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We have developed a revolutionary automotive catalyst that maintains high activity by the suppression of grain growth of precious metals. This catalyst contains Pd-perovskite crystal which has shown a capacity for self-regeneration of Pd in a cycle of solid solution and segregation in perovskite crystals [1, 2, 3, 4, 5 and 6]. We named this catalyst the “Intelligent Catalyst” and first commercialized it in the Japanese market in October 2002 [7, 8]. In this study, we investigated the activity of Pd at various temperatures to confirm that the self-regenerative mechanism worked well at low temperatures like those right after engine starting. We also examined the durability of perovskite structure at high temperatures and tested its catalytic activity after engine aging at high temperatures above 1000 °C up to 1100 °C. It is proved that the intelligent catalyst has both excellent activity and durability under practical conditions.

The catalyst of the crystalline ceramics known as a perovskite-type oxide was designed and controlled at the atomic level in order to create a new function for self-regeneration of precious metals in a usage ambience without auxiliary treatment. We have already reported that a catalyst with Pd supported on the perovskite-type oxide has higher activity than a catalyst with Pd supported on alumina. It was also found that Pd supported on the perovskite catalyst is finely dispersed [1, 2 and 3] The object of this study was to investigate the mechanism of self-regeneration by using hyper-analytical facilities. XAFS analysis, at SPring-8 (8 GeV), revealed that Pd is in six-fold coordinations with oxygen in a perovskite crystal, which indicating that Pd occupies the B site of the unit formula of ABO3 in the perovskite crystal structure under oxidation atmosphere.