CO2 absorbent with high cycle capacity and high cycle stability and application thereof

Abstract

The invention relates to a CO2 absorbent with high cycle capacity and high cycle stability and application of the CO2 absorbent, and belongs to the technical field of atmospheric CO2 pollution treatment in the environmental protection industry. The CO2 absorbent is a polyamide-amine dendritic polymer (represented by PAMAM-2 (2 + G) NH2, G is the algebra, and 2 (2 + G) is the number of terminal amino groups), wherein primary amino is used as a terminal group, alkylene diamine is used as a core, and the algebra G is 1-5. The polyamidoamine dendritic polymer provided by the invention has the advantages of high-density terminal amino groups, high CO2 absorption capacity, large circulation capacity and high circulation absorption stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of air CO2 pollution control in the environmental protection industry, in particular to a CO2 absorbent with high cycle capacity and high cycle stability and application thereof, wherein the dendritic polymer is an amino-terminated polyamide-amine dendrimer with a generation number G of 1-5. BACKGROUND

[0003] Carbon capture, utilization and storage technology (CCUS) is a technology for capturing CO2 from flue gas emitted by coal-fired power plants, steel, cement, chemical industry and other industries, and utilizing or storing it, so as to reduce the total amount of CO2 emitted into the atmosphere and achieve the goal of carbon neutralization. CO2 capture is the premise and basis of CCUS and is the key to the implementation of CCUS. At present, CO2 capture methods include physical solution absorption, chemical solution absorption, solid adsorption, membrane separation and low-temperature method, etc. Among them, the chemical solution absorption technology is mature, stable in operation and has realized commercial operation.

[0004] Chemical solution absorption method mainly includes ammonia method, potassium / sodium carbonate method and organic amine method, among which the organic amine solution absorption method has the advantages of large absorption capacity, good absorption effect, fast absorption rate and recyclable use of absorbent, etc. and is the most attractive and widely used CO2 capture technology so far. At present, large-scale CO2 capture mainly uses the organic amine absorption method. However, the existing organic amine absorption agent mainly consists of small molecule compounds such as monoethanolamine (MEA), 2-amino-2-methyl-propanol (AMP), diethanolamine (DEA), N-methylethanolamine (MMEA), N-methyldiethanolamine (MDEA), ethylenediamine (EDA), diethylenetriamine (DETA) and triethylenetetramine (TETA). These small molecule organic amines usually have low boiling points and are easy to volatilize. After multiple cycles of use, the loss is large, which leads to gradual decrease of the cycle absorption capacity and poor stability of the cycle absorption capacity. Therefore, in order to reduce the loss caused by volatilization, it is necessary to develop an organic amine absorption agent with high cycle stability.

[0005] Generally, the larger the molecular weight of an organic compound, the higher its boiling point and the smaller its volatility. The 0-generation polyamide-amine dendrimer is a macromolecular organic amine containing four terminal primary amine groups, and its molecular weight is 516, which is higher than that of conventional small-molecule organic amines such as monoethanolamine (MEA), 2-amino-2-methyl-propanol (AMP), diethanolamine (DEA), N-methylethanolamine (MMEA), N-methyldiethanolamine (MDEA), ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), etc. The research of the present inventors (CN120022715A) shows that, as a CO2 absorbent, the 0-generation polyamide-amine dendrimer has a higher cyclic absorption capacity and a higher cyclic stability compared with conventional small-molecule organic amine absorbents. With the increase of the generation number G (G≥1), the molecular weight of the polyamide-amine dendrimer gradually increases, and the number of terminal primary amine groups increases, which should theoretically have better cyclic absorption stability. SUMMARY

[0006] To solve the above technical problems, the present application provides a CO2 absorbent with high cyclic capacity and high cyclic stability and applications thereof.

[0007] The first object of the present application is to provide a CO2 absorbent with high cyclic capacity and high cyclic stability, comprising the polyamide-amine dendrimer.

