Phase change absorbent for CO2 capture and preparation method and application thereof

Abstract

The invention discloses a phase change absorbent for CO2 capture and a preparation method and application thereof, and belongs to the technical field of carbon dioxide capture and separation technologies, the phase change absorbent comprises 3-diethylaminopropylamine, TMPDA, isooctanol and water. The phase change absorbent provided by the invention has high absorption performance, small rich phase volume and high oxidative degradation resistance. The defect that a traditional MEA solution is prone to oxidative degradation is overcome, the problem that an existing phase change absorbent is not prone to phase splitting and high in rich phase volume is solved, and industrial popularization is facilitated.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon dioxide capture and separation technologies, and particularly relates to a phase change absorbent for CO 2 capture, a preparation method thereof, and an application thereof. Background Art

[0002] CO 2 The problem of global warming caused by a large amount of emissions has become the focus of global attention. The combustion and utilization of fossil fuels are the main sources of anthropogenic CO 2 emissions. Among the existing carbon emission reduction technologies, carbon capture, utilization, and storage technology (CCUS) is one of the important solutions to reduce CO 2 emissions. Therefore, adopting CO 2 capture technology is an effective means to control CO 2 emissions and address global warming.

[0003] The chemical absorption method represented by monoethanolamine (MEA) is the most commonly used CO 2 capture technology in industry at present. The absorption performance of the MEA aqueous solution is good, and it can rapidly absorb flue gas CO 2 However, due to the poor antioxidant degradation ability of the MEA solution, it is the main way of absorbent loss in industrial CO 2 capture applications. As a new absorbent that can replace MEA, the phase change absorbent has received extensive attention from researchers in recent years. When the phase change absorbent absorbs CO 2 , the CO 2 lean and rich liquid phase separation phenomenon is generated by the different solubilities of the CO 2 absorption products in the phase change absorbent system. Among them, more than about 95% of the CO 2 is concentrated in the rich phase. During regeneration, only the CO 2 rich liquid needs to be pumped into the desorption tower for heating and desorption, which can effectively reduce the amount of solution pumped in and heated. Li et al. developed a phase change absorption system of 1-(2-aminoethyl)piperazine (AEP), 1-propanol, and H 2 O. The CO 2 loading of this system is 1.26 mol / mol, which is 2.3 times that of a 30 wt% MEA aqueous solution, and the volume of the rich phase accounts for 58% of the total volume; Lv et al. proposed an absorption system of diethylenetriamine (DETA), pentamethyldiethylenetriamine (PMDETA), and H 2 O. The results show that the volume of the rich phase of this system only accounts for 38% of the total volume; Zhou et al. proposed a quaternary non-aqueous system absorbent composed of monoethanolamine (MEA), 2-amino-2-methyl-1-propanol (AMP), dimethyl sulfoxide (DMSO), and pentamethyldiethylenetriamine (PMDETA). The results show that the absorption of CO 2The volume of the rich phase accounts for 56.8% of the total volume, and the CO 2 reaches 0.88 mol / mol. It can be seen that the loading of the CO 2 capture system based on the phase change absorbent is generally higher than that of the commonly used MEA alkanolamine solution, and it has stronger absorption ability.

[0004] However, the phase change absorbents in the prior art generally have problems such as slow phase separation speed, difficult regulation of the phase separation process, poor stability, etc. In particular, their antioxidant degradation ability is poor, resulting in a series of problems such as absorbent loss and deteriorated phase separation. The oxidative degradation performance is an important index for investigating the phase change absorbent, which has a great impact on its economic cost, recycling, and commercial application. Developing a phase change absorbent with easy phase separation and strong antioxidant degradation ability is the key to current research. To sum up, the chemical absorption method based on MEA is generally used in industry to capture CO 2 , although the overall absorption performance of the MEA alkanolamine solution is good, its poor oxidation stability limits further application. The phase change absorbent system also generally has problems such as easy oxidative degradation and slow phase separation speed, which is not conducive to the recycling of the absorbent.

