摘要
通过溶胶凝胶—常压干燥法制备了不同Si/Ti摩尔比的SiO2-TiO2复合气凝胶,结合Uv-vis,FT-IR等表征手段研究Si/Ti摩尔比对其在以N,N-二甲基甲酰胺(DMF)为溶剂,H2O2((H2O2)=30%)为氧化剂的苯乙烯环氧化反应中催化性能的影响.结果表明:反应产物只有环氧苯乙烷(SO)和苯甲醛(BA).随着Si/Ti摩尔比的降低,催化剂的TON和双氧水的有效利用率逐渐降低,但苯乙烯的转化率先迅速增加后增加缓慢,SO的选择性先增加后降低,当Si/Ti摩尔比为16.4时,SO的选择性和收率最高,这归因于随着钛含量的增加,三种不同钛物种相对含量的变化.
SiO2-TiO2 composite aerogels with different molar ration of Si/Ti was prepared by sol- gel（atmosphereic pressure drying） method and characterized by SEM, N2 adsorption-desorption, Uv-Vis spectroscopies, and FT-IR analysis. The effects of Si/Ti ratio on the catalytic performances of SiO2-TiO2catalysts were investigated for the styrene epoxidation using DMF as the solvent as well as aqueous H2O2 as the oxidant. The results of characterization showed that the physical properties of all samples agreed with aerogels reported in literatures. Ti-O-Si Bonds were formed in SiO2-TiO2 composite aerogels. The content of isolated tetrahedral Ti slightly decreases, while the hydrated tetrahedral Ti species and extra-framework octahedral Ti species increase with the Ti content. The catalytic reaction results showed that styrene oxide（SO） and benzaldehyde（BA） were the only two products. As the molar ration of Si/Ti decreasing, the turnover number（TON） of catalysts and the utilization of hydrogen peroxide decreased, but the conversion of styrene increased, the selectivity of styrene oxide increased first and then decreased. The highest yield of styrene oxide could be achieved when the molar ration of Si/Ti were 16.4. It could be attributed to the change of the relative content of three different Ti species with the increase of Ti content.
出处
《浙江工业大学学报》
CAS
北大核心
2015年第4期374-378,共5页
Journal of Zhejiang University of Technology
