JP2005118747A - Honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb structure capable of depositing particulates and ash in large quantities, and capable of carrying a large quantity of catalysts without significantly increasing pressure loss. <P>SOLUTION: The pillar-shaped honeycomb structure has a number of perforated holes, separated with partition walls and placed in parallel in the longitudinal direction. The perforated holes comprise a group of large volume perforated holes the one ends of which are sealed so that the total sum of the areas of the longitudinally perpendicular sections may become relatively large, and a group of small volume perforated holes the other ends of which are sealed so that the total sum of the areas of the sections may become relatively small. The partition walls constituting the group of the large volume perforated holes and separating adjacent perforated holes are characteristically provided with selective catalyst carrier parts for selectively carrying the catalysts. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a filter for removing particulates and the like in exhaust gas discharged from an internal combustion engine such as a diesel engine, and a honeycomb structure used as a catalyst carrier.

Recently, it has become a problem that particulates such as soot contained in exhaust gas discharged from internal combustion engines such as vehicles such as buses and trucks and construction machinery cause harm to the environment and the human body.
Thus, various honeycomb structures made of porous ceramics have been proposed as filters that can collect particulates in exhaust gas and purify the exhaust gas.

Conventionally, as such a honeycomb structure, there are provided two types of through-holes: a large-volume through-hole (hereinafter also referred to as a large-volume through-hole) and a small-volume through-hole (hereinafter also referred to as a small-volume through-hole). The large-volume through hole is sealed with a sealing material at one end, and the small-volume through hole is sealed with a sealing material at an end opposite to the large-volume through hole. Further, in the honeycomb structure, a technique is disclosed in which a large volume through hole is opened on the gas inflow side of the filter and a small volume through hole is opened on the gas outflow side of the filter. (For example, refer patent documents 1-12).

Further, the number of through holes (hereinafter referred to as “inlet side through holes”) configured to open on the gas inflow side is determined from the number of through holes (hereinafter referred to as “outlet side through holes”) configured to open on the gas outflow side. In addition, a filter or the like in which the total amount of the surface area of the inlet-side through hole is relatively larger than the total surface area of the outlet-side through hole is also known (see, for example, FIG. 3 of Patent Document 5).

When viewed from the end face, these honeycomb structures have a large volume through-hole group (the total surface area / cross-sectional area of the through-hole is relatively large) and a small volume through-hole group (the total surface area / cross-sectional area of the through-holes). (Relatively small), the large volume through-hole group is made the gas inflow side, and the small volume through-hole group is made the gas outflow side. Compared to a honeycomb structure with the same total surface area of the through-holes, the thickness of the collected particulate deposit layer can be reduced, and as a result, an increase in pressure loss during particulate collection is suppressed. Or increase the limit of particulate collection.

However, in the honeycomb structure having a relatively large total surface area of the inlet-side through holes, the pressure loss of the base material itself is high, so the purpose is to remove particulates in the exhaust gas and harmful gas components such as HC and CO. However, when a large amount of catalyst is supported, the pressure loss of the honeycomb structure becomes too high. In the future, the honeycomb structure is required to carry a catalyst or the like for removing NOx, and while ensuring a large total surface area of the inlet-side through-holes, the catalyst can be prevented while suppressing an increase in pressure loss. There has been a demand for a technique that enables an increase in the amount of the supported carbon.

JP 56-124418 A JP 62-96717 A, JP 62-96717 A Japanese Utility Model Publication No. 58-92409 U.S. Pat. No. 4,416,676 JP 58-196820 A US Pat. No. 4,420,316 JP-A-58-150015 Japanese Patent Laid-Open No. 5-68828 French patent invention No. 2789327 International Publication No. 02 / 100514A1 Pamphlet International Publication No. 02 / 10562A1 Pamphlet International Publication No. 03 / 20407A1 Pamphlet

The present invention has been made to solve such a problem, and can deposit a large amount of particulates and ash, and can carry a large amount of catalyst without greatly increasing pressure loss. An object of the present invention is to provide a honeycomb structure that can be manufactured.

As a result of intensive studies, the inventors of the present invention have made it difficult for the exhaust gas to flow into the partition walls that separate the inlet-side through-holes. The inventors have found that the influence is small and have completed the present invention.

That is, the honeycomb structure of the first aspect of the present invention is a columnar honeycomb structure in which a large number of through holes are arranged in parallel in the longitudinal direction with partition walls therebetween.
The large number of through-holes have a large-capacity through-hole group sealed at one end so that the total area in the cross section perpendicular to the longitudinal direction is relatively large, and the total area in the cross section is relatively It consists of a small volume through-hole group sealed at the other end so as to become smaller,
A selective catalyst supporting portion for selectively supporting a catalyst is provided on the partition wall that constitutes the large-volume through-hole group and separates adjacent through-holes.

In the honeycomb structure according to the first aspect of the present invention, it is desirable that the catalyst is supported at least on the selective catalyst supporting portion, and the selective catalyst supporting portion includes through holes constituting adjacent large-volume through-hole groups. It is desirable that they are convex portions and / or concave portions provided in the partition walls.
In the honeycomb structure according to the first aspect of the present invention, the convex portion provided on the selective catalyst supporting portion has a thickness of 0.02 to 6 that is a partition wall thickness that separates through-holes constituting adjacent large-volume through-hole groups. It is desirable that the concave portion provided in the selective catalyst supporting part is 0.02 to 0.4 times the thickness of the partition wall separating the through holes constituting the adjacent large volume through hole group. It is desirable to have a depth of

In the honeycomb structure according to the first aspect of the present invention, the shape of the cross section perpendicular to the longitudinal direction of the through hole constituting the large volume through hole group and / or the small volume through hole group is a polygon. Is desirable.
In the honeycomb structure according to the first aspect of the present invention, the shape of the cross section perpendicular to the longitudinal direction of the through holes constituting the large volume through hole group is an octagon, and the above cross section of the through holes constituting the small volume through hole group The shape of is preferably a quadrangle.
In the honeycomb structure of the first aspect of the present invention, the sum of the areas in the cross section perpendicular to the longitudinal direction of the through holes constituting the large volume through hole group and the area in the cross section of the through holes constituting the small volume through hole group are as follows. It is desirable that the ratio to the sum is 1.5 to 2.7.
In the honeycomb structure of the first aspect of the present invention, partition walls that separate through-hole groups that constitute adjacent large-volume through-hole groups in a cross section perpendicular to the longitudinal direction, and through-holes that form adjacent large-volume through-hole groups It is desirable that at least one of the angles intersecting with the partition walls separating the through holes constituting the small volume through hole group is an obtuse angle.
In the honeycomb structure of the first aspect of the present invention, the vicinity of the corner portion of the cross section perpendicular to the longitudinal direction of the through hole constituting the large volume through hole group and / or the through hole constituting the small volume through hole group is constituted by a curve. It is desirable that
In the honeycomb structure of the first aspect of the present invention, the distance between the centroids in the cross section perpendicular to the longitudinal direction of the through-holes constituting the adjacent large-volume through-hole groups and the above-described through-holes constituting the adjacent small-volume through-hole groups It is desirable that the distance between the centers of gravity in the cross section is equal.

A honeycomb structure according to the second aspect of the present invention allows gas to pass through the outer peripheral surface of a honeycomb block formed by combining a plurality of honeycomb structures according to the first aspect of the present invention via a sealing material layer. A sealing material layer made of a difficult material is formed.
In addition to the case where the honeycomb structure of the first invention is used as a constituent member of the honeycomb structure of the second invention, only one may be used as a filter.
In the following, a honeycomb structure having a structure formed as a whole, such as the honeycomb structure of the first invention, is also referred to as an integral honeycomb structure, as in the honeycomb structure of the second invention. A honeycomb structure having a structure in which a plurality of ceramic members are combined through a sealing material layer is also referred to as an aggregate-type honeycomb structure. In addition, when there is no particular distinction between an integral honeycomb structure and an aggregated honeycomb structure, it is called a honeycomb structure.

The honeycomb structure of the first or second aspect of the present invention is preferably used in an exhaust gas purification device for a vehicle.

According to the honeycomb structure of the first aspect of the present invention, since the selective catalyst supporting portion is provided on the partition walls that separate the through holes constituting the adjacent through hole group, the partition walls (hereinafter, referred to as “catalysts”) in which a large amount of catalyst is supported. The function can be separated between the partition walls A and other partition walls (hereinafter referred to as partition walls B). That is, the partition wall A has a function of increasing the temperature by supplying heat to the filter by heat generated by an oxidation reaction via a catalyst such as HC or CO in the exhaust gas (heat supply function). B has a function (pressure loss increase suppression function) that allows the exhaust gas to pass through both during the accumulation of particulates and during the combustion thereof, and suppresses an increase in the pressure loss of the filter. Here, since the partition wall A is originally a partition wall through which exhaust gas hardly passes, even if a catalyst that needs to be supported in a large amount, such as a NOx storage catalyst, is supported, an increase in pressure loss hardly occurs. Further, when particulates burn and ash is generated, particulates are likely to burn on the catalyst in the partition wall A, so the ash is likely to be deposited on the partition wall A. However, since the partition wall A is a partition wall that is unlikely to cause an increase in pressure loss as described above, even if ash is deposited, the pressure loss is unlikely to increase.
Further, the ash deposited on the partition wall A also serves to prevent a temperature drop on the partition wall A and secure a heat supply function. On the other hand, the ash generated by the burning of the particulates due to the heat supplied from the partition wall A in the partition wall B is easy to peel off due to the small amount of catalyst adhering to the surface of the partition wall B. It is easy to scatter and accumulate, and an increase in pressure loss due to the partition wall B is suppressed.

