Method for directly preparing potassium diformate through CO2 electrolysis

Abstract

The invention relates to a method for directly preparing potassium diformate through CO2 electrolysis, which comprises the following steps: in an electrolytic bath containing a cathode chamber and an anode chamber, carrying out a reaction for preparing potassium diformate through CO2 electrolysis in the cathode chamber, and carrying out water electrolysis to prepare oxygen in the anode chamber; and a proton exchange membrane is arranged between the anode chamber and the cathode chamber of the electrolytic cell. Through the process, the potassium diformate can be prepared through CO2 one-step electrolysis and is used for a feed additive.

Description

Technical Field

[0001] The invention relates to a technology for directly preparing feed additive potassium diformate by electrochemical reduction of CO2. Technical Background

[0002] Since the Industrial Revolution, the excessive use of fossil fuels (coal, oil, natural gas, etc.) has caused the CO2 content in the atmosphere to increase year by year, which has seriously exceeded the carbon cycle limit in nature and caused a series of environmental problems, such as rising temperatures and drastic climate change.

[0003] Potassium diformate is a new type of feed additive used as a substitute for antibiotic growth promoters. Diformic acid is an organic acid salt, which is a dimer of formic acid and potassium formate linked by hydrogen bonds. It is reported that adding potassium diformate to piglet starter feed can reduce the content of anaerobic bacteria, lactobacillus, Escherichia coli and yeast in the digestive tract.

[0004] Electrochemical CO2 conversion can be carried out at room temperature and ambient pressure. Currently, due to the low conversion rate and high power consumption of chemicals above C2, more research directions are focused on the preparation of C1 products, such as CO, HCOOH, CH3OH or CH4.

[0005] For example, invention patent CN 113430547 A discloses a method for preparing potassium formate, rather than potassium diformate, by electrochemical reduction of CO2; and conventional CO2 electrolysis can only prepare formic acid, but cannot further prepare potassium diformate.

[0006] Invention patent CN111574358A discloses a method for preparing potassium diformate, which comprises preparing potassium diformate by chemical kettle reaction of formic acid and potassium formate at 70-80°C, and is a non-electrochemical synthesis method.

[0007] Most of the patents for the preparation of potassium diformate are preparation methods of mixing formic acid and potassium formate or formic acid and potassium carbonate. This method is a chemical method and cannot achieve CO2 emission reduction.

[0008] There is no patent report on the preparation of potassium diformate by CO2 electrolysis, and CO2 electrolysis can only directly prepare potassium formate, but cannot further prepare potassium diformate. Therefore, it is of great significance to develop a new CO2 electrochemical one-step preparation of potassium diformate. Summary of the invention

[0009] The purpose of the present invention is to provide a method for directly preparing potassium diformate by one step of CO2 electrolysis. Compared with the traditional chemical synthesis method, the method directly prepares potassium diformate by CO2 electrolysis, synthesizes potassium diformate in one step without using formic acid, and achieves CO2 emission reduction.

[0010] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is as follows:

[0011] A method for directly preparing potassium diformate by CO2 electrolysis. In an electrolytic cell containing a cathode chamber and an anode chamber, the cathode chamber conducts the reaction of preparing potassium diformate by CO2 electrolysis, and the anode chamber conducts the reaction of electrolyzing water to produce oxygen; a proton exchange membrane is arranged between the anode chamber and the cathode chamber of the electrolytic cell.

[0012] The cathode uses CO2 as a raw material, acidic potassium diformate as the starting reaction electrolyte, and potassium formate or potassium hydroxide as the cathode replenishing solution. CO2 in the cathode chamber is prepared into potassium diformate through one-step electroreduction. The anode uses acidic aqueous solution or pure water as the electrolyte, and the reaction of electrolyzing water to produce oxygen occurs. High-purity oxygen can be used as an oxidant. A proton exchange membrane is arranged between the cathode and the anode. Through this process, the one-step electrolysis of CO2 to produce potassium diformate can be realized and used as a feed additive.

[0013] In the present invention, the cathode chamber of the electrolytic cell uses CO2 as a raw material, acidic potassium diformate as the starting reaction electrolyte, and potassium formate or potassium hydroxide as the cathode replenishing solution, and the replenishing solution adjusts the reaction pH. The pH value of the cathode solution is controlled to be 1-5, preferably 2-4.

[0014] In the present invention, the cathode in the cathode chamber of the electrolytic cell is a gas diffusion electrode for strengthening CO2 mass transfer, and the gas diffusion electrode is an electrode prepared with carbon cloth, carbon paper or a PTFE membrane as the gas diffusion layer.

