Monolithic reactors such as honeycomb flow-through converters (FTC) and wall-flow filters (WFF) continue to be important components of diesel emission control systems, and include functionalities such as gas species oxidation (such as CO, hydrocarbons and NO), storage phenomena (such as NO_x and NH_3 storage), and soot particle filtration and oxidation. An indepth understanding of the coupled transport-reaction phenomena occurring inside the microstructure of the coated walls of FTCs and WFFs can provide useful guidance for catalyst placement and improved accuracy over idealized models, without a detailed treatment of the micro-structure. In the present work a previously developed simulation method for realistic representation of the microstructure of porous materials is applied to the case of NO, CO, HC and soot oxidation in a a WFF. The detailed geometry of the catalyst coated monolith wall is digitally reconstructed and micro-simulation (digital material) methods are used to obtain detailed descriptions of the transport and reaction phenomena taking place in the microstructure. A comparison is made for the particular case of soot oxidation by NO_2 (in the absence or the presence of an NO oxidation catalyst) with the predictions of approximate but analytical models and a procedure is developed to allow the incorporation of these results in a computationally efficient manner in large scale simulations of diesel emission control devices.
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