Hydrophobic bifunctional ionic liquid embedded supercrosslinked polymer, preparation method thereof and application of the polymer in adsorbing sulfur dioxide

Abstract

The application discloses a hydrophobic bifunctional ionic liquid embedded super-crosslinked polymer and a preparation method and application of the ionic liquid in adsorbing sulfur dioxide. A non-protic ionic liquid with a tertiary amine group is mixed with a lithium salt containing a fluorine compound, and the reaction is carried out under stirring in an aqueous phase. After the reaction is completed, the obtained organic phase liquid is vacuum dried. The collected product after drying is the required hydrophobic bifunctional ionic liquid. Under a nitrogen atmosphere, the hydrophobic bifunctional ionic liquid is mixed with a crosslinking agent in an organic solvent, a Lewis acid is used as a catalyst, and the super-crosslinking reaction is carried out under heating and stirring. After the reaction is completed, the reacted material is cooled to room temperature and filtered. The obtained precipitate is washed until the filtrate is clear and transparent. Finally, the precipitate after washing is dried, and the collected product after drying has the advantages of simple preparation process, large specific surface area of the prepared polymer, high sulfur dioxide capture capacity and wide market prospect.

Description

Technical Field

[0001] This invention belongs to the field of hydrophobic polymer synthesis technology, specifically relating to a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer, its preparation method, and its application in adsorbing sulfur dioxide. Background Technology

[0002] my country's coal resources have a relatively high sulfur content. During coal-fired power generation, sulfur dioxide (SO2) is formed, becoming a significant component of flue gas emissions. If not effectively treated, it is released into the atmosphere, increasing atmospheric SO2 concentration and contributing to acid rain. Therefore, SO2 emissions not only threaten public health but also hinder economic development. Limestone gypsum is commonly used as an SO2 absorbent in industry, but it is non-renewable and generates large amounts of low-grade gypsum, causing solid waste pollution. Therefore, developing novel adsorbents for efficient SO2 adsorption is crucial.

[0003] Currently, ionic liquids have attracted attention as a novel 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 imidazole-based ionic liquids can effectively capture SO2 at low concentrations (J. Am. Chem. Soc., 2011, 133 (31), 11916-11919), and Cui et al. reported that hydroxypyridine anionic ionic liquids can effectively capture SO2 (Ind. Eng. Chem. Res. 2020, 59, 49, 21522–21529). However, most ionic liquids are hydrophilic absorbents, and their SO2 absorption capacity decreases under conditions of water-containing flue gas. In addition, the high viscosity and low mass transfer of ionic liquids hinder their application.

[0004] Solid adsorbents based on ionic liquids (such as polyionic liquids) have attracted attention because they not only possess the advantages of ionic liquids but also overcome the shortcomings of pure ionic liquids. However, conventional polyionic liquids are usually non-porous, and their adsorption efficiency needs improvement. Ionic liquid-hypercrosslinked polymer adsorbents are prepared by combining ionic liquids with hypercrosslinked polymers prepared through the Friedel-Crafts reaction of crosslinking agents. These adsorbents, due to their large specific surface area, porosity, and simple preparation, have been used to adsorb carbon dioxide gas (Chem. Eng. J. 2024, 489 151102). However, there are few reports on their use for adsorbing gases such as SO2 under high humidity conditions. Therefore, developing novel composite adsorbents based on ionic liquids through structural adjustment to improve SO2 adsorption capacity under humid conditions is of great significance. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of this invention is to provide a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer, its preparation method, and its application in adsorbing sulfur dioxide. The hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer obtained by this invention has a hypercrosslinked network structure. Utilizing its high specific surface area, high total pore volume, and exposed ionic liquid sites, it significantly improves 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 objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer includes the following steps:

[0008] 1) Preparation of bifunctional ionic liquids: A nonprotic ionic liquid with tertiary amine groups is mixed with lithium salt containing fluorine compounds and reacted under aqueous stirring conditions. After the reaction is completed, the obtained organic phase liquid is vacuum dried. The product collected after drying is the desired hydrophobic bifunctional ionic liquid.