In addition, since the amount of catalyst supported increases, the exhaust gas purification performance is improved in combination with the above functions, and depending on the amount of catalyst supported, the particulates can be burned and removed without performing regeneration treatment at a high temperature. It becomes possible, and it becomes possible to suppress an increase in pressure loss during particulate collection.

Further, when the selective catalyst supporting part is a convex part and / or a concave part provided in a partition wall that separates through holes constituting adjacent large-volume through hole groups, the selective catalyst supporting part is selectively used as the selective catalyst supporting part. The catalyst is easily supported, and the convex portion provided on the selective catalyst supporting portion has a height of 0.02 to 6 times the thickness of the partition wall that separates the through holes constituting the adjacent large volume through hole group. Or when the concave portion provided in the selective catalyst supporting part has a depth of 0.02 to 0.4 times the thickness of the partition wall separating the through holes constituting the adjacent large volume through hole group, It is easy to selectively support the catalyst on the selective catalyst supporting portion, and it is possible to prevent the convex portion from being damaged or the partition wall from being damaged due to the pressure of the exhaust gas.

In the honeycomb structure according to the first aspect of the present invention, when the shape of the cross section perpendicular to the longitudinal direction of the through hole constituting the large volume through hole group and / or the through hole constituting the small volume through hole group is a polygon, Even if the area of the partition wall in the cross section perpendicular to the longitudinal direction is reduced to reduce the pressure loss and the aperture ratio is increased, a honeycomb structure having excellent durability and a long life can be realized. Furthermore, when the shape of the cross section perpendicular to the longitudinal direction of the through holes constituting the large-volume through-hole group is an octagon, and the shape of the cross-section of the through-hole constituting the small-volume through-hole group is a quadrangle, it is more durable And a long-life honeycomb structure can be realized.

In the honeycomb structure of the first aspect of the present invention, the sum of the areas in the cross section perpendicular to the longitudinal direction of the through holes constituting the large volume through hole group and the area in the cross section of the through holes constituting the small volume through hole group are as follows. When the ratio to the sum is 1.5 to 2.7, the opening ratio on the inlet side can be relatively increased to suppress an increase in pressure loss at the time of particulate collection, and the particulate trapping can be performed. It is possible to prevent the pressure loss before collection from becoming too high.

In the honeycomb structure of the first aspect of the present invention, partition walls that separate through-hole groups that constitute adjacent large-volume through-hole groups in a cross section perpendicular to the longitudinal direction, and through-holes that form adjacent large-volume through-hole groups Pressure loss can be reduced when at least one of the intersecting angles with the partition walls separating the through holes constituting the small volume through hole group is an obtuse angle.

In the honeycomb structure of the first aspect of the present invention, the vicinity of the corner portion of the cross section perpendicular to the longitudinal direction of the through hole constituting the large volume through hole group and / or the through hole constituting the small volume through hole group is constituted by a curve. If it is done, it can prevent that stress concentrates on the corner | angular part of a through-hole, generation | occurrence | production of a crack can be prevented, and pressure loss can be reduced.

In the honeycomb structure of the first aspect of the present invention, the distance between the centroids in the cross section perpendicular to the longitudinal direction of the through-holes constituting the adjacent large-volume through-hole groups and the above-described through-holes constituting the adjacent small-volume through-hole groups If the distance between the centers of gravity in the cross section is the same, heat will diffuse evenly during reproduction and the temperature distribution will tend to be uniform, and even if used repeatedly over a long period of time, it will have excellent durability against cracks caused by thermal stress. It will be.

According to the honeycomb structure of the second aspect of the present invention, a plurality of honeycomb structures of the first aspect of the present invention are combined through the sealing material layer. It is possible to freely adjust the size and the like by increasing the number of honeycomb structures of the first invention of the present invention.

The honeycomb structure according to the first or second aspect of the present invention, when used in an exhaust gas purification device for a vehicle, improves exhaust gas purification performance and suppresses an increase in pressure loss during particulate collection. It is possible to prolong the period until reproduction, improve heat resistance, and freely adjust its size.

The honeycomb structure of the first aspect of the present invention is a columnar honeycomb structure in which a large number of through holes are arranged in parallel in the longitudinal direction with partition walls therebetween.
The large number of through-holes have a large-capacity through-hole group sealed at one end so that the total area in the cross section perpendicular to the longitudinal direction is relatively large, and the total area in the cross section is relatively It consists of a small volume through-hole group sealed at the other end so as to become smaller,
A selective catalyst supporting portion for selectively supporting a catalyst is provided on the partition wall that constitutes the large-volume through-hole group and separates adjacent through-holes.

The combination of the large volume through hole group and the small volume through hole group includes (1) individual through holes constituting the large volume through hole group and individual through holes constituting the small volume through hole group. When the cross-sectional area perpendicular to the longitudinal direction is the same and the number of through-holes constituting the large-volume through-hole group is large, (2) individual through-holes constituting the large-volume through-hole group and small volumes When the cross-sectional areas are different and the numbers of the through-holes are different between the individual through-holes constituting the through-hole group, (3) the individual through-holes constituting the large-volume through-hole group and the small-volume through holes The individual through-holes constituting the hole group include a case where the cross-sectional area of the through-hole constituting the large-volume through-hole group is large and the number of both through-holes is the same.

The through-holes constituting the large-volume through-hole group and / or the through-holes constituting the small-volume through-hole group are each composed of one type of through-hole having the same shape, cross-sectional area perpendicular to the longitudinal direction, and the like. It may be configured by two or more types of through-holes having different shapes and cross-sectional areas perpendicular to the longitudinal direction.

Fig. 1 (a) is a perspective view schematically showing an example of the integral honeycomb structure of the present invention, and Fig. 1 (b) is an A- view of the integral honeycomb structure of the present invention shown in (a). It is A line sectional drawing, (c) is the front view which showed typically another example of the integrated honeycomb structure of this invention.

The integrated honeycomb structures 20 and 30 shown in FIGS. 1A to 1C correspond to the above (3) when a combination of a large volume through hole group and a small volume through hole group is considered. That is, when the individual through holes constituting the large volume through hole group are compared with the individual through holes constituting the small volume through hole group, the area of the cross section of the through hole constituting the large volume through hole group is large. The number of through holes in both is the same.
Hereinafter, the through holes constituting the large volume through hole group are simply referred to as large capacity through holes, and the through holes constituting the small volume through hole group are also referred to simply as small volume through holes.

As shown in FIGS. 1A and 1B, the integrated honeycomb structure 20 has a substantially quadrangular prism shape, and a large number of through holes 21 are arranged in parallel in the longitudinal direction with partition walls 23 therebetween. The through-hole 21 includes a large-volume through-hole 21a that is sealed with a sealing material 22 at an end portion on the gas outlet side of the integrated honeycomb structure 20 and an end portion on the gas inlet side of the integrated honeycomb structure 20. The large-capacity through-hole 21a has an area in a cross section perpendicular to the longitudinal direction of the small-volume through-hole 21b. The partition wall 23 that separates the through holes 21 functions as a filter. That is, the exhaust gas that has flowed into the large volume through hole 21a always passes through the partition wall 23 and then flows out from the small volume through hole 21b.
In the integrated honeycomb structure 20, a selective catalyst support portion including a convex portion 24 is provided on a partition wall 23 b that separates adjacent large-volume through holes 21 a.

In addition, as shown in FIG. 1C, in the integrated honeycomb structure 30 according to another embodiment, a large number of through holes 31 are arranged in parallel with the partition wall 33 in the longitudinal direction. The through-hole 31 has a large-capacity through-hole 31a that is sealed by a sealing material 32 at an end portion on the gas outlet side, and a small volume that is sealed by a sealing material 32 at an end portion on the gas inlet side. It consists of two types of through-holes with the through-hole 31b. The large-volume through-hole 31a has a relatively large area in a cross section perpendicular to the longitudinal direction relative to the small-volume through-hole 31b, and the partition wall 33 that separates these through-holes 31 functions as a filter. It has become. That is, the exhaust gas flowing into the large-volume through hole 31a always passes through the partition wall 33 and then flows out from the small-volume through hole 31b.
On the other hand, in this integrated honeycomb structure 30, a selective catalyst support portion including a recess 34 is provided in a partition wall 33b separating adjacent large-volume through holes 31a.

