Method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid

Abstract

The present invention provides a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid, comprising the following steps: preparing an electrolyte containing at least two cations; wherein the electrolyte contains at least one monovalent cation and at least one divalent cation; dissolving oxalic acid of a preset concentration into the electrolyte to obtain a reaction solution; assembling an anode catalyst, a cathode catalyst, a diaphragm, and the reaction solution into an electrolytic cell; and electrolyzing the electrolytic cell under preset temperature, preset voltage, and preset pH conditions to electrocatalytically reduce the oxalic acid at the cathode of the electrolytic cell to produce glycolic acid, and oxidize water at the anode of the electrolytic cell to produce oxygen. The present invention can solve the problems of harsh reaction conditions, high energy consumption, and numerous side reactions in existing methods for producing glycolic acid, and can improve the performance of oxalic acid electrocatalytic production of glycolic acid and solve the slow reaction rate by simply regulating the cations in the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of glycolic acid production, and more specifically, to a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid. Background Art

[0002] Glycolic acid is an important chemical intermediate used in metal cleaning, leather processing, adhesives, and other applications. In particular, its polymer (polyglycolic acid) exhibits unique biodegradability and biocompatibility and is widely used in agricultural films, medical sutures, and fracture fixation materials. Glycolic acid can be industrially obtained through oxalic acid reduction or ethylene glycol oxidation. Oxalic acid (OX) is an inexpensive, abundant resource that can be obtained from carbon dioxide, coal, and biomass. Therefore, the production of high-value-added glycolic acid using oxalic acid as a raw material has promising market prospects.

[0003] Currently, methods for producing glycolic acid from oxalic acid mainly include biological and chemical methods. While biological methods offer greater safety, they are complex to operate, have a long production cycle, and are difficult to achieve in large-scale production. Patent (CN112521265A, 2021) discloses a method for continuously producing glycolic acid from dimethyl oxalate, comprising the following steps: A) preheating a mixture of dimethyl oxalate and water, followed by an autocatalytic semi-hydrolysis reaction, whereupon the resulting hydrolysis product is purified by distillation to yield monomethyl oxalate; and B) catalytically hydrogenating the monomethyl oxalate obtained in step A) with hydrogen under catalytic conditions, whereupon the reaction product is purified by distillation to yield glycolic acid. While chemical methods are highly selective and suitable for large-scale production of glycolic acid, they have demanding reaction conditions, require the use of hazardous gases (hydrogen), and are conducted at high temperatures and pressures, resulting in high energy consumption. Therefore, the development of new, green glycolic acid production processes remains of great scientific and economic value.

[0004] Electrocatalytic reduction is an effective method for replacing the hydrogen evolution reaction at the cathode with the reduction of organic matter and obtaining high value-added products. The patent (CN 112725825 A, 2020) discloses a method for preparing glyoxylic acid by electrolysis of oxalic acid, comprising a desalted water storage tank, a cathode storage tank, an ion membrane electrolyzer, an anode storage tank, a desalted water pump, a cathode feed pump, and an anode circulation pump. An additive dissolution tank is provided on one side of the desalted water storage tank, and a cathode liquid buffer tank is provided between the cathode storage tank and the ion membrane electrolyzer. The main reaction at the cathode is that oxalic acid is reduced to glyoxylic acid (selectivity>85%), the main product is glyoxylic acid, and there are many side reactions.

[0005] Although the electrocatalytic production of glycolic acid from oxalic acid has been reported in a previous paper (Energy Environ. Sci., 2015, 8, 1456), they only used sodium sulfate as the electrolyte, which resulted in low current density and did not investigate the effect of cations in the electrolyte on performance. This patent focuses on the effect of cations on performance and finds that an electrolyte containing at least two cations can improve the performance of the electrocatalytic production of glycolic acid from oxalic acid. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide a method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid, so as to solve the problems of the current method for preparing glycolic acid, such as harsh reaction conditions, high energy consumption, many side reactions, and slow reaction rate.

