JP2011206635A - Honeycomb structure, and exhaust gas treatment device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a honeycomb structure hardly producing melt loss and cracks over a long period of time even if partition walls are made thin.SOLUTION: The honeycomb structure 1 includes a large number of flow holes 2 partitioned by air permeable partition walls 4 having wall surfaces 4a along an axial direction; and sealing materials 3 for alternately sealing a large number of the flow holes 2 on the inflow and outflow sides of the honeycomb structure 1. The partition walls 4 comprise a sintered body based on aluminum titanate and at least the partition walls 4 on the outflow side contain an additive comprising at least one kind of boron, chromium, zirconium and niobium. Even if the temperature of the partition walls rises during combustion, the additive is hard to melt because the melting point of the element used in the additive is 1,852°C or above. Since the specific heat capacity of the element is 265 J/(kg K) or above, the local temperature rise of the partition walls is suppressed and, since the partition walls gently cool even if combustion is completed, the melting loss or crack produced in the partition walls can be reduced.

Description

  The present invention relates to an internal combustion engine, an incinerator, and a power source for automobiles, forklifts, generators, ships, hydraulic excavators, bulldozers, wheel loaders, rough terrain cranes, tractors, combines, tillers, railway vehicles, and construction vehicles. Honeycomb structure used for a filter for collecting fine particles mainly composed of carbon contained in exhaust gas generated from a boiler, etc., a filter for decomposing and removing harmful dioxins, and an exhaust gas treatment apparatus equipped with the honeycomb structure It is about.

  Conventionally, fine particles mainly composed of carbon (particularly fine particles mainly composed of carbon in exhaust gas from diesel engines) and sulfur contained in exhaust gas generated from internal combustion engines, incinerators, boilers, etc. are oxidized. Since fine particles mainly composed of sulfate and fine particles such as unburned hydrocarbons made of polymers cause environmental pollution, for example, these fine particles are collected with a filter using a honeycomb structure. And removed.

  FIG. 6 shows a conventional honeycomb structure, in which (a) is a side view and (b) is a front view partially broken.

  The honeycomb structure 21 shown in FIG. 6 includes a partition wall 23 having a wall surface along the axial direction X, a plurality of flow holes 22 partitioned by the partition wall 23, and a seal that alternately seals both ends of the plurality of flow holes 22. It is a honeycomb structure provided with stopping materials 24a and 24b.

  The exhaust gas flowing in from the end face (IF) on the inflow side of the honeycomb structure 21 is introduced into the flow hole 22 and then enters the adjacent flow hole 22 through the partition wall 23 and from the end face (OF) on the outflow side. leak. When the exhaust gas passes through the partition wall 23, various fine particles contained in the exhaust gas are collected in the partition wall 23.

The honeycomb structure 21 must be regenerated by periodically removing the particulates because the air permeability of the partition walls 23 is gradually impaired due to the accumulation of the collected particulates when the particulates are continuously collected. The method for regenerating the honeycomb structure 21 includes heating to 600 ° C. or more to burn and remove the fine particles, or placing an oxidation catalyst on the exhaust gas inflow side of the honeycomb structure 21, and using this oxidation catalyst as light oil or the like For example, there is a method of burning and removing fine particles using heat generated by an oxidation reaction caused by supplying the fuel.

  However, when the honeycomb structure 21 is regenerated by these methods, the larger the amount of collected fine particles, the more time it takes to burn and remove the fine particles. During this time, the temperature of the honeycomb structure 21 rises and rises. In some cases, the honeycomb structure 21 may be cracked or melted due to the thermal stress due to.

Various honeycomb structures for preventing such cracks and melting damage have been proposed. For example, in Patent Document 1, a honeycomb structure whose main component is aluminum titanate, one end face of a predetermined cell (flow hole) of the honeycomb structure is sealed with a plugging material, and the remaining unsealed A diesel engine exhaust gas filter in which the other end surface of the stop cell (non-sealed flow hole) is similarly plugged is shown, and it is disclosed that a plugging material whose main component is aluminum titanate is used as a preferred example. ing. And according to this, since the aluminum titanate is used as the material of the filter, the coefficient of thermal expansion is small, and since the melting point is higher than that of cordierite, it is excellent in heat resistance and thermal shock resistance. Moreover, the firing cost is lower than that of cordierite. By reducing the difference in coefficient of thermal expansion between the honeycomb structure and the cell wall sealing material, cracks occurring at the interface between the cell wall and the sealing material during combustion regeneration can be eliminated.

  Such a honeycomb structure is used, for example, as a filter in the particulate matter removing device disclosed in Patent Document 2. The apparatus for removing particulate matter in the exhaust gas proposed in Patent Document 2 is shown schematically in FIG.

