Study Of Dopant Of CE-ZR Mixed Oxides And Application In Automotive Catalysis For Purifying Exhaust Gas

In this paper, series of Ce-Zr-La-Sr mixed odixes were prepared by citric acid sol-gel. The effect of Lanthanum and Strontium on the Ce-Zr mixed oxides was studied. The mixed odixes were characterized by BET, X-ray diffraction analysis (XRD), and in the experiment of flow-system microreactor, reduction properties and oxygen storage capacity (OSC) of samples were investigated by temperature programmed reduction (TPR) and pulse technique. It was shown that the dopant of Lanthanum and Strontium helped to enhance thermal stability, low reduction temperature and oxygen storage capacity (OSC) of Ce-Zr-La-Sr mixed odixes. The dopant content of Lanthanum and Strontium were affected on the properties of Ce-Zr mixed oxides, and there was the optimum content of Lanthanum and Strontium in the mixed odixes. The Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 mixed oxide had the largest specific surface area, and better reduction properties and better oxygen storage capacity. The XRD pattern of mixed oxides showed that the diffraction patterns of samples were well in agreement with that of the fluorite-type CeO₂. With the rising of calcined temperature of Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 mixed oxide, increase of the diffraction peak intensity was observed in XRD spectra, while new peaks cannot be found. Results of BET and X-ray diffraction analysis indicated that the Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 mixed oxide synthesized had good thermal stability.At the same time the effect of Ce₀.6Zr₀.4O₂, Ce₀.55Zr₀.4La₀.05O₁.975 and Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 on noble metal catalysts were investigated in the paper. The effect of Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 mixed oxide on the noble metal catalyst was best in the studied mixed oxides. The CO conversion temperture of the Pt-Rh-Pd/Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945/Al₂O₃ catalyst Calcined for 10h at high temperature rose less comparing with other catalysts. It was shown that Ce₀.52Zr₀.4La₀.05Sr₀.03O₁.945 mixed oxide improved oxidation activity of the catalysts and enhance its thermal stability.