Novel amine compound, acid gas absorbent, method for removing acid gas, and acid gas removal

Abstract

To provide an amine compound having a large absorption amount of an acidic gas and strong oxidation resistance, an absorbent containing the same, an acidic gas removal method and an acidic gas removal device.SOLUTION: In an acidic gas removal method and a device, an absorbent containing an amine compound expressed as formula (1a) or (1b) is used [where, R1-R3 are each a substituent group expressed as hydrogen or an alkyl group; a is independently 0 or 1; m is a number of 1-3; and n is a number of 1-4].SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Embodiments of the present invention relate to a novel amine compound, an acidic gas absorbent, a method for removing acidic gas, and an acidic gas removal apparatus.

Background Art

[0002] In recent years, it has been pointed out that the greenhouse effect due to the increase in carbon dioxide (CO2) concentration is one of the causes of global warming, and international measures to protect the environment on a global scale are urgently needed. The generation of CO2 is mainly due to industrial activities, and the momentum to suppress its emission into the environment is increasing.

[0003] As technologies for suppressing the increase in the concentration of acidic gases such as CO2, there are the development of energy-saving products, the technology of using acidic gases as resources or storing them in isolation, and the conversion to alternative energies such as natural energy or nuclear energy that do not emit acidic gases. Among them, the separation and recovery technology of discharged acidic gases is known.

[0004] As acidic gas separation technologies studied so far, there are absorption methods, adsorption methods, membrane separation methods, or cryogenic methods. Among them, the absorption method is suitable for treating a large amount of gas efficiently and economically, and since it is easy to increase the size of the removal device, its application to factories and power plants is being considered.

[0005] Mainly, as a method for power plants that use fossil fuels, a method of removing and recovering CO2 in combustion exhaust gas by bringing the exhaust gas generated when burning fossil fuels (coal, oil, natural gas, etc.) into contact with a chemical absorbent, and further storing the recovered CO2 is known. In addition, it has been proposed to remove acidic gases such as hydrogen sulfide (H2S) other than CO2 using a chemical absorbent.

[0006] Generally, alkanolamines typified by monoethanolamine (MEA) are known as chemical absorbents used in the absorption method. Such alkanolamines have been developed since the 1930s and are still in use today. General alkanolamines used in the absorption method include 2-amino-2-methylpropanolamine, methylaminoethanol, ethylaminoethanol, propylaminoethanol, diethanolamine, methyldiethanolamine, dimethylethanolamine, diethylethanolamine, triethanolamine, or dimethylamino-1-methylethanol.

[0007] When these conventionally used alkanolamines are used alone, the CO2 absorption rate may not be sufficient, and usually a compound having a reaction promoting effect is often used in combination. Cyclic diamines are known as such compounds having a reaction promoting effect, but they generally have a high vapor pressure and are likely to disperse, and may have poor handleability. In addition, for the recovery of carbon dioxide, the absorption step of carbon dioxide into the amine aqueous solution and the desorption step of carbon dioxide from the aqueous solution that has absorbed carbon dioxide are performed with high efficiency, and it is also required that the recovery energy consumed for carbon dioxide recovery during that time is low. To meet this requirement, an absorbent with a large absorption amount is effective as an absorbent. At the same time, it is required from the perspective of environmental impact to suppress the dispersion of amines released into the atmosphere as much as possible. For example, Patent Document 1 discloses an absorbent for removing acidic gas from a fluid. This absorbent contains a combination of a tertiary alkanolamine and hydroxyethylpiperazine or the like.

[0008] On the other hand, in the above CO2 recovery system, the exhaust gas (acidic gas) contains oxygen, and the CO2 release (recovery) from the absorbent that has absorbed the acidic gas is often heated at 100 °C or higher. In such an environment, it is known that the amine in the absorbent is oxidized by oxygen and deteriorates as the heating temperature increases.

[0009] For example, oxidation of alkanolamine in the acid gas absorption process and an increase in deterioration due to an increase in heating temperature have been reported.

[0010] Thus, conventional absorbents have a problem that their absorption characteristics deteriorate over time because of their low durability (oxidation resistance). Therefore, there is a demand for a new absorbent that satisfies both durability and acid gas absorption amount as an absorbent for acid gas.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Non-Patent Documents

[0012]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0013] An object of the present embodiment is to provide an amine compound having high oxidation resistance, an acid gas absorbent having high durability using the same, a method for removing acid gas using the same, and an acid gas removal apparatus.

Means for Solving the Problems

[0014] The acid gas absorbent according to the embodiment contains a solvent and at least one or more amine compounds selected from the group consisting of amine compounds represented by Formula (1a) and Formula (1b).

Chemical Formula

[0015] Also, the method for removing acidic gas according to the embodiment comprises contacting a gas containing acidic gas with the acidic gas absorbent to remove acidic gas from the gas containing the acidic gas.

[0016] Also, the acidic gas removal apparatus according to the embodiment includes an absorber that removes acidic gas from a gas containing acidic gas by absorbing the acidic gas into the acidic gas absorbent by contacting the gas containing acidic gas with the acidic gas absorbent, a regenerator that desorbs acidic gas from the acidic gas absorbent that has absorbed the acidic gas and regenerates the acidic gas absorbent and has The acidic gas absorbent regenerated by the regenerator is reused in the absorber.

[0017] Furthermore, the amine compound according to the embodiment is represented by the formula (1a). [Chemical formula] [In the formula, R 1 Each is independently hydrogen or an unsubstituted or substituted alkyl group having 3 or fewer carbon atoms, R 2 Each is independently hydrogen or an unsubstituted or substituted alkyl group having 3 or fewer carbon atoms, and one -CR2 R contained in 3 2 Among them, at least two are substituents represented by (not being hydrogen)), a is independently 0 or 1 respectively, m is a number from 1 to 3, n is independently a number from 1 to 4 respectively]

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. In the following embodiments, the case where the acid gas is carbon dioxide will be described as an example. However, the acid gas absorbent according to the embodiments of the present invention can obtain the same effects for other acid gases such as hydrogen sulfide. The acid gas absorbent according to the embodiment is particularly suitable for absorbing oxidizing gases such as carbon dioxide and hydrogen sulfide.

