To provide a catalyst system for use in an exhaust emission control device for automobiles which exhibits an excellent cleanability for nitrogen oxide by bringing an exhaust gas emitted from an internal combustion engine of an automobile into contact with a catalyst even in the case where hydrocarbon concentration is fluctuated, an exhaust emission control device using the same and an exhaust emission control method using the catalyst system.
The catalyst system comprises two or more exhaust emission control catalysts including a first catalyst 2 deposited on an inorganic structural carrier and a second catalyst 3 different from the former and the first catalyst is deposited in a portion of the inorganic structural carrier positioned in the upstream side in the case where the catalyst is arranged in an exhaust gas channel and on the other hand, the second catalyst is deposited in a portion of the inorganic structural carrier positioned in the downstream side in the case the catalyst is arranged in an exhaust gas channel and the catalyst system for use in an exhaust emission control device for automobiles contains a cerium-zirconium composite oxide (A) obtained by heating and melting a raw material mixture at a melting point or higher and successively crushing an ingot formed by cooling the melted raw material mixture.
HIRASAWA YOSHIAKI
KATO KATSUAKI
NE CHEMCAT CORP
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