[1]Pr-tented Dm 1S, 1.945 293919189 UNITED STATES PATENT OFFICE 2,391,189 ISOM=IZATION PROCESS Stephen F. Perry, Roselle, N. 1. aaixnor to Standard Oil Development Conivany, a eorpomtlon of Delaware No Dmwbu. APPUesUou September 19, 1942, serw No. 458.94Z 7 Claims. (Cl. 260--683.3) The 1)resent invention is concemed with the isomerizati on of straight chain or normal puefins containing at least four carbon atoms per molecule to produce the corresponding iso or branched chain Paratlns by means of catalysts 5 such as those of the Ftledel-Cmfte tYI)e, either in liquid or vapor phase and In the prewnee of pro. MOtiOnal amounts of halogen-containing promoters surh as. for example, hydrogen chloride, hydrogen bromide, chlorine, bromine, carbon tetra. 10 chloride, chloroform, the lower olkyl halides such as inethyl, ethyl, propyl and butyl chlorides and bromides. Aluminum chloride Is the most com. monly employed catalyst, although the- bromide may also be employed. 15 The isomerization proress as above described has been carried out both In liquid and in vapor phase and. alumInUm chloride. either in granular , or flnely divided.forin or on porous carriers, has been the chief catalyst used The carriers may 20 be RnY number Of different i;;m such as activated clays, bauxite. Porocel, %Iumln& gel, &Ctivated car. bon, activated alumina, silica gel and the like. The Present invention Is directed to an improvement in such isomerization processe3. More par_ 25 ticularly, the invention relates to a continuoua vapor Phase isomerimtion process in which butane or Pentane is pamd in vapor phaw at elevated temperatur es and pressures through a bed of alumirxum chloride sorbed in a partially dehy- 30 drated bauxite such as Porocel, the reaction being carried out In the Presence of small amounts of hydrogen chloride. Such a proce83 works very ,well and gives good yields of tsobutane or isopentrne, as the caw nitght be, where the feedstocks 35 are relatively Pure hydrocarbons Dredominating in straight chain constituents to be isonlerized, but often'Umes. P&rUcularlY in refting opmtionts, substRntiall Y Pure PMUMWC feed stocks m not to be found. &nd heretofore it has been found 40 diffteult to utilize all types of paraginic feed stocks because,of the @ prennee of numerous impurities, among which may be mentioned the riVur-c@mtaining impurities. A number of the cmdes which are reftwd contain smaii amounta of elementsl 4,5 sulfur, nierciLPta=. hydrogen sumde, carbon disulfide and various other orgwe sulfur-cmtsinitig@ COMPOUnds. Conventional treating operations m&Y be employed and are dedrilbly emPloYed to remove from reftery c# or C# cuts sub. so stantial smounts Of thew sulfur tn* bnptatties, but such tregLtnmnt4; do not completely reraove these lmpudlues and hence ei tn ibe but umtIng OwafAms 80-me veM small &=unto of one or more Of BY&OM =Mde. elementa &uMw, Mbon disWAde, mercaptms and the like do remain in the feed stocks which otherwiw would be suitable for direct processing in an isomerlzation unit. It has been discovered, however, that In the absence ofexpedients such as those embodied In the present invenuon when these feed stocks which have been previously treated to remove the bulk -of the sulfur impurities, but which do contain very small amounts of sulfur impurities after the treating operation,- are employed in the continuous vapor phm commercial isomerization units of the tym beretoforle described that dimculties &rise in the raaintenance of this operation In reftnery, practice. one method of running these large continuous isomerization units using liquid phase operatim bas been foiind to be undesirable because of numerous plant shutdowns due to the formauon of solid deposits in the various lines, valves, plates, etc, of the system. The fouflng and plugging of i@ese lines frequently Tiecessitates the complete shutdown of the system and laborious and expensive cleaning of the various plugged and fouled product lines. It has heretofore been thougbt that the fouling of the product recovery mtem was due to the precipitatton and depoaits of aluminum chloride, but In the recently improved, vapor phase operation the loss of aluminum chloride from the reaction catalpt maw ordbulri)y does not exceed 0.003 weight per cent of aluminum chloride which is well below the determined chloride in liquetled lso'or normal butane in the temperiture range employed. But in spite of this, when running with a feed stock containing -smad amounts of swur type Impurities. fouling and plugginx of the lines eventually occurs. After carem lnvaugation it was diwovered thet the demdted material was not aluminum chlorld6 but was in fact a complex of aluminum eblotide with hydrogen swilde. This material has an extremft low ijolubmty in Uquid normal or tso butane and Is formed by the contacting of vei7 sm&n amoimts ot bydrogeom sumde with aluminum chloride. Thb formation, was observed even In feed atodm which contained as Uttle as 96 gralns of hydrogerl sulfide per thousazid cubic feed of paramnic feed stock going to the isomerizatiori unit, by ream of the fact that the hydrogen sulnde buht up in the aydem because It was carried overhead with the bydrogen emoride promoter which wa& reepled to the tsmafttlon unit after being removed from the product effluent and t4MdedL to InM@aft Md L aggMV&te Ulb fo=atio]ft of A)Cb.%e emplax. It In an objed of the prmut invmtim to pre-
