Method for producing fe2c nanoparticles, and reduction catalyst comprising fe2c nanoparticles

Abstract

The present invention provides: a method for producing Fe2C nanoparticles, by which Fe2C nanoparticles are produced by a simple process by a one-step reaction; and a reduction catalyst which comprises Fe2C nanoparticles. The present invention relates to a method for producing Fe2C nanoparticles, the method including heating and mixing an iron carbonyl compound, a halide, a boron compound, and an alkylamine under an inert gas atmosphere, wherein the iron carbonyl compound comprises Fe3(CO)12 or Fe2(CO)9, the boron compound comprises a diboron compound that contains a heterocyclic ring represented by general formula (I) (wherein the description of the symbols is omitted), and 1-octadecene is not used. The temperature during the heating and mixing is preferably 80°C or higher and lower than 350°C. The time of the heating and mixing is preferably 2.5-50 hours.

Description

Method for producing Fe2C nanoparticles and reduction catalyst containing Fe2C nanoparticles

[0001] The present invention relates to a method for producing FeC nanoparticles and a reduction catalyst containing FeC nanoparticles.

[0002] Iron carbide is a compound of iron and carbon, and is primarily used to modify iron materials due to its high mechanical strength. Iron carbide is known to have various properties due to the presence of carbon atoms, and while it has a higher saturation magnetization than iron oxide, it also has superior chemical stability, such as corrosion resistance, compared to metallic iron. These properties make it promising for applications in the medical field, magnetic recording media, and catalysts.

[0003] Iron carbide is generally known as cementite, which has a composition of Fe3C, but it can also have various compositions such as Fe5C2, Fe7C3, and Fe2C, and only Fe3C exists as a stable phase under normal pressure.Of these, Fe2C is a metastable substance that exists as a stable phase only under an ultra-high pressure environment of 13 GPa and does not appear on the equilibrium phase diagram under atmospheric pressure.

[0004] Fe2C has been reported to exhibit higher catalytic activity than other iron carbides such as Fe5C2 in the Fischer-Tropsch synthesis of hydrocarbons from carbon monoxide and hydrogen and in the hydrogenation of oxalate esters. Furthermore, due to its high saturation magnetization and coercivity, it has attracted attention as a biomedical and magnetic recording material for applications such as bioimaging, drug delivery, and magnetic hyperthermia treatment (MHT). However, because iron carbide has various metastable phases, it is difficult to selectively synthesize Fe2C in a single phase, and this difficulty in synthesis has hindered the exploration of its functions.

[0005] The main methods reported for synthesizing FeC are the gas-solid reaction method, the thermal decomposition method, and the wet synthesis method. The gas-solid reaction method has the problem of using highly toxic CO as the carbon source, and the thermal decomposition method has the problem of carbon deposition on the surface.

[0006] As for wet synthesis methods, Y. Hou et al. have succeeded in synthesizing FeC in two stages by heating a compound (Fe@FeO: a core-shell structure in which Fe particles are the core and are surrounded by FeO) previously synthesized by thermal decomposition of Fe(CO) in a long-chain amine (Non-Patent Document 1). D. Ma et al. synthesized FeC in two stages using Fe(CO) as a precursor in an NH atmosphere (Non-Patent Document 2). NTK Thanh et al. synthesized FeC in two stages using Fe(CO) as a precursor in a long-chain amine (Non-Patent Document 3).

[0007] Yang, Z.; Zhao, T.; Huang, X.; Chu, X.; Tang, T.; Ju, Y.; Wang, Q.; Hou, Y.; Gao, S. “Modulating the Phases of Iron Carbide Nanoparticles: From a Perspective of Interfering with the Carbon Penetration of Fe@Fe3O4 by Selectively Adsorbed Halide Ions.” Chem Sci 2017, 8 (1), pp.473-481. https: / / doi.org / 10.1039 / C6SC01819J.Zhao, H.; Liu, J.-X.; Yang, C.; Yao, S.; Su, H.-Y.; Gao, Z.; Dong, M.; Wang, J.; Rykov, A. I.; Wang, J.; Hou, Y.; Li, W.-X.; Ma, D. “Synthesis of Iron-Carbide Nanoparticles: Identification of the Active Phase and Mechanism of Fe-Based Fischer-Tropsch Synthesis.”, CCS Chem. 2021, Vol. 3, Issue 11, pp.2712-2724. https: / / doi.org / 10.31635 / ccschem.020.202000555.LaGrow, A. P.; Famiani, S.; Sergides, A.; Lari, L.; Lloyd, D. C.; Takahashi, M.; Maenosono, S.; Boyes, E. D.; Gai, P. L.; Thanh, N. T. K. Environmental STEM Study of the Oxidation Mechanism for Iron and Iron Carbide Nanoparticles. Materials 2022, 15 (4), 1557. https: / / doi.org / 10.3390 / ma15041557.

[0008] However, these methods have the drawback of being complicated in synthesis and using Fe(CO)5, which is highly volatile and toxic and therefore unstable in supply.

[0009] Therefore, a simple method for synthesizing FeC nanoparticles through a one-step reaction has not yet been achieved, and a method for synthesizing FeC nanoparticles using low-toxicity, stable, and easily available iron as a raw material compound has not yet been achieved.

[0010] An object of the present invention is to provide a method for producing Fe2C nanoparticles by a simple one-step reaction method and a reduction catalyst containing Fe2C nanoparticles.

[0011] Another object of the present invention is to provide a method for producing FeC nanoparticles using iron as a raw material compound, which is low-toxicity, stable, and easily available, and a reduction catalyst containing FeC nanoparticles.

[0012] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by mixing an iron carbonyl compound, a halide, a boron compound, and an alkylamine under heating, in which the boron compound contains bis(pinacolato)diboron, without using 1-octadecene. Based on this finding, the present inventors have conducted further research and have completed the present invention.

[0013] The present invention includes the following inventions: [1] A method for producing a compound containing an iron carbonyl compound, a halide, a boron compound, and an alkylamine by heating and mixing them under an inert gas atmosphere, wherein the iron carbonyl compound is Fe3(CO) 12 or Fe2(CO)9, wherein the boron compound comprises a diboron compound containing a heterocycle represented by the following general formula (I): (In the formula, X1, X2, X3, and X4 are the same or different and represent an oxygen atom or a sulfur atom, and the heterocycles Z1 and Z2 are the same or different and represent a 4- to 8-membered ring which may have a substituent.) A method for producing Fe2C nanoparticles without using 1-octadecene. [2] The method for producing Fe2C nanoparticles according to [1], wherein the boron compound contains a diboron compound containing a heterocycle represented by the following general formula (I-1): (Wherein, heterocycles Z3 and Z4 may be the same or different and represent a 4- to 8-membered ring which may have a substituent.) [3] The method for producing Fe2C nanoparticles according to [1] or [2], wherein the boron compound contains at least one selected from the group consisting of bis(pinacolato)diboron, 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane, bis(neopentylglycolate)diboron, bis(hexyleneglycolate)diboron, and bis(2,4-dimethylpentane-2,4-glycolate)diboron. [4] The method for producing Fe2C nanoparticles according to [1] or [2], wherein the temperature during the heating and mixing is 80°C or higher and lower than 350°C. [5] The method for producing Fe2C nanoparticles according to [1] or [2], wherein the heating and mixing time is 2.5 to 50 hours. [6] The method for producing Fe2C nanoparticles according to [1] or [2], wherein the amount of the boron compound used is 0.55 to 8 equivalents relative to the amount of the iron carbonyl compound used. [7] A reduction catalyst containing iron carbide nanoparticles, wherein the iron carbide nanoparticles contain Fe2C nanoparticles, and the average particle size of the Fe2C nanoparticles is 10 nm to 800 nm. [8] The reduction catalyst according to [7], further containing a support. [9] The reduction catalyst according to [8], wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

[10] A composite containing iron carbide nanoparticles and a support, wherein the iron carbide nanoparticles contain Fe2C nanoparticles, and the average particle size of the Fe2C nanoparticles is 10 nm to 800 nm.

