Ti-Si介孔分子筛的转晶与控制

以季铵盐型阳离子Gemini表面活性剂C16H33(CH3)2N+(CH2)6N+(CH3)2C16H33]•2Br−(GEM16-6-16)为模板剂, 改变n(Ti)/n(Si)比值, 合成了系列Ti-Si介孔分子筛. X射线衍射(XRD)和透射电子显微镜(TEM)等表征结果表明, 在n(Ti)/n(Si)≤0.20时, 分子筛为高度有序六方介孔; 当 n(Ti)/n(Si)为 0.30时, 介孔转晶为立方相; 当n(Ti)/n(Si)为0.50时, 介孔转晶为层状相; n(Ti)/n(Si)为1.0时, 材料失去有序孔道结构. FT-IR分析表明, 在分子筛骨架间形成了Ti—O—Si键, 而且Ti—O—Si键的数目随n(Ti)/n(Si)的增加而增加, 达到一定饱和值后基本保持不变. 乙醇和丁醇对纯硅基介孔分子筛孔结构转晶控制作用呈现六方相→立方相→层状相递变规律, 因而钛酸正丁酯水解生成的丁醇对Ti-Si介孔分子筛转晶具有一定的控制作用.

The Mechanism of Mesoporous Phase Transition of Titanic-Silica Mesoporous Materials

A series of titanic-silica mesoporous materials have been synthesized by using the Gemini surfactant C16H33(CH3)2N+(CH2)6N+(CH3)2C16H33]•2Br− (GEM16-6-16) as a template. The XRD patterns and TEM images provide the evidence that the mesoporous phases are changed according to the following path by varying the molar ratio of n(Ti)/n(Si): hexagonal mesoporous structures are obtained when n(Ti)/n(Si)≤0.20; cubic when n(Ti)/n(Si)=0.30; lamellar when n(Ti)/n(Si)=0.50; and amorphous when n(Ti)/n(Si)=1.0. The FT-IR spectra suggest that the amount of Ti—O—Si bonds in the framework increases with increasing n(Ti)/n(Si) initially, and reaches to a limit when n(Ti)/n(Si)≥0.20. Additionally, the ethanol and butanol have been approved that they can control the evolvement of silica mesoporous phase transition. Following that, the process of titanic-silica mesoporous phase transition has been elucidated by the aggregation of Ti—O—Si bonds and the effect of butanol produced from the hydrolysis of tetrabutyl titanate(TBOT).