A model to predict adsorption of mixtures coupled with SAFT-VR Mie Equation of state

Abstract

We extend the Statistical Associating Fluid Theory for a Mie potential with a Variable Range (SAFT-VR Mie) equation of state for the prediction of multicomponent adsorption isotherms. A generalization for adsorbed mixtures of the model proposed by Franco et al. (Langmuir, 33, 11291–11298, 2017) is obtained through the derivation of the Helmholtz free energy contribution due to the interaction between the fluid mixture and the wall, which is considered as a square-well potential. The resulting model is completely predictive for mixtures and takes into account the pore size and geometry, and the wall-fluid interaction parameters. These parameters are calculated with combining rules using the pure component wall-fluid interaction parameters. The proposed model is applied to different systems: binary mixtures of methane, ethane, ethylene, and propane adsorbed in a carbon molecular sieve, nitrogen and methane on a Metal-Organic Framework (MOF), and a ternary mixture of methane, nitrogen, and hydrogen adsorbed in activated carbon. The predicted adsorption isotherms match the experimental data reasonably well, proving that the theoretical framework on which the proposed model is based comprises a promising and adequate strategy.