[0008] The polyamide-amine dendrimer is a polyamide-amine dendrimer with primary amine groups as end groups and alkylene diamines as cores, and has a structure as shown in Formula I: Formula I; In the formula, “A” represents a core, specifically an alkylene diamine [N(CH2) m m is a positive integer between 2 and 12; The line segment “—” represents an inner layer branch, specifically [CH2CH2CONHCH2CH2]; “N” represents an inner layer branching nitrogen atom; “G” represents the generation number, which is a positive integer; “B” is a terminal primary amine group (-NH2), and the number of terminal primary amine groups is 2 (G+2) .

[0009] In the present application, the generation number G is a positive integer between 1 and 5, preferably between 1 and 2.

[0010] In the present application, when the generation number G is 1, the polyamide-amine dendrimer is a 1-generation terminal amine group polyamide-amine dendrimer, and its structure is as shown in Formula II: Formula II; Wherein, n is a positive integer between 2~12.

[0011] When the algebra G=2, the polyamide-amine dendrimer is a 2-generation terminal amine polyamide-amine dendrimer, and its structure is shown as formula III: Formula III, Wherein, n is a positive integer between 2~12.

[0012] The second object of the present application is to provide the application of the CO2 absorbent in absorbing CO2 in a mixed gas.

[0013] In the present application, the application comprises the following steps: Dissolving the CO2 absorbent in water to obtain a CO2 absorbent solution; Contacting the CO2 absorbent solution with a mixed gas containing CO2 to occur an absorption reaction, and obtaining an absorption rich solution containing CO2; Heating the absorption rich solution containing CO2 to occur a desorption reaction, release CO2, and regenerate the CO2 absorbent solution, and the regenerated CO2 absorbent solution is a regenerated lean solution; Collecting the released CO2; and recycling the regenerated lean solution for the next round of CO2 absorption.

[0014] In the present application, the concentration of the polyamide-amine dendrimer in the CO2 absorbent solution is 10~60wt%.

[0015] In the present application, the temperature of the absorption reaction is 0℃~60℃, and the time of the absorption reaction is 0.5~3h.

[0016] In the present application, the temperature of the desorption reaction is 90℃~130℃, and the time of the heating desorption is 0.5~3h.

[0017] In the present application, the volume fraction of CO2 in the mixed gas containing CO2 is 1~99%.

[0018] The above technical solution of the present application has the following advantages compared with the prior art: The terminal amino polyamide-amine dendrimer as the CO2 absorbent has the following advantages when used for capturing and separating CO2 in a mixed gas: (1) high absorption capacity and fast speed; (2) high regeneration efficiency after absorbing CO2; (3) large molecular weight, low volatility, less volatile loss during regeneration, strong cyclic absorption stability, and high cyclic stability. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments of the present application and in combination with the drawings, wherein, Figure 1 CO2 absorption load vs. time profiles of the absorbent solutions of the 1st and 2nd generation polyamidoamine dendrimers of the present application, the amine-terminated 0th generation polyamidoamine dendrimer of Comparative Example 1, the conventional organic amines MEA and TETA of Comparative Examples 2-3; Figure 2 CO2 absorption load vs. time profiles of the absorbent solutions of the 1st and 2nd generation polyamidoamine dendrimers of the present application, the amine-terminated 0th generation polyamidoamine dendrimer of Comparative Example 1, the conventional organic amines MEA and TETA of Comparative Examples 2-3 at an oil bath temperature of 130°C; Figure 3 CO2 load vs. time profiles of Examples 1-3, Comparative Examples 1-3 in the first absorption-desorption cycle; Figure 4 CO2 absorption capacity vs. number of cycles in terms of molar molecular weight of Examples 1-3, Comparative Examples 1-3 in multiple absorption-desorption cycles; Figure 5 CO2 absorption capacity vs. number of cycles in terms of molar effective N of Examples 1-3, Comparative Examples 1-3 in multiple absorption-desorption cycles. DETAILED DESCRIPTION

