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

Technical Field

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

Background Art

[0002] In recent years, in order to reduce the amount of carbon dioxide in the atmosphere, carbon dioxide capture and storage (CCS) and carbon dioxide capture and utilization (CCU) have been studied. In CCS and CCU, carbon dioxide may be recovered by separating carbon dioxide 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 by an adsorbent and separated. The adsorbent used in the adsorption method can adsorb acidic gases, for example, by contacting the atmosphere.

[0004] Examples of the material of the adsorbent include amine compounds having a function of adsorbing acidic gases. As an example, Patent Document 1 discloses fibrillated cellulose into which an amino group has been introduced as an adsorbent. Patent Document 2 discloses an adsorbent in which an amino group has been introduced into the pores of a mesoporous material.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

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

Means for Solving the Problems

[0007] The present invention relates to 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, when the following adsorption test A1 is carried out, the adsorption amount a1 of carbon dioxide is 0.35 mmol / g or more, and when the following desorption test B1 is carried out, the desorption amount b1 of carbon dioxide is 0.2 mmol / g or more, and provides an acidic gas adsorbent. Adsorption test A1: Continuously feed a mixed gas composed of carbon dioxide, nitrogen and water vapor into a container containing the acidic gas adsorbent for 15 hours. Here, the concentration of carbon dioxide in the mixed gas is 400 volppm, and the mixed gas has a temperature of 23°C and a humidity of 50%RH. Desorption test B1: While continuously feeding the mixed gas into the container, heat the acidic gas adsorbent after the adsorption test A1 at 50°C for 1.5 hours.

[0008] Furthermore, the present invention relates to 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, 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 lower, and provides an acidic gas adsorbent.

[0009] Furthermore, the present invention relates to an acidic gas adsorption device including an adsorption part having a gas inlet and a gas outlet, wherein the adsorption part contains the above-mentioned acidic gas adsorbent.

Advantages of the Invention

[0010] According to the present invention, an acidic gas adsorbent suitable for adsorbing and desorbing acidic gas under relatively mild conditions can be provided.

Brief Description of Drawings

[0011]

Figure 1

Embodiments for Carrying Out the Invention

[0012] The acidic gas adsorbent according to the first 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, when the following adsorption test A1 is carried out, the adsorption amount a1 of carbon dioxide is 0.35 mmol / g or more, when the following desorption test B1 is carried out, the desorption amount b1 of carbon dioxide is 0.2 mmol / g or more. Adsorption test A1: Continuously send a mixed gas composed of carbon dioxide, nitrogen, and water vapor into a container containing the acidic gas adsorbent for 15 hours. Here, the concentration of carbon dioxide in the mixed gas is 400 volppm, and the mixed gas has a temperature of 23°C and a humidity of 50%RH. Desorption test B1: While continuously sending the mixed gas into the container, heat the acidic gas adsorbent after the adsorption test A1 at 50°C for 1.5 hours.

[0013] In the 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 the third aspect of the present invention, for example, in the acidic gas adsorbent according to the first or second aspect, when the following desorption test B2 is carried out, the desorption amount b2 of carbon dioxide is 0.25 mmol / g or more. Desorption Test B2: While continuously feeding the mixed gas into the container, heat the acidic gas adsorbent after the Adsorption Test A1 at 65°C for 1.5 hours.

[0015] In the 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 the 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 performed, the adsorption amount a2 of carbon dioxide is 0.05 mmol / g or more. Adsorption Test A2: Continuously feed the mixed gas into the container for 1 hour.

[0017] In the 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 performed, the adsorption amount a3 of carbon dioxide is 0.1 mmol / g or more. Adsorption Test A3: Continuously feed the mixed gas into the container for 4 hours.

[0018] In the 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 less.

[0019] In the 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] The acidic gas adsorbent according to the ninth aspect of the present invention is an acidic gas adsorbent containing 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 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 the tenth aspect of the present invention, for example, the acid gas adsorbent according to any one of the first to ninth aspects has a maintenance rate R1 of the amount of carbon dioxide (mmol / g) that can be adsorbed of 50% or more when heat treatment is performed for 100 hours in an environment of 85°C and 10% RH.

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

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

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

[0025] In the fourteenth aspect of the present invention, for example, in the acid gas adsorbent according to the thirteenth aspect, the 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.

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

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

[0028] In the 17th aspect of the present invention, for example, in the acid gas adsorbent according to the 14th aspect, the amine monomer contains an aliphatic amine.

[0029] In the 18th aspect of the present invention, for example, in the acid gas adsorbent according to any one of the 13th to 17th aspects, the epoxy equivalent of the epoxy monomer is 150 g / eq. or less.

[0030] In the 19th aspect of the present invention, for example, in the acid gas adsorbent according to any one of the 13th to 18th aspects, the epoxy monomer contains a polyfunctional epoxy compound having an ether group.

[0031] In the 20th aspect of the present invention, for example, the acid gas adsorbent according to any one of the 1st to 19th aspects has a porous structure.

[0032] The acid gas adsorption device according to the 21st aspect of the present invention comprises an adsorption part having a gas inlet and a gas outlet, and the adsorption part contains the acid gas adsorbent according to any one of the 1st to 20th aspects.

[0033] Hereinafter, the details of the present invention will be described, but the following description is not intended to limit the present invention to specific embodiments.

[0034] The acid gas adsorbent of the present embodiment contains a polymer P having an amino group. The density d of nitrogen element in the acid gas adsorbent is greater than 12.0 mmol / g.

[0035] The density d of 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, and even 17.5 mmol / g or more. The greater the density d of the nitrogen element, the greater the tendency for the acidic gas adsorbent to adsorb acidic gas and the rate of adsorbing acidic gas. The upper limit value of the density d of the nitrogen element is not particularly limited, and for example, it may be 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 substance of the nitrogen element contained in 1 g of the acidic gas adsorbent. In addition, when all the nitrogen elements contained in the acidic gas adsorbent are derived from amino groups, the density d of the nitrogen element can be regarded as the density of amino groups in the acidic gas adsorbent.

