Vegetable Oil-Based Carbon Dioxide Absorbent and Its Preparation Method and Antibacterial Application

Abstract

The present invention belongs to the technical field of polymer materials, and specifically relates to a vegetable oil-based carbon dioxide absorbent, its preparation method and antibacterial application. In the present invention, oleic acid chains or epoxidized oleic acid chains are introduced onto the molecules of typical amine absorbent polyethyleneimine. The non-polar long carbon chain fatty acid structure can significantly weaken the hydrogen bonds between polyethyleneimine molecules, reduce the intermolecular force, so that more amino groups are exposed to combine with carbon dioxide, realizing the efficient, high-capacity and low-energy consumption absorption of carbon dioxide. In the present invention, the unsaturated carbon-carbon double bonds on the oleic acid chains are epoxidized and modified, introducing more secondary amines, further improving the carbon dioxide absorption capacity. Moreover, after absorbing carbon dioxide, the tertiary amines in the molecular structure are converted into quaternary ammonium salt ions, endowing it with excellent antibacterial properties, showing excellent antibacterial effects against both Staphylococcus aureus and Escherichia coli, and can be used as an antibacterial agent.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a vegetable oil-based carbon dioxide absorbent, a preparation method thereof, and an antibacterial application thereof. Background Art

[0002] Under the background of global climate change, carbon dioxide (CO2), as one of the main greenhouse gases, the continuous growth of its emissions has become a global focus. According to the report of the International Energy Agency, the global annual CO2 emissions have exceeded 30 billion tons. Excessive carbon emissions will not only cause great pressure on the global climate environment, but also affect the survival and development of mankind. Therefore, how to reduce CO2 emissions is a key problem to be solved urgently. At present, carbon capture, utilization and storage is one of the most effective and direct methods for dealing with carbon emissions. Among them, how to achieve high-efficiency, low-energy consumption and high-capacity absorption of CO2 by absorbents is a problem to be solved urgently.

[0003] Polyethyleneimine is a commonly used amine absorbent at present. There is a strong intermolecular force between the molecules of this material, which makes it difficult for CO2 to diffuse into the material interior. After the material surface absorbs CO2, the reaction between the internal amino group and CO2 is very slow, resulting in a greatly reduced CO2 absorption efficiency. Therefore, it is necessary to modify polyethyleneimine to overcome the problems of traditional amine absorbents such as "low efficiency, low capacity, and high regeneration energy consumption". Summary of the Invention

[0004] The first object of the present invention is to provide a preparation method of a vegetable oil-based carbon dioxide absorbent. The second object of the present invention is to provide a vegetable oil-based carbon dioxide absorbent prepared by this preparation method. The third object of the present invention is to provide an application of this vegetable oil-based carbon dioxide absorbent.

[0005] According to the first aspect of the present invention, a preparation method of a vegetable oil-based carbon dioxide absorbent is provided, including the following steps:

[0006] (1) Mix first oleic acid or epoxidized oleic acid with dichloromethane, then cool to below 0 °C, add thionyl chloride, react first at below 0 °C for 15 - 35 min, and then stir and react at 50 - 70 °C for 3 - 5 h to obtain oleic acid acyl chloride or epoxidized oleic acid acyl chloride;

[0007] (2) Disperse polyethyleneimine in tetrahydrofuran, cool to below 0 °C, add the oleic acid acyl chloride or epoxidized oleic acid acyl chloride obtained in step (1), and then react at 15 - 35 °C for 4 - 8 h. Use the nucleophilic addition reaction of acyl chloride and amino group to generate amide and hydrogen chloride. After the reaction ends, add an extractant to extract to remove excess reactants and product impurities, and finally perform rotary evaporation to obtain a vegetable oil-based carbon dioxide absorbent.

