Decoupling type carbon dioxide electrochemical trapping system
By using a decoupled electrochemical carbon dioxide capture system, which utilizes the decoupled design of the anode and cathode regions and a non-electrochemical reduction and regeneration tower, the problems of stability and high energy consumption in existing electrochemical carbon dioxide capture under oxygen-containing environments are solved, achieving low-energy carbon dioxide capture and purification.
Patent Information
- Application Number
- CN202410535770.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-30
- Publication Date
- 2025-10-31
AI Technical Summary
Existing electrochemical carbon dioxide capture technology is difficult to operate stably in oxygen-containing environments and has high energy consumption. In particular, the effects of oxygen on the system and the instability of the three-phase reaction interface lead to electrode failure.
A decoupled carbon dioxide electrochemical capture system is adopted. Through the decoupling design of the anode and cathode regions, a proton-coupled electron transfer reaction is used to generate an acid-rich solution in the anode region and an alkaline-rich solution in the cathode region, which are used for carbon dioxide absorption and desorption, respectively. Combined with a non-electrochemical reduction and regeneration tower, low-energy carbon dioxide capture and purification are achieved.
A low-energy-consumption, continuous and stable electrochemical capture and purification process for carbon dioxide was achieved in an oxygen-containing environment, reducing energy consumption and expanding the range of PCET reactants, thereby improving the stability and efficiency of the system.
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Figure CN120860787A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of carbon dioxide capture technology, and more specifically, to a decoupled electrochemical carbon dioxide capture system. Background Technology
[0002] Air carbon dioxide capture involves absorbing and purifying extremely low concentrations of carbon dioxide (approximately 400 ppm) from the air to a high purity for subsequent storage or utilization. Currently, most air carbon dioxide capture technologies employ alkali metal hydroxide absorption, which uses alkali metal hydroxides to absorb carbon dioxide, forming corresponding alkali metal carbonates. Subsequent heating and desorption presents a high energy consumption bottleneck (8.0-10.0 GJ / ton of carbon dioxide). Existing electrochemical carbon dioxide capture technologies utilize electrochemical proton-coupled electron transfer (PCET) reactions to alter the pH environment of the solution, disrupting the absorption-desorption equilibrium of carbon dioxide in the solution, thereby achieving low-energy-consumption (<6 GJ / ton of carbon dioxide) air carbon dioxide capture and purification. A major challenge in using recycled hydrogen is that the electrochemical oxidation reaction requires a gas diffusion electrode. The difficult-to-control three-phase reaction interface easily causes electrode "flooding," leading to electrode failure and unstable reaction operation.
[0003] A major challenge in using organic PCET reactants lies in the impact of oxygen on system stability. Atmospheric carbon dioxide contains approximately 21% oxygen, and the presence of oxygen causes a rapid decay of electrochemical proton-coupled electron transfer reactants, making it difficult for the system to operate stably in a real carbon dioxide capture environment (containing O2). From a thermodynamic perspective, oxygen-resistant organic PCET reactants typically have high electrode potentials, inevitably leading to increased system energy consumption. Therefore, achieving low-energy-consumption and stable operation of the system in a real carbon dioxide capture environment (containing oxygen) is a critical technical challenge that urgently needs to be overcome in electrochemical carbon dioxide capture technology. Summary of the Invention
[0004] The present invention aims to solve at least one of the technical problems existing in the prior art.
[0005] Therefore, the present invention provides a decoupled electrochemical carbon dioxide capture system.
[0006] The present invention provides a decoupled electrochemical carbon dioxide capture system, comprising:
[0007] An electrolytic reactor includes an anode region, a cathode region, and a cation exchange membrane disposed between the cathode region and the anode region. The anode region contains a first medium, cations, and water molecules. The first medium undergoes a proton-coupled electron transfer reaction within the anode region, transforming from a reduced state to an oxidized state to produce an acid-rich anolyte. The cations carry water molecules through the cation exchange membrane into the cathode region. The cathode region contains water molecules, and a hydrogen evolution reaction occurs within the cathode region, decomposing the water molecules to produce hydrogen gas and hydroxide ions. The hydroxide ions combine with the cations entering the cathode region from the anode region to produce an alkaline-rich catholyte.
