JP5146752B2 - Method for producing exhaust gas purification catalyst - Google Patents

Description

The present invention relates to a method for producing an exhaust gas purification catalyst, and more particularly, at least a particulate (hereinafter referred to as “PM”) among substances contained in a gas discharged from an internal combustion engine such as a diesel engine. It is related with the manufacturing method of the catalyst which purifies exhaust gas.

Particulates are contained in the exhaust gas discharged from an internal combustion engine such as a diesel engine. Particulates contain substances that are harmful to the human body, and removal of these substances is a requirement for environmental conservation.
Conventionally, a filter catalyst has been used for removing particulates, and such filter catalysts are disclosed in, for example, Patent Document 1 and Patent Document 2.
JP 2002-295228 A Japanese Patent Laying-Open No. 2005-224666

However, in such a conventional filter catalyst, the catalyst layer formed on the catalyst support substrate narrows the opening diameter of the pores of the catalyst support substrate and the air holes (pores) have a sufficient opening diameter. There is a problem that the air holes are not opened or the air holes are not opened (closed).

Specifically, the catalyst layer of the filter catalyst is prepared as a slurry having alumina or the like, applied to the catalyst carrier substrate, dried and fired to form a support layer, and then supports the catalyst metal. It is manufactured by letting. However, when the slurry is applied to the catalyst carrier substrate, the slurry is not sufficiently dispersed (intruded) into the pores of the catalyst carrier substrate, so that the slurry is biased near the pore openings of the catalyst carrier substrate. It came to exist. Since the catalyst layer is formed by drying and firing in this state, the diameter of the opening of the vent (pore) is reduced or blocked, making it impossible to form a vent sufficient for the filter catalyst.

On the other hand, if the catalyst layer is simply formed on the surface of the substrate in the pores of the catalyst support substrate, clogging of the catalyst support substrate by the catalyst layer is suppressed, but the catalyst support supports the catalyst support substrate. There is a problem in that the pressure loss increases because the air holes are reduced.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a method for producing an exhaust gas purifying catalyst in which blockage of vent holes (pores) by a catalyst layer is suppressed. Is to provide.

As a result of intensive studies to achieve the above object, the present inventors include a step of applying a supported component-containing slurry having a predetermined particle size distribution, solid content, and viscosity to a three-dimensional structure carrier. The inventors have found that the above object can be achieved and have completed the present invention.

That is, the method for producing an exhaust gas purification catalyst of the present invention is a method for producing an exhaust gas purification catalyst comprising a step of applying a slurry containing a supported component to a three-dimensional structure carrier,
The average particle diameter of the slurry is 1 to 10 μm, and the existence ratio of particles of 1 μm or less is 20% or less, and the existence ratio of particles of 10 μm or more is 10% or less,
The slurry has a solid content with respect to moisture of 1.0% by mass to 30% by mass and a viscosity of 0.1 mPa.s. s-30 mPa.s s.
The exhaust gas purifying catalyst comprises a three-dimensional structure carrier having a plurality of cells partitioned by cell walls having pores, and a catalyst layer formed on the three-dimensional structure carrier.
The catalyst layer has a surface coating site formed along the surface of the cell wall, and a pore coating site formed along the pore of the cell wall,
At least the above-mentioned pore covering portion has active pores having a pore diameter of 0.1 to 10 μm derived from the supported component contained in the catalyst layer.

According to the present invention, since the step of applying a supported component-containing slurry having a predetermined particle size distribution, solid content, and viscosity to a predetermined three-dimensional structure carrier is included, the air holes (pores) by the catalyst layer (pores) ) Can be provided. A method for producing an exhaust gas purifying catalyst in which blockage of

Hereinafter, the manufacturing method of the exhaust gas purifying catalyst of the present invention will be described in detail.
As described above, the method for producing an exhaust gas purification catalyst of the present invention is a method for producing an exhaust gas purification catalyst comprising a three-dimensional structure carrier and a catalyst layer formed on the three-dimensional structure carrier.
Here, the three-dimensional structure carrier has a plurality of cells partitioned by cell walls, and the cell walls have pores through which exhaust gas passes. Such three-dimensional structure carriers include so-called honeycomb carriers and checkered honeycomb carriers (wall flow type carriers).

First, an exhaust gas purification catalyst obtained by the method for producing an exhaust gas purification catalyst of the present invention will be described.
FIG. 1 is a schematic partial sectional view showing the vicinity of a cell wall of a three-dimensional structure carrier in an example of an exhaust gas purifying catalyst obtained by the present invention.
In FIG. 1A, the three-dimensional structure carrier 10 has a cell wall 12 having pores 13 through which exhaust gas EG can pass, and is covered with a catalyst layer 20. Further, the catalyst layer 20 has a surface covering portion 21 formed along the surface of the cell wall 12 and a pore covering portion 22 formed along the pore 13.

1B is an enlarged cross-sectional view showing a part of FIG. 1A in an enlarged manner, and FIG. 1C is a view showing the part shown in FIG. 1B from a direction perpendicular to the surface of the cell wall 11. FIG.
As shown in these figures, the pore covering portion 22 formed along the pores 13 of the cell wall 12 is highly porous and has active pores having a pore diameter of 0.1 to 10 μm (not shown). ing.

