| 摘要 |
An apparatus of a catalyst for purifying exhaust gas suitable as a three-way catalyst (TWC) apparatus to be used for purifying carbon monoxide (CO), a hydrocarbon (HC) and a nitrogen oxide (NO x ) in exhaust gas exhausted from a gasoline automobile, as well as a method for purifying exhaust gas. This apparatus is provided by an apparatus of a catalyst for purifying exhaust gas for purifying a hydrocarbon (HC), carbon monoxide (CO) and a nitrogen oxide (NO x ), by providing two or more honeycomb structure-type catalysts, wherein the surface of a honeycomb-type structure is coated with two or more layers of catalyst compositions, in a flow passage of exhaust gas exhausted from an internal combustion engine, and making exhaust gas pass, characterized in that : the honeycomb structure-type catalyst (X) positioned at the upstream side and the honeycomb structure-type catalyst (Y) positioned at the downstream side contain the catalyst composition consisting a support material of an inorganic oxide which substantially does not contain an Rh component, and loads at least one of a Pt component or a Pd component, a cerium-containing oxide, and an alkaline earth metal component, in all of the lower layers; on the other hand, the catalyst composition of the upper layer loads the Rh component on an oxide support material; does not substantially contain the Pt component and the Pd component; and has a configuration which is different in the honeycomb structure-type catalyst (X) and the honeycomb structure-type catalyst (Y).
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