CO oixdation on CeO2-ZrO2 solid solution prepared by sol-gel technique under oxidizing and reducing conditions

Abstract

The promotive effects of ceria (CeO2)/zirconia (ZrO2) mixed oxides on commercial three-way catalysts (TWC) for purification of motor exhaust gases have been investigated in recent years. This work presented the cooperative effects of CeO2-ZrO2 mixed oxides prepared by urea hydrolysis on the CO conversion under oxidizing and reducing conditions. The ZrO2 contents investigated were varied between 25 and 100% mol. Noteworthy is that the versatility of the sol-gel technique allows for control of the composition, homogeneity particles and higher BET surface areas compared to conventional methods. The homogeneous nanometer-sized particles were observed using a scanning electron microscopy (SEM). From the results of an X-ray diffraction (XRD) and FT-Raman spectroscopy, the solid solutions were observed even though the catalysts were prepared at a low temperature (ca 100℃). Temperature-programmed reduction (TPR) in a H2/N2 mixture of the solid solutions revealed that the incorporation of ZrO2 into CeO2 lattice strongly promoted bulk reduction of the solid solutions, resulting in a CO conversion at low temperatures. In has been proposed that CeO2-ZrO2 mixed oxides would be one of the best supports for the TWC applications.