JP6436824B2 - Honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure used as a carrier for supporting a catalyst such as an SCR catalyst.

Automobile engines, construction machinery engines, industrial stationary engines, as a catalyst for purifying nitrogen oxides in an exhaust gas discharged from a combustion device such as a (NO _X), SCR catalyst mainly zeolite, vanadium, etc. Has been proposed. Note that “SCR” is an abbreviation for “Selective Catalytic Reduction: selective catalytic reduction”, and “SCR catalyst” means a catalyst (selective reduction catalyst) that selectively reduces a component to be purified by a reduction reaction. .

Usually, the SCR catalyst is used while being supported on a catalyst carrier. As a catalyst carrier for supporting an SCR catalyst, a honeycomb structure having a porous partition wall that forms a plurality of cells extending from an inflow end surface as one end surface to an outflow end surface as the other end surface is widely used. (For example, refer to Patent Document 1). When the SCR catalyst is supported on such a honeycomb structure, the exhaust gas flowing into the cell from the inflow end face of the honeycomb structure contacts the SCR catalyst until it flows out of the cell from the outflow end face of the honeycomb structure. NO _X in the exhaust gas is reduced to N ₂ .

JP 2013-53594 A

With the strengthening of the recent exhaust gas regulations, improving the purification rate of the NO _X by the SCR catalyst is an important technical problem. In order to improve the NO _x purification rate by the SCR catalyst, it is effective to increase the contact area between the exhaust gas and the SCR catalyst. However, in the honeycomb structure as a catalyst carrier, when the area of the partition wall supporting the SCR catalyst is increased, the overall size of the honeycomb structure becomes large due to the increase in the contact area. Become.

  The present invention has been made in view of such problems of the prior art. An object of the present invention is to provide a honeycomb structure in which when an exhaust gas purification catalyst is supported, the exhaust gas and the catalyst are easily in contact with each other, and high purification performance can be obtained without increasing the size. .

  According to the present invention, the following honeycomb structure is provided.

[1] A porous partition wall that partitions and forms a plurality of cells extending from an inflow end surface that is one end surface to an outflow end surface that is the other end surface, and the plurality of cells are in a cross section orthogonal to the cell extending direction. A plurality of divided cells provided with a dividing wall that divides the cell into two spaces (except that the dividing cell is closed), and a plurality of normal cells not provided with the dividing wall; (However, the normal cell is excluded) , the normal cell has a square shape in a cross section orthogonal to the cell extending direction, and the divided cell extends the cell. In the cross section orthogonal to the direction, the shape of the portion excluding the dividing wall is a square congruent with the shape of the normal cell, and each shape of the two spaces divided by the dividing wall The shape is a rectangle, and at least a part of the normal cells and at least a part of the divided cells are arranged adjacent to each other across the partition wall, and the number of the divided cells and the number of the normal cells The honeycomb structure in which the ratio of the number of the divided cells to the total number of the total is 30 to 80%.

[2] At least a part of the divided cells is a specific divided cell in which all of the four cells adjacent to the divided cell across the partition are the normal cells, and the number of the divided cells and the number of the normal cells The honeycomb structure according to [1], wherein the ratio of the number of the specific divided cells to the total number of the total number is 30 to 50%.

[3] In the cross section orthogonal to the cell extending direction, the cross section of each of the two spaces divided by the dividing wall is 35% or more of the cross section of the normal cell. 2].

[4] The honeycomb structure according to any one of [1] to [3], in which a catalyst for exhaust gas purification is supported.

[5] The honeycomb structure according to [4], wherein the catalyst is an SCR catalyst.

  In the honeycomb structure of the present invention, when exhaust gas is circulated, the exhaust gas easily diffuses in the cell. For this reason, when a catalyst for exhaust gas purification such as an SCR catalyst is supported on the honeycomb structure of the present invention, the exhaust gas and the catalyst are easily brought into contact, and the catalyst is effectively used. As a result, the honeycomb structure of the present invention can obtain high purification performance by the supported catalyst without increasing the size. Further, the honeycomb structure of the present invention exhibits high strength because the dividing wall of the dividing cell also functions as a reinforcing material.

1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. 1 is a partially enlarged sectional view schematically showing an embodiment of a honeycomb structure of the present invention. FIG. 5 is a partial enlarged cross-sectional view schematically showing another embodiment of the honeycomb structure of the present invention. Fig. 3 is a partially enlarged plan view schematically showing adjacent normal cells and divided cells, as viewed from one end surface side of the honeycomb structure. It is sectional drawing which shows typically the I-I 'cross section of FIG. 4A.

