Epoxidation of styrene by anhydrous t-butyl hydroperoxide over reusable gold supported on MgO and other alkaline earth oxides

Gold nanoparticles deposited on MgO, CaO, SrO, and BaO by homogeneous deposition–precipitation using urea are, for the first time, reported to be novel highly active/selective and reusable catalysts in the epoxidation of styrene to styrene oxide (SO) by anhydrous t-butyl hydroperoxide. Au/MgO prepared by deposition–precipitation using NaOH is also studied in styrene epoxidation. The slightly poorer performance of Au/MgO prepared by deposition–precipitation in epoxidation of styrene (conversion: 44.6%, SO selectivity: 36.1%), as compared with to the gold catalysts prepared on alkaline earth oxides by homogeneous deposition–precipitation (styrene conversion: ⩾53%, SO selectivity: 45–60%), is attributed to the lower loading (4.1 wt%), larger particle size (DAu = 17.9 nm), and possible presence of trace impurities (Na+ and Cl−) in the former. Higher gold loading (4.7–7.5 wt%) and smaller gold particles (DAu ≅ 8.0 nm) were observed in the alkaline earth-supported Au catalysts prepared by homogeneous deposition–precipitation.