WO2025263482A1 - Honeycomb structure and reactor - Google Patents

Abstract

A honeycomb structure according to an embodiment of the present invention includes a honeycomb structural part having an outer wall and a partition wall that is disposed inside the outer wall and that partitions and forms a plurality of cells that extend from a first end surface to a second end surface and serve as fluid flow paths. The cell density of the plurality of cells is more than 233/cm² and 3100/cm² or less.

Description

Honeycomb structure and reactor

The present invention relates to a honeycomb structure and a reactor.

Conventionally, reactors have been known in which a fluid is introduced into a space containing a catalyst, and the catalyst promotes a reaction. For example, a honeycomb structure has multiple cells defined by partition walls, with the partition walls supporting a catalyst. This increases the contact area between the catalyst and the fluid, thereby promoting a reaction in an optimal manner, and is therefore widely used as a reactor for promoting a reaction to purify automobile exhaust gases (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2022-170972

In reactors using conventional honeycomb structures, mass transfer from the fluid to the partition wall surface (and ultimately the catalyst) can be insufficient, resulting in insufficient reaction times and yields. One factor that affects mass transfer is the contact area between the fluid and catalyst, and this contact area can be increased by increasing the cell density. However, increasing cell density tends to increase pressure loss inversely proportional to the square of the hydraulic diameter of the cell. For this reason, no detailed study has been conducted on honeycomb structures with high cell densities of 1,200 cpsi or more.

The primary objective of the present invention is to provide a honeycomb structure that can be suitably used as a reactor by improving mass transfer from a fluid to the partition wall surface, etc.

[1] According to one aspect of the present invention, there is provided a honeycomb structure including a honeycomb structure part having an outer wall and partition walls arranged inside the outer wall, extending from a first end face to a second end face, and defining a plurality of cells that serve as fluid flow paths, wherein the cell density of the plurality of cells is greater than 233 cells/ ^cm2 and not more than 3100 cells/ ^cm2 .
[2] In the honeycomb structure according to the above [1], the cell density of the plurality of cells may be more than 775 cells/cm ² and not more than 3100 cells/cm ² .
[3] The honeycomb structure according to the above [1] or [2] may further include a functional material supported on the partition walls.
[4] In the honeycomb structure according to the above [3], the partition walls may have a functional layer containing the functional material.
[5] In the honeycomb structure described in [3] above, the partition walls may be porous partition walls having pores, and the functional material may be supported inside the pores of the porous partition walls.
[6] In the honeycomb structure according to the above [3], the partition walls may be formed of a material containing the functional material.
[7] According to another aspect of the present invention, there is provided a reactor including the honeycomb structure according to any one of [1] to [6] above.

According to an embodiment of the present invention, by increasing the cell density of the honeycomb structure to a range exceeding 1500 cpsi, it is possible to suitably improve the transfer of material from the fluid to the partition wall surface (and, consequently, the catalyst).

1 is a schematic perspective view showing a configuration of a honeycomb structure according to one embodiment of the present invention. 1 is a graph showing the relationship between cell density and mass transfer parameter. 10 is a graph showing the relationship between cell density and a contraction dominance parameter. 1 is a schematic perspective view showing a configuration of a honeycomb structure according to one embodiment of the present invention. 1 is a schematic perspective view showing a configuration of a honeycomb structure according to one embodiment of the present invention. 4B is a schematic cross-sectional view of the honeycomb structure shown in FIG. 4A, taken along a plane parallel to the direction in which the fluid inlet channels extend. FIG. 4B is a schematic cross-sectional view perpendicular to the direction in which the fluid inlet channels of the honeycomb structure shown in FIG. 4A extend. FIG. 1 is a schematic cross-sectional view of a honeycomb structure according to one embodiment of the present invention, taken along a plane parallel to the direction in which fluid inlet channels extend. 1 is a graph showing the relationship between mass transfer parameters and catalytic reaction efficiency based on simulation results.

Embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Furthermore, to make the explanation clearer, the drawings may show the width, thickness, shape, etc. of each part more schematically than in the embodiments, but this is merely an example and does not limit the interpretation of the present invention. Identical elements will be given the same reference numerals, and duplicate explanations may be omitted.

