Method for producing fine molybdenum disulfide particles

Abstract

Provided is a method for producing fine molybdenum disulfide particles, by which the fine molybdenum disulfide particles can be efficiently produced at a high conversion rate even with low energy consumption. This method for producing fine molybdenum disulfide particles includes a step in which molybdenum trioxide is irradiated with electromagnetic waves in the presence of sulfur and heated thereby and the heated molybdenum trioxide is reacted with the sulfur. The electromagnetic waves have a frequency in the range of 300-30,000 MHz.

Description

Method for producing molybdenum disulfide microparticles

[0001] The present invention relates to a method for producing molybdenum disulfide fine particles. This application claims priority to Japanese Patent Application No. 2023-199089, filed on November 24, 2023, the contents of which are incorporated herein by reference.

[0002] Molybdenum sulfide is known as a lubricant for reducing friction and wear, primarily in the automotive industry, and is used in various countries, particularly as a liquid lubricant such as in engine oil. ２ Molybdenum sulfides, such as those represented by the above-mentioned compounds, are known to be used as lubricants in solid sliding members and in greases (see Patent Documents 1 to 3).

[0003] A method for producing molybdenum disulfide powder by heating molybdenum trioxide powder consisting of fine particles of molybdenum trioxide at a temperature of 200 to 1000° C. in the presence of a sulfur source is known (see Patent Document 4).

[0004] Japanese Patent Application Laid-Open No. 2017-115920 Japanese Patent Application Laid-Open No. 2013-144758 Japanese Patent No. 6614471 Japanese Patent No. 7060170

[0005] However, in conventional methods for producing molybdenum disulfide powder, electric heating is performed in the presence of molybdenum trioxide powder and a sulfur source. Therefore, not only the molybdenum trioxide powder and the sulfur source but also the surrounding atmosphere are heated, resulting in high energy consumption and difficulty in ON / OFF control. That is, conventional electric heating also heats the atmosphere surrounding the raw materials (molybdenum trioxide, sulfur) to be heated. Therefore, even if the input of heating energy is cut off, the atmosphere itself is difficult to rapidly cool, making it difficult to efficiently produce molybdenum disulfide microparticles with a fine particle size. Therefore, there is a need for a production method that can efficiently produce molybdenum disulfide microparticles with low energy consumption and high conversion.

[0006] After extensive research, the inventors discovered that molybdenum trioxide absorbs electromagnetic waves well and rapidly increases its temperature, while sulfur has poor electromagnetic wave absorption and is therefore difficult to heat by electromagnetic wave irradiation. Therefore, when molybdenum trioxide and sulfur are mixed and irradiated with electromagnetic waves, molybdenum trioxide is preferentially heated, increasing its reactivity. The high-temperature molybdenum trioxide with increased reactivity reacts with the surrounding sulfur and immediately converts to molybdenum disulfide. This heating by electromagnetic wave irradiation activates the molybdenum trioxide and suppresses sulfur vaporization and distillation, enabling efficient production of molybdenum disulfide microparticles with low energy consumption and high conversion. In other words, in this embodiment, heating by electromagnetic wave irradiation is easily controlled by ON / OFF control and irradiation intensity, and selective heating to molybdenum trioxide is possible without heating the atmosphere. Therefore, an object of the present invention is to provide a method for producing molybdenum disulfide, which can efficiently produce molybdenum disulfide fine particles at a high conversion rate even with low energy consumption.

