Comparison of CO2, N2, CO, H2S, CH4, and H2O adsorptions onto sI methane hydrate surface

• Published in: Frontiers in Earth Science
• Main Authors: Zhang, Ming, Zhao, Baoli, Li, Jiahua, Li, Tiantai, Li, Jian
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2022
• Subjects: General Earth and Planetary Sciences; Methane hydrate
• Online Access: http://dx.doi.org/10.3389/feart.2022.965743; https://www.frontiersin.org/articles/10.3389/feart.2022.965743/full

By employing molecular dynamic (MD) and density functional theory (DFT) calculations, the adsorptions of CO 2 , N 2 , CO, H 2 S, CH 4 , and H 2 O onto methane hydrate (MH) surface are compared in this work. The methane hydrate planes of (001) and (110) and various cleaving sites are compared with cleavage energies. MH(001) has more tendency to form when compared with MH(110) in thermodynamics. Two different terminations of MH(001) surfaces are compared, and MH(001)-I (terminated with CH 4 +H 2 O) leads to more negative adsorption energies when compared with MH(001)-II (terminated with H 2 O only). The priority sequence of the adsorptions can be queued as: H 2 O > H 2 S > CO 2 > N 2 > CH 4 > CO. Namely, CO 2 , N 2 , and H 2 S have potential to replace CH 4 in methane hydrate. The interfacial hydrogen bond and electronic interactions are clarified for the adsorptions of CO 2 , N 2 , and H 2 S. The hydrogen bonds tend to form between O-H atom pairs of CO 2 -H 2 O, N-H atom pairs of N 2 -H 2 O, and S-H and H-O atom pairs of H 2 S-H 2 O, respectively. The bonds are mainly contributed from the dispersion interaction between the O-2 p in CO 2 and H-1 s in H 2 O, N-2 p in N 2 and H-1 s in H 2 O, S-3 p in H 2 S and H-1 s in H 2 O, and H-1 s in H 2 S and O-2 p in H 2 O, respectively.