Preparation method of eutectic solvent for absorbing carbon dioxide and eutectic solvent

Abstract

The invention provides a preparation method of a eutectic solvent for absorbing carbon dioxide and the eutectic solvent. The preparation method of the eutectic solvent for absorbing carbon dioxide comprises the following steps: respectively drying piperazine and tetraethylene glycol to obtain pretreated piperazine and pretreated tetraethylene glycol; the pretreated piperazine and the pretreated tetraethylene glycol are mixed according to the molar ratio of 1: 1-1: 5, and a mixed solution is obtained; continuously introducing nitrogen into the mixed solution for a first specified duration to establish a nitrogen protective atmosphere in the mixed solution; and placing the mixed solution in a sealed reaction bottle, heating and stirring for 2-3 hours at 70-80 DEG C, and then naturally cooling to room temperature to obtain the transparent eutectic solvent. According to the preparation method of the eutectic solvent for absorbing carbon dioxide and the eutectic solvent provided by the invention, the prepared eutectic solvent not only can realize efficient and rapid CO2 absorption, but also is simple in preparation process.

Description

Technical Field

[0001] This application relates to the field of gas separation technology, and in particular to a method for preparing a eutectic solvent for absorbing carbon dioxide and the eutectic solvent itself. Background Technology

[0002] In recent years, chemical absorption has become the most promising CO2 capture method for large-scale applications due to its high capture efficiency, CO2 recovery purity (>99%), and technological maturity.

[0003] Deep eutectic solvents (DES) are eutectic mixtures formed by mixing hydrogen bond acceptors (HBA) and hydrogen bond donors (HBD) in a specific molar ratio, resulting in a significantly lower melting point than either pure component. Due to their advantages such as simple preparation, tunable structure, low volatility, and high thermal stability, DES have shown broad application prospects in the selective absorption and efficient, mild conversion of CO2, providing new research ideas for the development of CO2 absorption technology. In recent years, improving the CO2 absorption capacity of deep eutectic solvents has become a current research hotspot. Summary of the Invention

[0004] In view of this, this application provides a method for preparing a eutectic solvent for absorbing carbon dioxide and a eutectic solvent, so as to provide an absorbent with a high absorption capacity for CO2 and which can be recycled.

[0005] Specifically, this application is implemented through the following technical solution:

[0006] The first aspect of this application provides a method for preparing a eutectic solvent for absorbing carbon dioxide, comprising:

[0007] Piperazine and tetraethylene glycol were dried separately to obtain pretreated pipeazine and pretreated tetraethylene glycol.

[0008] Pretreated piperazine and pretreated tetraethylene glycol were mixed in a molar ratio of 1:1 to 1:5 to obtain a mixed solution;

[0009] Nitrogen gas is continuously introduced into the mixed solution for a first specified time to establish a nitrogen protective atmosphere in the mixed solution;

[0010] The mixed solution was placed in a sealed reaction flask and heated and stirred at 70 ℃~80 ℃ for 2~3 h, and then naturally cooled to room temperature to obtain a transparent eutectic solvent.

[0011] A second aspect of this application provides a eutectic solvent for absorbing carbon dioxide, wherein the eutectic solvent is prepared using any of the preparation methods described in the first aspect of this application.

[0012] A third aspect of this application provides a method for absorbing carbon dioxide using a eutectic solvent, wherein the eutectic solvent is prepared using any of the preparation methods described in the first aspect of this application; the method for absorbing carbon dioxide using a eutectic solvent includes:

[0013] Carbon dioxide gas was absorbed using a eutectic solvent at a temperature of 30 ℃ to 40 ℃.

[0014] The method for preparing a eutectic solvent for absorbing carbon dioxide and the eutectic solvent provided in this application are as follows: First, by pre-drying piperazine and tetraethylene glycol, residual moisture in the raw materials can be effectively removed, avoiding competition between water molecules and hydrogen bonds, thereby ensuring the stability and reliability of the eutectic solvent formation process. Furthermore, nitrogen gas is introduced during the mixing process for protection, which can prevent the components from being oxidized or absorbing carbon dioxide, thus preventing the generation of impurities and ensuring the purity of the product. In addition, heating and stirring at a suitable temperature and allowing for full reaction helps to form a hydrogen bond network and generate a eutectic system, ultimately yielding a transparent and stable eutectic solvent. This eutectic solvent has a high absorption capacity for CO2, good recycling performance, and can achieve efficient and reversible absorption of CO2. Attached Figure Description

[0015] Figure 1 A flowchart of Example 1 of the method for preparing the eutectic solvent for absorbing carbon dioxide provided in this application;

[0016] Figure 2 This is a schematic diagram illustrating the state of a eutectic solvent before and after absorbing carbon dioxide, as shown in an exemplary embodiment of this application.

[0017] Figure 3 A thermogravimetric analysis result diagram of a eutectic solvent shown in an exemplary embodiment of this application;

[0018] Figure 4 A schematic diagram illustrating the refractive index of a eutectic solvent as shown in an exemplary embodiment of this application;

[0019] Figure 5 This is a schematic diagram illustrating the free volume of a eutectic solvent as shown in an exemplary embodiment of this application. Detailed Implementation

[0020] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0021] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0022] Figure 1 This is a flowchart of Example 1 of the method for preparing the eutectic solvent for absorbing carbon dioxide provided in this application. Please refer to... Figure 1 The method for preparing the eutectic solvent for absorbing carbon dioxide provided in this embodiment includes:

[0023] S101. Piperazine and tetraethylene glycol are dried separately to obtain pretreated pipeazine and pretreated tetraethylene glycol.

