Carbon dioxide absorbent, method for recovering carbon dioxide, and apparatus for separating and recovering carbon dioxide

Abstract

Provided are: a carbon dioxide absorbent comprising a non-azo solid amine compound (A) having two or more aromatic rings and two or more primary amino groups; a method for recovering carbon dioxide using the carbon dioxide absorbent; and an apparatus for separating and recovering carbon dioxide.

Description

Carbon dioxide absorbent, carbon dioxide capture method, and carbon dioxide separation and capture device

[0001] The present invention relates to a carbon dioxide absorbent, a carbon dioxide capture method, and a carbon dioxide separation and capture device.

[0002] From the perspective of global warming, there is a demand for reducing carbon dioxide emissions. One method for reducing carbon dioxide emissions is carbon dioxide capture and storage (CCS), a technology that efficiently captures high concentrations (approximately 10 to 30% by volume) of carbon dioxide from exhaust gases emitted from thermal power plants and stores the carbon dioxide by burying it underground or in the sea. Examples of technologies related to carbon dioxide absorbents used in CCS include those described in Patent Documents 1 and 2. Patent Document 1 describes a carbon dioxide capture method that uses specific alkanolamines as the carbon dioxide absorbent. Patent Document 2 describes the use of a carbon dioxide absorbing solution that contains a carbon dioxide chemically absorbing amine having a nitrogen-hydrogen bond and a tertiary amine solvent that does not have a nitrogen-hydrogen bond as the carbon dioxide absorbent.

[0003] As described in Patent Documents 1 and 2, many technologies using alkanolamines as carbon dioxide absorbents for use in CCS are known. In contrast to these, in recent years, attention has been focused on a technology (DAC: Direct Air Capture) that directly captures low-concentration carbon dioxide (approximately 0.04% by volume) in the air. The carbon dioxide absorbent used in DAC is required to have a higher carbon dioxide absorption capacity than the carbon dioxide absorbent used in CCS.

[0004] Various technologies related to DAC have also been studied. For example, Patent Document 3 discloses an absorbent for absorbing carbon dioxide in the air, which contains an alkylamine substituted with a hydroxy group or an optionally substituted amino group. Patent Document 4 discloses a carbon dioxide absorbent containing a predetermined amount or more of a polyamine compound having an alicyclic hydrocarbon structure. Patent Document 5 discloses a carbon dioxide absorbent containing a predetermined amount or more of an amine compound having a predetermined heterocyclic structure. Furthermore, Patent Document 6 discloses a carbon dioxide absorbent containing a specific cyclic amine compound and a porous material.

[0005] JP 2008-13400 A JP 2017-104776 A JP 2017-031046 A International Publication No. 2022 / 138302 International Publication No. 2022 / 163209 International Publication No. 2023 / 013397

[0006] The carbon dioxide absorbent disclosed in Patent Document 6 is a solid absorbent in which an amine compound is supported on a porous material. Typically, when reusing a solid absorbent, a method such as steam stripping is used to desorb carbon dioxide from the absorbent after absorbing carbon dioxide. However, when the amine compounds disclosed in Patent Documents 1 to 6 are used, there is a risk that the amine compound may elute from the porous material during steam stripping or volatilize due to heating during steam stripping. As such, conventionally known carbon dioxide absorbents have room for further improvement in terms of reusability. An object of the present invention is to provide a carbon dioxide absorbent that is excellent in carbon dioxide absorption and reusability, a carbon dioxide recovery method using the same, and a carbon dioxide separation and recovery apparatus.

[0007] The present inventors have found that the above-mentioned problems can be solved by a carbon dioxide absorbent containing a specific solid amine compound. Specifically, the present invention relates to the following: [1] A carbon dioxide absorbent containing a non-azo solid amine compound (A) having two or more aromatic rings and two or more primary amino groups. [2] The carbon dioxide absorbent according to [1], wherein the amine compound (A) is a non-polymer compound. [3] The carbon dioxide absorbent according to [1] or [2], wherein the amine compound (A) is an amine compound represented by the following general formula (1): In formula (1), X and Y each independently represent a single bond or an oxygen atom. n and m each independently represent a number from 1 to 6, and p represents a number from 0 to 2. [4] The carbon dioxide absorbent according to [3], wherein the amine compound represented by general formula (1) is any one of compounds represented by the following formulas (1-1) to (1-3): [5] The carbon dioxide absorbent according to any one of [1] to [4], wherein the carbon dioxide absorbent comprises the amine compound (A) and a porous material (B), and at least a portion of the amine compound (A) is supported on the porous material (B). [6] The carbon dioxide absorbent according to [5], wherein the porous material (B) comprises at least one selected from the group consisting of porous silica and porous alumina. [7] A method for recovering carbon dioxide, using the carbon dioxide absorbent according to any one of [1] to [6]. [8] The method according to [7], wherein the method comprises an absorption step of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to cause the carbon dioxide absorbent to absorb carbon dioxide, and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, and the desorption step comprises at least one step selected from the group consisting of the following (I) to (III): (I) a step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions; (II) a step of contacting the carbon dioxide absorbent that has absorbed carbon dioxide with an inert gas that does not contain carbon dioxide; and (III) a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide. [9] A carbon dioxide separation and capture system comprising: an absorption device equipped with a mechanism that brings the carbon dioxide absorbent according to any one of [1] to [6] into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide; and a desorption device equipped with a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0008] According to the present invention, it is possible to provide a carbon dioxide absorbent having excellent carbon dioxide absorption properties and reusability, a carbon dioxide recovery method using the same, and a carbon dioxide separation and recovery apparatus.

[0009] 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture apparatus according to the present invention. 2 is a graph showing the results of evaluating the carbon dioxide absorption ability using the carbon dioxide absorbents of Examples 1 to 6.

[0010] [Definitions] A mode for carrying out the present invention (hereinafter simply referred to as "the present embodiment") will be described in detail. The following present embodiment is an example for explaining the present invention, and does not limit the content of the present invention. The present invention can be carried out by appropriately modifying it within the scope of its gist. In the present embodiment, the definitions that are considered to be preferred can be adopted arbitrarily, and it can be said that a combination of preferred definitions is more preferable. In the present embodiment, the description "XX to YY" means "XX or more and YY or less."

[0011] In this specification, "good carbon dioxide absorbency" means that the carbon dioxide absorbent has a large carbon dioxide absorption capacity. Furthermore, "good carbon dioxide absorbency in air" means that the carbon dioxide absorbent has a large absorption capacity for low concentrations (about 0.04% by volume) of carbon dioxide in air. In this specification, "excellent reusability" means that the carbon dioxide absorbent has high mass retention and high carbon dioxide absorption capacity retention when subjected to a carbon dioxide absorption-desorption cycle test.

[0012] [Carbon Dioxide Absorbent] The carbon dioxide absorbent of the present invention contains a non-azo solid amine compound (A) (hereinafter, also simply referred to as "amine compound (A)") having two or more aromatic rings and two or more primary amino groups. Due to the above-described configuration, the carbon dioxide absorbent of the present invention has excellent carbon dioxide absorption properties and reusability. In particular, the carbon dioxide absorbent of the present invention has excellent reusability even when a steam stripping method is used to desorb carbon dioxide from the absorbent after carbon dioxide absorption. Furthermore, the carbon dioxide absorbent of the present invention exhibits good carbon dioxide absorption properties even in air with a carbon dioxide concentration as low as about 0.04% by volume. Therefore, it can be suitably used in a technology for directly capturing carbon dioxide from air (DAC). Furthermore, the carbon dioxide absorbent of the present invention can be suitably used, for example, when capturing carbon dioxide from a gas with a carbon dioxide concentration of 0.01% by volume or more and 1% by volume or less.

