Prof. S. Hirano, et al. of Nagoya University developed a hexa-aluminate catalyst for cleaning exhaust gas. This self-sufficient ceramic catalyst does not need an external power source and operates in wide range of temperature from low to high temperatures with superior heat resistance. The catalyst consists of aluminum, barium, and transition metals. An inorganic metal salt solution composed of these materials is added to ammonium aqueous solution to precipitate powder. The precursor powder is preheated at about 500℃, then at 1100℃. The catalyst include unique features. This catalyst was developed in a R&D on synergy ceramic project. The catalyst is active with carbon monoxide, hydrocarbon, and NO{sub}x, when it is prepared by changing the combination and ratio of its elements. Catalysts having different activity peaks depending on humidity are be prepared. The elimination of NO{sub}x was measured with the prepared catalyst at an automobile exhaust gas flow velocity. Elimination and peak temperature were less than 40% at 470℃ and less than 400℃, less than 35% at 550℃. They target development of catalysts of higher quality for practical use by fiscal 2003.
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