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 molecu lar designed dispersion method, using the vanadyl acetylacetonate complex ( VO(acac)(2)). The complex has been adsorbed on the support from solution, f ollowed by thermal conversion into the corresponding supported vanadium oxi de catalyst. The formation of the VO(acac)(2)-support material has been stu died by both spectroscopic (FTIR, FT-Raman, ESR, UV-VIS-DRS; DRS: diffuse r eflectance spectroscopy) and chemical methods. The present study reveals th at VO(acac)(2) complexes react preferentially with the hydroxy groups of th e 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 fun ction 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-FTI R and in situ IR, which provides additional information on the VO(acac)(2)- support interaction. Characterization of these supported vanadium oxide cat alysts by FTIR, FT-Raman and UV-VIS-DRS reveals the formation of highly dis persed VOx functionalities.