[0008] In some embodiments, the preparation method of epoxidized vegetable oil acid comprises the following steps:

[0009] Mix anhydrous copper chloride, 1,10-phenanthroline, and hexafluoroisopropanol, stir for 30 - 60 min, then cool to below 0 °C, and subsequently add second vegetable oil acid, hydroxylamine-o-sulfonic acid, and cesium hydroxide aqueous solution. React first at below 0 °C for 15 - 30 min, and then stir at 15 - 35 °C for 16 - 32 h to activate the unsaturated carbon-carbon double bonds in the second vegetable oil acid and form an epoxy-nitrogen structure, thus obtaining the product.

[0010] In some embodiments, by mass, the dosage of anhydrous copper chloride is 0.1 - 1 part, the dosage of 1,10-phenanthroline is 0.1 - 1 part, the dosage of hexafluoroisopropanol is 100 - 200 parts, the dosage of the second vegetable oil acid is 5 - 20 parts, the dosage of hydroxylamine-o-sulfonic acid is 3 - 10 parts, and the dosage of cesium hydroxide aqueous solution is 5 - 20 parts. Among them, the concentration of cesium hydroxide in the cesium hydroxide aqueous solution is 40 - 60 wt%.

[0011] In some embodiments, the second vegetable oil acid is selected from at least one of oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and eleostearic acid.

[0012] In some embodiments, the first vegetable oil acid is selected from at least one of oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and eleostearic acid.

[0013] In some embodiments, the extractant is obtained by mixing saturated brine and n-hexane in a volume ratio of 1:(1 - 3).

[0014] In some embodiments, when preparing vegetable oil acid acyl chloride or epoxidized vegetable oil acid acyl chloride, by mass, the dosage of the first vegetable oil acid or epoxidized vegetable oil acid is 5 - 20 parts, the dosage of dichloromethane is 30 - 80 parts, and the dosage of thionyl chloride is 10 - 30 parts;

[0015] When preparing the vegetable oil-based carbon dioxide absorbent, by mass, the dosage of polyethyleneimine is 1 - 5 parts, the dosage of tetrahydrofuran is 10 - 50 parts, and the dosage of vegetable oil acid acyl chloride or epoxidized vegetable oil acid acyl chloride is 1 - 10 parts.

[0016] According to the second aspect of the present invention, there is provided a vegetable oil-based carbon dioxide absorbent prepared by the above preparation method.

[0017] According to the third aspect of the present invention, there is provided the application of the above vegetable oil-based carbon dioxide absorbent in the preparation of an adsorbent for capturing carbon dioxide.

[0018] According to the fourth aspect of the present invention, there is provided the application of the above vegetable oil-based carbon dioxide absorbent in the preparation of an antibacterial agent.

[0019] The beneficial effects of the present invention include:

[0020] (1) By introducing oleic acid chains or epoxidized oleic acid chains onto the polyethyleneimine molecule, a typical amine absorbent, the unique non-polar long carbon chain fatty acid structure can significantly weaken the hydrogen bonds between polyethyleneimine molecules, reduce the intermolecular forces, expose more amino groups to combine with carbon dioxide, and achieve efficient, high-capacity, and low-energy consumption absorption of carbon dioxide, shortening the absorption time to saturation. Moreover, the long carbon chain fatty acid structure can endow the vegetable oil-based carbon dioxide absorbent of the present invention with good hydrophobic properties, overcome the limitation of amine absorbents being prone to moisture absorption, and expand its practical application scenarios.

[0021] (2) More energy is required to break the force between primary amines and carbon dioxide. The present invention uses fatty acid chains with different grafting degrees to reduce the proportion of primary amines in polyethyleneimine, greatly reducing the regeneration energy consumption of the vegetable oil-based carbon dioxide absorbent of the present invention after absorbing carbon dioxide.