[0013] The reason why the carbon dioxide absorbent of the present invention exhibits the above-mentioned effects is not clear, but is thought to be as follows. The amine compound (A) contained in the carbon dioxide absorbent has a structure having an aromatic ring and two or more primary amino groups, which is thought to facilitate the reaction of the amino groups with carbon dioxide to form a carbonate, thereby exhibiting excellent carbon dioxide absorption. When the amine compound (A) has two or more aromatic rings, the melting point of the amine compound (A) increases, making it more likely to become a solid amine, and its solubility in water decreases. This improves the reusability of the carbon dioxide absorbent, and in particular, even when a steam stripping method is used to desorb carbon dioxide after absorbing carbon dioxide, the amine compound (A) is less likely to elute, resulting in a carbon dioxide absorbent with excellent reusability. Furthermore, the amine compound (A) must be a non-azo compound in order to be applicable to a method using a heating means, such as a steam stripping method, when desorbing carbon dioxide, and to avoid denaturation due to photoreaction.

[0014] <Amine Compound (A)> The amine compound (A) is a non-azo solid amine compound having two or more aromatic rings and two or more primary amino groups. In this specification, the term "primary amino group" refers to an amino group having two hydrogen atoms on the nitrogen atom, i.e., -NH ２ The term "non-azo compound" as used herein means a compound that does not contain an azo bond (-N=N-) in the molecule. The term "solid amine compound" as used herein means an amine compound that has a melting point of more than 25°C and is solid at 25°C.

[0015] From the viewpoint of improving reusability, the melting point of the amine compound (A) is preferably 50°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, still more preferably 110°C or higher, and even more preferably 120°C or higher. There is no particular upper limit, but from the viewpoint of improving carbon dioxide absorption ability and improving supportability on the porous material (B) described below, it is preferably 300°C or lower, more preferably 280°C or lower, even more preferably 250°C or lower, still more preferably 200°C or lower, still more preferably 180°C or lower, still more preferably 160°C or lower, and still more preferably 150°C or lower. The melting point of the amine compound (A) can be specifically measured by the method described in the Examples.

[0016] From the viewpoints of improving carbon dioxide absorption ability and repeated useability, and of facilitating carbon dioxide desorption, the amine compound (A) has two or more aromatic rings. The number of aromatic rings in the amine compound (A) is preferably 2 or more and 10 or less, more preferably 2 or more and 6 or less, even more preferably 2 or more and 4 or less, still more preferably 2 or more and 3 or less, and still more preferably 2.

[0017] The number of amino groups in the amine compound (A) is 2 or more from the viewpoint of improving carbon dioxide absorbency, and from the viewpoint of reducing water solubility and improving repeated useability, it is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 3 or less. The number of primary amino groups in the amine compound (A) is 2 or more from the viewpoint of improving carbon dioxide absorbency, and from the viewpoint of reducing water solubility and improving repeated useability, it is preferably 8 or less, more preferably 6 or less, even more preferably 4 or less, and still more preferably 3 or less.

[0018] From the viewpoint of improving carbon dioxide absorbency, the amine compound (A) preferably has primary amino groups in an amount of 30 mol% or more, more preferably 40 mol% or more, even more preferably 50 mol% or more, still more preferably 60 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, and still more preferably 90 mol% or more, but not more than 100 mol% based on all amino groups contained in the amine compound (A).

[0019] The amine compound (A) is preferably a non-polymer compound from the viewpoint of improving carbon dioxide absorption and repeated useability, and from the viewpoint of improving supportability in the porous material (B) described below. In this specification, "non-polymer compound" means a low-molecular-weight compound, specifically a compound having a molecular weight of 1,000 or less. From the viewpoint of improving carbon dioxide absorption and supportability in the porous material (B), the molecular weight of the amine compound (A) is preferably 800 or less, more preferably 700 or less, even more preferably 600 or less, still more preferably 500 or less, still more preferably 400 or less, and still more preferably 350 or less, and from the viewpoint of improving repeated useability, it is preferably 212 or more.

[0020] From the viewpoint of improving the carbon dioxide desorption property and further improving the reusability, the maximum carbon dioxide dissociation temperature of the amine compound (A) is preferably 280°C or less, more preferably 250°C or less, even more preferably 200°C or less, still more preferably 180°C or less, and even more preferably 150°C or less. The lower limit of the maximum carbon dioxide dissociation temperature is not particularly limited, but is, for example, 40°C or more, preferably 80°C or more, and even more preferably 100°C or more. The maximum carbon dioxide dissociation temperature is a value measured by the following method. The amine compound (A) having absorbed carbon dioxide is heated from 23°C to 250°C at a temperature increase rate of 10°C / min, and the temperature at which the endothermic heat amount associated with the desorption of carbon dioxide becomes maximum is measured, and this temperature is taken as the maximum carbon dioxide dissociation temperature. Here, the amine compound (A) having absorbed carbon dioxide can be prepared, for example, by leaving 5 mmol of the amine compound (A) in air at 23°C and 50% RH for 24 hours.

[0021] From the viewpoint of improving carbon dioxide absorption and reusability, the amine compound (A) is preferably an amine compound represented by the following general formula (1): In formula (1), X and Y each independently represent a single bond or an oxygen atom, n and m each independently represent a number from 1 to 6, and p represents a number from 0 to 2.

[0022] In formula (1), X and Y may be the same or different, but from the viewpoint of ease of production, they are preferably the same. That is, X and Y in formula (1) are preferably both single bonds or both oxygen atoms.

[0023] In formula (1), n ​​and m may be the same or different, but are preferably the same from the viewpoint of ease of production. From the viewpoint of improving carbon dioxide absorbency, n and m are preferably 1 to 4, more preferably 1 to 3, even more preferably 1 to 2, and still more preferably 1. From the viewpoint of improving carbon dioxide absorbency and repeated use, p in formula (1) is preferably 0 or 1, and more preferably 0. When p is 2, X and Y in formula (1) are preferably oxygen atoms.

[0024] The amine compound represented by the general formula (1) is preferably any of the compounds represented by the following formulas (1-1) to (1-3) from the viewpoint of improving carbon dioxide absorbency and repeated use, and from the viewpoint of ease of production, and is more preferably a compound represented by the following formula (1-1) or (1-2), and even more preferably a compound represented by the following formula (1-2).

[0025] The amine compound (A) can be used alone or in combination of two or more. The amine compound (A) can be produced by a known method, or a commercially available product can also be used.

[0026] From the viewpoint of improving carbon dioxide absorbency and repeated usability, the content of the amine compound (A) in all amine compounds in the carbon dioxide absorbent of the present invention is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 98% by mass or more, but is 100% by mass or less.

[0027] From the viewpoint of improving carbon dioxide absorbency, the content of the amine compound (A) in the carbon dioxide absorbent of the present invention is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, still more preferably 40% by mass or more, still more preferably 45% by mass or more, and still more preferably 50% by mass or more, and is 100% by mass or less. From the viewpoint of improving carbon dioxide absorbency, when the carbon dioxide absorbent contains a porous material (B) described later, the content of the amine compound (A) in the carbon dioxide absorbent is preferably 90% by mass or less, more preferably 80% by mass or less, and still more preferably 70% by mass or less.

