JPS6032780A - Preparation of polyamine - Google Patents

Abstract

PURPOSE:To obtain a polyamine useful as an amine substance, etc. in high yield with suppressing formation of by-products, by reducing catalytically a cycanoethylated N-(2-aminoethyl)piperazine with a specific fatty amine. CONSTITUTION:Acrylonitrile is added to an N-(2-aminoethyl)piperazine to give a cyanoethyl derivative shown by the formula (Y is CH2CH2CN, or H), which is reacted with a primary amino group-containing fatty amine (e.g., methylamine, ethylenediamine, etc.) in a hydrogen gas atmosphere in the presence of a hydrogenating catalyst (e.g., Raney nickel, nickel supported on diatomaceous earth, etc.) under pressure at 1-300kg/cm<2>at 80-190 deg.C, preferably at 5-50kg/cm<2> at 100-170 deg.C to give the desired substance. An amount of the fatty amine added is 1-50wt% based on the cyanoethylated derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a polyamine by carrying out a catalytic reduction reaction of (minoethyl)piperazine.

Generally, a polyamine corresponding to the cyanoethylated amine is produced by subjecting a cyanoethylated amine, which is an amine compound having a primary or/and secondary amino group to which acrylonitrile is added, to a catalytic reduction reaction in the presence of a hydrogenation catalyst. The method is widely known. Furthermore, in order to further improve the yield of polyamines corresponding to the cyanoethylated amines, a method is already known in which ammonia is added to the reaction system to carry out a catalytic reduction reaction.

Based on these known methods, the present inventors have determined that N-(2
-Aminoethyl)piperazine (hereinafter abbreviated as N-AMP), a method for producing polyamines from cyanoethylated products revealed that in a reaction system without the addition of ammonia, a large amount of probylamine was produced as a by-product, and the cyanoetherization It has a structure in which the aminopropyl group has been removed from the polyamine corresponding to the body, that is, a polyamine with a lower molecular weight and a large amount of heavy amines with a molecular weight of 550 or more are produced as by-products,
It was found that the desired polyamine yield was not fully satisfactory.

Not only is there an economic loss due to a decrease in the yield of polyamine, but also an increase in the amount of by-products of low-boiling amines, mainly propylamine (boiling point 48°C), due to the removal of low-boiling amines from the reaction solution2.
The operation and equipment burden associated with recovery become large, resulting in disadvantages in the process.

Further, when the catalyst is separated and recovered from the reaction liquid obtained by carrying out the above reaction method, a decrease in filterability due to deterioration of the catalyst is observed, which increases the burden of catalyst separation operations. In addition, attempts were made to reduce the cost of using the catalyst by repeatedly using the recovered catalyst, but the catalyst was poisoned and almost deactivated after being used for one reaction. resulting in increased economic losses.

In reaction methods in which ammonia is added, liquid ammonia (boiling point -33° C.) is usually added, which adds complexity to equipment associated with handling, recovery, and abatement of ammonia. Further, addition of a small amount of ammonia does not have a small effect on improving the target polyamine yield, and it is necessary to add a large amount of ammonia to obtain a sufficiently satisfactory yield. At this time, since the ammonia gas partial pressure at a given reaction temperature becomes extremely large, taking into consideration the hydrogen gas partial pressure required for the reaction, the reaction must be carried out under relatively high pressure, and equipment with high pressure resistance is required. must be used, and the burden of increasing the amount of ammonia gas processed after the reaction is large, so it is not necessarily an advantageous manufacturing process from an industrial perspective.

As mentioned above, when cyanoethylated N-ARP is subjected to a catalytic reduction reaction using a conventional method, a large amount of low-boiling point amines, which are undesirable from the reaction point of view, are produced as by-products, which not only leads to a decrease in the desired polyamine yield, but also leads to a decrease in catalyst efficiency. It also causes poisoning. Further, in a method in which it is possible to improve the yield by using ammonia, the addition of a large amount of ammonia gas inevitably causes negative effects in terms of operation and equipment. An improved method for hydrogenation of the cyanethylated product, which allows production of useful polyamines in high yields under relatively low reaction pressures, allows the use of general-purpose equipment, and facilitates reaction and reaction solution post-treatment operations. A method is strongly desired.

