A method for synthesizing allantoin

Abstract

The present invention relates to the technical field of allantoin preparation, and specifically relates to a synthesis method of allantoin. The steps of the synthesis method include: (1) mixing and stirring glyoxal and nitric acid for reaction; (2) adding calcium hydroxide powder while stirring at room temperature, allowing to stand after white precipitate is precipitated; (3) filtering, washing the filter residue with water, adding calcium chloride to the filtered mother liquor, stirring and dissolving, then dropping sodium hydroxide aqueous solution, stopping adding alkali when the pH reaches 3.0 - 3.5, and allowing to stand to obtain fine-grained white calcium glyoxalate solid; (4) dissolving the obtained calcium glyoxalate with hydrochloric acid, adding urea and stirring for reaction, and white precipitate is formed as the reaction proceeds; filtering, washing and drying the obtained precipitate to obtain the product allantoin. The purpose of the present invention is to provide a synthesis method of allantoin, aiming to reduce production costs and improve the product yield and purity.

Description

Technical Field

[0001] The present invention relates to the technical field of allantoin preparation, and particularly relates to a synthesis method of allantoin. Background Art

[0002] Allantoin (C4H6N4O3) is an important organic compound with a wide range of application fields, such as medicine, cosmetics, and pesticides. The heterocyclic structure in its molecular structure endows it with unique chemical and biological activities, making it an important component in various products. The traditional extraction methods of allantoin mainly come from organisms, such as allantoic fluid, fetal urine, and some plants, but these methods are costly and difficult to meet the needs of large-scale industrial production.

[0003] There are various synthesis methods of allantoin, and the development and evolution of these methods have gone through a relatively long process. Early research mainly focused on preparing allantoin through chemical synthesis methods, such as the oxidation method of urea with permanganic acid, the hydrochloric acid dissolution method of calcium glyoxylate, and the condensation cyclization method of glyoxylic acid and urea. Although these methods can achieve the synthesis of allantoin to a certain extent, they have problems such as complex processes, high costs, and low yields, which limit their industrial applications.

[0004] With the progress of technology and the continuous development of chemical engineering technology, new allantoin synthesis methods have emerged continuously. Among them, the glyoxal oxidation-urea condensation cyclization method is the method commonly used in the industrial circles at home and abroad. This method makes urea react with glyoxylic acid under specific temperature and stirring conditions in an acidic medium to generate a white precipitate of allantoin. This process has the advantages of wide raw material sources, low production costs, simple process flow, few by-products, easy treatment of three wastes, and low energy consumption, showing good development potential.

[0005] In addition to the glyoxal oxidation-urea condensation cyclization method, there are also some other innovative allantoin synthesis methods. For example, a synthesis method using a mixture of bisulfate and sulfuric acid, a mixture of hydrogen phosphate and phosphoric acid, bisulfate or hydrogen phosphate as a catalyst with glyoxylic acid and urea as raw materials can significantly improve the yield of allantoin, while reducing the acidity of the synthesis mother liquor, making the mother liquor can be used as fertilizer after treatment, achieving green energy conservation and environmental protection and good ecological effects.

[0006] In addition, there is a synthesis method using acidic ionic liquid as a catalyst. This method also uses glyoxylic acid and urea as raw materials and realizes the high-yield synthesis of allantoin through a simple process flow. This process not only has easily available raw materials and is easy to be popularized industrially, but also has no pollution, is green, energy-saving and environmentally friendly, and has good social and economic benefits.

[0007] The synthesis method of allantoin has experienced a continuous development and optimization process from complexity to simplicity, from high cost to low cost, and from low yield to high yield. At present, the glyoxal oxidation-urea condensation cyclization method and its improved methods have become the mainstream technologies for industrial production of allantoin. However, with the progress of technology and the changes in market demand, it is still necessary to continuously explore and innovate the synthesis method of allantoin to meet the needs of allantoin in different fields. Based on this, the present invention proposes a synthesis method of allantoin. Summary of the Invention

[0008] The object of the present invention is to provide a synthesis method of allantoin, aiming to reduce production costs, improve the product yield and purity.

