US1754656A - Method of chlorinating unsaturated hydrocarbons - Google Patents

Description

April 15, 1930. c. J. STROSACKER METHOD OF CHLORINATING UNSATURATED HYDROCARBONS Filed May 16, 1928 EXHAUST (S45 5 m R a L H c OIL 6A6 026M288 J'Sfrosac/rr BY ay m g a g Patented A pr. 15, 1930 UNITED. STATES PATENT OFFICE GHABLES J. S'IBOSACKER, F MIDLAND, MICHIGAN, ASSIGNOR TO THE DOW CHEMICAL COMPANY, OF MIDLAND, MICHIGAN, A CORPORATION 013 MIGHIGQN METHOD OF GHLORINATING UNSATURA'I'ED HYDROGARBONS Application filed May 16,

The present improved rocess relates to the chlorination of hydrocar ons of the ethylene series, and more particularly to the chlorination of the gaseous lower members of said se- 6 ries, such as ethylene and propylene, and gas mixtures containing them.

The object of my invention is to provide a method of chlorination by addition that ex-- cludes the formation of chlor-substituted by- 10 products. A further object is to effect the chlorination of gas mixtures containing both eth lene hydrocarbons and saturated hydrocarbons, such as methane, ethane, etc., whereby only the ethylene hydrocarbons are chlormated, loss of chlorine through formation of chlor-substituted products is avoided, and a substantially pure product containing only di-chlorinated derivatives of ethylene hydro carbons is obtained. Still further my invention ermits the use of a more dilute chlorine gas t an in other methods now in commercial use.

As is well known the hydrocarbons of the ethylene series and chlorine react very readily upon-being brought together. Considerable heat is developed, and unless cooling means be provided, the reaction will pass beyond the stage wherein di-chlorinated products are formed by simple addition of chlorine, and a considerable amount of higher chlorinated products will also be formed, with the concomitant formation of hydrochloric acid which is destructive to the apparatus. Even with careful temperature control under the most favorable conditions, a pure end product will not be obtained, and the chlorinated product resulting must be purified by fractional distillation.

Furthermore it is difiicult so to regulate the supply of hydrocarbon gases and chlorine, respectively, that they are always present in combining proportions. Usually there will be an excess of one or the other gas, which excess must be recovered, or passes out of the stack, and is lost. The recovery of such excess gases burdens the process with added expense, especially in the event that the hydrocarbon gases are obtained in admixture with a-considerable amount of saturated hydrocarbon gases or other gases which act as dil- 1928. Serial No. 273,351.

the stack gases to the reaction impracticable.

Various methods have been proposed for overcoming the aforesaid .disadvantages, including the chlorination in a co-solvent for the respective gases. Such methods may be satisfactory when working with a rich chlorine gas. However, from the standpoint of cost it would be preferable to utilize a chlo' rine gas diluted with as much as 15% of air or more except that a loss of chlorine would occur due to a part being carried away by the air. Furthermore, such method is not adapted to preclude entirely the formation of high- :r chlorinated products, and it is necessary 0 tion.

methods is encountered when oil gas obtained by the cracking of oil is employed as the source of the ethylene hydrocarbons, which is desirable in practice, due to the lower cost of purify the product by fractional distilla- An additional disadvantage of existing of the oil gas consists of saturated hydrocarbons, chiefly methane and ethane, and hydrogen. When such gas is treatedwith chlorine by any of the usual methods there takes place a greater or less chlorination of the saturated hydrocarbons by substitution in addition to the desired chlorination of the ethylene hydrocarbons by addition, and such substitutive chlorination entails a loss of chlorine to the process, the formation of lay-products which must be separated from the principal prodnot, and the production of a corresponding amount of hydrochloric acid.

A further loss of chlorine may result from combination with the hydrogen contained in the gas, and leads to the formation of an additional amount of hydrochloric acid. It

has been proposed to separate the saturated hydrocarbons and hydrogen contained in the oil gas previous to chlorination by compressing at a very low temperature and fractionally distilling the condensate, but this would add materially to the expense of the process.

I have discovered that the chlorination of ethylene hydrocarbons, whether obtained from oil gas or from any other source may be accomplished in a manner remar ably free from the objections hereinbefore mentioned, by means of antimony pentachloride, when carried out in accordance with the conditions hereinafter disclosed.

