Method for efficiently synthesizing high-purity ferric glycerophosphate

Abstract

The invention relates to a method for efficiently synthesizing high-purity ferric glycerophosphate. The method comprises the following steps: dropwise adding a sodium hydroxide aqueous solution into a glycerophosphate aqueous solution at 40-50 DEG C in N2 atmosphere to adjust the pH value to 5-6, dropwise adding a ferrous salt aqueous solution, fully mixing, slowly dropwise adding an alkali aqueous solution to adjust the pH value to 7-8, carrying out a heat preservation reaction for 3 hours, reducing the temperature to room temperature, and continuing the heat preservation reaction; after the reaction is finished, discharging, concentrating to remove water, adding an alcohol solution for recrystallization, and filtering to obtain a ferrous glycerophosphate crude product; adding ethanol into the crude product to prepare turbid liquid, dropwise adding the turbid liquid into an oxidation kettle filled with glycerophosphate, carrying out curing reaction after dropwise adding to obtain an iron glycerophosphate crude product, and filtering, washing and drying the crude product to obtain an iron glycerophosphate pure product.

Description

Technical Field

[0001] This invention belongs to the field of organic chemistry, and in particular relates to a method for preparing high-purity ferric glycerol phosphate by preferentially preparing ferrous glycerol phosphate. Background Technology

[0002] Ferric glycerol phosphate is an organic iron compound commonly used in food additives and pharmaceuticals. Compared to traditional inorganic iron supplements, ferric glycerol phosphate is more stable, less irritating to the gastrointestinal tract, and more easily absorbed and transported by the human body. Ferric glycerol phosphate is also used as an additive to increase the iron content in food and beverages to meet the nutritional needs of specific populations. In animal feed, ferric glycerol phosphate can effectively prevent anemia, promote animal growth, and improve reproductive capacity. In the pharmaceutical field, ferric glycerol phosphate is used as a main ingredient in oral iron supplements and preparations, and can also be compounded for intravenous iron supplementation. In addition, ferric glycerol phosphate is also used in small quantities in skin care products for its antioxidant and cellular metabolism regulating effects.

[0003] Traditional methods for preparing ferric glycerol phosphate are limited by the precipitating nature of ferric ions, requiring stringent reaction conditions. Most methods employ low pH and low temperature conditions to reduce premature precipitation of ferric ions and improve reaction yield and product purity. However, this process is slow, time-consuming, and incomplete. Furthermore, subsequent pH adjustments can easily lead to the precipitation of unreacted ferric ions or the conversion of ferric glycerol phosphate into ferric hydroxide colloids, making subsequent purification difficult. Theoretical calculations show that the complete formation of ferric hydroxide precipitate occurs at pH 2.8, while the actual complete precipitation pH is approximately 4. The complete formation of ferrous hydroxide precipitate occurs at approximately pH 9. Therefore, prioritizing the preparation of ferrous glycerol phosphate can effectively avoid interference from ferric hydroxide colloids, improving reaction efficiency and product purity.

[0004] Furthermore, the selection of the oxidant and the dropping rate of ferrous glycerol phosphate are crucial factors affecting the reaction during the oxidation process. Choosing a suitable oxidant is essential to prevent over-oxidation and the introduction of byproducts, while minimizing the introduction and generation of water that could lead to excessive precipitation of iron ions. Adjusting the dropping rate of ferrous glycerol phosphate is also indispensable, effectively preventing excessively high local iron ion concentrations that could result in reduced yield and product purity. Summary of the Invention

[0005] To address the above problems, this invention provides a method for efficiently preparing high-purity glycerol ferric phosphate.

[0006] The technical solution adopted in this invention is a two-step method for preparing ferric glycerol phosphate. First, sodium hydroxide aqueous solution is added dropwise to an aqueous solution of glycerophosphate, followed by the addition of ferrous salt. After concentration, filtration, alcohol washing, secondary filtration, and drying, crude ferrous glycerol phosphate is prepared. Then, it is oxidized in alcohol and an oxidizing agent to prepare ferric glycerol phosphate.