As a result of extensive research in view of these circumstances, the present inventors added an aliphatic amine having a primary amino group to cyanoethylated N-A]iiP and performed a catalytic reduction reaction to convert propylamine into The present invention was completed based on new discoveries such as the ability to significantly suppress the amount of by-products and to produce a polyamine corresponding to the cyanoethylated product in high yield under relatively low reaction pressure.

That is, the present invention provides a cyanethylated compound represented by the following chemical structure in which acrylonitrile is added to 1'(2-aminoethyl)piperazi/ in a hydrogen gas atmosphere 1 and in the presence of a hydrogenation catalyst (Y= -OH2-aH,ON or -H) A method for producing a polyamine is provided, which is characterized in that an aliphatic amine having a primary amino group is added during the catalytic reduction reaction.

The raw material used in the present invention is N-(2-aminoethyl)
It is a cyanoethylated product represented by the chemical structural formula below, which is obtained by adding acrylonitrile to piperazine (N-mu11!p).

That is, N-(2-aminoethyl)-N'-(2-cyanoethyl)piperazine or N-['N'-(2-cyanoethyl)aminoethylcopiperazine with equimolar addition of acrylonitrile to N-mu'tcp. monocyanoethylated product, N-(N'-(2-cyanoethyl)aminethyl)-N'-(2-cyanoethyl)piperazine or N-ARP with twice the molar amount of acrylonitrile added.
-CM'-bis(2-cyanoethyl)aminoethyl] dicyanoethylated product of bipe2zine, N-t(bis(2-
A tricyanoethylated product of cyanoethyl))aminoethyl)-N'-(2-cyanoethyl)piperazine is exemplified and used as a raw material.

The monocyanoethylated product, dicyanoethylated product, or tricyanoethylated product shown above may be used alone as a raw material, or depending on the use of the polyamine product, the monocyanoethylated product may be used as a dicyanoethylated product.

Chemical 1? Raw materials such as 4-tylated derivatives of D-T-F7 may be mixed and used in any desired composition.

As the hydrogenation catalyst used in the present invention, metal catalysts widely used in general catalytic reduction reactions can be used, including nickel, copper, platinum, and ruthenium.

Palladium, rhodium, iridium, etc. are useful. These metals can also be used in the form of supported metal catalysts supported on carriers such as cane earth, alumina, activated clay, and activated carbon.

Among these, nickel-based catalysts are most suitable as catalysts for the reaction of the present invention in terms of catalytic activity and economic efficiency.

Nickel-based catalysts include Raney nickel, stabilized nickel supported on diatomaceous earth, and other copper.

Diatomaceous earth-supported nickel, which is mainly composed of nickel to which metals such as chromium, iron, and zinc are added, is used. As exemplified above (with nickel as the main metal component,
Catalysts to which a different metal other than nickel is added, or those supported together with nickel on various carriers, can be used as catalysts, and the type of the added different metal is not particularly limited. The amount of the catalyst to be used is not particularly limited, and is selected as an appropriate amount in consideration of the productivity related to the reaction rate, the influence on the polyamine yield, and the like. Generally, 1 to 1 to
20% by weight is added. If the amount of catalyst added is less than 1% by weight, the reaction rate becomes slow, which is not preferable in terms of productivity. 20
If the amount added is more than -20% by weight, it will not have a favorable effect on the reaction rate or the desired polyamine yield, and will simply increase the burden of separation operations due to the increase in the amount of catalyst, and will not be particularly advantageous. Since the catalyst used in the reaction method of the present invention still maintains high activity even after being used in the reaction,
It is usually separated and recovered from the reaction solution by operations such as filtration or decantation, and can be used repeatedly in the second and subsequent reactions, greatly contributing to reducing the cost of catalyst use and bringing great economic benefits.

The aliphatic amine having a primary amine group used in the present invention is an alkylamine represented by R-NH, (R is an alkyl group having 1 to 8 carbon atoms).

NH2-R'4NH-R') MHI (n = 0,
1, 2: R' and R# are alkylene groups having 2 to 6 carbon atoms; polyalkylene polyamines also include compounds containing a cyclic piperazine ring in the molecule) or polyalkylene polyamines. It is.

Specific examples of representative compounds include methylamine and ethylamine as alkylamines.

