Preparation method of hydroxybutyl acrylate

Abstract

The invention provides a preparation method of hydroxybutyl acrylate, which comprises the following steps: taking acrylic acid and 1, 4-butanediol as raw materials, in the presence of a compound catalyst and a compound solvent, simultaneously adding a polymerization inhibitor and a certain amount of 1, 4-butanediol diacrylate, and reacting to generate hydroxybutyl acrylate, wherein the compound catalyst comprises p-toluenesulfonic acid and a quaternary ammonium salt phase transfer catalyst, and the compound solvent comprises cyclohexane and aromatic hydrocarbon. The compound catalyst and the compound solvent used in the reaction stage can effectively reduce the generation amount of the byproduct tetrahydrofuran, and the compound solvent used in the reaction stage can reduce the loss of the product and improve the yield of the hydroxybutyl acrylate in the separation stage. The method solves the problems of high selectivity of the traditional byproduct tetrahydrofuran and low product yield in the separation process, and is suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of organic compound preparation, and specifically relates to a method for preparing hydroxybutyl acrylate. Background Technology

[0002] Hydroxybutyl acrylate, abbreviated as HBA, belongs to the category of specialty acrylate monomers. Its structure contains vinyl and hydroxyl groups, and the double bond can undergo free radical polymerization with other (meth)acrylic acid monomers. This substance endows materials with excellent scratch resistance, flexibility and chemical crosslinking ability, and is widely used in resins, adhesives and coatings.

[0003] Currently, the main industrial synthesis process for HBA is the direct esterification method, which involves the reaction of acrylic acid and 1,4-butanediol in the presence of a catalyst and a polymerization inhibitor to produce hydroxybutyl acrylate. Polymerization inhibitors include p-methoxyphenol, hydroquinone, 701 nitrile radical inhibitor, and 705 nitrile radical inhibitor, while commonly used catalysts include acidic catalysts such as p-toluenesulfonic acid, methanesulfonic acid, sulfonic acid resins, and concentrated sulfuric acid. Some literature also reports that HBA can be produced by transesterification of methyl acrylate and 1,4-butanediol in the presence of a catalyst and a polymerization inhibitor, using catalysts such as dialkyltin oxide and tetrabutyl titanate.

[0004] CN201380019941.3 discloses a method for manufacturing 4-hydroxybutyl acrylate, which employs a transesterification process and uses a dialkyltin oxide catalyst containing alkyl groups with 4-18 carbon atoms. When 1,4-butanediol undergoes a transesterification reaction with alkyl acrylate in the presence of the dialkyltin oxide catalyst, the amount of the dialkyltin oxide with 4-18 carbon atoms is adjusted to 0.00001-0.1 moles relative to 1 mole of alkyl acrylate.

[0005] US5637760A discloses a method for converting 1,4-butanediol to tetrahydrofuran, which mentions preparing hydroxybutyl acrylate by esterifying acrylic acid with 1,4-butanediol, in which unreacted 1,4-butanediol in the aqueous solution of hydroxybutyl acrylate is converted to tetrahydrofuran.

[0006] CN202211715315.5 discloses a method and system for producing hydroxybutyl acrylate, which employs a direct esterification process. Acrylic acid, a polymerization inhibitor, 1,4-butanediol, and a catalyst are mixed and fed into a first reactor for a primary esterification reaction. The material from the primary esterification reaction is then dehydrated and fed into a second reactor for a secondary esterification reaction. The material from the secondary esterification reaction is then dehydrated a second time and fed into a third reactor for a tertiary esterification reaction. The reaction solution from the tertiary esterification reaction is then sent to a neutralizer for neutralization. This production method does not use aqueous solvents, resulting in a lower acrylic acid conversion rate.

[0007] CN202410942085.9 discloses an apparatus and method for producing hydroxybutyl acrylate, employing a direct esterification process. The method includes a reactive distillation column, a product purification column, a byproduct separation column, a primary side reactor, a secondary side reactor, a 1,4-butanediol extractor, and a hydroxybutyl acrylate extractor. The use of reactive distillation + microreactor technology, along with secondary extraction and separation combined with high-efficiency distillation, effectively achieves efficient and energy-saving production of the high-end fine chemical hydroxybutyl acrylate. However, the generation of tetrahydrofuran as a byproduct is not specified.

