Global kinetic model for the regeneration of NOx storage catalyst with CO, H2 and C3H6 in the presence of CO2 and H2O

Heterogeneous 1D model with global kinetics is proposed for industrial NOx storage and reduction catalyst (NSRC) on the basis of lab experiments in a mini-reactor in the temperature range 100–500 imageC. The NOx reduction dynamics and selectivity towards N2 or NH3 are modelled for three main reducing components present in the rich exhaust gas: CO, H2, and unburned hydrocarbons (HCs). The following reactions are considered: CO, H2 and HC oxidation, NOx reduction, NO/NO2 transformation, NO and NO2 storage, oxygen storage effects, water gas shift and steam reforming, and reduction of the stored NOx by H2, CO and HC. Ammonia is formed mainly by the reaction of H2 with NOx, but also by the water-assisted reaction of CO with NOx (formation and consequent hydrolysis of isocyanates). Inclusion of the latter route is necessary to explain the NH3 formation in CO-rich mixtures without H2 at lower temperatures. At higher temperatures, water gas shift and steam reforming reactions enable in situ H2 production from CO, HC and H2O. The formed ammonia subsequently reacts with oxygen and NOx deposited on the catalyst surface downstream, which results in NH3 wave travelling along the catalytic monolith.