核壳结构TiO2@SiO2催化碳酸二甲酯与苯酚酯交换合成碳酸二苯酯

以反相微乳液法和沉淀法相结合制备了核壳结构TiO₂@SiO₂，首次用于碳酸二甲酯与苯酚酯交换合成碳酸二苯酯反应，显示较好的催化活性. 采用200 ℃焙烧的TiO₂@SiO₂，用量0.20 g，反应9 h，苯酚转化率达41.8%，酯交换选择性为100%. 透射电镜显示TiO₂@SiO₂核厚壳薄，TiO₂核直径220-300 nm，SiO₂壳厚度40-60 nm，具有介孔结构. TiO₂@SiO₂对碳酸二甲酯与苯酚酯交换反应有好的重复使用性，使用4次苯酚转化率仍保持在40%以上. TiO₂与SiO₂发生相互作用，Ti进入骨架形成Ti-O-Si键，骨架Ti的形成提高了TiO₂@SiO₂的催化性能.

Core-shell TiO2@SiO2 catalyst for transesterification of dimethyl carbonate and phenol to diphenyl carbonate

Core-shell TiO₂@SiO₂ was prepared using a combination of reverse microemulsion and precipitation methods and used as a heterogeneous catalyst for the transesterification of dimethyl carbonate and phenol. TiO₂@SiO₂ calcined at 200 ℃ gave the best catalytic performance. When the amount of catalyst was 0.20 g, the phenol conversion and transesterification selectivity were 41.8% and 100%, respectively. Transmission electron microscopy was used to characterize the core-shell TiO₂@SiO₂ structure, and the results showed that TiO₂@SiO₂ is bilayer with a TiO₂ core of diameter 220-300 nm and SiO₂ shell of thickness 40-60 nm. The TiO₂@SiO₂ was reusable, and phenol conversion remained above 40% when the TiO₂@SiO₂ was used four times. The catalytic performance of TiO₂@SiO₂ in the transesterification of dimethyl carbonate and phenol was promoted by the formation of Ti-O-Si bonds.