Study of Pt-Rh/CeO2-ZrO2-MxOy (M = Y, La)/Al2O3 three-way catalysts

CeO2-ZrO2-MxOy (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 H-2-temperature-programmed reduction (H-2-TPR) and O-2-temperature-programmed desorption (O-2-TPD). The results showed that the prepared CeO2-ZrO2-MxOy 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 m(2)/g surface area and 460 and 390 mu mol/g OSC before and after aging. The T-50 of fresh Pt-Rh/CZYL/LA is 170 degrees C for CO, 222 degrees C for C3H8 and 189 degrees C for NO, and shift to 205, 262 and 228 degrees 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 O-2 on the surface of catalysts are closely related to the catalytic activities. (C) 2013 Elsevier B.V. All rights reserved.