Method and system for purifying 4-hydroxybutyl acrylate based on film evaporation coupling extractive distillation

Abstract

The invention provides a method and a system for purifying 4-hydroxybutyl acrylate based on film evaporation coupled extractive distillation, a reaction solution obtained after esterification reaction of acrylic acid and 1, 4-butanediol is subjected to film evaporation to obtain light component acrylic acid and concentrated solution, and the concentrated solution comprises 1, 4-butanediol, 4-hydroxybutyl acrylate, 1, 4-butanediol, 1, 4-hydroxybutyl acrylate, 1, 4-butanediol, 1, 4-butanediol, 1, 4-butanediol, 1, 4-butanediol, 1, 4-butanediol, 1, 4-butanediol and 1, 4-butanediol. The preparation method comprises the following steps: adding 1, 4-butanediol diacrylate, an esterification reaction catalyst and a polymerization inhibitor; carrying out extractive distillation on the concentrated solution and an extractant ionic liquid to respectively obtain a product 4-hydroxybutyl acrylate and a post-reaction extractant; and rectifying the reacted extracting agent, recovering the extracting agent, and reusing the extracting agent for extractive distillation. By adopting thin film evaporation, the separation period can be effectively shortened, and the polymerization risk is reduced; extractive distillation not only shortens the separation period and reduces the risk of polymerization, but also the ionic liquid can break azeotropy among 1, 4-butanediol, 4-hydroxybutyl acrylate and 1, 4-butanediol diacrylate, the high-purity product 1, 4-butanediol is obtained through separation, and purification of 4-hydroxybutyl acrylate is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the chemical technology field, and in particular to a method and system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation. BACKGROUND

[0002] The information disclosed in this Background section is only for the purpose of increasing an understanding of the general context of the present application and does not necessarily constitute an acknowledgement or any form of suggestion that this information forms part of the prior art already known to a person of ordinary skill in the art.

[0003] 4-hydroxybutyl acrylate (4-HBA), also known as 1,4-butanediol monoacrylate (BDMA), is a high-activity bifunctional monomer that is soluble in water and general organic solvents, and is widely used in the fields of coatings, resins, adhesives and fiber reinforced materials, etc. 4-hydroxybutyl acrylate has been widely used in industrial coatings such as automotive topcoat, repair paint and furniture paint due to its low-temperature flexibility, scratch resistance, chemical resistance, weather resistance and many other excellent properties.

[0004] The synthesis methods of 4-hydroxybutyl acrylate mainly include direct esterification method, ester exchange method and acyl chloride method; the industrial production mainly uses acrylic acid (AA) and 1,4-butanediol as raw materials, and is carried out by direct esterification method. After esterification, the final product is obtained through separation steps such as extraction and rectification. Since the reaction is a reversible reaction and is accompanied by a series of side reactions, after the completion of the esterification reaction, the untreated mixed liquid mainly includes acrylic acid, 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, catalyst and polymerization inhibitor, etc. In the process of separating the product 4-hydroxybutyl acrylate, it is found that 1,4-butanediol, 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate all contain hydroxyl and ester groups (or diols), have similar polarity and close boiling points, and are easy to form azeotrope. Although the existing separation technologies including vacuum distillation, solvent extraction and crystallization can achieve preliminary purification, they have problems such as high energy consumption, complex process and low purity. In addition, 4-hydroxybutyl acrylate is easy to polymerize at high temperature, which further increases the difficulty of separation. Therefore, it is urgent to develop an efficient and stable separation and purification method for 4-hydroxybutyl acrylate mixed liquid. SUMMARY

[0005] In order to overcome the above problems, the present application provides a method and system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation.

