JP2017039633A - Zirconium hydroxide mesoporous body having carbon dioxide adsorptivity, manufacturing method therefor and carbon dioxide adsorbent consisting of zirconium hydroxide mesoporous body - Google Patents

Abstract

Disclosed is a zirconium hydroxide mesoporous material useful as an adsorbent having a high CO ₂ adsorption amount substantially equal to or higher than that of conventional zeolite. Providing CO ₂ adsorbent consisting of zirconium hydroxide mesoporous material having a predetermined CO ₂ adsorption amount.
By adding a zirconium raw material such as zirconyl nitrate to an aqueous solution of sodium hydroxide having a pH of 13.0 or more and reacting at room temperature, the solid precipitate generated in the liquid phase is separated from the liquid phase. A zirconium hydroxide mesoporous material having a high specific surface area and a high CO ₂ adsorption amount can be synthesized.
[Selection] Figure 10

Description

The present invention, zirconium hydroxide mesoporous material having a specific CO ₂ adsorptive, CO ₂ adsorbent consisting of water zirconium oxide mesoporous material, a method of manufacturing a water-zirconium oxide mesoporous material, and, the CO ₂ adsorption The present invention relates to a CO ₂ adsorption / desorption method using an agent.

Carbon dioxide (hereinafter sometimes referred to as “CO ₂ ”) emitted in large quantities from thermal power plants, integrated gasification combined cycle (IGCC), steelworks, chemical plants, etc. It is a big factor. CO ₂ capture and storage (CCS: Carbon dioxide Capture and Storage ) , since emission reduction effect on the atmospheric CO ₂ is large, it is expected as an option to global warming.
As a conventional CO ₂ separation / recovery technique, there is a chemical absorption method using an amine solution. The amine solution has a property of causing a chemical reaction with CO ₂ and binding strongly, and CO ₂ can be selectively absorbed by bringing CO _{2 in} the exhaust gas into contact with the amine solution in the absorption tower. The amine solution that has absorbed CO ₂ is separated into CO ₂ and an amine solution by high-temperature heating in the regeneration tower, and then only CO ₂ is recovered from the top of the regeneration tower and concentrated (Patent Documents 1 and 2).

However, the chemical absorption method (prior art) using an amine solution has the following problems.
(1) Since a large amount of heat energy is required when heat-separating strongly chemically bound CO ₂ and an amine solution, it is inevitable to increase the cost of the CO ₂ separation / recovery process.
(2) The amine solution has a short life because it causes thermal deterioration, oxygen deterioration, and the like in the CO ₂ separation / recovery process, and the CO ₂ recovery amount is remarkably reduced due to the performance deterioration of the amine solution. Further, with the generation of the deteriorated amine solution, it is necessary to treat and supplement the deteriorated amine solution, which leads to complicated processes and high costs.
(3) The amine solution is rich in reactivity, but on the other hand, it is highly toxic and corrosive, causing equipment corrosion and high environmental load. In addition, the amine solution is also flammable, causing explosions and fire in the facility.

To avoid the above problems, in recent years, the chemical absorption method has been required for the development of alternative to CO ₂ separation and recovery techniques are being considered for the development of CO ₂ separation and recovery technique utilizing solid adsorbent .
The solid adsorbent is a porous material having a nanoscale pore structure and has a high pore surface area. By imparting CO ₂ adsorption capacity in this pore surfaces, it can be adsorbed CO ₂ in porous material. The advantage of the solid adsorbent compared to the amine solution is that no heating operation is required when desorbing CO ₂ adsorbed on the pore surface of the solid adsorbent, and under the CO ₂ introduction pressure (10 to 3000 kPa). CO ₂ can be adsorbed and desorbed only by pressurizing and depressurizing operations (pressure swing adsorption / desorption method). The solid adsorbent is a low environmental load material that is less toxic, corrosive, and flammable than an amine solution, and is excellent in safety and handling. By using a solid adsorbent instead of an amine solution, cost reduction and energy saving of the CO ₂ separation / recovery process are expected.

The performance required for the solid adsorbent is described below.
(1) The material has a CO ₂ adsorption capacity and a high CO ₂ recovery amount that is almost equal to or higher than that of the existing zeolite 13X.
(2) Recyclable material that does not require heat energy for CO ₂ separation and recovery. At this time, room temperature (25 ° C.), CO ₂ introduction pressure (10～3000KPa) pressurization and depressurization under (pressure swing adsorption-desorption method) it is possible adsorption and desorption of CO ₂ by only.
(3) The material can be synthesized at low cost. Also, the synthesis method should be simple.
(4) The material must have low environmental impact, such as low toxicity, corrosivity, and flammability.
(5) To have high durability without causing material deterioration.

