Precursor Effect on the Molecular Structure, Reactivity, and Stability of Alumina-Supported Vanadia

This work studies the influence of specific vanadium precursors on alumina-supported vanadium oxide catalysts. Vanadyl sulfate, ammonium metavanadate, and vanadyl acetylacetonate were used as precursors. All catalysts have the same surface vanadium coverage (4 V atoms/nm 2 ). The structural features of surface vanadium oxide species were studied by 51 V-NMR, UV−vis, and Raman spectroscopy. The vanadium precursor determines the strength of interaction between supported VOx species and alumina. The reducibility of vanadium ions was estimated by conventional TPR/TPO cycles. The structural and electronic changes during reduction/oxidation cycles were studied by in situ Raman and UV−vis spectroscopy (TPR/TPO-Raman, TPR/TPO-UV−vis). Surface sulfate species reduce concomitantly to surface vanadium oxide species.