JP4972387B2 - Method for producing aliphatic nitrile - Google Patents

Description

  The present invention relates to a method for producing an aliphatic nitrile and a method for producing an aliphatic amine from the aliphatic nitrile produced by the method.

As a method for producing an aliphatic nitrile, a method in which an aliphatic carboxylic acid or a derivative thereof is reacted with ammonia is generally known industrially. As a reaction form, there are a gas phase method and a liquid phase method. As the reaction by the liquid phase method, a method in which an aliphatic carboxylic acid or a derivative thereof is heated and dissolved in the presence of a catalyst and ammonia gas is blown into the reaction to react in a batch or continuous manner is widely performed. .
When reacting by such a liquid phase method, for example, a method for producing an aliphatic nitrile using zinc oxide or an iron compound as a catalyst is known. In addition, a method for producing an aliphatic nitrile using, as a catalyst, an oxide in which an oxide of one or more elements selected from the group consisting of silicon, niobium, zirconium, tantalum, gallium, and germanium is combined with titanium oxide (Patent Document 1). 2), or a method for producing an aliphatic nitrile using titanium oxide supported on solid silica as a catalyst (see Patent Document 3).
However, in recent years, higher reactivity is also required in the above production method.

Japanese Unexamined Patent Publication No. 2000-80069 JP 2000-80070 A JP 2005-89361 A

  An object of the present invention is to provide a method for producing an aliphatic nitrile that is highly reactive and industrially advantageous, and a method for producing an aliphatic amine using the aliphatic nitrile as a raw material.

The present invention
(1) In the presence of at least one metal compound selected from the group consisting of zinc, cobalt, titanium, and aluminum and a sulfonic acid, an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, and an alkyl ester thereof (of an alkyl group) A method for producing an aliphatic nitrile by reacting ammonia with at least one selected from the group consisting of 1 to 5 carbon atoms, and (2) a method for producing an aliphatic amine having the following steps:
(B) A step of obtaining an aliphatic nitrile by the production method described in (1) above (b) A step of hydrogenating the obtained aliphatic nitrile in the presence of a hydrogenation catalyst.

  According to the present invention, an aliphatic nitrile can be obtained with high reactivity, and an aliphatic amine can be obtained at a low production cost by using the aliphatic nitrile as a raw material.

<Method for producing aliphatic nitrile>
The method for producing an aliphatic nitrile according to the present invention comprises an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, and an aliphatic carboxylic acid in the presence of at least one metal compound selected from the group consisting of zinc, cobalt, titanium, and aluminum and a sulfonic acid. Ammonia is reacted with at least one selected from the group consisting of these alkyl esters (the alkyl group has 1 to 5 carbon atoms).
The compound of at least one metal selected from the group consisting of zinc, cobalt, titanium and aluminum used in the present invention is such that the counter ion inhibits the reaction in the production method of the present invention, and the yield of aliphatic nitrile is reduced. The metal oxide is selected from the viewpoint of not lowering, and the metal oxide, hydroxide, carbonate, nitrate, sulfate, alkoxide, carboxylate, acetylacetonate and the like can be preferably exemplified. . In particular, the metal oxide, hydroxide, carboxylate or alkoxide is preferable. In addition, as the at least one metal selected from the group consisting of zinc, cobalt, titanium, and aluminum, zinc, aluminum, and titanium are preferable, and zinc and aluminum are more preferable from the viewpoint of reducing the catalyst cost for production. It is done.
These metal compounds can be used alone or in combination of two or more.

Examples of the sulfonic acids used in the present invention include aryl sulfonic acids and alkyl sulfonic acids which may be substituted with an alkyl group.
As the aryl sulfonic acid that may be substituted with an alkyl group, benzene sulfonic acid, or a mono-, di-, or tri-alkylated benzene sulfonic acid having a linear or branched alkyl group having 1 to 22 carbon atoms, Alternatively, naphthalene monosulfonic acid or polysulfonic acid can be mentioned, and the smaller the molecular weight, the smaller the amount of reaction charged. From the viewpoint of reducing the residue when purifying the product by distillation, it preferably has a linear alkyl group A monoalkyl benzene sulfonic acid is mentioned.

