Low-cost electrolytic reduction method taking hydrogen oxidation reaction as anodic reaction

Abstract

The invention discloses a low-cost electrolytic reduction method taking hydrogen oxidation reaction as anodic reaction, which adopts a diaphragm electrolytic cell, takes an aqueous solution containing inorganic acid as anolyte, takes a solution containing organic matters or metal ions as catholyte, and takes the hydrogen oxidation reaction as the anodic reaction. Carrying out electrolytic reduction by taking reduction reaction of organic matters or metal ions as cathode reaction; and a solvent of the cathode liquid is water or water and an organic solvent. According to the method, an iridium oxide anode and a lead anode are not used, so that the cost is greatly reduced; according to the method disclosed by the invention, the electrolysis voltage can be reduced to about 1.6 V (compared with an iridium oxide anode); according to the method, the product yield can be increased by 6-10%; the method provided by the invention can avoid anode failure (compared with a diaphragm-free method or a diaphragm method without pressure difference control).

Description

(1) Technical Field

[0001] The present invention relates to a low-cost electrolytic reduction method with a hydrogen oxidation reaction as the anodic reaction, belonging to the field of electrolytic synthesis. It is an electrolytic reduction method in which the hydrogen oxidation reaction on a membrane electrode or other diffusion electrodes serves as the anodic reaction, and the reduction reaction of an organic substance or metal ions on an electronic conductor serves as the cathodic reaction. (2) Background Art

[0002] Electrolytic reduction methods are widely used in fields such as organic synthesis, inorganic synthesis, and the preparation of electronic industrial products. For example, electrolytic reduction methods are used in the synthesis and preparation of p-aminophenol, glyoxylic acid, succinic acid, vanadium electrolyte, copper foil, etc. These electrolytic reduction methods in these fields have a common feature: their anodic reactions are all oxygen evolution reactions on lead electrodes or iridium oxide electrodes.

[0003] The lead electrode will be gradually consumed during the oxygen evolution process, which not only results in a short service life of the lead electrode (3 - 12 months), but also generates a large amount of highly polluting lead mud. In addition, the overpotential of the oxygen evolution reaction on the lead electrode is very high, resulting in relatively high electrolysis energy consumption. Therefore, iridium oxide electrodes have been gradually replacing lead electrodes in the past few decades. The service life of an iridium oxide electrode (usually a titanium-plated iridium oxide electrode) is basically proportional to the iridium content on the electrode. An iridium oxide electrode with an iridium content of 10 g / m² has a service life of about 2 years at a current density of 1000 A / m 2 ². Therefore, the loss of the iridium oxide electrode is one of the main costs of the electrolytic reduction industry using this electrode. At the beginning of 2021, the price of metallic iridium increased from 400 yuan / g to 1500 yuan / g and has remained at a high level since then. This has brought great cost pressure to enterprises using iridium oxide electrodes.

[0004] Therefore, there is an urgent need to develop an electrolytic reduction method that does not use the oxygen evolution reaction on lead electrodes or iridium oxide electrodes to replace the existing methods. (3) Summary of the Invention

[0005] The object of the present invention is to provide a low-cost electrolytic reduction method with a hydrogen oxidation reaction as the anodic reaction. This electrolytic reduction method can not only avoid the use of lead electrodes and iridium oxide anodes, greatly reduce the electrolysis voltage, but also improve the product yield.

[0006] The technical solution adopted by the present invention is:

[0007] The present invention provides a low-cost electrolytic reduction method with a hydrogen oxidation reaction as the anodic reaction. The method uses a diaphragm electrolytic cell (such as Figure 1As shown in the figure, an aqueous solution containing an inorganic acid is used as the anolyte (placed in the anodic chamber), a solution containing an organic substance or metal ions is used as the catholyte (placed in the cathodic chamber), the oxidation reaction of hydrogen is used as the anodic reaction, and the reduction reaction of the organic substance or metal ions is used for electrolytic reduction; the solvent of the catholyte is water or water + organic solvent.

[0008] Furthermore, the catholyte further includes one or more of an inorganic acid, an emulsifier, an electrolyte, or an organic acid. The emulsifier includes N,N-dimethyldodecylamine-N-oxide (DDAO); the electrolyte includes lithium acetate and tetrabutylammonium perchlorate; the organic acid includes acetic acid; the concentration of the emulsifier in the catholyte is 1-5 mmol / L; the concentration of the electrolyte in the catholyte is 0.1-0.2 mol / L; the volume concentration of the organic acid is 10%; the concentration of the inorganic acid is 1-3 mol / L.

[0009] Furthermore, the catholyte is one of the following: an aqueous solution containing an organic substance, an aqueous solution containing an inorganic acid, an organic substance, and an emulsifier, an aqueous solution containing an organic substance and an inorganic acid, an organic solution containing an organic substance, an organic acid, an electrolyte, and water, an organic solution containing an organic substance, water, and an electrolyte, and an aqueous solution containing a metal ion and an inorganic acid.

