Preparation method of ethylene glycol bis (propionitrile) ether

Abstract

The invention belongs to the technical field of preparation of ethylene glycol bis (propionitrile) ether, and particularly relates to a preparation method of ethylene glycol bis (propionitrile) ether. The preparation method of ethylene glycol bis (propionitrile) ether comprises the following steps: uniformly mixing ethylene glycol, a catalyst and a phase transfer agent, dropwise adding acrylonitrile in three stages for reaction, washing with deionized water after the reaction is finished, adjusting the pH value of the reaction liquid to be neutral, performing reduced pressure distillation, and removing water and a small amount of unreacted acrylonitrile, thereby obtaining the ethylene glycol bis (propionitrile) ether. The invention discloses a method for preparing ethylene glycol bis (propionitrile) ether.The method comprises the steps that ethylene glycol bis (propionitrile) ether is obtained after vacuum rectification, finally, a sulfuric acid solution is added into the crude product for decoloration and water washing to be neutral, a molecular sieve is added for dehydration, and ethylene glycol bis (propionitrile) ether.The preparation method is simple and feasible, and the prepared ethylene glycol bis (propionitrile) ether is high in yield and purity.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of ethylene glycol bis(propionitrile) ether, and particularly relates to a preparation method of ethylene glycol bis(propionitrile) ether. Background Art

[0002] Ethylene glycol bis(propionitrile) ether, abbreviated as DENE, is a functional additive for lithium-ion battery electrolytes. The cyano groups in its molecule can coordinate with metal ions, to a certain extent inhibit the dissolution of metal ions, prevent the destruction of the SEI film on the surface of the negative electrode, improve the low-temperature performance and conductivity of the electrolyte, improve the thermal stability of the electrolyte, improve the battery safety performance and the cycle stability of the electrolyte, and increase the charge-discharge cycle life of lithium-ion batteries. The electrochemical activity of DENE is higher than that of traditional succinonitrile and adiponitrile. The lithium-ion battery electrolyte added with DENE will form a stable film on the surface of the positive electrode during the first charge-discharge process, effectively inhibiting the oxidation of the electrolyte by the positive electrode, thereby inhibiting high-temperature gas swelling, and having better high-temperature performance and cycle performance. With the rapid development of the new energy vehicle industry, the demand for lithium-ion battery electrolytes is increasing day by day, and the requirements for their performance are also getting higher and higher. Therefore, the demand for and the quality requirements for their functional additives are also increasing.

[0003] Currently, the methods for preparing DENE disclosed in the literature are mainly: using ethylene glycol and acrylonitrile as reaction raw materials, and carrying out an addition reaction under the action of a basic catalyst. The yield of DENE prepared by this method is close to 90%, and the purity can usually reach about 95%. Patent CN 106146344A discloses a preparation method of ethylene glycol bis(propionitrile) ether, using an aqueous solution of triethylbenzylammonium hydroxide and an aqueous solution of sodium hydroxide as a composite base catalyst, which can reduce the generation of by-product bis(propionitrile) ether, and the molar yield of DENE can reach more than 90%, and the purity after purification reaches more than 95%. However, as an additive for lithium-ion battery electrolytes, stricter requirements are imposed on its purity. Generally, the purity is required to reach more than 98%. Only high-purity DENE can play a role in improving the performance indexes of lithium-ion battery electrolytes. Therefore, exploring a preparation method of ethylene glycol bis(propionitrile) ether with high yield, low cost and high purity is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method of ethylene glycol bis(propionitrile) ether. The ethylene glycol bis(propionitrile) ether prepared by using this method has high purity and high yield.

