A continuous process for the preparation of 1,3-cyclohexanediamine

Abstract

The application provides a continuous preparation method of 1,3-cyclohexane diamine, and belongs to the technical field of chemical reaction engineering.The method is that 1,3-phenylenediamine is dissolved in a solvent a to obtain a substrate solution, the substrate solution is pumped into a fixed bed reactor provided with a catalyst at a certain flow rate, is fully mixed with hydrogen, and is reacted under temperature and pressure control;after the reaction is completed, 1,3-cyclohexane diamine solution is obtained after temperature control and cooling, and then the solvent is removed under reduced pressure to obtain 1,3-cyclohexane diamine.The method has the advantages of accurate feeding and controllable temperature, and has the advantages of mild reaction condition, low energy consumption, good strengthening mixing effect, few side reactions, high production efficiency, stable product quality, less tail gas pollution and green environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis, specifically relating to a continuous preparation method of 1,3-cyclohexanediamine. Background Technology

[0002] 1,3-Cyclohexanediamine is widely used in plastics and dye production (primarily as a rubber compounding agent and epoxy resin curing agent in plastics; and as an important intermediate in the production of azo dyes and sulfur dyes in dyes). In recent years, with the increasing demand for high-temperature resistant materials, the demand for 1,3-cyclohexanediamine has also increased, giving it an important role in industrial production. Its chemical structure is shown below:

[0003] .

[0004] The existing methods for synthesizing 1,3-cyclohexanediamine include:

[0005] 1. Junya Cao, Fenggang Han, et al. used m-phenylenediamine as raw material and, under the action of a self-made Ru / g-C3N4 catalyst (25 wt% of the raw material weight), at a temperature of 130 °C and a pressure of 5 MPa, with tetrahydrofuran as solvent, the reaction achieved a conversion rate of 96% and a selectivity of 82%.

[0006] 2. Ma Hongxian used p-phenylenediamine as raw material, Ru / Al2O3 as catalyst, lithium hydroxide as auxiliary agent, and a mixture of water and isopropanol as solvent to investigate the preparation of the catalyst and the hydrogenation process. When investigating the stability of the catalyst, it was found that after the catalyst was reused four times, the raw material conversion rate decreased from 65% to 37%.

[0007] 3. Yang Yanmi studied the preparation process of 1,3-cyclohexanedimethylamine by selective hydrogenation of m-phenylenediamine. Tetrahydrofuran was used as solvent and LiOH-modified Ru / Al2O3 was used as catalyst. The initial reaction conversion rate reached 100% and the selectivity was 97%. However, when the solid bed continuous stability was investigated, it was found that the catalyst specific surface area and pore volume decreased, Ru was seriously lost, and the conversion rate dropped rapidly.

[0008] 4. Chinese patent CN117069594A uses m-dinitrobenzene as raw material and a two-step hydrogenation method to prepare 1,3-cyclohexanediamine. The operation is cumbersome and not conducive to large-scale industrial production.

[0009] In addition, 1,3-cyclohexanediamine exists in two isomers, trans-1,3-cyclohexanediamine and cis-1,4-cyclohexanediamine, with the following structural formulas:

[0010]

[0011] Polymers prepared from trans isomers have more stable and superior properties, and a higher proportion of trans isomers is often required in their synthesis.

[0012] In summary, the main problems with the synthesis process of 1,3-cyclohexanediamine are: first, poor catalyst stability, making industrialization difficult; second, difficulty in controlling the configuration and poor selectivity; and third, cumbersome steps, which are not conducive to large-scale industrial production. Summary of the Invention

[0013] To address the issues related to existing technologies and safety, this invention provides a continuous preparation method for 1,3-cyclohexanediamine.

[0014] A continuous preparation method for 1,3-cyclohexanediamine, characterized by the following reaction formula:

[0015]

[0016] Includes the following steps:

[0017] (1) Dissolve 1,3-phenylenediamine in solvent a to obtain a substrate solution, replace with nitrogen, and pump it into a fixed-bed reactor containing a catalyst at a certain flow rate to mix it thoroughly with hydrogen. The reaction is carried out under controlled temperature and pressure.

[0018] (2) After the reaction is complete, the solution of 1,3-cyclohexanediamine is obtained by cooling under controlled temperature. Then the solvent is removed under reduced pressure to obtain 1,3-cyclohexanediamine.

