JP2009148742A - Honeycomb carrying catalyst and its preparing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a honeycomb carrying a catalyst in which continuous regeneration properties of soot is improved and an amount of soot accumulated on a cell wall with passage of time is lowered. <P>SOLUTION: The honeycomb carrying a catalyst carries catalyst particles 204 on a column-shaped honeycomb structure formed with a plurality of cells partitioned by cell walls in a longitudinal direction, and comprises a large volume cell group with one end of the cells closed and a small volume cell group with the other end of the cells closed. The oxide catalyst particles 204 of an average diameter of 0.05-1 μm are carried. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to a catalyst-supporting honeycomb and a manufacturing method thereof.

Conventionally, a catalyst-carrying honeycomb that purifies exhaust gas by supporting a catalyst on the cell wall of the honeycomb structure and bringing the exhaust gas into contact with the catalyst is known. In the catalyst-supporting honeycomb disclosed in Patent Document 1, the catalyst is supported by heating the honeycomb structure after the honeycomb structure is impregnated with the slurry-like catalyst solution.

International Publication No. WO2007 / 10463

By the way, the average particle size of the soot aggregate particles in the exhaust gas is generally about 0.1 μm. However, in the catalyst-supporting honeycomb disclosed in Patent Document 1, the honeycomb structure is impregnated with a slurry-like catalyst solution. Therefore, as shown in FIG. 1A, the supported catalyst particles 202 tend to be much larger in particle size than the soot aggregated particles 201. According to this, there are few contact points 203 between the catalyst particles and the aggregate particles of the soot, and there is a problem that the soot combustion action by the active oxygen of the oxide catalyst cannot be sufficiently exhibited.
For this reason, the soot collected on the catalyst-supporting honeycomb is not easily oxidized except during forced regeneration with high-temperature exhaust gas. As a result, soot tends to accumulate on the cell wall, and forced regeneration must be frequently performed, resulting in a problem that fuel consumption deteriorates.
In view of the above points, the present invention makes it possible to make the soot combustion action by the active oxygen of the oxide catalyst by making it easy to contact the soot trapped on the cell wall with the catalyst in the catalyst supporting honeycomb on which the catalyst is supported. The purpose is to increase the amount of soot accumulated on the cell wall with time.

In order to achieve the above object, in the catalyst-supporting honeycomb according to claim 1, a plurality of cells separated by cell walls are formed along a longitudinal direction, and the plurality of cells are formed at one end of the cell. It consists of a large volume cell group that is sealed and a small volume cell group that is sealed at the other end,
Oxide catalyst particles are supported on a columnar honeycomb structure in which the total area of the large volume cell group in the cross section perpendicular to the longitudinal direction is larger than the total area of the small volume cell group, The average particle diameter is 0.05 μm to 1 μm.
Thereby, the average particle diameter of the supported oxide catalyst particles is set to 0.05 μm to 1 μm, which is approximately the same as the average diameter of the soot aggregate particles. Therefore, as shown in FIG. 1B, the contact points between the soot aggregate particles and the catalyst particles can be increased. That is, the soot and the catalyst can be easily brought into contact with each other, and the soot combustion action by the active oxygen of the oxide catalyst can be enhanced.
According to this action, the soot that has flowed into the catalyst-carrying honeycomb can be easily burned as compared with the catalyst-carrying honeycomb of Patent Document 1 other than during forced regeneration.
Furthermore, by making the cell group on the exhaust gas inflow side larger than the cell group on the outflow side, the area of the cell wall where the soot per unit volume of the catalyst supporting honeycomb is accumulated becomes larger, and the soot and the catalyst are more contacted. It can be made easy.
By doing so, the amount of soot accumulated on the cell wall over time can be reduced.

In particular, as in the catalyst-carrying honeycomb according to claim 2, if the cells of the large volume cell group are octagonal and the cells of the small volume cell group are square in the cross section perpendicular to the longitudinal direction, The area of the cell wall in which the soot per unit volume is accumulated can be made sufficiently large.

Further, like the catalyst supporting honeycomb according to claim 3, the honeycomb structure may be formed of a ceramic sintered body. Furthermore, if the silicon carbide sintered body is used as in the catalyst supporting honeycomb according to the fourth aspect, a honeycomb structure having excellent heat resistance can be configured. Thereby, it is excellent in a mechanical characteristic and can also make heat conductivity high. Furthermore, as in the catalyst-supporting honeycomb according to claim 5, the honeycomb structure may be configured by binding a plurality of honeycomb units.

