| 摘要 |
PURPOSE: Provided is an exhaust gas purification catalyst, which is capable of enhancing the NOx absorption efficiency of a NOx absorbent material, i.e., the lean NOx purification rate, in an environment of excess oxygen of high-level exhaust gas oxygen concentration while achieving an improvement in total exhaust gas purification efficiency, by providing an improved oxygen storage material in the lean NOx purification catalyst. CONSTITUTION: In a catalyst for exhaust gas purification which comprises (a) a NOx absorbent material which absorbs NOx in an exhaust gas in an environment of excess oxygen whose exhaust gas oxygen concentration level is high, whereas, when the exhaust gas oxygen concentration level becomes lower in a given temperature range, the NOx absorbent material releases the absorbed NOx and (b) a precious metal, the exhaust gas purification catalyst further comprises an oxygen storage material which releases a larger amount of oxygen in the given temperature range in comparison with other temperature ranges. As a result of such arrangement, the NOx absorption efficiency of the NOx absorbent material in an environment of excess oxygen of high exhaust gas oxygen concentration level, i.e., the lean NOx purification rate thereof, can be improved.
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