JP2015013833A - Production method of trans-diaminocyclohexane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method to gain a trans isomer by isomerization from a cis isomer of diaminocyclohexane efficiently.SOLUTION: When a cis isomer of diaminocyclohexane (including 1,4-diaminocyclohexane) is isomerized under presence of metal catalyst (including ruthenium-catalyst) and a trans isomer of the diaminocyclohexane is provided, the cis isomer is performed heating and pressure treatment in inert gas (including nitrogen gas). In such the isomerization processing, a reaction temperature can be more than 100°C (e.g., around 150-250°C), and a pressure of the inert gas can be more than 5 MPa (e.g., 7-20 MPa).

Description

  The present invention relates to a method for producing a trans isomer by isomerizing a cis isomer of diaminocyclohexane (such as 1,4-diaminocyclohexane).

  Diaminocyclohexane (such as 1,4-diaminocyclohexane) is a compound obtained by hydrogenation of p-phenylenediamine or the like, and is used in various applications. In particular, among diaminocyclohexanes, trans isomers (such as trans-1,4-diaminocyclohexane) have characteristics such as a higher melting point than cis isomers, and resin raw materials (for example, polyamide, polyimide, It is preferably used as a diamine component such as polyurethane.

  As a method for obtaining such a trans form, several methods have been known so far. For example, US Pat. No. 3,657,345 (Patent Document 1) includes an isomer mixture of 1,4-diaminocyclohexane (cis / trans = 70% / 30%), 5% ruthenium alumina catalyst and sodium methoxy. In the presence of a catalyst, the reaction was conducted under the conditions of 200 ° C. and hydrogen gauge pressure of 4500 pounds per square inch.

  Japanese Patent Application Laid-Open No. 2008-74754 (Patent Document 2) includes a hydrogenation reaction step of producing an isomer mixture of 1,4-diaminocyclohexane by hydrogenating p-phenylenediamine. In the reaction step, the alkaline earth metal oxide is added to the reaction system of the hydrogenation reaction to remove moisture contained in the reaction system, and the alkaline earth metal hydroxide is converted into the reaction system. Discloses a process for producing trans-1,4-diaminocyclohexane which acts as a promoter.

  In Example 1 of this document, calcium oxide was added to a reaction mixture obtained by hydrogenating p-nitroaniline at 120 ° C. under a hydrogen pressure of 4 MPa in the presence of a ruthenium / alumina catalyst. The reaction was performed for 2 hours under a hydrogen pressure of 8 MPa.

  However, in these documents, since further hydrogenation is required for the isomerization of the cis isomer, it is necessary to perform the isomerization reaction in high-pressure hydrogen gas.

US Pat. No. 3,657,345 (Example) JP 2008-74754 A (Claims, Examples)

  Accordingly, an object of the present invention is to provide a method capable of isomerizing a cis isomer of diaminocyclohexane into a trans isomer without requiring a high hydrogen pressure.

  Another object of the present invention is to provide a method capable of isomerizing cis-diaminocyclohexane with a simple reaction system.

  Still another object of the present invention is to provide a method capable of isomerizing cis-diaminocyclohexane with high safety.

  Another object of the present invention is to provide a method capable of efficiently isomerizing cis-1,4-diaminocyclohexane with less by-product formation.

  As described above, conventionally, in order to isomerize a cis form (cis-diaminocyclohexane) of diaminocyclohexane (or cyclohexanediamine) to obtain a trans form (trans-diaminocyclohexane), a reaction between the cis form and hydrogen (hydrogenation reaction) Therefore, it was necessary to maintain the cis body in high-pressure hydrogen gas, which is difficult to handle technically and is concerned about safety.

