Metal phosphide nanoparticle production method, reduction catalyst obtained by same, and method for producing hydrogenated organic compound by using same

Abstract

Provided is a metal phosphide nanoparticle production method with which it is possible to produce particles stably in terms of the shape and the size thereof by using, as raw materials, substances safe for the human body for both as a metal source and a phosphorus source. The present invention pertains to a metal phosphide nanoparticle production method comprising: mixing at least one metal source selected from the group consisting of prescribed compounds such as iron(II) chloride with a compound represented by general formula [1] X-Y-Z (in the formula, descriptions of symbols are omitted) in a solvent to obtain a metal complex of a metal constituting the metal source and a compound represented by general formula [1]; mixing a phosphorus compound (excluding sodium phosphide) with a surfactant while heating the same to obtain a first mixture; and heating a second mixture obtained by mixing the first mixture and the metal complex.

Description

Method for producing nano-metal phosphide particles, reduction catalyst obtained by the method, and method for producing hydrogenated organic compounds using the catalyst

[0001] The present invention relates to a method for producing nano-metal phosphide particles, a reduction catalyst obtained thereby, and a method for producing a hydrogenated organic compound using the same.

[0002] Nano-sized metal particles are expected to be applied in a wide range of fields, including electrode materials, magnetic materials, and catalyst materials, and in recent years, there has been active development of nano-sized metal particles. As one type of metal nanoparticle, for example, a method for producing nano-sized iron phosphide particles has also been proposed. For example, several synthesis methods under gas phase or liquid phase conditions have been reported for producing nano-sized iron phosphide (e.g., Non-Patent Documents 1 to 3).

[0003] In the gas phase synthesis method for producing iron phosphide particles, Na, a highly flammable phosphorus source, is used. ３ It is necessary to use P (Non-Patent Documents 2-3). ３ P also generates highly toxic phosphine through hydrolysis. This poses a safety issue during production. In addition, the liquid phase method, which prepares the product under milder reaction conditions, requires Fe(CO) as the iron source. ５ is used, and Na ３ By using an organic phosphorus compound as a phosphorus source without using P, it is possible to selectively synthesize iron phosphides of various shapes, sizes, and compositions (Non-Patent Document 1).

[0004] However, Fe(CO) ５ It is highly volatile and toxic to humans, so it must be handled with extreme care.

[0005] On the other hand, iron chloride and its hydrates are easy to handle and inexpensive to purchase, making them ideal iron sources. Several liquid-phase synthesis methods for iron phosphide using iron chloride as the iron source have been reported. However, conventional liquid-phase synthesis methods for iron phosphide using iron chloride as the iron source have been limited to those using the aforementioned highly hazardous phosphorus sources (Non-Patent Documents 2-3).

[0006] Therefore, there has not yet been a method for selectively producing iron phosphide nanoparticles that can be stably produced with particle shapes and sizes using materials that are safe for the human body as both the iron source and the phosphorus source.Furthermore, there has not yet been a method for selectively producing metal phosphide nanoparticles that can be stably produced with particle shapes and sizes using materials that are safe for the human body as both the metal source and the phosphorus source.

[0007] Furthermore, as one type of metal nanoparticle, for example, low-valent (zero-valent) iron nanoparticles are extremely effective catalytic materials for reactions essential to human society, such as the Haber-Bosch process for synthesizing ammonia from nitrogen and the Fischer-Tropsch reaction for synthesizing gasoline from carbon monoxide.

[0008] However, low-valent iron nanoparticles are extremely unstable and easily oxidized and inactivated by ppm-order oxygen. Therefore, the use of low-valent iron nanoparticles as catalysts has been limited to methods that involve in-situ pretreatment of the supported iron ions under high temperature and high hydrogen pressure conditions.

[0009] Furthermore, the catalytic activity of general nanoparticles is largely dependent on the size and shape of the particles, the type of support, and additives due to the instability of the nanoparticles themselves. However, with conventional preparation methods, it is difficult to precisely control the size of nanoparticles, and furthermore, the support and additives are limited to materials that can withstand the high temperatures of the reduction pretreatment.

[0010] Therefore, there is a need for an unconventional innovative technology that can control the contradictory properties of metal nanoparticles (e.g., iron nanoparticles) in which the metal atoms (e.g., iron atoms) that make up the nanoparticles are in a low valence state and are stable under atmospheric conditions.

[0011] “Control of Phase in Phosphide Nanoparticles Produced by Metal Nanoparticle Transformation: Fe2P and FeP”, E. Muthuswamy, et al., ACS Nano 2009, 3, 8, Pages 2383-2393 “A solvothermal synthesis of ultra-fine iron phosphide”, Gu Yunle et al., Materials Research Bulletin, Volume 37, Issue 6, May 2002, Pages 1101-1105“One-pot synthesis of magnetic iron phosphide nanoparticles”, D. Ahluwalia, et al., Inorg. Nano-Met. Chem., 2020, 50, 1-6

[0012] For example, in the production method of Non-Patent Document 2, in addition to using a highly hazardous phosphorus source, the solid produced does not have sufficient crystallinity, making it impossible to control the particle shape and composition. Therefore, it was found that it is difficult to produce a reduction catalyst that can be used in reduction reactions such as hydrogenation of organic compounds such as nitrile compounds at an industrially usable level.

[0013] The present invention aims to provide a method for producing nanometal phosphide particles that uses materials that are safe for the human body as both the metal source and the phosphorus source, and that can stably produce particles of any shape and size. The present invention also aims to provide a method for producing nanometal phosphide particles in which the metal atoms in the resulting nanometal phosphide particles are in a low-valence state and are stable under atmospheric conditions, as well as a reduction catalyst obtained thereby and uses thereof.

[0014] As a result of intensive research into solving the above problems, the inventors of the present invention have found that the above problems can be solved by producing a complex of iron (III) chloride and sodium oleate when producing nanometal phosphide particles, for example, when producing nanoiron phosphide particles, and using this complex to produce nanoiron phosphide particles. Based on this finding, the inventors have conducted further research and have completed the present invention.

[0015] The present invention encompasses the following inventions: [1] Mixing at least one metal source selected from the group consisting of iron(II) chloride, iron(III) chloride, iron(II) nitrate, iron(III) nitrate, iron(II) bromide, iron(III) bromide, cobalt(II) nitrate, cobalt(II) chloride, cobalt(II) bromide, nickel(II) nitrate, nickel(II) bromide, and nickel(II) chloride with a compound represented by the following general formula [1] X-Y-Z [1] (wherein X is an alkenyl group having 3 to 20 carbon atoms, Y is an alkylene group having 3 to 30 carbon atoms, and Z is a carboxy group, a sulfonic acid group, a phosphonic acid group, a phosphate group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a sulfonic acid group, a salt of a phosphonic acid group, a salt of a phosphate group, or a salt of a primary to tertiary amino group) in a solvent to obtain a metal complex of a metal constituting the metal source and the compound represented by the general formula [1], A method for producing nanometal phosphide particles, comprising: mixing a phosphorus compound (excluding sodium phosphide) and a surfactant under heating to obtain a first mixture; and heating a second mixture obtained by mixing the first mixture with the metal complex. [2] A method for producing nanometal phosphide particles according to [1], wherein the metal source is iron(II) chloride and / or iron(III) chloride. [3] A method for producing nanometal phosphide particles according to [1] or [2], wherein Z is a carboxy group, a phosphate group, an alkali metal salt of a carboxy group, or an alkali metal salt of a phosphate group. [4] A method for producing nanometal phosphide particles according to [1] or [2], wherein the compound represented by general formula [1] is oleic acid or sodium oleate. [5] A method for producing nanometal phosphide particles according to [1] or [2], wherein the phosphorus compound is a phosphite ester compound. [6] A method for producing nanometal phosphide particles according to [1] or [2], wherein the surfactant is an alkylamine. [7] The method for producing nanometal phosphide particles according to [1] or [2], wherein the metal source and the compound represented by the general formula [1] are mixed in an inert gas atmosphere. [8] The method for producing nanometal phosphide particles according to [1] or [2], wherein the metal source and the compound represented by the general formula [1] are mixed at a temperature in the range of 40 to 180°C.[9] The method for producing nanometal phosphide particles according to [1] or [2], wherein the heating temperature when mixing the phosphorus compound and the surfactant under heating is within a range of 70 to 200°C.

[10] The method for producing nanometal phosphide particles according to [1] or [2], wherein the heating temperature when heating the second mixture is within a range of 200 to 450°C.

[11] A method for producing a composite, comprising contacting the nanometal phosphide particles obtained by the method for producing according to [1] or [2] with a support to produce a composite of the nanometal phosphide particles and the support.

[12] The method for producing the composite according to

[11] , wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

[13] A method for producing a hydrogenated organic compound, comprising hydrogenating an organic compound using the nanometal phosphide particles obtained by the method for producing according to any one of [1] to

[10] , or a composite of the nanometal phosphide particles and a support, as a reduction catalyst.

[14] The method for producing a hydrogenated organic compound according to

[13] , wherein the organic compound is a nitrile compound, the hydrogenated organic compound is a primary amine compound, and the nitrile compound is hydrogenated in a hydrogen atmosphere in the presence of ammonia at a hydrogen pressure of 8 MPa or less.

[0016] The present invention provides a method for producing nano-metal phosphide particles, which uses both the metal source and the phosphorus source as raw materials and can produce particles of a stable shape and size. The method for producing nano-metal phosphide particles of the present invention is industrially advantageous because it uses only raw material compounds that are safe for the human body. The present invention also provides a method for producing nano-metal phosphide particles in which the metal atoms in the resulting nano-metal phosphide particles are in a low-valence state and stable under atmospheric conditions, as well as a reduction catalyst obtained thereby and its use. Furthermore, the method for producing nano-metal phosphide particles of the present invention can provide nano-metal phosphide particles in which the resulting nano-metal phosphide particles and reduction catalyst have catalytic activity capable of undergoing reduction reactions (e.g., hydrogenation reactions) to produce target compounds under milder conditions than those of conventional techniques. Furthermore, the method for producing nano-metal phosphide particles of the present invention can produce nano-metal phosphide particles of a stable size and shape. Furthermore, this facilitates the production of composites containing the nano-metal phosphide particles. Furthermore, the method for producing nano-metal phosphide particles of the present invention also has excellent raw material availability.

