Reaction system for supercritical CO2 electroreduction and working method thereof

Abstract

The invention discloses a supercritical CO2 electroreduction reaction system and a working method thereof. The supercritical CO2 electroreduction reaction system comprises a supercritical CO2 generation subsystem, an electrolytic bath, a catholyte circulation subsystem, a pressure balance subsystem, a gas outlet subsystem, a circuit control subsystem and an anolyte circulation subsystem which are connected through pipelines. The supercritical CO2 generation subsystem is used for sequentially pressurizing and heating liquid CO2 to form supercritical CO2, the electrolytic bath is used for electroreduction of the supercritical CO2, and catholyte and anolyte in the electrolytic bath circularly flow in the corresponding subsystem or are subjected to electroreduction reaction through a membrane electrode; the catholyte circulation subsystem is respectively communicated with an inlet and an outlet of the catholyte chamber of the electrolytic cell; the anolyte circulation subsystem is respectively communicated with an inlet and an outlet of an anolyte chamber of the electrolytic cell; the pressure balance subsystem is communicated with the gas chamber, the catholyte storage tank and the anolyte storage tank so as to ensure the pressure balance in the system; the gas outlet subsystem exhausts gas products and ethanol from the reaction process.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of electrochemistry, in particular to a reaction system for supercritical CO2 electro-reduction and a working method thereof. BACKGROUND

[0002] The consumption of fossil fuels leads to the continuous rise of atmospheric CO2 concentration, causing a series of problems such as greenhouse effect. CO2 electro-reduction reaction can directly store the power generated by renewable energy in carbon-neutral fuels such as CO, formic acid, methanol, ethanol, ethylene, etc. while reducing the atmospheric CO2 concentration, thus attracting widespread attention. In the CO2 electro-reduction reaction at normal pressure, the low CO2 concentration in the liquid and the mass transfer limitation result in serious competitive hydrogen evolution reaction and low single product selectivity problems.

[0003] The density of supercritical CO2 (critical pressure 7.38 MPa, critical temperature 31.1℃) is close to that of liquid, and the fluidity is similar to that of gas. At the same time, the solubility and mass transfer capacity in the liquid are greatly increased, which can solve the serious hydrogen evolution problem in the CO2 electro-reduction process. In addition, the increase of reaction temperature is beneficial to increase the reaction activity of CO2 electro-reduction, reduce the reaction barrier and improve the reaction energy efficiency.

[0004] CN 117305872A discloses a supercritical CO2 electro-reduction reaction system and working method. The reaction system includes a continuous flow electrolytic cell, a supercritical CO2 generating unit, a cathode gas outlet unit, an anode liquid pressurizing circulating device and a pressure balance control unit. The system can realize the electro-catalytic reduction test of continuous flow CO2, especially the electro-catalytic reduction test of supercritical CO2, and can ensure the normal operation of the continuous flow reactor. However, the current supercritical CO2 generating system and pressure balance control system are relatively complex in design, and it is difficult to stably generate supercritical CO2 and accurately control the flow rate and pressure balance among the gas chamber, the cathode liquid chamber and the anode liquid chamber. Therefore, the inventors believe that it is necessary to provide a simple and effective supercritical CO2 generating system and pressure balance system for supercritical CO2 electro-reduction reaction. SUMMARY

[0005] On this basis, the present application provides a reaction system for supercritical CO2 electro-reduction and a working method thereof. The reaction system includes two systems of electrolytic cell using flow reaction and membrane electrode electrolytic cell. In the reaction system of electrolytic cell using flow reaction, the cathode liquid and anode liquid in the electrolytic cell can circulate and flow, which improves the mass transfer efficiency and reaction efficiency of the reactor.

[0006] The purpose of the present application is achieved by the following technical solutions:

[0007] The first aspect of the present application is to provide a supercritical CO2 electro-reduction reaction system, comprising a supercritical CO2 generation subsystem, an electrolytic cell, a cathode liquid circulation subsystem, a pressure balance subsystem, a gas outlet subsystem, a circuit control subsystem and an anode liquid circulation subsystem connected by pipelines;

[0008] The electrolytic cell is used for supercritical CO2 electro-reduction, comprising a gas chamber, an anode liquid chamber, an ion exchange membrane, a cathode liquid chamber and a cathode; the cathode liquid in the electrolytic cell and the cathode liquid circulation subsystem circulates and flows; the anode liquid in the electrolytic cell and the anode liquid circulation subsystem circulates and flows; the ion exchange membrane is a cation exchange membrane;

