Preparation method of 3-ethoxy isoamyl propionate

Abstract

The invention relates to a preparation method of 3-ethoxy isoamyl propionate, and belongs to the technical field of organic solvent synthesis. The preparation method of the 3-ethoxy isoamyl propionate comprises the following steps: S1, adding ethanol, a polymerization inhibitor and a catalyst A into a reaction kettle, heating to 40-55 DEG C, then dropwise adding ethyl acrylate, preserving heat, and carrying out addition reaction for 1-3 hours to obtain a reaction mixture; s2, adding an acidic material for neutralization, and carrying out vacuum rectification to obtain ethyl 3-ethoxypropionate; s3, adding ethyl 3-ethoxypropionate and a catalyst B into a reaction kettle, heating to 100-120 DEG C, introducing isoamyl alcohol, controlling the reaction temperature to 100-115 DEG C, and carrying out transesterification for 2.5-4 hours to obtain a crude product; and S4, cooling to stop the reaction, separating to remove the catalyst B, and carrying out reduced pressure rectification on the obtained crude product to obtain the 3-ethoxypropionic acid isoamyl ester. The method has the effects of mild process, high conversion rate and high product yield.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of organic solvent synthesis, and more particularly relates to a preparation method of 3-ethoxypropionic acid isoamyl ester. BACKGROUND

[0002] Currently, high-boiling solvents on the market include ethylene glycol diacetate, dimethyl adipate, propylene glycol diacetate, dimethyl phthalate, propylene carbonate, and ethylene carbonate. The boiling points of these solvents are all above 200℃, but they have poor solubility for many functional silicone resins, PVDF resins, and inorganic toner color development. The main performance is that they cannot well reduce the viscosity of the paint and the application performance of the paint, and at the same time cannot well solve the problem of toner color development, so the market needs a high-boiling solvent with good solubility and toner color development.

[0003] 3-ethoxypropionic ester compounds are a class of important high-boiling, low-toxicity solvents, which have wide application in the fields of coatings, inks, and electronic chemicals. Among them, 3-ethoxypropionic acid isoamyl ester is an ester compound with special fragrance. Due to the branched isoamyl group in its molecular structure, it has lower volatility, better solubility, and special odor characteristics, and shows unique advantages in high-end coatings and fragrances.

[0004] 3-ethoxypropionic acid isoamyl ester has good solubility for many functional silicone resins, PVDF resins, and toner color development. The fluorocarbon paint and ink film produced by solvents such as ethylene glycol diacetate and propylene glycol diacetate have poor leveling and low gloss, which can be solved by using 3-ethoxypropionic acid isoamyl ester. Some coil fluorocarbon baking paint production lines require high production capacity, and the baking time is several minutes and the baking temperature is as high as 230℃. If only dimethyl adipate and other solvents with low boiling point are used, the leveling performance is poor and the gloss is low, which cannot meet the requirements. The use of 3-ethoxypropionic acid isoamyl ester can also solve this problem.

[0005] In the prior art, there are few reports on the synthesis method of 3-ethoxypropionic acid isoamyl ester. The conventional method usually uses 3-chloropropionic acid isoamyl ester to react with sodium ethoxide, or isoamyl acrylate to directly add with ethanol under the action of a catalyst, but these methods have problems such as difficult access to raw materials, many side reactions, difficult separation of products, and low yield. In addition, due to the high boiling point of 3-ethoxypropionic acid isoamyl ester, the product purification in the conventional synthesis method is difficult, and it is difficult to obtain high-purity products, which limits its application in high-end fields.

[0006] Therefore, it is of great significance to develop a 3-ethoxypropionic acid isoamyl ester preparation method with easy access to raw materials, simple process, high yield, and high product purity. SUMMARY

[0007] The purpose of this invention is to provide a method for preparing isoamyl 3-ethoxypropionate, which has the characteristics of low toxicity of raw materials, low pollution, mild reaction conditions, and high selectivity.

