A method for preparing high-purity sodium acetate trihydrate / anhydrous sodium acetate by a stepwise cooling process

Abstract

The application belongs to the technical field of sodium acetate production, and discloses a method for preparing high-purity sodium acetate trihydrate / anhydrous sodium acetate by using a cascade cooling process. The sodium hydroxide aqueous solution is placed in a reaction kettle, and acetic acid is added dropwise for neutralization reaction. The temperature of the reaction kettle is increased for concentration. The concentrated solution is cooled and crystallized by using a cascade cooling method. The crystallized mixed solution is centrifuged and separated to obtain high-purity sodium acetate trihydrate. The high-purity sodium acetate trihydrate is dried to obtain high-purity sodium acetate anhydrous. The slow-release and dynamic crystallization coupling process is adopted. By controlling the cooling and crystallization process, the impurity entrainment and wrapping are reduced, the purity and particle size uniformity of the product are improved, and secondary crystallization is avoided. The process flow is simpler without the need for decolorization and filtration process treatment. The impurity treatment and the crystallization stage are coupled, the impurity content is controlled in the process, the product purity is ensured, and finally the sodium acetate product with a purity of greater than or equal to 99.9% is obtained.

Description

Technical Field

[0001] This invention relates to the field of sodium acetate production technology, and in particular to a method for preparing high-purity trihydrate / anhydrous sodium acetate using a stepped cooling process. Background Technology

[0002] Sodium acetate is an important organic chemical product widely used in the food industry, pharmaceutical manufacturing, environmental protection, and chemical synthesis. It is commonly used as a food additive, pharmaceutical buffer system, wastewater treatment agent, dyeing and printing auxiliary agent, and chemical intermediate, and has considerable market potential. High-purity sodium acetate is also an important fine chemical. With its high purity, low impurity content, and excellent performance, it plays a crucial role in multiple industries. In food processing, sodium acetate is used as a food additive to adjust acidity, improve taste, and extend shelf life. In the pharmaceutical industry, sodium acetate is used to prepare drug formulations such as injections and oral solutions. In biopharmaceuticals, sodium acetate is used as a buffer to adjust pH in biological reaction systems such as vaccine production and monoclonal antibody culture. In the electronics industry, it is an indispensable auxiliary material in the manufacturing of high-end electronic products, used as a semiconductor etching solution and LCD panel cleaning agent.

[0003] With continuous technological advancements and sustained market growth, the requirements for sodium acetate preparation processes are constantly increasing. Currently, the main method for preparing sodium acetate involves a double decomposition reaction between acetic acid and sodium hydroxide or sodium carbonate to obtain a sodium acetate solution, which is then processed through impurity removal filtration, heating concentration, cooling crystallization, and centrifugal drying. These processes still have shortcomings, such as cumbersome production processes, low efficiency, and difficulty in meeting the needs of large-scale production. Furthermore, the sodium acetate products prepared by existing processes exhibit uneven particle size distribution, failing to meet the requirements of some applications with high particle size requirements. In addition, the purity of the prepared products is low, with residual unreacted raw materials and metallic impurities (such as Fe and K), which cannot meet the purity requirements of high-end applications such as pharmaceuticals, high-end chemical synthesis, electronic materials, and new material manufacturing, requiring further improvement. To address these issues, various improvement strategies have been implemented domestically. For example, Chinese patent CN106365980A discloses a method for preparing anhydrous sodium acetate, which involves reacting glacial acetic acid with sodium hydroxide, followed by activated carbon decolorization, filtration, and drying to obtain granular anhydrous sodium acetate. While eliminating the need for concentration, crystallization, and centrifugal dehydration, this process adds activated carbon treatment, resulting in a weaker effect on production efficiency. Furthermore, the purity of the prepared sodium acetate is not specified. Chinese patent CN114539049A discloses a sodium acetate production process including reaction, concentration, crystallization, centrifugal separation, recrystallization, and centrifugal drying. Although the prepared sodium acetate solid has a uniform particle size, the entire operation is overly cumbersome, and the purity of the prepared sodium acetate is also not specified. Additionally, Chinese patent CN109734582A discloses a sodium acetate production process that modifies the cooling method of the crystallization device by introducing cold air into the concentrated liquid for cooling. While the purity of the prepared sodium acetate reaches 99.9%, it still involves impurity removal and has a complex crystallization equipment design, limiting its large-scale application.

