US2804490A

US2804490A - Process for isomerization of 1-olefins and use of isomerized product in alkylation

Info

Publication number: US2804490A
Application number: US312123A
Authority: US
Inventors: Donald H Belden
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1952-09-29
Filing date: 1952-09-29
Publication date: 1957-08-27
Anticipated expiration: 1974-08-27

Description

Aug-27,1957 D H.BELDEN PRocRss RoR IsoMERIzATIoN 0R 1-oLER1Ns AND usR oF ISOMERIZED PRODUCT IN ALRYLATION Filed sept. 29, 1952 mman-Ehm mzFSmom. l:

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United States Patent PROCESS FOR ISVOMERIZATION F I-OLEFINS AND USE 0F ISOMERIZED PRODUCT IN ALKYLATION Donald H. Belden, North Riverside, Ill., assigner to Universal Uil Products Company, Chicago, Ill., a corpo- This invention relates to a process for alkylating hydrocarbons and as an integral, preliminary step of the process, to the method of converting the terminally bonded isomer component of an olefinic alkylating agent containing the same to olens having a more centrally located double bond. More specifically, the invention concerns a method for converting a l-olen into a 2-olelln or other more centrally bonded olefin position isomer by means of a combination process involving hydrolluorination of a l-olefln containing hydrocarbon fraction, subjecting the resulting product to dehydrofluorination and thereafter repeating the hydrofluorination-dehydrofluorination cycle until substantially all of the original 1- olefin is converted to the double bond position isomer thereof.

One object of the invention is to provide a process for converting a mixture of olefinic hydrocarbon isomers into an olefinic hydrocarbon having a particular structure more desirable for the production of a motor fuel or aviation alkylate therefrom. Another object of the invention is to convert a l-olefln to an isomer thereof in which the double bond occupies a more centrally located position in the carbon atom chain of the olefin molecule. Still another object of the invention is to provide a process for the manufacture of a more highly branched chain hydrocarbon alkylate having substantially greater antiknock value than the corresponding alkylate product obtainable from the olefinic hydrocarbon alkylating agent which is not subject to the pretreatment comprising the method of the present process.

In one of its embodiments the presenttinvention concerns a process for condensing an alkylatable hydrocarbon with a mono-oleflnic hydrocarbon containing at leas 4 carbon atoms per molecule which comprises subjecting an oleflnic hydrocarbon having a terminal double bond to at least one isomerizing reaction cycle wherein the terminal double bond of said olefinic hydrocarbon is shifted to an intermediate position inthe carbon atom chain, said isomerizing reaction comprising subjectingl said terminally bonded olefinic hydrocarbon to hydrofluorination in the presence of not more than the quantity of hydrogen fluoride which will completely dissolve in said olefinic hydrocarbon, thereafter subjecting the resulting alkyl fluoride to dehydrolluorination and reacting the resulting product with said alkylatable hydrocarbon. A

Another embodiment of the invention relates to the process for effecting substantially complete isomerization of a terminally bonded oleflnic hydrocarbon containing at least 4 carbon atoms per molecule to an isomer thereof having a double bond more. centrally located in the carbon atom chain of said olefin, which comprises subjecting said terminally bonded olenic hydrocarbon to hydroiluorination in thelpresence of not more than the quantity of hydrogen fluoride which will completely dissolve in said olenic hydrocarbon-and thereafter subjecting the resulting product to dehydrolluorination.

lt is commonly recognized that branched-chain hydrocarbons of the parallln series have less tendency to knock upon combustion under compression in a spark-red internal combustion engine than the corresponding straightchain isomers. It is also known that a more highly branched-chain aliphatic hydrocarbon is obtained in the alkylation of isoparafllns with oleflnic hydrocarbon alkylating agents in which the double bond of the olefin occupies a position in the carbon atom chain other than on the terminal carbon atom. That is, a 2-olefln hydrocarbon yields a more branched chain alkylate than a l-olen and the same is generally true for the 3-oleflns, 4-olefins, etc., the carbon atom containing the least hydrogen generally being involved in the alkylation reaction as the point of attachment to the isoparaflln alkyl acceptor. The same general principles are believed to obtain in the alkylation of aromatic hydrocarbons containing a replaceable nuclear hydrogen atom, an isoalkyl aromatic hydrocarbon alkylate being the product formed as a result of the alkylation reaction. For these reasons, it is preferred that the oleflnic hydrocarbon supplied to the alkylation reaction as the source of the alkyl group in the production of motor fuel or aviation alkylates or in the manufacture of isoalkyl aromatic hydrocarbons be an olellnic hydrocarbon in which the double bond occupies a more centrally located position in the carbon atom chain of the olefin molecule; that is, the preferred olenic hydrocarbons for use as alkylatingl agents are monooleflns other than the l-olefin isomers in which the double bond occupies a terminal carbon atom of the molecule. Thus, butene-Z is preferred over butene-l as alkylating agent for condensation with isobutane, isopentane, or other iso-parafllnic hydrocarbons. Similarly, pentene-2, pentene- 3, hexane-2, hexene-3, 2-rnethyl-hexene-3, 2,3-dimethylpentene-Z, octene-Z, octene-S, octene-4, etc. are preferred over the corresponding straight chain or branched chain pentene-l, heXene-l, octene-l, and higher l-olefln homologs for alkylation purposes. By mean-s of the process of the present invention, a method of isomerizing l-oleflns toV their olefin isomers containing a corresponding number of carbon atoms is provided whereby the more desirable intermediate position isomers may be obtained for alkylation purposes from any of the above l-isomers or mixtures thereof or hydrocarbon mixtures containing a substantial proportion of the l-isomer.