As a solid adsorbent that satisfies some of the above-mentioned performances, zeolite can be cited (see Non-Patent Documents 1 and 2).
Zeolite is a porous material with regular micro-scale pores, excellent durability, and at the same time low toxicity, corrosiveness and flammability, low environmental load and high safety. because having a CO ₂ adsorption capacity to the surface, without the need for heating operation, it is possible to adsorption and desorption of CO ₂ only pressure-vacuum operation.
However, when CO _{2 is} separated and recovered using zeolite, there are the following problems.
(1) The amount of CO ₂ recovered from zeolite is particularly insufficient in the high pressure region of 1000 kPa or more such as IGCC. For example, the zeolite recovers about 3.6 mmol / mL of CO ₂ in an environment of 25 ° C. and 1600 kPa. There is a need for the development of solid adsorbents with higher CO ₂ recovery than indicated.
(2) Since zeolite is a material with a low true density and a light weight, when this is filled in an adsorption tower and the exhaust gas is circulated, fluidization of the solid adsorbent occurs in the adsorption tower. The amount of CO ₂ adsorption decreases. In addition, granulation is required to prevent fluidization of the solid adsorbent, which significantly reduces the CO ₂ adsorption amount of the final solid adsorbent.
(3) In the case of zeolite, the effective adsorption amount when adsorbed and desorbed at a pressure of 10 to 3000 kPa is low (about 1.5 mmol / mL).
(4) The actual exhaust gas contains a trace amount of water, and in the case of zeolite, the CO ₂ adsorption performance is significantly reduced due to water inhibition. For this reason, when using zeolite, it is necessary to introduce a dehumidification process in advance to remove moisture adsorbed on the zeolite at a high temperature of 400 ° C. or higher. For this reason, the introduction of the dehumidification process increases the energy consumption for separation and recovery.

JP 7-313840 A JP 2011-194388 A Special table 2009-525250 gazette JP 2004-323257 A

R. Gupta et al. “Post-Combustion CO2 Capture Using Solid Sorbents: A Review” Ind. Eng. Chem. Res. 2012, 51, 1438-1463. J.R. Long et al. “Carbon Dioxide Capture: Prospects for New Materials” Angew. Chem. Int. Ed. 2010, 49, 6058-6082.

As described above, CO ₂ separation / recovery technology using a solid adsorbent has also been studied, but no solid adsorbent that can be substituted for an existing amine solution, including zeolite, has yet been found.

The present invention has been made in view of the present situation, and provides a zirconium hydroxide mesoporous material useful as a CO ₂ adsorbent having a high CO ₂ adsorption amount substantially equal to or higher than that of the conventional zeolite 13X. This is the issue.
Another object of the present invention is to provide a CO ₂ adsorbent comprising a zirconium hydroxide mesoporous material having a predetermined CO ₂ adsorption amount.
Moreover, this invention makes it an additional subject to provide the manufacturing method of the zirconium hydroxide mesoporous body which is simpler than the conventional method and can be manufactured without heating.
The present invention is directed to additional object is to provide a CO ₂ adsorption-desorption method using the CO ₂ adsorbent.

  The present inventor examined various solid adsorbents under the above-mentioned problems. In the process, (a) zirconium hydroxide has excellent durability similar to zeolite, and at the same time is nonflammable, toxic and corrosive. (I) Zirconium hydroxide is a material with higher true density and higher weight than zeolite, so it can reduce fluidization of the solid adsorbent due to exhaust gas circulation. Therefore, attention was paid to the zirconium hydroxide porous body.

A zirconium hydroxide porous body is known as a starting material for production of zirconium oxide, a catalyst and a catalyst carrier material, but has a high specific surface area (see Patent Documents 3 and 4).
For example, in Patent Document 3, a high specific surface area water is obtained by adding a sulfate to a starting solution in which sodium hydroxide and a zirconium raw material are mixed, keeping the solution temperature low (−2 ° C.), and then performing a hydrothermal treatment. It is described that the synthesis of zirconium oxide was successful.
Patent Document 4 describes that zirconium hydroxide having a specific surface area of 300 m ² / g or more was synthesized by aging a starting solution in which ammonia and a zirconium raw material were mixed at 70 ° C. or more for 8 hours or more. Yes.

