A method for preparing a quasi-ionic liquid carbon dioxide absorbent

Abstract

The present application relates to carbon dioxide absorbent technical field, especially relates to a kind of ionic liquid-like carbon dioxide absorbent preparation method.The present application includes the following steps: (one) synthesis preparation: the choline chloride and urea are made into low eutectic solvent DES, polyamide amine PAMAM G1 and low eutectic solvent DES are made into absorbent;(two) mixing and heating: after drying raw material is added to heating container, add dioxane as solvent, place in oil bath, stirring heating, mixture gradually from turbid solid becomes homogeneous, transparent, viscous liquid;(three) purification and water removal: after forming homogeneous liquid, in vacuum stirring, to remove moisture, and the final product is liquid ionic liquid carbon dioxide absorbent.The beneficial effect is: the preparation method of the present application is simple and controllable, reaction condition is mild, easy to scale production, provides a feasible technical scheme for industrial application;Solve the existing absorbent active site few, the problem of low carbon dioxide capture amount.

Description

Technical Field

[0001] This invention relates to the field of carbon dioxide absorbent technology, and in particular to a method for preparing an ionic liquid carbon dioxide absorbent. Background Technology

[0002] Carbon capture, utilization, and storage (CCUS) technology has become one of the important approaches to achieving carbon neutrality. Traditional solvent absorption of carbon dioxide is divided into two types: physical absorption and chemical absorption. Physical absorption utilizes the high solubility of carbon dioxide molecules in the adsorbent to achieve separation; chemical absorption utilizes the chemical reaction between carbon dioxide molecules and the adsorbent to achieve separation and recovery. Among these, chemical absorption is considered the most promising carbon capture technology due to its high maturity and wide application. Currently, amine-based adsorbents such as monoethanolamine and diethanolamine are widely used because of their high affinity for carbon dioxide. However, these traditional adsorbents have drawbacks such as volatility, easy oxidative degradation, and high regeneration energy consumption. Ionic liquids, as a novel solvent, are considered ideal solvents for capturing carbon dioxide due to their tunable structure and properties, extremely low vapor pressure, and low specific heat. In recent years, low eutectic solvents (DES) have emerged as alternatives to ionic liquids. They belong to a new class of ionic liquids and are formed by mixing substituted quaternary ammonium salts with metal halides or hydrogen bond donors to create eutectic crystals with relatively low melting points. Compared with ionic liquids, they are generally less sensitive to moisture and are mostly made of biodegradable components, thus having a greater industrialization prospect than traditional ionic liquids.

[0003] To address the problem of carbon dioxide absorption, the development of novel, efficient, environmentally friendly, and energy-saving carbon dioxide absorbents has become a key research focus. Eutectic solvent DES, as a novel green solvent, has shown great potential in the field of carbon dioxide capture. Developing an absorbent that can simultaneously meet the requirements of high absorption rate, high absorption load, and low energy consumption is of great significance for solving the global greenhouse effect caused by excessive carbon dioxide emissions.

[0004] Several invention patents have been developed to address the issues of carbon dioxide absorption efficiency and selectivity. For example, Chinese Patent Publication No. CN116212590A, entitled "Preparation and Application of a Low-Co-solution Solvent / Imide Composite System for Capturing Carbon Dioxide," describes an absorbent composed of a low-co-solution solvent and an imide compound. This absorbent is prepared by mixing a hydrogen bond donor and a hydrogen bond acceptor, choline chloride, adding an amide compound to dissolve it, and cooling to room temperature. The resulting absorbent uses a low-co-solution solvent / imide composite system to capture carbon dioxide. This absorbent is simple to prepare, exhibits high carbon dioxide absorption efficiency, is easily desorbed, has good stability, is recyclable, and has a low loss rate. However, this invention still faces the challenge of further optimizing the absorbent composition and ratio to improve both absorption and desorption efficiency.

