Studies on the structure and catalytic performance of S and P promoted Na-W-Mn-Zr/SiO₂ catalyst for oxidative coupling of methane

A series of Na-W-Mn-Zr/SiO₂ 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/SiO₂ 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/SiO₂ catalyst helps the formation of active phases, such as a-cristobalite, Na₂WO₄, ZrO₂, and Na₂SO₄. 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 C₂ hydrocarbons yield were obtained at a low temperature of 1023 K over the six-component Na-W-Mn-Zr-S-P/SiO₂ catalyst, which contained 2 wt% S and 0.4 wt% P simultaneously. The deactivation of Na-W-Mn-Zr-S-P/SiO₂ was due to the loss of surface active components.