[0009] The present invention provides a synthesis method of allantoin, and the steps include:

[0010] (1) Mix and stir glyoxal and nitric acid for reaction;

[0011] (2) Add calcium hydroxide powder while stirring at room temperature, and let it stand after white precipitate is precipitated;

[0012] (3) Wash the filter residue with water after filtration, add calcium chloride to the filtered mother liquor, stir and dissolve it, then dropwise add sodium hydroxide aqueous solution, and stop adding alkali when the pH reaches 3.0-3.5, and let it stand to obtain fine-grained white calcium glyoxalate solid;

[0013] (4) Dissolve the prepared calcium glyoxalate with hydrochloric acid, add urea and stir for reaction, and white precipitate will form during the reaction; filter, wash and dry the obtained precipitate to obtain the product allantoin.

[0014] Further, in the step (1), the reaction temperature is 40-45°C and the reaction time is 3-4 h.

[0015] Further, in the step (2), the pH is controlled to be 0.7-0.8.

[0016] Further, in the step (2), the standing time is 30-40 min.

[0017] Further, in the step (3), the volume fraction of the sodium hydroxide solution is 20-24%.

[0018] Further, in the step (4), the concentration of hydrochloric acid is 0.5-1 mol / L.

[0019] Further, the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:(1-1.5):(1-2):(2-3):(1-2).

[0020] Further, the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:(1 - 2):(4 - 6).

[0021] Further, the reaction temperature in step (4) is 72 - 75°C, and the reaction time is 2 - 3 h.

[0022] Further, in step (4), the drying temperature is 50 - 60°C, and the drying time is 3 - 4 h.

[0023] The beneficial effects of the present invention are as follows:

[0024] The main raw materials used in the method provided by the present invention, such as glyoxal, nitric acid, calcium hydroxide, calcium chloride, sodium hydroxide, and urea, are all common chemical raw materials, which are easy to purchase and have relatively low costs, facilitating the reduction of production costs.

[0025] During the preparation process of the present invention, by adjusting conditions such as pH value and temperature, the generation of by-products can be effectively controlled, reducing environmental pollution. At the same time, the amounts of the three wastes, namely wastewater, waste gas, and waste residue, generated are relatively small and easy to treat. The steps therein are simple to operate, and there are fewer by-products generated during the synthesis process, enabling the production of allantoin products with higher purity, which is easy to achieve industrial production. Specific Embodiments

[0026] The technical solutions of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0027] Example 1

[0028] This example provides a method for synthesizing allantoin, and the steps include:

[0029] (1) Mix and stir glyoxal and nitric acid; the reaction temperature is 42°C, and the reaction time is 3.5 h;

[0030] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears;

[0031] (3) After filtration, wash the filter residue with water, add calcium chloride to the filtered mother liquor, stir and dissolve it, then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 22%. Stop adding alkali when the pH reaches 3.25, and let it stand to obtain fine-grained white calcium glyoxylate solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0032] (4) Dissolve the prepared calcium glyoxylate in an aqueous hydrochloric acid solution with a concentration of 0.75 mol / L, add urea and stir to react. The reaction temperature is 73 °C and the reaction time is 2.5 h. A white precipitate is formed as the reaction proceeds. Filter, wash, and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h. The molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:1.5:5.

[0033] The final yield of allantoin prepared is 84%, and the purity is 92.8%.

[0034] Example 2

[0035] This example provides a method for synthesizing allantoin, and the steps include:

[0036] (1) Mix and stir glyoxal and nitric acid to react. The reaction temperature is 40 °C and the reaction time is 3 h.

[0037] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.7, let it stand for 30 min after a white precipitate appears.

[0038] (3) After filtration, wash the filter residue with water. Add calcium chloride to the filtered mother liquor, stir and dissolve it, then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 20%. Stop adding alkali when the pH reaches 3.0, and a fine-grained white solid of calcium glyoxylate can be obtained by standing. The molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1:1:2:1.