  Embodiments of the present invention will be described below. The present invention is not limited to the following embodiments, and appropriate modifications and improvements are added to the following embodiments on the basis of ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that what has been described also falls within the scope of the invention.

(1) Honeycomb structure:
FIG. 1 is a perspective view schematically showing one embodiment of the honeycomb structure of the present invention, and FIG. 2 is a partially enlarged sectional view schematically showing one embodiment of the honeycomb structure of the present invention. is there. As shown in these drawings, the honeycomb structure 100 includes a porous partition wall 1 that partitions and forms a plurality of cells 2 extending from an inflow end surface 11 that is one end surface to an outflow end surface 12 that is the other end surface. The plurality of cells 2 are provided with a plurality of divided cells 2b provided with a dividing wall 3 for dividing the cell into two spaces 4 and 4 in a cross section orthogonal to the cell extending direction, and such a dividing wall 3 is provided. A plurality of normal cells 2a not included are included. Usually, the cell 2a has a square shape in a cross section orthogonal to the cell extending direction. In the section perpendicular to the cell extending direction, the parting cell 2b has a shape of a portion excluding the parting wall 3 (a shape when it is assumed that the parting wall 3 is not provided) that is generally congruent with the shape of the cell 2a. It is a square. In the divided cell 2b, each of the two spaces 4 and 4 divided by the dividing wall 3 is rectangular (hereinafter, these two spaces may be referred to as “rectangular cells”). One divided cell 2b includes two rectangular cells 4 and 4.

  In the present invention, at least a part of the normal cell 2 a and at least a part of the divided cell 2 b are arranged so as to be adjacent to each other with the partition wall 1 therebetween. 4A is a partially enlarged plan view schematically showing adjacent normal cells and divided cells as viewed from one end face side of the honeycomb structure, and FIG. 4B schematically shows a cross section taken along line II ′ of FIG. 4A. It is sectional drawing shown. In the section perpendicular to the cell extending direction, the divided cell 2b has a square shape in which the portion excluding the divided wall 3 is congruent with the shape of the normal cell 2a. Therefore, the cross-sectional area of each of the two rectangular cells 4, 4 divided by the dividing wall 3 is smaller than the cross-sectional area of the normal cell 2a. For this reason, when the exhaust gas G is allowed to flow into the honeycomb structure 100, a difference occurs in the flow rate between the exhaust gas G1 passing through the normal cell 2a and the exhaust gas G2 passing through the rectangular cell 4, thereby causing the normal cell 2a to flow. And a rectangular cell 4 cause a pressure difference. And since the partition 1 is porous, when such a pressure difference arises, between the normal cell 2a and the rectangular cell 4 which adjoined across the partition 1, the high pressure side (inside the normal cell 2a) The exhaust gas G tends to move from the lower side to the lower side (inside the rectangular cell 4). As a result, the exhaust gas G diffuses in the cell and easily comes into contact with the partition wall 1.

  Therefore, when an exhaust gas purifying catalyst such as an SCR catalyst is supported on the honeycomb structure 100, the exhaust gas and the catalyst are easily in contact with each other, and the catalyst is effectively used. For this reason, even if the honeycomb structure 100 is not enlarged, a high purification performance can be obtained by the supported catalyst. In addition, the honeycomb structure 100 exhibits high strength because the dividing wall 3 of the dividing cell 2b also functions as a reinforcing material.

  In the present invention, the ratio of the number of divided cells 2b to the total number of divided cells 2b and the number of normal cells 2a is 30 to 80%, preferably 40 to 70%, more preferably 50 to 50%. 70%. By setting the ratio in such a range, the number of the divided cells 2b adjacent to the normal cell 2a can be increased, whereby the diffusion of the exhaust gas in the cell is promoted, and the honeycomb structure 100 is provided with a catalyst. The exhaust gas purification performance in the case of supporting is improved. When the ratio is less than 30%, the number of divided cells 2b is too small with respect to the normal cells 2a, and the number of divided cells 2b adjacent to the normal cells 2a is also reduced, and the exhaust gas purification performance is not sufficiently improved. There is. On the other hand, when the above ratio exceeds 80%, the number of divided cells 2b is too large compared to the normal cells 2a. Therefore, the number of divided cells 2b that are not adjacent to the normal cell 2a increases, and the exhaust gas purification performance may not be sufficiently improved. Moreover, the number of the dividing walls 3 increases too much, and pressure loss may increase excessively. Furthermore, when the number of rectangular cells 4 having a small cross-sectional area increases, clogging of the cells may easily occur when the catalyst is supported on the honeycomb structure 100.

