Electrolysis method, electrolysis device, electrolysis system, use, and plant

Abstract

The present invention relates to a carbon dioxide extraction method, which includes the steps of: a) anodic oxidation of hydrogen gas to obtain an acidic oxidation product; b) converting the acidic oxidation product with an alkaline carbonate-containing aqueous solution, particularly having a pH of 7 to 9, to obtain an acidic aqueous solution; c) removing carbon dioxide from the acidic aqueous solution to obtain carbon dioxide gas and a degassed acidic aqueous solution; and d) cathodically reducing the acidic components of the degassed acidic aqueous solution to produce cathodically produced hydrogen gas and an alkaline aqueous solution having a pH of 9.4 to 8 or more.

Description

[Technical Field]

[0001] The present invention relates to a method for carbon dioxide extraction, in particular from seawater or a carbon dioxide-containing gas, in particular from air or a point source, an electrolytic device for carbon dioxide extraction, an electrolysis system comprising such an electrolysis device, the use of said electrolysis device in a plant for electrolytic carbon dioxide extraction from seawater or a carbon dioxide-containing gas, in particular from air or a point source, as well as a plant for electrolytic carbon dioxide extraction from seawater. [Background technology]

[0002] As atmospheric carbon dioxide concentrations increase and global average temperatures rise as a result, systems for extracting carbon dioxide from the atmosphere become increasingly important. In addition to direct air capture (DAC), there is also the technical potential to extract or capture carbon dioxide from aqueous solutions containing carbonates, especially seawater.

[0003] Electrochemical methods can split water into basic and acidic components. In an acidic environment, the chemical equilibrium is [ka] from [ka] It then transitions to CO2 and H2O (see equation (1) below).

[0004] [ka]

[0005] Common electrochemical methods for splitting water into acidic and basic streams typically use one or more ion exchange membranes. These membranes selectively pass either cations (CEM) or anions (AEM). Additionally, bipolar membranes (BPM) can be used to split the aqueous system into acidic (H) and basic (H) streams. + ) stream and basic (OH - ) streams.

[0006] The so-called E-CEM (electrocatalytic cation exchange module) system operates using two cation exchange membranes between electrodes. Here, water flows through all three separated compartments. When a voltage is applied, H + The movement of ions increases the proton concentration in the central compartment. As a result, the pH value decreases, making it possible to extract CO2 from the solution. The energy consumption of such a system is approximately 20,000 kWh / t-CO2.

[0007] Compared to E-CEM systems, bipolar membrane electrodialysis systems (BPMEDs) are more energy efficient, requiring only approximately 920 kWh / t-CO2 or 1,400 kWh / t-CO2 to extract CO2 from aqueous solutions. The use of a redox-active electrolyte stream circulating directly at the cathode or anode suppresses redox reactions, such as the formation of H2(HER) and O2(OER) from H2O. Preferred electrolytes include systems containing Fe(II) and Fe(III) ions, such as potassium hexacyanoferrate(II) and potassium hexacyanoferrate(III), although other compounds can also be used. In bipolar membranes, water molecules are acidic (H + ) and basicity (OH - The acidic stream can be used for CO2 capture, and the basic stream is used to alkalize the process water.

[0008] According to the current state of the art, the highest energy efficiency in CO2 capture from aqueous systems has been achieved using an electrochemical hydrogen loop (EHL). This setup includes three compartments: the cathode compartment is filled with seawater, and H2 and OH are generated at the cathode. - The hydrogen produced is sent to the anode compartment, where H2 is converted to H + and migrate to the intermediate compartment, acidifying the incoming seawater.

[0009] Nanofiltration is typically required for removing or capturing carbon dioxide from seawater using electrochemical methods. When high pH conditions exist in parts of the system, such as the cathode compartment, mineral precipitation of divalent magnesium or calcium ions can occur. These ions are essential for maintaining seawater's high alkalinity and its ability to reabsorb atmospheric carbon dioxide. Furthermore, precipitated minerals can contaminate the system, causing problems such as electrode fouling, which can increase energy costs over time.

[0010] Nanofiltration is a very complex and costly process, with operating costs estimated at €0.20 per cubic metre of treated water. Extracting one tonne of CO2 from seawater with a dissolved CO2 concentration of 2.2mM at 90% efficiency requires 11,477m3 3 This calculation shows that nanofiltration costs alone would be around 2,000 euros to extract one tonne of CO2.

[0011] The present invention therefore aims to mitigate or eliminate these drawbacks. Summary of the Invention

[0012] The above objects are achieved by the present invention as defined in the independent claims.

[0013] According to a first aspect, the present invention relates to an electrolytic process for carbon dioxide extraction, in particular a continuously operated electrolytic process, said process comprising: a) anodizing hydrogen gas to obtain an acidic oxidation product; b) converting the acidic oxidation product with an aqueous solution containing an alkali carbonate, in particular with a pH between 7 and 9, to obtain an acidic aqueous solution; c) extracting carbon dioxide from the acidic aqueous solution to obtain carbon dioxide gas and a degassed acidic aqueous solution; d) cathodically reducing the acidic components of the degassed acidic aqueous solution to obtain cathode-generated hydrogen gas and an alkaline aqueous solution having a pH of 10 to 7.1 or higher.

[0014] According to a second aspect, the present invention provides an electrolytic apparatus for carbon dioxide extraction, said apparatus comprising: an anode compartment; ●Intermediate compartment and a cathode compartment; the intermediate compartment is disposed between the anode compartment and the cathode compartment, the anode compartment being connected to the intermediate compartment via a first transport membrane; The cathode compartment is connected to the intermediate compartment via a second transport membrane, the anode compartment and the cathode compartment are fluidly connected via a hydrogen gas line; The intermediate compartment has an inlet and an outlet, the outlet being fluidly connected to a carbon dioxide extraction device, which is fluidly connected directly to the inlet of the cathode compartment via a liquid line.

