Preparation and Characterization of Co0.2/Ce1-xZrxO2 Catalysts and Their Catalytic Activity for Soot Combustion

Abstract

A series of Ce1-xZrxO2 (x = 0, 0.2, 0.4, 0.5) solid solutions were prepared by the micropore-diffused coprecipitation method with ammonia solution as precipitation agent. Co0.2/Ce1-xZrxO2 catalysts were prepared by the ultrasound-assisted incipient-wetness impregnation method. The effect of the Ce/Zr molar ratio on the catalytic activity for soot combustion was investigated. The Co0.2/Ce1-xZrxO2 catalysts gave very high activity for soot combustion under loose contact conditions between soot and catalyst, and the catalytic activity of Co0.2/Ce0.8Zr0.2O2 catalyst was the highest for the soot combustion, whose T10, T50, T90, and SmCO2 were 316 °C, 385 °C, 413 °C, and 99.9%, respectively. Compared with when there was no catalyst, T10, T50, and T90 decreased by 136, 197, and 226 °C, respectively, and SmCO2 increased by 45.9%. This catalytic activity for soot combustion is as good as that of supported Pt catalysts, which was the best catalyst system so far reported for soot combustion under loose contact conditions. All the samples were characterized by the X-ray diffraction, transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV-Vis diffuse reflectance spectroscopy. The results showed that nanometer Ce1-xZrxO2 solid solution supports can be prepared by the micropore-diffused coprecipitation method. The average particle size of the Ce1-xZrxO2 solid solutions was about 10 nm. Doping Zr affected the dispersion of Co over the Ce1-xZrxO2 solid solutions. The right Ce/Zr molar ratio was beneficial in enhancing the catalytic activity. Temperature-programmed reduction with hydrogen measurements showed that the Co0.2/Ce0.8Zr0.2O2 catalyst had the lowest reduction temperature (203 and 298 °C), which was in good agreement with its best catalytic activity.