Water washing impurity removal and membrane separation combined process for recovering ethyl acetate in sucralose production and application

Abstract

The invention belongs to the technical field of fine chemical engineering, and particularly relates to a washing impurity removal and membrane separation combined process for recovering ethyl acetate in sucralose production and application. According to the method, ethyl acetate recovery in the sucralose alkaline hydrolysis workshop section is replaced by pure water cleaning, and impurities and moisture in ethyl acetate are removed and recovered through membrane separation, so that production instability factors caused by equipment corrosion are reduced, and the yield and the product quality of sucralose in the alkaline hydrolysis workshop are improved.

Description

Technical Field

[0001] This invention belongs to the field of fine chemical technology, specifically relating to the combined process and application of water washing and membrane separation for the recovery of ethyl acetate in sucralose production. Background Technology

[0002] Sucralose, a highly sweetener, holds an indispensable position in numerous fields such as food, beverages, pharmaceuticals, and daily chemicals due to its significant advantages, including high sweetness, low calories, and good stability. It not only satisfies people's demand for sweetness but also effectively reduces calorie intake, aligning with modern society's pursuit of healthy eating. Therefore, market demand continues to rise, and the optimization and improvement of its production process are crucial for ensuring market supply and enhancing product quality.

[0003] Ethyl acetate is widely used as an important solvent in the production of sucralose, and its recycling and reuse are of great significance for reducing production costs and improving resource utilization. However, existing technologies for processing recovered ethyl acetate have significant shortcomings, resulting in the quality of the recovered ethyl acetate failing to meet production requirements, thus hindering the improvement of sucralose production efficiency and product quality.

[0004] Currently, recovered ethyl acetate often contains a significant amount of impurities and moisture, which can negatively impact subsequent production processes. Firstly, the accumulation of impurities reduces the purity of ethyl acetate, affecting the dehydration effect in the secondary concentration process and resulting in higher moisture content in the extracted esterified sugars. Secondly, higher moisture content interferes with the esterification crystallization process, reducing the yield and purity of the crystallized sugars, thus affecting the overall yield of sucralose. This not only wastes raw materials and increases cost pressures for production companies but also negatively impacts their market competitiveness due to unstable product quality.

[0005] During production, the high temperature causes ethyl acetate to decompose, producing acetic acid which severely corrodes the feed heat exchanger and the primary vapor-phase condenser of the drying tower, leading to frequent tower maintenance and unstable production, sometimes even resulting in shutdowns. Furthermore, the consumption of medium-pressure steam is significant in daily production. Using membrane separation technology could greatly reduce production costs and minimize the impact of equipment issues on production. For example, if the moisture content of the finished product fluctuates, only the separation membrane needs to be replaced, eliminating the need for medium-pressure steam and significantly reducing production costs. At the same time, the existing processing technology lacks stability and controllability, making it difficult to accurately control the quality of the recovered ethyl acetate, leading to fluctuations in production. These fluctuations not only affect production efficiency and hinder the smooth execution of production plans but may also generate more waste due to substandard product quality, which contradicts the current concepts and requirements of green production and environmentally friendly development.

[0006] As market demands for sucralose quality and yield continue to rise, and environmental regulations become increasingly stringent, the problems with existing ethyl acetate recovery processes are becoming more and more apparent. Therefore, effectively reducing impurities and moisture in recovered ethyl acetate, improving its utilization rate, and optimizing key aspects of sucralose production have become pressing technical issues that the industry urgently needs to address. This is of significant practical importance for promoting the healthy and sustainable development of the sucralose industry. Summary of the Invention

[0007] The existing alkaline hydrolysis process for recovering ethyl acetate dehydration is prone to decomposition due to high temperature and pressure, causing significant corrosion to equipment. This results in high maintenance risks, long repair times, and high costs, impacting stable production. This invention provides a novel and efficient method that not only effectively improves the dehydration effect of recovered ethyl acetate but also reduces equipment corrosion, offering significant economic benefits.

[0008] The technical solution of this invention is as follows: On the one hand, the present invention provides a process for recovering ethyl acetate in sucralose production, comprising the following steps: (1) Pump the ethyl acetate recovered by the system into the bottom of the ethyl acetate washing tower, and add pure water from the top of the washing tower at the same time. Control the volume ratio of the recovered ethyl acetate to pure water to be 3:1-5:1, and carry out countercurrent extraction. After washing, the ethyl acetate is discharged from the top of the tower and the aqueous phase is discharged from the bottom of the tower. (2) Ethyl acetate after washing with water is fed into the primary and secondary membrane separation filters at a flow rate of 15 m³ / h. The ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.3-11 m³ / h and the aqueous phase outlet flow rate is 4-4.7 m³ / h to obtain anhydrous ethyl acetate.

