光谱学与光谱分析, 2020, 40 (3): 787, 网络出版: 2020-03-25   

红外光谱定量研究不同煤阶煤的化学结构

Quantitative Study of Chemical Structures of Different Rank Coals Based on Infrared Spectroscopy
作者单位
1 太原理工大学地球科学与工程系, 山西 太原 030024
2 煤与煤系气地质山西省重点实验室, 山西 太原 030024
3 煤与煤层气共采国家重点实验室, 山西 晋城 048000
4 中国石油天然气股份有限公司山西煤层气勘探开发分公司, 山西 晋城 048000
摘要
为定量研究不同煤阶煤的化学结构, 借助傅里叶红外光谱, 对河曲长焰煤、 柳林焦煤及晋城无烟煤进行了化学结构表征。 从红外的四个谱段来看, 每一谱段都发生了一定的变化。 在芳香结构中, 河曲煤有5个峰位, 柳林煤减小为3个峰位, 而后至晋城煤又增加到5个峰位。 在含氧官能团中, 随着煤阶的升高, 波数在1 100~1 350 cm-1的峰面积逐渐减小, 峰形变得平缓, 这说明煤化作用是富碳、 脱氧的过程。 在脂肪烃中, 谱图中波数在2 952 cm-1附近的肩峰加宽, 说明甲基的含量增加。 波数在2 895 cm-1附近的峰形逐渐变缓, 说明次甲基的含量减小。 在氢键范围内, 随着煤阶的增高, 谱图先变缓后变陡, 波数在3 400 cm-1附近变化尤为突出, 说明煤中自缔合羟基的含量先减小后增加。 并运用Origin7.5软件对所得到的红外谱图进行分峰拟合及归属。 结果表明: 苯环的取代方式主要以三取代为主, 随着煤阶的增高, 苯环三、 四取代含量下降, 二、 五取代含量升高; 其中苯环三取代的含量由63%降至32%, 苯环四取代由17.21%降至12.86%, 而苯环二取代则由12.36%增至24.44%, 苯环五取代由6.55%增至26.58%。 红外归属中, 不同煤阶煤灰分的百分含量, 与其工业分析中灰分含量有很好地对应。 随着煤阶的增高, 碳氧单键的比例由37.22%降至27.83%; 碳碳双键含量由31.02%升高到36.86%, 而后又降至25.42%; 碳氧双键含量有微小变化, 由13.07%降到13.02%, 然后又升至13.81%。 脂肪烃中, 随着煤化程度的加深, 甲基对称伸缩振动占比分别为11.67%, 11.81%和12.92%, 甲基反对称伸缩振动占比分别为18.74%, 18.94%, 24.76%, 而次甲基的伸缩振动占比分别为17.38%, 12.53%, 11.57%, 亚甲基对称伸缩振动占比分别为18.09%, 18.14%和15.43%, 亚甲基的反对称伸缩振动占比分别为34.41%, 38.58%和35.32%。 亚甲基的对称与反对称的比例都出现先增加后减小的趋势; 甲基的对称与反对称伸缩振动的比例则呈增加趋势; 次甲基的含量呈降低趋势。 羟基-N氢键存在于河曲煤与柳林煤中, 晋城煤无此类氢键; 煤阶越低, 其百分含量越大。 随着煤阶的增高, 环状缔合氢键由19.03%降至12.71%, 羟基-醚氢键由27.20%降至16.89%; 这是由于低煤阶煤中羧酸、 羟基等含氧官能团的含量高。 自缔合羟基含量先由39.63%减小到34.78%, 而后又增加至37.88%; 而羟基-π氢键的含量由9.84%上升至27.77%。 这些变化揭示了煤化作用是一个富碳、 去氢、 脱氧、 去除杂原子的复杂演化过程; 对探索煤大分子结构演化特征及控制机理有借鉴意义。
Abstract
The change of chemical structure of coals with different rank is of great significance to the study of macromolecular structure evolution in coal. The chemical structures of Hequ candle coal, Liulin coking coal and Jincheng anthracite coal are characterized by means of fourier transform infrared spectroscopy. From the four parts of the infrared spectrum, each part has undergone certain changes. In the aromatic structure, the Hequ coal has five peaks, and the Liulin coal is reduced to three peaks, and then the Jincheng coal is increased to five peaks. In the oxygen-containing functional group, as the coal rank increases, the peak area of the wave number between 1 100 and 1 350 cm-1 gradually decreases. And peaks tend to be flatter which indicates that coalification is a process of being carbon-rich and deoxidized. In aliphatic hydrocarbons, in the spectrum, the shoulder number of the wave number near 2 952 cm-1 is widened, which shows an increase in the content of methyl groups. The peak shape near the wave number of 2 895 cm-1 gradually slows down, indicating that the content of methine is decreased. In the range of hydrogen bonding, with the increase of coal rank, the spectrum becomes slower and then steeper, and the wave number is more prominent around 3 400 cm-1, indicating that the content of self-associated hydroxyl groups in coal decreases first and then increases. The peak spectrum of the obtained infrared spectrum is fitted and attributed by origin7.5 software. The results show