A gas phase deoxygenation method and system based on quinone compound redox cycling

Abstract

This disclosure pertains to the field of oxygen separation technology, providing a gas-phase deoxygenation method and system based on a quinone compound redox cycle. The method includes: oxygen-containing gas entering a gas-liquid contact reactor via a gas inlet, contacting a working liquid containing reduced quinone compounds, and then exiting through a product gas outlet; the gas inlet and product gas outlet form an open single-pass gas flow path; the reacted working liquid is transported to an electrolysis unit, where the oxidized quinone compounds are electrochemically reduced and regenerated; the regenerated working liquid is returned to the gas-liquid contact reactor to form a working liquid cycle. The gas-liquid contact reactor can be a bubbling reactor or a hollow fiber membrane gas-liquid contactor, and the electrochemical regeneration voltage and / or current can be adjusted according to the working liquid color parameters. In an embodiment, oxygen-containing nitrogen gas with an inlet oxygen volume fraction of 1.2% is treated to achieve an outlet oxygen content of 4.5–5 ppm.

Description

Technical Field

[0001] This disclosure belongs to the field of oxygen separation technology and relates to a gas-phase deoxygenation method and system based on the redox cycle of quinone compounds. Background Technology

[0002] In applications such as food preservation, fine chemical storage, and industrial nitrogen refining, it is often necessary to reduce the oxygen content in the gas phase to parts per million (ppm) or below to ensure product quality and storage stability. For example, industrial nitrogen still contains 1% to 2% residual oxygen after initial separation, while downstream processes often require even lower oxygen content.

[0003] In existing technologies, membrane separation is often used for rough deoxygenation. Taking membrane separation for nitrogen production as an example, the purity of nitrogen obtained after air is separated by a single-stage membrane is usually 95% to 99.5%. When the oxygen concentration in the gas phase has dropped to a low level, the partial pressure difference across the membrane decreases significantly, the driving force for oxygen permeation is insufficient, and the separation efficiency drops sharply. If multi-stage membranes are used in series or catalytic deoxygenation and other post-treatment processes are added, the equipment size and energy consumption will increase significantly.

[0004] Pressure swing adsorption (PSA) is another commonly used gas separation method, which achieves separation by selectively adsorbing oxygen and nitrogen by an adsorbent at different pressures. However, when the goal is to further reduce the oxygen content from a lower level, PSA usually requires increasing the number of adsorption towers, extending the pressure equalization and rinsing time, and equipping it with complex valve switching and vacuum desorption systems. This results in larger equipment, increased footprint, and higher maintenance costs, making it difficult to meet the economic and flexibility requirements of small and medium-sized applications.

[0005] Besides the physical separation methods mentioned above, electrochemical deoxygenation technology has also attracted attention in recent years. For example, Chinese invention patent CN119977086B discloses an electrochemical deoxygenation system using silicotungstic acid as a redox mediator, which removes gaseous oxygen from a closed container by applying a constant voltage in a flowing electrolyzer. However, this method is mainly for cyclic deoxygenation of a limited-volume closed system. For example, it takes about 42 minutes to reduce the oxygen content in a 50 mL closed container from about 21% to below 5%, and several hundred minutes to further reduce it to the level of about 1%. It operates under constant voltage and does not dynamically adjust the electrochemical regeneration load according to the redox state of the mediator.

[0006] Therefore, there is still a lack of deep deoxygenation solutions in industry that can reduce the gas phase oxygen content to one part per million (ppm) or less while maintaining a compact and miniaturized system structure. Summary of the Invention

[0007] This disclosure provides a gas-phase deoxygenation method and system based on the redox cycle of quinone compounds, which can effectively solve the above-mentioned problems.

[0008] This disclosure is implemented as follows: On one hand, this disclosure provides a gas-phase deoxygenation method based on a quinone compound redox cycle, comprising: introducing oxygen-containing gas into a gas-liquid contact reactor via a gas inlet, allowing the oxygen-containing gas to contact a working liquid containing a water-soluble quinone compound in a reduced state in a single-pass flow, and discharging the resulting deoxygenated gas through a product gas outlet; conveying the working liquid containing the water-soluble quinone compound in an oxidized state after the reaction to an electrolysis unit, allowing the oxidized state to be electrochemically reduced to the reduced state on the cathode side of the electrolysis unit; and conveying the regenerated working liquid back to the gas-liquid contact reactor; wherein the gas inlet and the product gas outlet constitute an open single-pass gas flow path, the working liquid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

[0009] On the other hand, this disclosure provides a gas-phase deoxygenation system based on a quinone compound redox cycle, comprising: The gas-liquid contact reactor is equipped with a gas inlet, a product gas outlet, a working liquid inlet, and a working liquid outlet, and is used to contact oxygen-containing gas with a working liquid containing water-soluble quinone compounds in a reduced state. An electrolysis unit includes an anode, a cathode, and an ion-conducting membrane disposed between the anode and the cathode, wherein the cathode is used to electrochemically reduce the oxidized state of the water-soluble quinone compound to the reduced state; The working fluid circulation loop connects the working fluid outlet of the gas-liquid contact reactor with the cathode side of the electrolysis unit, and the cathode side of the electrolysis unit with the working fluid inlet of the gas-liquid contact reactor, and is equipped with a circulation drive device. A power source for applying an electrolysis voltage between the anode and the cathode; The gas inlet and the product gas outlet form an open single-pass gas flow path. The working fluid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

[0010] The beneficial effects of this disclosure are: The gas-phase deoxygenation system disclosed herein integrates the deoxygenation reaction and electrochemical regeneration into the same circulation loop, achieving "consumption-regeneration-reuse" of the deoxygenating agent through working fluid circulation. Experiments have confirmed that this system has a significant deoxygenation effect on oxygen-containing gases with inlet oxygen content ranging from 1.2% to 21%. Specifically, when using a hollow fiber membrane gas-liquid contactor to treat oxygen-containing nitrogen gas with an inlet oxygen volume fraction of 1.2%, the outlet oxygen concentration can reach 4.5–5 ppm, and the entire deoxygenation process can operate under normal temperature and pressure conditions.

