Monte Carlo simulations of methane adsorption on kaolinite as a function of pore size
Monte Carlo simulations of methane adsorption on kaolinite as a function of pore size
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DOI：
10.1016/j.jngse.2017.11.026
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发表时间：
2018
影响因子：
--
通讯作者：
Bin Zhang;Jianting Kang;Tianhe Kang
中科院分区：
文献类型：
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作者：
Bin Zhang;Jianting Kang;Tianhe Kang
黏土矿物在微观、中观和宏观尺度上的吸附特性对页岩、煤等多孔介质的吸附性能有显著影响。在293.15 K和20 MPa压力条件下，考虑孔径（0.72、1.44、2.88、5.76和11.52 nm）的影响，利用GCMC模拟计算了甲烷（CH4）在高岭石（001）表面的吸附等温线、吸附量、重量密度分布和相互作用能。模拟结果表明，随着孔径的增大，甲烷的绝对吸附量呈指数级下降，特别是在较低压力下，最终在孔径为6 ~ 8 nm时达到稳定值。随着层距的增加，vls值呈线性下降，说明层距大的高岭石对甲烷的吸附能力较低。随着微孔间距的增大，甲烷分子在微孔表面保持紧密吸附，微孔中间的甲烷量逐渐增加。总相互作用能也随着孔径的增大呈指数递减。在总相互作用能中，范德华能贡献98%以上，静电能贡献不到2%。随着孔径的增大，范德华能呈指数递减，静电能呈线性递减。较大的人工微孔尺寸可能对页岩气和煤层气的产量有显著影响。希望本研究能为进一步勘探煤层气和页岩气提供基础。
The adsorption characteristics of clay minerals with micro, meso, and macro-scale pore sizes have significant effects on the adsorption properties of porous media such as shale and coal. In this study, the adsorption isotherms, adsorption capacity, weight density distributions, and interaction energies of methane (CH4) on the kaolinite (001) surface were calculated and discussed in detail at 293.15 K and pressures up to 20 MPa using a series of grand canonical Monte Carlo (GCMC) simulations considering the influence of pore size (0.72, 1.44, 2.88, 5.76, and 11.52 nm). The results of the simulations indicate that as the pore size is increased, the absolute adsorption of methane decreases exponentially, especially at lower pressures, eventually reaching a stable value after the pore size of 6–8 nm. TheVLvalues decreased linearly with increasing layer distance, indicating that kaolinite with large layer distances has lower methane adsorption capacities. With increasing spacing, the methane molecules remained tightly adsorbed on the surfaces, and the amount of methane gradually increased in the middle of the micropores. The total interaction energy also decreased exponentially with increasing pore size. Of the total interaction energy, the van der Waals energy contributed more than 98%, and the electrostatic energy contributed less than 2%. Moreover, the van der Waals energy decreased exponentially with increasing pore size, and the electrostatic energy decreased linearly with increasing pore size. Larger artificially produced micropore sizes may have significant effects on shale gas and coalbed methane production. We hope that our research can provide a foundation for further exploration of coalbed gas and shale gas.