As described above, in the integrated honeycomb structures 20 and 30 of the present invention, the selective catalyst supporting portion for selectively supporting the catalyst is provided on the partition wall that separates the adjacent large volume through holes 21a and 31a. However, the selective catalyst supporting portion may be formed in the partition walls 23b and 33b that separate the adjacent large-volume through holes 21a and 31a for the purpose of selectively (intensively) supporting the catalyst. There is no particular limitation, and for example, the convex portion 24 as shown in FIGS. 1A and 1B may be used, or the concave portion 34 as shown in FIG. , 33b may be a roughened surface having a larger surface roughness.

When the projecting portion 24 is provided on the partition wall 23b, when the honeycomb structure base material is impregnated with a solution containing the catalyst or the catalyst raw material and taken out, the projecting portion 24 is utilized by utilizing the surface tension of the solution. The liquid droplets can be held around the substrate, and then a large amount of catalyst can be supported on the convex portion 24 and the vicinity thereof by heating and drying.

The shape of the convex portion 24 provided on the partition wall 23b that separates the adjacent large-volume through-holes 21a is not particularly limited. However, the shape is a shape that can easily hold a droplet and can secure a certain level of strength. Specifically, it is desirable that it has a divergent shape. This is because the projecting portion having the end-spread shape can easily obtain higher strength than the projecting portion having an elongated shape. In addition, it is desirable that the monolithic honeycomb structure 20 is continuously formed from the end portion on the inlet side to the end portion on the outlet side. This is because high strength can be obtained and it can be formed by extrusion.

Although it does not specifically limit as the height of the convex part 24, A desirable minimum is 0.02 times with respect to the thickness of the partition 23b which separates adjacent large-volume through-holes 21a, and a desirable upper limit is 6.0 times is there. If it is less than 0.02 times, a sufficient amount of catalyst may not be supported on the convex portion 24 and its vicinity. If it exceeds 6.0 times, the strength of the convex portion 24 becomes insufficient and may be damaged by the pressure of the exhaust gas.

It does not specifically limit as the number of the convex parts 24, You may provide one each with respect to the partition 23b which separates each adjacent large volume through-hole 21a, and may provide two or more. In particular, if a large number of protrusions are provided on the partition walls 23b separating the adjacent large-volume through holes 21a and the surface of the partition walls 23b is corrugated, the amount of liquid droplets retained on each partition wall 23b is reduced. It can be increased and a sufficient amount of catalyst can be supported.

When the partition wall 33b is provided with a recess 34, when the honeycomb structure base material is impregnated with a solution containing the catalyst or the catalyst raw material and taken out, the liquid is placed inside the recess (groove) 34 due to surface tension or the like. Drops can be held, and then a large amount of catalyst can be supported in the recesses 34 by heating and drying.

The shape of the recess 34 is not particularly limited, but is preferably a shape that can easily hold a droplet, and specifically, a recess shape or a groove shape. In addition, it is desirable that the monolithic honeycomb structure 20 has a groove shape continuously formed from the end portion on the inlet side to the end portion on the outlet side. This is because it can be formed by extrusion.

The depth of the recess 34 is not particularly limited, but the desirable lower limit is 0.02 times and the desirable upper limit is 0.4 times the thickness of the partition wall 33a separating adjacent large-volume through holes 31a. . If it is less than 0.02 times, a sufficient amount of catalyst may not be supported on the convex portion 24 and its vicinity. If it exceeds 0.4 times, the strength of the partition wall 33a becomes insufficient, and it may be damaged by the pressure of the exhaust gas.

It does not specifically limit as the number of the recessed parts 34, You may provide one each with respect to the partition 33a which separates each adjacent large volume through-holes 31a, and you may provide two or more.

The thicknesses of the partition walls 23b and 33b separating the adjacent large-volume through holes 21a and 31a are not particularly limited, but a desirable lower limit is 0.2 mm and a desirable upper limit is 1.2 mm. If it is less than 0.2 mm, the partition walls 23b and 33b separating the adjacent large-volume through-holes 21a and 31a cannot be sufficiently supported, and the integrated honeycomb structures 20 and 30 are not strong enough. Sometimes. On the other hand, if it exceeds 1.2 mm, the air permeability of the partition wall 23b separating adjacent large-volume through-holes 21a decreases, the exhaust gas purification ability decreases, and the pressure loss of the integrated honeycomb structures 20 and 30 decreases. May rise.

Further, the thickness of the partition walls 23a and 33a separating the adjacent large volume through holes 21a and 31a and the small volume through holes 21b and 31b is not particularly limited, but the desirable lower limit is 0.2 mm, and the desirable upper limit is 1.2 mm. It is. If it is less than 0.2 mm, the catalyst cannot be sufficiently supported on the partition walls 23a and 33a separating the adjacent large-volume through-holes 21a and 31a and the small-volume through-holes 21b and 31b. The strength of 20, 30 may not be sufficient. On the other hand, if it exceeds 1.2 mm, the air permeability of the partition walls 23a and 33a separating the adjacent large volume through-holes 21a and 31a and the small volume through-holes 21b and 31b decreases, and the exhaust gas purification capacity decreases. The pressure loss of the integrated honeycomb structures 20 and 30 may increase.

The partition walls 23b and 33b separating the adjacent large volume through holes 21a and 31a are formed thicker than the partition walls 23a and 33a separating the adjacent large volume through holes 21a and 31a and the small volume through holes 21b and 31b. It is desirable. By increasing the thickness of the partition walls 23b and 33b, it is possible to support a large amount of catalyst on the partition walls 23b and 33b. However, the partition walls 23b and 33b, which are the partition walls separating the inlet-side through holes, are made thicker. This is because even if a large amount of catalyst is supported, the influence on the pressure loss is small.

In the monolithic honeycomb structure of the present invention, since the selective catalyst supporting part for selectively supporting the catalyst is provided on the partition walls separating the adjacent large-volume through holes, the exhaust gas is first First, it flows into a partition wall in which the selective catalyst support portion is not provided, that is, a partition wall (partition wall B) separating adjacent large-volume through holes and small-volume through holes, and particulates accumulate on the partition walls.
When a certain amount of particulate is deposited on the partition wall (partition B) that separates the adjacent large-volume through-holes from the small-volume through-hole, pressure loss increases. Exhaust gas also flows into the exhaust gas, and especially during filter regeneration, HC, CO, etc. in the exhaust gas are oxidized, heat is generated by the oxidation reaction, the temperature of the filter rises, and the accumulated particulates burn. It becomes easy.
When the particulates burn, the pressure loss becomes low, so the exhaust gas flows into the partition wall B, and then the above process is repeated.

Therefore, the partition wall A has a function of increasing the temperature by supplying heat to the filter (heat supply function), while the partition wall B emits exhaust gas both during particulate deposition and during combustion. It has a function of suppressing the pressure loss of the filter from increasing (pressure loss increase suppressing function). Here, since the partition wall A is originally a partition wall through which exhaust gas hardly passes, even if a catalyst that needs to be supported in a large amount, such as a NOx storage catalyst, is supported, an increase in pressure loss hardly occurs. Further, when particulates burn and ash is generated, particulates are likely to burn on the catalyst in the partition wall A, so the ash is likely to be deposited on the partition wall A. However, since the partition wall A is a partition wall that is unlikely to cause an increase in pressure loss as described above, even if ash is deposited, the pressure loss is unlikely to increase.
Further, the ash deposited on the partition wall A also serves to prevent a temperature drop on the partition wall A and secure a heat supply function. On the other hand, the ash generated by the burning of the particulates due to the heat supplied from the partition wall A in the partition wall B is easy to peel off due to the small amount of catalyst adhering to the surface of the partition wall B. It is easy to scatter and accumulate, and an increase in pressure loss due to the partition wall B is suppressed.

In the integral honeycomb structure of the present invention, a catalyst is supported on at least the selective catalyst supporting portion. Of course, a catalyst may be supported in addition to the selective catalyst support, and it is desirable that the catalyst be supported on the partition wall in the large-volume through hole.
The catalyst is not particularly limited, but a catalyst that lowers the activation energy of particulate combustion, a catalyst that can purify harmful gas components in exhaust gas such as CO, HC, and NOx is desirable. , Noble metals such as platinum, palladium and rhodium. Among these, a so-called three-way catalyst composed of platinum, palladium, and rhodium is desirable. In addition to the noble metal, an alkali metal (element periodic table group 1), an alkaline earth metal (element periodic table group 2), a rare earth element (element periodic table group 3), a transition metal element, or the like may be supported.

The catalyst may be supported on the surface of pores inside the partition walls, or may be supported with a certain thickness on the partition walls. Further, the catalyst may be uniformly supported on the surface of the partition wall and / or the surface of the pores, or may be supported unevenly at a certain place. The same applies to the partition walls constituting the selective catalyst support.

