US2972650A - Two-stage isomerization of normal paraffins - Google Patents

Description

' reformingoperation.

' One' method refinersfor obtaining stocks ofhigher octane value in: Jvolvejs the 'isomeriaation Qf hc; to C 'n parafiinie hydro- Uni d St es Pat f TWO-STAGE ISOMERIZATION OF NORMAL PARAFFINS Emmett H. Burk, Jr., Hazelcrest, John Mooi, Homewood,

and Owen H. Thomas, Chicago, Ill., assignors to Sinclair Refining Company, New York, N.Y., a corporation of Maine No Drawing. Filed May 7, 1959, Ser. No. 811,537 10 Claims. (Cl. 260-68366) This invention relates to a hydrocarbon Conversion process and particularly pertains to a two-stage process for isomerizing straight chain aliphatics to produce branch chain aliphatic structures, e,g. isomeric structures of n- I paraffins, which are especially useful in providing gasoline components of high octane rating.

In recent years automobile manufacturers have steadily increased the compression ratios of their spark-ignition engines as a means of obtaining more power and greater efiiciency. As the compression ratios of the engines in-i creases, the hydrocarbon fuel employed must be of higher octane rating to provide eflicient knock-free operation notwithstanding that fuel octane rating can be increased through the addition of tetraethyl lead, and other undesirable aspects of engine operation, for instance pre-ignition, can be overcome by the use of other additive components.. Thus the problem remainsfor petroleum refiners to produce higher octane base hydrocarbon fuels under economically feasible conditions.

These refiners now have installed a substantial number of units for reforming straight run petroleum fractions in the presence of free hydrogen and over a platinum metal-alumina catalyst to obtain relatively high octanev products. Primarilythese products, frequently called reformates, are blended with other gasoline components such as thermal and catalytically cracked g'asolines, alky late, etc., and additives such as'tet'raethyl lead inobtaining present-day motor fuels. The reformingoperation has a number of disadvantages. .First, as theoCtane' requirements of the blended engine fuels rise, the octane quality of the reformate must also "increase, if theblends be otherwise unaltered. This increase results .in .a sub stantial reduction in yield particularly in obtaining reforrnates having. octanes RQN"neat) of the, order of 90 was or above. ,When' 'thej severit'y' of the operation is increased, the-platinum metal-containing catalyst be comes fouled more o'ften with carbonaceous deposits whichiequires more frequent,.regenerationsor replace ments. The .platinum metalaalurn'ina catalysts; are 'relatively expensive, and either sreplacernentor withdraw! a1 fromuse during regenerationmaterially increases-the, cost'of providing. a given volurnn ,of freforrnate; These and other factorsfaffecting the yield-octane-. nuinberrcostrelationship make it'desirable for th'e'refiner to consider 7 .variou's ways in. which high octane hydrocarbon fuel components can be obtained" byjemploying proc essin 2,972,650 Patented Feb. 21, 1961.

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carbons, that is n-butane, n-pentane, n-hexane, n-heptane, n-octane, n-nonane and their mixtures with each other and with other hydrocarbons in the same approximate boiling range. In general, as the side chain branching of these n-parafiins increases, their octane ratings rise. A. number of catalysts are known as being useful in this type of operation. An example of such a system is that .described in US. Patent No. 2,798,105 wherein a plati-r hum-alumina catalyst is employed to isomerize n-butane and n-pentane at temperatures upwards of 600 F. At such temperatures the thermodynamic equilibrium between the feedstock and the isomeric product is such that conversion is unduly limited which means that the product contains undersirably large amounts of n-paraffins.

Due to the low octane rating of the n-paraffins .a given refiner may not be able to blend the entire product from. they high temperature isomerization system directly intov his gasolines. Rather, under present commercialconditions he will most likely be required to separate the n-,.

and iso-paraffins in the product stream by distillation and then recycle all or a part of theuncoverted 'n-paraffins to the isomerization reaction system It is, of course, immediately seen that the decreased yield of isomer structures at the highreaction, temperatures is disadvantageous, and in addition the provision of the required distillationfacilities materially adds to the cost" of octane.

enhancement. I e v e p In 'a process described in the copending application of Keith and Burk, Serial No. 683,931, filed September 16, 1957, C4 to C n-parafiinic-containing materials are isomerized at relatively low temperatures while obtaining satisfactory conversion to isomeric structures. Thisiso merizing process includes contacting a C -to C n-pa raflin in the vapor phase with a noble metal-FriedelaCrafts' component-alumina catalyst at a't emperature. ofaboutv 1.150 to 450 F., a space velocity in most cases of. about.

