JP2011098337A - Honeycomb filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb filter having an excellent NOx removal rate. <P>SOLUTION: The honeycomb filter includes a honeycomb-structured body, which is constituted so that a large number of cells are parted from one another by cell walls and arranged in parallel in the longitudinal direction of the honeycomb-structured body and each of the large number of cells is sealed at one end thereof, and zeolite deposited on the cell wall of the honeycomb-structured body. The amount of the zeolite deposited on the cell wall is 80-150 g/L. The large number of cells include large-volume cells and small-volume cells. The cell wall of the honeycomb-structured body has 55-65% porosity and pores of 15-25 μm average pore diameter. A pore diameter distribution of the cell wall of the honeycomb-structured body is characterized in that the sum of the pore volume A of pores having the pore diameter equal to or smaller than the half of the average pore diameter and the pore volume B of pores having the pore diameter equal to or larger than the twice of the average pore diameter is ≤20% of the total pore volume C. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a honeycomb filter.

The exhaust gas discharged from an internal combustion engine such as a diesel engine contains particulates such as soot (hereinafter also referred to as PM), and in recent years, it has become a problem that this PM is harmful to the environment and the human body. ing. Further, since the exhaust gas contains harmful gas components such as CO, HC and NOx, there is a concern about the influence of the harmful gas components on the environment and the human body.

Therefore, an exhaust gas purification device is used to collect PM in exhaust gas and purify harmful gas components.
Such an exhaust gas purification apparatus is manufactured using a honeycomb structure made of a material such as ceramic. The exhaust gas can be purified by passing the exhaust gas through the honeycomb structure.

In a honeycomb structure used for collecting PM in exhaust gas in an exhaust gas purification device, a large number of cells are arranged in parallel in the longitudinal direction across a cell wall, and either one end of the cell is sealed. Yes. Therefore, the exhaust gas flowing into one cell always flows out from other cells after passing through the cell wall separating the cells. That is, when such a honeycomb structure is provided in the exhaust gas purification device, PM contained in the exhaust gas is captured by the cell wall when passing through the honeycomb structure. Therefore, the cell wall of the honeycomb structure functions as a filter for purifying exhaust gas.

In Patent Document 1, a cell in which the end on the exhaust gas outflow side is sealed is a cell having a large capacity (hereinafter also referred to as a large capacity cell), and a cell in which the end on the exhaust gas inflow side is sealed has a small capacity. A honeycomb structure as a cell (hereinafter also referred to as a small capacity cell) is disclosed.
In such a honeycomb structure, a large amount of PM is collected when used as an exhaust gas purification filter by making the area of the opening on the gas inlet side relatively larger than the area of the opening on the gas outlet side. be able to.

Further, in Patent Document 1, the ratio of the volume of pores having an average pore diameter of 5 to 30 μm and having a pore diameter more than twice the average pore diameter is 30 with respect to the total pore volume. % Or less is disclosed.
According to Patent Document 1, such a honeycomb structure has a large effective filtration area, and can extend the period until regeneration treatment.

On the other hand, as the honeycomb structure used for purifying NOx in the exhaust gas in the exhaust gas purification device, neither end of the cell is sealed, and a catalyst for purifying NOx is supported on the cell wall. A honeycomb structure for NOx purification is used.

International Publication No. 2005/002709 Pamphlet

Up to now, the honeycomb structure used for collecting PM in exhaust gas and the honeycomb structure for NOx purification have been made of different members and arranged in separate metal containers, respectively, and have a large volume in the exhaust line. Accounted for.
Therefore, it has been desired to reduce the volume occupied by the exhaust gas purification device.

In recent years, a urea SCR (Selective Catalytic Reduction) device has been proposed to purify NOx in exhaust gas.
In the urea SCR device, urea water is sprayed into an exhaust gas purification device including a honeycomb structure in which a catalyst such as zeolite is supported on a cell wall. Then, ammonia is generated by thermal decomposition of urea, and NOx is reduced to N ₂ by the action of zeolite.
Thus, the urea SCR device can purify NOx.

The inventors have supported zeolite on a cell wall of a honeycomb structure in which either one end of the cell is sealed, and applied it to a urea SCR device to purify NOx and capture PM. An attempt was made to reduce the volume occupied by the honeycomb filter and the exhaust gas purification device in the exhaust line so that the collection can be performed by one honeycomb filter.
In the present specification, a honeycomb structure in which a catalyst such as zeolite is supported on a cell wall is referred to as a honeycomb filter.

In a honeycomb filter applicable to a urea SCR device, it is considered that it is necessary to increase the amount of zeolite supported on the cell walls of the honeycomb structure in order to increase the NOx purification rate in the exhaust gas.

It is known that in order to support a large amount of zeolite on the cell walls of the honeycomb structure, it is necessary to increase the porosity of the honeycomb structure before supporting the zeolite.
Accordingly, the present inventors have manufactured a honeycomb filter in which a large amount of zeolite is supported on the cell walls of the honeycomb structure by increasing the porosity of the honeycomb structure described in Patent Document 1.
However, in the honeycomb filter manufactured by the above method, the NOx purification rate when used in the urea SCR device was not a sufficient value.

The inventors of the present invention examined factors that affect the NOx purification rate when a honeycomb filter is used in a urea SCR device.
As a result, in order to improve the NOx purification rate, the present inventors have not only supported a large amount of zeolite by increasing the porosity of the honeycomb structure, but also sufficiently contacted NOx with the zeolite. We thought that it was necessary to let you.

Then, the inventors of the present invention have made a honeycomb structure having a large capacity cell and a small capacity cell, the porosity of the cell wall of the honeycomb structure, the average pore diameter of the cell wall of the honeycomb structure, and the honeycomb structure It has been found that by setting the cell wall pore size distribution within a predetermined range, a large amount of zeolite can be supported on the cell wall, and NOx can be sufficiently brought into contact with the zeolite, thereby completing the present invention.

That is, the honeycomb filter according to claim 1 includes a honeycomb structure in which a large number of cells are arranged in parallel in a longitudinal direction with a cell wall interposed therebetween, and one end of each of the cells is sealed, and the honeycomb structure. A honeycomb filter having zeolite supported on a cell wall of the body,
The amount of zeolite supported on the cell wall is 80 to 150 g / L,
The large number of cells consists of a large capacity cell and a small capacity cell.
The porosity of the cell wall of the honeycomb structure is 55 to 65%,
The average pore diameter of the cell wall of the honeycomb structure is 15 to 25 μm,
The pore size distribution of the cell walls of the honeycomb structure includes a pore volume A having a pore size less than half of the average pore size and a pore volume B having a pore size more than twice the average pore size. The total is characterized by being 20% or less of the total pore volume C.

In the honeycomb filter according to claim 1, the porosity of the cell wall of the honeycomb structure is 55 to 65%. Therefore, a large amount of zeolite can be supported on the cell walls of the honeycomb structure.
When the porosity of the cell wall of the honeycomb structure is less than 55%, when a large amount of zeolite is supported on the honeycomb structure, the pores of the cell wall are clogged with zeolite, and the exhaust gas hardly passes through the cell wall. Therefore, it becomes difficult for the exhaust gas to diffuse, and the function of zeolite may not be sufficiently exhibited.
On the other hand, if the porosity of the cell wall of the honeycomb structure exceeds 65%, the heat capacity becomes too small, so that the temperature of the honeycomb filter is likely to rise during the regeneration process for burning PM, and the catalyst tends to be deactivated.
Further, when the porosity of the cell wall of the honeycomb structure exceeds 65%, the strength of the honeycomb structure may be lowered.

