关键词: 钛酸四丁酯, 密度泛函理论, 聚酯预缩聚, 催化活性, 配体结构

Abstract: In recent years, the textile industry has been increasingly demanding environmentally friendly and sustainable practices in polyester fiber production. This paper systematically analyzes the catalytic mechanism of tetrabutyl titanate (TBOT) in the polyester pre-polycondensation reaction based on density functional theory (DFT) and explores the impacts of polyester types, molecular chain lengths, and changes in ligand structures on catalytic activity. Through theoretical modeling, this paper provides robust theoretical support for a deeper understanding of the intrinsic relationship between molecular structures and catalytic activities during the catalytic process.​ DFT calculations reveal significant differences in the activation energies for the pre-polycondensation reactions of three typical polyesters: polybutylene succinate (PBS), polybutylene terephthalate (PBT), and polyethylene terephthalate (PET). Specifically, PBS exhibits the lowest pre-polycondensation activation energy of 47.90 kJ/mol, while PBT and PET show activation energies of 52.39 kJ/mol and 77.44 kJ/mol, respectively. Due to the absence of benzene rings in PBS, the electronegativity of its ester carbonyl oxygen atoms is relatively concentrated, facilitating effective coordination with the titanium center of TBOT. Moreover, as the molecular chain length of the polyesters increases, the activation energy gradually rises—with PBS showing a particularly pronounced increase from 47.90 kJ/mol (monomer) to 83.78 kJ/mol (long-chain polymer)—demonstrating a strong influence of molecular weight on catalytic activity. By modifying the catalyst through the substitution of the butoxy groups in TBOT with heptacyclic (Cat1) and ester carbonyl (Cat2) structures, the calculations demonstrate that these modifications increase the pre-polycondensation activation energies by 10.49% and 26.07%, respectively. The introduction of these new groups leads to increased steric hindrance and a more negative electrostatic potential around the central titanium atom of the catalyst, thereby impeding effective coordination between the reactant groups and the titanium atom. Further validation of the regulatory effects of ligand group modifications on the electronic environment and reactivity of the titanium atom is achieved through electrostatic potential maps and surface distance projection analyses.​ This paper reveals that the catalytic activity of TBOT in the polyester pre-polycondensation reaction is synergistically regulated by the molecular structure, chain length of the polyester, and ligand modifications. The study indicates that flexible polyester systems characterized by lower activation energies are more suitable for TBOT catalysis, whereas rigid aromatic polyesters exhibit higher activation energies, making the reactions more challenging. As the molecular chain length increases, the activation energy for the pre-polycondensation reaction rises significantly. Excessive steric hindrance or an inappropriate electronic environment resulting from ligand modifications can both weaken the catalytic activity. This study not only deepens the understanding of the mechanism underlying the role of titanium-based catalysts in polyester synthesis but also provides a theoretical basis for designing efficient and eco-friendly polyester catalytic systems. Future studies will integrate experimental validation with the development of hybrid catalyst systems to further bridge the gap between theory and practical application, so as to advance the industrialization process of green polyester fiber production.​

Key words: tetrabutyl titanate, density functional theory, polyester pre-polycondensation, catalytic activity, ligandstructures