Polymer composite adsorbents, methods of synthesis, and methods of separating xylene isomers

Abstract

The application discloses a polymer composite adsorbent, a synthesis method and a method for separating dimethylbenzene isomers. According to the difference in molecular structures of dimethylbenzene isomers, a 1-amino pyrene polymer composite adsorbent material is designed and synthesized, dimethylbenzene isomers are dispersed by using water as a medium, and the dimethylbenzene isomers are separated through multi-stage adsorption-desorption by using the difference in acting force between the dimethylbenzene isomers and polymer units. By using the method, OX with a purity higher than 99.0% (gas chromatography analysis) can be obtained when the separation ratio of PX / intermediate dimethylbenzene (MX) / ortho-xylene (OX) is 1 / 1 / 1, and MX with a purity higher than 98.5% (gas chromatography analysis) can be obtained when the separation ratio of PX / MX is 1 / 1, and the method has the advantages of low energy consumption.

Description

TECHNICAL FIELD

[0001] The present application relates to materials and methods for separating xylene isomers. BACKGROUND

[0002] Xylene is a very important chemical raw material, widely used in paint, dye, medicine, explosive and pesticide industries. The physical and chemical properties of xylene isomers, p-xylene, m-xylene and o-xylene, are very similar, and their boiling points are very close. At present, industrial separation of xylene isomers mainly uses methods such as rectification, crystallization and adsorption, which consumes a large amount of energy and has low efficiency.

[0003] In recent years, various new solid adsorbents have been studied, such as MFI molecular sieves, molecular crystals, metal complexes, organic cages, metal-organic cages, porous coordination polymers (PCPs), metal-organic frameworks (MOFs), microporous organic polymers (MOPs), and switchable adsorbents, for separating xylene isomers. These materials and separation methods are mostly based on temperature-dependent adsorption molecular recognition or sieving, and the separation process consumes high energy.

[0004] New adsorbent materials for separating xylene isomers usually involve interactions between functional groups within the material and xylene molecules, and the selectivity of isomers is affected by different molecular sizes and interaction strengths. Therefore, a polymer adsorbent containing a large π-conjugated system unit can be designed to improve the adsorption capacity of xylene through π-π interactions. At the same time, the different relative positions of the two methyl groups in xylene isomers and the different interaction strengths between the two side groups of the polymer unit and the two methyl groups are used to produce selective adsorption of xylene isomers by the adsorbent, and by repeating the adsorption-desorption multiple times, the small difference in adsorption capacity is amplified to realize the separation of xylene isomers.

[0005] REFERENCES

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[0015]

[10] S. Q. Wang, et al., Angew. Chem. Int. Ed. 2019, 58, 6630. SUMMARY

[0016] The present application aims to overcome the deficiencies of the prior art, and provides a polymer composite adsorbent and a synthesis method thereof, and a method for separating xylene isomers using the same.

[0017] In a first aspect, the present application provides a polymer composite adsorbent, which is a composite of a 1-aminopyrene polymer and a supporting electrolyte, wherein the supporting electrolyte is 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6].

[0018] In a preferred embodiment of the first aspect, the supporting electrolyte is 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], and the polymerization degree of 1-aminopyrene in the 1-aminopyrene polymer is 14-130.

[0019] In a preferred embodiment of the first aspect, the supporting electrolyte is 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and the polymerization degree of 1-aminopyrene in the 1-aminopyrene polymer is 23-2790.

[0020] In a second aspect, the present application provides a synthesis method of a polymer composite adsorbent, which comprises adding 1-aminopyrene as a raw material into an electrolytic cell with an anode and a cathode, and adding 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] as a supporting electrolyte, and performing an electrochemical polymerization reaction in an organic solvent at a constant potential of 1.0-3.0 V to obtain a 1-aminopyrene polymer doped with the supporting electrolyte.

[0021] In a preferred embodiment of the second aspect, the electrolytic cell is preferably a single-cell electrolytic cell.

