A method for high-selectivity synthesis of 3-hydroxypropionitrile

Abstract

The application discloses a method for synthesizing 3-hydroxypropionitrile with high selectivity, and belongs to the technical field of organic synthesis. In the presence of a hydrophobic solvent and an alkaline catalyst, acrylonitrile and water are reacted to generate 3-hydroxypropionitrile. In the reaction system, the hydrophobic solvent and water constitute a two-phase reaction system, acrylonitrile is dissolved in the hydrophobic solvent, and the generated 3-hydroxypropionitrile is dissolved in water. The application introduces the hydrophobic solvent into the reaction system, increases the protection of the product 3-hydroxypropionitrile, reduces the further contact of the product 3-hydroxypropionitrile with acrylonitrile to generate di(cyanoethyl) ether, improves the selectivity of the reaction, and further improves the yield of 3-hydroxypropionitrile. The yield of 3-hydroxypropionitrile can reach about 72%, and the hydrophobic solvent and unreacted acrylonitrile can be recycled and used, thereby reducing the production cost. The application has the advantages of simple process, good reaction selectivity, high yield of the obtained product and low cost.

Description

Technical Field

[0001] The invention relates to a method for synthesizing 3-hydroxypropionitrile with high selectivity, and belongs to the technical field of organic synthesis. Background Art

[0002] 3-Hydroxypropionitrile (also known as 2-cyanoethanol) is an important chemical intermediate. Its hydrogenation yields 3-aminopropanol, which is commonly used in the preparation of the anti-tumor drug cyclophosphamide and the cardiovascular treatments propranolol and quinolones. It can also be used to synthesize D-panthenol, which is widely used in pharmaceuticals, food additives, and cosmetics. 3-Hydroxypropionitrile is also widely used as an auxiliary raw material in the papermaking, textile, and leather industries.

[0003] Currently, there are several main methods for chemically synthesizing 3-hydroxypropionitrile: (1) Reaction of chloroethanol with cyanide. Although this method can achieve high yields, the raw material 2-chloroethanol used is expensive, the reaction exotherm is difficult to control, a large amount of solid waste is generated, and cyanide is too dangerous. (2) Reaction of ethylene oxide with hydrocyanic acid. Although this method is highly economical, the ethylene oxide used is difficult to handle and the toxicity of hydrocyanic acid is high, which limits its large-scale application. (3) Acrylonitrile hydration. This method is to prepare 3-hydroxypropionitrile by the addition reaction of acrylonitrile and water in a 1:1 stoichiometric ratio under base catalysis. However, this method has poor selectivity. The generated 3-hydroxypropionitrile will further react with acrylonitrile to produce a large mixture of di(cyanoethyl)ethers, resulting in a low yield of 3-hydroxypropionitrile.

[0004] To improve the reaction selectivity and product yield of preparing 3-hydroxypropionitrile by acrylonitrile hydration, patent CN111100035A uses supercritical water to enhance the solubility of organic matter, reacting acrylonitrile with supercritical water or subcritical water. This allows acrylonitrile, which is insoluble in ordinary water, to react under homogeneous conditions, greatly reducing the formation of by-products and achieving a high product yield. However, this method has high safety requirements and high equipment investment costs. CN112300029A reacts acrylonitrile and deionized water in the presence of an alkaline catalyst in a microchannel reactor to obtain a mixed solution containing 3-hydroxypropionitrile. This method can be produced continuously with high reaction efficiency and purity, but has low production capacity, is difficult to achieve industrial production, and increases costs. CN1189449C reacts acrylonitrile with water under weak base catalysis to generate a mixture containing a large amount of di(cyanoethyl)ether, and then catalytically decomposes the reaction product over an alkaline catalyst to generate more 3-hydroxypropionitrile. Although the yield of 3-hydroxypropionitrile is improved in this method, the process is too complicated and requires two steps of reaction to obtain a high yield of 3-hydroxypropionitrile, resulting in high production costs. Summary of the Invention

[0005] The present invention aims to provide a method for synthesizing 3-hydroxypropionitrile with high selectivity. By introducing a hydrophobic solvent into a reaction system, the protection of the product 3-hydroxyacetonitrile is increased, the further contact between the product 3-hydroxyacetonitrile and acrylonitrile to form di(cyanoethyl)ether is reduced, the reaction selectivity is improved, and the generation of non-target product di(cyanoethyl)ether is reduced.

