JP2018034112A - Honeycomb filter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb filter hardly generating crack even when regeneration processing is conducted.SOLUTION: A honeycomb filter 300 has a ceramic honeycomb structure 120a having many columnar flow channel 110a and 110b in an axis direction, a catalyst carrying ceramic honeycomb structure 120 having a catalyst carried on the ceramic honeycomb structure 120a, a plurality of encapsulating parts 130 for closing an edge of a part of the flow channel of the plurality of flow channels and another edge of the remaining flow channels of the plurality of flow channels, and a ceramic coat layer 200 arranged on an outer peripheral surface of the catalyst carrying ceramic honeycomb structure 120. 1.1≤CTE/CTE≤7 is satisfied where heat expansion coefficient in a diameter direction of the catalyst carrying ceramic honeycomb structure 120 is CTEand heat expansion coefficient of the ceramic coat layer 200 is CTE.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a honeycomb filter having a catalyst-supporting ceramic honeycomb structure and a ceramic coating layer provided on the outer peripheral surface thereof.

  In order to reduce harmful substances contained in the exhaust gas of engines such as automobiles, a honeycomb filter for collecting fine particles having a ceramic honeycomb structure composed of ceramics is used.

  Patent Documents 1 to 4 disclose a honeycomb filter in which a ceramic coating layer is provided on the outer peripheral surface of a ceramic honeycomb structure in order to improve the strength of the honeycomb filter.

Japanese Patent No. 2604876 Japanese Patent No. 2613729 Japanese Patent No. 4457338 Japanese Patent Laying-Open No. 2015-166296

In recent years, in order to remove harmful gases such as nitrogen oxides contained in exhaust gas, the ceramic honeycomb structure is sometimes used in a state where a catalyst is supported and the function of a catalytic converter is imparted.
However, in a conventional honeycomb filter, when a catalyst is supported on a ceramic honeycomb structure, cracks often occur in the filter due to thermal stress during regeneration, that is, combustion of collected soot.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a honeycomb filter that has a catalyst-supporting ceramic honeycomb structure and is less likely to cause cracks in the regeneration process.

  As a result of investigations by the present inventors, when a catalyst is supported on the ceramic honeycomb structure, the thermal expansion coefficient is considerably increased, for example, about three times that before the support, and the thermal expansion of the catalyst-supported ceramic honeycomb structure is achieved. The coefficient of thermal expansion is higher than the coefficient of thermal expansion of the ceramic coating layer, and the expansion or contraction amount of the catalyst-supporting ceramic honeycomb structure and the expansion or contraction amount of the ceramic coating layer due to the temperature difference during regeneration are inconsistent. The inventors have found that cracks are generated due to the occurrence of stress based on the present invention, and have arrived at the present invention.

That is, the honeycomb filter according to the present invention includes a columnar ceramic honeycomb structure having a large number of flow paths in the axial direction, a catalyst-supporting ceramic honeycomb structure having a catalyst supported on the ceramic honeycomb structure, and the plurality of flow paths. A plurality of sealing portions for closing one end of a part of the channels and the other end of the remaining channels of the plurality of channels, and ceramics provided on the outer peripheral surface of the catalyst-supporting ceramic honeycomb structure A coating layer. Then, the thermal expansion coefficient in the radial direction of the catalyst-carrying ceramics honeycomb structure CTE _H, the thermal expansion coefficient of the ceramic coating layer is taken as CTE _C, satisfy _{1.1 ≦ CTE C / CTE H ≦} 7.

  Here, the ceramic coat layer may include amorphous silica particles, ceramic particles of the same type as the ceramics constituting the honeycomb structure, and an inorganic binder.

  The ceramic particles of the same type as the ceramics constituting the honeycomb structure may be a pulverized product.

  The catalyst-supporting ceramic honeycomb structure may have a porosity of 10 to 50%.

