JP2007275874A - Catalyst and particulate filter type catalyst for cleaning exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a catalyst capable of improving the PM reducing performance when a particulate filter type catalyst for cleaning exhaust gas using the catalyst, and a fiber structure for a catalyst carrier using the same. <P>SOLUTION: The catalyst is obtained by depositing a catalyst component on a three-dimensionally-reticulated structure containing an inorganic long fiber and an inorganic short fiber. Otherwise, the catalyst comprises the fiber structure, which has a three-dimensionally-reticulated structure containing a long fiber and a branched short fiber and is used as the catalyst carrier, and the catalyst component. The particulate filter type catalyst for cleaning exhaust gas is provided with: a structure having cells; and the catalyst obtained by depositing the catalyst component on the three-dimensionally-reticulated structure containing the inorganic long fiber and the inorganic short fiber or the catalyst comprising the fiber structure, which has the three-dimensionally-reticulated structure containing the long fiber and the branched short fiber and is used as the catalyst carrier, and the catalyst component so that the catalyst is arranged in cells of the structure. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a catalyst and a particulate filter type exhaust gas purification catalyst, and more specifically, a catalyst capable of improving particulate matter (PM) reduction performance, a particulate filter type exhaust gas purification catalyst using the same, and The present invention relates to a fiber structure for a catalyst carrier to be used.

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 conventional technology, and an object thereof is to provide a catalyst capable of improving PM reduction performance and a particulate filter type exhaust gas purification catalyst using the same. There is to do.

  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. It is necessary to make the structure capable of improving the contact rate of the catalyst, and it is also effective to use a catalyst in which a catalyst component is supported on a three-dimensional network structure including inorganic long fibers and short fibers. As a result, the present invention has been completed.

  That is, the catalyst of the present invention is characterized in that a catalyst component is supported on a three-dimensional network structure including inorganic long fibers and short fibers.

Moreover, the suitable form of the catalyst of this invention is characterized by the density of the said catalyst being 0.0005-0.5 g / cm < ³ >, or the porosity being 60 vol% or more.

  Furthermore, another catalyst of the present invention has a three-dimensional network structure containing long fibers and short fibers having branches, and includes a fiber structure used as a catalyst carrier and a catalyst component. And

  Furthermore, another preferred embodiment of the catalyst of the present invention is characterized in that the catalyst component is contained in long fibers and / or branched short fibers constituting the fiber structure.

  Further, the particulate filter type exhaust gas purification catalyst of the present invention comprises 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, The catalyst is arranged in a cell of the structure.

  Furthermore, a preferred embodiment of the particulate filter type exhaust gas purification catalyst of the present invention has a plurality of cells formed by walls through which gas can flow and closed at one end, and the closed end and open end of these cells are alternately arranged. A structure having an end face arranged, and a catalyst having a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers, and the catalyst has a gas flow direction of the structure. Is arranged in a cell having an open end on the upstream side.

  In addition, another particulate filter type exhaust gas purification catalyst of the present invention has a three-dimensional network structure including a structure having cells and short fibers having long fibers and branches, and is used as a catalyst carrier. A catalyst including a fiber structure and a catalyst component, wherein the catalyst is disposed in a cell of the structure.

  Furthermore, another preferred embodiment of the particulate filter type exhaust gas purifying catalyst of the present invention has a plurality of cells formed by walls through which gas can flow and closed at one end, and the closed end and open end of these cells. And a catalyst having a three-dimensional network structure including long fibers and short fibers having branches, and a fibrous structure used as a catalyst support and a catalyst component. And the catalyst is disposed in a cell having an open end on the upstream side with respect to the gas flow direction of the structure.

  According to the present invention, a catalyst comprising a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers is used, and the contact ratio between PM and the catalyst component can be improved. Therefore, it is possible to provide a catalyst capable of improving PM reduction performance, a particulate filter type exhaust gas purification catalyst using the same, and a fiber structure for a catalyst carrier used therefor.

Hereinafter, the catalyst of the present invention will be described in detail. In the present specification and claims, “%” for concentration, content, and the like represents a mass percentage unless otherwise specified.
As described above, the catalyst of the present invention comprises a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers.
By setting it as such a structure, the particulate filter type exhaust gas purification catalyst produced using this can improve PM reduction performance.