The isomerization process provided herein involves a method lof subjecting a l-olenic hydrocarbon or a mixture of hydrocarbons containing a 1olen to hydrofluorination whereby the corresponding allyl fluoride is formed and thereafter dehydrofluorinating the alkyl fluoride product. The hydrofluorination reaction is effected in the presence of suillcient hydrogen fluoride to react at least partially with the l-olefins present in the mixture, and preferably in the presence of not more than an amount of hydrogen fluoride which will completely dissolve in the hydrocarbon feed stock to the process, since in the presence of a free hydrogen fluoride phase, the olefinic components of the feed stock tend to undergo undesirable polymerization and hydrogen transfer reactions, rather than forming the desired alkyl fluoride therefrom. In the hydrolluorination reaction the l-isomer is believed to undergo conversion to a secondary alkyl fluoride which upon dehydroiluorination is converted into a position isomer of the original 1olefin which contains the double bond in an intermediate position in the olefin chain. It is also believed that the conversion of the l-oletn to the more centrally located double bond position isomer through intermediate secondary alkyl fluoride formation continues in the indicated direction until the l-'olefin is converted to the position isomer substantially to extinction of the l-olefin. Furthermore, it is believed that during the alternate hydrofluorination-dehydroiluorination reaction cycle, the intermediate alkyl fluoride doesv O not dehydrofluorinate to any substantial degree to the initial l-olen contained in the feed stock; therefore, the formation of the alkyl fluoride as an intermediate product of the reaction insures the ultimate complete conversion of the l-oleilns contained in the feed stock to the isomer having a centrally located double bond position.

Suitable olefinic hydrocarbon mixtures containing the l-olefln isomer may be obtained from any convenient source, but the olenic hydrocarbons formed by dehydrating normal primary, aliphatic alcohols are almost exclusively the l-olefln isomer and, therefore, are particularly adapted for use as feed stock in the present conversion process. Other sources of l-olens include the normally gaseous and normally liquid fractions of the hydrocarbon product formed by thermally or catalytically cracking a liquid hydrocarbon feed stock, the olenic products generally comprising a mixture of the various olefinic isomers, including l-olefins. Olenic hydrocarbons containing the l-isomer are also the end product of the dehydrohalogenation of alkyl halides, as for example, the dehydrochlorination product of an alkyl chloride such as butyl chloride, amyl chloride, octyl chloride etc.

The isomerization reaction involved in the present process is generally applicable to individual oleflnic hydrocarbons or mixtures thereof, the components of which contain at least 4, up to about l2, carbon atoms per molecule, that is, from butene-l to dodecene-l. ln the manufacture of motor fuel and/ or aviation alkylates for which the present process is a particularly useful improvement, a low molecular weight isoparafllnic hydrocarbon, such as isobutane, isopentane, one of the isohexanes or isoheptane is condensed in the presence of an alkylation catalyst with a butylene, amylene, and/or hexene. A fraction comprising predominantly low molecular weight olefns is separated from an oleiinic feed stock and subjected to the present isomerization treatment in a preliminary conversion reaction prior to the alkylation step.

It is to be emphasized that although the present isomerization method is particularly adapted to the conversion of mixtures of oleflnic hydrocarbon isomers in which the l-olefln isomer is predominant, the reaction may be applied with similarly advantageous results to olefnic mixtures in which the l-isomer constitutes merely a minor proportion of the total olefin content of the mixture, the conversion of the isoalkyl fluoride to a different position isomer being the principal reaction involved in the process. A particularly preferred feed stock is a mixture containing butene-l and isobutylene which upon alkylation with isobutane is converted to the highly desirable motor fuel and aviation alkylate: iso-octane (that is, 2,2,4-tn`methylpentane) which has high antiknock properties when used as fuel in internal combustion engines.

Suitable feed stocks which may be alkylated with the present isomerized oleflns include isoparaflinic hydrocarbons as well as aromatic hydrocarbons containing a nuclearly substitutable hydrogen atom. Thus, isoparaffins such as isobutane, the isopentane parafllns, such as 2,2-dimethylpropane, -methylbutane, the isohexane parafns such as 2,3-dimethylbutane, 2,2-dimethylbutane and Z-methylpentane and homologs thereof, generally containing not more than about l2 carbon atoms per molecule may be alkylated by means of the present process. Of the aromatic hydrocarbons which may be alkylatedwith the present isomerized olefins to form isoalkylarornatic alkylates, including phenyl as well as polycyclic aromatic hydrocarbons, generally the alkylbenzene derivatives are preferred because of the substantially greater yields of alkylate obtained therefrom. Suitable aromatic hydrocarbon feed stocks to the present alkylation process include benzene, toluene, a xylene or a mixture of xylene isomers, a trimethylbenzene or other mono, di, and trialkyl substituted benzenes; naphthalene, the monoand polyalkyl-substituted naphthalenes, phenanthrene, etc. the

aromatic hydrocarbon feed stock to the present process being characterized in that the aromatic nucleus contains a replaceable hydrogen atom.

