Carbon dioxide adsorbent

Abstract

To provide a carbon dioxide adsorbent having sufficiently high capacity for adsorbing carbon dioxide.SOLUTION: According to one embodiment, a carbon dioxide adsorbent includes a silica carrier and an amine supported on the silica carrier, wherein the silica carrier has a pore volume of 0.1 cm3 / g or more and 1.5 cm3 / g or less, a specific surface area of 1000 m2 / g or less, and an average pore diameter of 6 nm or more and 100 nm or less, and the geometrical thickness of the supported amine is 1 nm or more and 12 nm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present disclosure relates to a carbon dioxide adsorbent.

Background Art

[0002] In recent years, research on carbon dioxide adsorbents has been actively conducted for the purpose of reducing the emission of carbon dioxide into the atmosphere and separating and recovering carbon dioxide in the atmosphere or in a sealed space such as a submarine or a space station.

[0003] For example, Patent Document 1 discloses a carbon dioxide separation material containing a polyamine carrier in which a polyamine having at least two isopropyl groups on a nitrogen atom is supported on a carrier.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The inventors of the present invention have found that in a carbon dioxide adsorbent in which an amine is supported on a carrier, depending on the surface of the carrier and the state of pores, carbon dioxide may not be sufficiently adsorbed to the amine, resulting in a decrease in the amount of carbon dioxide adsorbed and desorbed.

[0006] An object of the present disclosure is to provide a carbon dioxide adsorbent having excellent carbon dioxide adsorption amount.

Means for Solving the Problems

[0007] As a result of intensive studies to solve the above problems, the inventors of the present invention have found that an excellent carbon dioxide adsorbent can be obtained by supporting an amine on a specific silica carrier with a specific geometric thickness, leading to the present disclosure.

[0008] Examples of the embodiments of the present invention are described as follows.

[0009] (1) A carbon dioxide adsorbent comprising a silica carrier and an amine supported on the silica carrier, wherein the pore volume of the silica carrier is 0.1 cm 3 / g or more and 1.5 cm 3 / g or less, the specific surface area is 1000 m 2 / g or less, and the average pore diameter is 6 nm or more and 100 nm or less, and the geometric thickness of the supported amine is 1 nm or more and 12 nm or less. (2) The carbon dioxide adsorbent according to (1), wherein the geometric thickness is 2 nm or more and 6 nm or less. (3) The carbon dioxide adsorbent according to (1), wherein the geometric thickness is 3 nm or more and 6 nm or less. (4) The carbon dioxide adsorbent according to any one of (1) to (3), wherein the silica carrier is silica powder having an average particle diameter of 0.2 μm or more and 40 μm or less. (5) The carbon dioxide adsorbent according to any one of (1) to (4), wherein the specific surface area of the silica carrier is 5 m 2 / g or more and 400 m 2 / g or less. [[Effect of the Invention]]

[0010] According to the present disclosure, a carbon dioxide adsorbent excellent in carbon dioxide adsorption amount can be provided. [[Mode for Carrying Out the Invention]]

[0011] Hereinafter, the carbon dioxide adsorbent of the present embodiment will be described in detail. (Carbon Dioxide Adsorbent) One aspect of the present embodiment is a carbon dioxide adsorbent comprising a silica carrier and an amine supported on the silica carrier, wherein the pore volume of the silica carrier is 0.1 cm 3 / g or more and 1.5 cm 3 / g or less, and the specific surface area is 1000 m 2 / g or less, it is a carbon dioxide adsorbent having an average pore diameter of 6 nm or more and 100 nm or less, and the geometric thickness of the supported amine is 1 nm or more and 12 nm or less. Note that the carbon dioxide adsorbent is also referred to as a CO 2 adsorbent. The carbon dioxide adsorbent of the present embodiment can efficiently adsorb carbon dioxide even at a concentration of about 400 ppm in the atmosphere.

