JP7316766B2 - N2O decomposition catalyst structure, manufacturing method thereof, and N2O removal device having said N2O decomposition catalyst structure - Google Patents

Description

The present invention provides an N ₂ O decomposition catalyst structure comprising a carrier having a porous structure and iron oxide functioning as an N ₂ O decomposition catalyst, a method for producing the same, and N ₂ having the N ₂ O decomposition catalyst structure. It relates to an O removal device.

N ₂ O is contained in exhaust gas from sewage sludge incinerators, exhaust gas from thermal power plants, exhaust gas from automobiles, and the like. N ₂ O is a gas with a strong greenhouse effect, and has 310 times the greenhouse effect of carbon dioxide. Therefore, there is a demand for reducing N ₂ O emissions into the atmosphere.

In order to reduce N ₂ O emissions, N ₂ O is decomposed before being released into the atmosphere. Examples of N ₂ O decomposition catalysts include iron oxide, platinum, cobalt, cobalt oxide, copper, copper oxide, nickel, nickel oxide, and various other metals and metal oxides.

As a structure of the N ₂ O decomposition catalyst, a catalyst packed bed filled with a pellet-shaped iron-zeolite catalyst is disclosed (Patent Document 1). As described above, the N ₂ O decomposition catalyst is sometimes used while supported on a carrier such as zeolite.

However, conventional N ₂ O decomposition catalysts such as iron oxide and platinum have the problem that they aggregate within the carrier in a high-temperature environment, suppressing catalytic activity. In addition, platinum catalysts have the problem of being more expensive than catalysts such as iron oxide. On the other hand, a catalyst such as iron oxide is less expensive than a platinum catalyst, but has a reaction initiation temperature as high as 300° C., which is higher than 100° C. for platinum, and has the problem of agglomeration at the reaction initiation temperature.

WO2011/114609

However, in the catalyst structure as described above, since the catalyst particles are supported on the surface or near the surface of the carrier, the force received from the fluid containing N ₂ O during N ₂ O decomposition and the temperature during the decomposition reaction are affected. The catalyst particles move within the carrier due to the influence, and agglomeration (sintering) of the catalyst particles tends to occur. Agglomeration of catalyst particles reduces the effective surface area of the catalyst and reduces the catalytic activity, shortening the life of the catalyst. However, there is a problem that the replacement work is complicated and resource saving cannot be achieved. Further, when the catalyst structure is used at a low temperature, the activity of the N ₂ O decomposition catalyst is lowered, so that the N ₂ O removal ability cannot be obtained.

An object of the present invention is to suppress deterioration of the N ₂ O decomposition function even when the usage temperature is high and to achieve a long life, and to have N ₂ O removal ability even when the usage temperature is low. An object of the present invention is to provide an N ₂ O decomposition catalyst structure, a method for producing the same, and an N ₂ O removal apparatus having the N ₂ O decomposition catalyst structure.

The present inventors have made intensive studies to achieve the above object, and as a result, provided a carrier with a porous structure composed of a zeolite-type compound and at least one metal oxide inherent in the carrier, The support has passages that communicate with each other, and the metal oxide is present in at least the passages of the support, thereby suppressing a decrease in the catalytic activity of the metal oxide and realizing a long service life. We have found that a catalyst structure for decomposing ₂ O can be obtained, and have completed the present invention based on this finding.

That is, the gist and configuration of the present invention are as follows.
[1] a carrier having a porous structure composed of a zeolite-type compound;
at least one metal oxide inherent in the support; and
with
the carrier has passages that communicate with each other;
A catalyst structure for decomposing N ₂ O, wherein the metal oxide is present in at least the passages of the carrier.
[2] The passage is defined by the framework structure of the zeolite-type compound, and any of the one-dimensional, two-dimensional, and three-dimensional pores, and the one-dimensional, two-dimensional, and three-dimensional pores. The catalyst structure for decomposing N ₂ O according to [1] above, characterized in that it has an enlarged diameter portion different from any of them, and the metal oxide is present at least in the enlarged diameter portion. body.
[3] The N ₂ according to [2] above, wherein the enlarged diameter portion communicates with a plurality of holes that constitute any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Catalyst structure for O decomposition.
[4] The N ₂ O decomposition catalyst structure according to the above [2] or [3], wherein the metal oxide is metal oxide fine particles.
[5] The N ₂ O decomposition according to [4] above, wherein the average particle diameter of the metal oxide fine particles is larger than the average inner diameter of the passage and equal to or smaller than the inner diameter of the expanded diameter portion. catalyst structure for
[6] _The above [ 4] or the N ₂ O decomposition catalyst structure according to [5].
[7] The N ₂ O decomposition catalyst structure according to any one of [4] to [6] above, wherein the metal oxide fine particles have an average particle size of 0.1 nm to 50 nm.
[8] The N ₂ O decomposition catalyst structure according to [7] above, wherein the metal oxide fine particles have an average particle size of 0.5 nm to 14.0 nm.
[9] The N according to any one of [4] to [8] above, wherein the ratio of the average particle size of the metal oxide fine particles to the average inner diameter of the passage is 0.06 to 500. ₂ O decomposition catalyst structure.
[10] The N ₂ O decomposition catalyst structure according to [9] above, wherein the ratio of the average particle size of the metal oxide fine particles to the average inner diameter of the passage is 0.1 to 45. .
[11] The N ₂ O decomposition catalyst according to [10] above, wherein the ratio of the average particle size of the metal oxide fine particles to the average inner diameter of the passage is 1.7 to 4.5. Structure.
[12] the passage has an average inner diameter of 0.1 nm to 1.5 nm;
The N ₂ O decomposition catalyst structure according to any one of [2] to [11] above, wherein the inner diameter of the enlarged diameter portion is 0.5 nm to 50 nm.
[13] The N ₂ O decomposition catalyst structure according to any one of [1] to [12] above, further comprising at least one other metal oxide held on the outer surface of the support. body.
[14] The content of the at least one metal oxide inherent in the support is higher than the content of the at least one other metal oxide retained on the outer surface of the support, The catalyst structure for N ₂ O decomposition according to the above [13].
[15] The N ₂ O decomposition catalyst structure according to any one of [1] to [14] above, wherein the zeolite-type compound is a silicate compound.
[16] An N ₂ O removal device comprising the N ₂ O decomposition catalyst structure according to any one of [1] to [15] above.
[17] A calcination step of calcining the precursor material (A) impregnated with a metal-containing solution for obtaining a carrier having a porous structure composed of a zeolite-type compound;
a hydrothermal treatment step of hydrothermally treating the precursor material (C) obtained by firing the precursor material (B);
A method for producing a catalyst structure for N ₂ O decomposition, characterized by comprising:
[18] The N ₂ according to [17] above, characterized in that 50 to 500% by mass of a nonionic surfactant is added to the precursor material (A) before the firing step. A method for producing an O decomposition catalyst structure.
[19] impregnating the precursor material (A) with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in multiple portions before the firing step; A method for producing an N ₂ O decomposition catalyst structure according to the above [17] or [18].
[20] When the precursor material (A) is impregnated with the metal-containing solution before the firing step, the amount of the metal-containing solution added to the precursor material (A) is In terms of the ratio (atomic ratio Si/M) of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to (A), The method for producing a catalyst structure for decomposition of N ₂ O according to any one of [17] to [19] above, wherein the adjustment is made to be 10 to 1000.
[21] The method for producing a catalyst structure for decomposition of N ₂ O according to [17] above, wherein the precursor material (C) and a structure-directing agent are mixed in the hydrothermal treatment step.
[22] The method for producing an N ₂ O decomposition catalyst structure according to [17] above, wherein the hydrothermal treatment step is performed in a basic atmosphere.

