Hoechst Aktiengesellschaft

Heinz-Josef Berns

Klaus Gehrmann

Alexander Ohorodnik

Udo Dettmeier

Production 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 between 2 and 4 carbon atoms at elevated temperature, and distilling off resulting 2-chlorobutadiene-(1,3). To this end, a reaction zone is continuously supplied with 3,4-dichlorobutene-(1), an alcohol and the aqueous hydroxide solution and the whole is heated to boiling therein while passing a stream of inert gas therethrough; resulting 2-chlorobutadiene-(1,3) is distilled off from the reaction zone and fractionated until pure; a reaction mixture which commences to separate into two layers comprising an upper layer and a lower layer is retained in the reaction zone; aqueous alcohol in excess is continuously removed from said upper layer through an overflow and the alcohol is recovered; the lower layer consisting of an aqueous/alkaline solution of unreacted hydroxide, chloride salt and minor amounts of alcohol is continuously removed through the bottom of the reaction zone; the lower layer is distilled so as to concentrate it; precipitated chloride salt is isolated, and concentrated liquor is recovered.

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Munich, Georgia

Heinz-Josef Berns