In this paper, a multi-region model based on the unified Maxwell-Stefan diffusion theory is developed to investigate the reaction-diffusion processes within catalyst pellets formed by micro-pore particles and meso/macro-pore support. The corresponding partial differential equation (PDE) systems, describing chemical reactions, bulk diffusion, Knudsen diffusion, surface diffusion and viscous flow, are converted to ODE systems based on finite volume method (FVM). The resulting multi-scale ODE systems are solved by reduced storage matrix method, where a quasi-stationary state assumption is adopted in the numerical solution to solve multi-scale problem in which the diffusivities of micro-pores and meso/macro-pores are significantly different. The alkylation of benzene over a single multi-porous pellet formed with H-ZSM-5 crystal particles was simulated as an example. The effects of volume fraction, size and spatial distribution of H-ZSM-5 crystal particles on the effectiveness factor of the catalyst pellet were then investigated and discussed. It is shown that the multi-region model is a potential bottom to up tool for reaction-diffusion processes in catalyst pellet exhibiting multi-scale time characteristic. (C) 2016 Elsevier Ltd. All rights reserved.