[0024] Specifically, piperazine (HBA) is a compound with the formula C4H 10 Organic compounds containing N2, where N contains a lone pair of electrons and can act as a hydrogen bond acceptor. Further, tetraethylene glycol (TEG) is a compound with the formula C6H2O. 14 The raw material for O4 contains two hydroxyl groups in its molecular structure, and hydroxyl hydrogen can act as a hydrogen bond donor (HBD).

[0025] In practice, piperazine can be dried using drying equipment, such as a drying oven or a vacuum drying oven. In this embodiment, piperazine is placed in a vacuum drying oven and dried at 30–40 °C for 2–3 hours to obtain pretreated piperazine. Similarly, tetraethylene glycol can be dried using drying equipment. In this embodiment, tetraethylene glycol can be placed in a desiccator and dried at room temperature for 10–12 hours to obtain pretreated tetraethylene glycol.

[0026] Understandably, drying piperazine and tetraethylene triethylene glycol effectively removes moisture, preventing interference with hydrogen bonding during the subsequent formation of the eutectic solvent, thus ensuring accuracy and stability. Furthermore, drying also improves the purity of both raw materials, resulting in a eutectic solvent with superior and more stable properties.

[0027] S102. Pretreated piperazine and pretreated tetraethylene glycol are mixed in a molar ratio of 1:1 to 1:5 to obtain a mixed solution.

[0028] Specifically, choosing a molar ratio of 1:1 to 1:5 can simultaneously balance hydrogen bonding, solution stability, and CO2 absorption performance. For example, at a molar ratio of 1:1, the active site density is high and the CO2 absorption capacity is strong, but the solution viscosity is relatively high. At a molar ratio of 1:5, the solution viscosity is relatively low, but hydrogen bonding is weakened, and the CO2 absorption capacity is reduced.

[0029] In a specific implementation, for example in this embodiment, the pretreated piperazine and pretreated tetraethylene glycol can be mixed in a molar ratio of 1:1 to obtain a mixed solution.

[0030] Understandably, the aforementioned ratio range not only ensures the formation of a stable and sufficient hydrogen bond network between the two components, thereby effectively lowering the melting point of the mixed solution and promoting the formation of a transparent eutectic solvent, but also ensures that the mixed solution has good carbon dioxide absorption capacity, enabling rapid absorption of carbon dioxide.

[0031] S103. Nitrogen gas is continuously introduced into the mixed solution for a first specified time to establish a nitrogen protective atmosphere in the mixed solution.

[0032] Specifically, the first specified duration is determined based on the experimental scale, container size, and nitrogen introduction rate. It is the duration used to ensure complete purging of air. In this embodiment, the specific value of the first specified duration is not limited. In practice, for example, in a 10 mL Erlenmeyer flask, nitrogen is introduced at a rate of 5 mL / min until nitrogen bubbles continuously escape from the surface of the mixed solution or the overall mass of the test tube no longer increases; this is considered to have reached the first specified duration. As another example, in another embodiment, the first specified duration is set to 2-3 minutes.

[0033] Understandably, continuously bubbling nitrogen into the mixed solution can prevent the raw materials from being oxidized by the air and avoid their reaction with water vapor in the air, ensuring that the heating process is in a more stable environment. This ensures that piperazine and tetraethylene glycol are mixed smoothly in proportion, and finally a eutectic solvent is prepared.

[0034] S104. Place the mixed solution in a sealed reaction flask and heat and stir at 70 ℃~80 ℃ for 2~3 h, then let it cool naturally to room temperature to obtain a transparent eutectic solvent.

[0035] Specifically, a sealed reaction flask isolates the mixture from external air, maintaining the airtightness and component stability of the reaction system. Sealed reaction flasks are typically equipment with high airtightness and high temperature resistance. Examples include conical flasks, round-bottom flasks, and screw-cap reaction flasks. In this embodiment, a conical flask is used as the sealed reaction flask.

[0036] In practice, in this step, the conical flask containing piperazine and tetraethylene glycol is placed in a constant temperature magnetic heating mantle and heated and stirred for 2-3 hours at 70 ℃~80 ℃ until a homogeneous and transparent solution is formed. The conical flask is then removed from the constant temperature magnetic heating mantle, allowed to cool at room temperature, and transferred to a reagent bottle.

[0037] Furthermore, selecting a temperature of 70℃ to 80℃ can provide suitable kinetic energy for the mixing process, accelerating hydrogen bonding. For example, at 70℃, hydrogen bond formation can be accelerated while preventing the volatilization of raw materials. At 80℃, molecular kinetic energy can be further increased, shortening the reaction time. Stirring at 70℃ to 80℃ for 2 to 3 hours, followed by natural cooling to room temperature after system equilibrium, avoids damage to the solution from sudden temperature changes.

[0038] In this specific implementation, the solvent is heated and stirred at 80 °C for 2-3 h, and then naturally cooled to room temperature to obtain a transparent eutectic solvent (DES).

[0039] It should be noted that the nitrogen atom of piperazine forms a strong hydrogen bond complex network with the hydroxyl group of tetraethylene glycol, that is, a stable structure formed between molecules through hydrogen bonding, which can yield a eutectic solvent.

