Preparation method of 1, 4-cyclohexanediamine with high trans-cis ratio

Abstract

The invention discloses a preparation method of 1, 4-cyclohexanediamine with a high trans-cis ratio. According to the method, 1, 4-phenylenediamine is adopted as a raw material, an ether compound is adopted as a solvent, under the action of a metal supported catalyst, a proper amount of benzene and / or a monosubstituted alkylbenzene compound is added, the trans-form proportion of 1, 4-CHDA can be effectively increased in the hydrogenation process of 1, 4-PDA, meanwhile, high selectivity of 1, 4-CHDA is maintained, and the application performance of the product in polyurethane is improved.

Description

Technical Field

[0001] The invention relates to a 1,4-PDA hydrogenation method, in particular to a method for preparing high-reverse-cis ratio 1,4-CHDA, belonging to the field of amine compound synthesis. Background Art

[0002] 1,4-CHDA is an important intermediate in the polyurethane industry. It has excellent light stability and air stability and can be widely used in the preparation of polyamide resins and aliphatic polyurethanes.

[0003] 1,4-CHDA can be synthesized by hydrogenation of 1,4-PDA. Since its molecular structure contains cyclohexyl, it has two stereoisomers, cis and trans. A large number of studies have found that compared with the cis, polyurethane or polyamide products prepared using trans 1,4-CHDA have better elasticity, heat resistance and stability. At present, the cis content of commercially available 1,4-CHDA products is about 60-80%, and the trans content is about 20-40%. Since the boiling points of the two stereoisomers in 1,4-CHDA are close, it is difficult to purify and separate them by distillation. At the same time, the cis produced during the hydrogenation of 1,4-PDA will further increase the production cost of 1,4-CHDA products. Therefore, how to effectively increase the proportion of trans in the hydrogenation process of 1,4-PDA has become a research focus of scientific researchers.

[0004]

[0005] CN102690204B uses o-phenylenediamine, m-phenylenediamine or p-phenylenediamine as raw materials, uses isopropanol aqueous solution or tetrahydrofuran aqueous solution as solvent, and reacts with ammonia and hydrogen, sodium nitrite and a catalyst in a slurry bed reactor, thereby achieving a phenylenediamine conversion rate of more than 99% and a cyclohexanediamine selectivity of up to 96.8. However, it does not mention the control of the ratio of the two cis and trans isomers in 1,4-CHDA.

[0006] Su Chengyan et al. [Study on the synthesis of CHDA by catalytic hydrogenation of PDA and purification process of trans-CHDA [D]. Xiamen University. 2007] used a 5% Ru / C catalyst activated at 500°C and treated with alkali. In isopropanol solvent, the reaction temperature was 140°C, the reaction pressure was 8 MPa, the reaction time was 20 min, and with composite sodium salt as an auxiliary agent, the conversion rate of p-phenylenediamine was close to 100%, and the selectivity of 1,4-CHDA reached 90%. However, the catalyst dosage reached 18.5% of the raw material and could only be recycled 3 times. Therefore, the catalyst cost is very high, which limits its promotion and use in industry.

[0007] The literature [ChemCatChem, 2013, vol.5, #10, p.2905-2912] reported that 1,4-cyclohexanediol was used as the raw material, and 1,4-CHDA was prepared by reacting the catalyst triruthenium dodecacarbonyl, the ligand 4,5-di(diisopropylphosphinomethyl)acridine, ammonia and the solvent tert-butyl alcohol at 170°C in a sealed tank, wherein the trans ratio was as high as 64.4%. However, the ligand is expensive, and the raw material 1,4-cyclohexanediol has no price advantage, so it is not suitable for industrial-scale production. Summary of the invention

[0008] In view of the above problems existing in the prior art, the present invention provides a method for preparing 1,4-cyclohexanediamine with a high trans-cis ratio, which can effectively increase the trans-cis ratio of 1,4-CHDA to above 4:1, while the 1,4-PDA conversion rate is close to 100%, and the 1,4-CHDA selectivity is maintained at above 98%, thereby improving the application performance of the product in polyurethane.

[0009] To achieve the above purpose, the technical solution of the present invention is as follows:

[0010] The present invention provides a method for preparing a CHDA with a high trans-cis ratio, comprising the following steps:

[0011] Under the action of metal-supported catalyst, 1,4-PDA is used as a reaction raw material, ether compounds are used as solvents, benzene and / or monosubstituted alkylbenzene are added, and 1,4-CHDA is prepared by hydrogenation reaction.

