Method for producing carbon dioxide adsorbent

Abstract

To provide a method for producing a carbon dioxide adsorbent modified with amino groups without using an organic solvent.SOLUTION: A method for producing a carbon dioxide adsorbent comprises: mixing a porous carrier, an amino group-containing silane coupling agent and water; and removing water by carrying out a treatment of evaporation to dryness by heating to produce a carbon dioxide adsorbent which is a porous carrier with its surface modified with amino groups. This method does not use an organic solvent that is concerned to cause toxicity and environmental pollution and, therefore, the method contributes to solving the problems of toxicity and environmental pollution when producing large amount of a carbon dioxide absorbent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a carbon dioxide adsorbing material. [Background technology]

[0002] Amino-group-containing silane coupling agents, such as aminopropyltrimethoxysilane, can be used to modify the surface of porous carriers to form carbon dioxide adsorption sites. Carbon dioxide adsorbents modified with amino groups are highly durable and have a fast adsorption rate, making them promising candidates for use in carbon dioxide capture.

[0003] Generally, in the production of carbon dioxide adsorbents modified with amino groups, a porous carrier and an amino group-containing silane coupling agent are placed in a solvent and heated and stirred. To prevent condensation of the silane coupling agents due to hydrolysis, an organic solvent such as dehydrated toluene or ethanol is used as the solvent (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-261670 Summary of the Invention [Problem to be solved by the invention]

[0005] To widely commercialize carbon dioxide adsorbents modified with amino groups, they must be synthesized in large quantities. When synthesizing them in large quantities, it is desirable to avoid using organic solvents, which are toxic and pose environmental pollution concerns.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing a carbon dioxide adsorbent modified with an amino group without using an organic solvent. [Means for solving the problem]

[0007] The method for producing a carbon dioxide adsorbing material according to the present invention includes the steps of: A porous carrier, an amino group-containing silane coupling agent, and water are mixed together, and performing a heating evaporation-to-dryness treatment to remove the water, thereby producing a carbon dioxide adsorbent in which the surface of the porous carrier is modified with amino groups. It is characterized by:

[0008] It is also preferable to use the porous carrier having oxygen-containing functional groups on the surface.

[0009] It is also preferable to use an (aminoalkyl)trialkoxysilane as the amino group-containing silane coupling agent.

[0010] It is also preferable to use an (aminoalkyl)trimethoxysilane as the (aminoalkyl)trialkoxysilane.

[0011] The blending ratio of the porous carrier to the amino group-containing silane coupling agent is preferably 85:15 to 60:40 by weight. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a method for producing a carbon dioxide adsorbing material modified with an amino group without using an organic solvent. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a graph showing the carbon dioxide adsorption amounts of adsorbents A, At, Ae, and Am. [Figure 2] 1 is a graph showing the carbon dioxide adsorption amounts of adsorbents B and C. DETAILED DESCRIPTION OF THE INVENTION

[0014] The method for producing a carbon dioxide adsorbent according to this embodiment includes the steps of mixing a porous carrier, an amino group-containing silane coupling agent, and water, and performing a heating evaporation-to-dryness treatment, thereby obtaining a carbon dioxide adsorbent in which the surface of the porous carrier is modified with amino groups.

[0015] (Porous carrier) There are no limitations on the porous carrier used, but from the viewpoint of forming a strong bond with the amino group-containing silane coupling agent, a porous carrier having an oxygen-containing functional group on the surface is preferred. Examples of the oxygen-containing functional group include a hydroxyl group, a phenolic hydroxyl group, a carboxyl group, and a quinone-type oxygen. In addition, a chemically stable substance that does not inhibit the adsorption of the target carbon dioxide is preferred. Examples include inorganic porous carriers such as silica, alumina, zeolite, and activated carbon that have surface hydroxyl groups.