[0017] Furthermore, when the nanometal phosphide particles obtained by the production method of the present invention (hereinafter also simply referred to as "nanometal phosphide particles of the present invention") are, for example, nanoiron phosphide particles, when the nanoiron phosphide particles are used as a reduction catalyst (e.g., a hydrogenation catalyst), a reduction reaction (e.g., a hydrogenation reaction) can be carried out under milder conditions than in conventional techniques such as the Haber-Bosch process, thereby making it possible to produce a target compound.

[0018] Furthermore, the nanometal phosphide particles and reduction catalyst of the present invention are industrially advantageous in terms of cost since they use a non-noble metal as the metal source.

[0019] Fig. 1 shows an image of nano-iron phosphide particles according to one embodiment of the present invention observed by a transmission electron microscope (TEM). Fig. 2 shows the measurement results of powder X-ray diffraction measurement of nano-iron phosphide particles according to one embodiment of the present invention (top) and Fe ２ The lower graph shows the peak positions of the crystal planes corresponding to P. The vertical axis of the lower graph represents the relative intensity.

[0020] Hereinafter, each embodiment of the present invention will be described. Note that in this specification, the upper and lower limits of numerical ranges (such as the size of nanometal phosphide particles, the amount of a certain component (material such as a compound) used, temperature, pressure, or values ​​calculated from each numerical range and each physical property) can be combined as appropriate. Furthermore, in this specification, ranges in which "equal to or less than" is read as "less than" or "equal to or greater than" is read as "greater than."

[0021] Some embodiments of the present invention relate to a method for producing nanometal phosphide particles. Each embodiment will be described below. However, the present invention is not limited to the following embodiments.

[0022] The method for producing nanometal phosphide particles of the present invention includes mixing at least one metal source selected from the group consisting of iron(II) chloride, iron(III) chloride, iron(II) nitrate, iron(III) nitrate, iron(III) bromide, iron(II) bromide, cobalt(II) nitrate, cobalt(II) chloride, cobalt(II) bromide, nickel(II) nitrate, nickel(II) bromide, and nickel(II) chloride with a compound represented by the following general formula [1] X-Y-Z [1] (wherein X is an alkenyl group having 3 to 20 carbon atoms, Y is an alkylene group having 3 to 30 carbon atoms, and Z is a carboxy group, a sulfonic acid group, a phosphonic acid group, a phosphate group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a sulfonic acid group, a salt of a phosphonic acid group, a salt of a phosphate group, or a salt of a primary to tertiary amino group) in a solvent to obtain a metal complex of a metal constituting the metal source and the compound represented by the general formula [1], A phosphorus compound (excluding sodium phosphide) and a surfactant are mixed under heating to obtain a first mixture, and the first mixture and the metal complex are mixed to obtain a second mixture, which is then heated.

[0023] Examples of metal sources used in the method for producing nanometal phosphide particles according to the present invention include iron(II) chloride, iron(III) chloride, iron(II) nitrate, iron(III) nitrate, iron(III) bromide, iron(II) bromide, cobalt(II) nitrate, cobalt(II) chloride, cobalt(II) bromide, nickel(II) nitrate, nickel(II) bromide, and nickel(II) chloride, because they facilitate the formation of metal complexes with the compound represented by general formula [1] and provide the resulting nanometal phosphide particles with excellent catalytic activity. Depending on the type of nanometal phosphide particles desired, one type of metal source may be used alone, or two or more types may be used in combination. For example, when producing nanometal phosphide particles, the metal source is preferably iron(II) chloride and / or iron(III) chloride.

[0024] In the method for producing nanometal phosphide particles according to the present invention, by using a compound represented by the following general formula [1], it is possible to form a metal complex with the metal source while suppressing aggregation of the nanometal phosphide particles, thereby producing the desired nanometal phosphide particles. Furthermore, by using a compound represented by the following general formula [1], the obtained nanometal phosphide particles have excellent catalytic activity: X-Y-Z [1] (wherein X is an alkenyl group having 3 to 20 carbon atoms, Y is an alkylene group having 3 to 30 carbon atoms, and Z is a carboxy group, a sulfonic acid group, a phosphonic acid group, a phosphate group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a sulfonic acid group, a salt of a phosphonic acid group, a salt of a phosphate group, or a salt of a primary to tertiary amino group.)

[0025] The alkenyl group of X may be linear, branched, or cyclic, preferably linear or branched, and more preferably linear. The number of carbon atoms in the alkenyl group of X is preferably 4 to 18, more preferably 5 to 16, and even more preferably 6 to 14, and particularly preferably 7 to 12, from the viewpoints of being more effective in suppressing aggregation of the nanometal phosphide particles and more easily forming a metal complex with the metal source. Examples of the alkenyl group for X include an allyl group (2-propenyl group), a 1-propenyl group, a 1-methylethenyl group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1-pentenyl group, a 4-pentenyl group, a 1-hexenyl group, a 1-heptenyl group, a 1-octenyl group, a 1-nonenyl group, a 1-decenyl group, a 1-undecenyl group, a 1-dodecenyl group, a 1-tridecenyl group, a 2-tridecenyl group, a 3-tridecenyl group, a 1-tetradecenyl group, a 1-pentadecenyl group, a 1-hexadecenyl group, a 1-heptadecenyl group, a 1-octadecenyl group, a 1-octadecenyl group, and a 1-nonadecenyl group.

[0026] The alkylene group represented by Y may be linear, branched, or cyclic, preferably linear or branched, and more preferably linear. The number of carbon atoms in the alkylene group represented by Y is preferably 4 to 18, more preferably 5 to 16, and even more preferably 6 to 14, and is particularly preferably 7 to 12, from the viewpoints of being more effective in suppressing aggregation of nanometal phosphide particles and more easily forming a metal complex with the metal source. Examples of the alkylene group represented by Y include an n-propylene group, an isopropylene group, a pentylene group, a hexylene group, a heptylene group, an octylene group, a nonylene group, a decylene group, a dodecylene group, a tetradecylene group, a hexadecylene group, an octadecylene group, and an eicosanylene group.

[0027] In the compound represented by the general formula [1], it is preferable that the compound represented by the general formula [1] has a double bond at the center, from the viewpoint of being more effective in suppressing the aggregation of nanometal phosphide particles and more easily forming a metal complex with the metal source. From the above viewpoint, when the number of carbon atoms in the alkenyl group of X and the number of carbon atoms in the alkylene group of Y are combined and compared with the number of carbon atoms on both sides of the unsaturated bond at the center, the difference in the number of carbon atoms between them is preferably 5 or less, more preferably 4 or less, and even more preferably 3 or less, from the viewpoint of being more easily forming a metal complex with the metal source. Furthermore, in the compound represented by the general formula [1], it is preferable that the sum of the number of carbon atoms in the alkenyl group of X and the number of carbon atoms in the alkylene group of Y is 12 or more, more preferably 13 or more, and even more preferably 14 or more, from the viewpoint of being more effective in suppressing the aggregation of nanometal phosphide particles and more easily forming a metal complex with the metal source.

[0028] Z is a carboxy group, a sulfonic acid group, a phosphonic acid group, a phosphoric acid group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a sulfonic acid group, a salt of a phosphonic acid group, a salt of a phosphoric acid group, or a salt of a primary to tertiary amino group. From the viewpoints of having a superior effect of inhibiting aggregation of nanometal phosphate particles and being more likely to form a metal complex with the metal source, Z is preferably a carboxy group, a phosphonic acid group, a phosphoric acid group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a phosphonic acid group, a salt of a phosphoric acid group, or a salt of a primary to tertiary amino group; more preferably a carboxy group, a phosphonic acid group, a phosphoric acid group, a salt of a carboxy group, a salt of a phosphonic acid group, or a salt of a phosphoric acid group; and even more preferably a carboxy group, a phosphoric acid group, an alkali metal salt of a carboxy group, or an alkali metal salt of a phosphoric acid group.

[0029] The compound represented by the general formula [1] is preferably in the cis form, since it has a superior effect of suppressing the aggregation of nanometal phosphide particles and is more likely to form a metal complex with the metal source. Examples of the compound represented by the general formula [1] include cis-monounsaturated fatty acids and their salts (alkali metal salts, ammonium salts). Examples of the alkali metal salts include lithium salts, sodium salts, potassium salts, rubidium salts, cesium salts, and francium salts.

[0030] Examples of the cis-monounsaturated fatty acids and their salts include myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, gadoleic acid, eicosenoic acid, erucic acid, nervonic acid, and their salts (e.g., alkali metal salts). Myristoleic acid, palmitoleic acid, sapienic acid, oleic acid, gadoleic acid, eicosenoic acid, erucic acid, and their alkali metal salts are preferred because they have superior performance as a dispersant in producing nanometal phosphate particles and are more likely to form a metal complex with the metal source. cis-9-monounsaturated fatty acids such as myristoleic acid, palmitoleic acid, oleic acid, and gadoleic acid and their alkali metal salts are more preferred. Oleic acid or sodium oleate is even more preferred because they have particularly superior performance as a dispersant in producing nanometal phosphate particles. The compounds represented by general formula [1] may be used alone or in combination of two or more.

[0031] The metal source and the compound represented by the general formula [1] can be mixed in a solvent to obtain a metal complex (hereinafter, also simply referred to as a "metal complex") of a metal constituting the metal source and the compound represented by the general formula [1].

