 39 to alkylator 24. Proceeding in this manner has the advantage that column i8 serves to regenerate continuously `hydrofiuoric acid spent in the alkylation step.

Many other modications and/or applications of my invention will be obvious to those skilled in the art of hydrocarbon conversion. For examu is given:

process, similar to that already described, total eiuent from an alkylator, together with hydrocarbon ei'iiuent from an isomerizing step, may beV passed to a distilling column from which an over head mixture of hydrouoric acid and isobutane is passed or-recycled to the alkylator, and from which a kettle fraction comprising normal butane,

motor-fuel hydrocarbons, and hydroiiuoric acidv is passed to an azeotropic distilling column used in the same manner as that hereinbeiore described for column is. From this column there is produced an overhead fraction comprising hydroiiuoric acid and normal butane in controlled proportions, such as in the range of 0.421 to 4:1 by weight, suitable for use as feed to the isomerizing step. Hydrouoric acid from the isomerizing step is passed as catalyst to the alkylating step. For this modification it is desirable to make the following changes: Column it is operated as an ordinary azeotrope column, sending an overhead azeotropic mixture of isobutane and hydroiiuoric acid through line t9 and valve l@ to alkylator 2Q; valve 28 is closed. Hydrouoric acid, normal butane, and alkylate pass from the kettle of coiumn i8 through valve 3d to fractionator Si, which is now operated in the manner that is a special feature of this invention. That is, valves s3 and 68 are closed; an overhead azeotropic mixture of normal butane and hydrouoric acid is passed through line ii and valve 'i2 to condenser is, from which it is passed through valve it to setltier or separator 1E for separation into two liquid phases. The heavier or acid phase is passed through valve l5 and conduit 32 to pump i3. Any desired portion less than 100 per cent of the lighter or normal butane phase is passed through valve il and conduit 32 to pump i3; the remainder of the butane phase is passed as reiiux through valve 82 and conduit t3 to column 3l. Valve i6 is closed, and the isomerizer emuent from reactor is is passed through valve 'i3 to separator i9, in which it is separated into two liquid phases. The lighter or hydrocarbon phase is passed through valve and conduit il to column 8; the heavier or hydrouoric acid phase is passed through valve El and conduit 82 for use as catalyst in alkylator 2d.

My invention is very advantageous for use in applications similar to the foregoing in that no separate acid-distilling equipment is necessary. For example, acid-soluble materials-dissolved in the acid passed into column 18 remain in the kettle fraction and subsequently act to increase the yield of motor fuel, or are` removed from the and isoparains so formed and including isopeny tane may be alkylated. In isomerlzing normal pentane a substantial amount of isobutane is gena erally also produced, and in such a case the combined isobutane and isopentane may be subjected to alkylation.

To further illustrate some of the many laspects of my invention, the following specic example In an arrangement similar to that illustrated in the accompanying drawing, normal butane and concentrated or substantially anhydrous hydrofluoric acid are charged to an isomerizing step. The isomerizing conditions are approximately as follows: temperature V350" F.; pressure, 1500 pounds per square inch (liquid-phase conditions) reaction time 200 minutes; acid"to-hydrocarbon ratio, 3:1 by weight. The total effluent from the isomerizing step is cooled and passed to an azeotropic distilling column having a special refluxlng arrangement whereby the overhead fraction is separated by cooling and gravity into two liquid phases. The lower or acid phase and a part of the upper or hydrocarbon phase are withdrawn in a weight ratio of about 2 :1; the remaining part of the upper phase is returned as reiiux to the top of the column. The hydrocarbon portion withdrawn is passed through a depropanizer wherewith most of the propane and incidental low-boiling materials are removed by distillation; the residual isobutane and the hydroiluoric acid withdrawn are passed together as feed to an alkylating step, wherein the isobutane is alkylated under alkylating conditions with an alkylating agent, such as a mixture of butylenes The conditions in the alkylator are as follows: temperature 90 to 115 F.; pressure, 125 to 175 pounds per square inch; average reaction time, 6 minutes, rapid agitation to maintain intimate contact between acid and hydrocarbon phases, isobutane-to-alkylating agent ratio, about 6:1 by weight, acid-to-hydrocarbon ratio, about 2:1 by weight.

