US2353098A - Catalytic isomerization process - Google Patents

Description

July 4, 1944 J. M.- wHrrELEY, JRQ, ET A1. 2,353,098v

` -I CATALYTIC ISOMERIZATION PROCESS l original Filed sept. 3o, 1939 Patented July 4, 1944 vCATALYTIC ISOMERIZATION PROCESS James M. Whiteley, Jr.,-Aruba, Curacao, NetherlandsA West Indies, and Charles S. Lynch, Plainiield, N. J., asslgnors to Standardil Development Company, a corporation of Delaware originel aspiration september so. 1939, serial No. 297,198. Divided and this 4, 1942, Serial No. 449,784

appllcationJuly Y 6 Claims. (Cl. 26o-683.5)

Thisv application is a-divlsion of application Serial N0. 297,198, Imed- Septemmer, 1939'.

'I'he process of the present invention relates t the isomerization, of hydrocarbons, and, more particularly, `to `the conversion of lnormal or straight-chain paraillnic hydrocarbons into isoor branched chain parainic, hydrocarbons by catalytic means. It is known that hydrocarbons, in particular the straight chain paraiiins, may be isomerlzed into branched vchain paraflins in the presence of various catalysts of the Friedel- Crafts type, such as aluminum'chloride, aluminum bromide, molybdenum trisulde, ferrlc chloride, zinc chloride, and the like, with or without the addition of promoters. The paraiiinic hydrocarbon products possess diilerent physical and chemical properties and are chie'ily branched chain in character. Heretofore various dliliculties have been encountered in attempting to place this operation upon a commercial scale. The Friedel-Crafts type catalysts are not easily controlled in their reaction. Furthermore, up to the present time a continuous liquid phase operation -has presented certain inherent diiculties due,

principally, to the problem of catalyst degradationv and formation of undesirable by-'products in major amounts. Furthermore, the ease of control of the operating conditions has not been perfected. As a result, -truly continuous processes have not been operated on a commercial scale.

The success of the present invention lies in the l fact that it has now been made possible to eilect an economical continuous isomerization process upon a commercial scale employing a liquid phase operation. Troubles incident to the mechanical agitation which has heretofore been thought nec- 'essary have been substantially completely eliminated and the operating variables are now easily and readily controlled. It has been found that, for example, a moving bed ltype of catalyst in which the ratio of catalyst to hydrocarbon feed is maintained large and wherein a spe'ciied thru- 'put is maintained under the operating conditions successfully accomplishes these advantages. lBy operating according to the process of the present invention, it has been found to be unnecessary to shut down the unit in order to effect a replacement of the spent catalyst.

It lsfan object ofthe present invention to effect an economical catalytic isomerization process, particularly with reference to the, lower parafdnic hydrocarbons, and to carry out such a process while maintaining the catalyst massin substantial excess to the quantity of hydrocarbon fed to the reaction. It is a further object of the invention to provide a moving isomerization catalyst and to continuously feed straight chain parailins containing at least four carbon atomsper molein parallel so as to make use of a large catalyst mass with a maximum eiliciency and with a maximum v production A,of branched chain parafnic hydrocarbons which are .known to be useful in various reiinery operations and in some casesas gasoline constituents perse. Still'another object of the invention is'to produce branched chain parailins from straight chain paraillns by isomerization while employing apparatus enabling operators to more accurately control the reaction conditions of the process. ,l

In order to accomplish these objects, as well as other objects which will be apparent from a full understanding ofthe invention` to be more fully hereinafter described, it has now been found that excellent yields of the desired isomerlc hydrocar` bons, in particular isolvor branched chain paraiilns of four or more carbon atoms per molecule, may -be obtained by employing a relatively large ratio of catalyst `to straight chain hydrocarbons fed to a reactor at any one time.

The isomerization may be eiected over a wide range of conditions of temperature, time of con` tact, catalyst form, concentration of promoter,

hydrocarbons with a lower n umber of carbon atoms. However, the presence of hydrogen formed in situ or added from extraneous/sources has a tendency to suppress suoni-decomposition reactions. In cases where normal butane is em- ,n ployed, a temperature range between about room temperatureand about 175 F. is advantageous.

Good Yields may be obtained within. these ranges using a contact time of from about 10 seconds to about 1'5 or 20=hours depending upon the temper'ature and the' form of catalyst employed. In

general, space velocities of fromV about 0.2 to

about 5.0 volumes` of straight chain paraflln per volume of catalyst per hour are employed.

Various promoters may be employed in the reaction, for example. hydrogen chloride, hy-l drogen bromide, and other hydrogen halides, lower alkyl halides, for example methyl chloride or bromide, ethyl chloride or bromide, butyl and amyl halides, and the like.

the reaction. The promoter is added in an amount equalto from about 0.5 to about .25%,

In some instances y. 1t 1s even advantageous to add free halogen to preferablybetwen aboutz' and about 10%,based not-completely lled with liquid phase compo:

nents but also contains a small gasphaseabove the liquid portion thereof. employing the partial pressure of the hydrogen chloride, the concentration of the hydrogen chloride in the liquid phase is more readily controlled.

