Epoxidation of Propylene over Ag/MgO Catalysts Modified Na~+ and Halogen Anions

A series of 5%(by mass)Ag/MgO catalysts modified with and without Na+ and halogen anions were prepared,and the performances of these catalysts for epoxidation of propylene were studied under O2-rich condition(p(C3H6)∶p(O2)=2.53∶98.8) by using oxygen as oxidant.It was found that catalysts modified with Na+ showed higher selectivity for PO formation.Furthermore,Cl-or Br-coexisted with Na+ in the catalysts could also lead to obvious increase of PO selectivity(20%).O2-TPD characterization suggested that Na+ and Cl-in the catalysts stabilized subsurface oxygen species Oβ,and this might favor the formation of PO.