JP5730631B2 - Honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure that can satisfy both high temperature rise performance and high heat capacity at the same time and efficiently purify exhaust gas discharged from a diesel engine or the like.

With the tightening of exhaust gas regulations regarding diesel engines, various methods of using a diesel particulate filter (DPF) for collecting particulate matter (PM) contained in exhaust gas from diesel engines have been proposed. In general, a catalyst for oxidizing PM is coated on the DPF, and a honeycomb structure coated with the catalyst is mounted on the front stage of the DPF. This NO that in the honeycomb structure included in the exhaust gas by a NO _2, or to burn the PM deposited in the DPF, the post injection performed by the engine control to raise the exhaust gas temperature by oxidizing the unburned fuel, The PM deposited on the DPF is burned and regenerated.

  In order to smoothly burn and regenerate PM deposited on the DPF, it is necessary to make the time for the catalyst coated on the honeycomb structure to reach the activation temperature as long as possible. However, the exhaust temperature of a diesel engine is low, and the honeycomb structure does not reach the catalyst activation temperature in a low load state, or the temperature of the honeycomb structure rapidly increases when the load is suddenly shifted to a low load even after a high load operation. In some cases, the temperature drops below the catalyst activation temperature, which impairs PM combustibility and does not complete forced regeneration. In recent years, even with the miniaturization of diesel engines, there has been a problem that the exhaust gas temperature is lowered and the catalyst does not reach the activation temperature.

  In view of the above-mentioned problems, the catalyst activation temperature is reached quickly by reducing the heat capacity of the honeycomb structure and improving the temperature rise characteristics of the substrate, such as by thinning the cell partition walls of the honeycomb structure and increasing the porosity. It has been done generally.

  However, lowering the heat capacity of the base material improves the temperature rise characteristics of the base material and allows the coated catalyst to reach the catalyst activation temperature quickly, but conversely, when the exhaust gas temperature decreases, the catalyst is activated rapidly. Below temperature. Further, if the heat capacity of the base material is increased in order to prevent the temperature of the base material from being lowered when the exhaust gas temperature is lowered, the temperature rise characteristic is deteriorated, which is a contradictory relationship. That is, it is difficult to extend the time for which the catalyst coated on the honeycomb structure reaches the activation temperature simply by changing the partition wall thickness or porosity of the substrate and changing the heat capacity.

  Therefore, a honeycomb structure composed of partition walls having two or more types of thickness is disclosed (see Patent Documents 1 and 2). The honeycomb structure of Patent Document 1 is a honeycomb structure that improves warm-up characteristics and mechanical strength. The honeycomb structure of Patent Document 2 solves the contradictory problem that it is difficult to satisfy both high temperature rise performance and high heat capacity at the same time, and collects particulate matter (PM) discharged from a diesel engine. It is possible to smoothly complete the regeneration of the PM collected by the filter or to efficiently purify the exhaust gas by installing the filter before the filter.

JP 2002-326035 A JP 2007-289924 A

  In Patent Document 1, although the thickness of the partition wall is changed, there is a problem that exhaust gas hardly flows to the outer peripheral portion. For this reason, heat retention is not sufficient, and further improvement in purification performance is desired. There is also a problem that pressure loss at the outer peripheral portion increases. In Patent Document 2, there is an effect of high heat retention due to the large heat capacity in the thick part of the partition wall, and high temperature rising property due to the small heat capacity in the thin part. A good honeycomb structure is desired.

  The present invention has been made in view of the above problems, and has a honeycomb structure that can satisfy both high temperature rise performance and high heat capacity at the same time and can efficiently purify exhaust gas discharged from a diesel engine or the like. The purpose is to provide.

  The inventors have made the partition wall thickness in the outer peripheral region thicker than the partition wall thickness in the central region, so that the cell pitch in the outer peripheral region is larger in at least one direction than the cell pitch in the central region. It has been found that the above-described problems can be solved by configuring. That is, according to the present invention, the following honeycomb structure is provided.