[0004] In view of the problems existing in the above research, it is particularly important to develop a high-efficiency, low-cost, high-purity sodium acetate preparation process with uniform particle size. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process, thereby overcoming the aforementioned deficiencies in the prior art.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process, comprising the following steps: (1) Neutralization reaction: Sodium hydroxide aqueous solution is placed in a reaction vessel, acetic acid is added dropwise to carry out the neutralization reaction, and sodium acetate solution is obtained; (2) Evaporation and concentration: Increase the temperature of the reaction vessel to concentrate the sodium acetate solution and obtain a concentrated solution; (3) Cooling and crystallization: The concentrate is transferred to a crystallization vessel and cooled and crystallized by step cooling to obtain a crystallized mixture; (4) Centrifugal separation: The crystallized mixture is placed in a centrifuge for centrifugal separation, and then filtered to obtain high-purity sodium acetate trihydrate; (5) Drying: Place the high-purity sodium acetate trihydrate in a drying oven to dry, and obtain high-purity anhydrous sodium acetate.

[0007] Preferably, in step (1), the mass fraction of the sodium hydroxide aqueous solution is 24-32%.

[0008] Preferably, in step (1), the conditions for the neutralization reaction are: a stirring rate of 100~300 rpm, a reaction vessel temperature of 60~80℃, and the reaction continues until the solution pH is 7~7.5.

[0009] Preferably, in step (2), the temperature of the reactor is 90°C; the concentration method is vacuum concentration; and the mass fraction of sodium acetate in the concentrate is 45-50%.

[0010] As a preferred embodiment, in step (3), the specific method of cooling crystallization by using a stepped cooling method is as follows: first, the temperature is lowered to 50-60℃ at a rate of 1.5-3℃ / min, sodium acetate solid is added as a seed crystal, and then the temperature is lowered to 10-30℃ at a rate of 0.5-2℃ / min, and maintained for 1-2 hours.

[0011] As a preferred method, in step (5), the specific drying method is as follows: first, dry in a forced-air dryer at 60~70℃ for 2~3 hours, and then dry in a vacuum dryer at 120~130℃ for 1~2 hours.

[0012] Preferably, in step (4), the purity of the high-purity sodium acetate trihydrate is 99.9~100%; in step (5), the purity of the high-purity anhydrous sodium acetate is 99.9~100%.

[0013] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: This invention discloses a method for preparing high-purity trihydrate / anhydrous sodium acetate using a stepped cooling process. The method employs a slow-release + dynamic crystallization coupling process. By controlling the cooling and crystallization process, impurity entrainment and encapsulation are reduced. Impurities are then retained in the aqueous solution via centrifugation, thereby improving product purity and particle size uniformity and preventing secondary crystallization. This slow-release + dynamic crystallization coupling process eliminates the need for decolorization and filtration, simplifying the process flow. Simultaneously, by coupling impurity treatment with the crystallization stage, the impurity content is controlled at the process level, ensuring product purity and ultimately yielding sodium acetate with a purity ≥99.9%. This not only improves production efficiency but also reduces the production cost of high-purity sodium acetate, meeting the quality requirements of the high-purity sodium acetate market. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0015] Figure 1 A schematic diagram of the process for preparing high-purity trihydrate / anhydrous sodium acetate using the stepped cooling process of this invention. Detailed Implementation

[0016] This invention provides a method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process, comprising the following steps: (1) Neutralization reaction: Sodium hydroxide aqueous solution is placed in a reaction vessel, acetic acid is added dropwise to carry out the neutralization reaction, and sodium acetate solution is obtained; (2) Evaporation and concentration: Increase the temperature of the reaction vessel to concentrate the sodium acetate solution and obtain a concentrated solution; (3) Cooling and crystallization: The concentrate is transferred to a crystallization vessel and cooled and crystallized by step cooling to obtain a crystallized mixture; (4) Centrifugal separation: The crystallized mixture is placed in a centrifuge for centrifugal separation, and then filtered to obtain high-purity sodium acetate trihydrate; (5) Drying: Place the high-purity sodium acetate trihydrate in a drying oven to dry, and obtain high-purity anhydrous sodium acetate.

[0017] In this invention, in step (1), the mass fraction of the sodium hydroxide aqueous solution is preferably 24-32%, and more preferably 30-32%.