The isomerization reaction of the present process is obtained by contacting the olefin feed stock containing the l-olen isomer with hydrogen fluoride or hydrouoric acid at isomerizing conditions, the quantity of hydrogen fluoride in the reaction being controlled and specifically limited to an amount less than that required to form a separate phase distinct from the hydrocarbon phase, that is, less than the amount soluble in the hydrocarbon feed stock. It has been observed that by limiting the amount of hydrogen fluoride charged with the butene-l containing olefin fraction into the isomerization reactor to an amount not more than the quantity which will dissolve completely in the olellnc feed, the reaction ocurring in the isomerization reactor `may be controlled so as to effect alternate hydrofluorination and dehydrofluorination of the butene-l feed without attending alkyl and hydrogen transfer, polymerization and other side reactions foreign to the present process, which reactions would otherwise ocur in the presence of a greater quantity of hydrogen fluoride to reduce the yield of isomerized olefin monomer. ln the presence of only sufllcient hydrogen fluoride to completely dissolve in the olellnic feed stock charged to the process, on the other hand, conversion of the lolens to secondary alkyl lluorides occurs substantially to the exclusion of the aforementioned side reactions and the objects of the present invention are realized. The olefmic feed is desirably mixed with a diluent, preferably a paraflinic hydrocarbon which is inert to the action of the hydrogen fluoride and dehydrofluorination catalyst prior to subjecting the l-olen containing feed stock to isomerization. Thus, a butene-l containing hydrocarbon feed may be diluted with iso-butane prior to the isomerization reaction, preefrably in an amount equivalent to from about 0.5 to about l0 volumes of butane per volume of butene-l in the olefin-containing fraction utilized as feed stocks.

In accordance with the present process, isomerization of the 1-olelin containing feed stock to an olefinic hydrocarbon having a more centrally located double bond is accomplished by subjecting a mixture of the oleilnic feed and hydrogen fluoride (dissolved in the inert paraillnic hydrocarbon diluent and containing less hydrogen fluoride than required to form a separate phase) to hydrofluorination, thereby forming secondary alkyl fluorides of the l-olefins contained in the mixed olefinic feed and thereafter passing the stream of hydrogen fluoride, inert hydrocarbon, and/or oleflns and alkyl fluorides into a reactor containing a dehydrofluorination catalyst wherein the alkyl fluorides undergo substantial conversion to hydrogen fluoride and an olefin in which the double bond is more centrally located in the carbon atom chain of the olefin molecule. The hydrotluorination and successive dehydrofluorination reactions may be alternately repeated in a number of successive cycles until the 1- olen components are substantially completely converted to their isomers having more centrally located double bonds, that is, until substantial extinction of the l-olefin components of the mixed feed. Hydrofluorination of the oleflnic feed may be obtained by mere contact between the olefinic feed and the hydrogen fluoride, preferably in liquid phase, at tempereatures of from about 0 to about 150 C. Since, however, the subsequent dehydrofluorination stage must generally be operated at a somewhat higher temperature level, the hydrofluorination reactor is preferably maintained at substantially the same temperature as the dehydrofluorinaton zone, thereby eliminating Vthe necessity f or alternate cooling and heating between the hydrofluorination and dehydrofluorination stages in a multiple cycle operation. Since hydrofluorination is more readily obtained by increasing the intermolecularcontact between the hydrogen fluoride and oleiinic feed stock, it is generally preferred to mix the reactants by any suitable form of mixing device or means. Accordingly, the hydrouorination zone is preferably packed with a hydrogen iluoride resistant solidcontact material in particle form, such as copper pellets, saddles or other distributed particles placed therein in such manner as to allow free llow of the mixture of hydrogen fluoridI and olenic feed through the bed of contact materia Dehydrouorination of the alkyl fluorides formed in the preceding hydrolluorination zone is preferably effected in the presence of a catalytic agent which enhances the rate of dehydrofluorination and the yield of isomerized olefin from the alkyl iluorides. Typical of such catalytic agents are solid inorganic materials such as aluminum fluoride, calcium lluoride, potassium fluoride, certain metals such as copper, nickel, chromium etc. and other metals and inorganic fluoride salts which are stable and retain their identity at the operating conditions maintained in the dehydrolluorination zone. In the presence of such dehydrofluorinating agents, the secondary alkyl iluorides formed in the preceding hydroiluorination zone undergo dehydrolluorination at temperatures of from about 30 to about 300 C., preferably at temperatures of from about 40 to about 150 C. The pressures at which the hydrolluorination and dehydrolluorination rei actions occur within the isomerization reactor are such as to maintain the feed and hydrogen fluoride reagent in substantially liquid state, preferably at pressures of from atmospheric to about 500 lbs./in.2, depending upon the temperature maintained in the respective zones.

