FT-IR and FT-FIR studies of Vanadium, Molybdenum and Tungsten oxides supported on different carriers

In the far IR region at low molybdenum loadings, Mo-SiO2 catalysts present a pseudomolybdate or a polymolybdate species, while bulk-like MoO3 appears at loadings close to the geometrical monolayer coverage. W-SiO2 and V-SiO2 spectra show bands close to those observed on the corresponding bulk oxides. In the case of TiO2, Al2O3, ZrO2 supported catalysts, a band is observed near 1000 cm-1 which is assigned to the Mo = O stretching vibration of coordinatively unsaturated Mon+ ions showing a stronger interaction with the support than one observed on silica. (Author)