Partial Oxidation of Methane to Formaldehyde on Fe-doped Silica Catalysts

Abstract The effect of the Fe doping on the catalytic pattern of commercial silica samples in the partial oxidation of methane to formaldehyde (MPO) with molecular O 2 at 650 °C has been investigated. The influence of loading (Fe 2 O 3 , 0.02-3.2 wt%) on the activity-selectivity pattern and steady-state of the surface of the Fe/SiO 2 system has been highlighted. EPR measurements of Fe/SiO 2 catalysts indicate the presence of “isolated Fe 3 + ions”, small Fe 2 O 3 clusters and Fe 2 O 3 particles, their relative concentration depending upon the surface loading. Whatever the loading, Fe promotes the reactivity of the silica surface, while the maximum in HCHO surface productivity, associated with a surface loading of 0.05-0.1 Fe at nm − 2 , signals that HCHO formation is mostly driven by “isolated Fe species”.