[0009] The electrolytic cell comprises a first liquid inlet, a second liquid inlet, a third liquid inlet, a first liquid outlet, a second liquid outlet and a third liquid outlet; the first liquid inlet is in communication with the outlet of the steam generator and the gas chamber respectively; the second liquid inlet is in communication with the anode liquid circulation subsystem and the anode liquid chamber respectively; the third liquid inlet is in communication with the cathode liquid circulation subsystem and the cathode liquid chamber respectively; the first liquid outlet is in communication with the pressure balance subsystem and the gas chamber respectively; the second liquid outlet is in communication with the anode liquid chamber and the anode liquid circulation subsystem respectively; the third liquid outlet is in communication with the cathode liquid circulation subsystem and the cathode liquid chamber respectively;

[0010] The supercritical CO2 generation subsystem is in communication with the first liquid inlet of the gas chamber, and is used for sequentially pressurizing and heating the liquid CO2 to enter the electrolytic cell, wherein the liquid entering the electrolytic cell comprises liquid CO2 carrying a certain concentration of water vapor or supercritical CO2;

[0011] The circuit control subsystem is connected with the electrolytic cell through wires, and provides the required voltage or current for the supercritical CO2 electrochemical reaction in the supercritical CO2 electrolytic cell;

[0012] The cathode liquid circulation subsystem is in communication with the third liquid inlet and the third liquid outlet of the cathode liquid chamber of the electrolytic cell, and is used for introducing the cathode liquid into the cathode liquid chamber, and receiving the backflow of the cathode liquid in the cathode liquid chamber and the discharged reaction liquid product of the cathode liquid chamber;

[0013] The anode liquid circulation subsystem is in communication with the second liquid inlet and the second liquid outlet of the anode liquid chamber of the electrolytic cell, and is used for introducing the anode liquid into the anode liquid chamber, and receiving the backflow of the anode liquid in the anode liquid chamber and the discharged oxygen of the anode liquid chamber;

[0014] The pressure balance subsystem is in communication with the first liquid outlet of the gas chamber, the top cavity of the cathode liquid storage tank of the cathode liquid circulation subsystem, and the top cavity of the anode liquid storage tank of the anode liquid circulation subsystem, so as to ensure the pressure balance in the system;

[0015] The gas outlet subsystem is connected with a pressure balance subsystem, and discharges gas products and ethanol from the reaction process; the gas products include CO and ethylene;

[0016] In the reaction system, the flow rate of the supercritical CO2 is in the range of 0.01-1 mL min -1 The flow rates of the catholyte and the anolyte are 5-10 mL min -1 and 10-20 mL min -1 , respectively.

[0017] Further, the supercritical CO2 generation system comprises, connected in sequence through pipelines, a first constant flow pump, a first stop valve, a high-pressure injection pump, a second stop valve, and a vapor generator.

[0018] Further, the catholyte circulation subsystem comprises, connected in sequence through pipelines, a third liquid inlet, a catholyte storage tank, a third constant flow pump, and a third liquid outlet. The catholyte circulation subsystem receives the catholyte from the catholyte chamber of the electrolytic cell, and after passing through the third constant flow pump and the catholyte storage tank, the catholyte flows back to the catholyte chamber through the third liquid inlet;

[0019] The anolyte circulation subsystem comprises, connected in sequence through pipelines, a second liquid inlet, an anolyte storage tank, a second constant flow pump, and a second liquid outlet. The anolyte circulation subsystem receives the anolyte from the anolyte chamber, and after passing through the anolyte storage tank and the second constant flow pump, the anolyte flows back to the anolyte chamber;

[0020] The pressure balance subsystem comprises, connected through pipelines, the first liquid outlet, a second three-way joint, and a first three-way joint. The other end of the first three-way joint is connected with the gas outlet subsystem. The first three-way joint is connected with the top cavity of the catholyte storage tank, and the second three-way joint is connected with the top cavity of the anolyte storage tank;

[0021] The gas outlet subsystem comprises, connected in sequence, a pressure gauge, a high-pressure back pressure valve, a cold trap, and a gas flow meter.

[0022] Further, the flow rate of the constant flow pump is set to 0.01-1 mL / min.

[0023] Further, the temperature of the liquid CO2 at the outlet of the vapor generator is higher than 31.1 ℃.

[0024] The working process of the supercritical CO2 electro-reduction reaction system comprises:

[0025] The catholyte and the anolyte are injected into the catholyte storage tank and the anolyte storage tank, respectively, and the third constant flow pump and the second constant flow pump are used to make the catholyte and the anolyte circulate and flow, respectively, and the flow rates are controlled to be kept at 5-20 mL min-1 in the range of 31.1℃ to 31.3℃;

[0026] opening the high-pressure back pressure valve of the gas outlet subsystem, so that the temperature of the pipeline in the supercritical CO2 generating subsystem exceeds 31.1℃; using the first constant flow pump, the first stop valve, the high-pressure injection pump, the second stop valve and the steam generator, liquid CO2 is pressurized and heated to form supercritical CO2 carrying water vapor with a certain concentration;

