Electrolytic processes, electrolytic cells, and plants

Abstract

The present invention relates to an electrolytic process for extracting carbon dioxide, wherein the process is a. The step of anodic oxidation of hydrogen gas in an electrolytic cell to obtain an acidic oxidation product, b. The step of reacting an acidic oxidation product with an electrolyte aqueous solution in an electrolytic cell to obtain an acidic aqueous solution, c. A step of reducing water by cathode in an electrolytic cell to obtain an alkaline aqueous solution and hydrogen gas, d. A step of reacting an alkaline aqueous solution with a carbon dioxide-containing gas, particularly air, outside the electrolytic cell to obtain a carbonate-containing aqueous solution, e. A step of reacting an alkaline carbonate-containing aqueous solution with an acidic aqueous solution outside the electrolytic cell to obtain dissolved carbon dioxide gas, Includes.

Description

[Technical Field]

[0001] The present invention relates in particular to a process for extracting carbon dioxide from air or a point source, an electrolytic cell, and in particular to a plant for electrolytically extracting carbon dioxide from air or a point source. [Background technology]

[0002] Increased greenhouse gas emissions are causing global temperature increases, leading to climate change and thus having devastating effects. Carbon dioxide (CO2) is the greenhouse gas most deeply involved in this phenomenon. Reducing CO2 emissions is essential to regulating global warming, but this alone is considered insufficient to achieve the targets set forth in the Paris Agreement. Direct air capture (DAC) technology is a promising approach to achieving these goals.

[0003] "CO2 capture" is a process that removes CO2 from the atmosphere using various technologies, including DAC, and involves various approaches such as adsorption, absorption, and electrochemical deposition.

[0004] In methods using solid adsorbents, zeolites or metal-organic frameworks (MOFs) are used to adsorb CO2 from the air. Other DAC approaches use chemical solutions such as amines to absorb CO2 from the air. In recent years, various methods have been attempted in electrochemical DAC processes. One promising approach is the so-called pH swing method.

[0005] While adsorption-based DAC efficiently recovers CO2, this process is energy-intensive, and the regeneration of the adsorbent is costly. Thermal desorption-based DAC consumes a lot of energy and requires large amounts of water and chemicals, making it expensive and unsustainable. Electrochemical DAC has lower energy requirements than the other two methods and can recover CO2 at high concentrations, making it easier to store or utilize. However, electrochemical DAC is a relatively new technology, and while it has potential for development, there are concerns regarding scalability and durability. For example, known electrolytic cells can experience overvoltage, leading to increased energy consumption.

[0006] Regardless of the principles of DAC, CO2 removal is extremely important. The Intergovernmental Panel on Climate Change (IPCC) recognizes DAC as an essential technology for achieving climate change targets. As stipulated in the Paris Agreement, removing CO2 from the atmosphere is necessary to limit the rise in global temperature due to global warming to 1.5°C compared to pre-industrial levels. DAC contributes to reducing CO2 emissions that are difficult to reduce in transportation, agricultural, and industrial processes. It is particularly noteworthy in industries where avoiding CO2 emissions is difficult, such as the cement, chemical, steel, aluminum, and waste incineration industries.

[0007] The present invention aims to address the above-mentioned drawbacks and achieve improvements. [Overview of the project]

[0008] The above objective is achieved by the present invention as described in the independent claim. According to a first aspect, the present invention relates to an electrolytic process for extracting carbon dioxide, a. The step of anodic oxidation of hydrogen gas in an electrolytic cell to obtain an acidic oxidation product, b. The step of reacting an acidic oxidation product with an electrolyte aqueous solution in an electrolytic cell to obtain an acidic aqueous solution, c. A step of reducing water by cathode in an electrolytic cell to obtain an alkaline aqueous solution and hydrogen gas, d. A step of reacting an alkaline aqueous solution with a carbon dioxide-containing gas, particularly air, outside the electrolytic cell to obtain a carbonate-containing aqueous solution, e. A step of reacting an alkaline carbonate-containing aqueous solution with an acidic aqueous solution outside the electrolytic cell to obtain dissolved carbon dioxide gas, This includes processes related to the process.

[0009] According to a second aspect, the present invention is a. Anode chamber and, b. Intermediate room and, c. Cathode chamber and, An electrolytic cell for carbon dioxide extraction, comprising: The intermediate chamber is located between the anode chamber and the cathode chamber, the anode chamber is connected to the intermediate chamber via a first transport membrane, the cathode chamber is connected to the intermediate chamber via a second transport membrane, and the anode chamber and the cathode chamber are fluidly connected via a hydrogen gas line. The present invention relates to an electrolytic cell, further including a pressure generating device designed to generate a pressure higher than atmospheric pressure, at least within an intermediate chamber.

[0010] According to a third aspect, the present invention relates to a plant for electrolytically extracting carbon dioxide from a gas, particularly air, for carrying out the process according to the first aspect, a. An electrolytic cell according to a second embodiment configured to generate an acidic aqueous solution and an alkaline aqueous solution, b. A contactor configured to react carbon dioxide obtained from a mixed gas with an alkaline aqueous solution to obtain a carbonate-containing aqueous solution, c. A mixing device located outside the electrolytic cell, configured to mix a carbonate-containing aqueous solution with an acidic aqueous solution to obtain dissolved carbon dioxide gas, Regarding a plant equipped with... [Effects of the Invention]

[0011] Some of the effects of the present invention are listed below, but these are neither exhaustive nor limiting.

