US2804489A - Conversion of olefinic hydrocarbons to isomers containing a more centrally located double bond - Google Patents

Description

CONVERSION OF SLEFINEQ HYDROCAREQNS TO ISOIVERS CONTAENHNG A MORE CENTRALLY LOCATED DQUBLE BGND Herman Pines, Chicago, Ill, and Vladimir N. lipatietf, deceased, late of Chicago, E11,, by Vladimir Haensel, Hinsdaie, and Herman Pines and Vincetta Kihort, Chicago, llL, executors, assignors to Universal H Products Company, Des Plaines, lit, a corporation of Delaware N 0 Drawing. Application March 30, 1953, Serial No. 345,716

13 Claims. (6i. 260-683.2)

This invention relates to an isomerization process for shifting the double bond of an olefinic hydrocarbon to a more centrally located position in the carbon atom chain, referred to generally as position isomerization. More specifically, the invention concerns an olefin isomerization process etfected in the presence of a catalyst comprising an alkali metal under conditions whereby the resulting olefinic product contains a more centrally located double bond than the olefin subjected to isomerization.

One embodiment of the present invention relates to a process for shifting the double bond of an olefinic hydrocarbon to a more centrally located position in the carbon atom chain thereof, which comprises subjecting said olefinic hydrocarbon to isomerizing reaction conditions in the presence of an alkali metal.

In one of its more specific embodiments the invention concerns an isomerization process wherein an olefinic hydrocarbon having a double bond in the 1-position is converted to an isomer thereof having a more centrally located double bond which comprises reacting said olefinic hydrocarbon with metallic sodium at a temperature of from about 150 to about 350 C. and in the presence of a promoter comprising a halogen-substituted hydrocarbon, said promoter being present in the reaction mixture in an amount of from about 0.01 to about 0.1 mol per mol of olefinic hydrocarbon.

It is generally recognized that motor fuels containing a greater proportion of highly branched chain hydrocarbon components are more suitable for motor fuel use in high compression ignition engines than their corresponding isomers of straight chain or relatively unbranched chain structure because of the lesser tendency of the branched chain hydrocarbons to knock on ignition under high compression. It is also generally known that such branched chain hydrocarbons may be produced from low molecular Weight hydrocarbons by the process known as alkylation in which an isoparafiin hydrocarbon is condensed with an olefinic hydrocarbon in the presence of an acidic condensation catalyst and that the more desirable alkylates of high anti-knock properties are produced from olefinic hydrocarbon alkylating agents in which the double bond of the olefin is in a centrally located position of the carbon atom chain rather than in the terminal position thereof. Thus, for example, the alkylate product derived from butene-Z is a more highly branched chain hydrocarbon, and hence a more desirable motor fuel com ponent, than the alkylate derived from l-butene, the former yielding a greater proportion of iso-octane than the l-isomer when condensed with iso-butane.

The olefinic feed stocks generally available for alkylation purposes and normally utilized for the present reaction are generally mixtures of olefinic hydrocarbons of approximately the same molecular weight, including both the l-isomer, Z-isomer, and other position isomers capable of undergoing isomerization to an olefin in which the rates Patent 6 ar 2,804,489 Patented Aug. 27, 1957 double bond occupies a more centrally located position in the hydrocarbon chain. In order to provide an olefinic feed stock for alkylation purposes containing an optimum proportion of the more centrally located double bonded isomers therein, it is desirable to convert the l-isomer or other position isomer component of the mixed feed stock into the corresponding 2-isomer or into olefins wherein the double bond is more centrally located in the carbon atom chain. When higher molecular weight olefinic feed stocks are utilized such as hexylene, the 1- and 2-position isomer components are desirably converted into isomers containing the double bond located in the 2- and 3- positions.

