Mathematical modelling of diffusion and reaction in blocked zeolite catalysts

A mathematical model for diffusion and reaction in blocked zeolites is developed which takes into account nonidealities arising from interaction between sorbed molecules as well as the effect of pore and surface blocking. The model combines a microscopic approach, in which expressions for chemical potential and diffusive fluxes are calculated within the lattice-gas framework, with the more traditional continuum approach which takes into account the effect of surface blocking. The effect of pore blocking on the diffusive fluxes in accounted for through an effective medium approximation. The effects of crystal size and blocking on the activity-selectivity characteristics of the crystal are illustrated through an example that is qualitatively similar to industrially important reactions such as alkylation of toluene in blocked ZSM-5 zeolite.