In the honeycomb filter according to claim 1, the amount of zeolite supported on the cell wall is 80 to 150 g / L.
When zeolite is supported on the cell wall at 80 to 150 g / L, NOx in exhaust gas can be sufficiently purified when the honeycomb filter is used as a urea SCR device.
If the amount of zeolite supported exceeds 150 g / L, the pores in the cell walls of the honeycomb structure may be clogged even if the pore size distribution is controlled, and the contact between the exhaust gas and the zeolite may be insufficient.

The average pore diameter of the cell wall of the honeycomb structure is 15 to 25 μm, and the pore diameter distribution of the cell wall of the honeycomb structure is a pore volume of pores having a pore diameter equal to or less than half of the average pore diameter. The sum of the pore volumes B of A and pores having a pore diameter more than twice the average pore diameter is 20% or less of the total pore volume C.

In the above definition, the large pore volume A means that when the average pore diameter is α (μm), the pores are distributed on the smaller side of the half pore diameter (hereinafter also referred to as 0.5α diameter in this specification). Indicates that the volume occupied by is large. On the other hand, a large pore volume B indicates that the volume of pores distributed on the side larger than the pore diameter twice the average pore diameter α (μm) (hereinafter also referred to as 2α diameter in this specification) is large. .
In the above definition, the total of the pore volume A and the pore volume B is 20% or less of the total pore volume C. This indicates that, of the total pore volume C, the volume occupied by pores in the range of 0.5α diameter to 2α diameter exceeds 80%. In other words, the ratio of pores having a pore size close to the average pore size is high, indicating that the pore size distribution is uniform (narrow).

If the pore size distribution is uniform (narrow), the cell wall does not have a portion where the exhaust gas is difficult to pass and a portion where the exhaust gas tends to concentrate and flows easily, so that the exhaust gas passes evenly through the cell wall. Therefore, the zeolite supported on the cell wall comes into sufficient contact with NOx in the exhaust gas. Therefore, a honeycomb filter having a high NOx purification rate can be obtained.

In the honeycomb filter according to claim 2, the pore volume A is 10% or less of the total pore volume C, and the pore volume B is 10% or less of the total pore volume C.

In the cell wall of the honeycomb structure, the portion having pores with a small pore diameter is easily clogged by the zeolite supported on the cell wall, and it becomes difficult for the exhaust gas to pass through. Makes it difficult for the exhaust gas to come into contact.
On the other hand, if there are pores with large pores in the cell walls of the honeycomb structure, it becomes difficult for zeolite to be supported on the cell walls, and the exhaust gas tends to concentrate on the portion and flow. It becomes difficult.
In the honeycomb filter according to claim 2, since the pore diameter distribution is controlled so that both the pore volume A and the pore volume B are 10% or less of the total pore volume C, the cell walls are more evenly distributed. Exhaust gas passes through. For this reason, the zeolite supported on the cell walls can more fully come into contact with NOx in the exhaust gas, and a honeycomb filter having a higher NOx purification rate can be obtained.

In the honeycomb filter according to claim 3, the cross-sectional shape perpendicular to the longitudinal direction of the large-capacity cell is substantially octagonal, and the cross-sectional shape perpendicular to the longitudinal direction of the small-capacity cell is substantially square. . A honeycomb filter having cells having such a cross-sectional shape is excellent in mechanical characteristics.
In the honeycomb filter according to claim 4, the shape of a cross section perpendicular to the longitudinal direction of the large-capacity cell is substantially square, and the shape of a cross section perpendicular to the longitudinal direction of the small-capacity cell is substantially square.
Since the honeycomb filter according to claims 3 and 4 has the cells having the cross-sectional shape as described above, PM in the exhaust gas can be suitably collected, and NOx in the exhaust gas is also preferably suitable. Can be purified.

In the honeycomb filter according to claim 5, the zeolite is at least one selected from the group consisting of β-type zeolite, ZSM-5-type zeolite, and SAPO.
Since these zeolites are excellent in gas diffusibility and hydrothermal durability, NOx can be particularly suitably purified.

In the honeycomb filter according to claim 6, the zeolite is ion-exchanged with copper ions and / or iron ions.

In the honeycomb filter according to a seventh aspect, the honeycomb structure is formed by binding a plurality of honeycomb fired bodies through an adhesive layer.

FIG. 1 is a perspective view schematically showing an example of a honeycomb structure constituting the honeycomb filter of the first embodiment of the present invention. Fig. 2 (a) is a perspective view schematically showing an example of a honeycomb fired body constituting the honeycomb structure shown in Fig. 1. FIG. 2B is a cross-sectional view taken along line AA of the honeycomb fired body illustrated in FIG. FIG. 3 is a graph showing an example of the pore size distribution of the cell walls of the honeycomb structure according to the present invention. FIG. 4 is a side view of the first end face schematically showing the cell structure of the substrate 1a. FIG. 5 is a side view of the first end face schematically showing the cell structure of the substrate 1b. FIG. 6 is a side view of the first end face schematically showing the cell structure of the substrate 1c. Fig.7 (a) is a perspective view which shows typically an example of the honeycomb structure which comprises the honeycomb filter of 2nd embodiment of this invention. Fig. 7 (b) is a cross-sectional view of the honeycomb structure shown in Fig. 7 (a) taken along line BB. 8 (a), 8 (b), 8 (c) and 8 (d) are schematic examples of the first end face of the honeycomb fired body constituting the aggregated honeycomb structure according to the present invention. It is the side view shown in.

(First embodiment)
Hereinafter, a first embodiment which is an embodiment of the honeycomb filter of the present invention will be described with reference to the drawings.

The honeycomb filter of the present embodiment is one in which zeolite is supported on the cell wall of the honeycomb structure.
Note that, as described above, in the present specification, “honeycomb structure” refers to those in which zeolite is not supported on the cell walls, and “honeycomb filter” refers to those in which zeolite is supported on the cell walls. The honeycomb structure is composed of a honeycomb fired body, and the cells and cell walls of the honeycomb structure refer to the cells and cell walls of the honeycomb fired body.

FIG. 1 is a perspective view schematically showing an example of a honeycomb structure constituting the honeycomb filter of the first embodiment of the present invention.
Fig. 2 (a) is a perspective view schematically showing an example of a honeycomb fired body constituting the honeycomb structure shown in Fig. 1. FIG. 2B is a cross-sectional view taken along line AA of the honeycomb fired body illustrated in FIG.

In the honeycomb structure 10 shown in FIG. 1, a plurality of honeycomb fired bodies 20 made of porous ceramics are bound together via an adhesive material layer 11 to form a ceramic block 13. A coat layer 12 for preventing leakage is formed. In addition, the coat layer 12 should just be formed as needed.
Such a honeycomb structure in which a plurality of honeycomb fired bodies are bundled is also referred to as an aggregated honeycomb structure.
As a main constituent material of the aggregated honeycomb structure, it is desirable to use silicon carbide or silicon-containing silicon carbide.

