Method for producing aromatic aminomethyl

Abstract

The present invention provides a method for producing an aromatic aminomethyl, wherein an aromatic nitrile is hydrogenated in an organic solvent that contains a polar organic solvent having a solubility parameter (SP value) of 9 or more in the presence of a quaternary ammonium compound, at least one metal hydroxide that is selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and a hydrogenation catalyst.

Description

[Technical field]

[0001] The present invention relates to a method for producing aromatic aminomethyl nitriles by hydrogenating aromatic nitriles. [Background technology]

[0002] Aromatic aminomethyls are useful as raw materials or intermediates for medicines, agricultural chemicals, resins, hardeners, etc. In particular, xylylenediamine, which has two aminomethyl groups, is a very useful compound as a raw material for polyamide resins, hardeners, etc., and as an intermediate for isocyanates.

[0003] A method for producing aromatic aminomethyl compounds is to hydrogenate aromatic nitriles. In the hydrogenation of aromatic nitriles, a method using liquid ammonia as a solvent is known. However, from the viewpoint of environmental friendliness, it is necessary to recover the liquid ammonia after the hydrogenation reaction without releasing it to the outside, which imposes a large burden on production. Therefore, various studies have been conducted on production methods that do not use liquid ammonia. For example, Patent Document 1 discloses a method for producing aromatic cyanoaminomethyl, which is one type of aromatic aminomethyl, by hydrogenating an aromatic nitrile in the presence of an alcohol and a tetraalkylammonium hydroxide using a palladium catalyst, with the aim of producing aromatic cyanoaminomethyl, which is one type of aromatic aminomethyl, in high yield under mild reaction conditions without using liquid ammonia and through simple reaction procedures while suppressing the by-production of aromatic diaminomethyl. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2002-205980 A Summary of the Invention [Problem to be solved by the invention]

[0005] Aromatic aminomethyl esters of extremely high purity are required for use as raw materials for polyamide resins, curing agents, etc., and as intermediates for isocyanates, and there has been a demand for a method for obtaining aromatic aminomethyl esters in high yields without using liquid ammonia. In addition, the method of Patent Document 1 does not use liquid ammonia and can perform hydrogenation under mild reaction conditions, but the problem is that the resulting aromatic aminomethyl contains impurities, which inhibit polymerization when the aromatic aminomethyl is used as a raw material for polyamide resins, etc., as described above. Therefore, there is a need for a synthesis method that can achieve high yields and minimize the generation of impurities. Therefore, an object of the present invention is to provide a production method which can obtain aromatic aminomethyl in high yield without substantially using liquid ammonia and which can suppress the formation of impurities. [Means for solving the problem]

[0006] As a result of intensive research, the present inventors have found that the above-mentioned problems can be solved by hydrogenating an aromatic nitrile in a specific solvent in the presence of a quaternary ammonium compound and a specific metal hydroxide. That is, the present invention provides a method for producing an aromatic aminomethyl compound, comprising hydrogenating an aromatic nitrile in the presence of at least one metal hydroxide selected from the group consisting of a quaternary ammonium compound, an alkali metal hydroxide, and an alkaline earth metal hydroxide, and a hydrogenation catalyst, in an organic solvent containing a polar organic solvent having a solubility parameter (SP value) of 9 or more. Effect of the Invention

[0007] According to the production method of the present invention, aromatic aminomethyl can be obtained in high yield without substantially using liquid ammonia, and the formation of impurities can be suppressed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The method for producing an aromatic aminomethyl compound of the present invention comprises hydrogenating an aromatic nitrile in an organic solvent containing a polar organic solvent having a solubility parameter (SP value) of 9 or more in the presence of at least one metal hydroxide selected from the group consisting of a quaternary ammonium compound, an alkali metal hydroxide and an alkaline earth metal hydroxide, and a hydrogenation catalyst. The production method of the present invention will be described in detail below.

[0009] [Organic solvents] The organic solvent used in the present invention contains a polar organic solvent having a solubility parameter (SP value) of 9 or more. In the production method of the present invention, it is believed that by using a polar organic solvent having an SP value of 9 or more, the product aromatic aminomethyl is distributed into the polar organic solvent, allowing the hydrogenation reaction to proceed efficiently. The organic solvent used in the present invention may consist only of the polar organic solvent. However, it is considered that the use of a nonpolar organic solvent having an SP value of less than 9 in addition allows the aromatic nitrile and hydrogen, which are raw materials, to be dissolved well, and the hydrogenation reaction to be carried out efficiently. The non-polar organic solvent having an SP value of less than 9 is not particularly limited, but is preferably a hydrocarbon solvent. Each solvent is described below.

