US2956941A

US2956941A - Radiation isomerization process

Info

Publication number: US2956941A
Application number: US655907A
Authority: US
Inventors: Carl E Heath; Peter J Lucchesi
Original assignee: Exxon Research and Engineering Co
Current assignee: ExxonMobil Technology and Engineering Co
Priority date: 1957-04-29
Filing date: 1957-04-29
Publication date: 1960-10-18
Anticipated expiration: 1977-10-18

Description

c. E. HEATH ETAL RADIATION ISOMERIZATION PROCESS Filed April 29,1957

NORMAL PARAFFINIC. 3 5 HYDROCARBON FEED 5 AICI 4 ISOPARAFFINS RADIATION 9 6 SOURCE 1 PRODUCT 6 SEPARATION f 4- 17 f METHYL CYCLOPENTANE Carl E. Heath mentors Peter J. Lucchesi Attorney 2,956,941 RADIATION ISOMERIIZATION rnocnss Carl E. Heath, Nixon, and Peter J. Lucchesi, Cranford,

N.J., assignors to Esso Research and Engineering Company, a corporation of Delaware Filed Apr. 29, 1957, Ser. ism 655,907 Claims. cifzo t-isz This invention relates to the isomerization ofparafiinic 2,956,941 Patented Oct 18,1960

a y, methyl cyclopentane is employed in the present'method as a cracking suppressor when'added to paraflins in concentrations-ol 2 to 20 wt. percent. Ad-

hydrocarbons. -More particularly, it relates to an im--.' proved method for producing saturated branched-chain hydrocarbons by the reaction of parafiinic hydrocarbons with an aluminum chloride catalyst in the presence of high energy ionizing radiation. The products are normally liquid saturated branched-chain hydrocarbons boiling chiefly within the motor fuel boiling range, i.e. 85 F. to 440 F.

In brief compass,- this invention proposes a radioisomerization process in which hydrocarbon cracking and secondary alkylation reactions are substantially eliminated. According to the present discovery, such beneficial results are surprisingly achieved when straight-chain parafiins are contacted under isomerization reaction conditions with aluminum chloride in the presence of promotional amounts of a naphthene, the reaction being carried out in the presence of high energy ionizing radiation.

Straight-chain parafiins of at least 4 carbon atoms per molecule heretofore have been isomerized in the' presence of Friedel-Crafts type catalysts to produce branched-chain parafiins. Greatly increased yields of isomerized hydrocarbons have now been obtained by isomerizing inthe presence of an aluminum chloride catalyst and exposing the catalyst to high energy ionizing radiation during the isomerization. In such a process, however, secondary reactions occur which lower the u lti mate yield of isomerized product. These reactions are I hydrocarbon cracking and secondary alkyla'tion pro'e'sses between the fragments. 1

8 carbon atomsare isomerized in the presence of aluminum chioricie in an amount of from about 2 to 200 wt.

percehtb'ased upon the weight of parafiin, by adding to the feed from about 2 to wt. percent based upon the weight of .paraflin, of a cycloparaffin having between 5 and 8 carbon atoms and exposing the aluminum chloride to high energy ionizing radiation until at least about 1 10 kwh. of radiation energy per pound of paratfin has been absorbed; Preferably paraffin conversion is carried out at a temperature in the range of about 40 to 300" F;

Suitablenaphthenes for the purposes of the present invention are cycloparatfins boiling in the range of from about 40 to 110 C. For example, methyl cyclopentane,

vantageously from about 5 to about 10% of methyl cyclopentane, based on the weight of hydrocarbons, is added as a cracking suppressor to a radioisomerization process according to this invention.

