JPH0558773B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is a cordierite honeycomb structure catalyst carrier, which is used in particular as a catalyst carrier for purifying automobile exhaust gas.It has low thermal expansion, excellent thermal shock resistance, easy catalyst support, and heat resistance after catalyst support. The present invention relates to a honeycomb structure catalyst carrier having excellent impact resistance and a method for producing the same. (Prior art and its problems) With the progress of industrial technology in recent years, the demand for materials with excellent heat resistance and thermal shock resistance has increased. In particular, thermal shock resistance is one of the important properties of ceramic honeycomb catalyst carriers used in automobile exhaust gas purification devices, and can prevent rapid heat generation due to the catalytic reaction of unburned hydrocarbons and carbon monoxide in the exhaust gas, and stop the engine from starting. High thermal shock resistance is required to withstand thermal stress caused by temperature differences that occur within the honeycomb structure due to temperature changes due to rapid heating and cooling. There are strong demands associated with driving. This thermal shock resistance is expressed by the rapid heating and cooling durability temperature difference, and it has been found that the durability temperature difference is inversely proportional to the thermal expansion coefficient among the characteristics of honeycomb, and the smaller the thermal expansion coefficient, the larger the durability temperature difference. It is known that in a honeycomb structure, the contribution rate in the direction perpendicular to the flow path is particularly large. Furthermore, in order to support the catalyst material, it has conventionally been necessary to coat the cell surface of the cordierite honeycomb structure with γ-alumina having a large specific surface area. High specific surface area materials and catalyst support are important properties required for cordierite honeycomb catalyst supports, and these are required for cordierite honeycomb structures for mass production of cordierite honeycomb catalysts. Porosity has been required as a means to solve this problem. In addition, honeycomb catalysts support a high specific surface area material such as activated alumina, which has a much higher thermal expansion coefficient on the surface of a low-expansion cordierite material. It is not possible to improve the thermal shock resistance of That is, there is a need for a technique that minimizes the increase in thermal expansion caused by supporting a material with a high specific surface area. It has been known that cordierite ceramic exhibits low expansion properties, for example, as described in U.S. Patent No.
As disclosed in Specification No. 3885977 (Japanese Unexamined Patent Publication No. 75611/1983), the coefficient of thermal expansion between 25°C and 1000°C is 11×10 ^-7 (1/°C) in at least one direction.
Smaller oriented cordierite ceramics are known, and the planar orientation caused by platy clays such as kaolin and laminated clays is described as the cause of this orientation. As shown in the example, the characteristic of the system using silica is that the coefficient of thermal expansion in the flow path direction (A axis) of the honeycomb structure is 0.62 to 0.78 × 10 ^-6 /℃. Direction perpendicular to the road (B axis)
The coefficient of thermal expansion is 1.01 to 1.08 × 10 ^-6 /℃, which is a very large difference between the A-axis and B-axis thermal expansion coefficients, and a low expansion of the B-axis thermal expansion coefficient, which substantially contributes to thermal shock resistance, has been achieved. It had not been done. Also, U.S. Patent No. 3950175 (Japanese Unexamined Patent Publication No.
-75612), by replacing part or all of the talc or clay in the raw material with a silica or silica alumina source raw material such as pyrophyllite, kyanite, quartz, or fused silica. It is disclosed that cordierite-based porous ceramics having pores with a diameter larger than 10 μm can be obtained. However, although this document discloses a composition that uses fused silica as a silica raw material and has many large pores of 10 μm or more, there is no description of the low expansion composition that is the objective of the present invention, and low expansion has not been achieved. I wasn't there. Furthermore, Japanese Patent Application Laid-Open No. 53-82822 discloses that by setting the average particle size of talc to 5 to 150 μm,
It is disclosed that a low expansion of 1.6×10 ^-6 /℃ or less can be obtained between 25 and 1000℃, but it is 0.9−6 /℃ between 25 and 1000℃.
There is no description of a composition that exhibits low expansion of less than 0 ^-6 /°C, and low expansion is still insufficient. Furthermore, the inventors' earlier patent application filed in 1983-
No. 183904 describes a combination of high-purity amorphous silica and fine alumina based on the use of fine talc of 5 μm or less for the purpose of densification with a porosity of 30% or less. A low expansion of less than 0.3 x 10 ^-6 /°C was not achieved between the two, and the low expansion was still insufficient. Regarding catalyst support, Japanese Patent Publication No. 51-44913 discloses that ceramic powder is deposited and fired on the thin wall surface of a honeycomb structure made of ceramic material, and the pore diameter is 5 μm.