[0028] From the viewpoint of further improving carbon dioxide absorbency and enabling carbon dioxide desorption with lower energy after carbon dioxide absorption, the carbon dioxide absorbent of the present invention preferably contains an amine compound (A) and a porous material (B), with at least a portion of the amine compound (A) supported on the porous material (B). The reason for improved carbon dioxide absorbency when the carbon dioxide absorbent contains the amine compound (A) and the porous material (B) and at least a portion of the amine compound (A) is supported on the porous material (B) is presumed to be because the surface area of ​​the portion of the solid amine compound (A) that can come into contact with carbon dioxide is increased. Furthermore, depending on the type of amine compound (A), the bonding state between the amine compound (A) and carbon dioxide changes, and the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent is lower than when the amine compound (A) is used alone, which is thought to enable carbon dioxide desorption to be performed under lower energy conditions.

[0029] <Porous Material (B)> The porous material (B) is preferably one that can support the amine compound (A) and can withstand the conditions for carbon dioxide recovery, and examples thereof include at least one selected from the group consisting of silica, alumina, silica alumina, magnesia, zirconia, zeolite, zeolite-related compounds, clay minerals, natural minerals, activated carbon, carbon molecular sieves (porous carbon), porous resins (synthetic adsorbents), metal-organic frameworks, and solid waste. Among these, from the viewpoint of further improving carbon dioxide absorbability and enabling carbon dioxide desorption with lower energy after carbon dioxide absorption, the porous material (B) preferably contains at least one selected from the group consisting of silica and alumina, more preferably contains silica, and even more preferably contains mesoporous silica. The content of silica and alumina, preferably silica, more preferably mesoporous silica, in the porous material (B) is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 98% by mass or more, but 100% by mass or less, from the viewpoint of further improving carbon dioxide absorbency and enabling carbon dioxide to be desorbed with less energy after carbon dioxide absorption.

[0030] The shape of the porous material (B) is preferably particulate, which increases the specific surface area of ​​the porous material (B) and increases the amount of the amine compound (A) supported, thereby further improving the carbon dioxide absorption amount of the carbon dioxide absorbent.

[0031] The volume median particle diameter (D ５０ ) is preferably 1 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more from the viewpoint of improving handleability, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, still more preferably 180 μm or less, and still more preferably 160 μm or less from the viewpoint of further increasing the amount of amine compound (A) supported.

[0032] The specific surface area of ​​the porous material (B) measured by the BET method is preferably 2 m or more from the viewpoint of further increasing the amount of the amine compound (A) supported. ２ / g or more, more preferably 10m ２ / g or more, more preferably 100m ２ / g or more, and even more preferably 200m ２ / g or more, and even more preferably 400m ２ / g or more, and even more preferably 600m ２ / g or more, and from the viewpoint of improving the handling property, it is preferably 3000m ２ / g or less, more preferably 1500m ２ / g or less, more preferably 1200m ２ / g or less, and even more preferably 1000m ２ / g or less.

[0033] The pore volume of the porous material (B) is preferably 0.1 cm 3 from the viewpoint of further improving the amount of the amine compound (A) supported. ３ / g or more, more preferably 0.3 cm ３ / g or more, more preferably 0.5 cm ３ / g or more, and from the viewpoint of improving repetitive use, it is preferably 5.0 cm ３ / g or less, more preferably 3.0 cm ３ / g or less, more preferably 2.5 cm ３ / g or less, and even more preferably 2.0 cm ３ / g or less, and even more preferably 1.5 cm ３ / g or less, and even more preferably 1.0 cm ３ / g or less. The specific surface area and pore volume can be measured, for example, using a constant volume method with a specific surface area / pore size distribution measuring device (e.g., "ASAP2020" manufactured by Shimadzu Corporation). A more specific gas adsorption measurement method using a specific surface area / pore size distribution measuring device involves, for example, pretreating the sample by heating and evacuating, and then placing 0.1 g of the measurement sample in a sample tube. The sample is then heated to 40°C and evacuated for 6 hours, after which it is cooled to room temperature and the sample mass is measured. In the measurement, the liquid nitrogen temperature is set and the pressure range is specified, and the specific surface area, pore volume, and pore size can be analyzed and calculated from the obtained nitrogen adsorption isotherm.

[0034] The porous material (B) may be a granulated product such as pellets or tablets obtained by granulating the particulate porous material by a known method. Examples of the granulation method include a dry granulation method using a compression molding machine and a wet granulation method using a binder. By granulating and using the particulate porous material, vibration resistance and abrasion resistance can be imparted, and physical stability can be improved.

[0035] When the carbon dioxide absorbent comprises an amine compound (A) and a porous material (B), from the viewpoint of further improving carbon dioxide absorbency and enabling carbon dioxide desorption with lower energy after carbon dioxide absorption, the content of the amine compound (A) in the carbon dioxide absorbent is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, even more preferably 30 parts by mass or more, still more preferably 40 parts by mass or more, still more preferably 50 parts by mass or more, still more preferably 70 parts by mass or more, still more preferably 80 parts by mass or more, and is preferably 1000 parts by mass or less, more preferably 500 parts by mass or less, still more preferably 250 parts by mass or less, still more preferably 200 parts by mass or less, still more preferably 150 parts by mass or less, and still more preferably 120 parts by mass or less, relative to 100 parts by mass of the porous material (B).

[0036] When the carbon dioxide absorbent contains the amine compound (A) and the porous material (B), from the viewpoint of further improving the carbon dioxide absorbency and enabling carbon dioxide to be desorbed with less energy after carbon dioxide absorption, the total content of the amine compound (A) and the porous material (B) in the carbon dioxide absorbent is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, still more preferably 95% by mass or more, and still more preferably 98% by mass or more, and is 100% by mass or less, when the total amount of the carbon dioxide absorbent is taken as 100% by mass.

[0037] <Other Components> The carbon dioxide absorbent can appropriately contain components other than the amine compound (A) and the porous material (B), as long as the effects of the invention are not impaired. Examples of the components other than the amine compound (A) and the porous material (B) include a deterioration inhibitor, an antifoaming agent, an antioxidant, and a desiccant for removing moisture (magnesium sulfate, molecular sieves, etc.).

[0038] From the viewpoint of improving carbon dioxide absorption ability and repeated use, the water content in the carbon dioxide absorbent is preferably 10% by mass or less, more preferably 5% by mass or less, even more preferably 1% by mass or less, still more preferably 0.5% by mass or less, still more preferably 0.1% by mass or less, and still more preferably 0.01% by mass or less, and it is even more preferable that the carbon dioxide absorbent is substantially free of water. Here, "substantially free of water" means that water is not intentionally added, and does not exclude the presence of a small amount of water as an impurity.

[0039] When the carbon dioxide absorbent contains the amine compound (A) and the porous material (B), the melting point of the carbon dioxide absorbent is, from the viewpoint of improving repeated use, preferably 50° C. or higher, more preferably 80° C. or higher, even more preferably 100° C. or higher, still more preferably 110° C. or higher, and still more preferably 120° C. or higher. There is no particular upper limit, but, from the viewpoint of improving carbon dioxide absorbency, it is preferably 300° C. or lower, more preferably 280° C. or lower, even more preferably 250° C. or lower, still more preferably 200° C. or lower, still more preferably 180° C. or lower, still more preferably 160° C. or lower, and still more preferably 150° C. or lower. The melting point of the carbon dioxide absorbent can be measured by the same method as above.

[0040] When the carbon dioxide absorbent contains the amine compound (A) and the porous material (B), from the viewpoint of improving the carbon dioxide desorption property and further improving the reusability, the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent is preferably 200° C. or lower, more preferably 180° C. or lower, even more preferably 160° C. or lower, and still more preferably 150° C. or lower. The lower limit of the maximum carbon dioxide dissociation temperature is not particularly limited, but is, for example, 40° C. or higher, preferably 80° C. or higher, and more preferably 100° C. or higher. The maximum carbon dioxide dissociation temperature can be measured by the same method as described above.