[11] The composite according to

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

[12] A method for producing a hydrogenated organic compound, comprising hydrogenating an organic compound using the reduction catalyst according to any one of [7] to [9] to obtain a hydrogenated organic compound.

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

[12] , wherein the organic compound is a nitrile compound, the hydrogenated organic compound is a primary amine compound, and the nitrile compound is hydrogenated under a hydrogen atmosphere in the presence of ammonia.

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

[12] or

[13] , wherein the hydrogenation temperature is 250° C. or less.

[15] The method for producing a hydrogenated organic compound according to any one of

[12] to

[14] , wherein the hydrogenation is carried out in the presence of a solvent.

[0014] According to the present invention, a method for producing FeC nanoparticles by a simple one-step reaction method and a reduction catalyst containing FeC nanoparticles can be provided. Furthermore, the method for producing FeC nanoparticles of the present invention is industrially advantageous in that it uses a low-toxicity, stable, and easily available iron compound as the iron source, thereby providing excellent biological safety. Furthermore, the method for producing FeC nanoparticles of the present invention is industrially advantageous in that it does not require iron pretreatment and the production process is simple. Furthermore, the method for producing FeC nanoparticles of the present invention is industrially advantageous in that it does not require high-pressure conditions or the like and produces FeC nanoparticles in a single phase by a simple stepwise reaction method under mild conditions, providing a reduction catalyst containing FeC nanoparticles.

[0015] Furthermore, the FeC nanoparticles and reduction catalyst of the present invention use iron, which is also present in living organisms, as a metal source, and therefore are low-toxic and highly safe. Furthermore, because of the large amount of iron (reserves) present on Earth, they are industrially advantageous in terms of cost.

[0016] FIG. 1 shows scanning electron microscope (SEM) images of FeC nanoparticles according to one embodiment of the present invention. FIG. 2 shows the results of powder X-ray diffraction measurement of FeC nanoparticles according to Example 1-1 of the present invention, along with the peak positions of the crystal planes corresponding to FeC. FIG. 3 is a schematic diagram illustrating the mechanism of action in the method for producing FeC nanoparticles according to the present invention. FIG. 4 shows the results of powder X-ray diffraction measurement of FeC nanoparticles according to Example 1-1 of the present invention at various reaction times (FIG. 4(a)) and the results of powder X-ray diffraction measurement of particles according to Comparative Example 1-7 at various reaction times (FIG. 4(b)). FIG. 5 shows the results of powder X-ray diffraction measurement of FeC nanoparticles according to Examples 1-1 to 1-3 and particles according to Comparative Example 1-1. FIG. 6 shows the results of powder X-ray diffraction measurement of FeC nanoparticles according to Examples 1-1 and 1-4 and particles according to Comparative Example 1-2. FIG. 7 shows the results of powder X-ray diffraction measurement of particles according to Comparative Example 1-3. FIG. 8 is a diagram showing the results of powder X-ray diffraction measurements of the FeC nanoparticles according to Examples 1-5 to 1-6 and the particles according to Comparative Examples 1-4 to 1-6.

[0017] Hereinafter, each embodiment of the present invention will be described. In this specification, the FeC nanoparticles of the present invention will also be referred to as "nano-FeC." In addition, in this specification, "crystallite" means the smallest unit portion that can be regarded as a single crystal among crystal grains. In this specification, "crystallite size" means the domain size of a single crystal in a crystal, and is a value calculated from the measured value of X-ray diffraction (XRD). A detailed calculation method of the crystallite size is as described in the Examples below. Note that, depending on the diffraction line width of the peak measured by XRD, the crystallite size can be more accurately determined by confirming the crystallite size by electron microscope observation (e.g., TEM observation) in addition to the measurement by XRD. In addition, when two or more crystal planes are observed by XRD, the smaller value of the crystallite size calculated by the method described in the Examples below (the smallest value when three or more crystal planes are present) can be used as the crystallite size. Furthermore, in this specification, with respect to the peak measured by XRD, "FeC" and "Fe 2.2 "FeC" is used without distinction, and both are included and treated as "FeC." In addition, in this specification, "under atmospheric conditions" means atmospheric pressure (1 atmosphere) and an oxygen concentration of about 21% in the atmosphere. Furthermore, in this specification, unless otherwise specified, the description of the amount of each component used means the total amount when two or more of the same components are used (for example, when two or more diboron compounds containing a heterocycle represented by general formula (I) are included, the total amount). In this specification, the upper and lower limits of numerical ranges (such as the size of iron carbide nanoparticles, the amount of a certain component (material such as a compound) used, temperature, pressure, time, average particle diameter, or values ​​calculated from each numerical range and each physical property, etc.) can be combined as appropriate.

[0018] One embodiment of the present invention relates to a reduction catalyst containing iron carbide nanoparticles, wherein the iron carbide nanoparticles are FeC nanoparticles, and the iron carbide nanoparticles have an average particle size of 10 nm or more and 800 nm or less. Each embodiment will be described below. Note that the present invention is not limited to the following embodiments.

[0019] The reduction catalyst of the present invention contains iron carbide nanoparticles. The iron carbide nanoparticles are FeC nanoparticles. The iron carbide nanoparticles constituting the reduction catalyst of the present invention are preferably composed solely of FeC nanoparticles, as this will result in superior catalytic activity.

[0020] First, the FeC nanoparticles used in the reduction catalyst of the present invention will be described.

[0021] The FeC nanoparticles of the present invention have peaks at diffraction angles of 37.7°, 41.5°, and 43.2° (2θ±0.5°) in powder X-ray diffraction measurement using CuKα radiation. The diffraction angles may be 2θ±0.2° or 2θ±0.5°.

[0022] The Fe2C nanoparticles of the present invention preferably further have a peak at 57.3° in the powder X-ray diffraction measurement.

[0023] The Fe2C nanoparticles of the present invention preferably further have a peak at 68.0° in the powder X-ray diffraction measurement.

[0024] The peaks at diffraction angles of 37.7°, 41.5°, 43.2°, 57.3°, and 68.0° in the X-ray diffraction pattern (hereinafter also referred to as "XRD pattern") of the FeC nanoparticles of the present invention using CuKα radiation correspond to the (100), (002), (101), (102), and (110) crystal planes of FeC, respectively. The FeC nanoparticles of the present invention are preferably hexagonal in terms of excellent catalytic activity.

[0025] The FeC nanoparticles of the present invention contain iron atoms in a low valence state (metallic state) and can maintain catalytic activity 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 iron (Fe) atoms contained in the FeC nanoparticles of the present invention are in a low valence state.

[0026] 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 Co., Ltd.).

[0027] The iron carbide FeC nanoparticles of the present invention (hereinafter simply referred to as "iron carbide nanoparticles") are in a low valence state and have the property of being able to stably maintain catalytic activity under atmospheric conditions (hereinafter also referred to as "atmospheric stability"). Therefore, the iron carbide nanoparticles of the present invention, i.e., FeC nanoparticles, do not require reduction pretreatment before use as a reduction catalyst. Furthermore, the crystal structure of the FeC nanoparticles of the present invention can be measured by powder X-ray diffraction measurement in the presence of oxygen.

