Visualization and Molecular Reconstruction of Micropores in Coal

Micropores contribute the majority of surface area in coal and play crucial roles in the storage of coalbed methane. However, although various methods have proven the existence of a large number of micropores in coal, due to the extremely small size of these micropores (5 million times), enabling clear observation of the rough surfaces and abundant micropore structures in the coal samples. Using carbon 13 nuclear magnetic resonance (13C NMR) and Fourier transform infrared spectroscopy (FT-IR) experimental data, combined with molecular characterization results, three-dimensional pore system molecular structures were constructed for both LJT and BLS coals. The micropore distribution derived from the molecular models showed strong agreement with experimentally measured pore volumes, with all deviations within 0.005 cm3/g. The constructed pore models exhibit rough surfaces and distinct pore structures, resembling the DS-AC-STEM images of the actual coal samples. Through micropore imaging characterization and pore structure reconstruction, this study presents the coal micropore structure in the form of three-dimensional molecular models. This approach contributes to understanding the storage and migration mechanisms of gases such as methane within coal micropores.