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

Abstract

A series of Ni₁Mg₂Al₁O_x, Mn₁Mg₂Al₁O_x, 0.5Pt/Ni₁Mg₂Al₁O_x and 0.5Pt/Mn₁Mg₂Al₁O_x catalysts were carefully prepared and their NO_x storage and reduction (NSR) performance including NO_x oxidation efficiency (NOE), NO_x storage capacity (NSC), NO_x conversion rate (X_NO), N₂ selectivity (S_N2), N₂O selectivity (S_N2O) and NH₃ selectivity (S_NH3), was systematically investigated. A SO₂ resistance test was also performed in the presence of 100 ppm SO₂. The NOE and NSC experimental results revealed that the Ni₁Mg₂Al₁O_x catalyst possesses a higher NSC, while the Mn₁Mg₂Al₁O_x catalyst possesses a better NOE. With regard to X_NO, 0.5Pt/Ni₁Mg₂Al₁O_x presented higher results at 200 °C and 400 °C, while 0.5Pt/Mn₁Mg₂Al₁O_x obtained the highest result at 300 °C, which was more than 60% for both. In addition, compared to 0.5Pt/Ni₁Mg₂Al₁O_x, 0.5Pt/Mn₁Mg₂Al₁O_x exhibited a relatively higher S_N2 and lower S_N2O and S_NH3. The NO_x-TPD and H₂-TPSR results indicated that NO_x adsorbed on Ni₁Mg₂Al₁O_x and 0.5Pt/Ni₁Mg₂Al₁O_x is more stable, and that NH₃ can be formed in large amounts in a lower temperature range. Both Pt-containing catalysts presented a quite stable X_NO in ten cycles in the presence of 100 ppm SO₂, and their S_N2 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.