Molecular self-diffusion data on methanol-water mixtures sorbed in pentasil-type zeolites having two different Si/Al ratios were reported. At medium loading and room temperature, the self-diffusion coefficients of sorbed methanol and water were found to be of the order of 10-9m2/s. For both sorbate molecules intracrystalline mobility was greater for the higher Si/Al ratio. While water self-diffusion was only slightly affected by sorbate concentration, in the case of methanol a decrease of approximately one order of magnitude with increasing loading was observed. In contrast to the liquid state, the sorbed state of binary mixtures exhibited no minima of the self-diffusion coefficients. The molecular mobilities observed could be correlated with structural features of the pentasils determined from 1H NMR measurements.

Nuclear Magnetic Resonance Self-Diffusion Studies of Methanol-Water Mixtures in Pentasil-Type Zeolites. J.Caro, M.Bülow, J.Richter-Mendau, J.Kärger, M.Hunger, D.Freude, L.V.C.Rees: Journal of the Chemical Society - Faraday Transactions 1, 1987, 83[6], 1843-9