Decomposition of diethylsulphide on tungsten. A dynamic treatment of surface catalysis

The mechanism of the decomposition of diethylsulphide on tungsten was studied by a dynamic treatment of adsorbed species during the reaction. When diethylsulphide was introduced to tungsten, the evolution of ethylene, ethane and hydrogen were observed in the initial stage of the reaction, and ethylmercaptan and hydrogen sulphide additionally in the later stage. In the initial stage, decomposed sulphur was consumed to form a surface sulphide layer, and after formation of the W8S and W4S layer, ethylmercaptan and hydrogen sulphide appeared in the gas phase. Further decomposition of diethylsulphide on the W4S layer produced no more layers of sulphide. The rate of decomposition of diethylsulphide in terms of ethylene and ethane formation was measured at the reaction temperature (250–300°C) as a function of the amount of adsorbed species. The rate of ethylene formation was first order with respect to the total amount of adsorbed C2 species, and that of ethane formation was first order with respect to the total amount of adsorbed C′2 species and the partial pressure of hydrogen respectively. It was therefore probable that the rate-determining step of the formation of ethylene was a surface reaction involving one molecule of the adsorbed diethylsulphide or corresponding species, and that of ethane formation was the hydrogenation of the intermediate of ethylene formation.