US2250118A - Isomerization of hydrocarbons - Google Patents

Description

Patented July-22 1941 ISOMERIZATION F HYDBOCABBONS Wilhelm Carol Brezesinska Smithuysen, Amsterdam, Netherlands, assignor to Shell Development Company, San Francisco, CaliL, a corporation of Delaware No Drawing. Application March a, 1939, Serial No. 260,147. In the Netherlands April 1, 1938 4 Claims. (Cl. 260-676) This invention relates to the catalytic isomerization of hydrocarbons. and it particularly relates to the catalytic isomerization of the saturated paraiiin hydrocarbons.

An object of the invention is to provide a practical and economical process. adapted to operation on a commercial scale, for the production of the commercially more valuable branched or more highly branched chain paraffin hydrocarbons from the corresponding normal or less branched chain paramn hydrocarbons.

Another object of the invention is to provide a process for the catalytic isomerization of the normal and slightly branched chain paraflin hydrocarbons to the corresponding isoor more highly branched chain hydrocarbons which is characterized by the use of a selective and particularly active isomerization catalyst which permits selective isomerization of the treated hydrocarbon or mixture of hydrocarbons under such conditions that practical conversions to the de-' sired branched or more branched chain isomers are obtained while undesirable side reactions such as cracking, dehydrogenation, etc., are reduced to a practical minimum.

The process of the invention is of great technical importance in that it provides a simple and effective method for converting the less valuable,

the corresponding oleflnes. The isoparamn hydrocarbons can be easily dehydrogenated to the corresponding tertiary olefines which in turn are valuable starting materials in the production of tertiary alcohols, tertiary alcohol derivatives, un saturated tertiary carbon atom-containing alcohols, etc., as well as in the production of high anti-.knock motor fuels and motor fuel constituents via copolymerization, or interpolymerization with ethylene or secondary olefines, followed by hydrogenation of the resulting polymer product. The isoparafiin hydrocarbons are also much more suitable than the normal paraflin hydrocarbons as starting material in the production of motor fuels by alkylation, that is, by reaction of the paraflin hydrocarbon with an olefine in the presence of a suitable catalyst.

The process of my invention comprises contacting the hydrocarbon to be isomerized, or a because less reactive, normal parafifln hydrocarbons to the corresponding more reactive and more valuable iso or branched'chain paraflin hydrocarbons. The branched chain paraflin hydrocarbons which boil within the gasoline boiling range are, because of their relatively much higher anti-knock value, of greater value and in more demand than the normal hydrocarbons of the may be applied directly to hydrocarbon fuel mixtures containing relatively high percentages of normal or only slightly branched paraflin hydrocarbons to isomerize said hydrocarbons and thus increase the total anti-knock value of the fuel mixture with a minimum of treatment and with substantially no loss of the treated material.

The lower boiling isoparaflin hydrocarbons such as isobutane, isopentane, the isohexanes, etc are relatively much more valuable than the normal compounds of the same number of carbon atoms because of their. greater activity per se and because of the much greater reactivity of mixture of such hydrocarbons, or one or more of such hydrocarbons in the presence of an inert diluent material incapable of isomerization such as aromatic hydrocarbons, substantially completely isomerized paraflin hydrocarbons, nitrogen, hydrogen, etc., with a catalyst consisting of or essentially comprising a double compound of an acid-acting metallic halide with an aromatic compound at a. temperature at which 'the isomerization proceeds at a practical rate but at a temperature below C., the material to be I isomerized being contacted with the catalyst for a time suflicient to eflfect the desired isomerization but insuflicient to effect any substantial decomposition such as cracking or dehydrogenation of the treated material.