These active pores are formed when the catalyst layer 20 is supported on the three-dimensional structure carrier 10 and are derived from the supported components contained in the catalyst layer 20, but have an appropriate pore size. Therefore, the exhaust gas can circulate well through the active pores, and the increase in pressure loss at that time is also effectively suppressed.
Moreover, from such an appropriate pore diameter, the active pores effectively collect the particulates and sufficiently oxidize the collected particulates.
Thus, in the exhaust gas purifying catalyst obtained by the present invention, the collected particulates can be effectively removed by the catalyst layer 20 collecting and oxidizing the particulates.

On the other hand, in the conventional exhaust gas purification catalyst, as shown in FIGS. 2A and 2B, the porosity of the pore covering portion 22 ′ is low, and the particulates can hardly be collected. Not only can it not be oxidized and purified, but also the flowability of the exhaust gas is reduced, resulting in an increase in pressure loss.

FIG. 3 is a partially cutaway perspective view showing an example of an exhaust gas purifying catalyst obtained by the present invention using a wall flow type carrier as a three-dimensional structure carrier, and a broken line portion in the figure is cut away.
In the figure, the exhaust gas-purifying catalyst 1 includes a checkered honeycomb carrier 10 which is an example of a three-dimensional structure carrier.

The checkered honeycomb carrier 10 has a columnar shape as a whole, and has a plurality of cells 11 partitioned by the cell walls 12 having the pores as described above. They are formed parallel to each other. Further, the cell 11 has a closed end face 16 whose end face on the exhaust gas inlet side or the outlet side is sealed, and between the adjacent cells, the closed end face 16 is alternately reversed with respect to the exhaust gas inlet side and the outlet side. It is comprised so that.

In the checkered honeycomb carrier 10, the entire end surface on the exhaust gas inlet side or the outlet side has a closed pattern such as a checkerboard (checkered pattern), more specifically, on the exhaust gas inlet side. A closing pattern in which opening and closing is reversed on the outlet side is formed.
In such a checkered honeycomb carrier 10, as a general rule, the exhaust gas EG passes through the open end face (cell inlet 14) of the cell 11 and through the pores 13 (see FIG. 1) of the cell wall 12 as shown. Then, it flows into the adjacent cell and is discharged from the open end face (cell outlet 15) of the adjacent cell.

The exhaust gas-purifying catalyst 1 shown in FIG. 3 is obtained by forming a catalyst layer (not shown) on such a checkered honeycomb carrier 10, and this catalyst layer, particularly its pore covering portion, is as described in FIG. Active pores. Therefore, the particulates contained in the exhaust gas are effectively collected and purified by such active pores while sufficiently suppressing an increase in pressure loss during exhaust gas circulation as described above.

As the three-dimensional structure carrier in the present invention, not only a checkered honeycomb carrier but also a normal honeycomb carrier can be used. In any carrier, 4 to 80% of the pores of the cell wall have a pore diameter of 10 to 50 μm. It is preferable that the porosity is 40 vol% or more.
If the pore size and porosity of the cell wall pores deviate from the above ranges, a relatively large amount of the catalyst component is present inside the support even if the catalyst component is attached to the surface of the three-dimensional structure support using a normal catalyst component slurry. It becomes difficult to exert catalytic activity effectively.

Examples of the material of the above three-dimensional structure carrier include ceramic, ceramic foam, and metal foam.
Specifically, cordierite, silicon carbide (SiC), mullite and other ceramics, ceramic foam filters, and foam metal include ferritic stainless steel.

Next, the catalyst layer and active pores of the exhaust gas purifying catalyst obtained by the present invention will be described in detail.
As described above, the catalyst layer, particularly the pore covering portion 22 (see FIG. 1) has active pores having a pore diameter of 0.1 μm to 10 μm, and these active pores are derived from the supported components of the catalyst layer. Is.
The surface coating portion 21 (see FIG. 1) of the catalyst layer usually has active pores as well as the pore coating portion 22, but the presence of the active pores in the surface coating portion 21 is an essential requirement. Absent.

By setting the pore diameter of the active pores to 10 μm or less, the exhaust gas that passes through the pores (pores 13) of the three-dimensional structure support can also pass through the catalyst layer, and the increase in pressure loss is suppressed.
In addition, it is conceivable that extremely small particulates, for example, several nanometers, enter into the active pores of the catalyst layer, but within the active pores, there is a contact property between the supported component, particularly the catalyst component and the particulates. It is extremely good and can be expected to improve the oxidation characteristics of the particulates. Furthermore, the increase in the contact property can be expected to increase the temperature of the catalyst layer due to the gas reaction.

On the other hand, if the pore diameter of the active pores exceeds 10 μm, the catalyst layer cannot be formed and held in the pores of the three-dimensional structure carrier, and the catalyst layer may block the pores of the carrier or the catalyst layer may be formed. As a result, the surface of the carrier is exposed, and when used as an exhaust gas purifying catalyst, not only the pressure loss increases, but also the contact area with the PM decreases and the oxidation performance of the PM decreases.
On the other hand, when the pore diameter of the active pores is smaller than 0.1 μm, the pore diameter is too small, so that a sufficient effect cannot be obtained.