[0007] The present invention provides a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid, comprising the following steps:

[0008] Preparing an electrolyte containing at least two cations; wherein the electrolyte contains at least one monovalent cation and at least one divalent cation;

[0009] dissolving oxalic acid of a preset concentration into the electrolyte to obtain a reaction solution;

[0010] Assembling an anode catalyst, a cathode catalyst, a separator and the reaction solution into an electrolytic cell;

[0011] Under the conditions of a preset temperature, a preset voltage and a preset pH, the electrolytic cell is electrolyzed so that the oxalic acid is electrocatalytically reduced at the cathode of the electrolytic cell to generate glycolic acid, and water is oxidized at the anode of the electrolytic cell to generate oxygen.

[0012] In addition, a preferred embodiment is that the monovalent cation is any one of sodium ion and potassium ion or a mixture of the two ions in any proportion; and / or,

[0013] The cation having a valence greater than or equal to two is one of magnesium ion, zinc ion, calcium ion, aluminum ion or a mixed ion in any proportion.

[0014] In addition, a preferred solution is that, in the electrolyte, the molar ratio of the monovalent cations to the divalent or greater cations is 1:1 or 1:2 or 1:3 or 2:3.

[0015] In addition, a preferred embodiment is that the anode catalyst is a transition metal compound or a noble metal; and / or the cathode catalyst is a transition metal compound.

[0016] In addition, a preferred embodiment is that the transition metal compound is one of transition metal sulfides, transition metal oxides, transition metal borides, and transition metal phosphides, or a mixture of several of them in any proportion.

[0017] In addition, a preferred solution is that the transition metal is one of tungsten, chromium, vanadium, manganese, zinc, and titanium, or a mixture of several of them in any proportion.

[0018] In addition, a preferred solution is that the noble metal is one of platinum, palladium, rhodium, and iridium, or a mixture of several of them in any proportion.

[0019] In addition, a preferred solution is that the diaphragm is any one of AMI7001, CMI7000, FAA-3-20, nafionXL, and nafion117.

[0020] In addition, a preferred solution is that the preset concentration is 0.5-10 g / L.

[0021] In addition, a preferred solution is that the preset temperature is 20° C. to 60° C.; and / or the preset voltage is -10-0 V; and / or the preset pH is 0-14.

[0022] As can be seen from the above technical scheme, the method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid provided by the present invention comprises dissolving oxalic acid into an electrolytic solution, assembling an anode catalyst, a cathode catalyst, a diaphragm and a reaction solution into an electrolytic cell, and directly electrolyzing oxalic acid using the electrolytic cell. The main product is glycolic acid, with few side reactions, high selectivity, high added value and wide application. The present invention not only obtains high-purity glycolic acid, but also achieves the purpose of converting oxalic acid into glycolic acid at a high rate at a relatively low voltage. The electrolytic solution used in the present invention is an electrolyte prepared containing at least two cations. The electrolyte contains at least one monovalent cation and at least one divalent cation. By using this electrolyte, low-valent, i.e., monovalent, cations and high-valent, i.e., divalent cations can be mixed, thereby enhancing the adsorption of carboxyl groups on the catalyst surface, thereby effectively improving the rate of glycolic acid preparation and the density of generated current.

[0023] In order to achieve the above and related purposes, one or more aspects of the present invention include the features that will be described in detail later. The following description and the accompanying drawings describe some exemplary aspects of the present invention in detail. However, these aspects indicate only some of the various ways in which the principles of the present invention can be used. In addition, the present invention is intended to include all of these aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] By referring to the following description in conjunction with the accompanying drawings, and with a more complete understanding of the present invention, other objects and results of the present invention will become more clear and easy to understand. In the accompanying drawings:

[0025] Figure 1 This is a flow chart of a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to an embodiment of the present invention;

[0026] Figure 2 This is a schematic diagram of a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to an embodiment of the present invention;

[0027] Figure 3 is a scanning electron microscope image of a cathode catalyst according to an embodiment of the present invention;

[0028] Figure 4 This is a polarization curve diagram of cation-regulated oxalic acid electrocatalytic reduction according to an embodiment of the present invention;

[0029] Figure 5 Schematic diagram of the reaction rate of oxalic acid electrocatalytic reduction to glycolic acid regulated by cations according to an embodiment of the present invention.

