Method for producing molybdenum trioxide fine particles

Abstract

To provide a method for producing molybdenum trioxide fine particles by which molybdenum trioxide fine particles can be produced at a high recovery rate even at low energy consumption by easy ON / OFF control and selective heating. A method for producing molybdenum trioxide fine particles according to the present invention comprises: a vaporization step in which molybdenum trioxide is heated and vaporized by irradiating molybdenum trioxide with electromagnetic waves; and a particle formation step in which the vaporized molybdenum trioxide is cooled in an unheated atmosphere and converted into particles to obtain molybdenum trioxide fine particles. The frequency of the electromagnetic waves is in the range of 300-30,000 MHz.

Description

Method for producing molybdenum trioxide fine particles

[0001] The present invention relates to a method for producing molybdenum trioxide fine particles. This application claims priority to Japanese Patent Application No. 2023-199113, filed on November 24, 2023, the contents of which are incorporated herein by reference.

[0002] Molybdenum trioxide microparticles have a wide range of applications, including as catalysts, additives for steel and corrosion-resistant alloys, raw materials for molybdenum metal and compounds, and antibacterial and antiviral agents. Molybdenum trioxide melts at temperatures of 800°C or higher and is sublimable. Therefore, by cooling the sublimated molybdenum trioxide gas or by contacting it with air or an inert gas at 800°C or lower, the molybdenum trioxide can be solidified and granulated (see, for example, Patent Document 1).

[0003] Patent No. 6455747

[0004] However, with conventional gas heating using a burner or electrical heating using a heater, the atmosphere surrounding the molybdenum trioxide being heated is also heated. Therefore, even if the input of heating energy is cut off, sublimation of molybdenum trioxide cannot be suppressed. As a result, it has been difficult to efficiently produce molybdenum trioxide microparticles having a fine particle size from the raw material molybdenum trioxide. A production method that can produce molybdenum trioxide microparticles with a high recovery rate even with low energy consumption is desired.

[0005] As a result of extensive research, the present inventors have found that molybdenum trioxide (powder) absorbs electromagnetic waves such as microwaves well and is rapidly heated and vaporized through temperature rise, and that because the electromagnetic waves do not heat the atmosphere, vaporization is immediately suppressed by cutting off the input of electromagnetic wave energy, thereby making it possible to control the amount of vaporized molybdenum trioxide and, as a result, to efficiently produce molybdenum trioxide microparticles. That is, in this embodiment, heating by electromagnetic wave irradiation is easily controlled by ON / OFF control and irradiation intensity control, and selective heating of molybdenum trioxide is possible without heating the atmosphere. Therefore, an object of this embodiment is to provide a method for producing molybdenum trioxide microparticles that can produce molybdenum trioxide microparticles with a high recovery rate even with low energy consumption.

[0006] The present embodiment is based on the findings of the present inventors, and provides the following means for solving the above problems. [1] A method for producing molybdenum trioxide microparticles, comprising: a vaporization step of irradiating molybdenum trioxide with electromagnetic waves to heat and vaporize the molybdenum trioxide; and a particulation step of cooling the vaporized molybdenum trioxide in an unheated atmosphere to particulate the molybdenum trioxide, wherein the frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz. [2] The method for producing molybdenum trioxide microparticles according to [1], wherein the frequency of the electromagnetic waves is in the range of 900 to 3,000 MHz. [3] The method for producing molybdenum trioxide microparticles according to [1] or [2], wherein 0.1 to 50 wt % of a metal oxide is blended with the molybdenum trioxide. [4] The method for producing molybdenum trioxide microparticles according to [3], wherein the metal oxide is at least one selected from the group consisting of aluminum hydroxide, boehmite, aluminum oxide, silica, titanium oxide, and iron oxide. [5] The method for producing molybdenum trioxide microparticles according to any one of [1] to [4], wherein the molybdenum trioxide microparticles have an average particle size of 10 nm to 100 μm. [6] The method for producing molybdenum trioxide microparticles according to any one of [1] to [4], wherein the molybdenum trioxide microparticles have a BET specific surface area of ​​0.01 m ２ / g~500m ２[7] The method for producing molybdenum trioxide microparticles according to any one of [1] to [6], wherein the molybdenum trioxide microparticles contain an α crystal structure. [8] The method for producing molybdenum trioxide microparticles according to any one of [1] to [7], wherein the molybdenum trioxide microparticles further contain a β crystal structure.