[0039] (4) Dissolve the prepared calcium glyoxylate in an aqueous hydrochloric acid solution with a concentration of 0.5 mol / L, add urea and stir to react. The reaction temperature is 72 °C and the reaction time is 2 h. A white precipitate is formed as the reaction proceeds. Filter, wash, and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 50 °C and the drying time is 3 h. The molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:1:4.

[0040] The final yield of allantoin prepared is 82%, and the purity is 92.2%.

[0041] Example 3

[0042] This example provides a method for synthesizing allantoin, and the steps include:

[0043] (1) Mix and stir glyoxal and nitric acid to react. The reaction temperature is 45 °C and the reaction time is 4 h.

[0044] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.8, let it stand for 40 min after a white precipitate appears.

[0045] (3) After filtration, wash the filter residue with water. Add calcium chloride to the filtered mother liquor, stir to dissolve it, and then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 24%. Stop adding alkali when the pH reaches 3.5, and let it stand to obtain fine granular white calcium glyoxylate solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.5:2:3:2;

[0046] (4) Dissolve the prepared calcium glyoxylate in a 1 mol / L hydrochloric acid aqueous solution, add urea and stir to react. The reaction temperature is 75 °C and the reaction time is 3 h. A white precipitate is formed as the reaction proceeds; filter, wash, and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 60 °C and the drying time is 4 h; the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:2:6.

[0047] The final yield of allantoin prepared is 80%, and the purity is 92.4%.

[0048] Example 4

[0049] This example provides a method for synthesizing allantoin, and the steps include:

[0050] (1) Mix and stir glyoxal and nitric acid to react; the reaction temperature is 40 °C and the reaction time is 4 h;

[0051] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.7, let it stand for 40 min after white precipitate appears;

[0052] (3) After filtration, wash the filter residue with water. Add calcium chloride to the filtered mother liquor, stir to dissolve it, and then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 20%. Stop adding alkali when the pH reaches 3.5, and let it stand to obtain fine granular white calcium glyoxylate solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1:2:2:2;

[0053] (4) Dissolve the prepared calcium glyoxylate in a 0.5 mol / L hydrochloric acid aqueous solution, add urea and stir to react. The reaction temperature is 75 °C and the reaction time is 2 h. A white precipitate is formed as the reaction proceeds; filter, wash, and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 60 °C and the drying time is 3 h; the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:2:4.

[0054] The final yield of allantoin prepared is 81%, and the purity is 92.0%.

[0055] Comparative Example 1

[0056] This comparative example provides a method for synthesizing allantoin, and the steps include:

[0057] (1) Mix glyoxal and nitric acid and stir to react; the reaction temperature is 30 °C and the reaction time is 3.5 h;

[0058] (2) Add calcium hydroxide powder with stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears;

[0059] (3) Wash the filter residue with water after filtration, add calcium chloride to the filtered mother liquor, stir to dissolve and then dropwise add 22% sodium hydroxide aqueous solution by volume. Stop adding alkali when the pH reaches 3.25, and let it stand to obtain fine-grained calcium glyoxylate white solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0060] (4) Dissolve the prepared calcium glyoxylate with 0.75 mol / L hydrochloric acid aqueous solution, add urea and stir to react. The reaction temperature is 73 °C and the reaction time is 2.5 h. White precipitate forms during the reaction; filter, wash, and dry the obtained precipitate to get the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h; the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:1.5:5.

[0061] The final yield of allantoin prepared is 78% and the purity is 90.3%.