[0006] The present invention proposes a method for synthesizing 3-hydroxypropionitrile with high selectivity, comprising reacting acrylonitrile with water in the presence of a hydrophobic solvent and an alkaline catalyst to generate 3-hydroxypropionitrile. In the reaction system, the hydrophobic solvent and water constitute a two-phase reaction system, acrylonitrile dissolves in the hydrophobic solvent, and the generated 3-hydroxypropionitrile dissolves in the water.

[0007] Preferably, the hydrophobic solvent includes at least one of ethyl acetate, petroleum ether, n-hexane, cyclohexane, benzene, and toluene; preferably cyclohexane or toluene.

[0008] In the present invention, the hydrophobic solvent includes but is not limited to the above-mentioned reagents. The hydrophobic solvent has good solubility for the raw material acrylonitrile, but poor solubility for the target product 3-hydroxypropionitrile, thereby effectively preventing 3-hydroxypropanol from further contacting and reacting with acrylonitrile to form di(cyanoethyl)ether; the di(cyanoethyl)ether is mainly present in the aqueous phase of the two-phase mixture.

[0009] Preferably, the alkaline catalyst is one or more of alkali metal carbonates and bicarbonates.

[0010] Preferably, acrylonitrile and water are reacted at 80-150° C. and 0.1-0.5 MPa for 1-8 hours.

[0011] Preferably, the mass ratio of the acrylonitrile to the hydrophobic solvent is 1:1-2.

[0012] Preferably, the molar ratio of acrylonitrile to water is 1:1-20; preferably 1:4-10.

[0013] Preferably, the amount of the alkaline catalyst used is 0.5-5 mol%, preferably 0.5-2 mol%, based on the amount of acrylonitrile.

[0014] Preferably, the specific steps are as follows:

[0015] S1, adding acrylonitrile, a hydrophobic solvent, water and an alkaline catalyst into a closed reaction vessel to form an organic-aqueous two-phase reaction system, and heating the reaction; in the reaction system, acrylonitrile is dissolved in the hydrophobic solvent, and the generated 3-hydroxypropionitrile is dissolved in water, and after the reaction is completed, a two-phase mixture is obtained;

[0016] S2. After cooling the two-phase mixture, separate the organic phase and recycle it;

[0017] S3. Separate 3-hydroxypropionitrile by distillation from the aqueous phase.

[0018] Preferably, S3 further comprises neutralizing the aqueous phase and then distilling and separating 3-hydroxypropionitrile.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention introduces a hydrophobic solvent into the reaction system so that acrylonitrile is dissolved in the hydrophobic solvent, while the 3-hydroxypropionitrile generated by the reaction is dissolved in water, reducing its further contact with acrylonitrile to generate di(cyanoethyl) ether, thereby increasing the protection of the product 3-hydroxyacetonitrile, improving the selectivity of the reaction, and increasing the yield of 3-hydroxypropionitrile. The single-pass yield can reach about 72%, and the hydrophobic solvent and unreacted acrylonitrile can be recycled, thereby reducing production costs.

[0021] 2. The process of the present invention is simple, the reaction selectivity is good, the generation of di(cyanoethyl) ether is reduced, no further cracking treatment is required, the reaction steps are shortened, and the cost is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the gas chromatogram of the aqueous phase in Example 4 of the present invention. DETAILED DESCRIPTION

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0024] The calculation formula for the acrylonitrile conversion rate described in the following examples is: [m (initial mass of acrylonitrile) - m (mass of unreacted acrylic acid)] / m (initial mass of acrylonitrile) × 100%;

[0025] The calculation formula for the yield of 3-hydroxypropionitrile described in the following examples is: m (actual yield of 3-hydroxypropionitrile) / m (theoretical yield of 3-hydroxypropionitrile) × 100%;

[0026] The single-pass conversion rate or single-pass yield described in the following examples refers to the conversion rate or yield of the reaction without recycle.

[0027] Example 1

[0028] a. Place 80g of a mixed solution containing 1wt% NaHCO₃ and 1wt% Na₂CO₃ aqueous solutions and 53.06g (1mol) acrylonitrile in a 0.5L autoclave. Replace the atmosphere with nitrogen three times. Start stirring, set the speed to 200rpm, raise the temperature to 110°C, and maintain the reaction at approximately 0.1MPa. After 2h of reaction, cool the reaction mixture.

