CAJ | 학술논문

β-O-4连接是木质素主体结构单元之间的主要联结方式。采用密度泛函理论方法B3LYP,在6-31G (d, p)基组水平上,对β-O-4型木质素二聚体模型化合物(1-愈创木基-2-(2-甲氧基苯氧基)-1,3丙二醇)的热解反应机理进行了研究。提出了三种热解反应途径：Cβ-O键均裂的后续反应、Cα-Cβ键均裂的后续反应以及协同反应。对各种反应的反应物、产物、中间体和过渡态的结构进行了能量梯度全优化,计算了各热解反应途径的标准动力学参数。分析了各种主要热解产物的形成演化机理以及热解过程中温度对热解机理的影响。计算结果表明,Cβ-O键的均裂反应和协同反应路径(1)和(3)是木质素二聚体热解过程中主要的反应路径,而Cα-Cβ键的均裂反应和协同反应路径(2)和(5)是主要的竞争反应路径；热解的主要产物是酚类化合物如愈创木酚、1-愈创木基-3-羟基丙酮、3-愈创木基-3-羟基丙醛、愈创木基甲醛和乙烯等。在热解低温阶段协同反应是热解过程中的主要反应形式,而在高温阶段自由基均裂反应是热解过程的主要反应形式。
β-O-4련접시목질소주체결구단원지간적주요련결방식。채용밀도범함이론방법B3LYP,재6-31G (d, p)기조수평상,대β-O-4형목질소이취체모형화합물(1-유창목기-2-(2-갑양기분양기)-1,3병이순)적열해반응궤리진행료연구。제출료삼충열해반응도경：Cβ-O건균렬적후속반응、Cα-Cβ건균렬적후속반응이급협동반응。대각충반응적반응물、산물、중간체화과도태적결구진행료능량제도전우화,계산료각열해반응도경적표준동역학삼수。분석료각충주요열해산물적형성연화궤리이급열해과정중온도대열해궤리적영향。계산결과표명,Cβ-O건적균렬반응화협동반응로경(1)화(3)시목질소이취체열해과정중주요적반응로경,이Cα-Cβ건적균렬반응화협동반응로경(2)화(5)시주요적경쟁반응로경；열해적주요산물시분류화합물여유창목분、1-유창목기-3-간기병동、3-유창목기-3-간기병철、유창목기갑철화을희등。재열해저온계단협동반응시열해과정중적주요반응형식,이재고온계단자유기균렬반응시열해과정적주요반응형식。
β-O-4 is the primary type of linkages among the main lignin structure units. The pyrolysis of lignin dimer model compound of β-O-4 linkage was investigated by using density functional theory B3 LYP methods at 6-31G ( d, p ) level. Three possible pyrolysis pathways were proposed: the subsequent reactions after the homolytic cleavage of Cβ-O bond, the subsequent reactions after the homolytic cleavage of Cα-Cβbond and the concerted reactions. The equilibrium geometries of the reactants, transition states, intermediates and products were optimized and the standard kinetic parameters for each reaction pathway were calculated. The formation mechanism of the main pyrolysis products and the effect of temperature on the pyrolysis mechanism of lignin dimer were analyzed. The calculation results show that the subsequent reaction pathways after the homolytic cleavage of Cβ-O bond and the concerted reaction pathways ( 1 ) and ( 3 ) are the major reaction channels, whereas the subsequent reaction pathways after the homolytic cleavage of Cα-Cβ and the concerted reaction pathways ( 2 ) and ( 5 ) are the competitive reaction channels in the pyrolysis process. The main pyrolysis products are phenolic compounds such as guaiacol, 1-guaiacyl-3-hydroxy- acetone, 1-guaiacyl-3-hydroxy-propaldehyde and guaiacyl-formaldehyde. In the pyrolysis process of the lignin dimer, the concerted reactions dominate over the free-radical homolytic reactions at low temperature, whereas but the free-radical reactions prevail over the concerted reactions at high temperatures.