Preparation and catalytic activity of P4VP–Cu(II) complex supported on silica gel

Micron-sized silica gel particles were chemically modified on their surfaces with the coupling agent, γ-methacryloxypropyl trimethoxysilane (MPS), double bond was introduced onto the surfaces of silica gel particles, and the modified particles MPS–SiO₂ were obtained. Then, poly(4-vinylpyridine) (P4VP) was grafted from the silica gel surfaces, and grafting particles P4VP/SiO₂ was prepared. Finally, the coordination between grafted P4VP and cupric ions Cu²⁺ was performed, and the supported complex Cu(II)–P4VP/SiO₂ was obtained. The grafting particles P4VP/SiO₂ and the supported complex Cu(II)–P4VP/SiO₂ were characterized with infrared spectra (FTIR), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM). Cu(II)–P4VP/SiO₂ was used as a catalyst for the oxidation of ethyl benzene into acetophenone with molecular oxygen under ordinary pressure. The experimental results show that the supported complex Cu(II)–P4VP/SiO₂ can be successfully prepared via grafting polymerization of 4VP and coordination between the grafted P4VP and cupric ions Cu²⁺. In oxidation of ethyl benzene into acetophenone by molecular oxygen under ordinary pressure, the supported complex Cu(II)–P4VP/SiO₂ displayed high catalytic activity and excellent catalytic selectivity up to more than 98% for the transformation of ethyl benzene to acetophenone.