Abstract:

CeO₂-ZrO₂ and CeO₂-ZrO₂-La₂O₃ catalysts with mass ratios of 60:40 and 60:30:10 were prepared by co-precipitation method, respectively. The catalytic activity in oxidation of the soluble organic fraction (SOF) in diesel exhausts was studied using thermogravimetric-differential thermal analysis (TGDTA). The results indicate that the catalytic activity of the La-modified CeO₂-ZrO₂ catalyst is better than that of the CeO₂-ZrO₂ catalyst; the light-off temperature of SOF is 164 ℃, and the weightlessness fastest point temperature is 212 ℃, whereas for CeO₂-ZrO₂, these temperatures are 168 and 221 ℃, respectively. X-ray diffraction (XRD) shows that modification with La is beneficial to decrease the growth rate of the crystallite size relative to that of CeO₂-ZrO₂ after high-temperature ageing. N₂ adsorption-desorption results suggest that the addition of La enlarges the surface area. O₂-temperature-programmed desorption (O₂-TPD) and X-ray photoelectron spectroscopy (XPS) show that modification with La increases the amount of chemisorbed oxygen on the CeO₂-ZrO₂ catalyst. The CeO₂-ZrO₂-La₂O₃ catalyst shows better activity and ageing resistance than the CeO₂-ZrO₂ catalyst.

Key words: CeO₂-ZrO₂, La-modified CeO₂-ZrO₂, Soluble organic fraction, Diesel oxidation catalyst, Chemisorbed oxygen