JP5867384B2 - Manufacturing method of honeycomb structure - Google Patents

Description

The present invention is a catalyst of noble metal by applying a water-containing catalyst slurry dispersed in water, a method for the preparation of the catalyst was supported catalyst-supporting honeycomb structure used.

As a catalyst carrier for exhaust gas purification in an internal combustion engine such as an automobile, a honeycomb structure for supporting a catalyst having a large number of cells surrounded by grid-like partition walls and a cylindrical outer peripheral wall covering the outer peripheral side surface is known. . The honeycomb structure is used as a carrier for supporting a catalyst such as a noble metal. Specifically, the honeycomb structure is coated with a hydrous catalyst slurry in which a catalyst such as a noble metal for exhaust gas purification is dispersed in water, and then heated to support the catalyst on the honeycomb structure.
In recent years, in order to improve exhaust gas purification performance, the honeycomb structure partition walls have been thinned to reduce the weight of the entire honeycomb structure, and its pressure loss (hereinafter referred to as pressure loss as appropriate) and weight have been reduced (specifically, heat capacity has been reduced). Attempts have been made to achieve early activation of the supported catalyst by reducing the amount of the catalyst.

  However, when the partition walls are thinned, there arises a problem that the strength of the entire honeycomb structure is lowered. In addition, due to the reduction in strength due to the thinning of the partition walls, so-called erosion phenomenon occurs in which the honeycomb structure wears and breaks when various foreign matters mixed in the exhaust gas collide with the axial end surface of the honeycomb structure, resulting in durability. Problem arises. This phenomenon becomes more prominent as the honeycomb structure is disposed closer to the internal combustion engine in order to further activate the catalyst early.

In general, it is known that when a catalyst such as a noble metal is supported on the honeycomb structure, the strength of the honeycomb structure itself is reduced as compared with that before the catalyst is supported. Therefore, the above-mentioned erosion phenomenon appears more remarkably in the honeycomb structure after supporting the catalyst.
In general, a catalyst such as a noble metal is supported on a honeycomb structure together with a coating material such as alumina. However, when the Mn component, the P component, and the like are contained in the exhaust gas, they may react and adhere to and deposit on the catalyst coat. As a result, the cells of the honeycomb structure may be clogged in the vicinity of the exhaust gas inlet side.

  Therefore, it is desired to partially form a region where no catalyst is supported, that is, a catalyst non-supported region, on the front end surface side which is the end surface on the exhaust gas inflow side in the honeycomb structure. Therefore, it is desired to develop a honeycomb structure in which a water-repellent region is previously formed in a region where a catalyst is not supported with respect to the honeycomb structure before the catalyst is supported by applying the hydrous catalyst slurry. In such a honeycomb structure, since the water-repellent region exhibits water repellency, even when the water-containing catalyst slurry is applied, the water-containing catalyst slurry hardly adheres to the honeycomb structure in the water-repellent region. Therefore, it is possible to prevent the catalyst from being supported on the front end surface side where the water repellent region is formed, and it is possible to form the catalyst non-supported region on the front end surface side of the honeycomb structure.

As the ceramic structure in which the water repellent region is formed, for example, the following technique is disclosed.
For example, Patent Document 1 discloses a catalyst support structure in which a hydrophobic coating is formed on the outer coating of a multicellular ceramic body such as a monolith, ceramic, or honeycomb.

Japanese Patent No. 4874123

  However, in the above-described conventional method, it is difficult to form a water-repellent region in a predetermined region, for example, from the front end surface of the honeycomb structure. For example, if the width of the water-repellent region formed on the front end face side is shortened, the strength on the front end face side in the honeycomb structure after supporting the catalyst cannot be sufficiently improved, and clogging such as Mn cannot be sufficiently suppressed. There is a fear. On the other hand, when the width of the water-repellent region is increased, the catalyst non-supported region becomes too large, and the catalyst-supported region is necessarily reduced. Therefore, the purification performance by the catalyst may be impaired. Conventionally, since it was difficult to control the formation width of the water-repellent region, it was difficult to form the water-repellent region in a desired region from the front end surface.

The present invention was made in view of such background, it is intended to provide a process for preparing a catalyst-supporting honeycomb structure can be formed easily water repellent region on a predetermined region from the front end face .

One aspect of the present invention is a method for producing a honeycomb structure for supporting a catalyst used by applying a hydrous catalyst slurry in which an exhaust gas purifying catalyst is dispersed in water and supporting the exhaust gas purifying catalyst.
The honeycomb structure for supporting a catalyst has a water-repellent region in which a water-repellent film is formed in a predetermined region from a front end surface that is an end surface on the exhaust gas inflow side, and in regions other than the water-repellent region, It has a non-water-repellent area where a water-repellent film is not formed,
On the plate-like substrate, a liquid film forming step of forming a liquid film having a predetermined thickness made of a coating liquid containing a coating agent that forms the water repellent film after heating,
In a state where the front end face side of the columnar honeycomb structure is immersed in the liquid film, the honeycomb structure is placed on the substrate with the axial direction of the honeycomb structure oriented in the vertical direction, An impregnation step of impregnating the coating liquid into a predetermined region from the front end face side of the honeycomb structure;
Heating the honeycomb structure after the impregnation step to form the water-repellent film to produce the catalyst-supporting honeycomb structure,
In the liquid film forming step, the thickness of the liquid film is adjusted from the specific gravity of the coating liquid, the weight of the liquid film formed on the substrate, and the formation area of the liquid film on the substrate. The method for producing a honeycomb structure for supporting a catalyst is as follows.

