A method for producing succinic acid by hydrolytic crystallization of succinic anhydride

Abstract

The application provides a method for producing succinic acid by hydrolytic crystallization of succinic anhydride, which comprises the following steps: adding water into an organic solution of succinic anhydride, mixing thoroughly, allowing the succinic anhydride in the solution to react with water, cooling after the reaction is completed, keeping temperature, precipitating succinic acid crystals from the solution, separating the solid and the liquid, drying the crystals, and obtaining the succinic acid product. The method directly adds water into the organic solution of succinic anhydride to perform the hydrolytic reaction of succinic anhydride, and the process of separating the succinic anhydride from the organic solvent by rectification is omitted. The reaction product after hydrogenation of succinic anhydride, which is generally tetrahydrofuran or gamma-butyrolactone in which succinic anhydride is dissolved, is directly treated, the process is simplified, and the equipment investment and operation energy consumption are reduced.

Description

Technical Field

[0001] This invention relates to the field of succinic acid production, specifically a method for producing succinic acid by hydrolysis and crystallization of succinic anhydride. Background Technology

[0002] Succinic acid, also known as succinic acid, is an important chemical and pharmaceutical intermediate and a key monomer in the production of biodegradable materials PBS and PBSA. Furthermore, succinic acid is widely used in numerous industries, including food, pharmaceuticals, agriculture, coatings, dyes, plastics, rubber, photographic chemicals, surfactants, lubricants, and electroplating.

[0003] The main production methods for succinic acid include electrochemical reduction, bio-fermentation, and catalytic hydrogenation. Among these, catalytic hydrogenation is the only method currently capable of matching the production capacity of PBS / PBSA due to its ease of scaling up production and its high conversion rate, selectivity, and product purity. This method uses an organic solution of maleic anhydride as raw material, and the hydrogenation product is an organic solution of succinic anhydride. Succinic anhydride is obtained through distillation, and succinic acid is obtained through hydrolysis and crystallization, as shown in CN103570650A. However, during distillation, a large amount of organic solvent is a lighter component compared to succinic anhydride and must be completely vaporized and separated. This distillation process is lengthy and energy-intensive. Furthermore, the hydrolysis and crystallization process suffers from high residual succinic acid in the mother liquor and low single-pass yield. Summary of the Invention

[0004] To address the above shortcomings, this invention provides a method for producing succinic acid by hydrolysis and crystallization of succinic anhydride. This method uses the organic solution of succinic anhydride obtained from maleic anhydride production as a direct raw material, without separating the succinic anhydride, and first performs hydrolysis, thus shortening the reaction process.

[0005] To address the above technical problems, the technical objective of this invention is as follows:

[0006] A method for producing succinic acid by hydrolysis and crystallization of succinic anhydride includes the following steps:

[0007] Water is added to an organic solution of succinic anhydride and mixed thoroughly to allow the succinic anhydride to undergo a hydrolysis reaction with the water. After the reaction is complete, the temperature is lowered and then kept warm. Succinic acid crystals precipitate out of the solution and are separated from the liquid phase. The crystals are then dried to obtain the succinic acid product.

[0008] Furthermore, an organic solution of succinic anhydride refers to a solution formed by dissolving succinic anhydride in an organic solvent. The solvent is an organic solvent with high solubility for succinic anhydride but low solubility for succinic acid and good miscibility with water.

[0009] Furthermore, the solvent in the organic solution of succinic anhydride is at least one of tetrahydrofuran and γ-butyrolactone.

[0010] Furthermore, in the organic solution of succinic anhydride, the content of the solute succinic anhydride does not exceed 50 wt%, preferably 10-20 wt%.

[0011] Furthermore, the amount of water added is slightly greater than the amount of succinic anhydride required for complete reaction in the organic solution of succinic anhydride, that is, the molar ratio of water added to succinic anhydride is not less than 1, preferably (1-1.5):1, more preferably (1-1.2):1.

[0012] Furthermore, the operating temperature and pressure of the reaction between succinic anhydride and water should be controlled so that the selected organic solvent and water neither solidify nor vaporize, with a pressure of 0.1-0.5 MPa, preferably atmospheric pressure, and a temperature of 20-50℃.

[0013] Furthermore, the reaction time of succinic anhydride and water is not less than 1 hour, preferably 3-5 hours.

[0014] Furthermore, after the succinic anhydride reacts with water, the temperature is lowered, and the final temperature of the cooling process is not higher than 40°C, preferably 10-30°C.

[0015] Furthermore, the heat preservation time is not less than 1 hour, preferably 1-2 hours.

[0016] Furthermore, the solid-liquid separation methods include, but are not limited to, filtration, sedimentation, and centrifugation.

[0017] Furthermore, the drying process can employ any industrially common drying method to dry succinic acid; the moisture content of the dried product should meet the product's factory qualification standards.

[0018] Furthermore, the liquid phase after solid-liquid separation contains organic solvent, a small amount of succinic acid, and a small amount of water. The water and succinic acid can be removed by distillation or other methods, and the solvent can be recovered and reused in the maleic anhydride hydrogenation reaction or used for other purposes.

[0019] The advantages of this invention compared to existing technologies are as follows:

[0020] (1) In this invention, water is directly added to the organic solution of succinic anhydride to carry out the hydrolysis reaction of succinic anhydride, which eliminates the process of separating succinic anhydride from organic solvent by means of distillation, etc. The reaction product after hydrogenation of maleic anhydride (generally tetrahydrofuran or γ-butyrolactone dissolved in succinic anhydride) is directly processed, which simplifies the process and reduces equipment investment and operating energy consumption.

