Computational fluid dynamics (CFD) is coupled with reaction and transport in a micro-scale pellet simulation to study CO oxidation over Rh/Al₂O₃ catalyst. The macro-pores are explicitly modeled to study the interaction of these phenomena in both the solid and fluid phases. A catalyst layer is computationally reconstructed using a distribution of alumina particles and a simple force model. The constructed geometry properties are validated using the existing data in the literature. A surface mesh is generated and modified for the geometry using the shrink-wrap method and the surface mesh is used to create a volumetric mesh for the CFD simulation. The local pressure and velocity profiles are studied and it is shown that extreme changes in velocity profile could be observed. Furthermore, the reaction and species contours show how fast reaction on the surface of the solid phase limits the transport of the reactants from the fluid to meso- and micro-porous solid structures and therefore limits the overall efficiency of the porous structure. Finally, the importance of using a bi-modal pore structure in the diffusion methods for reaction engineering models is discussed.