Examples of the alkyl sulfonic acid include a linear or branched alkyl monosulfonic acid or alkyl disulfonic acid having an alkyl group having 1 to 22 carbon atoms. From the viewpoint of the reactivity of the sulfonic acid, the alkyl sulfonic acid is preferably straight. A chain alkyl monosulfonic acid, more preferably an alkyl sulfonic acid in which some or all of the hydrogen atoms in the alkyl chain are substituted with halogens can be mentioned. Specific examples of halogen include fluorine, chlorine, bromine and iodine, with fluorine being preferred.
Specific examples of the sulfonic acids include benzenesulfonic acid, toluenesulfonic acid, p-ethylbenzenesulfonic acid, n-propylbenzenesulfonic acid, n-butylbenzenesulfonic acid, n-hexylbenzenesulfonic acid, octylbenzenesulfonic acid, n- Dodecylbenzenesulfonic acid, cetylbenzenesulfonic acid, octadecylbenzenesulfonic acid, triisobutylbenzenesulfonic acid, n-butylnaphthalenesulfonic acid, n-octanesulfonic acid, n-dodecylsulfonic acid, octadecylsulfonic acid, trifluoromethanesulfonic acid, 1 -Perfluorobutanesulfonic acid, 1-perfluorohexanesulfonic acid, 1-perfluorooctanesulfonic acid and the like can be mentioned. From the viewpoint of reactivity of sulfonic acids, preferably toluenesulfone P-ethylbenzenesulfonic acid, n-propylbenzenesulfonic acid, n-butylbenzenesulfonic acid, n-hexylbenzenesulfonic acid, trifluoromethanesulfonic acid, 1-perfluorobutanesulfonic acid, 1-perfluorohexanesulfonic acid. it can.

  In the present invention, in the presence of the metal compound and sulfonic acid, at least one selected from the group consisting of aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, and alkyl esters thereof (the alkyl group has 1 to 5 carbon atoms) It reacts with ammonia. The aliphatic monocarboxylic acid, aliphatic dicarboxylic acid or alkyl ester thereof (the alkyl group has 1 to 5 carbon atoms) used in the present invention is a linear or branched aliphatic group having 6 to 22 carbon atoms. Examples thereof include monocarboxylic acids, linear or branched aliphatic dicarboxylic acids having 6 to 22 carbon atoms, or alkyl esters of these aliphatic carboxylic acids (the alkyl group has 1 to 5 carbon atoms). Is an aliphatic monocarboxylic acid having 8 to 22 carbon atoms or an alkyl ester thereof (the alkyl group has 1 to 5 carbon atoms). Moreover, as said aliphatic monocarboxylic acid, aliphatic dicarboxylic acid, or these alkylesters, any of a saturated thing and an unsaturated thing can be used.

  The number of carbon atoms of the alkyl group of the alkyl ester is preferably within the above range from the viewpoint of the usefulness of the resulting nitrile. Specific examples of the alkyl group having 1 to 5 carbon atoms include methyl, ethyl, propyl, isopropyl and the like. From the above viewpoint, a methyl group is particularly preferable. These aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, or alkyl esters thereof (the alkyl group has 1 to 5 carbon atoms) can be used alone or in combination of two or more.

Specific examples of the aliphatic monocarboxylic acid and the aliphatic dicarboxylic acid include caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, dimethyloctanoic acid, butyl hepetylno Nanic acid, hexenoic acid, octenoic acid, decenoic acid, dodecenoic acid, tetradecenoic acid, hexadecenoic acid, octadecenoic acid, eicosenic acid, docosenoic acid, adipic acid, azelaic acid, sebacic acid, decamethylene dicarboxylic acid, hexadecamethylene dicarboxylic acid, Octadecamethylene dicarboxylic acid and the like can be mentioned, and aliphatic monocarboxylic acids are preferred from the viewpoints of reactivity and selectivity.
Specific examples of the aliphatic carboxylic acid alkyl ester (the alkyl group has 1 to 5 carbon atoms) include esters of the above aliphatic monocarboxylic acid or aliphatic dicarboxylic acid such as methyl, ethyl, propyl, and isopropyl. Of these, methyl and ethyl esters are preferred from the same viewpoint as described above.

