JP5601957B2 - Aluminum titanate honeycomb structure - Google Patents

Description

  The present invention relates to an aluminum titanate honeycomb structure.

  In order to purify exhaust gas discharged from an internal combustion engine such as a diesel engine, a ceramic honeycomb filter that collects particulate matter such as fine carbon particles contained in the exhaust gas by passing the exhaust gas inside is used. ing. Conventionally, a ceramic honeycomb filter has been proposed in which a honeycomb structure made of a ceramic material such as cordierite is loaded with a high specific surface area material such as activated alumina and a catalytic metal such as platinum.

  In recent years, the use of aluminum titanate has been studied as a ceramic material constituting the honeycomb structure, and its industrial utility value is increasing.

  As a method for producing aluminum titanate, a method is known in which at least an aluminum source powder and a titanium source powder are contained, and a raw material mixture containing a silicon source powder, a magnesium source powder, or the like is formed and fired as necessary (for example, , See Patent Document 1). Further, as a raw material mixture, a material containing organic additives such as an organic binder and a pore former is used, and the green molded body of this raw material mixture is heated at 150 to 900 ° C. in an oxygen-containing atmosphere to add the organic material. A method of firing at 1300 ° C. or higher after removing an object is also known (paragraphs 0031 to 0032 of Patent Document 1).

WO05 / 105704 pamphlet

  In recent years, in order to improve the exhaust gas purification performance of ceramic honeycomb filters, the porosity of partition walls separating a plurality of cells is increased to ensure air permeability, and the exhaust and Many wall-flow honeycomb structures having a structure that passes through the partition walls have been studied.

  FIG. 5 is a partial cross-sectional view showing an example of a conventional wall flow type honeycomb structure. FIG. 5 shows a cross-sectional structure near the center of the honeycomb structure. As shown in FIG. 4, the honeycomb structure 20 has a structure in which a plurality of cells 22 (22 a and 22 b) are arranged side by side with a porous partition wall 24 therebetween. In addition, one of the openings at both ends of the cell 22 is plugged, and in the cell 22a, a plugged portion 26 is provided on the inlet side (end face F1 side) of the exhaust gas (arrow in the figure). In the cell 22b, a plugging portion 26 is provided on the exhaust gas outlet side (end face F2 side). In the honeycomb structure 20, since the cells 22 a and the cells 22 b are alternately arranged, the exhaust gas passing through the honeycomb structure 20 is exhausted after passing through the porous partition walls 24.

  In the honeycomb structure 20 having such a structure, the exhaust gas supplied to the inlet side easily flows in the vicinity of the central portion of the honeycomb structure 20, and as indicated by the arrows in the figure, the cells 22a close to the central portion. The amount of exhaust gas that flows into the interior and passes through the partition wall 24 increases. Therefore, the cell 22a closer to the center portion collects particulate matter such as fine carbon particles contained in the exhaust gas more frequently, and the particulate matter is clogged due to the accumulation of the particulate matter, or heat deterioration occurs. There is a problem that it is easy.

  The present invention has been made in view of the above-described problems of the prior art, and can make the flow of exhaust gas passing through the inside uniform, and can suppress local cell deterioration. The purpose is to provide.

  In order to achieve the above object, the present invention provides a porous partition wall disposed so as to form a plurality of cells communicating between two end faces, and an opening at each end of each of the plurality of cells. An aluminum titanate honeycomb structure comprising: a plurality of plugged portions that plug one side; and a catalyst layer containing a catalyst that is supported in a layered manner on a surface that forms pores of the partition wall, The surface position of the plugging portion formed in the cell in the center of the honeycomb structure on the cell inner side perpendicular to the cell communication direction is formed in the cell in the peripheral portion of the honeycomb structure. Provided is an aluminum titanate honeycomb structure that is located on the inner side of the cell than the surface position of the plugged portion.

  According to such an aluminum titanate honeycomb structure, the surface position of the plugged portion formed in the cell in the central portion is set to the cell inner side with respect to the surface position of the plugged portion formed in the peripheral cell. By doing, the passage resistance of the exhaust gas in the center cell can be increased as compared with the peripheral cell. By providing a gradient in the passage resistance in this way, the amount of exhaust gas flowing into the central cell can be suppressed, and the exhaust gas flow in the entire honeycomb structure can be made uniform. Moreover, it can suppress that only the cell of a center part deteriorates intensively by this, and can maintain the exhaust gas purification performance of a honeycomb structure for a long term.

