JPH07237923A - Hollow particle containing ferrite - Google Patents

Abstract

PURPOSE:To obtain a ferrite-containing hollow particle having large specific surface area, reaction activity and catalytic activity and high durability of the activity. CONSTITUTION:This ferrite-containing hollow particle is composed of a shell containing ferrite expressed by MxNyFe3-x-yO4-z (M and N are same or different from each other and each is at least one kind of metal atom selected from manganese, cobalt, nickel, copper, zinc, vanadium, strontium, lithium, molybdenum, titanium, magnesium, aluminum, silane, chromium, tin and cadmium; 0<=x<3; 0<=y<3; 0<=x+y<3; 0<=z<4).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to hollow particles containing ferrite.

[0002]

2. Description of the Related Art In recent years, it has been said that the main cause of global warming is that carbon dioxide has been released into the atmosphere so that it exceeds the resilience of nature. As such, various technologies for decomposing and removing carbon dioxide and immobilizing carbon dioxide have been studied. So far, carbon dioxide immobilization techniques include, for example, chemical absorption methods, physical absorption methods, adsorption methods, membrane separation methods, and carbon dioxide decomposition and removal techniques include semiconductor photocatalysts, metal colloid catalysts, metal complexes. ,
A photochemical reduction method using oxygen or the like, an electrochemical reduction method, a chemical fixed conversion reaction method (for example, a reaction with a base, a transfer reaction, a dehydration reaction, an addition reaction, etc.), a biotechnology method, and the like are being studied. However, any of the above methods has problems such as reaction efficiency, cost, energy, secondary pollution generation, etc., and thus is difficult to put into practical use, and when the above methods are carried out, the products produced by the reaction are effective. The method to use is not found. On the other hand, it was reported that by heating carbon dioxide in the presence of magnetite having an oxygen deficiency structure (hereinafter referred to as “oxygen deficiency magnetite”), carbon dioxide can be decomposed into almost 100% carbon. (Y. Tamura et al., Nature, 34.
6, 255-256, (1990)). In the method of decomposing carbon dioxide by this oxygen-defective magnetite, 30
Since the reaction proceeds near the exhaust gas temperature of 0 to 400 ° C,
Since energy from the outside of the system is not required and the decomposed carbon dioxide can be recovered as carbon, there are advantages that various organic substances can be obtained using the recovered carbon as a starting material. However, the oxygen-defective magnetite has a drawback that its activity is immediately lowered. On the other hand, it was found that methane is produced by reacting carbon dioxide with hydrogen in the presence of ferrite having an oxygen deficiency structure (hereinafter referred to as "oxygen deficiency ferrite") (Tamaura et al., J. Mater. Sci., 28,
1220, (1993)). However, since only oxygen-defective ferrite having a small specific surface area was obtained, the reaction efficiency and catalyst efficiency were poor, and the yield of methane produced was at most 40%. Here, hydrogen used in the reaction for producing methane using the oxygen-deficient ferrite is produced by a method of heating petroleum at a high temperature (800 to 900 ° C.) to decompose it and a method of electrolyzing water, Both methods have problems such as exhausting carbon dioxide and requiring a large amount of electric energy. On the other hand, in the carbonaceous resource circulation system disclosed in Japanese Patent Laid-Open No. 5-184912, prior to the generation treatment of the carbonaceous resource gas,
It was found that hydrogen is produced by reacting carbon-attached iron oxide with water, but the hydrogen production reaction is inefficient because it occurs only at the portion of the iron oxide surface where carbon is attached. there were. Further, the carbon-adhered iron oxide used in the hydrogen generation reaction has a low activity of the carbon-adhesion reaction due to carbon dioxide decomposition during the production thereof, and thus has a low carbon adhesion rate to the iron oxide, and the obtained carbon. Since the specific surface area of the attached iron oxide is small, improvement has been desired for practical use.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide ferrite-containing hollow particles having a large specific surface area, a large reaction activity and a large catalytic activity, and good activity sustainability.