[0022] (3) The present invention obtains epoxidized oleic acid chains by epoxidizing the unsaturated carbon-carbon double bonds on oleic acid chains, introducing more secondary amines, further increasing the carbon dioxide absorption capacity, and the carbon dioxide absorption capacity can reach 7.53 mmol / g. Moreover, after absorbing carbon dioxide, the tertiary amines in the molecular structure are converted into quaternary ammonium salt ions, endowing it with excellent antibacterial properties, showing excellent antibacterial effects against both Staphylococcus aureus and Escherichia coli, and can be used as an antibacterial agent. Description of the Drawings

[0023] Figure 1 is the Fourier transform infrared spectrum of polyethyleneimine and the vegetable oil-based carbon dioxide absorbent of Example 1 of the present invention.

[0024] Figure 2 is the reaction route diagram of the vegetable oil-based carbon dioxide absorbent of Example 2 of the present invention.

[0025] Figure 3 is the Fourier transform infrared spectrum of epoxidized oleic acid, epoxidized oleic acid acyl chloride, and the vegetable oil-based carbon dioxide absorbent of Example 2 of the present invention.

[0026] Figure 4 is the carbon dioxide pressure change diagram in the closed reaction kettle containing the carbon dioxide absorbents of Examples 1-2 and Comparative Example 1.

[0027] Figure 5 is the carbon dioxide absorption capacity diagram of the carbon dioxide absorbents of Examples 1-2 and Comparative Example 1 of the present invention.

[0028] Figure 6It is the carbon dioxide desorption situation diagram of the carbon dioxide absorbents in Examples 1-2 of the present invention and Comparative Example 1.

[0029] Figure 7 It is the infrared diagram of the carbon dioxide absorbents in Examples 1-2 of the present invention and Comparative Example 1 for desorbing carbon dioxide.

[0030] Figure 8 It is the antibacterial result diagram of the carbon dioxide absorbents in Examples 1-2 of the present invention and Comparative Example 1. Specific Embodiments

[0031] The present invention will be further described in detail below in conjunction with specific embodiments, but the implementation manners of the present invention are not limited thereto. The materials involved in the following examples can all be obtained from commercial channels.

[0032] In the following examples, the stirring speed is 200-400 rpm, below 0 °C means 0 to -10 °C, and room temperature means 15-35 °C.

[0033] Oleic acid is derived from soybean oil.

[0034] The extractant is obtained by mixing 150 mL of saturated brine and 150 mL of n-hexane.

[0035] In the following examples and comparative examples, the molecular weight of polyethyleneimine is 7000, and it has a branched structure.

[0036] Example 1

[0037] The preparation method of the vegetable oil-based carbon dioxide absorbent in this example includes the following steps:

[0038] (1) Put 10 g of oleic acid and 50 mL of dichloromethane into a two-necked flask, pre-open the cold trap and cool it to below 0 °C in advance, then install the two-necked flask into the cold trap, and slowly drop 20 g of thionyl chloride into the two-necked flask. React at below 0 °C for 30 min first, and then stir and react at 60 °C for 4 h to obtain vegetable oil oleoyl chloride.

[0039] (2) Weigh 3 g of polyethyleneimine and disperse it in 30 mL of tetrahydrofuran, then put it into another clean two-necked flask, pre-open the cold trap and cool it to below 0 °C in advance, install the two-necked flask into the cold trap, and then slowly drop 5.22 g of the vegetable oil oleoyl chloride obtained in step (1) into the two-necked flask in the cold trap environment below 0 °C. Subsequently, take out the two-necked flask from the cold trap, react at room temperature for 6 h, then extract 3 times with the extractant, and finally perform rotary evaporation to obtain the vegetable oil-based carbon dioxide absorbent (abbreviated as PEI-OA).

[0040] The Fourier transform infrared spectra of the polyethyleneimine and the vegetable oil-based carbon dioxide absorbent in this example are asFigure 1 As shown in the figure, in the figure, the raw material is polyethyleneimine (denoted as PEI), and the product is a vegetable oil-based carbon dioxide absorbent (denoted as PEI-OA).

