Due to the complex internal structure of titanium silicalite-1 (TS-1), the active sites and mechanistic details of catalytic reactions using TS-1-based catalysts have not been well understood. In this work, density functional theory (DFT) calculations were conducted to provide fundamental insights into the reaction mechanism of oxidation–hydration of ethylene toward ethylene glycol production over the TS-1 catalyst model with perfect titanium(IV) active sites and the Al/TS-1 model with both Brønsted acid and titanium(IV) sites. The computational results revealed that the introduction of Al into TS-1 altered the reaction pathway, facilitated the H₂O₂ activation, and significantly reduced the energy barrier of the rate-limiting step for ethylene glycol generation, demonstrating a synergistic action of Ti–Al(H) sites. Over Al/TS-1, the titanium(IV) site participated in the ethylene epoxidation, while the Brønsted acid site was responsible for the hydration of ethylene oxide to ethylene glycol. The new insights into the catalytic mechanism and the identified role of bifunctional active sites offer a useful reference for the future design of Al/TS-1 catalysts with tailored catalytic performance for this important reaction.

中文翻译：

---

双功能Al/TS-1催化剂上乙烯氧化水合合成乙二醇的反应机理和活性位点解析

由于钛硅沸石-1 (TS-1) 复杂的内部结构，使用 TS-1 基催化剂进行催化反应的活性位点和机理细节尚未得到很好的了解。在这项工作中，进行了密度泛函理论（DFT）计算，以提供对在具有完美钛（IV）活性位点和Al/的TS-1催化剂模型上乙烯氧化-水合生产乙二醇的反应机制的基本见解。 TS-1 模型同时具有布朗斯台德酸和钛 (IV) 位点。计算结果表明，将Al引入到TS-1中改变了反应途径，促进了H ₂ O ₂的活化，并显着降低了乙二醇生成限速步骤的能垒，证明了Ti–的协同作用。 Al(H)位点。在Al/TS-1上，钛(IV)位点参与乙烯环氧化，而布朗斯台德酸位点负责环氧乙烷水合成乙二醇。对催化机制的新见解和双功能活性位点的确定作用为未来设计具有针对这一重要反应的定制催化性能的Al/TS-1催化剂提供了有用的参考。