CO₂ adsorption in LiY and NaY at high temperature: Molecular simulations compared to experiments

Grand Canonical Monte Carlo simulations combined with adsorption measurements have been carried out to gain further insight into the CO ₂ adsorption process at the microscopic scale in both LiY and NaY faujasites at various temperatures. A new Li⁺-CO₂ force field derived by ab initio calculations was validated by a reasonable agreement between the simulated isotherms and those obtained by experiments in a wide range of temperature (from 323 K to 473 K). In addition, the microscopic mechanisms of CO₂ adsorption in both systems, consistent with the trends observed for the simulated differential enthalpies of adsorption as a function of the loading, were proposed. It was observed that two different types of adsorption behaviour exist for NaY and LiY at 323 K and 373 K, mainly caused by the significant more exposed position of the SII Na⁺ from the six-ring plane of the supercage compared to those occupied by the SII Li ⁺, whereas at higher temperature, both faujasites exhibit the same flat profile for the differential enthalpy of adsorption as a function of loading.