A trimethylolpropane tris(2-piperazinylpropionate) and its use as a carbon dioxide absorbent

Abstract

The application belongs to the technical field of carbon neutralization and environmental protection, and particularly relates to a trimethylolpropane tris(2-piperazinyl propionate) and application thereof as a CO2 absorbent. The trimethylolpropane tris(2-piperazinyl propionate) provided by the application has the following advantages when applied to the capture of CO2 in a mixed gas as a CO2 absorbent: (1) high absorption capacity and fast speed; (2) fast desorption rate and high efficiency; (3) low desorption temperature and low regeneration energy consumption; (4) low volatility, less loss and strong cycle stability. The trimethylolpropane tris(2-piperazinyl propionate) provided by the application has a wide application prospect in the field of carbon neutralization and CO2 capture.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of carbon neutralization and environmental protection, and particularly relates to trimethylolpropane tris(2-piperazinyl propionate) and application thereof as a CO2 absorbent. BACKGROUND

[0002] CO2, as the most important greenhouse gas, is emitted in increasing amounts year by year, leading to a faster and faster global warming. In this context, CO2 capture, utilization and storage (CCUS) has gradually become an important choice for countries to combat climate change. Among them, CO2 capture is the basis and premise of CCUS technology. Only if CO2 is successfully captured, can it be recovered and further utilized or stored.

[0003] The capture technology of CO2 in mixed gas mainly includes physical solution absorption method, chemical solution absorption method, adsorption method, membrane separation method and low-temperature rectification method, etc. Among them, the chemical solution absorption method has the advantages of simple process, strong operability, easy to scale up and mature technology, and has obtained more applications. The commonly used chemical absorbents of the chemical solution absorption method mainly include ammonia, potassium / sodium carbonate and organic amine, etc. Among them, the ammonia absorption method needs low temperature and a large amount of water washing or even acid washing to inhibit the volatilization of ammonia due to the volatilization of ammonia, which causes serious environmental pollution and high operating cost; the potassium / sodium carbonate capture CO2, i.e. hot potassium / sodium base method, has a slow CO2 absorption rate and needs to be operated at a high temperature, which is suitable for high CO2 partial pressure gas, and has poor CO2 capture effect in low CO2 partial pressure flue gas and mixed gas of coal / gas power plants and industrial processes; the organic amine solution absorption method has the advantages of fast absorption rate, relatively simple operation and maintenance, relatively low cost and recyclable absorbent, etc., and has become the mainstream technology selection for CO2 capture in low CO2 partial pressure mixed gas. At present, most of the flue gas CO2 chemical absorption capture devices built or under construction at home and abroad adopt organic amine absorbent.

[0004] The organic amine solution absorption method utilizes the reaction of organic amine with CO2 in mixed gas in a low-temperature absorption tower, CO2 is absorbed into the solution to form a rich solution (containing a high concentration of CO2); then the rich and lean solution heat exchanger is entered into a high-temperature desorption tower (100-130℃) to carry out CO2 desorption reaction, release CO2, and at the same time, the organic amine solution is regenerated to form a lean solution (not containing or containing a low concentration of CO2); then the released CO2 is collected and utilized, and the lean solution is returned to the absorption tower through the lean and rich solution heat exchanger for cyclic absorption.

[0005] Theoretically, all the organic compounds containing amino groups can be used as CO2 absorbents, and there are many kinds of them. According to the number of hydrocarbon groups connected to the nitrogen, they can be classified into primary (primary) amines, secondary (secondary) amines and tertiary (tertiary) amines; according to the number of amino groups, they can be classified into monoamines, linear polyamines and cyclic polyamines. The most studied traditional organic amine absorbents are 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); linear polyamines such as ethylenediamine (EDA), hexamethylenediamine (HDA), diethylenetriamine (DETA), triethylenetetramine (TETA) and tetraethylenepentamine (TEPA); and cyclic polyamines such as piperazine (PZ), etc.

[0006] Among these traditional organic amine absorbents, primary amines (such as MEA) and secondary amines (such as DEA) have a relatively fast CO2 absorption rate; but the desorption rate is low, resulting in a low cyclic absorption capacity; the desorption temperature is high, leading to a high regeneration energy consumption; the high desorption temperature and long time mean a high volatility, resulting in a high amine loss and a poor cyclic absorption stability.

[0007] Tertiary amine absorbents (such as MDEA) have a high desorption rate and a low regeneration energy consumption, but their CO2 absorption rate is much slower than that of primary amines and secondary amines, resulting in a low absorption capacity and a low cyclic absorption capacity.

