Efficient Epoxidation of Styrene Using tert-Butyl Hydroperoxide Promoted by M0.5Cu0.5Co2Ox (M = Ca, Ni, and Cr) Ternary Catalysts

The epoxidation of styrene was studied over three ternary catalysts M0.5Cu0.5Co2Ox (M = Ca, Ni, and Cr) using tert-butyl hydroperoxide (TBHP) as an oxidant. Cr3+ was incorporated into the lattice of Co3O4, and the introduction of Cr3+ was conducive to the formation of highly dispersed amorphous CuO. Compared with pristine CuCo2Ox, the ternary catalysts exhibited considerably enhanced catalytic performance. The catalytic activities in terms of styrene conversion decreased in the order of Cr0.5Cu0.5Co2Ox > Ni0.5Cu0.5Co2Ox > Ca0.5Cu0.5Co2Ox, which was in line with the catalyst surface area, CuO dispersion, oxygen vacancies on the catalyst surface, and difficulty of Cu2+ reduction. Cr0.5Cu0.5Co2Ox presented a maximum styrene conversion (94.2%) with 90.4% selectivity to styrene oxide. The recycled catalyst showed no obvious loss in activity through five consecutive cycles. The catalytic activities and selectivity profiles in various reaction conditions such as the reaction time, reaction temperature, catalyst dosing, and styrene to TBHP ratio were discussed.