[0010] Furthermore, the pressure on the anolyte side (anodic chamber) of the diaphragm in the diaphragm electrolytic cell is greater than or equal to the pressure on the catholyte side (cathodic chamber) of the diaphragm. The pressure on the anolyte side is 1-3 atm, and the pressure difference between the anolyte side and the catholyte side is 0-2 atm, preferably 0.01-1 atm.

[0011] Furthermore, the inorganic acid in the catholyte or anolyte is one of sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, and nitric acid; the concentration of the inorganic acid in the anolyte is 0.1-4 mol / L.

[0012] Furthermore, the organic solvent is methanol, ethanol, acetonitrile, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), tetrahydrofuran, acetone, or dioxane; the organic substance is an organic substance containing a nitro group, a carboxyl group, a carbon-carbon double bond, a carbon-halogen bond, a nitroso group, a carbonyl group, a carboxylic acid ester, an amide, or a nitrile group (preferably nitrobenzene, oxalic acid, maleic acid, 2-chloro-5-trichloromethylpyridine, 4-bromobenzonitrile), the concentration of the organic substance in the catholyte is 0.20-2 mol / L; the metal ion is a vanadium ion, a copper ion, a zinc ion, a nickel ion, or a chromium ion (preferably vanadyl sulfate, copper sulfate, zinc sulfate), and the concentration of the metal ion in the catholyte is 0.5-3 mol / L.

[0013] Furthermore, the anodic reaction occurs on a gas diffusion electrode or a membrane electrode.

[0014] Further, the gas diffusion electrode is composed of a gas diffusion layer and a catalytic layer. The gas diffusion layer is a porous carbon material or metal material. The carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam. The metal material is titanium or silver. The catalytic layer is composed of a platinum-carbon catalyst and a binder. The binder is polytetrafluoroethylene resin or Nafion resin or a mixture of both. To improve the utilization rate of the platinum-carbon catalyst, a leveling layer can also be added between the gas diffusion layer and the catalytic layer. The leveling layer is composed of a carbon material and a binder. The Pt loading on the gas diffusion electrode is 0.1-1 mg / cm 2 .

[0015] Further, the membrane electrode is composed of a gas diffusion layer, a catalytic layer and a cation exchange membrane. The catalytic layer is located between the gas diffusion layer and the cation exchange membrane. The gas diffusion layer is a porous carbon material or metal material. The carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam. The metal material is titanium or silver. The catalytic layer is composed of a platinum-carbon catalyst and a binder. The binder is polytetrafluoroethylene resin or Nafion resin or a mixture of both. The cation exchange membrane is a sulfonic acid type cation exchange membrane. To improve the utilization rate of the platinum-carbon catalyst, a leveling layer can also be added between the gas diffusion layer and the catalytic layer. The leveling layer is composed of a carbon material and a binder. The Pt loading on the membrane electrode is 0.1-1 mg / cm 2 .

[0016] Further, the diaphragm used in the diaphragm electrolytic cell is a cation exchange membrane or a microporous membrane, preferably a Nafion-324 membrane or a PVDF microporous membrane. The diaphragm electrolytic cell is divided into a gas chamber, an anode chamber and a cathode chamber in sequence by an anode and a diaphragm. The gas chamber is used to introduce hydrogen. An anode is arranged between the gas chamber and the anode chamber. A diaphragm is arranged between the anode chamber and the cathode chamber. A cathode is arranged inside the cathode chamber. The cathode is made of Monel alloy, lead sheet, titanium sheet, copper mesh, silver mesh, graphite felt, copper sheet or aluminum sheet.

[0017] Further, in the electrolytic reduction method, an aqueous solution containing 0.1-4 mol / L inorganic acid is used as the anolyte, and an aqueous solution or a mixed solution of water + organic solvent containing metal ions or organic substances and / or emulsifiers and / or electrolytes and / or organic acids and / or inorganic acids is used as the catholyte. A gas diffusion electrode or a membrane electrode with a Pt or Pd loading of 0.1-1 mg / cm 2 is used as the anode, and Monel alloy, lead sheet, titanium sheet, copper mesh, silver mesh, graphite felt, copper sheet or aluminum sheet is used as the cathode. The anodic reaction is the oxidation reaction of hydrogen, and the cathodic reaction is the reduction reaction of organic substances or metal ions. The current density of the anode is 5-38.2 A / dm 2 , and the cathodic current density is 3.3-20 A / dm 2 ; The electrolysis temperature range is 0-100 °C.

[0018] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in: (1) The method of the present invention does not use iridium oxide anodes and lead anodes, greatly reducing the cost; (2) The method of the present invention can reduce the electrolysis voltage by about 1.6 V (compared with iridium oxide anodes); (3) The method of the present invention can increase the product yield by 6-10%; (4) The method of the present invention can avoid the failure of the anode (gas diffusion electrode or membrane electrode) (compared with the diaphragm-free method or the diaphragm method without controlling the pressure difference). (IV) BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of a diaphragm electrolytic cell with a hydrogen oxidation reaction as the anodic reaction.

