JP7404084B2 - Processing method - Google Patents

Description

The present invention relates to a method for treating a substrate having a plurality of cells.

Exhaust gas emitted from automobiles contains environmental pollutants such as hydrocarbons (HC), carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter (PM). In order to remove these environmental pollutants, various exhaust gas purifying catalysts have been developed. Such an exhaust gas purifying catalyst generally has a honeycomb-structured base material having a plurality of cells partitioned by walls, and a catalyst layer formed on the wall. When the exhaust gas supplied to the cells in the base material comes into contact with the catalyst layer, harmful components in the exhaust gas are purified by the action of the catalyst metal contained in the catalyst layer.

Examples of exhaust gas purifying catalysts include gasoline particulate filters (GPF) and diesel particulate filters (DPF) that use wall-flow type base materials.

A wash coating method can be mentioned as a method for forming a catalyst layer on the wall of the base material. The wash coat method includes a top surface coating method and a bottom surface coating method. In the bottom coating method, a honeycomb structure substrate is immersed in a container containing a slurry containing catalytic metal, and the walls are coated with the slurry by suctioning from above the substrate. Thereafter, a catalyst layer is formed by firing the base material. The bottom coating method can also be carried out when the walls of the substrate are impregnated with a metal solution.

However, in the bottom coating method, it is difficult to stably supply the slurry or metal solution into the cell, so it is necessary to prepare a larger amount of slurry or metal solution than is originally required. Therefore, a surplus will be generated in the slurry (the catalyst metal contained in the slurry) or the metal solution.

On the other hand, in the case of the top coating method, a slurry or metal solution containing a catalytic metal is placed on the top of the substrate, and the wall is coated with the slurry by suctioning from the bottom of the substrate. In this case, it becomes possible to stably supply the slurry into the cell. Similar to the bottom coating method, the top coating method can also be carried out when the walls of the substrate are impregnated with a metal solution.

Here, when the viscosity of the slurry or metal solution is low, in the top coating method, the slurry or metal solution flows into the cell before being sucked, making it difficult to perform uniform treatment. Therefore, the slurry or metal solution used in the top coating method needs to be adjusted to have a high viscosity. However, a slurry or a metal solution with high viscosity has low fluidity, so it is difficult to introduce into the cell, and even if it can be introduced into the cell, the thickness of the coating and the degree of impregnation are likely to vary. Therefore, when actually used as a catalyst for exhaust gas purification, problems such as increased pressure loss and decreased peel strength of the catalyst layer arise. Note that in the following description, "treatment" includes coating the wall of the base material with slurry and impregnating the base material with a metal solution.

Patent Document 1 discloses that a water-soluble thin film is arranged so as to cover the upper end surface of a base material, a raw material slurry is held in a storage part by the water-soluble thin film, and the water-soluble thin film is held by the pressure difference between the flow path and the storage part. A technique has been disclosed in which the raw material slurry is introduced into the flow path of the base material by breaking the base material.

Japanese Patent Application Publication No. 2018-103131

However, according to the technique disclosed in Patent Document 1, the raw material slurry is introduced into the channel (cell) of the base material by breaking the water-soluble thin film, and therefore the water-soluble thin film cannot be reused. Therefore, each time a single exhaust gas purification catalyst is manufactured, it is necessary to place a new water-soluble thin film on the base material, which is complicated.

An object of the present invention is to provide a slurry or metal solution containing a catalytic metal on the top surface of a base material, and to process the wall of the base material with the slurry or metal solution, the work is simple, and the slurry or metal solution The object of the present invention is to provide a processing method capable of reducing the surplus of.

The invention to achieve the above object is a treatment method for a base material having a plurality of cells partitioned by walls, the base material being arranged so that the openings of the cells face upward, and the bottom surface of the base material having a plurality of cells partitioned by walls. A container formed of a member having holes is placed on the upper end of the base material, and a predetermined amount of slurry or metal solution is supplied into the container to create a pressure difference between the inside of the cell and the inside of the container. In this processing method, the slurry or the metal solution is introduced into the cell from the opening through the bottom of the container to treat the wall.
Other features of the present invention will become clear from the description and drawings described below.

