| 摘要 |
PROBLEM TO BE SOLVED: To further improve NOx removing performance, suppress the poisoning of the NOx absorbing material with sulfur, and improve the durability by controlling the portion of a catalyst bearing layer existing within a specified depth from the surface to be a specified ratio or higher in the whole volume of the catalyst bearing layer. SOLUTION: In this exhaust gas purifying catalyst, the portion existing within 10 μm depth from the surface is controlled to be 80% or more of the whole volume of the catalyst bearing layer 2. Consequently, the contacting ratio of an exhaust gas with an NOx absorbing material and a catalyst noble metal is kept high and the NOx absorbing performance at the time of lean burning and the NOx desorbing and reducing performance at the time of pulsed rich burning are enhanced, so that NOx removing performance can be improved. Moreover, though sulfate is generated by the reaction of the NOx absorbing material and SOx , the exhaust gas and the sulfate are smoothly brought into contact with each other even at the time of pulsed rich burning, and consequently, SO2 is released from the sulfate before the sulfate crystal is grown and reduced to S and, at the same time, NOx absorbing performance of the NOx absorbing material is recovered. |