[0008] A carbon dioxide absorption tower receives a gas to be treated and an alkaline catholyte. The alkaline catholyte absorbs carbon dioxide contained in the gas to be treated within the carbon dioxide absorption tower and produces a liquid to be desorbed and a residual gas. The residual gas is discharged through the carbon dioxide absorption tower. The gas to be treated has at least a first concentration of carbon dioxide.
[0009] A carbon dioxide desorption tower is connected to an anode zone to receive an acid-rich anolyte and to a carbon dioxide absorption tower to receive a liquid to be desorbed. The acid-rich anolyte includes at least a first medium in an oxidized state and protons generated by a proton-coupled electron transfer reaction. Inside the carbon dioxide desorption tower, protons react with carbonate ions in the liquid to be desorbed to produce water and a second concentration of carbon dioxide. The second concentration is greater than the first concentration.
[0010] The decoupled electrochemical carbon dioxide capture system according to the above-described technical solution of the present invention may also have the following additional technical features:
[0011] In the above technical solution, the electrode potential used for the proton coupling electron transfer reaction in the anode region is higher than the potential for the hydrogen evolution reaction in the cathode region;
[0012] The potential at which the hydrogen evolution reaction occurs in the cathode region is the standard electrode potential of hydrogen gas or the standard electrode potential of hydrogen ions.
[0013] In the above technical solution, the first medium includes at least one of organic PCET reactants, inorganic PCET reactants, and polymers with PCET reaction performance;
[0014] Organic PCET reactants with PCET reactivity include, but are not limited to, pyridines, phenidines, quinones and their derivatives;
[0015] Inorganic PCET reactants with PCET reactivity include, but are not limited to, manganese hydroxide and nickel hydroxyl oxide;
[0016] Polymers with PCET reaction properties include, but are not limited to, polyaniline.
[0017] The above technical solution also includes:
[0018] A reduction and regeneration tower is connected to both the carbon dioxide desorption tower and the anode zone of the electrolysis reactor. The reduction and regeneration tower receives at least the residual medium after the desorption reaction is completed in the carbon dioxide stripping tower. The residual medium includes at least an oxidized first medium and cations released after the desorption reaction. In the reduction and regeneration tower, the oxidized first medium is mixed with hydrogen to undergo a non-electrochemical reduction and regeneration reaction to produce a reduced first medium. The reduced first medium and the cations released after the desorption reaction are circulated into the anode zone of the electrolysis reactor.
[0019] In the above technical solution, the non-electrochemical reduction and regeneration reaction uses a catalyst to react the oxidized first medium with hydrogen to produce the reduced first medium. The catalyst used includes, but is not limited to, platinum catalysts, platinum-carbon catalysts, or palladium-carbon catalysts.
[0020] The above technical solution also includes:
[0021] The gas-liquid separator is connected to the cathode zone of the electrolysis reactor and the carbon dioxide absorption tower, respectively. The hydrogen gas and alkaline catholy liquid generated in the cathode zone enter the gas-liquid separator for gas-liquid separation. The separated alkaline catholy liquid is sent to the carbon dioxide absorption tower, and the separated hydrogen gas is sent to the reduction and regeneration tower.
[0022] In the above technical solution, the cation includes, but is not limited to, one of potassium ions and sodium ions.
[0023] In the above technical solution, the concentration of hydroxide in the alkaline-rich cathode solution ranges from 1% to 32%.
[0024] In the above technical solutions, the catalysts used for the hydrogen evolution reaction in the cathode region include, but are not limited to, platinum-carbon catalysts, platinum-nickel coated mesh, or nickel foam.
[0025] In the above technical solution, the cation exchange membrane is a chlor-alkali perfluorinated ion membrane. Under normal working conditions, each cation can carry six water molecules into the cathode region simultaneously when it passes through the cation exchange membrane.
