JPH11349324A - Production of rare earth metal oxide and rare earth metal-containing compound oxide hollow particle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide rare earth metal oxide and rare earth metal-containing compound oxide hollow particles having excellent fluidity, dispersibility, weather resistance and heat resistance. SOLUTION: This method for producing rare earth metal oxide and rare earth metal-containing compound oxide hollow particles comprises suspending a rare earth metal hydroxide, oxide, compound hydroxide and compound oxide sol or slurry or their mixture in an organic solvent to prepare a W/O type emulsion in which the fine water drops containing the sol or slurry therein are homogeneously dispersed in the organic solvent, adding the W/O type emulsion to a >=2C alcohol, washing and filtering the obtained precipitates and subsequently drying and calcining the obtained particles. The obtained rare earth metal and rare earth metal-containing compound oxide particles are spherical, have an average particle diameter in the range of 0.001-500 μm, have a hollow structure, and have excellent fluidity, dispersibility, weather resistance and heat resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to rare earth oxide and composite oxide particles having a hollow interior and excellent dispersibility, fluidity, weather resistance and heat resistance, and a method for producing the same.

[0002]

2. Description of the Related Art Rare earth oxides include phosphor materials for color televisions, functional ceramic materials, catalysts, cocatalysts and catalyst carriers, pigments, abrasives, optical materials, ultraviolet shielding agents, and the like.
It is widely used as a sensor material, electronic material, etc., but in recent years, in these fields, where high precision has been accelerating, it is necessary to not only make the particle size uniform but also fill and disperse. It is required to be excellent in fluidity, weather resistance, heat resistance, operability and the like.

[0003] Conventional rare earth oxides and rare earth complex oxides have irregular particle diameters and are not homogenized, and require steps such as pulverization and classification for use in the above applications. There are problems such as complication of impurities and mixing of impurities.

[0004] Conventional methods for producing rare earth oxides and rare earth complex oxides include precipitation, coprecipitation, hydrolysis, uniform precipitation, and hydrothermal methods of hydroxide, carbonate or oxalate. These are collected, washed, dried,
There is known a method of forming an oxide by firing or the like. However, the rare earth oxides and composite oxides obtained by this method have problems that the particle size is not uniform, the particle size distribution is not uniform, and the fluidity and dispersibility are poor.

As a means for remedying the above drawbacks, an aqueous solution of a rare earth salt such as a rare earth nitrate is solubilized in reverse micelles, and the solubilized aqueous solution of a precipitant such as ammonia water or urea is similarly dissolved. Monodisperse rare-earth oxide ultrafine particles and composite oxide ultrafine particles having an average particle diameter of 5 nm or less, which are obtained by a reverse micelle solution and a reverse micelle method of reacting at room temperature under normal pressure, and a method for producing the same are known. (Japanese Patent Application Laid-Open No. 9-255331).

[0006] However, this has some difficulty in handling when used as various materials because its particle size is very fine.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a spherical and hollow structure which cannot be achieved by conventional methods such as coprecipitation, hydrolysis, uniform precipitation, hydrothermal method and reverse micelle method. And rare earth oxide and composite oxide particles having excellent fluidity, dispersibility, weather resistance, and heat resistance, and a method for producing the same.

[0008]

In order to achieve the above object, it is effective to promote the generation of particles in a reaction field having a physically spherical shape and a limited size. In the present invention, rare earth hydroxides, oxides, composite hydroxides, composite oxide sols or slurries, or a mixture thereof are dispersed and suspended in an organic solvent, and fine water droplets containing the sol or slurry are dispersed in the organic solvent. A W / O type emulsion, which is an emulsion uniformly dispersed therein, is formed, and added to an alcohol having 2 or more carbon atoms to extract water in the dispersed minute droplets, thereby obtaining a spherical and hollow yttrium oxide, Rare earth oxide particles including cerium oxide and composite oxide particles are manufactured.

According to the present invention, the average particle size is 0.001 μm.
m to 500 μm, having a spherical and hollow structure,
Rare earth oxide and composite oxide particles excellent in fluidity, dispersibility, weather resistance and heat resistance are provided.

According to the present invention, a W / O emulsion is prepared by dispersing and suspending a rare earth hydroxide, oxide, composite hydroxide, composite oxide sol or slurry or a mixture thereof in an organic solvent. A method for producing rare earth oxides and rare earth-containing composite oxide hollow particles, which is prepared, added to an alcohol having 2 or more carbon atoms, and the resulting precipitate is washed, filtered, dried or calcined, is provided. You.

BEST MODE FOR CARRYING OUT THE INVENTION

The rare earth oxide and the rare earth-containing composite oxide particles of the present invention have an average particle diameter of 0.001 μm to 500 μm.
m, having a spherical, hollow structure, and fluidity,
It is excellent in dispersibility, weather resistance and heat resistance.