[0007] The present embodiment is based on the findings of the present inventors, and provides the following means for solving the problems. [1] A method for producing molybdenum disulfide microparticles, comprising the steps of: irradiating molybdenum trioxide with electromagnetic waves in the presence of sulfur to heat the molybdenum trioxide and reacting the heated molybdenum trioxide with the sulfur, wherein the frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz. [2] A method for producing molybdenum disulfide microparticles according to [1], wherein the frequency of the electromagnetic waves is in the range of 900 to 2,450 MHz. [3] A method for producing molybdenum disulfide microparticles according to [1] or [2], wherein the average particle size of the molybdenum disulfide microparticles is 10 nm to 10 μm. [4] A method for producing molybdenum disulfide microparticles according to [1] or [2], wherein the BET specific surface area of ​​the molybdenum disulfide microparticles is 0.01 m ２ / g~500m ２ / g. [5] The method for producing molybdenum disulfide microparticles according to any one of [1] to [3], wherein the molybdenum disulfide microparticles contain a 2H crystal structure. [6] The method for producing molybdenum disulfide microparticles according to any one of [1] to [5], wherein the molybdenum disulfide microparticles contain a 3R crystal structure. [7] The method for producing molybdenum disulfide microparticles according to any one of [1] to [6], wherein the molybdenum trioxide has an average particle size of 10 μm or less. [8] The molybdenum trioxide has a BET specific surface area of ​​0.1 m ２ / g or more.

[0008] According to this embodiment, it is possible to provide a method for producing molybdenum disulfide fine particles that can efficiently produce molybdenum disulfide fine particles with low energy consumption and high conversion rate.

[0009] 1 is a schematic diagram of an example of an apparatus used to produce molybdenum disulfide fine particles according to one embodiment of the present invention.

[0010] (Method for Producing Molybdenum Disulfide Microparticles) A ​​method for producing molybdenum disulfide microparticles according to one embodiment of the present invention includes the steps of irradiating molybdenum trioxide with electromagnetic waves in the presence of sulfur, thereby heating the molybdenum trioxide and reacting the heated molybdenum trioxide with the sulfur. The frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz. The frequency of the electromagnetic waves is preferably in the range of 900 to 2,450 MHz. The method for producing molybdenum disulfide microparticles according to this embodiment may also include mixing molybdenum trioxide and sulfur, and irradiating the mixture with electromagnetic waves, thereby reacting the heated molybdenum trioxide with the sulfur.

[0011] In the method for producing molybdenum disulfide microparticles of this embodiment, the reaction between the molybdenum trioxide and the sulfur is preferably carried out, for example, according to the following reaction formula (1): Sulfide is released from the reaction system, leaving only molybdenum disulfide as the product in the system, and the sulfide can be easily captured with an alkali or the like without being released into the atmosphere.

[0012] 2MoO ３ + 7S -> 2MoS ２ + 3SO ２ (1)

[0013] The method for producing molybdenum disulfide microparticles of this embodiment can be suitably carried out, for example, using a molybdenum disulfide microparticle production apparatus 10 shown in FIG.

[0014] FIG. 1 is a schematic diagram of an example of an apparatus used to produce molybdenum disulfide 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 disulfide microparticle production apparatus 10 includes a chamber 1 in which electromagnetic waves generated by the electromagnetic wave irradiation device are irradiated onto a mixture of molybdenum trioxide and sulfur placed in a container 2, thereby heating the molybdenum trioxide (sometimes referred to as "electromagnetic wave heating") and causing the heated molybdenum trioxide to react with sulfur. The chamber 1 also has an external air intake 6 at its left end and an exhaust 8 at its right end. An exhaust device (not shown), which serves as a ventilation means, is connected to the intake 6. The molybdenum disulfide microparticle production apparatus 10 may also have an external cooling device (not shown), which allows for the reaction conditions in the chamber 1 to be controlled as desired.

[0015] [Molybdenum disulfide fine particles] The product obtained by the method for producing molybdenum disulfide fine particles of the present embodiment is molybdenum disulfide (MoS ２ The molybdenum disulfide fine particles according to the manufacturing method of this embodiment are made of molybdenum disulfide (MoS). ２ The molybdenum sulfide may contain molybdenum sulfides other than molybdenum trioxide (MoS). Here, molybdenum sulfide is a general term for compounds composed of molybdenum atoms and sulfur atoms. Examples of such molybdenum sulfides include those represented by MoSx (x = 1 to 3). The molybdenum disulfide (MoS) obtained can be obtained by balancing the molar ratio of molybdenum trioxide and sulfur. ２The fine particles of may also contain a certain amount of other molybdenum sulfides.

