The interaction of molybdenum and titanium in mesoporous materials for olefin epoxidation

A series of bimetallic Mo-Ti-SBA-15-(X), and monometallic Mo/Ti-SBA-15-(X) mesoporous materials were synthesized by direct one-step hydrothermal method. The materials were characterized by XRD, N-2 adsorption/desorption, XPS, SEM, EDX, TEM and ICP-AES. XRD results clearly demonstrated that the incorporation of molybdenum and titanium species in the SBA-15 framework little affect the mesoscopic nature of the material. The oxidation state and coordination environment of the active sites was confirmed by XPS. The results revealed that Mo6+ was in octahedral geometry whereas Mo6+ and Ti4+ were in tetrahedral coordination in the SBA-15 framework. The O1s XPS spectrum well established the framework incorporation of molybdenum and titanium species. The catalytic activity of Mo-Ti-SBA-15-(6.5) material was evaluated in the epoxidation of cyclohexene with TBHP. It was found that Mo-Ti-SBA-15-(6.5) catalyst showed high catalytic activity gave a 98% conversion and > 98% selectivity within 8 h. The Mo-Ti-SBA-15-(6.5) was a promising catalyst for the epoxidation of cyclohexene and other olefins. The results showed that the materials containing Ti and Mo exhibited higher catalytic activity than monometallic modified SBA-15.