Further, as the catalyst supporting honeycomb according to claim 6, _{CeO 2,} ZrO ₂ oxide _{catalyst, FeO 2, Fe 2 O 3} , CuO, CuO 2, Mn 2 O 3, MnO, K 2 O, and Composition formula A _n B _1-n CO ₃ (where A is La, Nd, Sm, Eu, Gd or Y, B is an alkali metal or alkaline earth metal, and C is Mn, Co, Fe or Ni) When the catalyst is at least one selected from the group consisting of the complex oxides represented by the formula (1), a catalyst having excellent active oxygen delivery performance can be supported on the honeycomb structure. As a result, the soot burning action of the catalyst supporting honeycomb can be improved.

Further, a plurality of cells separated by cell walls, such as the catalyst-supporting honeycomb according to claim 7, are formed along a longitudinal direction, and the plurality of cells are sealed at one end of the cell. A large volume cell group and a small volume cell group sealed at the other end,
Disperse the precursor solution of the oxide catalyst in the columnar honeycomb structure in which the total area of the large volume cell group in the cross section perpendicular to the longitudinal direction is larger than the total area of the small volume cell group If the catalyst-carrying honeycomb in which the oxide catalyst particles are carried on the cell walls by flowing the gas, the effect similar to the effect described in the catalyst-carrying honeycomb according to claims 1 to 6 is specifically obtained. Can play.

In the method for manufacturing a catalyst-supporting honeycomb according to claim 8, a plurality of cells separated by cell walls are formed along a longitudinal direction, and the plurality of cells are sealed at one end of the cell. Consisting of a large volume cell group and a small volume cell group sealed at the other end,
A step of manufacturing a honeycomb structure in which a total area of the large volume cell group in a cross section perpendicular to the longitudinal direction is larger than a total area of the small volume cell group, and a catalyst precursor solution is gasified And a step of flowing a gas containing a dispersed catalyst precursor solution into the honeycomb structure, and a step of heating the honeycomb structure to convert the catalyst precursor into catalyst particles. . According to the above method for manufacturing a catalyst-supporting honeycomb, a catalyst-supporting honeycomb having the effects described in the catalyst support honeycomb according to claims 1 to 6 can be manufactured.

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
A honeycomb structure made of a ceramic sintered body according to the first embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a perspective view schematically showing an example of a catalyst-supporting honeycomb according to the first embodiment of the present invention, and FIG. 3A is a perspective view of a honeycomb unit constituting the catalyst-supporting honeycomb shown in FIG. It is a figure and (b) is the sectional view on the AA line of the honeycomb unit shown to (a).
Note that the catalyst supporting honeycomb shown in FIG. 2 is formed by binding a plurality of honeycomb units, but the honeycomb structure of the present embodiment may be composed of one honeycomb unit as described later. Good.

In the honeycomb structure 45, a plurality of honeycomb units 50 made of a silicon carbide sintered body or the like are combined through a sealing material layer (adhesive layer) 41 to form a cylindrical ceramic block. In addition, a sealing material layer (coat layer) 42 is formed. A catalyst-supporting honeycomb 40 is obtained by supporting oxide catalyst particles (not shown) on the honeycomb structure 45.

In the honeycomb unit 50, as shown in FIGS. 3A and 3B, a large number of cells 51 are arranged in the longitudinal direction, and a cell wall (wall portion) 53 that separates the cells 51 functions as a filter. It is like that. That is, in the cell 51 formed in the honeycomb unit 50, as shown in FIG. 3B, either the inlet side or the outlet side end of the exhaust gas is sealed with the sealing material 52, and one cell is formed. The exhaust gas that has flowed into 51 always passes through the cell wall 53 that separates the cells 51, and then flows out from the other cells 51.
In addition, the shape of the cell is an octagonal shape of the cross section perpendicular to the longitudinal direction of the cells of the large volume cell group, and the cell is a quadrangular shape of the cross section perpendicular to the longitudinal direction of the small volume cell group cells.
The honeycomb unit 50 carries an oxide catalyst having an average particle diameter of 0.05 μm to 1 μm.

