| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a NOx occlusion reduction type catalyst which has a high NOx occlusion capacity in a high temperature region and can control sulfur poisoning even when exposed to SOx for a long time. <P>SOLUTION: The catalyst comprises a lower coat layer 2 which is formed from the powder of an oxide whose reactivity with a NOx occlusion material is lower than that of alumina and applied on the surface of a substrate and an upper coat layer 3 which is formed from powder mainly containing an acidic oxide and applied on the surface of the lower coat layer 2. By enriching the upper coat layer 3 with the acidic oxide, the proximity of SOx is suppressed to control the sulfur poisoning effectively. Since the lower coat layer 2 mainly contains the oxide whose reactivity with the NOx occlusion material is lower than that of alumina, the solid solution of the NOx occlusion material is controlled, and a high NOx occlusion capacity is developed in a high temperature region of at least 500°C. By the presence of the upper coat layer 3, the sulfur poisoning in the lower coat layer 2 is also controlled. <P>COPYRIGHT: (C)2004,JPO&NCIPI |