[0020] To solve the technical problems pointed out in the background art, the present application is realized by the following scheme: The present application provides a CO2 absorbent with high cycle capacity and high cycle stability, comprising the polyamidoamine dendrimer; the polyamidoamine dendrimer is a polyamidoamine dendrimer with primary amine group as end group and alkylene diamine as core, having a structure as shown in Formula I: Formula I; In the formula, "A" represents the core, specifically alkylene diamine [N(CH2) m m is a positive integer between 2 and 12; The line segment "--" represents the inner layer branch, specifically [CH2CH2CONHCH2CH2]; "N" represents the inner layer branching nitrogen atom; "G" represents the generation number, which is a positive integer; "B" is the terminal primary amine group (-NH2), the number of terminal primary amine groups is 2 (G+2) .

[0021] In the present application, the generation number G is a positive integer between 1 and 5, preferably 1-2.

[0022] In the present application, when the algebra G=1, the polyamide-amine dendrimer is a 1-generation terminal amino polyamide-amine dendrimer, and the structure is shown as formula II: Formula II; wherein n is a positive integer between 2 and 12.

[0023] When the algebra G=2, the polyamide-amine dendrimer is a 2-generation terminal amino polyamide-amine dendrimer, and the structure is shown as formula III: Formula III, wherein n is a positive integer between 2 and 12.

[0024] The present application further provides the application of the CO2 absorbent in absorbing CO2 in a mixed gas. The terminal amino formate polyamide-amine dendrimer formed after the terminal amino polyamide-amine dendrimer absorbs CO2 has a high CO2 desorption capacity, and has the advantages of high cyclic absorption capacity and high cyclic stability. It can be used for CO2 capture, separation or recovery in a mixed gas.

[0025] In the present application, the application comprises the following steps: dissolving the CO2 absorbent in water to obtain a CO2 absorbent solution; contacting the CO2 absorbent solution with a mixed gas containing CO2 to occur an absorption reaction, and obtaining an absorption rich solution containing CO2; heating the absorption rich solution containing CO2 to occur a desorption reaction, releasing CO2, and regenerating the CO2 absorbent solution, wherein the regenerated CO2 absorbent solution is a regenerated lean solution; collecting the released CO2; and recycling the regenerated lean solution for the next round of CO2 absorption.

[0026] In the present application, the concentration of the polyamide-amine dendrimer in the CO2 absorbent solution is 10-60wt%, for example, it can be 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, or any interval value between any two numerical values.

[0027] In the present application, the temperature of the absorption reaction is 0-60℃, and the reaction time is 0.5-3h. For example, the temperature can be 0, 10, 20, 30, 40, 50, 60℃, or any interval value between any two numerical values; the reaction time can be 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, or any interval value between any two numerical values.

[0028] In the present application, the temperature of the desorption reaction is 90-130℃, and can be 90℃, 100℃, 110℃, 120℃, 130℃, or any interval value between any two values.

[0029] In the present application, the volume fraction of CO2 in the mixed gas containing CO2 is 1-99%. It can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or 10-50%, 50%-60%, 50%-70%, 50%-80%, 50%-99%, or any interval value between any two values.

[0030] The present application will be further described below in conjunction with the drawings and specific examples, so that those skilled in the art can better understand the present application and implement it, but the examples are not limiting to the present application.

[0031] The PAMAM Dendrimer, 1,2-Ethylenediamine Core, Generation 1.0 used in Example 1 (molecular weight M=1429.02, abbreviated as PAMAM-EDA-G1-8NH2 in the present application) is a commercially available product, the PAMAM Dendrimer, 1,2-Ethylenediamine Core, Generation 2.0 used in Example 2 (molecular weight M=3250.31, abbreviated as PAMAM-EDA-G2-16NH2 in the present application) is a commercially available product, the PAMAM Dendrimer, 1,6-Diaminohexane Core, Generation 1.0 used in Example 3 (molecular weight M=3306.37, abbreviated as PAMAM-HDA-G2-16NH2 in the present application) is a commercially available product, the PAMAM Dendrimer, 1,2-Ethylenediamine Core, Generation 0.0 used in Comparative Example 1 (molecular weight M=516, abbreviated as PAMAM-EDA-G0-4NH2 in the present application) is a commercially available product, and the products of Example 1, Example 2, Example 3 and Comparative Example 1 are all 20% methanol solutions. The monoethanolamine used in Comparative Example 2 and the triethylenetetramine used in Comparative Example 3 are both commercially available products.

