Monte-Carlo simulations on H2 adsorption in kaolinite nanopore in the presence of CO2 and CH4 gases

Abstract

Hydrogen is being explored as a potential future energy source, but the effective storage of hydrogen in geological formations especially in clay-rich formations requires a significant understanding of its interaction mechanisms. In this study, we use Grand canonical Monte-Carlo (GCMC) simulations to investigate the H2 adsorption on kaolinite minerals in the presence of CO2 and CH4. Furthermore, we assess the average adsorption energy, Henry coefficient, and RDFs of hydrogen. In this study, at first, the CO2 adsorption is computed and validated with the published data. Later, different concentrations of hydrogen are introduced in the system to investigate the competitive adsorption of CO2/H2 mixture with kaolinite. Following that, we evaluate the pure H2 and the competitive H2/CH4 mixture adsorption. These simulations are carried out under elevated geological pressures and high-temperature conditions. The results show that the pressure increases while temperature reduces the hydrogen adsorption causing a rise in the average adsorption energy. This results in a decrease in Henry coefficient, and, consequently, a decrease in the overall hydrogen adsorption capacity. The results also reveal that increasing the concentration of CO2 and CH4 significantly reduces hydrogen adsorption. This phenomenon is driven by the high intermolecular attraction of CO2 and CH4 with the kaolinite surface. Such high affinity creates a strong adsorption layer, impeding the contact of hydrogen with the kaolinite surface. In addition, the contribution of all kaolinite atoms towards hydrogen adsorption is competitive with a slightly higher contribution by silicon. Our work provides significant insights into hydrogen interaction with the clay-rich mineral and reveals H2 adsorption mechanisms in the presence of both CO2 and CH4.