JP2013154300A - Honeycomb structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure which has a moderate temperature gradient to suppress an internal stress thereof.SOLUTION: A ceramic honeycomb structure 10 includes a plurality of cells 2 formed so as to be extended along a shaft center direction L, and a catalyst coating layer containing a metal catalyst and coated on a wall surface of the cell 2. The honeycomb structure 10 has a larger amount of the metal catalyst contained in the catalyst coating layer in a central region C corresponding to a shaft center of a cross-sectional surface that is normal to the shaft center direction than an amount of the metal catalyst contained in the catalyst coating layer per cell in an outer peripheral region E located on an outer side of the central region C.

Description

  The present invention relates to a cylindrical honeycomb structure in which a plurality of cells extending along the axial direction are formed, and a catalyst coat layer containing a metal catalyst is formed on a wall surface of the cells.

  Conventionally, a catalyst carrier utilizing catalytic action such as an internal combustion engine or a reformer for a fuel cell, a filter for collecting particulates such as soot in exhaust gas (particularly particulate matter (PM) in exhaust gas of a diesel engine) ( In DPF, etc., an exhaust gas purifying catalyst is used in which the surface of a ceramic honeycomb structure is covered with a catalyst coating layer in which a metal catalyst made of a noble metal is supported.

  Here, in general, a ceramic honeycomb structure is a cylindrical porous body formed by extrusion molding, and a plurality of cells serving as exhaust gas flow passages partitioned by partition walls are formed along the axial direction. ing.

  As an exhaust gas purification catalyst comprising a honeycomb structure, an electrically heated catalyst (EHC) in which a heater is provided in a catalytic converter that purifies engine exhaust gas may be used. The electrically heated catalyst has a structure in which a pair of electrodes are arranged so as to sandwich the honeycomb structure. When using an electrically heated catalyst, a current is passed between a pair of electrodes to heat the honeycomb structure itself, thereby increasing the catalyst activity of the catalyst coat layer early and removing PM. be able to.

  Here, during the durability test of the catalyst or when the catalyst is used after being mounted on an actual vehicle, an internal stress may be generated in the honeycomb structure due to a change in the temperature distribution of the honeycomb structure. When such internal stress is repeated, cracks may occur in the honeycomb structure itself. In view of this, Patent Documents 1 and 2 disclose honeycomb structures for the purpose of uniforming the change in temperature distribution and suppressing the generation of internal stress.

  The honeycomb structure disclosed in Patent Document 1 is a honeycomb structure formed by a fiber ceramic porous body formed by sintering aluminosilicate fibers, SiC whiskers, and ceramic raw material powders.

  According to the honeycomb structure disclosed in Patent Document 1, by combining SiC whiskers with excellent thermal conductivity in addition to aluminosilicate fibers, the thermal conductivity of the substrate itself of the honeycomb structure is increased and the honeycomb structure is improved. The amount of heat transferred to the outer peripheral region of the structure can be increased, and the temperature distribution of the honeycomb structure can be made uniform.

  Further, the honeycomb structure disclosed in Patent Document 2 is a mat member having a lower thermal conductivity than the honeycomb base material on the outer peripheral surface of the outer peripheral material layer formed on the outer periphery of the honeycomb base material made of porous ceramics. Is provided.

  Further, according to the honeycomb structure disclosed in Patent Document 2, the mat material is formed by forming the mat material disposed on the outer peripheral surface of the outer peripheral material layer with a material having a lower thermal conductivity than the honeycomb base material. Heat exchange with the outside can be suppressed, the temperature gradient inside the mat member, particularly the temperature gradient in the outer peripheral region of the honeycomb substrate, can be reduced, and the temperature distribution of the honeycomb structure can be made uniform to make the honeycomb The stress distribution of the substrate can be reduced.

