Lean NOx trap catalysts with high low-temperature activity and hydrothermal stability

Abstract

A combination of the Pt-BaO/CeO2 and Cu/CeO2 (PBC + CC) catalyst offers high NOx storage and reduction (NSR) performance at low temperatures; however, the PBC + CC catalyst is prone to deactivation upon hydrothermal aging. In this study, we used a reduced gamma-Al2O3 support with unsaturated penta-coordinated Al3+ sites, which can anchor catalytic materials (Pt, Cu, BaO, and CeO2). The physical mixture of Pt-BaO-CeO2 and Cu-CeO2 deposited on the reduced Al2O3 (PBCrA + CCrA) was prepared and tested for the NOx removal. The PBCrA + CCrA catalyst showed little degradation after hydrothermal aging at 750 degrees C. XRD, HR-TEM, CO chemisorption, N2O chemisorption, and N-2 physisorption results showed that catalytically active phases were barely changed even after the hydrothermal aging, particularly preventing ceria sintering. CO-TPR and XPS results demonstrated that the PBCrA + CCrA catalyst has a superior reducibility of lattice oxygen on CeO2, leading to excellent low-temperature activity.