Immobilization of a new (salen) molybdenum(VI) complex onto the ion-exchangeable polysiloxane as a heterogeneous epoxidation catalyst

Abstract

In this study, a new recoverable catalyst for the epoxidation of olefins was developed using a layered polysiloxane as a support for immobilizing  (salen) molybdenum(VI) complex by electrostatic interaction between the surface of the solid support and the electrically charged molybdenum complex. Characterization of the heterogeneous catalyst by Fourier transform infrared, XRD,1H NMR, and atomic absorption spectroscopes as well as thermogravimetric and CHN elemental analyses confirmed successful immobilization of the (salen) molybdenum(VI) complex to the support. The prepared catalyst catalyzed the epoxidation of olefins efficiently. The effect of different factors on the epoxidation of cyclooctene was investigated. Reaction conditions including reaction temperature, solvent type, substrate amount, catalyst amount and oxidant  amount  were systematically optimized in order to achieve the highest conversion of cyclooctene. Various other olefins showed high catalytic activity and selectivity under the optimal reaction conditions. Regenerability test demonstrated that the catalyst can be recycled for at least five times without leaching of molybdenum. Moreover, the catalyst showed good stability under the reaction conditions as determined by FT-IR and ICP-OES analyses.