Carbon dioxide solid capture material and its manufacturing method

Abstract

A solid recovery material for carbon dioxide according to the present disclosure contains from 1% by weight to 99% by weight of sodium ferrite and from 1% by weight to 99% by weight of a porous material. With respect to this solid recovery material for carbon dioxide, the average particle diameter is from 1 mm to 10 mm; the specific surface area is from 5 m2 / g to 1,500 m2 / g; and the ratio of the average major axis length to the average minor axis length of primary particles of the sodium ferrite is from 1 to 2.

Description

[Technical Field]

[0001] The present invention relates to a solid recovery material that fixes carbon dioxide and a method for producing the same, and more particularly to a solid recovery material containing sodium ferrite and a method for producing the same. [Background technology]

[0002] Research into the capture, storage, and utilization of carbon dioxide has been ongoing for some time now in order to reduce the amount of carbon dioxide released into the atmosphere. Large-scale sources of carbon dioxide include thermal power plants, boilers in manufacturing plants, and kilns in cement plants, which use coal, heavy oil, natural gas, etc. as fuel. Other sources include blast furnaces in steel plants that reduce iron oxide with coke, and transportation vehicles such as automobiles, ships, and airplanes that use gasoline, heavy oil, or light oil as fuel.

[0003] Currently, large-scale facilities such as thermal power plants use aqueous amine solutions to capture and fix carbon dioxide. This method uses a liquid capture material, which has the advantage that the material can be transported using a pump.

[0004] However, because the above-mentioned method uses a liquid containing hazardous materials, it is difficult to operate in small and medium-sized facilities such as waste incineration plants, and as a result, the current situation is that carbon dioxide fixation and capture is hardly ever carried out. For this reason, hopes are being placed on solid carbon dioxide capture materials made of solid, particularly non-hazardous inorganic materials. As a conventional solid carbon dioxide capture material, Patent Documents 1 and 2 disclose carbon dioxide capture materials containing sodium ferrite. In particular, α-sodium ferrite with a layered rock salt structure (trigonal system) reacts topochemically with carbon dioxide and sodium. That is, during the reaction with carbon dioxide, α-sodium ferrite reacts with Na 1-xIt forms a mixed phase of FeO2 and sodium carbonate. Therefore, it has been reported that the reaction rate is high and the repeated absorption and desorption of carbon dioxide due to this reaction is excellent. On the other hand, because sodium reacts with carbon dioxide in orthorhombic β-sodium ferrite, it has been reported that the β-sodium ferrite crystal phase absorbs more carbon dioxide than the α-sodium ferrite crystal phase.

[0005] Generally, the reaction formula for sodium ferrite with carbon dioxide is NaFeO2 + 1 / 2CO2 → 1 / 2Na2CO3 + 1 / 2Fe2O3 when the gas does not contain water vapor, and NaFeO2 + CO2 + 1 / 2H2O → NaHCO3 + 1 / 2Fe2O3 when water vapor is contained. Therefore, sodium ferrite has the theoretical ability to adsorb and desorb a maximum of 18 to 28% by weight of carbon dioxide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-3156 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-109198 Summary of the Invention [Problem to be solved by the invention]

[0007] As described above, the solid carbon dioxide capture materials described in Patent Documents 1 and 2 contain sodium ferrite, and are considered to be solid capture materials with relatively good carbon dioxide absorption performance in low-temperature regions. However, there is still a demand for carbon dioxide capture materials with higher carbon dioxide fixation and capture performance, and in addition to improving the properties of the sodium ferrite itself, it is necessary to further improve the properties of the sodium ferrite in the form in which it is installed in a carbon dioxide capture device. Specifically, sodium ferrite powder is difficult to handle in its powder form, and particularly when sodium ferrite is used by filling an adsorption tower, the fine powder tends to become dense and cause pressure loss. Therefore, it is used after being supported on a specified carrier or granulated into a specified shape. For this reason, the composition and physical properties of the carbon dioxide capture material in the state in which sodium ferrite is supported or granulated are also important.

[0008] The present invention has been made in consideration of the above-mentioned problems, and its object is to provide a solid carbon dioxide recovery material that can fix carbon dioxide in a low temperature range, such as from room temperature to 200°C, can recover carbon dioxide by heating at 50 to 200°C, and has excellent fixation and recovery performance, as well as a method for producing the same. [Means for solving the problem]

[0009] In order to achieve the above object, in the present invention, sodium ferrite is supported on a porous material under predetermined conditions or granulated by a porous material, thereby fixing carbon dioxide in a temperature range from room temperature to 200°C, and the fixed carbon dioxide can be recovered with high efficiency by heating at 50 to 200°C.

[0010] Specifically, the solid carbon dioxide capture material according to the present invention is a carbon dioxide capture material containing 1% by weight to 99% by weight of sodium ferrite and 1% by weight to 99% by weight of a porous material, and has an average particle size of 1 mm to 10 mm and a specific surface area of ​​5 m 2 / g~1500m 2 / g, and the sodium ferrite primary particles have an aspect ratio of an average major axis diameter to an average minor axis diameter of 1 to 2.

[0011] The solid carbon dioxide capture material according to the present invention can form a compact containing a high concentration of sodium ferrite by using a porous material. Therefore, the solid carbon dioxide capture material according to the present invention, which includes sodium ferrite and a porous material, has excellent properties: it fixes carbon dioxide in a gaseous state, traps it within the solid, and captures the carbon dioxide by heating. Furthermore, an average particle size of 1 to 10 mm ensures a flow path for exhaust gases and the like without reducing the pressure loss caused by the dense concentration of fine powder when packed into an adsorption tower or the like. As a result, carbon dioxide can be efficiently fixed. Furthermore, the primary particles have a small axial ratio of the average major axis diameter to the average minor axis diameter of 1 to 2, resulting in a nearly spherical shape. This results in high dispersibility, reduces the aggregation of the primary particles, and improves moldability and processability. These properties combine to enable the solid carbon dioxide capture material according to the present invention to fix carbon dioxide in a temperature range from room temperature to 200°C and capture carbon dioxide by heating at 50 to 200°C, demonstrating excellent fixation and capture performance.