Examples include propylamine, butylamine, cyclohexylamine, 2-ethylhexylamine, etc. In addition, diamines include ethylenediamine, propanediamine,
Examples include butanediamine, hexamethylenediamine, cyclohexyldiamine, and the like. Examples of polyalkylene polyamines include diethylenetriamine, N-(2-aminoethyl)piperazine, triethylenetetramine, diglobylenetriamine, tripropylenetetramine eN (
Examples include 3-aminopropyl)ethylenediamine. Alkylamines have the effect of suppressing the elimination reaction of cyanethyl groups or aminopropyl groups from raw materials or products, as well as suppressing catalyst poisoning. case,
It is preferable to use a primary alkylamine having a boiling point of 60° C. or higher, since this involves a slight increase in the burden on the recovery operation from the reaction solution. Furthermore, propylamine and molecular weight 40
Ethylenediamine is an additive amine with excellent practicality that suppresses the formation of undesirable ~N by-products such as heavy amines of 0 or more, and can produce the desired useful polyamine in high yield under relatively low reaction pressure. propylene diamine, diethylene triamine.

Examples include diamines or polyalkylene polyamines such as dipropylene triamine, N-(2-aminoethyl)piperazine, and N-aminoethylpropanediamine. These relatively low molecular weight diamines or polyalkylene polyamines not only significantly suppress the poisoning of the catalyst and provide a reaction solution consisting of high quality polyamine with extremely little coloring, but also provide a reaction solution consisting of a high quality polyamine with very little coloration. It is most preferably used because it is extremely easy to separate and recover and has excellent industrial operability.

These aliphatic amines are added to the cyanoethylated raw material core in an amount of usually 1 to 50 weights, and the reaction is carried out. If the amount added is less than 1 part il, the effect of suppressing the amount of by-products of low-boiling amines will be small, and the catalyst activity will be lowered due to poisoning. Adding more than 50% by weight does not provide any further excellent effects on the reaction, and only increases the burden of recovering the large excess of aliphatic amine added to the reaction system from the reaction solution, which is not particularly advantageous. No.

If it is an aliphatic amine having a primary amino group, it will bring many excellent effects in terms of reaction and operation, and there are no particular limitations on the type of aliphatic amine to be added or the amount added. The quality and molecular weight distribution of T#
Therefore, it is preferable to appropriately select the type and amount of aliphatic amine depending on the intended use of the produced polyamine. For example, when an alkylene diamine is added and a reaction is carried out, a polyamine having one more amine group in the molecule is produced in addition to the polyamine corresponding to the cyanoethylated product.

Polyalkylene polyamines with relatively high molecular weight, such as nato-2-ethylene pentamine and penta-ethylene hexamine, which are generally produced industrially, are a mixture of polyamines with different chemical structures, and are extremely useful amines in many industrial fields. It is widely used as a material. Taking these practical aspects into consideration, the reaction method of the present invention provides an extremely industrially superior method for producing polyamines that can flexibly produce polyamine mixtures with various functionalities by selecting and adding the type of aliphatic amine. It has the advantages that it can provide.

The reaction of the present invention is carried out under pressure of hydrogen gas, and the pressure range is not particularly limited, but usually 1 to 500
It can be carried out under a pressure of 5 to 50 Kf/cm, more preferably 5 to 50 Kf/cm, J.

In general, in the hydrogenation reaction of 2) U groups, it is known that hydrogen pressure has a large effect on the desired amine yield, so a relatively high hydrogen pressure of 9/cm" or higher is applied to 70. However, when an aliphatic amine having a primary amino group is added to the reaction system as in the present invention,
It was found that the desired polyamine could be produced in high yield even if the reaction was carried out under a relatively low hydrogen pressure of sokg/c-.

That is, the addition of the aliphatic amine enables the reaction under low hydrogen pressure, which is extremely advantageous in terms of equipment such as reaction equipment and compressors. The decrease in hydrogen pressure can be compensated for by extending the reaction time, but in consideration of practical productivity, it is usually carried out at a hydrogen pressure of 5 kg/cm or more.The upper limit of hydrogen pressure is also particularly limited. Since the selection of hydrogen pressure has an important effect on the reaction rate, it is preferable to set it appropriately taking into consideration the heat removal accompanying the exothermic reaction.

Reaction temperature also has an important effect on reaction rate and polyamine yield. The reaction of the present invention is usually carried out at a temperature of 80 to 190°C, preferably 100 to 170°C.