The honeycomb structure 10 has a large number of cells arranged in parallel in the longitudinal direction (in the direction of a double arrow a in FIG. 1) across a cell wall, a first end face 14, and a second end face 15. The positional relationship between the first end surface 14 and the second end surface 15 and the plurality of cells will be described below.

In the honeycomb fired body 20 shown in FIGS. 2 (a) and 2 (b), a large number of cells have a small cross-sectional area perpendicular to the longitudinal direction (the direction of the double-headed arrow b in FIG. 2 (a)). Large-capacity cells 21a that are relatively larger than the cells 21b and small-capacity cells 21b whose cross-sectional area perpendicular to the longitudinal direction is relatively smaller than that of the large-capacity cells 21a are alternately arranged.
The large-capacity cell 21a has a substantially octagonal cross-sectional shape in the longitudinal direction, and the small-capacity cell 21b has a substantially quadrangular cross-sectional shape in the longitudinal direction.
The honeycomb fired body 20 has a first end face 24 and a second end face 25.
In the large capacity cell 21a, the end portion on the first end face 24 side of the honeycomb fired body 20 is opened, and the end portion on the second end face 25 side is sealed with the sealing material 22a. On the other hand, in the small capacity cell 21b, the end portion on the second end face 25 side of the honeycomb fired body 20 is opened, and the end portion on the first end face 24 side is sealed with the sealing material 22b.
The cell wall 23 separating the large capacity cell 21a and the small capacity cell 21b functions as a filter.
That is, the exhaust gas G flowing into the large capacity cell 21a (the exhaust gas is indicated by G and the flow of the exhaust gas is indicated by an arrow in FIG. 2B) always separates the large capacity cell 21a from the small capacity cell 21b. After passing through the wall 23, it flows out of the small capacity cell 21b.

The honeycomb structure 10 is formed by bundling the plurality of honeycomb fired bodies 20 so that the first end faces 24 of the honeycomb fired bodies 20 become the first end faces 14 of the honeycomb structure 10. At this time, the second end face 25 of each honeycomb fired body 20 becomes the second end face 15 of the honeycomb structure 10.

Therefore, in the honeycomb structure 10, the large-capacity cells 21 a are opened at the end portion on the first end face 14 side of the honeycomb structure 10 and sealed at the end portion on the second end face 15 side. On the other hand, the small-capacity cell 21b is opened at the end portion on the second end face 15 side of the honeycomb structure 10 and sealed at the end portion on the first end face 14 side.

In addition, as the shape of the cross section perpendicular to the longitudinal direction of the large capacity cell and the small capacity cell, in addition to the shape shown in FIGS. 2A and 2B, the cross section perpendicular to the longitudinal direction of the large capacity cell The shape may be a substantially square shape, and the cross-sectional shape perpendicular to the longitudinal direction of the small capacity cell may be a substantially square shape.

Further, the ratio of the area of the cross section perpendicular to the longitudinal direction of the large capacity cell to the area of the cross section perpendicular to the longitudinal direction of the small capacity cell (the area of the cross section perpendicular to the longitudinal direction of the large capacity cell / the longitudinal direction of the small capacity cell) It is desirable that the cross-sectional area (perpendicular to) be 1.4 to 2.4.
If the area ratio is less than 1.4, the effect of providing a large capacity cell and a small capacity cell may not be sufficiently obtained. On the other hand, when the area ratio exceeds 2.4, the ratio of the cell walls separating the large capacity cells increases, and the ratio of the zeolite supported on the cell walls separating the large capacity cells relatively increases. Since the exhaust gas hardly passes through the cell walls separating the large-capacity cells, the zeolite supported on the cell walls hardly contributes to NOx purification. As a result, the NOx purification rate may decrease when the honeycomb filter is used in a urea SCR device.

The porosity of the cell wall of the honeycomb structure is 55 to 65%.
In the present specification, the porosity of the cell wall of the honeycomb structure can be measured by a conventionally known method such as a mercury intrusion method, an Archimedes method, a weight method, or a measurement using a scanning electron microscope (SEM).
In the present embodiment, the porosity of the cell wall of the honeycomb structure refers to the porosity of the cell wall of the honeycomb fired body constituting the honeycomb structure.

The average pore diameter of the cell wall of the honeycomb structure is 15 to 25 μm.
The pore size distribution of the cell walls of the honeycomb structure is the sum of the pore volume A of pores having a pore size less than half of the average pore size and the pore volume B of pores having a pore size more than twice the average pore size. Is 20% or less of the total pore volume C.
More preferably, the total of the pore volume A and the pore volume B is 9% or less of the total pore volume C.
The pore volume A is preferably 10% or less of the total pore volume C, and the pore volume B is preferably 10% or less of the total pore volume C.
In the present embodiment, the cell wall pore size distribution of the honeycomb structure refers to the cell wall pore size distribution of the honeycomb fired body constituting the honeycomb structure.

The average pore size and pore size distribution of the cell walls of the honeycomb structure can be obtained by a mercury intrusion method (based on JIS R 1655: 2003).
FIG. 3 is a graph showing an example of the pore size distribution (relationship between pore size (μm) and cumulative pore volume (%)) of the cell wall of the honeycomb structure (before supporting zeolite).
In the graph of FIG. 3, the thick line indicates the pore diameter distribution, and the intensity corresponds to the number of pores having the pore diameter indicated on the horizontal axis. The thin line indicates the cumulative pore volume, and the strength of the cumulative pore volume indicates the pore volume (%) occupied by pores having a pore diameter larger than the pore diameter indicated on the horizontal axis with the total pore volume C being 100%. ing.

In the graph of FIG. 3, the average pore diameter (α) of the cell walls of the honeycomb structure is 20 μm. The pore diameter that is half of the average pore diameter α is 10 μm (0.5α), and the pore diameter that is twice the average pore diameter α is 40 μm (2α). The graph of FIG. 3 shows the positions of the average pore diameter α, 0.5α diameter, and 2α diameter.
The pore volume A of the pores having a pore diameter of 0.5α or less can be read as 4.7% from the value of 95.3% in the pore diameter of 10 μm of the integrated pore volume (%) in the graph of FIG.
The pore volume B of the pores having a pore diameter of 2α or more can be read as 6.2% from the value 6.2% at the pore diameter of 40 μm of the cumulative pore volume (%) in the graph of FIG.
From the pore volume A and the pore volume B thus obtained, the total of the pore volume A and the pore volume B is calculated to be 10.9%.

In addition, zeolite is supported on the cell walls of the honeycomb structure.
In the present specification, the zeolite includes not only zeolite which is an aluminosilicate but also zeolite analogues such as aluminophosphate and aluminogermanate.

