Molybdenum compounds and methods of making the same

Abstract

A molybdenum compound is a molybdenum compound represented by the general formula MoX a (incidentally, X is a Group 14 element, a Group 15 element or a Group 16 element, and a is 0.5, 1 or 2.) The above-mentioned molybdenum compound represented by the general formula MoX a When X is a Group 14 element in the above-mentioned general formula MoX 2 The above-mentioned molybdenum compound represented by the general formula MoX a When X is a Group 15 element or a Group 16 element in the above-mentioned general formula MoX 2 Hereinafter, the particle diameter is 10 nm or more and less than 1000 nm.

Description

TECHNICAL FIELD

[0001] The present application relates to a molybdenum compound and a method for producing the same.

[0002] This application is based on Japanese Priority Application No. 2021-050482 filed on March 24, 2021, the content of which is incorporated herein by reference. BACKGROUND

[0003] Inorganic nanoparticles are materials expected to be used in various fields. In particular, inorganic nanoparticles have a large specific surface area, and thus sometimes exhibit high activity in uses such as catalysts. However, from the viewpoint of material design, a large specific surface area sometimes becomes a problem. For example, in terms of the compatibility of inorganic nanoparticles with organic materials, the larger the specific surface area of inorganic nanoparticles, the more the compatibility with organic materials decreases. On the other hand, inorganic materials that are superior to organic materials in terms of heat resistance and light resistance are expected to exhibit characteristics that cannot be exhibited when organic materials alone or inorganic materials alone are used by being mixed with organic materials, and thus the problem of the compatibility of inorganic nanoparticles with organic materials has become an important issue in material development.

[0004] Generally, inorganic nanoparticles have low compatibility with organic materials. As a method generally performed to improve the compatibility, surface modification of inorganic nanoparticles can be cited. This is a method of improving the compatibility with organic materials by modifying the surface of inorganic nanoparticles with organic materials. For example, Patent Literature 1 describes inorganic nanoparticles that have been surface-modified using a sol-gel method.

[0005] PRIOR ART DOCUMENTS

[0006] PATENT LITERATURE

[0007] Patent Literature 1: Japanese Patent Application Publication No. 2008-44835 SUMMARY

[0008] Problem to be solved by the invention

[0009] However, the present inventors have conducted research, and as a result, it has been found that the reason why inorganic nanoparticles have low compatibility with organic materials can be cited as the influence of functional groups present on the surface of inorganic nanoparticles. In particular, in the case of oxide nanoparticles, the surface thereof is covered with functional groups such as hydroxyl groups, and thus inorganic nanoparticles exhibit a surface state in which the hydrophilicity is high. Thus, there is a problem in that the compatibility with organic materials that have high hydrophobicity decreases.

[0010] The present application has been made in view of the above-described circumstances, and the problem to be solved by the present application is to provide inorganic nanoparticles that have good compatibility with organic materials.

[0011] Solution to the problem

[0012] The present application includes the following modes.

[0013] (1) A molybdenum compound which is a molybdenum compound represented by the general formula MoXa a wherein X is a Group 14 element, a Group 15 element or a Group 16 element, and a is 0.5, 1 or 2. a wherein X is a Group 14 element, the number of functional groups per unit area of the surface of the above molybdenum compound is 10 / nm 2 wherein X is a Group 14 element, the number of functional groups per unit area of the surface of the above molybdenum compound is 10 / nm a wherein X is a Group 15 element or a Group 16 element, the number of functional groups per unit area of the surface of the above molybdenum compound is 100 / nm 2 wherein X is a Group 15 element or a Group 16 element, the number of functional groups per unit area of the surface of the above molybdenum compound is 100 / nm

[0014] (2) The molybdenum compound according to the above (1), wherein a wherein X is a Group 14 element, X is C and a is 0.5 or 1, or X is Si and a is 2. a wherein X is a Group 15 element, X is N or P and a is 1 or 2. a wherein X is a Group 16 element, X is S, Se or Te and a is 2.

[0015] (3) The molybdenum compound according to the above (1) or (2), wherein the functional group is a hydroxyl group.

[0016] (4) A method for producing the molybdenum compound according to any one of the above (1) to (3), comprising the step of heating a molybdenum trioxide particle having an average particle diameter of 5 nm or more and less than 1000 nm in the presence of a Group 14 element, a Group 15 element or a Group 16 element at 400 to 1500°C.

[0017] Effects of the invention

[0018] According to the present application, it is possible to provide an inorganic nanoparticle having good compatibility with an organic material. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic view showing an example of an apparatus used in the production of a molybdenum trioxide particle which is a raw material of a molybdenum sulfide particle.

[0020] Figure 2 is an XRD spectrum of a molybdenum compound of an example. DETAILED DESCRIPTION

[0021] Embodiments of the present application will be explained in detail below with reference to the drawings.

[0022] <Molybdenum Compounds>

[0023] The molybdenum compound of this embodiment is such as the general formula MoX. a As shown. General formula MoX a In this context, X represents a group 14, 15, or 16 element, and a represents 0.5, 1, or 2.

[0024] The above general formula MoX a In the context of X, elements belonging to Group 14 can include C, Si, Ge, Sn, or Pb. From the perspective of applicability, safety, and raw material cost in various materials, C or Si are preferred as Group 14 elements in X. MoC compounds can be used as catalysts and additives in superhard alloys. Furthermore, MoSi compounds can be used in ultra-heat-resistant materials and thermoelectric conversion materials.

[0025] The above general formula MoX a In the case where X is C, from the perspective of the stability of molybdenum compounds, a is preferably 0.5 or 1.

[0026] The above general formula MoX a In the case where X is Si, from the perspective of the stability of molybdenum compounds, a is preferably 2.

[0027] The above general formula MoX a In the context of X, elements that are group 15 can include N, P, As, Sb, or Bi. Among these, N and P are preferred due to their low toxicity, while P is particularly preferred because it is easy to process.

[0028] The above general formula MoX a In the case where X is P, a is preferably 1 or 2.