The removal device 30 shown in FIG. 7 is a device that removes particulate matter in the exhaust gas discharged from the internal combustion engine 31, and is disposed downstream of the exhaust gas discharge portion of the internal combustion engine 31, and NO _x storage agent 33 that stores NO _x in the exhaust gas discharged from the exhaust gas, and releases the stored NO _x as NO and / or NO ₂ , and is disposed downstream of the NO _x storage agent 33, A device including a filter 34 for collecting particulate matter in exhaust gas discharged from the internal combustion engine 31, and further, a role of a catalyst that oxidizes NO in the exhaust gas to generate NO ₂ the oxidation catalyst 32 responsible for is made are disposed upstream of _the NO _x storage material 33. Further, in this removing device 30, fuel is supplied from the inlet 31 a of the engine 31 and burns in the engine 31, and then exhaust gas is discharged from the outlet 31 b of the engine 31 and flows into the NO _x storage agent 33. To do. After the NO _x storage agent 33 stores NO _x in the exhaust gas, the exhaust gas flows into the filter 34, and particulate matter in the exhaust gas is collected. Temperature of the exhaust gas, when the the NO ₂ and particulate matter has reached a temperature sufficient to react, NO _x, which have been stored in _the NO _x storage material 33 is released as NO and / or NO _2, the The released NO ₂ reacts with the particulate matter collected by the filter 34, and the reactant is discharged from the outlet 35. According to this, particulate matter contained in the exhaust gas of the internal combustion engine 31 can be effectively removed.

The NO _x storage agent 33 is configured by supporting a NO _x storage material and, if necessary, an active metal and a promoter on a carrier.

Examples of the NO _x storage material include one or more metals selected from the group of alkali metals, alkaline earth metals, rare earth metals, and transition metals. Specific examples of the carrier include a pellet type shape (granular shape) made of alumina, or a monolith type shape (honeycomb shape) made of a metal such as cordierite ceramics or stainless steel. Specific examples of the active metal include noble metals (such as platinum, palladium, rhodium, ruthenium, osmium, gold and silver) and base metals (such as nickel, copper, manganese, iron, cobalt and zinc), preferably noble metals. Is mentioned. Specific examples of the promoter include cerium oxide, zirconium oxide and titanium oxide.

  The oxidation catalyst 32 basically comprises an active metal, a support material, and a carrier. The support generally stabilizes the active metal and expands the contact area with the exhaust gas to improve the purification performance. Specific examples include aluminum oxide, cerium oxide, and titanium oxide. Etc.

JP-A-9-29022 JP 2002-364338 JP

However, in the diesel engine exhaust gas filter shown in Patent Document 1, there is a high demand for thinning the partition wall so that the pressure loss in the partition wall does not easily increase even when particulates accumulate on the partition wall during combustion regeneration. In order to meet such a demand, when the partition wall is made thin, there is a problem that cracks and melting damage are likely to occur. In particular, such cracks and erosion are likely to occur in the partition wall on the outflow side of the cell where the amount of particulates is large and the exhaust gas is temporarily retained by the sealing material on the outflow side and the temperature is likely to rise. There was a problem.

Moreover, although the particulate matter removal device proposed in Patent Document 2 can effectively remove particulate matter contained in the exhaust gas of an internal combustion engine, the oxidation catalyst, NO _x storage agent, and filter Since these are arranged in series, there is a problem that the space necessary for this arrangement becomes enormous.

  The present invention has been devised to solve the above problems, and a honeycomb structure that can prevent the occurrence of melting damage and cracks over a long period of time even when the partition wall is thinned, and the honeycomb structure An object of the present invention is to provide an exhaust gas treatment device that can be used to save space.

  The honeycomb structure of the present invention has a plurality of flow holes partitioned by a gas-permeable partition wall having an axial wall surface, and seals that alternately seal the inflow side and the outflow side of the plurality of flow holes. A honeycomb structure comprising a stopper, wherein the partition wall is made of a sintered body mainly composed of aluminum titanate, and at least one of boron, chromium, zirconium and niobium is added on the outflow side. It is characterized by containing a material.

  Moreover, the honeycomb structure of the present invention is characterized in that, in the above-described configuration, the additive material is contained in a larger amount on the outflow side than in the inflow side.

  The honeycomb structure of the present invention is characterized in that, in any one of the above-described configurations, the content of the additive on the outflow side of the partition wall is 5% by mass or more and 30% by mass or less.

  In addition, the honeycomb structure of the present invention is characterized in that, in any one of the above-described configurations, a catalyst is supported on the wall surface of the partition wall.

  In addition, the exhaust gas treatment device of the present invention includes the honeycomb structure having any one of the above-described configurations.

The honeycomb structure of the present invention has a plurality of flow holes partitioned by a gas-permeable partition wall having a wall surface along the axial direction, and sealing that alternately seals the inflow side and the outflow side of the plurality of flow holes The partition wall is made of a sintered body mainly composed of aluminum titanate, and includes at least an additive material composed of at least one of boron, chromium, zirconium and niobium on the outflow side. In this case, since the element used for the additive has a high melting point of 1852 ° C. or higher, the additive does not easily dissolve even when the temperature of the partition wall rises during the combustion of the fine particles, and these elements have a specific heat capacity of 265 J / ( (kg · K) or higher, local temperature rise is suppressed, and even after the combustion is finished, it does not cool rapidly but cools slowly, so it is possible to reduce melting and cracks generated in the partition walls. .

  Further, in the honeycomb structure of the present invention, when the additive material is contained more on the outflow side than on the inflow side, the outflow side partition wall where the temperature is likely to rise is less likely to cause melting damage and cracks. The entire partition can be efficiently regenerated.

