Method for producing molybdenum sulfide powder

Abstract

The method for producing molybdenum sulfide powder includes a crushing step of crushing a mixture containing molybdenum trioxide powder and a dispersant to produce a calcined molybdenum precursor, and a calcination step of heating the calcined molybdenum precursor at a temperature of 200 to 1000°C in the presence of a sulfur source.

Description

[Technical Field]

[0001] The present invention relates to a method for producing molybdenum sulfide powder. [Background technology]

[0002] Molybdenum sulfides such as molybdenum disulfide (MoS2) are widely used, for example, as lubricants, steel additives, and raw materials for molybdates. Conventionally, a method for producing molybdenum sulfide involves heating molybdenum oxide in the presence of a sulfur source at a temperature of 200 to 1000° C. (see, for example, Patent Document 1).

[0003] Furthermore, there is a method for producing molybdenum trioxide powder, which is a molybdenum oxide, which includes vaporizing a molybdenum oxide precursor compound to form molybdenum trioxide vapor and cooling the molybdenum trioxide vapor (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6614471 [Patent Document 2] International Publication No. 2021 / 060375 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, there has been an increasing demand for molybdenum sulfide powder having a large specific surface area. As a method for obtaining molybdenum sulfide powder having a large specific surface area and made up of fine molybdenum sulfide particles having a small particle size, for example, a method of crushing molybdenum sulfide powder having a small specific surface area and made up of coarse molybdenum sulfide particles having a large particle size can be considered.

[0006] However, in the method of crushing molybdenum sulfide powder with a small specific surface area, it is difficult to convert all of the molybdenum sulfide powder with a small specific surface area into molybdenum sulfide powder with a large specific surface area. Therefore, the molybdenum sulfide powder after crushing contains molybdenum sulfide powder with a small specific surface area. Therefore, in order to obtain molybdenum sulfide powder with a large specific surface area using the method of crushing molybdenum sulfide powder with a small specific surface area, it is necessary to classify and select the crushed molybdenum sulfide powder, which is time-consuming. Furthermore, there is the disadvantage that impurities are easily mixed in when the crushed molybdenum sulfide powder is classified.

[0007] Another method for obtaining a molybdenum sulfide powder having a large specific surface area is to calcinate a molybdenum trioxide powder having a large specific surface area in the presence of a sulfur source. Specifically, a method can be used in which a molybdenum trioxide powder having a large specific surface area is produced by cooling molybdenum trioxide (MoO) vapor, and the resulting molybdenum trioxide powder is calcined by heating at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0008] However, in a method of calcining a molybdenum trioxide powder having a large specific surface area in the presence of a sulfur source, in order to produce a molybdenum trioxide powder having a large specific surface area to be used as a raw material, it is necessary to vaporize the molybdenum trioxide to form vapor and then perform a step of cooling the vapor. Therefore, when producing a molybdenum sulfide powder having a large specific surface area by using a method of calcining a molybdenum trioxide powder having a large specific surface area in the presence of a sulfur source, a huge amount of energy is required. For this reason, in a method of producing a molybdenum sulfide powder having a large specific surface area using a molybdenum trioxide powder having a large specific surface area, it has been required to reduce the amount of energy used.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing molybdenum sulfide powder, which can produce molybdenum sulfide powder having a large specific surface area with little energy, without crushing the molybdenum sulfide powder. [Means for solving the problem]

[0010] In order to solve the above problems, the following means are provided.

[0011] [1] a crushing step of crushing a mixture containing molybdenum trioxide powder and a dispersant to produce a calcined molybdenum precursor; a calcination step of heating the calcined molybdenum precursor at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0012] [2] The specific surface area of ​​the calcined molybdenum precursor measured by the BET method is 10 m 2 / g~25m 2 The method for producing a molybdenum sulfide powder according to [1], wherein the molybdenum sulfide powder has a molecular weight of 1000 or more and a molecular weight of 1000 or more. [3] The method for producing molybdenum sulfide powder according to [1] or [2], wherein the mixture is physically crushed in the crushing step. [4] The method for producing molybdenum sulfide powder according to any one of [1] to [3], wherein the mixture is crushed using a ball mill in the crushing step.

[0013] [5] The method for producing a molybdenum sulfide powder according to any one of [1] to [4], wherein the mixture contains water, and in the crushing step, the mixture is crushed, and then the water in the mixture is removed to produce the calcined molybdenum precursor. [6] The method for producing molybdenum sulfide powder according to any one of [1] to [5], wherein the dispersant contains a basic polymer. [7] The method for producing a molybdenum sulfide powder according to any one of [1] to [6], wherein the mixture contains 0.1 to 20 parts by mass of the dispersant per 100 parts by mass of the molybdenum trioxide powder. [8] In the calcination step, the specific surface area measured by the BET method is 25 m 2 / g~75m 2 The method for producing molybdenum sulfide powder according to any one of [1] to [7], which produces molybdenum sulfide powder having a molecular weight in the range of 1 / g. [Effects of the Invention]

[0014] In the method for producing molybdenum sulfide powder of the present invention, a calcined molybdenum precursor produced by crushing a mixture containing molybdenum trioxide powder and a dispersant is heated and calcined in the presence of a sulfur source, thereby producing a molybdenum sulfide powder with a large specific surface area. Therefore, there is no need to crush the molybdenum sulfide powder. Furthermore, in the method for producing molybdenum sulfide powder of the present invention, a calcined molybdenum precursor is produced by crushing a mixture containing molybdenum trioxide powder and a dispersant, so there is no need to produce a molybdenum trioxide powder with a large specific surface area using a method of cooling molybdenum trioxide vapor, which requires a huge amount of energy. Therefore, the method for producing molybdenum sulfide powder of the present invention can produce a molybdenum sulfide powder with a large specific surface area using less energy than a method for producing a molybdenum trioxide powder with a large specific surface area using a method of cooling molybdenum trioxide vapor. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram illustrating a manufacturing apparatus used to manufacture the molybdenum trioxide powder used as the calcined molybdenum precursor in Comparative Example 2. As shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present inventors have conducted extensive research as described below in order to solve the above problems and produce a molybdenum sulfide powder having a large specific surface area. Generally, a method for obtaining powder with a large specific surface area is to crush powder with a small specific surface area.