In the present invention, it is preferable that the density of the catalyst is 0.0005~0.5g / cm ^3, more preferably 0.005~0.05g / cm ^3, 0.01~0. more preferably from 03g / cm ^3, particularly preferably 0.01~0.02g / cm ^3. Moreover, it is preferable that the porosity of a catalyst is 60 vol% or more. Furthermore, it is more preferable that both the density and the porosity of the catalyst are in the above ranges.
If the density of the catalyst is less than 0.0005 g / cm ³ may not be able to collect the PM. Further, when the density of the catalyst exceeds 0.5 g / cm ³ , clogging may occur. Furthermore, when the porosity is 90 vol% or more, it is easier to suppress the pressure loss of the exhaust gas.

Moreover, in this invention, it is preferable that a long fiber and a short fiber are contained in the ratio of 2: 8-5: 5 by mass ratio, and are included in the ratio of 3: 7-4: 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), there is a risk of blocking between the fibers.
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), PM may not be collected.

  Furthermore, in this invention, it is preferable that the fiber diameter of a long fiber and a short fiber is 60 micrometers or less, and it is more preferable that it is 50 micrometers or less. When the fiber diameters of long fibers and short fibers exceed 60 μm, the porosity and density necessary for PM collection may not be obtained.

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 7-15 micrometers.

On the other hand, 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.
Furthermore, in this invention, it is preferable that the fiber diameter of a short fiber is 1-10 micrometers, and it is still more preferable that it is 3-5 micrometers.
The three-dimensional network structure including the long fiber and the short fiber as described above can further improve the contact ratio between PM and the catalyst component in the catalyst in which the fibers are uniformly dispersed and the catalyst component is supported. A desired porosity can be obtained. However, short fibers are not limited to this because the lengths are not uniform.

  Further, in the present invention, the catalyst is obtained by using one or both of inorganic long fibers and short fibers, a catalyst component, carbon, and a foaming agent. The three-dimensional network structure including fibers and short fibers can improve the contact ratio between PM and the catalyst component in the catalyst in which the fibers are uniformly dispersed and support the catalyst component, and a desired porosity can be obtained. You will be able to.

  Furthermore, in the present invention, the catalyst is obtained using a conjugate fiber that forms a three-dimensional structure with inorganic long fibers and short fibers, a catalyst component, and the like as described above. The three-dimensional network structure including long fibers and short fibers can improve the contact ratio between PM and the catalyst component in the catalyst in which the fibers are uniformly dispersed and the catalyst component is supported. It will also be obtained.

  In the present invention, the inorganic fiber provided is not particularly limited as long as it can withstand use as a particulate filter type exhaust gas purification catalyst. For example, silicon carbide, alumina, silica, or alumina silica A fiber and a combination thereof can be exemplified, and a combination thereof can be exemplified by a mixture or a composite compound 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 fiber provided preferably contains 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.

Furthermore, in the present invention, the catalyst component to be provided is not particularly limited as long as it can promote PM reduction performance. For example, it is desirable that the catalyst component contains a noble metal such as platinum, palladium, or rhodium. Moreover, ceria, titania, etc. may be included as a co-catalyst.
Furthermore, in the present invention, the catalyst component provided is desirably contained in the fiber itself.

Next, another catalyst of the present invention will be described in detail.
As described above, another catalyst of the present invention has a three-dimensional network structure including long fibers and short fibers having branches, and includes a fiber structure used as a catalyst carrier and a catalyst component. .
Also by adopting such a configuration, the particulate filter type exhaust gas purification catalyst produced using the same can improve the PM reduction performance.

Here, examples of the catalyst component include oxides containing rare earth elements.
The content of the oxide containing rare earth elements is preferably 1 to 70%, more preferably 20 to 50%, and still more preferably 30 to 45%.
When the content is less than 1%, the catalytic reaction is insufficient, and when the content exceeds 70%, the fiber structure may not be maintained.
As the rare earth element, cerium, yttrium, praseodymium, lanthanum, neodymium, manganese, zirconium, gallium, or the like can be used alone or in combination.
Moreover, you may contain noble metals, such as platinum, palladium, and rhodium, as another catalyst component.

