Preparation method of 4-hydroxybutyl acrylate

Abstract

The invention relates to a preparation method of 4-hydroxybutyl acrylate, which is characterized in that acrylic acid and tetrahydrofuran are used as raw materials, in the presence of a polymerization inhibitor and a compound catalyst, the 4-hydroxybutyl acrylate is prepared, the compound catalyst comprises concentrated sulfuric acid and metal salt, and the concentrated sulfuric acid and the metal salt are mixed to prepare the 4-hydroxybutyl acrylate. The metal salt is selected from one or more of ferric trichloride, ferric formate, ferric acetate, ferric acrylate, ferric methacrylate, chromium trichloride, chromium acrylate, chromium methacrylate, chromium acetylacetonate, ferric acetylacetonate, chromium picolinate, chromium formate and chromium acetate. According to the method disclosed by the invention, the 4-hydroxybutyl acrylate can be prepared with high selectivity under a mild condition.

Description

Technical Field

[0001] The invention belongs to the field of esterification reaction, and specifically relates to a method for preparing 4-hydroxybutyl acrylate. Background Art

[0002] 4-Hydroxybutyl acrylate (4-HBA) is an acrylate monomer that has developed rapidly in recent years. It has two main characteristics: first, compared with conventional hydroxy ester monomers such as HPA and HEA, 4-HBA has lower irritation; second, the hydroxyl groups on its carbon chain are more active and reactive, and the coatings prepared from 4-HBA dry faster than other hydroxy ester products. Currently, 4-HBA is mainly used in the fields of coatings and adhesives.

[0003]

[0004] 4-Hydroxybutyl acrylate

[0005] At present, there are three main process routes for producing 4-hydroxybutyl acrylate:

[0006] (1) Direct esterification route

[0007] The direct esterification route uses acrylic acid and 1,4-butanediol as raw materials to generate 4-hydroxybutyl acrylate under the action of an acidic catalyst. However, due to the presence of two hydroxyl groups in the structure of 1,4-butanediol, a large amount of double esterification product 1,4-butanediol diacrylate is often generated during the reaction. The boiling point difference between 4-hydroxybutyl acrylate and 1,4-butanediol diacrylate is very small, making it difficult to separate by distillation and requiring extraction and other means to separate. The separation process is extremely complex and has high energy consumption (CN115947656A, CN109053449 A).

[0008]

[0009] Direct esterification method

[0010] (2) Transesterification route

[0011] The ester exchange route uses methyl acrylate and 1,4-butanediol as raw materials to produce 4-hydroxybutyl acrylate through an ester exchange reaction. Its disadvantages are similar to those of the direct esterification route. 1,4-butanediol diacrylate is inevitably produced during the reaction, and the separation process is also complicated and lengthy.

[0012]

[0013] Transesterification

[0014] (3) Tetrahydrofuran ring opening route

[0015] Since 1,4-butanediol as raw material will inevitably generate a large amount of by-product 1,4-butanediol diacrylate, which brings about the problem of lengthy separation process. It has been reported in the literature that 4-hydroxybutyl methacrylate can be prepared with high selectivity using tetrahydrofuran and methacrylic acid as raw materials, boron trifluoride and caprylic acid ester as catalysts, and the reaction process basically does not produce double esterification products. Excess tetrahydrofuran can be completely recovered by vacuum distillation, and the separation process is simple.

[0016]

[0017] Tetrahydrofuran ring opening method

[0018] This method solves the problem of the difficulty in separating the by-product 1,4-butanediol diacrylate and the main product 4-hydroxybutyl acrylate, but there are still three shortcomings: first, the key catalyst decanoic acid ester is difficult to obtain, which brings difficulties to large-scale industrial production; second, the two raw materials methacrylic acid and tetrahydrofuran need to be dehydrated before use, and the pretreatment is time-consuming and labor-intensive; third, the reaction temperature is high. Although an inhibitor is added, an inevitable polymerization reaction still occurs during the reaction, resulting in product loss and a decrease in yield.

[0019] In summary, the existing preparation methods have disadvantages such as complex separation process, strict requirements on raw materials, and difficulty in obtaining catalysts. Summary of the invention

[0020] The purpose of the present invention is to solve the problems faced in the background technology, thereby providing a method for preparing 4-hydroxybutyl acrylate with simple process and convenient operation to meet industrialization needs.

