对环氧化反应具有高催化活性的钛硅介孔分子筛的制备

Synthesis of Ti-Containing Silica Mesoporous Molecular Sieves with High Catalytic Activity for Epoxidation

使用短链二元羧酸 (包括草酸、戊二酸、柠檬酸和酒石酸 )为模板剂 ,采用溶胶 凝胶法合成了具有大比表面积 ,孔径在 3～ 7nm的钛硅介孔分子筛 .EDX和紫外可见漫反射光谱的研究结果表明 ,所合成的钛硅介孔分子筛中钛的分布均匀 ,钛物种以孤立态四面体构型为主 .

The discovery of the Ti containing molecular sieves, such as TS 1, has led to considerable interest in liquid phase selective oxidation catalysis using aqueous hydrogen peroxide as an environmentally friendly oxidant. However, the pore size of classical Ti containing microporous molecular sieves restricts large molecules entering the zeolite intracrystalline void space where the catalysis occurs. Synthesis of Ti containing silica mesoporous molecular sieves, therefore, is desirable. In this work we developed an easy way to directly introduce highly active, tetrahedral Ti 4+ centers into silica mesoporous molecular sieve through “one pot conversion” using short chain dicarboxylic acids, including oxalic acid, glutaric acid, citric acid and tartaric acid, as the templates. The BET surface area, pore volume, and pore size of the samples prepared are 600～800 m 2/g , 0 6～0 8 ml/g , and 3 4～6 6 nm, respectively. The samples have worm like, three dimensional pore structure and high hydrothermal stability. The Ti containing silica mesoporous molecular sieves show excellent catalytic performance in the epoxidation of cyclohexene with 80 7%conversion of cyclohexene and 91 5% selectivity for cyclohexene epoxide.