[0016] (Amino group-containing silane coupling agent) The amino group-containing silane coupling agent is a silane coupling agent having one or more amino groups. It is preferable to use an (aminoalkyl)trialkoxysilane as the amino group-containing silane coupling agent. Examples of the (aminoalkyl)trialkoxysilane include (3-aminopropyl)trimethoxysilane, N-[3-(trimethoxysilyl)propyl]ethylenediamine, 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane, (3-aminopropyl)triethoxysilane, N-[3-(triethoxysilyl)propyl]ethylenediamine, and 3-[2-(2-aminoethylamino)ethylamino]propyltriethoxysilane. These may be used alone or in combination of two or more.

[0017] The amino group-containing silane coupling agent is preferably blended so that its content in the carbon dioxide adsorbent is 20 to 30% by weight. Since almost all of the water solvent is evaporated in the evaporation-to-dryness treatment, the blending ratio of the porous carrier to the amino group-containing silane coupling agent during production of the carbon dioxide adsorbent is preferably 85:15 to 60:40 by weight, and more preferably 80:20 to 70:30.

[0018] If the amount of the amino group-containing silane coupling agent is small, the number of carbon dioxide adsorption sites, i.e., the number of amino groups, in the carbon dioxide adsorbent will decrease, leading to a decrease in the amount of carbon dioxide adsorbed.On the other hand, if the amount of the silane coupling agent is large, the pores of the porous carrier will be blocked by the silane coupling agent, leading to a decrease in the number of effective adsorption sites.

[0019] The temperature and time for the evaporation to dryness treatment may be any temperature and time that will evaporate almost all of the water solvent, but the temperature is preferably 65 to 75°C, and more preferably around 70°C.

[0020] It is believed that moisture hydrolyzes the alkoxy groups of the amino group-containing silane coupling agent to generate silanol groups, which migrate to the surface of the porous carrier via hydrogen bonding with the surface hydroxyl groups of the porous carrier, and then undergo a dehydration condensation reaction to form a strong covalent bond with the surface of the porous carrier, and in parallel with this reaction, the silanol groups condense with each other to form siloxane oligomers. This results in a carbon dioxide adsorbent whose surface is modified with amino groups.

[0021] The method for producing a carbon dioxide adsorbing material according to this embodiment does not use an organic solvent, which is liable to cause toxicity and environmental pollution, and therefore can contribute to solving the problems of toxicity and environmental pollution that arise when producing carbon dioxide adsorbing materials on a large scale. [Example]

[0022] (Synthesis of porous support (SBA-15)) 20 g of Pluronic P123 (Pluronic is a registered trademark) (poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol)) was added to 525 g of deionized water and stirred at 30° C. until completely dissolved. Next, 42.63 g of TEOS (Tetraethoxysilane) and 148.2 g of concentrated hydrochloric acid were added to the mixture, which was then heated to 30° C. in a metal bath while being stirred with a magnetic stirrer for a further 20 hours. The reaction vessel was then transferred to an oil bath and stirred under reflux for an additional 20 hours. The resulting gel was filtered and washed with water. The resulting solid was dried at 70° C. overnight. Finally, to remove the organic components, the product was calcined at 550°C for 8 hours in an air atmosphere to obtain SBA-15.

[0023] (Synthesis of carbon dioxide adsorbent) As a silane coupling agent, 3-aminopropyltrimethoxysilane (0.1 g), SBA-15 (0.3 g), and water (5 mL) were mixed and placed in a 10 mL glass bottle. The mixture was then dried at 70°C for 24 hours (evaporation to dryness) to completely remove water, yielding a carbon dioxide adsorbent containing 25 wt% of 3-aminopropyltrimethoxysilane. This carbon dioxide adsorbent is referred to as Adsorbent A.

[0024] Carbon dioxide adsorbents were also produced in the same manner as above, except that toluene, ethanol, and methanol were used instead of water. These adsorbents are referred to as adsorbents At, Ae, and Am, respectively.

