Preparation method and application of diamine porous ionic liquid

Abstract

The invention belongs to the technical field of environmental protection, and particularly relates to a preparation method and application of diamine porous ionic liquid. The preparation method comprises the following steps: firstly, carrying out in-situ synthesis on an MEA-loaded zeolite imidazole framework MEA (at) ZIF-8 through a hydrothermal method; then synthesizing amine functionalized imidazole ionic liquid [Amim] [NTf2] which takes trifluoromethanesulfonyl imide as an anion through an ion exchange method; finally, on the basis of the principle of similar dissolvability, the [Amim] [NTf2] and the MEA (at) ZIF-8 are combined through a solvent dispersing and mixing method, and the diamine porous ionic liquid MEA (at) ZIF-8-Amim-PIL is prepared. The diamine porous ionic liquid prepared by the method retains excellent carbon capture performance of the ionic liquid and ZIF-8, realizes a synergistic effect of low-pressure CO2 high-density distribution of liquid pore channels and an efficient electrostatic effect of diamine groups, can be used for low-pressure flue gas carbon capture, and is high in regeneration efficiency, low in energy consumption and beneficial to environmental protection.

Description

Technical Field

[0001] The invention belongs to the technical field of environmental protection, and in particular relates to a preparation method of a diamine porous ionic liquid and application thereof. Background Art

[0002] At present, the most mature and widely used CO2 capture process is to absorb CO2 in flue gas using aqueous organic amines such as monoethanolamine, diethanolamine, and methyldiethanolamine, and it has been widely used in industrial carbon removal of flue gas. However, there are many problems with the amine method of absorbing CO2 in flue gas, such as low regeneration efficiency, high desorption energy consumption, and easy corrosion of equipment by absorbents. Therefore, the development of new high-efficiency absorbents and their absorption processes has become a research hotspot in carbon capture technology today.

[0003] Porous ionic liquids (PILs) are a new type of liquid porous materials with permanent pores and fluidity. They combine the shape selectivity, strong adsorption, rapid mass transfer, high designability and stable kinetic performance of porous solid materials with ionic liquids, and show immeasurable development prospects in carbon capture. Among them, the third type of porous liquid with ZIF-8 as the main porous framework has attracted the attention of many researchers due to its simple preparation, easy-to-adjust structure and excellent performance. However, most pure ZIF-8 porous ionic liquids (ZIF-8-PILs) have unsatisfactory performance in carbon capture from flue gas with low CO2 partial pressure due to their high viscosity, instability in water, and insufficient active sites. Considering the advantage of easy regulation of porous ionic liquid structure, it is very desirable to design and develop ZIF-8-PILs rich in specific functional groups to regulate the capture of low-pressure flue gas CO2. To this end, some researchers introduced small molecule amines with good solubility and absorption of CO2 into the ZIF-8 framework in order to solve the above problems. However, the loading amount of a single small molecule amine in ZIF-8 is limited, and the electrostatic interaction between the monoamine-loaded ZIF-8 and the anions and cations of the ionic liquid in the porous ionic liquid structure is weak. The low-pressure flue gas CO2 absorption performance of monoamine ZIF-8-PILs has not achieved the ideal improvement effect.

[0004] In addition, studies have found that the introduction of amine functional groups such as primary amine and secondary amine into ionic liquids can effectively improve the electrostatic interaction between anions and cations, and significantly improve the CO2 absorption performance. However, most traditional amine-based ionic liquids have disadvantages such as high viscosity, large dosage, and poor CO2 solubility, which are not conducive to industrial production.

[0005] Based on the existence of the above problems, there is an urgent need for a low-energy, high-regeneration-efficiency carbon capture agent that can not only increase the amino content in ZIF-8-PILs, but also regulate the interaction between the components of ZIF-8-PILs and improve the CO2 absorption performance of low-pressure flue gas, which is more conducive to environmental protection. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a diamine porous ionic liquid, using MEA in situ loaded ZIF-8 (MEA@ZIF-8) as the porous framework body of the porous ionic liquid, using amine functionalized imidazolium ionic liquid [Amim][NTf2] as the steric solvent of the porous ionic liquid, and based on the principle of like dissolves like, using a solvent dispersion mixing method to combine [Amim][NTf2] with MEA@ZIF-8 to prepare a diamine porous ionic liquid MEA@ZIF-8-Amim-PIL. The present invention also provides an application of the diamine porous ionic liquid in low-pressure flue gas carbon capture.

