Process for the preparation of n,n-diaminopropylcyclohexylamine

Abstract

This invention provides a method for preparing N,N-diaminopropylcyclohexylamine, comprising the following steps: 1) mixing N,N-dicyanethylcyclohexylamine and solvent A to prepare a solution; 2) mixing Raney catalyst, solvent B, and water, then adding an alkaline buffer solution and a salt solution, followed by introducing hydrogen gas to adjust the system to the reaction pressure and heating to the reaction temperature, and then adding the solution prepared in step 1) under a hydrogen atmosphere to carry out a hydrogenation reaction to obtain N,N-diaminopropylcyclohexylamine. The process of this invention can use commercially available catalysts, is not demanding on the acidity of the raw materials, has mild reaction conditions, is simple, and the catalyst performance is stable. It can be reused for more than 30 batches, achieving a diaminopropylcyclohexylamine selectivity ≥95% and a total content of monoaminopropylcyclohexylamine and diaminopropylcyclohexylamine ≥96wt%, demonstrating excellent industrialization prospects.

Description

Technical Field

[0001] This invention relates to a method for cyano hydrogenation, specifically to a method for preparing N,N-diaminopropylcyclohexylamine. Background Technology

[0002] N,N-Diaminopropylcyclohexylamine is a novel alicyclic amine compound whose molecular structure combines the characteristics of both alicyclic and fatty amines. It is primarily used in epoxy curing agents and other untapped applications, such as decorative adhesives, tile grout, and epoxy flooring. Currently, many types of amines are applicable in epoxy curing agents, including fatty amines, alicyclic amines, and aromatic amines. Each amine compound has its own characteristics, among which alicyclic amines are favored by the market due to their strong resistance to yellowing, moderate activity, and low volatility. In today's society, with the rapid development of downstream applications, there is a certain demand for new molecular amines with specific structures. To meet the diversified needs of downstream customers, various methods are now used to modify alicyclic amines, including ethylene oxide / propylene oxide modification and acrylonitrile modification.

[0003] CN114835588A discloses a method for preparing diaminopropyl alicyclic amines by hydrogenation of dicyandiethyl alicyclic amines. This method uses dicyandiethyl alicyclic amines as a raw material and obtains the target product by hydrogenation under the action of anionic and cationic ligand catalysts. However, the catalysts used in this invention are difficult to prepare, which may pose certain problems for future industrialization. Furthermore, this invention does not demonstrate the continuous use of the catalyst and does not explain the catalyst stability.

[0004] CN113372241A discloses a one-step method for synthesizing dicyandiethyl tertiary amine from an aliphatic primary amine. This invention uses an aqueous glycolic acid solution as a catalyst, adding an aliphatic primary amine to acrylonitrile, and synthesizing the dicyandiethyl tertiary amine compound in one step under reflux conditions. After the reaction, low-boiling components are removed by vacuum distillation, and glycolic acid is decomposed at the operating temperature to obtain a dicyandiethyl tertiary amine compound with a yield higher than 95%. However, this patent does not specify the residual acid content in the product or how to utilize the dicyandiamide for hydrogenation to obtain the corresponding amine.

[0005] EP1229021A1 also discloses a method for the cyanoethylation of alicyclic primary diamines. This invention uses water and acetic acid as catalysts (pKa between -3.0 and 7.5), reacting acrylonitrile with alicyclic primary diamines to produce the corresponding cyanoethylated mixture. This invention also prepares cyanoethyl compounds under the action of an acidic catalyst, but does not address the issue of acid content in the product.

[0006] CN114591200A discloses a method for preparing dicyanoethyl tertiary amine. This method uses monocyanoethyl secondary amine and 3-cyanopropionic acid as raw materials, and obtains dicyanoethyl tertiary amine in the presence of an Fe-containing catalyst. The reaction process also utilizes the acidic catalytic effect of 3-cyanopropionic acid. However, this invention does not address the issue of residual acid in the product or how to utilize the dicyanoacetic acid for hydrogenation to obtain the corresponding amine. Furthermore, 3-cyanopropionic acid is not readily available and is expensive, which would affect the economic viability of the product.