[0012] The solid carbon dioxide recovery material according to the present invention contains 1% by weight to 70% by weight of the sodium ferrite and 30% by weight to 99% by weight of the porous material, and has a specific surface area of ​​100 m 2 / g~1500m 2 / g is preferred.

[0013] In this way, a large amount of sodium ferrite is supported on the surface of the porous material as a carrier, and a compact containing high-density sodium ferrite can be formed. Therefore, the solid carbon dioxide recovery material according to the present invention, which contains sodium ferrite and a porous material, can have excellent properties of fixing carbon dioxide in gas, trapping it in a solid, and recovering carbon dioxide by heating. Furthermore, when 1% to 70% by weight of sodium ferrite is supported on 30% to 99% by weight of a porous material, the specific surface area of ​​the material can be reduced to 100 m. 2 If the specific surface area is less than 1500 m / g, the carbon dioxide contained in the gas will not come into contact with the carbon dioxide, the carbon dioxide fixation and recovery performance will decrease, and 2If it exceeds 1 / g, industrial production becomes difficult.

[0014] In this case, the hardness is 5kgf / mm 2 ~35kgf / mm 2 and the bulk density is preferably 0.3 g / mL to 0.8 g / mL.

[0015] In this way, when packed in an adsorption tower or the like, the material is less likely to break due to gravity or friction caused by the flow of exhaust gases, etc., and gases such as exhaust gases can easily flow through it.

[0016] The solid carbon dioxide recovery material according to the present invention contains more than 70% by weight and not more than 99% by weight of the sodium ferrite, contains 1% by weight or more and less than 30% by weight of the porous material, and has a specific surface area of ​​5 m 2 / g~500m 2 / g is preferred.

[0017] In this way, the porous material promotes the aggregation of sodium ferrite particles, and a compact containing a high concentration of sodium ferrite can be formed. Therefore, the solid carbon dioxide recovery material according to the present invention, which contains sodium ferrite and a porous material, has the excellent property of adsorbing carbon dioxide in a gas, trapping it in the solid, and releasing the carbon dioxide by heating. Furthermore, when sodium ferrite of more than 70% by weight but not more than 99% by weight is granulated using a porous material of 1% by weight or more but less than 30% by weight, a compact having a specific surface area of ​​5 m 2 If the specific surface area is less than 500 m / g, it becomes difficult to come into contact with the carbon dioxide contained in the gas, the carbon dioxide fixation and recovery performance decreases, and 2 If it exceeds 1 / g, industrial production becomes difficult.

[0018] In this case, the hardness is 3kgf / mm 2 ~30kgf / mm 2 and the sphericity is preferably 1 to 2.

[0019] In this way, when packed in an adsorption tower or the like, the material is less likely to break due to gravity or friction caused by the flow of exhaust gases, etc., and gases such as exhaust gases can easily flow through it.

[0020] In the solid carbon dioxide recovery material according to the present invention, the powder pH value is preferably 8-14.

[0021] In this way, since the solid carbon dioxide capture material according to the present invention is basic, it becomes easier to capture carbon dioxide, which is weakly acidic.

[0022] In the solid carbon dioxide recovery material according to the present invention, the molar ratio of Na / Fe in the sodium ferrite is preferably 0.7 to 1.3.

[0023] Since the molar ratio of Na / Fe is 0.7 to 1.3, a large amount of sodium ferrite crystal phase can be contained, resulting in good carbon dioxide fixation and recovery performance.

[0024] In the solid carbon dioxide recovery material according to the present invention, the porous material is preferably a porous material selected from activated carbon, aluminosilicate, hydrotalcite, porous clay mineral, porous silica, and activated alumina.

[0025] The use of the porous material makes it possible to form a compact containing a high concentration of sodium ferrite, thereby improving the carbon dioxide fixation and recovery capacity.

[0026] The method for producing a solid carbon dioxide capture material according to the present invention is characterized by including a step of causing a solid-phase reaction between a material containing iron oxide and an alkaline compound containing sodium.

[0027] In the method for producing a solid carbon dioxide capture material according to the present invention, solids are mixed and reacted by transferring elements without the intervention of a solvent. This eliminates the need for a solvent as a reaction mother liquor, thereby reducing waste, such as that generated by a liquid-phase reaction. In particular, solid-phase reactions at low temperatures can result in extremely high-concentration reactions, reducing energy costs. Therefore, according to the method for producing a solid carbon dioxide capture material according to the present invention, carbon dioxide can be fixed at temperatures ranging from room temperature to 200°C, and the fixed carbon dioxide can be recovered with high efficiency by heating at 50 to 200°C, making it possible to produce a carbon dioxide capture material with excellent fixation and recovery performance. [Effects of the Invention]

[0028] The solid carbon dioxide capture material according to the present invention can fix carbon dioxide in the temperature range from room temperature to 200°C, and can be highly efficiently captured by heating at 50 to 200°C, providing excellent carbon dioxide fixation and capture performance. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 shows the results of thermogravimetric analysis after carbon dioxide was absorbed by the solid carbon dioxide recovery material obtained in Example 1. [Figure 2] FIG. 2 shows the results of thermogravimetric analysis after carbon dioxide was absorbed by the solid carbon dioxide recovery material obtained in Example 9. DETAILED DESCRIPTION OF THE INVENTION

[0030] DETAILED DESCRIPTION OF THE INVENTION The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its application, or its uses.

[0031] (First embodiment) First, a solid carbon dioxide capture material according to a first embodiment of the present invention will be described.

[0032] The solid carbon dioxide capture material according to this embodiment contains 1 to 70% by weight of sodium ferrite and 30 to 99% by weight of porous material. When the weight percentages are within this range, the sodium ferrite can be stably supported on the porous material while maintaining the carbon dioxide capture performance inherent to sodium ferrite.

