Enhanced low-temperature NOx storage and reduction performance using Cu-loaded lean NOx trap catalysts

Abstract

Lean NOx trap (LNT) used in diesel-powered vehicles exhibit poor NOx storage and reduction (NSR) performance during low-temperature operation, particularly under cold-start conditions. To overcome this limitation, Cu was added to a conventional LNT catalyst (Pt-Ba/γ-Al2O3, PBA) to improve the NOx storage and regeneration performance of the Cu-loaded Ba adsorbent (Cu-Ba/γ-Al2O3) during low-temperature operation. However, a Pt-Cu complex was formed when Pt and Cu were used together as a one-body catalyst (Pt-Cu-Ba/γ-Al2O3, PCBA), leading to decreased catalytic performance. Physical mixing was investigated as a method to prevent the catalytic performance degradation caused by the Pt-Cu complex. The physical mixture of Pt/γ-Al2O3 and Cu-Ba/γ-Al2O3 (PA + CBA) could prevent the formation of Pt-Cu complex and yielded the highest NSR performance at 150 ℃ among the synthesized LNT catalysts. PA + CBA maintained a significantly improved NSR performance in lean-rich cycling tests using CO or H2 as a reducing agent.