  Under these circumstances, as a result of intensive studies to achieve the above-mentioned problems, the present inventors considered that isomerization of the cis isomer does not necessarily require hydrogenation, and studied various isomerization reaction systems. However, it is very surprising that the isomerization reaction proceeds by a completely different mechanism. Instead of using a complicated reaction system, an inert gas is simply used instead of the hydrogen gas in the conventional reaction system. The isomerization reaction proceeds in a simple system. Furthermore, in such a reaction system, the side reaction is suppressed at a high level, or there is little by-product formation and the isomerization reaction can proceed efficiently. The present invention has been completed.

  That is, the method of the present invention is a step of isomerizing a cis form of cis [cis-diaminocyclohexane] of diaminocyclohexane to obtain a trans form of diaminocyclohexane [trans (diaminocyclohexane)], which is an inert gas. Among them, a trans isomer is produced through an isomerization step in which a cis isomer is heated (warmed) and pressurized. In such a method, the diaminocyclohexane may in particular be 1,4-diaminocyclohexane.

  In the isomerization step, only the cis isomer may be used as a raw material. Typically, the isomer mixture containing the cis isomer and the trans isomer may be heated and pressurized to increase the proportion of the trans isomer. .

  The isomerization step may be usually performed in the presence of a catalyst. Examples of the catalyst include a metal catalyst (for example, a transition metal catalyst), and a noble metal catalyst (for example, a platinum group metal catalyst such as a ruthenium catalyst) may be preferably used.

  Further, the isomerization step may be performed in the presence of a solvent (for example, ethers).

  In the isomerization step, the inert gas may in particular be nitrogen gas. Moreover, 100 degreeC or more may be sufficient as temperature (isomerization process temperature, reaction temperature, heat processing temperature). Furthermore, in the isomerization step, the pressure of the inert gas may be 5 MPa or more. Typically, heat and pressure treatment may be performed under conditions of a temperature (heat treatment temperature) of 150 to 250 ° C. and an inert gas pressure of 7 to 20 MPa.

  The isomerization step may be performed substantially in the absence of an active gas. For example, in the isomerization step, the hydrogen gas pressure may be 0.1 MPa or less.

  In the method of the present invention, cis-diaminocyclohexane can be isomerized to a trans form without requiring a high hydrogen pressure, which has been conventionally considered essential for isomerization of cis-diaminocyclohexane. In particular, in the method of the present invention, since an inert gas can be used without requiring a high hydrogen pressure that requires high technical accuracy, cis-diaminocyclohexane can be isomerized in a simple reaction system. In addition, since the method of the present invention does not require high-pressure hydrogen, cis-diaminocyclohexane can be isomerized with high safety. Furthermore, in the method of the present invention, cis-diaminocyclohexane can be efficiently isomerized even though high hydrogen pressure is not required as described above. For example, according to the method of the present invention, side products are not generated (or impurities), and side reactions can be suppressed (or prevented) at a high level.

  Thus, the method of the present invention is very useful as a method for isomerizing cis-diaminocyclohexane.

  The method of the present invention is a step of isomerizing a cis isomer of diaminocyclohexane (cis-diaminocyclohexane) to obtain a trans isomer of diaminocyclohexane (trans-diaminocyclohexane), wherein the cis isomer is heated and heated in an inert gas. A trans isomer is produced through an isomerization step (heating and pressurizing step) for pressure treatment.

[Isomerization process]
(Raw material substrate)
Examples of diaminocyclohexane include 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, and 1,4-diaminocyclohexane. The diaminocyclohexane may in particular be 1,4-diaminocyclohexane.

  In the isomerization step, the cis isomer is isomerized to the trans isomer. In the isomerization step, it is sufficient that at least an isomerization reaction from the cis form to the trans form occurs. Therefore, the cis isomer used in the isomerization step may be only the cis isomer (that is, diaminocyclohexane having 100% cis isomer), or may be a mixture of cis isomer and trans isomer (isomer mixture).

