Catalytic activity and structure of Mo oxide highly dispersed on ZrO2 for oxidation reactions

Abstract

The structure of Mo–Zr oxides has been investigated by X-ray diffraction and Fourier-transform infrared and laser Raman spectra. At low Mo content, MoO₃ is highly dispersed on ZrO₂, an amorphous phase being formed which is characterized as polymolybdates. The i.r. and Raman bands due to MoO in polymolybdate are shifted from 930 to 970 cm^–1 with increasing Mo content on ZrO₂, suggesting that with low Mo catalysts surface Mo species are more distorted. The rates of oxidation of ethanol and propene pass through maxima around 10 atom % Mo. These results provide evidence that the rates over polymolybdate are 10–20 times higher than those over crystalline MoO₃.