[0010] (Polar organic solvents with a solubility parameter (SP value) of 9 or more) The polar organic solvent used in the present invention has a solubility parameter (SP value) of 9 or more, preferably 10 or more, more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more. The upper limit is preferably 20 or less, more preferably 17 or less, and even more preferably 15 or less. The SP value in the present invention is a value determined by the following Hildebrand solubility parameter formula.

[0011] Solubility parameter (SP value) = (ΔH A V -RT) 0.5 / V A 0.5 ΔH A V : Enthalpy of vaporization of liquid A (polar organic solvent) R: gas constant T: Temperature V A : Molar volume of liquid A

[0012] The polar organic solvent used in the present invention is at least one selected from alcohols, esters, amides, sulfoxides, ketones and amines, with alcohols being preferred. The alcohol may be a monohydric alcohol or a polyhydric alcohol, with the monohydric alcohol being preferred. The monohydric alcohol may be an aliphatic alcohol or an aromatic alcohol, with the aliphatic alcohol being preferred. The aliphatic alcohol preferably has 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 1 or 2 carbon atoms, from the viewpoint of industrial availability. Specific examples of aliphatic alcohols include methanol (SP value 14.5), ethanol (SP value 12.7), n-propanol (SP value 11.9), isopropanol (SP value 11.5), n-butanol (SP value 11.4), sec-butanol (SP value 10.8), tert-butanol (SP value 10.6), pentanol, hexanol (SP value 10.7), heptanol (SP value 10.6), n-octanol (SP value 10.3), and the like. Of these, one or more selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, and n-butanol are preferred, one or more selected from the group consisting of methanol and ethanol are more preferred, and methanol is even more preferred.

[0013] (Hydrocarbon Solvent) The organic solvent used in the present invention preferably further contains a hydrocarbon solvent. The hydrocarbon solvent is at least one selected from aromatic hydrocarbon solvents and aliphatic hydrocarbon solvents, with aromatic hydrocarbon solvents being preferred. The solubility parameter (hereinafter also referred to as SP value) of the hydrocarbon solvent is preferably less than 9. The lower limit is preferably 7.0 or more, more preferably 8.0 or more. When the hydrocarbon solvent is an aromatic hydrocarbon solvent, it is considered that the raw materials, the aromatic nitrile and hydrogen, are well dissolved, and the hydrogenation reaction can be carried out efficiently. In addition, it is considered that the SP value being less than 9 also allows the raw materials, the aromatic nitrile and hydrogen, to be well dissolved, and the hydrogenation reaction can be carried out efficiently.

[0014] When the hydrocarbon solvent is an aromatic hydrocarbon solvent, the aromatic hydrocarbon solvent preferably has 7 to 12 carbon atoms, more preferably 7 to 9 carbon atoms, and even more preferably 8 to 9 carbon atoms. Specific examples of aromatic hydrocarbon solvents include monocyclic aromatic hydrocarbon compounds such as toluene, ethylbenzene, three isomers of xylene (o-xylene, m-xylene, p-xylene), mesitylene, pseudocumene, and the like, and polycyclic aromatic hydrocarbon compounds such as naphthalene and methylnaphthalene, and monocyclic aromatic hydrocarbon compounds are preferred. Among these, xylene and mesitylene are more preferred, xylene (SP value 8.8) is even more preferred, m-xylene and p-xylene are even more preferred, and m-xylene is even more preferred, from the viewpoint of good dissolution of aromatic nitrile and hydrogen as raw materials and industrial availability.

