JPH0479700B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a monolithic catalyst, and more particularly to a method for producing a monolithic catalyst in which the amount of catalyst components deposited varies depending on the position inside the catalyst.

When a monolithic catalyst manufactured by the method of the present invention is installed and used in an automobile exhaust system, etc., it is possible to perform optimal exhaust gas purification that matches the actual flow velocity distribution of exhaust gas inside the catalyst.

[Prior art] Conventionally, when manufacturing a monolithic catalyst, a monolithic catalyst base material is immersed in a slurry containing catalyst support layer components, pulled up, dried, and fired to support the catalyst on the inner surface of the pores of the base material. It formed a layer. still,
The catalyst component, such as a noble metal, can be supported by immersing the support layer in a solution containing the catalyst component after forming the support layer, or by incorporating the catalyst component into the slurry in advance and then forming the support layer. It was carried out in an integrated manner.

Therefore, in the monolithic catalyst manufactured by the conventional manufacturing method, the supporting density of catalyst components was almost uniform over the entire area of the monolithic catalyst.

However, when we consider the case where a monolithic catalyst is actually used by installing it in an automobile exhaust system, etc., exhaust gas does not pass through the monolithic catalyst at a uniform speed and pressure, but generally near the axial center of the monolithic catalyst. The amount of gas passing through increases. Therefore,
Considering the exhaust gas purification efficiency of the monolith catalyst and the durability of the catalyst, it is better to support a larger amount of catalyst components near the axial center of the monolith catalyst.
Additionally, if the catalyst support layer is made thicker near the shaft center and thinner at the outer periphery, the pressure loss near the shaft center will be higher than that at the outer periphery, the flow velocity distribution inside the catalyst will become smaller, and the catalyst performance will improve. .

However, a method for varying the amount of supported catalyst components and the amount of supported layer components locally within a monolithic catalyst has not been provided in the past.

[Object of the Invention] The present invention has been devised in view of the above circumstances. Therefore, an object of the present invention is to provide a new method for producing a monolithic catalyst in which the supporting layer of the catalyst component and the amount of the supporting layer component are varied locally depending on the usage status of the monolithic catalyst. .

[Structure of the Invention] In the present invention, when forming a catalyst support layer on the inner surface of the pores of a monolithic catalyst base material, after depositing a fluid such as a slurry containing a support layer component on the inner surface, Before drying the fluid, the fluid is blown away by a predetermined amount determined by the position inside the base material using an air flow having a predetermined flow velocity distribution.

That is, the present invention provides a monolithic catalyst in which a catalyst support layer is formed on the inner surface of the pores of a columnar monolithic catalyst substrate having a large number of pores extending in the axial direction. In the manufacturing method, the catalyst supporting layer is formed by depositing a fluid containing at least a component of the catalyst supporting layer on the inner surface of the pores, and then blowing a predetermined amount of the fluid into the inner surface of the pore with an air flow having a predetermined flow velocity distribution. This is a method for producing a monolithic catalyst, which is characterized in that it is formed by removing it from the surface, drying it, and firing it.

The monolith catalyst base defines the external shape of the catalyst, and its material is generally cordierite, but other materials such as mullite or spinel can also be used. The base material has an integrally molded structure, has a large number of pores (100 to 600 pores/square inch) extending in the direction of flow of exhaust gas, and has a columnar external shape (cylindrical, square prism, etc.), which is suitable for the installation of monolithic catalysts. (a shape that matches the internal shape of the exhaust system to be used).

In the present invention, first, a fluid such as a slurry containing a component of the catalyst support layer is deposited on the inner surface of the pores of the monolithic catalyst base material. This is generally carried out by immersing the monolithic catalyst substrate in the slurry, but the method is not limited to this, and for example, the method described below may be used. Although alumina is generally used as a component of the catalyst support layer, it is not limited to alumina. Note that the slurry may contain a solution of a catalyst component such as a catalytic precious metal, and the catalyst component may be supported simultaneously with the formation of the catalyst support layer.

Next, a gas (generally air is used) having a predetermined flow velocity distribution is pumped or sucked into the pores of the monolithic catalyst substrate to which the fluid has been adhered, and a small amount of the fluid is blown away. The amount blown away here is determined by the flow velocity distribution so as to vary depending on the position where the fluid is attached.

The flow velocity distribution can be determined, for example, by coaxially connecting a columnar flow regulator having a plurality of ventilation holes each having a predetermined opening cross-sectional area and extending in the axial direction to at least one end surface of the monolithic catalyst substrate, and This can be provided by rectifying the airflow that is forced into or sucked into the air by using the rectifying fluid. As the material of the flow regulator, ceramics, resin, metal, rubber, etc. can be used.

Here, when it is desired to obtain a monolithic catalyst that supports a large amount of catalyst components near the center and a small amount of catalyst components near the outer periphery, the above-mentioned flow regulation is performed using a ventilation hole near the shaft center. The cross-sectional area is small;
In addition, the cross-sectional area of the ventilation holes near the outer periphery is large. Then, the flow velocity distribution is small near the axial center and large near the outer periphery. Therefore, it is possible to form a thick catalyst support layer near the shaft center and a thin catalyst support layer near the outer circumference, thereby obtaining a desired monolithic catalyst.