[0008] The objective of this invention can be achieved through the following technical solutions: A method for preparing isoamyl 3-ethoxypropionate includes the following steps: S1. Add ethanol, polymerization inhibitor, and catalyst A to a reaction vessel, heat to 40-55°C, then add ethyl acrylate dropwise, and maintain the temperature for 1-3 hours to carry out the addition reaction to obtain a reaction mixture; wherein, the molar ratio of ethanol to ethyl acrylate is 1.05-1.5:1, and catalyst A is selected from at least one of sodium hydroxide, potassium carbonate, sodium methoxide, sodium ethoxide, or barium oxide; S2. Add an acidic substance to the reaction mixture to neutralize it, and then distill under reduced pressure to obtain ethyl 3-ethoxypropionate; S3. Add ethyl 3-ethoxypropionate and catalyst B to a reaction vessel, heat to 100-120℃, introduce isoamyl alcohol, and control the reaction temperature at 100-115℃ for transesterification reaction for 2.5-4 hours to obtain crude product; wherein, the molar ratio of ethyl 3-ethoxypropionate to isoamyl alcohol is 1:1.2-2, and catalyst B is selected from at least one of tetrabutyl titanate, Zn(OAC)2, Pb(OAC)2, dibutyltin oxide, or self-made molecular sieve catalyst; S4. Cool down to stop the reaction, separate and remove catalyst B, and distill the crude product under reduced pressure to obtain isoamyl 3-ethoxypropionate.

[0009] In this technical solution, the reaction formulas for preparing ethyl 3-ethoxypropionate from ethanol and ethyl acrylate in steps S1 and S2 are as follows: In steps S3 and S4, the reaction formulas for preparing isoamyl 3-ethoxypropionate from ethyl 3-ethoxypropionate and isoamyl alcohol are as follows: The isoamyl 3-ethoxypropionate prepared by this technical solution has a concentration >99%, a water content <500ppm, and an acid value <0.2mgKOH / g.

[0010] Specifically, the prerequisite for performing step S2 is preferably that the conversion rate of ethyl acrylate in the reaction mixture is ≥95%; the prerequisite for performing step S4 is preferably that the conversion rate of ethyl 3-ethoxypropionate in the crude product is ≥90%.

[0011] The preferred method for detecting the conversion rate of ethyl acrylate is gas chromatography. Gas chromatography separates the components in the reaction mixture, quantitatively analyzes the remaining amount of ethyl acrylate, and calculates the conversion rate. When the conversion rate of ethyl acrylate reaches 95% or higher (i.e., the remaining amount ≤ 5%), the next neutralization step is performed.

[0012] Furthermore, the preferred method for detecting the conversion rate of ethyl 3-ethoxypropionate is gas chromatography. Gas chromatography simultaneously separates and analyzes ethyl 3-ethoxypropionate, isoamyl 3-ethoxypropionate, isoamyl alcohol, and ethanol in the reaction system, and the conversion rate is calculated. When the conversion rate of ethyl 3-ethoxypropionate reaches 90% or higher, the reaction is terminated for post-processing.

[0013] Further, in step S1, the polymerization inhibitor is selected from at least one of p-hydroxyanisole, hydroquinone, 2,4-dimethyl-6-tert-butylphenol or tert-butylcatechol; the amount of catalyst A added is 0.5-2% of the weight of ethanol.

[0014] Preferably, the ethyl acrylate has a purity > 99.50% and a water content < 0.2%; the ethanol has a purity > 99.80% and a water content < 0.2%.

[0015] More preferably, the reaction temperature in step S1 is 48-50°C.

[0016] More preferably, in step S1, the dropping rate of ethyl acrylate is 0.5-1 mol / h.

[0017] Among them, catalyst A can efficiently catalyze the Michael addition reaction, and the dosage is small and easy to neutralize and remove; ethyl acrylate is prone to self-polymerization under heating conditions to generate polymer impurities, and the addition of polymerization inhibitors can suppress the polymerization reaction and ensure the utilization rate of raw materials.

