Preparation method of N-ethyl hexamethylenediamine

Abstract

The invention discloses a preparation method of N-ethyl hexamethylenediamine, which comprises the following steps: by taking acetaldehyde and 6-aminocapronitrile as raw materials, carrying out condensation hydrogenation reaction in the presence of a catalyst and an auxiliary agent to generate the N-ethyl hexamethylenediamine, the catalyst is a supported catalyst and / or a skeleton catalyst taking at least one of metals Ni, Co, Cu, Fe, Pd, Pt, Ru and Rh as an active component; the auxiliary agent is selected from inorganic base and / or quaternary ammonium base. According to the method, acetaldehyde and 6-aminocapronitrile are used as raw materials to prepare N-ethylhexamethylene diamine through condensation and hydrogenation in one step, the reaction yield is high, post-treatment is simple, and the method has industrial application prospects.

Description

Technical Field

[0001] The invention relates to a preparation method, in particular to a preparation method of N-ethylhexanediamine. Background Art

[0002] The main source of N-ethylhexanediamine (NET) is the byproduct of low-pressure hydrogenation of adiponitrile to produce hexanediamine. The reaction uses ethanol as a solvent, and ethanol reacts with hexanediamine under the action of a nickel catalyst to produce N-ethylated hexanediamine. Since the boiling point of N-ethylhexanediamine is close to that of hexanediamine, the two are difficult to separate, and multiple distillation and purification are required to obtain qualified products, resulting in high energy consumption in the post-processing process. Therefore, accurately determining the content of N-ethylhexanediamine in hexanediamine is very important for selecting appropriate separation methods and means to reduce energy consumption.

[0003] In industry, external standard quantitative method is usually used to determine the impurity content in hexamethylenediamine. Providing a high-purity N-ethylhexamethylenediamine standard sample is very important for the accurate determination of the impurity content in hexamethylenediamine. In addition, N-ethylhexamethylenediamine can also be used as an epoxy curing agent and adhesive in the coating industry, a crosslinking agent in the papermaking industry, etc.

[0004] Patent CN117550980A introduces a method for preparing N-ethylhexanediamine, which uses hexanediamine and ethane halide to prepare N-ethylhexanediamine in the presence of sodium hydroxide and a phase transfer catalyst. However, the process flow of this method is complicated. Since the substrate hexanediamine has a bifunctional group, it is easy to generate impurities such as disubstituted N,N'-diethylhexanediamine in the substitution reaction. Therefore, in order to ensure the high selectivity of N-ethylhexanediamine, a large excess of raw material hexanediamine is required, which increases the production and post-processing costs.

[0005] Therefore, it is necessary to develop a new reaction route, and it is expected that N-ethylhexanediamine can be prepared in high yield. Summary of the invention

[0006] In order to solve the above technical problems, the present invention provides a method for preparing N-ethylhexanediamine. The method uses acetaldehyde and 6-aminocapronitrile as raw materials to prepare N-ethylhexanediamine in one step through condensation and hydrogenation. The reaction yield is high, the post-treatment is simple, and the method has industrial application prospects.

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

[0008] A method for preparing N-ethylhexanediamine is to use acetaldehyde and 6-aminocapronitrile as raw materials, and to carry out 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 skeletal catalyst comprising at least one of metal Ni, Co, Cu, Fe, Pd, Pt, Ru, and Rh as an active component, preferably a supported catalyst and / or a skeletal catalyst comprising at least one of metal Ni and Co as an active component;

[0011] Preferably, the catalyst may be a skeleton catalyst such as Grace 2800 / Grace 2400 / Grace 2724 and 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-aminocapronitrile is (0.5-1.1):1, preferably (0.9-1):1.

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

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

[0016] In some examples of the present invention, the reaction adopts a batch or semi-batch process, the reaction temperature is 60-150°C, preferably 80-120°C, and the reaction pressure is controlled by continuous hydrogen flow to maintain at 2-10 MPaG, preferably 3-6 MPaG.

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

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

[0019] In some examples of the present invention, after the reaction is completed, the product is refined;

[0020] The refining includes desolventizing distillation, delightening distillation and product distillation; wherein, the desolventizing distillation performs a primary distillation according to the selection of the reaction solvent, the delightening distillation performs a secondary distillation on the reaction light components, and the product distillation is used to obtain an N-ethylhexanediamine product with a purity greater than 99.0%.

