JP2018202408A - NOx DECOMPOSITION CATALYST STRUCTURE AND METHOD FOR PRODUCING THE SAME, AND NOx TREATMENT DEVICE AND CATALYST MOLDED BODY - Google Patents

Abstract

To provide an NOx decomposition catalyst structure capable of exhibiting a stable function over a long period of time by suppressing aggregation of metal oxide particles and preventing the functional deterioration of metal oxide particles.SOLUTION: There is provided an NOx decomposition catalyst structure 1 which comprises a carrier 10 with a porous structure composed of a zeolite-type compound and at least one NOx decomposition catalyst substance 20 which is inherent in the carrier 10 and composed of a metal oxide containing a perovskite-type oxide and, wherein the carrier 10 has mutually communicating passages 11 and the NOx decomposition catalyst substance 20 is at least present in the passages 11 of the carrier 10.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a NOx decomposition catalyst structure comprising a porous support composed of a zeolite type compound, and a NOx decomposition catalyst material composed of a metal oxide containing a perovskite oxide, and a method for producing the NOx decomposition catalyst structure, and NOx The present invention relates to a processing apparatus and a catalyst molded body.

  As an environmental catalyst for removing, for example, nitrogen oxide (NOx), which is a harmful substance that has been conventionally generated from power plants and automobiles and pollutes the living environment, for example, a perovskite oxide is used (for example, non-oxide). Patent Document 1).

As an environmental catalyst using a perovskite oxide, for example, Patent Document 1 discloses that at least one composition of metal complex oxides which are active components of a nitrogen oxide decomposition catalyst has a general formula AB _1-x M _x O. _{3 + -z} (where A is one metal selected from alkaline earth elements, B is one metal selected from titanium group elements, and M is selected from iron group, platinum group or copper group elements) 1 type of metal, 0 <x <1, z is represented by the number of oxygen defects or the excess number of oxygen of the metal oxide at room temperature and atmospheric pressure), and at least one of the metal composite oxides that are catalytically active components is Describes a decomposition catalyst having a SrTiO ₃ perovskite crystal structure, and Patent Document 2 discloses that a metal composite oxide having such a perovskite crystal structure is used as a support for a basic metal oxide (such as MgO). Nitrogen oxide supported A cracking catalyst is described.

  However, perovskite type oxides tend to agglomerate due to heat during firing (about 600-1000 ° C.), so that the pores are blocked by this aggregation, reducing the specific surface area of the catalyst, and adsorption and decomposition performance. Tends to decrease. Further, a catalyst containing a perovskite oxide has a high temperature for activating the catalyst, and exhibits a relatively high catalytic performance at a temperature of 700 ° C. or higher, but hardly exhibits a catalytic performance at a temperature of 650 ° C. or lower. There is a case. The catalyst performance refers to, for example, nitrogen oxide adsorption performance.

  For example, Patent Document 3 discloses a conventional technique that can suppress the aggregation of the perovskite oxide that tends to occur due to the influence of heat generated during firing or high temperature use. According to the description in Patent Document 3, the catalyst is composed of a perovskite complex oxide, a complex oxide spacer, and a noble metal, and by containing the complex oxide spacer, the perovskite complex oxide is aggregated or aggregated. The specific surface area calculated by the BET method can be increased, and the catalyst is produced in the form of powder. When such a powdered catalyst (catalyst fine particles) is used, the specific surface area of the catalyst is increased. It can be made to.

  However, the catalyst described in Patent Document 3 does not disclose any use mode in which catalyst fine particles are supported on a carrier, and when the catalyst fine particles having the above-described structure are supported on a carrier, the catalyst is usually used. It is difficult to contain the catalyst fine particles inside, and it can only be configured to hold (adhere) the catalyst particles on the outer surface of the carrier. With this configuration, the catalyst fine particles are separated from exhaust gas (fluid) such as nitrogen oxides. There is a problem that aggregation (sintering) is likely to occur due to the influence (action) of the force (pressure) and heat received.

Japanese Patent Laid-Open No. 11-151440 JP 2000-197822 A JP 2010-99638 A

Tatsumi Ishihara, “<Special Feature> Current Status and Future Perspectives of Environmental Catalysts that Continue to Evolve: Current Status and Prospects for Environmental Catalysts-Smoke Deodorization, VOC, NO Decomposition Catalysts", Industrial Materials, Nikkan Kogyo Shimbun, January 2017 No. 65, No. 1, p.71-76

  The object of the present invention is to suppress the aggregation of NOx decomposition catalyst materials by adopting a configuration in which the NOx decomposition catalyst material is properly present by being contained in a porous structure support composed of a zeolite type compound. An object of the present invention is to provide a NOx decomposition catalyst structure that can prevent a decrease in the function of the NOx decomposition catalyst material and exhibit a stable function over a long period of time, a method for manufacturing the NOx decomposition catalyst structure, a NOx treatment apparatus, and a catalyst molded body.

  As a result of intensive studies to achieve the above object, the present inventors have obtained a porous structure carrier composed of a zeolite-type compound, and a metal oxide containing a perovskite oxide, which is present in the carrier. At least one NOx decomposition catalyst material, and the carrier has a passage communicating with each other, and the NOx decomposition catalyst material is present in at least the passage of the carrier, whereby the function of the NOx decomposition catalyst material (for example, the catalyst) It has been found that a NOx decomposition catalyst structure capable of realizing a long life can be obtained, and the present invention has been completed based on such knowledge.