[0021] In order to achieve the above object, the first aspect of the present invention provides a method for preparing 4-hydroxybutyl acrylate, wherein the method uses acrylic acid and tetrahydrofuran as raw materials, in the presence of a polymerization inhibitor and a composite catalyst, to prepare 4-hydroxybutyl acrylate, wherein:

[0022] The composite catalyst comprises concentrated sulfuric acid and a metal salt, wherein the metal salt is one or more selected from ferric chloride, ferric formate, ferric acetate, ferric acrylate, ferric methacrylate, chromium trichloride, chromium acrylate, chromium methacrylate, chromium acetylacetonate, chromium picolinate, chromium formate and chromium acetate.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The preparation method of the present invention uses tetrahydrofuran and acrylic acid as raw materials, and uses a combination of concentrated sulfuric acid and a metal salt as a composite catalyst, so that 4-hydroxybutyl acrylate can be prepared with high selectivity under mild conditions, the polymer content in the product is low, and 1,4-butanediol diacrylate is basically not generated during the reaction process, thereby avoiding the problems of difficulty in separating 4-hydroxybutyl acrylate from 1,4-butanediol diacrylate in traditional processes. In addition, the reaction solution obtained by the method of the present invention can be refined by a simple distillation method, and has the advantages of process conditions, temperature, and simple process. DETAILED DESCRIPTION

[0025] The present invention is further described below by means of specific embodiments. The embodiments of the present invention are only used as illustrations of the present invention and do not mean that the scope of the present invention is limited thereto.

[0026] One aspect of the present invention provides a method for preparing 4-hydroxybutyl acrylate, wherein the method uses acrylic acid and tetrahydrofuran as raw materials, in the presence of a polymerization inhibitor and a composite catalyst, to prepare 4-hydroxybutyl acrylate, wherein:

[0027] The composite catalyst comprises concentrated sulfuric acid and a metal salt, wherein the metal salt is selected from one or more of ferric chloride, ferric formate, ferric acetate, ferric acrylate, ferric methacrylate, chromium chloride, chromium acrylate, chromium methacrylate, chromium acetylacetonate, ferric acetylacetonate, chromium picolinate, chromium formate and chromium acetate.

[0028] Preferably, the metal salt is one or more selected from chromium acetylacetonate and iron acetylacetonate.

[0029] In some embodiments, in the composite catalyst, the mass ratio of concentrated sulfuric acid to the metal salt is 40 to 50:1.

[0030] In some embodiments, the concentrated sulfuric acid is a sulfuric acid solution with a mass fraction greater than or equal to 70%, preferably a sulfuric acid solution with a mass fraction greater than or equal to 90%, for example, concentrated sulfuric acid with a mass fraction of 98%.

[0031] In some embodiments, the amount of the composite catalyst is 3% to 6% of the mass of tetrahydrofuran.

[0032] In some embodiments, the preparation method comprises:

[0033] Step a): acrylic acid, the polymerization inhibitor and the metal salt are mixed, concentrated sulfuric acid is added dropwise, and the dropping speed of the concentrated sulfuric acid is controlled to maintain the temperature of the reaction liquid at 20° C. to 40° C. After the concentrated sulfuric acid is added dropwise, tetrahydrofuran is continued to be added dropwise. After the addition is completed, the mixture is stirred and reacted at 20° C. to 40° C. to obtain 4-hydroxybutyl acrylate.

[0034] In some embodiments, the molar ratio of acrylic acid to tetrahydrofuran is 1:0.8 to 2.0, preferably 1:0.8 to 1.2.

[0035] In some embodiments, the polymerization inhibitor is one or more selected from p-hydroxyanisole, hydroquinone, 2,5-di-tert-butylhydroquinone, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical, tetramethylpiperidinyl nitroxide free radical phosphite triester, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate nitroxide free radical and dibutyl copper dithiocarbamate.

[0036] In some embodiments, the amount of the polymerization inhibitor is 0.04% to 0.2% by mass of acrylic acid, preferably 0.04% to 0.08% by mass.

[0037] In some embodiments, in step a), after the tetrahydrofuran is added dropwise, the reaction is stirred at 20° C. to 40° C. for 3 to 6 hours.

