JP2007244951A - Manufacturing method of particulate filter type exhaust gas cleaning catalyst, and particulate filter type exhaust gas cleaning catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a particulate filter type exhaust gas cleaning catalyst which enhances the PM reduction performance and a particulate filter type exhaust gas cleaning catalyst made by the method. <P>SOLUTION: The manufacturing method of the particulate filter type exhaust gas cleaning catalyst comprises a step (1) of obtaining an inorganic fiber mixture by mixing the inorganic long fiber and short fiber, a step (2) of obtaining the catalyst component supported inorganic fiber mixture by supporting the catalyst components on the inorganic fiber mixture, a step (3) of obtaining the catalyst precursor by mixing a pore creating material with the catalyst component supported inorganic fiber mixture and a step (4) of obtaining the particulate filter type exhaust gas cleaning catalyst by calcining the catalyst precursor in the cell of the structure with the cell and extinguishing the perforating material to arrange the catalyst in the cell. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a particulate filter type exhaust gas purification catalyst and a particulate filter type exhaust gas purification catalyst. The present invention relates to a production method and a particulate filter type exhaust gas purification catalyst obtained thereby.

A diesel particulate filter (DPF) is generally used for reducing PM discharged from a diesel engine. In the conventional DPF, since PM is collected on the cell wall, PM accumulates on the cell wall surface, and the pressure loss of the exhaust gas rapidly increases.
For this reason, a system has been proposed in which overheating combustion processing at 600 ° C. or higher is periodically performed by fuel injection when the DPF self-regenerates (see Patent Documents 1 and 2).

Moreover, the system which processes inorganic fiber (mainly silicon carbide which is excellent in heat resistance) into a nonwoven fabric, collects PM using this, and also processes using a heat source is proposed (refer to patent documents 3). .
JP-A-6-294315 JP-A-8-189339 JP 2003-236391 A

However, the systems described in Patent Documents 1 and 2 have a problem that, for example, it is necessary to sense the amount of PM trapped, and the system becomes complicated. In addition, there is a problem that fuel efficiency deteriorates during self-regeneration.
On the other hand, the system described in Patent Document 3 requires a large heat source and system, and there is a problem that miniaturization is difficult. In addition, there is a problem that it is difficult to maintain the shape of inorganic fibers alone.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to produce a particulate filter type exhaust gas purification catalyst capable of improving PM reduction performance, and to be produced thereby. It is an object of the present invention to provide a particulate filter type exhaust gas purification catalyst.

  As a result of intensive studies to achieve the above object, the present inventors have found that the reason why the PM removal efficiency is not improved in the conventional DPF is that the catalyst component such as platinum supported on the DPF in order to improve the PM removal efficiency. Since PM is deposited on the cell wall surface while being buried in the cell wall, the performance of the catalyst component is not fully exhibited, and PM and the catalyst component are required to improve PM removal efficiency. The present inventors have found that it is necessary to have a structure capable of improving the contact rate of the present invention, and have completed the present invention.

That is, the method for producing a particulate filter type exhaust gas purification catalyst of the present invention includes a structure having cells, a catalyst comprising a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers, And the catalyst is a method for producing a particulate filter type exhaust gas purification catalyst disposed in the cell, characterized in that it includes the following steps (1) to (4).
(1) Step of obtaining an inorganic fiber mixture by mixing inorganic long fibers and short fibers (2) Step of obtaining a catalyst component-supported inorganic fiber mixture by supporting a catalyst component on the inorganic fiber mixture (3) Supporting the catalyst component Step of adding a pore former to the inorganic fiber mixture and mixing to obtain a catalyst precursor (4) The catalyst precursor is calcined in the cell of the structure, and the pore former is burned away in the cell. A step of obtaining a particulate filter type exhaust gas purification catalyst by disposing a catalyst

  In addition, the particulate filter type exhaust gas purification catalyst of the present invention is produced by the method for producing the particulate filter type exhaust gas purification catalyst of the present invention.

