Recent Developments in Heterogeneous Catalyzed Epoxidation of Styrene to Styrene Oxide

Epoxidation of styrene under heterogeneous catalyzed conditions provides environmentally friendly routes to produce styrene oxide, an important synthetic intermediate for synthesis of perfumes, epoxy resins, plasticizers, drugs, sweeteners and fine chemicals. The present review explores epoxidation of styrene under heterogeneous catalysed conditions using a variety of catalysts such as metal nanoparticles, metal oxides (of group 12 and 13 metals, transition metals, rare earth metals), transition metals and complexes, polyoxometallates, microporous and mesoporous materials (zeolites, modified zeolites, organic/inorganic porous hybrid materials, porous metal oxides, SBA 15) and polymers using hydrogen peroxide (H2O2), tert-butyl hydroperoxide (TBHP), air or oxygen as oxidants.The use of salen based transition metal complexes and of chiral porphyrins as catalysts in asymmetric epoxidation of styrene is also reviewed. The reaction mechanism studies of most of these reactions suggest an intermediate formation of a reactive metal-oxygen species, by interactions between the catalyst and oxidant.