In one embdoiment of the invention, pure straightchain parafiin hydrocarbons are employed as the feed stock for the novel conversion process. Normal butane, normal pentane, normal hexane, normal heptane and the like, as pure compounds, can be subjected to the isomerization treatment as hereinafter more fully described. The

processof the present invention equally as well applies to the treatment of mixtures of hydrocarbons predominantly composed of straight-chain parafiinic constituents. The invention is not limited to the isomerization of straighti chain hydrocarbons but encompasses also the conversion of branched-chain hydrocarbons to isomeric more highly branched-chain hydrocarbons. Mixed paraflins such as straight-run naphthas also can be converted by the present method into isomeric mixtures which have increased value with respect to anti-detonation qualities when used as motor fuels. In general, any hydrocarbon mixture comprising at least 75 wt. percent parafiinic hydrocarbons is suitable for use as a feed stock for the process herein outlined. Particularly advantageous for this process is a feed stock containing at least 75 Wt. percent based on the totalweight of hydrocarbon present of paraflins having from 4 to 8 carbon atoms and boiling in the range of from about to 200 F. A product containing substantial amounts of branched-chain isomers can be separated from the reaction medium and fractionated within the'desired boiling range. The unconverted hydrocarbons can then be returned to the isomerizing reactor, to be further isomerized in a normal recycle process.

cyclohexane,"methy1 cyclohexane, ethyl cyclopentane, 11,1-

e isomerization reaction of the present invention is carried out by exposing the reactants and the isomerization catalyst to high energy ionizing radiation, that is, high energy quanta (radiation wave length less than 50 A.), neutrons, and charged and uncharged particles of atomic and sub-atomic nature having energies greater than about 30 electron volts. Types of radiation suitable for the purposes of invention include high energy electromagnetic radiation such as gamma rays and X-rays and high velocity electrons, as well as beta rays and alpha particles. These types of radiation can be supplied by naturally-occurring radioactive materials which emit alpha, beta and gamma rays.

Fission by-products of processes generating atomic power, or fissionable materials which emit high energy gamma rays also afford a highly desirable and most abundant source of radioactivity suitable for the purposes of the invention. These by-products include those with atomic numbers ranging from 30 to 63 and their compounds. They are formed in the course of converting uranium and thorium and other fissionable materials in an atomic reactor. By high energy ionizing radiation is meant radiation from terrestrial sources of sufiicient intensity such that the dose rate is at least l l0 kwh./ hr./ lb. of reactant. This excludes radiation such as cosmic and ultraviolet which are ineffectual for the purposes of this invention.

Materials made radioactive by exposure to neutron irradiation, such as radioactive cobalt-60, which emits gamma rays, can likewise be used. Suitable sources of high velocity electrons are thebeams of electron accelerators, such as the Van de Graafi electrostatic accelerator. In general, however, high velocity electrons and high energy gamma radiation and its well-known sources such as nuclearfission by-products and materials made radioactive by neutron irradiation, are preferred for the purposes of the invention mainly because of the relatively high penetrating power of the rays and the availability and ease of application .of these sources of radiation.

For isomerization reactions in accordance with the present invention, a wide radiation dose range can be employed, for example, from about 10- to about 10 megaroentgens. This is approximately equal to a dosage of from 10- to 10 kWh/lb. of paratfin. Preferably the radiation dose utilized is between about 10- and 10 kWh/lb. Suitable temperatures include those from about 40 to 300 F. The higher temperatures, that is, from 150 to 300 F., are preferably employed when the feed stocks are in vapor phase. At lower temperatures, for example, from 40 to 150 F., isomerization can be effected in the liquid phase and without side reactions. The time of the reaction varies with other factors such as temperature, the amount of catalyst, the particular catalyst used and the particular feed stock treated. In general, however, the time of reaction can be from /2 to 30 hours and the conditions are usually adjusted so as to paraflin converted to ample, between 100 and 150 F. The surprising feature of the novel process of this invention was the discovery that at radiation dosages of between about 10- and 10 kWh f P aflin an isomerized. product can be obtained with a selcctivity substantially equal to 100 percent.