[0007] A method for preparing a diamine porous ionic liquid comprises the following steps:

[0008] Step 1: Synthesis of MEA@ZIF-8:

[0009] The mixed solution of ethanolamine and 2-methylimidazole was mixed with a methanol solution of zinc nitrate hexahydrate Zn(NO3)·6H2O, and the mixture was subjected to hydrothermal reaction and centrifugal drying to obtain white particles of MEA@ZIF-8.

[0010] Step 2: Synthesis of [Amim][NTf2] ionic liquid:

[0011] 1-Methylimidazole and 2-bromoethylamine hydrobromide are mixed and reacted in acetonitrile solvent; after the reaction, the product is recrystallized in ethanol and dried to obtain the intermediate [Amim][Br];

[0012] Subsequently, [Amim][Br] and Li[NTf2] were reacted in an acetonitrile-water mixed solvent, and the product was neutralized to pH = 7, and then washed and dried to obtain a light yellow [Amim][NTf2] ionic liquid;

[0013] Step 3: Synthesis of diamine porous ionic liquid:

[0014] MEA@ZIF-8 is used as the porous framework body, [Amim][NTf2] ionic liquid is used as the steric solvent, and a simple solvent dispersion and mixing method is adopted to prepare the product. The specific steps are as follows: MEA@ZIF-8 and [Amim][NTf2] are dispersed in methanol respectively, ultrasonically oscillated at room temperature to make them evenly dispersed, the dispersed homogeneous solutions are mixed, and dried to obtain a diamine porous ionic liquid, namely MEA@ZIF-8-Amim-PIL.

[0015] Preferably, in step 1, the molar ratio of 2-methylimidazole to zinc nitrate hexahydrate is 8:1, the mass ratio of ethanolamine to zinc nitrate hexahydrate is 0-1:5, and the volume ratio of zinc nitrate hexahydrate to methanol is (0.1-0.5:50) mol / ml.

[0016] Preferably, in the step 1, the hydrothermal reaction temperature is 50-60° C., and the reaction time is 20-24 h; the drying temperature is 80-90° C., and the drying time is 20-24 h.

[0017] Preferably, in step 2, the molar ratio of 1-methylimidazole to 2-bromoethylamine hydrobromide is 1:1; the dosage ratio of 1-methylimidazole to acetonitrile is (0.1-0.5:50) mol / ml.

[0018] Preferably, in the step 2, the temperature of the mixed reaction in the acetonitrile solvent is 60-70° C., and the reaction time is 20-24 h; the drying temperature is 80-90° C., and the drying time is 20-24 h.

[0019] Preferably, in the step 2, the molar ratio of [Amim][Br] to Li[NTf2] is 1:1; the dosage ratio of [Amim][Br] to acetonitrile-water mixed solvent is (0.1-0.5:50) mol / ml; in the acetonitrile-water mixed solvent, the volume ratio of acetonitrile to water is 1:1; and the solvent used for washing is a mixed solvent of methanol and chloroform.

[0020] Preferably, in the step 2, the reaction temperature in the acetonitrile-water mixed solvent is 25-30° C., and the reaction time is 20-24 h; the volume ratio of methanol to chloroform is 9:1; the drying temperature is 80-90° C., and the drying time is 20-24 h; and the neutralization is carried out using a NaOH solution.

[0021] Preferably, in step three, the mass ratio of MEA@ZIF-8 to [Amim][NTf2] is 0.05 to 0.1:1.

[0022] Preferably, in step three, the drying temperature is 80-90° C. and the drying time is 20-24 hours.

