The influence of pretreatment on the bond-breaking rules during pyrolysis of Shengli lignite and the construction of macromolecular structure model

IF 6.2 2区化学 Q1 CHEMISTRY, ANALYTICAL

Journal of Analytical and Applied Pyrolysis Pub Date : 2025-06-06 DOI:10.1016/j.jaap.2025.107215

Boyang Bai , Ming Sun , Luyao Qiang , Yufeng An , Shanshan Wei , Feifei Wang , Xiaoxun Ma

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Abstract

Coal pyrolysis is a critical method for the clean and efficient utilization of coal, with its structural characteristics playing a decisive role in pyrolysis behavior. By modifying the coal structure via pre-treatment and subsequently examining the effects of these structural alterations on its pyrolysis characteristics, we can more effectively clarify the pyrolysis mechanism of coal. In this study, hydrothermal pretreatment (HTP) and solvent swelling pretreatment (SSP) were used to change the structure and composition of Shengli (SL) lignite. The structural changes in the pretreated coal were characterized using Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and solid-state ¹³C nuclear magnetic resonance (NMR). A macromolecular structure model of SL lignite/pretreated coal were constructed. The bond-breaking rules and pyrolysis characteristics of SL lignite/pretreated were investigated using thermogravimetric-infrared (TG-IR) analysis and a fixed-bed reactor, respectively. The results of the macromolecular structure model indicate that: compared with the SL lignite (600 kcal/mol), the total energy of HTP (679 kcal/mol) and SSP (686 kcal/mol) has significantly increased, which is more conducive to the depolymerization of coal molecules during the pyrolysis. Specifically, HTP can increase the H/C ratio and the proportion of phenolic hydroxyl groups in coal, while reducing the content of oxygen-containing functional groups. It also disrupts the cross-linking structure of SL lignite, promoting the cleavage of C_ar-O and C_al-C_ar bonds, which resulted in an increase in the yields of pyrolysis tar and light tar from 7.48 %, 41.68–9.40 %, 47.62 % respectively. On the other hand, SSP primarily destroys non-covalent bonds in coal and dissolves small molecular compounds to weakening the cross-linking structure, facilitating the cleavage of C_al-C_al, C_ar-O and C_al-C_ar bonds during pyrolysis, promotes the generation of tar. Accordingly, the tar yield and the content of light tar increased to 9.75 % and 47.88 %.

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预处理对胜利褐煤热解断键规律的影响及大分子结构模型的构建

煤热解是实现煤炭清洁高效利用的重要手段，其结构特征对煤的热解行为起着决定性的作用。通过预处理对煤的结构进行改造，随后考察这些结构改变对煤热解特性的影响，可以更有效地阐明煤的热解机理。采用水热预处理（HTP）和溶剂膨胀预处理（SSP）对胜利褐煤的结构和组成进行了改变。采用傅里叶变换红外光谱（FT-IR）、x射线光电子能谱（XPS）和固态13C核磁共振（NMR）对预处理后煤的结构变化进行了表征。建立了SL褐煤/预处理煤的大分子结构模型。采用热重红外（TG-IR）分析和固定床反应器研究了SL褐煤/预处理后的断键规律和热解特性。大分子结构模型结果表明：与SL褐煤（600 kcal/mol）相比，HTP（679 kcal/mol）和SSP（686 kcal/mol）的总能量显著增加，更有利于煤分子在热解过程中的解聚。具体来说，HTP可以提高煤中H/C比和酚羟基的比例，同时降低含氧官能团的含量。它还破坏了SL褐煤的交联结构，促进了Car-O键和Cal-Car键的裂解，使热解焦油和轻焦油的产率分别从7.48 %、41.68 ~ 9.40 %和47.62 %提高。另一方面，SSP主要破坏煤中的非共价键，溶解小分子化合物，削弱交联结构，有利于热解过程中Cal-Cal、Car-O和Cal-Car键的裂解，促进焦油的生成。相应的，焦油收率和轻焦油含量分别提高到9.75 %和47.88 %。

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来源期刊

Journal of Analytical and Applied Pyrolysis 化学-分析化学

CiteScore

9.10

自引率

11.70%

发文量

340

审稿时长

44 days

期刊介绍： The Journal of Analytical and Applied Pyrolysis (JAAP) is devoted to the publication of papers dealing with innovative applications of pyrolysis processes, the characterization of products related to pyrolysis reactions, and investigations of reaction mechanism. To be considered by JAAP, a manuscript should present significant progress in these topics. The novelty must be satisfactorily argued in the cover letter. A manuscript with a cover letter to the editor not addressing the novelty is likely to be rejected without review.