[0005] Chinese patent publication number CN113842749A, entitled "A Composite Carbon Dioxide Absorbent of Alkylamine and Ionic Liquid and Its Preparation Method," describes an invention that uses a mixture of ionic liquid, ethanolamine, and water. The total concentration of the ionic liquid and ethanolamine is 0.2-2.5 mol / L, and the molar ratio of the ionic liquid to ethanolamine is 1:9-9:1. This absorbent significantly improves the CO2 capture rate, rapidly and efficiently capturing CO2 from a mixed gas under low energy consumption conditions. The preparation, use, and regeneration processes of the absorbent are simple, and the operating conditions are easy to control. However, this invention still faces the challenge of further improving the absorption rate and capacity of the absorbent.

[0006] Therefore, the existing technology has the following drawbacks: 1. Existing carbon dioxide absorbents have fewer active sites during the absorption process, resulting in low mass capture capacity for low concentrations of carbon dioxide. In addition, the absorbent itself has high viscosity, and the viscosity of the system will continue to increase during the carbon capture process, affecting the mass transfer process. 2. Existing carbon dioxide absorbents are difficult to simultaneously meet the requirements of high absorption rate, high absorption load and low energy consumption in practical applications, and cannot effectively solve the global greenhouse effect caused by excessive carbon dioxide emissions. Summary of the Invention

[0007] The purpose of this invention is to address the aforementioned deficiencies in the existing technology by providing a method for preparing an ionic liquid carbon dioxide absorbent. This method solves the problems of few active sites and low carbon dioxide capture capacity in absorbents, and has the advantages of readily available raw materials, low price, simple preparation process, and no need for purification.

[0008] The preparation method of the ionic liquid carbon dioxide absorbent mentioned in this invention includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea were mixed in a molar ratio of (1~4):(2~5) and added to a reaction vessel. The temperature of the material in the reaction vessel was controlled at 80±2℃, the stirring speed was controlled at 60~150 rpm, and the reaction was sealed for 1~2 hours to obtain the eutectic solvent DES. S2. Preparation of composite absorbent The dried polyamide amine PAMAM G1 and the eutectic solvent DES synthesized in step S1 were mixed in a molar ratio of (1~4):(4~10); the dried polyamide amine PAMAM G1 was added to the reactor for synthesizing the eutectic solvent DES, and dioxane was added as a co-solvent; nitrogen was introduced to replace the air in the reactor and a protective positive pressure of 0.02MPa~0.1MPa was maintained, the stirring was started, the temperature in the reactor was controlled at 60~80℃, and the stirring was carried out for 2~3 hours until the mixture became a homogeneous liquid; S3. Purification and Dehydration The homogeneous liquid formed in step S2 is subjected to vacuum pumping and rotary distillation for 0.5 to 2 hours to precipitate the co-solvent and water, forming the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent, which is then stored in a desiccator.

[0009] Preferably, in step S1 above, choline chloride and urea are weighed in a molar ratio of 1:2 or 2:3, and the generated eutectic solvent DES is sealed and stored at 60°C.

[0010] Preferably, in step S2, polyamidoamine PAMAM G1 and eutectic solvent DES are weighed in a molar ratio of 3:4, and the eutectic solvent DES and polyamidoamine PAMAM G1 are protected by nitrogen gas during the preparation process.

[0011] Preferably, in step S2 above, the amount of dioxane added is 20-30% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES.

[0012] Preferably, in step S2 above, after the reaction is completed, a solvent recovery unit is added to recover and reuse dioxane.

[0013] Preferably, the molecular structural formula of the above-mentioned polyamide amine PAMAM G1 is: .

[0014] Preferably, the above-mentioned polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent has the following typical hydrogen bond molecular structure: .

[0015] Preferably, the typical hydrogen bond molecular structure of choline chloride and urea in the above-mentioned eutectic solvent DES is as follows: .

