Preparation method and structure of active sites of FeOx/SiO2 catalysts in methane to formaldehyde selective oxidation

The effects of preparation method on surface structures and catalytic properties in the selective oxidation of CH4 to HCHO With O-2 (MPO) of low-loaded (0.09-0.43 wt.% Fe) FeOx/SiO2 catalysts have been addressed. The DR-UV-Vis patterns prove that the preparation route, based on "adsorption-precipitation" of Fe-II precursors on silica under anaerobic conditions (ADS/PRC), enhances the dispersion of the active phase in comparison to the conventional "incipient-wetness" route. FTIR of adsorbed NO data signal the presence on silica of several "isolated" Fe moieties with a different surface coordination. A higher FeOx dispersion confers a superior performance to ADS/PRC FeOx/SiO2 catalysts in terms of specific rate of CH4 conversion (sigma(CH4)) and HCHO formation (epsilon(HCHO)) of Fe atoms which result in quite larger HCHO productivity values (STYHCHO)