In the exhaust gas purifying catalyst obtained by the present invention, the total pore volume of pores having a pore diameter of 0.1 to 10 μm preferably accounts for 5 to 30% of the total pore volume of all pores.
That is, pores having a pore diameter of 0.1 to 10 μm include the above-mentioned active pores and pores possessed by the three-dimensional structure carrier itself, and the sum of these pore volumes is the exhaust gas purification. It is desirable to correspond to 5 to 30% of the total pore volume of the pore diameter in the catalyst for use.
If this ratio is less than 5%, a sufficient passage of exhaust gas is not secured in the catalyst layer, and the contact area between the exhaust gas and the catalyst is not sufficient, so that the exhaust pressure increases or the effect of the catalyst decreases. If it exceeds 30%, the average pore diameter of the cell walls of the three-dimensional structure carrier provided with the catalyst layer becomes small, and the pressure loss of the entire three-dimensional structure carrier provided with the catalyst layer may increase.

In the present invention, 5 to 100%, preferably 10 to 35% of the total pore volume of pores having a pore diameter of 0.1 to 10 μm corresponds to the total pore volume of active pores. Is preferred.
This relationship can be expressed by the following equation.
Pore volume of active pores / (pore volume of active pores + pore volume of three-dimensional structure carrier having pore diameter of 0.1 to 10 μm) × 100 = 5 to 100 (%)
The three-dimensional structure carrier itself may not have pores with a pore diameter of 0.1 to 10 μm. In this case, 100% of the pores with a pore diameter of 0.1 to 10 μm are composed of active pores.
This ratio means the ratio at which active pores are formed in the formation of the catalyst layer. However, when this ratio is less than 5%, the amount of catalyst is small and the PM that has entered the pores of 0.1 to 10 μm is small. It may not oxidize sufficiently.

On the other hand, in the exhaust gas purifying catalyst obtained by the present invention, the total pore volume of pores having a pore diameter of more than 10 μm and not more than 100 μm preferably accounts for 70 to 95% of the total pore volume of all pores.
That is, pores having a pore diameter of more than 10 μm and not more than 100 μm include the pores resulting from the formation of the catalyst layer and the pores of the three-dimensional structure carrier itself. It is desirable that the pore volume balance corresponds to 70 to 95% of the total pore volume of the pore diameter in the exhaust gas purification catalyst.
If this ratio exceeds 95%, the contact area between the exhaust gas and the catalyst is not sufficient, and thus the effect of the catalyst may be reduced. If the ratio is less than 70%, the average fineness of the cell walls of the three-dimensional structure carrier having the catalyst layer is reduced. Since the pore diameter is reduced, the pressure loss of the entire three-dimensional structure support including the catalyst layer may be increased.

Further, the total pore volume of pores having a pore diameter of more than 10 μm and not more than 100 μm is smaller than the total pore volume of pores in the same pore diameter range in the three-dimensional structure carrier, and this reduction rate is 1 to 35. % Is preferred.
This relationship can be expressed by the following equation.
(Pore volume of more than 10 μm and 100 μm or less before catalyst loading−pore volume of more than 10 μm and 100 μm or less after catalyst loading) / (pore volume of more than 10 μm and 100 μm or less before catalyst loading) × 100 = 1 to 35 (%)
That is, pores having a pore diameter of more than 10 μm and not more than 100 μm are reduced by the formation of the catalyst layer in principle, but this reduction rate is preferably 1 to 35%.
When this reduction rate is less than 1%, the number of catalyst layers formed in pores of 10 μm or more is reduced. Considering that gas having a larger diameter is easier to flow, the contact between the catalyst and the exhaust gas may be lowered when the number of formed catalyst layers is small. Since the average pore diameter of the cell walls of the provided three-dimensional structure support is reduced, the pressure loss of the entire three-dimensional structure support provided with the catalyst layer may be increased.

The porosity and various ratios described above are based on the measurement of the pore volume by the mercury intrusion method.

Next, the supported component constituting the catalyst layer will be described.
The supporting component includes a catalyst component and a supporting substrate, and as the supporting substrate, a heat-resistant inorganic material such as alumina or zirconia can be used.

On the other hand, the catalyst component preferably contains a metal oxide from the viewpoint of oxidizing and burning particulates by catalytic action, and suitable metal elements include cerium (Ce), praseodymium (Pr), gallium ( Ga), yttrium (Y), zirconium (Zr) or aluminum (Al), and elements related to any combination thereof can be given.
Specifically, as the metal oxide, cerium oxide (CeO ₂ ), praseodymium oxide (Pr ₆ O ₁₁ ), yttrium oxide (Y ₂ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), zirconium oxide (ZrO ₂ ). ) Or aluminum oxide (Al ₂ O ₃ ), and any combination thereof.

Moreover, in this invention, the oxide of the transition metal concerning iron (Fe), cobalt (Co), manganese (Mn), nickel (Ni), and these arbitrary combinations can be added as a catalyst component. By adding these, not only PM purification but also exhaust gas purification can be performed.
Specifically, iron oxide (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ), manganese oxide (MnO, Mn ₂ O ₃ , MnO ₂ ) and the like can be exemplified.
In addition to these, one or more of rare earth element oxides, alkali metal oxides, alkaline earth metal oxides, and composite oxides thereof can be used.