[0020] The acid gas absorbent according to the embodiment contains a solvent and a specific amine compound. One of the cyclic diamine compounds that can be used as this specific amine compound is represented by the formula (1a).

Chemical formula

[0021] More specifically, R 1 is a hydrogen, methyl, ethyl, propyl, or isopropyl group, and R 2 is a hydrogen, methyl, or ethyl group. Also, n is from 1 to 4, preferably 2 to 3, and m is from 1 to 3, preferably 2. The amine compound represented by such formula (1a) has not been known conventionally. Specific examples thereof include the following.

[0022]

Chemical formula

[0023]

Chemical formula

[0024] Another cyclic diamine compound that can be used in the acid gas absorbent according to the embodiment is represented by formula (1b).

[0025]

Chemical formula

[0026] More specifically, R 1 is a hydrogen, methyl, ethyl, n-propyl, or isopropyl group, and R 2 is a hydrogen, methyl, or ethyl group, R 3 is a hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, or tert-butyl group. Also, n is from 1 to 4, preferably 2 to 3, m is from 1 to 3, and preferably 2.

[0027] Specific examples of the amine compound represented by such formula (1b) include the following.

[0028]

Chemical formula

[0029]

Chemical formula

[0030] The acid gas absorbent according to the embodiment contains either formula (1b) or (1b). Here, two or more compounds represented by formula (1a) may be combined, two or more compounds represented by formula (1b) may be combined, or further, compounds of formula (1a) and formula (1b) may be combined. Note that the production methods of the compounds of formula (1a) or (1b) will be described later, but in their production processes, there may be a mixture in which those with a = 1 and those with a = 0 in the formula are mixed. In such a case, it can also be used as a mixture without separation in the acid gas absorbent according to the embodiment.

[0031] The content ratio of the cyclic diamine compound represented by the formula (1a) or formula (1b) contained in the acidic gas absorbent according to the embodiment is preferably 10 to 60% by mass, more preferably 20 to 50% by mass, based on the total mass of the acidic gas absorbent. Generally, the higher the content ratio of the amine compound, the larger the absorption amount and desorption amount of carbon dioxide per unit volume, and the faster the absorption rate and desorption rate of carbon dioxide. Therefore, it is preferable in terms of energy consumption and treatment efficiency. In general, if the content ratio of the amine compound in the acidic gas absorbent is too high, an increase in the viscosity of the absorbent is likely to occur. However, in the embodiment, such a tendency is not observed if the content ratio of the amine compound of the formula (1a) or formula (1b) is 60% by mass or less. Further, by setting the content ratio of the amine compound of the formula (1a) or (1b) to 10% by mass or more, a sufficient absorption amount and absorption rate of carbon dioxide can be obtained, and excellent treatment efficiency can be obtained. The acidic gas absorbent in which the content ratio of the amine compound of the formula (1a) or (1b) is in the above range is advantageous for long-term operation because it not only has a high carbon dioxide absorption amount but also high oxidation durability when used for carbon dioxide recovery.

[0032] In addition to the cyclic diamine compound, the acidic gas absorbent according to the embodiment may contain an additional amine compound represented by the following formula (2)

[0033] [Chemical formula] [In the formula, R 4 are each independently hydrogen or an unsubstituted or substituted alkyl group, at least one of the three Rs 4 is not hydrogen, and two Rs 4 may form a cyclic structure linked to each other.]

[0034] R 4Specific examples thereof include hydrogen, a methyl group, an ethyl group, an isopropyl group, a tert-butyl group, a sec-butyl group, a hydroxyethyl group, a hydroxypropyl group, a hydroxypentyl group, a hydroxyhexyl group, a hydroxyheptyl group, or a hydroxyoctyl group, an aminopropyl group, an aminopentyl group, an aminohexyl group, an aminoheptyl group, or an aminooctyl group, etc. Further, two Rs 4 can also be linked to each other to form a piperazine ring, a pyrrolidine ring, a morpholine ring, a piperidine ring, etc.

[0035] Specific examples of the amine compound represented by formula (2) include 1-(2-Hydroxyethyl)piperazine, 1-(2-Aminoethyl)piperazine, 1,4-Bis[3-aminopropyl]piperazine, N-Isopropyldiethanolamine, N-Isopropyldipropanolamine, N-Isopropyldibutanolamine, N-Isopropyldipentanolamine, N-Isopropyldihexanolamine, 3-[(2-Hydroxyethyl)(propan-2-yl)amino]propan-1-ol, 4-[(2-Hydroxyethyl)(propan-2-yl)amino]butan-1-ol, 5-[(2-Hydroxyethyl)(propan-2-yl)amino]pentan-1-ol, 6-[(2-Hydroxyethyl)(propan-2-yl)amino]hexan-1-ol, N-sec-Butyldiethanolamine, N-sec-Butyldipropanolamine, N-sec-Butyldibutanolamine, N-sec-Butyldipentanolamine, N-sec-Butyldihexanolamine, 3-[(2-Hydroxyethyl)(butan-2-yl)amino]propan-1-ol, 4-[(2-Hydroxyethyl)(butan-2-yl)amino]butan-1-ol, 5-[(2-Hydroxyethyl)(butan-2-yl)amino]pentan-1-ol, 6-[(2-Hydroxyethyl)(butan-2-yl)amino]hexan-1-ol, N-Cyclopentyldiethanolamine, N-Cyclopentyldipropanolamine, N-Cyclopentyldibutanolamine, N-Cyclopentyldipentanolamine, N-Cyclopentyldihexanolamine, 3-[(2-Hydroxyethyl)(cyclopentyl)amino]propan-1-ol, 4-[(2-Hydroxyethyl)(cyclopentyl)amino]butan-1-ol, 5-[(2-Hydroxyethyl)(cyclopentyl)amino]pentan-1-ol, 6-[(2-Hydroxyethyl)(cyclopentyl)amino]hexan-1-ol, 2-Azetidinemethanol, 2-(2-Aminoethyl)azetidine, 2-Pyrrolidinemethanol, 2-(2-Aminoethyl)pyrrolidine, 2-Piperidinemethanol, 3-Piperidineethanol, 2-(2-Aminoethyl)pyrrolidine, 1-(2-Hydroxyethyl)piperazine, 2-(Hydroxymethyl)piperazine, 3-Hydroxypyrrolidine, 3-Pyrrolidinemethanol, 2-(2-Hydroxyethyl)pyrrolidine, 4-Piperidineethanol, 3-Hydroxypiperidine, 4-Hydroxypiperidine, 4-(Hydroxymethyl)piperidine, and 3-Aminopiperidine Examples include, but are not limited to, these additional amine compounds.