[0038] In some embodiments, the preparation method further comprises:

[0039] Step b): adding an aqueous solution and an organic solution to the reaction solution for extraction, separating the upper aqueous phase and adding the organic solution to backwash the upper aqueous phase, combining the organic phases obtained by extraction and backwashing, performing vacuum distillation, and collecting fractions.

[0040] In some embodiments, the aqueous solution is water, such as ultrapure water, deionized water, distilled water, etc.; in some embodiments, the organic solution is one or more selected from dichloromethane, chloroform, 1,2-dichloroethane, isobutyl acetate and ethyl acetate, etc.

[0041] In some embodiments, during the vacuum distillation process of step b), a fraction at 121-123° C. at 200 Pa is collected.

[0042] The preparation method of 4-hydroxybutyl acrylate provided by the present invention is further described in detail below with reference to the examples, but the present invention is not limited thereto.

[0043] Source of raw materials:

[0044]

[0045] Example 1

[0046] Preparation of compounds: 144 g of acrylic acid, 0.072 g of hydroquinone, and 0.14 g of ferric chloride were added to a 500 mL three-necked flask, and stirred evenly at room temperature. 6.82 g of 98% concentrated sulfuric acid was added dropwise to the system using a constant pressure dropping funnel. The dropping speed was controlled to maintain the temperature of the reaction solution at 25-30°C. After the addition of concentrated sulfuric acid was completed, 144 g of tetrahydrofuran was continued to be added dropwise using a constant pressure dropping funnel. The system temperature was controlled at 30°C during the addition. After the addition of tetrahydrofuran was completed, stirring was continued at 30°C for 4.5 hours. After the reaction was completed, the obtained reaction solution was subjected to GPC (gel permeation chromatography) analysis, and the content of substances with a molecular weight exceeding 1000 was less than 1000 ppm.

[0047] Product separation: 200 mL of deionized water and 200 mL of dichloromethane were added to the reaction solution, and an aqueous phase and an organic phase were obtained after extraction. The separated upper aqueous phase was backwashed with dichloromethane (50 mL each time, three times), and the dichloromethane phase obtained by washing the aqueous phase was combined with the organic phase and subjected to vacuum distillation. The fraction at 121-123° C. under 200 Pa was collected to obtain 207.3 g of a colorless transparent liquid with a yield of 72%. The collected fraction was analyzed by gas chromatography, and the 4-HBA content was 97.68%.

[0048] Example 2

[0049] Preparation of compounds: 108 g of acrylic acid, 0.06 g of copper dibutyl dithiocarbamate, and 0.11 g of chromium acetylacetonate were added to a 500 mL three-necked flask, and stirred evenly at room temperature. 4.75 g of 98% concentrated sulfuric acid was added dropwise to the system using a constant pressure dropping funnel. The dropping speed was controlled to maintain the temperature of the reaction solution at 25-30 ° C. After the addition of 98% concentrated sulfuric acid was completed, 162 g of tetrahydrofuran was continued to be added dropwise using a constant pressure dropping funnel. During the addition, the system temperature was controlled at 35 ° C. After the addition of tetrahydrofuran was completed, stirring was continued at 35 ° C for 4 hours. After the reaction was completed, the obtained reaction solution was subjected to GPC analysis, and the content of substances with a molecular weight exceeding 1000 was less than 1000 ppm.

[0050] Product separation: 180 mL of deionized water and 180 mL of dichloromethane were added to the reaction solution, and an aqueous phase and an organic phase were obtained after extraction. The separated upper aqueous phase was backwashed with dichloromethane (40 mL each time, washed three times), and the dichloromethane phase obtained by washing the aqueous phase was combined with the organic phase and subjected to vacuum distillation. The fraction at 121-123° C. under 200 Pa was collected to obtain 164.2 g of a colorless transparent liquid with a yield of 76%. The collected fraction was analyzed by gas chromatography, and the 4-HBA content was 98.13%.

