Reductive amination catalyst

Abstract

To provide a ruthenium-based reductive amination catalyst having both high activity and high selectivity.SOLUTION: A reductive amination catalyst used for producing a primary amine by a reductive amination reaction using a carbonyl compound containing one or more carbonyl groups as a raw material, wherein the reductive amination catalyst includes catalyst particles composed of phosphorized ruthenium.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to reductive amination catalysts, and more particularly to catalysts used for the reductive amination of carbonyl compounds containing one or more carbonyl groups to form the corresponding primary amines. [Background technology]

[0002] Primary amines are widely used as intermediates and are important compounds in the production of various chemical products, such as resins, functional materials, pharmaceuticals, pesticides, and dyes. While these primary amines can be produced by various methods, the reductive amination of carbonyl compounds with ammonia and hydrogen is known to be an efficient method because it produces no by-products other than water. Therefore, various metal catalysts have been developed for use in reductive amination reactions.

[0003] Until now, precious metal catalysts, such as ruthenium and rhodium, have been mainly used as reductive amination catalysts using hydrogen as a reducing agent. In recent years, non-precious metal cobalt has been investigated as a reductive amination catalyst, and a method for synthesizing isophoronediamine from isophoronenitrile using a catalyst with metallic cobalt as the active component and activated carbon as the support has been proposed.

[0004] For example, Patent Document 1 discloses that a primary amine was synthesized by reacting a raw material compound containing a carbonyl group with hydrogen and nitrogen using Co / SiO2 or Ru / Nb2O5 as a reductive amination catalyst. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2021-177219 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the ruthenium catalysts developed to date have problems such as insufficient activity, the need for high-pressure hydrogen reaction conditions to efficiently promote the reaction, and low selectivity for the target product, primary amine. Therefore, there is still a strong demand for the development of a ruthenium catalyst that combines high activity and selectivity.

[0007] Therefore, an object of the present invention is to provide a ruthenium-based reductive amination catalyst that combines high activity and selectivity. [Means for solving the problem]

[0008] As a result of extensive research aimed at achieving the above object, the inventors have discovered that by converting a portion of the ruthenium catalyst particles into ruthenium phosphide (RuP), the reaction efficiency and selectivity can be dramatically improved when used as a reductive amination catalyst. The present invention is based on this finding. Specifically, the gist of the present invention is as follows.

[0009] [1] A reductive amination catalyst comprising catalyst particles made of ruthenium phosphide. [2] The reductive amination catalyst according to [1], wherein the catalyst particles are supported on a catalyst support. [3] The reductive amination catalyst according to [2], wherein the catalyst support comprises an inorganic support or a carbon support. [4] The reductive amination catalyst according to [3], wherein the catalyst particles have an average particle size of 0.1 to 1000 nm. [5] The reductive amination catalyst according to [1], wherein the catalyst particles have a phosphorus content of 10 to 90 mass % and a ruthenium content of 10 to 90 mass %. [6] The reductive amination catalyst according to [1], which is used to produce a primary amine by reductive amination using a carbonyl compound containing one or more carbonyl groups as a raw material. [Effects of the Invention]

[0010] According to the ruthenium-based reductive amination catalyst of the present invention, by converting a portion of the ruthenium catalyst particles into ruthenium phosphide (Ru2P), reaction efficiency and selectivity are dramatically improved when used as a reductive amination catalyst. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 shows the results of XRD evaluation of Ru2P / C prepared in the example. [Figure 2] FIG. 2 is a TEM image of Ru2P / C prepared in the example. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Reductive amination catalyst] The reductive amination catalyst according to the present invention is used to produce a primary amine by a reductive amination reaction using, for example, a carbonyl compound containing one or more carbonyl groups as a raw material, and includes catalyst particles made of ruthenium phosphide. In the present invention, "supported" catalyst particles refers to a state in which the catalyst particles are physically or chemically adsorbed or held on the outer surface or the inner pore surfaces of a support. Each of the components of the reductive amination catalyst according to the present invention will now be described.