[1] A plurality of cells communicating in parallel between two end faces are formed by a plurality of partition walls, and a central region including a central axis is a first thickness on a plane perpendicular to the communication direction of the cells. A first partition wall having a thickness, and an outer peripheral region outside the central region is formed by a second partition wall having a second thickness greater than the first thickness, and at least the outer peripheral region The cell pitch in one direction is larger than the cell pitch in the central region, the cell in the central region is a square cell, and the cell constituting the outer peripheral region is one of the cells constituting the central region. A honeycomb structure having an opening ratio of 0.00 to 1.10 times.

[2] A transition region formed by an intermediate partition wall having a thickness intermediate between the first thickness and the second thickness is provided between the central region and the outer peripheral region, and the outer peripheral portion. The cell constituting each region of the region and the transition region has an aperture ratio of 1.00 to 1.10 times that of the cell constituting the central region, and the size of the aperture ratio is the central portion The honeycomb structure according to [1], wherein region ≦ transition region ≦ outer peripheral region.

[3] The honeycomb structure according to [2], wherein an area of the transition region is 5 to 35% of the entire surface in a plane perpendicular to the communication direction.

[4] The honeycomb structure according to [2] or [3], wherein the central region, the transition region, and the outer peripheral region are formed concentrically on a plane perpendicular to the communication direction.

  By increasing the thickness of the partition wall in the outer peripheral region rather than the thickness of the partition wall in the central region, the heat capacity can be increased in the outer peripheral region and the heat retention can be improved. In addition, in the central region, the heat capacity can be reduced to improve the temperature rise performance. Thereby, since it can be set as the honeycomb structure which is easy to warm and is hard to cool, catalyst activity can be improved and purification performance can be improved.

  In addition, by configuring the cell pitch in the outer peripheral region to be larger in at least one direction than the cell pitch in the central region, it is possible to flow the gas uniformly in the cell and suppress an increase in pressure loss in the outer peripheral region. it can.

1 is a perspective view showing an embodiment of a honeycomb structure of the present invention. It is a partially expanded schematic diagram which shows one Embodiment of one end surface of a honeycomb structure. Fig. 3 is an enlarged schematic view of the vicinity of a cell on one end face of a honeycomb structure. FIG. 3 is a partially enlarged schematic view of one end face of a honeycomb structure in which a transition region is formed. It is a partially expanded schematic diagram which shows embodiment which the cell pitch of a transition area changes in radial direction. It is a partially expanded schematic diagram which shows embodiment which the cell pitch of a transition area | region and the thickness of a partition change in radial direction. FIG. 3 is a partially enlarged schematic view showing one end face of a honeycomb structure in which a central region, a transition region, and an outer peripheral region are formed concentrically.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and changes, modifications, and improvements can be added without departing from the scope of the invention.

  FIG. 1 is a perspective view showing an embodiment of a honeycomb structure of the present invention, and FIG. 2 is a partially enlarged schematic view showing an embodiment of one end surface S of the honeycomb structure shown in FIG. As shown in FIGS. 1 and 2, in the honeycomb structure 10 of the present embodiment, a plurality of cells 2 that communicate with each other in parallel between the two end faces S and S are formed by a plurality of partition walls 1. In the honeycomb structure 10, the central region 11 including the central axis 15 is formed by the first partition wall 1 a having the first thickness on the surface perpendicular to the communication direction in which the cells 2 communicate. Further, the outer peripheral region 12 outside the central region 11 is formed by the second partition wall 1b having a second thickness larger than the first thickness. Furthermore, the cell pitch in at least one direction of the outer peripheral region 12 is larger than the cell pitch of the central region 11. That is, the central region 11 where the partition wall 1 is thin has a narrow cell pitch, and the peripheral region 12 where the partition wall 1 is thick has a wide cell pitch. Further, the cell 2 in the central region 11 is a square cell, and the cell 2 constituting the outer peripheral region 12 has an aperture ratio that is 1.00 to 1.10 times that of the cell 2 constituting the central region 11.

