Model analysis of equilibrium adsorption isotherms of pure N₂, O₂, and their binary mixtures on LiLSX zeolite

Three analytical adsorption isotherm models for energetically homogeneous (Langmuir) and heterogeneous (Toth, Sircar) adsorbents were tested for describing recently measured pure gas isotherm data for adsorption of N ₂ and O₂ on pelletized LiLSX zeolite at three different temperatures and in the pressure range of 0-6 atm. Estimated binary gas isotherms for this system by these models and the Ideal Adsorbed Solution Theory (IAST) were compared with the corresponding experimental data. All three models describe the pure gas isotherms reasonably well, but the model that accounts for the differences in the degrees of adsorbent heterogeneity of the components of a mixture (Sircar) provided better correlation between experimental and estimated binary selectivities than the other models and IAST under various conditions of pressure, temperature, and gas composition. Predictions of multicomponent isotherm data by models must be extensively tested experimentally, since their ability to describe pure gas isotherms does not guarantee the quality of multicomponent isotherm predictions.