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) (C) 2004 Elsevier B.V. All rights reserved.