Method for producing iron phosphide nanoparticles, composite body containing iron phosphide nanoparticles obtained by same, and reductive amination catalyst using same

Abstract

The present invention provides: a method for producing iron phosphide nanoparticles, which is simple and is highly safe to the human body, wherein iron atoms in iron phosphide nanoparticles obtained by this method are in a low valence state and the iron phosphide nanoparticles are stable under atmospheric conditions; a composite body containing the iron phosphide nanoparticles obtained by the method; and a reductive amination catalyst using the same. The present invention relates to a method for producing iron phosphide nanoparticles, in which a phosphorus compound, an iron carbonyl compound, and a surfactant are mixed under heat, wherein the iron carbonyl compound is Fe3(CO)12, and 1-octadecene is not used.

Description

Method for producing nano-iron phosphide particles, composite containing nano-iron phosphide particles obtained by the method, and reductive amination catalyst using the same

[0001] The present invention relates to a method for producing nano-iron phosphide particles, a composite containing the nano-iron phosphide particles obtained by the method, and a reductive amination catalyst using the same.

[0002] Primary amines are very important compounds with a wide range of applications in pharmaceuticals, agricultural chemicals, polymer materials, etc. Reductive amination of carbonyl compounds is an attractive method for the inexpensive synthesis of primary amines from a variety of substrates.

[0003] Traditionally, this reaction has been promoted mainly by precious metal catalysts (Ru, Pd, Rh, etc.). Although these catalysts are active under mild conditions, their scarcity and high cost pose major problems. In contrast, iron, among transition metals, is abundant on Earth and very inexpensive, making it an extremely attractive catalytic material from the standpoints of cost and toxicity.

[0004] However, iron-based catalysts (e.g., low-valent iron nanoparticles) are extremely unstable. They are easily oxidized and inactivated by ppm-order oxygen. In other words, unstable iron nanoparticles must be handled under a strictly anaerobic atmosphere. Therefore, the only method for producing iron nanoparticles as iron-based catalysts is to reduce supported iron ions in situ under high temperature and high hydrogen pressure conditions.

[0005] Recently, the first iron-based solid catalyst that promotes reductive amination reactions was reported (Non-Patent Document 1). The developed iron-based solid catalyst was found to convert multiple carbonyl compounds to the corresponding amines under liquid-phase conditions at temperatures below 200°C.

[0006] Furthermore, other methods for producing nanosized iron phosphide particles have also been proposed. For example, several synthesis methods under gas phase or liquid phase conditions have been reported for producing nanosized iron phosphide (e.g., Non-Patent Documents 2 to 4).

[0007] “The Synthesis of Primary Amines through Reductive Amination Employing an Iron Catalyst”, Baumler, C., Bauer, C. & Kempe, R. ChemSusChem, Vol.13, Issue 12, pp 3110-3114, June 19, 2020. “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“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

[0008] However, the preparation of this catalyst requires hydrogen reduction at a high temperature of 750°C, and furthermore, the catalyst must be used in the reaction under oxygen-free conditions, so there are still issues to be addressed in terms of the synthesis and handling of the catalyst.

[0009] Furthermore, the gas-phase synthesis method for producing iron phosphide particles requires the use of Na3P, a highly flammable phosphorus source (Non-Patent Documents 2-3). Furthermore, Na3P also produces highly toxic phosphine upon hydrolysis. This poses safety concerns during production. Meanwhile, the liquid-phase method, which prepares iron phosphide particles under milder reaction conditions, uses Fe(CO)5 as the iron source. By using an organic phosphorus compound as the phosphorus source instead of Na3P, it is possible to selectively synthesize iron phosphides of various shapes, sizes, and compositions (Non-Patent Document 4). Fe(CO)5 is a stable precursor that is easy to use and can be handled as a liquid, allowing for easy control of reaction conditions, uniform nanoparticle size, and precise control of nanoparticle properties. Therefore, it has been widely used in the production of nanoparticles. On the other hand, since Fe(CO)5 is a highly volatile liquid compound that is toxic to the human body, it must be injected into the reaction system by hot injection, and there is room for improvement in terms of ease of handling. Therefore, the method for producing iron phosphide particles that uses Fe(CO)5 as the iron source cannot be said to be a synthesis method that is excellent in safety for the human body.

[0010] Therefore, there is a strong demand for the development of an iron catalyst that is safe for the human body, easy to synthesize, capable of promoting reductive amination reactions, and stable under atmospheric conditions.

[0011] The present invention aims to provide a method for producing nanoiron phosphide particles that is safe for the human body, simple, and in which the iron atoms in the obtained nanoiron phosphide particles are in a low-valence state and stable under atmospheric conditions, as well as a composite containing the nanoiron phosphide particles obtained thereby, and a reductive amination catalyst using the same.

[0012] As a result of extensive research to solve the above problems, the present inventors have discovered that Fe(CO) 12 The inventors have found that the above-mentioned problems can be solved by using as an iron source, alloying iron and phosphorus, and using nano-iron phosphide particles. Based on this finding, they have conducted further research and have completed the present invention.

[0013] The present invention includes the following inventions: [1] A method for producing a phosphorus compound, an iron carbonyl compound, and a surfactant by mixing them under heating, wherein the iron carbonyl compound is Fe3(CO) 12 a method for producing nano-iron phosphide particles, which does not use 1-octadecene. [2] The method for producing nano-iron phosphide particles according to [1], wherein the nano-iron phosphide particles are rod-shaped particles, and the maximum length of the rod-shaped particles in the major axis direction is less than 100 nm. [3] The method for producing nano-iron phosphide particles according to [1] or [2], wherein the phosphorus compound is a phosphite ester compound. [4] A composite comprising nano-iron phosphide particles and a carrier, wherein the carrier is at least one selected from the group consisting of a polymer, a chalcogen compound, a metal compound, a metal, and a solid carbon material. [5] The composite according to [4], wherein the carrier contains ZrO2. [6] A reductive amination catalyst comprising the composite according to [4] or [5]. [7] A method for producing a primary amine compound, which comprises reacting a carbonyl compound in the presence of the reductive amination catalyst according to [6] under a hydrogen atmosphere and in the co-presence of ammonia to obtain a primary amine compound. [8] A method for producing a primary amine compound according to [7], wherein heating is performed during the reaction of the carbonyl compound. [9] The method for producing a primary amine compound according to [8], wherein the heating temperature is less than 200° C.

[10] The method for producing a primary amine compound according to any one of [7] to [9], wherein the reaction is carried out in the presence of a solvent.