[0005] Therefore, how to provide a new type of phase change absorbent with a small rich phase volume, easy phase separation, and antioxidant degradation, so as to provide an economic and efficient new idea for carbon dioxide capture is a technical problem that those skilled in the art urgently need to solve. Summary of the Invention

[0006] To solve the above technical problems, the present invention proposes a phase change absorbent for CO 2 capture, its preparation method and application.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] A phase change absorbent for CO 2 capture, comprising 3-diethylaminopropylamine, TMPDA (N,N,N',N'-tetramethyl-1,3-propanediamine), isooctanol and water.

[0009] Preferably, by mass percentage, it comprises the following raw materials: 3-diethylaminopropylamine: 10% - 30%, TMPDA: 5% - 15%, isooctanol: 40% - 60% and water: 10% - 30%.

[0010] Beneficial effects: The present invention uses 3-diethylaminopropylamine (DEAPA) as the main absorbent, isooctanol as the phase separation agent, and TMPDA as the regulator. The DEAPA in the present invention has 1 primary amino group and 1 tertiary amino group, ensuring high absorption performance; isooctanol and CO 2The absorption products are immiscible, which can promote liquid-liquid phase separation and ensure a relatively low volume of the rich phase; TMPDA has two tertiary amino groups. On the basis of shortening the phase separation time, it can further improve the CO absorption capacity of the phase change system. The tertiary amino group also has a certain antioxidant degradation ability, which is also beneficial to improving the antioxidant degradation ability of the phase change system. 2 The absorption capacity of the phase change absorbent in the present invention can overcome the defect that general phase change absorbents are prone to oxidation and degradation because ferrous ions have reducibility. The main reason for using divalent iron in the present invention is that divalent iron can better simulate the iron in the storage tank during industrial flue gas absorption than trivalent iron.

[0011] Preferably, it further includes ferrous ions, and the concentration of the ferrous ions is 50 mg / L.

[0012] Preferably, the ferrous ions are derived from ferrous chloride tetrahydrate, and the mass of ferrous chloride tetrahydrate added is calculated based on the concentration of the ferrous ions.

[0013] Beneficial effects: The absorption products are immiscible, which can promote liquid-liquid phase separation and ensure a relatively low volume of the rich phase; TMPDA has two tertiary amino groups. On the basis of shortening the phase separation time, it can further improve the CO absorption capacity of the phase change system. The tertiary amino group also has a certain antioxidant degradation ability, which is also beneficial to improving the antioxidant degradation ability of the phase change system.

[0014] A method for preparing a phase change absorbent for CO capture, wherein the 3-diethylaminopropylamine, TMPDA, and isooctanol are dissolved in water to obtain the phase change absorbent. 2 Preferably, ferrous ions are further added until the concentration of the ferrous ions is 50 mg / L.

[0015] A method for preparing a phase change absorbent for CO capture, wherein the 3-diethylaminopropylamine, TMPDA, and isooctanol are dissolved in water to obtain the phase change absorbent.

[0016] An application of a phase change absorbent for CO capture in CO capture. 2 An application of a phase change absorbent for CO capture in CO capture. 2 An application of a phase change absorbent for CO capture in CO capture.

[0017] A CO capture and desorption method, comprising the following steps: 2 A CO capture and desorption method, comprising the following steps:

[0018] The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed. 2 The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed. 2 The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed. 2 The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed. 2 The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed. 2 The gas containing CO is passed into the above-mentioned phase change absorbent for CO absorption. After the phase change absorbent is converted into upper and lower liquid-liquid two phases, the liquid phase enriched with CO is separated and then heated for desorption, that is, CO is released, and the capture and desorption of CO are completed.

[0019] Preferably, during the CO absorption process, the temperature is 25 °C and the pressure is 1 to 1.1 atmospheres. 2 Preferably, during the CO absorption process, the temperature is 25 °C and the pressure is 1 to 1.1 atmospheres.