However, these zirconium hydroxide porous body has not been studied at all for the CO ₂ adsorption performance, to not be to have a mesoporous structure suitable for CO ₂ adsorption performance, also methods for their synthesis In order to obtain zirconium hydroxide having a large specific surface area, a high-temperature and long-time hydrothermal treatment and a long-time aging operation are required, which is not necessarily desirable in terms of the production process.

The present inventor noticed that the zirconium hydroxide porous body has a CO ₂ adsorption ability due to its surface characteristics in the process of further studying the possibility by paying attention to the zirconium hydroxide porous body, It has also been recognized that in order to achieve high CO ₂ adsorption performance, it is necessary to synthesize one having a mesoporous structure suitable for CO ₂ adsorption performance.

The present inventor has further studied the production method and production conditions in order to obtain a zirconium hydroxide mesoporous material having high CO ₂ adsorption performance, and as a result, the metal salt which is a zirconium raw material under specific conditions. It has been found that a zirconium hydroxide mesoporous material having high CO ₂ adsorption performance can be produced in a short time at room temperature or at a low temperature of the same degree by performing the hydrolysis / polycondensation reaction.

The present invention has been completed based on the above examination results and knowledge, and according to the present invention, the following inventions are provided.
(1) Zirconium hydroxide mesoporous, characterized in that the equilibrium CO ₂ adsorption amount Vcc (STP) / mL at the equilibrium pressures of 10 kPa, 100 kPa, 1000 kPa, and 3000 kPa is in the following ranges in an environment where water does not coexist. body.
20 cc (STP) / mL ≤ CO ₂ adsorption amount when 10 kPa V ≤ 40 cc (STP) / mL
40cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 60 cc when the 100kPa (STP) / mL
80 cc (STP) / when the mL ≦ 1000 kPa CO ₂ adsorption amount V ≦ 100cc (STP) / mL
110cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 140 cc when the 3000kPa (STP) / mL
(2) The zirconium hydroxide mesoporous material according to (1), wherein each equilibrium CO ₂ adsorption amount Vcc (STP) / mL at equilibrium pressures of 10 kPa, 100 kPa, 1000 kPa, and 3000 kPa is in the following range in the presence of water.
5 cc (STP) / mL ≤ CO ₂ adsorption amount at 10 kPa V ≤ 40 cc (STP) / mL
15 cc (STP) / mL ≤ CO ₂ adsorption amount when 100 kPa V ≤ 50 cc (STP) / mL
25cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 60 cc when the 1000kPa (STP) / mL
35cc (STP) / mL ≤ 3000kPa CO ₂ adsorption amount V ≤ 80cc (STP) / mL
(3) A carbon dioxide adsorbent comprising the mesoporous zirconium hydroxide according to (1) or (2).
(4) A method for producing a zirconium hydroxide mesoporous material according to (1) or (2), wherein a zirconium raw material is added to an aqueous sodium hydroxide solution having a pH of 13.0 or more at room temperature or at a temperature from room temperature to 60 ° C. A method for producing a zirconium hydroxide mesoporous material, comprising adding and reacting, and then separating a solid precipitate generated in the liquid phase from the liquid phase.
(5) The method for producing a zirconium hydroxide mesoporous material according to (4), wherein the separated solid precipitate is dried at 60 ° C. or lower.
(6) The zirconium hydroxide mesoporous material according to (4) or (5), wherein the zirconium raw material is one or more selected from zirconyl nitrate, zirconium chloride and ammonium zirconium carbonate Manufacturing method.
(7) A method for adsorbing and desorbing carbon dioxide, comprising using the carbon dioxide adsorbent according to (3) and adsorbing and desorbing carbon dioxide only by pressurizing and depressurizing operations at room temperature and under 0.1 to 3000 kPa.
(8) The method for adsorbing and desorbing carbon dioxide according to (7), wherein carbon dioxide is adsorbed and desorbed in the presence of water.