[0033] The solid carbon dioxide capture material according to this embodiment has an average particle size of 1 mm to 10 mm and a specific surface area of ​​100 m 2 / g~1500m 2 / g. If the average particle size is less than 1 mm, when the solid carbon dioxide recovery material according to this embodiment is filled into an adsorption tower or the like, the gaps between the powder particles become small, resulting in a large pressure loss in the adsorption tower. As a result, clogging may occur in the adsorption tower. If the average particle size exceeds 10 mm, the contact rate between the sodium ferrite and carbon dioxide decreases, resulting in a decrease in the carbon dioxide fixation recovery performance. The average particle size of the solid carbon dioxide recovery material is preferably 2 mm to 8 mm. In addition, if the specific surface area is 100 m 2 If the specific surface area is less than 1500 m / g, it becomes difficult to come into contact with the carbon dioxide contained in the gas, and the carbon dioxide fixation and recovery performance decreases. 2 If the specific surface area of ​​the solid carbon dioxide capture material exceeds 300 m / g, industrial production becomes difficult. 2 / g~1000m 2 / g is preferred.

[0034] In the solid carbon dioxide recovery material according to this embodiment, the axial ratio of the average major axis diameter to the average minor axis diameter of the primary particles of sodium ferrite (average major axis diameter / average minor axis diameter) is 1 to 2. If the axial ratio exceeds 2, the primary particles tend to aggregate, making it difficult to maintain high dispersibility of the sodium ferrite. In addition, the axial ratio cannot be smaller than 1. The axial ratio of the primary particles of the solid carbon dioxide recovery material is preferably 1.1 to 1.9.

[0035] The shape of the solid recovery material is not particularly limited, but is preferably spherical, spindle-shaped, rectangular, cuboid-shaped, cubic, cylindrical, or the like.

[0036] The solid carbon dioxide capture material according to this embodiment has a hardness of 5 kgf / mm 2 ~35kgf / mm 2 and the bulk density is preferably 0.3 g / mL to 0.8 g / mL. When the hardness and bulk density are within the above ranges, when packed in an adsorption tower or the like, the material is less likely to break due to friction caused by gravity or the flow of exhaust gas, etc., and gases such as exhaust gas can easily pass through. More preferably, the hardness is 6 kgf / mm 2 ~33kgf / mm 2 and the bulk density is 0.35 g / mL to 0.70 g / mL.

[0037] The solid carbon dioxide collection material according to this embodiment preferably has a powder pH value of 8 to 14. When the powder pH value is 8 to 14, the solid carbon dioxide collection material according to this embodiment is basic, and therefore easily captures carbon dioxide, which is weakly acidic. The powder pH value is more preferably 9 to 14.

[0038] In the solid carbon dioxide capture material according to this embodiment, the molar ratio of Na / Fe of the sodium ferrite is preferably 0.7 to 1.3. When the molar ratio is in this range, a large amount of sodium ferrite crystalline phase can be contained, resulting in good carbon dioxide capture performance.

[0039] The porous material according to this embodiment is a porous material selected from activated carbon, porous clay minerals such as zeolite, porous silica, and activated alumina. In addition to zeolite, other porous clay minerals that can be used include smectite, sepiolite, imogolite, varigorskite, kaolin, montmorillonite, bentonite, attapulgite, acid clay, cordierite, and limonite. Because the porous material has excellent adsorption properties, it is possible to support a large amount of sodium ferrite, thereby improving the carbon dioxide fixation and recovery capacity. In particular, activated carbon has a small pore diameter and therefore has a strong adsorption capacity. Therefore, activated carbon is preferred because it can support a large amount of sodium ferrite and improve the carbon dioxide fixation and recovery capacity.

[0040] The porous material preferably has a porosity of more than 50% and not more than 70%. If the porosity is 50% or less, the specific surface area of ​​the solid carbon dioxide capture material, i.e., the contact area with carbon dioxide, becomes small, which may result in a decrease in the carbon dioxide absorption rate. If the porosity exceeds 70%, the volume ratio of sodium ferrite becomes small, which reduces the carbon dioxide fixation and capture performance.

[0041] The solid carbon dioxide recovery material according to this embodiment can selectively adsorb and fix carbon dioxide from a gas containing carbon dioxide. The adsorption temperature is between room temperature and the exhaust gas outlet temperature, approximately 10°C to 200°C. Since no additional external heating is required, the energy cost required for adsorption can be kept low (this is the carbon dioxide fixation process).

[0042] The solid carbon dioxide recovery material according to this embodiment preferably recovers carbon dioxide by desorbing the carbon dioxide captured in the carbon dioxide fixation step described above in a gas atmosphere not containing carbon dioxide at a temperature of 50 to 200°C. By keeping the desorption temperature at a low level of 200°C or less, the energy cost required for desorption can be kept low (this is the carbon dioxide recovery step).

[0043] Next, a method for producing a solid carbon dioxide capture material according to the first embodiment of the present invention will be described.

[0044] The solid carbon dioxide recovery material according to this embodiment can be obtained by reacting a material containing iron oxide with an alkaline compound containing sodium in the presence of a porous material (support).

[0045] When a material containing iron oxide reacts with an alkaline compound containing sodium in the presence of a porous material (support), a large amount of sodium ferrite tends to be supported on the support surface. This improves the carbon dioxide capture performance and makes the material preferable as a solid carbon dioxide capture material. In addition, a characteristic of solid-state reactions is that the crystal growth of sodium ferrite tends to be isotropic, which tends to suppress the axial ratio of the primary particles.

[0046] As a specific manufacturing method, iron oxide and a sodium source powder are mixed, and then a porous material is mixed therewith to impregnate the surface of the porous material with the mixture of iron oxide and sodium source powder, followed by firing, thereby obtaining a solid carbon dioxide recovery material according to this embodiment. Granulation may be performed as necessary. Furthermore, firing may be performed by steam heating, microwave heating, ultrasonic heating, or the like, in addition to conventional firing.

[0047] Other production examples include: i) adsorbing an aqueous sodium source solution onto a porous material, drying the material as is, and adding iron oxide to perform solid-phase synthesis; ii) adsorbing an aqueous iron oxide slurry onto a porous material, drying the material as is, and adding sodium source powder to perform solid-phase synthesis; iii) reacting iron oxide and sodium source powder in a solid phase, and then impregnating the resulting material onto a porous material; and iv) reacting iron oxide and a sodium source in a wet state, further impregnating the resulting material onto a porous material in a wet state, and then drying. Methods such as the above i) to iv) can also be used.