[0008] In the direct esterification process for producing HBA, the main reaction is the reaction of acrylic acid and 1,4-butanediol to produce hydroxybutyl acrylate, with water as a byproduct. This reaction is reversible, and a dehydrating agent is needed to remove the generated water in time during the reaction to improve the conversion rate of AA. Commonly used dehydrating agents are alkanes such as cyclohexane and n-hexane, and aromatics such as toluene and xylene. Commonly used catalysts are methanesulfonic acid, p-toluenesulfonic acid, concentrated sulfuric acid, sulfonic acid resins, and other acidic catalysts.

[0009] Main reaction:

[0010] Side reactions:

[0011] During the reaction, acrylic acid will continue to react with hydroxybutyl acrylate to generate 1,4-butanediol diacrylate. This reaction is reversible, and adding a certain amount of 1,4-butanediol diacrylate before the reaction can prevent its formation.

[0012] Meanwhile, during the reaction, the starting material 1,4-butanediol undergoes ring-closure dehydration under acidic catalytic conditions to form tetrahydrofuran, reducing the product selectivity. Currently, there are no reports on inhibiting tetrahydrofuran formation. This is also a significant reason for the low yield of industrial-scale products.

[0013] Esterification reaction solutions are usually purified using an extraction process. First, non-polar solvents such as cyclohexane, n-hexane, and petroleum ether are used to remove 1,4-butanediol diacrylate. At the same time, hydroxybutyl acrylate is introduced into the extractant, resulting in a decrease in the yield of hydroxybutyl acrylate product. This is another important reason for the low yield of industrial products. Summary of the Invention

[0014] To address the aforementioned technical problems, this invention proposes a method for preparing hydroxybutyl acrylate. The method utilizes a compound catalyst and a compound solvent in the reaction stage, which effectively reduces the formation of the byproduct tetrahydrofuran. The compound solvent used in the reaction stage also reduces product loss during the separation stage, thereby increasing the yield of hydroxybutyl acrylate. This method solves the problems of high selectivity for byproduct tetrahydrofuran and low product yield during the separation process in traditional methods, making it suitable for industrial production.

[0015] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0016] A method for preparing hydroxybutyl acrylate includes the following steps:

[0017] Using acrylic acid and 1,4-butanediol as raw materials, in the presence of a compound catalyst and a compound solvent, a polymerization inhibitor and 1,4-butanediol diacrylate are added simultaneously to react and generate hydroxybutyl acrylate.

[0018] The composite catalyst includes p-toluenesulfonic acid and a quaternary ammonium salt phase transfer catalyst, and the composite solvent includes cyclohexane and aromatics.

[0019] The composite catalyst of the present invention includes p-toluenesulfonic acid and a quaternary ammonium salt phase transfer catalyst. The quaternary ammonium salt phase transfer catalyst added to the composite catalyst has basic properties that can inhibit the rate of 1,4-butanediol ring-closing reaction to form tetrahydrofuran.

[0020] In one embodiment, the mass ratio of p-toluenesulfonic acid to quaternary ammonium salt phase transfer catalyst in the composite catalyst is 4-5:1;

[0021] Optionally, the quaternary ammonium salt phase transfer catalyst is selected from one or more of tetramethylammonium chloride, tetrabutylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, hexadecyltrimethylbenzylammonium bromide, tetrabutylammonium bromide, and tetramethylammonium bromide.

[0022] In one embodiment, the mass ratio of acrylic acid to the compound catalyst is 10-20:1, including but not limited to 10:1, 12:1, 14:1, 16:1, 18:1, 20:1 or any combination thereof.

[0023] The compound solvent of the present invention includes cyclohexane and aromatic hydrocarbons. The solvent composed of the two has a good water-carrying effect, can adjust the composition of the reaction solution and the reaction temperature, and can ensure sufficient solvent in the reaction solution to maintain a good water-carrying effect in the reaction process. At the same time, the aromatic hydrocarbon solvent can reduce the loss of hydroxybutyl acrylate in subsequent extraction treatment.

