Catalyst for hydrogenation of cyclic aldehyde and method for producing alcohol compound by hydrogenation of cyclic aldehyde using same

Abstract

The present invention provides: a hydrogenation catalyst which can be used in a hydrogenation reaction of a cyclic aldehyde; and a method for producing an alcohol compound by hydrogenation of a cyclic aldehyde using the hydrogenation catalyst. The present invention pertains to a catalyst for hydrogenation of a cyclic aldehyde, the catalyst containing iron phosphide nanoparticles. It is preferable that the iron phosphide nanoparticles are rod-shaped particles and the maximum length of the rod-shaped particles in the major axis direction is less than 100 nm. It is preferable that the catalyst for hydrogenation of a cyclic aldehyde is a catalyst for hydrogenation of a furfural derivative.

Description

Catalyst for hydrogenation of cyclic aldehydes and method for producing alcohol compounds by hydrogenation of cyclic aldehydes using the same

[0001] The present invention relates to a catalyst for the hydrogenation of furfural derivatives and a method for producing alcohol compounds (preferably furfuryl alcohol compounds) by hydrogenation of cyclic aldehydes (preferably furfural derivatives) using the same.

[0002] As a type of aldehyde compound, furfural derivatives are extremely useful as platform compounds that can be obtained from biomass resources (Non-Patent Literature 1). The selective hydrogenation reaction of furfural derivatives is an important reaction for synthesizing substances that serve as raw materials for fuels and pharmaceuticals. To date, hydrogenation reactions of furfural derivatives using precious metal catalysts have been reported. These catalysts promote mild conditional reactions. However, stricter regulations on the use of precious metals and their high cost are challenges. Therefore, there is a need to develop highly active catalysts made from non-precious metals.

[0003] The present inventors' group previously developed cobalt phosphide nanocrystals (hereinafter also referred to as "Co2P NC") by alloying cobalt with phosphorus, and found high catalytic activity for the hydrogenation reaction of furfural derivatives by immobilizing Co2P NC on aluminum oxide (Al2O3) (Non-Patent Literature 2).

[0004] However, cobalt, the raw material used, is scarce, and there are special circumstances that prevent its mining from being easily expanded. One reason for this is that cobalt is a metal that is extracted in small amounts incidentally when copper or nickel is being mined. Therefore, mines are not developed solely for the purpose of obtaining cobalt.

[0005] “Catalytic Reduction of Biomass-Derived Furanic Compounds with Hydrogen”, Yoshinao Nakagawa Masazumi Tamura et al., ACS Catal. 2013, Vol.3, Issue 12, pp. 2655-2668 “Air-Stable and Reusable Cobalt Phosphide Nanoalloy Catalyst for Selective Hydrogenation of Furfural Derivatives”, Hiroya Ishikawa, Tomoo Mizugaki, Takato Mitsudome et al., ACS Catal. 2021, Vol.11, Issue 2, pp. 750-757

[0006] Iron is a metal that can solve the above problems. Iron is an extremely attractive catalytic material because it is inexpensive, abundant in the Earth's crust, and has low toxicity to living organisms and the environment. However, iron-based catalysts have problems such as the difficulty in controlling the reaction system to which they are applied, and no iron-based catalyst that can be used in the hydrogenation reaction of furfural derivatives has been developed. Therefore, there is a need to develop an iron-based catalyst that can efficiently promote the hydrogenation reaction of furfural derivatives.

[0007] The present invention aims to provide a hydrogenation catalyst that can be used in the hydrogenation reaction of cyclic aldehydes, and a method for producing alcohol compounds by hydrogenation of cyclic aldehydes using the same.

[0008] The inventors of this invention conducted extensive research to solve the above problems and found that the above problems could be solved by using nano-iron phosphide particles synthesized by the solvothermal method. Based on this finding, they furthered their research and completed the present invention.

[0009] The present invention encompasses the following inventions: [1] A catalyst for the hydrogenation of a cyclic aldehyde comprising nanoiron phosphide particles. [2] The catalyst for the hydrogenation of a cyclic aldehyde according to [1], wherein the nanoiron phosphide particles are rod-shaped particles, and the maximum length in the longitudinal direction of the rod-shaped particles is less than 100 nm. [3] The catalyst for the hydrogenation of a cyclic aldehyde according to [1] or [2], wherein the cyclic aldehyde is a furfural derivative. [4] The catalyst for the hydrogenation of a cyclic aldehyde according to any one of [1] to [3], further comprising a support, comprising a composite composed of the nanoiron phosphide particles and the support, wherein the support is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials. [5] The catalyst for the hydrogenation of a cyclic aldehyde according to [4], wherein the support comprises Al2O3. [6] The catalyst for the hydrogenation of a cyclic aldehyde according to any one of [1] to [5], wherein the nanoiron phosphide particles are Fe2P. [7] A method for producing an alcohol compound, comprising hydrogenating a cyclic aldehyde in a hydrogen atmosphere in the presence of a catalyst for hydrogenation of cyclic aldehydes described in any of [1] to [6] to obtain an alcohol compound. [8] The method for producing an alcohol compound according to [7], wherein the cyclic aldehyde is heated during the reaction. [9] The method for producing an alcohol compound according to [8], wherein the heating temperature is less than 200°C.

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

[11] The method for producing an alcohol compound according to any of [7] to

[10] , wherein the cyclic aldehyde is a furfural derivative and the alcohol compound is a furfuryl alcohol compound.

[0010] The present invention provides a hydrogenation catalyst that can be used in the hydrogenation reaction of cyclic aldehydes (preferably furfural derivatives) and a method for producing alcohol compounds (preferably furfuryl alcohol compounds) by hydrogenation of cyclic aldehydes (preferably furfural derivatives) using the same. Furthermore, the hydrogenation catalyst for cyclic aldehydes of the present invention is particularly suitable for use as a hydrogenation catalyst for furfural derivatives in the hydrogenation reaction of furfural derivatives. The hydrogenation catalyst for cyclic aldehydes of the present invention selectively reduces the formyl group of the cyclic aldehyde, and when the cyclic aldehyde has an unsaturated bond (e.g., a carbon-carbon double bond), it can produce the corresponding unsaturated alcohol compound without reducing the unsaturated bond.

[0011] Furthermore, nano-ferric phosphate particles obtained by the manufacturing method of the present invention (hereinafter referred to as "nano-Fe") x When used as a catalyst for the hydrogenation of cyclic aldehydes (preferably furfural derivatives), the hydrogenation reaction of cyclic aldehydes (preferably furfural derivatives) can be carried out under mild conditions to produce alcohol compounds (preferably furfuryl alcohol compounds).

[0012] Furthermore, the nano-ferrous phosphate particles of the present invention, the composite containing the nano-ferrous phosphate particles and a carrier, and the catalyst for hydrogenating cyclic aldehydes (preferably furfural derivatives) use iron, which is also present in living organisms, as a metal source, making them low in toxicity and highly safe. Moreover, since the nano-ferrous phosphate particles of the present invention contain only iron as a metallic element and no precious metals, they are industrially advantageous in terms of cost due to the large amount of iron present on Earth (reserves).

[0013] Furthermore, the hydrogenation catalyst for cyclic aldehydes (preferably furfural derivatives) of the present invention is a solid catalyst and is easily recovered after use. Moreover, the hydrogenation catalyst for cyclic aldehydes (preferably furfural derivatives) of the present invention can selectively hydrogenate many types of cyclic aldehyde compounds to produce alcohol compounds (preferably furfuryl alcohol compounds) and exhibits excellent substrate selectivity.

[0014] Figure 1 shows a transmission electron microscope (TEM) image of the nanoiron phosphide particles obtained in Example 1-1. Figure 2 shows the measurement results of powder X-ray diffraction of the nanoiron phosphide particles obtained in Example 1-1, indicating the peak position of the crystal plane corresponding to Fe2P.

[0015] The following describes various embodiments of the present invention. However, the present invention is not limited to the following embodiments. In this specification, the nano-ferric phosphide particles of the present invention are collectively referred to as "nano-Fe x It is also written as "P" (where x represents 1 or 2). In this specification, "cyclic aldehyde" means an aldehyde compound having an alicyclic group, an aromatic ring group, and / or a heterocyclic group. In this specification, "furfural derivative" means compounds of furfural and its derivatives. In this specification, the upper and lower limits of numerical ranges (such as the size of nano-ferrous phosphide particles, the amount of a certain component (material such as a compound) used, temperature, pressure, or values ​​and physical properties calculated from each numerical range) can be combined as appropriate.

[0016] In this specification, "atmospheric conditions" means an atmospheric oxygen concentration of approximately 21%. Furthermore, the nano-ferric phosphide particles of the present invention exhibit excellent stability under conditions where oxygen is present. The oxygen concentration under conditions where oxygen (O2) is present is not particularly limited and may be approximately 21% of the atmospheric oxygen concentration, or it may be approximately 22% to 100%. The nano-ferric phosphide particles of the present invention exhibit excellent atmospheric stability and can maintain a low-valence state under conditions where oxygen is present, regardless of the oxygen concentration.

[0017] One embodiment of the present invention relates to a hydrogenation catalyst for cyclic aldehydes (preferably furfural derivatives) containing nano-iron phosphide particles. One embodiment of the present invention involves the use of a hydrogenation catalyst for producing alcohol compounds from cyclic aldehydes (preferably furfural derivatives).

[0018] As the catalyst for hydrogenating the cyclic aldehyde of the present invention, it is preferably a catalyst for hydrogenating an aldehyde compound having an alicyclic group, an aromatic ring group, and / or a heterocyclic group, more preferably a catalyst for hydrogenating an aldehyde compound having a heterocyclic group, and even more preferably a catalyst for hydrogenating a furfural derivative.

