Simulation Study of the Air Separation Performance of Cr-MIL-101 in High-Altitude Environments

The most severe challenge for troops in a high-altitude environment is hypoxia. Pressure swing adsorption coupled with membrane separation is an ideal solution for oxygen production in high-altitude areas, but the molecular sieve membranes and organic membranes used in this technique are greatly affected by the ambient temperature, humidity, and pressure. Compared with traditional porous materials, metal-organic frameworks (MOFs) have outstanding features such as low densities, large specific surface areas, high crystallinities, and flexible structures. Cr-MIL-101 (MIL: Matérial Institut Lavoisier) and its derivatives are MOFs with high nitrogen adsorption capacities and can be used for oxygen production by air separation. However, since the plateau climate is complex, the applicability of Cr-MIL-101 for oxygen production in high-altitude environments awaits clarification. Therefore, this study constructed a molecular model of Cr-MIL-101, simulated the adsorption equilibrium of N2 and O2 molecules on this material using the grand canonical Monte Carlo (GCMC) method, and obtained their adsorption isotherms and densities. At 298 K and 100 kPa, the maximum adsorption capacities of Cr-MIL-101 for N2 and O2 were 0.94 per cell and 0.23 per cell, respectively. While at 238 K and 100 kPa, the maximum adsorption amounts of Cr-MIL-101 for N2 and O2 were 5.10 and 1.07 per cell, respectively. The thermodynamic parameters and adsorption equilibrium parameters during the adsorption process were analyzed. The conclusion of this study provides theoretical support for optimizing the N2/O2 separation performance of Cr-MIL-101 in high-altitude environments.