A low-volatility and low-energy liquid-liquid phase separation carbon dioxide absorbent system and a carbon dioxide absorption-desorption method thereof

Abstract

The present application relates to carbon dioxide (CO2) emission reduction and resource utilization technical field, provide a kind of low volatile low energy consumption liquid-liquid phase separation carbon dioxide absorbent system and its carbon dioxide absorption-desorption method.The absorption system with secondary diamine and amine additive as main absorbent, triethylene glycol dimethyl ether is phase separation agent, water is solvent, before absorbing CO2 It is homogeneous, after absorbing, phase separation behavior can occur, form upper layer with ether as the main CO2 lean phase and lower layer rich in absorption reaction product CO2 rich phase.Amino acid salt and other polar substances generated by the reaction of absorbent and CO2 can induce ether solvent to discharge from water phase and gather into hydrophobic organic phase, so as to realize phase separation.Rich phase has higher CO2 load and lower viscosity, which is convenient for subsequent desorption and recycling.The system has the advantages of high absorption capacity, low desorption energy consumption and low volatility, and the experimental results show that the CO2 load of rich phase can reach 2.7mol / L, the desorption energy consumption is reduced by about 40%, and the viscosity of rich phase is less than 50mPa·s, which has good industrial application prospect.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide emission reduction and resource utilization technology, specifically to a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system and its carbon dioxide absorption-desorption method. Background Technology

[0002] With the continuous development of the social economy and the acceleration of industrialization, large-scale human activities have led to a continuous increase in the concentration of greenhouse gases, especially carbon dioxide (CO2), in the atmosphere, exacerbating the problem of global warming. To address this environmental challenge, there is an urgent need to develop efficient, low-energy-consumption, and low-cost carbon dioxide capture technologies to achieve greenhouse gas emission reduction targets and mitigate the adverse effects of global climate change.

[0003] Among numerous CO2 capture technologies, chemical absorption is considered a mature and promising method for separating and recovering CO2 produced after combustion. This method is favored for its simple operation, rapid absorption rate, high CO2 removal efficiency, high product purity, and mature process technology. Among these technologies, chemical absorption using amine solutions as absorbents has significant advantages, rapidly absorbing CO2 through acid-base neutralization reactions. Currently, monoethanolamine (MEA), a commonly used amine, has attracted widespread attention due to its highly efficient reaction with CO2, but problems such as high regeneration energy consumption still exist.

[0004] For chemical absorption methods, the selection of the absorbent is a core element. Third-generation absorbents—amine-based phase-separation absorbents—have become a research hotspot. Compared to traditional 30wt% MEA solutions, this novel amine-based phase-separation absorbent can effectively reduce the amount of regenerated rich solution to be processed after CO2 absorption through phase separation (i.e., by reducing the volume of the CO2-rich phase solution), thus potentially reducing the energy consumption required for CO2 desorption. However, various phase-separation absorbents proposed in existing literature, such as the 2-(methylamino)ethanol + n-butanol CO2 absorption system, suffer from limited reductions in desorption energy consumption, and the volatility of n-butanol, resulting in significant losses during the absorption-desorption process and operational instability. Summary of the Invention

[0005] Therefore, the present invention aims to provide a liquid-liquid phase separation type carbon dioxide absorbent system with low volatility and low regeneration energy consumption, and a carbon dioxide absorption-desorption method thereof. This absorbent system can achieve highly efficient CO2 absorption and has technical advantages such as high absorption capacity, low desorption energy consumption, and low solvent volatility.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, the components of which include polyamines, amine additives, ethers and water.

[0008] The polyamine is 2-methylpiperazine or 1-(2-aminoethyl)piperazine, the amine additive is one or more of monoethanolamine, isobutanolamine, N,N-dimethylethanolamine, N-methyldiethanolamine, dimethylethanolamine, diethylethanolamine, etc., and the ether is triethylene glycol dimethyl ether or triethylene glycol monobutyl ether.

[0009] Preferably, in the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, the concentration of the polyamine is 1-4 mol / L, the concentration of the amine additive is 0.5-2 mol / L, and the mass percentage is 20-50% of the total.