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The eutectic solvent DES synthesized from choline chloride and urea used in this invention has physical absorption capacity for carbon dioxide, mainly relying on hydrogen bonding or cavitation physical dissolution; the surface of polyamide amine PAMAM G1 contains a large number of amine groups, which can undergo chemical absorption reaction with carbon dioxide. Dissolving polyamide amine PAMAM G1 in the eutectic solvent DES introduces a high density of chemical reaction sites into the physical solvent, realizing the dual effect of "physical absorption + chemical absorption", which significantly improves the overall absorption capacity and absorption rate of the absorbent. 2. This invention uses dioxane as a co-solvent to solve the compatibility problem of blending. Dioxane is a solvent with moderate polarity, which can simultaneously disperse the macromolecular chains of polyamide amine PAMAM G1 and the ionic network of the eutectic solvent DES. Through the "bridging" effect of the co-solvent, the originally turbid mixture can fully contact and dissolve under heating conditions, and finally form a homogeneous and transparent liquid, ensuring that polyamide amine PAMAM G1 will not agglomerate in the eutectic solvent DES. 3. The choline chloride and urea used in this invention are crystalline powder structures in the solid state. In step S1, when they are mixed and heated, they form a eutectic mixture through hydrogen bonding. The melting point is much lower than the melting point of each component, forming a stable liquid eutectic solvent DES at room temperature or lower temperature. This solves the problem that traditional absorbents are prone to crystallization and have low absorption efficiency at low temperatures. 4. In the preparation of carbon dioxide absorbent, this invention introduces polyamide amine PAMAM G1. Compared with conventional absorbents such as ethanolamine and diethanolamine, polyamide amine PAMAM G1 has multiple amine and amide groups on its molecule, giving it additional chemical absorption capacity for carbon dioxide. This significantly improves the absorption rate and capture efficiency of carbon dioxide, enhances the selectivity and efficiency of absorption, and overcomes the limitations of traditional single reaction pathways. It also significantly improves the absorption efficiency and capacity of carbon dioxide, solving the problem of the relatively insufficient carbon dioxide absorption capacity of traditional eutectic solvent DES (especially under low partial pressure). 5. This invention completes the synthesis of the eutectic solvent DES in a reaction vessel, and uses a co-solvent to dissolve the polyamide amine PAMAMG1, which simplifies the process and reduces losses and pollution risks during material transfer; at the same time, the dehydration process in step S3 ensures the stability and absorption efficiency of the absorbent. In addition, the preparation method of the present invention is simple and controllable, the reaction conditions are mild, the raw materials are readily available and inexpensive, and it is easy to scale up production. It has good reproducibility and provides a feasible technical solution for industrial application. Attached Figure Description

[0017] Figure 1 The 1H-NMR spectrum of PAMAM G1 / DES prepared in this invention; Figure 2 The infrared spectrum of PAMAM G1 / DES prepared in this invention. Detailed Implementation

[0018] The preferred embodiments of the present invention are described below. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention. Example 1:

[0019] The preparation method of the ionic liquid carbon dioxide absorbent mentioned in this invention includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea were mixed in a 1:2 molar ratio and added to a reaction vessel. The material temperature in the reaction vessel was controlled at 80°C and the stirring speed was controlled at 100 rpm. The reaction was carried out under sealed conditions for 2 hours to obtain the colorless eutectic solvent DES. The generated eutectic solvent DES was sealed and stored at 60°C. S2. Preparation of composite absorbent Weigh out dried polyamide amine PAMAM G1 and eutectic solvent DES synthesized in step S1 and mix them in a 1:4 molar ratio. Add polyamide amine PAMAM G1 and dioxane as a co-solvent. The amount of dioxane added is 20% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES. Purge the air in the reactor with nitrogen and maintain a protective positive pressure of 0.02 MPa. Start stirring and control the temperature in the reactor to be maintained at 60°C. Stir for 2 hours until the mixture becomes a homogeneous liquid. S3. Purification and Dehydration The homogeneous liquid formed in step S2 was subjected to vacuum pumping and rotary distillation for 1.5 hours to precipitate the co-solvent and water, yielding the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent (PAMAM G1 / DES), which was then stored in a desiccator. Example 2:

[0020] The preparation method of the ionic liquid carbon dioxide absorbent mentioned in this invention includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea were mixed in a molar ratio of 2:3 and weighed separately using a weighing system or platform scale. They were then added to a reaction vessel, and the temperature of the materials inside the reaction vessel was maintained at 80°C. The stirring speed was controlled at 80 rpm. The reaction was carried out under sealed conditions for 2 hours to obtain a colorless eutectic solvent DES. The generated eutectic solvent DES was sealed and stored at 60°C. S2. Preparation of composite absorbent Weigh out dried polyamide amine PAMAM G1 and eutectic solvent DES synthesized in step S1 and mix them in a 1:5 molar ratio. Add polyamide amine PAMAM G1 and dioxane as a co-solvent. The amount of dioxane added is 20% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES. Purge the air in the reactor with nitrogen and maintain a protective positive pressure of 0.05 MPa. Start stirring and control the temperature in the reactor at 70°C. Stir for 2.5 hours until the mixture becomes a homogeneous liquid. S3. Purification and Dehydration The homogeneous liquid formed in step S2 was subjected to vacuum pumping and rotary distillation for 1 hour to precipitate the co-solvent and water, yielding the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent (PAMAM G1 / DES), which was then stored in a desiccator. Example 3:

[0021] The preparation method of the ionic liquid carbon dioxide absorbent mentioned in this invention includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea were mixed in a molar ratio of 3:5 and weighed separately using a weighing system or platform scale. The mixture was then added to a reaction vessel. The temperature of the material inside the reaction vessel was maintained at 82°C and the stirring speed was controlled at 150 rpm. The reaction was carried out under sealed conditions for 1.5 hours to obtain a colorless eutectic solvent DES. The generated eutectic solvent DES was sealed and stored at 60°C. S2. Preparation of composite absorbent Weigh out dried polyamide amine PAMAM G1 and eutectic solvent DES synthesized in step S1 and mix them in a 3:4 molar ratio. Add polyamide amine PAMAM G1 and dioxane as a co-solvent. The amount of dioxane added is 30% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES. Purge the air in the reactor with nitrogen and maintain a protective positive pressure of 0.05 MPa. Start stirring and control the temperature in the reactor at 80°C. Stir for 3 hours until the mixture becomes a homogeneous liquid. S3. Purification and Dehydration The homogeneous liquid formed in step S2 is subjected to vacuum pumping and rotary distillation for 2 hours to precipitate the co-solvent and water until the liquid mass no longer changes, yielding the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent (PAMAM G1 / DES), which is then stored in a desiccator. Example 4:

[0022] The preparation method of the ionic liquid carbon dioxide absorbent mentioned in this invention includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea were mixed in a molar ratio of 4:5 and weighed separately using a weighing system or platform scale. The mixture was then added to a reaction vessel. The temperature of the materials in the reaction vessel was 78°C, the stirring speed was controlled at 60 rpm, and the reaction was carried out under sealed conditions for 1 hour to obtain a colorless eutectic solvent DES. The generated eutectic solvent DES was sealed and stored at 60°C. S2. Preparation of composite absorbent Weigh the dried polyamide amine PAMAM G1 and the eutectic solvent DES synthesized in step S1 and mix them in a 1:10 molar ratio. Add polyamide amine PAMAM G1 and dioxane as a co-solvent. The amount of dioxane added is 25% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES. Purge the air in the reactor with nitrogen and maintain a protective positive pressure of 0.1 MPa. Start stirring and control the temperature in the reactor at 60°C. Stir for 3 hours until the mixture becomes a homogeneous liquid. In addition, a solvent recovery unit can be added after the reaction is completed to recover and reuse the dioxane; S3. Purification and Dehydration The homogeneous liquid formed in step S2 is subjected to vacuum pumping and rotary distillation for 0.5 hours to precipitate the co-solvent and water, yielding the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent (PAMAM G1 / DES), which is then stored in a desiccator.

[0023] Comparative Example 1: The eutectic solvent DES synthesized in step S1 of Example 1 was used as a carbon dioxide absorbent.

[0024] Comparative Example 2: The eutectic solvent DES synthesized in step S1 of Example 3 was used as a carbon dioxide absorbent.

