A method for purifying sodium D-erythorbate

Abstract

The application provides a purification method of sodium D-erythorbate, which comprises the following steps: (1) adding dimethyl carbonate into a reaction kettle, adding a catalyst, and then adding 2-keto-D-gluconic acid, so as to obtain an esterification liquid through reaction; (2) adding an inorganic base into the esterification liquid obtained in the step (1) and reacting for 1-2 hours, so as to obtain a reaction liquid; (3) filtering the reaction liquid obtained in the step (2), so as to obtain a filtrate and a filter cake, and the filter cake is the catalyst; (4) heating and reducing-pressure distilling the filtrate obtained in the step (3), so as to obtain methanol, dimethyl carbonate and a remaining component which is a crude product of sodium D-erythorbate, respectively; and (5) purifying the crude product of sodium D-erythorbate obtained in the step (4), so as to obtain a pure product of sodium D-erythorbate with a purity of more than 99.8%. The method does not use concentrated sulfuric acid, is simple in process and convenient in operation, has high environmental friendliness of solvents used in the purification process, is high in product purity and can well solve the problems of the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of D-sodium erythorbate preparation, in particular to a purification method of D-sodium erythorbate. BACKGROUND

[0002] D-sodium erythorbate is also known as sodium isoascorbate, which is a safe and non-toxic food antioxidant recommended by the World Health Organization and the Ministry of Health. It can effectively reduce the oxidation of food, prevent the fading of color, flavor and taste, help color seafood, and inhibit the generation of carcinogenic substances nitrite in food. It also has the effects of lowering blood pressure, diuresis and detoxification in medicine. At present, the product has been widely used in meat, fruits, beverages and other foods, and can also be used in the textile, electroplating, feed processing, industrial water treatment and petroleum chemical industries.

[0003] At present, the preparation method of D-sodium erythorbate generally uses the process of combining biological fermentation and chemical synthesis at home and abroad. The main process is to hydrolyze starch into glucose with enzyme, then ferment 2-keto-D-gluconic acid with fluorescent pseudomonas, and then prepare D-sodium erythorbate by chemical synthesis.

[0004] CN105603018B discloses a method for indirectly preparing D-sodium erythorbate, which belongs to the technical field of biochemical separation and synthesis. The fermentation broth of Serratia marcescens SDSPY-136 strain is used as raw material, and D-sodium erythorbate is obtained through fermentation broth pretreatment, 2-keto-D-gluconic acid methyl ester reaction and conversion reaction. The product is obtained by refining and purifying D-sodium erythorbate. The present application uses Serratia marcescens as a production strain to ferment calcium 2-keto-D-gluconate, combines various impurity removal methods, and converts the treated liquid to synthesize D-sodium erythorbate. The fermentation broth has high yield and high conversion rate of 2-keto-D-gluconic acid, the crude D-sodium erythorbate has high purity, is easy to refine, the total yield is improved, and has good popularization and application prospect. However, the process is complex and long. SUMMARY

[0005] The purpose of the present application is to provide a purification method of D-sodium erythorbate, which does not use concentrated sulfuric acid, has simple process, easy operation, high environmental friendliness of solvent used in purification process, high product purity, and can well solve the problems of prior art.

[0006] To achieve the above purpose, the present application provides a purification method of D-sodium erythorbate, which comprises the following steps:

[0007] (1) Put dimethyl carbonate into the reactor, add catalyst, then add 2-keto-D-gluconic acid, start stirring, and heat to 60-80°C, and react for 1-3 hours to obtain an esterification solution with a yield of more than 98%;

[0008] (2) Add an inorganic base to the esterification solution obtained in step (1) and react for 1-2 hours to obtain a reaction solution;

[0009] (3) Filter the reaction solution obtained in step (2) to obtain a filtrate and a filter cake, and the filter cake is the catalyst which can be reused after regeneration;

[0010] (4) Heat and distill the filtrate obtained in step (3) under reduced pressure to obtain methanol, dimethyl carbonate, and the remaining component is a crude D-sodium erythorbate;

[0011] (5) Purify the crude D-sodium erythorbate obtained in step (4) to obtain a pure D-sodium erythorbate with a purity of more than 99.8%.

[0012] The esterification reaction uses dimethyl carbonate instead of methanol, and good results are achieved, the yield of the esterification process is more than 98%, and the reaction conditions are mild and the reaction time is short.

