Metal hydroxide particles having hollow structure

Abstract

The purpose of the present invention is to provide novel metal hydroxide particles having a hollow structure. Provided are metal hydroxide particles having a hollow structure.

Description

Metal hydroxide particles having a hollow structure

[0001] The present invention relates to metal hydroxide particles having a hollow structure.

[0002] Patent Document 1 includes a support having a plurality of mesopores and oxidation catalyst particles carried in the mesopores of the support and containing at least one of a noble metal, an oxide thereof, and an alloy of the noble metal and a transition metal. In the support, a mesoporous catalyst body in which one mesopore communicates with at least one other mesopore is disclosed.

[0003] Patent Document 2 discloses a porous body in which flakes containing iron oxide, at least a part of which is in a polycrystalline state, are aggregated in a state where a plurality of gaps communicating with the outside exist, and having pores formed by one gap communicating with another gap, and oxidation catalyst particles carried in the pores and containing one or more selected from the group consisting of a noble metal, an oxide of the noble metal, and an alloy of the noble metal and a transition metal, and the flakes have a thickness of 5 nm or more and 20 nm or less and a maximum length of 50 nm or more and 500 nm or less.

[0004] International Publication No. WO$2018 / 155432$ International Publication No. WO$2019 / 239936$ [[ID=???]]

[0005] An object of the present invention is to newly provide metal hydroxide particles having a hollow structure.

[0006] The present invention has developed a catalyst body that can oxidize carbon monoxide well by supporting a noble metal catalyst on metal hydroxide particles having a hollow structure and having pores (mesopores) in its wall. The catalyst body of the present invention is preferably iron oxide particles having a hollow structure supporting Au nanoparticles and has good CO oxidation catalytic ability. T

[0007] The present invention includes the following metal hydroxide particles having a hollow structure.

[0008] Item 1. A method for producing particles having a hollow structure, comprising: (1) a perovskite fluoride: KMF in a solution containing an alkali and an alcohol ３ Note: There seems to be an error in the original text where "International Publication No. WO2018 / 155432 International Publication No. WO2019 / 239936" is written without proper formatting. I have tried to keep it as close to the original as possible while still making it somewhat legible in the translation. Also, the "T" in the translation of line 19 seems to be an error in the original text, but I've translated it as it is. If you can correct these errors in the original text, it would be better for a more accurate translation.(a) A method for producing metal hydroxide particles having a hollow structure, comprising the steps of (1) adding (M) a metal element such as Zn, Mg, Co, Ni, Fe, or Mn to form a hydroxide shell of metal M on the surface of the perovskite-type fluoride (core), and (2) adding the perovskite-type fluoride (core) obtained in step (1) with a hydroxide shell of metal M formed on its surface to water, dissolving the perovskite-type fluoride (core) to obtain a hydroxide shell of metal M.

[0009] Item 2. Particles having a hollow structure, (a1) The particles consist of a shell of a metal M (where M represents a metallic element such as Zn, Mg, Co, Ni, Fe, or Mn), (a2) The particles have an average particle diameter of 50 nm to 10 μm, (a3) ​​The shell thickness of the particles is 5% to 35% of the average particle diameter (a2), (a4) The particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2), and (a5) The shells of the particles have mesopores with a diameter of 40 nm or less. (a) Particles of a metal hydroxide having a hollow structure.

[0010] Item 3. A method for producing catalyst particles, comprising: (1) adding (a) particles of a hollow metal hydroxide obtained by the production method described in claim 1, or (a) particles of a hollow metal hydroxide described in claim 2, to a solution containing a noble metal compound, and heating the reaction solution; and (2) separating a solid from the reaction solution obtained in step (1) and calcining the solid, wherein (b) catalyst particles of a hollow metal oxide supported by a noble metal.

[0011] Item 4. The manufacturing method according to item 3, wherein the (b) precious metal is at least one precious metal compound selected from the group consisting of gold (Au), platinum (Pt), and palladium (Pd).

[0012] Item 5. The manufacturing method described in Item 3, wherein the firing in step (2) is carried out at 120°C to 500°C.

[0013] Item 6. Catalyst particles, wherein the catalyst particles (a) have a hollow structure and (b) a noble metal supported on them, the (a) hollow structure metal oxide particles (a1) consist of a hydroxide shell of metal M (where M represents a metal element such as Zn, Mg, Co, Ni, Fe, or Mn), (a2) the average particle diameter of the particles is 50 nm to 10 μm, (a3) ​​the shell thickness of the particles is 5% to 35% of the average particle diameter (a2), (a4) the particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2), and (a5) the shells have pores with a diameter of 40 nm or less.