The isomer-ized 1olen Aremoved from the isomerization reactor in the form of the oleln or as an alkyl fluoride is thereafter mixed with a paratfinic fraction containing as isoparaflln, that is, a branched .chain paraffin hydrocarbon, or with an alkylatable aromatic hydrocarbon containing a nuclearly substitutable hydrogen atom and the resulting mixture subjected to alkylating conditions in the presence of liquid hydrogen fluoride or substantially anhydrous hydrofluoric acid containing less than about by Weight of water as the alkylation catalyst. Where the alkylatable hydrocarbon is an isoparalliln present in the stream of olefnic feed stock, as for example, when the process is utilized to produce aviation alkylate, the reactants are self-contained in the effluent stream of the isomerization zone, although additional isoparaffin is preferably added to the efuent to increase the isoparallin to olen mole ratio to the level desired for alkylation, as hereinafter described. The alkylation reaction is preferably effected in a stirred pressure autoclave wherein the reactants and hydrogen fluoride catalyst may be maintained in substantially liquid phase, generally at temperatures of from about to about 100 C., and preferably at from about 0 to about 50 C., although higher or lower temperatures may also be utilized to obtain the desired condensation of the hydrocarbon reactants. ln order to reduce side reactions such as polymerization,I polyalkylation etc., the reactants are charged into the alkylation reactor in a molar proportion of aromatic or isoparalllnic hydrocarbon to total olefin of at least 1 to l up to about 30 to 1 and preferably from about 10 to l to about 20 to 1, particularly when utilizing an aromatic hydrocarbon containing no other nuclear substituents, the latter being subject to po'lyalkylation.

The present invention is further illustrated with respect to specic embodiments thereof in the accompanying diagram and the description which follows. The diagram is described with respect to the alkylation' of an isoparalhnic hydrocarbon, which in the illustration shown is isobutane, with a C4 olen fraction as the oletlnic feed stock. The diagram also illustrates a miltiple cycle hydroiluorination-dehydroiluorination zone packed with a suitable contacting material in the hydroiluorination zone and a dehydrolluorination catalyst in the dehydrouorination zone. v g l Referring to the acompanying drawing, a C4 paratlinic '6 hydrocarbon fraction, such as a predominantly isobutane fraction is charged into the process flow from storage through line 1 in amounts controlled by valve 2, the added isobutane being supplied in an amount which in addition to the isobutane recycled in the process is sufficient to maintain the proper iso-parallln to olen ratio forl the subsequent alkylation stage of the process. Since the only isobutane removed from the process is the isobutane reacted with the olenic alkylating agent to form alkylate product, the amount of fresh isobutane charged into the process through line 1 is the isobutane equivalent to the alkylate removed as product. The remaining isobutane required to provide the desired isobutane to butylene ratio for alkylation purposes is made up by recycling isobutane within the process flow. The C4 fraction in liquid phase is transferred by means of pump 3 and line 4 into hydrogen fluoride saturator 5 comprising a fixed tower containing hydrogen fluoride in liquid phase wherein the parafnic hydrocarbon stream is saturated with dissolved hydrogen fluoride. Since the present process is essentially cyclic with respect to the hydrogen lluoride catalyst involved, the amount of the reagent required for this purpose may be continuously recycled from subsequent recovery stages of the process, as hereinafter described. The recycled hydrogen lluoride is charged into zone 5 through line 6 in amounts controlled by valve 7. The resulting stream of C4 paraillns containing dissolved hydrogen fluoride is removed from saturator vessel 5 through line 8 and mixed in line 8 with a butene-l containing C4 fraction introduced into the flow through line 9 in `amounts determined by valve 9a. The latter butene-l containing fraction may be obtained from any suitable source, such as the lightv pressure overhead from a thermally cracked petroleum fraction. Valve 9a controls the amount of butene-l and other olelins, if any, admitted into line S, the amount being determined by the rate of alkylate formation in subsequent stages of the process. The C4 hydrocarbon hydrogen fluoride mixture formed in line S is passed through a suitable heat exchange unit, such as heater 10 which raises the temperature of the stream to the level desired in the succeeding isomerization reactor, preferably to a temperature of from about 40 to about 150 C. The stream at the above temperature and pressure conditions is removed from heater 10 through line 11 and charged into the bottom of isomerization reactor 12 wherein the HF-hydrocarbon mixture is subjected to alternate hydrotluorination and dehydroiluorination reactions ocurring therein.

