JPS61201604A - Preparation of spherical superfine particle of metal oxide - Google Patents

Abstract

PURPOSE:To prepare spherical superfine particles of metal oxide suitable for pigment, catalyst, etc., by forming superfine particles of metal oxide by decomposing under heating vaporized or atomized volatile metal compd. and quenching the superfine particles immediately thereafter. CONSTITUTION:A volatile metal compd. such as titanium alkoxide, zirconium halide, etc., is heated in an evaporator 1 to vaporize, causing bubbling by introducing gaseous He into the evaporator 1. Gaseous He contg. the volatile metal compd. generated by this procedure is introduced into a reactor 3 installed with a cooler 2 and heated with a heater 5 at below 600 deg.C to cause thermal decomposition forming superfine metal oxide particles. Aimed spherical superfine particles of the metal oxide is obtd. by cooling immediately the generated metal oxide particles with the cooler 2 to a temp. causing no conglutination.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing ultrafine spherical metal oxide particles, and more specifically, a method for producing spherical metal oxide particles that can be used in a wide range of applications such as white pigments, adsorbents, catalysts, and catalyst supports. The present invention relates to a method for producing ultrafine oxide particles.

[Prior art and problems to be solved by the invention] Various methods are known for producing fine particles of metal oxides such as titanium and zirconium.For example, titanium oxide has excellent weather resistance and strong hiding power. Because of this, it is widely used in the fields of cosmetics, paints, etc. However, methods for producing titanium oxide include the sulfuric acid method, which involves neutralizing an aqueous titanium sulfate solution and then calcining the resulting precipitate. The chlorine method, which decomposes and oxidizes titanium tetrachloride at high temperatures, is known. However, in these conventional methods for producing rutile-type titanium oxide, particle growth occurs during the production process, so the particle size of the obtained titanium oxide is large, exceeding 1 μm.

Also, according to Momogi, Saeki et al., titanium tetrachloride and water were
Anatase-type fine particles of titanium oxide can be produced by mixing in the gas phase at 0 to 800°C, or anatase or anatase-type fine particles containing a slight amount of rutile can be produced by reacting titanium tetrachloride and water in the liquid phase. It has been confirmed that titanium oxide can be manufactured. However, these methods can only obtain irregularly shaped particles, and cannot obtain spherical particles.

The present inventors previously attempted to solve these conventional drawbacks by thermally decomposing titanium alkoxide to make it spherical.
Furthermore, we proposed a method for producing extremely fine-grained titanium oxide. (Patent Application 1983-Although particulate titanium oxide is produced, the produced ultrafine particulate titanium oxides bond with each other.
Because of the coalescence, there is a problem in that unless the concentration is extremely low, ultimately spherical and ultrafine particle titanium oxide cannot be obtained.

The present invention relates to an improvement of this method, and an object of the present invention is to prevent coalescence of particles when decomposing a volatile metal compound into ultrafine metal oxide particles, and to produce spherical ultrafine metal oxide J4 particles. That is.

[Means for solving problems]

That is, the present invention involves vaporizing or atomizing a volatile metal compound, decomposing it under heating to form ultrafine metal oxide particles, and immediately cooling it to a temperature at which the ultrafine metal oxide particles do not coalesce again after decomposition. Characteristic f: A method for producing to-shaped metal oxide superimitation particles is provided.

Various volatile metal compounds can be used as raw materials in the method of the present invention.

For example, volatile titanium compounds such as titanium alkoxide and titanium halide; volatile zirconium compounds such as zirconium alkoxide, zirconium halide, and organic zirconium compounds; scandium 1 yttrium;

Examples include alkoxides of rare earth metals such as lanthanum and cerium, and these can be used alone or in combination. For example, when titanium alkoxide is used as a volatile metal compound, in order to increase the stability of the titanium oxide produced, aluminum chloride, zirconium alkoxide is added in a range not exceeding 50% of the molar concentration of titanium alkoxide. , a volatile metal compound such as a rare earth chloride or a rare earth alkoxide may also be present.

Specifically, the titanium alkoxide is, for example,
Titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide.

Examples include titanium tetrabutoxide and jetoxytitanium oxide.