According to the present invention, even when the operating temperature is high, it is possible to suppress deterioration of the N ₂ O decomposition function and realize a long service life, and even when the operating temperature is low, it has the ability to remove N ₂ O. It is possible to provide an N ₂ O decomposition catalyst structure, a method for producing the same, and an N ₂ O removal apparatus having the N ₂ O decomposition catalyst structure.

1A and 1B schematically show the internal structure of an N ₂ O decomposition catalyst structure according to an embodiment of the present invention, and FIG. ), and FIG. 1(b) is a partially enlarged sectional view. FIG. 2 is a partially enlarged cross-sectional view for explaining an example of the function of the N ₂ O decomposition catalyst structure of FIG. 1, FIG. 2(a) explaining the sieve function, and FIG. It is a figure to do. FIG. 3 is a flow chart showing an example of a method for manufacturing the N ₂ O decomposition catalyst structure of FIG. FIG. 4 is a schematic diagram showing a modification of the N ₂ O decomposition catalyst structure of FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Structure of catalyst structure for N ₂ O decomposition]
FIG. 1 is a diagram schematically showing the configuration of an N ₂ O decomposition catalyst structure according to an embodiment of the present invention, (a) being a perspective view (partially shown in cross section), (b). is a partially enlarged cross-sectional view. Note that the N ₂ O decomposition catalyst structure in FIG. 1 shows an example thereof, and the shape, dimensions, etc. of each component according to the present invention are not limited to those in FIG. 1 .

As shown in FIG. 1(a), the N ₂ O decomposition catalyst structure 1 includes a carrier 10 having a porous structure made of a zeolite-type compound and at least one N ₂ O It comprises a metal oxide, preferably metal oxide fine particles 20, which is a catalytic material for decomposition.

In the N ₂ O decomposition catalyst structure 1 , the plurality of metal oxide fine particles 20 , 20 , . . . Details of the metal oxide fine particles 20 will be described later.

The carrier 10 has a porous structure, and as shown in FIG. 1(b), preferably has a plurality of holes 11a, 11a, . Here, the metal oxide fine particles 20 are present in at least the passages 11 of the carrier 10 and preferably held in at least the passages 11 of the carrier 10 .

With such a configuration, movement of the metal oxide fine particles 20 within the carrier 10 is regulated, and aggregation of the metal oxide fine particles 20, 20 is effectively prevented. As a result, the reduction in the effective surface area of the metal oxide fine particles 20 can be effectively suppressed, and the catalytic activity of the metal oxide fine particles 20, which is the N ₂ O decomposition catalyst material, is maintained over a long period of time. That is, according to the N ₂ O decomposition catalyst structure 1, it is possible to suppress the deterioration of the catalytic activity due to aggregation of the metal oxide fine particles 20, and it is possible to extend the life of the N ₂ O decomposition catalyst structure 1. . In addition, by extending the life of the N ₂ O decomposition catalyst structure 1, the replacement frequency of the N ₂ O decomposition catalyst structure 1 can be reduced, and the disposal amount of the used N ₂ O decomposition catalyst structure 1 can be greatly reduced. can be reduced to 2, and resource saving can be achieved.

Normally, when the N ₂ O decomposition catalyst structure is used in a fluid containing N ₂ O, it may receive an external force from the fluid. In this case, if the metal oxide fine particles 20 are only held on the outer surface of the carrier 10 in an adhered state, there is a problem that they tend to separate from the outer surface of the carrier 10 under the influence of the external force from the fluid. On the other hand, in the N ₂ O decomposition catalyst structure 1, the metal oxide fine particles 20 are present at least in the passages 11 of the carrier 10, so even if the carrier 10 is affected by an external force, metal oxidation from the carrier 10 does not occur. The particles 20 are difficult to separate. That is, when the N ₂ O decomposition catalyst structure 1 is in the fluid, the fluid flows into the passage 11 from the holes 11 a of the carrier 10 , so the speed of the fluid flowing in the passage 11 is reduced by the flow resistance ( It is thought that the speed of the fluid flowing on the outer surface of the carrier 10 becomes slower due to the frictional force). Due to the influence of such channel resistance, the pressure that the metal oxide fine particles 20 held in the passage 11 receive from the fluid is lower than the pressure that the metal oxide fine particles receive from the fluid outside the carrier 10 . Therefore, the separation of the metal oxide fine particles 20 inherent in the carrier 10 can be effectively suppressed, and the catalytic activity of the metal oxide fine particles 20, which is the catalyst material for decomposing N ₂ O, can be stably maintained for a long period of time. becomes possible. It is believed that the flow path resistance as described above increases as the passage 11 of the carrier 10 has a plurality of bends and branches and the inside of the carrier 10 has a more complicated three-dimensional three-dimensional structure. .

In addition, the passage 11 is defined by the framework structure of the zeolite-type compound, and any of the one-dimensional, two-dimensional, and three-dimensional pores, and the one-dimensional, two-dimensional, and three-dimensional pores It is preferable to have an enlarged diameter portion 12 different from any of them, and at this time, it is preferable that the metal oxide fine particles 20 are present at least in the enlarged diameter portion 12 and are enclosed by at least the enlarged diameter portion 12. more preferably. The one-dimensional pore here means a tunnel-shaped or cage-shaped pore that forms a one-dimensional channel, or a plurality of tunnel-shaped or cage-shaped pores that form a plurality of one-dimensional channels (a plurality of one-dimensional pores). channel). A two-dimensional pore refers to a two-dimensional channel in which a plurality of one-dimensional channels are two-dimensionally connected, and a three-dimensional pore refers to a three-dimensional channel in which a plurality of one-dimensional channels are three-dimensionally connected. Point. As a result, movement of the metal oxide fine particles 20 within the carrier 10 is further regulated, and detachment of the metal oxide fine particles 20 and aggregation of the metal oxide fine particles 20, 20 can be more effectively prevented. The inclusion refers to a state in which the metal oxide fine particles 20 are included in the carrier 10 . At this time, the metal oxide fine particles 20 and the carrier 10 do not necessarily have to be in direct contact with each other. The metal oxide fine particles 20 may be indirectly held by the carrier 10 with the intervening.

Although FIG. 1(b) shows the case where the metal oxide fine particles 20 are enclosed in the expanded diameter portion 12, the configuration is not limited to this, and the metal oxide fine particles 20 are partially expanded. It may be held in the passage 11 in a state of protruding outside the diameter portion 12 . Moreover, the metal oxide fine particles 20 may be partially embedded in a portion of the passage 11 other than the enlarged diameter portion 12 (for example, an inner wall portion of the passage 11), or may be held by adhesion or the like. Moreover, it is preferable that the diameter-enlarging portion 12 communicates with a plurality of holes 11a, 11a forming any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. As a result, separate passages different from the one-dimensional, two-dimensional, or three-dimensional holes are provided inside the carrier 10, so that the catalytic function of the metal oxide fine particles 20 can be exhibited more effectively.

