1. A pH asymmetric pair electrosynthesis system, comprising: the electric synthesis system is formed by connecting three electrolytic cells in series, and two adjacent electrolytic cells are separated by an ion exchange membrane.

2. The pH asymmetric pair electrosynthesis system as defined in claim 1 wherein: the three electrolytic cells are respectively a cathode cell, an intermediate cell and an anode cell which are connected in series in sequence.

3. The pH asymmetric pair electrosynthesis system as defined in claim 2 wherein: the electrolyte in the cathode pool is alkaline electrolyte, acidic electrolyte or buffer solution with any pH value.

4. The pH asymmetric pair electrosynthesis system as defined in claim 2 wherein: the electrolyte in the middle pool is buffer solution such as phosphate buffer solution, citric acid buffer solution, carbonic acid buffer solution or acetic acid buffer solution.

5. The pH asymmetric pair electrosynthesis system as defined in claim 2 wherein: the electrolyte in the anode pool is alkaline electrolyte, acidic electrolyte or buffer solution with any pH value.

6. The pH asymmetric pair electrosynthesis system as defined in claim 1 wherein: the ion exchange membrane is an anion exchange membrane or a cation exchange membrane; an anion exchange membrane is used between the electrolytic cell containing the alkaline electrolyte and the intermediate cell, and a cation exchange membrane is used between the electrolytic cell containing the acidic electrolyte and the intermediate cell.

7. The pH asymmetric pair electrosynthesis system as defined in claim 1 wherein: the electrosynthesis system uses a three-electrode or four-electrode system, a working electrode and a counter electrode are catalysts of two electrodes respectively, and a reference electrode is a hydrogen electrode, a calomel electrode, a mercury/mercury oxide electrode, a silver/silver chloride electrode or a mercury/mercurous sulfate electrode; the electrosynthesis process uses constant current or constant voltage experiments.

8. Use of a pH asymmetric paired electrosynthesis system as defined in claim 1 wherein: the electric synthesis system is applied to experiments needing electrochemical catalytic oxidation-reduction reaction under different electrolyte environments.

9. Use of a pH asymmetric paired electrosynthesis system as defined in claim 8 wherein: in the electrosynthesis process: the electrosynthesis reaction is carried out in a double-chamber electrolytic cell separated by an anion-cation exchange membrane and a middle cell, the concentration of reactants is 5-40mmol/L, and the reaction time is 0.1-5 h; both the cathode chamber and the anode chamber generate high value-added products during reaction.

10. Use of a pH asymmetric paired electrosynthesis system as defined in claim 8 wherein: compared with the common H-shaped electrolytic cell electric synthesis system, the three-electrolytic cell series electric synthesis system can improve the yield of a target product by 10-30 percent and reduce the voltage by 0.1-0.3V_RHEThe groove pressure is increased, the Faraday efficiency is improved by 10-30%, and the electric energy consumption is remarkably reduced by 100-200 kW.h; in the electrosynthesis system, the concentration of the raw material in one of the polar chambers is increased to regulate the overall reaction rate, so that the reaction time can be shortened by 3-5 h.

Background

With the increasing severity of energy and environmental problems, a green industrial revolution mainly for saving resources and energy and protecting ecological environment balance is rapidly emerging, and people are all supposing to redesign a synthetic route by an atomic economic scientific method so as to prevent pollution from being generated at the source. The method and technology for synthesizing the target in green color belong to electrochemical synthesis technologies, and the most attractive synthesis method is chemical catalytic synthesis and enzyme catalytic synthesis. The oxidant or reductant used for the electrochemical reaction is an electron, which is a clean and clean substance. At present, many advanced industrial countries in the world adopt an electrosynthesis method to continuously research and develop various environment-friendly products with high added value and corresponding technologies thereof, and the development speed is very rapid.

Currently, in the field of electrocatalytic synthesis, most of the reported reactions only produce high value-added products in one electrode chamber, and the other electrode chamber performs the traditional hydrogen or oxygen evolution reaction. This wasted electrons could be used for more meaningful electrosynthesis reactions. Therefore, a pair-wise electrosynthesis strategy is provided, and two high value-added products can be produced simultaneously. And as an effective strategy for coupling electrocatalysis, the pH asymmetric system has great potential in reactions requiring different electrosynthesis environments.

Disclosure of Invention

The invention aims to provide a pH asymmetric pair electrosynthesis system and application thereof, wherein the pH asymmetric electrosynthesis system can realize the simultaneous production of high value-added products in two polar chambers filled with different electrolytes, and can improve the yield of target products, reduce the cell voltage, improve the Faraday efficiency and obviously reduce the electric energy consumption. Further kinetic manipulation can significantly reduce the reaction time and yield a target product with a composition of about 100% in one polar chamber.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a pH asymmetric pair electric synthesis system is formed by connecting three electrolytic cells in series, and two adjacent electrolytic cells are separated by an ion exchange membrane.