[0010] Preferably, the ether-water volume ratio is 3:7 to 7:3, and the mass percentage is 30% to 80% of the total.

[0011] This invention provides a method for preparing the above-mentioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, comprising the following steps:

[0012] Cyclic polyamines, amine additives, ethers, and water are mixed in a preferred ratio to obtain a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent.

[0013] This invention provides the application of the above-mentioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system in CO2 capture.

[0014] This invention provides a method for the absorption and desorption of carbon dioxide gas, comprising the following steps:

[0015] When a gas containing CO2 is introduced into the above-mentioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, CO2 absorption is carried out for more than 30 minutes. The liquid-liquid phase separation system undergoes phase separation, with the upper layer being a CO2-poor phase and the lower layer being a CO2-rich phase.

[0016] The liquid-liquid phase separation system is separated by using a separatory funnel. The separated CO2-rich phase is then heated and desorbed to release the CO2 from the rich phase.

[0017] Preferably, the volume fraction of CO2 in the CO2-containing gas is 5% to 100%.

[0018] Preferably, the temperature at which CO2 is absorbed is 20–60°C, and the viscosity of the CO2-rich phase is 10–100 mPa·s.

[0019] Preferably, the temperature for heating and desorption is 90–130°C.

[0020] Preferably, after the heating and desorption, the process further includes mixing the CO2-rich phase and the CO2-poor phase after heating and desorption to obtain a regenerated low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system.

[0021] This invention provides a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, comprising a polyamine, an amine additive, an ether, and water; the polyamine is 2-methylpiperazine, the amine additive is isobutanolamine, and the ether is triethylene glycol dimethyl ether. This invention's low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system uses a polyamine as the main absorbent, triethylene glycol dimethyl ether as the phase-separating agent, and water as the solvent. After mixing, it constitutes a phase-separable liquid-liquid phase separation absorbent, enabling efficient CO2 absorption. The low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent provided by this invention exhibits phase separation characteristics, remaining homogeneous before CO2 absorption and separating into two phases after CO2 absorption, including an upper lean phase and a lower rich phase. In this invention, the phase separation principle of the liquid-liquid phase separation absorbent is as follows: After the main absorbent polyamine (2-methylpiperazine) and amine additive (isobutanolamine) react with CO2, the resulting products, such as carbamates, carbonates, and bicarbonates, exhibit polarity differences compared to ether solvents. When the concentration of these products reaches a certain level, triethylene glycol dimethyl ether separates from the solution and undergoes self-aggregation to form an organic phase, thereby initiating liquid-liquid phase separation. Ultimately, this results in a ether-dominated, ether-poor phase and a water / amine-dominated, water-rich phase.

[0022] The polyamine provided by this invention, when absorbed with different phase-separating agents ether under the same absorption conditions, will eventually exhibit a solid or liquid phase after phase separation of the CO2-rich phase. The solid phase is conducive to the enrichment of amine, while the liquid phase is conducive to transportation operations. Suitable ether phase-separating agents can be selected according to different needs. Specific data are shown in Table 1.

[0023] Table 1. Phase separation states of 2-methylpiperazine after CO2 absorption in different ether-based phase separation agents

[0024]

[0025] The low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent provided by this invention incorporates amine additives to adjust performance, compared to monoamine absorbents. The polyamine molecule used in this invention contains two secondary amino groups, exhibiting stronger absorption capacity than monoamines. Simultaneously, the amine additive molecule contains a primary amine, and its unique steric hindrance structure effectively prevents excessive binding of CO2 with the amine, allowing the generated carbamate to decompose at lower temperatures, significantly reducing regeneration energy consumption. Furthermore, the low viscosity of the AMP solution and the separation characteristics of the precipitate phase that may form after CO2 absorption further optimize heat and mass transfer efficiency, reducing the amount of rich solution required for regeneration. For details, see [link to details]. Figure 7 .