[0032] Examples of solvents include non-aromatic hydrocarbon solvents (e.g., alkanes such as pentane, hexane, heptane, octane, nonane, decane, dodecane, isododecane, and tridecane; cycloalkanes such as cyclohexane and methylcyclohexane; decahydronaphthalene; and liquid paraffin); alcohol solvents (e.g., monohydric alcohols such as ethanol, propanol, 1-butanol, 2-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-hexanol, 2-hexanol, benzyl alcohol, and oleyl alcohol; and polyhydric alcohols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and glycerin); aromatic hydrocarbon solvents (e.g., benzene, toluene, xylene, diethylbenzene, mesitylene, tetralin, indene, naphthalene, and methylnaphthalene); and halogenated hydrocarbon solvents (e.g., dichloromethane, dichloroethane, chloroform, and chlorobenzene). ether solvents (e.g., diethyl ether, diisopropyl ether, methyl t-butyl ether, diisoamyl ether, ethylene glycol derivatives (e.g., monoglyme (ethylene glycol dimethyl ether), methyl cellosolve, diethyl cellosolve, diglyme, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, triglyme, tetraglyme, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, poly(ethylene glycol) monomethyl ether), propylene glycol derivatives (e.g., 3-hexanol propylene glycol monopropyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether), 1,1-dimethoxycyclohexane, phenetole, veratrole, dioxane, tetrahydrofuran); Ester solvents (e.g., ethyl acetate, butyl acetate, isopropyl acetate, 3-methoxy-3-methylbutyl acetate, dimethyl carbonate, diethyl malonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, α-acetyl-γ-butyrolactone);Examples of suitable solvents include ketone solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, propiophenone, and isophorone); sulfur-containing solvents (e.g., dimethyl sulfoxide, sulfolane, and diphenyl sulfide); and nitrogen-containing solvents (e.g., amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacrylamide, N,N-dimethylacetoacetamide, N,N-diethylformamide, N,N-diethylacetamide, hexamethylphosphoramide, and methylpyrrolidone, amine solvents such as triethanolamine, and nitrile solvents such as acetonitrile and benzonitrile; nitro solvents such as nitrobenzene and o-nitrotoluene; and quinoline, tetrahydroquinoline, and dimethylimidazolidinone). These solvents may be used alone or in combination of two or more.

[0033] The temperature during mixing is not particularly limited, but from the viewpoint of excellent reactivity and ease of obtaining the target metal complex, it is preferably 40° C. or higher, more preferably 50° C. or higher, and even more preferably 55° C. or higher. Furthermore, from the viewpoint of reactivity, it is preferably 180° C. or lower, more preferably 150° C. or lower, and even more preferably 120° C. or lower.

[0034] The reaction time during mixing is not particularly limited, but is preferably 10 minutes or more, more preferably 30 minutes or more, and even more preferably 1 hour or more, from the viewpoint of excellent reactivity and ease of obtaining the target metal complex, and is preferably 40 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less.

[0035] When mixing the metal source and the compound represented by the general formula (1) to obtain a metal complex, stirring may be carried out as necessary.

[0036] The mixing of the metal source and the compound represented by the general formula [1] is preferably carried out under an inert gas atmosphere, such as argon gas, helium gas, neon gas, or nitrogen gas, in order to facilitate the production of the target metal complex.

[0037] After the mixing, the mixture may be purified by a known method to obtain the target metal complex. For example, a known purification method includes separating the organic layer of the obtained mixture, evaporating the solvent, drying under vacuum, and further washing the obtained product with ethanol and drying it, thereby obtaining the metal complex.

[0038] Next, a phosphorus compound (excluding sodium phosphide) and a surfactant are mixed under heating to obtain a first mixture, and the first mixture and the metal complex are mixed to obtain a second mixture, which is then heated.

[0039] In the method for producing nanometal phosphide particles of the present invention, the phosphorus compound used as the phosphide agent is preferably a phosphite ester compound.

[0040] Examples of the phosphite ester compound include triphenyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, tritolyl phosphite (tri-o-tolyl phosphite, tri-m-tolyl phosphite, tri-p-tolyl phosphite), trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, tris(2-t-butyl-5-methylphenyl) phosphite, trimethyl phosphite, triethyl phosphite, tripropyl phosphite, and triisopropyl phosphite. Aryl phosphites such as phenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, tritolyl phosphite, trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, and tris(2-t-butyl-5-methylphenyl) phosphite are preferred, triaryl phosphites such as triphenyl phosphite, tritolyl phosphite, trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, and tris(2-t-butyl-5-methylphenyl) phosphite are more preferred, and triphenyl phosphite is even more preferred. One type of phosphorus compound may be used alone, or two or more types may be used in combination.

[0041] In the method for producing nanometal phosphide particles according to the present invention, it is preferable that sodium phosphide is not included as the phosphorus compound from the viewpoint of safety for the human body.

[0042] An alkylamine is preferably used as the surfactant. The alkylamine is not particularly limited, but is preferably an amine having an alkyl group having 1 to 20 carbon atoms, since rod-shaped nano-metal phosphate particles are easily obtained. An amine having an alkyl group having 1 to 18 carbon atoms is more preferred, and an amine having an alkyl group having 1 to 16 carbon atoms is even more preferred, since the catalytic activity of the nano-metal phosphate particles is more excellent. One embodiment of the present invention relates to a method for producing nano-metal phosphate particles, in which an alkylamine having an alkyl group having 1 to 16 carbon atoms is used as the surfactant. Another embodiment of the present invention relates to a method for producing nano-metal phosphate particles, in which an alkylamine having an alkyl group having 8 to 18 carbon atoms is used as the surfactant. One type of alkylamine may be used alone, or two or more types may be used in combination.

[0043] The alkyl group of the alkylamine may be linear, branched, or cyclic. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a tert-pentyl group, a 1-ethylpropyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, an n-hexyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group (isohexyl group), a 1-ethylbutyl group, a 2-ethylbutyl group, a 1,1-dimethylbutyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 1,4-dimethylbutyl group, a 2,2-dimethylbutyl group, a 2,3-dimethylbutyl group, a 3,3-dimethylbutyl ...4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group), a 4-methylpentyl group (isohexyl group ethylbutyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, isooctyl group, tert-octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, isononyl group, 1-methyloctyl group, 2-ethylheptyl group, n-decyl group, 1-methylnonyl group, n-undecyl group, 1,1-dimethylnonyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, n-cyclopentyl group, n-cyclopentylmethyl group, cyclohexyl group, and cyclohexylmethyl group.

[0044] The alkyl group may have a substituent or may be unsubstituted. The number of substituents can vary depending on the number of carbon atoms in the alkyl group, and may be 1 to 10, 1 to 5, or 1 to 3. Examples of the substituent include a halogen atom, a cyano group (nitrile group), a lower alkyl group, a halo-lower alkyl group, a hydroxy-lower alkyl group, a hydroxyl group, and a halo-lower alkoxy group.

[0045] The phosphorus compound and the surfactant are mixed under heating to obtain a first mixture. The temperature in the heat treatment (hereinafter also referred to as "first heat treatment") is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher, from the viewpoint of facilitating the production of nanometal phosphide particles. The heating temperature is preferably 200°C or lower, more preferably 190°C or lower, from the viewpoint of facilitating the production of nanometal phosphide particles, and even more preferably 180°C or lower as a milder condition. The heating temperature can be appropriately changed depending on the desired degree of phosphorus content of the nanometal phosphide particles.

[0046] The step of mixing the phosphorus compound and the surfactant under heating is not particularly limited, and can be carried out using a known method and apparatus. The mixing step may be carried out under vacuum conditions.

[0047] The amount of the surfactant used may be 0.05 to 20 equivalents (molar equivalents) relative to the amount of the phosphorus compound used, or may be 0.1 to 15 equivalents, or may be 0.5 to 13 equivalents.

[0048] The first heat treatment is preferably carried out under stirring, since this promotes the reaction and allows for easier production of the nanometal phosphide particles of the present invention. In a preferred embodiment, the first heat treatment is preferably carried out under vacuum conditions or in an argon atmosphere, since this allows for easier production of the nanometal phosphide particles of the present invention.

[0049] The reaction time during mixing is not particularly limited, but is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. The reaction time is preferably 10 hours or less, more preferably 5 hours or less, and even more preferably 2 hours or less. The reaction time is not particularly limited and can be changed appropriately depending on the desired degree of phosphorus formation of the nano-phosphorized metal particles.

[0050] The first mixture thus obtained is mixed with the metal complex to obtain a second mixture, which is then heated.

[0051] The mixing and heating of the obtained first mixture and the metal complex may be carried out simultaneously, or the mixture may be heated after mixing. The temperature in the heating treatment (hereinafter also referred to as "second heating treatment") is preferably 200°C or higher, more preferably 220°C or higher, and even more preferably 250°C or higher, from the viewpoint of facilitating the production of nanometal phosphide particles. Furthermore, the heating temperature is preferably 450°C or lower, more preferably 400°C or lower, and even more preferably 380°C or lower, from the viewpoint of facilitating the production of nanometal phosphide particles. The heating temperature in the second heating treatment may be 5°C or higher, or may be 10°C or higher, than that in the first heating treatment.

[0052] The reaction time for the second heat treatment is not particularly limited, but is preferably 1 minute or more, more preferably 5 minutes or more, and even more preferably 10 minutes or more. The reaction time is also preferably 40 hours or less, more preferably 20 hours or less, and even more preferably 10 hours or less. The reaction time is not particularly limited and can be changed appropriately depending on the desired degree of phosphorus formation of the nano-phosphorized metal particles.

[0053] In the second heat treatment, the temperature rise rate can be adjusted to produce the desired nano-metal phosphide particles. For example, when the nano-metal phosphide particles are nano-iron phosphide particles, the temperature rise rate can be changed to produce FeP and Fe ２ For example, FeP can be produced by using a relatively slow heating rate. The heating rate is not particularly limited, but can be, for example, 5 to 600°C / min, or 10 to 300°C / min. When producing FeP, it can be 5 to 50°C / min, or 5 to 100°C / min. Fe ２ When producing P, the rate can be 120 to 600° C. / min, or 150 to 550° C. / min.

[0054] The second heat treatment may be performed in an argon atmosphere.

[0055] The step of mixing the first mixture with the metal complex is not particularly limited, and can be performed using a known method and apparatus. The mixing step may be performed under vacuum conditions.

[0056] After the mixing, the desired nanometal phosphide particles may be purified by a known method.

[0057] The method for producing nanometal phosphide particles of the present invention preferably further includes a washing step. An organic solvent can be used as the washing solution used in the washing step. The organic solvent is not particularly limited, and examples thereof include the same organic solvents as those used in the method for producing a composite herein. One organic solvent may be used alone, or two or more organic solvents may be used in combination. When two or more organic solvents are used in combination, the mixing ratio is not particularly limited, and for example, acetone and chloroform can be used in a volume ratio of 1:1. The method for producing nanometal phosphide particles of the present invention may further include a washing step using a washing solution containing an organic solvent, and after washing with the organic solvent, the product obtained after the second heat treatment is centrifuged and purified.

[0058] After the washing step, if necessary, the resulting mixture may be vacuum dried to obtain powdery nanometal phosphide particles.