  Further, the honeycomb structure of the present invention can reduce melting damage and cracks generated in the partition walls when the content of the additive on the outlet side of the partition walls is 5% by mass or more and 30% by mass or less. Since the mass of the partition wall hardly increases, it is possible to suppress a reduction in fuel consumption of the internal combustion engine due to an increase in the mass of the honeycomb structure.

  Further, in the honeycomb structure of the present invention, when the catalyst is supported on the wall surface of the partition wall, fine particles can be burned and removed at a lower temperature than when the catalyst is not supported. Can be further reduced.

When the exhaust gas treatment device of the present invention is provided with the honeycomb structure of the present invention, the partition walls are less likely to be melted or cracked, and thus can be used efficiently over a long period of time. Further, since a carrier carrying an active metal or a carrier carrying a NO _x storage material can be dispensed with, space saving can be realized.

An example of an embodiment of a honeycomb structure of the present invention is shown typically, (a) is a perspective view, and (b) is a sectional view in a B-B 'line in (a). FIG. 2A is a side view showing a part of the inflow side, and FIG. 2B is a side view showing a part of the outflow side, showing the honeycomb structure of the example shown in FIG. 1. The other example of embodiment of the honeycomb structure of this invention is shown, (a) is a side view which shows a part of end surface (IF) of an inflow side, (b) is an end surface (OF) of an outflow side. It is a side view which shows a part. The honeycomb structure of the present invention shows still another example of the embodiment, (a) is a side view showing a part of the end face (IF) on the inflow side, (b) is the end face (OF) on the outflow side. FIG. 1 is a schematic cross-sectional view showing an example of an embodiment of an exhaust gas treatment device provided with a honeycomb structure of the present invention. A conventional honeycomb structure is shown, (a) is a side view, and (b) is a partially broken front view. It is a schematic diagram which shows schematic structure of the conventional removal apparatus of particulate matter.

  Hereinafter, an example of an embodiment of a honeycomb structure of the present invention and an exhaust gas treatment apparatus using the honeycomb structure will be described.

  FIG. 1 shows an example of an embodiment of a honeycomb structure of the present invention, (a) is a perspective view, and (b) is a cross-sectional view taken along line B-B ′ in (a). FIG. 2 shows the honeycomb structure of the example shown in FIG. 1, (a) is a side view showing a part of the end face (IF) on the inflow side, and (b) is the end face (OF) on the outflow side. It is a side view which shows a part of.

  A honeycomb structure 1 shown in FIG. 1A includes a plurality of flow holes 2 partitioned by a gas-permeable partition wall 4 having a wall surface 4a along the axial direction A, and an inflow side and an outflow side of the plurality of flow holes 2. It is the honeycomb structure 1 provided with the sealing material 3 which seals each of these alternately. In addition, as shown in FIG.1 (b), it distribute | circulates the through-hole 2 sealed with the inflow side sealing material 3a through the through-hole 2b and the through-hole 2 sealed with the outflow side sealing material 3b. Let it be hole 2a.

  Further, in the honeycomb structure 1 shown in FIG. 2, the shapes of the openings of the flow holes 2a and 2b are both quadrangular and the opening area is the same.

The honeycomb structure 1 shown in FIG. 1 has, for example, a cylindrical shape with an outer diameter of 100 to 200 mm and a length in the axial direction A of 100 to 250 mm, and a flow hole in a cross section perpendicular to the axial direction A the number of 2 (2a, 2b) is from 5 to 124 per 100mm ² (32~800CPSI). Also,
The partition wall 4 has a width of 0.05 mm or more and 0.25 mm or less, and the sealing material 3 (3a, 3b) has a thickness of 1 mm or more and 5 mm or less. CPSI stands for Cells Per Square Inches.

  In addition, when a diesel engine (not shown) is arranged on the inflow side of the honeycomb structure 1 and this diesel engine (not shown) is operated, exhaust gas is generated, and this exhaust gas is as shown in FIG. Is introduced from the flow hole 2a of the honeycomb structure 1 and the outflow is blocked by the sealing material 3b. The exhaust gas from which the outflow is blocked passes through the air-permeable partition wall 4 and is introduced into the adjacent circulation hole 2b. When the exhaust gas passes through the partition walls 4, fine particles mainly composed of carbon in the exhaust gas on the wall surfaces 4 a of the partition walls 4 and the pores of the partition walls 4, fine particles mainly composed of sulfate formed by oxidation of sulfur, and Fine particles such as unburned hydrocarbons (hereinafter collectively referred to simply as fine particles) made of a polymer are collected. The exhaust gas in which the fine particles are collected is discharged to the outside through the circulation hole 2b in a purified state.

In such a honeycomb structure 1, the partition wall 4 is made of a sintered body mainly composed of aluminum titanate, and includes an additive material composed of at least one of boron, chromium, zirconium and niobium at least on the outflow side. It is important that Since the element used for the additive has a high melting point of 1852 ° C. or higher, the additive is difficult to dissolve even when the temperature of the partition wall 4 rises during the combustion of fine particles, and the specific heat capacity is as high as 265 J / (kg · K) or more. Further, local temperature rise is suppressed, and even after the combustion is finished, it does not cool rapidly but cools slowly, so that melting damage and cracks generated in the partition walls 4 can be reduced.

