Hyperbranched polymer pentaerythritol tetra (2-piperazinyl propionate), preparation method thereof and application of hyperbranched polymer pentaerythritol tetra (2-piperazinyl propionate) in trapping carbon dioxide

Abstract

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

Description

Technical Field

[0001] The invention belongs to the technical field of carbon neutralization, and specifically relates to a hyperbranched polymer pentaerythritol tetrakis (2-piperazine propionate) and a preparation method thereof and application of the same in capturing carbon dioxide. Background Art

[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 moving northward, resulting in frequent extreme climate phenomena such as snowstorms, droughts, hurricanes, floods, and high temperatures, which pose an increasing threat to human survival and development. Existing data show that since the beginning of the Industrial Revolution, CO2 emissions from the burning of fossil fuels have been increasing, leading to a gradual increase in the concentration of CO2 in the atmosphere, which is positively correlated with climate warming. What is not optimistic is that since 1960, the trend of a sharp increase in global CO2 emissions has not slowed down to this day. In 2023, global CO2 emissions hit a record 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 capture technologies of CO2 in flue gas generated by fossil fuel combustion mainly include 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, while post-combustion CO2 capture does not require modification of existing combustion systems, it is only necessary to set the CO2 capture system after the combustion system and downstream of the dust removal, desulfurization and denitrification systems. It has the advantages of wide adaptability, simple equipment modification and economical and practical.

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

[0005] The chemical solution absorption method utilizes the acidic characteristics of CO2, uses alkaline absorbents to react chemically with CO2 in solution to generate intermediate metastable compounds, and then uses the reverse reaction under certain conditions to achieve CO2 desorption, while the absorbent solution is regenerated. The chemical solution absorption method mainly includes inorganic hot alkaline solution absorption method (potassium alkali or sodium alkali), ammonia absorption method and organic amine solution absorption method. Among them, the organic amine solution absorption method has the advantages of large absorption capacity, good absorption effect, fast absorption rate and recyclable absorbent, and has been widely used.

[0006] The organic amine solution absorption method captures CO2 by chemically reacting the organic amine solution with the CO2 in the mixed gas in a low-temperature absorption tower to generate compounds in the solution to form an absorption rich liquid (rich in CO2); then after passing through a lean-rich liquid heat exchanger, it enters a desorption tower and is heated to release the absorbed CO2 by a reverse reaction, and at the same time, the organic amine solution is regenerated to form a desorption lean liquid (containing no or a low concentration of CO2); the released CO2 is collected and utilized, and the desorption lean liquid returns to the absorption tower through the lean-rich liquid 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, renewable and recyclable absorbent, and recoverable high-purity CO2.

[0007] There are many types of organic amine absorbents used in the organic amine solution absorption method. According to the number of hydrocarbon groups connected to nitrogen, they are divided into: primary amine, secondary amine and tertiary amine; according to the number of amino groups contained, they are divided into: monoamine, diamine, linear polyamine and cyclic polyamine.

[0008] Typical organic amines include primary amines, such as monoethanolamine (MEA) and 2-amino-2-methyl-propanol (AMP); secondary amines, such as diethanolamine (DEA) and N-methylethanolamine (MMEA); tertiary amines, such as triethanolamine (TEA) and N-methyldiethanolamine (MDEA); diamines, such as ethylenediamine (EDA) and hexamethylenediamine (HDA); linear polyamines, such as diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA); cyclic polyamines, such as piperazine (PZ), etc.

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

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

[0011] Although diamines (such as EDA) and straight-chain polyamines (such as DETA, TETA and TEPA) have strong CO2 absorption capabilities, their desorption temperatures are high and their desorption rates are low, which results in high regeneration energy consumption and limited cyclic absorption capacity. Moreover, these diamines and straight-chain polyamines usually have a strong ammonia odor and are highly volatile. Not only are they prone to secondary pollution during the desorption process, but they also suffer from large amine losses and low cyclic absorption stability.

[0012] Piperazine (PZ) is a cyclic diamine. It was first added as an activator to traditional MEA, MDEA and AMP solutions to accelerate the CO2 absorption rate. Piperazine has the advantages of low loss during use and strong cycle stability due to its lack of ammonia odor and low volatility. However, its disadvantages are high desorption temperature, low desorption rate, high regeneration energy consumption, limited solubility, and easy crystallization at high concentrations or low temperatures.