[0026] In summary, due to the adoption of the above-mentioned technical features, the beneficial effects of the present invention are:
[0027] This system enables the electrochemical capture and purification of ultra-low concentrations of carbon dioxide in an oxygen-containing carbon dioxide environment. In practical applications, the system can be powered by an external power source and utilizes an electrochemical PCET reaction to alter the pH environment at both the anode and cathode, promoting the absorption of OH- in the cathode region. - Enrichment and Anode Region H +Enrichment enables the absorption of ultra-low concentration carbon dioxide and the release of high-purity carbon dioxide. Hydrogen generated at the cathode is used to reduce and regenerate the anolyte outside the system, thereby achieving a low-energy-consumption, continuous, and stable carbon dioxide capture and purification process.
[0028] Additional aspects and advantages of the invention will become apparent in the following description or may be learned by practice of the invention. Attached Figure Description
[0029] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:
[0030] Figure 1 This is a schematic diagram illustrating the operating principle of a decoupled electrochemical carbon dioxide capture system according to an embodiment of the present invention.
[0031] Figure 2 This is a schematic diagram of the structure of a decoupled electrochemical carbon dioxide capture system according to an embodiment of the present invention;
[0032] Figure 3 This is a schematic diagram showing the results of a 280-hour electrolytic stability test of a decoupled carbon dioxide electrochemical capture system according to an embodiment of the present invention.
[0033] Figure 4 This is a schematic diagram illustrating the effect of the cathodic liquid in capturing air CO2 in a decoupled electrochemical carbon dioxide capture system according to an embodiment of the present invention.
[0034] in, Figure 1 and Figure 2 The correspondence between the reference numerals and component names in the attached drawings is as follows:
[0035] 1. External power supply; 2. Electrolysis reactor; 3. Anode zone; 4. Cation exchange membrane; 5. Cathode zone; 6. Gas-liquid separator; 7. Hydrogen dryer; 8. Carbon dioxide absorption tower; 9. Residual gas; 10. Gas to be treated; 11. Carbon dioxide desorption tower; 12. Carbon dioxide dryer; 13. Carbon dioxide collection bottle; 14. Reduction and regeneration tower; 15. Hydrogen storage tank. Detailed Implementation
[0036] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.
[0037] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and therefore the scope of protection of the invention is not limited to the specific embodiments disclosed below.
[0038] The following reference Figures 1 to 4 This describes a decoupled electrochemical carbon dioxide capture system provided according to some embodiments of the present invention.
[0039] Some embodiments of this application provide a decoupled electrochemical carbon dioxide capture system.
[0040] like Figure 1 As shown, the first embodiment of the present invention proposes a decoupled electrochemical carbon dioxide capture system, which includes at least: an electrolysis reactor, a carbon dioxide absorption tower and a carbon dioxide desorption tower.
[0041] The electrolytic reactor is connected to an external power source to obtain electrical energy for electrolysis. The electrolytic reactor includes an anode region, a cathode region, and a cation exchange membrane disposed between the cathode region and the anode region. The anode region is connected to the positive terminal of the external power source, and the cathode region is connected to the negative terminal of the external power source.
[0042] The anode region contains a first medium, cations, and water molecules. The first medium undergoes a proton-coupled electron transfer reaction within the anode region, transforming from a reduced state to an oxidized state. Specifically, Q represents the oxidized state of the first medium, and QH2 represents its reduced state. It is understood that although the reduced state of the first medium is represented as QH2, it does not simply mean adding two more hydrogen atoms to the oxidized state Q. Those skilled in the art should know that the difference in the number of hydrogen atoms between the reduced and oxidized states of the first medium depends on the specific compound. The reaction equation for the transformation of the first medium from the oxidized to the reduced state is: QH2 → Q + 2H₂ + +2e - During this process, under the excitation of an external power source, the first medium undergoes an electrochemical oxidation reaction, releasing H... + This increases the acidity of the anolyte, resulting in an acid-rich anolyte. The cations in the anolyte can carry water molecules across the cation exchange membrane into the cathode region. In some embodiments, the cations include, but are not limited to, at least one of potassium and sodium ions. The cathode region contains at least water molecules, and a hydrogen evolution reaction occurs there, decomposing the water molecules and producing hydrogen gas and hydroxide ions. The reaction equation for the hydrogen evolution reaction is: 2H₂O + 2e⁻. - →2OH - +H2; The hydroxide ions produced by the hydrogen evolution reaction combine with the cations entering the cathode region from the anode region to produce an alkaline catholy solution.
