Gas-phase hydrogenolysis of chloroethene: rates, products, and computer modelling

Abstract

Hydrogenolysis of chloroethene (vinyl chloride, VC) has been investigated in a tubular-flow reactor at atmospheric pressure between 872–1085 K. Ethene, ethyne, and HCl are major initial products of reaction. Hydrogen-atom addition to the substituted end of VC yields C₂H₄ after loss of a chlorine atom from the radical intermediate; addition to the unsubstituted end gives the 1-chloroethyl radical (1) and is reversible, but (1) may also be hydrogenated to chloroethane, which rapidly loses HCl. HCl elimination from VC to give C₂H₂ mainly occurs via a molecular reaction for which the parameters log k/s^–1= 14.0 – 290kJ mol^–1/θ,θ= 2.3 RT have been determined. Both C₂H₂ and C₂H₄ are hydrogenated and lead to C₂H₆ and, through splitting of the C–C bond in this product, to methane. Addition of HCl had only a small rate-enhancing effect on VC conversion, with increased production of ethene. A reaction model which accounts well for VC conversion rates and product, distributions has been developed. Features of VC hydrogenolysis have been compared with its pyrolysis.