[0032] Example 1 The present example provides a method for preparing an amine-terminated, ethylenediamine-core, 1st generation polyamide-amine (PAMAM-EDA-G1-8NH2) absorbent solution, which is as follows: 375.0 g of a methanol solution of PAMAM-EDA-G1-8NH2 having an effective content of 20% is distilled under reduced pressure at a temperature of less than 50°C using a vacuum rotary evaporator to remove the methanol, thereby obtaining 75.0 g of a viscous PAMAM-EDA-G1-8NH2; then 175.0 g of deionized water is added and stirred until uniform, thereby obtaining 250.0 g of an amine-terminated, ethylenediamine-core, 1st generation polyamide-amine absorbent solution (30 wt% PAMAM-EDA-G1-8NH2) having a solid content of 30.0 wt%.

[0033] wherein the amine-terminated, ethylenediamine-core, 1st generation polyamide-amine (PAMAM-EDA-G1-8NH2) dendrimer has a structure as shown in Formula IV: Formula IV.

[0034] The prepared absorbent solution is subjected to performance testing according to the test examples.

[0035] Example 2 The present example provides a method for preparing an amine-terminated, ethylenediamine-core, 2nd generation polyamide-amine (PAMAM-EDA-G2-16NH2) absorbent solution, which is as follows: The present example provides a method for preparing an amine-terminated, ethylenediamine-core, 2nd generation polyamide-amine (PAMAM-EDA-G2-16NH2) absorbent solution, which is as follows:

[0036] wherein the amine-terminated, ethylenediamine-core, 2nd generation polyamide-amine (PAMAM-EDA-G2-16NH2) dendrimer has a structure as shown in Formula V: Formula V.

[0037] The prepared absorbent solution is subjected to performance testing according to the test examples.

[0038] Example 3 The present example provides a preparation method of a 2nd generation polyamide-amine (PAMAM-HDA-G2-16NH2) absorbent solution with an amino-terminated hexanediamine core, which is specifically shown as follows: 375.0 g of a methanol solution of PAMAM-HDA-G2-16NH2 with an effective content of 20% was distilled under reduced pressure at less than 50°C using a vacuum rotary evaporator to remove methanol, to obtain about 75.0 g of PAMAM-HDA-G2-16NH2 in a viscous state; then 175.0 g of deionized water was added, and stirring was performed until a 30.0 wt% amino-terminated hexanediamine core 2nd generation polyamide-amine absorbent solution (30 wt% PAMAM-HDA-G2-16NH2) 250.0 g was obtained.

[0039] The structure of the amino-terminated hexanediamine core 2nd generation polyamide-amine (PAMAM-HDA-G2-16NH2) dendrimer is shown in formula VI as follows: Formula VI.

[0040] The prepared absorbent solution was subjected to performance tests according to the test examples.

[0041] Comparative Example 1 The present comparative example provides a preparation method of a 0th generation polyamide-amine (PAMAM-EDA-G0-4NH2) absorbent solution with an amino-terminated ethylenediamine core, which is specifically shown as follows: 375.0 g of a methanol solution of PAMAM-EDA-G0-4NH2 with an effective content of 20% was distilled under reduced pressure at less than 50°C using a vacuum rotary evaporator to remove methanol, to obtain about 75.0 g of PAMAM-EDA-0G in a viscous state; then 175.0 g of deionized water was added, and stirring was performed until a 30.0 wt% amino-terminated ethylenediamine core 0th generation polyamide-amine absorbent solution (30 wt% PAMAM-EDA-G0-4NH2) 250.0 g was obtained.

