Hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer, preparation method thereof and application of hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer in sulfur dioxide adsorption

Abstract

The invention discloses a hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer, a preparation method thereof and an application of the hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer in sulfur dioxide adsorption, and the hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer is prepared by the following steps: mixing aprotic ionic liquid with a tertiary amine group with a lithium salt of a fluorine-containing compound, and reacting under a water-phase stirring condition; and after the reaction is finished, carrying out vacuum drying on the obtained organic phase liquid, and collecting a product after drying, namely the required hydrophobic bifunctional ionic liquid. The method comprises the following steps: mixing hydrophobic bifunctional ionic liquid and a cross-linking agent in an organic solvent in a nitrogen atmosphere, carrying out a super-cross-linking reaction under heating and stirring conditions by using Lewis acid as a catalyst, cooling the reacted material to room temperature after the reaction is finished, filtering, washing the precipitate obtained by filtering until the filtrate is clear and transparent, and drying to obtain the hydrophobic bifunctional ionic liquid. According to the present invention, the preparation process is simple, and the prepared polymer has advantages of large specific surface area, high sulfur dioxide capture amount and the like, and has broad market prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of hydrophobic polymer synthesis, and specifically relates to a hydrophobic bifunctional ionic liquid embedded hyper-crosslinked polymer, a preparation method thereof and an application thereof in adsorbing sulfur dioxide. Background Art

[0002] The sulfur content in my country's coal resources is relatively high. In the process of coal-fired power generation, sulfur dioxide (SO2) is formed, which becomes an important component of flue gas emissions. If it is not effectively controlled, it will be discharged into the atmosphere, causing the concentration of SO2 in the atmosphere to increase and form acid rain. Therefore, the emission of SO2 in flue gas not only threatens people's health, but also affects economic development. The commonly used SO2 absorbent in industry is limestone gypsum, but it cannot be regenerated and the large amount of low-grade gypsum generated causes solid waste pollution. Therefore, it is very important to develop new adsorbents to efficiently adsorb SO2.

[0003] At present, ionic liquids have attracted attention as a new type of absorbent due to their extremely low volatility, no secondary pollution, good solubility, high thermal stability and designability. For example, Wang et al. reported that imidazolyl ionic liquids can effectively capture SO2 at low concentrations (J. Am. Chem. Soc., 2011, 133 (31), 11916-11919), and Cui et al. reported that hydroxypyridinium anion ionic liquids can effectively capture SO2 (Ind. Eng. Chem. Res. 2020, 59, 49, 21522–21529). However, most ionic liquids are hydrophilic absorbents, and the SO2 absorption capacity decreases under water-containing flue gas conditions. In addition, the high viscosity and low mass transfer of ionic liquids hinder the application of ionic liquids.

[0004] Solid adsorbents based on ionic liquids (such as polyionic liquids) not only have the advantages of ionic liquids, but also overcome the shortcomings of the above-mentioned pure ionic liquids, and have attracted people's attention. However, conventional polyionic liquids are usually non-porous, and the adsorption effect needs to be improved. Ionic liquid hyper-crosslinked polymer adsorbents are prepared by combining ionic liquids with hyper-crosslinked polymers prepared by Friedel-Crafts reaction of crosslinking agents. This type of adsorbent has been used for adsorption of carbon dioxide gas due to its large specific surface area, porosity, and simple preparation (Chem. Eng. J. 2024, 489 151102). However, there are few reports on the adsorption of gases such as SO2 under high humidity conditions. Therefore, it is very meaningful to develop new composite adsorbents based on ionic liquids to improve the SO2 adsorption capacity through structural adjustment for SO2 adsorption under humid conditions. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer, a preparation method thereof, and an application of adsorbing sulfur dioxide. The hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer obtained by the present invention has a hyper-crosslinked network structure, and utilizes a high specific surface area, a high total pore volume, and exposed ionic liquid sites to significantly improve the adsorption capacity of SO2 under high humidity conditions, thereby achieving efficient, high-capacity, and reversible selective adsorption of SO2.

[0006] To achieve the above object, the technical solution of the present invention is as follows: A method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer comprises the following steps: 1) Preparation of bifunctional ionic liquid: a non-protonic ionic liquid having a tertiary amine group is mixed with a lithium salt of a fluorine-containing compound, and reacted under stirring conditions of an aqueous phase. After the reaction is completed, the obtained organic phase liquid is vacuum dried, and the product collected after drying is the desired hydrophobic bifunctional ionic liquid; 2) Hypercrosslinking reaction: Under a nitrogen atmosphere, the hydrophobic bifunctional ionic liquid obtained in step 1) is mixed with a crosslinking agent in an organic solvent, and a Lewis acid is used as a catalyst to carry out a hypercrosslinking reaction under heating and stirring conditions. After the reaction is completed, the reacted material is cooled to room temperature and then filtered, and the precipitate obtained by filtration is washed until the filtrate is clear and transparent. Finally, the washed precipitate is dried. The product collected after drying is the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer to be prepared.

