A low-corrosive phase-change absorbent and its application in carbon dioxide capture

Abstract

The present invention discloses a low-corrosive phase-change absorbent and its application in carbon dioxide capture, belonging to the field of carbon dioxide capture and separation technology. The low-corrosive phase-change absorbent comprises the following components by weight: 10-30% of a main absorbent, 1-10% of an activator, 30-60% of a phase separator, and the balance being water. The phase-change absorbent of the present invention uses 3-aminopropanol (MPA) as the main absorbent, 3-dimethylaminopropylamine (DMAPA) as the activator, and polyethylene glycol dimethyl ether (NHD) as the phase separator, and has the advantages of low energy consumption and low corrosivity.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture and separation, and in particular to a low-corrosive phase-change absorbent and application thereof in carbon dioxide capture. Background Art

[0002] Chemical absorption, represented by monoethanolamine (MEA), is currently the most commonly used CO2 capture technology in industry. MEA aqueous solution has good absorption performance and can quickly absorb flue gas CO2. However, due to the extremely strong bonding effect between MEA and CO2, the regeneration energy consumption is too high. The regeneration energy consumption of MEA aqueous solution is generally 3.7 to 4.0 GJ / ton CO2, accounting for more than 60% of the total energy consumption of the capture process. On the other hand, MEA solution has a high corrosion rate on metals, resulting in increased investment costs for industrial applications.

[0003] Phase change absorbents have attracted extensive attention from researchers in recent years because they can effectively reduce the energy consumption of the absorbent regeneration process. When a phase change absorbent absorbs CO2, it uses the different polarity and solubility of the CO2 absorption product in the phase change absorbent system to produce a phase separation phenomenon of CO2-poor and CO2-rich liquids, of which more than 95% of the CO2 is concentrated in the rich phase. During regeneration, it is only necessary to pump the CO2-rich liquid into the desorption tower for heating and desorption, which can effectively reduce the amount of heated solution pumped in, thereby reducing the regeneration energy consumption. Aleixo et al. conducted absorption tests on more than 300 amine reagents and developed DMX TM Reagents can undergo a liquid-liquid phase transition within a certain concentration range due to changes in CO₂ loading or temperature, with the absorbed CO₂ primarily concentrated in one phase. The Svendsen group at the Norwegian University of Science and Technology mixed n-methyl-1,3-diaminopropylamine (MAPA) with diethylaminoethanol (DEEA) to construct a liquid-liquid phase-change absorbent. They found that the regeneration energy consumption of this phase-change system was approximately 2.2 to 2.4 GJ / ton CO₂. Ye et al. studied a triethylenetetramine (TETA) / DEEA mixed phase-change absorbent system and found that its regeneration energy consumption was 2.98 GJ / ton CO₂. While existing phase-change absorbents have achieved the goal of reducing regeneration energy consumption to a certain extent, they generally suffer from problems such as slow phase separation, difficulty in controlling the phase separation process, strong metal corrosion, and poor stability. For example, traditional alkanolamine + lipophilic amine phase-change systems experience difficulty in phase separation under high CO₂ loading conditions, increasing regeneration energy consumption. Compared with the alkanolamine + lipophilic amine phase change system, the alkanolamine + physical solvent + water phase change system is more stable and has a lower volume percentage of the rich phase. The physical solvent has higher stability, lower corrosiveness and lower vapor pressure, and is an excellent phase separation agent.

[0004] In summary, while current MEA-based chemical absorption CO2 capture processes offer generally good absorption performance, their high regeneration energy consumption limits their further application. Phase-change absorbent systems can effectively reduce regeneration energy consumption, but they also suffer from common issues such as high metal corrosion, hindering large-scale industrial application. Therefore, the development of new phase-change absorbents with low corrosion and energy consumption is urgently needed. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-corrosive phase-change absorbent and its application in carbon dioxide capture to solve the problems existing in the prior art. The phase-change absorbent prepared by the present invention has the advantages of low corrosion, low regeneration energy consumption, and easy control of the phase change process. The phase-change absorbent prepared by the present invention is used for CO2 capture, which can significantly improve economic benefits.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] One of the technical solutions of the present invention is a low-corrosive phase-change absorbent, comprising the following components in percentage by mass: 10-30% of a main absorbent, 1-10% of an activator, 30-60% of a phase separator, and the remainder being water.