[0040] In addition, piperazine or tetraethylene glycol has a high melting point or viscosity. When the two are mixed in a suitable ratio, the hydrogen bonding complexation disrupts the orderly arrangement of their respective crystal lattices, causing the lattice energy to drop significantly, thus forming a stable liquid with a melting point much lower than that of the single component, i.e., a eutectic solvent.

[0041] Furthermore, in this application, heating and stirring at 70–80 °C accelerates the rearrangement and stabilization of the hydrogen bond network. Under nitrogen protection and a sealed environment, interference from moisture and oxygen is avoided, ensuring that only hydrogen bonds of the target molecules exist in the system. After cooling to room temperature, the hydrogen bonds remain stable, maintaining a transparent and homogeneous eutectic solvent state.

[0042] The synergistic mechanism of the above experimental conditions (pre-drying, nitrogen protective atmosphere, molar ratio, temperature, and time) is briefly introduced below:

[0043] (1) By drying in advance, moisture interference is removed, and side reactions and structural defects of the eutectic solvent are avoided.

[0044] Specifically, piperazine (a cyclic organic amine containing an amino group) and tetraethylene glycol (an ether alcohol containing multiple hydroxyl groups) are both highly polar compounds that readily absorb moisture from the air through hydrogen bonds. Moisture can disrupt the preparation process in two ways: First, the amino group of piperazine is weakly basic, and if moisture is present, it will undergo slight hydrolysis with water (although the hydrolysis of piperazine is weak, even a small amount of moisture will reduce its effective concentration). More importantly, moisture will compete with piperazine for binding to the hydroxyl group (-OH) of tetraethylene glycol. The formation of the eutectic solvent depends on the directional hydrogen bonding between the hydrogen bond donor (the hydroxyl group of tetraethylene glycol) and the hydrogen bond acceptor (the amino group of piperazine). The presence of moisture will disrupt this directional bonding, making it difficult to form a stable hydrogen bond network structure, and the final product may appear cloudy or layered. Secondly, if tetraethylene glycol contains water, it will dilute its concentration, and the hydroxyl groups of water will form ineffective hydrogen bonds with their own hydroxyl groups, further weakening the interaction with piperazine; at the same time, during subsequent heating, water may evaporate, causing pressure fluctuations in the reaction system and disrupting the stability of the sealed reaction.

[0045] Therefore, targeted drying can completely remove free water and absorbed water from both components, laying the foundation for subsequent precise reactions.

[0046] (2) By using a nitrogen protective atmosphere, oxygen can be isolated, thus inhibiting the oxidation of components and the formation of by-products.

[0047] The key components in the reaction system are triethylene glycol (containing ether bonds and hydroxyl groups) and piperazine (containing amino groups). Both are easily oxidized by oxygen in the air under heating conditions (70~80 ℃). The hydroxyl group of triethylene glycol may be oxidized to an aldehyde group (-CHO) or a carboxyl group (-COOH) under heating. The resulting oxygen-containing compound will undergo an amidation reaction with the amino group of piperazine to generate a solid byproduct that is insoluble in eutectic solvents.

[0048] In addition, the amino group (-NH-) of piperazine may also be oxidized to an imine group (=N-) or a nitro group (-NO2) at high temperatures, which destroys its hydrogen bond acceptor function and prevents it from forming a stable eutectic solvent with tetraethylene glycol.

[0049] By continuously introducing nitrogen gas for a specified period of time, the air (especially oxygen) in the reaction system can be completely replaced, forming an inert protective layer on the surface of the mixed solution. This blocks the oxidation reaction pathway at its source, ensuring that the two components only undergo the target reaction of hydrogen bonding, without interference from byproducts.

[0050] (3) By setting the molar ratio to 1:1 to 1:5, the ratio of hydrogen bond donors and acceptors can be matched, thereby controlling the stability and performance of the formed eutectic solvent.

[0051] The core of forming a eutectic solvent is that hydrogen bond donors and hydrogen bond acceptors form a stable binary system through hydrogen bonds, and the molar ratio directly determines the integrity of the hydrogen bond network.

[0052] If the piperazine ratio is too high, the unbound piperazine will exist in a free state, which will cause the melting point of the eutectic solvent to rise (loss of eutectic properties), and the free piperazine is easy to volatilize, reducing the stability of the solvent;

[0053] If the proportion of triethylene glycol is too high, the proportion of unbound triethylene glycol will dilute the concentration of the eutectic solvent, weakening its ability to absorb CO2 (CO2 mainly reacts with the amino groups of piperazine, and excessive triethylene glycol will reduce the amino group density).

[0054] By setting the molar ratio to 1:1 to 1:5, the amino groups of piperazine and the hydroxyl groups of triethylene glycol can be precisely matched, allowing the amino groups of piperazine to form hydrogen bonds with the hydroxyl groups of triethylene glycol, thus constructing a dense and stable hydrogen bond network. This ensures both the low melting point (liquid at room temperature) and transparency of the eutectic solvent, while retaining sufficient amino group sites for subsequent CO2 absorption.

[0055] (4) By setting the temperature to 70 ℃~80 ℃, the hydrogen bonding reaction can be activated, avoiding the destruction of components due to high temperature.

[0056] Specifically, the core role of temperature is to provide the activation energy required for hydrogen bonding, while avoiding overheating that could lead to component decomposition. If the temperature is insufficient, the kinetic energy of the two groups of molecules is low, and the collision frequency between hydroxyl and amine groups is insufficient, making it impossible to overcome the energy barrier for hydrogen bond formation. This results in a purely physical mixture (layering or turbidity) and an inability to form a uniform eutectic solvent. If the temperature is too high, although it can accelerate hydrogen bond formation, it can cause slight volatilization of tetraethylene glycol (reducing the effective concentration); piperazine (boiling point 148.5 ℃, but easily volatilized above 80 ℃) can be lost in small amounts with nitrogen; and the two components may undergo thermal decomposition (such as the cleavage of the ether bond in tetraethylene glycol, generating a small molecule alcohol), ultimately destroying the hydrogen bond network.