  When such an isomer mixture is used, the ratio of the cis isomer to the trans isomer is not particularly limited. For example, the former / the latter = 99/1 to 20/80 (for example, 99/1 to 30/70). ) 98/2 to 40/60 (eg 97/3 to 45/55), preferably 95/5 to 50/50 (eg 93/7 to 55/45), more preferably May be about 90/10 to 60/40 (for example, 85/15 to 65/35). Usually, the ratio of the cis form to the trans form is, for example, the former / the latter = 99/1 to 50/50 (for example, 97/3 to 55/45), preferably 95/5 to 60/40 (for example, 93 / 7 to 65/35).

  In addition, the said ratio may be molar ratio or weight ratio, and may be an area ratio in various chromatography (gas chromatography etc.). In diaminocyclohexane, the area ratio in chromatography reflects a molar ratio or a weight ratio.

  In the isomerization step, it is only necessary to increase (increase or increase) the ratio of the trans isomer after the isomerization compared to the ratio of the trans isomer in the diaminocyclohexane before the isomerization. There is no need to

  In a typical isomerization step, an isomer mixture containing a cis isomer and a trans isomer is heated and pressurized to increase the proportion of the trans isomer in many cases.

  In addition, a commercial item may be used for a cis body and an isomer mixture, and what was synthesize | combined by the usual method (hydrogenation of p-phenylenediamine, p-nitroaniline, etc.) may be used.

(catalyst)
The isomerization step (heat pressure treatment step) may be usually performed in the presence of a catalyst. As the catalyst, at least a metal catalyst can be used.

  The metal catalyst (or a metal component or a metal catalyst component or a catalyst containing a metal as a catalyst component) is not particularly limited as long as it has a catalytic action in the isomerization reaction system of the present invention, and constitutes such a metal catalyst. Examples of the metal include a Group 8 metal (for example, ruthenium, osmium), a Group 9 metal (for example, cobalt, rhodium, iridium, etc.), a Group 10 metal (for example, nickel, palladium, etc.) of the periodic table. Transition metals such as platinum). In particular, the metal may be cobalt, nickel, or a noble metal, and among them, may be a platinum group metal (ruthenium, rhodium, palladium, osmium, iridium, platinum, etc.).

  The metals (metal components) may be used alone or in combination of two or more.

  In the metal catalyst, the valence of the metal is not particularly limited, and may be zero valent, and may be any of monovalent, divalent, trivalent, tetravalent, pentavalent, hexavalent, etc. depending on the type of metal. It may be.

  The metal (or metal component) contained in the metal catalyst may be in the form of a simple metal or in the form of a metal compound. The metal compound may form a coordination compound (or complex) with an appropriate ligand.

  In particular, the metal contained in the metal catalyst may be supported on a carrier. By supporting, aggregation and crushing under high pressure can be efficiently suppressed or prevented, and high catalytic activity (catalytic action) is easily exhibited. Examples of the carrier include metal oxides (eg, titania, zirconia, magnesia, alumina, silica, etc.), carbon materials (eg, activated carbon), and the like. The carriers may be used alone or in combination of two or more.

  When the metal (metal component) is supported on the carrier, the ratio of the metal is, for example, 0.01 to 100 parts by weight (for example, 0.05 to 80 parts by weight) with respect to 100 parts by weight of the total amount of the metal and the carrier. ), Preferably 0.1 to 60 parts by weight (for example, 0.3 to 50 parts by weight), more preferably about 0.5 to 30 parts by weight (for example, 1 to 20 parts by weight). About 0.1-15 weight part (for example, 1-10 weight part) may be sufficient.

  The proportion of the metal catalyst (metal component, in terms of metal component when supported) is 100 parts by weight with respect to 100 parts by weight of cyclohexanediamine (the total amount in the case of a mixture of a cis isomer and a trans isomer), for example, 0.001 to 20 parts by weight (for example, 0.005 to 15 parts by weight), preferably 0.01 to 10 parts by weight (for example, 0.03 to 8 parts by weight), more preferably 0.05 to 5 parts by weight (For example, about 0.1 to 3 parts by weight) or about 0.01 to 3 parts by weight (for example, 0.05 to 2 parts by weight) may be used.