[0030] Figure 6 Schematic diagram of the liquid phase results of the cation-regulated electrocatalytic reduction of oxalic acid to glycolic acid reaction according to an embodiment of the present invention.

[0031] The same reference numerals throughout the drawings indicate similar or corresponding features or functions. DETAILED DESCRIPTION

[0032] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. However, it will be apparent that these embodiments may be practiced without these specific details.

[0033] In view of the problems of the aforementioned current method for preparing glycolic acid, such as harsh reaction conditions, high energy consumption and many side reactions, a method for preparing glycolic acid by electrocatalytic reduction of oxalic acid is proposed.

[0034] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] To illustrate the method for preparing glycolic acid by electrocatalytic reduction of oxalic acid provided by the present invention, Figure 1 The flow chart of the method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to an embodiment of the present invention is shown; Figure 2 A schematic diagram showing a method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to an embodiment of the present invention is shown; Figure 3 shows a scanning electron microscope image of a cathode catalyst according to an embodiment of the present invention; Figure 4The polarization curve of cation-regulated oxalic acid electrocatalytic reduction according to an embodiment of the present invention is shown; Figure 5 Schematic diagram of the reaction rate of oxalic acid electrocatalytic reduction to glycolic acid regulated by cations according to an embodiment of the present invention; Figure 6 The schematic diagram of the liquid phase results of the electrocatalytic reduction of oxalic acid to glycolic acid according to the embodiment of the present invention is shown. Figures 1 to 6 As shown in the figures, the method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid provided by the present invention comprises the following steps:

[0036] S1. preparing an electrolyte containing at least two cations; wherein the electrolyte contains at least one monovalent cation and at least one divalent cation;

[0037] S2. dissolving oxalic acid of a preset concentration into the electrolyte to obtain a reaction solution;

[0038] S3, assembling an anode catalyst, a cathode catalyst, a diaphragm and a reaction solution into an electrolytic cell;

[0039] S4. Under the conditions of a preset temperature, a preset voltage, and a preset pH, electrolysis is performed on the electrolytic cell, so that oxalic acid is electrocatalytically reduced at the cathode of the electrolytic cell to generate glycolic acid, and water is oxidized at the anode of the electrolytic cell to generate oxygen.

[0040] The invention discloses a method for preparing glycolic acid by dissolving oxalic acid in an electrolytic solution, assembling an anode catalyst, a cathode catalyst, a diaphragm and a reaction solution into an electrolytic cell, and directly electrolyzing the oxalic acid in the electrolytic cell. The method has the advantages of few side reactions, high selectivity, high added value and wide application, etc. The method not only obtains high-purity glycolic acid, but also achieves the purpose of converting oxalic acid into glycolic acid at a high rate at a relatively low voltage. The electrolytic solution used in the invention is an electrolyte prepared by containing at least two cations. The electrolyte contains at least one monovalent cation and at least one divalent cation. The electrolyte can mix low-valent cations, i.e. monovalent cations, with high-valent cations, i.e. divalent cations, thereby enhancing the adsorption of carboxyl groups on the catalyst surface and effectively improving the efficiency and yield of glycolic acid preparation.

[0041] As a preferred embodiment of the present invention, the monovalent cation is any one of sodium ion and potassium ion, or a mixture of the two ions in any proportion; and / or,

[0042] The cation having a valence greater than or equal to two is one of magnesium ion, zinc ion, calcium ion, aluminum ion or a mixed ion in any proportion.

[0043] As a preferred embodiment of the present invention, in the electrolyte, the molar ratio of the monovalent cations to the divalent cations or greater is 1:1 or 1:2 or 1:3 or 2:3.