Zirconium hydroxide mesoporous material of the present invention, those having a high CO ₂ adsorption amount (CO ₂ adsorption amount per unit volume), the CO ₂ adsorption amount is higher than conventional zeolite, the conventional amine solution It is almost equal or better than that. Further, only by pressurizing and depressurizing operations under CO ₂ introduction pressure (CO ₂ introduction pressure 0.1～3000KPa) of CO ₂ a possible adsorption-desorption, of CO ₂ separation, such as chemical absorption method using amine solution Since no thermal energy is required, the use of zirconium hydroxide mesoporous material as a CO ₂ adsorbent enables an energy-saving CO ₂ separation and recovery process.
Further, the zirconium hydroxide mesoporous material of the present invention can adsorb and desorb CO ₂ only by pressurization and depressurization operations under CO ₂ introduction pressure (CO ₂ introduction pressure 0.1 to 3000 kPa) even in the presence of water, Since heat energy is not required during the dehumidification process of zeolite, the use of zirconium hydroxide mesoporous material as a CO ₂ adsorbent enables an energy-saving CO ₂ separation and recovery process in the presence of water.
According to the production method of the present invention, high temperature and long time hydrothermal treatment is not required, it has a high specific surface area of about 300 m ² / g or more in a short time at room temperature or at a low temperature of 60 ° C. or less, and high A zirconium hydroxide mesoporous material having a CO ₂ adsorption amount can be produced.
The zirconium hydroxide mesoporous material of the present invention exhibits a CO ₂ adsorption amount of about 4 mmol / mL at a CO ₂ introduction pressure of 1000 kPa, which is about 1.1 times that of zeolite (3.7 mmol / mL, measured value). CO ₂ introduction pressure 3000kPa at illustrates the CO ₂ adsorption amount of about 5.4 mmol / mL, indicating a 1.5-fold of the zeolite (3.7 mmol / mL, measured value) high CO ₂ adsorption amount.

Furthermore, the zirconium hydroxide mesoporous material of the present invention has an effective CO ₂ adsorption amount of about 3.8 mmol / mL (the equilibrium CO ₂ adsorption amount at 3000 kPa and 10 kPa when the pressure / decompression operation is performed at 10-3000 kPa. Difference), about 2.5 times higher than the existing zeolite (1.5 mmol / mL, measured value). The zirconium hydroxide mesoporous material shows an effective CO ₂ adsorption amount of about 3.2 mmol / mL (difference in equilibrium CO ₂ adsorption amount between 3000 kPa and 100 kPa) when pressurized and decompressed at 100-3000 kPa. , About 5.3 times higher than existing zeolite (0.6 mmol / mL, measured value). Zeolite does not substantially increase CO ₂ adsorption at 500 kPa or more, and effective adsorption / desorption can hardly be performed by pressurizing / depressurizing operation of 500-3000 kPa, whereas zirconium hydroxide mesoporous material of the present invention is 500 kPa or more However, since the amount of CO ₂ adsorption increases as the pressure increases, effective adsorption and desorption can be performed by pressurization and decompression operations of 500 to 3000 kPa.

Further, zirconium hydroxide mesoporous material of the present invention, even in presence of water, indicating the CO ₂ introduction pressure 1000kPa and CO ₂ adsorption amount of more thereof about 1.4 mmol / mL or more and 1.9 mmol / mL in 3000 kPa. On the other hand, in the presence of water, the amount of CO ₂ adsorbed on the zeolite is significantly reduced.

The schematic diagram of the zirconium hydroxide mesoporous material synthesis process having CO ₂ adsorption performance according to the present invention. The graph which showed the powder X-ray-diffraction (XRD) pattern of the zirconium hydroxide mesoporous material of the Example of this invention. The graph which showed the differential thermogravimetric analysis (TG-DTA) result of the zirconium hydroxide mesoporous material of the Example of this invention. The scanning electron microscope observation (FE-SEM) photograph of the zirconium hydroxide mesoporous material of the Example of this invention. at 77K zirconium hydroxide mesoporous material of Example of the present invention obtained by adding varying amounts of zirconyl nitrate dihydrate in aqueous sodium hydroxide pH13.27 showed N ₂ adsorption-desorption isotherms Graph. The RUN 2 isotherm is shifted in the vertical direction by 50 cm ³ (STP) / g. at 77K zirconium hydroxide mesoporous material of Example of the present invention obtained by adding varying amounts of zirconyl nitrate dihydrate in aqueous sodium hydroxide pH13.27 showed N ₂ adsorption-desorption isotherms Graph. Each isotherm of RUN 4 and 5 is shifted in the vertical axis by 50 cm ³ (STP) / g. at 77K zirconium hydroxide mesoporous material of Example of the present invention obtained by adding varying amounts of zirconyl nitrate dihydrate in aqueous sodium hydroxide pH13.39 showed N ₂ adsorption-desorption isotherms Graph. Each isotherm of RUN 7, 8, 9 is shifted in the vertical axis by 50 cm ³ (STP) / g. at 77K zirconium hydroxide mesoporous material of Example of the present invention obtained by adding varying amounts of zirconyl nitrate dihydrate in aqueous sodium hydroxide pH13.39 showed N ₂ adsorption-desorption isotherms Graph. Each isotherm of RUN 11, 12, 13 is shifted in the vertical axis by 50 cm ³ (STP) / g. at 77K zirconium hydroxide mesoporous material of Example of the present invention obtained by adding varying amounts of zirconyl nitrate dihydrate in aqueous sodium hydroxide pH13.49 showed N ₂ adsorption-desorption isotherms Graph. Each isotherm of RUN 15, 16, and 17 is shifted in the vertical axis direction by 50 cm ³ (STP) / g. Example zirconium hydroxide mesoporous RUN 10 of the present invention, the graph showing the commercial zirconia, and CO ₂ adsorption-desorption isotherm at 298K of commercial zeolite 13X (without water coexist). Example zirconium hydroxide mesoporous RUN 11 of the present invention, the graph showing the commercial zirconia, and CO ₂ adsorption-desorption isotherm at 298K of commercial zeolite 13X (without water coexist). Example zirconium hydroxide mesoporous RUN 12 of the present invention, the graph showing the commercial zirconia, and CO ₂ adsorption-desorption isotherm at 298K of commercial zeolite 13X (without water coexist). Example zirconium hydroxide mesoporous RUN 13 of the present invention, the graph showing the commercial zirconia, and CO ₂ adsorption-desorption isotherm at 298K of commercial zeolite 13X (without water coexist). Graph showing the CO ₂ adsorption-desorption isotherm at 298K zirconium hydroxide mesoporous RUN 10 and commercial zeolite 13X embodiment of the present invention (water presence). Graph showing the CO ₂ adsorption-desorption isotherm at 298K zirconium hydroxide mesoporous RUN 13 and commercial zeolite 13X embodiment of the present invention (water presence).