' directly in a gasoline poolwithout requiring distillation 0.5 to l0:l weights ofn-paraffin perweight ofcatalyst per hour (WI-ISV) -in the presence of free hydrogen and whileproviding about 0.0516 35 of a-hydrogen halide I based on the n-paraffini When following this'procedure the amount of isomer structures in the product are sufii cient such that-the overall product stream -can-be used foruseparating the n-paraffins from-the product. fflhe feeds employed in this process. are usually pretreated to l lower the amount of l'aromatic naphthene int-, .;purit ies: contained thereinjsince the impurities can; have to provide appreciable isomerization" of'th'e n-parafiins to enhance the octane. rating of-theifee'd, e.g-.' above about;

"methods other than; the platinum metal-alurninagcatalyst ow; under consideration by petroleuni 94, and at the sameftime providinghydrogenationfofthe; aromatics. The product 'frornthe-first stageisfurther; enhanced in octane rating in thesecond stage at -less sever e temperature conditions: than those employed, in the i I first Stage. andiising equivalent or greaterspace velocities:

for Qa I giVen entagon: of n-paraflin to isoparaffin than the above-mentioned copending application, Serial No. 683,931. In other words, due to the. use of our initial conversion zone the second stage of this invention can provide greater amounts of high octane product from a feedstock containing aromatic poisons for the second stage catalyst than would be obtained by employing the second stage alone. At set forth in the above copending application, hydrogen halide is advantageously included in the hydrogen recycle gases employed in this process. Accordingly, another advantageous feature of our two-stage procedure is the simplicity and the interdependent relationship between the two stages allowing use or": common hydrogenrecycle gases containing hydrogen halide in each stage since the catalyst employed in the first stage is stable in the presence of hydrogen halide.

In the first stage (stage I) of the present process, which can be conducted in the presence of hydrogen recycle gases containing hydrogen halide at atomic weight between 35 and 85, some isomerization of C to C n-paraffins is effected along with the hydrogenation of aromatics, e,g. benzene and toluene. Benzene, when present in substantial amounts, is converted to methyl cyclo pentane and cyclo hexane which are tolerable in the first stage and are tolerable in the second stage in amounts less than about 12' weight percent based upon the hydrocarbon feed. When large amounts of naphthenes are present in the feed, for instance, in amounts above about 12 and up to about or weight percent, temperatures from about 575 F. to650 F. can be provided in the first stage to reduce the naphthene content of the feed to less than about 12 weight percent and preferably less than about 10 weight percent, eg about 1 to 9 wcightpercent, by selectively cracking the naphthenes to, for instance, isoparafiins and other products, while effecting some isomerization of C to C n-paraffins along with the hydrogenation of aromatics. The selectivity to C and higher products for the isomerization of n-pentane in the first stage is generally up to about 94 volume percent or more. .The product of the first stage or any portion thereof is charged to the second stage (stage II) which isv char acterized by good selectivity, for instance generally above about 97% and frequently above about 98%, for the isomerization of normal pentane to iso-pentane.

In the initial stage of the process of the present inven tion, C to C n-paraffinic materials in the hydrocarbon regenerable, exhibits good activity as well as good aging characteristics and is stable in the presence of hydrogen halide employed in the second stage of the process. Another highly advantageous feature provided by the use Angstrom units size. Of the noble metals platinum, palladium and rhodium are preferred.

The boria component is surface dispersible on the support and seems essentially inert to hydrogen halide. It is employed in amounts sufficient to enhance the life of the alumina support and such amounts are, therefore, preferably added in direct proportion to the area of the support. For instance, the amount of boria will usually be about 3 or 5 to 20 weight percent and preferably about 8 to 15 Weight percent of the catalyst. These amounts are particularly effective on alumina having surface areas of about 350 to 550 square meters per gram (BET) before use.

in order for the catalyst to maintain its activity for long periods of time when isomerizing the C to C n-parafiins, it is highly desirable to provide a hydrogen halide of atomic weight between and 85, e.g. HCl, HBr and their mixtures, in the-reaction zone. The hydrogen halide can be added along with or in the n-paraflin feed and preferably in hydrogen recycle gases employable in either stage of the present process. The hydrogen halide is provided in an amount of at least about 1 up to about 25 percent, based on the hydrocarbon feed, preferably at least about 1% up to about 20% and advantageously about 5 to 15 weight percent of hydrogen halide or hydrogen halide of a hydrogen halide-producing material based on the hydrocarbon feed. The addition of the hydrogen halide in these concentrations is continued over the processing period in order to maintain an adequate concentration of this component and insure the stability of the catalyst against undue aging. The hydrogen halide can be added separately to the reaction zone, in the hydrogencontaining recycle gases, or in the n-paraifin feedstock.