That is, the gist configuration of the present invention is as follows.
[1] A support having a porous structure composed of a zeolite-type compound and at least one NOx decomposition catalyst material made of a metal oxide containing a perovskite oxide, which is present in the support, A NOx decomposition catalyst structure comprising passages communicating with each other, wherein the NOx decomposition catalyst material is present in at least the passage of the carrier.
[2] The NOx decomposition catalyst structure according to [1], wherein the NOx decomposition catalyst material is metal oxide fine particles.
[3] The passage includes any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. The NOx decomposition catalyst structure according to the above [2], having an enlarged diameter portion different from any of the above, and wherein the metal oxide fine particles are present at least in the enlarged diameter portion.
[4] The above-mentioned [3], wherein the enlarged-diameter portion communicates a plurality of holes constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. The NOx decomposition catalyst structure described in 1.
[5] The above-mentioned [3] or [4], wherein the average particle diameter of the metal oxide fine particles is larger than the average inner diameter of the passage and not more than the inner diameter of the expanded portion. NOx decomposition catalyst structure.
[6] 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 automobile reduction catalyst structure, [2] The NOx decomposition catalyst structure according to any one of to [5].
[7] The NOx decomposition catalyst structure according to any one of [2] to [6], wherein the metal oxide fine particles have an average particle diameter of 0.1 to 50 nm.
[8] The NOx decomposition catalyst structure according to the above [7], wherein the metal oxide fine particles have an average particle size of 0.5 nm to 14.0 nm.
[9] The ratio of the average particle diameter of the metal oxide fine particles to the average inner diameter of the passage is 0.06 to 500, according to any one of the above [2] to [8]. NOx decomposition catalyst structure.
[10] The NOx decomposition catalyst structure according to [9] above, wherein the ratio of the average particle diameter of the metal oxide fine particles to the average inner diameter of the passage is 0.1 to 45.
[11] The NOx decomposition catalyst structure according to [10] above, wherein the ratio of the average particle diameter of the metal oxide fine particles to the average inner diameter of the passage is 1.7 to 4.5.
[12] The passage includes any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Having an enlarged diameter part different from any of them, the average inner diameter of the passage is 0.1 to 1.5 nm, the inner diameter of the enlarged diameter part is 0.5 to 50 nm, The NOx decomposition catalyst structure according to any one of the above [1] to [11].
[13] The NOx decomposition catalyst structure according to any one of [1] to [12], further comprising another NOx decomposition catalyst substance held on the outer surface of the carrier.
[14] The above-mentioned [13], wherein the content of the NOx decomposition catalyst substance present in the carrier is larger than the content of the other NOx decomposition catalyst substance held on the outer surface of the carrier. The NOx decomposition catalyst structure described in 1.
[15] The NOx decomposition catalyst structure according to any one of [1] to [14] above, wherein the zeolite-type compound is a silicate compound.
[16] A NOx treatment apparatus comprising the NOx decomposition catalyst structure according to any one of [1] to [15] above.
[17] A reduction catalyst structure for automobiles according to any one of [1] to [15] provided on a surface of the honeycomb-shaped substrate and the honeycomb-shaped substrate. A catalyst molded body.
[18] A firing step of firing a precursor material (B) impregnated with a metal-containing solution into a precursor material (A) for obtaining a porous structure carrier 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 process for producing a NOx decomposition catalyst structure, comprising:
[19] The NOx decomposition according to the above [18], wherein a nonionic surfactant is added in an amount of 50 to 500 mass% with respect to the precursor material (A) before the firing step. A method for producing a catalyst structure.
[20] Before the firing step, the precursor material (A) is impregnated with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in a plurality of times. The method for producing a NOx decomposition catalyst structure according to the above [18] or [19], which is characterized by the following.
[21] 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 changed to the precursor material. In terms of the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to (A) (atomic ratio Si / M), It adjusts so that it may become 10-1000, The manufacturing method of the NOx decomposition | disassembly catalyst structure of any one of said [18]-[20] characterized by the above-mentioned.
[22] The method for producing a NOx decomposition catalyst structure according to [18], wherein the precursor material (C) and a structure directing agent are mixed in the hydrothermal treatment step.
[23] The method for producing a NOx decomposition catalyst structure according to the above [18], wherein the hydrothermal treatment step is performed in a basic atmosphere.

  According to the present invention, comprising: a porous support composed of a zeolite-type compound; and at least one NOx decomposition catalyst material comprising a metal oxide containing a perovskite oxide, which is present in the support, The carrier has passages communicating with each other, and the NOx decomposition catalyst material is present in at least the passage of the carrier, thereby suppressing aggregation of the NOx decomposition catalyst materials and reducing the function of the NOx decomposition catalyst material. It is possible to provide a NOx decomposition catalyst structure and a method for producing the same, a NOx treatment apparatus and a catalyst molded body capable of preventing the occurrence of a stable function over a long period of time.

BRIEF DESCRIPTION OF THE DRAWINGS It is shown roughly so that the internal structure of the NOx decomposition | disassembly catalyst structure which concerns on embodiment of this invention can be understood, Comprising: (a) is a perspective view (a part is shown with a cross section), (b) is. It is a partial expanded sectional view. It is a partial expanded sectional view for demonstrating an example of the function of the NOx decomposition | disassembly catalyst structure of FIG. 1, (a) is a sieving function, (b) is a figure explaining a catalyst function. It is a flowchart which shows the manufacturing method of the NOx decomposition | disassembly catalyst structure of FIG. FIG. 6 is a schematic diagram showing a modification of the NOx decomposition catalyst structure in FIG. 1.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of NOx decomposition catalyst structure]
FIG. 1 is a diagram schematically showing a configuration of a NOx decomposition catalyst structure according to an embodiment of the present invention, in which (a) is a perspective view (a part is shown in cross section), and (b) is a partially enlarged view. It is sectional drawing. Note that the NOx 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.

  As shown in FIG. 1 (a), a NOx decomposition catalyst structure 1 includes a porous structure carrier 10 composed of a zeolite-type compound and a metal oxide containing a perovskite oxide that is present in the carrier 10. And a NOx decomposition catalyst material 20 comprising: The NOx decomposition catalyst material 20 is preferably metal oxide fine particles. The metal oxide fine particle 20 is a substance having one or a plurality of functions either alone or in cooperation with the carrier 10. For example, in addition to the NOx decomposition catalyst function, the above functions include a light emission (or fluorescence) function, light absorption It may further have a function, an identification function, and the like.

  In the NOx decomposition catalyst structure 1, at least one metal oxide fine particle 20, in FIG. 1B, a plurality of metal oxide fine particles 20, 20,... Exist inside the porous structure of the carrier 10. Yes. The metal oxide fine particles 20 are preferably metal oxide fine particles containing one or more perovskite oxides. Details of the perovskite oxide 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 passage 11 of the carrier 10, and are preferably held in at least the passage 11 of the carrier 10.

  With such a configuration, the movement of the metal oxide fine particles 20 in the carrier 10 is restricted, and aggregation of the metal oxide fine particles 20 and 20 is effectively prevented. As a result, a reduction in the effective surface area of the metal oxide fine particles 20 can be effectively suppressed, and the function of the metal oxide fine particles 20 lasts for a long time. That is, according to the NOx decomposition catalyst structure 1, it is possible to suppress a decrease in function due to the aggregation of the metal oxide fine particles 20, and to extend the life of the NOx decomposition catalyst structure 1. In addition, by extending the life of the NOx decomposition catalyst structure 1, the replacement frequency of the NOx decomposition catalyst structure 1 can be reduced, and the amount of discarded NOx decomposition catalyst structure 1 can be greatly reduced, thereby saving resources. Can be achieved.

  Usually, when the NOx decomposition catalyst structure is used in a fluid (for example, exhaust gas containing nitrogen oxide (NOx) or the like), there is a possibility that an external force is received from the fluid. In this case, if the metal oxide fine particles 20 are merely held on the outer surface of the carrier 10, there is a problem that the metal oxide fine particles 20 are easily detached from the outer surface of the carrier 10 due to an external force from the fluid. On the other hand, in the NOx decomposition catalyst structure 1, the metal oxide fine particles 20 are present in at least the passage 11 of the carrier 10 and are preferably retained. The metal oxide fine particles 20 are not easily separated. That is, when the NOx decomposition catalyst structure 1 is in the fluid, the fluid flows into the passage 11 from the hole 11a of the carrier 10, so that the speed of the fluid flowing in the passage 11 is determined by the flow resistance (frictional force). This is considered to be slower than the speed of the fluid flowing on the outer surface of the carrier 10. Due to the influence of the flow path resistance, the pressure that the metal oxide fine particles 20 existing 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 support 10. Therefore, it is possible to effectively suppress the separation of the metal oxide fine particles 20 existing in the carrier 11, and it is possible to stably maintain the function of the metal oxide fine particles 20 for a long period of time. In addition, the flow path resistance as described above increases as the passage 11 of the carrier 10 has a plurality of curved portions and branch portions, and the inside of the carrier 10 has a more complicated and three-dimensional structure. Conceivable.

