Preparation of Ce Zr_1- O₂ by Different Methods and Its Catalytic Oxidation Activity for Diesel Soot

Novel Ce Zr_1- O₂ (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, N₂ adsorption-desorption, FT-IR, TEM, XPS, H₂-temperature programmed reduction (TPR), and O₂-temperature programmed desorption (TPD) techniques. The results indicated that Ce_0.8Zr_0.2O₂ 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 H₂-TPR results reveal that the structure and oxygen adsorption properties are crucial to soot oxidation activity, and Zr⁴⁺ is successfully doped into the CeO₂ lattice and forms a homogeneous solid solution. Nanostructured Ce_0.8Zr_0.2O₂ with 110.2 m²/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.