[0015] According to a third aspect, the present invention relates to an electrolysis system comprising at least one electrolysis device according to the second aspect of the invention.

[0016] According to a fourth aspect, the present invention relates to the use of an electrolysis device according to the second aspect of the invention in a plant for electrolytic carbon dioxide extraction from seawater.

[0017] According to a fifth aspect, the present invention relates to a plant for electrolytic carbon dioxide extraction from seawater, comprising an electrolysis device according to the second aspect of the invention or an electrolysis system according to the third aspect of the invention.

[0018] According to a sixth aspect, the present invention relates to the use of an electrolysis device according to the second aspect of the invention in a plant for the electrolytic extraction of carbon dioxide-containing gases, in particular carbon dioxide from air or point sources.

[0019] According to a seventh aspect, the present invention relates to a plant for the electrolytic extraction of carbon dioxide, in particular from air or from a carbon dioxide-containing gas from a point source, comprising an electrolysis device according to the second aspect of the invention or an electrolysis system according to the third aspect of the invention. [Effects of the Invention]

[0020] Aspects of the present invention allow for significantly more energy-efficient process operation than conventional electrolytic carbon dioxide extraction methods. Furthermore, these features reduce mineral precipitation from carbonate-containing solutions, especially in the cathode compartment, even in the presence of divalent cations. This allows for longer cathode maintenance intervals and gentler process operation, due to reduced fouling of the cathode material, particularly through mitigation of calcium and magnesium hydroxide precipitation. At the same time, Mg 2+ Ya Ca 2+ This allows divalent cations such as ammonium nitrate to be returned to the ocean, eliminating the need for nanofilters. This has ecological benefits by allowing for further CO2 absorption via carbonates, and also economic benefits by eliminating the need for expensive, high-maintenance nanofilters. Furthermore, the present invention allows for pH values ​​that do not deviate significantly from those of seawater, for example, about 8.1. This prevents the discharge of electrolysis wastewater into the ocean, which has a lower pH than seawater. Therefore, the method of the present invention is advantageous for marine ecosystems in terms of pH, as it avoids ocean acidification.

[0021] Additionally, aspects of the present invention allow for lower voltages to be achieved, thereby improving the energy efficiency of carbon dioxide extraction from air.

[0022] Further details regarding the technical advantages achieved by the present invention are set forth in the detailed description.

[0023] [Definition] Unless otherwise specified, all technical terms used herein conform to the common understanding of those skilled in the art.

[0024] The term "carbon dioxide extraction" is broadly understood to mean the removal of gaseous carbon dioxide from aqueous solutions containing carbonates, and is formally referred to as H + The cation is used to convert the carbonate / bicarbonate to dihydrogen carbonate, which then decomposes into water and carbon dioxide gas, as shown in equation (1) above.

[0025] The term "acidic" is understood broadly to refer to an "acidic aqueous solution" with a pH value of less than 7. Thus, "pH neutral" means a pH value of 7.

[0026] The terms "alkaline" or "basic" are also broadly understood to refer to "alkaline aqueous solutions" with a pH value above 7.

[0027] The term "pH value" corresponds to the understanding of those skilled in the art and can be measured with a pH meter. The pH values ​​disclosed herein can be measured, for example, using a VOLTCRAFT PHT-200 meter, which combines pH value and oxidation-reduction potential (ORP). The technical specifications of this measuring device are as follows: Measurement range (mV): -1999 to 1999 mV ●Accuracy (mV): ±0.5% Accuracy (pH): ±(0.02pH+2d) automatic temperature compensation yes operating temperature 0~50℃ resolution 0.01 Power supply (details) 9V size (Length x Width x Height) 68 x 30 x 195 mm weight 250g height: 195mm length: 68mm width: 30mm Measurement range (pH) pH 0-14 proofreading Factory Standard (No Certificate) display digital Interface RS-232 Measurement Function pH value Oxidation-reduction potential (ORP) Maximum pH measurement range 14pH Minimum pH measurement range 0 pH Product Type Combination Measuring Device

[0028] The specified measuring device is factory calibrated as standard and can also be calibrated further using the pH buffer solutions (pH=4 and pH=7) included in the delivery.

[0029] The term "acidic oxidation product" is understood in a broad sense and, without being bound by any particular theory, refers to the formal proton product produced by the oxidation of diatomic hydrogen, specifically hydrogen gas. In aqueous solution, this formal proton product is HO. + (aq) It exists solvated as Cl - (aq) may be present as counter anions and / or as part of the solid electrode and / or solid membrane materials, allowing for the transport of the formal proton products via known mechanisms. In addition to chloride, H2SO4, HCO3 - Other counter anions derived from acids such as H2CO3, H3BO3, and HBr may also be formally present in all the aforementioned cases.

[0030] The term "carbonate-containing aqueous solution" is understood in a broad sense and includes all chemical forms of carbonate. "Carbonate-containing aqueous solution" is usually alkaline, with a pH of >7-9, >7-9.4, or >7-10. This is because carbonate (CO3 2-) and / or bicarbonate. An example of a "carbonate-containing aqueous solution" is seawater. Carbonate-containing aqueous solutions include divalent cations, such as magnesium, calcium, and strontium, among others. Additionally, carbonate-containing aqueous solutions may also include monovalent cations, such as sodium.