[0012] Surprisingly, it has been found that overvoltage can be significantly reduced by reacting an alkaline carbonate-containing aqueous solution with an acidic aqueous solution outside the electrolytic cell, particularly according to the first aspect of the present invention. Surprisingly, the overvoltage of the electrolytic cell under overpressure can also be significantly reduced by using a pressure generator as part of the electrolytic cell according to the second aspect of the present invention. Furthermore, the overvoltage can be further significantly reduced by using a hydrophilic diffusion film on the cathode. The aforementioned significant reduction in overvoltage according to the present invention leads to a remarkable improvement in process energy efficiency, resulting in cost reduction, improved process economics, and especially expanded scalability.

[0013] Furthermore, because the present invention is highly flexible and does not depend on the carbon dioxide content in the gas or gas mixture from which carbon dioxide is to be extracted, the present invention can be implemented directly at a carbon dioxide point source, i.e., an industrial plant, and the carbon dioxide generated there can be directly recovered.

[0014] Further details regarding the technical effects achieved by the present invention are described in "Modes for Carrying Out the Invention".

[0015] (definition) Unless otherwise specified, all technical terms used herein are equivalent to those generally understood by those skilled in the art.

[0016] The term "gas containing carbon dioxide" is understood in a broad sense in this specification. In particular, air is included as such a gas. The composition of air at each location, or the method for measuring the composition, is known to those skilled in the art. Further, such a gas containing carbon dioxide can also be a point source. A point source usually refers to an industrial CO2 generation source, where more carbon dioxide gas is generated than the amount normally present in the air. Examples of point sources include exhaust gases generated in cement manufacturing and / or coal combustion. A point source may have a carbon dioxide content of from about 10 mol% to about 25 mol%, particularly from about 14 mol% to about 21 mol%, based on the total amount of the wet gas. Such a gas may have a carbon dioxide content of from about 10 vol% to about 20 vol%. Overall, the mass fraction / mass fraction / mole fraction of carbon dioxide in the gas containing carbon dioxide is generally not important for the functioning of the present invention and its embodiments.

[0017] The term "carbon dioxide extraction" is understood in a broad sense and in this specification refers to the overall process of removing carbon dioxide as a gas from an aqueous solution containing carbonate or a gas mixture such as air or a point source. Formally, as shown in the following formula (1), based on an aqueous solution, using a cation, carbonate / bicarbonate is converted to bicarbonate, and further the bicarbonate is decomposed into water and carbon dioxide gas. When removing carbon dioxide from a mixed gas, the carbon dioxide is first converted into an aqueous solution containing carbonate. The carbon dioxide extraction process involves electrolysis as described later. +

Number

[0018]

Number

[0019] The terms "alkaline" or "basic" are also understood in a broad sense, and an "alkaline aqueous solution" has a pH value exceeding 7.

[0020] The term "pH value" is used herein to mean what is generally understood by those skilled in the art and is measurable using a pH meter. The pH values ​​disclosed herein can be measured, for example, using a VOLTCRAFT PHT-200 combometer capable of measuring pH value and oxidation-reduction (oxidation-reduction potential: ORP).

[0021] [Table 1]

[0022] The above measuring instrument is calibrated to factory standard initial settings and can also be calibrated with the included common pH buffers (pH=4 and pH=7).

[0023] The term "acidic oxidation product" is understood broadly and is not bound by any particular theory, but it refers to the protonate form of oxides of diatomic hydrogen, especially hydrogen gas, such as H3O. + (aq) is solvated in aqueous solution, Cl - (aq) may formally exist as a counteranion and / or as part of the solid electrode and / or film material, through which the proton-form product is transported via a known mechanism. In addition to chlorides, acidic H2SO4, HCO3 - Other formally counter-anions derived from H2CO3, HNO3, HClO4, H3BO3, and HBr may be present in all of the aforementioned cases.

[0024] The term "carbonate-containing aqueous solution" is understood broadly herein and includes any carbonate in its chemical form, particularly its inorganic form. A "carbonate-containing aqueous solution" is typically alkaline, especially with a pH value higher than 7 to 14, for example, 7 to 9. This is because the aqueous solution contains dissolved carbonate CO3. 2-This means that it contains and / or bicarbonates. An example of a "carbonate-containing aqueous solution" is seawater. Carbonate-containing aqueous solutions also contain divalent cations such as magnesium, calcium, and / or strontium. Furthermore, carbonate-containing aqueous solutions may contain monovalent cations such as sodium. Carbonate-containing aqueous solutions may also contain monovalent cations such as sodium and potassium, either exclusively or non-exclusively. These monovalent cations may have counteranions selected from the group consisting of sulfate ions, perchlorate ions, nitrate ions, or combinations thereof, for example. In particular, the dissolved salt can be selected from the group consisting of Na2SO4, K2SO4, NaClO4, KClO4, NaNO3, and KNO3. The term "alkaline carbonate-containing aqueous solution" is used equivalently to "carbonate-containing aqueous solution."

[0025] The term "acidic component" usually refers to aqueous protons, i.e., H3O. + This refers to (aq).

[0026] The term “fluidically connected” is understood herein in a broad sense, and in particular refers to a connection, such as a pipeline, between two electrolytic units, which is configured to transport a fluid, such as a liquid or a gas such as hydrogen gas, from a first electrolytic unit to a second electrolytic unit. Such electrolytic units may have a cathode chamber, an anode chamber, or an intermediate chamber located between the anode and cathode chambers. In addition, “fluidically connected” may also refer to the presence of a mixing device in addition to, for example, one or more pipelines. Furthermore, the term “fluidically connected” also includes the possibility that pipelines may be branched and / or split.