[0016] Atoms other than molybdenum atoms and sulfur atoms may be contained in molybdenum disulfide to the extent that the effects of this embodiment are not impaired. Specific examples include silicon, aluminum, sodium, iron, titanium, potassium, calcium, yttrium, etc. These other atoms may be contained alone or in combination of two or more. The content of other atoms in molybdenum disulfide is preferably 10 mol% or less, more preferably 5 mol% or less, and most preferably 2 mol% or less.

[0017] The molybdenum disulfide microparticles obtained by the manufacturing method of this embodiment can be appropriately selected and used based on their surface and internal structures, depending on the intended application. For example, when used as a catalyst, it is effective to maximize the contact area with the molecules of the reaction raw materials in order to more effectively promote the intended chemical reaction. For example, molybdenum disulfide having a structure, such as a porous structure, with pores on the surface facing inward and pores inside that are independent and / or communicate with other pores, can exhibit better catalytic activity than molybdenum disulfide having a dense structure. The size and number of pores within the hexahedrons of molybdenum sulfide can be measured by known and commonly used methods, corresponding to micropores, mesopores, or macropores, as appropriate. Specifically, Japanese Industrial Standards (JIS) Z8831 and Japanese Industrial Standards (JIS) Z8830 can be used as measurement methods. Japanese Industrial Standard (JIS) Z8831 is a method for measuring the pore size distribution and pore characteristics of powders (solids) by mercury intrusion porosimetry, with respect to pore distribution and pore volume, mainly focusing on mesopores and macropores. Japanese Industrial Standard (JIS) Z8830 is a method for measuring the BET specific surface area by nitrogen gas adsorption, with respect to the surface size inside pores, mainly focusing on micropores. Of course, these measurements may be performed in combination, if necessary.

[0018] The molybdenum disulfide fine particles of this embodiment have a specific surface area of ​​0.01 m2 as measured by the BET method. ２ / g~500m２ / g. ２ / g or more is more preferable, and 10m ２ / g or more is more preferable, and 20m ２ / g or more is more preferable. ２ / g or less, and ２ / g or less, and ２ / g or less. ２ / g is most preferred.

[0019] The average particle size of the molybdenum disulfide microparticles of this embodiment is preferably 10 nm to 100 μm. The average particle size of the molybdenum disulfide microparticles of this embodiment can be measured, for example, by a known particle size distribution measurement method. The average particle size of the molybdenum disulfide microparticles of this embodiment is more preferably 10 nm or more, more preferably 20 nm or more, and even more preferably 50 nm or more. Alternatively, it may be 100 μm or less, 10 μm or less, or 1 μm or less.

[0020] The molybdenum disulfide microparticles according to this embodiment preferably contain a 2H crystal structure. The "2H crystal structure" is a hexagonal crystal structure, which is the most stable crystal structure of molybdenum disulfide. The inclusion of the 2H crystal structure has the effect of improving the stability of the structure. The method for producing molybdenum disulfide microparticles according to this embodiment can efficiently produce molybdenum disulfide microparticles containing a 2H crystal structure. The "2H crystal structure" can be confirmed by conventional XRD (X-ray diffraction) method.

[0021] The molybdenum disulfide fine particles may have a 3R crystal structure. A "3R crystal structure" is a rhombohedral crystal with a three-layer unit cell. The inclusion of the 3R crystal structure provides excellent catalytic effects. The method for producing molybdenum disulfide fine particles according to this embodiment makes it possible to efficiently produce molybdenum disulfide fine particles containing the 3R crystal structure. The "3R crystal structure" can be confirmed by conventional XRD (X-ray diffraction) method.

[0022] [Raw Materials] In the method for producing molybdenum disulfide microparticles of this embodiment, molybdenum trioxide and sulfur are used as raw materials.

[0023] The molybdenum trioxide used in the method for producing molybdenum disulfide microparticles of this embodiment may be used alone or in combination with other molybdenum oxides such as molybdenum dioxide. The sulfur may be used alone or in combination with a sulfur compound other than sulfur, such as hydrogen sulfide. Sulfur may also be used in the reaction in the form of a solid, or may be used in the form of a liquid or gas at a high temperature. Molybdenum trioxide may be used in the reaction in the form of a solid, or may be used in the form of a liquid or gas at a high temperature.