[0007] As can be seen from the above literature reports, the synthesis of N,N-dicyanoethylcyclohexylamine uses acid as a catalyst or acidic raw materials for catalytic reaction. Therefore, in summary, the current hydrogenation process of N,N-dicyanoethylcyclohexylamine faces numerous problems, including acidic raw materials or unsuitable process conditions leading to catalyst deactivation, short catalyst life, and low product yield, which hinder its industrialization. Summary of the Invention

[0008] In view of the above-mentioned deficiencies in the existing technology, the present invention provides a method for preparing N,N-diaminopropylcyclohexylamine. The method is to prepare N,N-diaminopropylcyclohexylamine by hydrogenation reaction of N,N-dicyanethylcyclohexylamine. The method can utilize existing commercially available Raney catalysts, and is not demanding on the acid content of the raw materials. The catalyst has a long lifespan, is not easily deactivated, and is simple, with good prospects for industrialization.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for preparing N,N-diaminopropylcyclohexylamine, wherein the method uses N,N-dicyanethylcyclohexylamine as a raw material and prepares it through a hydrogenation reaction under the action of Raney catalyst.

[0011] The main reaction equations involved in the method of this invention are as follows:

[0012]

[0013] In an embodiment of the present invention, a method for preparing N,N-dicyanethylcyclohexylamine includes the following steps:

[0014] 1) Mix N,N-dicyanethylcyclohexylamine and solvent A to prepare a solution;

[0015] 2) Mix Raney catalyst, solvent B and water, then add alkaline buffer solution and salt solution, then introduce hydrogen gas to adjust the system to the reaction pressure, and heat to the reaction temperature. Then add the solution prepared in step 1) under hydrogen atmosphere to carry out hydrogenation reaction to obtain N,N-diaminopropylcyclohexylamine.

[0016] In this invention, the N,N-dicyanethylcyclohexylamine described in step 1) has a purity of 80-100 wt%, preferably 90-100 wt%; wherein the acid content is controlled to be ≤1 wt%, preferably 0-0.5 wt%, and the remainder is monocyanethylcyclohexylamine and trace impurities; wherein the acid is derived from the acid catalyst used in the synthesis process or the residue of the acidic raw materials used, such as one or more of hydrochloric acid, sulfuric acid, phosphoric acid, glycolic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, etc.

[0017] The N,N-dicyanethylcyclohexylamine is an existing product. It can be obtained using pure N,N-dicyanethylcyclohexylamine or crude N,N-dicyanethylcyclohexylamine before purification. The present invention does not have any special requirements for its source. It can be obtained by purchase or self-production. Self-production can be carried out by any feasible method disclosed in the prior art. As a preferred method, in some specific examples of the present invention, it is obtained by acid-catalyzed reaction of cyanoethylcyclohexylamine with acrylonitrile. For example, it can be prepared by referring to the methods disclosed in patents CN113372241A, CN114890913A, CN114907216A, etc. The specific steps are not described in the present invention.

[0018] In this invention, solvent A in step 1) is selected from one or more of methanol, ethanol, tetrahydrofuran, and dioxane, preferably ethanol and / or tetrahydrofuran.

[0019] In this invention, the mass concentration of N,N-dicyanethylcyclohexylamine in the solution prepared in step 1) is 10-60 wt%, preferably 40-50 wt%.

[0020] In this invention, the Raney catalyst in step 2) is selected from one or more of Raney nickel catalyst and Raney cobalt catalyst, preferably one or more of Grace2400, Grace2800, Grace 2724, Xunkai 1200, and Xunkai 3300;

[0021] The amount of the Raney catalyst is 10-30 wt%, preferably 15-25 wt%, of the mass of N,N-dicyanethylcyclohexylamine in step 1).