It is disclosed that a surface layer having a pore volume of 0.1 cm ³ /g or more is formed to improve contact support properties. However, this method requires a step of applying ceramic powder, resulting in a significant increase in cost, and also has the disadvantage that it is difficult to provide fine pores of 0.5 to 5 μm as shown in the present invention. Furthermore, in Japanese Patent Application Laid-Open No. 58-14950, when coating a cordierite honeycomb structure with activated alumina, which is a material with a high specific surface area, an organic substance such as methyl cellulose is pre-coated to form microcracks in the cordierite honeycomb structure. discloses improvement in thermal shock resistance of cordierite honeycomb catalysts by infiltration of activated alumina into the catalyst. However, the adhesion between the high specific surface area material such as activated alumina and the cordierite honeycomb carrier deteriorated, and the coating layer was prone to peeling off. Another drawback was that the number of man-hours involved in coating increased, resulting in a significant increase in costs. An object of the present invention is to eliminate the above-mentioned problems and provide a cordierite honeycomb structure catalyst carrier having excellent heat resistance and thermal shock resistance, and a method for producing the same. Another object of the present invention is to provide a catalyst carrier with a cordierite honeycomb structure that exhibits less deterioration in thermal shock resistance by improving the catalytic support and supporting a material with a high specific surface area having a larger coefficient of thermal expansion than that of a cordierite carrier and a catalyst component, and a method for producing the same. This is what we are trying to provide. (Means for Solving the Problems) The cordierite honeycomb structure catalyst carrier of the present invention has a chemical composition of the main component of SiO ₂ 42 to 56 on a weight basis.
%, Al ₂ O ₃ 30-45%, MgO 12-16%, the main component of the crystal phase is cordierite, and the porosity of the honeycomb structure exceeds 30%.
42% or less, the total pore volume of pores with a diameter of 0.5 to 5 μm is 40% or more of the total pore volume, and the total volume of pores with a diameter of 10 μm or more is 30% or less of the total pore volume,
The coefficient of thermal expansion of the honeycomb structure between 40 and 800℃ in the flow path direction (A axis) is 0.3 × 10 ^-6 /℃ or less, and the thermal expansion coefficient in the direction perpendicular to the flow path (B axis) between 40 and 800℃ It is characterized by an expansion coefficient of 0.5×10 ^-6 /°C or less. In the method for producing the cordierite honeycomb structure catalyst carrier of the present invention, the chemical composition of the main components is based on weight.
_SiO2 42-56%, _{Al2O3 30-45} %, MgO12-16%
Talc with an average particle size of 5 to 15 μm, alumina with an average particle size of 2 μm or less, high-purity amorphous silica with an average particle size of 2 μm or less, and other cordierite forming raw materials are mixed together, and an organic binder is added to this mixture. and a plasticizer, mixed and kneaded to make it extrudable, and after extrusion molding into a honeycomb structure, 1350-1440
It is characterized by being fired at a temperature of °C. (Function) Low expansion can be obtained in the present invention because of the use of high-purity amorphous silica, the reaction system is significantly different from the cordierite formation reaction process of talc, kaolin, and alumina, and the cordierite crystallization stage shifts to the high temperature side. However, this is because it is possible to obtain domains with a maximum diameter of 20 μm or more in which the preferable cordierite crystal orientation, that is, the C-axis crystallization direction of the cordierite crystals are aligned in the same direction. Furthermore, when the average length of the cordierite crystal in the C-axis direction is 1 to 5 μm, the aspect ratio of the C-axis/A-axis of the cordierite crystal is more than 80%.
A microstructure with significantly developed euhedral cordierite crystals of 1.5 or higher is obtained. Furthermore, as a feature of this microstructure, the amount of microcracks is not significantly different from that of talc, kaolin, and alumina-based cordierite materials;
Many of the microcracks grow along the C-axis direction of the cordierite crystals within the domain structure, and the expansion of the microcracks is reduced because they absorb thermal expansion in the a-axis and b-axis directions of cordierite, which expands positively. This is thought to be due to the fact that the honeycomb structure has a lower expansion rate due to its larger contribution to . If fine activated alumina is used in a raw material system that does not use high-purity amorphous silica, the coefficient of thermal expansion will significantly increase, so the combination of high-purity amorphous silica and fine activated alumina is essential to achieve low expansion in the present invention. . Low expansion is achieved by changing the chemical composition of the honeycomb structure.