  ADVANTAGE OF THE INVENTION According to this invention, the honeycomb filter which has a ceramic honeycomb structure which carry | supported the catalyst, and is hard to produce a crack in a regeneration process is provided.

It is an axial sectional view of the honeycomb filter concerning the example of the present invention. FIGS. 2A and 2B are perspective views of a test piece for measuring the linear thermal expansion coefficient of the catalyst-supporting ceramic honeycomb structure and the ceramic coat layer, respectively.

  A honeycomb filter 300 according to an embodiment of the present invention will be described with reference to the drawings. The honeycomb filter 300 includes a porous catalyst-supporting ceramic honeycomb structure 120, a plurality of sealing portions 130, and a ceramic coat layer 200.

(Ceramics honeycomb structure and sealing part)
The catalyst-supporting ceramic honeycomb structure 120 includes a ceramic honeycomb structure 120a and a catalyst supported on the surface of the ceramic honeycomb structure 120a (including the surface of the pores).

  The ceramic honeycomb structure 120a has a column shape and includes a plurality of inlet channels (a plurality of first channels) 110a and a plurality of outlet channels (a plurality of second channels) 110b extending in the axial direction. The cross-sectional shapes of the inlet channel 110a and the outlet channel 110b can be, for example, a circle, an ellipse, a quadrangle, a hexagon, and an octagon. The ceramic honeycomb structure 120a functions as a partition wall that separates the inlet channel 110a and the outlet channel 110b adjacent to each other.

  Each inlet channel (a part of the channel) 110a is opened at the inlet end surface 100a and sealed by the sealing portion 130 at the outlet end surface 100b. Each outlet channel (remaining part of the channel) 110b is opened at the outlet end surface 100b and is sealed by the sealing portion 130 at the inlet end surface 100a. In FIG. 1, the sealing portion 130 has a plug shape, but the sealing portion 130 may be formed by deforming a part of the ceramic honeycomb structure 120 a (for example, a cone-shaped portion).

  Examples of ceramics constituting the ceramic honeycomb structure 120a are aluminum titanate-based ceramics, silicon carbide-based ceramics, cordierite-based ceramics, silicon carbide-based ceramics, and silicon nitride-based ceramics. Aluminum titanate-based ceramics can contain magnesium, silicon, and the like. The ceramics may contain trace components derived from raw materials or trace components inevitably contained in the production process. The sealing portion 130 can be made of the same or different kind of ceramics as the ceramic honeycomb structure 120a.

The cell density of the ceramic honeycomb structure 120a can be set to 35 to 80 cells / cm ² , for example.

(catalyst)
The catalyst supported on the ceramic honeycomb structure 120a decomposes harmful gases such as nitrogen oxides contained in the exhaust gas to be treated when the honeycomb filter 300 is used as a diesel particle filter or the like. The catalyst may be supported on the sealing portion 130 as well as the ceramic honeycomb structure 120a. Examples of the catalyst are oxide particles such as silica, alumina, magnesia, titania, zirconia, ceria, lanthanum oxide, and barium oxide, or composite oxide particles containing two or more of these. Preferable examples of the composite oxide include aluminosilicate, that is, zeolite which is a kind of composite oxide containing silica and alumina. The center particle diameter D50 of the catalyst can be 0.1 to 20 μm. The center particle size in this specification is D50 of the volume-based particle size distribution obtained by a laser diffraction particle size distribution meter.

  The amount of catalyst supported can be 1 to 200 g / L per apparent volume of the catalyst-supporting ceramic honeycomb structure 120.

  The porosity of the catalyst-supporting ceramic honeycomb structure 120 can be 10 to 50%. The porosity can be measured by mercury porosimetry.

Coefficient of thermal expansion CTE _H in the radial direction of the catalyst-supporting ceramic honeycomb structure 120 may be a ^{1.0 × 10 -6 /℃~6.0×10 -6 / ℃} .