[0027] in the electrolytic cell, the supercritical CO2 carrying water vapor with a certain concentration is reduced on the surface of the cathode; CO, formic acid, ethylene and ethanol are generated by the reduction reaction on the surface of the cathode, and the formic acid and most of the ethanol are dissolved in the catholyte in the catholyte chamber and flow in the catholyte circulation subsystem;

[0028] opening the first three-way joint and the high-pressure back pressure valve 52 of the gas outlet subsystem, CO, ethylene and part of the volatile ethanol are sequentially discharged through the first three-way joint, the high-pressure back pressure valve and the cold trap; wherein the ethanol is dissolved in the cold trap, and the CO and ethylene pass through the gas flow meter and enter the gas chromatograph, and the concentration of the gas products is monitored online in the gas chromatograph;

[0029] after the reaction is completed, a small amount of electrolyte in the catholyte storage tank and water in the cold trap are taken out and detected by a nuclear magnetic resonance spectrometer to detect the concentration of liquid products such as formic acid and ethanol.

[0030] A second aspect of the present application provides a supercritical CO2 electro-reduction reaction system, comprising a supercritical CO2 generating subsystem, an electrolytic cell, a pressure balance subsystem, a gas outlet subsystem, a circuit control subsystem and an anolyte circulation subsystem connected by pipelines;

[0031] The electrolytic cell is used for supercritical CO2 electro-reduction, and comprises a gas chamber, an anolyte chamber, an ion exchange membrane, a catholyte chamber and a cathode; the ion exchange membrane is a cation exchange membrane;

[0032] The electrolytic cell comprises a first liquid inlet, a second liquid inlet, a third liquid inlet, a first liquid outlet, a second liquid outlet and a third liquid outlet; the first liquid inlet is in communication with the outlet of the steam generator and the gas chamber; the second liquid inlet is in communication with the anolyte circulation subsystem and the anolyte chamber 22; the third liquid inlet is in communication with the catholyte circulation subsystem and the catholyte chamber; the first liquid outlet is in communication with the pressure balance subsystem and the gas chamber; the second liquid outlet is in communication with the anolyte chamber and the anolyte circulation subsystem; and the third liquid outlet is in communication with the catholyte circulation subsystem and the catholyte chamber;

[0033] The supercritical CO2 generating subsystem is connected with the first liquid inlet of the gas chamber, and is used for sequentially pressurizing and heating the liquid CO2 to enter the electrolytic cell, wherein the liquid entering the electrolytic cell includes liquid CO2 carrying a certain concentration of water vapor or supercritical CO2;

[0034] The circuit control subsystem is connected with the electrolytic cell through wires, and provides the required voltage or current for the supercritical CO2 electrochemical reaction in the supercritical CO2 electrolytic cell;

[0035] The anode liquid circulating system is connected with the second liquid inlet and the second liquid outlet of the anode liquid chamber of the electrolytic cell, and is used for introducing the anode liquid into the anode liquid chamber, and receiving the backflow of the anode liquid in the anode liquid chamber and the oxygen discharged from the anode liquid chamber;

[0036] The pressure balance subsystem is connected with the first liquid outlet of the gas chamber, the top cavity of the anode liquid storage tank of the anode liquid circulating subsystem, and the top cavity of the cathode liquid storage tank of the cathode liquid circulating subsystem, so as to ensure the pressure balance in the system;

[0037] The gas outlet subsystem is connected with the pressure balance subsystem;

[0038] The flow rate of the supercritical CO2 in the reaction system is in the range of 0.01-1 mL min -1 , and the flow rate of the anode liquid is in the range of 5-20 mL min -1 .

[0039] In another embodiment, the preset reaction pressure control value in the reaction system is greater than 7.38 MPa.

[0040] In another embodiment, the reaction pressure is controlled in the range of 5.5-7.38 MPa.

[0041] Compared with the prior art, the technical scheme of the present application has the beneficial effects that:

[0042] The reaction system of the present application includes two systems of the electrolytic cell using flow reaction and the membrane electrode electrolytic cell, wherein in the reaction system of the electrolytic cell using flow reaction, the cathode liquid and the anode liquid can circulate and flow, thereby improving the mass transfer efficiency and reaction efficiency of the reactor; both systems can realize efficient mass transfer and conversion of carbon dioxide under high pressure and high temperature conditions, and meet the needs of supercritical carbon dioxide electrocatalytic reduction reaction;

[0043] Moreover, the system is provided with a gas outlet subsystem, which can collect and monitor the concentration of the gas product online, and facilitate the analysis and evaluation of the reaction performance;

[0044] And the two systems provided by the application have basically same structure, and can be switched easily according to needs. BRIEF DESCRIPTION OF DRAWINGS

[0045] Figure 1 is a structural schematic diagram of a supercritical CO2 electric reduction flow reaction system shown in Example 1;

[0046] Figure 2 is a structural schematic diagram of a supercritical CO2 electric reduction membrane electrode reaction system shown in Example 2.

