A composite adsorbent, its preparation method and application

Abstract

The present invention discloses a composite adsorbent, a preparation method thereof and an application thereof, which comprises metal-organic framework nanoparticles having permanent pores and a nanoscale ionic liquid layer self-assembled on the outer surface of the metal-organic framework nanoparticles having permanent pores. The composite adsorbent in the present invention has excellent gas adsorption capacity and can realize the application of mixed gas adsorption and separation.

Description

Technical Field

[0001] The present invention relates to a composite adsorbent, a preparation method thereof and an application thereof, belonging to the technical field of chemical separation. Background Art

[0002] Common gas adsorbents in industry include zeolite molecular sieves, activated carbon, ionic liquids, and active organic solvents, etc. Ionic liquids are liquid salts composed of anions and cations, with high stability and extremely low volatility, and have great application value in the fields of gas adsorption and capture such as carbon dioxide (S. Zeng, X. Zhang, L. Bai, X. Zhang, H. Wang, J. Wang, D. Bao, M. Li, X. Liu, S. Zhang, Chemical Reviews 2017, 117, 9625). However, due to the high viscosity of conventional ionic liquids, limited gas-liquid interfaces, slow gas adsorption and diffusion rates, low absolute adsorption amounts, large amounts of solvents required for adsorption, and high costs, it is not conducive to large-scale applications (W. Fam, J. Mansouri, H. Li, J. Hou, V. Chen, ACS Appl. Mater. Interfaces 2018, 10, 7389). Therefore, the development of efficient adsorbents is of great significance for practical industrial applications. Summary of the Invention

[0003] The purpose of the present invention is to provide a composite adsorbent with excellent gas adsorption performance, a preparation method thereof and an application thereof, which can realize the application of mixed gas adsorption and separation.

[0004] The present invention first provides a composite adsorbent, comprising: metal-organic framework nanoparticles with permanent pores and a uniform ultra-thin nano-scale ionic liquid layer self-assembled on the outer surface of the metal-organic framework nanoparticles with permanent pores.

[0005] Wherein the ionic liquid layer has a thickness of 0.5 - 30 nm.

[0006] Wherein the particle size of the metal-organic framework nanoparticles is 10 - 1000 nm, the maximum pore diameter is located at 1.0 - 30 nm, and the specific surface area is greater than or equal to 1500 m 2 / g.

[0007] Wherein the ionic liquid includes but is not limited to 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, etc.

[0008] Among them, the metal-organic framework materials include but are not limited to MOF-808, UiO-66, ZIF-8, MIL-101, MOF-74, NU-1000.

[0009] On the other hand, the present invention provides a method for preparing the above composite adsorbent, comprising the following steps:

[0010] (1) Take a certain mass of ionic liquid and dissolve it in one or several mixed solvents of organic solvents such as methanol, ethanol, dichloromethane, toluene, N,N-dimethylformamide to form an ionic liquid solution with a mass fraction of 0.5%-30%.

[0011] (2) Disperse the pre-prepared nano metal-organic framework material in the above ionic liquid solution according to the mass ratio of ionic liquid to metal-organic framework material of 0.5-20:1, and stir at room temperature for 12-48 h.

[0012] (3) Centrifuge the above mixed system at a speed of 10000-20000 revolutions per minute for 2-15 minutes, and collect the solid.

[0013] (4) Vacuum-dry the solid at a temperature of 60-150 °C for 12-48 h to obtain an ionic liquid molecular layer with a certain thickness loaded on the surface of the metal-organic framework material nanoparticles.

[0014] On the other hand, the present invention provides the application of the above composite adsorbent in the adsorption and separation of mixed gases such as carbon dioxide / methane, carbon dioxide / nitrogen, etc.

[0015] Advantages of the present invention: By introducing an ultrathin ionic liquid coating on the surface of metal-organic framework nanoparticles with permanent pores, a composite adsorbent with a carbon dioxide adsorption capacity far exceeding that of the two parent raw materials is prepared. The composite adsorbent realizes the improvement of carbon dioxide capacity under the condition of using as little expensive ionic liquid as possible, and significantly reduces the cost of the adsorbent. Description of the Drawings

[0016] The attached Figure 6 drawings of the present invention:

[0017] Figure 1 is the X-ray powder diffraction pattern of the composite adsorbent 1 in Example 1;

[0018] Figure 2 is the high-resolution transmission electron microscopy image of the composite adsorbent 1 in Example 1;

[0019] Figure 3 is the adsorption isotherm of the composite adsorbent 1 for carbon dioxide at 298 K in Example 1;

[0020] Figure 4It is the dynamic breakthrough curve of composite adsorbent 1 in Example 1 for the carbon dioxide / nitrogen mixed gas at 298K;

[0021] Figure 5 It is the adsorption isotherm of composite adsorbent 2 in Example 2 for carbon dioxide at 298K;

[0022] Figure 6 It is the adsorption isotherm of composite adsorbent 3 in Example 3 for carbon dioxide at 298K. Detailed implementation manners

[0023] The following further illustrates the specific implementation of the present invention in conjunction with the examples and the drawings, but the implementation manners of the present invention are not limited thereto.

[0024] Example 1. Preparation and adsorption separation application of composite adsorbent 1, MOF-808 loaded with a 2.8 nm thick layer of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid

[0025] 150 mg of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide was dissolved in 10 ml of methanol to form a solution with a mass fraction of 2%. 150 mg of pre-prepared 500 nm MOF-808 metal-organic framework nanoparticles (J. Jiang, F. Gándara, Y. B. Zhang, K. Na, O. M. Yaghi, W. G. Klemperer, J. Am. Chem. Soc. 2014, 136, 12844, the mass ratio of ionic liquid to metal-organic framework material is 1:1) was added thereto, and stirred at room temperature for 24 h. The solid was collected by centrifugation at 15000 revolutions per minute for 5 minutes, and vacuum dried at 60 °C for 24 h to obtain the target adsorbent 1.

