Computational screening of porous carbons, zeolites, and metal organic frameworks for desulfurization and decarburization of biogas, natural gas, and flue gas

Eighteen kinds of porous materials from carbons, zeolites, and metal organic frameworks (MOFs) have been extensively investigated for desulfurization and decarburization of the biogas, natural gas, and flue gas by using a molecular modeling approach. By considering not only the selectivity but also capacity, Na-5A, zeolite-like MOF (zMOF), and Na-13X, MIL-47 are screened as the most promising candidates for removal of sulfide in the CH4CO2H2S and N2CO2SO2 systems, respectively. However, for simultaneous removal of sulfide and CO2, the best candidates are zMOF for the natural gas and biogas (i.e., CH4CO2H2S system) and MOF-74-Zn for the flue gas (i.e., N2CO2SO2 system). Moreover, the regeneration ability of the recommended adsorbents is further assessed by studying the effect of temperature on adsorption. It is found that compared to the zMOF and MIL-47 MOFs, the Na-5A and Na-13X zeolites are not easily regenerated due to the difficulty in desorption of sulfide at high temperature, which results from the stronger adsorbent-adsorbate interactions in zeolites. The effect of sulfide concentration on the adsorption properties of the recommended adsorbents is also explored. We observe that the zMOF and MIL-47 are also superior to the Na-5A and Na-13X for desulfurization of gas mixtures containing high sulfide concentration. This is because MOFs with larger pore volume lead to a greater sulfide uptake. The effects of porosity, framework density, pore volume, and accessible surface area on the separation performance are analyzed. The optimum porosity is about 0.5-0.6, to meet the requirements of both high selectivity and uptake. It is expected this work provides a useful guidance for the practical applications of desulfurization and decarburization. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 2928-2942, 2013