[1]Patented Oct. 4, 1949 2 1 4 8 3 , 4 8 7 UNITED STATES PATENT OF@FICE 2,483,487 SEPAP.AT]ION OF VOLATILIZABLE METAL HALIDES FROM ADSORBENTS Samuel C. Carney, Bartlesville, Okla., assignor to Phillips Petroleum. Company, a corporation of Delaware Application Se]@tember 27, 1946, Serial No. 699,664 12 Claims. (Cl. 23-96) 2 This invention relates to the separation of metal halides of the Friedel-Crafts type from solid adsorbents. In a particuiar embodiment, the invention relates to the desorption of such metal halides which have been adsorbed, on the 5 surface of solid inorganic adsorbents. The invention especially rel ates to the use of anhydrous hydroge n halides to aid in the recovery of metal halides. The invention in some aspects relates to the conversion of hydrocarbons in the presence 10 of a metal halide catalyst of the Friedel-Crafts type. Inone specific embodiment the invention relates to the isomerization of saturated hydrocarbons in the vapor phase wherein a fugitive metal halide catalyst is utiiized in the presence 15 of a hydrogen halide and a solid adsorbent material. A particular modification of the invention involves utilization of a solid adsorbent material both as a catalyst support and as a means ' of avoiding passage of catalyst vapors from the re- 20 action system by adsorption of catalyst vapors on the solid adsorbent, wherein periodic desorption of catalyst is accomplished through control of the hydroge?.i halide content of the vapors, This application is a continuation-in-part of 25 my copending application Serial No. 512,797, filed December 3, 1943, nov7 Patent No. 2,429,21@. The use of Friedel-Crafts type metal halides, such as aluminum ' iron, antimony, tin, zirconium and other polyvalent metal halides, as catalyst 30 in various hydrocarbon conversions has become well established. Among the conversions of the greatest interest at the present time may be mentioned the alky' ation of aromatic, cycloaliphatic and a]idhatic hydrocarbons by olefin@, alkyl hal- 35 ides and other alkylating reactants. Anoiher commer cially important process is the isomerization of saturated hydrocarbons. In such con-versions the aluminum halides, especially the c hloride and bromide, are most frequently applied as 40 catalysts due primarily to their low cost and siaitable activity. The present invention is particiilarly applicable in the isomerization of paraffliiie hydr,oca rbons as exer@,lplified by the conversion of normal biitane tb isobutahe aiid tvill be' described 45 with specific reference thereto. Method@ of applying the principles of the invention to other conversi ons will be apparent to those skilled in the art from the detailed disclosure offered herein. 50 Isobutan e is a valuable hydrocarbon which may for example be alkylated to produce normally liquid branched-chain paraffins, or which. md@r be dehydrogenated and the resulting oleftn@ polymerized and h drogenated, in oither case the r)5- y resulting products being important components of aviation gasolines. Aluminum chloride, activated with minor amounts of hydrogen chloride, has been used commercially for some tirne in the isomerization of normal butane to produce isobutane. The aluminum chloride has been used in lump or slurry form, and hgs also been supported on various solid inorganic materials, including non-porous supports such as porcelain, and porous supports such as activated charcoal, pumice, fuller's earth, adsorptive alumina, etc. Certain of these supports, in addition to providing a large surface area, seem to increase the catalytic effectiveness of the aluminum chloride, whileothers are substantially inert. Regardless of the type of catalyst used, considerable trouble has been encountered-in actual practice due to the volatility or solubility of aluminum chloride in gas,,ous or liquid reaction 1-.iixtures, which causes isomerization effluents to carry substantial quantities of catalyst out of the reaction zone and into the subsequent portions of the equipment. In an attempt to avoid this it has been proposed to contact isomerization effluents wi th and adsorptive alumina whereby aliiminuin chloride is retained by the alumin6. It has also been prop6sed -to operate such a bed of adsorptiv@e alumina at a relatively low temperature, and @,ifte-r it has become saturated with aluminum:chloride to raise the temperature and reverse the flow of gases through the system in order to revaporize and return some of the thus adsorbed aluminum chloride