Instead of supplying the hydrogen halide with an atomic weight between 35 and 85 as such, an organo-halogen compound or other substance which will produce the hydrogen halide under the isomerization conditions can be employed; Suitable hydrogen halide precursors of this 1 type include the elemental halogens, chlorine,brornine and fluorine; monoand polyhalo-alkanes such as carbon tetrachloride, chloroform and tertiary butyl chloride; or.

other available materials which-will be converted under the conditions of isomerization to provide the hydrogen halide.

The noble metal and boria constituents of the catalyst are deposited on an absorptive alumina base of the acti'- vated or calcined type. The alumina base is usually the major component of the catalyst, generally constituting at least about 75. weight percent on the basis of the cataof this catalyst in the initial stage lay in the lowering of a the aromatic and, when present in amounts aboveabout 12 weight percent and under favorable temperature conditions, naphthene ingredients contained in the feed since the catalyst has a relatively high tolerance limit for these 'as well as other ingredients.

7 Thus, for instance, feeds containing up to about 0.004 or more percent sulfur, up to about 10 percent aromatics and up to about 20 percent naphthenes canbe'tolerated';

*The catalyst employed in the initial stage of the present lyst and preferably at least about to percent; The

catalyst'b'ase is an activated or gamma-alumina such as' those fderived'by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate orjtheir mixtures The catalyst base precursor most adyarita geously is amixture predominating in, or containing a' major proportion of, forinstance about 65 to weight percent, one or more of the alumina trihydrates bayerit e. L

bayeriteflllrandomitel or gibbsite, and about 5' to 35 weight percent of alumina monohydrate (boebm'ite), amorphous hydrous alumina or theirimixture. The alu-j,

mina base can contain small amounts of other solidoriprocess includes catalytically efiective amounts of a noble;

or platinum group metal and boria supported on an alu mina base.

The catalyst generally contains about 0.01 to .2 weight percent,preferably 0.1 to 1 weight percent, ofone or more of'the platinum metals of group Vlll,

that is platinum, palladium, rhodium,- ruthenium, osmium' or iridium. The small amount of noble 'metal rnay be present in the metallic form or as a sulfide, oxide or other" combinedform. The metal may interact with other constituents of the catalyst, but if during usethe noblemetal be p'resentiin metallic form, then it is preferred that it be so finely divided that it is not detectable'by X -ray diffrae-c tioumeans, i.e. that it "exists as crystals ofless'th'an 50 ides sucha's silica, magnesia, natural or activated clays (such kaolinite, montmorillonite, halloysite, 'etc.). .titania, zirconia, etc'., 'or theirlmix'tures. Although the components of the catalyst 'can'vary as stated, the pre} ferred catalyst contains platinum and "boria deposited on activated alumina;

The f rst stage reaction conditions the method of the present invention include a temperature sufficient to maintain the n-parafiin feed the vapor phase under the pressure employed; Generally, this temperature yilf moving or fluidized bed or'in any otherconvenient type of handling system. The fixed bed system seems. most advantageous at thistime and the space velocity will in most cases be from about 0.5 to 20:1, preferably about 0.75 to :1, weights of n-paratfin per weight of catalyst per hour (WHSV). a.