The olefinic hydrocarbon feed stock to the present process containing the unbalanced double bond position isomers (unbalanced that is, with respect to the size of the hydrocarbon chains attached to the doubly bonded carbon atoms) may be derived from any suitable source and may consist of essentially pure l-isomer, 2-isomer, 3-isomer etc., or a mixture of the l-isomer with other position isomers or with higher or lower molecular weight olefinic or parafiinic hydrocarbons. One of the more readily available sources of such olefinic hydrocarbon feed stocks, particularly for alkylation purposes, is the normally gaseous and the light fractions of the products of thermal or catalytic hydrocarbon cracking reactions. Thus, a mixture containing l-butene, as well as isobutylene, 2-butene, n-butane and isobutane may be recovered as the light vapor overhead from the products of a thermally cracked gas oil fraction. The olefins may also be produced by dehydrating the normal or iso-alcohols, by dehydrogenation of paraffim'c hydrocarbons, dehydrohalogenation of alkyl halides and from other sources well known in the art. The term olefinic hydrocarbons as utilized herein also refers to di-olefins and aryl-substituted olefins in which at least one double bond of the carbon atom chain of the olefinic radical is in a position closer to the end of the hydrocarbon chain than the center of the chain, as in the case of the 1-position of olefins containing at least 4 carbon atoms per molecule, the 2- position in olefins containing at least 6 carbon atoms per molecule, the 3-position in olefins containing at least 9 carbon atoms per molecule, the 1,4-position in diolefins containing at least 5 carbon atoms per molecule (being isomerized to the corresponding 1,3- and/or 2,3-positions) etc. Other suitable olefinic feed stocks in the present isomerization process may include non-conjugated diolefins such as 1,4-pentadiene, 1,4-hexadiene, 1,5-hexadiene, 4-vinylcyclohexene, etc. An aromatic hydrocarbon containing an olefinic side chain (alkenyl or alkapolyenyl side chain) will undergo isomerization in the present process to form a compound in which the double bonds are conjugated in relation to the aromatic double bonds as for example, in allylbenzene (i. e., 2-propenyl benzene), 1*phenyl-3-butene, l-phenyl-3-pentene, lphenyl-4-pentene etc. Suitable feed stocks thus include, generally, olefinic hydrocarbons of straight chain,

branched chain, cyclic, or aryl-substituted structure. The invention is also useful in the position isomerization of cyclic olefins in which the olefinic double bond occurs in the cyclic ring or in a side chain attached to the ring, the isomerization resulting in the transfer of the double bond from the unsaturated side chain into the ring. Thus, limonene (p-menthadiene), having double bond in the ring, as well as a double bond in a propenyl side chain, is converted in the present process to 5,6-dihydro-p-isopropyltoluene, the latter undergoing dehydrogenation upon further contact with the present catalyst at the isomerization reaction herein provided to p-methylcumene. Other instances of such position isomerization in the case of cyclo-olefins containing an alkenyl or alkadienyl side chain and the dehydroisomerization of such compounds to the corresponding aromatic hydrocarbons is known, as in the case of isopropenylcyclohexene, butenylcyclohexene, butenylcyclohexadiene, etc. the products therefrom being the corresponding alkylbenzenes. The process is also applicable to the long. chain olefins and diolefins containing up to about 20 carb'onatomsper molecule, whereby a corresponding olefin or diolefin contain ing the double bonds in a more central position in the carbon atom chain are produced. For example, decene-l is converted to decene-Z when subjected to the present isomerization catalyst at isomerization reaction conditions and upon continued reaction, dehydroisomerization results, forming a diene.

The isomerization reaction of the present process wherein an olefinic hydrocarbon is converted to an isomer thereof containing a more centrally located double bond is elfected in the presence of an alkali metal maintained in the reaction zone in its metallic state or in the form of a sodium addition product with a compound which promotes the isomerization reaction hereinafter and more specifically described. Of the alkali metal catalysts utilizable in the process and selected from the group consisting of lithium, sodium, potassium, rubidium and cesium, the generally more plentiful sodium and potassium alkali metals are usually preferred in the process because of their relatively lower cost in'comparison with other alkali metals. The catalyst metal may also be deposited upon or supported by an inert refractory substance, preferably selected from the refractory metal oxides such as alumina, silica, magnesia, etc. or on a separating material which promotes intimate contact between the reactants and catalyst such as coke, charcoal, pumice, quartz, refractory metal particles such as iron turnings, copper shot, ceramic saddles etc. The use of a refractory support or a separating material to distribute the alkali metal catalyst in the reaction zone is particularly advantageous as a means of promoting an extensive reaction and to improve the yields of isomerization or deliydroisomerization product.

