Adsorption of CO2, CH4 and their binary mixture in Faujasite NaY: A combination of molecular simulations with gravimetry–manometry and microcalorimetry measurements

The adsorption of pure carbon dioxide and methane, and their equimolar mixture were explored in a model zeolite NaY by combining grand canonical Monte Carlo simulations and an original experimental approach based on gravimetry/manometry and manometry/microcalorimetry devices. Both experimental and calculated adsorption isotherms and enthalpy profiles obtained for the single gas and a 50/50 binary mixture are provided for pressures up to 30 bar. The gravimetry/manometry apparatus allows the determination of single gas and mixture isotherms whereas the manometry/microcalorimetry system allows a direct access to the enthalpies of adsorption enabling also a validation of the computational work. The aim here is to fully characterize the interactions of the gas mixture in NaY which are thus compared to those for the single gas adsorption. In this way, the computational studies allow an understanding of the complex adsorption phenomena in play. These calculations which are based on different interatomic potentials available in the literature to describe the adsorbate/adsorbent and adsorbate/adsorbate interactions, consist first of selecting the most convenient set of potential parameters able to reproduce well the adsorption data for the pure components. These reliable force fields are thus transferred to the study of the equimolar CO2/CH4 gas mixture. In agreement with the experiments, our simulations show a high selectivity of CO2 over CH4 in NaY for the whole range of pressure. We then report a complete exploration of the preferential adsorption sites for both adsorbates in the gas mixture which are compared to that observed for the pure component adsorption. The originality and the strength of this paper is thus to combine novel experimental tools and realistic models to provide a detailed picture of the microscopic adsorption and co-adsorption mechanisms in NaY.