The hydrogen fluoride dissolved in the C4 paraffin stream admitted into the process flow through line 1 or admitted with the isobutane recycle stream, hereinafter described, is generally sullcient to supply the required amount of hydrogen fluoride for isomerization of the butene-l component of the olenic feed to butene-Z; however, under some circumstances it may be preferable to eliminate the C4 paraflln hydrocarbon stream introduced by such means and introduce undiluted hydrogen fluoride from a separately maintained source of hydrogen fluoride in the form of hydroiluoric acid or liquefied hydrogen fluoride, as for example, from storage, through line 13 connecting with line 14 which diverts the hydrogen lluoride into isomerization reactor feed line 11 in amounts controlled by valve 15. The amount thus charged into the process flow, however, must be limited to that amount only which is necessary to eiect the desired isomerization reaction; that is, to an amount not more than that required merely to saturate the hydrocarbon stream without forming a separate hydrogen fluoride phase. A particularly preferred source of the hydrogen fluoride in isomerization reactor 12 is a hydrogen fluoride-containing isobutane stream recovered in a subsequent stage of the process by stripping a C4 hydrocarbon-hydrogen fluoridecontaining fraction from the alkylation reaction product. This stream is generally saturated with hydrogen tluoride and1 when mixed with the butene-l-containing olefinic hydrocarbon fraction, supplys a quantity of hydrogen fluoride suflcient to effect the desired isomerization of butenel to butene-Z; When operating the process on the basis of the latter generally preferred source of hydrogen fluoride the stream of C4 para'ns saturated with hydrogen fluoride is charged into isomerization reactor feed line 11 from line 16 in amounts controlled by valve 17. Since this stream is generally the most volatile fraction recovered from the alkylate product in the stripping column following the alkylation reactor, the fraction contains a higher proportion of isobutane than the less volatile nbutane which may be present in the alkylate product. The large proportion of isobutane in this fraction desirably increases the ratio of isobutane in the feed to the alkylation reactor when. recycled in the system and thus accomplishes a useful. purpose in the process.

The mixture of butene-l and hydrogen-fluoride stream charged into reactor .12 is contacted, therein with particles of a suitable solid contacting material, such as copper chips, which promotes mixing of the reactants and enhances the formation of isobutyl lluorides by reaction of butene-l with the limited quantity of hydrogen fluoride present in the stream. The resulting stream of secondary and tertiary butyl iluorides, butene-2, unconverted butene-l, if any, and other components of the stream formed in reactor 12 pass through hydrofluorination zone 18, and thereafter ow upwardly through a perforated plate suitable for supporting the solid contacting material in a superimposed dehydrofluorination zone 19, containing a solid contact catalyst capable of promoting dehydrouorination such as calcium fluoride, aluminum fluoride, copper pellets, etc. Dehydroiluorination in zone 19 may be effected at the same or at a higher temperature as that maintained in hydrofluorination zone 1S. Thus, zones `18 and 19 may be separately maintained reaction vessels each maintained at different temperatures, or a single combined reactor maintained at an essentially uniform temperature throughout. ln the case of a single chamber reaction zone, heating coils may be interposed in column 12 between Zones 18 and 19 to heat the uid stream leaving zone 18 and entering zone 19. At the temperature and pressure conditions maintained in reactor 12, the dehydrouorination occurring in zone 19 regenerates hydrogen fluoride from the secondary and tertiary butyl uorides contained in the stream and forms butene-2 as a result of the isomerization occurring through the intermediate isobutyl fluoride formation. The resulting mixture comprising butene-2, unconverted butenc-l, if any, and regenerated hydrogen fluoride thereafter progresses into a superimposed hydrofluorinatiou zone wherein an additional quantity of butene-l is converted to isobutyl fluoride Without substantial effect on the butene-2 component of the stream. The isomerization reactor 12, here illustrated as a vertical colurnn containing multiple superimposed hydrofluorinating and dehydrouorinating zones, may also consist merely of one hydrotluorinating zone followed by one dehydrouorinating zone; however, the conversion of butene-l to butene-2 through only one cycle of the reaction is generally incomplete because the amount of hydrogen fluoride present by solubility is less than the stoichiometric amount required for the complete conversion of the olefins present in the stream and it is, therefore, preferred to provide a multistage isomerization reactor wherein the remaining butene-l may be subjected to a succeeding series of hydrofluorination-dehydrofluorination cycles to convert butene-l substantially completely to butene-2.

The conversion products formed in isomerization reactor 12 are removed therefrom through line 20 and transferred directly, after cooling in heat exchanger 21, into the alklation reactor, although in some instances the products may be subjected to a preliminary fractionation, for example, in a depropanizer colummnot shown, to

remove. propane., nropylene and/or propyl uorde which may; beA present in the product of the isomerizationreaction by virtue of the propylene and propane usually present in the C4 fractions utilized as feed stock in the process.

The products of the; isomerization reaction carried in a stream of isobutane, and comprising butene-2, secbutyl fluoride, unconverted butene-l, if any, and tertbutyl fluoride,l if present are charged after cooling to the desired alkylation reaction temperature in heat exchanger 21, into alkylation reactor 22. The latter unit is preferably in the form of a stirred pressure autoclave wherein the temperature of the reactants charged thereto may be maintained at from about 30 to about 100 C., preferably from about 0 to about 50 C., and at a pressure sufficient to maintain the reactants and hydrogen fluoride charged thereto in-substantially liquid phase, generally at pressures. of from atmospheric to about l5 atmospheres. The contents ofI the reactor are desirably mixed by a suitable form of stirring device such as a series of paddles, orifice mixers or by other means well known in the art.