(base)
The isomerization step may be performed in the presence of a base. Examples of the base (basic compound) include inorganic bases [for example, metal hydroxides (alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide; magnesium hydroxide, calcium hydroxide, hydroxide) Alkaline earth metal hydroxides such as barium), metal oxides (or basic oxides, for example, alkali metal oxides such as sodium oxide and potassium oxide; alkaline earths such as magnesium oxide, calcium oxide and barium oxide) Metal oxides), metal carbonates (eg, alkali or alkaline earth metal carbonates such as cesium carbonate, sodium carbonate), metal hydrogen carbonates (eg, alkali or alkaline earth metal hydrogen carbonates such as sodium hydrogen carbonate) , Ammonia, etc.], organic bases [e.g. carboxylic acid metal salts (e.g. sodium acetate, Carboxylic acid alkali or alkaline earth metal salt such as calcium acid), alkoxide (or metal alkoxide such as lithium methoxide, sodium methoxide, potassium methoxide, sodium ethoxide, sodium propoxide, sodium t-butoxide, etc. Metal alkoxide (eg, C _1-10 alkoxide, preferably C _1-6 alkoxide, more preferably C _1-4 alkoxide), organometallic compound (eg, butyl lithium, phenyl lithium, isopropyl magnesium chloride, cyclohexyl magnesium bromide, phenyl Magnesium bromide, sodium amide, lithium diisopropylamide, etc.), amines, etc.].

  The bases may be used alone or in combination of two or more.

  Of these, preferred bases include metal hydroxides, metal oxides, metal alkoxides, and the like, and metal alkoxides are particularly preferred.

  In addition, you may use a base as a promoter of a catalyst (metal catalyst) normally.

  The ratio of the base is, for example, 0.01 to 20 parts by weight, preferably 0.05 to 15 parts by weight with respect to 100 parts by weight of cyclohexanediamine (the total amount in the case of a mixture of a cis isomer and a trans isomer). Part, more preferably about 0.1 to 10 parts by weight, and usually about 0.1 to 5 parts by weight (for example, 0.2 to 3 parts by weight).

  Moreover, the ratio of the base is 0.01 to 100 parts by weight, preferably 0.03 to 50 parts by weight (for example, 0.05 to 30 parts by weight), more preferably 0.0 to 100 parts by weight with respect to 1 part by weight of the metal catalyst. It may be about 1 to 20 parts by weight (for example, 0.2 to 10 parts by weight), and may be usually about 0.1 to 5 parts by weight.

  Furthermore, the ratio of the base is in the range of about 0.5 molar equivalents or more (for example, 0.7 to 30 molar equivalents) with respect to 1 mole of the metal catalyst (in terms of metal component, if supported). For example, 1 molar equivalent or more (for example, 1.2 to 25 molar equivalent), preferably 1.5 molar equivalent or more (for example, 1.8 to 20 molar equivalent), more preferably 2 molar equivalent or more ( For example, it may be 2.3 to 15 molar equivalents), particularly about 2.5 molar equivalents or more (for example, 2.8 to 10 molar equivalents), and usually 1 to 15 molar equivalents (for example, 1.5 to 10 molar equivalents). Molar equivalent, preferably about 2 to 7 molar equivalent).