In the present invention, ammonia to be reacted with at least one selected from the group consisting of the above aliphatic monocarboxylic acids, aliphatic dicarboxylic acids and their alkyl esters (alkyl group having 1 to 5 carbon atoms) is used in an aliphatic amount. In terms of reactivity and selectivity, 1 to 300 mol, more preferably 2 to 100 mol, and even more preferably 2 to 50 mol per 1 mol of monocarboxylic acid, aliphatic dicarboxylic acid or alkyl ester thereof. is there.
In the compound and sulfonic acid of at least one metal selected from the group consisting of zinc, cobalt, titanium and aluminum serving as a catalyst, the amount of the metal compound used is an aliphatic monocarboxylic acid from the viewpoint of catalyst activity and nitrile yield. 0.01-20 mass% is preferable with respect to an acid, aliphatic dicarboxylic acid, or these alkylesters, More preferably, it is 0.05-15 mass%, More preferably, it is the range of 0.05-10 mass%.

  The amount of sulfonic acids used is preferably 0.01 equivalents or more and less than 1 equivalent, more preferably 0.05 to 0.6 equivalents, more preferably from the viewpoint of catalytic activity, with respect to 1 equivalent of the metal. 0.1 to 0.3 equivalents. In particular, in the case of reacting ammonia with at least one selected from the group consisting of unsaturated aliphatic monocarboxylic acids, unsaturated aliphatic dicarboxylic acids or their alkyl esters, from the reaction product by catalytic activity, distillation, etc. From the viewpoint of the yield of nitrile, the amount of the sulfonic acid is preferably within the above range.

The method for producing the aliphatic nitrile of the present invention can be carried out by any of a batch system, a semi-batch system, a continuous system and a fixed bed flow system using a suspension bed.
In the production method using the batch or semi-batch method, the aliphatic monocarboxylic acid, the aliphatic dicarboxylic acid and / or their alkyl ester are dissolved, a predetermined amount of catalyst is charged, and the reaction tank is sufficiently purged with nitrogen. A method of injecting ammonia gas after raising the temperature to the reaction temperature can be used.
In the production method using the continuous type and fixed bed flow type, the catalyst is charged, and after heating up to the reaction temperature, the dissolved aliphatic monocarboxylic acid, aliphatic dicarboxylic acid or their alkyl ester and ammonia gas are introduced. The method can be used.

The reaction pressure is preferably performed in a slightly pressurized state, but may be performed at normal pressure. The reaction temperature is preferably 180 to 400 ° C, more preferably 230 to 370 ° C, and still more preferably 250 to 360 ° C, from the viewpoints of reactivity and selectivity.
Further, the method for separating and purifying the target aliphatic nitrile from the reaction solution obtained in the reaction step is not particularly limited, but known methods such as concentration, distillation, extraction, crystallization, recrystallization, column chromatography and the like are known. Separation and purification can be performed by a method or separation means combining these methods.

<Method for producing aliphatic amine>
In the method for producing an aliphatic amine of the present invention, an aliphatic nitrile is produced by the above production method (step (ii)), and the resulting aliphatic nitrile is used as a raw material, and a hydrogenation reaction is carried out in the presence of a hydrogenation catalyst. (Step (b))
As the hydrogenation catalyst used in the step (b), a known hydrogenation catalyst such as a cobalt-based catalyst, a nickel-based catalyst, a copper-based catalyst, or a noble metal-based catalyst can be used. From the viewpoint of reactivity and selectivity, preferably, a catalyst mainly composed of nickel, cobalt, and / or ruthenium can be used, more preferably a Raney catalyst or silica, alumina, silica alumina, diatomaceous earth, activated carbon, etc. A catalyst supported on a porous metal oxide is used. Further, it may contain a metal such as aluminum, zinc or silicon. These hydrogenation catalysts can contain a metal selected from chromium, iron, cobalt, manganese, tungsten, and molybdenum as a reaction accelerator.

