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

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.