[0004]

Means for Solving the Problems The above-mentioned object is defined by the following formula M _x N _y Fe _3-xy O _4-z (wherein M and N are the same or different,
Manganese, cobalt, nickel, copper, zinc, vanadium, strontium, lithium, molybdenum, titanium,
Represents at least one metal atom selected from the group consisting of magnesium, aluminum, silane, chromium, tin, and cadmium, and x and y are 0 ≦ x <3, 0 ≦ y <
3 and 0 ≦ x + y <3, and z satisfies 0 ≦ z <4), and the ferrite-containing hollow particles are characterized by comprising a ferrite-containing shell.

The ferrite-containing hollow particles obtained by the present invention have either an oxygen deficiency structure, carbon attached thereto, or a carbon atom incorporated into the crystal structure of ferrite, or these Including the case where are combined. The present invention will be described in detail below. This will clarify the purpose, structure and effect of the present invention. Ferrite-Containing Hollow Particles As a method for producing the ferrite-containing hollow particles of the present invention, for example, a coating layer containing ferrite is formed on particles made of an organic polymer (hereinafter referred to as “polymer particles”), and then heat treatment is performed. A method of decomposing the polymer particles to hollow the inside of the particles by applying, a coating layer made of iron oxide is formed on the polymer particles, and then a metal (hereinafter referred to as "ferrite constituent metal") is used as a constituent component of ferrite. ) And / or a metal compound thereof (for example, a metal oxide, a metal hydroxide, etc.) or after coating iron oxide and a ferrite constituent metal and / or a metal compound thereof on the polymer particles,
Examples of the method include a method of decomposing polymer particles by heat treatment to hollow the inside of the particles, a method of coating the iron oxide hollow particles with a ferrite-constituting metal and / or a metal compound thereof, and then performing heat treatment.

First, the above method will be described. Examples of the material of the polymer particles used in the method of (1) include (co) polymers of olefins such as ethylene and propylene; (co) polymers of aromatic vinyl compounds such as styrene and divinylbenzene; vinyl esters such as vinyl acetate. (Co) polymer; (co) polymer of vinyl cyanide compound such as acrylonitrile; (co) polymer of (meth) acrylic ester such as methyl methacrylate; vinyl halide compound such as vinyl chloride and tetrafluoroethylene (Co) polymer; polyacetal; polycarbonate; polyester; alkyd resin; unsaturated polyester; polyarylate; polysulfide; polysulfone;
Polyamide (eg nylon-6, nylon-12
Etc.); polyimide; polysiloxane; epoxy resin; phenol resin; urea resin; melamine resin; benzoguanamine resin; cellulose; ionomer and the like. These polymer particles can also have a crosslinked structure. In addition, these polymer particles are
The particles may be granulated and classified after kneading and mixing one or more materials, or may be a mixture of two or more particles made of different materials.

The method for preparing the polymer particles is not particularly limited, but for example, rolling granulation, fluidized bed granulation, stirring granulation, crushing / crushing granulation, compression granulation, extrusion granulation,
Physical granulation methods such as melt granulation, mixed granulation, spray cooling granulation, spray drying granulation, precipitation / precipitation granulation, freeze drying granulation, suspension coagulation granulation, and drop cooling granulation; emulsion polymerization, A chemical granulation method such as suspension polymerization or precipitation polymerization may be appropriately selected according to the material of the polymer particles, granulated, and classified as necessary. Further, when the polymer particles are available as a commercial product, they can also be used.

The average particle size of the polymer particles used in is generally 0.01 to 150 μm.

In the method (1), various methods such as a hetero-aggregation method, a spray drying method, a mechanical method, a vacuum method and a plating method can be adopted as a method for forming a coating layer containing ferrite on the polymer particles. Of these, a mechanical method, a vacuum method and a plating method are preferable.