JP-A-1-252588 JP 2009-85202 A

  However, in the honeycomb structure disclosed in Patent Document 1, since the entire substrate of the honeycomb structure has a uniform thermal conductivity, a large temperature difference is still generated between the center portion and the outer edge portion. Therefore, there is a problem that the internal stress of the honeycomb structure cannot be reduced.

  Moreover, in the honeycomb structure disclosed in Patent Document 2, although the thermal gradient can be improved by reducing the temperature gradient inside, a mat formed of a material having a lower thermal conductivity than the honeycomb substrate. The material is only disposed on the outer peripheral surface of the outer peripheral material layer, and the structure and material of the honeycomb structure itself are the same as before, so that the temperature gradient inside the honeycomb structure cannot be drastically reduced. There is. Further, since the mat material is disposed, the number of honeycomb base material parts increases and the manufacturing cost of the honeycomb structure increases.

  The present invention has been made in view of the above-described problems, and by reducing the temperature gradient inside the honeycomb structure and suppressing the internal stress of the honeycomb structure without increasing the number of parts, the honeycomb is affected by thermal shock. An object of the present invention is to provide a honeycomb structure that can prevent cracks from occurring in the structure.

  In view of such points, the inventors have made extensive studies and, as a result, in order to prevent cracks from occurring, thermal stress σ = EαΔT (E: longitudinal elastic modulus, α: linear expansion coefficient, ΔT: temperature change) ), Because E (longitudinal elastic modulus) and α (linear expansion coefficient), which depend on the physical properties of the material, are set by the selected material, it is considered preferable to reduce ΔT (temperature change). . Accordingly, the inventors have taken advantage of the fact that the heat capacity of the metal catalyst and the heat capacity of the ceramic are different, and the basis weight of the metal catalyst (catalyst coating layer) that covers the wall surfaces of the plurality of cells formed in the honeycomb structure. It was considered that the local heat capacity of the honeycomb structure can be changed by adjusting the amount. As a result, new knowledge was obtained that the honeycomb structure ΔT (temperature change) can be reduced and the internal stress of the honeycomb structure can be suppressed.

  The present invention is based on the inventors' new knowledge. Among the present inventions, the honeycomb structure according to the first invention has a plurality of cells extending along the axial direction, and a metal is formed on the wall of the cell. A ceramic honeycomb structure coated with a catalyst coating layer containing a catalyst, wherein the honeycomb structure has a catalyst per cell in a central region corresponding to the axial center in a cross section perpendicular to the axial direction. The amount of the metal catalyst contained in the coat layer is larger than the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region outside the center region.

  According to the present invention, the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region is larger than the amount of the metal catalyst contained in the catalyst coat layer per cell in the central region. Therefore, since the heat capacity of the central region of the honeycomb structure is higher than that of the outer peripheral region, the central region is less likely to be warmed than the outer peripheral region.

  That is, the outer peripheral region has a relatively lower heat capacity than the central region, and is more likely to be warmed than in the past. As a result, the temperature distribution of the honeycomb structure can be made substantially uniform. Thus, the temperature gradient inside the honeycomb structure can be reduced without increasing the number of parts, and the generation of internal stress in the honeycomb structure can be effectively suppressed.

  Here, the catalyst coat layer may be produced by forming a metal oxide slurry containing a metal catalyst in a layered form, drying, and firing. In addition, as the metal catalyst (noble metal) in the catalyst coat layer, at least one of platinum, rhodium, and palladium can be applied. As the metal oxide forming the matrix carrier on which the metal catalyst is supported, any one of mixed materials of zirconia and alumina, ceria and alumina, ceria-zirconia and alumina can be applied.

  The amount of the metal catalyst in the catalyst coat layer per cell in the outer peripheral region and the amount of the metal catalyst in the catalyst coat layer per cell in the central region include the above-described metal catalyst in the cell in the outer peripheral region or the central region. The end face of the honeycomb structure corresponding to the region is masked so that the slurry does not enter, and the desired metal catalyst per cell can be applied in a desired amount by applying the desired slurry. Moreover, you may adjust the quantity of the metal catalyst contained in the catalyst coating layer per cell in an outer peripheral area | region and center area | region by changing the frequency | count of applying a slurry.