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

[0037] Furthermore, when the following adsorption test A1 is performed on the acidic gas adsorbent of this embodiment, the carbon dioxide adsorption amount a1 is 0.35 mmol / g or more. Furthermore, when the following desorption test B1 is performed, the carbon dioxide desorption amount b1 is 0.2 mmol / g or more. Adsorption test A1: Continuously feed a mixed gas G composed of carbon dioxide, nitrogen, and water vapor into a container containing the acidic gas adsorbent for 15 hours. Here, the concentration of carbon dioxide in the mixed gas G is 400 volppm, and the mixed gas G has a temperature of 23°C and a humidity of 50% RH. Desorption Test B1: While continuously sending 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) Hereinafter, the details of the adsorption test A1 and the desorption test B1 will be described. The adsorption test A1 and the desorption test B1 can be measured, for example, using the measuring device 10 shown in FIG. 1. The measuring device 10 includes a first tank 30 and a second tank 31. As an example, the first tank 30 stores nitrogen in a dry state, 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 the 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 contacting the water 70. A mass flow controller 35 for adjusting the flow rate of nitrogen sent from the first tank 30 to the first container 40 is disposed in the first path 60.

[0040] The measuring device 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 nitrogen sent to the first container 40 and humidified is sent to the second container 41 through the second path 62. The bypass path 61 branches from the first path 60 at a position between the first tank 30 and the mass flow controller 35 and is connected to the second path 62. A part of the nitrogen sent from the first tank 30 flows into the bypass path 61 and is sent to the second container 41 through the second path 62. A mass flow controller 36 for adjusting the flow rate of nitrogen sent from the first tank 30 to the bypass path 61 is disposed in 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 for adjusting the flow rate of the mixed gas sent from the second tank 31 to the second path 62 is arranged in the third path 63. 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 houses water 71 and an adsorption part 21 arranged in the water 71. In the third container 42, the temperature of the water 71 is maintained at 23°C. The adsorption part 21 has a gas inlet 22 and a gas outlet 23. The adsorption part 21 functions as a container for housing an acidic gas adsorbent inside. The adsorption part 21 is configured so that the water 71 does not penetrate inside. The adsorption part 21 is typically a tube made of a hydrophobic resin, such as a fluororesin such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA). As an example, the tube as the adsorption part 21 has an inner diameter of 4 mm and an outer diameter of 6 mm. The adsorption part 21 is configured to be detachable from the measuring device 10.

[0043] Note that the measuring device 10 can also be used as an acidic gas adsorption device including the adsorption part 21. From another aspect of the present invention, there is provided an acidic gas adsorption device 20 including an adsorption part 21 having a gas inlet 22 and a gas outlet 23, and the adsorption part 21 houses an acidic gas adsorbent.

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

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

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

[0047] [Pretreatment] First, an acidic gas adsorbent is prepared and dried. As the acidic gas adsorbent, the one before performing the heat resistance test and the damp heat resistance test described later is used. The drying treatment is performed, for example, by treating the acidic gas adsorbent under a vacuum atmosphere at 60 °C for 2 hours or more. Next, in a dry room with a dew point of about -60 °C, the dried acidic gas adsorbent is filled into the adsorption part 21. The weight of the acidic gas adsorbent filled in the adsorption part 21 is, for example, 50 mg. Next, the fourth path 64 and the fifth path 65 are connected to both ends of the adsorption part 21, and the adsorption part 21 is immersed in the water 71 of 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 through the first path 60, the second path 62, the bypass path 61, and the third path 63 of the measuring device 10. Inside the second container 41, these gases are mixed to obtain a mixed gas G composed of carbon dioxide, nitrogen, and water vapor. Inside the second container 41, the concentration of carbon dioxide in the mixed gas G is adjusted to 400 volppm. 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 through the fourth path 64 at a flow rate sufficient for the weight of the acid gas adsorbent, for example, a flow rate of 300 mL / min for 50 mg of the acid gas adsorbent. Inside 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, with the mixed gas G being supplied to the adsorption unit 21, the adsorption unit 21 is taken out from the third container 42 and immersed in a hot water bath (not shown) at 80°C for 2 hours or more. The immersion of the adsorption unit 21 in the hot water bath is performed until the concentration of carbon dioxide measured by the first concentration meter 50 and the concentration of carbon dioxide measured by the second concentration meter 51 become substantially the same value. Thereby, the pretreatment of the acid gas adsorbent inside the adsorption unit 21 is completed.

[0050] [Adsorption test] Next, with the mixed gas G being supplied to the adsorption unit 21, the adsorption unit 21 is taken out from the hot water bath and immersed in the water 71 of the third container 42. Thereby, an adsorption test of carbon dioxide (adsorption test A1) is started for the acid gas adsorbent inside the adsorption unit 21. The adsorption test is performed until 15 hours have elapsed since the start. Specifically, the mixed gas G is continuously fed to the adsorption unit 21 for 15 hours. When the adsorption test is performed for 15 hours, the adsorption of carbon dioxide by the acid gas adsorbent can usually be considered to have reached equilibrium.

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

[0052] [Desorption test] Next, while continuously sending the mixed gas G to the adsorption unit 21, the adsorption unit 21 is taken out from the third container 42, and the adsorption unit 21 is immersed in a hot water bath (not shown) at 50°C. Thereby, a desorption test (desorption test B1) of carbon dioxide is started for the acid gas adsorbent in the adsorption unit 21. The desorption test is performed until 1.5 hours have elapsed since the start.

