NOx storage-reduction over combined catalyst Mn/Ba/Al2O3–Pt/Ba/Al2O3

Mn/Ba/Al2O3, Pt/Ba/Al2O3 and their combined catalyst for NOx storage-reduction by propylene were investigated. The results showed that Mn/Ba/Al2O3 exhibited good catalytic activity for NO oxidation-storage under lean burn condition. When Pt/Ba/Al2O3 was mixed with Mn/Ba/Al2O3 in equal weight proportion, the NOx conversion between 250 °C and 500 °C under the dynamic lean-rich burn conditions increased, and the maximum NOx conversion increased from 82.0% to 90.8% at 400 °C. The combined catalyst showed higher catalytic activity and better stability in the presence of 25 ppm SO2 in comparison to Pt/Ba/Al2O3. XRD and XPS characterizations of Mn/Ba/Al2O3 indicated that MnO2 and Mn2O3 disperse on the surface, while BaMnO3 exits in bulk phase.