ESR, FT-Raman spectroscopic and ethanol partial oxidation studies on MoO3/SnO2 catalysts made by metal oxide vapor synthesis

A series of SnO2-supported MoO3 catalysts were prepared by the metal oxide vapor synthesis (MOVS) technique. ESR studies indicated the presence of highly dispersed Mo5+ species in both octahedral and tetrahedral coordination environments at all the loadings studied. At the highest MoO3 loading of 12 wt%, the formation of MoO3 microcrystallites was indicated from the lower intensity of the ESR signal. Raman studies also showed the presence of well dispersed surface molybdate species up to 4.4 wt% MoO3 loading, and the peaks corresponding to microcrystallites of molybdena were observed at 12 wt% MoO3 loading. The ethanol partial oxidation activities of the catalysts increased with increase in MoO3 loading and the catalyst with 4.4 wt% molybdena content showed the highest activity; all the MOVS catalysts showed 100% selectivity to acetaldehyde at low conversions.