Further, the passage 11 is formed three-dimensionally inside the carrier 10 including a branched portion or a confluence, and the enlarged diameter portion 12 is preferably provided at the branched portion or the confluence of the passage 11. .

The average inner diameter D _F of the passages 11 formed in the carrier 10 is calculated from the average value of the short diameter and long diameter of the holes 11a constituting any one of the one-dimensional, two-dimensional and three-dimensional holes. It is 0.1 nm to 1.5 nm, preferably 0.5 nm to 0.8 nm. Further, the inner diameter D _E of the expanded diameter portion 12 is, for example, 0.5 nm to 50 nm, preferably 1.1 nm to 40 nm, more preferably 1.1 nm to 3.3 nm. The inner diameter D _E of the expanded diameter portion 12 depends, for example, on the pore diameter of the precursor material (A) described later and the average particle diameter D _C of the enclosed metal oxide fine particles 20 . The inner diameter D _E of the expanded diameter portion 12 is large enough to enclose the metal oxide fine particles 20 .

Carrier 10 is composed of a zeolite-type compound. Therefore, even if the operating temperature of the N ₂ O decomposition catalyst structure 1 is low and sufficient catalytic activity is not obtained, the N ₂ O contained in the fluid is zeolite type due to the adsorption ability of the zeolite type compound. The N ₂ O is removed from the fluid by being adsorbed by the compound.

Examples of zeolite-type compounds include zeolite (aluminosilicate), cation-exchanged zeolite, silicate compounds such as silicalite, zeolite-related compounds such as aluminoborates, aluminoarsenates, and germanates, and molybdenum phosphate. phosphate-based zeolite-like substances, and the like. Among them, the zeolite-type compound is preferably a silicate compound.

The skeleton structure of the zeolite type compound is FAU type (Y type or X type), MTW type, MFI type (ZSM-5), FER type (ferrierite), LTA type (A type), MWW type (MCM-22). , MOR type (mordenite), LTL type (L type), BEA type (beta type), etc., preferably MFI type, more preferably ZSM-5. A zeolite-type compound is formed with a plurality of pores having a pore size corresponding to each skeleton structure. be.

The metal oxide fine particles 20, which are the N ₂ O decomposition catalyst material, will be described in detail below.

The metal oxide fine particles 20 _may be primary particles or may be secondary particles formed by agglomeration of primary particles. It is larger than the average inner diameter D _F and equal to or less than the inner diameter D _E of the enlarged diameter portion 12 ( _DF <D _C ≤ D _E ). Such metal oxide fine particles 20 preferably exist in the enlarged diameter portion 12 within the passage 11 , and the movement of the metal oxide fine particles 20 within the carrier 10 is restricted. Therefore, even when the metal oxide fine particles 20 receive an external force from the fluid or when the N ₂ O decomposition catalyst structure 1 is used at a high temperature, the metal oxide fine particles 20 do not move within the carrier 10 . present in each of the enlarged diameter portions 12, 12, . .

In addition, the average particle diameter D _C of the metal oxide fine particles 20 is preferably 0.1 nm to 50 nm, more preferably 0.1 nm or more and less than 30 nm, in both primary particles and secondary particles. It is preferably 0.5 nm to 14.0 nm, particularly preferably 1.0 nm to 3.3 nm. In addition, the ratio of the average particle diameter D _C of the metal oxide fine particles 20 to the average inner diameter D _F of the passage 11 (D _C /D _F ) is preferably 0.06 to 500, more preferably 0.1 to 45. , more preferably 1.1 to 45, and particularly preferably 1.7 to 4.5. The metal element (M) of the metal oxide fine particles 20 _{is preferably contained in an amount of 0.5 to 2.5% by mass with respect to the catalyst structure 1 for N 2 O} decomposition. More preferably, it is contained in an amount of 0.5 to 1.5% by mass with respect to the catalyst structure 1. For example, when the metal element (M) is Co, the content (% by mass) of the Co element is {(mass of Co element)/(mass of all elements in N ₂ O decomposition catalyst structure 1)}× It is represented by 100.

The metal oxide fine particles 20 may be composed of a metal oxide, for example, may be composed of a single metal oxide, or may be composed of a mixture of two or more metal oxides. good too. In this specification, the “metal oxide” (as a material) constituting the metal oxide fine particles 20 means an oxide containing one kind of metal element (M) and an oxide containing two or more kinds of metal elements (M). It is a generic term for oxides containing one or more metal elements (M).

Examples of such metal oxides include cobalt oxide (CoO _x ), nickel oxide (NiO _{x ), iron oxide (FeO x )} , copper oxide (CuO _x ), zirconium oxide (ZrO _x ), cerium oxide (CeO _{x )} , ), aluminum oxide (AlO _x ), niobium oxide (NbO _x ), titanium oxide (TiO _x ), bismuth oxide (BiO _x ), molybdenum oxide (MoO _x ), vanadium oxide (VO _x ), chromium oxide (CrO _x ) , zinc oxide (ZnO _x ), etc., and it is preferable to use at least one of the above as a main component.

Further, the ratio of silicon (Si) constituting the carrier 10 to the metal element (M) constituting the metal oxide fine particles 20 (atomic ratio Si/M) is preferably 10 to 1000, more preferably 50 to 200. is more preferable. If the above ratio is more than 1000, there is a possibility that the activity as a catalytic substance for decomposition of N ₂ O may not be sufficiently obtained, such as low activity. On the other hand, when the ratio is less than 10, the ratio of the metal oxide fine particles 20 becomes too large, and the strength of the carrier 10 tends to decrease. The metal oxide fine particles 20 referred to here refer to metal oxide fine particles held or supported inside the carrier 10 and do not include metal oxide fine particles adhering to the outer surface of the carrier 10 .

[Catalytic activity of catalyst structure for N ₂ O decomposition]
As described above, the N ₂ O decomposition catalyst structure 1 includes the carrier 10 having a porous structure and at least one metal oxide fine particle 20 present in the carrier 10 . The N ₂ O decomposition catalyst structure 1 exerts catalytic activity corresponding to the metal oxide fine particles 20 when the metal oxide fine particles 20 contained in the carrier 10 come into contact with the fluid. Specifically, the fluid coming into contact with the outer surface 10a of the N ₂ O decomposition catalyst structure 1 flows into the carrier 10 through the holes 11a formed in the outer surface 10a, is guided into the passage 11, and is guided into the passage 11. , and exits the N ₂ O decomposition catalyst structure 1 through another hole 11a. When the fluid comes into contact with the metal oxide fine particles 20 present in the passage 11 on the path along which the fluid moves through the passage 11, a reaction (N ₂ O decomposition reaction) according to the catalytic activity of the metal oxide fine particles 20 occurs. occurs. Further, the N ₂ O decomposition catalyst structure 1 has a molecular sieving ability due to the porous structure of the carrier 10 .