(solvent)
The reaction may be performed in the presence of a solvent. Although it does not specifically limit as a solvent, For example, hydrocarbons (for example, aliphatic hydrocarbons, such as pentane, hexane, heptane, a cyclohexane), ethers [For example, diethyl ether, methyl t-butyl ether, dibutyl ether, etc. 1,3-dimethoxypropane, 1,2-dimethoxyethane, 1,2-diethoxyethane, glycol dialkyl ethers such as diethylene glycol dimethyl ether (such as (poly) alkylene glycol dialkyl ethers); methoxyethanol, Glycol monoalkyl ethers such as ethylene glycol monoethyl ether, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, diethylene glycol monoethyl ether ( Poly) alkylene glycol monoalkyl ethers; glycol ether esters such as propylene glycol monomethyl ether acetate (such as (poly) alkylene glycol monoalkyl ether acetates); tetrahydrofuran, tetrahydropyran, 1,4-dioxane, 1,3-dioxolane Cyclic ethers such as, etc.], ketones (eg, alkanones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; cycloalkanones such as cyclohexanone), esters (eg, methyl acetate, ethyl acetate, butyl acetate, etc.) ), amides (e.g., N- methylformamide, N, N- dimethyl formamide, and the like of N- mono- or _{di-C 1-4} alkyl formamide; N- methylacetamide, N, N- Methyl N- mono- or di-C _1-4 alkyl acetamide, such as dimethylacetamide; N- methylpyrrolidone), nitriles (e.g., acetonitrile, propionitrile and the like), sulfoxides (e.g., dimethyl sulfoxide) is an organic solvent such as Can be mentioned. The solvents may be used alone or in combination of two or more.

  The ratio of the solvent is, for example, 0.05 to 30 parts by weight, preferably 0.1 to 0.1 parts by weight with respect to 1 part by weight of diaminocyclohexane (the total amount in the case of a mixture of cis and trans isomers). It may be about 20 parts by weight, more preferably about 0.3 to 10 parts by weight (for example, 0.5 to 5 parts by weight).

(Reaction conditions)
The present invention is characterized in that the isomerization step is performed in an inert gas. The inert gas is not particularly limited as long as it is inert with respect to diaminocyclohexane, and examples thereof include nitrogen gas, rare gases (such as helium, neon, and argon), and carbon dioxide gas. The inert gas may be used alone or in combination of two or more. Among these inert gases, nitrogen gas can be suitably used.

  In the present invention, the reaction atmosphere may contain an active gas (oxygen gas, hydrogen gas, etc.) as long as it can be carried out in an inert gas. In many cases, the isomerization step is performed in a reaction atmosphere containing no gas. In particular, in the present invention, even when hydrogen gas is contained, it is often in a range that does not substantially contribute to the isomerization reaction (a very small amount remaining in the reactor).

  Even when the active gas is contained, the ratio of the active gas is 10 mol% or less (for example, 0 or the detection limit to 5 mol%), preferably based on the entire reaction atmosphere (total amount of the inert gas and the active gas). May be about 1 mol% or less (for example, 0.5 mol% or less), more preferably about 0.1 mol% or less (for example, 0.01 mol% or less). In particular, the ratio of hydrogen gas to the entire reaction atmosphere is, for example, 1 mol% or less (for example, 0 or a detection limit to 0.5 mol%), preferably 0.1 mol% or less, more preferably 0.01 mol%. It may be the following.

  The isomerization step is performed under heating (warming) and pressure conditions (that is, by holding diaminocyclohexane under heating and pressure).

  The temperature (heat treatment temperature, reaction temperature, isomerization reaction temperature) is, for example, 50 ° C. or higher (for example, 70 to 500 ° C.), preferably 80 ° C. or higher (for example, 100 to 400 ° C.), and more preferably 120 ° C. or higher. (For example, 130 to 350 ° C.), particularly 150 ° C. or more (for example, 170 to 300 ° C.), and usually 100 ° C. or more (for example, 120 to 300 ° C., preferably 150 to 250 ° C., more preferably 170 to 230 ° C.).

  The pressure of the inert gas (pressure treatment pressure, reaction pressure, isomerization reaction pressure) is, for example, 2 MPa or more (for example, 2.5 to 50 MPa), preferably 3 MPa or more (for example, 4 to 40 MPa), more preferably It may be 5 MPa or more (for example, 5 to 35 MPa), particularly 6 MPa or more (for example, 7 to 30 MPa), and may generally be about 5 to 30 MPa (for example, 6 to 25 MPa, preferably 7 to 20 MPa).