The mechanical method is as follows. The ferrite fine particles and the polymer particles are put into a mixer or a crusher having a high-speed rotating blade or a high-speed rotating arm such as a Henschel mixer, a hybridizer, and an Ong mill, and then 200 to 20,000 r.
pm, preferably at a rotation speed of 1,000 to 18,000 rpm for 1 to 120 minutes, preferably for 3 to 30 minutes, usually at room temperature, on the polymer particles by high-speed stirring with heating or cooling as necessary. This is a method of coating a layer containing ferrite.

The vacuum method is a method of performing vacuum vapor deposition, sputtering or ion plating for 1 to 30 minutes while oscillating the core fine particles to be treated at a vacuum degree of 10 ^{-5 to 2} Pa using ferrite as a vapor deposition source or target. is there.

In the plating method, the polymer particles are uniformly dispersed in an aqueous solution containing a hydrolyzable ferrous salt and a salt of a ferrite-constituting metal and then heated at room temperature or at a temperature of 40 ° C. or higher, if necessary. P such as ammonium acetate
It is a method of coating a layer containing ferrite on polymer particles by causing an oxidation reaction using an oxidizing agent such as sodium nitrite while controlling the pH to 7 to 12 in the presence of an H buffer solution.

Particles obtained by forming a coating layer containing ferrite on polymer particles by using the above method (hereinafter referred to as "ferrite-containing particles I") are treated with air, an inert gas (for example, N ₂ , Ar, Kr, He, Ne, etc.) and a reducing gas (eg, H ₂ , CO, SO ₂ , NH ₃ etc.) in an atmosphere of at least one gas selected from the group consisting of 35
By heating at 0 ° C. or higher, more preferably 500 ° C. or higher, and at a decomposition temperature of ferrite or lower, the polymer particles are decomposed, gasified and scattered from the inside of the particles,
It is possible to obtain ferrite-containing hollow particles having pores inside the particles. In the above, the polymer particles are preferably thermoplastic in order to completely decompose the polymer particles and facilitate gasification. When heating the ferrite-containing particles I, the temperature rising rate is 0 to 50 ° C./minute, and the cooling rate is -50 to 0 ° C./minute in order to prevent a decrease in the specific surface area due to the occurrence of cracks. It is preferable.

The following method will be described. As a method for producing particles in which a layer made of iron oxide is coated on polymer particles used in the method (hereinafter, referred to as “composite particles”), a method for forming a coating layer containing ferrite on the polymer particles is exemplified. The various methods and hydrolysis methods mentioned above can be mentioned.

In the hydrolysis method, polymer particles are uniformly dispersed in an aqueous solution of a hydrolyzable iron salt, and then urea, carbonic acid or the like is supplied as needed while heating at room temperature or at a temperature of 40 ° C. or higher. In the presence of a carbonate ion as a source, a hydrolysis reaction is caused to occur, and if necessary, alkali treatment is performed at room temperature, or by heating in air to 200 to 300 ° C., iron oxide is formed on the polymer particles. This is a method of forming a coating layer. Here, as the polymer particles, those similar to the polymer particles listed in the above method can be used, and the iron oxide is α-Fe ₂ O ₃ (hematite), γ-FeOOH, Fe ₃ O ₄ , γ. -Fe ₂ O ₃ (maghemite) can be used arbitrarily selected from. The amount of the hydrolyzable iron salt used per 1 liter of the hydrolysis reaction liquid is preferably 0.01 to 10,000 mmol, more preferably 0.1 to 1,000 mmol. Subsequently, the composite particles are coated with a ferrite constituent metal and / or a metal compound thereof. The method is carried out by replacing the polymer particles with composite particles in the method of forming a coating layer made of iron oxide on the polymer particles, and by replacing iron oxide with a ferrite constituent metal and / or a metal compound thereof. You can

Further, the method of coating the polymer particles with iron oxide and a ferrite-constituting metal and / or a metal compound thereof is carried out by converting the hydrolyzable iron salt into a hydrolyzable iron salt and a hydrolyzable ferrite in the above-mentioned hydrolysis method. It can be carried out by replacing with a hydrolyzable metal salt and / or a hydrolyzable metal alkoxide of the constituent metals.