[0023] A diamine porous ionic liquid prepared by the present invention is used in low-pressure flue gas carbon capture. The low-pressure CO2 absorption test of the porous ionic liquid is carried out using a gas adsorption instrument at room temperature and 0-1 bar; before the test, the porous ionic liquid is vacuum desorbed at 80°C for 24 hours to remove water vapor and impurity gases. Repeating the above CO2 absorption-desorption process can realize the recycling of the diamine porous ionic liquid, reduce costs, and benefit green ecology and environmental protection.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention adopts MEA@ZIF-8-Amim-PIL biamine porous ionic liquid as a low-pressure flue gas carbon capture agent, wherein the ionic liquid cation provides an -NH2 structure that reacts chemically with CO2; the imidazole ring in the MEA@ZIF-8 porous material can form an enhanced electrostatic effect with CO2, and the MEA loaded in ZIF-8 can react chemically with CO2 to form carbamate; in addition, there is a strong electrostatic effect between the functional amine group of the ionic liquid cation and the loaded MEA; more importantly, the unique liquid pores of the porous ionic liquid can release more absorption active sites, realizing a high-density distribution of CO2 in the cavity microenvironment under low pressure; under the synergistic effect of the above advantages, the low-pressure flue gas CO2 absorption performance of the biamine porous ionic liquid is effectively improved. The biamine porous ionic liquid of the present invention not only realizes the strong electrostatic synergy of the biamine group, but also the unique liquid pores of the porous ionic liquid realize the high-density distribution of CO2 under low pressure, significantly improving the low-pressure flue gas CO2 absorption performance.

[0026] (2) The biamine porous ionic liquid of the present invention uses the zeolite imidazole framework ZIF-8 with in-situ MEA loading as the porous framework body and the amino-functionalized imidazole trifluoromethanesulfonyl imide ionic liquid as the steric solvent. It is prepared based on the principle of like dissolves like and adopts a simple solvent dispersion and mixing method. It combines the shape selectivity and strong adsorption of porous solid materials and the rapid mass transfer, fluidity and stable kinetic properties of ionic liquid materials, thereby improving the absorption of low-pressure flue gas CO2, contributing to environmental protection, mitigating climate warming, etc.

[0027] (3) The present invention has a simple process, mild absorption conditions, high absorption capacity, high regeneration efficiency and low energy consumption, which is conducive to industrial application and provides a carbon capture agent for environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the characterization spectrum of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1; wherein a: infrared spectrum of MEA@ZI F-8 in Example 1 and ZIF-8 in Comparative Example 1; b: XRD spectrum of MEA@ZIF-8 in Example 1, ZIF-8 in Comparative Example 1 and fitted ZIF-8; c: N2 adsorption-desorption spectrum of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1; d: thermogravimetric curve of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1.

[0029] Figure 2 is the XPS spectra of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1; wherein a: the full XPS spectra of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1; b: the N / C and N / Zn of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 12+ Comparison; c: C1s fine spectrum of MEA@ZIF-8 in Example 1; d: C1s fine spectrum of ZIF-8 in Comparative Example 1; e: N1s fine spectrum of MEA@ZIF-8 in Example 1; f: N1s fine spectrum of ZIF-8 in Comparative Example 1.

[0030] Figure 3 These are the SEM, EDS and TEM spectra of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1; wherein a: SEM image of ZIF-8 in Comparative Example 1; b: SEM and EDS images of ZIF-8 in Comparative Example 1; c: TEM image of MEA@ZIF-8 in Example 1; d: SEM and EDS images of MEA@ZIF-8 in Example 1.

[0031] Figure 4 is [Amim][NTf2] in Example 1 1 H NMR spectrum.

[0032] Figure 5 It is a characterization spectrum of the porous ionic liquid MEA@ZIF-8-Amim-PIL and the ionic liquid [Amim][NTf2] in Example 1; wherein a: the infrared spectrum of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL and the ionic liquid [Amim][NTf2] in Example 1; b: the XRD spectrum of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1 and the ZIF-8-Amim-PIL in Comparative Example 1; c: the thermogravimetric curve of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL, the ionic liquid [Amim][NTf2] and the MEA@ZIF-8-Amim-PIL in Comparative Example 1; d: the diamine porous ionic liquid ME in Example 1 a: Full XPS spectrum of a@ZIF-8-Amim-PIL; e: C1sXPS fine spectrum of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1; f: N1sXPS fine spectrum of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1.

[0033] Figure 6It is a comparison chart of the absorption performance of porous ionic liquids; wherein a: CO2 absorption capacity data chart of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, MEA@ZIF-8 in Comparative Example 3 and ZIF-8 in Comparative Example 2; b: CO2 absorption capacity data chart of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, the porous ionic liquid ZIF-8-Amim-PIL in Comparative Example 1 and the ionic liquid [Amim][NTf2] in Comparative Example 4; c: Regeneration performance chart of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 2; d: Infrared spectra of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, the absorption saturated MEA@ZIF-8-Amim-PIL and the MEA@ZIF-8-Amim-PIL after 5 regeneration cycles and desorption treatment in Example 2. DETAILED DESCRIPTION

[0034] The accompanying drawings are only for illustrative purposes; they clearly and completely describe the technical solution of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] The raw materials, chemical reagents, instruments, etc. used in the present invention, unless the manufacturer, source, etc. are clearly stated, can be obtained through conventional commercial channels.