The hydrogenation catalyst can be used as a complete solid catalyst, but a supported solid catalyst such as nickel, cobalt, ruthenium, etc. supported on aluminum oxide, titanium oxide, zirconium oxide, magnesia / alumina, etc. can also be used. it can.
The amount of the hydrogenation catalyst used in the present invention is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass, based on the aliphatic nitrile, from the viewpoint of reactivity and selectivity.
The reaction pressure is preferably a hydrogen pressure of 0.1 to 5 MPaG, more preferably 0.5 to 4 MPaG, and even more preferably 0.8 to 3 MPaG. The reaction temperature is preferably 50 to 200 ° C., more preferably 80 to 170 ° C., and still more preferably 100 to 140 ° C. from the viewpoint of reactivity and selectivity. The reaction is performed continuously or stepwise during the hydrogenation reaction. It is preferable to raise the temperature.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
A four-necked separable flask equipped with a stirrer, a gas introduction tube, a thermometer, and a dehydrator was charged with hardened beef tallow fatty acid (main composition: C14 = 3.8%, C16 = 28.7%, C18 = 61.9). %) 500 g, zinc oxide 0.5 g (based on 0.10% by mass of fatty acid) and p-toluenesulfonic acid monohydrate 0.59 g (0.12% by mass (based on fatty acid), 0.25 equivalent (based on zinc) ) And stirred at 500 r / m. 1000 ml of ammonia gas was passed through the solution from 210 ° C. per minute, the temperature was raised to 300 ° C., and the reaction was carried out at this temperature.
The reaction product obtained 3 hours after the circulation of ammonia gas was subjected to gas chromatography [gas chromatograph: HEWLETT PACKARD Series 6890, column: HP-5 manufactured by J & W Scientific (column inner diameter x length: 0.25 mm x 60 m ), The column temperature is maintained at an initial value of 120 ° C. for 2 minutes, and the temperature is increased to 300 ° C. at a heating rate of 8 ° C./min, and then maintained at 300 ° C. for 5.5 minutes. The amount of hard beef tallow nitrile produced was measured by composition analysis. The results are shown in Table 1. The reaction end time is the time from when ammonia gas is circulated until the amount of aliphatic amide produced is below the detection limit in the gas chromatography measurement.

Comparative Example 1
In Example 1, the reaction was performed in the same manner as in Example 1 except that only zinc oxide was used without adding p-toluenesulfonic acid monohydrate, and the reaction product was analyzed in the same manner as in Example 1. The results are shown in Table 1.

Examples 2-4
In Example 1, instead of hardened beef tallow fatty acid, distilled beef tallow fatty acid (main composition: C16 = 27.1%, C16: 1 = 2.4%, C18 = 21.3%, C18: 1 = 36.9% , C18: 2 = 2.3%) using 500 g, and using cobalt stearate, aluminum hydroxide or tetraisopropoxytitanium in place of zinc oxide, respectively, and using the amounts shown in Table 1, respectively, and p -The reaction was conducted in the same manner as in Example 1 except that the amount of toluenesulfonic acid monohydrate used was as shown in Table 1, and the reaction product was analyzed in the same manner as in Example 1. The results are shown in Table 1.

Comparative Examples 2-4
In Comparative Example 1, 500 g of distilled beef tallow fatty acid was used instead of hardened beef tallow fatty acid, and cobalt stearate, aluminum hydroxide or tetraisopropoxytitanium was used instead of zinc oxide, respectively. The reaction was conducted in the same manner as in Comparative Example 1 except that the reaction product was analyzed in the same manner as in Comparative Example 1. The results are shown in Table 1.

＊脂肪族モノカルボン酸、脂肪族ジカルボン酸又はこれらのアルキルエステルに対する質量％。

* Mass% based on aliphatic monocarboxylic acid, aliphatic dicarboxylic acid or their alkyl ester.

Example 5
In Example 1, 500 g of distilled beef tallow fatty acid was used instead of hardened beef tallow fatty acid, and 0.15 g of trifluoromethanesulfonic acid (0.03% by mass (relative to 0.59 g of p-toluenesulfonic acid monohydrate) was used. Fatty acid) and 0.08 equivalents (vs. zinc)) were used in the same manner as in Example 1 and the reaction products were analyzed in the same manner as in Example 1. The amount of nitrile produced 3 hours after flowing ammonia gas was 98.6%, and the time until the amount of aliphatic amide produced was below the detection limit in the above gas chromatography measurement (reaction completion time). ) Was 3.6 hours.