[0017] However, the present inventors have focused on a method for obtaining a molybdenum sulfide powder having a large specific surface area by using a molybdenum trioxide powder having a large specific surface area as a raw material and calcining this in the presence of a sulfur source, and have conducted extensive research. The reason is that the method of calcining molybdenum trioxide powder having a large specific surface area as a raw material in the presence of a sulfur source does not require classification after production, as is the case when a method of crushing molybdenum sulfide powder is used, and a high-quality molybdenum sulfide powder with few impurities can be obtained.

[0018] Furthermore, in order to obtain molybdenum sulfide powder having a large specific surface area with less energy, the present inventors have conducted extensive research into a method for producing molybdenum sulfide powder having a large specific surface area without using molybdenum trioxide powder having a large specific surface area produced by a method of cooling molybdenum trioxide vapor.

[0019] First, the present inventors produced molybdenum trioxide powder with a large specific surface area by crushing molybdenum trioxide powder with a small specific surface area. However, the method of crushing molybdenum trioxide powder was unable to produce molybdenum trioxide powder with a sufficiently large specific surface area. Furthermore, even when molybdenum trioxide powder with an increased specific surface area obtained by crushing molybdenum trioxide powder was calcined in the presence of a sulfur source, the specific surface area of ​​the molybdenum trioxide powder was not sufficiently large, and therefore molybdenum sulfide powder with a sufficiently large specific surface area could not be produced.

[0020] Therefore, the present inventors have conducted further studies focusing on the state of molybdenum trioxide powder that has been calcined in the presence of a sulfur source, and have found that a calcined molybdenum precursor produced by crushing a mixture containing molybdenum trioxide powder and a dispersant can be used in place of molybdenum trioxide powder with a large specific surface area produced by cooling molybdenum trioxide vapor.

[0021] More specifically, it was found that even if the specific surface area of ​​the calcined molybdenum precursor used as a raw material is smaller than that of molybdenum trioxide powder produced by the method of cooling molybdenum trioxide vapor, by calcining the precursor in the presence of a sulfur source, a molybdenum sulfide powder having a large specific surface area comparable to that obtained when molybdenum trioxide powder produced by the method of cooling molybdenum trioxide vapor is used can be obtained.

[0022] Although the reason why a molybdenum sulfide powder with a large specific surface area can be obtained by using the above-mentioned calcined molybdenum precursor as a raw material is not clear, it is presumed to be due to the following function of the dispersant contained in the calcined molybdenum precursor: That is, it is presumed that the dispersant contained in the calcined molybdenum precursor prevents aggregation of the molybdenum trioxide powder contained in the calcined molybdenum precursor and suppresses fusion of the molybdenum trioxide particles in the molybdenum trioxide powder that has been calcined in the presence of a sulfur source.

[0023] Furthermore, the present inventors produced molybdenum sulfide powder by heating and calcining the calcined molybdenum precursor in the presence of a sulfur source, and confirmed that molybdenum sulfide powder having a large specific surface area comparable to that produced by cooling molybdenum trioxide vapor can be produced with less energy than that produced by cooling molybdenum trioxide vapor.

[0024] The method for producing molybdenum sulfide powder of the present invention will be described in detail below. Note that the present invention is not limited to the following embodiments. [Molybdenum sulfide powder] The molybdenum sulfide powder produced by the production method of this embodiment is made of molybdenum sulfide. In this specification, "molybdenum sulfide" is a general term for compounds composed of molybdenum atoms and sulfur atoms. Examples of molybdenum sulfides include compounds represented by MoSx (x = 1 to 3). The molybdenum sulfide may be, for example, only molybdenum disulfide (MoS2), only molybdenum trisulfide, or a mixture of molybdenum disulfide and molybdenum trisulfide.

[0025] The molybdenum sulfide powder produced by the production method of this embodiment may contain atoms other than molybdenum sulfide, as long as the effects of the present invention are not impaired. Examples of other atoms include silicon, aluminum, sodium, iron, titanium, potassium, calcium, and yttrium. These other atoms may be contained alone or in combination of two or more. The content of other atoms that may be contained in the molybdenum sulfide powder is preferably 10 mol % or less, more preferably 5 mol % or less, and most preferably 2 mol % or less.

[0026] [Method for producing molybdenum sulfide powder] The method for producing molybdenum sulfide powder of this embodiment includes a crushing step of crushing a mixture containing molybdenum trioxide powder and a dispersant to produce a calcined molybdenum precursor, and a calcination step of heating the calcined molybdenum precursor at a temperature of 200 to 1000°C in the presence of a sulfur source.

[0027] [Crushing process] In the crushing step of this embodiment, a mixture containing molybdenum trioxide powder and a dispersant is crushed to produce a calcined molybdenum precursor. The mixture may contain only one type of molybdenum trioxide powder or two or more types with different specific surface areas, and the mixture may contain only one type of dispersant or two or more types with different components.