The particles are not particularly limited as long as they are oxides of scandium, yttrium or a rare earth element having an atomic number of 57 to 71, and composite oxide particles containing at least one of these elements.

According to the present invention, rare earth oxides having a spherical and hollow structure and composite oxide particles can be easily produced without using a high-pressure, high-temperature process.

Further, in the present invention, since a highly pure reagent can be used as a starting material, it is useful as a means for obtaining extremely high purity rare earth oxide fine particles. Also,
By using a sol or a slurry containing two or more types of metal ions as a raw material, the sol or slurry at room temperature under normal pressure can be used.
Spherical and hollow multicomponent composite oxide fine particles can be produced in the same manner as the component oxide. Hereinafter, the present invention will be described in more detail.

By the operation and the manufacturing process shown in FIG. 1, spherical oxide hollow particles of various oxides including rare earth oxides and composite oxides can be manufactured.

The method for producing a rare earth oxide and a rare earth-containing composite oxide hollow particle having a spherical hollow structure and excellent fluidity, dispersibility, and weather resistance according to the present invention comprises: A hydroxide and a composite oxide sol or slurry, or a mixture thereof are suspended in an organic solvent to form a W / O emulsion, which is added to an alcohol having 2 or more carbon atoms, and the resulting precipitate is washed. It is characterized by drying or firing after filtration.

In order to produce the rare earth oxide and the rare earth-containing composite oxide hollow particles of the present invention, it is necessary to produce a rare earth hydroxide, an oxide, a composite hydroxide, and a composite oxide sol or slurry.

The sol or slurry is an aqueous solution containing rare earth ions such as rare earth chlorides, nitrates and sulfates,
Alternatively, a rare-earth-containing hydroxide produced by mixing an aqueous mixed solution of these and other metal salts with an aqueous alkaline solution such as aqueous ammonia, aqueous sodium hydroxide, aqueous potassium hydroxide, and aqueous urea is mixed with water or hydrochloric acid or sulfuric acid. Dispersed in mineral acids such as nitric acid, or the above alkaline solution,
It is obtained by suspending.

The rare earth hydroxides, oxides, composite hydroxides, and composite oxide sols or slurries used as starting materials in the present invention include precipitates, coprecipitates, mixtures, commercially available sols, Commercially available oxides, hydroxides, complex oxides, complex hydroxide reagents, water or mineral acids such as hydrochloric acid, sulfuric acid, nitric acid, or aqueous ammonia, aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous urea Any of sols, slurries, and mixtures thereof obtained by suspending in an aqueous alkaline solution such as those described above may be used, but a sol in which a precipitate or a coprecipitate is dispersed in a mineral acid is preferably used.

The organic solvent used in the present invention may be any one as long as it does not mix with water or an aqueous solution. Preferably, a non-polar organic solvent such as cyclohexane is used.

In the present invention, a stirrer such as a magnetic stirrer or a homogenizer is used to form a W / O emulsion. At this time, an appropriate amount of a surfactant may be added as a dispersion stabilizer. Any surfactant may be added as long as it is oil-soluble, but is preferably a polyhydric alcohol-type nonionic surfactant represented by a Span-based or Tween-based surfactant, or an alkylphenol-ethylene oxide adduct. A polyethylene glycol type nonionic surfactant to be used is used. Specific examples are Span60, Tween
80, nonylphenol ethylene oxide 5 mol adduct and the like.

The alcohol used as the water extractant in the present invention may be any alcohol as long as it has 2 or more carbon atoms, and preferably a middle alcohol having 4 to 6 carbon atoms. Specific examples include butyl alcohol, pentyl alcohol, and hexyl alcohol.

The precipitated particles produced in the present invention are separated by centrifugation or filtration, and the solvent, surfactant, impurity ions and the like are washed and removed with water, hydrocarbon, alcohol, acetone, petroleum ether or the like. Washing methods include centrifugation, filtration,
Decantation may be repeated, or a fine powder cleaning device using a ceramic filter or an ultrafiltration membrane may be used. The washed particles are dried by natural drying at room temperature or by heating and drying using an oven or the like. At this time, a vacuum dryer or a spray dryer may be used.

Next, in the production method of the present invention, the rare earth-containing hydroxide or the rare earth-containing hydrated oxide obtained by the drying is calcined at a specific temperature to have a spherical and hollow structure and a fluidity. , A rare-earth oxide and a rare-earth-containing composite oxide hollow particle having excellent dispersibility and weather resistance can be obtained. The firing is performed at a firing temperature of 150 to 10
It is carried out at 00C, preferably at 500-600C. The heating rate is 500 ° C./hour or less, preferably 100 ° C./hour, and the firing time is 30 minutes to 12 hours, preferably 1 to 12 hours.
Desirably, it is 3 hours.

[0025]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto.