  In the present invention, the surface position on the inner side of the cell perpendicular to the direction of cell communication is, among the two surfaces not in contact with the partition walls, of the plurality of plugged portions that plug each of the plurality of cells. It means the position of the surface on the inner side of the cell. The cell inner side means a side far from the end face and the center side in the cell communication direction. The other surface of the two surfaces not in contact with the partition wall of the plugged portion, that is, the surface outside the cell may be in a state where the surface position is aligned with the end surface of the honeycomb structure. It may be located on the inner side of the cell.

  In the aluminum titanate honeycomb structure of the present invention, the arrangement position of the plugging portions formed in the cells in the central portion of the honeycomb structure is the above-described cells formed in the cells in the peripheral portion of the honeycomb structure. You may be located in the cell inner side rather than the arrangement position of a plugging part.

  In the aluminum titanate honeycomb structure of the present invention, the length of the plugged portion formed in the cell in the central portion of the honeycomb structure is formed in the cell in the peripheral portion of the honeycomb structure. It may be longer than the length of the plugged portion. At this time, the difference between the maximum value and the minimum value of the length of the plurality of plugged portions is preferably 1 mm or more and 10 mm or less. Here, the length of the plugged portion is the length of the plugged portion in the cell communication direction.

  Thus, by adjusting one or both of the arrangement position and the length of the plugged portion, the surface position of the plugged portion on the cell inner side can be adjusted.

Furthermore, in the aluminum titanate honeycomb structure of the present invention, the catalyst is selected from the group consisting of a carrier coat made of activated alumina and Pt, Rh, and Pd dispersedly supported inside the carrier coat. and one or more precious metals, is contained in the carrier coating, cerium oxide, di-zirconia, and may include a one or more compounds selected from the group consisting of silica, the preferred.

  ADVANTAGE OF THE INVENTION According to this invention, the flow of the waste gas which passes through an inside can be equalize | homogenized, and the honeycomb structure which can suppress local deterioration of a cell can be provided.

FIG. 1 (a) is a perspective view showing an embodiment of the aluminum titanate honeycomb structure of the present invention, and FIG. 1 (b) is a partially enlarged view of FIG. 1 (a). 1 is a partial cross-sectional view showing a cross-sectional structure near the center of an aluminum titanate honeycomb structure according to an embodiment of the present invention. 1 is a partial cross-sectional view showing a cross-sectional structure near the center of an aluminum titanate honeycomb structure according to an embodiment of the present invention. It is the elements on larger scale which show the section structure of the partition of the aluminum titanate-like honeycomb structure concerning one embodiment of the present invention. FIG. 7 is a partial cross-sectional view showing a cross-sectional structure near the center of a conventional honeycomb structure.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

  Fig.1 (a) is a perspective view which shows suitable one Embodiment of the aluminum titanate honeycomb structure of this invention, FIG.1 (b) is the elements on larger scale of Fig.1 (a). 2 and 3 are partial cross-sectional views showing a cross-sectional structure in the vicinity of the center of the aluminum titanate honeycomb structure according to the embodiment of the present invention. FIG. 4 is a partially enlarged view showing the cross-sectional structure of the partition walls of the aluminum titanate honeycomb structure according to one embodiment of the present invention.

  As shown in FIG. 1A, the aluminum titanate honeycomb structure 10 has a cylindrical outer shape represented by an outer wall, and the inner structure forms a honeycomb structure. 1-4, the honeycomb structure 10 has a large number of pores arranged so that a plurality of cells 12 (12a and 12b) communicating between the two end faces F1 and F2 are formed. A porous partition wall 14, a plurality of plugging portions 16 plugging one of the openings at both ends of each of the plurality of cells 12, and the surface of the partition wall 14 forming the pores 15 are supported in layers. And a catalyst layer 18 containing a catalyst. As shown in FIGS. 2 and 3, in the honeycomb structure 10, the surface position of the plugging portion 16 formed in the central cell 12 on the cell inner side perpendicular to the communication direction of the cell 12. L (for example, the surface position L1) is located on the inner side of the cell from the surface position L (for example, the surface position L3) of the plugging portion 16 formed in the peripheral cell 12.

