Abstract
Two lean NOx trap (LNT) catalysts, Pt/BaO/CeO2 + Al2O3 and Pt/BaO/CeO2 − Al2O3, were prepared and compared for low-temperature (< 250 °C) NOx storage and reduction performance. The influence of the form of ceria on low-temperature NOx storage and reduction performance of LNT catalysts was investigated with the focus on NOx storage capacity, NOx reduction efficiency during lean/rich cycling, product selectivity and thermal stability. Inductively coupled plasma-atomic emission spectrometry (ICP-AES), Brunner–Emmet–Teller (BET), H2-pulse chemisorption and X-ray diffraction (XRD) were conducted to characterize the physical properties of LNT catalysts. NOx storage capacity and NOx conversion efficiency were measured to evaluate NOx storage and reduction performance of LNT catalysts. Pt/BaO/CeO2 − Al2O3 catalyst exhibits higher NOx storage capacity than Pt/BaO/CeO2 + Al2O3 catalyst in the temperature range of 150–250 °C. Meanwhile, Pt/BaO/CeO2 − Al2O3 catalyst shows better NOx conversion efficiency and N2 selectivity. XRD results indicate that the thermal stability of CeO2 − Al2O3 complex oxide is superior to that of pure CeO2. H2-pulse chemisorption results show that Pt/BaO/CeO2 − Al2O3 catalyst has higher Pt dispersion than Pt/BaO/CeO2 + Al2O3 catalyst over fresh and aged samples. The improved physical properties of Pt/BaO/CeO2 − Al2O3 catalyst are attributed to enhance the NOx storage and reduction performance over Pt/BaO/CeO2 + Al2O3 catalyst.
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