A Simple Mechanistic Multilayer Model for the Rigorous Description of Brunauer–Emmett–Teller Type Isotherms

The rigorous description of adsorption isotherms of gases or vapors on solids is of major interest for analytical methods such as chromatography and adsorbent-based separation processes (e.g., PSA). In the specific case of a multilayer adsorption mechanism, a complex isotherm pattern is obtained, which is most often described on the basis of the well-known Brunauer–Emmett–Teller (BET) model. However, large discrepancies between experimental data and BET model fitting occur for some systems. We report here a new simple mechanistic approach that takes into account the formation of multilayers. The resulting expression involves two parameters and shows an excellent fit compared to BET when applied to an experimental data set. The interest in the model for adsorbent characteristic determination and process simulation studies is discussed.