[0059] The method for producing nanometal phosphide particles of the present invention does not require the use of 1-octadecene. Since nanometal phosphide particles obtained by a production method using 1-octadecene cannot be obtained in an amount that exhibits sufficient catalytic activity, it is preferable not to use 1-octadecene in the method for producing nanometal phosphide particles of the present invention. The method for producing nanometal phosphide particles of the present invention does not require other additives such as 1-octadecene.

[0060] The nanometal phosphide particles of the present invention have metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) in a low valence state (metallic state) and are highly stable under atmospheric conditions. "Atomic valence" is a number that represents the ability of an atom of a certain element to bond with atoms of other elements. The metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) contained in the nanometal phosphide particles of the present invention are in a low valence state.

[0061] Hereinafter, the case where the nano-metal phosphide particles obtained by the production method of the present invention are nano-iron phosphide particles will be described as an example, but the same applies when the metal atoms are cobalt atoms or nickel atoms, except in cases specific to iron atoms.

[0062] The fact that the produced particles are nano-iron phosphide particles can also be confirmed by powder X-ray diffraction measurement using CuKα radiation. The nano-iron phosphide particles have peaks at diffraction angles of 48.3° and 32.7° (2θ±0.5°) in powder X-ray diffraction measurement using CuKα radiation, and when measured by X-ray photoelectron spectroscopy (XPS), they contain Fe2p ３／２ In the spectrum, the iron atoms contained therein have a peak in the range of 706.0 to 707.5 eV.

[0063] Furthermore, the nanoiron phosphide particles have peaks at diffraction angles of 48.3° and 32.7° (2θ±0.5°) in powder X-ray diffraction measurement using CuKα rays. The diffraction angles may be 2θ±0.2° or 2θ±0.5°. Furthermore, the nanoiron phosphide particles preferably further have a peak at 46.3° in the powder X-ray diffraction measurement. The nanocobalt phosphide particles and nanonickel phosphide particles can also be confirmed from their respective peaks in the powder X-ray diffraction measurement.

[0064] For powder X-ray diffraction analysis (XRD) using CuKα radiation, a known X-ray diffractometer can be used. Examples of the X-ray diffractometer include a commercially available fully automated multipurpose X-ray diffractometer (trade name "Philips X'PERT MPD diffractometer," manufactured by Philips Japan, Ltd.).

[0065] The nanometal phosphide particles of the present invention are in a low-valent state and have the property of being able to stably maintain the compound structure under atmospheric conditions (hereinafter also referred to as "atmospheric stability"), so that the crystal structure can be measured by X-ray diffraction measurement in the presence of oxygen.

[0066] In this specification, "under atmospheric conditions" means an oxygen concentration in the atmosphere (about 21%). The nanometal phosphide particles of the present invention are excellent in stability under conditions in which oxygen (O ２ The oxygen concentration in the presence of oxygen is not particularly limited, and may be about the atmospheric oxygen concentration (about 21%) or about 22% to 100%. The nanometal phosphide particles of the present invention have excellent atmospheric stability and can maintain a low valence state in the presence of oxygen, regardless of the oxygen concentration.

[0067] The nanoiron phosphide particles obtained by the production method of the present invention have peaks at diffraction angles of 32.7°, 46.3°, and 48.3° in an X-ray diffraction pattern (hereinafter also referred to as "XRD pattern") using CuKα radiation, which correspond to the (011), (112), and (211) crystal planes of FeP, respectively.

[0068] One preferred embodiment includes nano-iron phosphide particles made of FeP, which is in a low valent state and has air stability.

[0069] Another preferred embodiment includes nanoiron phosphide particles that further have peaks at 40.2°, 52.9°, and 54.6° in the powder X-ray diffraction measurement.

[0070] The nano-iron phosphide particles have peaks at diffraction angles of 40.2°, 52.9°, and 54.6° in the XRD pattern using CuKα radiation, which are respectively Fe ２ These correspond to the (111) plane, (002) plane, and (300) plane of P.

[0071] The peak at the diffraction angle indicates Fe ２ The identification of these compounds as P and FeP is also evident from the JCPDS cards (Files 51-0943 and 39-0809) in the International Centre for Diffraction Data (ICDD) database (Powder Diffraction File, Level 5 plus).

[0072] In this specification, the nano-iron phosphide particles obtained by the production method of the present invention are collectively referred to as "nano-Fe ｘ P" (x represents 1 or 2).

[0073] The nanometal phosphide particles of the present invention are not oxidized in the atmosphere, and the contained metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) can maintain a low valence state. The low valence of the metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) contained in the nanometal phosphide particles of the present invention can be confirmed, for example, by measurement using X-ray photoelectron spectroscopy (XPS). In the XPS measurement results, the vertical axis represents photoelectron intensity, and the horizontal axis represents binding energy (unit: eV). For example, in nanoiron phosphide particles, "the iron atoms are low valence" means that Fe2p in X-ray photoelectron spectroscopy (XPS) is ３／２ This means that the iron atoms contained in the nanometal phosphide particles have a peak in the range of 706.0 to 707.5 eV in the spectrum. ３／２ The spectrum can be measured by the method described in the XPS analysis in the Examples below.

[0074] For XPS, a known X-ray photoelectron spectrometer can be used. The X-ray photoelectron spectrometer may be a commercially available product (for example, an X-ray photoelectron analyzer (trade name "KRATOS ULTRA2" manufactured by Shimadzu Corporation), a photoelectron spectrometer (model number "JPS-9030" manufactured by JEOL Ltd.), or a scanning X-ray photoelectron spectrometer (model number "PHI Quantera II" manufactured by ULVAC-PHI, Inc.). As an excitation source, AlKα radiation, MgKα radiation, AgLα radiation, etc. can be used.

[0075] The nanometal phosphide particles of the present invention have metal atoms (e.g., iron, cobalt, and nickel atoms) contained therein that are in a low-valent state and stable under atmospheric conditions. That is, the metal atoms (e.g., iron, cobalt, and nickel atoms) constituting the nanometal phosphide particles of the present invention do not change in state over time under atmospheric conditions and can continue to exist in a low-valent state that has catalytic activity.

[0076] The valence of metal atoms (e.g., iron, cobalt, and nickel atoms) in the nanometal phosphide particles of the present invention can be analyzed, for example, by X-ray absorption fine structure (XAFS). Specifically, by irradiating metal atoms with high-intensity X-rays, preferably high-intensity X-rays with continuously varying energy, the core electrons of the metal atoms are excited to an energy level equal to or higher than the unoccupied orbitals. The excited metal atoms then emit photoelectrons with a kinetic energy corresponding to the difference between the excitation energy of the incident X-rays and the binding energy of the core electrons. This results in the appearance of a fine structure near the absorption edge in the X-ray absorption spectrum of the metal atoms. Analysis of this fine structure allows the electronic state of the metal atoms to be identified. Within the energy range of XAFS, this fine structure, which appears approximately several tens of eV near the absorption edge, is called the X-ray absorption near edge structure (XANES). On the other hand, the modulation structure that extends from the absorption edge to approximately 1000 eV higher energy within the XAFS energy range is called the extended X-ray absorption fine structure (EXAFS). EXAFS is a vibration structure obtained due to the interaction between excited electrons and scattered electrons from nearby atoms, and the radial distribution function obtained by Fourier transform contains information about the local structure of the metal atom (surrounding atomic species, number of coordinated atoms, and interatomic distance).

[0077] In the nanometal phosphide particles of the present invention, the presence of the contained metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) in a low valence state can also be confirmed by X-ray absorption near edge structure (XANES).

[0078] In the nanometal phosphide particles of the present invention, the contained metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) exist in a low valence state. For example, in the nanoiron phosphide particles, in a XANES spectrum obtained by XANES measurement of the K absorption edge of the Fe atom, the rise of the peak is the same as the rise of the peak of iron foil (Fe foil). In other words, the fact that the iron atoms constituting the nanoiron phosphide particles of the present invention exist in a low valence state can be confirmed by the fact that in the XANES spectrum obtained by the XANES measurement, the rise of the peak is the same as the rise of the peak of iron foil (Fe foil). Iron foil (Fe foil) is zero-valent Fe as a metal.

[0079] For XANES measurement of the K absorption edge of Fe atoms, a known measurement device (for example, an X-ray absorption spectrometer (device name "QuantumLeapH2000" (for measurement in atmosphere) or "QuantumLeapV210" (for measurement in vacuum), both manufactured by Canon Inc.)) or known measurement equipment (large-scale synchrotron radiation facility "SPring-8"; beamlines BL01B1 and BL14B2, 1-1 Hikarito, Sayo-cho, Sayo-gun, Hyogo Prefecture, 679-5198) can be used.

[0080] In the XPS Fe 2p spectrum, low-valent Fe atoms have a peak in the range of 706.7 to 707.0 eV, as shown in Appendix B, Chemical States Tables, Fe 2p, of Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data (Eds.: J. Chastain), Published by Perkin-Elmer Corporation, Electronics Division, Eden Prairie, MN, 1992.

[0081] The shape of the nanometal phosphide particles of the present invention is not particularly limited, but rod-shaped particles are preferred. The rod-shaped particles may have any shape as long as the major and minor axes are recognizable, and may not strictly have a rod shape. The particle shape of the rod-shaped particles can be confirmed by TEM observation, for example, as shown in Figure 1. Figure 1 shows a TEM image of the nanometal phosphide particles of the present invention.

[0082] The rod-shaped particles preferably have a length in the major axis direction (maximum length in the major axis direction) of less than 150 nm, more preferably 100 nm or less, and even more preferably 80 nm or less. In some embodiments, the length may be 70 nm or less, 60 nm or less, 50 nm or less, or 40 nm or less. By being in this range, the particles can exist stably in a low-valence state in the atmosphere, increasing the surface area of ​​each particle and further enhancing catalytic activity. In some embodiments, for example, the maximum length in the major axis direction of the rod-shaped particles is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more.

[0083] The length of the rod-shaped particles in the long axis direction (maximum length in the long axis direction) means the arithmetic mean value of the lengths of 100 particles in the long axis direction (maximum length in the long axis direction) observed under an electron microscope. If necessary, the number of particles to be measured may be 200 or 500.

[0084] When the nanometal phosphide particles of the present invention are rod-shaped particles, the cross-sectional shape of the surface (bottom surface) having the minor axis is not particularly limited, and may be, for example, a hexagon. The shape of the bottom surface is also not particularly limited, and may be flat, have projections or recesses, or may have only projections.