  As shown in FIGS. 2 and 3, the surface position of the plugging portion 16 in the central cell 12 is L1, and the surface position of the plugging portion 16 in the surrounding cells 12 is L2, from the side close to the central portion. In the case of L3, the cells are located on the inner side of the cell 12 in the order of L1, L2, and L3. In the honeycomb structure 10 shown in FIG. 2, the surface position L is adjusted by the length of the plugging portion 16, and in the honeycomb structure 10 shown in FIG. Thus, the surface position L is adjusted. By adjusting the surface position L of the plurality of plugged portions 16 as described above, the exhaust gas passage resistance in the central cell 12 can be made higher than that in the peripheral cell 12, and the central cell The amount of exhaust gas flowing into the gas 12 can be suppressed. Thereby, as shown by the arrows in FIG. 2 and FIG. 3, the flow of exhaust gas in the entire honeycomb structure 10 can be made uniform.

  Further, among the surface positions of the plurality of plugged portions 16, when the surface position on the innermost side of the cell 12 is L1, and the surface position on the outermost side of the cell 12 is L3, the surface position L1 and the surface position L3 The distance d is preferably 1 mm or more and 10 mm or less, and more preferably 1.5 mm or more and 5 mm or less. In the honeycomb structure 10 shown in FIG. 2, the value of the distance d corresponds to the difference between the maximum value and the minimum value of the lengths of the plurality of plugged portions 16. If the distance d is less than 1 mm, the effect of making the exhaust gas flow uniform tends to be reduced. If the distance d exceeds 10 mm, the exhaust gas passage resistance in the central cell 12 becomes too high, and the exhaust gas flow is not good. There is a tendency to be uniform.

  In the present invention, the surface position L of the plugging portion 16 formed in the central cell 12 is set to be closer to the inside of the cell than the surface position L of the plugging portion 16 formed in the peripheral cell 12. The adjustment of the surface position L of the plurality of plugging portions 16 needs to be performed on at least one side of the exhaust gas inlet side (end face F1 side) and the outlet side (end face F2 side). is there. In addition, since the effect of equalizing the flow of exhaust gas is more easily obtained, it is preferable that the above adjustment is performed at least on the outlet side (end face F2 side), and the inlet side (end face F1 side) and the outlet side ( It is more preferable that the above adjustment is performed on both of the end face F2 side. In addition, the adjustment state of the surface position L may be the same on the inlet side (end surface F1 side) and the outlet side (end surface F2 side), or may be different.

  In FIGS. 2 and 3, the surface position L of the plugging portion 16 of the cell 12 is gradually increased from the inner side of the cell from the center portion to the peripheral portion in three stages of the surface positions L1, L2, and L3. Although the case where the position is changed is shown, the present invention is not limited to this. For example, the surface position L2 is set to the same position as the surface position L1 or L3, and the surface positions L of a large number of plugged portions 16 are the same position, for example, the position is changed in two stages of the surface positions L1 and L3. It may be.

  The cross-sectional views shown in FIGS. 2 and 3 are partial cross-sectional views in the vicinity of the central portion of the honeycomb structure 10, and generally more cells 12 are formed as shown in FIG. In the above description, for convenience, the cell 12 in which the plugging portion 16 at the surface position L1 is formed is the central cell, and the cell 12 in which the plugging portion 16 at the surface position L3 is formed is the peripheral portion. Described as a cell. Therefore, in reality, the surface positions L of the plugging portions 16 of the cells 12 shown in FIGS. 2 and 3 are all the same in each of the end surfaces F1 and F2, and further to the peripheral portion than these cells. It is also preferable to adjust the surface position L of the plugging portion 16 of the arranged cell 12 so as to be located further outside the cell.

