초록 ▼

A particulate matter-oxidizing material which enhances the rate of oxidizing the particulate matter at low temperatures (not higher than about 300�� C.), and of which the action for purifying NOx by reduction at high temperatures (not lower than about 500�� C.) is not impaired by the oxidizing actio

A particulate matter-oxidizing material which enhances the rate of oxidizing the particulate matter at low temperatures (not higher than about 300�� C.), and of which the action for purifying NOx by reduction at high temperatures (not lower than about 500�� C.) is not impaired by the oxidizing action. The oxidizing material contains a cerium-zirconium composite oxide for purifying, by burning, the particulate matter in the exhaust gas from a lean-burn internal combustion engine, wherein the cerium-zirconium composite oxide contains cerium in an amount of 0.1 to 20 mol % based on the total mol number of metal atoms that are contained. Desirably, the cerium-zirconium composite oxide further contains at least one kind of metal (M) selected from the rare earth metals (excluding cerium), and the molar ratio of M/Ce is 0.1 to 10.

대표청구항 ▼

The invention claimed is: 1. A particulate matter-oxidizing material, comprising: a cerium-zirconium composite oxide for purifying, by burning, the particulate matter in the exhaust gas from a lean-burn internal combustion engine, wherein a lean-burn condition of a high air-fuel ratio is establishe

The invention claimed is: 1. A particulate matter-oxidizing material, comprising: a cerium-zirconium composite oxide for purifying, by burning, the particulate matter in the exhaust gas from a lean-burn internal combustion engine, wherein a lean-burn condition of a high air-fuel ratio is established for the steady operation and an instantaneous burning condition of a low air-fuel ratio is established intermittently, the cerium-zirconium composite oxide represented by the formula: description="In-line Formulae" end="lead"CenZr1-nO2 description="In-line Formulae" end="tail" wherein n is a number from 0.035 to 0.07. 2. The particulate matter-oxidizing material according to claim 1, further comprising: a cerium-free oxide, wherein a mass ratio of cerium-zirconium composite oxide/cerium-free oxide is from about 2/8 to about 8/2. 3. A particulate matter-oxidizing material, comprising: a cerium-zirconium composite oxide for purifying, by burning, the particulate matter in the exhaust gas from a lean-burn internal combustion engine, wherein a lean-burn condition of a high air-fuel ratio is established for the steady operation and an instantaneous burning condition of a low air-fuel ratio is established intermittently, the cerium-zirconium composite oxide represented by the formula: description="In-line Formulae" end="lead"MxCenZr1-n-xO2 description="In-line Formulae" end="tail" wherein: x is a number from 0.01 to 0.20; n is a number from 0.35 to 0.07; and M is at least one metal selected from the group consisting of the rare earth metals, excluding cerium. 4. The particulate matter-oxidizing material according to claim 3, wherein M is selected from the group consisting of lanthanum, samarium, neodymium, gadolinium, scandium, and yttrium. 5. The particulate matter-oxidizing material according to claim 3, wherein a molar ratio of M/Ce is in the range of 0.1 to 10.