A hyperbranched polymer pentaerythritol tetra(2-piperazinylpropionate) and a preparation method and a carbon dioxide capturing application thereof

Abstract

The application belongs to the technical field of carbon neutralization, and particularly relates to a hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) and preparation and application thereof in capturing carbon dioxide. The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided by the application has a structure shown in formula I. The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided by the application has the following advantages when used in capturing CO2 in mixed gas: (1) high absorption speed and high absorption capacity; (2) high desorption speed and high desorption rate; (3) low desorption temperature and low regeneration energy consumption; (4) low volatility, less regeneration loss, and strong cycle stability.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of carbon neutralization, and particularly relates to a hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) and a preparation method and application thereof in capturing carbon dioxide. BACKGROUND

[0002] In recent years, the problem of global warming caused by greenhouse gases has become increasingly serious. Glaciers are melting, oceans are acidifying, and climate zones are shifting northward, leading to an increase in extreme weather phenomena such as snowstorms, droughts, hurricanes, floods, and high temperatures, posing an increasingly serious threat to human survival and development. Existing data shows that since the industrial revolution, the emission of CO2 from the burning of fossil fuels has been increasing, leading to a gradual increase in the concentration of CO2 in the atmosphere, and a positive correlation with climate warming. Unfortunately, since 1960, the trend of a sharp increase in global CO2 emissions has not diminished at all, and in 2023, global CO2 emissions reached a new high of 37.4 billion tons. How to control and reduce CO2 emissions is a global problem that needs to be solved urgently.

[0003] The main CO2 capture technologies for flue gas generated by the burning of fossil fuels are pre-combustion CO2 capture, in-combustion CO2 capture (oxygen-enriched combustion), and post-combustion CO2 capture. Since pre-combustion CO2 capture and in-combustion CO2 capture require modification of existing combustion furnaces, post-combustion CO2 capture does not require modification of existing combustion systems, only needs to set the CO2 capture system after the combustion system, and downstream of the dust removal, desulfurization and denitrification system, and has the advantages of wide adaptability, simple equipment modification and economic practicality.

[0004] Post-combustion CO2 capture technologies mainly include physical solution absorption, chemical solution absorption, solid adsorption, membrane separation, and low-temperature methods. Among them, the chemical solution absorption method is relatively mature, stable in operation, and suitable for conditions with relatively low CO2 concentration in post-combustion flue gas. It is currently the main means to achieve large-scale CO2 emission reduction, and is also the main method used by most countries at the present stage.

[0005] The chemical solution absorption method takes advantage of the acidic nature of CO2, and uses an alkaline absorbent to react with CO2 in the solution to generate an intermediate metastable compound. Then, under certain conditions, the reverse reaction is used to achieve the desorption of CO2, and the absorbent solution is regenerated. The chemical solution absorption method mainly includes inorganic hot base solution absorption (potassium base or sodium base), ammonia absorption, and organic amine solution absorption. Among them, the organic amine solution absorption method has the advantages of large absorption capacity, good absorption effect, fast absorption rate, and recyclable use of absorbents, and has been widely applied.

[0006] The organic amine solution absorption method for capturing CO2 is by chemical reaction between the organic amine solution and CO2 in the mixed gas in a low-temperature absorption tower to generate a compound in the solution, forming an absorption rich solution (rich in CO2); then after the lean-rich solution heat exchanger, into the desorption tower, after heating, the inverse reaction releases the absorbed CO2, and the organic amine solution is regenerated to form a desorption lean solution (not containing or containing a lower concentration of CO2); the released CO2 is collected and utilized, and the desorption lean solution returns to the absorption tower through the lean-rich solution heat exchanger to enter the next cycle of absorption, completing the separation of CO2 from other gases in the exhaust gas. This method has the advantages of fast CO2 absorption rate, large absorption capacity, low cost, recyclable use of absorbent, and recovery of high-purity CO2.

[0007] The organic amine absorbent used in the organic amine solution absorption method has many types, which can be divided into primary (primary) amines, secondary (secondary) amines and tertiary (tertiary) amines according to the number of hydrocarbon groups connected to nitrogen; and monoamines, diamines, linear polyamines and cyclic polyamines according to the number of amino groups.

[0008] Typical organic amines mainly include primary amines such as monoethanolamine (MEA) and 2-amino-2-methyl-propanol (AMP); secondary amines such as diethanolamine (DEA) and N-methyl ethanolamine (MMEA); tertiary amines such as triethanolamine (TEA) and N-methyl diethanolamine (MDEA); diamines such as ethylenediamine (EDA) and hexanediamine (HDA); linear polyamines such as diethylene triamine (DETA), triethylene tetramine (TETA) and tetraethylene pentamine (TEPA); and cyclic polyamines such as piperazine (PZ) and the like.