  The sintered body forming the partition walls 4 is a sintered body containing aluminum titanate as a main component and, for example, magnesium titanate, iron titanate and silicon oxide as subcomponents, and at least the honeycomb structure 1 An additive material composed of at least one of boron, chromium, zirconium and niobium is included on the outflow side of the steel.

  Here, magnesium titanate and iron titanate are components for improving corrosion resistance and heat deterioration resistance, respectively, and each content is, for example, 16% by mass or more and 24% by mass, both of which are fixed to aluminum titanate. Melt.

Silicon oxide is a component constituting the grain boundary phase, and silicon dioxide having a composition formula of SiO ₂ is preferable because of its high stability, but the composition formula is SiO _2−x (where x is There is no problem even if the silicon oxide has a non-stoichiometric ratio represented by 0 <x <2. The silicon oxide content is, for example, 1.8% by mass or more and 3.2% by mass or less.

  The main component of the sintered body forming the partition wall 4 in the present invention refers to a component having the largest content among the components constituting the sintered body, and the main component and the above-described components and additives other than the main component. Each of these is identified by X-ray diffraction, and the contents of these components and additives can be determined by ICP (Inductively Coupled Plasma) emission analysis or fluorescent X-ray analysis. For example, for aluminum titanate that is the main component, the content of each element Ti and Al constituting aluminum titanate is measured by the above method, and the total content converted to oxide is the content of aluminum titanate. do it.

Moreover, in the honeycomb structure 1 of the present invention, it is preferable that the additive material is contained in a larger amount on the outflow side than in the inflow side. When the additive material is contained more on the outflow side than in the inflow side, melting and cracking of the outflow side partition, which is likely to cause a temperature rise, are less likely to occur, so that the entire partition 4 can be efficiently regenerated. . In particular, the additive is preferably contained in an amount of 5% by mass or more on the outflow side than on the inflow side.

  Here, when the honeycomb structure 1 of the present invention is divided into two along the axial direction A, the inflow side and the outflow side of the flow hole 2 are the side where the exhaust gas (EG) is introduced and the side where the exhaust gas (EG) is discharged. They are the inflow side and the outflow side, respectively. The length in the axial direction A on the outflow side is preferably 1/3 or more and 2/3 or less of the entire length.

  If the length in the axial direction A on the outflow side is less than 1/3, since the additive material is not contained in a place where the temperature becomes relatively high when the exhaust gas flows in, the additive material is not contained in a relatively high temperature. Melting and cracking are likely to occur in the partition walls that tend to rise. When the length in the axial direction A on the outflow side exceeds 2/3, a large amount of additive is contained in a place where the temperature is relatively difficult to rise, which is not preferable in terms of manufacturing cost.

Further, since the rising temperature of the honeycomb structure 1 gradually decreases from the outflow side to the inflow side when the exhaust gas flows in, the increase amount of the additive on the outflow side may be reduced as it approaches the inflow side. When the honeycomb structure 1 of the present invention is divided into three equal parts along the axial direction A, the exhaust gas (EG) introduction side and the exhaust side are the inflow side and the outflow side, respectively, When the sandwiched region is a central portion, the central portion may be 2.5 mass% or more than the inflow side and the outflow side may be 2.5 mass% or more than the central portion.

  Moreover, in the honeycomb structure 1 of the present invention, the content of the additive on the outflow side of the partition walls 4 is preferably 5% by mass or more and 30% by mass or less.

  If the content of the additive on the outflow side of the partition wall 4 is 5% by mass or more, the effect of the additive is relatively large, and even after the combustion is finished, it does not cool rapidly but cools more slowly. Loss and cracks can be reduced. Further, if the content of the additive on the outflow side of the partition wall 4 is 30% by mass or less, the mass of the partition wall 4 itself hardly increases, so that the decrease in fuel consumption of the internal combustion engine due to the increase in the mass of the honeycomb structure 1 is suppressed. be able to.

  Next, FIG. 3 shows another example of the embodiment of the honeycomb structure of the present invention, (a) is a side view showing a part of the end face (IF) on the inflow side, and (b) is the outflow. It is a side view which shows a part of side end surface (OF).

  The honeycomb structure 1 of this example shown in FIG. 3 has an octagonal shape of the opening portion of the flow hole 2a sealed with the outflow side sealing material 3b and is sealed with the inflow side sealing material 3a. In addition, the shape of the opening of the circulation hole 2b is a quadrangular shape, and the opening area of the circulation hole 2a is larger than that of the circulation hole 2b.

  As in the example shown in FIG. 3, the flow hole 2a and the flow hole 2b have an octagonal shape and a quadrangular shape, respectively, and the flow hole 2a has a larger opening area than the flow hole 2b. Since the respective surface areas of the partition wall 4 and the sealing material 3b capable of adsorbing fine particles are larger than when the opening areas of the holes 2a and the flow holes 2b are equal, the fine particles can be collected efficiently. .

  Next, FIG. 4 shows another example of the embodiment of the honeycomb structure of the present invention, (a) is a side view showing a part of the end face (IF) on the inflow side, and (b) is the outflow. It is a side view which shows a part of side end surface (OF).

