A process for the preparation of n-ethylhexanediamine

Abstract

The application discloses a preparation method of N-ethyl hexanediamine, which comprises the following steps: condensation and hydrogenation reaction of acetaldehyde and 6-aminocapronitrile as raw materials in the presence of a catalyst and an auxiliary agent to generate N-ethyl hexanediamine; the catalyst is a supported catalyst and / or a skeleton catalyst comprising at least one of metal Ni, Co, Cu, Fe, Pd, Pt, Ru and Rh as an active component; and the auxiliary agent is selected from inorganic alkali and / or quaternary ammonium alkali. The method can obtain N-ethyl hexanediamine through one-step condensation and hydrogenation of acetaldehyde and 6-aminocapronitrile as raw materials, has high reaction yield, simple post-treatment and an industrial application prospect.

Description

Technical Field

[0001] This invention relates to a preparation method, and more particularly to a method for preparing N-ethylhexanediamine. Background Technology

[0002] N-Ethylhexanediamine (NET) is currently mainly a byproduct of the low-pressure hydrogenation of adiponitrile to produce hexamethylenediamine. This reaction uses ethanol as a solvent, and ethanol reacts with hexamethylenediamine in the presence of a nickel catalyst to produce N-ethylhexamethylenediamine. Because the boiling points of N-ethylhexamethylenediamine and hexamethylenediamine are close, they are difficult to separate, requiring multiple distillations to obtain a qualified product, resulting in high energy consumption in the post-processing. Therefore, accurately determining the content of N-ethylhexamethylenediamine in hexamethylenediamine is crucial for selecting appropriate separation methods and techniques, thereby reducing energy consumption.

[0003] Industrially, external standard quantification is commonly used to determine the impurity content in hexamethylenediamine. Providing high-purity N-ethylhexamethylenediamine standard samples is crucial for the accurate determination of this impurity content in hexamethylenediamine. In addition, N-ethylhexamethylenediamine can also be used as an epoxy curing agent and adhesive in the coatings industry, and as a crosslinking agent in the paper industry.

[0004] Patent CN117550980A describes a method for preparing N-ethylhexanediamine, which uses hexanediamine and haloethane in the presence of sodium hydroxide and a phase transfer catalyst. However, this method has a complex process flow. Because the substrate hexanediamine has a bifunctional group, it easily generates impurities such as disubstituted N,N'-diethylhexanediamine during substitution reactions. Therefore, to ensure high selectivity of N-ethylhexanediamine, a large excess of the raw material hexanediamine is required, which increases production and post-processing costs.

[0005] Therefore, a new reaction route needs to be developed, with the expectation of preparing N-ethylhexanediamine in high yield. Summary of the Invention

[0006] To address the above technical problems, this invention proposes a method for preparing N-ethylhexanediamine. This method uses acetaldehyde and 6-aminohexanenitrile as raw materials to prepare N-ethylhexanediamine in one step through condensation and hydrogenation. The reaction yield is high, the post-processing is simple, and it has promising prospects for industrial application.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing N-ethylhexanediamine involves using acetaldehyde and 6-aminohexanonitrile as raw materials, and carrying out a condensation-hydrogenation reaction in the presence of a catalyst and an auxiliary agent to generate N-ethylhexanediamine. The reaction process is expressed as follows:

[0009]

[0010] The catalyst is a supported catalyst and / or a framework catalyst that includes at least one of the metals Ni, Co, Cu, Fe, Pd, Pt, Ru, and Rh as the active component, preferably a supported catalyst and / or a framework catalyst that includes at least one of the metals Ni and Co as the active component.

[0011] Preferably, the catalyst can be a framework catalyst such as Grace 2800 / Grace 2400 / Grace 2724, or a supported catalyst such as Xunkai 3100T and 6210P.

[0012] The auxiliary agent is selected from inorganic bases and / or quaternary ammonium bases, preferably one or more of LiOH, NaOH, KOH, tetramethylammonium hydroxide, and tetraethylammonium hydroxide.