[0027] In particular, the process according to the first embodiment of the invention and the electrolytic cell or plant according to the second embodiment of the invention are operated continuously. Therefore, the solution referred to in this context specifically refers to the mass flow rate of each solution. For example, an alkaline carbonate-containing aqueous solution can be understood as the mass flow rate of the "alkaline carbonate-containing aqueous solution" in continuous operation. Similarly, mass percentage may refer to the mass flow rate of each solution.

[0028] The terms “electrolytic cell” and “electrolysis or electrolytic process” are understood broadly herein. Both terms include, in particular, any electrochemical transformation that is forced using a voltage source. Specifically, an electrolytic cell is or may include a device for performing electrolysis. Furthermore, an electrolytic process is or may include an electrodialysis process.

[0029] The term "air" is understood in a broad sense, referring to the air present in the Earth's atmosphere. Its composition is basically the same, but may vary depending on location. In this invention, it is sufficient that the air contains carbon dioxide.

[0030] The term "overpressure" is understood broadly to refer to the difference between the pressure inside an electrolytic cell and the atmospheric pressure at each location. Acid-resistant "back pressure regulators" can be used to generate overpressure in electrolytic cells, particularly in the intermediate chamber. For this purpose, for example, Equilibar back pressure regulators are used, which are made of 100% PTFE (Teflon®) and feature a diaphragm controlled by air pressure via a gas pressure regulator. (https: / / www.equilibar.com / back-pressure-regulators / how-it-works / accessed March 31, 2023). Pressure measurement inside an electrolytic cell can be performed using conventional pressure measuring devices known to those skilled in the art. The same applies to atmospheric pressure.

[0031] The term "diffusion medium" is understood in a broad sense and refers to (micro)porous materials that promote the dispersion of liquids or gases. These materials utilize capillary action. The term "hydrophobic diffusion medium" is also understood in a broad sense and refers to materials in which capillary depression occurs when a liquid, such as water or neutral, acidic, or basic aqueous solutions, does not wet the material's pores. On the other hand, the term "hydrophilic diffusion medium" is also understood in a broad sense and refers to materials in which capillary rise occurs when a liquid, such as water or neutral, acidic, or basic aqueous solutions, wets the material's pores.

[0032] Unless otherwise specified, electrical voltage can be measured by measuring the electrical coupling between electrodes using a potentiostat, such as the Zennium Pro from Zahner.

[0033] The term "intermediate chamber width" is understood broadly in this specification. In particular, the intermediate chamber width is the distance between the first transport membrane and the second transport membrane when they are arranged parallel to each other.

[0034] The terms "aspects of the present invention" and "aspects of the invention" are used interchangeably herein. [Brief explanation of the drawing]

[0035] [Figure 1] This figure shows one embodiment of the process of the present invention according to a first aspect. [Figure 2] This figure shows one embodiment of the plant of the present invention according to a third aspect. [Figure 3] This diagram illustrates the equilibrium of carbon dioxide, bicarbonates, and carbonates according to their pH levels. [Figure 4] This figure shows the process according to the first embodiment or the pressure generation cycle within the electrolytic cell according to the second embodiment. [Figure 5] This is a simplified exploded view of an electrolytic cell according to the second embodiment. [Modes for carrying out the invention]

[0036] The embodiments described below illustrate advantageous configurations of the present invention and should not be construed as limiting the present invention. Each of the embodiments listed within the scope of various aspects of the invention can be freely combined unless otherwise specified.

[0037] (Electrolysis process) According to a first aspect, the present invention is an electrolysis process for extracting carbon dioxide, comprising: a. Anode-oxidizing hydrogen gas in an electrolytic cell to obtain an acidic oxidation product; b. Reacting the acidic oxidation product with an aqueous electrolyte solution in the electrolytic cell to obtain an acidic aqueous solution; c. Cathode-reducing water in the electrolytic cell to obtain an alkaline aqueous solution and hydrogen gas; d. Reacting the alkaline aqueous solution outside the electrolytic cell with a carbon dioxide-containing gas, particularly air, to obtain an aqueous solution containing carbonate; e. Reacting the alkaline aqueous solution containing carbonate outside the electrolytic cell with the acidic aqueous solution to obtain dissolved carbon dioxide gas. The present invention relates to a process including the above steps.

[0038] The anodic oxidation of hydrogen gas in step a can occur not only in an aqueous solution but also on a gas diffusion electrode, for example, on a zero-gap electrode. The acidic oxidation product formally corresponds to H in the following formula (2). <--Removed non-English text "に相当する。" as it seems to be a remnant from a non-English language -->as follows.

[0039]

Number

[0040] H + can exist, for example, as H3O + (aq) in an aqueous solution or as part of a solid electrode and / or membrane material. The acidic oxidation product H +The actual form may be any form available in step b. In certain embodiments, the hydrogen gas in step a can be oxidized with minimal humidification using a diffusion medium in the form of a gas diffusion electrode, without using an aqueous solution. Since the oxidation of hydrogen gas does not require the generation of oxygen, energy consumption in the process is reduced.

[0041] By using acidic oxidation products, a reaction occurs in the electrolyte aqueous solution within the electrolytic cell in step b. In other words, the electrolyte aqueous solution becomes acidic. Here, the electrolyte aqueous solution does not contain carbonates or bicarbonates in particular. This is because the presence of carbonates or bicarbonates can generate carbon dioxide gas, which can result in a high overpotential. For example, the oxidation product obtained in step a can be generated in the anode chamber, while step b can be carried out in the intermediate chamber of the electrolytic cell. The intermediate chamber can be located between the cathode chamber and the anode chamber. The acidic oxidation product can be supplied to the intermediate chamber via a transport membrane.