[0007] According to the present embodiment, it is possible to provide a method for producing molybdenum trioxide microparticles, which can produce molybdenum trioxide microparticles with a high recovery rate even with low energy consumption through simple ON / OFF control and selective heating.

[0008] 1 is a schematic diagram of an example of an apparatus used to produce molybdenum trioxide fine particles according to one embodiment of the present invention.

[0009] (Method for Producing Molybdenum Trioxide Particles) A ​​method for producing molybdenum trioxide particles according to one embodiment of the present invention comprises the following two steps: (I) Vaporization step: A step of irradiating molybdenum trioxide with electromagnetic waves to heat and vaporize the molybdenum trioxide; (II) Granulation step: A step of cooling the vaporized molybdenum trioxide in an unheated atmosphere to granulate the molybdenum trioxide, thereby obtaining molybdenum trioxide particles. The frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz.

[0010] The method for producing molybdenum trioxide fine particles of this embodiment can be suitably carried out using, for example, a molybdenum trioxide fine particle production apparatus 10 shown in FIG.

[0011] FIG. 1 is a schematic diagram of an example of an apparatus used to produce molybdenum trioxide microparticles according to this embodiment. A device capable of irradiating electromagnetic waves (sometimes referred to as an "electromagnetic wave irradiation device"; not shown) is disposed above the chamber 1. The molybdenum trioxide microparticle production apparatus 10 includes a chamber 1 that irradiates the molybdenum trioxide placed in a container 2 with electromagnetic waves generated by the electromagnetic wave irradiation device to heat the molybdenum trioxide (hereinafter sometimes referred to as "electromagnetic wave heating") and vaporize the molybdenum trioxide, and a particle recovery device 3 connected to the chamber 1 and that microparticulates the molybdenum trioxide vapor vaporized by the irradiation. The chamber 1 and the particle recovery device 3 are interconnected. The chamber 1 has an outside air intake 6 at its left end, and the particle recovery device 3 has an exhaust 8 at its right end. An exhaust device (not shown), which serves as a blower, is connected to the air intake 6. The production apparatus 1 may have an external cooling device (not shown), which makes it possible to arbitrarily control the cooling conditions for the molybdenum trioxide vapor generated from the chamber 1.

[0012] [Molybdenum trioxide fine particles] The molybdenum trioxide fine particles of this embodiment contain aggregates of primary particles having a crystalline structure of molybdenum trioxide. The molybdenum trioxide fine particles of this embodiment can also be referred to as the molybdenum trioxide powder of this embodiment. The crystalline structure may be, for example, an α-crystalline structure, a β-crystalline structure, or may contain both an α-crystalline structure and a β-crystalline structure. The molybdenum trioxide fine particles of this embodiment have better reactivity with other compounds, for example, sulfur, than conventional molybdenum trioxide fine particles.

[0013] In this embodiment, the α-crystalline structure of the molybdenum trioxide is MoO ３ The β-crystal structure can be confirmed by the presence of a peak on the (021) plane of the α-crystal (2θ: around 27.32°, No. 166363 (Inorganic Crystal Structure Database, ICSD)). ... ３This can be confirmed by the presence of a peak attributable to the (011) plane of the β crystal of SiO 2. The peak is located around 2θ: 23.01°, and is No. 86426 (Inorganic Crystal Structure Database, ICSD).

[0014] The average particle size of the molybdenum trioxide microparticles of this embodiment is preferably 10 nm to 100 μm. The average particle size of the molybdenum trioxide microparticles of this embodiment can be measured, for example, by a known particle size distribution measurement method. The average particle size of the molybdenum trioxide microparticles of this embodiment is more preferably 10 nm or more, and even more preferably 20 nm or more. It may also be 100 μm or less, 10 μm or less, or 1 μm or less. When the average particle size of the molybdenum trioxide microparticles of this embodiment is within the above preferred range, for example, when molybdenum sulfide is produced using the molybdenum trioxide microparticles, the reactivity of the molybdenum trioxide microparticles with sulfur tends to be better.

[0015] The BET specific surface area of ​​the molybdenum trioxide fine particles is 0.01 m ２ / g~500m ２ In the molybdenum trioxide fine particles of the present embodiment, the BET specific surface area is preferably 1 m / g from the viewpoint of further improving the reactivity with other compounds, for example, sulfur. ２ / g or more, and 10m ２ / g or more is more preferable, and 20m ２ / g or more is more preferable. In addition, in the molybdenum trioxide fine particles of this embodiment, it is preferable that the molybdenum trioxide fine particles have a particle size of 500 m / g or more because the production is easy. ２ / g or less, and ２ / g or less, and ２ / g or less.