[0014] The present invention provides a method for producing nano-iron phosphide particles, which is easy and safe for the human body to synthesize, in which the iron atoms in the obtained nano-iron phosphide particles are in a low valence state and stable under atmospheric conditions, as well as a composite containing the nano-iron phosphide particles obtained thereby and a reductive amination catalyst using the same. The method for producing nano-iron phosphide particles also provides a method for producing nano-iron phosphide particles, in which the iron source compound is solid Fe(CO) 12 Since the above is used, it is easy to handle.

[0015] Furthermore, nano-iron phosphide particles (hereinafter referred to as "nano-Fe") obtained by the manufacturing method of the present invention xWhen used as a reductive amination catalyst, the reductive amination reaction of a carbonyl compound can be carried out under milder conditions than those of the prior art to produce a primary amine compound.

[0016] Furthermore, the nanoiron phosphide particles, the composite containing the nanoiron phosphide particles and a support, and the reductive amination catalyst of the present invention are low-toxicity and excellent in safety because they use iron, which is also present in living organisms, as a metal source. Furthermore, the nanoiron phosphide particles of the present invention contain only iron as a metallic element without containing any precious metals, and therefore are industrially advantageous in terms of cost, given the large amount of iron present on Earth (reserves).

[0017] The reductive amination catalyst of the present invention is a solid catalyst, which can be easily recovered after use and has high reusability. Furthermore, the reductive amination catalyst of the present invention can selectively perform reductive amination reactions on many types of carbonyl compounds to produce primary amine compounds, and has excellent substrate selectivity.

[0018] Fig. 1 shows a transmission electron microscope (TEM) image of nanoiron phosphide particles obtained by a manufacturing method according to one embodiment of the present invention. Fig. 2 shows the results of powder X-ray diffraction measurement of nanoiron phosphide particles obtained by a manufacturing method according to one embodiment of the present invention, showing the peak position of the crystal plane corresponding to FeP. Fig. 3 shows the results of XPS measurement of nanoiron phosphide particles obtained by a manufacturing method according to Example 1-1. Fig. 4 shows the results of a durability test as a catalyst of the composite according to Example 3-2.

[0019] Hereinafter, various embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. In this specification, upper and lower limit values ​​of numerical ranges (such as the size of nanoiron phosphide particles, the amount of a certain component (a material such as a compound) used, temperature, pressure, or values ​​calculated from each numerical range and each physical property) can be combined as appropriate.

[0020] An embodiment of the present invention relates to a method for producing nano-iron phosphide particles. In this specification, the nano-iron phosphide particles of the present invention are collectively referred to as "nano-Fe x P" (x represents 1 or 2).

[0021] The method for producing nano-iron phosphide particles of the present invention comprises mixing a phosphorus compound, an iron carbonyl compound, and a surfactant under heating, and then heating the iron carbonyl compound to form Fe(CO) 12 This is a production method that does not use 1-octadecene.

[0022] A known prior art method for producing nanometal particles uses 1-octadecene as an essential component ("Triphenyl Phosphite as the Phosphorus Source for the Scalable and Cost-Effective Production of Transition Metal Phosphides", Chemistry of Materials, Junfeng Liu et al., 2018, 30, pp. 1799-1807). However, the present inventors confirmed that the production method using 1-octadecene does not yield nanoiron particles in an amount that exhibits sufficient catalytic activity. Therefore, the method for producing nanoiron phosphide particles of the present invention does not use 1-octadecene.

[0023] By not using 1-octadecene, the obtained nano-iron phosphide particles and composites containing the same have excellent catalytic activity and can be used as reductive amination catalysts. The method for producing nano-iron phosphide particles of the present invention does not require other additives such as 1-octadecene.

[0024] In the method for producing nano-iron phosphide particles of the present invention, the phosphorus compound used as the phosphide agent is preferably a phosphite ester compound.

[0025] 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.

[0026] The surfactant may be an alkylamine. The alkylamine is not particularly limited, but may include an alkylamine having an alkyl group having 1 to 20 carbon atoms. One type of alkylamine may be used alone, or two or more types may be used in combination.

[0027] 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.

[0028] The alkyl group may have a substituent or may be unsubstituted. The number of substituents can be changed 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. One preferred embodiment is a method for producing nanoiron phosphide particles, in which the surfactant is n-hexadecylamine.

[0029] The amount of the surfactant used may be 0.05 to 20 equivalents (molar equivalents), 0.1 to 15 equivalents, or 0.5 to 13 equivalents relative to the amount of the phosphorus compound used.

[0030] The mixing of the phosphorus compound, the iron carbonyl compound, and the surfactant under heating (hereinafter also referred to as the "mixing step") is not particularly limited, and can be carried out using known methods and devices.

[0031] In the method for producing nanoiron phosphide particles of the present invention, a phosphorus compound, an iron carbonyl compound, and a surfactant are mixed under heating. The heating temperature in the mixing step is preferably 80 to 280°C, more preferably 90 to 250°C, and even more preferably 100 to 220°C. The heating temperature may be less than 200°C or less than 180°C as a milder heating condition. For example, the heating temperature may be 90°C or higher and less than 180°C. The heating temperature can be appropriately changed depending on the desired degree of phosphorization of the nanoiron phosphide particles.

[0032] The iron carbonyl compound in the production method of the present invention is Fe(CO) 12 Use Fe3(CO) 12 can be obtained by a known method such as heating Fe2(CO)9 in an organic solvent. The heating device and temperature can be any known method and are not particularly limited. Fe3(CO) 12 The reason why the desired nano-iron phosphide particles were obtained by using FeCl3 or Fe(acac)3 is unclear, but is presumed to be as follows: The iron phosphide synthesized by the production of nano-iron phosphide particles has a low valence (the iron atom is in a low valence state), and when using iron precursors such as FeCl3 or Fe(acac)3, the iron must be reduced once. On the other hand, when using Fe3(CO) 12The iron atom in this compound is zero-valent, and phosphorus formation proceeds without a reduction step, making it easy to synthesize. Furthermore, in the method for producing nanoiron phosphide particles of the present invention, Fe(CO)5 is not used as the iron carbonyl compound from the viewpoints of safety to the human body, availability, and the fact that Fe(CO)5 is a liquid at atmospheric pressure (1 atm), highly volatile, and prone to sublimation. This requires hot injection into the reaction system, which poses handling problems. To avoid these issues, the hot injection method does not use Fe(CO)5 as the iron carbonyl compound. The hot injection method is a method for producing nanoparticles by adding a liquid (hereinafter also referred to as a "precursor solution") containing dissolved or dispersed compounds serving as sources of elements (e.g., a compound serving as a P source, a compound serving as an Fe source) to a solvent heated to a temperature within the range of, for example, approximately 100°C to 300°C, over a relatively short time (e.g., on the order of milliseconds) to generate many crystal nuclei in the early stages of the reaction. Alternatively, in the hot injection method, compounds that serve as sources of some elements may be dissolved or dispersed in an organic solvent in advance, and after heating, precursor solutions of the other elements may be added. 12 is a solid, and does not require hot injection in the manufacturing method of nano-iron phosphide particles, making it easy to handle. In addition, Fe(CO)5 is a compound that has multiple warnings regarding its effects on the human body, such as being life-threatening if swallowed, being life-threatening if in contact with the skin, and being life-threatening if inhaled, whereas Fe3(CO) 12 does not pose such a risk and is safer for the human body.