Composite particles having a coating layer composed of iron oxide and a ferrite-constituting metal and / or a metal compound thereof on the polymer particles obtained as described above (hereinafter referred to as
This is called "ferrite-containing particle II". By subjecting (1) to a heat treatment, it is possible to decompose the polymer particles in the ferrite-containing II particles, to provide pores inside the particles, and to convert the coating layer into ferrite. Specifically, the polymer particles are first heated at a temperature of 350 ° C. or higher, preferably 500 ° C. or higher and a decomposition temperature of ferrite or lower in an atmosphere of at least one gas selected from the group consisting of air, oxygen and an inert gas. Is decomposed, gasified and scattered from inside the particles, and the metal atoms of the ferrite constituent metal are incorporated into the crystal lattice of iron oxide. Then, if necessary, the ferrite-containing hollow particles can be obtained by heating in a reducing gas atmosphere at 250 ° C. or higher, preferably 270 ° C. or higher and at a decomposition temperature of ferrite or lower. When the ferrite-containing hollow particles II are heated, the temperature rising rate is 0 to 50 ° C./min and the cooling rate is −50 to 0 in order to prevent a decrease in the specific surface area due to the generation of cracks.
It is preferably in the range of ° C / min.

Next, the method will be described. The iron oxide hollow particles used in the method of (1) are obtained by mixing the composite particles used in (1) with at least one gas selected from the group consisting of air, oxygen and an inert gas, or in a reducing gas atmosphere at 350 ° C. or higher, preferably 500. It is obtained by heating at a temperature equal to or higher than ° C and lower than the decomposition temperature of iron oxide. Subsequently, the iron oxide hollow particles are coated with a ferrite constituent metal and / or a metal compound thereof. As the method, in the method of forming the coating layer made of the ferrite-constituting metal and / or its metal oxide on the composite particles, hollow iron particles can be used instead of the composite particles. Then, the ferrite-containing hollow particles are obtained by further subsequently heating in an inert gas and / or reducing gas atmosphere at 350 ° C. or higher, preferably 500 ° C. or higher and below the decomposition temperature of ferrite.

The average particle diameter of the ferrite-containing hollow particles obtained by the above-mentioned methods is 0.01 to 150 μm,
It is preferably 0.1 to 50 μm, and the ratio of the internal pore diameter to the particle outer diameter is 0.3 to 0.99, preferably 0.6.
Is about 0.99. The specific surface area of the particles of at least 50 m ² / g or more, preferably becomes 100 m ² / g or more, the ferrite particles specific surface area compared to a 0.1 to 10 m ² / g is greatly increased.

Hollow containing ferrite having oxygen deficiency structure
Particles In the present invention, when z in the above formula is in the range of 0 <z <4, the ferrite-containing hollow particles have an oxygen defect structure, and particularly stable when 0.1 ≦ z ≦ 1.5. And has an oxygen defect structure. The oxygen-deficient ferrite-containing hollow particles can be suitably used for applications in environmental technology, such as heavy metal treatment, carbon dioxide decomposition, and carbon dioxide methanation.
The oxygen-deficient ferrite-containing hollow particles are obtained by subjecting the ferrite-containing hollow particles obtained as described above to hydrogen, an inert gas, or a mixed gas atmosphere thereof, usually at 250 ° C.
Or higher, preferably 270 ° C. or higher, more preferably 29
It is obtained by performing a heat treatment at 0 ° C. or higher and partially reducing it. The average particle size of the oxygen-deficient ferrite-containing hollow particles obtained by the above method is 0.01 to 15
It is 0 μm, preferably 0.1 to 50 μm, and the ratio of the internal pore diameter to the particle outer diameter is 0.3 to 0.99, preferably 0.6 to 0.99. The specific surface area of the particles is at least 50 m ² / g or more, preferably 100
m ² / g or more.

