Method for producing molybdenum trioxide powder

Abstract

To provide a method for producing molybdenum trioxide powder that can reduce material costs and decrease the environmental burden and disposal costs associated with the disposal of by-products generated by calcination. [Solution] The manufacturing method comprises: a first calcination step S11 in which a first raw material mixture containing a molybdenum oxide precursor compound and metal compound particles other than the molybdenum compound is placed in a sheath and calcined; a first cooling step S12 to generate molybdenum trioxide powder; a first crushing step S13 to crush the residue containing metal oxides derived from the metal compound particles remaining in the sheath to form first crushed particles; a second calcination step S21 in which a second raw material mixture containing a molybdenum oxide precursor compound and the first crushed particles is placed in a sheath and calcined; a second cooling step S22 to generate molybdenum trioxide powder; and a second crushing step S23 to crush the residue containing metal oxides derived from the first crushed particles remaining in the sheath to form second crushed particles.

Description

[Technical Field]

[0001] This invention relates to a method for producing molybdenum trioxide powder. [Background technology]

[0002] Traditionally, molybdenum sulfides, such as molybdenum disulfide (MoS2), have been widely used as lubricants, steel additives, and raw materials for molybdate salts. One method for producing molybdenum sulfides involves using molybdenum trioxide powder as a precursor. Conventionally, one method for producing molybdenum trioxide powder involves vaporizing a molybdenum oxide precursor compound to form molybdenum trioxide vapor, and then cooling the molybdenum trioxide vapor.

[0003] For example, Patent Document 1 proposes a method for producing molybdenum trioxide powder by calcining a raw material mixture containing a molybdenum oxide precursor compound and a metal compound other than the molybdenum oxide precursor compound, thereby vaporizing the molybdenum oxide precursor compound and forming molybdenum trioxide vapor.

[0004] Furthermore, Patent Document 1 describes mixing aluminum hydroxide and molybdenum trioxide, placing the mixture in a casing, firing it at a temperature of 1100°C, and recovering the molybdenum trioxide using a dust collector. Patent Document 1 also describes removing aluminum oxide from the casing after firing. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] International Publication No. 2022 / 202757 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, when producing molybdenum trioxide powder using a method that involves calcining a raw material mixture containing aluminum hydroxide and molybdenum trioxide, a large amount of aluminum hydroxide was required as a material. Therefore, there was a need to reduce the amount of aluminum hydroxide used and lower material costs.

[0007] Furthermore, when molybdenum trioxide powder is produced using the above method, aluminum oxide is generated from aluminum hydroxide as a by-product during calcination. Therefore, when producing molybdenum trioxide powder using the above method, it is necessary to dispose of the by-product aluminum oxide, and there was a need to reduce the environmental burden and disposal costs associated with the disposal of aluminum oxide.

[0008] To solve the above problem, it is conceivable to use only molybdenum trioxide as a material, without using aluminum hydroxide, which is a by-product raw material. However, the aluminum hydroxide contained in the raw material mixture has the function of holding the molybdenum trioxide that has melted and liquefied when the raw material mixture in the scabbard is fired, and also the function of protecting the scabbard by reducing the contact area between the liquefied molybdenum trioxide and the scabbard.

[0009] For this reason, if molybdenum trioxide alone is used as a raw material, problems arise such as the liquefied molybdenum trioxide leaking from the casing during calcination, or the liquefied molybdenum trioxide coming into contact with the casing and severely corroding and degrading it. Therefore, it is preferable that the raw material mixture contains a sufficient amount of aluminum hydroxide along with molybdenum trioxide. Thus, it was difficult to use molybdenum trioxide alone as a raw material.

[0010] This invention has been made in view of the above problems, and aims to provide a method for producing molybdenum trioxide powder that can reduce material costs and decrease the environmental burden and disposal costs associated with the disposal of by-products generated by calcination. [Means for solving the problem]

[0011] To solve the above problems, reduce material costs, and decrease the environmental burden and disposal costs associated with the disposal of by-products generated by calcination, the inventors focused on the materials to be mixed with molybdenum trioxide in the raw material mixture and the by-products generated by calcining the raw material mixture, and diligently investigated them as shown below.

[0012] In other words, when molybdenum trioxide powder is produced by calcining a raw material mixture containing aluminum hydroxide and molybdenum trioxide, the residual material consisting of aluminum oxide remaining in the sac after calcination can be reused as a material for molybdenum oxide powder. However, since the residue remaining inside the scabbard after firing is in the form of lumps, it does not adequately provide the function of retaining the molten and liquefied molybdenum trioxide, nor does it adequately reduce the contact area between the liquefied molybdenum trioxide and the scabbard.

[0013] Therefore, the inventors crushed the lump-like residue of aluminum oxide remaining in the pod to obtain aluminum oxide particles. Then, the obtained aluminum oxide particles were placed in the pod together with a molybdenum oxide precursor compound and calcined. As a result, it was found that the aluminum oxide particles could sufficiently suppress the leakage of molybdenum trioxide liquefied by calcination from the pod, and the deterioration of the pod by the liquefied molybdenum trioxide. In other words, the inventors have discovered that the lumpy aluminum oxide produced as a by-product can be crushed into aluminum oxide particles and reused as a material when manufacturing molybdenum trioxide powder.

[0014] Furthermore, the inventors conducted further studies and confirmed the following (a) and (b), which led them to conceive of the present invention. (a) Even when a raw material mixture containing metal compound particles other than molybdenum compounds such as aluminum hydroxide, magnesium aluminate, titanium oxide, iron oxide, zinc oxide, and silica is placed in a crucible and fired together with a molybdenum oxide precursor compound, massive residues are formed inside the crucible after firing.

[0015] (b) By crushing the massive residues generated in (a) above into particles, putting them together with the molybdenum oxide precursor compound into the crucible, and firing them, it is possible to sufficiently suppress the leakage of molybdenum trioxide liquefied by firing from the crucible or the deterioration of the crucible by the liquefied molybdenum trioxide, similar to the case where a metal oxide containing aluminum oxide particles is placed in the crucible and fired. The present invention provides the following means.