[0043] A carbon dioxide absorption tower receives the gas to be treated and an alkaline-rich catholyte. The alkaline-rich catholyte absorbs the carbon dioxide contained in the gas to be treated within the tower, producing a desorbed liquid and residual gas. The residual gas is discharged through the carbon dioxide absorption tower. The gas to be treated contains at least a first concentration of carbon dioxide. It is understood that the gas to be treated can be air, flue gas from a coal-fired power plant, factory exhaust gas, or transportation tail gas, etc., containing a relatively low concentration of carbon dioxide. Inside the carbon dioxide absorption tower, the reaction equation is: CO₂ + 2OH⁻ - →CO3 2- +H2O. Through the above reaction, carbon dioxide in the gas to be treated can be absorbed as much as possible, thus forming a liquid to be desorbed. The remaining gas is defined as the residual gas. When the gas to be treated is air, the residual gas mainly consists of oxygen (O2) and nitrogen (N2). The oxygen is separated and discharged in the carbon dioxide absorption tower, eliminating the influence of oxygen on the subsequent PCET reaction. It is understood that in this disclosure, the liquid medium in the cathode area of the electrolysis reactor is restricted to flow from the carbon dioxide absorption tower to the carbon dioxide absorption tower in the entire system medium flow direction, so oxygen in the carbon dioxide absorption tower will not enter the electrolysis reactor. In a specific embodiment, in order to further increase the isolation effect and absorption efficiency, the gas to be treated and the alkaline-rich cathode liquid can be introduced into the lower part of the carbon dioxide absorption tower respectively. After the two are in full contact, the generated residual gas is discharged from the top of the carbon dioxide absorption tower.
[0044] A carbon dioxide desorption tower is connected to the anode zone to receive acid-rich anolyte, and a carbon dioxide desorption tower is connected to a carbon dioxide absorption tower to receive the liquid to be desorbed. The acid-rich anolyte includes at least an oxidized first medium and protons generated by a proton-coupled electron transfer reaction, namely Q and H. + It is understandable that at this time, protons and hydrogen ions (H+) + The terms refer to the same thing. Inside the carbon dioxide desorption tower, protons react with carbonate ions in the liquid to be desorbed to produce water and a second concentration of carbon dioxide. The reaction equation is: 2H₂O → 2H₂O + +CO3 2- →H2O+CO2; Thus, the purification of carbon dioxide is completed, producing high-concentration carbon dioxide, that is, the second concentration is greater than the first concentration; under ideal conditions, the concentration of carbon dioxide output from the carbon dioxide desorption tower can reach more than 95%.
[0045] Through the above setup, electrochemical capture of low-concentration carbon dioxide can be achieved, eliminating the influence of oxygen on PCET reactants and reducing the requirements for PCET reactants. Specifically, in conventional electrolysis reactors without oxygen isolation, oxygen-resistant organic PCET reactants are required, and the electrode potential of the organic PCET reactants in an aqueous environment needs to be greater than the O2 or H2O2 potential, i.e., the electrode potential in the anode region needs to be above 0.7V. However, in this disclosure, the electrode potential used for the proton-coupled electron transfer reaction in the anode region only needs to be higher than the potential for the hydrogen evolution reaction in the cathode region, i.e., the electrode potential of the PCET reactants in this disclosure is greater than the H2 / H2O2 potential. + The electrode potential is sufficient; the standard electrode potential of hydrogen gas or hydrogen ions is approximately 0V, meaning the electrode potential in the anolyte region only needs to be higher than 0V. Using this system can significantly reduce energy consumption and expand the range of PCET reactants. For PCET reactants, only two requirements need to be met: first, the electrode potential of the PCET reactant should be higher than the hydrogen evolution reaction potential to ensure the spontaneous occurrence of the non-electrochemical reduction reaction; second, the PCET reactant must undergo reversible or quasi-reversible electron (electrochemical) reactions under the operating environment. - ) / proton(H + Only through the gain-loss reaction can the electrochemical acidification of the anolyte be ensured.