[0014] Item 7. The catalyst particles according to item 6, wherein the (b) precious metal is at least one precious metal compound selected from the group consisting of (b1) gold (Au), platinum (Pt), and palladium (Pd).

[0015] Item 8. The catalyst particles have a specific surface area of ​​50 m². 2 / g~200m 2 The catalyst particles described in item 6 above, which are present in a quantity of / g.

[0016] The metal hydroxide particles of the present invention, having a hollow structure and pores (mesopores) in their walls, become a catalyst that effectively oxidizes carbon monoxide when a noble metal catalyst is supported on them. In particular, the catalyst of the present invention, iron oxide particles having a hollow structure on which Au nanoparticles are supported, exhibits good CO oxidation catalytic activity.

[0017] The present invention can provide metal hydroxide particles having a hollow structure.

[0018] Figure 1 shows the perovskite-type fluoride KMF3 (M=Zn, Mg, Co, Ni, Fe, Mn, etc.) used to produce hollow metal hydroxide particles according to the present invention. Perovskite-type fluoride KMF3 nanoparticles are synthesized by solvothermal synthesis. The particle size of the perovskite-type fluoride KMF3 nanoparticles is approximately 50 nm to 200 nm. The perovskite-type fluoride KMF3 nanoparticles dissolve in water and serve as a template that can be easily removed when producing hollow metal hydroxide particles. 1.19 g of FeCl2・4H2O is added to 40 mL of ethylene glycol, followed by 1.41 g of KF・2H2O, and a solvothermal reaction (180°C, 20 h) is carried out. Then, the mixture is washed with MeOH and dried to obtain perovskite-type fluoride KFeF3. Figure 2 shows the synthesis method for hollow iron hydroxide nanoparticles using perovskite fluoride KFeF3 as a template. Step (1) involves adding perovskite fluoride KFeF3 nanoparticles to a solution of KOHaq.:EtOH = 1:7 (volume ratio), first dispersing them in ethanol, and then introducing an aqueous potassium hydroxide solution to promote the surface reaction. Next, 8.57 mL of 0.1 M KOHaq. is added and stirred (5 min). Subsequently, filtration and drying are performed to obtain KFeF3-KOH, in which an iron hydroxide shell is formed on the surface of the perovskite fluoride KFeF3 nanoparticles (core). Subsequently, in step (2), KFeF3-KOH, in which an iron hydroxide shell is formed on the surface of perovskite-type fluoride KFeF3 nanoparticles (core), is added to water to dissolve the core perovskite-type fluoride KFeF3 nanoparticles and form the iron hydroxide shell. Figure 3 shows a TEM image of the hollow iron hydroxide nanoparticles. Figure 4 shows the synthesis method for iron oxide particles having a hollow structure supported by Au nanoparticles. To a 1,000 ppm HAuCl4 aqueous solution, 0.1 M NaOH aqueous solution is added dropwise at 70°C to adjust the aqueous solution to pH 7. Next, hollow iron hydroxide (0.05 g) is added and heated at 70°C for 1 hour. Then, the solution is filtered and washed. The sample after filtering and washing is calcined at an appropriate temperature for 2 hours (heating rate: 5°C / min) to obtain iron oxide particles having a hollow structure supported by Au nanoparticles.Examples: Precursor Au / Fe: The ratio of Au to Fe is 6.15 at%. Figure 5 shows the XRD of hollow iron oxide particles supported with Au nanoparticles. Figure 6 shows CO decomposition experiment (1) of hollow iron oxide particles supported with Au nanoparticles. Decomposition experiment of 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was used in which 0.15 g of the calcined catalyst was coated onto a glass plate. Gold-supported iron hydroxide with an atomic ratio of Au to Fe of 6.15 at% was used and calcined. Figure 7 shows CO decomposition experiment (2) of hollow iron oxide particles supported with Au nanoparticles. Decomposition experiment of 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was used in which 0.15 g of catalyst was coated onto a glass plate and then calcined. Gold-supported iron hydroxide with an atomic ratio of Au to Fe of 6.15 at% was used and calcined. Figure 8 shows the CO decomposition experiment (3) of hollow iron oxide particles supported with Au nanoparticles. Decomposition experiment of 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was used in which 0.15 g of catalyst was coated onto a glass plate and then calcined. During gold support, the amount of Au supported relative to iron hydroxide was varied. In the initial stage, the reaction was carried out in a 1,000 ppm HAuCl4 aqueous solution (base). The base (1,000 ppm) was used as the reference, and the amount was varied to 1 / 2 times (500 ppm), 3 times (3,000 ppm), and 5 times (5,000 ppm).