[0009] Specifically, the normalized content of ethyl acetate recovered by the system in step (1) is 95% ± 0.5%.

[0010] Specifically, in step (1), the volume ratio of ethyl acetate to pure water is 3:1, 4:1, or 5:1.

[0011] Specifically, in step (2), the primary and secondary membrane separation filters use hydrophilic molecular sieve membranes and PVA membranes, respectively, with a filtration accuracy of 0.3-0.5 μm.

[0012] Specifically, in step (2), the operating pressure of the membrane separation filter is 0.2-0.3 MPa and the operating temperature is 45-55℃.

[0013] Preferably, in step (2), the operating pressure of the membrane separation filter is 0.25 MPa and the operating temperature is 50 °C.

[0014] Specifically, in step (2), the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 11 cubic meters per hour and the aqueous phase outlet flow rate is controlled to be 4 cubic meters per hour; or the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.5 cubic meters per hour and the aqueous phase outlet flow rate is controlled to be 4.5 cubic meters per hour; or the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.3 cubic meters per hour and the aqueous phase outlet flow rate is controlled to be 4.7 cubic meters per hour.

[0015] On the other hand, the present invention provides the application of the aforementioned recycling process in the industrial production of sucralose.

[0016] Specifically, the yield of sucralose is increased by reducing the impurities and moisture content in esterified crystalline sugars.

[0017] The beneficial effects of this invention are as follows: (1) Significantly improve the purity of recovered ethyl acetate. The countercurrent extraction process of water washing tower is adopted, which utilizes the density difference and immiscibility of pure water and ethyl acetate to effectively remove impurities in the recovered ethyl acetate, greatly improve the normalized content of ethyl acetate, and significantly reduce the adverse effects of impurities on subsequent production processes.

[0018] (2) Efficient removal of water and optimization of dehydration effect. After being washed with water, ethyl acetate enters a hydrophilic molecular sieve membrane and PVA. Under precise control of feed temperature, flow rate and pressure, impurities and water in the recovered ethyl acetate are further removed to obtain essentially anhydrous ethyl acetate. This process significantly improves the dehydration effect of the secondary concentration single-effect and reduces the water content of the esterified sugars collected by the single-effect, creating favorable conditions for the subsequent crystallization process.

[0019] (3) Improve the yield and purity of ester-crystallized sugar. When high-purity, low-moisture ethyl acetate is used in the ester washing process of the two-in-one filter, it can more effectively remove impurities from the crystalline sugar, improve the ester washing and impurity removal effect, and thus improve the yield and purity of ester-crystallized sugar, laying a solid foundation for the high-quality production of sucralose.

[0020] (4) Increase sucralose production capacity. Due to the increased yield of ester crystallized sugar and the reduction of impurities during the production process, the production process is smoother and more efficient, ultimately achieving an increase in the overall production capacity of sucralose, which is conducive to improving the company's production efficiency and market competitiveness.

[0021] (5) The process is stable, reliable, and easy to control. A specific structure is set in the water phase outlet pipe at the bottom of the water washing tower, which effectively stabilizes the layer interface inside the tower and makes it easy to control the water phase outlet flow rate; the flow rate, pressure and other parameters of the membrane separation filter are precisely controlled to ensure the stability and repeatability of the process, which is conducive to large-scale industrial production applications. Attached Figure Description

[0022] Figure 1This is a flow chart of the ethyl acetate washing tower and drying tower.

[0023] Figure 2 This is a flow chart for a membrane separation filter. Detailed Implementation

[0024] The present invention will be further clearly and completely illustrated below through embodiments. These embodiments are only some examples of the present invention and are not intended to limit the present invention, but are only for illustrating the present invention. Unless otherwise specified, the experimental methods used in the following embodiments are all conventional experiments, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.

