Evaluation of Effectiveness Factors for Multicomponent Diffusion Models Inside 3D Catalyst Shapes

Abstract

On an industrial scale, the efficiency of heterogeneous catalysis is commonly subject to diffusive transport limitations. The binary friction model (BFM) combines Maxwell–Stefan-type diffusion, pore effects and viscous contributions for multicomponent reaction mixtures. A variety of catalyst shapes have been developed over the years to overcome transport problems. However, rigorous modeling of multicomponent diffusion–reaction problems in 3D geometries remains an ongoing challenge. We successfully applied the BFM to nine shapes, all varying in size and catalyst loading. The volume-to-surface ratio and the curvature of the bodies were found to be the characteristic features of the pellets, describing the reaction–diffusion interplay. With this, the 3D shape can be adequately approximated with straightforward 1D strategies. Finally, a comparison to Fickian diffusion models highlights the similarities and discrepancies to the Maxwell–Stefan concept of the BFM. These findings can contribute to an integral description of 3D reaction–diffusion problems in homogeneously distributed, mesoporous catalysts.