[0018] Further, in step S2, the acidic substance is selected from at least one of 5wt% hydrochloric acid aqueous solution, 2wt% phosphoric acid aqueous solution, and 10wt% acetic acid aqueous solution; the neutralization refers to an acid value of 0.5-2 mg KOH / g; and the amount of catalyst B added accounts for 0.1-1.5% of the weight of isoamyl alcohol.

[0019] More preferably, the reaction temperature in step S2 is 105-110℃.

[0020] Furthermore, in step S3, the ethyl 3-ethoxypropionate and isoamyl alcohol undergo transesterification under the catalysis of catalyst B, and the ethanol generated in the reaction is collected and returned to step S1 for reuse.

[0021] This invention designs a real-time ethanol removal and recovery system in transesterification reactions. Ethanol is effectively separated from the reaction system via a fractionating column / tower. The top temperature of the fractionating column is controlled at 78-82℃, which coincides with the boiling point range of ethanol. This allows the generated ethanol to be continuously distilled off, while isoamyl alcohol (boiling point approximately 132℃) is returned to the reaction system to continue participating in the reaction. This design not only improves the reaction conversion rate but also enables the recovery and reuse of ethanol, reducing raw material consumption and environmental pollution.

[0022] Furthermore, in step S4, the temperature of the vacuum distillation is 130-140℃, and the vacuum degree is -0.09 to -0.1MPa.

[0023] This invention employs vacuum distillation technology, which effectively separates the product from unreacted raw materials and a small amount of byproducts by controlling the distillation temperature and vacuum level, thereby obtaining a high-purity isoamyl 3-ethoxypropionate product.

[0024] More preferably, in step S4, the reflux ratio of the vacuum distillation is 1-3:1, and the product purity is ≥99.5%.

[0025] An isoamyl 3-ethoxypropionate was prepared by the above-described method.

[0026] As mentioned above, isoamyl 3-ethoxypropionate is used in the preparation of high-boiling-point solvents. The isoamyl 3-ethoxypropionate is used as a high-boiling-point solvent to dissolve functional organosilicon resins, PVDF resins, and other soluble or inorganic color powders.

[0027] Among them, the aforementioned isoamyl 3-ethoxypropionate exhibits excellent solubility and color development properties when applied to multifunctional organosilicon resins and PVDF resins.

[0028] The beneficial effects of this invention are: (1) The present invention adopts a two-step synthesis route. In the first step, ethyl 3-ethoxypropionate intermediate is prepared by addition reaction of ethanol and ethyl acrylate. Adding a polymerization inhibitor can prevent the self-polymerization of ethyl acrylate. The reaction temperature of 45-50℃ is mild. After neutralization, vacuum distillation can effectively purify the intermediate and ensure the efficiency of subsequent transesterification reaction. In the second step, transesterification reaction is used. Ethanol is removed by heating to drive the equilibrium to the right, thereby improving the conversion rate and yield. The ethanol recovery and utilization conforms to the concept of green chemical industry and reduces costs. The overall process does not have harsh reaction conditions. The product is purified by separation and distillation, which can ensure the purity of the product and meet the needs of industrial production.

[0029] (2) The process of the present invention is mild, has a high conversion rate and a high product yield; the product obtained by distillation purification has high purity and no polymer impurities; the raw materials are readily available and the generated ethanol can be recycled, reducing raw material consumption, and is environmentally friendly and economical, with good industrialization prospects. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0031] Example 1 A method for preparing isoamyl 3-ethoxypropionate includes the following steps: S1. Add 55.2g of ethanol, 0.1g of hydroquinone and 0.276g of sodium methoxide to the reaction vessel, heat to 48℃, add 100.12g of ethyl acrylate dropwise, and keep warm for 2 hours after the addition is complete; when the ethyl acrylate content is detected to be less than 1% by sampling, start cooling to 30℃. S2. Add 5wt% hydrochloric acid aqueous solution to the mixture obtained in step S1 to neutralize until the acid value is 1mgKOH / g. Then separate the aqueous layer, remove excess ethanol, water and trace amounts of ethyl acrylate by vacuum distillation, and obtain the intermediate product ethyl 3-ethoxypropionate after cooling. S3. Add ethyl 3-ethoxypropionate and 0.88g of dibutyltin oxide to the reactor, heat to 100℃, and then add 88g of isoamyl alcohol dropwise. Control the reaction temperature at 105-110℃ to carry out the transesterification reaction. The ethanol generated in the reaction is collected at the top of the column and reused. After 3 hours, take a sample for testing. When the content of ethyl 3-ethoxypropionate is less than 0.5%, cool down and stop the reaction. S4. Filter to remove dibutyltin oxide. The filtrate is heated in a distillation kettle and vacuum distilled to remove light components until the concentration of isoamyl 3-ethoxypropionate in the distillate reaches 99.5%, the water content is less than 500 ppm, and the acid value is less than 0.2 mg KOH / g. The product is then collected.

