Preparation method of calcium threonate

Abstract

The invention discloses a preparation method of calcium threonate, which comprises the following steps: (1) adding a certain amount of vitamin C into a closed high-pressure reaction kettle, degassing, injecting 99% pure oxygen, heating and stirring for dehydration reaction; (2) transferring calcium oxide powder into a reaction kettle by using a powder transfer machine, continuously degassing for a period of time, heating and stirring to generate calcium hydroxide; (3) injecting hydrogen into the reaction kettle after the hydroxylation reaction of calcium oxide, heating and stirring to synthesize calcium ascorbate; (4) after calcium ascorbate reaction synthesis, injecting 99% pure oxygen, heating and stirring to carry out calcium threonate synthesis reaction; and (5) after the synthesis reaction of the calcium threonate is completed, discharging nitrogen into a water recovery tank connected with the lower part of the reactor. The method is short in process route and free of solid waste, the prepared calcium threonate product is stable in performance, the purpose of balancing and supplementing microelements can be achieved, the process is simple, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of organic trace element chelates, and specifically relates to a preparation method of calcium threonate. Background Art

[0002] Calcium threonate is a nutritional enhancer that is almost odorless, tasteless, soluble in water, and easily soluble in hot water in the form of crystalline powder or granules. It has the advantages of high solubility and is easily absorbed by the human body. With the improvement of people's living standards and the increasing emphasis on health, nutritional enhancers are increasingly being used in various foods. With the development of the chemical industry, the demand for calcium L-threonate is increasing. The traditional process for preparing calcium threonate is to use hydrogen peroxide for oxidation, and a large amount of calcium carbonate needs to be added. The waste residue produced is 1.5 times that of the finished product, which is not environmentally friendly and is not conducive to industrial production. Alternatively, acetone is used to remove ascorbic acid browning products and alcohol solvents during the crystallization process, which will cause environmental pollution and skin irritation. Summary of the invention

[0003] Against this background, the present invention provides a method for preparing calcium threonate based on a stepwise addition reaction of oxygen and hydrogen, which has simple operation steps, can effectively overcome the characteristics of ascorbic acid being easily volatile when exposed to light and heat, and realizes industrialization. The process route is short and there are no solid pollutants.

[0004] The objective of the present invention is achieved through the following technical solutions: The invention provides a preparation method of calcium threonate, comprising the following steps: (1) adding a certain amount of vitamin C to a closed high-pressure reactor, degassing, then injecting 99% pure oxygen, heating and stirring to carry out a dehydration reaction; (2) transferring calcium oxide powder to the reactor by a powder transfer machine, continuing to degas for a period of time, heating and stirring to generate calcium hydroxide; (3) injecting hydrogen into the reactor after a hydroxylation reaction of calcium oxide, heating and stirring to synthesize calcium ascorbate; (4) injecting 99% pure oxygen after the reaction and synthesis of calcium ascorbate, heating and stirring to carry out a calcium threonate synthesis reaction; (5) after the calcium threonate synthesis reaction is completed, filling nitrogen into the reactor for gas drying, maintaining the internal pressure of the reactor to remove residual water after the reaction, and finally discharging the nitrogen into a water recovery tank connected to the lower part of the reactor.

[0005] Preferably, in step (1), the molar ratio of L-ascorbic acid to oxygen is 2:1, the reaction temperature is 35° C.-60° C., and the reaction time is 3 s-40 min.

[0006] Preferably, the molar ratio of water to calcium oxide in the dehydration reaction in step (2) is 1:2, the temperature is 25-60° C., and the reaction time is 10-55 minutes.

[0007] Preferably, in step (3), the molar ratio of hydrogen to dihydroascorbic acid is 2:1, the reaction temperature is 35-60° C., and the reaction time is 1-50 minutes.

[0008] Preferably, in step (4), the molar ratio of calcium ascorbate to oxygen is 2:1, the reaction temperature is 35-60° C., and the reaction time is 1-50 minutes.

[0009] Preferably, the nitrogen filling pressure in step (5) is 1-9 kg / cm 3 , drying time is 10-60min.

[0010] Compared with the prior art, the present invention has the following beneficial effects: (1) It can inhibit the browning caused by the oxidation and hydrolysis of ascorbic acid during the conventional calcium threonate synthesis process and improve stability; (2) The use of alcohol and organic solvents in the conventional calcium threonate synthesis process can be eliminated, thereby reducing environmental pollution and eliminating the risk of organic solvent residues in the product; (3) Improve production efficiency and speed and reduce product costs.

