A continuous process for the preparation of N,N,N',N'-tetra(2-hydroxyethyl)adipamide
By combining an overflow series autoclave reactor and a falling film evaporator, the problems of low yield and low purity in the preparation of N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide were solved, achieving efficient continuous production and improved product purity, while simplifying subsequent processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING BAOCHUN CHEMICAL INDUSTRY CO LTD
- Filing Date
- 2024-12-26
- Publication Date
- 2026-06-26
AI Technical Summary
Existing methods for preparing N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide suffer from low product yield, low purity, and inability to produce continuously. In particular, batch synthesis processes have drawbacks such as long reaction residence time, difficulty in completely removing byproducts, and low production efficiency.
The reaction was carried out continuously using an overflow series reactor with sodium methoxide as the catalyst. Diethanolamine and dimethyl adipate were fed in one batch and processed through a continuous reactor and falling film evaporator. The reaction conditions were controlled to ensure complete reaction and removal of by-products. Finally, a granulation process was used to obtain the solid product.
It achieves efficient and continuous production, high product purity, and effective removal of methanol by-product, avoiding complex steps such as solidification, crushing, and drying in traditional processes, thus improving production efficiency and product quality.
Smart Images
Figure CN122273447A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of compound synthesis, and specifically to a continuous preparation method of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide. Background Technology
[0002] Currently, the preparation of N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide generally uses diethanolamine and dimethyl adipate as raw materials, synthesized under alkaline catalytic conditions. In industrial production, there are two main mature production technologies: crystallization and a one-pot batch synthesis method. Numerous related patent documents have been reported. Regarding the crystallization process, methanol or methanol / acetone is mainly used as the crystallization solvent to prepare high-purity N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide, but the yield is low. Patent CN102633667B further improved the crystallization process by using a mixed crystallization solvent of methanol and ethyl acetate, achieving a higher yield and product purity of over 99%. Although the crystallization process can obtain high product purity, its drawbacks include a relatively low product yield, the need for solvent evaporation and recovery, relatively high energy consumption, and the need for drying to remove residual solvent after crystallization.
[0003] Regarding the one-pot batch synthesis process, the main patent reports include US5101073 and CN1075713A, which employ solvent-free production technology. This method can achieve a near 100% product yield, and the product quality meets application requirements, but the product purity is relatively low. Furthermore, in terms of specific process details, existing one-pot processes suffer from drawbacks such as long reaction residence times, difficulty in completely removing the byproduct methanol under industrial-scale reactor conditions, and lengthy subsequent processing steps. Moreover, because N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide has a melting point above 120°C, excessively long reaction residence times can lead to excessively high material viscosity or even solidification within the reactor in the later stages of the reaction. Therefore, a complex internal reactor structure is required to address this issue. Rapid discharge after reaction completion is necessary to prevent the material from solidifying. After solidification, the slurry-like product requires crushing, grinding, and further drying to remove residual methanol byproducts. Therefore, existing one-pot batch synthesis processes have numerous drawbacks, cannot be used for continuous production, and have low production efficiency. Summary of the Invention
[0004] To address the numerous drawbacks of existing one-pot batch synthesis processes, including their inability to produce continuously and low efficiency, this invention provides a continuous and efficient method for preparing N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide, comprising the following steps:
[0005] (1) Diethanolamine and dimethyl adipic acid are respectively passed into the first preheater and the second preheater and preheated to the reaction temperature. Then the catalyst and diethanolamine are mixed in the first mixer and then passed into the second mixer together with dimethyl adipic acid to obtain a mixture.
[0006] (2) Pass the mixture from step (1) into a continuous reactor and react under vacuum to obtain a crude product;
[0007] (3) The crude product from step (2) is passed into a falling film evaporator to remove residual volatile components and then solidified and granulated to obtain the target product.
[0008] In step (1), the preheating temperature is 90℃~100℃ and / or the mixing temperature is 90℃~100℃.