The reference invention is a honeycomb structure for supporting a catalyst obtained by the above production method .

In the manufacturing method, the catalyst supporting honeycomb structure is manufactured by performing the liquid film forming step, the impregnation step, and the heating step.
In the liquid film forming step, a liquid film made of the coating liquid is formed on the substrate. At this time, the thickness of the liquid film can be controlled by adjusting the weight of the liquid film made of the coating liquid. That is, the thickness of the liquid film can be calculated from the weight of the liquid film by obtaining the specific gravity of the coating liquid and the formation area of the liquid film on the substrate in advance.

  Next, in the impregnation step, the honeycomb structure is placed on the substrate in a state where the front end face side of the honeycomb structure is immersed in the liquid film formed with the predetermined thickness. Accordingly, the coating liquid is impregnated on the front end face side of the honeycomb structure. Since the thickness of the liquid film is controlled in the liquid film forming step, the amount of coating liquid impregnated in the impregnation step can be adjusted. Therefore, a desired region can be impregnated with the coating liquid from the front end face of the honeycomb structure.

Next, in the heating step, the honeycomb structure is heated to form a water repellent film in the region impregnated with the coating liquid.
In this way, it is possible to easily manufacture a honeycomb structure for supporting a catalyst having a water-repellent region in which a water-repellent film is formed in a predetermined region from the front end surface that is the end surface on the exhaust gas inflow side. The honeycomb structure for supporting a catalyst has a non-water-repellent region in which the water-repellent film is not formed in a region other than the water-repellent region.

  The honeycomb structure for supporting a catalyst is used by applying a water-containing catalyst slurry in which an exhaust gas purification catalyst is dispersed in water and supporting the exhaust gas purification catalyst. At this time, even if the catalyst-supporting honeycomb structure is coated with the water-containing catalyst slurry, the water-repellent region exhibits water repellency, so that the water-containing catalyst slurry does not adhere to the water-repellent region. The hydrous catalyst slurry adheres to the region. Therefore, by using the catalyst supporting honeycomb structure, it is possible to easily form a catalyst non-supporting region in a predetermined region from the front end face.

1 is a perspective view of a catalyst supporting honeycomb structure in Example 1. FIG. FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1. Explanatory drawing in the middle of the liquid film formation process in Example 1. FIG. FIG. 3 is an explanatory diagram of a liquid film forming process completion state in the first embodiment. FIG. 3 is an explanatory diagram of an impregnation process in Example 1. FIG. 3 is a cross-sectional explanatory diagram of the honeycomb structure at the time when the impregnation step is completed in Example 1. FIG. 3 is an explanatory diagram of a method for supporting an exhaust gas purifying catalyst in the first embodiment. FIG. 3 is a diagram showing the results of pressure loss evaluation of a honeycomb structure for supporting a catalyst in Example 1. FIG. 3 is a diagram showing the relationship between the water repellent distance and the emission ratio in Example 1. FIG. 3 is an explanatory diagram of an evaluation test of erosion resistance of a honeycomb structure for supporting a catalyst in Example 1. FIG. 3 is a diagram showing a relationship between a water repellent distance and erosion resistance in Example 1. The diagram which shows the relationship between the liquid film thickness of a water-system coating liquid, and the osmosis | permeation distance in Example 2. FIG. The diagram which shows the relationship between the immersion time in the water-system coating liquid in Example 2, and osmosis | permeation distance. The diagram which shows the relationship between the liquid film thickness of a solvent-type coating liquid in Example 3, and osmosis | permeation distance.

Next, preferred embodiments of the honeycomb structure and the manufacturing method thereof will be described.
In the liquid film forming step, a liquid film made of a coating liquid containing a coating agent that forms a water-repellent film after heating is formed on a plate-like substrate.
As the coating agent, for example, a fluorine-based coating agent such as fluoroalkylsilane, or a silane-based material having a terminal alkyl group can be used.
As the coating liquid, an aqueous coating liquid using water as a solvent or a solvent-based coating liquid can be used.

Preferably, the coating liquid is a water-based coating liquid using water as a solvent, and the substrate has a hydrophilic film on the surface, and in the liquid film forming step, the hydrophilic property of the substrate is set. The liquid film may be formed on the film (claim 2).
In this case, there is almost no adverse effect on the environment even if water that is the solvent of the coating solution is evaporated during the heating process, and it is not necessary to use special exhaust equipment. In addition, the presence of the hydrophilic film improves the wettability of the substrate with respect to the aqueous coating solution, so that the coating solution is easily adapted to the substrate and the influence of surface tension can be reduced. Therefore, the liquid film having a uniform thickness can be formed on the substrate. Therefore, in the impregnation step, the coating liquid can be uniformly impregnated in a predetermined region from the front end face of the honeycomb structure. As a result, it is possible to form a water-repellent film without variation in a predetermined region from the front end surface after the heating step.

  Instead of coating the hydrophilic film, the surface may be roughened to increase the surface area. As we derive from Wenzel's equation: cos φ = r cos θ (θ: contact angle of flat plate, φ: contact angle of roughened plate, r: surface area of roughened plate / surface area of flat plate) This is because the wettability is further amplified when it is increased.