[0013] In order to achieve the purpose of fast CO2 absorption and desorption rates, technicians often use mixed amines, such as MEA and MDEA, EDA and AMP, PZ and AMP, etc. However, due to the differences in boiling points, volatility, and thermal degradation efficiency of the components of the mixed amines, the proportions of the components will change after multiple cycles, thus affecting their performance. In addition, the cyclic absorption stability of the mixed amines has not been improved.

[0014] Therefore, the existing organic amines cannot well meet the industrial requirements for absorbents with good absorption and desorption performance, high desorption rate, low regeneration energy consumption, low volatility and strong cyclic absorption stability. Summary of the invention

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

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

[0017] The present invention provides a hyperbranched polymer pentaerythritol tetrakis (2-piperazine propionate) having a structure shown in Formula I:

[0018]

[0019] The present invention also provides a method for preparing the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) described in the above scheme, comprising the following steps:

[0020] 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-piperazine 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 includes pentaerythritol tetraacrylate and low-carbon alcohol; the low-carbon alcohol solution of piperazine includes piperazine and low-carbon alcohol; the low-carbon alcohol includes any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

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

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

[0025] Preferably, when the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the dropwise addition includes a first batch of dropwise addition and subsequent batches of dropwise addition performed sequentially; during the first batch of dropwise addition, the molar ratio of piperazine to pentaerythritol tetraacrylate is ≥8.00:1.00; during each subsequent batch of dropwise addition, the molar ratio of unreacted piperazine in the system to the pentaerythritol tetraacrylate added in the batch is ≥8.00:1.00.

[0026] Preferably, the temperature of the addition reaction is 10 to 50° C.; when the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise at one time, 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.

[0027] Preferably, during the dropwise addition, the temperature of the system is controlled to be less than 35°C.

[0028] The present invention also provides the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) described in the above scheme or the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) prepared by the preparation method described in the above scheme as a CO2 absorbent, and its use in capturing CO2 in mixed gas.

[0029] The hyperbranched polymer pentaerythritol tetrakis(2-piperazinyl propionate) provided by the present invention has a structure shown in Formula I; the molecular structure of the hyperbranched polymer pentaerythritol tetrakis(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 enables the hyperbranched polymer of the present invention to have good CO2 absorption performance, the cyclic tertiary amino group enables the hyperbranched polymer of the present invention to have efficient regeneration performance, four piperazine groups are grafted to the ends of the hyperbranched polymer, the molecular weight is larger than that of a single piperazine, so that the hyperbranched polymer of the present invention has lower volatility and less regeneration loss.

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

[0031] In addition, compared with traditional organic amine absorbents, the pentaerythritol tetrakis (2-piperazinyl propionate) provided by the present invention, when used as a CO2 absorbent, can be used for the capture, separation and recovery of CO2 in 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 mixed gases such as air, and has broad application prospects in the field of CO2 capture. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The CO2 absorption load of the absorption liquid of Examples 1 to 3 and Comparative Examples 1 to 4 changes with time;

[0033] Figure 2 The curves of CO2 desorption rate of the absorption rich liquid of Examples 1 to 3 and Comparative Examples 1 to 4 at an oil bath temperature of 120°C versus time are shown;

[0034] Figure 3 The curve of CO2 load variation over time of the absorbed rich liquid at different desorption temperatures in Example 1;

[0035] Figure 4 The curves showing the change of CO2 load in the solutions of Example 1 and Comparative Examples 1 to 4 over time in the first absorption-desorption cycle;

[0036] Figure 5 Comparison of the CO2 absorption capacity in the solutions of Example 1 and Comparative Examples 1 to 4 during multiple cycles. DETAILED DESCRIPTION

[0037] The present invention provides a hyperbranched polymer pentaerythritol tetrakis (2-piperazine propionate) having a structure shown in Formula I:

[0038]