  Further, the passage 11 includes any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite type compound, and the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. It is preferable that the metal oxide fine particles 20 are present at least in the diameter-enlarged portion 12 and include at least the diameter-enlarged portion 12. More preferably. As used herein, a one-dimensional hole means a tunnel-type or cage-type hole forming a one-dimensional channel, or a plurality of tunnel-type or cage-type holes forming a plurality of one-dimensional channels (a plurality of one-dimensional holes). Channel). A two-dimensional hole refers to a two-dimensional channel in which a plurality of one-dimensional channels are two-dimensionally connected. A three-dimensional hole refers to a three-dimensional channel in which a plurality of one-dimensional channels are three-dimensionally connected. Point to.

  Thereby, the movement of the metal oxide fine particles 20 in the carrier 10 is further regulated, and the separation of the metal oxide fine particles 20 and the aggregation of the metal oxide fine particles 20 and 20 can be more effectively prevented. Here, “inclusion” refers to a state in which the NOx decomposition catalyst material (preferably metal oxide fine particles) 20 is included in the carrier 10. At this time, the NOx decomposition catalyst material 20 and the carrier 10 do not necessarily need to be in direct contact with each other, and another substance (for example, a surfactant or the like) is present between the NOx decomposition catalyst material 20 and the carrier 10. The NOx decomposition catalyst material 20 may be indirectly held on the carrier 10 with the intervening state.

  FIG. 1B shows a case where the metal oxide fine particles 20 are enclosed by the enlarged diameter portion 12, but the present invention is not limited to this configuration, and the metal oxide fine particles 20 are partially expanded. You may hold | maintain at the channel | path 11 in the state protruded outside the diameter part 12. As shown in FIG. Further, 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 fixing or the like.

  Moreover, it is preferable that the enlarged diameter part 12 is connecting the some hole 11a and 11a which comprise either of the said one-dimensional hole, the said two-dimensional hole, and the said three-dimensional hole. Thereby, since a separate passage different from the one-dimensional hole, the two-dimensional hole, or the three-dimensional hole is provided inside the skeleton body 10, the function of the metal oxide fine particles 20 can be exhibited more.

  The passage 11 is formed in a three-dimensional manner inside the carrier 10 including a branch portion or a merge portion, and the enlarged diameter portion 12 is preferably provided in the branch portion or the merge portion of the passage 11. .

The average inner diameter _DF of the passage 11 formed in the carrier 10 is calculated from the average value of the short diameter and the long diameter of the hole 11a constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. It is 0.1-1.5 nm, Preferably it is 0.5-0.8 nm.
Moreover, the internal diameter _DE of the diameter expansion part 12 is 0.5-50 nm, for example, Preferably it is 1.1-40 nm, More preferably, it is 1.1-3.3 nm. The inner diameter D _E of the enlarged diameter section 12 depends on for example the pore size of which will be described later precursor material (A), and the average particle diameter D _C of the metal oxide particles 20 to be inclusion. The inner diameter _DE of the enlarged diameter portion 12 is a size that can enclose the metal oxide fine particles 20.

  The carrier 10 is composed of a zeolite type compound. Zeolite type compounds include, for example, zeolites (aluminosilicates), cation exchange zeolites, silicate compounds such as silicalite, zeolite related compounds such as aluminoborate, aluminoarsenate, germanate, molybdenum phosphate, etc. And phosphate-based zeolite-like substances. Among these, the zeolite type compound is preferably a silicate compound.

  The framework structure of zeolite type compounds 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. In the zeolite type compound, a plurality of pores having a pore size corresponding to each skeleton structure are formed. For example, the maximum pore size of the MFI type is 0.636 nm (6.36 mm), and the average pore size is 0.560 nm (5.60 mm). is there.

Metal oxide particles 20, and if the primary particle, there are the cases are secondary particles in which primary particles are formed by aggregation, the average particle diameter D _C of the metal oxide fine particles 20 are preferably passage 11 Is larger than the average inner diameter D _{F and not} more than the inner diameter D _E of the enlarged diameter portion 12 (D _F <D _C ≦ D _E ). Such metal oxide fine particles 20 are preferably enclosed by the enlarged diameter portion 12 in the passage 11, and the movement of the metal oxide fine particles 20 in the carrier 10 is restricted. Therefore, even when the metal oxide fine particles 20 receive an external force from the fluid, the movement of the metal oxide fine particles 20 in the carrier 10 is suppressed, and the enlarged diameter portions 12 dispersedly arranged in the passages 11 of the carrier 10. , 12,... Can be effectively prevented from contacting and aggregating the metal oxide fine particles 20, 20,.

The average particle diameter _{D C} of the metal oxide particles 20, in either case of the primary particles and the secondary particles is preferably 0.1 to 50 nm, more preferably less than 30nm over 0.1 nm, more preferably It is 0.5 nm-14.0 nm, Most preferably, it is 1.0-3.3 nm. 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 from 0.06 to 500, more preferably 0.1 to 45 More preferably, it is 1.1-45, Most preferably, it is 1.7-4.5.

  Further, the metal element (M) of the metal oxide fine particles is preferably contained at 0.5 to 2.5 mass% with respect to the NOx decomposition catalyst structure 1, and with respect to the NOx decomposition catalyst structure 1. It is more preferable that it is contained at 0.5 to 1.5% by mass. As used herein, “metal element (M)” refers to all of the metals contained in the oxide in a perovskite oxide containing a plurality of types of metals as described later, and the content is the total amount of these metals. Point to. For example, when the metal element (M) is La and Mn, the content (mass%) of the metal element is {(mass of La element + mass of Mn element) / (mass of all elements of the NOx decomposition catalyst structure 1). )} × 100.

Perovskite oxide is an ABO made of a metal ion (A ion) having a large ionic radius (> 0.90 ＞) and a metal ion (B ion) having a small ionic radius (> 0.51Å), such as rare earth alkaline earths. Perovskite, which is a type ₃ compound and important as a catalyst, is a compound based on a combination of a rare earth element (A site) and a transition metal (B site), and its catalytic properties mainly depend on the properties of the B site transition metal. Dependent.

The perovskite catalyst species to be included satisfies the general formula ABO _{3 of} perovskite (A: at least one element selected from rare earth elements and alkaline earth metals, B: at least one element selected from transition metals) and catalytic activity. it is not particularly limited as long as it is a compound having, specifically _{LaBO 3 (B = Mn, Cr} , Co, Fe, Al, Pd, Mg), BaZrO 3, La 0.8 Sr 0.2 Ga 0. ₈ Mg _0.2 O ₃ (LSGM), LaFe _0.57 Co _0.38 Pd _0.05 O ₃ , Ba _0.8 La _0.2 Mn _0.2 O _{3 and the} like.

