Acidic gas adsorbent and acidic gas adsorption device

Abstract

The present invention provides an acidic gas adsorbent which is suitable for performing adsorption and desorption of an acidic gas under relatively mild conditions. An acidic gas adsorbent according to the present invention contains a polymer P which has an amino group. The density of elemental nitrogen in the acidic gas adsorbent is higher than 12.0 mmol / g. If the acidic gas adsorbent is subjected to an adsorption test A1, the adsorption a1 of carbon dioxide is 0.35 mmol / g or more. If the acidic gas adsorbent is subjected to a desorption test B1, the desorption b1 of carbon dioxide is 0.2 mmol / g or more.

Description

Acid gas adsorbents and acid gas adsorption devices

[0001] The present invention relates to an acid gas adsorbent and an acid gas adsorption device.

[0002] In recent years, carbon capture and storage (CCS) and carbon capture and utilization (CCU) have been considered as a way to reduce the amount of carbon dioxide in the atmosphere. In CCS and CCU, carbon dioxide is sometimes captured by separating it from the atmosphere.

[0003] As a method for separating acidic gases such as carbon dioxide from the atmosphere, an adsorption method has been developed in which the acidic gas is adsorbed onto an adsorbent. The adsorbent used in the adsorption method can adsorb the acidic gas by, for example, contacting the atmosphere.

[0004] Examples of adsorbent materials include amine compounds that have the function of adsorbing acidic gases. For example, Patent Document 1 discloses fibrillated cellulose with amino groups introduced therein as an adsorbent. Patent Document 2 discloses an adsorbent with amino groups introduced inside the pores of a mesoporous material.

[0005] International Publication No. 2017 / 009241 U.S. Patent No. 7,767,004

[0006] There is a need for an acid gas adsorbent that is suitable for adsorbing and desorbing acid gases under relatively mild conditions.

[0007] The present invention provides an acidic gas adsorbent comprising a polymer having an amino group, wherein the density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, and when the following adsorption test A1 is performed, the adsorption amount a1 of carbon dioxide is 0.35 mmol / g or more, and when the following desorption test B1 is performed, the desorption amount b1 of carbon dioxide is 0.2 mmol / g or more. Adsorption test A1: A mixed gas composed of carbon dioxide, nitrogen, and water vapor is continuously fed into a container containing the acidic gas adsorbent for 15 hours. Here, the carbon dioxide concentration in the mixed gas is 400 vol ppm, and the mixed gas is at a temperature of 23°C and a humidity of 50% RH. Desorption test B1: While continuing to feed the mixed gas into the container, the acidic gas adsorbent after performing adsorption test A1 is heated at 50°C for 1.5 hours.

[0008] The present invention further provides an acidic gas adsorbent comprising a polymer having an amino group, wherein the density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, and the specific surface area of ​​the acidic gas adsorbent is 0.5 m 2 / g or more, and the glass transition temperature of the polymer is 40°C or less.

[0009] The present invention further provides an acidic gas adsorption device comprising an adsorption section having a gas inlet and a gas outlet, the adsorption section containing the above-mentioned acidic gas adsorbent.

[0010] According to the present invention, it is possible to provide an acidic gas adsorbent that is suitable for adsorbing and desorbing acidic gases under relatively mild conditions.

[0011] FIG. 2 is a diagram for explaining a method for measuring the amount of carbon dioxide adsorbed by an acidic gas adsorbent.

[0012] An acidic gas adsorbent according to a first aspect of the present invention is an acidic gas adsorbent comprising a polymer having an amino group, wherein the density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, and when the following adsorption test A1 is performed, the carbon dioxide adsorption amount a1 is 0.35 mmol / g or more, and when the following desorption test B1 is performed, the carbon dioxide desorption amount b1 is 0.2 mmol / g or more. Adsorption test A1: A mixed gas composed of carbon dioxide, nitrogen, and water vapor is continuously fed into a container containing the acidic gas adsorbent for 15 hours, wherein the carbon dioxide concentration in the mixed gas is 400 vol ppm, and the mixed gas is at a temperature of 23°C and a humidity of 50% RH. Desorption test B1: While continuing to feed the mixed gas into the container, the acidic gas adsorbent after performing adsorption test A1 is heated at 50°C for 1.5 hours.

[0013] In a second aspect of the present invention, for example, in the acidic gas adsorbent according to the first aspect, the ratio of the desorption amount b1 (mmol / g) to the adsorption amount a1 (mmol / g) is 50% or more.

[0014] In a third aspect of the present invention, for example, when the acidic gas adsorbent according to the first or second aspect is subjected to the following desorption test B2, the amount of carbon dioxide desorbed b2 is 0.25 mmol / g or more. Desorption test B2: While continuing to feed the mixed gas into the container, the acidic gas adsorbent after the adsorption test A1 is heated at 65°C for 1.5 hours.

[0015] In a fourth aspect of the present invention, for example, in the acidic gas adsorbent according to the third aspect, the ratio of the desorption amount b2 (mmol / g) to the adsorption amount a1 (mmol / g) is 70% or more.

[0016] In a fifth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the first to fourth aspects, when the following adsorption test A2 is carried out, the adsorption amount a2 of carbon dioxide is 0.05 mmol / g or more. Adsorption test A2: The mixed gas is continuously fed into the container for one hour.

[0017] In a sixth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the first to fifth aspects, when the following adsorption test A3 is carried out, the adsorption amount a3 of carbon dioxide is 0.1 mmol / g or more. Adsorption test A3: The mixed gas is continuously fed into the container for 4 hours.

[0018] In a seventh aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the first to sixth aspects, the glass transition temperature of the polymer is 40° C. or lower.

[0019] In an eighth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the first to seventh aspects, the specific surface area is 0.5 m 2 / g or more.

[0020] An acidic gas adsorbent according to a ninth aspect of the present invention is an acidic gas adsorbent containing a polymer having an amino group, wherein the density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, and the specific surface area of ​​the acidic gas adsorbent is 0.5 m 2 / g or more, and the glass transition temperature of the polymer is 40°C or less.

[0021] In a tenth aspect of the present invention, for example, an acidic gas adsorbent according to any one of the first to ninth aspects has a retention rate R1 of the amount of adsorbable carbon dioxide (mmol / g) of 50% or more when subjected to a heat treatment for 100 hours in an environment of 85°C and 10% RH.

[0022] In an eleventh aspect of the present invention, for example, an acidic gas adsorbent according to any one of the first to tenth aspects has a retention rate R2 of the adsorbable amount of carbon dioxide (mmol / g) of 50% or more when subjected to a heat treatment for 100 hours in an environment of 85°C and 85% RH.

[0023] In a twelfth aspect of the present invention, for example, the acidic gas adsorbent according to any one of the first to eleventh aspects contains the polymer as a main component.

[0024] In a thirteenth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the first to twelfth aspects, the polymer is an amine polymer containing constitutional units derived from epoxy monomers.

[0025] In a fourteenth aspect of the present invention, for example, in the acidic gas adsorbent according to the thirteenth aspect, the amine polymer comprises at least one selected from the group consisting of a polymer P1 of a monomer group containing an amine monomer and an epoxy monomer, and a reaction product P2 of a compound group containing an amine prepolymer and an epoxy monomer.

[0026] In a fifteenth aspect of the present invention, for example, in the acidic gas adsorbent according to the fourteenth aspect, the weight average molecular weight of the amine prepolymer is 300 or more.

[0027] In a sixteenth aspect of the present invention, for example, in the acidic gas adsorbent according to the fourteenth or fifteenth aspect, the amine prepolymer contains polyethyleneimine.

[0028] In a seventeenth aspect of the present invention, for example, in the acidic gas adsorbent according to the fourteenth aspect, the amine monomer includes an aliphatic amine.

[0029] In an eighteenth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the thirteenth to seventeenth aspects, the epoxy equivalent of the epoxy monomer is 150 g / eq. or less.

[0030] In a nineteenth aspect of the present invention, for example, in the acidic gas adsorbent according to any one of the thirteenth to eighteenth aspects, the epoxy monomer includes a polyfunctional epoxy compound having an ether group.

[0031] In a twentieth aspect of the present invention, for example, the acidic gas adsorbent according to any one of the first to nineteenth aspects has a porous structure.

[0032] An acidic gas adsorption device according to a twenty-first aspect of the present invention comprises an adsorption section having a gas inlet and a gas outlet, and the adsorption section contains an acidic gas adsorbent according to any one of the first to twentieth aspects.

[0033] The present invention will be described in detail below, but the following description is not intended to limit the present invention to a specific embodiment.