Free or molecular hydrogen must be present in our first stage reaction system and the hydrogen to n-parafi'in molar ratio will usually be from about 0.01 to :1 or more, preferably about 2 or 3 to 10:1. Conveniently, the hydrogen concentration is maintained by recycling hydrogen-rich gases from the reaction zones of either the first or second stages. These gases contain hydrogen halide at least after the initial processing period and as there is usually no substantial consumption of the halide after this period the desired concentration in the feed can be maintained for use in the second reaction zone merely by recycling the hydrogen halide-containing gases, for instance, with a hydrogen halide concentration on the order set forth above. As previously stated the preferred catalyst base material is an activated or gamma-alumina made by calcining a precursor predominating in alumina tribydrate. An alumina of this type is disclosed in US. Patent No. 2,838,444. The alumina base is derived from a precursor alumina hydrate composition containing about 65 to 95 weight percent of one or more of the alumina trihydrate forms gibbsite, bayerite I and bayerite II (randomite) as defined by X-ray diffraction analysis. The substantial balance of the hydrate is amorphous hydrous or monohydrate alumina. Trihydrates are present as well-defined crystallites, that is, they are crystalline inform when The crystallite examined by X-ray diffraction means!- size of the precursor alumina tribydrate is relatively large and usually is in the 100 to 1000 Angstrom'unitv range. The calcined alumina has a large portion of its pore volume in the pore size range of about 100 to 1000 Aug strom units generally having about 0.1 to about 0.5 and preferably about 0.15 to about 0.3 cc./ g. of pore volume in this range. As described in these applications the calcined catalyst base can be characterized by large surface area ranging from about 350 to about 550 or more state has substantially no pores of radius less than 10 Angstrom units andthe surface area of the catalyst isless than 350 square meters/ gram and most advantageously is in the range of about 150 to 300 gram'.

metal, by impregnation from a hot, heated or boiling solution of water. after it has been formed by tableting or extrusion and calcined. After the boria is added according to this procedure, the catalyst can be recalcined.

The catalyst of the initial stage of the present invention can be easily regenerated employing conventional procedures, for instance by subjecting it to an oxygencontaining gas at temperatures sufiicient to burn off carbon deposited on the catalyst during the conversion of petroleum hydrocarbon feedstock. This oxygen-contain ing gas, e.g. an oxygen-nitrogen mixture, can contain about 0.01 weight percent to 5 weight percent oxygen but preferably contains about 0.5 to 1.5 weight percent oxygen and is introduced at a flow rate such that the maximum temperature at the site of the combustion is below about 1000 F.

In the second stage of the present process, the product from the first stage is treated with a solid catalyst which is useful in the isomerization of the C to C n-paraflins in the presence of free hydrogen and at relatively low temperatures to afford highly satisfactory yields of isomer products. This catalyst, when employed under proper conditions, has an excellent stability against aging. Due to the high, isomer content of the resulting product from the second stage, a given refiner may find that it can be blended directly into his gasolines which avoids the necessity for providing distillation facilities to separate the unconverted n-parafiins. However, even if such facilities need to be provided inorder to obtain products more concentrated in isomeric structures the catalyst of the second'stage still provides increased conversion to as compared with others previously ically effective amounts of a noble or platinum group metahan aluminum halide Friedel-Crafts component and .at least ultimately in the reaction zone, a hydrogen halide metals offgroup VIII, that is platinum, palladium, rhodium, ruthenium, 'osmium or iridium. The small amount 'of" noble metal may be present in the metallic form or as a sulfide, oxideor other'combined form.

. The metal may interact with otherconstituents ofthe square meters/- The platinum group metal, e.g.' platinum; component ofthe catalyst can beadded t olth e alumin'a base'byknown procedures. For instance, the platinum metal; component can be deposited on a .calcinedjloractivatedalumina, but it is preferred to add -theplatinum metal 'ly 1s about- 2 to, 50 we1ght percent, preferably about .10 to. 30 weight percent-,of the catalyst andthis componentcomponent to the alumina-hydrate base precursor. Thus 7 platinum can'be added throughreaction ofafhalogen platinum-acid,- for instance, fluoro-,, ichloro-Qbromoor" iodo-platinic acid, and hydrogen sulfide inxan aqueous slurry .of' the alumina hydrate. Thehydrogen sulfide can be employed as a gas or an aqueous solution. Alternatively the platinum component {canbeprovided-by mixing an aqueous platinum' sufide sol with the alumina,

hydrate. ,This sol canbe; made by reac't'ionffin anja quegfous medium of a halogen platinicacid' with hydrogem, sulfide. I The alumina hydrate containing" "the platinum.

metal can be dried-and calcinedusually at a temperature activatedor lgamma alumina modifications. The, boria.

it'spfeparation. -It-j mayv be" incorpo ponent.

ucatalyst, but if during use the noble metal be present in metallic form then it is preferred that it be so finely divided that it is not detectable by X-ray diffraction means, i.e. that it existsas crystals of less than" 50 Augstrom units sizen p fer g q. a I