to the system. Howev I er, these proposed processes have not been entirely satisfactory. inasmuch as it is difficult to recover aluminiim chloride from the adsorbent to such an extent that the adsorbent may be reused 6fflcl 6iitly fo@ the same purpos6. Purtherrnore, la@ge alteiations in temperature are ineonvenient and ex-pensive. There are other instances in which alumin-uiii chloride and other rnetal halides are found in. ad.,nixture with sblid adsorbents. For pxample,, in man3i organic rea@ctions, partidula-@;ly those known a8 the Priedbl-Crafts reaction and modifications thereof the alumiiium chloride is used in the form of a liquid, complex, oir liquid complexes are formed during the reaction. Th6se cbrhplexes Are -composed of aluminum chloride and organic material and it is important to the economy of a process that as mtich aluminum@ chloride be recovered therefrom as possiblo. Such recovery ma3@ be accomplished by d6@true.tive distillation,. with bt- withqut: the..pjresence of, gases, which may inclu anhydrous 'hydrogeli
[2]eworide. Vap6rs withdrawn frotn the alum'mum chloride recovery step and carryin.- aluir-irum chloride may be passed in contact with a solid adsorbent either to recover the total aluminum chloride content from the vapors, or to recover residual aluminum chloride from the vapors after the bWk of the aliiminum chlcride has been separated therefrom by condensation or otlaerwise. The subsequent recovery of aluminurn chloride from the AIC13-enriched adsorbent presents problems, in that incomplete recovery is usually realized. Furtherinore, substantial. amounts of the alurninum chloride may be lost completely by formation of a-luminu im oxychloride or other oxygen-containing aluminum compounds, usuauy due to the acti-On of small amounts of water found in the adsorbent. In the commer.-ial manufacture of a-lu.-Lninuni chloride, which is iisually accomplisbed by direct chlorination of aluminum oxide-containing ores, either in the presence or absence of carbon, tail gases containing residual aluminum chloride may be contacted with an adsorbent for recovery of the aluminum chloride before discarding the gases or reusing same in the process. Separation of the thus-adsorbed aluminur-ri chloride from the adsorbent presents problems similar to those discussed above. It is an object of this invention to separate mixtures of metal hahdes with solid adsorbents into their components. Another object is to, increase the recovery of aluminum chloride which is being desorbed from a solid adsorbent. Yet another ol3-ject is to recover a solid inorganic adsorbent material from adrnixture with a metal halide, in a substantially metal halidef-ree condition. It is an important object of this invention to affect the vapor phase isomerization of normal butane with an alurainum chloride-hydrogen chloride cataly4t wherein the carrying out of catalyst in vaporous effluents from the reaction zone is avoided. It is a further object to eff ect the regeneration Of solid adsorbent material used to adsorb a fugitive catalyst. Another object is to effect the isomerization of saturated hydrocarbons in the presence of a supported metal halide catalyst of the Friedel-Crafts type. A still- further object is to eff ect a reactivation of such a catalyst in situ. Yet another object is to provide a continuous cyclic process for the catalytic isomerization of hydrocarbons. Further objects and advantages of the invention will be apparent, to one skilled in the art, from the accompanying disclosure and discussion. Broadly speaking, my invention involves the pa.ssage of a gas comprising an anhydrous hydrogen halide through a body of solid adsorbent which is admixed with a volatilizable metal halide under conditions which effect the carrying away of metal halide from the adsorbent in the hydrogen halide-containing gas. Preferably the hydrogen halide is used in adniixture with another gas which is substantially non-reactive with the metal halide under the conditions of the process. From the present specification it will be clear that by "gas which is substantially non-reactive with the metal halide under the conditions" I mean a gas and conditions which permit pro2,4s3,481 4 out quickly destroying the latter chemically, although the term obviously does not intend to exclude a slight amount of reaction of gas with metal halide such as for example the slow formation of hydrocarbon AIC13 complex or sludge which is known to occur when normal butane