  FIG. 2 is a partially enlarged schematic diagram showing ¼ of the end surface S. FIG. As shown in FIG. 2, the central region 11 is a region including the central axis 15, the cell pitch is smaller than that of the outer peripheral region 12, and the partition wall 1 is also thin. On the other hand, in the outer peripheral region 12, at least one cell pitch is larger than the cell pitch of the central region 11. In the embodiment of FIG. 2, the other cell pitch of the outer peripheral region 12 is the same as the cell pitch of the central region 11.

  By changing the thickness of the partition wall 1 depending on the region, the heat capacity is increased in the thick second partition wall 1b, and the heat retention is improved. Moreover, in the thin 1st partition 1a, a heat capacity becomes small and temperature rising property improves. That is, when the honeycomb structure 10 of the present invention is used for exhaust gas purification of a diesel engine or the like, the portion of the thin first partition wall 1a is heated first when heated by exhaust gas, and the catalyst coated on the honeycomb structure 10 is quickly The activation temperature is reached. Further, the temperature gradient with the thick second partition wall 1b becomes steep, and the temperature rise of the second partition wall 1b is accelerated by heat transfer from the thin first partition wall 1a in addition to the heat received from the exhaust gas. When the exhaust gas temperature is lowered, due to a phenomenon opposite to the above, the cooling of the thick second partition wall 1b is delayed, and the time for reaching the catalyst activation temperature range can be extended. Further, by changing the cell pitch, exhaust gas can be circulated uniformly in the central region 11 and the outer peripheral region 12, and an increase in pressure loss can be suppressed.

Furthermore, the cell 2 in the central region 11 is a square cell, and the cell 2 constituting the outer peripheral region 12 has an aperture ratio that is 1.00 to 1.10 times that of the cell 2 constituting the central region 11. The aperture ratio is more preferably 1.00 to 1.05 times, and further preferably 1.00 to 1.02 times. FIG. 3 is an enlarged schematic view of the vicinity of the cell 2 on one end face S of the honeycomb structure 10. The aperture ratio (Open Front Area) is (cell pitch−thickness of partition wall) ² / cell pitch ² . Since the cell 2 constituting the outer peripheral region 12 has an opening ratio of 1.00 to 1.10 times that of the cell 2 constituting the central region 11, the cell 2 in the outer peripheral region 12 is less likely to circulate exhaust gas. Can also circulate exhaust gas sufficiently.

  The honeycomb structure 10 has a transition region 13 formed by an intermediate partition wall 1c having a thickness intermediate between the first thickness and the second thickness between the central region 11 and the outer peripheral region 12. preferable. FIG. 4 shows a partially enlarged schematic view of the end surface S of the honeycomb structure 10 in which the transition region 13 is formed. The intermediate partition wall 1 c in the transition region 13 is thicker than the partition wall 1 in the central region 11 and thinner than the partition wall 1 in the outer peripheral region 12. Further, the cell pitch of the transition region 13 is larger than the cell pitch of the central region 11 and smaller than the cell pitch of the outer peripheral region 12. Providing such a transition region 13 facilitates heat transfer. By providing the intermediate partition wall 1c, the second partition wall 1b and the first partition wall 1a are not directly connected. For this reason, generation | occurrence | production of the deformation | transformation etc. of the cell 2 in a boundary is prevented, and intensity | strength does not fall.

  When the honeycomb structure 10 has the transition region 13, the cell 2 constituting each of the outer peripheral region 12 and the transition region 13 is 1.00 to 1.10 times as large as the cell 2 constituting the central region 11. It is preferable that the aperture ratio is such that the center region ≦ the transition region ≦ the outer peripheral region. By having such an aperture ratio, the exhaust gas can be circulated in these regions without disturbing the circulation of the exhaust gas even in the outer peripheral region 12 and the transition region 13. Therefore, exhaust gas can be distributed uniformly throughout. Thereby, pressure loss can be reduced.