[0013] <Catalyst particles> The reductive amination catalyst of the present invention contains catalyst particles made of ruthenium phosphide. Although the reason for the improved catalytic activity and selectivity in reductive amination reactions compared to conventional ruthenium catalysts is unclear, it is presumed that the ligand effect caused by the charge transfer from the ruthenium atom to the phosphorus atom due to the conversion of some of the ruthenium particles to ruthenium phosphide (RuP) improves the catalytic activity for reductive amination, while suppressing the activity for the side reaction of carbonyl hydrogenation, thereby improving selectivity.

[0014] The content of phosphorus in the catalyst particles is preferably 10 to 90 mass%, more preferably 20 to 80 mass%, and even more preferably 25 to 75 mass%. The content of ruthenium in the catalyst particles is preferably 10 to 90 mass%, more preferably 20 to 80 mass%, and even more preferably 25 to 75 mass%. That is, the ratio of ruthenium to phosphorus in the catalyst particles is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and even more preferably 75:25 to 25:75, by mass.

[0015] Ruthenium phosphide catalyst particles can be obtained by known methods, for example, as a precipitate from a mixed solution of a ruthenium compound solution and a phosphorus compound solution. Examples of methods for obtaining such precipitates include the method described in a literature (Junfeng Liu and Andreu Cabot et al., J. Mater. Chem. A, 2018, 6, 11453-11462). More specifically, a method can be used in which a ruthenium compound salt, a component that inhibits particle growth (i.e., particle size increase) during reduction of the ruthenium compound salt (hereinafter also referred to as a "particle growth inhibiting component"), a solvent, and a phosphorus compound that is easily soluble in the solvent are heated and maintained in an inert gas atmosphere.

[0016] The ruthenium compound salt is not particularly limited, but is preferably one that is easy to handle. Examples of such ruthenium compound salt include ruthenium chloride and hexaammineruthenium chloride.

[0017] Examples of particle growth inhibitors include those described in JP-A-2014-514451. More specifically, examples include one or more capping components selected from the group consisting of compounds having an amino group, such as propylamine, butylamine, octylamine, decylamine, dodecylamine, hexadecylamine, and oleylamine.

[0018] The solvent is not particularly limited, but examples thereof include water, aliphatic saturated hydrocarbons such as hexane, toluene, n-decane, n-dodecane, n-hexadecane, and n-octadecane; and aliphatic unsaturated hydrocarbons such as 1-undecene, 1-dodecene, 1-hexadecene, and 1-octadecene, with hexane, toluene, and n-dodecane being preferred.

[0019] The phosphorus compound that is easily soluble in the solvent is not particularly limited, but is preferably one that is easy to handle. Examples of such phosphorus compounds include tertiary phosphites such as triphenyl phosphite and tertiary phosphines such as triphenylphosphine. "Easily soluble in the solvent" means that the phosphorus compound can be completely dissolved in the solvent at a heating temperature below the temperature at which the catalyst particle precipitate is formed, and preferably can dissolve 14 g / L or more of the phosphorus compound at 100°C. Those skilled in the art can select a compound that meets these properties by appropriately changing the type of solvent and phosphorus compound.

[0020] The amounts of the ruthenium compound salt, the particle growth inhibiting component, and the phosphorus compound that is easily soluble in the solvent used are usually 0.1 to 10 mol, preferably 1 to 5 mol, of the platinum group compound salt, usually 1 to 100 mol, preferably 10 to 50 mol, of the particle growth inhibiting component, and usually 1 to 100 mol, preferably 10 to 50 mol, of the phosphorus compound.

[0021] The following conditions can be used for heating and maintaining the mixture in an inert gas atmosphere. Examples of inert gas include argon and nitrogen. The heating temperature is usually 250 to 350°C, preferably 280 to 320°C, and the maintenance time is about 2 to 6 hours. A precipitate can be obtained by heating and maintaining the mixture. The precipitate may be washed and filtered. After washing and filtration, the mixture may be further dried.

[0022] For the purpose of promoting the action of the reductive amination catalyst according to the present invention, a salt of a metal component such as nickel, manganese, copper, iron, chromium, or molybdenum may be added in place of a portion of the ruthenium compound salt.