[0036] Example 1

[0037] 1. Preparation of MEA@ZIF-8-Amim-PIL porous ionic liquid

[0038] (1) Preparation of ethanolamine-loaded zeolitic imidazole framework (MEA@ZIF-8)

[0039] 3.29g 2-methylimidazole and 0.48g MEA were dissolved in 50ml methanol solution, and then 1.48g Zn(NO3)·6H2O was added and mixed at 50°C for 12h. After the reaction was completed, the reaction solution was centrifuged to obtain a white precipitate, which was washed with methanol three times and freeze-dried to obtain MEA@ZIF-8.

[0040] (2) Preparation of [Amim][NTf2] ionic liquid

[0041] 0.1 mol of methylimidazole, 0.1 mol of 2-bromoethylamine hydrobromide and 50 ml of acetonitrile were added into a 100 mL three-necked flask respectively, and refluxed at 60 °C for 24 h under nitrogen protection. After the reaction was completed, acetonitrile was removed by rotary evaporation, and the product was recrystallized in ethanol and dried at 80 °C for 12 h to obtain the intermediate [Amim][Br].

[0042] Subsequently, 0.1 mol of the intermediate [Amim][Br] and 0.1 mol of Li[NTf2] were added to 50 mL of a 1:1 acetonitrile-water mixed solvent, and the mixture was refluxed at 60°C for 24 h under nitrogen protection. The product was neutralized with NaOH to pH = 7, and then washed three times with a 9:1 9:1 methanol and chloroform mixed solvent, and then dried at 80°C for 24 h to obtain an aminoimidazole trifluoromethanesulfonyl imide ionic liquid [Amim][NTf2].

[0043] (3) Preparation of porous ionic liquid MEA@ZIF-8-Amim-PIL

[0044] 0.95 g [Amim] [NTf2] ionic liquid and 0.05 g MEA@ZIF-8 were dissolved in 20 mL methanol respectively, and ultrasonically oscillated at room temperature to make them uniformly dispersed. The dispersed [Amim] [NTf2] ionic liquid methanol solution and MEA@ZIF-8 methanol solution were ultrasonically oscillated at room temperature to make them uniformly mixed, and then dried at 80 ° C for 24 h to obtain the diamine porous ionic liquid MEA@ZIF-8-Ami m-PIL.

[0045] 2. Low-pressure CO2 absorption application of diamine porous ionic liquid, the specific method is as follows:

[0046] 0.1g of diamine porous ionic liquid MEA@ZIF-8-Amim-PIL was filled into the absorption tube, and then heated to 80℃ under vacuum at a heating rate of 5℃ / min. The diamine porous ionic liquid was desorbed for 24h to remove impurity gases and solvents in the sample. After desorption, the temperature of the absorption tube was lowered to room temperature, and the CO2 absorption test was performed at 0-1bar. The CO2 absorption content at 1bar was 94.3mg / g. The specific results are shown in Figure 6 (b) as shown.

[0047] The absorption saturated MEA@ZIF-8-Amim-PIL was subjected to infrared detection, and its infrared spectrum is shown as follows: Figure 6 (d) as shown.

[0048] Example 2

[0049] According to the low-pressure CO2 absorption application of MEA@ZIF-8-Amim-PIL in Example 1, the absorbent is MEA@ZIF-8-Amim-PIL after completing a desorption-adsorption process in Example 1, and the desorption-adsorption process is repeated 4 times, and the other conditions are the same as in Example 1. The specific method is as follows:

[0050] 0.1g of porous ionic liquid MEA@ZIF-8-Amim-PIL was filled into the absorption tube, and then heated to 80°C at a heating rate of 5°C / min under vacuum conditions. The porous ionic liquid was desorbed for 24 hours to remove impurity gases and solvents in the sample. After desorption, the temperature of the absorption tube was lowered to room temperature, and a CO2 absorption test was performed at 0-1 bar. The above CO2 desorption-absorption process was repeated 4 times. The CO2 absorption content remained basically unchanged at 1 bar. The specific results are as follows: Figure 6 (c) as shown.

