US2914572A - Hydrocarbon chlorination process - Google Patents

Description

United HYDROCARBON CHLGRINATION PROCESS No Drawing. Application November 7, 1956 Serial No. 620,792

8 Claims. (Cl. 260-648) This invention relates to a hydrocarbon chlorination process. More particularly, this invention relates to a process for chlorinating saturated petroleum hydrocarbons.

It is frequently desirable to chlorinate hydrocarbons in order to improve the properties thereof. For example, it is frequently desirable to prepare unsaturated hydrocarbons by dehydrochlorination of chlorinated hydrocarbons.

It has been proposed to utilize irreversible hydrogenhalogen exchange reactions of the free radical initiated type for the preparation of chlorinated hydrocarbons. However, past results have not been entirely satisfactory, particularly with respect to the yields obtained and the amount of free radical generating compound consumed during the reaction. The amount of free radical generating compound consumed to provide a given quantity of chlorinated hydrocarbon is conveniently measured with respect to the G value of the reaction in question. This is also numerically referred to as chain length, which may be defined as the number of moles of product produced per mole of initiating free radicals consumed.

An object of the present invention is the provision of a treating process for obtaining high yields of chlorinated saturated hydrocarbons.

Another object is the provision of a free radical initiated chlorinating process for obtaining high yields of chlorinated saturated hydrocarbons with low consumption of the free radical generating compound.

These and other objects are attained by free radically promoting the reaction of carbon tetrachloride with about 2 to 6 moles of a C to C saturated hydrocarbon per mole of carbon tetrachloride at a temperature within the range of about 65 to about 150 C., for a reaction time within the range of about 0.1 to 24 hours, whereby chlorinated hydrocarbons and chloroform are formed, and continuously removing the chloroform from the reaction mixture as it is formed.

The hydrocarbon starting materials to be employed in accordance with the present invention are saturated C to C hydrocarbons including aliphatic and naphthenic hydrocarbons such as butane, pentane, hexane, heptane, octane, decane, dodecane, cyclohexane, methylcyclohexane, cycloheptane, n-propylcyclopentane, amylcyclop-i ntane, propylcyclohexane, methylcycloheptane, etc., aid mixtures thereof.

The hydrocarbon starting material is reacted with carhjan tetrachloride in accordance with the present inventhn in the presence of free radicals. The free radicals are preferably provided through the utilization of a free radical generating peroxy compound. Examples of such peroxides include alkali metals, persulfates, perborates, percarbonates, peroxides, etc., including compounds such as benzoyl peroxide, tertiary butyl hydroperoxide, ditertiarybutyl peroxide, lauroyl peroxide, tertiarybutylperbenzoate, etc. When a peroxide is to be employed as a source for free radicals it is generally preferably to employ from about 0.005 to about 0.5 mole of peroxide per mole of carbon tetrachloride. Other conventional means may be utilized for generating free radicals such as, for example, irradiation of the saturated hydrocarboncarbon tetrachloride mixture with ultraviolet light having a Wave length within the range of about 3500 to 2500 A.

The reaction temperature to be employed in accordance with the present invention should be at least about 65 C. and is preferably in the range from about 65 to about 100 C.

In addition, it is necessary that the chloroform by product of the reaction of the saturated hydrocarbon with the carbon tetrachloride be removed as formed. If this is not done, the G value or chain length of the reaction will be unsatisfactorily low.

The invention will be further illustrated by the following specific examples which are given as illustrations and are not intended as limitations on the scope of this invention.

EXAMPLE I Add about 154 grams (1.0 mole) of carbon tetrachloride and about 6.7 grams (0.028 mole) of benzoyl peroxide to about 420 grams (5.0 moles) of cyclohexane. Heat the resultant reaction mixture to reflux (temperature of about C.) for about 24 hours while continuously withdrawing chloroform by-product from the reaction zone as formed by fractional distillation. At the end of this time a reaction mixture is obtained containing chlorinated cyclohexane, together with unreacted cyclohexane and carbon tetrachloride. The results of a representative run conducted in this manner are summarized in the following table.

