Gas diffusion in an automotive catalyst in an unsteady state

Abstract

The influence of gas diffusion is often ignored because the washcoat layer is thin. Therefore, in addition to developing new catalytic materials, modifying the washcoat pores is important for improving effective gas diffusivity. The gas diffusion phenomena in an unsteady state in an experimentally simulated washcoat layer were evaluated by the pulse injection method. Wicke–Kallenbach diffusion cell was used. Effective diffusion coefficients obtained in an unsteady state were compared to those obtained in a steady state. The effective diffusion coefficients were similar to the values obtained under a steady state, except for low-molecular-weight gasses, due to the difference in mean molar speed between the evaluating gas and atmospheric gas.