US2313054A - Catalytic isomerization of saturated hydrocarbons - Google Patents

Description

Patented Mar. 9, 1943 UNITED. STATES PAT EN- JTQ C T CATALYTIC-ISOMERIZATION or" sA'rUnA'ran HYDROCARBONS 1 Martin deSim, Piedmont, and' Fi-ank Matthew I McMillan and Harry Ashley Cheney, Berkeley, Calif., assignors to Shell Development Company, San Francisco, Calif.,, a

Delaware corporation of. g

No Drawing. Application October 31, 1940, Serial N0. 363,670

6 Claims.

conversion of methylcyclopentaneand dimethyl-:

cyclopentane -to cyclohexane and methylcyclohexane, respectively. 7

The normal paraflin hydrocarbons may be obtained in a relatively pure state in large quantities from petroleum and natural gas. These hydrocarbons are chemically quite unreactive and have poor ignition characteristics. Their corresponding branched chain isomers, on the other hand, are chemically much more reactive and have excellent ignition characteristics but occur naturally only to very limited extents. The branched chain isomers may be readily alkylated with olefines, for example, to produce saturated .hydrocarbons which are especially desired for premium and aviation gasoline, and they may be readily dehydrogenated'to the respective tertiary olefines which, in turn, are excellent starting materials for the synthesis of a wide variety of useful and valuable products. In view of the abundance of these normal hydrocarbons and the ever increasing demand for their branched chain isomers, a commercially practicalprocess for the conversion of the normal isomers to their branched chain isomers is in demand- An object of the invention is to provide an improved, practical and economical process for the catalytic isomerization of saturated hydrocarbons to their more highly branched isomers. A particular object is to provide a more advantageous process whereby normal butane and nor,- mal pentane may be converted with improved yields and more practical catalyst life to isobutane and isopentane, respectively. Another particular object-is -to provideian improved method for the isomerization of saturated cycloparafiins such as cyclohexane, methylcyclohexane, methyl cyclopentane and dimethylcyclopentane.

Another particular object of the invention is to provide a process whereby lower boiling saturated distillates of the nature of gasoline may be isomerized efliciently and more advantageously to increase their ignition properties. Other objects of the invention will be apparent from the following description of the process.

In its more general aspect the process of the invention comprises isomerizing the hydrocar-' bons or mixture of hydrocarbons by treating them in the presenceoi a hydrogen :halide promoter with catalysts of a specified composition prepared in a specified manner.

While the process is generall applicable to the isomerization of saturated hydrocarbons, it

is especially advantageous for the isomerization of normal butane, normal pentana methylcyclopentane anddimethylcyclopentane; These hydrocarbons may be obtained in large quantities as individualcompounds in a relatively pure state. The hydrocarbon treated need not necessarily be a pure individual hydrocarbon, however, but may be a mixture of one or morehydrocarbons. Thus, the invention provides a practical process for converting the normal butane and normal pentane contents offcommercial hydrocarbon mixtures, such as'are obtained fromnatural gas, petroleum distillates, crackedIdistillates,

etc. to the more valuable branchedchain isomers;

Especially suitable mixtures of hydrocarbons are the so-called butane-butylene: fractions andpentane-amylene fractions from which unsaturated hydrocarbons have been substantially "removed.

Treatment of such mixtures, such' as obtained for instance as a byepr'oduct in" the sulfuric acid alkylation ofisoparafiins', results in very materially increasing theircontent of branched chain isomers and'convertingthem' to suitable raw materials for reuseinthealkylation-process.- Technical butane and pentane fractions, such as those containing from to of thenormal isomer and from 2% to 30% of the branched chain isomen'may be conveniently treated'in accordance with the process or the invention and their content of branched chain isomers materially increased without loss dueto. decomposition and side reactions, and While realizing a maximum active life of the catalyst employed, Other mixtures of saturated hydrocarbons, such as those; of straight run gasoline, casing head' gasoline, e. etc. containing appreciable quantities of normal butane, normal pentane, cyclohexane, methylcyclohexane or other lower-boiling non-branched saturated hydrocarbons, maybe advantageously treated to produce products-which are suitable for alkylation with olefines and havesuperior ig-' nition characteristics. j V

"The hydrocarbon or mixture of hydrocarbons treated is preferably, substantially free of materials which are polymerized by aluminum'chlor ride under the reaction conditions. According-to the preferred embodimentofthe inventiom any olefines, diolefines or other detrimental impurities in the hydrocarbon or'hydrocarbon mixture montmorillonite, the permutites and the like; the

lysts employed in the presentiprocess are pre-.

pared by mixing certain inorganic promoters with sufflcient-ailuminum chloride to'form a solid-cake and heating the mixture while under superatmospheric pressure to a temperature sufiiciently high to fuse the aluminum chloride, cooling-the mass to produce a solid cake, and then crushing said cake into small irregular fragments. The cata by older methods and possess valuable and unexpected properties and characteristics.