The honeycomb structure 1 of this example shown in FIG. 4 has both the opening shape of the flow hole 2a sealed by the outflow side sealing material 3b and the flow hole 2b sealed by the inflow side sealing material 3a. It is a quadrangular shape, and the corners of the opening are arcuate. Further, the honeycomb structure has a larger opening area in the flow hole 2a than in the flow hole 2b.

  As shown in FIG. 4, the flow hole 2 a and the flow hole 2 b are both quadrangular in the shape of the opening, and the corner of the opening is arcuate, so stress concentrates around the corner. Therefore, even if heating and cooling are repeated, cracks are less likely to occur from the corners, and the opening area is larger in the flow hole 2a than in the flow hole 2b, so that the partition wall 4 capable of adsorbing fine particles and the sealing The surface area of each material 3b is increased, and fine particles can be collected efficiently.

  In particular, in the honeycomb structure 1 of the present invention shown in FIGS. 3 and 4, the diameter of the flow hole 2a is preferably 1.55 times or more and 1.95 times or less than the diameter of the flow hole 2b. Thus, by setting the diameter ratio to 1.55 times or more, the respective surface areas of the partition wall 4 and the sealing material 3b capable of adsorbing the fine particles are increased, so that the amount of collected fine particles can be increased. At the same time, when the ratio of the diameters is 1.99 times or less, the partition wall 4 is not extremely thinned, so that the mechanical strength is hardly impaired. Here, the diameters of the flow holes 2a and 2b are the diameters of the inscribed circles in contact with the partition walls 4 of the openings on the inflow side end surface (IF) and the outflow side end surface (OF), and are measured using an optical microscope. can do.

  In addition, in the honeycomb structure 1 of the present invention of the example shown in FIGS. 1 to 4, the sintered body forming the partition walls 4 has a porosity of 35% to 60% by volume and an average pore size of 5 μm or more. It is preferable that it is 26 μm or less.

  This is because when the porosity and average pore diameter of the sintered body forming the partition walls 4 are in this range, the increase in pressure loss can be suppressed while maintaining the mechanical characteristics. May be determined according to the mercury intrusion method.

  FIG. 5 is a schematic cross-sectional view showing an example of an embodiment of an exhaust gas treatment apparatus provided with the honeycomb structure of the present invention.

In the exhaust gas treatment apparatus 10 of this example shown in FIG. 5, the honeycomb structure 1 of the present invention is accommodated in the case 6 with the outer periphery held by the heat insulating material layer 5, and the exhaust gas (EG) inlet 7 and outlet 8 are connected to exhaust pipes 9a and 9b, respectively. The heat insulating material layer 5 is formed of at least one of ceramic fiber, glass fiber, carbon fiber, and ceramic whisker, for example. The case 6 is made of, for example, stainless steel such as SUS303, SUS304, and SUS316, and has a central portion formed in a cylindrical shape and both end portions formed in a truncated cone shape.

  A diesel engine (not shown) is connected to the exhaust gas (EG) inflow side of the exhaust gas processing device 10 through an exhaust pipe 9a. When this diesel engine (not shown) is operated and exhaust gas (EG) is supplied to the case 6 through the exhaust pipe 9a, the exhaust gas (EG) is introduced into the flow hole 2a of the honeycomb structure 1. ) Is introduced, and the outflow is blocked by the sealing material 3b. Exhaust gas (EG) whose outflow is blocked passes through the air-permeable partition wall 4 and is introduced into the adjacent circulation hole 2b. When the exhaust gas (EG) passes through the partition walls 4, particulates in the exhaust gas (EG) are collected on the wall surfaces 4 a of the partition walls 4 and the pore surfaces of the partition walls 4. The exhaust gas (EG) in which the fine particles are collected is discharged from the circulation hole 2b in a purified state, and is discharged to the outside through the exhaust pipe 9b.

In the exhaust gas treatment device 10 of the example shown in FIG. 5, a catalyst may be supported on the wall surface 4 a of the partition wall 4 of the honeycomb structure 1. The supported catalyst includes a catalyst for oxidizing and burning fine particles in the exhaust gas (EG) and a catalyst for oxidizing NO in the exhaust gas (EG) to generate NO _2. Such a catalyst may be supported on the wall surface 4a of the partition wall 4, and it is more preferable to support both catalysts.

  Catalysts for oxidizing and burning fine particles in the exhaust gas (EG) include, for example, platinum group metals such as ruthenium, rhodium, palladium, osmium, iridium, platinum, and oxides thereof, gold, silver, copper, etc. It is preferable that it consists of at least any one of Group 11 metal and vanadium oxide. In addition, when a Group 11 metal of the periodic table such as gold, silver and copper is selected, the particles are preferably fine particles of nanometer level. If such a catalyst is supported on the wall surface 4a of the partition wall 4, the catalyst oxidizes and burns the fine particles in the exhaust gas (EG), so that the fine particles can be burned and removed at a lower temperature than when not supported. Therefore, it is possible to further reduce the occurrence of melting damage and cracks in the partition walls 4.

