Method for preparing glycollic acid through electrocatalytic reduction of oxalic acid

Abstract

The invention discloses a method for preparing glycollic acid by electrocatalytic reduction of oxalic acid, which comprises the following steps: preparing an acid aqueous solution with the concentration of 0.05-0.5 mol / L as an electrolyte, dividing the acid aqueous solution into two parts, adding oxalic acid into the first part of electrolyte, and preparing a solution with the final oxalic acid concentration of 0.05-0.2 mol / L as a cathode reaction solution; the electrolyte of the second part is an anode reaction solution; dividing the H-type electrolytic tank into a cathode chamber and an anode chamber by using a proton exchange membrane, and respectively adding a cathode reaction solution and an anode reaction solution into the cathode chamber and the anode chamber; the cathode and anode reaction solutions are equal in volume; the carbon cloth electrode loaded with the metal Bi serves as a cathode electrode, a platinum sheet electrode serves as an anode electrode, after the electrolytic tank is assembled, constant-current electrolysis is conducted, and glycollic acid is obtained.The carbon cloth electrode loaded with the metal Bi serves as a catalyst to conduct electrocatalytic reduction on oxalic acid, reaction conditions are mild, the operation process is convenient and simple, side reactions are few, and the method is environmentally friendly; the selectivity and the additional value are high.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of organic chemical synthesis, and particularly relates to a method for preparing glycolic acid by electrocatalytic reduction of oxalic acid. BACKGROUND

[0002] Glycolic acid is a fine chemical with great economic value and market demand, which can be used as a monomer for synthesizing biodegradable and biocompatible copolymer polyglycolic acid (PGA), and has wide application in food, textile and cosmetic industries. Oxalic acid (OX) is a well-known platform compound, which is one of the C2 products of CO2 electro-reduction, and can be obtained by oxidation of waste biomass, so it is widely available and cheap. Therefore, the method for further converting oxalic acid into glycolic acid (GC) by catalytic reduction is considered to be a promising synthesis method at present.

[0003] The method for synthesizing glycolic acid from oxalic acid mainly includes two types: heterogeneous catalytic reduction and electrocatalytic reduction. In the reported literature, the heterogeneous catalytic reduction of oxalic acid mainly uses ruthenium-based catalysts, and is operated at 75-130℃ under a hydrogen pressure of more than 80 bar, and the selectivity of the product glycolic acid is about 70% [Green Chemistry 2023, 25 (6), 2409-2426]. However, compared with the traditional thermal catalytic hydrogenation which requires high temperature and high pressure H2, the electrocatalytic reduction of oxalic acid has the characteristics of green and sustainable, avoiding energy loss caused by high temperature and high pressure, and efficiently generating glycolic acid under mild conditions by using water as hydrogen source.

[0004] The electrocatalytic route is a good way to replace the heterogeneous catalytic process and achieve sustainable development. In recent years, most of the literature reported in the electrocatalytic reduction of oxalic acid to generate glycolic acid is focused on titanium-based materials. However, since the reaction is carried out in an acidic solution, the working electrode will face problems such as acid corrosion and competitive hydrogen evolution side reaction, which greatly hinders the reaction, and the energy efficiency and selectivity of most reactions are low. SUMMARY

[0005] The purpose of the present application is to overcome the problems of harsh reaction conditions, high energy consumption, multiple side reactions and slow reaction rate in the prior art, and to provide a method for electrocatalytic reduction of oxalic acid to prepare glycolic acid, which is simple in method, mild in conditions, green and environmentally friendly, and high in selectivity.

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

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

[0008] 1) The acid aqueous solution with a concentration of 0.05-0.5 mol / L is divided into two parts, oxalic acid is added into the electrolyte of the first part to prepare a solution with a final concentration of 0.05-0.2 mol / L as the cathode reaction solution; the electrolyte of the second part is the anode reaction solution;

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

[0010] 3) The carbon cloth electrode loaded with metal Bi is used as the cathode electrode, and the platinum sheet electrode is used as the anode electrode, and after the electrolytic cell is assembled, constant current electrolysis is performed to obtain glycolic acid.

[0011] Preferably, the acid in the acid 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 metal Bi is prepared by the following method:

[0014] 1) 1.94 g of bismuth nitrate pentahydrate and 0.2 g of polyvinylpyrrolidone K30 are added into 10 mL of ethylene glycol, and ultrasonic dissolution is performed to obtain a uniform solution;

[0015] 2) A 2x3 cm 2 rectangular piece of carbon cloth is obtained by cutting, and is immersed in the solution obtained in step 1) for 2 h, taken out, dried in an oven at 120°C for 5 h, and calcined in a tube furnace under argon protection at 500-700°C for 2 h; taken out to obtain the carbon cloth electrode loaded with metal Bi.