[0029] The above general formula MoX a In the molybdenum compound, elements such as O, S, Se, or Te can be included as group 16 elements. Among these, S, Se, or Te are preferred. When X is S, Se, or Te, transition metal dichalcogenides (TMDs) can be obtained as molybdenum compounds. TMDs are promising materials for future applications in various fields such as electrical, environmental, and energy sectors.

[0030] The above general formula MoX a When X is S, Se or Te, from the perspective of the stability of molybdenum compounds, a is preferably 2.

[0031] For the molybdenum compound of this embodiment, the above general formula MoX a When X is a group 14 element, the number of functional groups per unit area is 10 / nm. 2 Below, 8 per nm is preferred.2 Further preferably, the number of functional groups per unit area is 7 / nm 2 Further.

[0032] The above general formula MoXa a When X is a Group 14 element, the number of functional groups per unit area is 10 / nm 2 When the above condition is satisfied, the surface energy of the molybdenum compound particles can be reduced, and thus the compatibility of the molybdenum compound with organic materials can be improved.

[0033] For the molybdenum compound of the present embodiment, when X is a Group 15 element or a Group 16 element in the above general formula MoXa, the number of functional groups per unit area is 100 / nm 2 Preferably, the number of functional groups per unit area is 80 / nm 2 More preferably, the number of functional groups per unit area is 70 / nm 2 Further.

[0034] The above general formula MoXa a When X is a Group 15 element or a Group 16 element, the number of functional groups per unit area is 100 / nm 2 When the above condition is satisfied, the surface energy of the molybdenum compound particles can be reduced, and thus the compatibility of the molybdenum compound with organic materials can be improved.

[0035] In the present embodiment, the number of functional groups per unit area of the surface of the above molybdenum compound is measured, for example, by the following method.

[0036] (Measurement method of the number of functional groups per unit area)

[0037] Measurement of a blank: 0.5 g of sodium chloride as a stabilizer was added to 20 ml of pure water, and the pH of the liquid was adjusted to about 4 with hydrochloric acid. To this, 0.01 N sodium hydroxide aqueous solution was slowly added until the pH reached about 9, which was taken as the end point. The amount of the sodium hydroxide aqueous solution required at this time was set as V blank .

[0038] Measurement of a sample: about 0.05 g of a sample of the molybdenum compound was accurately weighed, and 20 ml of pure water was added thereto. 0.5 g of sodium chloride was added and dissolved. The pH was adjusted to the same pH as the blank using hydrochloric acid. This was titrated with 0.01 N sodium hydroxide until the pH was adjusted to the same pH as the end point of the blank. The amount of the sodium hydroxide aqueous solution required at this time was set as V.

[0039] Number of functional groups per unit area: the number of functional groups per unit area was calculated using the following formula. Note that the value of the specific surface area was measured in advance using a BET specific surface area meter. Number of functional groups per unit area (number / nm 2 ) = 6.023 f (V - V blank) / WA, where f represents a factor of the sodium hydroxide aqueous solution, W represents the sample weight, and A represents the specific surface area.

[0040] Note that the factor f of the sodium hydroxide aqueous solution is calculated by the following formula.

[0041] f = [(true concentration of the standard solution obtained by calibration)] / (indicated concentration of the prepared standard solution)

[0042] Generally, surface functional groups have a tendency to form hydroxyl groups due to moisture in the air. Therefore, in the present embodiment, the number of functional groups per unit area of the surface of the molybdenum compound is preferably based on the number of hydroxyl groups from the viewpoint of being a standard of the compatibility of the molybdenum compound with organic materials.

[0043] The particle diameter of the molybdenum compound of the present embodiment is 10 nm or more and less than 1000 nm, preferably 15 nm or more and 800 nm or less, and more preferably 20 nm or more and 500 nm or less.

[0044] When the particle diameter of the molybdenum compound is 10 nm or more, the crystallinity is easily improved, and the performance thereof is easily exhibited. When the particle diameter is less than 10 nm, it is difficult to obtain a high-crystallinity particle, and it is difficult to obtain high performance. On the other hand, when the particle diameter of the molybdenum compound is less than 1000 nm, the surface energy of the molybdenum compound particle can be reduced, and thus the compatibility of the molybdenum compound with organic materials can be improved. When the particle diameter is 1000 nm or more, although the compatibility is improved, the specific surface area of the particle is very small, and thus it is difficult to obtain high performance.

[0045] Note that, regarding the particle diameter of the molybdenum compound in the present embodiment, the length of 50 particles is randomly measured using an electron microscope such as a transmission electron microscope (TEM), and the average thereof is taken as the particle diameter. For example, the average particle diameter of the primary particles of the molybdenum trioxide particles described later can be measured by the same method.

[0046] The molybdenum compound of the present embodiment has a reduced number of functional groups on the surface of the particle, and thus the surface energy of the particle is reduced. Therefore, the hydrophobicity of the surface of the particle of the molybdenum compound of the present embodiment is improved, and the compatibility with organic materials is improved. Thus, the molybdenum compound of the present embodiment exhibits excellent characteristics in organic-inorganic hybrid materials such as hydrogen production catalysts, photocatalysts, fuel cell catalysts, CO2 reduction catalysts, semiconductors, and thermoelectric materials.

[0047] <Method for producing molybdenum compound>

[0048] The method for producing the molybdenum compound of the present embodiment includes a step of heating molybdenum trioxide particles having an average particle diameter of primary particles of 5 nm or more and less than 1000 nm at 400 to 1500°C, preferably 500 to 1000°C, more preferably 700 to 900°C, in the presence of a Group 14 element, a Group 15 element, or a Group 16 element.

[0049] By setting the heating temperature within the above range, a molybdenum compound having a reduced number of functional groups present on the surface of the particles can be obtained.

[0050] In the method for producing the molybdenum compound of the present embodiment, the heating time is not particularly limited and can be a time sufficient for the reaction to proceed, and can be 1 to 48 hours, can be 2 to 24 hours, or can be 4 to 12 hours.