[0019] The present invention will be described in detail below. The embodiments illustrating the present invention are intended to provide a better understanding of the spirit of the invention and do not limit the scope of the invention unless otherwise specified.

[0020] In this specification, "contains" and "include" are concepts that encompass all of the following: "comprise," "consist essentially of," and "consist of."

[0021] In this specification, when a numerical range is indicated as "A to B", it means "greater than or equal to A and less than or equal to B".

[0022] In this specification, the terms parts, percentages, etc. are generally used to represent parts by mass, parts by weight, mass%, and weight (wt%).

[0023] [1] Method for producing particles having a hollow structure The method for producing particles having a hollow structure of the present invention (a) produces particles of a metal hydroxide having a hollow structure.

[0024] The present invention (a) a method for producing a hollow metal hydroxide comprises the following steps (1) and (2): (1) a perovskite-type fluoride: KMF in a solution containing an alkali and an alcohol. ３ (1) A step of adding (M represents a metallic element of Zn, Mg, Co, Ni, Fe, or Mn) to form a hydroxide shell of metal M on the surface of the perovskite-type fluoride (core). (2) A step of adding the perovskite-type fluoride (core) obtained in step (1) with a hydroxide shell of metal M formed on its surface to water, dissolving the perovskite-type fluoride (core) to obtain a hydroxide shell of metal M.

[0025] The metal hydroxide particles of the present invention, having a hollow structure and pores (mesopores) in their walls, become a catalyst that effectively oxidizes carbon monoxide when a noble metal catalyst is supported on them. In particular, the catalyst of the present invention, iron oxide particles having a hollow structure on which Au nanoparticles are supported, exhibits good CO oxidation catalytic activity.

[0026] Step (1) The present invention's method for producing a hollow metal hydroxide is (1) a perovskite-type fluoride: KMF in a solution containing alkali and alcohol. ３ The process includes adding (where M represents a metallic element such as Zn, Mg, Co, Ni, Fe, or Mn) to form a hydroxide shell of metal M on the surface of the perovskite-type fluoride (core).

[0027] (Perovskite-type fluoride) Perovskite-type fluoride: KMF ３ In this, M preferably represents a metallic element of Zn, Mg, Co, Ni, Fe, or Mn.

[0028] Perovskite fluorides can preferably be synthesized into nanoparticles by solvothermal synthesis. Solvothermal synthesis is a reaction using a solvent under moderate to high pressure (usually 1 atm to 10,000 atm) and temperature (usually 100°C to 1,000°C). Of the solvothermal synthesis methods, hydrothermal synthesis using water as the solvent is preferred. Synthesis under hydrothermal conditions is usually carried out below the supercritical temperature of water (374°C).

[0029] Perovskite-type fluorides can preferably be used to synthesize nanoparticles by calcination.

[0030] Perovskite-type fluorides are particles, preferably with a particle size of about 50 nm to 10 μm. Perovskite-type fluorides are also preferably nanoparticles, with a nanoparticle size of about 200 nm to 500 nm. Perovskite-type fluoride nanoparticles dissolve in water and form easily removable templates.

[0031] (Alkali) The alkali in the solution containing alkali and alcohol is, for example, potassium hydroxide (KOH). Preferably, alkalis are alkali metal hydroxides, alkaline earth metal hydroxides, various alkali metal salts, various alkaline earth metal salts, organic amine salts, ammonium salts, etc. Preferably, alkalis are alkali metal hydroxides, and more preferably potassium hydroxide, sodium hydroxide, etc.

[0032] Alkali and the alkali in the solution containing alcohol may be used individually or as a mixture (blend) of two or more types.

[0033] (Alcohol) In solutions containing alkali and alcohol, the solvent can preferably be either water or alcohol. Preferably, a lower alcohol such as methanol, ethanol, or isopropanol is used.

[0034] (a) The present invention provides a method for producing a hollow metal hydroxide, comprising the steps of (1) adding a perovskite-type fluoride to a solution containing an alkali and an alcohol, first dispersing it in ethanol, then introducing an aqueous potassium hydroxide solution to promote a surface reaction and form a metal M hydroxide shell on the surface of the perovskite-type fluoride (core). For example, ultrasonic treatment may be performed to disperse the ethanol in the solution.