[0020] Figure 2 Electrolytic reduction device diagram with a hydrogen oxidation reaction as the anodic reaction. (V) SPECIFIC EMBODIMENTS

[0021] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0022] Unless otherwise specified, the aqueous solutions of all experiments are prepared with deionized water; the pressures (atmospheric pressures) in the anode and cathode chambers are 1 atmosphere (1 atm).

[0023] In the following examples and comparative examples, the gas diffusion electrode (Pt loading is 0.1-1 mg / cm 2 ), the membrane electrode (Pt loading is 0.1-1 mg / cm 2 ), the titanium-coated iridium oxide electrode (iridium content is 1 mg / cm 2 ), and the lead electrode (lead content 99.9%) are all purchased from Hangzhou Sai'ao Electrochemical Instrument Co., Ltd.

[0024] The membrane electrode is composed of a gas diffusion layer, a catalytic layer, and a cation exchange membrane, and the catalytic layer is located between the gas diffusion layer and the cation exchange membrane. Among them, the carbon cloth is the gas diffusion layer, the catalytic layer is composed of a platinum-carbon catalyst and Nafion resin, and the cation exchange membrane is a Nafion-117 membrane.

[0025] The gas diffusion electrode is composed of a gas diffusion layer and a catalytic layer. Among them, the carbon paper is the gas diffusion layer, and the catalytic layer is composed of a platinum-carbon catalyst, Nafion resin, and polytetrafluoroethylene resin.

[0026] Example 1, Gas Diffusion Electrode - Diaphragm Electrolysis - Nitrobenzene

[0027] Using Figure 2The diaphragm electrolytic cell with the structure shown in A. The diaphragm electrolytic cell is successively divided into a gas chamber, an anode chamber, and a cathode chamber by an anode and a separator. An anode is arranged between the gas chamber and the anode chamber, a diaphragm is arranged between the anode chamber and the cathode chamber, and a cathode is arranged in the cathode chamber. Using a gas diffusion electrode as the anode (area: 3.14 cm 2 , Pt loading is 0.5 mg / cm 2 ), a Monel 400 alloy as the cathode (area: 6 cm 2 ), using a Nafion-324 membrane as the diaphragm, and the gas chamber is used to introduce hydrogen.

[0028] Using an aqueous solution containing 2 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N-dimethyldodecylamine-N-oxide (DDAO) as the catholyte (70 mL); the flow rate of hydrogen is controlled at 20 mL / min. The anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperature of the catholyte and anolyte is controlled at 80 °C, and an electrolysis is carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm 2 ). After 14 hours of electrolysis, the electrolysis is stopped. The yield of p-aminophenol in the catholyte is 84.8%, and the average voltage is 3.8 V (the initial voltage is 3.5 V, and the voltage at the end of electrolysis is 4.2 V).

[0029] Example 2 - 5, Electrolytic Synthesis of p-Nitrophenol under Different Anolyte Pressures

[0030] Using the method of Example 1, an electrolysis reaction is carried out under different anolyte pressures, and other operations are the same as in Example 1. The experimental conditions and results are shown in Table 1.

[0031] Table 1 Results of Electrolytic Synthesis of p-Nitrophenol under Different Anolyte Pressures a

[0032] Example Anode hydraulic pressure Average voltage Initial voltage Final voltage Product yield 2 1.0 atm 3.8+0.5V 3.5V 4.2+1V 84.4％ 3 1.1 atm 3.7V 3.5V 4.1V 83.9％ 4 2.0 atm 3.7V 3.5V 4.1V 84.5％ 5 3.0 atm 3.7V 3.5V 4.1V 84.9％

[0033] Remarks: a Other conditions not specified are the same as in Example 1.

[0034] Examples 6 - 15, Effects of Catalyst Loading, Electrolyte Composition, Current Density, Temperature, etc. on the Electroreduction of Nitrobenzene

[0035] Using the method of Example 1, an electrolysis reaction is carried out under different catalyst loadings, electrolyte compositions, current densities, and temperatures. The experimental conditions and results are shown in Table 2.

[0036] Table 2 Effects of Catalyst Type, Electrolyte Composition, Current Density, Temperature, etc. on Electroreductiona

[0037]

[0038] Remarks: a Other unspecified conditions are the same as those in Example 1; S indicates that this condition is the same as that in Example 1.

[0039] Example 16, Membrane Electrode - Diaphragm Electrolysis - Nitrobenzene

[0040] Use the diaphragm electrolytic cell with the structure shown as A in Example 1 Figure 2 As the anolyte (80 mL), an aqueous solution containing 2 mol / L sulfuric acid is used, and as the catholyte (70 mL), an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N - dimethyldodecylamine - N - oxide is used; use the membrane electrode as the anode (area: 3.14 cm 2 , Pt loading is 0.5 mg / cm 2 ), and Monel 400 alloy is used as the cathode (area: 6 cm 2 ), and Nafion - 324 membrane is used as the diaphragm. The flow rate of hydrogen is controlled at 20 mL / min. The anolyte pressure is 1.1 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 80 °C, and electrolysis is carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm 2 ). After electrolysis for 14 hours, electrolysis is stopped. The yield of p - aminophenol in the catholyte is 84.1%, and the average voltage is 4.1 V (the initial voltage is 3.8 V, and the voltage at the end of electrolysis is 4.4 V).

