An electrochemical synthesis method of glycine

Abstract

The application provides an electrochemical synthesis method of glycine, improves catalytic activity of nitrate reduction and C-N coupling process through atom-dispersed Co-N active sites, and improves mass transfer efficiency through ordered mesoporous structure, thereby relieving the problem of limited substrate diffusion in the reaction process, so that higher glycine Faraday efficiency and yield can be obtained; through taking cobalt acetate tetrahydrate, 1,10-phenanthroline and magnesium hydroxide as raw materials, and sequentially performing reflux coordination, high-temperature pyrolysis and acid washing template treatment, uniform anchoring and atomic-level dispersion of cobalt species in the carbon skeleton can be realized, agglomeration of cobalt particles in the heat treatment process is avoided, and therefore the utilization rate and catalytic activity of cobalt active sites are significantly improved. Meanwhile, the magnesium hydroxide as a template material is removed in the subsequent acid washing process, and rich mesoporous structure can be formed in the catalyst, which is beneficial to rapid diffusion and mass transfer of reactants, intermediates and products, and diffusion limitation in the reaction process is relieved.

Description

Technical Field

[0001] This invention relates to the fields of materials and electrocatalysis, and more specifically, to an electrochemical synthesis method for glycine. Background Technology

[0002] Glycine, as the simplest natural α-amino acid, has wide applications in medicine, food, agriculture, and chemical industries. Currently, industrial synthesis mainly relies on the ammonolysis of chloroacetic acid and the Strecker process. The former suffers from problems such as difficulty in separating byproducts and low catalyst recovery, while the latter uses highly toxic cyanide, posing a high safety risk.

[0003] In recent years, electrochemical synthesis has become a research hotspot due to its mild conditions, high selectivity, and low carbon emissions. However, the electrosynthesis of glycine involves complex CN coupling reactions involving multiple electron / proton transfers, which face challenges such as slow kinetics and numerous side reactions, such as hydrogen evolution reaction and over-reduction, making it difficult to achieve both high Faraday efficiency and high production rate.

[0004] In existing technologies, catalysts such as bimetallic catalysts and single-atom sites are used to optimize reaction pathways, but problems such as active site aggregation and limited mass transfer still exist. For example, although Co-based catalysts have high selectivity for nitrate reduction, nanoparticles are prone to aggregation, and the insufficient specific surface area of ​​the support limits the reaction efficiency. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an electrochemical synthesis method for glycine to solve the above problems.

[0006] The present invention adopts the following solution: This application provides an electrochemical synthesis method for glycine, comprising the following steps: S1: Atomically dispersed cobalt catalyst Co-NC-700 was prepared in advance; S2: The Co-NC-700 is loaded onto the cathode working electrode, and an H-type electrochemical reaction system containing nitrate and glyoxylic acid cathode solution is constructed. S3: Under this electrochemical reaction system, nitrate and glyoxylic acid undergo a CN coupling reaction to generate glycine; In this process, cobalt acetate tetrahydrate, 1,10-phenanthroline, and magnesium hydroxide are used as raw materials. The catalyst is prepared by sequentially passing it through reflux coordination, high-temperature pyrolysis, and acid washing of the template. The Co-NC-700 catalyst has a mesoporous structure and atomically dispersed Co-N coordination active sites.

[0007] As a further improvement, the preparation steps of the Co-NC-700 catalyst include at least: S11: Weigh out cobalt acetate tetrahydrate and dissolve it in anhydrous ethanol solution. First, add a first amount of 1,10-phenanthroline to the solution and then sonicate it. S12: Add a second amount of 1,10-phenanthroline and a suitable amount of magnesium hydroxide, and continue ultrasonic treatment to form a mixture; S13: The mixture is refluxed and coordinated at a preset temperature. After drying, it is ground by evaporating the solvent and then pyrolyzed under a nitrogen atmosphere to obtain a black solid. The template is then removed by stirring with nitric acid, the mixture is washed until neutral, and then vacuum dried to obtain the Co-NC-700 catalyst.

[0008] As a further improvement, the acetic acid tetrahydrate is 125 mg, the anhydrous ethanol is 40 mL; the first quantitative amount of 1,10-phenanthroline is 180 mg, the second quantitative amount of 1,10-phenanthroline is 90 mg; and the magnesium hydroxide is 4 g.

[0009] As a further improvement, the ultrasonic treatment is for more than 30 minutes; the reflux coordination time is 4 hours, the temperature is 60°C, and the solvent evaporation temperature is 70°C; the pyrolysis temperature is 700°C, the pyrolysis atmosphere is nitrogen, and the pyrolysis time is 2 hours.