[0048] The support may be a porous material selected from, for example, activated carbon, porous clay minerals such as zeolite, porous silica, and activated alumina. In addition to zeolite, other porous clay minerals that can be used include smectite, sepiolite, imogolite, varigorskite, kaolin, montmorillonite, bentonite, attapulgite, acid clay, cordierite, and limonite. The content of the porous material is preferably 30% to 99% by weight. As described above, supporting a large amount of sodium ferrite improves the carbon dioxide fixation and recovery capacity.

[0049] The material containing iron oxide is not particularly limited, but examples thereof include ferrous chloride tetrahydrate, iron (III) chloride hexahydrate, and iron (II) sulfate heptahydrate.

[0050] The sodium-containing compound is not particularly limited, and examples thereof include sodium nitrite, sodium sulfate, sodium carbonate, sodium bicarbonate, and sodium hydroxide. However, when considering industrial use, sodium nitrite, sodium sulfate, and the like should be avoided because they may generate toxic nitrous acid gas, sulfurous acid gas, and the like during production.

[0051] Generally, solid-phase reactions are synthesis methods in which solids are mixed and elements are transferred and reacted without the use of a solvent. Because no solvent is used as the reaction mother liquid, waste such as solvents that would be generated in a liquid-phase reaction can be reduced. Furthermore, in the case of solid-phase reactions at low temperatures, which is a feature of the present invention, extremely high-concentration reactions can be achieved, thereby reducing energy costs. Furthermore, because there is no need for high reaction concentrations or washing, a high yield of the product can be expected.

[0052] Second Embodiment Next, a solid carbon dioxide capture material according to a second embodiment of the present invention will be described.

[0053] The solid carbon dioxide capture material according to this embodiment contains more than 70% by weight and not more than 99% by weight of sodium ferrite and 1% by weight or more but less than 30% by weight of a porous material. When the weight percentages are within this range, the solid carbon dioxide capture material according to this embodiment can form a compact containing a high concentration of sodium ferrite while maintaining the carbon dioxide fixation and capture performance that sodium ferrite inherently has.

[0054] The solid carbon dioxide capture material according to this embodiment has an average particle size of 1 mm to 10 mm and a specific surface area of ​​5 m 2 / g~500m 2 / g. If the average particle size is less than 1 mm, when the solid carbon dioxide recovery material according to this embodiment is filled into an adsorption tower or the like, the gaps between the powder particles become small, resulting in a large pressure loss in the adsorption tower. This may cause clogging in the adsorption tower. If the average particle size exceeds 10 mm, the contact rate between the sodium ferrite and carbon dioxide decreases, resulting in a decrease in the carbon dioxide fixation recovery performance. The average particle size of the solid carbon dioxide recovery material is preferably 2 mm to 8 mm. In addition, if the specific surface area is 5 m 2 If the specific surface area is less than 500 m / g, it becomes difficult to come into contact with the carbon dioxide contained in the gas, and the carbon dioxide fixation and recovery performance decreases. 2 If the specific surface area of ​​the solid carbon dioxide capture material exceeds 30 m / g, industrial production becomes difficult. 2 / g~300m 2 / g is preferred.

[0055] In the solid carbon dioxide recovery material according to this embodiment, the axial ratio of the average major axis diameter to the average minor axis diameter of the primary particles of sodium ferrite (average major axis diameter / average minor axis diameter) is 1 to 2. If the axial ratio exceeds 2, the primary particles tend to aggregate, making it difficult to maintain high dispersibility of the sodium ferrite. In addition, the axial ratio cannot be smaller than 1. The axial ratio of the primary particles of the solid carbon dioxide recovery material is preferably 1.1 to 1.9.

[0056] In the solid carbon dioxide capture material according to this embodiment, the average primary particle size of the sodium ferrite primary particles is preferably 0.05 μm to 1.0 μm. If it is less than 0.05 μm, industrial production becomes difficult. If it exceeds 1.0 μm, the carbon dioxide absorption performance decreases. More preferably, it is 0.1 μm to 0.7 μm.

[0057] The solid carbon dioxide capture material according to this embodiment has a hardness of 3 kgf / mm 2 ~30kgf / mm 2and the sphericity is preferably 1 to 2. When the hardness and sphericity are within the above ranges, when the carbon dioxide capture material according to this embodiment is packed into an adsorption tower or the like, it is less likely to break due to gravity or friction caused by the flow of exhaust gas, etc., and gases such as exhaust gas can easily flow through it.

[0058] The shape of the solid carbon dioxide recovery material is not particularly limited, but in addition to a spherical shape, a spindle shape, a rectangular parallelepiped shape, a cube shape, a cylindrical shape, and the like are preferred.

[0059] The solid carbon dioxide collection material according to this embodiment preferably has a powder pH value of 8 to 14. When the powder pH value is 8 to 14, the solid carbon dioxide collection material according to this embodiment becomes basic and easily captures carbon dioxide, which is weakly acidic.

[0060] In the solid carbon dioxide capture material according to this embodiment, the molar ratio of Na / Fe of the sodium ferrite is preferably 0.7 to 1.3. When the molar ratio is within this range, a large amount of sodium ferrite crystalline phase can be contained, resulting in good carbon dioxide capture performance.

[0061] The porous material according to this embodiment is preferably a porous material selected from activated carbon, aluminosilicate, hydrotalcite, porous clay minerals, porous silica, and activated alumina. Porous clay minerals that can be used include zeolite, smectite, sepiolite, imogolite, varigorskite, kaolin, montmorillonite, bentonite, attapulgite, acid clay, cordierite, and limonite. Because the porous material has excellent adsorption properties, it is possible to form a molded body containing a high concentration of sodium ferrite, thereby improving the carbon dioxide capture and fixation capacity.

[0062] The porous material preferably has a porosity of more than 50% and not more than 70%. If the porosity is 50% or less, the specific surface area of ​​the solid carbon dioxide capture material, i.e., the contact area with carbon dioxide, becomes small, which may result in a decrease in the carbon dioxide absorption rate. If the porosity exceeds 70%, the volume ratio of sodium ferrite becomes small, which reduces the carbon dioxide fixation and capture performance.

[0063] The solid carbon dioxide recovery material according to this embodiment can selectively adsorb and fix carbon dioxide from a gas containing carbon dioxide. The adsorption temperature is between room temperature and the exhaust gas outlet temperature, approximately 10°C to 200°C. Since no additional external heating is required, the energy cost required for adsorption can be kept low (this is the carbon dioxide fixation process).