[0041] Example 17, Gas Diffusion Anode - Diaphragm Electrolysis - Oxalic Acid

[0042] Use Figure 2 the diaphragm electrolytic cell with the structure shown as A in

[0043] which is separated into a gas chamber, an anodic chamber, and a cathodic chamber by the anode and the diaphragm in sequence. An anode is arranged between the gas chamber and the anodic chamber, a diaphragm is arranged between the anodic chamber and the cathodic chamber, and a cathode is arranged in the cathodic chamber. The gas chamber is used for introducing hydrogen. 2 , Pt loading is 0.5 mg / cm 2 ), and a lead sheet is used as the cathode (area: 6 cm 2) Using a Nafion-324 membrane as the diaphragm. During the electrolysis process, the flow rate of hydrogen gas was controlled at 20 mL / min; the pressure of the anode liquid was 1.01 atm, and the pressure of the cathode liquid was 1 atm. The temperatures of the cathode liquid and the anode liquid were controlled at 10 °C, and an electrolysis was carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm 2 ). After 8 hours of electrolysis, the electrolysis was stopped. The yield of glyoxylic acid in the cathode liquid was 90.1%, the average voltage was 6.0 V, the initial voltage was 5.8 V, and the voltage at the end of electrolysis was 6.3 V.

[0044] Example 18 - 21, Electrolytic Synthesis of Glyoxylic Acid under Different Anode Liquid Pressures

[0045] Using the method of Example 17, the pressure of the anode liquid was changed while other operations remained the same. The experimental conditions and results are shown in Table 3.

[0046] Table 3 Results of Electrolytic Synthesis of Glyoxylic Acid under Different Anode Liquid Pressures a

[0047] Example Anode hydraulic pressure Average voltage Initial voltage Final voltage Glyoxylic acid yield 18 1.0 atm 6.0V+0.6 5.8V 6.3+1.2V 90.2％ 19 1.1 atm 6.1V 5.9V 6.4V 90.5％ 20 2.0 atm 6.0V 5.8V 6.3V 90.4％ 21 3.0 atm 6.0V 5.8V 6.3V 90.2％

[0048] a Other unspecified conditions were the same as those in Example 17.

[0049] Examples 22 - 30, Effects of Catalyst Type and Loading, Electrolyte Composition, Current Density, Temperature, etc. on the Electrochemical Reduction of Oxalic Acid

[0050] Using the method of Example 17, electrolysis reactions were carried out under different catalyst types and loadings, electrolyte compositions, currents, and temperatures while other operations remained the same. The experimental conditions and results are shown in Table 4.

[0051] Table 4 Effects of Catalyst Type, Electrolyte Composition, Current Density, Temperature, etc. on Electrochemical Reduction a

[0052]

[0053]

[0054] Remarks: a Other unspecified conditions were the same as those in Example 17; S indicates that this condition was the same as that in Example 17.

[0055] Example 31, Membrane Electrode - Diaphragm Electrolysis - Oxalic Acid

[0056] Using Figure 2The diaphragm electrolytic cell with the structure shown in A uses an aqueous solution containing 0.5 mol / L sulfuric acid as the anolyte (80 mL) and an aqueous solution containing 0.68 mol / L oxalic acid as the catholyte (60 mL); the membrane electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.5 mg / cm 2 ), the lead sheet is the cathode (area: 6 cm 2 ), and the Nafion-324 membrane is used as the diaphragm. During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 10 °C, and an electrolysis is carried out by applying a current of 300 mA (the cathode current density is: 5 A / dm 2 , and the anode current density is: 9.6 A / dm 2 ). After 8 hours of electrolysis, the electrolysis is stopped. The yield of glyoxylic acid in the catholyte is 90.6%, the average voltage is 6.0 + 0.5 V, the initial voltage is 5.8 + 0.5 V, and the voltage at the end of electrolysis is 6.3 + 0.5 V.

[0057] Example 32. Gas Diffusion Electrode - Diaphragm Electrolysis - Maleic Acid

[0058] Use the diaphragm electrolytic cell with the structure shown in A in Example 1 Figure 2 (the same as Example 1), use an aqueous solution containing 0.5 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L maleic acid + 0.5 mol / L sulfuric acid as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.3 mg / cm 2 ), the titanium sheet is the cathode (area: 6 cm 2 ), and the Nafion-324 membrane is used as the diaphragm. During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 50 °C, and an electrolysis is carried out by applying a current of 600 mA (the cathode current density is: 10 A / dm 2 , and the anode current density is: 19.1 A / dm 2 ). After 12 hours of electrolysis, the electrolysis is stopped. The yield of succinic acid in the catholyte is 94.5%, and the average voltage is 4.2 V (the initial voltage is 3.9 V, and the voltage at the end of electrolysis is 4.6 V).