[0010] As a further improvement, the pickling template is subjected to stirring treatment with 1M nitric acid for 2 hours to remove the magnesium hydroxide template; and the vacuum drying temperature is 60°C.

[0011] As a further improvement, in step S2, 5 mg of Co-NC-700 catalyst was dispersed in 500 µL of a water-ethanol mixture, 25 µL of 5 wt% Nafion solution was added, and the mixture was sonicated for 1 hour. The resulting solution was then coated onto 1 cm² of carbon paper, with a loading of 1 mg. -2 .

[0012] As a further improvement, the H-type electrolytic cell is specifically designed such that the cathode chamber and the anode chamber are separated by a Nafion 117 membrane, the working cathode electrode is carbon paper loaded with Co-NC-700, the counter electrode is a platinum mesh, and the reference electrode is Hg / Hg2SO4.

[0013] As a further improvement, the cathode electrolyte contains nitrate, glyoxylic acid, and an acidic supporting electrolyte; wherein the concentration of nitrate in the cathode electrolyte is 1M, the concentration of glyoxylic acid is 0.2M, and the concentration of sulfuric acid is 0.6M.

[0014] As a further improvement, the electrochemical reaction is carried out under constant potential conditions for at least 3 hours of electrolysis, and the potential is -0.85 V vs RHE.

[0015] As a further improvement, the molar ratio of nitrate to glyoxylic acid is 5:1, and the electrochemical reaction is carried out by magnetic stirring, and the cathode electrolyte is subjected to inert gas bubbling deoxygenation treatment before the reaction.

[0016] By adopting the above technical solution, the present invention can achieve the following technical effects: 1. The electrochemical synthesis method of glycine in this application improves the catalytic activity of nitrate reduction and CN coupling processes by atomically dispersing Co-N active sites, and the ordered mesoporous structure enhances mass transfer efficiency and alleviates the problem of limited substrate diffusion during the reaction. As a result, high glycine Faradaic efficiency and yield can be obtained. The catalyst has good cycle stability and is suitable for continuous operation. The process is green and mild, and the raw materials are widely available, which has the potential for further market expansion.

[0017] 2. By using cobalt acetate tetrahydrate, 1,10-phenanthroline, and magnesium hydroxide as raw materials, and sequentially subjecting the process to reflux coordination, high-temperature pyrolysis, and acid leaching template treatment, uniform anchoring and atomic-level dispersion of cobalt species within the carbon framework can be achieved. This avoids agglomeration of cobalt particles during heat treatment, thereby significantly improving the utilization rate of cobalt active sites and catalytic activity. Simultaneously, the magnesium hydroxide, as a template material, is removed during the subsequent acid leaching process, forming abundant mesoporous structures within the catalyst. This facilitates rapid diffusion and mass transfer of reactants, intermediates, and products, alleviating diffusion limitations during the reaction process. Attached Figure Description

[0018] Figure 1 This is a flowchart of the electrochemical synthesis method of glycine according to an embodiment of the present invention; Figure 2 Images of the Co-NC-700 catalyst are shown in the following images: (a) SEM image, (b) TEM image, (c) SAED image, (d) HR-TEM image, (e) HAADF-STEM image and corresponding EDS elemental maps of C, N and Co, and (f) aberration-corrected HAADF-STEM image. Figure 3 Specifically, the XRD patterns of Co-NC-700 before and after acid leaching are shown in (a), (b) the N2 adsorption-desorption isotherms of Co-NC-700 (where the inset is the pore size distribution of Co-NC-700), (c) the high-resolution X-ray photoelectron spectra of the Co 2p and (d) N 1s regions. Figure 4 The electrochemical performance test results are shown in (a) the LSV curve and (b) the curve obtained in 1M NO3. -(c) Electrolysis product distribution under different applied voltages in electrolytes of 0.2 M GX and 0.6 M H2SO4; (d) NO3- distribution under different applied voltages in electrolytes of -0.85 V vs RHE and 0.6 M H2SO4. - Electrolysis product distribution at a molar ratio of GX, (d) at -0.85V vs RHE, 1MNO3 - Distribution of electrolysis products at different H2SO4 concentrations under 0.2M GX conditions; (e) Change in glycine yield with H2SO4 concentration. Figure 5 The glycine in this embodiment of the invention is at -0.85V vs RHE, 1M NO3 - Figure 1 shows the cyclic stability test results of Co-NC-700 under the conditions of 0.2M GX and 0.6M H2SO4. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0020] Example Combination Figures 1 to 5 This embodiment provides an electrochemical synthesis method for glycine, comprising the following steps: S1: Atomically dispersed cobalt catalyst Co-NC-700 was prepared in advance; S2: The Co-NC-700 is loaded onto the cathode working electrode, and an H-type electrochemical reaction system containing nitrate and glyoxylic acid cathode solution is constructed. S3: Under this electrochemical reaction system, nitrate and glyoxylic acid undergo a CN coupling reaction to generate glycine; In this process, cobalt acetate tetrahydrate, 1,10-phenanthroline, and magnesium hydroxide are used as raw materials. The catalyst is prepared by sequentially passing it through reflux coordination, high-temperature pyrolysis, and acid washing of the template. The Co-NC-700 catalyst has a mesoporous structure and atomically dispersed Co-N coordination active sites.