[0006] To achieve the above technical purposes, the present application adopts the following technical solutions: The first aspect of the present application provides a method for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation, comprising the following steps: The reaction liquid after esterification reaction of acrylic acid and 1,4-butanediol is concentrated by thin film evaporation to obtain light components and concentrated liquid, wherein the concentrated liquid comprises 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, an esterification catalyst and a polymerization inhibitor; and the light components comprise acrylic acid; The concentrated liquid is subjected to extractive distillation with an extractant ionic liquid to obtain product 4-hydroxybutyl acrylate and post-reaction extractant, respectively; wherein the extractant ionic liquid is 1-ethyl-3-methylimidazolium bromide; The post-reaction extractant is subjected to distillation to recover the extractant.

[0007] In one or more embodiments, the composition of the reaction liquid after esterification reaction of acrylic acid and 1,4-butanediol, based on the total mass of the reaction liquid, comprises 0.5-5 wt% of acrylic acid, 30-50 wt% of 1,4-butanediol, 40-50 wt% of 4-hydroxybutyl acrylate, 0.3-2 wt% of 1,4-butanediol diacrylate, 0.5-2 wt% of a catalyst and 2-5 wt% of a polymerization inhibitor.

[0008] In one or more embodiments, the esterification catalyst is at least one of concentrated sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid, and preferably p-toluenesulfonic acid; and the polymerization inhibitor is at least one of phenothiazine, hydroquinone, p-methoxyphenol, ZJ-701, ZJ-705 and copper N,N-di-n-butyl dithiocarbamate, and preferably hydroquinone.

[0009] In one or more embodiments, the post-reaction extractant comprises 1,4-butanediol, 1,4-butanediol diacrylate, an esterification catalyst, a polymerization inhibitor and an extractant ionic liquid.

[0010] In one or more embodiments, the mass ratio of the extractant ionic liquid to the reaction liquid after esterification reaction of acrylic acid and 1,4-butanediol is (0.15-0.4):1.

[0011] In a second aspect, the present application provides a system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation, comprising a thin film evaporation unit and an extractive distillation unit. The thin film evaporation unit comprises a reaction liquid storage tank, a falling film evaporator and a gas-liquid separator; the reaction liquid storage tank is connected to the top feed inlet of the falling film evaporator; the middle steam outlet of the falling film evaporator is connected to the gas-liquid separator; and the bottom concentrated liquid outlet of the falling film evaporator and the liquid outlet of the gas-liquid separator are both connected to a concentrated liquid storage tank. The extractive rectification unit comprises an extractant raw material storage tank, an extractive rectification column, a 4-hydroxybutyl acrylate storage tank, and a post-reaction extractant storage tank; the extractant raw material storage tank is connected with the extractive rectification column top extractant inlet; the extractive rectification column top outlet is connected with the 4-hydroxybutyl acrylate storage tank; and the extractive rectification column bottom outlet is connected with the post-reaction extractant storage tank. The concentrated liquid storage tank is connected with the extractive rectification column.

[0012] In one or more embodiments, the reaction liquid storage tank is sequentially connected with a first feed pump, a preheater, and a top feed inlet of a falling film evaporator.

[0013] In one or more embodiments, the falling film evaporator is connected with a heat conducting oil circulation unit. Preferably, the heat conducting oil circulation unit comprises a heat conducting oil circulation all-in-one machine. Further preferably, the side wall of the falling film evaporator is respectively provided with a heat conducting oil inlet and a heat conducting oil outlet, the heat conducting oil circulation all-in-one machine is connected with the heat conducting oil inlet through an oil conveying pipe, and the heat conducting oil circulation all-in-one machine is connected with the heat conducting oil outlet through an oil return pipe.

[0014] In one or more embodiments, the gas outlet of the gas-liquid separator is sequentially connected with a first condenser and a first light component receiving tank.

[0015] In one or more embodiments, the concentrated liquid storage tank is sequentially connected with a second feed pump, a first reboiler, and the extractive rectification column.

[0016] In one or more embodiments, a second condenser is arranged between the extractive rectification column bottom outlet and the post-reaction extractant storage tank.

