阅读说明：本技术 功能性结构体以及功能性结构体的制造方法 (Functional structure and method for manufacturing functional structure ) 是由 增田隆夫 中坂佑太 吉川琢也 加藤祯宏 福岛将行 稻森康次郎 高桥寻子 马场祐一郎 于 2018-05-31 设计创作，主要内容包括：本发明提供一种功能性结构体,其能抑制金属氧化物微粒彼此的凝聚,防止金属氧化物微粒的功能降低,长期发挥稳定的功能。功能性结构体(1)具备：多孔质结构的骨架体(10),其由沸石型化合物构成；以及至少一种金属氧化物微粒(20),其存在于骨架体(10)内,含有钙钛矿型氧化物,骨架体(10)具有相互连通的通路(11),金属氧化物微粒(20)存在于骨架体(10)的至少通路(11)。(The invention provides a functional structure which can inhibit the agglomeration of metal oxide particles, prevent the function of the metal oxide particles from being reduced, and exert a stable function for a long time. A functional structure (1) is provided with: a porous-structure skeleton (10) composed of a zeolite-type compound; and at least one metal oxide fine particle (20) which is present in the skeleton body (10) and contains a perovskite-type oxide, the skeleton body (10) has passages (11) that communicate with each other, and the metal oxide fine particle (20) is present in at least the passages (11) of the skeleton body (10).)

1. A functional structure, comprising:

a porous-structure skeleton body composed of a zeolite-type compound; and

at least one metal oxide fine particle which is present in the skeleton body and contains a perovskite-type oxide,

the skeleton body has passages communicated with each other,

the metal oxide fine particles are present in at least the passages of the skeleton body.

2. The functional structure according to claim 1,

the passage has: any one of one-dimensional pores, two-dimensional pores, and three-dimensional pores defined by the framework structure of the zeolite-type compound; and a diameter expanding portion which is different from any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole, and which is provided with a hole having a diameter larger than that of the hole having the one-dimensional hole

The metal oxide fine particles are present at least in the diameter-expanded portion.

3. The functional structure according to claim 2,

the diameter expanding portion causes a plurality of holes constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole to communicate with each other.

4. The functional structure according to claim 2 or 3,

the metal oxide fine particles have an average particle diameter larger than an average inner diameter of the passage and equal to or smaller than an inner diameter of the enlarged diameter portion.

5. The functional structure according to any one of claims 1 to 4,

the metal oxide fine particles are a catalyst substance,

the skeleton body is a carrier supporting at least one of the catalyst substances.

6. The functional structure according to any one of claims 1 to 5,

the functional structure contains 0.5 to 2.5 mass% of the metal element M of the metal oxide fine particles.

7. The functional structure according to any one of claims 1 to 6,

the metal oxide fine particles have an average particle diameter of 0.1 to 50 nm.

8. The functional structure according to claim 7,

the metal oxide fine particles have an average particle diameter of 0.5 to 14.0 nm.

9. The functional structure according to any one of claims 1 to 8,

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.

10. The functional structure according to claim 9,

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 functional structure according to claim 10,

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 functional structure according to any one of claims 1 to 11,

the passage has: any one of one-dimensional pores, two-dimensional pores, and three-dimensional pores defined by the framework structure of the zeolite-type compound; and a diameter expanding portion different from any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole,

the average inner diameter of the passage is 0.1 to 1.5nm,

the inner diameter of the diameter-expanding part is 0.5-50 nm.

13. The functional structure according to any one of claims 1 to 12,

the composite material is also provided with at least one other metal oxide fine particle retained on the outer surface of the skeleton body.

14. The functional structure according to claim 13,

the content of the at least one metal oxide fine particle present in the matrix is greater than the content of the at least one other metal oxide fine particle remaining on the outer surface of the matrix.

15. The functional structure according to any one of claims 1 to 14,

the zeolite-type compound is a silicate compound.

16. A method for manufacturing a functional structure, comprising:

a firing step of firing a precursor material B obtained by impregnating a precursor material a for obtaining a framework having a porous structure composed of a zeolite-type compound with a metal-containing solution containing at least one element selected from rare earth elements and alkaline earth metals and at least one element selected from transition metals as a metal element M; and

a hydrothermal treatment step of subjecting a precursor material C obtained by firing the precursor material B to hydrothermal treatment.

17. The method for manufacturing a functional structure according to claim 16,

before the firing step, 50 to 500 mass% of a nonionic surfactant is added to the precursor material A.

18. The method of manufacturing a functional structure according to claim 16 or 17,

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 plurality of times.

19. The method for manufacturing a functional structure according to any one of claims 16 to 18,

when the precursor material A is immersed in the metal-containing solution before the firing step, the amount of the metal-containing solution added to the precursor material A is adjusted so that the atomic ratio Si/M, which is the ratio of silicon Si constituting the precursor material A to the metal element M contained in the metal-containing solution added to the precursor material A, is 10 to 1000.

20. The method for manufacturing a functional structure according to claim 16,

in the hydrothermal treatment step, the precursor material C is mixed with a structure-directing agent.

21. The method for manufacturing a functional structure according to claim 16,

the hydrothermal treatment step is performed in an alkaline environment.