  As a more preferred aspect, the outer peripheral region has a radial width of at least 3 to 10% of the diameter of the cross section of the honeycomb structure. According to the present invention, since the outer peripheral region has a radial width of at least 3 to 10% of the diameter of the cross section of the honeycomb structure, internal stress generated in the honeycomb structure can be suitably reduced.

  Here, when the radial width of the outer peripheral region is less than 3%, or when the radial width of the outer peripheral region exceeds 10%, the radial thermal conductivity distribution of the honeycomb structure becomes substantially uniform, Similar to the conventional structure, a temperature distribution may occur in the honeycomb structure.

  As a still more preferred embodiment, the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region is 50% or less of the amount of the metal catalyst contained in the catalyst coat layer per cell in the central region. . According to this aspect, the internal temperature of the honeycomb structure can be suppressed by reducing the temperature gradient inside the honeycomb structure. Here, when the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region exceeds 50% of the amount of the metal catalyst contained in the catalyst coat layer per cell in the center region In some cases, the thermal conductivity distribution in the radial direction of the honeycomb structure becomes substantially uniform, and a temperature distribution may occur in the honeycomb structure as in the conventional structure.

  Among the present inventions, the honeycomb structure according to the second aspect of the present invention is a ceramic honeycomb structure in which a plurality of cells extending along the axial center direction are formed and a wall of the cell is coated with a catalyst coating layer containing a metal catalyst. In the cross section perpendicular to the axial direction, the honeycomb structure is coated with a catalyst coat layer in a central region corresponding to the axis, and is not coated with a catalyst coat layer in an outer peripheral region. It is characterized by.

  According to the present invention, since the catalyst coat layer is coated so that the catalyst coat layer is coated in the center region and the catalyst coat layer is not coated in the outer peripheral region, the heat capacity of the center region of the honeycomb structure is Since it becomes high compared with the heat capacity of an outer peripheral area | region, it becomes difficult to warm a center area | region compared with the direction of an outer peripheral area | region.

  That is, as in the first invention, the outer peripheral region has a relatively lower heat capacity than the central region, and is easier to warm than the conventional one. As a result, the temperature distribution of the honeycomb structure can be made substantially uniform. Thus, the temperature gradient inside the honeycomb structure can be reduced without increasing the number of parts, and the generation of internal stress in the honeycomb structure can be effectively suppressed.

  Here, the catalyst coat layer in the central region may be produced by forming the slurry described above into layers, drying and firing, and the same material as in the first invention can be applied. The catalyst coat layer in the center region masks the end face of the honeycomb structure corresponding to the outer periphery region so that the slurry containing the metal catalyst described above does not enter the cells in the outer periphery region, and applies the slurry to the wall surface of the cell in the center region. Thus, the catalyst coat layer can be coated.

  Further, as a more preferable aspect similar to the first invention, the outer peripheral region has a radial width of at least 3 to 10% of the diameter of the cross section of the honeycomb structure. According to this aspect, since the outer peripheral region has a radial width of at least 3 to 10% of the diameter of the cross section of the honeycomb structure, internal stress generated in the honeycomb structure can be suitably reduced.

  Here, when the radial width of the outer peripheral region is less than 3%, or when the radial width of the outer peripheral region exceeds 10%, the radial thermal conductivity distribution of the honeycomb structure becomes substantially uniform, Similar to the conventional structure, a temperature distribution may occur in the honeycomb structure.

  The honeycomb structure described above can be used, for example, to purify exhaust gas by sealing the opposite end in the axial direction of adjacent cells. In particular, such a honeycomb structure can be suitably applied to an electric heating type (electric heating catalyst: EHC) in which the internal temperature distribution tends to be non-uniform.