  Further, the metal oxide fine particles 20 only need to contain a perovskite oxide, and may be composed of, for example, a single perovskite oxide or may be composed of two or more perovskite oxides. It may be composed of a complex oxide or a complex oxide composed of a perovskite oxide and another oxide. The ratio of Si constituting the carrier 10 (Si / M, atomic ratio) to the metal M constituting the metal oxide fine particle 20 is preferably 10 to 1000. If the abundance ratio is greater than 1000, the activity may be low and sufficient catalytic action may not be obtained. On the other hand, if the abundance ratio is less than 10, the abundance ratio of the perovskite catalyst becomes too large, and the support There is a tendency for the strength of the to decrease. The metal oxide fine particles 20 referred to here are fine particles held or supported inside the carrier 10 and do not include fine particles attached to the outer surface of the carrier 10.

  Examples of other oxides include cobalt oxide (CoOx), nickel oxide (NiOx), iron oxide (FeOx), copper oxide (CuOx), zirconium oxide (ZrOx), cerium oxide (CeOx), and aluminum oxide (AlOx). , Niobium oxide (NbOx), titanium oxide (TiOx), bismuth oxide (BiOx), molybdenum oxide (MoOx), vanadium oxide (VOx), or chromium oxide (CrOx) as a main component. A composite metal oxide is mentioned.

[Function of NOx decomposition catalyst structure]
The NOx decomposition catalyst structure 1 has a molecular sieving ability that permeates predetermined molecules contained in harmful substances such as nitrogen oxides (NOx) generated from, for example, power plants and automobiles. Specifically, as shown in FIG. 2A, nitrogen oxide (NOx) having a size equal to or smaller than the inner diameter of the hole 11 a formed on the outer surface 10 a of the carrier 10 enters the carrier 10. The other harmful substance 15 having a size exceeding the inner diameter of the hole 11a is restricted from entering the carrier 10. With this molecular sieving ability, nitrogen oxide (NOx) that can enter the holes 11a can be preferentially reacted.

  In addition, among the molecules generated in the pores 11a by the reaction, only molecules that can exit from the pores 11a to the outside of the carrier 10 can be obtained as products, and cannot exit from the pores 11a to the outside of the carrier 10. The molecules are converted into molecules of a size that can exit from the holes 11a, and then exit the support 10 through the holes 11a. Thereby, the product obtained by the catalytic reaction can be restricted to a predetermined molecule.

In the NOx decomposition catalyst structure 1, the metal oxide fine particles 20 are preferably present in the diameter-enlarged portion 12 of the passage 11, and more preferably are included. Therefore, NOx that has entered the passage 11 comes into contact with the metal oxide fine particles 20. Further, when the primary average particle diameter 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 enlarged diameter portion 12 (D _F <D _C <D _E ), A small passage 13 is formed between the metal oxide fine particles and the enlarged diameter portion 12 (arrow in the figure), and NOx that has entered the small passage 13 comes into contact with the metal oxide fine particles. At this time, the movement of the metal oxide fine particles 20 is restricted by being encapsulated by the enlarged diameter portion 12, and the contact area with the fluid containing molecules entering the passage 11 can be maintained.

When the NOx that has entered the passage 11 comes into contact with the metal oxide fine particles 20 containing the perovskite oxide in particular, it can be removed by decomposing nitrogen oxide (NOx) by the following reduction reaction.
2NO + 2Vo + 4e → 2N _ad + 2O _L ^2-
2N _ad → N ₂
2O _L ²⁻ → O ₂ + 2Vo + 4e
( _OL ^2- is lattice oxygen, Vo is oxygen defect)

The above NOx decomposition reaction has been energetically studied in an environmental purification catalyst, and since the reaction in which NOx is decomposed into N ₂ and O ₂ is stable in terms of chemical equilibrium, it is thermodynamically Can progress sufficiently. However, since the catalyst is actually deactivated by the generated O ₂ , the reaction hardly proceeds. For this reason, the operating temperature for proceeding with this reaction needs to be 700 ° C. or higher. In addition, the reaction at high temperature is characterized by being stable to oxygen coexisting with the NOx decomposition catalyst substance and not easily deactivated by water vapor. In the conventional NOx decomposition catalyst structure, when the operating temperature is higher than 700 ° C., the NOx catalysts are thermally aggregated (sintered), and the activity of the NOx catalyst is reduced. Even if the catalyst structure continues to be used at a high temperature of 700 ° C. or higher, it can suppress aggregation of NOx decomposition catalyst materials and prevent a decrease in the function of the NOx decomposition catalyst materials to exhibit a stable function over a long period of time. it can.

[NOx treatment equipment]
In one embodiment, a NOx treatment device (not shown) having the NOx decomposition catalyst structure 1 may be provided. The NOx treatment apparatus may have the NOx decomposition catalyst structure 1 alone, or may be combined with another catalyst structure such as an oxidation catalyst structure, a particulate matter collection filter, or the like. By using the NOx decomposition catalyst structure 1 in the NOx treatment apparatus having such a configuration, the same effects as described above can be obtained.

[Method for producing NOx decomposition catalyst structure]
FIG. 3 is a flowchart showing a method for manufacturing the NOx decomposition catalyst structure 1 of FIG. In FIG. 3, the case where the carrier 10 (carrier) is zeolite and the metal oxide fine particles 20 are made of a perovskite oxide will be described as an example.

(Step S1: Preparation process)
As shown in FIG. 3, first, a precursor material (A) for obtaining a porous support 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-type compound constituting the support of the NOx decomposition catalyst structure.

  Here, when the zeolitic compound constituting the support of the NOx decomposition catalyst structure is a silicate compound, the regular mesoporous material has pores having a pore diameter of 1 to 50 nm in one dimension, two dimensions or It is preferably a compound composed of a Si—O skeleton having a uniform size in three dimensions and regularly developed. Such regular mesoporous materials can be obtained as various composites depending on the synthesis conditions. Specific examples of the composites include, for example, SBA-1, SBA-15, SBA-16, KIT-6, FSM- 16, MCM-41, etc., among which MCM-41 is preferable. 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 -5 nm, MCM-41 has a pore diameter of 1-10 nm. Examples of such regular mesoporous materials include mesoporous silica, mesoporous aluminosilicate, and mesoporous metallosilicate.

  The precursor material (A) may be a commercially available product or a synthetic product. When the precursor material (A) is synthesized, it can be performed by a known method for synthesizing regular mesoporous materials. For example, a mixed solution containing a raw material containing the 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. Hydrothermal treatment (hydrothermal synthesis) is performed. Thereafter, the precipitate (product) obtained by hydrothermal treatment is recovered (for example, filtered), washed and dried as necessary, and further calcined to form a regular mesoporous material in powder form. A precursor material (A) is obtained. Here, as a solvent of the mixed solution, for example, water, an organic solvent such as alcohol, or a mixed solvent thereof can be used. Moreover, although a raw material is selected according to the kind of support | carrier, for example, silica agents, such as tetraethoxysilane (TEOS), fumed silica, quartz sand, etc. are mentioned. Further, as the templating agent, various surfactants, block copolymers and the like can be used, and it is preferable to select according to the type of the synthesized compound of regular mesoporous materials. For example, when preparing MCM-41 A surfactant such as hexadecyltrimethylammonium bromide is preferred. The hydrothermal treatment can be performed, for example, in a sealed container at 80 to 800 ° C., 5 hours to 240 hours, and treatment conditions of 0 to 2000 kPa. The baking treatment can be performed, for example, in air at 350 to 850 ° C. for 2 to 30 hours.

