Molecular Simulation and Experimental Study on Adsorptive Separation of the Ar/He Gas Mixture by Two Metal-Organic Frameworks at Room and Lower Temperatures.

Abstract

This study combines molecular simulation and experimental methods to investigate the adsorptive separation performance of two metal-organic frameworks (MOFs), ZIF-67 and MIL-53(Al), for Ar/He mixed gases. Experimental and simulation adsorption isotherm data were obtained at temperatures of 298, 200, and 150 K for both Ar and He single-component adsorbates. The ideal adsorbed solution theory (IAST) and grand canonical Monte Carlo (GCMC) simulations calculated the Ar/He selectivity coefficients at different temperatures. Breakthrough experiments analyzed the separation performance of the MOFs with varying feed ratios of Ar/He at 298, 200, and 150 K. Additionally, molecular simulations assessed the isosteric heat of adsorption, adsorption energy distribution, and binding energy, providing insights into competitive adsorption mechanisms. Results showed that both ZIF-67 and MIL-53(Al) preferentially adsorb Ar, with lower temperatures significantly enhancing the separation performance. This preference is linked to differences in the binding energy between the adsorbent sites and the two gas molecules. Breakthrough tests confirmed that both MOFs are effective for Ar/He separation with lower temperatures or higher He concentrations improving He extraction from the mixture.