According to the present invention, when a slurry or metal solution containing a catalytic metal is disposed on the upper surface of a base material and the wall of the base material is treated with the slurry or metal solution, the work is simple, and the slurry or metal solution surplus can be reduced.

It is a figure showing the base material concerning an embodiment. It is a figure showing the cross section of the base material concerning an embodiment. It is a figure showing a container concerning an embodiment. FIG. 2 is a diagram for explaining a processing method according to an embodiment. FIG. 2 is a diagram for explaining a processing method according to an embodiment.

<Embodiment>
Hereinafter, preferred embodiments of the present invention will be described in detail using the accompanying drawings, but the present invention is not necessarily limited thereto. Note that the objects, features, advantages, and ideas of the present invention will be apparent to those skilled in the art from the description of this specification, and those skilled in the art will be able to easily reproduce the present invention from the description of this specification. can. The embodiments and specific examples of the invention described below indicate preferred embodiments of the invention and are provided for illustration or explanation, and the invention is not limited thereto. It is not limited. It will be apparent to those skilled in the art that various changes and modifications can be made based on the description herein within the spirit and scope of the present invention disclosed herein.

==Base material==
The base material 1 is a structure that serves as a skeleton of an exhaust gas purifying catalyst. FIG. 1 is a perspective view of the base material 1, and FIG. 2 is a diagram showing a part of a cross section of the base material 1.

As shown in FIG. 1, the base material 1 is a cylindrical member. The base material 1 has a structure having a plurality of cells C partitioned by walls W. The cell C is a flow path for exhaust gas, and as shown in FIG. 2, it extends along the longitudinal direction of the base material 1. In this embodiment, the base material 1 is a wall flow type structure. In the case of a wall flow type structure, as shown in FIG. 2, the plurality of cells C are inflow cells CI whose openings on the exhaust gas outflow side are sealed, or outflow cells CO whose openings on the exhaust gas inflow side are sealed. It will be one of the following. The inflow cell CI and the outflow cell CO are separated by a porous wall. For example, the surface of the wall W of the inflow cell CI is coated with a slurry S containing a catalyst metal by a treatment method described below.

The size (diameter, length) of the base material 1 and the number of cells C are not particularly limited. Further, the base material 1 may be an elliptical or polygonal structure.

The material for the base material 1 preferably has high heat resistance. More specifically, the materials of the base material 1 include aluminum oxide (Al ₂ O ₃ ), cerium oxide (CeO ₂ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), silicon oxide (SiO ₂ ), Oxide ceramics such as aluminum titanate (Al ₂ TiO ₅ ) are preferred. Further, as other materials, composite oxide ceramics such as cordierite (2MgO.2Al ₂ O ₃ .5SiO ₂ ) and carbide ceramics such as silicon carbide (SiC) are also preferable. On the other hand, as the material of the base material 1, it is also possible to use an alloy such as stainless steel in addition to ceramics.

Note that the base material 1 may be a straight flow type structure in which both ends of the cells C are open. In the case of a straight flow type structure, for example, the surfaces of the walls W of all cells are coated with a slurry S containing a catalyst metal by a treatment method described later. Alternatively, a structure (HAC: High Ash Capacity) in which the cell C has a different diameter on the exhaust gas inflow side and the exhaust gas outflow side may be used as the base material 1. Further, the base material 1 may have a honeycomb structure composed of a plurality of regular hexagonal prism cells.

==Slurry, metal solution==
Slurry S is a paste-like suspended material in which a catalyst metal and a support are dispersed in an aqueous solvent such as water. Note that, in addition to the catalyst metal and the carrier, the slurry S may contain additives such as a thickener, metal elements other than the catalyst metal, and the like.

