Method and apparatus for preparing and purifying hydroxyalkyl (meth) acrylates

Abstract

The present application provides a method and apparatus for preparing and purifying hydroxyalkyl (meth) acrylate, the method comprising: subjecting C2-C6 alkane diol and (meth) acrylic acid to an esterification reaction to produce an esterification reaction product material; performing first extraction operation on the esterification reaction product material to obtain a first light component and a first heavy component; separating the first light component to obtain a second light component and a second heavy component; carrying out first rectification operation on the second light component to obtain a third light component and a third heavy component; performing second extraction operation on the third heavy component to obtain a fourth light component and a fourth heavy component; and carrying out third rectification operation on the fourth light component to obtain a fifth light component and the target product hydroxyalkyl (methyl) acrylate. According to the method and the equipment disclosed by the invention, the target product can be prepared and purified at extremely high efficiency on the premise of remarkably reducing the energy consumption, and the target product hydroxyalkyl (methyl) acrylate with excellent purity and quality is obtained.

Description

Technical Field

[0001] The present application relates to the chemical industry field, and more specifically to a method for preparing and purifying C2-C6 hydroxyalkyl (meth)acrylates, and an apparatus specifically for this method. Background Art

[0002] Hydroxyalkyl (meth)acrylates have a wide range of uses in various fields due to their unique excellent properties. As a typical example, 4-hydroxybutyl acrylate (4-HBA) is a water-soluble highly active bifunctional monomer. Its hydroxyl group can react with hydroxyl-active groups such as isocyanates to obtain a completely cross-linked and high-strength cross-linked structure, making the cross-linked product have excellent flexibility. Therefore, hydroxyalkyl (meth)acrylates represented by 4-HBA can be generally used in the synthesis of various resins such as PU, which can significantly improve the cross-linking density and chemical resistance of the resin, significantly enhance its weather resistance, wettability and adhesion to polar surfaces, and are suitable for preparing automotive coatings, architectural coatings and adhesives, etc. In particular, the acrylic polyurethane coating prepared by the hydroxy acrylic resin (HAR) synthesized from 4-HBA and isocyanate shows a significantly increased curing speed, and various film properties such as adhesion, gloss, scratch resistance, weather resistance, chemical resistance, water resistance, heat resistance and flexibility are very excellent, which makes 4-HBA very useful in low-temperature fast-drying automotive refinish paints. It can be foreseen that the demand for various hydroxyalkyl (meth)acrylates represented by 4-HBA in related fields will continue to increase.

[0003] However, in contradiction to the increasing demand in related fields, the synthesis process of such compounds always has significant defects. Specifically, at present, the direct esterification method is mainly used in industrial production, using (meth)acrylic acid and the corresponding alkyl diol as raw materials. The (meth)acrylic acid is added dropwise to the diol raw material for esterification reaction, and then the mixed material obtained from the esterification reaction is purified to obtain the target product hydroxyalkyl (meth)acrylate. However, in these existing methods, side reactions will inevitably occur during the reaction process as the depth of the reaction progresses, generating by-products such as alkane diol di(meth)acrylate; the unreacted diol raw materials, the target product and the above by-products contained in the esterification reaction product all have relatively high boiling points, and the diol raw materials and by-products often have boiling points close to that of the target product. It is very difficult to effectively separate the target product using conventional separation / purification techniques, and there are problems such as high energy consumption and easy further polymerization during the separation process.

[0004] In view of the above problems, relevant enterprises and research institutions have conducted a large number of studies. For example, they have tried to optimize and adjust various process conditions of the esterification reaction and purification process, and combined with various purification technologies. However, all these attempts have failed without exception. Not only can they not effectively solve the above defects, but they may also bring new problems. For example, the separation efficiency of organic solvents and by-products (such as extraction efficiency) is poor, which will further reduce the overall yield of the target product. Moreover, the newly selected or added purification technology may further cause polymerization or decomposition of the target product. Therefore, there is an urgent need in the art to develop a new technology that can solve the above problems. Summary of the Invention

[0005] In view of the above problems, through a large number of in-depth studies, the inventor has developed a novel method and device, successfully solving the problems that have long existed in the prior art. Specifically, the first aspect of the present application provides a method for preparing and purifying C2-C6 hydroxyalkyl (meth)acrylate, the method comprising:

[0006] Step 1: Reacting a C2-C6 alkane diol with (meth)acrylic acid to form an esterification reaction product material, the esterification reaction product material comprising C2-C6 hydroxyalkyl (meth)acrylate, by-products, and unreacted C2-C6 alkane diol;

[0007] Step 2: Performing a first extraction operation on the esterification reaction product material using a first extractant to obtain a first light fraction and a first heavy fraction;

[0008] Step 3: Adding a basic reagent to the first light fraction and performing a separation operation to obtain a second light fraction and a second heavy fraction;

[0009] Step 4: Performing a first rectification operation on the second light fraction to obtain a third light fraction and a third heavy fraction;

[0010] Step 5: Performing a second extraction operation on the third heavy fraction using a second extractant to obtain a fourth light fraction and a fourth heavy fraction;

[0011] Step 6: Performing a third rectification operation on the fourth light fraction to obtain a fifth light fraction and a target product, the target product being C2-C6 hydroxyalkyl (meth)acrylate.