[0033] The mixing step is preferably carried out under stirring in order to promote the reaction and more easily produce the nanoiron phosphide particles of the present invention. In a preferred embodiment, the mixing step is preferably carried out under vacuum conditions or in an argon atmosphere in order to more easily produce the nanoiron phosphide particles of the present invention.

[0034] The reaction time in the mixing step is not particularly limited and can be appropriately changed depending on the desired degree of phosphorus content of the nanoiron phosphide particles. The reaction time is, for example, preferably 10 to 120 minutes, more preferably 15 to 90 minutes, and even more preferably 20 to 80 minutes.

[0035] Following the mixing step, the resulting mixture may be further heated (hereinafter also referred to as "heating step [2]"). The heating step [2] is preferably carried out under an argon atmosphere.

[0036] The heating temperature in the heating step [2] is not particularly limited as long as it is higher than that in the mixing step, but is preferably 90 to 300°C, more preferably 100 to 290°C, and even more preferably 120 to 270°C. The heating temperature in the heating step [2] can be appropriately changed depending on the desired degree of phosphorus content of the nanoiron phosphide particles. The heating temperature in the heating step [2] may be 5°C or more higher, or may be 10°C or more higher than that in the mixing step.

[0037] The rate of temperature increase when raising the temperature to the temperature of the heating step [2] after mixing the iron carbonyl compound is not particularly limited and can be appropriately changed depending on the desired degree of phosphorus formation of the nano-iron phosphide particles. For example, the rate of temperature increase can be set low to allow the reaction to proceed slowly. The rate of temperature increase is preferably 5 to 150°C / min, more preferably 10 to 100°C / min, and even more preferably 15 to 90°C / min.

[0038] The reaction time in the heating step [2] is not particularly limited and can be appropriately changed depending on the desired degree of phosphorus formation of the nanoiron phosphide particles. The reaction time is, for example, preferably 10 to 120 minutes, more preferably 15 to 90 minutes, and even more preferably 20 to 80 minutes.

[0039] The method for producing nanoiron phosphide particles of the present invention preferably further includes a washing step. An organic solvent can be used as the washing liquid 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 above-mentioned method for producing a composite. 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, chloroform and acetone can be used in a volume ratio of 1:1. The washing step can include a method in which the product obtained after the mixing step is centrifuged using the organic solvent.

[0040] After the washing step, if necessary, the particles may be dried in a vacuum to obtain nano-iron phosphide particles in powder form.

[0041] Certain other embodiments of the present invention relate to nano iron phosphide particles.

[0042] The nano-iron phosphide particles obtained by the above-described manufacturing method have peaks at diffraction angles of 48.3° and 32.7° (2θ±0.5°) in powder X-ray diffraction measurement using CuKα rays, and Fe2p when measured by X-ray photoelectron spectroscopy (XPS). 3 / 2 In the spectrum, the iron atoms contained therein have a peak in the range of 706.0 to 707.5 eV.

[0043] The nanoiron phosphide particles of the present invention have iron 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 another element. The iron (Fe) atoms contained in the nanoiron phosphide particles of the present invention are in a low valence state.

[0044] In an embodiment, the nanoiron phosphide particles of the present invention have peaks at diffraction angles of 48.3° and 32.7° (2θ±0.5°) in powder X-ray diffraction measurement using CuKα radiation. The diffraction angles may be 2θ±0.2° or 2θ±0.5°.

[0045] 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.).

[0046] The nano-iron phosphide particles of the present invention are in a low-valence 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.

[0047] As used herein, "under atmospheric conditions" refers to an oxygen concentration of about 21% in the atmosphere. The nanoiron phosphide particles of the present invention have excellent stability under conditions in the presence of oxygen. The oxygen concentration under conditions in the presence of oxygen (O2) is not particularly limited, and may be about the oxygen concentration in the atmosphere (about 21%) or about 22% to 100%. The nanoiron phosphide particles of the present invention have excellent atmospheric stability and can maintain a low valence state under conditions in the presence of oxygen, regardless of the oxygen concentration.

[0048] The nanoiron phosphide particles of the present invention preferably further have a peak at 46.3° in the powder X-ray diffraction measurement.

[0049] The nanoiron phosphide particles 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.

[0050] In a preferred embodiment, the nano-iron phosphide particles of the present invention are nano-iron phosphide particles made of FeP. The nano-iron phosphide particles made of FeP are in a low valence state and have air stability.

[0051] Another preferred embodiment includes nano-iron phosphide particles having peaks at 40.2°, 52.9°, and 54.6° in the powder X-ray diffraction measurement. Another preferred embodiment includes nano-iron phosphide particles made of FeP. The nano-iron phosphide particles made of FeP are in a low-valent state and are stable in the atmosphere. Compared to FeP, the ratio of low-valent iron atoms to phosphorus atoms is higher, and it is thought that they have higher catalytic activity.

[0052] The nanoiron phosphide particles of the present invention have peaks at diffraction angles of 40.2°, 52.9°, and 54.6° in the XRD pattern using CuKα radiation, which correspond to the (111) plane, (002) plane, and (300) plane of Fe P, respectively. Furthermore, Fe P preferably has peaks at diffraction angles of 44.2° and 47.3°.

[0053] It is clear from the JCPDS card (File 51-0943) in the database (Powder Diffraction File, Level 4 plus) of the International Centre for Diffraction Data (ICDD) that FeP and FeP can be identified by the peaks at the diffraction angles.