The method for producing a zirconium hydroxide mesoporous material of the present invention is a method using a sol-gel reaction at room temperature or a temperature from room temperature to 60 ° C., in other words, utilizing a hydrolysis / polycondensation reaction of a zirconium raw material. Thus, by reacting a zirconium raw material with an aqueous sodium hydroxide solution at room temperature and separating a solid precipitate generated in the liquid phase at room temperature, about 302 m ^{2 is obtained.} The present invention provides a method for producing a zirconium hydroxide mesoporous material having a high specific surface area of at least 10 g / g, and a CO ₂ adsorbent comprising the zirconium hydroxide mesoporous material obtained by the production method.

FIG. 1 shows a process for producing a zirconium hydroxide mesoporous material according to the present invention.
After preparing an inorganic precursor solution containing a zirconium raw material under a strong base using water as a solvent, the mixture is stirred for several hours at room temperature to uniformly generate zirconium hydroxide nanoparticles (primary particles). Thereafter, the zirconium hydroxide nanoparticles aggregate in the liquid phase and precipitate as secondary particles having a size of about several μm. Finally, the precipitated particles separated from the liquid phase by centrifugation are air-dried, whereby mesopores are formed in the gaps between the aggregated particles, and a zirconium hydroxide mesoporous material is obtained. The surface of zirconium hydroxide having mesopores can be used as a CO ₂ adsorption site.

In the present invention, as a basic aqueous solution in the above synthesis process, a sodium hydroxide solution having a pH of 13.0 or more is used, and by adding a zirconium raw material thereto, the liquid phase is obtained at room temperature in a short time without heating. A zirconium hydroxide mesoporous material having a high specific surface area and a high CO ₂ adsorption amount as a solid precipitate can be obtained.

  In the present invention, as a zirconium raw material to be added to an aqueous sodium hydroxide solution, zirconyl nitrate, zirconium chloride, ammonium zirconium carbonate and the like are used, and preferably zirconyl nitrate is used.

After the addition of the zirconium raw material, after stirring for several hours at room temperature, preferably 24 hours, and then standing at room temperature for several hours, preferably 5 minutes or more, a solid in which zirconium hydroxide nanoparticles are aggregated in the liquid phase A precipitate is obtained. The obtained solid precipitate is washed with pure water after centrifugation to completely remove residual by-products such as sodium hydroxide and nitric acid components.
The method for drying the solid precipitate after washing is not particularly limited, but preferably it is dried in an air atmosphere at 25 to 60 ° C. for 12 to 24 hours.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this Example.

(Example 1: Production of zirconium hydroxide mesoporous material)
A zirconium hydroxide mesoporous material was produced by the following procedure.
Sodium hydroxide was added to 600 g of pure water and stirred at room temperature for 10 minutes to prepare four types of aqueous sodium hydroxide solutions having pHs of 12.84, 13.27, 13.39, and 13.49.
Next, 3, 5, 7, 10, 15, 20, 25 or 30 g of zirconyl nitrate dihydrate was added to the obtained aqueous sodium hydroxide solution, stirred at room temperature for 24 hours, and allowed to stand at room temperature for 5 minutes. (See Table 1 for composition conditions).
As a result, precipitation did not occur when an aqueous sodium hydroxide solution having a pH of 12.84 was used, but solid precipitates were obtained in the liquid phase with other aqueous sodium hydroxide solutions.