Carbon attached and / or carbon atoms crystallized
Ferrite-containing hollow particles incorporated in the lattice Carbon attached and / or carbon atoms incorporated in the crystal lattice (hereinafter "carbon attachment and / or incorporation")
Say. ) A ferrite-containing hollow particle is a group consisting of the ferrite-containing particle I and / or the ferrite-containing particle II before the hollowing treatment obtained by the method for producing the ferrite-containing hollow particle and / or the air, an inert gas and a reducing gas. In an atmosphere of at least one gas selected from the above, heating is performed at a temperature above the thermal decomposition starting temperature of the polymer particles and below 100% thermal decomposition temperature of the polymer particles, and at least a part of the surface of the ferrite-containing hollow particles, the inside of the shell and the inner wall It can be produced by attaching carbon or incorporating carbon atoms into the crystal lattice of ferrite. Here, when the polymer particles are polydivinylbenzene, the heating temperature is usually 350 to 600 ° C, and when the polymer particles are polystyrene, the heating temperature is 300 to 450 ° C. Further, the carbon-attached and / or embedded ferrite-containing hollow particles can be obtained by carrying out a carbon dioxide immobilization reaction as described later using the ferrite-containing hollow particles.
The average particle size of the carbon-attached and / or embedded ferrite-containing hollow particles obtained by the above method is 0.0
1 to 150 μm, preferably 0.1 to 50 μm,
The ratio of the inner pore diameter to the particle outer diameter is 0.3 to 0.9.
9, preferably 0.6 to 0.99. The specific surface area of the particles is at least 50 m ² / g or more, preferably 100 m ² / g or more.

Carbon deposition and / or built-in oxygen defects
Ferrite-Containing Hollow Particles Carbon-adhered and / or embedded oxygen-defective ferrite-containing hollow particles are obtained by subjecting the above-mentioned carbon-adhered and / or incorporated ferrite-containing hollow particles to hydrogen, an inert gas or a mixed gas atmosphere thereof, usually at 250 ° C. or higher, It can be produced by heat treatment at 270 ° C. or higher, preferably 290 ° C. or higher, and partial reduction. Further, the carbon-immobilized and / or embedded oxygen-defective ferrite-containing hollow particles can also be obtained by carrying out an immobilization reaction of carbon dioxide using the oxygen-defective ferrite-containing hollow particles as described later. The average particle diameter of the carbon-deposited and / or embedded oxygen-defective ferrite-containing hollow particles obtained by the above method is 0.01
˜150 μm, preferably 0.1 to 50 μm, and the ratio of the inner pore diameter to the particle outer diameter is 0.3 to 0.99,
It is preferably 0.6 to 0.99. The specific surface area of the particles is at least 50 m ² / g or more, preferably 1
It is more than 00 m ² / g.

Use of Ferrite-Containing Hollow Particles The ferrite-containing hollow particles obtained by the present invention are used, for example, as a carbon dioxide-immobilized catalyst by washcoating a honeycomb carrier having an integral structure, drying, and optionally firing. be able to.

The honeycomb carrier having the integral structure may be one generally called a ceramic honeycomb carrier, and particularly cordierite, mullite, α-alumina,
A honeycomb carrier made of zirconia, titanium oxide, titanium phosphate, aluminum titanate, petalite, spodumene, alumino silicate, magnesium silicate or the like is preferable, and cordierite is particularly preferable for an internal combustion engine. Others, stainless steel, Fe-
An integrated structure using an oxidation resistant heat resistant metal such as a Cr-Al alloy can also be used. These honeycomb carriers can be manufactured by an extrusion molding method, a method of winding and solidifying a sheet-shaped element, or the like. The shape (cell shape) of the gas vent may be any of a hexagon, a square, a triangle, and a corrugation shape. Cell density (number of cells / unit cross-sectional area) is 1
50 to 600 cells / (inch) ² is sufficiently usable and gives good results.

