Preparation of Ce_xZr_1–xO₂ by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot

Abstract

Novel Ce x Zr 1– x O 2 ( x = 0.67, 0.8, 0.9, 1.0) catalysts were designed and synthesized by solvothermal, calcination, and sol–gel methods and were used to catalyze oxidation of soot from diesel vehicle exhaust. The influence of catalysts synthesized by different methods and Ce/Zr molar ratios on the performance was investigated. These catalysts were characterized by XRD, N 2 adsorption–desorption, FT-IR, TEM, XPS, H 2 -temperature programmed reduction (TPR), and O 2 -temperature programmed desorption (TPD) techniques. The results indicated that Ce 0.8 Zr 0.2 O 2 prepared by the calcination method has excellent activity and stability at low temperature. The soot ignition point is 322 °C, and the ratio of soot conversion reaches 90% at 497 °C, which is lower than that from the solvothermal and sol–gel methods. The XRD, Raman, SEM, XPS and H 2 -TPR results reveal that the structure and oxygen adsorption properties are crucial to soot oxidation activity, and Zr 4+ is successfully doped into the CeO 2 lattice and forms a homogeneous solid solution. Nanostructured Ce 0.8 Zr 0.2 O 2 with 110.2 m 2 /g surface areas is produced. The proportion of chemical oxygen and surface adsorbed oxygen in the catalyst prepared from the calcination method is the highest at 23.18%. The structure may lead to charge imbalance, unsaturated bonds, and oxygen vacancies, thus increasing the adsorption of oxygen on the catalyst surface.