Technical Field

The present invention relates to a functional structure including a skeleton having a porous structure made of a zeolite-type compound and fine metal oxide particles containing a perovskite-type oxide, and a method for producing the functional structure.

Background

As toNitrogen Oxides (NO) exhausted to power plants, automobiles, etc_x) For example, a perovskite type oxide is cited as an environmental catalyst for exhaust gas and Volatile Organic Compounds (VOC) (for example, non-patent document 1).

As an environmental catalyst using a perovskite-type oxide, for example, patent document 1 describes a decomposition catalyst in which at least one kind of metal composite oxide having a composition represented by general formula AB is used as an active component of a nitrogen oxide decomposition catalyst_1-xM_xO_3+-z(wherein A is a metal selected from alkaline earth elements, B is a metal selected from titanium group elements, M is a metal selected from iron group, platinum group or copper group elements, 0<x<1, z is the oxygen defect number or oxygen excess number of the metal oxide at room temperature and atmospheric pressure), and at least one of the metal composite oxides as the catalytically active component has SrTiO₃In addition to the perovskite crystal structure, patent document 2 describes a nitrogen oxide decomposition catalyst in which a metal composite oxide having such a perovskite crystal structure is supported on a carrier of a basic metal oxide (such as MgO).

However, since the perovskite oxide is easily aggregated by heat generated when the raw material powder is fired (about 600 to 1000 ℃), the perovskite oxide tends to have the following tendency: the pores are closed by the aggregation, and the specific surface area of the catalyst is reduced, thereby reducing the adsorption and decomposition performance. In addition, in the catalyst containing the perovskite oxide, the temperature for activating the catalyst is high, and although high catalyst performance is exhibited at a temperature of 800 ℃ or higher, the catalyst performance may be hardly exhibited at a temperature of 650 ℃ or lower. The catalyst performance refers to, for example, the adsorption performance of nitrogen oxides.

As a conventional technique capable of suppressing the aggregation of perovskite oxide which is easily affected by heat generated during firing or high-temperature use, for example, patent document 3 discloses a technique. According to the description of patent document 3, the catalyst is composed of a perovskite-type composite oxide, a composite oxide spacer, and a noble metal, and the inclusion of the composite oxide spacer can suppress aggregation of perovskite-type composite oxides and blocking of pores by aggregation, and can increase the specific surface area calculated by the BET method, and the catalyst can be made into a powder form, and when such a powder-form catalyst (catalyst fine particles) is used, the specific surface area of the catalyst can be increased.

However, in the catalyst described in patent document 3, there is no disclosure of the use of the catalyst fine particles held (supported) in the skeleton body (carrier), and in the case of a structure in which the catalyst fine particles having the above-described configuration are held in the skeleton body, it is generally difficult to contain the catalyst particles in the inside of the skeleton body, and only a configuration in which the catalyst particles are held (fixed) on the outer surface of the skeleton body can be adopted, and if this configuration is adopted, there is a problem as follows: the catalyst fine particles are easily aggregated (sintered) by the influence (action) of force (pressure) or heat from exhaust gas (fluid) such as nitrogen oxide.

Disclosure of Invention

Problems to be solved by the invention

An object of the present invention is to provide a functional structure which can suppress aggregation of metal oxide fine particles, prevent a decrease in the function of the metal oxide fine particles, and exhibit a stable function for a long period of time, by adopting a structure in which metal oxide fine particles having a function (for example, a catalyst function or the like) are contained in a framework of a porous structure made of a zeolite-type compound and are appropriately present.

Technical scheme

As a result of intensive studies to achieve the above object, the present inventors have found the following facts, and have completed the present invention based on the findings, namely, a functional structure comprising: a porous-structure skeleton body composed of a zeolite-type compound; and at least one metal oxide fine particle present in the skeleton body, the skeleton body having mutually communicating passages, the metal oxide fine particle being present in at least the passages of the skeleton body, whereby a decrease in the function (for example, a catalyst function or the like) of the metal oxide fine particle can be suppressed, and a life can be extended.

That is, the gist of the present invention is as follows.

[1] A functional structure, comprising: a porous-structure skeleton body composed of a zeolite-type compound; and at least one metal oxide fine particle that is present in the skeleton body and contains a perovskite-type oxide, the skeleton body having mutually communicating passages, the metal oxide fine particle being present in at least the passages of the skeleton body.

[2] The functional structure according to [1], wherein the passage includes: any one of one-dimensional pores, two-dimensional pores, and three-dimensional pores defined by the framework structure of the zeolite-type compound; and a diameter expanding portion which is different from any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole, and which is provided with a hole having a diameter larger than that of the hole having the one-dimensional hole

The metal oxide fine particles are present at least in the diameter-expanded portion.

[3] The functional structure according to item [2], wherein the diameter-expanded portion causes a plurality of holes constituting any one of the one-dimensional holes, the two-dimensional holes, and the three-dimensional holes to communicate with each other.

[4] The functional structure according to the above [2] or [3], wherein an average particle diameter of the metal oxide fine particles is larger than an average inner diameter of the passage and is equal to or smaller than an inner diameter of the enlarged diameter portion.