One of the advantages of the present process is 'due to the greater'activity and selectivity of the catalyst employed. activity is very pronounced in some cases and less so in othersanddeperids primarily upon the method of preparation and the particular materlalwithfwhich the aluminum chloride is combined." The more active catalysts employed in the present invention are true catalyst combinations. I Their increased. catalytic activity is due to a promoting effect of the so-called carrier which is materially enhanced by the described method of preparation. Another important advantageous characteristic of thecatalystsf which is utilized in the present process is their superior mechanical strength. Due, to their superior properties in this respect they can be employed in place of lumpaluminum chloride in larger, more economically employed beds. They also suffer much less disintegration during use, and consequently can be used for much longer periods of time before the efilclencyof the bed becomes impaired by channeling, etc. dueto disintegration.

Preferred materials to; be combined with alum'inum chloride in the preparation of the catalysts for the present process arethe various siliceous and/or aluminous materials of natural or synthetic origin which may contain an appreciable amount of firmly boun'd or strongly ,adsorbed water. Suitable materials of this category are, for example, the naturally-occurring minerals and clays such as pipe clay, bauxite, fullers earth, bentonite, kaolin, Florida earth, meefschaum, infusorial earth; kieselguhr, diatomaoeous earth,

various treated clays and clay-like materials; the artificially prepared materials such as activated lysts produced by this procedure are quite dif ferent than the impregnated catalysts prepared,

is a'trade name for an especially adsorptive alumina prepared bythe Porocel Corporation from a selected bauxite. Although highly active (adsorptive) materials such as Activated Alumina and Porocel are much preferred, it is to be particularly noted that it is the particular surface composition and characteristics of these materials andj not their adsorptive quality which are responsible for their superiority in the catalyst used in the process of the present invention. These materials," as purchased, are usually activated (calcined) just sufliciently to produce their maximum adsorptive ability and further calcination results in a decrease in their adsorptive .properties.

' may exhibit an even, greater promoting effect upon This increased catalytic V alumina, the artificial permutites and the like.

Thesematerials are preferably but not necessarily partially dehydrated by heating in a dry atmosphere at a temperature somewhat higher than-that at which they are {to be employed. 7

Of thesematerials and similar materials of this category, Activated Alumina and ,Porocel are found to be particularly effective. Activated Alumina" is a trade-mark name for a highly adsorptive alumina prepared and'sold by theAluminimi'Ore Company. It is designated Actia vated Alumina.because of its active Iad sorptive 7 properties ;and should not bewconfused with various aluminas which have been ma e catalytically active and are thus said to havezbeen activated. Activated-Aluminaf'is said to beprepared accordingto the method more .fully described and claimed in United States Patent 1,868,869. Other the aluminum chloride if they are calcined somewhat further than to give the maximum adsorptlve ability. Care should be'exercised, however. not to over-calcine or dead-burn" the materials since if over-calcinedthey lose theirpromoting effect and instead of producing a superior promoted catalyst with aluminum chloride, they merely act as diluents. I

" Although materials of the aboveclasses are active in promoting the isomerizing ability of alu- 'minum chloride and produce the most active catalysts, any of the common catalyst carriers or supporting materials, such as activatedcharcoal, V

crushed coke, crushed brick, pumice, porcelain chips, chamotte, asbestos. and the like, may also be used, if desired. The most important'advantagesfoifered by these lattermaterials are their high mechanical strength and low cost. They are most advantageously used in conjunction with one or more of the above-mentioned promoting v materials. Y

The promoting and carrier material may be in theform of small broken pieces or as a fine powder, and may be employed either singly or in ad-.

mixture with one another. Thus, for example, an excellent catalyst of high mechanical strength and low cost may consistof anhydrous aluminum chloride, powdered Porocel, and 8-10 mesh' pumice. v

For the preparation of the catalyst any substantiallyanhydrous aluminum chloride such as the powdered commercial product may be used. The'catalyst is preferably prepared, however, from materials which are as low as practical in iron. In such cases where one or more of the materials contain appreciable quantities of iron, the deleterious effect of this substance may be counteracted to a considerable extent by the addition of a small quantity of aluminum into the mixture prior to fusing to form the cake. Instead of adding aluminum powder, filings, tumings or the like, the sameeflect may be achieved by performing the fusing operation in an aluminum or aluminum-lined vessel. i V The catalysts employed in the present process may contain various concentrations of aluminum chloride, for example, from about. 25% up'to about 95. The aluminum chloride, however, is

alwayspresentinsufiicient quantity to bind the catalyst promoter into a'solid cake;

