US2018345A - Chlorination of aliphatic hydrocarbons - Google Patents

Description

Patented a. 22, 1935 cnLoRmA'rIoN or ,ALrrnAnc HYDROCARBONS Edgar C. Britten, Gerald H. Coleman, and Bartholdt C. Hadler, Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Application February 1, 1933, Serial No. 654,770

- is claims. (01. 260 166) The present invention concerns an improved method of producing chlorinated aliphatic hydrocarbons through the direct chlorination of an aliphatic hydrocarbon containing from three 5 to five carbon atoms, inclusive. The invention more articularly concerns a treatment of a chlorinated aliphatic hydrocarbon mixture to convert undesirable olefinic by-products into saturated chloro-hydroc'arbons, whereby the yield of desirable products is increased and the procedure involved in isolating such desirable products from the chlorination mixture is rendered relatively simple and inexpensive.

In our co-pending application, Serial No. 636,-

0 9.96, filed October 10, 1932, we have disclosed that,

when an aliphatic hydrocarbon containing from three to five carbon atoms is chlorinated in vapor phase according to usual methods, a complex and difficultly separable mixture containing unreacted hydrocarbon; monochlorinated hydrocarbons, polychlorinated hydrocarbons, olefines,

chloro-olefines, and hydrogen chloride is 0b tained.

The presence of olefines and chloro-olefines in I the chlorinated mixture'is highly disadvantageous. After an aliphatic hydrocarbon has been chlorinated it usual practice to scrub the reacted mixture with water to remove hydrogen chloride therefrom, then to condense the chlorinated hydrocarbon products from the residual mixture. The condensate is fractionally distilled to separate the chlorinated hydrocarbon products. Vapors, which remain after condensing the chlorinated hydrocarbon products from the chlorination mixture, usually consist substantially of the unreacted aliphatic hydrocarbon along with one or more olefines derived therefrom. Such remaining vapors, are returned. to the chlorination wherein the unreacted hydrocarbon is chlorinated to form an additional quantity of chlorinated hydrocarbon products. During chlorination of such residual vapors, however, the olefines present are chlorinated to form polychlorinated products and frequently are polymerized to form tars.

The condensate, which is obtained when the chlorinated hydrocarbon products are condensed from a chlorination mixture in accordance with ihe above described usual procedure, ,consists substantially of a solution of saturated chlorinated hydrocarbons, i. e. alkyl chlorides and polychlorinated products, having the chloro-olefine by -products dissolved therewith Such chloroolefines-usually boil at substantially-the same temperature as does an alkyl chloride product,

hence the latter can not readily be separated in a form free from contamination with chloro-olefines and the so-contaminated alkyl chloride can a not be purified completely through fractional distillation thereof. For instance, during the vapor 5 phase chlorination of "isob'utanc, chloro isobutylenes are usually formed which boil at substantially the same temperature as does isobutyi chloride (one of the principal products from the chlorination) which latter we have been unable o satisfactorily to separate from such chloro-isobutylene through fractional distillation. Again, during chlorination of propane, chloro-propylenes, e. g. allyl chloride, are often formed. Allyl chloride (B. P. approximately 45 C.) can not readily be fractionally distilled from normal propyl chloride (B. P. 46.5" C.) which is one of the products from the chlorination. The presence of an appreciable quantity of a chloro-olefine in an alkyl chloride seriously reduces the value of the latter as a commercial product and such chloro-olefine impurity frequently interferes with reactions in which it is desired to employ the alkyl chloride as a reactant.

We have now found that, hen an aliphatic hydrocarbon containing from three to five car bon atoms is reacted with chlorine to. obtain a mixture consisting substantially of chlorinated hydrocarbon products, hydrogen chloride, olefines, and chloro-olefines along with any aliphatic Q hydrocarbon which may remain unreacted, such chlorination mixturemay'be treated to effect a chemical combination of the hydrogen chloride with the olefinic by-produets, e. g. olefines and chloro-olefines, whereby the latter are converted 5 into saturated chlorinated hydrocarbons. separation of chlorinated products from the mixture may then be carried out with relative ease. Any unreacted aliphatic hydrocarbon present may readily be separated in a form substantially 40 free of ole'fines, and such unreacted hydrocarbon may be returned to the chlorination without danger of appreciably increasing the quantity of polychlorinated products and/or tars formed during such chlorination.