[0031] The term "seawater" is used interchangeably and synonymously with "brine" and "saline" and broadly refers to aqueous solutions obtained from saline bodies, particularly saltwater bodies such as the oceans. Naturally, the exact chemical composition of the seawater may vary depending on the source. For example, the composition provided by Kester, DR, Duedall, IW, Connors, DN, and Pytkowicz, RM (1967), "Preparation of Artificial Seawater" (Archived 2008-12-17. Limnology & Oceanography, 12, 176-179), incorporated by reference, serves as an approximate example. Tables 1 and 2 from this publication are provided as approximate examples of seawater composition.

[0032] Table 1: Information on the approximate composition of seawater in terms of weight salts Weighted salt [Table 1]

[0033] Table 2: Information on the approximate composition of seawater in terms of volumetric salts Volumetric salt [Table 2]

[0034] The term "degassed aqueous acidic solution" broadly refers to an aqueous solution having a pH of less than 7 from which carbon dioxide gas has been essentially completely removed. Such a degassed aqueous acidic solution can be obtained, for example, by extracting carbon dioxide gas from the aqueous acidic solution via a membrane contactor. The degassed aqueous acidic solution retains divalent cations, particularly magnesium and calcium. Specifically, the degassed aqueous acidic solution contains no more than 10 wt. % carbon dioxide, preferably no more than 5 wt. % carbon dioxide, where the mass % is based on the original mass of carbon dioxide present as carbonate and / or bicarbonate in the aqueous alkali carbonate-containing solution. In other words, the separation efficiency is at least 90%, preferably at least 95%.

[0035] The term "acidic component" generally refers to protons in aqueous solution, i.e., HO + (aq).

[0036] The term "fluidly connected" is understood in a broad sense and refers in particular to a connection, such as a pipeline, between two electrolysis units designed to transport a fluid, such as a liquid or a gas, such as hydrogen gas, from one electrolysis unit to another. Such electrolysis units may include a cathode compartment, an anode compartment, or an intermediate compartment located between the anode and cathode compartments.

[0037] The term "carbon dioxide-containing gas" is understood in a broad sense. In particular, such gas can include air. Those skilled in the art are familiar with the composition of air at a particular location or know how to measure this composition. Furthermore, "carbon dioxide-containing gas" can originate from a point source. Point sources are typically industrial sources of CO2, where the process produces more carbon dioxide gas than is normally present in air. Examples include exhaust gases from industrial processes such as cement manufacturing and coal combustion. Point sources can contain gases with a carbon dioxide content of about 10 mol% to 25 mol%, particularly 14 mol% to 21 mol%, based on the total volume of wet gas. Such gases can also contain a carbon dioxide content of about 10 vol% to 20 vol%. Overall, the mass / volume / mole fraction of carbon dioxide in the carbon dioxide-containing gas is not fundamentally important to the function of the present invention and its embodiments.

[0038] A sample process for recovering carbon dioxide from a carbon dioxide-containing gas is shown in Figure 4. Various technical configurations are possible for CO2 absorption. For example, at low CO2 concentrations, such as those found in air, it may be advantageous to expose the gas to an alkaline solvent using a cross-flow method with a cooling tower-like structure. At high CO2 concentrations, such as those found in flue gas from industrial processes, a column using the countercurrent principle to contact the gas with an alkaline aqueous solution may be more suitable technically and economically. Furthermore, the carbonate-containing aqueous solution may contain monovalent cations such as sodium. The carbonate-containing aqueous solution may specifically or exclusively contain monovalent cations such as sodium or potassium. These monovalent cations may be paired with counteranions selected from the group consisting of sulfate, perchlorate, nitrate, iodide, or combinations thereof. Specifically, the dissolved salt may be selected from the group consisting of Na2SO4, K2SO4, NaClO4, KClO4, NaNO3, KNO3, NaI, and KI. The term "alkali carbonate-containing aqueous solution" is used interchangeably with "carbonate-containing aqueous solution." [Brief explanation of the drawings]

[0039] [Figure 1]1 shows an embodiment of an electrolysis device according to the present invention. [Figure 2] 1 illustrates an embodiment of an electrolysis system in a monopolar configuration according to the present invention. [Figure 3] An example of a Pourbaix diagram for water is shown below. [Figure 4] 1 illustrates an embodiment of an electrolysis system for extracting carbon dioxide from a carbon dioxide-containing gas according to the present invention. [Figure 5] 1 illustrates an embodiment of an electrolysis system in a bipolar configuration according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0040] The following embodiments are illustrative of advantageous configurations of the present invention and should not be understood as limiting the scope of the present invention. The features of the various embodiments in different aspects of the present invention can be freely combined unless otherwise specified. Electrolytic method:

[0041] According to a first aspect, the present invention relates to an electrolytic process for carbon dioxide extraction, in particular a continuously operated electrolytic process, comprising: a) anodizing hydrogen gas to obtain an acidic oxidation product; b) extracting the acidic oxidation product with an aqueous solution containing alkaline carbonates, such as seawater, particularly with a pH of >7-9, to obtain an acidic aqueous solution; c) extracting carbon dioxide from the acidic aqueous solution to obtain carbon dioxide gas and a degassed acidic aqueous solution; and d) cathodically reducing the acidic component of the degassed acidic aqueous solution to obtain an alkaline aqueous solution having a pH of 10-7.1 or higher, or 9.4-8 or higher. In particular, the pH value can be 9.2-8 or higher, specifically 8.5-8 or higher, optionally 8.8-7.1 or higher, and even optionally 8.0-7.1 or higher. A range of 8.4-7.1 or higher is also possible. Using the disclosed method, the pH value is measured at the cathode compartment outlet.