[0047] wherein,

[0048] 1: Supercritical CO2 generating subsystem; 2: Electrolytic cell; 3: Cathode liquid circulating subsystem; 4: Pressure balancing subsystem; 5: Gas outlet subsystem; 6: Circuit control subsystem; 7: Anode liquid circulating subsystem; 11: First constant flow pump; 12: First stop valve; 13: High-pressure injection pump; 14: Second stop valve; 15: Steam generator; 21: Gas chamber; 22: Anode liquid chamber; 23: Ion exchange membrane; 24: Cathode liquid chamber; 25: Cathode; 211: First liquid inlet; 212: Second liquid inlet; 213: Third liquid inlet; 214: First liquid outlet; 215: Second liquid outlet; 216: Third liquid outlet; 31: Third constant flow pump; 32: Cathode liquid storage tank; 41: First three-way joint; 42: Second three-way joint; 51: Pressure gauge; 52: High-pressure back pressure valve; 53: Cold trap; 54: Gas flow meter; 71: Second constant flow pump; 72: Anode liquid storage tank. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions, beneficial effects and significant progress of the embodiments of the application clearer, below, the technical solutions in the embodiments of the application will be described clearly and completely in combination with the drawings provided in the examples of the application. Obviously, all the described embodiments are only some of the embodiments of the application, rather than all the embodiments; based on the examples in the application, all other embodiments obtained by those skilled in the art without creative labor according to the content and embodiments of the application and the drawings also belong to the protection scope of the application.

[0050] It should be noted that the terms "first", "second", "third" and the like in the specification and claims of the application are only used to distinguish different objects, and are not used to describe a specific order.

[0051] It should also be noted that the following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments.

[0052] Example 1

[0053] As Figure 1 shown in the figure, a supercritical CO2 electro-reduction flow reaction system includes a supercritical CO2 generation subsystem 1, an electrolytic cell 2, a cathode liquid circulation subsystem 3, a pressure balance subsystem 4, a gas outlet subsystem 5, a circuit control subsystem 6 and an anode liquid circulation subsystem 7 connected by pipelines.

[0054] The supercritical CO2 generation subsystem 1 is used to sequentially pressurize and heat liquid CO2 to enter the flow reaction electrolytic cell 2, wherein the liquid entering the flow reaction electrolytic cell 2 includes liquid CO2 carrying a certain concentration of water vapor.

[0055] The supercritical CO2 generation system 1 includes a first constant flow pump 11, a first stop valve 12, a high-pressure injection pump 13, a second stop valve 14 and a steam generator 15 connected by pipelines in sequence. A high-pressure CO2 gas cylinder is connected to the liquid inlet of the first constant flow pump 11. The flow rate of the constant flow pump is set to 0.1-20 mL / min. The outlet of the steam generator 15 is connected to the liquid inlet of the flow reaction electrolytic cell 2, and the temperature of the liquid CO2 at the outlet of the steam generator 15 is higher than 31.1 ℃.

[0056] The electrolytic cell 2 for supercritical CO2 electro-reduction includes a gas chamber 21, an anode liquid chamber 22, an ion exchange membrane 23, a cathode liquid chamber 24 and a cathode 25, and the flow reaction electrolytic cell 2 includes a first liquid inlet 211, a second liquid inlet 212, a third liquid inlet 213, a first liquid outlet 214, a second liquid outlet 215 and a third liquid outlet 216. The ion exchange membrane 23 is a nafion 117 cation exchange membrane; the anode is a platinum mesh, and nano-copper agent is coated on a carbon paper with hydrophobicity as the cathode 25. The cathode liquid used is a 1 mol / L KCl solution, the anode liquid is a 1 mol / L KOH solution, and the reference electrode is a solid KCl electrode. The first liquid inlet 211 is respectively connected to the outlet of the steam generator 15 and the gas chamber 21; the second liquid inlet 212 is respectively connected to the anode liquid circulation subsystem 7 and the anode liquid chamber 22; the third liquid inlet 213 is respectively connected to the cathode liquid circulation subsystem 3 and the cathode liquid chamber 24; the first liquid outlet 214 is respectively connected to the pressure balance subsystem 4 and the gas chamber 21; the second liquid outlet 215 is respectively connected to the anode liquid circulation subsystem 7 and the anode liquid chamber 22; and the third liquid outlet 216 is respectively connected to the cathode liquid chamber 24 and the cathode liquid circulation subsystem 3.

[0057] Moreover, the circuit control subsystem 6 is connected to the flow reaction electrolytic cell 2 by wires, the working electrode of the circuit control subsystem is connected to the cathode 25, the counter electrode is connected to the anode, the reference electrode is connected to the solid KCl electrode, and the CO2 electro-reduction test is carried out in a constant current mode, and the current density is in the range of 10-1000 mA cm-2.