The hydrophilic film is preferably a silicon-based inorganic film (claim 3).
In this case, the wettability of the substrate with respect to the coating liquid can be further improved by taking advantage of the excellent hydrophilicity of the silicon-based hydrophilic film.
In addition to the above, for example, a titanium-based inorganic film can be used as the hydrophilic film.

Moreover, when using the said aqueous coating liquid, it is preferable to form the said liquid film with a thickness of 20-80 micrometers in the said liquid film formation process (Claim 4).
In this case, when the front end face side of the honeycomb structure is immersed in the liquid film in the impregnation step, the coating solution spreads from the front end face side to the honeycomb structure, and the range of 2 to 15 mm in the axial direction from the front end face of the honeycomb structure. The coating liquid can be impregnated inside. Therefore, a water-repellent film can be formed in the range of 2 to 15 mm in the axial direction from the front end face of the honeycomb structure after the heating step. A honeycomb structure for supporting a catalyst having a water-repellent coating in this range can sufficiently improve the strength on the front end face side and can support a sufficient amount of an exhaust gas purification catalyst in a non-water-repellent region.

In addition, a solvent-based coating liquid can be used as the coating liquid.
In this case, a liquid film having a uniform thickness can be easily formed without forming a hydrophilic film on the substrate as in the case of the aqueous coating liquid.

Moreover, when using a solvent-type coating liquid, it is preferable to form a 30-150-micrometer-thick liquid film in the said liquid film formation process (Claim 6).
Also in this case, when the front end face side of the honeycomb structure is immersed in the liquid film in the impregnation step, the coating solution spreads from the front end face side to the honeycomb structure, and the range of 2 to 15 mm in the axial direction from the front end face of the honeycomb structure. The coating liquid can be impregnated inside. Therefore, a water-repellent film can be formed in the range of 2 to 15 mm in the axial direction from the front end face of the honeycomb structure after the heating step.

In the liquid film forming step, it is preferable to form a liquid film on the entire surface of the liquid film forming surface of the substrate.
In this case, the formation area of the liquid film on the substrate becomes the area of the liquid film formation surface of the substrate. Therefore, the formation area of the liquid film can be determined before forming the liquid film. Therefore, by measuring the weight of the liquid film, the thickness of the liquid film in the liquid film forming step can be easily adjusted.

In the liquid film forming step, a liquid film having a uniform thickness can be formed by a squeegee method, a spin method, or a pulling method.
The squeegee method is a method of stretching using a spatula. Specifically, it is a method of forming a liquid film having a uniform thickness by dropping a coating liquid onto a substrate and stretching the coating liquid on the substrate using a spatula.
The spin method is a method of rotating on a turntable and extending by centrifugal force. Specifically, the coating liquid is dropped onto the substrate, and the substrate is rotated on a turntable to form a liquid film with a uniform film thickness by centrifugal force.
Also, the pulling method forms a liquid film with a uniform film thickness by completely immersing a plate-like substrate in the coating liquid with its surface direction set to the vertical direction and pulling it up from the coating liquid at a predetermined pulling speed. It is a method to do.
Among these, the squeegee method is preferable.
The coating liquid is preferably colored. In this case, it is possible to visually confirm the impregnation of the coating liquid in the impregnation step.

Next, in the impregnation step, with the front end face side of the columnar honeycomb structure immersed in a liquid film, the honeycomb structure is mounted on the substrate with the axial direction of the honeycomb structure oriented in the vertical direction. Put. Thereby, the coating liquid is impregnated into a predetermined region from the front end face side of the honeycomb structure.
As the honeycomb structure, various columnar shapes such as a columnar shape, an elliptical columnar shape, and a polygonal columnar shape can be used. A honeycomb structure is generally porous and includes a cylindrical outer peripheral wall, cell walls arranged in a polygonal lattice shape in the outer peripheral wall, and a plurality of cells partitioned in the cell wall. Have. The cell walls can be arranged in a polygonal lattice shape such as a triangle, a quadrangle, a pentagon, and a hexagon. A large number of cells partitioned by the cell walls are formed. The cell may have a polygonal shape such as a triangle, a quadrangle, a pentagon, or a hexagon in the end face in the axial direction of the columnar honeycomb structure and the cross section in the direction perpendicular to the axial direction. The cell can be formed so as to extend in the axial direction of the columnar honeycomb structure.

The outer skin and the cell wall of the honeycomb structure can be made of a porous body made of ceramics. The honeycomb structure is preferably made of cordierite, silicon carbide, silicon nitride, alumina, silica, titania or the like. More preferred is cordierite.
The columnar honeycomb structure can have an axial length of, for example, 80 to 130 mm, and a cell wall thickness of, for example, 110 μm or less.
The porous honeycomb structure can have a porosity of 20 to 65%, for example. The porosity of the honeycomb structure can be measured by a mercury porosimeter based on the principle of mercury porosimetry.