[0026] This invention proposes for the first time a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent, using cyclic polyamines and amine additives as the main absorbents, triethylene glycol dimethyl ether as the phase-separating agent, and water as the solvent. The liquid-liquid phase separation absorbent provided by this invention effectively improves CO2 absorption capacity, further enriches CO2 through phase separation, reduces the volume of the rich liquid, and achieves the goal of reducing desorption energy consumption. The selected polyamine and amine additives are a cyclic amine and a sterically hindered amine, respectively, both with high boiling points. The phase-separating agent, triethylene glycol dimethyl ether, can induce liquid-liquid phase separation and improve the CO2 mass transfer coefficient. The solvent, water, can reduce the viscosity of the CO2-rich phase and increase the CO2 absorption load. This promotes the application of phase separation chemical absorption in carbon capture. Example results show that the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system provided by this invention can achieve a rich phase CO2 load of up to 2.7 mol / L, and the rich phase desorption energy consumption is reduced by about 40% compared to 30% MEA, with the maximum rich phase viscosity not exceeding 100 mPa·s. Attached Figure Description

[0027] Figure 1 The diagram shows the amine molar CO2 loading of Examples 1-3 and Comparative Example 1.

[0028] Figure 2 The volume ratio of the upper and lower layers after CO2 absorption phase separation in the saturated solutions of Examples 1-3 and Comparative Examples 1-3;

[0029] Figure 3 The concentration distribution ratio of the upper and lower amines after absorption and phase separation in the saturated solutions of Examples 1-3 and Comparative Example 1;

[0030] Figure 4 The viscosity results of the upper and lower phases in Examples 1-3 are shown.

[0031] Figure 5 The desorption loading diagrams are for Examples 1-3 and Comparative Example 1;

[0032] Figure 6 The CO2-rich phase desorption conditions of Examples 1-3 and Comparative Example 1 are shown, where (a) is the change in desorption energy consumption over 60 minutes, and (b) is the cycle capacity and desorption efficiency.

[0033] Figure 7 The proton transfer process before and after the addition of AMP is compared in the absorbent systems of Examples 1-3 and Comparative Example 1. Detailed Implementation

[0034] This invention provides a low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, the components of which include polyamines, additives, ethers and water, wherein the concentration and ratio are the core selection.

[0035] The polyamine is 2-methylpiperazine, the amine additive is isobutanolamine, the ether is triethylene glycol dimethyl ether, and all the chemical reagents were purchased from Maclean's Reagent Company.

[0036] The CAS numbers of the chemical substances described in this invention are as follows: 2-methylpiperazine (CAS No. 109-07-9), isobutanolamine (CAS No. 124-68-5), and triethylene glycol dimethyl ether (CAS No. 112-49-2).

[0037] In this invention, in the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorption system, the concentration of the polyamine is preferably 1-3 mol / L, more preferably 1-2 mol / L, and even more preferably 1.5 mol / L.

[0038] In this invention, in the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorption system, the concentration of the amine additive is preferably 0.5–2 mol / L, more preferably 1.2–1.8 mol / L, and even more preferably 1.7 mol / L.

[0039] In this invention, the volume ratio of ether to water is preferably 3:7 to 7:3, and more preferably 3:7, 4:6, 5:5, 6:4, or 7:3.

[0040] This invention provides a method for preparing the above-mentioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorption system, comprising the following steps:

[0041] The polyamine, amine additives, ether, and water are mixed in the preferred proportions. The mixing method is not specifically limited; any mixing technique commonly used by those skilled in the art, such as heating and stirring, is acceptable. In this invention, the preferred mass ratio of 2-methylpiperazine to isobutanolamine is 8:2 to 3:7, and more specifically, 8:2, 7:3, 5:5, or 3:7. The resulting mixture yields the target low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system.

[0042] This invention provides the application of the aforementioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system in CO2 capture. This invention uses 2-methylpiperazine as the main absorbent, isobutanolamine as an amine additive, and triethylene glycol dimethyl ether as a phase-separating agent. Compared with traditional phase-separating absorbents, this low-volatility, low-energy-consumption liquid-liquid phase separation system not only achieves lean-rich phase separation, obtaining a low-viscosity CO2-rich phase, but also enables the main absorbent to absorb CO2 at an equimolar ratio, greatly improving the utilization rate of the main absorbent and significantly reducing desorption energy consumption.