[5] The functional structure according to any one of the above [1] to [4], wherein the metal oxide fine particles are a catalyst substance, and the skeleton body is a carrier on which at least one of the catalyst substances is supported.

[6] The functional structure according to any one of the above [1] to [5], characterized in that the metal element (M) of the metal oxide fine particles is contained in an amount of 0.5 to 2.5 mass% relative to the functional structure.

[7] The functional structure according to any one of the above [1] to [6], wherein the metal oxide fine particles have an average particle diameter of 0.1 to 50 nm.

[8] The functional structure according to the above [7], wherein the metal oxide fine particles have an average particle diameter of 0.5nm to 14.0 nm.

[9] The functional structure according to any one of the above [1] 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.

[10] The functional structure according to item [9], wherein a ratio of an average particle diameter of the metal oxide fine particles to an average inner diameter of the passage is 0.1 to 45.

[11] The functional structure according to item [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.

[12] The functional structure according to any one of the above [1] to [11], wherein the average inner diameter of the passage is 0.1 to 1.5nm, and the inner diameter of the expanded diameter portion is 0.5 to 50 nm.

[13] The functional structure according to any one of the above [1] to [12], further comprising at least one type of other metal oxide fine particles held on the outer surface of the skeleton body.

[14] The functional structure according to [13] above, characterized in that the content of the at least one metal oxide fine particle present in the skeleton body is greater than the content of the at least one other metal oxide fine particle held on the outer surface of the skeleton body.

[15] The functional structure according to any one of the above [1] to [14], wherein the zeolite-type compound is a silicate compound.

[16] A method for manufacturing a functional structure, comprising:

a firing step of firing a precursor material (B) obtained by impregnating a precursor material (a) for obtaining a framework body having a porous structure composed of a zeolite-type compound with a metal-containing solution containing, as a metal element (M), at least one element selected from rare earth elements and alkaline earth metals and at least one element selected from transition metals; and

a hydrothermal treatment step of subjecting a precursor material (C) obtained by firing the precursor material (B) to hydrothermal treatment.

[17] The method for producing a functional structure according to item [16], wherein 50 to 500 mass% of a nonionic surfactant is added to the precursor material (A) before the firing step.

[18] The method of producing a functional structure according to any one of [16] and [17], wherein the metal-containing solution is impregnated into the precursor material (A) by adding the metal-containing solution to the precursor material (A) a plurality of times before the firing step.

[19] The method for producing a functional structure according to any one of the above [16] to [18], wherein, when the metal-containing solution is immersed in the precursor material (a) before the firing step, the amount of the metal-containing solution added to the precursor material (a) is adjusted so that the ratio (atomic ratio Si/M) of silicon (Si) constituting the precursor material (a) to a metal element (M) contained in the metal-containing solution added to the precursor material (a) is 10 to 1000 in terms of the ratio.

[20] The method of producing a functional structure according to item [16], wherein the precursor material (C) is mixed with a structure-directing agent in the hydrothermal treatment step.

[21] The method of producing a functional structure according to item [16], wherein the hydrothermal treatment step is performed in an alkaline environment.

Advantageous effects

According to the present invention, it is possible to provide a functional structure which can suppress aggregation of metal oxide fine particles, suppress a decrease in the function (for example, a catalyst function) of the metal oxide fine particles, prolong the service life, and save resources without requiring a complicated replacement operation.

Drawings

Fig. 1 is a schematic view showing an internal structure of a functional structure according to an embodiment of the present invention, fig. 1(a) is a perspective view (partially shown in a cross section), 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 functional structure of fig. 1, fig. 2(a) is a view for explaining the sieve function, and fig. 2(b) is a view for explaining the catalyst function.

Fig. 3 is a flowchart illustrating an example of a method for manufacturing the functional structure of fig. 1.

Fig. 4 is a schematic diagram showing a modification of the functional structure of fig. 1.

Detailed Description

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

[ constitution of functional Structure ]

Fig. 1 is a view schematically showing the structure of a functional structure according to an embodiment of the present invention, fig. 1(a) is a perspective view (partially shown in cross section), and fig. 1(b) is a partially enlarged sectional view. The functional structure in fig. 1 is an example thereof, and the shape, size, and the like of each component of the present invention are not limited to fig. 1.

As shown in fig. 1(a), the functional structure 1 includes: a porous-structure skeleton 10 made of a zeolite-type compound; and at least one metal oxide fine particle 20 which is present in the skeleton body 10 and contains a perovskite-type oxide.

The metal oxide fine particles 20 are substances having one or more functions alone or by being combined with the skeleton body 10. Specific examples of the functions include: a catalyst function, a light (or fluorescence) function, a light absorption function, a recognition function, and the like. The metal oxide fine particles 20 are preferably, for example, a catalyst substance having a catalyst function. When the metal oxide fine particles 20 are catalyst substances, the skeleton body 10 is a carrier on which at least one catalyst substance is supported.

In the functional structure 1, in fig. 1(b), at least one type of the metal oxide fine particles 20 is a plurality of types of the metal oxide fine particles 20, 20 … … present inside the porous structure of the skeleton body 10. The metal oxide fine particles 20 are preferably metal oxide fine particles containing one or more perovskite-type oxides. The perovskite oxide will be described in detail later.