(Step 2: impregnation process)
Next, the prepared precursor material (A) is impregnated with the metal-containing solution to obtain the precursor material (B).

  The metal-containing solution may be a solution containing a metal component corresponding to the metal element (M) constituting the metal oxide fine particles of the NOx decomposition catalyst structure. For example, the metal-containing solution contains the metal element (M) in a solvent. It can be prepared by dissolving a metal salt. Examples of such metal salts include metal salts such as chlorides, hydroxides, oxides, sulfates, nitrates, etc. Among them, nitrates are preferable. 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, a plurality of metal-containing solutions are mixed while stirring the powdery precursor material (A) before the firing step described later. It is preferable to add in small portions in portions. Further, from the viewpoint of facilitating the penetration of the metal-containing solution into the pores of the precursor material (A), a surfactant as an additive is added in advance to the precursor material (A) before adding the metal-containing solution. It is preferable to add it. Such an additive has a 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), and the metal It is considered that the contained solution is more likely to enter 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 the metal-containing solution penetrates into the pores. It is thought not to interfere. As a method for adding the nonionic surfactant, for example, it is preferable to add the nonionic surfactant in an amount of 50 to 500% by mass with respect to the precursor material (A) before the firing step described later. When the addition amount of the nonionic surfactant to the precursor material (A) is less than 50% by mass, the above-described inhibitory action is hardly exhibited, and the nonionic surfactant is added to the precursor material (A) at 500. Addition of more than% by mass is not preferable because the viscosity increases excessively. Therefore, the addition amount of the nonionic surfactant with respect to the precursor material (A) is set to a value within the above range.

  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 in the precursor material (A) (that is, the precursor material (B It is preferable to adjust appropriately in consideration of the amount of the metal element (M) contained in (). For example, before the firing step described later, the addition amount of the metal-containing solution added to the precursor material (A) is the metal element (M) contained in the metal-containing solution added to the precursor material (A), In terms of the ratio of silicon (Si) constituting the precursor material (A) (atomic number ratio Si / M), it is preferably adjusted to be 10 to 1000, and adjusted to be 50 to 200. It is more preferable. For example, when a surfactant is added as an additive to the precursor material (A) before the metal-containing solution is added to the precursor material (A), the addition of the metal-containing solution to be added to the precursor material (A) By converting the amount to 50 to 200 in terms of the atomic ratio Si / M, the metal element (M) of the metal oxide fine particles is 0.5 to 2.5 mass% with respect to the NOx decomposition catalyst structure. It can be made to contain. In the state of the precursor material (B), the amount of the metal element (M) present in the pores is the same as the metal concentration of the metal-containing solution, the presence or absence of the additive, 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). The amount of the metal element (M) inherent in the precursor material (B) is proportional to the amount of the metal element constituting the metal oxide fine particles inherent in the support of the NOx decomposition catalyst structure. Therefore, by controlling the amount of the metal-containing solution added to the precursor material (A) within the above range, the metal-containing solution can be sufficiently impregnated inside the pores of the precursor material (A), and thus The amount of metal oxide fine particles contained in the support of the NOx decomposition catalyst structure can be adjusted.

  After impregnating the precursor material (A) with the metal-containing solution, a cleaning 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. In addition, it is preferable to impregnate the precursor material (A) with a metal-containing solution and perform a cleaning treatment as necessary, followed by a drying treatment. Examples of the drying treatment include natural drying overnight or high temperature drying at 150 ° C. or lower. In addition, the regular mesopores of the precursor material (A) are obtained by performing the baking treatment described later in a state where a large amount of moisture contained in the metal-containing solution and the moisture of the cleaning solution remain in the precursor material (A). Since the skeletal structure as a substance may be broken, it is preferable to dry it sufficiently.

(Step S3: Firing step)
Next, the precursor material (B) obtained by impregnating the precursor material (A) for impregnating the porous material structure composed of the zeolite type compound with the metal-containing solution is calcined to obtain the precursor material (C). Get.

  The firing treatment is preferably performed, for example, in the air at 350 to 850 ° C. for 2 to 30 hours. By such a baking treatment, the metal component impregnated in the pores of the regular mesoporous material grows in crystal, and metal oxide fine particles are formed in the pores.

(Step S4: Hydrothermal treatment process)
Next, a mixed solution in which the precursor material (C) and the structure directing agent are mixed is prepared, and the precursor material (C) obtained by firing the precursor material (B) is hydrothermally treated to decompose NOx. A catalyst structure is obtained.

  The structure directing agent is a templating agent for defining the skeleton structure of the support of the NOx 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 support of the NOx decomposition catalyst structure, for example, an interface such as tetramethylammonium bromide (TMABr), tetraethylammonium bromide (TEABr), tetrapropylammonium bromide (TPABr), etc. An activator is preferred.

  Mixing of the precursor material (C) and the structure directing agent may be performed during the main hydrothermal treatment step, or may be performed before the hydrothermal treatment step. Moreover, the preparation method of the said mixed solution is not specifically limited, A precursor material (C), a structure directing agent, and a solvent may be mixed simultaneously, or precursor material (C) and structure prescription | regulation are carried out to a solvent. After each agent is dispersed in each solution, each dispersion solution may be mixed. As the solvent, for example, water, an organic solvent such as alcohol, or a mixed solvent thereof can be used. In addition, the pH of the mixed solution is preferably adjusted using an acid or a base before hydrothermal treatment.

Hydrothermal treatment can be performed by a well-known method, for example, it is preferable to perform in 80-800 degreeC, 5 hours-240 hours, and processing conditions of 0-2000 kPa in an airtight container. 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 skeleton structure of the precursor material (C) as a regular mesoporous material gradually collapses. A new skeletal structure (porous structure) as a support for the NOx decomposition catalyst structure by the action of the structure-directing agent while maintaining the position of the metal oxide fine particles inside the pores of the precursor material (C) in general. Is formed. The NOx decomposition catalyst structure thus obtained comprises a porous support and metal oxide fine particles present in the support, and the support has a passage in which a plurality of pores communicate with each other due to the porous structure. At least a part of the metal oxide fine particles is held in the passage of the carrier.

  In this embodiment, in the hydrothermal treatment step, a mixed solution in which the precursor material (C) and the structure directing agent are mixed is prepared, and the precursor material (C) is hydrothermally treated. Not limited to this, the precursor material (C) may be hydrothermally treated without mixing the precursor material (C) and the structure directing agent.