The amount of a eqjnum' chloride catalyst to be used varies widely, dependin cm the particular hydrocarbon which is to be converted, Preferably an amount in the range of from 2% to 200%by weightof hydrocarbon material present in the reactor imemployed.

The reaction is preferably carried out under liquid phase conditions, hence any temperat re below the critical temperature of the feed stock may employed, although it is preferable to use the temperatu s specified above. Suliicient super-atmospheric pressu be employed to maintain the reactant as well as the eaction products in the liquid phase under the reaction conditions obtained. In particular, liquid phase operations are conducive to the production of ultimate high yields and to the carrying out of the process in a continuous manner. The aluminum chloride can be added to the feed before it enters the reactor. It is to be understood, however, that the process is not only applicable to continuous operations, but it is contemplated to carry the same out in batch-type apparatus for single batch operation. Where the reaction is carried out in the liquid phase, it is advantageous to intensively agitate the reaction mixture so that intimate contact is established between the feed and the catalyst. In the present where a bed-type of catalyst is employed, it is well to employ liquid phase operation and to force the liquid hydrocarbon feed into the reactor under pressure.

The invention can also be practiced by employing a "continuous batch-type of operation" in which the reaction is carried out in liquid phase and the liquid product is removed after each batch reaction and distilled or passed through a molecular sieve adsorption zone to separate the isomerized product. Unconverted paraflins can then be returned to the reaction zone in a subsequent charge. Preferably a recycle type of operation is employed.

The isomerization catalyst can be produced in situ by the reaction of a suitable metal such as aluminum with chlorine or a compound chemically reacting as the equivalent of free chlorine under the conditions of the reaction or may be added to the feed stock as chemically pure anhydrous aluminum chloride or as a commercial obtain a conversion of from 30% 195% basedon feed product, at a temperature of, for excreased yields of the desired isomers. In another modi.-.

fication, a catalyst bed can be made up of Porocel or some other suitable highly porous alumina and placed within the radiation zone. The catalyst mass employed can be formed by admixing granules of aluminum chloride with the desired quantities of dehydrated Porocel and the mass heated while passing through a stream of inert vapor. Preferably aluminum chloride, which 18 but sparingly soluble in hydrocarbons, is employed as the isomerization catalyst for the process of the present invention. Aluminum bromide particularly is less desirable since it leads to excessive cracking. This is believed to be attributable to the relatively high solubility of aluminum bromide in hydrocarbon mixtures.

No special type of apparatus is required for carrying out the novel isomerization process of this invention. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation will be understood more clearly and fully from the following description considered in connection with the accompanying drawing.

Referring to the drawing in detail, it will be seen that aluminum chloride is mixed with the normal parafiinic bymixture is exposed to high drocarbon to be converted and admitted to the process by line 1. In this manner the catalyst is fed into the radiation reactor zone 3. A suitable support can be employed within the radiation zone on which the aluminum chloride lays down. Advantageously this support comprises a highly porous aluminaof the Porocel type. Additional amounts of aluminum chloride are added from time to time if necessary by line 1. Methyl cyclopentane is added to the process by line 7.

The aluminum chlorideparaffin-methyl cyclopentane energy ionizing radiation in the radiation zone 3. A suitable source of radiation comprises atomic waste products obtained from nuclear reactors oratomic piles. This material can be suitably enclosed or concentrated as in an underground storage area, and the hydrocar on mixture can be passed through or around the waste rial.

The radiation 20115,; advantageously comprise a cohalt-60 source; Electron scelerators ot the linear type and Van de Graff geneia't rs can also be employed as a source of high energy electrons. \The electrons are directed through a thin reinforced window into the hydrocarbon-aluminum chloride-naphthene mixture.