[0009] Among them, primary amines (such as MEA) and secondary amines (such as DEA) have a relatively fast CO2 absorption rate in the CO2 absorption process, but the desorption rate is low, which makes the cycle capacity low; the desorption temperature is high, which makes the regeneration energy consumption high; the desorption temperature is high, and the desorption time is long, which means that there is a large amount of solvent volatilization, resulting in high amine loss and poor cycle absorption stability.

[0010] Compared with primary amines and secondary amines, tertiary amine absorbents have a fast desorption rate, a high desorption rate and a low regeneration energy consumption in the CO2 desorption process, but their CO2 absorption rate is much lower, resulting in a lower absorption capacity and a lower cycle absorption capacity.

[0011] Diamines (such as EDA) and linear polyamines (such as DETA, TETA and TEPA) have a relatively strong CO2 absorption capacity, but the desorption temperature is high and the desorption rate is not high, which makes the regeneration energy consumption high and the cycle absorption capacity limited; moreover, these diamines and linear polyamines usually have a strong ammonia odor and strong volatility, which not only causes secondary pollution in the desorption process, but also results in a large amine loss and poor cycle absorption stability.

[0012] Piperazine (PZ) is a cyclic diamine, which is first added to the traditional MEA, MDEA and AMP solution as an activator to accelerate the CO2 absorption rate. Piperazine has the advantages of no ammonia odor, low volatility, less loss during use and strong cycle stability, but has the disadvantages of high desorption temperature, low desorption rate, high regeneration energy consumption and limited solubility, and is easy to crystallize at high concentration or low temperature.

[0013] In order to achieve the purpose of fast CO2 absorption rate and desorption rate, technicians often use mixed amines such as MEA and MDEA, EDA and AMP, PZ and AMP, but due to the differences in boiling point, volatility and thermal degradation efficiency of each component of the mixed amines, the proportion of each component will change after multiple cycles, thereby affecting its performance effect, and in addition, the cycle absorption stability of the mixed amines has not been improved.

[0014] Therefore, the existing organic amines cannot well meet the requirements of industrialization for the absorbent, that is, good absorption and desorption performance, high desorption rate, low regeneration energy consumption, low volatility and strong cycle absorption stability. SUMMARY

[0015] Therefore, the purpose of the present application is to provide a CO2 absorbent with fast absorption rate, low desorption temperature, high regeneration efficiency, low regeneration energy consumption and strong cycle absorption stability in view of the shortcomings of the traditional organic amine absorbent.

[0016] In order to achieve the above purpose, the present application provides the following technical solutions:

[0017] The present application provides a hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) having the structure shown in formula I:

[0018]

[0019] The present application also provides a preparation method of the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) described in the above scheme, comprising the following steps:

[0020] The low-carbon alcohol solution of pentaerythritol tetraacrylate is added dropwise into the low-carbon alcohol solution of piperazine to carry out an addition reaction, so as to obtain the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate).

[0021] Preferably, after the addition reaction, the system obtained by the addition reaction is subjected to reduced pressure distillation.

[0022] Preferably, the low-carbon alcohol solution of pentaerythritol tetraacrylate comprises pentaerythritol tetraacrylate and a low-carbon alcohol; the low-carbon alcohol solution of piperazine comprises piperazine and a low-carbon alcohol; and the low-carbon alcohol comprises any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

[0023] Preferably, the total molar ratio of the piperazine and pentaerythritol tetraacrylate is (4.01-10.00):1.00.

[0024] Preferably, when the total molar ratio of the piperazine and pentaerythritol tetraacrylate is ≥8.00:1.00 and ≤10.00:1.00, the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is one-time dropping; when the total molar ratio of the piperazine and pentaerythritol tetraacrylate is ≥4.01:1.00 and <8.00:1.00, the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is batch dropping; when the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is batch dropping, the addition reaction is carried out in batches.

[0025] Preferably, when the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is batch dropping, the batch dropping includes a first batch dropping and a subsequent batch dropping carried out in sequence; the molar ratio of the piperazine and the pentaerythritol tetraacrylate in the first batch dropping is ≥8.00:1.00; the molar ratio of the unreacted piperazine in the system and the pentaerythritol tetraacrylate in each subsequent batch dropping is ≥8.00:1.00.