[0041] From Figure 1 It can be seen that compared with pure PEI, PEI-OA shows an obvious stretching vibration peak at 1749 cm -1 . This corresponds to the stretching vibration peak of C=O on the amide formed after the reaction of the amino group with acyl chloride, indicating that PEI has reacted with oleic acid (OA) to form the corresponding amide group. In addition, it is worth noting that PEI-OA shows an obvious stretching vibration peak at 1652 cm -1 . This corresponds to the unsaturated double bond on the oleic acid chain, further proving that OA has been successfully grafted onto the structure of PEI.

[0042] Example 2

[0043] The preparation method of the vegetable oil-based carbon dioxide absorbent in this example includes the following steps:

[0044] (1) Add 0.48 g of anhydrous copper chloride, 0.64 g of 1,10-phenanthroline, and 160 g of hexafluoroisopropanol into a round-bottom flask in sequence. After covering with a glass stopper and stirring for 30 min, transfer it to a cold trap until the system temperature is below 0 °C. Then slowly dropwise add 10 g of oleic acid, add 5.86 g of hydroxylamine-o-sulfonic acid, and then dropwise add 8.78 g of cesium hydroxide aqueous solution (the concentration of cesium hydroxide is 50 wt%). After reacting at 0 °C for 30 min, transfer it to room temperature and mechanically stir for 24 h to obtain epoxidized vegetable oil acid.

[0045] (2) Put 10 g of the epoxidized vegetable oil acid obtained in step (1) and 50 mL of dichloromethane into a two-necked flask. Open the cold trap in advance and cool it to below 0 °C. Then install the two-necked flask into the cold trap, and slowly dropwise add 20 g of thionyl chloride into the two-necked flask. First, react at 0 °C for 30 min, and then stir and react at 60 °C for 4 h to obtain epoxidized vegetable oil acid acyl chloride.

[0046] (3) Weigh 3 g of polyethyleneimine and disperse it in 30 mL of tetrahydrofuran, then put it into another clean two-necked flask. Open the cold trap in advance and cool it to below 0 °C. Install the two-necked flask into the cold trap, and then slowly dropwise add 5.22 g of the epoxidized vegetable oil acid acyl chloride obtained in step (2) into the two-necked flask in the cold trap environment below 0 °C. Then take out the two-necked flask from the cold trap, react at room temperature for 6 h, then add an extraction agent and extract 3 times, and finally perform rotary evaporation to obtain a vegetable oil-based carbon dioxide absorbent (abbreviated as PEI-N-OA).

[0047] The reaction route of the vegetable oil-based carbon dioxide absorbent in this embodiment is as follows Figure 2 shown

[0048] The Fourier transform infrared spectra of epoxidized vegetable oil fatty acid, epoxidized vegetable oil fatty acid acyl chloride, and vegetable oil-based carbon dioxide absorbent in this embodiment are as follows Figure 3 shown. In the figure, epoxidized vegetable oil fatty acid is denoted as N-OA, epoxidized vegetable oil fatty acid acyl chloride is denoted as N-OA-Cl, and vegetable oil-based carbon dioxide absorbent is denoted as PEI-N-OA

[0049] From Figure 3 the left figure, it can be seen that compared with pure N-OA, after acylation, an obvious stretching vibration peak appears at 1823 cm -1 for N-OA-Cl, which corresponds to the stretching vibration peak of C-Cl on the acyl chloride. Thus, it can be proved that N-OA reacts with thionyl chloride to form the corresponding acyl chloride group. From Figure 3 the right figure, it can be seen that the stretching vibration peak of C-Cl on the acyl chloride at 1823 cm -1 for PEI-N-OA disappears significantly, indicating that the acyl chloride reacts with the amino group, indicating that N-OA has been successfully grafted onto the structure of polyethyleneimine (PEI).