[0051] In the method for producing the molybdenum compound of the present embodiment, the molybdenum trioxide particles have an average particle diameter of primary particles of 5 nm or more and less than 1000 nm, preferably 5 nm or more and 500 nm or less, and more preferably 5 nm or more and 200 nm or less.

[0052] When the average particle diameter of the primary particles of the molybdenum trioxide particles is within the above range, the reactivity with the Group 14 element, the Group 15 element, or the Group 16 element becomes good, and in addition, a molybdenum compound having a reduced number of functional groups present on the surface of the particles can be easily obtained. The number of functional groups per unit area of the surface of the molybdenum compound of the present embodiment is 100 / nm 2 Hereinafter, in order to improve the compatibility of the molybdenum compound of the present embodiment with an organic material, the average particle diameter of the primary particles of the molybdenum trioxide particles used as a raw material is particularly preferably 5 nm or more and 200 nm or less.

[0053] The average particle diameter of the primary particles of the molybdenum trioxide particles refers to the average of the primary particle diameters of 50 randomly selected primary particles when the primary particle diameters are measured by taking a photograph of the molybdenum trioxide particles using a transmission electron microscope (TEM) and measuring the major axis (Feret diameter of the longest portion observed) and the minor axis (Feret diameter of the shorter portion perpendicular to the Feret diameter of the longest portion) of the particles constituting the smallest unit of the aggregate (i.e., the primary particles) on a two-dimensional image, and averaging the values. The average particle diameter of the primary particles of the molybdenum compound of the present embodiment can be measured in the same manner.

[0054] The molybdenum trioxide particles used in the production method of the molybdenum compound of the present embodiment preferably contain an aggregate of primary particles containing a β crystal structure of molybdenum trioxide. The molybdenum trioxide particles containing an aggregate of primary particles containing a β crystal structure of molybdenum trioxide have good reactivity with Group 14 elements, Group 15 elements, and Group 16 elements, and because of the β crystal structure of molybdenum trioxide, the conversion rate R to the molybdenum compound represented by the general formula MoX a C In addition, functional groups such as hydroxyl groups that are present on the surface of the molybdenum trioxide particles are not easily left, and thus a molybdenum compound in which the number of functional groups present on the surface of the particles is reduced is easily obtained.

[0055] The β crystal structure of molybdenum trioxide can be confirmed from the presence of a peak attributed to the (011) plane of the β crystal of MoO3 (2θ: around 23.01°, No. 86426 (Inorganic Crystal Structure Database (ICSD))) in a spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as an X-ray source. The α crystal structure of molybdenum trioxide can be confirmed from the presence of a peak of the (021) plane of the α crystal of MoO3 (2θ: around 27.32°, No. 166363 (Inorganic Crystal Structure Database (ICSD))).

[0056] As the Group 14 element in the production method of the molybdenum compound of the present embodiment, C, Si, Ge, Sn, Pb, or the like can be exemplified. Of these, C or Si is preferable as the Group 14 element from the viewpoint of the application properties, safety, and raw material cost of various materials. The MoC compound can be used in catalysts, superhard alloy additives, and the like. In addition, the MoSi compound can be used in superheat-resistant materials, thermoelectric conversion materials, and the like.

[0057] As the Group 15 element, N, P, As, Sb, Bi, or the like can be exemplified. Of these, N or P is preferable as the Group 15 element because of low toxicity, and P is particularly preferable because of easy handling.

[0058] As the Group 16 element, O, S, Se, Te, or the like can be exemplified. Of these, S, Se, or Te is preferable as the Group 16 element. When X is S, Se, or Te, a transition metal dichalcogenide (TMD) can be obtained as the molybdenum compound. TMDs are materials that are expected to be used in various fields such as electricity, the environment, and energy in the future.

[0059] ​In the production method of the molybdenum compound according to the present embodiment, the amount of the Group 14 element, the Group 15 element, or the Group 16 element relative to the amount of MoO3of the above-described molybdenum trioxide powder in the raw material ratio can be any value as long as the reaction can sufficiently proceed. The amount of the Group 14 element, the Group 15 element, or the Group 16 element relative to 100 mol% of the amount of MoO3of the above-described molybdenum trioxide powder is preferably 120 mol% or more, preferably 150 mol% or more, and preferably 200 mol% or more. The amount of the Group 14 element, the Group 15 element, or the Group 16 element relative to 100 mol% of the amount of MoO3of the above-described molybdenum trioxide powder can be 1000 mol% or less, can be 500 mol% or less, and can be 300 mol% or less.

[0060] In the production method of the molybdenum compound according to the present embodiment, the content ratio of MoO3of the above-described molybdenum trioxide powder measured by fluorescent X-ray (XRF) is preferably 99.6% or more, and thus the conversion rate R of the molybdenum compound represented by the above general formula MoX a C to the molybdenum compound represented by the above general formula MoX

[0061] In the production method of the molybdenum compound according to the present embodiment, in the spectrum obtained by powder X-ray diffraction (XRD) using Cu-Kα rays as an X-ray source of the above-described molybdenum trioxide powder, the ratio of the peak intensity of the (011) plane attributed to the β crystal of MoO3to the peak intensity of the (021) plane attributed to the α crystal of MoO3(β(011) / α(021)) is preferably 0.1 or more.

[0062] The above-described ratio (β(011) / α(021)) is obtained by reading the maximum intensity of the peak of the peak intensity of the (011) plane attributed to the β crystal of MoO3and the peak intensity of the (021) plane attributed to the α crystal of MoO3, respectively.

[0063] The above-described ratio (β(011) / α(021)) of the above-described molybdenum trioxide powder is preferably 0.1 to 10.0, more preferably 0.2 to 10.0, and particularly preferably 0.4 to 10.0.

[0064] The specific surface area of the above-described molybdenum trioxide powder measured by the BET method is preferably 10 m 2 / g or more and 100 m 2 / g or less.

