Epoxidation of Olefins with Molecular Oxygen Over Layered Double Hydroxide Catalyst in the Presence of Benzaldehyde

A Fe embedded MgAl layered double hydroxide (MgAlFe0.4-LDH) showed excellent performances in the epoxidation of various olefins with O2/benzaldehyde as oxidant at mild conditions. Under optimal conditions, the olefins including terminal aliphatic olefins, cyclohexene and styrene were all converted to the corresponding epoxides in conversions close to 100% and selectivity higher than 95%. The epoxidation is accomplished in two elementary steps, which are catalytic oxidation of benzaldehyde to peroxybenzoic acid, and epoxidation of olefin to epoxide by peroxybenzoic acid generated in situ. The catalyst also exhibited good stability and recyclability. The characterization results revealed that the Fe species are present in the state of Fe3+ fully incorporated into the Mg/Al-LDH layers, and act as active sites in the catalyst. The embedment of Fe into MgAl-LDH largely increased the surface area and pore volume of Mg/Al-LDH, which is another factor enhancing the activity of the catalyst.