[0019] As the alicyclic group in the aldehyde compound having an alicyclic group, an alicyclic group having 3 to 40 carbon atoms is preferable, an alicyclic group having 3 to 30 carbon atoms is more preferable, and an alicyclic group having 3 to 20 carbon atoms is even more preferable. Examples of the alicyclic group include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a methylcyclopropyl group, a norbornyl group, an adamantyl group, and the like. The aldehyde compound having an alicyclic group is not particularly limited as long as it is a compound having an alicyclic group and an aldehyde group, and examples thereof include cyclopropanecarboxaldehyde, cyclobutanecarboxaldehyde, cyclopentanecarboxaldehyde, cyclohexanecarboxaldehyde, and the like.

[0020] Examples of the aromatic ring in the aldehyde compound having an aromatic ring group include a benzene ring, a naphthalene ring, a fluorene ring, a phenanthrene ring, an anthracene ring, a triphenylene ring, a pyrene ring, a chrysene ring, a tetracene ring, a benzopyrene ring, a perylene ring, a coronene ring, a corannulene ring, a phenalene ring, a triangulene ring, and the like. The aromatic hydrocarbon ring is preferably a benzene ring or a naphthalene ring, and more preferably a benzene ring. The aldehyde compound having an aromatic ring group is not particularly limited as long as it is a compound having an aromatic ring group and an aldehyde group. The number of carbon atoms in the aromatic ring is not particularly limited, but is preferably, for example, 6 to 40.

[0021] Examples of heterocyclic groups in aldehyde compounds include three-membered rings containing one heteroatom, three-membered rings containing two heteroatoms, four-membered rings containing one heteroatom, four-membered rings containing two heteroatoms, five-membered rings containing one heteroatom, five-membered rings containing two heteroatoms, five-membered rings containing three or more heteroatoms, six-membered rings containing one heteroatom, six-membered rings containing two heteroatoms, six-membered rings containing three heteroatoms, six-membered rings containing four heteroatoms, six-membered rings containing five heteroatoms, seven-membered rings containing one heteroatom, and seven-membered rings containing two heteroatoms. Aldehyde compounds containing heterocyclic groups are not particularly limited as long as they contain both a heterocyclic group and an aldehyde group.

[0022] Examples of three-membered rings containing one heteroatom include saturated heterothree-membered rings such as oxirane, phosphylane, and thiirane; and unsaturated heterothree-membered rings such as oxilen, phosphylene, and thiirene. Examples of three-membered rings containing two heteroatoms include saturated heterothree-membered rings such as diazyridine, oxazyridine, and dioxirane; and unsaturated heterothree-membered rings such as diazirine. Examples of four-membered rings containing one heteroatom include saturated heterofour-membered rings such as azetidine, oxetane, and thiethane; and unsaturated heterofour-membered rings such as azeto, oxet, and thiette. Examples of four-membered rings containing two heteroatoms include saturated heterofour-membered rings such as diazetidine, dioxetane, and dithiethane; and unsaturated heterofour-membered rings such as diazeto, dioxet, and dioxet. Examples of the five-membered ring containing one heteroatom include saturated heterofive-membered rings such as pyrrolidine, tetrahydrofuran, and tetrahydrothiophene; and unsaturated heterofive-membered rings such as pyrrole, furan, thiophenepyrrole, furan, and thiophene. Examples of the five-membered ring containing two heteroatoms include saturated heterofive-membered rings such as imidazolidine, pyrazolidine, xazolidine, isoxazolidine, thiazolidin, isothiazolidine, dioxolane, and dithiolane; and unsaturated heterofive-membered rings such as imidazole, pyrazole, oxazole, isoxazole, thiazole, and isothiazole. Examples of the five-membered ring containing three or more heteroatoms include unsaturated heterofive-membered rings such as triazole, furazan, oxadiazole, thiadiazole, dioxazole, dithiazole, tetrazole, oxatetrazole, thiatetrazole, and pentazole. Examples of six-membered rings containing one heteroatom include saturated heterosix-membered rings such as piperidine and tetrahydropyran; and unsaturated heterosix-membered rings such as pyridine and pyran. Examples of six-membered rings containing two heteroatoms include saturated heterosix-membered rings such as piperazine, morpholine, thiomorpholine, dioxane, and dithiane; and unsaturated heterosix-membered rings such as diazine, oxazine, thiazine, dioxin, and dithiyne.Examples of the six-membered ring containing the three heteroatoms include saturated hetero six-membered rings such as hexahydro-1,3,5-triazine, trioxane, and trithiane; and unsaturated hetero six-membered rings such as triazine. Examples of the six-membered ring containing the four heteroatoms include unsaturated hetero six-membered rings such as tetrazine. Examples of the six-membered ring containing the five heteroatoms include unsaturated hetero six-membered rings such as pentazine. Examples of the seven-membered ring containing the one heteroatom include unsaturated hetero seven-membered rings such as azepane, oxepane, and thiepane; and unsaturated hetero seven-membered rings such as azepine, oxepine, and thiepine. Examples of the seven-membered ring containing the two heteroatoms include unsaturated hetero seven-membered rings such as diazepane; and unsaturated hetero seven-membered rings such as diazepine and thiazepine.

[0023] Examples of the heterocyclic ring include oxygen-containing heterocyclic rings, nitrogen-containing heterocyclic rings, sulfur-containing heterocyclic rings, etc. Examples of the heterocyclic ring also include, for example, a heterocyclic ring having only an oxygen atom as a heteroatom, a heterocyclic ring having only a nitrogen atom as a heteroatom, a heterocyclic ring having only a sulfur atom as a heteroatom, a heterocyclic ring having an oxygen atom and a nitrogen atom as heteroatoms, a heterocyclic ring having an oxygen atom and a sulfur atom as heteroatoms, and a heterocyclic ring having a sulfur atom and a nitrogen atom as heteroatoms. The heterocyclic ring is preferably a three-membered ring to a seven-membered ring. The heterocyclic ring may be a monocyclic ring, a condensed ring, or a spiro ring. Examples of the condensed ring include condensed rings between the above aromatic ring and heteroatoms, and specific examples include indole ring, indazole ring, benzimidazole ring, quinoline ring, isoquinoline ring, cinnoline ring, quinoxaline ring, phthalazine ring, naphthyridine ring, purine ring, acridine ring, phenazine ring, phenanthroline ring, benzofuran ring, benzoxazole ring, phenoxazine ring, benzothiazole ring, phenothiazine ring, etc. One embodiment is a catalyst for hydrogenation of a cyclic aldehyde containing nanolinated iron particles, wherein the cyclic aldehyde is a cyclic aldehyde having an oxygen-containing heterocyclic group. Another embodiment is a catalyst for hydrogenation of a cyclic aldehyde containing nanolinated iron particles, wherein the cyclic aldehyde is a furfural derivative.

[0024] The following describes the use of nano-ferric phosphide particles as a hydrogenation catalyst for furfural derivatives, using the case where the cyclic aldehyde is a furfural derivative as an example. Furthermore, the hydrogenation catalyst of the present invention can be used not only for cyclic aldehydes but also for chain-like alkylaldehydes having 2 to 20 carbon atoms (for example, 1-propanal, 1-butanal, 1-pentanal, 1-hexanal, 1-heptanal, 1-octanal, 1-decanal, 1-undecanal, 1-dodecanal, 2-methylpropanal, 2-methylbutanal, etc.). The chain-like alkylaldehyde is not particularly limited as long as it is an aldehyde having a linear or branched alkyl group. Even when used with chain-like alkylaldehydes, the hydrogenation catalyst of the present invention can selectively reduce the formyl group of the chain-like alkylaldehyde and efficiently promote the selective hydrogenation reaction.

[0025] The shape of the nano-ferrous phosphide particles of the present invention is not particularly limited, but rod-shaped particles are preferred. The rod-shaped particles only need to have recognizable long and short axes, and include those that do not strictly have a rod shape. The morphology of the rod-shaped particles can be confirmed, for example, by TEM observation.

[0026] In the rod-shaped particles, the length in the longitudinal direction (maximum length in the longitudinal direction) is preferably less than 100 nm, more preferably 90 nm or less, and even more preferably 80 nm or less. Depending on the embodiment, it may be 70 nm or less, 60 nm or less, 50 nm or less, or 40 nm or less. Being within this range allows for stable existence in a low-valence state in the atmosphere, increases the surface area of ​​a single particle, and further enhances catalytic activity. In one embodiment, for example, the maximum length in the longitudinal direction of the rod-shaped particles is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more.

[0027] The length along the long axis of a rod-shaped particle (maximum length along the long axis) represents the arithmetic mean of the lengths along the long axis (maximum length along the long axis) of any 100 particles observed in electron microscopy. The number of particles measured may be 200 or 500, if necessary.

[0028] One embodiment is a catalyst for the hydrogenation of furfural derivatives in which the nano-iron phosphide particles are rod-shaped particles, and the maximum length in the longitudinal direction of the rod-shaped particles is less than 100 nm.

[0029] When the nano-iron phosphide particles of the present invention are rod-shaped particles, the cross-sectional shape of the surface having a short axis (bottom surface) is not particularly limited, but may be hexagonal, for example. The shape of the bottom surface is not particularly limited and may be flat, have irregularities, or have only convex portions.

[0030] In the rod-shaped particles, the length in the short axis direction (maximum length in the short axis direction) is not particularly limited as long as it is shorter than the length in the long axis direction (maximum length in the long axis direction). For example, if the cross-sectional shape of the surface having the short axis (bottom surface) is hexagonal, the length in the short axis direction (maximum length) is the length of the diagonal, which is the longest length in the cross-section. The length in the short axis direction (maximum length) is preferably 50 nm or less, more preferably 40 nm or less, and even more preferably 30 nm or less. Depending on the embodiment, it may be 20 nm or less, or 10 nm or less. When the objective is to be able to exist stably in a low-valence state in the air, to increase the surface area of ​​a single particle, and to increase catalytic activity, the length in the short axis direction (maximum length) is preferably longer, and may be 1 nm or more, 5 nm or more, or 9 nm or more. The length in the short axis direction (maximum length) means the arithmetic mean of the diagonal lengths, which are the longest lengths in the cross-section of the surface having the short axis (bottom surface) of any 100 particles observed in electron microscope observation. If necessary, the number of particles to be measured may be set to 200, 500, or 600.