  The precipitate (NOx decomposition catalyst structure) obtained after the hydrothermal treatment is preferably washed, dried and calcined as necessary after collection (for example, filtration). As the cleaning solution, water, an organic solvent such as alcohol, or a mixed solution thereof can be used. Examples of the drying treatment include natural drying overnight or high temperature drying at 150 ° C. or lower. In addition, if the calcination treatment is performed in a state in which a large amount of moisture remains in the precipitate, the skeleton structure as the carrier of the NOx decomposition catalyst structure may be broken, and thus it is preferable to dry it sufficiently. Moreover, a baking process can be performed on the process conditions of 350-850 degreeC and 2 to 30 hours, for example in the air. By such a calcination treatment, the structure directing agent attached to the NOx decomposition catalyst structure is burned out. In addition, the NOx decomposition catalyst structure can be used as it is without subjecting the recovered precipitate to a firing treatment depending on the purpose of use. For example, when the environment in which the NOx decomposition catalyst structure is used is a high temperature environment in an oxidizing atmosphere, the structure directing agent is burned away by exposure to the environment for a certain period of time, and the NOx decomposition is the same as in the case of firing treatment. Since a catalyst structure is obtained, it can be used as it is.

[Modification of NOx Decomposition Catalyst Structure 1]
FIG. 4 is a schematic diagram showing a modification of the NOx decomposition catalyst structure 1 of FIG.
The NOx decomposition catalyst structure 1 of FIG. 1 shows a case where the support 10 and the metal oxide fine particles 20 included in the support 10 are provided. However, the present invention is not limited to this configuration. For example, FIG. As shown, the NOx decomposition catalyst structure 2 may further include at least one other metal oxide fine particle 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 functions. The functions of the other metal oxide fine particles 30 may be the same as or different from the functions of the metal oxide fine particles 20. Specific examples of the functions of the other metal oxide fine particles 30 are the same as those described for the metal oxide fine particles 20, and preferably have a catalytic function. At this time, the metal oxide fine particles 30 are a catalyst substance. . When both of the metal oxide fine particles 20 and 30 are substances having the same function, the material of the other metal oxide fine particles 30 may be the same as or different from the material of the metal oxide fine particles 20. It may be. According to this configuration, the content of the metal oxide fine particles held in the NOx decomposition catalyst structure 2 can be increased, and the function of the metal oxide fine particles can be further promoted.

  In this case, the content of the NOx decomposition catalyst material (metal oxide fine particles) 20 existing in the carrier 10 is larger than the content of at least one other NOx decomposition catalyst material 30 held on the outer surface 10a of the carrier 10. It is preferable. As a result, the function of the NOx decomposition catalyst material 20 held inside the carrier 10 becomes dominant, and the function of the NOx decomposition catalyst material is stably exhibited.

[Catalyst compact]
In one embodiment, a catalyst molded body having a NOx decomposition catalyst structure may be provided. The catalyst molded body may have a NOx decomposition catalyst structure alone or may have another catalyst structure. By using the NOx decomposition catalyst structure for the catalyst molded body, the same effects as described above can be obtained.

  The catalyst molded body preferably has a base material and a NOx decomposition catalyst structure provided on the surface of the base material. The base material is a member having a tubular passage through which exhaust gas passes in the axial direction. That is, by having a structure having a tubular passage through which the exhaust gas passes, the contact area of the NOx decomposition catalyst structure with the exhaust gas increases. As described above, by increasing the contact area of the NOx decomposition catalyst structure with the exhaust gas, the purification ability of the exhaust gas can be improved. As such a base material, Preferably, a honeycomb-shaped base material can be mentioned. The shape of the honeycomb substrate is not particularly limited, and can be selected from known honeycomb substrates (integral structure type carriers). Examples of the material for the honeycomb substrate include metals such as stainless steel and heat-resistant ceramics such as cordierite.

[Method for producing catalyst molded body]
In the method for producing a molded catalyst according to one embodiment, the NOx decomposition catalyst structure is pulverized to obtain a particulate NOx decomposition catalyst structure. Next, the particulate NOx decomposition catalyst structure is mixed with a medium such as water to obtain a slurry. Thereafter, the slurry is applied to the honeycomb substrate and dried to produce a catalyst molded body having the honeycomb substrate and the NOx decomposition catalyst structure provided on the surface of the honeycomb substrate. Can do. A method for applying the slurry to the honeycomb-shaped substrate is not particularly limited, but a wash coat method is preferable. 100-300 degreeC is preferable and the temperature at the time of the said drying has more preferable 100-200 degreeC. About a heating means, well-known heating means, such as an electric furnace and a gas furnace, can be used.

  Although the NOx decomposition catalyst structure according to the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications and changes can be made based on the technical idea of the present invention. .

(Examples 1 to 384)
[Synthesis of Precursor Material (A)]
A mixed aqueous solution in which a silica agent (tetraethoxysilane (TEOS), manufactured by Wako Pure Chemical Industries, Ltd.) and a surfactant as a templating agent was mixed was prepared, pH was adjusted as appropriate, and 80 to 80 in a sealed container. Hydrothermal treatment was performed at 350 ° C. for 100 hours. Thereafter, 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 precursor materials of the types and pore sizes (nm) shown in Tables 1 to 8 ( A) was 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)

[Preparation of precursor materials (B) and (C)]
Next, the metal salt containing the metal element (M) is dissolved in water according to the metal element (M) constituting the metal oxide fine particles (NOx decomposition catalyst substance) of the types shown in Tables 1 to 8. To prepare a metal-containing aqueous solution. The following metal salts were used according to the type of metal oxide fine particles (“metal oxide fine particles: metal salt”).
· LaMnO _3: La-Mn nitrate _{(La (NO 3) 3 ·} 6H 2 O (99%) and _{Mn (NO} 3) using _{2 · 9H 2 O (99%} ), both manufactured by Wako Pure Chemical Industries, Ltd.)
· BaMnO _3: Ba-Mn nitrate _{(Ba (NO 3) 2 (} 99%) and _{Mn (NO} 3) using _{2 · 9H 2 O (99%} ), both manufactured by Wako Pure Chemical Industries, Ltd.)
· LaAlO _3: La-Al nitrate _{(La (NO 3) 3 ·} 6H 2 O (99%) and _{Al (NO 3) 3 · 9H} 2 using O (99%), both manufactured by Wako Pure Chemical Industries, Ltd.)
LaCoO ₃ : La-Co nitrate (La (NO ₃ ) ₃ · 6H ₂ O (99%) and Co (NO ₃ ) ₂ · 6H ₂ O (99%) are used, both manufactured by Wako Pure Chemical Industries, Ltd.)

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

  In addition, when the column of the presence or absence of the addition of the additive shown in Tables 1 to 8 is “Yes”, the polyoxyethylene as the additive (A) is added to the precursor material (A) before the addition of the metal-containing aqueous solution. 15) A pretreatment of adding an aqueous solution of oleyl ether (NIKKOL BO-15V, manufactured by Nikko Chemicals Co., Ltd.) is performed, and then a metal-containing aqueous solution is added as described above. Further, in the case where the column indicating whether or not an additive is added is “None”, the pretreatment with the additive as described above is not performed.

  Moreover, the addition amount of the metal-containing aqueous solution added to the precursor material (A) is the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing aqueous solution ( The numerical values when converted to the atomic 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 baked in air at 600 ° C. for 24 hours to obtain a precursor material (C).

[Synthesis of NOx decomposition catalyst structure]
The precursor material (C) obtained as described above and the structure directing agent shown in Tables 1 to 8 are mixed to prepare a mixed aqueous solution, and 80 to 350 ° C. and Tables 1 to 8 in a sealed container. Hydrothermal treatment was performed under the conditions of pH and time shown in FIG. Thereafter, the formed 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. NOx decomposition catalyst structures having oxide fine particles were obtained (Examples 1 to 384).