In the exhaust gas purifying catalyst of the present invention, platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag), or gold (Au), or a noble metal associated with any combination thereof is used as a catalyst component. Can be added. By adding these, not only PM purification but also exhaust gas purification can be performed.

The exhaust gas purifying catalyst obtained by the present invention preferably has a catalyst loading of 25 g / L to 100 g / L per liter of the three-dimensional structure carrier.
When the amount of catalyst supported is less than 25 g / L, the amount of catalyst is small, the contact property between the particulate and the catalyst is deteriorated, and sufficient particulate oxidation performance may not be obtained. On the other hand, if the catalyst amount is more than 100 g / L, the particulates and the catalyst are sufficiently in contact with each other, and even if the catalyst amount is further increased, the effect reaches almost saturation. Therefore, not only can the particulate oxidation performance be improved, the amount of the catalyst supported in the pores of the three-dimensional structure carrier increases, and a large amount of catalytic component is also supported at the entrance of the pores. In some cases, the pores are clogged, and the pressure loss may increase.

Next, the manufacturing method of the exhaust gas purifying catalyst of the present invention will be described.
The production method of the present invention is a method for producing the exhaust gas-purifying catalyst described above, in which a catalyst layer is formed on a three-dimensional structure carrier such as a honeycomb carrier or a checkered honeycomb carrier.
Typically, it can be performed according to the following steps.

(1) Slurry preparation process First, a slurry containing a supporting component is prepared. That is, as a supporting component, a catalyst component that is a raw material of the catalyst layer, specifically, the above metal oxide, and a supporting substrate (binder component) such as boehmite alumina, zirconia sol, and silica sol as necessary, activated carbon particles, etc. Mix the vanished material and wet pulverize. A noble metal component such as Pt, Pd, Rh, Ag, and Au may be supported on the catalyst component by dipping in a metal oxide solution that is a catalyst component and firing.
The wet pulverization can be performed with a general vibration ball mill or the like, but in order to sharpen the particle size distribution, the particles are sized by a circulation type bead mill or a liquid cyclone and wet pulverized to prepare a slurry. At this time, the supported component powder contained in the slurry has an average particle diameter of 1 μm to 10 μm and a proportion of particles having a size of 1 μm or less, preferably 20% by mass or less, when the total amount of the supported component powder is 100% by mass. Is adjusted so that the abundance ratio of particles of 10% by mass or less and 10 μm or more is 10% by mass or less, preferably 5% by mass or less. Moreover, the solid content with respect to the water contained in the slurry is 1.0 mass% to 30 mass%, preferably 5 mass% to 15 mass%, and the viscosity at that time is 0.1 mPa.s. s-30 mPa.s s, preferably 1.0 mPa.s. s to 15 mPa.s Adjust to s.

By restricting the particle size of the supported component powder in the slurry as described above, the catalyst component is distributed to the inside of the pores of the three-dimensional structure carrier, and the catalyst layer formed inside the pores, particularly the above-mentioned Active pores capable of gas diffusion and improving catalytic activity can be formed in the pore-covering site (see FIG. 1).

The particle size distribution of the supported component powder in the slurry can be measured using, for example, a laser diffraction particle size distribution measuring device.
In the above particle size control, when the proportion of particles having a particle size of 1 μm or less exceeds 20% by mass, the amount of slurry entering the pores of the three-dimensional structure carrier increases, the pores are blocked, and the pressure loss increases. In addition, when the proportion of particles of 10 μm or more exceeds 10% by mass, the particles become too large, and the amount of catalyst supported in the pores of the three-dimensional structure carrier decreases, and the contact between the particulate and the catalyst component As a result, the oxidation performance of the particulates deteriorates.

Further, by regulating the solid content and the accompanying viscosity in the slurry as described above, the catalyst component is uniformly applied (coated) without blocking the pores of the three-dimensional structure carrier.
The solid content is less than 1.0% by mass, and the viscosity is 0.1 mPa.s. If it is less than s, the number of coats for ensuring the amount of catalyst formation is extremely increased, which is not efficient. The solid content exceeds 30% by mass, and the viscosity is 30 mPa.s. If it exceeds s, the catalyst component may block the pores of the three-dimensional structure carrier, and the uniformity of the coating state cannot be ensured.
The solid content can be measured using an infrared type or halogen type moisture meter, and the viscosity can be measured using a rotary type or vibration type viscometer.

In the production method of the present invention, cerium (Ce), praseodymium (Pr), gallium (Ga), yttrium (Y), zirconium (Zr) and aluminum are used as catalyst components among the supported components in preparing the slurry to be used. (Al) oxides, transition metal oxides such as iron (Fe), cobalt (Co), manganese (Mn) and nickel (Ni), platinum (Pt), palladium (Pd), rhodium (Rh) ), A powder carrying at least one of noble metals such as silver (Ag) and gold (Au) is preferably used.
By using such supported powder, not only PM purification but also exhaust gas purification can be performed.

