Synthesis and characterization of alumina-supported vanadium oxide catalysts prepared by the molecular designed dispersion of VO(acac)2 complexes

Alumina-supported vanadium oxide catalysts have been prepared by the molecular designed dispersion method, using the vanadyl acetylacetonate complex (VO(acac)2). The complex has been adsorbed on the support from solution, followed by thermal conversion into the corresponding supported vanadium oxide catalyst. The formation of the VO(acac)2–support material has been studied by both spectroscopic (FTIR, FT-Raman, ESR, UV–VIS–DRS; DRS: diffuse reflectance spectroscopy) and chemical methods. The present study reveals that VO(acac)2 complexes react preferentially with the hydroxy groups of the alumina, and only to a limited extent with the coordinatively unsaturated Al3+ sites. In addition, the deposition of the VO(acac)2 complex on the alumina surface yields different supported vanadium configurations as a function of the surface loading, due to both ligand exchange and hydrogen bond interactions. The thermal conversion of the adsorbed VO(acac)2 complexes into the supported vanadium oxide catalyst has been studied by TGA, GC-FTIR and in situ IR, which provides additional information on the VO(acac)2–support interaction. Characterization of these supported vanadium oxide catalysts by FTIR, FT-Raman and UV–VIS–DRS reveals the formation of highly dispersed VOx functionalities