A preparation method of sodium D-isoascorbate

Abstract

The invention relates to a method for preparing sodium D-isoascorbate. The method comprises the following steps: loading polyoxometalate and polydopamine on silica microspheres to obtain silica microspheres loaded with polyoxometalate; dissolving a 2-keto-D-gluconic acid concentrate with methanol, then adding H2O2 and the silica microspheres loaded with polyoxometalate and heating to carry out an esterification reaction; after completion of the reaction, filtering and separating the silica microspheres loaded with polyoxometalate under a heat preservation condition, cooling, crystallizing, and filtering to obtain 2-keto-D-gluconate; adding 2-keto-D-gluconate to methanol to obtain a methanol solution of 2-keto-D-gluconate, then gradually adding an alcohol solution of a sodium ion donor to carry out a conversion reaction, and after completion of the reaction, filtering, cooling, and centrifuging to obtain the product. The method has high production safety and high product yield.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of sodium D-isoascorbate, and particularly relates to a preparation method of sodium D-isoascorbate. Background Art

[0002] Sodium D-erythorbate is a food additive. It's currently produced using a combination of fermentation and chemical conversion. First, microbial fermentation produces 2-keto-D-gluconic acid, which is then chemically converted to sodium D-erythorbate.

[0003] During the conversion process, concentrated sulfuric acid is generally used to convert 2-keto-D-gluconic acid into 2-keto-D-gluconate. Concentrated sulfuric acid is a hazardous substance and the reaction process is relatively dangerous.

[0004] Wang Jianxiang et al. ("Synthesis of Sodium Isovitaminosis C by Solid Superacid SO42- / SiO2-TiO2 Catalysis", Wang Jianxiang et al., "Applied Chemistry", Vol. 22, No. 12, pp. 1347-1350) also used solid superacids to catalyze the conversion of 2-keto-D-gluconic acid into 2-keto-D-gluconate, but the yield was low. Summary of the Invention

[0005] The object of the present invention is to provide a method for preparing sodium D-isoascorbate, so as to improve the yield of sodium D-isoascorbate and enhance the safety of the preparation of sodium D-isoascorbate.

[0006] In order to achieve the above objectives, the technical solution adopted by the present invention is:

[0007] A method for preparing sodium D-isoascorbate comprises the following steps:

[0008] S1: loading polyoxometalate and polydopamine on silica microspheres to obtain polyoxometalate-loaded silica microspheres;

[0009] S2: Dissolving the concentrated 2-keto-D-gluconic acid solution with alcohol, then adding H2O2 and silica microspheres loaded with polyoxometalates and heating to carry out an esterification reaction. After the reaction is completed, filtering and separating the silica microspheres loaded with polyoxometalates under heat preservation conditions, cooling, crystallizing, and filtering to obtain 2-keto-D-gluconate;

[0010] S3: adding 2-keto-D-gluconate to alcohol to obtain an alcohol solution of 2-keto-D-gluconate, then gradually adding an alcohol solution of a sodium ion donor to carry out a conversion reaction. After the reaction is completed, filtering, cooling, and centrifuging to obtain the product.

[0011] Furthermore, the sodium ion donor is sodium hydroxide or sodium carbonate.

[0012] Furthermore, the alcohol is methanol or ethanol.

[0013] Furthermore, in step S1, the silica microspheres are dissolved in water, and then polyoxometalate and polydopamine are added, stirred, centrifuged, and dried to obtain silica microspheres loaded with polyoxometalate.

[0014] Furthermore, in step S1, the mass ratio of the silica microspheres to the polyoxometalate is 10:1 to 10:3; and the mass ratio of the silica microspheres to polydopamine is 10:0.1 to 10:0.3.

[0015] Furthermore, in step S1, the polyoxometalate is H4PV1Mo 11 O 40 or H3PMo 12 O 40 .

[0016] Furthermore, in step S2, the mass ratio of the 2-keto-D-gluconic acid concentrate to H2O2 is 10:1 to 10:2; the mass ratio of the 2-keto-D-gluconic acid concentrate to the polyoxometalate-loaded silica microspheres is 10:0.5 to 10:1.5.

[0017] Furthermore, in step S2, before the crystallization filtration, the silica microspheres loaded with polyoxometalate are filtered and separated under heat preservation conditions.

[0018] Furthermore, in step S2, the temperature of the esterification reaction is 50-60° C., and the reaction time is 1-2 hours.

[0019] Furthermore, in step S3, the mass ratio of the 2-keto-D-gluconate to the alcohol is 1:3 to 1:6.