Catalysts for oxidizing NO in the exhaust gas (EG) are, for example, ZSM-5, ZSM-11, ZSM-12, ZSM-18, ZSM-23, MCM zeolite, mordenite, farjasite, ferrier. It is preferable to consist of at least one of light and zeolite beta. By supporting such a catalyst on the wall surface 4a of the partition wall 4, harmful NO contained in the exhaust gas is oxidized to NO ₂ and released. The released NO ₂ can be reduced to nitrogen by ammonia. Thus, the exhaust gas (EG) purification performance can be improved by supporting the catalyst for oxidizing NO in the exhaust gas (EG) on the wall surface 4 a of the partition wall 4.

  These catalysts may be supported on at least one of the wall surfaces 4a of the partition walls 4 and the pore surfaces of the partition walls 4.

  Furthermore, in order to increase the contact area between the catalyst supported on the wall surface 4a and the exhaust gas, a component having a large specific surface area such as γ alumina, δ alumina, and θ alumina is supported on the wall surface 4a of the partition wall 4 as a support. It is advisable to support the catalyst after that.

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

First, a slurry obtained by mixing each powder of titanium oxide, aluminum oxide, magnesium oxide and iron oxide together with water, acetone or 2-propanol is dried by a spray drying method or the like. For example, granules having an average particle size of 50 μm to 300 μm are dried. obtain. Here, it is preferable to use a high-purity powder for each of the powders used, and the purity is more preferably 99.0% by mass or more, particularly 99.5% by mass or more.

  Next, the obtained granules are calcined in an air atmosphere at a temperature of 1400 ° C. or higher and 1500 ° C. or lower for 1 hour or more and 5 hours or less to form a pseudo brookite type in which elements Ti, Al, Mg and Fe are dissolved. A calcined powder made of the crystals can be obtained.

By passing the calcined powder through a sieve having a particle size number of 200 described in ASTM E 11-61, a calcined powder classified to a particle size of 74 μm or less is obtained. A part of the classified calcined powder is, for example, a silicon oxide powder having an average particle diameter of 1 μm to 3 μm, and at least boron, chromium, zirconium and niobium having an average particle diameter of 1 μm to 4 μm. After adding a predetermined amount of one kind of powder and a pore-forming agent such as graphite, starch or polyethylene resin, a plasticizer, a thickener, a slip agent, water, etc. are further added, and a universal stirrer, rotary mill or V-type A slurry (hereinafter, this slurry is referred to as slurry A) is prepared using a stirrer or the like. And this slurry A is knead | mixed using a three roll mill, a kneader, etc., and the plasticized clay (Hereafter, this clay is called the clay A) is obtained.

  In addition, the remainder of the classified calcined powder includes, for example, at least one of silicon oxide powder having an average particle size of 1 μm to 3 μm, boron, chromium, zirconium, and niobium having an average particle size of 1 μm to 4 μm. And after adding a predetermined amount of a pore-forming agent such as graphite, starch or polyethylene resin, which is adjusted to be less than the additive contained in the slurry A, further plasticizer, thickener, slip agent Then, a slurry (hereinafter, this slurry is referred to as “slurry B”) is prepared using a universal stirrer, rotary mill, V-type stirrer, or the like. And this slurry B is knead | mixed using a three roll mill, a kneader, etc., and the plasticized clay (Hereafter, this clay is called the clay B) is obtained.

  Further, when boron powder is added to at least one of the clays A and B, the boron may be either amorphous boron or crystalline boron, but from the viewpoint of activation of sinterability and reactivity. Amorphous boron powder is preferred.

  Next, the inner diameter that determines the outer diameter of the molded body is, for example, 100 mm or more and 250 mm or less, and is filled in an extrusion molding machine having a molding die having a slit for forming the partition walls 4 of the honeycomb structure 1. A and B are sequentially added, formed into a honeycomb shape by applying pressure, dried, then cut to a predetermined length, and the outflow side is made of the earth A and the inflow side is made of the earth B You can get a body. In addition, as a mechanism for extruding the dough in the extruder, a screw type that pushes out the dough by rotating the screw in the extruder, and a plunger type that pushes the dough under pressure with a piston cylinder etc. However, in the present invention, when extruding the clay A and the clay B, a plunger type extruder is used to avoid mixing the clay A and the clay B inside the extruder. Is preferred. In addition, when the clay is pushed downward in accordance with gravity, it is possible to reduce the deformation of the molded body due to its own weight, compared to when it is pushed sideways. It is preferable to use a vertical extruder.

  Moreover, when the thing shape | molded with the extrusion molding machine is cut | disconnected to predetermined length, you may color the clay A or the earth B so that the earth A and the earth B can be identified.

After placing the compact in a firing furnace such as an electric furnace or a gas furnace, the temperature is set to 800 in an oxidizing atmosphere.
A sintered body can be obtained by maintaining the temperature at 1300 ° C to 1380 ° C for 3 to 5 hours after holding at 1 ° C to 1000 ° C for 1 to 10 hours. The resulting sintered body is masked in a checkered pattern so that a portion sealed by the sealing material 3b is formed on the end surface (OF) side of the sintered body, and the end surface (OF) side of the sintered body is slurry A. Or it is immersed in the slurry B. Here, since the slurry A contains more powder of at least one of boron, chromium, zirconium and niobium than the slurry B, it is preferable that the outflow side of the sintered body is immersed in the slurry A. It is.

