Method for regenerating carbon dioxide adsorbent, method for adsorbing and separating carbon dioxide, and method for continuous adsorption and separation of carbon dioxide

Abstract

The present invention provides a method for regenerating a carbon dioxide adsorbent, a continuous adsorption and separation method for carbon dioxide including this regeneration method, and a carbon dioxide adsorption and separation method for easily separating carbon dioxide from a carbon dioxide adsorbent that has adsorbed carbon dioxide. [Solution] A method for regenerating a carbon dioxide adsorbent containing an alkali metal carbonate and a specific metal compound, comprising: a method for regenerating a carbon dioxide adsorbent in which the carbon dioxide adsorbent is brought into contact with water and then into contact with an aqueous solution containing an alkali metal carbonate; a continuous adsorption separation method in which an adsorption step of bringing the carbon dioxide adsorbent into contact with a gas containing carbon dioxide and a separation step of heating the carbon dioxide adsorbent that has adsorbed carbon dioxide to a specific temperature are repeatedly performed via the carbon dioxide adsorption separation method described above; and a carbon dioxide adsorption separation method comprising a separation step of heating the carbon dioxide adsorbent that has adsorbed carbon dioxide in the adsorption step to a specific temperature in an atmosphere of gas containing carbon dioxide.

Description

[Technical Field]

[0001] The present invention relates to a method for regenerating a carbon dioxide adsorbent, a method for adsorbing and separating carbon dioxide, and a method for continuous adsorption and separation of carbon dioxide. [Background technology]

[0002] In recent years, various studies have been conducted on methods for capturing carbon dioxide, which is considered a cause of global warming, and various capture methods have been proposed. For example, as one of the technologies for directly capturing carbon dioxide from gases such as the atmosphere (DAC), a method of adsorption and separation of carbon dioxide using solid adsorbents has been proposed. As an example, Patent Document 1 describes: "A process of bringing a specific carbon dioxide adsorbent into contact with a gas containing carbon dioxide, thereby adsorbing carbon dioxide onto the carbon dioxide adsorbent," A step of separating carbon dioxide from the carbon dioxide adsorbent by heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide, to 50°C to 900°C. A method for adsorbing and separating carbon dioxide, including It is stated. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2022 / 145217 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] As described in Patent Document 1, a carbon dioxide adsorption and separation method using alkali metal carbonate as the adsorption component allows for repeated adsorption and separation of carbon dioxide multiple times because alkali metal carbonate has properties and functions that cause reversible reactions to occur during the adsorption and separation (desorption) of carbon dioxide. However, when the carbon dioxide adsorption separation method is repeatedly performed, generally, the carbon dioxide adsorption performance of the carbon dioxide adsorbent gradually decreases. In particular, according to the study by the present inventor, it has been found that the decrease in adsorption performance (deterioration of the carbon dioxide adsorbent) is promoted depending on the gas brought into contact with the carbon dioxide adsorbent. However, in the conventional carbon dioxide adsorption separation methods including Patent Document 1, such examination from this viewpoint has not been conducted. Therefore, in the conventional carbon dioxide adsorption separation methods, the carbon dioxide adsorbent with decreased adsorption performance has to be discarded, and countermeasures against environmental conservation (environmental load) and cost are required.

[0005] An object of the present invention is to provide a method for regenerating a carbon dioxide adsorbent and a continuous carbon dioxide adsorption separation method including this regeneration method. Another object of the present invention is to provide a carbon dioxide adsorption separation method capable of easily separating carbon dioxide from a carbon dioxide adsorbent that has adsorbed carbon dioxide.

Means for Solving the Problems

[0006] The present inventors have intensively studied a carbon dioxide adsorption and separation technique using an alkali metal carbonate as an adsorption component. As a result, when the carbon dioxide adsorption and separation (adsorption and desorption) is repeatedly performed on the carbon dioxide adsorbent, rather than the deterioration (decomposition) of the adsorption component, components other than carbon dioxide in the gas brought into contact with the carbon dioxide adsorbent, particularly nitrogen oxides and sulfur oxides, affect the decrease in the carbon dioxide adsorption performance of the carbon dioxide adsorbent (in the present invention, sometimes simply referred to as "the adsorption performance of the carbon dioxide adsorbent" or "adsorption performance"). The present inventors further advanced the study and found that, rather than the main product formed by the reaction of carbon dioxide in the gas with the adsorption component, the by-products formed as a by-reaction of components other than carbon dioxide with the adsorption component are less likely to undergo a reverse reaction under the conditions in the separation step (desorption step) and gradually mix into the carbon dioxide adsorbent, which is one of the factors causing a decrease in the adsorption performance of the carbon dioxide adsorbent. In addition, it was also found that such by-products are water-soluble, and the by-products can be removed by washing the carbon dioxide adsorbent with reduced adsorption performance with water. Furthermore, it was found that when the separation step is carried out by heating the carbon dioxide adsorbent to 50 to 900 °C in an atmosphere of a gas containing carbon dioxide, the adsorbed carbon dioxide can be easily separated and desorbed from the carbon dioxide adsorbent. The present invention has been further studied based on these findings and has been completed.

[0007] That is, the problems of the present invention have been achieved by the following means. <1>A method for regenerating a carbon dioxide adsorbent that adsorbs carbon dioxide in a gas, comprising: the carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 elements and Group 4 elements of the periodic table; a method for regenerating a carbon dioxide adsorbent, wherein after bringing the carbon dioxide adsorbent into contact with water, the carbon dioxide adsorbent is brought into contact with an aqueous solution containing an alkali metal carbonate containing at least one alkali metal element. <2>The regeneration method according to <1>, wherein the metal compound contains at least one element selected from the group consisting of cerium, titanium, and zirconium. <3> The aforementioned metal compound contains the element zirconium. <1> or <2> The playback method is as described. <4> The aforementioned metal compound is zirconium oxide. <1> ~ <3> The playback method described in any one of the items. <5> The aforementioned gas is either the atmosphere or factory exhaust gas. <1> ~ <4> The playback method described in any one of the items. <6> The aforementioned gas is exhaust gas from a power plant. <1> ~ <4> The playback method described in any one of the items. <7> The gas comprises at least one selected from the group consisting of nitrogen oxides and sulfur oxides. <1> ~ <6> The playback method described in any one of the items. <8> The alkali metal carbonate contained in the aqueous solution is potassium carbonate. <1> ~ <7> The playback method described in any one of the items. <9> A continuous adsorption and separation method for carbon dioxide, comprising repeatedly performing an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50-900°C, The carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. After performing at least one adsorption step and one separation step, <1> ~ <8> A method for continuous adsorption and separation of carbon dioxide, comprising regenerating the carbon dioxide adsorbent after the separation step by the regeneration method described in any one of the items. <10> At least one of the multiple separation steps is heated in an atmosphere containing carbon dioxide. <9> The method for continuous adsorption and separation of carbon dioxide as described above. <11> A method for adsorbing and separating carbon dioxide, comprising an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50-900°C in an atmosphere of gas containing carbon dioxide. [Effects of the Invention]

[0008] The present invention can provide a method for regenerating a carbon dioxide adsorbent, and a continuous adsorption and separation method for carbon dioxide including this regeneration method. Furthermore, the present invention can provide a carbon dioxide adsorption and separation method that can easily separate carbon dioxide from a carbon dioxide adsorbent that has adsorbed carbon dioxide. [Modes for carrying out the invention]

[0009] In the present invention and this specification, when describing content, physical properties, etc., by indicating numerical ranges, if the upper and lower limits of the numerical range are described separately, either upper or lower limit can be appropriately combined to form a specific numerical range. On the other hand, when multiple numerical ranges represented by "~" are set and described, the upper and lower limits forming the numerical range are not limited to a specific combination of the upper and lower limits described before and after "~" as a specific numerical range, but can be a numerical range formed by appropriately combining the upper and lower limits of each numerical range. In the present invention and this specification, a numerical range represented by "~" means a range that includes the numbers described before and after "~" as the lower and upper limits.

[0010] [[Method for regenerating carbon dioxide adsorbent]] The present invention provides a method for regenerating carbon dioxide adsorbent materials (hereinafter sometimes simply referred to as "the present invention's regeneration method"), which is a method for regenerating carbon dioxide adsorbent materials used in a method for adsorbing carbon dioxide in a gas and separating (desorbing) the adsorbed carbon dioxide, that is, used carbon dioxide adsorbent materials used in a carbon dioxide adsorption and separation method. As described above, the carbon dioxide adsorbent material to be regenerated may contain by-products, or by-products may accumulate and deposit on its surface, and furthermore, main products resulting from the reaction of alkali metal carbonates and carbon dioxide may be present, or accumulated and deposited on the surface of the carbon dioxide adsorbent material. The regeneration method of the present invention specifically involves contacting (used) carbon dioxide adsorbent with water, and then contacting it with an aqueous solution containing an alkali metal carbonate containing at least one alkali metal element. This removes by-products that have been mixed into, accumulated, or deposited on the carbon dioxide adsorbent, recovers the metal compound (and porous material if necessary), and then regenerates the carbon dioxide adsorbent by contacting and mixing the recovered metal compound with a new alkali metal carbonate. In the regeneration method of the present invention, the degree of regeneration of the carbon dioxide adsorbent cannot be uniquely determined by variations in the contact conditions with water and with the aqueous solution containing the alkali metal carbonate, but by selecting the appropriate contact conditions, it is possible to achieve adsorption performance equivalent to that of the carbon dioxide adsorbent before use. Thus, the regeneration method of the present invention can also be described as a method for producing carbon dioxide adsorbent (regenerated carbon dioxide adsorbent) from used carbon dioxide adsorbent. In other words, the regeneration method of carbon dioxide adsorbent is synonymous with the production method of recycled carbon dioxide adsorbent, and is an invention of a method for producing a material (regenerated carbon dioxide adsorbent).