The

T0 theaccomplishment of the foregoing and hydrocarbon ways. In practice, we prefer to pass chlorine and the vaporized aliphatic hydrocarbon reactant into, a mixing chamber at such respective rates that a mixture of chlorine with at least its molecular equivalent. of the aliphatic hydrocarbon is formed. The aliphatic hydrocarbon may be employed in as great an excess as desired, but we usually find it most economical to mix chlorine with between 1 and 10 times its molecular equiv.- alent of the hydrocarbon reactant. The above reactants are preferablymixed in the dark at a temperature below about 125 C. F

Theanixture of chlorine and the hydrocarbon reactant\is \then passed in continuous flow through a reactiomphamber heated to a temperature usually above? 0., wherein a reaction takes place with form tion of a mixture containing hydrogen chloride, saturated chlorohydrocarbons, on oleflne, and chlorowlefines. When the chlorination is carried out at a temperature below'about 300 C., the reacting mixture may advantageously be exposed to actinic' light so as to assure rapid and complete reaction. Attemperatures above about 300 0., the chlor tion usually proceeds smoothly and with sufilci nt rapidity in the absence of light, although light may be used to catalyze'the reaction at such 1 higher temperatures, if desired.

The chlorination 'shouldbe carried out at a temperature below that at which organic components of the reaction mixture. are appreciably carbonized. The exact temperature above which carbonization will take place to an objectionable extent is dependent upon the particular aliphatic hydrocarbon to be chlorinated, the ratio of chicrine-to such hydrocarbon reactant, the period of time over which'a given quantity of reaction mixture is-maintained under the reaction conditions,

' the compositiorrof surfaces in contact with the reacting mixture, etc. The upper temperature observed during a chlorination, the reaction temperat-ure may be lowered to correct the difliculty. The chlorinated mixture is cooled to a temperature below about 200 0., preferably below .190 C., and the cooled mixture is subjected to conditions which cause reaction to take place between the hydrogen chloride and oleflnic byproducts from the chlorination, whereby said olefinic *by-productQare converted into desirable saturated compounds. e. g. alkylchlorides, dichloroehydrocarbons, etc., and the yield of said saturated compounds is increased. Such reactlonmaybe brought about by con'tacting the' cooled chlorination mixture with a catalyst capae ble of promoting -chemical combination of hydrogen chloride with oleflnesnor by subjecting the mixture to superatmospheric pressure, or both. Any of a wide variety of catalysts may be used for such purpose, among which are alkaline earth m tal chlorides, antimony trichloride,

I bismuth trichloride, ferric ,chloride, aluminum drohalogenation catalysts. With a catalyst, the

' reaction may be carried out at atmospheric or even at subatmospheric pressure. In the absence of a catalyst, the reaction may be brought about by subjecting the mixture to superatmos- -ucts may be condensed to leave a vapor mixture unreacted 2,018,345 preferably above 200 C., in any .of. the usual pheric pressure; e. g. 150 pounds per square inch.

However, regardless of whether or not a catalyst is used to promote such reaction, we prefer to carry the reaction out at a pressure considerably higher than atmospheric, e. g. 150 pounds per 5 consisting substantially of hydrogen chloride and aliphatic hydrocarbon. Hydrogen chloride may be removed from such vapor mix-. ture by scrubbing the latter with water and the residual u chlorinated hydrocarbons which had been condensed may be fractionally distilled to isolate the 7 'alkyl chloride and 'polychlorinated hydrocarbon products. 4

As procedure alternative to that described above, a chlorination mixture, which has been treated in the manner described so as to convert olefinic components thereof into saturated compounds, may be cooled (preferably under superatmospheric pressure) sufliciently to condense substantially all organic components thereof, the residual hydrogen chloride vapors may be separated directly from the condensate, and the latter may be fractionally distilled'toisolate the various reaction products. The unreacted hydrocarbon vifract on which is collected during such distillation m y, of course, be returned to the chlorination.