[0036] Among these, 1-(2-Hydroxyethyl)piperazine, 1-(2-Aminoethyl)piperazine, 1,4-Bis[3-aminopropyl]piperazine, N-Isopropyldiethanolamine, N-Isopropyldipropanolamine, 3-[(2-Hydroxyethyl)(propan-2-yl)amino]propan-1-ol, N-sec-Butyldiethanolamine, N-sec-Butyldipropanolamine, N-sec-Butyldibutanolamine, 3-[(2-Hydroxyethyl)(butan-2-yl)amino]propan-1-ol, N-Cyclopentyldiethanolamine, N-Cyclopentyldipropanolamine, and 3-[(2-Hydroxyethyl)(cyclopentyl)amino]propan-1-ol, are preferred.

[0037] The total amine content of the cyclic diamine compound represented by formula (1a) or (1b) and the additional amine compound represented by formula (2) contained in the acid gas absorbent is preferably 10 to 60% by mass, more preferably 20 to 50% by mass. Also, the content of the compound represented by formula (2) based on the total mass of the acid gas absorbent is preferably 1 to 40% by mass, more preferably 5 to 30% by mass. If the content of the compound represented by formula (2) contained in the acid gas absorbent is less than 1% by mass, there is a risk that the effect of improving the absorption rate of the acid gas cannot be sufficiently obtained. If the above content exceeds 30% by mass, the oxidation durability of the absorbent may be significantly reduced.

[0038] The acid gas absorbent according to the embodiment contains a solvent in which the above-mentioned amine compound is dissolved or dispersed. As the solvent, water, an organic solvent, or a mixed solvent thereof, for example, an aqueous solvent can be used. From the viewpoints of safety and cost, it is preferable to use water or an aqueous solvent as the solvent. However, in order to improve the solubility of the amine compound and the like, an organic solvent or a mixed solvent having a relatively high content of the organic solvent can also be used. The aqueous solvent mainly comprises water and contains a small amount of an organic solvent. However, if the boiling point of the organic solvent is low, it may volatilize in the acid gas absorption apparatus and cause damage to the apparatus. For this reason, the organic solvent has a boiling point equal to or higher than the boiling point of water, that is, 100°C or higher. When water is used as the solvent, its content is preferably 40 to 90% by mass, particularly preferably 50 to 80% by mass, based on the total mass of the acid gas absorbent. When the water content is within this range, it is preferable in terms of suppressing an increase in the viscosity of the absorbent and suppressing foaming when absorbing carbon dioxide. Further, the aqueous solvent contains a small amount of an organic solvent, but its content is preferably 1% by mass or less based on the acid gas absorbent.

[0039] In addition, the optional components include, for example, an antioxidant, a pH adjuster, an antifoaming agent, a corrosion inhibitor, and the like.

[0040] Preferable specific examples of the antioxidant include, for example, dibutylhydroxytoluene (BHT), butylhydroxyanisole (BHA), sodium erythorbate, sodium nitrite, sulfur dioxide, 2-mercaptoimidazole, 2-mercaptobenzimidazole, and the like. When using an antioxidant, the content based on the total mass of the acid gas absorbent is preferably 0.01 to 1% by mass, particularly preferably 0.1 to 0.5% by mass.

[0041] The antioxidant can prevent the deterioration of the acid gas absorbent and improve its lifespan. Preferred specific examples of the antifoaming agent include, for example, silicone-based antifoaming agents and organic antifoaming agents. When using an antifoaming agent, the content based on the total mass of the acid gas absorbent is preferably 0.00001 to 0.001% by mass, particularly preferably 0.0005 to 0.001% by mass. The antifoaming agent can prevent foaming of the acid gas absorbent, suppress a decrease in the absorption efficiency and desorption efficiency of the acid gas, and prevent a decrease in the fluidity or circulation efficiency of the acid gas absorbent.

[0042] Preferred specific examples of the corrosion inhibitor include, for example, phosphate esters, tolyltriazoles, and benzotriazoles. When using a corrosion inhibitor, the content based on the total mass of the acid gas absorbent is preferably 0.00003 to 0.0008% by mass, particularly preferably 0.00005 to 0.005% by mass. Such a corrosion inhibitor can prevent corrosion of the plant equipment and improve its lifespan.

[0043] In addition, the acid gas absorbent according to the embodiment preferably does not contain low-boiling-point materials, specifically compounds having a boiling point of less than 100°C. Since the acid gas absorbent is heated during the process of removing or recovering the acid gas, the low-boiling-point materials evaporate and are released into the atmosphere, or their concentration decreases and the removal efficiency of the acid gas changes. Specifically, the content of the material having a boiling point of less than 100°C is preferably 1% by mass or less, more preferably 0.1% by mass or less, based on the total mass of the acid gas absorbent.

