Molecular dynamics simulations of CH4 diffusion in kaolinite: influence of water content

• Published in: International journal of coal science & technology 2019-12, Vol.6 (4), p.556-563
• Main Authors: Zhang, Bin, Kang, Jianting, Kang, Tianhe, Kang, Guanxian, Zhao, Guofei
• Format: Article
• Language: English
• Subjects: Diffusion; Diffusion coefficient; Energy; Fossil Fuels (incl. Carbon Capture); Geotechnical Engineering & Applied Earth Sciences; Interaction energy; Kaolinite; Methane; Mineral Resources; Molecular dynamics; Research Article; Simulation; Water content
• ISSN: 2095-8293; 2198-7823
• DOI: 10.1007/s40789-019-00275-2

Understanding the interaction of CH 4 with kaolinite is significant for researchers in the fields of coalbed CH 4 and shale gas. The diffusion behaviors of CH 4 in kaolinite with water contents ranging from 0 to 5 wt% have been analyzed by molecular dynamics simulations. The results of the simulations indicate that CH 4 molecules can jump between adjacent holes in the kaolinite matrix. CH 4 diffusion coefficient was very low (3.28 × 10 −9  m 2 /s) and increased linearly with the increasing of water content. As the water content decreased, the value of radial distribution function first peak between CH 4 and oxygen was larger, meaning that with lower water content, the interaction energy between CH 4 and oxygen in kaolinite is stronger. The interaction between CH 4 and water is linearly positively correlated with water content, in contrast, the interaction energy between kaolinite and water as well as between kaolinite and CH 4 decreased linearly with increasing water content. On the other hand, the diffusion of CH 4 molecules adsorbed on the surfaces also can be accelerated by the fast diffusion of water molecules in the middle micropore of the kaolinite.