JPH0457602B2 - - Google Patents

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, so it is widely used in fields such as cosmetics and paints. Known methods include 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. 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. In addition, according to Funaki, Saeki et al., titanium tetrachloride and water are mixed in the gas phase at 200 to 800°C to produce anatase-type titanium oxide in the form of fine particles, and titanium tetrachloride and water are reacted in the liquid phase. It has been confirmed that it is possible to produce anatase or anatase-type titanium oxide in the form of fine particles mixed with a slight amount of rutile.
However, these methods can only obtain particles with irregular shapes, and not spherical particles. The present inventors have previously proposed a method for producing spherical and extremely fine-particle titanium oxide by thermally decomposing titanium alkoxide to overcome these conventional drawbacks. (Special application 1986-41290
issue). According to this method, spherical, ultrafine titanium oxide particles are generated with a relatively simple operation, but since the generated ultrafine titanium oxide particles bond and coalesce, the final result must be at an extremely low concentration. There is a problem that 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 ultrafine metal oxide particles in the form of spherical ultrafine particles. That is. [Means for Solving the Problems] First, the present invention provides a volatile metal alkoxide of a metal selected from the group consisting of titanium, zirconium, scandium, yttrium, lanthanum, and cerium, or a volatile metal consisting of zirconium phenoxide. The compound is vaporized or atomized, then decomposed at a temperature of less than 600°C, combined to form ultrafine metal oxide particles, and immediately after decomposition cooled to a temperature at which the ultrafine metal oxide particles do not coalesce again. The present invention provides a method for producing ultrafine spherical metal oxide particles. Furthermore, secondly, the present invention provides a method of vaporizing or atomizing a volatile metal compound consisting of a halide of a metal selected from the group consisting of titanium, zirconium, scandium, yttrium, lanthanum, and cerium, and then converting it into an oxygen-containing gas. Spherical metal oxide ultrafine particles that are decomposed at a temperature of less than 600°C in the presence of the metal oxide, combined to form metal oxide ultrafine particles, and immediately cooled to a temperature at which the metal oxide ultrafine particles do not coalesce again after decomposition. The present invention provides a method for manufacturing. The first and second aspects of the present invention use the same type of volatile metal and react in almost the same way, but differ in that the halide is reacted in the presence of an oxygen-containing gas. It is something. As mentioned above, the volatile metal compound used as a raw material in the method of the present invention is a metal alkoxide selected from the group consisting of titanium, zirconium, scandium, yttrium, lanthanum, and cerium, or zirconium phenoxide (the volatile metal compound of the present invention). (1), or halides of these metals (2nd of the present invention). In addition, when using titanium alkoxide as a volatile metal compound, in order to increase the stability of the titanium oxide produced, aluminum chloride or zirconium alkoxide is added within 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. Here, specific examples of the titanium alkoxide include titanium tetramethoxide, titanium tetraethoxide, titanium tetrapropoxide,
Examples include titanium tetrabutoxide and diethoxytitanium oxide. Further, specific examples of titanium halides include titanium tetrahalides such as titanium tetrachloride and titanium tetrabromide. 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 tetraalkoxyzirconiums such as zirconium tetramethoxide, zirconium tetraethoxide, zirconium tetraisopropoxide, and zirconium tetrabutoxide. Further, specific examples of zirconium halides include zirconium tetrahalides such as zirconium tetrachloride and zirconium tetrabromide, and monoalkoxyzirconium trihalides,
Monohalogenated trialkoxyzirconium, dihalogenated dialkoxyzirconium, etc. can also be used. 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 the titanium alkoxide is evaporated at a temperature higher than the boiling point, the titanium alkoxide decomposes in a non-uniform state, resulting in particles that are obtained with non-uniform specific surface area, particle diameter, etc. In addition, when vaporizing the above volatile metal compound, the volatile metal compound should be evaporated by 0.1 to 10
It is preferable to dilute to a ratio of % by volume. This diluent gas serves as a carrier gas for introducing the vaporized volatile metal compound into a decomposition furnace for decomposition. Here, as the diluent gas, an inert gas such as argon, helium, or nitrogen, water vapor, oxygen, or the like is used, and it is particularly preferable to use helium, nitrogen, or oxygen. In the method of the present invention, since the volatile metal compound is vaporized or atomized and then decomposed, an oxygen-containing gas is required for compounds other than oxygen-containing compounds such as alkoxides, that is, halides. Therefore, the diluent gas preferably used in this vaporization or atomization is as follows:
It should be determined appropriately taking into consideration 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; some or all of it may be introduced into the decomposition furnace as described below in the form of a mist 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, an oxygen-containing gas is required unless oxygen-containing compounds such as various alkoxides 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, since 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 needs to be less than 600°C, and particularly preferably 250 to 350°C.