[0026] Preferably, the temperature of the addition reaction is 10-50℃; when the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is one-time dropping, the reaction time of the addition reaction is 8-48h; when the dropping of the low-carbon alcohol solution of the pentaerythritol tetraacrylate is batch dropping, the reaction time of each batch addition reaction is 8-24h.

[0027] Preferably, the temperature of the system is controlled to be <35℃ during the dropping.

[0028] The application also provides the application of the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) prepared by the above-mentioned preparation method as a CO2 absorbent in the capture of CO2 in a mixed gas.

[0029] The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided by the application has the structure shown in Formula I; the molecular structure of the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) has four terminal piperazine groups, each piperazine group has one cyclic secondary amino group and one cyclic tertiary amino group, the cyclic secondary amino group makes the hyperbranched polymer of the application have good CO2 absorption performance, the cyclic tertiary amino group makes the hyperbranched polymer of the application have high regeneration performance, the four piperazine groups are branched at the end of the hyperbranched polymer, the molecular weight is larger than that of a single piperazine, and the hyperbranched polymer of the application has lower volatility and less regeneration loss.

[0030] The results of the examples and test examples show that, compared with the conventional organic amine absorbent, the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided by the application has the advantages of high absorption capacity, fast absorption speed, fast desorption rate and high desorption efficiency after absorbing CO2, low desorption temperature, low regeneration energy consumption, low volatility, less loss, and strong cyclic absorption stability when used as a CO2 absorbent.

[0031] In addition, compared with the conventional organic amine absorbent, the pentaerythritol tetra(2-piperazinyl propionate) provided by the application can be used for CO2 capture, separation and recovery in mixed gas such as flue gas (such as power plants and incineration plants), exhaust gas in industrial processes (such as oil refining, smelting, cement and chemical industry, etc.), energy gas (such as water gas, biogas, natural gas and hydrogen) and air, etc., and has a wide application prospect in the field of CO2 capture. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 Figure 2 is a CO2 absorption load-time curve of the absorption liquid of Examples 1-3 and Comparative Examples 1-4;

[0033] Figure 2 Figure 4 is a CO2 desorption rate-time curve of the absorption rich liquid of Examples 1-3 and Comparative Examples 1-4 at an oil bath temperature of 120℃;

[0034] Figure 3 Figure 6 is a CO2 load-time curve of the absorption rich liquid of Example 1 at different desorption temperatures;

[0035] Figure 4 Figure 8 is a CO2 load-time curve of the solution of Example 1 and Comparative Examples 1-4 in the first absorption-desorption cycle;

[0036] Figure 5 Figure 10 is a comparison of the CO2 absorption capacity of the solution of Example 1 and Comparative Examples 1-4 in multiple cycles. DETAILED DESCRIPTION

[0037] The application provides a hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) having the structure shown in formula I:

[0038]

[0039] The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided by the application has a piperazinyl group as an end group and a pentaerythritol as a core, and has a chemical formula of C[CH2OCOCH2CH2N(CH2CH2)2NH]4.

[0040] The present invention also provides a method for preparing the hyperbranched polymer pentaerythritol tetrakis(2-piperazinyl propionate) described in the above technical solution, comprising the following steps:

[0041] The low-carbon alcohol solution of pentaerythritol tetraacrylate is added dropwise to the low-carbon alcohol solution of piperazine to carry out an addition reaction, thereby obtaining the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate).

[0042] In the present invention, the pentaerythritol tetraacrylate low-carbon alcohol solution preferably includes pentaerythritol tetraacrylate and a low-carbon alcohol; the piperazine low-carbon alcohol solution preferably includes piperazine and a low-carbon alcohol. In the present invention, the low-carbon alcohol preferably includes any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol, and glycerol. In the present invention, the concentration of the pentaerythritol tetraacrylate low-carbon alcohol solution is not specifically limited.

[0043] In the present invention, the total molar ratio of piperazine to pentaerythritol tetraacrylate is preferably (4.01-10.00):1.00, more preferably 8.00:1.00.

[0044] In the present invention, when the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥8.00:1.00 and ≤10.00:1.00, the dropwise addition of the pentaerythritol tetraacrylate low-carbon alcohol solution is preferably a one-time dropwise addition; when the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥4.01:1.00 and <8.00:1.00, the dropwise addition of the pentaerythritol tetraacrylate low-carbon alcohol solution is preferably a batchwise addition; when the dropwise addition of the pentaerythritol tetraacrylate low-carbon alcohol solution is a batchwise addition, the addition reaction is carried out in batches.

