Modification of CeO2-ZrO2 catalyst by potassium for NOx-assisted soot oxidation.

Potassium-modified ceria-zirconia catalyst was synthesized by wetness impregnation method. The ageing treatment was performed in static air at 800degrees C for 20 hr to evaluate the thermal stability of the catalyst. The catalysts were characterized by X-ray diffraction, BET surface area, oxygen storage capacity, NO(x)-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (T(m)) of the ceria-zirconia based catalyst decreased from 525 to 428 degrees C in the presence of NO under a loose contact mode. The shift of T(m) of the K-modified catalyst after ageing is only 15 degrees C. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NO(x)/oxygen storage capacity as well as the soot-catalyst contact.