Yang Gon Seo

Vol. 31,  No. 2, pp. 100-110, Jun.  2025
10.7464/ksct.2025.31.2.100

Zeolite Si/Al ratio Carbon dioxide Selective adsorption

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Concern about global warming and the energy crisis have led to a growing interest in developing potential alternative energy sources. The methane contained in a biogas stream is higher than 50%. Thus, the proper separation and utilization of the bio-methane contained in biogas can convert this stream into a valuable renewable energy source. In this work, the adsorption capacities of pure carbon dioxide and methane and the selectivities of their mixtures on LTA, FAU and MFI zeolites with different numbers of sodium ions were calculated by a Monte Carlo simulation. Based on the MC data, ideal adsorbed solution theory (IAST) and real adsorbed solution theory (RAST) were discussed. At a low pressure, the number of sodium ions played an important role in the adsorption capacity of carbon dioxide, while the accessible volume of zeolites determined the maximum adsorption capacity of carbon dioxide and methane. In the context of binary CO2/CH4 adsorption, the selectivity of the MFI zeolite was well described by IAST over the investigated pressures and compositions. In the FAU framework, the selectivity was predicted fairly well by RAST with Si/Al ratios of 2.5 or higher. However, below 2.5, the selectivity was not well predicted due to strong non-ideal behavior in the adsorbed phase.