[0045] In the present invention, when the pentaerythritol tetraacrylate lower alcohol solution is added dropwise in batches, the dropwise addition preferably includes a first batch addition and subsequent batch additions performed sequentially. During the first batch addition, the molar ratio of piperazine to pentaerythritol tetraacrylate is preferably ≥8.00:1.00, more preferably 8.00:1.00. During each subsequent batch addition, the molar ratio of unreacted piperazine in the system to the pentaerythritol tetraacrylate added dropwise in the batch is preferably ≥8.00:1.00, more preferably 8.00:1.00.

[0046] In the present invention, during the dropwise addition, the system temperature is preferably controlled to be less than 35°C, more preferably 10 to 25°C.

[0047] In the present application, the temperature of the addition reaction is preferably 10-50℃, more preferably 20-30℃; when the dropping of the solution of pentaerythritol tetraacrylate in low-carbon alcohol is one-time dropping, the reaction time of the addition reaction is preferably 8-48h, more preferably 12-24h; when the dropping of the solution of pentaerythritol tetraacrylate in low-carbon alcohol is batch dropping, the reaction time of each batch of addition reaction is preferably 8-24h, more preferably 12-16h.

[0048] In the present application, the chemical reaction equation of the addition reaction is shown as formula II:

[0049]

[0050] In the present application, after the addition reaction, the obtained system is preferably subjected to vacuum distillation. In the present application, the temperature of the vacuum distillation is preferably 80-150℃, more preferably 90-120℃, and the distillation time is preferably 3-10h, more preferably 5-8h.

[0051] The preparation method of the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) provided in the present application has simple steps, raw materials are easy to obtain, and is easy to be industrialized.

[0052] The present application also provides the application of the hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) as a CO2 absorbent in capturing CO2 in a mixed gas.

[0053] The present application also provides a method for capturing CO2 from a mixed gas, which preferably comprises the following steps:

[0054] The CO2 absorbent hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) is mixed with water to obtain an absorbent solution; the mixed gas containing CO2 is introduced into the absorbent solution for CO2 absorption to obtain an absorption rich solution containing CO2; the absorption rich solution is heated to desorb CO2 and collect CO2 to obtain a desorption lean solution containing no or a small amount of CO2, and at the same time, the absorbent solution is regenerated, i.e. the desorption lean solution.

[0055] In the present application, the mixed gas preferably comprises flue exhaust gas, exhaust gas in industrial processes, energy gas, air, etc. In the present application, the flue exhaust gas comprises flue exhaust gas discharged by power plants and incineration plants; the exhaust gas in industrial processes comprises exhaust gas discharged in oil refining, smelting, cement, and chemical processes; the energy gas comprises water gas, biogas, natural gas, and hydrogen.

[0056] In the present application, the content of pentaerythritol tetra(2-piperazinylpropionate) in the absorbent solution is preferably 10 to 50 wt%, more preferably 25 to 35 wt%. In the present application, the volume fraction of CO2 in the mixed gas is preferably 0.1 to 99%.

[0057] In the present application, the temperature of CO2 absorption is preferably 40 to 60°C, more preferably 40 to 50°C, and the absorption time is preferably 0.1 to 3h, more preferably 0.5 to 1.5h.

[0058] In the present application, the temperature of CO2 desorption by heating is preferably 80 to 130°C, more preferably 90 to 100°C, and the desorption time is preferably 0.1 to 1.5h, more preferably 0.5 to 1h. The present application recovers CO2 while regenerating the absorbent solution by desorption, and recycles the regenerated absorbent solution.

[0059] The hyperbranched polymer pentaerythritol tetra(2-piperazinylpropionate) provided by the present application has the following advantages when used as a CO2 absorbent for the absorption of CO2 in a mixed gas: (1) high absorption capacity and fast absorption speed; (2) fast desorption rate and high desorption efficiency after absorbing CO2; (3) low desorption temperature and low energy consumption for regeneration; (4) low volatility, less loss during regeneration, and strong stability for cyclic absorption.

[0060] The technical solutions provided by the present application will be described in detail below in conjunction with the embodiments, but the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0061] Example 1

[0062] Prepare 275.20g of piperazine (Piperazine, hereinafter referred to as PZ) methanol solution (1.60mol, 50wt%), 140.80g of pentaerythritol tetraacrylate (Pentaerythritol Tetraacrylate, hereinafter referred to as PETA) methanol solution (0.20mol, 50wt%), wherein PZ:PETA=8:1(mol:mol).