[0008] Linear polyamines (such as EDA, DETA, TETA or TEPA, etc.) have a high absorption capacity, but the desorption temperature is high and the desorption rate is not high, resulting in a high regeneration energy consumption and a limited cyclic absorption capacity; due to their strong volatility and ammonia odor, they not only easily cause secondary pollution, but also have a poor cyclic absorption stability.

[0009] Cyclic diamine piperazine (PZ) has a fast absorption rate; compared with linear polyamines, it has the advantages of high boiling point, low volatility and no ammonia odor, and has a low loss and a strong cyclic absorption stability when used; but it has a high desorption temperature, a low desorption rate, a high regeneration energy consumption and a limited solubility, and is easy to crystallize and precipitate at high concentrations or low temperatures.

[0010] In order to achieve fast absorption and fast desorption, researchers often use mixed amines such as MEA+MDEA, EDA+AMP and PZ+AMP, but due to the differences in boiling point, volatility and thermal degradation efficiency of each component, the proportion of the components will change after multiple cycles, thereby affecting the absorption and desorption effect; in addition, the cyclic absorption stability of the mixed amines has not been improved.

[0011] In summary, the traditional organic amine absorbents cannot meet the requirements of industrialization for fast absorption rate, high desorption rate, low regeneration energy consumption and strong cyclic absorption stability. SUMMARY

[0012] Therefore, the present application aims to provide a CO2 absorbent with fast absorption rate, low desorption temperature, high regeneration efficiency, low energy consumption and strong cyclic absorption stability to overcome the shortcomings of the conventional organic amine absorbents.

[0013] To achieve the above-mentioned object, the present application provides a trimethylolpropane tris(2-piperazinyl propionate) with the structure as shown in formula I:

[0014]

[0015] The present application also provides a preparation method of the trimethylolpropane tris(2-piperazinyl propionate) as described in the above-mentioned scheme, which comprises the following steps:

[0016] The trimethylolpropane triacrylate solution is added dropwise into the piperazine solution to perform addition reaction, so as to obtain the trimethylolpropane tris(2-piperazinyl propionate).

[0017] Preferably, the trimethylolpropane triacrylate solution is trimethylolpropane triacrylate and a low-carbon alcohol solvent; and the piperazine solution is piperazine and a low-carbon alcohol solvent.

[0018] Preferably, the total molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution is (3.01-10.00):1.00.

[0019] Preferably, when the total molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution is ≥6.00:1.00 and ≤10.00:1.00, the trimethylolpropane triacrylate solution is added dropwise into the piperazine solution at one time to perform addition reaction at one time; when the total molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution is ≥3.01:1.00 and <6.00:1.00, the trimethylolpropane triacrylate solution is added dropwise into the piperazine solution in batches to perform addition reaction in batches.

[0020] Preferably, when the dropwise addition is in batches, the molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the first batch of trimethylolpropane triacrylate solution is (6.00-6.50):1.00 at the first batch of dropwise addition; and the amount of the trimethylolpropane triacrylate solution added in the subsequent batches is that: the molar ratio of unreacted piperazine in the system to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution added in each batch is ≥6.00:1.00.

[0021] Preferably, the addition reaction is carried out in a protective atmosphere; the temperature of the addition reaction is 10-50℃; when the dropwise addition is one-time dropwise addition, the time of the addition reaction is 8-48h; when the dropwise addition is batch dropwise addition, the time of each addition reaction is 8-24h.

[0022] Preferably, the addition reaction further comprises post-treatment of the obtained product; the post-treatment is reduced pressure distillation; the temperature of the reduced pressure distillation is 80-150℃, and the time is 3-12h.

[0023] Preferably, during the dropwise addition, the temperature of the reaction mixture is controlled to be <35℃.

[0024] The application further provides application of the trimethylolpropane tri(2-piperazinyl propionate) in the capture, separation or recovery of CO2 in a mixed gas as a CO2 absorbent.

[0025] The application provides a trimethylolpropane tri(2-piperazinyl propionate). The trimethylolpropane tri(2-piperazinyl propionate) provided by the application is a star branched polymer with piperazinyl as an end group and trimethylolpropane as a core, which has the structural characteristics of 3 end piperazinyl groups, 1 end piperazinyl group containing 1 cyclic secondary amino group and 1 cyclic tertiary amino group, the cyclic secondary amino group makes the star branched polymer have good CO2 absorption performance, the cyclic tertiary amino group makes the star branched polymer have high regeneration performance, and the star branched polymer has high CO2 desorption performance after absorbing CO2, 3 piperazinyl groups are branched at the end of the star branched polymer, and the increase of the molecular weight makes the star branched polymer have lower volatility and less loss in regeneration.