[0058] The catholyte circulation subsystem 3 comprises a third liquid outlet 216, a catholyte storage tank 32, a third constant flow pump 31 and a third liquid inlet 213 connected in sequence by pipelines. The catholyte circulation subsystem 3 receives the catholyte from the catholyte chamber 24 of the flow reaction electrolytic cell 2, and after passing through the third constant flow pump 31 and the catholyte storage tank 32, the catholyte flows back to the catholyte chamber 24 through the third liquid inlet 213.

[0059] The anolyte circulation subsystem 7 comprises a second liquid outlet 215, an anolyte storage tank 72, a second constant flow pump 71 and a second liquid inlet 212 connected in sequence by pipelines. The anolyte circulation subsystem 7 receives the anolyte from the anolyte chamber 22, and after passing through the anolyte storage tank 72 and the second constant flow pump 71, the anolyte flows back to the anolyte chamber.

[0060] The pressure balance subsystem 4 comprises a first liquid outlet 214, a second three-way joint 42 and a first three-way joint 41 connected by pipelines. The other end of the first three-way joint 41 is connected to the gas outlet subsystem 5. The first three-way joint 41 is connected to the top cavity of the catholyte storage tank 32, and the second three-way joint 42 is connected to the top cavity of the anolyte storage tank 72, so as to balance the pressure in the system.

[0061] The gas outlet subsystem 5 comprises a pressure gauge 51, a high-pressure back pressure valve 52, a cold trap 53 and a gas flow meter 54 connected in sequence.

[0062] Furthermore, the outer wall of the pipeline of the supercritical CO2 electro-reduction flow reaction system is covered with heating fins, and the electrolytic cell 2 is externally attached with heating fins.

[0063] The working process of the supercritical CO2 electro-reduction flow reaction system is as follows:

[0064] First, catholyte and anolyte are respectively injected into the catholyte storage tank 32 and the anolyte storage tank 72, and the third constant flow pump 31 and the second constant flow pump 71 are respectively used to make the catholyte and the anolyte circulate and flow, and the flow rate is controlled to be maintained at 10 min / L.

[0065] The high-pressure back pressure valve 52 of the gas outlet subsystem 5 is opened, and a preliminary pressure preset value (> 7.38 MPa) is set; liquid CO2 in the high-pressure CO2 gas cylinder is injected into the high-pressure injection pump 13 by using the first constant flow pump 11;

[0066] Then, the first stop valve 12 is closed, the second stop valve 14 is opened, and the high-pressure injection pump 13 is started, so that the supercritical CO2 generation subsystem 1 is filled with liquid CO2, and then the heating fins on the pipeline of the system and the heating fins outside the electrolytic cell are heated, so that the temperature of the pipeline in the supercritical CO2 generation subsystem 1 exceeds 31.1℃.

[0067] Then the flow rate of the high-pressure injection pump 13 is controlled at 0.01 mL / min, and the flow rate of the supercritical CO2 is adjusted by controlling the extrusion flow of the high-pressure injection pump 13, and the supercritical CO2 enters the steam generator 15 to make the temperature reach 31.1 ℃;

[0068] The supercritical CO2 carrying a certain concentration of water vapor from the supercritical CO2 generation subsystem 1 enters the gas chamber 21, and a reduction reaction occurs on the surface of the cathode 25 to generate CO, formic acid, ethylene, ethanol and other substances. Formic acid and most of the ethanol will dissolve in the catholyte in the catholyte chamber 24 and circulate in the catholyte circulation subsystem 7. The first three-way joint 41 and the high-pressure back pressure valve 52 of the gas outlet subsystem 5 are opened, and CO and ethylene and other gaseous substances and a small amount of ethanol and other volatile liquids are sequentially discharged through the first three-way joint 41, the high-pressure back pressure valve 52 and the cold trap 53. Among them, the CO2 is depressurized to normal temperature after flowing out of the high-pressure back pressure valve 52, and the ethanol is dissolved in the cold trap 53. The gas products pass through the gas flow meter 54 and enter the gas chromatograph (GC), and the concentration of the gas products is monitored online in the gas chromatograph.

[0069] After the reaction is completed, a small amount of electrolyte in the anolyte storage tank 72 and water in the cold trap 53 are taken out, and the concentrations of liquid products such as formic acid and ethanol are detected by a nuclear magnetic resonance spectrometer.

[0070] In the system, the flow rate of the supercritical CO2 is in the range of 0.1-20 mL min-1, and the flow rates of the catholyte and the anolyte are 5 and 20 mL min-1, respectively. -1 .

[0071] Example 2

[0072] As shown in Figure 2 , a supercritical CO2 electro-reduction membrane electrode reaction system includes a supercritical CO2 generation subsystem 1, a membrane electrode electrolysis cell 2, a pressure balance subsystem 4, a gas outlet subsystem 5, a circuit control subsystem 6 and an anolyte circulation subsystem 7 connected by pipelines.