[0051] The porous ionic liquid MEA@ZIF-8-Amim-PIL after five regeneration cycles and desorption treatment was subjected to infrared detection, and its infrared spectrum is shown in the figure below. Figure 6 (d) As shown in III.

[0052] Comparative Example 1

[0053] According to the method of preparing porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, the porous framework body is changed to ZIF-8. The remaining conditions are the same as in Example 1, and the specific method is as follows:

[0054] (1) Preparation of porous framework ZIF-8

[0055] 3.29 g of 2-methylimidazole was dissolved in 50 ml of methanol solution, and then 1.48 g of Zn(NO3)·6H2O was added and mixed and reacted at 50°C for 12 h. After the reaction was completed, the reaction solution was centrifuged to obtain a white precipitate, which was washed with methanol three times and freeze-dried to obtain ZIF-8.

[0056] (2) Preparation of porous ionic liquid ZIF-8-Amim-PIL

[0057] 0.95 g [Amim] [NTf2] ionic liquid and 0.05 g ZIF-8 were dissolved in 20 mL methanol respectively, and ultrasonically oscillated at room temperature to make them uniformly dispersed. The dispersed [Amim] [NTf2] ionic liquid methanol solution and ZIF-8 methanol solution were ultrasonically oscillated at room temperature to make them uniformly mixed, and then dried at 80 ° C for 24 h to obtain porous ionic liquid ZIF-8-Amim-PIL.

[0058] According to the low-pressure CO2 absorption application of porous ionic liquid in Example 1, ZIF-8-Amim-PIL was selected as the porous ionic liquid, and the remaining steps were the same as in Example 1. The CO2 absorption content was 82.4 mg / g at 1 bar.

[0059] Comparative Example 2

[0060] According to the low-pressure CO2 absorption application of porous ionic liquid in Example 1, ZIF-8 was selected as the adsorbent, and the remaining steps were the same as in Example 1. The CO2 absorption content was 27.4 mg / g at 1 bar. The specific results are as follows Figure 6 (a) shown.

[0061] Comparative Example 3

[0062] According to the low-pressure CO2 absorption application of porous ionic liquid in Example 1, MEA@ZIF-8 was selected as the adsorbent, and the remaining steps were the same as in Example 1. The CO2 absorption content was 41.7 mg / g at 1 bar. The specific results are as follows Figure 6 (a) shown.

[0063] Comparative Example 4

[0064] According to the low-pressure CO2 absorption application of porous ionic liquid in Example 1, the absorbent is selected from ionic liquid [Amim][NTf2], and the remaining steps are the same as in Example 1. The CO2 absorption content is 57.9 mg / g at 1 bar. The specific results are as follows Figure 6 (b) as shown.

[0065] like Figure 1 As shown, Figure 1 (a) is the infrared spectra of MEA@ZIF-8 (II) in Example 1 and ZIF-8 (I) in Comparative Example 1. It can be seen from the figure that the MEA@ZIF-8 spectrum shows four imidazole characteristic peaks of ZIF-8 at 3136 cm -1 , 2924cm -1 , 1583cm -1 , 1146cm -1 and the coordination peak of Zn atom and imidazole nitrogen at 3136 cm -1 At the same time, MEA's 1566cm -1 -NH2 peak, 3100 and 3170 cm -1 NH stretching vibration peak and 3626cm -1 The OH characteristic peaks are also clearly visible, proving that MEA is successfully loaded into the ZIF-8 framework structure.

[0066] Figure 1(b) is the XRD spectra of MEA@ZIF-8 in Example 1, ZIF-8 and fitting ZIF-8 in Comparative Example 1. As can be seen from the figure: all diffraction peaks of ZIF-8 in Comparative Example 1 can be well matched with fitting ZIF-8, indicating that ZIF-8 has been successfully synthesized. In addition, the characteristic diffraction peaks of ZIF-8 can still be observed in MEA@ZIF-8 without obvious shift changes, indicating that the loading of MEA will not destroy the crystal structure of ZIF-8.

[0067] Figure 1 (c) is the N2 adsorption-desorption curve of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1. It can be seen from the figure that, like ZIF-8, the N2 adsorption-desorption isotherm of MEA@ZIF-8 shows a typical microporous structure, and the specific surface areas of the two can reach 1719 and 1311 m 2 / g, further indicating that there are a large number of microporous structures in the synthesized ZIF-8 and MEA@ZIF-8 that can serve as permanent pores.