[0026] The results of the examples and test examples show that, when the trimethylolpropane tri(2-piperazinyl propionate) provided by the application is used as a CO2 absorbent, compared with a traditional organic amine absorbent, the trimethylolpropane tri(2-piperazinyl propionate) 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.

[0027] The application further provides a preparation method of the trimethylolpropane tri(2-piperazinyl propionate). The preparation method of the trimethylolpropane tri(2-piperazinyl propionate) provided by the application has simple steps, raw materials are easy to obtain, and feasibility is strong, and industrialization is easy to realize.

[0028] The application further provides application of the trimethylolpropane tri(2-piperazinyl propionate) in the capture, separation or recovery of CO2 in a mixed gas as a CO2 absorbent. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of these drawings.

[0030] Figure 1 CO2 absorption load comparison diagram of the absorbent of the application example 1 and the comparative examples 1-3;

[0031] Figure 2 CO2 load diagram of the absorption rich solution of the application example 1 at different desorption temperatures;

[0032] Figure 3 CO2 load change diagram of each absorbent with time in the first absorption-desorption cycle of the absorbent solution of the application example 1 and the comparative examples 1-3;

[0033] Figure 4 Cycle absorption capacity change diagram of each absorbent in the 10 absorption-desorption cycles of the absorbent solution of the application example 1 and the comparative examples 1-3. DETAILED DESCRIPTION

[0034] The application provides a trimethylolpropane tri(2-piperazinyl propionate), and the structure of the trimethylolpropane tri(2-piperazinyl propionate) is shown in formula I.

[0035]

[0036] In the application, the chemical formula of the trimethylolpropane tri(2-piperazinyl propionate) is CH3CH2C[CH2OCOCH2CH2N(CH2CH2)2NH]3.

[0037] The application also provides a preparation method of the trimethylolpropane tri(2-piperazinyl propionate) in the above-mentioned scheme, comprising the following steps:

[0038] The trimethylolpropane triacrylate solution is added dropwise into the piperazine solution to perform an addition reaction, so as to obtain the trimethylolpropane tri(2-piperazinyl propionate).

[0039] In the application, the total molar ratio of piperazine (Piperazine, abbreviated as PZ) in the piperazine solution to trimethylolpropane triacrylate (Trimethylolpropane triacrylate, abbreviated as TMPTA) in the trimethylolpropane triacrylate solution is preferably (3.01-10.00):1.00, more preferably (5.00-8.00):1.00, and further preferably (7.00-8.00):1.00.

[0040] In the application, the trimethylolpropane triacrylate solution is preferably trimethylolpropane triacrylate and a low-carbon alcohol solvent; the low-carbon alcohol solvent preferably has 1-3 carbon atoms; and the low-carbon alcohol solvent preferably includes any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

[0041] In the application, the piperazine solution is preferably piperazine and a low-carbon alcohol solvent; the low-carbon alcohol solvent preferably has 1-3 carbon atoms; and the low-carbon alcohol solvent preferably includes any one of methanol, ethanol, propanol, ethylene glycol, propylene glycol and glycerol.

[0042] In the application, the concentration of the piperazine solution is preferably 10-80 wt%, and more preferably 50 wt%; and the concentration of the trimethylolpropane triacrylate solution is preferably 10-80 wt%, and more preferably 50 wt%.

[0043] In the application, the temperature of the reaction mixture is preferably controlled to be <35°C, more preferably <30°C, and further preferably <25°C during the dropping process. By controlling the temperature of the reaction mixture within the above-mentioned range, the application prevents the dropping rate from being too fast.

[0044] In the present application, when the total molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution is ≥ 6.00:1.00 and ≤ 10.00:1.00, the trimethylolpropane triacrylate solution is preferably added dropwise into the piperazine solution at one time, and the addition reaction is carried out at one time; when the total molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the trimethylolpropane triacrylate solution is ≥ 3.01:1.0 and < 6.0:1.0, the trimethylolpropane triacrylate solution is preferably added dropwise into the piperazine solution in batches. The addition reaction of trimethylolpropane triacrylate and piperazine is carried out in batches.