[0025] Comparative Example 3: Choline chloride and urea were mixed at a molar ratio of 1:5, and the remaining operations were the same as step S1 in Example 1 to synthesize the eutectic solvent DES. Then, the dried polyamide amine PAMAM G1 was mixed with the synthesized eutectic solvent DES at a molar ratio of 1:4, and the amount of dioxane added was 20% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES. The remainder was compounded, and in step S3, the same rotary distillation conditions as in Example 1 were used for treatment. The weight of the product was stable after rotary distillation, indicating that no additional component loss occurred.

[0026] Comparative Example 4: The dried polyamide amine PAMAM G1 and the eutectic solvent DES synthesized in Example 1 were mixed at a molar ratio of 1:2. The amount of dioxane added was 20% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES, and the remainder was compounded. In step S3, the same rotary distillation conditions as in Example 1 were used for treatment. The weight of the product was stable after rotary distillation, indicating that no additional component loss occurred.

[0027] Comparative Example 5: Example 1 was repeated, but the amount of dioxane added was changed to 10% of the total mass of polyamidoamine PAMAM G1 and eutectic solvent DES. It was observed that in step S2, the mixture could not be transformed into a homogeneous transparent liquid within 2 hours and remained turbid, indicating that when the amount of cosolvent was insufficient, polyamidoamine PAMAM G1 could not be sufficiently dispersed in the eutectic solvent DES.

[0028] The comparative tests of the four embodiments and two comparative examples mentioned in this invention are as follows: Carbon dioxide absorption experiment test: 50 mL of carbon dioxide gas was introduced into the reactor, the pressure was controlled at 0.1 MPa, the temperature was 50 °C, and the gas was introduced for 30 min. The absorbent solutions of Examples 1-4 and Comparative Examples 1-4 were added to the reactor respectively, and the absorption was carried out for 2 h. The carbon dioxide was captured, and the amount of carbon dioxide captured was confirmed by weighing with a balance. The capture efficiency was calculated.

[0029] Table 1. Capacity of absorbents for carbon dioxide capture

[0030] Note: Comparative Example 5 was not tested for absorption performance because it could not form a homogeneous liquid, and is indicated by "—".

[0031] As shown in Table 1, Examples 1-4 exhibited higher carbon dioxide capture capabilities, relying on a dual absorption mechanism combining the physical properties of the eutectic solvent DES and the chemical properties of polyamide amine PAMAM G1. The absorbents prepared in Examples 1 and 3 contained a high proportion of polyamide amine PAMAM G1. Due to the large number of amine and amide groups on its surface, it possessed additional carbon dioxide chemical absorption capabilities, significantly improving the carbon dioxide absorption rate and capture efficiency, thus achieving higher capture efficiencies than Examples 2 and 4. Comparative Examples 1 and 2 used only the eutectic solvent DES synthesized from choline chloride and urea, where carbon dioxide molecules dissolved physically in the solvent, resulting in slightly lower absorption efficiencies. In Comparative Examples 3 and 4, when the proportions of urea or polyamide amine PAMAM G1 exceeded the specified range, the hydrogen bond network structure of the product was disrupted, preventing effective dispersion between components and hindering the full functioning of chemical absorption sites, leading to a decrease in capture efficiency. In Comparative Example 5, the amount of co-solvent added was too low, preventing the polyamide amine PAMAM G1 from being fully dispersed in the eutectic solvent DES, making it difficult to form the target product; therefore, no absorption performance test was conducted.

[0032] The above data fully demonstrates that polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent has good absorption efficiency for carbon dioxide.

[0033] The polyamide amine-eutectic solvent composite carbon dioxide absorbent (PAMAM G1 / DES) of this invention is formed by hydrogen bonding (-NH2 group and Cl) between urea and choline chloride. - The polyamide amine (PAMAM G1) is synthesized through interaction to form a eutectic solvent DES. Due to the presence of amine and amide groups on the surface of PAMAM G1, it undergoes secondary hydrogen bonding interactions with the already formed eutectic solvent DES, dissolving or uniformly dispersing in the matrix of the eutectic solvent DES, ultimately forming the target product.