[0057] By setting the temperature to 70–80 °C, sufficient kinetic energy can be provided to the molecules to promote the efficient combination of hydroxyl and amino groups to form a hydrogen bond network, while avoiding the volatilization and decomposition of components, ensuring complete reaction and stable product.

[0058] (5) By setting the reaction time to 2-3 h, the hydrogen bonding reaction can be ensured to be complete, and incomplete or excessive reaction can be avoided.

[0059] Specifically, the purpose of heating and stirring is to promote uniform mixing of the two components, ensuring that piperazine and tetraethylene glycol (TEG) come into full contact and form hydrogen bonds. If the time is insufficient, the mixed solution will not be completely homogeneous, and there may be excess piperazine or TEG in some areas, resulting in an incomplete hydrogen bond network. The product may exhibit microscopic stratification (turbid appearance), and the unreacted components will lead to unstable performance of the final eutectic solvent. On the other hand, if the time is too long, although no side reactions will occur (due to nitrogen protection and drying), it will increase energy consumption, and prolonged stirring may cause slight temperature fluctuations in the system (affecting the consistency of hydrogen bond bonding).

[0060] By setting the reaction time to 2-3 h, the two components can be uniformly mixed at the molecular level under a temperature of 70-80 °C, ensuring complete hydrogen bonding reaction and forming a single, transparent eutectic solvent system. Subsequent natural cooling to room temperature allows the hydrogen bond network to solidify and maintain a stable morphology.

[0061] It is understandable that the various conditions do not act independently, but rather form a progressive synergistic relationship, ultimately achieving the efficient preparation of eutectic solvents.

[0062] Specifically, after drying to remove moisture, the system contains only piperazine or tetraethylene triethylene glycol. At this point, nitrogen protection can precisely isolate oxygen (without needing to combat the dual interference of moisture and oxygen), maximizing the suppression of oxidation side reactions. Furthermore, without the interference of moisture and byproducts, a molar ratio of 1:1 to 1:5 can precisely correspond to the hydrogen bond binding sites of piperazine or tetraethylene triethylene glycol, avoiding impurities occupying binding sites and ensuring that the hydrogen bond network is formed in the target ratio. Finally, the precise ratio matching makes molecular collisions more efficient, further accelerating the reaction at an activation temperature of 70-80 °C, and achieving complete reaction in 2-3 h without the need to extend the reaction time.

[0063] In summary, by using five conditions—drying to remove moisture, nitrogen to isolate oxygen, matching hydrogen bond sites in proportion, temperature to provide activation energy, and time to ensure complete reaction—a transparent, stable, and byproduct-free eutectic solvent is ultimately formed, while retaining the amino groups of piperazine, thus ensuring high efficiency in subsequent CO2 absorption.

[0064] The method for preparing a eutectic solvent for carbon dioxide absorption provided in this application firstly involves pre-drying piperazine and tetraethylene glycol to effectively remove residual moisture from the raw materials, preventing water molecules from competing with hydrogen bonds and thus ensuring the stability and reliability of the eutectic solvent formation process. Introducing nitrogen gas during mixing provides protection, preventing the components from being oxidized or absorbing carbon dioxide, which could lead to impurity formation and ensure product purity. Heating and stirring at a suitable temperature to ensure a complete reaction promotes the formation of hydrogen bond networks and the generation of a eutectic system, ultimately yielding a transparent and stable eutectic solvent. The prepared eutectic solvent not only achieves efficient and rapid CO2 absorption but also features a simple preparation process.

[0065] Furthermore, this application also provides a eutectic solvent for absorbing carbon dioxide, wherein the eutectic solvent is prepared using the preparation method described in any one of the first aspects of this application.

[0066] In addition, this application also provides a method for absorbing carbon dioxide using a eutectic solvent, which is described below.

[0067] Specifically, the method for absorbing carbon dioxide using a eutectic solvent provided in this application is wherein the eutectic solvent is prepared using any of the preparation methods described in the first aspect of this application; the method for absorbing carbon dioxide using a eutectic solvent includes:

[0068] Carbon dioxide gas was absorbed by a eutectic solvent at a temperature of 30–40 °C.

[0069] It should be noted that the absorption mechanism of CO2 mainly includes two aspects: physical absorption and chemical absorption, as detailed below:

[0070] (1) Physical absorption mechanism

[0071] The triethylene glycol molecule contains multiple hydroxyl groups, which can form a stable hydrogen bond network with piperazine. This network provides a polar and highly ordered microenvironment, making CO2 molecules easier to dissolve and diffuse.

[0072] Furthermore, eutectic solvents have high polarity, which can effectively increase the solubility of CO2 in the solvent, achieving physical dissolution under van der Waals forces and dipole interactions. In addition, it is understandable that the physical absorption process is rapid and reversible, with a fast absorption rate.

[0073] (2) Chemical absorption mechanism

[0074] Piperazine molecules contain primary / secondary amine groups. In the presence of CO2, the amine groups react with CO2 to form carbamate or carbonate complexes.