[0085] In the rod-shaped particles, the length in the minor axis direction (maximum length in the minor axis direction) is not particularly limited as long as it is shorter than the length in the major axis direction (maximum length in the major axis direction). For example, when the cross-sectional shape of the surface (base surface) having the minor axis is hexagonal, the length in the minor axis direction (maximum length) is the length of the diagonal line that is the longest length in the cross section. The length in the minor axis direction (maximum length) is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. In some embodiments, it may be 20 nm or less, or 10 nm or less. When the purpose is to be able to exist stably in a low-valence state in the atmosphere, to increase the surface area of ​​each particle, and to enhance catalytic activity, the length in the minor axis direction (maximum length) may be 1 nm or more, 5 nm or more, or 9 nm or more. The length in the minor axis direction (maximum length) refers to the arithmetic average value of the diagonal line that is the longest length of the cross section of the surface (base surface) having the minor axis for any 100 particles observed under an electron microscope. If necessary, the number of particles to be measured may be 200 or 500.

[0086] The aspect ratio (length in the major axis direction:length in the minor axis direction) of the rod-shaped particles is not particularly limited, but is preferably 100:1 to 100:95, more preferably 100:5 to 100:75, and from the viewpoint of obtaining suitable catalytic activity, even more preferably 100:10 to 100:50. The aspect ratio can be calculated from the value calculated from the length in the major axis direction and the length in the minor axis direction of the rod-shaped particles.

[0087] The size of the nanometal phosphide particles of the present invention can be adjusted by adjusting the selection and concentration of raw material compounds, heating temperature, heating conditions (stirring speed, etc.), reaction time, etc. in the method for producing nanometal phosphide particles described below.

[0088] In nanoiron phosphide particles, the abundance ratio of iron atoms to phosphorus atoms as determined by scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDX) composition analysis is preferably Fe:P = 20%:80% to 80%:20%. From the viewpoint of further enhancing catalytic activity or superior atmospheric stability, it is more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%. In a preferred embodiment, nanoiron phosphide particles in which Fe:P = 60%:40% to 70%:30% are exemplified. In a preferred embodiment, from the viewpoint of stability, nanocobalt phosphide particles in which Co:P = 60%:40% to 70%:30% are exemplified. Furthermore, in a preferred embodiment, nanonickel phosphide particles in which Ni:P = 60%:40% to 70%:30% are exemplified.

[0089] The ratio of phosphorus atoms to metal atoms (e.g., iron atoms, cobalt atoms, nickel atoms) in the nano-metal phosphide particles of the present invention can be adjusted by adjusting the degree of metal phosphide. ｘ In P, the amount of the compound where x is 1 can be increased, or the amount of the compound where x is 2 can be increased. ｘ In P, x is 1 or 2. The nano-metal phosphide particles include FeP and Fe ２ In another embodiment, nano-Fe ｘ In P, x is 1. In another embodiment, nano-Fe ｘ In P, x is 2.

[0090] As a method for adjusting the degree of phosphide of a metal (e.g., iron, cobalt, nickel), for example, the heating temperature in the method for producing nano-phosphorized metal particles can be adjusted (e.g., increasing the heating temperature by 10°C, lengthening the reaction time by 1 hour, etc.) to adjust the degree of phosphide, such as promoting the phosphide of the metal. Conversely, when phosphide is to be suppressed and the progress of the phosphide is to be stopped at a certain level, the abundance ratio of phosphorus atoms to iron atoms can be adjusted by conversely adjusting the conditions such as the heating temperature (e.g., decreasing the heating temperature by 10°C, shortening the reaction time by 1 hour, etc.).

[0091] In the nanometal phosphide particles of the present invention, the abundance ratio of phosphorus atoms to iron atoms can be evaluated by elemental analysis (element mapping). The elemental analysis (element mapping) can be performed using a known energy-dispersive X-ray analysis (EDX) method. A known measuring device can be used for EDX. The measuring device can be a commercially available product (such as a transmission electron microscope equipped with a Super-X energy-dispersive X-ray spectroscopy (EDX) detector (single atom analysis transmission electron microscope, product name "Titan Cubed G2 60-300", accelerating voltage: 300 kV, manufactured by FEI (now Thermo Fisher Scientific (US))).

[0092] Furthermore, while EDX is a method for observing a single particle, the abundance ratio of phosphorus atoms to iron atoms may be evaluated by observing the entirety of multiple (large number of) nano-metal phosphide particles, as seen under a microscope. One such method is inductively coupled plasma atomic emission spectroscopy (ICP-AES). Known measuring devices can be used for ICP-AES. Commercially available measuring devices (such as an ICP optical emission spectrometer under the trade name "Optima 8300" manufactured by PerkinElmer, Inc.) can be used. The abundance ratio of phosphorus atoms to iron atoms can be evaluated by ICP-AES, for example, using the method shown in the Examples described below.

[0093] The abundance ratio of iron atoms to phosphorus atoms measured by ICP-AES is preferably Fe:P = 20%:80% to 80%:20%, more preferably 30%:70% to 70%:30% in terms of further enhancing catalytic activity or providing superior atmospheric stability, and even more preferably 35%:65% to 65%:35%. In a preferred embodiment, nano-iron phosphide particles with Fe:P = 60%:40% to 70%:30% are used. In terms of stability, in a preferred embodiment, nano-cobalt phosphide particles with Co:P = 60%:40% to 70%:30% are used. In addition, in a preferred embodiment, nano-nickel phosphide particles with Ni:P = 60%:40% to 70%:30% are used.

[0094] In one embodiment, the abundance ratio of phosphorus atoms to iron atoms in the nanometal phosphide particles of the present invention is such that the ratio evaluated by ICP-AES (e.g., sequential type) and the ratio evaluated by EDX are in a range close to each other. The closeness of both values ​​means that the nanometal phosphide particles of the present invention do not have excess phosphorus atoms.

[0095] The nanometal phosphide particles of the present invention not only have excellent atmospheric stability but also maintain their structure even when heated, resulting in excellent thermal stability. Being able to maintain their structure means being able to maintain a low valence state. Whether or not the structure can be maintained when heated can be confirmed by X-ray absorption fine structure (XAFS) measurement under atmospheric conditions.

[0096] The nanometal phosphide particles of the present invention can maintain their activity after use as a reduction catalyst (e.g., hydrogenation catalyst) and can be recovered. Therefore, they can be recovered and reused. The recovery method is not particularly limited, and known methods such as filtration can be used. Furthermore, the nanometal phosphide particles of the present invention have excellent durability because they retain high catalytic activity even after recovery and reuse.

[0097] Another embodiment of the present invention relates to a composite comprising any of the nanometal phosphide particles described above and a support. Another embodiment of the present invention relates to a method for producing a composite, which comprises contacting the nanometal phosphide particles obtained by any of the production methods described above with a support to produce a composite of the nanometal phosphide particles and the support.

[0098] The nano-metal phosphide particles of the present invention have excellent adsorption ability, and therefore, there are no limitations on the type of carrier, and when used as a composite in a reduction reaction, they are effective as a reduction catalyst. Although the reason for their excellent adsorption ability is not clear, it is thought that part of the reason is that they are nano-sized and stable under atmospheric conditions.

[0099] In the composite of the present invention, the iron atoms contained in the nanometal phosphide particles are in a low-valence state, and the nanometal phosphide particles are stable under atmospheric conditions. Therefore, unlike the prior art, which requires synthesizing catalytically active iron particles on a support and using them as a catalyst immediately after synthesis, or which requires pretreatment under high temperature and pressure to reduce the iron catalyst for use in a reduction reaction, the nanometal phosphide particles of the present invention do not have this requirement. Therefore, unlike the prior art, in which the type of support was limited by the conditions for using the iron particles as an iron catalyst, one of the advantageous effects of the present invention is that the type of support used in combination with the nanometal phosphide particles when the composite is used as a catalyst is not limited. Thus, the reason for limiting the support is eliminated, and there is no special circumstance that would prevent catalytic activity from being achieved if the support is not limited. Therefore, the type of support is not limited in the composite of the present invention, and many different types can be used.

[0100] In the composite of the present invention, the type of carrier is not limited as long as it can be used as a support capable of supporting nanometal phosphide particles. The carrier is preferably a liquid or solid at room temperature, and more preferably a solid. In another embodiment, the carrier does not have catalytic activity by itself. By using the nanometal phosphide particles together with a carrier, aggregation of the nanometal phosphide particles can be effectively suppressed, making it easier to recover the composite and further increasing reusability.

[0101] The support may be at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials. One support may be used alone, or two or more supports may be used in combination. Commercially available supports may be used.

[0102] The polymer may be either a natural polymer or a synthetic polymer. Examples of natural polymers include organic natural polymers such as natural rubber, protein, starch, and cellulose; and inorganic natural polymers such as quartz, mica, and feldspar. Examples of synthetic polymers include organic synthetic polymers such as polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polyvinyl chloride, polyvinylpyrrolidone, polyethylene glycol (PEG), polypropylene glycol (PPG), polyethylene terephthalate (PET), polyester, polyethylene, polypropylene, polystyrene, polyurethane, polyethyleneimine, polyethersulfone, polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyvinylidene fluoride, polylactic acid, epoxy resin, fluorine-based resins (such as PTFE (polytetrafluoroethylene), PFA, FEP, PCTFE, ETFE, and ECTFE), nylon resin, polyamide, polyimide, and rubber (such as silicone rubber, nitrile rubber, butyl rubber, and butadiene rubber); and inorganic synthetic polymers such as glass and silica gel. The synthetic polymer may be a homopolymer having one type of monomer as a constituent unit, or a copolymer having two or more types of monomer as constituent units. The polymer may be a thermoplastic resin or a thermosetting resin. The weight-average molecular weight (Mw) of the polymer is not particularly limited, and may be an oligomer or polymer of 1,000 to less than 10,000, a polymer of 10,000 to less than 1,000,000, or an ultra-high molecular weight polymer of 1,000,000 to 7,000,000. The weight-average molecular weight refers to the weight-average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

[0103] The chalcogen compound refers to a compound containing a Group 16 element (oxygen, sulfur, selenium, tellurium, polonium, livermorium). The Group 16 element contained in the chalcogen compound may be one type alone or two or more types. The chalcogen compound is not particularly limited, and may be H ２ X １ O ４ (X １ = chalcogens excluding tellurium), H ６ TeO ６, H ２ X ２ O ３ (X ２ a compound having the structure of MX = chalcogen) or a salt thereof, ３ (wherein M is Ti, Zr, Hf, V, Nb, Ta, Mo, or W, and X is S or Se), a compound represented by the formula MPX ３ (wherein M is Mg, V, Mn, Fe, Co, Ni, Zn, Cd, or In, and X is S or Se), and the like.