[0045] In the present application, when the addition is carried out in batches, the molar ratio of piperazine in the piperazine solution to trimethylolpropane triacrylate in the first batch of trimethylolpropane triacrylate solution is preferably (6.00-6.50):1.00, and more preferably 6.10:1.00, 6.20:1.00, 6.30:1.00, 6.40:1.00 or 6.50:1.00; the amount of trimethylolpropane triacrylate solution added in the subsequent batches (except the first batch) is preferably: the molar ratio of unreacted piperazine in the system to trimethylolpropane triacrylate in the batch of trimethylolpropane triacrylate solution added at each batch is ≥ 6.00:1.00, and more preferably 6.00:1.00, until the addition of trimethylolpropane triacrylate solution is completed.

[0046] The present application carries out an addition reaction to obtain the trimethylolpropane tri(2-piperazinyl propionate) (abbreviated as TMPTA-3PZ).

[0047] In the present application, the addition reaction is preferably carried out in a protective atmosphere; the protective atmosphere is preferably nitrogen; the temperature of the addition reaction is preferably 10-50°C, and more preferably 20-30°C; when the addition is carried out at one time, the time of the addition reaction is preferably 8-48h, and more preferably 12-24h; when the addition is carried out in batches, the time of each addition reaction is preferably 8-24h, and more preferably 12-16h.

[0048] The chemical reaction equation of the addition reaction in the present application is shown in formula II:

[0049]

[0050] In the present application, the addition reaction is preferably followed by post-treatment of the resulting product; the post-treatment is preferably reduced pressure distillation; the temperature of the reduced pressure distillation is preferably 80-150°C, more preferably 100-140°C, further preferably 120-130°C, and the time is preferably 3-12h, more preferably 5-10h, further preferably 7-8h. The present application, by reduced pressure distillation, obtains a colorless to light amber viscous product, i.e. trimethylolpropane tris(2-piperazinylpropionate).

[0051] The present application also provides the use of the trimethylolpropane tris(2-piperazinylpropionate) as described in the above scheme or obtained by the preparation method as described in the above scheme as a CO2 absorbent in the capture, separation or recovery of CO2 in a mixed gas.

[0052] In the present application, the use of the trimethylolpropane tris(2-piperazinylpropionate) as a CO2 absorbent in the capture, separation or recovery of CO2 in a mixed gas preferably comprises the following steps:

[0053] mixing trimethylolpropane tris(2-piperazinylpropionate) and water to obtain a CO2 absorbent solution; passing a mixed gas containing CO2 into the CO2 absorbent solution for CO2 absorption to obtain an absorption rich solution containing CO2; heating the absorption rich solution containing CO2 to desorb CO2 and collect the CO2, while the absorption rich solution containing CO2 is regenerated to obtain a desorption lean solution containing no or a small amount of CO2, which is recycled for the next CO2 absorption.

[0054] In order to further illustrate the present application, the schemes of the present application are described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0055] Example 1

[0056] (1) Prepare 206.40g of a methanol solution of piperazine (PZ) containing 1.20mol of piperazine, 50wt%, and 118.40g of a methanol solution of trimethylolpropane triacrylate (TMPTA) containing 0.20mol of trimethylolpropane triacrylate, 50wt%, respectively, wherein PZ:TMPTA = 6.00:1.00 (mol:mol).

[0057] (2) Under nitrogen protection, the methanol solution of piperazine was added into a round bottom flask with stirring device, reflux condenser, constant pressure dropping funnel and thermometer, the stirring was started and the temperature was cooled to <10°C; then the methanol solution of trimethylolpropane triacrylate was slowly added through the constant pressure dropping funnel, the temperature was controlled to be <25°C during the dropping process; after the dropping was completed, the reaction was carried out at 25°C for 24 h; then, the excess piperazine and methanol were distilled out at 130°C under reduced pressure for 8 h, 106.23 g of light amber colored viscous product was obtained, which was star branched polymer trimethylolpropane tri(2-piperazinyl propionate) (abbreviated as TMPTA-3PZ), the yield was 95.88%.

[0058] The nuclear magnetic resonance hydrogen spectrum and carbon spectrum data of the TMPTA-3PZ prepared in this example are as follows:

[0059] 1 HNMR (D2O, 400 MHz): δ 0.69 (t, 3H, CH3), 2.01 (t, 2H, CH2), 2.42 (t, 12H, CH2), 2.59 (t, 6H, CH2), 2.85 (t, 12H, CH2), 2.95 (t, 6H, CH2), CH2 3.97 (s, 6H, CH2).