The converted material is removed by line 4 and passed into a suitable product separation zone. This zone can comprise, for example, a distillation zone, a solvent extraction zone, an absorption zone, a molecular sieve, or a sieves have the property of separating straightchained from branch-chained hydrocarbon isomers, as'

well as from cyclic and aromatic compounds. These zeolites have innumerable pores of uniform size, and only molecules small enough to enter the pores can be absorbed. The pores may vary in diameter from 3 or 4 A. to about 15 A. or more, but it is a property of these zeolites or molecular sieves that any particular product has pores of substantially uniform size. Zeolites may vary somewhat in composition but generally contain the elements, silicon, aluminum, and oxygen occurring and synthetic and sometimes termed aswellasanalkali metal or an alkali earth metal. A large number of naturally occurring zeolites having molecular sieve activity, that is the ability to adsorb a straight-chained hydrocarbon and exclude or reject the branched-chained isomers and aromatics because of diiferences in molecular size, are described in an article entitled, Molecular Sieve Action of Solids, appearing in Quarterly Reviews, volume III, pages 293-320, 1949, published by the Chemical Society, London. Molecular sieves suitable for the present invention comprise sieves having pore openings in the range of from about 4 to A. The molecular sieve heretofore described is arranged in any desired manner in the adsorption zone of separation zone 5. It can, for example, be arranged on trays or packed therein with or without support. Conditions maintained in the molecular sieve treatment in adsorption zone 5 are flow rates of about 0.1 to about 5 v./v./hr., temperatures of about 200 to about 350 F. and pressures from atmospheric pressure to several p.s.i.g. With molecular sieves of the indicated size of pores, the normal paraffins contained in the feed are readily absorbed while the isoparaflinic product is not, but instead is passed by line 6 to suitable product containers. Unconverted normal parafiinic constituents are recovered readily by the utilization of molecular sieves and returned by recycle process to the reactor by line 2 as indicated.

In order to more fully disclose the invention, the following example is given to indicate the nature of the invention. However, it should be distinctly understood that this example is presented as merely illustrative of a specific type of operation of the invention.

EXAMPLE 1 In this illustration methyl cyclopentane was added to the feed in the aluminum chloride catalyzed isomerization of normal hexane in the presence of gamma radiation. In a typical experiment feed solution composed of 92% by weight normal hexane and 8% methyl cyclopentane was irradiated by cobalt-60 gammas of an intensity greater than l0 kwh./lb./hr. in the presence of anhydrous aluminum chloride. The weight ratio of aluminum chloride to feed was 1.5. The products obtained for the same reaction with and without added methyl cyclopentane and with and without high energy ionizing radiation are given in Table I.

Table I With Added Without Added Methyl Methyl Cyclo- Cyolopenpentane tane Reaction Conditions:

Dose (mr.) 0 7. 2 0 10 71. 2 Temperature F.) 116 115 115 115 115 Pressure (atm.) 1 1 1 1 1 Reactants (gins):

e.v 131 75 75 Product Yield (Wt. percent on Feed):

as 0 0 15. 8 23. 3 27. 8 n-hexane. 85.1 78. 4 38. 6 7. 2 3. 7 Co isomers 14.9 21. 6 23. 6 26. 5 26. 4 2,2-dimethyl butane 0.3 0. 8 7. 5 13. 9 13. 2 2-1nethyl pentane cyclopentane 2. 9 7. 8 12. 2 9. 3 9. 9 2,3-dimethyl butane 3-methyl pentane 1. 2 2. 3 3. 9 3. 3 3. 3 methyl cyclopentane. 5.1 1. 9 0 O 0 cyclohexane 5. 4 8.8 0 0 0 Other liquid products 2 0 0 22.0 43. 0 42. 1

1 Analysis by vapor-liquid partition chromatography does not distinguish between these compounds.

2 C4, O5, O7 and O8 isomers.

The above example clearly shows that the addition of a cyclo paraflin to the feed in the gamma radiolysis of aluminum chloride-hexane mixtures changes the selec tivity of the reaction and avoids cracking of the feed. It is seen that the reaction products in the case of the treated feed, that is, with added methyl cyclopentane, are

C isomers only, whereas products from cracking and alkylation also appear in the case of isomerization in the absence of a cracking suppressor. In addition to increasing the radiation yield, methyl cyclopentane also changes the distribution of products obtained in the normal hexane-aluminum chloride reaction. These results show that methyl cyclopentane can be used to suppress side reactions in radiation isomerization of saturates. In addition, radiation effectiveness is greater when these side reactions are inhibited. The total G value in terms of feed molecules reacted per E.V. was 131 as compared with a G value of 75 obtained from untreated feed.