[0028] Furthermore, the FeC nanoparticles of the present invention can maintain catalytic activity in the presence of oxygen. The oxygen concentration in the presence of oxygen (O) is not particularly limited, and may be about the same as the oxygen concentration in the atmosphere (about 21%), or about 22% to 100%. The FeC nanoparticles of the present invention have excellent atmospheric stability and can maintain catalytic activity in the presence of oxygen, regardless of the oxygen concentration.

[0029] The fact that the material can be identified as FeC based on the peak at the diffraction angle is also evident from the JCPDS card (File 36-1249) in the database (Powder Diffraction File, Level 4 plus 2023) of the International Centre for Diffraction Data (ICDD).

[0030] The shape of the FeC nanoparticles of the present invention is not particularly limited, but spherical particles are preferred. Spherical particles may be approximately spherical. For approximately spherical particles, the aspect ratio (long axis / short axis) of the particles is preferably 1 to 2.5, more preferably 1 to 2, even more preferably 1 to 1.5, and particularly preferably 1 to 1.2. The aspect ratio refers to the ratio (long axis / short axis) of the long side to the short side of the smallest rectangle (usually called the circumscribing rectangle) when a particle image projected onto a flat surface in an electron microscope photograph or the like is enclosed by a rectangle. The length of the long side is referred to as the "long axis" and the length of the short side is referred to as the "short axis." The closer the aspect ratio is to 1, the more spherical the particle is. The aspect ratio can be calculated as the arithmetic average of 100 particles projected onto a flat surface in an electron microscope photograph or the like. If necessary, the number of particles to be measured may be 200, 400, 500, or 800. The aspect ratio can be calculated using known particle analysis software (e.g., "MultiImageTool" manufactured by System In Frontier, Inc.). The particle morphology of the spherical particles can be confirmed by SEM observation, for example, as shown in Figure 1. Figure 1 shows an SEM image of FeC nanoparticles of the present invention.

[0031] The average particle size of the FeC nanoparticles of the present invention is 5 nm or more and 800 nm or less. The average particle size of the FeC nanoparticles of the present invention is preferably 7 nm or more, more preferably 8 nm or more, even more preferably 10 nm or more, and particularly preferably 12 nm or more. The average particle size of the FeC nanoparticles of the present invention is preferably 800 nm or less, more preferably 600 nm or less, even more preferably 400 nm or less, and particularly preferably 200 nm or less. One embodiment includes a reduction catalyst in which the average particle size of the FeC nanoparticles is 10 nm or more and 800 nm or less. Another embodiment includes a reduction catalyst in which the average particle size of the FeC nanoparticles is 10 nm or more and 100 nm or less. Another embodiment includes FeC nanoparticles having a hexagonal crystalline phase, a spherical shape, and an average particle size of 8 nm or more and 200 nm or less.

[0032] The average particle size of the FeC nanoparticles of the present invention refers to the arithmetic mean value of primary particles calculated from the results of electron microscope observation (e.g., SEM observation, TEM observation). Regarding the average particle size of the FeC nanoparticles of the present invention, the arithmetic mean value of the major axis lengths (maximum major axis lengths) of 100 or more (e.g., 200) particles (primary particles) observed in an electron microscope photograph (e.g., SEM image, TEM image) can be calculated as the average particle size. If necessary, the number of particles to be measured may be 400, 500, or 800. The average particle size can be calculated using known particle analysis software (e.g., "MultiImageTool" manufactured by System in Frontier, Inc.). Regarding the average particle size of the FeC nanoparticles of the present invention, the crystallite size of the FeC nanoparticles can be calculated by XRD measurement according to the diffraction line width of the peak measured by XRD, thereby predicting that a nano-sized particle size can be obtained.

[0033] It is believed that the Fe2C nanoparticles of the present invention have iron atoms in a low valence state and can maintain catalytic activity under atmospheric conditions.

[0034] The valence of iron atoms in the FeC nanoparticles 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 fine structure appears near the absorption edge in the X-ray absorption spectrum of the metal atoms, and analysis of this fine structure allows the electronic state of the metal atoms to be identified. Within the XAFS energy range, the fine structure that appears 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, the modulated structure that extends 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).

[0035] In the Fe2C nanoparticles of the present invention, the fact that the contained iron atoms are in a low valence state can also be confirmed by X-ray absorption near edge structure (XANES).

[0036] In the FeC nanoparticles of the present invention, the iron atoms contained therein exist in a low valence state, and therefore, in the XANES spectrum obtained by XANES measurement of the K absorption edge of the 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 FeC nanoparticles 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. In one embodiment, the ratio of (spectral intensity at 7110 eV of FeC nanoparticles) / (spectral intensity at 7110 eV of Fe foil) in the XANES spectrum obtained by XANES measurement of the K absorption edge of Fe atoms is 0.910 to 1.000. "eV" represents the binding energy.

[0037] 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.

[0038] The size of the Fe2C nanoparticles of the present invention can be adjusted by adjusting the selection and concentration of raw material compounds, heating conditions (heating temperature, stirring speed, etc.), reaction time, etc. in the method for producing Fe2C nanoparticles described below.

[0039] In the FeC nanoparticles of the present invention, the abundance ratio of carbon atoms to iron atoms as determined by scanning transmission electron microscope (STEM)-energy dispersive X-ray spectroscopy (EDX) composition analysis is not particularly limited, but from the viewpoint of further enhancing catalytic activity or achieving superior atmospheric stability, it is preferable that C:Fe=20%:80% to 80%:20%, more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%.

[0040] The ratio of carbon atoms to iron atoms in the FeC nanoparticles of iron carbide of the present invention can be adjusted by adjusting the degree of iron carbonization. The iron carbide nanoparticles contain FeC nanoparticles, and preferably consist of only FeC nanoparticles.

[0041] As a method for adjusting the degree of iron carbonization, for example, the heating temperature in the method for producing FeC nanoparticles can be adjusted (e.g., changing the heating temperature, changing the amount or concentration of raw material compounds (e.g., halides), changing the reaction time, etc.) to adjust the degree of carbonization, such as promoting iron carbonization. For example, to suppress carbonization and stop the progress of the carbonization to a certain extent, the ratio of carbon atoms to iron atoms can be adjusted by conversely adjusting the conditions such as the heating temperature (e.g., lowering the heating temperature by 10°C, lowering the amount or concentration of raw material compounds (e.g., halides), shortening the reaction time by 1 hour, etc.).

[0042] In the FeC nanoparticles of the present invention, the abundance ratio of carbon 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. A commercially available measuring device (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)))) can be used.

[0043] Furthermore, while EDX is a method for observing a single particle, the abundance ratio of carbon atoms to iron atoms may be evaluated by observing a plurality of (large amounts of) FeC nanoparticles 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. Commercially available measuring devices (such as an ICP optical emission spectrometer under the trade name "Optima 8300" manufactured by PerkinElmer, Inc.) can be used.

[0044] The ratio of carbon atoms to iron atoms in the FeC nanoparticles as determined by ICP-AES is not particularly limited, but from the viewpoint of further enhancing catalytic activity or achieving superior atmospheric stability, C:Fe=20%:80% to 80%:20%, more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%.

[0045] The FeC nanoparticles of the present invention not only have excellent atmospheric stability, but also maintain their structure even when heated, resulting in excellent thermal stability. "Maintaining the structure" means maintaining a low valence state. Whether or not the structure can be maintained when heated can also be confirmed by X-ray absorption fine structure (XAFS) measurement under atmospheric conditions.

[0046] The FeC nanoparticles 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 FeC nanoparticles of the present invention have excellent durability because they retain high catalytic activity even after recovery and reuse.

[0047] The reduction catalyst of the present invention preferably further contains a carrier in order to obtain more excellent catalytic activity.

