Method for producing molybdenum disulfide fine 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

[Technical Field]

[0001] This invention relates to a method for producing molybdenum disulfide fine particles. This application claims priority based on Japanese Patent Application No. 2023-199089, filed in Japan on November 24, 2023, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] Molybdenum sulfide is known as a lubricant for reducing friction and wear, mainly in the automotive industry, and is used in various countries, especially as a liquid lubricant such as engine oil. Molybdenum sulfide, represented by molybdenum disulfide (MoS2), is known to have applications as a lubricant contained in solid sliding parts and greases (see Patent Documents 1-3).

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

[0004] [Patent Document 1] Japanese Patent Publication No. 2017-115920 [Patent Document 2] Japanese Patent Publication No. 2013-144758 [Patent Document 3] Patent No. 6614471 [Patent Document 4] Patent No. 7060170 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] However, conventional methods for producing molybdenum disulfide powder involve electric heating in the presence of molybdenum trioxide powder and a sulfur source. As a result, not only the molybdenum trioxide powder and the sulfur source, but also the surrounding atmosphere is heated, leading to high energy consumption and making ON / OFF control difficult. In other words, conventional electric heating heats the atmosphere surrounding the raw materials being heated (molybdenum trioxide and sulfur). Therefore, even if the input of heating energy is cut off, the atmosphere itself does not cool rapidly, making it difficult to efficiently produce molybdenum disulfide fine particles with a fine particle size. Consequently, there is a need for a manufacturing method that can efficiently produce molybdenum disulfide fine particles with low energy consumption and a high conversion rate.

[0006] As a result of diligent research, the inventors have found that molybdenum trioxide absorbs electromagnetic waves well and its temperature rises rapidly, while sulfur has poor electromagnetic wave absorption, and therefore sulfur itself is not easily heated by electromagnetic wave irradiation. Thus, when molybdenum trioxide and sulfur are mixed and irradiated with electromagnetic waves, the molybdenum trioxide is preferentially heated, and its reaction activity increases. Some of this highly reactive, high-temperature molybdenum trioxide reacts with the surrounding sulfur and is immediately converted to molybdenum disulfide. This heating by electromagnetic wave irradiation activates the reaction of molybdenum trioxide, suppresses the vaporization and distillation of sulfur, and enables the efficient production of molybdenum disulfide fine particles with low energy consumption and a high conversion rate. In other words, 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, the objective is to provide a method for producing molybdenum disulfide that can efficiently produce molybdenum disulfide fine particles with a high conversion rate even with low energy consumption. [Means for solving the problem]

[0007] This embodiment is based on the aforementioned findings by the inventors, and the means for solving the aforementioned problems are as follows. [1] A step of heating molybdenum trioxide by irradiating electromagnetic waves to the molybdenum trioxide in the presence of sulfur, and reacting the heated molybdenum trioxide with the sulfur, is included. A method for producing molybdenum disulfide fine particles, characterized in that the frequency of the electromagnetic waves is in the range of 300 to 30000 MHz. [2] The method for producing molybdenum disulfide fine particles according to [1], wherein the frequency of the electromagnetic waves is in the range of 900 to 2450 MHz. [3] The method for producing molybdenum disulfide fine particles according to [1] or [2], wherein the average particle diameter of the molybdenum disulfide fine particles 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 500 m 2 / g. The method for producing molybdenum disulfide fine particles according to any one of [1] to [3]. [5] The method for producing molybdenum disulfide fine particles according to any one of [1] to [4], wherein the molybdenum disulfide fine particles contain a 2H crystal structure. [6] The method for producing molybdenum disulfide fine particles according to any one of [1] to [5], wherein the molybdenum disulfide fine particles contain a 3R crystal structure. [7] The method for producing molybdenum disulfide fine particles according to any one of [1] to [6], wherein the average particle diameter of the molybdenum trioxide is 10 μm or less. [8] The BET specific surface area of the molybdenum trioxide is 0.1 m 2 / g or more. The method for producing molybdenum disulfide fine particles according to any one of [1] to [7].

Advantages of the Invention

[0008] According to the present 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.