[0054] The nano-iron phosphide particles of the present invention are not oxidized in the atmosphere, and the contained iron atoms can maintain a low valence state. The fact that the iron atoms contained in the nano-iron phosphide particles of the present invention are low valence can be confirmed, for example, by measurement using X-ray photoelectron spectroscopy (XPS). The XPS measurement results are as shown in Figure 3. In Figure 3, the vertical axis represents photoelectron intensity, and the horizontal axis represents binding energy (unit: eV). "The iron atoms are low valence" refers to Fe2p in X-ray photoelectron spectroscopy (XPS). 3 / 2 This means that the iron atoms contained in the nano-iron phosphide particles have a peak in the range of 706.0 to 707.5 eV in the spectrum. 3 / 2The spectrum can be measured by the method described in the XPS analysis in the Examples below.

[0055] 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.

[0056] The nanoiron phosphide particles of the present invention are different from conventional techniques in that the iron atoms contained in the nanoiron phosphide particles are in a low-valent state and are stable under atmospheric conditions. That is, the iron atoms constituting the nanoiron 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.

[0057] The valence of iron atoms in the nanoiron 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 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 identification of the electronic state of the metal atoms. Within the XAFS energy range, such a fine structure appearing approximately several tens of eV near the absorption edge is called the X-ray absorption near-edge structure (XANES). On the other hand, within the XAFS energy range, a modulated structure extending from the absorption edge to approximately 1000 eV higher is called the extended X-ray absorption fine structure (EXAFS). EXAFS is a vibrational 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).

[0058] In the nanoiron phosphide particles of the present invention, the fact that the iron atoms contained therein are in a low valence state can also be confirmed by X-ray absorption near edge structure (XANES).

[0059] In the nano-iron phosphide particles of the present invention, the iron atoms contained therein are present in a low-valent state, and therefore, in a XANES spectrum obtained by XANES measurement of the K absorption edge of Fe atoms, 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 nano-iron phosphide particles of the present invention are present in a low-valent 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). The iron foil (Fe foil) is zero-valent Fe as a metal. In a preferred embodiment, in a XANES spectrum obtained by XANES measurement of the K absorption edge of Fe atoms, (nano-Fe x Examples of nano-iron phosphide particles and composites include those in which the ratio of the spectral intensity of P at 7110 eV to the spectral intensity of Fe foil at 7110 eV is 0.910 to 1.000. "eV" represents binding energy. XANES spectra can be measured at room temperature by transmission using a Si(111) monochromator at the large synchrotron radiation facility "SPring-8" (beamlines BL01B1, BL14B2, 1-1 Hikarito, Sayo-cho, Sayo-gun, Hyogo Prefecture, 679-5198), as described in WO2023 / 200015. The measurement time is, for example, 120 seconds for Fe foil and 120 seconds for nano-Fe foil. x P can be set to 600 seconds.

[0060] In the nano-iron phosphide particles and composites of the preferred embodiment, the spectral intensity at 7110 eV and the spectral intensity at 7111 eV are both (nano-Fe x The ratio of (spectral intensity of Fe foil) / (spectral intensity of Fe foil) is preferably 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000. xThe fact that the ratio of the spectral intensity of P to the spectral intensity of Fe foil is almost the same means that the nanoiron phosphide particles and the Fe foil have the same peak rise. The fact that the nanoiron phosphide particles and the Fe foil have the same peak rise means that the nanoiron phosphide particles are in a low valence state.

[0061] The XPS measurement results indicate that at least the surface side of the nanoiron phosphide particles can maintain a low valence state. When the XANES measurement results match the XPS measurement results, it can be said that the two measurement results support each other, and that the iron atoms contained in the nanoiron phosphide particles can maintain a low valence state not only on the surface but also throughout the entire nanoiron phosphide particles, including the interior.

[0062] For XANES measurements of the K absorption edge of Fe atoms, known measurement devices (for example, X-ray absorption spectrometers (device names "QuantumLeapH2000" (for measurements in air) and "QuantumLeapV210" (for measurements in vacuum), both manufactured by Canon Inc.)) or known measurement facilities (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.

[0063] 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.

[0064] In one preferred embodiment, Fe2p in X-ray photoelectron spectroscopy (XPS) 3 / 2 In the spectrum, the iron atoms contained in the nano-iron phosphide particles have a peak in the range of 706.0 to 707.5 eV, and in the XANES spectrum obtained by XANES measurement of the K absorption edge of the Fe atoms, (nano-Fe x The ratio of the spectral intensities of the XANES spectrum is preferably 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000. In addition, in the nano-iron phosphide particles of the preferred embodiment, the ratio of the spectral intensity of the XANES spectrum at two points, that is, the spectral intensity of 7110 eV and the spectral intensity of 7111 eV, ... x The ratio of (spectral intensity of Fe foil) / (spectral intensity of Fe foil) is preferably 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000.

[0065] The shape of the nanoiron 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, for example, by TEM observation.

[0066] The rod-shaped particles preferably have a length in the major axis direction (maximum length in the major axis direction) of less than 100 nm, more preferably 90 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 of the long side 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.

[0067] 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.

[0068] When the nanoiron 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, may have projections or recesses, or may have only projections.

[0069] 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) is preferably longer, and may be 1 nm or more, 5 nm or more, or even 9 nm or more. The length in the minor axis direction (maximum length) refers to the arithmetic average length 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.

[0070] 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 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.

[0071] The size of the nanoiron 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 nanoiron phosphide particles described below.

[0072] In the nanoiron phosphide particles of the present invention, the abundance ratio of phosphorus atoms to iron atoms as determined by scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDX) composition analysis is preferably P:Fe=20%:80% to 80%:20%, more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%, in terms of further enhancing catalytic activity or providing superior atmospheric stability.

[0073] The ratio of phosphorus atoms to iron atoms in the nano-iron phosphide particles of the present invention can be adjusted by adjusting the degree of iron 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-iron phosphide particles contain at least one of FeP and FeP, and preferably contain both. In another embodiment, nano-Fe x In P, x is 1. In another embodiment, nano-Fe x In P, x is 2.

[0074] As a method for adjusting the degree of iron phosphide, for example, the heating temperature in the method for producing nanoiron phosphide particles can be adjusted (e.g., by increasing the heating temperature by 10°C, lengthening the reaction time by 1 hour, etc.) to adjust the degree of phosphide, such as promoting iron phosphide. Conversely, when phosphide is to be suppressed and the progress of the degree of 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., by decreasing the heating temperature by 10°C, shortening the reaction time by 1 hour, etc.).