[0011] (4) Calcium hydroxide is directly produced using calcium oxide as a raw material and water from the dehydration reaction of ascorbic acid. Compared with the calcium carbonate and calcium hydroxide raw materials for the traditional synthesis of calcium threonate, the source of calcium raw materials is increased. DETAILED DESCRIPTION

[0012] In order to better understand the content of the present invention, further description is given below in conjunction with specific embodiments. It should be understood that these embodiments are only used to further illustrate the present invention, and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content described in the present invention, those skilled in the art make some non-essential changes or adjustments to the present invention, which still belong to the protection scope of the present invention. Example 1

[0013] (1) Add 100g of vitamin C to the autoclave, keep it sealed and use a vacuum pump to degas for 5 minutes, then inject 9.1g of 99% pure oxygen, raise the temperature to 60°C and stir for 31 minutes to dehydrate. (2) After the dehydration reaction is completed, use a pneumatically driven powder transfer machine to transfer 15.92g of calcium oxide powder to the reactor, then use a vacuum pump to degas for 5 minutes, raise the temperature to 60°C and react for 10 minutes to generate calcium hydroxide. (3) Inject 0.58g of hydrogen into the reactor, raise the temperature to 60°C and stir for 27 minutes to generate calcium ascorbate. (4) After the reaction is completed, inject 9.1g of 99% pure oxygen into the reactor, raise the temperature to 60°C and continue stirring for 30 minutes to generate calcium threonate. (5) After the calcium threonate synthesis reaction is completed, nitrogen is filled into the reactor for gas drying, and the internal pressure of the reactor is maintained at 8.0 kg / cm3 to remove the residual moisture after the reaction. The drying time is 30 minutes, and finally the nitrogen is discharged into the water recovery tank connected to the lower part of the reactor. Example 2

[0014] (1) Add 100g of vitamin C to the autoclave, keep it sealed and use a vacuum pump to degas for 5min, then inject 9.1g of 99% pure oxygen, raise the temperature to 58℃ and stir for 35min. (2) After the dehydration reaction is completed, use a pneumatically driven powder transfer machine to transfer 15.92g of calcium oxide powder to the reactor, and then use a vacuum pump to degas for 5min, raise the temperature to 60℃ and react for 10min to generate calcium hydroxide. (3) Inject 0.57g of hydrogen into the reactor, raise the temperature to 58℃ and stir for 30min to generate calcium ascorbate. (4) After the reaction is completed, inject 9.1g of 99% pure oxygen into the reactor, raise the temperature to 60℃ and continue stirring for 30min to generate calcium threonate. (5) After the calcium threonate synthesis reaction is completed, fill the reactor with nitrogen for gas drying, maintain the internal pressure of the reactor at 7.0kg / cm3 to remove the residual water after the reaction, and the drying time is 35min. Finally, discharge the nitrogen into the water recovery tank connected to the lower part of the reactor. Example 3

[0015] (1) Add 100g of vitamin C to the autoclave, keep it sealed and use a vacuum pump to degas for 5 minutes, then inject 9.1g of 99% pure oxygen, raise the temperature to 60℃ and stir for 30 minutes. (2) After the dehydration reaction is completed, use a pneumatically driven powder transfer machine to transfer 15.92g of calcium oxide powder to the reactor, and then use a vacuum pump to degas for 5 minutes, raise the temperature to 58℃ and react for 20 minutes to generate calcium hydroxide. (3) Inject 0.58g of hydrogen into the reactor, raise the temperature to 58℃ and stir for 35 minutes to generate calcium ascorbate. (4) After the reaction is completed, inject 9.1g of 99% pure oxygen into the reactor, raise the temperature to 60℃ and continue stirring for 40 minutes to generate calcium threonate. (5) After the calcium threonate synthesis reaction is completed, fill the reactor with nitrogen for gas drying, maintain the internal pressure of the reactor at 7.0kg / cm3 to remove the residual water after the reaction, and the drying time is 35 minutes. Finally, discharge the nitrogen into the water recovery tank connected to the lower part of the reactor.