[0024] The higher the purity of each of these raw materials, the more preferable it is, since by determining the appropriate molar numbers of each, molybdenum disulfide can be quantitatively obtained according to stoichiometry, and the content of by-products can be reduced to obtain high-purity molybdenum disulfide. However, when using molybdenum trioxide as a flux to produce particles of inorganic fillers such as alumina, spinel, and other metal composite oxides, or particles of gemstones such as ruby, sapphire, and red spinel, by a high-temperature flux method, gas containing molybdenum trioxide as a main component evaporates from the reaction system during the process. For this reason, this vapor can be recovered and reused in the production of the molybdenum disulfide microparticles of this embodiment, either as a gas or liquid, or as a solid after cooling as necessary. This method allows the production of the inorganic fillers and gemstones described above and molybdenum disulfide, useful as a catalyst, to be produced in parallel. As a result, the equipment required for recovering molybdenum trioxide, which is required for the production of the former alone, is not required. Compared to manufacturing each separately and independently, this method significantly increases the productivity of both, while reducing environmental impact, equipment costs, and installation space.

[0025] The molybdenum trioxide used in producing the molybdenum disulfide microparticles of this embodiment may have any properties. However, when used as a solid raw material in the above reaction, the molybdenum trioxide preferably has an average particle size of 10 μm or less. Furthermore, the average primary particle size of 50 molybdenum trioxide particles within the field of view of a two-dimensional image of a transmission electron microscope (TEM) photograph is more preferably 5 to 5,000 nm, and even more preferably 5 to 1,000 nm. This is because an average primary particle size of 5 to 5,000 nm or 5 to 1,000 nm not only enables a more efficient reaction but also makes it easier to obtain the molybdenum disulfide of this embodiment. The magnification of the TEM may be such that at least 50 molybdenum trioxide particles are included in one field of view in visual observation or image photography. However, based on the average vertical (length) × horizontal (width) × thickness range described below, an appropriate magnification is preferably selected from the range of 1,000 to 200,000 times. SEM may be used instead of TEM. ２ / g or more is preferred.

[0026] Any known, commonly used, commercially available molybdenum trioxide can be used as the molybdenum trioxide having the specific average primary particle size range. Furthermore, molybdenum trioxide powder having the specific average primary particle size range can be easily obtained from molybdenum trioxide having a larger average primary particle size. For example, by heating and vaporizing molybdenum trioxide, which is a relatively inexpensive, commercially available, room-temperature solid having a larger average primary particle size, and then rapidly cooling the resulting molybdenum trioxide gas, molybdenum trioxide powder having the specific average primary particle size range and which is an excellent raw material for obtaining molybdenum disulfide of this embodiment can be easily obtained.

[0027] The above-described preferable molybdenum trioxide powder can be obtained by contacting and cooling molecular molybdenum trioxide gas with a large amount of refrigerant in vast excess relative to the amount of the molybdenum trioxide gas. This principle is well known and can be realized using conventionally known equipment. When an extremely small amount of molybdenum trioxide gas is used, contacting it with a large excess of refrigerant dilutes the molybdenum trioxide gas with the refrigerant, resulting in a phase change from gas to solid, and cooling the molybdenum trioxide in an extremely short time. The larger the amount of refrigerant relative to the amount of gaseous molybdenum trioxide, the closer the state of infinite dilution becomes, enabling more rapid cooling. Cooling can be achieved by introducing a large amount of refrigerant into the system from the outside (outside the system) all at once, or intermittently or continuously by dividing the refrigerant into large amounts.

[0028] [Electromagnetic Wave Irradiation (Heating)] The frequency of the electromagnetic waves used in the method for producing molybdenum disulfide microparticles of this embodiment is in the range of 300 to 30,000 MHz. The frequency of the electromagnetic waves is preferably in the range of 900 to 3,000 MHz. For example, an electromagnetic wave generator used in a known electromagnetic wave heating device can be used as the electromagnetic waves in this embodiment. The electromagnetic wave generator may include, for example, a mechanism for ventilating a purge gas or the like, a sensor for measuring the temperature inside the furnace, and an exhaust pump for evacuating the inside of the furnace. Examples of commercially available electromagnetic wave generators include the MRK-3050 manufactured by Kyoei Electric Furnace Manufacturing Co., Ltd. and the microwave heating device AMU-RUSH manufactured by Motoyama Corporation.