In addition, the following can be given as the shape of the cell. 4 (a) to 4 (d) and FIGS. 5 (a) to 5 (f) schematically show a part of the cross section of the honeycomb unit 50 constituting the catalyst supporting honeycomb 40 according to the present embodiment. FIG.
4 (a), the aperture ratio is approximately 1.55, FIG. 4 (b) is approximately 2.54, FIG. 4 (c) is approximately 4.45, and FIG. 4 (d) is approximately 6.00. It is. 5 (a), (c), and (e), all the opening ratios are almost 4.45. In FIGS. 5 (b), (d), and (f), all the opening ratios are all. In FIG. 6, the aperture ratio is approximately 3.00.

4A to 4D, the large volume cell 54 has an octagonal cross section and the small volume cell 55 has a quadrangular (square) cross section. By changing the cross-sectional area of the cell 55 and slightly changing the cross-sectional shape of the large-capacity cell 54, the opening ratio can be easily changed arbitrarily. Similarly, the opening ratio of the honeycomb structures shown in FIGS. 5A to 5F and FIG. 6 can be arbitrarily changed.

In the honeycomb unit shown in FIGS. 5A to 5B, the large volume cell 54 has a pentagonal cross section, and three corners thereof are substantially perpendicular, and the small volume cell 55 has a cross section. The shape is a quadrangle, and each is configured to occupy a diagonally opposite portion of a large quadrangle. In the honeycomb unit shown in FIGS. 5C to 5D, the cross-sectional shape shown in FIGS. 4A to 4D is modified, and the large volume cell 54 and the small volume cell 55 share the same. It is a shape in which the partition wall is widened with a curvature on the small volume cell side. This curvature may be arbitrary.

In this example, the curve constituting the partition shared by the large volume cell 54 and the small volume cell 55 corresponds to a quarter circle.

In the honeycomb unit shown in FIGS. 5 (e) to 5 (f), the large volume cell 54 and the small volume cell 55 are formed of a quadrangle (rectangular shape), and as shown in the figure, two large volume cells 54 and two small volume cells 55 are formed. Are combined to form a substantially square shape.

In the present embodiment, it is desirable that the distance between the centers of gravity of the cross sections perpendicular to the longitudinal direction of the adjacent large volume cells 54 is equal to the distance between the centers of gravity of the cross sections perpendicular to the longitudinal direction of the adjacent small volume cells 55.
In the honeycomb structure, the cross-sectional shape perpendicular to the longitudinal direction of the cells (the large volume cell 54 and the small volume cell 55) is preferably a polygon, and more preferably a quadrangle and an octagon.

By using a polygonal shape, when the exhaust gas passes through the large-volume cell 54 and the small-volume cell 55, a portion with a large friction due to the shape of the cell is eliminated, and pressure loss due to the friction when passing through the cell is reduced. Or, it is possible to reduce the pressure loss caused by the resistance when passing through the partition wall by eliminating the part where the partition wall thickness is not uniform, that is, the part where the exhaust gas is difficult to pass locally. Because it can be obtained.

Further, among polygons, a polygon that is equal to or greater than a quadrangle is desirable, 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 passing through the exhaust gas inflow side and the friction at the time of passing through the exhaust gas outflow side can be reduced by doing as described above.

Further, in the present embodiment, in the cross section perpendicular to the longitudinal direction, the one large volume cell 54 shares the wall portion shared with the adjacent large volume cell 54 and the small volume cell 55 adjacent to the one large volume cell 54. It is desirable that at least one of the intersecting corners with the shared wall is an obtuse angle.

It is desirable that the vicinity of the corner of the cross section of the large volume cell 54 and / or the small volume cell 55 is configured by a curve as shown in FIGS. 5C and 5D, for example. This is because the occurrence of cracks due to stress concentration at the corners can be prevented by making the curve.

In the present embodiment, the ratio of the cross-sectional areas of the large volume cell group and the small volume cell group (large volume cell group / small volume cell group) is preferably 1.01 to 6.0.
When the ratio of the above areas (large volume cell group / small volume cell group) exceeds 6.0, the volume of the small volume cell group becomes too small, and the friction when passing through the exhaust gas outflow side and when passing through the partition wall The pressure loss due to the resistance increases, and the initial pressure loss increases. The area ratio (large volume cell group / small volume cell group) is more preferably 1.2 to 5.0. Furthermore, the area ratio (large volume cell group / small volume cell group) is more preferably 1.2 to 3.0.