[0042] The anodic oxidation of hydrogen gas in step a) can be carried out in aqueous solution or via a gas diffusion electrode, e.g., a zero-gap electrode. The acidic oxidation product is formally represented by the following formula (2): + is equivalent to H2→2H + +2e - E 0 =0V (2)

[0043] H + is H3O in aqueous solution + (aq) It may exist as a solid electrode and / or as part of the membrane material. + The exact form of hydrogen ions (H2O) is not important as long as it is available for use in step b). In certain embodiments, the hydrogen gas of step a) can be oxidized at a gas diffusion electrode without the use of an aqueous solution, minimizing the need to humidify the hydrogen gas. Oxidizing hydrogen gas eliminates the need for oxygen production, thereby reducing the energy demands within the process. As shown in Figure 3, the redox potential resulting from the oxidation of hydrogen is significantly lower than the redox potential resulting from the oxidation of water to produce oxygen.

[0044] In step b), the acidic oxidation product is used to convert the carbonate-containing aqueous solution. For example, the oxidation product from step a) can be produced in the anode compartment, while the reaction in step b) occurs in an intermediate compartment of the electrolysis device, which can be located between the cathode compartment and the anode compartment. The acidic oxidation product can be contacted with the carbonate-containing aqueous solution via a transport membrane for conversion. Preferably, the pH of the carbonate-containing aqueous solution is about 8 or higher to about 8.5. The conversion in step b) involves, in particular, a chemical reaction as described in equation (1) to form dissolved carbon dioxide. Due to the conversion using the acidic oxidation product, dissolved carbon dioxide is present after the conversion in step b). In the next step c), carbon dioxide gas is removed, in particular via a membrane contactor located downstream of step c) outside the intermediate compartment. Thus, carbon dioxide is removed from the acidic aqueous solution, resulting in a degassed acidic aqueous solution with a pH less than 7. In step d), which occurs in particular in the cathode compartment, the degassed acidic aqueous solution and the H in water are reacted. + (aq) Acidic components such as HCl are reduced to produce hydrogen gas and hydroxide ions, producing an alkaline aqueous solution having a pH of about 10 to 7.1 or more, or 9.4 to 8 or more, or within any one of the aforementioned ranges. In particular, the pH of the alkaline aqueous solution is about 7.1 to 9 or 8 to 9, preferably 7.1 to 8.5 or 8 to 8.5, for example, about 8.1. These reactions formally proceed according to the following equations (3) and (4):

[0045]

number

[0046]

number

[0047] The method according to the first aspect of the present invention can be operated at a DC voltage of less than 1.5 V, in particular 1.3 V or less. In this context, the sodium cations of formula (4) are transported, in particular, from the intermediate compartment to the cathode compartment, for example via a transport membrane. The reactions described in formulas (3) and (4) in step d) result in the following important technical advantages of the present invention:

[0048] Maintaining the pH range of the alkaline aqueous solution in step d) above 10-7.1 or above 9.4-8 or within any of the aforementioned ranges reduces the tendency for divalent cations, such as magnesium and calcium, particularly present in carbonate-containing aqueous solutions, to precipitate as solid hydroxides. This pH range is made possible by the presence of the deaerated acidic aqueous solution in step d). In particular, as explained above, the deaerated acidic aqueous solution may contain divalent cations, such as magnesium and / or calcium. The reduction reaction of equation (3) and the further reduction of water in equation (4) results in an alkaline aqueous solution with a pH of 9.4-7 or above. Outside this range, the pH becomes too high, resulting in undesirable precipitation of the aforementioned hydroxides, which can cause significant cathode fouling, as previously described. Reducing hydroxide precipitation allows divalent cations, such as calcium, magnesium, and strontium, to remain in the carbonate-containing aqueous solution, thereby eliminating the need for costly and maintenance-intensive nanofilters to remove them. Reducing or avoiding impurities resulting from precipitated hydroxides also improves efficiency; such impurities typically lead to reduced energy efficiency. Excessive hydroxide precipitation is undesirable because it lowers the pH of the aqueous alkaline solution.

[0049] Reintroducing the alkaline solution into saline water, such as seawater, is advantageous because the presence of divalent cations allows for further carbon dioxide binding. The achieved pH level therefore also has ecological benefits. Another environmental benefit is that acidic wastewater does not need to be discharged into saline waters, such as the ocean; instead, the alkaline solution has an environmentally friendly pH value. The low pH value of seawater would result in the release of CO2 into the atmosphere.

[0050] Surprisingly, it was also found that the partially acidic environment created by introducing a degassed acidic aqueous solution (see equation (2) above) to the cathode resulted in more energy-efficient hydrogen gas production due to kinetic and thermodynamic advantages.

[0051] Prior to introducing the carbonate-containing aqueous solution in step b), nitrogen and oxygen gases can be removed from the solution, for example by using a membrane contactor.

[0052] The electrolysis method according to the first aspect of the invention may be carried out using the electrolysis apparatus described in the second aspect of the invention. The method may also be used for the extraction of carbon dioxide from a carbon dioxide-containing gas, such as air or a point source.

[0053] In certain embodiments, the hydrogen gas produced cathodically in step d) is transferred to step a) and oxidized. In other words, the method comprises a hydrogen cycle (oxidation in step a, reduction in step b, and reoxidation in step d). Thus, the present invention can produce hydrogen largely autonomously, reducing the need for an external hydrogen supply. Because hydrogen production is typically energy intensive, the hydrogen cycle offers significant efficiency savings.