Below 8[1'C, the reaction rate is slow and impractical.

At temperatures above 190°C, the produced polyamine decomposes, and the amount of low-boiling amine by-products increases rapidly, and the molecular weight decreases to 5.
The amount of heavy amines of 50 or more produced increases, leading to a decrease in the desired polyamine yield.

During the hydrogenation reaction, an inactive organic solvent or diluent may be added to the nitrile or amine, but this will reduce the efficiency of reactor usage due to an increase in the amount of reaction liquid.
It's not particularly advantageous.

The method of supplying raw materials to the reactor is not particularly limited. After first charging the raw material cyanoethylated product, catalyst and primary amine into the reactor, hydrogen gas may be introduced and the reaction may be carried out at a predetermined temperature, or the catalyst, primary amine and necessary It is also possible to add a reaction-inert solvent depending on the reaction conditions and carry out the reaction at a predetermined temperature and under a predetermined hydrogen pressure while supplying the raw material cyanethylated product using a metering pump.

Himi's reaction method is usually carried out using a so-called suspended catalyst system in which the reaction is carried out under a hydrogen gas atmosphere with stirring using a pressurized reactor, but even when carried out in a fixed bed reaction method, primary amine groups are The addition of the aliphatic amine contained can similarly have a favorable effect on the reaction, and the reaction method is not particularly limited.

After the catalyst is separated and removed from the reaction solution obtained by the method of the present invention, a small amount of by-product low-boiling amines and the added aliphatic amine are removed by distillation. Depending on the use of the produced polyamine, it may be commercialized as a polyamine mixture as it is, or it may be commercialized as a polyamine mixture as it is, or it may be used as a product such as tetramine, which corresponds to the hydrogenated product of monocyanoethylated product, pentamine, or triamine, which corresponds to the hydrogenated product of dicyanoethylated product. Hexamine corresponding to the hydrogenated product of the cyanoethylated product, and further fractions such as heptamine produced by side reactions may be rectified to produce products. Even when the former is commercialized as a polyamine mixture, the reaction liquid obtained by the method of the present invention is a very clean product liquid with a slight yellow color, so its commercial value can be said to be high.

As described above, a method for producing a polyalkylene polyamine having a relatively large molecular weight by hydrogenating a cyanoethylated raw material having three amino groups in the molecule, such as a cyanoethylated N-(2-aminoether)piperazine. By applying the reaction method of the present invention under high pressure, the drawbacks such as severe catalyst poisoning and significant increase in the amount of 9-heavy amines and propylamine by-products, which were observed in known techniques, can be greatly improved. I came to the conclusion. In addition, the reaction method of the present invention opens the way to cost reduction by reusing the catalyst, makes it possible to improve the target useful polyamine yield, and furthermore realizes mild reaction conditions such as hydrogen pressure. , we have achieved the establishment of an industrial process that is extremely advantageous in terms of equipment and operation.

Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not particularly limited thereto. 2-aminoethyl)piperazine (N
-Air) cyanoethylated product 150v, ethylenediami 750F, Raney nickel 7,5? (dry base) was charged, and the gas phase was replaced with hydrogen gas. Heat to a predetermined reaction temperature and pressurize hydrogen gas to 9 reaction pressure 50
The hydrogenation reaction was carried out at the reaction temperature shown in Table 1 depending on the type of cyanoethylated N-AKP used as the raw material.The hydrogenation reaction was carried out at the temperature shown in Table 1. Thereafter, the reaction was continued for an additional 20 minutes at the same temperature.

After cooling the reaction solution, the catalyst was removed by filtration, and the resulting slightly yellow colored solution was quantitatively analyzed by gas chromatography. Further, heavy amines having a molecular weight of 400 or more were quantitatively analyzed by high performance liquid chromatography. The results are shown in Table 1.

Table 1 Triamine;? J-(2-aminoethyl)piperazine.