[0051] Example 3

[0052] Preparation of compounds: 504 g of acrylic acid, 0.504 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide free radical, and 0.86 g of ferric acetylacetonate were added to a 2L three-necked flask, and stirred evenly at room temperature. 34.41 g of 98% concentrated sulfuric acid was added dropwise to the system using a constant pressure dropping funnel, and the dropping speed was controlled to maintain the temperature of the reaction liquid at 25-30°C. After the addition of 98% concentrated sulfuric acid was completed, 1008 g of tetrahydrofuran was continued to be added dropwise using a constant pressure dropping funnel. During the addition, the system temperature was controlled at 40°C. After the addition of tetrahydrofuran was completed, stirring was continued at 40°C for 3 hours. After the reaction was completed, the reaction liquid was subjected to GPC analysis, and the content of substances with a molecular weight exceeding 1000 was less than 1000 ppm.

[0053] Product separation: 1L of deionized water and 1L of dichloromethane were added to the reaction solution, and an aqueous phase and an organic phase were obtained after extraction. The separated upper aqueous phase was backwashed with dichloromethane (250mL each time, three times), and the dichloromethane phase obtained by washing the aqueous phase was combined with the organic phase and subjected to vacuum distillation. The fraction at 121-123°C under 200Pa was collected to obtain 816.5g of colorless transparent liquid with a yield of 81%. The collected fraction was analyzed by gas chromatography, and the 4-HBA content was 98.09%.

[0054] Comparative Example 1

[0055] Compound preparation: Add 144 g of acrylic acid, 360 g of 1,4-butanediol, 1.44 g of 98% concentrated sulfuric acid, and 0.25 g of 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical into a 1L three-necked flask, and react at 100°C for 2 h. After the reaction, the resulting reaction solution was analyzed by GPC, and the content of substances with a molecular weight exceeding 1000 was 1.2%.

[0056] Product separation: 500 mL of deionized water and 500 mL of cyclohexane were added to the reaction solution, and an aqueous phase and a cyclohexane phase were obtained after extraction. The separated aqueous phase was further washed with cyclohexane (100 mL each time, washed three times), and then 600 mL of dichloromethane was added to the washed aqueous phase, and the dichloromethane phase was obtained after phase separation after extraction. The dichloromethane phase was subjected to vacuum distillation, and the fraction at 121-123° C. under 200 Pa was collected to obtain 181.4 g of colorless transparent liquid, with a yield of 63%. The collected fraction was subjected to gas chromatography analysis, and the 4-HBA content was 95.42%.

[0057] Comparative Example 2

[0058] Preparation of compounds: Add 504 g of acrylic acid and 0.504 g of 4-hydroxy-2,2,6,6-tetramethylpiperidine nitroxide free radical to a 2L three-necked flask, stir evenly at room temperature, and then use a constant pressure dropping funnel to drop 34.41 g of 98% concentrated sulfuric acid into the system. Control the dropping speed to maintain the temperature of the reaction liquid at 25-30°C. After the addition of 98% concentrated sulfuric acid is completed, continue to use a constant pressure dropping funnel to drop 1008 g of tetrahydrofuran. During the addition, the system temperature is controlled at 40°C. After the addition of tetrahydrofuran is completed, maintain 40°C and continue stirring for 3 hours. After the reaction is completed, the obtained reaction liquid is subjected to GPC analysis, and the content of substances with a molecular weight exceeding 1000 is less than 1000ppm.

[0059] Product separation: 1L of deionized water and 1L of dichloromethane were added to the reaction solution, and an aqueous phase and an organic phase were obtained after extraction. The separated upper aqueous phase was backwashed with dichloromethane (250mL each time, three times), and the dichloromethane phase obtained by washing the aqueous phase was combined with the organic phase and subjected to vacuum distillation. The fraction at 121-123°C under 200Pa was collected to obtain 433.4g of colorless transparent liquid with a yield of 43%. The collected fraction was analyzed by gas chromatography, and the 4-HBA content was 97.21%.

[0060] Comparative Example 3

[0061] Preparation of compounds: Add 504 g of acrylic acid, 0.504 g of 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical, and 0.86 g of ferric acetylacetonate into a 2L three-necked flask, stir evenly and then heat to 40°C. At this temperature, add 1008 g of tetrahydrofuran dropwise using a constant pressure dropping funnel. After the addition of tetrahydrofuran, maintain 40°C and continue stirring for 3 hours. After the reaction is completed, perform GPC analysis on the obtained reaction solution, and the content of substances with a molecular weight exceeding 1000 is less than 1000 ppm.