  The pressure corresponds to the pressure in the reaction atmosphere. That is, the pressure can be generally referred to as an inert gas pressure. When the reaction atmosphere is composed of two or more kinds of inert gases, the total of the respective partial pressures (the value obtained by multiplying the total pressure by the mole fraction of each gas) is the pressure of the reaction atmosphere.

  As described above, the reaction atmosphere may be an atmosphere that does not contain an active gas, and may contain an active gas as long as it is in a trace amount. Even when the reaction atmosphere contains an active gas, the pressure (partial pressure) of the active gas is, for example, 1 MPa or less (for example, 0 or a detection limit to 0.5 MPa), preferably 0.1 MPa or less, more preferably 0. It may be 01 MPa or less. In particular, the pressure (partial pressure) of hydrogen gas may be, for example, 0.1 MPa or less (for example, 0 or a detection limit to 0.05 MPa), preferably 0.01 MPa or less, more preferably 0.001 MPa or less. .

  The time (reaction time, heating and pressure treatment time) can be appropriately selected depending on the pressure, temperature, etc., for example, 5 minutes or more (for example, 7 to 24 hours), preferably 10 minutes or more (for example, 20 minutes) To 18 hours), more preferably 30 minutes or more (for example, 40 minutes to 12 hours), particularly about 1 hour or more (for example, 1.5 to 6 hours).

  The reaction vessel is not particularly limited as long as it can withstand heating and pressurization conditions, and a conventional vessel can be used according to the scale of the reaction.

  Through the isomerization step as described above, the ratio of the trans isomer in the diaminocyclohexane used as a raw material (before the isomerization step) increases (or rises). The rate of increase in the proportion of the trans isomer can be selected depending on the proportion of the cis isomer in the diaminocyclohexane used as a raw material, the type and amount of the catalyst, reaction conditions (temperature, pressure, time), and the like.

[Recovery process]
Recovery of the trans isomer (or the isomer mixture in which the ratio of the trans isomer is increased) from the content (reactant) obtained through the isomerization step can be performed by a conventional method, and is not particularly limited. Since the liquid and the trans form are solid at normal temperature, the trans form can be efficiently recovered by using crystallization.

  For example, the reaction product after the isomerization reaction may be cooled (cooled crystallization) to obtain a crystallized product (crystal) containing a trans isomer. The obtained (or recovered) crystallized product may be used as various raw materials as it is, and can be further purified, or the isomerization process can be performed again to further increase the purity of the trans isomer. .

  If necessary, solid content (such as a catalyst) may be removed by a conventional method (for example, filtration) before crystallization.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

Example 1
In a 500 mL autoclave, 1,4-diaminocyclohexane (cis isomer / trans isomer = 80/20, manufactured by Tokyo Chemical Industry Co., Ltd.) 100 g, propylene glycol monomethyl ether (PGME) 100 g, Ru catalyst (N.E. ), “AA-4501”, 5% Ru alumina powder) 7.5 g, and sodium methoxide (manufactured by Tokyo Chemical Industry Co., Ltd.) 0.63 g, then nitrogen (N ₂ ) gas (10 kgf / cm) ³ ) Sealing was repeated 3 times, and the inside of the system was replaced with nitrogen gas. While stirring at a stirring speed of 300 rpm, the reaction was held for 2 hours under the conditions of a temperature of 200 ° C. and a pressure (N ₂ gas pressure) of 12 MPa. After the reaction, the reaction mixture was cooled to room temperature and filtered under pressure using a 0.2 μm membrane filter to remove the catalyst and obtain a filtrate. When the obtained filtrate was analyzed by gas chromatography mass spectrometry (GC-MS), the cis-isomer ratio was 63.37 area%, the trans-isomer ratio was 34.7 area%, and other components (4-aminocyclohexane). By-product such as hexanol) was 1.93 area%, and cis / trans = 65/35.

  In addition, the ratio of a cis body and a trans body is an area ratio in GC-MS, and substantially reflects molar ratio.