[0022] In a preferred embodiment of the second aspect, the anode is preferably a graphite anode.

[0023] In a preferred embodiment of the second aspect, the cathode is preferably a graphite cathode.

[0024] In a preferred embodiment of the second aspect, the organic solvent is preferably acetonitrile.

[0025] In a third aspect, the present application provides an adsorbent for separating xylene isomers, which is made of the polymer composite adsorbent according to any one of the first aspect.

[0026] In a fourth aspect, the present application provides a method for separating xylene isomers, which comprises adsorbing and separating xylene isomers from an aqueous dispersion of xylene isomers using the polymer composite adsorbent according to any one of the first aspect.

[0027] The present application is based on the molecular structure difference of xylene isomers, a polymer composite adsorbent material is designed and synthesized, the adsorbent disperses xylene isomers with water as medium, and the xylene isomers are separated by multi-stage adsorption-desorption through the difference of the interaction force between the xylene isomers and the polymer units. The polymer composite adsorbent provided by the present application can be synthesized by electrochemical synthesis method, the raw material cost is low, the synthesis process is simple, and the separation method based on the adsorbent has the advantages of low energy consumption in the separation process and high purity of the obtained single xylene isomer. Especially, when the polymer composite adsorbent is used to separate p-xylene (PX) / m-xylene (MX) / o-xylene (OX) = 1 / 1 / 1, OX with a purity higher than 99.0% (gas chromatography analysis) can be obtained, and when PX / MX = 1 / 1, MX with a purity higher than 98.5% (gas chromatography analysis) can be obtained. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 .[BMIM][BF4] and PAP / [BMIM][BF4] 1 HNMR comparison chart (proving the structure of PAP / [BMIM][BF4] complex);

[0029] Figure 2 .[BMIM][PF6] and PAP / [BMIM][PF6] 1 HNMR comparison chart (proving the structure of PAP / [BMIM][PF6] complex);

[0030] Figure 3 SEM images of two compounds, wherein a) and b) are SEM images of PAP / [BMIM][BF4], and c) and d) are SEM images of PAP / [BMIM][PF6];

[0031] Figure 4 TEM images of two compounds, wherein a) is a TEM image of PAP / [BMIM][BF4], and b) is a TEM image of PAP / [BMIM][PF6];

[0032] Figure 5 Single crystal XRD structure of 1-aminopyrene dimer;

[0033] Figure 6 PAP / [BMIM][BF4] before and after adsorbing xylene 1 HNMR comparison chart;

[0034] Figure 7 PAP / [BMIM][PF6] before and after adsorbing xylene 1 HNMR comparison chart;

[0035] Figure 8Gas chromatogram of PAP / [BMIM][BF4] separating three-component xylene isomers;

[0036] Figure 9 Gas chromatogram of PAP / [BMIM][BF4] separating two-component xylene isomers;

[0037] Figure 10 Gas chromatogram of PAP / [BMIM][PF6] separating three-component xylene isomers. DETAILED DESCRIPTION

[0038] The present application will be further described and illustrated in connection with the accompanying drawings and specific examples.

[0039] The present application provides a polymer composite adsorbent, which is a composite of 1-aminopyrene polymer (PAP) and a supporting electrolyte, wherein the supporting electrolyte can be two kinds of ionic liquids with different X groups (BF4, PF6), namely 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methyl imidazolium hexafluorophosphate [BMIM][PF6], and the structural formulas of PAP and the two kinds of supporting electrolytes are as follows:

[0040]

[0041] The composite adsorbents corresponding to the two kinds of ionic liquids are respectively denoted as PAP / [BMIM][BF4] and PAP / [BMIM][PF6], and the structural formula of the composite can be represented as formula I:

[0042]

[0043] In formula I, the dotted line represents the electrostatic attraction between PAP and the supporting electrolyte through π-π interaction in the electrochemical synthesis process, and thus the two are doped in a certain ratio.