[0075] Furthermore, the hydroxyl groups of triethylene glycol can form hydrogen bonds with the generated carbamate ions to stabilize them, reducing their dissociation tendency and thus enhancing the stability of chemical absorption.

[0076] Understandably, chemical absorption processes have high selectivity and absorption capacity, enabling a significant degree of CO2 fixation.

[0077] Furthermore, in one possible implementation, after absorbing carbon dioxide gas using a eutectic solvent at a temperature of 30–40 °C, the method further includes:

[0078] The eutectic solvent that has absorbed carbon dioxide is heated to desorb the eutectic solvent and carbon dioxide gas, so that the desorbed eutectic solvent can be reused and the desorbed carbon dioxide gas can be collected.

[0079] Optionally, in one possible implementation, the heat treatment temperature is 70 ℃ to 90 ℃.

[0080] Understandably, when a eutectic solvent that has absorbed carbon dioxide is heated to 70°C–90°C, CO2 molecules physically dissolved in the solvent will escape due to the increased system temperature. Furthermore, the heat disrupts the van der Waals forces and hydrogen bonds between CO2 and solvent molecules, reducing the solubility of CO2 in the solvent, thus releasing CO2 as a gas. Further, the carbamate / bicarbonate complex formed by the reaction of piperazine amino groups with CO2 undergoes a decomposition reaction under heating conditions. In summary, this achieves the desorption function.

[0081] Specifically, Figure 2 This is a schematic diagram illustrating the state of a eutectic solvent before and after absorbing carbon dioxide, as shown in an exemplary embodiment of this application. Figure 2 Figure (A) in the diagram is a schematic diagram before absorption. Figure 2 Figure (B) in the diagram is a schematic diagram after absorption. Figure 2 See diagram (C) for a schematic representation of desorption. Please refer to... Figure 2 As can be seen, before absorption, the eutectic solvent in the three-necked flask was a transparent liquid. After absorption, a white turbid substance appeared in the three-necked flask, indicating the interaction between the eutectic solvent and carbon dioxide. After desorption, the liquid in the three-necked flask returned to a transparent liquid state, indicating that the absorbed carbon dioxide was released from the solvent.

[0082] As described above, it is understood that the eutectic flux generated in this embodiment can be recycled through absorption and desorption. It captures carbon dioxide at low temperatures through chemical and physical absorption, and releases carbon dioxide at high temperatures by breaking weak bonds and reversible chemical bonds with thermal energy. It not only possesses highly efficient absorption performance but also enables low-energy regeneration and recycling through temperature regulation.

[0083] The following are several specific embodiments to illustrate the technical solution of this application in detail:

[0084] Example 1

[0085] Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h. Tetraethylene triethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h. Piperazine and tetraethylene triethylene glycol were weighed in a molar ratio of 1:1 and added to an Erlenmeyer flask, mixed thoroughly, and then nitrogen gas was introduced for 5–10 min. Further, the Erlenmeyer flask containing piperazine and tetraethylene triethylene glycol was placed in a constant-temperature magnetic heating mantle and heated and stirred at 80 °C for 2 h (the Erlenmeyer flask remained sealed during heating) until a homogeneous and transparent solution formed in the flask, yielding the eutectic solvent.

[0086] Furthermore, after preparing the eutectic solvent, a carbon dioxide absorption test was conducted. Specifically, the eutectic solvent was placed in a gas absorption device, and pure carbon dioxide was introduced into the gas absorption device at a rate of 20 mL / min, while nitrogen was introduced at a rate of 50 mL / min. At 40 °C, the mixed gas and the eutectic solvent were thoroughly mixed until the CO2 concentration detected at the outlet of the gas absorption device remained constant, resulting in a mixed solution that had absorbed carbon dioxide. (It should be noted that the mixed gas composed of carbon dioxide and nitrogen enters the gas absorption device from the inlet, reacts with the eutectic solvent inside, and is then discharged through the outlet. A gas detection device is installed at the outlet to detect the carbon dioxide concentration. During the absorption process, the carbon dioxide concentration first decreases and then increases until it no longer changes, indicating complete absorption.) The absorption capacity of carbon dioxide was calculated using an electronic balance. In this embodiment, the calculated absorption capacity of carbon dioxide was 0.121 g CO2 / g DES.

[0087] It should be noted that in this application, the carbon dioxide absorption capacity (g CO2 / g DES) is calculated according to the following formula:

[0088] ;

[0089] ;

[0090] : Mass of CO2 absorbed (g);

[0091] : Mass of absorbent added to the absorber before absorption (g);

[0092] : The mass (g) of absorbent added to the absorber after absorption;

[0093] : Mass of absorbent (g); In this application, the absorbent is a eutectic solvent.

[0094] Furthermore, pure nitrogen gas was passed into the mixed solution that had absorbed carbon dioxide at a flow rate of 45 mL / min, and a desorption experiment was conducted under heating and stirring conditions at 90°C. The end of the desorption was determined by the change in the concentration of carbon dioxide at the outlet. When the CO2 concentration gradually increased and then remained constant, the desorption was considered to be complete. At this point, the desorption rate was calculated. In this embodiment, the desorption rate was determined to be 99%.

[0095] It should be noted that, in this embodiment, the desorption rate is calculated according to the following formula:

[0096] Desorption efficiency = ;

[0097] The number of moles of CO2 absorbed by the eutectic solvent;

[0098] The number of moles of CO2 remaining in the eutectic solvent after desorption.