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

[0054] [Adsorption amount and desorption amount] In the acid gas adsorbent of the present embodiment, the adsorption amount a1 of carbon dioxide when the 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, and further 2.3 mmol / g or more. The upper limit value of the adsorption amount a1 of carbon dioxide is not particularly limited, and is, for example, 10 mmol / g.

[0055] In the acid gas adsorbent of the present embodiment, when the desorption test B1 is performed, the desorption amount b1 of carbon dioxide 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, and further 1.8 mmol / g or more. The upper limit value of the desorption amount b1 of carbon dioxide is not particularly limited, and is, for example, 10 mmol / g.

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

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

[0058] When the following desorption test B2 is performed on the acid gas adsorbent of the present embodiment, the desorption amount b2 of carbon dioxide is preferably 0.25 mmol / g or more. Desorption test B2: While continuously sending the mixed gas G to the container (the above adsorption part 21) in which the acid gas adsorbent is accommodated, the acid gas adsorbent after the above adsorption test A1 is heated at 65 °C for 1.5 hours.

[0059] Desorption test B2 can be carried out in the same manner as the above-described desorption test B1, except that the adsorption part 21 is immersed in a hot water bath at 65°C. The amount of carbon dioxide desorbed b2 when desorption test B2 is carried out 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, and even 2.2 mmol / g or more. The upper limit value of the amount of carbon dioxide desorbed b2 is not particularly limited, and is, for example, 10 mmol / g.

[0060] The ratio (desorption rate at 65°C) of the desorption amount b2 (mmol / g) to the adsorption amount a1 (mmol / g) 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, and even 97% or more, or may be 100%.

[0061] When the following adsorption test A2 is carried out on the acid gas adsorbent of the present embodiment, the adsorption amount a2 of carbon dioxide is preferably 0.05 mmol / g or more. The adsorption amount a2 can be used as an index of the rate of adsorbing acid gas. That is, it can be said that the larger the adsorption amount a2, the higher the rate of the acid gas adsorbent adsorbing acid gas. Adsorption test A2: The mixed gas G is continuously fed into the container (the above-described adsorption part 21) containing the acid gas adsorbent for 1 hour.

[0062] Adsorption test A2 can be carried out in the same manner as the above-described adsorption test A1, except that the test time is changed from 15 hours to 1 hour. The adsorption amount a2 of carbon dioxide when adsorption test A2 is carried out 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, and even 0.9 mmol / g or more. The upper limit value of the adsorption amount a2 of carbon dioxide is not particularly limited, and is, for example, 5 mmol / g.

[0063] When the following adsorption test A3 is performed on the acid 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 of adsorbing acid gas. That is, the larger the adsorption amount a3, the higher the rate of the acid gas adsorbent adsorbing acid gas. Adsorption test A3: Continuously feed the mixed gas G into the container (the above-mentioned adsorption part 21) containing the acid gas adsorbent for 4 hours.

[0064] The adsorption test A3 can be performed by the same method as the above-mentioned adsorption test A1, except that the test time is changed from 15 hours to 4 hours. When the adsorption test A3 is performed, the carbon dioxide adsorption amount a3 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, and even 1.8 mmol / g or more. The upper limit value of the carbon dioxide adsorption amount a3 is not particularly limited, for example, it is 5 mmol / g.

[0065] (Heat resistance test) The acid gas adsorbent of this embodiment preferably has high heat resistance. The heat resistance of the acid gas adsorbent can be evaluated, for example, by performing a heat resistance test on the acid gas adsorbent. The heat resistance test can be carried out, for example, by performing a heat treatment on the acid gas adsorbent for 100 hours in an environment of 85°C and 10% RH. As an example, when the acid 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 (mmol / g) of carbon dioxide that can be adsorbed is, for example, 30% or more, and may be 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, and even 96% or more. The higher the maintenance rate R1, the higher the heat resistance of the acid gas adsorbent. It can be said that the acid gas adsorbent with high heat resistance has high durability in long-term use. The upper limit value of the maintenance rate R1 is not particularly limited, for example, it is 99%.

[0066] The retention rate R1 can be specifically determined by the following method. First, place the acid gas adsorbent in a glass container (e.g., a Labo Lance screw tube bottle manufactured by AS ONE Corporation) in a dry room with a dew point of approximately -60°C. Next, set the glass container in a thermo-hygrostat (e.g., PSL-2J manufactured by ESPEC Corporation) and perform a heat treatment at 85°C and 10% RH in the air for 100 hours. Next, set the acid gas adsorbent after the heat treatment in a vacuum dryer (e.g., VOS-310C manufactured by EYELA) in the dry room and treat it under a vacuum atmosphere at 60°C for 2 hours or more. Measure the carbon dioxide adsorption amount a4 when the above adsorption test A1 is performed on the treated acid gas adsorbent. Based on the obtained adsorption amount a4 and the carbon dioxide adsorption amount a1 when the adsorption test A1 is performed on the acid gas adsorbent before the heat resistance test, the retention rate R1 can be calculated by the following formula. Retention rate R1 (%) = Adsorption amount a4 (mmol / g) ÷ Adsorption amount a1 (mmol / g) × 100

[0067] Note that the carbon dioxide adsorption amount a4 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, and even 2.0 mmol / g or more. The upper limit value of the carbon dioxide adsorption amount a4 is not particularly limited and is, for example, 10 mmol / g.