[0039] The hyperbranched polymer provided by the present invention, pentaerythritol tetrakis (2-piperazinyl propionate), has piperazine as the terminal group and pentaerythritol as the 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-piperazine propionate) described in the above technical scheme, 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 low-carbon alcohol solution of pentaerythritol tetraacrylate preferably includes pentaerythritol tetraacrylate and low-carbon alcohol; the low-carbon alcohol solution of piperazine preferably includes piperazine and 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 low-carbon alcohol solution of pentaerythritol tetraacrylate 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, and 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 dripping of the low-carbon alcohol solution of pentaerythritol tetraacrylate is preferably a one-time dripping; when the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥4.01:1.00 and <8.00:1.00, the dripping of the low-carbon alcohol solution of pentaerythritol tetraacrylate is preferably batch-wise dripping; when the dripping of the low-carbon alcohol solution of pentaerythritol tetraacrylate is batch-wise dripping, the addition reaction is carried out in batches.

[0045] In the present invention, when the pentaerythritol tetraacrylate low-carbon alcohol solution is dripped in batches, the batch dripping preferably includes a first batch dripping and a subsequent batch dripping performed sequentially; in the first batch dripping, the molar ratio of piperazine to pentaerythritol tetraacrylate is preferably ≥8.00:1.00, more preferably 8.00:1.00. In each subsequent batch dripping, the molar ratio of unreacted piperazine in the system to the pentaerythritol tetraacrylate dripped 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 invention, the temperature of the addition reaction is preferably 10 to 50° C., more preferably 20 to 30° C.; when the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise at one time, the reaction time of the addition reaction is preferably 8 to 48 hours, more preferably 12 to 24 hours; when the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the reaction time of each batch of addition reaction is preferably 8 to 24 hours, more preferably 12 to 16 hours.

[0048] In the present invention, the chemical reaction equation of the addition reaction is shown in Formula II:

[0049]

[0050] In the present invention, after the addition reaction, it is preferred to further include subjecting the system obtained by the addition reaction to reduced pressure distillation. In the present invention, the temperature of the reduced pressure distillation is preferably 80 to 150°C, more preferably 90 to 120°C, and the distillation time is preferably 3 to 10 hours, more preferably 5 to 8 hours.

[0051] The preparation method of the hyperbranched polymer pentaerythritol tetrakis (2-piperazine propionate) provided by the invention has simple steps, readily available raw materials and is easy to industrialize.

[0052] The present invention also provides the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) described in the above technical scheme or the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) prepared by the above preparation method as a CO2 absorbent, and its application in capturing CO2 in mixed gas.

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

[0054] The CO2 absorbent hyperbranched polymer pentaerythritol tetrakis (2-piperazine propionate) and water are mixed to obtain an absorbent solution; a mixed gas containing CO2 is passed into the absorbent solution to absorb CO2 to obtain an absorption rich liquid containing CO2; the absorption rich liquid is heated to desorb CO2 and the CO2 is collected to obtain a desorption lean liquid containing no or a small amount of CO2, and at the same time the absorbent solution is regenerated to obtain a desorption lean liquid.

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

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

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

[0058] In the present invention, the temperature for heating and desorbing CO2 is preferably 80-130°C, more preferably 90-100°C, and the desorption time is preferably 0.1-1.5h, more preferably 0.5-1h. The present invention regenerates the absorbent solution while recovering CO2 through desorption, and recycles the regenerated absorbent solution.

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

[0060] The technical solution provided by the present invention is described in detail below in conjunction with the embodiments, but the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0061] Example 1

[0062] 275.20 g of a methanol solution of piperazine (PZ) (1.60 mol, 50 wt%) and 140.80 g of a methanol solution of pentaerythritol tetraacrylate (PETA) (0.20 mol, 50 wt%) were prepared respectively, wherein PZ:PETA=8:1 (mol:mol).

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

[0064] The present invention performs nuclear magnetic resonance detection on the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) of Example 1, and the carbon spectrum and hydrogen spectrum information are as follows:

[0065] 13 C NMR (D2O, 100MHz): δ30.92, 40.48, 44.92, 52.12, 54.94, 63.02, 173.93ppm.

[0066] 1 HNMR (D2O, 400MHz): δ2.41 (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] 206.40 g of a propanol solution of piperazine (PZ) (1.20 mol, 50 wt%) and 140.80 g of a propanol solution of pentaerythritol tetraacrylate (PETA) (0.20 mol, 50 wt%) were prepared respectively, wherein PZ:PETA=6.00:1.00 (mol:mol).