[0028] The molybdenum trioxide powder used as the raw material in the crushing process has a specific surface area of ​​0.01 m, as measured by the BET method, for example. 2 / g~15m 2 Molybdenum trioxide powder having a specific surface area of ​​0.01 m / g can be used because molybdenum trioxide powder having a sufficiently large specific surface area can be easily obtained by crushing. 2 It is preferable to use a molybdenum trioxide powder having a specific surface area of ​​0.05 m / g or more. 2 It is more preferable to use a molybdenum trioxide powder having a specific surface area of ​​15 m / g or more. 2 Molybdenum trioxide powder with a specific surface area of ​​15 m / g is difficult to obtain. 2 It is preferable to use one having a molecular weight of 10m / g or less. 2 It is more preferable to use one having a molecular weight of 5m / g or less. 2 It is more preferable to use one having a molecular weight of 1 / g or less.

[0029] The molybdenum trioxide powder is preferably one with high purity, since it allows the production of molybdenum sulfide powder quantitatively in accordance with stoichiometry and also allows the production of high-purity molybdenum sulfide powder with a smaller content of by-products. As the molybdenum trioxide powder, commercially available products can be used.

[0030] As the dispersant, any known dispersant can be used, and it is preferable to use a dispersant containing a basic polymer, because this effectively prevents aggregation of the molybdenum trioxide powder contained in the calcined molybdenum precursor, and the calcination step makes it easier to obtain a molybdenum sulfide powder with a large specific surface area.

[0031] When a dispersant containing a basic polymer is used, it is presumed that aggregation of molybdenum trioxide powder particles is suppressed by the following function. In a mixture containing molybdenum trioxide powder and a dispersant, the basic groups of the basic polymer are adsorbed to the molybdenum trioxide powder. As a result, the molybdenum trioxide powder particles are coated with the basic polymer. The molybdenum trioxide powder particles coated with the basic polymer repel each other due to the basic groups of the basic polymer. As a result, aggregation of molybdenum trioxide powder particles is suppressed.

[0032] The dispersant containing a basic polymer may be, for example, a dispersant containing a basic polymer having an amine group. Preferably, a dispersant containing a basic polymer with a high amine value of 1 mgKOH / G or more is used. This is because aggregation of the molybdenum trioxide powder particles can be more effectively prevented. Furthermore, the dispersant containing a basic polymer preferably contains a basic polymer with a molecular weight of 1,000 or more, because this more effectively prevents aggregation of the molybdenum trioxide powder particles.

[0033] Examples of dispersants containing a basic polymer having an amine group and a molecular weight of 1000 or more include commercially available PB821 (manufactured by Ajinomoto Fine-Tech, Inc.) and PB822 (manufactured by Ajinomoto Fine-Tech, Inc.) PB821 and PB822 have different amine values.

[0034] The mixture used in the crushing step preferably contains 0.1 to 20 parts by mass of a dispersant per 100 parts by mass of molybdenum trioxide powder. When the dispersant content per 100 parts by mass of molybdenum trioxide powder is 0.1 part by mass or more, the dispersant in the mixture is sufficiently effective in preventing aggregation of the molybdenum trioxide powder particles. As a result, the calcination step more easily produces a molybdenum sulfide powder with a large specific surface area. The dispersant content is more preferably 1 part by mass or more per 100 parts by mass of molybdenum oxide powder. Furthermore, when the dispersant content per 100 parts by mass of molybdenum trioxide powder is 20 parts by mass or less, the reaction between the calcined molybdenum precursor and the sulfur source is not inhibited in the subsequent calcination step due to an excessive amount of dispersant, which is preferable. The dispersant content is more preferably 10 parts by mass or less per 100 parts by mass of molybdenum oxide powder.

[0035] The mixture containing molybdenum trioxide powder and a dispersant contains molybdenum trioxide powder and a dispersant, and may contain water as needed. When the mixture contains water, a calcined molybdenum precursor containing a uniform amount of dispersant is easily produced by performing a crushing step. When a calcined molybdenum precursor containing a uniform amount of dispersant is used, a molybdenum sulfide powder with a large specific surface area is easily obtained, which is preferable.

[0036] The method for producing the mixture in the disintegration step of this embodiment can be a conventionally known method and is not particularly limited. When the mixture contains water, the mixture may be produced by a method in which all of the raw materials to be the mixture are placed in a container and then mixed, or by a method in which only a portion of the raw materials to be the mixture are placed in a container and mixed, and then at least a portion of the remaining raw materials are placed in the container and mixed, and this process is repeated until all of the raw materials have been placed in the container and mixed. Specifically, the mixture may be produced, for example, by a method in which a mixed solution containing water and a dispersant is mixed with molybdenum trioxide powder, a method in which a mixed solution containing water and molybdenum trioxide powder is mixed with a dispersant, or a method in which a mixture of molybdenum trioxide powder and a dispersant is mixed with water.

[0037] The method for crushing the mixture in the crushing step of this embodiment can be a conventionally known method and is not particularly limited. Molybdenum oxide powder is more easily crushed than molybdenum sulfide powder, and crushed particles of uniform size are easily obtained by crushing. Therefore, after the mixture is crushed in the crushing step, it can be used as a calcined molybdenum precursor without classification or sorting.

[0038] As a method for crushing the mixture in the crushing step, for example, a method for crushing the mixture using a ball mill, a method for crushing the mixture using a paint conditioner, or other physical methods for crushing the mixture can be used. As a method for crushing the mixture, a method for crushing the mixture using a ball mill is particularly preferred. This is because the molybdenum trioxide powder contained in the mixture can be efficiently crushed, and a calcined molybdenum precursor having a large specific surface area can be easily obtained.