[0044] The adsorbent utilizes the different relative positions of the two methyl groups in xylene isomers and the different interaction strengths between the two side groups of the polymer units and the two methyl groups, thereby producing selective adsorption of the adsorbent to xylene isomers, and through repeated adsorption-desorption, the small differences in adsorption capacity are amplified to realize the separation of xylene isomers.

[0045] In the polymer composite adsorbent, PAP is used as an adsorbent for separating xylene isomers, and the distances between the two methyl groups of para-xylene (PX), meta-xylene (MX) and ortho-xylene (OX) are respectively and When the 1-aminopyrene monomer is polymerized along its 1,6 axis, a "-NH-pyrene-NH-" unit is formed, which has a large π conjugated system and two adjacent amino groups with a spacing of Each unit can be identified and distinguished from different xylene isomers by a force field formed by π-π interactions and different strength van der Waals forces between -CH3- and -NH-. There are differences in interactions between the three xylene isomers PX, MX, OX and the "-NH-pyrene-NH-" unit. If water is used as a dispersion carrier, the isomers of xylene and the unit are repeatedly adsorbed and desorbed to amplify the differences in adsorption capacity and the slight differences in diffusion rate, thereby realizing separation at room temperature. Therefore, compared with temperature-dependent adsorbents based on the interaction between functional groups and xylene molecules and the size difference of xylene molecules, this liquid-solid phase separation of xylene isomers has the advantage of low energy consumption.

[0046] The present application also provides a synthesis method of a polymer composite adsorbent, which adds 1-aminopyrene as a raw material to an electrolytic cell with an anode and a cathode, and adds 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM] [BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM] [PF6] as a supporting electrolyte, and performs an electrochemical polymerization reaction in an organic solvent at a constant potential of 1.0-3.0 V to obtain a 1-aminopyrene polymer doped with a supporting electrolyte.

[0047] In the above synthesis method, the electrolytic cell is preferably a single-cell electrolytic cell, the anode is preferably a graphite anode, the cathode is preferably a graphite cathode, and the organic solvent is preferably acetonitrile.

[0048] The above polymer composite adsorbent can be used as an adsorbent for separating xylene isomers. Specifically, the method for separating xylene isomers is to use the above polymer composite adsorbent to adsorb and separate a water dispersion of xylene isomers. In practical applications, the above polymer composite adsorbent can be made into multiple stages of adsorption units in series, and the water dispersion of xylene isomers is sequentially passed through each stage of adsorption units to realize separation through multiple adsorption-desorption, thereby obtaining a single high-purity xylene isomer.

[0049] The following examples will help to understand the present application, but the scope of protection of the present application is not limited to the contents of the following examples: Example 1 Synthesis of 1-aminopyrene polymer composite adsorbent

[0050] In a 400 mL undivided electrolytic cell equipped with a graphite anode and a graphite cathode, 1-aminopyrene (400 mg, 1.84 mmol), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) (6 mL, 0.22 mmol) and acetonitrile 400 mL were added. The reaction was stirred at room temperature and electrolyzed at a constant voltage of 3.0 V for 24 h, and the reaction progress was tracked by thin layer chromatography (eluent volume ratio DCM:PE = 2:1). After the reaction was completed, the electrolyte was evaporated to dryness, washed with deionized water, transferred to a centrifuge tube, and the supernatant was removed by centrifugation, leaving a black powdery solid. The solid was washed with 80 mL acetonitrile, 80 mL tetrahydrofuran and 300 mL water, and centrifuged for 3 cycles. Finally, the supernatant was decanted and the precipitate was dried to constant weight to obtain 0.60 g of black solid powder.

[0051] Elemental analysis (wt%) of PAP / [BMIM][BF4]: C 79.57 H 4.08 N 6.03.