The resulting eilluent mixture from the alkylator is passed to a settler in which it is separated into an acid phase and a hydrocarbon phase. The acid phase is passed to the isomerizing step for use as catalyst, and the hydrocarbon phase, which comprises isobutane and motor-fuel hydrocarbons, is passed to the aforementioned azeotropio distliling commu. From the bottom of this column motor-fuel hydrocarbons produced by alkylation, together with normal butane and higher-boiling hydrocarbons originating in the isomerizing step, are passed to a debutanizing column for separating normal butane, which is recycled to the isomerizing step. The remaining material, which is mainly highly branched parafnic hydrocarbons suitable for use in aviation gasoline, is subjected to another distillation step` to remove relatively high-boiling impurities, and to a defluorination treatment to remove organic fluorine. 'Ihe resulting motor-duel fraction is substantially completely saturated, has a clear octane number of about 91, and is suitable for use in aviation gasoline It is not intended that mention ci' specic apparatus or of specific applications should be taken to limit unduly the scope of my invention. The special distilling and refluxing features of my invention are applicable, for example, to any case wherein it is desired to produce a distillation product of controlled proportions of a low-boiling saturated-type hydrocarbon and hydrofluoric acid in which product the proportion of hydrouoric acid is greater than that in a corresponding azeo.. tropic mixture. The invention should no-t be limited otherwise than as specified in the appended claims.

What I claim is:

A1. In a combination isomerization-alkylation process in which there is produced a mixture comprising isobutane, normal butane, hydrocarbons boiling higher than normal butane, and hydrou fluoric acid in excess of that required to form azeotropic mixtureswith al1 the isobutane and with all the normal butane, the steps which comprise distilling the mixture to produce an over? head azeotropic mixture comprising isobutane and hydrofiuoric acid and a bottom fraction comprising normal butane, hydrocarbons boiling higher than normal butane, and hydrofiuoric acid in excess of that required to form an azeotropic mixture with all the normal butane; passing said overhead azeotropic mixture comprising isobutane and hydrofluoric acid to an alkylating zone; passing said bottom fraction to a second distilling column and distilling 'an azeotroplc mixture of hydrofiuoric acid and normal butane overhead and retaining hydrocarbons boiling higher than normal butane in the kettle; cooling and separating the overhead distillate into two liquid phases, withdrawing substantially all of the hydrouoric acid phase and a substantial proportion of the ture comprising isobutane and hydrofluoric acid is distilled overhead and normal butane is retained vin the kettle; cooling and separating the overhead distillate into two liquid phases, withdrawing substantially all of the hydroiluoric acid phase and a substantial proportion of the isobutane phase;v passing these withdrawn materials to an alkylating zone; and returning the remainder of the isobutane phase as reflux to the distillation column.

3. In a process for isom'erizing normal butane to form isobutane and for alkylating isobutane so formed, the improvement which comprises isomerizing normal butane in the presence of concentrated hydroiiuoric acid as the isomerization "catalyst to form isobutane, passing eiiluents of said isomerizatlon to a fractional distillation column, removing from said fractional a` low-boiling mixture comprising isobutane and hydrofluoric acid, cooling and condensing at least a portion of said mixture to form a liquid isobutane phase and a liquid hydrofluoric acid phase, returning a portion of said liquid isobutane phase to said fractional distillation column, passing a further portion of said isobutane phase together' with said hydroiluoric acid to an alkylation zone, reacting said isobutane with an added alkylation reactant in the presence of said hydroiiuoric acid as the alkylation catalyst, separating from eilluents of said alkylation a maior part of the hydroiiuoric acid, passing a residual hydrocarbon material containing only a minor part of hydrouoric acid to said fractional distillation column, and removing as a high boiling traction from said fractiona1 distillation column a hydrocarbonfmaterial substantially free from isobutane 4. In a process for isomerizing a low-boiling normal parafiin of at least four carbon atoms per molecule and for alkylating resulting low-boiling isoparains, the improvement which comprises isomerizing a low-boiling normal paramn of at least four carbon atoms per molecule in the presence of concentrated hydrouoric acid as the isomerization catalyst to form low-boiling isoparaiiins, passing etlluents of said lsomerization to a,

distillation column zone a hydrocarbon material substantially free from hydroiiuorlc acid, passing said hydrocarbon material to the aforesaid fractional distillation means, and recovering also from said distillation s means a normally liquid isoparaiiinic hydrocarbon iractional distillation means, passing from said distillation means to an alkylating zone a lown boiling isoparain and hydroiiuoric acid, reacting in said alkylation zone said isoparamn with an added alkylating reactant in the presence of said hydrouoric acid to form higher-boiling isopaxains, separating from eiiluents of said alkylation material so produced.

JAMES D. GIBSON.

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