Microtomography-based CFD modeling of a fixed-bed reactor with an open-cell foam monolith and experimental verification by reactor profile measurements

CFD simulations of catalytic reactors provide detailed insight into the chemical and physical processes within these devices such as 2D or 3D concentration-, flow- and temperature fields or even 3D pictures of the coverages of the various species on the surface of the catalyst. The validation of CFD models of catalytic reactors is hampered by the lack of experimental data against which the simulation results can be compared. The present work addresses this problem by presenting a critical comparison between CFD simulation results and sub-millimeter resolved species and temperature profiles measured through a reactor employing a catalytic foam monolith. CO oxidation on Pt nanoparticles with narrow size distribution supported on an α-Al2O3 foam was chosen as simple catalytic system with well known microkinetics. To keep uncertainties in the CFD geometry as small as possible, the structure of the foam catalyst was resolved by X-ray microtomography. Simulation parameters and boundary conditions were determined as accurately as possible. The CFD model includes flow, thermal conduction in the struts of the foam, conjugated heat transfer and heat radiation. Catalytic chemistry is incorporated by means of a microkinetic reaction model taken from literature. The comparison of CFD simulation results with high resolution spatial temperature and concentration data allows a critical assessment of strengths and weaknesses of both, the model and the experiment serving as basis for a knowledge-based design of reactors employing catalytic foams or similar random geometries.