[0012] According to an embodiment of the first aspect of the present application, the C2-C6 alkane diol is selected from one or more of the following: ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol.

[0013] According to another embodiment of the first aspect of the present application, the C2-C6 hydroxyalkyl (meth)acrylate is selected from one or more of the following: 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate, 6-hydroxyhexyl methacrylate.

[0014] According to another embodiment of the first aspect of the present application, in the first step, in the presence of an organic solvent, an inhibitor and a catalyst, the (meth)acrylic acid reacts with a C2-C6 alkane diol to form an esterification reaction product material.

[0015] According to another embodiment of the first aspect of the present application, in the first step, the molar ratio of the (meth)acrylic acid to the C2-C6 alkane diol is from 1:1 to 1:3.

[0016] According to another embodiment of the first aspect of the present application, in the first step, the esterification reaction is carried out at a reaction temperature of 100-120 °C.

[0017] According to another embodiment of the first aspect of the present application, in the first step, the organic solvent is selected from one or more of the following: cyclohexane, cyclopentane, cyclooctane, cyclohexanone, toluene, xylene, pentane, hexane, octane, acetone, acetonitrile.

[0018] According to another embodiment of the first aspect of the present application, in the first step, the catalyst is selected from one or more of the following: benzenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, concentrated sulfuric acid.

[0019] According to another embodiment of the first aspect of the present application, in the first step, the inhibitor is selected from one or more of the following: hydroquinone, p-methoxyphenol, copper acetate.

[0020] According to another embodiment of the first aspect of the present application, in the second step, a first extractant, water and the esterification reaction product material are added to a first extraction column to carry out the first extraction operation. A first light component is obtained at the top of the first extraction column, and a first heavy component is obtained at the bottom of the first extraction column.

[0021] According to another embodiment of the first aspect of the present application, in the second step, the first extractant is selected from one or more of the following: (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid butyl ester, (meth)acrylic acid pentyl ester, (meth)acrylic acid hexyl ester.

[0022] According to another embodiment of the first aspect of the present application, in the second step, the first light component comprises: C2-C6 hydroxyalkyl (meth)acrylate, C2-C6 alkane diol di(meth)acrylate, organic solvent, inhibitor, catalyst, and a first extractant.

[0023] According to another embodiment of the first aspect of the present application, in the second step, the first heavy component comprises: C2-C6 alkane diol, inhibitor, catalyst, and water.

[0024] According to another embodiment of the first aspect of the present application, in the second step, the temperature of the first extraction column is 25-50 °C.

[0025] According to another embodiment of the first aspect of the present application, in the second step, the first heavy component is optionally recycled back to the esterification reaction in the first step for reuse.

[0026] According to another embodiment of the first aspect of the present application, in the third step, an alkaline reagent and the first light component are input into the separator, and a separation operation is performed. A second light component is obtained at the top of the separator, and a second heavy component is obtained at the bottom of the separator.

[0027] According to another embodiment of the first aspect of the present application, in the third step, the second light component comprises: C2-C6 hydroxyalkyl (meth)acrylate, C2-C6 alkane diol di(meth)acrylate, organic solvent, and a first extractant.

[0028] According to another embodiment of the first aspect of the present application, in the third step, the second heavy component comprises: inhibitor, salified catalyst, and water.

[0029] According to another embodiment of the first aspect of the present application, in the third step, the alkaline reagent is selected from one or more of the following: sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, and organic amines.

[0030] According to another embodiment of the first aspect of the present application, in the third step, the temperature of the separator is 25-50 °C.

[0031] According to another embodiment of the first aspect of the present application, in the fourth step, a first rectification operation is performed on the second light component in a first rectification column. A third light component is obtained at the top of the first rectification column, and a third heavy component is obtained from the middle or bottom of the first rectification column.

[0032] According to another embodiment of the first aspect of the present application, in the fourth step, the third light component comprises a first extractant and an organic solvent.

[0033] According to another embodiment of the first aspect of the present application, in step four, the third heavy component comprises C2-C6 hydroxyalkyl (meth)acrylate and C2-C6 alkane diol di(meth)acrylate.

[0034] According to another embodiment of the first aspect of the present application, in step four, the pressure of the first rectification column is 0.001-0.01 Mpa.

[0035] According to another embodiment of the first aspect of the present application, in step five, the second extractant and the third heavy component are input into the second extraction column together for a second extraction operation, a fourth light component is obtained at the top of the second extraction column, and a fourth heavy component is obtained at the bottom of the second extraction column.

[0036] According to another embodiment of the first aspect of the present application, in step five, the fourth light component comprises C2-C6 hydroxyalkyl (meth)acrylate and the second extractant.

