Combined\nExperimental and Molecular Simulation Characterization\nof CO<sub>2</sub> Adsorption Characteristics of Full Aperture in Bituminous\nCoal Pores

Adsorption characteristics of CO<sub>2</sub> in pores\nof different\nsizes were analyzed by the molecular simulation method, which provided\ntheoretical guidance for the storage of CO<sub>2</sub> in coal seams.\nThe pore structure parameters of bituminous coal were acquired by\nmercury injection, low-temperature N<sub>2</sub> adsorption, and low-pressure\nCO<sub>2</sub> adsorption experiments. The ultramicropores of bituminous\ncoal were constructed by molecular simulation. The pore structure\ncharacterization of a full aperture section was obtained by combining\nthe simulation results with parameters obtained from the experimental\ntests. Using coal molecules as a framework, a slit model was designed\nto represent pores. The adsorption pores of 0.63–100 nm were\nselected to construct the plate pore model, and adsorption data of\nCO<sub>2</sub> in this pore size range were obtained microscopically.\nThe findings unequivocally demonstrate that the intricate pore structure\nencompassing the entire size range can be accurately characterized\nthrough a synergistic integration of the constructed ultramicropore\nmodels derived from molecular simulations and the experimental test-derived\npore structure data. The interaction forces generated by the adsorption\nof CO<sub>2</sub> molecules in pores of smaller sizes are stronger,\nwhile in larger pores, the interaction forces are weaker; molecules\nwere easier to enter the larger pores but not easy to adsorb. The\nCO<sub>2</sub> adsorption ratio and adsorption heat decrease with\nthe increase of pore size. Larger pores can accommodate more molecules,\nbut more free molecules. Distribution of adsorption sites on the same\nmolecular species demonstrates uniformity across the distinct pore\nsizes.