First, the molecular sieving ability _of the N ₂ O decomposition catalyst structure 1 will be described with reference to FIG. As shown in FIG. 2( a ), N ₂ O molecules having a size equal to or less than the diameter of the holes 11 a , in other words, equal to or less than the inner diameter of the passage 11 can flow into the carrier 10 . On the other hand, non-N ₂ O molecules 15 having a size exceeding the pore diameter of the pores 11 a cannot flow into the carrier 10 . In this way, when the fluid contains multiple types of compounds, the reaction of the compounds that cannot flow into the carrier 10 is regulated, and the compounds that can flow into the carrier 10 can react.

Among the compounds produced in the carrier 10 by the reaction, only compounds composed of molecules having a size equal to or smaller than the pore diameter of the pores 11a can exit the carrier 10 through the pores 11a and are obtained as reaction products. On the other hand, compounds that cannot exit the carrier 10 through the pores 11a can be expelled from the carrier 10 by converting them into compounds composed of molecules having a size that allows them to exit the carrier 10. . Thus, by using the N ₂ O decomposition catalyst structure 1, a specific reaction product can be selectively obtained.

In the N ₂ O decomposition catalyst structure 1, as shown in FIG. 2(b), the metal oxide fine particles 20 are enclosed in the enlarged diameter portion 12 of the passage 11. As shown in FIG. When the average particle size D _C of the metal oxide fine particles 20 is larger than the average inner diameter D _F of the passage 11 and smaller than the inner diameter D _E of the expanded diameter portion 12 (D _F <D _C <D _E ), the metal A small passage 13 is formed between the oxide fine particles 20 and the enlarged diameter portion 12 . Therefore, as indicated by the arrows in FIG. 2B, the fluid flowing into the small passage 13 comes into contact with the metal oxide fine particles 20 . Since each metal oxide fine particle 20 is surrounded by the enlarged diameter portion 12 , movement within the carrier 10 is restricted. This prevents aggregation of the metal oxide fine particles 20 and 20 in the carrier 10 . As a result, a large contact area between the metal oxide fine particles 20 and the fluid can be stably maintained.

When the N ₂ O molecules flowing into the passage 11 come into contact with the metal oxide fine particles 20 , the N ₂ O molecules are decomposed into N ₂ and O ₂ by an oxidative decomposition reaction caused by oxygen in the metal oxide fine particles 20 . For example, when the iron oxide contained in the metal oxide fine particles 20 is used as a catalyst, when the N ₂ O molecules flowing into the passage 11 come into contact with the iron oxide fine particles, the N 2 O molecules are converted into N ₂ O molecules by an oxidation reaction caused by oxygen in the iron oxide fine particles. It is decomposed into N ₂ and O ₂ and can reduce the concentration of N ₂ O contained in the gas.

From the above, since the catalytic reaction initiation temperature of the metal oxide fine particles 20 such as iron oxide is as high as 300° C., even if the N ₂ O decomposition catalyst structure 1 is used at a high temperature, the metal oxide fine particles 20 can be produced. Since agglomeration is prevented, deterioration of the N ₂ O decomposition function of the metal oxide fine particles can be suppressed. That is, even if sufficient catalytic activity cannot be obtained under conditions where the operating temperature of the N ₂ O decomposition catalyst structure 1 is low, the N ₂ O contained in the fluid is reduced by the adsorption capacity of the zeolite-type compound. It is removed from the fluid by being adsorbed by the zeolite type compound, and even if the operating temperature of the catalyst structure 1 for N ₂ O decomposition becomes high, the deterioration of the N ₂ O decomposition function can be suppressed. It is possible to decompose and remove the N ₂ O adsorbed to and the N ₂ O contained in the fluid supplied at a high temperature.

Further, an N ₂ O removal device may be formed using the N ₂ O decomposition catalyst structure 1 . By using the N ₂ O decomposition catalyst structure 1 according to the above-described embodiment, it is possible to obtain an N ₂ O removal device that exhibits the same effects as described above.

[Method for producing catalyst structure for N ₂ O decomposition]
FIG. 3 is a flow chart showing a method of manufacturing the N ₂ O decomposition catalyst structure 1 of FIG. An example of a method for producing a catalyst structure for decomposing N ₂ O will be described below, taking as an example the case where the catalytic substance inherent in the carrier is metal oxide fine particles.

(Step S1: preparation process)
As shown in FIG. 3, first, a precursor material (A) for obtaining a carrier having a porous structure composed of a zeolite-type compound is prepared. The precursor material (A) is preferably a regular mesoporous material, and can be appropriately selected according to the type (composition) of the zeolite compound that constitutes the carrier of the N ₂ O decomposition catalyst structure.

Here, when the zeolite-type compound constituting the carrier of the catalyst structure for N ₂ O decomposition is a silicate compound, the regular mesoporous material has pores with a pore diameter of 1 to 50 nm. It is preferably a compound consisting of a Si—O skeleton that has a uniform size and is regularly developed two-dimensionally or three-dimensionally. Such regular mesoporous materials can be obtained as various synthetic products depending on the synthesis conditions. 16, MCM-41 and the like, among which MCM-41 is preferred. The pore diameter of SBA-1 is 10 to 30 nm, the pore diameter of SBA-15 is 6 to 10 nm, the pore diameter of SBA-16 is 6 nm, the pore diameter of KIT-6 is 9 nm, and the pore diameter of FSM-16 is 3 nm. ˜5 nm, and the pore size of MCM-41 is 1-10 nm. Examples of such ordered mesoporous materials include mesoporous silica, mesoporous aluminosilicate, mesoporous metallosilicate, and the like.

Precursor material (A) may be either commercially available or synthetic. Synthesis of the precursor material (A) can be carried out by a known method for synthesizing ordered mesoporous materials. For example, a mixed solution containing raw materials containing constituent elements of the precursor material (A) and a templating agent for defining the structure of the precursor material (A) is prepared, and the pH is adjusted as necessary. , perform hydrothermal treatment (hydrothermal synthesis). After that, the precipitate (product) obtained by the hydrothermal treatment is recovered (for example, filtered), washed and dried as necessary, and further calcined to obtain a powdery ordered mesoporous material. A precursor material (A) is obtained. Here, as the solvent of the mixed solution, for example, water, an organic solvent such as alcohol, or a mixed solvent thereof can be used. The raw material is selected according to the type of carrier, and examples thereof include silica agents such as tetraethoxysilane (TEOS), fumed silica, and quartz sand. As the templating agent, various surfactants, block copolymers, etc. can be used, and it is preferable to select them according to the type of synthetic material of the regular mesoporous material. is preferably a surfactant such as hexadecyltrimethylammonium bromide. The hydrothermal treatment can be carried out, for example, in a closed vessel under conditions of 80 to 800° C., 5 hours to 240 hours, and 0 to 2000 kPa. The calcination treatment can be performed, for example, in the air at 350 to 850° C. for 2 to 30 hours.

(Step S2: impregnation step)
Next, the prepared precursor material (A) is impregnated with a metal-containing solution to obtain a precursor material (B).

The metal-containing solution may be any solution containing a metal component corresponding to the metal element (M) (for example, metal ion) that constitutes the metal oxide fine particles of the N ₂ O decomposition catalyst structure. , can be prepared by dissolving a metal salt containing the metal element (M). Examples of such metal salts include metal salts such as chlorides, hydroxides, oxides, sulfates and nitrates, with nitrates being preferred. As the solvent, for example, water, an organic solvent such as alcohol, or a mixed solvent thereof can be used.