Comparative Example 5
In Comparative Example 1, the reaction was conducted in the same manner as in Comparative Example 1 except that 500 g of distilled beef tallow fatty acid was used instead of the hardened beef tallow fatty acid, and the reaction product was analyzed in the same manner as in Comparative Example 1. The nitrile production amount after 3 hours from the circulation of ammonia gas is 97.0%, and the time until the production amount of the aliphatic amide falls below the detection limit in the above gas chromatography measurement (reaction completion time) ) Was 4.1 hours.

Example 6
In Example 1, except that the amount of p-toluenesulfonic acid monohydrate used was changed from 0.59 g to 1.17 g (0.23% by mass (fatty acid), 0.50 equivalent (to zinc)). The reaction was carried out in the same manner as in Example 1, and the reaction product was analyzed in the same manner as in Example 1. The amount of nitrile produced after 3 hours was 99.5%, and the time from when ammonia gas was circulated in the above gas chromatography measurement until the amount of aliphatic amide produced was below the detection limit (reaction completion time). ) Was 3.1 hours.
In addition, the reaction product containing the catalyst obtained in the above reaction is charged into a glass container equipped with a thermometer, capillary tube, cooling tube, fraction receiver and vacuum gauge, and the system is evacuated to 0.53 kPa. The temperature was gradually raised, and distillation was performed until the bottom temperature reached a maximum of 240 ° C. The distillation yield of the obtained oleonitrile was 95.0%.

Example 7
In Example 1, the reaction was conducted in the same manner as in Example 1 except that 500 g of methyl stearate (purity 98.5%) was used in place of the cured beef tallow fatty acid, and the reaction product was analyzed in the same manner as in Example 1. . The production amount of stearonitrile after 4 hours from the circulation of ammonia gas is 87.9%, and the time until the production amount of aliphatic amide falls below the detection limit in the above gas chromatography measurement (reaction End time) was 6.3 hours.

Comparative Example 6
In Comparative Example 1, the reaction was conducted in the same manner as in Comparative Example 1 except that 500 g of methyl stearate (purity 98.5%) was used instead of the cured beef tallow fatty acid, and the reaction product was analyzed in the same manner as in Comparative Example 1. . The production amount of stearonitrile after 4 hours from the circulation of ammonia gas is 81.1%, and the time until the production amount of aliphatic amide falls below the detection limit in the above gas chromatography measurement (reaction End time) was 7.1 hours.

Example 8
Into a four-necked separable flask equipped with a stirrer, a gas inlet tube, a thermometer and a dehydrator, coconut fatty acid (main composition: C8 = 5.8%, C10 = 6.0%, C12 = 49.1%) , C14 = 19.3%, C16 = 9.6%, C18: 1 = 5.8%) 500 g, zinc oxide 1.0 g (0.20% by mass of fatty acid) and p-toluenesulfonic acid monohydrate 1.17 g (0.23% by mass (with respect to fatty acid), 0.25 equivalent (with respect to zinc)) was charged and stirred at 500 r / m. Through the solution, 1300 ml of ammonia gas was circulated from 210 ° C. per minute to raise the temperature to 280 ° C., and the reaction was carried out at this temperature.
The reaction product obtained 3 hours after the circulation of ammonia gas was analyzed in the same manner as in Example 1. The amount of nitrile produced was 96.3%. The time (reaction completion time) until the production amount of the aliphatic amide was below the detection limit in the gas chromatography measurement was 3.8 hours.

Comparative Example 7
In Example 8, the reaction was carried out in the same manner as in Example 8 except that only 1.0 g of zinc oxide was used without adding p-toluenesulfonic acid monohydrate, and the reaction product was the same as in Example 8. analyzed. The amount of nitrile produced 3 hours after flowing ammonia gas is 77.3%, and the time until the amount of aliphatic amide produced is below the detection limit in the above gas chromatography measurement (reaction completion time). ) Was 5.9 hours.