[0015] In the present invention, the catalyst of the cathode gas diffusion electrode is a catalyst stable under acidic electrolyte conditions. Preferably, the catalyst is a metal dual-atom catalyst doped with Sn and Ce with a carbon nanotube structure. The catalyst loading is 0.1-10 mg / cm 2 , preferably 1-2 mg / cm 2 .

[0016] As a preferred scheme, in the present invention, the preparation method of the metal dual-atom catalyst doped with Sn and Ce with a carbon nanotube structure is as follows: Take Sn powder, cerium acetylacetonate, pyridine, urea and single-walled carbon nanotubes and mix them in a certain proportion, and perform ball milling and mixing of the mixture in a ball mill at 200-500 rpm for 1-4 h. The ball-milled mixture is directly placed at 100-150 °C for 1-4 h. The treated mixture is centrifuged and then dried at 200-250 °C to obtain the final Sn and Ce dual-atom catalyst.

[0017] Preferably, the mass ratio of the Sn powder to acetylacetonate, pyridine, urea, and carbon nanotubes is 1:0.1-10:50-100:2-5:10-20.

[0018] As a preferred scheme, to control the hydrogen evolution side reaction under acidic electrolyte conditions in the cathode chamber of the electrolytic cell, the surface of the electrode catalyst needs to be carbonized before use.

[0019] In the present invention, the gas diffusion electrode needs to be supported by a current collector metal mesh to enhance the electrode strength and activity, and the metal mesh is a gold mesh, a silver mesh, a copper mesh or a titanium mesh.

[0020] In the present invention, the anode chamber of the electrolytic cell uses an acidic aqueous solution as the electrolyte, and an electrolytic water reaction to produce oxygen occurs. The protons generated by the reaction pass through the proton exchange membrane into the cathode, and potassium formate is generated inside the cathode. The acidic aqueous solution is preferably sulfuric acid.

[0021] In the present invention, the catalyst in the anode chamber of the electrolytic cell is iridium oxide.

[0022] In the present invention, the operating temperature of the electrolytic cell is 80 - 100 °C, and the operating pressure is 0.5 - 1 MPaG. The electrolyte can be further concentrated and crystallized to obtain solid potassium formate.

[0023] Compared with the prior art, the positive effects of the present invention are as follows:

[0024] A novel electrochemical synthesis method of potassium formate is provided. In this method, potassium formate can be prepared in one step with industrial waste gas CO2 as the raw material at the cathode, without using two chemical raw materials to prepare potassium formate. While reducing CO2 emissions, potassium formate that can be utilized is produced. Moreover, this patent proposes a novel electrochemical synthesis method, providing a feasible new synthesis method for the industrial synthesis of potassium formate. Detailed Description of the Invention

[0025] The following provides a specific and detailed description of the embodiments of the present invention. These embodiments are implemented on the premise of the technical solution of the present invention. Although it is impossible to list all cases, representative detailed implementation methods and specific operation processes are given based on experimental results. The protection scope of the present invention is not limited to the following embodiments.

[0026] Tin, 99.999% trace metals basis, Merck Chemicals, product number 204692.

[0027] Cerium(III) acetylacetonate hydrate, Merck Chemicals, product number 381403.

[0028] Pyridine, suitable for HPLC, ≥99.9%, Merck Chemicals, product number 270407.

[0029] Urea, Merck Chemicals, product number U5128.

[0030] Single-walled carbon nanotubes, amide functionalized, Merck Chemicals, product number 685380.

[0031] Raw materials for the CO2 electrolysis reaction to produce formic acid: CO2, liquid CO2 cylinder gas, Mingju Gas.

[0032] Potassium formate, BioUltra, ≥99.0% (NT), Merck Chemicals, product number 60246. Potassium diformate, purity 98%, Beijing Innochem Technology Co., Ltd., article number M161605.

[0033] Nafion 115 membrane, Shanghai Xianren.

[0034] DSA oxygen evolution anode, Shaanxi Titanium Plus.

[0035] Analysis method of potassium diformate, the actual production amount m of potassium diformate is determined by Agilent liquid chromatography analysis 实 . Or for the crystalline product, the C content is determined by combustion method, the K content is determined by flame photometry, and the actual production amount m of potassium diformate is determined by the mass of the crystalline product and the molar ratio of C and K 实 .