The skeleton body 10 has a porous structure, and preferably has a passage 11 communicating with each other by forming a plurality of holes 11a and 11a … …, as shown in fig. 1 (b). Here, the metal oxide fine particles 20 are present in at least the passages 11 of the skeleton body 10, and preferably remain in at least the passages 11 of the skeleton body 10.

With such a configuration, the movement of the metal oxide fine particles 20 in the skeleton body 10 is restricted, and the aggregation of the metal oxide fine particles 20, 20 is effectively prevented. As a result, the decrease 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 can be continued for a long period of time. That is, according to the functional structure 1, the decrease in the function due to the aggregation of the metal oxide fine particles 20 can be suppressed, and the life as the functional structure 1 can be extended. Furthermore, by extending the life of the functional structure 1, the frequency of replacement of the functional structure 1 can be reduced, the amount of waste of the used functional structure 1 can be greatly reduced, and resources can be saved.

In general, when a functional structure is used in a fluid (for example, nitrogen oxide (NOx), Volatile Organic Compound (VOC), or the like), an external force may be applied from the fluid. In this case, if the metal oxide fine particles 20 are held only in an adhered state on the outer surface of the skeleton body 10, there is a problem that the metal oxide fine particles are easily detached from the outer surface of the skeleton body 10 under the influence of an external force from a fluid. In contrast, in the functional structure 1, since the metal oxide fine particles 20 are present in at least the passages 11 of the skeleton body 10, and preferably are held in the passages 11 of the skeleton body 10, the metal oxide fine particles 20 are less likely to be detached from the skeleton body 10 even when affected by an external force from a fluid. Namely, it is considered that: when the functional structure 1 is in a fluid, the fluid flows from the holes 11a of the skeleton body 10 into the passage 11, and therefore the velocity of the fluid flowing in the passage 11 is lower than the velocity of the fluid flowing on the outer surface of the skeleton body 10 due to flow path resistance (frictional force). Due to the influence of the flow path resistance, the pressure that the metal oxide fine particles 20 present in the passages 11 receive from the fluid is smaller than the pressure that the metal oxide fine particles receive from the fluid outside the skeleton body 10. Therefore, the metal oxide fine particles 20 existing in the skeleton body 11 can be effectively inhibited from being detached, and the function of the metal oxide fine particles 20 can be stably maintained for a long period of time. It should be noted that: the passage 11 of the skeleton body 10 has a plurality of bent portions and branched portions, and the more complicated the three-dimensional structure inside the skeleton body 10, the greater the flow path resistance as described above.

Further, the passage 11 preferably has: any one of one-dimensional pores, two-dimensional pores, and three-dimensional pores defined by the framework structure of the zeolite-type compound; and an enlarged diameter portion 12 different from any of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole, in which case, the metal oxide fine particles 20 are preferably present at least in the enlarged diameter portion 12, and more preferably are included at least in the enlarged diameter portion 12. The one-dimensional hole as used herein means a tunnel-type or cage-type hole in which one-dimensional channels are formed, or a plurality of tunnel-type or cage-type holes (a plurality of one-dimensional channels) in which a plurality of one-dimensional channels are formed. The two-dimensional hole is a two-dimensional channel formed by two-dimensionally connecting a plurality of one-dimensional channels, and the three-dimensional hole is a three-dimensional channel formed by three-dimensionally connecting a plurality of one-dimensional channels.

This can further restrict the movement of the metal oxide fine particles 20 in the skeleton body 10, and can further effectively prevent the detachment of the metal oxide fine particles 20 and the aggregation of the metal oxide fine particles 20 and 20. The term "inclusion" as used herein means a state in which the metal oxide fine particles 20 are contained in the skeleton body 10. In this case, the metal oxide fine particles 20 and the skeleton body 10 do not necessarily have to be in direct contact with each other, and the metal oxide fine particles 20 may be held indirectly in the skeleton body 10 with another substance (for example, a surfactant) interposed between the metal oxide fine particles 20 and the skeleton body 10.

Fig. 1(b) shows a case where the metal oxide fine particles 20 are included in the enlarged diameter portion 12, but the present invention is not limited to this configuration, and the metal oxide fine particles 20 may be held in the passage 11 in a state where a part thereof protrudes from the outside of the enlarged diameter portion 12. The metal oxide fine particles 20 may be partially embedded in a part 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 fastening or the like.

Further, the enlarged diameter portion 12 preferably causes a plurality of holes 11a, 11a constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole to communicate with each other. Thus, since a separate passage different from the one-dimensional hole, the two-dimensional hole, or the three-dimensional hole is provided in the skeleton body 10, the metal oxide fine particles 20 can further function.

Preferably, the passage 11 is three-dimensionally formed so as to include a branching portion or a merging portion inside the skeleton body 10, and the diameter-enlarged portion 12 is provided at the branching portion or the merging portion of the passage 11.