[0025] Example 1 (1) The ethyl acetate recovered by the system (normalized content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, tap water is added from the top of the ethyl acetate washing tower according to the ratio of recovered ethyl acetate to pure water = 3:1. Utilizing the density difference between water and ethyl acetate, the water flows from top to bottom and performs countercurrent extraction with the ethyl acetate entering from the bottom of the tower. The ethyl acetate after washing (normalized content of more than 98%) comes out from the top of the ethyl acetate washing tower and enters the post-washing ethyl acetate tank. The aqueous phase comes out from the bottom of the tower and enters the deionized water tank.

[0026] (2) Turn on the feed pump of the membrane separator filter. After washing with water, the ethyl acetate is fed into the first-stage hydrophilic molecular sieve membrane at a rate of 15 cubic meters per hour and the temperature is controlled at about 55°C. The membrane is then filtered to remove impurities and some water from the ethyl acetate after washing. The ethyl acetate is then fed into the second-stage PVA membrane. The membrane separation pressure is adjusted and controlled at about 0.25 MPa. The ester phase outlet flow rate is 11 cubic meters per hour and the aqueous phase outlet flow rate is controlled at 4 cubic meters per hour. The water content of anhydrous ethyl acetate reaches 0.02 g / L and the ethyl acetate content reaches 99.9%.

[0027] Example 2 (1) The ethyl acetate recovered by the system (normalized content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, tap water is added from the top of the ethyl acetate washing tower according to the ratio of recovered ethyl acetate to pure water = 4:1. Utilizing the density difference between water and ethyl acetate, the water flows from top to bottom and performs countercurrent extraction with the ethyl acetate entering from the bottom of the tower. The ethyl acetate after washing (normalized content of 97.5%) exits from the top of the ethyl acetate washing tower and enters the post-washing ethyl acetate tank. The aqueous phase exits from the bottom of the tower and enters the deionized water tank.

[0028] (2) Turn on the feed pump of the membrane separator filter. After washing with water, the ethyl acetate is fed into the first-stage hydrophilic molecular sieve membrane at a rate of 15 cubic meters per hour and the temperature is controlled at about 55°C. The membrane is then filtered to remove impurities and some water from the ethyl acetate after washing. The ethyl acetate is then fed into the second-stage PVA membrane. The membrane separation pressure is adjusted and controlled at about 0.25 MPa. The ester phase outlet flow rate is 11 cubic meters per hour and the aqueous phase outlet flow rate is controlled at 4 cubic meters per hour. The water content of anhydrous ethyl acetate reaches 0.3 g / L and the ethyl acetate content reaches 99.5%.

[0029] Example 3 (1) The ethyl acetate recovered by the system (normalized content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, tap water is added from the top of the ethyl acetate washing tower according to the ratio of recovered ethyl acetate to pure water = 5:1. Taking advantage of the density difference between water and ethyl acetate, the water flows from top to bottom and performs countercurrent extraction with the ethyl acetate entering from the bottom of the tower. The ethyl acetate after washing (normalized content of 97%) comes out from the top of the ethyl acetate washing tower and enters the post-wash ethyl acetate tank. The aqueous phase comes out from the bottom of the tower and enters the deionized water tank.

[0030] (2) Turn on the feed pump of the membrane separator filter. After washing with water, the ethyl acetate is fed into the first-stage hydrophilic molecular sieve membrane at a rate of 15 cubic meters per hour and the temperature is controlled at about 55°C. The membrane is then filtered to remove impurities and some water from the ethyl acetate after washing. The ethyl acetate is then fed into the second-stage PVA membrane. The membrane separation pressure is adjusted and controlled at about 0.26 MPa. The ester phase outlet flow rate is 11 cubic meters and the aqueous phase outlet flow rate is controlled at 4 cubic meters. The water content of anhydrous ethyl acetate reaches 1 g / L and the ethyl acetate content reaches 98.9%.

[0031] Comparative Example 1 The ethyl acetate recovered by the system (with a normalized content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, the ratio of recovered ethyl acetate to system water is 3:1. After washing, the ethyl acetate (with a normalized content of only 96.5%) is fed into the drying tower for heating and pressurization to remove moisture. The feed volume is 15 cubic meters, and the output flow rate of anhydrous ethyl acetate is about 11 cubic meters. The moisture content is 0.8 g / L, and the ethyl acetate content is 99.2%.

[0032] Comparative Example 2 The ethyl acetate recovered by the system (with a normalization content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, the ratio of recovered ethyl acetate to system water is 4:1. After washing, the ethyl acetate (with a normalization content of only 96.3%) is fed into the drying tower for heating and pressurization to remove moisture. The feed volume is 15 cubic meters, and the output flow rate of anhydrous ethyl acetate is about 11 cubic meters. The moisture content is 1 g / L, and the ethyl acetate content is 98.9%.