[0031] In the rod-shaped particles, the aspect ratio (length in the long axis direction : length in the short axis direction) is not particularly limited, but is preferably 100:1 to 100:95, more preferably 100:5 to 100:75, and even more preferably 100:10 to 100:50. The aspect ratio can be calculated from the values ​​obtained from the length in the long axis direction and the length in the short axis direction of the rod-shaped particles.

[0032] The size of the nano-ferrous phosphide particles of the present invention can be adjusted by adjusting the selection and concentration of the raw material compound, heating temperature, heating conditions (stirring speed, etc.), reaction time, etc., in the method for producing nano-ferrous phosphide particles described later.

[0033] In one embodiment, the iron phosphide particles used as a hydrogenation catalyst for the furfural derivative of the present invention have peaks at diffraction angles of 48.3° and 32.7° (2θ ± 0.5°) in powder X-ray diffraction measurements using CuKα rays. When measured by X-ray photoelectron spectroscopy (XPS), Fe2p 3 / 2 In the spectrum, the iron atoms present have peaks in the range of 706.0 to 707.5 eV.

[0034] The nano-phosphated iron particles of the present invention have iron atoms in a low-valence state (metallic state) and exhibit excellent stability under atmospheric conditions. "Valence" is a number that represents the ability of an atom of an element to bond with an amount of atoms of other elements. The iron (Fe) atoms contained in the nano-phosphated iron particles of the present invention are in a low-valence state.

[0035] In one embodiment, the nano-iron phosphide particles of the present invention have peaks at diffraction angles of 48.3° and 32.7° (2θ ± 0.5°) in powder X-ray diffraction measurements using CuKα rays. The diffraction angles may also be 2θ ± 0.2°, 2θ ± 0.5°, or 2θ ± 0.8°.

[0036] For powder X-ray diffraction analysis (XRD) using CuKα rays, known X-ray diffractometers can be used. Commercially available X-ray diffractometers can be used (for example, the fully automated multi-purpose X-ray diffractometer (product name "Philips X'PERT MPD diffractometer," manufactured by Philips Japan, Ltd.)).

[0037] The iron nanophosphide particles used as a hydrogenation catalyst for furfural derivatives in the present invention are in a low-valence state and possess the property of being able to stably maintain the compound structure under atmospheric conditions (hereinafter also referred to as "atmospheric stability"). Therefore, the crystal structure can be measured by X-ray diffraction under conditions in which oxygen is present.

[0038] The iron phosphide nanoparticles used as a hydrogenation catalyst for furfural derivatives in the present invention preferably further have a peak at 46.3° in the powder X-ray diffraction measurement.

[0039] The nano-ferric phosphide particles used as a hydrogenation catalyst for furfural derivatives in the present invention have peaks at diffraction angles of 32.7°, 46.3°, and 48.3° in the X-ray diffraction pattern (hereinafter also referred to as the "XRD pattern") using CuKα rays, which correspond to the (011) plane, (112) plane, and (211) plane crystal plane of FeP, respectively.

[0040] In one embodiment, the hydrogenation catalyst for furfural derivatives of the present invention includes nano-ferric phosphide particles made of Fe2P. The Fe2P nano-ferric phosphide particles are in a low-valence state and have atmospheric stability. Furthermore, the hydrogenation catalyst for furfural derivatives of the present invention does not contain platinum, ruthenium, nickel, and cobalt, which is advantageous in terms of cost and biosafety.

[0041] Another embodiment includes nano-iron phosphide particles having peaks at 40.2°, 52.1°, and 54.6° in the powder X-ray diffraction measurement. Yet another embodiment includes nano-iron phosphide particles made of Fe2P. These nano-iron phosphide particles made of Fe2P are in a low-valence state and have atmospheric stability, and are thought to have higher catalytic activity compared to FeP, with a higher ratio of low-valence iron atoms to phosphorus atoms.

[0042] The peaks of the nano-iron phosphide particles of the present invention at diffraction angles of 40.2°, 43.8°, 52.1°, and 54.6° in the CuKα-ray-based XRD pattern correspond to the (111) plane, (201) plane, (002) plane and / or (300) plane and (112) plane of Fe2P, respectively. Furthermore, it is preferable that Fe2P has peaks at diffraction angles of 44.2° and 47.3°.

[0043] The fact that the peaks at the aforementioned diffraction angles can be identified as Fe2P and FeP is also evident from the JCPDS cards in the International Centre for Diffraction Data (ICDD) database (Powder Diffraction File, Level 4 plus) (Fe2P is File 51-0943; FeP is File 39-0809).

[0044] The nano-phosphated iron particles of the present invention can maintain a low-valence state of iron atoms without oxidation in the atmosphere. The low-valence state of iron atoms in the nano-phosphated iron particles of the present invention can be confirmed, for example, by measurement using X-ray photoelectron spectroscopy (XPS). In the XPS measurement results, the vertical axis represents photoelectron intensity, and the horizontal axis represents binding energy (unit: eV). "Low-valence iron atoms" refers to the Fe2p state measured by X-ray photoelectron spectroscopy (XPS). 3 / 2 In the spectrum, this means that the iron atoms contained in the nano-phosphate iron particles have peaks in the range of 706.0 to 707.5 eV.

[0045] XPS can use a known X-ray photoelectron spectroscopy analyzer. The X-ray photoelectron spectroscopy analyzer may be a commercially available product (for example, an X-ray photoelectron analyzer (product name "KRATOS ULTRA2", manufactured by Shimadzu Corporation), a photoelectron spectrometer (model number "JPS-9030", manufactured by JEOL Ltd.), a scanning X-ray photoelectron spectroscopy analyzer (model number "PHI Quantera II", manufactured by ULVAC-PHI, Inc.), etc.). AlKα rays, MgKα rays, AgLα rays, etc., can be used as excitation sources. Fe2p 3 / 2 The spectrum can be measured, for example, by XPS analysis using an X-ray photoelectron analyzer (product name "KRATOS ULTRA2", manufactured by Shimadzu Corporation) with AlKα rays as the excitation source.

[0046] The nano-phosphated iron particles of the present invention are stable under atmospheric conditions because the iron atoms contained in the nano-phosphated iron particles are in a low-valence state. In other words, the iron atoms constituting the nano-phosphated iron particles of the present invention can remain in a low-valence state with catalytic activity without changing their state over time under atmospheric conditions. In this respect, it differs from the prior art.

[0047] The valency of iron atoms in the nano-phosphate iron particles of the present invention can be analyzed, for example, by X-ray absorption fine structure (XAFS). Specifically, by irradiating a metal atom with high-intensity X-rays, preferably high-intensity X-rays with continuously changing energy, the inner-shell electrons of the metal atom are excited to energy levels above the unoccupied orbitals. The excited metal atom then emits photoelectrons with kinetic energy corresponding to the difference between the excitation energy of the incident X-rays and the binding energy of the inner-shell electrons. A fine structure appears near the absorption edge in the X-ray absorption spectrum of the metal atom, and by analyzing this, the electronic state of the metal atom can be determined. Within the energy range of such XAFS, the fine structure that appears near the absorption edge, around several tens of eV, is called the X-ray Absorption Near Edge Structure (XANES). On the other hand, within the energy range of XAFS, the modulated structure that extends from the absorption edge to an energy level approximately 1000 eV higher is called the Extended X-ray Absorption Fine Structure (EXAFS). EXAFS is a vibrational structure resulting from the interaction between excited electrons and scattered electrons from nearby atoms. The radial distribution function obtained by the Fourier transform contains information about the local structure of the metal atom (surrounding atomic species, number of coordinating atoms, interatomic distances).

[0048] In the nanophosphate iron particles of the present invention, the presence of iron atoms in a low-valence state can also be confirmed from the X-ray Absorption Near Edge Structure (XANES).

[0049] Since the iron atoms contained in the nanophosphated iron particles of the present invention exist in a low valence state, in the XANES spectrum obtained by XANES measurement at the K absorption edge of Fe atoms, the rise of the peak is the same as that of the peak of the iron foil (Fe foil). In other words, the fact that the iron atoms constituting the nanophosphated iron particles of the present invention exist in a low valence state can be confirmed by the fact that in the XANES spectrum obtained by the above XANES measurement, the rise of the peak is the same as that of the peak of the iron foil (Fe foil). The iron foil (Fe foil) is zero-valent Fe as a metal. In one embodiment, in the XANES spectrum obtained by XANES measurement at the K absorption edge of Fe atoms, (the spectral intensity of nano-Fe x P at 7110 eV) / (the spectral intensity of Fe foil at 7110 eV) has a ratio of 0.910 to 1.000, and a catalyst for hydrogenation of a fullerene derivative containing nanophosphated iron particles and a composite is mentioned. "eV" represents the energy of the incident X-ray. The method for measuring the XANES spectrum can be, for example, as described in International Publication No. 2023-200015, at the large synchrotron radiation facility "Spring-8" (beamlines BL01B1, BL14B2, 1 Koto 1, Mitsuto, Sayo-gun, Hyogo 679-5198), using the Si(111) monochromator of Spring-8, and the measurement can be performed by the transmission method at room temperature. The measurement time can be set, for example, to 120 sec for Fe foil and 600 sec for nano-Fe x P.