[0021] Preferably, a distillation tower with 30 plates is used for desolventization, light removal and product distillation. The desolventization distillation conditions are, for example, distillation pressure of tetrahydrofuran system is 48-58 kPaA, tower top temperature is 45-50°C, and reflux ratio is 1-5:1; dioxane system distillation pressure is 13-16 kPaA, tower top temperature is 45-50°C, and reflux ratio is 1-5:1. The light removal distillation conditions are distillation pressure of 1-3 kPaA, tower top temperature of 141-169°C, and reflux ratio of 1-10:1. The product distillation conditions are distillation pressure of 0.5-2 kPaA, tower top temperature of 135-158 kPaA, and reflux ratio of 1-10:1.

[0022] The beneficial effects of the present invention are:

[0023] By adopting the new process route, the raw material ratio does not need to be greatly excessive to ensure a high reaction conversion rate and a high selectivity of N-ethylhexanediamine; the reaction can complete the condensation hydrogenation to prepare N-ethylhexanediamine through a one-step process, the operation efficiency is high, and the post-treatment is simple, so that high-purity N-ethylhexanediamine can be obtained. DETAILED DESCRIPTION

[0024] The present invention is further described below by means of specific examples. The examples described in the present invention are only used to illustrate the present invention and do not limit the scope of the present invention.

[0025] Unless otherwise specified, the raw materials and reagents in the following examples of the present invention can be purchased from commercial sources. Among them, the manufacturer of Grace2800 skeleton nickel catalyst and Grace2724 skeleton cobalt catalyst is Grace Catalysts Technologies, and the manufacturer of CoCAT-3100T cobalt-based supported catalyst and SNCAT-6210P nickel-based supported catalyst is Xunkai Catalysis.

[0026] The gas chromatography analysis conditions of the reaction liquid components in the following examples are: Agilent DB-5 chromatographic 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 programmed temperature rise mode is 50°C for 2 min, heating to 80°C at 5°C / min, and then heating to 280°C at 15°C / min and holding for 10 min.

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

[0028] [Example 1]

[0029] Add 200g 6-aminocapronitrile, 139.3g tetrahydrofuran (THF), 7.9g Grace2800 skeleton nickel catalyst, 0.16g tetramethylammonium hydroxide pentahydrate into the reactor, supplement hydrogen to 3MPaG after nitrogen replacement, open stirring and warm up to 80 ℃, then use a horizontal flow pump to pass 78.6g of acetaldehyde into the reactor. After the feeding is completed, maintain 3MPaG pressure until the hydrogen consumption is zero (i.e., the flow meter shows that the instantaneous feed flow of hydrogen is 0), and the reaction stops. Then cool and filter to obtain a reaction mother solution. Detected by GC, acetaldehyde conversion is 99.5%, and N-ethylhexanediamine selectivity is 99.7%.

[0030] The mother liquor was subjected to desolventization, delightening and product distillation using a plate number of 30. The desolventizing distillation pressure was 48 kPaA, the tower top temperature was 45°C, and the reflux ratio was 1:1; the delightening distillation pressure was 3 kPaA, the tower top temperature was 161°C, the reflux ratio was 5:1, and the product distillation pressure was 1 kPaA, the tower top temperature was 148°C, and the reflux ratio was 10:1 to obtain the product. The product was analyzed by GC, and the N-ethylhexanediamine content was 99.8%.

[0031] [Example 2]

[0032] Add 100g 6-aminocapronitrile, 137.3g dioxane, 3g Grace2724 skeleton cobalt catalyst, 0.11g tetraethylammonium hydroxide into the reactor, add hydrogen to 5MPaG after nitrogen replacement, start stirring and heat to 110°C, then use a horizontal flow pump to pass 37.3g of acetaldehyde into the reactor. After the feeding is completed, maintain a pressure of 5MPaG until the hydrogen consumption is zero, and the reaction stops. Then cool and filter to obtain a reaction mother liquor. GC detection shows that the acetaldehyde conversion rate is 99.8% and the N-ethylhexanediamine selectivity is 99.8%.

[0033] The mother liquor was subjected to desolventization, delightening and product distillation using a plate number of 30. The desolventizing distillation pressure was 16 kPaA, the tower top temperature was 50°C, and the reflux ratio was 5:1; the delightening distillation pressure was 1 kPaA, the tower top temperature was 161°C, the reflux ratio was 1:1, and the product distillation pressure was 2 kPaA, the tower top temperature was 158°C, and the reflux ratio was 10:1 to obtain the product. The product was analyzed by GC, and the N-ethylhexanediamine content was 99.7%.

