A method for electrocatalytic reduction of oxalic acid to glycolic acid

Abstract

The application discloses a method for preparing glycolic acid by electrocatalytic reduction of oxalic acid, which comprises the following steps: preparing an acid aqueous solution with a concentration of 0.05-0.5 mol / L as an electrolyte, and then dividing the electrolyte into two parts; adding oxalic acid into the first part of the electrolyte to prepare a solution with a final concentration of 0.05-0.2 mol / L of oxalic acid as a cathode reaction liquid; the second part of the electrolyte is an anode reaction liquid; the H-type electrolytic cell is divided into a cathode chamber and an anode chamber by using a proton exchange membrane, and the cathode reaction liquid and the anode reaction liquid are added into the cathode chamber and the anode chamber respectively; the cathode reaction liquid and the anode reaction liquid are equal in volume; a carbon cloth electrode loaded with metal Bi is used as a cathode electrode, and a platinum sheet electrode is used as an anode electrode; after the electrolytic cell is assembled, constant current electrolysis is carried out to obtain glycolic acid; and the carbon cloth electrode loaded with metal Bi is used as a catalyst to electrocatalytically reduce oxalic acid, the reaction condition is mild, the operation process is simple, the side reaction is less, the method is green and environment-friendly, the selectivity is high, and the added value is high.

Description

Technical Field

[0001] This invention belongs to the field of organic chemical synthesis, specifically relating to a method for preparing glycolic acid by electrocatalytic reduction of oxalic acid. Background Technology

[0002] Glycolic acid is a highly valuable and in-demand fine chemical, used as a monomer in the synthesis of biodegradable and biocompatible copolymers, polyglycolic acid (PGA), and has wide applications in the food, textile, and cosmetic industries. Oxalic acid (OX), a well-known platform compound, is one of the C2 products of CO2 electroreduction and can also be obtained through the oxidation of waste biomass; it is widely available and inexpensive. Therefore, the catalytic reduction of oxalic acid to glycolic acid (GC) is considered a promising synthetic method.

[0003] There are two main methods for synthesizing glycolic acid from oxalic acid: heterogeneous catalytic reduction and electrocatalytic reduction. Currently reported literature mainly utilizes noble metal-based catalysts such as ruthenium for heterogeneous catalytic reduction of oxalic acid, operating at 75–130 °C and hydrogen pressures above 80 bar, with a glycolic acid selectivity of approximately 70% [Green Chemistry 2023, 25(6), 2409-2426]. However, compared to traditional thermocatalytic hydrogenation requiring high-temperature, high-pressure H2, electrocatalytic reduction of oxalic acid is green and sustainable, avoiding energy loss under high temperature and pressure, and efficiently generating glycolic acid under mild conditions using water as a hydrogen source.

[0004] Electrocatalysis is a promising alternative to heterogeneous catalysis for sustainable development. Recent literature on the electrocatalytic reduction of oxalic acid to glycolic acid has largely focused on titanium-based materials. However, because the reaction occurs in acidic solutions, the working electrode faces challenges such as acid corrosion and competitive hydrogen evolution side reactions, significantly hindering the reaction and resulting in low energy efficiency and selectivity for most reactions. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of harsh reaction conditions, high energy consumption, numerous side reactions, and slow reaction rates in the existing technology, and to provide a simple, mild, green, environmentally friendly, and highly selective method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid.

[0006] The technical solution of this invention is summarized as follows:

[0007] A method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid includes the following steps:

[0008] 1) Prepare an acid-water solution with a concentration of 0.05–0.5 mol / L as the electrolyte, and divide it into two parts. Add oxalic acid to the first part of the electrolyte to prepare a solution with a final oxalic acid concentration of 0.05–0.2 mol / L as the cathode reaction solution; the second part of the electrolyte is the anolyte reaction solution.

[0009] 2) The H-type electrolytic cell is divided into a cathode chamber and an anode chamber using a proton exchange membrane, and a cathode reaction solution and an anode reaction solution are added to the cathode chamber and the anode chamber respectively; the cathode reaction solution and the anode reaction solution are of equal volume;

[0010] 3) After assembling the electrolytic cell, a carbon cloth electrode loaded with metallic Bi is used as the cathode electrode and a platinum sheet electrode is used as the anode electrode. Then, constant current electrolysis is performed to obtain glycolic acid.

[0011] Preferably, the acid in the acidic aqueous solution is sulfuric acid or perchloric acid.

[0012] Preferably, the proton exchange membrane is Nafion 115 or Nafion 117.

