| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a catalyst for cleaning exhaust gas which has a furthermore improved early warm-up characteristic and ensures cleaning performance after warmed up. <P>SOLUTION: The catalyst for cleaning exhaust gas has an upstream-side catalyst layer 2 and a downstream-side catalyst layer 3. The weight percentage of a noble metal in the upstream-side catalyst layer 2 is made larger than that of the noble metal in the downstream-side catalyst layer 3. The formable volume of the upstream-side catalyst layer 2 per unit volume of a carrier base material is made smaller than that of the downstream-side catalyst layer 3 per unit volume of the carrier base material. Since the upstream-side catalyst layer contains more of the noble metal and the possibility that the nobel metal is brought into contact with exhaust gas in the upstream-side catalyst layer is higher, the cleaning activity of this catalyst can be improved when an engine is started. Since the formed volume of the upstream-side catalyst layer 2 is smaller than that of the downstream-side catalyst layer 3, namely, the heat capacity of the upstream-side catalyst layer becomes smaller, the early warm-up characteristic of this catalyst can be improved and the cleaning performance of this catalyst can be ensured after this catalyst is warmed up. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
