Xenon-129 NMR was used to determine intracrystalline concentration profiles during sorption experiments. In this way, a direct discrimination between the limiting cases of barrier-controlled and diffusion-controlled up-take became possible. For benzene in zeolite ZSM-5, molecular up-take was found to be controlled by intracrystalline diffusion. The determined value of 1.3 x 10-14m2/s at room temperature was in satisfactory agreement with the results of conventional up-take experiments.

Direct Observation of Intracrystalline Transport Diffusion and Conduction in Zeolites by Xenon-129 NMR. J.Kärger, H.Pfeifer, T.Wutscherk, S.Ernst, J.Weitkamp, J.Fraissard: Journal of Physical Chemistry, 1992, 96[12], 5059-63