[0065] The above-described specific surface area of the above-described molybdenum trioxide powder is preferably 10 m 2 / g or more, preferably 20 m 2 / g or more, and preferably 30 m 2 ​or more. Of the above-mentioned molybdenum trioxide powder, from the viewpoint of easier production, it is preferable that the particle diameter be 100 nm or less, more preferable that it be 90 nm or less, and even more preferable that it be 80 nm or less. 2 2 2

[0066] In the radial distribution function of the above-mentioned molybdenum trioxide powder, obtained from the extended X-ray absorption fine structure (EXAFS) spectrum of the K absorption edge of molybdenum, the ratio (I / II) of the peak intensity I derived from Mo-O to the peak intensity II derived from Mo-Mo is preferably greater than 1.1.

[0067] For the peak intensity I derived from Mo-O and the peak intensity II derived from Mo-Mo, the maximum intensity of the peak is read respectively, and the above-mentioned ratio (I / II) is calculated. It is considered that the above-mentioned ratio (I / II) can be a standard for the β crystal structure of MoO3 having been obtained in the molybdenum trioxide powder, and the greater the above-mentioned ratio (I / II) is, the more excellent the reactivity with the Group 14 element, the Group 15 element, or the Group 16 element is.

[0068] Of the above-mentioned molybdenum trioxide powder, the above-mentioned ratio (I / II) is preferably 1.1 to 5.0, more preferably 1.2 to 4.0, and even more preferably 1.2 to 3.0.

[0069] (Method for producing molybdenum trioxide powder)

[0070] The above-mentioned molybdenum trioxide powder can be produced by vaporizing a molybdenum oxide precursor compound to form molybdenum trioxide vapor, and cooling the above-mentioned molybdenum trioxide vapor.

[0071] The above-mentioned method for producing molybdenum trioxide powder includes the step of calcining a raw material mixture containing a molybdenum oxide precursor compound and a metal compound other than the above-mentioned molybdenum oxide precursor compound to vaporize the above-mentioned molybdenum oxide precursor compound to form molybdenum trioxide vapor, and the ratio of the above-mentioned metal compound is preferably 70 mass% or less, calculated as an oxide, with respect to 100 mass% of the above-mentioned raw material mixture.

[0072] The above-mentioned method for producing molybdenum trioxide powder can use the production apparatus 1 shown in Fig. 1. Figure 1 The production apparatus 1 shown in Fig. 1 is suitably implemented.

[0073] Figure 1 ​​​A schematic view of an example of an apparatus used for manufacturing the above-mentioned molybdenum trioxide powder. The manufacturing apparatus 1 has: a calcination furnace 2 that calcines a molybdenum oxide precursor compound or the above-mentioned raw material mixture and vaporizes the above-mentioned molybdenum oxide precursor compound; a cross-shaped cooling pipe 3 that is connected to the above-mentioned calcination furnace 2 and powderizes the molybdenum trioxide vapor vaporized by the above-mentioned calcination; and a recovery mechanism, i.e., a recovery machine 4, that recovers the molybdenum trioxide powder powderized in the above-mentioned cooling pipe 3. At this time, the above-mentioned calcination furnace 2 and the cooling pipe 3 are connected by means of an exhaust port 5. In addition, the above-mentioned cooling pipe 3 is provided with an opening degree adjustment damper 6 at the left end portion at an external gas suction port (not shown) and is provided with an observation window 7 at the upper end portion. The recovery machine 4 is connected with a first air supply mechanism, i.e., an exhaust device 8. The exhaust device 8 performs exhaust, whereby the recovery machine 4 and the cooling pipe 3 are suctioned and external gas is supplied to the cooling pipe 3 from the opening degree adjustment damper 6 provided in the cooling pipe 3. That is, the suction function is exerted by the exhaust device 8, whereby the supply is passively performed in the cooling pipe 3. Note that the manufacturing apparatus 1 can have an external cooling device 9, whereby the cooling conditions of the molybdenum trioxide vapor generated from the calcination furnace 2 can be arbitrarily controlled.

[0074] The molybdenum trioxide vapor vaporized in the calcination furnace 2 is cooled in an air atmosphere by means of the opening degree adjustment damper 6 from the external gas suction port, and the molybdenum trioxide powder is formed, whereby the above-mentioned ratio (I / II) can be set to be greater than 1.1 and the β crystal structure of MoO3 is easily obtained in the molybdenum trioxide powder. In the case where the molybdenum trioxide vapor is cooled using liquid nitrogen or the like in a state where the oxygen concentration in a nitrogen atmosphere is low, the cooling of the molybdenum trioxide vapor easily increases the oxygen defect density, and the above-mentioned ratio (I / II) is decreased.

[0075] As the molybdenum oxide precursor compound, there is no particular limitation as long as it is a precursor compound used for forming the molybdenum trioxide powder, and the precursor compound contains an aggregate of primary particles including the β crystal structure of molybdenum trioxide.

[0076] As the above-mentioned molybdenum oxide precursor compound, there is no particular limitation as long as it is a substance that forms molybdenum trioxide vapor by calcination, and examples thereof include metallic molybdenum, molybdenum trioxide, molybdenum dioxide, molybdenum sulfide, ammonium molybdate, phosphomolybdic acid (H3PMo 12 O 40 ), silicomolybdic acid (H4SiMo 12 O 40 ), aluminum molybdate, silicon molybdate, magnesium molybdate (MgMo n O 3n+1 (n = 1 to 3), sodium molybdate (Na2Mo n O 3n+1 (n = 1 to 3), titanium molybdate, iron molybdate, potassium molybdate (K2Mo n O 3n+1(n = 1 to 3), zinc molybdate, boron molybdate, lithium molybdate (Li2Mo n O 3n+1 (n = 1 to 3), zinc molybdate, boron molybdate, lithium molybdate (Li2Mo

[0077] As the molybdenum oxide precursor compound, commercially available α-crystal molybdenum trioxide is preferably used. In the case where ammonium molybdate is used as the molybdenum oxide precursor compound, it is converted to thermodynamically stable molybdenum trioxide by calcination, and thus the vaporized molybdenum oxide precursor compound becomes the above-described molybdenum trioxide.

