Determination of adsorption and separation of CO2/N2 and H2S/CH4 mixtures in porous materials by molecular simulation

Abstract

The major resources of power plant in the world rely on coal and natural gas which are economical for generating electricity. Flue gases, mainly N2 and CO2, are produced and released into the atmosphere. The zeolitic imidazolate framework-90 (ZIF-90) obtains a high potential as being a candidate for several applications. Consequently, the basic knowledge of adsorption and diffusion of gases in this material is the key factor of improving this gas separation technique. The effect of adsorbed CO2 molecules on the lattice structure of ZIF-90 can lead to gate opening depending on the amount of adsorbed guest molecules and the temperature but this is not observed for N2 molecules. The window diameter is increased up to 4.43 Å with increasing temperature. The separation factors of the CO2/N2 mixture in form of adsorption and diffusion selectivity show the highest values of about 6 and 12 at 298 K, respectively. In addition, the second major feedstock for power plants is natural gas which must be freed from H2S before using. All investigated materials are suited for the separation, but with different efficiency. For MIL-127(Fe) the CH4/H2S selectivity reaches values of about 250 at 2 bar and 250 K. The results can be initially concluded that the potential energy of each gas/material pair, free space inside the material and metal oxide are important keys for adsorption and separation of H2S from CH4.