The effect of pore blockage on the diffusivity in ZSM5: a percolation approach

The evolution of the effective diffusivity of a pseudo-continuum model of a ZSM5 particle in which progressive blockage occurs is calculated from a ne twork model using bond- and site-percolation theory and the effective mediu m approximation (EMA). Reduced clusters of varying complexity are evaluated with respect to their capability of accurately predicting the relationship between the evolution of the effective diffusivity with the blockage. A co mbination of EMA and scaling leads to an excellent agreement with the resul ts of Monte Carlo simulation on a 20 x 20 x 20 lattice. The retained relati onship is used in the simulation of reaction and diffusion in a ZSM5 partic le of a fixed bed reactor. The catalyst is subject to deactivation by coke formation leading to site coverage and pore blockage. (C) 2001 Elsevier Sci ence B.V. All rights reserved.