[0019] Further, the solvent a mentioned in step (1) is one or more of ethanol, tert-butanol, methanol, tetrahydrofuran, water, and isopropanol; preferably tert-butanol and / or ethanol.

[0020] Further, the solvents tert-butanol and ethanol mentioned in step (1) are used, wherein the volume ratio of tert-butanol to ethanol is 1 to 5:1; preferably, the volume ratio of tert-butanol to ethanol is 2:1.

[0021] Further, the catalyst mentioned in step (1) is a modified Ru / Al2O3 catalyst containing an additive, wherein Ru is the active component; Al2O3 is the support; and the additive is any one of LiOH, NaOH, KOH, LiNO3, NaNO3, and KNO3; preferably LiOH.

[0022] Further, in step (1), the mass content of the promoter in the catalyst is 0.1% to 0.5% of the catalyst mass; preferably 0.3%; the catalyst mass is 0.2% to 2% of the mass of the raw material 1,3-phenylenediamine, preferably 1% of the mass of the raw material 1,3-phenylenediamine.

[0023] Furthermore, the temperature control temperature mentioned in step (1) is 80-100℃; preferably 90℃.

[0024] Furthermore, the pressure in step (1) is controlled at 2-7 MPa; preferably 5 MPa.

[0025] Further, the mass concentration of 1,3-phenylenediamine in solution a in step (1) is 15wt%-30wt%, preferably 20wt%.

[0026] Further, the feed flow rate of the 1,3-phenylenediamine solution in step (1) is 2-7 L / h, preferably 5 L / h, and the feed flow rate of hydrogen is 10-30 L / h, preferably 20 L / h.

[0027] Furthermore, the temperature control and cooling temperature mentioned in step (2) is 20-60℃; preferably 40℃.

[0028] The beneficial effects of this invention are:

[0029] (1) Using a fixed-bed reactor for the reaction not only provides milder reaction conditions and enhances the reaction process, but also increases reaction efficiency and allows for continuous preparation of the final product.

[0030] (2) It achieves precise feeding of materials, especially the Ru / Al2O3 catalyst containing the auxiliary agent LiOH, which can improve the proportion of trans and the reaction selectivity, and reduce the occurrence of side reactions. Detailed Implementation

[0031] Example 1: Preparation of lithium hydroxide-modified ruthenium hydrotalcite catalyst by impregnation method.

[0032] (1) At room temperature, 0.27 g of RuCl 3。 Dissolve 3H2O in 10mL of deionized water, add 20g of aluminum oxide while stirring, and continue stirring for 10min to obtain a metal aqueous solution, which is then soaked for 4h.

[0033] (2) Filter the mixed solution obtained in step (1), wash and filter the precipitate with deionized water and ethanol, and dry it at 100°C for 8 hours to obtain a solid complex.

[0034] (3) The solid composite obtained in step (2) is calcined at 200°C for 5 hours in an air atmosphere, and then reduced and activated at 250°C for 6 hours in a mixed gas of H2 and N2 (H2 volume fraction is 10%) to obtain the reduced solid catalyst.

[0035] (4) Dissolve the catalyst obtained in step (3) in 50 mL of deionized water, add 0.3% lithium hydroxide (based on the total mass of the catalyst) while stirring, and continue stirring for 24 h.

[0036] (5) Filter the mixed solution obtained in step (4), wash and filter the precipitate with deionized water and ethanol, and dry it at 100°C for 12 h to obtain the modified Ru / Al2O3 catalyst modified with lithium hydroxide.

[0037] Example 2:

[0038] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0039] (1) 20.0 g of 1,3-phenylenediamine was dissolved in solvents tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 2:1; wherein the mass concentration of 1,3-phenylenediamine was 20 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst via a flow meter. The feed flow rate of 1,3-phenylenediamine solution was 5 L / h, the feed flow rate of hydrogen was 20 L / h, the pressure was controlled at 5 MPa, the reaction temperature was controlled at 90 °C, the mass of catalyst was 1% of the mass of raw material 1,3-phenylenediamine, and the mass of lithium hydroxide auxiliary was 0.3% of the mass of catalyst.

[0040] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 40°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 100%, the product content was 98.7%, and the trans content was 87.3%.