[0007] Furthermore, in step 1), the non-protonic ionic liquid having a tertiary amine group is one of N-hydroxyethyl-N,N-dimethylpiperazine bromide ([PPZ][Br]), N-ethyl-N,N,N',N'-tetramethylethylenediamine bromide ([TMEDA][Br]), and N-butyl-triethylenediamine chloride ([DABCO][Cl]); the lithium salt of the fluorine-containing compound is one of bistrifluoromethylsulfonyl imide lithium salt ([TF2N][Li]), phenyl trifluoromethyl acetylacetonate lithium salt ([BTFA][Li]), hexafluoroacetylacetonate lithium salt ([HFA][Li]), thiophene trifluoromethyl acetylacetonate lithium salt ([TTFA][Li]), furan trifluoromethyl acetylacetonate lithium salt ([FTFA][Li]), and lithium hexafluorophosphate ([PF6][Li]).

[0008] Furthermore, in step 1), the molar ratio of the non-protonic ionic liquid having a tertiary amine group to the lithium salt of the fluorine-containing compound is 1:1; the reaction temperature is 25-60° C.; and the reaction time is 3-24 h.

[0009] Furthermore, in step 2), the crosslinking agent is one of p-dichlorobenzyl (DCX), p-dibromobenzyl (DBX), benzyl chloride (BC), and benzyl bromide (BB); the organic solvent is one of dichloromethane (DCM), trichloromethane (TCM), and dichloroethane (DCE); and the Lewis acid is one of aluminum chloride, ferric chloride, and zinc dichloride.

[0010] Furthermore, in step 2), the molar ratio of the hydrophobic bifunctional ionic liquid to the cross-linking agent is 1:1-7; the molar ratio of the hydrophobic bifunctional ionic liquid to the Lewis acid is 1:1-50; the reaction temperature is 25-100°C; and the reaction time is 4-24h.

[0011] The invention provides a hydrophobic bifunctional ionic liquid embedded hyper-crosslinked polymer prepared by the method.

[0012] Furthermore, the typical chemical structure of the polymer is shown in Formula I below:

[0013] The present invention also proposes an application of a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer, wherein the application is to use the obtained hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer to adsorb sulfur dioxide.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention uses a hydrophobic bifunctional ionic liquid as an embedded body, and by adjusting the ratio of the ionic liquid to the cross-linking agent connecting the building blocks, the ionic liquid is embedded in the hyper-cross-linked polymer composed of the cross-linking agent, thereby obtaining a type of hydrophobic bifunctional ionic liquid embedded hyper-cross-linked polymer. The hydrophobic bifunctional ionic liquid embedded hyper-cross-linked polymer prepared by the present invention has a hyper-cross-linked network structure, a large specific surface area, and contains abundant ionic liquid sites. It not only has a high hydrophobicity, but also has a good adsorption capacity for sulfur dioxide, and can significantly capture sulfur dioxide in flue gas; 2) The hydrophobic bifunctional ionic liquid prepared by the present invention embeds the high specific surface area, high total pore volume and exposed ionic liquid sites of the hyper-crosslinked polymer, which significantly improves the adsorption and separation capacity of sulfur dioxide, thereby achieving efficient, high-capacity, selective and reversible adsorption of sulfur dioxide under high humidity conditions; 3) When the molar ratio of the hydrophobic bifunctional ionic liquid to the crosslinking agent is 1:3, the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer has abundant pores and a BET surface area of ​​400-800 m 2 . g -1 The water contact angle is 140°, and the adsorption capacity is 2.7 mmol g under 5% SO2 conditions. -1 ; 4) The hydrophobic bifunctional ionic liquid hyper-crosslinked polymer of the present invention has good cyclic absorption stability; 5) The present invention has the advantages of simple preparation process, large specific surface area of ​​the prepared hydrophobic bifunctional ionic liquid super-crosslinked polymer, high sulfur dioxide capture capacity, etc., and has broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is an infrared spectrum of the hydrophobic bifunctional ionic liquid embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention; Figure 2 This is a scanning electron microscope photograph of the hydrophobic bifunctional ionic liquid of the present invention encapsulating the hyper-crosslinked polymer [PPZ][BTFA]-HCP; Figure 3 The dispersion mapping energy spectrum of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention; Figure 4 The X-ray photoelectron spectrum of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention; Figure 5 This is the thermogravimetric curve of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention; Figure 6 The water contact angle of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention; Figure 7 This is the nitrogen adsorption curve of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP under 77K conditions of the present invention; Figure 8 The water absorption capacity and 5% SO2 absorption capacity of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP at 293K of the present invention; Fig. 9 The water absorption capacity of the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP at 293K and the absorption capacity under different pressures of SO2; Fig.10 This is the cyclic adsorption curve of 5% SO2 under 293K conditions for the hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP of the present invention. DETAILED DESCRIPTION

