Pt-free, LaMnO3 based lean NOx trap catalysts
Conventional lean NOx trap (LNT) catalysts require high loadings of Pt in order to oxidize NO to NO2, a critical step in LNT applications. This paper presents a concept study of using LaMnO3 perovskite as a substitute to Pt in LNT catalyst. The structure, morphology and redox property of LaMnO3 perovskite were probed by TPR, XRD and its performance on NO oxidation to NO2was also evaluated. A LaMnO3 based, PGM free LNT showed good NO oxidation activity and NOx storage capability under lean conditions, but it did not have sufficient NOx reduction activities during LNT regeneration. With the addition of Pd/Rh to provide NOx reduction activities, a LaMnO3-based, Pt-free LNT showed high NOx storage/reduction activities under lean and rich cycling conditions.
Graphical abstractThe feasibility of replacing of Pt by LaMnO3 in LNT catalysts was demonstrated and a LaMnO3 based LNT containing no Pt showed high NOx storage/reduction activities under lean and rich cycling conditions.Figure optionsDownload full-size imageDownload high-quality image (162 K)Download as PowerPoint slideHighlights► The feasibility of replacing of Pt by LaMnO3 in LNT catalysts was demonstrated and a LaMnO3 based LNT containing no Pt showed high NOxstorage/reduction activities. ► LaMnO3/BaO/Al2O3 catalyst was found to have excellent NOx storage capability; however, most of NOx released were not reduced during the short rich periods indicating LaMnO3 is not active for NOx reduction under rich conditions. ► The LaMnO3/BaO/Al2O3 catalyst, with the addition of Pd/Rh, showed high NOx conversions, demonstrating the potential for replacing Pt in LNT applications.
Journal: Catalysis Today - Volume 184, Issue 1, 30 April 2012, Pages 72–77