Gluconic acid-delta-lactone continuous crystallization production process and gluconic acid-delta-lactone
By controlling the temperature and stirring speed gradient in the continuous crystallization process of gluconate-δ-lactone, and using polyvinylpyrrolidone and sodium dodecyl sulfate as nucleating agents, the problem of difficult control of crystal nucleation and growth in the prior art has been solved, and efficient crystal growth and high yield and high purity gluconate-δ-lactone production have been achieved.
Patent Information
- Application Number
- CN202511049639.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-11-18
AI Technical Summary
In the existing crystallization process of gluconate-δ-lactone, crystal nucleation and growth are difficult to control effectively, resulting in low product yield and uneven particle size distribution, which affects product quality.
A continuous crystallization process using gluconate-δ-lactone was employed. By controlling the temperature and stirring speed gradients of each crystallizer, and combining polyvinylpyrrolidone and sodium dodecyl sulfate as nucleating agents, a concentration and supersaturation gradient was formed to promote crystal nucleation and growth. Polyvinylpyrrolidone was used to reduce the surface energy of the crystals, and sodium dodecyl sulfate was used to improve the wettability of the solution, thus achieving uniform crystal growth.
This improved the crystallization efficiency and product yield of gluconate-δ-lactone, resulting in larger and more uniformly distributed crystals, thus enhancing the purity and quality of the product.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of gluconolactone production technology, and more particularly to a continuous crystallization production process for gluconolactone-δ-lactone and gluconolactone-δ-lactone. Background Technology
[0002] Glucono-δ-lactone is a multifunctional food additive with wide applications in the food industry, such as as a tofu coagulant, preservative, and acidulant. Currently, the main method for preparing glucono-δ-lactone is separation and purification through gluconic acid crystallization. However, the nucleation and growth of crystals in the existing crystallization process are difficult to control effectively, resulting in low product yield and uneven crystal particle size distribution, which affects the quality and subsequent applications of glucono-δ-lactone. Summary of the Invention
[0003] To address the shortcomings of existing technologies, this invention provides the following technical solution:
[0004] The continuous crystallization process for gluconate-δ-lactone includes the following steps:
[0005] S1: After adding a nucleating agent to a gluconic acid solution with a concentration of 600-800 g / kg, two-stage cooling crystallization is carried out sequentially. The amount of the nucleating agent added is 0.1-1.0% of the mass of the gluconic acid solution.
[0006] S2: Add gluconic acid solution from the first-stage crystallizer and control the temperature of the first-stage crystallizer to 70-50℃. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 6-9 hours.
[0007] S3: After the first-stage crystallizer has been running for 6-9 hours, the material in the first-stage crystallizer will automatically flow into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer will be controlled at 50-38℃ and the stirring speed will be 20-25r / min.
[0008] S4: After the second-stage crystallizer has been running continuously for 1-1.5 hours, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
[0009] As an improvement to the above technical solution, the core-supporting agent includes polyvinylpyrrolidone and sodium dodecyl sulfate, wherein the mass ratio of polyvinylpyrrolidone to sodium dodecyl sulfate is (1-1.5):(1-3).
[0010] As an improvement to the above technical solution, the temperatures of the four temperature zones for the first-stage crystallization are as follows: first temperature zone 70℃-65℃; second temperature zone 65℃-60℃; third temperature zone 60℃-55℃; fourth temperature zone 55℃-50℃.
[0011] The temperatures of the four temperature zones for secondary crystallization are as follows: Zone 1: 50℃-47℃; Zone 2: 47℃-44℃; Zone 3: 44℃-41℃; Zone 44℃-38℃.
[0012] As an improvement to the above technical solution, in step S2, 5g of gluconate-δ-lactone is added for every 1kg of gluconic acid.
[0013] As an improvement to the above technical solution, in step S2, the stirring speed is 36-43 r / min, and in step S3, the stirring speed is 20-25 r / min.
[0014] Glucono-δ-lactone, prepared by the continuous crystallization process of glucono-δ-lactone described above.