[0005] The preparation method of ethylene glycol bis(propionitrile) ether described in the present invention comprises the following steps: (1) Mix ethylene glycol, a phase transfer agent, and a catalyst evenly to obtain a mixed solution, and then add acrylonitrile dropwise to the mixed solution in three stages. After the reaction ends, wash with water to adjust the pH value of the reaction solution to 7. Among them, the catalyst is one of sodium methoxide or sodium ethoxide, and the phase transfer agent is one of tetrabutylammonium iodide or tetrabutylammonium bromide; (2) Perform vacuum distillation on the reaction solution to remove water and unreacted acrylonitrile, and then perform high-vacuum rectification to obtain crude ethylene glycol bis(propionitrile) ether; (3) Add sulfuric acid solution to the crude ethylene glycol bis(propionitrile) ether for decolorization, then wash with water until pH = 7, and finally add molecular sieve for dehydration treatment to prepare ethylene glycol bis(propionitrile) ether; Among them: In the step (1) of adding acrylonitrile dropwise in three stages, the molar ratio of acrylonitrile in the first stage, acrylonitrile in the second stage, and acrylonitrile in the third stage is 0.7 - 0.9 : 1 - 1.2 : 0.9 - 1.1; In the step (1) of adding acrylonitrile dropwise in three stages, the dropping temperature of acrylonitrile in the first stage is 40°C, the dropping time is 1 - 2 h, and the reaction is carried out for 1 - 2 h after the dropping is completed; the dropping temperature of acrylonitrile in the second stage is 45°C, the dropping time is 2.3 - 3 h, and the reaction is carried out for 2 - 3 h after the dropping is completed; the dropping temperature of acrylonitrile in the third stage is 40°C, the dropping time is 2 - 3 h, and the reaction is carried out for 2 - 3 h after the dropping is completed.

[0006] The reason for adding acrylonitrile dropwise in three stages is as follows: In addition to reacting with ethylene glycol, acrylonitrile will undergo self-polymerization under the action of the catalyst itself. When a large amount of acrylonitrile enters the system, when acrylonitrile reacts with ethylene glycol to saturation, due to the high content of acrylonitrile in the system, the excess acrylonitrile will undergo self-polymerization under exothermic conditions, and the self-polymerization product of acrylonitrile is difficult to separate from the product, resulting in a decrease in the reaction yield. If added dropwise in three stages, on the one hand, it can make the reaction between ethylene glycol and acrylonitrile more complete, and on the other hand, the gradient heating can effectively prevent the self-polymerization reaction of acrylonitrile at the beginning, and the addition in the third stage prolongs the conversion of monoether to diether in the first and second stages, improving the reaction yield. In addition, ethylene glycol does not react when mixed with the catalyst and the phase transfer agent alone, while acrylonitrile is prone to polymerization under alkaline conditions. Adding acrylonitrile dropwise in three stages and controlling the dropping temperature are to make acrylonitrile react with ethylene glycol as soon as it drops into the system and reduce the occurrence of self-polymerization.

[0007] Preferably, the catalyst is sodium methoxide. Sodium methoxide belongs to a non-nucleophilic strong base, which can effectively enhance the electron cloud density of the C = C double bond of acrylonitrile, reduce the activation energy of the reaction between the double bond and -OH in ethylene glycol, and make the reaction proceed directionally. Pure sodium methoxide solid can be directly used in the reaction to achieve a good catalytic effect.

[0008] Preferably, the phase transfer agent is tetrabutylammonium iodide. Tetrabutylammonium bromide belongs to quaternary ammonium salt phase transfer agents, which can effectively make the reaction proceed in two organic phases, accelerating the directional reaction while reducing the occurrence of side reactions. Tetrabutylammonium bromide is inexpensive and has stable properties, making it suitable for the reaction. The usage amount of tetrabutylammonium bromide, calculated as the pure substance, is 0.1% - 0.5% of the weight of ethylene glycol, which can achieve a good phase transfer catalytic effect.

[0009] In step (1), the molar ratio of ethylene glycol to acrylonitrile is 1:2.6 - 3.2. Preferably, the molar ratio of ethylene glycol to acrylonitrile is 1:3.0. According to the reaction equation, 1 molecule of ethylene glycol needs to react with 2 molecules of acrylonitrile. Excessive acrylonitrile can ensure that all ethylene glycol reacts completely, and acrylonitrile can be recovered by vacuum distillation; from the reaction mechanism, this reaction actually proceeds in two steps. First, 1 molecule of ethylene glycol reacts with 1 molecule of acrylonitrile to form a monoether, and then the monoether reacts with 1 molecule of acrylonitrile to form a diether. If ethylene glycol is in excess, there will be a large amount of monoether intermediates in the reaction system, reducing the reaction yield.

[0010] Preferably, in step (1), acrylonitrile is added dropwise in three stages, and the molar ratio of the first-stage acrylonitrile, the second-stage acrylonitrile, and the third-stage acrylonitrile is 0.8:1.1:1.

[0011] In step (1), the mass of the catalyst is 1% - 4% of the mass of ethylene glycol.

[0012] In step (1), the mass of the phase transfer agent is 0.1% - 0.5% of the mass of ethylene glycol.