[0062] Product separation: 1L of deionized water and 1L of dichloromethane were added to the reaction solution, and an aqueous phase and an organic phase were obtained after extraction. The separated upper aqueous phase was backwashed with dichloromethane (250mL each time, washed three times). The dichloromethane phase obtained by washing the aqueous phase was combined with the organic phase and then subjected to vacuum distillation. The fraction at 121-123°C under 200Pa was collected. There was almost no fraction at this temperature, and no product was collected.

[0063] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as limiting the present invention. It will be appreciated by those skilled in the art that, under the guidance of this specification, some modifications or adjustments may be made to the present invention. These modifications or adjustments should also be within the scope of the present invention.

Claims

1. A method for preparing 4-hydroxybutyl acrylate, characterized in that: The preparation method uses acrylic acid and tetrahydrofuran as raw materials, and prepares 4-hydroxybutyl acrylate in the presence of a polymerization inhibitor and a composite catalyst, wherein: The composite catalyst comprises concentrated sulfuric acid and a metal salt, wherein the metal salt is one or more selected from ferric chloride, ferric formate, ferric acetate, ferric acrylate, ferric methacrylate, chromium trichloride, chromium acrylate, chromium methacrylate, chromium acetylacetonate, ferric acetylacetonate, chromium picolinate, chromium formate and chromium acetate.

2. The method for preparing 4-hydroxybutyl acrylate according to claim 1, characterized in that: The metal salt is one or more selected from chromium acetylacetonate and iron acetylacetonate.

3. The method for preparing 4-hydroxybutyl acrylate according to claim 1, characterized in that: In the composite catalyst, the mass ratio of the concentrated sulfuric acid to the metal salt is 40 to 50:1; The concentrated sulfuric acid is a sulfuric acid solution with a mass fraction greater than or equal to 70%, preferably a sulfuric acid solution with a mass fraction greater than or equal to 90%, and more preferably 98% concentrated sulfuric acid.

4. The method for preparing 4-hydroxybutyl acrylate according to claim 3, characterized in that: The dosage of the composite catalyst is 3% to 6% of the mass of tetrahydrofuran.

5. The method for preparing 4-hydroxybutyl acrylate according to any one of claims 1 to 4, characterized in that: The preparation method comprises Step a): acrylic acid, the polymerization inhibitor and the metal salt are mixed, and the concentrated sulfuric acid is added dropwise, and the dropping speed of the concentrated sulfuric acid is controlled to maintain the temperature of the reaction liquid at 20-40° C. After the concentrated sulfuric acid is added dropwise, tetrahydrofuran is continued to be added dropwise, and after the addition is completed, the reaction is stirred at 20-40° C. to obtain 4-hydroxybutyl acrylate.

6. The method for preparing 4-hydroxybutyl acrylate according to any one of claims 1 to 4, characterized in that: The molar ratio of acrylic acid to tetrahydrofuran is 1:0.8 to 2.0, preferably 1:0.8 to 1.

2.

7. The method for preparing 4-hydroxybutyl acrylate according to any one of claims 1 to 4, characterized in that: The polymerization inhibitor is one or more selected from p-hydroxyanisole, hydroquinone, 2,5-di-tert-butylhydroquinone, phenothiazine, 4-hydroxy-2,2,6,6-tetramethylpiperidinyl nitroxide free radical, tetramethylpiperidinyl nitroxide free radical phosphite triester, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate nitroxide free radical and dibutyl copper dithiocarbamate.

8. The method for preparing 4-hydroxybutyl acrylate according to claim 7, characterized in that: The amount of the polymerization inhibitor used is 0.04% to 0.2% of the mass of acrylic acid, preferably 0.04% to 0.08%.

9. The method for preparing 4-hydroxybutyl acrylate according to any one of claims 1 to 4, characterized in that: The preparation method further comprises: Step b): adding an aqueous solution and an organic solution to the reaction solution for extraction, separating the upper aqueous phase and adding the organic solution to backwash the upper aqueous phase, combining the organic phases obtained by extraction and backwashing, performing vacuum distillation, and collecting fractions.

10. The method for preparing 4-hydroxybutyl acrylate according to claim 9, characterized in that: The aqueous solution is water; the organic solution is one or more selected from dichloromethane, chloroform, 1,2-dichloroethane, isobutyl acetate and ethyl acetate; Preferably, during the vacuum distillation process in step b), a fraction at 121° C. to 123° C. at 200 Pa is collected.

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