[0050] In the nanophosphated iron particles and the composite of the above-mentioned one embodiment, at two points of the spectral intensity at 7110 eV and the spectral intensity at 7111 eV, in both cases, (the spectral intensity of nano-Fe x P) / (the spectral intensity of Fe foil) preferably has a ratio of 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000. At the above two points, nano-Fe xThe fact that the ratio of the spectral intensity of P to that of Fe foil is almost the same means that the peak rise times for nano-ferric phosphide particles and Fe foil are the same. The fact that the peak rise times for nano-ferric phosphide particles and Fe foil are the same means that the nano-ferric phosphide particles are in a low-valence state.

[0051] When measured by XPS, the XPS results indicate that at least the surface of the nano-ferrous phosphide particles can maintain a low valence state. If the XANES measurement results match the XPS measurement results, it can be said that the two measurement results support each other, and that the iron atoms contained in the nano-ferrous phosphide particles can maintain a low valence state not only on the surface but also throughout the entire particle, including the interior.

[0052] For XANES measurements of the K absorption edge of Fe atoms, known measuring devices (for example, X-ray absorption spectrometers (device names "QuantumLeapH2000" (for measurements under air), "QuantumLeaV210" (for measurements under vacuum), both manufactured by Canon Inc.)) or known measuring facilities (large synchrotron radiation facility "SPring-8"; beamlines BL01B1, BL14B2, 1-1 Koto, Sayo-cho, Sayo-gun, Hyogo Prefecture 679-5198) can be used.

[0053] In the Fe2p spectrum obtained from XPS, low-valence Fe atoms have a peak in the range of 706.7–707.0 eV. This is shown in Appendix B. Chemical States Tables for Fe 2p in Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data (Eds.: J. Chastain), Published by Perkin-Elmer Corporation, Electronics Division, Eden Prairie, MN, 1992.

[0054] One embodiment involves Fe2p in X-ray photoelectron spectroscopy (XPS). 3 / 2 In the spectrum, the iron atoms contained in the nano-ferric phosphide particles have a peak in the range of 706.0 to 707.5 eV, and in the XANES spectrum obtained by XANES measurement of the K absorption edge of the Fe atom, (nano-Fe x A catalyst for the hydrogenation of furfural derivatives is provided, which includes nano-iron phosphide particles in which the value (ratio) of (spectral intensity of P at 7110 eV) / (spectral intensity of Fe foil at 7110 eV) is 0.910 to 1.000. The ratio of spectral intensities of the XANES spectrum is preferably 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000. Furthermore, in the nano-iron phosphide particles of the above embodiment, at two points, the spectral intensities of 7110 eV and 7111 eV, (nano-Fe x The ratio of (spectral intensity of P) / (spectral intensity of Fe foil) is preferably 0.930 to 1.000, more preferably 0.950 to 1.000, and even more preferably 0.970 to 1.000.

[0055] In the nano-iron phosphide particles of the present invention, the ratio of phosphorus atoms to iron atoms determined by scanning transmission electron microscopy (STEM)-energy dispersive X-ray spectroscopy (EDX) compositional analysis is preferably P:Fe = 20%:80% to 80%:20%, more preferably 30%:70% to 70%:30%, and even more preferably 35%:65% to 65%:35%, as this is superior in terms of enhancing catalytic activity or atmospheric stability.

[0056] The ratio of phosphorus atoms to iron atoms in the nano-phosphated iron particles of the present invention can be adjusted by controlling the degree of iron phosphating. x In P, adjustments can be made, such as increasing the amount of compounds where x is 1, or increasing the amount of compounds where x is 2. In one embodiment, nano-Fe xIn P, x is 1 or 2. The nano-iron phosphide particles include at least one of FeP and Fe2P, and preferably both. In another embodiment, nano-Fe x In P, x is 1. In another embodiment, nano-Fe x At P, x is 2.

[0057] One way to adjust the degree of iron phosphating is to adjust the heating temperature in the manufacturing method of nano-phosphorus iron particles (for example, by increasing the heating temperature by 10°C or extending the reaction time by 1 hour), thereby adjusting the degree of phosphating, such as by promoting iron phosphating. Conversely, to suppress phosphating and limit the progression of phosphating, the ratio of phosphorus atoms to iron atoms can be adjusted by changing the heating temperature and other conditions (for example, by decreasing the heating temperature by 10°C or shortening the reaction time by 1 hour).

[0058] In the nano-phosphate iron particles of the present invention, the relative abundance of phosphorus atoms and iron atoms can be evaluated by elemental analysis (elemental mapping). Known energy-dispersive X-ray spectroscopy (EDX) can be used for elemental analysis (elemental mapping). Known measuring devices can be used for EDX. Commercially available measuring devices can include transmission electron microscopes equipped with Super-X energy-dispersive X-ray spectroscopy (EDX) detectors (single-atom analysis transmission electron microscope, trade name "Titan Cubed G2 60-300", acceleration voltage: 300 kV, manufactured by FEI (now Thermo Fisher Scientific (US))).

[0059] Furthermore, while EDX is a method for observing a single particle, it is also possible to observe multiple (large quantities of) nano-ferric phosphide particles as a whole, as can be seen under a microscope, and evaluate the relative abundance of phosphorus atoms to iron atoms. One such method is inductively coupled plasma emission spectroscopy (ICP-AES). Known measuring devices can be used for ICP-AES. Commercially available measuring devices (ICP emission spectrometers, product name "Optima 8300" (measurement method: multi-wavelength simultaneous multi-element analysis scanning photometric analysis, software: Winlab32), manufactured by PerkinElmer Co., Ltd., etc.) can be used.

[0060] In one embodiment, the ratio of phosphorus atoms to iron atoms obtained by ICP-AES is preferably P:Fe = 20%:80% to 80%:20%, more preferably 30%:70% to 70%:30% and even more preferably 35%:65% to 65%:35% because it is superior in terms of further enhancing catalytic activity or atmospheric stability.

[0061] In one embodiment, in the nano-iron phosphide particles of the present invention, the ratio of phosphorus atoms to iron atoms is in a range close to that of the ratio evaluated by ICP-AES (e.g., sequential type) and the ratio evaluated by EDX. The fact that the two values ​​are close means that there are no excess phosphorus atoms attached to the nano-iron phosphide particles.

[0062] The nano-ferric phosphide particles used in the hydrogenation catalyst for furfural derivatives of the present invention not only exhibit excellent atmospheric stability but also maintain their structure even when heated, demonstrating excellent thermal stability. Maintaining the structure means maintaining a low-valence state. The nano-ferric phosphide particles and composites of the present invention can be recovered after being used as a hydrogenation catalyst for furfural derivatives by heating. Therefore, the nano-ferric phosphide particles and composites of the present invention exhibit excellent thermal stability.

[0063] The nano-ferric phosphide particles and composites used as catalysts for the hydrogenation of furfural derivatives according to the present invention can maintain their activity after use and are recoverable. The recovery method is not particularly limited, and known methods such as filtration can be used. Another embodiment of the present invention relates to a method for producing nano-ferric phosphide particles.

[0064] As one embodiment, the method for producing nano-phosphate iron particles of the present invention involves mixing a phosphorus compound, an iron compound that serves as an iron source (preferably an iron carbonyl compound), and a surfactant under heating, wherein the iron compound (preferably an iron carbonyl compound) is composed of Fe(CO)5 and Fe3(CO) 12 A manufacturing method is one in which at least one is selected from the group consisting of the following, and does not use 1-octadecene.

[0065] Conventional techniques include methods for producing nanometal particles using 1-octadecene as an essential component ("Triphenyl Phosphite as the Phosphorus Source for the Scalable and Cost-Effective Production of Transition Metal Phosphides", Chemistry of Materials, Junfeng Liu et al., 2018, 30, pp 1799-1807). However, the present inventors have confirmed that nanoiron particles obtained by the production method using 1-octadecene cannot be obtained in an amount that exhibits sufficient catalytic activity. Therefore, the method for producing nanoiron phosphide particles of the present invention does not use 1-octadecene.

[0066] By not using 1-octadecene, the resulting nano-ferric phosphide particles and composites containing them exhibit excellent catalytic activity and can be used as catalysts for the hydrogenation of furfural derivatives. The method for producing nano-ferric phosphide particles of the present invention does not require other additives such as 1-octadecene.

[0067] In the method for producing nano-ferrous phosphide particles of the present invention, a phosphorus ester compound is preferred as the phosphorus compound used as the phosphating agent.

[0068] Examples of phosphite ester compounds include triphenyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, tritolyl phosphite (tri-o-tolyl phosphite, tri-m-tolyl phosphite, tri-p-tolyl phosphite), trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, tris(2-t-butyl-5-methylphenyl) phosphite, trimethyl phosphite, triethyl phosphite, tripropyl phosphite, and triisopropyl phosphite. Aryl phosphates such as phenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, tritlyl phosphite, trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, and tris(2-t-butyl-5-methylphenyl) phosphite are preferred, triaryl phosphates such as triphenyl phosphite, tritlyl phosphite, trixylyl phosphite, tris(2,4-di-t-butylphenyl) phosphite, tris(2,6-dimethylphenyl) phosphite, tris(2-t-butylphenyl) phosphite, and tris(2-t-butyl-5-methylphenyl) phosphite are more preferred, and triphenyl phosphite is even more preferred. The phosphorus compound may be used alone or in combination of two or more.

[0069] Examples of the surfactant include alkylamines. While the alkylamine is not particularly limited, examples include alkylamines having an alkyl group with 1 to 20 carbon atoms. Alkylamines may be used individually or in combination of two or more.

