Production of 2-chlorobutadiene-1,3

A process for the manufacture of 2-chlorobutadiene-(1,3) by the dehydrochlorination of 3,4-dichlorobutene-(1) in an aqueous solution of an alkali metal or alkaline earth metal hydroxide in the presence of an alcohol having 2-4 carbon atoms at elevated temperature, and distilling off resulting 2-chlorobutadiene-(1,3), which comprises continuously supplying the lower part of a circulation reaction zone with 3,4-dichlorobutene-(1), an alcohol and the aqueous hydroxide solution, the resulting reaction mixture containing between 10 and 90% by volume of alcohol, and heating the mixture to boiling therein;

• continuously delivering from the reaction zone resulting 2-chlorobutadiene-(1,3) together with an alcohol/water-azeotrope to a first distilling zone comprising a dephlegmatory zone;
• maintaining the said dephlegmatory zone at a temperature between 35.degree.C. and 50.degree.C., and continuously distilling off in said first distilling zone the said 2-chlorobutadiene-(1,3) and the said azeotrope, the alcohol/water-azeotrope being selectively condensed and recycled to said first distilling zone;
• condensing the resulting vaporous, crude and alcohol-containing 2-chlorobutadiene-(1,3) and introducing it into an extraction zone;
• scrubbing the 2-chlorobutadiene-(1,3) therein with water flowing countercurrently with respect thereto, drying it and fractionating it until pure;
• retaining in the reaction zone a reaction mixture which separates into an upper layer and a lower layer;
• continuously removing an aqueous hydroxide/alcohol solution in excess from said upper layer through an overflow and recovering the alcohol;
• continuously removing through the bottom of the reaction zone a part of the said lower layer consisting of an aqueous alkaline solution of unreacted hydroxide, chloride salt and minor proportions of alcohol;
• distilling the removed part of the lower layer so as to concentrate it;
• isolating precipitated chloride salt, and recovering concentrated liquor.