[0073] Among them, the supercritical CO2 electro-reduction membrane electrode reaction system of example 2 does not set up a cathode electrode liquid circulation system, and the first three-way joint 41 is not set up in the pressure balance subsystem 4. The supercritical CO2 generation subsystem 1, the gas outlet subsystem 5, the circuit control subsystem 6 and the anolyte circulation subsystem 7 are the same as example 1. The same content will not be described here, and only the differences from example 1 will be described below.

[0074] The pressure balance subsystem 4 includes a first liquid outlet 214 and a second three-way joint 42 connected by pipelines, and the other end of the second three-way joint 42 is connected to the gas outlet subsystem 5.

[0075] The electrolytic cell 2 includes a gas chamber 21, an anolyte chamber 22, an ion exchange membrane 23, a catholyte chamber 24 and a cathode 25. The structure of the electrolytic cell 2 is basically the same as that of Example 1, and the only difference is that the ion exchange membrane 23 is a FAA anion exchange membrane, the nano-copper agent is coated on a carbon paper with hydrophobicity as the cathode, the anode is a foamed nickel, the anolyte is a 1 mol / L KOH solution, the cathode, the anion exchange membrane 23 and the anode are tightly attached together as a membrane electrode by a hot pressing method, the working electrode of the circuit control subsystem 6 is connected to the cathode, the counter electrode and the reference electrode are connected to the anode, the CO2 electro-reduction test is performed in a constant current mode, the current density is in the range of 10-1500 mA cm-2, and the CO2 reduction product is analyzed by GC-MS. -2

[0076] In this embodiment, the flow rate of the supercritical CO2 is in the range of 0.1-20 mL min-1, and the flow rate of the anolyte is in the range of 5-20 mL min-1. -1 -1

[0077] Example 3

[0078] A supercritical CO2 electro-reduction flow reaction system includes a supercritical CO2 generation subsystem 1, an electrolytic cell 2, a catholyte circulation subsystem 3, a pressure balance subsystem 4, a gas outlet subsystem 5, a circuit control subsystem 6 and an anolyte circulation subsystem 7 connected by pipelines.

[0079] The structure of the embodiment is basically the same as that of Example 1, and the electrolytic cell, the cathode / anode and the ion exchange membrane, and the flow rates of CO2, the catholyte and the anolyte are the same as those of Example 1. The same content will not be described again, and only the different parts will be described below.

[0080] The reaction pressure of this embodiment is controlled in the range of 5.5-7.38 MPa, and CO2 is kept in a liquid state, i.e., liquid CO2 electro-reduction is performed. In the electrolytic cell, the liquid CO2 and the water-based liquid in the catholyte and anolyte storage tanks are not completely miscible, and the density of H2O is greater than that of liquid CO2, so H2O will be located below the liquid CO2. The liquid CO2 contacts the electrode liquid in the catholyte storage tank 32 and the anolyte storage tank 72, respectively, and balances the pressure in the system.

[0081] Example 4

[0082] ​​​A supercritical CO2 electro-reduction membrane electrode reaction system includes a supercritical CO2 generating subsystem 1, an electrolytic tank 2, a pressure balancing subsystem 4, a gas outlet subsystem 5, a circuit control subsystem 6 and an anolyte circulating subsystem 7 connected by pipelines. The embodiment structure is basically the same as that of embodiment 2, and the electrolytic tank, cathode / anode electrode and ion exchange membrane materials and CO2 and anolyte are also the same as those of embodiment 2.

[0083] The reaction pressure of the embodiment is controlled in the range of 5.5-7.38 MPa, and CO2 is kept in a liquid state, i.e. liquid CO2 electro-reduction is carried out. Liquid CO2 and water-based liquid are not completely miscible, and the density of H2O is greater than that of liquid CO2, so H2O will be located below liquid CO2. Liquid CO2 contacts with the electrode liquid in the anolyte storage tank, and the pressure in the system is balanced.

[0084] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacements to some or all of the technical features, and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application. The non-essential improvements and adjustments or replacements made by those skilled in the art according to the content of the present application are all within the scope of the present application.