[0011] [Carbon dioxide adsorbent] First, we will explain the carbon dioxide adsorbent (unused carbon dioxide adsorbent) used in the carbon dioxide adsorption and separation method. The carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. This carbon dioxide adsorbent may further contain a porous material.

[0012] The average pore diameter of the carbon dioxide adsorbent is not particularly limited, but from the viewpoint of carbon dioxide adsorption performance, it is preferably 0.3 to 500 nm, and more preferably 1 to 100 nm. The average pore diameter (in nm) of a carbon dioxide adsorbent can be analyzed and measured by nitrogen adsorption using a conventionally known and suitable specific surface area / pore distribution measuring device. Specifically, an isotherm of nitrogen adsorption / desorption for the carbon dioxide adsorbent is obtained, and from the obtained isotherm, the total pore volume (V) (in cm³) can be calculated.3 / g) and specific surface area (A) (unit: m 2 By further obtaining ( / g), the average pore diameter (D) can be calculated based on the formula: D = 4V / A.

[0013] The carbon dioxide adsorbent may have a porous material (substrate) supporting an alkali metal carbonate and a metal compound. In other words, the carbon dioxide adsorbent may be integrally constructed by supporting the alkali metal carbonate and the metal compound on a porous material. However, the embodiment of the carbon dioxide adsorbent having a porous material is not limited to this, and the alkali metal carbonate in particular may be present in the carbon dioxide adsorbent in a state free from the porous material. Furthermore, in a carbon dioxide adsorbent, the porous material may be a metal compound. In other words, a carbon dioxide adsorbent may be one in which an alkali metal carbonate is supported on a porous material made of a metal compound. In this case, since the metal compound is a porous material and forms a substrate, it is not usually supported on the porous material, but a metal compound other than the metal compound that forms the porous material may be supported on the porous material.

[0014] <Alkali metal carbonates> The carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element. The alkali metal carbonate functions as a carbon dioxide adsorbent by reacting with carbon dioxide in the presence of water as needed. For example, if the alkali metal carbonate is potassium carbonate, it becomes potassium bicarbonate (potassium hydrogen carbonate), and the resulting potassium bicarbonate is regenerated back into potassium carbonate by heating in the separation process described later. This method of adsorbing and separating carbon dioxide using alkali metal carbonates allows for repeated adsorption and separation by utilizing the reversible reaction of the alkali metal carbonate during adsorption and separation. The carbon dioxide adsorbent may contain one or more alkali metal carbonates.

[0015] The alkali metal carbonate preferably contains at least one alkali metal element selected from the group consisting of lithium, sodium, potassium, rubidium, and cesium. From the viewpoint of carbon dioxide adsorption performance, the alkali metal carbonate preferably contains sodium, potassium, or cesium, and more preferably contains potassium.

[0016] The alkali metal carbonate is not particularly limited, and examples include lithium carbonate, lithium bicarbonate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, rubidium carbonate, rubidium bicarbonate, cesium carbonate, and cesium bicarbonate. From the viewpoint of carbon dioxide adsorption performance, potassium carbonate and potassium bicarbonate are preferred, and potassium carbonate is more preferred.

[0017] The content of alkali metal elements in the carbon dioxide adsorbent is not particularly limited, but from the viewpoint of carbon dioxide adsorption performance, it is preferably 1.0 to 20.0 mmol per 1.0 g of metal compound, and more preferably 1.0 to 10.0 mmol.

[0018] <Metal compounds> The metal compound contained in the carbon dioxide adsorbent is a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. The carbon dioxide adsorbent may contain one or more metal compounds. The elements contained in the metal compound are preferably at least one element selected from the group consisting of cerium, titanium, and zirconium, from the viewpoint of carbon dioxide adsorption performance and availability, and more preferably the element zirconium is included.

[0019] The metal compound contained in the carbon dioxide adsorbent is not particularly limited, and examples include cerium compounds such as cerium oxide, cerium carbonate, cerium nitrate, cerium(III) hydroxide, cerium(IV) hydroxide, cerium chloride, cerium acetate, and cerium(III) acetylacetonate; titanium compounds such as titanium oxide, titanium hydroxide, tetramethyl titanate, tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate, tetrabutyl titanate, tetraisobutyl titanate, tetra(2-ethylhexyl) titanate, tetraoctadecyl titanate, titanium(IV) oxyacetylacetonate, and titanium(IV) disipropoxybisacetylacetonate; and zirconium compounds such as zirconium oxide, zirconium carbonate (IV), zirconium oxynitrate, zirconium hydroxide (IV), and zirconium chloride (IV). From the viewpoint of carbon dioxide adsorption performance, the metal compound contained in the carbon dioxide adsorbent preferably contains zirconium oxide, and more preferably zirconium oxide.

[0020] The above-mentioned metal compound may be included in the carbon dioxide adsorbent as the metal compound itself, or in the form of a composite with alkali metal carbonate, porous material described later, other metal compounds, and / or other components described later.

[0021] From the viewpoint of carbon dioxide adsorption performance, the content of the above elements in the metal compound is preferably 0.1 to 20.0 mmol / g, and more preferably 0.1 to 10.0 mmol / g.

[0022] <Porous material> The porous material that serves as the base for the carbon dioxide adsorbent is not particularly limited, and examples include oxides such as aluminum oxide and silicon oxide, composite oxides such as calcium silicate and silica alumina, and activated carbon. Among these, it is preferable to use at least one selected from the group consisting of silicon oxide, aluminum oxide, activated carbon, and calcium silicate, from the viewpoint of carbon dioxide adsorption performance.

[0023] Activated carbon is a flammable substance. Therefore, if the temperature (heating temperature) in the separation process described later is, for example, 250°C or higher, it is more preferable to use silicon dioxide as the porous material.

[0024] The porous material exemplified above can be manufactured by any suitable conventional manufacturing method. Furthermore, commercially available porous materials can also be used as the porous material exemplified above.

[0025] The type of aluminum oxide is not particularly limited; for example, any crystal system such as α-type, γ-type, or θ-type can be used. Furthermore, the method for producing aluminum oxide is not particularly limited. For example, aluminum oxide can be produced by washing bauxite, an aluminum-containing mineral, with a hot sodium hydroxide solution, cooling and precipitating the aluminum hydroxide dissolved in the sodium hydroxide solution, and then heating and dehydrating it.

[0026] When the porous material is silicon dioxide, examples of silicon dioxide include silica gel, mesoporous silica, and zeolites. Silicon dioxide can be produced by wet or dry methods. Examples of wet methods include precipitation and gel methods. Examples of dry methods include combustion.

[0027] When producing silica gel, a porous material, by a wet process, a compound represented by the general formula Na2O·nSiO2 is used and neutralized with sulfuric acid or hydrochloric acid to obtain a hydrogel via a silica sol having a polysilicic acid composition. Silica gel can then be obtained by removing water from the hydrogel. The method for removing water from the hydrogel is not particularly limited. The water in the hydrogel may be directly evaporated, or it may be replaced with a relatively low-boiling hydrophilic organic solvent such as an alcohol or ketone, followed by drying and heating. By replacing the water in the hydrogel with a low-boiling hydrophilic organic solvent such as an alcohol or ketone, drying, and heating, silicon oxide with a larger pore volume and pore diameter can be obtained.

[0028] Mesoporous silica is not particularly limited in type, as long as it has mesopores in its structure. The pore size of mesoporous silica is usually 1.5 to 50 nm. Furthermore, there are no particular limitations on the method of producing mesoporous silica. For example, mesoporous silica can be produced from a mixture of a sol-gel precursor and a structurally controlling amphiphilic substance by a self-assembly process. Specifically, first, liquid crystal micelles are formed in water using a surfactant such as cetyltrimethylammonium bromide, and hydrolysis and condensation occur by adding a ceramic sol-gel precursor such as tetraethyl orthosilicic acid, forming a silica network around the micelles. Next, mesoporous silica is obtained by removing the organic template by heat treatment or solvent extraction.

[0029] The type of zeolite is not particularly limited and includes, for example, synthetic zeolite, artificial zeolite, and natural zeolite. Furthermore, the method of producing zeolite is not particularly limited. For example, a mixture consisting of an alumina source, a silica source, an alkali source, an organic structure-regulating agent, and water can be subjected to a hydrothermal reaction, followed by drying and calcination to produce zeolite.

[0030] The type of calcium silicate is not particularly limited; for example, any crystalline form such as wollastonite, tobermorite, or xonotlite can be used. Furthermore, the method for producing calcium silicate is not particularly limited. For example, calcium silicate (secondary particles) can be produced by hydrothermally reacting a mixture consisting of a siliceous raw material, a calcareous raw material, and water while stirring.

[0031] When the porous material is activated carbon, activated carbon can be produced by heating a carbonaceous raw material to carbonize it into a carbide, and then activating it. The carbonaceous material used as the raw material for activated carbon is not particularly limited. Examples of carbonaceous materials include wood, sawdust, coconut shells, pulp wastewater, coal, petroleum products, and synthetic resins.