[0035] Step (2) The present invention's method for producing a hollow metal hydroxide (a) includes the steps of: (2) adding to water a perovskite-type fluoride (core) obtained in step (1) with a metal M hydroxide shell formed on its surface; and, for example, when using FeF3, dissolving the perovskite-type fluoride (core) in water, and immediately filtering it after dispersion in water to create a hollow structure and obtain a metal M hydroxide shell.

[0036] Perovskite-type fluoride nanoparticles dissolve in water and serve as easily removable templates.

[0037] [2] Particles having a hollow structure The particles having a hollow structure of the present invention are (a) particles of a metal hydroxide having a hollow structure.

[0038] The metal hydroxide particles having a hollow structure according to the present invention have the following characteristics (a1) to (a5): (a1) The particles consist of a shell of a hydroxide of metal M (where M represents a metallic element such as Zn, Mg, Co, Ni, Fe, or Mn). (a2) The particles have an average particle diameter of 50 nm to 10 μm. (a3) ​​The shell thickness of the particles is 5% to 35% of the average particle diameter (a2). (a4) The particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2). (a5) The particles have pores (preferably mesopores) with a diameter of 40 nm or less in the shell.

[0039] The metal hydroxide particles having a hollow structure and pores (mesopores) in their walls can serve as a catalyst for oxidizing carbon monoxide well by supporting a noble metal catalyst. The catalyst of the present invention, particularly, iron oxide particles having a hollow structure supporting Au nanoparticles, has good CO oxidation catalytic ability.

[0040] (a) The particles of the metal hydroxide having a hollow structure consist of (a1) a shell of the hydroxide of metal M. Metal M is a metal constituting a perovskite-type fluoride, and preferably, a metal element of Zn, Mg, Co, Ni, Fe, or Mn.

[0041] (a) The particles of the metal hydroxide having a hollow structure preferably have (a2) an average particle diameter of 50 nm to 10 μm, more preferably 100 nm to µm, and still more preferably 200 nm to 500 nm.

[0042] When using a perovskite-type fluoride of, for example, Ni or Co as metal M, it is possible to synthesize (a2) hollow hydroxide nanoparticles with an average particle diameter of 100 nm or less and about nm for the particles of the metal hydroxide having a hollow structure. With the perovskite-type fluoride of KFeF3, relatively small particles can be synthesized.

[0043] [[ID=,12]] When producing the particles of the metal hydroxide having a hollow structure by solid-phase synthesis, it is possible to adjust (a2) the average particle diameter to about 10 µm. <,

[0044] (a) The particles of the metal hydroxide having a hollow structure preferably have (a3) a shell thickness that is 5% to 35% of the shell thickness with respect to the (a2) average particle diameter, more preferably 10% to 25% of the shell thickness, and still more preferably 15% to 20% of the shell thickness. The shell thickness is, for example, 30 nm to 50 nm. The shell thickness is the length perpendicular to the surface (the surface having the largest area).

[0045] The (a2) average particle diameter of the particles and the (a3) shell thickness can be obtained as the average value by calculating the size in the image photograph of a transmission electron microscope (TEM).

[0046] (a) The metal hydroxide particles having a hollow structure preferably have hollow macropores whose diameter is 95% to 65% of the average particle diameter, more preferably 90% to 75%, and even more preferably 85% to 80%, based on the relationship between the diameter and the thickness of the shell (inverse percentage of the wall thickness) (a2). The size of the hollow macropores is, for example, 150 nm to 470 nm. The hollow macropores provide a catalyst with higher permeability, allowing the treated gas to permeate and diffuse more easily, and further suppressing the decrease in catalytic activity when the flow rate is increased.

[0047] (a) The metal hydroxide particles having a hollow structure preferably have (a5) pores (mesopores and micropores) with a diameter of 40 nm or less in the shell, more preferably pores with a diameter of 5 nm to 30 nm, and even more preferably fine pores (mesopores) with a diameter of 10 nm to 20 nm. (Mesopores and micropores) provide a catalyst with higher permeability, allowing the gas to be treated to permeate and diffuse easily, and further suppressing the decrease in catalytic activity when the flow rate is increased.

[0048] (a4) The size of the hollow macropores can be calculated by the mercury intrusion method, for example, using an automatic specific surface area / pore distribution measuring device based on the mercury intrusion method. (a5) The size of the mesopores can be calculated by the N2 adsorption / desorption measurement method.