[0059] Example 33. Gas Diffusion Electrode - Diaphragm Electrolysis - 2-Chloro-5-(trichloromethyl)pyridine - Methanol as Organic Solvent - Hydrochloric Acid Aqueous Solution as Anolyte

[0060] Use Figure 2The diaphragm electrolytic cell with the structure shown in A uses an aqueous solution containing 0.1 mol / L hydrochloric acid as the anolyte (80 mL), and a methanol solution containing 10% (volume fraction) acetic acid + 5% (volume fraction) water + 0.2 mol / L lithium acetate + 0.2 mol / L 2-chloro-5-trichloromethylpyridine as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.5 mg / cm 2 ), the copper mesh is the cathode (area: 6 cm 2 ), and the Nafion-324 membrane is used as the diaphragm. During the electrolysis process, the hydrogen flow rate is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 30 °C, and a current of 200 mA is applied for electrolysis (the cathode current density is: 3.3 A / dm 2 , and the anode current density is: 6.4 A / dm 2 .). After 7 hours of electrolysis, the electrolysis is stopped. The yield of 2-chloro-5-chloromethylpyridine in the catholyte is 81.3%, and the average voltage is 7.3 V (the initial voltage is 7.1 V, and the voltage at the end of electrolysis is 7.4 V).

[0061] Example 34. Gas Diffusion Electrode - Diaphragm Electrolysis - 2-Chloro-5-Trichloromethylpyridine - Ethanol as Organic Solvent - Hydrochloric Acid Aqueous Solution as Anolyte

[0062] Use Figure 2 the diaphragm electrolytic cell with the structure shown in A uses an aqueous solution containing 0.1 mol / L hydrochloric acid as the anolyte (80 mL), and an ethanol solution containing 10% (volume fraction) acetic acid + 5% (volume fraction) water + 0.2 mol / L lithium acetate + 0.2 mol / L 2-chloro-5-trichloromethylpyridine as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.5 mg / cm 2 ), the copper mesh is the cathode (area: 6 cm 2 ), and the Nafion-324 membrane is used as the diaphragm. During the electrolysis process, the hydrogen flow rate is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 30 °C, and a current of 200 mA is applied for electrolysis (the cathode current density is: 3.3 A / dm 2 , and the anode current density is: 6.4 A / dm 2 .). After 7 hours of electrolysis, the electrolysis is stopped. The yield of 2-chloro-5-chloromethylpyridine in the catholyte is 75.5%, and the average voltage is 7.5 V (the initial voltage is 7.3 V, and the voltage at the end of electrolysis is 7.6 V).

[0063] Example 35: Gas Diffusion Electrode - Diaphragm Electrolysis - 4 - Bromobenzonitrile - Acetonitrile as Organic Solvent - Aqueous Perchloric Acid Solution as Anolyte

[0064] Use Figure 2 the diaphragm electrolytic cell with the structure shown as A in 2 , with an aqueous solution containing 2 mol / L perchloric acid as the anolyte (80 mL), and an acetonitrile solution containing 0.1 mol / L tetrabutylammonium perchlorate + 10% (volume fraction) water + 0.2 mol / L 4 - bromobenzonitrile as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , Pt loading is 0.5 mg / cm 2 ), the silver mesh is the cathode (area: 6 cm 2 ), and the Nafion - 324 membrane is used as the diaphragm. During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 30 °C, and a current of 200 mA is applied for electrolysis (cathode current density: 3.3 A / dm 2 ), anode current density: 6.4 A / dm

[0065] Example 36: Gas Diffusion Electrode - Diaphragm Electrolysis - 4 - Bromobenzonitrile - DMF as Organic Solvent - Aqueous Perchloric Acid Solution as Anolyte

[0066] Use Figure 2 the diaphragm electrolytic cell with the structure shown as A in 2 , with an aqueous solution containing 2 mol / L perchloric acid as the anolyte (80 mL), and a DMF solution containing 0.1 mol / L tetrabutylammonium perchlorate + 10% (volume fraction) water + 0.2 mol / L 4 - bromobenzonitrile as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , Pt loading is 0.5 mg / cm 2 ), the silver mesh is the cathode (area: 6 cm 2 , cathode current density: 3.3 A / dm 2). After electrolysis for 3.5 hours, the electrolysis was stopped. The yield of benzonitrile in the catholyte was 99.3%, and the average voltage was 7.5 V (the initial voltage was 7.6 V, and the voltage at the end of electrolysis was 7.3 V).