Among these, the catalyst is desirably supported on the surface of the partition wall, and is desirably supported in a large amount on the surface of the selective catalyst supporting portion. This is because the catalyst and the particulates are easily in contact with each other, so that exhaust gas can be purified efficiently.

In addition, when applying the catalyst to the integral honeycomb structure, it is desirable to apply the catalyst after the surface is previously coated with a support material such as alumina. Thereby, a specific surface area can be enlarged, the dispersion degree of a catalyst can be improved, and the reaction site | part of a catalyst can be increased. Moreover, since the sintering of the catalyst metal can be prevented by the support material, the heat resistance of the catalyst is also improved. In addition, it is possible to reduce the pressure loss.

By supporting such a catalyst, the integral honeycomb structure functions as a filter that collects particulates in the exhaust gas, and purifies CO, HC, NOx, and the like contained in the exhaust gas. Can function as a catalytic converter.
The integral honeycomb structure of the present invention functions as a gas purification device similar to a conventionally known DPF with a catalyst (diesel particulate filter). Therefore, the detailed description about the function as a catalyst carrier of the integral honeycomb structure of the present invention is omitted here.

The monolithic honeycomb structure is preferably mainly composed of a porous ceramic, and examples of the material thereof include nitride ceramics such as aluminum nitride, silicon nitride, boron nitride, and titanium nitride, silicon carbide, zirconium carbide, titanium carbide, Examples thereof include carbide ceramics such as tantalum carbide and tungsten carbide, and oxide ceramics such as alumina, zirconia, cordierite, mullite, and silica. The integral honeycomb structure 20 may be formed of two or more kinds of materials such as a composite of silicon and silicon carbide and aluminum titanate.

The particle size of the ceramic used for manufacturing the monolithic honeycomb structure is not particularly limited, but it is desirable that the particle size is small in the subsequent firing step, for example, a powder having an average particle size of about 0.3 to 50 μm. A combination of 100 parts by weight and 5 to 65 parts by weight of powder having an average particle diameter of about 0.1 to 1.0 μm is desirable. By mixing the ceramic powder having the above particle diameter with the above composition, an integrated honeycomb structure made of porous ceramic can be manufactured.

It is more desirable that the sealing material and the partition walls constituting the integral honeycomb structure are made of the same porous ceramic. As a result, the adhesive strength between the two can be increased, and the porosity of the sealing material can be adjusted in the same manner as that of the partition wall so that the thermal expansion coefficient of the partition wall can be matched with the thermal expansion coefficient of the sealing material. It can prevent gaps between the sealing material and the partition due to thermal stress during manufacturing and use, and cracks in the partition in contact with the sealing material and the sealing material. be able to.

The porosity of the monolithic honeycomb structure is not particularly limited, but a desirable lower limit is 20% and a desirable upper limit is 80%. If it is less than 20%, the integrated honeycomb structure 20 may be clogged immediately. On the other hand, if it exceeds 80%, the strength of the integrated honeycomb structure may be reduced and easily broken. is there.
The porosity can be measured by a conventionally known method such as a mercury intrusion method, an Archimedes method, or a measurement using a scanning electron microscope (SEM).

The desirable lower limit of the average pore diameter of the monolithic honeycomb structure is 1 μm, and the desirable upper limit is 100 μm. If it is less than 1 μm, the particulates may easily clog. On the other hand, if it exceeds 100 μm, the particulates pass through the pores, and the particulates cannot be collected and may not function as a filter.

The integrated honeycomb structure shown in FIG. 1 has a substantially quadrangular prism shape, but the shape of the integrated honeycomb structure of the present invention is not particularly limited as long as it is a columnar body. For example, the shape of a cross section perpendicular to the longitudinal direction Can be mentioned columnar bodies made of polygons, circles, ellipses, sectors and the like.

In the integrated honeycomb structure of the present invention, the through-hole has a relatively large cross-sectional area perpendicular to the longitudinal direction, and is sealed at the end portion on the inlet side of the integrated honeycomb structure of the present invention. Two types of through-holes, ie, a large-volume through-hole and a small-volume through-hole having a relatively small cross-sectional area and sealed at the end portion on the outlet side of the integrated honeycomb structure of the present invention It consists of holes.

When regenerating an exhaust gas purification filter that has collected particulates and has increased pressure loss, the particulates are burned, but in addition to carbon that burns and disappears, the particulates also burn. Thus, oxides and other metals are contained, and these remain as ash in the exhaust gas purification filter. Since ash usually remains near the outlet of the exhaust gas purification filter, the through holes constituting the exhaust gas purification filter are filled with ash from the vicinity of the outlet, and the portion filled with ash The volume (area) of the portion that functions as the exhaust gas purifying filter gradually decreases. And if the amount of accumulated ash becomes too large, it will no longer function as a filter, and it will be removed from the exhaust pipe and backwashed to remove the ash from the exhaust gas purification filter, or the exhaust gas purification filter will be discarded. Become.

The integrated honeycomb structure of the present invention has a volume of a portion that functions as an exhaust gas purifying filter even if ash is accumulated (compared with the same volume of the inlet side through hole and the outlet side through hole) ( (Area) has a small reduction ratio, and pressure loss due to ash is also small. In addition, when particulates burn and ash is generated, particulates are likely to burn on the catalyst in the partition wall A, so the ash is likely to be deposited on the partition wall A. However, since the partition wall A is a partition wall that is unlikely to cause an increase in pressure loss, the increase in pressure loss due to ash deposition hardly occurs.
Further, the ash deposited on the partition wall A also serves to prevent a temperature drop on the partition wall A and secure a heat supply function. On the other hand, the ash generated by the burning of the particulates due to the heat supplied from the partition wall A in the partition wall B is easy to peel off due to the small amount of catalyst adhering to the surface of the partition wall B. It is easy to scatter and accumulate, and an increase in pressure loss due to the partition wall B is suppressed.
As described above, in the integral honeycomb structure of the present invention, the period until the reverse cleaning or the like is required is extended, and the life as the exhaust gas purifying filter can be extended. As a result, maintenance costs required for backwashing and replacement can be greatly reduced.

In recent years, in a honeycomb structure carrying a catalyst, a phenomenon in which ash is deposited on the coat layer of the catalyst has been reported. Even in such an ash accumulation state, in the integrated honeycomb structure of the present invention, the ash is originally supported on the partition walls in which the pressure loss is unlikely to increase, so that an increase in the pressure loss due to the ash accumulation is suppressed. be able to.

In the monolithic honeycomb structure of the present invention having the configuration shown in FIG. 1, the cross-sectional shape perpendicular to the longitudinal direction of the large volume through hole and / or the small volume through hole is preferably a polygon. By making it polygonal, it is possible to achieve a long-life honeycomb structure with excellent durability even when the partition area in the cross section perpendicular to the longitudinal direction of the honeycomb structure is reduced to increase the aperture ratio. Because it can. Among them, a polygon having a quadrangular shape or more is more preferable, and at least one of the corners is more preferably an obtuse angle. It is because the pressure loss resulting from the friction at the time of gas passing through a through-hole can be reduced. In addition, the shape of the cross-section only for the large-volume through hole may be a polygon such as a quadrangle, pentagon, trapezoid, octagon, etc. The shape of the cross-section only for the small-volume through-hole may be a polygon, and both are polygons It is good. In particular, it is desirable that the cross-sectional shape perpendicular to the longitudinal direction of the large-volume through hole is an octagon, and the cross-sectional shape of the small-volume through hole is a quadrangle.

In the integrated honeycomb structure of the present invention, the ratio of the total area in the cross section perpendicular to the longitudinal direction of the large volume through hole and the total area in the cross section of the small volume through hole (total cross section area of the large volume through hole / The desirable lower limit of the total cross-sectional area of the small volume through-hole; hereinafter referred to as the aperture ratio is 1.5, and the desirable upper limit is 2.7. If the area ratio is less than 1.5, the effect of providing a large volume through hole and a small volume through hole may not be obtained. On the other hand, when the area ratio exceeds 2.7, the volume of the small-volume through hole is too small, and thus the pressure loss before the particulate collection may become too large.

In the integrated honeycomb structure of the present invention, it is desirable that the vicinity of the corner of the cross section perpendicular to the longitudinal direction of the large volume through hole and / or the small volume through hole is constituted by a curve. By making it a curve, it is possible to prevent stress from concentrating on the corners of the through hole, prevent the generation of cracks, and reduce pressure loss caused by friction when passing through the through hole. be able to.

In the integrated honeycomb structure of the present invention, it is desirable that the distance between the centroids in the cross section perpendicular to the longitudinal direction of the adjacent large-volume through holes is equal to the distance between the centroids in the cross-section of the adjacent small-volume through holes. As a result, the heat is evenly diffused during regeneration, so that the temperature distribution is likely to be uniform, and a honeycomb structure having excellent durability in which cracks and the like due to thermal stress are unlikely to occur even after repeated use over a long period of time. .
In the present invention, “the distance between the centroids of the cross-sections perpendicular to the longitudinal direction of adjacent large-volume through holes” refers to the centroid of the cross-section perpendicular to the longitudinal direction of one large-volume through hole and the other large-volume through-holes. It means the minimum distance from the center of gravity in the cross section of the hole, while the “distance between the centers of gravity of the cross sections of adjacent small volume through holes” is a cross section perpendicular to the longitudinal direction of one small volume through hole. Means the minimum distance between the center of gravity and the center of gravity of the other small-volume through hole in the cross section.

