Adsorption behavior of H2 in quartz silt-pores at high temperature and pressure

Abstract

To understand the storage and transport of H2 in the Earth’s interior, the adsorption behaviors of H2 in the slit-like pore of quartz under different conditions were calculated by the grand canonical Monte Carlo method. The Poisson distributions of interaction energy show unimodal, indicating that the adsorption behavior is mainly affected by van der Waals interaction between molecular H2 and quartz, the adsorption potential energy increases, and when the pressure increases, the temperature and pore size decrease. Isosteric heat of adsorption is in the range of −5.0 to −1.7 kJ/mol, which indicates that the adsorption behavior belongs to physical adsorption. The results of isosteric heat of adsorption show that strong energy exchange occurs in the H2-quartz system at the initial stage of adsorption, which may affect the stability of quartz. The average isosteric heat of adsorption linearly increases with temperature. However, the increasing rate of average isosteric heat of adsorption decreases with the increase in the pore size. Adsorption snapshots show most of the H2 distributed randomly and there is no obvious adsorption layer of H2 in the pores. Excess adsorption amount increases with the decrease in temperature and the increase in pressure and pore size. The change rate of excess adsorption amount with temperature increases with the increase in pressure. Similarly, with the increase in pressure, the change rate of excess adsorption amount with pore size decreases slowly at first, then increases rapidly, and finally decreases. The results are helpful to reveal the migration and formation of H2 reservoirs in the Earth’s interior.