[0016] [1] A first firing step of putting a first raw material mixture containing a molybdenum oxide precursor compound and metal compound particles other than molybdenum compounds into a crucible and firing to vaporize the molybdenum oxide precursor compound to form molybdenum trioxide vapor, A first cooling step of cooling the molybdenum trioxide vapor generated in the first firing step to produce molybdenum trioxide powder, A first crushing step of crushing the residue containing the metal oxide derived from the metal compound particles remaining in the crucible after the first firing step into first crushed particles, A second firing step of putting a second raw material mixture containing a molybdenum oxide precursor compound and the first crushed particles into a crucible and firing to vaporize the molybdenum oxide precursor compound to form molybdenum trioxide vapor, A second cooling step of cooling the molybdenum trioxide vapor generated in the second firing step to produce molybdenum trioxide powder, A method for producing molybdenum trioxide powder, including a second crushing step of crushing the residue containing the metal oxide derived from the first crushed particles remaining in the crucible after the second firing step into second crushed particles.

[0017] [2] The method for producing molybdenum trioxide powder according to [1], wherein the average particle size of the first crushed particles and the second crushed particles is 1 mm or less. [3] The method for producing molybdenum trioxide powder according to [1] or [2], wherein the metal compound particles are one or more selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles.

[0018] [4] The first raw material mixture consists of the molybdenum oxide precursor compound and the metal compound particles, and in the first calcination step, it is calcined at a temperature of 800°C to 1200°C. A method for producing molybdenum trioxide powder according to [3], wherein the second raw material mixture comprises the molybdenum oxide precursor compound and the first crushed particles, and the second calcination step is performed at a temperature of 800°C to 1200°C.

[0019] [5] The first raw material mixture contains 50% to 200% by mass of the metal compound particles with respect to 100% by mass of the molybdenum oxide precursor compound. A method for producing molybdenum trioxide powder according to [3] or [4], wherein the second raw material mixture contains 50% to 200% by mass of the first crushed particles with respect to 100% by mass of the molybdenum oxide precursor compound.

[0020] [6] A method for producing molybdenum trioxide powder according to any one of [1] to [5], wherein the first cooling step and the second cooling step produce molybdenum trioxide powder having an average particle size of 5 nm or more and 100 nm or less. [7] In the first cooling step and the second cooling step, the specific surface area measured by the BET method is 10 m² 2 / g or more 500m 2 A method for producing molybdenum trioxide powder according to any one of [1] to [6], which produces molybdenum trioxide powder of less than or equal to / g. [8] A method for producing molybdenum trioxide powder according to any one of [1] to [7], wherein molybdenum trioxide powder containing a β-crystal structure is produced in the first cooling step and the second cooling step. [Effects of the Invention]

[0021] In the present invention's method for producing molybdenum trioxide powder, in the first calcination step, metal compound particles other than the molybdenum compound are used together with the molybdenum oxide precursor compound; in the first crushing step, the residue containing metal oxides derived from the metal compound particles remaining in the sac after calcination is crushed to obtain first crushed particles; and in the second calcination step, the first crushed particles are used together with the molybdenum oxide precursor compound.

[0022] Therefore, in the method for producing molybdenum trioxide powder of the present invention, residual material containing metal oxides derived from metal compound particles other than the molybdenum compound used in the first calcination step is crushed in the first crushing step to become first crushed particles, which are then reused as material in the second calcination step.

[0023] Therefore, the method for producing molybdenum trioxide powder according to the present invention can reduce material costs compared to, for example, a method in which residual material containing metal oxides derived from metal compound particles other than molybdenum compounds contained in the first raw material mixture is not reused. Furthermore, in the method for producing molybdenum trioxide powder according to the present invention, the residual material remaining in the casing after calcination is crushed to form first crushed particles, which are then reused in the second calcination process. Therefore, there is no need to discard the residual material remaining in the casing after calcination, and as is the case when the residual material remaining in the casing after calcination is discarded, there are no environmental burdens or disposal costs associated with disposal. [Brief explanation of the drawing]

[0024] [Figure 1] Figure 1 is a schematic diagram illustrating an example of a molybdenum trioxide powder manufacturing apparatus used in the molybdenum trioxide powder manufacturing method of this embodiment. [Figure 2]Figure 2 is a flowchart illustrating an example of a method for producing molybdenum trioxide powder according to this embodiment. [Modes for carrying out the invention]

[0025] The method for producing molybdenum trioxide powder according to this embodiment will be described in detail below, with reference to the drawings as appropriate. Note that, for convenience, the drawings used in the following description may show enlarged versions of characteristic parts to make the features of the present invention easier to understand. Therefore, the dimensional ratios of each component may differ from those of the actual product. The scope of the present invention is not limited to the embodiment described herein, and various modifications can be made without departing from the spirit of the invention. Furthermore, if multiple upper and lower limits are given for a particular parameter, any combination of these upper and lower limits can be used to create a suitable numerical range.

[0026] [Equipment for manufacturing molybdenum trioxide powder] Figure 1 is a schematic diagram illustrating an example of a molybdenum trioxide powder manufacturing apparatus used in the molybdenum trioxide powder manufacturing method of this embodiment. The molybdenum trioxide powder manufacturing apparatus 1 shown in Figure 1 comprises a calcination furnace 2, cooling pipes 3, a dust collector 4, and an exhaust air device 8.

[0027] The firing furnace 2 fires a raw material mixture containing a molybdenum oxide precursor compound, placed in a sheath (not shown), under predetermined firing conditions to vaporize the molybdenum oxide precursor compound. A known type of firing furnace 2 can be used. As shown in Figure 1, an exhaust port 5 is provided on the ceiling surface of the firing furnace 2.

[0028] The cooling pipe 3 cools and pulverizes molybdenum trioxide vapor, which is produced by calcining a raw material mixture containing a molybdenum oxide precursor compound in the calcination furnace 2. As shown in Figure 1, the cooling pipe 3 has a cross shape when viewed from the side. The lower end of the cooling pipe 3 is connected to the exhaust port 5 of the calcination furnace 2. An observation window 7 for observing the inside of the cooling pipe 3 is located at the upper end of the cooling pipe 3.

[0029] Furthermore, an outside air intake (not shown) is provided at the first horizontal end of the cooling pipe 3. As shown in Figure 1, an opening adjustment damper 6 is positioned at the outside air intake to adjust the opening degree of the outside air intake. A dust collection pipe is connected to the second horizontal end of the cooling pipe 3. As shown in Figure 1, the dust collection pipe connects the cooling pipe 3 to the dust collector 4. The molybdenum trioxide powder manufacturing apparatus 1 of this embodiment may be provided with a known external cooling device (indicated by reference numeral 9 in Figure 1) that cools the cooling pipe 3 from the outside, if necessary.