[0009] 2) Hypercrosslinking reaction: Under a nitrogen atmosphere, the hydrophobic bifunctional ionic liquid obtained in step 1) is mixed with the crosslinking agent in an organic solvent. A Lewis acid is used as a catalyst, and the hypercrosslinking reaction is carried out under heating and stirring conditions. After the reaction is completed, the reacted material is cooled to room temperature and then filtered. 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.

[0010] Further, in step 1), the aprotic ionic liquid with 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]), or N-butyl-triethylenediamine chloride ([DABCO][Cl]); the lithium salt containing fluorine is one of bis(trifluoromethanesulfonyl)imide lithium salt ([TF2N][Li]), phenyltrifluoromethylacetylacetone lithium salt ([BTFA][Li]), hexafluoroacetylacetone lithium salt ([HFA][Li]), thiophenetrifluoromethylacetylacetone lithium salt ([TTFA][Li]), furantrifluoromethylacetylacetone lithium salt ([FTFA][Li]), or lithium hexafluorophosphate ([PF6][Li]).

[0011] Further, in step 1), the molar ratio of the aprotic ionic liquid with tertiary amine groups to the lithium salt containing fluorine compounds is 1:1; the reaction temperature is 25~60°C; and the reaction time is 3~24h.

[0012] Further, 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.

[0013] Further, in step 2), the molar ratio of the hydrophobic bifunctional ionic liquid to the crosslinking agent is 1:1 to 7; the molar ratio of the hydrophobic bifunctional ionic liquid to the Lewis acid is 1:1 to 50; the reaction temperature is 25 to 100°C; and the reaction time is 4 to 24 hours.

[0014] This invention proposes a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer prepared using the method described above.

[0015] Furthermore, the typical chemical structural formula of this polymer is shown in Formula I below:

[0016]

[0017] The present invention also proposes an application of a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer, wherein the obtained hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer is used to adsorb sulfur dioxide.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1) This invention uses a hydrophobic bifunctional ionic liquid as the embedded body. By adjusting the ratio of the ionic liquid to the crosslinking agent connecting building blocks, the ionic liquid is embedded in a hypercrosslinked polymer composed of a crosslinking agent, thus obtaining a type of hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer. The hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer prepared by this invention has a hypercrosslinked network structure, a large specific surface area, and contains abundant ionic liquid sites. It not only has high hydrophobicity but also has a good adsorption capacity for sulfur dioxide, and can significantly capture sulfur dioxide in flue gas.

[0020] 2) The hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer prepared in this invention has a high specific surface area, high total pore volume, and exposed ionic liquid sites, 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.

[0021] 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 exhibits abundant pores, resulting in a BET surface area of ​​400-800 m². 2 . g -1With a water contact angle of 140°, the adsorption capacity was 2.7 mmol g under 5% SO2 conditions. -1 ;

[0022] 4) The hydrophobic bifunctional ionic liquid hypercrosslinked polymer of the present invention exhibits good cyclic absorption stability;

[0023] 5) The present invention has the advantages of simple preparation process, large specific surface area and high sulfur dioxide capture capacity of the prepared hydrophobic bifunctional ionic liquid hypercrosslinked polymer, and has broad market prospects. Attached Figure Description

[0024] Figure 1 The infrared spectrum of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention is shown below.

[0025] Figure 2 This is a scanning electron microscope image of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of the present invention;

[0026] Figure 3 The dispersive mapping energy spectrum of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention;

[0027] Figure 4 X-ray photoelectron spectroscopy of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention;

[0028] Figure 5 Thermogravimetric curve of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention;

[0029] Figure 6 The water contact angle of the hydrophobic bifunctional ionic liquid-encapsulated hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention;

[0030] Figure 7 The nitrogen adsorption curve of the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention is shown at 77K.