[0016] In the molybdenum trioxide microparticles of this embodiment, the shape of the primary particles in a two-dimensional image taken with a transmission electron microscope (TEM) may be, as determined by visual observation or photographic imaging, particulate, spherical, plate-like (sheet-like), needle-like, string-like, or ribbon-like, or may include a combination of these shapes. In this embodiment, the shape of the primary particles of the molybdenum trioxide microparticles may be ribbon-like or sheet-like having a thickness on the order of nanometers. The average size of 50 primary particles of the molybdenum trioxide particles is preferably in the range of length (vertical) × width (horizontal) = 5 to 2000 nm × 5 to 2000 nm, more preferably 5 to 1000 nm × 5 to 1000 nm, and particularly preferably 10 to 500 nm × 10 to 500 nm.

[0017] The β crystal structure of molybdenum trioxide is determined by Raman spectroscopy at wave numbers of 773 and 848 cm －１ and 905 cm －１ The α-crystalline structure of molybdenum trioxide can also be confirmed by the presence of peaks at wavenumbers 663 and 816 cm. －１ and 991 cm －１ This can be confirmed by the presence of a peak at

[0018] The molybdenum trioxide fine particles of the present embodiment have good reactivity with sulfur, and therefore, are suitable for use in molybdenum sulfide (MoS ２ ) Furthermore, the molybdenum trioxide microparticles of the present embodiment can be made highly pure, and therefore can be used in industrial grades. Furthermore, the molybdenum trioxide microparticles of the present embodiment are expected to be used in various catalytic applications.

[0019] [Vaporization Step] In the method for producing molybdenum trioxide microparticles of this embodiment, the vaporization step is a step of irradiating molybdenum trioxide with electromagnetic waves to heat the molybdenum trioxide (hereinafter referred to as "electromagnetic wave heating") and vaporize the molybdenum trioxide. The frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz.

[0020] <Molybdenum Trioxide> The molybdenum trioxide used as a raw material in the vaporization step according to this embodiment is a precursor of the molybdenum trioxide microparticles, and for example, commercially available α-crystalline molybdenum trioxide can be used. The molybdenum trioxide precursor of the molybdenum trioxide microparticles may be formed by electromagnetically heating a molybdenum oxide precursor compound. That is, the method for producing molybdenum trioxide microparticles according to this embodiment may further include, prior to the vaporization step, a step of electromagnetically heating the molybdenum oxide precursor compound to form molybdenum trioxide. Then, the molybdenum trioxide microparticles formed in the vaporization step may be used to produce the molybdenum trioxide microparticles.

[0021] The molybdenum oxide precursor compound is not particularly limited as long as it forms molybdenum trioxide vapor by electromagnetic heating. Examples of the molybdenum oxide precursor compound include molybdenum trioxide, metallic molybdenum, molybdenum dioxide, molybdenum sulfide, ammonium molybdate, and phosphomolybdic acid (H ３ PMo １２ O ４０ ), silicomolybdic acid (H ４ SiMo １２ O ４０ ), aluminum molybdate, silicon molybdate, magnesium molybdate (MgMo ｎ O ３ｎ＋１ (n=1 to 3)), sodium molybdate (Na ２ Mo ｎ O ３ｎ＋１ (n=1 to 3)), titanium molybdate, iron molybdate, potassium molybdate (K ２ Mo ｎ O ３ｎ＋１ (n=1 to 3)), zinc molybdate, boron molybdate, lithium molybdate (Li ２ Mo ｎ O ３ｎ＋１(n = 1 to 3)), cobalt molybdate, nickel molybdate, manganese molybdate, chromium molybdate, cesium molybdate, barium molybdate, strontium molybdate, yttrium molybdate, zirconium molybdate, copper molybdate, etc. These molybdenum oxide precursor compounds may be used alone or in combination of two or more. The form of the molybdenum oxide precursor compound is not particularly limited, and may be, for example, a powder such as molybdenum trioxide, or a liquid such as an aqueous solution of ammonium molybdate. A powder form that is easy to handle and energy efficient is preferred.