In addition, titanium halide specifically includes titanium tetrachloride,
Examples include titanium tetrahalides such as titanium tetrabromide. Furthermore, volatile titanium compounds such as trihalogenated monoalkoxytitanium, monohalogenated trialkoxytitanium, and dihalogenated dialkoxytitanium can also be used.

Further, a specific example of the zirconium alkoxide is zirconium tetramethoxide.

Tetraalkoxyzirconiums such as zirconium tetraethoxide, zirconium tetraisopropoxide, zirconyl, and tetrabutoxide can be mentioned.

Further, specific examples of zirconium halides include tetrahalogenated zirconiums such as zirconium tetrachloride and zirconium tetrabromide, and furthermore, trihalogenated monoalkoxyzirconium, monohalogenated trialkoxyzirconium, dihalogenated dialkoxyzirconium, etc. are used. You can also do that. Further, volatile organic zirconium compounds such as zirconium phenoxide can also be used.

In the method of the present invention, the above-mentioned volatile metal compound is first vaporized or atomized. Here, conditions for vaporizing or atomizing the volatile metal compound, that is, evaporating or atomizing the volatile metal compound, vary depending on the type of volatile metal compound, etc., and are difficult to determine unambiguously.

For example, when titanium alkoxide is used as the volatile metal compound, the temperature at which titanium alkoxide is evaporated is preferably a boiling point or a temperature slightly lower than the boiling point of titanium alkoxide.

This is because if evaporated at a temperature higher than the boiling point, it will evaporate and become non-uniform.

In addition, when vaporizing the above volatile metal compound,
It is preferable to dilute the volatile metal compound with a diluent gas to a proportion of 0.1 to 10% by volume. This diluent gas serves as a carrier gas for introducing the vaporized volatile metal compound into a decomposition furnace for decomposition.

Here, the diluent gas is argon or helium.

Inert gas such as nitrogen, water vapor, oxygen, etc. are used, and it is particularly preferable to use helium, nitrogen, or oxygen.

In addition, in the method of the present invention, since the volatile metal compound is decomposed after being vaporized or atomized, an oxygen-containing gas is required except for oxygen-containing compounds such as alkoxides. Therefore, the diluent gas preferably used in this vaporization or atomization should be appropriately determined in consideration of the type of volatile metal compound.

Here, to explain in more concrete terms the method of vaporizing a volatile metal compound, for example, a volatile metal compound used as a raw material is heated using an evaporator, etc., and a diluent gas is introduced into the heated material to evaporate the volatile metal compound. The gas containing the metal compound is introduced into a decomposition furnace which will be described later.

In addition, when using a carrier gas in this way, the volatile metal compound used as the raw material does not necessarily have to be completely vaporized, but it is also possible to introduce some or all of it in the form of a mist into the decomposition furnace described below using the carrier gas. good.

Next, the volatile metal compound thus vaporized or atomized is decomposed under heating to form ultrafine metal oxide particles.

That is, the volatile metal compound vaporized or atomized as described above is introduced into a decomposition furnace or the like using a carrier gas, and decomposed in the decomposition furnace.

In order to carry out the decomposition here, an oxygen-containing gas is required unless various oxygen-containing compounds such as Alfukisai 1 are used as the raw material volatile metal compound. therefore,
When using something other than oxygen-containing compounds such as various alkoxides as a raw material, it is preferable to use an oxygen-containing gas as the diluent gas as described above because there is no need to use an additional oxygen-containing gas. Note that decomposition here should be considered to include not only so-called normal thermal decomposition but also oxidation.

Further, the decomposition temperature is preferably 600°C or lower, particularly preferably 250 to 350°C. At temperatures below this, a sufficient decomposition rate cannot be obtained, and on the other hand, at high temperatures, particles with a large specific surface area cannot be obtained.

Further, there are no particular restrictions on the residence time, flow rate, etc. of the volatile metal compound in a vaporized or atomized state in the decomposition furnace in which the decomposition is performed, and the decomposition can be carried out under various conditions. Preferably, the residence time is 0.1-10 sec and the flow rate is 1-100 cm/sec.

Further, there are no particular restrictions on the decomposition furnace in which the decomposition is carried out, and any commonly used decomposition furnace can be used; however, in consideration of the cooling operation described below, it is preferable to use a decomposition furnace having a cooling means. Further, it is preferable to use a decomposition furnace with metal oxide fine particles adhered to the wall of the decomposition furnace in advance. By using a decomposition furnace in which metal oxide fine particles are attached to the vessel wall in this manner, the reaction temperature can be significantly lowered.