The average inner diameter D of the passage 11 formed in the skeleton body 10 is calculated from the average of the minor diameter and the major diameter of the hole 11a constituting any one of the one-dimensional hole, the two-dimensional hole, and the three-dimensional hole_FFor example, it is 0.1 to 1.5nm, preferably 0.5 to 0.8 nm. Further, the inner diameter D of the enlarged diameter portion 12_EFor example, the particle size is 0.5 to 50nm, preferably 1.1 to 40nm, and more preferably 1.1 to 3.3 nm. Inner diameter D of enlarged diameter portion 12_EFor example, the pore diameter of the precursor (A) described later and the average particle diameter D of the enclosed metal oxide fine particles 20_C. Inner diameter D of enlarged diameter portion 12_EIs of a size capable of containing the metal oxide particles 20.

The framework 10 is made of a zeolite-type compound. Examples of the zeolite-type compound include: silicate compounds such as zeolite (aluminosilicate), cation-exchange zeolite, and silicalite; zeolite-like compounds such as aluminoborate, aluminoarsenate, germanate and the like; and phosphate-based zeolite-like substances such as molybdenum phosphate. Among them, the zeolite-type compound is preferably a silicate compound.

The framework structure of the zeolite-type compound is selected from 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. The zeolite-type compound has a plurality of pores formed therein and having pore diameters corresponding to respective framework structures, and for example, the MFI-type compound has a maximum pore diameter of 0.636nm

Average pore diameter of 0.560nm

There are cases where the metal oxide fine particles 20 are primary particles and where the metal oxide fine particles 20 are secondary particles formed by agglomeration of primary particles, and the average particle diameter D of the metal oxide fine particles 20_CPreferably greater than the average internal diameter D of the passage 11_FAnd is not more than the inner diameter D of the enlarged diameter part 12_E(D_F<D_C≤D_E). The metal oxide fine particles 20 are preferably included in the diameter-enlarged part 12 in the passage 11 to restrict the movement of the metal oxide fine particles 20 in the skeleton body 10. Therefore, even when the metal oxide fine particles 20 receive an external force from a fluid, the movement of the metal oxide fine particles 20 in the skeleton body 10 can be suppressed, and the metal oxide fine particles 20, 20 … … respectively included in the diameter-enlarged portions 12, 12 … … dispersedly arranged in the passages 11 of the skeleton body 10 can be effectively prevented from being aggregated by being in contact with each other.

The average particle diameter D of the fine metal oxide particles 20_CIn the case of both the primary particles and the secondary particles, the particle size is preferably 0.1 to 50nm, more preferably 0.1nm or more and less than 30nm, still more preferably 0.5 to 14.0nm, and particularly preferably 1.0 to 3.3 nm. In addition, the method can be used for producing a composite materialAverage particle diameter D of the fine metal oxide particles 20_CRelative to the average inner diameter D of the passage 11_FRatio (D)_C/D_F) Preferably 0.06 to 500, more preferably 0.1 to 45, further preferably 1.1 to 45, and particularly preferably 1.7 to 4.5.

The content of the metal element (M) in the metal oxide fine particles is preferably 0.5 to 2.5% by mass relative to the functional structure 1, and more preferably 0.5 to 1.5% by mass relative to the functional structure 1. The "metal element (M)" as used herein means all metals contained in a perovskite-type oxide containing a plurality of metals as described later, and the content means the total amount thereof. For example, in the case where the metal element (M) is La and Mn, the content (mass%) of the metal element is represented by { (mass of La element + mass of Mn element)/(mass of all elements of the functional structure 1) } × 100.

The perovskite oxide contains rare earth and alkaline earth and has a large ionic radiusMetal ion (A ion) having a small ionic radius

ABO of metal ions (B ions)₃The perovskite, which is an important catalyst, is a compound based on a combination of a rare earth element (a site) and a transition metal (B site), and the catalytic properties thereof mainly depend on the properties of the transition metal at the B site.

The type of the perovskite catalyst to be encapsulated is any type as long as it satisfies the general formula ABO of perovskite₃(A: at least one element selected from rare earth elements and alkaline earth metals, B: at least one selected from transition metals) and a compound having a catalytic activity, and is not particularly limited, and specific examples thereof include: LaBO₃(B＝Mn、Cr、Co、Fe、Al、Pd、Mg)、BaZrO₃、La_0.8Sr_0.2Ga_0.8Mg_0.2O₃(LSGM)、LaFe_0.57Co_0.38Pd_0.05O₃、Ba_0.8La_0.2Mn_0.2O₃And the like.

The metal oxide fine particles 20 may contain a perovskite-type oxide, and may be composed of a single perovskite-type oxide, or may be composed of a composite oxide containing two or more perovskite-type oxides or a composite oxide containing a perovskite-type oxide and another oxide. The ratio (Si/M, atomic ratio) of Si constituting the skeleton body 10 to the metal M constituting the metal oxide fine particles 20 is preferably 10 to 1000. If the proportion of the perovskite catalyst is greater than 1000, the activity is low and sufficient catalytic action may not be obtained, while if the proportion of the perovskite catalyst is less than 10, the proportion of the perovskite catalyst is too large and the strength of the skeleton tends to be low. The metal oxide fine particles 20 referred to herein are fine particles present inside the skeleton body 10, preferably fine particles held or carried inside the skeleton body 10, and do not include fine particles adhering to the outer surface of the skeleton body 10.