[0049] [3] Method for producing catalyst particles The method for producing catalyst particles of the present invention produces catalyst particles of a metal oxide having a hollow structure on which a noble metal is supported.

[0050] The present invention provides a method for producing catalyst particles of a hollow metal oxide supported by a (b) noble metal, comprising the following steps (1) and (2): (1) Adding particles of a hollow metal hydroxide obtained by the method for producing particles having a hollow structure described in [1] above, or particles of a hollow metal hydroxide described in [2] above, to a solution containing a noble metal compound, and heating the reaction solution; (2) Separating a solid from the reaction solution obtained in step (1), and calcining the solid.

[0051] In the method for producing catalyst particles, preferably, (b) the noble metal is at least one noble metal compound selected from the group consisting of gold (Au), platinum (Pt), and palladium (Pd).

[0052] In the method for producing catalyst particles, preferably, the calcination in step (2) is carried out at 120°C to 500°C.

[0053] The metal hydroxide particles of the present invention, having a hollow structure and pores (mesopores) in their walls, become a catalyst that effectively oxidizes carbon monoxide when a noble metal catalyst is supported on them. In particular, the catalyst of the present invention, iron oxide particles having a hollow structure on which Au nanoparticles are supported, exhibits good CO oxidation catalytic activity.

[0054] Step (1) The present invention provides a method for producing catalyst particles of a hollow metal oxide supported by a (b) noble metal, comprising the step of adding (a) metal hydroxide particles having a hollow structure obtained by the method for producing particles having a hollow structure described in [1] above, or the metal hydroxide particles having a hollow structure described in [2] above, to a solution containing a noble metal compound, and then heating the reaction solution.

[0055] The precious metal compound is preferably at least one precious metal compound selected from the group consisting of gold (Au) compounds, platinum (Pt) compounds, and palladium (Pd) compounds.

[0056] Preferably, the gold (Au) compound used is HAuCl4・4H2O, NH4AuCl4, KAuCl4・nH2O, KAu(CN)4, Na2AuCl4, KAuBr4・2H2O, NaAuBr4, etc.

[0057] The platinum (Pt) compound used is preferably chloroplatinic acid, dinitrodiammineplatin, or dichlorotetraammineplatin.

[0058] The palladium (Pd) compound used is preferably dinitrodiaminepalladium, ammonium palladate chloride, or the like.

[0059] Step (1) (1) Add (a) hollow structure metal hydroxide particles to a solution containing a noble metal compound and heat the reaction mixture. (1) The solution containing the noble metal compound is heated to preferably 20°C to 90°C, more preferably 50°C to 70°C, and while stirring, is adjusted with an alkaline solution to preferably pH 3 to pH 10, more preferably pH 5 to pH 8. Then, (1) the hollow structure metal hydroxide particles are added to the solution containing the noble metal compound and heated at about 70°C for 1 hour, followed by heating and calcination at 200°C to 600°C to obtain metal oxide catalyst particles.

[0060] Step (2) The present invention provides a method for producing metal oxide catalyst particles having a hollow structure and supporting a (b) noble metal, comprising the steps of (2) separating a solid from the reaction solution obtained in step (1) and calcining the solid.

[0061] The firing in step (2) is preferably carried out at 120°C to 500°C, more preferably at 150°C to 300°C, and even more preferably at 200°C to 250°C. Sufficient conversion from metal oxide (iron oxide precursor, etc.) to metal oxide (iron oxide, etc.) is achieved through firing within an appropriate temperature range. The specific surface area of ​​the catalyst particles can be maintained through firing within an appropriate temperature range.

[0062] The baking time is preferably about 2 hours.

[0063] [4] Catalyst particles The catalyst particles of the present invention consist of (a) metal oxide particles having a hollow structure, on which (b) a noble metal is supported.

[0064] In the catalyst particles of the present invention, (a) metal oxide particles having a hollow structure have the following characteristics (a1) to (a5): (a1) The particles consist of an oxide shell of metal M (where M represents a metal element such as Zn, Mg, Co, Ni, Fe, or Mn). (a2) The particles have an average particle diameter of 50 nm to 10 μm. (a3) ​​The shell thickness of the particles is 5% to 35% of the average particle diameter (a2). (a4) The particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2). (a5) The particles have pores (preferably mesopores) with a diameter of 40 nm or less in the shell.

[0065] (a) The characteristics (a1) to (a5) of the metal hydroxide particles having a hollow structure are described in the same way as in [2] Particles having a hollow structure.

