Effects of Fe dopants and residual carbonates on the catalytic activities of the perovskite-type La0.7Sr0.3Co1−xFexO3 NOx storage catalyst

• The calcination in flowing air can suppress the bulk carbonate formation.
• The Fe-doping in the perovskite improved the sulfur tolerance significantly.
• The Sr was protected from sulfation by the surrounded Fe forming Fe2(SO4)3.
• La0.7Sr0.3Co0.8Fe0.2O3 is a possible NOx absorber for lean-burn engines.

Herein, we reported the NOx storage capacity, NO oxidation ability and sulfur resistance of the La0.7Sr0.3CoO3-based perovskite-type catalysts. NO could be readily oxidized to NO2 with around 83% of NO-to-NO2 conversion at 300 °C over the perovskite. After sulfation, the NSC of the La0.7Sr0.3CoO3 catalyst calcined in static air decreased 58.0%. Nevertheless, a significant improvement of the sulfur tolerance could be achieved through partial substitution of Co with Fe cations, as well as calcination in flowing air. The NSC of the pre-sulfated La0.7Sr0.3Co0.8Fe0.2O3 catalyst maintained 360.7 μmol/g and dropped only 6.4% as compared with the fresh one. The XPS results confirmed the presence of Fe2(SO4)3 in the sulfated La0.7Sr0.3Co0.8Fe0.2O3 catalyst. The EXAFS results further revealed that the formation of Fe2(SO4)3 in the perovskite inhibited the sulfation of neighboring strontium from the viewpoint of the local atomic level. These findings strongly suggest that the La0.7Sr0.3Co0.8Fe0.2O3 perovskite is a possible NOx absorber used for aftertreatment systems upon lean-burn engines with the advantages of the excellent NO oxidation ability, NOx storage capacity and the high sulfur tolerance.

Figure optionsDownload as PowerPoint slide