Studies On Epoxidation Of Styrene Over SiO₂-MO_x?M=Ti?Co?Mn? Aerogels

Styrene oxide?SO?is not only a fine chemical but also an important organic synthesis intermediate for production of epoxy resins,plasticizers,perfume,sweeteners,etc.The epoxidation of styrene using dilute H₂O₂ as oxidizing agent in heterogeneous catalysis system has become an important way to prepare styrene oxide due to its mild reaction condition,economic environment and convenient disposition.SiO₂-MO_X?M=Ti?Co?Mn?composite aerogels was prepared by sol-gel and atmosphereic pressure drying method,and characterized by XRD,XRF,N₂ adsorption-desorption,TG,FT-IR,Uv-vis and NH₃-TPD analysis.The catalytic performances of SiO₂-MO_X?M=Ti?Co?Mn?composite aerogels were investigated for the styrene epoxidation using DMF as the solvent as well as aqueous H₂O₂ as the oxidant.The results showed that the descending order of catalytic performances is SiO₂-TiO₂ composite aerogels>SiO₂-CoO composite aerogels>SiO₂-MnO₂ composite aerogels.When taking SiO₂-TiO₂ composite aerogels as catalyst,the optimized molar ration of Si/Ti is 9 and the optimized drying temperature is 120? and the optimized reaction condition are o.5 of n?H2O2?/n?styrene?,6 h of reaction time,60? of reaction temperature,0.25 g of catalyst.The improvement of surface hydrophilic properties of SiO₂-TiO₂composite aerogels is quite effective for the enhancement of catalytic activity.The catalytic activity unchanged but the selectivity of SO decreased while the SiO₂-TiO₂ composite aerogels silylated by HMDS.