It is to be understood that the above-described arrange ments and techniques are but illustrative of the applicaof the principles of the invention. Numerous other arrangements and procedures may be devised by those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. A radiation isomerization process which comprises contacting a hydrocarbon mixture comprising a paraflin hydrocarbon having in the range of 4 to 8 carbon atoms and in the range of 2 to 20 wt. percent of a naphthene having from 5 to 8 carbon atoms, with in the range of 2 to 200 wt. percent of aluminum chloride based on the weight of parafiin hydrocarbon, and exposing said aluminum chloride in contact with said hydrocarbon mixture at a temperature in the range of about 40 to 300 F. to. high energy ionizing radiation until a total dosage in the range of 10- to 10 kwh. of radiation energy per pound of paraflin has been absorbed.

2.. A radiation isomerization process which comprises contacting a paraflinic hydrocarbon having from about 4 to 8 carbon atoms with aluminum chloride in the amount of about 2 to 200 wt. percent based on the weight of paratlin, adding a naphthene having from 6 to 7 carbon atoms present in an amount of about 2 to- 20 wt. percent based upon the weight of paraffin, and exposing said aluminum chloride in contact with the parafiinic hydrocarbon and said naphthene at a temperature in the range of about 40 to 300 F. to high energy ionizing radiation until a total dosage in the range of 10- to 10 kwh. of radiation energy per pound of parafiin has been absorbed.

3. A radiation isomerization process which comprises contacting a hydrocarbon mixture consisting of from about 80 to 98 wt. percent of normal hexane and from about 2 to 20 wt. percent of methyl cyclopentane with wt. percent based on the weight of hexane, of aluminum chloride, and exposing said aluminum chloride in contact with said mixture at a temperature in the range of about 40 to 150 F. at a pressure sufiicient to maintain liquid phase conditions, to from about 10- to 10 megaroentgens of gamma radiation.

4. A hydrocarbon conversion process which comprises contacting a hydrocarbon feed comprising essentially paraflins having from about 4 to 8 carbon atoms, with aluminum chloride present in the amount of about 2 to 200 wt. percent and from about 2 to 20 wt. percent of a naphthene having from 6 to 7 carbon atoms, both based on the weight of paraffin in the feed, and exposing the aluminum chloride in contact with said feed and said naphthene at a temperature of from about 40 to 300 F. to high energy ionizing radiation until a total dosage in the range of 10 to 10 kwh. of radiation energy per pound of paraffin has been absorbed.

5. A hydrocarbon conversion process which comprises contacting a hydrocarbon feed comprising essentially paraflins selected from the group consisting of n-butane, n-pentane, n-hexane, n-heptane, n-octane and mixtures thereof, with (1) about 2 to 20 Wt. percent of a naphthene having from 6 to 7 carbon atoms and (2) about 2 to 200 wt. percent of aluminum chloride, both based on the weight of parafiin in the feed, at a temperature of about 40 to 300 F., in the presence of a total dosage of high energy ionizing radiation in the range of 10- to 10 kwh.

7 per pound of paratfin sufiicient to convert between about 30 and 95 wt. percent of said paraflins to reaction products.