  In the honeycomb structure 10, the cells 12 a and 12 b serve as a flow path for fluid such as exhaust gas. As shown in FIGS. 1 to 3, one of the openings at both ends is plugged. 1-3, the cell 12a is open and the cell 12b is plugged, and at the opposite end F2, the cell 12a is plugged and the cell 12b is open. ing. In the honeycomb structure 10, since the cells 12a and the cells 12b are alternately arranged, the exhaust gas passing through the inside of the honeycomb structure 10 passes through the porous partition walls 14 before being discharged, so that the particulate matter is formed. Removed. Further, as shown in FIG. 4, since the catalyst layer 18 exists on the surface of the partition wall 14 where the pores 15 are formed, the components to be purified contained in the exhaust gas passing through the partition wall 14 come into contact with the catalyst layer 18 and are decomposed. As a result, the exhaust gas is purified.

  The thickness of the partition wall 14 which is a wall between the cells 12a and 12b is not particularly limited, but a desirable lower limit is 0.05 mm, a more desirable lower limit is 0.10 mm, and a particularly desirable lower limit is 0. .15 mm. On the other hand, a desirable upper limit is 0.35 mm, a more desirable upper limit is 0.30 mm, and a particularly desirable upper limit is 0.25 mm. When the thickness of the partition walls 14 is less than 0.05 mm, the strength of the honeycomb structure 10 tends to decrease. On the other hand, when the thickness of the partition walls 14 exceeds 0.35 mm, the gas permeability decreases and the exhaust gas treatment efficiency increases. There is a tendency to decrease.

  The porosity of the partition wall 14 is preferably 30% by volume or more, more preferably 35% by volume or more, and particularly preferably 40% by volume or more. When the porosity of the partition wall 14 is less than 30% by volume, gas does not easily flow through the partition wall 14, pressure loss increases, and purification efficiency tends to decrease. The porosity of the partition wall 14 is preferably 50% by volume or less, and more preferably 46% by volume or less. When the porosity of the partition wall 14 exceeds 50% by volume, soot leakage during exhaust gas purification becomes intense and the amount of soot accumulation decreases, so the amount of heat generated during soot combustion decreases and the thermal expansion of the honeycomb structure 10 is suppressed. However, the purification efficiency tends to decrease. The porosity of the partition wall 14 can be adjusted by the particle diameter of the raw material, the amount of pore-forming agent added, and the firing conditions, and can be measured by a mercury intrusion method.

  The average pore diameter of the partition walls 14 is preferably 10 μm or more, and more preferably 12 μm or more. When the average pore diameter of the partition walls 14 is less than 10 μm, the pores are easily blocked by the deposition of fine particles, the pressure loss increases rapidly, and the purification efficiency tends to decrease. On the other hand, the average pore diameter of the partition walls 14 is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 16 μm or less, from the viewpoint of reducing fine particles that pass through the partition walls 14 without being collected. The average pore diameter of the partition 14 can be adjusted by the particle diameter of the raw material, the amount of pore-forming agent added, and the firing conditions, and can be measured, for example, by a mercury intrusion method.

Further, the cell structure of the honeycomb structure 10 has a desirable lower limit of 15.5 cells / cm ² (100 cpsi), a more desirable lower limit of 46.5 cells / cm ² (300 cpsi), and a more desirable lower limit of 62. Pieces / cm ² (400 cpsi). On the other hand, the desirable upper limit of the cell density is 186 cells / cm ² (1200 cpsi), the more desirable upper limit is 170.5 cells / cm ² (1100 cpsi), and the more desirable upper limit is 155 cells / cm ² (1000 cpsi). . When the cell density is less than 15.5 cells / cm ² , the area of the wall in contact with the exhaust gas inside the honeycomb structure 10 becomes small. When the cell density exceeds 186 cells / cm ² , the pressure loss increases and the honeycomb structure 10 increases. This is because it becomes difficult to manufacture.

The honeycomb structure 10 preferably has a BET specific surface area of 1 to ²⁰ m ² / g. If the BET specific surface area of the honeycomb structure 10 is less than 1 m ² / g, the purification efficiency tends to decrease. The BET specific surface area can be measured using, for example, a commercially available gas adsorption device.

  In addition, the cross-sectional shape of the cells 12a and 12b formed in the honeycomb structure 10 is not particularly limited. For example, a triangle, a rectangle, a hexagon, an octagon, a circle, etc. other than the square as shown in FIGS. It may be a combination of a plurality of shapes.