[0064] The solid carbon dioxide recovery material according to this embodiment preferably recovers carbon dioxide by desorbing the carbon dioxide captured in the carbon dioxide fixation step described above in a gas atmosphere not containing carbon dioxide at a temperature of 50 to 200°C. By keeping the desorption temperature at a low level of 200°C or less, the energy cost required for desorption can be kept low (this is the carbon dioxide recovery step).

[0065] Next, a method for producing a solid carbon dioxide recovery material according to a second embodiment of the present invention will be described.

[0066] The solid carbon dioxide recovery material according to this embodiment can be obtained by reacting a material containing iron oxide with an alkaline compound containing sodium in the presence of a porous material (support).

[0067] When a material containing iron oxide was reacted with an alkaline compound containing sodium in the presence of a porous material (support), a spherical compact containing a high concentration of sodium ferrite tended to form. This resulted in improved carbon dioxide capture performance and made it suitable as a solid carbon dioxide capture material. Furthermore, a characteristic of solid-state reactions is that the crystal growth of sodium ferrite tends to be isotropic, which tends to suppress the axial ratio of the primary particles.

[0068] In a specific production method, first, iron oxide and a sodium source powder are mixed and pulverized, and then calcined to obtain sodium ferrite particles. The obtained sodium ferrite particles are then mixed with a porous material and granulated using a granulator such as a tumbling granulator. Then, the mixture is calcined to obtain a solid carbon dioxide recovery material. Calcination may be performed by ordinary calcination, or by steam heating, microwave heating, ultrasonic heating, or the like.

[0069] The support may be a porous material selected from porous clay minerals such as activated carbon, aluminosilicate, hydrotalcite, and zeolite, porous silica, and activated alumina. In addition to zeolite, other porous clay minerals that can be used include smectite, sepiolite, imogolite, varigorskite, kaolin, montmorillonite, bentonite, attapulgite, acid clay, cordierite, and limonite. The content of the porous material is preferably 1% by weight or more and less than 30% by weight. As described above, forming a molded body containing a high concentration of sodium ferrite improves the carbon dioxide fixation and recovery capacity.

[0070] The material containing iron oxide is not particularly limited, but examples thereof include hematite, magnetite, maghemite, and goethite.

[0071] The sodium-containing compound is not particularly limited, and examples thereof include sodium nitrite, sodium hydroxide, sodium oxide, sodium carbonate, etc. However, when considering industrial use, sodium nitrite, sodium sulfate, etc., which may generate toxic nitrous acid gas, sulfurous acid gas, etc. during production, should be avoided.

[0072] In general, solid-phase reactions are synthesis methods in which solids are mixed and elements are transferred and reacted without the use of a solvent. Because no solvent is used as the reaction mother liquid, waste such as solvents that would be generated in a liquid-phase reaction can be reduced. Furthermore, in the case of solid-phase reactions at low temperatures, which is a feature of the present invention, extremely high-concentration reactions can be achieved, thereby reducing energy costs. Furthermore, because there is no need for the high-concentration reactions or washing, a high yield of the product can be expected. [Example]

[0073] A typical embodiment of the present invention is as follows.

[0074] The composition of the solid carbon dioxide recovery material according to the present invention was determined by crushing the solid carbon dioxide recovery material in a mortar and pelletizing it, and then identifying it with a BRUKER D8 ADVANCE fully automatic multipurpose X-ray diffractometer. The result was that the material was identified to be α-sodium ferrite and a porous material.

[0075] The content of sodium ferrite and porous material contained in the solid carbon dioxide recovery material according to the present invention was determined by crushing the solid carbon dioxide recovery material in a mortar and pelletizing it, and then performing elemental analysis (excluding oxygen) using a Rigaku ZSX Primus II scanning X-ray fluorescence analyzer.

[0076] The average particle size of the solid carbon dioxide recovery material according to the present invention was determined by measuring the major and minor axes of 80 particles using a vernier caliper, and averaging the results to determine the average particle size.

[0077] The BET specific surface area of ​​the solid carbon dioxide recovery material according to the present invention was measured by the BET method using nitrogen and a Multisorb-16 manufactured by QUANTA CHROME.

[0078] The hardness of the solid carbon dioxide recovery material according to the present invention was measured using a digital force gauge ZP-500N manufactured by Imada, and the average crushing hardness of 80 grains was taken as the hardness.

[0079] The bulk density of the solid carbon dioxide recovery material according to the present invention was measured in accordance with JIS Z2504.

[0080] The bulk density of the solid carbon dioxide recovery material according to the present invention was evaluated according to the following four-level scale. ◎: Bulk density is less than 0.3 to 0.5 g / mL ○: Bulk density is 0.5 to 0.8 g / mL △: Bulk density is more than 0.8 to less than 2 g / mL ×: Bulk density is less than 0.3 g / mL and 2 g / mL or more

[0081] The sphericity of the solid carbon dioxide recovery material according to the present invention was evaluated by calculating the ratio of the major axis to the minor axis and using the following two-level scale. ○: Sphericity is 1 or more but less than 2 ×: Sphericity is 2 or more

[0082] The pH value of the solid carbon dioxide recovery material according to the present invention was determined by weighing 5 g of sample into a 300 ml Erlenmeyer flask, adding 100 ml of boiled pure water, heating and maintaining the boiling state for approximately 5 minutes, then plugging the flask and allowing it to cool to room temperature, adding water equivalent to the weight lost, plugging it again, shaking for 1 minute, and leaving it to stand for 5 minutes. The pH of the resulting supernatant was measured in accordance with JIS Z8802-7, and the value obtained was taken as the pH value.

[0083] The molar ratio of Na / Fe of the sodium ferrite contained in the solid carbon dioxide recovery material according to the present invention was determined by crushing the solid carbon dioxide recovery material in a mortar, pelletizing it, and then performing elemental analysis (excluding oxygen) using a Rigaku ZSX Primus II scanning X-ray fluorescence analyzer.

[0084] The axial ratio of the sodium ferrite contained in the carbon dioxide capture material according to the present invention was determined by measuring the average major axis diameter and the average minor axis diameter of 350 primary particles shown in a micrograph taken with a Hitachi High-Technologies S-4800 scanning electron microscope, and expressing the ratio of the average major axis diameter to the average minor axis diameter (average major axis diameter / average minor axis diameter).