Claims

1. A supercritical CO2 electroreduction reaction system, characterized in that, It includes a supercritical CO2 generation subsystem (1), an electrolyzer (2), a cathode liquid circulation subsystem (3), a pressure balance subsystem (4), a gas outlet subsystem (5), a circuit control subsystem (6), and an anolyte circulation subsystem (7) connected by pipelines. The electrolytic cell (2) is used for supercritical CO2 electroreduction and includes a gas chamber (21), an anolyte chamber (22), an ion exchange membrane (23), a catholyte chamber (24), and a cathode (25). The catholyte circulates within the electrolytic cell and the catholyte circulation subsystem, and the anolyte circulates within the electrolytic cell and the anolyte circulation subsystem. The ion exchange membrane is a cation exchange membrane. The electrolytic cell (2) includes a first inlet (211), a second inlet (212), a third inlet (213), a first outlet (214), a second outlet (215), and a third outlet (216). The first inlet (211) is connected to the outlet of the steam generator (15) and the gas chamber (21), respectively. The second inlet (212) is connected to the anolyte circulation subsystem (7) and the anolyte chamber (22), respectively. The third inlet (213) is connected to the catholyte circulation subsystem (3) and the catholyte chamber (24), respectively. The first outlet (214) is connected to the pressure balance subsystem (4) and the gas chamber (21), respectively. The second outlet (215) is connected to the anolyte circulation subsystem (7) and the anolyte chamber (22), respectively. The third outlet (216) is connected to the catholyte chamber (24) and the catholyte circulation subsystem (3), respectively. The supercritical CO2 generating subsystem (1) is connected to the first liquid inlet (211) of the gas chamber (21) and is used to pressurize and heat the liquid CO2 in sequence to form liquid CO2 or supercritical CO2 and enter the electrolytic cell (2). The liquid entering the electrolytic cell (2) includes supercritical CO2 carrying a certain concentration of water vapor. The circuit control subsystem (6) is connected to the electrolytic cell (2) via wires to provide the required voltage or current for the supercritical CO2 electrochemical reaction in the supercritical CO2 electrolytic cell; The cathode liquid circulation subsystem (3) is connected to the third inlet (213) and the third outlet (216) of the cathode liquid chamber (24) of the electrolytic cell, and is used to introduce cathode liquid into the cathode liquid chamber, and to receive the cathode liquid flowing back into the cathode liquid chamber and the reaction liquid products discharged from the cathode liquid chamber. The anolyte circulation subsystem is connected to the second inlet (212) and the second outlet (215) of the anolyte chamber (22) of the electrolytic cell, and is used to introduce anolyte into the anolyte chamber, and to receive the anolyte flowing back into the anolyte chamber (22) and the oxygen discharged from the anolyte chamber; The pressure balance subsystem (4) is connected to the first liquid outlet (214) of the gas chamber (21), the top cavity of the cathode liquid storage tank (32) of the cathode liquid circulation subsystem (3), and the top cavity of the anolyte storage tank (72) of the anolyte circulation subsystem (7) to ensure pressure balance within the system. The gas outlet subsystem (5) is connected to the pressure balance subsystem (4) to discharge gaseous products and ethanol from the reaction process; the gaseous products include CO and ethylene; In the reaction system, the flow rate of supercritical CO2 is 0.01-1 mL / min. -1 Within this range, the flow rates of the catholyte and anolyte are 5-10 mL / min. -1 and 10-20 mL min -1 .

2. The supercritical CO2 electroreduction reaction system according to claim 1, characterized in that, The supercritical CO2 generating system (1) includes a first constant flow pump (11), a first shut-off valve (12), a high-pressure injection pump (13), a second shut-off valve (14), and a steam generator (15) connected in sequence through pipelines. The cathode liquid circulation subsystem (3) includes a third outlet (216), a cathode liquid storage tank (32), a third constant flow pump (31), and a third inlet (213) connected in sequence by pipelines. The cathode liquid circulation subsystem (3) receives cathode liquid from the cathode liquid chamber (24) of the electrolytic cell (2), and after passing through the third constant flow pump (31) and the cathode liquid storage tank (32), it flows back to the cathode liquid chamber (24) through the third inlet (213). The anolyte circulation subsystem (7) includes a second outlet (215), an anolyte storage tank (72), a second constant flow pump (71), and a second inlet (212) connected in sequence by pipelines. The anolyte circulation subsystem (7) receives anolyte from the anolyte chamber (22), flows through the anolyte storage tank (72) and the second constant flow pump (71), and then flows back to the anolyte chamber. The pressure balancing subsystem (4) includes a first outlet (214), a second tee connector (42), and a first tee connector (41) connected by a pipeline. The other end of the first tee connector (41) is connected to the gas outlet subsystem (5). The first tee connector (41) is connected to the top cavity of the cathode liquid storage tank (32), and the second tee connector (42) is connected to the top cavity of the anolyte liquid storage tank (72). The gas outlet subsystem (5) includes a pressure gauge (51), a high-pressure back pressure valve (52), a cold trap (53), and a gas flow meter (54) connected in sequence.

3. The supercritical CO2 electroreduction reaction system according to claim 2, characterized in that, The flow rate of the constant flow pump is set to 0.1-20 mL / min.

4. The supercritical CO2 electroreduction reaction system according to claim 2, characterized in that, The temperature of the liquid CO2 at the outlet of the steam generator (15) exceeds 31.1 °C.