[0037] According to another embodiment of the first aspect of the present application, in step five, the fourth heavy component comprises C2-C6 alkane diol di(meth)acrylate.

[0038] According to another embodiment of the first aspect of the present application, in step five, the second extractant is demineralized water.

[0039] According to another embodiment of the first aspect of the present application, in step five, the temperature of the second extraction column is 25-50 °C.

[0040] According to another embodiment of the first aspect of the present application, in step six, the fourth light component is subjected to a third rectification operation in the third rectification column, a fifth light component is obtained at the top of the third rectification column, and the target product is obtained in the middle or at the bottom of the third rectification column.

[0041] According to another embodiment of the first aspect of the present application, in step six, the fifth light component comprises the second extractant.

[0042] According to another embodiment of the first aspect of the present application, in step six, the pressure of the third rectification column is 0.001-0.005 Mpa.

[0043] According to another embodiment of the first aspect of the present application, the third light component is subjected to a second rectification operation in the second rectification column, an organic solvent is obtained at the top of the second rectification column, and the first extractant is obtained in the middle or at the bottom of the second rectification column. According to another embodiment of the first aspect of the present application, the pressure of the second rectification column is 0.01-0.02 MPa.

[0044] The second aspect of the present application provides a reaction-purification apparatus for implementing the method described in any one of the above embodiments. The apparatus includes: a reactor R101, a first extraction column T101, a separator T102, a first distillation column T103, a second distillation column T104, a second extraction column T105, and a third distillation column T106.

[0045] According to an embodiment of the second aspect of the present application, the outlet of the reactor R101 is communicated with the inlet of the first extraction column T101, the outlet at the top of the first extraction column T101 is communicated with the inlet of the separator T102, the outlet at the top of the separator T102 is communicated with the inlet of the first distillation column T103, the outlet at the top of the first distillation column T103 is communicated with the inlet of the second distillation column T104, the outlet at the bottom of the first distillation column T103 is communicated with the inlet of the second extraction column T105, and the outlet at the top of the second extraction column T105 is communicated with the inlet of the third distillation column T106.

[0046] In the following specific embodiment section, the method and polymer product of the present application are further introduced in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 Shows a schematic flow chart of an esterification reaction-purification method according to an embodiment of the present application;

[0048] Figure 2 Shows a gas chromatogram of the product 4-hydroxybutyl acrylate obtained according to another embodiment of the present application.

[0049] In Figure 1 the meanings of the reference numerals appearing are as follows:

[0050] R101 - reactor; T101 - first extraction column; T102 - separator; T103 - first distillation column; T104 - second distillation column; T105 - second extraction column; T106 - third distillation column;

[0051] 1 - mixture of acrylic acid and organic solvent (cyclohexane); 2 - mixture of polymerization inhibitor, catalyst and diol (1,4-butanediol); 3 - esterification reaction product material; 4 - first extractant; 5 - water; 6 - first heavy component; 7 - first light component; 8 - basic reagent (aqueous NaOH solution); 9 - second heavy component; 10 - second light component; 11 - third light component; 12 - third heavy component; 13 - organic solvent (cyclohexane); 14 - first extractant; 15 - second extractant; 16 - fourth light component; 17 - fourth heavy component (by-product 1,4-butanediol diacrylate); 18 - fifth light component (second extractant); 19 - target product (4-hydroxybutyl acrylate). Detailed implementation manners

[0052] The "ranges" disclosed herein are in the form of a lower limit and an upper limit. There can be one or more lower limits, and one or more upper limits respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the boundaries of a particular range. All ranges that can be defined in this way are inclusive and combinable, that is, any lower limit can be combined with any upper limit to form a range. For example, ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, and ranges of 60 - 110 and 80 - 120 are understood to be also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5.

[0053] In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations.

[0054] In this application, if there is no special instruction, all the implementation manners and preferred implementation manners mentioned herein can be combined with each other to form a new technical solution.

[0055] In this application, if there is no special instruction, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0056] In this application, if there is no special instruction, the "including" mentioned herein means open-ended, and can also be closed-ended. For example, the "including" can mean that other components not listed can also be included, or it can only include the listed components.

[0057] In the present invention, (meth)acrylic acid means acrylic acid, methacrylic acid, or a combination thereof; (meth)acrylate means acrylate, methacrylate, or a combination thereof.

[0058] The preparation-purification method of the present invention is used to obtain C2-C6 hydroxyalkyl (meth)acrylates with high purity and high quality. According to an embodiment of the present application, examples of the C2-C6 hydroxyalkyl (meth)acrylate include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate; preferably 4-hydroxybutyl (meth)acrylate. Hereinafter, 4-hydroxybutyl acrylate is taken as an example to illustrate the method, process equipment and process conditions of the present application, but the protection scope of the present invention is not limited thereto.