The three electrolytic cells are respectively a cathode cell, an intermediate cell and an anode cell which are connected in series in sequence.

The electrolyte in the cathode pool is alkaline electrolyte, acidic electrolyte or buffer solution with any pH value.

The electrolyte in the middle pool is buffer solution such as phosphate buffer solution, citric acid buffer solution, carbonic acid buffer solution or acetic acid buffer solution.

The electrolyte in the anode pool is alkaline electrolyte, acidic electrolyte or buffer solution with any pH value.

The ion exchange membrane is an anion exchange membrane or a cation exchange membrane; an anion exchange membrane is used between the electrolytic cell containing the alkaline electrolyte and the intermediate cell, and a cation exchange membrane is used between the electrolytic cell containing the acidic electrolyte and the intermediate cell.

The electrosynthesis system uses a three-electrode or four-electrode system, a working electrode and a counter electrode are catalysts of two electrodes respectively, and a reference electrode is a hydrogen electrode, a calomel electrode, a mercury/mercury oxide electrode, a silver/silver chloride electrode or a mercury/mercurous sulfate electrode; the electrosynthesis process uses constant current or constant voltage experiments.

The electric synthesis system is applied to experiments needing electrochemical catalytic oxidation-reduction reaction under different electrolyte environments.

In the electrosynthesis process: the electrosynthesis reaction is carried out in a double-chamber electrolytic cell separated by an anion-cation exchange membrane and a middle cell, the concentration of reactants is 5-40mmol/L, and the reaction time is 0.1-5 h; both the cathode chamber and the anode chamber generate high value-added products during reaction.

Compared with the common H-shaped electrolytic cell electric synthesis system, the three-electrolytic cell series electric synthesis system can improve the yield of a target product by 10-30 percent and reduce the voltage by 0.1-0.3V_RHEThe groove pressure improves the Faraday efficiency by 10-30%, and further obviously reduces the electric energy consumption by 100-200 kW.h.

The concentration of the raw material in one of the polar chambers is increased in the system to regulate the overall reaction rate, so that the reaction time can be shortened by 3-5 h.

The principle of the invention is as follows:

an electrolytic cell (middle cell) filled with a buffer solution (pH 7) is connected in series between the positive and negative electrolytic cells and is separated by a positive and negative ion exchange membrane respectively, and the pH value of the electrolyte in the positive and negative electrode chambers can be kept constant in the reaction process through an electrolytic water experiment, so that the reaction conditions of electrosynthesis under different electrolyte environments are met. The reaction current is kept in a higher state by increasing the concentration of the raw material in one of the polar chambers, so that the reaction rate is remarkably increased.

The invention has the following advantages:

1. the pH asymmetric pair electric synthesis system can improve the yield of target products, remarkably reduce the tank pressure, improve the total current efficiency and remarkably reduce the energy consumption.

2. When the two electrode chambers respectively contain raw materials with the same amount of substances, the electrochemical oxidation-reduction reaction can be simultaneously carried out to generate high value-added products with the yield of more than 90 percent.

3. The electrode reaction rate of the electric synthesis system can be adjusted by a kinetic method, and a target product with the component of about 100 percent is obtained.

Drawings

FIG. 1 is a schematic diagram of a pH asymmetric pair electrosynthesis system.

FIG. 2 shows the conversion of 4-nitrophenol (4-NP), the yield of 4-aminophenol (4-AP) and the total current efficiency (Faraday efficiency) in alkaline or acidic electrolytes.

FIG. 3 shows the time required for the transfer of 43.3c electrons at different 4-nitrophenol concentrations.

Detailed Description

The present invention will be described in detail with reference to examples.

The pH asymmetric paired electrosynthesis system is formed by connecting three electrolytic cells in series, two adjacent electrolytic cells are separated by an ion exchange membrane, and the three electrolytic cells are a cathode cell, an intermediate cell and an anode cell which are sequentially connected in series. The electrosynthesis system uses a three-electrode or four-electrode system, a working electrode and a counter electrode are catalysts of two electrodes respectively, and a reference electrode is a hydrogen electrode, a calomel electrode, a mercury/mercury oxide electrode, a silver/silver chloride electrode or a mercury/mercurous sulfate electrode; the electrosynthesis process uses constant current or constant voltage experiments.

The electric synthesis system is applied to experiments needing electrochemical catalytic oxidation-reduction reaction under different electrolyte environments.