Table I.-Chl0rinati0n of cyclohexane Products:

Carbon tetrachloride 7.6 g. (0.05 mole). Cyclohexane 350 g. (4.17 mole). Chlorocyclohexane 112.4 g. (0.953 mole). Dichlorocyclohexane 5.3 g. (0.035 mole). Conversion of cyclohexane 16.7% (based on cyclohexane recovered). Selectivity to monochlorocyclohexane 96.5 mole percent. Chain length 18.

From the table it will be noted that a high yield of chlorocyclohexane was obtained and that there was a high selectivity to the formation of monochlorocyclohexane. Further, it will be noted that the chain length for this particular run was 18, indicating that about 18 moles of chlorinated cyclohexane were formed per half mole of benzoyl peroxide consumed, since each molecule of benzoyl peroxide generates two free radicals.

In the reaction of Table I, about 121.4 grams (1.03 moles) of chloroform was evolved which was removed from the reaction vessel as formed.

EXAMPLE II Prepare a mixture of about 168 grams (2.0 moles) of cyclohexane with about 154 grams (1.0 mole) of carbon tetrachloride and about 2.42 grams (0.01 mole) of benzoylperoxide. Heat the resultant reaction mixture at a temperature of about 80 C. for about 24 hours and during this time continually remove the chloroform byproduct that is formed by reaction of the carbon tetrachloride with the cyclohexane. About 45.9 grams (0.386 mole) of chloroform is formed and removed as formed. The results obtained are set forth in the following table.

From Table II it .will be noted that, again, a high chain length reaction was obtained, accompan ed by a high selectivity to the formation of monochlorocyclohexane.

EXAMPLE 111 Repeat Example II with but one exception, namely, the utilization 'of'about 4.84 grams (0.02 mole) of benzo y1- peroxide rather than the 2.42 grams of benzoylperoxlde employed in the case of Example II. About 58.8 grams (0.494 mole) of chloroform is formed and the thusevolved chloroform is continuously distilled from the reaction mixture during the course of the reaction. The results obtained are set forth in the'following table.

. Table 111 Products:

Carbon tetrachloride- Recovered 76.6 g. (0.497 mole). v Consumed 77.4 g. (0.503 mole). Cyclohexane- A Recovered 125.5 g. (1.495 mole). Consumed 42.5 g. (0.505 mole). Chlorocyclohexane 56.8 g. (0.472 mole). Dichlorocyclohexane 5.1 g. (0.033 mole). Selectivity to monochlorocyclohexane 93.5 mole percent. Chain length 13.5.

From Table III it will be noted that there was again a high selectivity toward the formation of monochlorocyclohexane. In this instance, however, although a high chain length was obtained,'the chain length was less than that of Example II. V

' EXAMPLE 1v Repeat Example II with but one exception, namely, the substitution of 168 grams of-a saturated petroleum hydrocarbon fraction boiling inthe range between about 79 and 81 C. for the pure cyclohexane of Example II, the impure fraction containing about 85.9 weight percent .of cyclohexane. -About 35.3 grams (0.296 mole) of chloroform is formed and the thus-evolved .chloroform is continuously distilled from the reaction mixture duringthe course of the reaction. The'results are summarized in the following table.

Table IV Products:

.Carbon tetrachloride-- i Recovered 106.1 g. (0.690 mole). Consumed 47.9 g. (0.310 mole). Cyclohexane Recovered 120.3 g. (1.416 mole). Consumed 23.8 g. (0.284 mole). Chlorocyclohcxane 31.2 g. (0.269 mole). Dichlorocyclohexane 2.0 g. (0.013 mole). Selectivity to monochlorocyclohexane 95.2 mole percent. Chain length 15.

From Table IV it is seen that once again there was high selectivity with respect to the formation of monochlorocyclohexane. .Again, there was ahigh cha nlength but not so great as the chain length of Example II.

EXAMPLE v Heat a mixture of about 100 grams of n-heptane (1.0 mole) with about 154 grams (1.0 mole) of carbon tetrachloride and about 2.42 grams (0.01 mole) of benzoylperoxide to reflux temperature (about 87 C.) in a reaction vessel for about 6 hours while totally refluxing the reaction mixture to thereby prevent the substantially complete removal of chloroform from the reaction mixture. At the end of the reaction a total of about 4.7 grams of chlorinated heptane were obtained, corresponding to a chain length of about 1.8.

