F2008-06-058
Development of High-Performance Catalyzed DPF with New Soot Burning Mechanism
In application of the catalyzed DPF (Diesel Particulate Filter), which is effective in reduction of soot contained in exhaust gas of a diesel engine, DPF regeneration with the engine control has been required to burn the soot accumulating with specific amount in the DPF. It is necessary to shorten duration time and reduce frequency for the DPF regeneration. Therefore, high soot burning rate has been needed for a coated catalyst of the catalyzed DPF. In previous researches, it had been found out that lattice oxygen released from inside of the catalysts such as oxygen storage materials as typified by Ce-based Oxides was efficient in the soot burning. In this study, the new catalyst that was free from elements causing valence variation was developed to improve the soot burning performance. The developed catalyst indicated higher carbon burning performance than conventional catalysts in the gas condition with and without NOx. Additionally, the developed catalyst had the property that the carbon burning performance hardly degraded even with low PGM loading and high thermal durability. It was confirmed that the developed catalyst indicated superior effect to the conventional catalysts on the soot burning performance in real exhaust gas condition with the engine. As a result of characterization to investigate the mechanism of the developed catalyst to improve the soot burning, it was indicated that the developed catalyst had a new soot burning mechanism. As a result of evaluation of the lattice oxygen release using isotopic oxygen, the amount of the released lattice oxygen for the developed catalyst was more than the conventional catalysts. Thus, the developed catalyst promoted release of the lattice oxygen existing inside of the catalyst particles effectively as well as the lattice oxygen in the vicinity of surface of the catalyst particles. Additionally, the possibility that oxygen ion conductivity caused the soot burning was verified. As a result of measurement of current inside of the catalyst during the carbon burning, the current was detected only for the developed catalyst. Thus, it was presumed that the developed catalyst that was free from the elements causing the valence variation transferred the lattice oxygen inside of the catalyst with the oxygen ion conductivity and promoted the soot burning.
Session: Exhaust Gas Aftertreatment