[0041] Example 3:

[0042] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0043] (1) 20.0 g of 1,3-phenylenediamine was dissolved in solvents tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 5:1; wherein the mass concentration of 1,3-phenylenediamine was 30 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst via a flow meter. The feed flow rate of 1,3-phenylenediamine solution was 7 L / h, the feed flow rate of hydrogen was 30 L / h, the pressure was controlled at 7 MPa, the temperature was controlled at 100 °C, the mass of catalyst was 2% of the mass of raw material 1,3-phenylenediamine, and the mass of lithium hydroxide auxiliary was 0.5% of the mass of catalyst.

[0044] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 60°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 100%, the product content was 98.3%, and the trans content was 86.8%.

[0045] Example 4:

[0046] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0047] (1) 20.0 g of 1,3-phenylenediamine was dissolved in solvents tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 1:1; wherein the mass concentration of 1,3-phenylenediamine was 15 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst via a flow meter. The feed flow rate of the 1,3-phenylenediamine solution was 2 L / h, the feed flow rate of hydrogen was 10 L / h, the pressure was controlled at 2 MPa, the temperature was controlled at 80 °C, the mass of the catalyst was 0.2% of the mass of the raw material 1,3-phenylenediamine, and the mass of the lithium hydroxide auxiliary was 0.1% of the mass of the catalyst.

[0048] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 20°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 100%, the product content was 98.1%, and the trans content was 86.5%.

[0049] Example 5:

[0050] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0051] (1) 20.0 g of 1,3-phenylenediamine was dissolved in solvents tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 0.5:1; wherein the mass concentration of 1,3-phenylenediamine was 10 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst via a flow meter. The feed flow rate of 1,3-phenylenediamine solution was 1 L / h, the feed flow rate of hydrogen was 5 L / h, the pressure was controlled at 1 MPa, the temperature was controlled at 70 °C, the mass of the catalyst was 0.1% of the mass of the raw material 1,3-phenylenediamine, and the mass of the lithium hydroxide auxiliary was 0.05% of the mass of the catalyst.

[0052] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 10°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 93%, the product content was 91.3%, and the trans content was 51.5%.

[0053] Example 6:

[0054] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0055] (1) 20.0 g of 1,3-phenylenediamine was dissolved in solvents tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 6:1; wherein the mass concentration of 1,3-phenylenediamine was 35 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst via a flow meter. The feed flow rate of 1,3-phenylenediamine solution was 8 L / h, the feed flow rate of hydrogen was 35 L / h, the pressure was controlled at 8 MPa, the temperature was controlled at 110 °C, the catalyst mass was 2.5% of the mass of the raw material 1,3-phenylenediamine, and the mass of lithium hydroxide auxiliary agent was 0.7% of the mass of the catalyst.

[0056] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 70°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 91%, the product content was 92.6%, and the trans content was 57.8%.

[0057] Example 7:

[0058] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0059] (1) 20.0 g of 1,3-phenylenediamine was dissolved in tert-butanol to obtain a substrate solution, wherein the mass concentration of 1,3-phenylenediamine was 20 wt%. Nitrogen was used to purge the solution, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing lithium hydroxide-modified Ru / Al2O3 catalyst. The feed flow rate of the 1,3-phenylenediamine solution was 5 L / h, the feed flow rate of hydrogen was 20 L / h, the pressure was controlled at 5 MPa, and the temperature was controlled at 90 °C. The mass of the catalyst was 1% of the mass of the raw material 1,3-phenylenediamine, and the mass of the lithium hydroxide auxiliary was 0.3% of the mass of the catalyst.

[0060] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 40°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 100%, the product content was 95.3%, and the trans content was 73.5%.

[0061] Example 8:

[0062] A continuous preparation method for 1,3-cyclohexanediamine, comprising the following steps:

[0063] (1) 20.0 g of 1,3-phenylenediamine was dissolved in a mixture of tert-butanol and ethanol to obtain a substrate solution, wherein the volume ratio of tert-butanol to ethanol was 2:1; wherein the mass concentration of 1,3-phenylenediamine was 20 wt%, nitrogen was used for purging, and the solution was thoroughly mixed with hydrogen in a fixed-bed reactor containing Ru / Al2O3 catalyst via a flow meter. The feed flow rate of the 1,3-phenylenediamine solution was 5 L / h, the feed flow rate of hydrogen was 20 L / h, the pressure was controlled at 5 MPa, the temperature was controlled at 90 °C, and the mass of the catalyst was 1% of the mass of the raw material 1,3-phenylenediamine.

[0064] (2) After the reaction was completed, the solution of 1,3-cyclohexanediamine was obtained by cooling at 40°C. Then, the solvent was removed under reduced pressure to obtain the solution of 1,3-cyclohexanediamine. The conversion rate was 92%, the product content was 89.5%, and the trans content was 47.2%.

