First stoichiometric large-pore chromium(III) silicate catalyst

The first example of a large-pore framework chromium-silicate containing stoichiometric amounts of hexa-coordinated chromium(III) has been reported. Samples were characterised by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy ultraviolet–visible (DR UV–VIS) spectroscopy, thermogravimetry (TG), adsorption of different probe molecules and model catalytic tests; AV-15 is an active catalyst for the liquid phase epoxidation of cyclohexene to cyclohexene oxide, the oxidation of cyclohexane to cyclohexanol and cyclohexanone, and the oxidative dehydrogenation of cyclohexanol to cyclohexanone, under mild reaction conditions (using H2O2, at 50 °C). The catalyst is recyclable without significant loss of catalytic activity, but leaching tests indicate that catalysis is mainly due to some leached chromium species. In gas phase, AV-15 exhibits mainly oxydehydrogenation activity in the conversion of ethanol, 2-propanol and cyclohexanol, using air, yielding the corresponding carbonyl product. [Copyright &y& Elsevier]