GB627119A - A process for preparing 1.1.2-trichloroethane by the chlorination of 1.2-dichloroethane - Google Patents

Abstract

1.1.2-Trichloroethane is prepared by chlorinating 1.2-dichloroethane with chlorine gas in a reaction zone situated in a rectifying apparatus so that the maximum concentration of 1.1.2-trichloroethane in the vapour present is preferably less than 15 mol. per cent, e.g. 8 to 12 mol. per cent. These conditions are obtained by using a high reflux ratio and by selecting the level at which the reaction zone is adjusted in the rectifying apparatus in conformity with the 1.1.2-trichloroethane concentrations. Chlorination is preferably effected in the presence of chemically active rays and the 1.1.2-trichloroethane produced is substantially free from more highly chlorinated products. In an example, the chlorination of 1.2-dichloroethane p is effected in a rectifying apparatus consisting of a glass dish column 4 metres high, diameter 75 mms. with a steel boiler below and glass cooler on top, mercury vapour lamps being placed at levels of 2.5 and 3 metres above the bottom, 18 kgs. of a mixture consisting of 2.5 mol. per cent of 1.2-dichloroethane, 95 mol. per cent 1.1.2-trichloroethane and 2.5 mol. per cent of sym.tetrachloroethane are placed in the boiler and heated so that 40 kgms. of vapours per hour are condensed in the top cooler, dichloroethane being then pumped into the top cooler at 4.0 kgms. per hour and chlorine introduced at a level of 2 metres from the bottom of the column so that the temperature in the boiler does not fall below the boiling point of 1.1.2-trichloroethane, the process then being continued for 110 hours when the bottoms product is substantially 1.1.2-trichloroethane.