In the impregnation step, the coating liquid is preferably impregnated within a range of 2 to 15 mm from the front end surface in the axial direction of the honeycomb structure.
In this case, a water-repellent film can be formed within a range of 2 to 15 mm in the axial direction from the front end face of the honeycomb structure after the heating step. By forming the water-repellent film forming region, that is, the water-repellent region to be 2 mm or more from the front end surface, the effect of forming the water-repellent region can be sufficiently obtained. That is, in this case, when a hydrous catalyst slurry containing an exhaust gas purification catalyst such as a noble metal is applied to the catalyst supporting honeycomb structure and supported on the exhaust gas purification catalyst, the exhaust gas reaches the vicinity of the front end face of the catalyst supporting honeycomb structure. It is possible to prevent the purification catalyst from being supported. Therefore, a decrease in strength on the front end face side of the catalyst supporting honeycomb structure due to the support of the exhaust gas purification catalyst can be sufficiently suppressed. Therefore, the erosion phenomenon can be sufficiently prevented. In addition, a sufficient Mn clogging suppressing effect can be obtained.
Further, in the catalyst supporting honeycomb structure supporting the exhaust gas purifying catalyst, the exhaust gas purifying catalyst supported on the front end face side is preferentially activated when the catalyst is warmed up, and the catalyst supporting honeycomb structure is activated by the reaction heat. The whole is heated and the entire catalyst is activated. Therefore, by setting the water repellent region to 15 mm or less from the front end surface, the non-catalyst supporting region on the front end surface side of the catalyst supporting honeycomb structure does not increase too much after the catalyst is supported. It can be prevented that heat is sufficiently generated and emission is deteriorated.
More preferably, the coating liquid is impregnated within a range of 2 to 10 mm from the front end surface in the axial direction of the honeycomb structure, and more preferably within a range of 2 to 8 mm.

  The penetration distance of the coating liquid from the front end surface in the axial direction of the honeycomb structure can be controlled by adjusting the thickness of the liquid film in the liquid film forming step as described above. Further, the penetration distance tends to increase by increasing the immersion time in the impregnation step, but reaches the limit in a relatively short time. From the viewpoint of productivity, the immersion time is preferably 1 to 15 seconds. More preferably, it is 10 seconds or less.

In addition, the end face in the axial direction may not be flat due to the manufacturing process of the honeycomb structure. In this case, for example, a metal plate is preferably used as the substrate. That is, in this case, since the metal plate can be bent in accordance with the end face shape of the honeycomb structure, even if the end face of the honeycomb structure is not flat, the honeycomb structure is placed on the substrate in the impregnation step. By mounting, the entire front end surface can be brought into contact with the substrate.
Preferably, the substrate is plate-shaped with a thickness of 100 μm or less (claim 9). In this case, in the impregnation step, the substrate can be easily bent according to the end face shape of the honeycomb structure.

Next, in the heating step, the honeycomb structure after the impregnation step is heated. As a result, the catalyst-supporting honeycomb structure is manufactured by forming the water-repellent film.
In the heating step, it is preferable to form the water-repellent film by heating at a temperature of 150 to 300 ° C. for 10 minutes or more.
The heating and holding temperature is set to 150 ° C. or more and the heating and holding time is set to 10 minutes or more to prevent the water repellent film from being deteriorated in adhesion, and the water repellent film is peeled off from the honeycomb structure when supporting the exhaust gas purification catalyst. You can prevent that. On the other hand, by setting the heating holding temperature to 300 ° C. or lower, it is possible to prevent the water repellent film from being decomposed in the heating step. Further, from the viewpoint of productivity, the heating and holding time is preferably 3 hours or less, and more preferably 1 hour or less.

  The catalyst supporting honeycomb structure is used in such a manner that the catalyst supporting honeycomb structure is coated with a hydrous catalyst slurry containing an exhaust gas purifying catalyst, and the exhaust gas purifying catalyst is supported on the catalyst supporting honeycomb structure. As the hydrous catalyst slurry, a slurry obtained by dispersing an exhaust gas purification catalyst such as a noble metal or a carrier component such as alumina in water can be used.

Example 1
Next, examples of the catalyst supporting honeycomb structure will be described.
In the present example, a hydrous catalyst slurry 3 (FIG. 5) containing an exhaust gas purification catalyst is applied to produce a catalyst supporting honeycomb structure 1 that is used by supporting the exhaust gas purification catalyst.
As shown in FIGS. 1 and 2, the catalyst supporting honeycomb structure 1 of this example includes a cylindrical outer peripheral wall 11, cell walls 12 arranged in a hexagonal lattice shape in the outer peripheral wall 11, It has a plurality of cells 13 defined in the cell wall 12 and has a cylindrical shape as a whole. The honeycomb structure 1 for supporting a catalyst has a water-repellent region A in which a water-repellent film 16 is formed in a predetermined region from a front end surface 14 which is an end surface on the exhaust gas inflow side. The region has a non-water-repellent region B where no water-repellent film is formed.

The honeycomb structure 1 for supporting a catalyst of this example can be manufactured by performing the following liquid film forming step, impregnation step, and heating step.
In the liquid film forming step, as shown in FIGS. 3 and 4, a coating liquid 160 containing a coating agent that forms a water repellent film 16 after heating is dropped on the plate-like substrate 2, and coating is performed on the substrate 2. A liquid film 161 having a predetermined thickness is formed. At this time, the thickness of the liquid film 160 is adjusted from the specific gravity of the coating liquid 160, the weight of the coating liquid 160 dropped on the substrate 2, and the formation area of the liquid film 160 on the substrate 2.

Next, in the impregnation step, as shown in FIG. 5, with the front end face 14 side of the columnar honeycomb structure 10 immersed in the liquid film 161, the axial direction X of the honeycomb structure 10 is directed vertically. The honeycomb structure 10 is placed on the substrate 2. Thereby, as shown in FIG. 6, the coating liquid 160 is impregnated into the predetermined region a from the front end face 14 side of the honeycomb structure 10.
Next, in the heating step, the honeycomb structure 10 after the impregnation step is heated to form a water-repellent film 16 on the front end face 14 side as shown in FIG. A catalyst-supporting honeycomb structure 1 having B is prepared.