A catalytic metal is a metal that functions as an oxidation catalyst or a reduction catalyst. Specific examples include rhodium (Rh), palladium (Pd), platinum (Pt), ruthenium (Ru), osmium (Os), iridium (Ir), silver (Ag), gold (Au), and the like. Alternatively, an alloy of these catalyst metals can also be used. Among these, rhodium with high reduction activity, palladium and platinum with high oxidation activity are preferred, and combinations of two or more of these are more preferred.

The carrier is a support for the catalytic metal. A specific example is a ceramic body. In particular, a porous ceramic body having a large specific surface area and excellent heat resistance is preferred. Examples of the porous ceramic body include alumina (Al ₂ O ₃ ), ceria (CeO ₂ ), titania (TiO ₂ ), zirconia (ZrO ₂ ), and silica (SiO ₂ ). Alternatively, it may be a solid solution of these porous ceramic bodies (for example, ceria-zirconia composite oxide (CZ composite oxide)) or a combination of a plurality of porous ceramic bodies.

A metal solution is a transparent liquid in which a metal such as nickel (Ni) or barium (Ba) is dissolved in an aqueous solvent such as water.

Here, the treatment method described in this embodiment includes introducing slurry S into the cell C and coating the wall W, or introducing a metal solution into the cell C and coating the inside of the base material 1 through the wall W. Impregnate. Therefore, it is preferable that the viscosity of the slurry S or the metal solution is low. For example, the viscosity of the slurry S or metal solution is preferably 4.0 to 3000.0 mPas. Further, in relation to the shear rate, it is preferable that the viscosity at a shear rate of 6 seconds ^-1 is 500.0 to 1500.0 mPas, and the viscosity at a shear rate of 9 seconds ^-1 is 500.0 mPas or less.

==Container==
The container 2 temporarily stores the slurry S or metal solution to be introduced into the cells C of the base material 1 . As shown in FIG. 3, the container 2 is a cylindrical member having a bottom surface B. As shown in FIG. The upper side of the container 2 is open.

The bottom surface B of the container 2 is formed of a member having a plurality of holes. The member forming the bottom surface B is stainless steel, Teflon (registered trademark), or a resin material. Note that the member forming the bottom surface B preferably has water repellency. If the material itself is not water repellent, such as stainless steel, water repellent treatment may be applied.

The hole is, for example, a round hole, an oval hole, or a rectangular hole. The plurality of holes can be formed by various methods. For example, a plurality of holes can be formed by punching or laser processing the member forming the bottom surface B. Furthermore, when the member forming the bottom surface B is made of a resin material, the holes can also be formed by injection molding.

In the case of round holes, the diameter of one round hole is preferably 150.0-1200.0 μm. In the case of an oval hole, it is preferable that the major axis of one oval hole is 4000.0 μm and the short axis of 350.0 to 450.0 μm.

Further, the aperture ratio of the holes on the bottom surface B is preferably 18.3% to 40.3%.

==Processing method==
The treatment method of the present invention is a method of introducing a slurry into a cell and coating the cell wall, or a method of introducing a slurry into a cell and impregnating a metal into a base material through the cell wall. 4A and 4B are schematic diagrams illustrating a method of coating the walls of a cell. In FIGS. 4A and 4B, a cross section of the base material 1 and a cross section of the container 2 are shown. Note that the processing method described below is executed by a dedicated system.

In the method of coating the walls of the cells, first, the base material 1 is placed vertically so that the opening of the inflow cell CI faces upward. Then, the container 2 is placed on the upper end of the base material 1. Note that the lower end (the other opening side) of the base material 1 is attached to the suction device 3 (see FIG. 4A).

Next, a predetermined amount of slurry S is supplied into the container 2 placed on the base material 1 . The predetermined amount is an amount that is just enough to coat the surface of the wall W of the base material 1 with the slurry S. The predetermined amount is set in advance according to the length and diameter of the cell C.

