New expressions for single and binary permeation through zeolite membranes for different isotherm models

In this work, the permeation of pure adsorbable molecules and their mixtures through microporous materials has been studied. New expressions for the Maxwell–Stefan thermodynamic factors were derived for mono and multicomponent Nitta, Langmuir–Freundlich, and Toth isotherms, being tested with equilibrium and permeation data from the literature. In the whole, the results achieved evidence the new models are able to represent data for pure components and predict binary permeation. In the most interesting case of binary mixtures, the validation procedure adopted was very stringent: (i) multicomponent isotherms were predicted from pure gas data; (ii) diffusion parameters of pure components were fitted to single permeation data; (iii) the Maxwell–Stefan crossed diffusivities were estimated by the Vignes relation; finally, and (iv) the new equations were used with these parameters to predict binary permeation fluxes.