[0023] Ruthenium phosphide in the catalyst particles obtained as described above can be identified by comparing the peaks measured by X-ray diffraction (XRD) with known peaks. For example, ruthenium phosphide has the peaks described in Liu, T. et al., "A Highly Efficient Hydrogen Evolution Reaction Electrocatalyst in Both Acidic and Alkaline Media", Chem. Commun., 2018, 54, 3343-3346.

[0024] <Catalyst carrier> In the present invention, the catalyst particles themselves can be used as the reductive amination catalyst. However, it is preferable to use the catalyst particles supported on a catalyst carrier, as this facilitates separation of the catalyst from the reaction system, may improve the durability of the catalyst, and is expected to enable reuse, which is industrially advantageous.

[0025] The catalyst carrier capable of supporting catalyst particles is not particularly limited, and various catalyst carriers having a large specific surface area and widely used for catalyst applications can be used. The specific surface area of the catalyst carrier can be appropriately changed depending on the type of catalyst carrier. For example, in the case of silica, the specific surface area is 200 to 600 m 2 / g is preferred.

[0026] Examples of catalyst supports include inorganic supports. Examples of inorganic supports include carbon supports such as activated carbon, fine particles of metal oxides such as alumina, silica, titania, ceria, zirconia, and magnesia, inorganic oxide supports such as combinations of these metal oxides, and composite oxide supports of fine particles such as hydroxyapatite (HAP) and hydrotalcite (HT). Among these, carbon supports such as activated carbon are preferred. Note that the term "fine particles" used here refers to particles with a larger particle size than the catalyst particles they support, and examples include powders with a particle size of about 10 to 100 μm on a volume basis and spherical particles with a particle size of about 0.5 to 5 mm.

[0027] The method for supporting catalyst particles on a catalyst support is not particularly limited, and examples thereof include a method in which the catalyst support is charged into a solution containing a ruthenium compound salt or a phosphorus compound used when preparing ruthenium phosphide, and the catalyst support is impregnated with the ruthenium compound salt or the phosphorus compound, and then reduction, drying, or calcination is performed to support the ruthenium phosphide catalyst particles on the catalyst support; a method in which the catalyst support is impregnated with a solution in which ruthenium phosphide catalyst particles are dispersed; and a method in which the solution in which ruthenium phosphide catalyst particles are dispersed is mixed with the catalyst support.

[0028] As one embodiment of a method for supporting catalyst particles on a catalyst support, a method will be described in which the catalyst support is introduced into a solution containing a ruthenium compound salt and a phosphorus compound used in preparing ruthenium phosphide, the ruthenium compound salt and the phosphorus compound are impregnated into the catalyst support, and then reduction, drying, and calcination are carried out to support ruthenium phosphide on the catalyst support.

[0029] First, the catalyst carrier is added to an aqueous solution of a ruthenium halide compound (ruthenium chloride, hexaammineruthenium chloride), etc., and the mixture is stirred and then dried under reduced pressure. Next, the resulting catalyst precursor is heated and further dried, and then added to an aqueous solution of a phosphorus compound. After stirring the aqueous solution, it is dried under reduced pressure and heated and maintained at 500 to 600°C under hydrogen reflux. In this way, the catalyst particles can be supported on the catalyst carrier.

[0030] The shape of the catalyst particles of the reductive amination catalyst of the present invention is not particularly limited and may be cylindrical or spherical. The average particle size of the catalyst particles is preferably 0.1 to 1000 nm, more preferably 0.5 to 500 nm, and even more preferably 1 to 300 nm. The average particle size is a value calculated by observing approximately 200 particles with an electron microscope such as a transmission electron microscope and averaging the observation results.

[0031] In the present invention, the catalyst particles made of ruthenium phosphide are used as a reductive amination catalyst, i.e., to produce primary amines by reductive amination of a carbonyl compound containing one or more carbonyl groups as a raw material, but they may also be used in other reactions. Below, we will explain a method for producing primary amines from carbonyl compounds containing one or more carbonyl groups using the ruthenium-based reductive amination catalyst of the present invention.