The method for impregnating the precursor material (A) with the metal-containing solution is not particularly limited. For example, while stirring the powdery precursor material (A), the precursor material (A ), the metal-containing solution is preferably added little by little in multiple batches. In addition, from the viewpoint of making it easier for the metal-containing solution to penetrate into the pores of the precursor material (A), a surfactant is added as an additive to the precursor material (A) in advance before adding the metal-containing solution. It is preferable to add. Such an additive has the function of coating the outer surface of the precursor material (A), suppresses the metal-containing solution added thereafter from adhering to the outer surface of the precursor material (A), It is believed that the contained solution is more likely to penetrate into the pores of the precursor material (A).

Examples of such additives include nonionic surfactants such as polyoxyethylene oleyl ether, polyoxyethylene alkyl ether and polyoxyethylene alkylphenyl ether. Since these surfactants have a large molecular size and cannot penetrate into the pores of the precursor material (A), they do not adhere to the inside of the pores and prevent the metal-containing solution from entering into the pores. not considered to be a hindrance. As a method for adding the nonionic surfactant, for example, it is preferable to add 50 to 500% by mass of the nonionic surfactant to the precursor material (A) before the baking step described later. If the amount of the nonionic surfactant added to the precursor material (A) is less than 50% by mass, the above suppressing action is difficult to manifest, and the nonionic surfactant is added to the precursor material (A) in an amount of 500% by mass. Adding more than % by mass is not preferable because the viscosity increases too much. Therefore, the amount of the nonionic surfactant added to the precursor material (A) is set within the above range.

In addition, the amount of the metal-containing solution added to the precursor material (A) is the amount of the metal element (M) contained in the metal-containing solution impregnated into the precursor material (A) (that is, the amount of the precursor material (B ) is preferably adjusted as appropriate in consideration of the amount of the metal element (M) to be incorporated in ). For example, before the firing step to be described later, the addition amount of the metal-containing solution added to the precursor material (A) is set to In terms of the ratio of silicon (Si) constituting the precursor material (A) (atomic ratio Si/M), it is preferably adjusted to be 10 to 1000, and adjusted to be 50 to 200. is more preferable. For example, if a surfactant is added as an additive to the precursor material (A) before adding the metal-containing solution to the precursor material (A), the addition of the metal-containing solution to the precursor material (A) By setting the amount to 50 to 200 in terms of the atomic number ratio Si/M, the metal element (M) of the metal oxide fine particles is adjusted to 0.5 to 2.0 with respect to the N ₂ O decomposition catalyst structure. It can be contained at 5% by mass. In the state of the precursor material (B), the amount of the metal element (M) present inside the pores is the same under conditions such as the metal concentration of the metal-containing solution, the presence or absence of the above additives, and other conditions such as temperature and pressure. If so, it is roughly proportional to the amount of the metal-containing solution added to the precursor material (A). Also, the amount of the metal element (M) inherent in the precursor material (B) is in a proportional relationship with the amount of the metal element constituting the metal oxide fine particles inherent in the carrier of the catalyst structure for N ₂ O decomposition. Therefore, by controlling the addition amount of the metal-containing solution to be added to the precursor material (A) within the above range, the inside of the pores of the precursor material (A) can be sufficiently impregnated with the metal-containing solution. , the amount of the metal oxide fine particles contained in the carrier of the catalyst structure for N ₂ O decomposition can be adjusted.

After impregnating the precursor material (A) with the metal-containing solution, a washing treatment may be performed as necessary. As the cleaning solution, water, an organic solvent such as alcohol, or a mixed solution thereof can be used. Moreover, it is preferable that the precursor material (A) is impregnated with the metal-containing solution, washed as necessary, and then dried. Drying treatments include natural drying for about one night and high-temperature drying at 150° C. or less. In addition, when the precursor material (A) is subjected to the firing treatment described later in a state in which a large amount of water contained in the metal-containing solution or the washing solution remains in the precursor material (A), regular mesopores of the precursor material (A) Sufficient drying is preferable because the skeleton structure of the substance may be destroyed.

(Step S3: Firing step)
Next, the precursor material (B) in which the metal-containing solution is impregnated in the precursor material (A) for obtaining a carrier having a porous structure composed of a zeolite-type compound is calcined to obtain a precursor material (C). get

The calcination treatment is preferably carried out, for example, in the air at 350 to 850° C. for 2 to 30 hours. By such a calcination treatment, the metal component impregnated in the pores of the ordered mesoporous material undergoes crystal growth to form metal oxide fine particles in the pores.

(Step S4: hydrothermal treatment step)
Next, a mixed solution is prepared by mixing the precursor material (C) and a structure-directing agent, and the precursor material (C) obtained by calcining the precursor material (B) is hydrothermally treated with N ₂ A catalyst structure for O decomposition is obtained.

The structure directing agent is a templating agent for defining the skeleton structure of the carrier of the N ₂ O decomposition catalyst structure, and for example, a surfactant can be used. The structure-directing agent is preferably selected according to the skeleton structure of the carrier of the catalyst structure for N ₂ O decomposition. and other surfactants are suitable.

Mixing of the precursor material (C) and the structure-directing agent may be performed during the main hydrothermal treatment step or before the hydrothermal treatment step. The method for preparing the mixed solution is not particularly limited, and the precursor material (C), the structure-directing agent, and the solvent may be mixed at the same time, or the precursor material (C) and the structure-directing agent may be mixed together in the solvent. Each dispersion solution may be mixed after dispersing each of the agents into individual solutions. As the solvent, for example, water, an organic solvent such as alcohol, or a mixed solvent thereof can be used. Moreover, it is preferable that the mixed solution is adjusted in pH with an acid or a base before the hydrothermal treatment.

The hydrothermal treatment can be carried out by a known method, and is preferably carried out in a closed vessel under treatment conditions of 80 to 800° C., 5 hours to 240 hours, and 0 to 2000 kPa. Also, the hydrothermal treatment is preferably performed in a basic atmosphere. Although the reaction mechanism here is not necessarily clear, by performing hydrothermal treatment using the precursor material (C) as a raw material, the skeletal structure of the precursor material (C) as an ordered mesoporous substance gradually collapses. While the position of the metal oxide fine particles inside the pores of the precursor material (C) is generally maintained, the action of the structure-directing agent creates a new skeleton structure (porous structure) as a support for the catalyst structure for N ₂ O decomposition. structure) is formed. The catalyst structure for decomposition of N ₂ O thus obtained comprises a carrier having a porous structure and metal oxide fine particles contained in the carrier, and the porous structure of the carrier allows a plurality of pores to communicate with each other. At least a portion of the metal oxide fine particle exists in the channel of the carrier. In the present embodiment, in the hydrothermal treatment step, a mixed solution is prepared by mixing the precursor material (C) and the structure-directing agent, and the precursor material (C) is hydrothermally treated, but the present invention is not limited to this. Alternatively, the precursor material (C) may be hydrothermally treated without mixing the precursor material (C) and the structure-directing agent.