[0041] From the viewpoint of enabling carbon dioxide desorption at a temperature lower than the melting point of the carbon dioxide absorbent, the melting point of the carbon dioxide absorbent is preferably a temperature higher than the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent. Furthermore, it is preferable that the difference between the melting point of the carbon dioxide absorbent and the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent is large. If the difference between the melting point of the carbon dioxide absorbent and the maximum carbon dioxide dissociation temperature is small, the carbon dioxide absorbent may melt and aggregate simultaneously with carbon dioxide desorption, reducing its surface area and resulting in a decrease in carbon dioxide absorbability. However, if the difference between the melting point of the carbon dioxide absorbent and the maximum carbon dioxide dissociation temperature is large, carbon dioxide desorption at a temperature lower than the melting point of the carbon dioxide absorbent is possible, and a decrease in carbon dioxide absorbability due to melting of the carbon dioxide absorbent can be avoided. The difference between the melting point of the carbon dioxide absorbent and the maximum carbon dioxide dissociation temperature (melting point of the carbon dioxide absorbent - maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent) is preferably 5°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher, from the viewpoint of further improving carbon dioxide absorbability and enabling carbon dioxide desorption with less energy after carbon dioxide absorption.

[0042] When the carbon dioxide absorbent contains an amine compound (A) and a porous material (B), the method for preparing the carbon dioxide absorbent is not particularly limited, and known methods can be used. For example, the carbon dioxide absorbent can be prepared by blending the amine compound (A) and the porous material (B) and mixing them using a known device. When the carbon dioxide absorbent is an embodiment in which at least a portion of the amine compound (A) is supported on the porous material (B), the carbon dioxide absorbent can preferably be prepared by the following method. First, the amine compound (A) is dissolved in an organic solvent, and then the porous material (B) is added. The mixture is stirred, preferably at a temperature of 5 to 60°C for 1 to 24 hours to prepare a mixture. Next, the organic solvent is removed from the resulting mixture by distillation or the like, and the remaining solid is dried under reduced pressure to obtain the carbon dioxide absorbent. As the organic solvent, from the viewpoint of the solubility of the amine compound (A) and the ease of removal from the carbon dioxide absorbent, dichloromethane or a monohydric alcohol having 4 or less carbon atoms is preferred, and at least one selected from the group consisting of dichloromethane, methanol, ethanol, and isopropyl alcohol is more preferred.

[0043] [Method for recovering carbon dioxide] The method for recovering carbon dioxide of the present invention (hereinafter also simply referred to as the "method of the present invention") is characterized by using the carbon dioxide absorbent. According to the method of the present invention, the amount of carbon dioxide absorbed from a gas containing carbon dioxide can be increased, and the method can be particularly suitably used for a technology for directly recovering carbon dioxide from air (DAC). In addition, it becomes possible to recover carbon dioxide with less energy, and further, even when a steam stripping method is used to desorb carbon dioxide from the absorbent after carbon dioxide absorption, the repeated use of the carbon dioxide absorbent can be improved.

[0044] The method for recovering carbon dioxide according to the present invention preferably includes a step (absorption step) of bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide to allow the carbon dioxide absorbent to absorb carbon dioxide.

[0045] <Absorption Step> The absorption step is a step of bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide. The method of bringing the carbon dioxide absorbent into contact with the gas can be selected appropriately depending on the form of the carbon dioxide absorbent, and is not particularly limited. For example, the carbon dioxide absorbent can be brought into contact with the gas containing carbon dioxide by passing the gas containing carbon dioxide through the carbon dioxide absorbent, spraying the carbon dioxide absorbent in the gas containing carbon dioxide, or placing the carbon dioxide absorbent in the gas containing carbon dioxide.

[0046] Examples of carbon dioxide-containing gases include, but are not limited to, air, thermal power plant exhaust gas, steel mill exhaust gas, cement factory exhaust gas, chemical plant exhaust gas, biofermentation gas, and natural gas. Energy-saving carbon dioxide recovery from these gases is particularly required, and the present invention is particularly effective for this purpose. The carbon dioxide concentration, gas pressure, and gas temperature in the gas are not particularly limited, and the method of the present invention can be applied to gases under a wide range of conditions. Furthermore, the carbon dioxide-containing gas may contain acidic gases other than carbon dioxide. Examples of such acidic gases include CO, NOx, and SOx in the exhaust gas, formaldehyde generated in methanol-fueled power generation, and hydrogen chloride and hydrogen sulfide. When the carbon dioxide-containing gas contains acidic gases other than carbon dioxide, it is preferable to combine the method with a known process for removing the other acidic gases. Specifically, the carbon dioxide recovery method of the present invention may be applied to a gas containing acidic gases other than carbon dioxide, or the method of the present invention may be applied after removing the other acidic gases from a gas containing acidic gases other than carbon dioxide by known means. From the viewpoint of improving the efficiency of separating and recovering carbon dioxide, the relative humidity (RH) of the carbon dioxide-containing gas is preferably 30% RH or higher, more preferably 35% RH or higher, and even more preferably 40% RH or higher, and is preferably 70% RH or lower, more preferably 65% ​​RH or lower, and even more preferably 60% RH or lower. In this specification, a gas with a RH of less than 30% is defined as a dry gas.

[0047] In the absorption step, the temperature when the carbon dioxide absorbent is brought into contact with the gas containing carbon dioxide is not particularly limited, but from the viewpoint of improving the carbon dioxide absorption amount, the temperature is preferably 0°C or higher and lower than 60°C, and more preferably 20°C or higher and lower than 60°C.

[0048] More preferably, the method of the present invention comprises an absorption step of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to allow the carbon dioxide absorbent to absorb carbon dioxide, and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, the desorption step comprising at least one step selected from the group consisting of the following (I) to (III). This method makes it possible to easily separate and recover carbon dioxide from a gas containing carbon dioxide: (I) a step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions; (II) a step of contacting the carbon dioxide absorbent that has absorbed carbon dioxide with an inert gas that does not contain carbon dioxide; and (III) a step of heating the carbon dioxide absorbent that has absorbed carbon dioxide.

[0049] <Desorption Step> The desorption step is a step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step. A method for desorbing carbon dioxide from a carbon dioxide absorbent that has absorbed carbon dioxide preferably includes at least one step selected from the group consisting of steps (I) to (III) above. Two or more of steps (I) to (III) may be combined. Furthermore, from the viewpoint of the effectiveness of using the carbon dioxide absorbent of the present invention, the desorption step preferably includes step (III). Because the carbon dioxide absorbent of the present invention includes a solid amine compound (A), the mass retention rate and the carbon dioxide absorption amount retention rate of the carbon dioxide absorbent can be maintained within a high range, even when heating is performed in the desorption step.

[0050] (I) In the step of subjecting the carbon dioxide absorbent that has absorbed carbon dioxide to reduced pressure conditions (hereinafter also referred to as "step (I)"), the reduced pressure conditions are preferably 10 kPa or less, more preferably 5 kPa or less, and even more preferably 1 kPa or less, from the viewpoint of improving the efficiency of separating and recovering carbon dioxide. In step (I), the temperature when the carbon dioxide absorbent is subjected to reduced pressure conditions is not particularly limited, but is preferably 0°C or higher, more preferably 10°C or higher, from the viewpoint of improving the efficiency of separating and recovering carbon dioxide. Furthermore, from the viewpoint of suppressing thermal degradation of the amine compound (A) in the carbon dioxide absorbent, the temperature is preferably less than 50°C, more preferably 45°C or lower.

