Experimental and modeling study of a dual-layer (SCR + PGM) NH3 slip monolith catalyst (ASC) for automotive SCR after treatment systems. Part 2. Validation of PGM kinetics and modeling of the dual-layer ASC monolith

Abstract

We present herein the final part in the development and validation of a chemically and physically consistent mathematical model of a commercial dual-layer (SCR+PGM) monolithic NH3 slip converter (ASC). Specifically, in this conclusive Part 2 of the project we first validate the global kinetic model for the PGM catalyst component, previously developed in Part 1 over the precursor powders, against data collected over a single-layer coated monolith. Then, we incorporate validated kinetics for the two individual SCR and PGM components into a dual-layer ASC monolith catalyst model and proceed to a systematic validation against experimental catalytic activity data collected over core samples of the dual-layer ASC system. A DOE approach is also adopted in order to secure a uniform coverage of the operating field.A positive interaction of the PGM and SCR catalytic chemistries is emphasized by the data collected over the dual-layer SCR+PGM monolith catalyst, leading to largely enhanced N2 selectivities as compared to a single-layer PGM-only washcoat. We show that such a beneficial interaction between the PGM and SCR chemistries occurs via diffusion/reaction of NH3 and NOx in the SCR catalyst layer. Results prove that the dual-layer ASC model can simulate realistically the actual NH3 slip catalyst configuration over a wide range of representative conditions.