[0078] Among these molybdenum oxide precursor compounds, molybdenum trioxide is preferably contained from the viewpoint of easily controlling the purity, average particle diameter of primary particles, and crystal structure of the molybdenum trioxide powder to be obtained.

[0079] The molybdenum trioxide vapor can also be formed by calcining a raw material mixture containing the molybdenum oxide precursor compound and a metal compound other than the above-described molybdenum oxide precursor compound.

[0080] As the metal compound other than the above-described molybdenum oxide precursor compound, there is no particular limitation, and examples include aluminum compounds, silicon compounds, titanium compounds, magnesium compounds, sodium compounds, potassium compounds, zirconium compounds, yttrium compounds, zinc compounds, copper compounds, iron compounds, and the like. Among these, aluminum compounds, silicon compounds, titanium compounds, and magnesium compounds are preferably used.

[0081] The molybdenum oxide precursor compound and the metal compound other than the above-described molybdenum oxide precursor compound sometimes generate an intermediate, but even in this case, the intermediate can be decomposed by calcination to vaporize the molybdenum trioxide in a thermodynamically stable form.

[0082] As the metal compound other than the above-described molybdenum oxide precursor compound, among these, aluminum compounds are preferably used in order to prevent damage to the calcination furnace, and the above-described metal compound other than the molybdenum oxide precursor compound can also not be used in order to improve the purity of the molybdenum trioxide powder.

[0083] As the aluminum compound, examples include aluminum chloride, aluminum sulfate, basic aluminum acetate, aluminum hydroxide, boehmite, pseudoboehmite, transition alumina (γ-alumina, δ-alumina, θ-alumina, and the like), α-alumina, mixed alumina having two or more crystal phases, and the like.

[0084] When the raw material mixture containing the molybdenum oxide precursor compound and the metal compound other than the above molybdenum oxide precursor compound is fired, the content ratio of the above molybdenum oxide precursor compound with respect to 100 mass% of the above raw material mixture is preferably 40 to 100 mass%, can be 45 to 100 mass%, and can be 50 to 100 mass%.

[0085] As the firing temperature, it is generally preferable to set the temperature at which the intermediate can be decomposed, depending on the molybdenum oxide precursor compound, the metal compound, and the desired molybdenum trioxide powder, etc. to be used. For example, in the case where a molybdenum compound is used as the molybdenum oxide precursor compound and an aluminum compound is used as the metal compound, it is possible to form aluminum molybdate as the intermediate, and therefore, the firing temperature is preferably 500 to 1500°C, more preferably 600 to 1550°C, and further preferably 700 to 1600°C.

[0086] The firing time is not particularly limited, and for example, it can be set to 1 minute to 30 hours, can be set to 10 minutes to 25 hours, and can be set to 100 minutes to 20 hours.

[0087] The temperature increase rate also differs depending on the molybdenum oxide precursor compound, the above metal compound, and the characteristics of the desired molybdenum trioxide powder, etc. to be used, and from the viewpoint of manufacturing efficiency, it is preferably 0.1°C / minute or more and 100°C / minute or less, more preferably 1°C / minute or more and 50°C / minute or less, and further preferably 2°C / minute or more and 10°C / minute or less.

[0088] The internal pressure in the firing furnace is not particularly limited, and can be positive pressure or reduced pressure, and from the viewpoint of appropriately discharging the molybdenum oxide precursor compound from the firing furnace to the cooling pipe, the firing is preferably performed under reduced pressure. As a specific degree of reduced pressure, it is preferably -5000 Pa to -10 Pa, more preferably -2000 Pa to -20 Pa, and further preferably -1000 Pa to -50 Pa. When the degree of reduced pressure is -5000 Pa or more, the high airtightness and mechanical strength of the firing furnace are not excessively required, and the manufacturing cost can be reduced, and therefore, it is preferable. On the other hand, when the degree of reduced pressure is -10 Pa or less, the clogging of the molybdenum oxide precursor compound at the discharge port of the firing furnace can be prevented, and therefore, it is preferable.

[0089] Note that when the air supply gas is supplied to the firing furnace during the firing, the temperature of the supplied gas is preferably 5 to 500°C, and more preferably 10 to 100°C.

[0090] In addition, the air supply rate of the gas with respect to the effective volume 100 L of the firing furnace is preferably 1 L / minute or more and 500 L / minute or less, and more preferably 10 L / minute or more and 200 L / minute or less.

[0091] The temperature of the vaporized molybdenum trioxide vapor differs depending on the kind of the molybdenum trioxide precursor compound used, and is preferably 200 to 2000°C, more preferably 400 to 1500°C. Note that if the temperature of the vaporized molybdenum trioxide vapor is 2000°C or less, there is generally a tendency to be easily powderized by the blast of external air (0 to 100°C) in the cooling pipe.

[0092] The discharge rate of the molybdenum trioxide vapor discharged from the calcination furnace can be controlled by the amount of the above-mentioned molybdenum trioxide precursor compound used, the amount of the above-mentioned metal compound, the temperature of the calcination furnace, the blast of gas into the calcination furnace, and the diameter of the exhaust port of the calcination furnace. The discharge rate of the molybdenum trioxide vapor from the calcination furnace to the cooling pipe is preferably 0.001 g / min or more and 100 g / min or less, more preferably 0.1 g / min or more and 50 g / min or less, depending on the cooling capacity of the cooling pipe.

[0093] In addition, the content of the molybdenum trioxide vapor contained in the gas discharged from the calcination furnace is preferably 0.01 g / min or more and 1000 mg / L or less, more preferably 1 g / min or more and 500 mg / L g / min or less.

[0094] Then, the above-mentioned molybdenum trioxide vapor is cooled and powderized.

[0095] The cooling of the molybdenum trioxide vapor is performed by bringing the cooling pipe to a low temperature. At this time, as the cooling mechanism, there can be cited cooling based on the blast of gas into the cooling pipe as described above, cooling using a cooling mechanism possessed by the cooling pipe, cooling using an external cooling device, and the like.

