钛超强酸催化剂的特征及对酯化反应的催化作用

Structure Characteristics and Catalysis of SO_4^(2-) /TiO_2 Catalyst

TiCl4经水解、沉淀等步骤制备了由硫酸根促进的钛氧化物超强酸,分别用红外光谱仪和流动气相色谱法测定了其分子结构及比表面积和孔径分布,其催化活性通过乙酸与正丁醇反应生成乙酸丁酯的酯收率进行衡量。结果显示,该超强酸:(1)分子为桥式双配位结构,比表面积大于 100m2?g?1, 孔径分布在 1~4nm 之间,且其红外特征吸收峰在由 550℃升到 650℃时消失;(2)最佳制备条件为:硫酸浓度为 1mol?L?1,焙烧温度和时间分别为 500℃和 3 小时;(3)具有很好的重复使用性能,催化剂在不作任何处理连续使用 8 次,其酯收率不变,且将其应用于催化药物中间体布洛芬的合成上,收率高于 83%。

SO42-/TiO2 super acid catalyst used for esterification was prepared by the steps of hydrolysis, filtering, drying, acidating and calcinating. The structure was determined by IR, the specific surface area and its pore diameter distribution were measured by flowing gas-chromatography. The catalytic activity was measured by the ester yield obtained from the reaction of acetic acid with n-butanol. The results show that: (1) The catalyst molecular structure is bridging bidentate, the surface area is larger than 100 m2&middotg-1, the pore diameters distribute from l-4 nm, and the characteristic IR adsorption peak is disappeared gradually as the calcination temperature rises from 550°C to 650°C; (2) The ester yield is increased with the molecular weight of the esterified alcohol; (3) The optimum preparation conditions of the catalyst are: the concentration of H2SO4 1 mol&middotL-1, calcination temperature 500°C, calcination time 3 h; (4) the catalyst has very good reusing property and is easily regenerated and separated from the reaction mixture; (5) the ester quality is better than that obtained from using H2SO4 as catalyst, and can be used as a catalyst for the ibuprofen synthesis.