is used as the gas: as described he.rein; the term also obviously does not exclude isomerization or other reactions of the gas itself alone or with 10 materials other than the metal halide, a's such reactions- can occur in the presence of the metal halide concomitantly with the desorption of metal halide. The desorption procedure is desirably initiated with a gas containing only a minor pro15 portion of the hydrogen- halide. The otber component of the gas mixture may be a non-polar gas suell as a low-boiling saturated hydrocarbon, for example methane, propane, or butane, or it may be hydrogen, nitrogen, or other inert gas. 20 As the desorption proceeds, the hydrogen halide content of the gas may be increased, so that as the last quantities of metal halide are being removed the gas will ordinarily contain a major proportion of hydroaen halide and may even be 25 substantially pure @;drogen halide. For best results the halogen of the hydrogen halide shouid correspond to the halogen of the metal halide. By employing an increased- hydrogen halide content, the metal halide recovery is iricreased ove-r -,A that obtainable in the absence of the increased hydrogen halide content. Two possible reasons may be ascribed to this prenomenon, although the invention does not depend upon the accuracy of any particular theory. It is thbught that the 35 hydrogen halide, being more polar than the metal halidej is adsorbed preferentially over the metal halide' It is also believed that the inereased partial pressure of hydrogen halide serves to decompose, or at least minimize formation of, oxy4 fJ genated compounds of the metal halide. In one preferred embodiment, briefly described, the invention comprises passing a vaporized normal butane feed containing hydrogeia chloride in catalyst-actiyating amount through a first 45 zone containing a solid adsorbent niaterial having aluminum chloride adsorbed thereon under conditions such that some aluminum chloride is desorbed therefrom and incoi-pbrated in the vapor stream ' then passing the resulting vapors through 50 a reaction zone containing an aluminum chloride isomerization catalyst which may or may not be supported as desired, and which is maintained under isomerization conditions of temperature and pressure, then passing effluents from said re55 action zone through a second zone containing a solid adsorbent material under conditions effecting substantially complete adsorption of aluminum chloride vapors, and recovering isobutane from the essentially aluminum chloride-free ef60 fluents. After a period of time the efficiency of the desorption of aluminilm chloride from the first zone tencls to decrease, whereupon the proPortion of hydrogen ebloride in the vapors passing through said zone is increased. It has been 65 found that such an increase in hydrogen chloride concentration encourages the desorption of aluminum chloride, and Preferably the hydrogen chloi-,id-@ content is increased gradually until a vapor stream is passing through the first zone 70 which- is as rich in hydrogeri- chloride as is obtplinable in the system. By this.means a rnuch mor.e complete desorption of aluminum chloride is realized than. would otherwise be the case, and the adsorbent in the first zone is thus conditioned longed cbntact of gas with the rnetal halide with- 75' rnore e:ffectiv-ely fbr a subsequent use in treating
[3]9,48gi487@ efhuents. While this increase in hydrogen chloride content of the vapors in the first zone is being effected it is preferred to supply substantially constant amounts of hydrocarbon to the balance of the isomerization system, and this is readily done by diverting flow of normal butane vapors from the first zone to the inlet of the aforementioned reaction zone. Usually it is not necessary to increase the total amount of hydrogen chloride being supplied to the first zone. The various zones are so proportioned and the conditions are so maintained that the operation just described can be completed prior to a time at 'which the adsorbent in the second adsorb@ent-. containing zone becomes saturated with aluniinum cmoride, and in this manner the effluents from the process axe always maintained substantially free from aluminum chloride. The next step in the cyclic process, is a reversal in the, direction of flow of vapors thrrpugh the systern, so that aluminum chloride is now desorbed from the second zone containing adsorbent, vapors then pass through the reaction zone, and aluminum chloride is then adsor'oed from the vapors by the adsorbent in the first zone ,vhich has been conditioned for this function in the manner just described. Ordinarily when this reversal of fiow is effected the hydrogen ch'-@oride cop-tent of the vapors passing tothe inlet of the system, in this case the second adsorbent zozie, iS reduced to i-ts normal value, and the system @,nay be operated for an appreciable length of time before it is necessary to increase the hydrogen emoride content for the purpose of effecting a more complete de.