A. Honeycomb Structure A-1. Overall Configuration of Honeycomb Structure Fig. 1 is a schematic perspective view showing the configuration of a honeycomb structure according to one embodiment of the present invention. The honeycomb structure 100A includes a honeycomb structure portion 10 having an outer wall 16 and partition walls 14 disposed inside the outer wall 16, extending from a first end face 10a to a second end face 10b and defining a plurality of cells 12 that serve as fluid flow paths. Depending on the purpose, a functional material can be supported on the honeycomb structure portion 10.

The number of cells 12 per unit area (hereinafter referred to as "cell density") in a cross section perpendicular to the extension direction (hereinafter also referred to as the "length direction") of the cells 12 of the honeycomb structure section 10 is typically 233 cells/ ^cm2 or greater than 1500 cpsi. Such a cell density can favorably improve mass transfer from the fluid to the partition wall surface, which can contribute to improved reaction efficiency. Specifically, mass transfer can be improved by increasing the contact area between the fluid and the partition wall. Mass transfer can also be improved by reducing the cell diameter to shorten the distance between the fluid and the partition wall. In the case of a simple flow path, mass transfer can be improved inversely proportional to the square of the hydraulic diameter of the cell. Therefore, mass transfer can be evaluated by a mass transfer parameter (= GSA/(Hd) ² ) using the geometric area (GSA, unit: ^cm2 / ^cm3 ) of the honeycomb structure section and the hydraulic diameter (Hd, unit: μm). A larger value of the mass transfer parameter indicates better mass transfer. Here, a graph in which the horizontal axis represents the cell density and the vertical axis represents the mass transfer parameter is shown in Fig. 2A. As shown in Fig. 2A, there is a generally positive correlation between the cell density and the mass transfer parameter, but the slope of the correlation increases significantly at cell densities of around 1500 cpsi. This indicates that mass transfer can be significantly improved when the cell density exceeds 1500 cpsi compared to when the cell density is 1500 cpsi or less.

The cell density is preferably greater than 310 cells/cm ² or 2000 cpsi, preferably greater than 387 cells/cm ² or 2500 cpsi, preferably greater than 465 cells/cm ² or 3000 cpsi.

In one embodiment, the cell density is preferably greater than 775 cells/ ^cm² or 5000 cpsi, and may be, for example, greater than 930 cells/ ^cm² or 6000 cpsi, or greater than 1085 cells/ ^cm² or 7000 cpsi. Such a cell density can reduce the degree of dominance of contraction pressure loss in the pressure loss of the honeycomb structure, thereby contributing to improved product design flexibility and/or reaction efficiency. Specifically, the pressure loss of the honeycomb structure is expressed as the sum of contraction pressure loss, pipeline pressure loss, and divergence pressure loss. The degree of dominance of contraction pressure loss can be evaluated using a "constriction dominance parameter," which is calculated by normalizing the difference between the contraction pressure loss (unit: Pa) and the divergence pressure loss (unit: Pa). A larger value of the contraction dominance parameter indicates a greater degree of dominance of contraction pressure loss. Figure 2B shows a graph plotting the cell density and contraction dominance parameter on the horizontal and vertical axes, respectively. As shown in Figure 2B, the contraction dominance parameter increases as the cell density increases up to around 5000 cpsi. However, as the cell density increases further, the contraction dominance parameter decreases, i.e., the influence of contraction pressure loss decreases. This is thought to have the following advantages for a reactor. Specifically, a decrease in the influence of contraction pressure loss can suppress the increase in the stoppage area that occurs at the cell inlet. This prevents a decrease in the contact area between the fluid and the reactor, and avoids a decrease in reaction efficiency. Furthermore, the reduced influence of contraction pressure loss can be used to increase the design freedom of the inlet portion of the reactor, allowing for more flexible design of the shape and layout of the piping, making it possible to optimize the efficiency of the entire reactor system.

The upper limit of the cell density may be, for example, 3100 cells/ ^cm² or 20000 cpsi or less. When the cell density is within the above-mentioned range, the effect of improving mass transfer can be obtained while preventing an excessive increase in pressure loss. On the other hand, when the cell density exceeds the above-mentioned upper limit, manufacturing may become difficult.

