Effective modeling of coupled reaction and transport inside the catalytic filter wall

Abstract

A new extension of 1D mathematical model describing diffusion limitation in a catalytic filter wall is proposed. Transport limitations in the flowing gas inside free pores and in the coated catalyst are considered together with a Langmuir–Hinshelwood (LH) reaction kinetics including inhibition effects. Catalytic CO oxidation is investigated as a test reaction both at low and high reactant concentrations. The computed 1D concentration profiles are compared to detailed 3D pore-scale simulations involving the structure of a real filter wall obtained from X-ray tomography (XRT) scans. The best agreement is achieved when both gas-in-pores and intra-catalyst diffusion with LH effectiveness factor are considered in the 1D model. The impact of mass transfer limitations on CO light-off curves is then simulated using a 1D+1D model of the entire monolith filter. The extended model including diffusion limitation in free pores predicts the presence of undesired reactant slip at high flow rates as observed in experiments, which was not possible with the previously published models.