Surface functionalization of SBA-15-ordered mesoporous silicas: Oxidation of benzene to phenol by nitrous oxide

We report the preparation and catalytic properties of highly ordered mesoporous Fe–Ga–SBA-15 materials via direct hydrothermal synthesis. Gallium and iron ions were introduced directly into the synthesis gel typical for the preparation of SBA-15. The resulting materials had hexagonally ordered mesopores of about 6 nm and surface areas >1000 m2/g. In Fe–SBA-15, the iron species were mainly tetrahedrally coordinated in the amorphous silica walls. In the presence of Ga (Fe–Ga–SBA-15), Fe species were located at the silica surface as isolated species, as determined by Raman and diffuse-reflectance UV–Vis spectroscopy measurements. The Fe species in Fe–Ga–SBA-15 displayed similar properties as the FeZSM-5 zeolites toward nitrous oxide decomposition and were active in the oxidation of benzene to phenol by nitrous oxide. Ga–SBA-15 and Fe–SBA-15, on the other hand, showed no catalytic activity. Compared with Fe–Al–SBA-15, Fe–Ga–SBA-15 displayed greater selectivity to the desired phenol product.