The solid precipitate formed in the liquid phase was separated by suction filtration, and the obtained solid precipitate was washed several times with ultrapure water to completely remove the remaining sodium hydroxide and nitric acid components. .
After washing, the solid precipitate was dried at 60 ° C. for 12 hours in an air atmosphere.
In the case where the pH with sodium hydroxide solution 12.84 can not recovered too fine particles in the suction filtration through filter paper, centrifuged, the particles could be recovered by drying, N ₂ adsorption-desorption measurements described below According to the results, the recovered particles could not be said to have pores.

(Example 2: Characterization of solid precipitate after drying)
For the solid precipitate after drying obtained in Example 1, powder X-ray diffraction (XRD), differential thermogravimetric analysis (TG-DTA), scanning electron microscope observation (FE-SEM), N ₂ adsorption / desorption measurement, And CO ₂ adsorption / desorption measurement was performed.
For comparison, the commercial zeolite 13X was also characterized.

<Powder X-ray diffraction (XRD) results>
FIG. 2 shows an XRD diffraction pattern of a product (solid precipitate) obtained by adding zirconyl nitrate dihydrate to an aqueous sodium hydroxide solution having a pH = 13.39 (RUN 10). The diffraction pattern derived from the crystal was not confirmed, and a broad halo pattern was shown in the range of 2θ = 20-40 ° and 2θ = 40-70 °, and thus the product had an amorphous structure. Also in solid precipitates prepared with other compositions, an amorphous XRD pattern similar to RUN 10 was confirmed.
On the other hand, even when zirconyl nitrate dihydrate was added to an aqueous sodium hydroxide solution having a pH = 12.84, precipitation of zirconium hydroxide did not occur. In this experimental system, the pH of the aqueous sodium hydroxide solution was 13.27. It is desirable to prepare by the above.

<Results of differential thermogravimetric analysis (TG-DTA)>
FIG. 3 shows the results of differential thermogravimetric analysis (TG-DTA) of the solid precipitate obtained by adding zirconyl nitrate dihydrate to an aqueous sodium hydroxide solution prepared at pH = 13.39 (RUN 10). The weight loss (TG) seen from room temperature to 200 ° C. is due to the evaporation of moisture adsorbed in the product. The weight loss seen from 200 ° C. to 800 ° C. is due to the elimination of OH groups present on the product surface. In addition, the sharp DTA peak seen around 430 ° C shows the structural transition from zirconium hydroxide to zirconium oxide. From the results of XRD and TG-DTA, the product has a hydroxyl structure with an amorphous structure. It can be seen that it is zirconium. Similar TG-DTA profiles have been confirmed for products synthesized with other compositions.

<Results of scanning electron microscope observation (FE-SEM)>
FIG. 4 shows the results of FE-SEM observation of a solid precipitate obtained by adding zirconyl nitrate dihydrate to an aqueous sodium hydroxide solution prepared at pH = 13.39 (Run 10).
As a result of FE-SEM observation, secondary particles of micrometer order were obtained, and it was found that the zirconium hydroxide nanoparticles had an agglomerated structure when the particle surface was magnified.

<N ₂ adsorption / desorption measurement results>
5-9 show N ₂ adsorption / desorption isotherms at 77K of RUN 1-17. Pretreatment was performed before measurement, and the zirconium hydroxide mesoporous material (RUN 1 to 17) was evacuated at room temperature for 24 hours. The products obtained in RUN 1 to 17 showed hysteresis in the adsorption / desorption isotherm, suggesting that mesopores were formed in the aggregate structure of zirconium hydroxide nanoparticles. In addition, when the amount of zirconyl nitrate dihydrate was increased, the shape of hysteresis was also changed, suggesting that a change occurred in the aggregate structure.

<Calculation of specific surface area, pore volume, average primary particle size>
Table 2 shows the specific surface area and pore volume of the ceria mesoporous material calculated by the Brunauer-Emmett-Teller (BET) method and the Gurvich method from the N ₂ adsorption / desorption measurement results. The average primary particle diameter of zirconium hydroxide nanoparticles estimated from the BET specific surface area is shown in Table 2 (the average primary particle diameter is estimated by "Adsorpition by Powders" by F. Rouquerol, J. Rouuquerol, K. Sing). and Porous Solids, Principles, Methodology and Applications ”based on formula (1,1) described on page 6-8).