  In the honeycomb structure 10, the porous partition wall 14 is formed of a material containing at least aluminum titanate. The constituent material other than aluminum titanate is not particularly limited, and examples thereof include inorganic fibers, whiskers, and inorganic particles.

  Examples of the inorganic fibers and whiskers include inorganic fibers and whiskers made of alumina, silica, silicon carbide, silica-alumina, glass, potassium titanate, aluminum borate or the like. These may be used alone or in combination of two or more. Of these, aluminum borate whiskers are more desirable. In the present specification, inorganic fibers and whiskers mean those having an average aspect ratio (length / diameter) exceeding 5. Moreover, the desirable average aspect-ratio of the said inorganic fiber and a whisker is 10-1000.

  Examples of the inorganic particles include particles made of alumina, silica, zirconia, titania, ceria, mullite, zeolite, and the like. These particles may be used alone or in combination of two or more. Of these, alumina particles and ceria particles are preferable.

  Although the aluminum content rate in the aluminum titanate in the honeycomb structure 10 is not specifically limited, For example, it is 40-60 mol% in conversion of aluminum oxide. Although the content rate of titanium in aluminum titanate is not specifically limited, For example, it is 35-55 mol% in conversion of titanium oxide. The magnesium content in the aluminum titanate is preferably 1 to 5% by mass in terms of magnesium oxide. In addition, what is necessary is just to adjust suitably the composition of aluminum titanate with the composition of a raw material mixture. In addition to the above components, the aluminum titanate may contain a component derived from the raw material or a trace component inevitably mixed in the work-in-process in the production process.

  In the honeycomb structure 10, the constituent material of the plugging portion 16 is not particularly limited, but usually the same material as the constituent material of the honeycomb structure 10 is used.

The catalyst layer 18 is contained in the support coat made of activated alumina, one or more noble metals selected from the group consisting of Pt, Rh, and Pd dispersedly supported inside the support coat and the support coat. , cerium oxide, di-zirconia, and the one or more compounds selected from the group consisting of silica, it is preferable to include a. In addition, as said noble metal, Pt, Rh, Pd, Ru, Ni, and these alloys can be used, It is preferable to use at least one of Pt or Pd.

The total amount of noble metals is preferably 0.17 g or more and 7.07 g or less per liter of the volume of the honeycomb structure 10. The catalyst corresponds to a gasoline engine exhaust gas purification three-way catalyst. However, the honeycomb structure according to the present invention can be used as an oxidation catalyst for purifying exhaust gas from a gasoline engine or a diesel engine, or NO _X selective reduction. SCR catalyst, NO _X storage catalyst, etc. can be used.

  Next, the manufacturing method of the honeycomb structure of the present invention will be described.

  First, as an aluminum titanate raw material, an aluminum source, a titanium source, and an inorganic compound containing a magnesium source and a silicon source added as necessary, inorganic fibers, whiskers and inorganic particles used as necessary, and , Binder components and the like are mixed to obtain a raw material mixture. In addition to the above, a pore former, a lubricant, a plasticizer, a dispersant, a solvent, and the like can be added to the raw material mixture as necessary.

  Here, the inorganic compound is a raw material of aluminum titanate, but when a magnesium source is added to the inorganic compound, an aluminum magnesium titanate crystal is formed by firing to obtain a honeycomb structure having further improved heat resistance. be able to. In addition, it replaces with a part or all of the said inorganic compound which is a raw material of aluminum titanate, You may use the aluminum titanate and aluminum magnesium titanate crystallized previously.

  Moreover, an inorganic binder and an organic binder are mentioned as said binder component. As the inorganic binder, an inorganic sol, a clay binder, or the like can be used. Specific examples of the inorganic sol include alumina sol, silica sol, titania sol, and water glass. In addition, examples of the clay-based binder include double chain structure type clays such as clay, kaolin, montmorillonite, sepiolite, attapulgite, and the like. These may be used alone or in combination of two or more. Among these, at least one selected from the group consisting of alumina sol, silica sol, titania sol, water glass, sepiolite, and attapulgite is preferable.