[0030] The dust collector 4 recovers the molybdenum trioxide powder that has been pulverized in the cooling pipe 3. As the dust collector 4, for example, one can be used that recovers the molybdenum trioxide powder contained in the gas by passing the gas containing the molybdenum trioxide powder supplied from the cooling pipe 3 through a filter such as a bag filter.

[0031] As shown in Figure 1, the exhaust device 8 draws gas from the dust collector 4 via a suction pipe. A known device such as a blower can be used as the exhaust device 8. In the molybdenum trioxide powder manufacturing apparatus 1 shown in Figure 1, the exhaust device 8 draws in the dust collector 4 via the suction piping. Then, the cooling pipe 3 connected to the dust collector 4 is also drawn in via the dust collection piping. As a result, the gas inside the cooling pipe 3 is discharged, and outside air is blown into the cooling pipe 3 from the opening adjustment damper 6.

[0032] [Method for producing molybdenum trioxide powder] Next, as an example of a method for producing molybdenum trioxide powder according to this embodiment, we will explain in detail the case in which molybdenum trioxide powder is produced using the molybdenum trioxide powder production apparatus 1 shown in Figure 1.

[0033] Figure 2 is a flowchart illustrating an example of a method for producing molybdenum trioxide powder according to this embodiment. As shown in Figure 2, the method for producing molybdenum trioxide powder according to this embodiment includes a first calcination step S11, a first cooling step S12, a first crushing step S13, a second calcination step S21, a second cooling step S22, and a second crushing step S23. As shown in Figure 2, the second calcination step S21, the second cooling step S22, and the second crushing step S23 may be repeated multiple times after the first crushing step S13, or they may be performed only once.

[0034] (First firing process S11) In the first firing step S11, a first raw material mixture containing a molybdenum oxide precursor compound and metal compound particles other than the molybdenum compound is placed in a sieve and fired in the firing furnace 2 shown in Figure 1 to vaporize the molybdenum oxide precursor compound and form molybdenum trioxide vapor.

[0035] The molybdenum oxide precursor compound included in the first raw material mixture is not particularly limited, as long as it can form molybdenum trioxide vapor when calcined. The form of the molybdenum oxide precursor compound contained in the first raw material mixture is not particularly limited. For example, it may be in powder form, such as molybdenum trioxide powder, or in liquid form, such as an aqueous solution of ammonium molybdate. The form of the molybdenum oxide precursor compound is preferably in powder form because it is easy to handle and energy efficient.

[0036] Examples of molybdenum oxide precursor compounds included in the first raw material mixture include metallic molybdenum, molybdenum trioxide, molybdenum dioxide, molybdenum sulfide, ammonium molybdate, and phosphomolybdic acid (H3PMo). 12 O 40 ), silicic acid (H4SiMo12 O 40 ) Aluminum molybdate, silicon molybdate, magnesium molybdate (MgMo n O 3n+1 (n = 1 - 3)), sodium molybdate (Na2Mo n O 3n+1 (n = 1 - 3)), titanium molybdate, iron molybdate, potassium molybdate (K2Mo n O 3n+1 (n = 1 - 3)), zinc molybdate, boron molybdate, lithium molybdate (Li2Mo n O 3n+1 (n = 1 - 3)), cobalt molybdate, nickel molybdate, manganese molybdate, chromium molybdate, cesium molybdate, barium molybdate, strontium molybdate, yttrium molybdate, zirconium molybdate, copper molybdate, etc. can be mentioned. These molybdenum oxide precursor compounds may be used alone or in combination of two or more.

[0037] The molybdenum oxide precursor compound contained in the first raw material mixture preferably contains molybdenum trioxide from the viewpoint of easily controlling the purity, average particle size, and crystal structure of the produced molybdenum trioxide powder. In particular, as the molybdenum oxide precursor compound, it is preferable to use commercially available α - crystal molybdenum trioxide. Further, when ammonium molybdate is used as the molybdenum oxide precursor compound, since it is converted to thermodynamically stable molybdenum trioxide by firing, the vaporized molybdenum oxide precursor compound becomes molybdenum trioxide.

[0038] [[ID=2,7]]Examples of the metal compound particles other than the molybdenum compound contained in the first raw material mixture include aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, silica particles, etc. The metal compound particles other than the molybdenum compound may be used alone or in combination of two or more.

[0039] The metal compound particles other than the molybdenum compound contained in the first raw material mixture are preferably particles made of metal oxides that do not react with the molybdenum oxide precursor compound upon calcination. Examples of particles made of metal oxides that do not react with the molybdenum oxide precursor compound include particles made of one or more metal oxides selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles. Among these particles made of metal oxides, it is preferable that they be particles selected from aluminum oxide particles, magnesium aluminate particles, or titanium oxide particles. This is because these particles made of metal oxides are readily available and inexpensive.

[0040] Among the metal compound particles other than the molybdenum compound included in the first raw material mixture, it is particularly preferable to use particles made of aluminum oxide and / or magnesium aluminate. This is because they have low reactivity with the molybdenum oxide precursor compound, are readily available, and are inexpensive. Furthermore, when aluminum oxide is used as the metal compound particle other than the molybdenum compound, it is preferable that it has an α-crystalline structure.

[0041] The metal compound particles other than the molybdenum compound contained in the first raw material mixture are preferably particles with an average particle diameter of 1 mm or less, and more preferably particles with an average particle diameter of 1 μm or more and 100 μm or less. When the metal compound particles contained in the first raw material mixture have an average particle diameter of 1 mm or less, the function of holding the molten and liquefied molybdenum trioxide and the function of protecting the sheath by reducing the contact area between the liquefied molybdenum trioxide and the sheath are exhibited more effectively. When the metal compound particles contained in the first raw material mixture have an average particle diameter of 1 μm or more, it is preferable because they become metal compound particles that can be easily manufactured. When the metal compound particles contained in the first raw material mixture have an average particle diameter of 2 μm or more, it is more preferable.

[0042] The first raw material mixture preferably contains 50% to 200% by mass of metal compound particles other than the molybdenum compound, and more preferably 100% to 200% by mass of metal compound particles other than the molybdenum compound, based on 100% by mass of the molybdenum oxide precursor compound. When the first raw material mixture contains 50% by mass or more of metal compound particles other than the molybdenum compound, the functions of the metal compound particles in holding the molten and liquefied molybdenum trioxide, and in reducing the contact area between the liquefied molybdenum trioxide and the sheath, thereby protecting the sheath, are exhibited more effectively. Furthermore, when the content of metal compound particles in the first raw material mixture is 200% by mass or less, the amount of molybdenum trioxide vapor generated by calcining the first raw material mixture is reduced, which is preferable as it does not hinder the productivity of molybdenum trioxide powder.