[0017] In one or more embodiments, the extractive rectification column top outlet is sequentially connected with a third condenser and the 4-hydroxybutyl acrylate storage tank. Preferably, the third condenser is connected with a first reflux tank, and the first reflux tank is connected with the extractive rectification column reflux inlet.

[0018] In one or more embodiments, a third feed pump is arranged between the extractant raw material storage tank and the extractive rectification column top extractant inlet.

[0019] In one or more embodiments, the system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled extractive rectification further comprises an extractant recovery unit, and the extractant recovery unit comprises an extractant recovery column. The post-reaction extractant storage tank is sequentially connected with a fourth feed pump, a second reboiler, and the extractant recovery column.

[0020] Preferably, the extractant recovery column bottom outlet is connected with the fifth feed pump and the extractive distillation column top extractant inlet in sequence.

[0021] Preferably, the extractant recovery column top outlet is connected with the fourth condenser and the second light component receiving tank in sequence. Further preferably, the fourth condenser is connected with the second reflux tank and the extractant recovery column reflux inlet in sequence.

[0022] Preferably, the falling film evaporator, the extractive distillation column and the extractant recovery column are all connected with the nitrogen buffer tank.

[0023] The beneficial effects of the present application are: (1) The present application provides a method and system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation. The purity of the product 4-hydroxybutyl acrylate is improved by thin film evaporation coupled with extractive distillation. Specifically, the light component acrylic acid is obtained by thin film evaporation of the reaction liquid after esterification of acrylic acid and 1,4-butanediol; and the concentrated liquid, which includes 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, esterification catalyst and polymerization inhibitor; the concentrated liquid is subjected to extractive distillation with an extractant ionic liquid to obtain the product 4-hydroxybutyl acrylate and the reacted extractant, respectively; the reacted extractant is subjected to rectification to recover the extractant for use in extractive distillation again. Thin film evaporation can effectively shorten the separation period and reduce the risk of polymerization; at the same time, extractive distillation not only shortens the separation period and reduces the risk of polymerization, but also breaks the azeotrope between 1,4-butanediol, 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate with ionic liquid, so that high-purity product 1,4-butanediol is obtained, and the purification of 4-hydroxybutyl acrylate is realized.

[0024] (2) 1,4-butanediol, 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate can form azeotrope through hydrogen bond, and the ionic liquid can destroy the hydrogen bond, so that the azeotrope is dissociated into independent 1,4-butanediol, 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate, and then the azeotropy is eliminated, and high-concentration 4-hydroxybutyl acrylate is obtained by rectification separation. Since 1,4-butanediol contains two hydroxyl groups with strong polarity, it forms a strong hydrogen bond network with -OH (hydroxyl of lactate) and -COOH (carboxyl) in the extractant 1-ethyl-3-methyl imidazole bromide, thereby destroying the hydrogen bond between 1,4-butanediol, 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate. The 1,4-butanediol molecules are wrapped by the surrounding ionic liquid extractant molecules through hydrogen bond. Each 1,4-butanediol molecule needs to destroy multiple hydrogen bonds at the same time to evaporate into the gas phase. At the same time, the hydrogen bond network makes the 1,4-butanediol molecules in the liquid phase tend to be in an aggregated state, resulting in a decrease in the molecular density on the surface of the liquid phase. This effect significantly reduces the volatility of butanediol (decreases the vapor pressure), so that its concentration in the gas phase is much lower than that in the liquid phase, thereby being "fixed" in the raffinate phase. 4-hydroxybutyl acrylate contains only one hydroxyl group, so the interaction between 4-hydroxybutyl acrylate and 1-ethyl-3-methyl imidazole bromide is weaker than that of 1,4-butanediol. The relative volatility of 4-hydroxybutyl acrylate is improved, and it is enriched in the gas phase and evaporated from the top of the column. 1,4-butanediol diacrylate has no hydroxyl group and only contains an ester group with weak polarity, so the interaction between 1,4-butanediol diacrylate and 1-ethyl-3-methyl imidazole bromide is weak, and the relative volatility of 1,4-butanediol diacrylate is almost unaffected. Since 4-hydroxybutyl acrylate is separated in the form of gas phase at the top of the column, the azeotropic system is broken, and 1,4-butanediol diacrylate remains in the column.