[0022] In this invention, solvent B in step 2) is selected from one or more of methanol, ethanol, tetrahydrofuran, and dioxane, preferably ethanol and / or tetrahydrofuran;

[0023] The mass ratio of solvent B to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:1, preferably 1-2:1;

[0024] The solvent B may be the same as or different from solvent A, but is preferably the same as solvent A.

[0025] In this invention, the mass ratio of water in step 2) to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:1, preferably 1-2:1.

[0026] In this invention, the alkaline buffer solution in step 2) is an aqueous solution of sodium carbonate and sodium bicarbonate;

[0027] The sodium carbonate-sodium bicarbonate aqueous solution has a total mass concentration of 0.5-5 wt%, preferably 1-3 wt%, and the molar ratio of sodium carbonate to sodium bicarbonate is 0.1-9:1, preferably 1-5:1.

[0028] The mass ratio of the alkaline buffer solution to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:1, preferably 1-2:1.

[0029] In this invention, the salt solution in step 2) is an aqueous solution of salt, selected from one or more aqueous solutions of sodium chloride, potassium chloride, sodium bromide, and potassium bromide, preferably an aqueous solution of sodium chloride;

[0030] The concentration of the salt solution is 10-30 wt%, preferably 20-30 wt%.

[0031] The mass ratio of the salt solution to N,N-dicyanethylcyclohexylamine in step 1) is 0.1-1:1, preferably 0.3-0.6:1.

[0032] In this invention, the reaction pressure in step 2) is 3-8 MPaG, preferably 4-6 MPaG; the reaction temperature is 80-140℃, preferably 90-120℃.

[0033] In this invention, step 2) involves adding the solution prepared in step 1) under a hydrogen atmosphere. The solution prepared in step 1) is added continuously, preferably by dropwise addition, with a dropwise addition time of 2-8 hours, preferably 4-6 hours. After the addition is completed, the hydrogenation reaction is continued at a constant temperature.

[0034] In this invention, the hydrogenation reaction in step 2) has a reaction time of 0.2-2 hours after the feeding is completed, preferably 0.4-0.6 hours (excluding the feeding time mentioned above).

[0035] In this invention, step 2) after the hydrogenation reaction is completed includes cooling, filtration and other operations to obtain a mother liquor containing N,N-diaminopropylcyclohexylamine, and can be further purified by distillation, thin film evaporation and other methods to obtain a pure product. These are conventional operations in the field and are not specifically limited by this invention.

[0036] Currently, there are few reports on the synthesis of N,N-diaminocyclohexylamine both domestically and internationally. Based on its structural characteristics, it can be obtained by hydrogenation of N,N-dicyanoethylcyclohexylamine. However, in our research on the hydrogenation of N,N-dicyanoethylcyclohexylamine, we discovered that an acidic catalyst is required during the preparation of the raw material N,N-dicyanoethylcyclohexylamine. This acidic catalyst is difficult to completely remove during post-treatment, inevitably resulting in residual acid in the N,N-dicyanoethylcyclohexylamine product. In the subsequent hydrogenation process to prepare N,N-dicyanoethylcyclohexylamine, this residual acid significantly affects the catalyst activity. The main reason for this is that the nitrile functional group first undergoes hydrogenation to form an imine intermediate. Imines are highly reactive; if the imine cannot rapidly hydrogenate to form a primary amine on the catalyst surface, it easily condenses with the reaction intermediate and product. Furthermore, the presence of acid promotes the condensation process, leading to the formation of various high-boiling-point macromolecular byproducts. The blockage of catalyst surface pores and the covering of active sites by these macromolecular byproducts cause rapid catalyst deactivation. To address this, the researchers of this invention discovered through further research that using a Raney catalyst, combined with an alkaline buffer solution, and adding a salt solution to the reaction system can effectively solve the above problems, eliminate the influence of residual acid, reduce the requirements for acid content in the raw materials, and make the method of this invention more widely applicable. Even when using crude N,N-dicyanethylcyclohexylamine as a raw material, excellent results can still be obtained.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] (1) The present invention uses a conventional Raney catalyst and introduces an alkaline buffer solution. On the one hand, the residual acid in the N,N-dicyanethylcyclohexylamine raw material, especially the crude product, can be quickly neutralized, thereby avoiding the occurrence of acid-promoted condensation reaction to generate large molecular by-products and extending the life of the catalyst. On the other hand, the alkaline buffer solution can also modify the Raney catalyst, reduce the deamination of by-products and the generation of secondary amines, not only improving the yield of the main product, but also reducing the encapsulation of heavy components on the active center of the catalyst and maintaining the high activity state of the catalyst.