[0070] The alkyl group of the alkylamine may be linear, branched, or cyclic. Examples of alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, sec-pentyl, neopentyl, tert-pentyl, 1-ethylpropyl, 1,1-dimethylpropyl, 1,2-dimethylpropyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 3-methylpentyl, 4-methylpentyl (isohexyl), 1-ethylbutyl, 2-ethylbutyl, 1,1-dimethylbutyl, 1,2-dimethylbutyl, 1,3-dimethylbutyl, 1,4-dimethylbutyl, 2,2-dimethylbutyl, 2,3-dimethylbutyl, and 3,3-dimethylbutyl. Examples include ethylbutyl group, 1-ethyl-2-methylpropyl group, 1,1,2-trimethylpropyl group, n-heptyl group, 2-methylhexyl group, n-octyl group, isooctyl group, tert-octyl group, 2-ethylhexyl group, 3-methylheptyl group, n-nonyl group, isononyl group, 1-methyloctyl group, 2-ethylheptyl group, n-decyl group, 1-methylnonyl group, n-undecyl group, 1,1-dimethylnonyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group, n-nonadecyl group, n-eicosyl group, n-cyclopentyl group, n-cyclopentylmethyl group, cyclohexyl group, and cyclohexylmethyl group.

[0071] The alkyl group may have substituents or may be unsubstituted. The number of substituents can be changed according to the number of carbon atoms in the alkyl group, and may be 1 to 10, 1 to 5, or 1 to 3. Examples of substituents include halogen atoms, cyano groups (nitrile groups), lower alkyl groups, halo-lower alkyl groups, hydroxy-lower alkyl groups, hydroxyl groups, halo-lower alkoxy groups, etc. One embodiment is a method for producing nano-ferric phosphide particles in which the surfactant is n-hexadecylamine.

[0072] The amount of surfactant used may be 0.05 to 20 equivalents (molar equivalents), 0.1 to 15 equivalents, or 0.5 to 13 equivalents relative to the amount of phosphorus compound used.

[0073] The mixing of the phosphorus compound, the iron compound (preferably an iron carbonyl compound), and the surfactant under heating (hereinafter also referred to as the "mixing step") is not particularly limited and can be carried out using known methods and apparatus.

[0074] In the method for producing nano-iron phosphide particles of the present invention, a phosphorus compound, an iron compound (preferably an iron carbonyl compound), and a surfactant are mixed under heating. The heating temperature in the mixing step is preferably 80 to 280°C, more preferably 90 to 250°C, and even more preferably 100 to 220°C. The heating temperature may also be less than 200°C or less than 180°C as milder conditions. For example, the heating temperature may be 90°C or higher and less than 180°C. The heating temperature can be appropriately changed depending on the desired degree of phosphating of the nano-iron phosphide particles.

[0075] In the manufacturing method of the present invention, iron carbonyl compounds are preferred as the iron compound. Examples of iron carbonyl compounds include Fe(CO)5 and Fe3(CO) 12 Preferably, Fe3(CO) 12 This is more preferable. The iron carbonyl compound can be produced by known methods. For example, Fe3(CO) 12 This can be obtained by known methods such as heating Fe2(CO)9 in an organic solvent. The heating apparatus and temperature can be any known method and are not particularly limited. The iron compound may be used alone or two or more in combination. As the iron compound, Fe3(CO) 12 It is a solid, and unlike Fe(CO)5, it does not require injection by hot injection in the manufacturing method of nanoiron phosphide particles, making it easy to handle. Also, Fe3(CO) 12Compared to Fe(CO)5, it is superior in terms of safety for the human body. Furthermore, in the method for producing nano-ferrous phosphide particles of the present invention, it is preferable not to use Fe(CO)5 as an iron carbonyl compound from the standpoint of safety for the human body, ease of availability, and the fact that Fe(CO)5 is a liquid at atmospheric pressure (1 atm), is highly volatile, and sublimes, requiring injection into the reaction system by hot injection, which presents handling problems.

[0076] The mixing step is preferably carried out under stirring, as this promotes the reaction and makes it easier to produce the nano-iron phosphide particles of the present invention. In one embodiment, the mixing step is preferably carried out under vacuum conditions or an argon atmosphere, as this makes it easier to produce the nano-iron phosphide particles of the present invention.

[0077] The reaction time in the mixing step is not particularly limited and can be appropriately changed depending on the desired degree of phosphating of the nanoiron phosphide particles. The reaction time is preferably 10 to 120 minutes, more preferably 15 to 90 minutes, and even more preferably 20 to 80 minutes.

[0078] Following the mixing step, the resulting mixture may be further heated (hereinafter also referred to as "heating step [2]"). Heating step [2] is preferably carried out under an argon atmosphere.

[0079] The heating temperature in the heating step [2] is not particularly limited as long as it is higher than the mixing step, but is preferably 90 to 380°C, more preferably 120 to 350°C, and even more preferably 180 to 330°C. The heating temperature in the heating step [2] can be appropriately changed depending on the desired degree of phosphating of the nano-iron phosphide particles. The heating temperature in the heating step [2] may be 5°C or more higher than that of the mixing step, or 10°C or more higher.

[0080] The heating rate when raising the temperature to the temperature of the heating step [2] after mixing the iron carbonyl compound is not particularly limited and can be appropriately changed depending on the desired degree of phosphating of the nano-phosphated iron particles. For example, the heating rate can be set low in order to allow the reaction to proceed slowly. The heating rate is preferably 5 to 150°C / min, more preferably 10 to 100°C / min, and even more preferably 15 to 90°C / min.

[0081] The reaction time in the heating step [2] is not particularly limited and can be appropriately changed depending on the desired degree of phosphating of the nano-iron phosphide particles. The reaction time is preferably 10 to 600 minutes, more preferably 15 to 540 minutes, and even more preferably 20 to 420 minutes.

[0082] The present invention's method for producing nano-iron phosphide particles preferably further includes a washing step. An organic solvent can be used as the washing solution in the washing step. The organic solvent is not particularly limited and is similar to the organic solvent used in the above-described method for producing the composite. One organic solvent may be used alone, or two or more may be used in combination. When two or more organic solvents are used in combination, the mixing ratio is not particularly limited, but for example, chloroform and acetone can be used in a volume ratio of 1:1. The washing step may involve using the organic solvent to centrifuge the product obtained after the heating step.

[0083] After the washing process, if necessary, the material may be vacuum-dried to obtain powdered nano-ferrous phosphide particles.

[0084] Another embodiment of the present invention relates to a catalyst for the hydrogenation of cyclic aldehydes (preferably furfural derivatives) comprising a composite comprising any of the above-described nano-iron phosphide particles and a support. Another embodiment is a catalyst for the hydrogenation of furfural derivatives comprising a composite in which the support comprises Al2O3, which has excellent catalytic activity as a catalyst for the hydrogenation of cyclic aldehydes (preferably furfural derivatives).

[0085] The nano-phosphate iron particles of the present invention exhibit excellent adsorption capacity, and therefore are not limited to specific carriers. When used as a composite in a reduction reaction, they are effective as a catalyst for the hydrogenation of furfural derivatives. The reason for their excellent adsorption capacity is not entirely clear, but it is thought that their nano-size and stability under atmospheric conditions may be contributing factors.

[0086] In the composite of the present invention, the iron atoms contained in the nano-phosphated iron particles are in a low-valence state, and the nano-phosphated iron particles are stable under atmospheric conditions. Therefore, unlike the conventional technique, where catalytically active iron particles must be synthesized on a support and used instantaneously immediately after synthesis, or where pre-treatment under high temperature and high pressure is essential for using the iron catalyst in a reduction reaction, the nano-phosphated iron particles of the present invention do not have these limitations. Thus, unlike the conventional technique, where the type of support was limited by the conditions under which the iron particles were used as an iron catalyst, one of the advantageous effects of the present invention is that when the composite is used as a catalyst for the hydrogenation of furfural derivatives, the type of support used in combination with the nano-phosphated iron particles is not limited. In this way, the reason why the support must be limited is eliminated, and there is no special circumstance that catalytic activity cannot be obtained if the support is not limited, so in the composite of the present invention, the type of support is not limited, and many types can be used.

[0087] On the other hand, due to its superior catalytic activity, the support preferably contains Al2O3, and in addition to Al2O3, or in place of Al2O3, other supports other than Al2O3 (hereinafter also referred to as "other supports") can also be used. The reason why the catalytic activity is better when the support contains Al2O3 is thought to be as follows. The inventors previously found by IR analysis that when a composite consisting of nanocobalt phosphide particles and Al2O3 as a support was used, the formyl group was activated by Al2O3 (Fig. 5a of Non-Patent Literature 2). IR analysis confirmed that the corresponding absorption band of the formyl group on Al2O3 was shifted to the lower energy side. This is thought to be due to the activation of the formyl group by the Lewis acid site of Al2O3, which extended the C=O bond. In the present invention, among several supports, the reason why the activity is higher when nanoiron phosphide particles support Al2O3 is the high specific activation ability of Al2O3 for the formyl group, as described above. In this invention as well, the peak corresponding to the formyl group shifts to a lower energy side in Al2O3-supported nanoferrous phosphide particles compared to nanoferrous phosphide particles without a support, suggesting that the formyl group is activated by the Lewis acid site of Al2O3. The activated formyl group-containing aldehyde is then hydrogenated at the interface between Al2O3 and the nanoferrous phosphide particles, transforming into an alcohol product. Therefore, regardless of whether the aldehyde is a cyclic aldehyde or a chain aldehyde with a cyclic structure, the formyl group is activated by the Lewis acid site of Al2O3, and there are no factors that would hinder this activation. As a result, the same effect can be achieved, as shown in the examples. It is presumed that the reducing properties of Al2O3 are the reason why the composite containing nanoferrous phosphide particles using iron as a metal element and Al2O3 exhibits superior catalytic activity compared to other supports.

[0088] In the composite of the present invention, the type of other support is not limited as long as it can be used as a support capable of supporting nano-iron phosphide particles. The other support is preferably liquid or solid at room temperature, and more preferably solid. In other embodiments, the other support may not have catalytic activity on its own. By using nano-iron phosphide particles together with a support containing Al2O3, aggregation of the nano-iron phosphide particles can be effectively suppressed, and the composite can be recovered more easily. In particular, by combining nano-iron phosphide particles made of Fe2P with a support containing Al2O3, the catalytic activity as a catalyst for the hydrogenation of furfural derivatives is further enhanced, and aggregation of the nano-iron phosphide particles can be suppressed more effectively.