[0059] According to an embodiment of the present application, the esterification reaction in the first step of the present invention is carried out in a continuous manner. According to a preferred embodiment of the present application, all steps of the method of the present invention are carried out in a continuous manner, so that the method of the present invention can be carried out in a continuous manner, achieving a higher reaction yield while also achieving a higher production efficiency.

[0060] According to an embodiment of the present application, the raw materials for the esterification reaction used in the first step include C2-C6 alkane diols and (meth)acrylic acid. Examples of the C2-C6 alkane diols include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol; preferably 1,4-butanediol.

[0061] According to an embodiment of the present application, in the esterification reaction of the first step, the addition amount of the C2-C6 alkane diol is molar or in excess relative to the (meth)acrylic acid. For example, the molar ratio of the (meth)acrylic acid to the C2-C6 alkane diol can be 1:1 to 1:3, or can be between any two of the following ratios: 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2, 1:2.2, 1:2.5, 1:2.8, 1:3.

[0062] According to an embodiment of the present application, the reaction temperature of the esterification reaction is 100-120 °C, preferably 100-110 °C.

[0063] According to another embodiment of the present application, at least one of an organic solvent, a polymerization inhibitor and a catalyst can be used in the esterification reaction of the first step.

[0064] The organic solvent may include one or more of the following: cyclopentane, cyclooctane, cyclohexanone, toluene, xylene, pentane, hexane, octane, acetone, acetonitrile; preferably cyclohexane. In the first-step esterification reaction, the weight ratio of the organic solvent to the total amount of reaction raw materials (C2-C6 alkane diol and (meth)acrylic acid) may be 1:5 to 4:1, such as 1:3 to 2:1, or 1:2 to 1:1.

[0065] According to another embodiment of the present application, the catalyst is selected from one or more of the following: benzenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, concentrated sulfuric acid; preferably benzenesulfonic acid or p-toluenesulfonic acid. In the first-step esterification reaction, the weight ratio of the catalyst to the total amount of reaction raw materials (C2-C6 alkane diol and (meth)acrylic acid) may be 1:1000 to 1:50, such as 1:300 to 1:80, or 1:200 to 1:100.

[0066] According to another embodiment of the present application, a polymerization inhibitor needs to be added in the esterification reaction to prevent unwanted polymerization reactions and the formation of polyester by-products. The polymerization inhibitor may be selected from one or more of the following: hydroquinone, p-methoxyphenol, copper acetate; preferably the polymerization inhibitor is hydroquinone. In the first-step esterification reaction, the weight ratio of the polymerization inhibitor to the total amount of reaction raw materials (C2-C6 alkane diol and (meth)acrylic acid) may be 1:1500 to 1:100, such as 1:1000 to 1:200, or 1:500 to 1:300.

[0067] According to an exemplary embodiment of the present application, as Figure 1 shown, the first step of the method of the present invention can be carried out in reactor R101. In this exemplary embodiment, a stream 1 containing (meth)acrylic acid and an organic solvent and a stream 2 containing an alcohol raw material (as well as a catalyst and a polymerization inhibitor) can be continuously input into the reactor, and the reactor is heated to the required reaction temperature.

[0068] According to an embodiment of the present application, an esterification reaction product material is generated through the esterification reaction. For the case where the esterification reaction is carried out continuously, as Figure 1 shown, the esterification reaction product continuously flows out of the reactor as stream 3. The esterification reaction product mainly contains an organic solvent and the target product C2-C6 hydroxyalkyl (meth)acrylate, and may also contain by-products (the by-products are mainly C2-C6 alkyl di(meth)acrylate), unreacted C2-C6 alkane diol, catalyst, polymerization inhibitor, etc.

[0069] Next, in the second step, a first extraction operation is carried out on the esterification reaction product material using a first extractant to obtain a first light component and a first heavy component. For example, asFigure 1 As shown, the esterification reaction product material 3 is fed into the first extraction column T101, and the first extractant 4 and water 5 are continuously supplied to the first extraction column T101. The first light component 7 is withdrawn from the top of the column, and the first heavy component 6 is withdrawn from the bottom of the column.

[0070] According to an embodiment of the present application, the first light component mainly contains the target reaction product, by-products (the by-products are mainly C2-C6 alkyl di(methyl)acrylates), organic solvents, unreacted C2-C6 alkane diols, catalysts, inhibitors, the first extractant, etc.; the first heavy component mainly contains unreacted C2-C6 alkyl diols, catalysts, inhibitors, water, etc. The first heavy component can be directly recycled to the esterifier as needed, or recycled to the esterifier after purification (such as removing moisture) as needed.

[0071] According to an embodiment of the present application, the temperature of the first extraction operation can be 25-50°C, preferably 30-40°C.

[0072] According to another embodiment of the present application, the first extractant is selected from one or more of the following: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate; preferably butyl acrylate.

[0073] According to another embodiment of the present application, in the second step, the weight ratio of the esterification reaction product material to the first extractant can be 600:100 to 60:100, for example, it can be 400:100 to 100:100, or 200:100 to 150:100.

