Preparation method of alkaline functionalized I-type porous liquid and application of alkaline functionalized I-type porous liquid in CO2 separation and conversion

Abstract

The invention discloses a preparation method and application of an alkaline functionalized I-type porous liquid. The preparation method specifically comprises the following steps: carrying out equimolar acid-base neutralization reaction on an acid containing an aniline structural unit and an inorganic base to obtain an ionic salt; the preparation method comprises the following steps: grafting an ionic salt to the surface of ZIF-90 through a condensation reaction of aldehyde and amine to obtain a ZIF-90 grafted material; and finally, mixing the ZIF-90 grafting material with crown ether according to a certain proportion to obtain the porous liquid. The porous liquid obtained by the method has permanent pores, is large in CO2 absorption amount and high in CO2 / CH4 selectivity, can be used for separation and conversion of CO2 in flue gas or biogas, and is a CO2 absorbent with important application prospects. In addition, it can also be used as a catalyst to catalyze the reaction of CO2 and epoxy compounds and to convert them into cyclic carbonates.

Description

Technical Field

[0001] This invention relates to a method for preparing an alkaline functionalized type I porous liquid and its application in CO2 separation and conversion, belonging to the field of chemical separation. Background Technology

[0002] Excessive emissions of the greenhouse gas carbon dioxide (CO2) have caused various serious environmental problems, including global warming, which may ultimately threaten human survival and development. Therefore, effective CO2 capture and separation is of great significance for the efficient use of energy and for solving environmental problems such as the greenhouse effect.

[0003] Among numerous carbon capture materials, porous liquids (PLs) are a novel type of material that combines the permanent porosity of solid adsorbents with the fluidity of liquids. They overcome the problems of structural performance loss and slow mass and heat transfer inherent in solid adsorbents, while also possessing the advantages of liquid adsorbents such as easy pipeline transport and the high specific surface area and high porosity of solid adsorbents. Therefore, porous liquids show great potential in gas separation, capture, and catalysis. Currently, porous liquids can be classified into four different types based on their composition. Type I consists of a rigid host with a cavity structure and possesses its own fluidity; Type II and Type III are formed by the dissolution and dispersion of rigid host molecules with rigid cavities in sterically hindered solvents, respectively; and Type IV refers to molten salts with inherent pores. However, porous liquids still face challenges such as difficulties in structural functionalization and the tendency for porous host units to collapse, making the construction and maintenance of porous cavity structures challenging, resulting in limited reported examples to date. Therefore, developing novel porous liquids for CO2 adsorption and separation is essential.

[0004] Currently, several porous liquids for CO2 adsorption have been reported in the literature. In 2015, Zhang et al. first modified the surface of hollow silica spheres with organosilanes containing sulfonic acid groups, and then prepared hollow SiO2 porous liquids (HS-liquids) through ion exchange with poly(ethylene glycol) 4-nonylphenyl ether-3-sulfopropyl potassium salt (PEGS), thus preliminarily exploring the CO2 capture performance. In 2017, Li et al. prepared porous carbon liquids (HCS-liquids) using the same synthesis strategy. At 298 K and 1 bar, the CO2 absorption capacity was 0.445 wt%, which was much higher than that of pure sterically hindered solvent PEGS (0.261 wt%). In 2020, Jie et al. combined anionic porous organic cage molecules with crown ethers using a supramolecular complexation strategy to obtain porous liquids (18-C-6-PL and 15-C-5-PL). At 298 K and 10 bar, the CO2 absorbances of 18-C-6-PL and 15-C-5-PL were 0.429 and 0.375 mmol / g, respectively. In 2021, Zou et al. synthesized an imidazole-functionalized cationic framework (Deim-UiO-66) by ionizing the ligand of UIO-66, and then prepared a porous liquid (Im-UiO-PL) using an ion exchange strategy, achieving a CO2 absorbance of 5.93 mmol / g (298 K, 9 bar). In 2023, Dinker et al. used an imidazole bromide ionic liquid (IL-Br) as a sterically hindered solvent to disperse metal-organic polyhedra (RhMOP) in IL-Br, obtaining a type III porous ionic liquid (PIL-RhMOP). By grafting suitable organic molecules onto RhMOP, making them soluble in IL-Br, type II porous ionic liquids PIL-diz and PIL-CF3-Py were obtained. - RhMOP had CO2 adsorption capacities of 0.133 and 0.121 mmol / g (273 K, 1 bar), which were higher than those of PIL-RhMOP (0.088 mmol / g). -1 The synthesis of type I porous liquids is relatively rare. These liquids require specific grafting sites or structures for sterically hindered solvents, such as preventing the grafted organic oligomer chains from entering the pores or cavities of the porous host, and maintaining a homogeneous and stable liquid state at room temperature. Therefore, exploring a new strategy for synthesizing type I porous liquids has significant theoretical and practical implications.