[0008] Furthermore, the main absorbent includes 3-aminopropanol (MPA).

[0009] MPA has one primary amino group, which can ensure the high absorption performance of the phase change absorbent.

[0010] Furthermore, the activator includes 3-dimethylaminopropylamine (DMAPA).

[0011] DMAPA has a primary amino group and a tertiary amino group, which can promote the absorption rate and desorption rate of the phase change absorbent.

[0012] Furthermore, the phase separation agent includes polyethylene glycol dimethyl ether (NHD).

[0013] The large difference in polarity between NHD and the absorbed product CO2 allows the phase change absorbent to be converted into a liquid-liquid two-phase after capturing CO2. During desorption, the CO2 can be desorbed by simply heating the CO2-rich phase. This can also effectively reduce the amount of solution fed into the desorption tower, thereby reducing the regeneration energy consumption of the phase change absorbent.

[0014] The second technical solution of the present invention: A method for preparing the above-mentioned low-corrosion phase-change absorbent, comprising the following steps: weighing each component according to mass percentage, mixing them evenly, and obtaining the low-corrosion phase-change absorbent.

[0015] The third technical solution of the present invention: an application of the above-mentioned low-corrosive phase-change absorbent in carbon dioxide capture.

[0016] Furthermore, the application method specifically includes:

[0017] (1) Pure CO2 gas or a mixed gas containing CO2 is passed into a phase-change absorbent to capture CO2 (CO2 absorption). As the amount of CO2 absorbed increases, the phase-change absorbent transforms from a uniform liquid phase into a liquid-liquid two-phase with upper and lower layers. Most of the CO2 is enriched in the lower layer of the liquid-liquid two-phase (rich liquid phase), and the upper layer is a lean liquid phase.

[0018] (2) heating the rich liquid phase (CO2 desorption) to release CO2 and obtain a rich liquid phase that releases CO2;

[0019] (3) After the rich liquid phase and the lean liquid phase that release CO2 are fully mixed, they are sent to the absorption to capture CO2 again (recycling).

[0020] Furthermore, in step (1), the volume percentage of CO2 in the mixed gas containing CO2 is 5-20%; the temperature of the CO2 capture is 30-60°C, and the pressure is 1-1.1 standard atmospheres.

[0021] Furthermore, in step (2), the heating temperature is 100-120° C. and the heating time is 60-180 min.

[0022] The present invention discloses the following technical effects:

[0023] (1) The phase change absorbent of the present invention uses 3-aminopropanol (MPA) as the main absorbent, 3-dimethylaminopropylamine (DMAPA) as the activator, and polyethylene glycol dimethyl ether (NHD) as the phase separation agent, and has the advantages of low energy consumption and low corrosiveness.

[0024] (2) The phase-change absorbent of the present invention has high absorption performance (the CO2 loading capacity in the rich liquid phase reaches 5.19 mol / L), low regeneration energy consumption (2.66 GJ / ton CO2) and low corrosion performance (the corrosion rate of the rich phase is 96.6% lower than that of the MEA solution under the same experimental conditions).

[0025] (3) The MPA in the phase-change absorbent of the present invention has one primary amino group, which can ensure the high absorption performance of the phase-change absorbent; DMAPA has one primary amino group and one tertiary amino group, which can promote the absorption rate and desorption rate of the phase-change system; polyethylene glycol dimethyl ether (NHD) has a boiling point greater than 250°C, and its low vapor pressure can reduce the loss of solvent during the desorption process. In addition, polyethylene glycol dimethyl ether has the advantages of being non-toxic, highly stable, and low corrosive. The large difference in polarity between polyethylene glycol dimethyl ether and the CO2 absorption product can promote liquid-liquid phase separation and reduce regeneration energy consumption. The phase-change absorbent of the present invention overcomes the defects of high regeneration energy consumption and high corrosiveness of traditional MEA solutions, which is conducive to industrial promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 This is a comparison chart of the absorption performance of the absorbents prepared in Example 1 of the present invention and Comparative Examples 1 to 4;