[0096] The cooling of the molybdenum trioxide vapor is preferably performed in an air atmosphere. By cooling the molybdenum trioxide vapor in an air atmosphere, a molybdenum trioxide powder is formed, and it is thereby possible to set the above-mentioned ratio (I / II) to be greater than 1.1, and to easily obtain the β crystal structure of MoO3 in the molybdenum trioxide powder.

[0097] The cooling temperature (the temperature of the cooling pipe) is not particularly limited, and is preferably -100 to 600°C, more preferably -50 to 400°C.

[0098] The cooling rate of the molybdenum trioxide vapor is not particularly limited, and is preferably 100°C / s or more and 100000°C / s or less, more preferably 1000°C / s or more and 50000°C / s or less. Note that the faster the cooling rate of the molybdenum trioxide vapor, the more there is a tendency to obtain a molybdenum trioxide powder having a small particle diameter and a large specific surface area.

[0099] In the case where the cooling mechanism is cooling based on the blast of gas into the cooling pipe, the temperature of the gas for the blast is preferably -100 to 300°C, more preferably -50 to 100°C.

[0100] In addition, the air supply rate of the gas is preferably 0.1 m 3 / minute or more and 20 m 3 / minute or less, more preferably 1 m 3 / minute or more and 10 m 3 / minute or less. When the air supply rate of the gas is 0.1 m 3 / minute or more, a high cooling rate can be achieved, and clogging of the cooling pipe can be prevented, and thus it is preferable. On the other hand, when the air supply rate of the gas is 20 m 3 / minute or less, an expensive first air supply mechanism (exhaust fan or the like) is not required, and manufacturing costs can be reduced, and thus it is preferable.

[0101] The powder obtained by cooling the molybdenum trioxide vapor is transported to a recovery machine and recovered.

[0102] The method for producing the molybdenum trioxide powder can further include re-baking the powder obtained by cooling the molybdenum trioxide vapor at a temperature of 100 to 320°C.

[0103] That is, the molybdenum trioxide powder obtained by the method for producing the molybdenum trioxide powder can be re-baked at a temperature of 100 to 320°C. The re-baking temperature can be 120 to 280°C, and can be 140 to 240°C. The re-baking time can be, for example, 1 minute to 4 hours, 10 minutes to 5 hours, or 100 minutes to 6 hours. By re-baking, a part of the β crystal structure of the molybdenum trioxide disappears, and if the re-baking is performed at a temperature of 350°C or higher for 4 hours, the β crystal structure in the molybdenum trioxide powder disappears, the ratio (β(011) / α(021)) becomes 0, and the reactivity with the Group 14 element, the Group 15 element, or the Group 16 element is impaired.

[0104] According to the method for producing the molybdenum compound of the present embodiment, a molybdenum compound having a reduced number of functional groups on the surface of the particles can be obtained. In addition, according to the method for producing the molybdenum compound of the present embodiment, there are advantages that mass production is possible, a dangerous device such as high pressure is not required, and no cleaning and drying processes are required.

[0105] Example

[0106] The present application is further explained in detail by the following examples, but the present application is not limited by these examples.

[0107] [Method for measuring average particle diameter of primary particles of molybdenum trioxide powder and molybdenum compound]

[0108] The molybdenum trioxide particles constituting the molybdenum trioxide powder or the molybdenum compound particles constituting the molybdenum compound powder were dispersed in ethanol, and photographed using a transmission electron microscope (TEM). For the individual particles on a two-dimensional image or the particles constituting the smallest unit of the aggregate (i.e., primary particles), the long diameter (Feret diameter of the longest portion observed) and the short diameter (short Feret diameter in a direction perpendicular to the Feret diameter of the longest portion) were measured, and the average value thereof was taken as the primary particle diameter. The same operation was performed on 50 randomly selected primary particles, and the average particle diameter of the primary particles was calculated from the average value of the primary particle diameters of the primary particles.

[0109] [Crystal structure analysis: XRD method]

[0110] The sample of the molybdenum compound obtained in each example was filled in a measurement sample holder having a depth of 0.5 mm, and set in a wide-angle X-ray diffractometer (Ultima IV manufactured by Rigaku Co., Ltd.) to perform measurement under conditions of Cu / Ka rays, 40 kV / 40 mA, a scanning speed of 2° / minute, and a scanning range of 10 degrees or more and 70 degrees or less.

[0111] [Specific surface area measurement: BET method]

[0112] For the sample of the molybdenum trioxide powder or the molybdenum sulfide powder, measurement was performed using a specific surface area meter (BELSORP-mini manufactured by Microtrac BEL), and the surface area of the measured average 1 g of the sample was calculated from the amount of nitrogen adsorption based on the BET method, as the specific surface area (m 2 / g).

[0113] [Number of hydroxyl groups per unit area on the surface of the molybdenum compound]

[0114] Blank measurement: To 20 ml of pure water, 0.5 g of sodium chloride as a stabilizer was added, and the pH of the liquid was adjusted to about 4 with hydrochloric acid. To this, 0.01 N aqueous sodium hydroxide solution was slowly added until the pH reached about 9, which was taken as the end point. The amount of the aqueous sodium hydroxide solution required at this time was taken as V blank .

[0115] Measurement of the sample: About 0.05 g of the molybdenum compound sample obtained in each example and the comparative example was accurately weighed, and 20 ml of pure water was added thereto. 0.5 g of sodium chloride was added and dissolved. The same pH as the blank was adjusted using hydrochloric acid. This was titrated with 0.01 N sodium hydroxide to adjust the pH to the same pH as the end point of the blank. The amount of the aqueous sodium hydroxide solution required at this time was taken as V.

[0116] Calculation of the number of hydroxyl groups per unit area: The following formula was used to calculate the number of hydroxyl groups per unit area. Note that the value of the specific surface area was measured in advance using a BET specific surface area meter.

[0117] Surface hydroxyl group density (number / nm 2 ) = 6.023f (V - V blank ) / WA

[0118] Here, f represents the factor of the aqueous sodium hydroxide solution, W represents the sample weight, and A represents the specific surface area.