[0011] Furthermore, the system uses a color recognition unit to collect the color parameters of the working fluid in real time. The control module compares the color parameters with preset thresholds and dynamically adjusts the electrolysis voltage and / or current accordingly, ensuring that the hydroquinone regeneration rate matches the deoxygenation load in real time, thus achieving automated operation and energy efficiency optimization. The system has a compact structure and is easy to operate and maintain, making it suitable for small to medium-scale applications sensitive to oxygen content, such as semiconductor packaging, lithium battery production, food preservation, and fine chemical storage. Attached Figure Description

[0012] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 Image (a) is a schematic diagram of a gas-phase deoxygenation system provided in an embodiment of this disclosure. Figure 1 (b) in the diagram is a physical image of the corresponding device.

[0014] Figure 2 In the example, (a) represents the redox potential of the three quinone molecules in this disclosure; Figure 2 (b) shows the molecular structures of three quinone molecules; Figure 2 (c) in the figure is the cyclic voltammogram of anthraquinone-2,6-disulfonic acid disodium at different scan rates; Figure 2 (d) in the figure represents the relationship between the redox peak current of anthraquinone-2,6-disulfonic acid disodium and the square root of the scan rate.

[0015] Figure 3 (a) in the image is the UV-Vis absorption spectrum of sodium anthraquinone-2-sulfonate; Figure 3 (b) in the figure shows the linear relationship between the absorption and concentration of sodium anthraquinone-2-sulfonate at a colorimetric wavelength of 410 nm; Figure 3 (c) in the figure is the UV-Vis absorption spectrum of the reduced state (anthraquinone state) of sodium anthraquinone-2-sulfonate; Figure 3 (d) in the figure represents the linear relationship between the absorption and concentration of the reduced state (anthraquinone state) of sodium anthraquinone-2-sulfonate at a colorimetric wavelength of 420 nm; Figure 3 (e) in the figure shows the color change of the working fluid reacting with oxygen over time.

[0016] Figure 4 (a) in the diagram is a logic flowchart for controlling the electrolysis voltage based on color recognition; Figure 4(b) shows the color differences of working solutions containing different concentrations of hydroquinone (top), machine recognition diagram (middle), and their color parameters (bottom); Figure 4 (c) represents the concentration-HSV-voltage index mapping relationship.

[0017] Figure 5 (a) in Example 3 shows the gas chromatograms of purine nitrogen before and after treatment by the gas phase deoxygenation system; Figure 5 (b) in the middle is Figure 5 A magnified view of the oxygen peak in (a) of the image.

[0018] Figure 6 (a) in Example 3 shows the gas chromatograms of air before and after treatment by the gas phase deoxygenation system. Figure 6 (b) in the middle is Figure 6 A magnified view of the oxygen peak in (a) (vertical axis magnified 100 times).

[0019] Figure 7 (a) is a schematic diagram of the gas phase deoxygenation system using a hollow fiber membrane gas-liquid contactor in Example 4; Figure 7 (b) in the figure represents the cyclic voltammetry curve of the electrolysis unit; Figure 7 (c) in the figure shows the oxygen concentration and electrochemical regeneration data during multiple start-ups and shutdowns of the system. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure. Therefore, the following detailed description of the embodiments of this disclosure provided in the accompanying drawings is not intended to limit the scope of the claimed disclosure, but merely represents selected embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0021] Please refer to Figure 1 This disclosure provides a gas-phase deoxygenation system based on a quinone compound redox cycle, comprising: The gas-liquid contact reactor is equipped with a gas inlet, a product gas outlet, a working liquid inlet, and a working liquid outlet, and is used to contact oxygen-containing gas with a working liquid containing water-soluble quinone compounds in a reduced state. An electrolysis unit includes an anode, a cathode, and an ion-conducting membrane disposed between the anode and the cathode, wherein the cathode is used to electrochemically reduce the oxidized state of the water-soluble quinone compound to the reduced state; The working fluid circulation loop connects the working fluid outlet of the gas-liquid contact reactor with the cathode side of the electrolysis unit, and the cathode side of the electrolysis unit with the working fluid inlet of the gas-liquid contact reactor, and is equipped with a circulation drive device. A power source for applying an electrolysis voltage between the anode and the cathode; The gas inlet and the product gas outlet form an open single-pass gas flow path. The working fluid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

[0022] A gas-liquid contact reactor is used to introduce oxygen-containing gas and discharge deoxygenated gas. After the oxygen-containing gas contacts the working fluid, the oxygen in the gas phase reacts with the reduced state of quinone compounds in the working fluid in a redox reaction, removing the oxygen and simultaneously oxidizing the reduced state of the quinone compounds to their oxidized state. The reduced state is the hydroquinone state of the corresponding quinone compound, and the oxidized state is the quinone state of the corresponding quinone compound. In some embodiments, the oxygen-containing gas contacts the working fluid in a bubbling manner or through a hollow fiber membrane gas-liquid contact tube. After this gas-liquid contact, the outlet oxygen content can be significantly reduced.

[0023] In some embodiments, the water-soluble quinone compound is selected from at least one of sodium anthraquinone-2-sulfonate, disodium anthraquinone-2,6-disulfonate, and sodium 1,2-naphthoquinone-4-sulfonate.

[0024] In some embodiments, the oxygen-containing gas is air, oxygen-containing nitrogen, or an oxygen-containing inert gas. For example, the oxygen-containing nitrogen refers to industrial nitrogen or crude nitrogen, whose oxygen content is typically 0.5% to 5%, such as nitrogen products that still contain a small amount of residual oxygen after preliminary separation. In some embodiments, the oxygen content in the oxygen-containing gas is 1.2%. The system of this disclosure can directly use oxygen-containing nitrogen as the inlet gas, significantly reducing its residual oxygen content through a single gas-liquid contact under normal temperature and pressure conditions, and the deoxidizer (reduced quinone compounds) can be continuously regenerated through electrochemical cycling, without one-time consumption.