[0028] Figure 2 The distribution and phase volume ratio of the absorbent CO2 prepared in Example 1 of the present invention;

[0029] Figure 3 This is a graph showing the cycle performance change of the absorbent prepared in Example 1 of the present invention;

[0030] Figure 4 This is a graph of the regeneration energy consumption of the absorbent prepared in Example 1 of the present invention;

[0031] Figure 5 This is a comparison chart of the corrosion rates of the absorbents prepared in Example 1 of the present invention and Comparative Examples 1 to 4. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the present invention. The present description and examples are intended to be illustrative only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] Example 1

[0038] A method for preparing a low-corrosive phase-change absorbent:

[0039] The low-corrosive phase-change absorbent is composed of the following components in percentage by mass: 25% of 3-aminopropanol, 5% of 3-dimethylaminopropylamine, 60% of polyethylene glycol dimethyl ether, and the balance being water.

[0040] Preparation method: Weigh each raw material according to mass percentage, mix them evenly, and obtain a low-corrosive phase-change absorbent (MPA / DMAPA / NHD, liquid-liquid phase-change absorbent).

[0041] Comparative Example 1

[0042] Preparation method of absorbent:

[0043] 3-Aminopropanol (MPA), 3-dimethylaminopropylamine (DMAPA) and water were uniformly mixed in a mass ratio of 2.5:0.5:7 to obtain an MPA / DMAPA absorbent.

[0044] Comparative Example 2

[0045] Preparation method of absorbent:

[0046] 3-Aminopropanol (MPA), polyethylene glycol dimethyl ether (NHD) and water were uniformly mixed in a mass ratio of 3:6:1 to obtain an MPA / NHD phase change absorbent.

[0047] Comparative Example 3

[0048] Preparation method of absorbent:

[0049] Ethanolamine (MEA) and water were uniformly mixed in a mass ratio of 3:7 to obtain an ethanolamine aqueous solution (30 wt % MEA).

[0050] Comparative Example 4

[0051] Preparation method of absorbent:

[0052] 3-Aminopropanol (MPA) and water were uniformly mixed in a mass ratio of 3:7 to obtain a 3-aminopropanol aqueous solution (30 wt % MPA).

[0053] Effect Example 1

[0054] Under the conditions of a temperature of 40°C, a pressure of 1 standard atmosphere, a volume percentage of CO2 gas of 100%, and a flow rate of CO2 gas of 100 mL / min, the absorption performance of the absorbents prepared in Example 1 and Comparative Examples 1 to 4 for CO2 was measured.

[0055] The specific measurement method is as follows:

[0056] Weigh 50 g of the absorbent prepared in Example 1 and Comparative Examples 1 to 4 respectively, pour them into a three-necked flask, use a mass flow meter to maintain a constant air inlet flow rate, and use a mass flow meter to measure the gas flow rate at the outlet. Connect it to a computer and record the flow rate once every 1 second. When the readings of the two mass flow meters are the same and stabilize for 20 minutes, it means that the CO2 absorption is saturated (the change in the absorption load of the solution over time is calculated by the change in the gas flow rate at the outlet). After CO2 absorption is saturated, the absorbent containing CO2 is placed in a constant temperature water bath at 313.15K and stored for 12 hours to ensure that the phase separation process is completely completed. Use hydrochloric acid titration to calculate the upper phase (upper layer) and lower phase (lower layer) of the absorbents in Example 1 and Comparative Example 2, as well as the CO2 loading of the absorbents in Comparative Examples 1, 3, and 4. The results are shown in FIG. Figure 1 The CO2 distribution and phase volume ratio of the absorbent in Example 1 are shown in Figure 2 .