[0046] In some embodiments, the first medium includes at least one of organic PCET reactants, inorganic PCET reactants, and polymers having PCET reaction properties;
[0047] Organic PCET reactants with PCET reactivity include, but are not limited to, pyridines, phenidines, quinones and their derivatives, and their possible structures include, but are not limited to;
[0048]
[0049]
[0050] Wherein, Rn can be -H, -OH, -COOH, -SO3H, -NH2, -CH3, -O-, -S-, -CH 2- -F, -Cl, etc., n = 1, 2, 3...
[0051] Inorganic PCET reactants with PCET reaction properties include, but are not limited to, manganese hydroxide and nickel hydroxyl oxide.
[0052] Polymers with PCET reaction properties include, but are not limited to, polyaniline.
[0053] In some embodiments, a reduction and regeneration tower is also provided in the collection system to achieve stable circulation of the electrochemical collection system described above.
[0054] The reduction and regeneration tower is connected to both the carbon dioxide desorption tower and the anode zone of the electrolysis reactor. The reduction and regeneration tower receives at least the residual medium after the desorption reaction in the carbon dioxide desorption tower. It is understood that the liquid to be desorbed introduced into the carbon dioxide desorption tower contains at least the aforementioned cations in addition to carbonate ions, and the acid-rich anolyte introduced into the carbon dioxide desorption tower contains at least the oxidized first medium and hydrogen ions. The residual medium after the desorption reaction in the carbon dioxide desorption tower includes at least the oxidized first medium and the cations released after the desorption reaction. In the reduction and regeneration tower, the oxidized first medium mixes with hydrogen gas to undergo a non-electrochemical reduction and regeneration reaction, producing a reduced first medium. The reduced first medium and the cations released after the desorption reaction are then circulated back into the anode zone of the electrolysis reactor. This replenishes the cations, water, and reduced first medium in the anode zone.
[0055] In some embodiments, the non-electrochemical reduction and regeneration reaction uses a catalyst to react an oxidized first medium with hydrogen to produce a reduced first medium. The catalyst used includes, but is not limited to, a platinum catalyst, a platinum-carbon catalyst, or a palladium-carbon catalyst.
[0056] The chemical equation for the reaction inside the reduction and regeneration tower is: Q + H₂ → QH₂. The hydrogen used in the non-electrochemical reduction and regeneration reaction can be obtained from outside the system or from the hydrogen evolution reaction site inside the system.
[0057] Specifically, in some embodiments, the system further includes a gas-liquid separator. The gas-liquid separator is connected to the cathode zone of the electrolysis reactor, the carbon dioxide absorption tower, and the reduction and regeneration tower, respectively. Hydrogen gas and alkaline-rich catholyte generated in the cathode zone enter the gas-liquid separator for gas-liquid separation. The separated alkaline-rich catholyte is sent to the carbon dioxide absorption tower, and the separated hydrogen gas is sent to the reduction and regeneration tower. In one specific embodiment...
[0058] In the above embodiments, the reduction and regeneration of the first medium is carried out outside the electrolytic reactor. Under the action of the catalyst, the oxidized first medium undergoes a spontaneous redox reaction with H2 to produce the reduced first medium, and the cations are transported back to the anode area of the electrolytic reactor, thus realizing the reduction and regeneration cycle of the PCET reactants.
[0059] In some embodiments, the concentration of hydroxide in the alkaline catholyte ranges from 1% to 32%. Within this concentration range, complete absorption of carbon dioxide in the gas to be treated can be achieved.
[0060] In one specific embodiment, the cation exchange membrane is a chlor-alkali perfluorinated ion exchange membrane. Under normal operating conditions, each cation (potassium / sodium ion) can simultaneously carry six water molecules into the cathode region when passing through the cation exchange membrane, thereby generating a rich alkaline catholyte with a mass concentration of approximately 30%. Available cation exchange membranes include, but are not limited to: DuPont N2050, DuPont N2050K, DuPont N2030, DuPont N2030K, DuPont N2060, DuPont N2060K, and Dongyue DF2505, etc.
[0061] In some embodiments, if a hydrogen evolution electrode is used in the cathode region, the catalyst used for the hydrogen evolution reaction in the cathode region can be a platinum-carbon catalyst, a platinum-nickel plated mesh, or nickel foam, etc.