[0029] The method for producing molybdenum disulfide microparticles of this embodiment may include using an electromagnetic wave heating device to irradiate molybdenum trioxide with electromagnetic waves to heat the molybdenum trioxide and react the heated molybdenum trioxide with sulfur. The electromagnetic wave heating device may include an electromagnetic wave generator and a reaction section. Molybdenum trioxide and sulfur as raw materials may be placed in the reaction section.

[0030] In the method for producing molybdenum disulfide microparticles of this embodiment, the intensity of the irradiated electromagnetic waves can be appropriately selected depending on the form, composition (the blending ratio of molybdenum trioxide and sulfur), 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. When adjusting the irradiation intensity of the irradiated electromagnetic waves depending on the temperature of the raw material to be irradiated, for example, the (surface or internal) temperature of the raw material (sometimes referred to as the electromagnetic wave heating temperature) can be measured while the electromagnetic waves are being irradiated.

[0031] The electromagnetic wave time is not particularly limited as long as the time required to supply the heating energy necessary for the reaction can be ensured, and can be, for example, 10 minutes or more, 10 minutes to 10 hours, 20 minutes to 5 hours, or 30 minutes to 3 hours.

[0032] The electromagnetic wave irradiation may be continuous for a fixed period of time, or may be intermittently turned on and off. The electromagnetic wave irradiation intensity during irradiation may be constant, or the electromagnetic wave heating temperature may be changed at a constant rate. The manufacturing method of this embodiment is characterized by the ability to control the irradiation by turning the electromagnetic wave on and off, compared to conventional heating methods using an electric furnace or the like.

[0033] In the method for producing molybdenum disulfide microparticles of this embodiment, the reaction between molybdenum trioxide and sulfur can be carried out by determining the molar ratio of each of the molybdenum trioxide and sulfur charged stoichiometrically in accordance with the reaction formula (1) above. Specifically, when molybdenum trioxide and sulfur are used as the sulfur source, the molar ratio of the charged molybdenum trioxide is preferably in the range of 2.0 to 15.0 (molar ratio), for example. The molar ratio of the charged molybdenum trioxide is more preferably in the range of 2.0 to 12 (molar ratio). The greater the excess amount of sulfur, the more effectively the presence of unreacted molybdenum trioxide can be suppressed.

[0034] From the viewpoint of energy conservation, it is more preferable that the sulfur / molybdenum trioxide (molar ratio) be in the range of 3.0 to 10. In particular, since the production method of this embodiment uses the above-mentioned electromagnetic heating, the presence of unreacted molybdenum trioxide can be suppressed even with a smaller sulfur content than with conventional electric furnace heating, as demonstrated by a comparison of the following Examples and Comparative Examples. The reaction between molybdenum trioxide and sulfur can be carried out, for example, by uniformly mixing the two materials to form a powder and then heating the powder by irradiating it with electromagnetic waves at a temperature of 200 to 1000°C in a heat-resistant container (sometimes referred to as "electromagnetic heating"). The electromagnetic wave irradiation (heating) time can be selected, for example, from the range of 2 to 10 hours. The reaction is preferably carried out at a temperature of 300 to 600°C for an electromagnetic wave irradiation (heating) time of 2 to 7 hours.

[0035] The above-mentioned electromagnetic wave irradiation (heating) can be carried out according to any electromagnetic wave irradiation (heating) profile. Specifically, for example, the temperature may be increased at a constant rate from room temperature and maintained at a constant temperature within the above-mentioned heating temperature range for a certain period of time, or the heating temperature may be changed by increasing or decreasing the temperature stepwise within the above-mentioned temperature range and maintaining each temperature for a certain period of time. Heating is preferably carried out for a time until the amount of molybdenum disulfide produced does not increase and the amount of molybdenum disulfide produced does not change (it becomes saturated).