Thealuminum chloride and promoter materials, preferably well mixed, are heated at a temperature of at least about 200 C. to 300 C.) under a pressure of at least, 40 pounds per square inch. Excellent catalysts may be prepared using-pressure ranging It is found, however, that these materials C. (for instance, at r from about 100 to *800 pounds per squareinch. The desired pressure may be imposed by air, N2, C02, H2, HCl or the like. After heating the mixture for a few minutes or longer, the catalyst may be handled ineither one of two ways. Catalysts of the maximum physical strength may be prepared by allowing the fused m'assto cool and solidify, releasing the pressureand breaking the solid cake into fragments of the desired size. On

the other hand, more porous catalysts exhibitinga maximum surface and light weight may be prepared by causing the fused catalyst mass to swell or froth by decreasing the pressure just prior to solidification. The porous cake is then crushed or ground in the usualmanner, preferably in a'dry atmosphere. Undersized fines produced in grading the catalyst in either case may be added to the next batch of catalyst. These catalysts are more fully described and claimed in our copending application, Serial'No.

290,256, filed August 15, 1939, of which the present application is-a' continuation-in-part.

provided with means of establishing andmaina taining the desired temperature, and the material to be isomerized is passed in the vapor phase at a suitable space velocity therethrough. In operation in the liquid phase the catalyst may be conveniently suspended as a fixed bed in an elon-,

gated tower through which the liquid hydrocarbon to be isomerized is percolated.

In order to realize the full activity of the influenced by the deliberate addition of noncondensable gases such, in particular, as. the hydrogen halide promoter, H2, etc. ,In general, the isomerization is effected at moderately ele vated temperatures such, for example, as from about 50 C. to about 150 C. Lower or higher temperatures such, for example, as from room temperature up to about 300 employed, if desired. .Since, however, the object of theprocess is toisomerize saturated hydrocarbons or increase the ignition characteristics of saturated hydrocarbon fractions through isomerization, and since side reactions considerably decrease the efliciency and shorten the life of the catalyst, the temperatures or other conditions are not allowed to become so severe as to cause substantial degradation or other side reactions to take placea The isomerization reaction is somewhat exothermic. When employing catalytic reactors of comparatively large cross section such as can be employed with the present catalysts, andparticularly when the reaction temperature is adjusted catalyst it is most desirable to execute theisomerization in the presence of 'a hydrogen halide. The desired hydrogen halide may be added directly to the reaction zone of the feed or may be produced in the reaction zone by the addition of a small quantity of a substance which will react or decompose under the reaction conditions to liberate the desired hydrogen halide. Suitable materials of this latter category are, for exam--' ple, water, alcohols, alkyl halides, etc. The amount of hydrogen halide preferably employed depends somewhat upon the particular circumstances. When executing the isomerization in the vapor phase a small amount of hydrogen halide, for example, 0.1% to 5%, may be added to the feed and removed from the product by a suitable washing treatment. It is preferable, however, when it is economically feasible, to recover the hydrogen halide from the product, for example, by fractional distillation, and to recyle the same through the reaction zone. In-this way much higher concentrations of hydrogen halide, for example, 3% to 25%, may be economically employed. When operating in the liquid phase the hydrogen halide is preferably employed in such a concentration that its partial pressure over the reaction mixture is at least three atmospheres.

The isomerization process is usually executed at atmospheric pressure or somewhat elevated pressures, for example, 3 to 50 atmospheres' The prevailing pressure will depend somewhat upon the treating temperature but may also be not far below that at which appreciable side reactions begin, localized zones of higher temperature may be caused by the exothermic heat of reaction. This condition may be avoidedby'supplying the fresh feed at a plurality of points along the length of the catalyst, bed.

Example I Two parts-by weight of powdered anhydrous aluminum chloride were mixed 'with one part of activated alumina previously crushed to 150 to 200 mesh and dried for two hours at 300 C. The mixture was placed in a pressurevessel equipped with heating means, the vessel closed, nitrogen introduced, and the whole heated to about 210 C.

After heating for a time at a pressure of about 300 pounds per square inch, the mixture was pressure released prior gradually cooled and the to solidification, whereupon the mass swelled','or rose, and solidified into a hard porouscake. Upon crushing the cake and grading, anexcellent' cat- ;ayllst of uniform composition and particle size,

large surface area, high mechanical strength, low apparent density and low cost was obtained.