[0066] In the catalyst particles of the present invention, preferably, (b) the noble metal is at least one noble metal selected from the group consisting of (b1) gold (Au), platinum (Pt), and palladium (Pd). In the catalyst particles, (b) the noble metal is preferably at least one (or two or more) selected from the group consisting of gold, platinum, palladium, and their oxides, which have higher oxidation catalytic activity.

[0067] The constituent components of the catalyst particles are preferably Au, Pt, Pd, Au2O3, Ag2O, AgO, Ag2O・Ag2O3, PdO, PtO2, PtO2・H2O, platinum black, etc.

[0068] (b) The average particle size of the noble metal is preferably 9 nm or less, more preferably 1 nm or more and 9 nm or less, and even more preferably 2 nm or more and 6 nm or less, in that the specific surface area of ​​the catalyst particles is increased, the catalytic activity is dramatically improved, and the decomposition efficiency of the target compound in the gas to be treated is further increased.

[0069] (b) The average particle size of precious metals can be obtained by calculating the particle size from images taken with a transmission electron microscope (TEM) and taking the average value.

[0070] (a) When the metal oxide particles having a hollow structure are iron oxide, the iron oxide is preferably stable iron oxide such as FeO, Fe2O3, Fe3O4, etc.

[0071] (b) The noble metal (e.g., Au) is supported on the particles of the hollow metal hydroxide (e.g., Fe) in an atomic ratio (e.g., Au / Fe, atomic ratio of Au to Fe) preferably in an atomic ratio of 0.1 atomic% to 20 atomic%, and more preferably in an atomic ratio of 0.5 atomic% to 10 atomic%, respectively. (b) The noble metal is supported on the particles of the hollow metal hydroxide in (a), which suppresses aggregation of catalyst particles and allows for good catalytic activity.

[0072] (a) The amount of noble metal supported on metal oxide particles having a hollow structure (b) can be measured by inductively coupled plasma (ICP) emission spectroscopy or X-ray photoelectron spectroscopy (XPS).

[0073] In the catalyst particles of the present invention, preferably, the specific surface area of ​​the catalyst particles is 50 m². 2 / g~200m 2 It contains [amount] per gram. Catalyst particles have a large specific surface area, dramatically improving catalytic activity and further increasing the decomposition efficiency of the target compound in the gas being treated.

[0074] The catalyst of the present invention enables the decomposition of components such as organic gases, carbon monoxide, and ammonia in a gas to be treated into harmless substances such as carbon dioxide and water through an oxidation reaction, and their release into the atmosphere. Specific compounds that can be treated with the catalyst of the present invention include, for example, nitrogen-containing compounds such as carbon monoxide and ammonia contained in exhaust gases from internal combustion engines and cigarette smoke, compounds emitted from agricultural products and plants such as flowers, substances volatile from materials such as interior materials for automobiles, building materials and interior materials for houses, and casings and components of home appliances, as well as substances volatile from organic solvents such as paints, adhesives, and cleaning agents.

[0075] The metal hydroxide particles of the present invention, having a hollow structure and pores (mesopores) in their walls, become a catalyst that effectively oxidizes carbon monoxide when a noble metal catalyst is supported on them. In particular, the catalyst of the present invention, iron oxide particles having a hollow structure on which Au nanoparticles are supported, exhibits good CO oxidation catalytic activity.

[0076] The embodiments of the present invention will be described in more detail below based on the examples. However, the present invention is not limited to the scope of the examples.

[0077] [1] Production of particles with a hollow structure (1) Production of perovskite-type fluoride KMF3 (M=Zn, Mg, Co, Ni, Fe, Mn, etc.) Perovskite-type fluoride KMF3 nanoparticles were synthesized by solvothermal synthesis. 1.19 g of FeCl2・4H2O was added to 40 mL of ethylene glycol, followed by 1.41 g of KF・2H2O, and the solvothermal reaction (180°C, 20 h) was carried out. Then, the mixture was washed with MeOH and dried to obtain perovskite-type fluoride KFeF3.

[0078] The particle size of the perovskite-type fluoride KFeF3 nanoparticles was approximately 200 nm to 500 nm. These perovskite-type fluoride KFeF3 nanoparticles dissolve in water and serve as easily removable templates when producing hollow metal hydroxide particles.

[0079] Figure 1 shows a TEM image of the perovskite fluoride KFeF3 produced by solvothermal synthesis.

