基于DFT密度泛函理论的聚酯热降解反应机理研究

本文应用密度泛函理论（DFT）研究钛系催化剂催化聚酯热降解的反应机理。分别以Ti(OEt)4化合物以及Ti(OEt)3 阳离子化合物为催化剂，探讨了二苯甲酸乙二酯（EDB）解聚反应的Lewis酸催化热降解反应机理（M1机理）和烷氧基配位催化热降解反应机理（M2机理）。结果表明，Lewis酸催化热降解反应机理在两种催化剂下的解聚反应能垒与无催化剂反应非常相似，未表现出明显促进作用；Ti(OEt)3 催化剂在M2机理中明显降低了解聚反应能垒，是聚酯热降解反应的催化活性中心。经轨道相互作用分析发现，阳离子催化剂和反应物EDB之间存在较为明显的轨道相互作用。

DFT Study on the Mechanism of Thermal Degradation of Polyester

The mechanism of thermal degradation of polyester by Ti-based catalyst was investigated by density functional theory (DFT) calculations. The Lewis acid catalyzed thermal degradation mechanism (M1 mechanism) and the alkoxy ligand assisted thermal degradation mechanism (M2 mechanism) were investigated for the depolymerization of EDB catalyzed by Ti(OEt)4 and the cationic Ti(OEt)3 , respectively. The calculations showed that the activation energy barriers for the Lewis acid catalyzed thermal degradation by both catalysts is similar to the barrier in the absence of the catalyst. The cationic Ti(OEt)3 significantly reduced the activation barrier for thermal degradation of EDB (M2 mechanism), which is believed to be the active center for the depolymerization of EDB. The principal interacting orbital (PIO) analysis revealed more orbital interactions between the cationic catalyst and the EDB polyester.