Abstract

CeO₂–ZrO₂–M_xO_y (M = Y; La) mixed oxides, prepared by co-precipitation method and characterized by Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Raman spectra (RM) and oxygen pulse reaction, were comparatively investigated to elucidate the combinational effects of Y and/or La oxide promoters on the catalytic activity and anti-aging performance of monolithic cordierite honeycomb catalysts with low Pt and Rh content. The catalytic activities, water-gas shift (WGS) and steam reforming reaction (SR) were studied under a simulated gas mixture. The catalysts were also characterized by H₂-temperature-programmed reduction (H₂-TPR) and O₂-temperature-programmed desorption (O₂-TPD). The results showed that the prepared CeO₂–ZrO₂–M_xO_y oxides have a face-centered cubic fluorite structure and are nanosize. La³⁺ ions can significantly improve thermal stability and efficiently retard CeO₂–ZrO₂ crystal sintering and growth. Doped CeO₂–ZrO₂ with Y³⁺ and La³⁺ has 105 and 60 m²/g surface area and 460 and 390 μmol/g OSC before and after aging. The T₅₀ of fresh Pt–Rh/CZYL/LA is 170 °C for CO, 222 °C for C₃H₈ and 189 °C for NO, and shift to 205, 262 and 228 °C after hydrothermal aging, which are better than those of Pt–Rh/CZY/LA or Pt–Rh/CZL/LA. WGS and SR are relate to the OSC of oxygen storage materials and absorbed oxygen species on the catalyst surface and affect the three-way catalytic activities of catalysts. The reductive property of noble metals and the dissociatively adsorbed O₂ on the surface of catalysts are closely related to the catalytic activities.