[0025] In some embodiments, the flow rate of the oxygen-containing gas is 20–500 sccm (standard cubic centimeters per minute). This flow rate range covers two typical operating conditions: low flow rate with high oxygen content (e.g., 20 sccm air, 21% oxygen content) and high flow rate with low oxygen content (e.g., 200 sccm or 500 sccm nitrogen, 1.2% oxygen content). The oxygen molar loads (in O2) for these operating conditions are 4.2 sccm, 2.4 sccm, and 6 sccm, respectively. In some embodiments, the oxygen molar load of the oxygen-containing gas is 2–6 sccm (in O2), within which the system can achieve stable deep deoxygenation.

[0026] In some embodiments, the concentration of water-soluble quinone compounds in the working solution is 10-20 mM. That is, the total concentration of the oxidized and reduced states is 10-20 mM. At this concentration, the working solution has sufficient reducing equivalent reserve, enabling it to maintain a stable deoxygenation effect under continuous gas intake conditions.

[0027] Existing technologies use polyoxometalates such as silicotungstic acid as redox mediators. These mediators are electrochemically reduced to a reduced state capable of spontaneously reacting with oxygen, and the resulting oxidized mediator is then electrochemically reduced again. This type of technology avoids the direct electrochemical reduction of oxygen at the cathode surface and allows for mediator regeneration using non-precious metal cathodes such as carbon felt.

[0028] For example, existing silicotungstic acid electrochemical deoxygenation systems employ a two-electrode flow electrolytic cell separated by a proton exchange membrane. The silicotungstic acid-containing cathode electrolyte and the dilute phosphoric acid anolyte are circulated separately. The electrolytic cell is connected to a sealed container, and a pump drives the circulation of gas and electrolyte within the sealed container, gradually reducing the oxygen content in the sealed system under constant voltage conditions. This system is primarily used for cyclic deoxygenation in confined, sealed spaces, where the gas repeatedly circulates between the sealed container and the reaction zone, and the oxygen content gradually decreases over time.

[0029] The difference between this disclosure and the aforementioned technologies lies not only in the use of water-soluble quinone compounds to replace polyoxometalates, but also in the construction of a single-pass gas treatment process suitable for the deep purification of continuously flowing gases. The oxygen-containing gas to be treated enters the gas-liquid contact reactor through the gas inlet, comes into contact with the reduced working liquid containing quinone compounds, and is then directly discharged through the product gas outlet, without returning to the sealed container to form a closed gas cycle. The working liquid circulates between the gas-liquid contact reactor and the electrolysis unit, making the gas flow path and the working liquid circulation loop independent of each other.

[0030] In some embodiments, the electrolysis unit and the gas-liquid contact reactor can be spatially separated and connected by pipelines to form a working fluid circulation loop.

[0031] In other embodiments, the electrolysis unit and the gas-liquid contact reactor can also be integrated into the same housing, and functionally divided into a reaction zone and a regeneration zone by internal partitions or separation structures. The reaction zone and the regeneration zone are connected by a working fluid circulation loop to achieve the circulation of the working fluid between the gas-liquid contact reactor and the electrolysis unit. Regardless of whether the electrolysis unit and the gas-liquid contact reactor are deployed separately or integrated, the following conditions must be met: the gas flow path does not pass through the electrolysis unit, and the working fluid circulation loop is independent of the gas flow path.

[0032] The circulation drive device is used to drive the working fluid to circulate between the gas-liquid contact reactor and the electrolysis unit, to transport the working fluid containing the oxidized state of the water-soluble quinone compound after reacting with the oxygen-containing gas in the gas-liquid contact reactor to the electrolysis unit, so that the oxidized state is electrochemically reduced to the reduced state on the cathode side; and to transport the regenerated working fluid back to the gas-liquid contact reactor.

[0033] In some embodiments, a hollow fiber membrane gas-liquid contactor is used as the gas-liquid contact reactor, which can enhance the gas-liquid mass transfer efficiency between the low-oxygen gas and the working fluid, allowing oxygen to transfer from the gas phase to the liquid phase in a shorter contact time and react with the reduced state of quinone compounds. Unlike existing silicotungstic acid electrochemical deoxygenation systems, which require long-term circulation of high-oxygen-content gas in a closed system to reduce the oxygen content from about 21% to about 1%, this disclosure can be directly used for end-point deep purification of low-oxygen nitrogen gas (e.g., oxygen content of 1% to 2%) after membrane separation or pressure swing adsorption treatment, and can further reduce the residual oxygen concentration to trace oxygen levels under continuous gas flow conditions. In addition, existing silicotungstic acid electrochemical deoxygenation systems operate in a constant voltage mode, and the mediator regeneration load is not adjusted according to the working fluid state. This disclosure can further utilize the color or spectral differences between the oxidized and reduced states of quinone compounds to determine the deoxygenation capacity of the working fluid online and adjust the electrolysis voltage and / or current to match the electrochemical regeneration rate with the continuous gas deoxygenation load. Therefore, this disclosure forms a technical combination of "open single-pass gas flow path - gas-liquid contact - working fluid circulation - electrochemical regeneration - working fluid state feedback control", which solves the problem of deep purification at the end of continuous flow of low oxygen gas, rather than the problem of cyclic decay of oxygen concentration in a closed system with limited volume.

[0034] The specific chemical reaction pathways disclosed herein are as follows: Deoxygenation step: Oxygen-containing gas is passed into the working liquid containing reduced quinone compounds. The oxygen in the gas phase reacts with the reduced quinone compounds in the liquid phase in a redox reaction. The reduced quinone compounds are oxidized to their oxidized state, and the oxygen is reduced, resulting in a decrease in the oxygen content of the gas phase. After the reaction, the concentration of the reduced state (hydroquinone molecules) in the working liquid decreases, while the concentration of the oxidized state (quinone molecules) increases, thus reducing the deoxygenation capacity. The reaction equation for this step is: (Where H2Q represents the reduced state of quinone compounds and Q represents the oxidized state).