[0044] As a preferred embodiment of the present invention, the anode catalyst is a transition metal compound or a noble metal; and / or the cathode catalyst is a transition metal compound.

[0045] As a preferred embodiment of the present invention, the transition metal compound is one of transition metal sulfides, transition metal oxides, transition metal borides, transition metal phosphides, or a mixture of several of them in any proportion.

[0046] As a preferred embodiment of the present invention, the transition metal is one of tungsten, chromium, vanadium, manganese, zinc, and titanium, or a mixture of several of them in any proportion.

[0047] As a preferred embodiment of the present invention, the precious metal is one of platinum, palladium, rhodium, and iridium, or a mixture of several of them in any proportion.

[0048] As a preferred embodiment of the present invention, the diaphragm is any one of AMI7001, CMI7000, FAA-3-20, nafionXL, and nafion117.

[0049] As a preferred embodiment of the present invention, the preset concentration is 0.5-10 g / L.

[0050] As a preferred embodiment of the present invention, the preset temperature is 20° C. to 60° C.; and / or the preset voltage is -10-0 V; and / or the preset pH is 0-14.

[0051] In order to better illustrate the method for preparing glycolic acid by electrocatalytic reduction of oxalic acid provided by the present invention, the following specific examples are provided.

[0052] In order to avoid the possibility of accidental experimental results, the experiments in each of the following embodiments were verified 10 times, and the experimental results finally obtained were the average values ​​of the 10 experiments.

[0053] Example 1

[0054] Electrocatalytic reduction of oxalic acid to glycolic acid in pure sodium sulfate solution

[0055] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 28.4 mg / mL Na2SO4 solution (pH = 2).

[0056] 2. Using titanium dioxide as cathode catalyst (such as Figure 3 As shown), nickel foam was used as the anode, and polarization curve tests were performed in 28.4 mg / mL Na2SO4 solution and the reaction solution prepared in step 1 (voltage range: -1 to 0 V, scan rate: 0.02 V / s). Figure 4 As shown in Figure 2, after adding oxalic acid to the sodium sulfate solution, the maximum current density of the polarization curve is 100 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8V for 1 hour. Figure 5 As shown, the reaction rate is 0.89 mmol h -1 cm -2 .

[0057] 3. Titanium dioxide is used as the cathode catalyst, nickel foam is used as the anode catalyst, and the reaction solution prepared in step 1 is used to form an electrolytic cell. The reaction is carried out at 50°C and a constant voltage of -0.8V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95% (e.g. Figure 6 shown).

[0058] Example 2

[0059] Electrocatalytic reduction of oxalic acid to glycolic acid in pure potassium sulfate solution

[0060] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 34.85 mg / mL K2SO4 solution (pH = 2).

[0061] 2. Using titanium dioxide as the cathode catalyst and nickel foam as the anode, polarization curve tests were performed in the reaction solution prepared in step 1 and in a 34.85 mg / mL K2SO4 solution (voltage range -1 to 0 V, scan rate 0.02 V / s). After adding oxalic acid to the potassium sulfate solution, the maximum current density of the polarization curve was 103 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8 V for 1 h, with a reaction rate of 0.91 mmol h -1 cm -2 .

[0062] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0063] Example 3

[0064] Electrocatalytic reduction of oxalic acid to glycolic acid in a 1:3 potassium sulfate solution and sodium sulfate solution

[0065] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 7.10 mg / mL Na2SO4 and 26.14 mg / mL K2SO4 solution (pH = 2).

[0066] 2. Using titanium dioxide as the cathode catalyst and nickel foam as the anode, conduct polarization curve test in the reaction solution prepared in step 1 (voltage range is -1 to 0 V, scan rate is 0.02 V / s). Figure 4 As shown in Figure 2, after adding oxalic acid to the sodium sulfate solution, the maximum current density of the polarization curve is 98 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8 V for 1 h, with a reaction rate of 0.86 mmol h -1 cm -2 .

