Mathematical modelling of cold start effects over zeolite SCR catalysts for exhaust gas aftertreatment

Abstract In this contribution a mathematical model suitable to simulate cold start effects over metal-promoted zeolite SCR catalysts is developed and included into an existing SCR converter model. We start from a recently published microkinetic scheme, which describes the NO 2 related SCR reactions at temperatures above about 100 °C on the basis of a complex reaction network, taking into account NO 2 storage with formation of nitrates and their subsequent decomposition/reactivity. In order to describe material and thermal cold start effects observed from room temperature we extend such a kinetic scheme to include the low-T NO oxidation to NO 2 , NO 2 physisorption and H 2 O adsorption. The rate parameters are fitted to our data from lab-scale runs analyzing each individual step. We show that the resulting model can reproduce the transient effects related to cold start both at the lab scale and in engine test bench experiments.