[0043] The first raw material mixture contains a molybdenum oxide precursor compound and metal compound particles other than the molybdenum compound, and it is preferable that it contains only the molybdenum oxide precursor compound and particles made of one or more metal oxides selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles. When the first raw material mixture consists of a molybdenum oxide precursor compound and particles made of one or more of the above metal oxides, no intermediates are generated during the firing process of the first raw material mixture. For this reason, it is not necessary to set the firing temperature to a temperature higher than the decomposition temperature of the intermediates, and the firing temperature can be set to a low temperature of 900°C or less.

[0044] In the first firing process S11, firing conditions such as the heating rate, firing temperature (maximum temperature), and firing time (holding time at the maximum temperature) when firing the first raw material mixture can be appropriately determined according to the type and content of molybdenum oxide precursor compounds and metal compound particles other than molybdenum compounds contained in the first raw material mixture, the amount of the first raw material mixture, etc.

[0045] When the first raw material mixture consists only of a molybdenum oxide precursor compound and particles made of one or more metal oxides selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles, the firing temperature (maximum temperature) for firing the first raw material mixture is preferably 800°C to 1200°C, and more preferably 850°C to 900°C. When the firing temperature is 800°C or higher, the first raw material mixture can be fired and vaporized in a short time, and molybdenum trioxide vapor can be efficiently generated. Furthermore, when the firing temperature is 1200°C or lower, the amount of energy used in the production of molybdenum trioxide powder can be suppressed, which is preferable. Moreover, when the firing temperature is 900°C or lower, the deterioration of the scabbard and firing furnace 2 associated with firing can be suppressed, which is preferable.

[0046] If the first raw material mixture contains not only a molybdenum oxide precursor compound and particles consisting of one or more of the above-mentioned metal oxides, but also metal compounds other than the molybdenum oxide precursor compound and particles consisting of one or more of the above-mentioned metal oxides, an intermediate is generated during the calcination process in which the first raw material mixture is calcined.

[0047] Specifically, for example, if the first raw material mixture contains a molybdenum oxide precursor compound and aluminum hydroxide (Al(OH)3), Al2(MoO4)3 is produced as an intermediate during the calcination process of the first raw material mixture. Therefore, it is necessary to generate molybdenum trioxide (MoO3) vapor from the intermediate by setting the calcination temperature of the first raw material mixture to a temperature of 1000°C or higher, which is the decomposition temperature of the intermediate (Al2(MoO4)3) produced during the calcination process. Accordingly, if the first raw material mixture contains a metal compound other than the molybdenum oxide precursor compound and particles consisting of one or more of the above-mentioned metal oxides, the calcination temperature must be greater than 1000°C, for example, in the range of greater than 1000°C and less than or equal to 1100°C.

[0048] In the first firing step S11, the scabbard used when firing the first raw material mixture can be, for example, mullite cordierite (a mixture of mullite (3Al2O3·2SiO2) and cordierite (2MgO·2Al2O3·5SiO2)), mullite, alumina, or a conventionally known scabbard made of SiC.

[0049] (1st cooling step S12) In the first cooling step S12, molybdenum trioxide powder is produced by cooling the molybdenum trioxide vapor generated in the first firing step S11. In this embodiment, as shown in Figure 1, the exhaust device 8 discharges the gas in the cooling pipe 3 via the dust collector 4, thereby blowing outside air into the cooling pipe 3 from the opening adjustment damper 6. The outside air blown into the cooling pipe 3 cools the molybdenum trioxide vapor generated in the firing furnace 2, causing it to turn into powder.

[0050] In the molybdenum trioxide powder production method of this embodiment, it is preferable to produce molybdenum trioxide powder with an average particle size of 1 nm or more and 100 nm or less in the first cooling step S12. Molybdenum trioxide powder with an average particle size of 100 nm or less has good reactivity with sulfur and can therefore be preferably used as a precursor for molybdenum sulfide. It is more preferable that the average particle size of the molybdenum trioxide powder is 50 nm or less. Furthermore, molybdenum trioxide powder with an average particle size of 1 nm or more can be produced with good yield. It is more preferable that the average particle size of the molybdenum trioxide powder is 1 nm or more.

[0051] In the first cooling step S12, the specific surface area measured by the BET method is 10 m². 2 / g or more 500m 2 It is preferable to produce molybdenum trioxide powder with a specific surface area of ​​10 m² or less. 2 Molybdenum trioxide powder of 1 / g or more is preferable as a precursor for molybdenum sulfide because it has good reactivity with sulfur. The specific surface area of ​​the molybdenum trioxide powder produced is 30 m². 2 It is more preferable that the amount is greater than or equal to / g. Also, the specific surface area is 500m².2 Molybdenum trioxide powder at a concentration of less than / g can be manufactured with good yield. The specific surface area of ​​molybdenum trioxide powder is 300 m². 2 It is more preferable that the value be less than or equal to / g.

[0052] The average particle size and specific surface area of ​​the molybdenum trioxide powder generated in the first cooling step S12 can be adjusted by appropriately controlling conditions such as the content of the molybdenum oxide precursor compound in the first raw material mixture, the cooling rate of the molybdenum trioxide vapor in the cooling pipe 3, and the calcination temperature of the first raw material mixture.

[0053] Furthermore, it is preferable to generate molybdenum trioxide powder containing a β-crystal structure in the first cooling step S12. This is because molybdenum trioxide powder containing a β-crystal structure is less stable and more reactive with sulfur compared to molybdenum trioxide powder with an α-crystal structure, and therefore can be preferably used as a precursor for molybdenum sulfide.

[0054] (1st crushing step S13) In the first crushing step S13, the residue containing metal oxides derived from the metal compound particles remaining in the sac after the first calcination step S11 is crushed to form the first crushed particles. As a method for crushing the residue remaining inside the pod, known methods can be used, such as using one or more crushing devices selected from a roll crusher, pin mill, and hammer mill.

[0055] The first crushed particles (primary particles) formed in the first crushing step S13 preferably have an average particle diameter of 2 mm or less, and more preferably have an average particle diameter of 1 μm or more and 1000 μm or less. When the first crushed particles formed in the first crushing step S13 have an average particle diameter of 2 mm or less, the function of retaining molten and liquefied molybdenum trioxide and the function of protecting the sheath by reducing the contact area between the liquefied molybdenum trioxide and the sheath are exhibited more effectively when the first crushed particles are used as a material for the second raw material mixture in the second calcination step S21. Furthermore, first crushed particles with an average particle diameter of 1 μm or more are preferred because they can be easily and efficiently obtained by crushing the residue containing metal oxides derived from the metal compound particles using a roll crusher. It is more preferable that the first crushed particles have an average particle diameter of 0.7 mm or more.