[0063] Under the protection of nitrogen, the methanol solution of piperazine was added into a round bottom flask with stirring, reflux condenser, constant pressure dropping funnel and thermometer, the stirring was started and cooled to 10°C; then the methanol solution of pentaerythritol tetraacrylate was slowly added through the dropping funnel, and the temperature of the system was controlled at 20°C during the dropping process. After the dropping was completed, the addition reaction was carried out at 25°C for 24h, and then the excess piperazine and methanol were distilled out at 140°C under reduced pressure for 5h, to obtain 135.12g of the product, i.e. hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate), abbreviated as PETA-4PZ, with a yield of 97.07%.

[0064] The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) of Example 1 was subjected to nuclear magnetic resonance detection, and the carbon spectrum and hydrogen spectrum information were as follows:

[0065] 13 C NMR(D2O, 100 MHz): δ 30.92, 40.48, 44.92, 52.12, 54.94, 63.02, 173.93 ppm.

[0066] 1 HNMR(D2O, 400 MHz): δ 2.41(t, 12H, CH2), 2.54(t, 6H, CH2), 2.89(t, 12H, CH2), 3.02(t, 6H, CH2), 3.89(s, 6H, CH2) ppm.

[0067] Example 2

[0068] The propyl alcohol solution of 206.40g of piperazine (PZ) (1.20mol, 50wt%) and the propyl alcohol solution of 140.80g of pentaerythritol tetraacrylate (PETA) (0.20mol, 50wt%) were respectively prepared, wherein PZ:PETA=6.00:1.00 (mol:mol).

[0069] Under the protection of nitrogen, the propyl alcohol solution of piperazine was added into a round bottom flask with stirring, reflux condenser, constant pressure dropping funnel and thermometer, the stirring was started and cooled to 20°C; then the propyl alcohol solution of pentaerythritol tetraacrylate was added through the dropping funnel in two batches, the first batch was slowly added with 105.60g of the propyl alcohol solution of pentaerythritol tetraacrylate (PZ:PETA=8.00:1.00, mol:mol), and the temperature of the system was controlled at 20°C during the dropping process, and after the dropping was completed, the addition reaction was carried out at 25°C for 12h;

[0070] The second batch of 35.20 g of pentaerythritol tetraacrylate solution in propanol (unreacted PZ:PETA = 10.90:1.00, mol:mol) was slowly added, and the system temperature was controlled at 20°C during the dropwise addition. After the dropwise addition was completed, the addition reaction was carried out at 25°C for 24 h, and then excess piperazine and propanol were distilled off at 140°C under reduced pressure for 4 h to obtain 134.35 g of product, i.e., hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate), referred to as PETA-4PZ, with a yield of 96.52%.

[0071] The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) of Example 2 was subjected to nuclear magnetic resonance detection, and the carbon spectrum and hydrogen spectrum information are as follows:

[0072] 13 C NMR (D2O, 100 MHz): δ 30.18, 40.23, 45.01, 52.78, 54.23, 63.36, 173.12 ppm.

[0073] 1 HNMR (D2O, 400 MHz): δ 2.28 (t, 12H, CH2), 2.56 (t, 6H, CH2), 2.89 (t, 12H, CH2), 3.04 (t, 6H, CH2), 3.84 (s, 6H, CH2) ppm.

[0074] Example 3

[0075] An ethanol solution of 154.80 g of piperazine (PZ) (0.90 mol, 50 wt%) and an ethanol solution of 140.80 g of pentaerythritol tetraacrylate (PETA) (0.20 mol, 50 wt%) were respectively prepared, wherein PZ:PETA = 4.50:1.00 (mol:mol).

[0076] Under nitrogen protection, the piperazine solution was added into a round bottom flask with stirring, reflux condenser, constant pressure dropping funnel and thermometer, the stirring was started and cooled to 20℃; then the pentaerythritol tetraacrylate ethanol solution was added dropwise through the dropping funnel in 4 batches; the first batch of 70.40 g pentaerythritol tetraacrylate ethanol solution (PZ:PETA = 9.00:1.00, mol:mol) was slowly added dropwise, the system temperature was controlled at 20℃ during the dropwise addition, and after the dropwise addition was completed, the addition reaction was carried out at 25℃ for 8 h; the second batch of 35.20 g pentaerythritol tetraacrylate ethanol solution (unreacted PZ:PETA = 10.00:1.00, mol:mol) was slowly added dropwise, the system temperature was controlled at 20℃ during the dropwise addition, and after the dropwise addition was completed, the addition reaction was carried out at 25℃ for 8 h; the third batch of 17.60 g pentaerythritol tetraacrylate ethanol solution (unreacted PZ:PETA = 12.00:1.00, mol:mol) was slowly added dropwise, the system temperature was controlled at 20℃ during the dropwise addition, and after the dropwise addition was completed, the addition reaction was carried out at 25℃ for 8 h; the fourth batch of 17.60 g pentaerythritol tetraacrylate ethanol solution (unreacted PZ:PETA = 8.00:1.00, mol:mol) was slowly added dropwise, the system temperature was controlled at 20℃ during the dropwise addition, and after the dropwise addition was completed, the addition reaction was carried out at 25℃ for 24 h; then, excess piperazine and methanol were distilled off at 135℃ under reduced pressure for 4 h, and 132.98 g of the product, i.e. hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate), was obtained, which was abbreviated as PETA-4PZ, and the yield was 95.53%.