[0034] The acidic gas adsorbent of this embodiment contains an amino group-containing polymer P. The density d of nitrogen elements in the acidic gas adsorbent is greater than 12.0 mmol / g.

[0035] The density d of the nitrogen element in the acidic gas adsorbent is preferably 12.2 mmol / g or more, and may be 12.5 mmol / g or more, 13.0 mmol / g or more, 13.5 mmol / g or more, 14.0 mmol / g or more, 14.5 mmol / g or more, 15.0 mmol / g or more, 15.5 mmol / g or more, 16.0 mmol / g or more, 16.5 mmol / g or more, 17.0 mmol / g or more, or even 17.5 mmol / g or more. The larger the density d of the nitrogen element, the greater the amount of acidic gas adsorbed by the acidic gas adsorbent and the rate at which the acidic gas is adsorbed. The upper limit of the density d of the nitrogen element is not particularly limited and may be, for example, 30 mmol / g or 20 mmol / g. In this specification, the density d of the nitrogen element in the acidic gas adsorbent means the amount of nitrogen element contained in 1 g of the acidic gas adsorbent. When all of the nitrogen elements contained in the acidic gas adsorbent are derived from amino groups, the density d of the nitrogen elements can be considered to be the density of the amino groups in the acidic gas adsorbent.

[0036] The density d of the nitrogen element can be measured by the following method. First, the weight ratio w (wt%) of the nitrogen element contained in the acidic gas adsorbent is measured using a commercially available CHN elemental analyzer. Based on the obtained results, the density d of the nitrogen element can be calculated using the following formula: Density d (mmol / g) = (weight ratio w (wt%) × 1000) / (atomic weight of nitrogen × 100)

[0037] Furthermore, when the acidic gas adsorbent of this embodiment is subjected to the following adsorption test A1, the adsorption amount a1 of carbon dioxide is 0.35 mmol / g or more. Furthermore, when the following desorption test B1 is performed, the desorption amount b1 of carbon dioxide is 0.2 mmol / g or more. Adsorption test A1: A mixed gas G composed of carbon dioxide, nitrogen, and water vapor is continuously fed into a container containing the acidic gas adsorbent for 15 hours. Here, the carbon dioxide concentration in the mixed gas G is 400 vol ppm, and the mixed gas G has a temperature of 23°C and a humidity of 50% RH. Desorption test B1: While continuously feeding the mixed gas G into the above container, the acidic gas adsorbent after the adsorption test A1 is heated at 50°C for 1.5 hours.

[0038] (Adsorption Test and Desorption Test) The following describes the details of the adsorption test A1 and the desorption test B1. The adsorption test A1 and the desorption test B1 can be performed using, for example, a measurement device 10 shown in FIG. 1 . The measurement device 10 includes a first tank 30 and a second tank 31. As an example, the first tank 30 stores dry nitrogen, and the second tank 31 stores a mixed gas of dry nitrogen and dry carbon dioxide. The concentration of carbon dioxide in the mixed gas in the second tank 31 is, for example, 5 vol %.

[0039] The measuring device 10 further includes a first container 40 containing water 70, and a first path 60 for sending nitrogen from the first tank 30 to the first container 40. The first path 60 has one end connected to a gas outlet of the first tank 30 and the other end disposed in the water 70 of the first container 40. The nitrogen sent from the first tank 30 to the first container 40 is humidified by contact with the water 70. A mass flow controller 35 is disposed in the first path 60 for adjusting the flow rate of nitrogen sent from the first tank 30 to the first container 40.

[0040] The measuring apparatus 10 further includes a second container 41, a second path 62, and a bypass path 61. The second path 62 connects the first container 40 and the second container 41. The humidified nitrogen sent to the first container 40 is sent to the second container 41 via the second path 62. The bypass path 61 branches off from the first path 60 at a position between the first tank 30 and the mass flow controller 35 and connects to the second path 62. A portion of the nitrogen sent from the first tank 30 flows into the bypass path 61 and is sent to the second container 41 via the second path 62. A mass flow controller 36 is disposed in the bypass path 61 to adjust the flow rate of nitrogen sent from the first tank 30 to the bypass path 61.

[0041] The measuring device 10 further includes a third path 63 for sending the mixed gas from the second tank 31 to the second path 62. The third path 63 has one end connected to the gas outlet of the second tank 31 and the other end connected to the second path 62. A mass flow controller 37 is disposed in the third path 63 for adjusting the flow rate of the mixed gas sent from the second tank 31 to the second path 62. The mixed gas sent to the second path 62 is sent to the second container 41 through the second path 62.

[0042] The measuring device 10 further includes a third container 42 and a fourth path 64. The third container 42 contains water 71 and an adsorption unit 21 disposed in the water 71. In the third container 42, the temperature of the water 71 is maintained at 23°C. The adsorption unit 21 has a gas inlet 22 and a gas outlet 23. The adsorption unit 21 functions as a container that contains an acidic gas adsorbent therein. The adsorption unit 21 is configured to prevent the water 71 from penetrating into the interior. The adsorption unit 21 is typically a tube made of a hydrophobic resin, for example, a fluororesin such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA). As an example, the tube serving as the adsorption unit 21 has an inner diameter of 4 mm and an outer diameter of 6 mm. The adsorption unit 21 is configured to be detachable from the measuring device 10.

[0043] The measuring device 10 can also be used as an acidic gas adsorption device equipped with an adsorption unit 21. In another aspect, the present invention provides an acidic gas adsorption device 20 equipped with an adsorption unit 21 having a gas inlet 22 and a gas outlet 23, the adsorption unit 21 containing an acidic gas adsorbent.

[0044] The fourth path 64 connects the second container 41 and the third container 42. Specifically, the fourth path 64 is connected to the gas inlet 22 of the adsorption unit 21 in the third container 42. A first concentration meter 50 is disposed in the fourth path 64 to measure the concentration of carbon dioxide in the gas supplied to the adsorption unit 21. As the first concentration meter 50, for example, a CO2 / H2O gas analyzer LI-850-3 manufactured by LI-COR Corporation can be used.

[0045] The measurement device 10 further includes a fifth path 65 connected to the gas outlet 23 of the adsorption unit 21 for discharging gas from the adsorption unit 21 to the outside of the measurement device 10. A back pressure valve 55 and a second concentration meter 51 are disposed in the fifth path 65. The back pressure valve 55 allows the pressure inside the adsorption unit 21 to be adjusted to a constant value. The second concentration meter 51 can measure the concentration of carbon dioxide in the gas discharged from the adsorption unit 21. For example, an LI-850-3 CO2 / H2O gas analyzer manufactured by LI-COR Corporation can be used as the second concentration meter 51.

[0046] Each path of the measuring device 10 is made up of, for example, a metal or resin pipe.

[0047] [Pretreatment] First, an acidic gas adsorbent is prepared and dried. The acidic gas adsorbent is used before undergoing the heat resistance test and moist heat resistance test described below. The drying process is performed, for example, by treating the acidic gas adsorbent for two hours or more under conditions of 60°C in a vacuum atmosphere. Next, the dried acidic gas adsorbent is packed into the adsorption unit 21 in a dry room with a dew point of approximately -60°C. The weight of the acidic gas adsorbent packed into the adsorption unit 21 is, for example, 50 mg. Next, the fourth path 64 and the fifth path 65 are connected to both ends of the adsorption unit 21, and the adsorption unit 21 is immersed in water 71 in the third container 42.

[0048] Next, nitrogen from the first tank 30 and the mixed gas from the second tank 31 are supplied to the second container 41 via the first path 60, the second path 62, the bypass path 61, and the third path 63 of the measurement device 10. These gases are mixed in the second container 41 to obtain a mixed gas G composed of carbon dioxide, nitrogen, and water vapor. In the second container 41, the carbon dioxide concentration in the mixed gas G is adjusted to 400 vol ppm. The mixed gas G has a temperature of 23°C and a humidity of 50% RH. The mixed gas G is supplied to the adsorption unit 21 via the fourth path 64 at a flow rate sufficient for the weight of the acidic gas adsorbent, for example, a flow rate of 300 mL / min for 50 mg of acidic gas adsorbent. In the adsorption unit 21, the pressure of the mixed gas G is adjusted to, for example, 107 kPa by the back pressure valve 55.