[0068] Figure 1 (d) is the thermogravimetric curve of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1. It can be seen from the figure that ZIF-8 has no obvious mass loss below 450°C, indicating its good thermal stability. MEA@ZIF-8 shows a slight mass loss due to the addition of MEA in the skeleton, proving that MEA has been successfully loaded into the ZIF-8 skeleton structure.

[0069] like Figure 2 The XPS spectra of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1 are shown in FIG. Figure 2 It can be seen from (a) that the XPS spectra of ZIF-8 and MEA@ZIF-8 show the characteristic peaks of Zn, C and N at 1022 eV, 1045 eV, 400 and 280, respectively. Figure 2 As shown in (b), the N / C and N / Zn element ratios in MEA@ZIF-8 are slightly increased compared with those in ZIF-8. Figure 2 (c) is the C1s fine spectrum of MEA@ZIF-8 in Example 1, Figure 2 (d) is the C1s fine spectrum of ZIF-8 in Comparative Example 1. In addition, the N1s fine spectrum of MEA@ZIF-8 shows a new NH peak. Figure 2 (e) and (f). These results indicate that MEA has been successfully loaded into the ZIF-8 framework structure.

[0070] Figure 3 TEM, SEM and EDS spectra of MEA@ZIF-8 in Example 1 and ZIF-8 in Comparative Example 1. Figure 3As can be seen from (a), ZIF-8 is in the form of hexagonal blocks with uniform particle size. Figure 3 As can be seen from (b), the EDS patterns of C, N, and Zn are evenly distributed, indicating that ZIF-8 was successfully prepared. Figure 3 (c) and (d) show that the particle size of MEA@ZIF-8 becomes smaller, the surface becomes rougher, and the shape becomes more irregular. This is mainly due to the introduction of MEA, which accelerates the nucleation and growth of ZIF-8. The above results further prove that MEA is successfully loaded into the ZIF-8 skeleton structure. In addition, the SEM and TEM spectra of MEA@ZIF-8 clearly show that its particle edges tend to be blurred or even agglomerated, but the XRD spectrum shows that the crystallinity of MEA@ZIF-8 does not change much. Based on this, we speculate that the in situ synthesis strategy plays an important role in maintaining the structural integrity of MEA@ZIF-8.

[0071] Figure 4 is the ionic liquid [Amim][NTf2] in Example 1 1 H NMR spectrum. It can be seen from the figure that the hydrogen shifts on the imidazole ring of 1-methylimidazole are located at 7.52 and 7.48 ppm, the side chain methyl hydrogen is located at 3.93 ppm, and the active hydrogen of -NH2 is located at 4.32 and 4.27 ppm. These results combined with the ionic liquid structure diagram confirmed the successful synthesis of [Amim][NTf2].

[0072] Figure 5 (a) is the infrared spectra of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL (III), ionic liquid [Amim][NTf2] (II) and Li[NTf2] (I) in Example 1. It can be seen from the figure that compared with [Amim][NTf2], the spectrum of MEA@ZIF-8-Amim-PIL has the highest peaks at 421 and 1024 cm -1 The Zn-N bond and CN bond absorption peaks of ZIF-8 were observed respectively, proving that the porous ionic liquid MEA@ZIF-8-Amim-PIL was successfully prepared by combining [Amim][NTf2] with MEA@ZIF-8.

[0073] Figure 5 (b) is the XRD spectra of the porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1 and ZIF-8 in Comparative Example 1. It can be seen from the figure that the broad peak of [Amim][NTf2] and the typical characteristic peak of ZIF-8 were observed in the XRD spectrum of MEA@ZIF-8-Amim-PIL without obvious shift changes, indicating that the porous framework structure remains stable in the porous ionic liquid and is not destroyed.

[0074] Figure 5(c) is the thermogravimetric spectra of the porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, [Amim][NTf2] in Comparative Example 4, and ZIF-8-Amim-PIL in Comparative Example 1. It can be seen from the figure that the addition of porous framework MEA@ZIF-8 and ZIF-8 does not reduce the thermal stability of the ionic liquid [Amim][NTf2], further confirming the structural stability of the porous ionic liquid during the synthesis process.