[0065] Comparative Example 1: Batch Reaction Hydrogenation Experiment

[0066] (1) Add the following to the intermittent high-pressure reactor: 20.0 g of 1,3-phenylenediamine, 180.0 g of tetrahydrofuran solvent, 1.0 g of 5wt% Ru / Al2O3 hydrogenation catalyst, and 0.2 g of lithium hydroxide monohydrate additive; seal the reactor, first replace the air in the reactor with high-purity nitrogen three times, pressurize to 1.0 MPa each time and then release the pressure, and then replace with high-purity hydrogen three times;

[0067] (2) After the displacement is completed, hydrogen is introduced into the reactor to the initial pressure of 3.0 MPa, stirring is started, the stirring speed is controlled at 800 r / min, and the temperature is increased to the reaction temperature of 130 ℃. During the constant temperature reaction, hydrogen is continuously added to maintain a constant reaction pressure of 5.0 MPa in the reactor, and the hydrogen is added intermittently at a constant temperature for 6 h.

[0068] After the reaction was completed, heating was stopped, and the mixture was allowed to cool naturally to room temperature while stirring. The pressure was slowly released, and residual hydrogen in the reactor was replaced with nitrogen. The reactor was then opened, and the reaction liquid was separated and the solid catalyst was recovered through precision filtration. The filtrate was distilled at atmospheric pressure to recover the tetrahydrofuran solvent. The remaining crude product was subjected to vacuum distillation, with the top temperature of the column controlled at 120 °C and the vacuum degree at 2 kPa. The target fraction was collected, and a 1,3-cyclohexanediamine solution was obtained for analysis. The conversion rate was 99%, the product content was 95.1%, and the trans-form content was 70.3%.

[0069] While the specific embodiments of the present invention have been described above, they are not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A continuous preparation method for 1,3-cyclohexanediamine, characterized in that, The reaction formula is shown below: ； Includes the following steps: (1) Dissolve 1,3-phenylenediamine in solvent a to obtain a substrate solution, replace with nitrogen, and pump it into a fixed-bed reactor containing a catalyst at a certain flow rate to mix it thoroughly with hydrogen. The reaction is carried out under controlled temperature and pressure. (2) After the reaction is complete, the solution of 1,3-cyclohexanediamine is obtained by cooling under controlled temperature. Then the solvent is removed under reduced pressure to obtain 1,3-cyclohexanediamine.

2. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The solvent a mentioned in step (1) is one or more of ethanol, tert-butanol, methanol, tetrahydrofuran, water, and isopropanol; preferably tert-butanol and / or ethanol.

3. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The solvents tert-butanol and ethanol mentioned in step (1) have a volume ratio of tert-butanol to ethanol of 1 to 5:1; preferably, the volume ratio of tert-butanol to ethanol is 2:

1.

4. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The catalyst mentioned in step (1) is a modified Ru / Al2O3 catalyst containing an additive, wherein Ru is the active component; Al2O3 is the support; and the additive is any one of LiOH, NaOH, KOH, LiNO3, NaNO3, and KNO3; preferably LiOH.

5. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The mass content of the additive in the catalyst described in step (1) is 0.1%-0.5% of the catalyst mass; preferably 0.3%; the catalyst mass is 0.2%-2% of the raw material 1,3-phenylenediamine mass, preferably 1% of the raw material 1,3-phenylenediamine mass.

6. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The temperature control temperature mentioned in step (1) is 80-100℃; preferably 90℃.

7. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, The pressure in step (1) is controlled at 2-7 MPa; preferably 5 MPa.

8. The continuous preparation method of 1,3-cyclohexanediamine according to claim 1, characterized in that, In step (1), the mass concentration of 1,3-phenylenediamine in solution a is 15wt%-30wt%, preferably 20wt%.

9. The method for preparing 1,3-cyclohexanediamine based on a fixed-bed reactor according to claim 1, characterized in that, The feed flow rate of the 1,3-phenylenediamine solution in step (1) is 2-7 L / h, preferably 5 L / h, and the feed flow rate of hydrogen is 10-30 L / h, preferably 20 L / h.

10. A continuous preparation method for 1,3-cyclohexanediamine according to claim 1, characterized in that, The temperature control and cooling temperature mentioned in step (2) is 20-60℃; preferably 40℃.

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