  The radial direction of the catalyst-supporting ceramic honeycomb structure 120 is a straight direction including a central axis in a plane perpendicular to the central axis of the catalyst-supporting ceramic honeycomb structure 120 that is a columnar body.

  In this specification, a thermal expansion coefficient is an average value of the linear expansion coefficient when it heats up to 40-800 degreeC.

(Ceramics coating layer)
The ceramic coating layer 200 is provided on the outer peripheral surface of the catalyst-supporting ceramic honeycomb structure 120. The ceramics coat layer 200 can be provided over the entire circumference on the outer circumferential surface. The thickness of the ceramics coat layer 200 can be set to 0.2 to 2.0 mm, for example.

  The ceramic coating layer 200 can have ceramic particles and an inorganic binder constituting a matrix that binds these. The ceramic coat layer can be porous. The porosity of the ceramic coating layer 200 is smaller than that of the catalyst-supporting ceramic honeycomb structure 120 and may be 10 to 40%.

  The mixing ratio of the ceramic particles and the inorganic binder can be about 0.5 to 50.0 parts by mass of the inorganic binder with respect to 100 parts by mass of the ceramic particles.

  The ceramic particles of the ceramic coat layer 200 are not particularly limited. For example, alumina, silica, aluminum titanate, cordierite and the like. The ceramic particles may or may not include the same type of ceramic particles as the ceramics of the ceramic honeycomb structure 120a.

  Examples of the inorganic binder are amorphous silica and alumina.

  As the amorphous silica particles, fused silica can be typically used, and the center particle diameter may be in the range of about 1 to 20 μm.

  The ceramic particles are preferably a combination of the same kind of ceramic particles as the ceramic constituting the ceramic honeycomb structure 120a and amorphous silica particles. The mixing ratio of the same type of ceramic particles as the ceramics constituting the ceramic honeycomb structure 120a and the amorphous silica particles is 100 parts by mass of the same type of ceramic particles as the ceramics constituting the ceramic honeycomb structure 120a. Thus, the amorphous silica particles can be about 10 to 2000 parts by mass.

  An example of the same kind of ceramic particles as the ceramic constituting the ceramic honeycomb structure 120a is the same as the ceramic constituting the ceramic honeycomb structure 120a described above. The central particle size can be 3 to 50 μm. For example, the particles can be aluminum titanate particles or cordierite particles. Further, the particles may be a pulverized product of mill ends produced when the ceramic honeycomb structure 120a is manufactured.

  The ceramic coating layer may contain ceramic fibers such as alumina silicate fibers or biosoluble fibers as ceramic particles. The aspect ratio (ratio of major axis to minor axis) of the fiber can be 3 times or more. The minor axis of the fiber can be 2-10 μm.

  The inorganic binder serves as a matrix of the ceramic coat layer 200, and examples thereof include colloidal oxides such as colloidal silica, colloidal alumina, and water glass. Of these, colloidal oxides, particularly colloidal silica, are preferably used. When the inorganic binder is in the form of particles like a colloidal oxide, the center particle diameter is preferably in the range of about 5 to 50 nm.

Coefficient of thermal expansion CTE _C of ceramic coating layer 200 may be a ^{1.1 × 10 -6 /℃~7.0×10 -6 / ℃} . Coefficient of thermal expansion CTE _C of ceramic coating layer 200 is not particularly greatly different from the direction. Specifically, the thermal expansion coefficient in the axial direction of the ceramics coat layer 200 may be measured.

  The coefficient of thermal expansion of the ceramic coat layer 200 can be adjusted by its composition. For example, when a large amount of fused silica is added, the coefficient of thermal expansion decreases, and when the concentration of ceramic is increased, the coefficient of thermal expansion increases.