[0018] In this invention, in step (1), the conditions for the neutralization reaction are as follows: the stirring rate is preferably 100~300 rpm, more preferably 200~300 rpm, the reaction vessel temperature is preferably 60~80℃, more preferably 70~80℃, and the pH of the solution is preferably 7~7.5, more preferably 7.2~7.5.

[0019] In this invention, in step (2), the temperature of the reactor is preferably 90°C.

[0020] In this invention, in step (2), the concentration method is preferably vacuum concentration; the mass fraction of sodium acetate in the concentrate is preferably 45-50%, more preferably 48-50%.

[0021] In this invention, in step (3), the preferred method for cooling crystallization using a stepped cooling approach is: first, cooling to 50-60°C at a rate of 1.5-3°C / min, adding sodium acetate solid as a seed crystal, and then cooling to 10-30°C at a rate of 0.5-2°C / min, and maintaining for 1-2 hours; more preferably, cooling to 50-55°C at a rate of 2-3°C / min, adding sodium acetate solid as a seed crystal, and then cooling to 10-20°C at a rate of 0.5-1°C / min, and maintaining for 1-2 hours.

[0022] In this invention, the drying method in step (5) is preferably: first drying at 60~70℃ with forced air for 2~3 hours, and then drying under vacuum at 120~130℃ for 1~2 hours; more preferably: first drying at 65~70℃ with forced air for 2~3 hours, and then drying under vacuum at 120~125℃ for 1~2 hours.

[0023] In this invention, in step (4), the purity of the high-purity sodium acetate trihydrate is preferably 99.9~100%; in step (5), the purity of the high-purity anhydrous sodium acetate is preferably 99.9~100%.

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] A method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process includes the following steps: 140g of sodium hydroxide was dissolved in 360g of pure water to prepare a 28% sodium hydroxide solution. The solution was then placed in a reaction vessel, and acetic acid was added dropwise at a rate of 4mL / min at 60℃ and 200rpm to neutralize the solution until the pH reached 7.2. The reaction vessel temperature was then increased to 90℃, and the solution was concentrated under reduced pressure until the sodium acetate content was 48%. The cooling and crystallization process was as follows: the temperature was lowered to 50℃ at a rate of 3℃ / min, and solid sodium acetate (99.9% purity) was added as a seed crystal. The temperature was then lowered to 20℃ at a rate of 1℃ / min and maintained for 1 hour. The crystallized mixture was centrifuged and filtered to obtain solid sodium acetate trihydrate. The drying process was as follows: the product was dried at 60℃ with forced air for 3 hours, and then dried under vacuum at 130℃ for 1 hour to obtain anhydrous sodium acetate. HPLC analysis showed that the purity of the anhydrous sodium acetate product was 99.90%.

[0027] Example 2

[0028] A method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process includes the following steps: 160g of sodium hydroxide was dissolved in 340g of pure water to prepare a 32% sodium hydroxide solution. The solution was then placed in a reaction vessel, and acetic acid was added dropwise at a rate of 5mL / min at 70℃ and 200rpm to neutralize the solution until the pH reached 7.3. The reaction vessel temperature was then increased to 90℃, and the solution was concentrated under reduced pressure until the sodium acetate content was 49%. The cooling and crystallization process was as follows: the temperature was lowered to 50℃ at a rate of 2℃ / min, and solid sodium acetate (99.9% purity) was added as a seed crystal. The temperature was then lowered to 10℃ at a rate of 0.5℃ / min and maintained for 1 hour. The crystallized mixture was centrifuged and filtered to obtain solid sodium acetate trihydrate. The drying process was as follows: the product was dried at 70℃ with forced air for 2 hours, and then dried under vacuum at 120℃ for 2 hours to obtain anhydrous sodium acetate. HPLC analysis showed that the purity of the anhydrous sodium acetate product was 99.98%.

[0029] Example 3

[0030] A method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process includes the following steps: 150g of sodium hydroxide was dissolved in 350g of pure water to prepare a 30% sodium hydroxide solution. The solution was then placed in a reaction vessel, and acetic acid was added dropwise at a rate of 6mL / min at 80℃ and 100rpm to neutralize the solution until the pH reached 7.5. The reaction vessel temperature was then increased to 90℃, and the solution was concentrated under reduced pressure until the sodium acetate content was 48%. The cooling and crystallization process was as follows: the temperature was lowered to 50℃ at a rate of 3℃ / min, and solid sodium acetate (99.9% purity) was added as a seed crystal. The temperature was then lowered to 20℃ at a rate of 1.5℃ / min and maintained for 2 hours. The crystallized mixture was centrifuged and filtered to obtain solid sodium acetate trihydrate. The drying process was as follows: the product was dried at 70℃ with forced air for 2 hours, and then dried under vacuum at 120℃ for 2 hours to obtain anhydrous sodium acetate. The purity of the anhydrous sodium acetate product was determined by HPLC to be 99.93%.