[0074] According to another embodiment of the present application, in the second step, the weight ratio of the esterification reaction product material to the water added thereto can be 100:1 to 1:1, for example, it can be 60:1 to 10:1, or 50:100 to 20:1.

[0075] Next, in the third step, a basic reagent is added to the first light component and a separation operation is performed to obtain a second light component and a second heavy component. The second light component mainly contains the target reaction product, by-products (the by-products are mainly C2-C6 alkyl di(methyl)acrylates), organic solvents, the first extractant, etc.; the second heavy component mainly contains the catalyst (at this time, the acidic catalyst has reacted with the basic reagent to form a salt form), inhibitors and water, etc. The second heavy component can be treated as wastewater.

[0076] For example, in Figure 1In the illustrated embodiment, the first light component 7 is fed into the first separator T102, and an alkaline reagent 8 is added to the first separator T102. The second light component 10 is taken from the top of the first separator T102, and the second heavy component 9 is taken from the bottom of the first separator T102.

[0077] According to an embodiment of the present application, the temperature of the first separator may be 25 - 50 °C, for example, 30 - 40 °C.

[0078] According to another embodiment of the present application, the alkaline reagent is selected from one or more of the following: sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, organic amines; for example, an aqueous solution of these compounds. The concentration of the aqueous solution may be 5 - 50 wt%, for example, 10 - 30 wt%, preferably 15 - 20 wt%.

[0079] According to another embodiment of the present application, the mass ratio of the first light component to the alkaline reagent in step three may be 700:1 to 80:1, for example, 500:1 to 100:1, or 300:1 to 200:1.

[0080] Next, in step four, a first rectification operation is performed on the second light component to obtain a third light component and a third heavy component. The third light component mainly contains the first extractant and the organic solvent; the third heavy component mainly contains the target product and by-products (mainly C2 - C6 alkane diol di(methyl)acrylate).

[0081] The third light component can then be subjected to a second rectification operation to separate and recover the organic solvent and the first extractant, and recycle them as needed.

[0082] According to an embodiment of the present application, as Figure 1 shown, the second light component 10 is fed into the first rectification column T103, the third light component 11 is taken from the top of the column, and the third heavy component 12 is taken from the middle or bottom of the column kettle.

[0083] According to an embodiment of the present application, the pressure of the first rectification operation may be 0.001 - 0.01 Mpa, preferably 0.002 - 0.006 MPa.

[0084] According to an embodiment of the present application, the number of trays of the rectification column used in the first rectification operation may be 10 - 20, preferably 16; the reflux ratio may be 0.7 - 0.9, preferably 0.86. The second light component enters the rectification column from the 7th tray, the temperature of the column kettle is 50 - 80 °C, preferably 60 - 70 °C, more preferably 64 °C.

[0085] As described above, the third light component can undergo a second rectification operation to separate out the organic solvent and the first extractant, and these components can be recycled respectively. For example, the organic solvent can be recycled back to the esterification reaction, and the first extractant can be recycled back to the first extraction operation.

[0086] For example, in Figure 1 the embodiment shown, the third light component 11 is fed to the second rectification column T104 for the second rectification operation. The organic solvent 13 is withdrawn from the top of the second rectification column T104, and the first extractant 14 is withdrawn from the middle or bottom of the column kettle.

[0087] According to an embodiment of the present application, the pressure of the second rectification operation can be 0.01 - 0.02 Mpa.

[0088] According to an embodiment of the present application, the number of trays of the rectification column used in the second rectification operation can be 5 - 15, preferably 10; the reflux ratio is 2 - 4, preferably 3.6; the second light component enters the rectification column from the 6th tray, and the temperature of the column kettle is 77 °C.

[0089] Next, in step five, the third heavy component is subjected to a second extraction operation using a second extractant to obtain a fourth light component and a fourth heavy component. For example, as Figure 1 shown, the third heavy component 12 is input into the second extraction column T105, and the second extractant 15 is continuously supplied to the first extraction column T105. The fourth light component 16 is withdrawn from the top of the column, and the fourth heavy component 17 is withdrawn from the bottom of the column.

[0090] According to an embodiment of the present application, the fourth light component mainly contains the target product (such as C2 - C6 hydroxyalkyl (meth)acrylate) and the second extractant; the fourth heavy component mainly contains C2 - C6 alkane diol di(meth)acrylate.

[0091] According to an embodiment of the present application, the temperature of the first extraction operation can be 25 - 50 °C, preferably 30 - 40 °C.

[0092] According to another embodiment of the present application, the second extractant is demineralized water.

[0093] According to another embodiment of the present application, in the said step five, the weight ratio of the third heavy component to the second extractant can be 12:1 to 1:1, for example, it can be 8:1 to 2:1, or 5:1 to 3:1.

[0094] Next, in step six, the fourth light component is subjected to a third rectification operation to separate out a fifth light component and the target product. The fifth light component mainly contains the second extractant. The second extractant can be treated as waste or recycled to the second extraction step.