[0024] In one embodiment, the mass ratio of cyclohexane to aromatic solvent in the compound solvent is 3-4:1, including but not limited to 3:1, 3.2:1, 3.4:1, 3.6:1, 3.8:1, 4:1, or any combination thereof.

[0025] In one embodiment, the aromatic hydrocarbon is selected from one or more of toluene, o-xylene, and p-xylene.

[0026] In one embodiment, the mass ratio of the compound solvent to acrylic acid is 3-5:1, including but not limited to 3:1, 3.3:1, 3.5:1, 3.8:1, 4:1, 4.3:1, 4.5:1, 4.8:1, 5:1, or any combination thereof.

[0027] In one embodiment, the molar ratio of 1,4-butanediol to acrylic acid is 2-3:1, including but not limited to 2:1, 2.2:1, 2.4:1, 2.6:1, 2.8:1, 3:1, or any combination thereof.

[0028] In one embodiment, the polymerization inhibitor is a compound polymerization inhibitor, comprising hydroquinone and a copper salt polymerization inhibitor;

[0029] Optionally, the mass ratio of hydroquinone to copper salt polymerization inhibitor is 1-2:1, including but not limited to 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1 or any combination thereof.

[0030] Optionally, the copper salt polymerization inhibitor is selected from one or more of N,N-dibutyldithiocarbamate and copper acetate.

[0031] In one embodiment, the mass ratio of the polymerization inhibitor to acrylic acid is 0.05-0.1:1, including but not limited to 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1, 0.1:1, or any combination thereof.

[0032] In one embodiment, the mass ratio of 1,4-butanediol diacrylate to acrylic acid is 1.5-2.0:1, including but not limited to 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, or any combination thereof.

[0033] In one embodiment, the reaction is carried out at atmospheric pressure, and the reaction temperature is 90-100°C, including but not limited to 90°C, 92°C, 94°C, 96°C, 98°C, 100°C or any combination thereof; the reaction time is 5-10h, including but not limited to 5h, 6h, 7h, 8h, 9h, 10h or any combination thereof.

[0034] Optionally, the reaction adopts a reflux water separation operation, that is, after the top liquid evaporated during the reaction process is separated into water, the oil phase is refluxed back into the reaction system. This operation is a conventional treatment method for water removal during the reaction process. The present invention does not have any special requirements for its implementation form. For example, in actual production, a reactor with a condensation reflux device at the top can be used.

[0035] The method of the present invention yields a reaction solution containing hydroxybutyl acrylate after the above reaction is completed.

[0036] Specifically, after the above reaction is completed, the reaction system presents a liquid-liquid two-phase state, wherein the upper liquid is a compound solvent containing a small amount of 1,4-butanediol diacrylate, which can be recycled; the reaction system is directly separated into two phases and the lower liquid is taken, which is the reaction solution containing hydroxybutyl acrylate.

[0037] Analysis of the reaction solution showed that the acrylic acid conversion rate reached 99%, the hydroxybutyl acrylate selectivity reached 98% (based on 1,4-butanediol), and the tetrahydrofuran selectivity was less than 2% (based on 1,4-butanediol).

[0038] The method for preparing hydroxybutyl acrylate according to the present invention further includes the step of refining the reaction solution containing hydroxybutyl acrylate obtained from the above reaction by an extraction process and a distillation process to obtain the hydroxybutyl acrylate product.

[0039] In one embodiment, the extraction process includes the following steps:

[0040] E1) Use a nonpolar solvent to remove 1,4-butanediol diacrylate from the reaction solution to obtain the raffinate;

[0041] E2) Use dichloromethane to extract hydroxybutyl acrylate from the raffinate phase of step E1;

[0042] E3) Use water to remove 1,4-butanediol from the extract phase of step E2).

[0043] Optionally, the nonpolar solvent in step E1) is selected from one or more of cyclohexane and n-hexane, preferably cyclohexane.

[0044] Optionally, the mass ratio of the nonpolar solvent to the reaction solution in step E1) is 1-2:1, including but not limited to 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1 or any combination thereof.

