Catalytic converter and a method for producing the catalytic converter

Abstract

A catalytic converter having an excellent purification efficiency and small pressure loss and a method for producing the same is provided. A catalytic converter comprises a catalyst coating layer which is coated on the surface of the partition walls of the honeycomb structural body having partition walls which divide and form a plurality of cells functioning as fluid passages. 10% or more of the plurality of the cells are plugged by the plug portions which are formed at the one end or the middle of the passage, the average maximum distance of image of the honeycomb structural body is 10 μm or more and the porosity of the honeycomb structural body is 40% or more, the catalyst coating layer contains at least one oxide selected from the group consisting of alumina, ceria, titania, silica and zirconia, and also a catalyst containing at least one precious metal selected from the group consisting of platinum, rhodium and palladium, or metal exchanged zeolite or vanadium is supported in the catalyst coating layer as the catalytic active constituent, the average maximum distance of image of the catalyst coating layer is 10 μm or more, and the porosity of the catalyst coating layer is 40% or more.

Description

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic partial cross section showing an embodiment of the catalytic converter of the present invention.

FIG. 2( a) is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 2( b) is a schematic enlarged front elevation showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 3 is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 4 is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 5 is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 6 is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 7( a) is a schematic partial cross section showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 7( b) is a schematic enlarged front elevation showing an embodiment of the honeycomb structural body used in the present invention.

FIG. 8 is a schematic front elevation showing the conventional catalytic converter.

FIG. 9 is a schematic front elevation showing the conventional catalytic converter.

FIG. 10 is a schematic partial enlarged view showing the conventional catalytic converter.

FIG. 11 is a schematic plan view showing an enlarged cross section of an embodiment of the catalytic converter of the present invention.

FIG. 12 is a SEM picture of a cross section of a honeycomb structural body of an embodiment of a catalytic converter of the present invention.

FIG. 13 is a schematic plan view of an enlarged cross section of a part of an embodiment of a catalytic converter of the present invention.

Claims

1. A catalytic converter comprising: a porous honeycomb structural body having partition walls which divide and form a plurality of cells functioning as fluid passages, communicating from one end face to the other end face, anda catalyst coating layer coated on the partition walls, wherein 10% or more of the plurality of the cells are plugged by plug portions which are formed at the one end or the middle of the passage, the average maximum distance of image of the honeycomb structural body is 10 μm or more and the porosity of the honeycomb structural body is 40% or more, the catalyst coating layer contains at least one oxide selected from the group consisting of alumina, ceria, titania, silica and zirconia, and also a catalyst containing at least one precious metal selected from the group consisting of platinum, rhodium and palladium, or metal exchanged zeolite or vanadium is supported in the catalyst coating layer as the catalytic active constituent, the average maximum distance of image of the catalyst coating layer is 10 μm or more, and the porosity of the catalyst coating layer is 40% or more.

2. A catalytic converter according to claim 1, wherein the average maximum distance of image of the honeycomb structural body is 40 μm or more and the porosity of the honeycomb structural body is 50% or more.

3. A catalytic converter according to claim 1, wherein the average maximum distance of image of the catalyst coating layer is 40 μm or more, and the porosity of the catalyst coating layer is 50% or more.

4. A catalytic converter according to claim 1, wherein 50% or more of the plurality of the cells are plugged by the plug portions which are formed at the one end or the middle of the passage of the honeycomb structural body.

5. A catalytic converter according to claim 1, wherein the thickness of the catalyst coating layer is 60 μm or more.

6. A catalytic converter according to claim 1, wherein the thickness of the partition wall is 0.35 mm or less.

7. A catalytic converter according to claim 1, wherein the catalyst coating layer is also coated on the inner surface of a pore of the partition wall, the amount of the catalyst coating layer coated on the inner surface of the pore of the partition wall is less than 30% by mass of the total amount of the catalyst coating layer coated on the honeycomb structural body.

8. A catalytic converter according to claim 1, wherein the catalyst coating layer comprises a plurality of layers and each layer has the different kind of the oxides contained and/or the catalytic active constituent supported.

9. A method for producing a catalytic converter comprising: coating a catalyst coating layer on the surface of partition walls of a porous honeycombs structural body having partition walls which divide and form a plurality of cells functioning as fluid passages, communicating from one end face to the other end face,the method further comprising;coating a slurry of a catalyst coating layer material, in which an organic pore forming agent are mixed, on the surface of the partition walls of the honeycomb structural body, andremoving the pore forming agent by rising temperature to a predetermined temperature during or after drying the coated catalyst coating layer material to form pores in the catalyst coating layer.