JPH01145306A - Method for producing ultrafine metal oxide particles - Google Patents

Abstract

PURPOSE:To obtain ultrafine particles of metallic oxide having small particle diameters, narrow particle diameter distribution, excellent transmission properties of visible light and ultraviolet light screening properties, by hydrolyzing a volatile metallic compound in the presence of an extremely excess amount of steam. CONSTITUTION:In producing ultrafine particles of metallic oxide by vaporizing or atomizing a volatile metallic compound and hydrolyzing under heating, the volatile metallic compound is hydrolyzed in an atmosphere containing >=40 times as much steam as that in theoretical amount required for hydrolyzing the volatile metallic compound. In production of the fine particles of metallic oxide, first the volatile metallic compound is vaporized or atomized. On the other hand, the amount of the steam to hydrolyze the vaporized or atomized volatile metallic compound used is preferably 40-1,000times as much as the theoretical amount of steam. The steam is introduced into a reactor and added to the atmosphere in the hydrolysis. In this way, the vaporized or atomized volatile metallic compound and the steam are introduced into the reactor, mixed and hydrolyzed under heating.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing ultrafine metal oxide particles, which can be used in a wide range of applications such as cosmetics, white pigments, adsorbents, catalysts, and catalyst carriers. This invention relates to an efficient method for producing ultrafine metal oxide particles.

[Prior Art and Problems to be Solved by the Invention] Various methods have been 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, so it is widely used in the fields of cosmetics and paints. The sulfuric acid method, in which the resulting precipitate is then calcined, and the chlorine method, in which titanium tetrachloride is decomposed and oxidized at high temperatures, have been developed. 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 Funaki, Saeki et al., titanium tetrachloride and water were
By mixing in the gas phase at 0 to 800°C, we can produce anatase-type fine particles of titanium oxide, or by reacting titanium tetrachloride with water in the liquid phase, we can produce anatase or anatase-type fine particles with a slight mixture of rutile. Although it has been confirmed that titanium oxide can be produced using these methods, only amorphous particles could be obtained using these methods.

Furthermore, according to the method of hydrolyzing by introducing water vapor as shown in JP-A-61-201604, spherical and amorphous titanium oxide fine particles can be obtained from titanium alkoxide, but the particle size is 200 Å. In addition, the particle size distribution is wide, and moreover, 1% by weight or more of carbonaceous matter due to unreacted alkoxide remains in the fine particles.
There were problems with quality such as purity.

In addition, the Proceedings of the 20th Autumn Conference of the Society of Chemical Engineers (19
87) On page 188, etc., it is shown that ultrafine particles of titanium oxide are obtained by hydrolyzing titanium alkoxide with an excess amount of steam that is 2 to 30 times the theoretical amount required for hydrolysis. The particle size of the titanium oxide obtained at this time is 200 Å or more in all cases.

[Means for solving problems]

Therefore, the present inventors solved the problems of the above-mentioned conventional technology,
Metal oxides such as titanium oxide, which have extremely small particle size and narrow particle size distribution, have excellent visible light transmittance and ultraviolet shielding properties, are highly pure, and can be manufactured using simple processes. We conducted extensive research to develop a method for producing ultrafine particles. As a result, it has been found that the above problems can be solved by hydrolyzing a volatile metal compound in the presence of an extremely excessive amount of water vapor.

The present invention was completed based on this knowledge.

That is, the present invention vaporizes or atomizes a volatile metal compound and then decomposes it under heating to produce ultrafine metal oxide particles. The present invention provides a method for producing ultrafine metal oxide particles, characterized in that the volatile metal compound is hydrolyzed in an atmosphere containing twice as much water vapor.

In the method of the present invention, various volatile metal compounds can be used as raw materials. for example,
Volatile titanium compounds such as titanium alkoxide and titanium halide; zirconium alkoxide and zirconium halide.

Volatile zirconium compounds such as organic zirconium compounds; scandium, yttrium.

Examples include alkoxides of rare earth metals such as lanthanum and cerium. These can be used alone or in combination.

Here, specific examples of the titanium alkoxide include titanium tetramethoxide, titanium tetraethoxide, and titanium tetra-n-propoxide.

Examples include titanium tetraisopropoxide and titanium tetrabutoxide. Further, as the titanium halide, titanium tetrahalide such as titanium tetrachloride can be mentioned as a suitable titanium halide. Furthermore, volatile titanium compounds such as trihalogenated monoalkoxytitanium, monohalogenated trialkoxytitanium, and dihalogenated dialkoxytitanium can also be used.

Further, specific examples of the zirconium alkoxide include zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetra-n-propoxide, zirconium tetraisopropoxide, and zirconium tetrabutoxide.

Furthermore, as a zirconium halide, zirconium tetrachloride is used.