[0049] Next, while the mixed gas G is being supplied to the adsorption unit 21, the adsorption unit 21 is removed from the third container 42 and immersed in a water bath (not shown) at 80°C for two hours or more. The adsorption unit 21 is immersed in the water bath until the carbon dioxide concentration measured by the first concentration meter 50 and the carbon dioxide concentration measured by the second concentration meter 51 become substantially the same value. This completes the pretreatment of the acidic gas adsorbent in the adsorption unit 21.

[0050] [Adsorption Test] Next, while the mixed gas G is being supplied to the adsorption unit 21, the adsorption unit 21 is removed from the hot water bath and immersed in the water 71 in the third container 42. This starts a carbon dioxide adsorption test (adsorption test A1) for the acidic gas adsorbent in the adsorption unit 21. The adsorption test is carried out for 15 hours after the start. Specifically, the mixed gas G is continuously supplied to the adsorption unit 21 for 15 hours. When the adsorption test is carried out for 15 hours, it can usually be considered that the adsorption of carbon dioxide by the acidic gas adsorbent has reached equilibrium.

[0051] In the adsorption test A1, the amount of carbon dioxide adsorbed by the acid gas adsorbent during the 15 hours from the start of the test, M1, is measured. The amount of carbon dioxide adsorbed by the acid gas adsorbent can be calculated from the results of measuring the difference over time between the carbon dioxide concentration measured by the first concentration meter 50 and the carbon dioxide concentration measured by the second concentration meter 51. Based on the amount of substance M1, the amount of carbon dioxide adsorbed by 1 g of the acid gas adsorbent over 15 hours is calculated, and the calculated value is identified as the adsorption amount a1.

[0052] [Desorption Test] Next, while the mixed gas G continues to be supplied to the adsorption unit 21, the adsorption unit 21 is removed from the third container 42 and immersed in a water bath (not shown) at 50°C. This starts a carbon dioxide desorption test (desorption test B1) for the acidic gas adsorbent in the adsorption unit 21. The desorption test is continued for 1.5 hours after the start of the test.

[0053] In desorption test B1, the amount of carbon dioxide desorbed from the acid gas adsorbent within 1.5 hours from the start is measured, M2. The amount of carbon dioxide desorbed from the acid gas adsorbent can be calculated from the results of measuring the difference over time between the carbon dioxide concentration measured by first concentration meter 50 and the carbon dioxide concentration measured by second concentration meter 51. The amount of carbon dioxide desorbed from 1 g of the acid gas adsorbent in 1.5 hours is calculated based on the amount of substance M2, and the calculated value is identified as the desorption amount b1.

[0054] [Adsorption Amount and Desorption Amount] In the acidic gas adsorbent of this embodiment, the carbon dioxide adsorption amount a1 when adsorption test A1 is performed is preferably 0.4 mmol / g or more, and may be 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, 1.8 mmol / g or more, 2.0 mmol / g or more, 2.1 mmol / g or more, 2.2 mmol / g or more, or even 2.3 mmol / g or more. The upper limit of the carbon dioxide adsorption amount a1 is not particularly limited, and is, for example, 10 mmol / g.

[0055] In the acidic gas adsorbent of this embodiment, the carbon dioxide desorption amount b1 when desorption test B1 is performed is preferably 0.25 mmol / g or more, and may be 0.3 mmol / g or more, 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, or even 1.8 mmol / g or more. The upper limit of the carbon dioxide desorption amount b1 is not particularly limited and is, for example, 10 mmol / g.

[0056] The ratio of the desorption amount b1 (mmol / g) to the adsorption amount a1 (mmol / g) (50°C desorption rate) is, for example, 40% or more, and may be 45% or more, 50% or more, 60% or more, 70% or more, 80% or more, or even 90% or more. The upper limit of the 50°C desorption rate is not particularly limited and is, for example, 99%.

[0057] In another aspect, the present invention provides an acidic gas adsorbent comprising a polymer P having amino groups, wherein the density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, when the above-mentioned adsorption test A1 is performed, the adsorption amount a1 of carbon dioxide is 0.35 mmol / g or more, and when the above-mentioned desorption test B1 is performed, the ratio of the desorption amount b1 (mmol / g) of carbon dioxide when the above-mentioned desorption test B1 is performed to the adsorption amount a1 (mmol / g) (50°C desorption rate) is 40% or more. In this acidic gas adsorbent, the 50°C desorption rate may satisfy the above-mentioned range, and in particular may be 50% or more.

[0058] When the acidic gas adsorbent of this embodiment is subjected to the following desorption test B2, the amount of carbon dioxide desorbed b2 is preferably 0.25 mmol / g or more. Desorption test B2: While continuously supplying the mixed gas G to the container (the adsorption section 21) containing the acidic gas adsorbent, the acidic gas adsorbent after the above adsorption test A1 is heated at 65°C for 1.5 hours.

[0059] Desorption test B2 can be performed in the same manner as desorption test B1 above, except that the adsorption section 21 is immersed in a water bath at 65°C. The amount b2 of carbon dioxide desorption when desorption test B2 is performed is preferably 0.3 mmol / g or more, and may be 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, 1.8 mmol / g or more, 2.0 mmol / g or more, 2.1 mmol / g or more, or even 2.2 mmol / g or more. The upper limit of the amount b2 of carbon dioxide desorption is not particularly limited, and is, for example, 10 mmol / g.

[0060] The ratio of the desorption amount b2 (mmol / g) to the adsorption amount a1 (mmol / g) (65°C desorption rate) is, for example, 40% or more, and may be 45% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more, 95% or more, 96% or more, or even 97% or more, or may be 100%.

[0061] When the following adsorption test A2 is performed on the acidic gas adsorbent of this embodiment, the carbon dioxide adsorption amount a2 is preferably 0.05 mmol / g or more. The adsorption amount a2 can be used as an index of the rate at which acidic gases are adsorbed. In other words, the larger the adsorption amount a2, the faster the acidic gas adsorbent adsorbs acidic gases. Adsorption test A2: Mixed gas G is continuously fed into a container (the above-mentioned adsorption section 21) containing the acidic gas adsorbent for one hour.

[0062] Adsorption Test A2 can be performed in the same manner as Adsorption Test A1, except that the test time is changed from 15 hours to 1 hour. The carbon dioxide adsorption amount a2 when Adsorption Test A2 is performed is preferably 0.1 mmol / g or more, and may be 0.2 mmol / g or more, 0.3 mmol / g or more, 0.4 mmol / g or more, 0.5 mmol / g or more, 0.6 mmol / g or more, 0.7 mmol / g or more, 0.8 mmol / g or more, or even 0.9 mmol / g or more. The upper limit of the carbon dioxide adsorption amount a2 is not particularly limited and may be, for example, 5 mmol / g.

[0063] When the following adsorption test A3 is performed on the acidic gas adsorbent of this embodiment, the carbon dioxide adsorption amount a3 is preferably 0.1 mmol / g or more. The adsorption amount a3 can also be used as an index of the rate at which acidic gases are adsorbed. In other words, the larger the adsorption amount a3, the faster the acidic gas adsorbent adsorbs acidic gases. Adsorption test A3: Mixed gas G is continuously fed into a container (the above-mentioned adsorption section 21) containing the acidic gas adsorbent for 4 hours.

[0064] Adsorption Test A3 can be performed in the same manner as Adsorption Test A1, except that the test time is changed from 15 hours to 4 hours. The carbon dioxide adsorption amount a3 when Adsorption Test A3 is performed is preferably 0.3 mmol / g or more, and may be 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, 1.7 mmol / g or more, or even 1.8 mmol / g or more. The upper limit of the carbon dioxide adsorption amount a3 is not particularly limited and may be, for example, 5 mmol / g.

[0065] (Heat Resistance Test) The acidic gas adsorbent of this embodiment preferably has high heat resistance. The heat resistance of the acidic gas adsorbent can be evaluated, for example, by conducting a heat resistance test on the acidic gas adsorbent. The heat resistance test can be performed, for example, by subjecting the acidic gas adsorbent to a heat treatment for 100 hours in an environment of 85°C and 10% RH. As an example, when the acidic gas adsorbent is subjected to a heat treatment for 100 hours in an environment of 85°C and 10% RH, the maintenance rate R1 of the amount of adsorbable carbon dioxide (mmol / g) is, for example, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 92% or more, 94% or more, 95% or more, or even 96% or more. The higher the maintenance rate R1, the higher the heat resistance of the acidic gas adsorbent. An acidic gas adsorbent with high heat resistance can be said to have high durability in long-term use. The upper limit of the maintenance rate R1 is not particularly limited, and is, for example, 99%.