[0069] Under nitrogen protection, the propanol solution of piperazine was added to a round-bottom flask equipped with a stirrer, a reflux condenser, a constant pressure dropping funnel and a thermometer, and the stirring was started and cooled to 20° C.; then, the propanol solution of pentaerythritol tetraacrylate was added dropwise through the dropping funnel in 2 batches, and 105.60 g of the propanol solution of pentaerythritol tetraacrylate (PZ:PETA=8.00:1.00, mol:mol) was slowly added dropwise in the first batch, and the system temperature was controlled at 20° C. during the dropping process. After the dropping was completed, the addition reaction was carried out at 25° C. for 12 hours;

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

[0071] The present invention performs nuclear magnetic resonance detection on the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) of Example 2, and the carbon spectrum and hydrogen spectrum information are as follows:

[0072] 13 C NMR (D2O, 100MHz): δ30.18, 40.23, 45.01, 52.78, 54.23, 63.36, 173.12ppm.

[0073] 1 HNMR (D2O, 400MHz): δ2.28 (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] 154.80 g of an ethanol solution of piperazine (PZ) (0.90 mol, 50 wt%) and 140.80 g of an ethanol solution of pentaerythritol tetraacrylate (PETA) (0.20 mol, 50 wt%) were prepared respectively, wherein PZ:PETA=4.50:1.00 (mol:mol).

[0076] Under nitrogen protection, the piperazine solution was added to a round-bottom flask equipped with a stirrer, a reflux condenser, a constant pressure dropping funnel and a thermometer, the stirring was started and the mixture was cooled to 20°C; then, the ethanol solution of pentaerythritol tetraacrylate was added dropwise through the dropping funnel in 4 batches; in the first batch, 70.40 g of the ethanol solution of pentaerythritol tetraacrylate (PZ:PETA=9.00:1.00, mol:mol) was slowly added dropwise, and the system temperature was controlled at 20°C during the addition process. After the addition was completed, the addition reaction was carried out at 25°C for 8h; in the second batch, 35.20 g of the ethanol solution of pentaerythritol tetraacrylate (unreacted PZ:PETA=10.00:1.00, mol:mol) was slowly added dropwise, and the system temperature was controlled at 20°C during the addition process. After the addition was completed, the addition reaction was carried out at 25°C for 8h; 17.60 g of an ethanol solution of pentaerythritol tetraacrylate (unreacted PZ:PETA=12.00:1.00, mol:mol) was slowly added dropwise for 3 times, and the system temperature was controlled at 20° C. during the addition process. After the addition was completed, the addition reaction was carried out at 25° C. for 8 hours. 17.60 g of an ethanol solution of pentaerythritol tetraacrylate (unreacted PZ:PETA=8.00:1.00, mol:mol) was slowly added dropwise for the 4th time, and the system temperature was controlled at 20° C. during the addition process. After the addition was completed, the addition reaction was carried out at 25° C. for 24 hours. Then, the mixture was distilled under reduced pressure at 135° C. for 4 hours to evaporate excess piperazine and methanol, and 132.98 g of a product, i.e., a hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate), referred to as PETA-4PZ, was obtained, with a yield of 95.53%.

[0077] The present invention performs nuclear magnetic resonance detection on the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) of Example 3, and the carbon spectrum and hydrogen spectrum information are as follows:

[0078] 13 C NMR (D2O, 100MHz): δ30.26, 40.21, 44.98, 52.35, 54.67, 63.22, 173.65ppm.

[0079] 1 HNMR (D2O, 400MHz): δ2.25 (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), with the molecular formula HOCH2CH2NH2, contains one primary amino group.

[0082] Comparative Example 2

[0083] Piperazine (PZ), with the molecular formula NH(CH2CH2)2NH, contains two cyclic secondary amino groups.

[0084] Comparative Example 3

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

[0086] Comparative Example 4

[0087] N-Methyldiethanolamine (MDEA), with the molecular formula NH(CH2CH2)2NH, contains one tertiary amino group.

