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.