The precipitate (N ₂ O decomposition catalyst structure) obtained after the hydrothermal treatment is preferably recovered (for example, separated by filtration) and then washed, dried and calcined as necessary. As the cleaning solution, water, an organic solvent such as alcohol, or a mixed solution thereof can be used. Drying treatments include natural drying for about one night and high-temperature drying at 150° C. or less. It should be noted that if the calcination treatment is performed in a state in which a large amount of water remains in the precipitate, there is a risk that the skeleton structure as a carrier of the N ₂ O decomposition catalyst structure will be destroyed, so it is preferable to dry the precipitate sufficiently. Further, the calcination treatment can be performed, for example, in the air under the treatment conditions of 350 to 850° C. for 2 to 30 hours. By such calcination treatment, the structure-directing agent adhering to the N ₂ O decomposition catalyst structure is burned off. In addition, the N ₂ O decomposition catalyst structure can be used as it is without calcining the collected precipitate depending on the purpose of use. For example, when the environment in which the N ₂ O decomposition catalyst structure is used is a high-temperature environment in an oxidizing atmosphere, the structure-directing agent is burned away by exposing it to the environment for a certain period of time, which is the same as in the case of calcination. of the N ₂ O decomposition catalyst structure is obtained, it becomes possible to use it as it is.

[Modification of catalyst structure for N ₂ O decomposition]
FIG. 4 is a schematic diagram showing a modification of the N ₂ O decomposition catalyst structure 1 of FIG.
Although the N ₂ O decomposition catalyst structure 1 of FIG. 1 is provided with the carrier 10 and the metal oxide fine particles 20 contained in the carrier 10, it is not limited to this configuration. 4, the N ₂ O decomposition catalyst structure 2 may further include other metal oxide fine particles 30 held on the outer surface 10 a of the carrier 10 .

The other metal oxide fine particles 30 are substances that exhibit one or more catalytic functions. The catalytic ability of the other metal oxide fine particles 30 may be the same as or different from the catalytic ability of the metal oxide fine particles 20 . Further, when both of the metal oxide fine particles 20 and 30 are substances having the same catalytic ability, the material of the other metal oxide fine particles 30 may be the same as the material of the metal oxide fine particles 20, can be different. According to this configuration, the content of the N ₂ O decomposition catalyst material held in the N ₂ O decomposition catalyst structure 2 can be increased, further promoting the catalytic activity of the N ₂ O decomposition catalyst material. be able to.

In this case, the content of the metal oxide fine particles 20 inherent in the carrier 10 is preferably higher than the content of the other metal oxide fine particles 30 retained on the outer surface 10a of the carrier 10 . As a result, the catalytic activity of the metal oxide fine particles 20 held inside the carrier 10 becomes dominant, and the catalytic activity of the N ₂ O decomposition catalyst material is exhibited stably.

The present invention also provides an N ₂ O removal device having the N ₂ O decomposition catalyst structure. Such an N ₂ O removal device utilizes the N ₂ O decomposition catalyst structure to decompose N ₂ O molecules into N ₂ and O ₂ to reduce the N ₂ O concentration. There is no particular limitation, and a commonly used reactor or the like can be used. By using the N ₂ O decomposition catalyst structure according to the present invention in such an N ₂ O removal device, the N ₂ O removal device can also achieve the same effects as described above.

The N ₂ O decomposition catalyst structure, the manufacturing method thereof, and the N ₂ O removal apparatus having the N ₂ O decomposition catalyst structure according to the embodiments of the present invention have been described above. Various modifications and changes are possible based on the technical idea of the present invention.

(Examples 1 to 384)
[Synthesis of precursor material (A)]
A mixed aqueous solution is prepared by mixing a silica agent (tetraethoxysilane (TEOS), manufactured by Wako Pure Chemical Industries, Ltd.) and a surfactant as a template agent, and the pH is adjusted as appropriate. Hydrothermal treatment was performed at 350° C. for 100 hours. After that, the produced precipitate is filtered off, washed with water and ethanol, and further calcined in the air at 600° C. for 24 hours to obtain the precursor material (A) having the types and pore sizes shown in Tables 1 to 8. Obtained. The following surfactants were used according to the type of the precursor material (A) (“type of precursor material (A): surfactant”).
・ MCM-41: hexadecyltrimethylammonium bromide (CTAB) (manufactured by Wako Pure Chemical Industries, Ltd.)
・ SBA-1: Pluronic P123 (manufactured by BASF)

[Production of precursor materials (B) and (C)]
Next, according to the metal element (M) constituting the metal oxide fine particles of the types shown in Tables 1 to 8, a metal salt containing the metal element (M) is dissolved in water to obtain a metal-containing aqueous solution. was prepared. The following metal salts were used according to the type of metal oxide fine particles (“metal oxide fine particles: metal salt”).
・CoO _x : Cobalt (II) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
・ NiO _x : nickel (II) nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
・ FeO _x : iron (III) nitrate nonahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)
・ ZnO _x : zinc nitrate hexahydrate (manufactured by Wako Pure Chemical Industries, Ltd.)

Next, the metal-containing aqueous solution is added to the powdery precursor material (A) little by little in multiple portions, dried at room temperature (20° C.±10° C.) for 12 hours or more, and precursor material (B) is obtained. got

In addition, when the condition of the presence or absence of additives shown in Tables 1 to 8 is "Yes", polyoxyethylene (15) as an additive is added to the precursor material (A) before adding the metal-containing aqueous solution. Pretreatment was performed by adding an aqueous solution of oleyl ether (NIKKOL BO-15V, manufactured by Nikko Chemicals Co., Ltd.), and then a metal-containing aqueous solution was added as described above. In addition, in the case of "absent" in the condition of the presence or absence of additives, pretreatment with additives as described above was not performed.

The amount of the metal-containing aqueous solution added to the precursor material (A) is determined by the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing aqueous solution ( Numerical values when converted to the atomic number ratio (Si/M) were adjusted to the values shown in Tables 1-8.

Next, the precursor material (B) impregnated with the metal-containing aqueous solution obtained as described above was calcined in the air at 600° C. for 24 hours to obtain the precursor material (C).

[Synthesis of catalyst structure]
The precursor material (C) obtained as described above was mixed with the structure-directing agents shown in Tables 1 to 8 to prepare a mixed aqueous solution, which was heated at 80 to 350° C. in a closed container at Tables 1 to 8. Hydrothermal treatment was performed under the pH and time conditions shown in . After that, the produced precipitate is filtered off, washed with water, dried at 100° C. for 12 hours or more, and further calcined in air at 600° C. for 24 hours, and the metal as the carrier and catalyst material shown in Tables 1 to 8. Catalyst structures having fine oxide particles were obtained (Examples 1 to 384).

(Comparative example 1)
In Comparative Example 1, MFI-type silicalite was mixed with cobalt oxide powder (II, III) (manufactured by Sigma-Aldrich Japan G.K.) having an average particle size of 50 nm or less. A catalyst structure to which cobalt oxide fine particles were attached was obtained.

(Comparative example 2)
In Comparative Example 2, MFI-type silicalite was synthesized in the same manner as in Comparative Example 1, except that the step of adhering cobalt oxide fine particles was omitted.

[evaluation]
Various characteristic evaluations were performed on the catalyst structures of the above examples and the silicalite of the comparative examples under the following conditions.