@orption of aluminurn chloride in the second zone in a raanner similar to that described above with reference to the first zone. After such a desorption is accomplished the flow is again reverged and the complete cycle repeated. In effect, the first and second adsorbent zones are merely reversed in position with respect to the flow of vapors through the system, each zone going through a cycle comprising adsorption of aluminum c-hloride- vapors from aluminum chloride effluents and desorption of aluminum chloride into a stream of incoming vapors. It is generally preferred that the beds of adsorbeiit be relatively elonaated and -v-hat the direction of flow of gas therethrough be reversed periodically. When such an arrangement is utilized @t will be seen that the adsorbent bed first used in th- outlet portion will adsorb aiuminum chloride first at the end at which vapors are introduced and that the aluminum chloride content of the bed will -,radua@ily inclease in the direction of flow of vapors so that the vapors always contael. last the portion of the bed containing a minimum amount of aluminurq chloride. It has been found that many adsorbents provide an active isomerizatioii catalyst when carrying only a few per cent Of aluminum chloride by weight, such as froni 2 to 5 per cent and higher, and the bed in question accordingly acquires and maintains catalytic activity sufficient to efj':ect a slibstantial amoi!iit oiv ec,nversion, thi:ts serving a dual purpose. In fact, it is not necessary that a reaction zone pi,oper, as hereinbefore described, be used and the invention may be practiced in a syste@-n cornprising only two beds or one single elongated bed of adsorbent material with th@-@ isomerization reaction being effected in theintermediate portions of the bed or beds. I Numerous adsorbent solids may be utilized in the practice of my invenfion as wiU be readily appreciated by one @,killed in the art. However, it is understood that one adsorbent Will noi necegsarily give results which are exactly equival,,nt to those obtainable from any other adsorbent, and the choice for any particular situation will be made with regard to such factors as availability and price of adsorbent, catalytic activity of alurn,.nijm chloride when supported on a given adsorbent, effectiveness of the adsorbent in adsorbing and desorbing aluminum chloride vapors, etc. 10 Merely by way of example may be mentioned activated charcoal, aptivated alumina, fuller's earth, natural and artificial zeolites, silica gel, vatioiis natural and synthetically prepared c -1 materials, bauxite, particularly a specially prepared 15 low iron-content bauxite sold under the nay.-ie of "Porocel," etc. Tb-ese materials may first be calcined to any desired extent prior to use' It 4s not required that the same adsorbent be utilized in all parts of the same system, but a smoother op20 eration is generally obtainable if this is done. The adsorbents may be iised in such size as will provide opti-rxam contact with gases without unduly impediiig the flow of gases through the bed; generally from 2 to 16 mesh will be found satis25 factory. It 'Ls also sometimes advantageous to employ the adsorbent in finely divided or Powdered form, which may be suspended in the vapors from wh-ich - metal 1-ialide is being recovered or which are being used to desorb me al halide 30 from the powdered adsorbent. Wbile the temperatures of the adsorbent beds of this invention may be varied while the process is being carried out in order to encourage adsorption of alumiiium chloride on the one hand 35 by lower temperatures and desorption of aluminum chloride on the other by higher temperatures, it will 'oe found that such fluctuatio!ls in temperature need not be resorted to and the dis-. advantages of operating in such a manner fre40 quently outweigh advantages to be gained. It is, in fact, an important advantage of the present invention that such temperature changes are not required