Raman spectroscopic studies on tetragonal ZrO2 supported MoO3 and ZnO-MoO3 systems

A series of samples of MoO3 and/or ZnO supported on tetragonal ZrO2 (t-ZrO2) have been investigated by laser Raman spectroscopy and XRD. For these supported binary-oxide systems, the loading sequence of the oxide and the calcination temperature have notable effects on the interactions of the oxides and support and hence the nature of the catalysts. The experimentally measured dispersion capacities of ZnO or MoO3 on t-ZrO2, and ZnO on two MoO3-modified t-ZrO2 are consistent with the values predicted by the incorporation model. The dispersion capacity of MoO3 on ZnO-modified t-ZrO2 has not been measured due to the strong interaction between MoO3 and the supported ZnO, leading to the formation of a ZnMoO4 phase. The results are further proof of the effect of the nature and, in particular, the surface structure of the support on the dispersion behavior and the surface structure of the dispersed oxides. The effect of calcination temperature on the dispersion state of the oxides is also discussed.