Evidence for the existence of intracrystalline transport barriers in MFI-type zeolites:: a model consistency check using MC simulations

The results of Monte Carlo simulations of diffusion on cubic lattices with diffusion anisotropy and regularly spaced permeable transport barriers are reported. By varying the simulation parameters in a broad range it was attempted to reproduce the experimental dependencies of diffusivities on the root mean square displacement reported earlier for MFI-type zeolites. The experimental dependencies were originally attributed to the existence of permeable transport barriers in MFI-type zeolites. Using this assumption and applying a simple model based on the transition state theory a satisfactory agreement between the experimental and the simulation results for selected sets of simulation parameters is obtained. This supports the assumption about the existence of permeable internal transport barriers in MFI-type zeolites. (C) 2002 Elsevier Science Inc. All rights reserved.