[0015] (Composition of organic solvent) The organic solvent in the present invention refers to all liquid compounds (all liquid organic compounds) contained in the solution during the hydrogenation reaction, excluding the aromatic nitrile as a raw material and the aromatic aminomethyl as a product. As described above, the organic solvent used in the present invention may consist of only a polar organic solvent, but it is preferable to further use a non-polar organic solvent having an SP value of less than 9. The non-polar organic solvent having an SP value of less than 9 is not particularly limited, but is preferably a hydrocarbon solvent. When the organic solvent contains a hydrocarbon solvent and a polar organic solvent, the mass ratio of the hydrocarbon solvent to the polar organic solvent in the organic solvent (hydrocarbon solvent / polar organic solvent) is preferably 60 / 40 to 99 / 1, more preferably 70 / 30 to 99 / 1, more preferably 80 / 20 to 99 / 1, and even more preferably 82 / 18 to 99 / 1. By using a larger amount of the hydrocarbon solvent than the polar organic solvent, the concentration of nitriles dissolved in the hydrocarbon solvent decreases, making it difficult to generate high boiling point substances on the catalyst. The total content of the hydrocarbon solvent and the polar organic solvent in the organic solvent is preferably from 90 to 100% by mass, more preferably from 95 to 100% by mass, and even more preferably from 99 to 100% by mass. The content of water in the organic solvent is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less. By making the content of water 5% by mass or less, it is believed that side reactions with the raw material can be suppressed and the yield of the product can be improved. It is preferable that the organic solvent does not substantially contain water, and the lower limit value may be 0% by mass. In addition, the organic solvent of the present invention preferably does not substantially contain liquid ammonia, and more preferably does not contain liquid ammonia. By not containing liquid ammonia, the load during production for recovering ammonia can be reduced.

[0016] The difference in SP value between the hydrocarbon solvent and the polar organic solvent in the organic solvent is preferably 0.5 or more, more preferably 1.0 or more, even more preferably 2.0 or more, and even more preferably 4.0 or more, and is preferably 12 or less, more preferably 10 or less, even more preferably 8 or less, and even more preferably 6 or less.

[0017] The combination of the hydrocarbon solvent and the polar organic solvent in the organic solvent is preferably a monocyclic aromatic hydrocarbon compound and an alcohol, more preferably a xylene and an aliphatic alcohol having 1 or 2 carbon atoms, and further preferably m-xylene and methanol.

[0018] (Quaternary ammonium compounds) In the method for producing an aromatic aminomethyl compound of the present invention, a quaternary ammonium compound and at least one metal hydroxide selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides are used as the alkaline compound. By using a quaternary ammonium compound and a metal hydroxide at the same time, aromatic aminomethyl can be obtained in high yield and the generation of impurities can be suppressed. The reason why aromatic aminomethyl can be obtained in high yield and the generation of impurities can be suppressed is not clear, but it is thought to be as follows. Quaternary ammonium compounds are essential compounds for obtaining aromatic aminomethyl esters stably and in high yields without causing corrosion of reaction vessels or catalyst deterioration, but they react with aromatic aminomethyl esters during distillation to produce impurities. Since hydroxides of alkali metals or alkaline earth metals inhibit the reaction that produces these impurities, it is believed that the combined use of alkali metals or the like contributes to the reduction of impurities. Furthermore, since quaternary ammonium salts act preferentially on the catalyst during the reaction, it is believed that the yield is improved while reducing the catalyst deterioration caused by alkali metals and alkaline earth metals.

[0019] The quaternary ammonium compound used in the present invention includes tetraalkylammonium hydroxide and tetraalkylammonium organic acid. It is preferable to use one or more selected from these, and among these, tetraalkylammonium hydroxide is more preferable.

[0020] Examples of the tetraalkylammonium hydroxide include tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetrabutylammonium hydroxide. Of these, tetramethylammonium hydroxide and tetraethylammonium hydroxide are preferred, and from the viewpoint of suppressing impurities, tetraethylammonium hydroxide is more preferred. Examples of the organic acid tetraalkylammonium include tetraalkylammonium phenoxide, fatty acid tetraalkylammonium, and tetraalkylammonium tetraphenylborate. The fatty acid tetraalkylammonium includes tetramethylammonium acetate.

[0021] The amount of the quaternary ammonium compound is preferably 0.1 to 10 mmol, more preferably 0.2 to 5 mmol, and even more preferably 0.5 to 1 mmol, relative to 1 g of the hydrogenation catalyst. Also, the amount is preferably 1 to 20 mass % relative to the hydrogenation catalyst, more preferably 3 to 10 mass %, and even more preferably 5 to 10 mass %. By using the quaternary ammonium compound in the above amount, the catalyst does not deteriorate, the reaction rate is maintained, and the target aromatic aminomethyl can be obtained in a high yield. Also, when the amount is 20 mass % or less relative to the hydrogenation catalyst, the amount of water carried over can be suppressed even when the quaternary ammonium compound is used in an aqueous solution.