[0034] [Example 3]

[0035] 150g 6-aminocapronitrile, 322.2g dioxane, 6g CoCAT-3100T cobalt-based supported catalyst, 0.31g lithium hydroxide were added to the reactor, and hydrogen was added to 4MPaG after nitrogen replacement. Stirring was started and the temperature was raised to 100°C, and then 64.8g of acetaldehyde was introduced into the reactor with a horizontal flow pump. After the feeding was completed, the pressure of 4MPaG was maintained until the hydrogen consumption was zero, and the reaction was stopped. Then the temperature was lowered and filtered to obtain a reaction mother liquor. GC detection showed that the acetaldehyde conversion was 99.1% and the N-ethylhexanediamine selectivity was 99.2%.

[0036] The mother liquor was subjected to desolventization, delightening and product distillation using a plate number of 30. The desolventizing distillation pressure was 13 kPaA, the tower top temperature was 45°C, and the reflux ratio was 1:1; the delightening distillation pressure was 2 kPaA, the tower top temperature was 155°C, the reflux ratio was 2:1, and the product distillation pressure was 0.5 kPaA, the tower top temperature was 135°C, and the reflux ratio was 1:1 to obtain the product. The product was analyzed by GC, and the N-ethylhexanediamine content was 99.1%.

[0037] [Example 4]

[0038] In reactor, add 180g 6-aminocapronitrile, 487.3g tetrahydrofuran (THF), 1g SNCAT-6210P nickel-based supported catalyst, 0.6g sodium hydroxide, supplement hydrogen to 6MPaG after nitrogen replacement, open stirring and be warming up to 90 ℃, then pass into reactor 63.6g of acetaldehyde with advection pump. After feeding finishes, maintain 6MPaG pressure until hydrogen consumption is zero, and reaction stops. Then cool and filter to obtain reaction mother liquor. Through GC detection, acetaldehyde conversion 99.9%, N-ethylhexanediamine selectivity 99.8%.

[0039] The mother liquor was subjected to desolventization, delightening and product distillation using a plate number of 30. The desolventizing distillation pressure was 58 kPaA, the tower top temperature was 50°C, and the reflux ratio was 1:1; the delightening distillation pressure was 1 kPaA, the tower top temperature was 141°C, the reflux ratio was 5:1; the product distillation pressure was 0.5 kPaA, the tower top temperature was 135°C, and the reflux ratio was 5:1 to obtain the product. The product was analyzed by GC, and the N-ethylhexanediamine content was 99.5%.

[0040] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this field can make several improvements and supplements without departing from the method of the present invention. These improvements and supplements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing N-ethylhexanediamine, characterized in that: The process uses acetaldehyde and 6-aminocapronitrile as raw materials, and carries out condensation hydrogenation reaction in the presence of a catalyst and an auxiliary agent to generate N-ethylhexanediamine. The catalyst is a supported catalyst and / or a skeleton catalyst including at least one of metals Ni, Co, Cu, Fe, Pd, Pt, Ru, and Rh as an active component; 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.

2. The method for preparing N-ethylhexanediamine according to claim 1, characterized in that: The molar ratio of acetaldehyde to 6-aminocapronitrile is (0.5-1.1):1, preferably (0.9-1):

1.

3. The method for preparing N-ethylhexanediamine according to claim 1, characterized in that: The amount of the catalyst used is 0.1-50% of the mass of acetaldehyde, preferably 1-10%.

4. The method for preparing N-ethylhexanediamine according to any one of claims 1 to 3, characterized in that: The dosage of the auxiliary agent is 0.1-50% of the mass of the catalyst, preferably 1-20%.

5. The method for preparing N-ethylhexanediamine according to any one of claims 1 to 4, characterized in that: The reaction adopts a batch or semi-batch process, the reaction temperature is 60-150°C, preferably 80-120°C, and the reaction pressure is controlled by continuously passing hydrogen to maintain at 2-10 MPaG, preferably 3-6 MPaG.

6. The method for preparing N-ethylhexanediamine according to any one of claims 1 to 5, characterized in that: The solvent is selected from a protic solvent and / or an aprotic solvent, preferably an aprotic solvent, more preferably one or two of tetrahydrofuran and dioxane; Preferably, the amount of the solvent used is 0.5-5 times, preferably 0.5-2 times, the total mass of acetaldehyde and 6-aminocapronitrile.

7. The method for preparing N-ethylhexanediamine according to any one of claims 1 to 6, characterized in that: After the reaction is completed, the product is purified; The refining includes solvent removal distillation, light removal distillation and heavy removal distillation.

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