In the present invention, it is desirable that the catalyst component is contained in one or both of the long fibers constituting the fiber structure and the short fibers having branches.
In this way, the particulate filter type exhaust gas purification catalyst produced by using this is integrated with the catalyst component and the catalyst component is contained even in the center of the fiber, so that the PM reduction performance can be improved. It becomes. In addition, it is possible to suppress the catalyst component from dropping off and the deterioration of the catalyst performance due to thermal history when subjected to an impact. Furthermore, the degree of freedom in designing the catalyst is improved.
The long fiber integrated with such a catalyst component is prepared by mixing, for example, alumina and silica, the above-described catalyst component and a PVA solution which is an example of a dispersant, concentrating under reduced pressure, filtering and feeding, and dry-type. It is obtained by spinning, firing and crystallization. On the other hand, the short fiber having a branch integrated with such a catalyst component is obtained by mixing, for example, alumina, silica, the above-described catalyst component, and a PVA solution as an example of a dispersant, firing, and injection molding. .
In the case where the catalyst component is post-supported, in the alumina silica-based fiber which is an example of the inorganic short fiber or long fiber, the alumina is α-alumina, and when the catalyst component is integrated, the inorganic short fiber or In the alumina-silica fiber that is an example of the long fiber, the alumina is γ-alumina.

Next, the fiber structure of the present invention will be described in detail.
As described above, the fiber structure of the present invention has a three-dimensional network structure containing long fibers and branched short fibers, and is used as a catalyst carrier.
By adopting such a configuration, the catalyst to which this is applied can suppress the dropping of the catalyst component when subjected to an impact and the deterioration of the catalyst performance due to the thermal history. In addition, the degree of freedom in designing the catalyst is improved. Furthermore, the particulate filter type exhaust gas purification catalyst produced using this can improve the PM reduction performance.

In the present invention, it is preferable that the density of the fibrous structure is a 0.0005~0.5g / cm ^3, more preferably 0.005~0.05g / cm ^3, 0.01 more preferably from ~0.03g / cm ^3, particularly preferably 0.01~0.02g / cm ^3.
When the density of the fiber structure is less than 0.0005 g / cm ³ may not be able to collect the PM. Further, when the density of the fiber structure exceeds 0.5 g / cm ³ , clogging may occur.
And in this invention, it is preferable that the porosity of a fiber structure is 60 vol% or more. Furthermore, when the porosity is 90 vol% or more, it is easier to suppress the pressure loss of the exhaust gas.

  Furthermore, in this invention, it is preferable that the fiber diameter of a long fiber and a short fiber is 60 micrometers or less, and it is more preferable that it is 50 micrometers or less. When the fiber diameters of long fibers and short fibers exceed 60 μm, the porosity and density necessary for PM collection may not be obtained.

Furthermore, in the present invention, the fiber diameter of the long fibers is preferably 5 to 30 μm, the fiber diameter of the short fibers is preferably 1 to 10 μm, and both of the fiber diameters of the long fibers and the short fibers are the above. A range is more preferable.
Long fibers with a fiber diameter of less than 5 μm and long fibers with a fiber diameter of more than 30 μm cannot be produced for winding the fiber after spinning, and short fibers with a fiber diameter of less than 1 μm or fiber diameters of more than 10 μm. These short fibers cannot be produced because they are injection molded after spinning.

In the present invention, the fiber length of the long fibers is preferably 100 μm or more, the fiber length of the short fibers is preferably 100 μm to 40 mm, and both the fiber lengths of the long fibers and the short fibers are within the above range. More preferably.
A long fiber having a fiber length of less than 100 μm, a short fiber having a fiber length of less than 100 μm, or a short fiber having a fiber length of more than 40 mm may not be able to form a structure.

Furthermore, in the present invention, the long fibers preferably contain aluminum and silicon, and the Al / Si ratio is preferably 70/30 to 85/15 on a weight basis, and the short fibers contain aluminum and silicon, The Al / Si ratio is preferably 80/20 to 99.9 / 0.1 on a weight basis, and it is more preferable that both the Al / Si ratios of the long fiber and the short fiber are in the above range.
Since long fibers are formed by winding the fibers after spinning, if the Al / Si ratio exceeds 85/15, strength may be reduced and the fibers may not be produced. On the other hand, heat resistance falls that Al / Si ratio is less than 70/30.
In addition, since short fibers are injection-molded after spinning, those having an Al / Si ratio exceeding 99.9 / 0.1 may not be produced with a high yield. On the other hand, heat resistance falls that Al / Si ratio is less than 80/20.