[0077] The hyperbranched polymer pentaerythritol tetra(2-piperazinyl propionate) of Example 3 was subjected to nuclear magnetic resonance detection, and the carbon spectrum and hydrogen spectrum information were as follows:

[0078] 13 C NMR(D2O, 100 MHz): δ 30.26, 40.21, 44.98, 52.35, 54.67, 63.22, 173.65 ppm.

[0079] 1 HNMR(D2O, 400 MHz): δ 2.25(t, 12H, CH2), 2.57(t, 6H, CH2), 2.89(t, 12H, CH2), 3.07(t, 6H, CH2), 3.91(s, 6H, CH2) ppm.

[0080] Comparative Example 1

[0081] Ethanolamine (MEA) has a molecular formula of HOCH2CH2NH2 and contains one primary amino group.

[0082] Comparative Example 2

[0083] Piperazine (PZ), molecular formula NH(CH2CH2)2NH, containing 2 cyclic secondary amino groups.

[0084] Comparative Example 3

[0085] Triethylenetetramine (TETA), molecular formula NH2CH2CH2NHCH2CH2NHCH2CH2NH2, containing 2 primary amino groups and 2 secondary amino groups.

[0086] Comparative Example 4

[0087] N-methyldiethanolamine (MDEA), molecular formula NH(CH2CH2)2NH, containing 1 tertiary amino group.

[0088] Absorption capacity test of Test Example 1

[0089] The pentaerythritol tetra(2-piperazinylpropionate) hyperbranched polymers of Examples 1-3 and the organic amines of Comparative Examples 1-4 were respectively configured into aqueous organic amine solutions with a concentration of 30 wt% as CO2 absorption liquids.

[0090] 200.00 g of the aqueous organic amine solution with a concentration of 30.0 wt% was added into a round-bottom flask placed in an oil bath, the temperature of the oil bath was controlled at 40°C, a mixed gas of CO2 and N2 with a CO2 volume fraction of 15% was introduced, the flow rate of the mixed gas was 1800 mL / min, the pressure was 0.1 MPa, sampling was performed every 10 min, the CO2 loading of the CO2 absorption liquid was determined by the acidolysis gas method, the absorption time was 120 min, and the absorption rich liquid containing CO2 was obtained. The change of the CO2 loading of each CO2 absorption liquid with time is shown in Table 1. Figure 1 The maximum CO2 loading is shown in Table 1.

[0091] From Figure 1 It can be seen that the pentaerythritol tetra(2-piperazinylpropionate) hyperbranched polymers (PETA-4PZ) of Examples 1-3 have basically the same CO2 absorption capacity, the CO2 absorption loadings of each CO2 absorption liquid all show an upward trend with the increase of time, except for MDEA, the initial CO2 absorption loadings have a relatively large growth rate, the CO2 absorption loadings of the PETA-4PZ of the present application, MEA, PZ and TETA of the comparative examples gradually stabilize after 70 min, 50 min, 90 min and 110 min respectively, while the CO2 absorption loading of MDEA of the comparative example is slowly rising all the time, and still has not reached equilibrium after 120 min of absorption, indicating that the absorption rate of tertiary amine MDEA for CO2 is very slow, after 120 min of absorption, the CO2 absorption loadings of each absorption agent are in the order of PETA-4PZ > TETA > PZ > MEA > MDEA.

[0092] The structure of the PETA-4PZ of the present invention contains four terminal secondary amino groups, while the tetraamine TETA contains two primary and two secondary amino groups. Although both PETA-4PZ and TETA are tetraamines and contain four amino groups that can react with CO2 to form carbamates, PETA-4PZ has a significantly higher CO2 absorption capacity than TETA. The tetraamine TETA has a higher CO2 absorption capacity than the diamine PZ, which in turn has a higher CO2 absorption capacity than the monoamine MEA. The tertiary amine MDEA has a very slow CO2 absorption rate. This indicates that the PETA-4PZ of the present invention has the highest CO2 absorption capacity.