[0051] (II) In the step of contacting a carbon dioxide absorbent having absorbed carbon dioxide with an inert gas not containing carbon dioxide (hereinafter also referred to as "step (II)"), desorption of carbon dioxide can be promoted by lowering the partial pressure of carbon dioxide. Examples of the inert gas not containing carbon dioxide include nitrogen, helium, argon, etc., and one or more of these can be used. Among these, from the viewpoint of improving the efficiency of carbon dioxide separation and recovery, the inert gas not containing carbon dioxide is preferably at least one selected from the group consisting of nitrogen and argon. In step (II), examples of a method for contacting the carbon dioxide absorbent with an inert gas not containing carbon dioxide include the same contact method as described in the absorption step. In step (II), the temperature when contacting the carbon dioxide absorbent with an inert gas not containing carbon dioxide is not particularly limited. In step (II), the heating specified in step (III) may be performed simultaneously, or the temperature may be room temperature or lower. From the viewpoint of suppressing thermal degradation of the amine compound (A) in the carbon dioxide absorbent, the temperature is preferably less than 50°C, more preferably 45°C or lower. From the viewpoint of improving the efficiency of separating and recovering carbon dioxide, the temperature is preferably 0°C or higher, and more preferably 10°C or higher.

[0052] The heating temperature in the (III) step of heating the carbon dioxide absorbent that has absorbed carbon dioxide (hereinafter also referred to as "step (III)") can be appropriately selected depending on the melting point and maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent, but from the viewpoint of improving the efficiency of separation and recovery of carbon dioxide, it is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, still more preferably 70°C or higher, and still more preferably 80°C or higher. Furthermore, from the viewpoint of improving the repeated usability of the carbon dioxide absorbent, it is preferably 250°C or lower, more preferably 230°C or lower, even more preferably 220°C or lower, still more preferably 200°C or lower, and still more preferably 180°C or lower.

[0053] The heating in step (III) can be carried out by a known method using an apparatus equipped with a heating means, such as heating with steam or a heat medium, hot air heating, electromagnetic wave heating, ultrasonic heating, or induction heating.

[0054] In the method of the present invention, a carbon dioxide absorbent containing a solid amine compound (A) having low water solubility is used, and therefore, a steam stripping method is preferably used in step (III). The steam stripping method can be carried out by heating the carbon dioxide absorbent that has absorbed carbon dioxide in a steam atmosphere. The heating temperature in the steam stripping method is preferably 80°C or higher, more preferably 90°C or higher, and from the viewpoint of improving the reusability of the carbon dioxide absorbent, is preferably 250°C or lower, more preferably 230°C or lower, even more preferably 220°C or lower, still more preferably 200°C or lower, and even more preferably 180°C or lower.

[0055] The carbon dioxide absorbent and carbon dioxide separated in the desorption step can be recovered separately and reused.

[0056] [Carbon dioxide separation and capture apparatus] The carbon dioxide separation and capture apparatus of the present invention (hereinafter also referred to as "the apparatus of the present invention") comprises an absorption apparatus equipped with a mechanism for bringing the carbon dioxide absorbent into contact with a gas containing carbon dioxide, and causing the carbon dioxide absorbent to absorb carbon dioxide, and a desorption apparatus equipped with a mechanism for desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

[0057] The apparatus of the present invention will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing one embodiment of a carbon dioxide separation and capture apparatus 100 of the present invention, in which 1 is an absorption apparatus and 2 is a desorption apparatus.

[0058] <Absorption Device> The absorption device 1 in the carbon dioxide separation and capture system 100 is a mechanism that includes the carbon dioxide absorbent and brings the carbon dioxide absorbent into contact with a gas containing carbon dioxide, thereby causing the carbon dioxide absorbent to absorb carbon dioxide.

[0059] The absorption device 1 is not particularly limited as long as it has a configuration that brings the carbon dioxide absorbent into contact with a gas containing carbon dioxide, depending on the form of the carbon dioxide absorbent. For example, as shown in Fig. 1 , the absorption device 1 can be provided with an absorbent holding unit 12 that holds a carbon dioxide absorbent 12a inside a reaction tower 11, and further with a gas supply unit 13 that supplies a gas containing carbon dioxide to the absorbent holding unit 12. Furthermore, from the viewpoint of discharging the carbon dioxide absorbent that has absorbed carbon dioxide from the absorbent holding unit 12 and supplying new carbon dioxide absorbent, the absorption device 1 can also be provided with an absorbent discharge unit (not shown) that discharges the carbon dioxide absorbent 12a held in the absorbent holding unit 12, and an absorbent supply unit (not shown) that supplies new carbon dioxide absorbent to the absorbent holding unit 12.

[0060] The absorption device 1 may further include a heating / cooling mechanism to adjust the temperature when the carbon dioxide absorbent is brought into contact with the carbon dioxide-containing gas. The absorption device 1 may also include a carbon dioxide concentration measurement mechanism to measure the carbon dioxide concentration in the gas. Furthermore, the absorption device 1 may also include a pressurization / depressurization mechanism to adjust the pressure when the carbon dioxide absorbent is brought into contact with the carbon dioxide-containing gas.

[0061] The carbon dioxide separation and capture system 100 may have a connection part 3 for supplying the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1 to the desorption device 2. There are no particular limitations on the means for supplying the carbon dioxide absorbent that has absorbed carbon dioxide from the absorption device 1 to the desorption device 2, and the absorption device 1 may be stopped once after operating for a certain period of time, and the carbon dioxide absorbent in the reaction tower 11 provided in the absorption device 1 may be supplied all at once to the desorption device 2. Alternatively, the carbon dioxide absorbent may be supplied continuously or intermittently from the absorbent holding part 12 of the absorption device 1 to the desorption device 2 using the connection part 3.

[0062] <Desorption device> The desorption device 2 in the carbon dioxide separation and capture system 100 is a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1. The desorption device 2 is not particularly limited as long as it has a mechanism that desorbs carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption device 1, but it is preferable that it is equipped with a mechanism for performing at least one of the steps (I) to (III) above. Examples of such a mechanism include a pressure reduction mechanism, an inert gas supply mechanism, and a heating mechanism.

[0063] 1 , the desorption apparatus 2 may include, inside a reaction tower 21, an absorbent holding section 22 that holds a carbon dioxide absorbent 22a that has absorbed carbon dioxide, and may further include a gas discharge section 23 that discharges carbon dioxide desorbed from the carbon dioxide absorbent. The desorption apparatus 2 also includes at least one mechanism (not shown) selected from a pressure reduction mechanism for creating a reduced pressure condition inside the reaction tower 21, an inert gas supply mechanism for supplying an inert gas to the absorbent holding section 22, and a heating mechanism for heating the absorbent holding section 22. In addition to the pressure reduction mechanism, inert gas supply mechanism, and heating mechanism, the desorption apparatus 2 may also include a carbon dioxide concentration measurement mechanism, etc., similar to the absorption apparatus 1.

[0064] The carbon dioxide absorbent after desorbing carbon dioxide in the desorption device 2 can be supplied again to the absorption device 1 from the absorbent discharge section 24, which is used to supply the carbon dioxide absorbent after desorbing carbon dioxide to the absorption device 1, and can be reused.