[0067] Example 37: Gas diffusion electrode - diaphragm electrolysis - preparation of electrolyte containing trivalent vanadium

[0068] Use Figure 2 the diaphragm electrolytic cell with the structure shown as A in []. Use an aqueous solution containing 4 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L sulfuric acid + 2 mol / L vanadyl sulfate (tetravalent vanadium) as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , Pt loading is 0.3 mg / cm 2 ), and the graphite felt is the cathode (thickness: 3 mm, area: 6 cm 2 ), and use the Nafion-324 membrane as the diaphragm. During electrolysis, the flow rate of hydrogen is controlled at 20 mL / min; the pressure of the anolyte is 1.01 atm, and the pressure of the catholyte is 1 atm. The temperatures of the catholyte and anolyte are controlled at 40 °C, and an electrolysis is carried out by applying a current of 1200 mA (cathode current density: 20 A / dm 2 , anode current density: 38.2 A / dm 2 ). After electrolysis for 3 hours and 15 minutes, the electrolysis was stopped. The current efficiency was 82.3%, the conversion rate of vanadyl sulfate (tetravalent vanadium) in the catholyte was 99.8%, the yield of vanadium sulfate (trivalent vanadium) was 99.7%, and the average voltage was 4.1 V (the initial voltage was 3.7 V, and the voltage at the end of electrolysis was 4.3 V).

[0069] Example 38: Gas diffusion electrode - diaphragm electrolysis - copper deposition

[0070] Use Figure 2 the diaphragm electrolytic cell with the structure shown as A in []. Use an aqueous solution containing 1 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 1 mol / L sulfuric acid + 0.5 mol / L copper sulfate as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , Pt loading is 0.3 mg / cm 2 ), and the copper sheet is the cathode (thickness: 1 mm, area: 6 cm 2 ), and use the Nafion-324 membrane as the diaphragm. During electrolysis, the flow rate of hydrogen is controlled at 20 mL / min; the pressure of the anolyte is 1.01 atm, and the pressure of the catholyte is 1 atm. The temperatures of the catholyte and anolyte are controlled at 40 °C, and an electrolysis is carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm2 ) After electrolysis for 0.5 hours, the electrolysis was stopped. The current efficiency of metal copper deposition was 96.3%, and the average voltage was 4.3 V (the initial voltage was 4.0 V, and the voltage at the end of electrolysis was 4.6 V).

[0071] Example 39: Gas diffusion electrode - diaphragm electrolysis - zinc deposition

[0072] Adopt Figure 2 The diaphragm electrolytic cell with the structure shown in A in [reference]. Use an aqueous solution containing 1 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 0.1 mol / L sulfuric acid + 3 mol / L zinc sulfate as the catholyte (60 mL); the gas diffusion electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.3 mg / cm 2 ), the aluminum sheet is the cathode (thickness: 1 mm, area: 6 cm 2 ), and the Nafion-324 membrane is used as the diaphragm. During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min; the anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 40 °C, and an electrolysis is carried out by applying a current of 600 mA (the cathode current density is: 10 A / dm 2 , and the anode current density is: 19.1 A / dm 2 ). After electrolysis for 3 hours, the electrolysis was stopped. The current efficiency of metal copper deposition was 78.9%, and the average voltage was 6.2 V (the initial voltage was 5.9 V, and the voltage at the end of electrolysis was 6.3 V).

[0073] Comparative Example 1: Iridium oxide anode - diaphragm electrolysis - nitrobenzene

[0074] Adopt the diaphragm electrolytic cell with the structure shown in A in Example 1 Figure 2 . Use an aqueous solution containing 2 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N-dimethyldodecylamine-N-oxide as the catholyte (70 mL); use a titanium-plated iridium oxide electrode as the anode (area: 3.14 cm 2 ), a Monel 400 alloy as the cathode (area: 6 cm 2 ), and the Nafion-324 membrane as the diaphragm. The flow rate of hydrogen is controlled at 0 mL / min. The anolyte pressure is 1.01 atm, and the catholyte pressure is 1 atm. The temperatures of the catholyte and anolyte are controlled at 80 °C, and an electrolysis is carried out by applying a current of 300 mA (the cathode current density is: 5 A / dm 2 , and the anode current density is: 9.6 A / dm 2) Electrolysis was stopped after 14 hours. The yield of p-aminophenol in the catholyte was 74.6%, and the average voltage was 3.8 + 1.6 V (the initial voltage was 3.5 + 1.6 V, and the voltage at the end of electrolysis was 4.2 + 1.6 V).

[0075] In Comparative Example 1, the average voltage increased by 1.6 V, the amount of precious metal used increased to twice the original amount, and the price increased to about eight times the original; the yield of p-aminophenol decreased by about 10%.

[0076] Comparative Example 2: Lead anode - diaphragm electrolysis - nitrobenzene

[0077] Using the diaphragm electrolytic cell with the structure shown in A of Example 1 Figure 2 with an aqueous solution containing 2 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N-dimethyldodecylamine-N-oxide as the catholyte (70 mL); using a lead electrode as the anode (area: 3.14 cm 2 , thickness: 2 mm), a Monel 400 alloy as the cathode (area: 6 cm 2 ), and a Nafion-324 membrane as the diaphragm. The flow rate of hydrogen was controlled at 0 mL / min. The anolyte pressure was 1.01 atm, and the catholyte pressure was 1 atm. The temperatures of the catholyte and anolyte were controlled at 80 °C, and electrolysis was carried out by applying a current of 300 mA (the cathode current density was: 5 A / dm 2 , and the anode current density was: 9.6 A / dm 2 ). Electrolysis was stopped after 14 hours. The yield of p-aminophenol in the catholyte was 73.7%, and the average voltage was 3.8 + 2.3 V (the initial voltage was 3.5 + 2.3 V, and the voltage at the end of electrolysis was 4.2 + 2.3 V); the thickness of the lead electrode decreased to about 1.5 mm.