[0022] Furthermore, when ammonium molybdate is used as the molybdenum oxide precursor compound, it is converted into thermodynamically stable molybdenum trioxide by electromagnetic wave heating, and the vaporized molybdenum oxide precursor compound becomes the molybdenum trioxide.

[0023] <Other Metal Compounds> In the vaporization step according to this embodiment, in addition to the molybdenum trioxide, a metal compound such as another metal oxide may be further contained. When another metal oxide is further contained in addition to the molybdenum trioxide, the metal oxide is preferably blended in an amount of 0.1 to 50 wt %, more preferably 1 to 20 wt %, and even more preferably 5 to 10 wt %, relative to 100 wt % of the total of the molybdenum trioxide and the other metal oxide.

[0024] The metal compound other than molybdenum trioxide is not particularly limited. Examples of the metal compound other than molybdenum trioxide include aluminum compounds, silicon compounds, titanium compounds, magnesium compounds, sodium compounds, potassium compounds, zirconium compounds, yttrium compounds, zinc compounds, copper compounds, and iron compounds. Among these, aluminum compounds, silicon compounds, titanium compounds, magnesium compounds, and iron compounds are preferred, and aluminum compounds, silicon compounds, titanium compounds, and iron compounds are more preferred.

[0025] Molybdenum trioxide and a metal compound other than molybdenum trioxide may produce an intermediate, but even in this case, the intermediate is decomposed by electromagnetic heating, and molybdenum trioxide can be vaporized in a thermodynamically stable form.

[0026] Among these, it is preferable to use an aluminum compound as the metal compound other than molybdenum trioxide in order to prevent damage to the reaction apparatus used. Furthermore, it is also possible not to use any metal compound other than molybdenum trioxide in order to improve the purity of the molybdenum trioxide fine particles.

[0027] Examples of the aluminum compound include aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudo-boehmite, transition aluminum oxides (γ-aluminum oxide, δ-aluminum oxide, θ-aluminum oxide, etc.), α-aluminum oxide, mixed aluminum oxides having two or more crystal phases, etc. The aluminum compound is preferably at least one selected from the group consisting of aluminum hydroxide, boehmite, and aluminum oxide.

[0028] Examples of silicon compounds include silicon oxides such as silica.

[0029] Examples of titanium compounds include titanium oxides such as titanium oxide.

[0030] The iron compound may be an iron oxide such as iron oxide.

[0031] The metal oxide is preferably at least one selected from the group consisting of aluminum hydroxide, boehmite, aluminum oxide, silica, titanium oxide, and iron oxide.

[0032] <Electromagnetic Wave Irradiation> The frequency of the electromagnetic waves used in the vaporization step according to this embodiment is in the range of 300 to 30,000 MHz. Preferably, the frequency of the electromagnetic waves is in the range of 900 to 3,000 MHz. For example, the electromagnetic waves according to this embodiment can be generated by an electromagnetic wave generator used in a known electromagnetic wave heating device. Examples of the electromagnetic wave generator include the MRK-3050 manufactured by Kyoei Electric Furnace Manufacturing Co., Ltd. and the microwave heating device AMU-RUSH manufactured by Motoyama Corporation.

[0033] The vaporization step according to the present embodiment may be a step of irradiating the molybdenum trioxide with electromagnetic waves using an electromagnetic wave heating device to heat and vaporize the molybdenum trioxide. The electromagnetic wave heating device may include an electromagnetic wave generator and a heating unit. The heating unit may include, for example, a chamber 1 and a container 2 of an apparatus 10 for producing molybdenum trioxide particles shown in FIG. 1 .

[0034] In the vaporization process according to this embodiment, the intensity of the irradiated electromagnetic waves can be appropriately selected depending on the form, composition, weight, arrangement, installation location, etc. of the raw material to be irradiated. The intensity of the irradiated electromagnetic waves can be adjusted, for example, by the temperature of the raw material to be irradiated or the amount of vaporization. When adjusting the electromagnetic wave irradiation intensity according to the temperature of the raw material to be irradiated, for example, the irradiation intensity can be adjusted while measuring the (surface or internal) temperature of the raw material (sometimes referred to as the electromagnetic wave heating temperature) during electromagnetic wave irradiation. The electromagnetic wave heating temperature varies depending on the molybdenum trioxide and metal compound raw materials used, and the desired product molybdenum trioxide microparticles, etc. The electromagnetic wave heating temperature is preferably 800°C or higher, more preferably 850°C or higher, and even more preferably 900°C or higher. It may also be 1100°C or lower, or 1000°C or lower. When the molybdenum trioxide used as the raw material in the vaporization step is derived from the molybdenum oxide precursor compound, the electromagnetic heating temperature is preferably set to a temperature at which the molybdenum oxide precursor compound can produce molybdenum trioxide. Furthermore, when other metal compounds are contained, for example, when an aluminum compound is used as the metal compound, aluminum molybdate may be formed as an intermediate, and therefore the electromagnetic heating temperature is preferably a temperature at which the intermediate can be decomposed. In this case, the electromagnetic heating temperature is preferably, for example, 500°C to 1500°C, more preferably 600°C to 1550°C, and even more preferably 700°C to 1600°C.

