TS-1/H_2O_2催化活性中心结构及活性预测

Structure of catalytic active center and activity prediction for TS-1/H_2O_2

应用密度泛函理论,研究钛硅分子筛TS-1在H2O2水溶液中的钛氧活性中心结构及稳定性.计算在B3LYP/6-31G（d,p）理论水平进行.通过结构设计和优化,考察了4种活性氧结构在6个不同位点的生成能.结果表明在T10位,稳定性顺序为Ti-η^1（OOH）〉Ti-η^2（OOH）H2O,而其他T位都是Ti-η^2（OOH）H2O〉Ti-η^1（OOH）.吸附一个H2O分子后,都生成更为稳定的六配位钛氧络合物Ti-η^2（OOH）H2O和Ti-η^1（OOH）H2O.Ti-η^2（OOH）物种的活性氧带有更高的正电荷.在Ti-η^1（OOH）和Ti-η^2（OOH）活性中心上乙烯环氧化活化能垒分别为101和37kJ/mol.

Density functional theory was used to study the structure and stability of the Ti-peroxo active center of TS-1zeolite in aqueous H2O2 solution.The calculations were carried out at the B3LYP/6-31G（d,p）theoretical level.By structural design and geometry optimization,four kinds of Ti-peroxo species located at different T sites were examined.It was indicated that at the T10 site,the stability order is Ti-η^1（OOH） Ti-η^2（OOH）,while at other T sites,it is Ti-η^1（OOH）Ti-η^2（OOH）.Adsorption with one H2 O lead to more stable 6-coordinated Ti-η^2（OOH）H2O and Ti-η^1（OOH）H2O complexes.For the Ti-η^2（OOH）species,the active oxygen shows higher electropositive.The active energy barriers of ethylene epoxidation over Ti-η^1（OOH）and Ti-η^2（OOH）are101and 37kJ/mol,respectively.