6. A process for converting parafiin hydrocarbons which comprises contacting a hydrocarbon feed comprising essentially paraflins having from about 4 to 8 carbon atoms per molecule with (1) a naphthene having from 6 to 7 carbon atoms present in an amount of about 2 to 20 wt. percent based on the weight of paraifin and (2) aluminum chloride present in the amount of about 2 to 200 wt. percent based on the weight of parafiin, exposing the aluminum chloride in contact with said feed and said naphthene at a temperature of from about 40 to 300 F. to a total dosage of high energy ionizing radiation in the range of to 10 kwh. per pound of hydrocarbon feed per hour, and recovering a converted product in which the concentration of isomerized paraffin is substantially equal to 100 percent.

7. A hydrocarbon conversion process which comprises contacting a hydrocarbon feed containing from about 2 to parts of methyl cyclopentane and from about 80 to 98 parts of a paratfin having from 4 to 8 carbon atoms per molecule with aluminum chloride present in the amount of about 2 to 200 wt. percent based on the weight of paralfin in the feed, and exposing the aluminum chloride in contact with said feed at a temperature of from about 40 to 300 F. to high energy ionizing radiation until a total dosage in the range of 10- to 10 kwh. of radiation energy per pound of parafiin has been absorbed.

8. An isomerization process which comprises charging a reactor with a paraffinic hydrocarbon having from about 4 to 8 carbon atoms per molecule and an aluminum chloride catalyst, said catalyst being present in the amount of about 2 to 200 wt. percent based on the weight of said paralfinic hydrocarbon, adding a naphthene having in the range of 5 to 8 carbon atoms, said naphthene being present in an amount of about 2 to 20 wt. percent based on the weight of paraflin, exposing said catalyst in contact with. said hydrocarbon to high energy ionizing radiation until, a total dosage in the range of 10- to 10 kwh. per poundof parafiin has been absorbed, continuously removing the reaction product from the reactor, continuously separating the unconverted hydrocarbon from the desired isoparatfin product, recycling said unconverted hydrocarbon to said reactor, and continuously feeding a fresh supply of hydrocarbon and naphthene to the reactor.

9. A continuous isomerization process which comprises passing a hydrocarbon feed stock containing at least wt. percent of straight-chain paraflins having from 4 to 8 carbon atoms per molecule in contact with (1) in the range of 2 to 20 wt. percent of a naphthene having from 6 to 7 carbon atoms and (2) a slurry comprising in the range of 2 to 200 wt. percent of an aluminum chloride catalyst, through a reaction chamber wherein said catalyst in contact with said hydrocarbon feed and said naphthene is subjected to high energy ionizing radiation until a total dosage in the range of 10'- to 10 kwh. per pound of paraffin has been absorbed and continuously separating and withdrawing a product which has been isomerized with a selectivity substantially equal to percent.

10. A process according to claim 8 wherein said iso paraflin product is separated by absorption on a molecular sieve.

Proceedings of International Conference on Peaceful Uses of Atomic Energy, vol. 15 (1955), page 28.

Claims

1. A RADIATION ISOMERIZATION PROCESS WHICH COMPRISES CONTACTING A HYDROCARBON MIXTURE COMPRISING PARAFFIN HYDROCARBON HAVING IN THE RANGE OF 4 TO 8 CARBON ATOMS AND IN THE RANGE OF 2 TO 20 WT. PERCENT OF A NAPHTHENE HAVING FROM 5 TO 8 CARBON ATOMS, WITH THE RANGE OF 2 TO 200 WT. PERCENT OF ALUMINUM CHLORIDE BASED ON THE WEIGHT OF PARAFFIN HYDROCARBON, AND EXPOSING SAID ALUMINUM CHLORIDE IN CONTACT WITH SAID HYDROCARBON MIXTURE AT A TEMPERATURE IN THE RANGE OF ABOUT 40* TO 800* F. TO HIGH ENERGY IONIZING RADIATION UNTIL A TOTAL DOSAGE IN THE RANGE OF 10**-6 TO 10**3 KWH. OF RADIATION ENERGY PER POUND OF PARAFFIN HAS BEEN ABSORBED.