  In the plane perpendicular to the communication direction, the area of the transition region 13 is preferably 0 to 35% of the entire plane. More preferably, it is 5 to 30%, and most preferably 5 to 20%. The surface perpendicular to the communication direction is the end surface S or a cross section perpendicular to the communication direction. Further, the area of the central region 11 is 35 to 55% of the entire surface perpendicular to the communication direction of the honeycomb structure 10, and the area of the outer peripheral region 12 is the entire surface perpendicular to the communication direction of the honeycomb structure 10. It is preferable that it is 15 to 50% of. By forming each region in such a range, the balance between the temperature rising property and the heat retaining property is improved, and the purification efficiency is improved.

  The general outer diameter of the honeycomb structure 10 is 100 mm to 150 mm. In this case, the width 13 a of the transition region 13 is preferably 3 mm or more and 15 mm or less in the radial direction of the surface perpendicular to the communication direction. . The width 13a of the transition region 13 is the shortest distance from the start to the end point of the transition region 13 in the radial direction, and the shortest distance between the boundaries with other regions is preferably 3 mm or more and 15 mm or less. When the width 13a of the transition region is in this range, the heat conduction between the central region 11 and the outer peripheral region 12 is good, the balance between the temperature rise property and the heat retention property is improved, and the purification efficiency is improved. In addition, you may form the boundary with the other area | region of the four corners of the transition area | region 13 in step shape other than embodiment shown in FIG.

  FIG. 5 shows an embodiment in which the cell pitch of the transition region 13 changes. In the embodiment shown in FIG. 5, the cell pitch of the transition region 13 changes in two stages. Depending on the width of the transition region 13, the cell pitch may change in multiple steps, or gradually or linearly. Further, in the transition region 13, the thickness of the partition wall 1 may be changed in multiple steps, gradually or linearly or non-linearly so that the outer peripheral region 12 side is thicker than the central region 11 side. .

  FIG. 6 shows an embodiment in which the cell pitch and the thickness of the partition wall 1 change in the transition region 13. The cell 2 on the outer peripheral region 12 side has a larger cell pitch and the partition wall 1 is thicker than the cell 2 on the central region 11 side.

  FIG. 7 shows an embodiment of a honeycomb structure in which the central region 11, the transition region 13, and the outer peripheral region 12 are formed concentrically on a plane perpendicular to the communication direction. In the embodiment of FIG. 7, it is formed as a concentric circle. The concentric shape is not limited to a concentric circle, and may be a quadrangular shape or other polygonal shapes. In the case of a circular shape, a homogeneous effect can be obtained with respect to the purification efficiency and pressure loss of the central region 11 and the outer peripheral region 12 as compared to a rectangular shape. On the other hand, in the case of a quadrangular shape, it is easier to produce a die when the honeycomb structure 10 is produced by extrusion molding than a circular shape.

  In the honeycomb structure 10 as described above, the second thickness of the second partition wall 1b is preferably 100 to 300 μm. If it is 100 μm or more, the strength can be sufficient. If it is 300 μm or less, the heat capacity is not too high, and the temperature can be raised quickly. Thereby, purification performance can be improved.

  The first thickness of the first partition 1a of the honeycomb structure 10 is preferably 20 to 70% of the second thickness of the second partition. By setting it within this range, the strength can be sufficient and the temperature can be increased quickly. Thereby, purification performance can be improved.

  The intermediate partition wall 1c of the honeycomb structure 10 has a thickness between the second thickness and the first thickness. As long as the intermediate partition wall 1c has a thickness between the second thickness and the first thickness, the intermediate partition wall 1c may have a constant thickness in the transition region or may change within the region. However, when it changes, the center part area | region 11 side must be thin, and the outer peripheral part area | region 12 side must be formed thickly. In this case, the thickness may change stepwise or may change continuously.