[0039] When the mixture is crushed using a ball mill, known balls (crushing media) can be used in the ball mill, and it is preferable to use balls made of zirconium because they have high hardness and can crush the mixture efficiently. The diameter of the balls is not particularly limited and can be appropriately determined depending on the shape and size of the molybdenum trioxide powder used as a raw material. The diameter of the balls is preferably 0.03 mm to 30 mm, since this allows the molybdenum trioxide powder contained in the mixture to be efficiently crushed and a fired molybdenum precursor with a large specific surface area to be obtained using less energy.

[0040] When the mixture is crushed using a ball mill, the rotation speed of the rotating vessel containing the mixture and balls (crushing media) is not particularly limited and can be appropriately determined depending on the diameter of the balls, the shape and size of the molybdenum trioxide powder, the specific surface area of ​​the calcined molybdenum precursor produced in the crushing step, etc. The rotation speed of the rotating vessel is preferably 10 RPM to 600 RPM, more preferably 50 RPM to 400 RPM, because this allows the molybdenum trioxide powder contained in the mixture to be efficiently crushed and a calcined molybdenum precursor with a large specific surface area to be obtained using less energy.

[0041] When the mixture is crushed using a ball mill, the crushing time (the time from when the rotation of the rotating vessel starts to when it stops) is not particularly limited and can be appropriately determined depending on the rotation speed of the rotating vessel, the shape and size of the molybdenum trioxide powder, the specific surface area of ​​the calcined molybdenum precursor produced in the crushing step, etc. The crushing time is preferably 1 to 72 hours, and more preferably 3 to 50 hours, because it allows the molybdenum trioxide powder contained in the mixture to be crushed efficiently and a calcined molybdenum precursor with a large specific surface area to be obtained using less energy.

[0042] When the mixture contains water, it is preferable to produce a calcined molybdenum precursor by crushing the mixture in the crushing step and then removing the water from the mixture. As a method for removing the water from the mixture, a conventionally known method can be used, for example, a method can be used in which the mixture containing water obtained after crushing is heated to a temperature of 40°C to 120°C as necessary and dried.

[0043] The calcined molybdenum precursor produced by crushing the mixture has a specific surface area of ​​10 m as measured by the BET method. 2 / g~25m 2 / g. 2 By using a calcined molybdenum precursor having a specific surface area of ​​12 m / g or more, the effect of crushing the mixture can be fully obtained by performing a calcination step using the calcined molybdenum precursor. Therefore, by calcining in the presence of a sulfur source, a molybdenum sulfide powder having a sufficiently large specific surface area can be obtained. The specific surface area of ​​the calcined molybdenum precursor is 12 m / g or more. 2 It is more preferable that the specific surface area is 25 m / g or more by crushing the mixture. 2 It is difficult to produce a calcined molybdenum precursor having a specific surface area exceeding 25 m / g, and this is not preferable because it increases the amount of energy used in the crushing step. 2 / g or less, and 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0044] The calcined molybdenum precursor preferably has an average primary particle size in the range of 50 nm to 500 nm. This is because a molybdenum sulfide powder with a sufficiently large specific surface area can be easily obtained by calcining a calcined molybdenum precursor with an average primary particle size of 500 nm or less in the presence of a sulfur source. The average primary particle size of the calcined molybdenum precursor is more preferably 300 nm or less. Furthermore, it is difficult to produce a calcined molybdenum precursor with an average primary particle size of less than 50 nm by crushing the mixture, and this is undesirable because it requires a large amount of energy in the crushing step. For this reason, the average primary particle size of the calcined molybdenum precursor is preferably 50 nm or more, and more preferably 70 nm or more.

[0045] In this embodiment, the average primary particle size of the calcined molybdenum precursor refers to the average primary particle size of 50 particles within one field of view in a two-dimensional image of a transmission electron microscope (TEM). When performing transmission electron microscope (TEM) observation to measure the average primary particle size of the calcined molybdenum precursor, the magnification should be such that 50 or more particles of the calcined molybdenum precursor are included in one field of view in visual observation or image photography. Specifically, it is preferable to select an appropriate magnification from the range of, for example, 1,000 to 200,000 times. When measuring the average primary particle size of the calcined molybdenum precursor, a scanning electron microscope (SEM) may be used instead of a TEM.

[0046] [Firing process] In the calcination step of this embodiment, the calcined molybdenum precursor produced in the crushing step is calcined by heating at a temperature of 200 to 1000° C. in the presence of a sulfur source. Examples of sulfur sources include sulfur and hydrogen sulfide. Only one sulfur source may be used, or two sulfur sources, sulfur and hydrogen sulfide, may be used in combination. The sulfur source may be used in a solid state, a liquid state, or a gaseous state. Solid sulfur is preferred as the sulfur source because of its excellent workability.

[0047] It is preferable to use a sulfur source with a high purity, since this allows for quantitative production of molybdenum sulfide powder in accordance with stoichiometry and also results in a high-purity molybdenum sulfide powder with a lower content of by-products.

[0048] The firing step of this embodiment can be performed using, for example, a heat-resistant container such as a ceramic sagger. The heat-resistant container may have a container part with an opening on the top surface and a lid that is placed to cover the opening of the container part but does not seal the inside of the container part. The calcination step can be carried out, for example, by placing the calcined molybdenum precursor in a heat-resistant container, placing a sulfur source on the calcined molybdenum precursor, and heating the heat-resistant container in a calcination furnace. The calcined molybdenum precursor and the sulfur source may be mixed in advance and then placed in the heat-resistant container.

