Meng Junqing, Zhong Ruquan, Niu Jiaxing, Li Shichao, Nie Baisheng
School of Emergency Management and Safety Engineering, China University of Mining and Technology, Beijing 100083, China.
J Nanosci Nanotechnol. 2021 Jan 1;21(1):405-421. doi: 10.1166/jnn.2021.18720.
Four coals samples at different ranks were analyzed by Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and solid-state C nuclear magnetic resonance (NMR). The calculated coal molecular model was constructed according to the experimental data. The mode of evolution of four coal molecules with different metamorphic degrees was explored. The results indicate that the nanostructures of these four coal molecules mainly consist of aromatic structures, aliphatic structures and oxygen-containing functional groups. The coal metamorphic degree is the most important factor affecting the evolution of the coal molecular nanostructure. By increasing the coal rank, the aromatic carbon content and aromatic system increase, while the aliphatic carbon content and aliphatic system decrease, and the species and content of oxygen containing functional groups are also reduced. During the evolution of the molecular microcrystalline structure, the degree of vertical order of the aromatic structural unit, the flatness of the aromatic structural unit (), the average crystallite stacking height (), and the average number of crystallites in a stack () increase, while the interlayer distance between aromatic sheets () decreases; the short-range ordering of the coal structure is mainly caused by changes in the orientational arrangement from intramolecular aromatic layers to intermolecular aromatic layers when low-rank coal molecules evolve to high rank coal molecules. The structural evolution mechanism of coal molecules of different ranks has been revealed through the analysis of the mode of evolution of the molecular structure the coal. This study enables us to better understand the nanostructure evolution mechanism of coal molecules at different ranks.
对四个不同煤阶的煤样进行了傅里叶变换红外光谱（FTIR）、X射线光电子能谱（XPS）、X射线衍射（XRD）和固态碳核磁共振（NMR）分析。根据实验数据构建了计算得到的煤分子模型。探讨了四个不同变质程度煤分子的演化模式。结果表明，这四个煤分子的纳米结构主要由芳香结构、脂肪族结构和含氧官能团组成。煤变质程度是影响煤分子纳米结构演化的最重要因素。随着煤阶升高，芳香碳含量和芳香体系增加，而脂肪族碳含量和脂肪族体系减少，含氧官能团的种类和含量也降低。在分子微晶结构演化过程中，芳香结构单元的垂直有序度、芳香结构单元的平整度（）、平均微晶堆叠高度（）以及堆叠中微晶的平均数量（）增加，而芳香片层间的层间距（）减小；煤结构的短程有序主要是由于低阶煤分子向高阶煤分子演化时，分子内芳香层到分子间芳香层的取向排列变化所致。通过对煤分子结构演化模式的分析，揭示了不同煤阶煤分子的结构演化机理。本研究使我们能够更好地理解不同煤阶煤分子的纳米结构演化机理。