[0067] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0068] The glycolic acid reduction results of Examples 1 to 3 clearly show that the selectivity of oxalic acid to glycolic acid at the cathode is greater than 95% when using the method of preparing glycolic acid by directly electrolyzing oxalic acid in an electrolytic cell. This selectivity is higher than that of the prior art.

[0069] Example 4

[0070] Electrocatalytic reduction of oxalic acid to glycolic acid in a 1:3 molar ratio sodium sulfate and zinc sulfate electrolyte

[0071] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 7.10 mg / ml Na2SO4 and 24.21 mg / ml ZnSO4 solution (pH = 2).

[0072] 2. Use titanium dioxide as cathode catalyst, nickel sheet as anode, and the reaction solution prepared in step 1 to form an electrolytic cell, and perform polarization curve test (voltage range is -1~0V, scan rate is 0.02V / s). Figure 4 As shown in Figure 2, after adding oxalic acid to the electrolyte, the maximum current density of the polarization curve is 200 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8V for 1 hour. Figure 5 As shown, the reaction rate can reach 1.41 mmol h -1 cm -2 .

[0073] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0074] Example 5

[0075] Electrocatalytic reduction of oxalic acid to glycolic acid in a 1:3 molar ratio potassium sulfate and zinc sulfate electrolyte

[0076] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 7.10 mg / ml K2SO4 and 24.21 mg / ml ZnSO4 solution (pH = 2).

[0077] 2. Titanium dioxide was used as the cathode catalyst, nickel sheet was used as the anode, and the reaction solution prepared in step 1 was used to form an electrolytic cell. Polarization curve test was performed (voltage range: -1 to 0 V, scan rate: 0.02 V / s). After adding oxalic acid to the electrolyte, the maximum current density of the polarization curve was 195 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8 V for 1 h, and the reaction rate was 1.38 mmol h -1 cm -2 .

[0078] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0079] Example 6

[0080] Electrocatalytic reduction of oxalic acid to glycolic acid in an electrolyte containing sodium sulfate and aluminum sulfate at a molar ratio of 1:3

[0081] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 7.10 mg / ml Na2SO4 and 51.30 mg / ml Al2(SO4)3 solution (pH = 2).

[0082] 2. Titanium dioxide was used as the cathode catalyst, nickel sheet was used as the anode, and the reaction solution prepared in step 1 was used to form an electrolytic cell. Polarization curve test was performed (voltage range: -1 to 0 V, scan rate: 0.02 V / s). After adding oxalic acid to the electrolyte, the maximum current density of the polarization curve was 191 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8 V for 1 h, and the reaction rate was 1.36 mmol h -1 cm -2 .

[0083] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0084] Example 7

[0085] Electrocatalytic reduction of oxalic acid to glycolic acid in an electrolyte containing magnesium sulfate and zinc sulfate at a molar ratio of 1:3

[0086] 1. Dissolve 0.5 g of oxalic acid in 30 mL of 6.02 mg / ml MgSO4 and 24.21 mg / ml ZnSO4 solution (pH = 2).

[0087] 2. Titanium dioxide was used as the cathode catalyst, nickel sheet was used as the anode, and the reaction solution prepared in step 1 was used to form an electrolytic cell. Polarization curve test was performed (voltage range: -1 to 0 V, scan rate: 0.02 V / s). After adding oxalic acid to the electrolyte, the maximum current density of the polarization curve was 150 mA cm -2 The reaction was carried out at 50°C and a constant voltage of -0.8 V for 1 h, and the reaction rate was 1.03 mmol h -1 cm -2 .

[0088] 3. Use titanium dioxide as the cathode catalyst and nickel foam as the anode catalyst in an electrolytic cell with the reaction solution prepared in step 1. The reaction is carried out at 50°C and a constant voltage of -0.8 V for 12 hours. Oxalic acid is reduced to glycolic acid at the cathode with a selectivity of >95%.

[0089] like Figure 4 As shown, compared with Example 1 and Example 7, the polarization curve current density of Example 4 is significantly higher than that of Example 1. Figure 5 As shown, the reaction rate of Example 4 is significantly higher than the reaction rates of Example 1 and Example 7.