[0049] Furthermore, when a heat-resistant container having a container with an opening on the top surface and a lid installed to cover the opening of the container but not seal the container is used, the calcined molybdenum precursor and the sulfur source are placed in the container, the lid is placed to cover the opening of the container, and the heat-resistant container is then heated in a calcination furnace. This prevents the sulfur source from volatilizing before the calcined molybdenum precursor and the sulfur source react with each other. As a result, it is possible to prevent unreacted calcined molybdenum precursor from remaining after the calcination step.

[0050] The temperature (heating temperature) at which the calcined molybdenum precursor is heated in the presence of a sulfur source is 200°C to 1000°C, preferably 300°C to 600°C. By carrying out the heating at a temperature of 200°C or higher, the reaction between the calcined molybdenum precursor and the sulfur source is promoted, resulting in the production of molybdenum sulfide. Furthermore, since the heating is carried out at a temperature of 1000°C or lower, a molybdenum sulfide powder with a large specific surface area can be obtained with less energy consumption.

[0051] The time (heating time) for heating the calcined molybdenum precursor to 200°C to 1000°C in the presence of a sulfur source can be appropriately determined depending on the heating temperature, etc., and is preferably set to a range of 2 to 10 hours, more preferably 3 to 7 hours. When the heating time is 2 hours or more, molybdenum sulfide can be sufficiently produced by the reaction between the calcined molybdenum precursor and the sulfur source. When the heating time is 10 hours or less, productivity of molybdenum sulfide powder with a large specific surface area is not impaired and the amount of energy used in production is not excessively large, which is preferable.

[0052] The reaction between the calcined molybdenum precursor and the sulfur source in the calcination step is preferably carried out at a heating temperature of 300°C to 700°C for a heating time of 2 to 10 hours. The reaction between the calcined molybdenum precursor and the sulfur source is particularly preferably carried out at a heating temperature of 400°C to 600°C for a heating time of 3 to 6 hours, since this allows sufficient production of molybdenum sulfide powder with a large specific surface area and further reduces the amount of energy used in production.

[0053] In the calcination step, the calcined molybdenum precursor can be heated in the presence of a sulfur source according to any desired heating profile. Specifically, the heating temperature can be varied by continuously or stepwise increasing or decreasing the temperature within a range of 200°C to 1000°C, and the temperature can be maintained within the range for a certain period of time. For example, the temperature can be increased from room temperature at a constant rate of increase, maintained at a predetermined temperature within the range for a certain period of time, and then decreased to room temperature at a constant rate of decrease. Alternatively, the temperature can be increased from room temperature at a constant rate of increase, maintained at a first temperature within the range for a certain period of time, decreased to a predetermined temperature at a constant rate of decrease, increased again at a constant rate of increase, maintained at a second temperature within the range for a certain period of time, and then decreased to room temperature at a constant rate of decrease. In this case, the first and second temperatures may be the same or different.

[0054] In the calcination step, when the calcined molybdenum precursor is heated in the presence of a sulfur source, the temperature is increased from the start of heating to a temperature in the range of 200° C. to 1000° C. at a rate of preferably 1° C. / min or more, more preferably 5° C. / min or more. By increasing the temperature at a rate of 1° C. / min or more, it is possible to prevent the sulfur source from volatilizing out of the system before the calcined molybdenum precursor and the sulfur source react with each other, thereby preventing the sulfur source from becoming unavailable for reaction with the calcined molybdenum precursor.

[0055] In the calcination step, when the calcined molybdenum precursor is heated in the presence of a sulfur source, the calcination step is preferably carried out in an inert gas atmosphere such as nitrogen gas, helium, argon, etc. This is because carrying out the calcination step in an inert gas atmosphere makes it possible to quantitatively produce molybdenum sulfide powder in accordance with the stoichiometry of the calcined molybdenum precursor and the sulfur source, and to obtain high-purity molybdenum sulfide powder with a smaller content of by-products. The firing step of this embodiment is preferably carried out under atmospheric pressure.

[0056] The ratio of the calcined molybdenum precursor to the sulfur source used in the calcination step is determined so that the ratio between the number of moles of molybdenum contained in the calcined molybdenum precursor and the number of moles of sulfur contained in the sulfur source is stoichiometrically equivalent to the target molybdenum sulfide (a compound represented by MoSx (x = 1 to 3)). In other words, x in the compound represented by MoSx (x = 1 to 3) can be controlled by adjusting the ratio between the number of moles of molybdenum contained in the calcined molybdenum precursor used in the calcination step and the number of moles of sulfur contained in the sulfur source.

[0057] In the calcination step of this embodiment, the sulfur source may volatilize out of the system, leaving unreacted calcined molybdenum precursor after calcination. To prevent this, the ratio of the sulfur source to the calcined molybdenum precursor may be set to be greater than the number of moles of sulfur stoichiometrically corresponding to the target product.

[0058] In the calcination step of this embodiment, the ratio of sulfur to molybdenum trioxide in the calcined molybdenum precursor (sulfur / molybdenum trioxide) is preferably in the range of 5 to 20, more preferably in the range of 7 to 15. When the ratio of sulfur to molybdenum trioxide is 4 or more, the sulfur source is not insufficient, and a molybdenum sulfide powder with a large specific surface area is easily obtained. Furthermore, when the ratio of sulfur to molybdenum trioxide is 10 or less, it is possible to prevent unreacted calcined molybdenum precursor from remaining after calcination.