[0078] In Comparative Example 1, the average voltage increased by 2.3 V, and a lot of lead sludge was produced; the yield of p-aminophenol decreased by about 10%.

[0079] Comparative Example 3: Gas diffusion electrode - diaphragm electrolysis - 0.9 atm - nitrobenzene

[0080] Using the diaphragm electrolytic cell with the structure shown in A of Example 1 Figure 2 with an aqueous solution containing 2 mol / L sulfuric acid as the anolyte (80 mL), and an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N-dimethyldodecylamine-N-oxide as the catholyte (70 mL); using a gas diffusion electrode as the anode (area: 3.14 cm 2 , Pt loading was 0.5 mg / cm 2), Monel 400 alloy as the cathode (area: 6 cm 2 ), with a Nafion-324 membrane as the diaphragm. The flow rate of hydrogen is controlled at 20 mL / min. The anode hydraulic pressure is 0.9 atm, and the cathode hydraulic pressure is 1 atm. The temperatures of the cathode solution and the anode solution are controlled at 80 °C, and electrolysis is carried out with a current of 300 mA applied (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm 2 ). After 2 hours of electrolysis, the voltage rises from the initial 3.5 V to 11.5 V, and electrolysis is stopped.

[0081] Compared with Example 1, the electrolysis voltage rises rapidly during electrolysis.

[0082] Comparative Example 4: Gas diffusion electrode - diaphragmless electrolysis - nitrobenzene

[0083] Using Figure 2 the diaphragmless electrolytic cell with the structure shown in B in

[0084] , the diaphragmless electrolytic cell is separated into a gas chamber and an electrolysis chamber by the anode, a cathode is arranged in the electrolysis chamber, and the gas chamber is used for introducing hydrogen. 2 Taking an aqueous solution containing 2 mol / L sulfuric acid + 0.5 mol / L nitrobenzene + 5 mmol / L N,N-dimethyldodecylamine-N-oxide as the electrolyte (70 mL); using a gas diffusion electrode as the anode (area: 3.14 cm 2 , Pt loading is 0.5 mg / cm 2 ), Monel 400 alloy as the cathode (area: 6 cm 2 , anode current density: 9.6 A / dm 2 ). After 1 hour of electrolysis, the voltage rises from the initial 3.5 V to 10.5 V, and electrolysis is stopped.

[0085] Compared with Example 1, the electrolysis voltage rises rapidly during electrolysis.

[0086] Comparative Example 5: Membrane electrode - diaphragmless electrolysis - nitrobenzene

[0087] Using Figure 2 the diaphragmless electrolytic cell with the structure shown in B in 2 , Pt loading is 0.5 mg / cm 2), the Monel 400 alloy serves as the cathode (area: 6 cm 2 ). The flow rate of hydrogen is controlled at 20 mL / min. The temperature of the electrolyte is controlled at 80 °C, and an electrolysis is carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm 2 ). After 3 hours of electrolysis, the voltage rises from the initial 3.8 V to 11.6 V, and the electrolysis is stopped.

[0088] Comparing with Example 16, the electrolysis voltage rises rapidly during the electrolysis process.

[0089] Comparative Examples 6 - 8

[0090] According to the conditions in Table 5, using the method of Example 17, changing the anode hydraulic pressure to 0.9 atm as Comparative Example 6, the average voltage rises by 3 V. Changing the anode to a titanium-plated iridium oxide electrode, the product yield decreases by about 6%, and the average voltage rises by 1.6 V, the precious metal consumption rises to 2 times the original, and the price rises to about 8 times the original. Changing the anode to a lead electrode, the product yield decreases by about 6%, and the average voltage rises by 2.3 V.

[0091] Table 5 Electrolytic synthesis results of glyoxylic acid under different anode hydraulic pressures and different anodes a

[0092]

[0093] a S indicates the same as Example 17, and other conditions not specified are also the same as Example 17, / represents no hydrogen is introduced.

[0094] Comparative Example 9, gas diffusion electrode - diaphragmless electrolysis - oxalic acid

[0095] Adopt Figure 2 the diaphragmless electrolytic cell with the structure shown in B in

[0096] In the diaphragmless electrolytic cell, the anode divides it into a gas chamber and an electrolytic chamber. An anode is arranged between the gas chamber and the electrolytic chamber, a cathode is arranged in the electrolytic chamber, and the gas chamber is used for introducing hydrogen.