  In the present invention, as shown in FIG. 2, at least a part of the divided cell 2b is a specific divided cell 2b ′ in which all of the four cells adjacent to the divided cell 2b across the partition wall 1 are normal cells 2a. Preferably there is. The specific dividing cell 2b 'causes the exhaust gas to diffuse due to a pressure difference between all of the four normal cells 2a adjacent thereto. Therefore, the presence of the specific divided cell 2b 'greatly contributes to the improvement of exhaust gas purification performance when a catalyst is supported on the honeycomb structure 100. The ratio of the number of specific divided cells 2b ′ to the total number of divided cells 2b and the number of normal cells 2a is preferably 30 to 50%, more preferably 35 to 50%. 40 to 50% is particularly preferable. By setting the ratio in such a range, high exhaust gas purification performance can be obtained when a catalyst is supported on the honeycomb structure 100.

  In the present invention, the cross-sectional area of each of the two spaces (rectangular cells) 4 and 4 divided by the dividing wall 3 in the cross-section perpendicular to the cell extending direction is usually 35% or more of the cross-sectional area of the cell 2a. Preferably, it is 40% or more, more preferably 45% or more. By setting the cross-sectional area of the rectangular cell 4 within such a range, clogging of the rectangular cell 4 is less likely to occur when the catalyst is supported on the honeycomb structure 100. If the cross-sectional area of the rectangular cells 4 and 4 is less than 35% of the cross-sectional area of the normal cell, the cross-sectional area of the rectangular cell 4 is too small, and when the catalyst is loaded on the honeycomb structure 100, Clogging may occur easily. In each divided cell 2b, the cross-sectional areas of the two spaces (rectangular cells) 4 and 4 divided by the dividing wall 3 may be the same or different. The cross-sectional area of the rectangular cell 4 can be adjusted by the position and thickness of the dividing wall 3 in the dividing cell 2b.

  In the embodiment shown in FIG. 2, in the cross section orthogonal to the cell extending direction, the extending direction of the dividing wall 3 is the same direction in all the dividing cells 2b, but the extending direction of the dividing wall 3 is It is not necessary for the divided cells 2b to be the same. For example, as in another embodiment of the present invention shown in FIG. 3, in the cross section orthogonal to the cell extending direction, the dividing wall 3 in the dividing cell 2b for each cell row (cell group arranged in a certain direction). The extending direction of may be changed. In the embodiment shown in FIG. 2 and the embodiment shown in FIG. 3, all of the normal cell 2a and the divided cell 2b are in two orthogonal directions (X direction and Y direction) on the cross section orthogonal to the cell extending direction. Alternatingly arranged. However, the arrangement of cells in the present invention is not limited to this. For example, an arrangement in which a plurality of normal cells 2a and divided cells 2b are continuous in the X direction and / or the Y direction may be included.

  Moreover, the honeycomb structure 100 may include an outer peripheral wall 20 around the partition wall 1 as shown in FIG. In this case, the cell 2c located at the outermost peripheral portion may be in a different shape from other cells in a cross section orthogonal to the cell extending direction due to being in contact with the inner peripheral surface of the outer peripheral wall 20. The “plurality of cells 2” in the present invention may include cells 2c having shapes different from those of other cells.

  In the present invention, the thickness of the partition wall 1 is preferably 60 to 300 μm, more preferably 60 to 140 μm, and particularly preferably 60 to 120 μm. When the thickness of the partition wall 1 is less than 60 μm, sufficient strength may not be obtained. Moreover, when the thickness of the partition wall 1 exceeds 300 μm, the pressure loss may become too large.

  The thickness of the dividing wall 3 is preferably 50 to 250 μm, more preferably 50 to 110 μm, and particularly preferably 50 to 100 μm. If the thickness of the dividing wall 3 is less than 50 μm, sufficient strength may not be obtained. On the other hand, if the thickness of the dividing wall exceeds 250 μm, the pressure loss may become too large.