[0044] As described above, according to the acid gas absorbent of the present embodiment, the absorption amount of acid gases such as carbon dioxide can be increased, and the diffusibility of the reaction promoter can be decreased. And, the energy required for the recovery of acid gases is small. Further, since an amine compound having a plurality of hydroxyl groups, which are polar groups, in the molecule is used and the diffusibility is suppressed, the diffusion to the outside of the reaction apparatus is suppressed. From this, even when a reaction promoter having a low vapor pressure is used in combination, the acid gas can be stably processed over a long period of time. And, since it has high reactivity with acid gases (for example, carbon dioxide (CO2), hydrogen sulfide (H2S), carbonyl sulfide (COS)) and is excellent in solubility in water, it is difficult to precipitate during acid gas absorption. The acid gas absorbent of the embodiment of the present invention containing the compound has further improved the absorption amount of acid gas (particularly, carbon dioxide) per unit mole, the acid gas absorption amount per unit volume of the acid gas absorbent, and the acid gas absorption rate. And, the amount of amine released from the absorption tower and the regeneration tower can be decreased.

[0045] <Method for Removing Acid Gas> The method for removing acid gas according to the embodiment of the present invention is to bring a gas containing an acid gas into contact with the first or second acid gas absorbent described above, and remove the acid gas from the gas containing the acid gas described above.

[0046] The method for removing acid gas according to the embodiment of the present invention basically comprises a step of absorbing an acid gas into the acid gas absorbent according to the embodiment of the present invention described above (absorption step), and a step of desorbing the acid gas from the acid gas absorbent according to the embodiment of the present invention described above that has absorbed this acid gas. That is, the basic configuration of the method for removing acid gas according to the embodiment of the present invention is a step of bringing a gas containing an acid gas (for example, exhaust gas, etc.) into contact with an acid gas absorbent to absorb the acid gas into the acid gas absorbent (acid gas absorption step), and heating the acid gas absorbent having absorbed the acid gas obtained in the above acid gas absorption step to desorb and remove the acid gas (acid gas separation step).

[0047] The method of bringing a gas containing an acid gas into contact with an aqueous solution containing the above acid gas absorbent is not particularly limited. For example, a method of bubbling a gas containing an acid gas into the acid gas absorbent to absorb the acid gas by the absorbent, a method of spraying the acid gas absorbent in a mist form into a gas stream containing the acid gas (spraying or spraying method), or a method of countercurrently contacting a gas containing the acid gas with the acid gas absorbent in an absorber filled with a filler made of magnetic or metal mesh, etc. can be used.

[0048] When absorbing a gas containing an acid gas into an aqueous solution, the temperature of the acid gas absorbent is usually preferably from room temperature to 60 °C or lower. More preferably 50 °C or lower, particularly preferably 20 to 45 °C. The lower the temperature, the more the absorption amount of the acid gas increases, but the lower limit value of the treatment temperature can be determined by the gas temperature in the process, the heat recovery target, etc.

[0049] The pressure during acid gas absorption is usually approximately atmospheric pressure. Although it is also possible to pressurize to a higher pressure to enhance the absorption performance, it is preferably carried out under atmospheric pressure to suppress the energy consumption required for compression.

[0050] As a method of separating an acid gas from the acid gas absorbent that has absorbed the acid gas and recovering pure or high-concentration carbon dioxide, methods such as heating the acid gas absorbent in the same way as distillation and foaming in a kettle for desorption, a tray column, a spray column, and a method of heating while expanding the liquid interface in a regeneration column filled with a filler made of magnetic or metal mesh can be mentioned. Thereby, the acid gas is released by dissociation from the carbamate anion or bicarbonate ion.

[0051] The temperature of the acid gas absorbent during acid gas separation is usually 70 °C or higher, preferably 80 °C or higher, more preferably 90 to 120 °C. The higher the temperature, the more the desorption amount of the acid gas increases, but when the temperature is increased, the energy required for heating the absorbent increases, so the temperature can be determined by the gas temperature in the process, the heat recovery target, etc.

[0052] The pressure during acid gas separation can usually be about 1 to 3 atmospheres. In order to enhance the separation performance, it is also possible to reduce the pressure to a lower level, but it is preferably carried out within this range to suppress the energy consumption required for pressure reduction. The acid gas absorbent after separating the acid gas can be sent back to the acid gas absorption process and recycled. Also, the heat generated during acid gas absorption is generally heat-exchanged and cooled by a heat exchanger for preheating the aqueous solution injected into the regenerator in the recycling process of the aqueous solution.

[0053] The purity of the acid gas recovered in this way is usually extremely high, about 95 to 99% by volume. This pure acid gas or high-concentration acid gas can be used as a synthetic raw material for chemicals or polymer substances, a refrigerant for food refrigeration, etc. In addition, it is also possible to isolate and store the recovered acid gas underground or the like where technology is currently being developed.

[0054] Among the above-described processes, the process of separating acid gas from the acid gas absorbent and regenerating the acid gas absorbent is the part that consumes the most energy, and in this process, about 50 to 80% of the total energy of the entire process may be consumed. Therefore, by reducing the energy consumption in the regeneration process of the acid gas absorbent, the cost of the acid gas absorption and separation process can be reduced, and the removal of acid gas from the exhaust gas can be carried out economically and efficiently. According to the present embodiment, by using the acid gas absorbent of the above-described embodiment, the energy required for acid gas separation (regeneration process) can be reduced. For this reason, the carbon dioxide absorption and separation process can be carried out efficiently under economically advantageous conditions.

[0055] Also, the amine compound according to the above-described embodiment has significantly higher corrosion prevention properties against metal materials such as carbon steel compared to alkanolamines such as 2-aminoethanol that have conventionally been used as acid gas absorbents. Therefore, by adopting such an acid gas removal method using an acid gas absorbent, for example, in plant construction, it is not necessary to use high-cost high-grade corrosion-resistant steel, which is advantageous in terms of cost.