[0021] The preparation steps of the Co-NC-700 catalyst include at least the following: S11: Weigh out cobalt acetate tetrahydrate and dissolve it in anhydrous ethanol solution. First, add a first amount of 1,10-phenanthroline to the solution and then sonicate it. S12: Add a second amount of 1,10-phenanthroline and a suitable amount of magnesium hydroxide, and continue ultrasonic treatment to form a mixture; S13: The mixture is refluxed and coordinated at a preset temperature. After drying, it is ground by evaporating the solvent and then pyrolyzed under a nitrogen atmosphere to obtain a black solid. The template is then removed by stirring with nitric acid, the mixture is washed until neutral, and then vacuum dried to obtain the Co-NC-700 catalyst.

[0022] In the above-mentioned catalyst preparation, cobalt acetate tetrahydrate, 1,10-phenanthroline, and magnesium hydroxide were used as raw materials. Atomically dispersed Co-NC-700 catalyst was prepared through reflux coordination, high-temperature pyrolysis, and acid washing of the template. This catalyst possesses a high specific surface area (546.82 m²). 2 g -1 The ordered mesoporous structure (mesopores account for 34.67%) and atomically dispersed cobalt active sites effectively inhibit cobalt species aggregation and improve mass transfer efficiency.

[0023] For the construction of the electrochemical synthesis system, an H-type electrolytic cell was used, with Nafion 117 membranes separating the anode and cathode. The cathode electrolyte was an acidic solution containing nitrate and glyoxylic acid (e.g., 0.6 M H₂SO₄), and the anolyte was an acidic supporting electrolyte. The working electrode was carbon paper supported on Co-NC-700, the counter electrode was a platinum mesh, and the reference electrode was Hg / Hg₂SO₄.

[0024] For the electrosynthesis of glycine, the electrocatalytic reaction is carried out in a constant potential mode (e.g., -0.85 V vs RHE) to control NO3. - The molar ratio of GX was 5:1, and the reaction time was 3 hours. Magnetic stirring (600 rpm) was used during the reaction to promote mass transfer. Preferably, the pyrolysis temperature was 700°C, 1M nitric acid was used for template washing, and the catholyte contained 1M NO3. - And 0.2MGX.

[0025] like Figure 2 and Figure 3 As shown in this embodiment, the preparation of the Co-NC-700 catalyst is as follows: 0.5 mmol of cobalt acetate tetrahydrate (125 mg) was dissolved in 40 mL of anhydrous ethanol. 10 mL of 1,10-phenanthroline (18 mg / mL) was added dropwise to the ethanol solution, and the mixture was sonicated for 30 minutes. Then, 90 mg of 1,10-phenanthroline and 4 g of magnesium hydroxide were added, and the mixture was sonicated for another 30 minutes. The mixture was refluxed at 60 °C for 4 hours, the solvent was evaporated at 70 °C, and the powder was dried and ground. The powder was pyrolyzed at 700 °C for 2 hours under a nitrogen atmosphere (heating rate 2 °C / min) to obtain a black solid. The template was removed by stirring with 1 M nitric acid for 2 hours, the mixture was washed with a water-ethanol mixture until neutral, and then dried under vacuum at 60 °C to obtain the Co-NC-700 catalyst.

[0026] In this embodiment, the electrochemical synthesis system is constructed as follows: 5 mg of Co-NC-700 catalyst was dispersed in 500 µL of a water-ethanol mixture (1:1), 25 µL of 5 wt% Nafion solution was added, and the mixture was sonicated for 1 hour. The resulting solution was then coated onto carbon paper (1 cm²) with a loading of 1 mg. -2 In the H-type electrolytic cell, the catholyte consisted of 1 M NaNO3, 0.2 M GX, and 0.6 M H2SO4, while the anolyte was 0.6 M H2SO4. The counter electrode was a platinum mesh, the reference electrode was Hg / Hg2SO4, and the diaphragm was Nafion 117.

[0027] like Figure 4 and Figure 5 In this embodiment, the electrosynthesis and performance testing of glycine are detailed as follows: Before electrolysis, the catholyte Ar was pretreated by bubbling for 20 minutes, followed by electrolysis at a constant potential of -0.85 V vs RHE for 3 hours. After the reaction, the electrolyte was collected, and the products were quantified using nuclear magnetic resonance (¹H NMR) and ultraviolet-visible spectroscopy.