  Examples of the organic binder include polyvinyl alcohol, methyl cellulose, ethyl cellulose, carboxymethyl cellulose, and the like. These may be used alone or in combination of two or more. Of these, carboxymethylcellulose is preferred.

  The amount of the binder component contained in the raw material mixture is preferably 5% by mass, more preferably 10% by mass, and more preferably 15% by mass based on the total solid content of the raw material mixture. is there. On the other hand, a desirable upper limit is 50 mass%, a more desirable upper limit is 40 mass%, and a more desirable upper limit is 35 mass%.

  Examples of the pore-forming agent include carbon materials such as graphite; resins such as polyethylene, polypropylene, and polymethyl methacrylate; plant materials such as starch, nut shells, walnut shells, and corn; ice; and dry ice.

  Examples of the lubricant and plasticizer include alcohols such as glycerin; higher fatty acids such as caprylic acid, lauric acid, palmitic acid, alginic acid, oleic acid and stearic acid; and stearic acid metal salts such as Al stearate. .

  Examples of the dispersant include inorganic acids such as nitric acid, hydrochloric acid and sulfuric acid; organic acids such as oxalic acid, citric acid, acetic acid, malic acid and lactic acid; water; alcohols such as methanol, ethanol and propanol; ammonium polycarboxylate And surfactants such as polyoxyalkylene alkyl ethers.

  Examples of the solvent include water; alcohols such as methanol, ethanol, butanol, and propanol; glycols such as propylene glycol, polypropylene glycol, and ethylene glycol.

  The preparation of the raw material mixture is not particularly limited, but is preferably performed by mixing and / or kneading. Mixing can be performed using, for example, a mixer or an attritor. The kneading can be performed using, for example, a kneader.

  Next, by molding the raw material mixture obtained above, a honeycomb-shaped molded body (green molded body) is obtained. A method for molding the raw material mixture is not particularly limited, but it is preferable to mold the raw material mixture into a shape having cells.

  Next, the obtained molded body is subjected to a drying treatment using a dryer as necessary. Examples of the dryer include a microwave dryer, a hot air dryer, a dielectric dryer, a vacuum dryer, a vacuum dryer, and a freeze dryer.

  You may perform the plugging with respect to a molded object after shaping | molding or after drying. The plugging is performed, for example, by filling a predetermined position in the opening at one end of the cells 12a and 12b as shown in FIGS. In this case, the plugging is performed, for example, by bringing a mask provided with a plurality of through holes at desired positions into close contact with one end surface of the molded body and supplying a sealing material thereto to the end of the cell 12a. It can be performed by filling only the sealing material and filling the other end surface of the molded body with the sealing material only in the end portion of 12b. At this time, the surface position L of the plugging portion 16 in the finally obtained honeycomb structure 10 can be adjusted by appropriately adjusting the filling amount and filling position of the sealing material. As a result, as shown in FIGS. 1 to 3, the cells 12 a in which the opening at one end is plugged and the cells 12 b in which the opening on the side opposite to the cell 12 a is plugged are alternately arranged. A molded product can be obtained.

  As the sealing material, the same material as that of the molded body can be usually used. Further, as the sealing material, a material different from the molded body can be used.

  In addition, you may perform plugging after baking mentioned later. In that case, baking is performed again after plugging. In the case where plugging is performed on the molded body before firing, it is preferable because the firing process is performed only once.

  Next, the honeycomb formed body that has been subjected to a drying treatment as necessary is calcined (degreasing) and fired. The calcination (degreasing) is a process for removing the organic binder in the honeycomb formed body and the organic additive blended as necessary by burning, decomposition, or the like, and typically reaches the firing temperature. Up to a temperature rising stage (for example, a temperature range of 150 to 900 ° C.). In the calcination (degreasing) step, it is preferable to suppress the temperature increase rate as much as possible.