[0080] (2) Manufacturing process for hollow metal hydroxide particles (1) Figure 2 shows the synthesis method for hollow iron hydroxide nanoparticles using KFeF3 as a template. Figure 2 shows the process of manufacturing hollow particles, specifically (1) adding perovskite-type fluoride KFeF3 to a solution containing alkali (KOH) and alcohol (EtOH) to form a metal Fe hydroxide shell on the surface of the perovskite-type fluoride (core).

[0081] In step (1), 0.1 g of perovskite-type fluoride KFeF3 nanoparticles were added to a solution of KOH:EtOH = 1:7 (volume ratio) (60 mL of EtOH) to allow the surface reaction to proceed. At this time, an aqueous KOH solution was added to the ethanol and sonication was performed (20 min). Next, 8.57 mL of 0.1 M KOH was added and stirred (5 min). Subsequently, by filtration and drying, a shell of iron hydroxide was formed on the surface of the perovskite-type fluoride KFeF3 nanoparticles (core), yielding KFeF3-KOH.

[0082] Step (2) Hollow iron hydroxide nanoparticles were synthesized using KFeF3 as a template. Among the methods for producing particles with a hollow structure, (2) a perovskite-type fluoride (core) obtained in step (1) with a metallic iron hydroxide shell formed on its surface was added to water, and the perovskite-type fluoride (core) was dissolved to obtain iron hydroxide shells (iron hydroxide particles with a hollow structure).

[0083] In step (2), KFeF3-KOH, in which an iron hydroxide shell is formed on the surface of perovskite-type fluoride KFeF3 nanoparticles (core), is added to water. After dispersion in water at room temperature, it is filtered, and then water is further introduced into the filtration device to dissolve the perovskite-type fluoride KFeF3 nanoparticles of the core. Subsequently, the iron hydroxide shell is formed by filtration and drying.

[0084] [2] Evaluation of particles with a hollow structure Figure 3 shows a TEM image of hollow iron hydroxide nanoparticles.

[0085] [3] Manufacturing of catalyst particles Figure 4 shows a method for synthesizing iron oxide particles having a hollow structure supported by Au nanoparticles.

[0086] (b) A method for producing (a) hollow structured iron oxide catalyst particles supported by Au, (1) adding (a) hollow structured iron hydroxide particles obtained in the above step to a solution containing an Au compound and heating the reaction solution, and then (2) separating the solid from the reaction solution obtained in step (1) and calcining the solid to produce (b) Au-supported (a) hollow structured iron oxide catalyst particles.

[0087] To a 1,000 ppm HAuCl4 aqueous solution, a 0.1 M NaOH aqueous solution was added dropwise at 70°C to adjust the pH of the solution to 7. Then, hollow iron hydroxide (0.05 g) was added and the mixture was heated at 70°C for 1 hour. Next, the mixture was filtered and washed. The filtered and washed sample was calcined at an appropriate temperature for 2 hours (heating rate: 5°C / min) to obtain iron oxide particles having a hollow structure supporting Au nanoparticles. Example: The precursor Au / Fe had an atomic ratio of Au to Fe of 6.15 at%.

[0088] Figure 4 shows a TEM image of iron oxide particles with a hollow structure supported by Au nanoparticles.

[0089] [4] Evaluation of catalyst particles Figure 5 shows the XRD of iron oxide particles having a hollow structure supported by Au nanoparticles.

[0090] Table 1 shows the specific surface area of ​​hollow iron oxide particles supported with Au nanoparticles. Sintering (at appropriate temperature) 2h (heating rate: 5°C / min)

[0091]

[0092] It can be seen that increasing the firing temperature decreases the specific surface area of ​​the catalyst particles. Furthermore, when considered in conjunction with the results of XRD of the catalyst particles, it can be seen that catalyst particles with a high specific surface area and an amorphous structure are preferable.

[0093] (CO removal test) The CO oxidation reaction of hollow iron oxide particles supported with Au nanoparticles was evaluated using carbon monoxide (CO).

[0094] The inside of a box (AS ONE 1-5943-01 Vacuum Desiccator 150×150×150 mm VXS) was filled with 1,000 ppm CO, and iron oxide particles (catalysts) with a hollow structure supporting Au nanoparticles were placed inside. The rate of CO reduction was then tracked using a CO sensor (Micro IV, manufactured by Gesellschaft fur Geratebau mbH).