  According to the present invention, since a structure capable of improving the contact ratio between PM and the catalyst component is constructed, etc., a method for producing a particulate filter type exhaust gas purification catalyst capable of improving PM reduction performance, and a particle produced thereby. A curated filter type exhaust gas purification catalyst can be provided.

Hereinafter, the manufacturing method of the particulate filter type exhaust gas purification catalyst of the present invention will be described in detail. In the present specification and claims, “%” for concentration and addition amount represents a mass percentage unless otherwise specified.
As described above, the method for producing a particulate filter type exhaust gas purifying catalyst of the present invention comprises a catalyst having a structure having cells and a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers. And the catalyst is a method for producing a particulate filter type exhaust gas purification catalyst provided in the cell, and includes the following steps (1) to (4).
(1) Step of obtaining an inorganic fiber mixture by mixing inorganic long fibers and short fibers (2) Step (3) of obtaining a catalyst component-supported inorganic fiber mixture by supporting a catalyst component on the obtained inorganic fiber mixture Step of adding a pore former to the catalyst component-supported inorganic fiber mixture and mixing to obtain a catalyst precursor (4) By calcining the obtained catalyst precursor in a cell of the structure and burning out the pore former A step of obtaining a particulate filter type exhaust gas purification catalyst by disposing a catalyst in the cell

  By adopting such a configuration, a particulate filter type exhaust gas purification catalyst capable of improving the PM reduction performance can be obtained with high productivity.

Here, each said process (1)-(4) is demonstrated still in detail.
First, in the step (1) of mixing inorganic long fibers and short fibers to obtain an inorganic fiber mixture, the mixing method is not particularly limited as long as an inorganic fiber mixture is obtained. The mixing ratio and components of the long fibers and the short fibers are not particularly limited.
For example, in the present invention, long fibers and short fibers are preferably contained in a mass ratio of 2: 8 to 5: 5, and are contained in a ratio of 3: 7 to 4: 6. It is more preferable.
When the ratio of long fibers to short fibers is more than 2: 8 (for example, the ratio of long fibers to short fibers is 1: 9), the short fibers increase, leading to blockage of pores, and the contact ratio with PM is increased. May decrease.
On the other hand, when the ratio of long fibers to short fibers is less than 5: 5 (for example, the ratio of long fibers to short fibers is 6: 4), the short fiber structure is reinforced with the long fibers, so that the desired fiber It becomes difficult to form a structure. In addition, the density is lowered, and the PM collection efficiency is lowered.

Moreover, in this invention, it is preferable that the fiber length of a long fiber is 2-10 mm, and it is still more preferable that it is 2-4 mm.
Furthermore, in this invention, it is preferable that the fiber diameter of a long fiber is 5-35 micrometers, and it is still more preferable that it is 7-10 micrometers.

Furthermore, in this invention, it is preferable that the fiber length of a short fiber is 0.1-50 mm, and it is still more preferable that it is 0.1-2 mm. However, this is not the case because the short fiber has a non-uniform length due to manufacturing conditions.
Furthermore, in the present invention, the fiber diameter of the short fibers is preferably 1 to 10 μm, and more preferably 3 to 5 μm.
When long fibers and short fibers as described above are mixed, the fibers are uniformly dispersed, and in the catalyst supporting the catalyst component, the contact ratio between PM and the catalyst component can be further improved, and a desired porosity can be obtained. It will also be obtained.

  Further, in the present invention, the inorganic long fibers and short fibers are not particularly limited as long as they can withstand use as a particulate filter type exhaust gas purification catalyst. For example, silicon carbide, alumina, Silica or alumina silica fibers and any combination thereof can be exemplified, and examples of any combination thereof include mixtures and composite compounds thereof. Furthermore, so-called glass fibers containing an alkali metal or an alkaline earth metal can also be used.

Furthermore, in the present invention, the inorganic long fibers and short fibers are preferably those containing alumina and silica, and the alumina content is preferably 70% or more.
By containing alumina and silica, heat resistance and strength are excellent, and such inorganic fibers can easily maintain a structure capable of improving the contact ratio between PM and catalyst components, and can further improve PM reduction performance. Become.
Also, when the alumina content is 70% or more, the catalyst component loading performance is greatly improved, so that the contact rate between PM and the catalyst component can be further improved, and the PM reduction performance can be further improved. It will be a thing.