[0013] In some examples of the present invention, the molar ratio of acetaldehyde to 6-aminohexanonitrile is (0.5-1.1):1, preferably (0.9-1):1.

[0014] In some examples of the present invention, the amount of catalyst used is 0.1-50% of the mass of acetaldehyde, preferably 1-10%.

[0015] In some examples of the present invention, the amount of the auxiliary agent is 0.1-50% of the catalyst mass, preferably 1-20%.

[0016] In some examples of the present invention, the reaction is carried out in a batch or semi-batch process, the reaction temperature is 60-150°C, preferably 80-120°C, and the reaction pressure is maintained at 2-10 MPaG, preferably 3-6 MPaG, by continuously feeding hydrogen.

[0017] In some examples of the present invention, the solvent is selected from protic solvents and / or aprotic solvents, preferably aprotic solvents, and more preferably one or two of tetrahydrofuran and dioxane;

[0018] Preferably, the amount of solvent used is 0.5-5 times the total mass of acetaldehyde and 6-aminohexanonitrile, more preferably 0.5-2 times.

[0019] In some examples of this invention, after the reaction is complete, the product is purified.

[0020] The refining process includes solvent removal distillation, light component removal distillation, and product distillation. Solvent removal distillation is performed as a primary distillation based on the selection of the reaction solvent, light component removal distillation is performed as a secondary distillation of the light components, and product distillation is used to obtain N-ethylhexanediamine with a purity >99.0%.

[0021] Preferably, a distillation column with 30 trays is used for solvent removal, light component removal, and product distillation. Solvent removal distillation conditions are as follows: for the tetrahydrofuran system, distillation pressure 48-58 kPaA, top temperature 45-50°C, reflux ratio 1-5:1; for the dioxane system, distillation pressure 13-16 kPaA, top temperature 45-50°C, reflux ratio 1-5:1. Light component removal distillation conditions are: distillation pressure 1-3 kPaA, top temperature 141-169°C, reflux ratio 1-10:1. Product distillation conditions are: distillation pressure 0.5-2 kPaA, top temperature 135-158 kPaA, reflux ratio 1-10:1.

[0022] The beneficial effects of this invention are as follows:

[0023] The new process route eliminates the need for excessive amounts of raw materials, ensuring high reaction conversion and high selectivity for N-ethylhexanediamine. The reaction can complete the condensation and hydrogenation to prepare N-ethylhexanediamine in a single step, resulting in high operational efficiency and simple post-processing, yielding high-purity N-ethylhexanediamine. Detailed Implementation

[0024] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not limit the scope of the invention.

[0025] Unless otherwise specified, all raw materials and reagents used in the following embodiments of the present invention can be purchased commercially. Specifically, the Grace2800 framework nickel catalyst and Grace2724 framework cobalt catalyst are manufactured by Grace Catalysts Technologies, and the CoCAT-3100T cobalt-based supported catalyst and SNCAT-6210P nickel-based supported catalyst are manufactured by Xunkai Catalysis.

[0026] The gas chromatographic analysis conditions for the reaction solution components in the following examples were as follows: Agilent DB-5 column, injection port temperature 280°C, FID detector temperature 300°C, column flow rate 1.5 ml / min, hydrogen flow rate 30 ml / min, air flow rate 400 ml / min, and the temperature program was 50°C held for 2 min, then increased to 80°C at 5°C / min, and then increased to 280°C at 15°C / min and held for 10 min.

[0027] Reactor parameters: 1L volume, self-priming stirring paddle, heated by electric heating mantle.

[0028]

Example 1

[0029] 200g of 6-aminohexanonitrile, 139.3g of tetrahydrofuran, 7.9g of Grace2800 nickel skeletal catalyst, and 0.16g of tetramethylammonium hydroxide pentahydrate were added to the reactor. After nitrogen purging, hydrogen was added to bring the pressure to 3 MPaG. Stirring was started and the temperature was raised to 80℃. Then, 78.6g of acetaldehyde was introduced into the reactor using a horizontal flow pump. After the feed was completed, the pressure was maintained at 3 MPaG until the hydrogen consumption was zero (i.e., the flow meter showed an instantaneous hydrogen feed flow rate of 0), at which point the reaction was stopped. The mixture was then cooled and filtered to obtain the mother liquor. GC analysis showed that the acetaldehyde conversion rate was 99.5% and the N-ethylhexanediamine selectivity was 99.7%.

