Molecular dynamics study of CH4 adsorption in coal triggered by cyclic thermal treatment

Xuefen Lv, He Li, Shiliang Shi, Bo Li, Xianzhong Li, Xiongfei Pei and Jiexin Lu

Energy, 2025, vol. 319, issue C

Abstract: Examining the effect of cyclic thermal treatment on CH₄ adsorption in coal microscopically is crucial for advancing heat injection technology in coal reservoirs to boost production. In this study, we constructed macromolecular structure models of coal pre- and post-heat treatment using elemental analysis, 1³C NMR, and XPS. Materials Studio simulated methane's adsorption, diffusion, and CH₄ molecule distribution near functional groups. Results reveal that Huaibei Coal has a peribridge carbon ratio (XBP) of 0.241 and molecular formula C₁₃₅H₁₁₈N₄O₅S. After cyclic thermal treatment across different temperature gradients, the molecular structure's polycondensation and aromatic carbon ratio rose, the aliphatic carbon ratio fell, and the formula became C₁₂₄H₉₆N₃O₂S. CH₄'s maximum adsorption capacity dropped from 10 to 7, and its diffusion coefficient increased 1.72-fold. This shows cyclic thermal treatment effectively aids methane desorption and diffusion from the coal matrix, reducing gas content and enhancing seam permeability. Moreover, hydroxyl and carbonyl groups notably influence methane diffusion. This paper delves deep into the molecular-level impact of cyclic thermal treatment on coalbed methane adsorption and diffusion.

Keywords: Cyclic thermal treatment; Molecular model; MSD; RDF; 13C NMR; XPS (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:319:y:2025:i:c:s0360544225006838

DOI: 10.1016/j.energy.2025.135041

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