Cu- and Ni-Grafted Functionalized Mesoporous Silica as Active Catalyst for Olefin Oxidation

Abstract

Mesoporous silica has been functionalized with 3-aminopropyl triethoxy silane (3-APTES), followed by Schiff-base condensation with 2-hydroxy-1-naphthaldehyde. Incorporation of copper and nickel by covalent grafting onto the Schiff-base loaded materials gives two heterogenized catalysts namely, Cu–Cat and Ni-Cat, respectively. The materials have been characterized by PXRD analyses, nitrogen sorption studies, TEM, TGA, FT-IR, UV-visible and solid state MAS-NMR spectroscopy. The metal-contents in the samples are estimated using ICP-AES studies. Cu–Cat and Ni-Cat have been used as active catalyst in the oxidation of various olefins e. g. styrene, α-methyl styrene, cyclohexene, trans stilbene and cyclooctene in the presence of tert-butyl hydroperoxide as the oxidant in acetonitrile under mild conditions. Different products have been analyzed by gas chromatography and gas chromatography-mass spectrometry. The results show high conversion of the substrates, moderate to good product selectivity and high TOFs of the reactions. The catalysts are recycled without deteriorating their activities and heterogeneous nature.