[0119] Note that the factor f of the aqueous sodium hydroxide solution was calculated using the following formula.

[0120] f = [(true concentration of the standard solution obtained by calibration)] / (indicated concentration of the prepared standard solution)

[0121] (Manufacture of molybdenum trioxide powder)

[0122] A mixture of 1 kg of molybdenum trioxide (manufactured by Taiyo Kogyo Co., Ltd.) and 2 Kg of aluminum hydroxide (manufactured by Wakoh) was placed in a sagger, and a calcination furnace corresponding to a heat-resistant container, a cooling pipe provided with an external gas supply port, and a dust collector for recovering molybdenum oxides were connected. The calcination furnace, the cooling pipe, and the dust collector were connected, and the calcination furnace was heated to 1300°C and held for 10 hours to obtain α-aluminum, and the molybdenum trioxide was vaporized in the calcination furnace. Then, from the exhaust port of the calcination furnace, air in a large excess amount compared to the amount of the vaporized molybdenum trioxide was blown at a cooling rate of 2000°C / second through the external gas supply port of the cooling pipe, and the molybdenum trioxide was rapidly cooled to 200°C or lower to be powdered, and 900 g of molybdenum trioxide 1 was obtained using the dust collector. The average primary particle diameter was 20 nm when measured using TEM.

[0123] [Example 1] Synthesis of molybdenum carbide (Mo2C)

[0124] After 0.5 g of molybdenum trioxide 1, 0.25 g of Ketjen black (EC300J manufactured by Lion Speciality Chemicals Co., Ltd.), 0.38 g of sodium chloride, and 0.38 g of potassium chloride were mixed in a mortar for 1 minute, they were added to a crucible, and calcination was performed at 850°C for 4 hours under a nitrogen atmosphere. After natural cooling, the calcination product was washed with ion exchange water to remove the remaining Ketjen black and salts. The obtained substance was molybdenum carbide as determined by XRD measurement. The result of the surface hydroxyl group measurement using acid-base titration was that the number of hydroxyl groups per unit area (surface functional group density) was 6.5 number / nm 2 . The average primary particle diameter was 30 nm when measured using TEM.

[0125] [Example 2] Synthesis of molybdenum silicide (MoSi2)

[0126] The mixture of 0.5 g of molybdenum trioxide 1 and 0.4 g of metal silicon powder, 0.5 g of metal magnesium was added to a crucible, and fired at 900°C for 6 hours under a nitrogen atmosphere. After natural cooling, the fired product was washed with 0.1 M hydrochloric acid. The obtained substance was molybdenum silicide according to XRD measurement.

[0127] The result of the surface hydroxyl group measurement by acid-base titration was that the number of hydroxyl groups per unit area (surface functional group density) was 3.9 / nm 2 The average primary particle size was 70 nm when the length was measured by TEM.

[0128] [Example 3] Synthesis of molybdenum phosphide (MoP / MoP2)

[0129] The mixture of 0.5 g of molybdenum trioxide 1 and red phosphorus powder (Showa Chemicals) 0.47 g, zinc chloride 1.0 g was added to a crucible, and fired at 700°C for 4 hours under a nitrogen atmosphere. After natural cooling, the fired product was washed with ion exchange water. The obtained substance was molybdenum phosphide according to XRD measurement.

[0130] The result of the surface hydroxyl group measurement by acid-base titration was that the number of hydroxyl groups per unit area (surface functional group density) was 45.5 / nm 2 The average primary particle size was 120 nm when the length was measured by TEM.

[0131] [Example 4] Synthesis of molybdenum selenide (MoSe2)

[0132] The mixture of 0.5 g of molybdenum trioxide 1 and selenium powder (Showa Chemicals) 1.1 g, sodium phosphonate monohydrate 0.56 g, sodium chloride 1.0 g, potassium chloride 1.0 g was added to a crucible, and fired at 850°C for 4 hours under a nitrogen atmosphere. After natural cooling, the fired product was washed with ion exchange water. The obtained substance was molybdenum selenide according to XRD measurement.

[0133] The result of the surface hydroxyl group measurement by acid-base titration was that the number of hydroxyl groups per unit area (surface functional group density) was 60.1 / nm 2 The average primary particle size was 350 nm when the length was measured by TEM.

[0134] [Example 5] Synthesis of molybdenum telluride (MoTe2)

[0135] After mixing 0.5 g of molybdenum trioxide 1 and tellurium powder (reagent manufactured by Aldrich) 0.89 g, sodium phosphonate monohydrate 0.56 g, sodium chloride 1.0 g, potassium chloride 1.0 g, the mixture was charged into a crucible and fired at 900°C for 4 hours under a nitrogen atmosphere. After natural cooling, the fired product was washed with ion exchange water. The resulting substance was molybdenum telluride according to XRD measurement.

[0136] The result of the surface hydroxyl group measurement by acid-base titration was that the number of hydroxyl groups per unit area (surface functional group density) was 26.3 / nm 2 The average primary particle diameter was 110 nm when the length measurement was performed using TEM.

[0137] The crystal structure analysis was performed using the XRD method for each of the molybdenum compounds obtained in Examples 1 to 5. The XRD patterns of each of the molybdenum compounds obtained in Examples 1 to 5 are shown in Figure 1 .

[0138] [Comparative Examples 1 to 5]

[0139] Instead of molybdenum trioxide 1, commercially available molybdenum trioxide of micron size was used, and a molybdenum compound was produced in the same manner as in Examples 1 to 5 except for this. The result of the number of hydroxyl groups per unit area (surface functional group density) is shown in Table 2. In addition, the average primary particle diameter of each of the molybdenum compounds obtained by TEM length measurement is shown in Table 2.