Zeolite supported on the cell wall of the honeycomb structure includes β-type zeolite, Y-type zeolite, ferrierite, ZSM-5-type zeolite, mordenite, faujasite, A-type zeolite, L-type zeolite, SAPO (Silicoaluminophosphate, Silico). Aluminophosphate) or MeAPO (metalalluminophosphate). These may be used alone or in combination of two or more.
Among the above zeolites, β-type zeolite, ZSM-5 type zeolite, or SAPO is desirable. Among SAPO, SAPO-5, SAPO-11, or SAPO-34 is desirable, and SAPO-34 is more desirable. Among MeAPOs, MeAPO-34 is desirable.

The amount of zeolite supported on the cell walls of the honeycomb structure (hereinafter also referred to as zeolite supported amount) is 80 to 150 g / L. The amount of zeolite is desirably 120 to 150 g / L.
In this specification, the amount of zeolite supported on the cell walls of the honeycomb structure refers to the weight of zeolite per liter of apparent volume of the honeycomb structure.
The apparent volume of the honeycomb structure includes the volume of the adhesive layer and the coat layer.

The zeolite is preferably ion-exchanged with metal ions.
Examples of metal ions include copper ions, iron ions, nickel ions, zinc ions, manganese ions, cobalt ions, silver ions, or vanadium ions. These may be used alone or in combination of two or more.
Among the above metal ions, copper ions or iron ions are desirable.

Next, an example of a method for manufacturing the honeycomb filter of the present embodiment will be described. Here, a method for manufacturing a honeycomb filter in which zeolite is supported on the cell walls of a honeycomb structure formed of the honeycomb fired body shown in FIGS. 2 (a) and 2 (b) will be described.
First, a silicon carbide powder having a different average particle size, an organic binder, a pore former, a liquid plasticizer, a lubricant, and water are mixed as a ceramic raw material to prepare a wet mixture for manufacturing a molded body.

In the manufacturing method of the honeycomb structure of the present embodiment, a method of controlling the particle diameter of the hollow acrylic particles used as the pore former is used in order to control the pore size distribution of the cell wall of the honeycomb structure to a predetermined range. Can do.
Specifically, the hollow acrylic particles used as a pore-forming material are sieved to sufficiently remove coarse particles and fine particles, to prepare hollow acrylic particles having a uniform particle size distribution (narrow) for the manufacture of a honeycomb structure. Use.
The particle diameter range of the particles to be removed when the hollow acrylic particles are sieved can be arbitrarily set according to the degree of controlling the pore size distribution, for example, 90% in the particle size distribution of the hollow acrylic particles. Particles (volume) in the range of ± 5 μm of the average particle diameter. Further, for example, the particle size distributions D5 to D95 of the hollow acrylic particles may fall within a range of ± 5 μm of the average particle size.
Even when a pore former other than hollow acrylic particles is used, the pore size distribution of the cell wall can be controlled within a predetermined range by preparing particles having a uniform particle size distribution.

As another method for controlling the pore size distribution of the cell wall within a predetermined range, there is a method of aligning the particle size of the ceramic particles. Similarly to the method of aligning the particle diameters of the hollow acrylic particles described above, ceramic particles having a uniform particle diameter can be obtained by filtering the ceramic particles and removing the ceramic particles having a particle diameter in a predetermined range. Then, by using ceramic particles having a uniform particle size, the pore size distribution of the cell wall can be controlled within a predetermined range.

Subsequently, a molding process is performed in which the wet mixture is put into an extruder and extrusion molding is performed, and a honeycomb molded body having a predetermined shape is manufactured.
At this time, the shape of the cross section perpendicular to the longitudinal direction is substantially octagonal, and the large capacity cell having a large cross sectional area, and the small capacity cell having a cross sectional shape perpendicular to the longitudinal direction is substantially quadrangular and has a small cross sectional area. Are alternately arranged in the longitudinal direction of the large-capacity cell with respect to the cell density of the honeycomb molded body, the thickness of the cell wall, and the cross-sectional area perpendicular to the longitudinal direction of the small-capacity cell. A honeycomb formed body is manufactured using a mold that can form a honeycomb formed body in which the area ratio of the areas of the vertical cross sections falls within a predetermined range.

Next, a cutting process is performed in which both ends of the honeycomb formed body are cut using a cutting device, the honeycomb formed body is cut into a predetermined length, and the cut honeycomb formed body is dried using a dryer.
Next, a predetermined amount of a sealing material paste serving as a sealing material is filled in one end of either the large capacity cell or the small capacity cell of the dried honeycomb molded body, and the cells are sealed. A cell-sealed honeycomb formed body is manufactured through such steps.
A wet mixture can be used as the sealing material paste.

Next, a degreasing step of heating the organic matter in the cell-sealed honeycomb molded body in a degreasing furnace is performed to produce a honeycomb degreased body. The shape of this honeycomb degreased body is substantially the same as the shape of the honeycomb fired body shown in FIGS. 2 (a) and 2 (b).

Then, the honeycomb degreased body is conveyed to a firing furnace and subjected to a firing step of firing at 2000 to 2300 ° C. in an argon atmosphere, whereby the honeycomb fired body having the shape shown in FIGS. 2A and 2B is obtained. Make it.
The pore size distribution can also be changed by controlling the firing conditions (firing temperature, firing time).

Subsequently, an adhesive paste layer is applied between the honeycomb fired bodies to form an adhesive paste layer, and the adhesive paste layer is dried and solidified to form an adhesive layer. A bundling step is performed to produce a ceramic block that is bundled through.
As the adhesive paste, an adhesive paste containing inorganic fibers and / or whiskers, an inorganic binder, and an organic binder is suitably used.

In this binding step, a plurality of honeycomb fired bodies are bundled by aligning the directions of the honeycomb fired bodies so that the first end faces of the honeycomb fired bodies are in the same direction.

Then, the outer periphery grinding process which grinds the outer periphery of a ceramic block using a diamond cutter to make a substantially cylindrical ceramic block is performed.
Furthermore, a coating layer forming step is performed in which the coating material paste is applied to the outer peripheral surface of the substantially cylindrical ceramic block, and the coating material paste is dried and solidified to form a coating layer.
In addition, as the sealing material paste, a paste similar to the adhesive paste can be used.
Through the above steps, a honeycomb structure can be manufactured.

Subsequently, zeolite such as β-type zeolite ion-exchanged with iron ions is supported on the cell walls of the honeycomb structure.
Examples of the method for supporting zeolite on the cell walls of the honeycomb structure include a method in which the honeycomb structure is immersed in a slurry containing zeolite and then heated by heating.
The amount of zeolite supported can be adjusted by, for example, a method of repeating the step of immersing the honeycomb structure in the slurry and the step of heating, or a method of changing the slurry concentration.
Through the above steps, a honeycomb filter in which zeolite is supported on the cell walls of the honeycomb structure can be manufactured.

Hereinafter, the function and effect of the honeycomb filter of the present embodiment will be described.
(1) In the honeycomb filter of the present embodiment, a large number of cells included in the honeycomb structure include large-capacity cells and small-capacity cells. Therefore, a large amount of PM in the exhaust gas can be collected.

(2) In the honeycomb filter of the present embodiment, the porosity of the cell wall of the honeycomb structure is 55 to 65%. Therefore, a large amount of zeolite can be supported on the cell walls of the honeycomb structure.

