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

Abstract The effects of preparation method on surface structures and catalytic properties in the selective oxidation of CH 4 to HCHO with O 2 (MPO) of low-loaded (0.09–0.43 wt.% Fe) FeO x /SiO 2 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 FeO x dispersion confers a superior performance to ADS/PRC FeO x /SiO 2 catalysts in terms of specific rate of CH 4 conversion ( σ CH 4 ) and HCHO formation ( e HCHO ) of Fe atoms which result in quite larger HCHO productivity values (STY HCHO ).