[0093] Table 1 Maximum CO2 load of each absorption liquid (mol CO2 / mol organic amine)

[0094]

[0095] Test Example 2 Desorption Performance Test

[0096] Place the desorption bottle with a reflux condenser in an oil bath heater and heat it to a certain temperature. Then, place the absorption rich liquid obtained in Test Example 1 into the desorption bottle. Take samples at regular intervals and determine its CO2 load by the acid decomposition gas method. When there is no obvious change in the CO2 load of the absorption liquid, the desorption is complete. Then, vent the desorbed CO2 gas. After the desorption is completed, the regenerated CO2 absorption liquid is obtained, which is the desorption lean liquid.

[0097] CO2 desorption rate (%) = (CO2 load of absorbing rich liquid - CO2 load of desorbing lean liquid) / (CO2 load of absorbing rich liquid) × 100%.

[0098] When the oil bath temperature is 120℃, the desorption rate of CO2 loaded in each absorption rich liquid changes with heating time as shown in the following figure: Figure 2 As shown. Figure 2 As can be seen, the CO2 desorption rate of PETA-4PZ of the present invention reached 100% after 20 minutes of heating; the desorption rate of the comparative tertiary amine MDEA also reached 100% after 50 minutes of heating; while the desorption rates of MEA, PZ, and TETA of the comparative examples increased with increasing heating time and stopped increasing after 80 minutes, reaching 71.29%, 73.26%, and 65.34%, respectively. This shows that the hyperbranched polymer pentaerythritol tetrakis(2-piperazinylpropionate) of the present invention has extremely excellent CO2 desorption performance.

[0099] The desorption capacity of the PETA-4PZ rich solution of Example 1 of the present invention for CO2 at different temperatures is as follows: Figure 3 As shown. Figure 3It can be seen that at the desorption temperatures of 90℃, 100℃, 110℃ and 120℃, the desorption rate of CO2 reaches 100% in 90min, 70min, 50min and 20min respectively, and the absorbent is regenerated to 100%. It can be seen that the PETA-4PZ has excellent CO2 desorption performance.

[0100] The piperazine (PZ) contains two cyclic secondary amino groups. When the piperazine group is grafted to the end group of the hyperbranched polymer, one cyclic secondary amino group on the piperazine group is converted into a cyclic tertiary amino group. Therefore, one molecule of PETA-4PZ contains four cyclic secondary amino groups and four cyclic tertiary amino groups. The CO2 absorption rich solution of the hyperbranched polymer PETA-4PZ grafted with the piperazine group has significantly improved ability to desorb CO2 by heating, and can reach a desorption rate of 100%. The piperazine (comparative example 2) containing two cyclic secondary amino groups cannot be desorbed to 100% even at 130℃. It can be seen that the CO2 desorption performance of the hyperbranched polymer is greatly improved by changing the molecular structure.

[0101] The PETA-4PZ provided by the present application has a low desorption temperature and a fast desorption rate and a short desorption time compared with the traditional organic amine desorption temperature, such as MEA, PZ and TETA, and therefore the energy consumption for regeneration is greatly reduced.

[0102] Cyclic absorption capacity of test example 3

[0103] 200.00g of 30wt% CO2 absorption liquid (aqueous organic amine solution) of example 1 and comparative examples 1-4 was weighed and then added to an absorption bottle. CO2 absorption was carried out by passing a mixed gas of CO2 and N2 with a CO2 volume content of 15% at 40℃. The flow rate of the mixed gas was 1800mL / min, and the pressure was 0.1MPa. After 90min of absorption, an absorption rich solution was formed.

[0104] Then, the absorption rich solution was desorbed at an oil bath temperature of 120℃ for 60min to form a desorption lean solution. The desorption lean solution was subjected to the next absorption to obtain an absorption rich solution, and the absorption rich solution was desorbed to obtain a desorption lean solution. The above cycle was repeated for multiple times, and the CO2 load of the CO2 absorption liquid was measured to calculate the cyclic absorption capacity and the regeneration rate.

[0105] The cyclic absorption capacity is the difference between the CO2 load of the absorption rich solution and the CO2 load of the desorption lean solution. The regeneration rate is the percentage of the cyclic absorption capacity to the CO2 load of the absorption rich solution. The regeneration rate of the absorbent is the same as the CO2 desorption rate of the absorption rich solution.