[0025] (3) The extractant can be further recovered in the present application, realizing the recycling of the extractant and saving the production cost.

[0026] (4) The method and system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive rectification in the present application combines thin film evaporation and extractive rectification, effectively shortening the separation and purification path of the target product. The product is separated by a single extractive rectification column, while the investment cost and operating cost are saved. In addition, the system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive rectification in the present application has the characteristics of high selectivity, easy temperature control, low energy consumption, short separation time, and strengthened equipment production capacity. BRIEF DESCRIPTION OF DRAWINGS

[0027] The drawings constituting a part of the specification of the present application serve to provide a further understanding of the present application, and the illustrative embodiments of the present application and the description thereof serve to explain the present application, and do not constitute an improper limitation on the present application.

[0028] Figure 1A structure diagram of a system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation, wherein 1-reaction liquid storage tank, 2-first feed pump, 3-preheater, 4-falling film evaporator, 5-gas-liquid separator, 6-concentrated liquid storage tank, 7-second feed pump, 8-first reboiler, 9-extractive distillation column, 10-second condenser, 11-extracted agent storage tank after reaction, 12-fourth feed pump, 13-second reboiler, 14-extracted agent recovery column, 15-fourth condenser, 16-second light component receiving tank, 17-second reflux tank, 18-fifth feed pump, 19-extracted agent raw material storage tank, 20-third feed pump, 21-third condenser, 22-4-hydroxybutyl acrylate storage tank, 23-first reflux tank, 24-extractive distillation column inlet, 25-nitrogen buffer tank, 26-heat conducting oil circulation all-in-one machine, 27-heat conducting oil outlet, 28-heat conducting oil inlet, 29-falling film evaporator bottom concentrated liquid outlet, 30-falling film evaporator middle steam outlet, 31-falling film evaporator top feed port, 32-gas-liquid separator liquid outlet, 33-gas-liquid separator gas outlet, 34-first condenser, 35-first light component receiving tank, 36-extractive distillation column top extracted agent inlet, 37-extractive distillation column top outlet, 38-extractive distillation column reflux inlet, 39-extractive distillation column bottom outlet, 40-extracted agent recovery column top outlet, 41-extracted agent recovery column reflux inlet, 42-extracted agent recovery column bottom outlet, DETAILED DESCRIPTION It should be noted that the following detailed description is merely exemplary in nature and is intended to provide further description of the application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0029] It is also important to note that the terms "comprises", "comprising", "includes", "including", "contains", "containing" or variations thereof herein, do not specify an exhaustive or complete list of components or features as used by those skilled in the art. Unless otherwise expressed, the terms "comprises", "comprising", "includes", "including", "contains", "containing" or variations thereof herein, are intended to be inclusive or open-ended and not exclusive.

[0030] In order to enable persons skilled in the art to more clearly understand the technical solutions of the present application, the technical solutions of the present application will be described in detail below in combination with specific examples.

[0031] Example 1 Reference Figure 1 A system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation, comprising a thin film evaporation unit and an extractive distillation unit; The thin film evaporation unit comprises a reaction liquid storage tank 1, a falling film evaporator 4 and a gas-liquid separator 5; the reaction liquid storage tank 1 is connected with a top feed inlet 31 of the falling film evaporator; a middle steam outlet 30 of the falling film evaporator is connected with the gas-liquid separator 5; a bottom concentrated liquid outlet 29 of the falling film evaporator and a liquid outlet 32 of the gas-liquid separator are both connected with a concentrated liquid storage tank 6; The extractive rectification unit comprises an extractant raw material storage tank 19, an extractive rectification column 9, a 4-hydroxybutyl acrylate storage tank 22 and a post-reaction extractant storage tank 11; the extractant raw material storage tank 19 is connected with an extractant top inlet 36 of the extractive rectification column; a top outlet 37 of the extractive rectification column is connected with the 4-hydroxybutyl acrylate storage tank 22; a column bottom outlet 39 of the extractive rectification column is connected with the post-reaction extractant storage tank 11; The concentrated liquid storage tank 6 is connected with the extractive rectification column 9.