Moreover, in the manufacturing method of this invention, it is preferable to add and use the loss | disappearance material which concerns on activated carbon particle | grains, resin particle | grains, a cellulose particle, or rice husk, and these arbitrary mixtures to the slurry containing the said carrying | support component.
By adding such a disappearing material to the slurry, if a firing step for eliminating the disappearing material after coating of the slurry is performed, active pores are formed on the catalyst layer formed in the pores of the three-dimensional structure carrier. It becomes easy to form.

In addition, as this vanishing material, it is preferable to use a thing with an average particle diameter of 0.5-5 micrometers. If the average particle size is less than 0.5 μm, the particles of the disappearing material may be too small and the effect may be slight. If the average particle size exceeds 5 μm, the particle size of the disappearing material is too large and the catalyst layer is simply divided. The target gap may not be formed.
Moreover, as an addition amount of a loss | disappearance material, it is preferable to set it as the ratio of 10-30 mass% with respect to the slurry containing the said carrying | support component.
When the addition amount is less than 10% by mass, the effect may be slight. When the addition amount exceeds 30% by mass, the catalyst layer may be simply divided and a target void may not be formed.

(2) Coating step Next, this slurry is coated (coated) on a three-dimensional structure carrier such as a wall flow type carrier. At this time, the water content of the three-dimensional structure carrier is preferably 1% by mass to 50% by mass, and more preferably 5% by mass to 30% by mass. By adjusting the moisture content in this way, it is easier to apply the catalyst component particles uniformly without blocking the pores of the three-dimensional structure carrier. If the water content is less than 1% by mass, the slurry may be applied at a high concentration only to the first contacted part. If it exceeds 50% by mass, the number of coats for securing the catalyst formation amount is extremely large. In some cases, the catalyst layer is not efficient and the catalyst layer is not formed in the vent of the three-dimensional structure carrier.
In order to allow the three-dimensional structure carrier to contain a desired amount of water, for example, the carrier is immersed in water directly or absorbed by a shower and then adjusted to have a predetermined moisture content by dry air blow or constant humidity. It can be humidified using an oven. Further, by adding silica sol, a surfactant or the like in advance to the water for hydration and making it exist in the pores of the carrier, it is possible to further facilitate the uniform adhesion of the slurry in the pores.

When supplying the slurry to the three-dimensional structure carrier in this step, particularly when the three-dimensional structure carrier is a wall flow, 60% by mass to 100% by mass of the slurry used for coating, more preferably 80% by mass to It is preferable to supply 100% by mass from the same end face of the carrier. This is because it is easier to uniformly apply the catalyst component particles without blocking the pores of the three-dimensional structure carrier.

There are no particular limitations on the method of supplying the slurry to the three-dimensional structure carrier and coating it into the pores. For example, the slurry is applied to one end surface of the three-dimensional structure carrier and the surface is pressurized to press-fit the slurry. Or the method of sucking the slurry from the opposite end face by negative pressure or the method of immersing one end face of the three-dimensional structure carrier in the slurry tank and sucking the slurry from the opposite end face by negative pressure. A method of using the difference to spread the slurry throughout the pores can be mentioned. These methods are efficient because excess slurry is removed from the carrier by pressurization or pressurization.
At the time of construction, if the slurry is uniformly supplied to the entire end face in contact with the slurry first, unevenness of particle support in the pores is less likely to occur, and desired active pores can be stably obtained. In addition, the above-described pressurization and suction can be performed before, simultaneously with, and after supplying the slurry to one end face. When pressurizing, the opposite end face is opened. It is preferable to keep it. In addition, when the predetermined amount of slurry cannot be applied by one operation, the above operation can be repeated several times. In that case, it is preferable to supply from the end surface on the opposite side to the end surface to which the slurry was supplied most recently.
In addition, examples of the method of spreading the slurry throughout the pores include a method of immersing the entire three-dimensional structure carrier in the slurry.

(3) Drying step After applying the slurry to the three-dimensional structure carrier, the excess of the slurry and water can be removed, and then the slurry can be dried by a heated air flow. Thereby, a catalyst layer is formed on the carrier.
The excess slurry is preferably removed by negative pressure suction at room temperature using a blower or a vacuum pump. At this time, the direction of the airflow flowing through the carrier may be the direction from the end surface to which the slurry is supplied toward the opposite end surface, or the opposite direction. The room temperature referred to here is about 15 to 35 ° C.
Further, it is preferable to sufficiently remove moisture from the carrier simultaneously with the removal of the excess slurry. If moisture is not sufficiently removed, slurry may be blown up during drying by a heated air flow to be performed next, and may not be uniformly supported in the pores.

Drying by a heated air flow is preferably performed through an air flow of 30 ° C. to 200 ° C., preferably 70 ° C. to 150 ° C., thereby drying the slurry and fixing the supported components. If the temperature of the heated air flow is less than 30 ° C, the drying time may be longer and may be unsuitable from the viewpoint of production efficiency. If the temperature exceeds 200 ° C, the moisture evaporation (movement in the pores) speeds up and the catalyst component is increased. In some cases, the pores of the three-dimensional structure carrier are blocked, and it is difficult to ensure the uniformity of the coating state.
The flow rate of the heated air flow is 4 to 5 m ³ / min. It is preferable that Further, it is preferable that the air flow is reversed at regular intervals, and the air flow is alternately supplied from both end faces. As a result, it is possible to dry while dispersing the moisture near the end face opposite to the end face supplying the heated air to the entire carrier, so that the slurry can be prevented from being blown up and supported uniformly in the pores. Can be easily.

