Studies on the structure and catalytic performance of S and P promoted Na-W-Mn-Zr/SiO_2 catalyst for

A series of Na-W-Mn-Zr/SiO_2 catalysts promoted by different contents of S or/and P were prepared and their catalytic performance for oxidative coupling of methane was investigated to clarify the effect of S and P on the Na-W-Mn-Zr/SiO_2 catalyst.The catalysts were characterized by X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).From the characterization results,it is found that the addition of S and P to the Na-W-Mn-Zr/SiO_2 catalyst helps the formation of active phases,such as α-cristobalite,Na_2WO_4,ZrO_2,and Na_2SO_4.Moreover,the addition of S and P increases the concentration of surface-active oxygen species by improving the migration of active components from the bulk phase to the surface of the catalyst.According to the activity test,impressive methane conversion and C_2 hydrocarbons yield were obtained at a low temperature of 1023 K over the six-component Na-W-Mn-Zr-S-P/SiO_2 catalyst,which contained 2 wt% S and 0.4 wt% P simultaneously.The deactivation of Na-W-Mn-Zr-S-P/SiO_2 was due to the loss of surface active components.