Brief Description of the Drawings

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

Mode for Carrying Out the Invention

[0010] (Method for Manufacturing Molybdenum Disulfide Fine Particles) The method for manufacturing molybdenum disulfide fine particles according to an embodiment of the present invention includes a step of heating molybdenum trioxide by irradiating electromagnetic waves to molybdenum trioxide in the presence of sulfur, and reacting the heated molybdenum trioxide with the sulfur. The frequency of the electromagnetic waves is in the range of 300 to 30000 MHz. The frequency of the electromagnetic waves is preferably in the range of 900 to 2450 MHz. In the method for manufacturing molybdenum disulfide fine particles of this embodiment, molybdenum trioxide and sulfur may be mixed, and electromagnetic waves may be irradiated to the mixture to react the heated molybdenum trioxide with the sulfur.

[0011] [[ID=十六]]In the method for manufacturing molybdenum disulfide fine particles of this embodiment, the reaction between molybdenum trioxide and sulfur is preferably carried out, for example, according to the reaction formula shown in the following formula (1). Sulfide is released from the reaction system, and only molybdenum disulfide remains in the system as a product. Sulfide can be easily captured with an alkali or the like without being released into the atmosphere.

[0012] 2MoO3 + 7S -> 2MoS2 + 3SO2 (1)

[0013] The method for manufacturing molybdenum disulfide fine particles of this embodiment can be preferably carried out, for example, using the molybdenum disulfide fine particle manufacturing apparatus 10 shown in FIG. 1.

[0014] It should be noted that in the translation of item , the content in Chinese in the original text seems to be incorrect. I translated it according to the overall context. If there are any specific requirements or corrections, please let me know.Figure 1 is a schematic diagram of an example of an apparatus used for producing molybdenum disulfide fine particles in this embodiment. An electromagnetic wave irradiation device (sometimes referred to as an "electromagnetic wave irradiation device," not shown) is located at the top of the chamber 1. The molybdenum disulfide fine particle production apparatus 10 has a chamber 1 that heats the molybdenum trioxide (hereinafter sometimes referred to as "electromagnetic wave heating") by irradiating the mixture of molybdenum trioxide and sulfur, which is placed in a container 2, with electromagnetic waves generated by the electromagnetic wave irradiation device, and reacts the heated molybdenum trioxide with sulfur. The chamber 1 also has an outside air intake port 6 at its left end and an exhaust port 8 at its right end. An exhaust device (not shown), which is a means of blowing air, is connected to the intake port 6. The molybdenum disulfide fine particle production apparatus 10 may also have an external cooling device (not shown), which makes it possible to arbitrarily control the reaction conditions of the chamber 1.

[0015] [Molybdenum disulfide fine particles] The product obtained by the method for producing molybdenum disulfide fine particles of this embodiment is fine particles composed of molybdenum disulfide (MoS2). It has a certain preferred average particle size range as described later. The molybdenum disulfide fine particles according to the production method of this embodiment may also contain molybdenum sulfides other than molybdenum disulfide (MoS2). 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=1~3). Depending on the balance of the molar ratio of molybdenum trioxide and sulfur used, the obtained molybdenum disulfide (MoS2) fine particles may also contain a certain amount of other molybdenum sulfides.

[0016] Other atoms besides molybdenum and sulfur atoms may be included in molybdenum disulfide to the extent that they do not hinder the effects of this embodiment. Specific examples include silicon, aluminum, sodium, iron, titanium, potassium, calcium, and yttrium. These other atoms may be included individually or in a mixture 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 fine particles obtained by the production method of this embodiment can be appropriately selected and used according to the intended use, based on the surface and internal structures. For example, when using it as a catalyst itself, it is effective to increase the contact area with the molecules of the reaction raw materials as much as possible in order to make the intended chemical reaction proceed more effectively. For example, molybdenum disulfide having a structure with pore entrances facing inward on the surface and independent pores and / or pores communicating with other surfaces inside, such as a porous structure, can exhibit catalytic activity compared to that with a medium-density structure. Regarding the size and amount of pores inside the hexahedron of molybdenum disulfide, it can be appropriately measured by known and commonly used methods corresponding to each of micropores, mesopores or macropores. Specifically, Japanese Industrial Standard (JIS) Z8831 and Japanese Industrial Standard (JIS) Z8830 can be cited as measurement methods. Japanese Industrial Standard (JIS) Z8831 is a measurement method for the pore size distribution and pore characteristics of powder (solid) by mercury intrusion method regarding the pore distribution and pore volume centered on mesopores and macropores. Japanese Industrial Standard (JIS) Z8830 is a measurement method for the BET specific surface area by nitrogen gas adsorption method regarding the surface size inside the pores centered on micropores. Of course, if necessary, these can be combined for measurement.