Furthermore, in the present invention, it is preferable that long fibers and short fibers are contained in a mass ratio of 2: 8 to 5: 5, and a mass ratio of 3: 7 to 4: 6. More preferably it is included.
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), there is a risk of blocking between the fibers.
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), PM may not be collected.
In addition, the dispersibility of a catalyst component can be improved when a long fiber is made into the said more preferable range.

Next, the particulate filter type exhaust gas purification catalyst of the present invention will be described in detail.
As described above, the particulate filter type exhaust gas purification catalyst of the present invention comprises 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. Prepare.
And such a catalyst is arrange | positioned in the cell of this structure.
In addition, the catalyst provided can be suitably adjusted about the form and structure as above-mentioned.
By adopting such a configuration, for example, the contact ratio between the PM contained in the exhaust gas and the catalyst component is excellent, and the particulate filter type exhaust gas purification catalyst capable of improving the PM reduction performance is obtained.

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.1 (a) is an expanded sectional view of one Embodiment of the conventional particulate filter type | mold exhaust gas purification catalyst. As shown in the figure, the catalyst component 30 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 rate between the catalyst component 30 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 three-dimensional network structure 20 that is a structure such as a wall flow type honeycomb carrier and includes inorganic long fibers and short fibers is disposed inside a cell 12 of the structure 10. The catalyst component 30 is supported on the three-dimensional network structure 20.
At this time, the contact ratio between the catalyst component 30 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.

An example of a method for producing the particulate filter type exhaust gas purification catalyst as described above will be described.
Using a conventionally known DPF, a slurry containing a catalyst composed of a three-dimensional network structure containing inorganic long fibers and short fibers and supporting a catalyst component is placed in the cell, dried and calcined, and the catalyst is placed in the cell. Thus, the particulate filter type exhaust gas purification catalyst is completed.

The particulate filter type exhaust gas purification catalyst may be produced as follows.
For example, using a conventionally known DPF, a slurry containing a three-dimensional network structure containing inorganic long fibers and short fibers is put into the cell, dried and fired, and the three-dimensional network structure is placed in the cell. Disposed to form a particulate filter type structure.
After that, a solution or slurry containing the catalyst component is put into the cell of the obtained particulate filter structure, dried and fired, and the catalyst component is supported on the three-dimensional network structure in the cell. A curated filter type exhaust gas purification catalyst is completed.

Furthermore, this particulate filter type exhaust gas purification catalyst may be produced as follows.
For example, a conventionally known DPF is used, a slurry containing inorganic long fibers and short fibers supporting a catalyst component in the cell, and carbon is charged, dried and fired, the carbon is burned off, and the inorganic fiber is put into the cell. Thus, the particulate filter type exhaust gas purification catalyst is completed.

Next, another particulate filter type exhaust gas purification catalyst of the present invention will be described in detail.
As described above, another particulate filter type exhaust gas purification catalyst of the present invention has a three-dimensional network structure including a structure having cells and long fibers and short fibers having branches, and serves as a catalyst carrier. And a catalyst including a fibrous structure to be used and a catalyst component.
And such a catalyst is arrange | positioned in the cell of this structure.
In addition, the catalyst and structure provided can be appropriately adjusted with respect to its form and composition as described above.
For example, also in the present invention, a structure having a plurality of cells formed by walls through which gas can flow and closed at one end, and having end faces in which closed ends and open ends of these cells are alternately arranged, A three-dimensional network structure comprising long fibers and branched short fibers, and comprising a fiber structure used as a catalyst carrier and a catalyst containing a catalyst component, wherein the catalyst is arranged in the gas flow direction of the structure. On the other hand, it can be arranged in a cell having an open end on the upstream side.
By adopting such a configuration, for example, the contact ratio between the PM contained in the exhaust gas and the catalyst component is excellent, and the particulate filter type exhaust gas purification catalyst capable of improving the PM reduction performance is obtained. In addition, the catalyst with which the catalyst component can be removed can prevent the catalyst component from dropping off and deterioration of the catalyst performance due to thermal history, and the design freedom when molding the catalyst is improved. The filter-type exhaust gas purification catalyst also suppresses catalyst components from dropping and catalyst performance deterioration, and improves the degree of freedom in designing a particulate filter-type exhaust gas purification catalyst.

