α-O-4型木质素二聚体模型物热解解聚机理

Pyrolytic depolymerization mechanism of a lignin model compound with α-O-4 linkage

摘要:

为了解木质素α-O-4连接部分的热解机理，以4-(3-羟基-1-苯氧基丙基)-苯酚为α-O-4型木质素二聚体模型化合物，采用密度泛函理论M06-2X/6-31+G (d,p) 方法，对该二聚体热解过程中的反应物、中间产物、过渡态、产物进行几何结构的完全优化，通过计算各可能路径的反应能垒，确定了该模型化合物主要通过Cα-O键的均裂和协同断裂的方式发生裂解反应，主要生成苯酚、4-甲基苯酚、4-乙烯基苯酚和香豆醇等酚类产物以及乙醇、甲醇、甲醛等小分子物质，由此首次从理论上揭示了该模型化合物的详细热解解聚过程。

Abstract:

To understand the pyrolysis mechanism of lignin with α-O-4 linkage, 4-(3-hydroxy-1-phenoxypropyl)-phenol was selected as an α-O-4 type lignin dimer model compound, and its pyrolysis process was studied by density functional theory with M06-2X method at 6-31+G (d,p) level. Equilibrium geometries of the reactant, intermediates, transition states and products were fully optimized. The activation energies in each pyrolysis pathway were calculated. The dimer decomposed mainly through the homolytic cleavage and concerted decomposition of the Cα-O linkage. Pyrolytic products mainly included various phenolic compounds such as phenol, 4-methylphenol, 4-vinylphenol and p-coumaryl alcohol, as well as light compounds such as ethanol, methanol and formaldehyde. Pyrolytic depolymerization process has its potential in biomass-based fuels.