[2]2 vent Uw bum-up of kwdrom mmde in the loomerintion sydem. It Is a ftuther objwt of the ln"ntim to prolong the toorlierimtion catayst Hfe by minmizfn the pdisoning and removal cof aluminum enoride from the tsomerization catalyst man due to Its re&Won with sulfur impurities. It is a further object of the invention. to remove trom the system hydrogen sulfide at convenient'selected locations therein so as to prevent t)lugaing and fauunor of valves. pium, plates and the like at-lnwcesdble places In the avswm but to for7n complexes at these desirable locations go thilt they may be removed readfly as soud complexes. without the attendant removal of large amounts of NCI. Other objects wM be appamnt upon a fuller understanding of the Inventionhereinafter more completdy described. ]Weft, these objects are accomplished by the inwruon Into the recycle system of an Isomerimtion unit of a chamber charged with aluminum chloride or with met&Uic copper In a swtable coinminuted state. 7%e overhead from the stripping of the react6d mixture. which is coniposed @,hiefly, of hydrogen chloride but contains ap3reciable wnounts of hydrogen sulfide, is first Pmwd through this chamber wherein the hylrogen sulfi(i@ is reacted with the substances con!atned therein so that either a hydrogen chlolde substenti&Uy completely free of hydrogen mlflde or a hydrogen chloride containing a reluced amount of hydrogen sufflde Is recycled from the atzipping opemtion to the tsomerintion catalyst zone durhw the lwmekization reaction. rt is not necesury to employ solely aluminiim chloride or metame copper.. Any substance known to wlectively react with hydrogen suillde to form an Insoluble reaction product therewith iinder these conditions may be likewise employed. ;Iowever, thew two substances have been found :;o be quite satisfactory in accomplishing the dedred objects of theInvention. By so locatft thi unit for the removal of hydrogen sulftde the net reswt is to get the hydrogen s=de oved froin t,he vewm at a readily acceadble spot in prefermee to the formation of gLn insoluble complex or xmde in lnweesdble spots In the system such as in a product cooler, in a strippw twer, or in ftes or VAIVUL comectft Such pieces @ of equipment. Omer&Uy It is desimble to maintain a Am body or bed of alitminii ebloride or coppe. Wrnings, bvM3, pelletts, grindim, powder or the like through which the stripper gases pow, and if aluminum chloride is uwd It in likewiw dedmble to maintean the hydrogen sumde removal meam it &.somewhat lower temperature tbon my existmg in the product condenwr or Unes since it ban ban fouxia that the hydrogen sumde Is more 6amplet4ft removed by means of aluminum chloride complex formation therewith at lower tempemturol rn ploce of using fredh aluminum chloride for ',he re3hoval of hydrogen sulfide, amt or perdany Omt iaomerintion ciLtalYst mama of aluminunt chloride NWbed in poraml tyM Mrkr nW be emplaed in the removal of hydrogen SW Me fr-om the awpped gas etther with or without the additkm of fresh quantities of aliu@wn oblaide to am omt immerftuon catalyd Man. N trutw the chlodde rwyck strom to mnoy the hydrogen =Mde therefrom, x= anOU34r &dvmtmge wtrues in the mriLU eMoma of the prof-an by rwam of the fact that the Wrogen nifide pu-tw pmwure In the reCycle skmm b far gromw than Its partw presor otber d-il pimm= ut an dfluenta to ft bydrmn wmde and hydrogen chloride. 