[0048] Another embodiment of the present invention is a composite containing FeC nanoparticles and a carrier, wherein the FeC nanoparticles contain FeC nanoparticles, and the average particle size of the FeC nanoparticles is 10 nm or more and 800 nm or less.

[0049] The FeC nanoparticles of the present invention have excellent adsorption capacity, so 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. The reason for their excellent adsorption capacity is unclear, but it is thought that part of the reason is that they are nano-sized and stable under atmospheric conditions.

[0050] In the reduction catalyst and composite of the present invention, the iron atoms contained in the FeC nanoparticles are in a low-valent state, and the FeC nanoparticles 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 use the iron catalyst in a reduction reaction, the FeC nanoparticles 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 FeC nanoparticles 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 catalytic activity cannot be obtained without a limited support. Therefore, the type of support is not limited in the composite of the present invention, and many types can be used.

[0051] In the reduction catalyst and composite of the present invention, the type of support is not limited as long as it can be used as a support capable of supporting FeC nanoparticles. The support is preferably a liquid or solid at room temperature, more preferably a solid. Furthermore, the support itself may not have catalytic activity. By using FeC nanoparticles together with a support, aggregation of the FeC nanoparticles can be effectively suppressed, making it easier to recover them as a composite and further increasing reusability.

[0052] 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.

[0053] 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 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).

[0054] 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).

[0055] 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, TiO, and AlO. In the present invention, semimetals in the periodic table, such as "Si," are included in the metals.

[0056] Metals include Fe and metal alloys (stainless steel, etc.), which can be used as metallic supports.

[0057] Examples of solid carbon materials include silicon carbide (SiC), activated carbon, graphite, diamond, fullerene, carbon nanotubes, graphene, and amorphous carbon.

[0058] 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).

[0059] 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.

[0060] 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 FeC nanoparticles are left to stand or fixed on a support. The method for fixing the FeC nanoparticles on the 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 than the FeC nanoparticles.

[0061] Because the FeC nanoparticles of the present invention have excellent adsorption ability, any known method for supporting the nanoparticles 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.

[0062] 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.

[0063] 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; carbonate ester solvents such as ethylene carbonate and propylene carbonate;Examples of suitable solvents include cyclic esters such as γ-butyrolactone and α-acetyl-γ-butyrolactone; ketone solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, isophorone; aromatic ketone solvents such as acetophenone and propiophenone); sulfur-containing solvents (e.g., dimethyl sulfoxide, sulfolane, 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; nitrile solvents such as acetonitrile and benzonitrile; nitro solvents such as nitrobenzene and o-nitrotoluene; quinoline and tetrahydroquinoline).

[0064] Another embodiment of the present invention relates to a method for producing Fe2C nanoparticles.

[0065] The method for producing FeC nanoparticles of the present invention includes heating and mixing an iron carbonyl compound, a halide, a boron compound, and an alkylamine under an inert gas atmosphere, and then heating the iron carbonyl compound to form Fe(CO). 12 or Fe2(CO)9, the boron compound includes a diboron compound containing a heterocycle represented by the following general formula (I), and no 1-octadecene is used. (In the formula, X1, X2, X3, and X4 are the same or different and represent an oxygen atom or a sulfur atom, and heterocycles Z1 and Z2 are the same or different and represent a 4- to 8-membered ring which may have a substituent.)

[0066] In the method for producing FeC nanoparticles of the present invention, the iron carbonyl compound used as the iron source is preferably Fe(CO) because it generates CO by thermal decomposition. 12 or Fe2(CO)9, including Fe3(CO) 12is preferable. The iron carbonyl compound may be used alone or in combination of two or more. The method for producing FeC nanoparticles of the present invention can selectively produce the desired FeC nanoparticles by a simple one-step reaction. Furthermore, the method for producing FeC nanoparticles of the present invention can produce FeC nanoparticles without using Fe(CO)5, which is highly toxic, unstable, and difficult to obtain, and is therefore excellent in biological safety and industrially advantageous.

[0067] The alkylamine is not particularly limited, but examples thereof include alkylamines having an alkyl group having a carbon number of 8 to 24. The alkylamines may be used alone or in combination of two or more.

[0068] The alkyl group contained in the alkylamine may be linear, branched, or cyclic. Examples of the alkyl group include an n-octyl group, an isooctyl group, a tert-octyl group, a 2-ethylhexyl group, a 3-methylheptyl group, an n-nonyl group, an isononyl group, a 1-methyloctyl group, a 2-ethylheptyl group, an n-decyl group, a 1-methylnonyl group, an n-undecyl group, a 1,1-dimethylnonyl group, an n-dodecyl group, an n-tridecyl group, an n-tetradecyl group, an n-pentadecyl group, an n-hexadecyl group, an n-heptadecyl group, an n-octadecyl group, an n-nonadecyl group, an n-eicosyl group, an n-cyclopentyl group, an n-cyclopentylmethyl group, a cyclohexyl group, and a cyclohexylmethyl group. The alkyl group of the alkylamine preferably has 10 to 22 carbon atoms, more preferably 12 to 20 carbon atoms, and even more preferably 14 to 18 carbon atoms.

[0069] 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. In one embodiment, the alkylamine includes hexadecylamine in the method for producing FeC nanoparticles.

[0070] The amount of the alkylamine used is not particularly limited, and may be 0.05 to 200 equivalents (molar equivalents), 0.1 to 150 equivalents, or 0.5 to 130 equivalents relative to the amount of the iron carbonyl compound used.

[0071] Since nanoparticles obtained by a production method using 1-octadecene cannot produce Fe2C, 1-octadecene is not used in the production method of Fe2C nanoparticles of the present invention.

[0072] In the method for producing FeC nanoparticles of the present invention, the use of a halide creates strong Fe-halogen bonds (e.g., Fe-Cl bonds, Fe-Br bonds), which slows the process by which iron atoms adhere to the surface of iron core particles produced by decomposition of iron carbonyl compounds, resulting in nanoparticle growth. This is believed to result in the production of more thermodynamically stable α-Fe nanoparticles and the production of the desired FeC nanoparticles. In the absence of a halide, crystalline Fe is not produced, which weakens carbon monoxide adsorption and prevents the production of FeC. Therefore, the halide used in the method for producing FeC nanoparticles of the present invention is not particularly limited, and can be any compound in which a halogen element (chlorine, bromine, or iodine) exists in an ionic state, as long as it is capable of forming an Fe-Cl bond.

[0073] The halide may be an organic halide or an inorganic halide. Examples of the organic halide include aliphatic halides in which a halogen atom is bonded to an aliphatic hydrocarbon group, and aromatic halides in which a halogen atom is bonded to an aromatic ring. The aliphatic hydrocarbon in the aliphatic halide preferably has 1 to 50 carbon atoms, more preferably 5 to 45 carbon atoms, even more preferably 8 to 40 carbon atoms, and particularly preferably 10 to 35 carbon atoms. The aromatic halide may contain an aliphatic hydrocarbon group in addition to the aromatic ring. The aromatic halide may have 6 to 50 carbon atoms, more preferably 6 to 45 carbon atoms, even more preferably 6 to 40 carbon atoms, and particularly preferably 7 to 35 carbon atoms. Examples of the aliphatic halides include bromides such as cetyltrimethylammonium bromide (CTAB); chlorides such as cetyltrimethylammonium chloride (CTAC), benzyldimethyldodecylammonium chloride (BDDAC), tetrabutylammonium chloride (BNC), benzyltributylammonium chloride (BBAC), benzyltriethylammonium chloride (BTEAC), acetylcholine chloride (ACC), methyltri-n-octylammonium chloride (MOAC), and didecyldimethylammonium chloride (DDAC); and iodides such as cetyltrimethylammonium iodide. Examples of the aromatic halides include chlorides such as benzethonium chloride (BTC), benzyl chloride, and chlorobenzene; and iodides such as benzyldimethyldodecylammonium iodide (BDDAI). Examples of the inorganic halides include chlorides such as ammonium chloride. The halide is preferably an aliphatic halide or an inorganic halide, and more preferably CTAB, CTAC, or ammonium chloride because of its superior effect of improving the crystallinity of FeC. The halide may be used alone or in combination with two or more other compounds. The halide can be appropriately changed depending on the combination of the boron compound or the like with other components.