[0022] (metal hydroxide) The metal hydroxide used in the present invention is at least one selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides, and among these, alkali metal hydroxides are preferred. The alkali metal hydroxide is preferably at least one selected from the group consisting of sodium hydroxide and potassium hydroxide, and among these, sodium hydroxide is more preferable. The alkaline earth metal hydroxide is preferably at least one selected from the group consisting of calcium hydroxide and magnesium hydroxide, and among these, calcium hydroxide is more preferable. That is, the metal hydroxide is preferably one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, and among these, one or more selected from the group consisting of sodium hydroxide, potassium hydroxide, and calcium hydroxide is more preferable, one or more selected from the group consisting of sodium hydroxide and potassium hydroxide is even more preferable, and sodium hydroxide is even more preferable.

[0023] The amount of metal hydroxide is preferably 0.1 to 10 mmol, more preferably 0.2 to 5 mmol, and even more preferably 0.5 to 1 mmol, relative to 1 g of hydrogenation catalyst. Also, it is preferably 1 to 20 mass % relative to the hydrogenation catalyst, more preferably 3 to 10 mass %, and even more preferably 5 to 10 mass %. It is considered that by using the metal hydroxide in the above amount, impurities are suppressed, the reaction rate is maintained, and the target aromatic aminomethyl can be obtained in a high yield. Also, when the amount is 20 mass % or less relative to the hydrogenation catalyst, the amount of water carried over can be suppressed even when the metal hydroxide is used in an aqueous solution.

[0024] The molar ratio of the quaternary ammonium compound to the metal hydroxide (quaternary ammonium compound / metal hydroxide) is preferably 70 / 30 to 20 / 80, more preferably 60 / 40 to 30 / 70, more preferably 50 / 50 to 35 / 65, and even more preferably 45 / 55 to 40 / 60. This range is preferable because aromatic aminomethyl can be obtained in high yield, the catalyst deterioration rate is small, the catalyst can be used repeatedly, and impurities can be sufficiently reduced.

[0025] (Hydrogenation catalyst) The hydrogenation catalyst used in the production method of the present invention is not limited as long as it is a catalyst used for hydrogenating an organic compound, but a metal catalyst is preferred. Examples of metals contained in the metal catalyst include cobalt, nickel, palladium, and platinum, and one or more selected from cobalt and nickel are preferred, and cobalt is more preferred. That is, a metal catalyst containing one or more selected from cobalt, nickel, palladium, and platinum is preferred, a metal catalyst containing one or more selected from nickel and cobalt is more preferred, and a metal catalyst containing cobalt is even more preferred. By using a cobalt catalyst, it is possible to suppress the generation of high boiling point substances on the catalyst, improve the yield, and reduce the deterioration of the catalyst. Examples of the metal catalyst containing at least one selected from nickel and cobalt include supported metal catalysts and sponge metal catalysts, with sponge metal catalysts being preferred. Examples of the metal-supported catalyst include catalysts in which one or more selected from nickel and cobalt are supported on Al2O3, SiO2, diatomaceous earth, SiO2-Al2O3, and ZrO2 by a precipitation method. Examples of sponge metal catalysts include catalysts made by dissolving some components from an alloy of two or more components (nickel, cobalt, aluminum, iron, copper, etc.) using an acid or alkali, and sponge cobalt catalysts and sponge nickel catalysts are preferred, and sponge cobalt catalysts are more preferred. The above catalysts may be used alone or in combination of two or more. The amount of the catalyst is preferably 0.1 to 100 parts by mass, more preferably 1 to 50 parts by mass, and further preferably 10 to 20 parts by mass, relative to 100 parts by mass of the aromatic nitrile. By using the catalyst in the above amount, the yield of the obtained aromatic aminomethyl can be increased.