Example 9
In Example 1, 500 g of oleic acid (Kao-made Lunac OA) was used in place of the cured beef tallow fatty acid, and the amount of p-toluenesulfonic acid monohydrate used was 0.59 g to 2.34 g (0.47 mass). % (With respect to fatty acid) and 1.00 equivalent (with respect to zinc)). The reaction was conducted in the same manner as in Example 1. From the above gas chromatography measurement, the time from when the ammonia gas was circulated until the amount of aliphatic amide produced was below the detection limit (reaction completion time) was 2.9 hours.
In addition, the reaction product obtained in the above reaction is charged into a glass container equipped with a thermometer, capillary tube, cooling tube, fraction receiver and vacuum gauge, and the system is gradually reduced in pressure to 0.53 kPa. Distillation was carried out until the distillate ceased (bottom maximum temperature: 240 ° C.). Table 2 shows the distillation yield of the obtained oleonitrile.

Examples 10 and 11 and Comparative Example 8
In Example 9, the reaction was carried out in the same manner as in Example 9 except that p-toluenesulfonic acid monohydrate was used in the amount shown in Table 2, and the reaction end time was determined from the same measurement as in Example 9. It was. Further, the obtained reaction product was subjected to the same distillation operation as in Example 9. The results are shown in Table 2.

＊脂肪族モノカルボン酸、脂肪族ジカルボン酸又はこれらのアルキルエステルに対する質量％。

* Mass% based on aliphatic monocarboxylic acid, aliphatic dicarboxylic acid or their alkyl ester.

Example 12
After charging 400 g of the product obtained in Example 1, 1.4 g of Raney nickel catalyst, 0.8 g of 48% NaOH and 8.8 g of ion-exchanged water into the autoclave, the space in the autoclave was replaced with hydrogen, and a hydrogen pressure of 1. After adjusting to 9 MPaG, it heated up to 135 degreeC and reacted. The reaction end point was the time when hydrogen pressure absorption disappeared, and further aging was performed for 30 minutes. Hydrogen absorption proceeded smoothly and was completed in 2.2 hours. After completion of the reaction and ripening, the reaction product was taken out from the reaction vessel and the catalyst was removed, followed by distillation purification at 0.27 kPa and 220 ° C. to obtain a cured beef tallow amine in a yield of 96%.

  The aliphatic nitrile obtained by the method for producing an aliphatic nitrile of the present invention is suitably used for the production of an aliphatic amine, and the aliphatic amine is an important intermediate in the household and industrial fields, For example, it is suitably used for a wide range of applications such as fiber softeners, antistatic agents, gasoline additives, shampoos, rinses, disinfectants, and cleaning agents.

Claims (6)

In the presence of at least one metal compound selected from the group consisting of zinc, cobalt, titanium, and aluminum and a sulfonic acid, an aliphatic monocarboxylic acid, an aliphatic dicarboxylic acid, and an alkyl ester thereof (the carbon number of the alkyl group is 1-5) A method for producing an aliphatic nitrile by reacting at least one selected from the group consisting of 1 and ammonia with at least one selected from the group consisting of zinc, cobalt, titanium and aluminum. The manufacturing method of an aliphatic nitrile which is 0.05-0.6 equivalent with respect to 1 equivalent of seed metals . The amount of the compound of at least one metal selected from the group consisting of zinc, cobalt, titanium and aluminum is aliphatic monocarboxylic acid, aliphatic dicarboxylic acid and alkyl esters thereof (the alkyl group has 1 to 5 carbon atoms). ) relative to, 0.01 to 20 wt%, the production method of aliphatic nitriles of claim 1. The method for producing an aliphatic nitrile according to claim 1 or 2 , wherein the sulfonic acid is an aryl sulfonic acid or an alkyl sulfonic acid which may be substituted with an alkyl group. Zinc, cobalt, compounds of at least one metal selected from the group consisting of titanium and aluminum, an oxide of the metal, a hydroxide, carboxylate or alkoxide, according to any one of claims 1 to 3 Process for producing aliphatic nitriles. Making at least 1 type chosen from the group which consists of aliphatic monocarboxylic acid, aliphatic dicarboxylic acid, and these alkyl esters (C1-C5 of an alkyl group) and ammonia react at the temperature of 180-400 degreeC. Item 5. The method for producing an aliphatic nitrile according to any one of Items 1 to 4 . The manufacturing method of the aliphatic amine which has the following process.
(B) A step of obtaining an aliphatic nitrile by the production method according to any one of claims 1 to 5 (b) A step of subjecting the obtained aliphatic nitrile to a hydrogenation reaction in the presence of a hydrogenation catalyst.