[0007] A method for efficiently synthesizing high-purity glycerol ferric phosphate includes the following steps: a) In an inert atmosphere, an aqueous solution of glycerol phosphate is added dropwise to a weakly acidic environment, and the pH is adjusted to 7-8 with an alkaline solution. The reaction is then kept at a constant temperature. After the reaction, the temperature is lowered and the mixture is allowed to mature further. The matured reaction solution is then concentrated, precipitated with alcohol, filtered, and washed to obtain crude glycerol phosphate. b) Disperse the crude product obtained in step a) in alcohol, add an oxidizing agent and glycerophosphate, and after oxidative ripening reaction, pulp, filter and dry to obtain pure glycerophosphate.

[0008] In step a), the initial molar ratio of glycerophosphate to ferrous salt is (0.9-1.1):1; the mass concentration of the ferrous salt aqueous solution is 3-10 wt%, specifically any value or range of 3-10 wt%, preferably 5 wt%.

[0009] The ferrous salt is selected from at least one of ferrous chloride, ferrous sulfate, ferrous nitrate, and ferrous acetate, with ferrous chloride being preferred.

[0010] The weakly acidic environment refers to adjusting the pH of the purchased glycerophosphate aqueous solution to 5-6 by adding an alkaline solution.

[0011] To ensure a more homogeneous system, the ambient temperature should be maintained at 45-55 ℃ during the dropwise addition of the ferrous salt aqueous solution.

[0012] Step a) is carried out entirely in a nitrogen or argon atmosphere, with a reaction temperature of 45-55 ℃ and a reaction time of 2-4 h; after the reaction, the temperature is lowered to ≤10 ℃ (preferably ≤5 ℃ or ≤0 ℃), and the ripening time is 2-4 h, ensuring that the temperature inside the reactor is less than or equal to 10 ℃ at the end of the ripening reaction.

[0013] The alkaline solution in step a) is a 5-15 wt% aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, DBU or triethylamine, preferably a 10 wt% aqueous solution of sodium hydroxide.

[0014] In step b), the alcohol is a C1-C4 monohydric alcohol, including methanol, ethanol, isopropanol, n-butanol or any combination thereof, with ethanol being preferred.

[0015] In step b), the oxidant is at least one of air, oxygen, hydrogen peroxide, potassium permanganate, and potassium dichromate, with air being preferred.

[0016] In step b), the oxidation reaction temperature is 35-45 ℃, and the aging time is 40-50 h. During the oxidation process, glycerophosphate equivalent to 0.3-0.5 times ferrous chloride is added, preferably 0.5 times glycerophosphate.

[0017] In step b), a suspension of ferrous glycerophosphate is added dropwise to the glycerophosphate; the dropwise addition rate of the ferrous glycerophosphate is 20-60 mL / min, more preferably the rate is 30-35 mL / min for the first 20% volume, 50-55 mL / min for the middle 20% to 80% volume, and 15-20 mL / min for the last 20% volume.

[0018] The obtained glycerol has an iron phosphate content (on a dry basis) of 98 wt%~102 wt%, pH <1.5 mL / g (monobasic acid or monobasic base), free glycerol and alcohol solubles ≤0.5 wt%, phosphate (as PO4) ≤0.04 wt%, sulfate (as SO4) ≤0.1 wt%, chloride (as Cl) ≤0.07 wt%, arsenic ≤3.0 mg / kg, cadmium ≤0.5 mg / kg, lead ≤2.0 mg / kg, and drying loss ≤12 wt%.

[0019] In some specific embodiments, the preparation method of the present invention includes the following steps: Step 1: Perform multiple gas replacements on the 20 L reactor to ensure that the reactor is completely in a nitrogen atmosphere, and connect an external nitrogen cylinder to ensure nitrogen flow.

[0020] Step 2: Turn on the high and low temperature integrated machine, set the external temperature to 50 ℃, and heat up to the internal temperature of 45-50 ℃.

[0021] Step 3: Add glycerol phosphate to a 20 L reactor, add 10 wt% sodium hydroxide aqueous solution to adjust the pH to 5~6, add ultrapure water to dilute to a mass fraction of 25%~35%, and stir to mix evenly.