[0013] In step (2), the pressure of vacuum distillation is -0.1 MPa, and the temperature of vacuum distillation is 50°C.

[0014] In step (2), the temperature of high-vacuum rectification is 145°C, and the vacuum degree ≤ -0.1 MPa.

[0015] In step (3), the mass fraction of the sulfuric acid solution is 30%, and the addition amount is 5% of the mass of the crude ethylene glycol bis(propionitrile) ether.

[0016] In step (3), the molecular sieve is 3A molecular sieve, and the addition amount is 1.5 times the mass of the crude ethylene glycol bis(propionitrile) ether.

[0017] In step (3), the dehydration time is 5 h.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1)The preparation method of ethylene glycol bis(propionitrile) ether according to the present invention is as follows: First, ethylene glycol, a catalyst, and a phase transfer agent are mixed evenly, and then acrylonitrile is added dropwise in three stages for reaction. After the reaction is completed, deionized water is used for washing to adjust the pH value of the reaction solution to neutral, and then vacuum distillation is carried out to remove water and a small amount of unreacted acrylonitrile. After vacuum rectification, a crude product of ethylene glycol bis(propionitrile) ether is obtained. Finally, a sulfuric acid solution is added to the crude product for decolorization, washed to neutral, and dehydrated with molecular sieve to obtain ethylene glycol bis(propionitrile) ether. The preparation method is simple and feasible.

[0019] (2)The ethylene glycol bis(propionitrile) ether prepared by this method has high yield and purity. The prepared ethylene glycol bis(propionitrile) ether can meet the application requirements as an additive for high-quality lithium-ion battery electrolytes and is suitable for large-scale industrial production. Detailed implementation mode

[0020] The present invention will be further described below in conjunction with embodiments.

[0021] Example 1 The preparation method of ethylene glycol bis(propionitrile) ether described in Example 1 consists of the following steps: (1)2 mol of ethylene glycol (124.136 g), sodium methoxide (2.483 g) which is 2% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.248 g) which is 0.2% of the weight of ethylene glycol are added to a 500 mL three-necked flask and stirred evenly. The temperature is controlled at 40 °C, and 1.6 mol (84.896 g) of acrylonitrile in the first stage is slowly added dropwise to the flask over 2 h. After the addition is completed, the reaction is carried out for 1 h. The temperature is raised to 45 °C, and 2.2 mol (116.732 g) of acrylonitrile in the second stage is slowly added dropwise to the flask over 3 h. After the addition is completed, the reaction is carried out for 2 h. The temperature is lowered to 40 °C, and 2.0 mol (106.12 g) of acrylonitrile in the third stage is slowly added dropwise to the flask over 3 h. After the addition is completed, the reaction is carried out for 2 h. After the reaction is completed, deionized water is used for washing to adjust the pH of the solution to 7.

[0022] (2)The reaction solution is vacuum distilled at -0.1 MPa and 50 °C to remove water and unreacted acrylonitrile, and then the temperature is raised to 145 °C, and the crude product of ethylene glycol bis(propionitrile) ether, 302.18 g, is obtained by rectification under a vacuum of less than -0.1 MPa.

[0023] (3)Pickling and decolorization are carried out by adding a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight, washed to pH = 7, 3A molecular sieve with 1.5 times the mass of ethylene glycol is added, dehydrated for 5 h, the gas phase purity is measured to be 99.91%, and the molar yield based on ethylene glycol is 89.81%.

[0024] Example 2 The preparation method of ethylene glycol bis(propionitrile) ether described in this Example 2 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium ethoxide (1.242 g) which is 1% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.124 g) which is 0.1% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, slowly dropwise add 1.8 mol (95.508 g) of acrylonitrile in one portion to the flask over 1 h, and react for 1 h after the addition is complete; raise the temperature to 45 °C, slowly dropwise add 2.4 mol (127.344 g) of acrylonitrile in two portions to the flask over 2.3 h, and react for 2 h after the addition is complete; lower the temperature to 40 °C, slowly dropwise add 2.2 mol (116.732 g) of acrylonitrile in three portions to the flask over 2.0 h, and react for 2 h after the addition is complete. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0025] (2) Under the conditions of -0.1 MPa and 50 °C, distill the reaction solution under reduced pressure to remove water and unreacted acrylonitrile, then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 300.66 g of crude ethylene glycol bis(propionitrile) ether.