[0095] According to an embodiment of the present application, the pressure of the third rectification operation may be 0.001 - 0.005 Mpa, for example, 0.002 - 0.003 Mpa.

[0096] According to an embodiment of the present application, the number of trays of the rectification column used in the third rectification operation may be 10 - 20, preferably 19; the reflux ratio is 0.5 - 1.5, preferably 1.2; the second light component enters the rectification column from the 9th tray, and the bottom temperature of the column is 40 - 60 °C, or 42 - 50 °C, preferably 45 °C.

[0097] The reaction - purification equipment for implementing the method of the present invention is also included within the protection scope of the present invention. According to an embodiment of the present application, the equipment includes a reactor R101, a first extraction column T101, a separator T102, a first rectification column T103, a second rectification column T104, a second extraction column T105, and a third rectification column T106; the outlet of the reactor R101 is communicated with the inlet of the first extraction column T101, the outlet at the top of the first extraction column T101 is communicated with the inlet of the separator T102, the outlet at the top of the separator T102 is communicated with the inlet of the first rectification column T103, the outlet at the top of the first rectification column T103 is communicated with the inlet of the second rectification column T104, the outlet at the bottom of the first rectification column T103 is communicated with the inlet of the second extraction column T105, and the outlet at the top of the second extraction column T105 is communicated with the inlet of the third rectification column T106.

[0098] Without wishing to be bound by any particular theory, the method of the present invention can achieve one or more of the following advantages: By specifically designing the production - purification process flow and specifically selecting reagents (such as extraction agents, etc.) therein, the method of the present invention realizes a higher target product yield and by - product / impurity separation efficiency with significantly reduced energy consumption, significantly reduced production costs, and improved production efficiency, and the purity and quality of the obtained target product have been significantly improved.

[0099] In the following examples, specific examples are used to specifically illustrate the method of the present application, aiming to better understand the content of the present application. It should be understood that these examples are merely illustrative and not restrictive. The reagents used in the examples are all conventionally purchased from the market unless otherwise specified. The methods and conditions used in the examples are all conventional methods and conditions unless otherwise specified.

[0100] Embodiment

[0101] All reagents used in the following examples were commercially available analytical grade reagents, and deionized water was used. Gas chromatography was used to characterize the content of various components in the streams. The instrument used was an Agilent gas chromatograph, with an FID detector, helium as the carrier gas, and a DB-624-UI column. Alcohols and acids were quantitatively analyzed using the internal standard method, while esters were quantitatively analyzed using the area normalization method.

[0102] Unless otherwise indicated, all percentages in the examples are by weight.

[0103] This embodiment follows Figure 1 The reaction-purification apparatus was constructed as shown.

[0104] First, step 1 was performed: Stream 1 (comprising acrylic acid at a mass flow rate of 108.55 kg / h and cyclohexane at a mass flow rate of 190.02 kg / h) and Stream 2 (comprising hydroquinone at a mass flow rate of 1.14 kg / h, p-toluenesulfonic acid at a mass flow rate of 3.8 kg / h, and 1,4-butanediol at a mass flow rate of 271.5 kg / h) were introduced into reactor R101 and thoroughly mixed. The reactor was then heated to 100°C to allow an esterification reaction to occur between the acrylic acid and the excess 1,4-butanediol. The esterification product, stream 3, exited the reactor at a total flow rate of 547.88 kg / h. The esterification reaction product stream 3 was characterized by gas chromatography analysis and was found to contain 15.01% 4-hydroxybutyl acrylate, 2.02% 1,4-butanediol diacrylate, 0.09% hydroquinone, 0.31% p-toluenesulfonic acid, 15.71% cyclohexane, and 12.41% 1,4-butanediol.

[0105] Next, perform Step 2: Feed the esterification reaction product stream 3 into the first extraction column T101. Add butyl acrylate 4 to the first extraction column T101 at a mass flow rate of 301.7 kg / h, and add water 5 to the first extraction column T101 at a mass flow rate of 17.5 kg / h. Conduct extraction separation at 30°C. Withdraw the first light fraction 7 from the top of the first extraction column T101 and the first heavy fraction 6 from the bottom. Characterize the first light fraction 7 and the first heavy fraction 6 using gas chromatography analysis. It is measured that the first light fraction 7 includes the reaction product 4-hydroxybutyl acrylate, the by-product 1,4-butanediol diacrylate, cyclohexane, hydroquinone, p-toluenesulfonic acid, and butyl acrylate, and their mass flow rates are 181.54 kg / h, 24.49 kg / h, 190.02 kg / h, 0.91 kg / h, 1.25 kg / h, and 301.7 kg / h respectively; it is measured that the first heavy fraction 6 includes unreacted 1,4-butanediol, hydroquinone, p-toluenesulfonic acid, and water, and their mass flow rates are 146.89 kg / h, 2.55 kg / h, 0.23 kg / h, and 17.5 kg / h respectively. The first heavy fraction 6 can be recycled for the esterification reaction.