[0020] Furthermore, the mass ratio of the sodium ion donor to the alcohol is 1:3 to 1:6; the mass ratio of the alcohol solution of 2-keto-D-gluconate to the alcohol solution of the sodium ion donor is 1:0.4 to 1:0.6.

[0021] Furthermore, in step S3, the temperature of the conversion reaction is 40-50° C., and the reaction time is 2-3 hours.

[0022] Beneficial effects of the present invention:

[0023] The present invention's method for preparing sodium D-isoascorbate utilizes a combination of H2O2 and a polyoxometalate as catalysts for the esterification reaction of 2-keto-D-gluconate, thereby improving catalytic performance. The oxidizing properties of H2O2 combined with the acidic properties of the polyoxometalate increase product yield. The polyoxometalate is supported on silica microspheres, increasing the contact area between the polyoxometalate and the reactants and enhancing catalytic efficiency. The addition of polydopamine, combined with the polyoxometalate, enhances the stability of the supported polyoxometalate. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments of the present invention.

[0025] Preparation of silica microspheres: 3 L of anhydrous ethanol is added to 150 mL of aqueous ammonia and 50 mL of water. The mixture is stirred at 500 rpm for 15 minutes, and 100 mL of ethyl orthosilicate is gradually added. The mixture is stirred at 500 rpm for 5 hours. After stirring, 2.5 mL of anhydrous ethanol and 5 mL of silane coupling agent KH-560 are gradually added. The mixture is stirred at 500 rpm for 10 hours. The mixture is centrifuged at 15,000 rpm for 5 minutes and washed with anhydrous ethanol to obtain silica microspheres. The preparation of silica microspheres is conventional, and silica microspheres can also be purchased commercially.

[0026] Example 1

[0027] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0028] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 15 g of H4PV1Mo was added. 11 O 40 and 0.2 kg of polydopamine, stirred at 50° C. and 500 rpm for 10 min, centrifuged at 12000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0029] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 50 kg of methanol. 1.5 kg of H₂O₂ and 0.6 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 50°C for 2 hours. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled for crystallization, filtered, and washed with methanol until the pH of the washings reached 7, yielding a wet product of 2-keto-D-gluconate.

[0030] 3) Conversion reaction: Take 10 kg of sodium carbonate and 50 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of methanol and heat and stir evenly. Then add 30 kg of methanol solution of sodium carbonate in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 50°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 96.52%.

[0031] Example 2

[0032] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0033] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 20 kg of H4PV1Mo was added. 11 O 40 and 0.15 kg of polydopamine, stirred at 60° C. and 800 rpm for 10 min, centrifuged at 12000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0034] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 30 kg of methanol. 1 kg of H₂O₂ and 1.2 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 55°C for 1.5 hours. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled and crystallized, filtered, and washed with methanol until the pH of the washings reached 7, yielding a wet product of 2-keto-D-gluconate.

[0035] 3) Conversion reaction: Take 10 kg of sodium carbonate and 30 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 30 kg of methanol and heat and stir evenly. Then add 24 kg of methanol solution of sodium carbonate in a flow addition manner to carry out conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 3 hours, the reaction time is 45 ° C, the reaction is cooled to 20 ° C, and centrifugation is performed, and the yield is 96.31%.

[0036] Example 3

[0037] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0038] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 10 kg of H3PMo was added. 12 O 40 and 0.1 kg of polydopamine, stirred at 50° C. and 500 rpm for 10 min, centrifuged at 12000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0039] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 50 kg of ethanol. 1.8 kg of H₂O₂ and 1.5 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 60°C for 1 hour. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled for crystallization, filtered, and washed with ethanol until the pH of the washing solution reached 7, yielding a wet product of 2-keto-D-gluconate.

[0040] 3) Conversion reaction: Take 10 kg of sodium hydroxide and 50 kg of ethanol, mix sodium carbonate with ethanol to obtain an ethanol solution of sodium hydroxide. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of ethanol and heat and stir evenly. Then add 24 kg of ethanol solution of sodium hydroxide in a flow addition manner to carry out conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 40°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 96.63%.

[0041] Example 4

[0042] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0043] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 25 kg of H3PMo 12 O 40 and 0.3 kg of polydopamine, stirred at 50° C. and 500 rpm for 15 min, centrifuged at 12000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0044] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 60 kg of ethanol. 1.2 kg of H₂O₂ and 0.5 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 50°C for 1 hour. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting mixture was then cooled and crystallized, filtered, and washed with methanol until the pH of the washings reached 7, yielding a wet product of 2-keto-D-gluconate.