[0074] The amount of the halide used is preferably 0.001 to 5.0 equivalents (molar equivalents), more preferably 0.005 to 2.0 equivalents, even more preferably 0.01 to 1.0 equivalents, and particularly preferably 0.02 to 0.8 equivalents, relative to the amount of the iron carbonyl compound used.

[0075] In the method for producing FeC nanoparticles of the present invention, first, an iron carbonyl compound is thermally decomposed to produce α-Fe NPs. Subsequently, CO generated during the decomposition of the iron carbonyl compound dissociatively adsorbs onto the surface of the α-Fe NPs, cleaving them into atomic carbon and oxygen atoms. Next, a specific boron compound acts as a reducing agent, removing oxygen species from the surface. Carburization and carbonization are promoted by the carbon species on the surface, leading to the preferential production of FeC (see Figure 3). This series of one-step reactions allows for the easy production of FeC nanoparticles. Note that α-Fe refers to iron with a body-centered cubic lattice structure.

[0076] In the diboron compound containing a heterocycle represented by general formula (I) (hereinafter also simply referred to as "diboron compound"), the heteroatoms possessed by the heterocycles Z1 and Z2 may be the same or different and represent oxygen atoms or sulfur atoms, and Z1 and Z2 are preferably oxygen atoms in order to provide the diboron compound with a superior function as a reducing agent and a superior carbonization-promoting effect. That is, the boron compound preferably includes a diboron compound containing a heterocycle represented by the following general formula (I-1): (In the formula, heterocycles Z3 and Z4 may be the same or different and represent a 4- to 8-membered ring which may have a substituent.)

[0077] In the diboron compound, the heterocycles Z1, Z2, Z3, and Z4 may have a substituent or may be unsubstituted. However, a heterocycle having a substituent is preferred because it functions better as a reducing agent in the method for producing FeC nanoparticles of the present invention and promotes carbonization. The number of substituents in the heterocycles Z1, Z2, Z3, and Z4 can be varied depending on the structure of the heterocycle (e.g., a 5-membered ring, a 6-membered ring, a 7-membered ring, etc.). The number of substituents in the diboron compound may be 1 to 10, 1 to 5, or 1 to 3. The heterocycles Z1, Z2, Z3, and Z4 may be monoheterocycles or fused heterocycles. However, a monoheterocycle is preferred because it functions better as a reducing agent in the method for producing FeC nanoparticles of the present invention and promotes carbonization. For example, when the heterocycles Z1 and Z2 of the diboron compound containing the heterocycle represented by general formula (I) (preferably the heterocycles Z3 and Z4 of the diboron compound containing the heterocycle represented by general formula (I-1)) are five-membered rings, each heterocycle has 1 to 4 substituents, and a method for producing FeC nanoparticles can be mentioned.

[0078] Examples of the substituent include a halogen atom, a cyano group (nitrile group), an alkyl group, a halo-lower alkyl group, a hydroxy-lower alkyl group, a hydroxyl group, and a halo-lower alkoxy group. Alkyl groups are preferred because they function better as reducing agents in the FeC nanoparticle production method of the present invention and promote carbonization. The "lower" in the halo-lower alkyl group, hydroxy-lower alkyl group, and halo-lower alkoxy group preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and even more preferably 1 to 3 carbon atoms. The alkyl groups used as substituents in the heterocycles Z1, Z2, Z3, and Z4 may be linear, branched, or cyclic. However, linear or branched chains are preferred, with linear being more preferred, because the diboron compound functions better as a reducing agent and promotes carbonization. The number of carbon atoms in the alkyl group is preferably 1 to 10, more preferably 1 to 8, and even more preferably 1 to 6. 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 1-ethylpropyl group, a 1,1-dimethylpropyl group, a 1,2-dimethylpropyl group, an n-hexyl group, and an n-heptyl group.

[0079] The heterocycles Z1, Z2, Z3, and Z4 in the diboron compound are 4- to 8-membered rings, preferably 5- to 7-membered rings, and more preferably 5- or 6-membered rings, from the viewpoint of superior function as a reducing agent and superior carbonization-promoting effect. For example, when the heterocycles Z1, Z2, Z3, and Z4 are 5-membered rings, they mean a heterocycle structure containing two carbon atoms, and when they are 6-membered rings, they mean a heterocycle structure containing three carbon atoms.

[0080] Examples of the boron compounds include 2,2'-bi(1,3,2-dioxaborolane), 2,2'-bi(1,3,2-dioxaborinane), bis(pinacolato)diboron (also known as 4,4,4',4',5,5,5',5'-octamethyl-2,2'-bi-1,3,2-dioxaborolane), 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane, bis(neopentylglycolate)diboron, bis(hexyleneglycolate)diboron, bis Examples of the boron compound include bis(2,4-dimethylpentane-2,4-glycolate)diboron, and from the viewpoint of being particularly excellent in promoting carbonization, it is preferable to include at least one selected from the group consisting of bis(pinacolato)diboron, 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane, bis(neopentylglycolate)diboron, bis(hexyleneglycolate)diboron, and bis(2,4-dimethylpentane-2,4-glycolate)diboron. One type of the boron compound may be used alone, or two or more types may be used in combination.

[0081] The amount (addition amount) of the boron compound (preferably a diboron compound containing a heterocycle represented by general formula (I-1)) used (added amount) is preferably 0.01 to 15 equivalents (molar equivalents) relative to the amount of the iron carbonyl compound used, more preferably 0.1 to 10 equivalents from the viewpoint of a more excellent carbonization-promoting effect, and even more preferably 0.55 to 8 equivalents from the viewpoint of ease of obtaining single-phase FeC nanoparticles, and particularly preferably 0.8 to 6.5 equivalents. Since it has been extremely difficult in conventional techniques to produce single-phase FeC nanoparticles by a one-step reaction, a method for producing FeC nanoparticles in which the amount of the boron compound (preferably a diboron compound containing a heterocycle represented by general formula (I-1)) used is 0.55 to 8 equivalents exhibits significantly superior effects.

[0082] The gas pressure during mixing under heating is not particularly limited, but can be appropriately selected and may be 0.1 MPa or more. The upper limit of the gas pressure is also not particularly limited, but may be 8 MPa or less, or may be 4 MPa or less.

[0083] In the method for producing FeC nanoparticles of the present invention, an iron carbonyl compound, a halide, a boron compound, and an alkylamine are heated and mixed in an inert gas atmosphere (hereinafter also referred to as the "heating and mixing step"). The heating and mixing process is not particularly limited and can be carried out using a known method and device (such as a mixer or stirrer).

[0084] The heating and mixing temperature in the heating and mixing step is preferably 80°C or higher and lower than 350°C, and from the viewpoint of easier production of FeC nanoparticles, is more preferably 100°C or higher and 320°C or lower, even more preferably 120°C or higher and 290°C or lower, and particularly preferably 150°C or higher and 270°C or lower. The heating and mixing temperature can be appropriately selected from the suitable temperature range, and may be, for example, 170°C or higher and 260°C or lower. One embodiment is a method for producing FeC nanoparticles, in which the heating and mixing temperature is 210°C or higher and 240°C or lower.