The following table sets forth data collected 40 during two comparative chlorination'sof isobutane. Run 1 wascarried out according to usualprocedure without any attempt being made to convert the undesirable oleflnic by-products, e. g. isobutylene and chloro-isobutylepes, into saturated compounds and serves merely as a basis for comparison with run 2; which was carried out under similar conditions-except" that a step was introduced whereby oleflnic by-produ'cts were converted into useful saturated compounds in 0 accordance with our invention. In run 1 a mixture of chlorine with 1.12 times its molecular equivalent of 95 per cent pure isobutane was passed in continuous flow through a heated reaction chamberwherein the chlorine was completely reacted in the absence of light. The vapors issuing from the reaction chamber were cooled suiliciently to condense the major portion of the pclychlorinated products and still l av'ethe major portion of the monochlorinated products in vapor state. The remaining vapors were scrubbed with water to remove hydrogen chloride therefrom. During the scrubbing operation,

a relatively small quantity (about 50 grams) of organic material was condensed, which was separated from the wash water, combined with the condensate collected prior to the scrubbing operation, and the combined condensate (I) was analyzed. The analysis of said combined condensate is to be found in the following table under the heading Condensate I. The vapors remaining after the scrubbing operation were cooled to about -70 C. so as to condense substantially all organic components thereof. The

analysis of the condensate collected after the eacted hydrocarbon vapors may be 20 returned 0 the chlorination. The mixture of 4.

scrubbing operation is to be found in the table under the heading "Condensate 11. Y

Run 2 of the following table was made under operating conditions similar to those employedin riin 1, except that immediately following the step of condensing polychlorinated products from the crude chlorination mixture, the residual vapors were passed, at atmospheric pressure, through a 1 inchtube containing granular kaolin for 44 inches or its length. During passage .of vapors through said tube the latter was inaintained at a temperature between 70 and 80 C. The vapors were then scrubbed with water to remove hydrogen chloride therefrom, the residual vapors were condensed, and the condensate '(II) was analyzed. A small quantity of organic material which was condensed during the scrubbing operation was separated from the wash water, combined with the condensate collected prior to said scrubbing operation, and the combined condensate (I) was analyzed.

Analysis-per cent by weight:

I Isobutane Polychlorinated products. Isobutyl chloride Tertiary-butyl chloride- Chloro-isobutylenes Cb'ndemale II Weight-grams Analysis-per cent by weight:

Tcnhnfnnn Polychlorinated products Isobutyl chloride Tertiary-butyl chloride- Chloroqsobutylene--. 'Isobutylene In the foregoing table, the .comparative condensates (II) illustrate certain advantages of our invention. Condensate II of run 2 represents a fraction of a chlorination mixture which had been treated in accordance with our invention, to convert oleflnic by-products of the chlorination into the desired saturated compounds. Condensate (II) of run 1 is an analogus fraction from a similar chlorination, except that said condensate from run 1 did not receive treatment to convert the olefinic by-products into saturated compounds. A comparison of the condensates (II) shows that by a. simple application of the principle of our invention the percentage-by weight,

of tertiaryebutyl chloride in such condensate was increased from 7.6 to 11.74; the percentage of chloro-isobutylenes was decreased from 7.3 to 0.26; 'and the percentage of isobutylene in such condensate was decreased from 2.3 to 0.6. Stated in terms of the percentage change of actual quantities of said compounds incondensates (11),the application of our invention resulted in a 54.5

per cent increase in the-weight of'tertiary-butyl chloride obtained in a given quantity?! such vert the oleflnes and chloro-olefines present into in the weight of isobutylene obtained in a given quantity of such condensate.

The principle of our invention may be em- 5 ployedflin ways other thanthose hereinbefore' stated. For instance, the entire mixture obtained by chlorinating an aliphatic hydrocarbon may be treated according to our method tp conl0 desirable saturated compounds and the so-treated mixture may be separated into its components in any of the usual ways. Our improved method of making chlorinated aliphatic hydrocarbons is applicable to the chlo-. rination of any aliphatic hydrocarbon containing from three to five carbon atoms, e. g. propane, normal butane, normal pentane, isopentane, etc. During a vapor phase chlorination of any of said hydrocarbons, according to usual methods, olefinic by-products are formed which may readily be converted into valuable saturated compounds by our present method.

Our invention, in brief, comprises-chlorinating an aliphatic hydrocarbon, containing from three to five carbon atoms, in vapor phase at a temperature above 160 C. and then treating the reaction miiiture to convert olefinic by-products contained therein into valuable saturated compounds.