[0034] The molecular structural formula of the polyamide amine PAMAM G1 used in this invention is as follows: ; The typical hydrogen bond molecular structure of choline chloride and urea in the eutectic solvent DES synthesized in the above embodiments is as follows: ; The polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent prepared by this invention has the following typical hydrogen bond molecular structure: ; Among them, choline chloride (purity ≥98%, vacuum dried at 60℃ for 24 hours to constant weight before use) acts as a hydrogen bond acceptor, providing the core of the negatively charged atom, which is the basis for the formation of the hydrogen bond network; urea (purity ≥99%) acts as a hydrogen bond donor, providing hydrogen atoms to form a strong hydrogen bond interaction with the anion of choline chloride (such as chloride ion); polyamide amine PAMAM G1 is a dendritic polymer with a large number of amine and amide groups on its surface, which can serve as additional hydrogen bond interaction sites to form new hydrogen bonds with the eutectic solvent DES; dioxane (water content <0.01%) acts as a co-solvent.

[0035] In addition, Figure 1 This is a 1H-NMR spectrum of PAMAM G1 / DES. The horizontal axis represents chemical shift (δ, in ppm), reflecting the chemical environment of the hydrogen atom, such as the type of functional group it is connected to. The vertical axis represents signal intensity; the peak area is proportional to the number of corresponding hydrogen atoms and can be used for quantitative analysis. Peak splitting (such as singlets and doublets) is caused by the coupling of adjacent hydrogen atoms, following the "n+1 rule," revealing the connection relationship between hydrogen atoms. Specifically, the peak at chemical shift δ=1.51 ppm is the proton peak on the -NH2 chain end of the PAMAM macromolecule, the peak at δ=8.11 ppm is the proton peak on -NH-, the peak at δ=2.36 ppm is the proton peak on the methylene-CH2- between the central nitrogen atoms, the peak at δ=2.53 ppm is the carbonyl-beside-methylene-CH2- peak, and the peak at δ=2.76 ppm is the proton peak on the methylene-CH2- beside the -NH2 group. The peak at δ=3.09 ppm is the proton peak on the methylene-CH2- beside the -NH2 group. The peak at ppm corresponds to the proton peak on the methyl group (-CH3) of choline chloride in DES; the peak at δ=3.14 ppm corresponds to the proton peak on the -NH-paramethyl group (-CH2-) of the PAMAM chain; the peak at δ=4.24 ppm corresponds to the proton peak on the hydroxyl group (-OH) of choline chloride; and the peak at δ=6.19 ppm corresponds to the proton peak on the urea-NH2 group. Characterization by 1H NMR spectroscopy confirmed that the product possesses the expected molecular structure characteristics, demonstrating the successful preparation of PAMAMG1 / DES, i.e., a polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent, through this reaction.

[0036] Appendix Figure 2 The infrared spectrum of PAMAM G1 / DES shows the mixture at 3358 cm⁻¹. -1 and 3250 cm -1 Two overlapping absorption peaks appear at 1660 cm⁻¹, which are attributed to the stretching vibrations of urea-NH₂ / choline-OH in the eutectic solvent DES and the stretching vibration of the -NH₂ terminal of polyamide amine PAMAM G1, respectively; in the carbonyl stretching vibration region, at 1660 cm⁻¹... -1A single absorption peak appears at 1561 cm⁻¹, corresponding to the overlap of the urea C=O band and the polyamide I band of PAMAM G1 in the eutectic solvent DES; the mixture shows an absorption peak at 1561 cm⁻¹. -1 The absorption peak at 753 cm⁻¹ is attributed to the overlap of amide-NH₃ and urea-NH₃ groups in polyamide amine PAMAM G1, further confirming the perturbation of the N–H bending vibration by hydrogen bonding; -1 The characteristic hydrogen-bonded lattice mode of the eutectic solvent DES (Cl) is retained at this location. - The hydrogen bond network involved indicates that the intrinsic hydrogen bond structure of the eutectic solvent DES is partially retained after mixing, while chloride ions may interact additionally with the terminal –NH2 of polyamidoamine PAMAM G1.

[0037] In summary, both 1H NMR and infrared spectroscopy analyses indicate that PAMAM G1 / DES, a polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent, has been successfully prepared.