[0042] The structure of the amino-terminated ethylenediamine core 0th generation polyamide-amine (PAMAM-EDA-G0-4NH2) dendrimer is shown in formula VII as follows: Formula VII.

[0043] The prepared absorbent solution was subjected to performance tests according to the test examples.

[0044] Comparative Example 2 The present comparative example provides a preparation method of a monoethanolamine absorbent solution, which is specifically shown as follows: A 30.0 wt% solution of monoethanolamine (MEA) was prepared 250.0 g, including MEA 75.0 g, deionized water 175.0 g.

[0045] The prepared absorbent solution was tested for performance according to the test example.

[0046] Comparative Example 3 This comparative example provides a method for preparing a triethylenetetramine absorbent solution, as shown below: A 30.0 wt% solution of triethylenetetramine (TETA) was prepared 250.0 g, including TETA 75.0 g, deionized water 175.0 g.

[0047] The prepared absorbent solution was tested for performance according to the test example.

[0048] Test Example 1: Absorption Capacity Test 250.0 g of a 30.0 wt% organic amine absorbent solution of Examples 1-3 and Comparative Examples 1-3 was added to a round-bottom flask placed in an oil bath, the oil bath temperature was controlled at 40°C, a mixed gas of CO2 with a volume fraction of 15% and N2 was introduced, the flow rate of the mixed gas was 2200 mL / min, the pressure was 0.1 MPa, samples were taken every 10 min, the CO2 loading of the absorption liquid was determined by acidolysis gas method, until the CO2 absorption loading no longer changed, to obtain a CO2-rich absorption liquid.

[0049] The change of CO2 loading of each absorbent solution with time is shown in Figure 1 The absorbent solution of Examples 1-3 reached saturated absorption after 110 min, Comparative Example 1, Comparative Example 2, and Comparative Example 3 reached maximum saturated absorption at 100 min, 120 min, and 120 min, respectively, and the saturated absorption capacity is shown in Table 1, the absorption capacity size is: Example 2 ≈ Example 3 > Example 1 > Comparative Example 1 > Comparative Example 2 > Comparative Example 3.

[0050] The 1st generation end amino polyamide-amine dendrimer in Example 1 (PAMAM-EDA-G1-8NH2) contains 8 end primary amino groups, the 2nd generation end amino polyamide-amine dendrimer in Example 2 (PAMAM-EDA-G2-16NH2) and Example 3 (PAMAM-HDA-G2-16NH2) contains 16 end primary amino groups, the CO2 absorption load according to the number of end amino groups (effective N atoms) is shown in Table 1, which is 0.632, 0.597 and 0.589 mol CO2 / mol NH (end primary amino group) respectively, higher than 0.545 mol CO2 / mol NH (end primary amino group) in Comparative Example 1 (PAMAM-EDA-G0-4NH2) containing 4 end primary amino groups. Therefore, the maximum absorption capacity according to the effective nitrogen is: Example 1>Example 2≈Example 3>Comparative Example 1>Comparative Example 2>Comparative Example 3.

[0051] Therefore, the end amino polyamide-amine dendrimer PAMAM (G≥1) of the present application has higher absorption capacity than the end amino 0th generation polyamide-amine (PAMAM-EDA-G0-4NH2), and the maximum absorption capacity according to the number of end amino groups is G1>G2>G0.

[0052] Table 1 CO2 saturated absorption capacity of absorption rich liquid of each absorption agent Test Example 2 Influence of temperature on desorption performance The desorption bottle with a reflux condenser is placed in an oil bath heater, after heating to a certain temperature, the absorption rich liquid of the absorption agent obtained in Test Example 1 is placed in the desorption bottle, and the CO2 load is determined by acidolysis gas method every certain time, until the CO2 load has no obvious change, which is the complete desorption, the desorbed CO2 gas is vented, and the regenerated desorption liquid, i.e. the desorption lean liquid, is obtained.