The carbon dioxide-immobilized catalyst composed of the ferrite-containing hollow particles thus obtained is provided, for example, in a portion between an automobile engine and a muffler, in a portion between a combustion chamber of a thermal power plant and an exhaust duct, and It can be installed at a site between the heating furnace and the exhaust duct of a steel plant to contribute to the reduction of carbon dioxide emissions.

Here, the above-mentioned catalyst is installed at 150 ° C. or higher, more preferably 2 from the viewpoint of carbon dioxide immobilization efficiency.
It is a portion at 50 ° C. or higher, particularly preferably 300 ° C. or higher. In the carbon dioxide immobilization reaction using the above ferrite-containing hollow particles, it is preferable that the ferrite of the shell have an oxygen defect structure.

After the completion of the carbon dioxide immobilization reaction, the ferrite-containing hollow particles used as a catalyst and /
Alternatively, the oxygen-deficient ferrite-containing hollow particles are carbon-deposited and / or embedded ferrite-containing hollow particles and / or
Alternatively, it is converted into hollow particles containing carbon-deposited and / or incorporated oxygen-defective ferrite.

The ferrite-containing hollow particles of the present invention can also be used as a carbon dioxide methanation catalyst. Methanation of carbon dioxide can be carried out by heating the ferrite-containing hollow particles together with 4 mol of hydrogen to 1 mol of carbon dioxide at 250 to 400 ° C. In the above reaction using the ferrite-containing hollow particles, it is preferable that the ferrite of the shell have an oxygen deficiency structure. When carbon dioxide is methanated using the ferrite-containing hollow particles of the present invention, the yield of methane produced is 40 to 100% of the carbon dioxide used,
In particular, when a material having a specific surface area of 150 m ² / g or more is used, the yield is 80 to 100%.

On the other hand, when carbon-attached and / or embedded ferrite-containing hollow particles are reacted with air at 250 ° C. or higher, carbon monoxide is generated. Methanol can be produced by subsequently reacting the generated carbon monoxide with hydrogen, but the hydrogen required here is that the carbon-attached and / or embedded ferrite-containing hollow particles are reacted with water vapor at 250 ° C. or higher. Is obtained by In the above reaction using the carbon-attached and / or embedded ferrite-containing hollow particles, it is preferable that the ferrite of the shell have an oxygen defect structure.

[0030]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples unless the gist thereof is changed. Example 1 25 g of polystyrene particles having an average particle diameter of 2.0 μm, 200 ml of a 3% by weight polyvinylpyrrolidone aqueous solution, 30 ml of 1N hydrochloric acid and 620 ml of distilled water were mixed, sonicated for 2 minutes, and then heated to 95 ° C. Then, a solution prepared by dissolving 0.27 g of ferric chloride hexahydrate and 6.00 g of urea in 20 ml of distilled water was added at once, and 1 hour and 20 minutes later, 20.00 g of urea was dissolved in 30 ml of distilled water. Solution and 25.00 g of ferric chloride hexahydrate in distilled water 1
The solution dissolved in 00 ml was added over 3 hours and 30 minutes while controlling the pH of the reaction system to 2. Then, after heating for 1 hour, the reaction solution was added to 4 liters of ice-cold water to stop the reaction, and the mixture was filtered. After washing the obtained particles with distilled water, 60 ° C
And dried under reduced pressure for 12 hours. When the particles were observed with a scanning electron microscope, they were red-brown, spherical composite particles having an average particle diameter of 2.4 μm, a ratio of the inner diameter to the outer diameter of the particle of 0.83, and a uniform coating layer. When the composite particles were analyzed by X-ray diffraction and thermogravimetric analysis, the core was polystyrene and the shell was α-Fe ₂ O ₃ (hematite).
Met. This composite particle is referred to as particle A. Then particle A
After putting 30 g in 950 ml of distilled water and sonicating for 2 minutes, 5 g of nickel chloride dissolved in 50 ml of distilled water was added, and the pH was adjusted to 11 with an aqueous sodium hydroxide solution.
After stirring for another hour at room temperature, it was filtered. The obtained particles were washed with water and dried under reduced pressure at 60 ° C. for 12 hours. This particle is referred to as particle B. Subsequently, 30 g of the particles B were collected in a combustion boat, heated to 800 ° C. at a temperature rising rate of 10 ° C./minute in an air atmosphere using a tubular electric furnace, and held for 3 hours. After cooling to room temperature, the system was replaced with nitrogen gas and then with hydrogen gas, and then heated at 300 ° C. at a heating rate of 10 ° C./min.
Heated to and held for 2 hours. After cooling to room temperature, the obtained particles were observed with a scanning electron microscope to find that the average particle diameter was 2.0 μm and the ratio of the inner diameter to the outer diameter was 0.8.
The black hollow particles of No. 5 were. In addition, this hollow particle is
When analyzed by line diffraction, it was a spinel-type nickel ferrite and had a lattice constant value of 0.8375 nm. The chemical composition of the hollow particles was examined by colorimetric analysis and ICP emission analysis, and the results were as shown below. ^{Ni; 0.39 Fe 2+; 1.08 Fe} 3+; 1.53 O; 4.00 The specific surface area of the hollow particles was 170m ² / g. This hollow particle is referred to as particle C.