(Comparative Example 1)
In Comparative Example 1, the starting material for the hydroxide perovskite precursor was the same as in the example. A 0.1 mol / l La-Mn nitrate mixed aqueous solution was added dropwise to 19% aqueous ammonia under stirring. After dropping, the mixture was filtered and dried at 110 ° C. overnight to obtain a hydroxide perovskite precursor. The obtained perovskite hydroxide precursor and MFI-type silicalite were added to pure water so that the Si / M ratio was 100, dispersed with ultrasonic waves, evaporated to dryness, and fired. Silicalite carrying LaMnO ₃ on the outer surface was obtained. MFI type silicalite was synthesized in the same manner as in Examples 52 to 57 except for the step of adding metal.

(Comparative Example 2)
In Comparative Example 2, MFI type silicalite was synthesized by the same method as Comparative Example 1 except that the step of supporting LaMnO ₃ on the outer surface of the skeleton was omitted.

[Evaluation]
Various characteristics of the NOx decomposition catalyst structure of the above example and the metal oxide fine particle-supported silicalite of Comparative Example 1 were evaluated under the following conditions.

[A] Cross-sectional observation With respect to the NOx decomposition catalyst structure of the above example and the silicalite supporting metal oxide fine particles of Comparative Example 1, an observation sample was prepared by a pulverization method, and transmission electron microscope (TEM) (TITAN G2, FEI) Were used for cross-sectional observation.
As a result, in the NOx decomposition catalyst structures of the above examples, it was confirmed that the metal oxide fine particles were inherently held inside the support made of silicalite or zeolite. On the other hand, in the silicalite of Comparative Example 1, the metal oxide fine particles were only attached to the outer surface of the carrier and were not present inside the carrier.

[B] Average inner diameter of carrier passage and average particle diameter of metal oxide fine particles In a TEM image taken by cross-sectional observation performed in the above evaluation [A], arbitrarily select 500 carrier passages, The major axis and the minor axis were measured, the respective inner diameters were calculated from the average value (N = 500), and the average inner diameter value was further determined as the average inner diameter _DF of the carrier passage. Similarly, for metal oxide fine particles, 500 metal oxide fine particles are arbitrarily selected from the TEM image, each particle size is measured (N = 500), and an average value thereof is obtained. It was defined as the average particle diameter D _C of the metal oxide fine particles. The results are shown in Tables 1-8.

[C] Relationship between the addition amount of the metal-containing solution and the amount of metal included in the support The addition amount of the atomic ratio Si / M = 50, 100, 200, 1000 (M = Co, Ni, Fe, Cu) Then, a NOx decomposition catalyst structure in which metal oxide fine particles are included in the inside of the support is prepared, and then the amount of metal included in the support in the NOx decomposition catalyst structure manufactured in the above addition amount (mass%) ) Was measured. In this measurement, the NOx decomposition catalyst structure having an atomic ratio of Si / M = 100, 200, 1000 is the NOx decomposition catalyst having an atomic ratio of Si / M = 100, 200, 1000 in Examples 1 to 384, respectively. The NOx decomposition catalyst structure having an atomic ratio of Si / M = 50 was prepared by adjusting the addition amount of the metal-containing solution in the same manner as the structure, except that the addition amount of the metal-containing solution was varied. The NOx decomposition catalyst structure having an atomic ratio of Si / M = 100, 200, 1000 was prepared in the same manner.

  The amount of metal was determined by using ICP (high frequency inductively coupled plasma) alone or a combination of ICP and XRF (fluorescence X-ray analysis). XRF (energy dispersive X-ray fluorescence spectrometer “SEA1200VX”, manufactured by SSI Nanotechnology Co., Ltd.) was performed under the conditions of a vacuum atmosphere, an acceleration voltage of 15 kV (using a Cr filter), or an acceleration voltage of 50 kV (using a Pb filter). .

XRF is a method of calculating the abundance of a metal by fluorescence intensity, and a quantitative value (mass% conversion) cannot be calculated with XRF alone. Therefore, the amount of metal in the NOx decomposition catalyst structure added with metal at Si / M = 100 is determined by ICP analysis, and the amount of metal in the NOx decomposition catalyst structure added with metal at Si / M = 50 and less than 100 is The calculation was made based on the XRF measurement results and the ICP measurement results.
As a result, the amount of metal included in the NOx decomposition catalyst structure increases as the addition amount of the metal-containing solution increases at least in the atomic ratio Si / M in the range of 50 to 1000. confirmed.

[D] Performance Evaluation The catalytic ability (catalytic activity and durability) of the metal oxide fine particles (NOx decomposition catalyst substance) was evaluated for the NOx decomposition catalyst structures of the above examples and the silicalite of Comparative Example 1. The results are shown in Tables 1-8.

(1) Catalytic activity Each NOx decomposition catalyst structure of Examples 1 to 384 obtained above and silicalite of Comparative Example 1 were charged in 0.2 g in a normal pressure flow reactor, and NO (nitrogen monoxide). ) Was allowed to flow at a flow rate of 1.0 ml / min, and a direct decomposition reaction was performed.

  After completion of the reaction, the components of the collected product gas were analyzed by gas chromatography mass spectrometry (GC / MS). Note that TRACE1310GC (manufactured by Thermo Fisher Scientific Co., Ltd., detector: thermal conductivity detector) was used as the product gas analyzer.

Furthermore, based on the above analysis results, the yield (mol%) of N ₂ (nitrogen) was determined. The yield N ₂ is for the amount of substance of NO before the start of the reaction (mol), was calculated as a percentage (mol%) of the total amount of substance amount of _{N 2} contained in the produced gas (mol).

In this example, when the yield of N ₂ contained in the product gas is 80 mol% or more, it is determined that the catalytic activity (resolution) is excellent, and “」 ”is 50 mol% or more and less than 80 mol%. The case where the catalytic activity is good is judged as “◯”, and the case where it is 20 mol% or more and less than 50 mol% is judged that the catalytic activity is not good but the acceptable level is “△”, and 20 mol. The case where it was less than% was judged that the catalyst activity was inferior (impossible), and was set as “x”.

(2) Durability (life)
Each NOx decomposition catalyst structure was heated at 650 ° C. for 12 hours, then cooled to room temperature and allowed to stand for 30 minutes. After conducting a thermal cycle test 10 times, the same catalytic reaction test as in (1) above was performed. did. For durability, the ratio of the amount of CO ₂ produced in the product gas was calculated for both the CO oxidation reaction and the propane oxidation reaction, and the NOx decomposition catalyst structure was evaluated as “◎”, “ “○”, “△”, and “×” were evaluated.