Further, the ratio of the cross-sectional areas of the large volume cell 54 and the small volume cell 55 (large volume cell / small volume cell) is desirably 1.01 to 6.0. The area ratio (large volume cell / small volume cell) is also referred to as an opening ratio.
When the opening ratio exceeds 6.0, the volume of the small volume cell 55 becomes too small, and the pressure loss due to the friction when passing through the exhaust gas outflow side and the resistance when passing through the partition wall increases. The pressure loss will increase. The opening ratio is more preferably 1.2 to 5.0. Furthermore, the opening ratio is more preferably 1.2 to 3.0.

The honeycomb structure 45 is made of a porous ceramic. Examples of the material thereof include nitride ceramics such as aluminum nitride, silicon nitride, and boron nitride, carbide ceramics such as silicon carbide and zirconium carbide, cordierite, alumina, silica, Examples thereof include oxide ceramics such as aluminum titanate. The honeycomb structure 45 may be formed of two or more kinds of materials such as a composite of silicon and silicon carbide. In the case of using a composite of silicon and silicon carbide, it is desirable to add silicon so as to be 5 to 45% by weight of the whole.
As the material of the porous ceramic, silicon carbide ceramic is desirable. This is because it is particularly excellent in heat resistance, so that it does not melt during the regeneration process, and further has excellent mechanical properties and high thermal conductivity. The silicon carbide based ceramic means that the silicon carbide is 60% by weight or more.

In the honeycomb structure 45, the sealing material layer (adhesive layer) 41 is formed between the honeycomb units 50 and functions as an adhesive that binds the plurality of honeycomb units 50 together. (Coat layer) 42 is formed on the outer peripheral surface of the ceramic block, and prevents the exhaust gas passing through the cells from leaking from the outer peripheral surface of the ceramic block when the honeycomb structure 45 is installed in the exhaust passage of the internal combustion engine. It also functions as a sealing material and a reinforcing material for adjusting the shape.

In the honeycomb structure 45, the adhesive layer 41 and the coat layer 42 may be made of the same material or different materials. Furthermore, when the adhesive layer 41 and the coat layer 42 are made of the same material, the blending ratio of the materials may be the same or different. Further, it may be dense or porous.

It does not specifically limit as a material which comprises the adhesive material layer 41 and the coating layer 42, For example, what consists of an inorganic binder, an organic binder, an inorganic fiber, and / or an inorganic particle etc. are 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 fibers 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 made of silicon carbide, silicon nitride, boron nitride, and 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.

Next, a method for manufacturing the honeycomb structure will be described.
First, extrusion molding is performed using a raw material paste mainly composed of the ceramic as described above to produce a quadrangular prism shaped ceramic molded body.

The particle size of the ceramic powder is not particularly limited, but it is preferable that the size of the honeycomb unit produced in the subsequent firing step is less likely to be smaller than the size of the ceramic molded body, for example, an average of 0.3 to 70 μm A combination of 100 parts by weight of powder having a particle size and 5 to 65 parts by weight of powder having an average particle size of 0.1 to 1.0 μm is preferable.

The raw material paste may contain a binder and a dispersion medium liquid.
The binder is not particularly limited, and examples thereof include methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, and polyethylene glycol. The amount of the binder is usually preferably 1 to 15 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.

These ceramic powder, binder, and dispersion medium liquid are mixed with an attritor or the like, sufficiently kneaded with a kneader or the like to form a raw material paste, 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, fatty acid soap, and polyvinyl alcohol.

Furthermore, in consideration of a desired porosity, a pore-forming agent such as a balloon, which is a fine hollow sphere composed of an oxide ceramic, spherical acrylic particles, or graphite may be added to the raw material paste.
The balloon is not particularly limited, and examples thereof include an alumina balloon, a glass micro balloon, a shirasu balloon, a fly ash balloon (FA balloon), and a mullite balloon. Of these, alumina balloons are desirable.

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 in one end of one cell group and the other end of the other cell group to seal the cells.

Although it does not specifically limit as said sealing material paste, For example, the paste similar to the raw material paste which produces a honeycomb molded object can be used.

Next, the ceramic dry body filled with the sealing material paste is degreased (for example, 200 to 500 ° C.) and fired (for example, 1400 to 2300 ° C.) under predetermined conditions. It is possible to manufacture a honeycomb unit 50 that is composed entirely of one sintered body. As conditions for degreasing and firing the ceramic dry body, conditions conventionally used when manufacturing a honeycomb unit made of a porous ceramic can be applied.

