Density functional theory (DFT) calculations were performed to investigate propylene epoxidation mechanisms with H₂O₂ over various TS-1 models in terms of active site formation, intermediate identification, and oxygen transfer pathway. Over tripodal sites of the hydrolyzed model, a bidentate Ti-OOH intermediate assembled in the 3-membered ring (3MR) configuration (Ti-(η²-OOH)-3MR) was identified through the stepwise mechanism for propylene epoxidation while a monodentate Ti-H₂O₂ intermediate stabilized in the 5MR configuration (Ti-(η¹-H₂O₂)-5MR) was obtained via the concerted mechanism. Both stepwise and concerted paths were found to be possible over the hydrolyzed models. On Ti/defect site of the Si-vacancy model, a new mechanism through a 5MR Ti-(η¹-OOH) intermediate was demonstrated to be energetically the most favorable candidate to represent the propylene epoxidation chemistry in H₂O₂/TS-1. The barriers (5.1 and 10.4 kcal/mol) for H₂O₂ dissociation and epoxidation are both relatively lower as compared to literature, which can be attributed to the steric advantage of the Si-vacancy model as well as the H-bond networks formed with surrounding silanol groups. The effect of co-produced H₂O on propylene epoxidation kinetics was also examined and the calculation results showed that H₂O coordination to the Ti center facilitates the formation of 5MR Ti-(η¹-OOH) intermediate and dramatically lowers the barriers for both H₂O₂ dissociation and epoxidation over the Ti/defect site of TS-1.

进行密度泛函理论（DFT）计算以研究在各种TS-1模型上H ₂ O _2引起的丙烯环氧化机理，这些机理涉及活性位点形成，中间识别和氧转移途径。水解模型，双齿的Ti-OOH中间体在3元环组装超过三角架位点（3MR）配置（性Ti-（η ² -OOH）-3MR）通过逐步机制丙烯环氧化被认定而单齿的Ti -H ₂ Ó ₂在5MR配置（性Ti-（η稳定中间体¹ -H ₂ Ò ₂）-5MR）是通过协同机制获得的。发现在水解模型上，步进路径和协同路径都是可行的。对Ti /硅空位模型的缺损部位，通过5MR性Ti-的新机制（η ¹ -OOH）被证明是能量上最有利的候选来表示丙烯环氧化化学中间体H中₂ ö ₂ / TS- 1。与文献相比，H ₂ O ₂离解和环氧化的势垒（5.1和10.4 kcal / mol）都相对较低，这可以归因于Si空位模型的空间优势以及形成的H键网络与周围的硅烷醇基团。共同产生的H _2的作用上丙烯环氧化动力学O另检查和的计算结果表明使得h ₂ ö协调与Ti中心便于5MR性Ti-的形成（η ¹ -OOH）中间，并显着降低了均为H的障碍₂ Ò ₂解离和环氧化在TS-1的Ti /缺陷部位上。