[0106] Subsequently, perform Step 3: Feed the first light fraction 7 into the first separator T102, and at the same time, input the NaOH aqueous solution 8 with a concentration of 20 wt% into the first separator T102 at a mass flow rate of 3.11 kg / h. Conduct the separation operation at a temperature of 30°C. Withdraw the second light fraction 10 from the top of the first separator T102 and the second heavy fraction 9 from the bottom. Characterize the second light fraction 10 and the second heavy fraction 9 using gas chromatography analysis. It is measured that the total mass flow rate of the second light fraction 10 is 697.75 kg / h, which contains the reaction product 4-hydroxybutyl acrylate, 1,4-butanediol diacrylate, cyclohexane, and the first extractant, and their proportions are 26.02%, 3.51%, 27.23%, and 43.24% respectively; the total mass flow rate of the second heavy fraction 9 is 20 kg / h, which contains sodium hydroquinone, sodium p-toluenesulfonate, and water, and their proportions are 5.47%, 7.07%, and 87.47% respectively. The second heavy fraction 9 is treated as wastewater.

[0107] Subsequently, step four is carried out: The second light component 10 is fed into the first distillation column T103 and distilled under an operating pressure of 0.005 MPa. The third light component 11 is taken from the top of the first distillation column T103, and the third heavy component 12 is taken from the bottom of the column. The third light component 11 and the third heavy component 12 are characterized by gas chromatography analysis. The total mass flow rate of the third light component 11 is measured to be 491.72 kg / h, which contains 61.36% of the first extractant butyl acrylate and 38.64% of cyclohexane; the total mass flow rate of the third heavy component 12 is 206.03 kg / h, which contains 88.11% of the reaction product 4-hydroxybutyl acrylate and 11.89% of 1,4-butanediol diacrylate. The third light component 11 is further fed into the second distillation column T104 and distilled under an operating pressure of 0.01 MPa. Cyclohexane 13 is taken from the top of the second distillation column T104, and the first extractant 14 is taken from the bottom of the column. The cyclohexane 13 is recycled back to the esterification reaction R101 for reuse, and the first extractant 14 is recycled to the first extraction column T101 for reuse.

[0108] Next, step five is carried out: The third heavy component 12 is fed into the second extraction column T105, and at the same time, the second extractant 15 (demineralized water) is added to the second extraction column T105 at a mass flow rate of 40.24 kg / h for extraction separation. The fourth light component 16 is taken from the top of the second extraction column T105, and the by-product 1,4-butanediol diacrylate 17 is taken from the bottom. The fourth light component 16 is characterized by gas chromatography analysis. The total mass flow rate of the fourth light component 16 is measured to be 221.78 kg / h, which contains 81.86% of the reaction product 4-hydroxybutyl acrylate and 18.14% of the second extractant.

[0109] Finally, step six is carried out: The fourth light component 16 is fed into the third distillation column T106 and distilled under an operating pressure of 0.001 MPa. The second extractant 18 is taken from the top of the third distillation column T106, and the reaction product 4-hydroxybutyl acrylate 19 is taken from the bottom of the column.

[0110] As Figure 2 shown, the purity of the target product is measured to be 99.5% by gas chromatography analysis.

[0111] As can be seen from the above, the method of the present invention does not require the operation of separating the product 4-hydroxybutyl acrylate and the by-product 1,4-butanediol diacrylate at high temperature, reduces the dosage of the polymerization inhibitor, reduces the risk of polymerization of the reaction product during the separation process, and recovers and utilizes the extractant used in the separation process. Therefore, the process steps of the method for producing 4-hydroxybutyl acrylate of the present invention are simplified, the raw material utilization rate is high, the energy consumption is low, the production cost is low, and the product has excellent purity and quality.

Claims

1. A method for preparing and purifying C2-C6 hydroxyalkyl (meth)acrylates, the method comprising: Step 1: Reacting a C2-C6 alkane diol with (meth)acrylic acid to form an esterification reaction product material, the esterification reaction product material comprising a C2-C6 hydroxyalkyl (meth)acrylate, by-products, and unreacted C2-C6 alkane diol; Step 2: Performing a first extraction operation on the esterification reaction product material using a first extractant to obtain a first light fraction and a first heavy fraction; Step 3: Adding a basic reagent to the first light fraction and performing a separation operation to obtain a second light fraction and a second heavy fraction; Step 4: Performing a first rectification operation on the second light fraction to obtain a third light fraction and a third heavy fraction; Step 5: Performing a second extraction operation on the third heavy fraction using a second extractant to obtain a fourth light fraction and a fourth heavy fraction; Step 6: Performing a third rectification operation on the fourth light fraction to obtain a fifth light fraction and a target product, the target product being a C2-C6 hydroxyalkyl (meth)acrylate.