Example 1:

the pH asymmetric pair electrosynthesis system is shown in figure 1, and adopts a three-electrode system, copper/carbon paper as a cathode electrode (working electrode) and nickel/carbon paper as an anode electrode (pair)Electrode), mercury/mercuric oxide electrode is as the reference electrode, use three electrolytic cell series system, add concentration in the cathodic electrolytic cell 0.05mol/l sulfuric acid solution as electrolyte, add concentration in the anodic electrolytic cell 0.1mol/l potassium hydroxide solution as electrolyte, two electrolytic cells of negative and positive connect one electrolytic cell in series between, the phosphate buffer solution with pH 7 is filled in the inside, the anodic cell separates with middle electrolytic cell using anion exchange membrane, the cathodic cell separates with middle electrolytic cell using cation exchange membrane. The concentration of a cathode reactant 4-nitrophenol is 5mmol/L, the concentration of an anode reactant 5-hydroxymethylfurfural is 5mmol/L, and the reaction voltage is-0.05V_RHEThe system tank pressure is 1.42V_RHE. The reaction time required for completely oxidizing 5-hydroxymethylfurfural is 4-5 h, and electrochemical tests show that the yield of 4-aminophenol after the reaction is 90% -98%, the yield of 2, 5-furandicarboxylic acid is 92% -98%, and the total faradaic efficiency is 190.1% (fig. 2).

Comparative example 1:

adopting a three-electrode system, copper/carbon paper as a cathode electrode (working electrode), nickel/carbon paper as an anode electrode (counter electrode), mercury/mercury oxide or silver/silver chloride as a reference electrode, adopting a common H-shaped electrolytic cell system, respectively adding potassium hydroxide solution with the concentration of 0.1mol/L into a cathode electrolytic cell and an anode electrolytic cell as electrolyte, wherein the concentration of a cathode reactant 4-nitrophenol is 5mmol/L, the concentration of an anode reactant 5-hydroxymethylfurfural is 5mmol/L, and the reaction voltage is-0.25V_RHEThe system tank pressure is 1.62V_RHEAnd the reaction time required for completely oxidizing the 5-hydroxymethylfurfural is 4-5 h. Electrochemical tests show that the yield of the reacted 4-aminophenol is 71-77%, the yield of the 2, 5-furandicarboxylic acid is 96-98%, and the total Faraday efficiency is 172.3%. (FIG. 2)

Example 2:

the three-electrode system is adopted, copper/carbon paper is used as a cathode electrode (working electrode), nickel/carbon paper is used as an anode electrode (counter electrode), and a mercury/mercury oxide electrode is used as a reference electrode, the three-electrolytic cell series system is used, a sulfuric acid solution with the concentration of 0.05mol/l is added into a cathode electrolytic cell to be used as an electrolyte, and potassium hydroxide with the concentration of 0.1mol/l is added into an anode electrolytic cellThe solution serves as an electrolyte. An electrolytic cell is connected in series between the positive electrolytic cell and the negative electrolytic cell, a phosphate buffer solution with the pH value of 7 is filled in the electrolytic cell, the positive electrolytic cell and the middle electrolytic cell are separated by an anion exchange membrane, and the negative electrolytic cell and the middle electrolytic cell are separated by a cation exchange membrane. The concentration of a cathode reactant 4-nitrophenol is 40mmol/L, the concentration of an anode reactant 5-hydroxymethylfurfural is 5mmol/L, and the reaction voltage is-0.05V_RHE. The reaction time required for completely oxidizing the 5-hydroxymethylfurfural is 0.1-0.3 h. (FIG. 3)

Example 3:

the three-electrode system is adopted, copper/carbon paper is used as a cathode electrode (working electrode), nickel/carbon paper is used as an anode electrode (counter electrode), and a mercury/mercury oxide electrode is used as a reference electrode, the three-electrolytic cell series system is used, a sulfuric acid solution with the concentration of 0.05mol/l is added into a cathode electrolytic cell to be used as an electrolyte, and a potassium hydroxide solution with the concentration of 0.1mol/l is added into an anode electrolytic cell to be used as the electrolyte. An electrolytic cell is connected in series between the positive electrolytic cell and the negative electrolytic cell, a phosphate buffer solution with the pH value of 7 is filled in the electrolytic cell, the positive electrolytic cell and the middle electrolytic cell are separated by an anion exchange membrane, and the negative electrolytic cell and the middle electrolytic cell are separated by a cation exchange membrane. The concentration of a cathode reactant 4-nitrophenol is 10mmol/L, the concentration of an anode reactant 5-hydroxymethylfurfural is 5mmol/L, and the reaction voltage is-0.05V_RHE. The reaction time required for completely oxidizing the 5-hydroxymethylfurfural is 2.5-3 h. As shown in fig. 3.

From examples 2 to 3, it is understood that the reaction time can be adjusted by changing the current by controlling the concentration of the reactant.