[0022] Step 4: Slowly add 5 wt% ferrous chloride aqueous solution to a 20 L reactor. After the addition is complete, add 10 wt% sodium hydroxide aqueous solution to adjust the pH of the system to 7.5-8, and keep the reaction at this temperature for 3 h.

[0023] Step 5: Set the external temperature of the high and low temperature integrated machine to 5 ℃ and stir continuously for 3 h to ensure that the temperature inside the vessel is less than or equal to 10 ℃ at the end of the reaction.

[0024] Step 6: After the reaction is complete, discharge the material, concentrate the reaction volume to 5 L, add 2.5 L of ethanol for recrystallization, stir for 30 min and let stand for 1 h, filter, wash the filter cake with a small amount of ethanol and add 5 L of ethanol to prepare a turbid solution.

[0025] Step 7: Add 0.5 equivalents of glycerophosphate to the oxidation vessel and heat to 40 °C. Slowly add ferrous glycerophosphate suspension, continuously blow air, keep warm and stir for 48 h.

[0026] Step 8: After the reaction is complete, discharge the material, filter it, add a small amount of ethanol to the filter cake, and after multiple pulping and filtration processes, dry it to obtain a high-purity glycerol ferric phosphate product.

[0027] Another technical solution of the present invention is the use of the glycerol ferric phosphate prepared by the method in food, health products, pharmaceutical preparations or animal feed.

[0028] The advantages and positive effects of this invention are as follows: A novel method for preparing ferric glycerol phosphate by preferentially oxidizing crude ferrous glycerol phosphate: This method uses ferrous ions with a higher pH value to completely precipitate and preferentially react with the ferric ions, avoiding the influence of the ferric ions' tendency to form ferric hydroxide colloids on the reaction. This accelerates the reaction rate and improves the reaction yield. Furthermore, compared to the stringent temperature and pH requirements of traditional methods for preparing ferric glycerol phosphate, this method exhibits superior stability and applicability in scale-up equipment.

[0029] The technical solution of this invention almost eliminates the influence of trivalent iron hydrolysate colloid on the reaction and purification; the reaction is completed at atmospheric pressure and 40-50℃; the total yield is ≥64%, the glycerol ferric phosphate content (on a dry basis) is 98 wt%~102 wt%, the pH is <1.5 mL / g (monobasic acid or monobasic base), the soluble matter in free glycerol and alcohol is ≤0.5 wt%, phosphate (as PO4) is ≤0.04 wt%, sulfate (as SO4) is ≤0.1 wt%, chloride (as Cl) is ≤0.07 wt%, arsenic is ≤3.0 mg / kg, cadmium is ≤0.5 mg / kg, lead is ≤2.0 mg / kg, and the drying weight loss is ≤12 wt%; the process can be seamlessly scaled up to a thousand-ton-level plant.

[0030] (1) Almost no Fe was detected throughout the entire process. 3+ Hydrolysis simplifies product purification. (2) It can be oxidized in air without the need to add any additional oxidant. The oxidation conditions are mild, green and safe. (3) Adding an equivalent amount of glycerophosphate during the oxidation stage can induce crystal transformation, increase the formation rate of glycerophosphate iron, and inhibit Fe. 3+ free; (4) The reaction temperature is 40-50 ℃, the pressure is normal, and there are no special requirements for the material. Ordinary glass-lined kettles are sufficient. (5) It has been verified that the linear scale-up of 50 L-1000 L is less than 1.2% between batches, making it suitable for continuous production.

[0031] (6) The technical solution of the present invention can achieve a yield of more than 50%, more preferably more than 60%, more preferably more than 70%, more preferably more than 80%, and more preferably more than 90%. The glycerol ferric phosphate content is greater than 98%, more preferably greater than 99%, and more preferably greater than 100%. Detailed Implementation

[0032] The embodiments of the present invention will be described below.

[0033] This invention relates to a method for efficiently synthesizing high-purity ferric glycerol phosphate. Ferrous salt is added dropwise to an aqueous solution of sodium glycerophosphate, followed by concentration, filtration, alcohol washing, secondary filtration, and drying to prepare crude ferrous glycerophosphate. This crude ferric glycerophosphate is then oxidized in an alcohol solution and an oxidizing agent to prepare crude ferric glycerophosphate. After filtration, pulping purification, filtration, and drying, a high-purity ferric glycerophosphate product is obtained.