[0056] The residue remaining inside the scabbard after the first firing process S11 contains metal oxides derived from the metal compound particles used in the first firing process S11, and is formed into a lump by the first firing process S11. The residue remaining in the sac after the first calcination step S11 may contain molybdenum oxide precursor compounds that were not vaporized in the first calcination step S11 and remain in the sac. Even if the residue contains molybdenum oxide precursor compounds, it can be crushed to form first crushed particles, just as it can be if the residue does not contain molybdenum oxide precursor compounds. Furthermore, even if the first crushed particles contain molybdenum oxide precursor compounds, they can be used as material for the second raw material mixture and will not interfere with the second calcination step S21.

[0057] If the first raw material mixture consists only of a molybdenum oxide precursor compound and particles made of one or more metal oxides selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles, then the particles made of metal oxides do not vaporize in the first calcination step S11, and therefore almost the entire amount of the particles made of metal oxides used as material for the first raw material mixture remains in the sac. Consequently, if the entire amount of the first crushed particles produced in the first crushing step S13 is used as material for the second raw material mixture in the second calcination step S21, then almost the entire amount of the particles made of metal oxides used as material for the first raw material mixture can be reused in the second calcination step S21.

[0058] (Second firing process S21) In the second calcination step S21, the second raw material mixture, which includes the molybdenum oxide precursor compound and the first crushed particles formed in the first crushing step S13, is placed in a sieve and calcined in the calcination furnace 2 shown in Figure 1, vaporizing the molybdenum oxide precursor compound to form molybdenum trioxide vapor.

[0059] The second firing step S21 can be the same as the first firing step S11, except that the first crushed particles formed in the first crushing step S13 are used instead of the metal compound particles other than the molybdenum compound used as material for the first raw material mixture in the first firing step S11.

[0060] Therefore, the sac, the type and content of the molybdenum oxide precursor compound in the second raw material mixture (the type and content of the molybdenum oxide precursor compound in the first raw material mixture), and the firing conditions can all be the same in the second firing step S21 and the first firing step S11. However, if necessary, some or all of the sac, the type and content of the molybdenum oxide precursor compound, and the firing conditions may be different. Alternatively, the second raw material mixture may include the molybdenum oxide precursor compound and the first crushed particles, as well as metal compound particles other than the first crushed particles and the molybdenum compound.

[0061] The second raw material mixture preferably contains 50% to 200% by mass of the first crushed particles (or, if it contains metal compound particles other than the first crushed particles and the molybdenum compound, the sum of the metal compound particles and the first crushed particles) per 100% by mass of the molybdenum oxide precursor compound, and more preferably contains 100% to 200% by mass. When the first crushed particles (or, if it contains metal compound particles other than the first crushed particles and the molybdenum compound, the sum of the metal compound particles and the first crushed particles) are present at 50% by mass or more, the function of the first crushed particles (or, if it contains metal compound particles other than the first crushed particles and the molybdenum compound, the sum of the metal compound particles and the first crushed particles) is more effectively exerted, similar to when the first raw material mixture contains 50% by mass or more of metal compound particles. This function allows the first crushed particles (or, if it contains metal compound particles other than the first crushed particles, the sum of the metal compound particles and the first crushed particles) to hold the molten and liquefied molybdenum trioxide and to reduce the contact area between the liquefied molybdenum trioxide and the sheath to protect the sheath. Furthermore, if the content of the first crushed particles (or, if the mixture contains metal compound particles other than the first crushed particles and molybdenum compounds, the total of the metal compound particles and the first crushed particles) is 200% by mass or less, it is preferable that, similar to the case where the content of metal compound particles in the first raw material mixture is 200% by mass or less, the amount of molybdenum trioxide vapor generated by calcination is reduced, which does not impede the productivity of molybdenum trioxide powder.

[0062] The second raw material mixture contains a molybdenum oxide precursor compound and first crushed particles, and may consist only of the molybdenum oxide precursor compound and first crushed particles, or it may contain not only the molybdenum oxide precursor compound and first crushed particles, but also metal compound particles other than the molybdenum oxide precursor compound and first crushed particles. As metal compounds other than the molybdenum oxide precursor compound and the first crushed particles that may be included in the second raw material mixture, the same as those listed as metal compound particles other than molybdenum compounds that may be included in the first raw material mixture can be used.

[0063] The second raw material mixture preferably consists only of a molybdenum oxide precursor compound and first crushed particles. The first crushed particles do not generate intermediates during the calcination process in the second calcination step S21. Therefore, when the second raw material mixture consists only of a molybdenum oxide precursor compound and first crushed particles, the calcination temperature can be set to a low temperature of 900°C or less, which is preferable.

[0064] In the second firing process S21, the firing conditions such as the heating rate, firing temperature (maximum temperature), and firing time (holding time at the maximum temperature) when firing the second raw material mixture can be appropriately determined according to the type and content of the molybdenum oxide precursor compound, the first crushed particles, and any metal compounds other than the molybdenum oxide precursor compound and the first crushed particles that may be contained in the second raw material mixture, as well as the amount of the second raw material mixture.

[0065] When the second raw material mixture consists only of a molybdenum oxide precursor compound and first crushed particles, the firing temperature (maximum temperature) for firing the second raw material mixture is preferably 800°C to 1200°C, and more preferably 850°C to 900°C, similar to the case where the first raw material mixture consists only of a molybdenum oxide precursor compound and particles made of one or more metal oxides selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles.

[0066] (Second cooling step S22) In the second cooling step S22, molybdenum trioxide powder is generated by cooling the molybdenum trioxide vapor generated in the second calcination step S21, in the same manner as when molybdenum trioxide powder is generated in the first cooling step S12.

[0067] In the second cooling step S22, for the same reasons as in the first cooling step S12, the average particle diameter is between 5 nm and 100 nm, and / or the specific surface area measured by the BET method is 10 m². 2 / g or more 500m 2 It is preferable to produce molybdenum trioxide powder with a concentration of less than / g. In the second cooling step S22, for the same reasons as in the first cooling step S12, it is preferable to generate molybdenum trioxide powder containing a β-crystal structure.