[0035] Regeneration Step (Electrochemical Reduction): The working solution containing quinone compounds in their oxidized state after the reaction is transported to the electrolysis unit. Under the action of an applied electrolysis voltage, the oxidized state gains electrons and combines with protons on the cathode side, thus being reduced to the reduced state. This electrochemical reduction step is spatially separated from the deoxygenation step to avoid interference from gaseous oxygen in the reduction reaction. The reaction formula for this step is: Electrochemical reduction uses electrons as a clean reducing agent to directly drive the interconversion between oxidized and reduced states. Compared with chemical reduction, electrochemical reduction has multiple advantages, including: (1) electrons as a reducing agent do not produce chemical byproducts, and the reduction process is clean; (2) the reaction can be carried out at room temperature and pressure, without the need for high temperature and high pressure conditions, and without the need to introduce flammable and explosive reducing gases such as hydrogen; (3) the reduction rate can be precisely controlled by adjusting the electrolysis voltage and / or current, thereby dynamically matching the deoxygenation load.

[0036] The recycling step (working fluid reflux) involves returning the regenerated working fluid, containing quinone compounds in its reduced state, to the deoxygenation step to participate in the gas-phase deoxygenation reaction again, forming a closed-loop cycle of "consumption-regeneration-reuse". This cycle transforms the reduced state from a one-time consumption to continuous regeneration, allowing the method to operate continuously for a long time without the need for external replenishment of deoxygenating agents. The steady-state maintenance of the recycling process requires the following equilibrium relationship: regeneration rate ≥ deoxygenation consumption rate. This recycling mechanism fundamentally solves the core pain points of reagent consumption and waste treatment in traditional chemical deoxygenation methods, enabling the gas-phase deoxygenation process to operate in a green, continuous, and economical manner.

[0037] In some embodiments, an ion-conducting membrane is provided between the cathode and anode sides of the electrolysis unit. This ion-conducting membrane forms an ion conduction pathway between the cathode and anode sides and reduces the migration of quinone compounds to the anode side. The ion-conducting membrane can be selected from cation exchange membranes, anion exchange membranes, bipolar membranes, or other membranes with ion-conducting capabilities, depending on the acidity or alkalinity of the working solution, the types of ions involved in the conduction, and the structure of the electrolysis unit.

[0038] In acidic proton conduction systems, proton exchange membranes or cation exchange membranes can be used; in neutral or alkaline systems, ion exchange membranes suitable for the corresponding ion conduction can be used. In membrane electrode structures, the ion-conducting membrane can also form a continuous ion-conducting interface with a catalyst layer containing ionomers.

[0039] In some specific embodiments, the ion-conducting membrane is a Nafion 117 membrane, and the working solution is an aqueous solution containing perchloric acid, which is suitable for proton-conducting electrolysis structures.

[0040] In some embodiments, the working solution may contain a supporting electrolyte to improve the ionic conductivity of the working solution, reduce the internal resistance of the electrolytic unit, and maintain the electrochemical reduction reaction of the quinone compound. The supporting electrolyte can be selected based on the quinone compound used, the electrode material, the ion-conducting membrane, and the structure of the electrolytic unit; for example, an acid, base, or salt supporting electrolyte may be used. The working solution may be an acidic, neutral, or alkaline aqueous solution.

[0041] When using carbon felt, carbon cloth, carbon paper, metal felt, or other porous conductive electrodes immersed in the working fluid, the working fluid itself undertakes the main ion conduction function. Therefore, an appropriate amount of supporting electrolyte can be added to improve ionic conductivity and electrochemical regeneration efficiency.

[0042] When a membrane electrode structure is used, the cathode may include a thin catalytic layer loaded on or adjacent to the ion-conducting membrane, the catalytic layer containing a catalyst and an ionomer. The ion-conducting membrane and the ionomer in the catalytic layer form an ion conduction pathway, while the conductive components in the catalytic layer form an electron conduction pathway. With this structure, the concentration of the supporting electrolyte in the working solution can be reduced, or an external supporting electrolyte can be omitted. "Adjacent to the ion-conducting membrane" means that the distance between the catalytic layer and the ion-conducting membrane is within the effective ion conduction range of the catalytic layer, allowing a continuous ion conduction pathway to be formed between the ionomer in the catalytic layer and the ion-conducting membrane. In some embodiments, this distance is 0–500 μm.

[0043] In some embodiments, the supporting electrolyte is perchloric acid, sulfuric acid, phosphoric acid, alkali metal hydroxides, alkali metal sulfates, phosphates, or other substances that can improve the ionic conductivity of the liquid phase without significantly interfering with the redox cycle of quinone compounds. In some specific embodiments, a 0.05–0.2 M aqueous solution of perchloric acid is used as the supporting electrolyte. The above-mentioned supporting electrolytes and their concentrations are merely examples and do not constitute a limitation on the scope of protection of this disclosure.

[0044] In some embodiments, the cathode is a carbon felt, carbon cloth, carbon paper, graphite felt, metal felt, foamed metal, or other porous conductive electrode. The porous structure provides a larger electrochemical reaction interface and allows the working fluid to flow within the electrode channels, thereby promoting the mass transfer of quinone compounds to the electrode surface.

[0045] In other embodiments, the cathode is a catalyst layer in the membrane electrode structure. The catalyst layer comprises a conductive catalytic material and an ionomer, and is disposed on the surface of or adjacent to the ion-conducting membrane. The thickness of the catalyst layer can be adjusted according to the requirements of electron conduction, ion conduction, and quinone compound mass transfer. By reducing the thickness of the catalyst layer and establishing a continuous ionomer conduction network, the necessity of a liquid-phase supporting electrolyte for the electrochemical regeneration process can be reduced.