7be hydrogen xulllde - Is therefore more completely and conveniently removed from the system than could be accomplished by treatirig the food or - product stream. In the operation of the bydrogen sumde removal xtep It is only neceNUU7 to maintain conditiora such as to take out enough hydrogen sul:dde to maintain a substantially con20 -.stant yet exceedingly low putw prewure Of bl@drogen sulfide In that allmm and to correlate the hydrogen sulftde removsl conditions with the conditions malntained In the product Unes wid equipment so as to prevent hydrogen sumde com16 plex formation with aluminum cbloride In the product lines and to maxbnize the complex formation or reactant formation such as copper gulflde In the hydrogen B=de removal BteP. Several of the heretofore mentionedexpedients 26 tend to accomplish this over&U result. in order to more fully understand the precise nature of the Invention it might be pointed out that complexes of the hydrogen sul'ftde with aluminiim chloricle are known to exist in CrYstalline 26 forni and apparently they are simil In nature tO thecrystalune hydrates and have compositions ranging from AlWU.OlH2S UP to as high 83 Al2ck2H2S. UsusHy the proporuon of hydrogen suinde contained is greater at lower temperatures, 30 and at higher partial pressures of hydrogen mimde and this tends to give a PreferentW formatiorl of AIC]3.MS complex in the recycle stre&m cOming from the stripping tower bilek to the lsomerizgtion unit. particularly where the lower tem36 perature. is maintained in this removal drum. onoe,the complex Is formed In the hydrogen sW:ade removal step the AIC13 Is no longer useful (=til after regeneration) and it i$ neeeSgRry for free aluminum chloride to combine with further 40 quantities of hydrogen sumde in order to further remove the hydrogen sulfide from the recycle stream. if a parucular batch of aluminum chloride becomes fully chemically mwW so that substantially all of it is in the form of hydrogen 45 sulfide complex the maw may be regenersted simply by releasing the pmmm, raLibW the tempemture i;lighw, but at anY event not higher th- 200* P., and purging the bYdrogensuMde from the syswm' in a continuow opemtion the 50 hydrogen @oulfid@ absorber would be B.V-PMW momentarily wblle thb puminff of the aluminum cbloride mass was being carried out. The invention is not limited to the use of &nY particular or specifte tYPe of feed stock except 55 that the feed stock abould predominatl- In nOrmal paramng; of at least four carbon atoms, per molecule, and preterably less thgln nine carbon atoms per inoiecuie for best results. Thus, for example. nomal butane, normal pentane, nor60 mal heptane, normal hexane, or mixtures of two or more of these, :deld butlu% eadwhead gasoline, strwght run napbtbw and the Mm. are aU xultabie feed stocks - for uw in connection with the @ prewnt InVention. AS PMVJOUWY Poinw 65 out, hqwever, thew fftd stocks In orftr to fW]Y take advantage of the invenum Wm contain so-e small amounts of Impurities, ipMnciPallY sulfur-containing.impurities, even though Lthey have bm pmviously subjected to a swur and 70 sulfur compound removal pretreatment. 7be total sulfur content, either as sulfur or in organic combination, should of courw be in minimum but the pwm boa been sweendully opemted with concentrations of tot4mJ xulfur of about . 100 graft my o In the prodwt edbmt stream wbm buttim 75 per Uwusend ouble fed of gamma feed at*&,
[3]Vftch may be considered typical of feed stocks 'which are nomallv'available for isomerization. It is probilble that considerably htgher concentmtions could also be handled successfully. The hydrogen chloride or other suitable hydro- 5 gen halide promoter is employed in amounts ranging between about 1% and about 22%, preferably between about 5% and 9:bout 10%, all percentages being by weight based on the feed, and the aluminum chloride Is present in the reaction 10 zone, particularly for vapor phase isomerization reactions, impregnated or sorbed on a carrier, the aluminum chloride constituting between about 6 and about 18 weight per cent of the ca.rrier. preferably between about 8 and about 12 weight per 15 eent of the carrier. This carrier should contain ouly tenaciously absorbed aluminum chloride and the carrier should preferably have been dried pmviously at a temperature considerably higher than the highest temperature to be encountered 20 iii the isomerization reaction so that it is substantially dehydr'ated and no further quantities of free water wiU be given off during the isonierization rea@tion. The lmvregnation of the carrier with the aluminum chloride may be in 25 liquid phase as by the use of a solvent. or aluminum ebloride vapors may be passed Into the carrier masr, under temperatures around that to be employed in the isomerization reaction, and then the mass may be purged by heating 'uhe sa-@ne 30 up to from 100 to 200, P. higher tban that to be encountered in the reaction zoxie while passing through an Inert gas to remove any loosely held aluminum chloride particles or Vapors. hour. Exatnple A specifle example of an opemtion embodying this invention Is as follows - 70 A cylindrical vertIL'caI reaction chamber of approidmately 3 inehes In diarneter was substanti&IIY flued with a catalyst composition made up as follows: Meven pounds of Porocel which had been heated to about 