[0005] This invention reports a method for preparing an alkaline functionalized type I porous liquid. Structural units with active sites (such as N-sites and O-sites) that strongly interact with CO2 are grafted onto the surface of ZIF-90, and then mixed with crown ether in a certain proportion to obtain the porous liquid. This type of porous liquid possesses fluidity and a stable pore structure, making it well-suited for the separation and conversion of CO2 in flue gas or biogas. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an alkaline functionalized type I porous liquid, which can be used for the adsorption, separation and conversion of CO2.

[0007] The technical solution of the present invention is as follows:

[0008] A method for preparing an alkaline functionalized type I porous liquid is as follows: (I) Preparation of ionic salt: A structural unit containing aniline is reacted with sodium hydroxide / potassium hydroxide / lithium hydroxide in a molar ratio of 1:1 for acid-base neutralization reaction. The reaction temperature is room temperature to 40℃, and the reaction time is 4 to 12 h. After the reaction is completed, the solvent is removed by rotary evaporation, and then water is removed using a vacuum pump to obtain the ionic salt. (II) Preparation of ZIF-90 grafted material: The ionic salt prepared above is dissolved in methanol, ZIF-90 is added, and an aldehyde-amine condensation reaction is carried out. The reaction temperature is 40 to 80℃, and the reaction time is 24 to 48 h. After the reaction is completed, the product is collected by centrifugation and washed with methanol. Finally, the washed product is dried, and the solid obtained is the ZIF-90 grafted material. (III) Preparation method of ZIF-90 porous liquid: The ZIF-90 graft material prepared above is mixed with crown ether at a mass ratio of 1:1 to 1:5 and stirred at room temperature to 50°C for 4 hours. The product obtained is ZIF-90 porous liquid.

[0009] The structural formulas of the above-mentioned ionic salts are as follows:

[0010]

[0011] This invention proposes a method for preparing an alkaline functionalized type I porous liquid. The resulting porous liquid exhibits good fluidity and a stable pore structure, while also demonstrating excellent CO2 absorption capabilities. It shows significant promise for the selective separation of CO2 in flue gas or biogas. Furthermore, it can be used as a catalyst to catalyze the reaction of CO2 with epoxides and convert it into cyclic carbonates. Attached Figure Description

[0012] Figure 1 XRD and IR spectra of ZIF-90, ZIF-90-NNa, and ZIF-90-NNa-PL.

[0013] Figure 2ρ represents the density of ZIF-90 nanocrystals in PhNNa-IL colloidal solution. Detailed Implementation

[0014] The present invention will be further illustrated by the following examples.

