DIFFUSION BEHAVIOR OF BINARY-MIXTURES IN RESTRICTED REGIONS OF ZEOLITE NAY FROM MOLECULAR-DYNAMICS CALCULATIONS

Diffusion coefficients D-1 and D-2 of a binary mixture of adsorbates o f diameters sigma(1) and sigma(2) in the restricted regions of zeolite NaY have been obtained from molecular dynamics simulations. The resul ts suggest that the ratio of the diffusion coefficients zeta = D-1/D-2 exhibit unusual behaviour with an increase in the ratio of diameters eta = sigma(1)/sigma(2):D-1 > D-2 even when sigma(1) > sigma(2). Calcu lations on a single component adsorbate in zeolite NaY suggest that th e diffusion coefficient shows an anomaly when the adsorbate diameter a pproaches the diameter of the window, the narrowest portion of the por ous network. It is shown that the latter result explains the unexpecte d behaviour in the ratio of diffusion coefficients observed for the bi nary mixture.