[0009] In step (1), the amount of catalyst fed is 0.1% to 0.3% of the total amount of reactants, wherein the catalyst is a 30% sodium methoxide methanol solution. Using sodium methoxide as a catalyst provides better catalytic synthesis, further increasing the reaction rate. Simultaneously, under the same catalyst feeding conditions, the product has a lower free amine value.
[0010] The dimethyl adipate, mixed with diethanolamine and catalyst in a second mixer according to the process ratio, is then fed into a continuous reactor in one go. The molar ratio of diethanolamine to dimethyl adipate is controlled at 2.0:1.0 by a mass flow meter. Unlike the existing technology of dripping dimethyl adipate raw material, this one-time feeding of dimethyl adipate saves the dripping time. To ensure a complete reaction and reduce the generation of by-products, the one-time feeding preparation process needs to be carried out in a small-volume reactor. If the reactor is too large, the probability of backmixing will increase, resulting in a decrease in reaction selectivity. To minimize the backmixing problem in continuous batch reactors, this invention uses an overflow series batch reactor as the continuous reactor. Theoretically, the more reactors connected in series, the smaller the reactor volume, and the closer the reaction process can be to the ideal mixing state of a plug flow reactor. However, if the reactor volume is too small, in order to ensure the residence time required for the reaction, it is preferable to connect 3-8 reactors in series, with the effective volume of each reactor ≤50L. Since diethanolamine and dimethyl adipate have poor compatibility, there is still a certain phase interface between the reactants at the reaction temperature, and the reaction is not completely homogeneous. Therefore, in order to ensure the reaction proceeds to the maximum extent, the reactants need to be thoroughly stirred and mixed. Therefore, conventional tubular plug flow reactors are not suitable.
[0011] The total effective volume of the overflow series reactor is 70-120L. The effective volume of the final reactor and the intermediate reactor is the same, and the ratio of the effective volume of the final reactor to that of the first reactor is 0.2-0.5. The first reactor requires a larger reaction volume, which means that the residence time of the single reactor is increased, so that more than 90% of the reactants can complete the reaction and the product composition is relatively constant. This is beneficial for the reactants to maintain a relatively stable reaction process in the remaining reactors. The remaining reactors require a smaller reaction volume. The smaller volume can obtain a larger heat exchange area, which is beneficial for the subsequent heating operation of the reaction stream. At the same time, the smaller volume is more conducive to the removal of the by-product methanol.
[0012] The reaction temperature in the first reactor is 90℃-100℃, and the reaction temperature in the intermediate reactors gradually increases to 105℃ in the final reactor. The first reactor has a larger volume, and the material residence time should be relatively longer. Therefore, a lower temperature is sufficient to complete the reaction. However, the rearrangement reaction of hydroxyalkylamides generally occurs at temperatures above 110℃. Therefore, the reaction temperature must be strictly controlled at 110℃ or below to minimize esterification side reactions and product rearrangement reactions. The purpose of gradually increasing the temperature in the later stage of the reaction is to keep the reactants in a flowable liquid state, which also facilitates the removal of methanol byproduct and ensures complete conversion of raw materials.
[0013] In step (2), the vacuum conditions are -0.085 to -0.095 MPa, and the reaction time is 15 to 30 minutes. The crude product generated in step (2) will still contain about 3% methanol. This part of the impurity needs to be dried for more than half an hour under vacuum drying conditions at 110°C. The drying is relatively slow and the energy consumption is large. Therefore, the crude product is passed into a falling film evaporator. By forming a 0.5-1.0 mm falling liquid film inside the evaporator, the residual methanol can be quickly removed. In order to further reduce the impact of high temperature conditions on product quality, the residence time of the material inside the evaporator should not be too long. The preferred evaporation temperature of the falling film evaporator is 105-110°C, and the reaction time is 30-60 seconds.
[0014] In step (3), the crude product is in liquid state after being processed by the falling film evaporator. It needs to be solidified and granulated by equipment such as steel belt granulator and slicer. The above continuous granulation scheme can further shorten the curing time. The lower the temperature, the faster the curing speed. In order to balance the curing speed and energy consumption, the preferred curing temperature is -10℃~0℃ and the curing time is 15~25s.