[0032] Example 2 A method for preparing isoamyl 3-ethoxypropionate includes the following steps: S1. Add 55.2g of ethanol, 0.1g of tert-butylcatechol and 0.276g of sodium ethoxide to the reaction vessel, heat to 49℃, add 100.12g of ethyl acrylate dropwise, and keep warm for 2 hours after the addition is complete; when the ethyl acrylate content is detected to be less than 1% by sampling, start cooling to 30℃. S2. Add 2wt% phosphoric acid aqueous solution to the mixture obtained in step S1 to neutralize until the acid value is 0.5mgKOH / g. Then separate the aqueous layer, remove excess ethanol, water and trace amounts of ethyl acrylate by vacuum distillation, and obtain the intermediate product ethyl 3-ethoxypropionate after cooling. S3. Add 1g of ethyl 3-ethoxypropionate and 1g of self-made molecular sieve catalyst to the reactor. After heating to 105℃, add 88g of isoamyl alcohol dropwise. Control the reaction temperature at 105-110℃ to carry out the transesterification reaction. Collect the ethanol generated in the reaction at the top of the column and reuse it. Take a sample for testing after 3 hours of reaction. When the content of ethyl 3-ethoxypropionate is less than 0.5%, cool down and stop the reaction. S4. Filter to remove the self-made molecular sieve catalyst, and put the filtrate into a distillation kettle for heating. Vacuum distillation is used to remove light components until the concentration of isoamyl 3-ethoxypropionate in the distillate reaches 99.5%, the water content is less than 500 ppm, and the acid value is less than 0.2 mg KOH / g. The product is then collected.

[0033] Example 3 A method for preparing isoamyl 3-ethoxypropionate includes the following steps: S1. Add 55.2g of ethanol, 0.1g of p-hydroxyanisole and 0.276g of barium oxide to the reaction vessel, heat to 50℃, add 100.12g of ethyl acrylate dropwise, and keep warm for 2 hours after the addition is complete; when the sample shows that the ethyl acrylate content is less than 1%, start cooling to 30℃. S2. Add 2wt% phosphoric acid aqueous solution to the mixture obtained in step S1 to neutralize until the acid value is 0.8mgKOH / g. Then separate the aqueous layer, remove excess ethanol, water and trace amounts of ethyl acrylate by vacuum distillation, and obtain the intermediate product ethyl 3-ethoxypropionate after cooling. S3. Add 1.2g of a mixture of ethyl 3-ethoxypropionate, tetrabutyl titanate catalyst, and Zn(OAC)2 (tetrabutyl titanate:Zn(OAC)2=1:1) to the reactor. After heating to 105℃, add 88g of isoamyl alcohol dropwise. Control the reaction temperature at 105-110℃ to carry out the transesterification reaction. Collect the ethanol generated in the reaction at the top of the column and reuse it. After 3 hours of reaction, take a sample for testing. When the content of ethyl 3-ethoxypropionate is less than 0.5%, cool down and stop the reaction. S4. Filter to remove insoluble catalyst, and enter the distillation kettle for heating. Vacuum distillation is then used to remove light components until the concentration of isoamyl 3-ethoxypropionate in the distillate reaches 99.5%, the water content is less than 500 ppm, and the acid value is less than 0.2 mg KOH / g. The product is then collected.