[0032] The method for activating (revitalizing) carbides after carbonization of carbonaceous materials is not particularly limited. Examples of activation methods include gas activation and chemical activation.

[0033] Gas activation methods include, for example, high-temperature treatment with water vapor, carbon dioxide, or air. Gas activation is thought to proceed in two stages. In the first stage, the heating process, the unorganized parts of the carbide are selectively decomposed and consumed, releasing fine pores within the carbon structure and rapidly increasing the internal surface area. In the second stage, the gasification reaction process, the carbon crystals constituting the carbide, or the carbon constituting the fine pore areas, are reacted and consumed, forming large pores in a complex and organized manner. In this pore formation process, if the carbon reaction consumption rate is 50% or less, the activated carbon will be mainly composed of micropores, and if the carbon reaction consumption rate exceeds 75%, the activated carbon will have increased macropores. At intermediate carbon reaction consumption rates, activated carbon with both micropores and macropores can be obtained.

[0034] Methods for chemical activation include, for example, the use of zinc chloride, phosphoric acid, calcium chloride, and potassium sulfide. It is generally known that chemical activation increases the pore volume and average pore diameter of activated carbon. Furthermore, activated carbon can take on a variety of forms depending on the raw materials and manufacturing method, such as powder, granules, crushed, fibrous, and honeycomb, but the form of activated carbon that can be applied to the carbon dioxide adsorbent of the present invention is not particularly limited.

[0035] As the porous material, the aforementioned metal compounds can also be used.

[0036] <Other ingredients> The carbon dioxide adsorbent may further contain other components in addition to the components described above. These other components may be any components that do not fall under any of the alkali metal carbonates, metal compounds, or porous materials described above. Examples include alkali metal compounds such as cesium nitrate, cesium oxide, cesium hydroxide, and cesium acetate (excluding the alkali metal carbonates described above), and alkaline earth metal compounds such as magnesium carbonate, magnesium oxide, calcium carbonate, and calcium oxide.

[0037] Other components may be present in the carbon dioxide adsorbent as themselves, or in the form of alkali metal carbonates, metal compounds, composites with porous materials, or oxides derived therefrom. The total content of other components in the carbon dioxide adsorbent is not particularly limited and can be determined as appropriate.

[0038] <Shape of carbon dioxide adsorbent, etc.> The shape of the carbon dioxide adsorbent is not particularly limited. The carbon dioxide adsorbent is usually in powder or molded form. As a molded body, it can be a porous material formed into granular (spherical), pellet (columnar), ring, or honeycomb shapes, or a powdered carbon dioxide adsorbent can be molded into a predetermined shape by any suitable conventional method. For example, the carbon dioxide adsorbent can be molded into granular (spherical), pellet (columnar), extruded, ring, or honeycomb shapes, and furthermore, after being molded into a predetermined shape, it can be crushed and classified to obtain granules of any suitable size.

[0039] For example, the diameter of granular (spherical) carbon dioxide adsorbent is usually preferably 10 mm or less, and more preferably 5 mm or less, from the viewpoint of improving handling and maximizing carbon dioxide adsorption performance. There is no particular lower limit to the diameter of the carbon dioxide adsorbent. Here, the diameter of the carbon dioxide adsorbent refers to the diameter of the sphere if it is spherical, the diameter if it is pellet-shaped (columnar) and the cross-section when cut in a direction perpendicular to the direction of extension is circular, and the maximum width (maximum diameter) of the cross-section if it is of any other shape.

[0040] <Method for manufacturing carbon dioxide adsorbent> The method for producing carbon dioxide adsorbents is not particularly limited, and any suitable method can be applied. For example, one method includes contacting a metal compound with a solution containing an alkali metal carbonate (alkali metal carbonate solution), heating it, and obtaining a carbon dioxide adsorbent. Here, "heating" includes a drying step and / or a calcination step.

[0041] The alkali metal carbonate solution used in the above manufacturing method (the step of obtaining the carbon dioxide adsorbent) is not particularly limited as long as it is a solution containing the alkali metal carbonate described above. The solvent that can be used in the alkali metal carbonate solution is not particularly limited and includes, for example, water (ion-exchanged water, (ultra)pure water), alcohols such as methanol, ethanol, and isopropyl alcohol, polar organic solvents such as acetone, acetonitrile, and tetrahydrofuran, and mixed solvents containing two or more of these solvents. In the present invention, "solution" may also include dispersions, suspensions, etc.

[0042] The concentration of alkali metal carbonate in the alkali metal carbonate solution is not particularly limited, but is preferably 1 to 53% by mass, more preferably 5 to 50% by mass, and even more preferably 10 to 50% by mass, from the viewpoint of the production efficiency of the carbon dioxide adsorbent. Furthermore, if the carbon dioxide adsorbent contains the other materials mentioned above, a mixed solution of alkali metal carbonates containing the other materials (e.g., a mixed aqueous solution) can be used. The content of the other materials in this mixed solution is not particularly limited, but is preferably 0.01 to 90% by mass, more preferably 0.1 to 90% by mass, and even more preferably 1 to 90% by mass, from the viewpoint of the manufacturing efficiency of the carbon dioxide adsorbent.

[0043] The method of contact between the metal compound and the alkali metal carbonate solution is not particularly limited. For example, any conditions that allow the alkali metal carbonate solution to come into even contact with the metal compound are acceptable. If the metal compound is porous, any conditions that allow the alkali metal carbonate solution to penetrate into its pores and be uniformly absorbed are also acceptable. As contact methods, any conventionally known and suitable methods can be applied, such as dropping droplets of alkali metal carbonate solution onto the metal compound, spraying the alkali metal carbonate solution onto the metal compound, or immersing the metal compound in the alkali metal carbonate solution. The contact conditions are not particularly limited and can be, for example, at a temperature around room temperature (20-30°C), under an air atmosphere (atmospheric atmosphere) or an inert gas atmosphere.

[0044] The drying process is carried out by drying the metal compound in contact with the alkali metal carbonate solution until there is no change in mass. Specifically, for example, it can be carried out by drying at room temperature for about 1 hour, and then further heating using a conventionally known and suitable drying apparatus (e.g., an oven) at a temperature of preferably 30 to 120°C until there is no change in mass.

[0045] In the above manufacturing method, a firing process may be carried out following the drying process. Specifically, the firing process can be carried out by heating at a temperature of 30 to 500°C, more preferably 30 to 300°C, using a conventionally known and suitable heat treatment apparatus (e.g., an oven, a muffle furnace), until the mass change ceases.

[0046] The atmosphere in which the heating process (drying process and firing process) is carried out is not particularly limited, and examples include an air atmosphere (atmospheric atmosphere), as well as an inert gas atmosphere such as nitrogen gas, argon gas, or helium gas.

[0047] By the above manufacturing method, a carbon dioxide adsorbent can be obtained in which alkali metal carbonate is attached to the surface of the metal compound, and if the metal compound is porous, also to the pores.

[0048] A method for producing a carbon dioxide adsorbent having a porous material is not particularly limited, and for example, a method may be given that includes the steps of (1) bringing a porous material into contact with a solution containing a metal compound (metal compound solution) and heating to obtain a carbon dioxide adsorbent precursor, and (2) bringing the obtained carbon dioxide adsorbent precursor into contact with an alkali metal carbonate solution and heating to obtain a carbon dioxide adsorbent. Here, "heating" includes a drying step and / or a calcination step.

[0049] The metal compound solution used in step (1) is not particularly limited as long as it contains the metal compound described above. The solvent that can be used in the metal compound solution is not particularly limited and includes, for example, water (ion-exchanged water, (ultra)pure water), alcohols such as methanol, ethanol, and isopropyl alcohol, polar organic solvents such as acetone, acetonitrile, and tetrahydrofuran, and mixed solvents containing two or more of these solvents.

[0050] The concentration of the metal compound in the metal compound solution is not particularly limited, but is preferably 0.01 to 100% by mass, more preferably 0.1 to 100% by mass, and even more preferably 1 to 100% by mass, from the viewpoint of the production efficiency of the carbon dioxide adsorbent precursor. Furthermore, if the carbon dioxide adsorbent contains the other materials mentioned above, a mixed solution of metal compounds containing the other materials (e.g., a mixed aqueous solution) can be used. The content of the other materials in this mixed solution is not particularly limited, but is preferably 0.01 to 90% by mass, more preferably 0.1 to 90% by mass, and even more preferably 1 to 90% by mass, from the viewpoint of the production efficiency of the carbon dioxide adsorbent precursor.

[0051] The method of contact between the porous material and the metal compound solution is not particularly limited. For example, any method that allows the metal compound solution to come into even contact with the porous material so that the solution can penetrate into the pores of the porous material and be uniformly absorbed is acceptable. As contact methods, any conventionally known and suitable method can be applied, such as dropping droplets of the metal compound solution onto the porous material, spraying the metal compound solution onto the porous material, or immersing the porous material in the metal compound solution. The contact conditions are not particularly limited and can be, for example, at a temperature near room temperature, in an air atmosphere or an inert gas atmosphere.

[0052] The drying process is carried out by drying the porous material in contact with the metal compound solution until there is no change in mass. Specifically, for example, it can be carried out by drying at room temperature for about 1 hour, and then further heating using a conventionally known and suitable drying apparatus (e.g., an oven) at a temperature of preferably 30 to 120°C until there is no change in mass.

