Comparative study on the NOx storage and reduction performance of Pt/Ni1Mg2Al1Ox and Pt/Mn1Mg2Al1Ox catalysts

A series of Ni1Mg2Al1Ox, Mn1Mg2Al1Ox, 0.5Pt/Ni1Mg2Al1Ox and 0.5Pt/Mn1Mg2Al1Ox catalysts were carefully prepared and their NOx storage and reduction (NSR) performance including NOx oxidation efficiency (NOE), NOx storage capacity (NSC), NOx conversion rate (XNO), N2 selectivity (SN2), N2O selectivity (SN2O) and NH3 selectivity (SNH3), were systematically investigated. The SO2 resistance also performed in the presence of 100 ppm SO2. The NOE and NSC experimental results revealed that Ni1Mg2Al1Ox catalyst possesses higher NSC, while Mn1Mg2Al1Ox catalyst possesses better NOE. For XNO, 0.5Pt/Ni1Mg2Al1Ox presented higher results at 200 oC and 400 oC, while 0.5Pt/Mn1Mg2Al1Ox obtained the highest result at 300 oC，which was more than 60% for both. In addition, compared to 0.5Pt/Ni1Mg2Al1Ox, the 0.5Pt/Mn1Mg2Al1Ox exhibited a relative higher SN2, lower SN2O and SNH3. NOx-TPD and H2-TPSR results indicated that NOx adsorbed on Ni1Mg2Al1Ox and 0.5Pt/Ni1Mg2Al1Ox is more stable, and the NH3 can be formed in a large amount in a lower temperature range. Both Pt-containing catalysts presented a pretty stable XNO in ten cycles in the presence of 100 ppm SO2, and the SN2 can be remarkably enhanced to more than 80%, which could be attributed to the reactions of NH3-SCR and SO2 + NH3. We believe this new insight can provide a new way of thinking for the development of NSR catalysts.