In this way, a desired amount of the fluid containing the components of the catalyst support layer is left on the inner surface of the monolithic catalyst base material in a desired amount determined by the position within the base material, and then dried and fired to form the catalyst support layer. Form.

In the above manufacturing process, when the fluid is attached to the inner surface of the pores of the monolithic catalyst base material, the fluid is attached by force feeding or suction into the pores through the flow regulator. Good too. In that case, after adhesion, air can be continuously pumped or sucked into the pores of the monolith base material to blow away the fluid.

The supported catalyst components include conventionally known catalyst components such as platinum (Pt), palladium (Pd), iridium (Ir), ruthenium (Ru), rhodium (Rh), and osmius (Os). precious metals, or chromium (Cr), nickel (Ni),
Base metals such as panadium (V) and copper (Cu) can be used.

[Examples] The present invention will be described below based on specific examples.

(First Example) FIG. 1 is a schematic diagram showing how the slurry attached to the inner surface of the pores of the monolithic catalyst base material 1 is blown away with an air flow having a predetermined flow velocity distribution.
The figure is a schematic cross-sectional view of the flow regulator 2 used in FIG. 1.

(1) Adhesion process Alumina sol 700g (alumina content 10wt%)
Add alumina powder to a mixed suspension consisting of 150g (40wt%) of aluminum nitrate aqueous solution and 450ml of distilled water.
1000 g was added and stirred to prepare a fluid slurry. Next, a cylindrical monolith catalyst substrate (diameter 10.7 cm, length 15 cm, pore number 300) was placed in the slurry.
The slurry was immersed for 2 minutes to uniformly adhere the slurry to the inner surface of the pores of the monolithic catalyst substrate.

(2) Blowing process As shown in Figure 1, both ends of the monolithic catalyst base material 1 to which the slurry is evenly adhered are coaxially connected to the tubes 3 and 4, and a flow regulator is installed inside the tube 3. 2 was housed therein, and the flow regulator 2 was connected to the upper end surface of the monolithic catalyst substrate 1. As shown in FIG.
The cross-sectional area of 0 was small near the axial center and large near the outer periphery.

Subsequently, air was forced in the direction of the tube 3 to the tube 4 as shown by the arrow, and a predetermined amount of the slurry adhering to the inner surface of the pores of the monolithic catalyst substrate 1 was blown away.
Here, the amount of slurry blown out is small near the shaft center and large near the outer periphery. This is because the blowing amount is determined by the flow velocity distribution of the pressurized air provided by the fluid regulator, the air pressure feeding time, and the like.

(3) Drying and firing process After blowing off the slurry as described above, the monolithic catalyst base material was dried at 200°C for 1 hour, and then heated at 700°C.
A monolithic catalyst carrier having a catalyst supporting layer formed on its surface was obtained by firing at ℃ for 2 hours.

(4) Supporting process The monolithic catalyst carrier on which the supporting layer has been formed as described above is immersed in distilled water to absorb sufficient water, then pulled out and the excess moisture is blown off. It was immersed in a platinum aqueous solution for 1 hour, pulled out, blown off excess moisture, and dried at 200° C. for 1 hour to support Pt on the catalyst support layer.

A monolithic catalyst was produced as described above. In the monolithic catalyst of this example, a large amount of Pt, which is a catalyst component, is supported near the shaft center, and a small amount of catalyst component is supported near the outer periphery, so when installed in an actual exhaust system and used, the exhaust gas gas purification efficiency,
The durability of the catalyst was also good.

(Second Example) FIG. 3 is a schematic diagram showing the step of attaching the slurry 9 to the monolith catalyst base material 1 in the second example, and FIG. 4 is a flow regulating flow diagram 2 used in FIG.
FIG.

In the second example, the step of attaching a slurry containing a support layer component to the inner surface of a monolithic catalyst base material is as follows:
This is the case when using a rectifier.

(1) Adhesion process The monolithic catalyst base material 1 is attached to the tube 3 as shown in Fig. 3.
and a tube 4, and a flow regulator 3 having a cross-sectional shape shown in FIG. .

Subsequently, a slurry 9 having the same components as in the above example was pumped from the upper part of the tube 3 in the direction of the arrow, and the slurry 9 was adhered to the inner surface of the pores of the monolithic catalyst substrate 1. In this embodiment, as shown in FIG. 4, since the flow regulator 2 does not have ventilation holes near the outer periphery 21, the slurry 9 is also prevented from entering the outer periphery 11 of the monolithic catalyst base material 1. Does not stick. Note that from the viewpoint of preventing the slurry from entering the outer peripheral portion, a flow regulator may be used in which the ventilation hole near the axial center portion is constituted by a single ventilation hole. The single ventilation hole in FIG. 4 refers to a flow regulating system in which there is no grid dividing the ventilation hole 20.