[0059] When a calcined molybdenum precursor is calcined in the presence of a sulfur source, not only molybdenum sulfide but also sulfur oxides may be produced. If sulfur oxides are produced, they can be easily removed from the calcined product by a conventionally known method.

[0060] Whether the fired product obtained in the firing step of this embodiment is a molybdenum sulfide or not can be confirmed by identifying the fired product using a known, commonly used analytical method. Specifically, the fired product can be identified by, for example, X-ray diffraction (XRD) measurement and / or atomic absorption spectrometry (AAS) of the fired product. Furthermore, when the molybdenum sulfide does not consist of only one substance with a single composition, the composition of the molybdenum sulfide (a compound represented by MoSx (x = 1 to 3)) can be identified, for example, by measurement using inductively coupled plasma (ICP) atomic emission spectroscopy.

[0061] In the calcination step of this embodiment, the calcined molybdenum precursor produced in the crushing step is heated and calcined in the presence of a sulfur source, so that a molybdenum sulfide powder having a large specific surface area is produced. Specifically, by carrying out the calcination step of this embodiment, a molybdenum sulfide powder having a specific surface area of ​​25 m2 as measured by the BET method is produced. 2 / g~75m 2 / g and the average particle size of the primary particles is in the range of 50 nm to 500 nm. Therefore, according to the production method of this embodiment, it is possible to produce a molybdenum sulfide powder with a large specific surface area without crushing the molybdenum sulfide powder.

[0062] Furthermore, in the method for producing molybdenum sulfide powder of this embodiment, a calcined molybdenum precursor is produced by crushing a mixture containing molybdenum trioxide powder and a dispersant, so there is no need to produce a molybdenum trioxide powder with a large specific surface area using a method of cooling molybdenum trioxide vapor, which requires a huge amount of energy. Thus, according to the method for producing molybdenum sulfide powder of this embodiment, a molybdenum sulfide powder with a large specific surface area can be produced with less energy than when a method for producing a molybdenum trioxide powder with a large specific surface area is used, which method involves cooling molybdenum trioxide vapor.

[0063] The molybdenum sulfide powder having a large specific surface area obtained by the method for producing molybdenum sulfide powder of this embodiment can be suitably used for applications such as additives for lubricating oils and fats, additives to be kneaded into resins, durability improvers for semiconductor materials and coatings, solid lubricants, black pigments, etc. In particular, the molybdenum sulfide powder having a specific surface area of ​​25 m or less as measured by the BET method can be suitably used for applications such as lubricating oils and fats, additives to be kneaded into resins, durability improvers for semiconductor materials and coatings, solid lubricants, black pigments, etc. 2 / g~75m 2 Molybdenum sulfide powders having a molecular weight in the range of 1 / g can be suitably used for applications such as solid lubricants. [Example]

[0064] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0065] Example 1 (Crushing process) 250.0 g of balls (grinding media) made of zirconium with a diameter of 1.2 mm to 1.4 mm were placed in the rotating vessel (ball mill tank) of a ball mill (manufactured by NITTO KAGAKU Co., Ltd.). Next, a ball mill with a specific surface area of ​​0.85 m2 measured by the BET method was placed in the rotating vessel containing the balls. 225.0 g of molybdenum trioxide powder (trade name: MoO3-20220216, manufactured by Nippon Inorganic Industries) having a molecular weight of 1.0 g / g, 1.0 g of a dispersant (hereinafter referred to as "Dispersant A"), and 25.0 g of deionized water were placed in this order. The rotating vessel was then rotated at a rotation speed of 240 RPM for 24 hours to disintegrate the mixture containing the molybdenum trioxide powder, Dispersant A, and deionized water.

[0066] The balls in the rotating container were then washed with deionized water and removed, and the crushed mixture was collected. The crushed mixture was then heated and dried at 100°C for 24 hours to remove water from the crushed mixture. The lumpy portion of the dewatered mixture was then crushed three times for 10 seconds using a spoon to produce the calcined molybdenum precursor of Example 1.

[0067] The specific surface area measured by the BET method and the average particle size of the primary particles of the calcined molybdenum precursor thus obtained in Example 1 were measured by the methods described below. The results are shown in Table 1.

[0068] [Specific surface area measurement method: BET method] The amount of nitrogen gas adsorption of the calcined molybdenum precursor was measured by the BET method using a specific surface area meter (Microtrack Bell, BELSORP-mini), and the surface area per 1 g of sample was calculated from the results to determine the specific surface area (m 2 / g).

[0069] [Method for measuring the average particle size of primary particles] The calcined molybdenum precursor was photographed using a scanning electron microscope (SEM; manufactured by JEOL Ltd.). The major axis (the Feret diameter of the longest observed part) and minor axis (the shorter Feret diameter perpendicular to the Feret diameter of the longest part) of the smallest particle (i.e., primary particle) constituting the aggregate in the obtained two-dimensional image were measured, and the average value was taken as the primary particle size. The same procedure was performed on 50 randomly selected primary particles, and the average value of the primary particle diameters of the 50 primary particles was calculated, which was taken as the average particle size of the calcined molybdenum precursor primary particles.

[0070] (Firing process) As the heat-resistant container, a ceramic sagger was prepared, which had a container part with an opening on the top surface and a lid that was placed to cover the opening of the container part but did not seal the inside of the container part. 5.0 g of the calcined molybdenum precursor produced in the crushing step was placed in the container of a ceramic sagger, 22.22 g of powdered sulfur was placed on top of the calcined molybdenum precursor, and a lid was placed over the opening of the container. The ceramic sagger was then placed in a firing furnace, and the furnace was heated to 500°C at a heating rate of 5°C / min under atmospheric pressure in a nitrogen atmosphere. The temperature was maintained at 500°C for 4 hours and then allowed to cool. The calcined molybdenum precursor was calcined in the presence of a sulfur source to obtain the molybdenum sulfide powder of Example 1.