The GSA of the honeycomb structure 10 is preferably 3000 cm ² /cm ³ or more, more preferably 4000 cm ² /cm ³ or more, and may be 10000 cm ² /cm ³ or more or 12000 cm ² /cm ³ or more. The GSA is preferably 22000 cm ² /cm ³ or less, more preferably 20000 cm ² /cm ³ or less. The GSA is the value (S/V) obtained by dividing the total internal surface area (S cm ² ) of the multiple cells 12 by the total volume (V cm ³ ) of the honeycomb structure 10.

The hydraulic diameter (Hd) of the cells 12 is preferably 100 μm or more, more preferably 120 μm or more. The hydraulic diameter is preferably 720 μm or less, more preferably 600 μm or less, and may be 300 μm or less or 250 μm or less. The hydraulic diameter is a value calculated by Hd = 4A/B, where A ^μm2 is the cross-sectional area of the cell in a cross section perpendicular to the longitudinal direction of the honeycomb structure portion, and B μm is the perimeter of the cell.

The open area ratio (OFA) of the multiple cells 12 in a cross section perpendicular to the longitudinal direction of the honeycomb structure section 10 is preferably 30% or more, more preferably 40% or more, and even more preferably 50% or more. When the open area ratio is in the range above the lower limit, an increase in pressure loss can be suppressed. Furthermore, as a result of reducing the heat capacity, the energy required to heat the honeycomb structure section 10 can be reduced. From the viewpoint of strength, the open area ratio is preferably 95% or less. The OFA refers to the ratio of the "sum of the cross-sectional area of all cells 12" to the sum of the "sum of the cross-sectional areas of the partition walls 14 forming the honeycomb structure section 10" and the "sum of the cross-sectional areas of all cells 12" in a cross section perpendicular to the longitudinal direction of the honeycomb structure section 10.

The outer wall 16 typically has a cylindrical shape. The cross-sectional shape of the outer wall 16 perpendicular to the longitudinal direction of the honeycomb structure section 10 is preferably approximately rectangular, but may be other shapes such as other polygons (e.g., triangles, pentagons, hexagons), circles, or ellipses. In the illustrated example, the outer wall 16 is formed integrally with the partition walls 14. The outer wall 16 and the partition walls 14 may also be formed separately. The thickness of the outer wall 16 may be, for example, 0.1 mm to 10 mm.

The partition walls 14 are typically porous partition walls having a large number of pores. The porosity and pore size of the partition walls 14 can be set appropriately depending on the purpose. From the standpoint of strength, the porosity of the partition walls can be, for example, 70% or less, preferably 10% to 60%. The average pore size is preferably 90% or less, and more preferably 50% or less, of the thickness of the partition walls 14. The average pore size can be, for example, 280 μm or less, preferably 2.5 μm to 225 μm, and more preferably 5.0 μm to 180 μm. The porosity can be measured, for example, by mercury intrusion porosimetry. The average pore size is the value calculated by mercury intrusion porosimetry as the pore size that provides half the total pore volume.

The thickness of the partition walls 14 is preferably 5 μm or more, more preferably 25 μm or more, and even more preferably 50 μm or more. The thickness of the partition walls 14 is preferably 300 μm or less, more preferably 250 μm or less, and even more preferably 200 μm or less, and may be 160 μm or less, 150 μm or less, or 140 μm or less. When the thickness of the partition walls 14 is within the above range, the above cell density can be achieved while ensuring the desired strength of the honeycomb structure. For example, by forming the partition walls to a thickness of about 5 μm, a cell density of about 20,000 cpsi can be achieved.

Each of the multiple cells 12 is a space extending from the first end face to the second end face. In the illustrated example, the cross-sectional shape of each cell 12 perpendicular to the length direction is approximately rectangular, but it may also be other shapes such as polygonal, circular, or elliptical.

In one embodiment, the honeycomb structure 10 satisfies all of the above-mentioned preferred cell density, opening ratio, and partition wall 14 thickness. Such a honeycomb structure 10 can significantly improve material transfer from the fluid to the partition wall surface, thereby achieving improved reaction efficiency.