[0053] In the above manufacturing method, it is preferable to carry out a firing process following the drying process. Specifically, the firing process can be carried out by firing at 200 to 800°C for 1 to 12 hours using a conventionally known and suitable heat treatment apparatus (e.g., a muffle furnace).

[0054] The atmosphere in which the heating process (drying process and firing process) is carried out is not particularly limited and can be, for example, an air atmosphere, or an inert gas atmosphere such as nitrogen gas, argon gas, or helium gas.

[0055] By the above step (1), a carbon dioxide adsorbent precursor can be obtained in which a metal compound or a metal element derived from a metal compound, or a compound thereof, is attached to or solid-solved in the surface and / or pores of a porous material.

[0056] Next, the carbon dioxide adsorbent precursor obtained in this way is brought into contact with an alkali metal carbonate solution, and heated (drying step, calcination step as appropriate) to obtain a carbon dioxide adsorbent (step (2). The alkali metal carbonate solution used in step (2) above is not particularly limited as long as it is a solution containing the alkali metal carbonate described above. For example, the alkali metal carbonate solution that is brought into contact with the metal compound in the above-described manufacturing method can be used.

[0057] The method of contacting the carbon dioxide adsorbent precursor with the alkali metal carbonate solution is not particularly limited. For example, any condition that allows the alkali metal carbonate solution to be evenly contacted with the carbon dioxide adsorbent precursor so that it can penetrate into the pores of the carbon dioxide adsorbent precursor and be uniformly absorbed is acceptable. The contact method is not particularly limited and is, for example, the same as the contact method between the metal compound and the alkali metal carbonate solution in the manufacturing method described above. The contact conditions are not particularly limited and can be, for example, at a temperature near room temperature, in an air atmosphere or an inert gas atmosphere.

[0058] The drying process is carried out by drying the carbon dioxide adsorbent precursor, which has been in contact with the alkali metal carbonate solution, until there is no change in mass. Specifically, for example, it can be carried out by drying at room temperature for about 1 hour, and then further heating it using a conventionally known and suitable drying apparatus (e.g., an oven) at a temperature of preferably 30 to 120°C until there is no change in mass.

[0059] In this manufacturing method, a firing process may be carried out following the drying process. Specifically, the firing process can be carried out by heating at a temperature of 30 to 500°C, more preferably 30 to 300°C, using a conventionally known and suitable heat treatment apparatus (e.g., an oven, a muffle furnace), until the mass changes no longer occur.

[0060] The atmosphere in which the heating process (drying process and firing process) is carried out is not particularly limited, and is, for example, the same as the atmosphere in process (1) above.

[0061] By step (2) described above, a carbon dioxide adsorbent can be obtained in which a metal compound or a metal element derived from a metal compound, or a compound thereof, is attached to the surface and / or inside the pores of the porous material, in addition to alkali metal carbonates.

[0062] The carbon dioxide adsorbent used in the present invention and its manufacturing method have been described above. Regarding these, the contents of Patent Document 1 can be appropriately referenced, and those contents are incorporated directly as part of this specification.

[0063] [How to play] The regeneration method of the present invention involves contacting a used carbon dioxide adsorbent with water, and then contacting it with an aqueous solution containing an alkali metal carbonate that includes at least one alkali metal element. The regeneration method of the present invention will be described below in two parts: a step of contacting the used carbon dioxide adsorbent with water (also called the removal step), and a step of contacting the used carbon dioxide adsorbent obtained in the removal step with an aqueous solution containing an alkali metal carbonate containing at least one alkali metal element (alkali metal carbonate solution) (also called the re-adhesion step).

[0064] <Process of contact with water (removal process)> The carbon dioxide adsorbent used in the removal process is a used carbon dioxide adsorbent, such as a carbon dioxide adsorbent that has been subjected to the carbon dioxide adsorption and separation processes described later using a carbon dioxide adsorbent. As mentioned above, this carbon dioxide adsorbent contains (is mixed with), adsorbs or has attached by-products produced by the reaction of carbon dioxide in the gas with the adsorbent component (alkali metal carbonate), in addition to the main product produced by the reaction of components other than carbon dioxide with the adsorbent component. In the present invention, the amount of by-products contained in the carbon dioxide adsorbent is not particularly limited and is determined according to the decrease in the adsorption performance of the carbon dioxide adsorbent.

[0065] The water used in the removal process is not particularly limited, but pure water, ultrapure water, or deionized water can be used. Furthermore, mixed water with alcohol or other substances can be used, as long as it effectively removes the main product and by-products. The amount of water used is not particularly limited, but for example, it can be 1 to 500 parts by mass per 1 part by mass of carbon dioxide adsorbent, and is preferably 5 to 500 parts by mass, and more preferably 10 to 500 parts by mass, in terms of the efficiency of removing the main product and by-products.

[0066] The method of contact between the carbon dioxide adsorbent and water is not particularly limited, and any conventionally known and suitable method can be applied, such as dropping, spraying, or atomizing water onto the carbon dioxide adsorbent, or immersing the carbon dioxide adsorbent in water and mixing it by stirring as appropriate. The contact temperature between the carbon dioxide adsorbent and water is not particularly limited and can be, for example, 5 to 50°C. However, it is preferable to set it to 5 to 30°C in terms of the removal efficiency of the main and by-products, as well as ease of handling. The contact time can be appropriately determined considering the removal efficiency, etc., and can be, for example, 10 minutes to 24 hours.

[0067] In the removal process, after bringing the carbon dioxide adsorbent into contact with water as described above, the carbon dioxide adsorbent is separated from the water as needed and then dried. The method for separating the carbon dioxide adsorbent from water is not particularly limited, but examples include filtration, removal from water, and wiping. After contact with water, the carbon dioxide adsorbent can be dried using various conventionally known drying methods. For example, a suitable drying apparatus (e.g., oven, muffle oven) can be used to heat the material at a temperature of preferably 100 to 250°C for 1 to 12 hours. In addition, since the regeneration method of the present invention involves contact with an alkali metal carbonate solution after the removal step, the carbon dioxide adsorbent does not need to be dried until its mass changes completely.

[0068] The atmosphere in which the carbon dioxide adsorbent is brought into contact with water, and the atmosphere in which it is separated or dried, are not particularly limited, and examples include an air atmosphere and an inert gas atmosphere.

[0069] In the removal process, the main and by-products contained in, adsorbed, or attached to the used carbon dioxide adsorbent are removed and washed, and the aforementioned metal compounds, or porous materials to which the metal compounds are attached (sometimes referred to as "recovered adsorbent" for convenience), are recovered from the used carbon dioxide adsorbent.

[0070] <Step of contact with alkali metal carbonate solution (re-adhesion step)> In the regeneration method of the present invention, the next step is to bring the recovered adsorbent obtained in the removal step into contact with an alkali metal carbonate solution (re-adhesion step). The alkali metal carbonate solution used in the re-adhesion process is not particularly limited as long as it contains the alkali metal carbonate described above. The alkali metal carbonate contained in the alkali metal carbonate solution used in the re-adhesion process may be the same as or different from the alkali metal carbonate that was attached to the used carbon dioxide adsorbent. The alkali metal carbonate solution used in the re-adhesion process can be the same alkali metal carbonate solution used in the method for manufacturing the carbon dioxide adsorbent. The method and conditions of contact in the re-adhesion process are not particularly limited, and the methods and conditions of contact between a metal compound and an alkali metal carbonate solution in a method for manufacturing carbon dioxide adsorbents, or the methods and conditions of contact between a carbon dioxide adsorbent precursor and an alkali metal carbonate solution in a method for manufacturing carbon dioxide adsorbents, can be applied.

[0071] In the re-adhesion process, it is preferable to heat the recovered adsorbent that has been in contact with the alkali metal carbonate solution (drying process), and the recovered adsorbent can also be calcined after heating as appropriate. The heating and calcination steps for the recovered adsorbent are not particularly limited, and the heating and calcination steps in a method for manufacturing carbon dioxide adsorbent, or the heating and calcination steps in a method for contacting a carbon dioxide adsorbent precursor with an alkali metal carbonate solution in a method for manufacturing carbon dioxide adsorbent, can be applied.

[0072] The re-adhesion process allows alkali metal carbonates to be attached to the surface of the recovered adsorbent, and even to the pores of the recovered adsorbent, thereby regenerating the carbon dioxide adsorbent.

[0073] The characteristics and physical properties of the carbon dioxide adsorbent regenerated by the regeneration method of the present invention, such as the average pore diameter, alkali metal element content, and element content in the metal compound, are not particularly limited and can be set as appropriate. Preferably, the characteristics and physical properties of the regenerated carbon dioxide adsorbent are the same as (within the above range) as those of the carbon dioxide adsorbent used in the carbon dioxide adsorption separation method (unused carbon dioxide adsorbent), in terms of carbon dioxide adsorption performance.

[0074] [Uses of recycled carbon dioxide adsorbent] The carbon dioxide adsorbent regenerated by the regeneration method of the present invention has its carbon dioxide adsorption performance restored and is therefore suitable for carbon dioxide adsorption. Preferably, it can be used in a carbon dioxide adsorption and separation method, and can also be used in a continuous carbon dioxide adsorption and separation method in combination with a carbon dioxide adsorption step and a separation step. Specific applications in the industrial sector include the capture of carbon dioxide from exhaust gases emitted from chemical plants, coal and natural gas power plants, steel mills (e.g., blast furnaces and converters), cement plants (e.g., kilns), waste treatment plants, paint shops, natural gas refineries, LNG plants, and semiconductor manufacturing plants (e.g., semiconductor manufacturing processes). In the transportation and logistics sector, it includes the capture of carbon dioxide from exhaust gases emitted from automobiles, buses, trains, ships, and aircraft. Furthermore, in the air purification and environmental control sector, it includes the capture of carbon dioxide from air purifiers, air conditioners, automobile interiors, spacecraft and space stations, submarines and ships, bus and train interiors, aircraft interiors, air conditioners and water heaters in offices, buildings, schools, restaurants, kitchens, and agricultural greenhouses, as well as from the atmosphere.

