Measurement and Calculation of Multicomponent-Diffusion and Reaction in Catalyst Particles, Effect of the Catalyst Pore Structure (PDF)

A realistic diffusion system, multi-component diffusion, accompanied by a relatively simple reaction, a single reaction with simple molecules, is investigated experimentally using commercial pellets at mild conditions. The motivation was to elucidate the effect of pore structure for simultaneous diffusion/reaction systems in general. The results can be used to investigate the multi-component interactions between different components, to determine an optimum pore structure and/or to check if the whole internal surface area is utilized for reaction. Furthermore, the modeling of such systems was first shortly reviewed using a simple and a complicated pore model. Based on the conservation of mass principle, it is proven that an overall equilibrium between gas and surface phases is theoretically not possible. This has led to the development and introduction of a novel approach for modeling Knudsen flow, the projection approach. The approach is basically novel in two aspects: first, due to its architecture some commonly used assumptions can be avoided, and second, it makes use of new concepts (e.g., outer-surface) and incorporates them by a new calculation procedure. It is shown that this developed approach and modeling is convincing about its accuracy and potential. It allows for otherwise suppressed phenomena to take force and affect the behavior of the system. Moreover, it can be used to estimate the errors made in using common assumptions. It can be concluded that the results from both experimental studies and modeling stimulate the thirst for further research in this area.