木质素二聚体电化学氧化机理的密度泛函理论研究

Density Functional Theory Study on the Electrochemical Oxidation Mechanism of Lignin Dimer

摘要: 为了从分子层面了解木质素在碱性溶液中电化学氧化降解过程，构建了以愈创木基丙烷结构单体聚合而成的木质素二聚体理论模型，采用杂化密度泛函B3LYP/6-31G(d)基组对木质素二聚体理论模型进行优化和计算。通过键解离能计算、HOMO和LUMO轨道活性点位分析和势能分析方法研究木质素二聚体反应路径，发现二聚体模化物在电化学氧化反应中，苯环间连接处的C原子是主要反应活性位点，连接两个苯环间的C-C键易断裂，形成的异丁烯碳正离子与苯酚反应生成产物2,4-二叔丁基苯酚，该反应过程能垒为398.6 kJ/mol，吸收热量为0.59 kJ/mol。通过理论建模与计算，阐述了木质素电化学氧化的反应机理，为木质素电化学氧化耦合电解水制氢的优化提供理论支撑。

Abstract: In order to understand the electro-oxidative degradation process of lignin in alkaline solution from molecular level, a theoretical model of lignin dimer polymerization made of guaiac-based propane monomer was constructed. The hybrid density functional B3LYP/6-31G(d) base group was used to optimize and calculate the initial idea. The lignin dimer reaction pathway was studied by calculating bond dissociation energy, HOMO and LUMO orbital active point analysis and potential energy analysis. It is found that in the electrochemical oxidation reaction of dimer molds, the C atom at the junction between the benzene rings is the main potential reactive site, and the C-C bond connecting the two benzene rings is easy to break, the isobutylene carbodyl ions formed by the reaction process with phenol to form the product of 2,4-di-tert-butylphenol, which has a barrier of 398.6 kJ/mol and only absorbs 0.59 kJ/mol of heat. Through the combination of theoretical modeling and calculation, the reaction mechanism of lignin electrooxidation degradation of lignin is elaborated, which provides theoretical support for the optimization of hydrogen production by electrochemical oxidation of lignin coupled with water electrolysis.