(3) In the honeycomb filter of the present embodiment, the average pore diameter of the cell wall of the honeycomb structure is 15 to 25 μm, and the pore diameter distribution of the cell wall of the honeycomb structure is less than half of the average pore diameter. The sum of the pore volume A of the pores having a pore diameter and the pore volume B of the pores having a pore diameter more than twice the average pore diameter is 20% or less of the total pore volume C.
That is, the cell wall has a uniform pore size distribution (narrow), and there is no portion in the cell wall where the exhaust gas is difficult to pass through or the portion where the exhaust gas is concentrated and easy to flow, so that the exhaust gas passes through the cell wall evenly. Therefore, the zeolite supported on the cell wall comes into sufficient contact with NOx in the exhaust gas. Therefore, a honeycomb filter having a high NOx purification rate can be obtained.

(4) In the honeycomb filter of the present embodiment, the pore volume A is 10% or less of the total pore volume C, and the pore volume B is 10% or less of the total pore volume C. Therefore, the exhaust gas passes through the cell walls more evenly. As a result, the zeolite supported on the cell walls is more sufficiently brought into contact with NOx in the exhaust gas, and a honeycomb filter with a higher NOx purification rate can be obtained.

(5) In the honeycomb filter of the present embodiment, the amount of zeolite supported on the cell wall is 80 to 150 g / L. Therefore, when the honeycomb filter of the present embodiment is used as a urea SCR device, NOx in exhaust gas can be sufficiently purified.

(Example)
Examples that more specifically disclose the first embodiment of the present invention will be described below. In addition, this invention is not limited only to these Examples.
First, substrates 1 to 7 having different pore diameter distributions were produced.

(Preparation of substrate 1)
As the substrate 1, three types of substrates 1a, 1b and 1c having different cell cross-sectional shapes were produced.

(Preparation of substrate 1a)
46.6% by weight of silicon carbide coarse powder having an average particle size of 20 μm and 20.0% by weight of silicon carbide fine powder having an average particle size of 0.5 μm were mixed, and the resulting mixture was subjected to pore formation. 6.8% by weight of hollow acrylic particles having an average particle diameter of 21 μm as a material, 3.8% by weight of organic binder (methylcellulose), 3.5% by weight of lubricant (Unilube manufactured by NOF Corporation), plasticizer (glycerin) 6 wt% and 17.7 wt% of water were added and kneaded to obtain a wet mixture. Thereafter, an extrusion molding step of performing extrusion molding using a mold is performed, and a raw honeycomb having substantially the same shape as that shown in FIGS. 2 (a) and 2 (b) and having no cells sealed. A molded body was produced.
The hollow acrylic particles are removed with a sieve so that the total volume of particles larger than 26 μm and small particles smaller than 16 μm is 10% or less of the total particle volume in the particle size distribution. Then, those with uniform particle diameters were used.

Next, the raw honeycomb molded body is dried using a microwave dryer to obtain a dried honeycomb molded body, and then a predetermined cell is filled with a paste having the same composition as that of the generated molded body. Used to dry.

A degreasing process of degreasing the dried honeycomb molded body at 400 ° C. is performed under a normal pressure argon atmosphere at 2200 ° C. for 3 hours, a porosity of 60%, an average pore diameter of 20 μm, and a size Produced a honeycomb fired body comprising a silicon carbide sintered body having a size of 34.3 mm × 34.3 mm × 150 mm, a cell number (cell density) of 350 cells / inch ² , and a cell wall thickness of 0.28 mm (11 mil). did. The honeycomb fired body produced in the above process was used as the base material 1a.

FIG. 4 is a side view of the first end face schematically showing the cell structure of the substrate 1a.
In the base material 1a, as shown in FIG. 4, the cross-sectional shape of the large capacity cell 51a included in the honeycomb fired body 50 is an octagon, and the length indicated by the double arrow X is 1.21 mm. The cross-sectional shape of the small capacity cell 51b is a quadrangle (substantially square), and the length of one side (indicated by a double arrow Y in FIG. 4) is 0.97 mm. The thickness of the cell wall 53 between the large capacity cell 51a and the small capacity cell 51b (indicated by a double arrow Z in FIG. 4) is 0.28 mm.
The area of the cross section perpendicular to the longitudinal direction of the large capacity cell is 1.40 mm ² , and the area of the cross section perpendicular to the longitudinal direction of the small capacity cell is 0.94 mm ² . Therefore, the ratio of the area of the cross section perpendicular to the longitudinal direction of the large capacity cell to the area of the cross section perpendicular to the longitudinal direction of the small capacity cell is 1.5.

(Preparation of substrate 1b and substrate 1c)
FIG. 5 is a side view of the first end face schematically showing the cell structure of the substrate 1b, and FIG. 6 is a side view of the first end face schematically showing the cell structure of the substrate 1c.
In the manufacturing process of the base material 1a, the base material 1b and the base material 1c, which are honeycomb fired bodies having the cell structures shown in FIGS. Produced.

In the substrate 1b, as shown in FIG. 5, the cross-sectional shape of the large-capacity cell 61a included in the honeycomb fired body 60 is an octagon, and the length indicated by the double arrow X is 1.37 mm. Further, the cross-sectional shape of the small capacity cell 61b is a quadrangle (substantially square), and the length of one side (indicated by a double arrow Y in FIG. 5) is 0.87 mm. The thickness of the cell wall 63 between the large capacity cell 61a and the small capacity cell 61b (indicated by a double arrow Z in FIG. 5) is 0.28 mm.
The area of the cross section perpendicular to the longitudinal direction of the large volume cell is 1.81 mm ^2, the area of the cross section perpendicular to the longitudinal direction of the small volume cell is 0.76 mm ^2. Therefore, the area ratio of the area of the cross section perpendicular to the longitudinal direction of the large capacity cell to the area of the cross section perpendicular to the longitudinal direction of the small capacity cell is 2.4.

In the base material 1c, as shown in FIG. 6, the cross-sectional shape of the large-capacity cell 71a included in the honeycomb fired body 70 is a quadrangle (substantially square), and the length indicated by the double arrow X is 1.18 mm. The cross-sectional shape of the small capacity cell 71b is a quadrangle (substantially square), and the length of one side (indicated by a double arrow Y in FIG. 6) is 0.97 mm. The thickness of the cell wall 73 between the large capacity cell 71a and the small capacity cell 71b (indicated by a double arrow Z in FIG. 6) is 0.28 mm.
The area of the cross section perpendicular to the longitudinal direction of the large capacity cell is 1.39 mm ² , and the area of the cross section perpendicular to the longitudinal direction of the small capacity cell is 0.94 mm ² . Therefore, the ratio of the area of the cross section perpendicular to the longitudinal direction of the large capacity cell to the area of the cross section perpendicular to the longitudinal direction of the small capacity cell is 1.5.

The porosity, average pore diameter, and pore diameter distribution of the substrate 1b and the substrate 1c are the same as those of the substrate 1a.
Hereinafter, the base material 1a, the base material 1b, and the base material 1c are collectively referred to as the base material 1. Table 1 shows the composition and firing conditions of the wet mixture used for the production of the substrate 1.