Examples of the other oxide include a composite metal oxide containing one or two or more of the following as main components: 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)。

[ function of functional Structure ]

As described above, the functional structure 1 includes: a skeleton body 10 having a porous structure; and at least one metal oxide fine particle 20 present in the skeleton body 10. The functional structure 1 functions in accordance with the metal oxide fine particles 20 when the metal oxide fine particles 20 present in the matrix come into contact with a fluid. Specifically, the fluid that contacts the outer surface 10a of the functional structure 1 flows into the skeleton body 10 from the hole 11a formed in the outer surface 10a, is guided into the passage 11, moves through the passage 11, and flows out of the functional structure 1 through the other holes 11 a. In the path of the fluid moving through the inside of the passage 11, a reaction (e.g., catalytic reaction) corresponding to the function of the metal oxide fine particles 20 occurs by contact with the metal oxide fine particles 20 present in the passage 11. Since the skeleton has a porous structure, the functional structure 1 has a molecular sieve function.

First, the molecular sieve function of the functional structure 1 will be described by taking a case where the fluid is, for example, an exhaust gas containing nitrogen oxides (NOx) with reference to fig. 2 (a). As shown in fig. 2(a), an exhaust gas component (for example, a nitrogen oxide (NOx) component) composed of molecules having a size equal to or smaller than the pore diameter of the pores 11a, in other words, equal to or smaller than the inner diameter of the passages 11 can infiltrate into the skeleton body 10. On the other hand, the exhaust component 15 composed of molecules having a size larger than the pore diameter of the pores 11a cannot infiltrate into the skeleton body 10. In this way, when the fluid contains a plurality of exhaust gas components, the reaction of the exhaust gas components that cannot enter the skeleton body 10 is restricted, and the exhaust gas components (for example, nitrogen oxide (NOx) components) that can enter the skeleton body 10 can be reacted.

Among the molecules generated in the skeleton body 10 by the reaction, only molecules having a size equal to or smaller than the pore diameter of the pores 11a can be obtained as products. On the other hand, molecules that cannot flow out of the pores 11a to the outside of the skeleton 10 are converted into molecules having a size that can flow out of the skeleton 10, and then can flow out of the skeleton 10. In this manner, a specific reaction product can be selectively obtained by using the functional structure 1.

In the functional structure 1, as shown in fig. 2(b), the metal oxide fine particles 20 are preferably present in the enlarged diameter portion 12 of the passage 11, and more preferably included in the enlarged diameter portion 12 of the passage 11. The average particle diameter D of the fine metal oxide particles 20_CLarger than the average inner diameter D of the passage 11_FAnd is smaller than the inner diameter D of the diameter-enlarged part 12_EIn the case of (D)_F<D_C<D_E) Small passages 13 are formed between the metal oxide fine particles 20 and the diameter-enlarged portion 12. Therefore, as shown by the arrows in fig. 2(b), the fluid (e.g., NOx component, etc.) and the metal that have entered the small passages 13The oxide particles 20 are in contact. Since each metal oxide fine particle 20 is contained in the expanded diameter portion 12, the movement in the skeleton body 10 is restricted, and the contact area with the fluid containing the NOx component and the like in the inlet passage 11 can be maintained.

Then, when the NOx that has entered the passages 11 comes into contact with the metal oxide fine particles 20, nitrogen oxides (NOx) can be decomposed and removed as shown below by the reductive decomposition reaction by the metal oxide fine particles 20.

2NO+2Vo+4e→2N_ad+2O_L ^2-

2N_ad→N₂

2O_L ^2-→O₂+2Vo+4e

(O_L ^2-Is lattice oxygen, Vo is oxygen deficient)

In addition, the metal oxide fine particles 20 can also convert the VOC component (C) by oxidation reaction_yH_z) The carbon dioxide and water are decomposed and removed as follows.

C_yH_z+(y+z/4)O₂→yCO₂+z/2H₂O

[ method for producing functional Structure ]

Fig. 3 is a flowchart illustrating a method of manufacturing the functional structure of fig. 1. An example of a method for manufacturing a functional structure will be described below.

(step S1: preparation Process)

As shown in fig. 3, first, a precursor material (a) for obtaining a framework having a porous structure made of a zeolite-type compound is prepared. The precursor material (a) is preferably a regular mesoporous material, and may be appropriately selected depending on the kind (composition) of the zeolite-type compound constituting the framework of the functional structure.

Here, when the zeolite-type compound constituting the framework of the functional structure is a silicate compound, the regular mesoporous material is preferably a compound containing an Si — O framework in which pores having a pore diameter of 1nm to 50nm are uniformly and regularly developed in one-dimensional, two-dimensional, or three-dimensional size. Such a ordered mesoporous material is obtained as various compositions according to synthesis conditions, and specific examples of the compositions include: SBA-1, SBA-15, SBA-16, KIT-6, FSM-16, MCM-41 and the like, wherein MCM-41 is preferred. The pore diameter of SBA-1 is 10nm to 30nm, the pore diameter of SBA-15 is 6nm to 10nm, the pore diameter of SBA-16 is 6nm, the pore diameter of KIT-6 is 9nm, the pore diameter of FSM-16 is 3nm to 5nm, and the pore diameter of MCM-41 is 1nm to 10 nm. Examples of such a regular mesoporous material include: mesoporous silica, mesoporous aluminosilicates, mesoporous metallosilicates, and the like.