Next, in the step (2) of obtaining the catalyst component-supported inorganic fiber mixture by supporting the catalyst component on the obtained inorganic fiber mixture, the support method is particularly limited as long as the catalyst component-supported inorganic fiber mixture can be obtained. The catalyst component is not particularly limited as long as it can promote the PM reduction performance.
For example, in the present invention, the catalyst component may be supported by immersing the inorganic fiber mixture in a solution or slurry containing the catalyst component, or may be dried and calcined to support the catalyst component.
In the present invention, it is desirable that the catalyst component described above contains a noble metal such as platinum, palladium, or rhodium. Moreover, ceria, titania, etc. may be included as a co-catalyst.

Next, in the step (3) of adding a pore former to the obtained catalyst component-supporting inorganic fiber mixture and mixing to obtain a catalyst precursor, if the catalyst precursor can be obtained, a method for adding the pore former There is no particular limitation on the type and type.
For example, in the present invention, when the pore former is added, by sufficiently mixing with the catalyst component-supporting inorganic fiber mixture, it is easy to maintain a structure that can improve the contact ratio between PM and the catalyst component, and the PM reduction performance. And a desired porosity can be obtained.

In the present invention, the addition amount of the pore former is not particularly limited, but the pore former is preferably added so as to be 10 to 50% based on the total amount of the catalyst precursor. It is more preferable to add so that it may become, and it is still more preferable to add so that it may become 15 to 30%.
When the amount of pore former added is less than 10%, pores may be blocked. On the other hand, when the amount of pore former added exceeds 50%, the fiber structure may be destroyed.

  Furthermore, in the present invention, the type of pore former is not particularly limited as long as it is burned to form voids when fired, but for example, graphite, carbon fiber, activated carbon, blowing agent or pulp, and these Mixtures can be used.

  In addition, about the process (1)-(3) mentioned above, as long as a desired catalyst precursor can be obtained, you may carry out substantially simultaneously, for example, the inorganic long fiber and short fiber mentioned above, a catalyst component, and a pore making material. May be mixed to obtain a catalyst component precursor.

Next, the obtained catalyst precursor is calcined in a cell having a structure having cells, and the pore-forming material is burned out to dispose the catalyst in the cells to obtain a particulate filter type exhaust gas purification catalyst. In the step (4), as long as a desired particulate filter type exhaust gas purification catalyst can be obtained, the method for disposing the catalyst precursor in the cell, the firing method and the like are not particularly limited.
For example, in the present invention, a powder or slurry catalyst precursor may be filled in a cell and disposed in the cell. The firing conditions are not particularly limited as long as the pore former to be used is burned out, and the conditions vary depending on the type of the pore former. For example, the firing may be performed at about 100 to 400 ° C. in the air. .

Here, an example of the manufacturing method of the particulate filter type exhaust gas purification catalyst of the present invention will be described with reference to the drawings.
FIG. 1 is an explanatory view showing an example of a method for producing a particulate filter type exhaust gas purification catalyst of the present invention. As shown in FIG. 6A, the inorganic fiber mixture, the catalyst component, and the pore former are mixed to obtain a uniform slurry catalyst precursor 26 containing these, and then shown in FIG. As shown in FIG. 4C, the catalyst 20 is placed in the cell 12 of the structure 10 such as a conventional DPF, dried and fired, and the particulate filter is provided. Type exhaust gas purification catalyst is obtained.

Next, the particulate filter type exhaust gas purification catalyst of the present invention will be described.
As described above, the particulate filter type exhaust gas purification catalyst of the present invention is produced by the method for producing an exhaust gas purification catalyst of the present invention.
The particulate filter type exhaust gas purification catalyst obtained in this way can improve the PM reduction performance.