The promoter as specified herein is a substance which when added to the reactants promotes the isomerization reaction, that is, increases the yield of isomerization product or accelerates the rate of reaction. Among the substances which particularly have this desirable effect on the reaction are certain organic compounds which form addition compounds or complexes with the alkali metal catalyst, including such compounds as certain types of hydrocarbons containing an acetylem'c linkage, such as acetylene which forms sodium acetylide; polynuclear aromatic hydrocarbons such as naphthalene, fluorene etc. and the various alkyl-substituted polynuclear aromatic hydrocarbons such as methylnaphthalene; certain'heterocyclic nitrogen-containing ring compounds such as pyridine, quinoline, pyrrole and compounds containing an azo linkage, such as phenyldiazobenzene. Still other types of organic compounds which act in the capacity of promoters for the present isomerization reaction are such compounds as metallo-organic compounds comprising a metal combined directly through a valence bond with a carbon atom of a hydrocarbon radical, including such compounds as lead tetra-alkyls, lead tetra-aryls, zincalkyls, mercury dialkyls and diaryls, and mercury tetraalkyls, as well as alkyl metal halides such as alkyl lead chlorides and the like. Other organic compounds useful as promoters are the organic halides, particularly the henzene and alkylbenzene halides, such as tolylchlorides,

specifically including orthochlorotoluene and the like, as

well as the alkyl and alkenyl halides, including ethyl bromide, butyl chloride, allyl chloride, henzyl chloride etc.

This isomerization process of this invention is elfected at temperatures of from about 150 to about 350 C. and preferably at temperatures of from 225-275 C. and at super-atmospheric pressures of from about, 'to about 100 atmospheres. The olefinic hydrocarbon charged to the isomerization process is contacted with the alkali metal catalyst, preferably in the presence of one of the aforementioned promoters, under conditions whereby intimate contact between the alkali metal catalyst and the olefinic hydrocarbon is effected. In accordance with one method for obtaining the reaction, the olefinic hydrocarbon is led continuously through a fixed bed containing the alkali metal catalyst which is desirably supported on an inert refractory support of the type hereinbefore indicated, the isomerization reaction product being removed from the opposite end of the fixed bed reactor, also as a continuous stream. Another suitable method of effecting the reaction comprises charging the olefinic hydrocarbon reactant, the promoter, and alkali metal catalyst into an autoclave reactor maintained at the desired pressure, and continuing the reaction until the desired degree of isomerization is effected, usually within a reaction period of one hour or less. The latter batch-wise type of operation is particularly suitable when utilizing a liquid olefinic hydrocarbon charging stock, such as an olefinic hydrocarbon of relatively high molecular weight, including, for example, such olefins as octene-l, dodecylene, pentadecylene, alkadienes such as the alkenylcyclohexenes, their cyclic alkyl-substituted derivatives, etc. In the batch process of the above type the catalyst and olefinic hydrocarbon are preferably mixed during the course of the reaction, for example, by utilizing a reactor containing stirring paddles or a rotating autoclave.

The alkali metal catalyst utilized in the process is provided in a' quantity suflicient to form an alkali metal addition product wtih the promoter, for those promoters which undergo additional reaction with the catalyst. In general, a suitable quantity of catalyst charged to the process is from about 0.05 to about 0.5 atomic proportions of alkali metal per molecular portion of olefinic hydrocarbon charged to the reaction zone. The catalyst isgenerally useful for successive charges of olefinic hydrocarbon or until the catalyst becomes deactivated by contarnination with hydrocarbonaceous decomposition prodnets of the isomerization reaction. Although not necessarily essential to the isomerization reaction, the promoter generally increases the rate of the reaction and the yield of product therefrom, such that its inclusion in the reaction mixture is generally preferred over an exclusively thermal reaction. Depending upon the class of promoter compound utilized in the reaction, suitable quantit-ies thereof'in the reaction mixture are from about 0.01 to about 0.1 mol of the promoter compound per molecular proportion of olefinic hydrocarbon charging stock. In those instances wherein the promoter combines with the alkali metal to form an alkali metal addition product' thereof, the addition product may be formed prior-to the isometrization reaction in a separate reaction zone and thereafter added to the isomerization reactor in the desired quantity. In general, however, the alkali metal, promoter and olefinic hydrocarbon may be reacted together in the same contacting zone to obtain the desired isomerization reaction.

The isomerization of the olefinic hydrocarbon in the presence of the alkali metal catalyst generally approaches equilibrium within a reaction period of from about 5 minutes to about 1 hour, although either shorter or longer reaction periods may be provided for particular feed stocks, particularly when the dehydroisomerization type of reaction is desired to form the ultimate product of the process, such as an alkylbenzene hydrocarbon. When dehydroisomerization is desired as the ultimate process, the reaction may be continued for reaction periods'of from 0.5 to 6 hoursor longer, the time required, in general, depending upon the temperature of they reaction, the presence of a promoter, and the amount of alkali metalcatalyst present in the reaction mixture. After the reaction has reached the desired stage of completion, the reaction products are removed from the isomerization reactor and unconverted olefinic hydrocarbon separated from the product for recycling to the isomerlzation reactor. Although fresh catalyst is usually preferred for each succeeding charge of olefinic hydrocarbon, the same batch of catalyst may in particular instances be utilized in a successive series of reactions until the catalyst becomes contaminated or is otherwise unsuitable for catalyzing the isomerization.