[0068] (Second crushing process S23) In the second crushing step S23, the remaining material containing metal oxides derived from the first crushed particles remaining in the casing after the second calcination step S21 is crushed in the same manner as in the first crushing step S13 when crushing the remaining material containing metal oxides derived from the metal compound particles remaining in the casing after the first calcination step S11, thereby obtaining the second crushed particles. The second crushed particles (primary particles) formed in the second crushing step S23 preferably have an average particle diameter of 2 mm or less, and more preferably have an average particle diameter of 1 μm or more and 1000 μm or less, for the same reasons as the first crushed particles formed in the first crushing step S13.

[0069] The residue remaining in the sac after the second firing process S21 contains metal oxides derived from the first crushed particles used in the second firing process S21, and is formed into a lump again by performing the second firing process S21. The residue remaining in the sac after the second calcination step S21 may contain molybdenum oxide precursor compounds that were not vaporized during the second calcination step S21 and remain in the sac. Even if the residue contains molybdenum oxide precursor compounds, it can be crushed to produce second crushed particles, just as it can be crushed to produce second crushed particles, in the same way as when the residue does not contain molybdenum oxide precursor compounds. Furthermore, even if the second crushed particles contain molybdenum oxide precursor compounds, they can be used as material for the second raw material mixture and will not interfere with subsequent second calcination steps S21.

[0070] If the second raw material mixture consists only of a molybdenum oxide precursor compound and first crushed particles, the first crushed particles do not vaporize in the second calcination step S21. Therefore, almost the entire amount of the first crushed particles used as material for the second raw material mixture remains in the pod. Consequently, if the entire amount of first crushed particles produced in the second crushing step S23 is used as material for the second raw material mixture in the second calcination step S21, almost the entire amount of first crushed particles used as material for the second raw material mixture in the first calcination step S21 can be reused.

[0071] In this embodiment, as shown in Figure 2, after the first second crushing step S23, the second calcination step S21, the second cooling step S22, and the second crushing step S23 may be performed once or multiple times in this order.

[0072] The method for producing molybdenum trioxide powder according to this embodiment includes, as shown in Figure 2, a first calcination step S11, a first cooling step S12, a first crushing step S13, a second calcination step S21, a second cooling step S22, and a second crushing step S23. In the method for producing molybdenum trioxide powder according to this embodiment, metal compound particles other than the molybdenum compound are used together with the molybdenum oxide precursor compound in the first calcination step S11, the residue containing metal oxides derived from the metal compound particles remaining in the sac after calcination is crushed to form first crushed particles, and the first crushed particles are used together with the molybdenum oxide precursor compound in the second calcination step S21.

[0073] Therefore, in the molybdenum trioxide powder manufacturing method of this embodiment, the residue containing metal oxides derived from metal compound particles other than the molybdenum compound used in the first calcination step S11 is crushed in the first crushing step S13 to become first crushed particles, which are then reused as material in the second calcination step S21.

[0074] Therefore, the method for producing molybdenum trioxide powder according to this embodiment can reduce material costs compared to, for example, a method in which residual material containing metal oxides derived from metal compound particles other than molybdenum compounds contained in the first raw material mixture is not reused. Furthermore, in the molybdenum trioxide powder manufacturing method of this embodiment, the residual material remaining in the casing after calcination is crushed to form first crushed particles, which are then reused in the second calcination step S21. Therefore, there is no need to discard the residual material remaining in the casing after calcination, and as is the case when the residual material remaining in the casing after calcination is discarded, there are no environmental burdens or disposal costs associated with disposal.

[0075] Although preferred embodiments of the present invention have been described in detail above, the present invention is not limited to any particular embodiment, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Examples]

[0076] "Example 1" Using the molybdenum trioxide powder manufacturing apparatus 1 shown in Figure 1, molybdenum trioxide powder was manufactured by the method described below.

[0077] (First firing process S11) A first raw material mixture was prepared consisting of 500 g of molybdenum trioxide (MoO3) (manufactured by Nippon Inorganic Chemicals Co., Ltd., average particle size 5 μm) as a molybdenum oxide precursor compound, and 500 g of alumina (Al2O3) particles (manufactured by Sumitomo Chemical Co., Ltd., average particle size 4.8 μm), which are metal compound particles other than molybdenum compounds.

[0078] The first raw material mixture was placed in a scabbard made of mullite cordierite and fired in firing furnace 2 to form molybdenum trioxide vapor. The heating rate during firing of the first raw material mixture was 5°C / min, the firing temperature (maximum temperature) was 900°C, and the firing time (holding time at the maximum temperature) was 10 hours.

[0079] (1st cooling step S12) As shown in Figure 1, the exhaust device 8 discharges the gas in the cooling pipe 3 via the dust collector 4, thereby releasing 4.4 m³ of gas into the cooling pipe 3 from the opening adjustment damper 6. 3 Outside air was blown in at a flow rate of / min. This cooled the molybdenum trioxide vapor generated in the firing furnace 2 during the first firing process S11, and generated molybdenum trioxide powder.

[0080] Subsequently, the molybdenum trioxide powder captured by the dust collector 4 was recovered, and the average particle size and specific surface area measured by the BET method were measured using the method described below. The results are shown in Table 2.

[0081] [Method for measuring average particle size] Molybdenum trioxide powder was observed using a transmission electron microscope (TEM) at a magnification of 50,000x. For the smallest unit particle (i.e., primary particle) on the obtained two-dimensional image, its major axis (the Ferret diameter of the longest observed part) and minor axis (the shorter Ferret diameter perpendicular to the Ferret diameter of the longest part) were measured. The average of the major and minor axes of the primary particles was then calculated and defined as the primary particle diameter. Subsequently, the primary particle diameters of 50 randomly selected molybdenum trioxide powder samples from the two-dimensional image were calculated, and the average value of these values ​​was calculated as the average particle diameter of the molybdenum trioxide powder.

[0082] [Method for measuring specific surface area using the BET method] The amount of nitrogen gas adsorbed by molybdenum trioxide powder was measured using the BET method with a specific surface area meter (Microtrac Bell, BELSORP-mini). From the measurement results, the surface area per gram of molybdenum trioxide powder was calculated, and the specific surface area (m²) of the molybdenum trioxide powder was determined. 2 ( / g)

[0083] (1st crushing step S13) The remaining material inside the sac after the first firing process S11 was crushed using a roll crusher to obtain first crushed particles (primary particles), and the average particle size of the first crushed particles was measured using the method described below. The results are shown in Table 2. The average particle size of the first crushed particles was calculated by adding the first crushed particles to a 10% sodium hexametaphosphate aqueous solution, dispersing them using ultrasound, and measuring the wet particle size distribution of the dispersion using a laser diffraction particle size distribution analyzer (device name: MASTERSIZER3000, manufactured by Malvern).

