Method for electrocatalytic synthesis of glycine based on bulk silver foam and separation and purification method thereof

Abstract

The present application relates to a kind of based on block body foam silver electrocatalytic synthesis glycine method and its separation and purification method, the present application with ultra-light foam silver block as catalytic electrode, realize the purpose of efficient electrocatalytic synthesis glycine, reaction conversion rate reaches 99% in 2 hours, greatly improve the catalytic efficiency, and solution only contains glycine and sulfuric acid electrolyte after reaction, provide the convenience for subsequent separation and purification.The obtained acidic glycine solution can remove inorganic salts by sodium cation exchange resin, purify glycine, and then freeze-drying, obtain high-purity high-crystalline glycine powder.The present application realizes the purpose of simple catalyst efficient synthesis glycine and extract high-purity glycine powder, can effectively improve the synthesis and purification efficiency of glycine product.

Description

Technical Field

[0001] The invention relates to a method for synthesizing glycine based on block foam silver electrocatalysis and a separation and purification method thereof, belonging to the technical field of chemical industry. Background Art

[0002] Glycine is a vital component of protein synthesis and energy metabolism, and plays a vital role in the body's antioxidant, muscle repair, and detoxification processes. my country's demand for high-quality glycine, including food-grade, feed-grade, and medical-grade products, is growing. However, my country's current production capacity cannot fully meet this demand, and significant imports are still required. From an industrial perspective, over the past few decades, glycine has been primarily produced in my country through methods such as the Streeck process, the Hein process, the chloroacetic acid amination process, and the aminocapronitrile alkaline hydrolysis process. The Streeck process uses hydrocyanic acid as a raw material. While large-scale production is possible, its highly toxic raw material and difficult product purification pose significant challenges in ensuring safe production and obtaining high-purity glycine. The chloroacetic acid process is the most commonly used method for glycine production in my country. While it offers the advantage of a simple synthesis process, its high purification costs result in significant cost penalties for industrial production. While the direct Hein process can produce relatively pure glycine, the difficult storage of the raw material and the harsh reaction conditions mean that its industrial production is still in the exploratory stage. The aminocapronitrile alkaline hydrolysis method is rarely used industrially due to its high equipment requirements and difficulty in purification.

[0003] In contrast, electrocatalytic synthesis of glycine has emerged as a promising alternative due to its high efficiency, environmental friendliness, and high product yield. Electrocatalytic synthesis of glycine utilizes low-cost and renewable biomass derivatives, such as α-keto acids (such as glyoxylic acid), coupled with a nitrogen source for further reduction and hydrogenation to produce glycine. Currently, limited research has been reported in this area, and existing work has suffered from low catalytic efficiency, low glycine formation rate, low product yield, and low purity. Finding efficient catalysts to improve the efficiency and yield of green electrocatalytic glycine synthesis, as well as exploring and optimizing glycine product separation and purification technologies, are crucial for promoting the development of the glycine industry. Summary of the Invention

[0004] In view of the deficiencies of existing research, the present invention provides a method for synthesizing glycine based on bulk silver foam electrocatalysis and a method for separating and purifying glycine.

[0005] The application utilizes bulk super-light foam silver as a catalytic electrode, and through electrocatalytic reduction amination, biomass derivative glyoxylic acid and cheap hydroxylamine sulfate are used as raw materials, and sulfuric acid is used as an electrolyte to obtain a glycine-sulfuric acid solution with high conversion rate; through ion exchange method, sulfate ions and hydrogen ions are removed from the solution to obtain pure glycine aqueous solution, and high-purity glycine powder is obtained through freeze-drying, which has the advantages of high catalytic efficiency, high glycine generation rate, high product yield and high purity.

[0006] The technical scheme of the application is as follows:

[0007] A method for electrocatalytically synthesizing glycine based on bulk foam silver, which utilizes bulk super-light foam silver as a catalytic electrode, biomass derivative glyoxylic acid and cheap hydroxylamine sulfate as raw materials, and obtains a glycine-sulfuric acid solution through electrocatalytic reduction amination.

[0008] The bulk super-light foam silver is prepared by the following method:

[0009] (1) Pour silver nitrate solution into a reaction bottle, slowly drop ammonia water drop by drop, and stop dropping when the ammonia water and the silver nitrate solution are completely reacted, i.e., the solution becomes transparent, to obtain a silver ammonia solution; drop glucose solution into the silver ammonia solution, and immediately put melamine resin foam into the solution for water bath heating;

[0010] (2) The melamine resin foam after reaction is washed with water, and then dried in an oven; the dried melamine resin foam is calcined in an air atmosphere to obtain a super-light foam silver bulk.