[0026] (Aromatic Nitriles) The aromatic nitrile used as a raw material in the production method of the present invention has a nitrile group bonded to an aromatic ring (benzene ring), and the number of nitrile groups is preferably 1 or 2, and more preferably 2. In addition, other substituents may be bonded to the aromatic ring. Specific aromatic nitriles include benzonitrile and dicyanobenzene, with dicyanobenzene being preferred. Dicyanobenzene exists in three isomers: phthalonitrile (1,2-dicyanobenzene), isophthalonitrile (1,3-dicyanobenzene), and terephthalonitrile (1,4-dicyanobenzene). Of these, isophthalonitrile and terephthalonitrile are preferred, with terephthalonitrile being more preferred. The concentration of the aromatic nitrile during the hydrogenation reaction is preferably 2 to 30% by mass in the reaction solution, more preferably 5 to 25% by mass, and further preferably 7 to 20% by mass. The reaction solution does not contain a catalyst. The reaction solution contains a raw material, an organic solvent, liquid components other than the organic solvent such as water, a quaternary ammonium compound, and a metal hydroxide. The concentration of the aromatic nitrile during the hydrogenation reaction can be calculated as a concentration relative to the total mass of the components constituting the homogeneous solution when blended in the method for producing aromatic aminomethyl that will be described later. In other words, the concentration of the aromatic nitrile during the hydrogenation reaction can be calculated as a concentration relative to the total mass of the aromatic nitrile as a raw material, the organic solvent used in the hydrogenation reaction, liquid components other than the organic solvent such as water, a quaternary ammonium compound, and a metal hydroxide when blended.

[0027] (Aromatic aminomethyl) The aromatic aminomethyl obtained by the production method of the present invention has an aminomethyl group bonded to an aromatic ring (benzene ring), and the number of aminomethyl groups is preferably 1 or 2, and more preferably 2. In addition, other substituents may be bonded to the aromatic ring. Specific examples of the aromatic aminomethyl include benzylamine and xylylenediamine, with xylylenediamine being preferred. Xylylene diamine exists in three isomers, namely, ortho-xylylene diamine, meta-xylylene diamine, and para-xylylene diamine. Of these, meta-xylylene diamine and para-xylylene diamine are preferred, with para-xylylene diamine being more preferred. These xylylenediamine isomers can be obtained by the production process of the present invention using the corresponding dicyanobenzene as a raw material.

[0028] (Production method of aromatic aminomethyl) The method for producing an aromatic aminomethyl compound of the present invention involves hydrogenating an aromatic nitrile in an organic solvent containing a polar organic solvent having a solubility parameter (SP value) of 9 or more in the presence of at least one metal hydroxide selected from the group consisting of a quaternary ammonium compound, an alkali metal hydroxide and an alkaline earth metal hydroxide, and a hydrogenation catalyst.

[0029] In the present production method, the order of mixing the raw materials is not particularly limited, and it is preferable to place the organic solvent, the quaternary ammonium compound, the metal hydroxide, and the hydrogenation catalyst in a pressure vessel and then introduce hydrogen. In order to prevent the hydrogenation catalyst from containing water or gases other than hydrogen, such as air, it is preferable to add the hydrogenation catalyst as a catalyst slurry by immersing the catalyst in water and then replacing the water with the organic solvent. The reaction in the present production method can be carried out in either a batch system or a flow system, with the batch system being preferred.

[0030] In the present invention, the raw material hydrogen used for hydrogenation does not need to be particularly purified, and may be of industrial grade. The hydrogen pressure during the reaction is preferably 2.0 to 20.0 MPa, more preferably 3.0 to 15.0 MPa, and even more preferably 5.0 to 10.0 MPa. When the hydrogen pressure is within the above range, the product yield is sufficient, and a high-pressure resistant reactor is not required, which is preferable for reducing costs. The reaction temperature is preferably 20 to 150° C., more preferably 50 to 130° C., and further preferably 60 to 120° C. Within this range, the conversion rate of the aromatic dinitrile as the raw material is good and the production of by-products is suppressed, thereby improving the yield. The reaction time varies depending on the reaction temperature, hydrogen pressure, etc., but under the above conditions, it is usually 0.1 to 100 hours, and preferably 0.5 to 10 hours.

[0031] The obtained aromatic aminomethyl can be recovered by a known method. For example, it is preferable to separate the gaseous component and the liquid component from the reaction mixture at the end of the reaction, filter off the solid components such as the catalyst, and recover the liquid component by distillation. It is also preferable to further distill the obtained aromatic aminomethyl to increase the purity. EXAMPLES

[0032] The present invention will be described in detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, composition analysis was performed using a gas chromatograph.

[0033] <Gas chromatography (GC) analysis conditions> The gas chromatography analysis was carried out under the following conditions. Equipment used: Gas chromatograph Nexis GC-2030 (Shimadzu Corporation) Column: DB-1 (length 30 m, inner diameter 0.53 mm, film thickness 1.5 μm) Detector: FID (H2 30mL / min, Air 300mL / min) Carrier gas: He (constant flow; average linear velocity 38 cm / sec) Split ratio: 28.1 Inlet temperature: 300℃ Detector temperature: 300℃ Injection volume: 1.0μL Oven temperature: The oven was heated from 50°C to 150°C at 5°C / min, and after reaching 150°C, the oven was heated to 280°C at 10°C / min and held there for 7 minutes. The oven was then heated to 300°C at 10°C / min and held there for 5 minutes.