In the honeycomb structure 10, when the distance L between the first end face 10a and the second end face 10b (the length of the honeycomb structure 10 or the cell 12) is X cm and the total open area of the multiple cells 12 in a cross section perpendicular to the longitudinal direction is Y ^cm2 , Y/X is preferably 30 or more, more preferably 40 or more, and even more preferably 50 or more. When Y/X is equal to or greater than the above lower limit, the effect of suppressing an increase in pressure loss can be suitably obtained while ensuring the surface area of the cells 12. The upper limit of Y/X is not particularly limited, but may be, for example, 850,000 or less, or 50,000 or less. The distance L is preferably 0.3 cm to 5 cm, more preferably 0.3 cm to 4 cm, and even more preferably 0.3 cm to 3 cm. The total opening area Y of the plurality of cells 12 is preferably 5 cm ² to 250,000 cm ² , more preferably 10 cm ² to 250,000 cm ² , and even more preferably 100 cm ² to 160,000 cm ² .

Ceramics are a typical example of a material that constitutes the honeycomb structure 10. From the viewpoints of heat resistance and corrosion resistance, preferred examples of ceramics include cordierite, mullite, alumina, zirconia, silicon nitride, silicon carbide, silicon-silicon carbide composite materials, silicon carbide-cordierite composite materials, spinel, lithium aluminum silicate, and aluminum titanate. For example, cordierite, which has a low thermal expansion coefficient, is preferred from the viewpoint of reducing thermal stress. Furthermore, from the viewpoint of removing or utilizing the heat of exothermic reactions, silicon-silicon carbide composite materials, which have high thermal conductivity, are preferred. Materials that constitute the honeycomb structure 10 include paper, paper coated with a protective layer, synthetic paper, nonwoven fabric, and other materials other than ceramics, from the viewpoint of ease of manufacturing the honeycomb structure 10. The materials that constitute the honeycomb structure 10 can be used alone or in combination.

When a functional material is supported on the honeycomb structure 10, the functional material is typically supported on the partition walls 14 so that it can come into contact with the fluid passing through the cells 12. For example, the functional material can be supported on the partition walls 14 by forming a functional layer containing the functional material on the partition wall surface, by supporting the functional material inside the pores of the partition walls, or by forming the partition walls 14 using a material containing the functional material. Note that when a functional layer is formed on the partition wall surface, the above OFA is calculated by regarding the functional layer as part of the partition wall.

The functional material can be any material with an appropriate function depending on the purpose. Examples of functional materials include, but are not limited to, catalysts and adsorbents.

Specific examples of catalysts include, but are not limited to, ammonia production catalysts (Fe, Co, Ni, Mo, Ru, etc.), ammonia decomposition catalysts (Ni, Ru, etc.), fuel reforming catalysts (Ge, Mo, Sn, Re, Ir, Pt, etc.), methanation catalysts (Fe, Co, Ni, Mo, Ru, Rh, etc.), methanol synthesis catalysts (Co, Cu, Mo, Rh, Pd, W, Re, Ir, Pt, alkali metal alkoxides, etc.), turquoise hydrogen production catalysts (Fe, Co, Ni, molybdenum carbide, etc.), volatile organic compound (VOC) combustion removal catalysts (Pd, Pt, manganese oxide, Co-Ce composite oxide, perovskite oxide, etc.), and methylcyclohexane synthesis catalysts by toluene hydrogenation (Ni, Ru, Rh, Ir, Pt, etc.).

Specific examples of adsorbents include, but are not limited to, carbon dioxide adsorbents (porous carbon materials, zeolites, metal organic frameworks, amine compounds, alkali metal carbonates, etc.), moisture absorbents (zeolites, silica gel, activated carbon, alumina, silica, low-crystalline clay, amorphous aluminum silicate complexes, etc.), and adsorbents for allergens, odor components, etc. (zeolites, alumina zinc silicate, silica gel, activated carbon, silica, amorphous aluminum silicate complexes, magnesia, zinc oxide, titanium oxide, metal organic frameworks, etc.).

A-2. Modification 1
The honeycomb structure may be a joined body including a plurality of honeycomb structure parts arranged adjacent to each other in a direction perpendicular to the longitudinal direction and a joining layer joining the plurality of honeycomb structure parts. When joining a plurality of honeycomb structure parts satisfying the above cell density, the occurrence of cracks can be suitably prevented compared to when similar honeycomb structure parts are manufactured with a wider diameter.

Figure 3 is a schematic perspective view showing the configuration of a honeycomb structure including four honeycomb structure sections and bonding layers that bond them together.