  The porosity of the first partition wall 1a and the second partition wall 1b is preferably 20 to 70%. More preferably, it is 25 to 55%. By setting the porosity within this range, the temperature rise and strength can be improved.

  In the present embodiment, the partition walls 1 constituting the honeycomb structure 10 are preferably made of ceramics, and are made of cordierite, alumina, mullite and lithium aluminosilicate (LAS), aluminum titanate, zirconia, More preferably, it is made of at least one ceramic selected from the group consisting of silicon carbide, silicon nitride, activated carbon, and zeolite.

  A catalyst-coated honeycomb structure can be obtained by coating a catalyst on the honeycomb structure 10 described above (not limited to the above embodiment). Here, examples of the catalyst include an oxidation catalyst, a NOx occlusion reduction catalyst, and an SCR catalyst. The catalyst coat amount is preferably 100 to 300 g / L.

  Moreover, it can be used as a purification device in which the honeycomb structure 10 described above or the catalyst-coated honeycomb structure described above is installed in the front stage of the filter. Specifically, the present invention can be used as a honeycomb for a DOC (Diesel Oxidation Catalyst, an oxidation catalyst for diesel) installed in a front stage of a filter of a purification device for a diesel vehicle. The exhaust gas temperature of diesel vehicles is low, and the catalyst attached to the DOC may not work effectively. As a technique for improving this, a technique for realizing early temperature rise and slow temperature fall is important. However, the honeycomb structure 10 of the present invention is easy to rise in temperature and has heat retention. Further, even with a three-way catalyst used in a gasoline vehicle, an early temperature increase and a slow temperature decrease can be realized. Therefore, further exhaust gas purification can be realized by using it as a purification device for a gasoline vehicle.

  Next, the manufacturing method of the honeycomb structure of the present invention will be described. For example, when obtaining a cordierite honeycomb structure 10, talc, kaolin, alumina, silica, etc. are prepared at a predetermined blending ratio so as to be cordierite after firing, and a binder, a surfactant, and water are added. Then, the kneaded material is obtained by mixing at a predetermined mixing ratio. Regarding the cordierite-forming raw material, the particle size, components, etc. ultimately affect the porosity and thermal expansion rate, but can be selected by those skilled in the art as appropriate, and the binder and surfactant are also selected. It is possible to set appropriately. The obtained clay is extruded using an extruder. And the honeycomb structure 10 of the present invention can be obtained by firing (1420 to 1430 ° C., 10 to 30 hours) the extruded honeycomb structure (honeycomb formed body).

  In addition, the die for extruding the honeycomb formed body to be the honeycomb structure 10 of the present invention using an extruder can be formed to have a desired slit width by grinding, for example. Moreover, when changing the thickness of the partition 1 in steps, it can be adjusted by electric discharge machining or the like.

  The honeycomb structure 10 of the present invention can be coated with a catalyst to form a honeycomb catalyst body. Examples of the catalyst include an oxidation catalyst, a NOx occlusion reduction catalyst, an SCR catalyst, and a three-way catalyst.

The catalyst is, for example, a three-way catalyst (a platinum group metal prepared such that the ratio of platinum (Pt) to rhodium (Rh) (Pt: Rh) in the honeycomb structure is 5: 1 to 3: 1). The catalyst containing the γ-alumina supporting the catalyst) is supported so that the amount of the catalyst supported is 160 to 290 g / 1000 cm ^3, and the honeycomb catalyst body can be manufactured. As the promoter for the supported catalyst, cerium (Ce) oxide (CeO ₂ ) and zirconium (Zr) oxide (ZrO ₂ ) can be used. In addition, when the platinum group metal loading is 1 to 10 g / 1000 cm ³ , the catalyst coating amount is preferably 50 to 300 g / 1000 cm ³ . If it is less than 50 g / 1000 cm ³ , the effect of improving heat retention and temperature rise cannot be obtained sufficiently. When it exceeds 300 g / 1000 cm ³ , clogging easily occurs due to the catalyst coating.