[0011] According to the application, preferably, in step (1), the mass concentration of the silver nitrate solution is 2-3 wt%, and the volume is 10 mL.

[0012] According to the application, preferably, in step (1), the mass concentration of the ammonia water solution is 2-3 wt%, and the volume is 2.5 mL.

[0013] According to the application, preferably, in step (1), the volume ratio of the silver nitrate solution to the ammonia water is 4:1.

[0014] According to the application, preferably, in step (1), the mass concentration of the glucose solution is 5-15 wt%.

[0015] According to the application, preferably, in step (1), the volume ratio of the glucose solution to the silver nitrate solution is (1-5):(8-12).

[0016] According to the application, preferably, in step (1), the size of the melamine resin foam is 2 cm x 2 cm.

[0017] According to the preferred embodiment of the present invention, in step (1), the water bath heating temperature is 65-75° C., and the water bath heating time is 8-15 minutes.

[0018] Most preferably, in step (1), the water bath heating temperature is 70° C. and the water bath heating time is 10 minutes.

[0019] According to the preferred embodiment of the present invention, in step (2), the melamine resin foam washing time is 0.5-5 minutes.

[0020] Preferably, according to the present invention, in step (2), the drying temperature of the melamine resin foam is 100-120° C., and the drying time is 30-50 minutes.

[0021] According to the preferred embodiment of the present invention, in step (2), the calcination temperature is 600-700° C., and the calcination time is 10-15 minutes.

[0022] The present invention successfully obtains an ultralight foam silver block by a simple silver mirror reaction, controlling the water bath heating temperature at about 70°C and the water bath heating time at about 10 minutes. If the water bath heating temperature is lower than 60°C, no complete block can be obtained, and only powder can be obtained.

[0023] The method for synthesizing glycine based on bulk silver foam electrocatalysis is as follows:

[0024] 1) A three-electrode system is formed by using bulk ultralight silver foam as the working electrode, a Pt sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode.

[0025] 2) The three-electrode system is placed in an electrolyte to test the electrocatalytic performance of the bulk ultralight silver foam electrode in the glyoxylic acid reductive amination reaction, i.e., to test the linear sweep voltammetry curve, and to conduct the cathode electrocatalytic glyoxylic acid reductive amination reaction under constant current conditions.

[0026] According to a preferred embodiment of the present invention, in step 1), the electrolytic cell used for electrocatalysis is an H-type two-chamber glass electrolytic cell, wherein the cathode chamber and the anode chamber are separated by a Nafion 117 membrane.

[0027] According to the present invention, preferably, in step 2), the electrolyte includes a cathode electrolyte and an anolyte, the working electrode and the reference electrode are placed in the cathode electrolyte, and the counter electrode is placed in the anolyte, the cathode electrolyte is a mixture of glyoxylic acid, hydroxylamine sulfate and sulfuric acid, and the anolyte is a 0.1-0.3 mol / L sulfuric acid solution.

[0028] According to the preferred embodiment of the present invention, in step 2), the molar concentration of glyoxylic acid in the electrolyte is 0.16 mol / L, the molar concentration of hydroxylamine sulfate is 0.08 mol / L, and the molar concentration of sulfuric acid is 0.2 mol / L.

[0029] According to the application, preferably, in step 2), before the electrocatalytic reduction amination reaction of glyoxylic acid is carried out, no glyoxylic acid and hydroxylamine is added to the cathode electrolyte, and the electrode is firstly scanned cyclic voltammetry 100 times in 0.2 mol / L sulfuric acid solution, and the scanning rate is 100 mV / s -1 , and the potential is from 0.00 V to -0.45 V (versus reversible hydrogen electrode E RHE ). The reversible hydrogen electrode conversion formula is: E RHE = E SCE + 0.24 + 0.059×pH.

[0030] According to the application, preferably, in step 2), when the linear sweep voltammetry is carried out, the potential is from 0.00 V to -0.45 V (versus reversible hydrogen electrode E RHE ), and the scanning rate is 10 mV / s -1 .

[0031] According to the application, preferably, in step 2), the constant current is -200 mA.

