| 摘要 |
<p>It is aimed at ensuring a NOx decreasing capability over a wide temperature range from low to high temperatures. A first catalytic layer (11a), which is formed to be porous for allowing an exhaust gas to pass therethrough, is provided in an exhaust passage, and a second catalytic layer (11b),which is formed to be porous for allowing the exhaust gas to pass therethrough, is stacked on the exhaust-gas downstream-side surface of the first catalytic layer. The first catalytic layer comprises an iron-zeolite catalyst to exhibit catalytic activity to decrease 60% or more of NOx contained in the exhaust gas within an exhaust-gas temperature range of 150 to 400°C. The second catalytic layer comprises one or more kinds of a single catalyst, a mixed catalyst, and a complex oxide catalyst selected from a group consisting of iron-alumina, iron-zirconia, iron-ceria, andiron-titania, in a manner to exhibit catalytic activity to decrease 60% or more of NOx contained in the exhaust gas within an exhaust-gas temperature range of 400 to 700°C. Both the first and second catalytic layers cooperatively exhibit catalytic activity to decrease 70% ormore of NOx contained in the exhaust gas within an exhaust-gas temperature range of 150 to 700°C.</p> |