[0075] Figure 5 (d, e, f) are the XPS spectra, C 1sXPS fine spectra, and N 1sXPS of the porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1. It can be seen from the figure that the full XPS spectrum of MEA@ZIF-8-Amim-PIL has obvious characteristic peaks at 1022eV (Zn 2p), 689eV (F 1s), 533eV (O 1s), 400eV (N 2p), 285eV (C 1s) and 167eV (S2p), among which the coexistence of Zn 2p and F, O, S characteristic peaks proves that [Amim][NTf2] is effectively combined with MEA@ZIF-8 to successfully prepare MEA@ZIF-8-Amim-PIL. In addition, the slight changes in the C1s and N1s fine spectra of MEA@ZIF-8-Amim-PIL compared with MEA@ZIF-8 indicate that there is a strong non-covalent interaction between [Amim][NTf2] in the porous ionic liquid MEA@ZIF-8-Amim-PIL and MEA@ZIF-8, which may be caused by the transfer or redistribution of electron density during the interaction.

[0076] Figure 6 (a) is a data graph of the CO2 absorption capacity of the porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, MEA@ZIF-8 in Comparative Example 3, and ZIF-8 in Comparative Example 2. It can be seen from the figure that in the range of 0 to 1 bar, the CO2 adsorption of MEA@ZIF-8 and ZIF-8 shows a linear upward trend. Among them, the CO2 adsorption of MEA@ZIF-8 at 1 bar is 41.68 mg / g, which is significantly higher than the 27.36 mg / g of ZIF-8. This shows that MEA has a significant effect on improving the CO2 adsorption performance. Compared with MEA@ZIF-8 and ZIF-8, the CO2 adsorption of MEA@ZIF-8-Amim-PIL is significantly improved, reaching 94.3 mg / g at 1 bar, which is equivalent to 5 times the CO2 adsorption of ZIF-8, indicating that the ionic liquid [Amim][NTf2] plays an important role in improving the CO2 adsorption performance.

[0077] Figure 6(b) is a data graph of the CO2 absorption capacity of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 1, the ionic liquid [Amim][NTf2] in Comparative Example 4, and the porous ionic liquid ZIF-8-Amim-PIL in Comparative Example 1. It can be seen from the figure that the CO2 absorption capacity of MEA@ZIF-8-Amim-PIL, ZIF-8-Amim-PIL and [Amim][NTf2] also shows an upward trend in the range of 0 to 1 bar. Compared with [Amim][NTf2], the CO2 absorption capacity of the two porous ionic liquids is significantly improved, indicating that the porous channels of the liquid play an important role in improving the CO2 adsorption capacity. In addition, the CO2 absorption capacity of MEA@ZIF-8-Amim-PIL is significantly higher than that of ZIF-8-Amim-PIL, indicating that the efficient electrostatic effect of the functionalized diamine group also plays a vital role in improving the CO2 adsorption capacity.

[0078] Figure 6 (c) is a graph showing the regeneration performance of the porous ionic liquid MEA@ZIF-8-Amim-PIL in Example 2. As can be seen from the figure, the CO2 absorption capacity has almost no change after 5 regeneration cycles, indicating that the porous ionic liquid MEA@ZIF-8-Amim-PIL of the present invention has good cycle stability and is expected to become an efficient industrial CO2 capture agent.

[0079] Figure 6 (d) is the infrared spectra of the diamine porous ionic liquid MEA@ZIF-8-Amim-PIL (I) in Example 1, the absorption saturated MEA@ZIF-8-Amim-PIL (II) and the MEA@ZIF-8 / [Amim][NTf2] (III) after 5 regeneration cycles and desorption treatment in Example 2. It can be seen from the figure that the FT-IR spectrum of the porous ionic liquid MEA@ZIF-8-Amim-PIL after absorbing CO2 is 1547cm -1 There appears a + This result is consistent with the literature report, indicating that CO2 forms a strong interaction with the functionalized diamine group. Therefore, we can speculate that the permanent liquid pores of the porous ionic liquid provide an efficient storage space for the reversible action of CO2, thereby significantly improving the CO2 capture performance. In addition, the FT-IR of MEA@ZIF-8-Amim-PIL remains basically unchanged before and after regeneration, indicating that the structural composition of the characteristic groups of the porous ionic liquid has not changed before and after regeneration, further proving that the porous ionic liquid described in the present invention has good regeneration stability.