[0065] The carbon dioxide separation and capture system 100 may further include a capture device for capturing the desorbed carbon dioxide. The captured carbon dioxide can be used for agricultural purposes such as enhanced oil recovery and plant factories; industrial gas purposes such as beverages and welding; chemical synthesis; or carbon dioxide capture and storage (CCS). The captured carbon dioxide may also be concentrated before being used for these purposes.

[0066] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples. In the examples, various measurements and evaluations were carried out by the following methods.

[0067] (Specific Surface Area and Pore Volume of Porous Material) The specific surface area and pore volume of the porous material were measured using a specific surface area / pore size distribution measuring device ("ASAP2020" manufactured by Shimadzu Corporation).

[0068] (Volume median particle diameter of porous material (D ５０ The particle distribution of the porous material was measured using a laser diffraction / scattering particle size distribution analyzer (Malvern Instruments, "LMS-200e"). The particle size corresponding to a cumulative volume frequency of 50%, calculated from the smallest particle size in the particle distribution, was defined as the volume median particle size (D ５０ )

[0069] (Carbon dioxide absorbent carbon dioxide (CO ２ ) Absorbency) In an air environment of 23°C and 50% RH, a carbon dioxide concentration meter and a petri dish were placed in an openable desiccator (inner dimensions: 370 mm x 260 mm x 272 mm). Thereafter, a carbon dioxide absorbent was added to the petri dish in the desiccator in an amount such that the number of amino groups in the amine compound contained in the carbon dioxide absorbent was 10 mmol (5 mmol of amine compound in this example), and the door was immediately closed, and the carbon dioxide absorbent was left to stand in the desiccator. The carbon dioxide concentration (ppm) in the desiccator after a certain time had passed was measured as CO ２The concentration was measured using a concentration meter ("CO2 / Temperature / Humidity Data Logger TR-76Ui" manufactured by T&D Corporation), and the carbon dioxide absorption ability of the carbon dioxide absorbent was evaluated based on the concentration. Figure 2 shows a graph plotting the carbon dioxide concentration (ppm) in the desiccator on the vertical axis and the elapsed time (min) on the horizontal axis. A larger decrease in carbon dioxide concentration means a higher carbon dioxide absorption ability of the carbon dioxide absorbent.

[0070] (Carbon dioxide absorbent carbon dioxide (CO ２ ) Maximum dissociation temperature) A carbon dioxide concentration meter and a petri dish were placed in an openable desiccator (inner dimensions: 370 mm x 260 mm x 272 mm) in an air environment of 23°C and 50% RH. Then, an amount of carbon dioxide absorbent such that the number of amino groups in the amine compound contained in the carbon dioxide absorbent was 10 mmol (5 mmol of amine compound in this example) was added to the petri dish in the desiccator, the door was immediately closed, and the carbon dioxide absorbent was left to stand in the desiccator for 24 hours. The initial carbon dioxide concentration was adjusted to approximately 400 ppm. Next, the carbon dioxide absorbent was removed from the desiccator to obtain a carbon dioxide absorbent that had absorbed carbon dioxide. The carbon dioxide absorbent that had absorbed carbon dioxide was subjected to DSC measurement as follows to measure the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent. First, differential scanning calorimetry was performed on the carbon dioxide absorbent using a differential thermogravimeter ("DTG-60" manufactured by Shimadzu Corporation) under conditions of a measurement temperature range of 23 to 250°C, a temperature rise rate of 10°C / min, and a nitrogen atmosphere. From the DSC curve obtained, the temperature at which the endothermic heat associated with carbon dioxide desorption was maximized was determined to be the maximum carbon dioxide dissociation temperature of the carbon dioxide absorbent.

[0071] (Melting Point of Carbon Dioxide Absorbent) DSC measurement was carried out using a thermogravimetric differential scanning calorimeter ("STA200RV" manufactured by Hitachi, Ltd.). The measurement conditions were set to a nitrogen flow rate of 50 mL / min, a temperature rise rate of 10°C / min, and a measurement temperature range of 40-350°C, and the measurement was carried out by weighing out about 16 mg of the carbon dioxide absorbent. The maximum endothermic peak temperature in the obtained DSC chart was taken as the melting point.

[0072] (Moisture content of carbon dioxide absorbent after carbon dioxide absorption) Measurement was performed using an autosampler moisture meter ("CA-310" manufactured by Nitto Seiko Analytech Co., Ltd.) The sample amount was 0.1 g, and the measurement conditions were a vaporization temperature of 105°C and a heating time of 20 minutes. The moisture content was calculated by dividing the sample weight by the sample weight before measurement by 100%.

[0073] (Solubility of Amine Compound in Water) An aqueous solution was prepared so that the concentration of the amine compound was 0.1% by mass, and whether or not the amine compound was dissolved was visually observed at 25° C. A solution in which no residual amine compound was found was judged to be soluble, and a solution in which residual amine compound was found was judged to be soluble. These results are shown in Examples 1 to 3 in Table 2.

[0074] (Cycle Test) Using a TG-DTA device ("STA200RV" manufactured by Hitachi, Ltd.), the CO ２ An absorption-desorption cycle test was carried out. Approximately 16 mg of carbon dioxide absorbent was placed in a deep aluminum pan, which was then set in a TG-DTA device. The temperature history of the temperature programs Nos. 1 to 11 shown in Table 1 was applied. ２ An absorption-desorption cycle test was conducted. The measurement atmosphere during each program run is shown in the "Gas" column in Table 1, and the flow rate of the gas is shown in the "Gas Flow Rate" column. "Moisture-absorbing air" in Table 1 refers to air (30-70% RH) that has been subjected to a drying process and then immersed in water to adjust the humidity. Note that X (°C) in Table 1 corresponds to the regeneration temperature (°C) in the cycle test described below.

[0075]

[0076] [2nd cycle CO ２ Absorption amount (mg / g)] The weight increase (mg) of the absorbent at the end of Program No. 6 in Table 1 divided by the weight (g) of the absorbent at the start of Program No. 6 is the CO 2 absorption amount (mg / g) of the second cycle. ２ The absorption amount (mg / g) was expressed. A larger value means better carbon dioxide absorption.

[0077] [CO ２Regeneration rate (%) of the second absorption-desorption cycle] The weight (g) of the absorbent at the start of Program No. 6 in Table 1 divided by the weight (g) of the absorbent at the end of Program No. 8 is multiplied by 100 to obtain the CO ２ The regeneration rate (%) after the second absorption-desorption cycle was calculated. A higher regeneration rate indicates better reusability.

[0078] [Mass Retention Rate (2nd Cycle / 3rd Cycle) (%)] The weight (g) of the absorbent at the end of Program No. 11 in Table 1 was divided by the weight (g) of the absorbent at the end of Program No. 8, and the result was multiplied by 100 to obtain the mass retention rate (2nd Cycle / 3rd Cycle) (%). A higher mass retention rate indicates better repeated use.

[0079] [CO ２ Absorption retention rate (2nd cycle / 3rd cycle) (%)] The weight increase (mg) of the absorbent at the end of Program No. 6 in Table 1 divided by the weight (g) of the absorbent at the start of Program No. 6 is the CO 2 absorption rate at the 2nd cycle. ２ The absorbed amount Y (mg / g) was calculated by dividing the weight increase (mg) of the absorbent at the end of Program No. 9 in Table 1 by the weight (g) of the absorbent at the start of Program No. 9. ２ The absorption amount was Z (mg / g). Z / Y x 100 was calculated as the CO ２ The absorption retention rate (second cycle / third cycle) (%) was calculated. A higher retention rate indicates better reusability.

[0080] In the examples and comparative examples, the following amine compounds and porous materials were used.