[0066] Specifically, the retention rate R1 can be determined by the following method. First, in a dry room with a dew point of approximately -60°C, the acidic gas adsorbent is placed in a glass container (for example, a Labolan screw cap bottle manufactured by AS ONE Corporation). Next, the glass container is placed in a thermo-hygrostat (for example, a PSL-2J manufactured by Espec Corporation) and heat-treated in air at 85°C and 10% RH for 100 hours. Next, the heat-treated acidic gas adsorbent is placed in a vacuum dryer (for example, a VOS-310C manufactured by EYELA Corporation) in the dry room and treated for 2 hours or more under a vacuum atmosphere at 60°C. The carbon dioxide adsorption amount a4 when the above-mentioned adsorption test A1 is performed on the treated acidic gas adsorbent is measured. Based on the obtained adsorption amount a4 and the carbon dioxide adsorption amount a1 when the adsorption test A1 is performed on the acidic gas adsorbent before the heat resistance test, the retention rate R1 can be calculated by the following formula. Maintenance rate R1 (%) = adsorption amount a4 (mmol / g) ÷ adsorption amount a1 (mmol / g) x 100

[0067] The carbon dioxide adsorption amount a4 may be, for example, 0.35 mmol / g or more, 0.4 mmol / g or more, 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, 1.8 mmol / g or more, or even 2.0 mmol / g or more. The upper limit of the carbon dioxide adsorption amount a4 is not particularly limited and is, for example, 10 mmol / g.

[0068] (Moist Heat Resistance Test) The acidic gas adsorbent of this embodiment preferably has high moist heat resistance. The moist heat resistance of the acidic gas adsorbent can be evaluated, for example, by conducting a moist heat resistance test on the acidic gas adsorbent. The moist heat resistance test can be performed, for example, by subjecting the acidic gas adsorbent to a heat treatment at 85°C and 85% RH for 100 hours. As an example, when the acidic gas adsorbent is subjected to a heat treatment at 85°C and 85% RH for 100 hours, the retention rate R2 of the amount of adsorbable carbon dioxide (mmol / g) is, for example, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or even 96% or more. The higher the retention rate R2, the higher the moist heat resistance of the acidic gas adsorbent. An acidic gas adsorbent with high moist heat resistance can be said to have high durability in long-term use. The upper limit of the maintenance rate R2 is not particularly limited, and is, for example, 99%.

[0069] Specifically, the retention rate R2 can be determined by the following method. First, the acidic gas adsorbent is placed in a glass container (e.g., a Labolan screw cap bottle manufactured by AS ONE Corporation) in a dry room with a dew point of approximately -60°C. Next, the glass container is placed in a thermo-hygrostat (e.g., a PSL-2J manufactured by Espec Corporation) and heat-treated in air at 85°C and 85% RH for 100 hours. Next, the heat-treated acidic gas adsorbent is placed in a vacuum dryer (e.g., a VOS-310C manufactured by EYELA Corporation) in the dry room and treated for 2 hours or more under a vacuum atmosphere at 60°C. The carbon dioxide adsorption amount a5 of the treated acidic gas adsorbent when the above-mentioned adsorption test A1 is performed is measured. The retention rate R2 can be calculated by the following formula based on the obtained adsorption amount a5 and the carbon dioxide adsorption amount a1 when the adsorption test A1 is performed on the acidic gas adsorbent before the moist heat resistance test. Maintenance rate R2 (%) = adsorption amount a5 (mmol / g) ÷ adsorption amount a1 (mmol / g) x 100

[0070] The carbon dioxide adsorption amount a5 is, for example, 0.35 mmol / g or more, and may be 0.4 mmol / g or more, 0.5 mmol / g or more, 0.8 mmol / g or more, 1.0 mmol / g or more, 1.3 mmol / g or more, 1.5 mmol / g or more, 1.8 mmol / g or more, 2.0 mmol / g or more, or even 2.1 mmol / g or more. The upper limit of the carbon dioxide adsorption amount a5 is not particularly limited and is, for example, 10 mmol / g.

[0071] (Polymer) In the acidic gas adsorbent, the polymer P has the function of adsorbing acidic gases due to amino groups. The polymer P, for example, contains at least one amino group selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group. From the viewpoint of acidic gas adsorption, the polymer P preferably contains at least one selected from the group consisting of a primary amino group and a secondary amino group, and particularly preferably contains a secondary amino group. In other words, the amino group possessed by the polymer P preferably contains a secondary amino group. The polymer P having a secondary amino group also tends to easily desorb the adsorbed acidic gas. In other words, the polymer P having a secondary amino group allows the regeneration treatment of the acidic gas adsorbent to be performed under relatively mild conditions. The polymer P may contain a tertiary amino group, but it does not have to contain a tertiary amino group.

[0072] The weight ratio of nitrogen elements in polymer P is, for example, 5 wt% or more, preferably 10 wt% or more. The higher this weight ratio, the more the acidic gas adsorbent tends to improve its acidic gas adsorption ability. The upper limit of the weight ratio of nitrogen elements in polymer P is not particularly limited, and is, for example, 30 wt%. Note that when all of the nitrogen elements contained in polymer P are derived from amino groups, the weight ratio of nitrogen elements described above can be regarded as the weight ratio of amino groups in polymer P.

[0073] The density of the nitrogen element in the polymer P is, for example, greater than 12.0 mmol / g, preferably 12.2 mmol / g or more, 12.5 mmol / g or more, 13.0 mmol / g or more, 13.5 mmol / g or more, 14.0 mmol / g or more, 14.5 mmol / g or more, 15.0 mmol / g or more, or even 15.5 mmol / g or more. The upper limit of the density of the nitrogen element is not particularly limited, and may be, for example, 30 mmol / g or 20 mmol / g. In this specification, the density of the nitrogen element in the polymer P means the amount of nitrogen element contained in 1 g of the polymer P, and can be measured, for example, by the same method as the density d of the nitrogen element in the acidic gas adsorbent described above. Note that when all the nitrogen elements contained in the polymer P are derived from amino groups, the density of the nitrogen element can be regarded as the density of the amino groups in the polymer P.

[0074] The polymer P may contain a functional group other than an amino group. Examples of the functional group include a hydroxyl group, an ether group, an ester group, and an amide group. The polymer P preferably contains an ether group as the functional group.

[0075] The polymer P is, for example, an amine polymer containing a structural unit U1 derived from an epoxy monomer. This amine polymer contains at least one selected from the group consisting of a polymer P1 of a monomer group containing an amine monomer and an epoxy monomer, and a reactant P2 of a compound group containing an amine prepolymer and an epoxy monomer, and is preferably reactant P2. Reactant P2 tends to not only have a high nitrogen element density, but also to have high heat resistance and moist heat resistance. A specific example of reactant P2 is an amine prepolymer crosslinked with an epoxy monomer (crosslinked product).

[0076] As described above, the monomers for forming the polymer P1 include amine monomers and epoxy monomers, and preferably consist only of these monomers. That is, the polymer P1 is preferably a polymer of amine monomers and epoxy monomers.

[0077] The amine monomer is a monomer containing at least one amino group, for example, at least one primary amino group. The number of primary amino groups contained in the amine monomer is preferably 2 or more, may be 3 or more, or may be 4 or more. The upper limit of the number of primary amino groups is not particularly limited, and is, for example, 10. The amine monomer may contain a secondary amino group or a tertiary amino group in addition to the primary amino group, but may not contain a tertiary amino group. In the amine monomer, the ratio of the number of primary amino groups to the number of all amino groups is not particularly limited, and is, for example, 10% or more, preferably 20% or more, more preferably 30% or more, and may even be 40% or more. The upper limit of this ratio is not particularly limited, and may be, for example, 80% or 60%.

[0078] The molecular weight of the amine monomer is, for example, 50 or more, preferably 100 or more, and more preferably 150 or more. The larger the molecular weight of the amine monomer, the easier it is to adjust the density of the nitrogen element in the polymer P1. The upper limit of the molecular weight of the amine monomer is not particularly limited, and is, for example, less than 1,000, preferably 500 or less, and may be 300 or less. The amine equivalent of the amine monomer is, for example, 10 g / eq. or more, preferably 20 g / eq. or more, and more preferably 30 g / eq. or more. The larger the amine equivalent of the amine monomer, the easier it is to adjust the density of the nitrogen element in the polymer P1. The upper limit of the amine equivalent of the amine monomer is not particularly limited, and is, for example, 150 g / eq. or less, preferably 100 g / eq. or less, and may be 50 g / eq. or less. In this specification, the amine equivalent means the mass of the amine monomer relative to 1 equivalent of active hydrogen of the primary amino group contained in the amine monomer.