The catalyst component (as oxide) contained in the supported component of the catalyst layer thus formed is preferably 25 g to 100 g per liter (apparent) volume of the three-dimensional structure carrier. Specifically, when the average particle diameter of the slurry is 1 μm to 10 μm and the abundance ratio of the particles of 1 μm or less is 20% or less, the abundance ratio of the particles of 10 μm or more is 10% or less, it is preferably 50 g or less. . In addition, when the average particle diameter is 1 μm to 10 μm and the abundance ratio of particles of 1 μm or less is 10% or less, the abundance ratio of particles of 10 μm or more is 5% or less, the amount is preferably 100 g or less. This carrying amount can be determined by the change in mass of the carrier before and after coating.
In addition, noble metal components such as Pt, Pd, Rh, Ag, and Au can be supported by immersing the noble metal component in a metal oxide solution that is a catalyst component and firing, as described above. The catalyst layer made of the metal oxide can be formed on a three-dimensional structure carrier, and the carrier can be supported by immersing or spraying the carrier in an aqueous solution of a noble metal component, drying and firing.

EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to these Examples.

Example 1
A mixture of 1000 g of water and 488 ml of dinitrodiamine platinum aqueous solution (8.02 mass%) and 450 g of a complex oxide of Ce and Pr (Ce: Pr = 7: 3 (mol ratio)), and a complex oxide of Ce and Pr The platinum was impregnated and supported thereon. The amount of platinum supported was 8% by mass.
The above platinum-supported CePr composite oxide powder (450 g) and alumina sol (50 g) were mixed in 2000 g of water, and stirred and pulverized to prepare a slurry of powder component / water content = 20 mass%. The viscosity measured with a rotary viscometer at that time was 20 mPa.s. s, the average particle diameter measured by the laser diffraction method was 2.9 μm, the presence ratio of particles of 1 μm or less was 12%, and the presence ratio of particles of 10 μm or more was 10%.
Next, a three-dimensional structure carrier having a diameter of 143.764 mm, a height of 152.4 mm, a cell density of 300 cells / in ² , an average pore diameter of 18 μm, and a porosity of 59 vol% (a cordierite honeycomb carrier, the carrier moisture content at that time is 3 (Mass%) was prepared, the slurry was immersed from the lower end surface of the carrier, and 70 mass% of the total weight of the slurry supplied to the carrier was supplied from the lower end surface. Thereafter, excess slurry was removed by air blowing, followed by drying for 1 hour through an air stream at 150 ° C., and further calcining at 400 ° C. for 4 hours to form a catalyst layer, thereby obtaining an exhaust gas purifying catalyst of this example. The amount of catalyst layer formed was 50 g per liter of the exhaust gas purifying catalyst.
In the used honeycomb carrier, one of two openings formed at both ends of each cell is alternately sealed with a sealing material. That is, of the many cells, about half of the cells open at one end face, and the remaining open at the other end face. Sealed cells and open cells are alternately arranged on the end face of the carrier. Therefore, it is a wall flow type carrier in which the end face of the carrier has a checkered pattern.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, the physical properties of the slurry used, the coating method, and the like.

(Example 2)
A slurry was prepared so that the powder component / water content = 5% by mass, and the viscosity at that time was 7 mPa.s. Except for using the slurry as s, the same operation as in Example 1 was repeated to produce an exhaust gas purifying catalyst of this example. Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Example 3)
Except that the water content of the cordierite honeycomb carrier to which the slurry was adhered was adjusted to 30% by mass by water treatment, the same operation as in Example 1 was repeated to produce an exhaust gas purification catalyst of this example.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

