Epoxidation of propylene with cumene hydroperoxide over MoO3/SiO2 catalyst prepared by sol-gel method

MoO3/SiO2 catalyst was prepared by sol-gel method at low temperature, in which ammonium heptamolybdate and tetraethoxysilane (TEOS) were used as molybdenum and silica precursor, respectively. The catalyst samples were characterized by N-2 adsorption, XRD and FT-IR. The results show that the MoO3/SiO2 has higher surface area (e. g. A = 363.8 m(2)/g for 10% MoO3/SiO2) and MoO3 is highly dispersed on SiO2. Different acidic hydrolysts (HCl, HNO3 and HAc) used in the preparation of catalyst can affect obviously the surface area of MoO3 /SiO2 catalyst and the dispersion of MoO3 on SiO2. MoO3 /SiO2 catalyst, prepared using HCl as acidic hydrolyst, exhibits higher surface area and more uniform dispersion of MoO3 on support than that prepared using other hydrolysts. The catalytic performance of MoO3/SiO2 for the epoxidation of propylene to propylene oxide by 30% cumene hydroperoxide was examined and the effects of reaction conditions (such as temperature, time, pressure, solvent and basic depressor) were studied in detail. The results show that the tertbutanol is an available solvent and the epoxidation of propylene can be promoted by adding basic depressor into the solvent. When NaHCO3 (p = 2.5 g/L) was used as basic depressor, the selectivity for propylene oxide could increase. 15%MoO3/SiO2 catalyst, prepared using HCl as acidic hydrolyst, showed higher activity and selectivity for propylene oxide, for instance, using tert-butanol as solvent and at 110 degreesC and 0.6 MPa for 2 h, the conversion of cumene hydroperoxide is 89% and the selectivity for propylene oxide is 80%.