[0015] The beneficial effects of this invention are:
[0016] 1. This invention uses an overflow series-type reactor as a continuous reactor, which has a shorter reaction time than the traditional batch reaction and the reaction products maintain a liquid state with good fluidity throughout the process, avoiding the situation where materials condense in the reactor and are difficult to clean; at the same time, diethyl adipate is added to the reactor in one go, which further shortens the reaction time compared with the dropwise addition of the prior art.
[0017] 2. The synthesis method of the present invention produces products with high purity, and the solidification and granulation process of the products is simple to operate, without the need for traditional solidification, crushing, drying and granulation processes, thus improving the production efficiency of the equipment.
[0018] 3. The byproduct methanol in the product of this invention can be effectively removed, eliminating the need for drying and impurity removal processes on the solid particle / powder product. Attached Figure Description
[0019] Figure 1 This is a flowchart of the preparation process of the present invention;
[0020] Figure 2 The chromatogram of N,N,N',N'-tetra(β-hydroxyethyl)hexamethylenediamide of the present invention is shown below.
[0021] Figure 1 In the middle: 1-First preheater, 2-Second preheater, 3-First mixer, 4-Second mixer, 5-Continuous reactor, 51-First batch, 52-Final batch, 6-Falling film evaporator, 7-Methanol condenser. Detailed Implementation
[0022] The technical solution of the present invention will be further described in detail below with reference to specific embodiments.
[0023] Example 1
[0024] Diethanolamine feedstock is preheated to 95°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 95°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 95°C in the second preheater 2. The mixing temperature is 95°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 2.0 kg / min, and the flow rate of dimethyl adipate is 1.631 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.3% of the total feedstock. After mixing, the above materials are fed into a series of five reactors. The reactor consists of four reactors, each with an effective volume of 50L. The first reactor (51) has an effective volume of 50L, and the subsequent four reactors each have an effective volume of 10L, for a total effective reaction volume of 90L. The residence time of the material in the first reactor (51) is approximately 14 minutes, and the reaction temperature is 95℃. After passing through the four subsequent reactors, the temperature gradually increases to 105℃, with a total residence time of approximately 11 minutes for the four reactors and a total reaction residence time of 25 minutes. The synthesis reaction vacuum is -0.085MPa. The crude product is passed into a falling film evaporator (6) and held at 110℃ for 30 seconds. The evaporated material is then uniformly sprayed onto a 0℃ steel plate surface and cured for 25 seconds to obtain a solid granular product.
[0025] In the above process, the purity of the product exiting the first batch was 91.3%, the purity of the product exiting the last batch was 93.6%, the purity of the product exiting the evaporator was 96.3%, and the volatile matter content was 0.2%.
[0026] Example 2
[0027] Diethanolamine feedstock is preheated to 90°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 90°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 90°C in the second preheater 2. The mixing temperature is 90°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 1.298 kg / min, and the flow rate of dimethyl adipate is 1.057 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.3% of the total feedstock. After mixing, the above materials enter... The reactor consists of three reactors connected in series. The first reactor (51) has an effective volume of 50L, and the subsequent two reactors have an effective volume of 10L each, for a total effective reaction volume of 70L. The residence time of the material in the first reactor (51) is approximately 21 minutes, and the reaction temperature is 90℃. After passing through the subsequent two reactors, the temperature of the material gradually increases to 105℃, with a total residence time of approximately 9 minutes for the two reactors and a total reaction residence time of approximately 30 minutes. The synthesis reaction vacuum is -0.095MPa. The crude product is passed into a falling film evaporator (6) and held at 110℃ for 60 seconds. The evaporated material is then uniformly sprayed onto the surface of a 0℃ steel plate and cured for 25 seconds to obtain a solid granular product.
[0028] In the above process, the purity of the product exiting the first batch was 93.3%, the purity of the product exiting the last batch was 94.7%, the purity of the product exiting the evaporator was 96.5%, and the volatile matter content was 0.1%.