[0045] Optionally, the mass ratio of dichloromethane in step E2) to the raffinate phase in step E1) is 1-2:1, including but not limited to 1:1, 1.2:1, 1.4:1, 1.6:1, 1.8:1, 2:1 or any combination thereof.

[0046] Optionally, the mass ratio of water in step E3) to the extract phase in step E2) is 0.2-1:1, including but not limited to 0.2:1, 0.4:1, 0.6:1, 0.8:1, 1:1 or any combination thereof.

[0047] In one embodiment, the distillation process includes the following steps:

[0048] E4) Remove the extractant by vacuum distillation;

[0049] E5) Secondary vacuum distillation yielded hydroxybutyl acrylate product.

[0050] Optionally, the single-stage vacuum distillation in step E4) is carried out at a pressure of 30-60 kPaA and a top temperature of 20-70°C, including but not limited to 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, or any combination thereof.

[0051] Optionally, the secondary vacuum distillation described in step E5) has a pressure of 0.1-0.3 kPaA, including but not limited to 0.1 kPaA, 0.2 kPaA, 0.3 kPaA, or any combination thereof, and a column top temperature of 75-85°C, including but not limited to 75°C, 77°C, 79°C, 81°C, 83°C, 85°C, or any combination thereof.

[0052] In this invention, the single-pass yield of hydroxybutyl acrylate can reach over 95% through extraction and distillation processes.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] In this invention, a compound catalyst is added to the reaction. The quaternary ammonium salt catalyst can suppress the rate of the side reaction 1,4-butanediol ring-closure dehydration to form tetrahydrofuran, thereby improving the selectivity and reaction yield of hydroxybutyl acrylate.

[0055] In this invention, a compound solvent is added to the reaction. The added high-boiling-point aromatic hydrocarbons act as dehydrating agents, increasing the reaction temperature and simultaneously reducing the concentration of 1,4-butanediol in the reaction solution, thereby decreasing the formation rate of the byproduct tetrahydrofuran and increasing the product yield. Furthermore, the high-boiling-point aromatic hydrocarbons can also reduce product loss during the extraction stage, further improving the product yield.

[0056] The polymerization inhibitors added to the reaction of this invention, especially the compounded polymerization inhibitors, can effectively prevent the polymerization of acrylic acid and hydroxybutyl acrylate in the reaction solution. Detailed Implementation

[0057] The present invention will be further illustrated below by way of embodiments, but the present invention is not limited to the embodiments described below. The present invention extends to any new feature or any new combination disclosed in the specification, as well as any new method or process step or any new combination disclosed.

[0058] It should be noted that the endpoints and any values ​​of the ranges disclosed in this specification are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0059] 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 invention pertains. The term "and / or" may be used herein to include any and all combinations of one or more of the associated listed items.

[0060] Unless otherwise specified, the reagents, materials and instruments used in the following examples are all conventional reagents, materials and instruments in the art, and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0061] I. Sources of main raw materials in the embodiments:

[0062] Acrylic acid, Wanhua Chemical Group Co., Ltd., industrial grade;

[0063] 1,4-Butanediol, Beijing Innocare Technology Co., Ltd., Industrial Grade;

[0064] p-Toluenesulfonic acid, Beijing Innocare Technology Co., Ltd., analytical grade;

[0065] Tetramethylammonium chloride, Zhejiang Kent Catalytic Materials Technology Co., Ltd., industrial grade;

[0066] Tetrabutylammonium bromide, Zhejiang Kent Catalytic Materials Technology Co., Ltd., industrial grade;

[0067] Trimethylbenzylammonium chloride, Zhejiang Kent Catalytic Materials Technology Co., Ltd., industrial grade;

[0068] Hydroquinone, Jiangsu Sanjili Chemical Co., Ltd., industrial grade;

[0069] N,N-Dibutyldithiocarbamate copper, Beijing Innocare Technology Co., Ltd., analytical grade;

[0070] Cyclohexane, Shandong Haike New Energy Materials Technology Co., Ltd., industrial grade;

[0071] n-Hexane, Beijing Innocare Technology Co., Ltd., industrial grade;

[0072] Toluene, Beijing Innocare Technology Co., Ltd., analytical grade;

[0073] o-Xylene, Beijing Innocare Technology Co., Ltd., analytical grade;

[0074] p-Xylene, Beijing Innocare Technology Co., Ltd., analytical grade;

[0075] Dichloromethane, Shandong Jinling Chemical Co., Ltd., industrial grade.