[0075] In the nanoiron phosphide particles of the present invention, the abundance ratio of phosphorus atoms to iron atoms can be evaluated by elemental analysis (element mapping). A known energy-dispersive X-ray analysis (EDX) can be used for the elemental analysis (element mapping). 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", acceleration voltage: 300 kV, manufactured by FEI (now Thermo Fisher Scientific (US)))).

[0076] 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 a plurality of (large number of) nano-iron phosphide particles as a whole, as can be 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. Examples of measuring devices that can be used include a commercially available ICP optical emission spectrometer (product name "Optima 8300") (measurement method: multi-wavelength simultaneous multi-element analysis scanning photometric analysis, software: Winlab32), manufactured by PerkinElmer, Inc.

[0077] In one embodiment, the abundance ratio of phosphorus atoms to iron atoms as determined by ICP-AES is preferably P:Fe=20%:80% to 80%:20%, more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%, in terms of further enhancing catalytic activity or providing superior atmospheric stability.

[0078] In one embodiment, the abundance ratio of phosphorus atoms to iron atoms in the nanoiron 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 nanoiron phosphide particles do not have excess phosphorus atoms.

[0079] The nanoiron 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. Maintaining their structure means maintaining a low valence state. The nanoiron phosphide particles and composites of the present invention can be heated and used as reductive amination catalysts, then recovered and reused as active catalysts by heating. Therefore, the nanoiron phosphide particles and composites of the present invention have excellent thermal stability.

[0080] The nanoiron phosphide particles and composite of the present invention can maintain their activity after use as a reductive amination catalyst and can be recovered. Therefore, the nanoiron phosphide particles and composite of the present invention can be recovered and reused again, providing high reusability. The recovery method is not particularly limited, and known methods such as filtration can be used. Furthermore, the nanoiron phosphide particles of the present invention have excellent durability because they retain high catalytic activity even after being recovered and reused.

[0081] Another embodiment of the present invention relates to a composite comprising any of the nano-iron phosphide particles described above and a support, and in another preferred embodiment, the support contains ZrO2, which has excellent catalytic activity as a reductive amination catalyst.

[0082] The nano-iron phosphide particles of the present invention have excellent adsorption ability, and therefore, there is no limitation on the type of carrier, and when used as a composite in a reduction reaction, they are effective as a reductive amination 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.

[0083] In the composite of the present invention, the iron atoms contained in the nanoiron phosphide particles are in a low-valence state, and the nanoiron 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 a reduction pretreatment under high temperature and pressure before the iron catalyst can be used in a reduction reaction, the nanoiron 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 under which the iron particles were used as an iron catalyst, the composite of the present invention does not limit the type of support used in combination with the nanoiron phosphide particles when used as a reductive amination catalyst, which is one of its advantageous effects. Thus, the need for a specific support is eliminated, and there is no special circumstance that would prevent catalytic activity from being achieved without a specific support. Therefore, the composite of the present invention is not limited to a specific type of support, and many different types can be used. Meanwhile, in terms of excellent catalytic activity, the support preferably contains ZrO2. However, other supports (hereinafter also referred to as "other supports") can also be used in addition to or instead of ZrO2. The reason why the catalytic activity is superior when the support contains ZrO2 is thought to be as follows: Nano-iron phosphide particles supported on ZrO2 receive electrons from ZrO2, thereby forming electron-rich iron species. Although it is not clear why ZrO2 can donate electrons to nano-iron phosphide particles, it is thought that electron-rich iron species promote the activation of compound bonds and therefore have superior catalytic activity.

[0084] In the composite of the present invention, the type of other carrier is not limited as long as it can be used as a support capable of supporting nano-iron phosphide particles. The other carrier is preferably a liquid or solid at room temperature, and more preferably a solid. In another embodiment, the other carrier may not have catalytic activity by itself. Using nano-iron phosphide particles together with a carrier containing ZrO2 can effectively prevent the nano-iron phosphide particles from agglomerating, making recovery as a composite easier and increasing reusability. In particular, combining nano-iron phosphide particles made of Fe2P with a carrier containing ZrO2 can further enhance catalytic activity and more effectively prevent the nano-iron phosphide particles from agglomerating.

[0085] The other carrier may be, for example, at least one selected from the group consisting of a polymer, a chalcogen compound, a metal compound, a metal, and a solid carbon material. One type of other carrier may be used alone, or two or more types may be used in combination. Commercially available carriers may be used.

[0086] 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), polyetheretherketone (PEEK), polyvinylidene fluoride, polylactic acid, epoxy resins, fluorine-based resins (PTFE (polytetrafluoroethylene), PFA, FEP, PCTFE, ETFE, ECTFE, etc.), nylon resins, polyamides, polyimides, and rubbers (silicone rubber, nitrile rubber, butyl rubber, butadiene rubber, etc.); and inorganic synthetic polymers such as glass and silica gel. The synthetic polymer may be a homopolymer containing one type of monomer as a constituent unit, or a copolymer containing two or more types of monomers 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 means the weight average molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC).

[0087] 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 H2X 1 O4 (X 1 = chalcogens excluding tellurium), H6TeO6, H2X 2 O3 (X 2= chalcogen) or salts thereof; a compound represented by MX3 (wherein M is Ti, Zr, Hf, V, Nb, Ta, Mo, or W, and X is S or Se); and a metal chalcogenide represented by MPX3 (wherein M is Mg, V, Mn, Fe, Co, Ni, Zn, Cd, or In, and X is S or Se).

[0088] 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, 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, TiO, and AlO. In the present invention, semimetals in the periodic table, such as "Si," are included in the metals.

[0089] Metals include Fe and metal alloys (stainless steel, etc.), which can be used as metallic supports.

[0090] Examples of solid carbon materials include silicon carbide (SiC), activated carbon, graphite, diamond, fullerene, carbon nanotubes, graphene, and amorphous carbon.

[0091] 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).

[0092] 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 reductive amination catalyst.

[0093] The composite of the present invention is not particularly limited and can be produced depending on the type of support. One embodiment includes a method for producing a composite in which nanoiron phosphide particles are left to stand or fixed on a support. The method for fixing nanoiron phosphide particles on a support is not particularly limited and may be, for example, a heat treatment or a pressure bonding treatment. The heating temperature may be, for example, 100°C or lower. The support may be, for example, a solid support (e.g., sheet-shaped) that is sufficiently larger in size than the nanoiron phosphide particles.

