FTIR spectroscopic investigation of the active sites on different types of silica catalysts for methane partial oxidation to formaldehyde

Several commercial silica samples showing different catalytic activities in the partial oxidation of methane (MPO) to formaldehyde have been investigated using FTIR technique. Two IR absorption bands at 893 and 909 cm^–1, observed upon dehydroxylation of the silica catalysts and assigned to reactive siloxane sites on the surface (strained siloxane bridges), were found to disappear upon heating in methane at high temperature. The catalytic activity increases together with the intensity of the bands due to such strained sites in the different SiO₂ samples.