(Preparation of base materials 2 to 5)
Except that the composition of the wet mixture and the firing conditions were changed as shown in Table 1, honeycomb fired bodies were produced in the same manner as the production of the substrate 1a, and substrates 2 to 5 were produced. Its shape is the same as that of the substrate 1a.

(Preparation of base materials 6 and 7)
Of the composition of the wet mixture, as the hollow acrylic particles, those having a particle diameter not uniform with a sieve were used, and the composition of the wet mixture and the firing conditions were changed as shown in Table 1 to prepare the substrate 1a. In the same manner, a honeycomb fired body was produced, and base materials 6 and 7 were produced. Its shape is the same as that of the substrate 1a.
Table 1 summarizes the composition of the wet mixture and the firing conditions used for the production of the substrates 1 to 7.

(Measurement of porosity, average pore size, and pore size distribution)
About the base materials 1-7, the porosity was measured by the gravimetric method and the average pore diameter and the pore diameter distribution (up to 0.2 to 500 μm) were measured by a mercury intrusion method (based on JIS R 1655: 2003).
As a specific measurement procedure by the mercury intrusion method, each base material was cut into a cube of about 0.8 cm, ultrasonically washed with ion-exchanged water, and sufficiently dried to obtain a measurement sample. Next, the pore diameter of this sample was measured using Shimadzu Corp., Micromeritics automatic porosimeter, Autopore III 9405. At this time, the measurement range was 0.2 to 500 μm, and further measured for each pressure of 0.1 psia in the range of 100 to 500 μm, and measured for each pressure of 0.25 psia in the range of 0.2 to 100 μm. . Thereby, the pore size distribution and the total pore volume C are calculated.
The average pore diameter α was calculated as (4 × S (cumulative pore area) / V (cumulative pore volume)).
In addition, a pore diameter (0.5α diameter) that is half of the average pore diameter and a pore diameter (2α diameter) that is twice the average pore diameter are calculated. The pore volume B of pores having a pore diameter was calculated.
Furthermore, the ratio (%) of the pore volume A to the total pore volume C and the ratio (%) of the pore volume B to the total pore volume C were calculated. Moreover, the sum (A + B) of the two ratios was obtained.
The measurement results are shown in Table 2.

(Preparation of honeycomb structure)
Honeycomb structures 1 to 7 were produced using the substrates 1 to 7 as the honeycomb fired bodies.
The honeycomb structures manufactured using the substrates 1a, 1b, and 1c are referred to as honeycomb structures 1a, 1b, and 1c, respectively. The honeycomb structures 1a, 1b, and 1c are collectively referred to as the honeycomb structure 1.
In addition, the honeycomb structures manufactured using the substrates 2 to 7 as the honeycomb fired bodies are referred to as honeycomb structures 2 to 7, respectively.

The honeycomb structures 1 to 7 were produced according to the following procedure.
By applying an adhesive paste between the honeycomb fired bodies to form an adhesive paste layer, and drying and solidifying the adhesive paste layer to form an adhesive layer, 16 honeycomb fired bodies are interposed via the adhesive layer. A substantially prismatic ceramic block formed by bundling was produced.
At this time, the honeycomb fired bodies were aligned so that the first end faces of the honeycomb fired bodies were in the same direction, and a plurality of honeycomb fired bodies were bundled.
As the adhesive paste, 30% by weight of alumina fibers having an average fiber length of 20 μm, 21% by weight of silicon carbide particles having an average particle diameter of 0.6 μm, 15% by weight of silica sol (solid content of 30% by weight), carboxymethylcellulose 5.6 An adhesive paste containing wt% and 28.4 wt% water was used.

Then, the cylindrical ceramic block of 142 mm in diameter was produced by grinding the outer periphery of a prismatic ceramic block using a diamond cutter.

Next, a coating material paste was applied to the outer peripheral portion of the cylindrical ceramic block, and the coating material paste was dried and solidified at 120 ° C., thereby forming a coating layer on the outer peripheral portion of the ceramic block.
As the coating material paste, the same paste as the adhesive paste was used.
Through the above steps, a cylindrical honeycomb structure having a diameter of 143.8 mm and a length of 150 mm was produced.

Next, in each of the examples, reference examples, and comparative examples, a honeycomb filter was manufactured by supporting zeolite on the honeycomb structures 1 to 7 manufactured using the substrates 1 to 7.
Example 1
A β-type zeolite powder (average particle size 2 μm) ion-exchanged with iron ions was mixed with a sufficient amount of water and stirred to prepare a zeolite slurry. The honeycomb structure 1a was immersed in this zeolite slurry with one end face down and held for 1 minute. Subsequently, a drying step of heating the honeycomb structure 1a at 110 ° C. for 1 hour was performed, and further a firing step of firing at 700 ° C. for 1 hour was performed to form a zeolite supporting layer.
At this time, the immersion in the zeolite slurry, the drying step, and the firing step were repeated so that the formation amount of the zeolite supporting layer was 120 g per liter of the apparent volume of the honeycomb structure.
Thus, a honeycomb filter having a zeolite loading of 120 g / L (apparent volume) was produced.

(Examples 2-7, Reference Example 1, Comparative Examples 1-5)
In Examples 2 to 7, Reference Example 1 and Comparative Examples 1 to 5, honeycomb filters manufactured using the respective base materials shown in Table 2 were loaded with the amount of zeolite shown in Table 2 to prepare honeycomb filters. .
The amount of zeolite supported was adjusted by changing the number of times the immersion in the zeolite slurry, the drying step, and the firing step were repeated.

(Measurement of NOx purification rate)
The NOx purification rate was measured for the honeycomb filters produced in each example, reference example, and comparative example.
In measuring the NOx purification rate, one honeycomb fired body (34.3 mm × 34.3 mm × 150 mm) was cut out from the honeycomb filter produced in each example, reference example, and comparative example by using a diamond cutter, The cut honeycomb fired body was further cut to shorten the length, thereby producing a short body of 34.3 mm × 34.3 mm × 40 mm.
Next, similarly to the sealing step and the degreasing step described above, the short cell is sealed with an adhesive paste so that either one end of the short cell is sealed, and the cell is sealed. The obtained short body was degreased at 400 ° C. to prepare a NOx purification rate measurement sample.

The measurement of the NOx purification rate was performed using a NOx purification rate measuring device (Catalyst evaluation device SIGU-2000 manufactured by Horiba, Ltd.).
The NOx purification rate measuring device is composed of a gas generation part and a reaction part, and the pseudo exhaust gas generated in the gas generation part is circulated through the reaction part in which the sample for evaluation is set.
The composition of the pseudo exhaust gas is NO: 175 ppm, NO ₂ : 175 ppm, NH ₃ : 350 ppm, O ₂ : 14%, CO ₂ : 5%, H ₂ O: 10%, N ₂ : balance, and the flow rate of each gas Was adjusted using a flow controller to obtain the above composition.
In addition, the temperature of the reaction part was constant at 200 ° C. The space velocity (SV) was set to 70000 hr ⁻¹ as a condition for the contact between the zeolite and the pseudo exhaust gas.
The NOx concentration N ₀ before the simulated exhaust gas passed through the evaluation sample and the NOx concentration N ₁ after the simulated exhaust gas passed through the evaluation sample were measured, and the NOx purification rate was calculated from the following equation.
NOx purification rate (%) = [(N ₀ −N ₁ ) / N ₀ ] × 100
Table 2 shows the measurement results of the NOx purification rate.
In Table 2, the types of base materials of Examples, Reference Examples and Comparative Examples, cell shape, porosity, average pore diameter α, pore volume with respect to total pore volume C (pore volume A, pore volume B, total (A + B) )), Zeolite loading (apparent volume), and NOx purification rate are shown together.