[0032] [Method of producing primary amines] A method for producing a primary amine by reductive amination using the ruthenium-based reductive amination catalyst of the present invention will be described. More specifically, the method comprises reacting a compound represented by the general formula (I): [ka] (In the formula, R1 and R2 each independently represent a hydrogen atom, an aryl group which may be substituted with a substituent, or an alkyl group which may be substituted with a substituent, with the proviso that R1 and R2 may be bonded to each other to form a ring.) From a carbonyl compound represented by general formula (II): [ka] (In the formula, R1 and R2 have the same meanings as above.) A primary amine represented by the formula:

[0033] In the present invention, the term "aryl group" refers to, for example, a phenyl group, a naphthalen-1-yl group, a naphthalen-2-yl group, a pyridinyl group (a pyridin-2-yl group, a pyridin-3-yl group, a pyridin-4-yl group), a pyrimidinyl group (a pyrimidin-2-yl group, a pyrimidin-4-yl group, a pyrimidin-5-yl group), a furanyl group (a furan-2-yl group, a furan-3-yl group), a thienyl group (a thiophen-2-yl group, a thiophen-3-yl group), a pyrrolyl group (a pyrrol-2-yl group, a pyrrol-3-yl group), and the like.

[0034] In the present invention, the "alkyl group" includes, for example, 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, and the like.

[0035] In the present invention, the "substituent" in the "aryl group which may be substituted by a substituent" and the "alkyl group which may be substituted by a substituent" includes, for example, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, a trifluoromethyl group, a hydroxymethyl group, etc.

[0036] R1 and R2 in general formula (I) and general formula (II) may be a hydrogen atom, an aryl group which may be substituted with a substituent, or an alkyl group which may be substituted with a substituent, but preferably one is a hydrogen atom and the other is an aryl group which may be substituted with a substituent, more preferably one is a hydrogen atom and the other is a phenyl group which may be substituted with a substituent or a furanyl group which may be substituted with a substituent, and even more preferably one is a hydrogen atom and the other is a furanyl group.

[0037] R and R in general formula (I) and general formula (II) may be bonded to each other to form a ring. Specific examples of the ring to be formed include, but are not limited to, cycloalkanes such as cyclopentane, cyclohexane, and cycloheptane, aryl-fused cycloalkanes such as indane and tetralin, and heterocyclic compounds such as tetrahydrofuran, tetrahydropyran, pyrrolidine, piperidine, coumaran, chroman, indoline, and tetrahydroquinoline.

[0038] Preferred examples of the carbonyl compound represented by general formula (I) include aromatic ketone compounds such as acetophenone, and aromatic aldehyde compounds such as furfural. Preferred examples of the amine represented by general formula (II) include 1-phenylethylamine and furfurylamine.

[0039] The reducing agent can be a hydrogen-donating compound commonly used in reductive amination reactions, and examples thereof include hydrogen molecules, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, 1-pentanol, cyclopentyl alcohol, 1-hexanol, cyclohexyl alcohol, benzyl alcohol, formic acid, sodium formate, potassium formate, lithium formate, and ammonium formate. Of these, it is preferable to use hydrogen molecules.

[0040] The amount of the reducing agent used may be 1 to 30 equivalents relative to the carbonyl compound.

[0041] The amount of catalyst used is not particularly limited, but can be, for example, 20 to 60 mg, or 30 to 50 mg, per 1 mmol of the carbonyl compound represented by general formula (I).

[0042] The step of obtaining the amine represented by general formula (II) from the carbonyl compound represented by general formula (I) is preferably carried out at low temperature and low hydrogen pressure. For example, the temperature can be 100° C. or less, 90° C. or less, 80° C. or less, 70° C. or less, or 60° C. or less. The hydrogen pressure can be 1.0 MPa or less, 0.9 MPa or less, 0.8 MPa or less, 0.7 MPa or less, or 0.6 MPa or less. [Example]

[0043] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples in any way as long as the gist of the invention is not exceeded. In other words, the materials, amounts used, proportions, treatment contents, treatment procedures, etc. shown in the following examples can be changed as appropriate as long as they do not deviate from the spirit of the present invention.