In the honeycomb filter according to the present embodiment, the thermal expansion coefficient in the radial direction of the catalyst-supporting ceramic honeycomb structural body 120 CTE _H, the thermal expansion coefficient of the ceramic coating layer 200 is taken as _{CTE C,} 1.1 ≦ CTE _C / CTE _H ≦ 7 is satisfied. 1.12 ≦ CTE _C / CTE _H , 1.13 ≦ CTE _C / CTE _H , 1.2 ≦ CTE _C / CTE _H , 1.3 ≦ CTE _C / CTE _H , and 1.35 ≦ CTE _C / CTE _H It can be. Further, CTE _C / CTE _H ≦ 5 and CTE _C / CTE _H ≦ 3 can be satisfied.

According to the invention according to the present embodiment, the honeycomb filter 300 that has the catalyst-supporting ceramic honeycomb structure 120 and does not easily generate cracks in the regeneration process by satisfying 1.1 ≦ CTE _C / CTE _H ≦ 7. Provided.

  Then, an example of the manufacturing method of the above honeycomb filters is demonstrated.

  The ceramic honeycomb structure 120a can be manufactured by starting from a paste of a ceramic raw material mixture, and through an extrusion process, a drying process, a sealing process, and a firing process, and if necessary, processing steps such as cutting and polishing of the outer peripheral surface. . The paste of the ceramic raw material mixture is prepared by mixing ceramic raw material powder, an organic binder, other additives and a solvent with a kneader or the like.

(Source of ceramics)
The ceramic source is a powder containing an element constituting the ceramic. Examples thereof include alumina, silica, mullite, cordierite, glass, oxide powder such as aluminum titanate, hydroxide powder such as aluminum hydroxide, and the like. Moreover, the end material produced until the ceramic honeycomb structure is obtained can be reused as a part of the raw material.

  For example, when manufacturing a ceramic honeycomb structure made of aluminum titanate or aluminum magnesium titanate, the raw material powder is an aluminum source powder such as α-alumina powder and a titanium source powder such as anatase type or rutile type titania powder. Can be included. The raw material powder can further contain a magnesium source powder such as magnesia powder and magnesia spinel powder and / or a silicon source powder such as silicon oxide powder and glass frit as required.

  Examples of the organic binder include celluloses such as methylcellulose, carboxymethylcellulose, hydroxyalkylmethylcellulose, and sodium carboxymethylcellulose; water-soluble polymers such as polyvinyl alcohol; and lignin sulfonate.

  Examples of other additives include a pore-forming agent, a lubricant and a plasticizer, and a dispersant.

  The pore-forming agent may be composed of, for example, carbon materials such as graphite; resins such as polyethylene, polypropylene, and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells, and corn; ice; or dry ice it can.

  Lubricants and plasticizers include, for example, polyhydric alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, arachidic acid, oleic acid and stearic acid; metal stearates such as aluminum stearate; or It can be composed of a polyoxyalkylene alkyl ether. These function as both a lubricant and a plasticizer.

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid; lower alcohols such as methanol, ethanol and propanol; or ammonium polycarboxylate It can be comprised with the following surfactant.

  As the solvent, alcohols or water can be used. As alcohols, for example, monohydric alcohols such as methanol, ethanol, butanol and propanol; or dihydric alcohols such as propylene glycol, polypropylene glycol and ethylene glycol can be used. As the solvent, water, or purified water such as pure water or ion exchange water, is preferably used, but the above alcohols can be used in combination as necessary.

(Extrusion process and drying process)
In the extrusion step, a long columnar body is obtained by extruding a ceramic raw material mixture paste obtained by mixing and kneading the above components from a die of an extruder. Since the extrusion die has a lattice-shaped opening, a plurality of through holes extending in the longitudinal direction are formed in the columnar body. The obtained columnar body is cut to a predetermined length in the longitudinal direction to form an unsealed green of the ceramic honeycomb structure 120a. In the drying step, the unsealed green of the ceramic honeycomb structure 120a is dried with hot air, microwaves, or the like to remove the solvent.