Examples include tetrahalogenated zirconium such as zirconium tetrabromide, and trihalogenated monoalkoxyzirconium, monohalogenated trialkoxyzirconium, dihalogenated dialkoxyzirconium, etc. can also be used. It is also possible to use volatile organic silconium compounds such as zirconium phenoxide.

In the method of the present invention, the above-mentioned volatile metal compound is first vaporized or atomized. The conditions for vaporizing or atomizing the volatile metal compound, that is, evaporating or atomizing the volatile metal compound, vary depending on the type of the volatile metal compound and cannot be unambiguously determined.

Here, when vaporizing or atomizing the above-mentioned volatile metal compound, the volatile metal compound is 0.01
It is preferable to dilute to a ratio of ~10% by volume. This diluent gas serves as a carrier gas to introduce the vaporized volatile metal compound into the decomposition furnace, and if the amount is too small, the vaporization temperature of the volatile metal compound must be increased. First, there is a risk that the raw material (volatile metal compound) may thermally decompose before being mixed with water vapor, which will be described later, and may clog a vaporizer such as a vaporizer.

The diluent gas used here is argon, helium,
Inert gas such as nitrogen, oxygen, air, etc. are used, and helium or nitrogen is particularly suitable. This diluent gas is
The most suitable one may be selected depending on the type of volatile metal compound used as a raw material, the structure of the device, etc.

In addition, as a means to vaporize a volatile metal compound, for example, the volatile metal compound used as a raw material is heated using a vaporizer, and a diluent gas is introduced into the vaporizer to convert the volatile metal compound into a gas containing the volatile metal compound. It is introduced into the reactor described later. In addition, when using a diluent gas (carrier gas) in this way, the volatile metal compound used as the raw material does not necessarily need to be completely vaporized, but some or all of it is atomized and sent to the reactor by the carrier gas. May be introduced.

On the other hand, the amount of water vapor used to hydrolyze the vaporized or atomized volatile metal compound is 40 times or more, preferably 40 to 5000 times, the theoretical amount of water vapor required to hydrolyze the raw material volatile metal compound. , particularly preferably from 40 to
This is used in a range of 1000 times, and introduced into the reactor to be included in the atmosphere during hydrolysis. If the content of water vapor in the atmosphere is less than 40 times the theoretical amount, the particle size of the obtained metal oxide fine particles becomes large and the particle size distribution becomes broad. On the other hand, although there is no upper limit to the amount of water vapor, if it exceeds 5000 times, the raw material concentration during the reaction will inevitably be low, resulting in a decrease in production efficiency.

This water vapor may be introduced into the reactor by simply heating water with a vaporizer or the like to evaporate it, or it may be introduced into the reactor using a carrier gas as in the case of the volatile metal compound.

In the method of the present invention, the thus vaporized or atomized volatile metal compound and water vapor are introduced into a reactor and mixed,
The hydrolysis reaction is carried out under heating. This hydrolysis reaction can be carried out using, for example, titanium tetraalkoxide (Ti(OR)4;
R represents an alkyl group. ), Ti(OR)4 + 2 H2O→ T i O□+4
Titanium oxide (TiO
□) is generated.

The temperature during this hydrolysis is preferably 600°C or less,
Particularly preferred is a temperature range of 100 to 450°C.

If the temperature during hydrolysis is too low, the hydrolysis reaction will not proceed sufficiently and the amount of undecomposed raw materials remaining as hydrocarbons will increase, and if the temperature is too high, particles with a large specific surface area will not be obtained. Particularly suitable spherical amorphous particles cannot be obtained.

In addition, the residence time and flow rate of the raw material (vaporized or atomized volatile metal compound) and water vapor in the reactor for hydrolysis are not particularly limited and can be set as appropriate conditions depending on the situation. Usually, it is preferred that the residence time be 0.01 to 10 seconds and the flow rate be 0.01 to 10 m/sec.

There are no particular restrictions on the reactor that performs this hydrolysis.
Just use what is normally used.

In the method of the present invention, ultrafine metal oxide particles can be obtained by reacting the volatile metal compound thus vaporized or atomized with water vapor in a large excess of 40 times or more relative to the theoretical amount. can. These metal oxide ultrafine particles have an extremely small particle size of 50 to 200, have a sharp particle size distribution, and have excellent transparency to visible light.