[0035] The duration of electromagnetic wave irradiation (heating) is not particularly limited, and may be, for example, 10 minutes or more, 20 minutes to 10 hours, or 30 minutes to 5 hours. The duration of irradiation may be selected arbitrarily depending on the amount of molybdenum trioxide to be treated.

[0036] The electromagnetic wave irradiation (heating) may be performed continuously for a fixed period of time, or may be performed by turning the irradiation on and off intermittently. The electromagnetic wave irradiation intensity may be constant, or the electromagnetic wave irradiation intensity may be changed while maintaining the electromagnetic wave heating temperature. The manufacturing method of this embodiment is characterized in that the ON / OFF can be easily controlled compared to conventional heating methods using an electric furnace or the like.

[0037] The rate of temperature rise in the electromagnetic heating varies depending on the molybdenum oxide precursor compound used, the metal compound, the properties of the desired molybdenum trioxide fine particles, etc. The rate of temperature rise in the electromagnetic heating is preferably 1 to 200°C / min, more preferably 2 to 100°C / min, and even more preferably 5 to 50°C / min.

[0038] In the vaporization step according to this embodiment, the internal pressure near the raw material (for example, the atmospheric pressure of chamber 1 in the example shown in FIG. 1 ) is not particularly limited and may be either positive or reduced pressure. Furthermore, from the viewpoint of suitably discharging molybdenum trioxide from the container used in the vaporization step to the container used in the particulate formation step, the vaporization step is preferably carried out under reduced pressure. Specifically, the degree of reduced pressure is preferably −5000 to −10 Pa, more preferably −2000 to −20 Pa, and even more preferably −1000 to −50 Pa. A degree of reduced pressure of −5000 Pa or more is preferred because it does not require excessively high airtightness or mechanical strength from the container used in the vaporization step (for example, chamber 1 in the example shown in FIG. 1 ), thereby reducing manufacturing costs. On the other hand, a degree of reduced pressure of −10 Pa or less is preferred because it prevents clogging of the molybdenum oxide precursor compound at the outlet of the container used in the vaporization step.

[0039] In addition, a gas may be blown into the vaporization step during the electromagnetic heating in the vaporization step. In this case, the temperature of the gas blown is preferably 5 to 500°C, and more preferably 10 to 100°C.

[0040] The gas blowing speed is preferably 1 to 500 L / min, and more preferably 10 to 200 L / min, relative to an effective volume of 100 L of the container in the vaporization step.

[0041] The temperature of the vaporized molybdenum trioxide vapor varies depending on the type of molybdenum trioxide used, but is preferably 200 to 2000° C., and more preferably 400 to 1500° C. When the temperature of the vaporized molybdenum trioxide vapor is 2000° C. or lower, it usually tends to be easily atomized in a cooling pipe by blowing outside air (0 to 100° C.).

[0042] The discharge rate of molybdenum trioxide vapor discharged from the vessel in the vaporization step can be controlled by the amount of molybdenum trioxide used, the amount of the metal compound blended as needed, the temperature of electromagnetic wave heating, the gas blown into the vessel in the vaporization step, and the diameter of the exhaust port. Although it differs depending on the cooling capacity of the cooling piping, the discharge rate of molybdenum trioxide vapor from the vessel in the vaporization step to the cooling piping is preferably 0.001 to 100 g / min, and more preferably 0.1 to 50 g / min.

[0043] The content of molybdenum trioxide vapor contained in the gas discharged from the vessel in the vaporization step is preferably 0.01 to 1000 mg / L, and more preferably 1 to 500 mg / L.