Here, the bottom surface B of the container 2 is formed of a member having a plurality of holes. Therefore, even if the slurry S is supplied into the container 2, if the diameter and opening ratio of the holes are set appropriately (for example, diameter: 150.0-1200.0 μm, opening ratio: 18.3-40. 3%), the slurry S does not flow out into the cell C under its own weight.

Next, by driving the suction device 3 to suck the air inside the inflow cell CI (see the arrow in FIG. 4A), the inside of the inflow cell CI is made to have a negative pressure. By creating a negative pressure inside the inflow cell CI, the slurry S in the container 2 is introduced into the inflow cell CI from the opening of the inflow cell CI through the mesh on the bottom surface B, and covers the surface of the wall W. The suction pressure difference is appropriately set depending on the viscosity of the slurry S, the size of the base material 1, and the like. For example, the pressure difference may be -10 kPa or more, and may be in the range of -10 kPa to -70 kPa. On the other hand, in the outflow cell CO, since the bottom B side of the container 2 is sealed, the slurry S is not introduced into the cell.

Note that in order to introduce the slurry S into the inflow cell CI, a pressure difference may be created between the inside of the inflow cell CI and the inside of the container 2. For example, the container 2 placed on the upper end of the base material 1 is provided with a pressurizing device. Then, the slurry S in the container 2 may be introduced into the inflow cell CI by driving the pressurizing device to increase the internal pressure of the container 2 and relatively lower the pressure in the inflow cell CI. That is, according to the processing method according to one embodiment, the slurry in the container can be introduced into the cell using the differential pressure between the inside of the cell and the inside of the container. The same applies to the method of impregnating metal into the base material through the cell walls.

==Baking treatment==
After introducing the slurry S into the inflow cell CI and coating the surface of the wall W with the slurry S, the base material 1 is subjected to a firing treatment. By performing the calcination treatment, an exhaust gas purifying catalyst having a catalyst layer formed on the surface of the wall W is obtained. The specific method and conditions of the firing process are the same as those of the conventional method, so detailed explanations will be omitted.

As described above, according to the processing method described in this embodiment, by creating a negative pressure in the inflow cell CI of the base material 1, the slurry S is introduced into the inflow cell CI from the opening through the bottom surface B of the container 2. The surface of the wall W can be coated with the slurry S. Alternatively, by creating a negative pressure in the inflow cell CI of the base material 1, the metal solution is introduced into the inflow cell CI from the opening through the bottom surface B of the container 2, and the metal solution is introduced into the base material 1 through the surface of the wall W. It can be impregnated with. According to such a processing method, one container can be used repeatedly. Therefore, there is no need to prepare a new container every time one base material is processed, which is convenient. Further, since the slurry S or metal solution can be introduced into the inflow cell CI from the upper surface of the base material 1, the surplus of the slurry S or metal solution can be minimized.

<Example>
1. Round Hole According to Examples 1-5 and Comparative Example 1, tests were conducted on cases in which the holes formed in the bottom surface B were round holes.

(Base material)
In all Examples and Comparative Examples, a cylindrical wall flow type structure was used as the base material. The diameter of the base material is 118 mm, the height is 90 mm, and the number of cells is approximately 300 (the number of inflow cells and outflow cells are approximately equal).

(slurry)
In all Examples and Comparative Examples, the slurry used contained palladium as a catalyst metal and had a viscosity of 3000.0 mPas. Further, in all Examples and Comparative Examples, the amount of slurry (amount supplied to the container) was the same (200 g).

(container)
In all Examples and Comparative Examples, a container with a diameter of 118 mm and a depth of 45 mm was used. Further, the bottom of the container was made of water-repellent treated stainless steel. The water repellent treatment was performed by directly spraying a water repellent (MSN-02 manufactured by AGC Corporation) onto the bottom surface of the mesh.

On the other hand, the diameters, pitches, and aperture ratios of round holes were different depending on the examples and comparative examples (see Table 1).

