Zirconia-supported Cu-KNO3 catalyst:: Characterization and catalytic behavior in the catalytic combustion of soot with a NO/O2 mixture

The catalytic combustion of diesel soot was studied in the presence of catalysts: CuZrO(2), KNO(3)ZrO(2), and CuKNO(3)ZrO(2). The catalysts were prepared by impregnation of ZrO(2)center dot nH(2)O into an aqueous solution of Cu(NO(3))(2), KNO(3), or both salts simultaneously. The catalysts were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and temperature-programmed reduction (TPR). Cu(n)KNO(3)ZrO(2) catalysts present high activity, and the value of the combustion temperature decreases 200 degrees C with respect to the temperature of the process without catalyzing, with T(max) values between 370 and 380 degrees C. The activity is associated with KNO(3) presence, and the role of KNO(3) can be attributed to (i) an increase of contact between soot and the surface of the catalyst and (ii) a redox reaction in which the nitrate is reduced to nitrite by reaction with carbon and again reoxidized to nitrate. The copper contribution is associated with the reaction selectivity toward CO(2) formation.