[0012] In the carbon dioxide adsorbent of the present embodiment, the geometric thickness (geometric film thickness) of the amine is 2 nm or more and 6 nm or less in one embodiment, and 3 nm or more and 6 nm or less in one embodiment. In another embodiment, the geometric thickness of the amine is 2 nm or more and 4 nm or less. The geometric thickness of the amine can be obtained by dividing the volume of the amine supported in the carbon dioxide adsorbent (amine loading volume) by the specific surface area of the silica support, as shown in the following formula. Further, the amine loading volume can be calculated from the amine loading amount and the amine density. Geometric thickness of amine = Amine loading volume / Specific surface area of silica support

[0013] According to the studies of the present inventors, when the loading amount of the amine constituting the carbon dioxide adsorbent is small and the geometric film thickness is too thin, the amine is deactivated by the influence of the silica support surface, and the carbon dioxide adsorption amount decreases. In addition, since the rate at which carbon dioxide diffuses into the amine is slow, when the loading amount of the amine constituting the carbon dioxide adsorbent is large and the geometric film thickness exceeds a certain thickness, it is considered that carbon dioxide is not adsorbed by the amine existing at a depth greater than a certain depth. For this reason, the geometric film thickness of the amine is one of the preferred embodiments within the above range.

[0014] The carbon dioxide adsorbent of the present embodiment contains a silica support and an amine, and the amount thereof is not particularly limited as long as the geometric thickness of the amine is within the above range. For example, the carbon dioxide adsorbent may have an amine loading amount of 5% by weight or more and 80% by weight or less, or 15% by weight or more and 45% by weight or less.

[0015] (Silica support) The carbon dioxide adsorbent of the present embodiment contains a silica carrier. The silica carrier has a pore volume of 0.1 cm 3 / g or more and 1.5 cm 3 / g or less, a specific surface area of 1000 m 2 / g or less, and an average pore diameter of 6 nm or more and 100 nm or less. The silica carrier may be used alone or in combination of two or more. Also, as the silica carrier, a commercially available product may be used, or one appropriately manufactured may be used.

[0016] In one embodiment, the pore volume of the silica carrier is 0.1 cm 3 / g or more and 1.5 cm 3 / g or less, and in one embodiment, it is 0.2 cm 3 / g or more and 1.0 cm 3 / g or less.

[0017] In one embodiment, the specific surface area of the silica carrier is 5 m 2 / g or more and 1000 m 2 / g or less, and in one embodiment, it is 5 m 2 / g or more and 400 m 2 / g or less, and in one embodiment, it is 30 m 2 / g or more and 100 m 2 / g or less. In this range, it is preferable that a smaller specific surface area tends to result in higher carbon dioxide adsorption amount and carbon dioxide desorption amount after carbon dioxide adsorption.

[0018] In one embodiment, the average pore diameter of the silica carrier is 6 nm or more and 100 nm or less, and in one embodiment, it is 10 nm or more and 80 nm or less.

[0019] The shape of the silica carrier is not particularly limited. As the silica carrier, for example, silica powder, silica beads, silica pellets, etc. can be used. From the viewpoint of particle size, silica powder is one of the preferred embodiments as the silica carrier. In one embodiment, the silica carrier is silica powder with an average particle size of 0.2 μm or more and 40 μm or less. In this range, it is preferable that a smaller particle size tends to result in excellent carbon dioxide adsorption performance.

[0020] (amine) The carbon dioxide adsorbent of this embodiment contains an amine supported on a silica carrier. There is no particular limitation on the amine. For example, polyethyleneimine (PEI), monoethanolamine, diethanolamine, triethanolamine, tetraethylenepentamine, methyldiethanolamine, dibutylamine, ethylenediamine, diethylenetriamine, triethylenetetramine, hexaethylenediamine, benzylamine, etc. may be mentioned. The amine may be a monoamine or a polyamine. The amine may be used alone or in combination of two or more. Also, as the amine, a commercially available product may be used, or a product appropriately manufactured may be used.