[0018] The specific surface area of the molybdenum disulfide fine particles of this embodiment by the BET method is 2 / g to 500 m 2 / g, preferably. It is more preferably 1 m 2 / g or more, more preferably 10 m 2 / g or more, and even more preferably 20 m 2 / g or more. It may be 500 m 2 / g or less, may be 200 m 2 / g or less, and may be 100 m 2It may be less than / g. 20-200m 2 It is most preferable that the value be / g.

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

[0020] The molybdenum disulfide fine particles 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 for molybdenum disulfide. Including the 2H crystal structure has the effect of improving structural stability. The method for producing molybdenum disulfide nanoparticles according to this embodiment allows for the efficient production of molybdenum disulfide nanoparticles containing a 2H crystal structure. Conventional XRD (X-ray diffraction) methods can be used to confirm the "2H crystal structure".

[0021] The molybdenum disulfide nanoparticles may also contain a 3R crystal structure. A "3R crystal structure" refers to a rhombohedral crystal with a three-layer unit cell. The presence of a 3R crystal structure results in excellent catalytic effects. The method for producing molybdenum disulfide nanoparticles according to this embodiment allows for the efficient production of molybdenum disulfide nanoparticles containing a 3R crystal structure. Conventional XRD (X-ray diffraction) methods can be used to confirm the "3R crystal structure".

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

[0023] The molybdenum trioxide used in the method for producing molybdenum disulfide fine particles 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 other sulfur compounds such as hydrogen sulfide. The sulfur may be used in solid form during the reaction, or in liquid or gaseous form at high temperatures. The molybdenum trioxide may be used in solid form during the reaction, or in liquid or gaseous form at high temperatures.

[0024] The higher the purity of each of these raw materials, the more desirable it is, because by determining the appropriate number of moles to use for each, molybdenum disulfide can be obtained quantitatively in accordance with stoichiometry, and the lower the by-product content, the higher the purity of the molybdenum disulfide can be obtained. However, when using molybdenum trioxide as a flux to produce particles of inorganic fillers such as alumina, spinel, and other metal composite oxides, or gemstones such as ruby, sapphire, and red spinel, using a high-temperature flux method, a gas mainly composed of molybdenum trioxide evaporates from the reaction system during the process. Therefore, this vapor can be recovered and reused in the production of molybdenum disulfide fine particles in this embodiment, either as a gas or liquid, or cooled to a solid as needed. With this method, the production of the inorganic fillers and gemstones mentioned above can be carried out in parallel with the production of molybdenum disulfide, which is useful as a catalyst, for example. As a result, the equipment required to recover molybdenum trioxide, which is necessary when producing the former alone, becomes unnecessary. Compared to producing each separately and independently, it is possible to significantly increase the productivity of both while suppressing environmental impact, equipment costs, and installation space.

[0025] The molybdenum trioxide used in the production of molybdenum disulfide fine particles in this embodiment may have any properties, but when used as a solid raw material in the above reaction, it is preferable that the average particle size of the molybdenum trioxide be 10 μm or less. Furthermore, it is more preferable that the average primary particle size of 50 molybdenum trioxide particles within the field of view of the two-dimensional image of the transmission electron microscope (TEM) photograph is 5 to 5000 nm, and even more preferable that it is 5 to 1000 nm. This is because when the average primary particle size is 5 to 5000 nm or 5 to 1000 nm, not only can a more efficient reaction be carried out, but the molybdenum disulfide of this embodiment described above can be obtained more easily. The TEM magnification should be such that at least 50 molybdenum trioxide particles are included in one field of view in the visual observation or image photograph, but it is preferable to select an appropriate magnification from the range of 1000 to 200000x on average, based on the range of length × width × thickness, as described later. SEM can be used instead of TEM. Furthermore, the BET specific surface area of ​​the molybdenum trioxide is 0.1 m². 2 It is preferable that the amount is 1 / g or more.