[0036] The proportion of molybdenum disulfide microparticles containing molybdenum disulfide produced based on the above-described reaction can be determined by quantifying the amount of molybdenum disulfide. A method for quantifying the amount of molybdenum disulfide includes, for example, fixing conditions other than the time in a predetermined heating profile, sampling the product at each heating time, and quantifying the amount of molybdenum disulfide in the cooled product by inductively coupled plasma (ICP) atomic emission spectroscopy. By understanding the relationship between time and molybdenum disulfide in this way, the end point of the reaction can be determined solely by the heating time when implementing the production method of this embodiment industrially.

[0037] If necessary, the reaction can be carried out under ventilation. Specifically, the reaction can be carried out in a heat-resistant container while passing an inert gas such as helium or argon, or nitrogen or air.

[0038] When producing molybdenum disulfide from molybdenum trioxide and sulfur, the electromagnetic wave irradiation (heating) conditions may be within the above-described ranges. Furthermore, by appropriately selecting the electromagnetic wave irradiation (heating) rate, ON / OFF control, and the like, it is possible to prevent the reaction with molybdenum trioxide from proceeding sufficiently, resulting in a large amount of unreacted molybdenum trioxide remaining. If the electromagnetic wave irradiation (heating) rate, ON / OFF control, and the like are not appropriately selected, the temperature rise rate is slow, and sulfur volatilizes out of the system before the reaction. As a result, the reaction with molybdenum trioxide may not proceed sufficiently, resulting in a large amount of unreacted molybdenum trioxide remaining. Furthermore, by placing a lid on the heat-resistant container in which the reaction is carried out so as not to seal it, it is possible to similarly prevent the sulfur from volatilizing out of the system, thereby further preventing a large amount of unreacted molybdenum trioxide from remaining. These methods can also be used in combination. The rate of temperature rise can be controlled, for example, by measuring the temperature of the mixture of molybdenum trioxide and sulfur being heated, and controlling the ON / OFF of the electromagnetic wave irradiation or the irradiation intensity so that the rate of temperature rise is constant. Examples of methods for measuring the temperature of the mixture include a method of measuring the temperature by inserting a thermocouple into the mixture, and a method of measuring the temperature of the mixture by thermography. Furthermore, even when maintaining a constant temperature after heating, the temperature of the mixture can be measured using the temperature measurement method described above, and the ON / OFF of the electromagnetic wave irradiation or the irradiation intensity can be controlled so as to maintain that temperature.

[0039] [MoS ２ In the method for producing molybdenum disulfide microparticles of this embodiment, as explained above, the reaction occurs stoichiometrically according to the reaction formula shown in the above formula (1). Therefore, when the molar ratio of molybdenum trioxide to sulfur charged is in a range in which sulfur is in excess, the presence of unreacted molybdenum trioxide can be suppressed. This can be evaluated by the MoS ２ The conversion rate of MoS２ The "conversion rate (unit: %)" refers to the number of moles of molybdenum disulfide contained in the produced molybdenum disulfide microparticles per 100 moles of molybdenum trioxide blended as a raw material. For example, when 80 moles of molybdenum disulfide are produced using 100 moles of molybdenum trioxide, the conversion rate of MoS is ２ In the method for producing molybdenum disulfide fine particles of this embodiment, the conversion rate of MoS of the produced molybdenum disulfide fine particles is 80%. ２ The conversion rate of molybdenum trioxide is related to the molar ratio of molybdenum trioxide to sulfur. When the molar ratio of molybdenum trioxide to sulfur is in a range where sulfur is in excess, MoS ２ Furthermore, as will be demonstrated in the examples and comparative examples below, the method for producing molybdenum disulfide fine particles of this embodiment can directly heat only molybdenum trioxide using electromagnetic waves. Therefore, compared to the conventional electric furnace heating method, even if the molar ratio of molybdenum trioxide to sulfur is the same, a high MoS conversion rate can be achieved. ２ A conversion rate of MoS is obtained. ２ Since the conversion rate of MoS is high, the excess amount of sulfur in the production method of this embodiment may be lower than that in the conventional electric furnace heating method. ２ The method for evaluating the conversion rate will be described in detail in the Examples.