[0012] In the present invention, the benzene and / or monosubstituted alkylbenzene includes one or more of benzene, toluene, ethylbenzene and isopropylbenzene, preferably benzene and / or toluene. The molar addition amount of the benzene or monosubstituted alkylbenzene is 0.1-1.0 times the molar amount of 1,4-PDA, preferably 0.2-0.5 times.

[0013] In the present invention, the active metal of the metal-supported catalyst comprises one or more of Ru, Rh, Ni, Pt, and Pd. The catalyst carrier is one or more of diatomaceous earth, alumina, activated carbon, lithium aluminate, and zirconium oxide. The active metal content in the metal-supported catalyst is 1-10wt%, preferably 3-5wt%, calculated based on the total weight of the metal-supported catalyst.

[0014] As a preferred solution, the amount of the metal-supported catalyst is 1-10 wt %, preferably 3-6 wt %, based on the mass of 1,4-PDA.

[0015] In the present invention, the ether compound is selected from one or more of tetrahydrofuran, 1,4-dioxane, methyl ether, ethyl ether and methyl tert-butyl ether, preferably tetrahydrofuran and / or 1,4-dioxane.

[0016] As a preferred solution, the mass ratio of 1,4-PDA to solvent is 0.03-0.3, preferably 0.1-0.15.

[0017] In the present invention, there are no special requirements for the reaction conditions involved in the hydrogenation reaction process. Those skilled in the art can screen them according to existing published methods as needed. For example, the hydrogenation reaction temperature is 100-190°C, such as 100°C, 130°C, 160°C, 190°C, preferably 110-130°C.

[0018] Preferably, the hydrogenation reaction has a pressure of 3-15 MPaA, such as 3 MPaA, 5 MPaA, 7 MPaA, 9 MPaA, 11 MPaA, 13 MPaA, 15 MPaA, preferably 5-10 MPaA; specifically, the reaction pressure can be controlled by the amount of hydrogen introduced.

[0019] Preferably, when the introduction of hydrogen is stopped, the pressure of hydrogen consumed in the reaction drops to less than 0.01 MPa / min, such as 0.009 MPa / min, 0.008 MPa / min, 0.007 MPa / min, 0.005 MPa / min, etc., at which time the reaction is complete, which is the end point of the hydrogenation reaction.

[0020] In the present invention, the reactor used in the method is an intermittent autoclave reactor with a catalyst filtering device; preferably, the catalyst filtering device is a built-in filter or an external filter, more preferably a built-in filter of the autoclave.

[0021] In the present invention, after the hydrogenation reaction is completed, the metal-supported catalyst can be recovered and reused; the metal-supported catalyst is separated and recovered by conventional means such as filtration, and the present invention has no special requirements; preferably, the catalyst separation method is as follows: when the temperature of the reaction liquid drops to 50°C or below, N2 not exceeding 0.6MPaA is used to filter and separate the product liquid and the catalyst through the catalyst filtration device in the kettle.

[0022] According to the method of the present invention, the ratio of 1,4-CHDA to anti-cis isomer is above 4:1, while the conversion rate of 1,4-PDA is close to 100%, and the selectivity of 1,4-CHDA is above 98%.

[0023] The trans-isomer of 1,4-CHDA is a thermodynamically stable product. To obtain a higher content of the trans-isomer product, the conventional 1,4-PDA hydrogenation method uses a higher reaction temperature, which is conducive to the conversion of the cis-isomer 1,4-CHDA to the trans-isomer 1,4-CHDA. However, when the cis-to-cis ratio of 1,4-CHDA reaches 4:6, if the reaction temperature is further increased to increase the trans-isomer content, the 1,4-CHDA will undergo an ammonia depolymerization reaction to form a large amount of heavy component tar, thereby significantly reducing the selectivity of 1,4-CHDA.

[0024] Compared with the prior art, the positive effect of the method of the present invention is that an appropriate amount of benzene or monosubstituted alkylbenzene is added to the 1,4-PDA hydrogenation reaction system. Due to the electron-donating effect of the alkyl substituent and the low steric hindrance of benzene, benzene or monosubstituted alkylbenzene has a higher hydrogenation reaction activity than 1,4-PDA. Therefore, at a lower reaction temperature, benzene or monosubstituted alkylbenzene will be adsorbed on the catalyst surface before 1,4-PDA, and a hydrogenation reaction will occur. At the same time, a large amount of reaction heat generated will cause the hot spot temperature on the catalyst surface to rise significantly. At this time, 1,4-PDA enters the high-temperature active area of ​​the catalyst to undergo a hydrogenation reaction, which is beneficial to increase the trans-isomer content in 1,4-CHDA. During the reaction process, the liquid phase temperature of the reaction system does not change, but the hot spot temperature on the catalyst surface rises rapidly. Therefore, the conversion of high-content trans-isomer 1,4-CHDA can be achieved at a lower liquid phase temperature, while avoiding the generation of a large amount of ammonia depolymerization tar at a high liquid phase temperature, which wraps the catalyst surface and causes a decrease in activity, and can always maintain a high selectivity for 1,4-CHDA, greatly reducing the production cost.