[0032] In order to realize preheating of the reaction liquid after esterification of acrylic acid and 1,4-butanediol and then entering the top feed inlet 31 of the falling film evaporator, the reaction liquid storage tank 1 is connected with a first feed pump 2, a preheater 3 and the top feed inlet 31 of the falling film evaporator in sequence.

[0033] In order to realize efficient heat transfer and temperature control in the falling film evaporator 4, the falling film evaporator 4 is connected with a heat conducting oil circulation unit; the heat conducting oil circulation unit comprises a heat conducting oil circulation all-in-one machine 26; a side wall of the falling film evaporator 4 is respectively provided with a heat conducting oil inlet 28 and a heat conducting oil outlet 27; the heat conducting oil circulation all-in-one machine 26 is connected with the heat conducting oil inlet 28 through an oil conveying pipe; the heat conducting oil circulation all-in-one machine 26 is connected with the heat conducting oil outlet 27 through an oil return pipe.

[0034] In order to recover light components in the gas separated by the gas-liquid separator, a gas outlet 33 of the gas-liquid separator is connected with a first condenser 34 and a first light component receiving tank 35 in sequence.

[0035] In order to realize preheating of the liquid in the concentrated liquid storage tank 6 and then entering the extractive rectification column 9, the concentrated liquid storage tank 6 is connected with a second feed pump 7, a first reboiler 8 and a middle inlet 24 of the extractive rectification column in sequence.

[0036] In order to cool the components of the column bottom outlet 39 of the extractive rectification column, a second condenser 10 is arranged between the column bottom outlet 39 of the extractive rectification column and the post-reaction extractant storage tank 11.

[0037] In order to collect high-purity 4-hydroxybutyl acrylate, the top outlet 37 of the extractive rectification column is connected with a third condenser 21 and the 4-hydroxybutyl acrylate storage tank 22 in sequence; in order to realize material reflux, the third condenser 21 is connected with a first reflux tank 23, and the first reflux tank 23 is connected with a reflux inlet 38 of the extractive rectification column.

[0038] In order to realize the delivery of the extraction agent raw material, the third feed pump 20 is arranged between the extraction agent raw material storage tank 19 and the extraction agent inlet 36 of the top of the extractive rectification tower.

[0039] In order to realize the recycling of the extraction agent, the system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive rectification further comprises an extraction agent recovery unit, the extraction agent recovery unit comprising an extraction agent recovery tower 14; The post-reaction extraction agent storage tank 11 is sequentially connected with the fourth feed pump 12, the second reboiler 13 and the extraction agent recovery tower 14. The extraction agent recovery tower kettle outlet 42 is sequentially connected with the fifth feed pump 18 and the extraction agent inlet 36 of the top of the extractive rectification tower. The extraction agent recovery tower top outlet 40 is sequentially connected with the fourth condenser 15 and the second light component receiving tank 16; the fourth condenser 15 is sequentially connected with the second reflux tank 17 and the extraction agent recovery reflux inlet 41.

[0040] In order to balance the pressure, at the same time, in order to reduce the polymerization in the falling film evaporator 4, the extractive rectification tower 9 and the extraction agent recovery tower 14, the falling film evaporator 4, the extractive rectification tower 9 and the extraction agent recovery tower 14 are all connected with the nitrogen buffer tank 25.

