Vanadium containing crystalline mesoporous molecular sieves Leaching of vanadium in liquid phase reactions Original Research Article

Vanadium (V) containing mesoporous molecular sieves, V-HMS have been synthesized at room temperature in the presence of dodecylamine as template and vanadyl(IV) sulfate hydrate or vanadium(V) triisopropoxide as vanadium source. The presence of V in the silicate matrix was investigated by UV-visible spectroscopy, 51V MAS NMR and catalytic measurements. Samples were also characterized using chemical analysis, XRD, SEM, FTIR and adsorption properties. It was found that the vanadium centers in V-HMS molecular sieves consist of three-legged (SiO)3VO species, similar to those in amorphous VSiO2. V-HMS materials catalyze the oxidation of organic substrates such as phenol, 2,6-di-tert-butyl phenol, naphthalene and cyclododecanol in the presence of either dilute hydrogen peroxide or tert-butyl hydroperoxide as the oxidant. Leaching of active vanadium species from the silicate matrix during reaction was investigated. The stability of vanadium during liquid phase reactions was found to depend on the nature of the substrate, the solvent and the oxidant.