[0021] (2) After the hydrolysis reaction, the succinic acid produced has very low solubility in organic solvents, which avoids the problem of high residual succinic acid content in the crystallization mother liquor in the existing hydrolysis crystallization process, resulting in low single-pass yield.

[0022] Other features and advantages of the present invention will be described in detail in the following detailed description section. Detailed Implementation

[0023] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way.

[0024] Example 1

[0025] Take 1000g of an organic solution of succinic anhydride, specifically composed of 900g of γ-butyrolactone and 100g of succinic anhydride, add 18g of water (molar ratio of water to succinic anhydride 1:1), and mix thoroughly at atmospheric pressure and 50℃ for 3 hours. After mixing, cool to 30℃ and maintain this temperature for 1 hour. Filter to separate the crystals from the liquid phase. After drying the crystals, 92.0g of product is obtained. The water content is determined to be 0.3%, and the purity of succinic acid (excluding water) is >99.7%, with a yield of 77.7%.

[0026] Example 2

[0027] Take 1000g of an organic solution of succinic anhydride, specifically composed of 800g of γ-butyrolactone and 200g of succinic anhydride, add 54g of water (molar ratio of water to succinic anhydride 1.5:1), and mix thoroughly at atmospheric pressure and 20℃ for 5h. After mixing, cool to 10℃ and maintain the temperature for 2h. Separate the crystallization and liquid phases by centrifugation. After drying the crystals, 223.3g of product was obtained. The water content was determined to be 0.4%, and the purity of succinic acid (excluding water) was >99.8%, with a yield of 94.2%.

[0028] Example 3

[0029] Take 1000g of an organic solution of succinic anhydride, specifically composed of 850g tetrahydrofuran and 150g succinic anhydride, add 34g of water (molar ratio of water to succinic anhydride 1.26:1), and mix thoroughly at 0.2MPa and 30℃ for 4h. After mixing, cool to 15℃ and maintain the temperature for 2h. Separate the crystallization and liquid phases by precipitation. After drying the crystals, 158.8g of product was obtained. The water content was determined to be 0.4%, and the purity of succinic acid (excluding water) was >99.7%, with a yield of 89.4%.

[0030] Example 4

[0031] Take 2000g of an organic solution of succinic anhydride, specifically composed of 1600g tetrahydrofuran and 400g succinic anhydride, add 100g of water (molar ratio of water to succinic anhydride 1.39:1), and mix thoroughly at 0.5MPa and 50℃ for 3 hours. After mixing, cool to 30℃ and maintain this temperature for 2 hours. Separate the crystallization and liquid phases by precipitation. After drying the crystals, 388.5g of product was obtained. The water content was determined to be 0.4%, and the purity of succinic acid (excluding water) was >99.7%, with a yield of 82.0%.

[0032] Example 5

[0033] Take 2000g of an organic solution of succinic anhydride, specifically composed of 1900g of butyrolactone and 100g of succinic anhydride, add 20g of water (molar ratio of water to succinic anhydride 1.11:1), and mix thoroughly at atmospheric pressure and 20℃ for 5h. After mixing, cool to 10℃ and maintain the temperature for 2h. Separate the crystallization and liquid phases by precipitation. After drying the crystals, 84.0g of product is obtained. The water content is determined to be 0.3%, and the purity of succinic acid (excluding water) is >99.7%, with a yield of 70.9%.

[0034] Comparative Example 1

[0035] 1000g of succinic anhydride organic solution, specifically composed of 900g of γ-butyrolactone and 100g of succinic anhydride, was distilled under reduced pressure to obtain liquid succinic anhydride. This liquid anhydride was mixed with 350g of water and hydrolyzed at 80℃ for 1 hour. After the reaction was completed, a succinic acid solution was generated. The solution was cooled to 30℃ to crystallize, filtered to obtain succinic acid crystals, and dried to obtain 82g of succinic acid with a water content of 0.4%. Excluding water, the purity of the succinic acid was >99.7%, and the yield of succinic acid was 69.2%.

Claims

1. A method for producing succinic acid by hydrolysis and crystallization of succinic anhydride, comprising the following steps: Water is added to an organic solution of succinic anhydride and mixed thoroughly to allow the succinic anhydride to undergo a hydrolysis reaction with the water. After the reaction is complete, the temperature is lowered and then kept warm. Succinic acid crystals precipitate out of the solution and are separated from the liquid phase. The crystals are then dried to obtain the succinic acid product.

2. The method according to claim 1, characterized in that, The solvent in the organic solution of succinic anhydride is at least one of tetrahydrofuran and γ-butyrolactone.

3. The method according to claim 1, characterized in that, In organic solutions of succinic anhydride, the content of the solute succinic anhydride does not exceed 50 wt%.

4. The method according to claim 1, characterized in that, In organic solutions of succinic anhydride, the content of the solute succinic anhydride is 10-20 wt%.

5. The method according to claim 1, characterized in that, The molar ratio of water to succinic anhydride should not be less than 1.

6. The method according to claim 5, characterized in that, The molar ratio of water to succinic anhydride is 1-1.5:

1.

7. The method according to claim 1, characterized in that, The reaction of succinic anhydride with water occurs at a pressure of 0.1-0.5 MPa and a temperature of 20-50℃.

8. The method according to claim 1, characterized in that, The reaction time of succinic anhydride and water should not be less than 1 hour.

9. The method according to claim 8, characterized in that, The reaction time for succinic anhydride and water is 3-5 hours.

10. The method according to claim 1, characterized in that, After succinic anhydride reacts with water, the temperature is lowered, and the final temperature of the cooling process should not exceed 40℃.

11. The method according to claim 10, characterized in that, After succinic anhydride reacts with water, it is cooled down, with the final temperature being 10-30℃.

12. The method according to claim 1, characterized in that, The heat preservation time is 1-2 hours.