Hereinafter, the manufacturing method of this example will be described in detail.
First, a plate-like substrate 2 (120 mm long × 120 mm wide × 0.5 mm thick) made of SUS304 having a silicon-based hydrophilic film (“Zero Clear” manufactured by Gogo Co., Ltd.) formed on the surface was prepared (FIG. 3). reference). The commercially available substrate is baked with a silicon-based hydrophilic film at a temperature of 260 ° C. However, since the hydrophilicity is improved by further heating at a high temperature of 280 ° C. or higher, in this example, the commercially available product is electrically The substrate 2 refired in a furnace at a temperature of 300 ° C. for 1 hour was used. You may heat at the temperature of 280 degreeC or more at the time of formation of a hydrophilic membrane | film | coat.

  Next, a coating liquid 160 containing a coating agent that forms a water-repellent film after heating was prepared. As the coating solution, an aqueous coating solution prepared by dissolving a coating agent (main agent) made of C4 fluoroalkylsilane, a crosslinking agent made of trifunctional alkylsilane, a fluorosurfactant and a catalyst (ammonia) in water is used. It was. The concentration of the solid content of the main agent and the crosslinking agent in the coating liquid 160 is 5% by mass.

  Next, as shown in FIG. 3, a predetermined weight of the coating liquid 160 was dropped onto the plate-like substrate 2. The coating liquid 160 is dropped on the liquid film forming surface 21 on the substrate 2 on which the silicon-based hydrophilic film is formed, and the coating liquid 160 is stretched to a uniform thickness using a spatula, and the liquid film 161 is formed as shown in FIG. Formed. In this example, the specific gravity of the coating liquid 160 was measured in advance, and the weight of the coating liquid dropped on the substrate 2 was measured. In this example, the liquid film 161 is formed on the entire surface of the liquid film forming surface 21 of the plate-like substrate 2. Then, the film thickness of the liquid film 161 formed on the substrate 2 was calculated from the specific gravity and weight of the coating liquid 160 and the area of the liquid film forming surface 21. In this example, a liquid film 161 having a thickness of 20 μm was formed.

  Next, cordierite having a cylindrical outer peripheral wall 11, cell walls 12 arranged in a hexagonal lattice shape in the outer peripheral wall 11, and a plurality of cells 13 partitioned in the cell wall 12. A honeycomb structure 10 comprising: As shown in FIG. 5, in a state where the front end face 14 side of the columnar honeycomb structure 10 is immersed in the liquid film 161, the honeycomb structure 10 is placed on the substrate with the axial direction X of the honeycomb structure 10 oriented in the vertical direction. Placed on 2 for 5 seconds. As a result, as shown in FIG. 6, the coating liquid 160 was impregnated into the predetermined region a from the front end face 14 side of the honeycomb structure 10. In this example, a = 5 mm.

Next, the honeycomb structure 10 impregnated with the coating liquid 160 from the front end face 14 was heated at a temperature of 200 ° C. for 60 minutes to form the water repellent film 16 in the region impregnated with the coating liquid 160 (see FIG. 2). The water repellent coating 16 is formed so as to cover the cell walls 12 of the honeycomb structure 10 and imparts water repellency to the cell walls 12. And after heating, it cooled to room temperature.
In this way, as shown in FIGS. 1 and 2, the water repellent region A having the water repellent film 16 formed in the region 5 mm from the front end surface 14 which is the end surface on the exhaust gas inflow side is provided. In a region other than the water region A, a catalyst-supporting honeycomb structure 1 having a non-water-repellent region B in which a water-repellent film was not formed was obtained.
The amount of Si component in the water-repellent coating 16 is larger than the amount of Si component in the honeycomb structure 10 and is within + 10% by mass relative to this.

In the manufacturing method of this example, the catalyst supporting honeycomb structure 1 is manufactured by performing a liquid film forming step, an impregnation step, and a heating step.
In the liquid film formation step, as shown in FIGS. 3 and 4, a liquid film 161 made of the coating liquid 160 is formed on the substrate 2. At this time, the thickness of the liquid film 161 can be controlled by adjusting the weight of the liquid film 161 made of the coating liquid 160. That is, by obtaining the specific gravity of the coating liquid 160 and the formation area of the liquid film 161 on the substrate 2 in advance, the thickness of the liquid film 161 can be calculated from the weight of the liquid film 161. In the film forming process of this example, the liquid film 161 is formed on the entire surface of the liquid film forming surface 21 of the substrate 2. Therefore, the formation area of the liquid film 161 on the substrate 2 becomes the area of the liquid film formation surface 21 of the substrate 2. Therefore, the formation area of the liquid film 161 can be determined before the liquid film 161 is formed. Therefore, by measuring the weight of the liquid film 161, the thickness of the liquid film 161 in the liquid film forming step can be easily adjusted.

  Next, in the impregnation step, as shown in FIGS. 5 and 6, the honeycomb structure 10 is immersed in the liquid film 161 formed with the predetermined thickness on the front end face 14 side of the honeycomb structure 10. Is placed on the substrate 2. Thereby, the coating liquid 160 is impregnated on the front end face 14 side of the honeycomb structure 10. Since the thickness of the liquid film 161 is controlled in the liquid film forming process, the amount of the coating liquid 160 impregnated in the impregnation process can be adjusted. Therefore, it becomes possible to impregnate the coating liquid 160 from the front end face 14 of the honeycomb structure 10 to the desired region a.