[A] Cross-sectional observation For the catalyst structure of the above example and the silicalite with cobalt oxide microparticles attached thereto of Comparative Example 1, observation samples were prepared by a pulverization method and observed with a transmission electron microscope (TEM) (TITAN G2, manufactured by FEI). Cross-sectional observation was performed using As a result, it was confirmed that in the catalyst structures of the above examples, the metal oxide fine particles were inherently present and held inside the carrier made of silicalite or zeolite. On the other hand, in the silicalite of Comparative Example 1, the metal oxide fine particles adhered only to the outer surface of the carrier and were not present inside the carrier.

Further, for the catalyst structure in which the metal oxide is iron oxide fine particles (FeOx) among the above examples, the cross section is cut out by FIB (focused ion beam) processing, and is subjected to SEM (SU8020, manufactured by Hitachi High-Technologies Corporation) and EDX. (X-Max, manufactured by Horiba, Ltd.) was used to perform cross-sectional elemental analysis. As a result, Fe element was detected from inside the carrier. From the results of cross-sectional observation by TEM and SEM/EDX, it was confirmed that iron oxide fine particles were present inside the carrier.

[B] The average inner diameter of the carrier passage and the average particle diameter of the catalyst material. The minor diameters _were measured, and the average inner diameter was calculated (N=500). In the same manner, 500 catalyst substances were arbitrarily selected from the TEM image, the particle size of each was measured (N = 500), and the average value was obtained. The particle size was defined as D _C. The results are shown in Tables 1-8.

In addition, in order to confirm the average particle diameter and dispersion state of the catalyst substance, analysis was performed using SAXS (small angle X-ray scattering). Measurements by SAXS were performed using Spring-8 beamline BL19B2. The obtained SAXS data was fitted with a spherical model by the Guinier approximation method to calculate the particle size. The particle size was measured for a catalyst structure in which the metal oxide was fine iron oxide particles. As a comparative object, commercially available iron oxide fine particles (manufactured by Wako) were observed and measured by SEM.

As a result, the iron oxide fine particles of various sizes with a particle size range of about 50 nm to 400 nm exist randomly in the commercial product, whereas the average particle size obtained from the TEM image is 1.2 nm to 2.0 nm. In the catalyst structure of each example, a scattering peak with a particle size of 10 nm or less was also detected in the SAXS measurement results. From the SAXS measurement results and SEM/EDX cross-sectional measurement results, it was found that catalytic substances with particle sizes of 10 nm or less were present inside the carrier in a highly dispersed state with a uniform particle size.

[C] Relationship between the amount of metal-containing solution added and the amount of metal clathrated inside the support Amounts added at atomic number ratios Si/M = 50, 100, 200, 1000 (M = Co, Ni, Fe, Zn) , a catalyst structure in which metal oxide fine particles were included inside the carrier was produced, and then the amount (mass%) of the metal enclosed inside the carrier of the catalyst structure produced with the above addition amount was measured. . In this measurement, the catalyst structures with atomic ratios Si/M = 100, 200, and 1000 are the same as the catalyst structures with atomic ratios Si/M = 100, 200, and 1000 in Examples 1 to 384, respectively. The catalyst structure with the atomic ratio Si/M = 50 was prepared by adjusting the amount of the metal-containing solution added by the method of No., except that the amount of the metal-containing solution added was changed. = 100, 200 and 1000 catalyst structures.

The amount of metal was quantified by ICP (inductively coupled plasma) alone or by combining ICP and XRF (X-ray fluorescence analysis). XRF (energy dispersive X-ray fluorescence spectrometer "SEA1200VX", manufactured by SSI Nanotechnology Co., Ltd.) was performed under the conditions of a vacuum atmosphere and an acceleration voltage of 15 kV (using a Cr filter) or an accelerating voltage of 50 kV (using a Pb filter). . XRF is a method of calculating the amount of metal present based on fluorescence intensity, and a quantitative value (converted to % by mass) cannot be calculated using XRF alone. Therefore, the metal amount of the catalyst structure to which the metal was added at Si/M = 100 was quantified by ICP analysis, and the metal amount of the catalyst structure to which the metal was added at Si/M = 50 and less than 100 was obtained from the XRF measurement result. and calculated based on the ICP measurement results.

As a result, it was confirmed that at least within the range of the atomic number ratio Si/M of 50 to 1000, the amount of the metal included in the catalyst structure increased as the amount of the metal-containing solution added increased. rice field.

[D] Performance Evaluation The catalytic ability (performance) of the catalyst material was evaluated for the catalyst structures of the above examples and the silicalite of the comparative example. The results are shown in Tables 1-8.

(1) Catalytic activity Catalytic activity was evaluated under the following conditions.

First, 0.5 g of the catalyst structure was filled in a normal pressure flow reactor to form a catalyst layer, and the reaction gas having the following gas composition was adjusted to a space velocity of 10,000 hr ^-1 and the reaction temperature was 350 ° C. Nitrous oxide (N ₂ O) decomposition activity was measured.

<Composition of synthesis gas>
_N2O : 300 ppm, NO: 50 ppm, _CO2 : 300 ppm, _O2 : 16%, _H2O : 10%, _N2 : balance

After completion of the reaction, the components of the collected generated gas were analyzed by gas chromatography/mass spectrometry (GC/MS). A TRACE 1310GC (manufactured by Thermo Fisher Scientific Co., Ltd., detector: thermal conductivity detector) was used as a generated gas analyzer.

The nitrous oxide concentrations in the synthesis gas on the inlet side and the outlet side of the catalyst layer were measured by a gas chromatograph, and the N ₂ O decomposition rate was calculated by the following formula.
N ₂ O decomposition rate (%) = 100 × (N ₂ O concentration on the inlet side of the catalyst layer - N ₂ O concentration on the outlet side of the catalyst layer) / N ₂ O concentration on the inlet side of the catalyst layer

Nitrous oxide decomposition performance was measured 20 hours after the introduction of the synthesis gas.

In this example, when the N ₂ O decomposition rate (%) is 75% or more, the catalyst activity (N ₂ O decomposition rate) is judged to be excellent, and "⊚" is 60% or more and less than 75%. If the catalyst activity is good, it is judged to be "○", and if it is 55% or more and less than 60%, it is judged that the catalyst activity is not good but is at a passing level (acceptable). %, the catalyst activity was judged to be inferior (improper), and was marked as "x".

(2) Durability (service life)
Durability was evaluated under the following conditions.

First, the catalyst structure used in the above evaluation (1) was collected and heated at 650° C. for 12 hours to prepare a heated catalyst structure. Next, using the obtained heated catalyst structure, an N ₂ O decomposition reaction was carried out in the same manner as in the above evaluation (1).

Based on the obtained analysis results, the N ₂ O decomposition rate was obtained in the same manner as in the above evaluation (1). Furthermore, it was compared with the decomposition rate of the catalyst structure before heating (decomposition rate obtained in the above evaluation (1)) to see how much the decomposition rate of the catalyst structure after heating was maintained. . Specifically, the yield of the compound from the catalyst structure after heating (this evaluation (2)) is compared with the yield of the compound from the catalyst structure before heating (yield determined in the evaluation (1)). The percentage (%) of the yield obtained in ) was calculated.