[0016] The present invention will be further described below in conjunction with the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the described scope. Example 1

[0017] Synthesis of [PPZ][BTFA]-HCP 1) N-hydroxyethyl-N,N-dimethylpiperazine bromide ([PPZ][Br]) and equimolar bistrifluoromethylsulfonyl imide lithium salt ([BTFA][Li]) were mixed, and stirred for 3 hours under the condition of 60°C water as a solvent, and then the reacted material was cooled to room temperature to form a phase-separated, transparent and stable liquid, and the obtained organic phase was vacuum dried at 60°C for 12 hours to obtain [PPZ][BTFA] ionic liquid; 2) Under a nitrogen atmosphere, a reaction mixture containing [PPZ][BTFA] (10 mmol), benzyl dichloride (DCX) (30 mmol), dichloroethane (DCE) (100 ml) and ferric chloride (50 mmol) was stirred at 80°C for 24 hours, and then the reacted material was cooled to room temperature and filtered, and the precipitate obtained by filtration was washed with water and ethanol until the filtrate was clear and transparent. Finally, the solid was vacuum dried at 80°C for 24 hours. After drying, a hyper-crosslinked polymer [PPZ][BTFA]-HCP based on [PPZ][BTFA] was obtained.

[0018] Material Characterization: Depend on Figure 1 It can be seen that the FT-IR spectrum analysis of the sample shows that at 1610, 1501 and 1450 cm -1 A series of characteristic peaks at 1670 cm reflect the stretching vibration of the backbone benzene ring in the hydrophobic bifunctional ionic liquid hypercrosslinked polymer; -1 The adsorption peaks at 1176 and 960 cm-1 are attributed to the C=O vibration of the anion [BTFA]. -1 The absorption peak is the S=O stretching vibration of the anion.

[0019] Depend on Figure 2 SEM image analysis shows that there are abundant pores in the hydrophobic bifunctional ionic liquid hyper-cross-linked polymers.

[0020] Depend on Figure 3 From the EDS mapping image analysis, it can be seen that nitrogen, fluorine and oxygen elements are evenly dispersed throughout the polymer backbone, indicating that the hydrophobic bifunctional ionic liquid is evenly dispersed in the network of the hyper-cross-linked polymer.

[0021] Depend on Figure 4 X-ray photoelectron spectroscopy analysis revealed the presence of characteristic peaks of C 1s, N 1s, O 1s, and F 1s.

[0022] Depend on Figure 5Thermogravimetric analysis shows that the polymer begins to decompose as the temperature rises at around 360 °C, and the decomposition ends at 500 °C; the mass loss in the range of 360-500 °C can be attributed to the direct sublimation of the ionic liquid in the polymer. After calculation, it was found that the mass loss in this range is about 30%. The results show that the polymer has excellent thermal stability and can satisfy the desorption of SO2 by heating the adsorbent.

[0023] Depend on Figure 6 The water contact angle analysis showed that the water contact angle of the sample was 140.95°, indicating that the bifunctional ionic liquid-embedded hyper-cross-linked polymer had excellent hydrophobicity. Example 2

[0024] Nitrogen adsorption measurement: The absorption device adopts the BET method. The hydrophobic ionic liquid-embedded hyper-cross-linked polymer [PPZ][BTFA]-HCP synthesized in Example 1 is first subjected to vacuum degassing activation treatment, and then the gas adsorption temperature is controlled to 77K and the gas pressure is controlled to 0~100kPa. The equilibrium absorption capacity is measured and the data is recorded.

[0025] The nitrogen adsorption results are as follows Figure 7 As shown, it is converted into a BET specific surface area of ​​494 m 2 . g -1 . Example 3

[0026] Adsorption measurement of water vapor and 5% SO2 at 20 °C: The adsorption was carried out by weighing method. The hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer [PPZ][BTFA]-HCP synthesized in Example 1 and the comparison sample crosslinker direct self-crosslinked DCX-HCP were first subjected to vacuum degassing activation treatment, and then the gas adsorption temperature was controlled to 20 °C. The water vapor adsorption and SO2 adsorption were measured respectively, the adsorption capacity was weighed, and the data was recorded.