  Firing can be performed, for example, by placing the green molded body in a firing furnace and heating. The firing temperature is usually 1300 ° C. or higher, preferably 1400 ° C. or higher. On the other hand, from the viewpoint of making the obtained honeycomb fired body easy to process, the firing temperature is usually 1650 ° C. or lower, preferably 1600 ° C. or lower, more preferably 1550 ° C. or lower. The rate of temperature increase up to the firing temperature is not particularly limited, but is usually 1 ° C./hour to 500 ° C./hour. When the honeycomb formed body includes the silicon source powder, it is preferable to provide a step of holding at a temperature range of 1100 to 1300 ° C. for 3 hours or more before the firing step. Thereby, melting and diffusion of the silicon source powder can be promoted.

  Firing is usually performed in the air, but depending on the components and component ratio of the raw material mixture, firing may be performed in an inert gas such as nitrogen gas or argon gas, or carbon monoxide gas, hydrogen gas, etc. You may bake in such reducing gas. Further, the firing may be performed by lowering the water vapor partial pressure in the firing atmosphere.

  Firing is usually performed using a conventional firing furnace such as a tubular electric furnace, a box-type electric furnace, a tunnel furnace, a far-infrared furnace, a microwave heating furnace, a shaft furnace, a reflection furnace, a rotary furnace, or a roller hearth furnace. Firing may be performed batchwise or continuously. Moreover, baking may be performed by a stationary type or may be performed by a fluid type.

  The firing time varies depending on the type of firing furnace, firing temperature, firing atmosphere, and the like, but is usually from 10 minutes to 300 hours.

  As described above, it is possible to obtain a columnar honeycomb fired body in which a large number of cells are arranged side by side across the partition walls. The obtained honeycomb fired body has a shape that substantially maintains the shape of the honeycomb formed body immediately after forming. The obtained honeycomb fired body can be processed into a desired shape by grinding or the like.

  Next, a catalyst layer containing a catalyst is formed in layers on the surface of the honeycomb fired body obtained where pores are formed. The formation method of a catalyst layer is not specifically limited, It can form by a well-known method. Specifically, first, a catalyst slurry containing a catalyst is prepared, and the pores of the partition walls of the honeycomb fired body are coated with the catalyst slurry by a method such as a suction method. Then, a catalyst layer can be formed by drying at room temperature or heating conditions. As described above, the honeycomb structure of the present invention can be obtained.

  The honeycomb structure of the present invention described above is incorporated and used as a catalytic converter in, for example, an exhaust gas treatment system in various industrial fields that require purification of components to be purified contained in exhaust gas. In particular, it is effectively used in industrial fields such as the automobile industry, the machine industry, and the ceramic industry that require purification of exhaust gas from internal combustion engines and combustion equipment.

DESCRIPTION OF SYMBOLS 10 ... Honeycomb structure, 12a, 12b ... Cell, 14 ... Partition, 16 ... Plugging part, 18 ... Catalyst layer.

Claims (3)

A porous partition wall arranged to form a plurality of cells communicating between the two end faces;
A plurality of plugged portions plugging one of the openings at both ends of each of the plurality of cells;
A catalyst layer containing a catalyst, supported in layers on the surface of the partition walls forming pores;
An aluminum titanate honeycomb structure comprising:
The surface position on the cell inner side perpendicular to the cell communication direction of the plugging portions formed in the cells in the center of the honeycomb structure is formed in the cells in the peripheral portion of the honeycomb structure. It is located inside the cell from the surface position of the plugged part ,
The length of the plugged portions formed in the cells in the center of the honeycomb structure is longer than the length of the plugged portions formed in the cells in the peripheral portion of the honeycomb structure,
An aluminum titanate honeycomb structure in which a difference between a maximum value and a minimum value of the lengths of the plurality of plugged portions is 1 mm or more and 10 mm or less .   The arrangement position of the plugging portions formed in the cells at the center of the honeycomb structure is closer to the inside of the cell than the arrangement position of the plugging portions formed in the cells at the peripheral edge of the honeycomb structure. The aluminum titanate honeycomb structure according to claim 1, which is located in The catalyst is
A carrier coat made of activated alumina;
One or more precious metals selected from the group consisting of Pt, Rh, and Pd dispersedly supported within the carrier coat;
Said being contained in a carrier coating, cerium oxide, di-zirconia, and one or more compounds selected from the group consisting of silica,
The aluminum titanate honeycomb structure according to claim 1 or 2 , comprising:

Images