[0054] In certain embodiments, the acidic oxidation product from step a) is transported for conversion in step b) through a first transport membrane that contacts the alkaline carbonate-containing solution at the point where the acidic oxidation product is discharged. For example, the first transport membrane may include a gas diffusion electrode, a gas diffusion layer (GDL), and / or a zero-gap membrane electrode (CEM). The gas diffusion layer may also be considered part of the first transport membrane. In particular, the first transport membrane may include a perfluorosulfonic acid membrane. Preferably, such a transport membrane is based on a perfluorosulfonic acid / polytetrafluoroethylene copolymer. The material of the transport membrane may also or alternatively be selected from the group consisting of membranes based on PTFE / PTFE (polytetrafluoroethylene / Teflon), hydrocarbon membranes, and sPPS (sulfonated polyphenylene sulfone) membranes, among others. Examples include membranes known under the names Nafion, Gore, Fumasep, Fumapem, Aquivion, and / or Xion, with Nafion or Gore-Select membranes being preferred. In particular, acidic oxidation products may be generated in the anode compartment in step a) and diffuse through the first transport membrane, while the reaction in step b) occurs in the intermediate compartment.

[0055] In certain embodiments, metal cations, such as sodium cations, migrate from the carbonate-containing aqueous solution through a second transport membrane to the cathodic reduction step d) during the reaction. The second transport membrane can have the same characteristics as the first transport membrane described above. Specifically, sodium cations from the carbonate-containing aqueous solution can be transported from the intermediate compartment to the cathode compartment of step d) through the second transport membrane. These cations formally serve to balance the charge, as described in equation (4).

[0056] In certain embodiments, the pH of the degassed acidic aqueous solution is less than 5. Specifically, the pH can range from about 2 to <5, preferably from 3 to about 4.5. This pH can be achieved by the anodic oxidation in step 1. The acidic pH has the advantages described above.

[0057] According to certain embodiments, the degassed acidic aqueous solution of step d) may also be contacted with an alkaline aqueous solution, e.g., due to the reduction described in equation (4), the alkaline aqueous solution may accumulate in the cathode compartment over time, creating a pH gradient due to the acidity of the degassed acidic aqueous solution at the inlet. Electrolysis device for carbon dioxide extraction

[0058] According to a second aspect, the present invention relates to an electrolysis device for carbon dioxide extraction, the electrolysis device comprising: an anode compartment; ●Intermediate compartment and a cathode compartment; the intermediate compartment is disposed between the anode compartment and the cathode compartment, the anode compartment being connected to the intermediate compartment via a first transport membrane; The cathode compartment is connected to the intermediate compartment via a second transport membrane, the anode compartment and the cathode compartment are fluidly connected via a hydrogen gas line; The intermediate compartment has an inlet and an outlet, the outlet being fluidly connected to a carbon dioxide extraction device, which is fluidly connected directly to the inlet of the cathode compartment via a liquid line.

[0059] It will be appreciated that the electrolysis device equally possesses the characteristics and technical effects of the electrolysis method. In particular, the electrolysis device according to the second aspect of the present invention is designed to carry out the electrolysis method according to the first aspect of the present invention. Therefore, the electrolysis device can also be used for carbon dioxide extraction from seawater.

[0060] Additionally, electrolytic devices can be used in methods for extracting carbon dioxide from carbon dioxide-containing gases, such as air or point sources, in which case the solvent-air contactors described herein may be used.

[0061] Specifically, the anode compartment is configured to perform step a) of the method according to the first aspect of the invention. Furthermore, the intermediate compartment is specifically configured to perform step b) of the method according to the first aspect of the invention. Accordingly, the cathode compartment is configured to perform step d) of the method according to the first aspect of the invention. Furthermore, the carbon dioxide extraction device is configured to perform step c) of the method according to the first aspect of the invention.

[0062] In certain embodiments, the carbon dioxide extraction device is selected from the group consisting of a membrane contactor (preferably 3MLiqui-Cel), a heat exchanger, and a combination thereof. Preferably, a membrane contactor is used. In the case of a heat exchanger, it is configured to heat the acidic aqueous solution to allow degassing of carbon dioxide gas.

[0063] Specifically, the first transport membrane is an ion transport membrane configured to transport acidic oxidation products from the anode compartment to the cathode compartment. Additionally or alternatively, the second transport membrane can be configured as an ion transport membrane designed to transport monovalent cations, such as sodium cations, from the intermediate compartment to the cathode compartment.

[0064] As is clear from the above description, the electrolyzer does not include a nanofilter.

[0065] Furthermore, except for the extraction of carbon dioxide, no additional operation is performed between the outlet of the intermediate compartment and the inlet of the cathode compartment. Specifically, the fluid connection between the outlet of the intermediate compartment and the inlet of the cathode compartment does not include any additional mixing device, ensuring that the pH of the acidic aqueous solution and the degassed acidic aqueous solution remains essentially constant.

[0066] In certain embodiments, the anode compartment contains an anode material in direct contact with the first transport membrane. The anode active material is specifically selected from the group consisting of platinum, nickel / iron, nickel / cobalt, nickel, cobalt / platinum, stainless steel, iridium, iridium oxide, ruthenium, ruthenium oxide, palladium, and combinations thereof. Preferably, the anode active material is platinum. The anode material can be configured as a zero-gap electrode, in which there is no gap between the anode material and the first transport membrane. Furthermore, the anode material can be applied to a carrier. Such a carrier can be selected from the group consisting of iron, steel, titanium, carbon paper, or combinations thereof. Alternatively, the anode can be configured as a gas diffusion electrode. The gas diffusion electrode can include, for example, a Gore-Primea series product variation.

[0067] In certain embodiments, a device for removing oxygen and nitrogen from the aqueous alkali carbonate-containing solution may be provided before the inlet to the intermediate compartment, and such a device may be configured similarly to a carbon dioxide extraction device.

[0068] In certain embodiments, the anode compartment may include an external source of hydrogen gas, which can compensate for any hydrogen shortages that may occur during hydrogen recycling.

[0069] In certain embodiments, the cathode compartment can have a side opposite the second transport membrane, and the inlet of the cathode compartment can be positioned closer to this side than the second transport membrane. This can alkalinize the aqueous solution in the cathode compartment, creating a high pH gradient between the cathode and the second transport membrane. As a result, cation transport into the cathode compartment can be significantly improved.