[0044] [Particle Forming Step] The particle forming step in the production method of this embodiment is a step of cooling the vaporized molybdenum trioxide in an unheated atmosphere to form particles, thereby obtaining molybdenum trioxide fine particles.

[0045] The molybdenum trioxide vapor may be cooled, for example, by providing a cooling pipe (not shown) inside the particle recovery device 3 shown in Fig. 1 or between the particle recovery device 3 and the chamber 1. The cooling is performed by lowering the temperature of the cooling pipe. In this case, examples of the cooling means include cooling by blowing gas into the cooling pipe as described above, cooling by a cooling mechanism included in the cooling pipe, and cooling by an external cooling device.

[0046] The cooling temperature (temperature of the cooling pipe) is not particularly limited, but is preferably from -100 to 600°C, and more preferably from -50 to 400°C.

[0047] The cooling rate of the molybdenum trioxide vapor is not particularly limited, but is preferably 100 to 100,000°C / s, and more preferably 1,000 to 50,000°C / s. Note that as the cooling rate of the molybdenum trioxide vapor increases, there is a tendency for molybdenum trioxide fine particles to be obtained that have a smaller particle size and a larger specific surface area.

[0048] When the cooling means is a method of cooling by blowing gas into a cooling pipe, the temperature of the blown gas is preferably -100 to 300°C, more preferably -50 to 100°C.

[0049] The gas blowing speed is 0.1 to 20 m ３ / min, and 1 to 10 m ３ It is more preferable that the gas blowing speed is 0.1 m / min. ３ When the gas blowing speed is 20 m / min or more, a high cooling rate can be achieved and clogging of the cooling pipe can be prevented, which is preferable. ３ / min or less is preferable because it eliminates the need for an expensive first blowing means (exhaust fan, etc.), thereby reducing manufacturing costs.

[0050] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0051] (Raw materials, etc.) Molybdenum trioxide: manufactured by Taiyo Koko Co., Ltd., average particle size 5 μm Aluminum hydroxide: manufactured by Nippon Light Metal Co., Ltd.

[0052] (Method for Evaluating Recovery Rate of Molybdenum Trioxide Fine Particles) The recovery rate of molybdenum trioxide fine particles was calculated by the following formula: Amount of recovered molybdenum trioxide fine particles (g) / Amount of charged molybdenum trioxide powder (g)*100=Recovery rate (%)

[0053] (Method for evaluating the amount of power consumed per 1 kg of molybdenum trioxide) Output value of the heating device's wattmeter (kW·hr) / Weight of molybdenum trioxide (1 kg)

[0054] Example 1: 100 g of molybdenum trioxide (Taiyo Koko Co., Ltd., average particle size 5 μm) was placed in an alumina crucible and placed in a stainless steel chamber equipped with an electromagnetic wave irradiation port, a gas inlet, a gas outlet, and a particle collection filter. Ambient air was supplied to the chamber at a flow rate of 10 L / min using a blower. Subsequently, the molybdenum trioxide was irradiated with electromagnetic waves at a frequency of 2450 MHz at an intensity of 1000 W from the electromagnetic wave irradiation port at the top of the chamber until the surface temperature reached 850°C. After reaching 850°C, electromagnetic wave irradiation was continued to maintain 800°C by ON / OFF control of the electromagnetic wave irradiation intensity. After 75 minutes, a rapid temperature drop was observed, indicating that the molybdenum trioxide in the crucible had volatilized. The electromagnetic wave irradiation was immediately stopped, and the inside of the crucible was inspected, confirming that almost no raw molybdenum trioxide remained. The molybdenum trioxide fine particles captured on the particle collection filter were then collected. The recovery rate of the micronized molybdenum trioxide fine particles was 90%. The integrated power consumption of the input electromagnetic waves was 0.5 kW-hr, and the power consumption was 5 kW-hr / kg per 1 kg of the raw material molybdenum trioxide.

[0055] Example 2 Molybdenum trioxide microparticles were obtained in the same manner as in Example 1, except that nitrogen was supplied at 2 L / min from a cylinder and that electromagnetic waves with a frequency of 900 MHz were irradiated. The amount of electromagnetic wave power required to produce the molybdenum oxide microparticles was 0.7 kW hr, and the power consumption was 7 kW hr / kg per kg of the raw material molybdenum trioxide. The recovery rate of the molybdenum trioxide microparticles was 88%.