[0068] (Damp heat resistance test) The acid gas adsorbent of this embodiment preferably has high moisture and heat resistance. The moisture and heat resistance of the acid gas adsorbent can be evaluated, for example, by conducting a moisture and heat resistance test on the acid gas adsorbent. The moisture and heat resistance test can be carried out, for example, by performing a heat treatment on the acid gas adsorbent for 100 hours in an environment of 85°C and 85% RH. As an example, when the acid gas adsorbent is subjected to a heat treatment for 100 hours in an environment of 85°C and 85% RH, the retention rate R2 of the amount of carbon dioxide (mmol / g) that can be adsorbed is, for example, 30% or more, and may be 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, and even 96% or more. The higher the retention rate R2, the higher the moisture and heat resistance of the acid gas adsorbent can be said. It can be said that an acid gas adsorbent with high moisture and heat resistance has high durability in long-term use. The upper limit value of the retention rate R2 is not particularly limited and is, for example, 99%.

[0069] The retention rate R2 can be specified in detail by the following method. First, place the acid gas adsorbent in a glass container (for example, a Lablance screw tube bottle manufactured by AS ONE Corporation) in a dry room with a dew point of about -60°C. Next, set the glass container in a thermo-hygrostat (for example, PSL-2J manufactured by ESPEC Corporation) and perform a heat treatment at 85°C and 85% RH in the air for 100 hours. Next, set the acid gas adsorbent after the heat treatment in a vacuum dryer (for example, VOS-310C manufactured by EYELA) in the dry room and process it under a vacuum atmosphere at 60°C for 2 hours or more. Measure the carbon dioxide adsorption amount a5 when the adsorption test A1 described above is performed on the acid gas adsorbent after the treatment. Based on the obtained adsorption amount a5 and the carbon dioxide adsorption amount a1 when the adsorption test A1 is performed on the acid gas adsorbent before the moisture and heat resistance test, the retention rate R2 can be calculated by the following formula. Retention rate R2 (%) = Adsorption amount a5 (mmol / g) ÷ Adsorption amount a1 (mmol / g) × 100

[0070] Note that 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, and even 2.1 mmol / g or more. The upper limit value of the carbon dioxide adsorption amount a5 is not particularly limited and is, for example, 10 mmol / g.

[0071] (Polymer) In the acid gas adsorbent, the polymer P has a function of adsorbing acid gas due to the amino group. The polymer P contains, for example, at least one selected from the group consisting of a primary amino group, a secondary amino group, and a tertiary amino group as the amino group. From the viewpoint of the adsorbability of acid gas, 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. According to the polymer P having a secondary amino group, the adsorbed acid gas also tends to be easily desorbed. That is, according to the polymer P having a secondary amino group, the regeneration treatment of the acid gas adsorbent can be performed under relatively mild conditions. Note that the polymer P may contain a tertiary amino group or may not contain a tertiary amino group.

[0072] The weight ratio of nitrogen element in the polymer P is, for example, 5 wt% or more, preferably 10 wt% or more. The higher this weight ratio, the more the adsorbability of acid gas in the acid gas adsorbent tends to improve. The upper limit value of the weight ratio of nitrogen element in the polymer P is not particularly limited and is, for example, 30 wt%. When all the nitrogen elements contained in the polymer P are derived from amino groups, the above weight ratio of nitrogen element can be regarded as the weight ratio of amino groups in the polymer P.

[0073] The density of nitrogen element in polymer P is, for example, greater than 12.0 mmol / g, 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, and even 15.5 mmol / g or more. The upper limit value of the density of nitrogen element is not particularly limited, and may be, for example, 30 mmol / g or 20 mmol / g. In this specification, the density of nitrogen element in polymer P means the amount of substance of nitrogen element contained in 1 g of polymer P, and can be measured, for example, by the same method as the density d of nitrogen element in the above-mentioned acidic gas adsorbent. When all the nitrogen elements contained in polymer P are derived from amino groups, the density of nitrogen element can be regarded as the density of amino groups in polymer P.

[0074] Polymer P may contain other functional groups other than amino groups. Examples of other functional groups include hydroxyl group, ether group, ester group, amide group, etc. Polymer P preferably contains an ether group as other functional groups.

[0075] Polymer P is, for example, an amine polymer containing a structural unit U1 derived from an epoxy monomer. This amine polymer includes, for example, 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 the reactant P2. The reactant P2 not only tends to have a high density of nitrogen element, but also tends to have high heat resistance and high heat and humidity resistance. A specific example of the reactant P2 is a cross-linked product (cross-linked product) of an amine prepolymer by an epoxy monomer.

[0076] The monomer group for forming the polymer P1 includes an amine monomer and an epoxy monomer as described above, and is preferably composed of only these monomers. That is, the polymer P1 is preferably a polymer of an amine monomer and an epoxy monomer.

[0077] An amine monomer is a monomer containing at least one amino group, for example, containing 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, and may be 4 or more. The upper limit value of the number of primary amino groups is not particularly limited, for example, it is 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, for example, it is 10% or more, preferably 20% or more, more preferably 30% or more, and may be 40% or more. The upper limit value of this ratio is not particularly limited, for example, it is 80%, and may be 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 greatly adjust the density of nitrogen element in the polymer P1. The upper limit value of the molecular weight of the amine monomer is not particularly limited, for example, it is less than 1000, 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 greatly adjust the density of nitrogen element in the polymer P1. The upper limit value of the amine equivalent of the amine monomer is not particularly limited, for example, it is 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 with respect to 1 equivalent of active hydrogen of the primary amino group contained in the amine monomer.

[0079] Examples of amine monomers include aliphatic amines such as 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’ - bis(3 - aminopropyl)ethylenediamine, polymethylenediamine, trimethylhexamethylenediamine, polyetherdiamine; 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 monomer 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 larger the number of epoxy groups, the more cross - linking points in the epoxy monomer increase, and the cross - linked structure in the polymer P1 becomes denser. As a result, the heat resistance and heat - humidity resistance tend to be improved. The upper limit value 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 1000, 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 more likely the density of nitrogen element in the polymer P1 is to increase. 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 1 equivalent of epoxy groups.

