(178c) A Novel Kinetic Model for the Adsorption Dynamics in Carbon Molecular Sieve and Titanium Silicate Adsorbents

Current Kinetics models, typically LDF models, have been applied on the basis that the presence of a second, slower diffusing, adsorbate affects the equilibrium of the first, faster diffusing, adsorbate in a gas mixture via its gas phase partial pressure. However, this premise is contrary to experimental observations involving either butane or ethane with CO₂ on carbon molecular sieves.

The objective of the work is to present a new non-equilibrium model that augments the equilibrium driving force in the LDF kinetic model, such that the equilibrium loading of one component depends on the actual loading of the other component in a gas mixture. Further, in this new model, the equilibrium loading of one component depends on the actual loading of the other component, with both leading to the extended Langmuir model predictions at equilibrium. This new non-equilibrium model successfully captures experimental data in carbon molecular sieve (CMS) and titanium silicate (ETS-4) adsorbents. This includes predicting the intrinsic roll up feature of the faster diffusing species, even better than the Fickian diffusion models. It also requires a limited number of fitting parameters, just two or three with the latter accounting for non-isothermal behavior. Hence, it should be very useful in an adsorption process simulator.