Abstract Various compositional, depositional and maturity related influencing factors affect the complex pore structure of coal. To study the pore structural evolution at nanoscale, a well characterized sample set of vitrinite-rich Carboniferous coals from the Ukrainian Donets Basin, covering a maturity interval from 0.69 to 1.47%Rr, was selected. Conventional bright field transmission electron microscopy (BF TEM) and high-resolution TEM (HRTEM) imaging was used to directly determine pore size distributions, pore morphology, geometry factors and other structural features, while gas invasion techniques such as low-pressure gas adsorption (CO2 and N2) were used for the investigation of micro- and mesopore structural parameters. High-pressure CH4 sorption experiments revealed changes in the methane storage capacity within the investigated maturity range, while associated structural changes of vitrinite were monitored by Raman spectroscopy. The results indicate pore occlusion in vitrinite mainly at peak oil window maturity, the sensibility of micro- and mesopore structure to thermal maturity and the importance of organic sulphur as a catalyst for kinetics of structural modification. Observed structural changes at 1.10%Rr were related to the onset of wet-gas generation. A structural control on micromechanical properties of vitrinite is indicated by the correlation between reduced elastic moduli from a previous study and average nanopore diameters obtained by HRTEM. The applied comprehensive approach improved the understanding of depositional and maturity-related processes that may affect pore evolution and resulting gas storage capacity of coals.

中文翻译：

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乌克兰顿涅茨盆地石炭纪煤的纳米级孔隙结构：HRTEM 和气体吸附联合研究

摘要 各种成分、沉积和成熟度相关的影响因素影响着煤的复杂孔隙结构。为了研究纳米尺度的孔隙结构演化，选择了一组充分表征的来自乌克兰顿涅茨盆地的富含镜质体的石炭纪煤样品，其成熟度区间为 0.69 至 1.47%Rr。采用常规明场透射电子显微镜（BF TEM）和高分辨透射电镜（HRTEM）成像直接确定孔径分布、孔隙形态、几何因素等结构特征，同时采用低压气体吸附等气体侵入技术。 CO2 和 N2) 用于研究微孔和中孔结构参数。高压 CH4 吸附实验揭示了在研究的成熟度范围内甲烷储存能力的变化，同时通过拉曼光谱监测了镜质体的相关结构变化。结果表明镜质体中的孔隙闭塞主要发生在油窗成熟度峰值、微孔和中孔结构对热成熟度的敏感性以及有机硫作为结构改性动力学催化剂的重要性。在 1.10%Rr 观察到的结构变化与湿气生成的开始有关。先前研究中降低的弹性模量与 HRTEM 获得的平均纳米孔径之间的相关性表明了对镜质体微机械性能的结构控制。