Ti接枝MCM-41催化剂的结构设计及化学亲和选择性研究

 用二氯化钛茂作为活性物种的来源，利用Si－MCM－41催化剂表面羟基的反应性，得到了Ti接枝MCM－41催化剂的两种结构模型．结构表征结果表明，Ti接枝MCM－41催化剂不仅长程结构好，孔径分布均一，而且催化剂表面活性中心含量高．两种结构模型催化剂上芳烃羟化反应性能表明，Ti接枝MCM－41催化剂表面的亲水／憎水性可以在较宽的范围内调变，从而可实现控制芳烃羟化的化学亲和选择性．另外，研究结果还表明，Ti接枝MCM－41催化剂具有很好的活性稳定性．

Study on Structure Design and Chemical Affinity-Selectivity of Titanium-Grafted MCM-41 Catalyst

Two structural polytypes of titanium-grafted MCM-41 material were prepared by reaction of titanocene dichloride with the surface hydroxyl groups of MCM-41. The surface Ti centers in one of the structural polytypes are present as titanocene. In the other structural polytype the surface Ti centers are present as Ti-OH. The former can be changed into the latter by calcination. The XRD result showed that the titanium-grafted material retains its long-range structural order of its precursor. The uniform mesoporous structure of the titanium-grafted material was evidenced by TEM. In addition, the XPS result showed that titanium is grafted on the surface of MCM-41 and the covalent bond between oxygen and titanium is formed. The hydrophilicity/hydrophobicity of the material can vary over a wide range in a controlled fashion by adjusting the loading of the grafted titanium centers. The material shows excellent activity and stability as a catalyst for aromatic hydroxylation, and the selectivity of the catalyst can be enhanced by optimizing its surface hydrophobicity.