Preparation methods and thermal stability of Ba-Mn-Ce oxide catalyst for NO(x)-assisted soot oxidation.

Manganese oxide-loaded and -doped ceria as well as the corresponding barium-modified oxide catalysts were prepared for soot oxidation in the presence of NO(x), and were characterized by using X-ray diffraction, Brunauer-Emmett-Teller and NO temperature-programmed oxidation measurements. The activity of catalyst depended strongly on the NO2 production capacity, and the importance of surface nitrates was weakened without heat transfer limitations. The formation of perovskite-type oxides after the high-temperature calcination caused the loss of NO(x) storage capacity for the Ba-modified catalysts, but did not seem to affect the NO oxidation activity obviously. The addition of barium did not prevent the phase separation of MnO(x)-CeO2 solid solutions, whereas it inhibited the sintering of oxide crystallites effectively. This, as well as the relatively high surface area, resulted in a small increase in soot oxidation temperature for the thermally aged Ba/Mn-Ce catalyst.