[0042] The alkaline solution produced in step c, such as a sodium hydroxide solution, is discharged from the electrolytic cell, just like the acidic aqueous solution produced in step b, and these two solutions do not come into contact with each other during discharge. In this example, the alkaline aqueous solution is brought into contact with a carbon dioxide-containing gas outside the electrolytic cell. The carbon dioxide-containing gas is, for example, air. Using a suitable contactor, carbon dioxide is absorbed into the alkaline solution by a chemical reaction. In this example, carbon dioxide is bonded via hydroxide ions using a carbonate or bicarbonate. Thus, a carbonate-containing aqueous solution is obtained. Finally, the carbonate-containing aqueous solution obtained in step d is combined with the acidic aqueous solution obtained in step b and reacted in a mixing device outside the electrolytic cell, for example, in a continuous stirring tank. The reaction outside the electrolytic cell after step d can reduce the overpotential remarkably. Dissolved carbon dioxide gas is obtained, and this gas can be removed as a gas in step f by degassing the dissolved carbon dioxide gas solution in a carbon dioxide gas extractor, as described herein. Thus, carbon dioxide gas is obtained. The carbon dioxide extractor is, for example, a membrane contactor. In addition to carbon dioxide gas, an electrolyte aqueous solution with a pH value of approximately 3 to 8 is also obtained.

[0043] In certain embodiments, the hydrogen gas generated in the cathode in step c is transferred and oxidized in step a. In other words, a hydrogen cycle takes place within the process (oxidation in step a, reduction in step c, and re-oxidation in step a). Thus, the process of the present invention can generate hydrogen almost autonomously, reducing the need for an external hydrogen supply. Since hydrogen generation generally involves significant energy consumption, this hydrogen cycle represents an efficient saving.

[0044] In certain embodiments, the acidic oxidation product obtained in step a is transported through a first transport membrane for the reaction in step b. This first transport membrane comes into contact with an aqueous electrolyte solution at the outlet of the acidic oxidation product. This aqueous electrolyte solution does not contain carbonates in particular. Otherwise, carbon dioxide will be generated in the electrolytic cell, causing a significant overpotential. For example, such a first transport membrane may have a gas diffusion electrode, a gas diffusion layer (GDL), and / or a zero-gap membrane electrode (CEM). The gas diffusion layer can be considered as the first transport membrane. In particular, the first transport membrane may have a perfluorosulfonic acid membrane. Preferably, such a transport membrane may be based on a perfluorosulfonic acid / polytetrafluoroethylene copolymer. The material of the transport membrane can be further selected from, or alternatively, from the group consisting of PTFE / PTFE (polytetrafluoroethylene / Teflon) based membranes, hydrocarbon membranes, and sPPS (sulfonated polyphenylene sulfone) membranes. Examples include membranes particularly well known to those skilled in the art, marketed under the names Nafion, Gore, Fumasep, Fumapem, Aquivion, Ionomr Pemion, and / or Xion, with Nafion membranes or Gore Select membranes being preferred. In particular, the acidic oxidation product can be generated in the anode chamber in step a, diffuse through this first transport membrane, and then the reaction in step b takes place in the intermediate chamber.

[0045] In certain embodiments, step b is carried out under a pressure higher than atmospheric pressure, in other words, under overpressure. Suitable pressure regulators and controllers are as described above. The overpressure can be particularly from about 0.2 bar to about 20 bar. The overpressure is preferably from about 0.2 bar to about 1 bar, and particularly preferably from about 0.2 bar to about 0.8 bar. Surprisingly, it has been found that the overvoltage of the electrolytic cell can be significantly reduced by utilizing overpressure. While not bound by theory, it is thought that the conductive diffusion medium is pressed more strongly against the electrodes by the overpressure, reducing the electrical resistance of the process. This is an additional advantage, and the electrolytic cell or electrolytic process according to the present invention is significantly more energy efficient than others.

[0046] In certain embodiments, step c is performed at the cathode, which contains a hydrophilic diffusion medium. Preferably, the hydrophilic diffusion medium may include a porous material selected from the group consisting of iron, nickel, titanium, and carbon, or combinations thereof. Particularly preferably, the diffusion medium may be selected from the group consisting of titanium mesh, nickel mesh, carbon paper, or combinations thereof. It was also a surprising discovery here that the use of a hydrophilic diffusion medium significantly reduces the overpotential of the electrolytic cell. Although not bound by theory, hydrophobic materials are used in the art to enable gas removal. Therefore, using a hydrophilic diffusion medium in the cathode is counterintuitive.

[0047] In certain embodiments, step a is performed at the anode, which contains a hydrophobic diffusion medium. For example, such a hydrophobic diffusion medium may include a carbon fiber material pretreated with PTFE.

[0048] In certain embodiments, the oxidation potential in step a is approximately 0V. Therefore, in this example, the anode also serves as the reference electrode. In this case, hydrogen is oxidized on the platinum electrode to a pH of 0.

[0049] In certain embodiments, the reduction potential at step c is approximately 0.2V to approximately 0.9V, and particularly approximately 0.4V to approximately 0.9V. The reduction potential is calculated according to the Nernst equation in particular. Overall, the total cell voltage, including the overvoltage, can be, for example, approximately 0.2V to approximately 3V, preferably approximately 0.2V to approximately 1.8V, and particularly preferably approximately 0.2V to approximately 0.6V.

[0050] In certain embodiments, the hydrogen gas generated in the cathode in step c is transferred and oxidized in step a.