[0075] <Method for adsorption and separation of carbon dioxide> The carbon dioxide adsorption and separation method using carbon dioxide adsorbent regenerated by the regeneration method of the present invention is not particularly limited, and examples include an adsorption and separation method that includes an adsorption step of bringing the regenerated carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in this adsorption step, to 50 to 900°C. The adsorption step is an example of the adsorption step using regenerated carbon dioxide adsorbent in the continuous adsorption and separation method of carbon dioxide of the present invention, which will be described later. The separation step is an example of the separation step in the continuous adsorption and separation method of carbon dioxide of the present invention, which will be described later (including the separation step in the carbon dioxide adsorption and separation method of the present invention, which will be described later).

[0076] [[The present invention: a method for continuous adsorption and separation of carbon dioxide]] The present invention provides a continuous adsorption and separation method for carbon dioxide (hereinafter sometimes referred to as "the present invention's continuous adsorption and separation method"), which involves repeatedly performing, in this order, an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50 to 900°C, wherein the adsorption step and separation step are performed at least once each, and then the regeneration method of the present invention is performed to regenerate the carbon dioxide adsorbent after the separation step, and then at least one adsorption step of bringing the regenerated carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50 to 900°C, is performed. As described above, the continuous adsorption and separation method of the present invention is a method in which the carbon dioxide adsorbent whose adsorption performance has deteriorated by performing at least one adsorption step and one separation step is regenerated by the regeneration method of the present invention, and then the adsorption step and separation step are performed at least one more time using the regenerated carbon dioxide adsorbent (regenerated carbon dioxide adsorbent). In the continuous adsorption and separation method of the present invention, the number of cycles of the adsorption and separation steps performed before the regeneration method of the present invention is carried out, and the number of cycles of the adsorption and separation steps performed after the regeneration method of the present invention are not particularly limited and can be appropriately determined according to the amount of decrease in the adsorption performance of the carbon dioxide adsorbent, etc.

[0077] The continuous adsorption and separation method of the present invention allows the adsorption and separation processes to be carried out continuously over multiple cycles, since the regeneration method of the present invention is performed between the adsorption and separation cycles. In the present invention, "continuous" and "repeated" mean performing a predetermined process one after another (repeatedly), and do not mean performing them continuously in time, or not performing other processes between predetermined processes. Therefore, in the continuous adsorption separation method of the present invention, a series of processes of the adsorption process and the separation process, as well as a series of processes of the separation process, the regeneration method and the adsorption process, can be performed with time intervals, for example, with stops or pauses, or with other processes in between, as long as the effects of the present invention are not impaired.

[0078] The carbon dioxide adsorbent used in the continuous adsorption separation method of the present invention is a carbon dioxide adsorbent containing an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. The carbon dioxide adsorbent used in the continuous adsorption separation method of the present invention may be the unused carbon dioxide adsorbent described above, or it may be a carbon dioxide adsorbent regenerated by the regeneration method of the present invention. The regenerated carbon dioxide adsorbent used in the continuous adsorption separation method of the present invention is the same as the regenerated carbon dioxide adsorbent used in the carbon dioxide adsorption separation method described above. It is preferable that the carbon dioxide adsorbent used in the first adsorption step is the same as the unused carbon dioxide adsorbent described above.

[0079] (Adsorption process) The adsorption step in the continuous adsorption separation method of the present invention is a step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide adsorbent to adsorb carbon dioxide from the gas. The carbon dioxide adsorbent used in the adsorption step is determined according to, for example, the number of times of implementation in the continuous adsorption separation method of the present invention. For example, the carbon dioxide adsorbent used in the first adsorption step in the continuous adsorption separation method of the present invention is usually an unused carbon dioxide adsorbent or a regenerated carbon dioxide adsorbent, and the carbon dioxide adsorbent used in the adsorption step performed after the separation step described later is a carbon dioxide adsorbent that has adsorbed carbon dioxide or a regenerated carbon dioxide adsorbent, and the carbon dioxide adsorbent used in the adsorption step performed after the regeneration method of the present invention is a regenerated carbon dioxide adsorbent. Note that an unused carbon dioxide adsorbent can also be used instead of a regenerated carbon dioxide adsorbent in one or several of the adsorption steps performed multiple times.

[0080] In the adsorption step, the gas brought into contact with the carbon dioxide adsorbent only needs to contain carbon dioxide, and may also contain other components. Examples of the gas containing carbon dioxide include, for example, air and a gas having a higher carbon dioxide concentration (partial pressure) than air. Further, since the regeneration method of the present invention and the continuous adsorption separation method of the present invention can regenerate the used carbon dioxide adsorbent, a gas containing nitrogen oxides (NOx) and / or sulfur oxides (SOx) at a high concentration can be used instead of air. Examples of such a gas include gases discharged from various applications described in the above uses of the regenerated carbon dioxide adsorbent, such as factory exhaust gas and power plant exhaust gas. The concentration (partial pressure) of carbon dioxide in the gas is not particularly limited, and can be about 4.0×10 2 ppm in the air, or can be a higher concentration. For example, the concentration of carbon dioxide in the gas can be 4.0×10 2 ~2.0×10 5 ppm, and is preferably 4.0×10 2 ~1.0×10 5 ppm, and more preferably 4.0×10 2 ~5.0×10 4 ppm.

[0081] The components other than carbon dioxide in a gas containing carbon dioxide are not particularly limited, but examples include water vapor, nitrogen, hydrogen, carbon monoxide, hydrocarbons such as methane, and various gases such as nitrogen oxides (NOx) and sulfur oxides (SOx). As a gas containing components other than carbon dioxide, a gas containing water vapor is one preferred embodiment, a gas containing at least one selected from the group consisting of nitrogen oxides and sulfur oxides is also a preferred embodiment in that it allows effective use of the regeneration method of the present invention, and a gas containing water vapor and at least one selected from the group consisting of nitrogen oxides and sulfur oxides is a more preferred embodiment. Examples of nitrogen oxides (NOx) include nitric oxide (NO), nitrogen dioxide (NO2), nitrogen trioxide (NO3), nitrous oxide (dinitrogen monoxide, N2O), dinitrogen trioxide (N2O3), dinitrogen tetroxide (N2O4), and dinitrogen pentoxide (N2O5). Examples of sulfur oxides (SOx) include sulfur monoxide (SO), sulfur dioxide (sulfurous acid gas, SO2), and sulfur trioxide (SO3). The concentrations (partial pressures) of other components in the gas are not particularly limited. For example, the concentration of nitrogen oxides (NOx) in the gas is 0 to 1.2 × 10⁻⁶. 3 It can be expressed in ppm, 0-5.0 × 10 2 It is preferably ppm, and 0 to 1.5 × 10 2 It is preferable that the concentration be ppm. The concentration of sulfur oxides (SOx) in the gas is 0 to 1.2 × 10⁻⁶. 4 It can be expressed in ppm, 0-5.0 × 10 3 Preferably, the concentration is ppm. The concentration of water vapor in the gas is not particularly limited and can be the concentration that corresponds to the humidity in the adsorption process described later, for example, 4.0 × 10⁻⁶. 2 ~2.0×10 5 It can be expressed in ppm, 4.0 × 10 2 ~1.0×10 5 It is preferable that the concentration be in ppm. The gas may contain one or more components other than carbon dioxide.

[0082] In the adsorption process, examples of gases to be brought into contact with the carbon dioxide adsorbent include air, various exhaust gases as described in the section on the applications of the recycled carbon dioxide adsorbent, and air, various factory exhaust gases, power plant exhaust gases, etc., can be suitably used.

[0083] The temperature during the adsorption process (the temperature at which the carbon dioxide adsorbent is used) is not particularly limited, but is preferably 0 to 100°C, and more preferably 5 to 80°C. In the adsorption process, it is preferable to bring the carbon dioxide adsorbent into contact with a gas containing carbon dioxide at a temperature of 100°C or lower (e.g., room temperature) as described above, but it is also possible to bring it into contact with the gas at a temperature higher than 100°C. Temperature adjustment in the adsorption process can be performed by heating or cooling the carbon dioxide adsorbent and / or the gas using a heater or cooler. When heating or cooling the carbon dioxide adsorbent or the gas, it is preferable to make effective use of the heat, such as by exchanging heat with the gas discharged from the separation process. The humidity during the adsorption process (humidity of the carbon dioxide adsorbent) is not particularly limited, but since water may be necessary for carbon dioxide adsorption, 1 to 100 RH% is preferred, and 5 to 90 RH% is more preferred. Humidity during the adsorption process can be adjusted by the presence of moisture (water or water vapor) or by adding moisture to the gas by bubbling, etc. If the gas contains water vapor, the water vapor in the gas can also be used to adjust the humidity.

