Search Results

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.

We have developed a Pd-intelligent catalyst with a self-regenerative function that is realized by the passage of Pd through consecutive solid solution and segregation states in and out of a perovskite crystal, and commercialized it for the first time in the world [1, 2, 3, 4, 5, 6, 7, 8 and 9]. In this study, we investigated the self-regenerative function of Rh as an alternative for Pd, in two types of Rh-perovskite (LaFeRhO3 and CaTiRhO3), and found that a CaTiRhO3 perovskite has an excellent capacity for the self-regenerative function of Rh. In a LaFeRhO3 perovskite with a composition similar to the Pd-perovskite (LaFePdO3), Rh was fixed so stably in the perovskite structure that it hardly segregated from the perovskite even in high temperature reduction atmospheres. However, in the CaTiRhO3 perovskite, with its A2+B4+O3 formula, the amount of Rh that actually segregated increased greatly in reduction atmospheres.

We have reported the innovation of “An Intelligent Catalyst” which has the function for self-regeneration of Pd realized through the solid solution and segregation of Pd in a perovskite crystal [1, 2, 3, 4 and 5]. We have looked for a design configuration for LaFePdO3 perovskite in the washcoat by comparing single and double layer washcaots as well as different loading locations for precious metals in order to maximize the Intelligent Catalyst's function in the practical conditions. The catalysts were attached to an engine exhaust system and subjected to an accelerated aging. The bed temperature of the catalysts reached to 1050 °C. The performance of the catalysts was evaluated on the engine dynamometer. Catalytic activity and long durability were improved by development of the washcoat configuration. The optimum design of the washcoat was double-layer with a tri-metal (Pt, Rh and Pd) system. The perovskite was located in the lower layer.

With emission regulations getting tighter and tighter, catalysts will need to be active at ever lower temperatures in order to meet future standards. To meet this need, automotive catalysts are being installed closer to the engine so as to be active immediately after start-up. In this location, catalysts must have high temperature durability. In this paper, we examined a heat-resistant support material, “hexa-aluminate”, for possible use in future automotive catalysts. Catalytic activity of hexa-aluminate was more better than La added γ - alumina after redox treatment in model gas and after engine aging. Since hexa-aluminate had the excellent thermal durability, and Pd, which are supported on it, maintains finer particles than those on La added γ-alumina. We suggest that hexa-aluminate is a effective support material for automotive catalysts. More specifically, hexa-aluminate is expected to be a key technology for meeting the stringent emission standards of the future.