The honeycomb structure 100B has four honeycomb structure sections 10 and a bonding layer 20 that bonds the honeycomb structure sections 10 together. Each honeycomb structure section 10 has an outer wall 16 and partition walls 14 that are arranged inside the outer wall 16 and extend from the first end face 10a to the second end face 10b to define a plurality of cells 12 that serve as fluid flow paths. Each honeycomb structure section 10 preferably has the same length, and is bonded so that the first end faces 10a are flush with each other and the second end faces 10b are flush with each other.

The honeycomb structure section 10 is as described above. Each honeycomb structure section 10 may have the same structure as the others, or may have a different structure. Specifically, in each honeycomb structure section 10, the arrangement, thickness, forming material, etc. of the partition walls 14 may be the same as or different from each other, and as a result, the cross-sectional shape, cell density, opening rate, etc. of the cells 12 may be the same as or different from each other.

The bonding layer 20 can be formed from any suitable bonding material. For example, a ceramic material with a solvent such as water added to form a paste can be used as the bonding material. The bonding layer 20 may contain the same ceramic as the outer wall 16 and/or partition wall 14. An outer wall can also be formed by applying the above-mentioned bonding material to the periphery of multiple bonded honeycomb structure sections. The thickness of the bonding layer 20 can be, for example, 0.1 mm to 5 mm.

A-3. Modification 2
The honeycomb structure may have a configuration including two or more honeycomb structure sections arranged with at least a portion spaced apart so that the inflow end faces or the outflow end faces face each other, when one of the first end face and the second end face is an inflow end face and the other is an outflow end face, a fluid inflow channel forming the inflow end face side space of the honeycomb structure section, one end being open and the other being closed, and a fluid outflow channel forming the outflow end face side space of the honeycomb structure section, one end being open and the other being closed. In the above configuration, the fluid inflow channel and the fluid outflow channel communicate with the plurality of cells at the inflow end face and the outflow end face of the honeycomb structure section, respectively.

In one embodiment, the two or more honeycomb structure sections are all formed from forming materials of the same composition and have partition walls of the same structure (resulting in the same cell density and opening ratio). In another embodiment, the two or more honeycomb structure sections may be formed from forming materials of different compositions and/or may have partition walls of different structures.

Figure 4A is a schematic perspective view showing the configuration of an example of a honeycomb structure having the above-mentioned configuration, Figure 4B is a schematic cross-sectional view (cross-sectional view taken along line A1-A1 in Figure 4A) parallel to the direction in which the fluid inlet channels of the honeycomb structure shown in Figure 4A extend, and Figure 4C is a schematic cross-sectional view (cross-sectional view taken along line A2-A2 in Figure 4B) perpendicular to the direction in which the fluid inlet channels of the honeycomb structure shown in Figure 4A extend.

The honeycomb structure 100C has opposing fluid inlet and outlet end faces 100a and 100b, and includes five honeycomb structure sections 10. Each honeycomb structure section 10 has an inlet end face 10c and an outlet end face 10d, and is arranged spaced apart from one another with the inlet end faces 10c facing each other, or with the outlet end faces 10d facing each other. The number of honeycomb structure sections included in the honeycomb structure is not limited to the illustrated example and can be set appropriately depending on the purpose. For example, the number of honeycomb structure sections included in the honeycomb structure can be set so that the total number of fluid inlet channels and fluid outlet channels is preferably 3 to 1,000, and more preferably 5 to 500.

The five honeycomb structure sections 10 are housed in a cylindrical can 110. Specifically, a buffer member 120 is arranged along the inner periphery of the can 110. Positioning members 130, each with recesses corresponding to the length of the honeycomb structure section 10, are arranged at predetermined intervals on both sides of the internal space of the buffer member 120. Plate-shaped holding members 140 are arranged on the top and bottom surfaces. Each of the five honeycomb structure sections 10 is fixed by fitting into the recesses of the positioning members 130. The can 110 and holding members 140 may be formed, for example, from a metal material such as stainless steel or a ceramic material such as ferrite. The buffer member 120 may be formed, for example, from a ceramic fiber such as alumina fiber or mullite fiber. This configuration allows the honeycomb structure sections 10 to be maintained in an optimally housed state even when subjected to external impact. However, the configuration of the honeycomb structure is not limited to the illustrated example. For example, the buffer members, positioning members, and/or retaining members may be omitted depending on the purpose.