In the following claims, the expression chloroisobutanes" shall be understood to refer to saturated chlorine derivatives of isobutane, e. g. isobutyl chloride, tertiary-butyl chloride, 1.3-dichloro-isobutane, etc.. and the expression monochloro-isobutanes shall beunderstood to' refer to isobutyl chloride and tertiary-butyl chloride.

Other modes of applying the principle of our invention may be employed instead of those explained, change being made as regards the method herein disclosed, provided the step or steps 40 stated by any of the following claims or the equivalent of such stated step or steps be employed. l

We therefore particularly point out and distinctly claim as our invention:

1. In a method of chlorinating saturated aliphatic hydrocarbons wherein chlorine is reacted with a saturated aliphatic hydrocarbon, containing from three tofive carbon atoms, to form a mixture containing saturated chloro-hydrocar-JD bons, hydrogen chloride, and oleflnic compounds, the step which consists in reacting hydrogen chloride, formed during'the chlorination, with said olefinic compounds at a temperature below about 200 C. to convert the latterinto saturatedchlorohydrocarbons. x

2. In a method of chlorinating saturated aliphatic hydrocarbons, the steps-which consist in reacting chlorine with a saturated aliphatic hydrocarbon, containing from three to live carbon 00 'phatic hydrocarbons, the stepswhich consist in reacting chlorine with a saturated aliphatic hydrocarbon, containing from three to five carbon atoms, in vapor phase at a temperature above about 160 C., to form a mixture containing saturated .chloro-hydrocarhons, hydrogen chloride, and oleflnic compounds, and then-reacting the hydrogen chloride with the oleflnic components of such mixture while maintaining the latter at a temperature below about 200 C'.

4. In a method of chlorinating saturated aliphatic hydrocarbons, the steps which consist in reacting .chlorine with a saturated aliphatic hydrocarbon containing from three'to five carbon atoms, in vapor phase at a temperature above about 200 C., to form a mixture containing hydrogen chloride and oleflnic compounds and then contacting the chlorination mixture, at a temperature below about 200 C., with a hydrohalogenation catalyst to effect chemical combination between said hydrogen chloride and oleflnic compounds.

5. Ina method of chlorinating saturated aliphatic hydrocarbons, the steps which consist in reacting chlorine with a saturated aliphatic hydrocarbon, containing from three to five carbon atoms, in vapor phase at'a temperature above about 200 C., to form a mixture containing monochlorinated hydrocarbons, polychlorinated hydrocarbons, hydrogen chloride and oleflnic compounds, cooling the reacted mixture sumciently to condense polychlorinated hydrocarbon products therefrom, and contacting the residual vapors, at a temperature below about 100 C., with a hydrohalogenation catalyst to effect chemical combination between said hydrogen chloride and oleflnic compounds.

6. In a method of chlorinating saturated aliphatic hydrocarbons, the steps which consist in reacting a mixture of chlorine with at least its molecular equivalent of a saturated aliphatic hydrocarbon containing from three to five carbon atoms, in vapor phase at a temperature above about 200 C., to form a mixture containing unreacted hydrocarbon, monochlorinated hydrocarbons,- polychlorinated hydrocarbons, hydrogen chloride and oleflnic compounds, cooling the reacted mixture sufllciently to condense polychlo- I rinated hydrocarbons therefrom and still leave the major portion of the monochlorinated hydro-. carbon-products in vapor state, contacting the vapors, at a temperature below about 100 C., with a hydrohalogenation catalyst to effect chemical combination between said hydrogen chloride and oleflnic compounds, thereafter scrubbing the vapor mixture withwater to remove hydrogen chloride therefrom, condensing and separating chlorinated hydrocarbon products from the residual vapors to leave vapors consisting substantially of the unreacted aliphatic hydrocaribion, and returning the latter to the chlorina on.

7. In a method of chlorinating saturated ali-' phatic hydrocarbons, the steps' which consist in reacting chlorine with a saturated aliphatic hydrocarbon, containing from three to five carbon atoms, in vapor phase at a temperature above about 160 C., to form a mixture containing saturated 'chloro-hydrocarbons, hydrogen chloride, and oleflnic compounds, and thereafter subjecting the chlorination mixture to a sufliciently high pressure to cause reaction between the hydrogen chloride and oleflnic components of. the mixture with resultant formation of an additional tity of saturated chloro-hydrocarbons.