[0085] In the method for producing FeC nanoparticles of the present invention, the above-mentioned components are heated and mixed under an inert gas atmosphere. Heating and mixing under vacuum conditions prevents the CO generated by the thermal decomposition of the iron carbonyl compound from being used as a carbon source, making it impossible to produce the desired FeC. By performing the heating and mixing process under an inert gas atmosphere (i.e., in the absence of oxygen), the generation of iron oxide is suppressed, enabling the efficient production of the FeC nanoparticles of the present invention. The heating and mixing process is preferably performed under stirring, as this promotes the reaction and facilitates the production of the FeC nanoparticles of the present invention. Examples of inert gases include argon gas and nitrogen gas. Furthermore, in the method for producing FeC nanoparticles of the present invention, CO generated by the thermal decomposition of the iron carbonyl compound serves as a carbon source for the production of FeC, eliminating the need for additional carbon source gases such as CO gas and CO gas, which is industrially advantageous.

[0086] The reaction time (heating time) in the heating and mixing step is not particularly limited and can be appropriately changed depending on the desired degree of carbonization of the FeC nanoparticles. The reaction time is, for example, preferably 2.5 to 50 hours, more preferably 3 to 40 hours, and even more preferably 4 to 30 hours.

[0087] The rate of temperature increase when heating to the desired heating temperature after mixing the iron carbonyl compound is not particularly limited and can be appropriately changed depending on the desired degree of carbonization of the FeC nanoparticles. 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 0.1 to 150°C / min, more preferably 1 to 100°C / min, and even more preferably 5 to 90°C / min.

[0088] The method for producing FeC nanoparticles 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 composite production method. 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 be performed by centrifuging the product obtained after the heating and mixing step using the organic solvent.

[0089] After the washing step, if necessary, the resulting particles may be vacuum-dried to obtain powdered iron carbide nanoparticles. The FeC nanoparticles obtained by the method for producing FeC nanoparticles of the present invention are as described above. In one embodiment, the FeC nanoparticles have an average particle size of 10 nm to 800 nm.

[0090] Another embodiment of the present invention relates to a reduction catalyst comprising any one of the FeC nanoparticles described above. Reduction reactions using the reduction catalyst include, for example, hydrogenation reactions.

[0091] In some embodiments, the reduction catalyst of the present invention may contain only FeC nanoparticles because of their superior catalytic activity. The FeC nanoparticles may be used as they are as the reduction catalyst. In other embodiments, the reduction catalyst of the present invention may contain FeC nanoparticles and a support, and the FeC nanoparticles and the support may form a composite.

[0092] The following describes an example in which the reduction catalyst of the present invention is used as a hydrogenation catalyst. Unless otherwise specified, the term "reduction catalyst" can be read as "hydrogenation catalyst" in this specification. One embodiment includes a hydrogenation catalyst containing any of the iron carbide nanoparticles described above. Another embodiment includes a hydrogenation catalyst containing any of the iron carbide nanoparticles described above and a support, wherein the iron carbide nanoparticles and the support form a composite. Note that the reduction catalyst is not limited to a hydrogenation catalyst.

[0093] One embodiment includes a method for producing a hydrogenated organic compound, in which an organic compound is hydrogenated using the reduction catalyst (FeC nanoparticles or a composite containing FeC nanoparticles) to obtain a hydrogenated organic compound. In the embodiment, the organic compound is a nitrile compound, and the hydrogenated organic compound is a primary amine compound. The method for producing a hydrogenated organic compound preferably includes hydrogenating the nitrile compound in a hydrogen atmosphere and in the presence of ammonia in the presence of the reduction catalyst. In terms of excellent catalytic activity, the support in the composite is preferably a support containing at least one selected from the group consisting of ZrO, SiO, and TiO, and more preferably a support containing ZrO.

[0094] Examples of the organic compound include a nitrile compound, an aldehyde compound, and an unsaturated compound.

[0095] Examples of hydrogenated organic compounds produced by hydrogenation include primary amine compounds, alcohol compounds, saturated compounds, and the like.

[0096] 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.

[0097] A method for producing a primary amine compound will be described below, taking the case where the organic compound is a nitrile compound as an example, in which the nitrile compound is hydrogenated using the hydrogenation catalyst (FeC nanoparticles or a composite thereof) to obtain a primary amine compound. Note that, since the method for producing a primary amine compound is merely an example and is not limited thereto, the term "method for producing a primary amine compound" can be read as "method for producing a hydrogenated organic compound."

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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, fluoroacetonitrile, difluoroacetonitrile, trifluoroacetonitrile, 2-fluoropropionitrile, 3 ...methylpropionitrile, 3-methylpropionitrile, 3-methylpropionitrile linear or branched aliphatic nitriles such as propionitrile, 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.

[0102] 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.

[0103] 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.

[0104] 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;

[0105] 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.

[0106] 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.

[0107] 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.

[0108] The method for producing a primary amine compound is preferably carried out under heating. The reaction temperature (temperature of the hydrogenation treatment) 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 250° C. or lower, or may be 200° C. or lower.

[0109] 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.

[0110] In the method for producing a primary amine compound, the hydrogen pressure is preferably 8 MPa or less, and when the method is 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.

[0111] The pressure during the reaction is not particularly limited, but is preferably, for example, H:NH = 0.5 MPa: 0.01 MPa to 7 MPa: 0.9 MPa, more preferably 0.8 MPa: 0.02 MPa to 6 MPa: 0.8 MPa, and even more preferably 0.8 MPa: 0.03 MPa to 5 MPa: 0.7 MPa. Within the above range, the hydrogenation reaction proceeds sufficiently.

[0112] In one embodiment, a method for producing a hydrogenated organic compound includes hydrogenating a nitrile compound in a hydrogen atmosphere in the presence of ammonia at a hydrogen pressure of 8 MPa or less.

[0113] 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 and type of solvent can be selected depending on the type of substrate, etc. One embodiment is a method for producing a primary amine compound, in which the hydrogenation treatment is carried out in the presence of a solvent.

[0114] 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.

[0115] In the method for producing a primary amine compound, the hydrogenation reaction may be carried out in the presence of a base.

[0116] 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.

[0117] (a) Examples of tertiary amines include trimethylamine, triethylamine, 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, N-methylpyrrolidine, N -methylpiperidine, N-methylmorpholine, N-ethylmorpholine, N,N'-dimethylpiperazine, N-methylpyrrolidone, N-vinylpyrrolidone, bis(2-dimethylamino-ethyl)ether, N,N,N,N',N''-pentamethyl-diethylenetriamine, triethanolamine, tripropanolamine, dimethylethanolamine, dimethylaminoethoxyethanol, N,N-dimethylaminopropylamine, N,N,N',N',N''-pentamethyldipropylenetriamine, tris(3-dimethylaminopropyl)amine, tetramethylimino-bis(propylamine), N-diethyl-ethanolamine, and the like.

[0118] (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'-bipyridyl, 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.

[0119] (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.

[0120] (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.

[0121] (e) Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0122] 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.

[0123] The present invention includes embodiments in which some or all of the above configurations are combined in various ways within the scope of the technical idea of ​​the present invention, as long as the effects of the present invention are achieved.