[0052] Table 1. TEM-EDS data of PAP / [BMIM][BF4]

[0053]

[0054] The TEM-EDS data proved that [BMIM][BF4] was contained in PAP / [BMIM][BF4].

[0055] The FTIR spectra of [BMIM][BF4] and PAP / [BMIM][BF4] 1 HNMR comparison chart (attached Figure 1 ) proved that PAP / [BMIM][BF4] was a composite of 1-aminopyrene polymer (PAP) and supporting electrolyte [BMIM][BF4]. The mass percentage of [BMIM][BF4] in PAP / [BMIM][BF4] was 19.0%. SEM images (attached Figure 3 ) and TEM images (attached Figure 4 ) showed that PAP / [BMIM][BF4] had a porous layered structure.

[0056] The average molecular weight of the polymer in PAP / [BMIM][BF4] was 10675 g / mol, the minimum molecular weight was 3000 g / mol, and the maximum molecular weight was 28000 g / mol, and the monomer molecular weight was 215 g / mol, so the polymerization degree range n of PAP in PAP / [BMIM][BF4] was calculated to be 14-130. In addition, the contact angle of PAP / [BMIM][BF4] was measured to be 68°.

[0057] The concentration changes of the single component of xylene isomer aqueous solution before and after PAP / [BMIM][BF4] adsorption were quantitatively analyzed by UV-Vis absorption spectroscopy. The saturated adsorption amounts of PAP / [BMIM][BF4] for PX, MX and OX were 247.68 mg / g, 235.66 mg / g and 200.84 mg / g, respectively. This indicated that the adsorption capacity of PAP / [BMIM][BF4] for PX, MX and OX was different.

[0058] Example 2 Synthesis of 1-aminopyrene polymer composite adsorbent

[0059] In a 150 mL undivided cell equipped with a 20 x 20 x 3 mm graphite anode and a graphite cathode, 1-aminopyrene (1.09 g, 5 mmol), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) (4.55 g, 3.3 mL, 16 mmol) and acetonitrile 120 mL were added. The reaction was stirred at room temperature and electrolyzed at a constant voltage of 3.0 V for 24 h. The reaction progress was tracked by thin layer chromatography (eluent volume ratio of DCM:PE = 2:1) during the reaction. After the reaction was completed, the electrolyte was rotary evaporated to dryness, washed with deionized water, transferred to a centrifuge tube, and the supernatant was removed by centrifugation to leave a black powdery solid. The solid was washed with 80 mL acetonitrile, 80 mL tetrahydrofuran and 300 mL water in turn, and centrifuged for 3 cycles. Finally, the supernatant was poured out by centrifugation, and the precipitate was separated and dried to constant weight to obtain 0.71 g of black solid powder. Elemental analysis (wt%) of PAP / [BMIM][PF6]: C 78.44 H 4.35 N 5.69.

[0060] Table 2. TEM-EDS data of PAP / [BMIM][PF6]

[0061]

[0062] The TEM-EDS data proved that [BMIM][PF6] was contained in PAP / [BMIM][PF6].

[0063] The FTIR spectra of [BMIM][PF6] and PAP / [BMIM][PF6] 1 HNMR comparison chart (attached Figure 1 ) proved that PAP / [BMIM][PF6] was a composite of 1-aminopyrene polymer (PAP) and supporting electrolyte [BMIM][PF6]. The mass percentage of [BMIM][PF6] in PAP / [BMIM][PF6] was 16.7%. SEM chart (attached Figure 3 ) and TEM chart (attached Figure 4) shows that PAP / [BMIM][PF6] is a porous layered structure, and has fewer and larger pores than PAP / [BMIM][BF4].

[0064] The average molecular weight of the polymer in PAP / [BMIM][PF6] is 127040 g / mol, the minimum molecular weight is 5000 g / mol, and the maximum molecular weight is 600000 g / mol, as measured by gel permeation chromatography (GPC). The molecular weight of the monomer is 215 g / mol, and thus the polymerization degree range n of PAP in PAP / [BMIM][PF6] is 23-2790. In addition, the contact angle of PAP / [BMIM][PF6] is 78°.