N-(5-aminopropyl)piperazine; 5 □ia, 7~kah 4, 5@@i, polyalkylene polyamine hexamine in which two of the 5 are primary amino groups; Composition of the cyanoethylated polyalkylene polyamine raw material having 6 7 groups, of which 2 to 5 are primary 7 groups Monocyanoethylated product: N-AMP 214° Monocyanoethylated product 97.9% by weight Dicyanoethylated product; Monocyanoethylated product 6.4 Thidi7 Ano-engineered product 92.8 Dicyanoethylated product [L8 weight based lycyanoethylated product; Dicyanoethylated product 14.7
% tricyanoethylated product 85.3% by weight heavy amine; polyalkylene polyamine with a molecular mass of 350 or more Example 4 In the same reactor as in Example 1, zineanoethylated product 150F of N-AMP, 1,3-propanediamyz Of
, 9Ni 6V (dry base) was charged, the gas phase was replaced with hydrogen gas, and the pressure was further increased. The reaction temperature is 13
Control in the range of 5-140'C, reaction pressure 25k
The hydrogenation reaction was carried out at a rate of 1.5 g/cm". Hydrogen absorption was completed 1 hour after the start of the reaction, so the temperature was continued for another 20 minutes at 140°C. After the reaction solution was cooled, the catalyst was removed from door to door, and the reaction mixture was colored yellow. The liquid was quantitatively analyzed using a gas chromatograph.The quantitative analysis of the heavy amine was performed using a high performance liquid chromatograph.The Raney nickel separated and recovered from the above reaction liquid was used in the reaction as it was, repeated five times under the same reaction conditions.First Table 2 shows the reaction results of the first and third tests.

Table 2 Example 5 50 tons of dioxane was placed in the same reactor as in Example 1.

7.5 tons of Raney nickel (dry pace) and 7.5 tons of ethylenediamine were charged, the gas phase was replaced with hydrogen gas, and the mixture was further pressurized. Reaction temperature 155℃ 9 Reaction pressure 55yu/C
150 t of dicyanoethylated material of N-Al!!P, which is a raw material, was supplied over 2 hours using a metering pump under the conditions of ``m''. After the supply, the reaction was further carried out under the same conditions for 1 hour, and then
After cooling, the catalyst was distributed from house to house. The composition of the slightly yellow colored reaction solution was analyzed using the same analytical method as in Example 1. As a result, propylamine 1. Of,) diamine 113r,
Tetramine 9.41, Pentamine 122.1v, Hexame/11.2f.

Heavy amine 1 [LOr was obtained.

Example 6 In the same reactor as in Example 1, 150 y of dianoethylated N-AFiP and 15f of ethylenediamine were added.

65mm nickel supported on diatomaceous earth (reduction stable nickel)
6f was charged, the gas phase was replaced with hydrogen gas, and the pressure was further increased. The hydrogenation reaction was carried out at a reaction temperature of 135°C and a reaction pressure of 31 kg/cm. Hydrogen absorption was completed 1.3 hours after the start of the reaction, and the reaction was continued for another 10 minutes under the same conditions. After cooling the reaction solution, the catalyst was The slightly yellow colored reaction solution was analyzed for its composition using the same analytical method as in Example 1.The results showed that propylamine [LOr, )diamine 0?, tetraline 7.9?, and pentamine 119.5? t, hexamine 16,51° heavy amine 1α6v was obtained.

Example 7.8 Into the same reactor as in Example 1, 150 tons of dicyanoethylated N-AEP and a sulfur-resistant nickel catalyst (Ni45-47
%, Or2~5%, Qu3~496゜Diatomaceous earth 27
~29%, graphite 4-5%, Ni form Ni+Ni0)7.
5? , diethylenetriamine 1st in Example 7, N-(2-aminoether)piperazine 15f in Example 8
The gas phase was replaced with hydrogen gas and further pressurized. The hydrogenation reaction was carried out at a reaction temperature of 140° C. and a reaction pressure of 28 kg/C11t. After hydrogen absorption was completed 1.2 hours after the start of the reaction, the same conditions were continued for an additional 15 minutes. After cooling the reaction solution, the catalyst was separated from each other, and the composition of the slightly yellow colored solution was analyzed using the same analysis method as in Example 1. As a result, in Example 7, propylamine α79. Tetraminergic 5? , pentamine 121.5F, hexamine a2t, heptamine &8f9 heavy amine 17.2f were obtained. In addition, in Example 8, propylamine α7f, Futrami ya3F
, BayJ Amine 19.8F.

Hexamine a, St, heptamine 7.2 f and heavy amine 1a22 were obtained.