[0041] The working process of the system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive rectification includes: The reaction liquid after the esterification reaction of acrylic acid and 1,4-butanediol is fed into the falling film evaporator 4 from the top feed port 31 of the falling film evaporator through the first feed pump 2 under the preheating of the preheater 3, and thin film evaporation is carried out; the gas-liquid mixture containing the first light component and the concentrated liquid is collected at the middle steam outlet 30 of the falling film evaporator, and the concentrated liquid is collected at the bottom concentrated liquid outlet 29 of the falling film evaporator; the gas-liquid mixture containing the first light component and the concentrated liquid is separated in the gas-liquid separator 5 to obtain gaseous first light component and liquid concentrated liquid; the gaseous first light component is condensed after passing through the first condenser 34 and enters the first light component receiving tank; the liquid concentrated liquid separated in the gas-liquid separator 5 and the concentrated liquid collected at the bottom concentrated liquid outlet 29 of the falling film evaporator are fed into the extractive rectification tower 9 through the second feed pump 7 for extractive rectification. The composition of the first light component is acrylic acid; the concentrated liquid comprises 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, an esterification catalyst and a polymerization inhibitor.

[0042] The extractant ionic liquid stored in the extractant raw material storage tank 19 is introduced into the extractive rectification tower 9 under the action of the third feed pump 20 from the extractive rectification tower top extractant inlet 36 to carry out extractive rectification with the concentrated liquid; the gaseous 4-hydroxybutyl acrylate collected from the extractive rectification tower top outlet 37 is condensed into liquid 4-hydroxybutyl acrylate after passing through the third condenser 21, and is introduced into the 4-hydroxybutyl acrylate storage tank; the post-reaction extractant is collected from the extractive rectification tower bottom outlet 39, and is condensed into the post-reaction extractant storage tank 11 after passing through the second condenser 10. The post-reaction extractant includes 1,4-butanediol, 1,4-butanediol diacrylate, esterification catalyst, polymerization inhibitor and extractant ionic liquid.

[0043] The post-reaction extractant is introduced into the extractant recovery tower 14 under the action of the fourth feed pump, and is heated by the second reboiler to carry out rectification recovery; the second light component in gaseous state is collected from the extractant recovery tower top outlet 40, and is condensed into the second light component receiving tank 16 after passing through the fourth condenser 15; the second light component includes 1,4-butanediol, 1,4-butanediol diacrylate, esterification catalyst and polymerization inhibitor; the recovered extractant ionic liquid is collected from the extractant recovery tower bottom outlet 42, and is returned to the extractive rectification tower 9 under the action of the fifth feed pump 18 for recycling.

[0044] Example 2 A method for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive rectification, comprising the following steps: The reaction liquid after esterification reaction of acrylic acid and 1,4-butanediol is subjected to thin film evaporation to obtain light components and concentrated liquid, wherein the concentrated liquid includes 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, esterification catalyst and polymerization inhibitor; the light components include acrylic acid; The concentrated liquid is subjected to extractive rectification with extractant ionic liquid to obtain product 4-hydroxybutyl acrylate and post-reaction extractant, respectively; wherein the extractant ionic liquid is 1-ethyl-3-methylimidazolium bromide; The post-reaction extractant is subjected to rectification to recover the extractant.

[0045] The total mass of the reaction liquid after esterification reaction of acrylic acid and 1,4-butanediol is 100%, and the composition includes: 0.5-5 wt% of acrylic acid, 30-50 wt% of 1,4-butanediol, 40-50 wt% of 4-hydroxybutyl acrylate, 0.3-2 wt% of 1,4-butanediol diacrylate, 0.5-2 wt% of catalyst and 2-5 wt% of polymerization inhibitor.

[0046] The esterification catalyst is p-toluenesulfonic acid; The polymerization inhibitor is hydroquinone.

[0047] The mass ratio of the extractant ionic liquid to the reaction liquid after esterification of acrylic acid and 1,4-butanediol is (0.15-0.4):1.

[0048] The reaction liquid after reaction includes 1,4-butanediol, 1,4-butanediol diacrylate, an esterification catalyst, a polymerization inhibitor, and the extractant ionic liquid.