42-56% by weight in _SiO2 , preferably 47-53% by weight,
30-45% by weight, preferably 32-38% by weight in Al ₂ O ₃
It is suitable that the amount of MgO is 12 to 16% by weight, preferably 12.5 to 15% by weight, and even if unavoidably mixed components such as TiO ₂ , CaO, KNaO, Fe ₂ O ₃ are contained in a total amount of 2.5% by weight or less. good. It is preferable that the crystal phase consists essentially of cordierite crystals, and the amount of cordierite crystals is 90
At least % by weight of mullite and spinel (including saphirin) as other crystals contained. Further, in the present invention, the supported number of catalyst carriers has excellent thermal shock resistance by improving the supporting characteristics of the high specific surface area material, and the reason for this is described below. Concerning the catalyst supporting properties of high specific surface area materials such as activated alumina, it has been pointed out that there is a correlation with water absorption and porosity, but this time it has been pointed out that there is a correlation between water absorption and porosity. It has become clear that this significantly contributes to the loading performance. In addition, it was found that pores of 10 μm or more, which were conventionally introduced into cordierite supports to maintain porosity, actually deteriorated the catalyst support and further increased the variation in the amount supported. The reason for the contribution of pores of 0.5 to 5 μm is thought to be that the deposition rate is maximum for pore diameters in this range due to the particle size of high specific surface area materials such as activated alumina and the capillary water absorption phenomenon. In addition, for pores of 10 μm or more, it is thought that the amount supported will vary due to the intrusion of the high specific surface area material into the surface pores. A correlation between catalyst support and porosity was also observed, and the porosity
If it is less than 30%, the catalyst supporting property deteriorates. On the other hand, 0.5~
Maintaining the 5 μm pore volume ratio and increasing the porosity improves catalyst support, but it degrades mechanical strength, another important property required for honeycomb catalysts. It was newly discovered that pores of 10 μm or more play an important role in thermal shock resistance after support. The high specific surface area activated alumina particle size commonly used to maintain catalytic activity has a particle size of 5 to 10 μm. Therefore, although the adhesion rate of activated alumina is low, these activated alumina particles easily enter pores of 10 μm or more, and in particular, enter into the inside of the honeycomb partition walls, resulting in a significant increase in thermal expansion of the carrier. Therefore, pores of 10 μm or more, which have been introduced to improve catalyst support, are
It has become clear that this is a cause of undesirable effects in terms of both catalyst support properties and thermal shock resistance after support. The reasons for limiting the numerical values in the present invention will be explained below. If the porosity is less than 30%, the catalyst supporting property will deteriorate, and if it exceeds 42%, the strength will decrease and the thermal shock resistance after supporting the catalyst will deteriorate.
It was limited to 42% or less. If the total pore volume of pores with a diameter of 0.5 to 5 μm is less than 40% of the total pore volume, catalyst support will deteriorate, so the pore volume is limited to 40% or more, and the diameter
The total pore volume of pores larger than 10 μm is 30% of the total pore volume.
If it exceeds 30%, the catalyst support will deteriorate, the amount of support will vary widely, and the thermal shock resistance will deteriorate.
Limited to the following. In addition, if the total pore volume of pores with a diameter of 0.5 to 5 μm is 50% or more of the total pore volume, the diameter
The total pore volume of pores larger than 10 μm is 20% of the total pore volume.
It is preferable to have the following. The coefficient of thermal expansion between 40 and 800℃ exceeds 0.3×10 ^-6 /℃ in the flow path direction (A axis) of the honeycomb structure, and 0.5× in the direction perpendicular to the flow path (B axis) of the honeycomb structure.