[0070] In certain embodiments, the inlet of the cathode compartment and the inlet of the intermediate compartment can be arranged so that the flow of liquid into the cathode compartment is countercurrent or parallel to the flow of liquid through the electrolyzer into the intermediate compartment. In particular, a countercurrent arrangement has the advantage of maintaining the same pH gradient direction and promoting the migration of positively charged cations into the cathode compartment.

[0071] In certain embodiments, the cathode compartment preferably contains a cathode material selected from the group consisting of platinum, nickel, titanium, carbon paper, or a combination thereof. Platinum is particularly preferred as the positive electrode active material. Carbon paper coated with a Pt / C catalyst is particularly preferred.

[0072] In a particular embodiment, the process according to the first aspect of the invention is carried out at a total pressure above atmospheric pressure, in particular between 2 bar and 50 bar.

[0073] The electrolysis device according to the first aspect of the present invention can operate at a temperature below 100°C. Specifically, the electrolysis device can operate at a temperature between 60 and 80°C. Furthermore, the electrolysis device can also operate at a temperature between 95°C and below 100°C.

[0074] Electrolysis System According to a third aspect of the invention, the invention relates to an electrolysis system comprising at least one electrolysis device according to the second aspect of the invention.

[0075] It will be appreciated that such an electrolysis system is designed to carry out the method according to the first aspect of the invention, and therefore includes the method steps of the first aspect of the invention and the corresponding technical advantages. The same applies to the electrolysis device according to the first aspect of the invention.

[0076] For example, multiple electrolyzers can be used together in an electrolysis system. These electrolyzers can be connected in a stacked configuration. For example, two electrolyzers can share a common anode compartment. Another electrolyzer can be linked to these two electrolyzers via a shared cathode. Yet another electrolyzer can also be connected via a shared anode compartment, etc.

[0077] Use of electrolysis equipment According to a fourth aspect, the present invention relates to the use of an electrolysis device according to the second aspect of the invention in a plant for electrolytic carbon dioxide extraction from seawater.

[0078] According to a sixth aspect, the present invention relates to the use of an electrolysis device according to the second aspect of the invention in a plant for the electrolytic extraction of carbon dioxide-containing gases, in particular carbon dioxide from air or point sources, in which case a solvent-air contactor as described herein may be used.

[0079] The uses according to the fourth and sixth aspects include the technical features, effects and advantages of the method described in the first aspect and the electrolysis device described in the second aspect.

[0080] Plant for electrolytic carbon dioxide extraction from seawater or carbon dioxide-containing gases: According to a fifth aspect, the present invention relates to a plant for electrolytic carbon dioxide extraction from seawater, comprising an electrolysis device according to the second aspect of the invention or an electrolysis system according to the third aspect of the invention.

[0081] Such plants may be installed in saltwater bodies such as the ocean, and may also operate using seawater as the carbonate-containing solution.

[0082] According to a seventh aspect, the present invention relates to a plant for the electrolytic extraction of carbon dioxide, in particular from air or a carbon dioxide-containing gas from a point source, comprising an electrolysis device according to the second aspect of the invention or an electrolysis system according to the third aspect of the invention, in which case a solvent-air contactor as described herein may be used.

[0083] Furthermore, a plant according to the fifth or seventh aspect may also be operated according to a method according to the first aspect of the invention, and to avoid repetition, the plant will include the features, technical advantages and effects described in the first, second, third and fourth aspects of the invention.

[0084] DESCRIPTION OF THE DRAWINGS The following figures illustrate exemplary, non-limiting embodiments of the present invention.

[0085] FIG. 1 illustrates an exemplary embodiment of an electrolysis device 1 for extracting carbon dioxide from seawater according to a second aspect of the present invention. Fresh alkaline seawater having a pH of approximately 8.1 is introduced into a first membrane contactor 17a via a first inlet line 13, where oxygen and nitrogen are removed from the seawater. The alkaline seawater is introduced into an intermediate compartment 51 via a second inlet line 14, which is disposed between an anode compartment 50 containing an anode 45 and a cathode compartment 52 containing a cathode 46. The anode compartment 50 and the intermediate compartment 51 are separated by a first ion transport membrane 61 configured to transport protons from the anode compartment 50 to the intermediate compartment 51. The intermediate compartment 51 and the cathode compartment 52 are separated by a second ion transport membrane 62 configured to transport sodium ions from the intermediate compartment 51 to the cathode compartment 52. These electrochemical reactions are driven by an AC voltage source 44. In the anode compartment 50, hydrogen gas is oxidized at the anode 45 to produce an acidic oxidation product. This acidic oxidation product is transported through the first ion transport membrane 61 to the intermediate compartment 51, where it reacts with seawater to form an acidic aqueous solution. Hydrogen gas for oxidation is transported to the anode compartment 50 via the hydrogen line 23 from the cathode compartment 52, where it is produced, for example, at the cathode 46. The acidic aqueous solution formed in the intermediate compartment contains dissolved carbon dioxide produced according to equation (1). The acidic aqueous solution (pH approximately 4) is sent through the first outlet line 4 to the second and third membrane contactors 17b and 17c, where carbon dioxide gas is removed. The degassed acidic aqueous solution (pH approximately 4) is then sent through the second outlet line 5 to the cathode compartment 52. A pH gradient exists in the cathode compartment (lighter hues indicate lower pH, darker hues indicate higher pH). Within the cathode compartment, a pH gradient exists (lighter hues indicate lower pH, darker hues indicate higher pH). The degassed acidic aqueous solution is neutralized by hydroxide ions along the flow paths within the cathode compartment 52.Furthermore, the pH increases as formal protons are consumed during the production of hydrogen gas according to equation (3). Thus, an alkaline aqueous solution with a pH greater than 8.1 is formed in the cathode compartment, which can be returned to the sea via seawater outlet line 11.