The zirconium hydroxide mesoporous material obtained at pH = 13.27 to 13.49 shows a specific surface area of 302 to 396 m ² / g and a pore volume of 0.168 to 0.275 cm ³ / g, and the zirconium hydroxide mesoporous material RUN 10 is the most. The high specific surface area was 396 m ² / g, and RUN 13 had the largest pore volume of 0.275 cm ³ / g.

As described above, as a result of XRD, TG-DTA, SEM, and N ₂ adsorption / desorption measurement, by introducing zirconyl nitrate dihydrate as a zirconium raw material into an aqueous sodium hydroxide solution adjusted at pH ≧ 13.0, a diameter of about 4.9˜ It was found that 6.2 nm polyhedral zirconium hydroxide nanoparticles were formed and aggregated to form a three-dimensional structure. As a result of N ₂ adsorption / desorption measurement, zirconium hydroxide having a high specific surface area of about 300 to 400 m ² / g and a pore volume of 0.17 to 0.28 cm ³ / g by forming an aggregated structure of zirconium hydroxide nanoparticles. It was found that mesoporous materials can be synthesized in a short time.

<CO ₂ a result of the adsorption-desorption measurement>
FIGS. 10 to 13 show CO ₂ adsorption and desorption isotherms at 298 K of zirconium hydroxide mesoporous material, commercially available zirconia, and commercially available zeolite 13X.
Here, zirconium hydroxide mesoporous materials (RUN 10, 11, 12, 13) were selected and evaluated for CO ₂ adsorption capacity.

As shown in FIGS. 10 to 13, the zirconium hydroxide mesoporous material can adsorb and desorb CO ₂ only by pressurization and depressurization operations under room temperature CO ₂ introduction pressure (CO ₂ introduction pressure 10 to 3000 kPa). all right.

It should be noted that the zirconium hydroxide mesoporous material exhibits higher CO ₂ adsorption than commercial zirconia and zeolite 13X in the pressure range of 1000-3000 kPa.
In FIG. 10, for example, RUN 10 has a CO ₂ introduction pressure of 3000 kPa, zeolite 13X of about 83 cm ³ / mL (3.7 mmol / mL in terms of conversion), and zirconia of about 4 cm ³ / mL (0.2 mmol / mL in terms of conversion). The amount of CO ₂ adsorption was shown. When these are compared, the zirconium hydroxide mesoporous material RUN 10 shows 132 cm ³ / mL (converted to 5.9 mmol / mL), so the amount of CO ₂ adsorption is about 1.6 times that of zeolite 13X and about 30 times that of zirconia. I found it.

As in the above [0041], in FIGS. 11 to 13, RUN 11, 12, and 13 show that the zirconium hydroxide mesoporous material shows higher CO ₂ adsorption than commercial zirconia and zeolite 13X in the pressure range of 1000 to 3000 kPa. .

More importantly, it is necessary to evaluate the CO ₂ adsorption amount at the equilibrium pressure difference in order to perform CO ₂ capture by pressure fluctuation. When pressurization / decompression operation is performed at 10-3000 kPa (difference in equilibrium CO ₂ adsorption between 3000 kPa and 10 kPa), the zirconium hydroxide mesoporous material RUN 10 is approximately 94 cm ³ / mL (converted to 4.2 mmol / mL) ) effective CO ₂ shows the adsorption amount of existing zeolites 33cm ³ /mL(1.5mmol/mL, about 2.8 times higher than the actual value). When pressurization and depressurization operations are performed at 100-3000 kPa (difference in equilibrium CO ₂ adsorption between 3000 kPa and 100 kPa), the zirconium hydroxide mesoporous material RUN 10 is approximately 76 cm ³ / mL (converted to 3.4 mmol / mL) ) effective CO ₂ shows the adsorption amount of about 5.4 times higher than the existing zeolite 14cm ³ / mL (in terms to 0.6 mmol / mL, measured value). Zeolite does not substantially increase CO ₂ adsorption at 500 kPa or more, and effective adsorption / desorption can hardly be performed by pressurizing and depressurizing operations of 500 to 3000 kPa. However, the zirconium hydroxide mesoporous material of the present invention has a pressure of 500 kPa or more. Since the amount of CO ₂ adsorption increases with the increase in the pressure, effective adsorption / desorption can be performed by pressurization and depressurization operations of 500-3000 kPa.