[0046] The anode can be made of titanium, titanium felt, porous titanium, coated titanium, carbon materials, metal oxide electrodes, or other electrode materials capable of performing the corresponding anodic reaction. The anodic reaction can be selected based on the electrolyte conditions and the structure of the electrolysis unit.

[0047] The system disclosed herein utilizes the significant spectral difference (color-changing effect) between the oxidized and reduced states of quinone compounds in the visible light region to transform microscopic chemical reaction processes into macroscopic visual signals. This allows the system to achieve accurate identification of the deoxidizer state and real-time closed-loop adjustment of electrolysis voltage / current without the need for expensive electrochemical sensors, requiring only a low-cost machine vision module. The oxidized state (Q) and reduced state (H₂Q) of quinone compounds exhibit significantly different absorption characteristics in the visible light region. The oxidized state has characteristic absorption in the 400–410 nm wavelength range, resulting in a transparent, slightly yellow to pale yellow solution; the reduced state shows enhanced absorption in the 400–450 nm wavelength range, resulting in a deep yellow-green to blackish-green solution. This color difference is the physical basis for the optical detection achieved by the system disclosed herein.

[0048] Specifically, the color recognition unit is composed of a constant LED light source and a color recognition module. The LED light source provides stable broadband illumination, eliminating the interference of ambient light fluctuations on detection accuracy; the color recognition module periodically acquires image frames of the working liquid in the gas-liquid contact reactor and extracts color parameters. The color parameters include HSV hue, saturation, and brightness.

[0049] To achieve automated closed-loop feedback, the control module has a pre-set index mapping relationship between color, concentration, and electrochemical parameters. These electrochemical parameters include voltage and / or current. During operation, the control module operates without manual intervention, executing the following data processing flow: The control module receives the color signal output by the color recognition unit and extracts the color parameters. The extracted color parameters are compared with the pre-set index mapping relationship. When the comparison determines that the real-time color parameter is close to the characteristic parameter of the oxidized state (e.g., the HSV value corresponding to a transparent, slightly yellow solution), it indicates a decrease in the system's deoxygenation capacity and an increase in load, and the control module immediately generates an adjustment command to increase the electrolysis voltage / current. When the comparison determines that the real-time color parameter is close to the characteristic parameter of the reduced state (e.g., the HSV value corresponding to a deep yellow-green solution), it indicates sufficient reducing equivalent in the working solution, and the control module generates a command to decrease or maintain the current electrolysis voltage. This machine vision feedback control logic, based on offline calibration of the correspondence between color parameters and concentration ranges, transforms the traditional electrochemical trial-and-error voltage regulation process into objective and precise computer data instruction execution steps. This enables real-time matching of the reduced regeneration rate with the deoxygenation load, achieving dynamic optimization of power distribution. Furthermore, this control logic directly utilizes the intrinsic optical properties of quinone / hydroquinone molecules, eliminating the need for complex chemical analysis or electrochemical impedance fitting, resulting in fast response and intuitive, reliable judgment. In some implementations, the control module includes a hardware platform and a computer-based control program running on it, achieving bidirectional data interaction with the color recognition unit and the controllable power supply via a serial communication protocol. The system is configured with dual independent serial communication channels: the vision data channel receives detection data sent by the color recognition unit, and the power control channel sends voltage / current setting instructions to the controllable power supply. The system has a built-in color state manager; upon receiving a color data frame, it performs index mapping to a preset color database, triggering corresponding voltage / current output instructions to complete dynamic automatic control.

[0050] The controllable power supply receives control commands generated by the control module and dynamically adjusts the output electrolysis voltage / current to match the reduction regeneration rate with the deoxygenation load in real time, avoiding energy waste or insufficient regeneration under constant pressure operation, and achieving a balance between automated operation and energy efficiency optimization.

[0051] Unlike traditional electrochemical deoxygenation systems that rely on electrical signals such as current and voltage to indirectly infer the system state, the color recognition feedback of the system disclosed in this invention directly reflects the redox state of quinone compounds in the working fluid, without directly relying on electrical signals such as electrode current or cell voltage. This can reduce the influence of electrode state or membrane resistance changes on the judgment of the working fluid state.

[0052] The color recognition unit establishes a correspondence between HSV color parameters and reduced state concentration ranges through offline calibration, and pre-sets this correspondence in the control module in the form of a color-concentration-electrochemical parameter index mapping. During operation, the control module determines the degree of deoxidizer consumption and generates corresponding adjustment commands based on the comparison between real-time HSV parameters and the preset index mapping.

[0053] In some implementations, the electrolysis voltage is adjusted in the range of 1.4 to 3 V, which is dynamically matched to the reduced concentration range: low voltage is used when the reduced concentration is high to save energy, and high voltage is used when the reduced concentration is low to accelerate regeneration.

[0054] Furthermore, the system disclosed herein can achieve deep deoxygenation (oxygen content ≤ 5 ppm) using a single gas-liquid contact reactor and electrolysis unit in a circulating combination, and the system size is less than 10 × 20 × 30 cm. 3 Compared to pressure swing adsorption, which requires multiple parallel towers, complex valve control and vacuum desorption systems, and membrane separation nitrogen production processes, which require multiple series stages and post-processing steps for deep oxygen removal, the system equipment disclosed in this paper has a small footprint and is easy to operate and maintain. It is especially suitable for laboratories, small and medium-sized production lines, and other scenarios where space and flexibility are required.

[0055] This disclosure provides a gas-phase deoxygenation method based on the redox cycle of quinone compounds, comprising: Oxygen-containing gas is introduced into the gas-liquid contact reactor through the gas inlet, so that the oxygen-containing gas comes into contact with the working liquid containing water-soluble quinone compounds in a reduced state in a one-pass flow manner, and the resulting deoxygenated gas is discharged through the product gas outlet. The working solution containing the oxidized form of the water-soluble quinone compound after the reaction is transported to the electrolysis unit, whereby the oxidized form is electrochemically reduced to the reduced form at the cathode side of the electrolysis unit. The regenerated working fluid is then transported back to the gas-liquid contact reactor. The gas inlet and the product gas outlet form an open single-pass gas flow path. The working fluid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

[0056] The following specific embodiments further illustrate the system of this disclosure and its deoxygenation effect.