[0051] In certain embodiments, the aqueous electrolyte solution contains cations selected from the group consisting of sodium and potassium, or combinations thereof. Furthermore, or alternatively, the aqueous electrolyte solution contains anions selected from the group consisting of nitrate ions, sulfate ions, and perchlorate ions, or combinations thereof. In particular, the aqueous electrolyte solution is an aqueous sodium sulfate solution, preferably having a molar ratio of about 1 M to about 3 M, and especially preferably about 2 M. Furthermore, or alternatively, the aqueous electrolyte solution is particularly an aqueous sodium perchlorate solution, preferably having a molar ratio of about 4 M to about 6 M, and especially preferably about 5 M.

[0052] In certain embodiments, the acidic oxidation product obtained from the anode chamber is transported through a first transport membrane to react in an intermediate chamber, which comes into contact with an alkaline carbonate-containing solution at the outlet of the acidic oxidation product. For example, such a first transport membrane may have a gas diffusion electrode, a gas diffusion layer (GDL), and / or a zero-gap membrane electrode (CEM). The gas diffusion layer can be considered as the first transport membrane. In particular, the first transport membrane may have a perfluorosulfonic acid membrane. Preferably, such a transport membrane may be based on a perfluorosulfonic acid / polytetrafluoroethylene copolymer. The material of the transport membrane can be further selected from, or alternatively, from the group consisting of PTFE / PTFE (polytetrafluoroethylene / Teflon) based membranes, hydrocarbon membranes, and sPPS (sulfonated polyphenylene sulfone) membranes. Examples include membranes particularly well known to those skilled in the art, marketed under the names Nafion, Gore, Humacep, Humapem, Pemion, Aquivion, and / or Kion, with Nafion membranes or GoreSelect membranes being preferred. In particular, the acidic oxidation product can be generated in the anode chamber in step a, diffuse through such a first transport membrane, and then the reaction in step b takes place in the intermediate chamber.

[0053] In certain embodiments, a metal cation, such as a sodium cation, is transported from the electrolyte aqueous solution to the cathode chamber via a second transport membrane during the reaction. The second transport membrane may, in particular, have the characteristics of the first transport membrane described above. Specifically, the sodium cation can be transported from the carbonate-containing aqueous solution obtained from the intermediate chamber to the cathode chamber via the second transport membrane.

[0054] In certain embodiments, the process is carried out using alternating current (AC) or direct current (DC). In particular, the electrolytic cell can be operated with a DC voltage of up to 3V, especially lower than 1.5V, preferably 1.3V or less. Specifically, the process is carried out using a DC voltage of about 0.6V to 1.5V.

[0055] Furthermore, all embodiments mentioned relate to the first embodiment of the invention, and therefore, any embodiment described as "in a particular embodiment" can be combined with or exclude from each other unless otherwise stated.

[0056] (Electrolytic cell) According to a second aspect, the present invention is a. Anode chamber and, b. Intermediate room and, c. Cathode chamber and, An electrolytic cell for carbon dioxide extraction, comprising: The intermediate chamber is located between the anode chamber and the cathode chamber, the anode chamber is connected to the intermediate chamber via a first transport membrane, the cathode chamber is connected to the intermediate chamber via a second transport membrane, and the anode chamber and the cathode chamber are fluidly connected via a hydrogen gas line. The present invention relates to an electrolytic cell, further including a pressure generating device designed to generate a pressure higher than atmospheric pressure within an intermediate chamber.

[0057] A pressure generator can also be designed to generate a pressure higher than atmospheric pressure primarily in the intermediate chamber, or only in the intermediate chamber.

[0058] Naturally, the electrolytic cell also includes the characteristics and technical effects of the electrolytic process. In particular, the electrolytic cell according to the second aspect of the present invention is configured to carry out the electrolytic process according to the first aspect of the present invention. Therefore, the electrolytic cell according to the first aspect of the present invention can also be used for carbon dioxide extraction using the process according to the second aspect of the present invention.

[0059] In particular, the anode chamber is configured to carry out step a of the process according to the first aspect of the present invention. Furthermore, the intermediate chamber is configured to carry out step b of the process according to the first aspect of the present invention. Thus, the cathode chamber is configured to carry out step c of the process according to the first aspect of the present invention. In particular, step e of the process according to the first aspect of the present invention is carried out in a mixing device outside the electrolytic cell with respect to the electrolytic cell according to the second aspect of the present invention. Such a mixing device is fluidly connected to the intermediate chamber but is located outside the electrolytic cell. The mixing device may be any device as long as it is configured to mix a carbonate-containing aqueous solution with an acidic aqueous solution to obtain dissolved carbon dioxide gas. Such a mixing device may be, for example, a continuous stirring tank.

[0060] The pressure generator can be any device, as long as it is designed to generate a pressure higher than atmospheric pressure in the intermediate chamber. For example, the pressure generator is located downstream from the inlet of the intermediate chamber, where the fluid flows.

[0061] In certain embodiments, the cathode chamber has a cathode active material selected from the group consisting of platinum, iron, carbon, and nickel, or combinations thereof. Furthermore, or alternatively, the anode chamber has an anode active material selected from the group consisting of platinum and carbon, or combinations thereof.