[0039] (2) In this invention, adding a salt solution to the reaction system promotes the phase separation of the solvent and water. Since N,N-dicyanethylcyclohexylamine is poorly soluble in water, while N,N-diaminopropylcyclohexylamine is readily soluble, the entire system exhibits two phases: N,N-dicyanethylcyclohexylamine is mainly in the solvent phase, and N,N-diaminopropylcyclohexylamine is mainly in the aqueous phase. The entire reaction occurs at the interface between the two phases. By controlling the amount of salt solution, maintaining a certain solubility of N,N-dicyanethylcyclohexylamine in the aqueous phase reduces the poisoning of the catalyst by the raw material N,N-dicyanethylcyclohexylamine, thereby improving the catalyst's lifetime.

[0040] (3) The process of the present invention has mild reaction conditions and simple process. Existing commercial Raney catalysts can be used. There are no strict requirements on the acid content (≤1%) in the raw materials. The use of crude N,N-dicyanethyl can also ensure the stability of the catalyst performance. The catalyst can be reused for more than 30 batches. The selectivity of N,N-diaminopropylcyclohexylamine is ≥95%. The total content of monoaminopropylcyclohexylamine and diaminopropylcyclohexylamine in the product is ≥96wt%. The content of condensation macromolecule by-products is ≤3wt%. It has a good industrialization prospect. Detailed Implementation

[0041] To better understand the technical solution of the present invention, the following embodiments will further illustrate the method provided by the present invention. However, the present invention is not limited to the listed embodiments, but should also include any other known modifications within the scope of the claims of the present invention.

[0042] The conditions for gas chromatography analysis in the following examples were as follows: Agilent DB-5 column, injection port temperature 280°C, FID detector temperature 300°C, column flow rate 1.3 ml / min, hydrogen flow rate 40 ml / min, air flow rate 400 ml / min, and temperature program as follows: hold at 50°C for 2 min, increase to 80°C at 5°C / min, then increase to 300°C at 15°C / min and hold for 15 min.

[0043] The conditions for analyzing the acid content of the raw material N,N-dicyanethylcyclohexylamine in the following examples are as follows:

[0044] Instrument: Metrohm potentiometric titrator (Switzerland);

[0045] Standard solution: 0.02 mol / L potassium hydroxide-methanol standard solution;

[0046] Solvent: 100ml methanol;

[0047] Electrode: Non-aqueous phase acid-base electrode;

[0048] Operating procedure: Weigh 10g of sample, add 100ml of methanol, stir to dissolve, and then titrate with 0.02mol / L potassium hydroxide-methanol standard solution on a potentiometric titrator using a non-aqueous acid-base electrode as the indicator electrode.

[0049] The main raw materials used in the following examples or comparative examples are from the following sources; unless otherwise specified, all other raw materials are common commercially available materials:

[0050] Crude N,N-dicyanethylcyclohexylamine: prepared in-house; a reaction solution was prepared using cyclohexylamine and acrylonitrile as raw materials according to the method disclosed in patent CN113372241A, and then the reaction solution was separated to obtain crude N,N-dicyanethylcyclohexylamine.

