选用5-5′键型连接的木质素二聚体为研究对象,基于B3 LYP/6-31 g基组和密度泛函理论(DFT)对其进行了高温热解微观化学反应机理研究,设计了5-5′型木质素二聚体高温热解反应的5条初反应路径,并在分析初反应结果的基础上设计了7条次反应路径,对每条路径的反应物及其产物进行了结构优化,计算了1500 K 温度下每条反应路径的热力学及动力学参数。结果表明,5-5′型木质素苯环位上的甲氧基具有很强的活性,甲氧基中 O-CH3键以及Caromatic-OCH3键较易断裂；通过计算得出初反应的 R3、R4反应焓变较小,分别为192.7 kJ/mol 和270.5 kJ/mol,认为该热解反应的主反应路径以R3及R4为主；该热解反应得到的最终产物有3-4,二羟基甲苯、对羟基甲苯、2-乙烯-4-甲基-3,5-二烯环己酮、甲烷、甲醇及甲醛。
The 5-5′type lignin dipolymer was chosen as the research obj ect.The microscopic chemical reaction mechanism of the 5-5′type lignin dipolymer under high temperature pyrolysis reaction was carried out based on B3LYP/6-31g group and density functional theory (DFT).Five initial reaction paths were designed,and seven se-condary reaction paths were designed according to the analysis of the initial reaction results.The reaction paths and products were optimized,and the thermodynamic and kinetic parameters at the temperature of 1500 K were calculated. Results show that the methoxyl group in the benzene ring of the 5-5′type lignin has high activity,the O-CH3 and Caromatic-OCH3 are easily broken.The enthalpy changes of R3 and R4 the initial reaction are 192.7 kJ/mol and 270.5 kJ/mol respectively,which proves that the mainly pyrolysis reaction paths are R3 and R4.The final products via this pyrolysis reaction include 3,4-2 dihydroxytoluene,hydroxy toluene,2-ethylene-4-methyl-3,5-two alkene cy-clohexanone,methane,methanol and formaldehyde.
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