[0106] Table 2: Regeneration rate and cyclic capacity of the first absorption-desorption cycle of the absorption liquid (120℃)

[0107]

[0108] The CO2 load of the absorbent solution in the first absorption-desorption cycle changes with time as shown in the following figure: Figure 4 As shown in Table 2, the regeneration rate of the absorbent solution and the cycle absorption capacity of the first absorption-desorption cycle are shown in Table 2. Figure 4 As can be seen from Table 2, the pentaerythritol tetrakis(2-piperazinylpropionate) (PETA-4PZ) of the present invention can be fully regenerated in 20 minutes, which is a short time consumption, and the cyclic absorption capacity is the highest. In contrast, the regeneration rates of MEA, PZ, and TETA in the comparative examples are 71.29%, 73.26%, and 65.34%, respectively, at 90 minutes, failing to achieve 100% regeneration and entering a new absorption-desorption cycle with a CO2 load. Although the comparative example MDEA achieves a 100% regeneration rate within 80 minutes, the corresponding cyclic absorption capacity is relatively low, at only 0.267 mol CO2 / mol organic amine.

[0109] The change of the absorption capacity of the absorbent solution for CO2 during multiple cycles is as follows: Figure 5 As shown. Figure 5 As can be seen, pentaerythritol tetrakis(2-piperazinylpropionate) (PETA-4PZ) of the present invention has a 100% regeneration rate for the absorbent solution, so the absorption capacity in the second cycle is consistent with the first cycle. Furthermore, even after 10 cycles, the absorption capacity shows no significant attenuation, indicating strong cyclic absorption stability. In contrast, MEA, TETA, PZ, and MDEA, due to their inability to fully regenerate, exhibit lower absorption capacities in the second cycle than in the first cycle. Furthermore, the absorption capacity gradually decreases from the third to the tenth cycle, with PZ exhibiting a relatively slow attenuation. Compared to piperazine (PZ), grafting piperazine groups onto a hyperbranched polymer (PETA-4PZ) reduces volatility and enhances cyclic absorption stability, likely due to the increased molecular weight.

[0110] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. Other embodiments can be obtained based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. A hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate), characterized in that Having the structure shown in formula I: Formula I.

2. The method for preparing the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) according to claim 1, wherein The following steps are involved: adding a low-carbon alcohol solution of pentaerythritol tetraacrylate dropwise to a low-carbon alcohol solution of piperazine to carry out an addition reaction to obtain the hyperbranched polymer pentaerythritol tetrakis(2-piperazinyl propionate); The low-carbon alcohol solution of pentaerythritol tetraacrylate comprises pentaerythritol tetraacrylate and a low-carbon alcohol; the low-carbon alcohol solution of piperazine comprises piperazine and a low-carbon alcohol; the low-carbon alcohol is selected from any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

3. The preparation method according to claim 2, wherein After the addition reaction, the system obtained by the addition reaction is subjected to reduced pressure distillation.

4. The preparation method according to claim 2, wherein The total molar ratio of the piperazine to pentaerythritol tetraacrylate is (4.01-10.00):1.

00.

5. The preparation method according to claim 4, wherein When the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥ 8.00:1.00 and ≤ 10.00:1.00, the pentaerythritol tetraacrylate lower alcohol solution is added dropwise in one go; When the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥ 4.01:1.00 and < 8.00:1.00, the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches; when the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the addition reaction is carried out in batches.

6. The preparation method according to claim 2 or 5, characterized in that When the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the dropwise addition includes sequentially adding a first batch and adding subsequent batches; When the first batch is added dropwise, the molar ratio of piperazine to pentaerythritol tetraacrylate is ≥ 8.00:1.00; Each time the subsequent batches are added dropwise, the molar ratio of unreacted piperazine in the system to the pentaerythritol tetraacrylate added dropwise in the batches is ≥ 8.00:1.

00.

7. The preparation method according to claim 2 or 5, characterized in that The temperature of the addition reaction is 10-50°C; When the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise at once, the reaction time of the addition reaction is 8 to 48 hours; When the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the reaction time of each batch of addition reaction is 8 to 24 hours.

8. The preparation method according to claim 5, characterized in that During the dropwise addition, the temperature of the system was controlled to be less than 35°C.

9. Use of the hyperbranched polymer pentaerythritol tetrakis(2-piperazinyl propionate) according to claim 1 or the hyperbranched polymer pentaerythritol tetrakis(2-piperazinyl propionate) prepared by the preparation method of any one of claims 2 to 8 as a CO2 absorbent in capturing CO2 in a mixed gas.

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