By use of the special catalyst herein defined, the desired degree of isomerization can be effected while undesirable side reactions are reduced to a practical minimum, and, in some cases, substantially completely obviated. The special catalyst is, when used under the conditions herein specified, a selective isomerization catalyst, it accelerates substantially only the isomerization reaction and permits the isomerization to be effected rapidly and to the desired extent 'under conditions at which the occurrence of undesirable side reactions can be substantially obviated. It is known that aluminum chloride is a catalyst for the isomerimtion of paramn hy drocarbons. However, this knowledge has failed drocarbon molecule toward the center of the carbon chain; consequently the process can be advantageously applied to the treatment of any hydrocarbon possessing a structure capable of modifications in such a way as to result in a hydrocarbon molecule containing the same-number of carbon atoms but being of a more condensed type. The process can be applied to the isomerization to an isoparaflin of any of the normal paraflin hydrocarbons higher than propane. The class of suitable normal paraflin hydrocarbons starts with normal butane, which is normally gaseous, and includes the normally liquid normal paraflin hydrocarbons such as normal pentane, normal hexane, normal heptane, normal octane, normal nonane and the like. Suitable already branched chain hydrocarbons which can be isomerlzed to still more branched chain hydrocarbons in accordance with the process of the invention may be pentanes, hexanes, heptanes, octanes, nonanes, etc. The hydrocarbons or hydrocarbon mixtures treated are preferably those which boil at a temperature not greater than about 100 C. and thus comprise the hydrocarbons with from four to seven carbon atoms inclusive.

For purposes of convenience and clearness of description only, the process will hereinafter be described with reference to its use to convert a normal paraflin hydrocarbon containing at least four carbon atoms to the corresponding isopar aflin hydrocarbon.

V The process may be applied to the treatment of a pure or substantially purenormal paraflin hydrocarbon, or tea hydrocarbon mixture comprising one or -more normal parafiin hydrocarbons.

For example a suitable starting material may comprise, besides a substantial amount of a normal paraflin hydrocarbom one or a plurality of other-hydrocarbons which may not be capable of isomerization under the conditions of the operation, or the treated mixture may comprise one or more normal paraffin'hydrocarhons and a substantially'inert diluent material such as hydrogen, nitrogen and the like. The invention provides means for converting to isoparaflin'hydrocarbons the normal parafiin hydrocarbon content 3 of cracked gasolines and other commercial hydrocarbon mixtures such as are obtained by the cracking of higher molecular weight hydrocarbons and hydrocarbon mixtures such as 'petro leum oils, shale oils, petroleum products, animal and vegetable oils, waxes and the like. Conveniently treatednormal paraflin hydrocarbon-containing mixtures are the so-called alkane-alky lene fractions such; as the butane-butyiene fraction, the pentane-pcntylene fraction, etc. from which the olefines havejpreferably been removed. Treatment of such mixtures results in materially increasing their isoparaflin hydrocarbon content.

The catalysts used'in the process essentially comprise a double compound of an acid-acting halide and an aromatic compound. The term acid-acting halide i used herein and in the appended claims to designate those metallic or non-metallic halides (other than the hydrogen halides) which will give anacid reaction in water. Representative acid-acting halides are the boron halides, the halides of aluminum, zinc,

iron, zirconium, tin, beryllium, and the like. The acid-acting halide is present in the catalyst as a double compound with an aromatic compound. These double compounds may be regarded as the additive compound of an acid-acting halide with an aromatic compound.

A preferred group of catalysts for use in the process of the invention comprises the double compounds of the aluminum halides (aluminum chloride, aluminum bromide, aluminum iodide and aluminum fluoride) with an aromatic hydrocarbon, particularly an aromatic hydrocarbon which has been substituted by one or more alkyl groups. Representative catalysts of this preferred group are the double compounds of an aluminum halide, preferably aluminum chloride, with an aromatic hydrocarbon such as toluene, dimethyl benzene, trimethyl benzene, ethyl benzene, triethyl benzene, propyl benzene, di-

propyl benzene, the isopropyl benzenes, the normal butyl benzenes, the tertiary butyl benzenes,

the amyl benzenes, the mixed alkyl benzenes such as ethyl toluene, dipropyl toluene, etc., the monoand polymethyl naphthalenes, the mono-' and polyethyl, p'ropyl, butyl and the like alkyl naph thalenes, the mixed alkyl naphthalenes, the alkyl anthracenes, the alkenyl benzenes, naphthalenes, anthracenea'eta, the mixed alkyl-alkenyl benzenes,naphthalenes,anthracenes and the like, and their homologues, analogues and suitable substitution products. 7

The aluminum halide-aromatic hydrocarbon double compounds may, in general, be regarded as the additive compounds of two mols of the aluminum halide with one mol of the aromatic hydrocarbon which may or may not be alkyl and/oralkenyl substituted. A representative catalyst, namely, the double compound of an aluminmn halide with a dialkyl benzene, may be represented by the formula 2Al(Hal) a.CsH4(R) 2, wherein R represents an alkyl radical.