[0082] Examples of the epoxy monomer 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, t-butylphenyl glycidyl ether; diepoxyalkanes such as 1,5-hexadiene diepoxide, 1,7-octadiene diepoxide, 1,9-decadiene diepoxide; polyfunctional epoxy compounds having an ether group such as (poly)ethylene glycol diglycidyl ether, (poly)propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane polyglycidyl ether, pentaerythritol polyglycidyl ether; polyfunctional epoxy compounds having an amino group such as N,N,N’,N’-tetraglycidyl metaxylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

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

[0084] The epoxy monomer can be used alone or in combination of two or more. When using a monofunctional epoxy compound, 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 monomer group for forming the polymer P1.

[0085] The epoxy monomer preferably contains a polyfunctional epoxy compound having an ether group, such as ethylene glycol diglycidyl ether (EDE) and 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 contain, together with the polyfunctional epoxy compound having an ether group or in place of the polyfunctional epoxy compound, a polyfunctional epoxy compound having an amino group, such as N,N,N',N'-tetraglycidyl metaxylenediamine and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane.

[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 2 or more, may be 3 or more, and may be 4 or more. The upper limit of the number of primary amino groups is not particularly limited and is, for example, 100. The amine prepolymer may contain a secondary amino group or a tertiary amino group in addition to the primary amino group. 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 is, for example, 10% or more, preferably 20% or more, more preferably 30% or more, and may be 40% or more. The higher this ratio, the more the crosslinking points in the amine prepolymer increase and the denser the crosslinked structure in the reactant P2 becomes, thereby tending to improve the heat resistance and heat and humidity resistance. The upper limit of this ratio is not particularly limited and is, for example, 80% and may be 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 large weight average molecular weight tend to be safer to handle. Furthermore, when an amine prepolymer with a large weight average molecular weight is used, the density of the nitrogen element 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 100 g / eq. or less. The number of constitutional units contained in the amine prepolymer (degree of polymerization) is not particularly limited, and is, for example, 5 to 100.

[0088] Examples of the amine prepolymer 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 may be used alone or in combination of two or more.

[0089] Amine prepolymers, particularly PEI, tend to be safer to handle than amine monomers. As an example, the amine prepolymer may not be a hazardous material under the Fire Service Act, and may not be 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 be a mild or moderate irritant in a skin irritation test (primary skin irritation test using rabbits).

[0090] Examples of the epoxy monomer for forming the reactant P2 include those described above for the polymer P1.

[0091] As described above, the polymer P as an amine polymer contains a structural unit U1 derived from an epoxy monomer. When the polymer P is the polymer P1, the polymer P further contains a structural unit U2 derived from an amine monomer. The content of the structural unit U1 in the polymer P, particularly the polymer P1, is, for example, 20 wt% to 70 wt%. The content of the structural unit U2 in the polymer P, particularly the polymer P1, is, for example, 30 wt% or more, preferably 50 wt% or more. The upper limit value of the content of the 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, still more preferably 15 °C or lower, may be 10 °C or lower, may be 5 °C or lower, or may be 0 °C or lower. When the glass transition temperature Tg of the polymer P is this low, in the acidic gas adsorbent, the rate of adsorbing acidic gas tends to be high. The lower limit value of the glass transition temperature Tg of the polymer P is, from the viewpoints of sufficiently ensuring the adsorbability of acidic gas in the acidic gas adsorbent and heat resistance, for example, -100 °C, preferably -50 °C, more preferably -10 °C. In this specification, the glass transition temperature Tg means the midpoint glass transition temperature (T mg ) determined in accordance with the provisions of JIS K7121:1987. Note that the polymer P usually corresponds to a thermosetting resin. The polymer P is solid, for example, at 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, still more preferably 100000 or more. The upper limit value of the weight average molecular weight of the polymer P is, for example, 10000000.

[0094] The acid gas adsorbent contains, for example, polymer P as the main component. In this specification, the "main component" means the component contained in the largest amount by weight in the acid gas adsorbent. The content of polymer P in the acid gas adsorbent is, for example, 50 wt% or more, preferably 70 wt% or more, more preferably 90 wt% or more, may be 95 wt% or more, or may be 99 wt% or more. The acid gas adsorbent may be substantially composed of only polymer P. The higher the content of polymer P, the more likely the adsorbability of acid gas in the acid gas adsorbent will improve.

[0095] The acid gas adsorbent may be substantially composed of only polymer P, but may further contain other components other than polymer P. Examples of other components include reaction accelerators, plasticizers, pigments, dyes, anti-aging agents, conductive materials, antistatic agents, ultraviolet absorbers, flame retardants, antioxidants, etc. The reaction accelerator is used, for example, when synthesizing polymer P. Examples of reaction accelerators include tertiary amines such as triethylamine and tributylamine; imidazoles such as 2-phenol-4-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenol-4,5-dihydroxyimidazole. These reaction accelerators can promote the reaction for synthesizing polymer P1, for example.

[0096] The weight ratio of nitrogen element in the acid gas adsorbent is, for example, 5 wt% or more, preferably 10 wt% or more. The higher this weight ratio, the more likely the adsorbability of acid gas in the acid gas adsorbent will improve. The upper limit value of the weight ratio of nitrogen element in the acid gas adsorbent is not particularly limited and is, for example, 30 wt%. When all the nitrogen elements contained in the acid gas adsorbent are derived from amino groups, the above weight ratio of nitrogen element can be regarded as the weight ratio of amino groups in the acid gas adsorbent.

[0097] The shape of the acid gas adsorbent is not particularly limited and is, for example, block-shaped, sheet-shaped, particulate, etc. In this specification, particulate includes spherical, ellipsoidal, flaky, fibrous, etc.