[0020] Preferably, the temperature of the heating desorption is 120 °C and the time is 120 min.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects:

[0022] The present invention uses 3 - diethylaminopropylamine (DEAPA) as the main absorbent, isooctanol as the phase - separating agent, and TMPDA as the regulator to obtain a phase - change absorbent that is easy to phase - separate and resistant to oxidative degradation. This phase - change absorbent has high absorption performance (absorption load is 0.88 mol·mol -1 ), a small rich - phase volume (42.2%), and high antioxidant degradation performance (the oxidative degradation rate is 8% lower than that of MEA under the same experimental conditions). It overcomes the defect that traditional MEA solutions are prone to oxidative degradation and the problem that existing phase - change absorbents are not easy to phase - separate and have a high rich - phase volume, which is conducive to industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings forming a part of this application are used to provide a further understanding of this application. The schematic embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation of this application. In the drawings:

[0024] Figure 1 shows the proportion of lean and rich liquid phases in Example 1 of the present invention;

[0025] Among them, the lower layer is the rich liquid phase;

[0026] Figure 2 shows the different CO 2 loadings between Example 1 of the present invention and Comparative Example 1;

[0027] Among them, D / T / Y / H is the phase - change absorbent obtained in Example 1, and MEA is the absorbent obtained in Comparative Example 1;

[0028] Figure 3 is a comparison graph of the initial phase - separation load interval of the present invention with other systems;

[0029] Among them, D / T / Y / H is the phase - change absorbent obtained in Example 1, D / D / D / H is the absorbent obtained in Comparative Example 2, D / D / H is the absorbent obtained in Comparative Example 3, and D / A / B / H is the absorbent obtained in Comparative Example 4;

[0030] Figure 4 compares the static phase - separation time of the present invention after absorption saturation with other systems;

[0031] Among them, D / T / Y / H is the phase - change absorbent obtained in Example 1, D / D / D / H is the absorbent obtained in Comparative Example 2, D / D / H is the absorbent obtained in Comparative Example 3, and D / A / B / H is the absorbent obtained in Comparative Example 4;

[0032] Figure 5 shows the ammonia emissions during the oxidative degradation process of Example 2 of the present invention and Comparative Examples 5 and 6;

[0033] Among them, D / T / Y / H is the phase change absorbent obtained in Example 2, D / T / H is the absorbent obtained in Comparative Example 6, and 30% MEA is the absorbent obtained in Comparative Example 5;

[0034] Figure 6 This is the alkalinity loss rate during the oxidative degradation of Example 2 of the present invention and Comparative Examples 5 and 6;

[0035] Among them, D / T / Y / H is the phase change absorbent obtained in Example 2, D / T / H is the absorbent obtained in Comparative Example 6, and 30% MEA is the absorbent obtained in Comparative Example 5. Detailed implementation manners

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0037] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific implementation manners.

[0038] The embodiment of the present invention discloses an antioxidant degradation phase change absorbent, which is composed of a main absorbent, a regulator, a phase separation agent, and water. The main absorbent is 3-diethylaminopropylamine (DEAPA), the phase separation agent is isooctanol, and the regulator is TMPDA. By mass percentage, it includes the following raw materials: 3-diethylaminopropylamine: 10% - 30%, TMPDA: 5% - 15%, isooctanol: 40% - 60%, and water: 10% - 30%.

[0039] The phase change absorbent of the present invention, CO 2 The main absorbent is DEAPA. DEAPA has two amino groups, namely a primary amino group and a tertiary amino group, which can ensure the high absorption performance of the phase change absorbent system.

