The most rigorous description of catalytic fixed-bed reactors is particle-resolved CFD simulations. Pore processes can have a large effect toward reactor performance, since they limit internal mass transport. In this study, three pore models of different complexity are incorporated into the CFD software STAR-CCM+. Instantaneous diffusion, effectiveness-factor approach, and three-dimensional reaction-diffusion model are validated firstly with experimental data of CO oxidation in a stagnation-flow reactor from Karadeniz et al. (2013). The 3D approach predicts the experiments with high accuracy over the entire temperature range followed by the computationally cheaper effectiveness-factor. In a second study, the effect of the three pore models is evaluated on a catalytic single sphere with Reynolds numbers varying between 10 and 2000. The local interplay between kinetics and transport phenomena are quantified. For all investigated cases internal mass transfer limitations are larger than external ones. This study can be applied for entire packed-bed simulations. (C) 2017 Elsevier Ltd. All rights reserved.