OXIDATIVE CONVERSION OF METHANE TO C2-HYDROCARBONS OVER LITHIUM, MANGANESE, CADMIUM AND ZINC PROMOTED MGO CATALYSTS .1. CATALYST PERFORMANCE IN PRESENCE OF FREE OXYGEN

Oxidative coupling of methane to C2-hydrocarbons over MgO, LiMgO, MnOxMgO, LiMnOxMgO, CdOMgO, LiCdOMgO, ZnOMgO and LiZnOMgO catalysts at 823-1103 K in presence of free oxygen has been investigated. The C2-selectivity of the catalysts and the ethylene-to-ethane ratio in the products were found to increase with the increase in the reaction temperature. The addition of lithium, zinc and cadmium promoters to MgO caused a very significant catalyst sintering resulting in a decrease in the catalyst surface area but an increase in the catalyst C2-selectivity. The catalyst C2-selectivity was found to be increased almost linearly with the decrease in the catalyst surface area. The lithium-promoted catalysts, however, showed a strong dependence of their methane conversion activity and C2-selectivity on the time on-stream and are sintered extensively during the catalytic process. Among the catalysts, the LiZnOMgO and LiCdOMgO showed superior performance in the methane conversion process. © 1990.