Influence of cesium and vanadium contents on the oxidation functionalities of heteropoly molybdate catalysts

• Heteropoly molybdate modified with Cs and V to tune its acid and redox properties.
• The oxidation activity varies with the amount of Cs and V in the catalysts.
• More amount of V destabilizes the Keggin structure of heteropoly molybdate.

Keggin-type heteropoly molybdates with different cesium and vanadium contents were synthesized and characterized by X-ray diffraction, FT-infrared, in situ Laser Raman, X-ray photo electron spectroscopy and temperature programmed desorption of NH3 techniques. The catalytic functionalities were evaluated for vapor phase aerobic oxidation of benzyl alcohol. Raman spectral studies suggest the partial destabilization of Keggin structure of the catalyst with more than two vanadium atoms per one Keggin unit in the primary structure. The conversion of benzyl alcohol and selectivity to benzaldehyde was influenced by both Cs and V contents. The correlation between catalytic activity and physico-chemical properties of the catalysts suggested that the acidity and redox nature of the catalysts have an important role in the oxidation of benzyl alcohol and these properties are influenced by the amounts of Cs and V, respectively, in heteropoly molybdates. A plausible mechanism for CsxMPAVy/TiO2 catalyzed oxidation of benzyl alcohol has been proposed.

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