8. In a method of chlorinating saturated aliphatic hydrocarbons, the steps which consist in reacting a mixture of chlorine with at least its molecular equivalent of a saturated aliphatic hydrocarbon, containing from three to five carquanbon atoms, in vapor phase at a temperature above about 200 C., cooling the reacted mixture suiliciently to condense polychlorinated hydrocarbons aoiasac therefrom and still leave the major portion of the monochlorinated hydrocarbon products in vapor state, and subjecting the residual. vapor. mixture, at-a temperature below about 200 C.,

to a sufliciently high pressure to cause reaction 5 between the hydrogen chloride and oleflnic components of the mixture with resultant formation "of an additional quantity of saturated chlorohydrocarbons.

9. In a method wherein chlorine is reacted with isobutane to form a mixture containing chloroisobutanes, hydrogen chloride, isobutylenes, and chloro-isobutylene, the step which consists in reacting the hydrogen chloride with the isobutylene and chloro-isobutylene to form an additional quantity of chloro-isqbutanes.

10. The method which comprises chlorinating isobutane to form a mixture containing chloroisobutanes', hydrogen chloride, isobutylene,- and chloro-isobutylene, and then reacting the hydrogm chloride with the isobutylene andchloro-isobutylene to form an additional quantity of chloro-isobutanes.

11. The method which comprises reacting chlorine with isobutane, in vapor phase at a temperature above about 160 C., to form a mixture containing chloro-isobutanes', hydrogen chloride, isobutylene, and chloro-isobutylene, and then reacting the hydrogen chloride with the isobutylene and chloro-isobutylene at a temperature below about 200 C. to form an additional quantity of chloro-isobutanes.

124 The method which comprises reacting chlorine with isobutane in vapor phase at a temperature above about 200 C., to form a mixture containing hydrogen chloride and oleflnic compounds, and then contacting the chlorination mixture, at a temperature below about 200 C., with a hydrohalogenation catalyst to eil'ect chemical combination between said hydrogen chloride 40 v and oleflnic compounds. I

13. The method which comprises reacting chlorine with isobutane in vapor phase at a temperature above about 200 C., to form a. mixture containing monochlor-isobutanes, polychlor-isobutanes, hydrogen chloride and oleflnic compounds, cooling the reacted mixture sufliciently to condense polychloro-isobutanes therefrom and still leave the major portion of the monochloro-iso- .butane products in vapor state, and contacting the residual vapor mixture, at a temperature below about 100 C., with a hydrohalogenation catalyst to effect chemical combination between said hydrogen chloride and oleflnic compounds.

14. The method which comprises reacting a mixture of chlorine with at least its molecular equivalent of isobutane in vapor phase at a temperature above about 200 C., to form a mixture containing unreacted isobutane, monochlor-isobutanes, polychlor-isobutanes, hydrogen chloride 00 and'olefinic compounds. cooling the reacted mixture sufllciently to condense polychloro-isobutanes therefrom and still leave the major portion of I the monochloro-isobutane products in vapor state, contacting the vapors, at a temperature 5 below about 100 C., with a hydrohalogenation catalyst to effect chemical combination between said hydrogen chloride and oleflnic compounds, thereafter scrubbing the vapor mixture with water to remove hydrogen chloride therefrom, condensing and separating chloro-isobutane products from the residual vapors to leave vapors consisting substantially of unreacted isobutane, and returning the latter to the chlorination.

15. The method which comprises reacting chlo- 76 rine with isobutane, in vapor phase at a tempera!- ture above about 160 C., to form a mixture containing chloro-isobutanes, hydrogen chloride, isobutylene, and chloro-isobutylene, and thereafter a subjecting the chlorination mixture to a sufliciently high pressure to cause the hydrogen chloride to react with isobutylene and chloro-isobutylene to form an additional quantity of chloro-isobutaries. v a 16. The method which comprises reacting a. mixture of chlorine with at least its molecular equivalent of isobutane, in vapor phase at a. temperature above about200 6., cooling the reacted 'tity of chloro-isobutanes.

mixture, at a temperature below about 200 C., 5

to a .su'mciently high pressureto cause the hydrogen chloride to react with the isobutylene and chloro-isobutylene components of the mixture with resultant formation of an additional quan- EDGAR C. BRI'I'ION. GERALD H. COLEMAN. BARTHOLDT C. HADLER.