The proportion of isobutane to butylenes (or their equivalent butyl iluorides) provided in alkylation zone 22 is maintained at molar ratios of from about 5 to 1 to about 15 to 1, the isobutane being made up of fresh isobutane stock charged into the process flow through line 1 and recycle isobutane recovered from the alkylation reaction product stream as an HF-isobutane overhead distilled from the butane stripping column operated in a subsequent stage of the process, as hereinafter described. This fraction comprising predominantly isobutane is charged, into reactor 22 through line 23 in an amount controlled by valve 24 or through line 17 into isomerization reactor 12. The total amount of isobutane thus present in alkylation 22 is determined by the amount available from the subsequent isobutane stripper and also the amount available in the Ci paraffin feed stock charged intothe process ow through line 1.

A sufficient quantity of hydrogen fluoride is charged into reactor 22 tocatalyze the condensation of isobutane with the butylene or their equivalent butyl lluorides in `the stream of isomerization product from reactor 12. Hydrogen fluoride for this purpose is of catalytic conf centration, herein specified as substantially anhydrous hydrouoric acid containing not more than about 10% by weight of water, although liquid anhydrous hydrogen fluoride and hydrouoric acid containing at least hydrogen fluoride is preferred. A major proportion of the hydrogen fluoride required in reactor 22 may be supplied through line 25l as recycled spent alkylation acid recovered from the alkylation reaction products in the settling zone following the alkylation reactor. Desirably, at least a portion of the hydrogen fluoride is fresh make-up acid removed Ifrom storage through line 13 which connects with line 14 or from a continuously operated 'acid regeneration system, the amount charged into alkylation reactor 22 being determined by valve 26 in line 14.

The products of the alkylation reaction which are maintained in liquid phase by the temperature and pressure maintained in zone 22 are removed therefrom through line 27 and valve 28 and charged into receiver vessel 29 wherein a hydrocarbon product phase is separated from a used or spent acid phase. These phases separate in vessel 29 into al upper hydrocarbon layer saturated with hydrogen fluoride and a lower spent acid layer which settles to the bottom of vessel 29. The spent acid may be allowed to ow into a settling leg on the receiver vessel such as 30 and withdrawn therefrom through line 31. At least a portion of the spent discharge from the process; the latter withdrawn portion may be subjected to fractional distillation to regenerate substantially anhydrous acid suitable for recycling to the alkylation reactor. Regeneration of the acid by means not shown on the diagram is a wellknown procedure in the art and is not directly concerned 9 with the present invention. A portion of the spent acid may be recycled to the alkylation zone from line 32 through valve 34 by means of pump 3S which discharges the spent acid into line 25 leading into alkylation reactor 22, as aforesaid.

The upper, substantially hydrocarbon layer in receiver vessel 29 is removed therefrom through line 36 with the aid of pump 37 which transfers the HF-saturated hydrocarbon phase into line 38, the latter conduit leading the hydrocarbon into heater 39 wherein the hydrocarbon stream is heated to a temperature sufiicient to vaporize a major proportion of the C4 components from the hydrocarbon alkylate and substantially all of the hydrogen uoride dissolved in the hydrocarbon alkylate. The hydrocarbon stream at a temperature of from about to about 50 C. is removed from heater 39 through line 40 and valve 41 and charged into isobutane stripping column 42 operated at a temperature and pressure suitable for vaporizing a hydrogen uoride saturated isobutane stream therefrom. Additional heat for effecting such vaporiz'ation may be supplied by a suitable reboiler coil in the lower portion of shipping column 42, such as reboiler 43. The light vapor overhead from column 42 comprising a hydrogen fluoride-isobutane mixture is removed from the column through line 44, liqueed in condenser 45 and the liqueed overhead charged into receiver vessel 46 through line 47 and valve 48. A portion of the hydrogen fluoride component of the vapor overhead may settle out as a dense liquid layer in receiver vessel 46 and may be removed from settling leg 49 through line 6 and pump 6a for recycle to HF saturator column 5 or alkylation reactor 22. The upper hydrocarbon layer saturated with hydrogen iluoride accumulating in receiver 46 is removed therefrom through line 50 by means of pump 51 which discharges the predominantly isobutane stream into line 52. In the preferred method of operating isobutane stripping column 42 at least a portion of the C4 overhead from the column is returned to the top of column 42 as liquid reux, the amount of the recycled portion being determined by valve S3 in line 52. The upper layer isobutane fraction accumulating in receiver vessel 46 is saturated with hydrogen fluoride and thus comprises a convenient hydrogen fluoride carrying medium for mixing with the butene-l containing olenic feed stock charged into the isomerization stage of the process. The isobutane fraction saturated with hydrogen uoride may comprise the predominant or sole source of hydrogen uoride in the isomerization reactor, and in the preferred method of operating the process, said fraction is the sole source of hydrogen uoride mixed with the olen fraction subjected to isomerization. In accordance with such preferred method of operation, hydrogen fluoride saturator column S may be eliminated from the process ow and the hydrogen uoride required for isomerization in reactor 12 supplied by the hydrogen uoride-saturated isobutane recycle stream returned to reactor 12 through line 17. Further, under such modified ow, make-up isobutane (to replace the isobutane converted to alkylate which is removed from the process as product) is introduced with the butene-l containing olenic feed or alternatively introduced or a separate stream into alkylation reactor 22. p