due to the novel method of desorbing aluminum chloride by use of increased hydrogen 45 6hloride concentrations as described. Accordingly, the ordinary and Preferred manner of operation used in carrying out my invention involves the maintenance of all portions of the isomerization zone, or zones, including both the 50 inlet and outlet beds of adsorbent, at temperatures and pressures withiii the range of isomerization reaction conditions. For example, in the isomerization of normal butane temperatures of from about 175 to about 4001 P. are suitable, Nvhile 55 iii isomerizing higher boiling saturated h@Tdrocai@bons, such as normal pentane, methyleyeloPentane, etc., lower temperatures are generally preferked in order to minimize cracking and other undesired side reactions. Pressures may range 60 from atmospheric or less on up to several hundred pounds per square inch ai-id are lim@@'ted to a certain extent by the volatility of the hydrocarbon or hydrocarbons being isomerized and by the Phase conditions desired within the system. 65 The normal concentration of hydrogen chloride in the gaseous reaction mixture will generally vary from about one to about ten mol per cent. During the latter stages of desorption the hydrogen chloride content of the vapors in the bed of 7o adsorbent being subjected to such desorption may range uli to as high as 75 or 80 mol per cent and even as high as 100, per cent if hydrogen chloride of such purity is readily available in the system. Usually the recycle stream of hydrogen chloride 75 will not be absolutely pure, containing some light
[4]7 gases@ s Lich as hydrogen, methane, ethane and-./or propane, but the required desorption is readily effected by such a recycle streani, and any iiicreased concer-tration of HC1 over that no--Inally used for the isomeriz,@ttion may be utilized to advaiitage. Preferably the hydrogen ebloride concentration in the priiicipal regions of isome-i-ization is maintained at or near the normal level even while desorptio-.i is being effected in another part of the system. "he ilive-,--t'tio-@i -.mey be more fully understood byreferencp- to the a,--co-.mpanying drawing which is a diagrammatic rer,,resentation of one preferred arrange-f,,ic,it of elementssuitable for carrying out the isomerization of no-emal butane in the vapor W,iase. it will be appreciated that the drawinq is schematic iTi nat,,@.re, aiid no attempt has been made to show or indicate various other pieces of equipme,@at v.,hich a.--e required in actual operation, such as pum,@,,,, heat exchangers, tempc-rature and pressure controlliig devices, and nunierous other itetns, si-,nee thec;e elem@,nts are readily stipplied by one skihled in the art o-@ice given the princip'-es lipon whicii the inve,-qtion is based. In the drawing, unit 4 represents a pririary reaction @-hariiber contai,.iing an alumi-@ium chloride catalyst' whiie uiiits 2 ard 6 represen4, chambers containing a suitable solid adsorbent -,apable of adsorling aluminum chloride from the vapo-cs in the systei-.i and desorbing the same upder the cond,.tions recited herei,n. The catalyst in cha,--ibey 4 may cornprise inerely It,.mps of soli-d a . iihydro,,is alum-inum chloride or it may comprise aluminum chloride on a solid adsorbent th@@ sq@rr@e as or dif-ferer@t from that used in chambers 2 and 6. In starti-ig @an the system norr@ial butare charging stock is vaporized by means iiot shown and passed through line I i_nto the top of chgmber 2. The vapors ar-@ passed dowiaward through ei.,a@n-iber 2, th,.,ough line 3 to the bottom of chamber 4, upivarcl theret.L-,rei-igh, thence via line 5 to th-- bottom of cl-,-amber 6, then out of the top of a=@ber P. ir-to 14-,ne 7. Frcm line 7 the isomerization reacta'on Paiyt,.ire effllients pass through 8 wherein they are subjected to partial or coin-,olell-e conciensatiori, @-,nd thence via line 9 into sur@6,e ta-iik I Pi. Hydrogen chloride is charged from cyliqder 21 tbrou,-h valve 22, together Nvith .i,ny available from recycle, passes through lirie 23 in whic'.-i r-iay be iii-ternosed a heater 34 if des,red, and i-s admixed with t'--ie hydro,-arbon feed in desired ainount by me-,tns of lines 26 and 1 7 and valve 30. Du--!.@n.@ the initial neriod of operation the adsorbent ir@ chomber 2 1,,eco--qes sattirated w-ith butar@e a,@id i@iydrog.,r4 chloride at coiiditions prevailing therein, i-Somerization of the r-ormal buta-ie to forra- isobut,@lne is effected in chamber 4, apd ei@qi-ie@nts the7.