[0034] Comparative Example 1 Compared with Example 1, this comparative example differs in that catalyst A: sodium methoxide is replaced with an equal amount of hydrochloric acid, while the other components, preparation steps and parameters are the same.

[0035] Comparative Example 2 Compared with Example 1, the difference in this comparative example is that catalyst B: dibutyltin oxide is replaced with an equal amount of toluenesulfonic acid, while the other components, preparation steps and parameters are the same.

[0036] Comparative Example 3 Compared with Example 1, this comparative example is different in that it lacks step S2, while the other components, preparation steps and parameters are the same.

[0037] The preparation method of this comparative example is as follows: S1. Add 55.2g of ethanol, 0.1g of hydroquinone and 0.276g of sodium methoxide to a reaction vessel, heat to 48℃, add 100.12g of ethyl acrylate dropwise, and keep warm for 2 hours after the addition is complete; after cooling, the intermediate product ethyl 3-ethoxypropionate is obtained. S3. Add ethyl 3-ethoxypropionate and 0.88g of dibutyltin oxide to the reactor, heat to 100℃, and then add 88g of isoamyl alcohol dropwise. Control the reaction temperature at 105-110℃ to carry out the transesterification reaction. The ethanol generated in the reaction is collected at the top of the column and reused. After 3 hours, cool down and stop the reaction. S4. Filter to remove dibutyltin oxide, and the filtrate is heated in a distillation kettle. Vacuum distillation is then used to remove light components, and the product is collected.

[0038] Comparative Example 4 Compared with Example 1, this comparative example differs in that it uses a one-step method to prepare isoamyl 3-ethoxypropionate, while the other components, preparation steps, and parameters are the same.

[0039] The preparation method of this comparative example is as follows: Add 55.2g ethanol, 0.1g hydroquinone, 0.276g sodium methoxide, 100.12g ethyl acrylate, 5wt% hydrochloric acid aqueous solution, and 0.88g dibutyltin oxide to a reaction vessel. After heating to 100℃, add 88g isoamyl alcohol dropwise. Control the reaction temperature at 105-110℃. After reacting for 3 hours, cool down and stop the reaction. Filter to remove impurities, and enter a distillation vessel for heating. Vacuum distillation is used to remove light components, and the product is collected.

[0040] The final products obtained in Examples 1-3 and Comparative Examples 1-4 were tested using gas chromatography-mass spectrometry, moisture analysis, and acid value titration. The test results are shown in Table 1.

[0041] Table 1 As shown in Table 1, compared with Comparative Examples 1-4, Examples 1-3 had higher product content, lower moisture content, lower acid value, and higher yield. In Comparative Example 1, the replacement of catalyst A may have reduced the efficiency and selectivity of ethyl 3-ethoxypropionate synthesis, resulting in insufficient conversion of ethyl acrylate, poor selectivity, and the generation of more byproducts such as polymers and diethoxy compounds. This led to a decrease in product content, an increase in moisture, an increase in acid value, and a low conversion rate and yield in the main reaction. Similarly, in Comparative Example 2, the replacement of catalyst B may have reduced the efficiency and selectivity of the second transesterification reaction, resulting in an increase in byproduct content and a decrease in the main product content. In Comparative Example 1, the product content decreased, moisture increased, and acid value rose, indicating incomplete transesterification and a lower yield. In Comparative Example 3, the lack of a neutralization step with an acidic substance allowed the acidic substance to directly enter the transesterification system, potentially triggering various side reactions at high temperatures. This exacerbated the decrease in product content, increased moisture, and higher acid value. Furthermore, the side reactions consumed a large amount of raw materials, and the main product was prone to decomposition under acidic high-temperature conditions, leading to a lower yield. In Comparative Example 4, the two-step reaction was combined into one, with etherification and transesterification occurring simultaneously at high temperatures. This resulted in a chaotic reaction pathway, with multiple competing reactions occurring concurrently, significantly affecting product content, and causing extremely high moisture and acid value, leading to a substantial decrease in yield. In summary, Examples 1-3 achieved high yield and high purity through precise control of catalyst selection, reaction conditions, and process steps.