  As can be understood from the above description, cracks are generated in the honeycomb structure due to thermal shock by suppressing the internal stress of the honeycomb structure by reducing the temperature gradient inside the honeycomb structure without increasing the number of parts. Can be prevented.

1 is a perspective view schematically showing a honeycomb structure according to the present invention. It is an AA arrow directional view of the honeycomb structure shown in FIG. It is a model of a honeycomb structure, (a) is a general view, (b) is an enlarged view. It is the figure which showed the result of having analyzed the generated stress inside a base material using the heat distribution by CAE analysis of Examples 1-4 and Comparative Examples 1-3. It is a measurement result of the temperature inside the honeycomb structure, (a) is a diagram showing a temperature measurement result of Comparative Example 2, (b) is a temperature measurement result of Example 3, (c) These are the figures which showed the temperature measurement result of Example 1. FIG. FIG. 6 is a view showing a result of stress analysis (CAE analysis) of honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2 based on the temperature measurement result (see FIG. 5) in the actual machine described above. FIG. 3 is a diagram showing the results of pressure loss of honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view schematically showing a honeycomb structure 10 according to the present invention, and FIG. 2 is an AA arrow view of the honeycomb structure shown in FIG.

  A honeycomb structure 10 shown in FIG. 1 includes a cylindrical outer wall portion 5 and a honeycomb structure portion 3 composed of a plurality of cells 2 extending in the axial center L direction of the outer wall portion 5 defined by the partition walls 1 in the outer wall portion 5. It is equipped with. In the case of an electrically heated catalyst, a pair of electrodes are arranged on the cylindrical outer wall 5 so as to sandwich the outer wall 5 (not shown).

  Here, the honeycomb structure 10 is a ceramic honeycomb structure, for example, a porous structure mainly composed of any one of alumina, zirconia, cordierite, titania, silicon carbide, silicon nitride, and the like. Formed from ceramics. Further, an appropriate cross-sectional shape can be applied as the cross-sectional shape of the cells 2 constituting a part of the honeycomb structure 10, and a polygonal shape such as a square is applied in addition to a regular hexagon as shown in FIG. be able to. Further, the outer wall 5 may be a polygonal column or the like in addition to the cylindrical shape.

  A wall of the partition wall 1 that partitions the cell 2 is covered with a catalyst coat layer containing a metal catalyst. Specifically, the honeycomb structure 10 is included in the catalyst coat layer per cell in the central region C corresponding to the axis L in the cross section perpendicular to the direction of the axis L of the honeycomb structure 10 shown in FIG. The amount of the metal catalyst to be produced is larger than the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region E outside the center region C.

  The outer peripheral region E is a radially outer region of the cross section perpendicular to the axis L direction of the honeycomb structure 10 and has a diameter from the outer wall of the outer wall portion 5 toward the center with respect to the cross sectional diameter φ. This is a region having a direction width W.

  In addition, the catalyst coat layer is formed of platinum with respect to any one of the metal oxides forming the matrix carrier, more specifically, a mixed material of zirconia and alumina, ceria and alumina, ceria-zirconia and alumina. , Rhodium, and palladium are supported on at least one kind of noble metal (metal catalyst).

  Here, the catalyst coat layer is obtained by forming a metal oxide slurry containing a metal catalyst in layers, drying and firing, thereby obtaining a catalyst coat layer in which the metal catalyst is uniformly dispersed. I can do it. In order to increase the amount of the metal catalyst of the catalyst coat layer per cell in the central region C with respect to the amount of the metal catalyst of the catalyst coat layer per cell in the outer peripheral region E, first, it corresponds to the outer periphery region E. The end face of the honeycomb structure 10 is masked so as to close the cells 2, and the honeycomb structure 10 is immersed in the slurry described above, and the walls of the partition walls of the cells 2 corresponding to the central region C are coated with the slurry. Repeat this work as necessary.