[0034] Example 1: Under a nitrogen atmosphere, 1.97 kg of 35 wt% glycerophosphate (4 mol) aqueous solution was added to a 20 L reactor. The temperature was raised to the set internal temperature, and 800 g of 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 10.14 kg of 5 wt% ferrous chloride aqueous solution was added dropwise to the 20 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was added slowly to adjust the pH of the system to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature reactor was set to 10 ℃, and stirring was continued for 3 h. At the end of the reaction, the internal temperature of the reactor was 11 ℃. The reaction mixture was discharged, and the reaction volume was concentrated to 5 L. 2.5 L of ethanol was added for recrystallization. After stirring for 30 min, the mixture was allowed to stand for 1 h, filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of ethanol. This solution was then added dropwise at a rate of 50-55 mL / min to an oxidation reactor containing 344.16 g of glycerophosphate at 40 ℃. Air was continuously blown in, and the reactor was kept at this temperature and stirred for 48 h. After the reaction is complete, the material is discharged, filtered, and the filter cake is mixed with 0.5 L of ethanol and then dried after three slurry-filtration processes.

[0035]

[0036] Example 2: Under a nitrogen atmosphere, 1.97 kg of 35 wt% glycerophosphate (4 mol) aqueous solution was added to a 20 L reactor. The temperature was raised to 50 °C, and 800 g of 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 10.14 kg of 5 wt% ferrous chloride aqueous solution was added dropwise to the 20 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the system to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature integrated reactor was set to a certain temperature, and stirring was continued for 3 h. The temperature inside the reactor at the end of the reaction was recorded. The material was discharged, and the reaction volume was concentrated to 5 L. 2.5 L of ethanol was added for recrystallization. After stirring for 30 min, the mixture was allowed to stand for 1 h, filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of ethanol. This solution was then added dropwise at a rate of 50-55 mL / min to an oxidation reactor containing 344.16 g of glycerophosphate at 40 °C. Air was continuously blown in, and the reactor was kept at this temperature and stirred for 48 h. After the reaction is complete, the material is discharged, filtered, and the filter cake is mixed with 0.5 L of ethanol and then dried after three slurry-filtration processes.

[0037]

[0038] Example 3: Under a nitrogen atmosphere, 1.97 kg of 35 wt% glycerophosphate (4 mol) aqueous solution was added to a 20 L reactor. The temperature was raised to 50 °C, and 800 g of 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 10.14 kg of 5 wt% ferrous chloride aqueous solution was added dropwise to the 20 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature reactor was set to 5 °C, and stirring was continued for 3 h. The internal temperature was maintained at 7 °C at the end of the reaction. The mixture was discharged, and the reaction volume was concentrated to 5 L. 2.5 L of ethanol was added for recrystallization. After stirring for 30 min, the mixture was allowed to stand for 1 h, filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of alcohol solvent. This solution was then added dropwise at a rate of 50-55 mL / min to an oxidation reactor containing 344.16 g of glycerophosphate at 40 °C. Air was continuously blown in, and the mixture was kept at this temperature and stirred for 48 h. After the reaction is complete, the material is discharged, filtered, and the filter cake is mixed with 0.5 L of ethanol and then dried after three slurry-filtration processes.

[0039]

[0040] Example 4: Under a nitrogen atmosphere, 1.97 kg of a 35 wt% glycerophosphate (4 mol) aqueous solution was added to a 20 L reactor. The temperature was raised to 50 °C, and 800 g of a 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. Then, 4 mol of Fe2+ was added dropwise to the 20 L reactor at a uniform rate. 2+ A ferrous salt aqueous solution (5%–10% by mass) was slowly added dropwise with 10 wt% sodium hydroxide aqueous solution to adjust the pH of the system to 7.5–8, and the reaction was maintained at this temperature for 3 hours. The external temperature of the high-low temperature integrated reactor was set to 5 °C, and stirring was carried out continuously for 3 hours. At the end of the reaction, the internal temperature was 7 °C. The material was discharged, the reaction volume was concentrated to 5 L, 2.5 L of ethanol was added for recrystallization, and the mixture was stirred for 30 minutes and allowed to stand for 1 hour. The mixture was then filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of ethanol. This solution was then added dropwise at a rate of 50–55 mL / min to an oxidation reactor containing 344.16 g of glycerophosphate at 40 °C. Air was continuously blown out, and the mixture was kept at this temperature and stirred for 48 hours. After the reaction was completed, the material was discharged, filtered, and the filter cake was added with 0.5 L of ethanol and subjected to three slurry filtrations before drying.

