Modified van der Waals Equation for the Prediction of Multicomponent Isotherms.

A modified two-dimensional van der Waals equation model was proposed for the prediction of multicomponent gas-solid adsorption isotherms from corresponding single-component adsorption equilibrium data. The model was used to predict adsorption isotherms of CO-CO2 mixtures and CO2-N2 mixtures on Cu(I)-NaY zeolite. Experimental adsorption equilibrium data of the two systems were compared with results calculated from the model and three other models in the literature: the ideal adsorbed solution model, the vacancy solution theory of adsorption using the Flory-Huggins activity coefficient equation, and the two-dimensional van der Waals equation. The results indicated that the modified van der Waals equation predicted the experimental results better than the three other models for the two systems studied, especially for the CO-CO2 system, which involved chemical reaction during adsorption and exhibited azeotropic behavior. Copyright 1998 Academic Press.