If the temperature is too low, a sufficient decomposition rate cannot be obtained. On the other hand, at high temperatures, particularly at temperatures above 600°C, particles with a large specific surface area cannot be obtained. Furthermore, in the decomposition furnace where decomposition is carried out,
There are no particular restrictions on the residence time, flow rate, etc. of the volatile metal compound in a vaporized or atomized state, and it can be carried out under various conditions. Preferably the residence time is between 0.1 and
10 sec., and the flow rate is 1 to 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 this continues, the generated ultrafine particles may coalesce 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 as they are (primary particles). It is preferable to perform this operation as quickly as possible. Further, the cooling temperature is 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 and the like. Usually, it is preferable to cool to a temperature of 100°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 inside the cracking furnace that uses air, water, etc. as a cooling means, it is possible to shorten the time even more. can be efficiently cooled. It is also possible to cool the particles produced after the reaction outside the reaction system. Although ultrafine metal oxide particles are obtained as described above, they can be further 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 infiltrated 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 ₂ , etc.). reactor 3
(for example, an infrared imaging furnace), where it is decomposed (reaction, thermal decomposition, etc.), and the product is immediately led to the cooling chamber 10 and brought into contact with cooling helium to rapidly cool it into ultrafine particles, which are then further transferred to a receiving tank. 1
1 and filtered through a filter 12 to obtain the desired spherical metal oxide ultrafine particles. [Effects of the Invention] In the method of the present invention, since the metal oxide is rapidly cooled immediately after decomposition, even if the concentration at the time of decomposition is high, the generated ultrafine metal oxide particles aggregate and coalesce to form large particles. This can be prevented. Therefore, according to the present invention, ultrafine metal oxide particles with extremely small particle size distribution of 100 to 1000 Å (average particle size 200 Å) can always be obtained. Furthermore, the metal oxide ultrafine particles obtained by the present invention are spherical and uniform, and have a specific surface area of 5×10 ⁴
It is very large, ~20×10 ⁴ m ² /Kg (BET method). Therefore, the metal oxide ultrafine particles of the present invention are
It can be effectively used in various industries as a white pigment, adsorbent, catalyst, catalyst carrier, etc. [Example] Next, the present invention will be explained with reference to an example. Example 1 Metal oxide particles were produced using the apparatus shown in FIG. That is, zirconium tetraisopropoxide as a raw material was heated to a temperature of 240° C. using an evaporator 1 to vaporize it, and helium gas was bubbled into the evaporator 1 at a rate of 600 cm ³ /min. This operation generates helium gas containing 0.08 mol% of zirconium tetraisopropoxide, which is then transferred to the cooler 2.