The aluminum halide Friedel-Crafts-cornponent usual 'can'be, for instance, AlCl AlBr "and-similar metal halideswhere one or more 'Of the. anions are replaced. with. another anion such as hydroxide. Mixtures'of these, i. Friedel-Crafts,components can also be usedf'aluminum' chloride is, however, thepreferred Friedel-Crafts. com-. i

A hydrogenhalide of atomic 'weight between35 and is p'rovided'in the reaction zone of' theseeorid stage I in order for the catalystto maintain the activity of th- "catalystffoi long' periods of time when isomerizing the C to C n-paraffins from the firststage The amounts, mannerfof employment and types of hydrogen halide pro: I vided in' the second stageare essentia lly'fthe. same as in the first stagedescribedabove. .Thus we have found that the catalyst should contain about 0.5 to15%;or

V nioreof the hydrogen halide. The hydrogen jhalide's of atomic weight-between35 and 85 ,includegifor, instance, mn ee e d tfl me s-"mama It is frequently added to the catalyst -Of the noble metals, platinum.-is

' 0.5 to; 105i weights of'mparailin tures'a'nd preferably the amount of this component on the-alumina baseis less than about of the catalyst. Usually this halide will be added to the catalyst after it is placed in the isomerization reaction. Conveniently this can be done by including in the charge stock from the initial stage about 1 to 01 weight percent, advantageously about 5 to 15 weight percent of the hydrogenhalide or of a hydrogenhalldoproducing material. The addition of the hydrogen halide in these concentrations based on the n-parafiin in the second stage, as in the case of the first stage, is continued over the processing period in order to maintain an adequate concentration of this component on the alumina base and insure the stability of the catalyst against undue aging. The hydrogen halide can be added separately to the reaction system, in the hydrogen-containing recycle gases or in the charge stock from the initial stage. Also the hydrogen halide might be added to the catalyst before charging it to the reactor.

instead of supplying the hydrogen halide of atomic Weight between and 85 as such, an organo-halogen compound or other substance which will produce the hydrogen halide under the isomerization conditions can be employed. Suitable hydrogen halide precursors include the elemental halogens, chlorine and bromine; monoand polyhalo-alltanes such as carbon tetrachloride, chloroform and tertiary butyl chloride; or other available materials which will be converted underthe'conditions of isomerization' to obtain the hydrogen halide. Most advantageously about 5 to 15 weight percent of hydrogen chloride is employed as the hydrogen halide on the catalyst and is supplied during the processing period.

The noble metal, Friedel-Crafts and hydrogen halide, of atomic weight between 35 and 85, constituents of the catalyst are deposited on an absorptive aluminahase of the activated or calcined type, as described in connection with the catalyst employedin the first stage. The base is usually the major component of the catalyst, constituting about 40 to 88 or 98 weight percent, preferably at least about The catalyst base is an activated or gamma alumina such as those derived by calcination of amorphous hydrous alumina, alumina monohydrate, alumina trihydrate or their mixtures, for instance as in the catalyst of our first stage reaction zone. The catalyst boria, natural or-activated clays (such as kaoliuite, montmorillonite, halloysite, etc.), titania, zirconiap etc., for their mixtures. Although the components ofthe catalyst can vary as stated, the preferred catalyst contains platinunnaluminu'm chloride and hydrogen chlo zde; deposited on activated alumina.

The isomerization reaction conditions used. the second'stage otlthe method Of::l .h present invention. include a temperature sufificient to maintain the ri -paraffin feed in zthevapor phase'under the pressure employed. General- I ly, .this.temperature.will be from about 150 to 450 F preferably about 250 to 400 5., while the pressure Will be superatmospheric ranging fromabout 50 to 1000 to n-paraffin molar ratio will usually be from about 0.01

These gases contain hydrogen halide at least after the initial processing period and as there is usually no substantial consumptionof the halide afterthis period the desired concentration in the feed can be maintained merely by recycling the hydrogen gases containing hydrogen halide of atomic weight between 35 and 85 since, for instance, the hydrogen halide concentration can with advantage be about 0.5 to 35 weight percent of the recycled gases.

A convenient manner in which the catalyst of the sec end stage of the present invention can be prepared is to add the Friedel-Crafts component to the base containing.

the platinum metal component. It is highly desirable to keep the catalyst protected from moisture to avoid hyrolysis and the resulting loss of aluminum halide from the catalyst. Thus it is most advantageous to employ this catalyst under essentially anhydrous conditions including the provision of the hydrogen halide in anhydrous form. During regeneration of the catalyst to remove carbonaceous deposits by burning in an oxygen-containing gas, some aluminum halde may be lost. Thus, it may be necessary to add additional amounts of this halide as by sublimation before continuing the isomerization.