[0051] Raney nickel catalysts: Grace 2400 / 2800, purchased from Grace Catalysts; Xunkai 1200, purchased from Shanghai Xunkai New Materials Technology Co., Ltd.

[0052] Raney cobalt catalysts: Grace 2724, purchased from Grace Catalysts; Xunkai 3300, purchased from Shanghai Xunkai New Materials Technology Co., Ltd.

[0053] The main equipment information is as follows:

[0054] High-pressure reactor: 1L capacity, manufactured by Yantai Keli Equipment;

[0055] Horizontal flow pump: Model 2PB00C, manufactured by Beijing Satellite.

[0056] Example 1

[0057] The steps for preparing N,N-diaminopropylcyclohexylamine are as follows:

[0058] The crude N,N-dicyanoethylcyclohexylamine was used as raw material, and its composition included 95wt% N,N-dicyanoethylcyclohexylamine, 0.5wt% glycolic acid, 4.4wt% monocyanoethylcyclohexylamine, and 0.1wt% other impurities.

[0059] The alkaline buffer solution is an aqueous solution of sodium carbonate and sodium bicarbonate, wherein the total mass concentration of sodium carbonate and sodium bicarbonate is 1 wt%, and the molar ratio of the two is 9:1.

[0060] The crude N,N-dicyanethylcyclohexylamine was prepared into a 50 wt% ethanol solution with ethanol.

[0061] 10g of Raney cobalt catalyst (Xunkai 3300), 50g of ethanol, and 50g of water were added to a high-pressure reactor. Then, 50g of sodium carbonate-sodium bicarbonate aqueous solution and 15g of sodium chloride aqueous solution (salt concentration of 20wt%) were added. After purging with nitrogen and hydrogen three times in sequence, the reactor was purged with hydrogen to 2MPaG and the temperature was raised. When the reaction temperature reached 100℃, the hydrogen pressure was raised to 4MPaG and maintained at this pressure. 50wt% of crude N,N-dicyanethylcyclohexylamine ethanol solution was added dropwise to the reaction system. When 100g of the feed was reached, the total addition time was 4h. The feed was stopped, and the reaction was continued for 0.2h. The reactor was then cooled and filtered to obtain the N,N-diaminopropylcyclohexylamine reaction solution. A sample was taken for gas chromatography analysis (quantification was performed using the area normalization method, and the content of each component was calculated based on the total mass of the sample after deducting the solvent). The catalyst was left in the reactor for reuse.

[0062] The catalyst was reused in 30 batches under the same conditions, and the results are shown in Table 1 below.

[0063] Table 1

[0064]

[0065] As can be seen from the data in the table above, the catalyst performance remained very stable after being reused 30 times.

[0066] Example 2

[0067] The steps for preparing N,N-diaminopropylcyclohexylamine are as follows:

[0068] The crude N,N-dicyanoethylcyclohexylamine was used as raw material, and its composition included 90wt% N,N-dicyanoethylcyclohexylamine, 1.0wt% glycolic acid, 8.9wt% monocyanoethylcyclohexylamine, and 0.1wt% other impurities.

[0069] The alkaline buffer solution is an aqueous solution of sodium carbonate and sodium bicarbonate, wherein the total mass concentration of sodium carbonate and sodium bicarbonate is 5 wt%, and the molar ratio of the two is 5:1.

[0070] The crude N,N-dicyanethylcyclohexylamine was prepared by mixing it with methanol to form a 60 wt% methanol solution of crude N,N-dicyanethylcyclohexylamine.