Next, an adhesive paste serving as the adhesive layer 41 is applied to the side surface of the honeycomb unit 50 with a uniform thickness to form an adhesive paste layer, and another honeycomb unit is sequentially formed on the adhesive paste layer. The process of laminating 50 is repeated to produce a honeycomb unit aggregate of a predetermined size.
In addition, since it has already demonstrated as a material which comprises the said adhesive paste, the description is abbreviate | omitted here.

Next, the honeycomb unit aggregate is heated to dry and solidify the adhesive paste layer to form the adhesive layer 41.
Next, using a diamond cutter or the like, the honeycomb unit assembly in which a plurality of honeycomb units 50 are bonded through the adhesive layer 41 is cut to produce a cylindrical ceramic block.

Then, the sealing material layer 42 is formed on the outer periphery of the ceramic block by using the sealing material paste, so that a plurality of honeycomb units 50 are sealed to the outer peripheral portion of the cylindrical ceramic block bonded via the adhesive material layer 41. A honeycomb structure 45 provided with the material layer 42 can be manufactured.
Thereafter, oxide catalyst particles are supported on the honeycomb structure 45 to manufacture the catalyst-supporting honeycomb 40.

First, a catalyst precursor solution is prepared. The precursor of the catalyst, after condensation, thermal decomposition, by _{crystallization, CeO 2, ZrO 2, FeO} 2, Fe 2 O 3, CuO, CuO 2, Mn 2 O 3, MnO, K 2 O, and Compositional formula A _n B _1-n CO ₃ (where A is La, Nd, Sm, Eu, Gd or Y, B is an alkali metal or alkaline earth metal, C is Mn, Co, Fe or Ni) What becomes complex oxide represented by these is preferable. These may be used alone or in combination of two or more. Specifically, for example, it may be a nitrate, carbonate, acetate, or the like containing a metal element of the oxide, and may be represented by the general formula M (OR ¹ ) _p (R ² COCHCOR ³ ) _q (wherein M is Ce , Zr, Fe, Cu, Mn, and K are selected from the group consisting of K, p and q are integers determined so that the metal complex has a 2-8 conformation, p, q May be 0. When R ¹ , R ² and R ³ are 2 or more, each R ¹ , R ² and R ³ may be the same or different. ¹ and R ² each represents an alkyl group having 1 to 6 carbon atoms, and R ³ represents an alkyl group having 1 to 6 carbon atoms and / or an alkoxy group having 1 to 16 carbon atoms). Can also be mentioned. Examples of the solvent include water and organic solvents such as toluene and alcohol.

This solution is dispersed in a gas by a conventionally known spray method or the like. At this time, by making the dispersed droplets have a certain size, the particle diameter of the oxide catalyst particles supported later on the honeycomb structure 45 can be made a certain size.

Next, the gas in which the precursor solution is dispersed is put on a carrier gas and is introduced from one end face of the honeycomb structure 45. The inflow speed of the carrier gas at this time is preferably the same as that of the actual engine exhaust gas. For example, the space speed may be about 72000 (1 / h). The carrier gas flows in from one end face of the honeycomb structure, passes through the cell walls, and flows out from adjacent cells (see the arrow in FIG. 3b). At this time, the catalyst precursor solution dispersed and mixed in the carrier gas adheres to the cell walls 53 of the honeycomb structure 45.

Further, by heating the honeycomb structure from 300 ° C. to 800 ° C., the catalyst precursor attached to the cell wall 53 is condensed, pyrolyzed, and crystallized and supported on the honeycomb structure as an oxide catalyst. .

In addition, by flowing the carrier gas in a state where the honeycomb structure 45 is heated, adhesion of the precursor solution and condensation, thermal decomposition, and crystallization of the precursor are performed at the same time, and the oxide catalyst is applied to the honeycomb structure. More preferably, it is supported. This is because the particles adhere to the honeycomb structure 45 as catalyst particles and are more easily supported.

Note that the honeycomb structure 45 may be an integral honeycomb structure including one honeycomb unit. Such an integral honeycomb structure can be manufactured in the same manner as the above-described method for manufacturing a honeycomb unit, except that the honeycomb formed body formed by extrusion molding has a large size and a different shape. it can.
As a main constituent material of the integral honeycomb structure, cordierite or aluminum titanate having excellent thermal shock resistance is desirably used.