[0094] Because the nanoiron phosphide particles of the present invention have excellent adsorption ability, known methods for supporting the particles on a carrier are not particularly limited and can be used. Another embodiment includes a method for producing a composite, in which the nanoiron phosphide particles are dispersed in an organic solvent, and the carrier is added to the organic solvent and stirred to obtain a composite. There are no particular limitations on the method for producing any of the composites, and a heat treatment, for example, may be performed. The heating temperature may be, for example, 150°C or lower, or 120°C or lower.

[0095] 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.

[0096] 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).

[0097] Another embodiment of the present invention relates to a reduction catalyst comprising any of the nano-iron phosphide particles described above.

[0098] In one embodiment, the reductive amination catalyst of the present invention may comprise nanoiron phosphide particles and a support, wherein the nanoiron phosphide particles and the support (preferably a support containing ZrO) form a composite. Another preferred embodiment includes a composite comprising nanoiron phosphide particles and a support, wherein the nanoiron phosphide particles are made of FeP, and the support contains ZrO.

[0099] The reductive amination catalyst of the present invention will be described below taking as an example the case where it is used to produce a primary amine compound. One embodiment includes a reductive amination catalyst containing any of the nanoiron phosphide particles described above. Another embodiment includes a reductive amination catalyst containing any of the nanoiron phosphide particles described above and a carrier, in which the nanoiron phosphide particles and the carrier form a composite.

[0100] In one embodiment, a method for producing a primary amine compound includes reacting a carbonyl compound with the above-described reductive amination catalyst complex in a hydrogen atmosphere and in the presence of ammonia to obtain a primary amine compound. The support in the complex is preferably a support containing ZrO2 because of its excellent catalytic activity.

[0101] Examples of the carbonyl compound include a carbonyl compound having one carbonyl group (monocarbonyl compound), a carbonyl compound having two carbonyl groups (dicarbonyl compound), a carbonyl compound having three carbonyl groups (tricarbonyl compound), and a carbonyl compound having four or more carbonyl groups.

[0102] Examples of carbonyl compounds having one carbonyl group include aliphatic carbonyl compounds, aromatic carbonyl compounds having one or two aromatic rings and / or heterocyclic rings which may have a substituent, and carbonyl compounds having a heterocyclic ring. In this specification, when a carbonyl compound has an aromatic ring or a heterocyclic ring, it is included in the aromatic carbonyl compounds.

[0103] Examples of the aliphatic carbonyl compound include aliphatic carbonyl compounds having 1 to 30 carbon atoms. The aliphatic carbonyl compound having 1 to 30 carbon atoms may be linear, branched, or cyclic. The aliphatic carbonyl compound having 1 to 30 carbon atoms may be substituted with a halogen atom or may be unsubstituted. The number of carbon atoms contained in the aliphatic carbonyl compound is not particularly limited, but may be 1 to 20 or 1 to 15.

[0104] Examples of the aliphatic carbonyl compound as a monocarbonyl compound include aldehydes such as formaldehyde, acetaldehyde, pentanal, hexanal, 2-ethylhexanal, 2-methylheptanal, heptanal, octanal, cyclohexanecarboxaldehyde, and 1-adamantylcarboxaldehyde; and ketones such as acetone, methyl isobutyl ketone, cyclohexanone, 2-adamantanone, and 1-adamantyl methyl ketone.

[0105] Examples of the aromatic ring of the aromatic carbonyl compound having one or two aromatic rings which may have a substituent as a monocarbonyl compound include benzene, naphthalene, biphenyl, etc. Examples of the heterocycle of the aromatic carbonyl compound having one or two heterocycles which may have a substituent include heterocycles containing only nitrogen atoms as heteroatoms such as 5-membered rings such as pyrrole, imidazole, pyrazole, etc., and 6-membered rings such as pyridine, pyridazine, pyrimidine, pyrazine, etc.; heterocycles containing only oxygen atoms as heteroatoms such as furan, etc.; heterocycles containing only sulfur atoms as heteroatoms such as thiophene, etc.; heterocycles containing nitrogen and oxygen atoms as heteroatoms such as oxazole, etc.; heterocycles containing nitrogen and sulfur atoms as heteroatoms such as thiazole, isothiazole, etc.; condensed heterocycles such as benzothiazole, benzoxazole, benzimidazole, quinoline, quinoxaline, chroman, indole, etc.

[0106] 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.

[0107] Examples of the aromatic carbonyl compound having one or two aromatic rings and / or heterocyclic rings, which may have a substituent, as the monocarbonyl compound include benzaldehyde, 4-methylbenzaldehyde, 4-methoxybenzaldehyde, 4-fluorobenzaldehyde, 4-chlorobenzaldehyde, 4-bromobenzaldehyde, 4-aminobenzaldehyde, 4-phenylbenzaldehyde, 2-pyridinecarbaldehyde, 3-pyridinecarbaldehyde, 4-pyridinecarbaldehyde, phenylacetaldehyde, benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, methyl-o-benzoylbenzoate, 4-phenylbenzophenone, 2-phenyl butyrophenone, dibenzyl ketone, fluorenone, indenone, acetophenone, propiophenone, 1-naphthaldehyde, 2-naphthaldehyde, 1-acetylnaphthalene, 4-(4-methylphenylthio)phenyl-ethanone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(1,3-acryloyl-1,3,3'-dimethyl-4-methoxybenzophenone, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone, 2,4-diethylthioxanthone, 2,4-dichlorothioxanthone, 1-chloro-4-propoxythioxanthone, and the like. Examples of carbonyl compounds having a heterocycle as monocarbonyl compounds include furfural (2-furancarboxaldehyde), 2-furanone, and 3-pyridinecarboxaldehyde.

[0108] Examples of aliphatic carbonyl compounds as dicarbonyl compounds include linear or branched alkyl diketones having 1 to 30 carbon atoms, such as 1,2-propanedione, 1,3-propanedione, 2,3-pentanedione, 2,5-hexanedione, 1,7-heptanedione, 1,6-heptanedione, 2,6-heptanedione, and 2,7-octanedione; saturated alicyclic ketones such as cycloalkyl diketones having 3 to 30 carbon atoms, such as 1,3-cyclopentanedione, 1,3-cycloheptanedione, and 1,7,7-trimethylbicyclo[2.2.1]heptane-2,3-dione; and α,β-unsaturated alicyclic ketones having 3 to 30 carbon atoms, such as isophorone. The number of carbon atoms in the aliphatic carbonyl compound is not particularly limited, and may be 1 to 20 or 1 to 15.