The precursor (a) may be any of commercially available products and synthetic products. In the case of synthesizing the precursor material (a), it can be carried out by a known method for synthesizing a regular mesoporous substance. For example, a mixed solution containing a raw material containing a constituent element of the precursor material (a) and a template agent for specifying the structure of the precursor material (a) is prepared, and hydrothermal treatment (hydrothermal synthesis) is performed by adjusting the pH as necessary. Then, the precipitate (product) obtained by the hydrothermal treatment is recovered (for example, filtered), washed and dried as necessary, and further fired, whereby the precursor material (a) as a regular mesoporous substance in a powder form can be obtained. Here, as the solvent of the mixed solution, for example, an organic solvent such as water or alcohol, or a mixed solvent thereof can be used. The raw material is selected depending on the type of the skeleton, and examples thereof include: silica agents such as Tetraethoxysilane (TEOS), fumed silica, quartz sand, and the like. Further, as the template agent, various surfactants, block copolymers and the like can be used, and it is preferably selected according to the kind of the composition of the ordered mesoporous material, and for example, in the case of preparing MCM-41, a surfactant such as cetyltrimethylammonium bromide is preferred. The hydrothermal treatment may be carried out, for example, in a closed vessel under the treatment conditions of 80 to 800 ℃ for 5 to 240 hours and 0 to 2000 kPa. The firing treatment may be carried out, for example, in air under the treatment conditions of 350 to 850 ℃ for 2 to 30 hours.

(step 2: impregnation step)

Next, the prepared precursor material (a) is immersed in a metal-containing solution to obtain a precursor material (B).

The metal-containing solution may be a solution containing at least one element selected from rare earth elements and alkaline earth metals and at least one element selected from transition metals as the metal element (M), and may be prepared, for example, by dissolving a metal salt containing the metal element (M) in a solvent. Examples of such metal salts include: metal salts such as chlorides, hydroxides, oxides, sulfates, nitrates, etc., among which nitrates are preferable. As the solvent, for example, an organic solvent such as water or alcohol, or a mixed solvent thereof can be used.

The method for immersing the metal-containing solution in the precursor material (a) is not particularly limited, and for example, it is preferable to add the metal-containing solution in small amounts in a plurality of times while stirring the powdery precursor material (a) before the firing step described later. In addition, from the viewpoint that the metal-containing solution is more likely to infiltrate into the inside of the pores of the precursor material (a), it is preferable to add a surfactant as an additive in advance before adding the metal-containing solution to the precursor material (a). It is considered that such an additive has an effect of covering the outer surface of the precursor material (a), and it suppresses the metal-containing solution added later from adhering to the outer surface of the precursor material (a), and the metal-containing solution is more likely to infiltrate into the inside of 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. Consider that: these surfactants have large molecular sizes and cannot enter the pores of the precursor material (a), and therefore do not adhere to the inside of the pores and do not inhibit the metal-containing solution from entering the inside of the pores. As a method for adding the nonionic surfactant, for example, it is preferable to add 50 to 500 mass% of the nonionic surfactant to the precursor material (a) before the firing step described later. If the amount of the nonionic surfactant added to the precursor material (a) is less than 50 mass%, the above-described inhibiting effect is difficult to be exhibited, and if the amount of the nonionic surfactant added to the precursor material (a) is more than 500 mass%, the viscosity is excessively increased, which is not preferable. Therefore, the amount of the nonionic surfactant added 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 preferably adjusted as appropriate in consideration of the amount of the metal element (M) contained in the metal-containing solution impregnated in the precursor material (a) (that is, the amount of the metal element (M) present in the precursor material (B)). For example, the amount of the metal-containing solution added to the precursor material (a) is preferably adjusted so that the ratio (atomic ratio Si/M) of silicon (Si) constituting the precursor material (a) to a metal element (M) contained in the metal-containing solution added to the precursor material (a) is 10 to 1000, more preferably 50 to 200, before the firing step described later. 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 content of the metal element (M) in the metal oxide fine particles can be set to 0.5 to 2.5 mass% relative to the functional structure by setting the amount of the metal-containing solution added to the precursor material (a) to 50 to 200 in terms of atomic ratio Si/M. In the state of the precursor material (B), if the metal concentration of the metal-containing solution, the presence or absence of the additive, and other conditions such as temperature and pressure are the same, the amount of the metal element (M) present in the pores thereof is substantially proportional to the amount of the metal-containing solution added to the precursor material (a). Further, the amount of the metal element (M) present in the precursor material (B) is in proportional relation to the amount of the metal element constituting the metal oxide fine particles present in the skeleton body of the functional 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 into the pores of the precursor material (a), and the amount of the metal oxide fine particles present in the matrix of the functional structure can be adjusted.