[0057] Example 1 Three commercially available quinone molecules with good solubility and stability were selected: sodium anthraquinone-2-sulfonate, disodium anthraquinone-2,6-disulfonate, and sodium 1,2-naphthoquinone-4-sulfonate, whose molecular structures are shown below. Figure 2 As shown in (b) above. The three molecules were electrochemically characterized using cyclic voltammetry, and the results are as follows. Figure 2As shown in (a), all three quinone molecules exhibit highly symmetrical redox peaks with small potential differences, indicating their excellent electrochemical reversibility. This reversibility means that the redox transformation between quinone molecules and their corresponding hydroquinone states is easy to carry out, requires a small overpotential, and has high electrochemical regeneration efficiency, making them suitable as deoxygenation active components that can be recycled through electrochemical reduction. Furthermore, variable scan rate tests were performed on the three molecules. The test results for the anthraquinone-2,6-disulfonic acid disodium molecule are shown below. Figure 2 As shown in (c) and (d) in the figure. Figure 2 (c) shows the results at different scan rates (from 0.02 V·s). -1 up to 0.2 V·s -1 The cyclic voltammetry curves were obtained under [a certain condition]. With increasing scan rate, the current densities of both the oxidation and reduction peaks increased significantly. Figure 2 (d) shows a highly linear relationship between the redox peak current and the square root of the scan rate, with a coefficient of determination Rd. 2 =0.997. The other two quinone molecules also showed similar linear characteristics, indicating that the quinone molecule-hydroquinone molecular system exhibits obvious diffusion-controlled electrochemical response under the test conditions and can undergo reversible electrochemical redox transformation.

[0058] Example 2 The spectral absorption characteristics of quinone compounds in their oxidized (Q) and reduced (H₂Q) states were determined using ultraviolet-visible spectrophotometry. A series of Q solutions (0.016–10 mM) were prepared, and their ultraviolet-visible absorption spectra were measured. The test results for the anthraquinone-2-sulfonate sodium molecule in its oxidized (Q) state are shown below. Figure 3 As shown in (a), it exhibits characteristic absorption in the chromogenic region of 400–410 nm. A graph was plotted comparing the absorbance at 410 nm with the concentration, as shown below. Figure 3 As shown in (b), a good linear relationship is observed, with a coefficient of determination R0. 2 =0.979. Similarly, a series of H₂Q solutions of different concentrations were prepared, and their UV-Vis absorption spectra were measured. The test results of sodium anthraquinone-2-sulfonate in the reduced state (H₂Q) solution are as follows: Figure 3 As shown in (c), it exhibits significant absorption in the chromogenic region of 400–450 nm. A plot of absorbance at 420 nm versus concentration is extracted, as shown below. Figure 3 As shown in (d), a good linear relationship is observed, with a coefficient of determination Rd. 2 =0.902. The other two quinone molecules also exhibited similar spectral characteristics and a linear relationship with concentration. The above results indicate that, for both quinone molecules and hydroquinone molecules, there is a quantitatively analyzable linear relationship between concentration and color, and the color development differences between the two are significant and easily distinguishable.

[0059] Oxygen (99.99% purity) was bubbled into the reaction tank containing the working solution at a flow rate of 20 sccm. The working solution was a mixed aqueous solution of 10 mM sodium anthraquinone-2-sulfonate (hydroquinone molecule) and 0.1 M HClO4. The solution was initially dark green. Figure 3 As shown in (e), as the deoxygenation reaction proceeds, hydroquinone molecules are consumed and converted into oxidized quinone molecules. The solution color gradually lightens within 60 seconds, eventually becoming transparent with a slight yellow tint. This rapid color change phenomenon indicates that: firstly, the color change between the oxidized and reduced states can serve as a direct indicator of the reaction progress; secondly, the reaction kinetics between oxygen and the reduced state of quinone compounds are rapid, making the reduced state of quinone compounds suitable for use as a deoxygenating agent; and thirdly, the short residence time of the bubbles allows the reaction to proceed fully.

[0060] To verify the feasibility of color recognition, such as Figure 4 As shown in (b), four groups of anthraquinone-2-sulfonate sodium solutions (including their oxidized and reduced states) were pumped into cuvettes in a mixed aqueous solution of 0.1 M HClO4. The total concentration of the oxidized and reduced states in each group was 10 mM, and the concentrations of the reduced state in groups 1-4 were 8 mM, 6 mM, 4 mM, and 0 mM, respectively (the remainder being the oxidized state). Under a constant LED light source, images of the four solutions were simultaneously acquired by a color recognition unit, and HSV color parameters were extracted. When the solution contained 8 mM of hydroquinone molecules, the extracted HSV parameters were: Hue 59°, Sat. 10%, Value 8%; when the deoxygenating agent was depleted and completely converted into quinone molecules, the HSV parameters changed to: Hue 55°, Sat. 13%, Value 90%. Furthermore, by setting a specific HSV threshold range, selective identification of solutions at different oxidation stages can be achieved: when the HSV parameter matches the current oxidation stage, the solution area in the image frame is displayed normally, while solution areas in other oxidation stages are identified as background (displayed as black), indicating that machine vision can distinguish specific quinone / hydroquinone molecule ratios based on HSV color parameters. This result demonstrates that the color difference between quinone and hydroquinone molecules is significant and can be selectively identified through HSV color parameter thresholds, providing an intuitive and reliable basis for online determination of deoxidizer status.

[0061] To achieve automated feedback control, offline calibration establishes the correspondence between HSV color parameters and reduced-state concentration ranges, and forms a color-concentration-voltage index mapping (e.g., ...). Figure 4 As shown in (c)). Figure 4As shown in (a), during operation, the control module compares the real-time collected HSV parameters with the preset index to determine the degree of consumption of the reduced state of quinone compounds and triggers corresponding voltage adjustment commands. When the system identifies characteristic parameters that the solution color is close to the oxidized state, it indicates that the deoxygenation capacity of the working solution has decreased, and the control module immediately increases the electrolysis voltage to accelerate the regeneration of the reduced state of quinone compounds; conversely, it decreases the electrolysis voltage to achieve energy efficiency optimization.