An example of a method for producing another particulate filter type exhaust gas purification catalyst as described above will be described.
Using a conventionally known DPF, a slurry containing an integrated long fiber containing a catalyst component and an integrated branched short fiber containing a catalyst component is charged into the cell, and dried and fired. And a catalyst is arrange | positioned in a cell and a particulate filter type | mold exhaust gas purification catalyst is completed. According to such a method, there is an advantage that a post-supporting step is not required, the number of steps can be reduced, and blockage of fiber pores can be avoided at that time.

The particulate filter type exhaust gas purification catalyst may be produced as follows.
For example, a conventionally known DPF is used, and in the cell, integrated long fibers containing a catalyst component, integrated short fibers containing a catalyst component, and carbon or a blowing agent or conjugate A slurry containing fibers is charged, dried and fired to burn off carbon and the like, and the catalyst is disposed in the cell to complete a particulate filter type exhaust gas purification catalyst.
Further, a noble metal such as platinum, rhodium or palladium may be supported by a conventionally known method.

  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: 0.1 to 2 mm, fiber diameter: 3) of alumina-silica fiber (Al / Si = 80/20) To 10 μm). These were mixed so that long fibers and short fibers were in a mass ratio of 1: 9, and put into a vibration mill to obtain a mixture of long fibers and short fibers.
50 g of the above-obtained mixture was immersed in 500 mL of 3% Pt solution, then dried at 100 ° C. for 1 hour, and then fired at 400 ° C. for 1 hour to obtain 55 g of Pt-supported alumina-silica fiber. (Pt loading was 3%).
1160 g of the obtained Pt-supported alumina-silica fiber was placed in a honeycomb carrier (capacity: 1.0 L, number of cells: 400 Cpsi) so as to form a three-dimensional network structure, and the particulate filter type of this example An exhaust gas purification catalyst was obtained.

(Example 2)
The particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 1 except that the long fibers and the short fibers were mixed so as to have a mass ratio of 2: 8.

(Example 3)
A particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 1 except that the long fibers and the short fibers were mixed so that the mass ratio was 5: 5.
FIG. 2 is a scanning electron microscope (SEM) photograph of the catalyst formed in this example.

Example 4
The particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 2 except that the fiber containing Pt as the catalyst component was used and no post-Pt support was carried out.

(Example 5)
A particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 3 except that the fiber containing Pt as the catalyst component was used and no support after Pt was carried out.

(Comparative Example 1)
A particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 1 except that only long fibers were used.

(Comparative Example 2)
A particulate filter type exhaust gas purification catalyst of this example was obtained by repeating the same operation as in Example 1 except that only short fibers were used.

[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. Moreover, while measuring the density of the catalyst arrange | positioned in the cell, the state was visually evaluated. 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 5 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.
In addition, in the particulate filter type exhaust gas purification catalyst of Examples 1 to 3, since the catalyst component is post-supported after the fiber formation, 5% to 50% of the catalyst falls off. In the curated filter type exhaust gas purification catalyst, the catalyst component is mixed at the time of fiber formation, so that the catalyst does not fall off.

It is an expanded sectional view showing one embodiment of the conventional particulate filter type exhaust gas purification catalyst of the present invention. 4 is a SEM photograph of the catalyst formed in Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Structure 12 Cell 12a Cell wall 20 Three-dimensional network structure 30 Catalyst component

Claims (30)