[0071] <Examples 2 to 8> Calcined molybdenum precursors of Examples 2 to 8 were produced in the same manner as in Example 1, except that in the crushing step, the type of molybdenum trioxide powder, the type of dispersant, the rotation speed of the rotating container of the ball mill, and the rotation time were as shown in Table 1. Thereafter, molybdenum sulfide powders of Examples 2 to 8 were obtained in the same manner as in Example 1, except that in the firing step, the ratio of sulfur to molybdenum trioxide in the fired molybdenum precursor and the heating time were set as shown in Table 2.

[0072] <Examples 9 and 10> The molybdenum sulfide powders of Examples 9 and 10 were obtained in the same manner as in Example 1, except that in the crushing step, the amount of dispersant was changed to 0.1 g in Example 9 and 5 g in Example 10 to generate the calcined molybdenum precursor.

[0073] <Comparative Example 1> A calcined molybdenum precursor of Comparative Example 1 was produced in the same manner as in Example 8, except that no dispersant was used in the crushing step. Thereafter, a molybdenum sulfide powder of Comparative Example 1 was obtained in the same manner as in Example 1, except that the calcined molybdenum precursor of Comparative Example 1 was used as the calcined molybdenum precursor.

[0074] <Comparative Example 2> The specific surface area measured by the BET method is 54.2 m 2 A molybdenum sulfide powder of Comparative Example 2 was obtained in the same manner as in Example 5, except that the obtained molybdenum trioxide powder was used as a calcined molybdenum precursor.

[0075] (Method for producing calcined molybdenum precursor of Comparative Example 2) The molybdenum trioxide powder used as the calcined molybdenum precursor in Comparative Example 2 was produced using the production apparatus shown in Fig. 1 described in Patent Document 2. The production apparatus 1 shown in Fig. 1 includes a calcination furnace 2, a cross-shaped cooling pipe 3 connected to the calcination furnace 2 and for powdering molybdenum trioxide vapor vaporized by calcination, a recovery machine 4 for recovering the molybdenum trioxide powder powdered in the cooling pipe 3, an exhaust port 5, an opening-adjusting damper 6, an observation window 7, an exhaust device 8, and an external cooling device 9.

[0076] A mixture of 1 kg of transition aluminum oxide (activated alumina, average particle size 45 μm, manufactured by Wako Pure Chemical Industries, Ltd.) and 600 g of molybdenum trioxide (manufactured by Nippon Inorganic Industries Co., Ltd.) was placed in a ceramic sagger and then placed in firing furnace 2 of manufacturing apparatus 1 shown in FIG. 1. In firing furnace 2, the mixture was fired at 1,100°C for 10 hours to vaporize it, cooled in an air atmosphere through cooling pipe 3, precipitated as particles near recovery machine 4, and recovered by recovery machine 4. The recovered molybdenum trioxide powder was used as a fired molybdenum precursor in Comparative Example 2.

[0077] <Comparative Example 3> Commercially available molybdenum disulfide powder (manufactured by Sigma-Aldrich) was prepared as the molybdenum sulfide powder of Comparative Example 3.

[0078] X-ray diffraction (XRD) measurements were performed on the molybdenum sulfide powders of Examples 1 to 10 and Comparative Examples 1 and 2 obtained in this manner. As a result, only diffraction peaks attributed to molybdenum disulfide were observed in all of the molybdenum sulfide powders of Examples 1 to 10 and Comparative Examples 1 and 2. From this, it was confirmed that all of the molybdenum sulfide powders of Examples 1 to 10 and Comparative Examples 1 and 2 were molybdenum disulfide (MoS2).

[0079] Furthermore, the specific surface area measured by the BET method and the average particle size of the primary particles were measured for the calcined molybdenum precursor used in producing the molybdenum sulfide powders of Examples 2 to 10 and Comparative Examples 1 and 2, and for the molybdenum sulfide powders of Examples 1 to 10 and Comparative Examples 1 to 3, using the same method as for the calcined molybdenum precursor of Example 1. The results are shown in Tables 1 and 2.

[0080] Furthermore, the amount of energy used in the crushing step was calculated by the method shown below for each of the molybdenum sulfide powders of Examples 1 to 10 and Comparative Examples 1 and 2. The results are shown in Table 2.

[0081] [Energy consumption in the crushing process] In the crushing step of Examples 1 to 10 and Comparative Example 1, the amount of energy used to rotate the rotary vessel of the ball mill was calculated by the method shown below, and this was taken as the amount of energy used in the crushing step. A watt-hour meter was installed between the ball mill device and the power source, and the watt-hour meter measured the amount of power (W) consumed by the ball mill while it was rotating. The energy consumption (kWh) was calculated by multiplying the obtained amount of power (W) consumed by the ball mill while it was rotating by the crushing time.

[0082] In Comparative Example 2, the energy used to produce the molybdenum trioxide powder used as the calcined molybdenum precursor was taken as the amount of energy used in the crushing step. That is, in Comparative Example 2, the amount of electricity (W) used for heating inside the firing furnace 2, which is recorded on the control panel that controls the firing furnace 2, was observed every minute, and the results were used to integrate the amount of electricity for each hour to calculate the amount of energy used in production (kWh), which was used as the energy consumption in the crushing process.