[0065] The concentration changes of the single component aqueous solutions of xylene isomers before and after adsorption by PAP / [BMIM][PF6] were quantitatively analyzed by UV-visible absorption spectroscopy, and the saturated adsorption amounts of PX, MX, and OX by PAP / [BMIM][PF6] were measured to be 167.54 mg / g, 154.93 mg / g, and 127.89 mg / g, respectively. This shows that the adsorption capacity of PAP / [BMIM][PF6] for PX, MX, and OX is different, and is less than the adsorption amounts of PX, MX, and OX by PAP / [BMIM][BF4], respectively, i.e., the adsorption capacity of PAP / [BMIM][PF6] for xylene is weaker than that of PAP / [BMIM][BF4].

[0066] Example 3 Degradation reaction of PAP / [BMIM][BF4]

[0067] The structure of the degradation product was analyzed to verify the structure of the polymer (PAP) in PAP / [BMIM][BF4] prepared in Example 1. 226 mg of PAP / [BMIM][BF4] was weighed and dispersed in 200 mL of THF, and then 0.05 mL of hydrazine hydrate was added dropwise, and the mixture was stirred for 3 h. The reaction liquid was analyzed by thin layer chromatography (developing agent: DCM:PE=2:1). After the reaction was completed, the reaction liquid was rotary evaporated, 200 mL of water was added, and the mixture was stirred and mixed by ultrasonic. Then, dichloromethane was used for back extraction three times (200 mL x 3). After the organic phase was concentrated under reduced pressure, it was purified by silica gel column chromatography (DCM:PE=2:1) to obtain 15 mg of 1-aminopyrene dimer yellow solid powder. Its structure was confirmed by single crystal XRD (attached Figure 5 ) to prove that the structure of the 1-aminopyrene polymer (PAP) is the polymerization of 1-aminopyrene monomer at 1,6 positions.

[0068] Example 4 Experiment of PAP / [BMIM][BF4] and PAP / [BMIM][PF6] adsorbing xylene isomers

[0069] PAP / [BMIM][BF4] and PAP / [BMIM][PF6] were added to the aqueous solution of OX, MX and PX (25ul of xylene in 200ml water) respectively. The mixture was ultrasonically dispersed for 2 hours and left for 2 hours to ensure the adsorption process reached equilibrium. The filter cake was dried overnight, then dissolved and dispersed in deuterated DMSO for testing 1 HNMR spectra. Attached Figure 6 PAP / [BMIM][BF4] before and after adsorbing xylene 1 HNMR comparison spectra show that PAP / [BMIM][BF4] adsorbed xylene, where 6.92-7.16ppm and 2.18-2.28ppm are the H signal peaks of xylene; attached Figure 7 PAP / [BMIM][PF6] before and after adsorbing xylene 1 HNMR comparison spectra show that PAP / [BMIM][PF6] adsorbed xylene, where 6.92-7.16ppm and 2.18-2.28ppm are the H signal peaks of xylene.

[0070] Example 5 PAP / [BMIM][BF4] separates xylene isomers

[0071] 60mg PAP / [BMIM][BF4] was weighed into a 100ml round bottom flask, 60ml water was added, and the mixture was ultrasonically dispersed for 30min until the dispersion was a uniform black opaque liquid. A 5ml syringe was used to extract 5ml of the PAP / [BMIM][BF4] dispersion and inject it into a filter head (0.22μ), the filtrate was water and the PAP / [BMIM][BF4] filter cake remained in the filter head. 25ul of PX, 25ul of MX and 25ul of OX were mixed with 5ml water and ultrasonically dispersed for 30min to obtain a PX / MX / OX (1 / 1 / 1) water dispersion, which was injected into the filter head loaded with PAP / [BMIM][BF4] prepared above through a 1ml syringe, and the filtrate was collected. The filtrate was sampled and analyzed by gas chromatography to determine the ratio of xylene isomers, which was PX / MX / OX = 1 / 1.4 / 2.5 (as shown in Figure 8 step 1).