[0040] The phase change absorbent of the present invention, the phase separation agent is isooctanol. Isooctanol and CO 2 The absorption product cannot be miscible, which can make the phase change absorbent transform into a liquid-liquid two-phase after absorbing CO 2

[0041] The phase change absorbent of the present invention, the regulator is TMPDA, which has two tertiary amino groups. On the basis of promoting the phase separation time, it can further improve the absorption capacity of the phase change system for CO 2 The absorption capacity, and the tertiary amino group also has a certain antioxidant degradation ability, which is also beneficial to improving the antioxidant degradation ability of the phase change system.​

[0042] The embodiments of the present invention also disclose the application of an easily phase-separable and antioxidant-degradable phase change absorbent in CO 2 capture. The steps of capturing CO 2 by the phase change absorbent include:

[0043] 1) During the CO 2 absorption process, pure CO 2 gas or a mixed gas containing CO 2 is introduced into the easily phase-separable and antioxidant-degradable phase change absorbent. As the CO 2 absorption amount increases, the easily phase-separable and antioxidant-degradable phase change absorbent is transformed from a homogeneous liquid phase into a liquid-liquid two-phase with upper and lower layers, and most of the CO 2 is enriched in one of the phases, which is called the rich liquid phase;

[0044] 2) During the CO 2 desorption process, the rich liquid phase is heated to release CO 2 ; after the rich liquid phase releasing CO 2 is fully mixed with the lean liquid phase, it is recycled and sent back to the absorption tower to capture CO 2 .

[0045] In step 1), the volume percentage of the pure CO 2 gas is 100%, and the conditions of the CO 2 absorption process are: the absorption temperature is 25°C, and the absorption pressure is 1 to 1.1 atmospheres.

[0046] In step 2), the conditions of the CO 2 desorption process are: the desorption temperature is 120°C, and the desorption time is 120 min.

[0047] During the absorption process, the absorption temperature is 25°C, the absorption pressure is 1 to 1.1 atmospheres, and it contains pure CO 2 gas. The pure CO 2 gas-containing is introduced into the phase change absorbent, and the phase change absorbent quickly phase-separates and is transformed into a CO 2 rich phase and a lean phase. When the absorption temperature is 25°C, the absorption pressure is 1 atmosphere, and the volume percentage of CO 2 is 100%, the absorption load is 0.88 mol·mol -1 , and the volume ratio of the rich phase is 42.2%.

[0048] Unless otherwise specified, the raw materials in the embodiments of the present invention are all obtained through commercial channels;

[0049] Unless otherwise specified, the room temperature or normal temperature in the embodiments of the present invention both refer to 25±3°C.

[0050] Example 1

[0051] A preparation method of a phase change absorbent for CO 2 capture, comprising the following steps:

[0052] Prepare a mixed solution of 3 - diethylaminopropylamine (DEAPA), TMPDA, isooctanol and water, wherein 3 - diethylaminopropylamine: 30%, TMPDA: 5%, isooctanol: 50% and water: 15% to obtain a DEAPA - TMPDA - isooctanol liquid - liquid phase change absorbent.

[0053] Example 2

[0054] A preparation method of a phase change absorbent for CO 2 capture, comprising the following steps:

[0055] Prepare a mixed solution of 3 - diethylaminopropylamine (DEAPA), TMPDA, isooctanol and water, wherein 3 - diethylaminopropylamine: 30%, TMPDA: 5%, isooctanol: 50% and water: 15% to obtain a DEAPA - TMPDA - isooctanol liquid - liquid phase change absorbent, and then add Fe 2+ to 50 mg / L, and after mixing evenly, prepare a DEAPA - TMPDA - isooctanol liquid - liquid phase change absorbent.

[0056] Comparative Example 1

[0057] An absorbent for CO 2 capture is an aqueous solution of ethanolamine (MEA) with a mass fraction of 30%.

[0058] Comparative Example 2

[0059] An absorbent for CO 2 capture, mix diethylenetriamine (DETA), diethanolamine (DEA), N,N - dimethylacetamide (DMAC) and water in a mass ratio of 2:1:6:6 to obtain an absorbent solution.

[0060] Comparative Example 3

[0061] An absorbent for CO 2 capture, mix diethylenetriamine (DETA), N,N - dimethylformamide (DMF) and water in a mass ratio of 2:4:4 to obtain an absorbent solution.

[0062] Comparative Example 4

[0063] An absorbent for CO 2The captured absorbent, diethylaminoethanol (DEEA), N-(2-hydroxyethyl)ethylenediamine (AEEA), n-butanol (BUT) and water were mixed at a mass ratio of 1:4:2.5:2.5 to obtain an absorbent solution.

