| 摘要 |
PROBLEM TO BE SOLVED: To provide a catalyst for and a method of cleaning exhaust gas in which NOx purification performance is enhanced in such even a low temperature region and a low HC/NOx ratio that sufficient cleaning capacity is not shown in the conventional catalyst and also deterioration of the catalyst is inhibited in even the hydrothermal conditions at high temperature. SOLUTION: The catalyst for cleaning exhaust gas incorporates a first catalyst layer which contains at least one kind of component selected from a group consisting of platinum(Pt), palladium(Pd) and rhodium(Rh) and contains at least one kind of component selected from a group consisting of alkali metal, alkaline earth metals and rare earth metals, a second catalyst layer which contains β-zeolite containing copper(Cu) and/or cobalt(Co) component and a third catalyst layer which contains MFI zeolite containing copper and/or cobalt component. The second catalyst layer is provided on the first catalyst layer and the third catalyst layer is provided on the second catalyst layer. The catalyst for cleaning exhaust gas is suitable used for an internal combustion engine in which air fuel ratio of exhaust gas is >=14.7 and concentration of oxygen is >=5% and HC/NOx ratio exceeds 0 and is <=10. |