[0029] Example 3
[0030] Diethanolamine feedstock is preheated to 100°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 100°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 100°C in the second preheater 2. The mixing temperature is 100°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 4.439 kg / min, and the flow rate of dimethyl adipate is 3.614 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.3% of the total feedstock. After mixing, the above materials enter the 8th batch. The reactor is connected in series. The effective volume of the first reactor (51) is 50L, and the effective volume of the subsequent seven reactors is 10L each, for a total effective reaction volume of 120L. The residence time of the material in the first reactor (51) is approximately 6.0 min, and the reaction temperature is 100℃. After passing through the subsequent seven reactors, the temperature of the material gradually increases to 105℃, with a total residence time of approximately 9 min for the seven reactors and a total reaction residence time of 15.3 min. The synthesis reaction vacuum is -0.090MPa. The crude product is passed into a falling film evaporator (6) and held at 110℃ for 40 s. The evaporated material is then uniformly sprayed onto the surface of a -10℃ steel plate and cured for 15 s to obtain a solid granular product.
[0031] In the above process, the purity of the product exiting the first batch is 90.5%, the purity of the product exiting the last batch is 95.3%, the purity of the product exiting the evaporator is 96.7%, and the volatile matter content is 0.2%.
[0032] Example 4
[0033] Diethanolamine feedstock is preheated to 100°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 100°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 100°C in the second preheater 2. The mixing temperature is 100°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 1.850 kg / min, and the flow rate of dimethyl adipate is 1.506 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.3% of the total feedstock. After mixing, the above materials are then... The material is fed into a three-reactor series reactor. The effective volume of the first reactor (51) is 50L, and the effective volumes of the subsequent two reactors are 25L each, for a total effective reaction volume of 100L. The residence time of the material in the first reactor (51) is approximately 15 minutes, and the reaction temperature is 100℃. After passing through the subsequent two reactors, the temperature of the material is gradually increased to 105℃, with a total residence time of approximately 15 minutes for the two reactors. The total reaction residence time is 30 minutes. The synthesis reaction vacuum is -0.095MPa. The crude product is passed into a falling film evaporator at 105℃ and held for 60 seconds. The evaporated material is then uniformly sprayed onto the surface of a -10℃ steel plate and cured for 15 seconds to obtain a solid granular product.
[0034] In the above process, the purity of the product exiting the first batch was 92.5%, the purity of the product exiting the last batch was 94.8%, the purity of the product exiting the evaporator was 96.2%, and the volatile matter content was 0.3%.
[0035] Example 5
[0036] Diethanolamine feedstock is preheated to 95°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 95°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 95°C in the second preheater 2. The mixing temperature is 95°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 1.979 kg / min, and the flow rate of dimethyl adipate is 1.631 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.1% of the total feedstock. After mixing, the above materials are fed into a series of five reactors. The reactor consists of four reactors. The first reactor (51) has an effective volume of 50L, and the subsequent four reactors each have an effective volume of 10L, for a total effective reaction volume of 90L. The residence time of the material in the first reactor (51) is approximately 14 minutes, and the reaction temperature is 95℃. After passing through the four subsequent reactors, the temperature gradually increases to 105℃, with a total residence time of approximately 11 minutes for the four reactors and a total reaction residence time of approximately 25 minutes. The synthesis reaction vacuum is -0.085MPa. The crude product is passed into a falling film evaporator (6) and held at 110℃ for 30 seconds. The evaporated material is then uniformly sprayed onto a 0℃ steel plate surface and cured for 25 seconds to obtain a solid granular product.
[0037] In the above process, the purity of the product exiting the first batch was 90.4%, the purity of the product exiting the last batch was 92.7%, the purity of the product exiting the evaporator was 96.1%, and the volatile matter content was 0.3%.