[0062] The decoupled electrochemical carbon dioxide capture system proposed in the above embodiments is used for carbon dioxide capture, comprising four main processes: external power supply, electrochemical PCET reaction to change the solution pH environment to capture and purify CO2, non-electrochemical reaction to reduce and regenerate organic PCET reactants, and mixing of anode and cathode electrolytes. This achieves a low-energy, stable electrochemical capture and purification process for air CO2. First, an external power supply provides energy for the electrochemical reaction. Second, an electrochemical hydrogen evolution reaction occurs at the cathode to generate OH-, and alkali metal ions in the anolyte pass through the cation exchange membrane to the cathode, forming an approximately 30% concentration alkaline solution for CO2 absorption, forming alkali metal carbonates. At the anode, an oxidation reaction of the organic PCET reactants occurs, releasing and enriching H+. + Alkali metal carbonates are transported to the anode and enriched with H₂. + The anolyte is then mixed with the rest of the solution, where a carbon dioxide desorption reaction occurs, releasing high-purity CO2. Finally, the hydrogen produced at the cathode, under the action of a catalyst, is used to reduce the organic PCET reactants at the anode, thus regenerating the anolyte. This disclosure uses organic PCET reactants on the anode side, avoiding the use of an anode H2 gas diffusion electrode. On the cathode side, a hydrogen evolution reaction occurs, simultaneously generating a high concentration of alkali metal hydroxides, accelerating the CO2 absorption rate and completely avoiding the influence of O2 in CO2 and dissolved oxygen in the cathode on the organic PCET reactants at the anode. Simultaneously, the H2 produced at the cathode can act as a reducing agent to regenerate the organic PCET reactants, thereby achieving continuous and stable operation of this electrochemical CO2 capture system.
[0063] Figure 2A schematic diagram of a decoupled electrochemical carbon dioxide capture system in a specific embodiment is shown, which includes an external power supply 1, an electrolytic reactor 2, a gas-liquid separator 6, a hydrogen dryer 7; a carbon dioxide absorption tower 8, a carbon dioxide desorption tower 11, a carbon dioxide dryer 12, a carbon dioxide collection bottle 13, a reduction and regeneration tower 14, and a hydrogen storage tank 15. The electrolytic reactor 2 includes an anode zone 3, a cation exchange membrane 4, and a cathode zone 5. The gas to be treated 10 is introduced into the carbon dioxide absorption tower 8, where carbon dioxide is absorbed, producing residual gas 9, which is discharged from the top of the carbon dioxide absorption tower 8.
[0064] Unlike the above embodiments, in this embodiment, the hydrogen separated from the gas-liquid separator 6 passes through the hydrogen dryer 7 and the hydrogen storage tank 15 in sequence before entering the reduction and regeneration tower 14, thereby improving the purity of the hydrogen entering the reduction and regeneration tower 14 and controlling the reduction and regeneration reaction time in the reduction and regeneration tower 14. When the reduction and regeneration reaction is not required, the hydrogen generated in the cathode area can be temporarily stored in the hydrogen storage tank 15.
[0065] Similarly, the high-concentration carbon dioxide produced by the carbon dioxide desorption tower 11 can pass through the carbon dioxide dryer 12 and then enter the carbon dioxide collection bottle 13, thereby completing the drying and collection of high-concentration carbon dioxide.
[0066] Specifically, the entire system can be designed as a simple, integrated device according to requirements, or it can be designed into a large-scale integrated device through series and parallel connections. It can be applied to carbon dioxide capture in environments including flue gas from coal-fired power plants, factory exhaust gas, transportation exhaust gas, and even the atmosphere. Moreover, it can operate continuously without interruption, without being limited by time or space.
[0067] The decoupled carbon dioxide electrochemical capture system proposed in this embodiment employs an asymmetric electrochemical reaction structure—that is, the cathode region performs the electrochemical hydrogen evolution reaction, while the anode region performs the electrochemical oxidation reaction of organic PCET reactants. The hydrogen generated in the cathode region is circulated outside the electrolysis system, where it spontaneously reduces and regenerates the oxidized organic PCET reactants in the anolyte under the action of a Pt catalyst. This system achieves continuous and stable circulation of organic PCET reactants by decoupling the electrochemical oxidation reaction of organic PCET from the non-electrochemical reduction reaction.