[0071] 15g of Raney nickel catalyst (Grace 2400), 100g of tetrahydrofuran, 25g of water, 100g of sodium carbonate-sodium bicarbonate aqueous solution, and 5g of potassium chloride aqueous solution (salt concentration of 30wt%) were added to a high-pressure reactor. After purging with nitrogen and hydrogen three times in sequence, the reactor was purged with hydrogen to 1MPaG and the temperature was raised. When the reaction temperature reached 80℃, the hydrogen pressure was raised to 3MPaG and maintained at this pressure. 60wt% of crude N,N-dicyanethylcyclohexylamine methanol solution was added dropwise to the reaction system. When the feed reached 83.3g, the total addition time was 6h. The feed was stopped, and the reaction was continued for 0.4h. The reactor was then cooled and filtered to obtain the N,N-diaminopropylcyclohexylamine reaction solution. A sample was taken for gas chromatography analysis. The catalyst was left in the reactor for reuse.

[0072] The catalyst was reused in 30 batches under the same conditions, and the results are shown in Table 2 below.

[0073] Table 2

[0074]

[0075]

[0076] As can be seen from the data in the table above, the catalyst performance remained very stable after being reused 30 times.

[0077] Example 3

[0078] The steps for preparing N,N-diaminopropylcyclohexylamine are as follows:

[0079] The crude N,N-dicyanoethylcyclohexylamine was used as raw material, and its composition included 80wt% N,N-dicyanoethylcyclohexylamine, 0.3wt% glycolic acid, 19.6wt% monocyanoethylcyclohexylamine, and 0.1wt% other impurities.

[0080] The alkaline buffer solution is an aqueous solution of sodium carbonate and sodium bicarbonate, wherein the total mass concentration of sodium carbonate and sodium bicarbonate is 0.5 wt%, and the molar ratio of the two is 0.1:1.

[0081] The crude N,N-dicyanethylcyclohexylamine was prepared into a 10 wt% tetrahydrofuran solution with tetrahydrofuran.

[0082] Add 5g of Raney cobalt catalyst (Grace 2724), 50g of dioxane, and 100g of water to a high-pressure reactor. Then add 25g of sodium carbonate-sodium bicarbonate aqueous solution and 30g of sodium bromide aqueous solution (salt concentration of 10wt%). After purging with nitrogen and hydrogen three times in sequence, purge with hydrogen to 3MPaG and start heating. When the reaction temperature reaches 140℃, pressurize with hydrogen to 6MPaG and maintain this pressure. Start adding 10wt% of crude N,N-dicyanethylcyclohexylamine tetrahydrofuran solution to the reaction system. When the feed reaches 500g, the total addition time is 2h. Stop feeding and continue the reaction for 2h. After cooling and filtration, obtain N,N-diaminopropylcyclohexylamine reaction solution. Take a sample for gas chromatography analysis. The catalyst is left in the reactor for reuse.

[0083] The catalyst was reused in 30 batches under the same conditions, and the results are shown in Table 3 below.

[0084] Table 3

[0085]

[0086] As can be seen from the data in the table above, the catalyst performance remained very stable after being reused 30 times.

[0087] Example 4

[0088] The steps for preparing N,N-diaminopropylcyclohexylamine are as follows:

[0089] The raw material is pure N,N-dicyanethylcyclohexylamine, and the composition is 100wt% N,N-dicyanethylcyclohexylamine.

[0090] The alkaline buffer solution is an aqueous solution of sodium carbonate and sodium bicarbonate, wherein the total mass concentration of sodium carbonate and sodium bicarbonate is 3 wt%, and the molar ratio of the two is 1:1.

[0091] Prepare a 40 wt% N,N-dicyanethylcyclohexylamine-dioxane solution by mixing pure N,N-dicyanethylcyclohexylamine with dioxane.

[0092] 7.5g of Raney nickel catalyst (Xunkai 1200), 150g of ethanol, and 50g of water were added to a high-pressure reactor. Then, 150g of sodium carbonate-sodium bicarbonate aqueous solution and 50g of potassium bromide aqueous solution (salt concentration of 15wt%) were added. After purging with nitrogen and hydrogen three times in sequence, the reactor was purged with hydrogen to 3MPaG and the temperature was raised. When the reaction temperature reached 90℃, the hydrogen pressure was increased to 8MPaG and maintained at this pressure. 40wt% of N,N-dicyanethylcyclohexylamine dioxane solution was added dropwise to the reaction system. When the feed reached 125g, the total addition time was 8h. The feed was stopped, and the reaction was continued for 0.2h. The reactor was then cooled and filtered to obtain N,N-diaminopropylcyclohexylamine reaction solution. A sample was taken for gas chromatography analysis. The catalyst was left in the reactor for reuse.