[0031] Example 4

[0032] A method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process includes the following steps: 160g of sodium hydroxide was dissolved in 340g of pure water to prepare a 32% sodium hydroxide solution. The solution was then placed in a reaction vessel, and acetic acid was added dropwise at a rate of 5mL / min at 70℃ and 100rpm to neutralize the solution until the pH reached 7.2. The reaction vessel temperature was then increased to 90℃, and the solution was concentrated under reduced pressure until the sodium acetate content was 49%. The cooling and crystallization process was as follows: the temperature was lowered to 50℃ at a rate of 3℃ / min, and solid sodium acetate (99.9% purity) was added as a seed crystal. The temperature was then lowered to 10℃ at a rate of 1℃ / min and maintained for 1 hour. The crystallized mixture was centrifuged and filtered to obtain solid sodium acetate trihydrate. The drying process was as follows: the product was dried at 70℃ with forced air for 2 hours, and then dried under vacuum at 120℃ for 2 hours to obtain anhydrous sodium acetate. HPLC analysis showed that the purity of the anhydrous sodium acetate product was 99.97%.

[0033] Comparative Example 1

[0034] 160g of sodium hydroxide was dissolved in 340g of pure water to prepare a 32% sodium hydroxide solution. The solution was then placed in a reaction vessel, and acetic acid was added dropwise at a rate of 5mL / min at 70℃ and 100rpm to neutralize the solution until the pH reached 7.4. The reaction vessel temperature was then increased to 90℃, and the solution was concentrated under reduced pressure until the sodium acetate content was 49%. The solution was then rapidly cooled to 10℃ and maintained for 1 hour. The crystallized mixture was centrifuged and filtered to obtain sodium acetate trihydrate solid. The drying process was as follows: drying at 60℃ for 2 hours, followed by vacuum drying at 120℃ for 1 hour, finally yielding anhydrous sodium acetate product. HPLC analysis showed that the purity of the anhydrous sodium acetate product was 96.28%.

[0035] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process, characterized in that, Includes the following steps: (1) Neutralization reaction: Sodium hydroxide aqueous solution is placed in a reaction vessel, acetic acid is added dropwise to carry out the neutralization reaction, and sodium acetate solution is obtained; (2) Evaporation and concentration: Increase the temperature of the reaction vessel to concentrate the sodium acetate solution and obtain a concentrated solution; (3) Cooling and crystallization: The concentrate is transferred to a crystallization vessel and cooled and crystallized by step cooling to obtain a crystallized mixture; (4) Centrifugal separation: The crystallized mixture is placed in a centrifuge for centrifugal separation, and then filtered to obtain high-purity sodium acetate trihydrate; (5) Drying: Place the high-purity sodium acetate trihydrate in a drying oven to dry, and obtain high-purity anhydrous sodium acetate.

2. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (1), the mass fraction of the sodium hydroxide aqueous solution is 24-32%.

3. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (1), the conditions for the neutralization reaction are: stirring speed of 100~300 rpm, reaction vessel temperature of 60~80℃, and reaction until the solution pH is 7~7.

5.

4. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (2), the temperature of the reactor is 90°C; the concentration method is vacuum concentration; and the mass fraction of sodium acetate in the concentrate is 45-50%.

5. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (3), the specific method for cooling crystallization by using a stepped cooling method is as follows: first, the temperature is lowered to 50-60℃ at a rate of 1.5-3℃ / min, sodium acetate solid is added as a seed crystal, and then the temperature is lowered to 10-30℃ at a rate of 0.5-2℃ / min and maintained for 1-2 hours.

6. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (5), the specific drying method is as follows: first, dry in a forced-air dryer at 60~70℃ for 2~3 hours, and then dry in a vacuum dryer at 120~130℃ for 1~2 hours.

7. The method for preparing high-purity sodium acetate trihydrate / anhydrous using a stepped cooling process according to claim 1, characterized in that, In step (4), the purity of the high-purity sodium acetate trihydrate is 99.9~100%; in step (5), the purity of the high-purity anhydrous sodium acetate is 99.9~100%.

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