In this example, the N ₂ O decomposition rate of the catalyst structure after heating (the N 2 O decomposition rate obtained in this evaluation (2)) was the _{N 2 O} decomposition rate of the compound by the catalyst structure before heating. Compared to the yield (N ₂ O decomposition rate obtained in the above evaluation (1)), the case where the durability (heat resistance) is maintained at 80% or more is judged to be excellent, and "⊚", 60% If the durability (heat resistance) is maintained at 80% or more, it is determined that the durability (heat resistance) is good, and the durability (heat resistance) is not good if it is maintained at 40% or more and less than 60%. The durability (heat resistance) was judged to be inferior (improper) and was judged to be "X" when it was judged to be at a pass level (acceptable) of 40%.

Performance evaluations similar to the above evaluations (1) and (2) were also performed for Comparative Examples 1 and 2. Incidentally, Comparative Example 2 is the carrier itself and does not have a catalytic substance. Therefore, in the above performance evaluation, only the carrier of Comparative Example 2 was filled instead of the catalyst structure. Table 8 shows the results.

As is clear from Tables 1 to 8, in the catalyst structures (Examples 1 to 384) in which it was confirmed that the catalyst substance was retained inside the carrier by cross-sectional observation, the catalyst substance was simply deposited on the outer surface of the carrier. Compared to the catalyst structure that is only attached (Comparative Example 1) and the carrier itself that does not have any catalytic substance (Comparative Example 2), the catalyst exhibits excellent catalytic activity in the decomposition reaction of N ₂ O. It was also found to be excellent in durability as.

In addition, the relationship between the amount (% by mass) of the metal enclosed inside the carrier of the catalyst structure measured in the above evaluation [C] and the catalytic activity in the above evaluation (1) was evaluated. The evaluation method was the same as the evaluation method performed in “(1) Catalytic activity” in [D] “Performance evaluation” above. As a result, in each example, the amount of the metal-containing solution added to the precursor material (A) was 50 to 200 in terms of the atomic ratio Si/M (the metal element of the metal oxide fine particles to the catalyst structure It was found that when the content of (M) is 0.5 to 2.5% by mass, the catalytic activity tends to improve in the decomposition reaction of N ₂ O.

On the other hand, the catalyst structure of Comparative Example 1, in which the catalyst substance was attached only to the outer surface of the carrier, was found to be a catalyst in the decomposition reaction of N ₂ O, compared with the carrier itself of Comparative Example 2, which did not have any catalyst substance. Although the activity was improved, the durability as a catalyst was inferior to that of the catalyst structures of Examples 1-384.

From the above results, it can be inferred that the N ₂ O decomposition catalyst structure according to the present invention exhibits excellent catalytic activity in the decomposition reaction of N ₂ O and has excellent durability as a catalyst.

Reference Signs List 1 N ₂ O decomposition catalyst structure 10 Carrier 10a Outer surface 11 Passage 11a Hole 12 Expanded diameter portion 20 Metal oxide fine particles 30 Metal oxide fine particles D _C average particle diameter D _F average inner diameter D _E inner diameter

Claims (18)

a carrier having a porous structure composed of a zeolite-type compound;
at least one metal oxide inherent in the support; and
with
the carrier has passages that communicate with each other;
The passageway is defined by the framework structure of the zeolite-type compound, and any one of the one-dimensional, two-dimensional, and three-dimensional pores. having a different enlarged diameter portion from each other,
The average inner diameter of the passage is calculated from the average value of the short diameter and the long diameter of the holes that constitute any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole,
The metal oxide includes a metal oxide composed of at least one of cobalt oxide, nickel oxide, iron oxide and zinc oxide,
The metal oxide is present surrounded by at least the enlarged diameter portion of the support ,
the metal oxide is a metal oxide fine particle,
A catalyst structure for decomposing N ₂ O , wherein the average particle size of the metal oxide fine particles is larger than the average inner diameter of the passage and equal to or smaller than the inner diameter of the expanded diameter portion. 2. The catalyst for decomposition of N ₂ O according to claim 1, wherein the enlarged diameter portion communicates with a plurality of holes forming any one of the one-dimensional hole, the two-dimensional hole and the three-dimensional hole. Structure. Claim 1 or 2, wherein the metal element (M) of the metal oxide fine particles is contained in an amount of 0.5 to 2.5% by mass with respect to the N ₂ O decomposition catalyst structure. 3. The catalyst structure for N ₂ O decomposition according to . The N ₂ O decomposition catalyst structure according to any one of claims 1 to 3 , wherein the metal oxide fine particles have an average particle size of 0.1 nm to 50 nm. 5. The N ₂ O decomposition catalyst structure according to claim 4 , wherein the average particle size of said metal oxide fine particles is 0.5 nm to 14.0 nm. For N ₂ O decomposition according to any one of claims 1 to 5 , wherein the ratio of the average particle size of the metal oxide fine particles to the average inner diameter of the passage is 1.1 to 500. catalyst structure. 7. The N ₂ O decomposition catalyst structure according to claim 6 , wherein the ratio of the average particle diameter of said metal oxide fine particles to the average inner diameter of said passage is 1.1 to 45. 8. The N ₂ O decomposition catalyst structure according to claim 7 , wherein the ratio of the average particle size of the metal oxide fine particles to the average inner diameter of the passage is 1.7 to 4.5. The average inner diameter of the passage is 0.1 nm to 1.5 nm,
The catalyst structure for N ₂ O decomposition according to any one of claims 1 to 8 , wherein the inner diameter of the enlarged diameter portion is 0.5 nm to 50 nm. 10. The N ₂ O decomposition catalyst structure according to any one of claims 1 to 9 , further comprising at least one other metal oxide retained on the outer surface of said support. Claim 10 , characterized in that the content of said at least one metal oxide inherent in said support is greater than the content of said at least one other metal oxide retained on the outer surface of said support. 3. The catalyst structure for N ₂ O decomposition according to . The N ₂ O decomposition catalyst structure according to any one of claims 1 to 11 , wherein the zeolite type compound is a silicate compound. An N ₂ O removal device comprising the N ₂ O decomposition catalyst structure according to any one of claims 1 to 12 . Precursor material (A) for obtaining a carrier having a porous structure composed of a zeolite-type compound, impregnated with a metal-containing solution containing at least one metal selected from cobalt, nickel, iron and zinc A firing step of firing the material (B);
a hydrothermal treatment step of mixing the precursor material (C) obtained by sintering the precursor material (B) and a structure-directing agent and performing hydrothermal treatment;
A method for producing a catalyst structure for decomposing N ₂ O, wherein the precursor material (A) is an ordered mesoporous material. 15. The catalyst for decomposing N ₂ O according to claim 14 , wherein a nonionic surfactant is added in an amount of 50 to 500% by mass with respect to the precursor material (A) before the calcination step. A method of manufacturing a structure. The precursor material (A) is impregnated with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in multiple batches before the firing step. 16. The method for producing a N ₂ O decomposition catalyst structure according to claim 14 or 15 . When the precursor material (A) is impregnated with the metal-containing solution before the firing step, the amount of the metal-containing solution added to the precursor material (A) is 10 to 1000 in terms of the ratio (atomic ratio Si/M) of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to 17. The method for producing an N ₂ O decomposition catalyst structure according to any one of claims 14 to 16 , wherein the adjustment is made so that 15. The method for producing an _N2O decomposition catalyst structure according to claim 14 , wherein the hydrothermal treatment step is performed in a basic atmosphere.

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