[0099] Example 2

[0100] Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h. Tetraethylene triethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h. Piperazine and tetraethylene triethylene glycol were weighed in a molar ratio of 1:2, and added to an Erlenmeyer flask and mixed thoroughly. Nitrogen gas was then introduced for 5–10 min. Further, the Erlenmeyer flask containing piperazine and tetraethylene triethylene glycol was placed in a constant-temperature magnetic heating mantle and heated and stirred at 80 °C for 2 h (the Erlenmeyer flask remained sealed during heating) until a homogeneous and transparent solution formed in the flask, yielding the eutectic solvent.

[0101] Furthermore, after preparing the eutectic solvent, a carbon dioxide absorption test was conducted. Specifically, the eutectic solvent was placed in a gas absorption device, and pure carbon dioxide was introduced into the gas absorption device at a rate of 20 mL / min, while nitrogen gas was introduced into the gas absorption device at a rate of 50 mL / min. At 40 °C, the mixed gas and the eutectic solvent were thoroughly mixed until the CO2 concentration detected at the outlet of the gas absorption device remained constant, resulting in a mixed solution that had absorbed carbon dioxide. The carbon dioxide absorption capacity was calculated by weighing using an electronic balance. In this embodiment, the calculated carbon dioxide absorption capacity was determined to be 0.097 g CO2 / g DES.

[0102] Furthermore, pure nitrogen gas was introduced into the mixed solution that had absorbed carbon dioxide at a flow rate of 45 mL / min, and a desorption experiment was conducted under heating and stirring conditions at 85°C. The end of the desorption was determined by the change in the concentration of carbon dioxide at the outlet. When the CO2 concentration gradually increased and then remained constant, the desorption was considered to be complete. At this point, the desorption rate was calculated. In this embodiment, the desorption rate was determined to be 98%.

[0103] Example 3

[0104] Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h. Tetraethylene triethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h. Piperazine and tetraethylene triethylene glycol were weighed in a molar ratio of 1:3, and added to an Erlenmeyer flask and mixed thoroughly. Nitrogen gas was then introduced for 5–10 min. Further, the Erlenmeyer flask containing piperazine and tetraethylene triethylene glycol was placed in a constant-temperature magnetic heating mantle and heated and stirred at 70 °C for 2 h (the Erlenmeyer flask remained sealed during heating) until a homogeneous and transparent solution formed in the flask, yielding the eutectic solvent.

[0105] Furthermore, after preparing the eutectic solvent, a carbon dioxide absorption test was conducted. Specifically, the eutectic solvent was placed in a gas absorption device, and pure carbon dioxide was introduced into the gas absorption device at a rate of 20 mL / min, while nitrogen gas was introduced into the gas absorption device at a rate of 50 mL / min. At 40 °C, the mixed gas and the eutectic solvent were thoroughly mixed until the CO2 concentration detected at the outlet of the gas absorption device remained constant, resulting in a mixed solution that had absorbed carbon dioxide. The carbon dioxide absorption capacity was calculated by weighing using an electronic balance. In this embodiment, the calculated carbon dioxide absorption capacity was determined to be 0.064 g CO2 / g DES.

[0106] Furthermore, pure nitrogen gas was introduced into the mixed solution that had absorbed carbon dioxide at a flow rate of 45 mL / min, and a desorption experiment was conducted under heating and stirring conditions at 85°C. The end of the desorption was determined by the change in the concentration of carbon dioxide at the outlet. When the CO2 concentration gradually increased and then remained constant, the desorption was considered to be complete. At this point, the desorption rate was calculated. In this embodiment, the desorption rate was determined to be 95%.

[0107] Example 4

[0108] Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h. Tetraethylene triethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h. Piperazine and tetraethylene triethylene glycol were weighed in a molar ratio of 1:1 and added to an Erlenmeyer flask, mixed thoroughly, and then nitrogen gas was introduced for 5–10 min. Further, the Erlenmeyer flask containing piperazine and tetraethylene triethylene glycol was placed in a constant-temperature magnetic heating mantle and heated and stirred at 70 °C for 2 h (the Erlenmeyer flask remained sealed during heating) until a homogeneous and transparent solution formed in the flask, yielding the eutectic solvent.

[0109] Furthermore, after preparing the eutectic solvent, a carbon dioxide absorption test was conducted. Specifically, the eutectic solvent was placed in a gas absorption device, and pure carbon dioxide was introduced into the gas absorption device at a rate of 20 mL / min, while nitrogen gas was introduced into the gas absorption device at a rate of 50 mL / min. At 40 °C, the mixed gas and the eutectic solvent were thoroughly mixed until the CO2 concentration detected at the outlet of the gas absorption device remained constant, resulting in a mixed solution that had absorbed carbon dioxide. The absorption capacity of carbon dioxide was calculated by weighing using an electronic balance. In this embodiment, the calculated absorption capacity of carbon dioxide was determined to be 0.042 g CO2 / g DES.

[0110] Furthermore, pure nitrogen gas was introduced into the mixed solution that had absorbed carbon dioxide at a flow rate of 45 mL / min, and a desorption experiment was conducted under heating and stirring conditions at 90°C. The end of the desorption was determined by the change in the concentration of carbon dioxide at the outlet. When the CO2 concentration gradually increased and then remained constant, the desorption was considered to be complete. At this point, the desorption rate was calculated. In this embodiment, the desorption rate was determined to be 96%.