  Next, the masking of the end faces of the cells 2 corresponding to the outer peripheral region E is peeled off, and the walls of the partition walls of all the cells 2 are coated with the slurry. Thereby, the layer thickness of the catalyst coat layer in the center region C is thicker than the catalyst coat layer in the outer periphery region E, and the center region is larger than the amount of the metal catalyst in the catalyst coat layer per cell in the outer periphery region E. The amount of the metal catalyst in the catalyst coat layer per cell in C can be increased.

  Further, as another aspect, the end surface of the honeycomb structure 10 is masked so as to block the cells 2 corresponding to the outer peripheral region E, and the honeycomb structure 10 is immersed in the slurry described above, so that the cells corresponding to the central region C are obtained. The wall of the partition wall 1 is coated with slurry.

  Next, the end face of the honeycomb structure 10 is masked so as to block the cells 2 corresponding to the central region C, and a slurry having a metal catalyst content less than that used in the outer peripheral region E is prepared. Then, the honeycomb structure 10 is immersed, and the walls of the partition walls 1 of the cells 2 corresponding to the outer peripheral region E are coated with the slurry.

  Accordingly, the catalyst coat layer in the outer peripheral region E and the catalyst coat layer in the central region C have substantially the same thickness, and with respect to the amount of the metal catalyst in the catalyst coat layer per cell in the outer peripheral region E. The amount of the metal catalyst in the catalyst coat layer per cell in the central region C can be increased.

  In the present embodiment, the amount of the metal catalyst in the catalyst coat layer per cell in the center region C is increased with respect to the amount of the metal catalyst in the catalyst coat layer per cell in the outer peripheral region E. Although the catalyst coat layer is provided on the wall surfaces of the partition walls of the cells 2 in both the region C and the outer peripheral region E, the catalyst coat layer may not be provided in the outer peripheral region E.

  As shown in FIG. 2, regardless of the presence or absence of the catalyst coat layer in the outer peripheral region E, the outer peripheral region E described above has a radial width W that is at least 3 to 10% of the diameter φ of the cross section of the honeycomb structure 10. Have. Since the outer peripheral region E has a radial width of at least 3 to 10% of the diameter of the cross section of the honeycomb structure 10, the internal stress generated in the honeycomb structure 10 can be suitably reduced. When the radial width of the outer peripheral region E is less than 3%, or when the radial width of the outer peripheral region E exceeds 10%, the radial thermal conductivity distribution of the honeycomb structure 10 becomes substantially uniform, Similar to the conventional structure, a temperature distribution may occur in the honeycomb structure 10.

  Thus, (1) the amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region C is larger than the amount of the metal catalyst contained in the catalyst coat layer per cell in the central region C. Or (2) by not providing the catalyst coat layer on the outer peripheral region E, the heat capacity of the central region C of the honeycomb structure 10 becomes larger than the heat capacity of the peripheral region E. Becomes more difficult to warm than the outer peripheral region E.

  That is, the outer peripheral area E has a relatively lower heat capacity than the central area C, and is more likely to be warmed than in the past. As a result, the temperature distribution of the honeycomb structure 10 can be made substantially uniform. Thus, the temperature gradient inside the honeycomb structure 10 can be reduced without increasing the number of parts, and the generation of internal stress in the honeycomb structure 10 can be effectively suppressed.

  Hereinafter, the present invention will be described by way of examples.

<CAE analysis>
Example 1
A model of the honeycomb structure shown in FIGS. 3A and 3B was created, and CAE analysis (thermal analysis) was performed below. Specifically, the honeycomb structure was analyzed using the models shown in FIGS. 3 (a) and 3 (b). The honeycomb structure is 5.3 mil / 600 cpsi. The cell wall thickness is mil (milli inch length, 1/1000 inch), and the number of cells is cpsi (cells per square inch, the number of cells per square inch). The length in the axial direction is 100 mm, the diameter is 93 mm, and the capacity is 679.29 cc.