[0015] Example 1: 2-Imidazole formaldehyde (60 mmol, 5.77 g) was dissolved in methanol (100 ml), and then an aqueous solution of triethylamine (60 mmol, 6.07 g) and zinc acetate dihydrate (15 mmol, 3.29 g) (20 ml) was added. The reaction was carried out at 50 °C for 2 h. After the reaction was completed, the solid product was collected by centrifugation and washed with methanol. The product was then dried under vacuum to obtain ZIF-90. 4-Aminophthalimide (10 mmol, 1.62 g) and sodium hydroxide (10 mmol, 0.4 g) were dissolved in methanol (50 ml). The mixture was stirred at room temperature for 2 h. After the reaction was completed, the solvent was removed by rotary evaporation, and then water was removed using a vacuum pump to obtain sodium 4-aminophthalimide (Ph-NNa). The Ph-NNa was dissolved in methanol (50 ml), and ZIF-90 (11 mmol, 2.83 g) was added. The reaction was carried out at 60 °C for 36 h. After the reaction was completed, the product was collected by centrifugation and washed with methanol. Finally, the washed product was dried under vacuum to obtain the solid ZIF-90-NNa. ZIF-90-NNa (1 g) and 15-crown ether-5 (1.5 g) were weighed and added to a screw-top flask and stirred at room temperature for 2 h to obtain the liquid ZIF-90-NNa-PL.

[0016] The synthesis of the materials was confirmed by X-ray diffraction (XRD) and infrared spectroscopy (IR). The XRD patterns of ZIF-90, ZIF-90-NNa, and ZIF-90-NNa-PL are shown below. Figure 1 a, IR spectrum see Figure 1 b. In addition, through density measurement ( Figure 2 This confirmed that the pores of ZIF-90 were not occupied. At 303.2 K, the density of the porous liquid ZIF-90-NNa-PL was 1.2832 g·cm³. -3 The viscosity was 0.6815 Pa·s. 1.0 g of ZIF-90-NNa-PL was placed in a glass bottle, and the solubility of CO2 was determined using a gas absorption apparatus. At 303.2 K and 1.0 bar, the CO2 adsorption capacity of ZIF-90-NNa-PL was 0.5221 mol / kg, and the IAST selectivity for CO2 / CH4 (50 / 50) was 23.3.

[0017] The porous liquid ZIF-90-NNa-PL was used as a catalyst for the cycloaddition reaction of CO2 with epoxides to generate cyclic carbonates: epichlorohydrin (2 mmol) and catalyst (0.1 g) were placed in a Schlenk tube connected to a CO2 balloon (0.1 MPa). The reaction tube was then placed in a magnetically stirred tube reactor and reacted at 80 °C for 24 h. After the reaction, 3 mL x 5 ethyl acetate was added to the reaction system to extract the liquid phase. All extracts were combined and analyzed by chromatography; the solid was ZIF-90-NNa. The yield of cyclic carbonate was determined by gas chromatography and gas chromatography-mass spectrometry (GC-MS), and the yield of cyclochloropropene carbonate was 93.7%. The supernatant after centrifugation was extracted with water to obtain 15-crown ether-5. ZIF-90-NNa and 15-crown ether-5 were then physically mixed to obtain ZIF-90-NNa. a -PL, the resulting porous liquid can be recycled.

[0018] Example 2: 10 mmol (1.62 g) of 4-aminophthalimide and 10 mmol (0.4 g) of sodium hydroxide were added to methanol (50 ml). The mixture was stirred at room temperature for 2 h. After the reaction was complete, the solvent was removed by rotary evaporation, and then water was removed using a vacuum pump to obtain the product, sodium 4-aminophthalimide (Ph-NNa). 1 g of Ph-NNa was dissolved in methanol (50 ml), and 3 g of 15-crown ether-5 was added. The mixture was reacted at 50 °C for 4 h. After the reaction was complete, the methanol was removed by rotary evaporation, and water was removed using a vacuum pump at 60 °C for 2 h to obtain the ionic liquid Ph-NNa-IL.