that the substitution of benzene ring is mainly based on tri-substituted, with the deepening of the coal rank, the content of benzene ring tri- or tetra-substituted decreases, and the content of di- and penta-substituted increases; in which the content of the tri-substituted benzene ring is reduced from 63% to 32%, and the content of the benzene ring tetra-substituted is reduced from 17.21% to 12.86%, however, the percentage of di-substituted is from 12.36% to 24.44%, and the percentage of penta-substituted is increased from 6.55% to 26.58%. The ash content in the infrared attribution is higher, and the ash percentage in the industrial analysis is also higher. As the degree of coalification increases, the proportion of the carbon-oxygen single bond decreases from 37.22% to 27.83%. The carbon-carbon double bond content increases from 31.02% to 36.86%, and then decreases to 25.42%, and the carbon-oxygen double bond content changes slightly, from 13.07% to 13.02%, and then increases to 13.81%. In the aliphatic hydrocarbons, with the deepening of the coal rank, the percentage of the methyl symmetric stretching vibration is 11.67%, 11.81% and 12.92% respectively. The percentage of the methyl anti-symmetric stretching vibration is 18.74%, 18.94%, 24.76%, and the methyl content increases. However, the proportion of stretching vibration of methine decreases from 17.38% to 12.53%, and finally decreases to 11.57%. The content of methine decreases. The proportion of methylene symmetric stretching vibration is 18.09%, 18.14% and 15.43% respectively, the proportion of methylene anti-symmetric stretching vibration is 34.41%, 38.58% and 35.32% respectively, and the content of methylene first increases and then decreases. In addition, the hydroxyl-N hydrogen bond is present in the Hequ coal and the Liulin coal, while there is no such hydrogen bond in Jincheng coal, the lower the coal rank, the higher the percentage content, the ring-associated hydrogen bond is reduced from 19.03% to 12.71%, the hydroxyl-ether hydrogen bond is reduced from 27.20% to 16.89%, which is that the content of oxygen-containing functional groups such as carboxylic acid and hydroxyl group in the lower rank coal is higher. The self-associated hydroxyl content decreases from 39.63% to 34.78% and then increases to 37.88%. The content of hydroxy-π hydrogen bond increases from 9.84% to 27.77%. These changes reveal that coalification is a complex evolutionary process of being carbon-rich, dehydrogenation, deoxygenation, and removal of heteroatoms. The research results have reference significance for exploring the evolution characteristics and control mechanism of coal macromolecular structure.

郝盼云, 孟艳军, 曾凡桂, 闫涛滔, 徐光波. 红外光谱定量研究不同煤阶煤的化学结构[J]. 光谱学与光谱分析, 2020, 40(3): 787. HAO Pan-yun, MENG Yan-jun, ZENG Fan-gui, YAN Tao-tao, XU Guang-bo. Quantitative Study of Chemical Structures of Different Rank Coals Based on Infrared Spectroscopy[J]. Spectroscopy and Spectral Analysis, 2020, 40(3): 787.

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