[0040] The present invention will be described in more detail below based on examples, but the present invention is not limited to the following examples.

[0041] (Raw materials, etc.) Molybdenum trioxide: manufactured by Taiyo Koko Co., Ltd., average particle size 5 μm Sulfur (manufactured by Kanto Chemical Co., Ltd.)

[0042] (Apparatus) XRD measurement apparatus: Rigaku Corporation, Ultima IV

[0043] (MoS ２ Method for evaluating the conversion rate of molybdenum disulfide particles MoS ２ Conversion rate R Ｃ can be calculated by the RIR (reference intensity ratio) method from profile data obtained by measuring molybdenum disulfide particles by X-ray diffraction (XRD). ２ Conversion rate RＣ can be obtained. R Ｃ (%) = (I Ａ / K Ａ ) / ((I Ａ / K Ａ ) + Σ(I Ｂ / K Ｂ )) × 100 (2) In the above formula (2), K Ａ However, molybdenum disulfide (MoS ２ ) is the RIR value of I Ａ , but molybdenum disulfide (MoS ２ is the integrated intensity of the peak at about 2θ=14.4°±0.5°, which is attributed to the (002) or (003) plane of the crystal; Ｂ However, each molybdenum oxide (raw material MoO ３ , and the reaction intermediate Mo ９ O ２５ , Mo ４ O １１ , MoO ２ ) is the RIR value of I Ｂ However, each molybdenum oxide (raw material MoO ３ , and the reaction intermediate Mo ９ O ２５ , Mo ４ O １１ , MoO ２ The RIR value is the integrated intensity of the strongest peak of the inorganic crystal structure database (ICSD) (manufactured by the Japan Chemical Information Association), and the analysis can be performed using integrated powder X-ray analysis software (PDXL2, manufactured by Rigaku Corporation).

[0044] Synthesis Example 1 Molybdenum trioxide was produced using a method similar to that described in Example 1 of Patent Document 4. 1 kg of transition aluminum oxide (activated alumina, average particle size 45 μm, manufactured by Wako Pure Chemical Industries, Ltd.) was mixed with 1 kg of molybdenum trioxide (manufactured by Taiyo Koko Co., Ltd.). The resulting mixture was then charged into a sagger and fired at 1100°C for 10 hours in the firing furnace 2 of the production apparatus 1 shown in Figure 1 of Patent Document 4. During firing, outside air (air flow rate: 50 L / min, outside air temperature: 25°C) was introduced from the side and bottom of the firing furnace 2. Molybdenum trioxide evaporated in the firing furnace 2, cooled near the recovery device 4, and precipitated as particles. An RHK simulator (manufactured by Noritake Co., Ltd.) was used as the firing furnace 2, and a VF-5N dust collector (manufactured by Amano Corporation) was used as the recovery device 4.

[0045] After calcination, 1.0 kg of blue powder, aluminum oxide, and 0.85 kg of molybdenum trioxide powder were taken out from the scabbard and recovered by recovery machine 4. The recovered molybdenum trioxide powder had an average primary particle size of 80 nm, and X-ray fluorescence (XRF) measurement confirmed that the purity of the molybdenum trioxide was 99.7%. The specific surface area (SA) of this molybdenum trioxide powder measured by the BET method was 44.0 m. ２ The evaluation method of Synthesis Example 1 was the same as that used in Example 1 of Patent Document 4.