[0111] Example 5

[0112] Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h. Tetraethylene triethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h. Piperazine and tetraethylene triethylene glycol were weighed in a molar ratio of 1:1 and added to an Erlenmeyer flask, mixed thoroughly, and then nitrogen gas was introduced for 5–10 min. Further, the Erlenmeyer flask containing piperazine and tetraethylene triethylene glycol was placed in a constant-temperature magnetic heating mantle and heated and stirred at 70 °C for 2 h (the Erlenmeyer flask remained sealed during heating) until a homogeneous and transparent solution formed in the flask, yielding the eutectic solvent.

[0113] Furthermore, after preparing the eutectic solvent, a carbon dioxide absorption test was conducted. Specifically, the eutectic solvent was placed in a gas absorption device, and pure carbon dioxide was introduced into the gas absorption device at a rate of 20 mL / min, while nitrogen gas was introduced at a rate of 50 mL / min. At 40 °C, the mixed gas and the eutectic solvent were thoroughly mixed until the CO2 concentration detected at the outlet of the gas absorption device remained constant, resulting in a mixed solution that had absorbed carbon dioxide. The absorption capacity of carbon dioxide was calculated by weighing using an electronic balance. In this embodiment, the calculated absorption capacity of carbon dioxide was determined to be 0.039 g CO2 / g DES.

[0114] Furthermore, pure nitrogen gas was introduced into the mixed solution that had absorbed carbon dioxide at a flow rate of 45 mL / min, and a desorption experiment was conducted under heating and stirring conditions at 90°C. The end of the desorption was determined by the change in the concentration of carbon dioxide at the outlet. When the CO2 concentration gradually increased and then remained constant, the desorption was considered to be complete. At this point, the desorption rate was calculated. In this embodiment, the desorption rate was determined to be 96%.

[0115] Example 6

[0116] Following the steps described above, the eutectic solvent from Example 1 was used for five cycles of absorption and desorption. The absorption capacity of the eutectic solvent for CO2 remained essentially stable. Specific results are shown in the table below:

[0117] Table 1. Experimental results of CO2 absorption in eutectic solvent after 5 cycles

[0118] Loop count <![CDATA[Absorption capacity (g CO2 / g DES)]]> 1 0.121 2 0.11 3 0.106 4 0.08 5 0.07

[0119] Furthermore, to further verify the performance of the eutectic solvent prepared in this application, its thermal stability was determined using a thermogravimetric analyzer (Netzsch TG 209 F3, Germany). The specific results are as follows: Figure 3 As shown ( Figure 3 (A thermogravimetric analysis result diagram of a eutectic solvent shown in an exemplary embodiment of this application); wherein, Figure 3In this context, PZ represents piperazine; TEG represents tetraethylene triethylene glycol; PE / TEG (1:1) indicates a eutectic solvent prepared as shown in Example 1 with a molar ratio of piperazine to tetraethylene triethylene glycol of 1:1; PE / TEG (1:2) indicates a eutectic solvent prepared as shown in Example 2 with a molar ratio of piperazine to tetraethylene triethylene glycol of 1:2; PE / TEG (1:3) indicates a eutectic solvent prepared as shown in Example 3 with a molar ratio of piperazine to tetraethylene triethylene glycol of 1:3; PE / TEG (1:4) indicates a eutectic solvent prepared as shown in Example 4 with a molar ratio of piperazine to tetraethylene triethylene glycol of 1:4; and PE / TEG (1:5) indicates a eutectic solvent prepared as shown in Example 5 with a molar ratio of piperazine to tetraethylene triethylene glycol of 1:5. Please refer to... Figure 3 Eutectic solvents exhibit good thermal stability up to 300 °C. They do not decompose due to temperature increases during absorption or desorption, thus maintaining good stability.

[0120] Furthermore, the refractive index of the eutectic solvents prepared in Examples 1 to 5 was tested using an Abbe refractometer, specifically as follows: Figure 4 As shown ( Figure 4 This is a schematic diagram illustrating the refractive index of a eutectic solvent as shown in an exemplary embodiment of this application. Furthermore, based on the refractive index, the free volume of the eutectic solvent can be calculated, and the specific calculation process is as follows:

[0121] Relative molecular mass:

[0122] ;

[0123] Molar volume:

[0124] ;

[0125] Mohr's refractive index:

[0126] ;

[0127] Free volume:

[0128] ;

[0129] in, The relative molecular mass of the synthesized DES is given in g / mol.

[0130] The relative molecular mass of the hydrogen bond acceptor used is in g / mol.

[0131] The relative molecular mass of the hydrogen bond donor used is in g / mol;

[0132] The number of moles of hydrogen bond acceptors used, in mol;

[0133] The number of moles of hydrogen bond donors used, in mol;

[0134] The molar volume of the synthesized eutectic solvent is given in cm³ / mol.

[0135] The density of the synthesized eutectic solvent is given in g / cm³. 3 ;

[0136] is the molar refractive index of the synthesized eutectic solvent, cm³ / mol;

[0137] The refractive index of the synthesized eutectic solvent;

[0138] denoted as the free volume of the synthesized eutectic solvent, in cm³ / mol.

[0139] Furthermore, calculations show that the free volume of the eutectic solvent is as follows: Figure 5 As shown ( Figure 5 (This is a schematic diagram illustrating the free volume of a eutectic solvent in an exemplary embodiment of this application. Please also specify the parameters.) Figure 4 and Figure 5 Both refractive index and free volume show a linear relationship with temperature; as temperature increases, refractive index decreases and free volume increases. The free volume of all eutectic solvents increases with increasing temperature, following the same trend. Furthermore, the free volume also increases with increasing TEG proportion, indirectly confirming that TEG primarily plays a role in the physical absorption of carbon dioxide.