[0056] <Acid gas removal device> The acid gas removal device according to an embodiment of the present invention contacts a gas containing an acid gas with the first or second acid gas absorbent described above, and absorbs the acid gas in the acid gas absorbent to remove the acid gas from the gas containing the acid gas. It has an absorber and a regenerator that desorbs the acid gas from the acid gas absorbent that has absorbed the acid gas and regenerates the acid gas absorbent, and is an acid gas removal device that reuses the acid gas absorbent regenerated by the regenerator in the absorber. FIG. 1 is a schematic diagram of the acid gas removal device of the embodiment.

[0057] This acid gas removal device 1 includes an absorber 2 that contacts a gas containing an acid gas (for example, exhaust gas) with an acid gas absorbent and absorbs and removes the acid gas from the gas containing the acid gas, and separates the acid gas from the acid gas absorbent that has absorbed the acid gas. And a regenerator 3 for regenerating the acid gas absorbent. Hereinafter, the case where the acid gas is carbon dioxide will be described as an example.

[0058] FIG. 1 is a schematic diagram of the acid gas removal device of the embodiment. This acid gas removal device 1 includes an absorber 2 that contacts a gas containing an acid gas (for example, exhaust gas) with an acid gas absorbent and absorbs and removes the acid gas from the gas containing the acid gas, and separates the acid gas from the acid gas absorbent that has absorbed the acid gas. And a regenerator 3 for regenerating the acid gas absorbent. Hereinafter, the case where the acid gas is carbon dioxide will be described as an example.

[0059] As shown in FIG. 1, exhaust gas containing carbon dioxide, such as combustion exhaust gas discharged from a thermal power plant or the like, is guided to the lower part of the absorber 2 through the gas supply port 4. This exhaust gas is pushed into the absorber 2 and comes into contact with the acid gas absorbent supplied from the acid gas absorbent supply port 5 at the upper part of the absorber 2. As the acid gas absorbent, the acid gas absorbent according to the above-described embodiment is used.

[0060] In addition to the above amine compounds and solvents such as water, this acidic gas absorbent may also contain other compounds such as nitrogen-containing compounds, antioxidants, pH adjusters, etc. that improve the carbon dioxide absorption performance, in any proportion.

[0061] In this way, when the exhaust gas comes into contact with the acidic gas absorbent, carbon dioxide in the exhaust gas is absorbed and removed by the acidic gas absorbent. The exhaust gas after carbon dioxide is removed is discharged from the gas outlet 6 to the outside of the absorber 2.

[0062] The acidic gas absorbent that has absorbed carbon dioxide is sent by the rich liquid pump 8 to the heat exchanger 7 and then further sent to the regenerator 3. The acidic gas absorbent sent into the regenerator 3 moves from the upper part to the lower part of the regenerator 3. During this process, the acidic gas in the acidic gas absorbent is desorbed, and the acidic gas absorbent is regenerated.

[0063] The acidic gas absorbent regenerated in the regenerator 3 is sent by the lean liquid pump 9 to the heat exchanger 7 and the absorbent cooler 10, and then returned to the absorber 2 from the acidic gas absorbent supply port 5.

[0064] On the other hand, the acidic gas separated from the acidic gas absorbent comes into contact with the reflux water supplied from the reflux drum 11 at the upper part of the regenerator 3 and is discharged to the outside of the regenerator 3.

[0065] The reflux water in which carbon dioxide is dissolved is cooled by the reflux cooler 12 and then separated from the liquid component in which water vapor accompanied by carbon dioxide is condensed in the reflux drum 11. This liquid component is led to the acidic gas recovery process by the recovered acidic gas line 13. On the other hand, the reflux water from which the acidic gas has been separated is sent to the regenerator 3.

[0066] According to the acidic gas removal device 1 of the present embodiment, by using an acidic gas absorbent excellent in the absorption characteristics and desorption characteristics of acidic gas, it is possible to efficiently absorb and remove acidic gas.

[0067] In addition, the reflux water from which the acid gas has been separated is fed to the regenerator 3 by the reflux water pump 14. According to the acid gas removal apparatus 1 of the present embodiment, by using an acid gas absorbent having excellent absorption characteristics and desorption characteristics of the acid gas, it is possible to efficiently absorb and remove the acid gas.

[0068] Hereinafter, embodiments of the present invention will be described in more detail with examples.

[0069] [Synthesis Example] Synthesis of 1,4-bis(2-isopropylaminoethyl)piperazine (1a-1) (i) Synthesis of 1-chloro-2-(N-isopropyl)amino)ethane (M1) 36.4 g (0.91 mol) of sodium hydroxide was weighed into a beaker, dissolved in water to make the solution 300 ml, and 0.6 mol of 1-chloro-2-(N-isopropyl)amino)ethane hydrochloride (2·HCl) synthesized by the above method was added thereto. After stirring well and dissolving, it was extracted three times with ether. After drying the ether phase with anhydrous sodium sulfate, it was concentrated until a little ether remained to obtain 1-chloro-2-(N-isopropyl)amino)ethane (M1). (However, when all the ether is removed, compound 2 gradually undergoes a self-decomposition reaction.)

[0070] For the synthesized compound, measurement was carried out using a 400 MHz NMR apparatus of the model JMTC0-400 / 54 / SS, JELO type NM-SCM40SS / AL) manufactured by JEOL Ltd. to identify the compound.