If it exceeds 10 ^-6 /°C, the thermal shock resistance deteriorates in any case, so the A-axis direction was limited to 0.3 x 10 ^-6 /°C or less, and the B-axis direction was limited to 0.5 x 10 ^-6 /°C or less. Regarding the particle size of the talc used in the production method, if the average particle size is less than 5 μm, the coefficient of thermal expansion will increase, and if the average particle size exceeds 15 μm, the above-mentioned pore volume limit cannot be met, resulting in poor catalyst support. The thickness was limited to 5 to 15 μm because of the deterioration of the thickness. Note that the talc particle size preferably has an average particle size of 7 to 12 μm. The alumina particle size was limited to an average particle size of 2 μm or less because the coefficient of thermal expansion increases if the average particle size exceeds 2 μm. When the average particle size of silica particles exceeds 12 μm, the coefficient of thermal expansion in the direction (B axis) perpendicular to the flow path of the honeycomb structure increases, the porosity also increases, and the above-mentioned limit on the amount of pores cannot be met. Since the supporting property deteriorates, the thickness was limited to 12 μm or less. Note that the silica particle size is preferably an average particle size of 8 μm or less. Further, when crystalline silica is used as the silica raw material, the thermal expansion coefficient increases and the porosity also increases, so the use of amorphous silica was limited. Kaolin particle size has an average particle size of 2 μm or less,
It is preferable to use talc having an average particle diameter of 1/3 or less because the orientation of cordierite crystals is promoted and low expansion can be achieved. (Example) An actual example will be described below. Example 1 Raw materials with chemical analysis values and particle sizes shown in Table 1 were
The mixtures were prepared according to the proportions of Nos. 1 to 35 in the table, and after adding a plasticizer, they were kneaded to obtain extrusion moldable clay. Next, the clay of each batch was molded by a known extrusion method to form square cells with a rib thickness of 152 μm and a cell count of 62 cells per square centimeter, a diameter of 93 mm, and a height of 93 mm.
It was molded into a 100mm cylindrical honeycomb structure. After drying the honeycomb structure, it is fired at the maximum temperature shown in Table 2, and the characteristics of the sintered body are the thermal expansion coefficients of the A and B axes,
Porosity, pore distribution, cordierite crystal, and thermal shock resistance were evaluated. The evaluation results are also shown in Table 2. Note that the average particle diameters in Table 1 were set using Sedigraph.

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[Table] * Uses low soda alumina ** Uses crystalline silica *1 Mercury intrusion method Total pore volume equivalent value (cordierite true specific gravity is 2.52)
*2 Quantitative value using X-ray diffraction ZnO internal standard *3 Example of durability temperature when put into an electric furnace, held for 30 minutes, and taken out to room temperature A coating slurry 20 having a solid content of 25% was prepared by using 70% by weight of γ-alumina having an average particle diameter of 10 μm, 25% by weight of ceria powder, 5% by weight of alumina sol, and dilute nitric acid as a PH adjuster. The honeycomb structures of test numbers shown in Table 3 in Example 1 were each immersed for 3 minutes, excess slurry was blown out in an air stream, and dried at 50°C. After performing the steps of soaking and drying the slurry three times each.
It was fired at 650℃. The supported amount was determined by date piing a total of three times based on the weight after firing, and the thermal shock resistance temperature of the cordierite honeycomb structure after being supported is also shown in Table 3.

[Table] Based on the obtained results, Figure 1 shows the amount of catalyst supported and
Figure 2 shows the relationship between the proportion of pore volume of 0.5 to 5 μm in the total pore volume, and Figure 3 shows the relationship between the amount of catalyst supported and the proportion of pore volume of 10 μm or more in the total pore volume. The relationship between the A-axis thermal expansion coefficient and thermal shock resistance temperature is shown in FIG. 4, and the relationship between the B-axis thermal expansion coefficient and thermal shock resistance temperature is shown in FIG. From the above results, test No. 2-5, 8-13, 15, 17, 19-34 whose thermal expansion coefficient is within the range limited by the present invention
Comparative test outside the scope of the present invention〓No. 6, 7,
It was found that the thermal shock resistance was higher than that of 14, 16, and 18, and that the thermal shock resistance was good. In addition, from Table 3 showing the relationship between the pore distribution, the amount of catalyst supported, and the thermal shock resistance after supporting, it is clear that the total pore volume of pores with a diameter of 0.5 to 5 μm, which is the limited range of the present invention, is It was found that if the total volume of pores with a diameter of 10 μm or more and 40% or more of the volume was 30% or less of the total pore volume, the amount of catalyst supported would be good and the thermal shock resistance after catalyst support would be high. Example 3 Several types of samples among the samples shown in Table 2 were prepared in the same manner as in Example 1, and the minimum domain major axis, average cordierite crystal length, crystal mass ratio with aspect ratio of 1.5 or more, honeycomb I of cordierite crystal on wall surface (plane parallel to honeycomb extrusion direction)
The ratio [I(110)/{I(110)+I(002)}] was determined respectively. The crystals are shown in Table 4. In Table 4, the minimum domain major axis of each sample is
It was determined from the length of the minimum domain that could be confirmed from the SEM photograph. In addition, the cordierite crystal length and the ratio of the amount of crystals with an aspect ratio of 1.5 or more were determined by randomly selecting cordierite crystals from the SEM photograph of each sample, measuring the length and width of each crystal, and calculating the aspect ratio. Ta.