[0028] Table 1 illustrates that the Co-NC-700 catalyst has a high specific surface area (546.82 m²). 2 g -1 The structure is ordered mesoporous (mesopores account for 34.67%), as detailed below: Table 1 Summary of BET Measurements for Co-NC-700 Catalyst

[0029] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions that fall within the scope of the present invention are within the scope of protection of the present invention.

Claims

1. An electrochemical synthesis method for glycine, characterized in that, Includes the following steps: S1: Atomically dispersed cobalt catalyst Co-NC-700 was prepared in advance; S2: The Co-NC-700 is loaded onto the cathode working electrode, and an H-type electrochemical reaction system containing nitrate and glyoxylic acid cathode solution is constructed. S3: Under this electrochemical reaction system, nitrate and glyoxylic acid undergo a CN coupling reaction to generate glycine; Among them, using cobalt acetate tetrahydrate, 1,10-phenanthroline and magnesium hydroxide as raw materials, atomically dispersed Co-NC-700 catalysts were prepared by sequentially passing them through reflux coordination, high-temperature pyrolysis and acid washing template; Furthermore, the Co-NC-700 catalyst is configured to have at least a mesoporous structure and atomically dispersed Co-N coordination active sites.

2. The electrochemical synthesis method of glycine according to claim 1, characterized in that, The preparation steps of the Co-NC-700 catalyst include at least the following: S11: Weigh out cobalt acetate tetrahydrate and dissolve it in anhydrous ethanol solution. First, add a first amount of 1,10-phenanthroline to the solution and then sonicate it. S12: Add a second amount of 1,10-phenanthroline and a suitable amount of magnesium hydroxide, and continue ultrasonic treatment to form a mixture; S13: The mixture is refluxed and coordinated at a preset temperature. After drying, it is ground by evaporating the solvent and then pyrolyzed under a nitrogen atmosphere to obtain a black solid. The template is then removed by stirring with nitric acid, the mixture is washed until neutral, and then vacuum dried to obtain the Co-NC-700 catalyst.

3. The electrochemical synthesis method of glycine according to claim 2, characterized in that, The acetic acid tetrahydrate is 125 mg, the anhydrous ethanol is 40 mL; the first quantitative amount of 1,10-phenanthroline is 180 mg, the second quantitative amount of 1,10-phenanthroline is 90 mg; and the magnesium hydroxide is 4 g.

4. The electrochemical synthesis method of glycine according to claim 3, characterized in that, The ultrasonic treatment lasts for more than 30 minutes; the reflux coordination time is 4 hours, the temperature is 60°C, and the solvent evaporation temperature is 70°C; the pyrolysis temperature is 700°C, the pyrolysis atmosphere is nitrogen, and the pyrolysis time is 2 hours.

5. The electrochemical synthesis method of glycine according to claim 4, characterized in that, The pickling template is treated with 1M nitric acid and stirred for 2 hours to remove magnesium hydroxide template; and the vacuum drying temperature is 60°C.

6. The electrochemical synthesis method of glycine according to claim 1, characterized in that, In step S2, 5 mg of Co-NC-700 catalyst was dispersed in 500 µL of a water-ethanol mixture, 25 µL of 5 wt% Nafion solution was added, and the mixture was sonicated for 1 hour. The resulting solution was then coated onto 1 cm² of carbon paper, with a loading of 1 mg. -2 .

7. The electrochemical synthesis method of glycine according to claim 6, characterized in that, The H-type electrolytic cell is specifically designed with a cathode chamber and an anode chamber separated by a Nafion 117 membrane. The cathode working electrode is carbon paper loaded with Co-NC-700, the counter electrode is a platinum mesh, and the reference electrode is Hg / Hg2SO4.

8. The electrochemical synthesis method of glycine according to claim 7, characterized in that, The cathode electrolyte contains nitrate, glyoxylic acid, and an acidic supporting electrolyte; wherein the concentration of nitrate in the cathode electrolyte is 1M, the concentration of glyoxylic acid is 0.2M, and the concentration of sulfuric acid is 0.6M.

9. The electrochemical synthesis method of glycine according to claim 1, characterized in that, The electrochemical reaction is carried out under constant potential conditions for at least 3 hours of electrolysis, and the potential is -0.85 V vs RHE.

10. The electrochemical synthesis method of glycine according to claim 9, characterized in that, The molar ratio of nitrate to glyoxylic acid is 5:1, and the electrochemical reaction is carried out by magnetic stirring, and the cathode electrolyte is subjected to inert gas bubbling deoxygenation treatment before the reaction.

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