Preparation method of amino carboxylic acid type chelating agent

Abstract

The invention discloses a preparation method of an aminocarboxylic acid type chelating agent, and belongs to the technical field of organic synthesis. Dropwise adding a sodium nitrite solution into the mixed solution of aminocarboxylic acid and hydrogen halide for 2-3 hours, and carrying out heat preservation reaction for 1-2 hours; after the reaction is finished, evaporating water to dryness, purifying the solid, adding water into the obtained solid, and adjusting the pH value of the system to 6.5-7.5; the temperature is raised to 80-90 DEG C, iminodiacetic acid and water are dropwise added and stirred for 2-3 h, the pH is kept at 7-8 in the dropwise adding process, a heat preservation reaction is conducted for 1-2 h after dropwise adding is completed, concentration and filtration desalination are conducted after the reaction is completed, and the aminocarboxylic acid type chelating agent is obtained. According to the preparation method, one-step substitution of iminodiacetic acid and halogen is used for replacing traditional two-step substitution of amido, so that residues caused by incomplete subsequent reaction of a monosubstituted intermediate of amido in the product can be avoided, the yield and the chelation performance of the product are improved, and the market competitiveness is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of organic synthesis, and specifically relates to a method for preparing an aminocarboxylic acid type chelating agent. Background Art

[0002] Aminocarboxylic acid chelating agents, also known as green chelating agents, are a type of sulfur-free and phosphorus-free, environmentally friendly chelating agents that have emerged in recent years. They have excellent performance, good ecological and toxicological characteristics, and meet the OECD biodegradability test requirements. At present, the aminocarboxylic acid chelating agents widely used in the market include tetrasodium glutamate diacetate (GLDA), trisodium methylglycine diacetate (MGDA), tetrasodium aspartate diacetate (ASDA), etc.

[0003] The mainstream production method of aminocarboxylic acid chelating agents is to use amino acids as the main raw materials and react with hydrocyanic acid or chloroacetic acid to prepare amino acid diacetic acid sodium salt. For example, patents DE4211713A1, CN101784513A and CN101959847A all mention the use of amino dicarboxylic acid, formaldehyde and hydrocyanic acid to react and hydrolyze to produce amino dicarboxylic acid diacetic acid (salt); this method uses highly toxic raw material hydrocyanic acid, and there will be by-products such as aminotriacetic acid, which are not easy to separate. Patents CN114163340A, CN109369427A and CN109503402A disclose the use of sodium glutamate and chloroacetic acid as raw materials to react in the aqueous phase to produce glutamic acid diacetic acid sodium salt; this method avoids the use of highly toxic hydrogen cyanide, but when sodium glutamate reacts with the second chloroacetic acid, the reaction activity is reduced due to factors such as steric hindrance, the reaction is incomplete, and sodium chloride is produced as a by-product, which cannot be completely separated, and the minimum chloride ion content in the product is about 1%. Patent CN112028785A discloses the use of sodium glutamate, glyoxylic acid and formic acid as raw materials to prepare glutamic acid diacetate sodium salt by Eschweiler-Clarke reaction; this method avoids the use of highly toxic substances and has no sodium salt by-product, but because the reaction activity of glyoxylic acid is lower than that of acetaldehyde and formaldehyde, and the method adopts a step-by-step reaction: the amine group first reacts with two glyoxylic acids to form a tertiary amine, and then reacts with formic acid for hydrogenation, resulting in excessive steric hindrance when reacting with the second glyoxylic acid, incomplete reaction, and generation of glutamic acid monoacetic acid sodium salt, which reduces the yield and product quality.

[0004] Therefore, it is of great significance to develop an aminocarboxylic acid type chelating agent with high yield, low impurity content and good chelating performance. Summary of the invention

[0005] In view of the problems existing in the prior art, the present invention provides a method for preparing an aminocarboxylic acid type chelating agent, which improves the yield of the aminocarboxylic acid type chelating agent and the chelating performance of the product, thereby improving the market competitiveness.