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

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

[0100] The specific surface area of the acid gas adsorbent (porous body S) is not particularly limited, and is, for example, 0.5 m 2 / g or more, 1.0 m 2 / g or more, 2.0 m 2 / g or more, 3.0 m 2 / g or more, 4.0 m 2 / g or more, 5.0 m 2 / g or more, 6.0 m 2 / g or more, 7.0 m 2 / g or more, 8.0 m 2 / g or more, and further may be 9.0 m 2 / g or more. The larger the specific surface area of the acid gas adsorbent, the more the rate of adsorbing acid gas in the acid gas adsorbent tends to increase. The upper limit value of the specific surface area of the acid gas adsorbent is not particularly limited, and is, for example, 100 m 2 / g. The specific surface area of the acidic gas adsorbent means the BET (Brunauer-Emmett-Teller) specific surface area 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 of the present invention, an acidic gas adsorbent containing 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, 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 lower, to provide an acidic gas adsorbent. This acidic gas adsorbent has, for example, the above-described adsorption characteristics and desorption characteristics with respect to carbon dioxide. As an example, for the acidic gas adsorbent, the adsorption amounts a1 to a3, desorption amounts b1 to b2, 50°C desorption rate, 65°C desorption rate, etc. measured by the above method may satisfy the ranges exemplified above.

[0102] The pore volume of the acidic gas adsorbent (porous body S) is not particularly limited, and is, for example, 0.1 cm 3 / g or more, 0.2 cm 3 / g or more, 0.3 cm 3 / g or more, 0.5 cm 3 / g or more, 1.0 cm 3 / g or more, and further may be 2.0 cm 3 / g or more. The upper limit value of the pore volume of the acidic gas adsorbent is not particularly limited, and is, for example, 5.0 cm 3 / g, 4.0 cm 3 / g, or 3.0 cm 3 / g. The pore volume of the acidic gas adsorbent can be measured by the mercury intrusion method. The mercury intrusion method is carried out under the condition of an initial pressure of 21 kPa using a commercially available pore size distribution analyzer (for example, AutoPore V9620 manufactured by Micromeritics).

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

[0104] When the acid gas adsorbent is in particulate form, the average particle diameter of the acid gas adsorbent is not particularly limited, and for example, it is 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 diameter of the acid gas adsorbent may be 200 μm or less, 100 μm or less, or less than 75 μm. In this specification, the average particle diameter of the acid gas adsorbent means the particle diameter (d50) corresponding to 50% volume cumulative in the particle size distribution measured by a laser diffraction particle size analyzer or the like.

[0105] (Method for producing acid gas adsorbent) The method for producing the acid gas adsorbent of this embodiment includes, for example, reacting a compound group containing an amine monomer or an amine prepolymer and an epoxy monomer to form a polymer P. The compound group is, for example, a monomer group containing an amine monomer and an epoxy monomer. However, the compound group may contain an amine prepolymer instead of or together with the amine monomer.

[0106] The compound group may contain only the epoxy monomer E1 containing two epoxy groups, or may contain, instead of or together with the epoxy monomer E1, an epoxy monomer E2 containing three or more, for example, four epoxy groups. 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 for example, it is 4 / 6 to 8 / 2.

[0107] When preparing the polymer P, the mixing ratio of the epoxy monomer and the amine monomer or amine prepolymer is such that the ratio E / A of the equivalent weight (E) of the epoxy groups contained in the epoxy monomer to the equivalent weight (A) of the active hydrogen of the primary amino groups contained in the 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 more likely the density d of nitrogen element in the acidic gas adsorbent is to increase. The lower limit value of the ratio E / A is not particularly limited and is, for example, 0.1.

[0108] The reaction of the compound group is, for example, a polymerization reaction of an amine monomer and an epoxy monomer. However, the reaction of the compound group may be a cross-linking reaction of an amine prepolymer with an epoxy monomer. In the reaction of the compound group, the amino groups of the amine monomer or amine prepolymer react with the epoxy groups of the epoxy monomer. The reaction of the compound group can be carried out by applying energy to the compound group. The energy applied to the compound group is preferably thermal energy. As an example, the reaction of the compound group can be advanced by heating the compound group at a temperature of 40°C to 100°C. However, the energy applied to the compound group may be light energy.

[0109] An acidic gas adsorbent having a porous structure can be produced, for example, by the following method. First, the above compound group is mixed with a porogen to prepare a mixed solution. The porogen is a solvent that can dissolve monomers and prepolymers contained in the compound group, for example, and can further cause reaction-induced phase separation after the compound group reacts. Specific examples of the porogen 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 glycol are 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, isopropanol, a nonpolar solvent such as toluene, or a mixed solvent thereof. The porogen can be used alone or in combination of two or more.

[0110] Other components other than the compound group may be further added to the mixed solution. Examples of other components include the above-mentioned reaction accelerators.

[0111] Next, the compound group is reacted in the mixed solution. As an example, the compound group is reacted by filling the mixed solution into a mold and then performing heat treatment. Thereby, a cured body containing the polymer P and the porogen is obtained. In this cured body, a co-continuous structure is formed by phase separation of the polymer P and the porogen.

[0112] Next, the porogen is extracted from the cured body and removed. By doing so, an acidic gas adsorbent having a porous structure can be obtained. The extraction of the porogen can be carried out, for example, by immersing the cured body in a solvent. As this solvent, water, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, aliphatic alcohol solvents, ester solvents, ether solvents, halogen-containing organic solvents, etc. can be used. Examples of aliphatic hydrocarbon solvents include n-hexane, cyclohexane, methylcyclohexane, n-heptane, n-octane, isooctane, petroleum ether, benzene, etc. Examples of aromatic hydrocarbon solvents include toluene, xylene, mesitylene, benzene, etc. Examples of aliphatic alcohol solvents include methanol, ethanol, isopropanol, butanol, cyclohexanol, ethylene glycol, propylene glycol, propylene glycol monomethyl ether, diethylene glycol, etc. Examples of ester solvents include ethyl acetate, etc. 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, anisole, etc. Examples of halogen-containing organic solvents include dichloromethane, chloroform, carbon tetrachloride, dichloroethane, chlorobenzene, etc. These solvents can be used alone or in combination of two or more.