[0109] Examples of the dicarbonyl compound having one or two aromatic rings and / or heterocyclic rings, which may have a substituent, include aromatic carbonyl compounds having one aromatic ring and / or heterocyclic ring, such as terephthalaldehyde, phthaldialdehyde, 2,5-dibromoterephthalaldehyde, and 2,5-diformylfuran; and aromatic carbonyl compounds having two aromatic rings and / or heterocyclic rings, such as benzoyl peroxide, 2-ethylanthraquinone, and 9,10-phenanthrenequinone.

[0110] The amount of the reductive amination 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 carbonyl compound, in order to have sufficient catalytic activity. Within the above range, the reductive amination reaction proceeds sufficiently. The reductive amination catalyst of the present invention functions as a catalyst even in an extremely small amount, and has excellent catalytic activity.

[0111] 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 less than 200°C. Even when the heating temperature is less than 200°C, the catalytic activity of the reductive amination catalyst is excellent, and therefore a primary amine compound can be obtained with high production efficiency.

[0112] 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.

[0113] 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.

[0114] The pressure during the reaction is not particularly limited, but for example, H:NH = 0.5 MPa: 0.01 MPa to 7 MPa: 0.9 MPa is preferred, 0.8 MPa: 0.02 MPa to 6 MPa: 0.8 MPa is more preferred, and 0.8 MPa: 0.03 MPa to 5 MPa: 0.7 MPa is even more preferred. Within the above range, the reductive amination reaction proceeds sufficiently.

[0115] A preferred embodiment of the present invention is a method for producing a primary amine compound, which comprises reductively amminating a carbonyl compound in a hydrogen atmosphere in the presence of ammonia at a hydrogen pressure of 8 MPa or less.

[0116] In the production method of the present invention, the type of solvent can be selected depending on the type of substrate, etc. On the other hand, an embodiment includes a method for producing a primary amine compound, in which a carbonyl compound is reacted in the presence of a solvent.

[0117] 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.

[0118] In the method for producing a primary amine compound, the reductive amination reaction may be carried out in the presence of a base.

[0119] 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.

[0120] (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.

[0121] (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.

[0122] (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.

[0123] (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.

[0124] (e) Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0125] 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, relative to 1 mol of the carbonyl compound.Within the above range, the reductive amination reaction proceeds sufficiently.

[0126] 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.

[0127] 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.

[0128] [Example 1: Nano-iron phosphide particles] <Example 1-1> Nano-iron phosphide particles were produced by the following method. First, 10 molar equivalents of triphenyl phosphite, 10 molar equivalents of hexadecylamine, and Fe(CO) were placed in a Schlenk flask. 12 The mixture was stirred under vacuum at 120° C. for 30 minutes, and then heated to 320° C. at a rate of 50° C. / min, and reacted for 4 hours to obtain a mixed solution.

[0129] The mixture was cooled to room temperature, and the product was precipitated in acetone to isolate nano-iron phosphide particles. The obtained nano-iron phosphide particles (nano-FeP) were evaluated by the following method.

[0130] <Electron Microscope Observation of Nanoiron Phosphide Particles> The nanoiron 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. Figure 1 confirms the formation of nanoparticles.

[0131] <Powder X-ray Diffraction Measurement of Nanoiron Phosphide Particles> The nanoiron 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) and about 40 mg of sample placed on a glass sample plate under the following conditions without pretreatment. The results are shown in Figure 2. [Measurement Conditions] Tube voltage: 45 kV Tube current: 40 mA Measurement temperature: room temperature Measurement angle range: 30.00 to 60.00° Sampling interval: 0.013° Scan rate: 0.42° / min

[0132] As shown in Fig. 2, in powder X-ray diffraction measurement using CuKα radiation in the presence of oxygen, the nanoiron phosphide particles obtained in this example exhibited the maximum intensity of the peak (diffraction angle (2θ): 40.2°) corresponding to the (111) plane of FeP. Therefore, it was confirmed that the nanoiron phosphide particles obtained in Example 1-1 were FeP.

[0133] <X-ray Photoelectron Spectroscopy (XPS) of Nano Iron Phosphide Particles> The nano iron phosphide particles obtained in the examples were measured by XPS using an X-ray photoelectron analyzer (trade name "KRATOS ULTRA2", Shimadzu Corporation) and AlKα radiation as an excitation source. The results are shown in Figure 3. As shown in Figure 3, Fe2p 3 / 2 The spectrum confirmed that the iron atoms contained therein had a peak at 706.8 eV. The XPS results confirmed that the iron atoms were in a low valence state on the surface of the nanoiron phosphide particles (up to a depth of about 10 nm).

[0134] [Example 2: Composite] <Example 2-1: Composite of Nanoiron Phosphide Particles and ZrO2> A composite was produced using the nanoiron phosphide particles produced in Example 1-1 and ZrO2 as a carrier. Specifically, the nanoiron phosphide particle powder produced in Example 1-1 was dissolved in chloroform. ZrO2 with an average particle size ranging from 0.01 μm to 1 μm was added thereto so that the mass ratio of nanoiron phosphide particles to ZrO2 was 1:25, and the mixture was stirred at 25°C for 6 hours to obtain a composite of nanoiron phosphide particles and ZrO2. The average particle size of ZrO2 can be calculated using 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) using a 0.2% sodium hexametaphosphate aqueous solution as a dispersion medium.

[0135] Example 2-2: Composite of nanoiron phosphide particles and MgO A composite was produced using the nanoiron phosphide particles produced in Example 1-1 and MgO as a carrier. Specifically, except for using MgO as the carrier instead of ZrO2, the composite was produced using nanoiron phosphide particles and MgO as a carrier in the same manner as in Example 2-1, including the average particle size of the carrier and the mass ratio of the carrier to the nanoiron phosphide particles. The method for measuring the average particle size of MgO was the same as the method for measuring the average particle size of ZrO2.

[0136] Example 2-3: Composite of nanoiron phosphide particles and TiO2 A composite was produced using the nanoiron phosphide particles produced in Example 1-1 and TiO2 as a carrier. Specifically, except for using TiO2 as the carrier instead of ZrO2, the composite was produced using nanoiron phosphide particles and TiO2 as a carrier in the same manner as in Example 2-1, including the average particle size of the carrier and the mass ratio of the carrier to the nanoiron phosphide particles. The method for measuring the average particle size of TiO2 was the same as the method for measuring the average particle size of ZrO2.