[0057] The low-corrosive phase-change absorbent (MPA / DMAPA / NHD) prepared in Example 1 of the present invention is a homogeneous solution before absorbing CO2. After absorbing a certain amount of CO2, a liquid-liquid phase change will occur. When the absorption is saturated, it is found through hydrochloric acid titration and calculation that more than 98% of CO2 is enriched in the lower phase, which only accounts for 46.4% of the total solution volume, but the CO2 loading capacity is as high as 5.19 mol / L. The CO2 loading capacity of the rich phase of the 3-aminopropanol and polyethylene glycol dimethyl ether (MPA / NHD) phase-change absorbent is 4.75 mol / L, the CO2 loading capacity of the 3-aminopropanol and 3-dimethylaminopropylamine (MPA / DMAPA) absorption liquid is only 2.71 mol / L, the CO2 loading capacity of the 3-aminopropanol aqueous solution (30 wt% MPA) is only 2.58 mol / L, and the CO2 loading capacity of the ethanolamine aqueous solution (30 wt% MEA) is only 2.89 mol / L; the absorbent prepared in Example 1 of the present invention The CO2 loading capacity of the absorbent is 8.5% higher than that of the rich phase of 3-aminopropanol and polyethylene glycol dimethyl ether phase change absorbent, 47.8% higher than that of 3-aminopropanol and 3-dimethylaminopropylamine aqueous solution, 50.3% higher than that of 3-aminopropanol aqueous solution, and 44.3% higher than that of ethanolamine aqueous solution; the low-corrosive phase change absorbent prepared in Example 1 of the present invention can maintain a high CO2 ratio while maintaining a small volume ratio after absorbing CO2, which is conducive to desorption and reduction of regeneration energy consumption (for specific performance comparison, see Figure 1 and Figure 2 ).

[0058] Effect Example 2

[0059] The cyclic performance of the low-corrosive phase-change absorbent (MPA / DMAPA / NHD) prepared in Example 1 was measured under the conditions of a temperature of 40°C, a pressure of 1 standard atmosphere, a volume percentage of CO2 gas of 100%, and a CO2 gas flow rate of 150 mL / min.

[0060] The specific measurement method is as follows:

[0061] 200 g of the absorbent prepared in Example 1 was weighed separately and poured into a three-necked flask. A mass flow meter was used to maintain a constant inlet flow rate, and a mass flow meter was used to measure the gas flow rate at the outlet. The flow rate was recorded once every 1 s when the two mass flow meters showed the same value and stabilized for 20 min, indicating that CO2 absorption was saturated (the change in the absorption load of the solution over time was calculated by changing the gas flow rate at the outlet). After CO2 absorption was saturated, the absorbent containing CO2 was placed in a constant temperature water bath at 313.15 K and stored for 12 h to ensure that the phase separation process was completely completed to obtain a rich liquid phase and a lean liquid phase. The rich liquid phase was titrated with hydrochloric acid to calculate the absorbent lower phase ( The CO2 loading capacity of the lower layer, rich liquid phase); then the absorbent lower phase (rich liquid phase) is poured into a three-necked flask and desorbed at 120°C. The three-necked flask is connected to a condenser and a drying tube and then connected to a mass flow meter. After about 60 minutes of analysis, when the mass flow meter shows 0 and there is no change for 20 minutes, it means that the desorption is completed, and the rich liquid phase that releases CO2 is obtained. The desorption amount of the rich liquid phase is calculated by the change of the outlet mass flow meter, and the CO2 loading capacity of the rich liquid phase that releases CO2 is titrated with hydrochloric acid. Subsequently, the rich liquid phase that releases CO2 is mixed with the lean phase solution to continue the absorption experiment. The cycle is repeated 3 times, and the CO2 loading capacity and desorption capacity of the rich liquid phase are counted. The results are shown in FIG. Figure 3 .

[0062] from Figure 3 It can be seen that the CO2 loading capacity of MPA / DMAPA / NHD decreased by 3.3% after three cycles of absorption, and the desorption rate was still as high as 91.0% after three cycles of desorption. The experimental results show that the MPA / DMAPA / NHD phase change absorbent can still maintain a high absorption-desorption performance after multiple desorptions.

