NOx storage and reduction properties of model ceria-based lean NOx trap catalysts

Three kinds of model ceria-containing LNT catalysts, corresponding to Pt/Ba/CeO2, Pt/CeO2/Al2O3 and Pt/BaO/CeO2/Al2O3, were prepared for comparison with a standard LNT catalyst of the Pt/BaO/Al2O3 type. In these catalysts ceria functioned as a NOx storage component and/or a support material. The influence of ceria on the microstructure of the catalysts was investigated, in addition to the effect on NOx storage capacity, regeneration behavior and catalyst performance during lean/rich cycling. The Pt/Ba/CeO2 and Pt/BaO/CeO2/Al2O3 catalysts exhibited higher NOx storage capacity at 200 and 300 °C relative to the Pt/BaO/Al2O3 catalyst, although the latter displayed better storage capacity at 400 °C. Catalyst regeneration behavior at low temperature was also improved by the presence of ceria, as reflected by TPR measurements. These factors contributed to the superior NOx storage-reduction performance exhibited by the Pt/Ba/CeO2 and Pt/BaO/CeO2/Al2O3 catalysts under cycling conditions in the temperature range 200–300 °C. Overall, Pt/BaO/CeO2/Al2O3 (which displayed well balanced NOx storage and regeneration behavior), showed the best performance, affording consistently high NOx conversion levels in the temperature range 200–400 °C under lean-rich cycling conditions.

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► Model BaO- and CeO2-containing LNT catalysts were prepared.
► The use of ceria as a support was beneficial for the dispersion of BaO.
► The presence of ceria improved catalyst regeneration at low temperature.
► Ceria was beneficial for NOx storage capacity at 200 °C and 300 °C.
► A Pt/BaO/CeO2/Al2O3 catalyst showed the best performance during lean-rich cycling.