[0026] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until the pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas-phase purity to be 99.11%, and the molar yield based on ethylene glycol is 89.16%.

[0027] Example 3 The preparation method of ethylene glycol bis(propionitrile) ether described in this Example 3 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium methoxide (4.965 g) which is 4% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.621 g) which is 0.5% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, slowly dropwise add 1.4 mol (74.284 g) of acrylonitrile in one portion to the flask over 1 h, and react for 2 h after the addition is complete; raise the temperature to 45 °C, slowly dropwise add 2.0 mol (106.12 g) of acrylonitrile in two portions to the flask over 2.3 h, and react for 3 h after the addition is complete; lower the temperature to 40 °C, slowly dropwise add 1.8 mol (95.508 g) of acrylonitrile in three portions to the flask over 2.0 h, and react for 3 h after the addition is complete. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0028] (2) The reaction solution was subjected to vacuum distillation to remove water and unreacted acrylonitrile under the conditions of -0.1 MPa and 50 °C, and then the temperature was raised to 145 °C. The crude ethylene glycol bis(propionitrile) ether (301.58 g) was obtained by rectification while controlling the vacuum degree below -0.1 MPa.

[0029] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until the pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity of 99.82%, and the molar yield based on ethylene glycol is 89.63%.

[0030] Comparative Example 1 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 1 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium methoxide (2.483 g) accounting for 2% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.248 g) accounting for 0.2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, and slowly add 307.748 g of acrylonitrile dropwise to the flask over 8 h. After the dropping is completed, continue to keep the temperature for reaction for 5 h. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0031] (2) The reaction solution was subjected to vacuum distillation to remove water and unreacted acrylonitrile under the conditions of -0.1 MPa and 50 °C, and then the temperature was raised to 145 °C. The crude ethylene glycol bis(propionitrile) ether (278.65 g) was obtained by rectification while controlling the vacuum degree below -0.1 MPa.

[0032] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until the pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity of 89.98%, and the molar yield based on ethylene glycol is 82.82%.

[0033] Comparative Example 2 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 2 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g) and sodium methoxide (2.484 g) which is 2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, and slowly add 1.6 mol (84.896 g) of acrylonitrile in one portion to the flask over a period of 2 h. After the addition is completed, react for 1 h. Raise the temperature to 45 °C, and slowly add 2.2 mol (116.732 g) of acrylonitrile in the second portion to the flask over a period of 3 h. After the addition is completed, react for 2 h. Lower the temperature to 40 °C, and slowly add 2.0 mol (106.12 g) of acrylonitrile in the third portion to the flask over a period of 3 h. After the addition is completed, react for 2 h. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0034] (2) Under the conditions of -0.1 MPa and 50 °C, carry out vacuum distillation of the reaction solution to dehydrate and remove unreacted acrylonitrile. Then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 286.52 g of crude ethylene glycol bis(propionitrile) ether.

[0035] (3) Add a sulfuric acid solution (mass fraction 30%) which is 5% of the total weight for pickling and decolorization, wash with water until pH = 7, add 3A molecular sieve which is 1.5 times the mass of ethylene glycol, dehydrate for 5 h, measure the gas-phase purity to be 87.26%, and the molar yield based on ethylene glycol is 85.16%.

[0036] Comparative Example 3 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 3 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g) and tetrabutylammonium bromide (0.248 g) which is 0.2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, and slowly add 1.6 mol (84.896 g) of acrylonitrile in one portion to the flask over a period of 2 h. After the addition is completed, react for 1 h. Raise the temperature to 45 °C, and slowly add 2.2 mol (116.732 g) of acrylonitrile in the second portion to the flask over a period of 3 h. After the addition is completed, react for 2 h. Lower the temperature to 40 °C, and slowly add 2.0 mol (106.12 g) of acrylonitrile in the third portion to the flask over a period of 3 h. After the addition is completed, react for 2 h. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0037] (2) Under the conditions of -0.1 MPa and 50 °C, carry out vacuum distillation of the reaction solution to dehydrate and remove unreacted acrylonitrile. Then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 299.89 g of crude ethylene glycol bis(propionitrile) ether.

[0038] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity to be 91.52%, and the molar yield based on ethylene glycol is 89.13%.