[0060] 13 C NMR (D2O, 100 MHz): δ 7.21, 21.06, 30.92, 40.48, 44.92, 51.26, 53.94, 63.87, 172.93 ppm.

[0061] Example 2

[0062] (1) The ethanol solution of 172.00 g of piperazine (containing 1.00 mol of piperazine, 50 wt%) and the ethanol solution of 118.40 g of trimethylolpropane triacrylate (containing 0.20 mol of trimethylolpropane triacrylate, 50 wt%) were prepared respectively, wherein PZ: TMPTA = 5.00: 1.00 (mol:mol).

[0063] (2) Under nitrogen protection, the ethanol 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 the temperature was cooled to <10°C; then the ethanol solution of trimethylolpropane triacrylate (TMPTA) was added by constant pressure dropping funnel in 2 batches, the first batch was 94.72 g of the ethanol solution of trimethylolpropane triacrylate (equivalent to PZ:TMPTA = 6.25:1.00, mol:mol), the temperature was controlled to be <30°C during the dropping process; after the dropping was completed, the addition reaction was carried out at 25°C, the incubation time was 12 h; the second batch was 23.68 g of the ethanol solution of trimethylolpropane triacrylate (equivalent to unreacted PZ:TMPTA = 6.50:1.00, mol:mol), the temperature was controlled to be <30°C during the dropping process; after the dropping was completed, the addition reaction was carried out at 25°C, the incubation time was 24 h; then, the excess piperazine and ethanol were distilled out at 140°C under reduced pressure for 6 h, 106.39 g of light amber viscous product was obtained, which was star branched polymer trimethylolpropane tri(2-piperazinyl propionate) (TMPTA-3PZ), the yield was 96.02%.

[0064] The nuclear magnetic resonance hydrogen spectrum and carbon spectrum data of the TMPTA-3PZ prepared in this example are as follows:

[0065] 1 HNMR (D2O, 400 MHz): δ 0.73 (t, 3H, CH3), 2.06 (t, 2H, CH2), 2.41 (t, 12H, CH2), 2.58 (t, 6H, CH2), 2.86 (t, 12H, CH2), 2.98 (t, 6H, CH2), CH2 3.99 (s, 6H, CH2).

[0066] 13 C NMR (D2O, 100 MHz): δ 7.08, 21.35, 30.88, 41.32, 45.22, 51.29, 53.78, 63.85, 172.31 ppm.

[0067] Example 3

[0068] (1) 123.84 g of piperazine (PZ) was prepared into a propyl alcohol solution (containing 0.72 mol of piperazine, 50 wt%), 118.40 g of trimethylolpropane triacrylate (TMPTA) was prepared into a propyl alcohol solution (containing 0.20 mol of trimethylolpropane triacrylate, 50 wt%), wherein PZ:TMPTA = 3.60:1.00 (mol:mol).

[0069] (2) Under nitrogen protection, 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 the temperature was cooled to <10°C; then the solution of trimethylolpropane triacrylate (TMPTA) was added dropwise through the constant pressure dropping funnel in 3 batches, 60% of the total amount of the first dropwise addition of the propyl alcohol solution of trimethylolpropane triacrylate (PZ:TMPTA = 6.00:1.00, mol:mol), the temperature was controlled to be <25°C during the dropwise addition, after the dropwise addition was completed, the addition reaction was carried out at 25°C for 8h; 30% of the total amount of the second dropwise addition of the propyl alcohol solution of trimethylolpropane triacrylate (unreacted PZ:TMPTA = 6.00:1.00, mol:mol), the temperature was controlled to be <25°C during the dropwise addition, after the dropwise addition was completed, the reaction was carried out at 25°C for 8h; 10% of the total amount of the third dropwise addition of the propyl alcohol solution of trimethylolpropane triacrylate (unreacted PZ:TMPTA = 9.00:1.00, mol:mol), the temperature was controlled to be <25°C during the dropwise addition, after the dropwise addition was completed, the addition reaction was carried out at 25°C for 24h; then, under the condition of 135°C, the excess piperazine and methanol were distilled off under reduced pressure for 4h, 132.98g of light amber colored viscous product was obtained, which was star branched polymer trimethylolpropane tri(2-piperazinyl propionate) (TMPTA-3PZ), the yield was 95.53%.

[0070] The nuclear magnetic resonance hydrogen spectrum and carbon spectrum data of the TMPTA-3PZ prepared in this example are as follows:

[0071] 1 HNMR (D2O, 400MHz): δ 0.72 (t, 3H, CH3), 2.05 (t, 2H, CH2), 2.43 (t, 12H, CH2), 2.56 (t, 6H, CH2), 2.83 (t, 12H, CH2), 2.99 (t, 6H, CH2), CH2 3.89 (s, 6H, CH2) ppm.