[0124] Next, the present invention will be explained in more detail with reference to examples. However, the present invention is not limited to these examples, and many modifications within the scope of the technical concept of the present invention are possible by those skilled in the art. The following products manufactured by Sigma-Aldrich Japan Co., Ltd. were used: Fe(CO) 12 Borane-trimethylamine complex The following was used from Tokyo Chemical Industry Co., Ltd.: Bis(pinacolato)diboron (B2pin2) 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane, bis(neopentylglycolato)diboron, hexadecylamine, cetyltrimethylammonium chloride (CTAC) Tetrahydroxydiboron, benzonitrile The following was used from Tokyo Chemical Industry Co., Ltd.: Trihexyl borate The following was used from Fujifilm Wako Pure Chemical Industries, Ltd.: Cetyltrimethylammonium bromide (CTAB) Chloroform, hexane, 2-propanol

[0125] [Example 1: FeC nanoparticles] <Example 1-1> FeC nanoparticles were produced by the following method. Hexadecylamine (20 mmol) and cetyltrimethylammonium bromide (CTAB) (0.06 mmol) were added to a Schlenk flask and stirred at 120°C under vacuum for 1 hour. Then, the mixture was cooled to room temperature and stirred under an argon gas atmosphere with Fe(CO) 12 (0.33 mmol) and bis(pinacolato)diboron (Bpin) (2.0 mmol) were added (Fe(CO) 12 0.18 equivalents of CTAB and Fe(CO) 12 The mixture was mixed at room temperature with 6.0 equivalents of B2pin2 in hexadecylamine to prepare a mixed solution. The mixture was then heated to 220°C at a rate of 5°C / min and stirred at 220°C for 18 hours to synthesize Fe2C. The amount of hexadecylamine was 100% by weight of Fe3(CO) 12 The amount was 60 equivalents.

[0126] The solution after the reaction was cooled to room temperature, and the product was washed with hexane and chloroform and dried in a vacuum to isolate FeC nanoparticles as a black powder. The obtained FeC nanoparticles were evaluated by the following method.

[0127] <Powder X-ray diffraction measurement of FeC nanoparticles> The FeC nanoparticles obtained in Example 1-1 were subjected to X-ray diffraction measurement under atmospheric conditions using a fully automatic multipurpose X-ray diffractometer (trade name "Philips X'PERT MPD diffractometer", manufactured by Philips Japan Co., Ltd.) using CuKα1 radiation (λ: 1.5405 Å) with approximately 10 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: 20.00 to 70.00° Sampling interval: 0.013° Scan rate: 2θ = 3.0° / min

[0128] As shown in FIG. 2, in powder X-ray diffraction measurements using CuKα radiation in the presence of oxygen for the FeC nanoparticles obtained in Example 1-1, the peak corresponding to the (101) plane of FeC (diffraction angle (2θ): 43.2°) was observed as the maximum intensity. Characteristic peaks corresponding to the (100), (002), (102), and (110) planes of FeC (diffraction angles (2θ): 37.5°, 41.5°, 57.2°, and 67.9°) were also observed. Furthermore, the XRD pattern of the FeC nanoparticles obtained in Example 1-1 confirmed that hexagonal FeC crystals were obtained. Furthermore, peaks derived from iron oxides such as FeO, iron carbides of other compositions such as FeC, and graphite were not observed. VESTA (Visualization for Electronic and Structural Analysis) was used as the software for analyzing the crystal structure. The full width at half maximum (FWHM) of the peak indexed to the (101) plane was calculated by fitting analysis, and the crystallite diameter was calculated to be 9.5 nm by applying the obtained FWHM value to the Scherrer equation below: D = K λ / B cos θ (1) (D represents the crystallite size (nm), K represents the Scherrer constant of 0.64, λ represents the wavelength of the X-ray (nm), B represents the broadening of the diffraction line width (rad), and θ represents the Bragg angle (rad).) Furthermore, in Example 1-1, the reaction was stopped at predetermined intervals for each time shown in Figure 4(a), and powder X-ray diffraction measurements were performed under an argon gas atmosphere. The results are shown in Figure 4(a).

[0129] <Electron Microscope Observation of FeC Nanoparticles> The FeC nanoparticles obtained in the examples were observed using a scanning electron microscope (product name "S-5000(H)", acceleration voltage: 20 kV, manufactured by Hitachi High-Technologies Corporation). The results are shown in Figure 1. As shown in Figure 1, nano-sized FeC nanoparticles having a particle size close to the calculated crystallite size were confirmed.

[0130] Example 1-2 FeC nanoparticles were produced in the same manner as in Example 1-1, except that cetyltrimethylammonium bromide (CTAB) was replaced with cetyltrimethylammonium chloride (CTAC). Powder X-ray diffraction measurements were performed on the obtained FeC nanoparticles in the same manner as in Example 1-1. The results are shown in FIG.

[0131] Example 1-3 FeC nanoparticles were produced in the same manner as in Example 1-1, except that cetyltrimethylammonium bromide (CTAB) was replaced with ammonium chloride. Powder X-ray diffraction measurements were performed on the obtained FeC nanoparticles in the same manner as in Example 1-1. The results are shown in FIG.

[0132] From FIG. 5, it was confirmed that FeC nanoparticles can be easily produced even when the halide is changed.

[0133] Comparative Example 1-1 A reaction was carried out in the same manner as in Example 1-1, except that cetyltrimethylammonium bromide (CTAB) was not added, and α-Fe with low crystallinity was obtained. The obtained particles were subjected to powder X-ray diffraction measurement in the same manner as in Example 1-1. The results are shown in Figure 5. In Figure 5, "W / O halide" represents the results of Comparative Example 1-1.

[0134] Example 1-4 FeC nanoparticles were produced in the same manner as in Example 1-1, except that the amount of bis(pinacolato)diboron (B2pin2) used was changed from 2.0 mmol to 0.5 mmol. Powder X-ray diffraction measurements were performed on the obtained FeC nanoparticles in the same manner as in Example 1-1. The results are shown in Figure 6. As in Example 1-1, a peak of FeC was confirmed in Figure 6.

[0135] Example 1-5 Particles were produced in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was changed to 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane. Powder X-ray diffraction measurements were carried out on the obtained particles in the same manner as in Example 1-1. The results are shown in Figure 8. The top result in Figure 8 represents Example 1-5.

[0136] Example 1-6 Particles were produced in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was changed to bis(neopentylglycolate)diboron. Powder X-ray diffraction measurements were performed on the obtained particles in the same manner as in Example 1-1. The results are shown in Figure 8. The second result from the top in Figure 8 represents Example 1-6.

[0137] Comparative Example 1-2 Particles were obtained by carrying out a reaction in the same manner as in Example 1-1, except that the amount of bis(pinacolato)diboron (B2pin2) used was changed from 2.0 mmol to 2.2 mmol. Powder X-ray diffraction measurement was carried out on the obtained particles in the same manner as in Example 1-1. The results are shown in FIG.

[0138] Comparative Example 1-3: Particles were obtained by the same reaction method as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was not added, and the reaction mixture was heated at 220°C for 1 hour, then evacuated to a vacuum. B2pin2 was added in the same amount as in Example 1-1. Powder X-ray diffraction analysis was performed on the resulting particles in the same manner as in Example 1-1. No peaks due to Fe2C were observed, but peaks due to Fe3O4 and Fe5C2 were observed. Furthermore, the results of powder X-ray diffraction analysis performed in the same manner as in Example 1-1 are shown in Figure 7. The results shown in Figure 7 suggest that CO generated by the thermal decomposition of the iron carbonyl compound served as a carbon source for the production of Fe2C.

[0139] Comparative Example 1-4 Particles were produced in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was changed to tetrahydroxydiboron. Powder X-ray diffraction measurements were performed on the obtained particles in the same manner as in Example 1-1. The results are shown in Figure 8. The third result from the top in Figure 8 represents Comparative Example 1-4.