<Criteria for evaluating catalyst activity>
“A”: When the ratio of the amount of CO ₂ produced with respect to the total amount of all collected product gases is maintained at 90% or more in both oxidation reactions compared to the catalytic activity performed in the above (1).
“◯”: The ratio of the amount of CO ₂ generated to the total amount of all the collected product gases is maintained at 70% or more in both oxidation reactions as compared to the catalytic activity performed in the above (1), and at least one of them When the oxidation reaction is less than 90%.
“Δ”: The ratio of the amount of CO ₂ generated to the total amount of all the recovered product gases is maintained at 20% or more in both oxidation reactions compared to the catalytic activity performed in the above (1), and at least one of them When the oxidation reaction is less than 70%.
“X”: When the ratio of the amount of CO ₂ produced to the total amount of all the produced gas collected is less than 20% in at least one of the oxidation reactions compared to the catalytic activity performed in the above (1).

About Comparative Examples 1-2, the same performance evaluation as said evaluation (1) and (2) was performed. In addition, the comparative example 2 is a support | carrier itself, and does not have a NOx decomposition | disassembly catalyst substance. Therefore, in the performance evaluation, only the carrier of Comparative Example 2 was filled instead of the NOx decomposition catalyst structure.
These evaluation results are shown in Tables 1 to 8.

  As is apparent from Tables 1 to 8, the NOx decomposition catalyst structures (Examples 1 to 384) in which the metal oxide fine particles were confirmed to be held inside the support by cross-sectional observation were simply metal oxide fine particles. Compared with silicalite (Comparative Example 1) in which only the metal adheres to the outer surface of the carrier and the carrier itself without any metal oxide fine particles (Comparative Example 2), any oxidation reaction of CO and propane Also showed excellent catalytic activity, and was found to be excellent in durability as a catalyst.

  On the other hand, the silicalite of Comparative Example 1 in which the metal oxide fine particles are attached only to the outer surface of the carrier is either CO or propane as compared with the carrier of Comparative Example 2 which does not have any metal oxide fine particles. Although the catalytic activity was also improved in this oxidation reaction, the durability as a catalyst was inferior to the NOx decomposition catalyst structures of Examples 1 to 384.

  Further, the support itself of Comparative Example 2 that does not have any metal oxide fine particles shows almost no catalytic activity in the NOx reduction reaction, and compared with the NOx decomposition catalyst structures of Examples 1 to 384, the catalytic activity and Both durability was inferior.

Although not shown in the above embodiment, the present inventors have conducted experiments to purify exhaust gas containing nitrogen oxides (NOx) using the NOx decomposition catalyst structure of the present invention, Nitrogen oxide (NOx) can be decomposed into N ₂ and O ₂ with high efficiency and purified by the reaction by the NOx decomposition catalyst structure, and the efficiency can be maintained for a long time without significantly decreasing. I have confirmed.

The average particle diameter _{D F} passages 1 NOx decomposition catalyst structure 10 support 10a outer surface 11 passages 11a hole 12 enlarged diameter portion 20 NOx decomposition catalyst material 30 other NOx decomposition catalyst material _D C NOx decomposition catalyst material (metal oxide particles) Average inner diameter D _E inner diameter of expanded part

Claims (23)

A porous structure carrier composed of a zeolite-type compound;
At least one NOx decomposition catalyst material comprising a metal oxide containing a perovskite oxide, which is inherent in the carrier;
With
The carrier has passages communicating with each other;
The NOx decomposition catalyst structure, wherein the NOx decomposition catalyst material is present in at least the passage of the carrier.   The NOx decomposition catalyst structure according to claim 1, wherein the NOx decomposition catalyst material is metal oxide fine particles.   The passage is any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. 3. The NOx decomposition catalyst structure according to claim 2, wherein the NOx decomposition catalyst structure has a different enlarged diameter portion, and the metal oxide fine particles are present at least in the enlarged diameter portion.   4. The NOx according to claim 3, wherein the enlarged diameter portion communicates a plurality of holes constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Decomposition catalyst structure.   5. The NOx decomposition catalyst structure according to claim 3, wherein an average particle diameter of the metal oxide fine particles is larger than an average inner diameter of the passage and equal to or smaller than an inner diameter of the expanded portion.   6. 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 automobile reduction catalyst structure. The NOx decomposition catalyst structure according to claim 1.   The NOx decomposition catalyst structure according to any one of claims 2 to 6, wherein an average particle diameter of the metal oxide fine particles is 0.1 to 50 nm.   8. The NOx decomposition catalyst structure according to claim 7, wherein an average particle diameter of the metal oxide fine particles is 0.5 nm to 14.0 nm.   The NOx decomposition catalyst structure according to any one of claims 2 to 8, wherein a ratio of an average particle diameter of the metal oxide fine particles to an average inner diameter of the passage is 0.06 to 500. .   The NOx decomposition catalyst structure according to claim 9, wherein the ratio of the average particle diameter of the metal oxide fine particles to the average inner diameter of the passage is 0.1 to 45.   11. The NOx decomposition catalyst structure according to claim 10, wherein a ratio of an average particle diameter of the metal oxide fine particles to an average inner diameter of the passage is 1.7 to 4.5. The passage is any one of a one-dimensional hole, a two-dimensional hole, and a three-dimensional hole defined by a skeleton structure of the zeolite-type compound, and any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole. Have different diameter expansion parts,
An average inner diameter of the passage is 0.1 to 1.5 nm,
12. The NOx decomposition catalyst structure according to claim 1, wherein an inner diameter of the expanded portion is 0.5 to 50 nm.   The NOx decomposition catalyst structure according to any one of claims 1 to 12, further comprising another NOx decomposition catalyst substance held on the outer surface of the carrier.   14. The NOx according to claim 13, wherein the content of the NOx decomposition catalyst substance existing in the carrier is larger than the content of the other NOx decomposition catalyst material held on the outer surface of the carrier. Decomposition catalyst structure.   The NOx decomposition catalyst structure according to any one of claims 1 to 14, wherein the zeolite-type compound is a silicate compound.   A NOx treatment apparatus comprising the NOx decomposition catalyst structure according to any one of claims 1 to 15.   A catalyst molded body comprising a honeycomb-shaped substrate and the reduction catalyst structure for automobiles according to any one of claims 1 to 15 provided on a surface of the honeycomb-shaped substrate. . A firing step of firing a precursor material (B) impregnated with a metal-containing solution into a precursor material (A) for obtaining a porous structure carrier 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 process for producing a NOx decomposition catalyst structure, comprising:   The NOx decomposition catalyst structure according to claim 18, wherein a nonionic surfactant is added in an amount of 50 to 500 mass% with respect to the precursor material (A) before the firing step. Production method.   Before the firing step, the precursor material (A) is impregnated with the metal-containing solution by adding the metal-containing solution to the precursor material (A) in a plurality of times. 20. A method for producing a NOx decomposition catalyst structure according to claim 18 or 19.   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 changed to the precursor material (A). 10 to 1000 in terms of the ratio of silicon (Si) constituting the precursor material (A) to the metal element (M) contained in the metal-containing solution added to (atom ratio Si / M) It adjusts so that it may become, The manufacturing method of the NOx decomposition | disassembly catalyst structure of any one of Claims 18-20 characterized by the above-mentioned.   The method for producing a NOx decomposition catalyst structure according to claim 18, wherein the precursor material (C) and a structure directing agent are mixed in the hydrothermal treatment step.   The method for producing a NOx decomposition catalyst structure according to claim 18, wherein the hydrothermal treatment step is performed in a basic atmosphere.

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