Example 9 In the same reactor as in Example 1, 150 f of the dicyanoethylated N-AIIIP, 152° of monoethylamine, and 6 tons of Raney nickel were charged, the gas phase was replaced with hydrogen gas, and hydrogen was further pressurized. Reaction temperature: 135°C.

The hydrogenation reaction was carried out at a reaction pressure of 55 kg/e1 m''. Hydrogen absorption was completed 4 hours after the start of the reaction, and the reaction was continued for another 10 minutes under the same conditions. After cooling the reaction solution, the catalyst was separated from each other, and the obtained The composition of the reaction solution was analyzed using the same analysis method as in Example 1. As a result, propylamine 1.2F,
Reamine of, Tetramine 14.8t, Pentamine 12
Engineering Sy, Hexamine Q, 4f.

Heavy amines12. Of was obtained.

Comparative Example 1 In the same reactor as in Example 1, 150 f of dicyanoethylated N-up and 7.5 t of Raney nickel (dry base) were charged, the gas phase was replaced with hydrogen gas, and the hydrogen gas was further pressurized. Reaction temperature: 140℃9 Reaction pressure: 30℃/cm”
A hydrogenation reaction was carried out. Hydrogen absorption was completed 7 hours after the start of the reaction. Thereafter, the reaction was continued for an additional 30 minutes at the same temperature. The reaction solution was cooled, the catalyst was separated, and the brown colored reaction solution was quantitatively analyzed using the same analysis method as in Example 1. As a result, propylamine 17.9 t, )riamine A
1F, Tetramine 22.7 t, Pentamine 845
21.01 of a heavy amine was obtained.

The catalyst separated and recovered in the above reaction was repeatedly used in a second reaction under the same reaction conditions, but no hydrogen absorption was observed.

Comparative Example 2 In the same reactor as in Example 1, dicyanoethylated N-AIIIP 150f and Raney; Tsukel z5? (dry base) and the gas phase was replaced with hydrogen gas. Liquid ammonia 1aOf was collected into a sample introduction tube, pressurized with hydrogen gas, and introduced into the reactor. Reaction temperature 140℃9 reaction pressure 55k
The hydrogenation reaction was carried out at 3 hours and 40 minutes after the start of the reaction.The reaction was then continued for an additional 30 minutes at the same temperature.The reaction solution was cooled and the internal pressure was released. , and ammonia was purged. The yellow-brown colored reaction solution was analyzed to quantify the products using the same analytical method as in Example 1. As a result, propylamine 44f,) rearmy y1.
Of, Tetramin 22A3t, Bear fi mi y1074t
, 1.5 f of hexamine, and 16.3 f of heavy amine were obtained.

Comparative Example 5 In the same reactor as in Example 1, 150 tons of dicyanoethylated N-AIIIP and Raney nickel Z5f (dry base) were charged, and the gas phase was replaced with hydrogen gas. Liquid ammonia was collected into an Aof sample introduction tube, pressurized with hydrogen gas, and introduced into the reactor. Reaction temperature: 140℃9 Reaction pressure: 55 kg
/ Cm*, the reaction stopped when 60% of the theoretical amount of hydrogen was absorbed.

Patent Applicant Toyo Soda Kogyo Co., Ltd. Procedural Amendment May 30, 1980 Commissioner of the Patent Office Kazuo Wakasugi 1 Indication of Case 1982 Patent Application No. 140571 2 Name of Invention Process for Producing Polyamine 3 Amendment Relationship with the case Patent applicant telephone number (585) 3311 4. Date of amendment order 6. 1. Detailed explanation of the invention in the specification to be amended 7. Contents of the amendment (1) Page 10 of the specification, line 18 Correct the "propylene diamine" in the eyes to "propanediamine".

(2) On page 24 of the specification, lines 10 and 11, “
Correct "CH" to 11.

Claims (2)

[Claims] (1) When carrying out a catalytic reduction reaction of the cyanoethylated product shown by the chemical structural formula below, which is obtained by adding acrylonitrile to N-(2-aminoethyl)piperazine, in a hydrogen gas atmosphere and the presence of a hydrogenation catalyst, A method for producing a polyamine, which comprises adding an aliphatic amine having 7 primary amine groups. (2) The production method according to claim (1), wherein the hydrogenation catalyst is 2N nickel or nickel supported on silica earth.