Even though the catalysts used in each of the first and second stages can be employed directly in the isomerization system, it is preferred that they be pretreated with free or molecular hydrogen or a mixture of hydrogen and hydrogen halide. For instance, the catalyst used in the first stage can be pro-reduced or preactivated by treatment with hydrogen at an elevated temperature, for instance about800 to 1000" F. The catalyst used in the second stage can be heated to about 650 F. in a slowly flowing stream of hydrogen or hydrogen-hydrogen chloride mixture for a period of time sufiicient to activate the catalyst. It may be desirableto employ lower temperatures in the pretreatment of the second stage catalystto avoid undue loss of aluminum halide by sublimation even though this may decrease the rate of activation. After the activation the pressure can be increased as desired and the product from the first stage is charged to the reaction system. Generally, the activity of the catalyst hydrogen halidesupported on the alumina base.

p.'s.i.'g., preferably about 200 to- 600 p.s.i.g. The. catalyst can be used as a fixed, moving or fluidized bed or in any other convenient'type of handling system. The

fixed bed system s'eemsmost. advantageous at this tim e and the space velocity will in niost cases be from about per Weight of catalyst per hour-(WHSV). p free or molecular hydrogen 'must' alsobe present in l s se o s t st ut ca i sy tem-r the h dro en Eriedel-Crafts component. I

-As previously- -stated the preferred catalyst base terial is anactivated or gamma-alumina made by ,cal-

cining'a precursor predominating in alumina trihydrate as exemplified-in U.S .Patents 2,838,444 and 2,838,445. The platinum metal component of ourjcatalys'ts can be added to the alu'minaflbase. by l nown procedures deponent-to thehigh areacatalyst baseof US. Patent .No.

2,838,444 hasbeenfound to decrease the surface area,

for instance-frequently in proportion to the amount of Friedel-Crafts component added. Use of the catalyst in the isomerization system or hydrogenpretreatment seems to tend to increase the area apparently through loss ofthe The following specific example will 7 p serve toillustrate the-inventiontbut'it isnot to beTconsidered limiting? I I 9 EXAMPLE I A noble metal-alumina composition of the kind described in U. S. Patent No. 2,838,444, can beremployed in preparing the catalyst used in the process of our invention. The composition of this application can be made as follows. Pure aluminum metal is dissolved in pure hydrochloric acid, and the resulting solution is mixed with deionized water to form an aqueous aluminum chloride solution and an alumina gel is prepared equivalent to approximately 65 grams of A1 per liter. A separate deionized water solution of NH OH is prepared containing approximately 65 grams of ammonia per liter. These two reagents in approximate volume ratio of 1:1 are intimately mixed as a flowing stream at a pH of'8.0. The flowing stream is passed to a stoneware container and an alumina hydrate is visible. The precipitated hydrate is filtered from the mother liquid and washed to 0.2% chloride by successive filtrations and reslurryings in deionized water until the desired chloride concentration is reached. In each reslurrying ammonia is added to give a pH of about 9. The washed hydrate is. covered with water in a container and aged at about 90 F. until it is approximately 70% trihydrate, the remaining being substantially of the amorphous orfmonohydrate forms. The total hydrate compositon is comprised of 42% bayerite, 18% randomite, 11% gibbsite, 20% boehmite, and 9% amorphous as determined by X-ray diffraction, analysis. The aged hydrate is mixed with deionized water in a rubber lined container to provide a slurry of about 7 weight percent A1 0 at a pH of about 8.0. A chloroplatinic acid solution in deionized Water (0.102 gram platinum per milliliter) is stirred into the slurry and the slurry is then contacted with a deionized water solution which has been saturated with H at 78 F. to pre cipitate the platinum. The pH of the slurry is adjusted to 6.0 to 6.5 by ammonium hydroxide addition and the solids of the slurry are dried on a horizontal drum drier to give a powder of' generally less than 20 mesh. The drum dried powder is mixed in a, planetary type dough beater with sufiicient deionized water to indicate 26 weight percent water on a Central Scientific Company Infra-Red Moisture Meter containing a 125 watt bulb, Cat. No 26675. The resulting mixture is forced through a die plate having holes in diameter bolted to a 3 /2" welding engineers screw extruder. The resulting strands are broken to particles of length varying generally etween about to 1 The particles 'are dried aty230 F. and calcinedrby heating to 925 F. in a flow of nitrogen gas followedby a'flow of air while the composition is maintained at a temperature in the range of 865 F.to 920 F. [The composition thus produced analyzes about 0.6'fweight percent of platinum-which is in sufficiently divided form so as to exhibit by X-ray diffraction studies the substantial absence of crystallites. or crystals of size larger than 50 Angstromunits After the calcination'the composition has an area (BET method) within the range from about to 550 square meters/gram. A

