Synthesis of Stable, Hydrophobic MCM-48/VOx Catalysts Using Alkylchlorosilanes as Coupling Agents for the Molecular Designed Dispersion of VO(acac)2

The use of dimethyldichlorosilane as a coupling agent for the grafting of VO x structures on the MCM-48 surface produces a material that is simultaneously hydrophobic (immiscible with water) and very active (all V centers are accessible, even for water molecules). The VO x surface species are grafted by the molecular designed dispersion of VO(acac) 2 on the silylated surface, followed by a calcination in air at 450 °C. These hydrophobic MCM-48 supported VO x catalysts are thermally stable up to 500 °C. The grafted VO x surface species are very resistant toward leaching-out in aqueous media. Also, the structural and hydrothermal stability has improved enormously. The crystallinity of the materials does not decrease when the samples are subjected to a hydrothermal treatment at 150 °C and 4.7 atm pressure. A reaction mechanism is proposed and consolidated by FT-IR, Raman spectroscopy, and UV−vis diffuse reflectance. Pore size distributions, water adsorption isotherms, and X-ray diffractograms confirm the structural stability of these materials.