Infrared, laser-Raman and X-ray diffraction investigation of MoO3/ZrO2 and the oxidation of (Z)-but-2-ene

Abstract

Molybdenum oxide supported on zirconia has been studied by XRD, FTIR and laser-Raman spectroscopy, together with the oxidation of (Z)-but-2-ene. Mo–Zr catalysts with less than 11 wt % of Mo loadings are mainly composed of amorphous polymolybdates. Mo–Zr catalysts with high MoO₃ loading exhibit high selectivities to acetaldehyde and acetic acid and both Lewis- and Brønsted-acidic sites by pyridine adsorption. On the other hand, the catalysts with low MoO₃ loading exhibit selectivities to furan and buta-1,3-diene and only Lewis sites. In situ FTIR and Raman spectra show the different character of Mo oxides with MoO₃ loading. This difference of Mo character leads to the difference in selectivities for butene oxidation.