[0064] Comparative Example 5

[0065] A kind of absorbent for CO 2 The captured absorbent, Fe was added to 30% aqueous ethanolamine (MEA) solution 2+ to a concentration of 50 mg / L to obtain an absorbent solution.

[0066] Comparative Example 6

[0067] A kind of absorbent for CO 2 Preparation method of phase change absorbent for CO capture, comprising the following steps:

[0068] Prepare a mixed solution of 3-diethylaminopropylamine (DEAPA), TMPDA and water, wherein, 3-diethylaminopropylamine: 30%, TMPDA: 5% and water: 65%, and then add Fe 2+ to 50 mg / L, and after fully mixing evenly, the phase change absorbent for CO capture is obtained. 2 capture.

[0069] Technical effects:

[0070] 1. Investigate the absorption performance of the phase change absorbent DEAPA / TMPDA / isooctanol aqueous solution in Example 1 and the MEA aqueous solution in Comparative Example 1.

[0071] At an absorption temperature of 25 °C, an absorption pressure of one standard atmosphere, a carbon dioxide gas volume percentage of 100%, and a gas flow rate of 100 mL / min, take 50 g each of the DEAPA / TMPDA / isooctanol aqueous solution in Example 1 and the MEA aqueous solution in Comparative Example 1, and pour them into a bubbling absorption bottle respectively. A gas drying tube is installed at the gas outlet of the absorption bottle. Use an electronic balance to weigh the total weight m of the bubbling absorption bottle at this time 0 , introduce pure CO 2 gas and take it out at the same time intervals, dry the moisture on the surface of the absorption bottle and weigh the total weight and record it until the total weight of the bubbling absorption bottle no longer increases. At this time, the solution is saturated with absorption, and record the total weight m of the absorption bottle at this time n . The increase in the total weight of the absorption bottle m = m n -m 0 , which is the weight of CO 2 completely absorbed by the solution, and the total loading of the solution is obtained by calculation.

[0072] The results are as Figure 1As shown, it can be seen that when the lower phase of the solution is rich after the DEAPA / TMPDA / isooctanol water absorption reaches saturation, and CO 2 The volume fraction of the rich phase is 42.2%.

[0073] As Figure 2 shown, when the DEAPA / TMPDA / isooctanol water absorption reaches saturation, the absorption loading is 0.88 mol / mol, and that of MEA is only 0.58 mol / mol. Therefore, after the DEAPA / TMPDA / isooctanol phase change solvent system absorbs CO 2 The rich liquid phase can maintain a high CO 2 absorption loading while maintaining a small volume fraction.

[0074] 2. Investigate the phase separation loading range and static phase separation time of the phase change absorbent.

[0075] Prepare 20 g of the solution respectively, stir evenly and pour it into the bubbling absorption bottle. Install a gas drying tube at the gas outlet of the absorption bottle. Weigh the total weight m 0 of the bubbling absorption bottle at this time with an electronic balance, and introduce pure CO 2 gas until the solution becomes turbid and then weigh it again and record it as m 1 , and then continue to introduce pure CO 2 gas until the solution mass no longer changes and then weigh and record m 2 . After absorption saturation, stir the solution evenly, take 10 mL and put it into a sample bottle, wait for the solution to re-phase separate and record the phase separation time.

[0076] The results are as Figure 3 shown. The phase separation loading range of the DEAPA / TMPDA / isooctanol / water system is significantly higher than that of the three phase change systems of Comparative Examples 2, 3, and 4, reaching 73.4%, proving that the present invention is easier to phase separate than other systems.

[0077] As Figure 4 shown, after the DEAPA / TMPDA / isooctanol / water system absorbs saturation, the static phase separation time is 9 min, which is lower than that of the three groups of systems in Comparative Examples 2, 3, and 4, further confirming that the DEAPA / TMPDA / isooctanol / water system is easy to phase separate.