[0053] Desorption rate calculation: CO2 desorption rate (%) = (CO2 load of absorption rich liquid-CO2 load of desorption lean liquid) / (CO2 load of rich liquid)100%.

[0054] The CO2 desorption rates of the absorption rich solution at 120 min and 180 min when the oil bath temperature is 110℃, 120℃ and 130℃ respectively are shown in Table 2, and the results show that the desorption capacity is improved with the increase of the desorption temperature. When the oil bath temperature is 130℃, the desorption rate of the absorption rich solution of Example 1 is 100% after heating for 180 min, and the absorbent is completely regenerated, which is similar to the desorption performance of Comparative Example 1. Under the same conditions, the desorption rates of the absorption rich solution of Example 2 and Example 3 are 98.32% and 98.16% respectively after heating for 180 min, which are lower than those of Example 1 and Comparative Example 1, but are much higher than 74.12% of Comparative Example 2 (MEA) and 72.38% of Comparative Example 3 (TETA). It is shown that the 1st generation and 2nd generation polyamidoamine dendrimers with terminal amino groups have excellent CO2 desorption capacity.

[0055] Table 2 Desorption rates of the absorption rich solution at different oil bath temperatures Test Example 3 Maximum cyclic capacity test Since the desorption temperature is 130℃, the oil bath is heated to 130℃, and the absorption rich solution of the absorbent obtained in Test Example 1 is put into a desorption bottle. The CO2 load is determined by the acidolysis gas method every certain time, and the desorption is complete when the CO2 load has no obvious change. The change of the CO2 load with time is shown in Figure 2 Table 3. The maximum cyclic capacity is the difference between the CO2 load of the absorption rich solution in saturated absorption and the CO2 load of the desorption lean solution in complete desorption. The regeneration rate is the percentage of the maximum cyclic capacity in the CO2 load of the rich solution in saturated absorption, and the regeneration rate value is the same as the desorption rate. It can be seen from Table 3 that the 1st generation and 2nd generation polyamidoamine dendrimers with terminal amino groups have good cyclic absorption capacity. After absorbing CO2, the regeneration rates of Example 1, Example 2 and Example 3 are 100%, 98.32% and 98.13% respectively, and the maximum cyclic capacity is reduced. The regeneration rate of the 1st generation polyamidoamine dendrimer with terminal amino groups is consistent with that of the 0th generation polyamidoamine dendrimer of Comparative Example. The regeneration rates of the traditional organic amine absorbents MEA and TETA are relatively low, and the maximum cyclic capacity is reduced compared with the initial absorption.

[0056] Table 3 Maximum cyclic capacity and maximum CO2 desorption rate of each absorbent solution at 130℃ oil bath temperature Test Example 4 Stability of cyclic absorption capacity Stability experiment method: 250.00 g of 30 wt% CO2 absorbent solution of examples 1-3 and comparative examples 1-3 were respectively added into absorption bottles, and CO2 with a volume fraction of 15% and N2 were mixed and absorbed at 40℃, the mixed gas flow rate was 2200 mL / min, the pressure was 0.1 MPa, and after 120 min of absorption, the absorption rich liquid containing CO2 was obtained. Then the absorption rich liquid was desorbed at an oil bath temperature of 130℃, the desorption time was 120 min, and the desorption lean liquid was obtained. The desorption lean liquid was subjected to the next round of absorption to obtain the absorption rich liquid, and the absorption rich liquid was desorbed to obtain the desorption lean liquid, and the cycle was repeated for several times, while the CO2 load of the solution was measured, and the cycle capacity and regeneration rate were calculated.

[0057] The results of the change of the CO2 load of the first round of absorption-desorption cycle with time are shown in Figure 3

[0058] The comparison of the initial absorption load of the absorbent solution of the first round of cycle and the cycle capacity is shown in Table 4.