[0013] Preferably, the molar ratio of dimethyl carbonate to 2-keto-D-gluconic acid in step (1) is 3-6:1. The amount of dimethyl carbonate added is excessive, i.e., it serves as both a solvent and a reaction substrate, and the excess dimethyl carbonate can be recycled.

[0014] Preferably, the catalyst in step (1) is one of natural zeolite, hydrogen-type β molecular sieve, WO 3 / ZrO2 solid acid. This avoids using traditional concentrated sulfuric acid as a catalyst, is more environmentally friendly, and is safer in the reaction process.

[0015] Preferably, the mass of the catalyst in step (1) is 5-10% of the mass of 2-keto-D-gluconic acid.

[0016] Preferably, the inorganic base in step (2) is at least one of sodium bicarbonate, sodium carbonate, sodium hydroxide, and concentrated ammonia water, and the amount of inorganic base added is 30-60% of the mass of 2-keto-D-gluconic acid. Preferably, when concentrated ammonia water is used, the yield is higher.

[0017] Preferably, the dimethyl carbonate in step (4) can be reused.

[0018] Preferably, the purification process in step (5) is that the crude D-sodium erythorbate is dissolved in deionized water to obtain a D-sodium erythorbate aqueous solution, and then slowly added into ethanol with a temperature of -5-10°C to precipitate solid, and the solid is filtered, washed and dried to obtain the pure D-sodium erythorbate. The mass ratio of deionized water to the crude D-sodium erythorbate is 7-10:1, and the mass ratio of ethanol to the D-sodium erythorbate aqueous solution is 3-5:1. Because low-temperature ethanol almost does not dissolve dimethyl carbonate, the pure D-sodium erythorbate can be obtained at a high yield.

[0019] Preferably, the purification process in step (5) is that the crude D-sodium erythorbate is dissolved in deionized water to obtain a D-sodium erythorbate aqueous solution, and then slowly added into ethanol with a temperature of -5-10°C to precipitate solid, and the solid is filtered, washed and dried to obtain the pure D-sodium erythorbate. The mass ratio of deionized water to the crude D-sodium erythorbate is 7-10:1, and the mass ratio of ethanol to the D-sodium erythorbate aqueous solution is 3-5:1. Because low-temperature ethanol almost does not dissolve dimethyl carbonate, the pure D-sodium erythorbate can be obtained at a high yield. DETAILED DESCRIPTION

[0020] It should be understood that the specific embodiments described herein are merely exemplary and not intended to limit the present application.

[0021] Example 1

[0022] A method for purifying D-sodium erythorbate, comprising the following steps:

[0023] (1) dimethyl carbonate is added into a reaction kettle, 2-keto-D-gluconic acid is added, the molar ratio of dimethyl carbonate to 2-keto-D-gluconic acid is 3:1, 5% of hydrogen type β molecular sieve based on the mass of 2-keto-D-gluconic acid is added, stirring is started, the temperature is raised to 60-70°C, and reaction is carried out for 3h to obtain an esterification liquid, and the esterification yield is 98.1%;

[0024] (2) sodium bicarbonate is added into the esterification liquid obtained in step (1), the amount of sodium bicarbonate added is 50% of the mass of 2-keto-D-gluconic acid, and reaction is carried out for 1h to obtain a reaction liquid;

[0025] (3) the reaction liquid obtained in step (2) is filtered to obtain a filtrate and a filter cake, the filter cake is a catalyst which can be reused after regeneration;

[0026] (4) the filtrate obtained in step (3) is heated and distilled under reduced pressure to obtain methanol, dimethyl carbonate and the remaining component which is crude D-sodium erythorbate, respectively;

[0027] (5) The D-sodium erythorbate crude product obtained in step (4) is dissolved in 10 times the mass of deionized water to obtain a D-sodium erythorbate aqueous solution, which is then slowly added to ethanol at a temperature of 0-5°C, the mass ratio of ethanol to the D-sodium erythorbate aqueous solution being 4:1, and a solid is precipitated, which is filtered, washed, and dried to obtain a D-sodium erythorbate pure product, the total yield being 95.6% and the purity being 99.87%.