[0043] This invention provides a CO2 gas absorption-desorption method, comprising the following steps:

[0044] The gas containing CO2 is passed into the above-mentioned low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system for CO2 absorption. The liquid-liquid phase separation system undergoes phase separation, with the upper layer being a CO2-poor phase and the lower layer being a CO2-rich phase.

[0045] The CO2-rich phase is heated and desorbed to release the CO2 in the CO2-rich phase.

[0046] In this invention, the volume fraction of CO2 in the CO2-containing gas is preferably 5-30%; the remaining gases in the CO2-containing gas are preferably one or more of N2, H2O, O2 and SO2.

[0047] In this invention, the temperature for CO2 absorption is preferably 20–60°C, more preferably 40°C. In this invention, the phase separation is preferably carried out under static conditions, and the static time is preferably 0.5–12 h, more preferably 2–10 h.

[0048] In this invention, the viscosity of the CO2-rich phase is preferably 10–100 mPa·s. In this invention, the volume of the rich phase is preferably 50–80% of the total volume of the liquid-liquid phase separation system.

[0049] In this invention, the preferred temperature for the heating desorption is 90–130°C, more preferably 100–110°C. The preferred heating desorption time is 0.5–2 hours, more preferably 1 hour. During the heating desorption process, the carbamate, carbonate, and bicarbonate in the CO2-rich phase decompose upon heating, regenerating 2-methylpiperazine, isobutanolamine, and high-purity CO2.

[0050] This invention only requires heating the CO2-rich phase for desorption, while the lean phase is reserved for the next absorption.

[0051] After the heating and desorption, the present invention preferably further includes mixing the CO2-rich phase and the CO2-poor phase after heating and desorption to obtain a regenerated low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system for a new round of absorption-desorption process.

[0052] The following detailed description, in conjunction with embodiments, illustrates the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system and the carbon dioxide gas absorption-desorption method provided by the present invention. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] This embodiment provides a highly efficient, low-volatility, and low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, composed of a polyamine, an amine additive, triethylene glycol dimethyl ether, and water. The polyamine is 2-methylpiperazine with a concentration of 2.5 mol / L, serving as the main absorbent. The amine additive is isobutanolamine with a concentration of 0.55 mol / L, serving as the amine additive. The volume ratio of triethylene glycol dimethyl ether to water is 5:5, serving as the phase separator and solvent. 37.5 g of polyamine (2-methylpiperazine), 7.5 g of amine additive (isobutanolamine), and 52.5 g of triethylene glycol dimethyl ether are weighed and placed in a 150 ml volumetric flask. Water is added to the mark of the volumetric flask and the mixture is shaken well to obtain 150 mL of low-volatility, low-energy-consumption liquid-liquid phase separation absorbent.

[0055] Example 2

[0056] This embodiment provides a high-efficiency, low-volatility, and low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, composed of a polyamine, an amine additive, triethylene glycol dimethyl ether, and water. The polyamine is 2-methylpiperazine with a concentration of 2 mol / L, serving as the main absorbent; the amine additive is isobutanolamine with a concentration of 1.1 mol / L, serving as the amine additive; and the volume ratio of triethylene glycol dimethyl ether to water is 5:5, serving as the phase separator and solvent. Weigh 30 g of the polyamine (2-methylpiperazine), 15 g of the amine additive (isobutanolamine), and 52.5 g of triethylene glycol dimethyl ether, place them in a 150 ml volumetric flask, add water to the mark of the volumetric flask, and shake well to obtain 150 mL of low-volatility, low-energy-consumption liquid-liquid phase separation absorbent.