I am aware that mention was made by Wohler in 1828 (Annalen der Physik, 13, 297 of an experiment in which he passed ole ant gas into antimony gentachloride and obtained ethylene dichlori e in the roduct of the reaction. However, this brie notice disclosed no details as to conditions for carr ing out the method so as to control the character and purity of the product, or to obtain a commercially satisfactor yield. Since then, so far as I am aware, t ere has been no further publication relative to the aforesaid method, and it has remained for me to discover the operating conditions according to which the method may be successfully used.-

To the accomplishment of the foregoing and related ends the invention, then, consists of the steps hereinafter fully described and particularly pointed out in the claims, the annexed drawing and the following description setting forth in detail certain steps embodying the invention, such disclosed means constituting, however, but several of the various ways in which the principle of the invention may be used.

When hydrocarbons of the ethylene series, havin the general formula C H are broug t together with antimony pentachloride, a reaction takes place according to the following equation:

The reaction proceeds rapidly and completely to its end with the production exclusively of dichloraddition compounds, no further chlorination taking place by substitution. The product is a mixture of dichlor-hydrocarbons and-antimony trichloride, free from higher chlorinated compounds. Separation is easily effected by distillation.

If oil gas is reacted with antimony pentachloride, the ethylene hydrocarbons contained therein are chlorinated as in the above equation, but there is no chlorination of the saturated hydrocarbons and hydrogen, and loss of chlorine is avoided which would occur thereby if other methods were employed. In either case the formation of hydrochloric acid is avoided, and its troublesome removal, which is associated with other methods, is absent from my process.

The antimony pentachloride is preferably dissolved in a suitable solvent, which most conveniently may be ethylene dichloride, or the dichlorinated roduct of its action on ethylene hydrocar ns. The temperature may va between wide limits from say 0 to 100 but it will be found best to hold the temperature well below the boiling point of the product of the reaction. Inasmuch as considerable heat is liberated, cooling means should be provided for controlling the temperature.

One method of bringing the ethylene gases and antimony pentachlorlde solution in contact is to form a shower of said antimony pentachloride solution in a suitable enclosed vessel, and introduce the gases so that they rise in said vessel against the downflowing shower. The same result, however, may be accomplished in various other Ways, as, for example, by bubbling the gases through the solution, or by passing gases and solution in countercurrent through a tower filled with any suitable packing. V

The solution passing from the reaction zone, which contains antimony trichloride, is treated with chlorine to regenerate antimony pentachloride and returned to the reaction. Thus the chlorinating agent is continuously employed in alternately giving up a art of its chlorine to the reaction, and ad ing on fresh chlorine, which it in turn carries to the reaction. As the chlorinated reaction product accumulates, it is drawn off and distilled to separate it from the dissolved antimony chlorides. A part of the dichlorinated product suflicient to act as solvent for the antimony chloride is left in the still, and this solution returned to the c cle of chlorinating reactions. Antimony tr1chloride takes up chlorine so readily that complete absorption of the latter takes place at once, even when the chlorine is diluted with air. This feature of my process permits the use of more dilute chlorine gas than other processes for chlorinating ethylene hydrocarbons.

In the accompanying illustration I have shown diagrammatically one arrangement of apparatus suitable for carrying out my process, but I do not limit myself to such arrangement, as it is apparent that various other ways of operating may be devised without departing from the spirit of my invention.

In the drawing, the inlet 1 for gas containing ethylene hydrocarbons, leads to a point near the bottom of the reaction chamber 2, the outlet for spent gases being pipe 3. A pipe 4 leads from the reacting chamber to the chlorinating chamber 5, provided with a cooling coil 6, and a perforated pipe 11 for introducing chlorine. A connection 7 to a circulating pump 8 allows for the return of liquid to the reacting chamber through pipe 9, and perforated pipe 10 to which are attached a plurality of spray nozzles. A separate pipe 12 connects the chlorinating chamber with a still 13, provided with a steam coil or other heating means, from which ethylene chloride vapors pass through pipe 14 and from still 13 is returned to the reaction cir- 1 cuit through pipe 17. e