EXAMPLE VI Repeat Example V, but in this instance continually distill the "chloroform by-product from the reaction mixture as formed. About 6.4 grams of chloroheptane are formed as a result ofthis reaction, this corresponding to a chain length of about 2.4.

r EXAMPLE vn grams of .chloroheptane are formed, this corresponding to a chain length of about 10.9.

EXAMPLE DC Prepare a mixture of about 168 grams of cyclohexane with about 154 grams of carbon tetrachloride and heat the resultant mixture at a temperature of about 80 for about 18 hours while irradiating the reaction mixture with.2537 A. radiation from' a mercury resonance lamp. Continuously remove by-product chloroform during the reaction. About 30 grams of monochlorocyclohexane is formed as a result of the reaction.

vWhat is claimed is:

r 1. A process which comprises the steps of heating a mixtureof carbon'tetrachloride with about 2 to 6 moles per mole of carbon tetrachloride of a saturated C to C hydrocarbon in a reaction zone at a temperature of about to about 150 C., for a'reaction time within the range of-about 0.5 to.24 hours and inducing reaction of said carbon tetrachloride with said hydrocarbon during said reaction time through the generation of free radicals in said reaction mixture, whereby chloroform and chlorinated hydrocarbons are formed, continually selectively removing said chloroform from said reaction zone as formed by distillation during the course of said reaction and thereafter recovering said chlorinated hydrocarbons from-the other products of said reaction.

' 2. A process as in claim 1 wherein said free radical-9" are generated by irradiating said reaction mixture ultraviolet light having a wave length within the range fof about 3500 to 2500 A. V i 1.

3. A process as in claim 1 wherein the free radihals V are generated through the addition to said reaction mixture of a compound capable of yielding free radicals in' the reaction conditions.

4. A process as ;in claim ,3 wherein the compound is an organic peroxy compound.

'5. YA process ,for preparing monochlorocyclohexane in high yield which comprises heating a mixture of carbon tetrachloride, about-2 to 6 moles of cyclohexane per mole of carbon tetrachloride and from about 0.005 to about 0.5 mole of an organic peroxy compound per mole of carbon tetrachloride in a reaction zone at a temperature within the range of about 65 to about 150 C. for about 0.5 to 24 hours, to thereby react the carbon tetrachloride with the cyclohexane to form primarily monochlorocyclohexane and chloroform, continually selectively removing said chloroform from said reaction zone as formed by distillation during the course of said reaction and thereafter recovering said monochlorocyclohexane from the other products of said reaction.

6. A process as in claim 5 wherein the peroxy compound is benzoylperoxide.

7. A process for preparing chloroheptane in high yield which comprises heating a mixture of carbon tetrachloride, about 2 to 6 mole of n-heptane per mole of carbon tetrachloride, and from about 0.005 to about 0.5 mole of an organic peroxy compound per mole of carbon tetrachloride in a reaction zone at a temperature within the References Cited in the file of this patent UNITED STATES PATENTS Archibald Jan. 22, 1946 West et al May 22, 1951 OTHER REFERENCES Ellis: The Chemical Action of Ultraviolet Rays, page 400.

Claims (1)

1. A PROCESS WHICH COMPRISES THE STEPS OF HEATING A MIXTURE OF CARBON TETRACHLORIDE WITH ABOUT 2 TO 6 MOLES PER MOLE OF CARBON TETRACHLORISE OF A SATURATED C4 TO C12 HYDROCARBON IN A REACTION ZONE AT A TEMPERATURE OF ABOUT 65* TO ABOUT 150* C., FOR A REACTION TIME WITHIN THE RANGE OF ABOUT 0.5 TO 24 HOURS AND INDUCING REACTION OF SAID CARBON TETRACHLORIDE WITH SAID HYDROCARBON DURING SAID REACTION TIME THROUGH THE GENERATION FREE RADICALS IN SAID REACTION MIXTURE, WHEREBY CHLOROFORM AND CHLORINATED HYDROCARBONS ARE FORMED, CONTINUALLY SELECTIVELY REMOVING SAID CHLOROFORM FROM SAID REACTION ZONE AS FORMED BY DISTILLATION DURING THE COURSE OF SAID REACTION AND THEREAFTER RECOVERING SAID CHLORINATED HYDROCARBONS FORM THE OTHER PRODUCTS OF SAID REACTION.