[0041]

[0042] Example 5: Under a nitrogen atmosphere, 1.97 kg of 35 wt% glycerophosphate (4 mol) aqueous solution was added to a 20 L reactor. The temperature was raised to 50 °C, and 800 g of 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 10.14 kg of 5 wt% ferrous chloride aqueous solution was added dropwise to the 20 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH of the system to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature reactor was set to 5 °C, and stirring was continued for 3 h. The internal temperature was 7 °C at the end of the reaction. The mixture was discharged, and the reaction volume was concentrated to 5 L. 2.5 L of ethanol was added for recrystallization. After stirring for 30 min, the mixture was allowed to stand for 1 h, filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of ethanol. This solution was then added dropwise at a controlled rate to an oxidation reactor containing 344.16 g of glycerophosphate at 40 °C. Air was continuously blown in, and the reactor was kept at this temperature and stirred for 48 h. After the reaction is complete, the material is discharged, filtered, and the filter cake is mixed with 0.5 L of ethanol and then dried after three slurry-filtration processes.

[0043]

[0044] Example 6: Under a nitrogen atmosphere, 1.97 kg of a 35 wt% glycerophosphate aqueous solution was added to a 20 L reactor. The temperature was raised to 50 °C, and 800 g of a 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 10.14 kg of a 5 wt% ferrous chloride aqueous solution was added dropwise to the 20 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was slowly added dropwise to adjust the pH of the system to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature reactor was set to 5 °C, and stirring was continued for 3 h. The internal temperature was 7 °C at the end of the reaction. The reaction mixture was discharged, concentrated to a volume of 5 L, and recrystallized with 2.5 L of ethanol. After stirring for 30 min, it was allowed to stand for 1 h, filtered, and the filter cake was washed with 0.5 L of ethanol and dissolved in 5 L of ethanol. The solution was then added dropwise to an oxidation reactor containing 344.16 g of glycerophosphate at 40 °C at a rate of 30-35 mL / min for the first 20% of the volume, 15-20 mL / min for the next 20%, and 50-55 mL / min for the remaining 20% ​​to 80% of the volume. The oxidant was added simultaneously with the addition of ferrous glycerophosphate. After the addition was complete, the mixture was kept at this temperature and stirred for 48 h. After the reaction was complete, the mixture was discharged, filtered, and the filter cake was added to 0.5 L of ethanol and subjected to three slurry-filtration processes before drying.

[0045]

[0046] Example 7: Under a nitrogen atmosphere, 4.91 kg of a 35 wt% glycerophosphate (10 mol) aqueous solution was added to a 50 L reactor. The temperature was raised to 50 °C, and 800 g of a 10 wt% sodium hydroxide aqueous solution was added dropwise to adjust the pH to 6. 25.4 kg of a 10 wt% ferrous chloride aqueous solution was added dropwise to the 50 L reactor at a uniform rate, and 10 wt% sodium hydroxide aqueous solution was slowly added dropwise to adjust the pH of the system to 7.5-8. The reaction was maintained at this temperature for 3 h. The external temperature of the high-low temperature reactor was set to 5 °C, and stirring was continued for 3 h. The internal temperature was 8 °C at the end of the reaction. The reaction mixture was discharged, concentrated to a volume of 9 L, and recrystallized by adding 5 L of ethanol. After stirring for 30 min, the mixture was allowed to stand for 1 h, filtered, and the filter cake was washed with 1 L of ethanol and dissolved in 10 L of ethanol. The solution was then added dropwise to an oxidation reactor containing 860.4 g of glycerophosphate at 40 °C at a rate of 30-35 mL / min for the first 20% of the volume, 15-20 mL / min for the next 20%, and 50-55 mL / min for the remaining 20% ​​to 80% of the volume. Air was continuously blown through the reactor, and the mixture was kept at this temperature and stirred for 48 h. After the reaction was complete, the mixture was discharged, filtered, and the filter cake was added to 1 L of ethanol and subjected to three slurry-filtration processes before drying. A total of 5.84 kg of light yellow glycerophosphate powder was obtained, with a yield of 94%. The test results showed that the glycerol ferric phosphate content (on a dry basis) was 100.1 wt%, the acidity was 1.1 mL / g, the free glycerol and alcohol solubles were 0.1 wt%, the phosphate (as PO4) was 0.01 wt%, the sulfate (as SO4) was 0.01 wt%, the chloride (as Cl) was 0.05 wt%, the arsenic was 0.1 mg / kg, the cadmium was 0.06 mg / kg, the lead was 0.1 mg / kg, and the drying weight loss was 8.4 wt%.

