CATALYST FOR CLEANING EXHAUST GAS

PROBLEM TO BE SOLVED: To produce a catalyst for cleaning exhaust gas which satisfies both of HC (hydrocarbon) purifying performance in a low temperature region and NOx purifying performance in a high load region. SOLUTION: A maldistribution part 3 having a Pd area 31 which is the outer peripheral part of this catalyst and in which Pd of high concentration is deposited and a Pt area 30 which is the inner peripheral part of the Pd area and in which Pt of high concentration is deposited is formed in this catalyst at least on the upstream side of exhaust gas. In the low temperature region, HC and CO flowing in the Pd area 31 being the outer peripheral part are oxidized by Pd and the heat of the oxidation reaction is transmitted to the inner peripheral part. Therefore, the activity of Pt in the Pt area 30 is also expressed in its early stages and the HC purifying performance in the low temperature region is improved as a whole. In a high load region such as the time when a car travels at a high speed, since exhaust gas flows mainly in the Pt area 30 existing in the inner peripheral part of this catalyst, NOx is reduced/purified efficiently by high-concentration Pt deposited in the Pt area 30. COPYRIGHT: (C)2006,JPO&NCIPI