[0080] The Chinese meanings of the English abbreviations in this invention are:

[0081] ZIF-8: zeolitic imidazole framework material, transition metal zinc ion (Zn 2+ ) and 2-methylimidazole ligand, the full English name is Zeolitic Imidazolate Framework-8;

[0082] PILs: porous ionic liquids;

[0083] ZIF-8-PILs: Porous ionic liquids made of zeolitic imidazolate framework materials;

[0084] [Amim][NTf2]: aminoimidazole trifluoromethanesulfonimide ionic liquid;

[0085] MEA: ethanolamine;

[0086] Li[NTf2]: lithium trifluoromethanesulfonyl imide;

[0087] Zn(NO3)·6H2O: zinc nitrate hexahydrate;

[0088] MEA@ZIF-8: ethanolamine-supported zeolitic imidazolyl framework;

[0089] [Amim][Br]: 1-methyl-3-allylimidazolium bromide;

[0090] MEA@ZIF-8-Amim-PIL: diamine porous ionic liquid.

[0091] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing a diamine porous ionic liquid, characterized in that: The steps include: Step 1: Synthesis of MEA@ZIF-8: The mixed solution of ethanolamine and 2-methylimidazole was mixed with the methanol solution of Zn(NO3)·6H2O, and the mixture was subjected to hydrothermal reaction and centrifugal drying to obtain white particles of MEA@ZIF-8. Step 2: Synthesis of [Amim][NTf2] ionic liquid: 1-Methylimidazole and 2-bromoethylamine hydrobromide are mixed and reacted in acetonitrile solvent; after the reaction, the product is recrystallized in ethanol and dried to obtain the intermediate [Amim][Br]; Subsequently, [Amim][Br] and Li[NTf2] were reacted in an acetonitrile-water mixed solvent, and the product was neutralized to pH = 7, and then washed and dried to obtain a light yellow [Amim][NTf2] ionic liquid; Step 3: Synthesis of diamine porous ionic liquid: Taking MEA@ZIF-8 as the porous framework body and [Amim][NTf2] ionic liquid as the steric solvent, MEA@ZI F-8 and [Amim][NTf2] were dispersed in methanol respectively, and ultrasonic oscillation was used to make them uniformly dispersed at room temperature. The dispersed homogeneous solutions were mixed and dried to obtain the diamine porous ionic liquid, namely MEA@ZIF-8-Amim-PIL.

2. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 1, the molar ratio of 2-methylimidazole to zinc nitrate hexahydrate is 8:1, the mass ratio of ethanolamine to zinc nitrate hexahydrate is 0-1:5, and the volume ratio of zinc nitrate hexahydrate to methanol is (0.1-0.5:50) mol / ml.

3. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 1, the hydrothermal reaction temperature is 50-60° C., and the reaction time is 20-24 h; the drying temperature is 80-90° C., and the drying time is 20-24 h.

4. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 2, the molar ratio of 1-methylimidazole to 2-bromoethylamine hydrobromide is 1:1; the dosage ratio of 1-methylimidazole to acetonitrile is (0.1-0.5:50) mol / ml.

5. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 2, the temperature of the mixed reaction in the acetonitrile solvent is 60-70° C., and the reaction time is 20-24 hours; the drying temperature is 80-90° C., and the drying time is 20-24 hours.

6. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 2, the molar ratio of [Amim][Br] to Li[NTf2] is 1:1; the dosage ratio of [Amim][Br] to acetonitrile-water mixed solvent is (0.1-0.5:50) mol / ml; in the acetonitrile-water mixed solvent, the volume ratio of acetonitrile to water is 1:1; the solvent used for washing is a mixed solvent of methanol and chloroform; and NaOH solution is used for neutralization.

7. The method for preparing a diamine porous ionic liquid according to claim 6, characterized in that: In the step 2, the reaction temperature in the acetonitrile-water mixed solvent is 25-30° C., the reaction time is 20-24 h; the volume ratio of methanol to chloroform is 9:1; the drying temperature is 80-90° C., and the drying time is 20-24 h.

8. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 3, the mass ratio of MEA@ZIF-8 to [Amim][NTf2] is 0.05-0.1:

1.

9. The method for preparing a diamine porous ionic liquid according to claim 1, characterized in that: In the step 3, the drying temperature is 80-90° C. and the drying time is 20-24 hours.

10. Use of the diamine porous ionic liquid prepared by the preparation method according to any one of claims 1 to 9 in low-pressure flue gas carbon capture.

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