(2) Blowing process Next, air is forced as shown by the arrow into the pores of the monolithic catalyst substrate to which the slurry 9 has been attached as described above, and a predetermined amount of the slurry 9 attached to the inner surface of the monolithic catalyst substrate is blown away. I blew it away. The flow velocity distribution of the pressurized air inside the monolithic catalyst base material 1 is given by the flow regulator 2 shown in FIG.
Therefore, by the compressed air, a small amount of the slurry 9 adhering to the vicinity 10 of the shaft center of the monolithic catalyst base is blown away, and a large amount of slurry 9 is blown away near the inner side 12 of the outer circumference 11.

(3) Drying and firing step Slurry 9 was deposited on the inner surface of the pores of the monolithic catalyst substrate in varying amounts in places as described above, and then dried and fired under the same conditions as in the first example to form a catalyst support layer. was formed.

(4) Supporting process Catalyst components were supported on the monolithic catalyst carrier on which the catalyst supporting layer was formed as described above under the same conditions as in the first example.

In the monolithic catalyst manufactured in the second example, no catalyst component was supported near the outer peripheral portion 11. Generally, when a monolithic catalyst is used by being attached to an automobile exhaust system, the outer periphery of the end face of the catalyst is covered with a retainer, which is a holding material. Therefore, even if a catalyst component is supported on the covered portion, the supported catalyst component does not contribute to exhaust gas purification. In other words, it is a waste. However, the monolithic catalyst produced by the method of this example is economical because no catalyst component is supported on the covered portion.

Although the supporting step was provided separately in the above two examples, the catalyst component may be contained in the slurry and formed simultaneously with the supporting layer.

[Effects of the Invention] In summary, the present invention provides, when forming a catalyst support layer on the inner surface of the pores of a monolithic catalyst base material, after adhering the support layer forming component to the inner surface of the pores of the base material in a fluidized state. , an air flow having a predetermined flow velocity distribution is pumped or sucked into the pores, and the adhered fluid is left on the inner surface of the pores so that the amount of residual adhesion varies depending on the location, and then dried and baked. It is formed by

As is clear from the above, when a monolithic catalyst is produced by the method of the present invention, the amount of catalyst components supported within the monolithic catalyst can be arbitrarily changed depending on the location. Therefore, it is possible to obtain a monolithic catalyst having a supported distribution of catalyst components suitable for actual use of the monolithic catalyst. Additionally, if the catalyst support layer is made thicker near the shaft center and thinner at the outer periphery, the pressure loss near the shaft center will be higher than that at the outer periphery, the flow velocity distribution inside the catalyst will become smaller, and the catalyst performance will improve. . Therefore, the exhaust gas purification efficiency is high and the durability is also good. Moreover, unnecessary amounts of raw materials are not required.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram illustrating the blowing process of the first embodiment of the present invention, and FIG. 2 is a schematic cross-sectional diagram of a flow regulator used in the first embodiment. FIG. 3 is a schematic diagram illustrating the adhesion process and the blowing process in the second embodiment of the present invention, and FIG. 4 is a schematic cross-sectional diagram of a flow regulator used in the second embodiment. 1...monolith catalyst base material, 2...fluid regulator.

Claims (1)

[Scope of Claims] 1. A monolithic catalyst, which is produced by forming a catalyst support layer on the inner surface of the pores of a columnar monolithic catalyst substrate having a large number of pores extending in the axial direction. In the method for manufacturing the catalyst support layer, a fluid containing at least a component of the catalyst support layer is deposited on the inner surface of the pores, and then a predetermined amount of the fluid is applied to the catalyst support layer by an air flow having a predetermined flow velocity distribution. A method for producing a monolithic catalyst, characterized in that the monolithic catalyst is formed by removing it from the inner surface, drying it, and then firing it. 2. The predetermined flow velocity distribution is such that on at least one end surface of the monolithic catalyst base material,
A columnar flow regulator having a plurality of ventilation holes each having a predetermined opening cross-sectional area and extending in the axial direction is coaxially connected to the monolith catalyst base material, and the airflow rectified by the flow regulator is directed to the base. The manufacturing method according to claim 1, which is provided by passing a material through pores. 3. The manufacturing method according to claim 1, wherein the fluid contains a catalyst component. 4. The manufacturing method according to claim 2, wherein the predetermined opening cross-sectional area is small in the ventilation holes near the axial center of the flow regulator, and large in the ventilation holes near the outer peripheral part. 5. The adhesion of the fluid onto the inner surface of the pores includes:
2. The manufacturing method according to claim 1, wherein said manufacturing method is carried out via said flow regulator. 6. The manufacturing method according to claim 5, wherein the ventilation holes near the outer periphery of the fluid regulator are masked to prevent the fluid from entering the pores at the outer periphery. 7. The manufacturing method according to claim 6, wherein the ventilation hole in the unmasked portion of the flow regulator is a single ventilation hole.