PFG NMR study of diffusion in MFI-type zeolities: evidence of the existence of intracrystalline transport barriers

The intracrystalline diffusion of methane and n-butane molecules in MFI-type zeolites at several temperatures and over a wide range of diffusion times is investigated applying the PFG NMR technique. The results of the study reveals that diffusion coefficients progressively decreasing with increasing root-meansquare displacements.