[0086] Figure 2 shows an example of an electrolysis system 100a in a monopolar configuration according to a third aspect of the present invention. As shown in Figure 1, arrows indicate material inputs and outputs. Only components relevant to this description are numbered. In this configuration, a first electrolyzer 1a and a second electrolyzer 1b are connected via their respective anode compartments 50. Additionally, a third electrolyzer 1c is connected to the second electrolyzer 1b via the cathode 46. As indicated by the ellipsis in Figure 2, an additional electrolyzer 1n can be connected to the third electrolyzer 1c via the shared anode compartment 50.

[0087] For illustrative purposes, Figure 3 shows the Pourbaix diagram for water.

[0088] FIG. 4 illustrates an example of a plant 200 capable of carrying out the method described in the first embodiment, according to a third aspect of the present invention. A gas, such as air, is introduced into the plant 200 via an air supply system 30 and can be absorbed into an aqueous alkaline solution through an air-liquid contactor 31. The resulting carbonate-containing aqueous solution is mixed with an aqueous acid solution in a mixing vessel 32, and carbon dioxide gas can be removed from the system, for example, through one or more membrane contactors 33. The degassed acid solution is then split into two portions and sent to an electrolysis device 34, according to a second aspect of the present invention. The first portion of the degassed acid solution is sent to an intermediate compartment 52, where it reacts with the acidic oxidation product from the anode compartment 51. The second portion of the degassed acid solution is sent to a cathode compartment 53, where it is reduced to produce an aqueous alkaline solution. Hydrogen gas can then be separated from the aqueous alkaline solution in a gas-water separator 35, and the hydrogen is sent to the anode compartment 51, where it is positively oxidized according to the reaction described above, and sent to the intermediate compartment 52, for example, via a first ion transport membrane 61.

[0089] Figure 5 shows an example of an electrolysis system 100b in a bipolar configuration according to a third aspect of the invention. As shown in Figure 1, arrows indicate material inputs and outputs. Only components relevant to this description are numbered. In this configuration, a first electrolysis device 1a and a second electrolysis device 1b are connected via their respective anode compartments 50. According to the stacking technique described above, another electrolysis device 1n can be linked to an adjacent electrolysis device via the anode compartment 50, as shown in Figure 2, for example, with three dots.

[0090] Example

[0091] Experimental setup

[0092] The experiments were carried out in a plant with the configuration shown in Figure 4. The electrolysis device used in the experiments consisted of an electrolysis cell with two steel end plates, a graphite current collector with an integrated flow field on the anode side, and a titanium mesh current collector on the cathode side, as described in the second aspect of the present invention. The flow channels in the intermediate compartment were made of 1 mm thick PTFE. Seals were made using PTFE and FKM gaskets. Two Nafion cation-exchange membranes were used. Carbon fiber diffusion media were employed as the diffusion media for both electrodes. Carbon-supported platinum was used as the catalyst for both electrodes. The catalyst was applied to the gas diffusion media on the anode side and directly to the membrane on the cathode side using the decal method.

[0093] The electrolyte used in the experiments was a 0.5 M sodium chloride solution in distilled water with a conductivity of 30 mS / cm.

[0094] A Zahner Elektrik Zennium Pro model potentiostat / galvanostat was used for power supply and measurements.

[0095] A Shenchen LabN6III peristaltic pump with two pump heads was used to circulate the liquid. The electrolyte flow rate was set at 80 mL / min. An external hydrogen supply, along with hydrogen gas separated using a gas-liquid separator, was controlled via a Bronkhorst mass flow controller, model F201-CV. Experiment Description

[0096] The electrolysis cell was assembled with two graphite flow fields on both the anode and cathode sides. Two types of FKM-based gaskets were used, with thicknesses of 0.2 mm and 0.3 mm, respectively. The 0.3 mm thick gasket was placed between the graphite flow channels and the membrane. A thinner 0.2 mm gasket was placed between the membrane and the flow field in the middle compartment.

[0097] In all experiments, the flow rate was kept constant at 80 mL / min. The active cell area was 10.2 cm. 2 , and the applied current was varied between 0.02 A, 0.05 A, and 0.1 A during the experiment. Different fluid flow configurations

[0098] Two series of experiments were performed, differing only in the fluid flow configuration. In the first experiment, the cathode compartment and the intermediate compartment were powered by the same tank containing 0.5 M electrolyte in deionized water, which was pH 7.3 before being introduced into the cell.

[0099] In the second experiment, the outlet of the intermediate compartment was fluidly connected to the inlet of the cathode compartment, so that the pH at the outlet of the intermediate compartment matched the pH at the inlet of the cathode compartment, which was the main difference from the first experiment. result

[0100] In experiments conducted in accordance with the present invention, voltages were measured for various applied currents, as described above. Table 3 shows the results of experiments where the same solution with a slightly basic pH was introduced into both the intermediate and cathode compartments. Table 4 shows the measurements for the system of the present invention. In this case, the pH at the outlet of the intermediate compartment was the same as the pH at the inlet of the cathode compartment, and the pH 中間,出口 = pH カソード,入口 It is expressed as:

[0101] Table 3: Cell voltage and pH values ​​measured by introducing the same solution (here, the pH at the inlet of both the cathode compartment and the intermediate compartment is the same). [Table 3]

[0102] Comparative examples were determined according to the experimental setup and procedures described in L. Yan et al., ACS Energy Lett. 2022, 7, 1947-1952.