[0081] (Amine Compound) HQ-BA: A compound represented by the following formula (1-1) (C ２０ H ２０ N ２ O ２ , Mw: 320.4) It was produced by the method described in Production Example 1 below.

[0082] DAMB: a compound represented by the following formula (1-2) (C １４ H １６ N ２, Mw: 212.3). It was produced by the method described in Production Example 2 below.

[0083] TP-DMA: a compound represented by the following formula (1-3) (C ２０ H ２０ N ２ , Mw: 288.4). It was synthesized according to the method described in J. Am. Chem. Soc., No. 136, Vol. 22, pp. 7899-7906 (2014).

[0084] Production Example 1 (Production of HQ-BA) Hydroquinone and 4-chlorobenzonitrile (4CBN) were reacted according to the method described in Polymer Degradation and Stability, Vol. 95, pp. 2445-2452 (2010) to synthesize a dinitrile compound (HQ-BEN) represented by the following structural formula. HQ-BEN was then hydrogenated according to the following method to produce HQ-BA.

[0085] 2.99 g of granular Raney cobalt catalyst was weighed in water and transferred to a 200 cc autoclave, where it was purged with isopropyl alcohol three times. After removing the substituted isopropyl alcohol, 15 g of the solvent meta-xylene and 6 g of HQ-BEN were added. The autoclave was airtight, and the interior of the autoclave was purged with nitrogen (1 MPaG) and hydrogen (5 MPaG) three times each. Furthermore, 15 g of liquid ammonia was charged, and hydrogen was sealed at 5 MPaG (including the liquid ammonia's own pressure). Heating was initiated while stirring at approximately 750 rpm, and the reaction was carried out at 80°C. The reaction time was 3 hours from the start of heating. After completion of the reaction, the mixture was cooled with ice water, and the hydrogen and ammonia were purged to reduce the pressure inside the system, and the autoclave was opened. The reaction solution was washed with methanol to remove the catalyst, and the solvent was then distilled off using an evaporator to obtain the target product, HQ-BA.

[0086] Production Example 2 (Production of DAMB) 4,4'-dicyanobiphenyl (DCB, reagent) was hydrogenated by the following method to produce 4,4-di(aminomethyl)biphenyl (DAMB). 3.0 g of granular Raney cobalt catalyst was weighed in water, transferred to a 100 mL autoclave, and reduced at 270°C under atmospheric pressure and a hydrogen flow for 2 hours. The catalyst was then transferred to an argon-purged 200 mL autoclave, and a punched metal tube for catalyst immobilization was installed. 10 g of meta-xylene as a solvent and 1.5 g of DCB as a substrate were added to the autoclave, and the autoclave was airtight. The pressure inside the autoclave was then purged with nitrogen (1 MPaG) and hydrogen (10 MPaG) three times each. Furthermore, 10 g of liquid ammonia was charged, and hydrogen was sealed in at 10 MPaG (including the autogenous pressure of the liquid ammonia). Heating was started while stirring at about 750 rpm, and the reaction was carried out for 1.5 hours after the internal temperature reached 80°C. After completion of the reaction, the autoclave was cooled with ice water, hydrogen and ammonia were purged to reduce the pressure inside the system, and the autoclave was opened. The reaction liquid was washed with methanol to remove the catalyst, and the solvent was then distilled off using an evaporator to obtain the target product, DAMB.

[0087] MXDA: metaxylylenediamine (manufactured by Mitsubishi Gas Chemical Co., Inc.), a diamine represented by the following formula that is liquid at 25°C Spirobisamine: 2,2'-(2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropan-1-amine) represented by the following formula, produced by the method described in Example 1 of WO 2022 / 255037.

[0088] (Porous material) Mesoporous silica SBA15 (manufactured by Merck) Specific surface area by BET method: 800 m ２ / g, volume median particle diameter (D ５０ ): 100 μm, pore volume: 0.8 cm ３ / g Pellet silica (pellets obtained by molding the raw silica below) Specific surface area by BET method: 253 m ２ / g, average pellet diameter: 1.90 mm, average pellet length: 10.86 mm Raw material silica ("CARIACT G-10" manufactured by Fuji Silysia Chemical Ltd., specific surface area: 300 m ２ / g, particle size: 10 μm, pore volume: 1.3 mL / g, average pore size: 10 nm)

[0089] Examples 1 to 3 (Evaluation of Carbon Dioxide Absorbents) The amine compounds shown in Table 2 were used as carbon dioxide absorbents, and the carbon dioxide absorbency was evaluated by the above-mentioned method. The results are shown in Figure 2. Furthermore, the results of evaluation of the maximum carbon dioxide dissociation temperature, melting point, and solubility in water by the above-mentioned method are also shown in Table 2.

[0090] Examples 4 to 6 (Preparation and Evaluation of Carbon Dioxide Absorbent) (Preparation of Carbon Dioxide Absorbent) A nitrogen-purged glass container was charged with 1.5 g of the amine compound (A) shown in Table 2 and a large excess of methanol (dichloromethane in Examples 5 and 6), and the mixture was stirred with a stirrer at room temperature (23 ° C.) to dissolve the amine compound (A). Next, 1.5 g of a porous material was added, and nitrogen substitution was performed again, followed by stirring for 3 hours to achieve uniformity. Methanol or dichloromethane was distilled off from the resulting mixture at 40 ° C. under a reduced pressure of 50 hPa, and then the mixture was vacuum-dried at 80 ° C. for 3 hours to obtain a carbon dioxide absorbent in which the amine compound (A) was supported on a porous material (B).

[0091] (Evaluation of Carbon Dioxide Absorbent) The obtained carbon dioxide absorbent was used to measure carbon dioxide (CO ２ The results of evaluating carbon dioxide (CO ) absorption are shown in Figure 2. ２ The maximum dissociation temperature, melting point, and moisture content after carbon dioxide absorption were measured and the results are shown in Table 2.

[0092] Comparative Example 1 In Example 1, MXDA (metaxylylenediamine) was used as the carbon dioxide absorbent instead of the amine compound (A), and the maximum carbon dioxide dissociation temperature, melting point, and solubility in water were evaluated by the above-mentioned method. The maximum carbon dioxide dissociation temperature was 135°C, the melting point was 14°C, and the solubility in water was determined to be "yes." The carbon dioxide absorbent of Comparative Example 1 is a liquid at 25°C and dissolves in water, so if a steam stripping method is applied during regeneration of the absorbent, MXDA is likely to dissolve in steam, and it is thought that good repeated usability cannot be obtained.

[0093] Comparative Example 2 In Example 1, the spirobisamine was used as a carbon dioxide absorbent instead of the amine compound (A), and carbon dioxide (CO ２ However, the spirobisamine did not exhibit carbon dioxide absorption.

[0094] Comparative Example 3 An attempt was made to prepare a carbon dioxide absorbent in which the spirobisamine was supported on the porous material (B) in the same manner as in Example 4, except that the spirobisamine was used instead of the amine compound (A) in Example 4. However, since the spirobisamine had almost no solubility in solvents, it was not possible to support it on the porous material (B).

[0095]

[0096] 2, the carbon dioxide absorbent of this example exhibited carbon dioxide absorption properties even in a system with a low carbon dioxide concentration (0.04 to 0.05% by mass). Furthermore, a comparison of Examples 1 to 3 with Examples 4 to 6 reveals that the carbon dioxide absorption properties of the amine compound (A) used in Examples 1 to 3 were further improved by being supported on the porous material (B). This is presumably because the surface area of ​​the portion of the amine compound (A) that can come into contact with carbon dioxide is increased.