[0033] Comparative Example 3 The ethyl acetate recovered by the system (with a normalized content of about 95%) is pumped into the bottom of the ethyl acetate washing tower. At the same time, the ratio of recovered ethyl acetate to system water is 5:1. After washing, the ethyl acetate (with a normalized content of only 96.3%) is fed into the drying tower for heating and pressurization to remove moisture. The feed volume is 15 cubic meters, and the output flow rate of anhydrous ethyl acetate is about 11 cubic meters. The moisture content is 2.5 g / L, and the ethyl acetate content is 97.3%.

[0034] As can be seen from the above examples and comparative data, the ethyl acetate recovered from the alkaline hydrolysis process is washed with pure water at a ratio of 3:1 to remove impurities. Then, it passes through a hydrophilic molecular sieve membrane and PVA at a feed temperature of 55°C and a pressure controlled at 0.25 MPa to remove moisture, resulting in anhydrous ethyl acetate with relatively stable moisture content. Sampling analysis shows that the moisture content of the anhydrous ethyl acetate is below 0.02 g / L, and the feed-to-output ratio is over 70%. In contrast, the anhydrous ethyl acetate obtained by washing the system with water and then removing moisture in a drying tower has an average moisture content of 1.5 g / L, with a feed-to-output ratio of only about 60%. It is evident that using pure water to wash the recovered ethyl acetate and then separating it through a membrane separation device yields a significantly higher quantity of anhydrous ethyl acetate than the original process, and the quality of the anhydrous ethyl acetate is relatively stable with less corrosion to the equipment. This has a certain effect on stabilizing production in the workshop.

[0035] The above detailed description is a specific illustration of one feasible embodiment of the present invention, and this embodiment is not intended to limit the patent scope of the present invention. It should be noted that all equivalent implementations or modifications made without departing from the present invention should be included within the scope of the technical solution of the present invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims

1. A process combining water washing and membrane separation for the recovery of ethyl acetate in sucralose production, characterized in that, Includes the following steps: (1) Pump the ethyl acetate recovered by the system into the bottom of the ethyl acetate water washing tower, and add pure water from the top of the water washing tower at the same time. Control the volume ratio of the recovered ethyl acetate to pure water to be 3:1-5:1, and carry out countercurrent extraction. After water washing, the ethyl acetate is discharged from the top of the tower and the aqueous phase is discharged from the bottom of the tower. (2) Ethyl acetate after washing with water is fed into the primary and secondary membrane separation filters at a flow rate of 15 m³ / h. The ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.3-11 m³ / h and the aqueous phase outlet flow rate is 4-4.7 m³ / h to obtain anhydrous ethyl acetate.

2. The recycling process according to claim 1, characterized in that, The normalized content of ethyl acetate recovered by the system in step (1) is 95% ± 0.5%.

3. The recycling process according to claim 1, characterized in that, In step (1), the volume ratio of ethyl acetate to pure water is 3:1, 4:1, or 5:

1.

4. The recycling process according to claim 1, characterized in that, In step (2), the primary and secondary membrane separation filters use hydrophilic molecular sieve membranes and PVA membranes, respectively, with a filtration accuracy of 0.3-0.5 μm.

5. The recycling process according to claim 1, characterized in that, In step (2), the operating pressure of the membrane separation filter is 0.2-0.3 MPa and the operating temperature is 45-55℃.

6. The recycling process according to claim 5, characterized in that, In step (2), the operating pressure of the membrane separation filter is 0.25 MPa and the operating temperature is 50 °C.

7. The recycling process according to claim 1, characterized in that, In step (2), the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 11 cubic meters per hour and the aqueous phase outlet flow rate is 4 cubic meters per hour; or the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.5 cubic meters per hour and the aqueous phase outlet flow rate is 4.5 cubic meters per hour; or the ester phase outlet flow rate of the secondary membrane separation filter is controlled to be 10.3 cubic meters per hour and the aqueous phase outlet flow rate is 4.7 cubic meters per hour.

8. The application of the recycling process according to any one of claims 1-7 in the industrial production of sucralose.

9. The application according to claim 8, characterized in that, By reducing the impurities and moisture content in esterified crystalline sugars, the yield of sucralose can be increased, thereby increasing the production of sucralose.

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