[0032] After the electrocatalytic reduction amination reaction of glyoxylic acid is carried out, the reaction solution is separated and purified to obtain the glycine powder, and the specific process is as follows:

[0033] a. The sodium type cation exchange resin is soaked and cleaned with deionized water to remove water-soluble impurities, and then is subjected to acid-base pretreatment to remove iron impurities and organic impurities, and then is repeatedly cleaned by soaking and washing with deionized water until the washing liquid is neutral.

[0034] b. The solution after the electrocatalytic reduction amination reaction of glyoxylic acid is soaked in the pretreated sodium type cation exchange resin, so that the glycine cation is fully adsorbed on the cation exchange resin.

[0035] c. The sodium type cation exchange resin after soaking and reaction is washed with deionized water to remove inorganic salts, and then is washed with ammonia water to obtain a pure glycine aqueous solution;

[0036] d. The eluent is collected and freeze-dried to obtain the glycine powder.

[0037] After the electrocatalytic reduction amination reaction of glyoxylic acid is carried out, the solution mainly contains glycine and sulfuric acid solvent, and the direct freeze-drying or evaporation method cannot remove the sulfuric acid from the mixed solution, and the obtained product is a thick yellowish liquid, and the glycine powder cannot be obtained.

[0038] According to the application, preferably, in step a, the sodium type cation exchange resin is soaked with deionized water for 48 hours; the hydrochloric acid concentration used in acid treatment is 4-5 wt%, and the soaking time is 8 hours; the sodium hydroxide solution concentration used in alkali treatment is 4-5 wt%, and the soaking time is 8 hours.

[0039] According to the preferred embodiment of the present reaction, in step b, the solution after the electrocatalytic reductive amination reaction of glyoxylic acid is immersed in the pretreated sodium ion exchange resin for 1-2 hours.

[0040] According to the preferred embodiment of the present reaction, in step c, the cation exchange resin after soaking in the reaction solution is rinsed with deionized water 3-5 times; the pH of the ammonia eluent is 10, and the number of rinses is 3-5 times. When the pH of the effluent is greater than 5.97, the solution is collected.

[0041] According to the preferred embodiment of the present reaction, in step d, the freeze-drying temperature is -40°C to -60°C, and the freeze-drying time is 20-30 hours.

[0042] The technical features and excellent effects of the present invention are:

[0043] 1. The present invention uses a simple silver mirror reaction to precisely control the water bath heating temperature and time to obtain a high-purity, ultra-light foam silver block with a high specific surface area and high conductivity, which can be directly used as a catalytic electrode. This method has the characteristics of simple operation, good reproducibility, low preparation cost, low equipment requirements, and high product purity.

[0044] 2. The present invention uses ultra-light foam silver blocks as catalytic electrodes to achieve the goal of efficient electrocatalytic synthesis of glycine. The reaction conversion rate reaches 99% within 2 hours, greatly improving the catalytic efficiency. The post-reaction solution contains only glycine and sulfuric acid electrolyte, which provides convenience for subsequent separation and purification.

[0045] 3. The present invention adopts reusable cation exchange resin for separation and purification based on the specificity of the product solution. By utilizing the characteristics of ion exchange, the final product is pure and has excellent crystallinity, making it easy to obtain a high-purity glycine powder product. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is an optical photograph of the foamed silver block prepared in Example 1 of the present invention;

[0047] Figure 2 This is the XRD spectrum of the foamed silver block prepared in Example 1 of the present invention;

[0048] Figure 3 This is an SEM image of the foamed silver block prepared in Example 1 of the present invention;

[0049] Figure 4 is the electrochemical performance diagram of Example 2;

[0050] Figure 5 This is the two-hour electrolysis diagram of Example 2;

[0051] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of the two-hour product solution of Example 2;

[0052] Figure 7 This is the XRD spectrum of the glycine powder obtained in Example 3. DETAILED DESCRIPTION

[0053] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited thereto.

[0054] In the examples, sulfuric acid (H2SO4, Chinese medicine, 95.0% to 98.0%), hydroxylamine sulfate (2NH2OH·H2SO4, Macklin, 99.0%), glyoxylic acid (C2H2O3·H2O Macklin, 98%), ammonia water (NH3OH, Macklin, 3% NH3 inH2O), sodium cation exchange resin (Amberlite HNC-120Na form, Bidepharm), silver nitrate (AgNO3, Chinese medicine, 99.8%), glucose (C6H5O5, Macklin, 98%), and melamine resin foam (BASF) are all commercially available products.