[0104] The metal compound is not particularly limited, but examples thereof include oxides of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Si, Zr, Fe, Ti, Al, Mg, Co, Ni, Mn, Cr, Mo, W, V, Zn, and Sn, solid solutions thereof, and composite oxides thereof. Specific examples include SiO ２ , TiO ２ , and Al ２ O ３ In the present invention, semimetals in the periodic table such as "Si" are included in the metals.

[0105] Metals include Fe and metal alloys (stainless steel, etc.), which can be used as metallic supports.

[0106] Examples of solid carbon materials include silicon carbide (SiC), activated carbon, graphite, diamond, fullerene, carbon nanotubes, graphene, and amorphous carbon.

[0107] The shape and size of the carrier can be changed depending on the form of use and are not particularly limited. For example, the carrier may be in the form of a sheet, film, or plate. The size of the carrier may be nano-sized, and may be 1 μm or more, 1 mm or more, or 1 cm or more. The carrier may be, for example, a nanosheet (e.g., about 1 nm to 100 nm thick).

[0108] The complex of the present invention contains iron atoms in a low valence state, is stable under atmospheric conditions, and has catalytic activity as a reduction catalyst.

[0109] The composite of the present invention is not particularly limited and can be produced depending on the type of support. An example of an embodiment is a method for producing a composite in which nanometal phosphide particles are left to stand or fixed on a support. The method for fixing the nanometal phosphide particles on the support is not particularly limited and may be, for example, a heat treatment or a pressure bonding treatment. The temperature of the heat treatment may be, for example, 100°C or lower. For example, a solid support (e.g., sheet-shaped) having a size sufficiently larger than the nanometal phosphide particles may be used as the support.

[0110] Because the nanometal phosphide particles of the present invention have excellent adsorption ability, any known method for supporting the particles on a carrier can be used without any particular limitations. The method for producing any of the composites is not particularly limited, and may involve, for example, heat treatment. The temperature for the heat treatment may be, for example, 150°C or less, or 120°C or less.

[0111] The organic solvent used in the method for producing the composite is not particularly limited, and a polar organic solvent or a non-polar organic solvent can be used. The organic solvent may be used alone or in combination of two or more kinds.

[0112] Examples of organic solvents that can be used in the method for producing a composite include: non-aromatic hydrocarbon solvents (e.g., alkanes such as pentane, hexane, heptane, octane, nonane, decane, dodecane, isododecane, and tridecane; cycloalkanes such as cyclohexane and methylcyclohexane; decahydronaphthalene; and liquid paraffin); aromatic hydrocarbon solvents (e.g., benzene, toluene, xylene, diethylbenzene, mesitylene, tetralin, indene, naphthalene, and methylnaphthalene); halogenated hydrocarbon solvents (e.g., dichloromethane, dichloroethane, chloroform, and chlorobenzene); and alcohol solvents (e.g., monohydric alcohols such as ethanol, propanol, 1-butanol, 2-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-hexanol, 2-hexanol, benzyl alcohol, and oleyl alcohol; and polyhydric alcohols such as ethylene glycol, polyethylene glycol, propylene glycol, polypropylene glycol, and glycerin). ether solvents (e.g., diethyl ether, diisopropyl ether, methyl t-butyl ether, diisoamyl ether, ethylene glycol derivatives (e.g., monoglyme (ethylene glycol dimethyl ether), methyl cellosolve, diethyl cellosolve, diglyme, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, triglyme, tetraglyme, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, ethylene glycol monobenzyl ether, ethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, poly(ethylene glycol) monomethyl ether), propylene glycol derivatives (e.g., 3-hexanol propylene glycol monopropyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether), 1,1-dimethoxycyclohexane, phenetole, veratrole, dioxane, tetrahydrofuran); Ester solvents (e.g., ethyl acetate, butyl acetate, isopropyl acetate, 3-methoxy-3-methylbutyl acetate, dimethyl carbonate, diethyl malonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, α-acetyl-γ-butyrolactone);Examples of suitable solvents include ketone solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, propiophenone, and isophorone); sulfur-containing solvents (e.g., dimethyl sulfoxide, sulfolane, and diphenyl sulfide); and nitrogen-containing solvents (e.g., amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, N,N-dimethylacrylamide, N,N-dimethylacetoacetamide, N,N-diethylformamide, N,N-diethylacetamide, hexamethylphosphoramide, and methylpyrrolidone, amine solvents such as triethanolamine, and nitrile solvents such as acetonitrile and benzonitrile; nitro solvents such as nitrobenzene and o-nitrotoluene; and quinoline, tetrahydroquinoline and dimethylimidazolidinone).

[0113] Another embodiment of the present invention relates to a reduction catalyst comprising any of the nanometal phosphide particles described above. Reduction reactions using the reduction catalyst include, for example, hydrogenation reactions.

[0114] In some embodiments, the reduction catalyst of the present invention may contain only nanometal phosphide particles. The nanometal phosphide particles may be used as they are as the reduction catalyst. In other embodiments, the reduction catalyst of the present invention may contain nanometal phosphide particles and a support, and the nanometal phosphide particles and the support may form a composite.

[0115] The following description will be given taking as an example a case where the reduction catalyst of the present invention is used as a hydrogenation catalyst. In this specification, unless otherwise specified, the term "reduction catalyst" can be read as "hydrogenation catalyst." One embodiment includes a hydrogenation catalyst containing any of the nanometal phosphide particles described above. Another embodiment includes a hydrogenation catalyst containing any of the nanometal phosphide particles described above and a support, wherein the nanometal phosphide particles and the support form a composite. It should be noted that the reduction catalyst is not limited to a hydrogenation catalyst.

[0116] In one embodiment, there is mentioned a method for producing a hydrogenated organic compound, in which an organic compound is hydrogenated using the hydrogenation catalyst described above to obtain a hydrogenated organic compound.

[0117] Examples of the organic compound include a nitrile compound, an aldehyde compound, and an unsaturated compound.

[0118] Examples of hydrogenated organic compounds produced by hydrogenation include primary amine compounds, alcohol compounds, saturated compounds, and the like.

[0119] Another embodiment is a method for producing a sulfide compound, in which a sulfoxide compound is reduced using the reduction catalyst described above to obtain a sulfide compound.

[0120] Specific examples of the method for producing a hydrogenated organic compound include a method for producing a primary amine compound by hydrogenating a nitrile compound using the above-mentioned hydrogenation catalyst to obtain a primary amine compound; a method for producing an alcohol compound by hydrogenating an aldehyde compound using the above-mentioned hydrogenation catalyst to obtain an alcohol compound; and a method for producing a saturated compound by hydrogenating an unsaturated compound using the above-mentioned hydrogenation catalyst to obtain a saturated compound.

[0121] Taking the case where the organic compound is a nitrile compound as an example, a method for producing a primary amine compound will be described below, in which the nitrile compound is hydrogenated using the hydrogenation catalyst (nanophosphorous metal particles or composite) to obtain a primary amine compound.

[0122] Examples of the nitrile compound include a nitrile compound having one cyano group (mononitrile compound), a nitrile compound having two cyano groups (dinitrile compound), a nitrile compound having three cyano groups (trinitrile compound), and a nitrile compound having four or more cyano groups.

[0123] Examples of nitrile compounds having one cyano group include aliphatic nitrile compounds, aromatic nitrile compounds having one or two aromatic rings and / or heterocyclic rings which may have a substituent, etc. In this specification, when a nitrile compound has an aromatic ring or a heterocyclic ring, it is included in the aromatic nitrile compound.

[0124] Examples of the aliphatic nitrile compound include aliphatic nitrile compounds having 1 to 30 carbon atoms excluding the cyano group. The aliphatic nitrile compound having 1 to 30 carbon atoms excluding the cyano group may be linear, branched, or cyclic. The aliphatic nitrile compound having 1 to 30 carbon atoms excluding the cyano group may be substituted with a halogen atom or may be unsubstituted. The number of carbon atoms excluding the cyano group in the aliphatic nitrile compound is not particularly limited, but may be 1 to 20 or 1 to 15.

[0125] Examples of aliphatic nitrile compounds as mononitrile compounds include acetonitrile, propionitrile, butyronitrile, isobutyronitrile, pentanenitrile (valeronitrile), isovaleronitrile, hexanenitrile, heptanenitrile, octanenitrile, decanenitrile, lauronitrile, octadecanenitrile, 3-methoxypropionitrile, 2-methylbutyronitrile, trimethylacetonitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropane ... linear or branched aliphatic nitriles such as propionitrile, 3-fluoropropionitrile, 2,2-difluoropropionitrile, 2,3-difluoropropionitrile, 3,3-difluoropropionitrile, 2,2,3-trifluoropropionitrile, 3,3,3-trifluoropropionitrile, 3,3'-oxydipropionitrile, 3,3'-thiodipropionitrile, pentafluoropropionitrile, and methoxyacetonitrile; and cyclic aliphatic nitriles such as cyclopentanecarbonitrile, cyclohexanecarbonitrile, and 1-adamantylcarbonitrile.

[0126] Examples of the aromatic ring contained in the aromatic nitrile compound having one or two aromatic rings, which may have a substituent as a mononitrile compound, include benzene, naphthalene, biphenyl, etc. Examples of the heterocycle contained in the aromatic nitrile compound having one or two heterocycles, which may have a substituent, include heterocycles containing only nitrogen atoms as heteroatoms, such as five-membered rings such as pyrrole, imidazole, and pyrazole, and six-membered rings such as pyridine, pyridazine, pyrimidine, and pyrazine; heterocycles containing only oxygen atoms as heteroatoms, such as furan; heterocycles containing only sulfur atoms as heteroatoms, such as thiophene; heterocycles containing nitrogen and oxygen atoms as heteroatoms, such as oxazole; heterocycles containing nitrogen and sulfur atoms as heteroatoms, such as thiazole and isothiazole; and condensed heterocycles, such as benzothiazole, benzoxazole, benzimidazole, quinoline, quinoxaline, chroman, and indole.