The high boiling bottoms of the isobutane stripping column 42 contain the desired alkylate product formed in the preceding alkylation reaction, a predominant proportion of which consists of Ca paraffin hydrocarbons, such as iso-octane (2,2,4-trimethylpentane), the alkylate product being highly desirable for motor fuel use in high compression automotive and aviation engines because of its high performance rating. When operating the process in the manner indicated wherein the butene-l component of the olenic hydrocarbon feed stock is isomerized to butene-2 prior to alkylation, the alkylate product has a rich rating performance number (P14 performance number) of from 145 to 155. The stripper bottoms thus formed are removed from column 42 through line 54 and valve 55 to storage or to additional fractionation means for separating a more desirable heartcut, as preferred. 1

The present invention is further illustrated with respect to certain of its specific embodiments in the following eX- ample, the specified reaction conditions therein not being intended to limit the broad scoperof the invention strictly in accordance thereto. Y p

A synthetic butylene-containing light hydrocarbon fraction was prepared and utilized in the following series of reactions as a source of C4 olenic hydrocarbon alkylating agent for condensation with isobutane to form an aviation alkylate. The composition of this fraction in mol percent of its constituents is indicated as follows:

346 grams of lthe above fraction containing 112 grams of mixed butylenes was mixed with 20 grams of hydrogen fluoride (5.4 weight percent), an amount of hydrogen fluoride which completely dissolved in the hydrocarbons. The mixture was thereafter heated to a temperature of C. for 24 minutes. The normally liquid product of the reaction (i. e. boiling at a tempertaure above 40 C.) was 13 grams and contained 2.72% by weight of fluorine. The condensable gases were liquefied, 343 grams being recovered. A uorine analysis of this product indicated that it contains 2.72% by weight of fluorine and has the following composition, expressed as mol percent of the indicated component:

The condensable gas portion of the effluent of the hydrofluorination reaction and the butyl fluoride formed in the preceding reaction are charged at a temperature of C. over a dehydrouorination catalyst consisting of pellet-s of metallic copper at a rate corresponding to 0.8 volume of gas per volume of catalyst per hour. The products of the reaction are separated into a condensable gas fraction and a liquid fraction containing componen-ts boiling above 40 C. The condensable gas, containing all of the C4 components of the product and 2.4% by weight of uorine is composed of the following constituents in their indicated proportions, expressed as mol percent.

The dehydrofluorination product containing dissolved hydrogen fluoride is thereafter heated under the conditions employed in the initial hydrofluorination reaction and the product separated as indicated above. The organic Portion of` thec onrtensable gaseshas the-.following com-f Position, expressed; in mol, percent..

The condensable gas fractions contains approximately 105 grams equivalent ofbutylene alkylating agent, about 12 mol percent of which is butene-Zl and about 67 mol percent of which is isobutyl tluoride, is capable of acting as an alkylating agent similar to butene-2 in the presence of an alkylation catalyst.

The condensable gas fraction is mixed with sullcient isobutane to form a mixture containing an isobutane to butylene (including isobutyl fluoride, isobutylene and butene-l) mole ratio of 15 to 1, 1400 grams of isobutane from an external source being mixed with the above condensable gas fraction for this purpose. The resulting hydrocarbon mixture at a temperature of 43 C. and pressure of 150lbs./in.2 is run into a stirred pressure autoclave of the turbo-mixer type containing about 0.6 volume proportions of the total hydrocarbon feed of anhydrous hydrogen tluoride maintained in liquid phase at a pressure of 150 lbs/in.2 forming thereby a mixture containing a hydrocarbon to acid volume ratio in the reactor of about 1.67. The mixture is 'stirred for a reaction period of about minutes, cooled to about 30 F. and thereafter discharged into a settling vessel to separate a lower spent acid phase from the upper layer hydrocarbon product. The decanted hydrocarbon product after waterwashing and treatment with caustic soda to remove acid lluorides is fractionally distilled to separate a debutanized gasoline-boiling range `fraction from the alkylate. This fraction has an end boiling point of 338 F. and a rich rating performance number (4.6 cc. per gallon of tetraethyl lead) of 152.

Under the same conditions of alkylation, that is, utilizing a similar ratio of isobutane to butylenes, a similar hydrocarbon to hydrogen iluoride ratio, the same temperature and residence time, the alkylate produced by reacting isobutane with the non-isomerizedY light hydrocarbon f-raction subjected to isomerization in the preceding experiment which contains 32 mole percent lbutene-l, 1.0 mole percent butene-2 andl 0.0 mole-percent isobutene yielded a debutanized aviation ygasoline stock having a rich rating performance number (plus 4.6 cc. of tetraethyl lead per gallon) of 142.