[0050] Comparative Example 1

[0051] Take the typical amine-based carbon dioxide absorbent polyethyleneimine (abbreviation: PEI) as a comparative case

[0052] To illustrate the comprehensive performance of the vegetable oil-based carbon dioxide absorbent prepared by the present invention, the following performance tests are carried out on the vegetable oil-based carbon dioxide absorbent (PEI-OA) prepared in Example 1, the vegetable oil-based carbon dioxide absorbent (PEI-N-OA) prepared in Example 2, and the amine-based carbon dioxide absorbent polyethyleneimine (PEI) in Comparative Example 1

[0053] (1) Carbon dioxide absorption test

[0054] 3 MPa of carbon dioxide is respectively introduced into a closed reaction kettle filled with a carbon dioxide absorbent, and the pressure change inside the closed reaction kettle is monitored. The carbon dioxide pressure change diagrams of the closed reaction kettles filled with the carbon dioxide absorbents of Examples 1-2 and Comparative Example 1 are as follows Figure 4 shown, and the carbon dioxide absorption capacity diagrams of the carbon dioxide absorbents of Examples 1-2 and Comparative Example 1 are as follows Figure 5 shown

[0055] From Figure 4It can be seen that as time goes by, the carbon dioxide pressure in the reaction kettle weakens. Compared with pure polyethyleneimine (PEI), the pressure in the closed reaction kettle of PEI-OA grafted with oleic acid chains of vegetable oil and PEI-N-OA grafted with cyclonitrogenated oleic acid chains of vegetable oil drops faster, and the time to reach the adsorption saturation state (constant pressure, no longer absorbing carbon dioxide) is shorter. This indicates that the absorption efficiency of carbon dioxide has been improved after grafting oleic acid chains or cyclonitrogenated oleic acid chains of vegetable oil onto PEI, and the carbon dioxide absorption efficiency is higher after grafting cyclonitrogenated oleic acid chains. Then, by observing the pressure of the remaining carbon dioxide in the closed reaction kettle, it can be found that the pressure of the remaining carbon dioxide in the reaction kettle is higher when pure PEI reaches the adsorption saturation state (constant pressure, no longer absorbing carbon dioxide), while the pressure of the remaining carbon dioxide in the reaction kettle is lower when PEI-OA grafted with oleic acid chains of vegetable oil and PEI-N-OA grafted with cyclonitrogenated oleic acid chains of vegetable oil reach the adsorption saturation state. This shows that the carbon dioxide absorption capacity of PEI-OA grafted with oleic acid chains of vegetable oil and PEI-N-OA grafted with cyclonitrogenated oleic acid chains of vegetable oil has been increased, and the carbon dioxide absorption capacity of PEI-N-OA grafted with cyclonitrogenated oleic acid chains of vegetable oil is more. From Figure 5 It can be seen that the carbon dioxide absorption capacities of PEI, PEI-OA, and PEI-N-OA are 4.82 mmol / g, 6.61 mmol / g, and 7.53 mmol / g, respectively.