[0068] An electrochemical hydrogen evolution reaction occurs in the cathode region of this system, decomposing water to produce H2 and OH. -Simultaneously, due to charge balance, alkali metal ions at the anode permeate through the cation exchange membrane, generating an additional volume of high-concentration alkaline solution (approximately 30% by mass). This additional alkaline solution is used to absorb ultra-low concentrations of CO2, producing carbonates. The system employs a cation exchange membrane to separate the anode and cathode solutions, completely preventing interference from O2 on the anode organic PCET reactants on the cathode CO2 absorption side, thus enabling the direct capture of real oxygen-containing CO2 (atmosphere).
[0069] The anode of this system uses a water-soluble organic PCET reactant, which releases and enriches H through electrochemical oxidation. + The carbonate solution after absorbing CO2 is mixed with H2-enriched solutions. + The anolyte is then mixed with the solution, and the reaction produces high-purity CO2 and water, achieving CO2 purification and regeneration, while simultaneously regenerating alkali metal ions. Because the anode side involves only a solid-liquid two-phase electrochemical reaction, the use of a gas diffusion electrode is avoided, completely eliminating the electrochemical "gas-liquid-solid" three-phase reaction interface and significantly improving the system's long-term operational stability.
[0070] According to thermodynamic analysis, the redox potential of the organic PCET reactants is higher than the hydrogen potential under this environment, which ensures the spontaneous reduction of the organic PCET reactants by H2 under the action of a catalyst outside the electrochemical system. Simultaneously, the potential difference between the organic PCET reactants and the hydrogen evolution reaction reflects the theoretical minimum input energy. To ensure that the anolyte can be spontaneously reduced by hydrogen under the action of a catalyst, while avoiding high electrolysis energy consumption, this system uses pyrrolizine / isopyrrolizine derivatives (such as FMN), phenazine derivatives (such as DHPS, DHPC, BHPC), or anthraquinone derivatives (such as sodium anthraquinone-2,6-disulfonate, sodium anthraquinone-2,7-disulfonate) with suitable potentials as organic PCET reactants, achieving spontaneous reduction of the anolyte and a low-energy CO2 capture process.
[0071] The catalyst in the reduction and regeneration tower of this system can be activated carbon / spherical carbon / alumina supported platinum / palladium / nickel catalyst. This type of catalyst is widely used in industrial H2 reduction reactions, and its preparation is simple and low cost.
[0072] In one specific embodiment, such as Figure 3 As shown, when this system is used for electrolysis at a current density of 1000 A / m2, the voltage is stable for more than 280 hours, the average electrolysis voltage is 1.30 V, and the CO2 capture energy consumption is about 5.72 GJ / t, demonstrating the ability to generate catholyte with low energy consumption.
[0073] like Figure 4As shown, air was directly introduced into the alkaline-rich catholyte produced by electrolysis via a sampling pump, and the inlet carbon dioxide concentration, outlet carbon dioxide concentration, and gas flow rate were monitored in real time. Experimental results show that the alkaline-rich catholyte can absorb CO2 concentrations from approximately 420 ppm to approximately 60 ppm, demonstrating its extremely strong absorption capacity for ultra-low concentrations of CO2.
[0074] Figure 3 and Figure 4 Together, they demonstrate the system's ability to capture airborne CO2 with low energy consumption.
[0075] In this specification, the illustrative expressions of the terms used do not necessarily refer to the same embodiments or examples. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0076] Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention shall be included within the scope of protection of this invention.