[0049] Example 3 The system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled with extractive distillation in Example 1 is used to process the reaction liquid after esterification of acrylic acid and 1,4-butanediol. The composition of the reaction liquid after esterification of acrylic acid and 1,4-butanediol is 2.56 wt% of acrylic acid, 45.15 wt% of 1,4-butanediol, 47.82 wt% of 4-hydroxybutyl acrylate, 1.27 wt% of 1,4-butanediol diacrylate, 1.20 wt% of a catalyst, and 2 wt% of a polymerization inhibitor, based on the total mass of 100% of the reaction liquid after esterification of acrylic acid and 1,4-butanediol.

[0050] The operating parameters are as follows: the operating conditions of the falling film evaporator are an operating pressure of 20 kPa and an operating temperature of 95 ℃; the operating conditions of the extractive distillation column are an operating pressure of 0.2 MPa, a column top temperature of 55.6 ℃, a column bottom temperature of 100.23 ℃, a mass ratio of the extractant ionic liquid to the reaction liquid after esterification of acrylic acid and 1,4-butanediol of (0.15-0.4):1, and a reflux ratio of 6; and the operating conditions of the solvent recovery column are an operating pressure of 0.3 MPa, a column top temperature of 76.45 ℃, a column bottom temperature of 160.23 ℃, and a reflux ratio of 6.

[0051] The results are shown in Table 1. As can be seen from Table 1, by increasing the amount of the extractant, the extractant is fully contacted with the reaction liquid after esterification of acrylic acid and 1,4-butanediol, and the product purity of 4-hydroxybutyl acrylate is improved. This is because more ionic liquid can destroy more hydrogen bonds among 1,4-butanediol, 4-hydroxybutyl acrylate, and 1,4-butanediol diacrylate. Due to the presence of polar functional groups, more 1,4-butanediol molecules (containing hydroxyl groups) are wrapped by the extractant (containing hydroxyl groups and carboxyl groups) through hydrogen bonding, so that the 1,4-butanediol molecules cannot diffuse to the gas-liquid interface through molecular motion, more independent 1,4-butanediol, 4-hydroxybutyl acrylate, and 1,4-butanediol diacrylate are dissociated from the azeotrope, and then the azeotrope is eliminated, and high-concentration 4-hydroxybutyl acrylate is obtained by distillation separation.

[0052] Table 1 Product purity and extractant recovery rate

[0053] The above merely provides the preferred embodiments of the present application, and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the principles and technical scope of the present application shall fall into the scope of the present application.

Claims

1. A method for purifying 4-hydroxybutyl acrylate based on thin-film evaporation coupled extractive distillation, characterized in that, The method comprises the following steps: The reaction liquid after the esterification reaction of acrylic acid and 1,4-butanediol is concentrated by thin film evaporation to obtain light components and concentrated liquid, wherein the concentrated liquid comprises 1,4-butanediol, 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, an esterification catalyst and a polymerization inhibitor; and the light components comprise acrylic acid; The concentrated liquid is subjected to extractive distillation with an extractant ionic liquid to obtain product 4-hydroxybutyl acrylate and post-reaction extractant, wherein the extractant ionic liquid is 1-ethyl-3-methylimidazolium bromide; The post-reaction extractant is subjected to rectification to recover the extractant.

2. The method of claim 1, wherein, The total mass of the reaction liquid after the esterification reaction of acrylic acid and 1,4-butanediol is 100%, and the composition comprises 0.5-5 wt% of acrylic acid, 30-50 wt% of 1,4-butanediol, 40-50 wt% of 4-hydroxybutyl acrylate, 0.3-2 wt% of 1,4-butanediol diacrylate, 0.5-2 wt% of a catalyst and 2-5 wt% of a polymerization inhibitor; Or, the post-reaction extractant comprises 1,4-butanediol, 1,4-butanediol diacrylate, an esterification catalyst, a polymerization inhibitor and an extractant ionic liquid; Or, the mass ratio of the extractant ionic liquid to the reaction liquid after the esterification reaction of acrylic acid and 1,4-butanediol is (0.15-0.4):

1.