[0034] <Conversion rate and yield> The conversion rate of the raw material (terephthalonitrile) and the yield of the product (paraxylenediamine) were calculated from the amounts of the raw material and the product in the reaction mixture after the hydrogenation reaction obtained in the Examples and Comparative Examples, which were measured by the internal standard method using gas chromatography. Since diphenylmethane was used as the internal standard, a calibration curve was prepared in advance using solutions of terephthalonitrile and paraxylenediamine of known concentrations. A sample was prepared by adding 0.5 g of diphenylmethane to 5.0 g of the reaction mixture, and the sample was subjected to gas chromatography under the above-mentioned conditions, and the conversion rate and yield were calculated by the following formulas. Conversion rate (mol%) = [1 - (amount of terephthalonitrile in the reaction mixture [mol]) / (amount of terephthalonitrile at the time of charging [mol])] × 100 Yield (mol%) = (amount of paraxylenediamine in the reaction mixture [mol]) / (amount of terephthalonitrile at the time of charging [mol]) × 100

[0035] <Impurity concentration> The impurity concentration was calculated from the amount of impurities relative to the amount of the product after distillation obtained in the examples and comparative examples. The impurity concentration was measured by the simple area method using gas chromatography. The area of ​​the impurities was defined as the sum of the areas of the peaks having the same retention time as those of the main components of the impurities, 1-(4-(aminomethyl)phenyl)-N-methylmethanamine and 1-(4-(aminomethyl)phenyl)-N-ethylmethanamine (total area of ​​N-alkylated compounds), and the area of ​​the product was defined as the area of ​​all peaks excluding the dilution solvent (area of ​​the product). The impurity concentration was calculated by the following formula. Impurity concentration (%) = (total area of ​​N-alkylated substances) / (area of ​​product) x 100

[0036] <Example 1> (Preparation of catalyst slurry) The following procedure was carried out using a 50 mL beaker. 5.90 g of Raney cobalt catalyst (sponge cobalt catalyst) (RANEY2724, manufactured by W.R. Grace) was placed in 30 mL of water, left to stand to allow the catalyst to settle, and the supernatant was removed by decantation. Next, 30 mL of methanol was added and stirred for 1 minute, after which the supernatant was removed in the same manner. The above-mentioned replacement with methanol was repeated five times to prepare a methanol slurry of the catalyst.

[0037] (Hydrogenation reaction) A 500 mL autoclave vessel was charged with a methanol slurry of the catalyst (catalyst amount 5.90 g) and adjusted so that the total mass of methanol was 39.5 g. Then, 51.8 g of terephthalonitrile, 197.3 g of m-xylene, 0.76 g of 25% aqueous tetramethylammonium hydroxide solution (2.1 mmol, 0.19 g as tetramethylammonium hydroxide), and 0.084 g (2.1 mmol) of sodium hydroxide were charged. Nitrogen replacement was performed by pressurizing the inside of the reactor with nitrogen up to 0.5 MPa and then returning it to atmospheric pressure. This nitrogen replacement was performed three times in total, and then hydrogen replacement was performed three times in total using the same method. The hydrogen pressure was set to 8.0 MPa, and the temperature was raised to 100°C while stirring at 1200 rpm, and the reaction was carried out under the condition of 100°C while maintaining 8.0 MPa while supplying hydrogen. The reaction was terminated when hydrogen was no longer consumed. After the reaction was completed, the reaction mixture was cooled to 50°C, and then pressure-filtered at a pressure of 0.4 MPa to filter out the catalyst and obtain a reaction mixture containing the reaction product, paraxylenediamine. The same hydrogenation reaction was carried out two more times, and the reaction mixtures from the three reactions were mixed and combined into one to obtain a reaction mixture to be used for distillation and measurement and calculation of the conversion rate and yield. The above-mentioned conversion rate and yield were calculated using this reaction mixture.