[0042] Taking the blue paint of hot-melt fluoropolymer (PVDF) coating as an example, a comparative test sample was conducted. The four formulations are shown in Table 2 below.

[0043] Table 2 The substrates for all samples were aluminum alloy plates, with a coating thickness of 25±2μm. The sample preparation process followed HG / T3793-2019, resulting in plates A, B, C, and D. Colorimetric analysis was performed according to GB / T 9761-2008, and the results are shown in Table 3 below.

[0044] Table 3 As can be seen from the test results in Table 3, the overall difference values ​​of hue difference (DH), chroma difference (DC), and lightness difference (DL) of plate A are the lowest, indicating that isoamyl 3-ethoxypropionate has better performance than the other three commonly used solvents. When used in multifunctional organosilicon resins and PVDF resins, isoamyl 3-ethoxypropionate has excellent solubility and excellent color development properties for pigments.

[0045] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing isoamyl 3-ethoxypropionate, characterized in that, Includes the following steps: S1. Add ethanol, polymerization inhibitor, and catalyst A to a reaction vessel, heat to 40-55°C, then add ethyl acrylate dropwise, and maintain the temperature for 1-3 hours to carry out the addition reaction to obtain a reaction mixture; wherein, the molar ratio of ethanol to ethyl acrylate is 1.05-1.5:1, and catalyst A is selected from at least one of sodium hydroxide, potassium carbonate, sodium methoxide, sodium ethoxide, or barium oxide; S2. Add an acidic substance to the reaction mixture to neutralize it, and then distill under reduced pressure to obtain ethyl 3-ethoxypropionate; S3. Add ethyl 3-ethoxypropionate and catalyst B to a reaction vessel, heat to 100-120℃, introduce isoamyl alcohol, and control the reaction temperature at 100-115℃ for transesterification reaction for 2.5-4 hours to obtain crude product; wherein, the molar ratio of ethyl 3-ethoxypropionate to isoamyl alcohol is 1:1.2-2, and catalyst B is selected from at least one of tetrabutyl titanate, Zn(OAC)2, Pb(OAC)2, dibutyltin oxide, or self-made molecular sieve catalyst; S4. Cool down to stop the reaction, separate and remove catalyst B, and distill the crude product under reduced pressure to obtain isoamyl 3-ethoxypropionate.

2. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, In step S1, the polymerization inhibitor is selected from at least one of p-hydroxyanisole, hydroquinone, 2,4-dimethyl-6-tert-butylphenol, or tert-butylcatechol; the amount of catalyst A added is 0.5-2% of the weight of ethanol.

3. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, The reaction temperature in step S1 is 48-50℃; the dropping rate of ethyl acrylate is 0.5-1 mol / h.

4. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, In step S2, the acidic substance is selected from at least one of 5wt% hydrochloric acid aqueous solution, 2wt% phosphoric acid aqueous solution, and 10wt% acetic acid aqueous solution; the amount of catalyst B added accounts for 0.1-1.5% of the weight of isoamyl alcohol.

5. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, The reaction temperature in step S2 is 105-110℃; the neutralization refers to an acid value of 0.5-2 mgKOH / g.

6. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, In step S3, ethyl 3-ethoxypropionate and isoamyl alcohol undergo transesterification under the catalysis of catalyst B. The ethanol generated in the reaction is collected and returned to step S1 for reuse.

7. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, In step S4, the temperature of the vacuum distillation is 130-140℃ and the vacuum degree is -0.09 to -0.1MPa.

8. The method for preparing isoamyl 3-ethoxypropionate according to claim 1, characterized in that, In step S4, the reflux ratio of the vacuum distillation is 1-3:1, and the product purity is ≥99.5%.

9. An isoamyl 3-ethoxypropionate, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of isoamyl 3-ethoxypropionate as described in claim 9 in the preparation of high-boiling-point solvents, characterized in that, The isoamyl 3-ethoxypropionate is used as a high-boiling-point solvent to dissolve functional organosilicon resins, PVDF resins, and other soluble or inorganic color powders.

Images