MCM-48-supported vanadium oxide catalysts, prepared by the molecular designed dispersion of VO(acac)2:: A detailed study of the highly reactive MCM-48 surface and the structure and activity of the deposited VOx

The molecular designed dispersion of vanadyl acetylacetonate (VO(acac)(2)) is used to prepare MCM-48-supported vanadium oxide catalysts. The complex is deposited on the MCM-48 surface and subsequently thermally converted into the supported vanadium oxide. A thorough study of the interaction of the VO(acac)(2) with the MCM-48 support by ESR spectroscopy and chemical methods reveals that the MCM-48 surface exhibits a remarkably higher chemical reactivity in comparison to amorphous silica, which is attributed to the presence of very reactive strained siloxane bridges on the MCM-48 surface. According to the BET, XRD, and FTIR study of the supported vanadium oxide catalysts the unique structural properties of MCM-48 are maintained. Characterization by FTIR, Raman, and UV-vis diffuse reflectance spectroscopy reveals the presence of different VO, structures (monomers, polymers, and crystals) as a function of the vanadium loading (0-6.5 wt% V). The oxidation of methanol similarly shows increasing conversion and formaldehyde yields with increasing loading. Structural characterization of the catalyst after the reaction reveals that the MCM-48-supported vanadium oxides withstand catalytic reaction conditions. (C) 2001 Academic Press.