[0072] 13 C NMR (D2O, 100MHz): δ 6.98, 21.75, 30.82, 41.78, 45.57, 51.24, 53.56, 63.75, 172.42 ppm.

[0073] Example 4

[0074] (1) Prepare 104.92 g of a methanol solution of piperazine (PZ) (containing 0.61 mol of piperazine, 50 wt%), and 118.40 g of a methanol solution of trimethylolpropane triacrylate (TMPTA) (containing 0.20 mol of trimethylolpropane triacrylate, 50 wt%), wherein PZ:TMPTA = 3.05:1.00 (mol:mol).

[0075] (2) Under nitrogen protection, the piperazine solution is added to a round-bottom flask with stirring, reflux condenser, constant-pressure dropping funnel, and thermometer, and stirring is started and cooled to <10°C; then the trimethylolpropane triacrylate (TMPTA) solution is added dropwise through the dropping funnel in 7 batches, 50% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the first batch (PZ:TMPTA = 6.10:1.00, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 25% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the second batch (unreacted PZ:TMPTA = 6.20:1.00, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 13% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the third batch (unreacted PZ:TMPTA = 6.2:1, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 6.0% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the fourth batch (unreacted PZ:TMPTA = 6.8:1, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 3.0% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the fifth batch (unreacted PZ:TMPTA = 7.7:1, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 2.0% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the sixth batch (unreacted PZ:TMPTA = 7.10:1.00, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 6 h; 1.0% of the total amount of the trimethylolpropane triacrylate methanol solution is added in the seventh batch (remaining PZ:TMPTA = 7.00:1.00, mol:mol), the temperature is controlled to be <25°C during the dropwise addition, after the dropwise addition is complete, addition reaction is carried out at 25°C for 12 h; then, excess piperazine and methanol are distilled off at 140°C under reduced pressure for 4 h, and 136.26 g of a light amber colored viscous product is obtained, which is the star-branched polymer trimethylolpropane tri(2-piperazinyl propionate) (TMPTA-3PZ), with a yield of 97.89%.

[0076] The nuclear magnetic resonance hydrogen spectrum and carbon spectrum data of the TMPTA-3PZ prepared in this example are as follows:

[0077] 1 HNMR (D2O, 400 MHz): δ 0.64 (t, 3H, CH3), 2.07 (t, 2H, CH2), 2.23 (t, 12H, CH2), 2.61 (t, 6H, CH2), 2.87 (t, 12H, CH2), 2.94 (t, 6H, CH2), CH2 3.95 (s, 6H, CH2) ppm.

[0078] 13 C NMR (D2O, 100 MHz): δ 6.91, 21.72, 30.09, 41.35, 45.52, 51.19, 53.43, 63.68, 172.09 ppm.

[0079] Comparative Example 1

[0080] Monoethanolamine (MEA) has a molecular formula of HOCH2CH2NH2 and contains one primary amino group.

[0081] Comparative Example 2

[0082] Piperazine (PZ) has a molecular formula of NH(CH2CH2)2NH and contains two cyclic secondary amino groups.

[0083] Comparative Example 3

[0084] Diethylenetriamine (DTEA) has a molecular formula of NH2CH2CH2NHCH2CH2NH2 and contains two primary amino groups and one secondary amino group.

[0085] Test Example 1: Absorption Capacity Test

[0086] The trimethylolpropane tris(2-piperazinylpropionate) of Examples 1-4 and the organic amines of Comparative Examples 1-3 were each configured into a 30% aqueous solution as a CO2absorbent solution for use in the test example.

[0087] 200.0 g of the CO2absorbent solution was added to an absorption bottle, and at 40°C, a mixed gas of CO2with a volume fraction of 15% and N2was introduced at a flow rate of 1800 mL / min and a pressure of 0.1 MPa. Every 10 min, a sample was taken and the CO2loading of the absorbent was determined by the acidolysis gas method, the absorption time was 120 min, and the CO2-rich absorption solution was obtained. The corresponding CO2absorption loadings of each absorbent at 30 min, 60 min, 90 min, and 120 min are shown in Table 1.

[0088] Table 1 CO2 absorption load of the absorbents of Examples 1-4 and Comparative Examples 1-3

[0089]

[0090] As can be seen from Table 1, the CO2 absorption load of the star-branched polymer trimethylolpropane tri(2-piperazinylpropionate) (TMPTA-3PZ) of Examples 1-4 is substantially consistent.