As a result, since PM can be reduced under a temperature condition lower than that in the prior art, continuous PM reduction can be realized.
Further, since continuous PM reduction can be realized, it is not always necessary to perform overheat combustion processing at 600 ° C. or higher by fuel injection that is regularly performed for self-regeneration in the conventional DPF, thereby improving fuel efficiency. It becomes possible. Furthermore, simplification and miniaturization can be achieved when constructing a system.
Furthermore, it is possible to arrange them appropriately so that the performance of the catalyst component can be sufficiently exhibited, and there is an advantage that the amount of noble metal used as an example of the catalyst component can be reduced.
Needless to say, the catalyst component may be supported on the inner wall of the cell.

Here, in the present invention, the shape of the structure provided is particularly limited as long as it has a structure capable of circulating exhaust gas and a structure capable of holding inorganic fibers in the cells of the structure. is not. For example, a structure having a plurality of cells such as a so-called honeycomb carrier or a structure such as a so-called wall flow type honeycomb carrier can be used.
Further, in the present invention, the material of the structure provided is not particularly limited, but may include ceramics such as cordierite and ferritic stainless steel, particularly those made of porous ceramics. Can be used.

Further, in the present invention, when the structure provided is a structure having a plurality of cells such as the so-called honeycomb carrier described above, PM is removed to such an extent that the pressure loss of the exhaust gas is not significantly increased. The inorganic fiber carrying the catalyst component may be disposed in the cell of the structure.
By setting it as such a structure, PM reduction performance can be improved.
At this time, the structure may be either a wall flow type or a straight flow type.

On the other hand, in the present invention, when the structure provided is a structure such as the so-called wall flow type honeycomb carrier described above, that is, it has a plurality of cells formed with walls through which gas can flow and closed at one end. In the case of a structure having an end face in which the closed end and the open end of these cells are alternately arranged, the catalyst component is contained in the cell having the open end upstream of the gas flow direction of the structure. What is necessary is just to arrange | position the supported inorganic fiber.
By adopting such a configuration, the PM reduction performance can be improved, and the PM removal performance can be further improved.

Here, an embodiment of the particulate filter type exhaust gas purification catalyst of the present invention will be described with reference to the drawings.
FIG. 2A is an enlarged cross-sectional view of an embodiment of a conventional particulate filter type exhaust gas purification catalyst. As shown in the figure, the catalyst component 24 is supported on the cell wall 12a of the cell 12 of the structure 10 which is a structure such as a wall flow type honeycomb carrier.
At this time, the contact ratio between the catalyst component 24 supported on the cell wall 12a and the PM is not sufficient, and in the exhaust gas flow indicated by the arrow A, PM in the exhaust gas accumulates on the surface of the cell wall 12a.
On the other hand, FIG. 5B is an enlarged cross-sectional view of an embodiment of the particulate filter type exhaust gas purification catalyst of the present invention. As shown in the figure, a structure such as a wall flow type honeycomb carrier, in which a three-dimensional network structure 22 including inorganic long fibers and short fibers is disposed inside a cell 12 of the structure 10. Thus, the catalyst component 24 is supported on the three-dimensional network structure 22, and the catalyst 20 is formed.
At this time, the contact ratio between the catalyst component 24 inside the cell 12 and the PM becomes sufficient, and in the exhaust gas flow indicated by the arrow A, the PM is reduced before the PM in the exhaust gas is deposited on the surface of the cell wall 12a. can do.

  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
Long fibers (fiber length: 2 to 4 mm, fiber diameter: 3 to 10 μm) and short fibers (fiber length: 0.05 to 2 mm, fiber diameter) of alumina-silica fiber (Al / Si = 80/20) 3 to 10 μm) were prepared. These were mixed such that the long fibers and the short fibers were in a mass ratio of 5: 5 and put into a vibration mill to obtain an inorganic fiber mixture of long fibers and short fibers.
50 g of the inorganic fiber mixture obtained above was immersed in 500 mL of 3% Pt solution, then dried at 100 ° C. for 1 hour, and then calcined at 400 ° C. for 1 hour to obtain 55 g of the catalyst component-supported inorganic fiber mixture. Obtained (Pt loading was 3%).
To the obtained catalyst component-supported inorganic fiber mixture, 1 L of mixing water and activated carbon as a pore former were added to obtain a catalyst precursor (the amount of activated carbon added was 10% based on the total amount of the catalyst precursor). ).
1160 g of the obtained catalyst precursor was put into a cell of a honeycomb carrier (capacity: 1.0 L, number of cells: 400 Cpsi), fired, the pore former was burned out, a catalyst was disposed, and A curated filter type exhaust gas purification catalyst was obtained.

