Abstract
Keywords: Soot, Particulate Trap, Catalyst, Soot Burning Mechanism, Active Oxygen
In application of the catalyzed DPF (Diesel Particulate Filter) effective in reduction of soot contained in an exhaust gas of a diesel engine, DPF regeneration control is necessary to burn the soot trapped with specific amount in the DPF. To improve the fuel economy during the regeneration, shortening duration and reducing frequency are required. Thus, high soot burning rate has been needed for a coated catalyst on the DPF. In the previous studies [1-4], it was cleared that active oxygen released from the catalysts such as oxygen storage materials as typified by CeO2-based oxides via oxygen exchange reaction was efficient in the soot burning.
In this study, the new catalysts different from CeO2-based catalysts were developed. The catalysts indicated high carbon burning performance and superior thermal durability. Characterizations indicated that the developed catalysts had a new soot burning mechanism. As a result of the evaluation of the active oxygen related to the carbon burning from the catalyst using isotopic oxygen, the amount of the oxygen for the developed catalysts was more than the conventional catalysts. Thus, the developed catalysts released the active oxygen which was derived from the lattice of the oxides effectively as well as in the vicinity of the surface. As a result of amperometry of inside of the catalysts during the carbon burning, current was detected only for the developed catalysts. Presumably, for the developed catalysts, oxygen ion in the lattice of the oxides transferred with oxygen ion conduction and promoted the carbon burning. The test simulating the forced regeneration showed the potential that regeneration duration was shortened by ca. 40% for the developed catalyst compared with the conventional catalyst. Also, the developed catalyst indicated superior effect to the conventional catalyst on the soot burning in the engine exhaust gas condition.