[0103] Table 4: pH values ​​measured at the inlet and outlet of the intermediate and cathode compartments according to the invention [Table 4]

[0104] The results in Table 3 show qualitative agreement with the comparative example. The difference in the magnitude of the pH swing may be due to the lower flow rate of 40 mL / min in the comparative example. In both cases, the flow rate was only 10 mA / cm. 2 pH values ​​above 10 were observed at current densities of 0.01, indicating a high probability of divalent ion precipitation. Surprisingly, Table 4 shows that rerouting the acidic solution to the cathode compartment in accordance with the present invention significantly reduces the pH. This reduction leads to the formation of Ca. 2+ and Mg 2+Another notable observation is that the measured cell voltages at all three current densities were significantly lower than in the control experiment, indicating that this method can operate much more energy efficiently. [Explanation of symbols]

[0105] Reference symbol list 1 Electrolyzer 1a 1st electrolyzer 1b Second electrolyzer 1c 3rd electrolyzer 1n Additional electrolyzer 11 Seawater outlet line 13 First Entrance Line 14 Second Entrance Line 17a 1st membrane contactor 17b Second membrane contactor 17c Third membrane contactor 23 Hydrogen Line 30 Air Supply 31 Air-solvent contactor 32 Mixing Tank 33 Detachable Device 34 Electrolyzer 35 Gas-liquid separator 44 DC power supply 45 anode 46 cathode 50 anode compartment 51 Intermediate Compartment 52 cathode compartment 55 Cathode inlet 61 First ion transport membrane 62 Second ion transport membrane 100a Single-electrode electrolysis system 100b Bipolar Electrolysis System 200 Direct Air Recovery Plant

Claims

1. 1. An electrolytic process for carbon dioxide extraction comprising: a) anodizing hydrogen gas to obtain an acidic oxidation product; b) converting the acidic oxidation product with an aqueous solution containing an alkali carbonate, in particular with a pH between 7 and 9, to obtain an acidic aqueous solution; c) extracting carbon dioxide from the acidic aqueous solution to obtain carbon dioxide gas and a degassed acidic aqueous solution; d) cathodically reducing the acidic component of the degassed acidic aqueous solution to produce cathode-produced hydrogen gas and to produce an alkaline aqueous solution having a pH of 10 to 7.1 or higher, or 9.4 to 8 or higher.

2. 10. The method of claim 1, wherein the hydrogen gas cathodically produced in step d) is transferred to step a) and oxidized.

3. 3. The method of claim 1 or 2, wherein the acidic oxidation product from step a) is transported through a first transport membrane for conversion in step b), and the transport membrane contacts an alkali carbonate-containing aqueous solution at an exit point for the acidic oxidation product.

4. 10. The method of any one of the preceding claims, wherein metal cations from the carbonate-containing aqueous solution are transported through a second transport membrane during reaction to step d) for cathodic reduction.

5. 10. The method according to any one of the preceding claims, wherein the pH of the degassed acidic aqueous solution is less than 5.

6. 10. The method according to any one of the preceding claims, wherein the degassed aqueous acidic solution in step d) is contacted with an aqueous alkaline solution.

7. 10. The method according to any one of the preceding claims, wherein the method is operated at a total pressure above atmospheric pressure, in particular between 2 bar and 50 bar.

8. 1. An electrolytic device for carbon dioxide extraction, comprising: an anode compartment; ●Intermediate compartment and a cathode compartment; the intermediate compartment is disposed between the anode compartment and the cathode compartment, and the anode compartment is connected to the intermediate compartment via the first transport membrane; the cathode compartment is connected to the intermediate compartment via the second transport membrane; the anode compartment and the cathode compartment are fluidly connected via a hydrogen gas line; an electrolysis device, wherein the intermediate compartment has an inlet and an outlet, the outlet being fluidly connected to a carbon dioxide extraction device, the carbon dioxide extraction device being fluidly connected directly to the inlet of the cathode compartment via a liquid line.

9. 9. An electrolysis device according to claim 8, wherein the anode compartment contains an anode material in direct contact with the first transport membrane, the anode material being in particular platinum.

10. 10. An electrolysis device according to claim 8 or 9, wherein a device for removing oxygen and nitrogen from the aqueous alkali carbonate-containing solution is provided upstream of the inlet of the intermediate compartment.

11. 11. An electrolysis device according to any one of claims 8 to 10, wherein the anode compartment contains an external source of hydrogen gas.

12. 12. The electrolysis device according to claim 8, wherein the cathode compartment has an opposite side to the second transport membrane, and the inlet of the cathode compartment is closer to the opposite side than the second transport membrane.

13. 13. An electrolysis device according to any one of claims 8 to 12, wherein the inlets of the cathode compartment and the intermediate compartment are arranged such that liquid flow entering the inlet of the cathode compartment is countercurrent or parallel to liquid flow through the electrolysis device and entering the inlet of the intermediate compartment.

14. 14. The electrolysis device of any one of claims 8 to 13, wherein the cathode compartment contains a cathode material, the cathode material being selected from the group consisting of nickel, titanium, or a combination thereof.

15. Electrolysis system comprising at least one electrolysis device according to any one of claims 8 to 14.

16. Use of the electrolysis device according to any one of claims 8 to 14 in a plant for electrolytic carbon dioxide extraction from seawater.

17. A plant for electrolytic carbon dioxide extraction from seawater, comprising the electrolysis device according to any one of claims 8 to 14 or the electrolysis system according to claim 15.

18. Use of an electrolytic device according to any one of claims 8 to 14 in a plant for the electrolytic extraction of carbon dioxide from a carbon dioxide-containing gas, in particular from air or a point source.

19. A plant for electrolytic carbon dioxide extraction from a carbon dioxide-containing gas, comprising an electrolysis device according to any one of claims 8 to 14 or an electrolysis system according to claim 15.

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