Precursor Nuclearity Effects in Supported Vanadium Oxides Prepared by Organometallic Grafting

Despite widespread importance in catalysis, the active and selective sites of supported vanadium oxide (VOx) catalysts are not well understood. Such catalysts are of great current interest because of their industrial significance and potential for selective oxidation process.(14) However the fear that the nature of the active and selective sites is ambiguous hinders molecular level understanding of catalytic reactions and the development of new catalysts. Furthermore, complete structural elucidation requires isolation and characterization of specific vanadium oxide surface species, the preparation of which presents a significant synthetic challenge. In this study, we utilize the structural uniformity inherent in organometallic precursors for the preparation of supported vanadium oxide catalysts. The resulting catalysts are characterized by UV-visible diffuse reflectance spectroscopy (UV-vis DRS). X-ray adsorption spectroscopy (XAS), UV-Raman spectroscopy and H-2-temperature programmed reduction (H-TRR). Significant structural and reactivity differences are observed in catalysts prepared from different organometallic precursors, indicating that the chemical nature of surface vanadia can be influenced by the nuclearity of the precursor used for grafting.