Predicting Mixture Diffusion in Zeolites: Capturing Strong Correlations with a Simplified Theory and Examining the Role of Adsorption Thermodynamics

The Maxwell–Stefan (MS) equations describing diffusion in zeolites are simplified to predict mixture diffusion behavior in the case of strong correlation effects. Intermolecular exchange coefficients are not required. No empirical relations are employed. This simplified model is used to predict single-file diffusion behavior in a binary system. The effect of using only the pure component thermodynamic correction factors in predicting mixture diffusion behavior is also examined with application to two systems of practical interest. In all cases, predictions from the simplified models are favorably compared to results from the more complex MS equations or experiments, indicating that the simplified models can serve as good starting approximations, and can also speed up mixture diffusion calculations in zeolites.