[0078] 3. Investigate the oxidative degradation performance of the DEAPA / TMPDA / isooctanol / water phase change absorbent of Example 2, the DEAPA / TMPDA / water homogeneous solution of Comparative Example 6, and the MEA aqueous solution of Comparative Example 5.

[0079] Prepare 200 g each of the DEAPA / TMPDA / isooctanol / water phase change absorbent of Example 2, the DEAPA / TMPDA / water homogeneous solution of Comparative Example 6, and the MEA aqueous solution of Comparative Example 5. Bubble pure CO 2 to make their loadings all 0.4 mol·mol -1 . Use a Leici ZDJ-5 automatic titrator to measure the initial total alkalinity of the three solutions respectively. Transfer the solutions to a 250-milliliter three-necked flask, pass in pure oxygen, and place it in a 40°C constant temperature water bath for uniform stirring to start the oxidation degradation experiment. The experiment lasts for 336 hours in total. Take samples every 48 hours to measure their total alkalinity. Use a GT-903 multi-functional composite gas detector to measure the ammonia emission concentration at the outlet every day. Use the total alkalinity and the outlet ammonia concentration to quantify the concentration of amine groups in the solution that can still react with CO 2 . The experimental working conditions are as follows: reaction temperature 40°C, reaction pressure 1 standard atmosphere, oxygen gas volume percentage 100%, gas flow rate 80 mL / min, and condensation reflux temperature 5°C.

[0080] The results are as shown in Figure 5 and 6 . It can be seen that after 336 hours of oxidation degradation, the alkalinity loss rate of the DEAPA / TMPDA / isooctanol / water phase change absorption system is 3%, the alkalinity loss rate of the DEAPA / TMPDA / water homogeneous solution is 4.3%, and the oxidation degradation rate of the 30% MEA system is 10.3%. Under the same conditions, the alkalinity loss rate of the DEAPA / TMPDA / isooctanol / water phase change absorption system is 7.3% lower than that of the 30% MEA solution. Therefore, the DEAPA / TMPDA / isooctanol / water phase change absorbent provided by the present invention overcomes the defect of easy oxidation degradation of general phase change absorbents and is beneficial to large-scale industrial application.

[0081] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A phase change absorbent for CO2 capture, characterized in that: Includes 3-diethylaminopropylamine, TMPDA, isooctyl alcohol and water.

2. A phase change absorbent for CO2 capture according to claim 1, characterized in that: The invention comprises the following raw materials in percentage by mass: 10% to 30% of 3-diethylaminopropylamine, 5% to 15% of TMPDA, 40% to 60% of isooctyl alcohol and 10% to 30% of water.

3. A phase change absorbent for CO2 capture according to claim 1, characterized in that: It also includes ferrous ions, and the concentration of the ferrous ions is 50 mg / L.

4. A phase change absorbent for CO2 capture according to claim 3, characterized in that: The ferrous ions are derived from ferrous chloride tetrahydrate.

5. A method for preparing a phase change absorbent for CO2 capture according to any one of claims 1 to 4, characterized in that: The phase change absorbent is obtained by dissolving the 3-diethylaminopropylamine, TMPDA and isooctyl alcohol in water.

6. The method for preparing a phase change absorbent for CO2 capture according to claim 5, characterized in that: The method also includes adding ferrous ions until the concentration of ferrous ions is 50 mg / L.

7. Use of the phase change absorbent for CO2 capture as described in any one of claims 1 to 4 in CO2 capture.

8. A CO2 capture and desorption method, characterized in that: The following steps are involved: The gas containing CO2 is passed into the phase-change absorbent described in any one of claims 1 to 4 to absorb CO2. After the phase-change absorbent is converted into a liquid-liquid two-phase structure with upper and lower layers, the liquid phase enriched with CO2 is separated and heated for desorption, thereby releasing CO2 and completing the capture and desorption of CO2.

9. A CO2 capture and desorption method according to claim 8, characterized in that: The absorption pressure of CO2 is 1 to 1.1 atmospheres.

10. A CO2 capture and desorption method according to claim 8, characterized in that: The temperature of the heating desorption is 120° C. and the time is 120 min.

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