[0039] Comparative Example 4 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 4 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium methoxide (2.483 g) accounting for 2% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.248 g) accounting for 0.2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 40 °C, slowly dropwise add 1.6 mol (84.896 g) of acrylonitrile in one stage to the flask, with the dropping time being 2 h, and react for 1 h after the dropping is completed; raise the temperature to 45 °C, slowly dropwise add 2.2 mol (116.732 g) of acrylonitrile in the second stage to the flask, with the dropping time being 3 h, and react for 2 h after the dropping is completed; lower the temperature to 30 °C, slowly dropwise add 2.0 mol (106.12 g) of acrylonitrile in the third stage to the flask, with the dropping time being 3 h, and react for 2 h after the dropping is completed. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0040] (2) Under the conditions of -0.1 MPa and 50 °C, distill the reaction solution under reduced pressure to dehydrate and remove unreacted acrylonitrile, then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 300.01 g of crude ethylene glycol bis(propionitrile) ether.

[0041] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity to be 90.28%, and the molar yield based on ethylene glycol is 89.17%.

[0042] Comparative Example 5 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 5 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium methoxide (2.484 g) which is 2% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.248 g) which is 0.2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 45 °C, and slowly dropwise add 1.6 mol (84.896 g) of acrylonitrile in one portion to the flask over 2 h. After the addition is complete, react for 1 h. Raise the temperature to 50 °C, and slowly dropwise add 2.2 mol (116.732 g) of acrylonitrile in the second portion to the flask over 3 h. After the addition is complete, react for 2 h. Lower the temperature to 40 °C, and slowly dropwise add 2.0 mol (106.12 g) of acrylonitrile in the third portion to the flask over 3 h. After the addition is complete, react for 2 h. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0043] (2) Under the conditions of -0.1 MPa and 50 °C, distill the reaction solution under reduced pressure to remove water and unreacted acrylonitrile, then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 289.96 g of crude ethylene glycol bis(propionitrile) ether.

[0044] (3) Add a sulfuric acid solution (mass fraction 30%) accounting for 5% of the total weight for pickling and decolorization, wash with water until the pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity of 88.72%, and the molar yield based on ethylene glycol is 86.18%.

[0045] Comparative Example 6 The preparation method of ethylene glycol bis(propionitrile) ether described in this Comparative Example 6 consists of the following steps: (1) Add 2 mol of ethylene glycol (124.136 g), sodium methoxide (2.484 g) which is 2% of the weight of ethylene glycol, and tetrabutylammonium bromide (0.248 g) which is 0.2% of the weight of ethylene glycol into a 500 mL three-necked flask, and stir evenly. Control the temperature at 30 °C, and slowly dropwise add 1.6 mol (84.896 g) of acrylonitrile in one portion to the flask over 2 h. After the addition is complete, react for 1 h. Raise the temperature to 35 °C, and slowly dropwise add 2.2 mol (116.732 g) of acrylonitrile in the second portion to the flask over 3 h. After the addition is complete, react for 2 h. Lower the temperature to 40 °C, and slowly dropwise add 2.0 mol (106.12 g) of acrylonitrile in the third portion to the flask over 3 h. After the addition is complete, react for 2 h. After the reaction is completed, wash with deionized water to adjust the pH of the solution to 7.

[0046] (2) Under the conditions of -0.1 MPa and 50 °C, distill the reaction solution under reduced pressure to remove water and unreacted acrylonitrile, then raise the temperature to 145 °C, and control the vacuum degree below -0.1 MPa for rectification to obtain 288.47 g of crude ethylene glycol bis(propionitrile) ether.

[0047] (3) Add sulfuric acid solution with a total weight of 5% (mass fraction 30%) for pickling and decolorization, wash with water until pH = 7, add 3A molecular sieve with a mass 1.5 times that of ethylene glycol, dehydrate for 5 h, measure the gas phase purity of 88.52%, and the molar yield based on ethylene glycol is 85.74%.

[0048] From the comparison between Comparative Example 1 and Example 1 based on the above examples and comparative examples, it can be seen that for the one-stage reaction, only using one-stage reaction to produce one-stage substitution products is not sufficient to effectively improve the purity and yield of the final product. Comparative Examples 2 and 3 show that single addition of a catalyst or a phase transfer agent will affect the degree of reaction to a certain extent, thus affecting the purity of the product. It can be seen from Comparative Example 4 that changing the dropping reaction temperature of acrylonitrile in the third stage will also affect the product purity and yield to a certain extent. Comparative Examples 5 and 6 show that changing the dropping reaction temperature of acrylonitrile in the first and second stages will affect the product purity and yield to a certain extent. The above example part is not simply lengthening the reaction stage, but there is a synergistic cooperation between the products of the one-stage reaction and the two-stage reaction to improve the selectivity of the three-stage reaction and avoid the self-polymerization of acrylonitrile.