[0057] Example 3

[0058] This embodiment provides a highly efficient, low-volatility, and low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, composed of a polyamine, an amine additive, triethylene glycol dimethyl ether, and water. The polyamine is 2-methylpiperazine with a concentration of 1.5 mol / L, serving as the main absorbent; the amine additive is isobutanolamine with a concentration of 1.65 mol / L, serving as the amine additive; and the volume ratio of triethylene glycol dimethyl ether to water is 5:5, serving as the phase separator and solvent. 22.5 g of the polyamine (2-methylpiperazine), 22.5 g of the amine additive (isobutanolamine), and 52.5 g of triethylene glycol dimethyl ether are weighed and placed in a 150 ml volumetric flask. Water is added to the mark of the volumetric flask and the mixture is shaken well to obtain 150 mL of low-volatility, low-energy-consumption liquid-liquid phase separation absorbent.

[0059] Comparative Example 1

[0060] This comparative example uses 150 mL of a 5 mol / L MEA (CSA: 141-43-5) aqueous solution.

[0061] Comparative Example 2

[0062] This comparative example uses another primary amine: MEA, replacing the amine additive (isobutanolamine) in Example 2, at a concentration of 1.65 mol / L; the volume ratio of triethylene glycol dimethyl ether and water is 5:5, serving as the phase separation agent and solvent. Weigh 30 g of polyamine (2-methylpiperazine), 15 g of primary amine (MEA), and 52.5 g of triethylene glycol dimethyl ether, place them in a 150 mL volumetric flask, add water to the mark of the volumetric flask, and shake well to obtain 150 mL of liquid-liquid phase separation absorbent.

[0063] Comparative Example 3

[0064] In this comparative example, another tertiary amine, N-methyldiethanolamine (CSA: 105-59-9), was used to replace the amine additive (isobutanolamine) in Example 2, with a concentration of 1.65 mol / L. Triethylene glycol dimethyl ether and water were used in a volume ratio of 5:5 as the phase separator and solvent. 30 g of polyamine (2-methylpiperazine), 15 g of tertiary amine (N-methyldiethanolamine), and 52.5 g of triethylene glycol dimethyl ether were weighed and placed in a 150 mL volumetric flask. Water was added to the mark and the flask was shaken well to obtain 150 mL of liquid-liquid phase separation absorbent.

[0065] Comparative Example 4

[0066] This comparative example does not contain any amine additives. The volume ratio of triethylene glycol dimethyl ether to water is 5:5, serving as both the phase separator and solvent. Weigh 45g of polyamine (2-methylpiperazine) and 52.5g of triethylene glycol dimethyl ether, place them in a 150ml volumetric flask, add water to the mark, and shake well to obtain 150mL of liquid-liquid phase separation absorbent.

[0067] Performance testing

[0068] I. CO2 Absorption Performance Test

[0069] Method: 150 mL of the low-volatility, low-energy-consumption liquid-liquid phase separation systems of Examples 1, 2, and 3, and a 5 mol / L MEA solution of Comparative Example 1, were placed in a bubbling absorption apparatus. The absorption temperature of the bubbling absorption apparatus was controlled at 40°C by a water bath. A gas containing 12% CO2 (12% CO2 + 88% N2) was introduced. The CO2 content in the exhaust gas was monitored using a CO2 analyzer to obtain the change in absorption rate of different absorbents over time. The total absorption load of the absorbent was obtained by integrating the absorption rate versus time. When the CO2 analyzer reading showed 12%, it indicated that the absorption process was complete and the absorbent had reached saturation.

[0070] The amine absorption loading diagrams of Examples 1-3 and Comparative Example 1 are shown below. Figure 1As shown, the molar absorption loading of amines in Examples 1, 2, and 3 of this invention is 0.61, 0.61, and 0.57 mol CO2 / mol amine, respectively. Example 1 achieves 0.5 mol CO2 / mol amine. However, the molar absorption capacity of amine in Comparative Example 1 is lower than that in Examples 1, 2, and 3 of this invention. This is related to the unique polyamine and sterically hindered amine structure used in this invention. The interaction between the intramolecular groups and steric hindrance ensures the absorption rate while significantly improving the absorption capacity.

