Novel two-phase catalysis with organometallic compounds for epoxidation of vegetable oils by hydrogen peroxide

A series of new organometallic catalysts for epoxidized vegetable oils using H₂O₂ in a biphasic system were investigated. The effect of reaction parameters such as the amount of hydrogen peroxide, reaction time and temperature in the epoxidation of soybean oil are discussed in detail. A selectivity of 83.8% was obtained in 4 h at 60 °C, when [(C ₁₈H₃₇)₂N(CH₃)₂] ₃{PO₄[WO(O₂)₂]₄} was used as the catalyst. When methyltrioxorhenium (MTO), imidazole and CH₃CN were used as the catalyst, adduct, and solvent respectively, a selectivity of 99.90% was achieved in 4 h at 20 °C. The catalytic system was used for the epoxidation of other oils, whose results showed it was active in the epoxidation of long-chain unsaturated compounds. Furthermore, the reaction of H ₂O₂ with methyltrioxorhenium was studied by UV-Vis spectroscopy, which revealed the active peroxorhenium complexes formed during the reaction. Epoxidation of these oils with organometallic compounds occurred through the interactions between the oils unsaturated sites HOMO π(C-C) and the unoccupied peroxo σ*(O-O) orbital.