Thermodynamic Characteristics of CH 4 /CO 2 Adsorption in Different Rank Coals and Its Molecular Mechanism

作者：Zhiming Wang, Shuo Zhang, Xiaodong Zhang, Jianwei Cheng, Weiyong Lu, Erhu Bai, Zhenjiang You · 发表于：Langmuir · 年份：2025 · DOI：10.1021/acs.langmuir.4c04977 · 被引用次数：24 · 研究领域：Coal Properties and Utilization、Hydrocarbon exploration and reservoir analysis、Coal and Its By-products

In order to investigate the essence of CH 4 /CO 2 adsorption in coal for CO 2 -enhanced coalbed methane recovery (CO 2 -ECBM), this study established the coal structure models from the chemical composition and structure information on different rank coals to conduct CH 4 and CO 2 adsorption simulation under different environmental conditions. Thus, the differences and connections between integral heat and isosteric heat of CH 4 /CO 2 adsorption in coal and its micro-mechanism were discussed. The results show that as the coal metamorphism degree deepens, the integral heat of CH 4 /CO 2 adsorption, similar to adsorption capacity, presents a decreasing first and then increasing trend. While the adsorption equilibrium time of high-rank coal gives a significantly decreasing characteristic with pressure. Then, on the basis of adsorption simulation behavior, it finds that because complex functional groups exist in the coal macromolecular structure, the adsorption capacity shows a different characteristic compared with the experimental results; that is, it decreases with the coal metamorphism degree. Meanwhile, compared to CO 2 adsorption, the isosteric heat of CH 4 adsorption appears to have an obvious downward trend with increasing pressure and then gradually stabilizes. Further, there is always a clear linear relationship between CH 4 adsorption capacity, and isosteric heat for aromatic pores in different rank coals. While for slit pores, both CH 4 and CO 2 molecules exhibit signi...