[0045] 3) Conversion reaction: Take 10 kg of sodium carbonate and 60 kg of ethanol, mix the sodium carbonate and ethanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 60 kg of ethanol and heat and stir evenly. Then add 35 kg of sodium carbonate ethanol solution in a flow addition manner to carry out conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 50°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product with a yield of 95.98%.

[0046] Example 5

[0047] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0048] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water, and 30 kg of H4PV1Mo was added. 11 O 40 and 0.25 kg of polydopamine, stirred at 50° C. and 500 rpm for 10 min, centrifuged at 15000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0049] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 30 kg of methanol. 2 kg of H₂O₂ and 0.8 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 60°C for 2 hours. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled for crystallization, filtered, and washed with methanol until the pH of the washings reached 7, yielding a wet product of 2-keto-D-gluconate.

[0050] 3) Conversion reaction: Take 10 kg of sodium hydroxide and 30 kg of methanol, mix the sodium hydroxide and methanol to obtain a methanol solution of sodium hydroxide. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of methanol and heat and stir evenly. Then add 16 kg of methanol solution of sodium hydroxide in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 3 hours, the reaction time is 40°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 97.12%.

[0051] Example 6

[0052] The method for preparing sodium D-isoascorbate of this embodiment comprises the following steps:

[0053] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 15 g of H3PMo was added. 12 O 40 and 0.25 kg of polydopamine, stirred at 40° C. and 500 rpm for 10 min, centrifuged at 12000 rpm for 8 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0054] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 40 kg of methanol. 1.5 kg of H₂O₂ and 1.5 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 55°C for 1.5 hours. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled and crystallized, filtered, and washed with methanol until the pH of the washing solution reached 7, yielding a wet product of 2-keto-D-gluconate.

[0055] 3) Conversion reaction: Take 10 kg of sodium carbonate and 40 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 40 kg of methanol and heat and stir evenly. Then add 30 kg of methanol solution of sodium carbonate in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 40°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 96.55%.

[0056] Comparative Example 1

[0057] The preparation method of sodium D-isoascorbate in this comparative example comprises the following steps:

[0058] 1) Silica-loaded polyoxometalates: 100 g of silica microspheres were dispersed in 500 mL of water and 15 g of H4PV1Mo was added. 11 O 40 The mixture was stirred at 50° C. and 500 rpm for 10 min, centrifuged at 12000 rpm for 5 min, and dried to obtain silica microspheres loaded with polyoxometalate.

[0059] 2) Esterification: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 50 kg of methanol. 1.5 kg of H₂O₂ and 0.6 kg of polyoxometalate-loaded silica microspheres were then added and heated for an esterification reaction at 50°C for 2 hours. After the esterification reaction, the polyoxometalate-loaded silica microspheres were separated by filtration under insulated conditions. The resulting solution was then cooled for crystallization, filtered, and washed with methanol until the pH of the washings reached 7, yielding a wet product of 2-keto-D-gluconate.

[0060] 3) Conversion reaction: Take 10 kg of sodium carbonate and 50 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of methanol and heat and stir evenly. Then add 30 kg of methanol solution of sodium carbonate in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 50°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 76.23%.

[0061] Comparative Example 2

[0062] The preparation method of sodium D-isoascorbate in this comparative example comprises the following steps:

[0063] 1) Esterification reaction: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 50 kg of methanol, and then 1.5 kg of H2O2 and 0.6 kg of H4PV1Mo were added. 11 O 40 The esterification reaction was carried out by heating at 50°C for 2 hours. After the esterification reaction was completed, H4PV1Mo was separated by filtration under heat preservation conditions. 11 O 40 , then cooled and crystallized, filtered and washed with methanol until the pH value of the washing liquid reached 7 to obtain a wet product of 2-keto-D-gluconate.

[0064] 2) Conversion reaction: Take 10 kg of sodium carbonate and 50 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of methanol and heat and stir evenly. Then add 30 kg of methanol solution of sodium carbonate in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 50°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 62.44%.

[0065] Comparative Example 3

[0066] The preparation method of sodium D-isoascorbate in this comparative example comprises the following steps:

[0067] 1) Esterification: Dissolve 10 kg of 2-keto-D-gluconic acid concentrate in 50 kg of methanol, then add 1.5 kg of H₂O₂ and heat to carry out the esterification reaction at 50°C for 2 hours. After the esterification reaction, cool and crystallize, filter, and wash with methanol until the pH of the washings reaches 7. This yields a very small amount of wet 2-keto-D-gluconate, which is unreactive.

