Catalytic Oxidation of Soluble Organic Fraction in Diesel Exhausts Using Composite Oxides (CeO2)x(La-Al2O3)1-x

A series of catalytic composite oxides (CeO2)(x)-(La-Al2O3)(1-x) (with mass fractions x=0.00, 0.25, 0.50, 0.75, 1.00) was prepared using a co-precipitation method. Thermogravimetric-differential thermal analysis (TG-DTA) was used to determine the performances of these composite oxides in the catalytic oxidation of the soluble organic fraction (SOF) of diesel exhaust. The results show that the catalyst with the highest activity, i.e., x=0.75, enabled the SOF to light-off at 125 degrees C and completely converted the SOF at 355 degrees C. The catalysts were characterized using low-temperature N-2 absorption-desorption, oxygen-storage capacity (OSC) measurements, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and H-2 temperature-programmed reduction (H-2-TPR). The results indicate that co-doping appropriate amounts of La and Al into the catalyst increases the specific surface area of the cerium oxide and the proportion of Ce3+ in the catalyst. This may improve the catalyst's adsorption abilities at low temperature and its OSC, enhancing its activity in SOF oxidation. These (CeO2)(0.75)(La-Al2O3)(0.25) composite oxides are promising catalysts for diesel oxidation.