[0031] Figure 8 The water absorption capacity and 5% SO2 absorption capacity of the hydrophobic bifunctional ionic liquid-encapsulated hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention at 293K;

[0032] Figure 9The water absorption capacity of the hydrophobic bifunctional ionic liquid-encapsulated hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention at 293K and the absorption capacity of SO2 under different pressures are shown.

[0033] Figure 10 The cyclic adsorption curve of the hydrophobic bifunctional ionic liquid-encapsulated hypercrosslinked polymer [PPZ][BTFA]-HCP of this invention at 293K with 5% SO2 is shown. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited to the scope described. Example 1

[0035] Synthesis of [PPZ][BTFA]-HCP

[0036] 1) N-hydroxyethyl-N,N-dimethylpiperazine bromide ([PPZ][Br]) was mixed with an equimolar amount of lithium bis(trifluoromethanesulfonylimide) ([BTFA][Li]), and stirred for 3 hours at 60°C with water as the solvent. Then, the reacted material was cooled to room temperature to form a phase-separated, transparent and stable liquid. The obtained organic phase was vacuum dried at 60°C for 12 hours to obtain the [PPZ][BTFA] ionic liquid.

[0037] 2) Under a nitrogen atmosphere, the reaction mixture containing [PPZ][BTFA] (10 mmol), p-dichlorobenzyl (DCX) (30 mmol), dichloroethane (DCE) (100 ml) and ferric chloride (50 mmol) was stirred at 80°C for 24 hours. After the reaction mixture was cooled to room temperature, it was filtered. 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, the hypercrosslinked polymer [PPZ][BTFA]-HCP based on [PPZ][BTFA] was obtained.

[0038] Material characterization:

[0039] Depend on Figure 1 It can be seen that the FT-IR spectral analysis of the sample shows that the wavelengths at 1610, 1501, and 1450 cm⁻¹ are within the range of 1610, 1501, and 1450 cm⁻¹. -1 A series of characteristic peaks at 1670 cm⁻¹ reflect the stretching vibrations of the skeletal 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 at that point is due to the S=O stretching vibration of the anion.

[0040] Depend on Figure 2SEM image analysis revealed that the hydrophobic bifunctional ionic liquid hypercrosslinked polymers all have abundant pores.

[0041] Depend on Figure 3 EDS mapping image analysis shows that nitrogen, fluorine, and oxygen elements are uniformly dispersed throughout the polymer backbone, indicating that the hydrophobic bifunctional ionic liquid is uniformly dispersed in the network of the hypercrosslinked polymer.

[0042] Depend on Figure 4 X-ray photoelectron spectroscopy analysis revealed the presence of characteristic peaks for C 1s, N 1s, O 1s, and F 1s.

[0043] Depend on Figure 5 Thermogravimetric analysis revealed that the polymer begins to decompose at around 360 °C with increasing temperature, and the decomposition ends at 500 °C. The mass loss in the 360–500 °C range can be attributed to the direct sublimation of the ionic liquid within the polymer. Calculations showed that the mass loss in this range is approximately 30%. These results indicate that the polymer possesses excellent thermal stability, and SO2 desorption can be achieved by heating the adsorbent.

[0044] Depend on Figure 6 Water contact angle analysis showed that the water contact angle of the sample was 140.95°, indicating that the bifunctional ionic liquid-embedded hypercrosslinked polymer has excellent hydrophobicity. Example 2

[0045] Nitrogen adsorption measurement: The absorption device adopts the BET method. First, the hydrophobic ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP synthesized in Example 1 is subjected to vacuum degassing and activation treatment. Then, the gas adsorption temperature is controlled at 77K and the gas pressure is 0~100kPa. The equilibrium absorption capacity is measured and the data is recorded.