At 200 F.v an increase in pressure of 50 lbs. will result in a hydrogen chloride concentration of 2% in the liquid phase. An increase in pressure of 100 lbs/sq. in. corresponds, roughly, to about 5% hydrogen chloride in the liquid phase and an increase in pressure of 150 lbs. corresponds to about 8% of -hydrogen chloride in the liquid phase. These data apply when employing normal butane as the reactant. Similar data on the solubility of hydrogen chloride in normal pentane at '15 F. show that the solubility is quite high and is proportional to the applied pressure o f hydrogen chloride. i

From the very nature ofthe lprocess herein described the catalyst concentration is necessarily quite high. A concentration between about 100% and about 100070 and higher is usually employed. Fresh catalyst is added to the bed continuously or intermittently, depending upon the rate atwhichthe catalyst becomes substantially completely degraded. The` spent or partially spent catalyst is removed in like manner l"from the bottom of the bed in. order to make room for the newly added catalyst.

The process is applicable to the treatment of normal `butane,gnorrnal pentane, normal hexane, normal heptane, normal octane, andthe corresponding higher homologues of the parafn series.. It is within the scope of the present invention to also employ mixtures of two or more of these paraillnic hydrocarbons. Likewise, the invention is applicable to the-treatment of the straight run naphthas of relatively low octane number which' are composed predominantly of normal paraflinic hydrocarbons. Such isomerizationtreatment as herein described materially increases the octane number of these naphthas.

lThe invention is likewlse applicable to the treatment of field butanes, parafiinic mixtures resulting from the removal of oleilnic constituents of renery C4 and Cs cuts, waste gases of parafnic nature evolved from thermal and/or catalytic alkylation and polymerization units, and similar paraflinic hydrocarbons. In general, any hydrocarbon mixture composed predominantly of satu- In this way, `when sures in order to maintain liquid phase operation under the conditions obtaining.

In order to more fully understandthe process of the present invention, reference may be had to the drawing which is a more or less purely dla# grammat'lc 'representation in sectional elevation of a suitable ow plan showing some structural detail. The apparatus is capable of'quite wide modification to suit the exigencies of any particular isomerization process. However, the drawing will be described with reference to the use of alu' minum chloride as the catalyst, hydrogen chloceous earth, Super Filtrol, silica gel, alumina gel,

etc., and then powdered, is introduced into a pressure chamber 225v by means of pipe 226 controlled by valve 221. The pressure is then increased to that maintained in the reaction zone by opening valves 235 in line 234 and 231 in line 236, valve 239 in line 238 remaining closed. Once the pressure in the chamber 225 has reached that of the reaction zone, valve 231 is closed and valve 224 opened to permit the catalyst to pass thru line 223 into the cyclonesseparator 228. 'I'heY catalyst, when operating the process according to the apparatus disclosed, should preferably beA a fairly iinely divided powder of the order of 100 to 200 mesh. The catalyst in' cyclone separator 2l8 is conveyed to reaction chamber 206 by means of a screw conveyor or slurry pump represented in the drawing as element 2I9. This screw or pump may be driven by any suitable mechanical means, for'example, a motor 222. Fresh feed is introduced into the system lthru line 202 controlled by valve 203. Fresh activator, i. e. hydrogen chloride, is introduced into the system, thru 'line 232 controlled by valve 233. The two streams are united and enter a preheater 205 thru pipe 204 which in turn empties into the bottom of reactor 200. A pump (not shown) maintains a suilicient velocity of flow of the fresh feed, which is in the liquid phase, to create a swirling motion within the reactor 206 equipped with spiral baille plates 2l0 so that the catalyst powder entering by means of screw conveyor or slurry pump`2 l 9 is taken up as a slurry in the liquid reactant and carried thru the series of baiiles upwardly for the desired time. Reactor 20,0 is equipped with a heating Jacket 201 provided with inlet 200 and outlet 208 whereby it is possible to maintain the desired vreaction temperature of -175 F. during the residence of the catalyst and reactants in the reactor 206. Any suitable heating medium, such as heavy oil, steam or ue gases, and the like, may be employed as a heating medium in the jacket 201. The etlluent from reactor 200, which consists of a slurry of small amounts of decomposition products; n-parailln (n-butane), isoparafilns, i. e. isobutane, catalyst and spent catalyst, together with small quantities ture may be returned to thel reaction zone thruline 2| 8 by opening valve 2I1. On the other hand. if the mixture is suiliciently'isomerized,