2. The method according to claim 1, characterized in that, The C2-C6 alkane diol is selected from one or more of the following: ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol; The C2-C6 hydroxyalkyl (meth)acrylate is selected from one or more of the following: 2-hydroxyethyl acrylate, 3-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 5-hydroxypentyl acrylate, 6-hydroxyhexyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, 5-hydroxypentyl methacrylate, 6-hydroxyhexyl methacrylate.

3. The method according to claim 1, wherein In the step 1, in the presence of an organic solvent, an inhibitor, and a catalyst, the (meth)acrylic acid reacts with the C2-C6 alkane diol to form an esterification reaction product material; The molar ratio of the (meth)acrylic acid to the C2-C6 alkane diol is 1:1 to 1:3; The esterification reaction is carried out at a reaction temperature of 100-120 °C; The organic solvent is selected from one or more of the following: cyclohexane, cyclopentane, cyclooctane, cyclohexanone, toluene, xylene, pentane, hexane, octane, acetone, acetonitrile; The catalyst is selected from one or more of the following: benzenesulfonic acid, methanesulfonic acid, ethanesulfonic acid, p-toluenesulfonic acid, concentrated sulfuric acid; The inhibitor is selected from one or more of the following: hydroquinone, p-methoxyphenol, copper acetate.

4. The method according to any one of claims 1 to 3, characterized in that, In the step 2, a first extractant, water, and the esterification reaction product material are added to a first extraction column to perform the first extraction operation. A first light fraction is obtained at the top of the first extraction column, and a first heavy fraction is obtained at the bottom of the first extraction column; The first extractant is selected from one or more of the following: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate; The first light component comprises: C2-C6 hydroxyalkyl (meth)acrylate, C2-C6 alkane diol di(meth)acrylate, organic solvent, inhibitor, catalyst, first extractant; The first heavy component comprises: C2-C6 alkane diol, inhibitor, catalyst, water; The temperature of the first extraction column is 25-50 °C; The first heavy component is optionally recycled back to the esterification reaction in step one for reuse.

5. The method according to any one of claims 1-3, characterized in that, In step three, an alkaline reagent and the first light component are input into the separator, and a separation operation is carried out. A second light component is obtained at the top of the separator, and a second heavy component is obtained at the bottom of the separator; The second light component comprises: C2-C6 hydroxyalkyl (meth)acrylate, C2-C6 alkane diol di(meth)acrylate, organic solvent, first extractant; The second heavy component comprises: inhibitor, salified catalyst, water; The alkaline reagent is selected from one or more of the following: sodium hydroxide, potassium hydroxide, lithium hydroxide, ammonium hydroxide, organic amine; The temperature of the separator is 25-50 °C.

6. The method according to any one of claims 1-3, characterized in that, In step four, a first rectification operation is carried out on the second light component in a first rectification column. A third light component is obtained at the top of the first rectification column, and a third heavy component is obtained from the middle or bottom of the first rectification column; The third light component comprises the first extractant and the organic solvent; The third heavy component comprises C2-C6 hydroxyalkyl (meth)acrylate and C2-C6 alkane diol di(meth)acrylate; The pressure of the first rectification column is 0.001-0.01 Mpa.

7. The method according to any one of claims 1 to 3, characterized in that, In step five, a second extractant and the third heavy component are input into a second extraction column together for a second extraction operation. A fourth light component is obtained at the top of the second extraction column, and a fourth heavy component is obtained at the bottom of the second extraction column; The fourth light component comprises C2-C6 hydroxyalkyl (meth)acrylate and the second extractant; The fourth heavy component comprises C2-C6 alkane diol di(meth)acrylate; The second extractant is demineralized water; The temperature of the second extraction column is 25-50 °C.

8. The method according to any one of claims 1 to 3, characterized in that, In step six, a third rectification operation is carried out on the fourth light component in a third rectification column. A fifth light component is obtained at the top of the third rectification column, and the target product is obtained from the middle or bottom of the third rectification column; The fifth light component comprises the second extractant; The pressure of the third rectification column is 0.001-0.005 Mpa.

9. The method according to any one of claims 1-3 and 6, characterized in that, The third light component is subjected to a second rectification operation in a second rectification column. The organic solvent is obtained at the top of the second rectification column, and the first extractant is obtained from the middle or bottom of the second rectification column; The pressure of the second rectification column is 0.01-0.02 MPa.

10. A reaction-purification apparatus for implementing the method according to any one of claims 1-9, the apparatus comprising: Reactor (R101), first extraction column (T101), separator (T102), first rectification column (T103), second rectification column (T104), second extraction column (T105), third rectification column (T106); The outlet of the reactor (R101) is connected to the inlet of the first extraction column (T101). The outlet at the top of the first extraction column (T101) is connected to the inlet of the separator (T102). The outlet at the top of the separator (T102) is connected to the inlet of the first distillation column (T103). The outlet at the top of the first distillation column (T103) is connected to the inlet of the second distillation column (T104). The outlet at the bottom of the first distillation column (T103) is connected to the inlet of the second extraction column (T105). The outlet at the top of the second extraction column (T105) is connected to the inlet of the third distillation column (T106).

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