Theoretical Study on Elementary Reaction Steps in Thermal Decomposition Processes of Syringol-Type Monolignol Compounds
Theoretical Study on Elementary Reaction Steps in Thermal Decomposition Processes of Syringol-Type Monolignol Compounds
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DOI：
10.1021/acs.jpca.7b09450
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发表时间：
2018-01-25
影响因子：
2.9
通讯作者：
Norinaga, Koyo
中科院分区：
文献类型：
--
作者：
Furutani, Yuki;Dohara, Yuki;Norinaga, Koyo
本文从理论上研究了大量的反应途径和动力学，以描述由木质素的初级热解衍生的几种顺式单萜化合物的气相热解行为：1-（4-羟基-3，5-二甲氧基苯基）丙-2-烯-1-酮（HDPP）、芥子醇、3-羟基-1（4-羟基-3，5-二甲氧基苯基）丙-1-酮（HHDPP）、1-（4-羟基-3，5-二甲氧基苯基）丙-1，3-二醇（HDPPD）和姜油酚。通过比较在B3 LYP/6-311+ +G（d，p）水平上计算的能垒，研究了单分子分解反应、加成反应和夺取反应等可能的热解途径.在所提出的途径中，所有含有侧链的顺式然后丁香酚转化为两种产物：（a）通过O-CH 3键的均裂和氢化作用转化为焦性没食子酸，或（B）通过在丁香酚中添加一个H原子和一个含碳甲氧基并随后进行脱甲氧基反应转化为愈创木酚。焦性没食子酸的热解途径分为两个过程：（a）两个羟基H原子脱氢和单分子分解生成乙炔（C2 H2）、乙炔醇（C2 HOH）和CO;或（B）OH被H置换生成邻苯二酚和间苯二酚。另外，HDPP经历O-CH 3键裂解以形成丁-1-烯-3-炔。根据过渡态理论计算了所有基元反应步骤的高压极限速率常数。协调一致
This paper theoretically investigated a large number of reaction pathways and kinetics to describe the vapor-phase pyrolytic behavior of several syringol-type monolignol compounds that are derived from the primary pyrolysis of lignin: 1-(4-hydroxy-3,5-dimethoxyphenyl)prop-2-en-1-one (HDPP), sinapyl alcohol, 3-hydroxy-1(4-hydroxy-3,5-dimethoxyphenyl)prop an-1-one (HHDPP), 1-(4-hydroxy-3,5-dimethoxyphenyl)propane-1,3-diol (HDPPD), and syringol. The possible pyrolytic pathways involving unimolecular decomposition, addition, and abstraction reactions were investigated by comparing the energy barriers calculated at the B3LYP/6-311+ +G(d,p) level. In the proposed pathways, all syringol-type monolignols containing a side chain undergo its cleavage to form syringol through the formation of syringaldehyde or 4-vinylsyringol. Syringol is then converted into two products: (a) pyrogallol via the homolysis of the O-CH3 bond and hydrogenation or (b) guaiacol via addition of an H atom with a carbon bearing methoxyl group in syrignol and the subsequent demethoxylation. The pyrolytic pathways of pyrogallol are classified into two processes: (a) the dehydrogenation of the two hydroxyl H atoms and the unimolecular decomposition to produce acetylene (C2H2), ethynol (C2HOH), and CO or (b) the displacement of an OH with H to produce catechol and resorcinol. Additionally, HDPP undergoes O-CH3 bond cleavage to form but-1-en-3-yne. The high-pressure limit rate constants for all the proposed elementary reaction steps were evaluated on the basis of transition state theory. concerted