After the precursor material (a) is immersed in the metal-containing solution, a cleaning treatment may be performed as needed. As the cleaning solution, water, an organic solvent such as alcohol, or a mixed solution thereof can be used. Further, it is preferable that the precursor material (a) is immersed in a metal-containing solution, and after a cleaning treatment is performed as necessary, a drying treatment is further performed. Examples of the drying treatment include natural drying at about evening-out and high-temperature drying at 150 ℃. When the firing treatment described later is performed in a state where a large amount of moisture contained in the metal-containing solution or moisture in the cleaning solution remains in the precursor (a), the skeleton structure of the regular mesoporous material as the precursor (a) may be broken, and therefore, it is preferable to sufficiently dry the precursor (a).

(step S3: firing Process)

Next, a precursor material (B) obtained by impregnating a precursor material (a) for obtaining a framework having a porous structure composed of a zeolite-type compound with a metal-containing solution is fired to obtain a precursor material (C).

The firing treatment is preferably carried out in air at a temperature of 350 to 850 ℃ for 2 to 30 hours, for example. By such firing treatment, the metal component crystals impregnated into the pores of the regular mesoporous material grow, 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 subjected to hydrothermal treatment to obtain the functional structure.

The structure-directing agent is a template agent for defining the skeleton structure of the skeleton of the functional structure, and a surfactant, for example, can be used. The structure-directing agent is preferably selected according to the skeleton structure of the skeleton of the functional structure, and is preferably a surfactant such as tetramethylammonium bromide (TMABr), tetraethylammonium bromide (TEABr), tetrapropylammonium bromide (TPABr), or the like.

The mixing of the precursor material (C) and the structure-directing agent may be performed in the present hydrothermal treatment step, or may be performed 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 dispersed in the solvent in the respective solutions and then the respective dispersed solutions may be mixed. As the solvent, for example, an organic solvent such as water or alcohol, or a mixed solvent thereof can be used. It is preferable that the pH of the mixed solution is adjusted in advance with an acid or an alkali 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, for example, 80 to 800 ℃ for 5 to 240 hours and 0 to 2000 kPa. Further, it is preferable to perform hydrothermal treatment in an alkaline environment.

Although the reaction mechanism is not necessarily clear here, when the precursor material (C) is subjected to hydrothermal treatment as a raw material, the skeleton structure of the regular mesoporous material as the precursor material (C) is gradually destroyed, but the position of the metal oxide fine particles inside the pores of the precursor material (C) is substantially maintained, and a new skeleton structure (porous structure) as a skeleton of the functional structure is formed by the action of the structure-directing agent. The functional structure obtained in this way includes a skeleton body having a porous structure and metal oxide fine particles present in the skeleton body, the skeleton body further includes passages that communicate the plurality of pores with each other through the porous structure, and at least a part of the metal oxide fine particles are present in the passages of the skeleton body, and are preferably retained in the passages of the skeleton body.

In the present 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 hydrothermal treatment is performed on the precursor material (C), but the present invention is not limited thereto, and the hydrothermal treatment may be performed on the precursor material (C) without mixing the precursor material (C) and the structure-directing agent.

It is preferable that the precipitate (functional structure) obtained after the hydrothermal treatment is recovered (e.g., filtered), and then washed, dried, and fired as necessary. 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 at about evening-out and high-temperature drying at 150 ℃. When the sintering treatment is performed in a state where a large amount of moisture remains in the precipitate, the skeleton structure of the skeleton body as the functional structure may be broken, and therefore, sufficient drying is preferable. The firing treatment may be performed, for example, in air under the treatment conditions of 350 to 850 ℃ for 2 to 30 hours. By such a firing treatment, the structure directing agent attached to the functional structure is burned off. In addition, depending on the purpose of use, the functional structure can be used as it is without firing the collected precipitate. For example, when the use environment of the functional structure is a high-temperature environment that is an oxidizing environment, the structure-directing agent is burned off by exposure to the use environment for a certain period of time, and the same functional structure as in the case of performing the firing treatment can be obtained, and therefore, the functional structure can be used as it is.

[ modified example of functional Structure 1]

Fig. 4 is a schematic diagram showing a modification of the functional structure 1 of fig. 1.

The functional structure 1 in fig. 1 is shown to have the skeleton body 10 and the metal oxide fine particles 20 present in the skeleton body 10, but the present invention is not limited to this configuration, and for example, as shown in fig. 4, the functional structure 2 may further have at least one type of other metal oxide fine particles 30 held on the outer surface 10a of the skeleton body 10.

The other metal oxide fine particles 30 are substances that perform one or more functions. The functions of the other metal oxide fine particles 30 may be the same as or different from those 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 among them, the metal oxide fine particles 30 preferably have a catalytic function, and in this case, the metal oxide fine particles 30 are a catalytic substance. In the case where both the metal oxide fine particles 20 and 30 have 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. According to the present configuration, the content of the metal oxide fine particles held in the functional structure 2 can be increased, and the function of the metal oxide fine particles can be further promoted.

In this case, it is preferable that the content of the at least one type of metal oxide fine particles 20 present in the skeleton body 10 is greater than the content of the at least one type of other metal oxide fine particles 30 held on the outer surface 10a of the skeleton body 10. Thus, the function of the metal oxide fine particles 20 held inside the skeleton body 10 becomes dominant, and the function of the metal oxide fine particles is stably exhibited.

The functional structure according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various modifications and changes can be made based on the technical idea of the present invention.