[0021] (Method for producing carbon dioxide adsorbent) There is no particular limitation on the method for producing the carbon dioxide adsorbent. As an example of the method for producing the carbon dioxide adsorbent, an amine is dissolved in a solvent to prepare an amine-containing solution, the silica carrier is impregnated in the amine-containing solution, and the solvent is removed by drying such as drying under reduced pressure to obtain the carbon dioxide adsorbent. The method for producing the carbon dioxide adsorbent can be appropriately set based on the description of the examples, for example. Examples of the solvent include alcohols such as ethanol, methanol, and propanol, and water. When drying is performed by drying under reduced pressure, in one embodiment, the temperature is room temperature or higher and 110°C or lower. Also, the temperature may be constant or may be changed during the process. There is no particular limitation on the drying time either, and in one embodiment, it is 1 hour or more and 10 hours or less.

Examples

[0022] Hereinafter, the present embodiment will be described with reference to examples, but the present disclosure is not limited by these examples.

[0023] The following silica was used as the silica carrier. QS30: Silica powder (manufactured by Tokuyama), pore volume 0.75 cm 3 / g, specific surface area 305 m 2 / g, average pore diameter 11 nm, average particle size 40 μm QS09: Silica powder (manufactured by Tokuyama), pore volume 0.2 cm 3 / g, specific surface area 85 m 2 / g, average pore diameter 11 nm, average particle diameter 0.2 μm Q30 beads: Silica beads (manufactured by Fuji Silysia), pore volume 1 cm 3 / g, specific surface area 300 m 2 / g, average pore diameter 30 nm, particle diameter 1.1 - 2.4 mm Q30 pellets: 10 g of the above Q30 beads were put into a mill and crushed into a powder. After that, it was compressed by a pellet forming machine to obtain pellets. Then, using sieves with mesh sizes of 1 mm and 2 mm, pellets with a particle diameter of 1 - 2 mm were prepared and designated as Q30 pellets (silica pellets). Pore volume 1 cm 3 / g, specific surface area 300 m 2 / g, average pore diameter 30 nm, particle diameter 1 - 2 mm

[0024] [Comparative Example 1] Polyethyleneimine (PEI) (manufactured by Fuji Film Wako Pure Chemical Corporation; average molecular weight of about 600) was weighed so that the amine loading amount of the adsorbent was 18 wt%, and this was dissolved in 25 g of ethanol (manufactured by Fuji Film Wako Pure Chemical Corporation; special grade) measured into a 300 cc eggplant flask to obtain a PEI ethanol solution. 2

[0025] After that, 6 g of separately weighed carrier (QS30) was added to the PEI ethanol solution, stirred at room temperature for 1 hour, and then while heating this to 60 °C with a rotary evaporator, the pressure inside the system was reduced to 0.02 MPa to remove the ethanol solvent. Further, it was heated at 100 °C for 3 hours while reducing the pressure to 0.02 MPa with a vacuum dryer to uniformly support the amine on the carrier to prepare a CO 2 adsorbent (c1).

[0026] [Example 1] PEI was weighed so that the amine loading amount of the adsorbent was 39 wt%, and this was dissolved in 50 g of ethanol measured into a 300 cc eggplant flask to obtain a PEI ethanol solution. 2 ​​

[0027] Subsequently, 6 g of separately weighed carrier (QS30) was added to the PEI ethanol solution, and after stirring at room temperature for 1 hour, this was heated to 60 °C with a rotary evaporator while reducing the pressure in the system until the pressure reached 0.02 MPa to remove the ethanol solvent. Further, it was heated at 100 °C for 3 hours while reducing the pressure to 0.02 MPa with a vacuum dryer to uniformly support the amine on the carrier, obtaining a CO 2 adsorbent (1).

[0028] [Example 2] PEI was used as CO 2 The procedure was the same as in Example 1 except that the amount of amine supported on the adsorbent was weighed to be 53 wt%, and a CO with the amine uniformly supported on the carrier was obtained 2 adsorbent (2).

[0029] [Example 3] PEI was used as CO 2 The procedure was the same as in Example 1 except that the amount of amine supported on the adsorbent was weighed to be 69 wt%, and a CO with the amine uniformly supported on the carrier was obtained 2 adsorbent (3).