[0137] Example 2-4: Composite of nanoiron phosphide particles and Al2O3> A composite was produced using the nanoiron phosphide particles produced in Example 1-1 and Al2O3 as a carrier. Specifically, except for using Al2O3 as the carrier instead of ZrO2, a composite was produced using nanoiron phosphide particles and Al2O3 as a carrier in the same manner as in Example 2-1, including the average particle size of the carrier and the mass ratio of the carrier to the nanoiron phosphide particles. The method for measuring the average particle size of Al2O3 was the same as the method for measuring the average particle size of ZrO2.

[0138] Example 2-5: Composite of nanoiron phosphide particles and SiO2 A composite was produced using the nanoiron phosphide particles produced in Example 1-1 and SiO2 as a carrier. Specifically, except for using SiO2 as the carrier instead of ZrO2, the composite was produced using nanoiron phosphide particles and SiO2 as a carrier in the same manner as in Example 2-1, including the average particle size of the carrier and the mass ratio of the carrier to the nanoiron phosphide particles. The method for measuring the average particle size of SiO2 was the same as the method for measuring the average particle size of ZrO2.

[0139] Example 3: Production of benzylamine Example 3-1: Benzaldehyde was reductively aminated using the nanoiron phosphide particles of Example 1-1 as a catalyst to produce benzylamine. Specifically, 0.1 g of the nanoiron phosphide particles of Example 1-1 (Fe content: 0.1 mmol (Fe content: 10 mol%) relative to 100 mol% benzaldehyde), 5 ml of ethanol, 1 mmol of benzaldehyde, hydrogen gas, and NH gas were placed in an autoclave and pressurized to a H:NH ratio of 3.7 MPa:0.3 MPa, heated to 150°C, and reacted for 3 hours. The results are shown in Table 1 below.

[0140] Examples 3-2 to 3-7 Benzylamine was produced in the same manner as in Example 3-1, except that the type of catalyst used was changed to the composites produced in Examples 2-1 to 2-5, and the reaction conditions were changed as shown in Table 1 below. The results are shown in Table 1 below.

[0141] Comparative Examples 3-1 and 3-2 Benzylamine was produced in the same manner as in Example 3-1, except that the type of catalyst used was changed as shown in Table 1. The results are shown in Table 1.

[0142]

[0143] As shown in Table 1, the nanoiron phosphide particles and composite of the present invention had remarkably excellent catalytic activity as a reductive amination 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, composites of nanoiron phosphide particles and ZrO2 could be produced at 25°C, and the composites exhibited catalytic activity, confirming that the nanoiron phosphide particles have excellent atmospheric stability.

[0144] [Evaluation of durability] The composite of nano-iron phosphide particles and ZrO2 produced in Example 2-1 was used to evaluate its durability as a catalyst. The composite (nano-Fe2P / ZrO2) used in Example 3-2 was filtered and recovered, and then the reaction to produce benzylamine from benzaldehyde was repeated three times under the following reaction conditions. The results are shown in Figure 4. [Reaction conditions] Benzaldehyde (substrate): 1 mmol nano-Fe2P / ZrO2 (catalyst): 0.2 g Ethanol: 5 ml H2:NH3 = 3.7 MPa: 0.3 MPa Reaction time: 1 hour or 3 hours

[0145] In FIG. 4, for example, after Example 3-2, when the product was recovered by filtration and then used again in the reaction under the above conditions with a reaction time of 3 hours, the yield was 89% (yield after one cycle in FIG. 4).

[0146] 4, it was confirmed that the reductive amination catalyst of the present invention has high catalytic activity and is not deactivated even when recovered and reused, and therefore has excellent durability. Therefore, it can be said that the nanoiron phosphide particles, composite, and reductive amination catalyst of the present invention have advantageous effects such as reducing waste and enabling recovery and reuse.

[0147] Example 4: Production of primary amine Example 4-1: Benzylamine was produced by reductive amination of benzaldehyde using the composite (nano-FeP / ZrO) produced in Example 2-1 as a catalyst. Specifically, 0.1 g of the composite (nano-FeP / ZrO) of Example 2-1 (0.036 mmol of Fe (10 mol% Fe relative to 100 mol% benzaldehyde)), 5 ml of ethanol, 1 mmol of benzaldehyde, hydrogen gas, and NH gas were placed in an autoclave. The mixture was pressurized to a H:NH pressure of 3.7 MPa:0.3 MPa, heated to 150°C, and reacted for 3 hours. The yield was 94%. The yield was measured by gas chromatography (GC) (a gas chromatograph (product name "GC-2014") manufactured by Shimadzu Corporation equipped with an amine inert cap) using an internal standard.

[0148] Examples 4-2 to 4-25 Primary amines were produced in the same manner as in Example 4-1, except that the type of substrate compound used was changed to the carbonyl compound shown in Table 2 below. The yield was measured in the same manner as in Example 4-1. Table 3 shows the correspondence between the example number and the obtained primary amine (primary amine in Table 4). The obtained primary amines and their yields are shown in Table 4 below.

[0149]

[0150]

[0151]

[0152] From the above results, it was confirmed that the reductive amination catalyst of the present invention has a wide range of catalytic activity for many substrate compounds and also has excellent substrate selectivity.

[0153] The nanoiron phosphide particles and composite of the present invention are useful as reductive amination catalysts in reductive amination reactions, particularly in methods for producing primary amine compounds.

Claims

1. A phosphorus compound, an iron carbonyl compound, and a surfactant are mixed under heating, and the iron carbonyl compound is converted into Fe3(CO) 12 and a method for producing nano-iron phosphide particles without using 1-octadecene.

2. The method for producing nano-iron phosphide particles according to claim 1, wherein the nano-iron phosphide particles are rod-shaped particles, and the maximum length of the rod-shaped particles in the major axis direction is less than 100 nm.

3. The method for producing nano-iron phosphide particles according to claim 1 or 2, wherein the phosphorus compound is a phosphite ester compound.

4. A composite comprising nano-iron phosphide particles and a support, wherein the support is at least one selected from the group consisting of a polymer, a chalcogen compound, a metal compound, a metal, and a solid carbon material.

5. The composite of claim 4, wherein the support comprises ZrO2.

6. A reductive amination catalyst comprising the complex of claim 4 or 5.

7. A method for producing a primary amine compound, comprising reacting a carbonyl compound in the presence of the reductive amination catalyst according to claim 6 under a hydrogen atmosphere and in the presence of ammonia to obtain a primary amine compound.

8. The method for producing a primary amine compound according to claim 7, wherein the carbonyl compound is heated during the reaction.

9. The method for producing a primary amine compound according to claim 8, wherein the heating temperature is less than 200°C.

10. The method for producing a primary amine compound according to claim 7, wherein the reaction is carried out in the presence of a solvent.

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