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 800°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, NOx-temperature programmed desorption and soot-temperature programmed oxidation measurements. By introduction of potassium, the maximum soot oxidation rate temperature (Tm) of the ceria-zirconia based catalyst decreased from 525 to 428°C in the presence of NO under a loose contact mode. The shift of Tm of the K-modified catalyst after ageing is only 15°C. The enhanced activity of the aged catalyst mainly lies in the promotional effect of potassium on the NOx/oxygen storage capacity as well as the soot-catalyst contact.