3. The method of claim 1, wherein, The esterification catalyst is at least one of concentrated sulfuric acid, p-toluenesulfonic acid and methanesulfonic acid, and is preferably p-toluenesulfonic acid; and the polymerization inhibitor is at least one of phenothiazine, hydroquinone, p-methoxyphenol, ZJ-701, ZJ-705 and copper N,N-di-n-butyl dithiocarbamate, and is preferably hydroquinone.

4. A system for purifying 4-hydroxybutyl acrylate based on thin film evaporation coupled extractive distillation, characterized by, The method comprises a thin film evaporation unit and an extractive distillation unit. The thin film evaporation unit comprises a reaction liquid storage tank, a falling film evaporator and a gas-liquid separator; the reaction liquid storage tank is connected to the top feed inlet of the falling film evaporator; the middle steam outlet of the falling film evaporator is connected to the gas-liquid separator; and the bottom concentrated liquid outlet of the falling film evaporator and the liquid outlet of the gas-liquid separator are both connected to a concentrated liquid storage tank. The extractive distillation unit comprises an extractant raw material storage tank, an extractive distillation column, a 4-hydroxybutyl acrylate storage tank and a post-reaction extractant storage tank; the extractant raw material storage tank is connected to the top extractant inlet of the extractive distillation column; the top outlet of the extractive distillation column is connected to the 4-hydroxybutyl acrylate storage tank; and the column bottom outlet of the extractive distillation column is connected to the post-reaction extractant storage tank. The concentrated liquid storage tank is connected to the extractive distillation column.

5. The system of claim 4, wherein, The reaction liquid storage tank is sequentially connected to a first feed pump, a preheater and the top feed inlet of the falling film evaporator. Or, the falling film evaporator is connected to a heat conducting oil circulation unit; preferably, the heat conducting oil circulation unit comprises a heat conducting oil circulation all-in-one machine; further preferably, the sidewall of the falling film evaporator is respectively provided with a heat conducting oil inlet and a heat conducting oil outlet, the heat conducting oil circulation all-in-one machine is connected to the heat conducting oil inlet through an oil conveying pipe, and the heat conducting oil circulation all-in-one machine is connected to the heat conducting oil outlet through an oil return pipe.

6. The system of claim 4, wherein, The gas outlet of the gas-liquid separator is sequentially connected to a first condenser and a first light component receiving tank. Or, the concentrated liquid storage tank is connected with a second feed pump, a first reboiler and the extractive distillation column in sequence. Or, a second condenser is arranged between the extractive distillation column bottom outlet and the post-reaction extractant storage tank.

7. The system of claim 4, wherein, The extractive distillation column top outlet is connected with a third condenser and a 4-hydroxybutyl acrylate storage tank in sequence; preferably, the third condenser is connected with a first reflux tank, and the first reflux tank is connected with a reflux inlet of the extractive distillation column. Or, a third feed pump is arranged between the extractant raw material storage tank and an extractant inlet of the extractive distillation column top.

8. The system of claim 4, wherein, The system for purifying 4-hydroxybutyl acrylate based on the thin-film evaporation coupled extractive distillation further comprises an extractant recovery unit, and the extractant recovery unit comprises an extractant recovery column. The post-reaction extractant storage tank is connected with a fourth feed pump, a second reboiler and the extractant recovery column in sequence.

9. The system of claim 8, wherein, The extractant recovery column bottom outlet is connected with a fifth feed pump and an extractant inlet of the extractive distillation column top in sequence. Or, an extractant recovery column top outlet is connected with a fourth condenser and a second light component receiving tank in sequence; preferably, the fourth condenser is connected with a second reflux tank and a reflux inlet of the extractant recovery column in sequence.

10. The system of claim 8, wherein, The falling-film evaporator, the extractive distillation column and the extractant recovery column are all connected with a nitrogen buffer tank.

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