[0096] Using an aqueous solution containing 0.68 mol / L oxalic acid as the electrolyte (60 mL); the gas diffusion electrode serves as the anode (area: 3.14 cm 2 , Pt loading is 0.3 mg / cm 2 ), and a lead sheet serves as the cathode (area: 6 cm 2 ). During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min. The temperature of the electrolyte is controlled at 10 °C, and an electrolysis is carried out by applying a current of 300 mA (cathode current density: 5 A / dm 2 , anode current density: 9.6 A / dm2 .) After electrolysis for 2 hours, the voltage increased from 5.1 V to 9.9 V, and the electrolysis was stopped.

[0097] Compared with Example 17, the electrolysis voltage increased rapidly during the electrolysis process.

[0098] Comparative Example 10, Membrane Electrode - Diaphragmless Electrolysis - Oxalic Acid

[0099] Adopt Figure 2 a diaphragmless electrolytic cell with the structure shown in B in [reference], and use an aqueous solution containing 0.68 mol / L oxalic acid as the electrolyte (60 mL); the membrane electrode is the anode (area: 3.14 cm 2 , the Pt loading is 0.5 mg / cm 2 ), and the lead sheet is the cathode (area: 6 cm 2 ). During the electrolysis process, the flow rate of hydrogen is controlled at 20 mL / min. The temperature of the electrolyte is controlled at 10 °C, and an electrolysis is carried out by applying a current of 300 mA (the cathode current density is: 5 A / dm 2 , and the anode current density is: 9.6 A / dm 2 .) After electrolysis for 2 hours, the voltage increased from 5.8 + 0.5 V to 7.9 V, and the electrolysis was stopped.

[0100] Compared with Example 31, the electrolysis voltage increased rapidly during the electrolysis process.

Claims

1. A low-cost electrolytic reduction method with a hydrogen oxidation reaction as the anodic reaction, characterized in that, The method uses a diaphragm electrolytic cell, with an aqueous solution containing inorganic acid as the anolyte, a solution containing organic matter or metal ions as the catholyte, the oxidation reaction of hydrogen as the anodic reaction, and the reduction reaction of organic matter or metal ions as the cathodic reaction for electrolytic reduction; the solvent of the catholyte is water or water + organic solvent.

2. The method according to claim 1, wherein The catholyte includes one or more of inorganic acid, emulsifier, electrolyte or organic acid; the emulsifier includes N,N-dimethyldodecylamine-N-oxide; the electrolyte includes lithium acetate, tetrabutylammonium perchlorate; the organic acid includes acetic acid; the concentration of the emulsifier in the catholyte is 1-5 mmol / L; the concentration of the electrolyte in the catholyte is 0.1-0.2 mol / L; the volume concentration of the organic acid is 10%; the concentration of the inorganic acid is 1-3 mol / L.

3. The method according to claim 1, wherein The pressure on the anolyte side of the diaphragm in the diaphragm electrolytic cell is greater than or equal to the pressure on the catholyte side of the diaphragm.

4. The method according to claim 3, wherein The pressure on the anolyte side is 1-3 atm, and the pressure difference between the anolyte side and the catholyte side is 0-2 atm.

5. The method according to claim 1, wherein The inorganic acid is sulfuric acid, hydrochloric acid, perchloric acid, phosphoric acid, nitric acid; the concentration of the inorganic acid in the anolyte is 0.1-4 mol / L.

6. The method according to claim 1, wherein The organic solvent is methanol, ethanol, acetonitrile, N,N-dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, acetone or dioxane; the organic matter is an organic matter containing nitro, carboxyl, carbon-carbon double bond, carbon-halogen bond, nitroso, carbonyl, carboxylic ester, amide or nitrile group; the metal ions are vanadium ions, copper ions, zinc ions, nickel ions, chromium ions.

7. The method according to claim 1, wherein The concentration of the organic matter in the catholyte is 0.25-1.5 mol / L, and the concentration of the metal ions in the catholyte is 1-3 mol / L.

8. The method according to claim 1, wherein The anodic reaction occurs on a gas diffusion electrode or a membrane electrode.

9. The method according to claim 8, characterized in that, The gas diffusion electrode is composed of a gas diffusion layer and a catalytic layer. The gas diffusion layer is a porous carbon or metal material. The carbon material is carbon paper, carbon cloth, graphite felt, carbon felt or carbon foam. The metal material is titanium or silver. The catalytic layer is composed of a platinum-carbon catalyst and a binder. The binder is polytetrafluoroethylene resin or Nafion resin or a mixture of both. The platinum loading on the gas diffusion electrode is 0.1 - 1 mg / cm 2 .

10. The method according to claim 8, wherein The membrane electrode is composed of a gas diffusion layer, a catalytic layer, and a cation exchange membrane. The catalytic layer is located between the gas diffusion layer and the cation exchange membrane. The gas diffusion layer is a porous carbon or metal material. The carbon material is carbon paper, carbon cloth, graphite felt, carbon felt, or carbon foam. The metal material is titanium or silver. The catalytic layer is composed of a platinum-carbon catalyst and a binder. The binder is polytetrafluoroethylene resin, Nafion resin, or a mixture of the two. The cation exchange membrane is a sulfonic acid type cation exchange membrane. The platinum loading on the membrane electrode is 0.1 to 1 mg / cm 2 .

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