[0076] II. Product Analysis Methods in the Examples:

[0077] Gas chromatography analysis was performed using the correction factor method. Instrument manufacturer and model: Shimadzu 1020-plus. Parameters: DB-5 column, column temperature: 250℃, vaporization chamber temperature: 280℃, detector temperature: 300℃, air flow rate: 300ml / min, hydrogen flow rate: 30ml / min, carrier gas flow rate: 1.35ml / min, split ratio: 1:30.

[0078]

Example 1

[0079] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0080] 7.2 kg (100 mol) of acrylic acid, 18 kg (200 mol) of 1,4-butanediol, 576 g of p-toluenesulfonic acid and 144 g of tetramethylammonium chloride catalysts, 180 g of hydroquinone and 180 g of N,N-dibutyldithiocarbamate inhibitors, 16.2 kg of cyclohexane and 5.4 kg of toluene solvents, and 10.8 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 90 °C. During the reaction, the top liquid distilled from the top was separated into water and the oil phase was refluxed back into the reactor. The reaction was carried out for 5 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0081] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.6%, a tetrahydrofuran selectivity of 1.5% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.5% (based on 1,4-butanediol).

[0082] 2. Hydroxybutyl acrylate refining and extraction process:

[0083] E1: Add 30 kg of the above reaction solution containing hydroxybutyl acrylate and 30 kg of extractant cyclohexane to a 100 L reactor and stir evenly. After standing and phase separation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.88% according to the test and calculation.

[0084] E2: Add 20 kg of the raffinate obtained from E1 and 20 kg of dichloromethane as extractant to a 100 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.52%.

[0085] E3: Add 30 kg of the extract phase obtained from E2 and 6 kg of extractant water to a 50 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.19%.

[0086] 3. Hydroxybutyl acrylate refining and distillation process:

[0087] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 30 kPaA and a top temperature of 20°C to remove toluene, cyclohexane, and dichloromethane.

[0088] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.1 PaA and the top temperature is 75℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.3%.

[0089] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.2%.

[0090]

Example 2

[0091] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0092] 7.2 kg (100 mol) of acrylic acid, 27 kg (300 mol) of 1,4-butanediol, 300 g of p-toluenesulfonic acid catalyst, 60 g of tetrabutylammonium bromide catalyst, 180 g of hydroquinone inhibitor and 180 g of N,N-dibutyldithiocarbamate copper, 16.2 kg of cyclohexane solvent, 5.4 kg of toluene, and 10.8 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 100 °C. During the reaction, the top liquid evaporated from the top separated into phases, and the oil phase was refluxed back into the reactor. The reaction was carried out for 8 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0093] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.6%, a tetrahydrofuran selectivity of 1.6% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.4% (based on 1,4-butanediol).

[0094] 2. Hydroxybutyl acrylate refining and extraction process:

[0095] E1: Add 30 kg of the above reaction solution containing hydroxybutyl acrylate and 60 kg of hexane as the extractant to a 100 L reactor and stir evenly. After standing and phase separation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.80% according to the test and calculation.

[0096] E2: Add 20 kg of the raffinate obtained from E1 and 40 kg of dichloromethane as extractant to a 100 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.33%.

[0097] E3: Add 30 kg of the extract phase obtained from E2 and 30 kg of extractant water to a 50 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.27%.

[0098] 3. Hydroxybutyl acrylate refining and distillation process:

[0099] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 60 kPaA and a top temperature of 70°C to remove toluene, cyclohexane, and dichloromethane.

[0100] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.3 PaA and the top temperature is 85℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.4%.

[0101] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.7%.