  The porosity of the partition wall 1 is preferably 40 to 70%, more preferably 45 to 60%, and particularly preferably 50 to 60%. When the porosity of the partition wall 1 is less than 40%, even if a pressure difference is generated between the normal cell 2a and the rectangular cell 4 adjacent to each other across the partition wall 1, the exhaust gas may not be sufficiently diffused in the cells. is there. Moreover, when the porosity of the partition 1 exceeds 70%, sufficient strength may not be obtained. The “porosity” is a value measured with a mercury porosimeter.

  The average pore diameter of the partition wall 1 is preferably 10 to 25 μm, more preferably 10 to 20 μm, and particularly preferably 12 to 20 μm. When the average pore diameter of the partition walls 1 is less than 10 μm, even if a pressure difference occurs between the normal cells 2a and the rectangular cells 4 that are adjacent to each other across the partition walls 1, the exhaust gas may not sufficiently diffuse in the cells. is there. Moreover, when the average pore diameter of the partition wall 1 exceeds 25 μm, sufficient strength may not be obtained. The “average pore diameter” is a value measured with a mercury porosimeter.

  The cell pitch of the honeycomb structure 100 is preferably 1.04 to 1.47 mm, more preferably 1.09 to 1.47 μm, and particularly preferably 1.14 to 1.47 μm. If the cell pitch of the honeycomb structure 100 is less than 1.04, sufficient strength may not be obtained. In addition, when the cell pitch of the honeycomb structure 100 exceeds 1.47 mm, the pressure loss may become too large. The “cell pitch” is a value when the divided cell 2b is regarded as one cell by combining the divided wall 3 and the two spaces (rectangular cells) 4 and 4 divided by the divided wall 3. It is.

  The shape (outer shape) of the honeycomb structure 100 is not particularly limited. Examples of the shape of the honeycomb structure 100 include a columnar shape, a cross section perpendicular to the cell extending direction being an ellipse, a racetrack shape, a polygonal columnar shape such as a triangle, a quadrangle, a pentagon, a hexagon, and an octagon. be able to.

When the honeycomb structure 100 has a columnar shape, the honeycomb structure 100 preferably has a diameter of 143.8 to 330.2 mm and a length of 101.6 to 203.2 mm. The honeycomb structure 100 having such dimensions has good mountability in an automobile or the like when the SCR catalyst is supported and nitrogen oxide (NO _x ) in the exhaust gas is used for purification. In addition, if the honeycomb structure 100 has such dimensions, when the SCR catalyst is supported and nitrogen oxide (NO _x ) in the exhaust gas is used for purification, the honeycomb structure 100 exhibits sufficient purification performance.

  In the manufacturing process of the honeycomb structure 100, it is preferable that the partition walls 1 and the dividing walls 3 are integrally formed. Since the partition wall 1 and the dividing wall 3 are integrally formed, high strength can be obtained. Further, the honeycomb structure 100 can be easily manufactured by integrally forming the partition wall 1 and the dividing wall 3 by an extrusion molding method or the like.

  As a constituent material of the honeycomb structure 100, ceramics is preferable. In particular, at least one ceramic selected from the group consisting of cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, alumina, aluminum titanate, silicon nitride, and silicon carbide-cordierite based composite material is preferable. . This is because such ceramics are excellent in strength and heat resistance.

  The honeycomb structure 100 of the present invention is preferably used as a carrier for supporting a catalyst, particularly as a carrier for supporting an SCR catalyst.

  Examples of the substance that becomes the SCR catalyst include metal-substituted zeolite. Examples of the metal that replaces zeolite with metal include iron (Fe) and copper (Cu). As a zeolite, a beta zeolite can be mentioned as a suitable example.

  In addition, the SCR catalyst may be a catalyst containing at least one selected from the group consisting of vanadium and titania as a main component. The content of vanadium and titania in the SCR catalyst is preferably 60% by mass or more.

  There is no particular limitation on the amount of SCR catalyst supported. However, if the amount of the SCR catalyst supported is too small, sufficient purification performance may not be obtained. Therefore, the amount supported per unit volume (1 liter) of the honeycomb structure 100 is preferably 150 g or more. On the other hand, when the amount of the SCR catalyst supported is too large, the pressure loss of the honeycomb structure 100 may increase excessively. Therefore, the upper limit of the supported amount of the SCR catalyst is preferably about 400 g as the supported amount per unit volume (1 liter) of the honeycomb structure 100.