For example, FIG. 6 is a cross-sectional view schematically showing a cross section of the integral catalyst-supporting honeycomb according to the present embodiment.
In the honeycomb structure 60 shown in FIG. 6, a rectangular small-volume cell 55 is formed in a portion that hits the grid, and the large-volume cell 54 has a shape in which four corners of a square lack a small rectangular shape. A cell wall (partition wall) 53 that separates them is formed.

Example 1
A coarse powder of silicon carbide having an average particle size of 22 μm, 23.4% by weight of fine powder of silicon carbide having an average particle size of 0.5 μm, 4.3% by weight of methylcellulose as an organic binder, and a lubricant (Nippon Yushi Co., Ltd. Unilube) 2.6% by weight, glycerin 1.2% by weight and water 13.9% by weight were mixed and kneaded to obtain a mixed composition, which was then subjected to extrusion molding to produce a shaped product Was made. At this time, the cell shape of the generated feature is an octagonal cross-sectional shape perpendicular to the longitudinal direction of the cells of the large volume cell group, as shown in FIG. A die having a square shape was used. The ratio of the cross-sectional area of the large-capacity cell group and the cross-section perpendicular to the longitudinal direction of the small-capacity cell group, and the ratio of the cross-sectional area of the large-capacity cell and small-capacity cell cross-section perpendicular to the longitudinal direction are both 2.54. It was made to become.

Next, using the microwave dryer etc., the said production | generation form was dried and it was set as the ceramic dry body, Then, the sealing material paste of the composition similar to the said production | generation form was filled into the predetermined | prescribed cell.
Next, after drying again using a dryer, degreasing is performed at 400 ° C., and firing is performed at 2200 ° C. for 3 hours under an atmospheric pressure of argon atmosphere, whereby the porosity is 42% and the average pore diameter is 11 μm. A honeycomb structure made of a silicon carbide sintered body having a size of 34 mm square × length 150 mm, the number of cells 45.6 cells / cm ² (300 cpsi), and a cell wall thickness of 0.25 mm was manufactured.

Next, an oxide catalyst is supported on the obtained honeycomb structure.
First, cerium nitrate was dissolved in water to prepare a CeO ₂ precursor solution. The gas in which the precursor solution was dispersed was put on a carrier gas and allowed to flow into the large volume cell group from the end face of the honeycomb structure heated to 700 ° C. At this time, the carrier gas was set at a space velocity of 72000 (1 / h). In this way, a catalyst-supporting honeycomb in which CeO ₂ having an average particle diameter of 0.1 μm was supported on a honeycomb structure made of a silicon carbide sintered body was obtained. CeO ₂ was supported at a rate of 20 g per 1 L of catalyst supporting honeycomb. Moreover, the average particle diameter of the oxide catalyst was measured using a SEM photograph.

(Comparative Example 1)
A honeycomb structure made of a silicon carbide sintered body obtained in the same manner as in Example 1 was immersed in a solution in which 10 g of CeO ₂ , 40 ml of water and a pH adjusting agent were mixed in an appropriate amount for 5 minutes, and then 500 ° C. A catalyst-supporting honeycomb supporting CeO ₂ was obtained. At this time, the average particle diameter of CeO ₂ was 2 μm, and the supported amount was 20 g / L.

(Comparative Example 2)
A catalyst-supporting honeycomb was manufactured in the same manner as in Example 1 except that the cross-sectional shape of the cells was all square as shown in FIG.

(Comparative Example 3)
A catalyst-supporting honeycomb was manufactured in the same manner as in Comparative Example 1 except that the cross-sectional shape of the cells was all square as shown in FIG.

(Comparative Example 4)
The honeycomb structure obtained in Example 1 was used as a sample of Comparative Example 4. (Catalyst is not supported.)

(Comparative Example 5)
The honeycomb structure obtained in Comparative Example 2 was used as the sample of Comparative Example 5. (Catalyst is not supported.)