[0055] Example 1:

[0056] The preparation steps of bulk ultra-light silver foam are as follows:

[0057] (1) Place 10 mL of 2 wt% silver nitrate solution in a reaction flask. Then, add 2 wt% ammonia solution dropwise to the silver nitrate solution and stir thoroughly. Stop adding the solution when the solution is completely transparent. At this point, the silver nitrate and ammonia solution have completely reacted.

[0058] (2) 2.5 mL of 10 wt% glucose was added to the mixed solution of step (1), and then a 2 cm × 2 cm piece of melamine resin foam was immediately added to the solution. The mixture was incubated in a water bath at 70° C. for 10 minutes. The color of the solution was observed to change from dark turbidity to light turbidity, indicating that silver had grown on the melamine resin foam.

[0059] (3) placing the melamine resin foam with silver nanoparticles grown thereon obtained in step (2) in a clean beaker filled with deionized water, rinsing for 1 minute, and then drying in an oven at 120° C. for 0.5 hour;

[0060] (4) The dried melamine resin foam obtained in step (3) is placed in a muffle furnace and calcined at 700° C. for 10 minutes to remove the melamine resin foam template and obtain a block of ultra-light silver foam.

[0061] Comparative Example 1:

[0062] The same preparation method as described in Example 1, except that:

[0063] In step (2), the water bath temperature is 60°C.

[0064] Other steps were carried out as in Example 1. It was found that when the water bath heating temperature was 60° C., no complete block could be obtained, and only powder could be obtained.

[0065] Test Example 1:

[0066] The optical photograph of the ultralight silver foam prepared in Example 1 is shown in Figure 1 ,pass Figure 1 It can be seen that self-supporting block-shaped ultra-light silver foam was successfully prepared. The silver foam was cut into electrode size and can be directly used as an electrode for electrocatalytic reduction reaction.

[0067] The XRD spectrum of the ultralight silver foam prepared in Example 1 is shown in Figure 2 ,pass Figure 2 It can be seen that ultra-light foam silver with high crystallinity and high purity was successfully prepared, and its crystallinity is excellent.

[0068] The SEM image of the ultralight silver foam prepared in Example 1 is shown in Figure 3 ,pass Figure 3 It can be seen that the microscopic morphology of the silver foam is a network nanowire structure, indicating that the silver foam was originally loaded on the melamine resin foam. After calcination, the silver foam basically follows the network morphology of the original melamine resin foam.

[0069] Example 2:

[0070] The method for synthesizing glycine based on bulk silver foam electrocatalysis is as follows:

[0071] (1) First, a three-electrode system was assembled. The block of ultralight silver foam prepared in Example 1 was cut into electrode size as the working electrode, a saturated calomel electrode was used as the reference electrode, and a Pt sheet electrode was used as the counter electrode. The electrocatalytic reduction amination reaction of glyoxylic acid was carried out in an electrolyte. The electrolyte included a cathode electrolyte and an anode electrolyte. The working electrode and the reference electrode were placed in the cathode electrolyte, and the counter electrode was placed in the anode electrolyte. The cathode electrolyte was a mixture of glyoxylic acid, hydroxylamine sulfate, and sulfuric acid. The molar concentration of glyoxylic acid in the mixture was 0.16 mol / L, the molar concentration of hydroxylamine sulfate was 0.08 mol / L, and the molar concentration of sulfuric acid was 0.2 mol / L. The anode electrolyte was a 0.2 mol / L sulfuric acid solution. The electrolytic cell used was an H-type two-chamber glass electrolytic cell. The cathode chamber and the anode chamber were separated by a Nafion 117 membrane.

[0072] (2) Before the electrocatalytic reductive amination reaction of glyoxylic acid, glyoxylic acid and hydroxylamine were not added to the cathode electrolyte. The electrode was first subjected to 100 cycles of cyclic voltammetry in a 0.2 mol / L sulfuric acid solution at a scan rate of 100 mV s -1, from 0.00 V to -0.45 V (vs. reversible hydrogen electrode E RHE ). Then linear sweep voltammetry was performed, from 0.00 V to 0.45 V (vs. reversible hydrogen electrode E RHE ), with a scan rate of 10 mV s -1 .