[0006] The present invention is achieved through the following technical solutions: A method for preparing an aminocarboxylic acid type chelating agent comprises the following steps: (1) Add sodium nitrite solution dropwise to the mixed solution of aminocarboxylic acid and hydrogen halide over 2-3 hours, and keep warm for 1-2 hours; (2) After the reaction in step (1) is completed, the water is evaporated to dryness, the solid is purified, water is added to the obtained solid, and the pH of the system is adjusted to 6.5-7.5; (2) Step (2) The reaction system is heated to 80-90°C, and iminodiacetic acid and water are added dropwise with stirring. The addition is completed over 2-3 hours, and the pH is maintained at 7-8 during the addition. After the addition is completed, the reaction is kept warm for 1-2 hours. After the reaction is completed, the reaction is concentrated, filtered and desalted to obtain an aminocarboxylic acid type chelating agent.

[0007] Furthermore, the aminocarboxylic acid in step (1) is one of glutamic acid, aspartic acid or alanine, the mass fraction of the hydrogen halide aqueous solution is 20-30%, and the mass fraction of the sodium nitrite aqueous solution is 40-50%.

[0008] Furthermore, in step (1), the molar ratio of aminocarboxylic acid, hydrogen halide and sodium nitrite is 1:1.05~1.2:1~1.05.

[0009] Furthermore, the temperature of the heat preservation reaction in step (1) is 5-25°C.

[0010] Furthermore, the method for purifying the solid in step (2) is: dissolving the solid in ethanol, filtering, and evaporating the filtrate to dry the solvent.

[0011] Furthermore, in step (2), the amount of ethanol added is 2 to 3 times the mass of the aminocarboxylic acid.

[0012] Furthermore, the amount of water added in step (2) is 1 to 2 times the mass of the aminocarboxylic acid.

[0013] Furthermore, the molar ratio of iminodiacetic acid in step (3) to the aminocarboxylic acid in step (1) is 1-1.1:1; and the mass ratio of water to iminodiacetic acid in step (3) is 0.5-1:1.

[0014] Furthermore, in step (2) and step (3), sodium hydroxide is added to adjust the pH, and the mass percentage concentration of sodium hydroxide is 50%. Beneficial Effects

[0015] The preparation method of the aminocarboxylic acid type chelating agent provided by the present invention replaces the traditional two-step substitution on the amine group by one-step substitution of iminodiacetic acid and halogen, thereby avoiding the residue of the monosubstituted intermediate of the amine group in the product caused by incomplete subsequent reaction, improving the yield and the chelating performance of the product, and improving the market competitiveness. DETAILED DESCRIPTION

[0016] The above contents of the present invention are further described in detail below through examples, but this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples, and all technologies implemented based on the above contents of the present invention belong to the scope of the present invention.

[0017] The main raw material equipment specifications of the embodiment of the present invention are as follows: the aminocarboxylic acid is selected from glutamic acid and alanine, which are industrial grade; the hydrogen halide is selected from hydrogen bromide, which is commercially available 48% hydrobromic acid (diluted with water to a hydrobromic acid with a mass fraction of 30%); the sodium hydroxide solution (liquid caustic soda) is selected from commercially available liquid caustic soda with a content of 50%; the remaining raw materials are all commercially available industrial grade; sodium nitrite is prepared with water to form a sodium nitrite aqueous solution with a mass fraction of 40%. Example 1

[0018] (1) Add 147 kg of glutamic acid and 283 kg of hydrobromic acid to the reactor, start stirring, control the temperature in the reactor at 10±5°C, and begin to dropwise add 172 kg of sodium nitrite aqueous solution at a uniform rate. The addition is completed within 2 hours and the temperature is kept at this temperature for 1 hour. (2) Under a pressure of -80 KPa, water was distilled off, and then 294 kg of anhydrous ethanol was added. After stirring and dissolving, the mixture was filtered. The filtrate was distilled off again under a pressure of -80 KPa to recover the ethanol. The remaining solid was put into a dissolving kettle, 147 kg of pure water was added, and liquid alkali was added dropwise to adjust the pH value to 6.58 for standby use; (3) Add 133 kg of iminodiacetic acid and 67 kg of pure water into the reactor, start stirring, raise the temperature to 80 °C, and then uniformly add the prepared solution in the reactor. The addition is completed within 2 hours. During the addition, the temperature in the reactor is maintained at 85 ± 5 °C, and liquid alkali is added to maintain the pH value of the reaction solution at 7-8. After keeping the temperature for 1 hour, condense the solution by external evaporation at -80 KPa, remove the salt by suction, and then dilute with water to form 729.4 kg of tetrasodium glutamate diacetate aqueous solution with an activity of 47.25%.