The present invention is further illustrated with respect to several of its specific embodiments in the following examples which, however, are not intended to limit the generally broad scope of the invention in strict accordance therewith.

Example I In the following experiment l-butene was subjected to isomerization in the present of metallic sodium, resulting in the conversion of a substantial proportion of the 1- butene to 2-butene. 3.5 g. of metallic sodium was charged into a glass-lined rotatable steel autoclave of 450 cc. capacity, together with 23.5 g. of l-butene, which was added to the autoclave as a liquid. The autoclave was sealed and thereafter heated to a temperature of 250 C. for three hours while the autoclave was slowly rotated. Following the indicated period of reaction, the contents of the autoclave were cooled to C. and the liquid product separated from the remaining catalyst. 21.6 g. of butene was recovered, 66.5% of which is 2- butene.

Example 11 In a reaction similar to the experiment described in Example I utilizing the same reactor and feed stock, except that 21.3 g. of l-butene and 1.0 g. of orthochlorotoluene were charged to the rotating autoclave, 18.0 g. of butene were recovered of which 84.5% was 2-butene.

Example HI A mixture of 25 g. of allylbenzene, 4.0 g. of sodium and 1.0 g. of tetraethyl lead are charged into a rotating steel autoclave of 450 cc. capacity. The pressure within the autoclave is increased to 300 lbs. per square inch by charging nitrogen into the reactor, following which the autoclave and its contents are slowly rotated as the temperature is increased to 275 C. Following a reaction period of three hours after the reaction at the above temperature and pressure, the contents of the autoclave are filtered to remove sodium and to recover the hydrocarbon product. The latter contains 87% isoallyl benzene as the isomerization product of the allyl benzene feed stock.

Example IV In the following experiment l-decene (consisting of substantially pure l-decene, prepared by the dehydration of n-decanol) was isomerized to isomeric decenes of the formula R--CH=CHR1 by refluxing the l-decene in the presence of sodium as catalysts and o-chlorotoluene as a promoter. t was also found that the isomerization does not proceed to completion in the absence of the promoter. In the presence of anthracene as a promoter, the isomerization of the reaction yields the isomerized decene product.

35 grams of l-decene, 3,6 grams of metallic sodium cut into small pieces and 1.0 gram of o-chlc-rotoluene were charged into a distillation flask connected to a reflux condenser and the mixture heated under refluxing conditions at a temperature of 166-168 C. for 20 hours. The hydrocarbon product was distilled from the catalyst and promoter and the hydrocarbon distillate examined by infrared method of analysis to determine the extent of isomerization of the l-decene to isomers thereof. It was found that 98% of the product consisted of olefinic hydrocarbons having the general formula:

and only 2% of the charged l-decene failed to undergo isomerization.

In a similar experiment in which only 35.1 grams of 1- decene and 3.5 grams of metallic sodium were charged into a distillation flask containing a reflux condenser and the resulting mixture heated at 165-166" C. for 20 hours, the product separated from the catalyst consisting of 91% l-decene and only 4% of the l-decene underwent isomerization to olefins of the structural formula:

H H RO=CR1 and 12% of l-decene which failed to undergo the desired isomerization.

Example V In the following experiment d-limonene was isomerized to conjugated menthadienes and dehydroisomerized to pcymene in accordance with the present process. 20.8 grams of d-limonene, 3.5 grams of sodium and 1.0 ochlorotoluene were charged into a reflux distillation flask and the mixture heated at 174-176 C. for 20 hours. Provision Was made for the collection of any gaseous byproducts of the reaction by continuously collecting the gases issuing from the tube of the reflux condenser in a gas collection receiver. It was found that no gas was released for the first 4 /2 hours, followed by a gradually accelerated rate of gas evolution until the end of 20 hours total reaction time. The hydrocarbon product was distilled from the catalyst and separately collected, yielding a total product weighing 24.1 grams. The hydrocarbon product was redistilled and ut No. 1, boiling from 170.5 to 173 C., weighing 16.6 grams, and having a refractive index of n 1.4882 was separately collected. 7.4 grams of bottoms remained in the distillation flask, having a refractive index, 11 of 1.5019. The first cut was subjected to infrared and ultra-violet analysis and found to contain 62% p-cymene and 20% of conjugated menthadienes. 4.15 liters of gas were collected from the reaction which was found to consist solely of hydrogen of an air-free basis.

