| 摘要 |
PROBLEM TO BE SOLVED: To prevent NOx purification performance after being exposed at a high temperature of at least 700 deg.C from being decreased and to prevent especially NOx purification performance in a low temperature region of at most 350 deg.C from being decreased. SOLUTION: This catalyst comprises a carrier with ZrO2 as the main ingredient, a strontium compound with a crystalline particle diameter of at most 40 nm carried on the carrier and a noble metal carried on the carrier. As solid phase reactivity between ZrO2 and the strontium compound is low, stabilization of the strontium compound is suppressed. In addition, the crystalline particle diameter of the strontium compd. is at most 40 nm, being extremely fine. Therefore, as the surface area is large, activity is improved and as it is suppressed to bring ZrO2 particles into contact with each other, sintering is suppressed and as sulfate salt is easily decomposed, poisoning with sulfur is also suppressed. |