Reactor 3 (reactor inner diameter: 4.0 cm, outer diameter of cooling inner tube 4: 2.3 cm, heater 5 from the reactor inlet)
(distance to heater 5: 3 cm, length of heater 5: 20 cm). This reactor 3 is heated to 400 m
Thermal decomposition was carried out by heating to a temperature of °C. The zirconium oxide particles generated by thermal decomposition are brought into contact with a cooler 2 in which room temperature air is flown, and immediately
Cooled to a temperature below 150°C. This cooler 2 is arranged in the center of the reactor 3 in a double pipe structure,
Cooling air was sent into this tube for 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 obtained zirconium oxide particles had a specific surface area of 180 m ² /g, an average particle size of 300 Å, a particle size distribution range of 200 to 600 Å, and were extremely uniform zirconium oxide (zirconia) ultrafine particles. Further, an electron micrograph of this product is shown in FIG. In addition, this thing is
X-ray diffraction analysis and plasma emission spectroscopy revealed that the purity as ZrO ₂ was 98%. The X-ray diffraction pattern measured here (Cu-
(using Kα radiation) 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 was about 3000 Å, and the particle size distribution range was wide ranging from 200 to 5000 Å, and the particle size was extremely nonuniform. 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(OC ₃ H ₈ ) ₄ ), which is 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 to produce a carrier gas. Using helium gas, the mixture was fed into a reactor 3 with an inner diameter of 30 mm, in which fine titanium oxide particles had been attached to the inner wall in advance, and thermally decomposed at 350° C. to obtain a product. 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. Electron micrographs revealed that the average particle diameter of these ultrafine particles was 200 Å, and the particle size distribution range was 100 to 1000 Å. Furthermore, by the BET method, the specific surface area is
320 m ² /g, and X-ray diffraction analysis revealed that the crystal form was amorphous. Furthermore, the true specific gravity of these ultrafine particles was determined to be 2.4 g/cm ³ (at 23°C) and 2.9 g/cm ³ as a result of measurement using a He gas displacement method using a pentapycnometer (manufactured by Canterthorpe).
(drying at 115°C for 4 hours). In addition, this electron micrograph 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 diameter of 3000 Å, a particle size distribution range of 300 to 6000 Å, a specific surface area of 90 m ² /g, and an amorphous crystalline form. Incidentally, an electron micrograph of the titanium oxide fine particles is shown in FIG. Example 3 (Example in which steam was added to the reaction system) Metal oxide particles were produced using the reaction apparatus shown in FIG. To introduce water vapor into the reaction system, water is heated with a heater 15 heated to 200°C.
Dry air was bubbled into it at a flow rate of 10/min. Thermometer 16 in FIG. 9 indicated approximately 50°C. Through this operation, air containing 0.1 mol percent of water was prepared. A vaporizer 7 in which the raw material titanium tetraisopropoxide (Ti(OC ₃ H ₇ ) ₄ ) is heated in extremely small amounts to 200°C using a chemical pump 6.
It was soaked in glass wool 8 and evaporated. 0.06 mol% of titanium tetraisopropoxide was contained using air as a carrier gas. The air was simultaneously sent to reactor 3 (inner diameter: 55 mm, length: 100 mm) with air containing 0.1 mol% of water, and heated to 300°C.
A product was obtained. Table 1 shows the yield (%, based on TiO ₂ ), physical properties, and composition of the resulting product. Further, FIG. 10 shows the relationship between the molar ratio of water and raw materials and the yield. Furthermore, an electron micrograph of the obtained product is shown in FIG. As for the analysis method, titanium was dissolved in potassium pyrosulfate and then quantified by inductively coupled plasma analysis. After decomposing the sample at 850°C, carbon and hydrogen were quantified using an MT-Z CHN coder manufactured by Yanagimoto Seisakusho. Oxygen was determined using a trace oxygen analyzer manufactured by Mitamura Riken Kogyo Co., Ltd. after decomposing the sample at 940°C. This oxygen value does not include oxygen derived from titanium oxide. Example 4 In Example 3, all operations were performed in the same manner as in Example 3 except that water was not included in the air. Table 1 shows the yield, physical properties, and composition of the resulting product. Furthermore, an electron micrograph of the obtained product is shown in FIG. Example 5 (Example in which steam was added to the reaction system and the reaction temperature was lowered) The same operation as in Example 3 was performed except that the temperature of reactor 3 was lowered to 150°C. Summer. Table 1 shows the yield, physical properties, and composition of the resulting product. Furthermore, an electron micrograph of the obtained product is shown in FIG. Example 6 (Example in which water was added to the reaction system and steam was generated in the reactor) Metal oxide particles were produced using the reaction apparatus shown in FIG. The water vapor was introduced into the reactor by feeding extremely small amounts of water into the vicinity of the nozzle in the reactor 3, where it was evaporated, so that 0.05 mol% of water was contained in the carrier gas. The raw material, tetraisopropoxide (Ti(OC ₃ H ₇ ) ₄ ), is evaporated by impregnating the glass wool 8 of the vaporizer 7 heated to 200°C with a chemical pump 6 in very small amounts, and using air as a carrier gas. Then, 0.06 mol% of titanium isopropoxide was added. The air was sent into reactor 3 (inner diameter: 55 mm, length: 100 mm) and reacted at 300°C to obtain a product. Table 1 shows the yield, physical properties, and composition of the resulting product. Furthermore, an electron micrograph of the obtained product is shown in FIG. Example 7 (Example in which steam was added as a heat source) Metal oxide particles were produced using the reaction apparatus shown in FIG. 16. The introduction of water vapor was carried out using high temperature steam as a heating heat source. This was also used as a carrier gas. Steam is 300℃
I used the one from The raw material was made to contain 0.06 mol% of air in the same manner as in Examples 2, 3, and 6, and was sent to reactor 3 (inner diameter: 55 mm, length: 100 mm).