[0085] The average primary particle size of the sodium ferrite particles contained in the carbon dioxide capture material according to the present invention is expressed as the average value of the average major axis diameter and the average minor axis diameter.

[0086] In order to investigate the carbon dioxide fixation and recovery capacity of the carbon dioxide capture material according to the present invention, 1.00 parts by weight of the sample was placed on a combustion boat and inserted into an acrylic pipe equipped with inlet and outlet piping. A (carbon dioxide + nitrogen) mixed gas adjusted to a humidity range of 20 to 100% and a carbon dioxide concentration range of 1 to 100 vol% was introduced into the inlet at a rate of 500 mL / min, and the amount of carbon dioxide adsorbed after 2 hours was measured using a Hitachi High-Technologies STA7000 simultaneous differential thermal and thermogravimetric analyzer, by heating the sample from room temperature to 200°C, and the amount of carbon dioxide fixed and recovered was calculated from the loss in weight due to heat.

[0087] <Method of manufacturing solid carbon dioxide capture material> [Experimental Example 1] Example 1 9.0 parts by weight of ferrous chloride tetrahydrate was dissolved in 900 parts by weight of pure water, and 10.0 parts by weight of granulated activated carbon (Kuraray Coal 4GG, 4x6 mesh, manufactured by Kuraray) was added as a porous support and immersed for 1 hour. 27 parts by weight of urea dissolved in 100 parts by weight of pure water was added, heated to 90°C, stirred for 3 hours, and then allowed to cool and stirred for 10 hours. The mixture was then passed through a 1 mm mesh sieve, and the solid matter remaining on the sieve was dried at 80°C for 12 hours to obtain iron oxide-supported activated carbon. The obtained iron oxide-supported activated carbon and 1.80 parts by weight of sodium hydroxide were mixed as a solid, placed in a crucible, and subjected to a solid-state reaction at 400°C for 16 hours in a nitrogen stream. The mixture was then cooled to room temperature to obtain a solid carbon dioxide recovery material. The obtained solid carbon dioxide recovery material was pulverized and qualitatively analyzed by X-ray diffraction, which revealed it to be sodium ferrite and amorphous carbon. X-ray fluorescence analysis revealed that the sodium ferrite content was 33%. The porous material was 67%. The BET specific surface area of ​​this solid carbon dioxide capture material was 678 m 2 The powder had a pH of 13. The minor axis was 4 mm, the major axis was 8 mm, and the average particle size was 6 mm.

[0088] The hardness of the obtained solid carbon dioxide capture material is 20 kgf / mm 2 and the bulk density was 0.48 g / mL. From these results, it is clear that when the carbon dioxide capture material according to Example 1 is packed into a carbon dioxide adsorption tower or the like, it is not easily broken by gravity or friction caused by the flow of exhaust gas, etc., and gases such as exhaust gas can easily pass through it. The hardness of the obtained carbon dioxide capture material was evaluated according to the following three levels. ○: Crushing hardness is 10kgf / mm 2 More than this △: Crushing hardness is 5 to 10 kgf / mm 2 Less than ×: Crushing hardness is 5kgf / mm 2 Less than

[0089] The molar ratio of Na / Fe in the sodium ferrite contained in the obtained solid carbon dioxide recovery material was 1.0, which was almost the same as the ratio of the raw materials used.

[0090] To examine the carbon dioxide capture performance of the obtained solid carbon dioxide capture material, 1.00 parts by weight of the sample was placed on the No. 2 combustion boat (12 x 60 x 9 mm) and aerated with a model combustion flue gas at 500 mL / min for 2 hours. Generally, the flue gas produced when fuel is burned in the atmosphere is composed of a maximum of 80 vol% nitrogen, 20 vol% carbon dioxide, and a relative humidity of 80-100% RH. Therefore, at room temperature (25°C), a mixture of 400 mL / min of nitrogen and 100 mL / min of carbon dioxide was bubbled into water to produce a model flue gas with 20 vol% carbon dioxide and a relative humidity of 80% RH.

[0091] After aeration, 10 mg of the sample was weighed and measured using a thermogravimetric analyzer (TG) by heating the sample to 200 °C at a rate of 10 °C / min while aerating with dry air at 300 mL / min. The desorption temperature and amount of carbon dioxide adsorbed by the sample were measured. Figure 1 shows a measurement chart with sample temperature on the horizontal axis. The TG curve represents the weight percent of the remaining sample at each temperature, with the initial weight taken as 100 wt%, and the loss of sample was considered to be due to the release of carbon dioxide. The DTG curve is a differential curve of the TG curve, and the temperature at which the DTG curve reaches its maximum was considered to be the carbon dioxide desorption temperature. The DTA curve showed a downward convex curve, indicating that an endothermic reaction was occurring near 114 °C. Quantifying this as the thermal decomposition of NaHCO3 revealed that the carbon dioxide desorption temperature was 114 °C and the amount of carbon dioxide desorbed was 10 wt% of the sample solids, demonstrating excellent carbon dioxide capture and recovery performance.

[0092] Furthermore, the sample after aeration was reprepared and weighed, which was found to be 1.15 parts by weight, confirming a mass increase of 15% by weight. X-ray diffraction analysis of the surface of this sample revealed that 85% by weight of Na 1-x FeO2 and 15 wt% NaHCO3 were confirmed, indicating that carbon dioxide was fixed in the sodium ferrite component. Furthermore, this sample was heated in an electric furnace at 120°C for 1 hour and weighed to be 1.05 parts by weight, indicating that 0.10 parts by weight (10 wt% relative to the solid carbon dioxide capture material) of carbon dioxide could be adsorbed and desorbed in this cycle. X-ray diffraction analysis of the surface of this sample confirmed 90 wt% NaFeO2 and 10 wt% Na2CO3. Furthermore, when this sample was contacted with carbon dioxide as described above, the weight increased to 1.15 parts by weight, and when heated, the weight decreased to 1.05 parts by weight, indicating that 0.10 parts by weight (10 wt% relative to the solid carbon dioxide capture material) of carbon dioxide could be adsorbed and desorbed. This operation was repeated 10 times, and it was confirmed that there was no change in the mass increase or decrease. This demonstrates that the solid carbon dioxide capture material of Example 1 has excellent carbon dioxide fixation and capture performance, particularly excellent repeatability.