[0127] Examples of the substituent include an alkyl group having 1 to 6 carbon atoms, a phenyl group, a phenylalkyl group having 7 to 10 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, a halogen atom, a hydroxyl group, an amino group, a substituted amino group of an alkyl group having 1 to 6 carbon atoms, a formyl group, an acyl group, a carboxyl group, a cyano group, a nitro group, a sulfo group, an alkylthio group of an alkyl group having 1 to 6 carbon atoms, an azo group, an azide group, etc. The number of substituents can be appropriately selected depending on the structure of the compound and may be, for example, 1 to 6, 1 to 4, or 1 to 3.

[0128] Examples of aromatic nitrile compounds having one or two aromatic rings and / or heterocyclic rings which may have substituents include benzonitrile; alkylbenzonitriles such as p-trinitrile, methylbenzonitrile (2-methylbenzonitrile, 3-methylbenzonitrile, 4-methylbenzonitrile), 4-ethylbenzonitrile, 4-t-butylbenzonitrile, and 4-(aminomethyl)benzonitrile; alkoxybenzonitriles such as methoxybenzonitrile (o-methoxybenzonitrile, m-methoxybenzonitrile, p-methoxybenzonitrile); mercaptobenzonitriles such as mercaptobenzonitrile and 2,5-dimercaptobenzonitrile; alkylthiobenzonitriles such as 4-(methylthio)benzonitrile; bromobenzonitrile (o-bromobenzonitrile, m-bromobenzonitrile, p-bromobenzonitrile), chlorobenzonitrile (o-chlorobenzonitrile, m-chlorobenzonitrile, p-chlorobenzonitrile), dichlorobenzonitrile (2,3-dichlorobenzonitrile, 2,4-dichlorobenzonitrile, 2,5- halogenated benzonitriles such as dichlorobenzonitrile, 2,6-dichlorobenzonitrile, 3,4-dichlorobenzonitrile, 3,5-dichlorobenzonitrile), trichlorobenzonitrile (2,3,4-trichlorobenzonitrile, 2,3,5-trichlorobenzonitrile, 2,3,6-trichlorobenzonitrile, 2,4,6-trichlorobenzonitrile), fluorobenzonitrile (o-fluorobenzonitrile, m-fluorobenzonitrile, p-fluorobenzonitrile), difluorobenzonitrile (2,3-difluorobenzonitrile, 2,4-difluorobenzonitrile, 2,5-difluorobenzonitrile, 2,6-difluorobenzonitrile, 3,4-difluorobenzonitrile, 3,5-difluorobenzonitrile), trifluorobenzonitrile (2,3,4-trifluorobenzonitrile, 2,3,5-trifluorobenzonitrile, 2,3,6-trifluorobenzonitrile, 2,4,6-trifluorobenzonitrile), trifluoromethylbenzonitrile, and 4-(3-chloro-4-methylphenyl)benzonitrile;Acetoxybenzonitrile, phenylacetonitrile, 2-phenylbutyronitrile, 3-phenylpropionitrile, 4-phenylbenzonitrile, phenoxybenzonitrile (2-phenoxybenzonitrile, 3-phenoxybenzonitrile, 4-phenoxybenzonitrile), 4-(4-methylphenyl)benzonitrile, 2-(p-tolyl)benzonitrile, 2-naphthalenecarbonitrile, 6-methoxy-2-naphthalenecarbonitrile, 2-pyridinecarbonitrile, 3-pyridinecarbonitrile, 4- Examples include pyridinecarbonitrile, 6-chloro-2-pyridinecarbonitrile, 6-methoxy-3-pyridinecarbonitrile, pyrrole-2-carbonitrile, 1H-indole-3-carbonitrile, 1H-indole-6-carbonitrile, piperonylnitrile, 2-furancarbonitrile, 3-furancarbonitrile, 2-thiophenecarbonitrile, 3-thiophenecarbonitrile, 3-methylthiophene-2-carbonitrile, thiophene-2-acetonitrile, and thiophene-3-acetonitrile;

[0129] Examples of aliphatic nitrile compounds as dinitrile compounds include linear or branched alkyldinitriles having 1 to 30 carbon atoms excluding cyano groups, such as malononitrile, pentanedinitrile, hexanedinitrile (adiponitrile), heptanedinitrile, octanedinitrile, and decanedinitrile; and cycloalkyldinitriles having 3 to 30 carbon atoms excluding cyano groups, such as 1,4-cyclohexanedicarbonitrile. The number of carbon atoms excluding cyano groups that the aliphatic nitrile compound has is not particularly limited, and may be 1 to 20 or 1 to 15.

[0130] Examples of aromatic nitrile compounds having one or two aromatic rings and / or heterocyclic rings which may have a substituent as dinitrile compounds include aromatic nitrile compounds having one aromatic ring and / or heterocyclic ring such as 1,2-benzenedicarbonitrile, 1,3-benzenedicarbonitrile, 1,4-benzenedicarbonitrile, 2,5-difluoro-1,4-benzenedicarbonitrile, etc.; and aromatic nitrile compounds having two aromatic rings and / or heterocyclic rings such as 2-benzhydrylcyclohexane-1,1-dicarbonitrile.

[0131] The amount of the hydrogenation catalyst used is preferably 0.1 to 15 mol%, more preferably 0.15 to 12 mol%, and even more preferably 0.2 to 10 mol%, converted into the amount of Fe, relative to 100 mol% of the nitrile compound, in order to have sufficient catalytic activity. Within the above range, the hydrogenation reaction proceeds sufficiently. The hydrogenation catalyst of the present invention functions as a catalyst even in an extremely small amount, and has excellent catalytic activity.

[0132] The method for producing a primary amine compound is preferably carried out by heating. The heating temperature is not particularly limited, but is preferably 80 to 350° C., more preferably 90 to 280° C., and even more preferably 100 to 250° C. When the reaction is carried out under milder conditions, the temperature may be 200° C. or lower.

[0133] The reaction time is not particularly limited, and may be about 5 minutes to 60 hours, about 10 minutes to 30 hours, or about 20 minutes to 15 hours. Depending on the purpose, it may be set to 8 hours or less.

[0134] In the method for producing a primary amine compound, the hydrogen pressure is 8 MPa or less, and when carried out under milder conditions, the hydrogen pressure may be 5 MPa or less, 4.5 MPa or less, 3.0 MPa or less, or 1.0 MPa or less.

[0135] In the method for producing a primary amine compound, it is preferable to use ammonia gas in addition to hydrogen gas. When hydrogen gas and ammonia gas are used in combination, the pressure during the reaction is not particularly limited, but may be, for example, H ２ :NH３ = 1 MPa:0.005 MPa to 1 MPa:0.8 MPa is preferred, 1 MPa:0.01 MPa to 1 MPa:0.5 MPa is more preferred, and 1 MPa:0.02 MPa to 1 MPa:0.2 MPa is even more preferred. Within the above range, the hydrogenation reaction proceeds sufficiently.

[0136] A preferred embodiment of the present invention is a method for producing a hydrogenated organic compound, in which a nitrile compound is hydrogenated in a hydrogen atmosphere in the presence of ammonia at a hydrogen pressure of 8 MPa or less.

[0137] In the production method of the present invention, since the nitrile compound can also serve as a solvent, it is not necessarily necessary to use a separate solvent. The presence or absence of a solvent and the type of solvent can be selected depending on the type of substrate, etc.

[0138] As the solvent, for example, those exemplified as organic solvents used in the method for producing a composite can be used. Preferred are alcohol solvents such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol; ketone solvents such as acetone and methyl ethyl ketone; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; and ether solvents such as 1,2-dimethoxyethane and diethylene glycol dimethyl ether, with alcohol solvents being more preferred.

[0139] In the method for producing a primary amine compound, the hydrogenation reaction may be carried out in the presence of a base.

[0140] Examples of the base include, but are not limited to, organic bases ((a) tertiary amines, (b) nitrogen-containing aromatic heterocyclic compounds, (c) compounds having an imine skeleton (-C=N-C-) (in this specification, these compounds are also referred to as "imine bases")), (d) inorganic bases, and (e) tetraalkylammonium hydroxide. One type of base may be used alone, or two or more types may be used in combination.

[0141] (a) Examples of tertiary amines include trimethylamine, triethylamine, N-ethyldiisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, trioctylamine, tridecylamine, triphenylamine, tribenzylamine, tris(2-ethylhexyl)amine, N,N-diisopropylethylamine, N,N-dimethyldecylamine, N-benzyldimethylamine, N-butyldimethylamine, N,N-dimethylcyclohexylamine, N,N,N',N'-tetramethylethylenediamine, N,N-dimethylaniline, N,N-diethylaniline, 1,4-diazabicyclo[2.2.2]octane, and N-methyl Examples of suitable amines include pyrrolidine, N-methylpiperidine, N-methylmorpholine, N-ethylmorpholine, N,N'-dimethylpiperazine, N-methylpyrrolidone, N-vinylpyrrolidone, bis(2-dimethylaminoethyl)ether, N,N,N,N',N''-pentamethyldiethylenetriamine, triethanolamine, tripropanolamine, dimethylethanolamine, dimethylaminoethoxyethanol, N,N-dimethylaminopropylamine, N,N,N',N',N''-pentamethyldipropylenetriamine, tris(3-dimethylaminopropyl)amine, tetramethyliminobis(propylamine), and N-diethylethanolamine.

[0142] (b) Examples of nitrogen-containing aromatic heterocyclic compounds include pyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine, lutidine, pyrimidine, pyridazine, pyrazine, oxazole, isoxazole, thiazole, isothiazole, imidazole, 1,2-dimethylimidazole, 3-(dimethylamino)propylimidazole, pyrazole, furazan, quinoline, isoquinoline, purine, 1H-indazole, quinazoline, cinnoline, quinoxaline, phthalazine, Examples include pteridine, phenanthridine, 2,6-di-t-butylpyridine, 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridyl, 5,5'-dimethyl-2,2'-bipyridyl, 6,6'-t-butyl-2,2'-dipyridyl, 4,4'-diphenyl-2,2'-bipyridyl, 1,10-phenanthroline, 2,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline.

[0143] (c) Examples of imine bases include 1,8-diazabicyclo[5.4.0]undec-7-ene (diazabicycloundecene), 1,5-diazabicyclo[4.3.0]non-5-ene, and the like.