[0140] [Table 1]

[0141] Units Example 1 Example 2 Example 3 Example 4 Example 5 Particle composition Mo2C MoSi2 MoP / MoP2 MoSe2 MoTe2 Average primary particle size nm 30 70 120 350 110 Surface functional group density nm 2 ]] 6.5 3.9 45.5 60.1 26.3 Molybdenum trioxide (nanometer size) g 0.5 0.5 0.5 0.5 0.5 Molybdenum trioxide (micrometer size) g Ketjen black g 0.25 Metallic silicon powder g 0.4 Metallic magnesium g 0.5 Red phosphorus powder g 0.47 Selenium powder g 1.1 Tellurium powder g 0.89 Sodium phosphonate monohydrate g 0.56 0.56 NaCl g 0.38 1 1 KCl g 0.38 1 1 ZnCl g 1 Baking temperature / N2 ℃ 850 900 700 850 900 Baking time hr 4 6 4 4 4

[0142] [Table 2]

[0143] Units Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Particle composition Mo2C MoSi2 MoP / MoP2 MoSe2 MoTe2 Average primary particle size nm 1300 3000 1500 2800 2100 Surface functional group density nm 2 ]] 13.7 20.9 185.0 240.2 140.1 Molybdenum trioxide (nanometer size) g Molybdenum trioxide (micrometer size) g 0.5 0.5 0.5 0.5 0.5 Ketjen black g 0.25 Metallic silicon powder g 0.4 Metallic magnesium g 0.5 Red phosphorus powder g 0.47 Selenium powder g 1.1 Tellurium powder g 0.89 Sodium phosphonate monohydrate g 0.56 0.56 NaCl g 0.38 1 1 KCl g 0.38 1 1 ZnCl g 1 Baking temperature / N2 ℃ 850 900 700 850 900 Baking time hr 4 6 4 4 4

[0144] [Example 6]

[0145] To the molybdenum compound (Mo2C, 1 g) of Example 1, Light Acrylate L-A (KAYARAD, 10 g) as a UV-curable acrylate monomer was added, and after 10 minutes of ultrasonic treatment, it was left in the dark. No precipitate was observed after 3 days of standing, showing good dispersibility.

[0146] [Examples 7 to 10]

[0147] Instead of the molybdenum compound (Mo2C, 1 g) of Example 1, 1 g of each of the inorganic particles of Examples 2 to 5 was used, and the same procedure as in Example 6 was performed, and evaluation was performed. The result of the dispersibility is shown in Table 3.

[0148] [Comparative Examples 6 to 10]

[0149] Instead of the molybdenum compound (Mo2C, 1 g) of Example 1, each of the molybdenum compounds of Comparative Examples 1 to 5 was used at 1 g, and the same as Example 6 was performed except for this, and evaluation was performed. The results of dispersibility are shown in Table 4.

[0150] [Table 3]

[0151] Units Example 6 Example 7 Example 8 Example 9 Example 10 Particles used Example 1 Example 2 Example 3 Example 4 Example 5 Molybdenum compound g 1 1 1 1 1 LIGHT ACRYLATE L-A g 10 10 10 10 10 Dispersion ◎ ◎ ○ ○ ○

[0152] ◎: no precipitation for 3 days ○: no precipitation for 1 day X: precipitation after 1 day

[0153] [Table 4]

[0154] Units Comparative Example 6 Comparative Example 7 Comparative Example 8 Comparative Example 9 Comparative Example 10 Particles used Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Molybdenum compound g 1 1 1 1 1 LIGHT ACRYLATE L-A g 10 10 10 10 10 Dispersion ○ ○ × × ×

[0155] ◎: no precipitation for 3 days ○: no precipitation for 1 day X: precipitation after 1 day

[0156] Industrial applicability

[0157] The molybdenum compound of the present application has reduced number of functional groups on the surface of the particles, and thus the hydrophobicity of the surface of the molybdenum compound is improved, and the compatibility with organic materials is improved. Therefore, the molybdenum compound of the present application exhibits excellent properties in organic-inorganic hybrid materials such as hydrogen production catalysts, photocatalysts, fuel cell catalysts, CO2 reduction catalysts, semiconductors, thermoelectric materials, and the like.

[0158] The preferred embodiments of the present application have been described above, but the present application is not limited to these embodiments. Addition, omission, substitution, and other changes of features can be made within the scope of the gist of the present application. The present application is not limited by the above description, but is limited only by the scope of the appended claims.

[0159] Explanation of reference numerals

[0160] 1 manufacturing apparatus

[0161] 2 calcination furnace

[0162] 3 cooling pipe

[0163] 4 recovery machine

[0164] 5 exhaust port

[0165] 6 opening adjustment damper

[0166] 7 observation window

[0167] 8 exhaust device

[0168] 9 external cooling device

Claims

1. A molybdenum compound of the general formula MoXa wherein X is a Group 14 element, a Group 15 element, or a Group 16 element, and a is 0.5, 1, or 2. a 1. A molybdenum compound of the general formula MoXa wherein X is a Group 14 element, a Group 15 element, or a Group 16 element, and a is 0.5, 1, or 2. The general formula MoX a When X is a Group 14 element, the number of functional groups per unit area of the surface of the molybdenum compound is 10 / nm 2 Hereinafter, The general formula MoX a When X is a Group 15 element or a Group 16 element, the number of functional groups per unit area of the surface of the molybdenum compound is 100 / nm 2 Hereinafter, the functional group is a hydroxyl group, the particle size of the molybdenum compound is 10 nm or more and less than 1000 nm.

2. The molybdenum compound according to claim 1, wherein, The general formula MoX a When X is a Group 14 element, X is C and a is 0.5 or 1, or X is Si and a is 2. The general formula MoX a When X is a Group 15 element, X is N or P and a is 1 or 2, The general formula MoX a When X is a Group 16 element, X is S, Se or Te and a is 2.

3. The method for producing a molybdenum compound according to claim 1 or 2, comprising the step of heating a molybdenum trioxide particle having an average particle size of primary particles of 5 nm or more and less than 1000 nm, the molybdenum trioxide particle containing an aggregate of primary particles including a β crystal structure of molybdenum trioxide, in the presence of a Group 14 element, a Group 15 element, or a Group 16 element, at 400 to 1500°C.

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