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

[0027] The molybdenum trioxide powder, a suitable raw material as described above, can be obtained by cooling the molecularly formed molybdenum trioxide gas with a large amount of refrigerant that is in a large excess compared to the amount of molybdenum trioxide gas. This principle itself is well known and can be realized with commonly known and conventional equipment. If the amount of molybdenum trioxide gas is very small, contact with a large excess of refrigerant will dilute the molybdenum trioxide gas with the refrigerant, and the molybdenum trioxide will be cooled in a very short time, undergoing a phase change from gas to solid. The larger the amount of refrigerant compared to the amount of gaseous molybdenum trioxide, the closer it approaches an infinite dilution state, enabling rapid cooling. Cooling can be performed 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 large amount of refrigerant.

[0028] [Electromagnetic wave irradiation (heating)] The frequency of the electromagnetic waves used in the method for producing molybdenum disulfide fine particles in this embodiment is in the range of 300 to 30000 MHz. Preferably, the frequency of the electromagnetic waves is in the range of 900 to 3000 MHz. The electromagnetic waves in this embodiment can be generated using, for example, an electromagnetic wave generator used in a known electromagnetic wave heating device. The electromagnetic wave generator may include, for example, a mechanism for supplying purge gas, a sensor for measuring the furnace temperature, and an exhaust pump for creating a vacuum inside the furnace. Examples of commercially available electromagnetic wave generators include the MRK-3050 manufactured by Kyoei Electric Furnace Works Co., Ltd. and the AMU-RUSH microwave heating device manufactured by Motoyama Corporation.

[0029] In this embodiment, the method for producing molybdenum disulfide fine particles may involve using an electromagnetic wave heating device to heat molybdenum trioxide by irradiating it with electromagnetic waves, and then reacting the heated molybdenum trioxide with sulfur. The electromagnetic wave heating device may include an electromagnetic wave generator and a reaction section. In the reaction section, molybdenum trioxide and sulfur can be placed as raw materials.

[0030] In the method for producing molybdenum disulfide fine particles of this embodiment, the intensity of the irradiated electromagnetic waves can be appropriately selected according to the form, composition (ratio of molybdenum trioxide to sulfur), weight, arrangement, and installation location 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 electromagnetic waves based on the temperature of the raw material being irradiated, for example, the temperature of the raw material (surface or internal) (sometimes called the electromagnetic wave heating temperature) can be measured while the electromagnetic waves are being irradiated.

[0031] Regarding the duration of electromagnetic wave exposure, there are no particular restrictions as long as sufficient time is available to supply the heating energy necessary for the reaction. For example, it can be 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 it may be irradiated intermittently by switching it ON / OFF. The irradiation intensity of the electromagnetic waves during irradiation may be constant, or the electromagnetic wave heating temperature may be kept constant and vary. The manufacturing method of this embodiment is characterized by the fact that it can be controlled by switching it ON / OFF, compared to conventional heating methods such as electric furnaces.

[0033] In the method for producing molybdenum disulfide fine particles of this embodiment, the reaction between molybdenum trioxide and sulfur can be carried out stoichiometrically according to the reaction equation shown in formula (1) above, and the respective molar ratios for each component should be determined accordingly. Specifically, when using molybdenum trioxide and sulfur as the sulfur source, the molar ratios for each component are preferably in the range of sulfur / molybdenum trioxide (molar ratio) = 2.0 to 15.0. It is more preferable that the sulfur / molybdenum trioxide (molar ratio) is in the range of 2.0 to 12. The amount of sulfur added is such that the greater the excess amount of sulfur, the more the presence of unreacted molybdenum trioxide can be suppressed.