(test)
The test confirmed retention and passage properties. Retention is the ability of the bottom of the container to retain the slurry. Retentivity was determined by whether the slurry flowed out into the cell under its own weight. Permeability is the ability of the bottom surface of the container to allow the slurry to pass through when the air inside the cell is suctioned by a suction device. Permeability was determined by how much slurry remained in the container after the air in the cell was sucked out. The suction pressure difference was the same (-10 kPa) in all Examples and Comparative Examples.

Specifically, the base material was placed vertically so that the cell openings faced upward. Then, a container was placed on the upper end of the base material. The lower end of the substrate was also attached to a suction device. Next, the slurry was supplied into the container 2, and it was confirmed whether the slurry would flow out into the cell under its own weight. A case in which the slurry did not flow into the cell was maintained for 5 minutes or more was evaluated as "○", and a case in which the state remained for less than 5 minutes was evaluated as "x".

Thereafter, the slurry in the container was introduced into the cell by driving the suction device to suck the air in the cell. At this time, the case where almost no slurry remained in the container was judged as "O", and the case where a large amount of slurry remained in the container was judged as "x".

As is clear from Table 1, when the diameter of the round hole was 1500.0 μm (Comparative Example 1), almost no slurry remained in the container after suction, but the slurry flowed out into the cell in less than 5 minutes. became. On the other hand, when the diameter of the round hole is 150.0 μm (Example 1) to 1200.0 μm (Example 4), the slurry will not flow out into the cell due to its own weight, and when suction is performed, the slurry will not flow into the container. Almost no slurry remained.

2. Oval Holes According to Examples 6 and 7, tests were conducted where the holes were oval.

(Base material)
The same base material as in "1. Round hole" was used.

(slurry)
The same slurry as in "1. Round hole" was used.

(container)
In all Examples, a container with a diameter of 118 mm and a depth of 45 mm was used. Further, the bottom of the container was made of water-repellent treated stainless steel. The water repellent treatment was performed by directly spraying a water repellent (MSN-02 manufactured by AGC Corporation) onto the bottom surface of the mesh.

On the other hand, in Example 6 and Example 7, round holes having different short diameters and aperture ratios were used (see Table 2).

(test)
Tests and judgments were conducted in the same manner as in "1. Round hole".

As is clear from Table 2, when the major axis of the oval hole is 4000.0 μm and the minor axis is 350.0 μm (Example 6) to 450.0 μm (Example 7), the slurry flows out into the cell under its own weight. There was no problem, and when suction was applied, very little slurry remained in the container.

3. Viscosity of Slurry The viscosity of slurry was investigated using Example 8-30 and Comparative Example 2-9.

(Base material)
The same base material as in "1. Round hole" was used.

(slurry)
In Example 8-13 and Comparative Example 2-4, the slurry used contained palladium as the catalyst metal and had a viscosity of 4.0 mPas. In Examples 14-19 and Comparative Examples 5-7, the slurry used contained palladium as the catalyst metal and had a viscosity of 15.0 mPas. In Examples 20, 27, and 29 and Comparative Example 8, the slurry used contained palladium as the catalyst metal and had a viscosity of 600.0 mPas. In Examples 21-26, 28, and 30, and Comparative Example 9, the slurry used contained palladium as the catalyst metal and had a viscosity of 1500.0 mPas. The amount of slurry (the amount supplied to the container) was the same (200 g) in all Examples and Comparative Examples.

(container)
In all Examples and Comparative Examples, a container with a diameter of 118 mm and a depth of 45 mm was used. Further, the bottom of the container was made of water-repellent treated stainless steel. The water repellent treatment was carried out by directly spraying a water repellent (MSN-02 manufactured by AGC Corporation) onto the bottom surface of the mesh.

On the other hand, the shape of the hole (the diameter in the case of a round hole, the major axis and the minor axis in the case of an oblong hole), pitch, and aperture ratio are as shown in Table 3 in Examples and Comparative Examples.

(test)
Tests and judgments were conducted in the same manner as in "1. Round hole".