' The aluminumhalide-aromatic hydrocarbon double compound catalysts may be prepared in any suitable manner. A convenient method of preparing the aluminum halide-alkylated aromatic hydrocarbon double compound catalysts comprises adding the preferably anhydrous aluminum halide to the liquid non-alkylated aromatic hydrocarbon such as benzene and adding to the mixture in a regulated amount the desired quantity of the alkylhalide corresponding to the alkyl radical which it-is desired to substitute m b the aromatic hydrocarbon. The alkyl halide is preferably added slowly while intensively agitating the reaction mixture, as by mechanical stirring, and while maintaining the reaction mixsame type in any suitable manner as hereinafter quently the presence of water during their preparation, storage and use should be avoided.

The process of the invention is executed at temperatures below 150 C. and preferably at temperatures of from 20 C. to 140 C. A favorable conversion of the treated hydrocarbon material is often obtained at room temperature or only slightly elevated temperatures. In general, temperatures equal to or higher than 150 C. are not suitable because at about this temperature the catalysts used in the process lose their selective isomerization power and begin to accelerate cracking and other decomposition reactions.

The process may be executed with the hydrocarbon compound to be treated in either the gaseous or the liquid phase. When operation in the liquid phase is desired, the hydrocarbon material to be treated and the catalyst may be charged to a suitable reaction vessel in the desired relative amounts and the mixture maintained at the desired temperature for a time necessary to effect the desired extent of isomerization. The, relative proportions of the catalyst and the hydrocarbon material to be treated may vary overa comporatively wide range, and will, in general, depend upon the particular hydrocarbon material to be treated, upon the particular catalyst used, and upon thespeciflc temperature and contact time employed. In general,-

the hydrocarbon to be treated is present in relatively great excess over the catalyst. If desired,

the gaseous hydrocarbon or hydrocarbon mixture may be contacted with the catalyst. This may be done in a variety of suitable manners. For example, when the catalyst-is a liquid, it may be maintained at the desired temperature, with stirring if desired, while the gaseous hydrocarbon material is bubbled through it at the desired rate. If desired, the liquid or solid catalyst may be adsorbed on or supported on the surface of a suitable solid carrier material such as clay, charcoal, alumina, pumice, diatomaceous earth. The gaseous or liquid hydrocarbon material may be contacted with the solid or adsorbed catalyst in the conventional manners.

The presence in the reaction system of a hydrogen halide or substance capable of yielding a hydrogen halide under the conditions existing in the reaction system, in some cases, has a beneficial effect upon the' life and activity of the catalyst. Thus, a hydrogen halide, such as hydrogen chloride and hydrogen bromide, may be added to the reaction mixture or separately added to the reaction zone in the desired amount in any convenient manner, intermittently or continuously. In lieu of a hydrogen halide per se,

a controlled amount of a 'compound,- such as propyl chloride, tertiary butyl chloride, propyl bromide, tertiary butyl bromide and the like alkyl halides, which will decompose under the reacisomerization reaction, th process is preferably tion conditions to yield a hydrogen halide, may be intermittently or continuously added.

The process may be executed under atmospheric, subatmospheric or 'superatmospheric pressure. Since pressure, in general, favors the executed at atmospheric or at a superatmospheric pressure. When operation under pressure is resorted to, pressures up to about 30 atmospheres are generally sufiicient. I! desired,

relatively inert diluent materials such as hydrogen, nitrogen, methane, ethane, propane, etc.,.

may be added to the'material treated or separately introduced into the reaction zone to aid in establishing and/or maintaining the desired operating pressure. For example, the process may be executed with a substantial partial pressure of hydrogen in the reaction zone. Such added hydrogen or other inert'gas may have the The process may be executed in a batch, in-

When sepa-.

termittent or continuous manner. ration of isomerized hydrocarbon from the unreacted material is desired, such separation may.

be eifected in any suitable manner as by tractional distillation, selective absorption, selective reaction, etc.

The following examples illustrate suitable modes of executing the process of the invention.

The invention is not to be regarded as restricted to the particular catalysts, the particular modes of operation, the particular hydrocarbons treated, or the particular operating conditions specified in the examples.

