Abstract The present study investigates the microstructural framework of coals from the Raniganj and the Jharia Basins as well as from the Himalayan fold-thrust belts of Sikkim, India, by vitrinite reflectance, Raman spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The mean random vitrinite reflectance data may imply that the coal samples from the Raniganj and the Jharia Basins range from the bituminous D to B, and would have experienced the burial heating corresponding to ~92 °C to 143 °C unlike the anthracite A samples that might have undergone the hydrothermal metamorphism at ~333 °C to 367 °C. The Raman spectra exhibit preferential removal of sp3 hybridized moieties from the anthracite samples at anchizonal metamorphic stage due to thermo-stress degradation effect induced by the Himalayan orogeny. Further, this study records the reduction of net dipole moment change due to the expulsion of functional groups from the aromatic rings making them infrared inactive. Additionally, the C1s spectra reveal the thinning of C C peaks and the lowering of the C O peak intensity with an increase in coal rank. This study, hence, documents the microstructural transformations in coal that can be used for structural maneuvering to control the liquefaction, gasification, pyrolysis, combustion as well as synthetic graphitization behavior.

中文翻译：

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煤变质作用的光谱表现：从煤微观结构框架看

摘要 本研究通过镜质体反射、拉曼光谱、傅里叶变换红外光谱和X射线光电子能谱研究了来自Raniganj和Jharia盆地以及印度锡金喜马拉雅褶皱冲断带的煤的微观结构框架。平均随机镜质反射率数据可能意味着来自 Raniganj 和 Jharia 盆地的煤样品范围从沥青 D 到 B，并且与无烟煤 A 样品不同，它们经历了对应于 ~92 °C 到 143 °C 的埋藏加热可能在~333°C 到 367°C 经历了热液变质作用。由于喜马拉雅造山运动引起的热应力降解效应，拉曼光谱显示出在近地带变质阶段从无烟煤样品中优先去除 sp3 杂化部分。此外，该研究记录了由于从芳环中排出官能团而使它们的红外线失活导致净偶极矩变化的减少。此外，C1s 光谱揭示了随着煤阶的增加，CC 峰变细和 CO 峰强度降低。因此，这项研究记录了煤的微观结构转变，可用于结构操纵以控制液化、气化、热解、燃烧以及合成石墨化行为。