[0036] The theoretical production amount of potassium diformate is m 理 = j * s * t * A / nF

[0037] where j is the current density, unit A / m 2 ;

[0038] S is the electrode area, unit m 2 ;

[0039] t is the reaction time, unit h;

[0040] A is the molar mass of potassium diformate, 130 g / mol;

[0041] n is the number of electrons transferred in the reaction, 4;

[0042] F is the Faraday constant, 26.8 A·h / mol electron.

[0043] The current efficiency of potassium diformate = m 实 / m 理 * 100%

[0044] Example 1

[0045] Catalyst preparation:

[0046] Weigh 1 g of Sn powder, and weigh cerium acetylacetonate, pyridine, urea and single-walled carbon nanotubes according to the mass ratio of Sn powder to acetylacetonate, pyridine, urea, and carbon nanotubes of 1:5:50:5:12. After weighing, the materials are ball-milled and mixed in a ball mill at 500 rpm for 2 h. The ball-milled mixture is directly placed at 150 °C for 3 h. The treated mixture is centrifuged and then dried at 200 °C to obtain the final Sn and Ce dual-atom catalyst.

[0047] Electrode Preparation: Weigh 1 g of the prepared catalyst, and weigh the thickener methyl cellulose and the hydrophobic substance PTFE according to the ratio of catalyst: thickener methyl cellulose: hydrophobic substance PTFE = 1:0.3:0.1. Mix the above substances to prepare a catalyst slurry, evenly coat the slurry on the base gold mesh, and after the electrode is dried, press the gas diffusion layer PTFE onto the gold mesh under a pressure of 4 MPa. Bake the pressed electrode at 250 °C for 1 h to prepare the electrode.

[0048] Prepare a gas diffusion electrode with the catalyst, and the catalyst loading is 2 mg / cm 2 , the electrode substrate is a gold mesh, and the gas diffusion layer is a PTFE membrane.

[0049] Electrolysis Reaction:

[0050] In a three-chamber electrolytic cell, a DuPont N115 proton exchange membrane is set between the cathode and the anode. The anode is an oxygen evolution DSA electrode. The cathode electrolyte of the electrolytic cell is 3 mol / L potassium diformate with a pH of 2, and the anode is 1 mol / L H2SO4. Control the reaction temperature of the electrolytic cell at 80 °C and 1 MPaG, start the reaction, and introduce KOH into the electrolyte to adjust the electrolysis pH to 2. The current efficiency of the product potassium diformate is 65%.

[0051] Example 2

[0052] Catalyst Preparation:

[0053] Weigh 1 g of Sn powder, and weigh cerium acetylacetonate, pyridine, urea, and single-walled carbon nanotubes according to the mass ratio of Sn powder to acetylacetonated, pyridine, urea, and carbon nanotubes of 1:10:70:4:15. After weighing, perform ball milling and mixing in a ball mill at 400 rpm for 3 h. Directly put the ball-milled mixture into a treatment at 130 °C for 4 h. After centrifuging the treated mixture, perform a drying treatment at 220 °C to obtain the final Sn and Ce dual-atom catalyst.

[0054] Refer to Example 1 for electrode preparation. Prepare a gas diffusion electrode with the catalyst, and the catalyst loading is 1 mg / cm 2 , the electrode substrate is a silver mesh, and the gas diffusion layer is a carbon cloth.

[0055] Electrolysis Reaction:

[0056] In a three-chamber electrolytic cell, a DuPont N115 proton exchange membrane is set between the cathode and the anode. The anode is an oxygen evolution DSA electrode. The cathode electrolyte of the electrolytic cell is 2 mol / L potassium diformate with a pH of 4, and the anode is 1 mol / L H2SO4. Control the reaction temperature of the electrolytic cell at 85 °C and 0.5 MPaG, start the reaction, and introduce KOH into the electrolyte to adjust the electrolysis pH to 4. The current efficiency of the product potassium diformate is 62%.

[0057] Example 3

[0058] Catalyst preparation:

[0059] Weigh 1 g of Sn powder, and weigh cerium acetylacetonate, pyridine, urea, and single-walled carbon nanotubes according to the mass ratio of Sn powder to cerium acetylacetonate, pyridine, urea, and carbon nanotubes of 1:0.1:90:3:10. After weighing, the materials are ball-milled and mixed in a ball mill at 300 rpm for 1 h. The ball-milled mixture is directly placed at 100 °C for 2 h. The treated mixture is centrifuged and then dried at 240 °C to obtain the final Sn and Ce dual-atom catalyst.

[0060] The electrode preparation refers to Example 1, and the catalyst is used to prepare a gas diffusion electrode with a catalyst loading of 0.1 mg / cm 2 , the electrode substrate is a copper mesh, and the gas diffusion layer is a carbon paper.