[0056] (2)Carbon dioxide desorption test

[0057] The carbon dioxide desorption tests were carried out on the carbon dioxide absorbents PEI, PEI-OA, and PEI-N-OA that reached the adsorption saturation state above, and the desorption of carbon dioxide by PEI, PEI-OA, and PEI-N-OA at 80 °C was monitored. The carbon dioxide desorption diagrams of the carbon dioxide absorbents in Examples 1-2 and Comparative Example 1 are as Figure 6 shown. From Figure 6It can be seen that after desorbing carbon dioxide at 80 °C, there is still 50% - 55% of carbon dioxide remaining in PEI. This may be because after carbon dioxide combines with amino groups, the hydrogen bond force inside becomes larger, and 80 °C is not sufficient to break the force between them, resulting in part of the carbon dioxide remaining in PEI and not being released. After desorbing carbon dioxide at 80 °C, there is still 35% - 40% of carbon dioxide remaining in PEI - OA. Compared with pure PEI, the remaining amount of carbon dioxide in PEI - OA is reduced. This may be because the addition of the vegetable oleic acid chain opens the hydrogen bonds inside PEI, weakens the intermolecular force, and leads to a reduction in the energy required during the desorption process. Therefore, under the same condition of 80 °C, PEI - OA has less remaining carbon dioxide than PEI. After desorbing carbon dioxide at 80 °C, there is still about 10% of carbon dioxide remaining in PEI - N - OA. Compared with PEI and PEI - OA, the remaining amount of carbon dioxide in PEI - N - OA is reduced. This may be because on the one hand, the addition of the cyclo - nitrided vegetable oleic acid chain opens the hydrogen bonds inside PEI, weakens the intermolecular force, and leads to a reduction in the energy required during the desorption process. On the other hand, the introduced secondary amine further increases the carbon dioxide binding sites. Therefore, under the same condition of 80 °C, PEI - N - OA has less remaining carbon dioxide and more absorption capacity than PEI - OA and PEI.

[0058] (3)Infrared test for carbon dioxide desorption

[0059] The desorption of carbon dioxide by PEI, PEI - OA, and PEI - N - OA at 80 °C was monitored by infrared. The infrared spectra of the carbon dioxide absorbents in Examples 1 - 2 and Comparative Example 1 for carbon dioxide desorption are as Figure 7 shown. As Figure 7 can be seen, at the early stage of carbon dioxide desorption by PEI at 80 °C, the amount of carbon dioxide escaping is relatively small, so the signal peak of carbon dioxide is relatively weak; compared with PEI, more carbon dioxide escapes at the early stage of the infrared spectrum of PEI - OA, and the signal peak is more obvious. This further verifies that the addition of the vegetable oleic acid chain opens the hydrogen bonds inside PEI, weakens the intermolecular force, and leads to less energy required during the desorption process. Therefore, the carbon dioxide in PEI - OA is released earlier than that in PEI. It can be found from the infrared spectrum of PEI - N - OA that more carbon dioxide escapes at the early stage, and the signal peak is more obvious. This is because on the one hand, the addition of the cyclo - nitrided vegetable oleic acid chain opens the hydrogen bonds inside PEI, weakens the intermolecular force, and leads to a reduction in the energy required during the desorption process. On the other hand, the introduced secondary amine further increases the carbon dioxide binding sites, resulting in a larger absorption capacity.

[0060] (4)Antibacterial test

[0061] The carbon dioxide absorbents PEI, PEI-OA, and PEI-N-OA that reached the adsorption saturation state above were irradiated under ultraviolet light for 30 minutes respectively, and then soaked in PBS solution with a pH of 7 for 30 minutes for standby; the carbon dioxide absorbent samples soaked in PBS solution and 1 mL of Staphylococcus aureus bacterial solution or Escherichia coli bacterial solution (the bacterial solution concentration was 0.5 McFarland turbidity) were co-cultured for 3.5 hours respectively, and then the samples were filtered. 30 μL of the co-cultured bacterial solution was taken and evenly spread on the surface of the agar, and the growth of bacteria was observed after culturing in a 37 °C incubator for 16 hours.

[0062] The antibacterial results of the carbon dioxide absorbents in Example 1-2 and Comparative Example 1 are as Figure 8 shown. From Figure 8 it can be seen that PEI showed weak antibacterial properties, and a large number of strains appeared on the corresponding agar surface. Compared with PEI, PEI-OA and PEI-N-OA showed more excellent antibacterial effects. PEI-OA has the property of resisting Staphylococcus aureus, while PEI-N-OA showed good antibacterial properties and excellent antibacterial effects against both Staphylococcus aureus and Escherichia coli. This is related to the molecular structure of the carbon dioxide absorbent. Compared with PEI and PEI-OA, PEI-N-OA has more tertiary amine groups on its molecule, and more quaternary ammonium salt ions are formed after absorbing carbon dioxide, so it has stronger antibacterial properties. This shows that the vegetable oil-based carbon dioxide absorbent of the present invention can be used as an antibacterial agent after absorbing carbon dioxide.