[0071] NMR spectrum of M1 1 H-NMR, (CDCl3, ppm) δ: 1.08 (d, 6H, J = 6.4 Hz), 2.84 (m, 1H), 2.95 (t, 2H, J = 5.7 Hz), 3.66 (t, 2H, J = 5.7 Hz), 13 C-NMR (CDCl3, ppm) δ: 22.95, 45.12, 48.02, 48.45

[0072] (ii) Synthesis of 1,4-bis(2-isopropylaminoethyl)piperazine (1a-1) Next, 51.71 g (0.60 mol) of piperazine, 72.88 g (0.72 mol) of triethylamine and 200 ml of acetonitrile were added to a four-necked flask equipped with a reflux condenser, a mechanical stirrer, a thermometer and a dropping funnel, and heated to 70 °C. Thereto was added a solution obtained by adding 100 ml of acetonitrile to a 0.6 mol ether solution of 1-chloro-2-(N-isopropyl)amino)ethane (M1) synthesized by the above method and performing solvent exchange by removing ether. After dropping, the mixture was reacted at 70 °C for 13 hours and then cooled to room temperature. The precipitate was filtered off from the reaction mixture, the filtrate was concentrated, the concentrate was redissolved in ether, and the precipitate was further filtered. The filtrate was dried over anhydrous sodium sulfate and then concentrated to obtain 37.49 g of a reaction mixture (orange liquid). This reaction product was purified by column chromatography (activated alumina, chloroform:hexane = 85:15 in volume ratio of the developing solvent) to obtain 15.62 g (19.8% based on raw material 2) of the target compound (1a-1) as a yellow transparent liquid and 9.75 g (9.5%) of 1-(2-isopropylaminoethyl)piperazine (M2) as a yellow transparent liquid.

[0073] 1H-NMR spectrum of 1a-1 1 1H-NMR, (CDCl3, ppm) δ: 1.06 (d, 12H, J = 5.9 Hz), 2.49 (t, 4H, J = 6.4 Hz), 2.4 - 2.7 (m, 8H), 2.69 (t, 4H, J = 6.4 Hz), 2.76 (m, 2H) 13 13C-NMR (CDCl3, ppm) δ: 23.03, 44.13, 48.90, 53.30, 58.04

[0074] 1H-NMR spectrum of M2 1 1H-NMR, (CDCl3, ppm) δ: 1.07 (d, 6H, J = 6.4 Hz), 2.48 (t, 2H, J = 6.4 Hz), 2.3 - 2.6 (m, 4H), 2.70 (t, 2H, J = 6.4 Hz), 2.78 (m, 1H), 2.89 (t, J = 6.4 Hz, 4H), 13 13C-NMR (CDCl3, ppm) δ: 23.07, 44.97, 46.20, 48.92, 54.69, 58.72

[0075] · Synthesis of 1,4-bis[3-(N-isopropylamino)propyl]piperazine (1a-2) 100.33 g (0.500 mol) of 1,4-bis(3-aminopropyl)piperazine, 165.9 g (1.20 mol) of potassium carbonate, and 200 ml of anhydrous acetonitrile were added to a four-necked flask equipped with a reflux condenser with an argon inlet tube, a mechanical stirrer, a thermometer, and a dropping funnel under an argon atmosphere. It was heated to about 70 °C. A solution prepared by dissolving 147.7 g (1.18 mol) of 2-bromopropane in 50 ml of anhydrous acetonitrile was added dropwise thereto from the dropping funnel. After the addition, the mixture was reacted at 70 °C for 8 h, and then a solution prepared by dissolving 36.94 g (0.30 mol) of 2-bromopropane in 50 ml of anhydrous acetonitrile was further added dropwise. Further, the mixture was reacted at 70 °C for 12 h and then cooled to room temperature. The precipitate was filtered off from the reaction mixture, the filtrate was concentrated, the concentrate was redissolved in ether, and the precipitate was further filtered. The filtrate was dried over anhydrous sodium sulfate and then concentrated to obtain 120.7 g (yield 84.7%) of a pale yellow transparent liquid of 1,4-bis[3-(N-isopropylamino)propyl]piperazine (1a-2).

[0076] 1H NMR spectrum of 1a-2 1 1H-NMR, (CDCl3, ppm) δ: 1.05 (d, 6H, J = 6.4 Hz), 1.67 (m, 4H), 2.39 (t, 2H, J = 7.3 Hz), 2.3 - 2.6 (m, 8H), 2.63 (t, 2H, J = 7.1 Hz), 2.78 (m, H) 13 13C-NMR (CDCl3, ppm) δ: 22.88, 27.27, 46.31, 48.63, 55.22, 57.08

[0077] · Synthesis of 1,4-bis[3-(N-sec-butylamino)propyl]piperazine (1a-3) A four-necked flask equipped with a reflux condenser with an argon inlet tube, a mechanical stirrer, a thermometer, and a dropping funnel was charged with 100.33 g (0.500 mol) of 1,4-bis(3-aminopropyl)piperazine, 165.8 g (1.20 mol) of potassium carbonate, and 200 ml of anhydrous acetonitrile under an argon atmosphere. It was heated to about 70 °C. A solution prepared by dissolving 164.54 g (1.18 mol) of 2-bromobutane in 50 ml of anhydrous acetonitrile was added dropwise thereto from the dropping funnel. After the addition, the mixture was reacted at 70 °C for 24 h and then cooled to room temperature. The precipitate was removed by filtration from the reaction mixture, and the precipitate was washed with chloroform and the filtrate was concentrated. The concentrate was redissolved in hexane, the precipitate was removed by filtration, and the filtrate was dried over anhydrous sodium sulfate and then concentrated. The reaction product was separated by column chromatography (silica, developing solvent volume ratio hexane) and concentrated to obtain 95.2 g (yield%) of a pale yellow transparent liquid of 1,4-bis[3-(N-sec-butylamino)propyl]piperazine (1a-3). The compound was identified by NMR.