  Furthermore, the solvent was depressurizingly distilled from the filtrate at 120 degreeC with the rotary evaporator, the concentrated liquid was obtained, and this concentrated liquid was cooled to 5 degreeC and left overnight, and the crystallized substance was obtained. The cis isomer is liquid at room temperature, and the trans isomer is solid at room temperature (melting point: 67 to 72 ° C.).

  When the crystallized product was dissolved in methanol and analyzed by GC-MS, the ratio of cis isomer was 22.4 area%, the ratio of trans isomer was 72.49 area%, and the other components were 5.11 area%. And cis / trans isomer = 24/76.

(Comparative Example 1)
In Example 1, a filtrate was obtained in the same manner as in Example 1 except that the nitrogen gas was changed to hydrogen (H ₂ ) gas and the pressure of 12 MPa was changed to 12 MPa.

  When the obtained filtrate was analyzed by GC-MS, the cis-isomer ratio was 58.52 area%, the trans-isomer ratio was 37.69 area%, and the other components were 3.79 area%. / Trans isomer = 61/39.

  Further, the crystallization product obtained in the same manner as in Example 1 was analyzed by GC-MS. As a result, the cis-isomer ratio was 24.86 area%, the trans-isomer ratio was 66.59 area%, and other components. Was 8.55 area%, and cis / trans = 27/73.

(Comparative Example 2)
In Example 1, 1,4-diaminocyclohexane is converted into 1,4-diaminocyclohexane (produced by Tokyo Chemical Industry Co., Ltd.) having a cis / trans = 80/20, and nitrogen gas is converted into hydrogen (H ₂ ) gas. A filtrate was obtained in the same manner as in Example 1, except that the temperature was changed from 200 ° C. to 180 ° C. and the pressure of 12 MPa was changed to 8 MPa with the pressure of hydrogen gas.

  When the obtained filtrate was analyzed by GC-MS, the cis isomer ratio was 65.77 area%, the trans isomer ratio was 33.07 area%, and the other components were 1.16 area%. / Trans isomer = 67/33.

  Further, the crystallized product obtained in the same manner as in Example 1 was analyzed by GC-MS. As a result, the cis isomer ratio was 35.4 area%, the trans isomer ratio was 62.57 area%, and other components. Was 2.03 area% and cis / trans = 36/64.

  A summary of these results is shown in the table.

  The method of the present invention is useful as a method for obtaining a trans isomer from a cis isomer of diaminocyclohexane by isomerization. In particular, since isomerization can be performed without requiring high-pressure hydrogen gas, the reaction system can be simplified and the safety of the reaction can be improved, so that it is extremely useful.

Claims (10)

  A step of isomerizing a cis isomer of diaminocyclohexane to obtain a trans isomer of diaminocyclohexane in the presence of a metal catalyst, wherein the cis isomer is heated and pressurized in an inert gas, How to manufacture.   The process according to claim 1, wherein the diaminocyclohexane is 1,4-diaminocyclohexane.   The production method according to claim 1 or 2, wherein in the isomerization step, an isomer mixture containing a cis isomer and a trans isomer is heated and pressurized to increase the ratio of the trans isomer.   The production method according to claim 1, wherein the metal catalyst is a noble metal catalyst.   The manufacturing method in any one of Claims 1-4 which perform an isomerization process in presence of a solvent.   The production method according to claim 1, wherein the inert gas is nitrogen gas.   The manufacturing method according to claim 1, wherein the heat treatment temperature is 100 ° C. or higher.   The manufacturing method according to any one of claims 1 to 7, wherein the pressure of the inert gas is 5 MPa or more.   The manufacturing method according to claim 1, wherein the heat treatment temperature is 150 to 250 ° C. and the pressure of the inert gas is 7 to 20 MPa.   The production method according to claim 1, wherein in the isomerization step, the pressure of hydrogen gas is 0.1 MPa or less.