[0049] In summary, Examples 1-3 and Comparative Examples 1-6 can prove that there is a specific coordination relationship between the temperature and reaction time of the three-stage reaction and the above addition amount and addition speed, and it is not possible to simply avoid the self-polymerization of acrylonitrile by reducing the reaction temperature or slowing down the addition speed. There is also a specific coordination relationship between the dosage of the catalyst and the phase transfer agent and the raw materials. In Examples 1-3, a specific coordination relationship is used to control the progress of the reaction, and then ethylene glycol bis(propionitrile) ether with high purity and high yield is obtained.

[0050] In conclusion, Examples 1-3 utilize specific addition amounts of the catalyst and the phase transfer catalyst, and the coordination of the dropping amounts, temperatures, and addition speeds of acrylonitrile in the one-stage reaction and the two-stage reaction to avoid the self-polymerization of the addition of acrylonitrile in the three stages and improve the purity of ethylene glycol bis(propionitrile) ether.

Claims

1. A method for preparing ethylene glycol bis(propionitrile) ether, characterized in that: It consists of the following steps: (1) Ethylene glycol, a phase transfer agent and a catalyst are uniformly mixed to obtain a mixed solution, and then acrylonitrile is added dropwise to the mixed solution in three stages. After the reaction is completed, the reaction solution is washed with water to adjust the pH value to 7, wherein the catalyst is one of sodium methoxide or sodium ethoxide, and the phase transfer agent is one of tetrabutylammonium iodide or tetrabutylammonium bromide; (2) subjecting the reaction solution to vacuum distillation to remove water and unreacted acrylonitrile, and then subjecting the reaction solution to high vacuum distillation to obtain a crude product of ethylene glycol bis(propionitrile) ether; (3) adding sulfuric acid solution to the crude product of ethylene glycol bis(propionitrile) ether for decolorization, then washing with water until the pH value is 7, and finally adding molecular sieves for dehydration to prepare ethylene glycol bis(propionitrile) ether; in: In step (1), acrylonitrile is added dropwise in three stages, wherein the molar ratio of acrylonitrile in the first stage, acrylonitrile in the second stage, and acrylonitrile in the third stage is 0.7-0.9: 1-1.2: 0.9-1.1; In step (1), acrylonitrile is added dropwise in three stages. The dropping temperature of acrylonitrile in the first stage is 40° C., the dropping time is 1-2 hours, and the reaction is carried out for 1-2 hours after the dropping is completed; the dropping temperature of acrylonitrile in the second stage is 45° C., the dropping time is 2.3-3 hours, and the reaction is carried out for 2-3 hours after the dropping is completed; the dropping temperature of acrylonitrile in the third stage is 40° C., the dropping time is 2-3 hours, and the reaction is carried out for 2-3 hours after the dropping is completed.

2. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: In step (1), the molar ratio of ethylene glycol to acrylonitrile is 1:2.6-3.

2.

3. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: The catalyst is sodium methoxide, the phase transfer agent is tetrabutylammonium iodide, and the step (1) is to dropwise add acrylonitrile in three stages, wherein the molar ratio of acrylonitrile in the first stage, acrylonitrile in the second stage, and acrylonitrile in the third stage is 0.8:1.1:

1.

4. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: The mass of the catalyst in step (1) is 1%-4% of the mass of ethylene glycol.

5. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: The mass of the phase transfer agent in step (1) is 0.1%-0.5% of the mass of ethylene glycol.

6. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: In step (2), the vacuum distillation pressure is -0.1 MPa and the vacuum distillation temperature is 50°C.

7. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: In step (2), the high vacuum distillation temperature is 145°C and the vacuum degree is ≤-0.1MPa.

8. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: The mass fraction of the sulfuric acid solution in step (3) is 30%, and the amount added is 5% of the mass of the crude ethylene glycol bis(propionitrile) ether.

9. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, wherein: The molecular sieve in step (3) is a 3A grade molecular sieve, and the amount added is 1.5 times the quality of the crude ethylene glycol bis(propionitrile) ether.

10. The method for preparing ethylene glycol bis(propionitrile) ether according to claim 1, characterized in that: The dehydration time in step (3) is 5 h.