[0046] Example 1: 1.00 g of molybdenum trioxide (5 μm, manufactured by Taiyo Koko Co., Ltd.) and 1.57 g of sulfur (manufactured by Kanto Chemical Co., Ltd.) were mixed using a stirrer. The mixed raw material was then placed in an alumina crucible. The crucible was then placed in a stainless steel chamber equipped with an electromagnetic wave irradiation port, a gas inlet, and a gas outlet. Nitrogen was then supplied to the chamber at a flow rate of 0.5 L / min using a nitrogen gas cylinder, and the chamber interior was completely replaced with nitrogen. Subsequently, under a nitrogen gas flow rate of 0.5 L / min, the mixed raw material in the crucible was irradiated with electromagnetic waves at a frequency of 2450 MHz and an intensity of 100 W from the electromagnetic wave irradiation port at the top of the chamber, and heated until the temperature of the mixed raw material reached 450°C. The temperature of the mixed raw material was monitored non-contact from the electromagnetic field irradiation port using a radiation thermometer. After the mixed raw material temperature reached 450°C, the electromagnetic wave irradiation intensity was adjusted to maintain the temperature at 450°C. The electromagnetic wave irradiation was stopped one hour after the temperature reached 450°C, and after waiting for the internal temperature of the crucible to drop to 50°C or less, the supply of nitrogen was stopped and the powder was recovered from the crucible. ２ There are characteristic peaks derived from MoS ２ The formation of fine particles was confirmed. ２ It was confirmed that the conversion rate was 60% or more.

[0047] Example 2 Synthesis of molybdenum sulfide fine particles was carried out in the same manner as in Example 1, except that the molybdenum trioxide obtained in Synthesis Example 1 was used. ２ There are characteristic peaks derived from MoS ２ The formation of fine particles was confirmed. ２ It was confirmed that the conversion rate was 80% or more.

[0048] Comparative Example 1 With reference to Comparative Example 2 of Patent Document 4, molybdenum sulfide fine particles were produced by electrical heating. ２ It was confirmed that the conversion rate to molybdenum sulfide was low, at 53%. It was confirmed that the energy consumption for producing 1 kg of molybdenum sulfide fine particles was higher than that for heating by electromagnetic wave irradiation.

[0049] (Discussion) Examples 1 and 2 have higher MoS than Comparative Example 1. ２A conversion rate of 1000 ppm was obtained. In Examples 1 and 2, electromagnetic wave heating was used, so molybdenum trioxide absorbed electromagnetic waves (microwaves) well and its temperature rose quickly. On the other hand, sulfur has poor electromagnetic wave absorption, so sulfur itself is not easily heated by electromagnetic wave irradiation. Therefore, sulfur vaporization was suppressed. When molybdenum trioxide and sulfur were mixed and irradiated with electromagnetic waves, molybdenum trioxide was heated preferentially, increasing its reactivity. Some of the high-temperature molybdenum trioxide with increased reactivity reacted with the surrounding sulfur and was immediately converted to molybdenum disulfide. This heating by electromagnetic wave irradiation activated the molybdenum trioxide and suppressed the vaporization and distillation of sulfur, enabling efficient production of molybdenum disulfide microparticles.

[0050] In Example 2, the molybdenum trioxide fine particles obtained in Synthesis Example 1 were used, and the reaction efficiency with sulfur was further increased compared to Example 1. As a result, Example 2 exhibited a higher MoS than Example 1. ２ A conversion of 100% was obtained.

[0051] REFERENCE SIGNS LIST 1 chamber 2 container 6 intake port 8 exhaust port 10 manufacturing device (molybdenum disulfide microparticle manufacturing device)

Claims

1. A method for producing molybdenum disulfide fine particles, comprising the steps of: irradiating molybdenum trioxide with electromagnetic waves in the presence of sulfur, thereby heating the molybdenum trioxide and reacting the heated molybdenum trioxide with the sulfur; wherein the frequency of the electromagnetic waves is in the range of 300 to 30,000 MHz.

2. The method for producing molybdenum disulfide microparticles according to claim 1, wherein the frequency of the electromagnetic waves is in the range of 900 to 2450 MHz.

3. The method for producing molybdenum disulfide microparticles according to claim 1 or 2, wherein the average particle size of the molybdenum disulfide microparticles is 10 nm to 10 μm.

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

5. A method for producing molybdenum disulfide microparticles according to claim 1 or 2, wherein the molybdenum disulfide microparticles contain a 2H crystal structure.

6. A method for producing molybdenum disulfide microparticles according to claim 1 or 2, wherein the molybdenum disulfide microparticles contain a 3R crystal structure.

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

8. The BET specific surface area of ​​the molybdenum trioxide is 0.1 m ２ The method for producing molybdenum disulfide fine particles according to claim 1 or 2, wherein the molybdenum disulfide content is 1 / g or more.

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