[0038] (distillation) Paraxylylenediamine was rectified using a glass jacketed distillation column (distillation plate number: 10 plates). The reaction mixture was charged into a three-neck flask. The distillation was carried out in the following four stages (1) to (4). The impurity concentrations were determined using the product obtained after the distillation. (1) Pressure: 760 torr, reflux ratio: 5, bottom temperature: 74°C → 149°C, top temperature: starting temperature 64°C. The reaction was stopped when the top temperature reached 139°C. (2) Pressure: 300 torr, reflux ratio: 1, bottom temperature: starting temperature 115°C, top temperature: 108°C. The reaction was terminated when the bottom temperature reached 170°C. (3) Pressure: 10 torr, reflux ratio: 15, bottom temperature: 123° C. to 142° C., top temperature: 139° C. The reaction was terminated when 10% by mass of the initial reaction mixture was distilled off. (4) Pressure: 10 torr, reflux ratio: 1, bottom temperature: starting temperature 142°C, top temperature: 139°C. The reaction was terminated when the bottom temperature reached 155°C.

[0039] <Example 2> Except for using 0.67 g of 35% tetraethylammonium hydroxide aqueous solution (1.6 mmol, 0.19 g as tetraethylammonium hydroxide) instead of 25% tetramethylammonium hydroxide aqueous solution and changing the amount of sodium hydroxide to 0.096 g (2.4 mmol), the same operation as in Example 1 was carried out to carry out three hydrogenation reactions to obtain a reaction mixture. The reaction mixture was used to determine the conversion rate and yield. In addition, the reaction mixture was used to carry out distillation in the same manner as in Example 1 to obtain a product. The impurity concentration was determined using the product obtained after distillation.

[0040] <Comparative Example 1> The same operation as in Example 1 was carried out except that sodium hydroxide was not used, and the hydrogenation reaction was carried out three times to obtain a reaction mixture. The reaction mixture was used to determine the conversion rate and yield. The reaction mixture was also used to perform distillation in the same manner as in Example 1 to obtain a product. The impurity concentration was determined using the product obtained after distillation.

[0041] [Table 1]

[0042] From the results in Table 1, it is understood that by using the production method of the Example, paraxylylenediamine can be obtained in high yield, and further, the impurity concentration in the product is low, and the generation of impurities can be suppressed.

Claims

1. A method for producing an aromatic aminomethyl ester, comprising the steps of: hydrogenating an aromatic nitrile in the presence of at least one metal hydroxide selected from the group consisting of a quaternary ammonium compound, an alkali metal hydroxide, and an alkaline earth metal hydroxide, and a hydrogenation catalyst, in an organic solvent containing a polar organic solvent having a solubility parameter (SP value) of 9 or more, wherein the polar organic solvent is at least one selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, and n-butanol, and the organic solvent further contains a hydrocarbon solvent.

2. 2. The method for producing an aromatic aminomethyl ester according to claim 1, wherein the quaternary ammonium compound is at least one selected from the group consisting of tetraalkylammonium hydroxide and tetraalkylammonium organic acid.

3. The method for producing an aromatic aminomethyl ester according to claim 1 or 2, wherein the metal hydroxide is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide.

4. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 3, wherein a mass ratio of the hydrocarbon solvent to the polar organic solvent in the organic solvent (hydrocarbon solvent / polar organic solvent) is 60 / 40 to 99 / 1.

5. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 4, wherein the total amount of the hydrocarbon solvent and the polar organic solvent in the organic solvent is 90 to 100 mass%.

6. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 5, wherein the hydrogenation catalyst is a metal catalyst containing at least one selected from nickel and cobalt.

7. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 6, wherein the amount of the quaternary ammonium compound is 1 to 20% by mass relative to the hydrogenation catalyst.

8. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 7, wherein the amount of the metal hydroxide is 1 to 20 mass% based on the hydrogenation catalyst.

9. The method for producing aromatic aminomethyl according to any one of claims 1 to 8, wherein the molar ratio of the quaternary ammonium compound to the metal hydroxide (quaternary ammonium compound / metal hydroxide) is 70 / 30 to 20 / 80.

10. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 9, wherein the hydrocarbon solvent is an aromatic hydrocarbon solvent.

11. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 10, wherein the organic solvent does not contain liquid ammonia.

12. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 11, wherein the content of water in the organic solvent is 5 mass% or less.

13. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 12, wherein the aromatic nitrile is dicyanobenzene.

14. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 13, wherein the aromatic nitrile is terephthalonitrile.

15. The method for producing an aromatic aminomethyl ester according to any one of claims 1 to 14, wherein the aromatic aminomethyl ester is xylylenediamine.

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