[0140] Comparative Example 1-5 Particles were produced in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was changed to tetrahydroxydiboron. Powder X-ray diffraction measurements were performed on the obtained particles in the same manner as in Example 1-1. The results are shown in Figure 8. The fourth result from the top in Figure 8 represents Comparative Example 1-5.

[0141] Comparative Example 1-6 Particles were produced in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was changed to monoborane. Powder X-ray diffraction measurements were performed on the obtained particles in the same manner as in Example 1-1. The results are shown in Figure 8. The fifth result from the top in Figure 8 represents Comparative Example 1-6.

[0142] As shown in FIG. 8, when boron compounds other than the specific diboron compound were used, FeC nanoparticles could not be produced.

[0143] Comparative Example 1-7 Particles were obtained by carrying out a reaction in the same manner as in Example 1-1, except that bis(pinacolato)diboron (B2pin2) was not added. The reaction was stopped at the specified time intervals shown in FIG. 4(b), and powder X-ray diffraction measurements were performed on the obtained particles in the same manner as in Example 1-1. The results are shown in FIG. 4(b). No peaks due to Fe2C were observed, but peaks due to FeO, Fe3O4, and Fe5C2 were observed.

[0144] [Example 2: Composite] <Example 2-1: Composite of FeC nanoparticles and ZrO> A composite was produced using the FeC nanoparticles produced in Example 1-1 and ZrO as a carrier. Specifically, 40 mg of the powder of the FeC nanoparticles produced in Example 1-1 was dissolved in 2-propanol to obtain a solution. The obtained solution was subjected to ultrasonic treatment at room temperature for 1 hour and further stirred. Next, white powder ZrO (trade name "RC-100", BET specific surface area: 25 to 35 m) was added to the solution. 2 1 g of ZrO2 nanoparticles (Fe2C / g, manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was added and stirred at 25°C for 6 hours, followed by filtration and vacuum drying to obtain a composite of Fe2C nanoparticles and ZrO2.

[0145] Example 2-2: Composite of FeC nanoparticles and SiO Spherical particles of SiO (product name "CARiACT (registered trademark) Q-6", BET specific surface area: 400 m 2 A composite of FeC nanoparticles and SiO was obtained in the same manner as in Example 2-1, except that ZrO was replaced with FeC nanoparticles (FeC / g, manufactured by Fuji Silysia Chemical Ltd.).

[0146] Example 2-3: Composite of FeC nanoparticles and TiO Hydrophilic filler TiO (trade name "AEROXIDE (registered trademark) TiO P25", BET specific surface area: 30 to 65 m 2 A composite of FeC nanoparticles and TiO was obtained in the same manner as in Example 2-1, except that SiO2 (SiO2 / g, manufactured by Nippon Aerosil Co., Ltd.) was used instead of ZrO2. The BET specific surface areas of ZrO2, SiO2, and TiO2 can be measured using known methods and measuring devices (for example, a specific surface area / pore distribution measuring device with the trade name "BELSORP MR1", BET single-point method, manufactured by Microtrac-Bell Co., Ltd.).

[0147] Example 3: Production of benzylamine Example 3-1 Benzonitrile was hydrogenated using the FeC nanoparticles of Example 1-1 as a catalyst to produce benzylamine. Specifically, 2.2 mg of the FeC nanoparticles of Example 1-1 (7.6 mol% Fe relative to 100 mol% benzonitrile), 3 ml of 2-propanol, 0.5 mmol of benzonitrile, hydrogen gas, and NH gas were placed in an autoclave and pressurized to a H:NH ratio of 3.8 MPa:0.2 MPa, heated to 180°C, and reacted for 2 hours. The results are shown in Table 1 below.

[0148] Examples 3-2 to 3-4 Benzylamine was produced in the same manner as in Example 3-1, except that the type of catalyst used was changed to that produced in Examples 2-1 to 2-3. The composite of Example 3-2 used the composite obtained in Example 2-1, the composite of Example 3-3 used the composite obtained in Example 2-2, and the composite of Example 3-4 used the composite obtained in Example 2-3. The results are shown in Table 1 below.

[0149]

[0150] As shown in Table 1, it was confirmed that the FeC nanoparticles and composite thereof produced in Example 1-1 have catalytic activity as a hydrogenation catalyst. Furthermore, as shown in Table 1, it was confirmed that the FeC nanoparticles and composite thereof of the present invention have remarkably excellent catalytic activity even under mild conditions of 200°C or less.

[0151] From the above results, it was confirmed that the reduction catalyst (for example, hydrogenation catalyst) of the present invention has catalytic activity.

[0152] The FeC nanoparticles and composites of the present invention are useful as reduction catalysts in reduction reactions (e.g., hydrogenation reactions), particularly as hydrogenation catalysts in methods for producing amine compounds.

Claims

1. An iron carbonyl compound, a halide, a boron compound, and an alkylamine are heated and mixed in an inert gas atmosphere, and the iron carbonyl compound is converted into Fe3(CO) 12 or Fe2(CO)9, wherein the boron compound comprises a diboron compound containing a heterocycle represented by the following general formula (I): (In the formula, X1, X2, X3, and X4 are the same or different and represent an oxygen atom or a sulfur atom, and heterocycles Z1 and Z2 are the same or different and represent a 4- to 8-membered ring which may have a substituent.) A method for producing Fe2C nanoparticles without using 1-octadecene.

2. The method for producing Fe2C nanoparticles according to claim 1, wherein the boron compound comprises a diboron compound containing a heterocycle represented by the following general formula (I-1): (In the formula, heterocycles Z3 and Z4 may be the same or different and represent a 4- to 8-membered ring which may have a substituent.) 3. The method for producing Fe2C nanoparticles according to claim 1 or 2, wherein the boron compound comprises at least one selected from the group consisting of bis(pinacolato)diboron, 4,4,4',4',5,5,5',5'-octaethyl-2,2'-bi-1,3,2-dioxaborolane, bis(neopentylglycolato)diboron, bis(hexyleneglycolato)diboron, and bis(2,4-dimethylpentane-2,4-glycolato)diboron.

4. The method for producing Fe2C nanoparticles according to claim 1 or 2, wherein the temperature during the heating and mixing is 80°C or higher and lower than 350°C.

5. The method for producing Fe2C nanoparticles according to claim 1 or 2, wherein the heating and mixing time is 2.5 to 50 hours.

6. The method for producing Fe2C nanoparticles according to claim 1 or 2, wherein the amount of the boron compound used is 0.55 to 8 equivalents relative to the amount of the iron carbonyl compound used.

7. A reduction catalyst comprising iron carbide nanoparticles, wherein the iron carbide nanoparticles comprise Fe2C nanoparticles, and the Fe2C nanoparticles have an average particle size of 10 nm or more and 800 nm or less.

8. The reduction catalyst of claim 7, further comprising a support.

9. The reduction catalyst according to claim 8, wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

10. A composite comprising iron carbide nanoparticles and a carrier, wherein the iron carbide nanoparticles contain Fe2C nanoparticles, and the average particle size of the Fe2C nanoparticles is 10 nm or more and 800 nm or less.

11. The composite according to claim 10, wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

12. A method for producing a hydrogenated organic compound, comprising hydrogenating an organic compound using the reduction catalyst according to any one of claims 7 to 9 to obtain a hydrogenated organic compound.

13. The method for producing a hydrogenated organic compound according to claim 12, 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.

14. The method for producing a hydrogenated organic compound according to claim 12, wherein the temperature of the hydrogenation treatment is 250°C or less.

15. The method for producing a hydrogenated organic compound according to claim 12, wherein the hydrogenation is carried out in the presence of a solvent.

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