(Evaluation methods)
The catalyst-supporting honeycombs and samples obtained in Example 1 and Comparative Examples 1 to 5 were mixed with Matter Engineering A. G. Using a soot generator CAST2 manufactured by the company, 2.0 g / L of soot having an average particle diameter of 82 μm was collected at a flow rate of 30 L / min. Next, the catalyst-supported honeycomb with soot accumulated is set in the soot oxidation rate evaluation apparatus shown in FIG. 8, and the inflow gas temperature is adjusted so that the position 15 mm from the sample entrance is 560 ° C. while introducing only nitrogen gas. Then, after maintaining a stable state for 10 minutes, 10% oxygen was introduced at a space velocity of 72000 (1 / h) by switching the valve to burn soot. The concentration of carbon monoxide and carbon dioxide generated by soot combustion at this time was measured with a CO / CO ₂ analyzer manufactured by SHIMADZU, and converted to oxidized soot weight, assuming an ideal gas. Asked. The result is shown in FIG. 9 as a change with time of the integrated amount of oxidized soot per unit time.

(Example 2)
Next, the honeycomb structure (honeycomb unit) obtained in Example 1 was prepared by using 30% by weight of alumina fibers having an average fiber length of 20 μm, 21% by weight of silicon carbide particles having an average particle diameter of 0.6 μm, 15% by weight of silica sol, carboxymethylcellulose 5 A plurality of heat-resistant adhesive pastes containing 6% by weight and 28.4% by weight of water were used for adhesion. Furthermore, after drying at 120 ° C., a cylindrical ceramic block having an adhesive layer thickness of 1 mm was produced by cutting with a diamond cutter. Next, 23.3% by weight of silica-alumina fiber having an average fiber length of 100 μm, an average fiber diameter of 10 μm, 30.2% by weight of silicon carbide powder having an average particle diameter of 0.3 μm, 7% by weight of silica sol, and 0.5% by weight of carboxymethylcellulose. A sealing material layer having a thickness of 0.2 mm was formed on the outer peripheral portion of the ceramic block using a sealing material paste (coat layer paste) containing 1% by weight and 39% by weight of water. And it dried at 120 degreeC and obtained the cylindrical honeycomb structure of (PHI) 143.8mm x length 150mm.
Thereafter, an oxide catalyst was supported in the same manner as in Example 1. At this time, the average particle diameter of CeO ₂ was 0.1 μm, and the supported amount was 20 g / L.

(Comparative Example 6)
The honeycomb structure obtained in Example 2 was used as the sample of Comparative Example 6. (Catalyst is not supported.)

(Comparative Example 7)
Using the adhesive structure paste and the sealing material paste (coat layer paste) used in Example 2 for the honeycomb structure (honeycomb unit) obtained in Comparative Example 2, similarly, a cylindrical shape of Φ143.8 mm × length 150 mm A honeycomb structure was obtained.
Thereafter, an oxide catalyst was supported in the same manner as in Example 1. At this time, the average particle diameter of CeO ₂ was 0.1 μm, and the supported amount was 20 g / L.

(Comparative Example 8)
The honeycomb structure obtained in Comparative Example 7 was used as a sample of Comparative Example 8. (Catalyst is not supported.)

(Evaluation methods)
The initial weight of the catalyst-supporting honeycombs and samples obtained in Example 2 and Comparative Examples 6 to 8 were measured in advance at a position 0.6 m away from the engine turbocharger in the exhaust gas path discharged from the 2L common rail engine. And then mounted. After the engine warmed up, the NEDC mode was continuously operated for 30 cycles, the weight of the filter (catalyst-supported honeycomb and sample) after 30 cycles was measured again, and the amount of soot accumulated during that time was determined. The obtained results are shown in FIG. 10 as an index of continuous reproducibility. The continuous reproducibility index is defined as the number of cycles until 1.0 g / L of soot is deposited on the catalyst-supporting honeycomb.

From the results shown in FIG. 9 (Example 1 and Comparative Examples 1 to 5), the catalyst and soot were prepared by providing a large volume cell group and a small volume cell group, and supporting an oxide catalyst of 0.05 to 1 μm on the cell wall. It can be read that the number of contact points increases with so that the oxidation rate of soot can be dramatically improved. Further, from the results shown in FIG. 10 (Example 2 and Comparative Examples 6 to 8), a large volume cell group and a small volume cell group are provided, and a 0.05 to 1 μm oxide catalyst is supported on the cell wall. It can be read that the continuous reproducibility is improved and the amount of soot accumulated on the cell wall with time can be reduced.

FIG. 11 shows the cross section of the cell wall of the catalyst-supporting honeycomb of Example 1 by SEM. It can be observed that the oxide catalyst is supported on the surface of the cell wall in a cake shape.

