Role of mesoporous silica supported mixed oxides of ceria and samaria for the synthesis of ε-caprolactone at room temperature

Mesoporous silica was prepared from rice husk by pyrolysis method. Mixed oxides of ceria and samaria (50/50) were dispτersed on silica by rotavapor assisted wet impregnation method. Catalysts were further modified by doping with MoO3, La2O3 and mixed MoO3–La2O3. The prepared systems were characterized by various physicochemical techniques such as BET surface area analysis, scanning electron microscopy, elemental detection analysis, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, Thermogravimetric analysis, n-butylamine titration and X-ray photoelectron spectroscopy analysis. The catalytic activity of all the systems were studied in the oxidation of cyclohexanone to e-caprolactone. Various parameters such as time, molar ratio of cyclohexanone–H2O2, temperature, solvent and the amount of catalyst were studied thoroughly to optimize the favorable conditions for the oxidation reaction. Higher e-caprolactone selectivity of 88.9% was observed in the presence of hydrogen peroxide in acetonitrile medium. The recyclability tests were performed up to six cycles without any appreciable loss in activity, which confirmed the stability of the prepared systems. Good yield with high selectivity was achieved at room temperature, which makes the protocol greener.