[0140] In addition, to verify the effectiveness of the above preparation method, relevant comparative experiments were also conducted in this application. The relevant comparative experiments are described below:

[0141] Comparative Example 1

[0142] Piperazine and tetraethylene glycol were dried separately to obtain pretreated piperazine and pretreated tetraethylene glycol. The pretreated piperazine and pretreated tetraethylene glycol were mixed in a molar ratio of 2:1 to obtain a mixed solution. Nitrogen gas was continuously introduced into the mixed solution for a first specified time to establish a nitrogen protective atmosphere in the mixed solution. The mixed solution was placed in a sealed reaction flask and heated and stirred at 80 °C for 2 h, and then naturally cooled to room temperature. The product was a solid-liquid mixture, and no eutectic solvent was synthesized.

[0143] Comparative Example 2:

[0144] Eutectic solvents were prepared using other raw materials, and the carbon dioxide absorption capacity of the prepared eutectic solvents was measured using the aforementioned method. The specific results are shown in Table 2.

[0145] Table 2 Carbon dioxide absorption capacity of eutectic solvents prepared from various raw materials (DES represents eutectic solvent)

[0146] Serial Number raw material <![CDATA[Carbon dioxide absorption capacity (g CO2 / g DES)]]> 1 Imidazole and tetrabutylammonium chloride in a 1:1 molar ratio 0.01 2 Imidazole and tetraethylene glycol in a 1:1 molar ratio 0.02 3 Piperazine and tetraethylene glycol in a 1:1 molar ratio 0.12

[0147] Please refer to Table 2. The preparation method provided in this embodiment produces a eutectic solvent with good carbon dioxide absorption capacity.

[0148] Referring to the descriptions in the preceding embodiments, it will be understood that the method provided in this application has at least the following advantages:

[0149] (1) This application provides a method for absorbing carbon dioxide using a eutectic solvent, which achieves efficient CO2 absorption and significantly improves the CO2 absorption rate. This method has the potential for large-scale industrial application and provides theoretical support for the development of efficient and low-cost CO2 absorbents.

[0150] (2) This application achieves both process simplification and enhanced absorption efficiency by using a eutectic solvent. The eutectic solvent has the outstanding advantages of simple preparation process and high chemical stability, effectively reducing system complexity and operating costs.

[0151] (3) The desorption temperature of the eutectic solvent described in this application after absorbing CO2 is as low as 75~90 ℃, and the desorption rate is higher than 95%, which has excellent regeneration stability and energy consumption economy.

[0152] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a eutectic solvent for absorbing carbon dioxide, characterized in that, The preparation method includes: Piperazine and tetraethylene glycol were dried separately to obtain pretreated pipeazine and pretreated tetraethylene glycol. Pretreated piperazine and pretreated tetraethylene glycol were mixed in a molar ratio of 1:1 to 1:5 to obtain a mixed solution; Nitrogen gas is continuously introduced into the mixed solution for a first specified time to establish a nitrogen protective atmosphere in the mixed solution; The mixed solution was placed in a sealed reaction flask and heated and stirred at 70 ℃~80 ℃ for 2~3 h, and then naturally cooled to room temperature to obtain a transparent eutectic solvent.

2. The method according to claim 1, characterized in that, Pretreated piperazine and pretreated tetraethylene glycol were mixed in a molar ratio of 1:1 to 1:5 to obtain a mixed solution comprising: Pretreated piperazine and pretreated tetraethylene glycol were mixed in a molar ratio of 1:1 to obtain a mixed solution.

3. The method according to claim 2, characterized in that, The mixed solution was placed in a sealed reaction flask and heated and stirred at 70 ℃~80 ℃ for 2~3 h, then allowed to cool naturally to room temperature to obtain a transparent eutectic solvent, comprising: The mixed solution was placed in a sealed reaction flask and heated and stirred at 80 °C for 3 h, and then naturally cooled to room temperature to obtain a transparent eutectic solvent.

4. The method according to claim 1, characterized in that, The piperazine is dried, including: Piperazine was placed in a vacuum drying oven and dried at 30–40 °C for 2–3 h to obtain pretreated piperazine.

5. The method according to claim 1, characterized in that, The process of drying triethylene glycol includes: Tetraethylene glycol was placed in a desiccator and dried at room temperature for 10–12 h to obtain pretreated tetraethylene glycol.

6. A eutectic solvent, characterized in that, The eutectic solvent is used to absorb carbon dioxide, and the eutectic solvent is prepared using the preparation method according to any one of claims 1-5.

7. A method for absorbing carbon dioxide using a eutectic solvent, characterized in that, The eutectic solvent is prepared using the preparation method according to any one of claims 1-5; the method for absorbing carbon dioxide using the eutectic solvent includes: Carbon dioxide gas was absorbed using a eutectic solvent at a temperature of 30 ℃ to 40 ℃.

8. The method according to claim 7, characterized in that, After absorbing carbon dioxide gas using a eutectic solvent at a temperature of 30°C to 40°C, the method further includes: The eutectic solvent that has absorbed carbon dioxide is heated to desorb the eutectic solvent and carbon dioxide gas, so that the desorbed eutectic solvent can be reused and the desorbed carbon dioxide gas can be collected.

9. The method according to claim 8, characterized in that, The heat treatment temperature is 70 ℃~90 ℃.

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