(Sealing process)
In the sealing step, among the plurality of through holes formed in the unsealed green of the ceramic honeycomb structure 120a, some of the through holes are closed on one end face side of the columnar body, and the remaining through holes are formed in the columnar body. Each through-hole is sealed so as to be blocked by the other end surface of the. Thus, the flow path in which one end face is open and the other end face is sealed, and the flow path in which one end face is sealed and the other end face is open are almost alternately arranged. . The sealing can be performed by attaching a mask having an opening only at a position corresponding to the through-hole to be sealed to the end surface to be sealed, and pushing the sealing material there, and keep the opening. A method in which a wedge-shaped jig is pushed into a plurality of through-holes, the cell walls are brought down to the through-hole side to be sealed, and the cell walls forming the through-holes to be sealed are joined and closed (called a deformation seal) Can also be done. The sealing material used in the former method can be made of the same material as the ceramic raw material mixture paste described above.

(Baking process)
In the subsequent firing step, the ceramic honeycomb structure 120a having the sealing portion is temporarily fired (degreasing) and further fired. The calcination (degreasing) is a process for removing the organic binder in the green of the ceramic honeycomb structure 120a and the organic additive blended as necessary by combustion, decomposition, or the like. Usually, calcination (degreasing) is performed in an initial stage of the firing process, that is, a temperature raising stage (for example, a temperature range of 300 to 900 ° C.) until the green of the ceramic honeycomb structure 120a reaches the firing temperature.

  The firing temperature is preferably 1300 ° C. or higher, more preferably 1400 ° C. or higher, and preferably 1650 ° C. or lower, more preferably 1550 ° C. or lower. The rate of temperature rise until reaching the firing temperature is selected from the range of 1 ° C./hr to 500 ° C./hr, for example. Among them, it is preferable to set the temperature rising rate to be smaller in the temperature range where the calcining (degreasing) is performed.

  Firing is usually performed in the air. Depending on the type and usage ratio of the aluminum source powder, titanium source powder, magnesium source powder and silicon source powder when the raw material powder to be used, for example, an aluminum titanate ceramic honeycomb structure is used, nitrogen gas, argon gas, etc. Firing may be performed in an inert gas, or firing may be performed in a reducing gas such as carbon monoxide gas or hydrogen gas. Moreover, it can also be set as the baking atmosphere which made water vapor | steam partial pressure small.

  Firing is usually performed using a common firing furnace such as a tubular electric furnace, a box-type electric furnace, a tunnel furnace, a far-infrared furnace, a microwave heating furnace, a shaft furnace, a reflection furnace, a rotary furnace, or a roller hearth furnace. Firing may be performed batchwise or continuously. Moreover, you may carry out by a stationary type and may carry out by a fluid type. The time required for firing varies depending on the composition and amount of the raw material powder constituting the green, the form of the firing furnace, the firing temperature, the firing atmosphere, and the like, but from the range of about 10 minutes to 24 hours after reaching the above firing temperature. It is selected appropriately.

  As described above, the sealing portion 130 and the porous ceramic honeycomb structure 120a can be obtained. The ceramic honeycomb structure 120a thus obtained is subjected to cutting and / or polishing of the outer peripheral surface as necessary, and then the catalyst is supported and the ceramic coating layer 200 is formed on the outer peripheral surface. Either catalyst loading or ceramic coat layer 200 formation may be performed first, but here, the catalyst loading and ceramic coat layer 200 formation will be described in this order.

(Catalyst loading)
The catalyst can be supported on the ceramic honeycomb structure 120a by, for example, a method in which the target catalyst is dispersed in water to form a slurry, and the ceramic honeycomb structure 120a having the sealing portion is immersed therein. . After immersion, it is dried to remove water.

(Formation of ceramics coating layer 200)
The ceramic coating layer 200 can be formed by applying a coating material containing the above-mentioned raw material for the ceramic coating layer on the outer peripheral surface of the ceramic honeycomb structure 120a and drying it. A drying temperature can be 40-200 degreeC. This coating material can also contain an organic binder in order to easily set after coating. The example of the organic binder is the same as the example of the organic binder mentioned above as the raw material of the ceramic honeycomb structure 120a. The application method is not particularly limited, and examples thereof include a brush coating method, a roller brush method, and a doctor blade method.

