木质素二聚体模型化合物热解机理的量子化学研究  

Quantum chemistry study on pyrolysis mechanism of lignin dimer model compound

作　　者：黄金保[1] 武书彬[2] 雷鸣[2] 程皓[2] 梁嘉晋[2] 童红[1] 

机构地区：[1]贵州民族大学理学院,贵州贵阳550025 [2]华南理工大学制浆造纸工程国家重点实验室,广东广州510640

出　　处：《燃料化学学报》2015年第11期1334-1343,共10页Journal of Fuel Chemistry and Technology

基　　金：国家自然科学基金(51266002);国家重点基础研究发展规划(973计划;2013CB228101);贵州省教育厅自然科学研究招标项目(黔教科研发[2013]405号)资助~~

摘　　要：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-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 at6-31G（ 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-Cβ bond 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-hydroxypropaldehyde 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.

关 键 词：木质素 β-O-4连接二聚体 热解机理 密度泛函理论 

分 类 号：TK6[动力工程及工程热物理—生物能] O642[理学—物理化学]