[0113] When producing a cured body, the greater the reaction rate of the compound group, the finer the dispersion of the porogen in the cured body tends to be. By removing the porogen from the cured body in which the porogen is finely dispersed, an acidic gas adsorbent having a large specific surface area can be produced. The reaction rate of the compound group varies depending on, for example, the types and blending ratios of the monomers and prepolymers contained in the compound group. As an example, when an epoxy monomer E2 containing three or more, for example four, epoxy groups is used, or when a polyethyleneimine having a large weight average molecular weight is used as an amine prepolymer, the reaction rate of the compound group tends to be large.

[0114] (Use of acidic gas adsorbent) The acidic gas adsorbent of this embodiment can adsorb acidic gases. Examples of acidic gases include carbon dioxide, hydrogen sulfide, carbonyl sulfide, sulfur oxides (SOx), hydrogen cyanide, nitrogen oxides (NOx), etc., 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 brought into contact with the acidic gas adsorbent. The mixed gas contains, for example, other gases other than the acidic gas. Examples of other gases include non-polar gases such as hydrogen and nitrogen, and inert gases such as helium, and nitrogen is preferred. The mixed gas is typically air. The mixed gas may be the off-gas of a chemical plant or a 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 at standard conditions (0°C, 101 kPa), it is, for example, 0.01 vol% (100 vol ppm) or more, preferably 0.04 vol% (400 vol ppm) or more, and may be 1.0 vol% or more. The upper limit value of the concentration of carbon dioxide in the mixed gas is not particularly limited, and at standard conditions, it is, for example, 10 vol%. The pressure of the mixed gas is typically equal to the atmospheric pressure in the use environment of the acidic gas adsorbent. However, the mixed gas brought into contact with the acidic gas adsorbent may be pressurized.

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

[0118] Next, a regeneration treatment is performed on the acid gas adsorbent that has adsorbed the acid gas. The regeneration treatment can be carried out, for example, by heating the acid gas adsorbent. The heating temperature of the acid gas adsorbent is, for example, 50 to 80°C. The acid gas adsorbent may be heated in a reduced-pressure atmosphere or a vacuum atmosphere. By heating the acid gas adsorbent, the acid gas desorbs from the acid gas adsorbent. As a result, the acid gas adsorbent is regenerated and can be used repeatedly. The acid gas desorbed from the acid gas adsorbent, particularly carbon dioxide, can be used as a raw material for chemical synthesis or dry ice. Note that the operation of adsorbing the acid gas by the acid gas adsorbent and the regeneration treatment of the acid gas adsorbent can be carried out using the above-described measuring device 10 (acid gas adsorption device).

Example

[0119] Hereinafter, the present invention will be described in more detail 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 (manufactured by NOF Corporation, UNION PB-500) and 0.43 g of polyoxypropylene diglyceryl ether (manufactured by NOF Corporation, UNILUBE DGP-700) were added to a 6 mL screw vial (manufactured by AS ONE Corporation). By dissolving 0.74 g of ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX Corporation, EX-810) and 0.74 g of pentaerythritol tetraglycidyl ether (manufactured by Showa Denko KK, SHOWFREE PETG) in the obtained mixed solution, a mixed solution of an epoxy monomer and a porogen was prepared.

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

[0122] Next, a tabletop shaker (Enzel Vibrator Digital 60 Hz) was set to intensity 5, and the mixed solution was shaken for 2 minutes. Next, this mixed solution was cured by allowing it to stand in a constant temperature bath at 80°C for 2 hours. As a result, a block-shaped cured body containing the polymer P having an amino group was obtained. This cured body was taken out of the screw vial and cut into approximately 3 mm squares. Next, the operation of immersing the cured body in ethyl acetate at 60°C for 1 hour was repeated twice with liquid replacement. As a result, the porogen was removed from the cured body, and a porous body containing the polymer P was formed. This porous body was dried at 60°C for 1 hour and further vacuum dried for 2 hours to obtain the acidic gas adsorbent of Example 1.

[0123] (Examples 2 to 11) Except that the types and amounts of the raw materials were changed as shown in Table 1, the acidic gas adsorbents of Examples 2 to 11 were obtained by the same method as in Example 1.

[0124] (Comparative Example 1) First, 2.63 g of polypropylene glycol (manufactured by ADEKA Corporation, Adeka Polyether P-400) and 0.36 g of polyethylene glycol (manufactured by Sigma-Aldrich, average molecular weight 200) were added to a 6 mL screw vial (manufactured by AS ONE Corporation). A mixed solution of an epoxy prepolymer and a porogen was prepared by dissolving 1.58 g of bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER828) in the obtained mixed solution.

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

[0126] Next, a tabletop shaker (Enzel Vibrator Digital 60 Hz) was set to intensity 5, and the mixed solution was shaken for 2 minutes. Next, this mixed solution was cured by allowing it to stand in a constant temperature bath at 80°C for 4 hours. As a result, a block-shaped cured product containing the polymer P having an amino group was obtained. This cured product was taken out of the screw tube bottle and cut into approximately 3 mm squares. Next, the operation of immersing the cured product in isopropyl alcohol at 60°C for 1 hour was repeated twice with liquid replacement. Further, the operation of immersing the cured product in ultrapure water at 60°C for 1 hour was repeated twice with liquid replacement. Next, the cured product was immersed in methanol at room temperature for 1 hour. The cured product was air-dried at room temperature for 12 hours and further vacuum-dried at 60°C for 8 hours to obtain the acid gas adsorbent of Comparative Example 1.

