| 摘要 |
<p>A NOx absorbing agent, characterized in that it comprises a crystalline ZrO2 composite oxide containing at least one element of trivalent rare earth metals and divalent alkaline earth metals added thereto and, carried thereon, at least one element of alkali metals and alkaline earth metals; and an absorption reduction type catalyst for removing NOx, characterized in that it comprises the NOx absorbing agent and a noble metal. Preferably, the NOx absorbing agent further comprises aluminum carried on the ZrO2 composite oxide. The NOx absorbing agent is supposed to absorb NOx through a mechanism wherein an electron released from an alkali metal or the like is incorporated into an oxygen defect portion of the crystalline ZrO2 composite oxide and the resultant oxygen defect portion acts as a strong basic point donating an electron to an electrophilic component such as NOx. The absorption reduction type catalyst for removing NOx exhibits high performance capability of removing NOx even under a condition wherein an exhaust gas has a temperature of 500°C or higher.</p> |