[0063] The above are only some embodiments of the present invention. For those of ordinary skill in the art, without departing from the creative concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention.

Claims

1. Preparation method of vegetable oil-based carbon dioxide absorbent, characterized in that, It includes the following steps: (1) Mix the first vegetable oleic acid or epoxidized vegetable oleic acid with dichloromethane, then cool it below 0 °C, add thionyl chloride, react at below 0 °C for 15 - 35 min first, and then stir and react at 50 - 70 °C for 3 - 5 h to obtain vegetable oleoyl chloride or epoxidized vegetable oleoyl chloride; the preparation method of the epoxidized vegetable oleic acid includes the following steps: mix anhydrous copper chloride, 1,10 - phenanthroline, and hexafluoroisopropanol, stir for 30 - 60 min, then cool it below 0 °C, then add the second vegetable oleic acid, hydroxylamine - o - sulfonic acid, and cesium hydroxide aqueous solution, react at below 0 °C for 15 - 30 min first, and then stir at 15 - 35 °C for 16 - 32 h to obtain it; (2) Disperse polyethyleneimine in tetrahydrofuran, cool it below 0 °C, add the vegetable oleoyl chloride or epoxidized vegetable oleoyl chloride obtained in step (1), then react at 15 - 35 °C for 4 - 8 h, add an extractant for extraction after the reaction, and finally perform rotary evaporation to obtain a vegetable - based carbon dioxide absorbent.

2. The preparation method according to claim 1, wherein By mass, the dosage of anhydrous copper chloride is 0.1 - 1 part, the dosage of 1,10 - phenanthroline is 0.1 - 1 part, the dosage of hexafluoroisopropanol is 100 - 200 parts, the dosage of the second vegetable oleic acid is 5 - 20 parts, the dosage of hydroxylamine - o - sulfonic acid is 3 - 10 parts, the dosage of the cesium hydroxide aqueous solution is 5 - 20 parts, and the concentration of cesium hydroxide in the cesium hydroxide aqueous solution is 40 - 60 wt%.

3. The preparation method according to claim 1 or 2, characterized in that, The second vegetable oleic acid is selected from at least one of oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and tung oil acid.

4. The preparation method according to claim 1 or 2, characterized in that, The first vegetable oleic acid is selected from at least one of oleic acid, linoleic acid, linolenic acid, ricinoleic acid, and tung oil acid.

5. The preparation method according to claim 1 or 2, characterized in that, The extractant is obtained by mixing saturated brine and n - hexane in a volume ratio of 1:(1 - 3).

6. The preparation method according to claim 1 or 2, characterized in that, When preparing vegetable oleoyl chloride or epoxidized vegetable oleoyl chloride, by mass, the dosage of the first vegetable oleic acid or epoxidized vegetable oleic acid is 5 - 20 parts, the dosage of dichloromethane is 30 - 80 parts, and the dosage of thionyl chloride is 10 - 30 parts; When preparing the vegetable - based carbon dioxide absorbent, by mass, the dosage of polyethyleneimine is 1 - 5 parts, the dosage of tetrahydrofuran is 10 - 50 parts, and the dosage of vegetable oleoyl chloride or epoxidized vegetable oleoyl chloride is 1 - 10 parts.

7. A vegetable - based carbon dioxide absorbent prepared by the preparation method according to any one of claims 1 - 6.

8. Use of the vegetable - based carbon dioxide absorbent according to claim 7 in the preparation of an adsorbent for capturing carbon dioxide.

9. Use of the vegetable - based carbon dioxide absorbent according to claim 7 in the preparation of an antibacterial agent.

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