Normal butane vapor containing. a small amount of HCl was passed at various rates atll atmospheres pressure through a reaction tube filled with the catalyst prepared as described and r maintained at approximately C. The following conversions to isobutane were obtained:

Conversion percent N- butane converted Space velocity (vials) (liter) (hr)' I j to isobutana Example [I t Normal butane vapor containing a small amount oi. H01 was passed at of 5.4 mols per liter per hour and square inch through a, catalytic with a catalyst prepared as described in Example I and maintained at 100 C. At'thebeginnlng, the conversion of normal was about 46% to 48%. of continuous operation, mal butane to isobutane the catalyst showed no pounds per was still about 45%, and indication of exhaustion. were negligible.

C. may, however,be v

a space velocity chamber filled butane to isobutane At the end of 318 hours 7 the conversion of nor- As will be seen from these examples, the isomerization of normal butane (which is most difllcult to isomerize) according to the present 7 process takes place readily at comparatively low temperatures. Excellent conversions are obtained over protracted periods of time at high sentially of saturated hydrocarbons containing from four to nine carbon atoms in the presence of a hydrogen halide at a-temperature between 20 C. and 300 C. under isomerization conditions with a bed of a foraminous promoted aluminum chloride catalyst prepared by fusing together a finely divided mineral promoter selected from the group consisting of partially dehydrated siliceous and aluminous materials normally containing firmly bound water with sufficient anhydrous aluminum chloride to form a solid cake upon cooling, at a temperature of at least 190 C. under a pressure of at least 40 pounds per square inch, causing the fused mass to swell or foam by decreasing the pressure just prior to solidification. cooling the swollen mass to produce a foraminous cake, and breaking -said foraminous cake into irregular fragments.

2. A process for the isomerization of butane comprising the step of contacting normal butane vapors in the presence of a hydrogenhalide at a temperature between 50 C. and 300 C. under isomerization conditions with a bed of a foraminous promoted aluminum chloride catalyst prepared by fusing together a finely divided mineral promoter selected from the group consisting of partially dehydrated siliceous and :aluminous materials normally containing firmly bound water with sufficient anhydrous aluminum chloride to form a solid cake upon cooling, at a temperature of at least 190 C. under a pressure of at least 40 pounds per square inch, causing the fused mass to swell or foam by decreasing the pressure just prior to solidification, cooling the swollen mass to produce a foraminous cake, and breaking said foraminous cake into irregular fragments.. a

3. A process for the isomerization of pentane comprising the step of contacting normal pentane in the vapor phase in the presence of a i hydrogen halide under isomerization conditions with a bed of a foraminous promoted aluminum chloride catalyst prepared by fusing together finely divided mineral promoter selected from the group consisting of partially dehydrated siliceous and aluminous materials normally containing firmly bound water with sufficient anhydrous aluminum chloride to form a solid'cake upon to swell or foam by decreasing the pressure just a sentially of saturated hydrocarbons containing from four to nine carbon atoms in the presence of a hydrogen halideat a temperature between 20 C. and 300 C. under isomerization conditions with a bed of a foraminous promoted aluminum chloride catalyst prepared by fusing together a finely divided partially dehydrated alumina normally containing firmly bound water with sumclent anhydrous aluminum chloride to form a solid cake upon cooling, at a temperature of at least C. under a pressure of at least 40 pounds per square inch, causing the fused mass prior to solidification, cooling the swollen mass to produce a foraminous cake, and breaking said foraminous cake into irregular fragments.

5. A process for the isomerization of butane comprising the step of contacting normal butane vapors in the presence of a hydrogen halide at a temperature between 50 C. and 300 C. under isomerization conditions with a bed of afforaminous promoted aluminum chloride catalyst prepared by fusing together a finely divided partially dehydrated alumina normally containing firmly bound water with sufficient anhydrous aluminum chloride to form a solid cake upon cooling, at a temperature of at least 190 C. under a pressure of at least 40 pounds per square inch, causing the fused mass to swell or foam by decreasing the pressure just prior to solidification, cooling the swollen mass to produce a foraminous cake, and breaking said foraminous cake into irregular fragments.

6. A process for the isomerization of pentane comprising the step of contacting normal pentane in the vapor phase in the presence of a hydrogen halide under isomerization conditions with a bed of a foraminous promoted; aluminum chloride catalyst prepared by fusing; together finely divided partially dehydrated alumina nor-' mally containing firmly bound water with sufficient anhydrous aluminum chloride to form a solid cake upon cooling, at a temperature of at least 190 C. under a pressure of at least 40 pounds per square inch, causing the fused mass to swell or foam by decreasing the pressure just prior to solidification, cooling the swollen mass to produce a foraminous cake into irregular fragments.

MARTIN DE snvro.

FRANK MAT'I'HEW'MCMILLAN. HARRY ASHLEY CHENEY.