[0144] (d) Examples of inorganic bases include hydrides of alkali metals or alkaline earth metals (sodium hydride, potassium hydride, lithium hydride, calcium hydride, etc.), hydroxides of alkali metals or alkaline earth metals (sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, etc.), carbonates of alkali metals or alkaline earth metals (sodium carbonate, potassium carbonate, lithium carbonate, calcium carbonate, etc.), hydrogen carbonates of alkali metals (sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, etc.), oxides of alkali metals or alkaline earth metals (lithium oxide, sodium oxide, potassium oxide, Examples of the alkali metal alkoxide include lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, cesium chloride, and the like; alkali metal alkoxides (lithium methoxide, sodium methoxide, potassium methoxide, lithium ethoxide, sodium ethoxide, potassium ethoxide, lithium isopropoxide, sodium isopropoxide, potassium isopropoxide, lithium tert-butoxide, sodium tert-butoxide, and potassium tert-butoxide); and the like.

[0145] (e) Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0146] The amount of base used is preferably 0.01 to 10 mol, more preferably 0.02 to 8 mol, and even more preferably 0.05 to 4 mol, per mol of the nitrile compound.Within the above range, the hydrogenation reaction proceeds sufficiently.

[0147] The present invention includes embodiments in which the above-described configurations are combined in various ways within the scope of the technical concept of the present invention, as long as the effects of the present invention are achieved.

[0148] Next, the present invention will be explained in more detail by way of examples, but the present invention is not limited to these examples in any way, and many modifications within the technical scope of the present invention are possible by those skilled in the art.

[0149] Example 1 Nanometal Phosphide Particles Example 1-1 Nanoiron phosphide particles were produced by the following method. First, an aqueous solution of iron (III) chloride and sodium oleate were added to a mixed solvent of ethanol and hexane, and the mixture was stirred and mixed at 70°C for 4 hours under an argon atmosphere. The resulting product was washed with ethanol and then dried to obtain the target iron complex (hereinafter referred to as "iron-oleic complex").

[0150] Next, 10 equivalents (molar equivalents) of triphenyl phosphite and hexadecylamine were added to the Schlenk flask and stirred under vacuum at 120° C. for 30 minutes. Next, the iron-olein complex was added under an argon atmosphere, and the temperature was raised to 320° C. at a rate of 50° C. / min., and the reaction was carried out for 4 hours to obtain a mixed solution.

[0151] The mixture was cooled to room temperature, and the product was washed with a washing solution of acetone and chloroform (volume ratio 1:1), and then dried to isolate nano-iron phosphide particles. ｘ The evaluation of the porosity (also referred to as "P") was carried out by the following method.

[0152] <Electron Microscope Observation of Nanometal Phosphide Particles> The nanometal phosphide particles obtained in the examples were observed using a field emission transmission electron microscope (trade name "Tecnai (registered trademark) G2 20ST", acceleration voltage: 200 kV, manufactured by FEI (now Thermo Fisher Scientific (US))). The results are shown in Figure 1.

[0153] <Powder X-ray Diffraction Measurement of Nanometal Phosphide Particles> The nanometal phosphide particles obtained in the examples were subjected to powder X-ray diffraction measurement under atmospheric conditions using a fully automated multipurpose X-ray diffractometer (trade name "Philips X'PERT MPD diffractometer", manufactured by Philips Japan, Ltd.) with CuKα radiation (λ: 1.5405 Å). Approximately 40 mg of the sample was placed on a glass sample plate and subjected to powder X-ray diffraction measurement under the following conditions without any pretreatment. The results are shown in the upper part of Figure 2. [Measurement conditions] Tube voltage: 45 kV Tube current: 40 mA Measurement temperature: room temperature Measurement angle range: 20.00 to 70.00° Sampling interval: 0.013° Scan rate: 0.42° / min

[0154] As shown in the upper part of FIG. 2, the nano-iron phosphide particles obtained in the examples were subjected to powder X-ray diffraction measurement using CuKα radiation in the presence of oxygen, and Fe ２ The maximum intensity was observed for the peak (diffraction angle (2θ): 40.2°) corresponding to the (111) plane of P. Therefore, it was confirmed that the nano-iron phosphide particles obtained in Example 1-1 contained at least Fe. ２ It was confirmed that it contained P.

[0155] [Example 2: Composite] <Example 2-1: Nano-metal phosphide particles and TiO ２ Nano-iron phosphide particles (nano-Fe) prepared in Example 1-1 ｘ P) and TiO as a support ２ Specifically, the powder of nano-iron phosphide particles produced in Example 1-1 was dissolved in n-hexane. ２ TiO having an average particle size in the range of 0.01 μm to 1 μm so that the ratio of the total particle size is 1:25. ２ was added and stirred at 25°C for 6 hours to obtain nano-iron phosphide particles and TiO ２ A composite with TiO was obtained. ２The average particle size of the nano-iron phosphide particles and TiO 2 can be calculated by a laser diffraction scattering method. Specifically, for example, it can be measured on a volume basis using a laser diffraction particle size distribution analyzer (SALD-2300, manufactured by Shimadzu Corporation) and a 0.2% aqueous solution of sodium hexametaphosphate as a dispersion medium. ２ The fact that we were able to produce a composite with nano-metal phosphide particles also confirmed that they have excellent atmospheric stability.

[0156] [Example 3: Production of benzylamine] <Example 3-1> Nano-iron phosphide particles (nano-Fe) of Example 1-1 ｘ Benzonitrile was hydrogenated to produce benzylamine using benzonitrile (P) as a catalyst. Specifically, 0.04 g of the nano-iron phosphide particles of Example 1-1 (Fe amount: 0.076 mmol (Fe amount: 7.6 mol % relative to 100 mol % of benzonitrile)), 3 ml of 2-propanol, 0.5 mmol of benzonitrile, hydrogen gas, and NH ３ Gas, H ２ :NH ３ The mixture was pressurized to 0.3 MPa and heated to 180° C., and the reaction was carried out for 2 hours. The results are shown in Table 1 below.

[0157] Example 3-2 The catalyst used was changed to the nano-iron phosphide particles produced in Example 2-1 and TiO ２ Benzylamine was produced in the same manner as in Example 3-1, except that the complex was changed to a complex of Benzylamine. The results are shown in Table 1 below.

[0158]

[0159] As shown in Table 1, it was confirmed that the nanoiron phosphide particles produced in Example 1-1 have catalytic activity as a hydrogenation catalyst. Unlike conventional surface-shielded iron nanoparticles, the nanoiron phosphide particles of the present invention are atmospherically stable and can maintain a low valence state even on the particle surface, which is thought to be why they have catalytic activity. Furthermore, as shown in Table 1, the composite of the present invention had significantly superior catalytic activity as a hydrogenation catalyst.

[0160] [Example 4: Production of diphenyl sulfoxide sulfide] <Example 4-1> The nano-iron phosphide particles (nano-Fe) of Example 1-1 were prepared. ｘ Diphenyl sulfide was produced by deoxygenating diphenyl sulfoxide using 2,4-dimethylamino-3,4-trimethylamino-1 ...

[0161] From the above results, it was confirmed that the reduction catalyst of the present invention has a wide range of catalytic activity for various substrates and is excellent in substrate versatility.

[0162] The nanometal phosphide particles and composite of the present invention are useful as reduction catalysts in reduction reactions (e.g., hydrogenation reactions), and are particularly useful as hydrogenation catalysts in methods for producing amine compounds.

Claims

1. At least one metal source selected from the group consisting of iron(II) chloride, iron(III) chloride, iron(II) nitrate, iron(III) nitrate, iron(II) bromide, iron(III) bromide, cobalt(II) nitrate, cobalt(II) chloride, cobalt(II) bromide, nickel(II) nitrate, nickel(II) bromide, and nickel(II) chloride is mixed in a solvent with a compound represented by the following general formula [1]: X-Y-Z [1] (wherein X represents an alkenyl group having 3 to 20 carbon atoms, Y represents an alkylene group having 3 to 30 carbon atoms, and Z represents a carboxy group, a sulfonic acid group, a phosphonic acid group, a phosphate group, a primary to tertiary amino group, a salt of a carboxy group, a salt of a sulfonic acid group, a salt of a phosphonic acid group, a salt of a phosphate group, or a salt of a primary to tertiary amino group), to obtain a metal complex of a metal constituting the metal source and the compound represented by the general formula [1], A method for producing nanometal phosphide particles, comprising: mixing a phosphorus compound (excluding sodium phosphide) and a surfactant under heating to obtain a first mixture; and heating a second mixture obtained by mixing the first mixture with the metal complex.

2. The method for producing nanometal phosphide particles according to claim 1, wherein the metal source is iron (II) chloride and / or iron (III) chloride.

3. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein Z is a carboxy group, a phosphate group, an alkali metal salt of a carboxy group, or an alkali metal salt of a phosphate group.

4. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the compound represented by the general formula [1] is oleic acid or sodium oleate.

5. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the phosphorus compound is a phosphite ester compound.

6. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the surfactant is an alkylamine.

7. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the metal source and the compound represented by general formula [1] are mixed in an inert gas atmosphere.

8. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the metal source and the compound represented by general formula [1] are mixed at a temperature in the range of 40 to 180°C.

9. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the heating temperature when mixing the phosphorus compound and the surfactant under heating is within the range of 70 to 200°C.

10. The method for producing nanometal phosphide particles according to claim 1 or 2, wherein the second mixture is heated to a temperature within the range of 200 to 450°C.

11. A method for producing a composite, comprising contacting nanometal phosphide particles obtained by the method of claim 1 or 2 with a support to produce a composite of the nanometal phosphide particles and the support.

12. The method for producing a composite according to claim 11, wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

13. A method for producing a hydrogenated organic compound, comprising hydrogenating an organic compound using nano-metal phosphide particles obtained by the production method described in claim 1 or 2, or a composite of said nano-metal phosphide particles and a support, as a reduction catalyst, to obtain a hydrogenated organic compound.

14. The method for producing a hydrogenated organic compound according to claim 13, wherein the organic compound is a nitrile compound, the hydrogenated organic compound is a primary amine compound, and the nitrile compound is hydrogenated in a hydrogen atmosphere in the presence of ammonia at a hydrogen pressure of 8 MPa or less.

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