[0062] In certain embodiments, the width of the intermediate chamber is approximately 0.05 mm to approximately 8 mm, particularly approximately 0.1 mm to approximately 8 mm, or approximately 0.2 mm to approximately 8 mm. Preferably, the width of the intermediate chamber is approximately 0.05 mm to approximately 5.5 mm, particularly approximately 0.1 mm to approximately 5.5 mm, or approximately 0.2 mm to approximately 5.5 mm. Particularly preferably, the width of the intermediate chamber is approximately 0.2 mm to 2.0 mm, particularly approximately 0.5 mm. In the art, in particular, other electrolytic cells that do not correspond to the electrolytic cell according to the first embodiment of the invention do not use overpressure, and the reaction between the acidic solution and the alkaline solution is carried out in the intermediate chamber, and furthermore, other processes according to the first embodiment of the invention are used. It was assumed that if the area of ​​the intermediate chamber is small, for example 0.5 mm, the path of the charge carriers would be shorter, and therefore overpotential could be reduced, but in reality the opposite was true. On the other hand, in this example, surprisingly, it was found that such a narrow area of ​​intermediate chamber width combined with the overpressure of this disclosure significantly reduces overpotential.

[0063] Furthermore, a carbon dioxide extraction device is set up, and step f of the process according to the first embodiment of the present invention is carried out.

[0064] As described above, in certain embodiments, the cathode chamber has a hydrophilic diffusion medium and / or the anode chamber has a hydrophobic diffusion medium. The diffusion medium may also have a cathode active material or an anode active material.

[0065] An electrolytic cell according to a second aspect of the present invention can be operated at temperatures lower than 100°C. In particular, it can be operated from 10°C to 80°C or from 20°C to 80°C, or optionally from about 60°C to about 80°C. Furthermore, it is also possible to operate the electrolytic cell at temperatures between 95°C and 100°C.

[0066] The intermediate chamber of the electrolytic cell can be defined by a frame directly connected to both sides of the first and second transport membranes via seals. Furthermore, the anode or cathode chamber can be defined by a diffusion medium, seals, and a current collector, for example, made of titanium, as described herein. Herein, the diffusion medium is in direct contact with the first and second transport membranes in particular, followed in layers by seals and a current collector, the current collector also including a flow path.

[0067] Furthermore, all embodiments mentioned relate to the second embodiment of the invention, and therefore, any embodiment described as "in a particular embodiment" can be combined with or exclude from each other unless otherwise stated.

[0068] (plant) According to a third aspect, the present invention relates to a plant for electrolytically extracting carbon dioxide from a gas, particularly air, for carrying out the process according to the first aspect, a. An electrolytic cell according to a second embodiment configured to generate an acidic aqueous solution and an alkaline aqueous solution, b. A contactor configured to react carbon dioxide obtained from a mixed gas with an alkaline aqueous solution to obtain a carbonate-containing aqueous solution, c. A mixing device located outside the electrolytic cell, configured to mix a carbonate-containing aqueous solution with an acidic aqueous solution to obtain dissolved carbon dioxide gas, Regarding a plant equipped with...

[0069] For example, several electrolytic cells according to the first aspect of the present invention can be used in combination within a plant. These multiple electrolytic cells can be stacked and connected to each other. For example, two electrolytic cells can be connected via a common anode chamber. Another electrolytic cell can be connected to these two electrolytic cells via a common cathode. Yet another electrolytic cell can be connected to this additional electrolytic cell via a common anode chamber, and so on, with electrolytic cells being stacked and connected.

[0070] Furthermore, this plant can also be operated in a process according to the first aspect of the present invention.

[0071] Furthermore, the electrolytic cell according to the second embodiment includes a contactor, which is configured to react carbon dioxide obtained from a mixed gas with an alkaline aqueous solution to obtain a carbonate-containing aqueous solution. Such contactors are well known to those skilled in the art, and their type is not important to the present invention. An example of such a contactor is the 3M Liqui-Cel EXF-10×28 series.

[0072] To avoid repetition, it should be noted that this plant appropriately possesses the features, technical advantages, and effects of the first and second embodiments of the present invention.

[0073] Furthermore, all embodiments mentioned relate to the third aspect of the invention, and therefore, any embodiment described as "in a particular embodiment" can be combined with or exclude from each other unless otherwise stated.

[0074] (Drawing description) The following figures illustrate exemplary embodiments of the present invention and should not be construed as limiting.

[0075] Figure 1 schematically and illustratively illustrates the process according to the first embodiment. In this figure, CO2-containing air is supplied to a gas-liquid contactor, where CO2 from this air is absorbed through interaction with an alkaline aqueous solution, forming an alkaline carbonate-containing solution according to reaction 11, and thus the separated air has a reduced CO2 content. Next, the pH value of the alkaline carbonate-containing solution decreases according to reaction 12 with sulfuric acid, and the equilibrium of the inorganic dissolved carbonate shifts mainly to CO2 according to the Bjerrum system in Figure 3, and the CO2 can then be separated as a gas. The CO2 gas thus obtained can be stored or used further in subsequent reactions and various applications. Furthermore, reactions 13 and 15 show reactions at the cathode, or reactions within the cathode chamber, where water is reduced to hydroxide ions and hydrogen, forming an aqueous sodium hydroxide solution. Reaction 14 shows the oxidation of hydrogen to hydrated protons, which occurs at the anode. Subsequently, the hydrated protons can move, for example, through a transport membrane to an intermediate chamber in an electrolytic cell according to a second embodiment of the invention, where sulfuric acid is produced according to reaction 16.