[0059] The cycle absorption capacity is the difference between the CO2 load of the absorption rich liquid and the CO2 load of the desorption lean liquid; the regeneration rate is the percentage of the cycle absorption capacity to the CO2 load of the absorption rich liquid, and the absorbent regeneration rate and the CO2 desorption rate of the absorption rich liquid have the same value.

[0060] Table 4 Regeneration rate and cycle capacity (130℃) of the first round of cycle of the absorption liquid The cycle absorption capacity of the absorbent solution of examples 1-3 and comparative examples 1-3 to CO2 in multiple cycles is shown in Figure 4 , Figure 5 The attenuation of the terminal amine group polyamide amine dendrimer of examples 1-3 of the application is extremely slow, and the cycle absorption stability is stronger than that of the 0 generation polyamide amine dendrimer of the comparative examples; and the capacity of the second cycle absorption is not as good as that of the first cycle absorption due to the relatively low regeneration rate of MEA and TETA, and the cycle absorption capacity of the third to twentieth cycle is gradually attenuated.

[0061] Obviously, the above examples are only examples for clearly illustrating, and are not limitations to the embodiments. Other different forms of changes or variations can be made by those skilled in the art on the basis of the above description. All the embodiments do not need to be exhausted, and the obvious changes or variations derived therefrom are still within the protection scope of the application.​

Claims

1. A CO2 absorbent with high cycling capacity and high cycling stability, characterized in that, Including polyamide-amine dendritic polymers; the polyamide-amine dendritic polymers are polyamide-amine dendritic polymers with primary amine groups as end groups and alkylene diamines as cores, having the structure described in Formula I: Equation I; In the formula, "A" represents the core, specifically an alkylene diamine [N(CH2)] m N], where m is a positive integer between 2 and 12; The line segment "—" indicates an inner branch, specifically [CH2CH2CONHCH2CH2]; "N" represents an inner-shell branched nitrogen atom; "G" represents algebra and is a positive integer; "B" represents a terminal primary amino group (-NH2), and the number of terminal primary amino groups is 2. (G+2) .

2. The CO2 absorbent with high cycling capacity and high cycling stability according to claim 1, characterized in that, The algebra G is a positive integer between 1 and 5.

3. The CO2 absorbent with high cycling capacity and high cycling stability according to claim 1, characterized in that, When the generation number G=1, the polyamide-amine dendritic polymer is a first-generation terminal amine polyamide-amine dendritic polymer, and its structure is shown in Formula II: Formula II; Where n is a positive integer between 2 and 12.

4. The CO2 absorbent with high cycling capacity and high cycling stability according to claim 1, characterized in that, When the generation number G=2, the polyamide-amine dendritic polymer is a second-generation terminal amine polyamide-amine dendritic polymer, and its structure is shown in Formula III: Formula III, Where n is a positive integer between 2 and 12.

5. The application of the CO2 absorbent according to any one of claims 1 to 4 in absorbing CO2 in a mixed gas.

6. The application according to claim 5, characterized in that, Includes the following steps: Dissolve the CO2 absorbent in water to obtain a CO2 absorbent solution; The CO2 absorbent solution is contacted with a mixed gas containing CO2 to undergo an absorption reaction, resulting in a CO2-rich absorbent solution. Heating the CO2-rich absorbent solution causes a desorption reaction, releasing CO2. Simultaneously, the CO2 absorbent solution is regenerated, and the regenerated CO2 absorbent solution becomes the regenerated lean solution. The released CO2 is collected; the regenerated lean solution is recycled for the next round of CO2 absorption.

7. The application according to claim 6, characterized in that, The concentration of polyamide-amine dendritic polymer in the CO2 absorbent solution is 10~60wt%.

8. The application according to claim 6, characterized in that, The absorption reaction temperature is 0℃~60℃; the absorption reaction time is 0.5~3 h.

9. The application according to claim 6, characterized in that, The desorption reaction temperature is 90℃~130℃, and the heating desorption time is 0.5~3h.

10. The application according to claim 6, characterized in that, The volume fraction of CO2 in the CO2-containing gas mixture is 1-99%.

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