Ti-MCM-41分子筛的合成、表征及其催化作用

用过氧化氢异丙苯(CHP)控制钛酸四丁酯(TBOT)的水解速率,用水热晶化法合成了Ti-MCM-41分子筛,并用X射线衍射和紫外漫反射光谱对其结构进行了表征,用X射线荧光光谱法测定了Ti-MCM-41分子筛中的钛含量,考察了晶化时间、晶化温度及n(CHP)∶n(TBOT)对Ti-MCM-41分子筛的结构和钛物种分布的影响,得出了较佳合成条件:晶化温度100℃、晶化时间3 d、n(CHP)∶n(TBOT)=8~12。表征结果显示,CHP的加入影响了钛物种的分布,可减少锐钛矿TiO2的生成。将不同条件下合成的Ti-MCM-41分子筛用于催化CHP作为氧化剂的丙烯环氧化反应,实验结果表明,适当的晶化温度、合理的n(CHP)∶n(TBOT)及较长的晶化时间有利于提高CHP的有效转化率;产物中有部分丙二醇生成;Ti-MCM-41分子筛的催化活性与骨架钛的含量有关。

Synthesis,Characterization and Catalysis of Ti-MCM-41 Molecular Sieve

Ti-MCM-41 molecular sieve was prepared by hydrothermal crystallization,and by addition of cumene hydroperoxide(CHP)to control hydrolysis rate of tetrabutyl titanate(TBOT).The molecular sieves were characterized by means of XRD,UV-Vis and XRF.Effects of n(CHP) ∶n(TBOT),crystallization temperature and time on structure of Ti-MCM-41 molecular sieve and titanium species distribution in it were investigated.The optimal synthesis conditions were obtained:crystallization temperature 100℃,crystallization time 3d and n(CHP) ∶n(TBOT)8-12.Addition of CHP can affect distribution of titanium species and decrease production of anatase TiO_2.Ti-MCM-41 molecular sieves prepared under different conditions were evaluated by epoxidation of propylene,with cumene hydroperoxide as oxidant.The byproduct propylene glycol was detected during the epoxidation.Activity of the catalyst relates to content of Ti in framework of molecular sieve.