I claim as my invention:

1. A process, for producing an olen having an intermediate double bond in its carbon atom chain from a hydrocarbon fraction containing a mono-olefin of at leastV 4 carbon atoms per molecule and having a terminal double bond, which comprises subjecting the hydrocarbon fraction to a hydrotluorination reaction with an amount of hydrogen fluoride not in excess of that which will completely dissolve in said fraction, thereby forming alkyl lluoride in the hydrocarbon fraction, thereafter subjecting said fraction to dehydrolluorinationin contact with a dehydrotluorination catalyst to convert said alkyl fluoride CTX to an isomer, of s aidmono-olen having itsdoublel bond more*V centrally located-,in thev carbon atomchain, thereby liberating; freehydrogen, tluoridtfvY reaction with additional Hwnofolefn:` in4 thehydrocarbon fraction, andalternately subjecting said fraction to said hydroriluorination and dehydrotluorinationI reactions until, substantially all of said mono-olefin therein has been converted to said isomer.

2. The process of` claim 1 further characterized in that said hydrocarbonfractionis apredominantly C4 fraction and said mono-oleiinis butene-l.

3. The process ofclaim 1y further characterized in that said hydrotluorination andI dehydroiluorination reactions are eilected in the presencel of aY dilu-ent comprising4 an isoparafn which is.- subsequently alkylated vwith said isomer in the presence; of hydrogen iluoridey from said reactions.

4. The process of claim 3 furthercharacterized in that said, hydrocarbon fraction is4 a predominantly C4 fraction containing butene-l as. said mono-olefin, and said isoparaflin is isobutane which. is alkylated with butene-2 produced from the butene-l.,

5. The process of claim 1,1 further characterized in that an isoparafn isalkylatedwith said isomer in the presence of hydrogen fluoride catalyst, including the hydrogen tluoride frornthefhydrolluorination-dehydrotluorination operation, separating from the resultant products an unconverted isoparafln-A fraction saturated with hydrogen lluoride and supplying a sutlicient amount of the last-named fraction to said operation to furnish the hydrogen iluoride required therein.

6. A process for the alkylation of an isoparatln which comprises passing a stream of liquid isoparatllnic hydrocarbon through a body of hydrogen tluoride-containing liquid to dissolve hydrogen iluoride in the isoparatlin liquid, separating thev HF-isoparatlin solution from said body and adding thereto-aimono-olen of at least 4 carbon atoms per molecule and, having a terminal double bond, subjecting the mixture thus formed to alternatinghydrollnorination and dehydrotluorination reactions until substantially all of said mono-olen is converted to an isomer havingv its double bond more centrally located in the carbon atom chain, supplying the resultant mixture of said isomer, isoparatin and hydrogen luoride to an alkylating zone, introducing to said zonesutliciernt additionalhydrogen fluoride tol provide therein` a catalytic amount of hydrogen tluoride, and reacting: said isomer with the isoparallin in the alkylating zone in the presence of the hydrogenv fluoride catalyst,

7. The process of. claim 6 further. characterized in that said isoparailin is isobutane and said mono-olefin is butene-l which is converted to butene-2 by the isomerization.

References Cited in the le of this patent UNITED STATES PATENTS 2,399,368 Matuszak Apr. 30, 1946 2,434,000 Matuszak Jan. 6, 1948 2,450,039 Frey Sept. 28, 1948 2,502,015 Matuszak Mar. 28, 1950 .2,579,669 Hillyer et al. Dec. 25, 1951 2,591,367 McAllister Apr. 1, 1952

Claims

6. A PROCESS FOR THE ALKYLATION OF AN ISOPARAFFIN WHICH COMPRISES PASSING A STREAM OF LIQUID ISOPARAFFIN HYDROCARBON THROUGH A BODY OF HYDROGEN FLUORIDE-CONTAINING LIQUID TO DISSOLVE HYDROGEN FLUORIDE IN THE ISOPARAFFIN LIQUID, SEPARATING THE HF-ISOPARAFFIN SOLUTION FROM SAID BODY AND ADDING THERETO A MONO-OLEFIN OF AT LEAST 4 CARBON ATOMS PER MOLECULE AND HAVING A TERMINAL DOUBLE BOND, SUBJECTING THE MIXTURE THUS FORMED TO ALTERNATING HYDROFLUORINATION AND DEHYDROFLUORINATION REACTIONS UNTIL SUBSTANTIALLY ALL OF SAID MONO-OLEFIN IS CONVERTED TO AN ISOMER HAVING ITS DOUBLE BOND MORE CENTRALLY LOCATED IN THE CARBON ATOM CHAIN, SUPPLYING THE RESULTANT MIXTURE OF SAID ISOMER, ISOPARAFFIN AND HYDROGEN FLUORIDE TO AN ALKYLATING ZONE, INTRODUCING TO SAID ZONE SUFFICIENT ADDITIONAL HYDROGEN FLUORIDE TO PROVIDE THEREIN A CATALYTIC AMOUNT OF HYDROGEN FLUORIDE, AND REACTING SAID ISOMER WITH THE ISOPARAFFIN IN THE ALKYLATING ZONE IN THE PRESENCE OF THE HYDROGEN FLUORIDE CATALYST.