[0013] The carbon cloth electrode loaded with Bi metal is fabricated using the following method:

[0014] 1) Add 1.94g of bismuth nitrate pentahydrate and 0.2g of polyvinylpyrrolidone K30 to 10mL of ethylene glycol, and dissolve by sonication to obtain a homogeneous solution;

[0015] 2) Cut the carbon cloth to obtain a 2×3cm 2 The rectangular sheet is immersed in the solution obtained in step 1) for 2 hours, then removed and dried in an oven at 120°C for 5 hours. It is then calcined in a tube furnace at 500-700°C for 2 hours under argon protection to obtain a carbon cloth electrode loaded with metallic Bi.

[0016] Preferably, in step 3), the constant current electrolysis temperature is 25–55°C and the current density is 10–20 mA / cm². 2 The electrolysis time is 9-12 hours.

[0017] Advantages of this invention:

[0018] This invention uses a carbon cloth electrode loaded with metallic Bi as a catalyst for the electrocatalytic reduction of oxalic acid. The reaction conditions are mild, the operation is convenient and simple, there are few side reactions, it is green and environmentally friendly, and it has high selectivity and high added value. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the liquid phase reaction results of the electrocatalytic reduction of oxalic acid to prepare glycolic acid according to the present invention. Detailed Implementation

[0020] The method for preparing the Bi-loaded carbon cloth electrode of the present invention is referenced in [Applied Catalysis B: Environmental 2021, 284].

[0021] The following embodiments further illustrate the present invention, but do not limit the invention to the scope of the embodiments described.

[0022] Example 1

[0023] The method for preparing a carbon cloth electrode loaded with metallic Bi includes the following steps:

[0024] 1) Add 1.94g of bismuth nitrate pentahydrate and 0.2g of polyvinylpyrrolidone K30 to 10mL of ethylene glycol, and dissolve by sonication to obtain a homogeneous solution;

[0025] 2) Cut the carbon cloth to obtain a 2×3cm 2 The rectangular sheet is immersed in the solution obtained in step 1) for 2 hours, then removed and dried in an oven at 120°C for 5 hours. It is then calcined in a tube furnace at 700°C for 2 hours under argon protection to obtain a carbon cloth electrode loaded with metallic Bi.

[0026] Example 2

[0027] The method for preparing a carbon cloth electrode loaded with metallic Bi includes the following steps:

[0028] 1) Add 1.94g of bismuth nitrate pentahydrate and 0.2g of polyvinylpyrrolidone K30 to 10mL of ethylene glycol, and dissolve by sonication to obtain a homogeneous solution;

[0029] 2) Cut the carbon cloth to obtain a 2×3cm 2 The rectangular sheet is immersed in the solution obtained in step 1) for 2 hours, then removed and dried in an oven at 120°C for 5 hours. It is then calcined in a tube furnace at 500°C for 2 hours under argon protection to obtain a carbon cloth electrode loaded with metallic Bi.

[0030] Example 3

[0031] The method for preparing a carbon cloth electrode loaded with metallic Bi includes the following steps:

[0032] 1) Add 1.94g of bismuth nitrate pentahydrate and 0.2g of polyvinylpyrrolidone K30 to 10mL of ethylene glycol, and dissolve by sonication to obtain a homogeneous solution;

[0033] 2) Cut the carbon cloth to obtain a 2×3cm 2 The rectangular sheet is immersed in the solution obtained in step 1) for 2 hours, then removed and dried in an oven at 120°C for 5 hours. It is then calcined in a tube furnace at 600°C for 2 hours under argon protection to obtain a carbon cloth electrode loaded with metallic Bi.

[0034] Example 4

[0035] A method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid includes the following steps:

[0036] 1) Prepare a 0.05 mol / L sulfuric acid aqueous solution (or perchloric acid aqueous solution) as the electrolyte, and divide it into two parts. Add oxalic acid to the first part of the electrolyte to prepare a solution with a final oxalic acid concentration of 0.1 mol / L as the cathode reaction solution; the second part of the electrolyte is the anode reaction solution.

[0037] 2) The H-type electrolytic cell is divided into a cathode chamber and an anode chamber using a proton exchange membrane Nafion 117. Cathode reaction solution and anode reaction solution are added to the cathode chamber and anode chamber respectively; the cathode reaction solution and anode reaction solution are of equal volume.

[0038] 3) Using the carbon cloth electrode loaded with metallic Bi prepared in Example 1 as the cathode electrode (electrocatalyst) and the platinum sheet electrode as the anode electrode, after assembling the electrolytic cell, the electrolysis cell was operated at a temperature of 25°C and a current density of 20 mA / cm². 2 The glycolic acid was obtained by constant current electrolysis for 12 hours.

[0039] Oxalic acid is reduced to glycolic acid at the cathode, and the product is directly analyzed by liquid chromatography (see [link to liquid chromatography]). Figure 1 The conversion rate of oxalic acid was 99%, and the selectivity of glycolic acid was 80%.

