(587c) Detailed Modeling of Flow-through Monoliths for Automotive Exhaust Gas Aftertreatment

A growing number of automotive exhaust gas aftertreatment technologies rely on flow-through monoliths. Besides the three-way catalytic converter (TWC) for gasoline driven engines, diesel vehicles call for more innovation to meet the pollution limits of the future. Among these are diesel oxidation catalysts (DOC), NOx storage catalysts (NSC) and catalysts for the selective catalytic reduction of NOx (SCR) using hydrocarbons or ammonia.

All these systems are characterized by highly transient operating conditions and complex interactions between heat and mass transfer as well as chemical reactions. Thus, our modeling approach is to describe these processes as detailed as possible. The reaction mechanisms are based on elementary-step kinetics and have been validated using experimental data in various set-ups. We have studied the transport in the porous structure of washcoats with several levels of detail ranging from 0-d effectiveness factor models to full 2-d reaction-diffusion models. The influence of the shape of the channels on heat and mass transport has been studies by various 1-d ? 3-d flow models. Finally, the single channel models can be assembled in to a model of the flow-through monolith in order to describe the transient behavior of the complete system.