[0025] It is worth noting that the amount of benzene or monosubstituted alkylbenzene added should be 0.1-1.0 times the molar amount of 1,4-PDA, preferably 0.2-0.5 times. If the amount added exceeds the range described in this article, the selectivity of 1,4-CHDA will be reduced. This is mainly because when the content of benzene or monosubstituted alkylbenzene compounds in the reaction system exceeds the standard, its strong hydrogenation reaction activity will cause 1,4-PDA to lack hydrogen in the reaction, thereby forming an unsaturated Schiff base intermediate compound, and then the molecules condense into heavy component tar, resulting in a decrease in the selectivity of 1,4-CHDA. DETAILED DESCRIPTION

[0026] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the listed embodiments.

[0027] In the embodiments and comparative examples of the present invention, the sources of the main raw materials used are as follows. Unless otherwise specified, other raw materials and reagents were purchased from commercial sources:

[0028] 5wt% Ru / C and 3wt% Rh / Al2O3 were purchased from Johnson Matthey;

[0029] Tetrahydrofuran and 1,4-dioxane were purchased from Komiou Company with analytical grade;

[0030] 1,4-PDA was purchased from Acros Reagent Company with a purity greater than 99%.

[0031] Benzene, toluene and p-xylene were purchased from Aladdin Reagent Company with a purity greater than 99%.

[0032] The main equipment information is as follows:

[0033] Test method: The conditions for gas chromatography analysis in the following examples are: Agilent 7890 and DB-5 chromatographic columns, injector temperature of 280°C, detector temperature of 300°C. The heating program is as follows: the initial column temperature is 50°C, maintained for 2 min; the temperature is increased to 80°C at 5°C / min, maintained for 0 min; the temperature is increased to 300°C at 15°C / min, maintained for 15 min. The content of each component is determined by normalization method.

[0034] Example 1

[0035] In a high-pressure reactor, add 0.65g of 5wt% Ru / C catalyst, 21.6g of 1,4-PDA, 216g of THF and 3.12g of benzene. After the reactor is leak-proof, it is replaced three times with 1MPaA of N2, and then replaced three times with 1MPaA of H2. Raise the temperature to 110°C, and continuously introduce H2 into the reactor through a hydrogen flow controller during the reaction to ensure that the reaction pressure is maintained at 3MPaA. When the hydrogen flow reading of the hydrogen flow controller is lower than 100sccm, stop introducing H2. When the pressure drop of the reactor is less than 0.01MPa / min, stop the reaction, cool and depressurize the reactor, and filter out the reaction liquid for gas chromatography analysis.

[0036] Example 2

[0037] In a high-pressure reactor, add 1.3g of 3wt% Rh / Al2O3 catalyst, 21.6g of 1,4-PDA, 144g of 1,4-dioxane and 9.2g of toluene. After the reactor is leak-proof, it is replaced three times with 1MPaA of N2, and then replaced three times with 1MPaA of H2. Raise the temperature to 130°C, and continuously introduce H2 into the reactor through a hydrogen flow controller during the reaction process to ensure that the reaction pressure is maintained at 10MPaA. When the hydrogen flow reading of the hydrogen flow controller is lower than 100sccm, stop introducing H2. When the pressure drop of the reactor is less than 0.01MPa / min, stop the reaction, cool the reactor and release the pressure, and filter out the reaction liquid for gas chromatography analysis.

[0038] Example 3

[0039] In a high-pressure reactor, add 2.16g of 5wt% Ru / C catalyst, 21.6g of 1,4-PDA, 72g of 1,4-dioxane and 18.4g of toluene. After the reactor is leak-proof, it is replaced three times with 1MPaA of N2, and then replaced three times with 1MPaA of H2. Raise the temperature to 160°C, and continuously introduce H2 into the reactor through a hydrogen flow controller during the reaction to ensure that the reaction pressure is maintained at 10MPaA. When the hydrogen flow reading of the hydrogen flow controller is lower than 100sccm, stop introducing H2. When the pressure drop of the reactor is less than 0.01MPa / min, stop the reaction, cool and depressurize the reactor, and filter out the reaction liquid for gas chromatography analysis.