Next, in the heating step, the honeycomb structure 10 is heated to form the water repellent film 16 in the region impregnated with the coating liquid 160.
In this way, as shown in FIGS. 1 and 2, the catalyst-supporting honeycomb having the water-repellent region A in which the water-repellent film 16 is formed in a predetermined region from the front end surface 14 which is the end surface on the exhaust gas inflow side. The structure 1 can be manufactured easily. The honeycomb structure 1 for supporting a catalyst has a non-water-repellent region B in which a water-repellent film is not formed in a region other than the water-repellent region A.

  The catalyst supporting honeycomb structure 1 is used by supporting an exhaust gas purification catalyst. In order to support the exhaust gas purification catalyst on the catalyst supporting honeycomb structure 1, a suction coating method is used. Specifically, as shown in FIG. 7, first, the catalyst-supporting honeycomb structure 1 is installed with the front end face 14 facing vertically upward. Then, the catalyst slurry 3 having thixotropy adjusted to a predetermined viscosity is disposed on the front end face 14 of the catalyst supporting honeycomb structure 1, and sucked with a blower from the other end face (arrow B). As a result, the catalyst is applied to the cell walls 12 of the catalyst supporting honeycomb structure 1. At this time, since the water-repellent region A of the honeycomb structure 1 for supporting a catalyst exhibits water repellency, the catalyst slurry 3 does not adhere to the water-repellent region A, and the hydrous catalyst slurry 3 is present in the non-water repellent region B Adhere to.

In this example, the coating liquid 160 is an aqueous coating liquid using water as a solvent, and the substrate 2 has a hydrophilic film (not shown) on the surface. In the liquid film forming step, A liquid film 161 is formed on the hydrophilic film of the substrate 2.
Therefore, even if the solvent (water) of the coating liquid 160 is evaporated during the heating process, there is almost no adverse effect on the environment, and there is no need to use special exhaust equipment. In addition, the presence of the hydrophilic film improves the wettability of the substrate 2 with respect to the aqueous coating solution, so that the coating solution 160 is easily adapted to the substrate 2 and the influence of surface tension can be reduced. Therefore, the liquid film 161 having a uniform thickness can be formed on the substrate 2. Therefore, in the impregnation step, the coating liquid 160 can be uniformly impregnated in a predetermined region from the front end face 14 of the honeycomb structure 10. As a result, the water-repellent coating 16 can be formed from the front end face 14 to a predetermined region without variation after the heating step.

Next, an exhaust gas purification catalyst was actually supported on the catalyst supporting honeycomb structure 1 of this example.
Specifically, first, a catalyst slurry 3 was prepared by dispersing noble metal (Pt, Rh, Pd) powder, alumina powder, and a dispersant in water (see FIG. 7). Next, the catalyst slurry 3 was applied to the catalyst supporting honeycomb structure 1 by using the above-described suction coating method.
Thereafter, the catalyst supporting honeycomb structure 1 was heated at a temperature of 500 ° C. for 1 hour. As a result, the exhaust gas purification catalyst made of noble metal powder, alumina powder, and the like was baked on the non-water-repellent region B of the catalyst supporting honeycomb structure 1. In the water repellent area A, no exhaust gas purification catalyst is supported.

Next, pressure loss (hereinafter referred to as “pressure loss”) was evaluated using the catalyst supporting honeycomb structure (sample E) supporting the exhaust gas purification catalyst as described above.
Specifically, a honeycomb structure for supporting a catalyst was installed at a predetermined position in an exhaust pipe of a 4.3 L V8 gasoline engine. Then, the differential pressure (pressure loss) before and after the catalyst supporting honeycomb structure was measured. Measurements are as follows: center temperature of honeycomb structure for supporting catalyst: 890 ° C., exhaust gas flow rate: 16.25 g / second (per one bank), fuel cut: 1 time / 30 seconds, 2 seconds per time, Mn content in fuel The amount was 55 mg / L.
For comparison with Sample E, the honeycomb structure having no water-repellent film was also loaded with an exhaust gas purification catalyst as in Sample E. This is designated as Sample C. Since the sample C does not have the water-repellent region as in the sample E, the exhaust gas purification catalyst is supported on the entire honeycomb structure. For this sample C, the pressure loss was evaluated in the same manner as for sample E.
These results are shown in FIG. 8 as the relationship between operating time and pressure loss.

As can be seen from FIG. 8, it can be seen that Sample E can suppress an increase in pressure loss compared to Sample C. The reason is considered as follows.
That is, in the sample C, the Mn component, the P component and the like in the exhaust gas react with the coating material such as alumina supported together with the noble metal catalyst on the front end face side of the honeycomb structure. As a result, the cells of the honeycomb structure are clogged in the vicinity of the exhaust gas inlet side. On the other hand, sample E uses a honeycomb structure for supporting a catalyst having a water-repellent region on the front end surface, so that a region where no catalyst is supported, that is, a catalyst non-supported region is formed on the front end surface side. Yes. Therefore, in the sample E, the clogging of the cell on the front end face side can be suppressed as compared with the sample C, and the increase in pressure loss can be suppressed as described above.