5. The supercritical CO2 electroreduction reaction system according to claim 2, characterized in that, The working process of the supercritical CO2 electroreduction reaction system includes: Cathodic liquid and anodic liquid are injected into the cathodic liquid storage tank (32) and the anodic liquid storage tank (72) respectively, and the cathodic liquid and anodic liquid are circulated by the third constant flow pump (31) and the second constant flow pump (71) respectively, and the flow rate is controlled to be maintained at 0.1-20 mL / min. -1 Within the range; Open the high-pressure back pressure valve (52) of the gas outlet subsystem (5) to make the pipeline temperature in the supercritical CO2 generation subsystem (1) exceed 31.1℃; use the first constant flow pump (11), the first shut-off valve (12), the high-pressure injection pump (13), the second shut-off valve (14) and the steam generator (15) to pressurize and heat the liquid CO2 to form supercritical CO2 carrying a certain concentration of water vapor; Inside the electrolytic cell, supercritical CO2 carrying a certain concentration of water vapor undergoes a reduction reaction on the cathode (25) surface to generate CO, formic acid, ethylene, and ethanol. Formic acid and most of the ethanol will dissolve in the catholy liquid in the catholy liquid chamber (24) and circulate in the catholy liquid circulation subsystem (7). Open the first three-way connector (41) and the high-pressure back pressure valve (52) of the gas outlet subsystem (5). CO, formic acid, ethylene and ethanol are discharged after passing through the first three-way connector (41), the high-pressure back pressure valve (52) and the cold trap (53) in sequence with CO2. Ethanol will dissolve in the cold trap (53). CO, formic acid and ethylene pass through the gas flow meter (54) and enter the gas chromatograph. The concentration of gas products is monitored online in the gas chromatograph. After the reaction is complete, a small amount of electrolyte in the anolyte storage tank (72) and water in the cold trap (53) are taken and the concentrations of liquid products such as formic acid and ethanol are detected by nuclear magnetic resonance spectrometer.

6. A reaction system for the supercritical electroreduction of CO2, characterized in that, It includes a supercritical CO2 generation subsystem (1), an electrolyzer (2), a pressure balancing subsystem (4), a gas outlet subsystem (5), a circuit control subsystem (6), and an anolyte circulation subsystem (7) connected by pipelines. The electrolytic cell (2) is used for supercritical CO2 electroreduction and includes a gas chamber (21), an anolyte chamber (22), an ion exchange membrane (23), a catholyte chamber (24), and a cathode (25); the ion exchange membrane is an anion exchange membrane. The electrolytic cell (2) includes a first inlet (211), a second inlet (212), a third inlet (213), a first outlet (214), a second outlet (215), and a third outlet (216). The first inlet (211) is connected to the outlet of the steam generator (15) and the gas chamber (21), respectively. The second inlet (212) is connected to the anolyte circulation subsystem (7) and the anolyte chamber (22), respectively. The third inlet (213) is connected to the catholyte circulation subsystem (3) and the catholyte chamber (24), respectively. The first outlet (214) is connected to the pressure balance subsystem (4) and the gas chamber (21), respectively. The second outlet (215) is connected to the anolyte circulation subsystem (7) and the anolyte chamber (22), respectively. The third outlet (216) is connected to the catholyte chamber (24) and the catholyte circulation subsystem (3), respectively. The supercritical CO2 generating subsystem (1) is connected to the first liquid inlet (211) of the gas chamber (21) and is used to pressurize and heat the liquid CO2 sequentially before it enters the electrolytic cell (2). The liquid entering the electrolytic cell (2) includes liquid CO2 or supercritical CO2 carrying a certain concentration of water vapor. The circuit control subsystem (6) is connected to the electrolytic cell (2) via wires to provide the required voltage or current for the supercritical CO2 electrochemical reaction in the supercritical CO2 electrolytic cell; The anolyte circulation system is connected to the second inlet (212) and the second outlet (215) of the anolyte chamber (22) of the electrolytic cell, and is used to introduce anolyte into the anolyte chamber, and to receive the anolyte flowing back into the anolyte chamber (22) and the oxygen discharged from the anolyte chamber; The pressure balance subsystem (4) is connected to the first liquid outlet (214) of the gas chamber (21) and the top cavity of the anolyte storage tank (72) of the anolyte circulation subsystem (7) to ensure pressure balance within the system. The gas outlet subsystem (5) is connected to the pressure balance subsystem (4); The flow rate of supercritical CO2 in the reaction system is between 0.1 and 20 mL / min. -1 Within this range, the anolyte flow rate is 5-20 mL / min. -1 Within the range.

7. The supercritical CO2 electroreduction reaction system according to claim 1, characterized in that, The preset reaction pressure control value in the reaction system is greater than 7.38 MPa.

8. The supercritical CO2 electroreduction reaction system according to claim 1, characterized in that, The reaction pressure within the reaction system is controlled within the range of 5.5-7.38 MPa.

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