[0040] Example 4

[0041] In a high-pressure reactor, add 0.22g of 3wt% Rh / Al2O3 catalyst, 21.6g of 1,4-PDA, 720g of THF and 3.12g of benzene. After the reactor is leak-proof, it is replaced three times with 1MPaA of N2, and then replaced three times with 1MPaA of H2. Raise the temperature to 100°C, and continuously introduce H2 into the reactor through a hydrogen flow controller during the reaction process to ensure that the reaction pressure is maintained at 4MPaA. When the hydrogen flow reading of the hydrogen flow controller is lower than 100sccm, stop introducing H2. When the pressure drop of the reactor is less than 0.01MPa / min, stop the reaction, cool and depressurize the reactor, and filter out the reaction liquid for gas chromatography analysis.

[0042] Comparative Example 1

[0043] Except that benzene is not added, the rest is the same as Example 1.

[0044] Comparative Example 2

[0045] Except that toluene is not added, the rest is the same as Example 2.

[0046] Comparative Example 3

[0047] The same procedures as in Example 3 were followed except that 21.2 g of p-xylene was added instead of toluene.

[0048] Comparative Example 4

[0049] The same procedures as in Example 4 were followed except that the amount of benzene added was increased to 31.2 g.

[0050] The results of the embodiments and comparative examples are shown in Table 1.

[0051] Table 1 Examples and Comparative Examples Results

[0052] 1,4-PDA conversion rate / % 1,4-CHDA selectivity / % Reverse cis ratio Example 1 100 99.5 93:7 Example 2 100 98.9 91:9 Example 3 100 98.1 88:12 Example 4 100 98.3 85:15 Comparative Example 1 100 95.2 42:58 Comparative Example 2 100 94.3 45:55 Comparative Example 3 100 91.1 51:49 Comparative Example 4 100 81.2 61:39

Claims

1. A method for preparing 1,4-cyclohexanediamine with a high trans-cis ratio, comprising the following steps: Under the action of metal-supported catalyst, 1,4-phenylenediamine is used as a reaction raw material, ether compounds are used as solvents, benzene and / or monosubstituted alkylbenzene are added, and 1,4-cyclohexanediamine is prepared by hydrogenation reaction.

2. The method according to claim 1, characterized in that The benzene and / or monosubstituted alkylbenzene include one or more of benzene, toluene, ethylbenzene and isopropylbenzene, preferably benzene and / or toluene.

3. The method according to claim 1 or 2, characterized in that: The molar amount of benzene and / or monosubstituted alkylbenzene added is 0.1-1.0 times, preferably 0.2-0.5 times, the molar amount of 1,4-phenylenediamine.

4. The method according to any one of claims 1 to 3, characterized in that: The active metal of the metal-supported catalyst comprises one or more of Ru, Rh, Ni, Pt, and Pd; and the catalyst carrier is one or more of diatomaceous earth, alumina, activated carbon, lithium aluminate, and zirconium oxide.

5. The method according to any one of claims 1 to 4, characterized in that: The active metal content in the metal-supported catalyst is 1-10 wt%, preferably 3-5 wt%, calculated based on the total weight of the metal-supported catalyst.

6. The method according to any one of claims 1 to 5, characterized in that: The amount of the metal supported catalyst is 1-10 wt % of the mass of 1,4-phenylenediamine, preferably 3-6 wt %.

7. The method according to any one of claims 1 to 6, characterized in that: The ether compound is selected from one or more of tetrahydrofuran, 1,4-dioxane, methyl ether, ethyl ether and methyl tert-butyl ether, more preferably tetrahydrofuran and / or 1,4-dioxane, wherein the mass ratio of 1,4-phenylenediamine to the solvent is 0.03-0.3, preferably 0.1-0.

15.

8. The method according to any one of claims 1 to 7, characterized in that: The hydrogenation reaction temperature is 100-190°C, preferably 110-130°C; the hydrogenation reaction pressure is 3-15MPaA, preferably 5-10MpaA.

9. The method according to any one of claims 1 to 8, characterized in that: The hydrogenation reaction ends when the pressure of hydrogen consumed by the reaction drops below 0.01 MPa / min after the introduction of hydrogen is stopped.

10. The method according to any one of claims 1 to 9, characterized in that: The trans-cis ratio of the high trans-cis ratio 1,4-cyclohexanediamine is greater than 4:1.

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