[0034] From an energy-saving perspective, it is even more preferable to set the sulfur / molybdenum trioxide (molar ratio) to a range of 3.0 to 10. In particular, since the manufacturing method of this embodiment uses electromagnetic wave heating as described above, as will be demonstrated by the comparison between the later examples and comparative examples, the presence of unreacted molybdenum trioxide can be suppressed even with a smaller amount of sulfur than when using conventional electric furnace heating. The reaction between molybdenum trioxide and sulfur can be carried out, for example, by pre-mixing the two substances uniformly into a powder and heating it in a heat-resistant container by irradiating it with electromagnetic waves at a temperature of 200 to 1000°C (sometimes referred to as "electromagnetic wave heating"). The electromagnetic wave irradiation (heating) time can be selected from, for example, a range of 2 to 10 hours. Preferably, the reaction is carried out at a temperature of 300 to 600°C and with an electromagnetic wave irradiation (heating) time of 2 to 7 hours.

[0035] The electromagnetic wave irradiation (heating) described above can be performed using any electromagnetic wave irradiation (heating) profile. Specifically, for example, the temperature may be raised from room temperature at a constant rate and maintained at a constant temperature within the above heating temperature range for a certain period of time, or the heating temperature may be changed by gradually raising or lowering the temperature within the above temperature range and maintaining each temperature for a certain period of time. It is preferable to perform the heating for a period of time until the amount of molybdenum disulfide produced does not increase and its production amount stops changing (saturation).

[0036] The proportion of molybdenum disulfide fine particles containing molybdenum disulfide produced based on the reaction described above can be determined by quantifying the molybdenum disulfide. One method for quantifying molybdenum disulfide is to fix all conditions except time in a predetermined heating profile, sample the product at each heating time, and quantify the molybdenum disulfide in the cooled product using inductively coupled plasma (ICP) emission spectroscopy. By understanding the time-molybdenum disulfide relationship in this way, the reaction endpoint can be determined solely by the heating time when industrially implementing the manufacturing method of this embodiment.

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

[0038] When obtaining molybdenum disulfide from molybdenum trioxide and sulfur, the electromagnetic wave irradiation (heating) conditions should be within the range described above. Furthermore, by appropriately selecting the electromagnetic wave irradiation (heating) rate and ON / OFF control, it is possible to suppress insufficient reaction with molybdenum trioxide and the resulting retention of a large amount of unreacted molybdenum trioxide. If the electromagnetic wave irradiation (heating) rate and ON / OFF control are not appropriately selected, the heating rate will be slow, and sulfur will volatilize out of the system before the reaction occurs. As a result, the reaction with molybdenum trioxide may not occur sufficiently, and a large amount of unreacted molybdenum trioxide may remain. Similarly, by covering the heat-resistant container used for this reaction with a lid that does not seal it tightly, the volatilization of sulfur out of the system can be suppressed, further reducing the retention of a large amount of unreacted molybdenum trioxide. These methods can also be used in combination. Regarding methods for controlling the heating rate, for example, the temperature of the mixture of molybdenum trioxide and sulfur being heated can be measured, and the ON / OFF or irradiation intensity of electromagnetic wave irradiation can be controlled so that the heating rate remains constant. Methods for measuring the temperature of the mixture include, for example, inserting a thermocouple into the mixture and measuring the temperature, or measuring the temperature of the mixture using thermography. Furthermore, when maintaining a constant temperature after heating, the temperature of the mixture can be measured using the above temperature measurement method, and the ON / OFF or irradiation intensity of electromagnetic wave irradiation can be controlled to maintain that temperature.

[0039] [Conversion rate of MoS2] In the method for producing molybdenum disulfide fine particles of this embodiment, the reaction proceeds stoichiometrically according to the reaction equation shown in formula (1) above, as described above. Therefore, when the molar ratio of molybdenum trioxide to sulfur is within a range where sulfur is in excess, the presence of unreacted molybdenum trioxide can be suppressed. This can be confirmed by the conversion rate of MoS2. Here, "MoS2 conversion rate (in %)" refers to the number of moles of molybdenum disulfide contained in the generated molybdenum disulfide nanoparticles for every 100 moles of molybdenum trioxide blended as a raw material. For example, if 80 moles of molybdenum disulfide are produced using 100 moles of molybdenum trioxide, the MoS2 conversion rate is 80%. In the method for producing molybdenum disulfide fine particles of this embodiment, the conversion rate of MoS2 in the produced molybdenum disulfide fine particles is related to the molar ratio of molybdenum trioxide and sulfur used in the charge. When the molar ratio of molybdenum trioxide and sulfur is within a range where sulfur is in excess, the conversion rate of MoS2 is high. Furthermore, as demonstrated in the later examples and comparative examples, the method for producing molybdenum disulfide fine particles of this embodiment can directly heat only molybdenum trioxide using electromagnetic waves. Therefore, compared to conventional electric furnace heating methods, a higher MoS2 conversion rate can be obtained even with the same molar ratio of molybdenum trioxide and sulfur. Also, because of the high MoS2 conversion rate, the excess amount of sulfur in the manufacturing method of this embodiment may be lower than in conventional electric furnace heating methods. The method for evaluating the conversion rate of MoS2 will be explained in detail in the examples. [Examples]

