PROCESS FOR REDUCING THE CONCENTRATION OF 2-CHLOROBUTADIENE-1(1,3) IN 1,2-DICHLOROETHANE RECOVERED IN THE INCOMPLETE THERMAL CRACKING INTO VINYL CHLORIDE

1275698 Purifying 1 ,2-dichloroethane KNAPSACK AG 19 Nov 1970 [26 Nov 1969] 55069/70 Heading C2C 1,2-Dichloroethane recovered in the incomplete thermal cracking of 1,2-dichloroethane into vinyl chloride and being contaminated with low boilers boiling below 83À7‹ C. (760 mm. Hg) and highboilers boiling higher than 83À7‹ C., has the concentration of 2-chlorobutadiene- (1,3) low boiler therein reduced, by transformation of the 2-chlorobutadiene-(1,3) into a high boiler contaminant by: distillatively freeing the 1,2-dichloroethane from the low boiler contaminants therein in a low boiler column; continuously withdrawing all or a portion of the low boiler contaminants concentrating near the head of said low boiler column; treating the low boiler concentrate withdrawn from the said low boiler column with gaseous chlorine at 10- 120‹ C. under 1-3 atmospheres absolute, with irradiation of U.V. and/or visible light in the absence of catalysts, and recycling the chlorinetreated low boiler concentrate to the said low boiler column; continuously delivering material accumulating in the base of the said low boiler column from the low boiler column to a high boiler column; and distilling off pure dichloroethane from the high boiler contaminants in the said high boiler column.