(Example 2)
In the same manner as in Example 1 except that activated carbon is added as a pore former to the obtained catalyst component-supporting inorganic fiber mixture to obtain a catalyst precursor, the amount of activated carbon added is 20% based on the total amount of the catalyst precursor. The above operation was repeated to obtain a particulate filter type exhaust gas purification catalyst of this example.

(Example 3)
In the same manner as in Example 1 except that activated carbon is added as a pore former to the obtained catalyst component-supported inorganic fiber mixture to obtain a catalyst precursor, the amount of activated carbon added is 30% based on the total amount of the catalyst precursor. The above operation was repeated to obtain a particulate filter type exhaust gas purification catalyst of this example.

(Comparative Example 1)
The particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 1 except that no pore former was added to the obtained catalyst component-supporting inorganic fiber mixture.

(Comparative Example 2)
Particulate filter type exhaust gas purification of this example by applying a Pt solution to the inner wall of the cell of the same honeycomb carrier as in Example 1, then drying at 100 ° C. for 1 hour, and then firing at 400 ° C. for 1 hour. A catalyst was obtained. The amount of Pt supported is the same as that of the particulate filter type exhaust gas purification catalyst of Example 1.

[Performance evaluation]
The particulate filter type exhaust gas purification catalyst of each of the above examples was installed in an evaluation apparatus, and the conversion rate of methane was measured under the following conditions. The obtained results are shown in Table 1.

(Test conditions)
・ Gas composition: methane; 4 vol%, oxygen; 10 vol%, balance: nitrogen, gas flow rate: 200 cm ³ / min
Catalyst temperature: 500 ° C

From Table 1, it can be seen that Examples 1 to 3 included in the scope of the present invention have a higher methane conversion rate than Comparative Examples 1 and 2 outside the present invention.
This is presumed to be because the contact ratio between the catalyst component and methane is improved, and such a particulate filter type exhaust gas purification catalyst can improve the PM reduction performance.

It is explanatory drawing which shows an example of the manufacturing method of the particulate filter type exhaust gas purification catalyst of this invention. It is an expanded sectional view showing one embodiment of the conventional particulate filter type exhaust gas purification catalyst of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Structure 12 Cell 12a Cell wall 20 Catalyst 22 Three-dimensional network structure 24 Catalyst component 26 Catalyst precursor

Claims (4)

A structure having cells, and a catalyst comprising a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers,
A method for producing a particulate filter type exhaust gas purification catalyst in which the catalyst is disposed in the cell, wherein the following steps (1) to (4)
(1) A step of mixing inorganic long fibers and short fibers to obtain an inorganic fiber mixture,
(2) a step of obtaining a catalyst component-supported inorganic fiber mixture by supporting a catalyst component on the inorganic fiber mixture;
(3) adding a pore former to the catalyst component-supported inorganic fiber mixture and mixing to obtain a catalyst precursor;
(4) The step of calcining the catalyst precursor in the cell of the structure and disposing the pore former to dispose the catalyst in the cell to obtain a particulate filter type exhaust gas purification catalyst;
A method for producing a particulate filter type exhaust gas purifying catalyst, comprising:   In the said process (3), the said pore making material is added so that it may become 10 to 50% on the said catalyst precursor whole quantity basis, The manufacturing method of the particulate filter type | mold exhaust gas purification catalyst of Claim 1 characterized by the above-mentioned.   The particulate according to claim 1 or 2, wherein in the step (3), at least one selected from the group consisting of graphite, carbon fiber, activated carbon, a foaming agent and pulp is used as the pore former. A method for producing a filter-type exhaust gas purification catalyst.   A particulate filter type exhaust gas purification catalyst produced by the method for producing a particulate filter type exhaust gas purification catalyst according to any one of claims 1 to 3.

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