  Further, as conditions such as physical property values, the outer peripheral region has a radial width of at least 5% of the diameter of the cross section of the honeycomb structure (5 mm outside from the outer wall with respect to a diameter of 93 mm of the honeycomb structure) In the cross section perpendicular to the axial direction as shown in Table 1, when the amount of metal catalyst contained in the catalyst coating layer per cell in the central region corresponding to the axial center is 100% by mass, the outer peripheral region The physical property value was set such that the amount of the metal catalyst contained in the catalyst coat layer per cell was 50% by mass.

  The honeycomb structure itself (base material) was a general material of Si / SiC or Fe—SiC, and the catalyst coat layer was a component as shown in Table 2. And the thermal condition which assumed exhaust gas was provided to the honeycomb structure, and it analyzed. Example 1 corresponds to the first invention of the present application.

(Examples 2 to 4)
In the same manner as in Example 1, a honeycomb structure model was created, and CAE analysis was performed below. Specifically, as shown in Table 3, the difference from Example 1 is that the honeycomb structure is coated with a catalyst coating layer in a central region corresponding to the axial center in a cross section perpendicular to the axial direction. A physical property value such that the outer peripheral region was not coated with the catalyst coat layer was imparted, and a thermal condition assuming exhaust gas was imparted to the honeycomb structure in the same manner as in Example 1 for analysis.

  Here, the outer peripheral region of Example 2 had a radial width of at least 3% of the diameter of the cross section of the honeycomb structure (3 mm outside from the outer wall with respect to a diameter of 93 mm of the honeycomb structure). The outer peripheral region of Example 3 had a radial width of at least 5% of the diameter of the cross section of the honeycomb structure (5 mm outside from the outer wall with respect to a diameter of 93 mm of the honeycomb structure). The outer peripheral area of Example 4 had a radial width of at least 10% of the diameter of the cross section of the honeycomb structure (10 mm outside from the outer wall with respect to a diameter of 93 mm of the honeycomb structure). Examples 2 to 4 correspond to the second invention of the present application.

(Comparative Example 1)
In the same manner as in Example 1, a honeycomb structure model was created, and CAE analysis was performed below. Specifically, as shown in Table 3, the difference from Example 1 is that Comparative Example 1 does not cover the honeycomb structure with a catalyst coating layer (only the base material: no coating). Example 2 is that the catalyst structure layer is not entirely coated on the honeycomb structure (all is not coated). In Comparative Example 3, the catalyst structure layer is not formed only on the outer wall of the honeycomb structure (only the outer wall is coated). In order to satisfy these conditions, the physical property values shown in Table 3 were given, and in the same manner as in Example 1, the thermal condition assuming exhaust gas was given to the honeycomb structure, and the analysis was performed.

  FIG. 4 is a diagram showing the results of analyzing the generated stress inside the base material using the heat distribution by CAE analysis of Examples 1 to 4 and Comparative Examples 1 to 3. As shown in FIG. 4, the maximum main stress was higher in Comparative Examples 1 to 4 than in Examples 1 to 4. In the honeycomb structures of Comparative Examples 1 to 3, it is difficult to make a difference in the heat capacity between the center and the outer wall. Therefore, it is considered that the temperature difference between the center and the outer wall is not reduced and the maximum principal stress is increased. On the other hand, the maximum principal stress decreases in the order of Example 1 (6), Example 2 (7), Example 4 (5), and Example 3 (4). Since the difference in heat capacity between the central region where the coated catalyst coat layer is formed and the outer peripheral region decreases in this order, it is considered that the temperature at the center and the outer periphery decreased and the maximum principal stress decreased.

<Temperature measurement test>
Next, under the conditions described above, honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2 were mounted on an actual machine, and the temperature inside the honeycomb structure was measured. FIG. 5 shows the measurement results of the temperature inside the honeycomb structure, (a) shows the temperature measurement results of Comparative Example 2, and (b) shows the engine load conditions. (B) which is the temperature measurement result of Example 3 is the figure which showed the temperature measurement result of Example 1. FIG.