@efrom which include a small proportion c-f volatilized aluipinlim chloride are passed through chamber 8 wherein the alumi-,ium eMoride is adsorbed. As the catalyst is thus carried froi--Yi el-iamber 4 into t-tie bottoin of clianiber 6 the lower port.-ions of tie adsorbep-t in chaiiiber 6 soon becoi-qe sufficier@+lly im-,oregnoted with al-Liminum chlo@-ide to act as a sup?,aorted catalyst and farther coil-ve--Si-on is thus obta@hied. -As the :ffow contiiaues, alunii.,ium chloride gradually works its we@y ,@,p,,@,-ard in cliatnber 6 so that more and mo- e of the adsorbent therein becomes laden with t@lle catalyst, altbough the upper parts of t-he adsorben@u are still siifqcient',Iy lov-7 in aluminum chloride to effect slibstantially complete gdsorption so that a catalystfree effluent is obtained in line 7. 8 Prior t(y the. ti@-ne a-t- whtch catalyst- vapor wolild begirito escapefronithe@topof chaniber 6,.the entire vapor flow, including hydrogen chloride,. is nversed and- delivered through line l@7 and valve 31 in-Lo the. top of and@ down tluough chamber 6. The vaporous reaetion ml:xture then flows from the bottom of chamber 6 through Iiile@ 1!8, upward tlzough column 4, through line 19 into chamber Z, upward through ichamber 2, and out through 10 line 20 into line T. The direction of flow is th-,ts reversed through chamber 6 and chamber 2,, but is in the same direction through chamber 4. Tlie direction, of flow through chamber 4 in the arrangement-showii is not particularly critical wlien 15@ solid al-ominum chloride is used therein, but the direction of flow throu.-h chainbers 6 and 2 is importaiat. It will be seen that by reversing the flow throtigh these two chambers tl-ie al@uminuni chloride will be desorbed from chai,-iber 6 most 20 efficiently and will be adsorbed in chamber 2 in such a man@r-er ti-iat the last increments of adsorbent in chamber 2 which are contacted by the effluent vapors have the: '@owest content of aluirinum chlori@de, This reversal of flow begins t'.-ie 25, r,,@,eiieration oi chamber 6 as an adsorbent and @@L-he actival.-ion of chamber 2 as a catalyst. As the activ@ity of chamber & declines due to the rrogrr@ssive remc-%,,ai of aluminlim chloride tl-lerefr,-im- t'ri:e actlvi",y of chaniber 2 increases. The 30 catalys'@ in chamber 4 serves to effect a desired ailouilt of i@-,o-nerization thereiri and any a'@umi-ii-am chloride volatilized therefrom passes in'@o '6he lower part of charnber 2 and@ is there adsorbed. It is fouad that the amourt of catalyst which -@ 5 can be desorbed- from, the solid adsorbent in chainber 6 by the flow o.@' vapors having a normal hydro.@eii chloride content is limited. Accordingly, wheii t-qe rate of desorption in chamber 6 '-.egins to decrease to an undesired exten't, and 10 when char.,iber 2 iQ still olily partly charged with adsorbed alumi,@ium cl,,Ior;de a change in the vapor floiv is initiated. Valve 28 iii line 21 is part,y opened, valve 30 in line 26 is entire,y closed, valve 3 i: in line 17 learling into the top of 45 chari-,ber 6 is partly closed, and valve 3-2 iia ',ine 2@5 is r-artly ope-@ied-. By suitable control of the valves n@q@-ntiop-(-d, while observing the tempe,,atures in chamber 6,. the@ congentration of hyd,,,ogen chloride eiiteri_ng the top of cliaw-ber 6 is 50 ine-reased, preferably gradually. This inci:eased concentration serves to effee@'. a further desorpti-On of aluininum chloride from the solid aA sorbent. it is believed that the hydrogen ch:loride is. selectively adsorbed by the adsorbent 55 material, with t-be al:umiiium chloride being concornitantly disrlaced or desorbed. However, regaxdless of any theories that n-iay lye advanced to e,.,,-Plain the action of increased hydrogen chloride concentrnt--Ions, the adsorbent iT-i char,,i60 ber 6, is re.-enerated to@ such an, extent by tlie '017-4culce of this invention tliat when it i.9 again placed, iii use. for treating effluent va,3ors it r@lay be used. j'.or a considerably longer period of time than w.ould otherwise be possible before alumi65 nu@-n chloride is noted in the effluents. In regenerating chamber 6 as an adsorbent, the full concei-itration of hydrogen chloride in line 23 is@ finally used to, coriiplete the desorption. At 70 this time the entry of butane vapor through the top of chamber 6 is entirely shut off and the butane is passed into the base of chamber 4 through line 27 controlled by valve 28. By the proper manipulation of the valves the amount 75 of' butane and of hydrogen. chloride entering