[0076] Figure 2 shows an exemplary configuration of plant 100a of the present invention according to a third embodiment of the invention, and the process according to the first embodiment of the invention can be carried out using this plant 100a. The plant, acting as an air supply unit 1, supplies gas that can be supplied via the gas-liquid contactor 2 to plant 100a by being absorbed into an alkaline aqueous solution. The resulting carbonate-containing aqueous solution is then mixed with an acidic aqueous solution in a mixing container 3, and, for example, carbon dioxide gas is extracted from the plant via one or more membrane contactors 4. The acidic degassed solution is then supplied to the first and second parts of each electrolytic unit 5. The first part of the acidic degassed aqueous solution is supplied to the intermediate chamber 52, where the acidic degassed aqueous solution is supplied together with the acidic oxidation product obtained from the anode chamber 51. The second part of the acidic degassed aqueous solution is reduced in the cathode chamber 53 to produce an alkaline aqueous solution according to reactions 13 and 15. Subsequently, in the gas-water separator 6, hydrogen gas can be separated from the alkaline aqueous solution, and the hydrogen is supplied to the anode chamber 51, where it is oxidized to protons according to reaction equation 14 and supplied to the intermediate chamber via the diffusion medium 54 and transport membrane 55.

[0077] Figure 3 shows the Bielm system, which displays the composition of each component of inorganic dissolved carbonate in an aqueous solution based on its pH value.

[0078] Figure 4 shows exemplary configurations of plant 100b according to the present invention according to the first and third embodiments of the invention, and exemplary configurations of electrolytic cell 50 according to the present invention according to the second embodiment of the invention. Here, water is reduced to hydrogen and an alkaline aqueous solution in a hydrophilic diffusion medium 57 on a catalyst layer coated on a transport membrane 56. The cathode chamber 53 is fluidly connected to a gas-water separator 6 via a line, where hydrogen gas is separated from the alkaline aqueous solution. Here, hydrogen is first supplied to the anode chamber 51 via the fluid connection, where it is oxidized in a hydrophobic diffusion medium 54, and the resulting protons are supplied to the intermediate chamber 52 via a transport membrane 55, where the aqueous solution is acidified, and sodium ions can be transported to the cathode chamber 53 via a second transport membrane 56. Here, the width of the intermediate chamber 52 is 0.5 mm as an example. Furthermore, a pressure regulator 8 is provided as an example at the outlet of the intermediate chamber according to the second embodiment of the invention, thereby applying overpressure to the intermediate chamber 52 to maximize the conductivity between the conductive diffusion medium 54 and the current collector flow path 58, or between the conductive diffusion medium 57 and the current collector flow path 59, and thus minimizing the overvoltage in the cell according to the following embodiment. Furthermore, the gas that can be supplied via the gas-liquid contactor 2 can be absorbed into an alkaline aqueous solution and supplied to the plant 100b via the plant acting as the air supply unit 1. Subsequently, the alkaline carbonate-containing aqueous solution is mixed with an acidic aqueous solution in the mixing container 3 to extract, for example, carbon dioxide gas from the plant 100b via one or more membrane contactors 4. Then, as illustrated in the second embodiment of the invention, the acidic degassed solution is supplied to the first and second parts of each hydrogen circulation cell 50.

[0079] Figure 5 shows an exemplary configuration of a hydrogen circulation cell 50 as part of an electrolytic cell 5 according to a second embodiment of the invention. This figure shows the layer-by-layer arrangement of each component described in the following reference numerals. [Examples]

[0080] (Experimental setup) In this experiment, an improved electrolytic cell was developed, consisting of two steel end plates and two graphite current collectors, with integrated flow channels. Two flow channels for the intermediate chamber, 1 mm and 5 mm thick, are made of polypropylene. Each has an electrolyte inlet and outlet, and a back pressure valve manufactured by Equilibrium is installed behind the outlet. This back pressure valve is controlled by a pneumatic regulator, allowing for the generation of liquid overpressure. PTFE gaskets and FKM gaskets were used for sealing. Two Nafion cation exchange membranes were used. Carbon fiber diffusion media were used for each membrane, but different materials were used. A hydrophobic material from Freudenberg was used for the anode, and a platinum-carbon (pt / c) catalyst was directly coated onto the electrode material. On the other hand, two different materials were tested for the cathode, as described below. Unlike the anode, the Pt / C catalyst was coated onto the cathode membrane using the so-called decal method.

[0081] For the experiment, a solution of 0.5 M concentrated sodium sulfate dissolved in distilled water with a conductivity of 65 mS / cm was used as the electrolyte.

[0082] For power supply and measurement, we used the Zennium Pro potentiostat / galvanostat model from Zahner Elektrik.

[0083] A LabN6III peristaltic pump with two pump heads manufactured by Shenzhen was used to move the liquid. The electrolyte flow rate was set to 200 mL / min. In addition to the hydrogen separated by the gas-liquid separator, hydrogen was also supplied from an external source and regulated with a Bronkhorst F201-CV hydrogen gas mass flow controller.

[0084] (Explanation of the experiment) This cell was constructed by providing graphite channels in both the anode and cathode. Furthermore, two types of FKM-based gaskets, 0.2 mm and 0.3 mm thick, were used. The 0.3 mm thick gasket was placed between the graphite channel and the membrane. The thinner 0.2 mm thick gasket was placed between the membrane and the intermediate chamber channel.

[0085] The flow rate was set to 200 mL / min in all experiments. The active area of ​​the cell was 30 cm². 2 In all experiments, the applied current was 0.5 amperes.

[0086] (Hydrophobic diffusion media and hydrophilic diffusion media) Here, only the material of the cathode diffusion medium was initially changed. One experiment used a hydrophobic SGL carbon material of type Sigraset 22BB. Furthermore, a hydrophilic material of type E35 from Freudenberg was also tested. Both diffusion mediums are based on microporous carbon materials.