[0038] Example 6
[0039] Diethanolamine feedstock is preheated to 95°C in the first preheater 1, and then mixed with a 30% sodium methoxide methanol solution in the first mixer 3 and heated to 95°C. This mixture is then pumped separately to the second mixer 4 with dimethyl adipate feedstock preheated to 95°C in the second preheater 2, and mixed at a mixing temperature of 95°C. The flow rate of the diethanolamine and sodium methoxide solution mixture is 1.991 kg / min, and the flow rate of dimethyl adipate is 1.631 kg / min. The molar ratio of the two feedstocks is 2.0:1. The sodium methoxide catalyst accounts for 0.2% of the total feedstock. After mixing, the above materials are fed into five reactors in series. The reactor has an effective volume of 50L for the first reactor (51), and 10L for each of the subsequent four reactors, for a total effective reaction volume of 90L. The residence time of the material in the first reactor (51) is approximately 14 minutes, and the reaction temperature is 95℃. After passing through the subsequent four reactors, the temperature gradually increases to 105℃, with a total residence time of approximately 11 minutes for the four reactors and a total reaction residence time of approximately 25 minutes. The synthesis reaction vacuum is -0.095MPa. The crude product is passed into a falling film evaporator (6) and held at 110℃ for 30 seconds. The evaporated material is then uniformly sprayed onto a -5℃ steel plate surface and cured for 20 seconds to obtain a solid granular product.
[0040] In the above process, the purity of the product exiting the first batch was 91.4%, the purity of the product exiting the last batch was 92.9%, the purity of the product exiting the evaporator was 96.1%, and the volatile matter content was 0.4%.
[0041] Example 7: Preparation of N,N,N',N'-Tetra(2-hydroxyethyl)hexamethylenediamide using reactors of different volumes
[0042] This embodiment will verify and explain the effectiveness of the technical solution of the present invention by using intermittent reaction and one-time raw material feeding methods to verify the effective volume of the reactor.
[0043] Verification was conducted using 0.5L, 5.0L, 10L, 50L, and 100L reactors, respectively. The specific procedures are as follows: The synthesis reaction conditions were as described in Example 3. Diethanolamine raw material, catalyst, and dimethyl adipate raw material were mixed after heating and then introduced into reactors of different volumes at the described flow rate. Stirring and vacuum were started to begin the reaction. When the product in the reactor reached a milky white slurry state, samples were taken and analyzed. When the material in the reactor was completely solidified, vacuum and heating were stopped, and the solid product was ground into powder. The powder product was then vacuum dried at 110℃ for 30 minutes before analysis. The volatile content was determined according to GB / T 1725. The test results are shown in Table 1.
[0044] Table 1. Curing time and synthesis reaction results of products from reactors of different volumes
[0045]
[0046] As shown in Table 1, using sodium methoxide as a catalyst, the purity of the reactants before solidification decreased continuously with increasing reactor volume, dropping below 90% at a volume of 100L. Under these conditions, the obtained solid powder product, even under vacuum drying, only achieved a purity of 94.1%, and exhibited a high free amine value. This is because a larger reaction vessel hinders the removal of the byproduct methanol, thus affecting the reaction process. Although the material can remain in a fluid state for a longer period, excessive heating time leads to increased intramolecular rearrangement of N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide, generating more amino ester byproducts, resulting in lower purity and a higher free amine value. Therefore, for the technical solution of this invention, controlling the effective volume of a single reactor to below 50L is more advantageous.
[0047] Comparative Example 1:
[0048] The catalysts used were NaOH, KOH and potassium methoxide, respectively, and the remaining steps were the same as in Example 1.
[0049] Comparative Example 2:
[0050] This embodiment uses an existing batch reactor preparation technology, specifically as follows: 714 kg of diethanolamine (6.8 kmol) and 12 kg of sodium methoxide (catalyst at 0.9% of the total mass of the reactants) are added to the reactor, stirred and heated to 100°C. Under vacuum conditions of -0.090 to -0.098 MPa, 592.0 kg of dimethyl adipate (3.4 kmol) is added over 1.5 hours. After the addition is complete, the temperature is raised to 105°C and the reaction is continued for 1 hour. A viscous white material forms in the reactor. A sample is taken and discharged to a slicer for solidification and granulation at -5°C. The granules are ground, dried, and tested. The analysis results are shown in Table 2. The material in the reactor solidifies after about 40 minutes of granulation.
