The kinetics of the thermal decomposition and polymerization of ethane and ethylene

Abstract

The pyrolysis of ethane, ethylene and mixtures of the two gases, has been studied by heating the reactants to 600° C for short time intervals and measuring the products of reaction by chemical analysis. In the case of ethane, the first products are ethylene, hydrogen and a small amount of methane. This reaction is inhibited by nitric oxide. The subsequent reactions, none of which is affected by nitric oxide, involve both ethane and ethylene, and result in the formation of methane (in far greater quantity than that produced from ethane direct), propylene, a compound of the formula C 4 H 8 which may be 1-butene, and higher hydrocarbons. The C 4 H 8 , which attains a constant concentration after a few minutes, is produced by two bimolecular reactions, one involving both ethane and ethylene, and the other ethylene alone. Methane is formed from decomposition of the C 4 H 8 . Propylene and higher hydrocarbons are produced as a result of a bimolecular reaction between C 4 H 8 and ethylene. The kinetics of the proposed mechanism hold good over the widest possible range of ethane + ethylene mixtures. Values for the velocity constants of all these reactions are given, and approximate values of the activation energies have been calculated following a further set of experiments at 450° C.