[0071] II. Phase separation and viscosity characteristics after CO2 absorption

[0072] Methods: 150 mL of the low-volatility, low-energy-consumption liquid-liquid phase separation systems of Examples 1-3 and the absorbents of Comparative Examples 1-3 were placed in a bubbling absorption device, with the absorption temperature controlled at 40°C by a water bath. A gas containing 12% CO2 (12% CO2 + 88% N2) was introduced. When the absorption time of the absorbent in Comparative Example 1 remained consistent (30 min), the absorption process was considered complete. The absorbent was then allowed to stand for 12 hours to separate the phases, yielding the phase volume ratios of different absorbents. The loading of the upper and lower liquid phases after phase separation was measured using the acid overflow method to determine the CO2 content in each phase. The viscosity of the rich phase was measured using a viscometer to determine the viscosity changes of different absorbents after phase separation.

[0073] Figure 2 The volume ratios of the upper and lower layers after phase separation in the saturated solutions of Examples 1-3 and Comparative Examples 1-3 are shown. It can be seen that Examples 1, 2, and 3 of this invention can all separate into upper and lower phases after absorbing CO2, thereby reducing the amount of rich liquid required for desorption and regeneration. Example 1 achieves a minimum rich phase volume ratio of 68%, reducing the solution volume during desorption and significantly reducing the heat load during regeneration. The phase separation principle of Examples 1-3 proposed in this invention is as follows: After the main absorbent polyamine (2-methylpiperazine) and amine additive (isobutanolamine) react with CO2, they generate ionic or neutral reaction products such as carbamates, carbonates, and bicarbonates. There is a significant polarity difference between these products and the triethylene glycol dimethyl ether contained in the system. When the concentration of these reaction products reaches a certain threshold, the triethylene glycol dimethyl ether is displaced from the aqueous phase and spontaneously aggregates under the drive of intermolecular forces to form a hydrophobic organic phase dominated by ethers. As the reaction continues, triethylene glycol dimethyl ether further migrates from the hydrophilic phase to the organic phase, eventually achieving liquid-liquid phase separation. The upper layer forms a CO2-poor phase dominated by triethylene glycol dimethyl ether and containing a small amount of water, while the lower layer forms a CO2-rich phase dominated by amines and the products of amines absorbing CO2.

[0074] Figure 3The figures show the CO2 loading of the lower rich phase in Examples 1, 2, and 3. It can be seen that the loading of the lower rich phase after phase separation is much higher than that of the upper lean phase. More than 90% of the CO2 absorption products accumulate in the lower rich phase, resulting in a lower rich phase loading of 7.6 mol / L in Example 3. Experimental results combining key performance indicators such as rich phase volume distribution, rich phase viscosity, and rich phase CO2 loading demonstrate that the liquid-liquid phase separation absorbent system provided by this invention can achieve efficient CO2 capture and low-viscosity phase separation absorption.

[0075] Viscosity is a key parameter for evaluating phase separation absorbents. The viscosity results of the lower CO2-rich phase in Examples 1, 2, and 3 of this invention are as follows: Figure 4 As shown, the viscosity of the rich phase in Example 3 is the highest at 31.68 mPa·s, and the viscosity of the rich phase in all examples is less than 50 mPa·s, so the effect on the transport of the rich phase is negligible.

[0076] III. CO2 Desorption Characteristics Test

[0077] Method: 150 mL of the low-volatility, low-energy-consumption liquid-liquid phase separation absorbent from Example 3 and the 5 mol / L LMEA solution from Comparative Example 1 were placed in a bubbling absorption apparatus, with the absorption temperature controlled at 40°C by a water bath. A gas containing 12% CO2 (12% CO2 + 88% N2) was introduced until the absorbent was saturated, and the saturated absorbent was allowed to stand for 2 hours for phase separation. The lower rich phase was regenerated using high-temperature thermal desorption for 1 hour. N2 was mixed with the high-purity CO2 generated by desorption, and the concentration change was detected using a CO2 analyzer. The desorption rate of the absorbent over time was calculated, and the total desorption load of the absorbent was obtained by integrating the desorption rate versus time. The ratio of the desorption load to the absorption load is the desorption efficiency. The desorption regeneration temperature was controlled at 102°C by a heating mantle.