We claim as our invention:

'1. A process for converting an olefinic hydrocarbon to an isomerization product thereof having a more centrally located double bond in the carbon atom chain which comprises subjecting said olefinic hydrocarbon to isomerization in the presence of an alkali metal and a halogen-substituted hydrocarbon promoter at reaction conditions which effect said double bond position isomerization.

2. The process of claim 1 further characterized in that said isomerization reaction is effected at a temperature of from about to about 350 C.

3. The process of claim 1 further characterized in that said isomerization reaction is effected at a temperature of from about 225 to about 275 C.

4. The process of claim 1 further characterized in that said promoter is a halogen-substituted benzene hydrocarbon.

5. The process of claim 1 further characterized in that said alkali metal is selected from the group consisting of sodium and potassium.

6. The process of claim 1 further characterized in that said alkali metal is present in the reaction mixture in an amount of from about 0.05 to about 0.5 atomic proportion of alkali metal per molecular proportion of olefinic hydrocarbon.

7. An isomerization process wherein an olefinic hydrocarbon having a double bond in the 1-position is converted to an isomer thereof having a more centrally located double bond which comprises reacting said olefinic hydrocarbon with metallic sodium at a temperature of from about 150 to about 350 C. and in the presence of a promoter comprising a halogen-substituted benzene hydrocarbon, said promoter being present in the reaction mixture in an amount of from about 0.01 to about 0.1 mol per mol of olefinic hydrocarbon.

8. An isomerization process wherein a cyclo-olefin having an alkenyl side-chain substituent is converted to a cyclic hydrocarbon containing at least one additional double bonded pair of carbon atoms in the cycli ring, which comprises reacting said cyclo-olefin in the presence of an alkali metal and a halogen-substituted hydrocarbon at isomerization reaction conditions whereby the double bond in said alkenyl side-chain is transferred into the cyclic hydrocarbon ring.

9. The process of claim 8 further characterized in that said cyclo-olefin is an alkenyl-substituted cyclohexene.

10. The process of claim 9 further characterized in that said alkenyl substituted cyclohexene is limonene.

11. The process of claim 8 further characterized in that said isomerization is continued for a reaction period sufficient to effect dehydroisomerization thereof.

12. A process for converting an olefinic hydrocarbon to an isomerization product thereof having a more centrally located double bond in the carbon atom chain which comprises subjecting said olefinic hydrocarbon to isomerization conditions which efiect said double bond position isomerization in the presence of an alkali metal and a halogen substituted benzene hydrocarbon promoter which forms an addition product with the alkali metal at said conditions.

13. The process of claim 12 further characterized in that said promoter is o chlorotoluene.

References Cited in the file of this patent UNITED STATES PATENTS 2,217,252 Hoog Oct. 8, 1940 2,333,903 Thomas et a1. Nov. 9, 1943 2,492,693 Freed Dec. 27, 1949 2,666,798 Condon Jan. 19, 1954 2,740,820 Wilson et a1. Apr. 3, 1956 OTHER REFERENCES I. Russ, Phys., Chem. Soc., Mereshkovski, 45, p. 1940-74 (1913).

I. Russ, Phys, Chem. Soc., Stscherbak, 45, p. 379 (1913) (Note: Above two Russian-Journals are cited in Isomerization of Pure Hydrocarbons, Eglotf et 211., pages 272 and 304).

-Hans1ey: Ind. Eng. Chem, v01. 43 (1951), pages 1759-66.

Claims (1)

1. A PROCESS FOR CONVERTING AN OLEFINIC HYDROCARBON TO AN ISOMERIZATION PRODUCT THEREOF HAVING A MORE CENTRALLY LOCATED DOUBLE BOND IN THE CARBON ATOM CHAIN WHICH COMPRISES SUBJECTING SAID OLEFINIC HYDROCARBON TO ISOMERIZATION IN THE PRESENCE OF AN ALKALI METAL AND A HALOGEN-SUBSTITUTED HYDROCARBON PROMOTER AT REACTION CONDITIONS WHICH EFFECT SAID DOUBLE BOND POSITION ISOMERIZATION.