Claims
1. A decoupled electrochemical carbon dioxide capture system, characterized in that, include: An electrolytic reactor includes an anode region, a cathode region, and a cation exchange membrane disposed between the cathode region and the anode region. The anode region contains a first medium, cations, and water molecules. The first medium undergoes a proton-coupled electron transfer reaction within the anode region, transforming from a reduced state to an oxidized state to produce an acid-rich anolyte. The cations carry water molecules through the cation exchange membrane into the cathode region. The cathode region contains water molecules, and a hydrogen evolution reaction occurs within the cathode region, decomposing the water molecules to produce hydrogen gas and hydroxide ions. The hydroxide ions combine with the cations entering the cathode region from the anode region to produce an alkaline-rich catholyte. A carbon dioxide absorption tower receives a gas to be treated and an alkaline catholyte. The alkaline catholyte absorbs carbon dioxide contained in the gas to be treated within the carbon dioxide absorption tower and produces a liquid to be desorbed and a residual gas. The residual gas is discharged through the carbon dioxide absorption tower. The gas to be treated has at least a first concentration of carbon dioxide. A carbon dioxide desorption tower is connected to an anode zone to receive an acid-rich anolyte and to a carbon dioxide absorption tower to receive a liquid to be desorbed. The acid-rich anolyte includes at least a first medium in an oxidized state and protons generated by a proton-coupled electron transfer reaction. Inside the carbon dioxide desorption tower, protons react with carbonate ions in the liquid to be desorbed to produce water and a second concentration of carbon dioxide. The second concentration is greater than the first concentration.
2. The decoupled electrochemical carbon dioxide capture system according to claim 1, characterized in that, The electrode potential used for the proton coupling electron transfer reaction in the anode region is higher than the potential used for the hydrogen evolution reaction in the cathode region. The potential at which the hydrogen evolution reaction occurs in the cathode region is the standard electrode potential of hydrogen gas or the standard electrode potential of hydrogen ions.
3. The decoupled carbon dioxide electrochemical capture system according to claim 1, characterized in that, The first medium includes at least one of organic PCET reactants, inorganic PCET reactants, and polymers with PCET reaction properties; Organic PCET reactants with PCET reactivity include, but are not limited to, pyridines, phenidines, quinones and their derivatives; Inorganic PCET reactants with PCET reactivity include, but are not limited to, manganese hydroxide and nickel hydroxyl oxide; Polymers with PCET reaction properties include, but are not limited to, polyaniline.
4. The decoupled electrochemical carbon dioxide capture system according to claim 1, characterized in that, Also includes: A reduction and regeneration tower is connected to both the carbon dioxide desorption tower and the anode zone of the electrolysis reactor. The reduction and regeneration tower receives at least the residual medium after the desorption reaction is completed in the carbon dioxide stripping tower. The residual medium includes at least an oxidized first medium and cations released after the desorption reaction. In the reduction and regeneration tower, the oxidized first medium is mixed with hydrogen to undergo a non-electrochemical reduction and regeneration reaction to produce a reduced first medium. The reduced first medium and the cations released after the desorption reaction are circulated into the anode zone of the electrolysis reactor.
5. The decoupled electrochemical carbon dioxide capture system according to claim 4, characterized in that, The non-electrochemical reduction and regeneration reaction uses a catalyst to react the oxidized first medium with hydrogen to produce the reduced first medium. The catalyst used includes, but is not limited to, platinum catalysts, platinum-carbon catalysts, or palladium-carbon catalysts.
6. The decoupled electrochemical carbon dioxide capture system according to claim 4, characterized in that, Also includes: The gas-liquid separator is connected to the cathode zone of the electrolysis reactor and the carbon dioxide absorption tower, respectively. The hydrogen gas and alkaline catholy liquid generated in the cathode zone enter the gas-liquid separator for gas-liquid separation. The separated alkaline catholy liquid is sent to the carbon dioxide absorption tower, and the separated hydrogen gas is sent to the reduction and regeneration tower.
7. The decoupled electrochemical carbon dioxide capture system according to claim 1, characterized in that, The cations include, but are not limited to, one of potassium ions and sodium ions.
8. The decoupled carbon dioxide electrochemical capture system according to claim 1, characterized in that, The concentration of hydroxide in the alkaline-rich catholyte ranges from 1% to 32%.
9. The decoupled electrochemical carbon dioxide capture system according to claim 1, characterized in that, The catalysts used for the hydrogen evolution reaction in the cathode region include, but are not limited to, platinum-carbon catalysts, platinum-nickel coated mesh, or nickel foam.
10. The decoupled electrochemical carbon dioxide capture system according to claim 1, characterized in that, The cation exchange membrane is a chlor-alkali perfluorinated ion exchange membrane. Under normal operating conditions, each cation can carry six water molecules into the cathode region simultaneously when passing through the cation exchange membrane.