  A1 is the temperature at the center position of the cross section at the center in the axial center (position 50 mm from the end face) when the honeycomb structure has a length of 100 mm in the axial direction, and A2 is the outer wall of the cross section at the center in the axial direction. A3 is the temperature at the position of the outer wall of the cross section at the center in the axial center direction, and is the temperature measured by inserting a thermocouple into the honeycomb structure. The temperature difference indicates the difference in temperature measured at the same time between the thermocouple on the outer wall (position A2) and the thermocouple 5 mm from the outer wall (position A3).

  As shown in FIGS. 5A to 5B, the temperature difference was smaller in the honeycomb structures of Examples 1 and 3 than in Comparative Example 2. As described above, this is considered to be caused by the difference in heat capacity between the central region and the outer peripheral region due to the separate application of the catalyst coat layer.

<Stress analysis from measured temperature>
FIG. 6 shows the result of stress analysis (CAE analysis) of the honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2 based on the temperature measurement results (see FIG. 5) in the actual machine described above. FIG. As shown in FIG. 6, the maximum principal stress of Example 3 was the smallest, and the maximum principal stresses of Examples 1 and 3 were smaller than those of Comparative Example 2. It was confirmed that this tendency was consistent with the analysis result shown in FIG.

<Pressure loss measurement test>
Next, under the conditions described above, the honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2 were mounted on an actual machine, and the pressure loss of the honeycomb structures was measured. FIG. 7 is a graph showing the results of pressure loss of the honeycomb structures corresponding to Examples 1 and 3 and Comparative Example 2.

  The pressure loss increased in the order of Examples 3 and 1 and Comparative Example 2. This is presumably because the honeycomb structures of Examples 1 and 3 have a larger amount of coating in the central region (thickness of the catalyst coating layer) than in the outer peripheral region.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there are design changes and the like without departing from the gist of the present invention. They are also included in the present invention.

DESCRIPTION OF SYMBOLS 1 ... Partition, 2 ... Cell, 3 ... Honeycomb structure part, 5 ... Outer wall part, 10 ... Honeycomb structure, C ... Center area | region of a honeycomb structure, E ... Outer periphery area | region of a honeycomb structure, L ... Axis of a honeycomb structure Core, W: radial width of outer peripheral region, φ: diameter of honeycomb structure

Claims (5)

A honeycomb structure made of ceramics in which a plurality of cells extending along the axial direction is formed, and a catalyst coat layer containing a metal catalyst is coated on the wall surface of the cells,
In the honeycomb structure, in the cross section perpendicular to the axial direction, the amount of the metal catalyst contained in the catalyst coating layer per cell in the central region corresponding to the axial center is in the outer peripheral region outside the central region. A honeycomb structure characterized by being larger than the amount of metal catalyst contained in the catalyst coat layer per cell.   The honeycomb structure according to claim 1, wherein the outer peripheral region has a radial width of at least 3 to 10% of a diameter of the cross section of the honeycomb structure.   The amount of the metal catalyst contained in the catalyst coat layer per cell in the outer peripheral region is 50% or less of the amount of the metal catalyst contained in the catalyst coat layer per cell in the central region. Item 3. The honeycomb structure according to Item 1 or 2. A honeycomb structure made of ceramics in which a plurality of cells extending along the axial direction is formed, and a catalyst coat layer containing a metal catalyst is coated on the wall surface of the cells,
The honeycomb structure is characterized in that, in a cross section perpendicular to the axial direction, a catalyst coating layer is coated in a central region corresponding to the axial center, and an outer peripheral region is not coated with a catalyst coating layer. Honeycomb structure.   The honeycomb structure according to claim 4, wherein the outer peripheral region has a radial width of at least 3 to 10% of a diameter of the cross section of the honeycomb structure.

Images