As a result, spherical and ultrafine metal oxide particles are generated, but if left as is, there is a bottom where the generated ultrafine particles coalesce with each other in the gas phase.

Therefore, in the method of the present invention, immediately after decomposition, the obtained ultrafine metal oxide particles are cooled to a temperature at which they do not coalesce again. By immediately quenching the metal oxide ultrafine particles obtained in this way, coalescence of the metal oxide ultrafine particles can be prevented.

That is, this rapid cooling prevents the metal oxide particles from coalescing, and the resulting spherical and ultrafine metal oxide particles are collected in the form B (primary particles) as they are.

It is preferable to perform this operation as quickly as possible.

Further, the cooling temperature is set to a temperature at which the obtained ultrafine metal oxide particles do not coalesce, but it is difficult to determine it unambiguously depending on the cooling rate. Usually 10
It is preferable to cool to a temperature of 0'C or less in as short a time as possible. Note that there are no particular restrictions on the cooling means, and for example, air, water, etc. may be used. Conversely, the same effect as cooling can be achieved by locally heating the area using an infrared image furnace or the like to create a temperature difference.

Furthermore, there are no particular restrictions on the cooling method; for example, cooling may be performed from outside the cracking furnace, but by installing a cooling device that uses air, water, etc. as a cooling means in the cracking furnace,
Cooling can be performed more efficiently in a shorter time. It is also possible to cool the particles produced after the reaction outside the reaction system.

Ultrafine metal oxide particles can be obtained in the form of ridges, but
Furthermore, this can be separated and collected by filtration using a membrane filter or the like to obtain a final product.

Further, when a cooling device is placed in the reaction system, the generated ultrafine particles can be collected on this device by utilizing thermophoresis.

Incidentally, the method of the present invention can also be carried out using an apparatus as shown in FIG. That is, according to this device, a volatile metal compound as a raw material is impregnated into heated glass wool 8 in a vaporizer 7 little by little by a chemical pump 6 and evaporated, and then evaporated into a carrier gas (He, O□, etc.). into the reactor 3 (for example, an infrared image furnace),
Decomposition (reaction, thermal decomposition, etc.) is carried out here, and the product is immediately led to the cooling chamber 10 and brought into contact with cooling helium to be rapidly cooled into ultrafine particles, which are further led to the receiving tank 11 and filtered by the filter 12. The desired spherical ultrafine metal oxide particles are obtained.

〔Effect of the invention〕

In the method of the present invention, since the method is rapidly cooled immediately after decomposition, even if the concentration at the time of decomposition is high, it is possible to prevent the generated ultrafine metal oxide particles from agglomerating and coalescing into large particles. I can do it.

Therefore, according to the present invention, the particle size distribution is always 100.
Ultrafine metal oxide particles as small as ~1000 particles (average particle size 200 particles) can be obtained. Further, the metal oxide ultrafine particles obtained by the present invention are spherical and uniform, and have a specific surface area of 5 x 10' to 20 x 10
'nf/kg (BET method), which is extremely large.

Therefore, the metal oxide ultrafine particles of the present invention can be effectively used in various industries as white pigments, adsorbents, catalysts, catalyst carriers, and the like.

〔Example〕

Next, the present invention will be explained by examples.

Example 1 Metal oxide particles were produced using the apparatus shown in FIG. That is, zirconium tetraisopropoxide as a raw material is heated to a temperature of 240° C. using an evaporator 1 to vaporize it, and then poured into the evaporator 1 at a temperature of 600° C.
Helium gas was bubbled at a rate of ca"/min. Through this operation, helium gas containing 0.08 mol% of zirconium tetraisopropoxide was generated, and this was transferred to reactor 3 (reactor 3) equipped with cooler 2. Inner diameter: 4
．． Qcm.

Outer diameter of cooling inner tube 4: 2.3 cm, distance from reactor inlet to heater 5: 3 cm, length of heater 5 = 2
0c11). This reactor 3 was heated to a temperature of 400° C. by a heater 5 to perform thermal decomposition. The zirconium oxide particles produced by thermal decomposition were brought into contact with a cooler 2 through which air at room temperature was flowing, and immediately cooled to a temperature of 150° C. or lower. This cooler 2 was arranged in a double tube structure in the center of the reactor 3, and cooling air was sent into this tube to effect cooling.