[0084] Furthermore, the composition of the first fragmented particles was identified by elemental analysis using an X-ray fluorescence analyzer (XRF instrument) (product name: Primus IV, manufactured by Rigaku Corporation). As a result, it was confirmed that the first fragmented particles (residual material) contained more than 90% by mass of alumina (Al2O3) and were clumps formed by the adhesion of particles to each other.

[0085] Furthermore, the crystal structure analysis was performed on the first crushed particles and the alumina (Al2O3) particles, which are metal compound particles other than the molybdenum compound used in the first raw material mixture, using X-ray diffraction (XRD) charts obtained from an X-ray diffraction (XRD) instrument (product name: Smart lab, manufactured by Rigaku Corporation). As a result, no significant differences were observed between the crystal structure of the first crushed particles and the crystal structure of the alumina (Al2O3) particles, which are metal compound particles other than the molybdenum compound.

[0086] (Second firing process S21) The process was the same as in the first calcination step S11, except that the first crushed particles formed in the first crushing step S13 were used instead of the alumina (Al2O3) particles used as the material for the first raw material mixture in the first calcination step S11.

[0087] (Second cooling step S22) In the same manner as when molybdenum trioxide powder is generated in the first cooling step S12, molybdenum trioxide powder was generated by cooling the molybdenum trioxide vapor generated in the second calcination step S21.

[0088] Subsequently, the molybdenum trioxide powder captured by the dust collector 4 was recovered, and the average particle size and specific surface area measured by the BET method were measured in the same manner as in the first cooling step S12. The results are shown in Table 2.

[0089] (Second crushing process S23) In the first crushing step S13, the remaining material in the sac after the second calcination step S21 was crushed in the same manner as when crushing the remaining material in the sac after the first calcination step S11, to obtain second crushed particles. Then, the average particle size of the second crushed particles was measured in the same manner as in the first crushing step S13. The results are shown in Table 2.

[0090] Subsequently, the second firing process S21, the second cooling process S22, and the second crushing process S23 were repeated twice in this order. In the second second firing process S21, the second crushed particles obtained in the first second crushing process S23 were used instead of the first crushed particles, and in the third second firing process S21, the second crushed particles obtained in the second second crushing process S23 were used. Furthermore, in the second second crushing process S23, the residue containing metal oxides derived from the second crushed particles obtained in the first second crushing process S23 was crushed instead of the residue containing metal oxides derived from the first crushed particles, and in the third second crushing process S23, the residue containing metal oxides derived from the second crushed particles obtained in the second second crushing process S23 was crushed.

[0091] Then, each time the second cooling step S22 was performed, the average particle diameter and the specific surface area measured by the BET method were measured in the same manner as in the first cooling step S12. The results are shown in Table 2. Furthermore, each time the second crushing step S23 was performed, the average particle size of the second crushed particles was measured in the same manner as in the first crushing step S13. The results are shown in Table 2.

[0092] Example 2 Molybdenum trioxide powder was produced in the same manner as in Example 1, except that in the first calcination step S11, 500 g of magnesium aluminate (MgAl2O4) particles (manufactured by Itochu Corporation, average particle size 20 μm) were used instead of alumina (Al2O3) particles as metal compound particles other than molybdenum compounds.

[0093] In Example 2, the composition of the first crushed particles obtained in the first crushing step S13 was identified using the same method as in Example 1. As a result, it was confirmed that the first crushed particles (residual material) consisted solely of magnesium aluminate (MgAl2O4) and were in the form of clumps formed by the particles adhering to each other.

[0094] Furthermore, the crystal structure analysis was performed on the first crushed particles and the magnesium aluminate (MgAl2O4) particles, which were metal compound particles other than the molybdenum compound used in the first raw material mixture, in the same manner as in Example 1. As a result, no significant differences were observed between the crystal structure of the first crushed particles and the crystal structure of the magnesium aluminate (MgAl2O4) particles, which were metal compound particles other than the molybdenum compound.

[0095] "Example 3" Molybdenum trioxide powder was produced in the same manner as in Example 1, except that the firing temperature (maximum temperature) when firing the first raw material mixture in the first firing step S11 and the firing temperature (maximum temperature) when firing the second raw material mixture in the second firing step S21 were set to 850°C.

[0096] "Comparative Example 1" Molybdenum trioxide powder was produced in the same manner as in Example 1, except that 750g of aluminum hydroxide (Al(OH)3) particles (manufactured by Nippon Light Metal Co., Ltd., average particle size 1 μm) were used instead of alumina (Al2O3) particles, which are metal compound particles other than molybdenum compounds, and the firing temperature was 1100°C (maximum temperature), with only the first firing step S11 and the first cooling step S12 being performed.

[0097] Next, the durability of the sheaths used in the molybdenum trioxide powder manufacturing methods of Examples 1 to 3 was measured by the method described below and evaluated according to the criteria described below. [Method for measuring the durability of the pod] We visually inspected the pods to determine whether there was any obvious corrosion and whether any cracks in the pods rendered them unusable. "Obvious corrosion" means that the erosion of the pod walls was visible to the naked eye. "Unusable due to cracks" means that cracks visible on the inside of the pod were also visible on the outside.

[0098] [Criteria for evaluating the durability of the pods] ○: There is no obvious corrosion on the sheath, and the sheath is not unusable due to any cracks present. △: There is obvious corrosion on the sheath, but the cracks in the sheath do not render it unusable. ×: The sheath does not show obvious corrosion, and the sheath is unusable due to cracks present in the sheath. Or, the sheath shows obvious corrosion, and the sheath is unusable due to cracks present in the sheath.

[0099] Table 1 shows the materials used in the production of molybdenum trioxide powder in Examples 1 to 3 and Comparative Example 1, as well as the calcination temperature.

[0100] [Table 1]

[0101] Table 2 also shows the average particle size and specific surface area measured by the BET method of the molybdenum trioxide powder obtained after each cooling step in Examples 1 to 3 and Comparative Example 1. Furthermore, Table 2 shows the average particle size (primary particles after crushing) of the first crushed particles (or second crushed particles) obtained after each crushing step in Examples 1 to 3. Furthermore, in Examples 1 to 3 and Comparative Example 1, the molybdenum trioxide powder obtained after each cooling step was examined using an X-ray diffraction (XRD) apparatus (product name: Smart lab, manufactured by Rigaku Corporation) to confirm whether or not it contained a β-crystal structure. The results are shown in Table 2.