[0016] Comparative Example 1 100g of ascorbic acid was added to the reactor, and then 250g of water was added to dissolve, and 190g of a hydrogen peroxide solution with a mass concentration of 30% was added, and the reaction was carried out for 31 minutes. 21.04g of calcium hydroxide was transferred to a closed container by a powder transfer machine, and the reaction temperature was controlled at 60°C, and the reaction time was 57 minutes. After adding catalase to remove molecular oxygen in the solution, the solution was filtered, and then vacuum distilled and concentrated at 50°C, and finally 280mL of ethanol was added, crystallized, filtered, and dried to obtain a calcium threonate product. The calcium content of the prepared calcium threonate was 12.81%, the yield was 61.6%, the ascorbic acid conversion rate was 54.25%, and the product purity was 99.2%.

[0017] Comparative Example 2 100g of ascorbic acid was added to the reactor, and 225g of a hydrogen peroxide solution with a mass concentration of 30% was added, and the reaction was carried out for 31min. Then, 28.4g of calcium carbonate was added to 100ml of water to prepare a suspension, and the suspension was added dropwise to the reaction system in batches. The reaction temperature was controlled to be 60°C, and the reaction time was 57min. At the same time, the excess hydrogen peroxide was decomposed, filtered, and a mother liquor was obtained, and then vacuum distilled and concentrated at 50°C. Finally, 280mL of ethanol was added, crystallized, filtered, and dried to obtain a calcium threonate product. The calcium content of the calcium threonate product was 12.72%, the yield was 43%, the ascorbic acid conversion rate was 37.87%, and the product purity was 98.1%.

[0018] Table 1 Test results of calcium L-threonate powder prepared in Example 1 and Comparative Examples 1-2 project Example 1 Comparative Example 1 Comparative Example 2 Calcium content 12.92% 12.81% 12.72% Ascorbic acid conversion rate 78.56% 54.25% 37.87% Yield 89.2% 61.6% 43% purity 99.8% 99.2% 98.1% According to the test results in Table 1, the difference between Comparative Examples 1-2 and Example 1 is that the means of providing oxidation are different. Comparative Example 1 uses hydrogen peroxide for catalytic oxidation under the catalysis of catalase, and the final product yield is lower than that of Example 1, and the ascorbic acid conversion rate is not as high as that of Example 1. Comparative Example 2 uses a conventional process for preparing calcium threonate for verification, and the effect is not as good as that of Comparative Example 1, let alone Example 1.

Claims

1. A method for preparing calcium threonate, characterized in that: The following steps are involved: (1) Add a certain amount of vitamin C into a sealed autoclave and degas for 5 minutes, then inject 99% pure oxygen, heat and stir to carry out dehydration reaction; (2) using a powder transfer machine to transfer the calcium oxide powder to the reactor, continue degassing for 5 minutes, and heat and stir to generate calcium hydroxide; (3) After the calcium oxide hydroxylation reaction, hydrogen is injected into the reactor, and the temperature is increased and stirred to synthesize calcium ascorbate; (4) After the calcium ascorbate is synthesized, 99% pure oxygen is injected, and the temperature is raised and stirred to carry out the calcium threonate synthesis reaction; (5) After the calcium threonate synthesis reaction is completed, nitrogen is filled into the reactor for gas drying, the internal pressure of the reactor is maintained to remove the residual water after the reaction, and finally the nitrogen is discharged into a water recovery tank connected to the lower part of the reactor.

2. The method for preparing calcium threonate according to claim 1, characterized in that: In the step (1), the molar ratio of L-ascorbic acid to oxygen is 2:1, the reaction temperature is 35°C-60°C, and the reaction time is 3s-40min.

3. The method for preparing calcium threonate according to claim 1, characterized in that In the dehydration reaction in step (2), the molar ratio of water to calcium oxide is 1:2, the reaction temperature is 25-60° C., and the reaction time is 10-55 minutes.

4. The method for preparing calcium threonate according to claim 1, characterized in that In the step (3), the molar ratio of hydrogen to dihydroascorbic acid is 2:1, the reaction temperature is 35-60° C., and the reaction time is 1-50 minutes.

5. The method for preparing calcium threonate according to claim 1, characterized in that In the step (4), the molar ratio of calcium ascorbate to oxygen is 2:1, the reaction temperature is 35-60° C., and the reaction time is 1-50 minutes.

6. The method for preparing calcium threonate according to claim 1, characterized in that The nitrogen filling pressure in step (5) is 1-9 kg / cm 3 , drying time is 10-60min.