[0097] From Table 2, a comparison between Examples 1 and 4 and a comparison between Examples 3 and 6 shows that the amine compound (A) used in Examples 1 and 3 can be supported on the porous material (B) to produce CO ２The maximum dissociation temperature is significantly reduced, and CO ２ It can be seen that the difference between the maximum dissociation temperature and the melting point also becomes large. This makes it easy to desorb carbon dioxide at temperatures lower than the melting point of the carbon dioxide absorbent, and also makes it possible to avoid a decrease in carbon dioxide absorbency due to melting of the carbon dioxide absorbent. Furthermore, since all of the carbon dioxide absorbents of the present example have low solubility in water or low water absorption, even if a steam stripping method is applied during the regeneration of the absorbent, the amine compound (A) is unlikely to elute in steam, and good repeated usability is expected.

[0098] Furthermore, a cycle test was carried out by the above-described method for the carbon dioxide absorbents of Examples 4 to 6 containing the amine compounds (A) of Examples 1 to 3. The results are shown in Table 3.

[0099]

[0100] From Table 3, it can be seen that the carbon dioxide absorbent of this example has high mass retention and carbon dioxide absorption capacity retention even after repeated cycles of carbon dioxide absorption and carbon dioxide desorption by heating.

[0101] Examples 7 and 8 (Preparation and Evaluation of Carbon Dioxide Absorbent) (Preparation of Carbon Dioxide Absorbent) In a nitrogen-purged glass container, 8 g of HQ-BA as the amine compound (A) and 500 g of methanol were charged, and the mixture was stirred with a stirrer at room temperature (23 ° C.) to dissolve the amine compound (A). Next, 12 g of pellet silica was added as the porous material (B), and nitrogen substitution was performed again, followed by stirring for 3 hours to homogenize. From the resulting mixture, methanol was distilled off under a reduced pressure of 40 ° C. and 50 hPa, and then vacuum dried at 80 ° C. for 3 hours to support the amine compound (A) on the porous material (B), and a carbon dioxide absorbent A having an amine compound (A) content of 40% by mass was obtained.

[0102] (Evaluation of Carbon Dioxide Absorbent) Using the obtained carbon dioxide absorbent A, a carbon dioxide absorption operation described below was carried out, followed by a regeneration operation of the carbon dioxide absorbent A described below. This cycle was repeated three times in total to evaluate the CO ２An absorption-desorption cycle test was carried out, and the results of the carbon dioxide absorption amounts obtained are shown in Table 4.

[0103] [Carbon dioxide absorption operation] In Example 7, first, air cylinder gas and CO ２ / N ２ Using gas cylinders, CO ２ Dry simulated air (0% RH) with a concentration of 400 ppm was prepared. This dry simulated air was passed through a column (diameter 30 mm, length 10 cm) packed with 10 g of carbon dioxide absorbent A at a rate of 5 L / min, and the carbon dioxide concentration (ppm) was measured at each of the inlet and outlet of the dry simulated air in the column using NDIR (non-dispersive infrared) CO ２ The carbon dioxide absorption amount of the carbon dioxide absorbent A was calculated from the integrated amount of the difference in carbon dioxide concentration measured at the inlet and outlet of the column during a predetermined time (300 minutes) during which the dry simulated air was passed through. In Example 8, first, air cylinder gas was passed through water to obtain a high humidity gas with a humidity of 100% RH and a CO ２ / N ２ Mixing cylinder gas with air cylinder gas to produce CO ２ High CO concentration adjusted to 800 ppm ２ These gases were mixed in a volume ratio of 1:1 to obtain CO ２ Humidity-conditioned simulated air (50% RH) with a concentration of 400 ppm was prepared. This humidity-conditioned simulated air was passed through a column (diameter 30 mm, length 10 cm) packed with 10 g of carbon dioxide absorbent A at a rate of 5 L / min, and the carbon dioxide concentration (ppm) was measured at each of the inlet and outlet of the humidity-conditioned simulated air in the column using NDIR (non-dispersive infrared) CO ２ The carbon dioxide absorption amount of the carbon dioxide absorbent A was calculated from the integrated value of the difference in carbon dioxide concentration measured at the inlet and outlet of the column within a predetermined time (300 minutes) during which the humidity-controlled simulated air was circulated.

[0104] [Regeneration operation of carbon dioxide absorbent] After the absorption operation, the pressure in the entire column was reduced to 47.4 kPa, and water vapor at 80°C was passed through the column for 10 minutes to desorb the carbon dioxide adsorbed in the carbon dioxide absorbent A. Thereafter, dry nitrogen gas was passed through the column at 5 L / min for 30 minutes while the temperature inside the column was maintained at 80°C, to dry the carbon dioxide absorbent A.

[0105]

[0106] From Table 4, it can be seen that the carbon dioxide absorbent of this example absorbs a larger amount of carbon dioxide when the humidity of the gas containing carbon dioxide is high than when the gas is dry.

[0107] According to the present invention, it is possible to provide a carbon dioxide absorbent having excellent carbon dioxide absorption properties and reusability, a carbon dioxide recovery method using the same, and a carbon dioxide separation and recovery apparatus.

[0108] REFERENCE SIGNS LIST 100 Carbon dioxide separation and capture apparatus 1 Absorption device 2 Desorption device 3 Connection section 11, 21 Reaction towers 12, 22 Absorbent holding section 12a Carbon dioxide absorbent 13 Gas supply section 21 Reaction tower 22a Carbon dioxide absorbent that has absorbed carbon dioxide 23 Gas discharge section 24 Absorbent discharge section

Claims

1. A carbon dioxide absorbent comprising a non-azo solid amine compound (A) having two or more aromatic rings and two or more primary amino groups, The carbon dioxide absorbent, wherein the non-azo solid amine compound (A) is an amine compound represented by the following general formula (1): 【Chemistry 1】 In formula (1), X and Y each independently represent a single bond or an oxygen atom, n and m each independently represent a number from 1 to 6, and p represents a number from 0 to 2.

2. The carbon dioxide absorbent according to claim 1, wherein the amine compound represented by the general formula (1) is any one of compounds represented by the following formulas (1-1) to (1-3): 【Chemistry 2】

3. 2. The carbon dioxide absorbent according to claim 1, wherein the carbon dioxide absorbent comprises the amine compound (A) and a porous material (B), and at least a part of the amine compound (A) is supported on the porous material (B).

4. The carbon dioxide absorbent according to claim 3, wherein the porous material (B) comprises at least one selected from the group consisting of porous silica and porous alumina.

5. A method for recovering carbon dioxide using the carbon dioxide absorbent described in any one of claims 1 to 4.

6. The method according to claim 5, comprising: an absorption step of contacting the carbon dioxide absorbent with a gas containing carbon dioxide to cause the carbon dioxide absorbent to absorb carbon dioxide; and a desorption step of desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide in the absorption step, wherein the desorption step comprises at least one step selected from the group consisting of the following (I) to (III): (I) A step of subjecting the carbon dioxide absorbent having absorbed carbon dioxide to reduced pressure conditions (II) A step of contacting the carbon dioxide absorbent having absorbed carbon dioxide with an inert gas not containing carbon dioxide. (III) A step of heating the carbon dioxide absorbent having absorbed carbon dioxide.

7. A carbon dioxide separation and recovery device comprising: an absorption device equipped with a mechanism for bringing the carbon dioxide absorbent according to any one of claims 1 to 4 into contact with a gas containing carbon dioxide, causing the carbon dioxide absorbent to absorb carbon dioxide; and a desorption device equipped with a mechanism for desorbing carbon dioxide from the carbon dioxide absorbent that has absorbed carbon dioxide.

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