The space between the opposing inlet end faces 10c constitutes the fluid inlet channel 30. Specifically, the fluid inlet channel 30 is defined by two inlet end faces 10c facing each other at a predetermined distance, or by the inlet end face 10c and the holding member 140, and a connecting member that connects them. One end of the fluid inlet channel 30 is open, and the other end is closed by providing a sealing portion 52. In the illustrated example, the positioning members 130 arranged on both side surfaces function as connecting members, but this configuration is not limited to this. For example, sealing portions may be provided at both ends in a direction perpendicular to the extension direction of the fluid inlet channel to serve as connecting members.

The space between the opposing outflow end faces 10d constitutes the fluid outflow channel 40. Specifically, the fluid outflow channel 40 is defined by two opposing outflow end faces 10d separated by a predetermined distance, or by the outflow end face 10d and the retaining member 140, and the connecting members (in the illustrated example, positioning members 130 arranged on both side faces) that connect them. One end of the fluid outflow channel 40 is open, and the other end is closed by the provision of a sealing portion 54.

The fluid inlet channel 30 communicates with multiple cells 12 at the inlet end face 10c, and the fluid outlet channel 40 communicates with multiple cells 12 at the outlet end face 10d. With this configuration, fluid that flows into the fluid inlet channel 30 from the open end flows into the cells 12 from the inlet end face 10c, flows out from the outlet end face 10d, transitions to the fluid outlet channel 40, and can flow out from the open end. In addition, two adjacent honeycomb structure sections 10 can share the fluid inlet channel 30 and/or the fluid outlet channel 40.

From the viewpoint of efficiently allowing fluid to flow in and out of the honeycomb structure 100C, it is preferable that the fluid inlet channel 30 and the fluid outlet channel 40 extend in opposite directions. The angle formed between the extension direction of the fluid inlet channel 30 (in other words, the direction from the open end toward the closed end) and the extension direction of the fluid outlet channel 40 (in other words, the direction from the open end toward the closed end) is, for example, in the range of 180°±30°, and preferably in the range of 180°±25°.

In the honeycomb structure 100C shown in Figures 4A to 4C, each honeycomb structure section 10 is arranged in parallel so that the distance between the opposing inflow end faces 10c or outflow end faces 10d is constant, forming a fluid inflow channel or a fluid outflow channel. Unlike the illustrated example, each honeycomb structure section 10 may be arranged obliquely relative to an adjacent honeycomb structure section 10 so that the distance between the opposing inflow end faces 10c or outflow end faces 10d gradually increases or decreases. For example, two opposing honeycomb structure sections 10 may be arranged so that the inflow end faces 10c or outflow end faces 10d are spaced apart at one end and in contact at the other end, thereby leaving one end open and the other closed.

The angle formed by the extension direction of the opposing inlet end face 10c and outlet end face 10d may be, for example, in the range of 0°±30°, and is preferably in the range of 0°±25°. When the angle is within the above range, a space-saving effect can be suitably achieved.

A-4. Modification 3
The honeycomb structure may be configured to be able to heat the honeycomb structure part. For example, the honeycomb structure may have a magnetic material supported on the honeycomb structure and a coil wiring arranged to surround the outer periphery of the outer wall. With this configuration, the honeycomb structure part can be induction heated by passing an AC current through the coil wiring.

A magnetic material with a maximum magnetic permeability of 10,000 or more is preferably used as the magnetic body. Specific examples of magnetic bodies include balance Fe-10% Si-5% Al by mass, 49% Co-49% Fe-2% V by mass, balance Fe-36% Ni by mass, and balance Fe-45% Ni by mass.

The magnetic material can be supported on the honeycomb structure, for example, by being placed within some of the cells, or by forming partition walls or bonding layers containing magnetic particles.

A-5. Manufacturing method of honeycomb structure The above honeycomb structure can be typically manufactured by a method including a molding step of extruding a molding material containing a ceramic raw material to obtain a honeycomb formed body, and a firing step of drying the honeycomb formed body and firing the resulting dried honeycomb body to obtain a honeycomb structure part.