[0084] The conditions in the adsorption process can be appropriately determined, such as the concentration of carbon dioxide in the gas containing carbon dioxide, and the contact amounts of carbon dioxide and gas with the carbon dioxide adsorbent, within a range where the adsorption amount is less than or equal to the maximum (theoretical) adsorption amount of carbon dioxide by the carbon dioxide adsorbent.

[0085] The method of bringing the carbon dioxide adsorbent into contact with the gas containing carbon dioxide in the adsorption process is not particularly limited. For example, this could involve circulating the gas containing carbon dioxide through a container containing the carbon dioxide adsorbent, or placing the carbon dioxide adsorbent in the gas containing carbon dioxide to bring it into direct contact.

[0086] In a method of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide via a flow mechanism, the supply amount of gas containing carbon dioxide (space velocity SV) under standard conditions (0°C, 0.1 MPa) is not particularly limited, but is preferably 10 to 1.0 × 10 7 / h, more preferably 1.0 × 10 2 ~5.0×10 6 / h, and more preferably 1.0 × 10 3 ~1.0×10 6 It is / h. Let the spatial velocity SV be 10 or greater, then 1.0 × 10 7 Setting the rate to less than / h can improve the carbon dioxide adsorption efficiency per unit time. Furthermore, while there are no particular restrictions on the supply rate (linear velocity LV) of the gas containing carbon dioxide under standard conditions (0°C, 0.1 MPa), it is preferably 1.0 × 10⁻¹⁶ to improve the contact efficiency between the carbon dioxide adsorbent and the gas containing carbon dioxide. -4 It is ~100 m / s, more preferably 1.0 × 10 -3 The pressure is approximately 10 m / s. The processing pressure on the carbon dioxide adsorbent is preferably 0.1 to 5 MPa, and more preferably 0.1 to 1 MPa. In the method of contacting the gases in a flow manner, a gas containing carbon dioxide can be flowed together with the carrier gas. Preferably, the carrier gas is one that is not adsorbed by the carbon dioxide adsorbent, such as an inert gas, specifically a rare gas like nitrogen, helium, or argon. The supply amount (space velocity SV) and supply rate (linear velocity LV) of the carrier gas are not particularly limited and can be appropriately determined considering the above-mentioned supply amount of the gas containing carbon dioxide.

[0087] (separation process) In the continuous adsorption separation method of the present invention, the separation step is performed on a carbon dioxide adsorbent that has adsorbed carbon dioxide in the adsorption step. The heating temperature in the separation process is set to a temperature that does not impair the function of the carbon dioxide adsorbent, the equipment containing the carbon dioxide adsorbent, etc. For example, it can be 50 to 900°C, preferably 50 to 600°C, more preferably 50 to 300°C, and even more preferably 120 to 300°C. The processing pressure is not particularly limited, but is preferably 0.001 to 5 MPa, and more preferably 0.01 to 1 MPa.

[0088] The gas (atmosphere) used during heating in the separation process is not particularly limited. For example, air (atmosphere) can be used as the heating atmosphere. From the viewpoint of more efficiently separating and removing carbon dioxide, an inert gas such as nitrogen gas may be used. Furthermore, the inventors have found that carbon dioxide adsorbed on the carbon dioxide adsorbent can be separated and desorbed by heating the carbon dioxide adsorbent to the above heating temperature, even in an atmosphere of carbon dioxide-containing gas. Therefore, the separation process can also be carried out by heating the carbon dioxide adsorbent to the above temperature in an atmosphere of carbon dioxide-containing gas. The concentration of carbon dioxide in the carbon dioxide-containing gas used at this time can be appropriately determined within the same range as the concentration of carbon dioxide in the carbon dioxide-containing gas used in the adsorption process, taking into consideration the amount of carbon dioxide to be separated, and it is preferable that the concentration be higher than the concentration of carbon dioxide in the atmosphere, for example, 4.0 × 10⁻⁶ 2 It is preferable that the concentration be around ppm ~ 100%, and 4.0 × 10 2 ~2.0×10 5 It is more preferable that the concentration be in ppm. Carbon dioxide gas can also be used as the gas containing carbon dioxide.

[0089] The humidity in the separation process (humidity at which the carbon dioxide adsorbent is used) is not particularly limited and can be, for example, 1 to 100 RH, with 5 to 90 RH being preferred. The humidity in the adsorption process is adjusted as described above. The method of bringing the carbon dioxide adsorbent into contact with the gas in the separation process is not particularly limited. For example, methods include circulating the gas through a container containing the carbon dioxide adsorbent to bring it into contact with the gas, or placing the carbon dioxide adsorbent in the gas to bring it into direct contact.

[0090] In a method of bringing a carbon dioxide adsorbent into contact with a gas in a flow manner, the amount of gas supplied (space velocity SV) under standard conditions (0°C, 0.1 MPa) is not particularly limited, but is preferably 10 to 1.0 × 10 7 / h, more preferably 1.0 × 10 2 ~5.0×10 6 / h, and more preferably 1.0 × 10 3 ~1.0×10 6 It is / h. Let the spatial velocity SV be 10 or greater, then 1.0 × 10 7 Setting the rate to less than / h can improve the carbon dioxide separation efficiency per unit time. Furthermore, while there are no particular limitations on the supply rate (linear velocity LV) of the gas containing carbon dioxide under standard conditions (0°C, 0.1 MPa), it is preferably 1.0 × 10⁻¹⁶ to improve the contact efficiency between the carbon dioxide adsorbent and the gas containing carbon dioxide. -4 It is ~100 m / s, more preferably 1.0 × 10 -3 The pressure is approximately 10 m / s. The processing pressure on the carbon dioxide adsorbent is preferably 0.001 to 5 MPa, and more preferably 0.01 to 1 MPa. In this invention, the lower limit of the processing pressure can also be 0.1 MPa. In the method of contacting the gas via a flow system, the gas can be flowed together with the carrier gas. The carrier gas and its supply amount are the same as the gas and its supply amount used in the adsorption process.

[0091] In the separation process, the carbon dioxide separated from the carbon dioxide adsorbent can be recovered by any suitable conventional method. Specifically, examples include recovering the separated carbon dioxide as dry ice by pressurizing, compressing, and cooling it; recovering it as a gas with an increased carbon dioxide concentration using a separation membrane; and recovering it as a gas with an increased carbon dioxide concentration by adsorbing and removing components other than carbon dioxide. The components other than carbon dioxide are those mentioned above.

[0092] (Regeneration method of the present invention) As described above, if the adsorption performance of the carbon dioxide adsorbent decreases after performing at least one adsorption step and one separation step, the carbon dioxide adsorbent is regenerated before the next adsorption step in the cycle. The carbon dioxide adsorbent is regenerated in the same way as the regeneration method of the present invention described above. In the continuous adsorption and separation method of the present invention, the timing of the carbon dioxide adsorbent regeneration method (number of adsorption and separation steps) can be appropriately determined according to the amount of decrease in the adsorption performance of the carbon dioxide adsorbent, the amount of carbon dioxide adsorbed, and the work efficiency. For example, it can be set when the amount of carbon dioxide adsorbed by the initial carbon dioxide adsorbent (the carbon dioxide adsorbent used in the first adsorption step, or the carbon dioxide adsorbent used in the first adsorption step after regeneration) has decreased to, for example, 10%, and preferably to 50%.

[0093] (Adsorption and separation processes using recycled carbon dioxide adsorbent) After regenerating the carbon dioxide adsorbent whose carbon dioxide adsorption performance has deteriorated in this manner, at least one carbon dioxide adsorption step and one carbon dioxide separation step are performed using the regenerated carbon dioxide adsorbent. The adsorption step and separation step using the regenerated carbon dioxide adsorbent are the same as the adsorption step and separation step performed before the regeneration of the carbon dioxide adsorbent, except that the regenerated carbon dioxide adsorbent is used.

[0094] In the continuous adsorption separation method of the present invention, the number of times the regeneration method of the present invention is performed is not particularly limited as long as it is at least once, and can be appropriately determined according to work efficiency and other factors. Since the regeneration method of the present invention can restore the adsorption performance of the carbon dioxide adsorbent to a level equivalent to the desired adsorption performance, the regeneration method of the present invention can be performed many times, and the continuous adsorption separation method of the carbon dioxide adsorbent, which includes multiple regeneration methods of the present invention, can be carried out semi-permanently.

[0095] [[The present invention's method for adsorbing and separating carbon dioxide]] The carbon dioxide adsorption separation method of the present invention (which may be referred to as "the adsorption separation method of the present invention" in this specification) comprises an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50 to 900°C in an atmosphere of gas containing carbon dioxide.

[0096] The carbon dioxide adsorbent used in the adsorption separation method of the present invention is a carbon dioxide adsorbent containing an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table, and is the same as the carbon dioxide adsorbent used in the continuous adsorption separation method of carbon dioxide described above. This carbon dioxide adsorbent may be unused or may be regenerated by the regeneration method of the present invention.

[0097] (Adsorption process) The adsorption step in the adsorption separation method of the present invention is the same as the adsorption step in the continuous adsorption separation method of the present invention.

[0098] (separation process) The separation step in the adsorption separation method of the present invention is the same as the separation step in the continuous adsorption separation method of the present invention, except that a gas containing carbon dioxide is used as the gas used in the separation step instead of air or an inert gas, that is, the separation step is performed in an atmosphere of a gas containing carbon dioxide. The gas containing carbon dioxide used is the same as the gas containing carbon dioxide used in the separation step of the continuous adsorption separation method of the present invention described above. The method for recovering the carbon dioxide separated from the carbon dioxide adsorbent is also the same as the recovery method in the separation step described above.