[0044] [Preparation of catalyst particles] <Preparation of activated carbon-supported ruthenium phosphide nanoparticles (Ru2P / C)> Ruthenium chloride (Ru: 0.08 g) was dissolved in distilled water (50 mL), and activated carbon (0.91 g, manufactured by Osaka Gas Chemicals) was added. While heating and stirring in an 80°C oil bath, 1 M NaOH aqueous solution was added dropwise to adjust the pH to approximately 11.5. After adjusting the pH, the mixture was heated and stirred in an 80°C oil bath for 12 hours. After cooling, the solid component (activated carbon supporting ruthenium) was recovered by filtration, washed with distilled water until the pH of the filtrate became neutral, and then dried overnight in a dryer at 110°C. The solid after drying was in the form of a powder. Next, 0.028 g of ammonium hypophosphite (NH4H2PO2) was dissolved in 50 mL of distilled water, and the dried powder (0.5 g) was added and stirred at room temperature for 1 hour. The water was removed using a rotary evaporator, and the remaining solid component was dried overnight in a dryer at 60 °C. The dried solid was in powder form. The resulting powder was heat-treated for 1 hour at 550 °C (heating rate: 5 °C / min) under a flow of H2 (100 mL / min) to obtain the desired activated carbon-supported ruthenium phosphide nanoparticles (Ru2P / C).

[0045] When the Ru2P / C obtained as described above was evaluated by XRD, peaks specific to ruthenium phosphide were observed, indicating that it contained orthorhombic Ru2P (Figure 1). The XRD evaluation was performed using an X-ray diffractometer (trade name "X'Pert-MPD diffractometer", manufactured by Philips) by irradiating it with Cu-Kα characteristic X-rays (45 kV, 40 mA).

[0046] Furthermore, transmission electron microscopy of the obtained Ru2P / C revealed that Ru2P particles with an average particle size of 5.3 nm were highly dispersed and fixed on the activated carbon support (Figure 2: area surrounded by the white dotted line). The average particle size was calculated from the average value (n=200) of catalyst particles in a transmission electron microscope photograph taken at an accelerating voltage of 200 kV using a transmission electron microscope (FEI Tecnai G2 20 ST).

[0047] Furthermore, elemental analysis of the obtained Ru2P / C revealed that the amounts of Ru and P contained in Ru2P / C were 7.04% by mass and 1.85% by mass, respectively. For elemental analysis, Ru2P / C was dissolved as much as possible by acid treatment and microwave treatment, and the Ru and P contained in Ru2P / C were quantified by a standard method using an inductively coupled plasma optical emission spectrometer (Optima 8300, manufactured by Perkin Elmer).

[0048] <Preparation of silica-supported ruthenium phosphide nanoparticles (Ru2P / SiO2)> This was prepared based on the method described in the literature (T. Mitsudome et al., JACS Au, 2022, 2, 419-427; T. Mitsudome et al., ACS Catal., 2023, 13, 5744-5751). First, ruthenium chloride (Ru: 0.08 g) was dissolved in distilled water (50 mL), and SiO2 (0.91 g, CAriACT G-6, Fuji Silysia) was added. After stirring at room temperature for 1 hour, the water was removed using a rotary evaporator, and the remaining solid component was dried overnight in a dryer at 110 °C. The dried solid was in the form of a powder. Next, 0.027 g of ammonium hypophosphite (NH4H2PO2) was dissolved in 50 mL of distilled water, and the dried powder (0.5 g) was added and stirred at room temperature for 1 hour. The water was removed using a rotary evaporator, and the remaining solid component was dried overnight in a dryer at 60 °C. The dried solid was in powder form. The resulting powder was heat-treated for 1 hour at 550 °C (heating rate: 5 °C / min) under a flow of H2 (100 mL / min) to obtain the desired silica-supported ruthenium phosphide nanoparticles (Ru2P / SiO2).

[0049] XRD analysis of Ru2P / SiO2, performed in the same manner as above, revealed peaks characteristic of ruthenium phosphide, indicating the presence of orthorhombic Ru2P. Transmission electron microscopy, performed in the same manner as above, revealed that highly dispersed Ru2P particles with an average particle size of 2.9 nm were fixed onto the silica particles used as the support. Elemental analysis, performed in the same manner as above, revealed that the amounts of Ru and P contained in Ru2P / SiO2 were 7.07% by mass and 1.68% by mass, respectively.