As is clear from Table 3, it is clear that even when the viscosity is low, the requirements for retention and permeability can be met by adjusting the pore diameter and aperture ratio. For example, when the hole was a round hole, the requirements for retention and permeability were satisfied at viscosities of 4.0 mPas, 15.0 mPas, and 1500.0 mPas, within the range of the diameter of the round hole from 450.0 to 1200.0 μm. In addition, when the hole was an oval hole, the requirements for retention and passage were satisfied at viscosities of 600.0 mPas and 1500.0 mPas, with the major axis in the range of 4000.0 μm and the minor axis in the range of 350.0-450.0 μm.

4. Pressure difference As is clear from the examples in “1. Round hole”, “2. Oval hole”, and “3. can meet the requirements of Therefore, it is considered that by creating a pressure difference larger than that, the requirements for retention and permeability can be naturally satisfied. This point was investigated using Examples 30-43.

(Base material)
The same base material as in "1. Round hole" was used.

(slurry)
In Examples 31, 34, 38, 40, and 42, the slurry used contained palladium as the catalyst metal and had a viscosity of 15.0 mPas. In Examples 32, 37, 39, 41, and 44, the slurry used contained palladium as the catalyst metal and had a viscosity of 3000.0 mPas. In Example 33, the slurry used contained palladium as the catalyst metal and had a viscosity of 4.0 mPas. In Examples 35 and 43, the slurry used contained palladium as the catalyst metal and had a viscosity of 600.0 mPas. In Example 36, the slurry used contained palladium as the catalyst metal and had a viscosity of 1500.0 mPas. The amount of slurry (the amount supplied to the container) was the same (200 g) in all Examples and Comparative Examples.

(container)
In all Examples, a container with a diameter of 118 mm and a depth of 45 mm was used. Further, the bottom of the container was made of water-repellent treated stainless steel. The water repellent treatment was performed by directly spraying a water repellent (MSN-02 manufactured by AGC Corporation) onto the bottom surface of the mesh.

On the other hand, the hole diameter, pitch, and aperture ratio in Examples are as shown in Table 4.

(test)
Tests and judgments were conducted in the same manner as in "1. Round hole". However, the suction pressure difference was set to -70 kPa in all Examples.

As is clear from Table 4, it was found that even when the pressure difference was -70 kPa, the requirements for retention and permeability were met. For example, even in the case of Example 31, which differed from Example 14 only in the pressure difference, the requirements for retention and permeability were met.

1 Base material 2 Container 3 Suction device C Cell W Wall

Claims (5)

A method for treating a base material having a plurality of cells partitioned by walls, the method comprising:
arranging the base material so that the openings of the cells face upward;
placing a container whose bottom surface is formed of a member having a plurality of holes on the upper end of the base material;
The hole is a round hole,
The diameter of one of the round holes is 150.0-1200.0 μm,
supplying a predetermined amount of slurry or metal solution into the container;
The viscosity of the slurry or the metal solution is 4.0-3000.0 mPas,
A processing method in which the slurry or the metal solution is introduced into the cell from the opening through the bottom surface of the container by creating a pressure difference between the inside of the cell and the inside of the container to treat the wall. A method for treating a base material having a plurality of cells partitioned by walls, the method comprising:
arranging the base material so that the openings of the cells face upward;
placing a container whose bottom surface is formed of a member having a plurality of holes on the upper end of the base material;
The hole is an oblong hole,
The major axis of one of the oval holes is 4000.0 μm, the minor axis is 350.0-450.0 μm,
supplying a predetermined amount of slurry or metal solution into the container;
The viscosity of the slurry or the metal solution is 600.0-3000.0 mPas,
A processing method in which the slurry or the metal solution is introduced into the cell from the opening through the bottom surface of the container by creating a pressure difference between the inside of the cell and the inside of the container to treat the wall. 3. The processing method according to claim 1, wherein the pressure difference is -10 kPa or less. 4. The processing method according to claim 3, wherein the pressure difference is between -10 kPa and -70 kPa. 5. The processing method according to claim 1, wherein the member is made of metal.

Images