Note that the metal oxide ultrafine particles generated in this manner may coalesce with each other in the gas phase if they are kept in a heated state, and may not be able to maintain their ultrafine particle state. Therefore, it is desirable to cool the metal oxide ultrafine particles produced by hydrolysis in the reactor to quickly react to prevent the above-mentioned coalescence. This cooling is carried out to a temperature below which the obtained ultrafine metal oxide particles do not coalesce. Although it varies depending on the type of product, it is usually 100°C or below, and air, nitrogen, water, etc. are used as the cooling source. After the reaction, a cooler is installed downstream of the reactor.
It is desirable to carry out this process by continuously introducing the following products. By such a method, the generated ultrafine metal oxide particles can be collected in their ultrafine form, that is, as primary particles, without being combined. The collection of the metal oxide ultrafine particles can be carried out by means such as boat fishing, for example, a membrane filter, a bag filter-1 electrostatic precipitator, etc. can be used.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Example 1 Ultrafine metal oxide particles were produced using the reaction apparatus shown in FIG. That is, the raw material titanium tetraisopropoxide (Ti(OC2H?)4) was fed at 44 g/hr,
Nitrogen gas as Kikiri gas 1.05Nrrf/h
The raw material was introduced into vaporizer 6 heated to 130° C. to completely vaporize the raw material.

On the other hand, 880g/hr water is 2.65 Nrrf/hr
was introduced into vaporizer 5 heated to 450° C. to prepare superheated steam. The amount of steam relative to the raw material at this time was 157 times the theoretical amount required to hydrolyze the raw material. This superheated steam was introduced into the reactor 8 at the same time as the vaporized raw material, and a hydrolysis reaction was carried out at 260° C. to obtain ultrafine titanium oxide particles. The flow rate introduced into the reactor at this time was 1.3 m/m on the raw material side.
2.6 m/sec on the steam side, and the flow rate in the reactor was 0.32 m/sec. Table 1 shows the yield and physical properties of the obtained product.

Example 2 In Example 1, the raw material titanium tetraisopropoxide was 189 g/hr, and the water was 1200 g/hr.
The same operation as in Example 1 was performed except that superheated steam was used together with nitrogen gas at 2.26 Nrd/hr. The amount of steam relative to the raw material at this time was 50 times the theoretical amount. The yield and physical properties of the obtained product are
Shown in the table.

Comparative Example 1 In Example 1, water 5.5g/hr nitrogen gas 3,75
The same operation as in Example 1 was performed except that superheated steam was used together with Nnf/hr, that is, the amount of steam was set to the theoretical amount required for hydrolysis of the raw material. Table 1 shows the yield and physical properties of the obtained product.

Comparative Example 2 In Example 1, the water vapor side was heated with nitrogen gas at 3.75 Nrd.
The same operation as in Example 1 was performed except that only /hr was used, that is, no water vapor was introduced. Table 1 shows the yield and physical properties of the obtained product.

Comparative Example 3 In Example 2, the water vapor side was heated with nitrogen gas at 3.75Nrr.
The same operation as in Example 2 was performed except that only f/hr was used, that is, no water vapor was introduced. Table 1 shows the yield and physical properties of the obtained product.

Comparative Example 4 In Example 2, 803 g/hr of water was
The same operation as in Example 2 was performed except that superheated steam was used at 5 N rd /hr. The amount of steam relative to the raw material at this time was 33 times the theoretical amount. Table 1 shows the yield and physical properties of the obtained product.

(The following is a blank space) [Effect of the invention] As described above, according to the method of the present invention, the particle size is 50 to 20
It is possible to efficiently produce ultrafine metal oxide particles that are extremely small (0 particles), have a sharp particle size distribution, and have excellent transparency to visible light and shielding properties to ultraviolet rays.

In addition, the obtained ultrafine metal oxide particles have a low amount of residual unreacted hydrocarbons, have high purity, and are of extremely good quality. Furthermore, since it is only necessary to introduce a large excess of water vapor, it is possible to easily produce ultrafine metal oxide particles with desired properties using equipment with a simple configuration, and the amount of carrier gas used can be reduced. Costs can be reduced significantly.

Therefore, the metal oxide ultrafine particles obtained by the method of the present invention can be effectively used in various industries as high-quality cosmetics, paints, adsorbents, catalysts, catalyst carriers, etc.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing an example of a reaction apparatus used in the method of the present invention. 1... Nitrogen cylinder, 2... Flow meter. 3...Water charge pump, 5...Water vaporizer, 6...Rice vaporizer. 7... Heater, 8... Reactor. 9... Cooling chamber, 10... Bag filter - Figure 1

Claims (3)

[Claims] (1) After vaporizing or atomizing the volatile metal compound,
When producing ultrafine metal oxide particles by decomposition under heating, the volatile metal compound is hydrolyzed in an atmosphere containing water vapor 40 times or more the theoretical amount of water vapor required to hydrolyze the volatile metal compound. A method for producing ultrafine metal oxide particles, characterized by: (2) The manufacturing method according to claim 1, wherein after hydrolysis, the produced ultrafine metal oxide particles are cooled to a temperature at which they do not coalesce again. (3) The manufacturing method according to claim 1, wherein the hydrolysis is carried out at a temperature of 600° C. or lower.