[0102]

Example 3

[0103] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0104] 3.6 kg (50 mol) of acrylic acid, 9 kg (100 mol) of 1,4-butanediol, 150 g of p-toluenesulfonic acid catalyst, 30 g of trimethylbenzylammonium chloride, 240 g of hydroquinone inhibitor and 120 g of N,N-dibutyldithiocarbamate copper, 14.4 kg of n-hexane solvent, 3.6 kg of o-xylene, and 7.2 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 90 °C. During the reaction, the top liquid evaporated from the top separated into phases, and the oil phase was refluxed back into the reactor. The reaction was carried out for 5 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0105] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.6%, a tetrahydrofuran selectivity of 1.7% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.3% (based on 1,4-butanediol).

[0106] 2. Hydroxybutyl acrylate refining and extraction process:

[0107] E1: Add 15 kg of the above reaction solution containing hydroxybutyl acrylate and 30 kg of hexane as extractant to a 100 L reactor and stir evenly. After standing and phase separation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.80% according to the test and calculation.

[0108] E2: Add 15 kg of the raffinate obtained from E1 and 27 kg of dichloromethane as extractant to a 100 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.33%.

[0109] E3: Add 30 kg of the extract phase obtained from E2 and 30 kg of extractant water to a 50 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.27%.

[0110] 3. Hydroxybutyl acrylate refining and distillation process:

[0111] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 60 kPaA and a top temperature of 70°C to remove toluene, cyclohexane, and dichloromethane.

[0112] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.3 PaA and the top temperature is 85℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.4%.

[0113] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.7%.

[0114]

Example 4

[0115] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0116] 7.2 kg (100 mol) of acrylic acid, 18 kg (200 mol) of 1,4-butanediol, 300 g of p-toluenesulfonic acid catalyst, 60 g of tetramethylammonium chloride, 180 g of hydroquinone inhibitor and 180 g of N,N-dibutyldithiocarbamate copper, 16.2 kg of n-hexane solvent, 5.4 kg of o-xylene, and 10.8 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 95 °C. During the reaction, the top liquid evaporated from the top separated into phases, and the oil phase was refluxed back into the reactor. The reaction was carried out for 10 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0117] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.5%, a tetrahydrofuran selectivity of 1.6% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.4% (based on 1,4-butanediol).

[0118] 2. Hydroxybutyl acrylate refining and extraction process:

[0119] E1: Add 30 kg of the above reaction solution containing hydroxybutyl acrylate and 42 kg of hexane as extractant to a 100 L reactor and stir until homogeneous. Allow to stand and separate phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.81%.

[0120] E2: Add 20 kg of the raffinate obtained from E1 and 32 kg of dichloromethane as extractant to a 100 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.35%.

[0121] E3: Add 30 kg of the extract phase obtained from E2 and 12 kg of extractant water to a 50 L reactor and stir until homogeneous. Allow to stand and separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.21%.

[0122] 3. Hydroxybutyl acrylate refining and distillation process:

[0123] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 40 kPaA and a top temperature of 50°C to remove toluene, cyclohexane, and dichloromethane.

[0124] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.2 PaA and the top temperature is 80℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.2%.

[0125] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.4%.

[0126]

Example 5

[0127] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0128] 3.6 kg (50 mol) of acrylic acid, 9 kg (100 mol) of 1,4-butanediol, 288 g of p-toluenesulfonic acid catalyst, 72 g of tetramethylammonium chloride, 240 g of hydroquinone inhibitor and 120 g of N,N-dibutyldithiocarbamate copper, 14.4 kg of cyclohexane solvent, 3.6 kg of p-xylene, and 5.4 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 100 °C. During the reaction, the top liquid evaporated from the top separated into phases, and the oil phase was refluxed back into the reactor. The reaction was carried out for 10 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0129] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.6%, a tetrahydrofuran selectivity of 1.5% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.5% (based on 1,4-butanediol).

[0130] 2. Hydroxybutyl acrylate refining and extraction process:

[0131] E1: Add 30 kg of the above reaction solution containing hydroxybutyl acrylate and 48 kg of extractant cyclohexane to a 100 L reactor and stir evenly. After standing and phase separation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.82% according to the test and calculation.

[0132] E2: Add 20 kg of the raffinate obtained from E1 and 28 kg of dichloromethane as extractant to a 100 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.35%.