Example I The catalyst was prepared'in the following manner: About 2.5 mols of anhydrous aluminum chloride were suspended in about 3.0 mols of benzene. This mixture was stirred and maintained at a; temperature of about 0" C. while a total of about 2.0 mols of tertiary butyl chloride was added slowly, a small quantity at a time. When all of the tertiary butyl chloride had been added, and the reaction was apparently complete, the unreacted aluminum chloride was separated from the liquid by decantation. The liquid was then heated to about C. under reduced pressure to remove the unreacted benzene. The residue was an oily liquid consisting of the complex double compound 0f aluminum chloride and tertiary butyl benzene, and containing about 66% by weight oi aluminum chloride.

About 40 cc. of the liquid catalyst were added to about gm. of normal pentane and the mixture maintained at a temperature of about 35 C. for about 2.5 hours and later allowed to stand for some time at about room temperature. The hydrocarbon material was then separated from the catalyst material, washed with water, dried and analyzed. It was found that about 18.3% of the treated normal pentane had been isomerized to isopentane, with no appreciable amount of decomposition. About 73% of the appliednormal pentane was recovered unchanged.

Example II carbon double compound catalysts was prepared.

' Among the catalysts of this group prepared and treatment, and with the aluminum chloride-iso- -propyl benzene catalyst about 13.5% of the normal pentane was converted to isopentane in a single treatment.

Example III 100 gm. of normal pentane were heated with 30 cc. of the complex catalyst prepared as described in Example I and with 30 gm. of hydrogen chloride during 120 hours at a temperature of 120 C. in a closed vessel of 1 liter capacity.- After separation from the catalyst material. the

reaction product was proved to contain 40 gm.

isopentane, 44 gm. non-converted normal pentane, 12 gm. isobutane, 2 gm. normal butane and 2' gm. propane.

While I have described my invention in a, detailed manner and provided specific examples illustrating. suitable modes of executing the.

same,- it is to be understood that modifications may be made and that no limitations other than those; imposed by the scope of the appended claims are intended. I

I- claim as my invention: 1. A process for the production of isopentan which comprises contacting a saturated hydro carbon traction consisting essentially of normal pentane in the liquid phase in the presence oi hydrogen chloride with a preformed complex compound oi aluminum chloride and an alkylated aromatic hydrocarbon in which the aluminum chloride is present in the greater mol ratio in the substantial absence 01' solid" aluminumchloride and at a temperature of from 20 C. to

nating reaction the isomerization of normal pentane toisopentane.

2. A process for the conversionxoi a ndrmal paramn hydrocarbon to a branched chain parailln hydrocarbon containing the same number of carbon atoms which comprises contacting a saturated hydrocarbon traction consisting essentially of a normal paraflln hydrocarbon having four to nine carbon atoms in'the liquid phase in the presence of hydrogen chloride with a preformed complex compound of aluminum chloride and an alkylated aromatic hydrocarbon in which the aluminum chloride is present in the greater mol .ratio in the substantial absence of solid aluminum chloride and at a temperature of from 20 C. to 140 C. whereby there is effected as the predominant reaction the isomerization ofv said normal paraflln hydrocarbon to a corresponding branched chain isomer.

3. A process for the isomerization of saturated hydrocarbons which comprises contacting a saturated hydrocarbon fraction consisting essen tially of saturated hydrocarbons having between four and nine carbon atoms in the presence ofhydrogen chloride with a preformed complex compound of aluminum chloride and an alkylated aromatic hydrocarbon in which the aluminum chloride is present in thegreater mol ratio in the substantial absence of solid aluminum chloride and at a temperature ofi'rom 20' C. to 140 C. whereby there is effected as the predominant reaction the isomerization of the saturated hydrocarbons of said fraction.

4. A process for the isomerization of saturated hydrocarbons which comprises contacting a saturated hydrocarbon traction consisting essentially of saturated hydrocarbons having between four and nine carbon atoms in'the presence of a hydrogen halide with a preformed complex compound of an aluminum halide and an alkylated aromatic hydrocarbon in which the aluminum halide is present in the greater mol ratio in the substantial absence 01' solid aluminum halide and at a temperature of from 20 C; to 140 C. whereby there is eflectedas the predominant reaction the isomerization oi the saturated hydrocarbons of said fraction.

' WIL'HELM CAREL BREZESINSKA sm'rnoysnn.