A Molecular Dynamics Study on Xe/Kr Separation Mechanisms Using Crystal Growth Method.

The separation of xenon/krypton gas mixtures is a valuable but challenging endeavor in the gas industry due to their similar physical characteristics and closely sized molecules. To address this, we investigated the effectiveness of the hydrate-based gas separation method for mixed Xe-Kr gas via molecular dynamics (MD) simulations. The formation process of hydrates facilitates the encapsulation of guest molecules within hydrate cages, offering a potential strategy for gas separation. Higher temperatures and pressures are advantageous for accelerating the hydrate growth rate. The final occupancy of guest molecules and empty cages within 5 12 , 5 12 6 4 , and all hydrate cages were thoroughly examined. An increase in the pressure and temperature enhanced the occupancy rates of Xe in both 5 12 and 5 12 6 4 cages, whereas elevated pressure alone improved the occupancy of Kr in 5 12 6 4 cages. However, the impact of temperature and pressure on Kr occupancy within 5 12 cages was found to be minimal. Elevated temperature and pressure resulted in a reduced occupancy of empty cages. Predominantly, 5 12 6 4 cages were occupied by Xe, whereas Kr showed a propensity to occupy the 5 12 cages. With increasing simulated pressure, the final occupancy of Xe molecules in all cages rose from 0.37 to 0.41 for simulations at 260 K, while the final occupancy of empty cages decreased from 0.24 to 0.2.