(B) Preparation of noble metal-boriaflrluntind catalyst A platinum-alumina composition prepared essentially A at 140 C., for 4 hours. The catalyst was stirred occa-' sionally while drying. The oven dried catalyst was transferred to a sagger and placed in a muffle furnace preheated to 1000" F. The catalyst was held at1000- for 2 hours and cooled in a desiccator. Analysis: 9.95% B 0 7 An example of pre-activation follows: 40 grams of this catalyst were supported on glass beads in the center of a 1-inch I. D.v Universal Stainless Steel Reactor. The

;reactor was s'etLin place in a bronze-block furnace controlled by Microswitch thermostats. The catalyst was heated to--800- -'F. under atmospheric pressure of pure hydrogen flowing at about 2 cu. ft./hr. These conditions were. maintained for'lohours. At this time the reactor is cooled to operating temperatures and reaction conditions are established for processing the parafiin feed.

(C) Preparation of noble metal-aluminum halide-alumina catalyst A platinum-alumina catalyst prepared essentially as described above in Example I(A), except that air was used for the complete calcination procedure and containing about 0.6 percent platinum was employed in the process of the present invention by the following procedure. A one-liter, three-necked flask was fitted with a heating mantle, thermometer and an air inlet line having a drying tower filled with Drierite. The flask was fastened to .a Syntron Paper Jogger which provided agitation of the catalyst during the impregnation. The flask was swept out with dry air for about 10 minutes. 150 grams of the platinum-alumina catalyst and 45 grams of aluminum chloride were charged to the flask.- The air I (D) The two stage process 7 V 1 ANALYSIS on nnnnstroon Feed (wt. percent) 3 i-C 4 i-C 0. 1:1-(:5 V 2.2 dimethyl benzene 2,3 dimethyl benzene+2 methyl pentane .z... 3 methyl pentane 11-C6 V i MCP Benzene i-C i-C The'present inventionv is illustrated by Run A, presented below in Table I,,which was conducted under the conditions specified above for the two-stage process of the present invention. The results are also presented in this table. The catalyst employed in stage I was prepared by essentially the same procedure set forth in Example I(B) above except that the catalyst comprised 0.6

TABLE I Run A Stage I Stage II Feed Samev feed analyzed i Product E -.am' le 1 from StageI Condition:

Wt. percent H01 based on feed 12. 5 12. 5 Pressure, p s is 500 500 625 300 V 3 2 5. 6' 5. 6 Product:

54. 0 64. 6 75. 2 86. 0 2, 2 D 7. 2 20. 8 Selectivity C5 97. 2 99. 3

It is claimed: 1. In a method for isomerizing C to C n-paraflins in a feed containing aromatics, the steps comprising contacting said n-parafiins under first stage conditions with a first stage catalyst at a temperature of about 200 to 750 F. and in the presence of free hydrogen to produce 'a first stage reaction product, contacting the first stage reaction product under second stage conditions with a second stage catalyst at a temperature from about 150 'to 450 F. and in the presence of free hydrogen and while providing about 1 to 25 percentof a hydrogen halide with an atomic weight between 35 and 85 based on the first stage reaction product; said first stage catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and about 3' to of boria on activated alumina and said second stage catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and about 2 to 50% of an aluminum halide Friedel-Crafts component on activated alumina.

2. In a method for isomerizing C to C n -paraifins in a feed containing aromatics, the steps comprising contacting said n-parafiins under first stage conditions with .a first-stage catalyst at a temperature of about 200 to 750 F. and in the presence of free hydrogen while providing about 1 to percent, based on the feed, of

jaydrogen halide with an atomic weight between '35 and 85 to produce a first stage reaction product, contacting on the first stage reaction product; said first stage catalyst consisting essentially of about 0.01 to 2 percent of a.

platinumgroup noble metal and about.5 to 20 percent of boria on activated alumina and said second stage catalyst consisting essentially of about 0.01 to 2. percent of a platinum group noble metal and about 2 to 50 percent of an aluminum halide Friedel-Crafts component on activated alumina.

