Oxidative coupling of methane over Mn–Na2WO4/SiO2 catalyst with continuous supply of alkali chloride vapor

Abstract

The oxidative coupling of methane (OCM) to ethylene is an attractive direct route to produce valuable chemicals from methane. We previously demonstrated that alkali chloride–Mn–Na2WO4/SiO2 catalysts exhibit high ethylene yields in the OCM reaction. However, these catalysts are rapidly deactivated through the evaporation of the alkali chloride. We herein attempted to maintain constant high yields of ethylene through the continuous supply of alkali chloride vapor to a Mn–Na2WO4/SiO2 catalyst. Experiments were carried out using a flow reactor, where sodium chloride or potassium chloride powder was placed in front of the catalyst bed to allow generation of the alkali chloride vapor and direct feeding into the catalyst bed. The alkali chloride was transferred to the catalyst in the gas phase and catalytically promoted the OCM reaction. Ethylene yields obtained with this reaction system were comparable to those obtained using the alkali chloride–Mn–Na2WO4/SiO2 catalysts. An ethylene yield of 27% was obtained using the Mn–Na2WO4/SiO2 catalyst in the presence of potassium chloride at 973K and no catalyst deactivation was observed over 28h.