Effects of molecular simulation parameters on predicting gas separation performance of ZIFs

Abstract

BACKGROUNDA significant number of molecular simulation studies exist in the literature for assessing single-component gas adsorption capacities of ZIFs and all these simulations were performed using different force field parameters. In this study, molecular simulations were carried out to predict both adsorption-based and membrane-based separation performances of ZIF-68 and ZIF-69 for CH4/H-2, CH4/N-2, CO2/CH4, CO2/H-2 and CO2/N-2 mixtures using three different force fields. RESULTSResults showed that adsorption selectivity of ZIFs may vary significantly depending on the force field parameters whereas membrane selectivity is much less sensitive to the force field. In addition to adsorption and membrane selectivities, various separation properties of ZIFs were estimated such as working capacity, sorbent selection parameter, regenerability, permeability and compared with the properties of other well-known nanoporous adsorbents and membranes. CONCLUSIONComparison of separation performance of ZIF-68 and ZIF-69 with traditional zeolites showed that ZIFs can be promising adsorbent materials for CH4/H-2, CH4/N-2, CO2/CH4, CO2/H-2 separations and promising membrane materials for CH4/H-2 and CO2/H-2 separations. It is better to use ZIFs as adsorbents rather than membranes since they offer higher adsorption selectivity than permeation selectivity for the gas mixtures we studied.