[0078] Figure 5 The changes in desorption load of Examples 1, 2, 3 and Comparative Example 1 over 60 minutes are shown respectively. It can be seen that the desorption rates of Examples 1, 2 and 3 proposed in this invention are all greater than those of Comparative Example 1, which shows that the low volatility and low energy consumption liquid-liquid phase separation carbon dioxide absorbent system proposed in this invention has excellent desorption characteristics.

[0079] Figure 6The changes in desorption energy consumption (a), regeneration efficiency, and circulation capacity (b) of Examples 1, 2, 3, and Comparative Examples 1 and 4 over 60 minutes are shown. As can be seen from the figures, the desorption energy consumption of Example 2 proposed in this invention is significantly lower than that of Comparative Example 1. At 20 minutes and 60 minutes of desorption, the desorption energy consumption is reduced by 85.4% and 44.4% compared to Comparative Example 1, respectively. The regeneration efficiency and circulation capacity reach 69% and 1.55 mol / L, respectively, representing increases of 64% and 23% compared to Comparative Example 1. This demonstrates that the low-volatility, low-energy liquid-liquid phase separation carbon dioxide absorbent system proposed in this invention has excellent characteristics of reducing energy consumption and increasing circulation capacity.

[0080] Figure 7 The diagram shows the overall proton transfer process within the absorbent before and after the addition of amine additives. It can be seen that the addition of isobutanolamine, an amine additive, is beneficial to the proton transfer process in solution, accelerates the desorption rate, and improves the overall desorption performance.

[0081] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system, characterized in that, The absorbent system consists of 2-methylpiperazine, isobutanolamine, triethylene glycol dimethyl ether, and water; wherein the concentration of 2-methylpiperazine is 2 mol / L, the concentration of isobutanolamine is 1.1 mol / L, and the volume ratio of triethylene glycol dimethyl ether to water is 5:5; the absorbent system is homogeneous before absorbing CO2, and undergoes liquid-liquid phase separation after absorbing CO2, forming an upper CO2-poor phase dominated by triethylene glycol dimethyl ether and a lower CO2-rich phase dominated by amines and their CO2 absorption products.

2. The absorbent system according to claim 1, characterized in that, After the absorbent system absorbs CO2 and undergoes liquid-liquid phase separation, more than 90% of the CO2 absorption products accumulate in the lower CO2-rich phase, and the viscosity of the lower CO2-rich phase is less than 50 mPa·s.

3. The method for preparing the absorbent system according to claim 1 or 2, characterized in that, include: Weigh 30 g of 2-methylpiperazine, 15 g of isobutanolamine, and 52.5 g of triethylene glycol dimethyl ether, place them in a 150 mL volumetric flask, add water to the mark of the volumetric flask and mix well to obtain the low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system.

4. The application of the absorbent system according to claim 1 or 2 or the absorbent system prepared by the preparation method according to claim 3 in carbon dioxide capture.

5. A method for absorbing and desorbing carbon dioxide gas, characterized in that, Includes the following steps: A gas containing CO2 is introduced into the absorbent system of claim 1 or 2 or the absorbent system prepared by the preparation method of claim 3 for CO2 absorption. The absorbent system undergoes liquid-liquid phase separation to form an upper CO2-poor phase and a lower CO2-rich phase. The lower CO2-rich phase is heated for desorption to release the CO2 in the lower CO2-rich phase.

6. The method according to claim 5, characterized in that, The CO2-containing gas is a mixture of 12% CO2 and 88% N2 by volume. The CO2 absorption temperature is 40°C. The heating and desorption temperature of the lower CO2-rich phase is 102°C, and the desorption time is 1 h. After heating and desorption, the CO2-rich phase after heating and desorption is mixed with the CO2-poor phase to obtain a regenerated low-volatility, low-energy-consumption liquid-liquid phase separation carbon dioxide absorbent system.

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