Insight into the structural features of Zhaotong lignite using multiple techniques
Insight into the structural features of Zhaotong lignite using multiple techniques
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DOI：
10.1016/j.fuel.2015.02.117
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发表时间：
2015-08-01
期刊：
影响因子：
7.4
通讯作者：
Zong, Zhi-Min
中科院分区：
文献类型：
--
作者：
Li, Zhan-Ku;Wei, Xian-Yong;Zong, Zhi-Min
采用多种直接工具对昭通褐煤（ZL）的化学结构进行了表征，包括固态C-13核磁共振（NMR）、X射线光电子能谱仪（XPS）、傅里叶变换红外（FTIR）光谱仪和热重（TG）分析仪，并结合ZL乙醇分解和随后的电喷雾电离傅里叶变换离子回旋共振质谱仪（ESI FT-ICR MS）对所得乙醇可溶部分进行分析（ESP）。根据13C NMR分析，ZL主要由脂肪族(52.3%)和芳香族(42.2%)碳组成。亚甲基是脂肪族碳中最丰富的。每个芳香族簇平均包含2个环，每个芳香环上的取代基数为3或4个。XPS分析表明氧原子主要存在于C-O部分，这与13C NMR和FTIR分析一致，吡咯氮是ZL中主要的氮形式。根据TG分析，C-al-O和C-al-C-al键的断裂应该是ZL乙醇解过程中的主要反应。通过负离子 ESI FT-ICR MS 分析检测到 ESP 中的一系列中性氮化合物（NNC，即吡咯氮）。确定的 NNC 是 N1Ox (x = 0-5) 类物质，具有 3-13 双键当量 (DBE) 值和 10-31 个碳数，其中 N1O2 类物质是主要的 NNC。根据 NNC 的 DBE 分布，吡咯、吲哚和咔唑占 ZL 中中性氮的大部分。事实证明，这种多重表征是充分了解煤（尤其是褐煤）化学结构的有效方法。 (C) 2015 Elsevier Ltd. 保留所有权利。
The chemical structures of Zhaotong lignite (ZL) were characterized with multiple direct tools, including solid-state C-13 nuclear magnetic resonance (NMR), X-ray photoelectron spectrometer (XPS), Fourier transform infrared (FTIR) spectrometer, and thermogravimetric (TG) analyzer, combined with ZL ethanolysis and subsequent electrospray ionization Fourier transform ion cyclotron resonance mass spectrometer (ESI FT-ICR MS) analysis of the resulting ethanol-soluble portion (ESP). According to 13C NMR analysis, ZL mainly consists of aliphatic (52.3%) and aromatic (42.2%) carbons. Methylene is the most abundant among the aliphatic carbons. Each aromatic cluster contains 2 rings on average and the number of substituents on each aromatic ring is 3 or 4. XPS analysis suggests that oxygen atoms mainly exist in C-O moieties, which is consistent with 13C NMR and FTIR analyses, and pyrrolic nitrogen species are the main nitrogen form in ZL. Based on TG analysis, cleavage of C-al-O and C-al-C-al bonds should be the major reactions during ZL ethanolysis. A series of neutral nitrogen compounds (NNCs, i.e., pyrrolic nitrogen) in the ESP were detected by negative-ion ESI FT-ICR MS analysis. The identified NNCs are N1Ox (x = 0-5) class species with 3-13 double bond equivalent (DBE) values and 10-31 carbon numbers, in which N1O2 class species are predominant NNCs. According to DBE distributions of NNCs, pyrroles, indoles, and carbazoles account for most of the neutral nitrogen occurrences in ZL. Such multiple characterizations proved to be an effective method for fully understanding the chemical structures of coals, especially lignites. (C) 2015 Elsevier Ltd. All rights reserved.