[0028] Example 2

[0029] A method for purifying D-sodium erythorbate, comprising the following steps:

[0030] (1) Dimethyl carbonate is added to a reaction kettle, and 2-keto-D-gluconic acid is added, the molar ratio of dimethyl carbonate to 2-keto-D-gluconic acid being 5:1, and the amount of 2-keto-D-gluconic acid added being 8% of the mass of the 2-keto-D-gluconic acid; 3 / ZrO2 solid acid, stirring is started, the temperature is raised to 70-80°C, and the reaction is carried out for 2 h to obtain an esterification liquid, the esterification yield being 98.3%;

[0031] (2) Sodium carbonate is added to the esterification liquid obtained in step (1), the amount of sodium carbonate added being 35% of the mass of the 2-keto-D-gluconic acid, and the reaction is carried out for 2 h to obtain a reaction liquid;

[0032] (3) The reaction liquid obtained in step (2) is filtered to obtain a filtrate and a filter cake, the filter cake being a catalyst which can be reused after regeneration;

[0033] (4) The filtrate obtained in step (3) is heated and distilled under reduced pressure to obtain methanol, dimethyl carbonate, and the remaining component, which is a D-sodium erythorbate crude product;

[0034] (5) The D-sodium erythorbate crude product obtained in step (4) is dissolved in 10 times the mass of deionized water to obtain a D-sodium erythorbate aqueous solution, which is then slowly added to ethanol at a temperature of 0-5°C, the mass ratio of ethanol to the D-sodium erythorbate aqueous solution being 4:1, and a solid is precipitated, which is filtered, washed, and dried to obtain a D-sodium erythorbate pure product, the total yield being 95.6% and the purity being 99.87%.

[0035] Example 3

[0036] A method for purifying D-sodium erythorbate, comprising the following steps:

[0037] (1) adding dimethyl carbonate into a reactor, adding 2-keto-D-gluconic acid, the molar ratio of dimethyl carbonate and 2-keto-D-gluconic acid being 4:1, adding 10% of the mass of 2-keto-D-gluconic acid of natural zeolite, starting stirring, and heating to 70-80°C, and reacting for 2h to obtain an esterification liquid, the esterification yield being 99.0%;

[0038] (2) adding concentrated ammonia water into the esterification liquid obtained in step (1), the amount of the concentrated ammonia water being 38% of the mass of 2-keto-D-gluconic acid, and reacting for 2h to obtain a reaction liquid;

[0039] (3) filtering the reaction liquid obtained in step (2) to obtain a filtrate and a filter cake, the filter cake being a catalyst which can be reused after regeneration;

[0040] (4) heating and distilling under reduced pressure the filtrate obtained in step (3) to obtain methanol, dimethyl carbonate, and a remaining component which is a crude D-sodium erythorbate;

[0041] (5) dissolving the crude D-sodium erythorbate obtained in step (4) in 7 times of the mass of deionized water to obtain a D-sodium erythorbate aqueous solution, then slowly adding the D-sodium erythorbate aqueous solution into a saturated sodium chloride aqueous solution at a temperature of -10 to -5°C, the mass ratio of the saturated sodium chloride aqueous solution to the D-sodium erythorbate aqueous solution being 3:1, precipitating a solid, and filtering, washing, and drying to obtain a pure D-sodium erythorbate, the total yield being 97.1% and the purity being 99.95%.

[0042] Example 4

[0043] A method for purifying D-sodium erythorbate, comprising the following steps:

[0044] (1) adding dimethyl carbonate into a reactor, adding 2-keto-D-gluconic acid, the molar ratio of dimethyl carbonate and 2-keto-D-gluconic acid being 6:1, adding 10% of the mass of 2-keto-D-gluconic acid of natural zeolite, starting stirring, and heating to 70-80°C, and reacting for 2h to obtain an esterification liquid, the esterification yield being 98.4%;

[0045] (2) adding concentrated ammonia water into the esterification liquid obtained in step (1), the amount of the concentrated ammonia water being 40% of the mass of 2-keto-D-gluconic acid, and reacting for 2h to obtain a reaction liquid;

[0046] (3) filtering the reaction liquid obtained in step (2) to obtain a filtrate and a filter cake, the filter cake being a catalyst which can be reused after regeneration;

[0047] (4) heating and distilling under reduced pressure the filtrate obtained in step (3) to obtain methanol, dimethyl carbonate, and a remaining component which is a crude D-sodium erythorbate;

[0048] (5) The crude D-sodium erythorbate obtained in step (4) is dissolved in 10 times its mass of deionized water to obtain a D-sodium erythorbate aqueous solution, which is then slowly added to a saturated sodium chloride aqueous solution at a temperature of -10 to -5°C, the mass ratio of the saturated sodium chloride aqueous solution to the D-sodium erythorbate aqueous solution being 5:1, and a solid is precipitated, which is filtered, washed, and dried to obtain pure D-sodium erythorbate, the total yield being 94.2% and the purity being 99.91%.

