Theoretical study of the pyrolysis of β-1,4-xylan: a detailed investigation on unimolecular concerted reactions,Physical Chemistry Chemical Physics

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Theoretical study of the pyrolysis of β-1,4-xylan: a detailed investigation on unimolecular concerted reactions
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2021-1-13 , DOI: 10.1039/d0cp06024k
M. Goussougli _{1,

2,

3,

4,

5} , B. Sirjean _{1,

2,

3,

4,

5} , P.-A. Glaude _{1,

2,

3,

4,

5} , R. Fournet _{1,

2,

3,

4,

5}

Affiliation

A theoretical study of the thermal decomposition of β-1,4-xylan, a model polymer of hemicelluloses, is proposed for the first time. A mechanism based on unimolecular concerted reactions is elaborated in a comprehensive way. Elementary reactions, such as dehydrations, retro-aldol, retro Diels–Alder, retro-ene, glycosidic bond fissions, isomerizations, etc., are applied to β-1,4-xylan, as well as to the fragments formed. At each stage of the construction of the mechanism, the fragments previously retained are decomposed and the low energy paths are selected to define new fragments. Energy barriers are computed at the CBS-QB3 level of theory and rate coefficients of important reactions are calculated. It is shown that the main reaction pathways can be modelled by reactions involving two specific fragments, which react in closed sequences, similarly to chain-propagating reactions. The proposed reaction scheme allows to predict important species observed during the pyrolysis of xylan, such as aldehydes or CO. In addition, we show that dehydrations require high activation energy and cannot compete with the other reactions. Therefore, it seems difficult to explain, by means of unimolecular homogeneous gas phase reactions, the significant formation of specific species such as furfural as reported by several authors.

中文翻译：

β-1,4-木聚糖热解的理论研究：单分子协同反应的详细研究

首次提出了对半纤维素模型聚合物β-1,4-木聚糖进行热分解的理论研究。全面阐述了基于单分子协同反应的机理。基本反应，例如脱水，逆醛醇，逆Diels-Alder，逆烯，糖苷键裂变，异构化等。应用于β-1,4-木聚糖以及形成的片段。在该机构构造的每个阶段，将先前保留的碎片分解，并选择低能路径定义新的碎片。在CBS-QB3的理论水平上计算能垒，并计算重要反应的速率系数。结果表明，可以通过涉及两个特定片段的反应来模拟主要反应路径，该片段以闭合序列进行反应，类似于链增长反应。拟议的反应方案可以预测在木聚糖热解过程中观察到的重要物种，例如醛或一氧化碳。此外，我们证明了脱水需要高活化能并且不能与其他反应竞争。因此，似乎很难解释，

更新日期：2021-01-22

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