[Table] *3 Cordierite euhedral crystals have many unclear parts and few domains that can be determined.
From the results in Table 4, in some samples of the present invention, the minimum domain major axis is 20 μm or more, the average length of cordierite crystals is 1 to 5 μm, and the aspect ratio is
It was found that the crystal content ratio of 1.5 or more was in the range of 80% or more, and these ranges were found to be the preferred ranges in the present invention. Furthermore, it was found that the preferable range of the I ratio of the honeycomb wall surface is 0.78 or more. In addition, Fig. 5 a, b shows 50x and 2000x SEM photographs of Test No. 31 (invention), and Fig. 6 a, b show 50x and 2000x SEM photographs of Test No. 35 (reference example). Showed the photo. Furthermore, Fig. 7 shows the information shown in Fig. 5 a.
Diagrams are shown to explain each region of the SEM photograph. From Fig. 5a, b and Fig. 7, in the case of sample No. 31 of the present invention, long columnar cordierite euhedral crystals with an average length of 3.5 μm extending in the C-axis direction are extremely developed. It can be seen that domains with a major axis of 20 μm or more are formed. Also, the aspect ratio is 1.5
The above crystals account for 85% of the total, and many of the microcracks are also aligned in the C-axis direction of the crystal within the domain. In the 50x SEM photograph shown in Figure 5a, there are some areas where the domains are not clear, but if you enlarge that area, you can confirm the euhedral crystals and domains. In addition, large domains have a long axis of 100 μm or more, making it difficult to confirm with SEM. In contrast, sample No. 35 shown in Figure 6 a and b
In the reference example, cordierite euhedral crystals are not observed in most parts, and the average length of the euhedral crystals is 0.8 μm. Therefore, the formation of relatively small domains (major axis of 10 μm or more) is only observed in a small portion. The 2000x photograph shown in Figure 6b shows an area where euhedral crystals are relatively well-developed, but even here there are only a few crystals with an aspect ratio of 1.5 or more, accounting for only 30% of the total. Microcracks also exist, but their relationship with cordierite crystals is not clear. Further, FIGS. 8a and 8b show SEM photographs of Test No. 31 (invention) at room temperature and 800° C. in the same field of view. By comparing Figure 8a and b, it can be seen that the microcracks that are open at room temperature are almost completely closed at 800℃, which indicates that the microcracks contribute to the low expansion of the cordierite honeycomb. It shows that you are doing it. Furthermore, Fig. 9 shows Test No. 31 (present invention) and Test No.
The thermal expansion hysteresis curve of No. 35 (reference example) up to 1200℃ is shown. From Figure 9, the maximum hysteresis amount (the maximum value of the difference in coefficient of thermal expansion at the same temperature between the heating expansion curve and the cooling contraction curve) for Test No. 31 is 0.086%, and the maximum hysteresis amount for Test No. 35 is 0.068%. It is.
The magnitude of the maximum hysteresis amount is thought to represent the amount of microcracks and the magnitude of their contribution to low expansion, and no large difference was observed in the amount of microcracks between No. 31 and No. 35 in microstructural observation. This shows that No. 31 has a greater effect of microcracks on reducing expansion. (Effects of the Invention) As is clear from the detailed explanation above, according to the cordierite honeycomb structure catalyst carrier and the method for producing the same of the present invention, the cordierite honeycomb structure catalyst carrier of the present invention can be cordierized to have a predetermined porosity, pore distribution, and coefficient of thermal expansion. By adjusting the ELITE honeycomb catalyst carrier, the thermal shock resistance of the catalyst carrier is improved, and the catalyst support property of the catalyst is improved.Thermal shock resistance is improved by supporting a high specific surface area material with a higher coefficient of thermal expansion than the cordierite carrier and the catalyst component. A cordierite honeycomb structure catalyst carrier with little deterioration can be obtained.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the amount of catalyst supported and the proportion of the pore volume of 0.5 to 5 μm in the total pore volume, and Figure 2 is the graph showing the relationship between the amount of catalyst supported and the proportion of the pore volume of 10 μm or more in the total pore volume. Graph showing the relationship with the ratio, 3rd
The figure is a graph showing the relationship between the coefficient of thermal expansion on the A axis and the thermal shock resistance temperature, Figure 4 is a graph showing the relationship between the coefficient of thermal expansion on the B axis and the thermal shock resistance temperature, and Figure 5 a and b are graphs for Test No. 31. 50x and 2000x showing the structure of the crystal
SEM photographs, Figures 6a and b are 50x and 2000x SEM photographs showing the structure of the crystal of test No. 35, and Figure 7 is a SEM photograph for explaining each region of the SEM photograph shown in Figure 5a. Figures 8a and 8b show the crystal structure at room temperature and 800°C in the same field of view in Test No. 31.