  After coating the coating material on the outer peripheral surface of the ceramic honeycomb structure 120a, the inorganic binder becomes a matrix, for example, an amorphous oxide matrix, by treating at a high temperature of 400 to 1000 ° C. The ceramic coating layer 200 is formed in which the amorphous silica particles and the ceramic particles having the same kind of substance as the ceramic constituting the honeycomb structure main body are dispersed. When a coating material containing an organic binder is used, the organic binder is burned and removed by the above high temperature treatment. The heat treatment temperature can be 500 to 1000 ° C.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, there is no particular limitation on the outer shape of the ceramic honeycomb structure and the arrangement of the flow paths. For example, the ceramic honeycomb structure may not be a cylinder, but may be a prism such as a quadrangular prism or a hexagonal prism. The shape of the flow path may also be a quadrangle, an octagon, or a plurality of shapes. The arrangement of the flow paths can take various forms such as a triangular arrangement and a square arrangement.

  Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1
Alumina, fused silica, titania and magnesia powder are mixed at a predetermined ratio to obtain an aluminum titanate forming raw material powder. To this, an appropriate amount of a binder, a lubricant and a pore former are added and mixed thoroughly in a dry process. A specified amount of water was added and sufficient kneading was performed to produce a plasticized ceramic clay. Methylcellulose and hydroxypropylmethylcellulose were used as the binder, and potato starch was used as the pore former.

Next, the obtained ceramic clay was passed through an extrusion die to obtain a green body having a honeycomb structure in which an outer peripheral wall and a cell wall were integrally formed. The shape of the cell was a hexagon. Then, one end or the other end of each flow path was sealed with the same ceramic viscosity. Thereafter, the sealed green body is dried and fired to form a cylindrical aluminum titanate ceramic honeycomb having a cell wall of 0.3 mm, an outer diameter of 170 mm, and an outer wall of 140 mm in total length and a cell wall integrally formed. A structure was obtained. A test piece was cut out from the structure, and the porosity, the pore size distribution, and the thermal expansion coefficient in the radial direction were measured. Here, the porosity and pore size distribution were measured by a mercury intrusion method, and the thermal expansion coefficient was determined as an average thermal expansion coefficient between room temperature (40 ° C.) and 800 ° C. As a result, the porosity of the cell wall was 60.0%, the center pore diameter was 18 μm, and the thermal expansion coefficient in the radial direction was 1.6 × 10 ⁻⁶ / ° C.

  The outer peripheral surface of the obtained aluminum titanate-based ceramic honeycomb sintered body is removed by cutting so as to have a predetermined outer diameter using a cylindrical grinder, so that the outer diameter of the ceramic honeycomb has a specified value. A structure was obtained.

  Separately, a center obtained by pulverizing fused silica particles having a center particle diameter of 5 μm as a coating material and the end materials (peripheral cutting powder, etc.) of the aluminum titanate ceramic honeycomb structure obtained by the above production method Predetermined combination of aluminum titanate particles having a particle diameter of 25 μm, alumina silicate fiber (short diameter 4-6 μm, aspect ratio 8-13), colloidal silica having a center particle diameter of 12 nm, hydroxypropylmethylcellulose, and water The mixture was mixed in a ratio to prepare a paste that could be applied to the honeycomb structure. The blending ratio of the coating agent was 60 parts by mass of fused silica particles, 140 parts by mass of aluminum titanate particles, 40 parts by mass of alumina silicate fiber, and 10 parts by mass of colloidal silica.