[0019] 1.0 g of Ph-NNa-IL was placed in a glass bottle, and the solubility of CO2 was determined using an absorption apparatus. At 303 K and 1.0 bar, the CO2 adsorption capacity of Ph-NNa-IL was 0.3049 mol / kg. Ph-NNa-IL was used as a catalyst for the cycloaddition reaction of CO2 with epoxides to generate cyclic carbonates. Epichlorohydrin (2 mmol) and the catalyst (0.1 g) were placed in a Schlenk tube connected to a CO2 balloon (0.1 MPa). The reaction tube was then placed in a magnetically stirred tube reactor and reacted at 80 °C for 24 h. After the reaction, 3 mL x 5 ethyl acetate was added to the reaction system to extract the liquid phase, and the extract was analyzed by chromatography. The yield of the cyclic carbonate was determined using gas chromatography and gas chromatography-mass spectrometry (GC-MS), and the yield of cyclochloropropene carbonate was 69%.

[0020] Examples 3-14: Following the conditions in Example 1, the grafting material, inorganic base, and steric solvent were changed. The specific results are shown in the table below:

[0021]

[0022] Examples 15-22: Following the conditions in Example 2, the grafting material, inorganic base, and steric solvent were changed. The specific results are shown in the table below:

[0023]

[0024] By comparing the CO2 solubility of porous liquids and ionic liquids in the examples, it can be seen that the CO2 adsorption capacity of porous liquids is significantly improved compared to ionic liquids, which proves the existence of porosity in porous liquids. Similarly, when porous liquids are used as catalysts for the cycloaddition reaction of CO2 with epoxides, the yield of cyclic carbonates is also higher than that of ionic liquids.

[0025] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing an alkaline functionalized type I porous liquid and its use for CO2 separation and conversion, the preparation process consists of the following four steps: (1) an acid containing aniline structural units and an inorganic base are neutralized by an acid-base reaction to obtain an ionic salt; (2) the ionic salt is grafted onto the ZIF-90 surface by a condensation reaction of aldehyde and amine; (3) the ZIF-90 graft material is mixed with crown ether in a specific ratio to obtain a porous liquid.

2. The method according to claim 1, characterized in that: The aniline-containing structural unit described in step (1) is subjected to an acid-base neutralization reaction with an inorganic base at a molar ratio of 1:

1. The reaction temperature is room temperature to 40°C, and the reaction time is 4 to 12 hours. After the reaction is completed, the ionic salt is obtained by drying and removing water or organic solvent.

3. The method according to claim 1, characterized in that: The acid containing the aniline structural unit mentioned in step (1) is preferably one of 4-aminophthalimide, p-aminophenol, 2-amino-5-hydroxypyridine, p-aminobenzoic acid, 5-aminopyridine-2-carboxylic acid, 4-amino-3-fluorophenol, and 4-amino-3-methylphenol, with the following structural formula:

4. The method according to claim 1, characterized in that: The inorganic base mentioned in step (1) is preferably one of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

5. The method according to claim 1, characterized in that: The solvent used in the condensation reaction in step (2) is methanol or ethanol, the reaction temperature is 40-80℃, and the reaction time is 24-48h. After the reaction is completed, the product is collected by centrifugation, washed with methanol or ethanol, and then vacuum dried to obtain ZIF-90 grafted material.

6. The method according to claim 1, characterized in that: In step (3), the mass ratio of ZIF-90 graft material to crown ether is 1:1 to 1:5, the reaction temperature is room temperature to 50℃, and the reaction time is 2 to 6 hours.

7. The method according to claim 1, characterized in that: The crown ether mentioned in step (3) is preferably one of 18-crown-6, 15-crown-5, 12-crown-4, and benzo-18-crown-6-ether, with the following structural formula:

8. An alkaline functionalized type I porous liquid according to claim 1, which is mainly used in the field of CO2 separation and conversion in flue gas or biogas.

9. The CO2 conversion according to claim 8 is mainly used for the cycloaddition reaction of CO2, with a reaction temperature of 60-80℃ and a reaction time of 12-24h.

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