[0078] 1H-NMR spectrum of 1a-3 1 1H-NMR, (CDCl3, ppm) δ: 0.88 (t, 6H, J = 7.3 Hz), 1.02 (d, 6H, 6.9 Hz), 1.30 (m, 2H), 1.47 (m, 2H), 1.67 (m, 4H), 2.2~2.9 (m, 14H), 2.39 (t, 4H, J = 7.3 Hz), 13 13C-NMR (CDCl3, ppm) δ: 10.34, 19.83, 27.36, 29.53, 46.21, 53.33, 54.74, 57.21

[0079] Synthesis of 1-[3-(N-isopropylamino)propyl]-4-[3-(N-diisopropylamino)propyl]piperazine (1a-4) In a four-necked flask equipped with a reflux condenser with an argon inlet tube, a mechanical stirrer, a thermometer, and a dropping funnel, 10.1 g (0.0355 mol) of compound 1a-2, 11.77 g (0.0852 mol) of potassium carbonate, and 20.2 g (0.164 mmol) of 2-bromopropane were added under an argon atmosphere, and 10 ml of anhydrous acetonitrile was added. The mixture was reacted at reflux temperature for 16 h and then cooled to room temperature. The precipitate was filtered off from the reaction mixture, the filtrate was concentrated, and after the concentrate was redissolved in hexane, the precipitate was further filtered. After concentration, the reaction product was separated by column chromatography (silica, developing solvent volume ratio hexane) and concentrated to obtain 5.21 g (yield 45%) of a pale yellow transparent liquid of 1-[3-(N-isopropylamino)propyl]-4-[3-(N-diisopropylamino)propyl]piperazine (1a-4). The compound was identified by NMR.

[0080] 1H-NMR spectrum of 1a-4 1 1H-NMR, (CDCl3, ppm) δ: 0.99 (d, 12H, J = 6.4 Hz), 1.05 (d, 6H, J = 6.4 Hz), 1.58 (m, 4H), 1.67 (m, 2H), 2.32 (t, 2H, J = 7.3 Hz), 2.39 (t, 1H, J = 7.3 Hz), 2.3 - 2.7 (m, 8H), 2.63 (t, 2H, J = 7.1 Hz), 2.78 (m, 1H), 3.0 (m, 2H) 13 13C-NMR (CDCl3, ppm) δ: 20.67, 22.96, 27.34, 28.46, 43.15, 46.37, 48.32, 48.87, 53.35, 56.70, 57.15

[0081] Synthesis of 1-isopropyl-4-[2-(N-isopropylamino)ethyl]piperazine (1b-1) 38.76 g (0.300 mol) of 1-(2-aminoethyl)piperazine was added to a four-necked flask equipped with a reflux condenser with an argon inlet tube, a thermometer, a dropping funnel, and a mechanical stirrer, and 150 ml of anhydrous acetonitrile was added and dissolved. 99.59 g (0.720 mol) of potassium carbonate (K2CO3) was added thereto. 49.29 g (0.401 mol) of 2-bromopropane dissolved in 40 ml of anhydrous acetonitrile at room temperature was gradually added dropwise through the dropping funnel under an argon atmosphere. After completion of the dropwise addition, the mixture was heated in an oil bath and reacted at 65 °C for 4 hours. However, after the reaction solution was cooled to room temperature, hardly any progress of the reaction was observed. The precipitate was filtered, and the precipitate was washed with chloroform. The washing solution was combined with the previous filtrate, and the solvent of the filtrate was concentrated using an evaporator. Diethyl ether was added to the residue to dissolve it, and it was filtered. After the filtrate was dried over anhydrous sodium sulfate, the solvent was concentrated using an evaporator to obtain 51.17 g of a pale yellow transparent liquid as the product. Further, it was purified by distillation under reduced pressure, and 15.6 g of the product was obtained at a distillation fraction (distillation temperature 85 - 89 °C (220 Pa)).

[0082] 1 H-NMR (CDCl3, ppm) δ: 1.06 (d, J = 6.7 Hz, 6H), 1.09 (d, J = 6.2 Hz, 6H), 2.4~2.8 (m, 14H) 13C-NMR (CDCl3, ppm) δ 18.62, 22.84, 44.07, 48.67, 48.82, 53.34, 54.34, 58.03

[0083] [Examples 1 - 10, Comparative Examples 1 - 6] The amines (1a-1 to 1a-4) synthesized as shown in the synthesis examples, 1-isopropyl-4-[2-(N-isopropylaminol ethyl] piperazine (1b-1), 2-(N-methylamino) ethanol (MEA), methyldiethanolamine (MDEA), 2-methyl-2-amino-1-propanol (AMP), 1-(2-hydroxyethyl) piperazine (HEPZ), and 1-(2-aminoethyl) piperazine (AEPZ) were dissolved in water at the concentrations shown in Table 1 to obtain acidic gas absorbents. Further, a mixture of 1a-2 and 1-(2-hydroxyethyl) piperazine (HEPZ) and 1-(2-aminoethyl) piperazine (HEPZ), 1,4-bis(3-aminopropyl) piperazine (bisAPPZ) was dissolved in water to a concentration of 30 to 50% by mass to obtain an aqueous solution (hereinafter referred to as an absorbent).

[0084] [Evaluation of carbon dioxide absorption amount] These acidic gas absorbents were filled in test tubes and heated to 40°C, and a mixed gas containing 10% by volume of carbon dioxide (CO2) and 90% by volume of nitrogen (N2) gas was passed through the acidic gas absorbent at a flow rate of 400 mL / min. The concentration of carbon dioxide (CO2) in the gas at the outlet of the test tube was measured using an infrared gas concentration measuring device (manufactured by Shimadzu Corporation, trade name "CGT-700") to evaluate the absorption performance. The obtained results are as shown in Table 1.

[0085] [Accelerated degradation test (oxidation resistance test)] A degradation test of the acidic gas absorbent was conducted at a temperature higher than the normally assumed temperature of 120°C in the regeneration tower. 20 ml of the acidic gas absorbent that had absorbed CO2 in the above example and oxygen gas were sealed in a pressure-resistant sealed container with a volume of 50 ml, and left standing for one week under sealed conditions in an oxygen atmosphere at 140°C to examine the remaining situation of the amine. The absorbent before and after the degradation test was analyzed using GC / MS, and the disappearance amount was calculated as the amine disappearance weight (k / kg) per 1 kg of the absorbent from the decrease in the integrated value of the chromatogram. The selected results are as shown in Table 1.

[0086]

Table 1

[0087] [Results] As is clear from the above results, compared with the conventional acid gas absorbent, the acid gas absorbent according to the embodiment shows a similar carbon dioxide absorption amount, and it is clearly shown that the amine disappearance weight of the absorbent according to the embodiment is very low and it is very resistant to deterioration against the thermal cycle in the presence of oxygen.

