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The generation of benzene carboxylic acids from lignite and the change in structural characteristics of the lignite during oxidation

机译：褐煤中苯羧酸的生成及氧化过程中褐煤结构特征的变化

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摘要

Production of carboxylic acids (including 12 types of benzene carboxylic acids (BCAs) and small-molecule fatty acids) from lignite via oxidation has been widely studied, but few studies addressed the relationship between distribution of BCAs and structure of lignite. This work studies alkali-oxygen oxidation of Xiaolongtan lignite and distributions of BCAs with C-13 NMR as well as the relationship between the distributions of BCAs and the lignite structures. The results indicate that the dominant aromatic structures in the lignite are naphthalene and benzene with a mole ratio of around 3, and an alkyl-substituted degree of aromatic rings of 0.359. These structure characters determine that the yields of benzene tricarboxylic acids, benzene tetracarboxylic acids, benzene pentacarboxylic acid and mellitic acid are more than those of other BCAs. In the oxidation process, the organic matter of lignite is first converted to humic acids (HAs), then to water soluble acids, and last to carboxylic acids. The last conversion step is the rate-controlling step. Analyses of the residues and HAs indicate that C-O bond of lignite is easily cleaved. The aromatic structures (except condensed aromatic rings) are easily depolymerized from lignite, but the condensed aromatic rings and long alkyl chains are difficult to be oxidized. With an increase in oxidation time, in the residues, the contents of aromatic structures decrease, but the contents of condensed aromatic rings and long alkyl chains both increase. While in HAs, the contents of condensed aromatic rings increase, but the average methylene chain length (C-n) decreases. (C) 2017 Elsevier Ltd. All rights reserved.
机译：褐煤通过氧化生产羧酸（包括12种苯甲酸（BCA）和小分子脂肪酸）的方法已得到广泛研究，但很少有研究探讨BCA的分布与褐煤结构之间的关系。本文利用C-13 NMR研究了小龙潭褐煤的碱-氧氧化和BCA的分布以及BCA的分布与褐煤结构的关系。结果表明，褐煤中主要的芳族结构是萘和苯，摩尔比约为3，芳环的烷基取代度为0.359。这些结构特征决定了苯三羧酸，苯四羧酸，苯五羧酸和苯四甲酸的收率要高于其他BCA。在氧化过程中，褐煤的有机物首先转化为腐殖酸（HAs），然后转化为水溶性酸，最后转化为羧酸。最后的转换步骤是速率控制步骤。残基和HA的分析表明，褐煤的C-O键易于断裂。芳族结构（稠合的芳环除外）很容易从褐煤中解聚，但是稠合的芳环和长烷基链很难被氧化。随着氧化时间的增加，残基中芳族结构的含量降低，但稠合芳环和长烷基链的含量均增加。在HA中，稠合芳环的含量增加，但平均亚甲基链长（C-n）降低。 （C）2017 Elsevier Ltd.保留所有权利。

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  • 来源
    《Fuel》 |2017年第1期|214-221|共8页
  • 作者

    Yang Fan; Hou Yucui; Wu Weize; Liu Zhenyu;

  • 作者单位

    Beijing Univ Chem Technol, State Key Lab Chem Resource Engn, Beijing 100029, Peoples R China;

    Taiyuan Normal Univ, Dept Chem, Taiyuan 030031, Peoples R China;

    Beijing Univ Chem Technol, State Key Lab Chem Resource Engn, Beijing 100029, Peoples R China;

    Beijing Univ Chem Technol, State Key Lab Chem Resource Engn, Beijing 100029, Peoples R China;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

    Lignite; Benzene carboxylic acids; C-13 NMR; Structural characteristics; Oxidation;

    机译：褐煤;苯甲酸;C-13 NMR;结构特征;氧化;

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