(2) Manufacturing method of honeycomb structure:
Hereinafter, an example of a method for manufacturing a honeycomb structure according to the present invention will be described. First, a forming raw material containing a ceramic raw material is mixed and kneaded to obtain a clay. The ceramic raw material is selected from the group consisting of cordierite forming raw material, cordierite, silicon carbide, silicon-silicon carbide based composite material, mullite, alumina, aluminum titanate, silicon nitride, and silicon carbide-cordierite based composite material. At least one of these is preferred. The cordierite-forming raw material is a raw material that becomes cordierite when fired. Specifically, the cordierite forming raw material is a raw material blended to have a chemical composition that falls within the range of 42 to 56% by mass of silica, 30 to 45% by mass of alumina, and 12 to 16% by mass of magnesia. It is.

  The forming raw material is preferably prepared by mixing the ceramic raw material with a dispersion medium, a sintering aid, an organic binder, a surfactant, a pore former, and the like.

  It is preferable to use water as the dispersion medium. The content of the dispersion medium is appropriately adjusted so that the clay obtained by kneading the molding raw material has a hardness that facilitates molding. The specific content of the dispersion medium is preferably 20 to 80% by mass with respect to the entire forming raw material.

  As a sintering aid, for example, yttria, magnesia, strontium oxide and the like can be used. The content of the sintering aid is preferably 0.1 to 0.3% by mass with respect to the entire forming raw material.

  Examples of the organic binder include methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The content of the binder is preferably 2 to 10% by mass with respect to the entire forming raw material.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type. The content of the surfactant is preferably 2% by mass or less with respect to the whole forming raw material.

  The pore former is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, hollow resin, water absorbent resin, and silica gel. The pore former content is preferably 10% by mass or less based on the entire forming raw material.

  Next, the forming raw material is kneaded to form a clay. There is no restriction | limiting in particular as a method of kneading | mixing a shaping | molding raw material and forming a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned.

  Next, the obtained kneaded material is formed to form a honeycomb formed body. A honeycomb formed body is a formed body having partition walls that partition and form a plurality of cells that serve as fluid flow paths. There is no particular limitation on the method for forming the kneaded clay to form the honeycomb formed body. For example, known molding methods such as extrusion molding and injection molding can be employed. For example, a preferable example includes a method of extrusion molding using a die having a desired cell shape, partition wall thickness, cell pitch, and the like. As the material of the die, a cemented carbide which does not easily wear is preferable. In this extrusion molding, the dividing wall of the dividing cell is preferably formed integrally (simultaneously) with the partition wall.

  The honeycomb formed body thus obtained is dried and then fired. Examples of the drying method include hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, freeze drying, and the like. Among them, it is preferable to perform dielectric drying, microwave drying, or hot air drying alone or in combination.

  The dried honeycomb formed body is preferably calcined before firing (main firing). Calcination is performed for degreasing. There is no restriction | limiting in particular about the method of calcination. For example, it is sufficient that at least a part of the organic matter in the honeycomb formed body can be removed. Examples of the organic material include an organic binder, a surfactant, and a pore former. The combustion temperature of the organic binder is about 100 to 300 ° C. For this reason, calcination is preferably performed at about 200 to 1000 ° C. for about 10 to 100 hours in an oxidizing atmosphere.

  The firing (main firing) of the honeycomb formed body is performed to sinter and densify the forming raw material constituting the calcined honeycomb formed body to ensure a predetermined strength. Since the firing conditions differ depending on the type of molding raw material, appropriate conditions may be selected according to the type. For example, when the cordierite forming raw material is used, the firing temperature is preferably 1350 to 1440 ° C. In addition, the firing time is preferably 3 to 10 hours as the keep time at the maximum temperature. Examples of the apparatus for performing calcination and main firing include an electric furnace and a gas furnace.

  The honeycomb structure of the present invention can be obtained by the manufacturing method as described above.

(3) SCR catalyst loading method:
Next, an example of a method for supporting the SCR catalyst on the honeycomb structure manufactured as described above will be described. First, a catalyst slurry containing an SCR catalyst is prepared. This catalyst slurry is coated (coated) on the surfaces of the partition walls and the partition walls of the honeycomb structure. The coating method is not particularly limited. For example, a method (suction method) of sucking from the other end surface of the honeycomb structure in a state where one end surface of the honeycomb structure is immersed in the catalyst slurry can be mentioned as a suitable coating method. Then, after the catalyst slurry is coated on the surfaces of the partition walls and the partition walls of the honeycomb structure, the catalyst slurry is dried. Further, the dried catalyst slurry may be fired. In this way, a honeycomb structure carrying the SCR catalyst can be obtained.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
As a ceramic raw material, a cordierite forming raw material made of alumina, talc, and kaolin was used. The mass ratio of alumina, talc, and kaolin was the mass ratio at which cordierite was obtained after firing. The ceramic raw material was mixed with a binder (methyl cellulose) and water to obtain a ceramic forming raw material.