Example 4
Exhaust gas purification catalyst of this example was manufactured by repeating the same operation as in Example 1 except that the entire amount of slurry was supplied from the upper end surface of the honeycomb carrier and sucked from the lower end surface to remove excess slurry.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Example 5)
This operation was repeated by repeating the same operation as in Example 1 except that the slurry was immersed in the lower end surface of the honeycomb carrier, the slurry was sucked up from the upper end surface by negative pressure and supplied in its entirety, and then the excess slurry was removed by suction from the lower end surface. An example exhaust gas purification catalyst was produced.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Example 6)
In the drying after applying the slurry to the honeycomb carrier, the same operation as in Example 1 was repeated except that an air flow of 50 ° C. was supplied and the drying treatment was performed for 3 hours, thereby producing an exhaust gas purification catalyst of this example. .
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Example 7)
Except that the amount of catalyst layer formed was 25 g per liter of the exhaust gas purification catalyst, the same operation as in Example 6 was repeated to produce the exhaust gas purification catalyst of this example.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Example 8)
Except that the amount of catalyst layer formed was 100 g per liter of the exhaust gas purification catalyst, the same operation as in Example 6 was repeated to produce the exhaust gas purification catalyst of this example.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Comparative Example 1)
A mixture of 1000 g of water and 488 ml of dinitrodiamine platinum aqueous solution (8.02 mass%) and 450 g of a complex oxide of Ce and Pr (Ce: Pr = 7: 3 (mol ratio)), and a complex oxide of Ce and Pr The platinum was impregnated and supported thereon. The amount of platinum supported was 8% by mass.
450 g of platinum-supported CePr composite oxide powder and 50 g of alumina sol were mixed in 1000 g of water and stirred and pulverized to prepare a slurry of powder component / water content = 33% by mass. The viscosity measured with a rotary viscometer at that time was 45 mPa.s. It was s.
The average particle diameter measured by the laser diffraction method was 0.17 μm, the existence ratio of particles of 1 μm or less was 100%, and the existence ratio of particles of 10 μm or more was 0%. Using the resulting slurry, the same operation as in Example 1 was repeated to obtain an exhaust gas purifying catalyst of this example.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Comparative Example 2)
A mixture of 1000 g of water and 488 ml of dinitrodiamine platinum aqueous solution (8.02 mass%) and 450 g of a complex oxide of Ce and Pr (Ce: Pr = 7: 3 (mol ratio)), and a complex oxide of Ce and Pr The platinum was impregnated and supported thereon. The amount of platinum supported was 8% by mass.
450 g of platinum-supported CePr composite oxide powder and 50 g of alumina sol were mixed in 1000 g of water and stirred and pulverized to prepare a slurry of powder component / water content = 33% by mass. The viscosity measured with a rotary viscometer at that time was 45 mPa.s. It was s.
The average particle diameter measured by the laser diffraction method was 0.17 μm, the existence ratio of particles of 1 μm or less was 100%, and the existence ratio of particles of 10 μm or more was 0%. The same operation as in Example 1 was repeated except that the obtained slurry was immersed and controlled so that the same amount of slurry was supplied to the carrier from both end faces to obtain an exhaust gas purifying catalyst of this example.
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

(Comparative Example 3)
A mixture of 1000 g of water and 488 ml of dinitrodiamine platinum aqueous solution (8.02 mass%) and 450 g of a complex oxide of Ce and Pr (Ce: Pr = 7: 3 (mol ratio)), and a complex oxide of Ce and Pr The platinum was impregnated and supported thereon. The amount of platinum supported was 8% by mass.
450 g of platinum-supported CePr composite oxide powder and 50 g of alumina sol were mixed in 1000 g of water and stirred and pulverized to prepare a slurry of powder component / water content = 33% by mass. The viscosity measured with a rotary viscometer at that time was 45 mPa.s. It was s.
The average particle diameter measured by the laser diffraction method was 0.17 μm, the existence ratio of particles of 1 μm or less was 100%, and the existence ratio of particles of 10 μm or more was 0%. Using the obtained slurry, the same operation as in Example 1 was repeated except that the carrier was dried at 150 ° C. for 2 hours without supplying an air flow to obtain an exhaust gas purification catalyst of this example. .
Table 1 shows the components of the exhaust gas purifying catalyst of this example, the amount of catalyst layer formed, and the physical properties of the slurry used.

[Performance evaluation]
The following performance evaluation was performed on the exhaust gas purifying catalysts of Examples and Comparative Examples obtained as described above.

(Measurement of average pore diameter and pore volume)
With respect to the catalyst layers of the exhaust gas purifying catalysts of the above Examples and Comparative Examples, the pore volume sum of the predetermined pore diameters shown in Table 2 was measured, and the volume sum of active pores, the presence rate, and the like were calculated.
The obtained results are shown in Table 2. In addition, the measurement of the average pore diameter and pore volume required when calculating these values was performed using a mercury porosimeter (manufactured by Shimadzu Corporation, trade name: Autopore 9500).

(Measurement of pressure loss)
First, the exhaust gas purifying catalyst of each example was installed in the exhaust system of a vehicle having a supply type direct injection diesel engine with a displacement of 2.5 liters. For the evaluation, a 4-cylinder engine with a displacement of 2500 cc made by Nissan Motor was used.
At this time, pressure sensors were attached before and after the exhaust gas purification catalyst installed in the exhaust system, and steady operation was performed at a rotational speed of about 2000 rpm. The pressure loss was measured from the measured value of the pressure sensor when about 4 g of particulate was deposited on the exhaust gas purification catalyst.
The pressure loss was defined as the difference between the measured values of the two pressure sensors. Further, the determination of particulate accumulation was made by confirming the increase in weight after measurement with the engine operating time constant, and Table 2 shows the obtained results.

(Measurement of oxidation rate of particulates)
The exhaust gas purification catalyst of each example was installed in the exhaust system of a vehicle having a supply type direct injection diesel engine with a displacement of 2.5 liters. For the evaluation, a 4-cylinder engine manufactured by Nissan Motor and a displacement of 2500 cc was used. A pressure sensor was attached before and after the exhaust gas purifying catalyst, and a steady operation was performed at a rotational speed of about 2000 rpm.
First, about 10 g of particulates is deposited on the exhaust gas purification catalyst in a temperature range where the oxidation reaction of the particulates hardly occurs in the exhaust gas purification catalyst, and then the oxidation reaction of the particulates of the exhaust gas purification catalyst is sufficiently activated. Raise the temperature rapidly to the temperature range.
When particulate oxidation starts, measure the time until the differential pressure of the pressure sensor attached before and after the exhaust gas purification catalyst decreases and no longer changes, and the amount of particulates previously deposited on the exhaust gas purification catalyst and its time From this, the oxidation rate of the particulates was determined. The obtained results are also shown in Table 2.