[0088] Test Example 1 Absorption capacity test

[0089] The pentaerythritol tetrakis(2-piperazinyl propionate) hyperbranched polymers of Examples 1 to 3 and the organic amines of Comparative Examples 1 to 4 were respectively prepared with deionized water to form an organic amine aqueous solution with a concentration of 30 wt % as a CO 2 absorbing liquid.

[0090] 200.00g of 30.0wt% organic amine aqueous solution was added to a round-bottom flask placed in an oil bath. The oil bath temperature was controlled at 40°C. A mixture of CO2 and N2 with a CO2 volume fraction of 15% was introduced. The flow rate of the mixed gas was 1800mL / min and the pressure was 0.1MPa. Samples were taken every 10 minutes. The CO2 load of the CO2 absorption liquid was determined by the acid hydrolysis gas method. The absorption time was 120 minutes to obtain an absorption rich liquid containing CO2. The CO2 load of each CO2 absorption liquid changes with time as shown in the figure. Figure 1 As shown, its maximum CO2 load is shown in Table 1.

[0091] from Figure 1 It can be seen that the pentaerythritol tetrakis (2-piperazinyl propionate) hyperbranched polymer (PETA-4PZ) of Examples 1 to 3 have basically the same CO2 absorption capacity, and the CO2 absorption load of each CO2 absorption liquid shows an upward trend with the increase of time. Except for MDEA, the initial CO2 absorption load growth rate is relatively large. The CO2 absorption load of PETA-4PZ of the present invention, MEA, PZ, and TETA of the comparative example gradually stabilizes after 70 min, 50 min, 90 min, and 110 min, respectively, while the MDEA of the comparative example has been slowly increasing with the extension of the absorption time, and has not reached equilibrium after 120 min of absorption, indicating that the absorption rate of CO2 by the tertiary amine MDEA is very slow. After 120 min of absorption, the CO2 absorption load of each absorbent is in the order of PETA-4PZ>TETA>PZ>MEA>MDEA.

[0092] The structure of the PETA-4PZ of the present invention contains 4 terminal secondary amino groups, and the tetraamine TETA contains 2 primary amino groups and 2 secondary amino groups. Although both PETA-4PZ and TETA are tetraamines and contain 4 amino groups that can react with CO2 to form carbamate, the CO2 absorption load of PETA-4PZ is significantly higher than that of TETA; the CO2 absorption load of the tetraamine TETA is higher than that of the diamine PZ, which is higher than that of the monoamine MEA, while the CO2 absorption rate of the tertiary amine MDEA is very slow. It can be seen that the PETA-4PZ of the present invention has the largest absorption capacity for CO2 absorption.

[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 into 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 Figure 2 As shown. Figure 2 It can be seen that the desorption rate of CO2 by PETA-4PZ of the present invention reaches 100% when heated for 20 minutes; the desorption rate of tertiary amine MDEA of the comparative example also reaches 100% when heated for 50 minutes; while the desorption rates of MEA, PZ and TETA of the comparative example increase with the increase of heating time, and no longer increase after 80 minutes, and are 71.29%, 73.26% and 65.34% respectively. It can be seen that the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) of the present invention has extremely good 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 desorption temperatures of 90°C, 100°C, 110°C and 120°C, the desorption rate of CO2 reaches 100% in 90min, 70min, 50min and 20min respectively, and the absorbent reaches 100% regeneration. It can be seen that the PETA-4PZ of the present invention has excellent CO2 desorption performance.

[0100] Piperazine (PZ) contains two cyclic secondary amino groups. When it 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 ability of the hyperbranched polymer PETA-4PZ grafted with piperazine groups to absorb CO2 and desorb CO2 by heating the rich liquid is significantly improved, and can reach a desorption rate of 100%, while piperazine containing two cyclic secondary amino groups (Comparative Example 2) still cannot desorb 100% even at 130° C. It can be seen that the CO2 desorption performance of the hyperbranched polymer is greatly improved by changing the molecular structure of the present invention.

[0101] Compared with conventional organic amines such as MEA, PZ and TETA, the PETA-4PZ provided by the present invention has a lower desorption temperature, a faster desorption rate and a shorter desorption time, so that the regeneration energy consumption is greatly reduced.