[0062] Example 3 Please refer to Figure 1 In (a) and (b) of this disclosure, embodiments provide a gas-phase deoxygenation system based on a quinone compound redox cycle.

[0063] The gas-liquid contact reactor is equipped with a gas inlet and a product gas outlet. The inlet is used to introduce oxygen-containing gas to be treated, and the product gas outlet is used to discharge the treated deoxygenated gas. The working solution is a mixed aqueous solution of 20 mM anthraquinone-2-sulfonate sodium and 0.1 M HClO4.

[0064] The electrolysis unit consists of two cylindrical chambers measuring 6 cm × 10 cm, separated by a Nafion 117 membrane. The anode is a titanium electrode array with dimensions of 6 electrodes × 5 cm × 9 cm, and the cathode is a carbon felt electrode with dimensions of 9 cm × 50 cm, wound around a graphite plate. The graphite plate acts as a current collector to achieve conductivity and current collection.

[0065] The circulation drive device is a circulation pump, which drives the working fluid to circulate between the gas-liquid contact reactor and the electrolysis unit.

[0066] The power supply is a KA6005P programmable power supply, and the color recognition unit is an ESP32 camera module.

[0067] The specific operation steps are as follows: Step 1: Following the same method as in Example 2, recalibrate the correspondence between HSV color parameters and reduced state concentration range offline with a total concentration of 20 mM as the baseline, and establish a color-concentration-voltage index mapping suitable for the operating concentration of this example.

[0068] Step 2: Turn on the computer control program, circulation pump, and power supply in sequence. Start the working fluid circulation loop, allowing the working fluid to circulate between the gas-liquid contact reactor and the electrolysis unit at a flow rate of 20 mL / min; simultaneously, the control module automatically adjusts the electrolysis voltage applied to the anode and cathode based on the real-time collected HSV color parameters of the working fluid.

[0069] Step 3: The oxygen-containing gas to be treated is continuously introduced into the working fluid at a predetermined flow rate through the gas inlet, and the resulting deoxygenated gas is discharged from the gas-liquid contact reactor through the product gas outlet.

[0070] Step 4: After the system has stabilized (usually about 2 minutes), take a sample from the product gas outlet and introduce it into a gas chromatograph to detect the oxygen content.

[0071] Experiment 1: The oxygen-containing gas to be treated was nitrogen (purity approximately 99%, with an O2 content of 1.2% as determined by gas chromatography), and the flow rate was 200 sccm. Gas chromatographic data of the gas before and after deoxygenation treatment are as follows: Figure 5 As shown in (a), the oxygen peak of the gas almost disappears after deoxygenation. A magnified view of the oxygen peak reveals... Figure 5 As shown in (b) in the figure, the oxygen content of the deoxygenated gas is 0.052% after integral calculation.

[0072] Experiment 2: The oxygen-containing gas to be treated was air (O2 content approximately 21%), and the flow rate was 20 sccm. Gas chromatographic data of the gas before and after deoxygenation are as follows: Figure 6 As shown in (a), similarly, the oxygen peak of the gas almost disappears after deoxygenation. After magnifying the oxygen peak locally and multiplying the ordinate by 100, as shown... Figure 6 As shown in (b) in the figure, the oxygen content of the deoxygenated gas is 0.067% after integral calculation.

[0073] This embodiment uses perchloric acid as the supporting electrolyte to adapt to the carbon felt immersion cathode and proton exchange membrane structure; this specific electrolyte condition does not constitute a limitation on other acidic, neutral, alkaline or electrolytic structures without external supporting electrolyte.

[0074] Example 4 This disclosure provides a continuously operating gas-phase deoxygenation system based on a quinone compound redox cycle, employing a hollow fiber membrane gas-liquid contactor. Please refer to [link / reference]. Figure 7 (a) in the middle.

[0075] The gas phase deoxygenation system includes a plate-shaped electrolysis unit and an oxygen concentration analyzer.

[0076] The plate-shaped electrolysis unit consists of clamp-type end plates, sheet-shaped carbon felt (cathode), sheet-shaped titanium felt and porous titanium gas diffusion electrode (anode), and a Nafion 117 membrane disposed between the two, which divides the electrolysis cell into a cathode side and an anode side. The electrode reaction area is 3 cm × 3 cm, and the internal resistance of the electrolysis cell is approximately 1 Ω. A 0.1 M HClO4 aqueous solution is introduced to the anode side, and a mixed aqueous solution of 20 mM anthraquinone-2-sulfonate and 0.1 M HClO4 is introduced to the cathode side. The cyclic voltammogram of the electrolysis unit is shown below. Figure 7 As shown in (b), a significant electrochemical reaction occurs at a voltage of approximately 1.4 V.

[0077] The gas-liquid contact reactor is a hollow fiber membrane gas-liquid reaction tube (model WH-PP-300). The hollow fiber membrane is made of porous polyethylene with a pore size of 0.01~0.2 μm. Gas flows through the inside of the hollow fiber membrane tube, and the working fluid flows through the outside of the hollow fiber membrane tube.

[0078] The oxygen concentration analyzer used is the JNL-500 online trace oxygen analyzer.

[0079] The circulation drive device is a circulation pump, which drives the working fluid to circulate between the gas-liquid contact reactor and the electrolysis unit.

[0080] Nitrogen gas (approximately 99% purity, with an oxygen content of 1.2% as determined by gas chromatography) was continuously introduced into the hollow fiber membrane tube. During normal system operation, the gas flow rate was 100 sccm. A constant voltage of 1.8 V was applied to the electrolysis unit to electrochemically reduce the oxidized quinone compounds in the working fluid to their reduced state. Simultaneously, the working fluid was driven to circulate between the gas-liquid contact reactor and the electrolysis unit at a flow rate of 20 mL / min. After approximately 10 minutes, the working fluid filled the gas-liquid contact reactor and established a stable circulation.