[0019] After testing and calculation, the product yield (based on glutamic acid) was 98.18%, and the bromide ion content was 2.87%. Example 2

[0020] (1) Add 147 kg of glutamic acid and 324 kg of hydrobromic acid into the reactor, start stirring, control the temperature in the reactor at 20±5°C, and begin to dropwise add 181 kg of sodium nitrite aqueous solution at a uniform rate. The addition is completed within 3 hours and the temperature is kept at this temperature for 2 hours. (2) Under a pressure of -90 KPa, water was distilled off, and then 441 kg of anhydrous ethanol was added. After stirring and dissolving, the mixture was filtered. The filtrate was distilled off again under a pressure of -90 KPa to recover the ethanol. The remaining solid was put into a dissolving kettle, 294 kg of pure water was added, and liquid alkali was added dropwise to adjust the pH value to 7.46 for standby use; (3) Add 146 kg of iminodiacetic acid and 146 kg of pure water into the reactor, start stirring, raise the temperature to 80 °C, and then uniformly add the prepared solution in the reactor. The addition is completed within 3 hours. During the addition, the temperature in the reactor is maintained at 85 ± 5 °C, and liquid alkali is added to maintain the pH value of the reaction solution at 7-8. After keeping the temperature for 2 hours, condense the solution by external evaporation at -90 KPa, remove the salt by suction, and then dilute with water to form 730.8 kg of tetrasodium glutamate diacetate aqueous solution with an activity of 47.17%.

[0021] After testing and calculation, the product yield (based on glutamic acid) was 98.21%, and the bromide ion content was 2.65%. Example 3

[0022] (1) Add 89 kg of alanine and 283 kg of hydrobromic acid to the reactor, start stirring, control the temperature in the reactor at 10±5°C, and begin to dropwise add 172 kg of sodium nitrite aqueous solution at a uniform rate. The addition is completed within 2 hours and the temperature is kept at this temperature for 1 hour. (2) Under a pressure of -80 KPa, water was distilled off, and then 178 kg of anhydrous ethanol was added. After stirring and dissolving, the mixture was filtered. The filtrate was distilled off again under a pressure of -80 KPa to recover the ethanol. The remaining solid was put into a dissolving kettle, 89 kg of pure water was added, and liquid alkali was added dropwise to adjust the pH value to 6.55 for standby use; (3) Add 133 kg of iminodiacetic acid and 67 kg of pure water into the reactor, start stirring, raise the temperature to 80 °C, and then uniformly add the prepared solution in the reactor. The addition is completed within 2 hours. During the addition, the temperature in the reactor is maintained at 85 ± 5 °C, and liquid alkali is added to maintain the pH value of the reaction solution at 7-8. After keeping the temperature for 1 hour, condense the solution by external evaporation at -80 KPa, remove the salt by suction, and then dilute with water to form 664.8 kg of methylglycine diacetate trisodium aqueous solution with an activity of 40.12%.