[0091] The CO2 absorption load of the absorbents of Example 1 and Comparative Examples 1-3 over time is shown in Figure 1. Figure 1 As can be seen from Figure 1, the CO2 absorption load of the absorbents of Example 1 and Comparative Examples 1-3 all shows an upward trend over time, and the initial CO2 absorption load increases rapidly, and the increase slows down after 40 min. The CO2 absorption load of the TMPTA-3PZ of Example 1 and the MEA of Comparative Example 1 no longer increases after 50 min, and the CO2 absorption of the DETA of Comparative Example 3 and the PZ of Comparative Example 2 no longer increases after 90 min of absorption. The order of the maximum CO2 absorption load of the absorbents is: TMPTA-3PZ > DETA > PZ > MEA. Figure 1

[0092] The TMPTA-3PZ provided by the present application contains 3 cyclic secondary amines and 3 cyclic tertiary amines, the DETA contains 2 primary amines and 1 secondary amine, and both the TMPTA-3PZ and the DETA belong to tertiary amines, containing 3 amines that can react with CO2 to form carbamate, but the CO2 absorption load of the TMPTA-3PZA is significantly higher than that of the DETA, which may be because the 3 cyclic tertiary amines promote the absorption of CO2 by the MPTA-3PZ; the CO2 absorption load of the tertiary amine DETA is higher than that of the secondary amine PZ, and the CO2 absorption load of the secondary amine PZ is higher than that of the primary amine MEA; thus, it can be seen that the CO2 absorption capacity of the TMPTA-3PZ provided by the present application is the largest.

[0093] Test Example 2 desorption performance test

[0094] The desorption bottle with a reflux condenser was placed in an oil bath heater, and after heating to a certain temperature, the absorption rich liquid obtained in Test Example 1 was placed in the desorption bottle, and samples were taken every certain time and the CO2 load was determined by the acid decomposition gas method. When the CO2 load of the absorption liquid has no obvious change, it means that the desorption is complete, and the desorbed CO2 gas is vented. The desorbed liquid after regeneration is the lean liquid. The calculation formula of the CO2 desorption rate is as follows:

[0095] CO2 desorption rate (%) = (rich liquid CO2 load - lean liquid CO2 load) / (rich liquid CO2 load) x 100%.

[0096] ​The CO2 desorption rates of the absorption rich solution of each absorbent at 20 min, 30 min, 60 min, 90 min and 120 min when the oil bath temperature is 120℃ are shown in Table 2.

[0097] Table 2 CO2 desorption rates of absorption rich solution of each absorbent (%)

[0098]

[0099] As shown in Table 2, the CO2 desorption rate of the absorption rich solution of TMPTA-3PZ of Examples 1-4 reaches 100% after heating for 30 min; the CO2 desorption rates of the absorption rich solution of Comparative Examples 1-3 are all less than 40%; and the CO2 desorption rates of the absorption rich solution of Comparative Examples MEA, PZ and DTEA are basically unchanged after heating for 90 min, and are 71.29%, 73.26% and 63.16% respectively. It can be seen that the trimethylolpropane tris (2-piperazinyl propionate) has excellent CO2 desorption capacity.

[0100] The CO2 desorption capacity of the absorption rich solution of TMPTA-3PZ of Example 1 at different temperatures is shown in Table 4. Figure 2 At a desorption temperature of 90℃, 100℃, 110℃ and 120℃, the CO2 desorption rate of the absorption rich solution of TMPTA-3PZ reaches 100% at 120 min, 90 min, 70 min and 30 min respectively, indicating that the absorbent can be completely regenerated.

[0101] The comparison of the CO2 desorption rates of the absorption rich solution of TMPTA-3PZ of Example 1 and the absorption rich solution of Comparative Examples 1-3 at different desorption temperatures is shown in Table 3.

[0102] Table 3 Influence of oil bath temperature on CO2 desorption rate of absorption rich solution

[0103]

[0104]

[0105] As shown in Table 3, although the desorption rates of the absorption rich solution of Comparative Examples 1-3 increase with the increase of temperature, even at 130℃, the CO2 desorption rates of MEA, PZ and DTEA of Comparative Examples are only 83.56%, 85.34% and 79.32% at 90 min respectively, and the desorption rates do not increase even if the desorption time is increased. It can be seen that the TMPTA-3PZ provided by the present application has excellent CO2 desorption capacity.