[0050] For reference, the following six types of supported ruthenium catalysts were prepared. <Preparation of activated carbon-supported ruthenium nanoparticles (Ru / C)> Activated carbon-supported ruthenium nanoparticles (Ru / C) were obtained in the same manner as above, except that the operation of supporting ammonium hypophosphite in the preparation of Ru2P / C was not carried out.

[0051] <Preparation of silica-supported ruthenium nanoparticles (Ru / SiO2)> Silica-supported ruthenium nanoparticles (Ru / SiO2) were obtained in the same manner as above, except that the operation of supporting ammonium hypophosphite in the preparation of Ru2P / SiO2 was not carried out.

[0052] <Preparation of alumina-supported ruthenium nanoparticles (Ru / Al2O3)> Ruthenium chloride (Ru: 0.08 g) was dissolved in distilled water (50 mL) and Al2O3 (0.91 g [JRC-ALO-9: Reference Catalyst from the Catalysis Society of Japan]) was added. While heating and stirring in an 80 °C oil bath, 1 M NaOH aqueous solution was added dropwise to adjust the pH to approximately 11.5. After adjusting the pH, the mixture was heated and stirred in an 80 °C oil bath for 12 hours. After cooling, the solid component (ruthenium-loaded Al2O3) was collected by filtration, washed with distilled water until the filtrate reached a neutral pH, and then dried overnight in a dryer at 110 °C. The dried solid was in powder form. The resulting powder was heat-treated for 1 hour at 550 °C (heating rate: 5 °C / min) under a flow of H2 (100 mL / min). This gave the desired Ru / Al2O3.

[0053] <Preparation of Ruthenium Nanoparticles Supported on TiO2 (Ru / TiO2)> Al2O3 (0.91 g (JRC-ALO-9: distributed as a reference catalyst by the Catalysis Society)) was changed to TiO2 (JRC-TIO-17: distributed as a reference catalyst by the Catalysis Society), and the target Ru / TiO2 was obtained in the same manner as above.

[0054] <Preparation of Ruthenium Nanoparticles Supported on ZrO2 (Ru / ZrO2)> Al2O3 (0.91 g (JRC-ALO-9: distributed as a reference catalyst by the Catalysis Society)) was changed to ZrO2 (JRC-ZRO-7: distributed as a reference catalyst by the Catalysis Society), and the target Ru / ZrO2 was obtained in the same manner as above.

[0055] <Preparation of Ruthenium Nanoparticles Supported on Nb2O5 (Ru / Nb2O5)> Al2O3 (0.91 g (JRC-ALO-9: distributed as a reference catalyst by the Catalysis Society)) was changed to Nb2O5 (JRC-NBO-2: distributed as a reference catalyst by the Catalysis Society), and the target Ru / Nb2O5 was obtained in the same manner as above.

[0056] [Examples 1 - 2, Comparative Examples 1 - 6] Using acetophenone as the carbonyl compound, the reductive amination reaction was used as a model reaction, and the activities of the eight prepared catalysts were evaluated. The reaction conditions were as follows: 0.5 mmol of acetophenone was dissolved in 2 mL of 1,4-dioxane, the catalyst was added at a ratio of 2.5 mol%, the reaction temperature was 100 °C, the hydrogen pressure was 3 bar, the ammonia pressure was 2 bar, and the reaction time was 1 hour. The conversion rate of acetophenone was calculated using a GC-MS apparatus (trade name "GCMS-QP2010 SE", manufactured by Shimadzu Corporation). Also, the yields of the 2a compound and the 3a compound were calculated by a conventional method using a GC-MS apparatus.