Example 2 10 g of particles C were sampled in a combustion boat and heated in a tubular electric furnace in a hydrogen gas atmosphere at a temperature rising rate of 10 ° C./min to 300.
It was heated to 0 ° C., held for 30 minutes, and then cooled to room temperature. When the obtained particles were analyzed by X-ray diffraction, the value of the lattice constant was 0.8379 nm and it had an oxygen defect structure. Further, the chemical composition was examined by colorimetric analysis and IPC emission analysis, and the results were as shown below. ^{Ni; 0.39 Fe 2+; 1.10 Fe} 3+; 1.51 O; 3.76 The specific surface area of the oxygen defects ferrite-containing hollow particles was 155m ² / g. This particle is referred to as particle D.

Example 3 30 g of the particles B were sampled in a combustion boat, heated to 400 ° C. at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere using a tubular electric furnace, and held for 3 hours. After that, the system was cooled to room temperature, the system was replaced with hydrogen gas, and the system was heated to 300 ° C. at a temperature rising rate of 10 ° C./min in a hydrogen atmosphere and kept for 2 hours. After cooling to room temperature, the obtained particles were observed with a scanning electron microscope to find that they were black hollow particles having an average particle diameter of 2.0 μm and a ratio of the inner diameter to the outer diameter of 0.85. Further, when the hollow particles were analyzed by X-ray diffraction, they were found to be spinel type nickel ferrite, and the value of the lattice constant was 0.8375 nm.
Met. Further, the chemical composition of the hollow particles was examined by colorimetric analysis and ICP emission analysis, and the results were as shown below. ^{Ni; 0.39 Fe 2+; 1.05 Fe} 3+; 1.57 O; 4.00 C; 0.14 The specific surface area of the hollow particles was 150m ² / g. This hollow particle is referred to as particle E.

Example 4 10 g of the particles E were sampled in a combustion boat and heated to 300 ° C. at a temperature rising rate of 10 ° C./min in a hydrogen gas atmosphere using a tubular electric furnace, and this was kept for 30 minutes and then to room temperature. Cooled. When the obtained particles were analyzed by X-ray diffraction, the value of the lattice constant was 0.8379 nm, and the particles had an oxygen defect structure. Further, the chemical composition was examined by colorimetric analysis and IPC emission analysis, and the results were as shown below. ^{Ni; 0.39 Fe 2+; 1.10 Fe} 3+; 1.51 O; 3.76 C; 0.14 The specific surface area of the carbon deposition and / or incorporation of oxygen defects ferrite hollow particles, 140 m ² / G. This particle is referred to as particle F.