[0073] (3) Finally, constant current electrolysis was performed at a current density of -200 mA, and after 2 h, the catholyte was collected, diluted with deuterium water (D2O), and then subjected to 1 H NMR (400 MHz) analysis to detect the yield of glycinic acid, glycinic acid oxime and glycine, and to calculate the conversion rate and the production rate.

[0074] (4) When performing nuclear magnetic quantitative detection of the product, 150 μL of the catholyte was mixed with 450 μL of a D2O solution containing 1.82*10 –5 mol of maleic acid (wherein the maleic acid served as an internal standard), and the above diluted liquid was transferred to a 5 mm NMR tube for testing. After 2 h, the yield of glycine reached 794 μmol h –1 cm –2 . This result shows that the foamed silver electrode has excellent catalytic activity and selectivity for the electrocatalytic reduction amination reaction of glyoxylic acid, and is a high-efficiency catalyst for the electrocatalytic synthesis of glycine.

[0075] Test Example 2:

[0076] The linear sweep voltammetry curve obtained in Example 2 is shown in Figure 4 , and it can be seen from Figure 4 that the current rapidly increased at a potential of -0.09 V, which shows that the foamed silver has excellent catalytic performance for the electrocatalytic reduction amination reaction of glyoxylic acid.

[0077] The two-hour electrolysis graph obtained in Example 2 is shown in Figure 5 , and it can be seen from Figure 5 that the potential did not change significantly within two hours, and was basically maintained at about -0.3 V, which shows that the foamed silver has good stability for the reduction amination reaction of glyoxylic acid.

[0078] The nuclear magnetic resonance hydrogen spectrum of the two-hour product solution of Example 2 is shown in Figure 6 , and it can be seen from Figure 6 that after two hours of constant current electrolysis, the product was basically only glycine, and the content was very high, which shows that the foamed silver has excellent selectivity for the synthesis of glycine.

[0079] Example 3:

[0080] After the reaction of Example 2, high-purity glycine powder was obtained by separating, purifying and freeze-drying the cathode chamber solution, and the specific process was as follows:

[0081] (1) Soak the commercial sodium cation exchange resin in deionized water for 48 hours and wash it repeatedly until the water is clear; then soak it in a 4-5 wt% hydrochloric acid solution for 8 hours, and then wash the sodium cation exchange resin with deionized water until it is neutral; finally, soak the resin in a 4 wt% sodium hydroxide solution for 8 hours, and then wash the sodium cation exchange resin with deionized water until it is neutral.

[0082] (2) Take 10 mL of resin and load 10 mL of sample solution. Soak the resin in the sample solution for 1 hour. At this time, the pH is about 1-2. The amino acids exist in the form of cations and are adsorbed on the resin. The sodium ions are exchanged. Rinse the resin with deionized water 3-5 times to remove inorganic salts. Then elute with ammonia water with a pH of about 10. When the pH is greater than 5.59, glycine is converted into anions and removed from the resin. The eluate can be collected.

[0083] (3) The collected solution was freeze-dried in a freeze dryer at -40 to -60°C for 20-30 hours, and the sample was collected and then dried in an oven at 60°C for 6 hours to obtain glycine powder.

[0084] Test Example 3:

[0085] The XRD spectrum of the purified glycine powder obtained in Example 3 is shown in Figure 7 ,pass Figure 7 It can be seen that sulfuric acid was successfully removed through the ion exchange method, and glycine was obtained with high purity and good crystallinity.

[0086] Comparative Example 2:

[0087] The same preparation method as described in Example 3, except that:

[0088] The resin volume was 5 ml, the product obtained in this comparative example was less, and the purified glycine powder had poor quality, low yield and low yield.