[0068] Comparative Example 4

[0069] The preparation method of sodium D-isoascorbate in this comparative example comprises the following steps:

[0070] 1) Esterification reaction: 10 kg of 2-keto-D-gluconic acid concentrate was dissolved in 50 kg of methanol, and then 0.6 kg of H4PV1Mo was added. 11 O 40 The esterification reaction was carried out by heating at 50°C for 2 hours. After the esterification reaction was completed, H4PV1Mo was separated by filtration under heat preservation conditions. 11 O 40 , then cooled and crystallized, filtered and washed with methanol until the pH value of the washing liquid reached 7 to obtain a wet product of 2-keto-D-gluconate.

[0071] 2) Conversion reaction: Take 10 kg of sodium carbonate and 50 kg of methanol, mix the sodium carbonate and methanol to obtain a methanol solution of sodium carbonate. Add the 2-keto-D-gluconate obtained in step 2) to 50 kg of methanol and heat and stir evenly. Then add 30 kg of methanol solution of sodium carbonate in a flow addition manner to carry out the conversion reaction, and the flow addition time is 2 hours. Stirring is continued during the conversion reaction, the conversion reaction temperature is 2 hours, the reaction time is 50°C, the reaction is cooled to 20°C, and centrifugation is performed to obtain the product, with a yield of 45.16%.

[0072] Test example

[0073] The reusability of the silica microspheres loaded with polyoxometalates catalysts in Example 1 and Comparative Example 1 was measured. The silica microspheres loaded with polyoxometalates in Example 1 were designated as Sample A, and the silica microspheres loaded with polyoxometalates in Comparative Example 1 were designated as Sample B.

[0074] Table 1 Reusability of catalyst-loaded polyoxometalate silica microspheres

[0075]

[0076] As can be seen from Table 1, the silica microspheres loaded with polyoxometalate without adding polydopamine have poor catalyst stability and cannot be reused.

Claims

1. A method for preparing sodium D-isoascorbate, characterized in that: The following steps are involved: S1: Polyoxometalate and polydopamine are loaded on silica microspheres to obtain silica microspheres loaded with polyoxometalate; the polyoxometalate is H4PV1Mo 11 O 40 or H3PMo 12 O 40 ; S2: Dissolving the concentrated 2-keto-D-gluconic acid solution with alcohol, then adding H2O2 and silica microspheres loaded with polyoxometalates and heating to carry out an esterification reaction. After the reaction is completed, filtering and separating the silica microspheres loaded with polyoxometalates under heat preservation conditions, cooling, crystallizing, and filtering to obtain 2-keto-D-gluconate; S3: adding 2-keto-D-gluconate to alcohol to obtain an alcohol solution of 2-keto-D-gluconate, then gradually adding an alcohol solution of a sodium ion donor to carry out a conversion reaction. After the reaction is completed, filtering, cooling, and centrifuging to obtain the product.

2. The method for preparing sodium D-isoascorbate according to claim 1, wherein In step S1, the silica microspheres are dissolved in water, and then polyoxometalate and polydopamine are added, stirred, centrifuged, and dried to obtain polyoxometalate-loaded silica microspheres.

3. The method for preparing sodium D-isoascorbate according to claim 1 or 2, wherein: In step S1, the mass ratio of the silica microspheres to the polyoxometalate is 10:1 to 10:3; the mass ratio of the silica microspheres to polydopamine is 10:0.1 to 10:0.

3.

4. The method for preparing sodium D-isoascorbate according to claim 1, wherein In step S2, the mass ratio of the 2-keto-D-gluconic acid concentrate to H2O2 is 10:1 to 10:2; the mass ratio of the 2-keto-D-gluconic acid concentrate to the polyoxometalate-loaded silica microspheres is 10:0.5 to 10:1.

5.

5. The method for preparing sodium D-isoascorbate according to claim 1 or 4, wherein: In step S2, before the crystallization is filtered, the silica microspheres loaded with polyoxometalate are separated by filtration under heat preservation conditions.

6. The method for preparing sodium D-isoascorbate according to claim 1 or 4, wherein: In step S2, the temperature of the esterification reaction is 50-60° C., and the reaction time is 1-2 hours.

7. The method for preparing sodium D-isoascorbate according to claim 1, wherein In step S3, the mass ratio of the 2-keto-D-gluconate to the alcohol is 1:3 to 1:

6.

8. The method for preparing sodium D-isoascorbate according to claim 1, wherein In step S3, the mass ratio of the sodium ion donor to the alcohol is 1:3 to 1:6; the mass ratio of the alcohol solution of 2-keto-D-gluconate to the alcohol solution of the sodium ion donor is 1:0.4 to 1:0.

6.

9. The method for preparing sodium D-isoascorbate according to any one of claims 1, 7 or 8, wherein: In step S3, the temperature of the conversion reaction is 40-50° C., and the reaction time is 2-3 hours.

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