[0089] Examples of other carriers include at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials. These other carriers may be used individually or in combination of two or more. Commercially available carriers may also be used.

[0090] The polymer may be either a natural polymer or a synthetic polymer. Examples of natural polymers include organic natural polymers such as natural rubber, protein, starch, and cellulose; and inorganic natural polymers such as quartz, mica, and feldspar. Examples of synthetic polymers include organic synthetic polymers such as polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polyvinyl chloride, polyvinylpyrrolidone, polyethylene glycol (PEG), polypropylene glycol (PPG), polyethylene terephthalate (PET), polyester, polyethylene, polypropylene, polystyrene, polyurethane, polyethyleneimine, polyethersulfone, polyphenylene sulfide (PPS), polyetheretherketone (PEEK), polyvinylidene fluoride, polylactic acid, epoxy resins, fluororesins (PTFE (polytetrafluoroethylene), PFA, FEP, PCTFE, ETFE, ECTFE, etc.), nylon resins, polyamides, polyimides, and rubbers (silicone rubber, nitrile rubber, butyl rubber, butadiene rubber, etc.); and inorganic synthetic polymers such as glass and silica gel. The synthetic polymer may be a homopolymer composed of one type of monomer, or a copolymer composed of two or more types of monomers. 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).

[0091] A 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 a single element or two or more elements. The chalcogen compound is not particularly limited, and H2X 1 O4(X 1 = chalcogens excluding tellurium), H6TeO6, H2X 2 O3(X 2Examples include compounds having the structure of (= chalcogen) or salts thereof, compounds represented by MX3 (wherein M is Ti, Zr, Hf, V, Nb, Ta, Mo, or W, and X is S or Se), and metal chalcogenides represented by MPX3 (wherein M is Mg, V, Mn, Fe, Co, Ni, Zn, Cd, or In, and X is S or Se).

[0092] Examples of metal compounds are not particularly limited, but include oxides of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Si, Fe, Ti, Al, Mg, Co, Ni, Mn, Cr, Mo, W, V, Zn, and Sn, their solid solutions, and their composite oxides. Specifically, examples include SiO2, TiO2, and Al2O3. In this invention, metalloids of the periodic table such as "Si" are included in the definition of metal.

[0093] Examples of metals include Fe and metal alloys (such as stainless steel). The aforementioned metals can be used as metal carriers.

[0094] Examples of solid carbon materials include silicon carbide (SiC), activated carbon, graphite, diamond, fullerene, carbon nanotubes, graphene, and amorphous carbon.

[0095] The shape and size of the support can be changed depending on the form of use and are not particularly limited. For example, the support may be a sheet, film, or plate. The size of the support may be nanoscale, and may be 1 μm or larger, 1 mm or larger, or 1 cm or larger. As a support, for example, it may be a nanosheet (for example, with a thickness of about 1 nm to 100 nm). Also, as a support, for example, it may have a BET specific surface area of ​​5 to 900 m². 2 It may also be / g, and 10 to 800m 2 It may also be / g, and 15-700m 2 It may also be / g, and 20-500m 2 It may also be / g. The method for measuring the BET specific surface area is as described in the examples below.

[0096] The composite of the present invention contains iron atoms in a low-valence state, is stable under atmospheric conditions, and has catalytic activity as a catalyst for the hydrogenation of cyclic aldehydes (preferably furfural derivatives).

[0097] The composite of the present invention is not particularly limited and can be manufactured depending on the type of carrier. One embodiment is a method for manufacturing the composite in which nano-iron phosphide particles are placed or fixed on a carrier. The method for fixing the nano-iron phosphide particles on the carrier is not particularly limited and may be, for example, heat treatment or compression treatment. The heat treatment temperature may be, for example, 100°C or less. The carrier may be, for example, a solid carrier (e.g., in the form of a sheet) that is sufficiently larger than the nano-iron phosphide particles.

[0098] Because the nano-ferric phosphide particles of the present invention have excellent adsorption capacity, the method of supporting them on known carriers is not particularly limited and can be used. Another embodiment is a method for producing a composite, in which the nano-ferric phosphide particles are dispersed in an organic solvent, and the carrier is added to the organic solvent and stirred to obtain a composite. In any of the methods for producing the composite, there are no particular limitations, and for example, heat treatment may be performed. The heat treatment temperature may be, for example, 150°C or lower, or 120°C or lower.

[0099] The organic solvent used in the method for producing the composite is not particularly limited, and polar or non-polar organic solvents can be used. One organic solvent may be used alone, or two or more may be used in combination.

[0100] Organic solvents used in the method for producing the complex include, for example, 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); 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., monoglime (ethylene glycol dimethyl ether), methyl cellosolve, diethyl cellosolve, diglime, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, triglime, tetraglime, 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-hexanolpropylene glycol monopropyl ether, dipropylene glycol monoethyl ether, tripropylene glycol monomethyl ether), 1,1-dimethoxycyclohexane, phenethole, veratrol, dioxane, tetrahydrofuran); Ester solvents (e.g., ethyl acetate, butyl acetate, isopropyl acetate, 3-methoxy-3-methylbutyl acetate, dimethyl carbonate, diethyl malonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, α-acetyl-γ-butyrolactone);Examples include ketone solvents (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, acetophenone, propiophenone, isophorone); 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-dimethylacetacetamide, N,N-diethylformamide, N,N-diethylacetamide, hexamethylphosphoramide, methylpyrrolidone, etc.; amine solvents such as triethanolamine; nitrile solvents such as acetonitrile and benzonitrile; nitro solvents such as nitrobenzene and o-nitrotoluene; quinoline, tetrahydroquinoline, dimethylimidazolidinone, etc.).

[0101] Another embodiment of the present invention relates to a catalyst for the hydrogenation of cyclic aldehydes (preferably furfural derivatives) comprising any of the aforementioned nano-iron phosphide particles.

[0102] In one embodiment, the hydrogenation catalyst for cyclic aldehydes (preferably furfural derivatives) of the present invention comprises nano-iron phosphide particles and a support, wherein the nano-iron phosphide particles and the support (preferably a support containing Al2O3) constitute a composite. Another embodiment is a hydrogenation catalyst for furfural derivatives comprising a composite, wherein the nano-iron phosphide particles are made of Fe2P and the support contains Al2O3. The hydrogenation catalyst for furfural derivatives of the present invention may also consist of the above composite.

[0103] The following describes the production of furfuryl alcohol compounds using the hydrogenation catalyst according to the present invention, with the cyclic aldehyde being a furfural derivative as an example. One embodiment is a hydrogenation catalyst for furfural derivatives containing any of the aforementioned nano-ferric phosphide particles. Another embodiment is a hydrogenation catalyst for furfural derivatives containing any of the aforementioned nano-ferric phosphide particles and a support, wherein the nano-ferric phosphide particles and the support constitute a composite.

[0104] One embodiment is a method for producing an alcohol compound, in which, under a hydrogen atmosphere, a cyclic aldehyde (preferably a furfural derivative) is hydrogenated in the presence of a catalyst for hydrogenation of the aforementioned complex, and an alcohol compound (preferably a furfuryl alcohol compound) is obtained. Another embodiment is a method for producing an alcohol compound in which the cyclic aldehyde is a furfural derivative and the alcohol compound is a furfuryl alcohol compound. The support in the complex is preferably a support containing Al2O3 because of its excellent catalytic activity.

[0105] Examples of the furfural derivatives include furfural represented by the following general formula (1) and its derivatives. (In the formula, R 1 , R 2 and R 3 (This represents a hydrocarbon group that may have a hydrogen atom or substituents, either identical or different.)

[0106] R 1 Examples of hydrocarbon groups in this context include aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, aromatic hydrocarbon groups, and groups formed by the bonding of two or more of these groups.

[0107] Examples of the aliphatic hydrocarbon group include alkyl groups having 1 to 20 carbon atoms (preferably 1 to 10), such as methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, n-decyl, and n-dodecyl groups; alkenyl groups having 2 to 20 carbon atoms (preferably 2 to 10), such as vinyl, allyl, and 1-butenyl groups; and alkynyl groups having 2 to 20 carbon atoms (preferably 2 to 10), such as ethynyl and propynyl groups. The aliphatic hydrocarbon group may be linear or branched.

[0108] Examples of the alicyclic hydrocarbon group include cycloalkyl groups with 3 to 20 members (preferably 3 to 15 members, more preferably 5 to 8 members) such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, and cyclooctyl group; cycloalkenyl groups with 3 to 20 members (preferably 3 to 15 members, more preferably 5 to 8 members) such as cyclopentenyl group and cyclohexenyl group; perhydronaphthalene-1-yl group, norbornyl group, adamantyl group, and tetracyclo[4.4.0.1 2,5 1. 7,10 Examples include bridged cyclic hydrocarbon groups such as the dodecane-3-yl group.

[0109] Examples of aromatic hydrocarbon groups include aromatic hydrocarbon groups having 6 to 14 carbon atoms (preferably 6 to 10), such as phenyl and naphthyl groups. In this specification, R 1 If the hydrocarbon group in a given molecule has an aromatic ring, it is included in the category of aromatic hydrocarbon groups.

[0110] Hydrocarbon groups formed by the bonding of an aliphatic hydrocarbon group and an alicyclic hydrocarbon group include, for example, cycloalkyl-alkyl groups such as cyclopentylmethyl, cyclohexylmethyl, and 2-cyclohexylethyl (for example, C 3~12 Cycloalkyl-C 1~4 Examples include alkyl groups, etc.