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

[0017] Advantages of the present application:

[0018] The present application uses the carbon cloth electrode loaded with metal Bi as a catalyst to electrocatalytically reduce oxalic acid, and has the advantages of mild reaction conditions, convenient and simple operation process, less side reactions, green environmental protection, high selectivity and high added value. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 FIG. 1 is a schematic diagram of the reaction liquid phase results of the electrocatalytic reduction of oxalic acid in the present application. DETAILED DESCRIPTION

[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 electrocatalytic reduction of oxalic acid to glycolic acid, comprising the following steps:

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

[0037] 2) Use proton exchange membrane Nafion 117 to separate the H-type electrolytic cell into a cathode chamber and an anode chamber, and add the cathode reaction liquid and the anode reaction liquid to the cathode chamber and the anode chamber, respectively; the cathode reaction liquid and the anode reaction liquid are equal in volume;

[0038] 3) Use the carbon cloth electrode loaded with metal Bi prepared in Example 1 as the cathode electrode (electrocatalyst), and use a platinum sheet electrode as the anode electrode, assemble the electrolytic cell, and after completion, perform constant current electrolysis at a temperature of 25°C and a current density of 20 mA / cm 2 , and the electrolysis time is 12 h, to obtain glycolic acid.

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

[0040] Example 5

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

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

[0043] 2) Use proton exchange membrane Nafion 117 to separate the H-type electrolytic cell into a cathode chamber and an anode chamber, and add the cathode reaction liquid and the anode reaction liquid to the cathode chamber and the anode chamber, respectively; the cathode reaction liquid and the anode reaction liquid are equal in volume;

[0044] 3) Use the carbon cloth electrode loaded with metal Bi prepared in Example 2 as the cathode electrode (electrocatalyst), and use a platinum sheet electrode as the anode electrode, assemble the electrolytic cell, and after completion, perform constant current electrolysis at a temperature of 35°C and a current density of 17 mA / cm 2 , and the electrolysis time is 10 h, to obtain glycolic acid.

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

[0046] Example 6

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

[0048] 1) An aqueous solution of sulfuric acid (or perchloric acid) with a concentration of 0.5 mol / L is prepared as an electrolyte, and divided into two parts. Oxalic acid is added to the electrolyte in the first part to prepare a solution with a final concentration of 0.2 mol / L as the cathode reaction liquid. The electrolyte in the second part is the anode reaction liquid;

[0049] 2) The H-type electrolytic cell is separated into a cathode chamber and an anode chamber by using a proton exchange membrane Nafion 115, and the cathode reaction liquid and the anode reaction liquid are added to the cathode chamber and the anode chamber, respectively. The cathode reaction liquid and the anode reaction liquid are equal in volume;

[0050] 3) The carbon cloth electrode loaded with metal Bi prepared in Example 3 is used as the cathode electrode (electrocatalyst), and a platinum sheet electrode is used as the anode electrode. After the electrolytic cell is assembled, constant current electrolysis is carried out at a temperature of 55°C and a current density of 10 mA / cm 2 , and the electrolysis time is 9h, obtaining glycolic acid.

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

Claims

1. A method for electrocatalytic reduction of oxalic acid to glycolic acid, characterized by The method comprises the following steps: 1) configuring an acid aqueous solution with a concentration of 0.05-0.5 mol / L as an electrolyte, and dividing the electrolyte into two parts, adding oxalic acid into the electrolyte in the first part to prepare a solution with a final oxalic acid concentration of 0.05-0.2 mol / L as a cathode reaction liquid; the electrolyte in the second part is an anode reaction liquid; 2) using a proton exchange membrane to separate the H-type electrolytic cell into a cathode chamber and an anode chamber, and adding the cathode reaction liquid and the anode reaction liquid into the cathode chamber and the anode chamber respectively; the cathode reaction liquid and the anode reaction liquid are equal in volume; 3) using a carbon cloth electrode loaded with metal Bi as a cathode electrode, and using a platinum sheet electrode as an anode electrode, after assembling the electrolytic cell, constant current electrolysis is performed to obtain glycolic acid.

2. The method of claim 1, wherein The acid in the acid aqueous solution is sulfuric acid or perchloric acid.

3. The method of claim 1, wherein The proton exchange membrane is Nafion 115 or Nafion 117.

4. The method of claim 1, wherein The carbon cloth electrode loaded with metal Bi is prepared by the following method: 1) adding 1.94 g of bismuth nitrate pentahydrate and 0.2 g of polyvinylpyrrolidone K30 into 10 mL of ethylene glycol, and ultrasonically dissolving to obtain a uniform solution; 2) Cutting the carbon cloth to obtain 2 x 3 cm 2 The rectangular piece was immersed in the solution obtained in step 1) for 2 h, taken out, dried in an oven at 120 °C for 5 h, and calcined in a tube furnace under argon protection at 500-700 °C for 2 h; taken out to obtain a carbon cloth electrode loaded with metal Bi.

5. The method of claim 1, wherein The temperature of the constant current electrolysis in step 3) is 25-55°C, the current density is 10-20 mA / cm 2 , and the electrolysis time is 9-12 h.

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