Claims

1. A method for synthesizing glycine using bulk silver foam electrocatalysis. This method uses bulk ultralight silver foam as a catalytic electrode, biomass derivatives glyoxylic acid and hydroxylamine sulfate as raw materials, and produces a glycine-sulfuric acid solution via an electrocatalytic reductive amination process. The specific method is as follows: 1) A three-electrode system is formed by using bulk ultralight silver foam as the working electrode, a Pt sheet electrode as the counter electrode, and a saturated calomel electrode as the reference electrode. 2) The three-electrode system was placed in an electrolyte, and a cathodic electrocatalytic reductive amination reaction of glyoxylic acid was carried out under constant current conditions. The electrolyte included a catholyte and an anolyte. The working electrode and the reference electrode were placed in the catholyte, and the counter electrode was placed in the anolyte. The catholyte was a mixture of glyoxylic acid, hydroxylamine sulfate, and sulfuric acid, and the anolyte was a 0.1-0.3 mol / L sulfuric acid solution. The molar concentration of glyoxylic acid, hydroxylamine sulfate, and sulfuric acid in the electrolyte was 0.16 mol / L, 0.08 mol / L, and 0.2 mol / L. The electrocatalytic cell used was an H-type two-chamber glass electrolytic cell, with the cathode and anode compartments separated by a Nafion 117 membrane. Before the electrocatalytic reductive amination reaction of glyoxylic acid, no glyoxylic acid and hydroxylamine sulfate were added to the catholyte. The electrodes were first subjected to cyclic voltammetry in a 0.2 mol / L sulfuric acid solution for 100 cycles at a scan rate of 100 mV s. -1 , linear sweep voltammetry was performed from 0.00 V to -0.45 V relative to the reversible hydrogen electrode E RHE , the scan rate was 10 mV s -1 , constant current is -200 mA; The bulk ultralight silver foam is prepared according to the following method: (1) Pour the silver nitrate solution into the reaction flask, slowly add ammonia water drop by drop, and stop adding until the ammonia water and the silver nitrate solution react completely, that is, the solution becomes transparent, to obtain a silver ammonia solution; add glucose solution dropwise to the silver ammonia solution to reduce it, and immediately put the melamine resin foam into the solution and heat it in a water bath; (2) The melamine resin foam after the reaction is washed with water and then placed in an oven for drying. The dried melamine resin foam is calcined in an air atmosphere to obtain an ultra-light bulk silver foam.

2. The method according to claim 1, characterized in that In step (1), the mass concentration of the silver nitrate solution is 2-3 wt%, the volume is 10 mL, the mass concentration of the ammonia solution is 2-3 wt%, the volume is 2.5 mL, the volume ratio of the silver nitrate solution to the ammonia solution is 4:1, the mass concentration of the glucose solution is 5-15 wt%, the volume ratio of the glucose solution to the silver nitrate solution is (1-5): (8-12), the water bath heating temperature is 65-75°C, the water bath heating time is 8-15 minutes, and the melamine resin foam water washing time is 0.5-5 minutes.

3. The method according to claim 1, characterized in that In step (2), the melamine resin foam is dried at a temperature of 100-120° C. for a drying time of 30-50 minutes, and is calcined at a temperature of 600-700° C. for a calcination time of 10-15 minutes.

4. The method according to claim 1, wherein The reaction liquid after the electrocatalytic reductive amination reaction of glyoxylic acid is separated and purified to obtain glycine powder, as follows: a. Soak the sodium cation exchange resin in deionized water to remove water-soluble impurities; then perform acid-base pretreatment to remove iron and organic impurities; then rinse and soak with deionized water, repeatedly washing until the rinse solution is neutral; b. soaking the solution after the electrocatalytic glyoxylic acid reductive amination reaction in a pretreated sodium cation exchange resin so that the glycine cation is fully adsorbed on the cation exchange resin; c. Rinse the sodium cation exchange resin soaked in the reaction solution with deionized water to remove inorganic salts; then elute with ammonia water to obtain a pure glycine aqueous solution; d. Collect the eluate and freeze-dry it to obtain glycine powder.

5. The method according to claim 4, characterized in that In step a, the sodium cation exchange resin is soaked in deionized water for 48 hours; the hydrochloric acid concentration used in the acid treatment is 4-5 wt%, and the soaking time is 8 hours; the sodium hydroxide solution concentration used in the alkali treatment is 4-5 wt%, and the soaking time is 8 hours. In step b, the solution after the electrocatalytic reductive amination reaction of glyoxylic acid is soaked in the pretreated sodium ion exchange resin for 1-2 hours.

6. The method according to claim 4, characterized in that In step c, the cation exchange resin after soaking in the reaction solution is rinsed with deionized water 3-5 times; the pH of the ammonia eluent is 10, and the number of rinses is 3-5 times. When the pH of the effluent is greater than 5.97, the solution is collected. In step d, the freeze-drying temperature is -40°C to -60°C, and the freeze-drying time is 20-30 hours.

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