Role of sodium in the oxidative coupling of methane over Na-W-Mn/SiO_2 catalysts

摘要

Na-W-Mn/SiO_2 catalysts with different sodium contents (wt/100) were prepared and sued for the oxidative coupling of methane (OCM). The catalysts were characterized by XPS and XRD. It was found that the catalysts with sodium contents between 0.39wt/100 and 2.34wt/100 exhibited good catalytic performances and the crystalline phases of the manganese oxides which favoured the reaction were formed. Owing to the addition of Na to the WO_4Mn/SiO_2 catalyst, W and Mn moved towards the surface. These results suggested that the sodium is an essential active component for A high CH_4 conversion and a high C_2H_4 selectivity.