ADSORPTION SIMULATIONS OF SMALL MOLECULES AND THEIR MIXTURES IN A ZEOLITE MICROPORE

We simulate the adsorption of small molecules (Xe, Ar, CH4) and their binary mixtures in zeolite NaA using the grand canonical ensemble Mont e Carlo method. We report the isotherm, energy, entropy, and adsorbate density distribution. The effects of nonideal mixing in the pore are assessed by comparing the simulated binary isotherms to those predicte d by a pore filling model (Ruthven, D. M. Nat. Phys. Sci. 1971, 232, 7 0. Ruthven, D. M.; Loughlin, K. F.; Holborow, K. A. Chem. Eng. Sci. 19 73, 28, 701). At low pore loadings, we observe strong selectivity for a more polarizable molecule, but at higher pore loadings, a smaller, l ess polarizable molecule can adsorb selectively. This occurs at signif icantly lower pressures in our simulations than would be predicted by the pore filling model. This increased selectivity for the smaller mol ecule occurs because of differences in the two component's ability to pack efficiently in the pore beyond that accounted for by the pore fil ling model.