  With the configuration described above, when the honeycomb structure 10 (honeycomb catalyst body) is used as a purification device for a diesel vehicle, a gasoline vehicle, or the like, the central region 11 has excellent temperature rise characteristics when the engine is started. It is possible to reach quickly. Further, since the outer peripheral region 12 is excellent in heat retention during traveling, it is possible to maintain the catalytically active region even when stopping frequently during city traveling. Therefore, at the start of operation after idling, the central region 11 reaches the catalyst activation temperature very quickly, and the outer peripheral region 12 maintains a relatively high temperature even during idling. The function can be demonstrated in all honeycomb structures.

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

(Examples 1-17)
Talc, kaolin, alumina, silica and the like were prepared at a predetermined blending ratio so as to be cordierite after firing, and a binder, a surfactant and water were added and mixed at a predetermined blending ratio to obtain a clay. Regarding the cordierite-forming raw material, the particle size, components, etc. ultimately affect the porosity and thermal expansion rate, but can be selected by those skilled in the art as appropriate, and the binder and surfactant are also selected. It is possible to set appropriately. The obtained clay is dried so as to have the cell structure shown in Table 1 after firing, and is subjected to extrusion molding using an extrusion molding machine with a base having an adjusted slit width in consideration of the shrinkage rate in the firing stage. After performing, drying and firing, a honeycomb structure 10 having a diameter of 143.8 mm and a length of 75 mm was produced.

  In addition, each area | region of the produced honeycomb structure 10 was measured with the following method. The central region 11 was measured up to the boundary where the thickness of the partition wall 1 was the smallest and the thickness of the partition wall 1 changed, and the central region 11 was measured with calipers or the like. The area ratio of the central region 11 was determined by the area of the central region / the overall cross-sectional area.

  The transition region 13 was measured with a caliper from the boundary where the thickness of the partition wall 1 changed from the thinnest value to an intermediate thickness to the boundary where the thickness of the partition wall 1 became the thickest. The area ratio of the transition region 13 was determined by the area of the transition region / the entire cross-sectional area.

  In the outer peripheral region 12, the boundary from the boundary where the partition wall 1 has an intermediate thickness to the thickest partition wall 1 to the outermost periphery was measured with calipers or the like. The area ratio of the outer peripheral region 12 was determined by the area of the outer peripheral region / the entire cross-sectional area.

(Comparative Example 1)
In the same manner as in the example, a honeycomb structure 10 in which the partition wall 1 had the same thickness in all the regions (the partition wall thickness in the central region 11 and the outer peripheral region 12 was the same) was produced.

(Comparative Example 2)
In the same manner as in the example, a honeycomb structure 10 having no transition region 13 and having an opening ratio of the outer peripheral region 12 smaller than that of the central region 11 was produced.

(Comparative Example 3)
In the same manner as in the example, a honeycomb structure 10 having no transition region 13 and having an opening ratio of the outer peripheral region 12 of 1.15 times that of the central region 11 was manufactured.

(Comparative Example 4)
A honeycomb structure 10 was manufactured in which the partition wall thickness in the outer peripheral region 12 was smaller than the partition wall thickness in the central region 11 and the cell pitch in the outer peripheral region 12 was smaller than the cell pitch in the central region 11.

(Comparative Example 5)
A honeycomb structure 10 in which the aperture ratio of the outer peripheral region 12 is 0.79 times the aperture ratio of the central region 11 and the size of the aperture ratio is the central region> the transition region> the peripheral region is manufactured. .

(Comparative Example 6)
In the same manner as in the example, a honeycomb structure 10 in which the opening ratio of the outer peripheral region 12 was 0.97 times that of the central region 11 was manufactured.