[0111] A hydrocarbon group formed by the bonding of an aliphatic hydrocarbon group and an aromatic hydrocarbon group may have an aralkyl group (for example, C 7~18Aralkyl groups, alkyl-substituted aryl groups (for example, 1 to 4 carbon atoms) 1~4 (An alkyl-substituted phenyl group or naphthyl group, etc.), aryl-substituted C 2~10 Examples include alkenyl groups (for example, 2-phenylvinyl group).

[0112] R 1 The hydrocarbon group in may have various substituents, such as halogen atoms, oxo groups, hydroxyl groups, substituted oxy groups (e.g., alkoxy groups having 1 to 6 carbon atoms, aryloxy groups having 6 to 14 carbon atoms, aralkyloxy groups having 7 to 15 carbon atoms, acyloxy groups, etc.), carboxyl groups, substituted oxycarbonyl groups (alkoxycarbonyl groups having 1 to 6 carbon atoms, aryloxycarbonyl groups having 6 to 14 carbon atoms, aralkyloxycarbonyl groups having 7 to 15 carbon atoms), cyano groups, nitro groups, acyl groups, substituted or unsubstituted amino groups (hydrocarbon group-substituted amino groups, acyl group-substituted amino groups, unsubstituted amino groups, etc.), sulfo groups, azo groups, azide groups, heterocyclic groups, etc. The hydroxyl group and carboxyl group may be protected with protecting groups commonly used in the field of organic synthesis. Furthermore, heterocyclic rings with aromatic or non-aromatic attributes may be fused to the rings of alicyclic hydrocarbon groups and aromatic hydrocarbon groups. Furthermore, the number of substituents can be appropriately selected depending on the structure of the compound; for example, it may be 1 to 6, 1 to 4, or 1 to 3.

[0113] Examples of furfural derivatives used as substrates in the present invention include 5-methylfurfural, 5-ethylfurfural, 4-n-propyl-5-methylfurfural, 4-n-propyl-5-ethylfurfural, 5-hydroxymethylfurfural, 3-hydroxy-4-methyl-5-methylfurfural, and 2-isopropyl-5methylfurfural.

[0114] The amount of catalyst used for the hydrogenation of furfural derivatives is preferably 0.1 to 15 mol%, more preferably 0.15 to 12 mol%, and even more preferably 0.2 to 10 mol%, in terms of the amount of Fe, relative to 100 mol% of the furfural derivative, in order to have sufficient catalytic activity. Within the above range, the hydrogenation reaction of the furfural derivative proceeds sufficiently. The catalyst for the hydrogenation of furfural derivatives of the present invention functions as a catalyst even in very small amounts and exhibits excellent catalytic activity.

[0115] The method for producing furfuryl alcohol compounds is preferably carried out by heating. The heating temperature is not particularly limited, but is preferably 80 to 350°C, more preferably 90 to 280°C, and even more preferably 100 to 250°C. If the reaction is carried out under more moderate conditions, the temperature may be less than 200°C or less than 180°C. One embodiment is a method for producing furfuryl alcohol compounds in which the furfural derivative is heated during the reaction, and the heating temperature is less than 200°C. Even if the heating temperature is less than 200°C, the catalytic activity of the hydrogenation catalyst for the furfural derivative is excellent, so furfuryl alcohol compounds can be obtained with high production efficiency.

[0116] The reaction time is not particularly limited and may range from 5 minutes to 60 hours, 10 minutes to 30 hours, or 20 minutes to 15 hours. Depending on the purpose, the reaction time may be set to 8 hours or less.

[0117] In the method for producing furfuryl alcohol compounds, hydrogen molecules (hydrogen gas) are used as a reducing agent. Therefore, the production of furfuryl alcohol compounds is carried out under a hydrogen atmosphere. The reaction in this production method is superior in that it has high atomic efficiency, unlike the previously reported reaction process that uses an iron catalyst and the reaction solvent as the hydrogen source, because the hydrogen source is used as the reaction atmosphere.

[0118] One embodiment of this method involves hydrogenating a furfural derivative in a hydrogen atmosphere in the presence of the hydrogenation catalyst at a hydrogen pressure of 8 MPa or less to produce a furfuryl alcohol compound.

[0119] In the method for producing furfuryl alcohol compounds, the hydrogen pressure is 8 MPa or less, and under milder conditions, it may be 5.0 MPa or less, 4.8 MPa or less, 4.5 MPa or less, or 2.9 MPa or less. The hydrogen pressure may be, for example, 0.4 MPa or more, or 0.5 MPa or more. The hydrogen pressure may be between 0.4 MPa and 5.0 MPa. If the hydrogen pressure adjusted using hydrogen gas is within the above range, the hydrogenation reaction of the furfural derivative will proceed sufficiently.

[0120] In the manufacturing method of the present invention, the type of solvent can be selected according to the type of substrate, etc. On the other hand, one embodiment is a method for producing an alcohol compound (preferably a furfuryl alcohol compound) by reacting a cyclic aldehyde (preferably a furfural derivative) in the presence of a solvent.

[0121] As solvents, for example, those exemplified as organic solvents used in the method for producing the complex can be used, and alcohol solvents such as methanol, ethanol, n-propanol, 2-propanol, n-butanol, 2-butanol, and t-butanol are preferred; ketone solvents such as acetone and methyl ethyl ketone are preferred; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide are preferred; and ether solvents such as 1,2-dimethoxyethane and diethylene glycol dimethyl ether are preferred, with alcohol solvents being more preferred.

[0122] In the method for producing furfuryl alcohol compounds, the hydrogenation reaction of the furfural derivative may be carried out in the presence of a base.

[0123] Examples of bases 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. A single base may be used alone, or two or more bases may be used in combination.

[0124] (a) Examples of tertiary amines include trimethylamine, triethylamine, N-ethyldiisopropylamine, tri-n-propylamine, triisopropylamine, tri-n-butylamine, trioctylamine, tridecylamine, triphenylamine, trimenzylamine, 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-methyl Examples include lupyrrolidine, N-methylpiperidine, N-methylmorpholine, N-ethylmorpholine, N,N'-dimethylpiperazine, N-methylpyrrolidone, N-vinylpyrrolidone, bis(2-dimethylaminoethyl) ether, N,N,N,N',N''-pentamethyldiethylenetriamine, triethanolamine, trippropanolamine, dimethylethanolamine, dimethylaminoethoxyethanol, N,N-dimethylaminopropylamine, N,N,N',N',N''-pentamethyldipropylenetriamine, tris(3-dimethylaminopropyl)amine, tetramethyliminobis(propylamine), and N-diethylethanolamine.

[0125] (b) Examples of nitrogen-containing aromatic heterocyclic compounds include pyridine, 2,4,6-trimethylpyridine, 4-dimethylaminopyridine, lutidine, pyrimidine, pyridazine, pyrazine, oxazole, isoxazole, thiazole, isothiazole, imidazole, 1,2-dimethylimidazole, 3-(dimethylamino)propylimidazole, pyrazole, furazan, quinoline, isoquinoline, purine, 1H-indazole, quinazoline, cinnoline, quinoxaline, phthalazine, Examples include pteridine, phenanthridine, 2,6-di-t-butylpyridine, 2,2'-bipyridine, 4,4'-dimethyl-2,2'-bipyridyl, 5,5'-dimethyl-2,2'-bipyridyl, 6,6'-t-butyl-2,2'-dipyridyl, 4,4'-diphenyl-2,2'-bipyridyl, 1,10-phenanthroline, 2,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, and 4,7-diphenyl-1,10-phenanthroline.

[0126] (c) Examples of imine bases include 1,8-diazabicyclo[5.4.0]undeca-7-ene (diazabicycloundecene), 1,5-diazabicyclo[4.3.0]non-5-ene, etc.

[0127] (d) Examples of inorganic bases include alkali metal or alkaline earth metal hydrides (sodium hydride, potassium hydride, lithium hydride, calcium hydride, etc.), alkali metal or alkaline earth metal hydroxides (sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, etc.), alkali metal or alkaline earth metal carbonates (sodium carbonate, potassium carbonate, lithium carbonate, calcium carbonate, etc.), alkali metal bicarbonates (sodium bicarbonate, potassium bicarbonate, lithium bicarbonate, etc.), alkali metal or alkaline earth metal oxides (lithium oxide, sodium oxide, potassium oxide, Examples include calcium oxide, magnesium oxide), alkali metals, or alkaline earth metal halides (lithium fluoride, sodium fluoride, potassium fluoride, cesium fluoride, magnesium fluoride, calcium fluoride, cesium chloride, etc.), 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).

[0128] (e) Examples of tetraalkylammonium hydroxides include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, and tetra-n-butylammonium hydroxide.

[0129] 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 cyclic aldehyde (preferably a furfural derivative). Within these ranges, the hydrogenation reaction of the cyclic aldehyde proceeds sufficiently.

[0130] When a compound represented by the general formula (1) is used as the cyclic aldehyde (preferably a furfural derivative), a furfuryl alcohol compound represented by the general formula (2) below (a furfuryl alcohol compound which is a compound obtained by reducing the compound represented by the general formula (1)) is obtained. (In the formula, R 1 , R 2 and R 3 (This has the same meaning as above.)

[0131] The present invention includes embodiments that combine the above configurations in various ways, within the scope of the technical idea of ​​the present invention, as long as they achieve the effects of the present invention.

[0132] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited in any way by these examples, and many modifications can be made within the scope of the technical idea of ​​the present invention by those with ordinary skill in the art.

[0133] [Example 1: Nano-iron phosphate particles] <Example 1-1> Nano-iron phosphate particles were produced by the following method. First, 10 equivalents (molar equivalents) of triphenyl phosphite and 10 equivalents of hexadecylamine and Fe3(CO) were placed in a Schlenk tube. 12 The mixture was then stirred under vacuum conditions at 120°C for 30 minutes. Furthermore, the temperature was increased to 320°C at a rate of 50°C / min under an argon atmosphere and the mixture was reacted for 4 hours to obtain the mixed solution.