[0015] The beneficial effects of this invention are:
[0016] In the gradient crystallization process, by controlling the temperature and stirring speed gradients of each crystallization vessel, a concentration gradient and a supersaturation gradient of the gluconic acid solution are formed. The decrease in temperature reduces the solubility of gluconic acid-δ-lactone, thereby generating supersaturation in the solution. In the first-stage crystallization vessel, the higher temperature and stirring speed are conducive to the rapid nucleation of gluconic acid-δ-lactone. As the solution flows into the subsequent crystallization vessels, the temperature decreases and the stirring speed slows down, and the supersaturation gradually decreases, providing suitable conditions for crystal growth. This gradient change allows the crystal to complete the nucleation and growth process at different stages, avoiding the generation of a large number of tiny crystals and facilitating the formation of crystals with larger particle size and uniform distribution.
[0017] In nucleation aids, polyvinylpyrrolidone (PVP) can adsorb onto the surface of gluconate-δ-lactone crystals, reducing the surface energy of the crystals and thus lowering the energy required for nucleation, promoting crystal nucleus formation. Simultaneously, the network structure formed by PPVP in solution restricts the movement of gluconate molecules, making them more readily aggregate to form crystal nuclei. Sodium dodecyl sulfate (SOS) reduces the surface tension of the solution, increasing its wettability and facilitating contact between gluconate molecules and potential crystal nuclei. When PPVP and SOS are used in combination, they exert a synergistic effect. PPVP primarily acts in the early stages of crystal nucleus formation, reducing surface energy and promoting nucleus formation, while SOS mainly improves the interfacial properties of the solution, promoting crystal nucleus growth and aggregation. Through this synergistic effect, the combined nucleation aids can significantly increase the nucleation rate of gluconate-δ-lactone, increase the number of crystal nuclei, and thus improve crystallization efficiency and product yield. Detailed Implementation
[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0019] Example 1
[0020] S1: After adding a nucleating agent to a 60 g / kg gluconic acid solution, two-stage cooling crystallization is carried out sequentially. The amount of the nucleating agent added is 0.1% of the mass of the gluconic acid solution.
[0021] S2: Add gluconic acid solution into the first-stage crystallizer, control the temperature of the first-stage crystallizer at 70-55℃, and the stirring speed at 36r / min. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 6-9 hours. The temperatures of the four temperature zones of the first-stage crystallization are as follows: first temperature zone 70℃; second temperature zone 65℃; third temperature zone 60℃; fourth temperature zone 55℃.
[0022] S3: After the first-stage crystallizer has been running for 6 hours, the material in the first-stage crystallizer automatically flows into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer is controlled at 50-41℃, and the stirring speed is 20r / min. The temperatures of the four temperature zones of the second-stage crystallizer are as follows: first temperature zone 50℃; second temperature zone 47℃; third temperature zone 44℃; fourth temperature zone 41℃.
[0023] S4: After the second-stage crystallizer has been running continuously for 1 hour, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
[0024] Example 2
[0025] S1: After adding a nucleating agent to a 70 g / kg gluconic acid solution, two-stage cooling crystallization is carried out sequentially. The amount of the nucleating agent added is 0.5% of the mass of the gluconic acid solution.
[0026] S2: Add gluconic acid solution into the first-stage crystallizer, control the temperature of the first-stage crystallizer at 68℃-53℃, and the stirring speed at 40r / min. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 7 hours. The temperatures of the four temperature zones of the first-stage crystallization are as follows: first temperature zone 68℃; second temperature zone 63℃; third temperature zone 58℃; fourth temperature zone 53℃.
[0027] S3: After the first-stage crystallizer has been running for 7.5 hours, the material in the first-stage crystallizer automatically flows into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer is controlled at 48-39℃, and the stirring speed is 23r / min. The temperatures of the four temperature zones of the second-stage crystallization are as follows: first temperature zone 48℃; second temperature zone 46℃; third temperature zone 42℃; fourth temperature zone 39℃.
[0028] S4: After the second-stage crystallizer has been running continuously for 1.2 hours, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
[0029] Example 3
[0030] S1: After adding gluconic acid with a concentration of 80 g / kg to the nucleating agent, two-stage cooling crystallization is carried out sequentially. The amount of the nucleating agent added is 1.0% of the mass of the gluconic acid solution.
[0031] S2: Add gluconic acid solution into the first-stage crystallizer, control the temperature of the first-stage crystallizer at 65-50℃, and the stirring speed at 43r / min. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 9 hours. The temperatures of the four temperature zones of the first-stage crystallization are as follows: first temperature zone 65℃; second temperature zone 60℃; third temperature zone 55℃; fourth temperature zone 50℃.