The reaction was carried out at 300°C to obtain a product. The yield, physical properties and composition of the product are shown in Table 1. Furthermore, an electron micrograph of the obtained product is shown in FIG. 【table】

[Brief explanation of the drawing]

Figure 1 is an electron micrograph showing the particle structure of the zirconium oxide fine particles obtained in Example 1 (50,000
Figure 2 is an electron micrograph (10,000x) showing the particle structure of the zirconium oxide fine particles obtained in Comparative Example 1, and Figure 3 is an electron micrograph showing the particle structure of the titanium oxide fine particles obtained in Example 2. Micrograph (30,000 times) FIG. 4 is an electron micrograph (30,000 times) 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 Bragg angle. 6th~
FIG. 8 is an explanatory diagram showing each aspect of the apparatus used in the method of the present invention. FIG. 9 is an explanatory diagram showing the aspect of the apparatus used in Examples 3 to 5 of the present invention, and FIG. 10 is a graph showing the relationship between the molar ratio of water and raw materials and the yield in Example 3 of the present invention. Figure 11 is an electron micrograph showing the particle structure (TEM image) of the titanium oxide fine particles obtained in Example 3 of the present invention, and Figure 12 is the particle structure (TEM image) of the titanium oxide fine particles obtained in Example 4 of the present invention. Electron micrograph showing TEM image), 1st
Figure 3 is an electron micrograph showing the particle structure (TEM image) of titanium oxide fine particles obtained in Example 5 of the present invention, Figure 14 is an explanatory diagram showing the mode of the apparatus used in Example 6 of the present invention, Figure 15 is an electron micrograph showing the particle structure (TEM image) of titanium oxide fine particles obtained in Example 6 of the present invention, Figure 16 is an explanatory diagram showing the mode of the apparatus used in Example 7 of the present invention, FIG. 17 is an electron micrograph showing the particle structure (TEM image) of the titanium oxide fine particles obtained in Example 7 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, 13...
...Motor, 14...Raw material, 15...Heater,
16...Thermometer.

Claims (1)

[Scope of Claims] 1. A volatile metal compound consisting of a metal alkoxide or zirconium phenoxide selected from the group consisting of titanium, zirconium, scandium, yttrium, lanthanum and cerium,
After being vaporized or atomized, it is decomposed and combined to form ultrafine metal oxide particles at a temperature of less than 600°C, and immediately after decomposition, it is cooled to a temperature at which the ultrafine metal oxide particles do not coalesce again. Method for producing ultrafine metal oxide particles. 2. After vaporizing or atomizing a volatile metal compound consisting of a metal halide selected from the group consisting of titanium, zirconium, scandium, yttrium, lanthanum, and cerium, the mixture is heated at a temperature below 600°C in the presence of an oxygen-containing gas. 1. A method for producing spherical ultrafine metal oxide particles, which comprises decomposing the metal oxide ultrafine particles, combining them to form ultrafine metal oxide particles, and immediately cooling the metal oxide ultrafine particles to a temperature at which the metal oxide ultrafine particles do not coalesce again after decomposition.