[0046] Nitrogen adsorption results are as follows Figure 7 As shown, the BET specific surface area is 494 m². 2 . g -1 . Example 3

[0047] Adsorption measurements of water vapor and 5% SO2 at 20 °C: Adsorption was performed by weighing. First, the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP synthesized in Example 1 and the control sample crosslinking agent directly self-crosslinked DCX-HCP were subjected to vacuum degassing activation treatment. Then, the gas adsorption temperature was controlled at 20 °C, and the adsorption of water vapor and SO2 were measured respectively. The adsorption capacity was weighed and the data were recorded.

[0048] Depend on Figure 8As shown, the cross-linking agent without ionic liquid participation, DCX-HCP, has a greater adsorption capacity for moisture than SO2, while the hypercross-linked polymer adsorbent modified with hydrophobic bifunctional ionic liquid has a greater adsorption capacity for SO2 than for water vapor. Example 4

[0049] SO2 adsorption was measured under different pressures at 20 °C: The adsorption was performed by weighing. First, the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP synthesized in Example 1 was subjected to vacuum degassing and activation treatment. Then, the gas adsorption temperature was controlled at 20 °C, and the adsorption capacity under different SO2 conditions was measured and the data were recorded.

[0050] Depend on Figure 9 As shown, the results indicate that the higher the partial pressure of SO2, the greater the adsorption capacity, with an adsorption capacity of 12 mmol / g under 100% conditions. Example 5

[0051] Cyclic adsorption measurement of 5% SO2 at 20 ℃: The adsorption and desorption device adopted the weighing method. First, the hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer [PPZ][BTFA]-HCP synthesized in Example 1 was subjected to vacuum degassing activation treatment. Then, the gas adsorption temperature was controlled at 293K, the adsorption capacity was measured by weighing, and the data were recorded.

[0052] Desorption was performed under vacuum at 333 K and was completed. The results of 33 cycles of absorption-desorption are shown in Figure 10, indicating good stability of the cyclic absorption.

Claims

1. A method for preparing a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer, characterized in that... Includes the following steps: 1) Preparation of bifunctional ionic liquids: A nonprotic ionic liquid with tertiary amine groups is mixed with lithium salt containing fluorine compounds and reacted under aqueous stirring conditions. After the reaction is completed, the obtained organic phase liquid is vacuum dried. The product collected after drying is the desired hydrophobic bifunctional ionic liquid. In step 1), the aprotic ionic liquid with a tertiary amine group is N-hydroxyethyl-N,N-dimethylpiperazine bromide; the lithium salt containing fluorine is lithium benzoyltrifluoroacetylacetonate. 2) Hypercrosslinking reaction: Under a nitrogen atmosphere, the hydrophobic bifunctional ionic liquid obtained in step 1) is mixed with the crosslinking agent in an organic solvent. A Lewis acid is used as a catalyst, and the hypercrosslinking reaction is carried out under heating and stirring conditions. After the reaction is completed, the reacted material is cooled to room temperature and then filtered. 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. In step 2), the crosslinking agent is either p-dichlorobenzyl or p-dibromobenzyl.

2. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer according to claim 1, characterized in that... In step 1), the molar ratio of the aprotic ionic liquid with tertiary amine groups to the lithium salt containing fluorine compounds is 1:1; the reaction temperature is 25~60°C; and the reaction time is 3~24h.

3. The method for preparing a hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer according to claim 1, characterized in that... In step 2), the organic solvent is one of dichloromethane, trichloromethane, or dichloroethane; and the Lewis acid is one of aluminum chloride, ferric chloride, or zinc chloride.

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

5. A hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer prepared by the method according to any one of claims 1-4.

6. The hydrophobic bifunctional ionic liquid-embedded hypercrosslinked polymer according to claim 5, characterized in that... The chemical structural formula of the polymer is shown in Formula I below: Formula I.

7. An application of the hydrophobic bifunctional ionic liquid-encapsulated hypercrosslinked polymer as described in claim 5, characterized in that... The application involves using the obtained hydrophobic bifunctional ionic liquid to encapsulate the hypercrosslinked polymer for the adsorption of sulfur dioxide.

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