[0099] The adsorption separation method and the continuous adsorption separation method of the present invention can be carried out with a carbon dioxide adsorbent attached to an appropriate device, or without attaching a carbon dioxide adsorbent to an device. The device for attaching the carbon dioxide adsorbent is not particularly limited and is appropriately determined according to the application mode of the adsorption separation method and the continuous adsorption separation method of the present invention. For example, the device for attaching the carbon dioxide adsorbent can be an air purifier, an air conditioner, a building material, a container (for example, a filter, a cartridge), a factory exhaust gas device for discharged gases from a chemical plant, an exhaust gas device for discharged gases from a power plant, or a gas transfer device for carbon dioxide-containing gases. Various known devices (filters, cartridges) can be applied without particular limitation as the device for attaching the carbon dioxide adsorbent (filter, cartridge), and for example, the contents described in Patent Document 1 can be appropriately referred to, and those contents are incorporated as part of this specification.

[0100] Furthermore, when the carbon dioxide adsorbent is attached to the apparatus and the adsorption separation method and the continuous adsorption separation method of the present invention are performed, the separation process can be carried out with the adsorbent attached to the apparatus or with the adsorbent removed from the apparatus. Also, when the adsorption separation method and the continuous adsorption separation method of the present invention are carried out in a flow-through format, the gas flowing through the apparatus can be switched to the gas used in the separation process while the carbon dioxide adsorbent is attached to the apparatus.

[0101] The carbon dioxide adsorbent used in the present invention can be suitably applied, for example, to a method for recovering carbon dioxide from a gas containing carbon dioxide, and to a method for selectively removing and recovering carbon dioxide from a gas with a high concentration (partial pressure) of carbon dioxide. More preferably, it can be applied to the continuous adsorption separation method and the carbon dioxide adsorption separation method of the present invention. Furthermore, the carbon dioxide adsorbent used in the present invention can be suitably applied, for example, to a carbon dioxide recovery device for recovering carbon dioxide from a gas containing carbon dioxide or for selectively removing and recovering carbon dioxide from a gas with a particularly high concentration (partial pressure) of carbon dioxide. [Examples]

[0102] The following are examples of the present invention, but the present invention is not limited thereto.

[0103] <Manufacturing of carbon dioxide adsorbent (base material)> An aqueous solution was prepared by completely dissolving potassium carbonate (anhydrous) (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) in an amount of 2.5 mmol per gram of zirconium oxide in molded zirconium oxide pellets (Daiichi Rare Elements Chemical Industry Co., Ltd., product name Z-3203). After evenly dropping and contacting the zirconium oxide pellets with this potassium carbonate aqueous solution (contact step), it was dried at room temperature for 1 hour. Next, using a multi-oven (manufactured by ETTAS, product name MOV300S), it was dried under air at 40°C until there was no further change in mass (drying step) to obtain (unused) carbon dioxide adsorbent (base material).

[0104] <Evaluation method for carbon dioxide adsorbents> The amount of carbon dioxide adsorbed by the carbon dioxide adsorbent in the examples was evaluated and quantified based on a calibration curve prepared as described below, using a catalyst analyzer (Microtrac-Bel Co., Ltd., BELCATII (product name)) and a micro GC (Agilent, CP-4900 (product name)) installed on the outlet gas line of this analyzer. The analytical conditions are as shown below. -Analysis conditions- Carrier gas: Helium Column used: 10m PPQ Unheated Column temperature: 100℃ Pressure: 170 kPa

[0105] <Creating a calibration curve> To quantify the amount of carbon dioxide adsorbed onto the carbon dioxide adsorbent, a calibration curve was created using the following procedure. An empty measurement cell was set in the catalyst analyzer, and a mixture of 2 vol% carbon dioxide gas and helium was introduced from 0 to 25 cm using the gas flow meter built into the instrument. 3 (0℃, 0.1013 MPa (absolute)) / min, helium gas at 75-100 cm 3 (At 0°C, 0.1013 MPa (absolute)) / min, total 100 cm 3 The gas was circulated at a rate of [number] minutes, and gas analysis was performed. From the resulting GC chart, the peak position of carbon dioxide was identified, the area value was recorded, and a calibration curve was created for the volume percentage of carbon dioxide in the gas relative to the GC area value.

[0106] [Experimental Example 1: Regeneration of carbon dioxide adsorbent] <Evaluation 1: Evaluation of carbon dioxide adsorption capacity of carbon dioxide adsorbent material (base material)> The carbon dioxide adsorbent (base material) manufactured as described above was crushed and sieved to a particle size of 500 μm or less. 0.2 g of this powdered carbon dioxide adsorbent (base material) was then placed into the catalyst analyzer described above. Next, helium gas is released at 100 cm. 3 The carbon dioxide adsorbent was pre-treated by flowing it at (0°C, 0.1013 MPa (absolute)) / min while heating at a rate of 10°C / min to 150°C for 1 hour. Next, after cooling the temperature to 50°C, a mixture of 2 volume% carbon dioxide gas and helium was added in 15 cm³. 3 (0℃, 0.1013 MPa (absolute)) / min, helium gas at 85 cm 3 The adsorption process was carried out by flowing (0°C, 0.1013 MPa (absolute)) / min of helium gas. 3The water was bubbled in 35°C water and supplied through a condenser set to 25°C (space velocity (SV) was 2.2 × 10⁻¹⁶). 4 The linear velocity (LV) is 1.3 × 10⁻¹⁰ / h. -2 (m / s). The outlet gas was analyzed by microGC approximately every minute to calculate the carbon dioxide concentration in the outlet gas. The concentration difference obtained by subtracting the carbon dioxide concentration in the outlet gas from the carbon dioxide concentration in the inlet gas was used to calculate the amount of gas flowed per minute (here, 100 cm³). 3 The amount of carbon dioxide gas adsorbed onto the powdered carbon dioxide adsorbent (base material) was determined by multiplying by (0℃, 0.1013 MPa (absolute)). The values ​​of carbon dioxide gas amounts on the powdered carbon dioxide adsorbent (base material) obtained from a 60-minute measurement were integrated to determine the total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent (mmol) [total amount of carbon dioxide adsorbed (mmol) / g - carbon dioxide adsorbent]. This value is listed in Table 1 as "Evaluation 1 (base material)".

[0107] <Evaluation 2: Evaluation of carbon dioxide adsorption capacity of carbon dioxide adsorbent treated with nitrogen dioxide> (Nitrogen dioxide treatment) 4.2 g of the carbon dioxide adsorbent (base material) manufactured as described above was placed in the catalyst analyzer described above. The temperature was set to 50°C, and a mixed gas of nitrogen dioxide and helium at a concentration of 225-275 ppm by volume was introduced at 100 cm³. 3 The carbon dioxide adsorbent (pellets) was prepared by flowing the material at (0°C, 0.1013 MPa (absolute)) / min for 3 hours after nitrogen dioxide treatment.

[0108] (Evaluation of the adsorption process and carbon dioxide adsorption amount) Next, the prepared nitrogen dioxide-treated carbon dioxide adsorbent was crushed and sieved to a particle size of 500 μm or less. 0.2 g of this powdered nitrogen dioxide-treated carbon dioxide adsorbent was placed in a catalyst analyzer, and the adsorption process was carried out in the same manner as in <Evaluation 1> above. The amount of carbon dioxide adsorbed at this time was determined. The total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent obtained from the 60-minute measurement [total amount of carbon dioxide adsorbed (mmol) / g-carbon dioxide adsorbent] was calculated as the total amount of carbon dioxide adsorbed per gram of powdered nitrogen dioxide-treated carbon dioxide adsorbent (mmol), and this value is listed in Table 1 as "Evaluation 2 (after nitrogen dioxide treatment)".

[0109] <Evaluation 3: Evaluation of carbon dioxide adsorption capacity in recycled carbon dioxide adsorbent material> (Regeneration process for carbon dioxide adsorbent) The carbon dioxide adsorbent (pellets) prepared in <Evaluation 2> above after nitrogen dioxide treatment was weighed into a beaker, and 10 parts by mass of ultrapure water (Millipore water) were added to 1 part by mass of the carbon dioxide adsorbent. A stirring bar was placed therein, and the mixture was stirred at 25°C for 1 hour using a stirrer. After stirring, the mixture was filtered using filter paper (size 5A), and the obtained carbon dioxide adsorbent was dried in a muffle furnace at 100°C for 2 hours (removal step of the regeneration method of the present invention). After drying, the carbon dioxide adsorbent (zirconium oxide) was subjected to a re-adhesion step of the regeneration method of the present invention in the same manner as the contact step and drying step in the above-mentioned <production of carbon dioxide adsorbent (base material)> to adsorb potassium carbonate, thereby obtaining a carbon dioxide adsorbent (regenerated material) after regeneration treatment.

[0110] (Evaluation of the adsorption process and carbon dioxide adsorption amount) Next, 0.2 g of the carbon dioxide adsorbent (recycled material) obtained by crushing the regenerated carbon dioxide adsorbent (recycled material) and sieving it to a particle size of 500 μm or less was placed in a catalyst analyzer, and the adsorption process was carried out in the same manner as in <Evaluation 1> above, and the amount of carbon dioxide adsorbed at this time was determined. The total amount of carbon dioxide adsorbed (mmol) per gram of regenerated carbon dioxide adsorbent (carbon dioxide adsorbent (mmol) / g-carbon dioxide adsorbent) obtained from the 60-minute measurement was calculated as the total amount of carbon dioxide adsorbed (mmol) per gram of powdered carbon dioxide adsorbent (recycled material), and this value was listed in Table 1 as "Evaluation 3 (recycled material)".