[0088] As described above, several embodiments have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various combinations, omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0089] 1... Acid gas removal device, 2... Absorber, 3... Regenerator, 4... Gas supply port, 5... Acid gas absorbent supply port, 6... Gas discharge port, 7... Heat exchanger, 8... Rich liquid pump, 9... Lean liquid pump, 10... Absorbent cooler, 11... Reflux drum, 12... Reflux cooler, 13... Recovered acid gas carbon line

Claims

1. A solvent and at least one or more amine compounds selected from the group consisting of amine compounds represented by the formula (1a): [wherein, 【Chemical 1】 a is each independently 0 or 1, R １ is each independently hydrogen or an unsubstituted or substituted alkyl group having 3 or less carbon atoms, R ２ is each independently a hydrogen or an unsubstituted or substituted alkyl group having 3 or less carbon atoms, and at least two of the Rs contained in one - CR ２ ３ are not hydrogen) is a substituent represented by ２ ​ m is a number from 1 to 3, n is each independently a number from 1 to 4], and 1-(2-hydroxyethyl)piperazine, 1-(2-aminoethyl)piperazine, 1,4-bis(3-aminopropyl)piperazine, N-isopropyldiethanolamine, N-isopropyldipropanolamine, N-isopropyldibutanolamine, N-isopropyldipentanolamine, N-isopropyldihexanolamine, 3-[(2-hydroxyethyl)(propan-2-yl)amino]propan-1-ol, 4-[(2-hydroxyethyl)(propan-2-yl)amino]butan-1-ol, 5-[(2-hydroxyethyl)(propan-2-yl)amino]pentan-1-ol, 6-[(2-hydroxyethyl)(propan-2-yl)amino]hexan-1-ol, N-sec-butyldiethanolamine, N-sec-butyldipropanolamine, N-sec-butyldibutanolamine, N-sec-butyldipentanolamine, N-sec-butyldihexanolamine, 3-[(2-hydroxyethyl)(butan-2-yl)amino]propan-1-ol, 4-[(2-hydroxyethyl)(butan-2-yl)amino]butan-1-ol, 5-[(2-hydroxyethyl)(butan-2-yl)amino]pentan-1-ol, 6-[(2-hydroxyethyl)(butan-2-yl)amino]hexan-1-ol, N-cyclopentyldiethanolamine, N-cyclopentyldipropanolamine, N-cyclopentyldibutanolamine, N-cyclopentyldipentanolamine, N-cyclopentyldihexanolamine, 3-[(2-hydroxyethyl)(cyclopentyl)amino]propan-1-ol, 4-[(2-hydroxyethyl)(cyclopentyl)amino]butan-1-ol, 5-[(2-hydroxyethyl)(cyclopentyl)amino]pentan-1-ol, 6-[(2-hydroxyethyl)(cyclopentyl)amino]hexan-1-ol, 2-azetidinemethanol, 2-(2-aminoethyl)azetidine, 2-pyrrolidinemethanol, ​ 2-(2-Aminoethyl)pyrrolidine, 2-Piperidinemethanol, 3-Piperidineethanol, 2-(2-Aminoethyl)pyrrolidine, 1-(2-Hydroxyethyl)piperazine, 2-(Hydroxymethyl)piperazine, 3-Hydroxypyrrolidine, 3-Pyrrolidinemethanol, 2-(2-Hydroxyethyl)pyrrolidine, 4-Piperidineethanol, 3-Hydroxypiperidine, 4-Hydroxypiperidine, 4-(Hydroxymethyl)piperidine, and 3-Aminopiperidine At least one additional amine compound selected from the group consisting of: An acidic gas absorbent comprising: Based on the total amount of the acidic gas absorbent, the content of the amine compound represented by the formula (1a) is 10 to 60% by mass, and the content of the additional amine compound is 1 to 50% by mass. Acidic gas absorbent.

2. The acidic gas absorbent according to claim 1, wherein n is 2 or 3.

3. The acidic gas absorbent according to claim 1 or 2, wherein m is 2.

4. The acidic gas absorbent according to any one of claims 1 to 3, wherein all of a are 1.

5. The additional amine compound is 1-(2-Hydroxyethyl)piperazine, 1-(2-Aminoethyl)piperazine, 1,4-Bis(3-aminopropyl)piperazine, N-Isopropyldiethanolamine, N-Isopropyldipropanolamine, 3-[(2-Hydroxyethyl)(propan-2-yl)amino]propan-1-ol 、 N-sec-Butyldiethanolamine, N-sec-Butyldipropanolamine, N-sec-Butyldibutanolamine, 3-[(2-Hydroxyethyl)(butan-2-yl)amino]propan-1-ol, N-Cyclopentyldiethanolamine, N-Cyclopentyldipropanolamine, and 3-[(2-Hydroxyethyl)(cyclopentyl)amino]propan-1-ol The acidic gas absorbent according to any one of claims 1 to 4, which is at least one selected from the group consisting of:

6. The acidic gas absorbent according to any one of claims 1 to 5, further comprising an additive selected from the group consisting of an antioxidant, a pH adjuster, an antifoaming agent, and a corrosion inhibitor.

7. A method for removing acidic gas, comprising contacting a gas containing acidic gas with the acidic gas absorbent according to any one of claims 1 to 6 to remove the acidic gas from the gas containing the acidic gas.

8. An absorber for removing acidic gas from a gas containing acidic gas by causing the acidic gas absorbent according to any one of claims 1 to 7 to absorb the acidic gas by contacting the gas containing acidic gas with the acidic gas absorbent, a regenerator for desorbing the acidic gas from the acidic gas absorbent that has absorbed the acidic gas and regenerating the acidic gas absorbent and having an acidic gas removal apparatus that reuses the acidic gas absorbent regenerated by the regenerator in the absorber.

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