  The coating material was applied to the outer peripheral surface of the ceramic honeycomb structure using a spatula, and then dried at 40 ° C. Then, in order to burn organic matter, it heated at 550 degreeC for 3 hours, and formed the ceramic coat layer of 0.7 mm in the outer peripheral surface of the ceramic honeycomb structure.

  Subsequently, after immersing the ceramic honeycomb structure having the ceramic coating layer and the sealing portion obtained above in an aqueous slurry containing 30% by mass of the zeolite catalyst (ZSM-5) for 2 minutes, excess slurry is removed by air blowing. And dried at 100 ° C. for 1 hour. The dried catalyst-impregnated ceramic honeycomb structure was held in an electric furnace maintained at 500 ° C. in an air atmosphere for 1 hour to obtain a honeycomb filter having a catalyst-supported aluminum titanate ceramic honeycomb structure. By supporting the catalyst, the porosity of the ceramic honeycomb structure is lower than 60% before supporting the catalyst.

  From the obtained honeycomb filter, as shown in FIGS. 2 (a) and 2 (b), the test piece Sc for measuring the linear thermal expansion coefficient of the ceramic coating layer and the linear thermal expansion coefficient measurement of the catalyst-supporting ceramic honeycomb structure are obtained. A test specimen Sh was cut out. As shown in FIG. 2 (a), from the outer periphery of the honeycomb filter 300, the honeycomb filter 300 has a size of 20 mm in length, 8 mm in width, and 3 mm in thickness. The transverse direction was a direction perpendicular to the radial direction, and a small piece including the outer peripheral surface was cut out and used as a test piece Sc for measuring the linear thermal expansion coefficient of the ceramics coating layer. In addition, the catalyst-supporting ceramic honeycomb structure 120 of the honeycomb filter 300 has a length of 5 mm in length, 20 mm in width, and 5 mm in thickness from the center in the axial direction not including the sealing portion. A rectangular parallelepiped piece having a radial direction and a thickness direction being an axial direction was cut out to obtain a test piece Sh for measuring the linear thermal expansion coefficient of the catalyst-supporting ceramic honeycomb structure 120. The shapes of the test piece Sc for measuring the linear thermal expansion coefficient of the outer periphery including the ceramic coat layer and the test specimen Sh for measuring the linear thermal expansion coefficient of the ceramic honeycomb structure are schematically shown in FIGS. 2 (a) and 2 (b), respectively. Shown in the figure. A part of the catalyst-supporting ceramic honeycomb structure 120 remains on the test piece Sc for measuring the linear thermal expansion coefficient of the ceramic coat layer. The remaining catalyst-supporting ceramic honeycomb structure 120 touches the thermal expansion measurement unit. In order to prevent this, it was set in the following thermomechanical analyzer so that only the linear thermal expansion coefficient of the ceramics coating layer was obtained.

  In a thermomechanical analyzer (TMA6300 from SII Technology Co., Ltd.), the test piece SH for the catalyst-supporting ceramic honeycomb structure is in the horizontal direction, and the test piece Sc for the ceramic coating layer is in the vertical direction in the direction of thermal expansion measurement. The temperature was increased from room temperature (25 ° C.) to 1000 ° C. at a rate of 600 ° C./hr, and then cooled again to near room temperature to obtain the linear expansion coefficient of the small piece at each temperature, Based on the above, an average coefficient of thermal expansion between 40 ° C. and 800 ° C. was calculated.

The results were as follows.
Catalyst-supporting ceramic honeycomb structure: 3.8 × 10 ⁻⁶ / ° C.
Ceramic coating layer: 4.3 × 10 ⁻⁶ / ° C.

(Example 2)
To change the thermal expansion coefficient of the ceramic coating layer, except that the fused silica particles are 60 parts by mass, the aluminum titanate particles are 140 parts by mass, the alumina silicate fiber is 0 parts by mass, and the colloidal silica is 8.3 parts by mass. Same as Example 1.
The results were as follows.
Catalyst-supporting ceramic honeycomb structure: 3.8 × 10 ⁻⁶ / ° C.
Ceramics coating layer: 5.2 × 10 ⁻⁶ / ° C.