[0029] b. Add a weak acid to the reaction solution of step a and neutralize it to a pH of 6.0-7.0;

[0030] c. The mixed solution obtained in step b was subjected to reduced pressure distillation to remove unreacted 20.6 g of acrylonitrile and water; 42.1 g of a mixture of di(cyanoethyl) ether and 3-hydroxypropionitrile was obtained (gas phase composition: 3-hydroxypropionitrile 42.5%, di(cyanoethyl) ether 56.8%, acrylamide 0.5%);

[0031] d. Pyrolyzing the mixture obtained in step c, adding 0.3 wt % sodium acetate as a catalyst, the pyrolysis temperature is 120° C.-130° C., and the pyrolysis pressure is 0.5 KPa-20 KPa to obtain 11.0 g of acrylonitrile and 27.7 g of 3-hydroxypropionitrile as a product;

[0032] e. The purity of 3-hydroxypropionitrile was 97.8% as determined by gas chromatography. Calculations showed that the per-pass conversion rate of the acrylonitrile hydration reaction was 61%, and the yield of 3-hydroxypropionitrile was 39%.

[0033] The results of Example 1 show that under these conditions, the per-pass conversion rate of acrylonitrile in the hydration reaction of acrylonitrile is only 61%, and a large amount of di(cyanoethyl)ether is generated. After cracking the di(cyanoethyl)ether, the target product 3-hydroxypropionitrile is obtained with a per-pass yield of 39%, which is low and the process is relatively complicated.

[0034] Example 2

[0035] a. Place 80g of a mixed solution containing 1wt% NaHCO₃ and 1wt% Na₂CO₃ aqueous solutions, 53.06g (1mol) acrylonitrile, and 53g ethyl acetate in a 0.5L autoclave. Replace the atmosphere with nitrogen three times. Start stirring, set the speed to 200rpm, and heat to 110°C (to a pressure of approximately 0.12MPa). Hold the mixture at this temperature for 2h, then cool.

[0036] b. Allow the reaction solution obtained in step a to stand and separate;

[0037] c. The upper organic layer obtained in step b was recovered and reused, and a sample was taken and the residual acrylonitrile content was 15.9 g by gas chromatography;

[0038] d. Neutralize the lower aqueous layer obtained in step b with weak acid to pH 6.0-7.0;

[0039] e. Concentrate the mixture obtained in step d under reduced pressure to obtain a light yellow liquid, take sample, and detect its content by gas chromatography (3-hydroxypropionitrile 79%, di(cyanoethyl)ether 20%, acrylamide 0.6%);

[0040] f. Distill the yellow liquid obtained in step e through a rectification column to obtain 3-hydroxypropionitrile 37.7 g (GC purity 99.2%). It is calculated that the single-pass conversion rate of the acrylonitrile hydration reaction reaches 70%, and the yield of 3-hydroxypropionitrile is 53%.

[0041] The results of Example 2 show that after adding the hydrophobic solvent ethyl acetate, the selectivity of the acrylonitrile hydration reaction is improved, the amount of the byproduct di(cyanoethyl)ether is reduced, the single-pass yield of 3-hydroxypropionitrile is improved, and the single-pass conversion rate of acrylonitrile is also improved.

[0042] Example 3

[0043] a. Put 80 g of a mixed solution containing NaHCO3 (1 wt%) and Na2CO3 (1 wt%) aqueous solution and 53.06 g (1 mol) of acrylonitrile 53 g of toluene into a 0.5 L high-pressure reaction kettle, replace the internal gas three times with nitrogen. Turn on the stirring, set the stirring speed to 200 rpm, heat to 110°C, the pressure in the tank is about 0.1 MPa, after heat preservation for 2 h, cool down;

[0044] b. Let the reaction liquid obtained in step a stand and separate;

[0045] c. Recover and reuse the upper organic layer obtained in step b, and detect the residual amount of acrylonitrile by gas chromatograph, which is 14.8 g;

[0046] d. Neutralize the lower aqueous layer obtained in step b with weak acid to pH 6.0-7.0;

[0047] e. Concentrate the mixture obtained in step d under reduced pressure to obtain a light yellow liquid, take sample, and detect its content by gas chromatography (3-hydroxypropionitrile 84%, di(cyanoethyl)ether 14.5%, acrylamide 0.6%);

[0048] f. Distill the yellow liquid obtained in step e through a rectification column to obtain 3-hydroxypropionitrile 42.7 g (GC purity 99.2%). It is calculated that the single-pass conversion rate of the acrylonitrile hydration reaction reaches 74%, and the yield of 3-hydroxypropionitrile is 60%.