  From Table 2, in the exhaust gas purifying catalysts of Examples 1 to 8 obtained by the production method belonging to the scope of the present invention, the pores of the three-dimensional support are not clogged, and desired active pores are present in the catalyst layer. Is formed. Therefore, in the exhaust gas purifying catalyst of these examples, it is possible to suppress an increase in pressure loss when particulates are deposited. Further, it can be seen that the oxidation performance of the particulates is improved because the contact area with the particulates is increased.

As mentioned above, although this invention was demonstrated using some Examples and comparative examples, this invention is not limited to these Examples, A various deformation | transformation is possible within the range of the summary of this invention.
For example, the exhaust gas purification catalyst obtained by the present invention can be applied not only to particulate processing of diesel engines and gasoline engines but also to exhaust gas purification catalysts for air purifiers.

In an example of the exhaust gas purifying catalyst obtained by the present invention, it is a schematic partial sectional view showing the vicinity of a cell wall of a three-dimensional structure carrier. It is a schematic fragmentary sectional view which shows the cell wall vicinity of the three-dimensional structure of the conventional catalyst for exhaust gas purification. 1 is a partially cutaway perspective view showing an example of an exhaust gas purifying catalyst obtained by the present invention using a wall flow type carrier as a three-dimensional structure carrier. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exhaust gas purification catalyst 10 Support | carrier 11 Cell 12 Cell wall 13 Pore 14 Cell inlet 15 Cell outlet 16 Closed end surface 20 Catalyst layer 21 Surface coating part 22, 22 'Pore coating part EG Exhaust gas

Claims (9)

In a method for producing an exhaust gas purifying catalyst comprising a three-dimensional structure carrier having a plurality of cells partitioned by cell walls having pores, and a catalyst layer formed on the three-dimensional structure carrier,
The catalyst layer has a surface coating site formed along the surface of the cell wall, and a pore coating site formed along the pore of the cell wall,
At least the above-mentioned pore covering portion has active pores having a pore diameter of 0.1 to 10 μm derived from the supported component contained in the catalyst layer,
Including a coating step of applying a slurry containing the support component to the three-dimensional structure carrier;
The average particle diameter of the slurry is 1 to 10 μm, and the existence ratio of particles of 1 μm or less is 20% or less, and the existence ratio of particles of 10 μm or more is 10% or less,
The slurry has a solid content with respect to moisture of 1.0% by mass to 30% by mass and a viscosity of 0.1 mPa.s. s-30 mPa.s A method for producing an exhaust gas purifying catalyst, characterized by being s.
  2. The method for producing an exhaust gas purifying catalyst according to claim 1, wherein the moisture content of the three-dimensional structure carrier used in the coating step is 1% by mass to 50% by mass.   In the said application | coating process, 60 mass%-100 mass% of the said slurry used at this process is supplied from the same end surface of the said three-dimensional structure support | carrier, The exhaust gas purification of Claim 1 or 2 characterized by the above-mentioned. For producing a catalyst for use.   Further, a drying step is included. In the drying step, surplus of the slurry and water are removed through an air flow at room temperature to the three-dimensional structure carrier on which the slurry is applied, and then the air flow at 30 to 200 ° C. The method for producing an exhaust gas purifying catalyst according to any one of claims 1 to 3, wherein the slurry is dried and the supported component is fixed. The catalyst component contained in the said support component of the said catalyst layer is contained in the ratio of 25g / L-100g / L with respect to the said three-dimensional structure support | carrier, The claim 1 characterized by the above-mentioned. The manufacturing method of the catalyst for exhaust gas purification as described in any one of .
  The catalyst component contained in the support component is at least one selected from the group consisting of cerium (Ce), praseodymium (Pr), gallium (Ga), yttrium (Y), zirconium (Zr), and aluminum (Al). The method for producing an exhaust gas purifying catalyst according to any one of claims 1 to 5, comprising an oxide containing an element.   The catalyst component further contains an oxide of at least one transition metal selected from the group consisting of iron (Fe), cobalt (Co), manganese (Mn), and nickel (Ni). A method for producing an exhaust gas purifying catalyst according to claim 6.   The catalyst component further contains at least one noble metal selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), silver (Ag), and gold (Au). A method for producing an exhaust gas purifying catalyst according to claim 6 or 7. The catalyst component contained in the support component is at least one selected from the group consisting of cerium (Ce), praseodymium (Pr), gallium (Ga), yttrium (Y), zirconium (Zr), and aluminum (Al). To oxides containing elements,
An oxide of at least one transition metal selected from the group consisting of iron (Fe), cobalt (Co), manganese (Mn) and nickel (Ni), and platinum (Pt), palladium (Pd), rhodium (Rh) ), A powder carrying at least one of at least one noble metal selected from the group consisting of silver (Ag) and gold (Au),
The method for producing an exhaust gas purifying catalyst according to any one of claims 1 to 8, wherein a slurry containing the supported component is prepared.

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