[0025] (Verification of CO2 adsorption amount) CO2 adsorption experiments under dry conditions were carried out using a thermogravimetric (TG) apparatus (STA200, Hitachi, Ltd.). 5 mg of adsorbent A was packed into the sample pan of the thermogravimetric analyzer, and nitrogen (80°C) was introduced at a rate of 500 mL / min until the weight loss of adsorbent A stopped. The temperature was then lowered to 30°C under nitrogen flow and continued for another 0.5 hours. Thereafter, carbon dioxide diluted with nitrogen to 400 ppm was introduced at 400 mL / min for 60 minutes to allow the adsorbent A to adsorb the carbon dioxide. The amount of carbon dioxide adsorbed was calculated from the weight increase of adsorbent A.

[0026] In the same manner as above, carbon dioxide was also adsorbed onto the adsorbents At, Ae, and Am, and the amounts of adsorbed carbon dioxide were calculated.

[0027] The results are shown in Figure 1. The carbon dioxide adsorption capacity of adsorbent A was 0.35 mmol / g. The carbon dioxide adsorption capacity of adsorbent A was slightly lower than that of adsorbents At and Ae obtained using toluene and ethanol, but higher than that of adsorbent Am obtained using methanol.

[0028] (Synthesis of other carbon dioxide adsorbents, verification of CO2 adsorption capacity) Carbon dioxide adsorbents were synthesized in the same manner as above, except that N-[3-(trimethoxysilyl)propyl]ethylenediamine was used as the silane coupling agent. This carbon dioxide adsorbent is referred to as adsorbent B. Adsorbents B were synthesized so that the content of N-[3-(trimethoxysilyl)propyl]ethylenediamine in adsorbent B was 15, 20, 25, 30, or 40 wt%, respectively.

[0029] Carbon dioxide adsorbents were synthesized in the same manner as above, except that 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane was used as the silane coupling agent. This carbon dioxide adsorbent is referred to as adsorbent C. Adsorbents C were synthesized so that the content of 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane was 15, 20, 25, 30, or 40 wt%.

[0030] A CO2 adsorption experiment was carried out in the same manner as above using the produced adsorbents B and C. Carbon dioxide diluted with nitrogen to 5 vol% was passed through the adsorbents at a flow rate of 400 mL / min for 60 minutes.

[0031] The results are shown in Figure 2. It was confirmed that all adsorbents adsorbed carbon dioxide. Adsorbents B and C showed high adsorption amounts when the content of N-[3-(trimethoxysilyl)propyl]ethylenediamine and 3-[2-(2-aminoethylamino)ethylamino]propyltrimethoxysilane was 20 to 30 wt%, and the highest adsorption amount was observed at a content of 25 wt%. [Industrial Applicability]

[0032] Since it is possible to produce carbon dioxide adsorbents modified with amino groups without using organic solvents, this method is expected to lead to mass production of carbon dioxide adsorbents and be applied to technology for capturing and removing CO2 from the atmosphere.

Claims

1. A porous carrier, an amino group-containing silane coupling agent, and water are mixed together, and performing a heating evaporation-to-dryness treatment to remove the water, thereby producing a carbon dioxide adsorbent in which the surface of the porous carrier is modified with amino groups. A method for producing a carbon dioxide adsorbing material, comprising:

2. The porous carrier having oxygen-containing functional groups on the surface is used. The method for producing a carbon dioxide adsorbing material according to claim 1 .

3. (aminoalkyl)trialkoxysilane is used as the amino group-containing silane coupling agent. The method for producing a carbon dioxide adsorbing material according to claim 1 .

4. (aminoalkyl)trimethoxysilane is used as the (aminoalkyl)trialkoxysilane. The method for producing a carbon dioxide adsorbing material according to claim 3 .

5. The blending ratio of the porous carrier to the amino group-containing silane coupling agent is 85:15 to 60:40 by weight. The method for producing a carbon dioxide adsorbing material according to claim 1 .

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