[0038] Table 2. Molecular weight test results of PAMAM G1 / DES

[0039] Table 2 shows the gel permeation chromatography (GPC) results of PAMAM G1 / DES. The number-average molecular weight (Mn) of polyamidoamine PAMAM G1 is 1430 Da, the weight-average molecular weight (Mw) is 1444 Da, the peak molecular weight (Mp) is 1433 Da, and the polydispersity index (PDI) is 1.03, indicating good monodispersity. The Z-average molecular weight (Mz) is 1466 Da, slightly higher than Mw, suggesting the presence of a small amount of high molecular weight components. The main peak area percentage (%Area) is 96.58%, indicating high sample purity. The number-average molecular weight (Mn) of the eutectic solvent DES is 257.7 Da, the weight-average molecular weight (Mw) is 259.6 Da, and the polydispersity index (PDI) is 1.0, showing high agreement with theoretical values ​​and confirming accurate stoichiometry; the %Area is 99.12%, indicating good purity.

[0040] The above results indicate that the polyamide amine PAMAM G1 and the eutectic solvent DES used in this invention both have definite molecular weights and narrow molecular weight distributions, satisfying the above preparation requirements.

[0041] The above description is merely a partial preferred embodiment of the present invention. Any person skilled in the art can modify the above-described technical solutions or modify them into equivalent technical solutions. Therefore, any simple modifications or equivalent transformations made based on the technical solutions of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing an ionic liquid carbon dioxide absorbent, characterized in that: Includes the following steps: Synthesis of S1 and eutectic solvent DES Choline chloride and urea are mixed in a molar ratio of 1:2, 2:3, 3:5 or 4:5 and added to a reaction vessel. The temperature of the material inside the reaction vessel is controlled at 80±2℃, the stirring speed is controlled at 60~150 rpm, and the reaction is sealed for 1~2 hours to obtain the eutectic solvent DES. S2. Preparation of composite absorbent The dried polyamide amine PAMAM G1 and the eutectic solvent DES synthesized in step S1 were mixed in a molar ratio of (1~4):(4~10); the dried polyamide amine PAMAM G1 was added to the reactor for synthesizing the eutectic solvent DES, and dioxane was added as a co-solvent; nitrogen was introduced to replace the air in the reactor and a protective positive pressure of 0.02MPa~0.1MPa was maintained, the stirring was started, the temperature in the reactor was controlled at 60~80℃, and the stirring was carried out for 2~3 hours until the mixture became a homogeneous liquid; The amount of dioxane added is 20-30% of the total mass of polyamide amine PAMAM G1 and eutectic solvent DES; S3. Purification and Dehydration The homogeneous liquid formed in step S2 is subjected to vacuum pumping and rotary distillation for 0.5 to 2 hours to precipitate the co-solvent and water, forming the final product, polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent, which is stored in a desiccator. The molecular structural formula of the polyamide amine PAMAM G1 is as follows: 。 2. The preparation method of the ionic liquid carbon dioxide absorbent according to claim 1, characterized in that: in In step S1 above, choline chloride and urea are weighed in a molar ratio of 1:2 or 2:3, and the generated eutectic solvent DES is sealed and stored at 60°C.

3. The method for preparing the ionic liquid carbon dioxide absorbent according to claim 1, characterized in that: In step S2, polyamide amine PAMAM G1 and eutectic solvent DES are weighed in a molar ratio of 3:

4. During the preparation process, the eutectic solvent DES and polyamide amine PAMAM G1 are protected by nitrogen gas.

4. The preparation method of the ionic liquid carbon dioxide absorbent according to claim 3, characterized in that: in In step S2 above, after the reaction is completed, a solvent recovery unit is added to recover and reuse dioxane.

5. The method for preparing the ionic liquid carbon dioxide absorbent according to claim 1, characterized in that: The polyamide amine-eutectic solvent-based ionic liquid carbon dioxide absorbent described above has the following typical hydrogen bond molecular structure: 。 6. The method for preparing the ionic liquid carbon dioxide absorbent according to claim 1, characterized in that: The typical hydrogen bond molecular structure of choline chloride and urea in the eutectic solvent DES is as follows: 。

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