Chemical formula

[0057] The evaluation results are shown in Table 1 below. [Table 1]

[0058] As is clear from the evaluation results in Table 1, Ru / C (Comparative Example 1) showed almost no activity in the target reductive amination reaction, and a large amount of alcohol (compound 3a) was produced as a by-product. On the other hand, Ru2P / C (Example 1) of the present invention selectively promoted reductive amination, and the target amine (compound 2a) was obtained in 59% yield. These results demonstrate that phosphidation of ruthenium significantly improves catalytic activity and selectivity for reductive amination reactions. Furthermore, Ru2P / C (Example 1) exhibits higher activity and selectivity than Ru2P / SiO2 (Example 2). Furthermore, Ru2P / C (Example 1) exhibits higher activity than ruthenium catalysts prepared using typical metal oxide supports (Comparative Examples 2 to 6).

[0059] [Examples 3 to 23] Reductive amination of various carbonyl compounds was carried out using the Ru2P / C used in Example 1. 0.5 mmol of the carbonyl compound was dissolved in 2 mL of 1,4-dioxane, and Ru2P / C was added at a ratio of 2.5 mol %. The reaction temperature was 100°C, the hydrogen pressure was 3 bar, and the ammonia pressure was 2 bar. Using a GC system (trade names "GC-2014" and "Nexis GC2030", both manufactured by Shimadzu Corporation) and the above-mentioned GC-MS system, the yield of the product (primary amine) was calculated by a standard method. In Examples 4 and 9, the hydrogen pressure was 0.6 bar and the ammonia pressure was 0.4 bar; in Examples 12, 13, 15, 21, and 22, 2 mL of methanol was used instead of 2 mL of 1,4-dioxane, the reaction temperature was 50°C, and the ammonia pressure was 7 bar; in Example 18, 5 mL of methanol was used instead of 2 mL of 1,4-dioxane, the reaction temperature was 50°C, and the ammonia pressure was 7 bar; and in Example 19, 0.5 mmol of carbonyl compound was changed to 0.25 mmol. In Examples 19, 20, 21, and 23, the yield of primary amine was calculated by H-NMR using the internal standard method. The results are shown in Tables 2 and 3.

[0060] [Table 2]

[0061] [Table 3]

[0062] It has been found that the reductive amination catalyst containing catalyst particles made of ruthenium phosphide of the present invention exhibits good activity and selectivity in the reductive amination reaction of various carbonyl compounds (ketones and aldehydes), and the corresponding primary amines can be obtained in high yields (Examples 3 to 23). Although Ru2P / C requires higher pressure of NH3 than ketones, it was also applicable to the reductive amination of aldehydes (Examples 12, 13, 15, 18, 21, and 22). Ru2P / C also showed activity under a H2:NH3 mixed gas atmosphere at 1 atm (Examples 4 and 9).

[0063] Furthermore, it was found that Ru2P / C can also be applied to sulfur-containing carbonyl compounds (Examples 14, 15, 20-23). It is generally known that sulfur-containing organic compounds act as catalyst poisons and deactivate metal nanoparticle catalysts. On the other hand, the reductive amination catalyst of the present invention, which contains catalyst particles made of ruthenium phosphide, was not deactivated by sulfur and efficiently promoted the reductive amination of sulfur-containing carbonyl compounds under mild conditions.

[0064] This catalytic reaction system can also be applied to the synthesis of 1-(1-naphthyl)ethylamine, a synthetic intermediate for cinacalcet, a calcium receptor agonist (Example 16), and 3-(1-aminoethyl)phenyl ethyl(methyl)carbamate, a synthetic intermediate for rivastigmine, an acetylcholinesterase inhibitor (Example 19).

Claims

1. A reductive amination catalyst comprising catalyst particles composed of ruthenium phosphide.

2. The reductive amination catalyst according to claim 1, wherein the catalyst particles are supported on a catalyst carrier.

3. The reductive amination catalyst according to claim 2, wherein the catalyst carrier includes an inorganic carrier or a carbon carrier.

4. The reductive amination catalyst according to claim 1, wherein the average particle diameter of the catalyst particles is 0.1 to 1000 nm.

5. The reductive amination catalyst according to claim 1, wherein the content of phosphorus element in the catalyst particles is 10 to 90% by mass, and the content of ruthenium element is 10 to 90% by mass.

6. The reductive amination catalyst according to claim 1, which is used for producing a primary amine by a reductive amination reaction using a carbonyl compound containing one or more carbonyl groups as a raw material.

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