When the porosity is 55 to 65%, the zeolite loading is 80 to 150 g / L, and the total of the pore volume A + the pore volume B is 20% or less of the total pore volume C as in each of the examples and reference examples The NOx purification rate was as high as 50% or more.
Further, when the pore volume A was 10% or less of the total pore volume C and the pore volume B was 10% or less of the total pore volume C, the NOx purification rate was a higher value. (In Example 5, the total of pore volume A + pore volume B is 9.3% of the total pore volume C, and the NOx purification rate is 63%.)
On the other hand, as in Comparative Examples 1 to 5, when any one of the porosity, zeolite loading amount, pore volume A + pore volume B is not within the above range, the NOx purification rate is as low as less than 50%. Met.
In Examples, Reference Examples, and Comparative Examples, B-type zeolite ion-exchanged with iron ions was supported, but similar results were obtained with zeolites other than B-type zeolite ion-exchanged with copper ions or B-type zeolite. it is conceivable that.

(Second embodiment)
Hereinafter, a second embodiment which is an embodiment of the present invention will be described.
In the present embodiment, the honeycomb structure constituting the honeycomb filter is composed of one honeycomb fired body. Such a honeycomb structure made of one honeycomb fired body is also referred to as an integral honeycomb structure.

Fig.7 (a) is a perspective view which shows typically an example of the honeycomb structure which comprises the honeycomb filter of 2nd embodiment of this invention. Fig. 7 (b) is a cross-sectional view of the honeycomb structure shown in Fig. 7 (a) taken along line BB.
A honeycomb structure 80 shown in FIG. 7A has a substantially cylindrical shape having a first end face 84 and a second end face 85, and is perpendicular to the longitudinal direction (the direction of a double-headed arrow c in FIG. 7A). The large-capacity cell 91a has a relatively large cross-sectional area larger than that of the small-capacity cell 91b, and the small-capacity cell 91b has a cross-sectional area perpendicular to the longitudinal direction smaller than that of the large-capacity cell 91a.
The large-capacity cell 91a has a substantially octagonal cross-sectional shape in the longitudinal direction, and the small-capacity cell 91b has a substantially quadrangular cross-sectional shape in the longitudinal direction.
A coat layer 82 is provided on the outer peripheral side surface of the honeycomb structure 80.
Moreover, it is desirable to use cordierite or aluminum titanate as the main constituent material of the integral honeycomb structure.

The large-capacity cell 91a is opened at the end portion on the first end face 84 side of the honeycomb structure 80, and is sealed with the sealing material 92a at the end portion on the second end face 85 side. On the other hand, in the small capacity cell 91b, the end portion on the second end face 85 side of the honeycomb structure 80 is opened, and the end portion on the first end face 84 side is sealed with the sealing material 92b. A cell wall 93 separating the large capacity cell 91a and the small capacity cell 91b functions as a filter.
That is, the exhaust gas flowing into the large-capacity cell 91a always passes through these cell walls 93 and then flows out from the small-capacity cell 91b.

The porosity, average pore diameter, and pore size distribution of the cell wall of the honeycomb structure of the present embodiment are the same as those of the cell wall of the honeycomb structure of the first embodiment.

The honeycomb filter of the present embodiment is such that zeolite is supported on the cell walls of such a honeycomb structure.
The type of zeolite and the amount of zeolite supported on the cell walls of the honeycomb structure are the same as in the first embodiment.

When manufacturing the honeycomb filter of the present embodiment, the size of the honeycomb formed body formed by extrusion is larger than the size of the honeycomb formed body described in the first embodiment, and the outer shape is different. In the same manner as in the first embodiment, a honeycomb formed body is manufactured.

Other processes are almost the same as the manufacturing process of the honeycomb filter in the first embodiment. However, in the present embodiment, since the honeycomb structure constituting the honeycomb filter is composed of one honeycomb fired body, it is not necessary to perform a bundling process. In addition, when a substantially cylindrical honeycomb formed body is manufactured, it is not necessary to perform the outer periphery grinding process.

And a urea SCR apparatus can be manufactured like the first embodiment using the manufactured honeycomb filter.
Also in the honeycomb filter of the present embodiment, the same operational effects (1) to (5) as in the first embodiment can be exhibited.

(Other embodiments)
In the case of manufacturing a honeycomb filter using an aggregated honeycomb structure, in the first embodiment, the honeycomb structure is supported with zeolite. However, after a plurality of honeycomb fired bodies are supported with zeolite, the zeolite is supported. The honeycomb fired body may be bound through an adhesive layer.

In the honeycomb filter of the present invention, the shapes of the large-capacity cells and the small-capacity cells included in the honeycomb structure are not limited to the shapes described in the above embodiments.
8 (a), 8 (b), 8 (c) and 8 (d) are schematic examples of the first end face of the honeycomb fired body constituting the aggregated honeycomb structure according to the present invention. It is the side view shown in.
These drawings are all side views as seen from the first end face side of the honeycomb fired body, that is, the end face side where the small-capacity cells are sealed.
Other embodiments of the cross-sectional shapes of the large capacity cell and the small capacity cell of the honeycomb structure will be described with reference to these drawings.

In the honeycomb fired body 110 shown in FIG. 8 (a), the shape of the cross section perpendicular to the longitudinal direction of the large-capacity cell 111a is a substantially quadrangle in which portions corresponding to the corners are arc-shaped, The shape of the cross section perpendicular to the longitudinal direction of 111b is a substantially square shape.

In the honeycomb fired body 120 shown in FIG. 8B, the cross section perpendicular to the longitudinal direction of the large capacity cell 121a and the small capacity cell 121b has a shape in which each side of the cell is a curve.
That is, in FIG. 8B, the cross-sectional shape of the cell wall 123 indicated by the solid line is a curve.
The cross-sectional shape of the large-capacity cell 121a is a shape in which the cell wall 123 is convex outward from the center of the cell cross-section, while the cross-sectional shape of the small-capacity cell 121b is the cell wall 123 from the outside of the cell cross-section. Convex shape toward the center.
The cell wall 123 has a “corrugated” shape that undulates in the horizontal direction and the vertical direction of the cross section of the honeycomb fired body, and the corrugated peak portion of the adjacent cell wall 123 (maximum of amplitude in a sine curve). When the value portion is closest to each other, a large-capacity cell 121a in which the cross-sectional shape of the cell expands outward and a small-capacity cell 121b in which the cross-sectional shape of the cell is recessed inward are formed. The amplitude of the waveform may be constant or may vary, but is preferably constant.