3. In the method of claim 2 wherein the platinum 52 group noble metal of the second stage catalyst is platinum.

4. In a method of claim 3 wherein the first stage temperature conditions are from about 500 to 650 F.

5. In a method for isomerizing C to C n-parafiins in a feed containing aromatics, the steps comprising contacting said n-parafiins under first stage conditions with a first stage catalyst at temperatures of about 500 to 650 F., superatmospheric pressure, and the presence of free hydrogen while providing about 1 to 25%, based on the feed, of hydrogen halide with an atomic weight between 35 and to produce a first stage reaction product of enhanced octane rating and containing hydrogenated aromatics, and contacting the first stage reaction product under less severe second stage conditions, to further enhance the octane rating of the first stage reaction product, with a second stage catalyst at temperatures from about 250 to 400 F, in the presence of free hydrogen and while providing about 1 to 25% of a hydrogen halide with an atomic Weight between 35 and 85, based on the first stage reaction product; said first stage catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and about 5 to 20% of boria on activated alumina and said second stage catalyst consisting essentially of about 0.01 to 2% of a platinum group noble metal and about 2 to 50% of an aluminum halide Friedel-Crafts component on activated alumina.

6. The method of claim 5 wherein the first stage catalyst consists essentially of about 0.1 to 1 weight percent of a platinum group noble metal and about 8 to 15 weight percent of boria on activated alumina and the second stage catalyst consists essentially of about 0.1 to 0.75 weight percent of a platinum group noble metal and about 10 to 30 weight percent of an aluminum halide Iriedel-Crafts component on activated alumina.

7. The method of claim 5 wherein the first stage catalyst consists essentially of about 0.1 to 1 weight percent of platinum and about 8 to 15 weight percent of boria on activated alumina and the second stage catalyst consists essentially of about 0.1 to 0.75 weight percent of platinum and about 10 to 30 weight percent of aluminum chloride on activated alumina.

8. The method of claim 7' wherein the first stage con ditions include a pressure of about 400 to 1500 p.s.i.g.

and about 5 to 35% of a member selected from the group consisting of amorphous hydrous alumina, alumina monohydrate and their mixture, and the activated alumina has an area of about 350 to 500 square meters per gram.

10. The method of'claim 9 wherein the n-parafiin is pentane.

References (Iited in the file of this patent V UNITED STATES PATENTS 2,349,516 Pines etal May 23, 1944 2,493,499 Perry Jan. 3, 1950 2,751,333 Heinernann -June 19, 1956 FOREIGN PATENTS 555,861 Great Britain Sept. 9, 1943

Claims (1)

1. IN A METHOD FOR ISOMERIZING C5 TO C9 N-PARAFFINS IN A FEED CONTAINING AROMATICS, THE STEPS COMPRISING CONTACTING SAID N-PARAFFINS UNDER FIRST STAGE CONDITIONS WITH A FIRST STAGE CATALYST AT A TEMPERATURE OF ABOUT 200 TO 750* F. AND IN THE PRESENCE OF FREE HYDROGEN TO PRODUCE A FIRST STAGE REACTION PRODUCT, CONTACTING THE FIRST STAGE REACTION PRODUCT UNDER SECOND STAGE CONDITIONS WITH A SECOND STAGE CATALYST AT A TEMPERATURE FROM ABOUT 150 TO 450*F. AND IN THE PRESENCE OF FREE HYDROGEN AND WHILE PROVIDING ABOUT 1 TO 25 PERCENT OF A HYDROGEN HALIDE WITH AN ATOMIC WEIGHT BETWEEN 35 AND 85 BASED ON THE FIRST STAGE REACTION PRODUCT, SAID FIRST STAGE CATALYST CONSISTING ESSENTIALLY OF ABOUT 0.01 TO 2% OF PLATINUM GROUP NOBLE METAL AND ABOUT 3 TO 20% OF BORIA ON ACTIVATED ALUMINA AND SAID SECOND STAGE CATALYST CONSISTING ESSENTIALLY OF ABOUT 0.01 TO 2% OF A PLATINUM GROUP NOBLE METAL AND ABOUT 2 TO 50% OF AN ALUMINUM HALIDE FRIEDEL-CRAFTS COMPONENT ON ACTIVATED ALUMINA.