[0027] Depend on Figure 8 As shown, the cross-linked DCX-HCP without the participation of ionic liquid has a greater ability to adsorb water than SO2, while the super-cross-linked polymer adsorbent modified with hydrophobic bifunctional ionic liquid has a greater ability to adsorb SO2 than water vapor. Example 4

[0028] Adsorption measurement of SO2 at different pressures at 20°C: The adsorption was carried out by weighing method. The hydrophobic bifunctional ionic liquid-embedded hyper-cross-linked polymer [PPZ][BTFA]-HCP synthesized in Example 1 was first subjected to vacuum degassing activation treatment, and then the gas adsorption temperature was controlled to 20°C. The weighing adsorption capacity under different SO2 conditions was measured and the data was recorded.

[0029] Depend on Fig. 9 As shown, the results show that the higher the SO2 partial pressure, the greater the adsorption capacity, and the adsorption capacity under 100% conditions reaches 12mmol / g. Example 5

[0030] Cyclic adsorption measurement of 5% SO2 at 20°C: The adsorption and desorption device adopts a weighing method. The hydrophobic bifunctional ionic liquid-embedded hyper-cross-linked polymer [PPZ][BTFA]-HCP synthesized in Example 1 is first subjected to a vacuum degassing activation treatment, and then the gas adsorption temperature is controlled to 293K, the weighed adsorption capacity is measured, and the data is recorded.

[0031] The desorption was completed under vacuum at 333 K. The results of 33 cycles of absorption-desorption are shown in 10, indicating good cyclic absorption stability.

Claims

1. A method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer, characterized in that The steps include: 1) Preparation of bifunctional ionic liquid: a non-protonic ionic liquid having a tertiary amine group is mixed with a lithium salt of a fluorine-containing compound, and reacted under stirring of an aqueous phase. After the reaction is completed, the obtained organic phase liquid is vacuum dried, and the product collected after drying is the desired hydrophobic bifunctional ionic liquid; 2) Hypercrosslinking reaction: Under a nitrogen atmosphere, the hydrophobic bifunctional ionic liquid obtained in step 1) is mixed with a crosslinking agent in an organic solvent, and a Lewis acid is used as a catalyst to carry out a hypercrosslinking reaction under heating and stirring conditions. After the reaction is completed, the reacted material is cooled to room temperature and then filtered, and the precipitate obtained by filtration is washed until the filtrate is clear and transparent. Finally, the washed precipitate is dried. The product collected after drying is the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer to be prepared.

2. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer according to claim 1, characterized in that In step 1), the non-protonic ionic liquid having a tertiary amine group is one of N-hydroxyethyl-N,N-dimethylpiperazine bromide, N-ethyl-N,N,N',N'-tetramethylethylenediamine bromide, and N-butyl-triethylenediamine chloride; the lithium salt of the fluorine-containing compound is one of bistrifluoromethylsulfonyl imide lithium salt, phenyl trifluoromethyl acetylacetonate lithium salt, hexafluoroacetylacetonate lithium salt, thiophene trifluoromethyl acetylacetonate lithium salt, furan trifluoromethyl acetylacetonate lithium salt, and lithium hexafluorophosphate.

3. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer according to claim 1, characterized in that In step 1), the molar ratio of the non-protonic ionic liquid having a tertiary amine group to the lithium salt of the fluorine-containing compound is 1:1; the reaction temperature is 25-60° C.; and the reaction time is 3-24 h.

4. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer according to claim 1, characterized in that In step 2), the crosslinking agent is one of p-dichlorobenzyl, p-dibromobenzyl, benzyl chloride and benzyl bromide; the organic solvent is one of dichloromethane, chloroform and dichloroethane; and the Lewis acid is one of aluminum chloride, ferric chloride and zinc chloride.

5. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer according to claim 1, characterized in that In step 2), the molar ratio of the hydrophobic bifunctional ionic liquid to the cross-linking agent is 1:1-7; the molar ratio of the hydrophobic bifunctional ionic liquid to the Lewis acid is 1:1-50; the reaction temperature is 25-100°C; and the reaction time is 4-24h.

6. A hydrophobic bifunctional ionic liquid-embedded hyper-crosslinked polymer prepared by the method according to any one of claims 1 to 5.

7. The hydrophobic bifunctional ionic liquid embedded hyper-crosslinked polymer according to claim 6, characterized in that The typical chemical structure of the polymer is shown in Formula I below:

8. A use of a hydrophobic bifunctional ionic liquid to embed a hyper-crosslinked polymer as claimed in claim 6, characterized in that The application is to use the obtained hydrophobic bifunctional ionic liquid to embed the hyper-crosslinked polymer for adsorbing sulfur dioxide.

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