PETR 12 |
| Epoxidation of olefins is an important reaction in the laboratory and the chemical industry. While the catalytic epoxidation with H2O2 as an oxidant might offer some advantages, a chlorine-using non-catalytic process (the chlorohydrin process) and catalytic processes based on organic peroxides and peracids are still used extensively. Here, we report an efficient epoxidation of a wide range of olefins with H2O2 catalyzed by the lacunary and transition-mental-substituted polyoxometalates of [γ-SiW10O34(H2O)2]4–, [γ-SiV2W10O38(OH)2]4–, and [{γ-SiTi2W10O36(OH)2}2(μ-O)2]8– including the application to heterogeneous catalysts. The structurally well-defied polynuclear active sites of the polyoxometalates activate H2O2 effectively. In addition, unique stereospecificity and regioselectivity caused by the rigid structures of the polyoxometalates are observed. The heterogenized polyoxometalate catalysts can epoxidize a broad range of olefins with maintenance of the catalytic performance of the corresponding homogeneous polyoxometalates and the recovered catalyst can be reused. |
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Mechanism in Homogeneous and Heterogeneous Catalytic Epoxidation
8:15 AM-12:00 PM, Sunday, August 19, 2007 Boston Park Plaza -- Whittier Rm, Oral
Division of Petroleum Chemistry |