[0032] S3: After the first-stage crystallizer has been running for 9 hours, the material in the first-stage crystallizer automatically flows into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer is controlled at 47-38℃, and the stirring speed is 25r / min. The temperatures of the four temperature zones of the second-stage crystallizer are as follows: Zone 1: 47℃; Zone 2: 44℃; Zone 3: 41℃; Zone 4: 38℃.
[0033] S4: After the second-stage crystallizer has been running continuously for 1.5 hours, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
[0034] Comparative Example 1
[0035] S1: The gluconic acid solution with a concentration of 70 g / kg was subjected to two-stage cooling crystallization.
[0036] S2: Add gluconic acid solution into the first-stage crystallizer, control the temperature of the first-stage crystallizer at 68℃-53℃, and the stirring speed at 40r / min. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 7 hours. The temperatures of the four temperature zones of the first-stage crystallization are as follows: first temperature zone 68℃; second temperature zone 63℃; third temperature zone 58℃; fourth temperature zone 53℃.
[0037] S3: After the first-stage crystallizer has been running for 7.5 hours, the material in the first-stage crystallizer automatically flows into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer is controlled at 48-39℃, and the stirring speed is 23r / min. The temperatures of the four temperature zones of the second-stage crystallization are as follows: first temperature zone 48℃; second temperature zone 46℃; third temperature zone 42℃; fourth temperature zone 39℃.
[0038] S4: After the second-stage crystallizer has been running continuously for 1.2 hours, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
[0039] Detect the yield of the crystal:
[0040]
[0041] The purity determination method is as follows: Prepare a 10.0 mg / mL gluconate-δ-lactone standard solution, and successively dilute it to concentrations of 10.0 mg / mL, 8.0 mg / mL, 6.0 mg / mL, 4.0 mg / mL, 2.0 mg / mL, 1.0 mg / mL, 0.5 mg / mL, and 0.25 mg / mL. Measure the peak area of the gluconate-δ-lactone standard solution using a high-performance liquid chromatography (HPLC) system. Plot a standard curve with the peak area (average of three parallel samples) on the ordinate and the solution concentration on the abscissa. Analyze the gluconate-δ-lactone content in the example and comparative examples based on the standard curve.
[0042] Yield (%) purity(%) Example 1 78.8 99.9 Example 2 80.2 99.9 Example 3 79.2 99.8 Comparative Example 1 70.2 96
[0043] Table 1
[0044] According to the test results in Table 1, the yield of gluconate-δ-lactone generated by the crystallization method in Examples 1-3 of this application can reach more than 78%. The addition of the nucleating agent can provide a large number of tiny particles or surface sites. These sites can serve as the core for the growth of gluconate-δ-lactone crystals, inducing gluconate-δ-lactone molecules to aggregate and crystallize on their surface, reducing the energy barrier for nucleation, and enabling more crystal nuclei to form, thereby increasing the number of crystals generated and improving the yield.
[0045] The purity of gluconate-δ-lactone produced by the crystallization method in Examples 1-3 of this application can reach over 99.8%. The nucleating agent helps to form a regular and complete crystal structure. During the crystal growth process, the nucleating agent can regulate the growth direction and growth rate of the crystal, making the crystal growth more uniform and orderly, reducing defects and impurities inside the crystal, thereby improving the purity of the crystal.
[0046] The inventors accidentally discovered that there is a synergistic effect between polyvinylpyrrolidone and sodium dodecyl sulfate in the core-forming agent of this application. With appropriate addition amounts and ratios, the yield and purity of gluconate-δ-lactone can be further improved. The synergistic effect of the two is verified in Examples 4-8 below.
[0047] Based on Example 2, Examples 4-8 were designed. Except for changes in the addition of polyvinylpyrrolidone and sodium dodecyl sulfate, the other components and crystallization method remained unchanged. The specific ratio of polyvinylpyrrolidone to sodium dodecyl sulfate is shown in Table 2.
[0048]
[0049] Table 2
[0050] The crystallization methods of Examples 5-8 and Comparative Examples 1-2 were used to test the crystals, and the specific results are shown in Table 3.