[0026] 0.13 g of composite adsorbent 1 was filled into a stainless steel column with a length of 150 mm and an inner diameter of 2.1 mm to make a fixed bed adsorbent. 2 ml / min -1 CO2 / N2 (volume ratio 15:85) mixed gas was introduced for testing, and a gas chromatograph was used to record the concentration of the effluent.

[0027] Example 2. Preparation of composite adsorbent 2, MOF-74 loaded with a 5.0 nm layer of 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid

[0028] Dissolve 300 mg of 1-butyl-3-methylimidazolium hexafluorophosphate in 10 ml of ethanol to form a solution with a mass fraction of 3%. Add 150 mg of pre-prepared 300-nm MOF-74 metal-organic framework nanoparticles (J.E. Bachman, Z.P. Smith, T. Li, T. Xu, J.R. Long. Nat. Mater. 2016, 15, 845-849, the mass ratio of ionic liquid to metal-organic framework material is 2) into it, and stir at room temperature for 20 h. Centrifuge at 12,000 revolutions per minute for 8 minutes to collect the solid, and dry it in vacuum at 80 °C for 12 h to obtain the target adsorbent 2.

[0029] Example 3. Preparation of composite adsorbent 3, UiO-66 loaded with a 20-nm 1-butyl-3-methylimidazolium hexafluorophosphate ionic liquid layer

[0030] Dissolve 1500 mg of 1-ethyl-3-methylimidazolium tetrafluoroborate in 10 ml of N,N-dimethylformamide to form a solution with a mass fraction of 16%. Add 150 mg of pre-prepared 200-nm UiO-66 metal-organic framework nanoparticles (H.R. Abid, H. Tian, H.-M. Ang, M.O. Tade, C.E. Buckley, S. Wang, Chem. Eng. J. 2012, 187, 415, the mass ratio of ionic liquid to metal-organic framework material is 10) into it, and stir at room temperature for 30 h. Centrifuge at 12,000 revolutions per minute for 10 minutes to collect the solid, and dry it in vacuum at 100 °C for 12 h to obtain the target adsorbent 3.

[0031] Figure 1 It is the powder X-ray diffraction pattern of the composite adsorbent 1 in Example 1. After assembling the ionic liquid layer on its surface, it still maintains its original crystallinity. Figure 2 It is the high-resolution transmission electron microscopy image of the composite adsorbent 1 in Example 1. The ultra-thin ionic liquid layer with a thickness of about 2.8 nm outside the MOF-808 particles can be clearly distinguished. Figure 3 It is the adsorption isotherm of the composite adsorbent 1 in Example 1 for carbon dioxide at 298 K. Compared with MOF-808 and bulk ionic liquid (1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide), the adsorption capacity of the composite adsorbent is significantly improved. Figure 4 It is the adsorption dynamic breakthrough curve of the composite adsorbent 1 for carbon dioxide / nitrogen mixed gas. Nitrogen flows out 197 minutes per gram earlier than carbon dioxide. Through the simulated fixed-bed adsorption experiment, it is confirmed that the two gases are completely separated. Figure 5 It is the adsorption isotherm of the composite adsorbent 2 in Example 2 for carbon dioxide at 298 K. Compared with MOF-74 and bulk ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate), the adsorption capacity of the composite adsorbent is significantly improved. Figure 6It is the adsorption isotherm of composite adsorbent 3 for carbon dioxide at 298K in Example 3. Compared with UiO-66 and bulk ionic liquid (1-ethyl-3-methylimidazolium tetrafluoroborate), the adsorption capacity of the composite adsorbent is significantly improved.

Claims

1. Application of a composite adsorbent in gas adsorption separation, characterized in that, The composite adsorbent includes: metal-organic framework nanoparticles with permanent pores and a nanoscale ionic liquid layer self-assembled on the outer surface of the metal-organic framework nanoparticles with permanent pores; The metal-organic framework nanoparticles are MOF-808, UiO-66, ZIF-8, MIL-101, MOF-74 or NU-1000; The ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetrafluoroborate or 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride; The thickness of the ionic liquid layer is 0.5 - 30 nm; The preparation method of the composite adsorbent includes the following steps: (1) Dissolve the ionic liquid in an organic solvent to form an ionic liquid solution with a mass fraction of 0.5% - 30%; The organic solvent is one or more of methanol, ethanol, dichloromethane, toluene, N,N-dimethylformamide; (2) Disperse the metal-organic framework nanoparticles in the above ionic liquid solution according to the mass ratio of ionic liquid to metal-organic framework nanoparticles of 0.5 - 20:1, and stir at room temperature for 12 - 48 h; (3) Centrifuge the above mixed system, collect the solid, and dry it to obtain an ionic liquid molecular layer loaded on the surface of the metal-organic framework nanoparticles; The gas is a mixed gas of carbon dioxide / methane or carbon dioxide / nitrogen.

2. The application according to claim 1, characterized in that, The particle size of the metal-organic framework nanoparticles is 10 - 1000 nm, the maximum pore size is 1.0 - 30 nm, and the specific surface area is greater than or equal to 1500 m 2 / g.

3. The application according to claim 1, characterized in that, The speed of centrifugation is 10,000 - 20,000 revolutions per minute.

4. The application according to claim 1, characterized in that, The drying conditions are: vacuum drying at 60 - 150 °C for 12 - 48 h.

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