Surface Optimization and Redox Behavior of Vanadium Oxides Supported on γ-Al2O3

This report describes optimization of the synthesis of γ-Al2O3 supported vanadium oxides using three different vanadium precursors: OV(O i Pr)3, OV(OEt)3 and OV(OPr)3. It was observed that the actual loading of the metal oxide is controlled by a number of factors, including the kinetics and thermodynamics of the grafting process, the time allowed for the grafting reaction to proceed, the amount of available precursor, the concentration of the grafting solution, and temperature at which grafting is pursued. From TPR (temperature programmed reduction) and XPS (X-ray photoelectron spectroscopy) studies it was observed that V4+ and V5+ were the predominant oxidation states present under both normal and rigorous reducing conditions simulating those prevalent in the steam reforming process.