[0049] The results of Example 3 show that after the hydrophobic solvent is replaced by toluene from ethyl acetate, the single-pass conversion rate and yield of the acrylonitrile hydration reaction are improved. This may be because the polarity of toluene is lower than that of ethyl acetate, which reduces the solubility of the product in the organic solvent, thereby more effectively alleviating the further reaction of acrylonitrile with the product 3-hydroxypropionitrile to form the side reaction product di(cyanoethyl) ether, thereby improving the selectivity of the acrylonitrile hydration reaction.

[0050] Example 4

[0051] a. Place 80g of a mixed solution containing 1wt% NaHCO3 and 1wt% Na2CO3 aqueous solutions, 53.06g (1mol) acrylonitrile, and 53g cyclohexane in a 0.5L autoclave. Replace the atmosphere with nitrogen three times. Start stirring, set the speed to 200rpm, and heat to 110°C (to a pressure of approximately 0.12MPa). Hold the mixture at this temperature for 2h, then cool.

[0052] b. Allow the reaction solution obtained in step a to stand and separate;

[0053] c. The upper organic layer obtained in step b was recovered and reused, and a sample was taken and the residual acrylonitrile content was 10.6 g by gas chromatography;

[0054] d. Neutralize the lower aqueous layer obtained in step b with a weak acid to a pH of 6.0-7.0;

[0055] e. The mixed solution obtained in step d was concentrated under reduced pressure to obtain a light yellow liquid, and a sample was taken. The content thereof was detected by gas chromatography (3-hydroxypropionitrile 88.2%, di(cyanoethyl)ether 11.1%, acrylamide 0.6%).

[0056] f. The yellow liquid obtained in step e was distilled in a distillation tower to obtain 51.2 g of 3-hydroxypropionitrile (GC purity 99.2%). Testing showed that the acrylonitrile conversion rate in the acrylonitrile hydration reaction reached 80%, and the yield of 3-hydroxypropionitrile was 72%.

[0057] The results of Example 4 show that replacing the hydrophobic solvent from toluene with the less polar cyclohexane significantly improved the single-pass conversion and yield of the acrylonitrile hydration reaction. The formation of di(cyanoethyl)ether as a side reaction product between acrylonitrile and the product 3-hydroxypropionitrile was further alleviated, significantly improving product selectivity. This suggests that reducing solvent polarity is beneficial to the selectivity of the hydration reaction.

[0058] Figure 1 : This is the gas chromatogram of the light yellow liquid after the aqueous phase is concentrated in this example, wherein the peak at 17.4 min corresponds to the 3-hydroxypropionitrile peak, and the peak at 27.3 min corresponds to the di(cyanoethyl)ether peak.

[0059] Example 5

[0060] a. Place 80g of a mixed solution containing 1wt% NaHCO3 and 1wt% Na2CO3 aqueous solutions, 53.06g (1mol) acrylonitrile, and 53g cyclohexane in a 0.5L autoclave. Replace the atmosphere with nitrogen three times. Start stirring, set the speed to 200rpm, and heat to 120°C (to a pressure of approximately 0.15MPa). Hold the mixture at this temperature for 2h, then cool.

[0061] b. Allow the reaction solution obtained in step a to stand and separate;

[0062] c. The upper organic layer obtained in step b was recovered and reused, and a sample was taken and the residual amount of acrylonitrile was detected by gas chromatography and was 8.4 g;

[0063] d. Neutralize the lower aqueous layer obtained in step b with a weak acid to a pH of 6.0-7.0;

[0064] e. The mixed solution obtained in step d was concentrated under reduced pressure to obtain a light yellow liquid, and a sample was taken, and its content was detected by gas chromatography (3-hydroxypropionitrile 87.2%, di(cyanoethyl) ether 11.2%, acrylamide 0.6%);

[0065] f. The yellow liquid obtained in step e was distilled through a distillation tower to obtain 50.8 g of 3-hydroxypropionitrile (GC purity 99.2%). Ultimately, the acrylonitrile per-pass conversion rate reached 84%, and the 3-hydroxypropionitrile yield was 71.3%.