(A) shows the catalyst and soot supported by the conventional method, and (b) shows the catalyst and soot of the present application. It is a perspective view showing typically an example of a catalyst carrying honeycomb of a first embodiment of the present invention. (A) is a perspective view of a honeycomb unit constituting the catalyst supporting honeycomb shown in FIG. 2, and (b) is a cross-sectional view of the honeycomb unit taken along line AA. (A)-(d) is sectional drawing of the direction perpendicular | vertical to the longitudinal direction of the cell of the honeycomb unit which comprises the catalyst carrying | support honeycomb of this invention. (A)-(f) is sectional drawing of the direction perpendicular | vertical to the longitudinal direction of the cell of the honeycomb unit which comprises the catalyst carrying | support honeycomb of this invention. It is a figure which shows the example of the integral-type catalyst carrying | support honeycomb of this invention. FIG. 6 is a cross-sectional view in a direction perpendicular to the longitudinal direction of a cell of a honeycomb unit constituting a conventional catalyst-supporting honeycomb. It is a figure of a soot oxidation rate evaluation apparatus. It is a graph which shows a time-dependent change of the integrated amount of the oxidized soot amount of a catalyst carrying honeycomb. 3 is a graph showing continuous regeneration characteristics of a catalyst-supporting honeycomb. 3 is a view showing a cross-sectional SEM image of a cell wall of a catalyst-supporting honeycomb of Example 1. FIG.

Explanation of symbols

40 ... catalyst-supporting honeycomb, 45, 60 ... honeycomb structure, 50 ... honeycomb unit,
51 ... Cell, 53 ... Cell wall, 54 ... Large volume cell, 55 ... Small volume cell.

Claims (8)

A catalyst-supporting honeycomb in which catalyst particles are supported on a columnar honeycomb structure in which a plurality of cells separated by cell walls are formed along the longitudinal direction,
The plurality of cells are composed of a large volume cell group sealed at one end of the cell and a small volume cell group sealed at the other end,
The sum of the areas of the large-capacity cell group in the cross section perpendicular to the longitudinal direction is larger than the sum of the areas of the small-volume cell group;
The catalyst-supporting honeycomb, wherein the catalyst particles are particles made of an oxide catalyst and have an average particle diameter of 0.05 μm to 1 μm. 2. The catalyst-supporting honeycomb according to claim 1, wherein the cells of the large volume cell group are octagonal and the cells of the small volume cell group are square in a cross section perpendicular to the longitudinal direction. The catalyst-supporting honeycomb according to claim 1 or 2, wherein the honeycomb structure is made of a ceramic sintered body. The catalyst-supporting honeycomb according to claim 3, wherein the honeycomb structure is made of a silicon carbide sintered body. The catalyst supporting honeycomb according to any one of claims 1 to 4, wherein the honeycomb structure is formed by binding a plurality of honeycomb units. The oxide catalyst is CeO ₂ , ZrO ₂ , FeO ₂ , Fe ₂ O ₃ , CuO, CuO ₂ , Mn ₂ O ₃ , MnO, K ₂ O, and a composition formula _An B _1-n CO ₃ (where , A is La, Nd, Sm, Eu, Gd or Y, B is an alkali metal or alkaline earth metal, and C is Mn, Co, Fe, or Ni). The catalyst-supporting honeycomb according to any one of claims 1 to 5, wherein there is at least one. A plurality of cells separated by a cell wall are formed along the longitudinal direction, and the plurality of cells are sealed at one end of the cells and sealed at the other end. A small volume cell group,
Disperse the oxide catalyst precursor solution in a columnar honeycomb structure in which the total area of the large volume cell group in the cross section perpendicular to the longitudinal direction is larger than the total area of the small volume cell group A catalyst-supporting honeycomb characterized in that oxide catalyst particles are supported on the cell walls by allowing the gas to flow. A plurality of cells separated by a cell wall are formed along the longitudinal direction, and the plurality of cells are sealed at one end of the cells and sealed at the other end. A small volume cell group,
A step of manufacturing a honeycomb structure in which a total area of the large volume cell group in a cross section perpendicular to the longitudinal direction is larger than a total area of the small volume cell group;
Dispersing a catalyst precursor solution in a gas;
Flowing a gas containing a dispersed catalyst precursor solution into the honeycomb structure; and
And a step of heating the honeycomb structure to form catalyst precursors as catalyst particles.

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