Selectively catalytic epoxidation of α-pinene with dry air over the composite catalysts of Co–MOR(L) with Schiff-base ligands

Abstract Twelve bi-/tridentate Schiff-base ligands ( L 1 – L 12 ) have been designed, synthesized and coordinated with ion-exchanged Co–MOR (Mordenite) forming a series of Co–MOR( L ) composite catalysts, for which various analyzes and characterizations are conducted. Selectively catalytic epoxidation of α -pinene with dry air over Co–MOR( L ) catalysts has been carried out, where uses TBHP in small amounts as the initiator. Among these Co–MOR( L ) catalysts, Co–MOR( L 8 ) exhibits the best activity for the titled reaction to obtain 85.8 mol% conversion and 90.8% selectivity of epoxide. Some factors such as the structure of ligands, the oxidants, the solvents, the catalyst amount, the reaction temperature and time play important roles in controlling the epoxidation. The recyclable stability of the Co–MOR( L 8 ) catalyst is confirmed. The studies on the electrochemical behaviors of Co species in Co–MOR( L 8 ) reveal the importance of reversible change between Co oxidation states for the epoxidation.