Effect of the Temperature on Interfacial Properties of CO2/H2 Mixtures Contacting with Brine and Hydrophilic Silica by Molecular Dynamics Simulations

C Chen and J Xia and H Bahai, ENERGY & FUELS, 37, 18986-18995 (2023).

DOI: 10.1021/acs.energyfuels.3c03164

Underground H-2 storage (UHS) is a promising technology to achieve large-scale, long-term H-2 storage. Using CO(2 )as a cushion gas to maintain the pressure of the reservoir and withdraw stored H-2 in the saline aquifer simultaneously enables the implementation of UHS and underground CO(2 )storage (UCS). The difference in the molecular properties of CO2 and H-2 leads to distinct interfacial behavior when in contact with the brine and rock, thereby affecting the flow patterns and trapping mechanisms of gases in geological formations. Accurate prediction of the interfacial properties of CO2, H-2, and the mixtures when interacting with brine and rock is crucial to minimizing the uncertainties in UHS and UCS projects. In this study, molecular dynamics (MD) simulations are performed to predict the interfacial tension, surface excess, bubble evolution, and contact angle of CO2 , H-2, and the mixtures at 10 MPa and 300-400 K. The MD results show that the interaction of CO(2 )with H2O and hydrophilic silica is considerably stronger than that of H-2. The interfacial tension reduces linearly with the temperature in H-2-dominated mixture systems, and the surface adsorption of H-2 can diminish in a CO2 -dominated system or at high- temperature conditions. The hydrophilic silica is more CO2 -wet than H-2-wet, and the attached CO(2 )bubble is more easily disconnected. Ions and the temperature play different roles in the contact angle.

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