Diffusion and Reaction in Catalyst Pellets with Bidisperse Pore Size Distribution

Catalysts with bidisperse pore structures are extensively used in chemical industries. In such catalysts, diffusion and reaction in the microporous particles are preceded by diffusion in the macropores. The relative significance of macro- and micropore diffusion resistances on the observed reaction rates with linear and nonlinear rate forms, heat effects, catalyst deactivation and selectivity problems in bidisperse catalysts are investigated in number of published works. In this article, a review of the models proposed in the literature is presented together with a critical analysis of assumptions involved. Criteria are presented to test the relative significance of transport limitations. Also, a review of experimental techniques and experimental values of micro- and macropore effective diffusivities of gases in solids with bidisperse pore structures, such as zeolite pellets and supported porous catalysts, is given.