[0030] The mother liquor was subjected to solvent removal, light component removal, and product distillation using a 30-plate column. The solvent removal distillation pressure was 48 kPaA, the top temperature was 45°C, and the reflux ratio was 1:1; the light component removal distillation pressure was 3 kPaA, the top temperature was 161°C, and the reflux ratio was 5:1; the product distillation pressure was 1 kPaA, the top temperature was 148°C, and the reflux ratio was 10:1. The product was obtained. GC analysis showed that the N-ethylhexanediamine content was 99.8%.

[0031]

Example 2

[0032] 100g of 6-aminohexanonitrile, 137.3g of dioxane, 3g of Grace2724 cobalt skeletal catalyst, and 0.11g of tetraethylammonium hydroxide were added to the reactor. After purging with nitrogen, hydrogen was added to bring the pressure to 5 MPaG. Stirring was started and the temperature was raised to 110℃. Then, 37.3g of acetaldehyde was introduced into the reactor using a horizontal flow pump. After the feed was completed, the pressure was maintained at 5 MPaG until the hydrogen consumption was zero, at which point the reaction was stopped. The mixture was then cooled and filtered to obtain the mother liquor. GC analysis showed that the acetaldehyde conversion rate was 99.8% and the N-ethylhexanediamine selectivity was 99.8%.

[0033] The mother liquor was subjected to solvent removal, light molecule removal, and product distillation using a 30-plate column. The solvent removal distillation was carried out at a pressure of 16 kPaA, a top temperature of 50°C, and a reflux ratio of 5:1; the light molecule removal distillation was carried out at a pressure of 1 kPaA, a top temperature of 161°C, and a reflux ratio of 1:1; the product distillation was carried out at a pressure of 2 kPaA, a top temperature of 158°C, and a reflux ratio of 10:1. The product was obtained. GC analysis showed that the N-ethylhexanediamine content was 99.7%.

[0034]

Example 3

[0035] 150g of 6-aminohexanonitrile, 322.2g of dioxane, 6g of CoCAT-3100T cobalt-based supported catalyst, and 0.31g of lithium hydroxide were added to the reactor. After purging with nitrogen, hydrogen was added to bring the pressure to 4 MPaG. Stirring was started and the temperature was raised to 100℃. Then, 64.8g of acetaldehyde was introduced into the reactor using a horizontal pump. After the feed was completed, the pressure was maintained at 4 MPaG until the hydrogen consumption was zero, at which point the reaction was stopped. The mixture was then cooled and filtered to obtain the mother liquor. GC analysis showed that the acetaldehyde conversion rate was 99.1% and the N-ethylhexanediamine selectivity was 99.2%.

[0036] The mother liquor was subjected to solvent removal, light component removal, and product distillation using a 30-plate column. The solvent removal distillation pressure was 13 kPaA, the top temperature was 45°C, and the reflux ratio was 1:1; the light component removal distillation pressure was 2 kPaA, the top temperature was 155°C, and the reflux ratio was 2:1; the product distillation pressure was 0.5 kPaA, the top temperature was 135°C, and the reflux ratio was 1:1. The product was obtained. GC analysis showed that the N-ethylhexanediamine content was 99.1%.

[0037]

Example 4

[0038] 180g of 6-aminohexanonitrile, 487.3g of tetrahydrofuran, 1g of SNCAT-6210P nickel-based supported catalyst, and 0.6g of sodium hydroxide were added to the reactor. After purging with nitrogen, hydrogen was added to bring the pressure to 6 MPaG. Stirring was started and the temperature was raised to 90℃. Then, 63.6g of acetaldehyde was introduced into the reactor using a horizontal flow pump. After the feed was completed, the pressure was maintained at 6 MPaG until the hydrogen consumption was zero, at which point the reaction was stopped. The mixture was then cooled and filtered to obtain the mother liquor. GC analysis showed that the acetaldehyde conversion rate was 99.9% and the N-ethylhexanediamine selectivity was 99.8%.