[0030] [Example 4] PEI was used as CO 2 The amount of amine supported on the adsorbent was weighed to be 12 wt%, dissolved in 50 g of ethanol measured into a 300 cc eggplant flask to obtain a PEI ethanol solution.

[0031] Subsequently, 6 g of separately weighed carrier (QS09) was added to the PEI ethanol solution, and after stirring at room temperature for 1 hour, this was heated to 60 °C with a rotary evaporator while reducing the pressure in the system until the pressure reached 0.02 MPa to remove the ethanol solvent. Further, it was heated at 100 °C for 3 hours while reducing the pressure to 0.02 MPa with a vacuum dryer to uniformly support the amine on the carrier, obtaining a CO 2 adsorbent (4).

[0032] [Example 5] PEI was used as CO 2Except for weighing so that the amine loading amount of the adsorbent becomes 29% by weight, it was carried out in the same manner as in Example 4, and CO with the amine uniformly supported on the carrier 2 An adsorbent (5) was prepared.

[0033] [Example 6] PEI was used for CO 2 Except for weighing so that the amine loading amount of the adsorbent becomes 48% by weight, it was carried out in the same manner as in Example 4, and CO with the amine uniformly supported on the carrier 2 An adsorbent (6) was prepared.

[0034] [Example 7] PEI was used for CO 2 The adsorbent was weighed so that the amine loading amount became 14% by weight, and this was dissolved in 50 g of ethanol measured into an eggplant flask with a volume of 300 cc to obtain a PEI ethanol solution.

[0035] After that, 6 g of separately weighed carrier (Q30 beads) was added to the PEI ethanol solution, stirred at room temperature for 1 hour, and then while heating this to 60 °C with a rotary evaporator, the pressure in the system was reduced to 0.02 MPa to remove the ethanol solvent. Further, it was heated at 100 °C for 3 hours while reducing the pressure to 0.02 MPa with a vacuum dryer, and CO with the amine uniformly supported on the carrier 2 An adsorbent (7) was prepared.

[0036] [Example 8] PEI was used for CO 2 Except for weighing so that the amine loading amount of the adsorbent becomes 29% by weight, it was carried out in the same manner as in Example 7, and CO with the amine uniformly supported on the carrier 2 An adsorbent (8) was prepared.

[0037] [Example 9] PEI was used for CO 2 Except for weighing so that the amine loading amount of the adsorbent becomes 34% by weight, it was carried out in the same manner as in Example 7, and CO with the amine uniformly supported on the carrier 2 An adsorbent (9) was prepared.

[0038] [Example 10] PEI to CO 2 A CO adsorbent (10) was prepared in the same manner as in Example 7, except that the amine loading of the adsorbent was weighed so as to be 44% by weight, and the amine was uniformly supported on the carrier. 2 Adsorbent (10) was prepared.

[0039] [Example 11] PEI to CO 2 The amine loading of the adsorbent was weighed so as to be 14% by weight, dissolved in 50 g of ethanol measured into a 300 cc eggplant flask, and a PEI ethanol solution was obtained.

[0040] Then, 6 g of separately weighed carrier (Q30 pellets) was added to the PEI ethanol solution, stirred at room temperature for 1 hour, and then heated to 60 °C with a rotary evaporator while reducing the pressure in the system until the pressure reached 0.02 MPa to remove the ethanol solvent. Further, it was heated at 100 °C for 3 hours while reducing the pressure to 0.02 MPa with a vacuum dryer to uniformly support the amine on the carrier, and a CO adsorbent (11) was prepared. 2 Adsorbent (11) was prepared.

[0041] [Example 12] PEI to CO 2 A CO adsorbent was prepared in the same manner as in Example 11, except that the amine loading of the adsorbent was weighed so as to be 29% by weight, and the amine was uniformly supported on the carrier. 2 Adsorbent (12) was prepared.

[0042] [Example 13] PEI to CO 2 A CO adsorbent was prepared in the same manner as in Example 11, except that the amine loading of the adsorbent was weighed so as to be 34% by weight, and the amine was uniformly supported on the carrier. 2 Adsorbent (13) was prepared.

