The diffusion coefficients, D1 and D2, of a binary mixture of adsorbates of diameters, σ1 and σ2, in restricted regions of NaY zeolite were obtained from simulations. The results suggested that the region of the diffusion coefficients with ζ = D1/D2 exhibited unusual behaviour, with an increase in the ratio of diameters, η = σ1/σ2: D1 > D2, even for σ1 > σ2. Calculations of a single-component adsorbate in this zeolite suggested that the diffusion coefficient exhibited an anomaly as the adsorbate diameter approached the diameter of the window; the narrowest portion of the porous network. It was shown that the latter result explained the unexpected behaviour in the ratio of diffusion coefficients which was observed for the binary mixture.

Diffusion Behaviour of Binary Mixtures in Restricted Regions of Zeolite NaY from Molecular Dynamics Calculations. Chitra, R., Yashonath, S.: Chemical Physics Letters, 1995, 234[1-3], 16-20