[0087] (Atmospheric pressure and overpressure) To generate overpressure in the cell's intermediate chamber, an Equilibrium back pressure regulator was installed at the outlet of the intermediate chamber. The valve was made entirely of PTFE, and the liquid pressure was controlled via a diaphragm before the liquid passed through the valve. The control pressure was applied as pneumatic pressure using an SMC ITV0030-0N device. Here, pneumatic pressure corresponds to hydrodynamic pressure. In each experiment, the hydrodynamic overpressure was varied from 0 bar to 1.5 bar.

[0088] (result) In the experiments conducted according to the present invention, the voltage was determined by a constant current of 0.5A. Therefore, the current density was 16.67mA / cm² in all experiments conducted (Examples 1-3). 2 It was. Equivalent current density: 15 mA / cm² 2 A comparative example was then conducted. The experimental results are shown in Table 1 below.

[0089] [Table 2]

[0090] The results in Table 1 surprisingly show that reacting a carbonate-containing alkaline aqueous solution with an acidic aqueous solution outside the electrolytic cell according to the present invention achieves a significant reduction in overpotential, in contrast to comparative experiments where the reaction occurs inside the electrolytic cell. Furthermore, Table 1 clearly demonstrates the properties that reduce overpotential and enable more energy-efficient process control. [Explanation of Symbols]

[0091] 1. Air supply unit 2. Gas-liquid contactor 3 Mixing container 4 Membrane contactor 5 Electrolytic Unit 50 Hydrogen Circulation Cells 51 Anode Chamber 52 Intermediate Room 53 Cathode Chamber 54 Hydrophobic diffusion media 55 First ion transport membrane 56. Second ion transport membrane with catalyst coating on one side. 57 Hydrophilic diffusion media 58 Anode-side current collector flow path 59 Cathode-side current collector flow path 6 Steam water separator 71 Seal between the anode channel and the first ion transport membrane 72 Seal between the first ion transport membrane and the intermediate chamber 73 Seal between the intermediate chamber and the second ion transport membrane 74 Seal between the cathode channel and the second ion transport membrane 8 Back pressure regulator 100a System 100b System

Claims

1. An electrolytic process for extracting carbon dioxide, a. The step of anodic oxidation of hydrogen gas in an electrolytic cell to obtain an acidic oxidation product, b. The step of reacting the acidic oxidation product with an electrolyte aqueous solution in the electrolytic cell to obtain an acidic aqueous solution, c. The step of reducing water by cathode in the electrolytic cell to obtain an alkaline aqueous solution and hydrogen gas, d. A step of reacting the alkaline aqueous solution with a carbon dioxide-containing gas, particularly air, outside the electrolytic cell to obtain a carbonate-containing aqueous solution, e. A step of reacting the alkaline carbonate-containing aqueous solution with the acidic aqueous solution outside the electrolytic cell to obtain dissolved carbon dioxide gas, A process that includes this.

2. The process according to claim 1, wherein step b is carried out under a pressure higher than atmospheric pressure, the overpressure higher than atmospheric pressure being particularly about 0.2 bar to about 20 bar.

3. The process according to claim 1 or 2, wherein step c is performed in a cathode, and the cathode comprises a hydrophilic diffusion medium.

4. The process according to any of the preceding claims, wherein step a is performed at an anode, the anode comprising a hydrophobic diffusion medium.

5. The process according to any of the preceding claims, wherein the oxidation potential of step a is approximately 0V.

6. The process according to any of the preceding claims, wherein the reduction potential at step c is approximately 0.2 V to approximately 0.9 V.

7. The process according to any of the preceding claims, wherein the hydrogen gas generated in the cathode in step c is transferred from step c to step a, and oxidized in step a.

8. The process according to any of the preceding claims, wherein the aqueous electrolyte solution contains a cation selected from the group consisting of sodium and potassium, or a combination thereof, and / or the aqueous electrolyte solution contains an anion selected from the group consisting of nitrate ions, perchlorate ions, and sulfate ions, or a combination thereof.

9. Following the steps, f. Step of extracting carbon dioxide gas as a gas. The process according to any of the prior claims, further including the process described in any of the prior claims.

10. a. Anode chamber and, b. Intermediate chamber and, c. Cathode chamber and, An electrolytic cell for carbon dioxide extraction, comprising: The intermediate chamber is positioned between the anode chamber and the cathode chamber, the anode chamber is connected to the intermediate chamber via a first transport membrane, the cathode chamber is connected to the intermediate chamber via a second transport membrane, and the anode chamber and the cathode chamber are fluidly connected via a hydrogen gas line. An electrolytic cell further comprising a pressure generating device designed to generate a pressure higher than atmospheric pressure in the aforementioned intermediate chamber.

11. The electrolytic cell according to claim 10, wherein the anode chamber contains an anode active material containing platinum, and / or the cathode chamber contains a cathode active material containing platinum.

12. The electrolytic cell according to claim 10 or 11, wherein the width of the intermediate chamber is approximately 0.05 mm to approximately 8 mm.

13. The electrolytic cell according to any one of claims 10 to 12, wherein the cathode chamber contains a hydrophilic diffusion medium and / or the anode chamber contains a hydrophobic diffusion medium.

14. A plant for electrolytically extracting carbon dioxide from a gas, particularly air or a point source, for carrying out the process described in any one of claims 1 to 9, a. An electrolytic cell according to any one of claims 10 to 13, configured to produce an acidic aqueous solution and an alkaline aqueous solution, b. A contactor configured to convert carbon dioxide obtained from a mixed gas into a carbonate-containing aqueous solution using the aforementioned alkaline aqueous solution, c. A mixing device located outside the electrolytic cell and configured to mix the carbonate-containing aqueous solution with the acidic aqueous solution to obtain dissolved carbon dioxide, A plant equipped with these features.

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