[0093] The catalyst was reused in 30 batches under the same conditions, and the results are shown in Table 4 below.

[0094] Table 4

[0095]

[0096]

[0097] As can be seen from the data in the table above, the catalyst performance remained very stable after being reused 30 times.

[0098] Comparative Example 1

[0099] N,N-Diaminopropylcyclohexylamine was prepared according to the method in Example 1, except that the sodium carbonate-sodium bicarbonate buffer solution was replaced with an equal volume of sodium carbonate aqueous solution (concentration 1 wt%), while other parameters and operations remained unchanged. The results are shown in Table 5 below.

[0100] Table 5

[0101]

[0102] Comparative Example 2

[0103] N,N-Diaminopropylcyclohexylamine was prepared according to the method in Example 1, except that the sodium carbonate-sodium bicarbonate buffer solution was replaced with an equal volume of sodium bicarbonate aqueous solution (concentration 1 wt%), while other parameters and operations remained unchanged. The results are shown in Table 6 below.

[0104] Table 6

[0105]

[0106]

[0107] Comparative Example 3

[0108] N,N-Diaminopropylcyclohexylamine was prepared according to the method in Example 1, except that sodium carbonate-sodium bicarbonate buffer was not added, while other parameters and operations remained unchanged. The results are shown in Table 7 below.

[0109] Table 7

[0110]

[0111] Comparative Example 4

[0112] N,N-Diaminopropylcyclohexylamine was prepared according to the method in Example 1, except that no salt solution was added, while other parameters and operations remained unchanged. The results are shown in Table 8 below.

[0113] Table 8

[0114]

[0115]

[0116] Although the present invention has been described in detail through the preferred embodiments described above, it should be understood that the above description should not be considered as a limitation of the present invention. Those skilled in the art will understand that modifications or adjustments can be made to the present invention based on the teachings of this specification. These modifications or adjustments should also be within the scope defined by the claims of the present invention.

Claims

1. A method for preparing N,N-diaminopropylcyclohexylamine, characterized in that the step... include: 1) Mix N,N-dicyanethylcyclohexylamine and solvent A to prepare a solution; 2) Mix Raney catalyst, solvent B and water, then add alkaline buffer solution and salt solution, then introduce hydrogen gas to adjust the system to the reaction pressure, and heat to the reaction temperature. Then add the solution prepared in step 1) under hydrogen atmosphere to carry out hydrogenation reaction to obtain N,N-diaminopropylcyclohexylamine. In step 2), the mass ratio of the salt solution to N,N-dicyanethylcyclohexylamine in step 1) is 0.1-1:1; The alkaline buffer solution is an aqueous solution of sodium carbonate and sodium bicarbonate. The salt solution is an aqueous solution of salt, selected from one or more aqueous solutions of sodium chloride, potassium chloride, sodium bromide, and potassium bromide.

2. The preparation method according to claim 1, characterized in that, The N,N-dicyanethylcyclohexylamine mentioned in step 1) has a purity of 80-100 wt%, wherein the acid content is controlled to be ≤1 wt%.

3. The preparation method according to claim 2, characterized in that, The purity of the N,N-dicyanethylcyclohexylamine is 90-100 wt%.

4. The preparation method according to claim 2, characterized in that, The acid content should be controlled at 0-0.5 wt%.

5. The preparation method according to claim 1, characterized in that, In step 1), solvent A is selected from one or more of methanol, ethanol, tetrahydrofuran, and dioxane; In step 1), the mass concentration of N,N-dicyanethylcyclohexylamine in the prepared solution is 10-60 wt%.