[0133] E3: Add 30 kg of the extract phase obtained from E2 and 18 kg of extractant water to a 50 L reactor and stir evenly. Let it stand to separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.22%.

[0134] 3. Hydroxybutyl acrylate refining and distillation process:

[0135] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 45 kPaA and a top temperature of 50°C to remove toluene, cyclohexane, and dichloromethane.

[0136] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.1 PaA and the top temperature is 75℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.4%.

[0137] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.6%.

[0138]

Example 6

[0139] 1. Preparation of hydroxybutyl acrylate reaction solution:

[0140] 7.2 kg (100 mol) of acrylic acid, 27 kg (300 mol) of 1,4-butanediol, 576 g of p-toluenesulfonic acid catalyst, 144 g of trimethylbenzylammonium chloride, 180 g of hydroquinone inhibitor and 180 g of N,N-dibutyldithiocarbamate copper, 28.8 kg of n-hexane solvent, 7.2 kg of o-xylene, and 14.4 kg of 1,4-butanediol diacrylate were added to a 100 L reactor equipped with a top reflux condenser. The temperature of the oil bath in the reactor jacket was adjusted to 115-125 °C, and the temperature inside the reactor was controlled at 95 °C. During the reaction, the top liquid evaporated from the top separated into phases, and the oil phase was refluxed back into the reactor. The reaction was carried out for 8 hours. After the reaction was completed, the lower layer containing hydroxybutyl acrylate was taken after standing and phase separation.

[0141] The composition of the reaction solution was determined and calculated, with an acrylic acid conversion of 99.5%, a tetrahydrofuran selectivity of 1.7% (based on 1,4-butanediol), and a hydroxybutyl acrylate selectivity of 98.3% (based on 1,4-butanediol).

[0142] 2. Hydroxybutyl acrylate refining and extraction process:

[0143] E1: Add 30 kg of the above reaction solution containing hydroxybutyl acrylate and 54 kg of hexane as the extractant to a 100 L reactor and stir until homogeneous. Allow to stand and separate phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.85%.

[0144] E2: Add 20 kg of the raffinate obtained from E1 and 24 kg of the extractant dichloromethane to a 100 L reactor and stir until homogeneous. Allow to stand and separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the raffinate is 0.35%.

[0145] E3: Add 30 kg of the extract phase obtained from E2 and 24 kg of extractant water to a 50 L reactor and stir until homogeneous. Allow to stand and separate the phases. After testing and calculation, the loss rate of hydroxybutyl acrylate in the extract phase is 0.28%.

[0146] 3. Hydroxybutyl acrylate refining and distillation process:

[0147] E4: The raffinate obtained from E3 is subjected to vacuum distillation at a top pressure of 50 kPaA and a top temperature of 60°C to remove toluene, cyclohexane, and dichloromethane.

[0148] E5: The bottom liquid obtained from E4 is further distilled under reduced pressure. The top pressure is 0.2 PaA and the top temperature is 80℃. Hydroxybutyl acrylate is obtained at the top of the column with a purity of 99.6%.

[0149] The overall yield of hydroxybutyl acrylate after the reaction and separation processes was calculated to be 95.8%.

[0150] Comparative Example 1

[0151] The method for preparing hydroxybutyl acrylate in Example 1 was followed, except that tetramethylammonium chloride catalyst was not added, while other operating conditions and ratios remained unchanged. After the reaction, the selectivity of tetrahydrofuran was 6.9% (based on 1,4-butanediol), and the selectivity of hydroxybutyl acrylate decreased to 93.1% (based on 1,4-butanediol). After subsequent purification processes such as extraction and distillation, the overall yield of hydroxybutyl acrylate was low, at only 90.1%.

[0152] Comparative Example 2

[0153] The method for preparing hydroxybutyl acrylate in Example 1 was followed, except that toluene solvent was not added. Other operating conditions and ratios remained unchanged. Under normal pressure, the reaction temperature reached a maximum of 82°C. After the reaction, the conversion rate of acrylic acid was 90.5%. After subsequent extraction and distillation purification processes, the overall yield of hydroxybutyl acrylate was low, only 85.4%.