[0079] Examples of the amine monomers include ethylamine, ethylenediamine, 1,4-butylenediamine, 1,5-pentanediamine, 1,6-hexanediamine, 1,7-heptanediamine, 1,8-octanediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, iminobispropylamine, bis(hexamethylene)triamine, 1,3,6-trisaminomethylhexane, tris(2-aminoethyl)amine, N,N' Examples of the amine monomer include aliphatic amines such as 3,9-bis(3-aminopropyl)ethylenediamine, polymethylenediamine, trimethylhexamethylenediamine, and polyetherdiamine; and alicyclic amines such as isophoronediamine, menthanediamine, piperazine, N-aminoethylpiperazine, 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro(5,5)undecane adduct, bis(4-amino-3-methylcyclohexyl)methane, bis(4-aminocyclohexyl)methane, and modified products thereof. The amine monomer preferably contains an aliphatic amine, particularly triethylenetetramine (TETA). The amine monomers can be used alone or in combination of two or more.

[0080] The epoxy monomer is a monomer containing at least one epoxy group. The number of epoxy groups contained in the epoxy monomer is preferably 2 or more, and may be 3 or more, or 4 or more. The greater the number of epoxy groups, the more crosslinking points in the epoxy monomer and the denser the crosslinked structure in the polymer P1, which tends to improve heat resistance and moist heat resistance. The upper limit of the number of epoxy groups contained in the epoxy monomer is not particularly limited and is, for example, 10.

[0081] The molecular weight of the epoxy monomer is not particularly limited and is, for example, less than 1,000, preferably 500 or less. The epoxy equivalent of the epoxy monomer is not particularly limited and is, for example, 150 g / eq. or less, preferably 100 g / eq. or less. The smaller the epoxy equivalent of the epoxy monomer, the higher the density of nitrogen elements in polymer P1 tends to be. The lower limit of the epoxy equivalent of the epoxy monomer is not particularly limited and is, for example, 50 g / eq. Note that the epoxy equivalent means the mass of an epoxy monomer containing one equivalent of an epoxy group.

[0082] Examples of epoxy monomers include monofunctional epoxy compounds such as n-butyl glycidyl ether, higher alcohol glycidyl ether, allyl glycidyl ether, 2-ethylhexyl glycidyl ether, phenyl glycidyl ether, cresyl glycidyl ether, p-sec-butylphenyl glycidyl ether, and t-butylphenyl glycidyl ether; diepoxy alkanes such as 1,5-hexadiene diepoxide, 1,7-octadiene diepoxide, and 1,9-decadiene diepoxide; and (poly)ethylene glycol diglycidyl ether. polyfunctional epoxy compounds having an ether group such as N,N,N',N'-tetraglycidyl metaxylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane; and polyfunctional epoxy compounds having an amino group such as N,N,N',N'-tetraglycidyl metaxylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[0083] The epoxy monomer may be an aromatic epoxy resin, a non-aromatic epoxy resin, or the like, depending on the circumstances. Examples of aromatic epoxy resins include polyphenyl-based epoxy resins, epoxy resins containing a fluorene ring, epoxy resins containing triglycidyl isocyanurate, and epoxy resins containing a heteroaromatic ring (e.g., a triazine ring). Examples of polyphenyl-based epoxy resins include bisphenol A-type epoxy resins, brominated bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, bisphenol AD-type epoxy resins, stilbene-type epoxy resins, biphenyl-type epoxy resins, bisphenol A novolac-type epoxy resins, cresol novolac-type epoxy resins, diaminodiphenylmethane-type epoxy resins, and tetrakis(hydroxyphenyl)ethane-based epoxy resins. Examples of non-aromatic epoxy resins include aliphatic glycidyl ether-type epoxy resins, aliphatic glycidyl ester-type epoxy resins, alicyclic glycidyl ether-type epoxy resins, alicyclic glycidyl amine-type epoxy resins, and alicyclic glycidyl ester-type epoxy resins.

[0084] The epoxy monomers can be used alone or in combination of two or more. When a monofunctional epoxy compound is used, it is preferably used in combination with another epoxy monomer containing two or more epoxy groups. The monofunctional epoxy compound can also be used as a reactive diluent for adjusting the viscosity of the monomers for forming the polymer P1.

[0085] The epoxy monomer preferably includes a multifunctional epoxy compound having an ether group, such as ethylene glycol diglycidyl ether (EDE) or pentaerythritol tetraglycidyl ether (PETG). EDE and PETG have a small epoxy equivalent and can easily lower the glass transition temperature Tg of the polymer P. These epoxy compounds also tend to be low in cost. The epoxy monomer may include a multifunctional epoxy compound having an amino group, such as N,N,N',N'-tetraglycidylmetaxylenediamine or 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, in addition to or instead of the multifunctional epoxy compound having an ether group.

[0086] The amine prepolymer for forming the reactant P2 contains, for example, at least one amino group, particularly a primary amino group. The number of primary amino groups contained in the amine prepolymer is preferably two or more, may be three or more, or may be four or more. The upper limit of the number of primary amino groups is not particularly limited and may be, for example, 100. The amine prepolymer may contain secondary amino groups or tertiary amino groups in addition to primary amino groups. In the amine prepolymer, the ratio of the number of primary amino groups to the total number of amino groups is not particularly limited and may be, for example, 10% or more, preferably 20% or more, more preferably 30% or more, or even 40% or more. The higher this ratio, the more crosslinking points in the amine prepolymer increase, and the denser the crosslinked structure in the reactant P2 becomes, which tends to improve heat resistance and moist heat resistance. The upper limit of this ratio is not particularly limited and may be, for example, 80% or 60%.

[0087] The weight-average molecular weight of the amine prepolymer is not particularly limited and may be, for example, 200 or more, 300 or more, 500 or more, 1000 or more, or even 1500 or more. Amine prepolymers with a high weight-average molecular weight tend to be safer to handle. Furthermore, when an amine prepolymer with a high weight-average molecular weight is used, the density of nitrogen elements in the reactant P2 tends to increase. The upper limit of the weight-average molecular weight of the amine prepolymer is not particularly limited and is, for example, 5000. The amine equivalent of the amine prepolymer is, for example, 10 g / eq. or more, preferably 20 g / eq. or more, and more preferably 30 g / eq. or more. The upper limit of the amine equivalent of the amine prepolymer is not particularly limited and may be, for example, 200 g / eq. or less, 150 g / eq. or less, or even 100 g / eq. or less. The number of structural units contained in the amine prepolymer (degree of polymerization) is not particularly limited and is, for example, 5 to 100.

[0088] Examples of amine prepolymers include aliphatic polyamines such as polyethyleneimine and polyalkylenepolyamines; (meth)acrylic polymers having amino groups such as aminoethylated acrylic polymers; and aliphatic polyamidoamines formed by the reaction of polyamines with dimer acids. The amine prepolymer preferably contains an aliphatic polyamine, particularly polyethyleneimine (PEI). The amine prepolymers can be used alone or in combination of two or more.

[0089] Amine prepolymers, particularly PEI, tend to be safer to handle than amine monomers. For example, the amine prepolymer may not be classified as a hazardous material under the Fire Service Act or as a target substance under the Poisonous and Deleterious Substances Control Act. The amine prepolymer may have a negative result in a mutagenicity test (Ames test). The amine prepolymer may also be classified as a mild or moderate irritant in a skin irritation test (primary skin irritation test using rabbits).

[0090] Epoxy monomers for forming reactant P2 include those described above for polymer P1.

[0091] As described above, polymer P as an amine polymer contains a structural unit U1 derived from an epoxy monomer. When polymer P is polymer P1, polymer P further contains a structural unit U2 derived from an amine monomer. The content of structural unit U1 in polymer P, particularly polymer P1, is, for example, 20 wt % to 70 wt %. The content of structural unit U2 in polymer P, particularly polymer P1, is, for example, 30 wt % or more, preferably 50 wt % or more. The upper limit of the content of structural unit U2 is not particularly limited, and is, for example, 80 wt %.

[0092] The glass transition temperature Tg of the polymer P is not particularly limited, and is, for example, 40°C or lower, preferably 30°C or lower, more preferably 20°C or lower, and even more preferably 15°C or lower, and may be 10°C or lower, 5°C or lower, or 0°C or lower. When the glass transition temperature Tg of the polymer P is low to this extent, the rate at which the acidic gas adsorbent adsorbs the acidic gas tends to be high. The lower limit of the glass transition temperature Tg of the polymer P is, for example, -100°C, preferably -50°C, and more preferably -10°C, from the viewpoint of sufficiently ensuring the adsorption ability of the acidic gas in the acidic gas adsorbent and from the viewpoint of heat resistance. In this specification, the glass transition temperature Tg is the midpoint glass transition temperature (T mg ) The polymer P generally corresponds to a thermosetting resin. The polymer P is solid at, for example, 25°C, preferably in the range of 25°C to 80°C.