As in the above [0043], when pressurization and depressurization operations are performed at 10-3000 kPa and 100-3000 kPa, the zirconium hydroxide mesoporous material RUN 11, 12, 13 has a higher CO ₂ pressure difference than the existing zeolite. The amount of adsorption is shown.
In addition, CO ₂ adsorption amount is not confirmed for RUN 1 to 9, 14 to 17, but it has the same specific surface area as RUN 10 to 13 and hysteresis in the N ₂ adsorption / desorption isotherm like RUN 10 to 13 Therefore, it is considered that the CO ₂ adsorption performance is the same as that of RUN 10-13.

FIGS. 14 and 15 show the results of CO ₂ adsorption / desorption measurement in which zirconium hydroxide mesoporous materials (RUN 10 and 13) and zeolite 13X were preliminarily adsorbed, and without pretreatment. Here, the measurement was performed by adjusting the water adsorption amounts of zirconium hydroxide mesoporous material (RUN 10 and 13) and zeolite 13X to about 23 wt% and 19-26 wt%, respectively.

The zirconium hydroxide mesoporous material maintained CO ₂ adsorption / desorption performance in the pressure range of 100 to 3000 kPa, although a decrease in the CO ₂ adsorption amount was observed in the presence of a large amount of moisture. At this time, the zirconium hydroxide mesoporous material is about 22 cm ³ / mL at a CO ₂ introduction pressure of 100 kPa (converted to 1 mmol / mL or more, about 35 cm ³ / mL at a CO ₂ introduction pressure of 1000 kPa (converted to 1.4 mmol / mL). As described above, the CO ₂ adsorption amount was about 43 cm ³ / mL (converted to 1.9 mmol / mL) or more at a CO ₂ introduction pressure of 3000 kPa.On the other hand, zeolite 13X was inhibited from adsorbing CO ₂ by the prior adsorption of water. The CO ₂ adsorption performance was significantly reduced, and the CO ₂ adsorption amount was almost close to 0 in the pressure range of 10 to 3000 kPa.

Claims (8)

A zirconium hydroxide mesoporous material characterized in that the equilibrium CO ₂ adsorption amount Vcc (STP) / mL at equilibrium pressures of 10 kPa, 100 kPa, 1000 kPa, and 3000 kPa is in the following ranges in an environment where water does not coexist.
20 cc (STP) / mL ≤ CO ₂ adsorption amount when 10 kPa V ≤ 40 cc (STP) / mL
40cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 60 cc when the 100kPa (STP) / mL
80 cc (STP) / when the mL ≦ 1000 kPa CO ₂ adsorption amount V ≦ 100cc (STP) / mL
110cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 140 cc when the 3000kPa (STP) / mL _{2. The} zirconium hydroxide mesoporous material according to claim 1, wherein each of the equilibrium CO ₂ adsorption amounts Vcc (STP) / mL at the equilibrium pressures of 10 kPa, 100 kPa, 1000 kPa, and 3000 kPa is in the following range in the presence of water.
5 cc (STP) / mL ≤ CO ₂ adsorption amount at 10 kPa V ≤ 40 cc (STP) / mL
15 cc (STP) / mL ≤ CO ₂ adsorption amount when 100 kPa V ≤ 50 cc (STP) / mL
25cc (STP) / mL ≦ CO 2 adsorption amount V ≦ 60 cc when the 1000kPa (STP) / mL
35cc (STP) / mL ≤ 3000kPa CO ₂ adsorption amount V ≤ 80cc (STP) / mL   A carbon dioxide adsorbent comprising the zirconium hydroxide mesoporous material according to claim 1 or 2.   A method for producing a zirconium hydroxide mesoporous material according to claim 1 or 2, wherein a zirconium raw material is added to a sodium hydroxide aqueous solution having a pH of 13.0 or more at room temperature or at a temperature from room temperature to 60 ° C to be reacted. And then separating the solid precipitate produced in the liquid phase from the liquid phase.   The method for producing a zirconium hydroxide mesoporous material according to claim 4, wherein the solid precipitate after separation is dried at 60 ° C. or lower.   The method for producing a zirconium hydroxide mesoporous material according to claim 4 or 5, wherein the zirconium raw material is one or more selected from zirconyl nitrate, zirconium chloride, and ammonium zirconium carbonate.   A method for adsorbing and desorbing carbon dioxide, comprising using the carbon dioxide adsorbent according to claim 3 to adsorb and desorb carbon dioxide only by pressurizing and depressurizing operations at room temperature and under 0.1 to 3000 kPa.   The method for adsorbing and desorbing carbon dioxide according to claim 7, wherein carbon dioxide is adsorbed and desorbed in the presence of water.

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