Catalytic oxidation of diesel soot on mixed oxides derived from hydrotalcites

MAlO (where M = Ni2+, Co2+ and Cu2+) mixed oxides derived from hydrotalcites and potassium-promoted MAlO catalysts (designated as K/MAlO; K: 5 wt.%) have been studied for diesel soot oxidation. The catalysts were characterized by XRD, N-2 adsorption, TPR, FT-IR and TPO techniques. The hydrotalcites calcined at 800 degrees C have large surface areas in the range 17-88 m(2)/g and uniform mesoporous features, which resulted in high activity for diesel soot oxidation under the conditions of tight contact between soot and catalyst powders. Potassium increased the activity due to the improvement of surface mobility. The presence of NOx considerably enhanced the catalytic soot oxidation rate. The enhancement was attributed to the acceleration of soot oxidation due to NO2 as a strong oxidizing agent and intermediates of nitrate and/or nitrite species formed on the catalyst surface.