[0093] The weight average molecular weight of the polymer P is not particularly limited and is, for example, 500 or more, preferably 1000 or more, more preferably 10000 or more, and even more preferably 100000 or more. The upper limit of the weight average molecular weight of the polymer P is, for example, 10,000,000.

[0094] The acidic gas adsorbent contains, for example, polymer P as a main component. In this specification, "main component" means the component contained in the acidic gas adsorbent in the largest amount by weight. The content of polymer P in the acidic gas adsorbent is, for example, 50 wt% or more, preferably 70 wt% or more, more preferably 90 wt% or more, and may be 95 wt% or more, or may be 99 wt% or more. The acidic gas adsorbent may be composed essentially of polymer P only. The higher the content of polymer P, the more the acidic gas adsorbent tends to improve its ability to adsorb acidic gases.

[0095] The acidic gas adsorbent may be composed substantially of polymer P alone, or may further contain other components in addition to polymer P. Examples of other components include reaction accelerators, plasticizers, pigments, dyes, antioxidants, conductive materials, antistatic agents, UV absorbers, flame retardants, and antioxidants. The reaction accelerator is used, for example, when synthesizing polymer P. Examples of the reaction accelerator include tertiary amines such as triethylamine and tributylamine; and imidazoles such as 2-phenol-4-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenol-4,5-dihydroxyimidazole. These reaction accelerators can, for example, accelerate the reaction for synthesizing polymer P1.

[0096] The weight ratio of nitrogen elements in the acidic gas adsorbent is, for example, 5 wt% or more, preferably 10 wt% or more. The higher this weight ratio, the more the acidic gas adsorbent tends to improve its ability to adsorb acidic gases. The upper limit of the weight ratio of nitrogen elements in the acidic gas adsorbent is not particularly limited, and is, for example, 30 wt%. Note that when all of the nitrogen elements contained in the acidic gas adsorbent are derived from amino groups, the weight ratio of the nitrogen elements can be considered to be the weight ratio of amino groups in the acidic gas adsorbent.

[0097] The shape of the acidic gas adsorbent is not particularly limited and may be, for example, a block, a sheet, a particle, etc. In this specification, the particle shape includes a spherical shape, an ellipsoidal shape, a scale shape, a fiber shape, etc.

[0098] The acidic gas adsorbent may have a porous structure. As an example, the acidic gas adsorbent may include a porous body S containing a polymer P. The porous body S is typically composed only of the polymer P. The shape of the porous body S is, for example, block-like, sheet-like, or particulate. The acidic gas adsorbent may include a porous resin sheet as the porous body S, but may not include a porous resin sheet. The acidic gas adsorbent may not include any member other than the porous body S, such as a carrier for supporting the polymer P. When the acidic gas adsorbent does not include a carrier, the shape of the acidic gas adsorbent tends to be easily adjustable by cutting or machining.

[0099] The porous body S has, for example, a three-dimensional network skeleton made up of a polymer P. In the porous body S, for example, the above-mentioned three-dimensional network skeleton extends continuously. The pores contained in the porous body S are, for example, continuous pores formed continuously in a three-dimensional manner. The porous body S may have closed pores or may have through-holes that penetrate the porous body S.

[0100] The specific surface area of ​​the acidic gas adsorbent (porous body S) is not particularly limited, and may be, for example, 0.5 m 2 / g or more, and 1.0m 2 / g or more, 2.0m 2 / g or more, 3.0m 2 / g or more, 4.0m 2 / g or more, 5.0m 2 / g or more, 6.0m 2 / g or more, 7.0m 2 / g or more, 8.0m 2 / g or more, and even 9.0m 2 / g or more. The larger the specific surface area of ​​the acidic gas adsorbent, the faster the rate at which the acidic gas adsorbent adsorbs the acidic gas tends to increase. The upper limit of the specific surface area of ​​the acidic gas adsorbent is not particularly limited, and may be, for example, 100 m 2 / g. The specific surface area of ​​the acidic gas adsorbent means the Brunauer-Emmett-Teller (BET) specific surface area determined by nitrogen gas adsorption. The specific surface area of ​​the acidic gas adsorbent can be measured by a method conforming to the provisions of JIS Z8830:2013.

[0101] In another aspect, the present invention provides an acidic gas adsorbent comprising a polymer P having an amino group, wherein the density d of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g, and the specific surface area of ​​the acidic gas adsorbent is 0.5 m 2 / g or more, and the glass transition temperature of the polymer P is 40°C or less. This acidic gas adsorbent has the above-mentioned adsorption and desorption properties, for example, for carbon dioxide. As an example, the adsorption amounts a1 to a3, desorption amounts b1 to b2, 50°C desorption rate, 65°C desorption rate, and the like measured by the above-mentioned methods for the acidic gas adsorbent may satisfy the above-exemplified ranges.

[0102] The pore volume of the acidic gas adsorbent (porous body S) is not particularly limited, and may be, for example, 0.1 cm 3 / g or more, and 3 / g or more, 0.3cm 3 / g or more, 0.5cm 3 / g or more, 1.0cm 3 / g or more, and even 2.0 cm 3 The upper limit of the pore volume of the acidic gas adsorbent is not particularly limited, and may be, for example, 5.0 cm 3 / g, and 4.0 cm 3 / g, and 3.0 cm 3 The pore volume of the acidic gas adsorbent can be measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is performed using a commercially available pore size distribution analyzer (e.g., Autopore V9620 manufactured by Micromeritics) under an initial pressure of 21 kPa.

[0103] The average pore diameter of the acidic gas adsorbent (porous body S) is not particularly limited and may be, for example, 0.1 μm or more, 0.2 μm or more, 0.3 μm or more, or even 0.5 μm or more. The upper limit of the average pore diameter of the acidic gas adsorbent is not particularly limited and may be, for example, 50 μm. In this specification, the average pore diameter of the acidic gas adsorbent means the median diameter measured by mercury intrusion porosimetry. Mercury intrusion porosimetry is performed using a commercially available pore size distribution analyzer (e.g., Autopore V9620 manufactured by Micromeritics) under an initial pressure of 21 kPa.

[0104] When the acidic gas adsorbent is particulate, the average particle size of the acidic gas adsorbent is not particularly limited and is, for example, 0.5 μm or more, preferably 1 μm or more, and may be 10 μm or more, 20 μm or more, or 30 μm or more. The average particle size of the acidic gas adsorbent may be 200 μm or less, 100 μm or less, or less than 75 μm. In this specification, the average particle size of the acidic gas adsorbent means the particle size (d50) corresponding to 50% cumulative volume in the particle size distribution measured by a laser diffraction particle sizer or the like.

[0105] (Method for producing an acidic gas adsorbent) The method for producing an acidic gas adsorbent of this embodiment includes reacting a group of compounds including, for example, an amine monomer or an amine prepolymer, and an epoxy monomer to form a polymer P. The group of compounds is, for example, a group of monomers including an amine monomer and an epoxy monomer. However, the group of compounds may include an amine prepolymer instead of or in addition to the amine monomer.

[0106] The compound group may contain only an epoxy monomer E1 containing two epoxy groups, or may contain an epoxy monomer E2 containing three or more, for example, four, epoxy groups instead of or together with the epoxy monomer E1. When the compound group contains the epoxy monomers E1 and E2, the weight ratio E1 / E2 of the epoxy monomer E2 to the epoxy monomer E1 is not particularly limited and is, for example, 4 / 6 to 8 / 2.

[0107] When preparing polymer P, the blending ratio of epoxy monomer to amine monomer or amine prepolymer is preferably set so that the ratio E / A, i.e., the equivalent weight (E) of epoxy group contained in epoxy monomer to the equivalent weight (A) of active hydrogen of primary amino group contained in amine monomer or amine prepolymer, is, for example, 1 or less, preferably 0.9 or less, more preferably 0.5 or less. The smaller the ratio E / A, the higher the density d of nitrogen element in the acidic gas adsorbent tends to be. The lower limit of the ratio E / A is not particularly limited and is, for example, 0.1.