In the integrated honeycomb structure 10 shown in FIG. 1, the large-volume through-holes 21a and the small-volume through-holes 21b are alternately arranged in the vertical direction and the horizontal direction across the partition wall 23. The center of gravity of the cross section perpendicular to the longitudinal direction of the large volume through hole 21a and the center of gravity of the cross section perpendicular to the longitudinal direction of the small volume through hole 21b are in a straight line.
Therefore, the “distance between centroids in the cross section perpendicular to the longitudinal direction of the adjacent large-volume through-holes” and “distance between centroids in the cross-section of the adjacent small-volume through-holes” are the longitudinal direction of the integrated honeycomb structure 10. The distance between the centers of gravity of the large-volume through-holes 21a and the small-volume through-holes 21b that are obliquely adjacent to each other in a cross section perpendicular to the vertical axis.

In the integrated honeycomb structure of the present invention, the numbers of the large volume through holes and the small volume through holes are not particularly limited, but are desirably substantially the same. With such a configuration, it is possible to minimize the partition wall that is not easily involved in exhaust gas filtration, and is caused by friction when passing through the inlet side through hole and / or friction when passing through the outlet side through hole. It is possible to suppress the pressure loss to increase more than necessary. For example, when compared with the honeycomb structure 100 in which the number of through holes as shown in FIG. 2 is substantially 1: 2 between the large volume through holes 101 and the small volume through holes 102, the number of through holes is substantially equal. In the case of the same number, the pressure loss due to friction when passing through the outlet side through hole is low, so the pressure loss of the entire honeycomb structure is low.

Next, a specific example of the configuration of the large volume through hole and the small volume through hole in a cross section perpendicular to the longitudinal direction of the integral honeycomb structure of the present invention will be described.
FIGS. 3A to 3D and FIGS. 4A to 4F are cross-sectional views schematically showing a cross section perpendicular to the longitudinal direction in the integral honeycomb structure of the present invention. e) is a cross-sectional view schematically showing a cross section perpendicular to the longitudinal direction in a conventional integrated honeycomb structure.

The integrated honeycomb structure 110 shown in FIG. 3A has an aperture ratio of approximately 1.55, and the integrated honeycomb structure 120 shown in FIG. 3B has approximately 2.54, FIG. The integrated honeycomb structure 130 shown in c) is approximately 4.45, and the integrated honeycomb structure 140 shown in FIG. 3D is approximately 6.00. 4 (a), (c), and (e) all have an aperture ratio of about 4.45, and FIGS. 4 (b), (d), and (f) all have about 6.00. It is.
Note that, as in the integrated honeycomb structure 140 shown in FIG. 3D, if the ratio of the aperture ratio is large, the volume of the small-volume through-hole 141b is too small, and the initial pressure loss may be too large. is there.

In the integrated honeycomb structures 110, 120, 130, and 140 shown in FIGS. 3A to 3D, the convex portions 114, 124, 134, and 144 are formed on the partition walls that separate the large-volume through holes 111a, 121a, 131a, and 141a. The cross-sectional shape excluding the convex portions 114, 124, 134, 144 of the large-volume through holes 111a, 121a, 131a, 141a is an octagon, and the small-volume through holes 111b, 121b, 131b, 141b The cross-sectional shape is a quadrangle, and large-volume through holes 111a, 121a, 131a, 141a and small-volume through holes 111b, 121b, 131b, 141b are alternately arranged. In addition, in the integrated honeycomb structure shown in FIGS. 3A to 3D, the opening ratio is changed by changing the cross-sectional area of the small-volume through hole and slightly changing the cross-sectional shape of the large-volume through hole. It can be easily changed arbitrarily. Similarly, the aperture ratio of the integrated honeycomb structure shown in FIG. 4 can be arbitrarily changed. Further, as shown in FIGS. 3A to 3D, it is desirable that the corners on the outer periphery of the integrated honeycomb structure of the present invention be chamfered.
In the integrated honeycomb structure 150 shown in FIG. 3E, the cross-sectional shapes of the inlet-side through holes 152a and the outlet-side through holes 152b are both quadrangles, and they are alternately arranged.

In the integral honeycomb structures 160 and 260 shown in FIGS. 4A to 4B, the partition walls separating the large volume through holes 161a and 261a are provided with convex portions 164 and 264, and the large volume through holes 161a, The cross-sectional shape excluding the convex portions 164 and 264 of 261a is a pentagon, and three corners thereof are substantially perpendicular, and the cross-sectional shapes of the small-volume through-holes 161b and 261b are quadrangular, each having a large square shape. It is comprised so that the part which diagonally faces may be occupied. In the integrated honeycomb structures 170 and 270 shown in FIGS. 4C to 4D, convex portions 174 and 274 are provided on the partition walls that separate the large-volume through holes 171a and 271a. The cross-sectional shapes of the integrated honeycomb structures 170 and 270 shown in FIGS. 4C to 4D are obtained by modifying the cross-sectional shapes shown in FIGS. The partition walls shared by the volume through-holes 171a and 271a and the small volume through-holes 171b and 271b are widened with a curvature on the small volume through-hole side. This curvature may be arbitrary, for example, the curve which comprises a partition may correspond to 1/4 circle. In this case, the aperture ratio is 3.66. Therefore, in the integrated honeycomb structures 170 and 270 shown in FIGS. 4C to 4D, the small volume through-holes 171 b and 271 b described above are more than those in which the curves constituting the partition walls correspond to ¼ circle. The cross-sectional area is small. In the integrated honeycomb structures 180 and 280 shown in FIGS. 4E to 4F, convex portions 184 and 284 are provided on the partition walls separating the large-volume through-holes 181a and 281a, and the large-volume through-holes 181a and 281a, The cross-sectional shape excluding the convex portions 184 and 284 of 281a and the cross-sectional shape of the small-volume through holes 281b and 281b are quadrangular (rectangular), and two large-volume through holes and two small-volume through-holes are combined. And it is comprised so that it may become a substantially square.

As another specific example of the configuration of the large volume through-holes and the small volume through-holes in the cross section perpendicular to the longitudinal direction of the integral honeycomb structure of the present invention, for example, the large size in the integral honeycomb structure 190 shown in FIG. The structure etc. which provided the volume through-hole 191a, the small volume through-hole 191b, and the convex part 194 can be mentioned.

Although the single unitary honeycomb structure of the present invention may be used as a single unit filter, it is desirable that a plurality of unitary honeycomb structures are bound together via a sealing material layer and used as an aggregate type filter. By using the aggregate filter, the thermal stress is reduced by the sealing material layer to improve the heat resistance of the filter, and the size can be freely increased by increasing or decreasing the number of integral honeycomb structures of the present invention. This is because it is possible to adjust the thickness.
The integral filter and the aggregate filter have the same function.

In the integrated filter comprising the integrated honeycomb structure of the present invention, an oxide ceramic such as cordierite is usually used as the material. This is because the filter can be manufactured at a low cost and has a relatively small coefficient of thermal expansion, so that the filter is less likely to be damaged by thermal stress during manufacture and use.

Although not shown in FIG. 1, in the integral filter comprising the integral honeycomb structure of the present invention, the integral honeycomb structure of the present invention is formed on the outer peripheral surface as in the aggregated honeycomb structure of the present invention described below. It is desirable that a sealing material layer made of a material that hardly allows gas to pass through than the structure is formed. By forming the sealing material layer on the outer peripheral surface, the integral honeycomb structure of the present invention can be compressed by the sealing material layer, and the strength is improved and the ceramic particles are prevented from degranulating due to the occurrence of cracks. can do.

The aggregated honeycomb structure of the present invention has a gas that is more gas than the integrated honeycomb structure of the present invention on the outer peripheral surface of a honeycomb block in which a plurality of the integrated honeycomb structures of the present invention are combined through a sealing material layer. A sealing material layer made of a material that is difficult to pass through is formed, and functions as an aggregate filter.

FIG. 6 is a perspective view schematically showing an example of the aggregated honeycomb structure of the present invention.
As shown in FIG. 6, the aggregated honeycomb structure 10 is used as an exhaust gas purifying filter, and a plurality of integrated honeycomb structures 20 are bundled through a sealing material layer 14 to form a honeycomb block 15. The sealing material layer 13 for preventing leakage of exhaust gas is formed around the honeycomb block 15. Note that the sealing material layer 13 is made of a material that is less likely to allow gas to pass than the integrated honeycomb structure 20.

In the aggregated honeycomb structure 10, silicon carbide having excellent thermal conductivity, heat resistance, mechanical characteristics, chemical resistance, and the like is desirable as a material constituting the integrated honeycomb structure 20.