[0039] The mother liquor was subjected to solvent removal, light component removal, and product distillation using a 30-plate column. The solvent removal distillation pressure was 58 kPaA, the top temperature was 50°C, and the reflux ratio was 1:1; the light component removal distillation pressure was 1 kPaA, the top temperature was 141°C, and the reflux ratio was 5:1; the product distillation pressure was 0.5 kPaA, the top temperature was 135°C, and the reflux ratio was 5:1. The product was obtained. GC analysis showed that the N-ethylhexanediamine content was 99.5%.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that those skilled in the art can make several improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention.

Claims

1. A process for the preparation of N-ethylhexanediamine, characterized in that, is prepared by condensation and hydrogenation of acetaldehyde and 6-aminocapronitrile in the presence of a catalyst and an auxiliary; the catalyst is a supported catalyst and / or a skeletal catalyst comprising at least one of Ni, Co, Pd, Pt, Ru and Rh as an active component; the auxiliary is selected from one or more of LiOH, NaOH, KOH, tetramethylammonium hydroxide and tetraethylammonium hydroxide.

2. The process for the preparation of N-ethylhexamethylenediamine according to claim 1, characterized in that, the molar ratio of acetaldehyde to 6-aminocapronitrile is (0.5-1.1):

1.

3. The process for the preparation of N-ethylhexamethylenediamine according to claim 2, characterized in that, the molar ratio of acetaldehyde to 6-aminocapronitrile is (0.9-1):

1.

4. The process for the preparation of N-ethylhexamethylenediamine according to claim 1, characterized in that, the amount of the catalyst is 0.1-50% of the mass of acetaldehyde.

5. The process for the preparation of N-ethylhexamethylenediamine according to claim 4, characterized in that, the amount of the catalyst is 1-10% of the mass of acetaldehyde.

6. The process for the preparation of N-ethylhexamethylenediamine according to any one of claims 1 to 5, characterized in that, the amount of the auxiliary is 0.1-50% of the mass of the catalyst.

7. The process for the preparation of N-ethylhexamethylenediamine according to claim 6, characterized in that, the amount of the auxiliary is 1-20% of the mass of the catalyst.

8. The process for the preparation of N-ethylhexamethylenediamine according to any one of claims 1 to 5, characterized in that, the reaction is carried out in a batch or semi-batch process, the reaction temperature is 60-150℃, and the reaction pressure is maintained at 2-10 MPaG by continuously feeding hydrogen.

9. The process for the preparation of N-ethylhexamethylenediamine according to claim 8, characterized in that, the reaction is carried out in a batch or semi-batch process, the reaction temperature is 80-120℃, and the reaction pressure is maintained at 3-6 MPaG by continuously feeding hydrogen.

10. The process for the preparation of N-ethylhexamethylenediamine according to any one of claims 1 to 5, characterized in that, the solvent is selected from protic solvents and / or aprotic solvents.

11. The process for the preparation of N-ethylhexamethylenediamine according to claim 10, characterized in that, the solvent is selected from aprotic solvents.

12. The process for the preparation of N-ethylhexamethylenediamine according to claim 11, characterized in that, the solvent is selected from one or both of tetrahydrofuran and dioxane.

13. The method for preparing N-ethylhexanediamine according to claim 10, characterized in that, the amount of the solvent is 0.5-5 times the total mass of acetaldehyde and 6-aminocapronitrile.

14. The process for the preparation of N-ethylhexamethylenediamine according to claim 13, characterized in that, the amount of the solvent is 0.5-2 times the total mass of acetaldehyde and 6-aminocapronitrile.

15. The process for the preparation of N-ethylhexamethylenediamine according to any one of claims 1 to 5, characterized in that, the product is obtained by purification after the reaction; the purification is selected from desolventization rectification, light-removing rectification and heavy-removing rectification.

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