[0047] As can be seen from the above embodiments, the above descriptions are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments, and all technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for efficiently synthesizing high-purity glycerol ferric phosphate, characterized in that, Includes the following steps: a) In an inert atmosphere, an aqueous solution of glycerol phosphate is added dropwise to a weakly acidic environment, and the pH is adjusted to 7-8 with an alkaline solution. The reaction is then kept at a constant temperature. After the reaction, the temperature is lowered and the mixture is allowed to mature further. The matured reaction solution is then concentrated, precipitated with alcohol, filtered, and washed to obtain crude glycerol phosphate. b) Disperse the crude product obtained in step a) in alcohol, add an oxidizing agent and glycerophosphate, and after oxidative ripening reaction, pulp, filter and dry to obtain pure glycerophosphate.

2. The method according to claim 1, characterized in that, In step a), the initial molar ratio of glycerophosphate to ferrous salt is (0.9-1.1):1; the mass concentration of the ferrous salt aqueous solution is 3-10 wt%; the ferrous salt is selected from at least one of ferrous chloride, ferrous sulfate, ferrous nitrate, and ferrous acetate, preferably ferrous chloride.

3. The method according to claim 1, characterized in that, Step a) is carried out entirely in a nitrogen or argon atmosphere at a reaction temperature of 45-55 ℃ for 2-4 h; after the reaction, the temperature is lowered to ≤10 ℃ and the curing time is 2-4 h.

4. The method according to claim 1, characterized in that, The alkaline solution in step a) is a 5-15 wt% aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, ammonia, DBU or triethylamine, preferably a 10 wt% aqueous solution of sodium hydroxide.

5. The method according to claim 1, characterized in that, In step b), the alcohol is a C1-C4 monohydric alcohol, including methanol, ethanol, isopropanol, n-butanol or any combination thereof, with ethanol being preferred.

6. The method according to claim 1, characterized in that, In step b), the oxidant is at least one of air, oxygen, hydrogen peroxide, potassium permanganate, and potassium dichromate, with air being preferred.

7. The method according to claim 1, characterized in that, In step b), the oxidation reaction temperature is 35-45℃, and the aging time is 40-50 h. During the oxidation process, add glycerophosphate equivalent to 0.3-0.5 times the amount of ferrous chloride.

8. The method according to claim 1, characterized in that, In step b), the rate of adding the glycerol ferrous phosphate suspension is 30-35 mL / min for the first 20% volume, 15-20 mL / min for the next 20% volume, and 50-55 mL / min for the middle 20% to 80% volume.

9. The method according to any one of claims 1-8, characterized in that, The obtained glycerol has an iron phosphate content (on a dry basis) of 98 wt%~102 wt%, pH <1.5 mL / g (monobasic acid or monobasic base), free glycerol and alcohol solubles ≤0.5 wt%, phosphate (as PO4) ≤0.04 wt%, sulfate (as SO4) ≤0.1 wt%, chloride (as Cl) ≤0.07 wt%, arsenic ≤3.0 mg / kg, cadmium ≤0.5 mg / kg, lead ≤2.0 mg / kg, and drying loss ≤12 wt%.

10. Use of the glycerol ferric phosphate prepared by the method according to any one of claims 1-9 in food, health products, pharmaceutical preparations or animal feed.

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