[0023] After testing and calculation, the product yield (based on glutamic acid) was 98.42%, and the bromide ion content was 2.72%. Example 4

[0024] (1) Add 89 kg of alanine and 324 kg of hydrobromic acid to the reactor, start stirring, control the temperature in the reactor to 20±5°C, and begin to dropwise add 181 kg of sodium nitrite aqueous solution at a uniform rate. The addition is completed within 3 hours and the temperature is kept at this temperature for 2 hours; (2) Under a pressure of -90 KPa, water was distilled off, and then 267 kg of anhydrous ethanol was added. After stirring and dissolving, the mixture was filtered. The filtrate was distilled off again under a pressure of -90 KPa to recover the ethanol. The remaining solid was put into a dissolving kettle, 178 kg of pure water was added, and liquid alkali was added dropwise to adjust the pH value to 7.44 for use; (3) Add 146 kg of iminodiacetic acid and 146 kg of pure water into the reactor, start stirring, raise the temperature to 80 °C, and then uniformly add the prepared solution in the reactor. The addition is completed within 3 hours. During the addition, the temperature in the reactor is maintained at 85 ± 5 °C, and liquid alkali is added to maintain the pH value of the reaction solution at 7-8. After keeping the temperature for 2 hours, condense the solution by external evaporation at -90 KPa, remove the salt by suction, and then dilute with water to form 662.9 kg of methylglycine diacetate trisodium aqueous solution with an activity of 40.19%.

[0025] After testing and calculation, the product yield (based on glutamic acid) was 98.31%, and the bromide ion content was 2.59%.

[0026] The calcium chelating properties of the samples of Examples 1 to 4 and commercially available samples were determined. The test standard was based on the method for determining the calcium chelating value provided in the national standard "GB / T 26324-2010 Hydroxyethylidene Diphosphonic Acid". The test results are shown in Table 1.

[0027] Table 1 ; From the results of the performance test, it can be seen that the calcium chelating performance of GLDA and MGDA prepared by the method provided by the present invention at the same content is significantly greater than that of the commercially available products prepared by the traditional method, indicating that the amino group of the aminocarboxylic acid type chelating agent prepared by the present method is substituted with two acetic acids, and there is no intermediate aminomonoacetic acid, which improves the chelating performance of the unit product.

[0028] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing an aminocarboxylic acid type chelating agent, characterized in that: The following steps are involved: (1) Add sodium nitrite solution dropwise to the mixed solution of aminocarboxylic acid and hydrogen halide over 2-3 hours, and keep warm for 1-2 hours; (2) After the reaction in step (1) is completed, the water is evaporated to dryness, the solid is purified, water is added to the obtained solid, and the pH of the system is adjusted to 6.5-7.5; (2) Step (2) The reaction system is heated to 80-90°C, and iminodiacetic acid and water are added dropwise with stirring. The addition is completed over 2-3 hours, and the pH is maintained at 7-8 during the addition. After the addition is completed, the reaction is kept warm for 1-2 hours. After the reaction is completed, the reaction is concentrated, filtered and desalted to obtain an aminocarboxylic acid type chelating agent.

2. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: The aminocarboxylic acid described in step (1) is one of glutamic acid, aspartic acid or alanine, the mass fraction of the hydrogen halide aqueous solution is 20-30%, and the mass fraction of the sodium nitrite aqueous solution is 40-50%.

3. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: In step (1), the molar ratio of aminocarboxylic acid, hydrogen halide and sodium nitrite is 1:1.05-1.2:1-1.

05.

4. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: The temperature of the heat preservation reaction in step (1) is 5~25°C.

5. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: The method for purifying the solid in step (2) is as follows: dissolving the solid in ethanol, filtering, and evaporating the filtrate to dry the solvent.

6. The method for preparing an aminocarboxylic acid type chelating agent according to claim 5, characterized in that: In step (2), the amount of ethanol added is 2 to 3 times the mass of the aminocarboxylic acid.

7. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: The amount of water added in step (2) is 1 to 2 times the mass of the aminocarboxylic acid.

8. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: The molar ratio of iminodiacetic acid in step (3) to the aminocarboxylic acid in step (1) is 1-1.1:1; and the mass ratio of water to iminodiacetic acid in step (3) is 0.5-1:

1.

9. The method for preparing an aminocarboxylic acid type chelating agent according to claim 1, characterized in that: In step (2) and step (3), sodium hydroxide is added to adjust the pH, and the mass percentage concentration of sodium hydroxide is 50%.