Application Example 1 and Comparative Application Examples 1-2 Particles D1 collected in a combustion boat in a quartz tube of a tubular electric furnace.
g was set, heated to 300 ° C., and carbon dioxide was circulated at a flow rate of 20 ml / min to cause a carbon dioxide decomposition reaction. The amount and type of gas coming out of the quartz tube were measured by gas chromatography with a thermal conductivity type detector, and the decomposition rate of carbon dioxide was calculated. In addition, commercially available ferrite particles (average particle size = 0.3 μm, specific surface area =
15 m ² / g; Comparative application example 1) and oxygen-defective ferrite particles (specific surface area = 15 m ² / g; comparative application example 2) obtained by treating the commercially available ferrite particles in the same manner as in Example 2 A carbon dioxide decomposition reaction was performed to calculate the carbon dioxide decomposition rate. The results are shown together in Table 1.

[0035]

[Table 1]

Application Example 2 and Comparative Application Examples 3 to 4 Particles D1 collected in a combustion boat in a quartz tube of a tubular electric furnace.
g was set, and while being heated to 300 ° C., a mixed gas of carbon dioxide / hydrogen = 1: 4 (molar ratio) was passed at a flow rate of 40 ml / min to cause a methanation reaction of carbon dioxide. The amount and type of gas coming out of the quartz tube was measured by gas chromatography with a thermal conductivity detector, and the methanation rate of carbon dioxide was calculated. Further, commercially available ferrite particles (average particle size = 0.3 μm, specific surface area = 15 m ² / g; Comparative Application Example 3) and the above-mentioned commercially available ferrite particles were treated in the same manner as in Example 2 to obtain oxygen-deficient ferrite. The carbon dioxide methanation reaction was performed using the particles (specific surface area = 15 m ² / g; Comparative Application Example 4), and the carbon dioxide methanation rate was calculated. The results are shown together in Table 2.

[0037]

[Table 2]

Application Example 3 and Comparative Application Examples 5 to 6 Particles F1 collected in a combustion boat in a quartz tube of a tubular electric furnace.
g was set, and 10 ml of water was injected into the nitrogen stream to bring them into contact with each other while heating to 300 ° C. The amount and type of gas coming out of the quartz tube were measured by gas chromatography with a thermal conductivity type detector, and the hydrogen yield was calculated. In addition, commercially available ferrite particles (average particle size = 0.3 μm, specific surface area 1
5 m ² / g; Comparative Application Example 5) and oxygen-defective ferrite particles (specific surface area = 15 m ² / g; Comparative Application Example 6) obtained by treating the commercially available ferrite particles in the same manner as in Example 4 The decomposition reaction of water was performed and the yield of hydrogen was calculated. The results are shown together in Table 3.

[0039]

[Table 3]

[0040]

Industrial Applicability According to the present invention, there are provided ferrite-containing hollow particles having a large specific surface area, a large reaction activity and a large catalytic activity, and a good activity sustainability. The ferrite-containing hollow particles obtained by the present invention are useful as catalysts or magnetic materials for heavy metal treatment, carbon dioxide decomposition, carbon dioxide immobilization, carbon dioxide methanation, and the like.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01J 23/74 ZAB 23/745 23/755 23/78 ZAB A 23/80 ZAB A 23/835 ZAB 23/84 ZAB A 23/86 ZAB A 23/88 ZAB A C07C 29/151 31/04 9155-4H B01J 23/74 321 A 23/82 ZAB A

Claims (1)

[Claims] 1. The following formula M _x N _y Fe _3-xy O _4-z (wherein M and N are the same or different,
Manganese, cobalt, nickel, copper, zinc, vanadium, strontium, lithium, molybdenum, titanium,
Represents at least one metal atom selected from the group consisting of magnesium, aluminum, silane, chromium, tin, and cadmium, and x and y are 0 ≦ x <3, 0 ≦ y <
3 and 0 ≦ x + y <3, and z satisfies 0 ≦ z <4), wherein the ferrite-containing hollow particles are characterized by comprising a ferrite-containing shell.