(Comparative Example 7)
In the same manner as in the example, a honeycomb structure 10 having an aperture ratio of the outer peripheral area 12 of 0.96 times that of the central area 11 was manufactured.

(Measurement method of pressure loss)
Exhaust gas was passed through the sample (honeycomb structure 10) using an engine (8L / 6 cylinder), the exhaust gas pressure at the front and rear stages of the sample was measured, and the pressure loss was calculated. Table 1 shows the pressure loss ratio based on Comparative Example 1. If the pressure loss ratio (pressure loss ratio) is smaller than 1, it indicates that the pressure loss is lower than that of Comparative Example 1.

(Purification rate measurement method)
The obtained honeycomb structure was canned in an exhaust pipe of a gasoline engine having a displacement of 2.0 L. HC emissions by sampling exhaust gas from a pipe connected to the exhaust pipe during travel in exhaust gas regulation mode (JC-08), storing it in a bag called a bag, and passing the accumulated exhaust gas through an analyzer after travel Was measured (according to the provisions of JC-08). The purification performance was determined as the ratio of the reciprocal of the HC emission. Table 1 shows the purification performance ratio based on Comparative Example 1. If the purification performance ratio is greater than 1, it indicates that the purification performance is improved as compared with Comparative Example 1.

(result)
In Examples 1 and 2, the transition region 13 was not provided, but the partition wall of the outer peripheral region 12 was thick and the cell pitch was large, so that the pressure loss was lower than that of Comparative Example 1 and the purification performance was improved. . Of Examples 3 to 17 having the transition region 13, Examples 5 to 16 in which the transition region was 5 to 30% improved the purification performance ratio, and the pressure loss ratio was more preferable. In Examples 5 to 13 in which the transition region was 5 to 20%, the purification performance ratio was further improved and the pressure loss ratio was also improved. Among them, Examples 8 to 13 in which the transition region was 10 to 20% had particularly good purification performance ratios.

  The honeycomb structure of the present invention is particularly effective for exhaust gas purification of a diesel engine having a relatively low exhaust gas temperature. In addition to the honeycomb structure for the DPF front stage, SCR (Selective Catalytic Reduction) for NOx purification in exhaust gas. It can be effectively used as a base material for a catalyst and a diesel oxidation catalyst. In addition, gasoline engines that are relatively hot exhaust gas are also effectively used for exhaust.

1: partition wall, 1a: first partition wall (thin wall), 1b: second partition wall (thick wall), 1c: intermediate partition wall, 2: cell, 10: honeycomb structure, 11: central region, 12: outer peripheral region , 13: transition region, 13a: width of the transition region, 15: central axis.

Claims (4)

A plurality of cells communicating with each other in parallel between the two end faces are formed by the plurality of partition walls,
A central region including a central axis is formed by a first partition wall having a first thickness on a plane perpendicular to the communication direction of the cells.
An outer peripheral region outside the central region is formed by a second partition wall having a second thickness greater than the first thickness;
A cell pitch in at least one direction of the outer peripheral region is larger than a cell pitch of the central region;
A honeycomb structure in which the cells in the central region are square cells, and the cells constituting the outer peripheral region have an opening ratio of 1.00 to 1.10 times that of the cells constituting the central region. . A transition region formed by an intermediate partition wall having an intermediate thickness between the first thickness and the second thickness between the central region and the outer peripheral region;
The cell constituting each of the outer peripheral region and the transition region has an aperture ratio that is 1.00 to 1.10 times that of the cell constituting the central region, and the size of the aperture ratio is The honeycomb structure according to claim 1, wherein the center region ≦ the transition region ≦ the outer peripheral region.   The honeycomb structure according to claim 2, wherein an area of the transition region is 5 to 35% of the entire surface in a plane perpendicular to the communication direction.   The honeycomb structure according to claim 2 or 3, wherein the central region, the transition region, and the outer peripheral region are formed concentrically on a plane perpendicular to the communication direction.

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