The SEM photograph, FIG. 9, is a diagram showing the thermal expansion hysteresis curves of Test No. 31 and No. 35 up to 1200°C.

Claims (1)

[Claims] 1. The chemical composition of the main component is SiO ₂ 42 to 56 on a weight basis.
%, Al ₂ O ₃ 30-45%, MgO 12-16%, the main component of the crystal phase is cordierite, and the porosity of the honeycomb structure exceeds 30%.
42% or less, the total pore volume of pores with a diameter of 0.5 to 5 μm is 40% or more of the total pore volume, and the total volume of pores with a diameter of 10 μm or more is 30% or less of the total pore volume,
The coefficient of thermal expansion of the honeycomb structure between 40 and 800℃ in the direction of the flow path is 0.3×10 ^-6 /℃ or less, and the coefficient of thermal expansion between 40 and 800℃ in the direction perpendicular to the flow path is 0.5×10 ^-6 /℃ A cordierite honeycomb structured catalyst carrier characterized by the following: 2 The total pore volume of the pores with a diameter of 0.5 to 5 μm in the honeycomb structure is 50% or more of the total pore volume and the diameter
The cordierite honeycomb structure catalyst carrier according to claim 1, wherein the total pore volume of pores of 10 μm or more is 20% or less. 3. The cordierite honeycomb structure catalyst carrier according to claim 1, which has cordierite aggregates (domains) having a maximum diameter of 20 μm or more and arranged in the same direction as the C-axis crystallization direction of the cordierite crystals. 4 The average length of the cordierite crystals in the C-axis direction is 1 to 5 μm, and the C of the cordierite crystals is 80% or more.
The cordierite honeycomb structured catalyst carrier according to claim 1, wherein the axis/A-axis length ratio (aspect ratio) is 1.5 or more. 5. The cordierite honeycomb structure catalyst carrier according to claim 1, wherein the microcracks grow along the C-axis direction of the cordierite crystals within the domain structure. 6 Cordierite crystal I ratio of honeycomb wall surface (plane parallel to honeycomb extrusion direction) I=I(110)/I(110)+I
The cordierite honeycomb structure catalyst carrier according to claim 1, wherein (002) is 0.78 or more. 7 The chemical composition of the main component is SiO ₂ 42-56 on a weight basis
%, Al ₂ O ₃ 30-45%, MgO 12-16% with talc with an average particle size of 5-15 μm and an average particle size of 2 μm
The following alumina, high-purity amorphous silica with an average particle size of 2 μm or less, and other cordierite forming raw materials are mixed, and an organic binder and a plasticizer are added to this mixture, mixed and kneaded to make it plastic for extrusion molding. 1. A method for producing a cordierite honeycomb structure catalyst carrier, which comprises extruding the cordierite honeycomb structure into a honeycomb structure, followed by firing at a temperature of 1350 to 1440°C. 8. Claim 7, wherein the average particle diameter of talc among the cordierite-forming raw materials is 7 to 12 μm.
A method for producing a cordierite honeycomb structured catalyst carrier as described in 2. 9 Among the raw materials for forming cordierite, alumina
The method for producing a cordierite honeycomb structure catalyst carrier according to claim 7, wherein Na ₂ O is 0.12 or less. 10. The method for producing a cordierite honeycomb structure catalyst carrier according to claim 7, wherein the average particle diameter of high-purity amorphous silica among the cordierite forming raw materials is 8 μm or less. 11. The method for producing a cordierite honeycomb structured catalyst carrier according to claim 7, wherein the average particle diameter of kaolin in the cordierite forming raw material is 2 μm or less.