Further, in this example, the thickness of the liquid film in the liquid film forming step is changed, and a plurality of catalyst supporting types having different water repellent region formation lengths from the front end face (hereinafter referred to as “water repellent distance”) are used. A honeycomb structure was fabricated and the emission ratio was examined.
Specifically, an exhaust gas purification catalyst is supported on these catalyst supporting honeycomb structures in the same manner as the sample E, and the catalyst supporting honeycomb structure is disposed at a predetermined position in the exhaust pipe of a 4.3 L V8 gasoline engine. Was installed. Then, the emission discharged when the engine was operated in the LA # 4 mode was measured. Here, the emission means the total amount of HC, CO, and NOx discharged after passing through the catalyst during mode travel. The ratio of this value to the emission when using the catalyst supporting honeycomb structure in which the water-repellent region is not formed is shown in FIG. 9 as the emission ratio.

  As can be seen from FIG. 9, when the water repellent distance exceeds 15 mm, the emission ratio increases rapidly. This is because when the water repellent distance exceeds 15 mm, the non-catalyst carrying region on the front end face side of the catalyst supporting honeycomb structure becomes large after carrying the catalyst, and the heat of reaction from the front end face is not sufficiently generated during warming, This is probably because the entire catalyst is hardly activated.

Next, as shown in FIGS. 10 and 11, the erosion resistance of the catalyst supporting honeycomb structure 1 of this example is evaluated in relation to the water repellent distance, that is, the length of the catalyst non-supporting region. As an evaluation method, as shown in FIG. 10, when a large number of glass beads collide continuously from the nozzle 4 against the front end face 14 of the catalyst supporting honeycomb structure 1, the honeycomb structure for catalyst supporting is used. The weight change caused by the partial breakage of 1 is measured. The glass beads have a diameter of 60 μm, an injection pressure of 10 kg / cm ² , an incident angle of the glass beads with respect to the front end face 14 of 45 °, a nozzle diameter of 8 mm, a distance between the nozzle 4 and the front end face 14 of 100 mm, and an injection time of 1 minute. It was.

  The weights of the catalyst-supporting honeycomb structure 1 before and after the collision test are m1 and m2, respectively, and 1 / (m1-m2) is defined as erosion resistance. FIG. 11 shows the ratio of the water-repellent distance of 0 mm, that is, the erosion resistance of the catalyst-supporting honeycomb structure having no catalyst non-supporting region while performing the above test with various water-repellent distances. In the figure, each plot is actually measured data, and a curve L is a curve that approximately connects the actually measured data.

  From the figure, it can be seen that the erosion resistance can be improved by setting the water repellent distance to 2 mm or more. Therefore, it can be said that the water repellent distance is desirably 2 to 15 mm. That is, it can be said that the water repellent film is preferably formed by impregnating the coating liquid within a range of 2 to 15 mm from the front end face 14.

(Example 2)
In this example, as shown in FIG. 12, the relationship between the liquid film thickness of the aqueous coating liquid in the liquid film forming step and the impregnation distance (penetration distance) of the coating liquid from the front end face of the catalyst supporting honeycomb structure was examined. It is an example.
In this example, a water-based fluorine coating agent manufactured by DuPont was used as the water-based coating solution. This coating agent is prepared by mixing water as a solvent, fluoroalkylsilane as a main agent, alkylsilane as a crosslinking agent, and fluoroalkyl as a surfactant.

  That is, in the liquid film forming step of the manufacturing method of the catalyst supporting honeycomb structure shown in Example 1, the thickness of the liquid film of the aqueous coating liquid was changed, and the permeation distances were measured. The immersion time in the impregnation step was 5 seconds. Other conditions are the same as in Example 1. Moreover, n number is set to 3 with respect to each film thickness, and the average value, the maximum value, and the minimum value of the measured value of the penetration distance in each film thickness are shown in FIG.

As can be seen from the figure, the permeation distance can be controlled to at least 2 to 15 mm as long as the thickness of the liquid film is in the range of 20 to 80 μm. The permeation distance is equivalent to the water repellent distance shown in the first embodiment. That is, as long as the thickness of the liquid film is in the range of 20 to 80 μm, the permeation distance is at least within the preferable water repellent distance derived from the result shown in FIG. 9 of Example 1, that is, the permeation distance of 2 to 15 mm. Can do.
Further, the more preferable range of the permeation distance (water repellent distance) is 2 to 8 mm. From this point of view, however, it is more preferable that the film thickness of the liquid film in the film forming step is 20 to 30 μm. I understand that.

Further, as shown in FIG. 13, the relationship between the immersion time of the catalyst supporting honeycomb structure in the liquid film of the aqueous coating liquid in the impregnation step and the impregnation distance (penetration distance) of the coating liquid from the front end surface was examined.
That is, first, in the liquid film forming step of the method for manufacturing the catalyst supporting honeycomb structure shown in Example 1, a liquid film of an aqueous coating liquid was formed to a thickness of 20 μm. Thereafter, in the impregnation step, the permeation distance was measured by changing the immersion time. Other conditions are the same as in Example 1. Moreover, n number is set to 3 with respect to each immersion time, and the average value, the maximum value, and the minimum value of the measured value of the penetration distance in each immersion time are shown in FIG.

As can be seen from the figure, the penetration distance can be controlled between at least 2 and 15 mm as long as the immersion time is in the range of 1 to 15 seconds. That is, as long as the immersion time is in the range of 1 to 15 seconds, the permeation distance can be at least within the preferable water repellent distance, that is, the permeation distance of 2 to 15 mm.
Further, the more preferable range of the penetration distance (water repellent distance) is 2 to 8 mm. From this point of view, it is understood that the immersion time in the impregnation step is more preferably 1 to 10 seconds from FIG. .