[0108] The reaction of the compounds is, for example, a polymerization reaction of an amine monomer and an epoxy monomer. However, the reaction of the compounds may also be a crosslinking reaction of an amine prepolymer with an epoxy monomer. In the reaction of the compounds, the amino group of the amine monomer or amine prepolymer reacts with the epoxy group of the epoxy monomer. The reaction of the compounds can be carried out by applying energy to the compounds. The energy applied to the compounds is preferably thermal energy. As an example, the reaction of the compounds can be promoted by heating the compounds at a temperature of 40°C to 100°C. However, the energy applied to the compounds may also be light energy.

[0109] An acidic gas adsorbent having a porous structure can be prepared, for example, by the following method. First, the above-described compounds are mixed with a porogen to prepare a mixed solution. The porogen is a solvent that can dissolve, for example, the monomers and prepolymers contained in the compounds and can cause reaction-induced phase separation after the compounds have reacted. Specific examples of porogens include cellosolves such as methyl cellosolve and ethyl cellosolve, esters such as ethylene glycol monomethyl ether acetate and propylene glycol monomethyl ether acetate, glycols such as polyethylene glycol, polypropylene glycol, and polyoxyalkylene glycol, and ethers such as polyoxyethylene monomethyl ether and polyoxyethylene dimethyl ether. Specific examples of polyoxyalkylene glycols include poly(1,2-butanediol)-6 propylene glycol and polyoxypropylene diglyceryl ether. The porogen may be a polar solvent such as ethyl acetate, N,N-dimethylformamide (DMF), acetonitrile, ethanol, or isopropanol, a nonpolar solvent such as toluene, or a mixture thereof. The porogens may be used alone or in combination of two or more.

[0110] The mixture may further contain components other than the compounds, such as the above-mentioned reaction accelerators.

[0111] Next, the compounds are reacted in the mixture. For example, the mixture is filled into a mold and then heated to react the compounds. This results in a cured product containing the polymer P and the porogen. In this cured product, the polymer P and the porogen undergo phase separation to form a co-continuous structure.

[0112] Next, the porogen is extracted and removed from the cured product. This allows for the production of an acidic gas adsorbent having a porous structure. The porogen can be extracted, for example, by immersing the cured product in a solvent. Examples of the solvent that can be used include water, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, aliphatic alcohol solvents, ester solvents, ether solvents, and halogen-containing organic solvents. Examples of aliphatic hydrocarbon solvents include n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, isooctane, petroleum ether, and benzine. Examples of aromatic hydrocarbon solvents include toluene, xylene, mesitylene, and benzene. Examples of aliphatic alcohol solvents include methanol, ethanol, isopropanol, butanol, cyclohexanol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, and diethylene glycol. Examples of ester solvents include ethyl acetate. Examples of ether solvents include diethyl ether, diisopropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, dioxane, and anisole. Examples of halogen-containing organic solvents include dichloromethane, chloroform, carbon tetrachloride, dichloroethane, and chlorobenzene. These solvents can be used alone or in combination of two or more.

[0113] When preparing a cured product, the higher the reaction rate of the compounds, the more finely the porogen tends to be dispersed in the cured product. By removing the porogen from a cured product in which the porogen is finely dispersed, an acidic gas adsorbent with a large specific surface area can be prepared. The reaction rate of the compounds varies depending on, for example, the types and blending ratios of the monomers and prepolymers contained in the compounds. For example, the reaction rate of the compounds tends to be high when an epoxy monomer E2 containing three or more, e.g., four, epoxy groups is used, or when polyethyleneimine with a high weight-average molecular weight is used as the amine prepolymer.

[0114] (Uses of Acidic Gas Adsorbent) The acidic gas adsorbent of the present embodiment can adsorb acidic gases. Examples of acidic gases include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, and nitrogen oxides (NOx), and carbon dioxide is preferred.

[0115] The acidic gas adsorbent can be used, for example, by the following method. First, a mixed gas containing an acidic gas is contacted with the acidic gas adsorbent. The mixed gas contains, for example, other gases in addition to the acidic gas. Examples of other gases include non-polar gases such as hydrogen and nitrogen, and inert gases such as helium, with nitrogen being preferred. The mixed gas is typically atmospheric air. The mixed gas may also be off-gas from a chemical plant or thermal power plant.

[0116] The temperature of the mixed gas is, for example, room temperature (23°C). The concentration of the acidic gas in the mixed gas is not particularly limited and, under standard conditions (0°C, 101 kPa), is, for example, 0.01 vol% (100 volppm) or more, preferably 0.04 vol% (400 volppm) or more, and may be 1.0 vol% or more. The upper limit of the carbon dioxide concentration in the mixed gas is not particularly limited and, under standard conditions, is, for example, 10 vol%. The pressure of the mixed gas is typically equal to atmospheric pressure in the environment in which the acidic gas adsorbent is used. However, the mixed gas to be contacted with the acidic gas adsorbent may be pressurized.

[0117] The acidic gas adsorbent that has come into contact with the mixed gas adsorbs the acidic gas contained in the mixed gas. The operation of bringing the mixed gas into contact with the acidic gas adsorbent is carried out, for example, until the adsorption of the acidic gas by the acidic gas adsorbent reaches equilibrium.

[0118] Next, the acidic gas adsorbent that has adsorbed the acidic gas is regenerated. The regeneration can be performed, for example, by heating the acidic gas adsorbent. The heating temperature of the acidic gas adsorbent is, for example, 50 to 80°C. The acidic gas adsorbent may be heated under a reduced pressure or a vacuum. By heating the acidic gas adsorbent, the acidic gas is desorbed from the acidic gas adsorbent. This regenerates the acidic gas adsorbent, allowing it to be reused. The acidic gases, particularly carbon dioxide, desorbed from the acidic gas adsorbent can be used as raw materials for chemical synthesis or as dry ice. The adsorption of acidic gases by the acidic gas adsorbent and the regeneration of the acidic gas adsorbent can be performed using the measuring device 10 (acidic gas adsorption device) described above.

[0119] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited thereto.

[0120] Example 1 First, 1.73 g of poly(1,2-butanediol)-6 propylene glycol (NOF Corporation, Uniol (registered trademark) PB-500) and 0.43 g of polyoxypropylene diglyceryl ether (NOF Corporation, Unilube (registered trademark) DGP-700) were added to a 6 mL screw tube bottle (manufactured by AS ONE Corporation). 0.74 g of ethylene glycol diglycidyl ether (Nagase ChemteX Corporation, EX-810) and 0.74 g of pentaerythritol tetraglycidyl ether (Showa Denko K.K., Showfree (registered trademark) PETG) were dissolved in the resulting mixture to prepare a mixture of epoxy monomer and porogen.

[0121] Next, 1.56 g of polyethyleneimine (Epomin SP-003, manufactured by Nippon Shokubai Co., Ltd.) was added to this mixture to prepare a mixture of epoxy monomer, amine prepolymer, and porogen. In this mixture, the ratio E / A of the equivalent weight (E) of epoxy groups contained in the epoxy monomer to the equivalent weight (A) of active hydrogen of primary amino groups contained in the amine prepolymer was 0.5.

[0122] Next, the mixture was shaken for 2 minutes using a tabletop shaker (Angel Vibrator Digital 60 Hz) set to intensity 5. Next, the mixture was allowed to stand in a thermostatic chamber at 80°C for 2 hours to harden. This resulted in a block-shaped cured product containing polymer P having amino groups. The cured product was removed from the screw cap and cut into approximately 3 mm square pieces. The cured product was then immersed in ethyl acetate at 60°C for 1 hour, and this operation was repeated twice with liquid exchange. This removed the porogen from the cured product, forming a porous body containing polymer P. The porous body was dried at 60°C for 1 hour and then vacuum-dried for another 2 hours to obtain the acidic gas adsorbent of Example 1.

[0123] Examples 2 to 11 Acidic gas adsorbents of Examples 2 to 11 were obtained in the same manner as in Example 1, except that the types and amounts of raw materials were changed as shown in Table 1.

[0124] Comparative Example 1 First, 2.63 g of polypropylene glycol (ADEKA Corporation, Adeka Polyether P-400) and 0.36 g of polyethylene glycol (Sigma-Aldrich Corporation, average molecular weight 200) were added to a 6 mL screw tube bottle (AS ONE Corporation). 1.58 g of bisphenol A epoxy resin (Mitsubishi Chemical Corporation, JER828) was dissolved in the resulting mixture to prepare a mixture of epoxy prepolymer and porogen.