In the honeycomb fired body 130 shown in FIG. 8C, the shape of the cross section perpendicular to the longitudinal direction of the large-capacity cell 131a is a substantially pentagon, and three corners thereof are substantially perpendicular. The shape of the cross section perpendicular to the longitudinal direction of the small-capacity cell 131b is a substantially quadrangular shape, and is configured so as to occupy diagonally opposing portions of a large substantially rectangular shape.

In the honeycomb fired body 140 shown in FIG. 8 (d), both the large-capacity cells 141a and the small-capacity cells 141b have substantially quadrangular (substantially rectangular) cross-sectional shapes, and two large-capacity cells and two When small capacity cells are combined, they are configured to be substantially square.

Note that the integrated honeycomb structure also has the cross-sectional shapes of the large-capacity cell and the small-capacity cell as shown in FIGS. 8 (a), 8 (b), 8 (c), and 8 (d). It may be. The cross-sectional shape of the cells perpendicular to the longitudinal direction of the honeycomb structure refers to the shape of the cells excluding incomplete cells (cells in which a part of the cross section is missing).

The shape of the honeycomb filter is not limited to a substantially cylindrical shape, and may be any column shape such as a substantially elliptical column shape or a substantially polygonal column shape.

The cell density in the cross section perpendicular to the longitudinal direction of the honeycomb structure is not particularly limited, but a desirable lower limit is 31 cells / cm ² (200 cells / in ² ), and a desirable upper limit is 93 cells / cm ² (600 cells / in ² ). ² ), the more desirable lower limit is 38.8 / cm ² (250 / in ² ), and the more desirable upper limit is 77.5 / cm ² (500 / in ² ).
The thickness of the cell wall of the honeycomb structure is not particularly limited, but is preferably 0.2 to 0.4 mm.

The main component of the constituent material of the honeycomb fired body and the integral honeycomb structure constituting the aggregated honeycomb structure is not limited to silicon carbide, and other ceramic raw materials include, for example, aluminum nitride and silicon nitride. Ceramic powders such as nitride ceramics such as boron nitride and titanium nitride, carbide ceramics such as zirconium carbide, titanium carbide, tantalum carbide and tungsten carbide, oxide ceramics such as alumina, zirconia, cordierite, mullite and aluminum titanate Can be mentioned.
Of these, non-oxide ceramics are preferred, and silicon carbide is particularly preferred. It is because it is excellent in heat resistance, mechanical strength, thermal conductivity and the like. In addition, ceramic raw materials such as silicon-containing ceramics in which metallic silicon is mixed with the above-mentioned ceramics, and ceramics in which the above-described ceramics are bonded with silicon or a silicate compound can be cited as constituent materials. Those containing silicon (silicon-containing silicon carbide) are desirable.
In particular, a silicon-containing silicon carbide ceramic containing 60% by weight or more of silicon carbide is desirable.

Further, the particle size of the ceramic powder in the honeycomb fired body constituting the aggregated honeycomb structure and the wet mixture used when the integral honeycomb structure is manufactured is not particularly limited, but is manufactured through a subsequent firing step. It is preferable that the size of the fired honeycomb fired body is smaller than the size of the honeycomb degreased body manufactured through the degreasing process. For example, the powder 100 having an average particle diameter of 1.0 to 50 μm A combination of parts by weight and 5 to 65 parts by weight of powder having an average particle diameter of 0.1 to 1.0 μm is preferable.
As described above, ceramic particles having a uniform particle diameter are obtained by sieving ceramic particles to remove ceramic particles having a predetermined range of particle diameters, and by using ceramic particles having a uniform particle diameter, the pore size distribution is Control within a predetermined range is possible.

There is no particular limitation on the organic binder in the honeycomb fired body constituting the aggregated honeycomb structure and the wet mixture used when producing the integral honeycomb structure. For example, methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene Glycol and the like. Of these, methylcellulose is desirable. In general, the blending amount of the organic binder is desirably 1 to 10 parts by weight with respect to 100 parts by weight of the ceramic powder.

It does not specifically limit as a plasticizer contained in a wet mixture, For example, glycerol etc. are mentioned.
The lubricant contained in the wet mixture is not particularly limited, and examples thereof include polyoxyalkylene compounds such as polyoxyethylene alkyl ether and polyoxypropylene alkyl ether.
Specific examples of the lubricant include polyoxyethylene monobutyl ether and polyoxypropylene monobutyl ether.
In some cases, the plasticizer and the lubricant may not be contained in the wet mixture.

In preparing the wet mixture, a dispersion medium liquid may be used. Examples of the dispersion medium liquid include water, an organic solvent such as benzene, and an alcohol such as methanol.
Furthermore, a molding aid may be added to the wet mixture.
The molding aid is not particularly limited, and examples thereof include ethylene glycol, dextrin, fatty acid, fatty acid soap, polyalcohol and the like.

The pore former to be added to the wet mixture is not limited to hollow acrylic particles, and balloons that are fine hollow spheres containing oxide ceramics, graphite, and the like may be added.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

10, 80 Honeycomb structure 11 Adhesive layer 20, 50, 60, 70, 110, 120, 130, 140 Honeycomb fired bodies 21a, 51a, 61a, 71a, 91a, 111a, 121a, 131a, 141a Large capacity cell 21b, 51b, 61b, 71b, 91b, 111b, 121b, 131b, 141b Small capacity cell 23, 53, 63, 73, 93, 123 Cell wall

Claims (7)

A large number of cells are arranged in parallel in the longitudinal direction across the cell wall, and each of the cells has a honeycomb structure sealed at one end, and a zeolite supported on the cell wall of the honeycomb structure. A honeycomb filter,
The amount of zeolite supported on the cell wall is 80 to 150 g / L,
The large number of cells includes a large capacity cell and a small capacity cell.
The porosity of the cell wall of the honeycomb structure is 55 to 65%,
The average pore diameter of the cell wall of the honeycomb structure is 15 to 25 μm,
The pore size distribution of the cell walls of the honeycomb structure includes a pore volume A having a pore size less than half of the average pore size and a pore volume B having a pore size more than twice the average pore size. A honeycomb filter, wherein the total is 20% or less of the total pore volume C. The honeycomb filter according to claim 1, wherein the pore volume A is 10% or less of the total pore volume C, and the pore volume B is 10% or less of the total pore volume C. The honeycomb filter according to claim 1 or 2, wherein a shape of a cross section perpendicular to the longitudinal direction of the large capacity cell is substantially octagonal, and a shape of a cross section perpendicular to the longitudinal direction of the small capacity cell is substantially square. . The honeycomb filter according to claim 1 or 2, wherein a shape of a cross section perpendicular to the longitudinal direction of the large-capacity cell is substantially square, and a shape of a cross section perpendicular to the longitudinal direction of the small-capacity cell is substantially square. The honeycomb filter according to any one of claims 1 to 4, wherein the zeolite is at least one selected from the group consisting of β-type zeolite, ZSM-5-type zeolite, and SAPO. The honeycomb filter according to any one of claims 1 to 5, wherein the zeolite is ion-exchanged with copper ions and / or iron ions. The honeycomb filter according to any one of claims 1 to 6, wherein the honeycomb structure is formed by binding a plurality of honeycomb fired bodies through an adhesive layer.

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