In the aggregated honeycomb structure 10, the sealing material layer 14 is formed between the integrated ceramic structures 20, and preferably functions as an adhesive that binds the plurality of integrated ceramic structures 20 together. . On the other hand, the sealing material layer 13 is formed on the outer peripheral surface of the honeycomb block 15, and when the aggregated honeycomb structure 10 is installed in the exhaust passage of the internal combustion engine, the exhaust gas passing through the through hole from the outer peripheral surface of the honeycomb block 15 is formed. It functions as a sealing material for preventing leakage.
In the aggregated honeycomb structure 10, the sealing material layer 13 and the sealing material layer 14 may be made of the same material or different materials. Furthermore, when the sealing material layer 13 and the sealing material layer 14 are made of the same material, the blending ratio of the materials may be the same or different.

However, the sealing material layer 14 may be made of a dense body, or may be made of a porous body so that exhaust gas can flow into the inside thereof, but the sealing material layer 13 Is preferably a dense body. This is because the sealing material layer 13 is formed for the purpose of preventing the exhaust gas from leaking from the outer peripheral surface of the honeycomb block 15 when the aggregated honeycomb structure 10 is installed in the exhaust passage of the internal combustion engine.

It does not specifically limit as a material which comprises the sealing material layer 13 and the sealing material layer 14, For example, what consists of an inorganic binder, an organic binder, an inorganic fiber, and / or an inorganic particle etc. can be mentioned.

Examples of the inorganic binder include silica sol and alumina sol. These may be used alone or in combination of two or more. Among the inorganic binders, silica sol is desirable.

Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. These may be used alone or in combination of two or more. Among the organic binders, carboxymethyl cellulose is desirable.

Examples of the inorganic fiber include ceramic fibers such as silica-alumina, mullite, alumina, and silica. These may be used alone or in combination of two or more. Among the inorganic fibers, silica-alumina fibers are desirable.

Examples of the inorganic particles include carbides and nitrides, and specific examples include inorganic powders or whiskers made of silicon carbide, silicon nitride, boron nitride, or the like. These may be used alone or in combination of two or more. Of the inorganic particles, silicon carbide having excellent thermal conductivity is desirable.

As described above, when the integrated honeycomb structure of the present invention is used as it is as an exhaust gas purification filter, the same sealing material layer as that of the aggregated honeycomb structure of the present invention is used. It may be provided on the outer peripheral surface of the body.

The aggregate-type honeycomb structure 10 shown in FIG. 6 has a columnar shape, but the shape of the aggregate-type honeycomb structure of the present invention is not particularly limited as long as it is a columnar body, and for example, a cross section perpendicular to the longitudinal direction A columnar body whose shape is a polygon, an ellipse or the like can be mentioned.
The aggregated honeycomb structure of the present invention is formed by binding a plurality of the integral honeycomb structures of the present invention, and then forming an outer peripheral portion so that the cross-sectional shape perpendicular to the longitudinal direction is a polygon, a circle, an ellipse, or the like. The cross-sectional shape perpendicular to the longitudinal direction may be polygonal, circular, or elliptical by processing the cross-sectional shape of the integral honeycomb structure of the present invention in advance and binding them with an adhesive. For example, the column-shaped aggregate-type honeycomb of the present invention may be formed by bundling four columnar integral honeycomb structures of the present invention having a sector shape in which a cross-section perpendicular to the longitudinal direction is divided into four circles. A structure can be manufactured.

Next, an example of a method for manufacturing the above-described honeycomb structure of the present invention will be described.
When the honeycomb structure of the present invention is an integral filter composed entirely of a single sintered body, first, extrusion molding is performed using a raw material paste mainly composed of ceramic as described above, A selective catalyst supporting portion is formed, and a ceramic molded body having substantially the same shape as the integral honeycomb structure of the present invention is manufactured. In addition, the shape of the selective catalyst support can be adjusted by changing the shape of the opening of the die used for the extrusion molding.

The raw material paste is not particularly limited, but it is desirable that the porosity of the integrated honeycomb structure of the present invention after manufacture is 20 to 80%. For example, a binder and a dispersion in a powder made of ceramic as described above. The thing which added the liquid medium etc. can be mentioned.

The binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, polyethylene glycol, phenol resin, and epoxy resin.
In general, the amount of the binder is desirably about 1 to 10 parts by weight with respect to 100 parts by weight of the ceramic powder.

The dispersion medium liquid is not particularly limited, and examples thereof include organic solvents such as benzene, alcohols such as methanol, and water.
An appropriate amount of the dispersion medium liquid is blended so that the viscosity of the raw material paste falls within a certain range.

These ceramic powder, binder and dispersion medium liquid are mixed with an attritor or the like, sufficiently kneaded with a kneader or the like, and then extruded.

Moreover, you may add a shaping | molding adjuvant to the said raw material paste as needed.
The molding aid is not particularly limited, and examples thereof include ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like.

Furthermore, a pore-forming agent such as balloons that are fine hollow spheres containing oxide ceramics, spherical acrylic particles, and graphite may be added to the raw material paste as necessary.
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. Among these, a fly ash balloon is desirable.

Next, the ceramic molded body is dried using a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, a freeze dryer, or the like to obtain a ceramic dried body. Next, a predetermined amount of a sealing material paste serving as a sealing material is filled into the end portion on the outlet side of the large-volume through hole and the end portion on the inlet side of the small-volume through hole, and the through holes are sealed.

Although it does not specifically limit as said sealing material paste, The thing from which the porosity of the sealing material manufactured through a post process becomes 20 to 80% is desirable, For example, the thing similar to the said raw material paste can be used. However, it is more desirable to add a lubricant, a solvent, a dispersant, a binder and the like to the ceramic powder used in the raw material paste. This is because it is possible to prevent the ceramic particles and the like in the sealing material paste from being settled during the sealing process.

Next, the ceramic dry body filled with the sealing material paste is degreased and fired under predetermined conditions.
Conventionally used conditions for producing a filter made of porous ceramics can be applied to the degreasing and firing conditions of the ceramic dried body.

Next, an alumina film having a high specific surface area is formed on the surface of the ceramic fired body obtained by firing, and a catalyst such as platinum is applied to the surface of the alumina film, whereby the catalyst is supported on the surface. An integral honeycomb structure of the present invention, which is made of ceramic and is entirely composed of one sintered body, can be manufactured.

As a method of forming an alumina film on the surface of the ceramic fired body, for example, a method in which a ceramic fired body is impregnated with a solution of a metal compound containing aluminum such as Al (NO ₃ ) ₃ and heated, γ-alumina is used. Examples include a method in which a ceramic fired body is impregnated with a slurry solution containing pulverized γ-alumina powder having a high surface area and heated.
Examples of the method for imparting a promoter or the like to the alumina film include a method in which a ceramic fired body is impregnated with a solution of a metal compound containing a rare earth element such as Ce (NO ₃ ) ₃ and heated. it can.
Examples of a method for imparting a catalyst to the alumina membrane include a method in which a ceramic fired body is impregnated with a dinitrodiammine platinum nitrate solution ([Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ] HNO ₃ ) and heated. Can be mentioned.

In addition, the honeycomb structure of the present invention is an aggregate type honeycomb structure 10 in which a plurality of integrated honeycomb structures 20 of the present invention are bundled through a sealing material layer 14 as shown in FIG. In some cases, the process of applying the adhesive paste to be the sealing material layer 14 with a uniform thickness and sequentially stacking the other integrated honeycomb structure 20 to which the adhesive paste has been applied is repeated to a predetermined size. A laminated body of the prismatic integrated honeycomb structure 20 is produced.
In addition, since it has already demonstrated as a material which comprises the said adhesive paste, the description is abbreviate | omitted here.

Next, the laminated body of the integrated honeycomb structure 20 is heated to dry and solidify the adhesive paste layer to form the sealing material layer 14, and then the outer peripheral portion is shown in FIG. 6 using a diamond cutter or the like. The honeycomb block 15 is manufactured by cutting into a shape like this.
Then, by forming the sealing material layer 13 on the outer periphery of the honeycomb block 15 using the above-mentioned adhesive paste, a plurality of the integrated honeycomb structures 20 are bound through the sealing material layer 14. The aggregate filter 10 can be manufactured.
When manufacturing the aggregate filter 10 of the present invention, the formation of the alumina film, the application of the catalyst, etc. may not be performed after the ceramic fired body is manufactured, but may be performed after the honeycomb block 15 is manufactured.

The application of the honeycomb structure of the present invention is not particularly limited, but it is desirable to use it for an exhaust gas purification device of a vehicle.
FIG. 7 is a cross-sectional view schematically showing an example of an exhaust gas purifying device for a vehicle in which the honeycomb structure of the present invention is installed.