In the above-mentioned molding process, the molding material is typically extruded from a die with slits formed that correspond to the partition walls of the honeycomb structure, to obtain a cylindrical honeycomb molded body with partition walls and outer walls that define the cells that serve as fluid flow paths. By selecting an appropriate die and jig shape, it is possible to control the shape and density of each cell, as well as the shape and thickness of the partition walls and outer walls. Furthermore, by adopting a brace structure, triangular cell configuration, etc., it is possible to achieve an optimal balance between cell density and strength.

The molding material typically includes a ceramic raw material. Examples of ceramic raw materials that can be used include powders of the aforementioned ceramics and raw material powders that will become the aforementioned ceramics upon firing (e.g., cordierite raw materials). The cordierite raw material is a raw material that will become cordierite upon firing. The cordierite raw material preferably has a chemical composition of 30% to 45% by mass of alumina (Al ₂ O ₃ ) (including aluminum hydroxide converted to alumina), 11% to 17% by mass of magnesia (MgO), and 42% to 57% by mass of silica (SiO ₂ ). The molding material may further include a binder, a pore-forming agent, a dispersant, water, an organic solvent, etc. Furthermore, by blending a functional material into the molding material, a honeycomb structure (specifically, partition walls and outer walls) formed from a material containing the functional material can be obtained. The porosity and pore size of the honeycomb structure can be controlled by appropriately selecting the types and amounts of the ceramic raw materials, binder, pore-forming agent, and dispersant.

The honeycomb formed body is dried to obtain a dried honeycomb body. Before drying, the honeycomb formed body may be cut to a predetermined length.

Methods for drying honeycomb formed bodies include, for example, hot air drying, microwave drying, dielectric drying, reduced pressure drying, vacuum drying, and freeze drying. These may be used alone or in combination of two or more. Of these, a drying method that combines hot air drying with microwave drying or dielectric drying is preferred, as it allows the entire honeycomb formed body to be dried quickly and uniformly.

The dried honeycomb body is fired to obtain a honeycomb structure. Any appropriate firing conditions can be used. The firing temperature is, for example, 1400°C to 1500°C. The firing time is, for example, 20 to 80 hours. Firing may be carried out continuously or in multiple stages at different temperatures. When firing in multiple stages, the firing time is the total of the firing times for each stage.

Before subjecting the dried honeycomb body to firing, the dried honeycomb body may be calcined. The calcination temperature may be determined, for example, according to the combustion temperature of the organic matter contained in the dried honeycomb body. The calcination temperature is, for example, 200°C to 1000°C. The calcination time is, for example, 10 hours to 100 hours. Note that calcination and firing may be carried out consecutively. Specifically, calcination may be carried out during the temperature rise process of firing.

If necessary, the above manufacturing method can further include a functional material loading step in which a functional material is loaded onto the honeycomb structure portion. The functional material loading step is preferably carried out after the firing step.

Any appropriate method can be used to support a functional material on a honeycomb structure. For example, a functional layer containing a functional material can be formed on the partition wall surfaces and/or pore inner surfaces by a method including: immersing a honeycomb structure in a functional material dispersion containing a functional material, a binder, and a dispersion medium to form a coating layer on the partition wall surfaces and/or pore inner surfaces; or flowing a functional material dispersion through the cells of the honeycomb structure to form a coating layer on the partition wall surfaces and/or pore inner surfaces; and drying the coating layer. When immersing a honeycomb structure in a functional material dispersion, the functional material dispersion adhering to the end faces and outer wall surfaces of the honeycomb structure after immersion can be removed by blowing, wiping, or the like. The drying temperature can be, for example, 120°C to 600°C. The formation of the functional layer (i.e., the formation and drying of the coating layer) can be performed only once or can be repeated multiple times. By repeating the process multiple times, the desired amount of functional material can be preferably supported on the honeycomb structure. In this way, partition walls carrying functional materials on the surface and/or inside the pores can be obtained.

The dispersion medium may include water, organic solvents (e.g., toluene, xylene, ethanol, n-butanol, ethyl acetate, butyl acetate, terpineol, dihydroterpineol, texanol, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether acetate, diethylene glycol monobutyl ether), and mixtures thereof.