[0081] When performing outlet oxygen concentration testing, briefly adjust the inlet nitrogen flow rate to 500 sccm and connect it to a JNL-500 online trace oxygen analyzer. Figure 7 As shown in (c), the outlet oxygen concentration was measured to be stable at 4.5~5 ppm.

[0082] During system operation, several shutdown and restart tests were conducted, with shutdown durations ranging from several hours to overnight. Upon restart, because the reduced quinone compounds in the working fluid were not electrochemically regenerated and replenished during the shutdown, and were continuously consumed by residual oxygen in the system and trace amounts of oxygen infiltrating from the environment, the concentration of oxidized compounds in the working fluid increased and the concentration of reduced compounds decreased. Therefore, the cathode reduction reaction rate was high after the electrolytic unit started, resulting in a large instantaneous current spike (e.g., ...). Figure 7 (As indicated by the circled dots in (c)). As the electrolysis unit continues to operate, the oxidized state in the working solution is gradually reduced to the reduced state, and the current density gradually decreases and stabilizes at approximately 28 mA·cm⁻¹. -2 This indicates that the system has reached a relatively stable working fluid regeneration state under the above operating conditions. The current spike reflects the natural depletion of the working fluid's reduced state reserve during shutdown and the recovery process upon restart, rather than a sudden increase in oxygen load during continuous operation.

[0083] This embodiment uses perchloric acid as the supporting electrolyte to adapt to the carbon felt immersion cathode and proton exchange membrane structure; this specific electrolyte condition does not constitute a limitation on other acidic, neutral, alkaline or electrolytic structures without external supporting electrolyte.

[0084] The above description is merely a preferred embodiment of this disclosure and is not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A gas-phase deoxygenation method based on the redox cycle of quinone compounds, characterized in that, include: Oxygen-containing gas is introduced into the gas-liquid contact reactor through the gas inlet, so that the oxygen-containing gas comes into contact with the working liquid containing water-soluble quinone compounds in a reduced state in a one-pass flow manner, and the resulting deoxygenated gas is discharged through the product gas outlet. The working solution containing the oxidized form of the water-soluble quinone compound after the reaction is transported to the electrolysis unit, whereby the oxidized form is electrochemically reduced to the reduced form at the cathode side of the electrolysis unit. The regenerated working fluid is then transported back to the gas-liquid contact reactor. The gas inlet and the product gas outlet form an open single-pass gas flow path. The working fluid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

2. The method according to claim 1, characterized in that, The water-soluble quinone compound is selected from at least one of anthraquinone-2-sulfonate sodium, anthraquinone-2,6-disulfonate disodium, and 1,2-naphthoquinone-4-sulfonate sodium, and the total concentration of the oxidized state and the reduced state is 10-20 mM.

3. The method according to claim 1, characterized in that, The oxygen-containing gas is air, oxygen-containing nitrogen, or an oxygen-containing inert gas.

4. The method according to claim 1, characterized in that, The oxygen-containing gas comes into contact with the working fluid through bubbling contact or membrane-isolated gas-liquid contact.

5. The method according to claim 1, characterized in that, Also includes: A color image of the working fluid is acquired under a constant light source, and HSV color parameters are extracted from the color image; The HSV color parameters are compared with the pre-established correspondence between color parameters and reduced state concentration ranges; The voltage and / or current of the electrolysis unit are adjusted according to the comparison results to match the electrochemical regeneration rate of the water-soluble quinone compound with the gas-phase deoxygenation load.

6. A gas-phase deoxygenation system based on a quinone compound redox cycle, characterized in that, include: The gas-liquid contact reactor is equipped with a gas inlet, a product gas outlet, a working liquid inlet, and a working liquid outlet, and is used to contact oxygen-containing gas with a working liquid containing water-soluble quinone compounds in a reduced state. An electrolysis unit includes an anode, a cathode, and an ion-conducting membrane disposed between the anode and the cathode, wherein the cathode is used to electrochemically reduce the oxidized state of the water-soluble quinone compound to the reduced state; The working fluid circulation loop connects the working fluid outlet of the gas-liquid contact reactor with the cathode side of the electrolysis unit, and the cathode side of the electrolysis unit with the working fluid inlet of the gas-liquid contact reactor, and is equipped with a circulation drive device. A power source for applying an electrolysis voltage between the anode and the cathode; The gas inlet and the product gas outlet form an open single-pass gas flow path. The working fluid circulation loop is independent of the gas flow path, and the gas flow path does not pass through the electrolysis unit.

7. The system according to claim 6, characterized in that, The water-soluble quinone compound is selected from at least one of anthraquinone-2-sulfonate sodium, anthraquinone-2,6-disulfonate disodium, and 1,2-naphthoquinone-4-sulfonate sodium, and the total concentration of the oxidized state and the reduced state is 10-20 mM.

8. The system according to claim 6, characterized in that, The gas-liquid contact reactor is a bubbling reactor or a hollow fiber membrane gas-liquid contactor; when the gas-liquid contact reactor is a hollow fiber membrane gas-liquid contactor, the hollow fiber membrane gas-liquid contactor includes a porous hollow fiber membrane, the inside of the hollow fiber membrane forms a gas flow path, and the outside of the hollow fiber membrane forms a working fluid flow path.

9. The system according to claim 6, characterized in that, The cathode is a porous conductive electrode.

10. The system according to claim 6, characterized in that, Also includes: Constant light source, color recognition unit, and control module; The color recognition unit is used to acquire a color image of the working fluid under the constant light source and extract HSV color parameters from the color image; The control module is used to compare the HSV color parameters with the pre-established correspondence between HSV color parameters and reduced state concentration ranges, and generate control commands to adjust the power supply output voltage and / or current based on the comparison results.

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