In the operation of the apparatus, oil gas, or other as containing ethylene hydrocarbons, is a mitted to the reaction chamber 2, where it meets a fine spray of, antimony pentachloride solution. Substantially quantitative chlorination of ethylene hydrocarbons takes place readily, the liquid product together with antimony pentachloride collects at the bottom of the chamber, and spent gases consisting of saturated hydrocarbons, hydrogen, et cetera pass out through 3. The 1i uid product flows through pipe 4 into the o lorinating chamber 5 where chlorine gas is bubbled through it to convert the antimony trichloride formed in the reaction back to antimony pentachloride, the temperature of the liquid being controlled by means of the cooling coil 6. The solution of antimony pentachloride is returned to the reaction chamber by means of the circulating pump 8 through pipes 7 and 9. The dichlorinated reaction product, containing dissolved antimony pentachloride accumulates in 5, whence it is drawn oil periodically through pipe-12 to the still 13. where the dichlorinated hydrocarbons are distilled oii, condensed in 15 and collected in receiver 16. A portion of the still contents is reserved, containing the antimony pentachloride in solution, and returned to the reaction circuit through ipe 17.

Other modes of applying t e principle of my invention may be employed instead of the one explained, change being made as regards the process herein disclosed, provided the step or steps stated by any of the following claims or the equivalent of such stated step or steps be employed.

I therefore particularly point out and distinctly claim as m invention:

1. A method 0 chlorinating unsaturated hydrocarbons which comprises reacting upon hydrocarbons of the ethylene series with antimony pentachloride in the presence of a solvent containing the chlorinated product of the reaction.

2. In a method of chlorinating unsaturated hydrocarbons, the step which consists in reacting upon hydrocarbons of the ethylene series with antimony pentachloride at a temperature between 0 C. and 100 C. in the presence of a solvent containing the chlorinated product of the reaction.

. 3. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon oil gas with antimony pentachloride in the presence of a solvent containing the chorinated product of the reaction.

4. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon hydrocarbons of the ethylene series with antimony pentachloride dissolved in the liquid product of the reaction.

' ,5. .A method of chlorinating unsaturated hydrocarbons which comprises reacting upon 011 as with antimony pentachloride dissolved in t e liquid product of the reaction.

6. A- method of chlorinating unsaturated hydrocarbons which comprises reacting upon ethylene hydrocarbons with antimony pentachloride, treating the product of said step with chlorine to regenerate antimony pentachloride, and returning same to the reaction.

7. Ina method of chlorinating unsaturated hydrocarbons, the steps which consist in reacting ethylene hydrocarbons at a temperature between 0 6. and 100 C. with anti mony pentachloride, treating the'product of said step with chlorine to regenerate antimony pentachloride, and returning same to the reaction. I

8. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon oil gas with antimony pentachloride, treating the product of said step with chlorine to regenerate antimony pentachloride, and returning same to the reaction.

9. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon ethylene hydrocarbons with antimony pent-achloride, regenerating said antimony pentachloride by .treating with chlorine, separating therefrom the dichlorinated hydrocarbons produced in said first step and returning said antimony pentachloride to the reaction.

10. A method of ohlorinating unsaturated hydrocarbons which comprises reacting upon Oll gas with antimony pentachloride, regenerating said antimony pentachloride by treating with chlorine, separating therefrom the dichlorinated hydrocarbons produced in said first step and returning said antimony pentachloride to the reaction.

11. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon ethylene hydrocarbons with antimony pentachloride dissolved in the liquid product of the reaction, regenerating said antimony pentachloride by treating with chlorine, separating a portion of the dichlorinated reaction product of said first step therefrom, and returning to the reaction the remaining portion containing said antimony pentachloride dissolved therein.

12. A method of chlorinating unsaturated hydrocarbons which comprises reacting upon oil gas with antimony pentachloride dissolved in the liquid product of the reaction, regenerating said antimony pentachloride by treating wlth chlorine, separating a portion of the dichlorinated reaction product of said first step therefrom, and returning to the reaction the remaining portion containing said antimony pentachloride dissolved therein.

13. In a method of chlorinating unsaturated hydrocarbons, the steps which consist in reacting oil gas at a temperature between 0 C. and 100 C. with antimony pentachlo-

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