Claims

1. A method for preparing hydroxybutyl acrylate, characterized in that, Includes the following steps: Using acrylic acid and 1,4-butanediol as raw materials, in the presence of a compound catalyst and a compound solvent, a polymerization inhibitor and 1,4-butanediol diacrylate are added simultaneously to react and generate hydroxybutyl acrylate. The composite catalyst includes p-toluenesulfonic acid and a quaternary ammonium salt phase transfer catalyst, and the composite solvent includes cyclohexane and aromatics.

2. The preparation method according to claim 1, characterized in that, The mass ratio of p-toluenesulfonic acid to quaternary ammonium salt phase transfer catalyst in the compound catalyst is 4-5:1; and / or, The quaternary ammonium salt phase transfer catalyst is selected from one or more of tetramethylammonium chloride, tetrabutylammonium chloride, trimethylbenzylammonium chloride, triethylbenzylammonium chloride, hexadecyltrimethylbenzylammonium bromide, tetrabutylammonium bromide, and tetramethylammonium bromide; and / or, The mass ratio of acrylic acid to the compound catalyst is 10-20:

1.

3. The preparation method according to claim 1 or 2, characterized in that, The mass ratio of cyclohexane to aromatic solvent in the compound solvent is 3-4:1; and / or, The aromatic hydrocarbon is selected from one or more of toluene, o-xylene, and p-xylene; and / or The mass ratio of the compound solvent to acrylic acid is 3-5:

1.

4. The preparation method according to any one of claims 1-3, characterized in that, The molar ratio of 1,4-butanediol to acrylic acid is 2-3:1; and / or, The polymerization inhibitor is a compound polymerization inhibitor, comprising hydroquinone and a copper salt polymerization inhibitor; optionally, the mass ratio of hydroquinone to the copper salt polymerization inhibitor is 1-2:1; optionally, the copper salt polymerization inhibitor is selected from one or more of N,N-dibutyldithiocarbamate and copper acetate; and / or, The mass ratio of the polymerization inhibitor to acrylic acid is 0.05-0.1:

1.

5. The preparation method according to any one of claims 1-4, characterized in that, The mass ratio of 1,4-butanediol diacrylate to acrylic acid is 1.5-2.0:1; and / or, The reaction is carried out under normal pressure at a temperature of 90-100℃ for 5-10 hours. Optionally, the reaction employs a reflux water separation operation.

6. The preparation method according to any one of claims 1-5, characterized in that, After the reaction is completed, a reaction solution containing hydroxybutyl acrylate is obtained. The process also includes a step of refining the reaction solution containing hydroxybutyl acrylate through an extraction process and a distillation process to obtain the hydroxybutyl acrylate product.

7. The preparation method according to claim 6, characterized in that, The extraction process includes the following steps: E1) Use a nonpolar solvent to remove 1,4-butanediol diacrylate from the reaction solution to obtain the raffinate phase; E2) Use dichloromethane to extract hydroxybutyl acrylate from the raffinate phase of step E1; E3) Use water to remove 1,4-butanediol from the extract phase of step E2).

8. The preparation method according to claim 7, characterized in that, Step E1) The nonpolar solvent is selected from one or more of cyclohexane and n-hexane, preferably cyclohexane; and / or, In step E1), the mass ratio of the nonpolar solvent to the reaction solution is 1-2:1; and / or, The mass ratio of dichloromethane in step E2) to the raffinate phase in step E1) is 1-2:1; and / or, The mass ratio of water in step E3) to the extract phase in step E2) is 0.2-1:

1.

9. The preparation method according to claim 6, characterized in that, The distillation process includes the following steps: E4) Remove the extractant by vacuum distillation; E5) Secondary vacuum distillation yielded hydroxybutyl acrylate product.

10. The preparation method according to claim 9, characterized in that, Step E4) describes a single-stage vacuum distillation at a pressure of 30-60 kPaA and a top temperature of 20-70°C; and / or, The secondary vacuum distillation described in step E5) has a pressure of 0.1-0.3 kPaA and a top temperature of 75-85℃.

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