Activity and thermal stability of Pt/Ce0.64Mn0.16R0.2Ox (R = Al, Zr, La, or Y) for soot and NO oxidation

Abstract

In this study, Al2O3, ZrO2, La2O3, and Y2O3 were separately introduced into Pt/CeO2-MnOx catalyst to improve the thermal stability of catalysts and obtain a better soot and NO oxidation activity after thermal treatment. CeO2-MnOx-ROx (R=Al, La, Y, or Zr) mixed oxides were prepared by a co-precipitation method. The catalysts were characterized by XRD, BET, H2-TPR, CO chemisorption, XPS, TG analysis, soot–TPO, and NO–TPO. It is found that the introduction of Rn+ into CeO2-MnOx markedly increases the thermal stability of the catalysts for soot and NO oxidation, remaining a better catalytic oxidation activity. On the one hand, after high-temperature aging, for the modified catalyst Pt/CeMnROx, the ignition temperature of soot oxidation (Ti) and maximal soot oxidation rate temperature (Tm) increase by 30–50°C and 4–32°C, respectively, whereas Al3+-modified catalyst shows the best thermal stability. On the other hand, due to a key role of NO2 as a strong oxidizing agent in soot oxidation process, the NO oxidation activity is often considered as an important aspect. This work shows that Rn+-modified catalysts display a better stability on NO oxidation activity after aging. Some factors leading to the thermal deactivation of catalysts are also discussed in this paper.