[0040] Example 5

[0041] A method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid includes the following steps:

[0042] 1) Prepare a 0.1 mol / L sulfuric acid aqueous solution (or perchloric acid aqueous solution) as the electrolyte, and divide it into two parts. Add oxalic acid to the first part of the electrolyte to prepare a solution with a final oxalic acid concentration of 0.05 mol / L as the cathode reaction solution; the second part of the electrolyte is the anode reaction solution.

[0043] 2) The H-type electrolytic cell is divided into a cathode chamber and an anode chamber using a proton exchange membrane Nafion 117. Cathode reaction solution and anode reaction solution are added to the cathode chamber and anode chamber respectively; the cathode reaction solution and anode reaction solution are of equal volume.

[0044] 3) Using the carbon cloth electrode loaded with metallic Bi prepared in Example 2 as the cathode electrode (electrocatalyst) and the platinum sheet electrode as the anode electrode, after assembling the electrolytic cell, the electrolysis cell was operated at a temperature of 35°C and a current density of 17 mA / cm². 2 The glycolic acid was obtained by constant current electrolysis for 10 hours.

[0045] Oxalic acid was reduced to glycolic acid at the cathode. The product was directly analyzed by liquid chromatography, and the conversion rate of oxalic acid was 95% and the selectivity of glycolic acid was 87%.

[0046] Example 6

[0047] A method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid includes the following steps:

[0048] 1) Prepare a 0.5 mol / L sulfuric acid aqueous solution (or perchloric acid aqueous solution) as the electrolyte, and divide it into two parts. Add oxalic acid to the first part of the electrolyte to prepare a solution with a final oxalic acid concentration of 0.2 mol / L as the cathode reaction solution; the second part of the electrolyte is the anode reaction solution.

[0049] 2) The H-type electrolytic cell is divided into a cathode chamber and an anode chamber using a Nafion 115 proton exchange membrane. Cathode reaction solution and anode reaction solution are added to the cathode chamber and anode chamber respectively; the cathode reaction solution and anode reaction solution are of equal volume.

[0050] 3) Using the carbon cloth electrode loaded with metallic Bi prepared in Example 3 as the cathode electrode (electrocatalyst) and the platinum sheet electrode as the anode electrode, after assembling the electrolytic cell, the electrolytic cell was operated at a temperature of 55°C and a current density of 10 mA / cm². 2 The glycolic acid was obtained by constant current electrolysis for 9 hours.

[0051] Oxalic acid was reduced to glycolic acid at the cathode. The product was directly analyzed by liquid chromatography, and the conversion rate of oxalic acid was 70% and the selectivity of glycolic acid was 89%.

Claims

1. A method for the electrocatalytic reduction of oxalic acid to prepare glycolic acid, characterized in that... Includes the following steps: 1) Prepare an acid-water solution with a concentration of 0.05–0.5 mol / L as the electrolyte, and divide it into two parts. Add oxalic acid to the first part of the electrolyte to prepare a solution with a final oxalic acid concentration of 0.05–0.2 mol / L as the cathode reaction solution; the second part of the electrolyte is the anolyte reaction solution. 2) The H-type electrolytic cell is divided into a cathode chamber and an anode chamber using a proton exchange membrane, and a cathode reaction solution and an anode reaction solution are added to the cathode chamber and the anode chamber respectively; the cathode reaction solution and the anode reaction solution are of equal volume; 3) After assembling the electrolytic cell, a carbon cloth electrode loaded with metallic Bi is used as the cathode electrode and a platinum sheet electrode is used as the anode electrode. Then, constant current electrolysis is performed to obtain glycolic acid. The carbon cloth electrode loaded with Bi metal is fabricated using the following method: 1) Add 1.94 g of bismuth nitrate pentahydrate and 0.2 g of polyvinylpyrrolidone K30 to 10 mL of ethylene glycol, and dissolve by sonication to obtain a homogeneous solution; 2) Cut the carbon cloth to obtain 2 × 3 cm 2 The rectangular sheet is immersed in the solution obtained in step 1) for 2 h, removed, dried in an oven at 120 ℃ for 5 h, and calcined in a tube furnace at 500-700 ℃ for 2 h under argon protection; removed to obtain a carbon cloth electrode loaded with metallic Bi.

2. The method according to claim 1, characterized in that... The acid in the aqueous solution is sulfuric acid or perchloric acid.

3. The method according to claim 1, characterized in that... The proton exchange membrane is Nafion 115 or Nafion 117.

4. The method according to claim 1, characterized in that... In step 3), the constant current electrolysis temperature is 25–55°C and the current density is 10–20 mA / cm². 2 The electrolysis time is 9-12 hours.

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