[0102] Test Example 3 Cyclic Absorption Capacity

[0103] Weigh 200.00 g of 30 wt% CO2 absorption liquid (organic amine aqueous solution) of Example 1 and Comparative Examples 1 to 4, respectively, and add them into absorption bottles, respectively. At 40°C, a mixed gas of CO2 and N2 with a CO2 volume content of 15% is introduced to absorb CO2. The flow rate of the mixed gas is 1800 mL / min and the pressure is 0.1 MPa. After 90 minutes of absorption, an absorption rich liquid is formed.

[0104] Then, the absorption rich liquid is desorbed at an oil bath temperature of 120°C for 60 minutes to form a desorption lean liquid. The desorption lean liquid is subjected to the next absorption to obtain an absorption rich liquid, and the absorption rich liquid is desorbed again to obtain a desorption lean liquid, and this cycle is repeated for multiple times. At the same time, the CO2 load of the CO2 absorption liquid is measured to calculate the cycle absorption capacity and regeneration rate.

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

[0106] Table 2 Regeneration rate and cycle 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 Figure 4 As shown in Table 2, the regeneration rate and cyclic absorption capacity of the absorbent solution in the first absorption-desorption cycle are shown in Table 2. Figure 4 As can be seen from Table 2, pentaerythritol tetrakis (2-piperazinyl propionate) (PETA-4PZ) of the present invention can be completely regenerated in 20 minutes, with a short time consumption and a maximum cycle absorption capacity; while the regeneration rates of MEA, PZ and TETA in the comparative examples are 71.29%, 73.26% and 65.34% respectively at 90 minutes, and cannot be 100% regenerated, and enter a new absorption-desorption cycle with CO2 load; although the comparative example MDEA reaches a regeneration rate of 100% within 80 minutes, the corresponding cycle absorption capacity is relatively low, 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 It can be seen that the pentaerythritol tetrakis (2-piperazinyl propionate) (PETA-4PZ) of the present invention has a regeneration rate of 100% of the absorbent solution, so the absorption capacity of the second cycle is consistent with the first cycle, and the absorption capacity is still not significantly attenuated after 10 cycles, and the cycle absorption stability is strong; while MEA, TETA, PZ, and MDEA cannot be completely regenerated, so the absorption capacity of the second cycle is not as good as the first cycle, and the absorption capacity of the third to tenth cycles gradually decays, among which PZ decays relatively slowly. Compared with piperazine (PZ), after the piperazine group is grafted onto the hyperbranched polymer (PETA-4PZ), the volatility is reduced and the cycle absorption stability is enhanced, probably due to the increase in molecular weight.

[0110] Although the above embodiment describes the present invention in detail, 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 protection scope of the present invention.

Claims

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

2. The method for preparing the hyperbranched polymer pentaerythritol tetrakis (2-piperazinyl propionate) according to claim 1, characterized in that: The following steps are involved: 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).

3. The preparation method according to claim 2, characterized in that 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, characterized in that: The low-carbon alcohol solution of pentaerythritol tetraacrylate includes pentaerythritol tetraacrylate and low-carbon alcohol; the low-carbon alcohol solution of piperazine includes piperazine and low-carbon alcohol; the low-carbon alcohol includes any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

5. The preparation method according to claim 2 or 4, characterized in that: The total molar ratio of piperazine to pentaerythritol tetraacrylate is (4.01-10.00):1.

00.

6. The preparation method according to claim 5, characterized in that: When the total molar ratio of piperazine to pentaerythritol tetraacrylate is ≥8.00:1.00 and ≤10.00:1.00, the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise at one time; 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.

7. The preparation method according to claim 2 or 6, characterized in that: When the pentaerythritol tetraacrylate low-carbon alcohol solution is added dropwise in batches, the dropwise addition includes a first batch of dropwise addition and subsequent batches of dropwise addition performed sequentially; 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.

8. The preparation method according to claim 2 or 6, characterized in that: The temperature of the addition reaction is 10 to 50° C. When the pentaerythritol tetraacrylate low-carbon alcohol solution is added 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.

9. The preparation method according to claim 6, characterized in that: During the dropwise addition, the temperature of the system was controlled to be less than 35°C.

10. 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 any one of the preparation methods of claims 2 to 9 as a CO2 absorbent in capturing CO2 in mixed gases.

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