[0111] [Table 1]

[0112] As shown in Table 1, although nitrogen dioxide treatment reduces the adsorption performance (adsorption amount) of the carbon dioxide adsorbent (Evaluation 2), the regeneration method of the present invention (water washing) removes components derived from potassium carbonate that were adsorbed on the nitrogen dioxide-treated carbon dioxide adsorbent, and then re-supports (adheres) potassium carbonate, thereby regenerating the adsorption performance of the carbon dioxide adsorbent (Evaluation 3). By using this recycling method, it becomes possible to reuse zirconium dioxide, which makes up the majority of the material composition forming the carbon dioxide adsorbent used in Experimental Example 1. Furthermore, since zirconium dioxide is generally more expensive than potassium carbonate, the amount of zirconium dioxide waste can be reduced, and a low-cost carbon dioxide adsorbent can be provided. In Experimental Example 1, nitrogen dioxide, a type of nitrogen oxide, was used as the component other than carbon dioxide in the gas brought into contact with the carbon dioxide adsorbent. However, it is presumed that the adsorption performance of the carbon dioxide adsorbent can be restored by the regeneration method of the present invention, similar to the results for nitrogen dioxide, even if other nitrogen oxides or various sulfur oxides are used as the component other than carbon dioxide.

[0113] [Experimental Example 2: Separation of carbon dioxide using carbon dioxide] <Evaluation 4: Carbon dioxide desorption treatment using a gas containing carbon dioxide 1> (Carbon dioxide separation process) The carbon dioxide adsorbent (powder) obtained by performing the adsorption process in <Evaluation 3> of Experimental Example 1 above was heated to 150°C at a heating rate of 10°C / min using a catalyst analyzer, while a mixed gas of 2 volume% carbon dioxide gas and helium was added in 15 cm³. 3 (0℃, 0.1013 MPa (absolute)) / min, helium gas at 85 cm 3 The separation process was carried out by flowing (0°C, 0.1013 MPa (absolute)) / min for 1 hour. Of the gases flowed, 50 cm³ of helium gas was used. 3 The gas was bubbled into 35°C water and supplied through a condenser set to 25°C. In this way, a carbon dioxide separation process was carried out using a gas containing carbon dioxide, and a carbon dioxide adsorbent for carbon dioxide desorption treatment 1 was obtained.

[0114] (Evaluation of the adsorption process and carbon dioxide adsorption amount) Next, 0.2 g of the carbon dioxide adsorbent obtained from carbon dioxide desorption treatment 1 was placed in a catalyst analyzer, the temperature of the carbon dioxide adsorbent was set to 50°C, and the adsorption process was carried out in the same manner as in <Evaluation 1> above, and the amount of carbon dioxide adsorbed at this time was determined. The total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent obtained from the 60-minute measurement [total amount of carbon dioxide adsorbed (mmol) / g-carbon dioxide adsorbent] was determined as the total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent from carbon dioxide desorption treatment 1, and this value was recorded in Table 2 as "Evaluation 4 (Desorption study by carbon dioxide 1)".

[0115] <Evaluation 5: Carbon dioxide desorption treatment using a gas containing carbon dioxide 2> (Adsorption process) As described above, the carbon dioxide adsorbent (base material) produced in Experimental Example 1 was crushed and sieved to a particle size of 500 μm or less. 0.2 g of this powdered carbon dioxide adsorbent was then placed in a catalyst analyzer. Next, helium gas is released at 100 cm. 3The carbon dioxide adsorbent was pre-treated by flowing it at (0°C, 0.1013 MPa (absolute)) / min while heating at a rate of 10°C / min to 150°C for 1 hour. Next, after cooling the temperature to 50°C, a mixture of 2 volume% carbon dioxide gas and helium was added in 15 cm³. 3 (0℃, 0.1013 MPa (absolute)) / min, helium gas at 85 cm 3 The adsorption process was carried out by flowing (0°C, 0.1013 MPa (absolute)) / min for 1 hour. Of the gases flowed, 50 cm³ of helium gas was used. 3 The water was supplied by bubbling it in 35°C water and passing it through a condenser set to 25°C.

[0116] (Carbon dioxide separation process) Following the above adsorption process, the temperature of the carbon dioxide adsorbent is raised to 150°C while 100% carbon dioxide gas is added at a rate of 100 cm³. 3 The separation process was carried out by flowing the mixture at (0°C, 0.1013 MPa (absolute)) / min for 1 hour. In this way, a carbon dioxide separation process was performed using a gas containing carbon dioxide, and a carbon dioxide adsorbent for carbon dioxide desorption treatment 2 was obtained.

[0117] (Evaluation of the adsorption process and carbon dioxide adsorption amount) Next, the temperature of the carbon dioxide adsorbent in the catalyst analyzer was set to 50°C, and the adsorption process was performed in the same manner as in <Evaluation 1> above, and the amount of carbon dioxide adsorbed at this time was determined. The total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent (mmol) obtained from the 60-minute measurement [total amount of carbon dioxide adsorbed (mmol) / g-carbon dioxide adsorbent] was used to determine the total amount of carbon dioxide adsorbed per gram of carbon dioxide adsorbent (mmol) for carbon dioxide desorption treatment 2, and this value was recorded in Table 2 as "Evaluation 5 (Desorption study by carbon dioxide 2)".

[0118] [Table 2]

[0119] The results shown in Table 2 indicate that by increasing the temperature of the carbon dioxide adsorbent, the carbon dioxide adsorbed on the adsorbent can be completely desorbed, even when using a gas with the same carbon dioxide concentration as the gas composition used in the adsorption process (Evaluation 4). Furthermore, even when using 100% carbon dioxide gas as the gas containing carbon dioxide, the adsorbent has the ability to adsorb and desorb carbon dioxide with an efficiency of approximately 50% (Evaluation 5). The results in Table 2 show that the carbon dioxide adsorption and separation method using the carbon dioxide adsorbent makes it possible to recover carbon dioxide from the atmosphere and exhaust gases and then adjust the carbon dioxide concentration when reusing the carbon dioxide, thus enabling the material to be provided to a wide range of fields.

[0120] As is clear from the results shown in Tables 1 and 2, the regeneration method of the present invention can regenerate used carbon dioxide adsorbent materials used in the carbon dioxide adsorption separation method to an adsorption performance preferably equivalent to the desired adsorption performance. Therefore, by incorporating the regeneration method of the present invention into the carbon dioxide adsorption separation method, it is possible to realize the continuous adsorption separation method of the present invention, which continuously performs the carbon dioxide adsorption separation method via the regeneration method of the present invention. Furthermore, it is clear that, in addition to the separation process using air or an inert gas, the separation process in the continuous adsorption separation method of the present invention can also be applied to a separation process using a gas having the same carbon dioxide adsorption concentration as the gas composition used in the adsorption process, and even a separation process using 100% carbon dioxide gas. Moreover, the regeneration method of the present invention can be implemented using water, which has a low environmental impact, and can meet the growing demands for environmental protection (reducing environmental impact) and cost reduction in recent years.

Claims

1. A method for regenerating a carbon dioxide adsorbent that adsorbs carbon dioxide in a gas, The carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. A method for regenerating a carbon dioxide adsorbent, comprising contacting the carbon dioxide adsorbent with water, and then contacting it with an aqueous solution containing an alkali metal carbonate containing at least one alkali metal element.

2. The regeneration method according to claim 1, wherein the metal compound comprises at least one element selected from the group consisting of cerium, titanium, and zirconium.

3. The regeneration method according to claim 2, wherein the metal compound contains the element zirconium.

4. The regeneration method according to claim 3, wherein the metal compound is zirconium oxide.

5. The regeneration method according to claim 1, wherein the gas is atmospheric air or factory exhaust gas.

6. The regeneration method according to claim 1, wherein the gas is exhaust gas from a power plant.

7. The regeneration method according to claim 1, wherein the gas comprises at least one selected from the group consisting of nitrogen oxides and sulfur oxides.

8. The regeneration method according to claim 1, wherein the alkali metal carbonate contained in the aqueous solution is potassium carbonate.

9. A continuous adsorption and separation method for carbon dioxide, comprising repeatedly performing an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50 to 900°C, The carbon dioxide adsorbent contains an alkali metal carbonate containing at least one alkali metal element and a metal compound containing at least one element selected from the group consisting of Group 3 and Group 4 elements of the periodic table. A continuous adsorption and separation method for carbon dioxide, comprising performing at least one of the adsorption step and the separation step, and then regenerating the carbon dioxide adsorbent after the separation step by the regeneration method described in any one of claims 1 to 8.

10. The continuous adsorption separation method for carbon dioxide according to claim 9, wherein at least one of the multiple separation steps is heated in an atmosphere of carbon dioxide-containing gas.

11. A method for adsorbing and separating carbon dioxide, comprising an adsorption step of bringing a carbon dioxide adsorbent into contact with a gas containing carbon dioxide, and a separation step of heating the carbon dioxide adsorbent, which has adsorbed carbon dioxide in the adsorption step, to 50 to 900°C in an atmosphere of gas containing carbon dioxide.

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