Process for production of 2,3-dichlorobutadiene-1,3

Abstract

2,3-dichlorobutadiene-1,3 of high purity is produced from 1,2,3,4-tetrachlorobutane by a process comprising the steps of dehydrochlorination, chlorination of the reaction product obtained in the dehydrochlorination step and subsequent separation of a 2,3-dichlorobutadiene-1,3 composition from the reaction product of the chlorination step.

1 . A composition comprising 2,3-dichlorobutadiene-1,3, prepared by a process comprising the steps of:
 A. contacting a composition comprising 1,2,3,4-tetrachlorobutane with an aqueous mixture comprising a base having a K b  of at least 10 −9 , at a temperature sufficient to dehydrochlorinate the 1,2,3,4-tetrachlorobutane, thereby forming a first reaction product having at least two phases, 1) a first phase comprising a mixture of a) 2,3-dichlorobutadiene-1,3 and b) a chlorinated byproduct comprising chlorinated butenes other than 2,3-dichlorobutadiene-1,3 and 2) a second phase comprising an aqueous phase;   B. separating said first phase from said aqueous phase;   C. contacting said first phase after it has been separated from said aqueous phase with chlorine having a purity of at least 96% in an amount sufficient to further chlorinate said chlorinated byproduct but insufficient to cause conversion of more than 20% of the 2,3-dichlorobutadiene-1,3 present in said first phase to more highly chlorinated species, thereby producing a second reaction product; and   D. isolating from said second reaction product a composition comprising 2,3-dichlorobutadiene-1,3 wherein at least 90 weight percent of said composition is 2,3-dichlorobutadiene-1,3, based on the total weight of said composition.   
     
     
         2 . A composition of  claim 1  wherein step A is conducted in the presence of a phase transfer catalyst. 
     
     
         3 . A composition of  claim 1  prepared by a process wherein step C is conducted in the presence of an ionic catalyst. 
     
     
         4 . A composition of  claim 1  prepared by a process wherein step A is conducted in a bubble reactor.