[0093] Examples 2 to 8 Solid recovered materials according to Examples 2 to 8 were obtained in the same manner as in Example 1, except that the types and amounts of the iron raw material and the support were variously changed.

[0094] The production conditions in these examples are shown in Table 1, the properties of the obtained solid carbon dioxide recovery materials are shown in Table 2, and the effects are shown in Table 3.

[0095] Comparative Example 1 9.0 parts by weight of ferrous chloride tetrahydrate was dissolved in 900 parts by weight of pure water and stirred for 1 hour. 27 parts by weight of urea dissolved in 100 parts by weight of pure water was added to this, and the mixture was heated to 90°C and stirred for 3 hours. After cooling, the mixture was stirred for 10 hours, filtered, washed with water, and dried at 80°C for 12 hours to obtain iron oxide microparticles. The obtained iron oxide microparticles and 1.80 parts by weight of sodium hydroxide were mixed as a solid, placed in a crucible, and subjected to a solid-state reaction at 400°C for 16 hours in a nitrogen gas flow. The obtained powder was pulverized and confirmed to be sodium ferrite by X-ray diffraction. Furthermore, fluorescent X-ray analysis revealed that the sodium ferrite content was 90% by weight. The remaining 10% by weight was maghemite. The obtained powder was suspended in 100 parts by weight of pure water, and 10 parts by weight of activated carbon was added as a porous support. After stirring for 16 hours, the mixture was rotated in an evaporator to remove water, resulting in a solid carbon dioxide recovery material. The obtained solid recovery material was crushed and qualitatively analyzed by X-ray diffraction, which revealed that it consisted of maghemite, sodium ferrite, and amorphous carbon. Fluorescent X-ray analysis revealed that the content of maghemite and sodium ferrite was 33%. The porous material accounted for 67%. The BET specific surface area of ​​this solid carbon dioxide recovery material was 700 m 2 / g. The minor axis was 4 mm, the major axis was 8 mm, and the average particle size was 6 mm. Furthermore, when the carbon dioxide fixation and recovery performance was investigated in the same manner as in the examples, the temperature was raised to 200°C, but desorption of carbon dioxide was not confirmed.

[0096] The manufacturing conditions for this comparative example are shown in Table 1, the properties of the obtained solid carbon dioxide recovery material are shown in Table 2, and the effects are shown in Table 3.

[0097] [Table 1]

[0098] [Table 2]

[0099] [Table 3]

[0100] [Experimental Example 2] Example 9 Iron oxide fine particles 1 (Toda Kogyo 100ED, hematite, specific surface area 11 m 2 The sodium nitrite particles as the sodium raw material were weighed out so that the molar ratio of Na / Fe was 1.0, and the mixture was ground in a sample mill. The ground mixture was placed in a crucible and fired at 400°C for 16 hours. The mixture was then cooled to room temperature and ground in a sample mill to obtain sodium ferrite particles. The BET specific surface area of ​​the obtained sodium ferrite particles was 4.0 m 2 The average particle size was 0.7 μm, the average minor axis diameter was 0.4 μm, the average primary particle diameter was 0.57 μm, and the axial ratio was 1.6. The powder pH was relatively high at 13.8. 100 parts by weight of the resulting sodium ferrite particle powder was mixed with 5 parts by weight of powdered activated carbon as a porous material and granulated at 40 rpm in a tumbling granulator to obtain spherical granules with a particle size of 5 mm. These were placed in a crucible and sintered at 400°C for 16 hours in a nitrogen gas stream. They were then cooled to room temperature to produce a solid carbon dioxide recovery material. The resulting solid carbon dioxide recovery material was pulverized and characterized by X-ray diffraction, revealing it to be composed of sodium ferrite and amorphous carbon. Furthermore, fluorescent X-ray analysis revealed that the sodium ferrite content was 95%. The porous material content was 5%. The BET specific surface area of ​​this solid carbon dioxide recovery material was 54 m. 2 The powder had a particle size of 5 mm, a minor axis of 5 mm, an average particle size of 5 mm, and a pH of 13.

[0101] The hardness of the obtained solid carbon dioxide capture material is 10 kgf / mm 2 and the sphericity was 1.0. From these results, it is clear that when the carbon dioxide capture material according to Example 9 is packed into a carbon dioxide adsorption tower or the like, it is less likely to break due to gravity or friction caused by the flow of exhaust gas, etc., and gases such as exhaust gas can easily pass through it. The hardness of the obtained carbon dioxide capture material was evaluated according to the following three levels. ○: Crushing hardness is 10kgf / mm 2 More than this △: Crushing hardness is 3kgf / mm 2 More than 10kgf / mm 2 Less than ×: Crushing hardness is 3kgf / mm 2 Less than

[0102] The molar ratio of Na / Fe in the sodium ferrite contained in the obtained solid carbon dioxide recovery material was 1.0, which was almost the same as the feed ratio of the raw materials.

[0103] To examine the carbon dioxide capture performance of the obtained solid carbon dioxide capture material, 1.00 parts by weight of the sample was placed on the No. 2 combustion boat (12 x 60 x 9 mm) and aerated with a model combustion flue gas at 500 mL / min for 2 hours. Generally, the flue gas produced when fuel is burned in the atmosphere is composed of a maximum of 80 vol% nitrogen, 20 vol% carbon dioxide, and a relative humidity of 80-100% RH. Therefore, at room temperature (25°C), a mixture of 400 mL / min of nitrogen and 100 mL / min of carbon dioxide was bubbled into water to produce a model flue gas with 20 vol% carbon dioxide and a relative humidity of 80% RH.