[0062] Comparative Example 2

[0063] This comparative example provides a method for synthesizing allantoin, and the steps include:

[0064] (1) Mix glyoxal and nitric acid and stir to react; the reaction temperature is 50 °C and the reaction time is 3.5 h;

[0065] (2) Add calcium hydroxide powder with stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears;

[0066] (3) Wash the filter residue with water after filtration, add calcium chloride to the filtered mother liquor, stir to dissolve and then dropwise add 22% sodium hydroxide aqueous solution by volume. Stop adding alkali when the pH reaches 3.25, and let it stand to obtain fine-grained calcium glyoxylate white solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0067] (4) Dissolve the prepared calcium glyoxylate with an aqueous hydrochloric acid solution with a concentration of 0.75 mol / L, add urea and stir for reaction. The reaction temperature is 73 °C and the reaction time is 2.5 h. A white precipitate is formed as the reaction proceeds. Filter, wash and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h. The molar ratio of calcium glyoxylate, hydrochloric acid and urea is 1:1.5:5.

[0068] The yield of allantoin finally prepared is 75%, and the purity is 91.4%.

[0069] Comparative Example 3

[0070] This comparative example provides a method for synthesizing allantoin. The steps include:

[0071] (1) Mix and stir glyoxal and nitric acid for reaction. The reaction temperature is 42 °C and the reaction time is 3.5 h.

[0072] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears.

[0073] (3) Wash the filter residue with water after filtration. Add calcium chloride to the filtered mother liquor, stir and dissolve, then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 22%. Stop adding alkali when the pH reaches 3.25, and let it stand to obtain a fine-grained white solid of calcium glyoxylate. The molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5.

[0074] (4) Dissolve the prepared calcium glyoxylate with an aqueous hydrochloric acid solution with a concentration of 0.75 mol / L, add urea and stir for reaction. The reaction temperature is 60 °C and the reaction time is 2.5 h. A white precipitate is formed as the reaction proceeds. Filter, wash and dry the obtained precipitate to obtain the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h. The molar ratio of calcium glyoxylate, hydrochloric acid and urea is 1:1.5:5.

[0075] The yield of allantoin finally prepared is 79%, and the purity is 89.4%.

[0076] Comparative Example 4

[0077] This comparative example provides a method for synthesizing allantoin. The steps include:

[0078] (1) Mix and stir glyoxal and nitric acid for reaction. The reaction temperature is 42 °C and the reaction time is 3.5 h.

[0079] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears.

[0080] (3) After filtration, the filter residue is washed with water. Calcium chloride is added to the filtered mother liquor, stirred and dissolved, and then an aqueous sodium hydroxide solution with a volume fraction of 22% is added dropwise. When the pH reaches 3.25, the addition of alkali is stopped, and after standing, a fine-grained white solid of calcium glyoxylate can be obtained; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0081] (4) The prepared calcium glyoxylate is dissolved in an aqueous hydrochloric acid solution with a concentration of 0.75 mol / L, urea is added and stirred for reaction. The reaction temperature is 80 °C and the reaction time is 2.5 h. A white precipitate is formed during the reaction. The obtained precipitate is filtered, washed, and dried to obtain the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h; the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:1.5:5.

[0082] The yield of the finally prepared allantoin is 74%, and the purity is 88.1%.

[0083] Comparative Example 5

[0084] This comparative example provides a method for synthesizing allantoin, and the steps include:

[0085] (1) Glyoxal and nitric acid are mixed and stirred for reaction; the reaction temperature is 42 °C and the reaction time is 3.5 h;

[0086] (2) Calcium hydroxide powder is added while stirring at room temperature, the pH is controlled to be 0.75, and after a white precipitate appears, it is left standing for 35 min;

[0087] (3) After filtration, the filter residue is washed with water. Calcium chloride is added to the filtered mother liquor, stirred and dissolved, and then an aqueous sodium hydroxide solution with a volume fraction of 22% is added dropwise. When the pH reaches 3.25, the addition of alkali is stopped, and after standing, a fine-grained white solid of calcium glyoxylate can be obtained; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0088] (4) The prepared calcium glyoxylate is dissolved in an aqueous hydrochloric acid solution with a concentration of 0.75 mol / L, urea is added and stirred for reaction. The reaction temperature is 73 °C and the reaction time is 2 h. A white precipitate is formed during the reaction. The obtained precipitate is filtered, washed, and dried to obtain the product allantoin. The drying temperature is 55 °C and the drying time is 3.5 h; the molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:1.5:5.