[0043] [Example 14] PEI to CO 2 A CO adsorbent was prepared in the same manner as in Example 11, except that the amine loading of the adsorbent was weighed so as to be 44% by weight, and the amine was uniformly supported on the carrier. 2 Adsorbent (14) was prepared.

[0044] <Amine loading amount> The amine loading amount was measured for the Pt plate with CO 2 An adsorbent was weighed at 10 mg and measured by TG-DTA (Thermo Plus manufactured by Rigaku). The sample was held at 100 °C for 20 minutes in an inert gas atmosphere to remove moisture, then heated to 950 °C in the presence of oxygen, and the decreased weight was taken as the amine loading amount.

[0045] <CO 2 Desorption amount evaluation test> The CO obtained in the examples and comparative examples 2 The CO of the adsorbent 2 The desorption amount was measured by performing breakthrough measurement and TPD measurement using BELLCAT2 manufactured by MicrotracBEL.

[0046] After weighing approximately 0.05 g of the measurement sample (each CO 2 adsorbent) into the sample tube, the sample tube was held at 30 °C, and while flowing helium gas at 50 ml / min through the sample tube, the temperature was raised to 100 °C at 10 °C / min and held at 100 °C for 1 h for pretreatment of the sample. Then, helium gas containing 400 ppm of CO 2 was flowed at 30 ml / min for 3 hours to adsorb CO 2 (breakthrough measurement).

[0047] After that, after switching to helium gas (100%), the temperature of the sample tube was raised to 100 °C at 10 °C / min and further held at 100 °C for 1 hour to desorb CO 2 This desorbed gas was detected by a TCD detector, and the concentration of the desorbed CO 2 was measured, and the CO desorption amount per 1 g of the sample 2 was taken as the desorption amount.

[0048] <Geometric thickness of amine (geometric film thickness)> The geometric thickness (geometric film thickness) of the amine supported on the CO adsorbents obtained in the examples and comparative examples was calculated by the following formula. 2 Geometric film thickness = Amine loading amount volume / Specific surface area of silica support Geometric film thickness = Amine loading amount volume / Specific surface area of silica support

[0049] The silica carriers, amine loading amounts, geometric film thicknesses, and CO 2 desorption amounts in each example and comparative example are shown in Table 1.

[0050]

Table 1

[0051] From Table 1, it can be seen that the carbon dioxide adsorbent of the present invention has a large amount of carbon dioxide desorbed. Since the amount of carbon dioxide desorbed is large, it is suggested that the carbon dioxide adsorption amount of the carbon dioxide adsorbent of the present invention is large.

[0052] The upper limit value and / or lower limit value of the numerical range described in this specification can each be arbitrarily combined to define a preferable range. For example, the upper limit value and the lower limit value of the numerical range can be arbitrarily combined to define a preferable range, the upper limit values of the numerical range can be arbitrarily combined to define a preferable range, and also the lower limit values of the numerical range can be arbitrarily combined to define a preferable range.

[0053] Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope not departing from the gist of the present disclosure, they are included in the present disclosure.

Claims

**Claim 1** A carbon dioxide adsorbent comprising a silica carrier and an amine supported on the silica carrier, The pore volume of the silica carrier is 0.1 cm ３ / g or more and 1.5 cm ３ / g or less, the specific surface area is 1000 m ２ / g or less, and the average pore diameter is 6 nm or more and 100 nm or less, and wherein the geometric thickness of the supported amine is 1 nm or more and 12 nm or less. The carbon dioxide adsorbent. **Claim 2** The carbon dioxide adsorbent according to claim 1, wherein the geometric thickness is 2 nm or more and 6 nm or less. **Claim 3** The carbon dioxide adsorbent according to claim 1, wherein the geometric thickness is 3 nm or more and 6 nm or less. **Claim 4** The carbon dioxide adsorbent according to claim 1, wherein the silica carrier is silica powder having an average particle diameter of 0.2 μm or more and 40 μm or less. **Claim 5** The specific surface area of the silica carrier is 5 m ２ / g or more and 400 m ２ / g or less. The carbon dioxide adsorbent according to claim 1.

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