Influence of H2, CO, C3H6, and C7H8 as Reductants on DeNOx Behavior of Dual Monoliths for NOx Storage/Reduction Coupled with Selective Catalytic Reduction

The effects of feeding hydrogen, carbon monoxide, and propylene as reductants are analyzed in the combined NOx storage and reduction with selective catalytic reduction technology (NSR-SCR), with Pt–Ba/Al2O3 and Pt–Ba–Ce/Al2O3 monoliths as NSR catalysts, and Cu/BETA and Cu/SAPO-34 monoliths as SCR catalysts. Feed streams including CO2 and H2O mimic the real composition of the diesel engine exhaust. Also, the reaction temperature and reductant concentration are analyzed on NOx removal and product distribution at the converter outlet. H2 is the most efficient reductant at low temperature. The reducing capacity of CO is comparable to H2 from 300 °C and onward. Higher temperature (400 °C) is needed for propylene to be as effective reductant as H2 or CO due to the promotion of storage and reduction reaction. Benefits in dual NSR-SCR configurations are enhanced with H2 as reductant, due to higher internal generation of NH3 to be used in the SCR catalyst.