  Then, after the outflow side of the sintered body is immersed in the slurry A or the slurry B, a pin coated with a water repellent resin is inserted from the end surface (IF) on the inflow side, and the position of the tip of the pin is adjusted. Then, it is dried at room temperature to form the sealing material 3b. After forming the sealing material 3b, the pin is pulled out, and the same operation as described above is performed on the inflow side of the sintered body to form the sealing material 3a.

  The honeycomb structure 1 of the present invention can be obtained by forming the sealing materials 3a and 3b, and firing again at 1250 ° C. to 1300 ° C. using a firing furnace such as an electric furnace or a gas furnace. .

Furthermore, in order to obtain the honeycomb structure 1 carrying the catalyst on the wall surface 4a of the partition wall 4, the honeycomb structure 1 obtained by the above-described manufacturing method is used as a catalyst, for example, ruthenium, rhodium, palladium, osmium, iridium. And after being immersed in a slurry composed of a soluble salt of a platinum group metal such as platinum, a binder such as polyvinyl alcohol, and water, the temperature is set to 100.
What is necessary is just to dry by hold | maintaining at 1 degreeC or more and 48 hours or less at 150 degreeC or more.

Here, examples of the soluble salt include palladium nitrate (Pd (NO ₃ ) ₂ ), rhodium nitrate (Rh (NO) ₃ ) ₃ ), ruthenium chloride (RuCl ₃ ), chlorinated iridium acid (H ₂ IrCl _6. nH ₂ O), chloroplatinic acid (H ₂ PtCl ₆ .nH ₂ O), dinitrodiammine platinum (Pt (NO ₂ ) ₂ (NH ₃ ) ₂ ), etc., and these are soluble depending on the catalyst to be supported Choose from the salt. In order to prevent impurities from being mixed, the water is preferably ion-exchanged water.

  Then, after drying, the honeycomb structure 1 in which the catalyst is supported on the wall surface 4a of the partition wall 4 can be obtained by holding at 400 to 600 ° C. for 1 to 10 hours.

  Examples of the present invention will be specifically described below, but the present invention is not limited to the following examples.

First, the aluminum oxide powder is 30% by mass, the ferric oxide powder is 14% by mass, the magnesium oxide powder is 10% by mass, and the titanium oxide powder is 36% by mass. The slurry mixed together is dried by spray drying, and the average particle size is 175
Granules that were μm were obtained. Here, each powder of aluminum oxide, ferric oxide, magnesium oxide, and titanium oxide was a powder having a purity of 99.5% by mass.

  Next, the obtained granule is calcined in an air atmosphere at a temperature of 1450 ° C. for 3 hours, thereby calcining powder composed of pseudo-brookite crystals in which elements Ti, Al, Mg and Fe are dissolved in each other. Got.

This calcined powder was passed through a mesh sieve having a particle size number of 200 described in ASTM E 11-61 to obtain a calcined powder classified to a particle size of 74 μm or less. Then, a part of the classified calcined powder is taken out, and with respect to 100 parts by mass of this part of the calcined powder, the addition amount is 2.5 parts by mass, the silicon oxide powder having an average particle diameter of 2 μm, the type And the addition amount shown in Table 1, after adding the powder of each additive having an average particle diameter of 2.5 μm and the polyethylene resin having an addition amount of 7 parts by mass, and further adding a plasticizer, a thickener, a slip agent and water Etc. were added and the slurry A was produced using the universal stirrer. And this slurry A was knead | mixed using the kneading machine, and the plasticized clay A was obtained.

Further, with respect to the remaining 100 parts by mass of the calcined powder, the addition amount is 2.5 parts by mass, the silicon oxide powder having an average particle size of 2 μm, the type and the addition amount are shown in Table 1, and the average particle size is 2.5. After adding the powder of each additive of μm and the polyethylene resin having an addition amount of 7 parts by mass, a plasticizer, a thickener, a slipping agent, water and the like were further added, and a slurry B was prepared using a universal stirrer. And this slurry B was knead | mixed using the kneading machine, and the plasticized clay B was obtained.

Next, the inner diameter that determines the outer diameter of the molded body is 250 mm, and the clay is put into a plunger-type vertical extruder equipped with a mold having a slit for forming the partition walls 4 of the honeycomb structure 1. A and B are sequentially added, formed into a honeycomb shape by applying pressure, dried, and then the length of the portion made of the top A and the portion made of the top B (in the direction of the A axis shown in FIG. 1). The molded body was cut so that the outflow side was made of the earthen A and the outflow side was made of the earthen B.

And after arrange | positioning a molded object to an electric furnace, the sintered compact was obtained by hold | maintaining for 5 hours by making temperature into 1380 degreeC in oxidizing atmosphere. The end face (OF) on the outflow side of the obtained sintered body is masked in a checkered pattern so that the sealing material 3b is sealed, and the end face (OF) side on the outflow side of the sintered body is made into slurry A. Soaked.