[0125] Next, 0.60 g of triethylenetetramine was added to the mixture to prepare a mixture of epoxy prepolymer, amine monomer, and porogen. In this mixture, the ratio E / A of the equivalent weight (E) of epoxy groups contained in the epoxy prepolymer to the equivalent weight (A) of active hydrogen of primary amino groups contained in the amine monomer was 0.5.

[0126] Next, the mixture was shaken for 2 minutes using a benchtop shaker (Angel Vibrator Digital 60 Hz) set to intensity 5. Next, the mixture was allowed to stand in a thermostatic chamber at 80°C for 4 hours to harden. This resulted in a block-shaped cured product containing polymer P having amino groups. The cured product was removed from the screw cap and cut into approximately 3 mm square pieces. The cured product was then immersed in isopropyl alcohol at 60°C for 1 hour, this operation being repeated twice with liquid changes. Furthermore, the cured product was immersed in ultrapure water at 60°C for 1 hour, this operation being repeated twice with liquid changes. The cured product was then immersed in methanol at room temperature for 1 hour. The cured product was air-dried at room temperature for 12 hours and then vacuum-dried at 60°C for 8 hours to obtain an acidic gas adsorbent of Comparative Example 1.

[0127] Comparative Examples 2 and 3 Acidic gas adsorbents of Comparative Examples 2 and 3 were obtained in the same manner as in Comparative Example 1, except that the types and amounts of raw materials were changed as shown in Table 1.

[0128] [Density of Nitrogen Element] The density d of nitrogen element of the prepared acidic gas adsorbent was measured by the method described above. Vario EL III manufactured by Elementar was used as the CHN element analyzer.

[0129] [Specific Surface Area] The specific surface area of ​​the prepared acidic gas adsorbent was measured by a method conforming to the provisions of JIS Z8830: 2013. For the measurement, a specific surface area measuring device (manufactured by Microtrac-Bell, product name "BERSORP-mini") was used.

[0130] [Glass Transition Temperature Tg] The glass transition temperature Tg of the polymer contained in the prepared acidic gas adsorbent was measured by the following method. First, about 5 mg of the acidic gas adsorbent was placed in a differential scanning calorimeter (TA Instruments, DSC2500). Using this device, the temperature was raised from 30 ° C. to 200 ° C. at a heating rate of 10 ° C. / min under a nitrogen atmosphere and held at that temperature for 1 minute. Next, the temperature was cooled to -50 ° C. at a heating rate of 10 ° C. / min, held at that temperature for 1 minute, and then heated to 200 ° C. at a heating rate of 10 ° C. / min. In the DSC curve during the second heating, the first baseline before the specific heat change appeared, the second baseline after the specific heat change appeared, and the tangent passing through the point where the slope of the bending portion due to the specific heat change is maximum were identified. The intermediate temperature between the intersection of the first baseline and the tangent and the intersection of the second baseline and the tangent was identified as the glass transition temperature Tg.

[0131] [Amount of carbon dioxide adsorption] The adsorption amounts a1 to a3 and desorption amounts b1 to b2 of the prepared acidic gas adsorbents were measured by the method described above. Furthermore, based on these results, the ratio of the desorption amount b1 (mmol / g) to the adsorption amount a1 (mmol / g) (50°C desorption rate) and the ratio of the desorption amount b2 (mmol / g) to the adsorption amount a1 (mmol / g) (65°C desorption rate) were calculated.

[0132] [Heat resistance test] The heat resistance test was performed on the prepared acidic gas adsorbent by the method described above, and the carbon dioxide adsorption amount a4 was measured. Furthermore, the ratio of the adsorption amount a4 (mmol / g) to the adsorption amount a1 (mmol / g) (retention rate R1) was calculated.

[0133] [Moisture and heat resistance test] The prepared acidic gas adsorbents were subjected to a moisture and heat resistance test by the method described above to measure the carbon dioxide adsorption amount a5. Furthermore, the ratio of the adsorption amount a5 (mmol / g) to the adsorption amount a1 (mmol / g) (retention rate R2) was calculated.

[0134]

[0135] In Table 1, epoxy monomers and epoxy prepolymers are simply referred to as epoxy compounds, and amine monomers and amine prepolymers are simply referred to as amine compounds.

[0136] The abbreviations in Table 1 are as follows: EDE: ethylene glycol diglycidyl ether (EX-810, manufactured by Nagase ChemteX Corporation) JER828: bisphenol A epoxy resin (JER828, manufactured by Mitsubishi Chemical Corporation) PETG: pentaerythritol tetraglycidyl ether (SHOWFREE (registered trademark) PETG, manufactured by Showa Denko K.K.) TC: 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane (TETRAD-C, manufactured by Mitsubishi Gas Chemical Company, Inc.) T-X: N,N,N',N'-tetraglycidyl metaxylenediamine (TETRAD-X, manufactured by Mitsubishi Gas Chemical Company, Inc.) PEI300: polyethyleneimine (Epomin SP-003, weight-average molecular weight: approximately 300, manufactured by Nippon Shokubai Co., Ltd.) PEI1200: polyethyleneimine (Epomin SP-012, weight-average molecular weight: approximately 1200, manufactured by Nippon Shokubai Co., Ltd.) PEI1800: polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin SP-018, weight average molecular weight approximately 1800) TETA: triethylenetetramine (manufactured by Tosoh Corporation) PB-500: poly(1,2-butanediol)-6 propylene glycol (manufactured by NOF Corporation, Uniol (registered trademark) PB-500) P-400: polypropylene glycol (manufactured by ADEKA Corporation, Adeka Polyether P-400) DGP-700: polyoxypropylene diglyceryl ether (manufactured by NOF Corporation, Unilube (registered trademark) DGP-700) PB-700: copolymer of butylene glycol and propylene glycol (manufactured by NOF Corporation, Uniol (registered trademark) PB-700) PEG: polyethylene glycol (manufactured by Sigma-Aldrich, average molecular weight 200)

[0137] The safety indexes for handling of the amine compounds used in the examples and comparative examples are shown in Table 2 below.

[0138]

[0139]

[0140] As can be seen from Table 3, the acidic gas adsorbents of the Examples had a large nitrogen element density d, and also had large adsorption amounts a1 and desorption amounts b1. It can be said that the acidic gas adsorbents of the Examples are suitable for adsorbing and desorbing acidic gases under relatively mild conditions.

[0141] The acidic gas adsorbent of this embodiment can adsorb, for example, carbon dioxide in the atmosphere.

Claims

1. An acidic gas adsorbent comprising a polymer having an amino group, The density of nitrogen element in the acidic gas adsorbent is greater than 12.0 mmol / g; The specific surface area of ​​the acid gas adsorbent is 0.5 m 2 / g or more, The acidic gas adsorbent, wherein the polymer has a glass transition temperature of 40° C. or lower.

2. 2. The acidic gas adsorbent according to claim 1, wherein when heat-treated for 100 hours in an environment of 85°C and 10% RH, the maintenance rate R1 of the amount of adsorbable carbon dioxide (mmol / g) is 50% or more.

3. 2. The acidic gas adsorbent according to claim 1, wherein when heat-treated for 100 hours in an environment of 85°C and 85% RH, the maintenance rate R2 of the amount of adsorbable carbon dioxide (mmol / g) is 50% or more.

4. The acid gas adsorbent according to claim 1 , comprising the polymer as a main component.

5. 2. The acid gas adsorbent of claim 1, wherein the polymer is an amine polymer containing constitutional units derived from epoxy monomers.

6. The acidic gas adsorbent according to claim 5, wherein the amine polymer comprises at least one selected from the group consisting of a polymer P1 of a monomer group including an amine monomer and an epoxy monomer, and a reactant P2 of a compound group including an amine prepolymer and an epoxy monomer.

7. 7. The acid gas adsorbent according to claim 6, wherein the amine prepolymer has a weight average molecular weight of 300 or more.

8. 7. The acid gas adsorbent of claim 6, wherein the amine prepolymer comprises polyethyleneimine.

9. 7. The acid gas adsorbent of claim 6, wherein the amine monomer comprises an aliphatic amine.

10. 6. The acid gas adsorbent according to claim 5, wherein the epoxy equivalent of the epoxy monomer is 150 g / eq. or less.

11. The acid gas adsorbent according to claim 5 , wherein the epoxy monomer comprises a polyfunctional epoxy compound having an ether group.

12. The acid gas adsorbent according to claim 1 , which has a porous structure.

13. An adsorption section having a gas inlet and a gas outlet, An acid gas adsorption device, wherein the adsorption section contains the acid gas adsorbent according to claim 1 .