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

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

[0042] (Device) XRD measuring device: Rigaku Corporation, UltimaIV

[0043] (Method for evaluating the conversion rate of MoS2) Conversion rate R of molybdenum disulfide particles to MoS2 C The conversion rate R to MoS2 can be determined from profile data obtained by X-ray diffraction (XRD) measurement of molybdenum disulfide particles using the RIR (reference intensity ratio) method. The conversion rate R to MoS2 can be obtained from the following equation (2). C It is possible to find this. R C (%)=(I A / K A ) / ((I A / K A )+Σ(I B / K B )) × 100 (2) In the above equation (2), K A However, this is the RIR value for molybdenum disulfide (MoS2), I A However, this is the integrated intensity of the peak around 2θ = 14.4° ± 0.5°, which is attributed to the (002) or (003) plane of molybdenum disulfide (MoS2). K B However, each molybdenum oxide (MoO3 as the starting material, and Mo9O as the reaction intermediate) 25 Mo4O 11 This is the RIR value (such as MoO2), I B However, each molybdenum oxide (MoO3 as the starting material, and Mo9O as the reaction intermediate) 25 Mo4O 11 This is the integrated intensity of the strongest peak (e.g., MoO2). Here, the RIR values ​​can be those listed in the Inorganic Crystal Structure Database (ICSD) (manufactured by the Japan Chemical Information Association), and the integrated powder X-ray diffraction software (PDXL2, manufactured by Rigaku Corporation) can be used for the analysis.

[0044] (Synthesis Example 1) Molybdenum trioxide was produced using the same method as in Example 1 of Patent Document 4 described above. One kilogram of transition aluminum oxide (manufactured by Wako Pure Chemical Industries, Ltd., activated alumina, average particle size 45 μm) and one kilogram of molybdenum trioxide (manufactured by Taiyo Mining Co., Ltd.) were mixed. The resulting mixture was then placed in a sieve and calcined at a temperature of 1100°C for 10 hours in the calcination furnace 2 of the manufacturing apparatus 1 shown in Figure 1 of Patent Document 4. During calcination, outside air (airflow rate: 50 L / min, outside air temperature: 25°C) was introduced from the sides and bottom of the calcination furnace 2. After the molybdenum trioxide evaporated in the calcination furnace 2, it was cooled near the recovery unit 4 and precipitated as particles. An RHK simulator (manufactured by Noritake Co., Ltd.) was used as the calcination furnace 2, and a VF-5N dust collector (manufactured by Amano Corporation) was used as the recovery unit 4.

[0045] After firing, 1.0 kg of blue aluminum oxide powder and 0.85 kg of molybdenum trioxide powder recovered by recovery machine 4 were taken from the sac. The recovered molybdenum trioxide powder had an average primary particle size of 80 nm, and its purity was confirmed to be 99.7% by X-ray fluorescence (XRF) measurement. The specific surface area (SA) of this molybdenum trioxide powder, as measured by the BET method, was 44.0 m². 2 The result was / g. The evaluation method for Synthesis Example 1 is the same as the method used in Example 1 of Patent Document 4.