[0106] Piperazine (PZ) contains two cyclic secondary amino groups, when it is grafted on the end group of branched polymer, one cyclic secondary amino group on piperazine group is converted to cyclic tertiary amino group, so one molecule of TMPTA-3PZ contains three cyclic secondary amino groups and three cyclic tertiary amino groups, the CO2 absorption rich solution of star branched polymer TMPTA-3PZ grafted with piperazine group has significantly improved ability of heating desorption of CO2, and can reach 100% desorption rate, while piperazine containing two cyclic secondary amino groups (comparative example 2) still cannot reach 100% desorption rate even at 130℃. It can be seen that the CO2 desorption capacity of TMPTA-3PZ is greatly improved by changing the molecular structure.

[0107] Cyclic absorption capacity of test example 3

[0108] 200.00 g of the absorbent of example 1 and comparative examples 1-3 with a concentration of 30 wt% was respectively added to an absorption bottle, and absorption was carried out at 40℃ by passing in a mixed gas of CO2 and N2 with a CO2 volume content of 15%, the flow rate of the mixed gas was 1800 mL / min, and the pressure was 0.1 MPa, after 90 min of absorption, an absorption rich solution was formed; then desorption was carried out at an oil bath temperature of 120℃, the desorption time was 60 min, a desorption lean solution was formed; 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, and the cycle was repeated for multiple times, while the CO2 load of the absorption rich solution and the desorption lean solution was measured, and the cyclic absorption capacity and the regeneration rate were calculated.

[0109] The cyclic absorption capacity was the difference between the CO2 load of the absorption rich solution and the CO2 load of the desorption lean solution; the regeneration rate (%) was the percentage of the cyclic absorption capacity to the CO2 load of the absorption rich solution, and the regeneration rate of the absorbent was the same as the value of the CO2 desorption rate of the absorption rich solution.

[0110] The results of the change of the CO2 load with time in the first absorption-desorption cycle are shown in Figure 3 The regeneration rate of the CO2 absorbent solution in the first absorption-desorption cycle and the cyclic absorption capacity are shown in table 4, and the change of the absorption capacity of the absorbent after 10 cycles is shown in Figure 4

[0111] Table 4 Regeneration rate and cyclic absorption capacity of the absorbent (120℃)

[0112]

[0113] According to Figure 3 ​As can be seen from Table 4, the trimethylolpropane tri(2-piperazinyl propionate) (TMPTA-3PZ) provided by the present application is completely regenerated in 30 min, has a short time consumption, and has the maximum cyclic capacity; the regeneration rates of the MEA, PZ and DTEA of the comparative examples are only 71.29%, 73.26% and 63.16% respectively at 90 min, cannot be 100% regenerated, and enter the next absorption-desorption cycle with CO2 load.

[0114] According to Figure 4 As can be seen, since the regeneration rate of the trimethylolpropane tri(2-piperazinyl propionate) (TMPTA-3PZ) provided by the present application is 100%, the absorption capacity of the second cycle remains unchanged, and the absorption capacity does not decrease after 10 cycles, and has high cyclic absorption stability; the absorption capacity of the second cycle of the MEA, PZ and DETA of the comparative examples is not as high as that of the first cycle due to incomplete regeneration, and the absorption capacity of the third to tenth cycles gradually decreases, in which the MEA and DETA decrease faster, and the PZ decreases relatively slower. Compared with piperazine, the piperazine group is grafted on the star branched polymer, which may be due to the increase of molecular weight, resulting in the decrease of volatility and the increase of cyclic stability.

[0115] As can be seen from the above examples, the trimethylolpropane tri(2-piperazinyl propionate) provided by the present application has the advantages of fast absorption rate, fast desorption rate after absorbing CO2, high efficiency, high absorption capacity, low desorption temperature, low regeneration energy consumption, high regeneration efficiency, low volatility, low loss, and strong cyclic stability as a CO2 absorbent for absorbing, separating and recovering CO2 in a mixed gas.

[0116] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A use of trimethylolpropane tris (2-piperazinyl propionate) as a CO2 absorbent in the capture, separation or recovery of CO2 in a mixed gas, characterized in that: The structure of the trimethylolpropane tris(2-piperazinyl propionate) is shown in Formula I: Formula I; The CO2 absorbent is an aqueous solution of trimethylolpropane tris(2-piperazinyl propionate); The mass concentration of trimethylolpropane tris(2-piperazinyl propionate) in the aqueous solution of trimethylolpropane tris(2-piperazinyl propionate) is 30%.

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