[0134] The mixture was cooled to room temperature, and the product was isolated as nano-ferrous phosphide particles by precipitation in acetone. The obtained nano-ferrous phosphide particles (nano-Fe2P) were evaluated by the following method.

[0135] <Electron Microscope Observation of Nano Iron Phosphate Particles> The nano iron phosphate particles obtained in Example 1-1 were observed using a field emission transmission electron microscope (product name "Tecnai® G2 20ST", acceleration voltage: 200 kV, manufactured by FEI (now Thermo Fisher Scientific (US))). The results are shown in Figure 1. From Figure 1, it was confirmed that rod-shaped nanoparticles were formed. Furthermore, it was confirmed that the maximum length in the longitudinal axis direction of the observed rod-shaped nano iron phosphate particles was approximately 60 nm.

[0136] <Powder X-ray Diffraction Measurement of Nano Iron Phosphate Particles> The nano iron phosphate particles obtained in Example 1-1 were subjected to X-ray diffraction measurement under atmospheric conditions using a fully automated multi-purpose X-ray diffractometer (product name "Philips X'PERT MPD diffractometer", manufactured by Philips Japan, Ltd.) with CuKα rays (λ: 1.5418 Å). Approximately 40 mg of the sample was placed on a glass sample plate, and X-ray diffraction measurement was performed under the following conditions without any pretreatment. The results are shown in Figure 2. [Measurement Conditions] Tube voltage: 45 kV Tube current: 40 mA Measurement temperature: Room temperature Measurement angle range: 30.00 to 60.00° Sampling interval: 0.013° Scan rate: 0.42° / min

[0137] As shown in Figure 2, in powder X-ray diffraction measurements using CuKα radiation under oxygen-containing conditions, the intensity of the peak corresponding to the (111) plane of Fe2P (diffraction angle (2θ): 40.1°) was observed as the maximum intensity for the nano-iron phosphide particles obtained in Example 1-1. From the results shown in Figure 2, it was confirmed that the nano-iron phosphide particles obtained in Example 1-1 are Fe2P.

[0138] [Example 2: Composite] <Example 2-1: Composite of nano-iron phosphide particles and Al2O3> A composite was prepared using the nano-iron phosphide particles produced in Example 1-1 and Al2O3 as a carrier. Specifically, the powder of nano-iron phosphide particles produced in Example 1-1 was dissolved in chloroform. Al2O3 (product name "JRC-ALO-8", spherical, BET specific surface area: 148 m²) was added to the mixture so that the mass ratio of nano-iron phosphide particles:Al2O3 was 1:25. 2 ( / g, manufactured by Sumitomo Chemical Co., Ltd.) was added and stirred at 25°C for 12 hours to disperse the nano-ferrous phosphate particles, thereby obtaining a composite of nano-ferrous phosphate particles and Al2O3.

[0139] <Example 2-2: Composite of Nano-Iron Phosphate Particles and ZrO2> A composite was prepared using the nano-iron phosphate particles produced in Example 1-1 and ZrO2 as a support. Specifically, ZrO2 (product name "JRC-ZRO-6", BET specific surface area: 279.3 m²) was used instead of Al2O3. 2A composite of nano-ferrous phosphide particles and ZrO2 as a support was prepared in the same manner as in Example 2-1, except that ZrO2 (manufactured by Daiichi Rare Elements Chemical Industry Co., Ltd.) was used as the support, including the mass ratio of the support to the nano-ferrous phosphide particles.

[0140] <Example 2-3: Composite of Nano-Iron Phosphate Particles and TiO2> A composite was prepared using the nano-iron phosphate particles produced in Example 1-1 and TiO2 as a support. Specifically, TiO2 (product name "JRC-TIO-16", BET specific surface area: 109.5 m²) was used instead of Al2O3. 2 A composite of nano-ferric phosphide particles and TiO2 as a support was prepared in the same manner as in Example 2-1, except that ( / g, manufactured by Nippon Aerosil Co., Ltd.) was used as the support, including the mass ratio of the support to the nano-ferric phosphide particles.

[0141] <Example 2-4: Composite of Nano-Iron Phosphate Particles and SiO2> A composite was prepared using the nano-iron phosphate particles produced in Example 1-1 and SiO2 as a support. Specifically, SiO2 (product name "CARiACT® Q-6", BET specific surface area: 400 m²) was used instead of Al2O3. 2 A composite of nanoferrous phosphide particles and SiO2 as a support was prepared in the same manner as in Example 2-1, including the mass ratio of the support to the nanoferrous phosphide particles, except that SiO2 (1 / g, manufactured by Fuji Silysia Chemical Co., Ltd.) was used as the support. The BET specific surface area of ​​the aforementioned supports (Al2O3, ZrO2, TiO2, and SiO2) can be measured using known methods and measuring devices (for example, the specific surface area and pore distribution analyzer, trade name "BELSORP MR1", BET 1-point method, manufactured by Microtrac-Bell Co., Ltd.).

[0142] [Example 3: Production of 5-methylfurfuryl alcohol] <Example 3-1> Using the nano-iron phosphide particles of Example 1-1 as a catalyst, 5-methylfurfural was hydrogenated to produce 5-methylfurfuryl alcohol. Specifically, 1.4 mg of the nano-iron phosphide particles of Example 1-1 (amount of Fe 0.019 mmol (7 mol% of Fe relative to 100 mol% of 5-methylfurfural)), 3 ml of methanol, 0.5 mmol of 5-methylfurfural, and hydrogen gas were placed in an autoclave under pressure to H2 = 4.5 MPa, heated to 150°C, and the reaction was carried out for 1 hour. The results are shown in Table 1 below.

[0143] <Examples 3-2 to 3-6> 5-methylfurfuryl alcohol was produced in the same manner as in Example 3-1, except that the type of catalyst used was changed to the composite produced in Examples 2-1 to 2-4, and the reaction conditions were changed as described in Table 1 below. The results are shown in Table 1 below.

[0144] <Comparative Example 3-1> 5-hydroxymethylfurfural was produced in the same manner as in Example 3-1, except that the type of catalyst used was changed as shown in Table 1 below. The results are shown in Table 1 below. The Fe / Al2O3 used in Comparative Example 3-1 was produced by the following method: 0.5 mmol of iron nitrate Fe(NO3)3·9H2O and 50 mL of water were added to a round-bottom flask and dispersed by stirring for 10 minutes. Al2O3 (1 g) was added to the dispersed iron nitrate aqueous solution as in Example 2-1 and stirred for 1 hour at room temperature and atmospheric pressure. After 1 hour, the solvent was evaporated using an evaporator. The obtained solid was calcined at 600°C for 2 hours under a hydrogen flow (H2: 10 mL / min, N2: 300 mL / min) to obtain Fe / Al2O3.

[0145]

[0146] As shown in Table 1, the nano-iron phosphide particles and composites of the present invention exhibited remarkably excellent catalytic activity as a catalyst for the hydrogenation of furfural derivatives. Unlike conventional iron nanoparticles with shielded surfaces, the nano-iron phosphide particles of the present invention are considered to possess catalytic activity because they have atmospheric stability and can maintain a low valence state even on the particle surface. Furthermore, the ability to produce composites of nano-iron phosphide particles with various supports (preferably Al2O3) at 25°C, and the fact that these composites exhibited catalytic activity, confirmed that the nano-iron phosphide particles have excellent atmospheric stability. Moreover, from the above results, it was confirmed that the catalyst for the hydrogenation of cyclic aldehydes of the present invention, in particular as a catalyst for the hydrogenation of furfural derivatives, can selectively reduce the formyl group of cyclic aldehydes, efficiently promote the selective hydrogenation reaction, and exhibit excellent catalytic activity.

[0147] The nano-phosphate iron particles and composites of the present invention are useful as catalysts for the hydrogenation of cyclic aldehydes (preferably furfural derivatives) in hydrogenation reactions of cyclic aldehydes (preferably furfural derivatives). In particular, they are useful as catalysts for the hydrogenation of cyclic aldehydes (preferably furfural derivatives) in methods for producing alcohol compounds (preferably furfuryl alcohol compounds).

Claims

1. A catalyst for the hydrogenation of cyclic aldehydes, containing nano-iron phosphide particles.

2. The catalyst for hydrogenating cyclic aldehydes according to claim 1, wherein the nano-iron phosphide particles are rod-shaped particles, and the maximum length in the longitudinal direction of the rod-shaped particles is less than 100 nm.

3. The catalyst for hydrogenation of a cyclic aldehyde according to claim 1 or 2, wherein the cyclic aldehyde is a furfural derivative.

4. The catalyst for hydrogenating cyclic aldehydes according to claim 1 or 2, further comprising a carrier, and comprising a composite composed of the nano-iron phosphide particles and the carrier, wherein the carrier is at least one selected from the group consisting of polymers, chalcogen compounds, metal compounds, metals, and solid carbon materials.

5. The catalyst for hydrogenation of cyclic aldehydes according to claim 4, wherein the support comprises Al2O3.

6. The catalyst for hydrogenation of cyclic aldehydes according to claim 1 or 2, wherein the nano-iron phosphide particles are Fe2P.

7. A method for producing an alcohol compound, comprising hydrogenating a cyclic aldehyde in a hydrogen atmosphere in the presence of a catalyst for hydrogenation of cyclic aldehydes as described in claim 1 or 2 to obtain an alcohol compound.

8. A method for producing an alcohol compound according to claim 7, wherein the cyclic aldehyde is heated during the reaction.

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

10. A method for producing an alcohol compound according to claim 7, wherein the reaction is carried out in the presence of a solvent.

11. The method for producing an alcohol compound according to claim 7, wherein the cyclic aldehyde is a furfural derivative and the alcohol compound is a furfuryl alcohol compound.

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