[0066] The results of Example 5 show that under the action of a mixed base catalyst and the addition of a weakly polar hydrophobic solvent, cyclohexane, increasing the temperature slightly improves the conversion rate but has little effect on the yield.

[0067] Example 6

[0068] a. Place 80g of a mixed solution containing 1wt% NaHCO3 and 1wt% Na2CO3 aqueous solution, 53.06g (1mol) acrylonitrile, and 53g cyclohexane in a 0.5L autoclave. Replace the atmosphere with nitrogen three times. Start stirring, set the speed to 200rpm, and heat to 110°C (to a pressure of approximately 0.12MPa). Hold the mixture at this temperature for 4h, then cool.

[0069] b. Allow the reaction solution obtained in step a to stand and separate;

[0070] c. The upper organic layer obtained in step b was recovered and reused, and a sample was taken and the residual acrylonitrile content was 8.6 g by gas chromatography;

[0071] d. Neutralize the lower aqueous layer obtained in step b with a weak acid to a pH of 6.0-7.0;

[0072] e. The mixture obtained in step d was concentrated under reduced pressure to obtain a light yellow liquid. The sample was detected by gas chromatography. The content was 3-hydroxypropionitrile 88.0%, di(cyanoethyl)ether 10.9%, and acrylamide 0.7%.

[0073] f. The yellow liquid obtained in step e was rectified by a rectification tower to obtain 50.5 g of 3-hydroxypropionitrile (GC purity 99.2%). Finally, the one-way conversion rate of acrylonitrile was 83.7%, and the yield of 3-hydroxypropionitrile was 71.0%.

[0074] The results of Example 6 show that, under the action of a mixed base catalyst and with the addition of a weakly polar hydrophobic solvent cyclohexane, extending the reaction time slightly improves the conversion rate and has little effect on the yield.

[0075] The above description is merely preferred embodiments of the present application, and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made without departing from the technical principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for synthesizing 3-hydroxypropionitrile with high selectivity, characterized in that, In the presence of a hydrophobic solvent and an alkaline catalyst, acrylonitrile and water are stirred and reacted at 80-150° C. and 0.1-0.5 MPa to generate 3-hydroxypropionitrile. In the reaction system, the hydrophobic solvent and water constitute a two-phase reaction system, acrylonitrile dissolves in the hydrophobic solvent, and the generated 3-hydroxypropionitrile dissolves in the water. Wherein, the hydrophobic solvent is selected from at least one of ethyl acetate, petroleum ether, n-hexane, cyclohexane, benzene and toluene.

2. The method for synthesizing 3-hydroxypropionitrile with high selectivity according to claim 1, wherein The alkaline catalyst is one or more of alkali metal carbonates and bicarbonates.

3. The method for highly selectively synthesizing 3-hydroxypropionitrile according to claim 1, wherein The stirring reaction time is 1-8h.

4. The method for highly selectively synthesizing 3-hydroxypropionitrile according to claim 1, wherein The mass ratio of the acrylonitrile to the hydrophobic solvent is 1:1-2.

5. The method for highly selectively synthesizing 3-hydroxypropionitrile according to claim 1, wherein The molar ratio of acrylonitrile to water is 1:1-20.

6. The method for highly selectively synthesizing 3-hydroxypropionitrile according to claim 1, wherein Based on the molar amount of acrylonitrile, the amount of the alkaline catalyst is 0.5-5 mol%.

7. The method for synthesizing 3-hydroxypropionitrile with high selectivity according to any one of claims 1 to 6, wherein Here are the steps: S1, adding acrylonitrile, a hydrophobic solvent, water and an alkaline catalyst into a closed reaction vessel to form an organic-aqueous two-phase reaction system, and heating the reaction; in the reaction system, acrylonitrile is dissolved in the hydrophobic solvent, and the generated 3-hydroxypropionitrile is dissolved in water, and after the reaction is completed, a two-phase mixture is obtained; S2. After cooling the two-phase mixture, separate the organic phase and recycle it; S3. Separate 3-hydroxypropionitrile by distillation from the aqueous phase.

8. The method for highly selectively synthesizing 3-hydroxypropionitrile according to claim 7, wherein S3 also includes neutralizing the aqueous phase and then distilling and separating 3-hydroxypropionitrile.

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