valve 2I1 remains closed and valve 2I5 is open thereby permitting the slurry to pass by means of pipe 2M into the catalyst separator 2N.v In practical operation it is desirable to partially open both valves 2l5 and 2H. Inv catalyst separator 2 I 8 the slurry is broken, the catalyst mass settling to the bottom and substantially clear supernatant liquid is-withdrawn by means'ofpipe 223 for further processing to isolate the desired product. The spent'catalyst, having settled to the bottom of separator 2I8, may either be returned to the reactor 206 by means of lscrew conveyor or slurry pump 219, or if it has reached a point where it is no longer useful in the reaction because of degradation, it may be withdrawn' from the system by meanspf pipe 220 controlled by valve 22 I. The product withdrawn thru pipe 229 may be subjected to a filtering operation o'r other suitable separating operation wherein the last traces of the catalyst are separated from thehydrocarbon product.' Said hydrocarbon product may then be subjected to fractionation treatment` to eifect a separation of the desired isomers from the product. Unreacted reactants and activator maythen be collected and returned to the reactor 206 thru line 230 controlled by valve 231. In operating pressure chamber 225, it is necessary, before refilling said chamber with fresh catalyst, to reduce the pressure to the pressure of the catalyst hopper 228. This is accomplished by closing valve 235 and opening valves 231 and 239. Valve 239 is then closed, valve 221' is opened, pressure chamber 225 is allowed to fill the catalyst, valve 221 is then closed and' pressure from the' system connecting the reactor is permitted to enter the.

chamber by means of valves 235 and 231 as heretofore described prior to introducing the catalyst inA chamber 225 into the catalyst separator 2 I3 by means of line 223 controlled by valve 224.

A single spiral baille tower reactor has been described. However, itis within the contemplation of the invention to operate simultaneously and in inter-connection witheach other a series of spiral baille tower reactors. No diillculty is encountered in assembling a single reactor of the type disclosed into a series of inter-connected reactors capable of series and/or parallel operation. It is maintaining a slurry. Any apparatus, therefore.

which is capable of accomplishing this type of operation. will be entirely suitable for carrying out the process of the present invention.

The present invention is not intended to be limited to any theory or mechanism of operation but only in so far as limited by the following claims in which it is desired to claim all novelty inher.- ent in the invention. The nature and objects of the invention having been thus fully described, what is claimed as new and useful and is desired to be secured'by Letters Patent is:

1. A process comprising forming a slurry-of a powdered aluminum chloride catalyst mass and at least one normal parain containing at least four carbon atoms per molecule in the liquid phase by jetting, under isomerization reactionl conditions in the presence of a promoter, the liquid normal paraiiin feed into said powdered catalyst mass with sufcient velocity to maintain the slurry, maintaining the said slurry under Athe reaction conditions for a sufilcient length of time v Ato effect substantial isomerization, withdrawing a portion of the reactionmixture from the reaction4 zone, separating the same into a predominantly liquid phase and a-predominantly solid phase, re-

covering' iso-paraln from the predominantly 4. A process as inv claim 1 wherein the aluminum chloride is present in the reaction zone in a preponderating amount, the promoter is hydroare well aware of the fact that a suillcient velocity l ofthe feed entering the reactor must b e maintained to pick up and carry in suspension `the powdered catalyst entering the reactor by means of the screw conveyor or slurrypump. It is therefore not possible in this type or apparatus to maintain a catalyst concentration as high as may be maintained in connection with a bed type rof operation. However, the results obtainable with the baille tower slurry process are proportipnately as excellent as those obtained with a bed type percolation method.-

However, it should be distinctly understood that the process of the invention is not limited to any particular type of apparatus since it is only necessary, inl carrying ont the process ot lthe present invention, to effect the isomerization reaction in the presence of large quantities of catalyst per unit volume of -paramnic reactant while genV chloride, the reacting mixture continuously ilows as a. circulating stream from which a portion of reacted mixture is withdrawn, a portion of said circulating stream constituting the reaction zone through which the reacted mixture flows spirally upwardly aided by the letting of the fresh feed into said stream. Y

5.A process as in claim l wherein the aluminum chloride is present in the reaction zone in a vpreponderating amount and wherein the feed stock comprises essentially normal butane, the product -recovered comprising essentially isobutane, the promoter is .hydrogen chloride and the catalystmass is of a particlesizebetween about and about 200 mesh.

8. A process as in claim 1 wherein the aluminum chloride is present in the .reaction sone in a preponderatins amount and wherein the'feed stock comprises essentially normal butane. the product recovered comprising essentially isobutane, the promoter is hydrogen chloride and the catalyst mass is of a particle sise between about 100 and about 200 mesh. 'andwherein the catalyst mass is prepared by lmpregnating aluminum chloride in a porous alumina carrier and comminutins vthe resultant mass to the stated particle size.

' JAMES ll. WHITEIIY, Jl.

CHARLES 8. LYNCH.

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