[0095] Figure 6 shows the CO decomposition experiment (1) of hollow iron oxide particles supported with Au nanoparticles. The decomposition experiment was performed on 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was used in which 0.15 g of the calcined catalyst was coated onto a glass plate. Gold-supported iron hydroxide with an atomic ratio of Au to Fe of 6.15 at% was used and calcined.

[0096] Figure 7 shows the CO decomposition experiment (2) of hollow iron oxide particles supported with Au nanoparticles. The decomposition experiment was performed on 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was prepared by coating a glass plate with 0.15 g of catalyst and then calcining it. Gold-supported iron hydroxide with an atomic ratio of Au to Fe of 6.15 at% was used and calcined.

[0097] Figure 8 shows the CO decomposition experiment (3) of hollow iron oxide particles supported with Au nanoparticles. The decomposition experiment was performed on 1,000 ppm CO (prepared with 2,000 ppm CO + N2 and air). Catalyst: A sample was used in which 0.15 g of catalyst was coated onto a glass plate and then fired. When gold was supported, the amount of Au supported relative to iron hydroxide was varied. In the initial stage, the reaction was carried out in a 1,000 ppm HAuCl4 aqueous solution (base). The base (1,000 ppm) was used as the reference, and the amount was varied to 1 / 2 times (500 ppm), 3 times (3,000 ppm), and 5 times (5,000 ppm).

[0098] [5] Industrial applicability of particles having a hollow structure The metal hydroxide particles of the present invention, having a hollow structure and pores (mesopores) in their walls, become a catalyst that effectively oxidizes carbon monoxide when a noble metal catalyst is supported on them. In particular, the iron oxide particles having a hollow structure on which Au nanoparticles are supported have good CO oxidation catalytic activity.

Claims

1. A method for producing particles having a hollow structure, comprising: (1) a perovskite-type fluoride: KMF in a solution containing alkali and alcohol. ３ (a) A method for producing metal hydroxide particles having a hollow structure, comprising the steps of (1) adding (M) a metal element such as Zn, Mg, Co, Ni, Fe, or Mn to form a hydroxide shell of metal M on the surface of the perovskite-type fluoride (core), and (2) adding the perovskite-type fluoride (core) obtained in step (1) with a hydroxide shell of metal M formed on its surface to water, dissolving the perovskite-type fluoride (core) to obtain a hydroxide shell of metal M.

2. Particles having a hollow structure, (a1) The particles consist of a shell of a metal hydroxide of metal M (where M represents a metallic element such as Zn, Mg, Co, Ni, Fe, or Mn), (a2) The particles have an average particle diameter of 50 nm to 10 μm, (a3) ​​The shell thickness of the particles is 5% to 35% of the average particle diameter (a2), (a4) The particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2), and (a5) The particles have pores in the shell with a diameter of 40 nm or less. (a) Particles of a metal hydroxide having a hollow structure.

3. A method for producing catalyst particles, comprising: (1) adding (a) particles of a metal hydroxide having a hollow structure obtained by the production method described in claim 1, or (a) particles of a metal hydroxide having a hollow structure described in claim 2, to a solution containing a noble metal compound, and heating the reaction solution; and (2) separating a solid from the reaction solution obtained in step (1) and calcining the solid, wherein (b) catalyst particles of a metal oxide having a hollow structure supported on a noble metal are produced.

4. The manufacturing method according to claim 3, wherein the (b) precious metal is at least one precious metal selected from the group consisting of gold (Au) compounds, platinum (Pt), and palladium (Pd).

5. The manufacturing method according to claim 3, wherein the firing in step (2) is carried out at 120°C to 500°C.

6. Catalyst particles, wherein the catalyst particles (a) have a hollow structure and (b) a noble metal supported on them, the (a) hollow structure metal oxide particles (a1) consist of a hydroxide shell of metal M (where M represents a metal element such as Zn, Mg, Co, Ni, Fe, or Mn), (a2) the average particle diameter of the particles is 50 nm to 10 μm, (a3) ​​the shell thickness of the particles is 5% to 35% of the average particle diameter (a2), (a4) the particles have hollow macropores with a diameter of 95% to 65% of the average particle diameter (a2), and (a5) the shells have mesopores with a diameter of 40 nm or less.

7. The catalyst particle according to claim 6, wherein the (b) precious metal is at least one precious metal selected from the group consisting of (b1) gold (Au), platinum (Pt), and palladium (Pd).

8. The catalyst particles have a specific surface area of ​​50 m². 2 / g~200m 2 The catalyst particles according to claim 6, which are present in a quantity of / g.

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