[0104] After aeration, 10 mg of the sample was weighed and measured using a thermogravimetric analyzer (TG) by heating the sample to 200 °C at a rate of 10 °C / min while aerating with dry air at 300 mL / min. The desorption temperature and amount of carbon dioxide adsorbed by the sample were measured. Figure 2 shows a measurement chart with sample temperature on the horizontal axis. The TG curve represents the weight percent of the remaining sample at each temperature, with the initial weight taken as 100 wt%, and the loss of sample was considered to be due to the release of carbon dioxide. The DTG curve is a differential curve of the TG curve, and the temperature at which the DTG curve reaches its maximum was considered to be the carbon dioxide desorption temperature. The DTA curve showed a downward convex curve, indicating that an endothermic reaction was occurring near 114 °C. Quantifying this as the thermal decomposition of NaHCO3 revealed that the carbon dioxide desorption temperature was 114 °C and the amount of carbon dioxide desorbed was 17 wt% of the sample solids, demonstrating excellent carbon dioxide capture and recovery performance.

[0105] Furthermore, the sample after aeration was reprepared and weighed, which was found to be 1.27 parts by weight, a mass increase of 27% by weight. X-ray diffraction analysis of the surface of this sample revealed that 79% by weight of Na 1-x FeO2 and 21% by weight of NaHCO3 were confirmed, and it was found that carbon dioxide was fixed in the sodium ferrite component. Furthermore, when this sample was heated in an electric furnace at 120°C for 1 hour and its weight was measured, it was found to be 1.10 parts by weight, and it was found that 0.17 parts by weight (17% by weight of the solid carbon dioxide recovery material) of carbon dioxide could be adsorbed and desorbed in this cycle. When X-ray diffraction was measured on the surface of this sample, it was found that 90% by weight of Na 1-x FeO2 and 10 wt% Na2CO3 were confirmed. Furthermore, when this sample was contacted with carbon dioxide in the same manner as above, the amount increased to 1.27 parts by weight, and when heated, the amount decreased to 1.10 parts by weight, allowing the adsorption and desorption of 0.17 parts by weight (17 wt% relative to the solid carbon dioxide capture material). This operation was repeated 10 times, and it was confirmed that there was no change in the increase or decrease in mass. This revealed that the solid carbon dioxide capture material of Example 9 has excellent carbon dioxide fixation and capture performance, particularly excellent repeatability.

[0106] Examples 10 to 16 Solid recovered materials according to Examples 10 to 16 were obtained in the same manner as in Example 9, except that the types and amounts of the iron raw material and the support were variously changed.

[0107] The production conditions in these examples are shown in Table 4, the properties of the obtained solid carbon dioxide recovery materials are shown in Table 5, and the effects are shown in Table 6.

[0108] Comparative Example 2 100 parts by weight of the sodium ferrite particles obtained in Example 9 were granulated at 40 rpm in a tumbling granulator while adding a small amount of 1% aqueous carboxymethyl cellulose solution, and the granules were placed in a crucible and subjected to a solid-phase reaction at 400°C for 16 hours in a nitrogen gas flow. The granules were then cooled to room temperature to obtain a solid carbon dioxide recovery material. The obtained solid carbon dioxide recovery material was pulverized and qualitatively analyzed by X-ray diffraction, revealing that it was sodium ferrite. Furthermore, fluorescent X-ray analysis revealed that the sodium ferrite content was 100%. The BET specific surface area of ​​this solid carbon dioxide recovery material was 4m 2 / g. The minor axis was 4 mm, the major axis was 9 mm, and the average particle size was 6.5 mm. The powder pH was 10.

[0109] The hardness of the obtained solid carbon dioxide capture material is 1 kgf / mm 2 The result was an unsatisfactory rating. The sphericity was 2.3, which was also rated as unsatisfactory. From these results, it is clear that when the carbon dioxide capture material is packed into a carbon dioxide absorption tower or the like, it is prone to breakage due to gravity and friction caused by the flow of exhaust gas, and its shape is irregular, making it difficult to pack.

[0110] The manufacturing conditions for this comparative example are shown in Table 4, the properties of the obtained solid carbon dioxide recovery material are shown in Table 5, and the effects are shown in Table 6.

[0111] [Table 4]

[0112] [Table 5]

[0113] [Table 6]

[0114] As described above, it is clear that the solid carbon dioxide capture material according to the present invention is excellent in adsorbing and capturing carbon dioxide. Furthermore, since the solid capture material has high hardness, high sphericity, and low bulk density, it can be packed directly into a carbon dioxide adsorption tower.

Claims

1. A carbon dioxide solid recovery material containing 1% by weight to 99% by weight of sodium ferrite and 1% by weight to 99% by weight of a porous material, the material having an average particle size of 1 mm to 10 mm and a specific surface area of ​​5 m ２ / g~1500m ２ / g, the axial ratio of the average major axis diameter to the average minor axis diameter of the primary particles of the sodium ferrite is 1 to 2; the porous material is activated carbon, zeolite, aluminosilicate, hydrotalcite, porous clay mineral, porous silica, or activated alumina; The sodium ferrite is supported on the porous material or granulated together with the porous material.

2. The sodium ferrite is contained in an amount of 1% by weight to 70% by weight, the porous material is contained in an amount of 30% by weight to 99% by weight, and the specific surface area is 100 m ２ / g~1500m ２ The carbon dioxide solid capture material according to claim 1, wherein the carbon dioxide solid capture material has a molecular weight of 1000 or more.

3. Hardness is 5 kgf / mm ２ ~35 kgf / mm ２ and the bulk density is 0.3 g / mL to 0.8 g / mL.

4. The sodium ferrite is contained in an amount of more than 70% by weight and not more than 99% by weight, the porous material is contained in an amount of 1% by weight or more and less than 30% by weight, and the specific surface area is 5 m ２ / g~500m ２ The carbon dioxide solid capture material according to claim 1, wherein the carbon dioxide solid capture material has a molecular weight of 1000 or more.

5. Hardness is 3 kgf / mm ２ ~30 kgf / mm ２ The carbon dioxide solid capture material according to claim 4, wherein the sphericity is 1 to 2.

6. The carbon dioxide solid recovery material according to any one of claims 1 to 5, wherein the powder pH value is 8 to 14.

7. The solid carbon dioxide capture material according to any one of claims 1 to 6, wherein the molar ratio of Na / Fe of the sodium ferrite is 0.7 to 1.

3.

8. The method for producing a solid carbon dioxide capture material according to any one of claims 1 to 7, comprising a step of solid-phase reaction of a material containing iron oxide with an alkaline compound containing sodium.

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