[0090] Therefore, it can be clearly seen from the above Examples 1 to 7 that the electrolyte prepared by using a monovalent cation and a divalent cation or greater in the embodiments of the present invention has a polarization curve current density that is significantly higher than the polarization curve current density of the electrolyte prepared by using only a monovalent cation or only a divalent cation; the reaction rate is also significantly higher than the reaction rate of the electrolyte prepared by using only a monovalent cation or only a divalent cation.

[0091] It can be seen from the above specific embodiments that the method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid provided by the present invention comprises dissolving oxalic acid into an electrolytic solution, assembling an anode catalyst, a cathode catalyst, a diaphragm and a reaction solution into an electrolytic cell, and directly electrolyzing oxalic acid using the electrolytic cell. The main product is glycolic acid, and there are few side reactions, high selectivity, high added value, and wide application. The present invention not only obtains high-purity glycolic acid, but also achieves the purpose of converting oxalic acid into glycolic acid at a high rate at a relatively low voltage. The electrolytic solution used in the present invention is an electrolyte prepared containing at least two cations. The electrolyte contains at least one monovalent cation and at least one divalent cation. By using this electrolyte, low-valent, i.e., monovalent cations and high-valent cations, i.e., divalent cations, can be mixed to enhance the adsorption of carboxyl groups on the catalyst surface, thereby effectively improving the rate of glycolic acid preparation and the density of generated current.

[0092] The method for producing glycolic acid by electrocatalytic reduction of oxalic acid according to the present invention has been described above by way of example with reference to the accompanying drawings. However, those skilled in the art will appreciate that various modifications may be made to the above-described method for producing glycolic acid by electrocatalytic reduction of oxalic acid regulated by cations without departing from the scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for producing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid, characterized in that: The steps include: An electrolyte containing at least two cations is prepared; wherein the electrolyte contains at least one monovalent cation and at least one divalent cation; in the electrolyte, the molar ratio of the monovalent cation to the divalent cation is 1:1, 1:2, 1:3, or 2:3; dissolving oxalic acid of a preset concentration into the electrolyte to obtain a reaction solution; Assembling an anode catalyst, a cathode catalyst, a separator and the reaction solution into an electrolytic cell; Under the conditions of a preset temperature, a preset voltage and a preset pH, the electrolytic cell is electrolyzed so that the oxalic acid is electrocatalytically reduced at the cathode of the electrolytic cell to generate glycolic acid, and water is oxidized at the anode of the electrolytic cell to generate oxygen.

2. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 1, characterized in that: The monovalent cation is any one of sodium ion and potassium ion, or a mixture of the two ions in any proportion; and / or, The cation having a valence greater than or equal to two is one of magnesium ion, zinc ion, calcium ion, aluminum ion or a mixed ion in any proportion.

3. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 1, characterized in that: The anode catalyst is a transition metal compound or a noble metal; and / or, The cathode catalyst is a transition metal compound.

4. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 3, characterized in that: The transition metal compound is one of transition metal sulfides, transition metal oxides, transition metal borides, and transition metal phosphides, or a mixture of the above-mentioned transition metal compounds in any proportion.

5. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 4, characterized in that: The transition metal is one of tungsten, chromium, vanadium, manganese, zinc, and titanium, or a mixture of several of them in any proportion.

6. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 4, characterized in that: The noble metal is one of platinum, palladium, rhodium and iridium, or a mixture of several of them in any proportion.

7. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 1, characterized in that: The diaphragm is any one of AMI7001, CMI7000, FAA-3-20, nafion XL, and nafion117.

8. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 1, characterized in that: The preset concentration is 0.5-10 g / L.

9. The method for preparing glycolic acid by cation-regulated electrocatalytic reduction of oxalic acid according to claim 1, characterized in that: The preset temperature is 20°C to 60°C; and / or, The preset voltage is -10-0V; and / or, The preset pH is 0-14.

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