As shown in FIG. 7, the exhaust gas purification apparatus 600 mainly includes a honeycomb structure 60, a casing 630 that covers the outside of the honeycomb structure 60, and a holding member that is disposed between the honeycomb structure 60 and the casing 630. It is composed of a sealing material 620 and heating means 610 provided on the exhaust gas inflow side of the honeycomb structure 60, and an end of the casing 630 on the side where the exhaust gas is introduced is connected to an internal combustion engine such as an engine. A connected introduction pipe 640 is connected, and a discharge pipe 650 connected to the outside is connected to the other end of the casing 630. In FIG. 7, arrows indicate the flow of exhaust gas.
In FIG. 7, the honeycomb structure 60 may be the integrated honeycomb structure 20 shown in FIG. 1 or the aggregated honeycomb structure 10 shown in FIG. 6.

In the exhaust gas purifying apparatus 600 having such a configuration, exhaust gas discharged from an internal combustion engine such as an engine is introduced into the casing 630 through the introduction pipe 640, and is passed through the large volume through hole 21a into the honeycomb structure 60. Then, after passing through the partition wall 23, the particulates are collected and purified by the partition wall 23, and then discharged from the small volume through hole 21 b to the outside of the honeycomb structure 60 and to the outside through the discharge pipe 650. Will be discharged.

Further, in the exhaust gas purification apparatus 600, when a large amount of particulates accumulates on the partition walls of the honeycomb structure 60 and the pressure loss increases, the regeneration process of the honeycomb structure 60 is performed.
In the regeneration process, the gas heated using the heating means 610 is caused to flow into the through holes of the honeycomb structure 60, whereby the honeycomb structure 60 is heated and the particulates deposited on the partition walls are removed by combustion. Further, the particulates may be burned and removed using a post-injection method. In addition, a filter provided with an oxidation catalyst may be provided in a portion of the introduction pipe 640 in front of the casing 630, and a filter provided with an oxidation catalyst on the exhaust gas inflow side from the heating means 610 inside the casing 630. May be installed.

Hereinafter, the present invention will be described in more detail with reference to the drawings with reference to examples. However, the present invention is not limited to these examples.

(Example 1)
(1) Wet-mixing α-type silicon carbide powder 60% by weight with an average particle size of 10 μm and 40% by weight β-type silicon carbide powder with an average particle size of 0.5 μm, and with respect to 100 parts by weight of the resulting mixture, 5 parts by weight of an organic binder (methylcellulose) and 10 parts by weight of water were added and kneaded to obtain a mixed composition. Next, after adding a small amount of a plasticizer and a lubricant to the mixed composition and further kneading, extrusion molding is performed, and the opening on the inlet side has a cross-sectional shape substantially the same as the cross-sectional shape shown in FIG. A shaped product having a rate of 37.97% and an aperture ratio of 1.55 was produced. In addition, the thickness of the partition that separates the adjacent large-volume through-holes from the small-volume through-hole is 0.3 mm, the thickness of the partition that separates the adjacent large-volume through-holes is 0.6 mm, and the adjacent large-volume through-holes The height of the projections provided on the partition walls separating each other was set to 0.1 mm.

Next, the generated shaped body was dried using a microwave dryer or the like to form a ceramic dried body, and then a predetermined through-hole was filled with a sealing material paste having the same composition as the generated shaped body.
Next, after drying again using a dryer, degreasing at 400 ° C., and firing at 2200 ° C. for 3 hours under an atmospheric pressure of argon atmosphere, the porosity is 42%, the average pore diameter is 9 μm, The size is 34.3 mm × 34.3 mm × 150 mm, the number of through holes is 28 / cm ² (large volume through holes: 14 / cm ² , small volume through holes: 14 / cm ² ), silicon carbide An integrated honeycomb structure made of a sintered body was produced.
In the integrated honeycomb structure, only the large-volume through holes were sealed with a sealing material on the end face on the outlet side, and only the small-volume through holes were sealed on the end face on the inlet side with the sealing material.

(2) Next, a collective honeycomb structure was manufactured using the obtained integral honeycomb structure.
Heat resistance comprising 30% by weight of alumina fiber having a fiber length of 0.2 mm, 21% by weight of silicon carbide particles having an average particle diameter of 0.6 μm, 15% by weight of silica sol, 5.6% by weight of carboxymethylcellulose, and 28.4% by weight of water A cylindrical honeycomb block having a diameter of 144 mm and a length of 150 mm was manufactured by binding a large number of the integrated honeycomb structure 20 using a conductive sealing material paste and then cutting the honeycomb structure 20 using a diamond cutter.
At this time, the thickness of the sealing material layer 14 for binding the integral honeycomb structure 20 was adjusted to 1.0 mm.

(3) Next, ceramic fibers made of alumina silicate as inorganic fibers (shot content: 3%, fiber length: 0.1 to 100 mm) 23.3% by weight, silicon carbide having an average particle diameter of 0.3 μm as inorganic particles Mixing and kneading 30.2% by weight of powder, 7% by weight of silica sol (content of SiO _{2 in} the sol: 30% by weight) as inorganic binder, 0.5% by weight of carboxymethyl cellulose and 39% by weight of water as organic binder Thus, a sealing material paste was prepared.

Next, a sealing material paste layer having a thickness of 1.0 mm was formed on the outer peripheral surface of the honeycomb block using the sealing material paste. Then, this sealing material paste layer was dried at 120 ° C. to produce an aggregated honeycomb structure that has a cylindrical shape and functions as an exhaust gas purifying honeycomb filter.

(4) Next, γ-alumina is mixed with water and a nitric acid solution that is a dispersant, and further ground by a ball mill at 90 min ⁻¹ for 24 hours to prepare an alumina slurry having a particle size of 2 μm. The resulting slurry was poured into an integral honeycomb structure and an aggregated honeycomb structure and dried at 200 ° C.
The above process was repeated until the alumina layer reached an amount of 60 g / L and baked at 600 ° C.

Ce (NO ₃ ) ₃ was put into ethylene glycol and stirred at 90 ° C. for 5 hours to prepare an ethylene glycol solution containing 6% by weight of Ce (NO ₃ ) ₃ . The integral honeycomb structure and the aggregated honeycomb structure in which the alumina layer is formed in this ethylene glycol solution are immersed, and then heated at 150 ° C. for 2 hours and at 650 ° C. in a nitrogen atmosphere for 2 hours to fire the ceramic A rare earth oxide-containing alumina layer for supporting the catalyst on the surface of the body was formed.

The above-mentioned ceramic firing in which dinitrodiammine platinum nitric acid ([Pt (NH ₃ ) ₂ (NO ₂ ) ₂ ] HNO ₃ ) having a platinum concentration of 4.53 wt% is diluted with distilled water to form the rare earth oxide-containing alumina layer. After the body was immersed, it was heated at 110 ° C. for 2 hours and at 500 ° C. for 1 hour in a nitrogen atmosphere to support 2 g / L of a platinum catalyst having an average particle diameter of 2 nm on the surface of the ceramic fired body, thereby supporting the catalyst. The production of the integrated honeycomb structure and the aggregated honeycomb structure was completed.

(Examples 2 to 28)
As shown in Table 1, except that the cross-sectional shape perpendicular to the longitudinal direction and the height and width of the protrusions provided on the partition walls separating adjacent large-volume through holes were changed, the same as in Example 1. An integral honeycomb structure and a collective honeycomb structure were manufactured.
Note that the cross-sectional shape perpendicular to the longitudinal direction of the integral honeycomb structure and the height of the protrusions provided on the partition walls separating adjacent large-volume through-holes are the same as those of the die when the mixed composition is extruded. Adjustment was made by changing the shape.

(Reference Examples 1-4)
The cross-sectional shape perpendicular to the longitudinal direction was changed to the shape shown in Table 1, and a recess having a depth of 0.1 mm as shown in FIG. Otherwise, the integrated honeycomb structure and the aggregated honeycomb structure were manufactured in the same manner as in Example 1.
Note that the cross-sectional shape perpendicular to the longitudinal direction of the integral honeycomb structure and the depth of the recesses provided in the partition walls separating adjacent large-volume through-holes are the shape of the die when the mixed composition is extruded. Adjusted by changing.

(Reference Examples 5-8)
As shown in Table 1, except that the cross-sectional shape perpendicular to the longitudinal direction, the height of the convex portions provided on the partition walls separating adjacent large-volume through holes, and the amount of the alumina coat layer were changed. The monolithic honeycomb structure and the aggregated honeycomb structure were manufactured in the same manner as in Example 1.
Note that the cross-sectional shape perpendicular to the longitudinal direction of the integral honeycomb structure and the height of the protrusions provided on the partition walls separating adjacent large-volume through-holes are the same as those of the die when the mixed composition is extruded. Adjustment was made by changing the shape.

