Insights into the adsorption performance and separation mechanisms for CO2 and CO on NaX and CaA zeolites by experiments and simulation.

[Display omitted] • Separation mechanisms for CO2/CO mixture were studied systematically by experiments and simulations. • The NaX zeolites showed low adsorption heat and high separation coefficients on CO2/CO. • The CaA zeolites showed excellent separation stability under different ratios for CO2/CO mixture. • The above separation performances were revealed by the number, distribution and charge of cations and characteristics of gas adsorption complexes. Adsorption and recovery of CO 2 from industrial gases are of great environmental significance in the field of environmental protection with reducing greenhouse gas emissions and increasing CO concentration. A comprehensive investigation with thermodynamics and kinetics experiments of CO 2 and CO on NaX and CaA zeolites were studied and the separation mechanism explained by molecular simulation methods. The experiments show that the NaX zeolites have significant differences on CO 2 and CO adsorption amounts leading the high CO 2 /CO selectivity, while the CaA zeolites exhibit separation stability under various partial pressures of mixed gas, which is supported by the standard deviation results. The theoretical simulations verify the above-mentioned experimental phenomena and provide a visual mechanism explanation for adsorption selectivity from the aspect of systematic interaction between cations and gas molecules. Compared with NaX, the same number and homogeneous distributions of Ca2+ and Na+ in the CaA provide stable separation performance. The strong electrostatic interactions between divalent Ca2+ and gas molecules especially CO make differences in the order of adsorption capacity and adsorption heat. Deeper insights into the cations-gas adsorption complexes revealed that the significant differences in the types of adsorption complexes for CO and CO 2 in NaX contribute to the improvement of the adsorption selectivity. [ABSTRACT FROM AUTHOR]