1000* P. for about 5 hours In 75 'P. and 325' P. The pressures are usually adJusted so that they range betiween 100 and 450 pounds per'square Inch. For butane isomeriza- 45 tion, these Pressures are preferably between 150 and 300 pounds per square inch. The temperature maintained in the hydrogen sulfide removal unit when using aluminurn cholride Is usually between O' IF. and 750 P. lower than the lowest temperature maintained In the isomerization unit 50 and Product effluent stream before stripping Where metallic copper is used as the removal agent for hydrogen sulfide in the hydrogen halide recycle stream, room temperature or slightly higher Is satisfactory, although temperatures (f 55 40-50' P. were employed for the hydrogen sulflde removal In a specific run wherein the metallic copper was maintained 'Under a Pressure of about 250 pounds per square Inch with the stripper gas Containing about 75% hydrogen 60 chloride. The throughput of norinal paraffinic feed stock throukh the isomerization unit mav vary co.nsiderably, but for butane isomerization it ranges -between about 0.5. and ab6ut 2 liquid order to substantially dehydrate it and free it from any readily separable water was charged on top of about 1.5 lbs. of granular aluminum chloride in this reaction chamber. The mass was then heated to about 300' P. and a stream of butane was passed,upwardly tlierethrough at atmospheric press@re for about 24 hours. The reaction chamber was then closed to the atinosphere and a feed stock containing about 6.6 volume per cent isobutane, about 93.1 volume per cent normal butane and about 0.3 volume per cent of Cs and heavier parai%ns, and which also contained, by. analysis, 96 grains of sulfur and sulfur-containing impurities per thousand cubic feet of gas, was admixed with dry hydrogen chloride in an amount of about 6 weight per cent of hydrogen chloride based on the feed mixture and this mixture was then pas@ed upwardly through the cataly@t mass under a,pressure of about 200 lbs./sq. In. and at a temperature of between a.bout 250- ]F. and about 300- P. at a throughput of about 1 liquid volume of butane feed Per volume of catalyst per hour. The effluent was withdrawn from the upper portion of the reaction chamber and was then passed to a stripping tower having a bottom ternperature of between about 200' P. and about 215' P. and a top temperature of between about 400 P. and about 50@ F., t@.ie eyitire tower being maintained up-der a preFs-,li7e. about 250 in. At the top of this tower a, refri-gerated condenser was inserted and the hydrogen chloride which passed Gverhead contacted the walls of this condenser. The surfaces of the condenser so exposed to the overhead gases had been volumes of feed stock per volume of catalyst per 6-5 finery operations. These organic sulfur comremained, the hydrogen sulfide concentration was kept sumetently low so that precipitation of AIC13--H2S complexes in the isomerization unit proper was avoided. The process as above described was cartied out continuousiy over a Period of 650 hours and during the opemtion the yield of lsabutane ranged between abgut 30% and' 50% based on the normal butane charged, with an average yield of over 40 %, with about 95 % of the normal butane that reacted being isomerized to lsobutane. In the specification and annexed claims where mention Is made of sulfur type impurities or some similar expression is used, it is intended that Ms expression be broa,d;,enough:@t6.cover.;not oaly,:th6 presence Of elemental. sulfur and hydtog@n. gulild6 but also the Presence of othei,naturauy oceiirrihg organic sulfur compounds such as mercaptans, disulfldes, thioethers and the like, either as present In feeds from natural sources or present ds prepared synthetically during the various treatmg . operations and from which suitable feed stocks for isomerizatidn units originate in reThe temperature under which the isdmeriza- 35 sprayed with metallic copper, and hydrogen sultion reattion Is carrled out In the vapor phase is flde which came overhead with the hydrogen more or less well kriown. However, In general, it chloride was found to react with the metallic ranges between about 200- P. and 375- F. or as copper surface to such an extent as to be e,,isenhigh as 400' P. depending on the particular feed tially completely removed from the recycle gas. stock employed. in the case of normal butane, 40 as copper sulfide. In fact. as long as any apprethe preferred temperature range Is between 2501 ciable amounts of unreacted surface of copper Pounds tend to be broken up by the isomerization catalyst, forming hydrogen sulfide. Having thus fully described and illustrated the character of the invention, what is desired to be secured by