  A catalyst comprising a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers. The catalyst according to claim 1, wherein the catalyst has a density of 0.0005 to 0.5 g / cm ³ or a porosity of 60 vol% or more.   The catalyst according to claim 1 or 2, wherein the long fibers and the short fibers are contained in a mass ratio of 2: 8 to 5: 5.   The catalyst according to claim 1 or 2, wherein the long fibers and the short fibers are contained in a mass ratio of 3: 7 to 4: 6.   The catalyst according to any one of claims 1 to 4, wherein a fiber diameter of the long fibers and the short fibers is 60 µm or less.   The catalyst according to any one of claims 1 to 5, wherein the long fiber has a fiber length of 2 to 10 mm.   The catalyst according to any one of claims 1 to 6, wherein the long fiber has a fiber diameter of 5 to 35 µm.   The catalyst according to any one of claims 1 to 6, wherein a fiber diameter of the long fibers is 7 to 10 µm.   The catalyst according to any one of claims 1 to 8, wherein a fiber length of the short fibers is 0.1 to 50 mm.   The catalyst according to any one of claims 1 to 8, wherein a fiber length of the short fibers is 0.1 to 2 mm.   The fiber diameter of the said short fiber is 1-10 micrometers, The catalyst as described in any one of Claims 1-10 characterized by the above-mentioned.   The fiber diameter of the said short fiber is 3-5 micrometers, The catalyst as described in any one of Claims 1-10 characterized by the above-mentioned.   The said catalyst is obtained using an inorganic long fiber and a short fiber, a catalyst component, carbon, and / or a foaming agent, The statement as described in any one of Claims 1-12 characterized by the above-mentioned. catalyst.   The catalyst according to any one of claims 1 to 12, wherein the catalyst is obtained using inorganic long fibers and short fibers, a catalyst component, and a conjugate fiber.   The catalyst according to any one of claims 1 to 14, wherein the catalyst component contains a noble metal.   The catalyst according to any one of claims 1 to 15, wherein the catalyst component is contained in the fiber itself. A particulate filter type exhaust gas purification catalyst comprising a structure having cells and a catalyst having a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers,
A particulate filter type exhaust gas purification catalyst, wherein the catalyst is disposed in a cell of the structure. A particulate filter type exhaust gas purification catalyst, which is formed of a wall through which gas can flow, has a plurality of cells closed at one end, and has an end face in which closed ends and open ends of these cells are alternately arranged A structure, and a catalyst comprising a catalyst component supported on a three-dimensional network structure including inorganic long fibers and short fibers,
The particulate filter type exhaust gas purification catalyst according to claim 17, wherein the catalyst is disposed in a cell having an open end on the upstream side with respect to the gas flow direction of the structure.   A fiber structure having a three-dimensional network structure comprising long fibers and branched short fibers and used as a catalyst carrier. The density of the said fiber structure is 0.0005-0.5 g / cm < ³ >, and the porosity is 60 vol% or more, The fiber structure of Claim 19 characterized by the above-mentioned.   The fiber structure according to claim 19 or 20, wherein a fiber diameter of the long fibers and the short fibers is 60 µm or less.   The fiber structure according to any one of claims 19 to 21, wherein a fiber diameter of the long fibers is 5 to 30 µm, and a fiber diameter of the short fibers is 1 to 10 µm.   The fiber structure according to any one of claims 19 to 22, wherein a fiber length of the long fibers is 100 µm or more, and a fiber length of the short fibers is 100 µm to 40 mm.   The long fiber contains aluminum and silicon, the Al / Si ratio is 70/30 to 85/15 on a weight basis, and the short fiber contains aluminum and silicon, and the Al / Si ratio is on a weight basis. The fiber structure according to any one of claims 19 to 23, wherein the fiber structure is 80/20 to 99.9 / 0.1.   25. The fiber structure according to any one of claims 19 to 24, wherein the long fibers and the short fibers are contained in a mass ratio of 2: 8 to 5: 5.   The fiber structure according to any one of claims 19 to 24, wherein the long fibers and the short fibers are contained in a mass ratio of 3: 7 to 4: 6.   27. A catalyst comprising the fiber structure according to any one of claims 19 to 26 and a catalyst component.   28. The catalyst according to claim 27, wherein the catalyst component is contained in a long fiber and / or a short fiber having a branch constituting the fiber structure. Particulate filter type exhaust gas purification catalyst having a structure having cells and a three-dimensional network structure comprising long fibers and short fibers having branches, and a fiber structure and catalyst used as a catalyst carrier A catalyst containing components,
A particulate filter type exhaust gas purification catalyst, wherein the catalyst is disposed in a cell of the structure. A particulate filter type exhaust gas purification catalyst, which is formed of a wall through which gas can flow, has a plurality of cells closed at one end, and has an end face in which closed ends and open ends of these cells are alternately arranged A structure, a catalyst having a three-dimensional network structure including long fibers and branched short fibers, and including a fiber structure used as a catalyst carrier and a catalyst component;
30. The particulate filter exhaust gas purification catalyst according to claim 29, wherein the catalyst is disposed in a cell having an open end on the upstream side with respect to the gas flow direction of the structure.

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