[0051] Yield (%) purity(%) Example 4 80.5 99.9 Example 5 82.3 99.9 Example 6 81.3 99.8 Example 7 79.9 99.9 Example 8 81.3 99.9
[0052] Table 3
[0053] As shown in Table 3 from Examples 4-8, when the ratio of polyvinylpyrrolidone to sodium dodecyl sulfate is 1.2:(1-3), gradually increasing the sodium dodecyl sulfate ratio and keeping it between 1 and 3 results in the highest yield of glucono-δ-lactone. Polyvinylpyrrolidone can attract glucono-δ-lactone molecules through hydrogen bonding and other interactions, providing sites for crystal nucleation and promoting crystal formation. Sodium dodecyl sulfate, as a surfactant, can reduce the surface tension of the solution, making it easier for glucono-δ-lactone molecules to arrange and crystallize on the surface of the crystal nuclei. As the proportion of sodium dodecyl sulfate increases, its effect of reducing surface tension becomes more significant, enabling more gluconate-δ-lactone molecules to rapidly deposit and grow on the crystal nucleus surface provided by polyvinylpyrrolidone, thereby improving the yield. However, as the proportion of sodium dodecyl sulfate increases, excessive adsorption on the crystal nucleus surface may alter the charge properties and physicochemical environment of the crystal nucleus surface, leading to changes in the adsorption and arrangement of gluconate-δ-lactone molecules on the crystal nucleus surface. This, in turn, affects the growth direction and growth rate of the crystal, causing abnormal crystal growth and affecting the yield.
[0054] When the ratio of polyvinylpyrrolidone to sodium dodecyl sulfate is (1-1.5):2, gradually increasing the polyvinylpyrrolidone ratio results in the highest yield of gluconate-δ-lactone when the ratio is between 1 and 1.5. Polyvinylpyrrolidone can make the distribution of gluconate-δ-lactone molecules in the solution more uniform, reducing the situation of excessively high or low local concentrations, providing a stable and suitable environment for crystal growth, which is conducive to the continuous growth of crystals. When the ratio of polyvinylpyrrolidone is too high, an overly dense adsorption layer may be formed on the surface of the crystal nucleus, which will hinder the diffusion and deposition of gluconate-δ-lactone molecules to the surface of the crystal nucleus, thereby inhibiting the growth rate of crystals, resulting in insufficient crystal growth and ultimately affecting the yield.
[0055] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.
Claims
1. A continuous crystallization process for gluconate-δ-lactone, characterized in that, Includes the following steps: S1: After adding a nucleating agent to a gluconic acid solution with a concentration of 600-800 g / kg, two-stage cooling crystallization is carried out sequentially. The amount of the nucleating agent added is 0.1-1.0% of the mass of the gluconic acid solution. S2: Add gluconic acid solution from the first-stage crystallizer and control the temperature of the first-stage crystallizer to 70-50℃. After the temperature stabilizes, add gluconic acid-δ-lactone as seed crystals and run continuously for 6-9 hours. S3: After the first-stage crystallizer has been running for 6-9 hours, the material in the first-stage crystallizer will automatically flow into the second-stage crystallizer. As the solution flows into the second-stage crystallizer, the temperature of the second-stage crystallizer will be controlled at 50-38℃ and the stirring speed will be 20-25r / min. S4: After the second-stage crystallizer has been running continuously for 1-1.5 hours, the material in the second crystallizer is pumped into a horizontal screw centrifuge for solid-liquid separation.
2. The continuous crystallization process for gluconate-δ-lactone according to claim 1, characterized in that: The core-supporting agent comprises polyvinylpyrrolidone and sodium dodecyl sulfate, wherein the mass ratio of polyvinylpyrrolidone to sodium dodecyl sulfate is (1-1.5):(1-3).
3. The continuous crystallization process for gluconate-δ-lactone according to claim 2, characterized in that: The temperatures of the four temperature zones for primary crystallization are as follows: Zone 1: 70℃-65℃; Zone 2: 65℃-60℃; Zone 3: 60℃-55℃; Zone 4: 55℃-50℃. The temperatures of the four temperature zones for secondary crystallization are as follows: Zone 1: 50℃-47℃; Zone 2: 47℃-44℃; Zone 3: 44℃-41℃; Zone 44℃-38℃.
4. The continuous crystallization process for gluconate-δ-lactone according to claim 1, characterized in that: In step S2, 5g of gluconate-δ-lactone is added for every 1kg of gluconic acid.
5. The continuous crystallization process for gluconate-δ-lactone according to claim 1, characterized in that: In step S2, the stirring speed is 36-43 r / min, and in step S3, the stirring speed is 20-25 r / min.
6. Glucono-δ-lactone, characterized in that: Glucono-δ-lactone prepared by any one of the continuous crystallization processes of glucono-δ-lactone according to claims 1-5.