[0061] Electrolysis reaction:

[0062] In a three-chamber electrolytic cell, a DuPont N115 proton exchange membrane is set between the cathode and the anode. The anode is an oxygen evolution DSA electrode. The cathode electrolyte of the electrolytic cell is potassium diformate with a concentration of 3 mol / L and a pH of 5, and the anode is 1 mol / L H2SO4. The reaction temperature of the electrolytic cell is controlled at 90 °C and 0.8 MPaG. The reaction is started, and formate is introduced into the electrolyte to adjust the electrolytic pH to 5, and the current efficiency of the product potassium diformate is 55%.

[0063] Catalyst preparation in Example 4:

[0064] Weigh 1 g of Sn powder, and weigh cerium acetylacetonate, pyridine, urea, and single-walled carbon nanotubes according to the mass ratio of Sn powder to cerium acetylacetonate, pyridine, urea, and carbon nanotubes of 1:1:100:2:20. After weighing, the materials are ball-milled and mixed in a ball mill at 200 rpm for 4 h. The ball-milled mixture is directly placed at 120 °C for 1 h. The treated mixture is centrifuged and then dried at 250 °C to obtain the final Sn and Ce dual-atom catalyst.

[0065] The electrode preparation refers to Example 1, and the catalyst is used to prepare a gas diffusion electrode with a catalyst loading of 10 mg / cm 2 , the electrode substrate is a titanium mesh, and the gas diffusion layer is a PTFE membrane.

[0066] Electrolysis reaction:

[0067] In a three-chamber electrolytic cell, a DuPont N115 proton exchange membrane is set between the cathode and the anode. The anode is an oxygen evolution DSA electrode. The cathode electrolyte of the electrolytic cell is potassium diformate with a concentration of 2 mol / L and a pH of 1, and the anode is 1 mol / L H2SO4. The reaction temperature of the electrolytic cell is controlled at 100 °C and 0.6 MPaG. Start the reaction, and introduce KOH into the electrolyte to adjust the electrolytic pH to 1. The current efficiency of the product potassium diformate is 58%.

Claims

1. A method for directly preparing potassium dimethylformate by CO2 electrolysis, characterized in that: In an electrolytic cell containing a cathode chamber and an anode chamber, the cathode chamber conducts the reaction of electrolyzing CO2 to produce potassium dimethylformate, and the anode chamber conducts the reaction of electrolyzing water to produce oxygen; a proton exchange membrane is arranged between the anode chamber and the cathode chamber of the electrolytic cell.

2. The method according to claim 1, wherein The cathode chamber of the electrolytic cell uses CO2 as a raw material, acidic potassium dimethylformate as the starting reaction electrolyte, and potassium formate or potassium hydroxide as the cathode replenishing solution, and the replenishing solution adjusts the reaction pH.

3. The method according to claim 2, wherein The pH of the cathode solution is adjusted by the cathode replenishing solution, and the pH value of the cathode solution is controlled to be 1-5, preferably 2-4.

4. The method according to any one of claims 1 to 3, characterized in that The cathode in the cathode chamber of the electrolytic cell is a gas diffusion electrode for enhancing CO2 mass transfer, and the gas diffusion electrode is an electrode prepared with a carbon cloth, a carbon paper or a PTFE membrane as the gas diffusion layer.

5. The method according to claim 4, characterized in that, The catalyst loaded on the cathode gas diffusion electrode is a metal diatomic catalyst doped with Sn and Ce in a carbon nanotube structure, and / or the catalyst loading is 0.1-10 mg / cm 2 , preferably 1-2 mg / cm 2 .

6. The method according to claim 5, wherein The catalyst loaded on the cathode gas diffusion electrode needs to be carbonized before use.

7. The method according to any one of claims 4 to 6, characterized in that The gas diffusion electrode needs to be supported by a current collector metal mesh, and the metal mesh is a gold mesh, a silver mesh, a copper mesh or a titanium mesh.

8. The method according to any one of claims 1-7, characterized in that, The anode chamber of the electrolytic cell uses an acidic aqueous solution as the electrolyte, conducts the reaction of electrolyzing water to produce oxygen, and the generated protons enter the cathode through the proton exchange membrane and potassium dimethylformate is generated in the cathode.

9. The method according to any one of claims 1-8, characterized in that, The catalyst in the anode chamber of the electrolytic cell is iridium oxide.

10. The method according to any one of claims 1-9, characterized in that, The operating temperature of the electrolytic cell is 80-100 °C, and the operating pressure is 0.5-1 MPa G.