After the reaction was stopped, the particles attached to the outer wall of the cooler 2 were taken out and their physical properties were measured. The specific surface area of the obtained zirconium oxide particles was 180 m'/g, the average particle size was 300 mm, the particle size distribution range was 200 to 600 mm, and they were extremely uniform zirconium oxide (zirconia) ultrafine particles. Ta. Further, an electron micrograph of this product is shown in FIG.

In addition, the purity of ZrO was found to be 98% by X-ray diffraction analysis and plasma/emission spectroscopy analysis. The X-ray diffraction pattern measured here (Cu
(using K and C lines) is shown in Figure 5.

Comparative Example 1 The same operation as in Example 1 was performed except that cooling was not performed after thermal decomposition. The average particle size of the zirconium oxide particles obtained through the filter 6 is about 3000, and the particle size distribution range is 200 to 5000.
The particle size was extremely non-uniform over a wide range. Further, an electron micrograph of this product is shown in FIG.

Example 2 Metal oxide particles were produced using the apparatus shown in FIG. That is, titanium tetraisopropoxide (Ti(OCzHs)4) as a raw material is impregnated in very small amounts with a chemical pump 6 into the glass wool 8 of a vaporizer 7 heated to 200°C and evaporated, and helium 11 is used as a carrier gas. Using gas, titanium oxide particles were fed into a reactor 3 with an inner diameter of 30 mm, in which fine particles of titanium oxide were attached to the inner wall in advance,
The product was obtained by thermal decomposition at 350°C. A cooling pipe 9 for water cooling was inserted into the reactor 3, and the above-mentioned product was immediately cooled and adhered to the surface of the cooling pipe 9 as ultrafine particles of titanium oxide. The ultrafine particles of titanium oxide were collected and their physical properties were measured.

From the electron micrograph, the average particle diameter of these ultrafine particles is 200.
It was found that the particle size distribution range was 100 to 100 people. Furthermore, by the BET method, the specific surface area was 3
20 mz/g, and X-ray diffraction analysis revealed that the crystal form was amorphous. Further, the true specific gravity of the ultrafine particles was determined using a bentabictumeter (manufactured by Cantasorb Co., Ltd.), and an electron micrograph of this is shown in FIG.

Comparative Example 2 The same operation as in Example 2 was performed except that cooling with a cooling pipe was not performed. The obtained titanium oxide fine particles had an average particle size of 3000 and a particle size distribution range of 300 to 6.
000 people, specific surface area 90 m”/g.

The crystal form was amorphous. Incidentally, an electron micrograph of the titanium oxide fine particles is shown in FIG.

[Brief explanation of drawings]

Figure 1 is an electron micrograph (50,000x) showing the particle structure of the zirconium oxide fine particles obtained in Example 1;
The figure is an electron micrograph (10,000x magnification) showing the particle structure of the zirconium oxide fine particles obtained in Comparative Example 1. Figure 3 is an electron micrograph (30,000x magnification) showing the particle structure of the titanium oxide fine particles obtained in Example 2. ), FIG. 4 is an electron micrograph (30,000 times magnification) showing the particle structure of the titanium oxide fine particles obtained in Comparative Example 2. FIG. 5 is an X-ray diffraction pattern of the zirconium oxide fine particles obtained in Example 1. Note that θ in the figure indicates the bra-knob angle. 6 to 8 are explanatory diagrams showing various aspects of the apparatus used in the method of the present invention. 1... Evaporator, 2... Cooler. 3...Reactor, 4...Inner tube for cooling. 5...Heater, 6...Chemical pump. 7...vaporizer, 8...glass wool. 9... Cooling pipe, 10... Cooling chamber. 11...Receiving tank, 12...Filter.

Claims (2)

[Claims] (1) After vaporizing or atomizing the volatile metal compound,
1. A method for producing ultrafine spherical metal oxide particles, which comprises decomposing them under heating to form ultrafine metal oxide particles, and immediately after decomposition, cooling to a temperature at which the ultrafine metal oxide particles do not coalesce again. (2) The method according to claim 1, wherein the volatile metal compound is decomposed at a temperature of 600° C. or lower.