[0056] Example 3 Molybdenum trioxide microparticles were obtained in the same manner as in Example 1, except that a mixture of 50 g of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd., average particle size 5 μm) and 50 g of aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd.) was used. The molybdenum trioxide microparticles captured on the particle collection filter were collected. The cumulative power consumption of electromagnetic waves required to produce the molybdenum oxide microparticles was 0.6 kW hr, which was 12 kW hr / kg per kg of the raw material molybdenum trioxide. The recovery rate of the molybdenum trioxide was 85%.

[0057] Comparative Example 1 With reference to the manufacturing method described in Example 1 of Patent Document 1, molybdenum oxide microparticles were manufactured using 100 g of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd., average particle size 5 μm) placed in an alumina crucible and electrically heated (SiC heater (1000 W)). The molybdenum trioxide microparticles captured on a particle collection filter were collected, and the recovery rate was 70%. The cumulative power consumption used for heating was 2.1 kW-hr, which required a heating power of 21 kW-hr / kg, calculated per kg of molybdenum trioxide. It was confirmed that the energy consumption required to produce 1 kg of molybdenum oxide microparticles was higher than that required for electromagnetic wave irradiation.

[0058] (Discussion) The results of Examples 1 and 2 indicate that molybdenum trioxide (powder) absorbs electromagnetic waves such as microwaves (2450 MHz in Example 1, 900 MHz in Example 2) well, rapidly increasing its temperature and vaporizing. Furthermore, because the electromagnetic waves do not heat the atmosphere, vaporization is immediately suppressed by cutting off the input of electromagnetic energy, allowing for control of the amount of molybdenum trioxide vaporization. As a result, molybdenum trioxide microparticles with a fine particle size could be produced with a high recovery rate. That is, because the atmosphere surrounding molybdenum trioxide (air or an inert gas such as nitrogen) does not absorb electromagnetic waves, it is at a low temperature, but only the molybdenum trioxide is heated, resulting in vaporization by sublimation. The vaporized molybdenum trioxide is immediately cooled by the atmosphere or mixed with an externally supplied atmospheric gas (air or an inert gas) to cool and granulate. For example, favorable results were obtained in terms of recovery rate and power consumption per kg compared to Comparative Example 1, which used a conventional electric furnace firing method.

[0059] In Example 3, aluminum hydroxide or boehmite was added to the raw material molybdenum trioxide. In this case, both molybdenum trioxide fine particles and oxide (alumina) were obtained. This is thought to suppress the melting and liquefaction of molybdenum trioxide and reduce corrosiveness.

[0060] REFERENCE SIGNS LIST 1 chamber 2 container 3 particle collection device 6 intake port 8 exhaust port 10 manufacturing device (molybdenum trioxide particle manufacturing device)

Claims

1. A method for producing molybdenum trioxide microparticles, comprising: a vaporization step of heating and vaporizing molybdenum trioxide by irradiating the molybdenum trioxide with electromagnetic waves; and a particulation step of cooling the vaporized molybdenum trioxide in an unheated atmosphere to particulate the molybdenum trioxide, thereby obtaining molybdenum trioxide microparticles, wherein the frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz.

2. The method for producing molybdenum trioxide fine particles according to claim 1, wherein the frequency of the electromagnetic waves is in the range of 900 to 3000 MHz.

3. The method for producing molybdenum trioxide fine particles according to claim 1 or 2, wherein 0.1 to 50% by weight of a metal oxide is mixed with the molybdenum trioxide.

4. The method for producing molybdenum trioxide microparticles according to claim 3, wherein the metal oxide is at least one selected from the group consisting of aluminum hydroxide, boehmite, aluminum oxide, silica, titanium oxide, and iron oxide.

5. A method for producing molybdenum trioxide microparticles according to claim 1 or 2, wherein the average particle size of the molybdenum trioxide microparticles is 10 nm to 100 μm.

6. The BET specific surface area of ​​the molybdenum trioxide fine particles is 0.01 m ２ / g to 500m ２ The method for producing molybdenum trioxide fine particles according to claim 1 or 2, wherein the molybdenum trioxide content is 1 / g.

7. A method for producing molybdenum trioxide microparticles according to claim 1 or 2, wherein the molybdenum trioxide microparticles include an α crystal structure.

8. A method for producing molybdenum trioxide fine particles according to claim 1 or 2, wherein the molybdenum trioxide fine particles further contain a β crystal structure.

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