| 摘要 |
PURPOSE: To obtain an NOx occlusion material excellent in heat resistance in an excess oxygen atmosphere and exhibiting excellent NOx occluding power even at a high temp. by carrying each specific quantity of silver, at least one kind of alkaline earth metal elements and at least one kind of platinum group elements on an alumina based metal oxide carrier. CONSTITUTION: This nitrogen oxide occlusion composition used for a purifying device of nitrogen oxides contained in the exhaust gas discharged from internal engine or the like is prepared by carrying 5-40wt.% silver, 5-40wt.% at least one kind of alkaline earth metal elements and 0.05-8wt.% at least one kind of platinum group elements expressed in terms of metal per total weight of the carrier and the carried components on the alumina based metal oxide carrier. In the carried components, sum of the contents of silver and at least one kind of alkaline earth metal elements is controlled to 10-50wt.%. Nitrogen oxides in the exhaust gas is removed by providing an NOx occlusion material- containing layer on the upstream side of the exhaust gas flow and a ternary catalyst on the downstream side. |