[0049] Comparative Example 1

[0050] Comparative Example 1 differs from Example 3 in that in step (1), methanol is used instead of dimethyl carbonate, and the other steps are the same as in Example 3, which will not be repeated. The final esterification yield is 86.5%, the total yield is 82.5%, and the purity is 98.3%.

[0051] Comparative Example 2

[0052] Comparative Example 2 differs from Example 3 in that in step (1), concentrated sulfuric acid is used instead of a catalyst, and the other steps are the same as in Example 3, which will not be repeated. The final esterification yield is 87.1%, the total yield is 83.1%, and the purity is 97.9%.

[0053] Comparative Example 3

[0054] Comparative Example 3 differs from Example 3 in that in step (1), the purification process is crystallization with deionized water, and the other steps are the same as in Example 3, which will not be repeated. The final total yield is 92.1%, and the purity is 98.3%.

Claims

1. A method for purifying sodium D-erythorbate, comprising the following steps: (1) adding dimethyl carbonate into a reactor, adding a catalyst, then adding 2-keto-D-gluconic acid, starting stirring, and heating to 60-80℃, and reacting for 1-3 hours to obtain an esterification solution with an esterification yield of greater than 98%; (2) adding an inorganic base into the esterification solution obtained in step (1) and reacting for 1-2 hours to obtain a reaction solution; (3) filtering the reaction solution obtained in step (2) to obtain a filtrate and a filter cake, and the filter cake is the catalyst which can be reused after regeneration; (4) heating and distilling the filtrate obtained in step (3) under reduced pressure to obtain methanol and dimethyl carbonate, and the remaining component is a crude sodium D-erythorbate product; (5) purifying the crude sodium D-erythorbate product obtained in step (4) to obtain a pure sodium D-erythorbate product with a purity of greater than 99.8% and a total yield of greater than or equal to 94.2%; The catalyst in step (1) is a natural zeolite, hydrogen-type β molecular sieve, WO 3 / one of ZrO2 solid acids; In step (2), the inorganic base is at least one of sodium carbonate and concentrated ammonia water, and the inorganic base is added in an amount of 30-60% of the mass of 2-keto-D-gluconic acid.

2. The purification method according to claim 1, characterized by, In step (1), the molar ratio of dimethyl carbonate to 2-keto-D-gluconic acid is 3-6:

1.

3. The purification method according to claim 1, characterized by, In step (1), the mass of the catalyst is 5-10% of the mass of 2-keto-D-gluconic acid.

4. The purification method according to claim 1, characterized by, In step (4), the dimethyl carbonate can be reused.

5. The purification method according to claim 1, characterized by, In step (5), the purification process is that the crude sodium D-erythorbate product is dissolved in deionized water to obtain a sodium D-erythorbate aqueous solution, then slowly added to ethanol with a temperature of -5-10℃, and the solid is precipitated, filtered, washed, and dried to obtain the pure sodium D-erythorbate product.

6. The purification method according to claim 5, characterized by, The mass ratio of the deionized water to the crude sodium D-erythorbate product is 7-10:1, and the mass ratio of the ethanol to the sodium D-erythorbate aqueous solution is 3-5:

1.

7. The purification method according to claim 1, characterized by, In step (5), the purification process is that the crude sodium D-erythorbate product is dissolved in deionized water to obtain a sodium D-erythorbate aqueous solution, then slowly added to saturated sodium chloride aqueous solution with a temperature of -10--5℃, and the solid is precipitated, filtered, washed, and dried to obtain the pure sodium D-erythorbate product.

8. The purification method according to claim 7, characterized by, The mass ratio of the deionized water to the crude sodium D-erythorbate product is 7-10:1, and the mass ratio of the saturated sodium chloride aqueous solution to the sodium D-erythorbate aqueous solution is 3-5:1.