  Next, this forming raw material was kneaded using a kneader to obtain a cylindrical clay. This kneaded material was formed into a honeycomb shape using a vacuum extrusion molding machine to obtain a honeycomb formed body. The obtained honeycomb formed body was dried with a microwave dryer and further dried with a hot air dryer to obtain a dried honeycomb body.

  Subsequently, this dried honeycomb body was calcined (degreasing) in an air atmosphere at 450 ° C. for 5 hours. Thereafter, the honeycomb structure was fired at 1425 ° C. for 7 hours to obtain a honeycomb structure having normal cells and divided cells. This honeycomb structure had a cylindrical shape with a diameter of 266.7 mm and a length of 152.4 mm. Further, the ratio of the number of divided cells to the total number of divided cells and the number of normal cells was 30%. Further, the ratio of the number of specific divided cells to the total number of divided cells and the number of normal cells was 30%. In the cross section perpendicular to the cell extending direction, the cross sectional area of the smallest rectangular cell was 35% when the cross sectional area of the normal cell was taken as 100%. Further, the partition wall thickness was 139.7 μm, the cell pitch was 1.27 mm, the partition wall porosity was 50%, the partition wall average pore diameter was 20 μm, and the partition wall thickness was 76.2 μm. In addition, the porosity and average pore diameter of a partition are the values measured with the mercury porosimeter. The cell pitch is a value when the divided cell is regarded as one cell by combining the divided wall and the two spaces (rectangular cells) divided by the divided wall.

  Subsequently, an SCR catalyst was supported on the honeycomb structure. Cu-substituted zeolite was used as the SCR catalyst. As a specific loading method, first, a catalyst slurry containing Cu-substituted zeolite was prepared. Water was used as a dispersant for the catalyst slurry. The amount of water was adjusted so that the viscosity of the slurry was 7 mPa · s. The catalyst slurry was coated on the surfaces of the partition walls and the partition walls of the honeycomb structure by a suction method. Thereafter, this honeycomb structure was dried with a hot air dryer to obtain a honeycomb structure carrying an SCR catalyst. The amount of SCR catalyst supported per unit volume (1 liter) of the honeycomb structure was 150 g.

(Examples 2-7, Comparative Examples 1-3)
A honeycomb structure carrying an SCR catalyst was obtained in the same manner as in Example 1 except that the dimensions of the honeycomb structure, the cell structure, and the like were as shown in Table 1. Note that the honeycomb structure of Comparative Example 1 does not have divided cells, and therefore does not have divided walls and rectangular cells. Further, the amount of SCR catalyst supported per unit volume (1 liter) of the honeycomb structure was set to 150 g as in Example 1.

(Evaluation)
The honeycomb structures of Examples 1 to 7 and Comparative Examples 1 to 3, the following method was evaluated for "NO _X purification rate", "catalyst coat" and "pressure loss". The results are shown in Table 2.

[NO _X purification rate]
Combustion gas having an NO concentration of 300 ppm and an NH ₃ concentration of 300 ppm was caused to flow into the honeycomb structure on which the SCR catalyst was supported under the conditions of a space velocity (SV) of 80000 h ⁻¹ and a temperature of 200 ° C. The NO _X purification rate (%) was calculated from the NO _X concentration of the combustion gas before and after the inflow. Then, the following evaluation was performed based on the purification rate of the honeycomb structure of Comparative Example 1 (the honeycomb structure having a conventional structure that does not have the divided cells).
“AA”: Compared with the NO _X purification rate of the honeycomb structure of Comparative Example 1, the NO _X purification rate is higher by 10% or more.
“A”: Compared with the NO _X purification rate of the honeycomb structure of Comparative Example 1, the NO _X purification rate is higher in the range of 7% or more and less than 10%.
“B”: Compared with the NO _X purification rate of the honeycomb structure of Comparative Example 1, the NO _X purification rate is high in the range of 4% or more and less than 7%.
“C”: Compared with the NO _X purification rate of the honeycomb structure of Comparative Example 1, the NO _X purification rate is high in the range of 1% or more and less than 4%.
“D”: Compared with the NO _X purification rate of the honeycomb structure of Comparative Example 1, the NO _X purification rate is high in the range of less than 1% or less than or equal to.

