Abstract: The oxidative coupling of methane to C2 hydrocarbons (C2H4 and C2H6) was examined on Mn-Na2SO4/SiO2. The catalysts were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, laser Raman spectroscopy, and temperature-programmed reduction with H2. The addition of Na2SO4 to Mn/SiO2 led to the exclusive transformation of amorphous SiO2 to α-cristobalite and the concurrent oxidation of Mn3O4 to Mn2O3. The observed effects on the structure and catalytic performance suggest that Mn2O3 species act as the active sites for the methane activation, which may provide the basis for the rational design of new efficient catalysts for the oxidative coupling of methane.

Key words: oxidative coupling of methane, active site, manganese sesquioxide, silica, supported catalyst, sodium sulfate