A shape-selective catalyst for epoxidation of cyclic olefins:The nanoporous nickel phosphate VSB-5

摘要

Nickel in the form of porous nickel phosphate VSB-5 has been used as a shape-selective catalyst for epoxidation of cyclic olefins such as cyclo-hexene and cyclooctene using hydrogen peroxide.The VSB-5 showed high selectivity to cyclohexene oxide and cyclohexane diol,much higher productivity per catalyst weight in the epoxidation of cyclohexene,and high selectivity to cyclooctene oxide in the epoxidation of cyclooctene.The VSB-5 behaved as a heterogeneous catalyst in the epoxidation and can be used many times without structure degradation,leaching of active nickel species,or significant activity loss.It has been concluded that the epoxidation reaction with VSB-5 proceeds via a free-radical mechanism by taking into consideration a sharp activity loss in the presence of a radical scavenger,hydroquinone.The effect of radical scavengers with different molecular dimension on the catalytic activity also indicates the shape selectivity in the pores of VSB-5.