[0051] Table 2 Evaluation of Catalytic Synthesis Effect of Catalyst
[0052]
[0053] According to the results in Table 2, the technical solution of this invention can shorten the reaction time to less than 30 minutes, and the product purity can reach more than 96% without further impurity removal. The volatile matter can be reduced to less than 0.5%. The results of Comparative Example 1 show that sodium methoxide is the optimal catalyst, and higher product purity can be obtained at a lower catalyst ratio. At the same time, combined with Comparative Example 2, the existing batch reactor reaction has a long synthesis reaction time. In order to avoid the product solidification in the reactor, rapid discharge is required, which requires a large granulation equipment to meet the requirements of rapid discharge. At the same time, due to the excessive heating time, the product purity is also low.
[0054] The purity of the products described in the above embodiments was detected by high-performance liquid chromatography (HPLC). The detection method is as follows:
[0055]
[0056] Figure 2 In the diagram, 1 represents N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide, 2 represents the saponification formed by dimethyl adipate and the catalyst, 3 represents an unknown impurity peak, and 4 represents a synthesis byproduct. According to... Figure 2 The results showed that the N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide prepared by the method of the present invention had high purity and extremely low content of impurities and byproducts in the product.
[0057] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them; although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of the present invention or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the technical solutions claimed in the present invention.
Claims
1. A process for the continuous preparation of N,N,N',N'-tetra(2-hydroxyethyl)adipamide, characterized in that, Includes the following steps: (1) Diethanolamine and dimethyl adipic acid are preheated in the first preheater (1) and the second preheater (2), respectively. Then, the catalyst and diethanolamine are mixed in the first mixer (3) and then mixed with dimethyl adipic acid in the second mixer (4) to obtain a mixture. (2) The mixture from step (1) is fed into the continuous reactor (5) in one go, and the reaction is carried out under vacuum to obtain the crude product; (3) The crude product from step (2) is fed into a falling film evaporator (6) to remove residual volatile components and then solidify and granulate to obtain the target product.
2. The preparation method according to claim 1, characterized in that, The preheating temperature and / or mixing temperature in step (1) is 90℃~100℃.
3. The preparation method according to claim 1, characterized in that, In step (1), the amount of catalyst fed is 0.1% to 0.3% of the total amount of raw materials fed, the molar ratio of diethanolamine to dimethyl adipate is 2:1, and the catalyst is a 30% sodium methoxide methanol solution.
4. The preparation method according to claim 1, characterized in that, In step (2), the continuous reactor (5) is an overflow series reactor with a total effective volume of 70-120L, and the number of series reactors is 3-8.
5. The preparation method according to claim 4, characterized in that, The effective volume of a single vessel in the overflow series reactor is ≤50L, wherein the effective volume ratio of the first vessel (51) to the last vessel (52) is 0.2 to 0.5, and the effective volume of the last vessel (52) is the same as that of the intermediate reactor.
6. The preparation method according to claim 4, characterized in that, The reaction temperature of the first reactor (51) in the overflow series reactor is 90℃~100℃, and the temperature of the intermediate reactor gradually rises to 105℃ in the last reactor (52).
7. The preparation method according to claim 1, characterized in that, In step (2), the vacuum conditions are -0.085 to -0.095 MPa, and the reaction time is 15 to 30 min.
8. The preparation method according to claim 1, characterized in that, In step (3), the evaporation temperature of the falling film evaporator (6) is 105℃~110℃, and the evaporation time is 30s~60s.
9. The preparation method according to claim 1, characterized in that, In step (3), the curing temperature is -10℃ to 0℃ and the curing time is 15 to 25 seconds.
10. N,N,N',N'-tetrakis(2-hydroxyethyl)hexamethylenediamide prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The purity of the N,N,N',N'-tetra(2-hydroxyethyl)hexamethylenediamide is greater than 96%.