And in the state which immersed the outflow side of the sintered compact in the slurry A, it was equipped with the front-end | tip part coat | covered with water-repellent resin, and the pin by which this front-end | tip part was formed flatly from the inflow side end surface (IF) After inserting into the flow hole 2 forming the sealing material 3b and adjusting the position of the tip of the pin so that the thickness of the sealing material 3b is 2.5 mm, it enters the flow hole 2 on the outflow side. The resulting slurry A was dried at room temperature to form a sealing material 3b on the outflow side of the molded body. Then, the pin was removed, and the same operation as described above was performed on the inflow side end face (IF) side to form the inflow side sealing material 3a of the molded body.

  Then, the molded body is held at a temperature of 1300 ° C. for 2 hours using an electric furnace, and the inflow side end face (IF) and the outflow side end face (OF) are shown in FIGS. 4A and 4B, respectively. Sample No. which is a honeycomb structure shown in FIG. 1-15 were obtained.

  Sample No. 1 to 15 are honeycomb structures in which the outer diameter and the length in the axial direction A are 144 mm and 156 mm, respectively, and the number per unit area of the flow holes 2 in the cross section perpendicular to the axial direction A is 300 CPSI Body 1 was designated.

  And the content of the additive contained in the partition wall 4 forming each of the inflow side and the outflow side of the flow hole 2 was determined using a fluorescent X-ray analysis method. The values are shown in Table 1.

Then, separately connect the end face (IF) on the inflow side of each sample to a diesel particulate generator (not shown), and then dry air containing particulates from this device at a temperature of 25 ° C. has a flow rate per unit time of 2.27 Nm. ^{3 /} min as by spraying toward each sample, relative to the volume 0.001 m ³ of the honeycomb structure, and the fine particles are 12g collected.

  The honeycomb structure was regenerated by burning and removing the collected fine particles using an electric heater (not shown) arranged on the end face (IF) side on the inflow side of the honeycomb structure.

The regeneration condition is that the combustion temperature and combustion time near the end face (IF) on the inflow side are 1200 ° C. and 10 minutes, respectively, and air is supplied to the honeycomb structure, and the flow rate of this air per unit time is 1.0 m ³ / min. It was. After regenerating the honeycomb structure, again by the same method as described above,
In each sample, 12 g of fine particles were collected for a volume of 0.001 m ³ of the honeycomb structure. This collection and regeneration was regarded as one cycle. After repeating this cycle and regenerating, the partition walls were visually observed, and the number of cycles in which cracks were observed for the first time is shown in Table 1.

Further, in order to evaluate the erosion resistance, a honeycomb structure in which 12 g of fine particles were collected with a volume of 0.001 m ³ was held at 1600 ° C. in an air atmosphere by a method described above, and 4 hours passed. Thereafter, the partition walls were visually confirmed every 30 minutes, and the time at which melting was first confirmed was shown in Table 1.

  As shown in Table 1, sample no. 1 does not contain an additive composed of at least one of boron, chromium, zirconium, and niobium on both the inflow side and the outflow side, so that a local temperature rise occurs and it cools relatively quickly after combustion. Cracks and erosion are observed at an early stage.

On the other hand, sample no. Nos. 2 to 15 contain an additive consisting of at least one of boron, chromium, zirconium, and niobium at least on the outflow side, so the element of the additive has a high melting point of 1852 ° C. or higher. Even if the temperature of the partition wall rises, the additive is difficult to melt, and the specific heat capacity is as high as 265 J / (kg · K) or more, so that the local temperature rise is suppressed and it does not cool rapidly even after combustion is finished. Since it cools slowly, it is difficult for the partition wall 4 to be melted or cracked.

  In particular, sample no. Since 3-5 and 8-15 contain more additive on the outflow side than in the inflow side, the outflow side partition where the temperature rise is likely to occur is less susceptible to melting and cracking. It can be said that the whole can be efficiently reproduced.

  Sample No. In Nos. 3 to 8, since the content of the additive on the outflow side of the partition wall 4 is 5% by mass or more, the effect of the additive is relatively large, and the partition wall 4 is less likely to be melted or cracked. In addition, since the content of the additive on the outflow side of the partition walls 4 is 30% by mass or less, the mass of the partition walls themselves hardly increases, so that a reduction in fuel consumption of the internal combustion engine due to an increase in the mass of the honeycomb structure can be suppressed.

1: honeycomb structure 2, 2a, 2b: flow hole 3, 3a, 3b: sealing material 4: partition wall 5: heat insulating material layer 6: case 7: inlet 8: outlet 9: exhaust pipe
10: Exhaust gas treatment equipment

Claims (5)

A honeycomb comprising a plurality of flow holes partitioned by a gas-permeable partition wall having an axial wall surface, and a sealing material that alternately seals the inflow side and the outflow side of the plurality of flow holes The structure is characterized in that the partition wall is made of a sintered body mainly composed of aluminum titanate, and contains an additive material composed of at least one of boron, chromium, zirconium and niobium at least on the outflow side. A honeycomb structure. The honeycomb structure according to claim 1, wherein the additive is contained in a larger amount on the outflow side than in the inflow side. The honeycomb structure according to claim 1 or 2, wherein the content of the additive on the outflow side of the partition wall is 5 mass% or more and 30 mass% or less. The honeycomb structure according to any one of claims 1 to 3, wherein a catalyst is supported on the wall surface of the partition wall. An exhaust gas treatment apparatus comprising the honeycomb structure according to any one of claims 1 to 4.

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