HMS和NaY固载酒石酸钛配合物的研究

Studies on Titanium Tartrate Complex Assembled HMS and NaY

利用化学键合和“瓶中造船”方法,成功地将酒石酸钛配合物接枝到HMS(heragonal mesoporous sili-cas)上或包络合于微孔NaY内.FT-IR表征表明酒石酸钛在HMS上是通过与载体表面羟基发生交换作用而被固载的;在NaY载体上则是通过包络合被封装在载体的超笼内.UV-Vis可见漫反射表征表明两类固载型催化剂有着相似的钛配位环境.在催化肉桂醇环氧化反应中,HMS键合型催化剂的反应转化率比NaY包络型催化剂的高;但后者在环氧化选择性上要高于前者.回收样品的重复使用实验结果表明,两类固载型催化剂在重复使用过程中均存在不同程度的失活.

Titanium tartrate complex has been successfully grafted onto hexagonal mesoporous silicas (HMS) or encapsulated into microporous NaY zeolite by means of chemically bonding or 'ship in bottle' methods. The UV-Vis diffuse reflection spectra confirmed that two kinds of heterogeneous catalysts had very similar Ti sites. The FT-IR confirmed that Ti tartrate could be bound to the surface hydroxyls of HMS, leading to the appearance of a weak band at 960 cm(-1) and a ligand's carbonyl band at 1 736 similar to 1 744 cm(-1) in their spectra; and only a ligand's carbonyl band was observed in the IR spectra of fresh and recycling Ti tartrate encapsulated NaY samples, indicating that Ti tartrate complex could be steadily encapsulated into the super cages of NaY zeolite. In catalyzing the epoxidation of cinnamyl alcohol with tetrabutyl hydroperoxide (TBHP) as an oxidant, the Ti tartrate grafted HMS showed a higher catalytic activity than the Ti tartrate encapsulated NaY, this is mainly due to the former has a higher Ti loading than the latter. As for as their selectivity for the epoxides, the latter (near 100%) was by far better than the former (about 80%), this is perhaps due to the Na+ located in the super cages and the particular microporous structure of NaY can efficiently restrain the by-reaction such as opening, addition and polymerization of the epoxides.