6. The preparation method according to claim 1, characterized in that, The mass concentration of N,N-dicyanethylcyclohexylamine in the prepared solution is 40-50 wt%.

7. The preparation method according to claim 1, characterized in that, Step 2) The Raney catalyst is selected from one or more of Raney nickel catalyst and Raney cobalt catalyst; The amount of Raney catalyst used is 10-30 wt% of the mass of N,N-dicyanethylcyclohexylamine in step 1).

8. The preparation method according to claim 7, characterized in that, The Raney catalyst is selected from one or more of Grace2400, Grace2800, Grace 2724, Xunkai 1200, and Xunkai 3300.

9. The preparation method according to claim 7, characterized in that, The amount of the Raney catalyst used is 15-25 wt% of the mass of N,N-dicyanethylcyclohexylamine in step 1).

10. The preparation method according to claim 1, characterized in that, In step 2), solvent B is selected from one or more of methanol, ethanol, tetrahydrofuran, and dioxane; The mass ratio of solvent B to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:1; Solvent B may be the same as or different from solvent A.

11. The preparation method according to claim 10, characterized in that, The mass ratio of solvent B to N,N-dicyanethylcyclohexylamine in step 1) is 1-2:

1.

12. The preparation method according to claim 10, characterized in that, Solvent B is the same as solvent A.

13. The preparation method according to claim 1, characterized in that, The mass ratio of water in step 2) to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:

1.

14. The preparation method according to claim 13, characterized in that, The mass ratio of the water to N,N-dicyanethylcyclohexylamine in step 1) is 1-2:

1.

15. The preparation method according to claim 1, characterized in that, Step 2) The sodium carbonate-sodium bicarbonate aqueous solution has a total mass concentration of 0.5-5 wt% for sodium carbonate and sodium bicarbonate, and a molar ratio of sodium carbonate to sodium bicarbonate of 0.1-9:

1. The mass ratio of the alkaline buffer solution to N,N-dicyanethylcyclohexylamine in step 1) is 0.5-3:

1.

16. The preparation method according to claim 15, characterized in that, The sodium carbonate-sodium bicarbonate aqueous solution has a total mass concentration of 1-3 wt% for sodium carbonate and sodium bicarbonate.

17. The preparation method according to claim 15, characterized in that, The molar ratio of sodium carbonate to sodium bicarbonate is 1-5:

1.

18. The preparation method according to claim 15, characterized in that, The mass ratio of the alkaline buffer solution to N,N-dicyanethylcyclohexylamine in step 1) is 1-2:

1.

19. The preparation method according to claim 1, characterized in that, The concentration of the salt solution in step 2) is 10-30 wt%.

20. The preparation method according to claim 19, characterized in that, The concentration of the salt solution is 20-30 wt%.

21. The preparation method according to claim 19, characterized in that, The mass ratio of the salt solution to N,N-dicyanethylcyclohexylamine in step 1) is 0.3-0.6:

1.

22. The preparation method according to claim 1, characterized in that, Step 2) The reaction pressure is 3-8 MPaG; the reaction temperature is 80-140℃.

23. The preparation method according to claim 22, characterized in that, The reaction pressure is 4-6 MPaG.

24. The preparation method according to claim 22, characterized in that, The reaction temperature is 90-120℃.

25. The preparation method according to claim 1, characterized in that, The solution prepared in step 1) as described in step 2) is fed continuously; after the feeding is completed, the hydrogenation reaction is continued at a constant temperature. The hydrogenation reaction described in step 2) takes 0.2-2 hours after the addition of the feed.

26. The preparation method according to claim 25, characterized in that, The solution prepared in step 1) is added by dripping for 2-8 hours.

27. The preparation method according to claim 26, characterized in that, The dripping time is 4-6 hours.

28. The preparation method according to claim 25, characterized in that, The hydrogenation reaction takes 0.4-0.6 hours after the feeding is completed.

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