[0063] Effect Example 3

[0064] The regeneration energy consumption of the low-corrosive phase-change absorbent (MPA / DMAPA / NHD) prepared in Example 1 of the present invention was measured.

[0065] The specific measurement method is as follows:

[0066] The low-corrosive phase-change absorbent prepared in Example 1 of the present invention was taken to evaluate its regeneration energy consumption. The regeneration energy consumption mainly involves the energy consumed by the reboiler in the desorption tower. The regeneration energy consumption mainly consists of three parts: reaction heat, sensible heat, and latent heat of vaporization. The reaction heat is calculated by the reaction enthalpy; the sensible heat is calculated by the specific heat capacity of the phase change solution and the mass of the required amine; the latent heat of vaporization is calculated by the evaporation enthalpy, and a lean liquid with a certain CO2 load gradient is prepared. The total pressure and equilibrium partial pressure data are measured using a high-pressure reactor, and the latent heat of vaporization is calculated. The calculation formula is as follows, and the results are shown in FIG. Figure 4 .

[0067] Q reg =Q rxn +Q sen +Q latent (1)

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] Where Q reg is the total regeneration energy consumption, calculated by formula (1); Q rxn is the reaction heat, calculated by formula (2) and (3); Q sen is the sensible heat, which can be calculated by formula (4); Q latent It refers to the latent heat of vaporization and can be calculated using formulas (5) and (6).

[0074] In these equations, ΔH rxn is the reaction enthalpy (kJ / mol); M CO2 is the molecular weight of CO2 (44 g / mol), P CO2 (T1, α) and P CO2 (T2, α) is the partial pressure of CO2 in equilibrium at temperatures T1 and T2 under a certain CO2 load α (kPa), R is the universal gas constant (8.314 J / (mol·K)); m am The molar amount of amine required to absorb each ton of CO2, (mol); c am 、c w 、c CO2 are the specific heat capacities of amine, water, and CO2 (kJ / (mol·K)); r W is the molar ratio of water in the unloaded CO2 absorbent; α lean is the lean solution CO2 load (mol / mol); T bot -T top is 10K, which is the temperature difference between the bottom and top of the stripping tower; m W is the molar amount of water required to absorb each ton of CO2 (mol); λ is the latent heat of water (kJ / mol); M is the molar amount of CO2 per ton (mol); P w is the partial pressure of water vapor (kPa); P CO2 (T top ,αtop ) is the equilibrium CO2 partial pressure (kPa).

[0075] from Figure 4 As can be seen from the data, the low-corrosive phase-change absorbent prepared in Example 1 of the present invention has a minimum regeneration energy consumption of 2.66 GJ / ton CO₂, including a reaction heat of 1.73 GJ / ton CO₂, a sensible heat of 0.52 GJ / ton CO₂, and a latent heat of vaporization of 0.41 GJ / ton CO₂. Furthermore, the MPA / DMAPA / NHD phase-change absorbent reduces the regeneration energy consumption of the ethanolamine aqueous solution by approximately 30% compared to 3.8 GJ / ton CO₂. Therefore, the MPA / DMAPA / NHD phase-change absorbent overcomes the high regeneration energy consumption of conventional ethanolamine solutions, facilitating large-scale industrial applications.

[0076] Effect Example 4

[0077] The metal corrosion rates of the absorbents prepared in Example 1 and Comparative Examples 1 to 4 were measured.

[0078] The specific measurement method is as follows:

[0079] Weigh 120 g of the low-corrosion phase-change absorbent (MPA / DMAPA / NHD) prepared in Example 1 of the present invention and the absorbent (MPA / NHD) of Comparative Example 2, and 50 g of the absorbents prepared in Comparative Examples 1, 3, and 4, respectively. Adopt the method of Example 1 to absorb CO2 to saturation, then use a separatory funnel to separate the absorbent that has formed liquid-liquid two phases, take the phase solution (rich liquid phase) as the test solution, and use a graduated cylinder to measure 40 mL of the test solution. At the beginning of the experiment, first calibrate the working electrode [20# carbon steel (exposed area 1 cm 2 )] for pretreatment, and the carbon steel surface was polished with 600-grit sandpaper to remove the corrosion products on the carbon steel surface. A constant temperature water bath was set to 313.15K, the test solution was placed in the electrolytic cell, and the three-electrode system [electrode (20# carbon steel), reference electrode (calomel electrode) and auxiliary electrode-platinum electrode] was fixed and connected to the electrochemical workstation, and the electrolytic cell was sealed. The open circuit potential (OPC) of the working electrode in the test solution was measured by the CHI602E electrochemical analyzer software, and the open circuit voltage of ±0.2V was selected as the scanning interval, the scanning rate was 0.0002mV / s, and the scanning time was 2000s. The Tafel curve of carbon steel in the test solution was obtained, and the corrosion rate was calculated using the Tafel curve extrapolation method. The results are shown in Figure 5 .

[0080] from Figure 5It can be seen that the corrosion rates of MPA / NHD, MPA / DMAPA, 30wt% MPA and MPA / DMAPA / NHD systems in fresh solution without CO2 loading are all low, which are 1.42×10 -3 mm.year -1 , 1.36×10 -3 mm.year -1 , 1.52×10 -3 mm.year -1 and 1.42×10 -3 mm.year -1 , less than 30wt% MEA (3.36×10 -3 mm.year -1 However, under CO2 saturation, MPA / DMAPA, 30wt% MPA and 30wt% MEA aqueous solutions showed high corrosion to 20# carbon steel, with corrosion rates of 0.32 mm.year, respectively. -1 、0.52mm.year -1 and 0.88mm.year -1 In contrast, after the absorption saturated MPA / NHD system and MPA / DMAPA / NHD system separated into phases, the CO2 lean solution and CO2 rich solution still maintained a low corrosion rate for 20# carbon steel. The corrosion rates of the MPA / DMAPA / NHD system CO2 lean solution and rich solution were 9.4×10 -4 mm.year -1 and 0.03mm.year -1 Under the same conditions, the corrosion rate of the CO2-rich phase of the MPA / DMAPA / NHD phase-change absorbent was 90.6% lower than that of the MPA / DMAPA aqueous solution, 94.2% lower than that of a 30wt% MPA aqueous solution, and 96.6% lower than that of a 30wt% MEA aqueous solution. Therefore, the MPA / DMAPA / NHD phase-change absorbent prepared in Example 1 of the present invention overcomes the high corrosion rate disadvantage of the baseline solvent (30wt% MEA solution), facilitating large-scale industrial applications.

[0081] The embodiments described above are merely descriptions of preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Without departing from the spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by persons skilled in the art should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A phase change absorbent having a low corrosion rate under CO2 saturation conditions, characterized in that: The invention comprises the following components in percentage by weight: 25% of a main absorbent, 5% of an activator, 60% of a phase separator, and the balance being water; The main absorbent includes 3-aminopropanol; The activator includes 3-dimethylaminopropylamine; The phase separation agent includes polyethylene glycol dimethyl ether.

2. A method for preparing a phase-change absorbent having a low corrosion rate under CO2 saturation conditions according to claim 1, characterized in that: The following steps are involved: The components are weighed according to mass percentage and mixed evenly to obtain the phase change absorbent.

3. Use of the phase change absorbent having a low corrosion rate under CO2 saturation conditions as claimed in claim 1 in carbon dioxide capture.

4. The use according to claim 3, characterized in that The application method specifically includes: (1) CO2 gas is passed into the phase change absorbent to capture CO2, thereby obtaining a liquid-liquid two-phase structure with upper and lower layers, wherein the lower layer is a CO2-rich liquid phase and the upper layer is a lean liquid phase; (2) heating the rich liquid phase to release CO2, thereby obtaining a rich liquid phase that releases CO2; (3) The rich liquid phase that releases CO2 and the lean liquid phase are mixed and used again for CO2 capture.

5. The use according to claim 4, characterized in that In step (1), the temperature of CO2 capture is 30-60°C and the pressure is 1-1.1 standard atmospheres.

6. The use according to claim 4, characterized in that In step (2), the heating temperature is 100-120° C. and the heating time is 60-180 min.

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