A honeycomb structure having multiple honeycomb structure sections bonded via a bonding layer can be produced by a method that includes producing multiple honeycomb structure sections as described above, applying a bonding material to the outer walls of the honeycomb structure sections to form a coating layer, combining the multiple honeycomb structure sections via the coating layer to produce an assembly, and drying the assembly to turn the coating layer into a bonding layer. There are no particular restrictions on the bonding material, and materials used to form bonding layers in conventionally known honeycomb structures can be used.

A honeycomb structure including two or more honeycomb structure sections arranged with at least a portion spaced apart so that their inflow end faces or outflow end faces face each other, a fluid inflow channel, and a fluid outflow channel can be manufactured by a method that further includes arranging the two or more honeycomb structure sections in predetermined positions in a can body using buffer members, holding members, positioning members, pressing members, etc., as necessary. The manufacturing method can further include providing a plug at one end of the fluid inflow channel or the fluid outflow channel.

The method for fitting multiple honeycomb structure sections into predetermined positions in the can body is not particularly limited, and any known method can be used. For example, in addition to fastening methods using fitting such as clearance fitting, interference fitting, and shrink fitting, brazing, welding, diffusion bonding, etc. can also be used.

Alternatively, the honeycomb structure can be manufactured by a method that includes creating a honeycomb structure section in the shape of a rectangular pillar with a long cell length, and then slitting the resulting honeycomb structure section from opposing outer wall surfaces alternately in a direction intersecting the cell extension direction to provide slit sections. The slitting is performed so that a predetermined distance of the honeycomb structure section remains. This method can produce a honeycomb structure 100D, as shown in FIG. 5, in which two or more honeycomb structure sections 10 (six in the illustrated example) are integrally formed via remaining slit sections 62 that connect adjacent honeycomb structure sections 10 to each other. Since one end of the slit section 60 is open and the other end is closed, the slit section 60 can function as a fluid inlet channel 30 or a fluid outlet channel 40. The remaining slit sections 62 can also function as sealing sections.

B. Reactor The honeycomb structure described in Section A can be used as a reactor for carrying out various reactions. When the honeycomb structure itself does not have a configuration capable of heating the honeycomb structure portion, the reactor may include, in addition to the honeycomb structure, a heating device (e.g., an electric heater) arranged in contact with or in close proximity to the honeycomb structure. Heating the honeycomb structure can promote chemical reactions, adsorption/desorption reactions, etc.

[Trends of mass transfer parameters in simulation]
For a honeycomb structure including a honeycomb structure part in which a catalyst is supported on the partition walls, the total hydrocarbon (THC) conversion efficiency was simulated by varying the GSA of the honeycomb structure part and the hydraulic diameter of the cell, assuming vehicle driving under specified conditions. Figure 6 shows a graph in which the mass transfer parameters and the conversion efficiency obtained by the simulation are normalized and plotted on the X axis and the Y axis, respectively.

As shown in Figure 6, as the mass transfer parameter increased, the THC conversion rate (in other words, catalytic reaction efficiency) also increased.

The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, the configuration shown in the above-described embodiment can be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiment, a configuration that provides the same effects, or a configuration that can achieve the same purpose.

The honeycomb structure of the present invention can be suitably used as a variety of reactors.

10: Honeycomb structure portion, 10a: First end face, 10b: Second end face, 10c: Inlet end face, 10d: Outlet end face, 12: Cell, 14: Partition wall, 16: Outer wall, 30: Fluid inlet channel, 40: Fluid outlet channel, 100A-D: Honeycomb structure.

Claims (7)

a honeycomb structure portion having an outer wall and partition walls disposed inside the outer wall, extending from a first end face to a second end face, and defining a plurality of cells that serve as fluid flow paths;
A honeycomb structure, wherein the cell density of the plurality of cells is more than 233 cells/cm ² and not more than 3100 cells/cm ² . The honeycomb structure according to claim 1, wherein the cell density of the plurality of cells is more than 775 cells/cm ² and not more than 3100 cells/cm ² . The honeycomb structure according to claim 1, further comprising a functional material supported on the partition walls. The honeycomb structure according to claim 3, wherein the partition walls have a functional layer containing the functional material. the partition wall is a porous partition wall having pores,
The honeycomb structure according to claim 3 , wherein the functional material is supported inside the pores of the porous partition walls. The honeycomb structure according to claim 3, wherein the partition walls are formed from a material containing the functional material. A reactor comprising the honeycomb structure according to any one of claims 1 to 6.