DIESEL PARTICULATE FILTER

Abstract

Walls forming exhaust gas channels in a DPF are coated with a catalyst layer for promoting the burning of particulates trapped thereon. The catalyst layer contains alumna and a composite oxide containing Ce as a major component and rare earth metal other than Ce or alkali earth metal. Pt is loaded on the alumina and the composite oxide.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exhaust gas purification system for a diesel engine.

FIG. 2 is a front view schematically showing a DPF.

FIG. 3 is a vertically cross-sectional view schematically showing the DPF.

FIG. 4 is an enlarged cross-sectional view schematically showing a wall that separates an exhaust gas inflow channel from an exhaust gas outflow channel in the DPF.

FIG. 5 is a conceptual diagram illustrating an example of the structure of components contained in a catalyst layer in the DPF.

FIG. 6 is a graph showing carbon burning rates of various oxides on which Pt is loaded.

FIG. 7 is a graph showing the exhaust gas purification performance of the DPF according to an embodiment of the present invention using a Ce—Sm composite oxide.

FIG. 8 is a graph showing the carbon burning rate of the DPF according to the above embodiment.

Claims

1. A diesel particulate filter, disposed in an exhaust passage of a diesel engine, for trapping particulates exhausted from the engine, wherein walls forming exhaust gas channels in a filter body on which the particulates are trapped are coated with a catalyst layer for promoting the burning of the trapped particulates,the catalyst layer contains alumina and a composite oxide containing Ce as a major component and rare earth metal other than Ce or alkali earth metal, andPt is loaded on the alumina and the composite oxide.

2. The diesel particulate filter of claim 1, wherein the ratio of the amount of Pt loaded on the alumina to the total amount of Pt loaded on the composite oxide and Pt loaded on the alumina is not less than 35 mass %.

3. The diesel particulate filter of claim 2, wherein the ratio is not more than 90 mass %.

4. The diesel particulate filter of claim 1, wherein Pd is further loaded on the alumina on which Pt is loaded.

5. The diesel particulate filter of claim 1, wherein the rare earth metal comprises at least one selected from Sm and Gd.

6. The diesel particulate filter of claim 4, wherein the rare earth metal comprises at least one selected from Sm and Gd.

7. The diesel particulate filter of claim 1, wherein the alkali earth metal comprises at least one selected from Mg, Ca, Sr and Ba.

8. The diesel particulate filter of claim 4, wherein the alkali earth metal comprises at least one selected from Mg, Ca, Sr and Ba.

9. The diesel particulate filter of claim 5, wherein the alkali earth metal comprises at least one selected from Mg, Ca, Sr and Ba.

10. The diesel particulate filter of claim 6, wherein the alkali earth metal comprises at least one selected from Mg, Ca, Sr and Ba.