(Comparative Examples 1-7)
As shown in Table 1, the embodiment is the same as the embodiment except that the partition wall separating adjacent large-volume through-holes is not provided with a convex portion or a concave portion, and the cross-sectional shape perpendicular to the longitudinal direction of the integrated honeycomb structure is changed. The monolithic honeycomb structure and the aggregated honeycomb structure were manufactured in the same manner as in Example 1.
Note that the cross-sectional shape perpendicular to the longitudinal direction of the integral honeycomb structure and the height of the protrusions provided on the partition walls separating adjacent large-volume through-holes are the same as those of the die when the mixed composition is extruded. Adjustment was made by changing the shape.

(Evaluation 1: Pressure loss)
As shown in FIG. 7, the aggregated honeycomb structure according to each of the examples, reference examples, and comparative examples is disposed in the exhaust passage of the engine to form an exhaust gas purification device, and the engine has a rotational speed of 3000 min ⁻¹ , torque Operating at 50 N · m, 8 g / L of particulate was collected in the aggregated honeycomb structure, and then the pressure loss of the aggregated honeycomb structure was measured. The results are shown in Table 2.

(Evaluation 2; CO-Light off temperature, HC-Light off temperature)
The integrated honeycomb structure according to each example, reference example and comparative example is installed in a reaction tester, and the component concentration of the simulated gas is C ₃ H ₆ (200 ppm), CO (300 ppm), NO _X (160 ppm), It is assumed to contain SO _X (8 ppm), CO ₂ (0.038%), H ₂ O (10%), O ₂ (13%), and the simulated gas of the above components is kept at a space velocity (SV) of 45000 / h. It is introduced into the body-type honeycomb structure, the simulated gas temperature is gradually increased, the gas concentration before and after entering the honeycomb structure is analyzed, and the temperature at which the purification rate of CO and HC becomes 50% is set to the CO-Light off temperature, respectively. HC-Light off temperature. The results are shown in Table 2.

(Evaluation 3: Filter regeneration test)
As shown in FIG. 7, the aggregated honeycomb structure according to each of the examples, the reference examples, and the comparative example is disposed in the exhaust passage of the engine to form an exhaust gas purification device, and the engine is operated to collect the honeycomb Particulate was collected at 7 g / L in the structure. Next, the aggregated honeycomb structure in which the particulates are collected is placed in a reaction tester, and the aggregated honeycomb structure is introduced while introducing nitrogen gas into the aggregated honeycomb structure at a flow rate of 130 L / min. Maintained at 200 ° C.
Next, a simulated gas having almost the same composition as the exhaust gas of a diesel engine except that it does not contain particulates is introduced into the aggregated honeycomb structure at a temperature of 650 ° C., a pressure of 8 kPa, and a time of 7 minutes, The particulate was burned. At this time, a catalyst carrier having a honeycomb structure made of commercially available cordierite (diameter: 144 mm, length: 100 mm, cell density: 400 cells / inch, platinum: 5 g / L) on the simulated gas inflow side from the aggregated honeycomb structure. The simulated gas that passed through the honeycomb structure carrier was introduced into the aggregated honeycomb structure.
Finally, the weight of the aggregated honeycomb structure was measured to determine the ratio of the burned particulates (filter regeneration rate) out of the particulates collected at 7 g / L, and the particulate purification performance was evaluated. The results are shown in Table 2.
The simulated gas contains 6540 ppm of C ₃ H ₆ , 5000 ppm of CO, 160 ppm of NOx, 8 ppm of SOx, 0.038% of CO ₂ , 10% of H ₂ O, and 10% of O _2. did. The aggregated honeycomb structure was heated to about 600 ° C. by introducing the simulated gas.

As shown in Tables 1 and 2, the aggregated honeycomb structures according to the respective examples in which convex portions or concave portions that are selective catalyst supporting portions are provided on the partition walls separating adjacent large-volume through holes are adjacent to each other. Compared to the aggregate type honeycomb structure according to the comparative example in which the partition walls separating the large volume through holes are not provided with a convex portion or a concave portion, the pressure loss is low even when a certain amount of particulates are collected, and the regeneration rate of the filter is also high. It has increased.
In addition, the integrated honeycomb structure according to each example in which the convex portions or the concave portions that are selective catalyst supporting portions are provided in the partition walls that separate the adjacent large-volume through-holes is formed in the partition walls that separate the adjacent large-volume through-holes. The CO-Light off temperature and the HC-Light off temperature are slightly lower than those of the integrated honeycomb structure according to the comparative example in which no convex portion or concave portion is provided.

(A) is the perspective view which showed typically an example of the integral honeycomb structure of this invention, (b) is the AA line of the integral honeycomb structure of this invention shown to (a). It is sectional drawing. FIG. 3 is a cross-sectional view schematically showing a cross section perpendicular to the longitudinal direction of a honeycomb structure configured such that the number of through holes is substantially 1: 2 between the large volume through holes 101 and the small volume through holes 102; is there. (A)-(d) is sectional drawing which showed typically the cross section perpendicular | vertical to the longitudinal direction in the integrated honeycomb structure of this invention, (e) is the longitudinal direction in the conventional integrated honeycomb structure. FIG. (A)-(f) is sectional drawing which showed typically a part of cross section perpendicular | vertical to the longitudinal direction in the integral-type honeycomb structure of this invention. FIG. 3 is a cross-sectional view schematically showing an example of a cross section perpendicular to the longitudinal direction in the integral honeycomb structure of the present invention. 1 is a perspective view schematically showing an example of an aggregated honeycomb structure of the present invention. 1 is a cross-sectional view schematically showing an example of an exhaust gas purifying device for a vehicle in which a honeycomb structure of the present invention is installed.

Explanation of symbols

10 Aggregate Type Honeycomb Structures 13 and 14 Sealing Material Layer 15 Honeycomb Block 20 Integrated Honeycomb Structure 21 Through Hole 21a Large Volume Through Hole 21b Small Volume Through Hole 22 Sealing Material 23 Partition Wall 23a Adjacent Large Volume Through Hole 21a and Small Partition wall 23b separating volume through hole 21b Adjacent partition wall 24 separating large volume through hole 21a

Claims (13)

A columnar honeycomb structure in which a large number of through holes are arranged in parallel in the longitudinal direction across a partition wall,
The large number of through holes have a large volume through hole group sealed at one end so that the total area in the cross section perpendicular to the longitudinal direction is relatively large, and the total area in the cross section is relatively It consists of a small volume through-hole group sealed at the other end so as to become smaller,
A honeycomb structure having a selective catalyst supporting portion for selectively supporting a catalyst on the partition wall constituting the large-volume through-hole group and separating adjacent through-holes . The honeycomb structure according to claim 1, wherein a catalyst is supported on at least the selective catalyst support. The honeycomb structure according to claim 1 or 2, wherein the selective catalyst supporting part is a convex part and / or a concave part provided in a partition wall that separates through-holes constituting adjacent large-volume through-hole groups. The convex part provided in the selective catalyst support part has a height of 0.02 to 6 times the thickness of the partition wall separating the through holes constituting the adjacent large volume through hole group. The honeycomb structure according to any one of the above. The recessed part provided in the selective catalyst carrying | support part has a depth of 0.02-0.4 times the thickness of the partition which separates the through-holes which comprise adjacent large-volume through-hole groups. The honeycomb structure according to any one of the above. The shape of the cross section perpendicular | vertical to the longitudinal direction of the through-hole which comprises a large volume through-hole group and / or the through-hole which comprises a small volume through-hole group is a polygon. Honeycomb structure. The shape of the cross section perpendicular to the longitudinal direction of the through holes constituting the large volume through hole group is an octagon, and the shape of the cross section of the through holes constituting the small volume through hole group is a quadrangle. 8. The honeycomb structure according to any one of 7 above. The ratio of the total area in the cross section perpendicular to the longitudinal direction of the through holes constituting the large volume through hole group to the total area in the cross section of the through holes constituting the small volume through hole group is 1.5-2. The honeycomb structure according to any one of claims 1 to 7, which is 7. A partition that separates through-holes constituting adjacent large-volume through-hole groups in a cross section perpendicular to the longitudinal direction, and a through-hole that constitutes the adjacent large-volume through-hole groups and a through-hole that constitutes a small-volume through-hole group; The honeycomb structure according to any one of claims 1 to 8, wherein at least one of the intersecting angles with the partition walls is an obtuse angle. The vicinity of the corner | angular part of the cross section perpendicular | vertical to the longitudinal direction of the through-hole which comprises a large volume through-hole group and / or the through-hole which comprises a small volume through-hole group is comprised by the curve. 2. The honeycomb structure according to 1. The distance between the centroids in a cross section perpendicular to the longitudinal direction of the through-holes constituting the adjacent large-volume through-hole groups is equal to the distance between the centroids in the cross-section of the through-holes constituting the adjacent small-volume through-hole groups. To 10 honeycomb structures. A seal made of a material that prevents gas from passing through the outer peripheral surface of a honeycomb block in which a plurality of honeycomb structures according to any one of claims 1 to 11 are combined with a sealing material layer interposed therebetween. A honeycomb structure in which a material layer is formed. The honeycomb structure according to any one of claims 1 to 12, which is used in an exhaust gas purification device for a vehicle.

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