[0089] The yield of the finally prepared allantoin is 76%, and the purity is 85.7%.

[0090] Comparative Example 6

[0091] This comparative example provides a method for synthesizing allantoin, and the steps include:

[0092] (1) Mix and stir glyoxal and nitric acid; the reaction temperature is 42 °C and the reaction time is 3.5 h;

[0093] (2) Add calcium hydroxide powder while stirring at room temperature, control the pH to 0.75, let it stand for 35 min after white precipitate appears;

[0094] (3) Wash the filter residue with water after filtration, add calcium chloride to the filtered mother liquor, stir and dissolve it, then dropwise add an aqueous sodium hydroxide solution with a volume fraction of 22%, stop adding alkali when the pH reaches 3.25, and let it stand to obtain fine-grained calcium glyoxalate white solid; the molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:1.25:1.5:2.5:1.5;

[0095] (4) Dissolve the prepared calcium glyoxalate with a 0.75 mol / L hydrochloric acid aqueous solution, add urea and stir to react, the reaction temperature is 73 °C and the reaction time is 3 h, and a white precipitate forms during the reaction; filter, wash, and dry the obtained precipitate to obtain the product allantoin, the drying temperature is 55 °C and the drying time is 3.5 h; the molar ratio of calcium glyoxalate, hydrochloric acid, and urea is 1:1.5:5.

[0096] The final yield of allantoin prepared is 78% and the purity is 86.1%.

[0097] Finally, it should be noted that: The inventor declares that the present invention uses the above-mentioned examples to illustrate the product and detailed preparation method of the present invention, but the present invention is not limited to the above-mentioned product and detailed preparation method, that is, it does not mean that the present invention must rely on the above-mentioned product and detailed preparation method to be implemented. Those skilled in the art should understand that any improvement to the present invention, equivalent substitution of each raw material of the product of the present invention, addition of auxiliary ingredients, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0098] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple deformations can be made to the technical solutions of the present invention. These simple deformations all fall within the protection scope of the present invention.

[0099] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any appropriate way without contradiction. To avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0100] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A method for synthesizing allantoin, characterized in that the steps Comprising: (1) Mix and stir glyoxal and nitric acid for reaction; (2) Add calcium hydroxide powder with stirring under room temperature conditions, let it stand after white precipitate appears; (3) Wash the filter residue with water after filtration, add calcium chloride to the filtered mother liquor, stir to dissolve and then dropwise add sodium hydroxide aqueous solution, stop adding alkali when the pH reaches 3.0 - 3.5, and fine granular calcium glyoxylate white solid can be obtained after standing; (4) Dissolve the prepared calcium glyoxylate with hydrochloric acid, add urea and stir for reaction, and white precipitate will form during the reaction; Filter, wash and dry the obtained precipitate to obtain the product allantoin; In the step (1), the reaction temperature is 40 - 45 °C and the reaction time is 3 - 4 h; In the step (2), the pH is controlled to be 0.7 - 0.8; In the step (2), the standing time is 30 - 40 min; In the step (3), the volume fraction of the sodium hydroxide solution is 20 - 24%; In the step (4), the concentration of hydrochloric acid is 0.5 - 1 mol / L; The molar ratio of glyoxal, nitric acid, calcium hydroxide, calcium chloride, and sodium hydroxide is 1:(1 - 1.5):(1 - 2):(2 - 3):(1 - 2); The molar ratio of calcium glyoxylate, hydrochloric acid, and urea is 1:(1 - 2):(4 - 6); In the step (4), the reaction temperature is 72 - 75 °C and the reaction time is 2 - 3 h; In the step (4), the drying temperature is 50 - 60 °C and the drying time is 3 - 4 h.