(Example 3)
In this example, a water-repellent film is formed using a solvent-based coating liquid.
In this example, a fluoroalkylsilane (model: TSL8257) manufactured by Momentive Performance Material Japan was used as the coating solution. The molecular structure of the main component of this solution is CF ₃ (CF ₂ ) ₅ CH ₂ CH ₂ Si (OMe) ₃ .
Others are the same as in the first embodiment.

In this example, the relationship between the film thickness of the liquid film in the film formation step and the permeation distance was examined.
That is, in the liquid film forming step of the method for manufacturing the catalyst supporting honeycomb structure shown in Example 1, the thickness of the liquid film of the solvent-based coating liquid was changed, and the permeation distances were measured. The immersion time in the impregnation step was 5 seconds. Other conditions are the same as in Example 1. Moreover, the n number is set to 3 for each film thickness, and the average value, the maximum value, and the minimum value of the measured values of the penetration distance in each film thickness are shown in FIG.

As can be seen from the figure, the permeation distance can be controlled between at least 2 and 15 mm as long as the thickness of the liquid film is in the range of 30 to 150 μm. That is, as long as the thickness of the liquid film is in the range of 30 to 150 μm, the permeation distance can be at least within the preferable water repellent distance, that is, the permeation distance of 2 to 15 mm.
Further, the more preferable range of the permeation distance (water repellent distance) is 2 to 8 mm. From this viewpoint, it is more preferable that the film thickness of the liquid film in the film forming step is 30 to 100 μm. I understand that.

DESCRIPTION OF SYMBOLS 1 Honeycomb structure for catalyst support 10 Honeycomb structure 14 Front end surface 16 Water-repellent film 160 Coating liquid 161 Liquid film 2 Substrate 3 Hydrous catalyst slurry A Water-repellent area B Non-water-repellent area X Axial direction

Claims (10)

A method for producing a honeycomb structure for supporting a catalyst (1) used by applying a hydrous catalyst slurry (3) in which an exhaust gas purification catalyst is dispersed in water and supporting the exhaust gas purification catalyst,
The catalyst supporting honeycomb structure (1) has a water repellent region (A) in which a water repellent film (16) is formed in a predetermined region from a front end surface (14) which is an end surface on the exhaust gas inflow side. In addition, the region other than the water-repellent region (A) has a non-water-repellent region (B) where no water-repellent film is formed,
A liquid film forming step of forming a liquid film (161) having a predetermined thickness comprising a coating liquid (160) containing a coating agent that forms the water-repellent film (16) after heating on the plate-like substrate (2); ,
With the front end face (14) side of the columnar honeycomb structure (10) immersed in the liquid film (161), the axial direction (X) of the honeycomb structure (10) is directed vertically. By placing the honeycomb structure (10) on the substrate (2), the coating liquid (160) is impregnated into a predetermined region from the front end face (14) side of the honeycomb structure (10). An impregnation step;
Heating the honeycomb structure (10) after the impregnation step to form the water-repellent film (16) to produce the catalyst-supporting honeycomb structure (1),
In the liquid film forming step, the specific gravity of the coating liquid (160), the weight of the liquid film (161) formed on the substrate (2), and the liquid film (161) on the substrate (2) A method for producing a honeycomb structure for supporting a catalyst (1), wherein the thickness of the liquid film (161) is adjusted from a formation area.   The manufacturing method according to claim 1, wherein the coating liquid (160) is a water-based coating liquid using water as a solvent, and the substrate (2) has a hydrophilic film on a surface thereof. In the liquid film forming step, the liquid film (161) is formed on the hydrophilic film of the substrate (2), and the method for producing a honeycomb structure (1) for supporting a catalyst.   The method for manufacturing a honeycomb structure (1) for supporting a catalyst according to claim 2, wherein the hydrophilic coating is a silicon inorganic coating.   The manufacturing method according to claim 2 or 3, wherein, in the liquid film forming step, the liquid film (161) having a thickness of 20 to 80 µm is formed. Method.   The method for manufacturing a honeycomb structure (1) for supporting a catalyst according to claim 1, wherein the coating liquid (160) is a solvent-based coating liquid.   6. The manufacturing method according to claim 5, wherein the liquid film (161) having a thickness of 30 to 150 [mu] m is formed in the liquid film forming step.   In the manufacturing method according to any one of claims 1 to 6, in the liquid film formation step, the liquid film (161) is formed on the entire surface of the liquid film formation surface (21) of the substrate (2). A method for producing a honeycomb structure for supporting a catalyst (1), wherein:   In the manufacturing method of any one of Claims 1-7, in the said impregnation process, it exists in the range of 2-15 mm from the said front end surface (14) in the axial direction (X) of the said honeycomb structure (1). A method for producing a honeycomb structure for supporting a catalyst (1), wherein the coating liquid (160) is impregnated into the honeycomb structure.   The method for manufacturing a honeycomb structure (1) for supporting a catalyst according to any one of claims 1 to 8, wherein the substrate (2) has a plate shape with a thickness of 100 µm or less. 10. The catalyst according to claim 1, wherein, in the heating step, the water-repellent film is formed by heating at a temperature of 150 to 300 ° C. for 10 minutes or more. A method for manufacturing a supporting honeycomb structure (1) .

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