Example 1 200 ml of a 1 mol / l cerium nitrate aqueous solution and 200 ml of a 3 mol / l aqueous ammonia were prepared. Both were simultaneously charged into a 1-liter container and mixed with stirring. The pH of this solution was about 10. After stirring for 2 hours, decantation and water washing were repeated, and a cerium hydroxide sol was obtained using nitric acid adjusted to pH = 2 as a dispersion medium.

Next, the obtained cerium hydroxide sol 20
0 ml was added to 1 liter of a cyclohexane solution containing 4 g / l of Span80, and 2 ml was added using an emulsifier.
Emulsify for 1 minute to prepare a W / O emulsion. This emulsion was poured into 3 liters of stirring n-butyl alcohol, and after stirring was continued for 10 minutes, the formed precipitate was separated by centrifugation and suction filtration, washed with water, washed with methanol, and dried. A pale yellow cerium hydroxide powder having good properties is obtained. This at 500 ° C
The powder obtained by air calcination for a time is a spherical cerium oxide powder, and from SEM observation and cross-sectional SEM observation,
Its average particle size was 20 μm, and it had a hollow structure.

Example 2 A treatment was carried out in the same manner as in Example 1 except that hydrochloric acid adjusted to pH = 2 was used as a dispersion medium for the cerium hydroxide sol. The result was almost the same as the result of Example 1.

Example 3 A treatment was performed in the same manner as in Example 1 except that the concentration of the cerium nitrate aqueous solution was changed to 0.5 mol / L. As a result, spherical cerium oxide hollow particles having an average particle diameter of 1 μm were obtained.

Example 4 A treatment was carried out in the same manner as in Example 1 except that the aqueous cerium nitrate solution was changed to an aqueous yttrium nitrate solution. As a result, spherical yttrium oxide hollow particles having an average particle diameter of 20 μm were obtained.

Example 5 A treatment was carried out in the same manner as in Example 1 except that the cerium nitrate aqueous solution was changed to a mixed aqueous solution of cerium nitrate and zirconyl nitrate, and nitric acid adjusted to pH = 2 was used as a dispersion medium for the sol. As a result, spherical cerium oxide-zirconium oxide composite oxide hollow particles having an average particle diameter of 15 μm were obtained.

Comparative Example 1 200 ml of a 1 mol / l cerium nitrate aqueous solution and 200 ml of a 3 mol / l aqueous ammonia were prepared. Both were simultaneously charged into a 1-liter container and mixed with stirring. The pH of this solution was about 10. After stirring for 2 hours, decantation and water washing were repeated to remove nitrate ions and ammonium ions, followed by centrifugation and suction filtration to obtain cerium hydroxide. This is dried at 80 ° C. in air,
The powder obtained by air calcination for hours did not have a hollow structure, but was strongly aggregated cerium oxide particles having an irregular particle size.

Comparative Example 2 200 ml of a 1 mol / l yttrium nitrate aqueous solution and 200 ml of a 3 mol / l aqueous ammonia solution were prepared. Both were simultaneously charged into a 1-liter container and mixed with stirring. The pH of this solution is about 10
Met. After stirring for 2 hours, decantation and water washing were repeated to remove nitrate ions and ammonium ions, followed by centrifugation and suction filtration to obtain cerium hydroxide. This was subjected to hydrothermal treatment at 200 ° C. for 5 hours, then dried at 80 ° C. in air, and calcined in air at 500 ° C. for 2 hours. The yttrium oxide particles had irregular diameters.

[0034]

The rare-earth oxide and rare-earth-containing composite oxide particles of the present invention have a spherical hollow structure and are excellent in fluidity, dispersibility, and weather resistance. It is useful as a material for conductive ceramics, a catalyst, a co-catalyst and a catalyst carrier, a pigment, an abrasive, an optical material, an ultraviolet shielding agent, a sensor material, and an electronic material.

[Brief description of the drawings]

FIG. 1 is a production process diagram of spherical hollow particles of a rare earth oxide and a rare earth-containing composite oxide in the present invention.

FIG. 2 is a cross-sectional SEM photograph of the cerium oxide hollow particles produced in Example 1.

FIG. 3 is a cross-sectional SEM photograph of the cerium oxide-zirconium oxide composite oxide hollow particles produced in Example 5.

Claims (2)

[Claims] 1. A rare earth oxide or composite oxide particle having a spherical hollow structure having an average particle diameter in a range of 0.001 μm to 500 μm. 2. Rare earth hydroxides, oxides, composite hydroxides,
And a composite oxide sol or slurry or a mixture thereof is dispersed and suspended in an organic solvent to prepare a W / O emulsion which is an emulsion in which fine water droplets containing the sol or slurry are uniformly dispersed in the organic solvent. A method for producing rare earth oxides and rare earth-containing composite oxide hollow particles, comprising washing the precipitate obtained by adding it to an alcohol having 2 or more carbon atoms, filtering the precipitate, and then drying or calcining the precipitate.