[0102] [Table 2]

[0103] In the molybdenum trioxide powder production methods of Examples 1 to 3, the first calcination step S11, the first cooling step S12, and the first crushing step S13 were performed, followed by the second calcination step S21, the second cooling step S22, and the second crushing step S23 being repeated three times. Therefore, in the molybdenum trioxide powder production methods of Examples 1 to 3, metal compound particles other than the molybdenum compound were used together with the molybdenum oxide precursor compound in the first calcination step S11, the residue containing metal oxides derived from the metal compound particles remaining in the sac after calcination was crushed to form the first crushed particles, and the first crushed particles were used together with the molybdenum oxide precursor compound in the second calcination step S21.

[0104] Therefore, in the molybdenum trioxide powder manufacturing methods of Examples 1 to 3, the residue containing metal oxides derived from metal compound particles other than the molybdenum compound used in the first calcination step S11 was crushed in the first crushing step S13 to become first crushed particles, which were then reused as material in the second calcination step S21. Furthermore, the residue containing metal oxides derived from the first crushed particles used in the first (second) second calcination step S21 was crushed in the first (second) second crushing step S23 to become second crushed particles, which were then reused as material in the second (third) second calcination step S21.

[0105] Therefore, the methods for producing molybdenum trioxide powder in Examples 1 to 3 can reduce material costs compared to Comparative Example 1, which does not reuse residual material containing metal oxides derived from metal compound particles other than molybdenum compounds (aluminum hydroxide (Al(OH)3) particles) in the first raw material mixture.

[0106] Furthermore, in the molybdenum trioxide powder production methods of Examples 1 to 3, the residual material remaining in the casing after calcination was crushed to form first crushed particles (or second crushed particles), which were then reused in the second calcination step S21. Therefore, there is no need to discard the residual material remaining in the casing after calcination, and thus no environmental burden or disposal costs are incurred, as would be the case if the residual material remaining in the casing after calcination were to be discarded.

[0107] As shown in Table 2, no differences were observed in the average particle size of the molybdenum trioxide powder obtained after each cooling step, or in the specific surface area measured by the BET method, in the molybdenum trioxide powder production methods of Examples 1 to 3. This confirmed that molybdenum trioxide powder of similar quality can be obtained whether metal compound particles other than molybdenum compounds are used together with the molybdenum oxide precursor compound, or whether first crushed particles (or second crushed particles) are used together with the molybdenum oxide precursor compound.

[0108] Furthermore, as shown in Table 2, it was confirmed that the molybdenum trioxide powder production methods of Examples 1 to 3 improved the durability of the pods and suppressed pod deterioration compared to the molybdenum trioxide powder production method of Comparative Example 1. This is presumed to be because, in Examples 1 to 3, the firing temperature was 900°C or lower, which suppressed the deterioration of the pods during firing. Furthermore, in the molybdenum trioxide powder manufacturing methods of Examples 1 to 3, the calcination temperature is 900°C or lower, which allows for the reduction of the amount of energy used in the production of molybdenum trioxide powder.

[0109] Furthermore, as shown in Table 2, in the molybdenum trioxide powder production methods of Examples 1 to 3, it was confirmed that molybdenum trioxide powder containing a β-crystal structure was generated in the first and second cooling steps. [Explanation of symbols]

[0110] 1; Manufacturing equipment, 2; Firing furnace, 3; Cooling piping, 4; Dust collector, 5; Exhaust port, 6; Opening adjustment damper, 7; Observation window, 8; Exhaust device, 9; External cooling device, S11; First firing process, S12; First cooling process, S13; First crushing process, S21; Second firing process, S22; Second cooling process, S23; Second crushing process.

Claims

1. A first calcination step involves placing a first raw material mixture containing a molybdenum oxide precursor compound and metal compound particles other than the molybdenum compound into a scabbard and calcining it to vaporize the molybdenum oxide precursor compound and form molybdenum trioxide vapor, A first cooling step is performed to generate molybdenum trioxide powder by cooling the molybdenum trioxide vapor generated in the first calcination step, A first crushing step is performed to crush the residue containing metal oxides derived from the metal compound particles remaining in the sac after the first firing step to obtain first crushed particles, A second calcination step involves placing a second raw material mixture containing a molybdenum oxide precursor compound and the first crushed particles into a scabbard and calcining it to vaporize the molybdenum oxide precursor compound and form molybdenum trioxide vapor, A second cooling step is performed to generate molybdenum trioxide powder by cooling the molybdenum trioxide vapor generated in the second calcination step, A method for producing molybdenum trioxide powder, comprising: a second crushing step of crushing the residue containing metal oxides derived from the first crushed particles remaining in the sac after the second calcination step to obtain second crushed particles.

2. The method for producing molybdenum trioxide powder according to claim 1, wherein the average particle size of the first crushed particles and the second crushed particles is 1 mm or less.

3. The method for producing molybdenum trioxide powder according to claim 1, wherein the metal compound particles are one or more selected from aluminum oxide particles, magnesium aluminate particles, titanium oxide particles, iron oxide particles, zinc oxide particles, and silica particles.

4. The first raw material mixture consists of the molybdenum oxide precursor compound and the metal compound particles, and in the first firing step, it is fired at a temperature of 800°C to 1200°C. The method for producing molybdenum trioxide powder according to claim 3, wherein the second raw material mixture consists of the molybdenum oxide precursor compound and the first crushed particles, and the second calcination step is performed by calcining at a temperature of 800°C to 1200°C.

5. The first raw material mixture contains 50% to 200% by mass of the metal compound particles with respect to 100% by mass of the molybdenum oxide precursor compound. The method for producing molybdenum trioxide powder according to claim 3, wherein the second raw material mixture contains 50% by mass or more and 200% by mass or less of the first crushed particles with respect to 100% by mass of the molybdenum oxide precursor compound.

6. A method for producing molybdenum trioxide powder according to claim 1, wherein in the first cooling step and the second cooling step, molybdenum trioxide powder having an average particle diameter of 5 nm or more and 100 nm or less is produced.

7. In the first and second cooling steps, the specific surface area measured by the BET method is 10 m². ２ / g or more 500m ２ A method for producing molybdenum trioxide powder according to claim 1, which produces molybdenum trioxide powder of less than / g.

8. A method for producing molybdenum trioxide powder according to claim 1, wherein the first cooling step and the second cooling step produce molybdenum trioxide powder containing a β-crystal structure.

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