(Comparative Example 1)
Example 1 except that the fused silica particles were changed to 110 parts by mass, the aluminum titanate particles to 90 parts by mass, the alumina silicate fiber to 40 parts by mass, and the colloidal silica to 10 parts by mass in order to change the thermal expansion coefficient of the ceramic coating layer. And the same.
The results were as follows.
Catalyst-supporting ceramic honeycomb structure: 3.8 × 10 ⁻⁶ / ° C.
Ceramic coating layer: 2.8 × 10 ⁻⁶ / ° C.

(Comparative Example 2)
The procedure was the same as Example 1 except that the ceramic coat layer was not formed. The results were as follows.
Catalyst-supporting ceramic honeycomb structure: 3.8 × 10 ⁻⁶ / ° C.

(Evaluation)
The “soot combustion maximum temperature” of each honeycomb filter was measured as follows. Soot was generated by a burner type soot generator, and a predetermined amount of soot (particulate matter) was deposited on the manufactured honeycomb filter. Thereafter, high-temperature combustion gas generated by the burner was caused to flow into the honeycomb filter to raise the temperature of the gas (inlet gas), and soot was ignited. Thereafter, when the temperature of the inlet gas reached a predetermined temperature, the supply of the high-temperature gas from the burner was stopped, the apparatus was switched to the idle state, and soot combustion was completed. Thereafter, the presence or absence of cracks was confirmed. Next, the soot accumulation amount before the regeneration treatment was gradually increased, and the same test was repeated until cracks occurred in the honeycomb filter. At this time, the temperature near the center in the vicinity of the end face on the outlet side of the exhaust gas of the honeycomb filter was measured with a thermocouple. The highest temperature in the honeycomb filter when no cracks occurred in the honeycomb filter was defined as “the soot combustion maximum temperature”. The presence or absence of cracks was confirmed visually. The results are shown in Table 1.

表１より、実施例１，２のハニカムフィルタは「スス燃焼最大温度」が高く、ハニカムフィルタへクラックが発生することを抑制されていることがわかる。

From Table 1, it can be seen that the honeycomb filters of Examples 1 and 2 have a high “soot combustion maximum temperature”, and the occurrence of cracks in the honeycomb filter is suppressed.

  DESCRIPTION OF SYMBOLS 120a ... Ceramics honeycomb structure, 120 ... Catalyst support ceramic honeycomb structure, 110a ... Inlet flow path (flow path), 110b ... Outlet flow path (outlet), 130 ... Sealing part, 200 ... Ceramics coat layer, 300 ... Honeycomb filter .

Claims (4)

A columnar ceramic honeycomb structure having a large number of channels in the axial direction, and a catalyst-supporting ceramic honeycomb structure having a catalyst supported on the ceramic honeycomb structure;
A plurality of sealing portions for closing one end of a part of the plurality of channels and the other end of the remaining part of the plurality of channels; and
A ceramic coating layer provided on the outer peripheral surface of the catalyst-supporting ceramic honeycomb structure,
The thermal expansion coefficient in the radial direction of the catalyst-carrying ceramics honeycomb structure CTE _H, the thermal expansion coefficient of the ceramic coating layer is taken as CTE _C,
A honeycomb filter satisfying 1.1 ≦ CTE _C / CTE _H ≦ 7.   The honeycomb filter according to claim 1, wherein the ceramic coat layer includes amorphous silica particles, ceramic particles of the same type as the ceramics constituting the ceramic honeycomb structure, and an inorganic binder.   The honeycomb filter according to claim 2, wherein the ceramic particles of the same type as the ceramic constituting the ceramic honeycomb structure are a pulverized product.   The honeycomb filter according to any one of claims 1 to 3, wherein the catalyst-supporting ceramic honeycomb structure has a porosity of 10 to 50%.

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