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Deactivation Process of Close-Coupled, Three-Way Catalytic Converter-Catalysts From In-Use Vehicles and Bench-Aged One
Published May 21, 2003 by Society of Automotive Engineers of Japan in Japan
Event: JSAE Spring Conference
Deactivation of current palladium-based warm-up catalysts has been studied. The catalysts from the in-use vehicles with various mileage and engine bench-aged ones have been investigated. Two major aspects of aging process were studied; catalyst poisoning and thermal damage. The palladium particle size distribution showed that the degree of thermal damage was slightly higher at the rear part, while the accumulation of oil-derived poisons was enriched at the inlet. NMR and IR studies elucidated that majority of the phosphorous contaminants were present as aluminum phosphates within the washcoat layer, which caused the densification of the washcoat and reduced the accessibility of the reactants. The point-wise activity of the in-use catalyst showed that the activity of the inlet part was severely damaged, which is indicative of the importance of poisoning deactivation. Though the engine bench aging can simulate the thermal degradation, it could not properly express the poisoning effects of vehicles. This imposes another challenge for the development of new engine bench aging cycle with simulated oil poisoning.