[0046] (Example 1) 1.00 g of molybdenum trioxide (manufactured by Taiyo Kogyo Co., Ltd., 5 μm) and 1.57 g of sulfur (manufactured by Kanto Chemical Co., Ltd.) were mixed using a stirring rod. The mixed raw materials were then placed in an alumina crucible. Subsequently, the crucible was placed in a stainless steel chamber equipped with an electromagnetic wave irradiation port, a gas inlet, and a gas exhaust port. Nitrogen gas was then supplied to the chamber at a flow rate of 0.5 L per minute using a nitrogen gas cylinder, completely replacing the inside of the chamber with nitrogen. After that, under a nitrogen gas flow of 0.5 L per minute, electromagnetic waves with a frequency of 2450 MHz were irradiated from the electromagnetic wave irradiation port at the top of the chamber at an intensity of 100 W, heating the mixed raw materials in the crucible until the temperature of the mixed raw materials reached 450°C. The temperature of the mixed raw materials was observed non-contact from the electromagnetic field irradiation port using a radiation thermometer. After the temperature of the mixed raw materials reached 450°C, the irradiation intensity of the electromagnetic waves was adjusted to maintain the temperature at 450°C. One hour after reaching 450°C, electromagnetic irradiation was stopped, and after waiting for the internal temperature of the crucible to drop below 50°C, the supply of nitrogen was stopped, and the powder was recovered from the crucible. XRD measurements revealed characteristic peaks originating from MoS2, confirming the formation of MoS2 nanoparticles. The conversion rate of MoS2 was confirmed to be over 60%.

[0047] (Example 2) Aside from using the molybdenum trioxide obtained in Synthesis Example 1 above, the synthesis of molybdenum sulfide nanoparticles was carried out in the same manner as in Example 1. XRD measurements revealed characteristic peaks originating from MoS2, confirming the formation of MoS2 nanoparticles. The conversion rate of MoS2 was confirmed to be over 80%.

[0048] (Comparative Example 1) Based on Comparative Example 2 of Patent Document 4 mentioned above, molybdenum sulfide nanoparticles were produced by electric heating. Due to the electric heating method, the conversion rate to MoS2 was low, confirmed to be 53%. It was confirmed that the energy consumption for producing 1 kg of molybdenum sulfide nanoparticles was higher than that for heating by electromagnetic wave irradiation.

[0049] (Consideration) Examples 1 and 2 showed higher MoS2 conversion rates compared to Comparative Example 1. In Examples 1 and 2, electromagnetic wave heating was used, and molybdenum trioxide absorbed electromagnetic waves (microwaves) well, causing its temperature to rise rapidly. On the other hand, sulfur has poor absorption of electromagnetic waves, so sulfur itself is not easily heated by electromagnetic wave irradiation. Therefore, the vaporization of sulfur is suppressed. When molybdenum trioxide and sulfur were mixed and irradiated with electromagnetic waves, molybdenum trioxide was preferentially heated, and its reaction activity increased. Some of the high-temperature molybdenum trioxide with increased reaction activity reacted with the surrounding sulfur and was immediately converted to molybdenum disulfide. This heating by electromagnetic wave irradiation activated the reaction of molybdenum trioxide and suppressed the vaporization and distillation of sulfur, making it possible to efficiently produce molybdenum disulfide fine particles.

[0050] In Example 2, since the molybdenum trioxide fine particles obtained in Synthesis Example 1 were used, the reaction efficiency with sulfur was further improved compared to Example 1. As a result, Example 2 obtained a higher MoS2 conversion rate than Example 1. [Explanation of Symbols]

[0051] 1 Chamber 2 containers 6. Air intake 8 exhaust vents 10. Manufacturing equipment (equipment for manufacturing molybdenum disulfide fine particles)

Claims

1. The process includes heating molybdenum trioxide by irradiating it with electromagnetic waves in the presence of sulfur, and reacting the heated molybdenum trioxide with the sulfur, A method for producing molybdenum disulfide fine particles, characterized in that the frequency of the electromagnetic wave is in the range of 300 to 30,000 MHz.

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

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

4. The BET specific surface area of ​​the molybdenum disulfide fine particles is 0.01 m². ２ / g to 500m ２ A method for producing molybdenum disulfide fine particles according to claim 1 or 2, wherein the amount is / g.

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

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

7. A method for producing molybdenum disulfide fine particles 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 aforementioned molybdenum trioxide is 0.1 m². ２ A method for producing molybdenum disulfide fine particles according to claim 1 or 2, wherein the amount is 1 / g or more.

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