[0127] (Comparative Examples 2 to 3) Except that the types and blending amounts of the raw materials were changed as shown in Table 1, the acid gas adsorbents of Comparative Examples 2 to 3 were obtained by the same method as in Comparative Example 1.

[0128] [Density of nitrogen element] For the prepared acid gas adsorbent, the density d of the nitrogen element was measured by the method described above. As the CHN elemental analyzer, Vario EL III manufactured by Elementar was used.

[0129] [Specific surface area] For the prepared acid gas adsorbent, the specific surface area 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·BEL, trade name “BERSORP-mini”) was used.

[0130] [Glass transition temperature Tg] For the polymer contained in the prepared acid gas adsorbent, the glass transition temperature Tg was measured by the following method. First, about 5 mg of the acid gas adsorbent was set in a differential scanning calorimeter (DSC2500 manufactured by TA Instruments). Using this apparatus, 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, it was cooled to -50 °C at a cooling rate of 10 °C / min, held at that temperature for 1 minute, and then further 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 appears, the second baseline after the specific heat change appears, and among the bent portions due to the specific heat change, the tangent line passing through the point where the slope is maximum are specified. The intermediate temperature between the intersection of the first baseline and the tangent line and the intersection of the second baseline and the tangent line was specified as the glass transition temperature Tg.

[0131] [Carbon dioxide adsorption amount] For the prepared acid gas adsorbent, the adsorption amounts a1 to a3 and the desorption amounts b1 to b2 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) (desorption rate at 50 °C) and the ratio of the desorption amount b2 (mmol / g) to the adsorption amount a1 (mmol / g) (desorption rate at 65 °C) were calculated.

[0132] [Heat resistance test] For the prepared acid gas adsorbent, a heat resistance test was conducted 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) (maintenance rate R1) was calculated.

[0133] [Moisture and heat resistance test] For the prepared acid gas adsorbent, a moisture and heat resistance test was conducted by the method described above, and the carbon dioxide adsorption amount a5 was measured. Furthermore, the ratio of the adsorption amount a5 (mmol / g) to the adsorption amount a1 (mmol / g) (maintenance rate R2) was calculated.

[0134]

Table 1

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

[0136] The abbreviations in Table 1 are as follows. EDE: Ethylene glycol diglycidyl ether (manufactured by Nagase ChemteX Corporation, EX-810) JER828: Bisphenol A type epoxy resin (manufactured by Mitsubishi Chemical Corporation, JER828) PETG: Pentaerythritol tetraglycidyl ether (manufactured by Showa Denko K.K., ShoFree (registered trademark) PETG) T-C: 1,3-Bis(N,N-diglycidylaminomethyl) cyclohexane (manufactured by Mitsubishi Gas Chemical Company, Inc., TETRAD-C) T-X: N,N,N’,N’-Tetraglycidyl metaxylene diamine (manufactured by Mitsubishi Gas Chemical Company, Inc., TETRAD-X) PEI300: Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin SP-003, weight average molecular weight of about 300) PEI1200: Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin SP-012, weight average molecular weight of about 1200) PEI1800: Polyethyleneimine (manufactured by Nippon Shokubai Co., Ltd., Epomin SP-018, weight average molecular weight of about 1800) TETA: Triethylenetetramine (manufactured by Tosoh Corporation) PB-500: Poly(1,2-butanediol)-6 propylene glycol (manufactured by NOF Corporation, Unionol (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, Unionol (registered trademark) PB-700) PEG: Polyethylene glycol (manufactured by Sigma - Aldrich, average molecular weight 200)

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

[0138] [Table 2]

[0139] [Table 3]

[0140] As can be seen from Table 3, the acid gas adsorbent of the example had a large density d of nitrogen element, and the adsorption amount a1 and the desorption amount b1 were also large values. It can be said that the acid gas adsorbent of the example is suitable for adsorbing and desorbing acid gas under relatively mild conditions.

Industrial Applicability

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

Claims

1. 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 acid gas adsorbent is 0.5 m 2 / g or more, and the glass transition temperature of the polymer is 40°C or lower. The acidic gas adsorbent.

2. When heat treatment is performed for 100 hours in an environment of 85°C and 10% RH, the maintenance rate R1 of the amount of carbon dioxide that can be adsorbed (mmol / g) is 50% or more. The acidic gas adsorbent according to Claim 1.

3. When heat treatment is performed for 100 hours in an environment of 85°C and 85% RH, the maintenance rate R2 of the amount of carbon dioxide that can be adsorbed (mmol / g) is 50% or more. The acidic gas adsorbent according to Claim 1.

4. The acidic gas adsorbent according to Claim 1, which contains the polymer as a main component.

5. The polymer is an amine polymer containing a structural unit derived from an epoxy monomer. The acidic gas adsorbent according to Claim 1.

6. The 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 reaction product P2 of a compound group containing an amine prepolymer and an epoxy monomer. The acidic gas adsorbent according to Claim 5.

7. The weight average molecular weight of the amine prepolymer is 300 or more. The acidic gas adsorbent according to Claim 6.

8. The amine prepolymer contains polyethyleneimine. The acidic gas adsorbent according to Claim 6.

9. The amine monomer contains an aliphatic amine. The acidic gas adsorbent according to Claim 6.

10. The epoxy equivalent of the epoxy monomer is 150 g / eq. or less. The acidic gas adsorbent according to Claim 5.

11. The epoxy monomer contains a polyfunctional epoxy compound having an ether group. The acidic gas adsorbent according to Claim 5.

12. Having a porous structure. The acidic gas adsorbent according to Claim 1.

13. An adsorption unit having a gas inlet and a gas outlet, and the adsorption unit houses the acidic gas adsorbent according to Claim 1. The acidic gas adsorption device.

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