[0083] The firing conditions are the same in Examples 1 to 5, 9, 10, Comparative Examples 1 and 2. Therefore, the amount of energy used in the firing step is the same in Examples 1 to 5, 9, 10, Comparative Examples 1 and 2.

[0084] [Table 1]

[0085] The "type of molybdenum trioxide powder" and "type of dispersant" listed in Table 1 are as follows: "Types of molybdenum trioxide powder" MoO3-20220216; specific surface area measured by BET method: 0.85 m 2 / g (Nippon Muki Co., Ltd.) MoO3-20210926; specific surface area measured by BET method 0.85m 2 / g (Nippon Muki Co., Ltd.) MoO3-20220223; specific surface area measured by BET method: 0.85 m 2 / g (Nippon Muki Co., Ltd.) MoO3-20211009; specific surface area measured by BET method: 0.85 m 2 / g (Nippon Muki Co., Ltd.) MoO3-20211206; specific surface area measured by BET method: 0.85 m 2 / g (Nippon Muki Co., Ltd.) MoO3-20211129; specific surface area measured by BET method: 0.85 m 2 / g (Nippon Muki Co., Ltd.)

[0086] "Types of dispersants" Dispersant A: A dispersant containing 8 parts by weight of PB821 (manufactured by Ajinomoto Fine-Tech Co., Ltd.) and 2 parts by weight of butyl acetate. Dispersant B: A dispersant containing 8 parts by weight of PB822 (manufactured by Ajinomoto Fine-Tech Co., Ltd.) and 2 parts by weight of butyl acetate.

[0087] Furthermore, the "dispersant content" shown in Table 1 is the content (parts by mass) of dispersant relative to 100 parts by mass of molybdenum trioxide powder.

[0088] [Table 2]

[0089] As shown in Table 2, the molybdenum sulfide powders of Examples 1 to 10 all had a specific surface area of ​​35 m as measured by the BET method. 2 / g or more, and had a large specific surface area. In contrast, the molybdenum sulfide powder of Comparative Example 3, which is a commercially available molybdenum disulfide powder, has a specific surface area of ​​0.30 m 2 / g. Therefore, the molybdenum sulfide powders of Examples 1 to 10 had a very large specific surface area compared to the commercially available molybdenum disulfide powder of Comparative Example 3.

[0090] Furthermore, as shown in Table 2, the energy consumption used in the production of each of the molybdenum sulfide powders of Examples 1 to 10 was 7 kWh or less. In contrast, in Comparative Example 2, in which a molybdenum trioxide powder with a large specific surface area was produced by cooling molybdenum trioxide (MoO) vapor and used as a calcined molybdenum precursor, the energy consumption used in production was 139.0 kWh. Therefore, the molybdenum sulfide powders of Examples 1 to 10 were produced in much smaller amounts of energy than Comparative Example 2.

[0091] Furthermore, as shown in Tables 1 and 2, in Comparative Example 1, in which a calcined molybdenum precursor produced without using a dispersant was used, the specific surface area of ​​the molybdenum sulfide powder measured by the BET method was 5.00 m 2 / g. Therefore, the molybdenum sulfide powder of Comparative Example 1 had a smaller specific surface area measured by the BET method than the molybdenum sulfide powders of Examples 1 to 10, which used calcined molybdenum precursors produced using dispersants. The reason for this is that the calcined molybdenum precursor did not contain a dispersant, causing the calcined molybdenum precursor to aggregate in Comparative Example 1. As a result, it is presumed that in Comparative Example 1, the aggregated molybdenum trioxide particles in the molybdenum trioxide powder calcined in the presence of a sulfur source in the calcination step fused together to form coarse particles. [Explanation of symbols]

[0092] 1 Manufacturing equipment, 2 Sintering furnace, 3 Cooling piping, 4 Recovery machine, 5 Exhaust port, 6 Opening adjustment damper, 7 Observation window, 8 Exhaust device, 9 External cooling device 9.

Claims

1. a crushing step of crushing a mixture containing molybdenum trioxide powder and a dispersant to produce a calcined molybdenum precursor; a calcination step of heating the calcined molybdenum precursor at a temperature of 200 to 1000°C in the presence of a sulfur source.

2. The specific surface area of ​​the calcined molybdenum precursor measured by the BET method is 10 m ２ / g~25m ２ The method for producing molybdenum sulfide powder according to claim 1, wherein the molybdenum sulfide powder has a molybdenum content of 1000 ppm or less.

3. 3. The method for producing molybdenum sulfide powder according to claim 1, wherein the mixture is physically crushed in the crushing step.

4. 3. The method for producing molybdenum sulfide powder according to claim 1, wherein the mixture is crushed using a ball mill in the crushing step.

5. 3. The method for producing a molybdenum sulfide powder according to claim 1, wherein the mixture contains water, and in the crushing step, the mixture is crushed and then the water in the mixture is removed to produce the calcined molybdenum precursor.

6. 3. The method for producing molybdenum sulfide powder according to claim 1, wherein the dispersant contains a basic polymer.

7. 3. The method for producing molybdenum sulfide powder according to claim 1, wherein the mixture contains 0.1 to 20 parts by mass of the dispersant relative to 100 parts by mass of the molybdenum trioxide powder.

8. In the firing step, the specific surface area measured by the BET method is 25 m ２ / g~75m ２ 3. The method for producing molybdenum sulfide powder according to claim 1 or claim 2, wherein the molybdenum sulfide powder has a molybdenum sulfide content in the range of 1 / g.

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