[Catalyst coating]
With respect to the honeycomb structure on which the SCR catalyst was supported by coating the catalyst slurry by the method as described above, the number of cells clogged by the supported catalyst was examined and evaluated as follows.
“A”: No cell is clogged.
“B”: The number of clogged cells is less than 5% of the total number of cells.
“C”: The number of clogged cells is 5% or more and less than 10% of the total number of cells.
“D”: The number of clogged cells is 10% or more of the total number of cells.

[Pressure loss]
A test piece having a length of 36 mm, a width of 36 mm, and a length of 50 mm was cut out from the honeycomb structure carrying the SCR catalyst. The test piece was cut out so that the length direction of the test piece became the direction in which the cells of the honeycomb structure extended. Air was circulated through the cut specimen at a flow rate of 2 Nm ³ / min under room temperature conditions, and the pressure on the upstream side and the pressure on the downstream side of the specimen were measured. The pressure difference between the pressure on the upstream side and the pressure on the downstream side was defined as pressure loss, and evaluation was performed as follows.
“A”: Pressure loss is less than 1.4 kPa.
“B”: Pressure loss is 1.4 kPa or more and less than 1.8 kPa.
“C”: Pressure loss is 1.8 kPa or more and less than 2.2 kPa.
“D”: Pressure loss is 2.2 kPa or more.

(Discussion)
As shown in Table 2, the honeycomb structures of Examples 1 to 7 had good evaluations in all evaluation items. On the other hand, the honeycomb structure of Comparative Example 1 that does not have divided cells and the honeycomb structure of Comparative Example 2 in which the ratio of the divided cells is less than 30% are compared with the honeycomb structures of Examples 1 to 7, NO _X purification rate was clearly inferior. Moreover, the honeycomb structure of Comparative Example 3 in which the ratio of the divided cells exceeded 80% was inferior in all evaluation items as compared with the honeycomb structures of Examples 1 to 7. The honeycomb structure of Comparative Example 3 was particularly inferior in catalyst coatability and pressure loss.

  The honeycomb structure of the present invention can be suitably used as a carrier for supporting a catalyst such as an SCR catalyst.

1: partition wall, 2: cell, 2a: normal cell, 2b: divided cell, 2b ′: specific divided cell, 2c: cell located at the outermost periphery, 3: divided wall, 4: space (rectangular cell), 11: Inflow end surface, 12: Outflow end surface, 20: Outer peripheral wall, 100: Honeycomb structure.

Claims (5)

A porous partition wall defining a plurality of cells extending from an inflow end surface that is one end surface to an outflow end surface that is the other end surface;
A plurality of divided cells provided with a dividing wall that divides the cell into two spaces in a cross section orthogonal to the cell extending direction (except for the one in which the divided cell is blocked). ) And a plurality of normal cells not provided with the dividing wall (provided that the normal cells are excluded)
The normal cell has a square shape in a cross section orthogonal to the extending direction of the cell,
In the cross section perpendicular to the cell extending direction, the divided cell has a square shape that is the same as the shape of the normal cell except for the divided wall, and the two divided by the divided wall. Each shape of the space is rectangular,
At least a part of the normal cell and at least a part of the divided cell are arranged so as to be adjacent to each other across the partition;
A honeycomb structure in which a ratio of the number of divided cells to a total number of the divided cells and the number of normal cells is 30 to 80%.   At least a part of the divided cells is a specific divided cell in which all of the four cells adjacent to the divided cell across the partition are the normal cells, and the number of the divided cells and the number of the normal cells are The honeycomb structure according to claim 1, wherein a ratio of the number of the specific divided cells to the total number of the combined cells is 30 to 50%.   3. The honeycomb according to claim 1, wherein a cross-sectional area of each of the two spaces divided by the dividing wall in a cross section perpendicular to the cell extending direction is 35% or more of a cross-sectional area of the normal cell. Structure.   The honeycomb structure according to any one of claims 1 to 3, wherein a catalyst for exhaust gas purification is supported.   The honeycomb structure according to claim 4, wherein the catalyst is an SCR catalyst.

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