[0072] Example 6 PAP / [BMIM][BF4] separates xylene isomers

[0073] A water dispersion of PX / MX / OX = 1 / 1.4 / 2.5 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5, and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 1.6 / 3.6 (as shown in Figure 2, step 2). Figure 8

[0074] Example 7 PAP / [BMIM][BF4] separation of xylene isomers

[0075] A water dispersion of PX / MX / OX = 1 / 1.6 / 3.6 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5, and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 1.9 / 5.6 (as shown in Figure 2, step 3). Figure 8

[0076] Example 8 PAP / [BMIM][BF4] separation of xylene isomers

[0077] A water dispersion of PX / MX / OX = 1 / 1.9 / 5.6 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5, and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 2.6 / 11.5 (as shown in Figure 2, step 4). Figure 8

[0078] Example 9 PAP / [BMIM][BF4] separation of xylene isomers

[0079] A water dispersion of PX / MX / OX = 1 / 2.6 / 11.5 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5, and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 3.6 / 21 (as shown in Figure 2, step 5). Figure 8

[0080] Example 10 PAP / [BMIM][BF4] separation of xylene isomers

[0081] ​​​​A water dispersion of PX / MX / OX = 1 / 3.6 / 21 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5 and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 5 / 42 (as shown in Figure 5, step 6). Figure 8

[0082] Example 11 PAP / [BMIM][BF4] separation of xylene isomers

[0083] A water dispersion of PX / MX / OX = 1 / 5 / 42 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5 and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 1 / 7 / 96 (as shown in Figure 5, step 7). Figure 8

[0084] Example 12 PAP / [BMIM][BF4] separation of xylene isomers

[0085] A water dispersion of PX / MX / OX = 1 / 7 / 96 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5 and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as PX / MX / OX = 0 / 1 / 23 (as shown in Figure 5, step 8). Figure 8

[0086] Example 13 PAP / [BMIM][BF4] separation of xylene isomers

[0087] A water dispersion of MX / OX = 1 / 23 was injected through a 1 mL syringe into the PAP / [BMIM][BF4] loaded filter head prepared as in Example 5 and the filtrate was collected. A sample of the filtrate was analyzed by gas chromatography for the ratio of xylene isomers as MX / OX = 1 / 44 (as shown in Figure 5, step 9). Figure 8

[0088] Example 14 PAP / [BMIM][BF4] separation of xylene isomers

[0089] ​​​​A water dispersion of MX / OX = 1 / 44 was injected into the filter head (0.22 μ) prepared in Example 5 through a 1 mL syringe, and the filtrate was collected. The filtrate was sampled and analyzed by gas chromatography for the ratio of xylene isomers, which was MX / OX = 1 / 104.3. The purity of the obtained OX was greater than 99.0% (as shown in Table 1). Figure 8 step 10.

[0090] Thus, the above Examples 5 to 14 achieved high-purity separation of OX from a mixed dispersion by multistage adsorption based on the difference in adsorption capacity and diffusion rate of PAP / [BMIM][BF4] for MX and OX.

[0091] Example 15 Separation of xylene isomers by PAP / [BMIM][BF4]

[0092] A water dispersion of PX / MX = 1 / 1 was injected into the filter head (0.22 μ) prepared in Example 5 through a 1 mL syringe, and the filtrate was collected. The filtrate was sampled and analyzed by gas chromatography for the ratio of xylene isomers, which was PX / MX = 1 / 1.6. Then, the above operation was repeated to separate the water dispersion of xylene isomers obtained, and PX / MX = 1 / 69.4 was obtained at the 10th time. The purity of the obtained MX was greater than 98.5% (as shown in Table 2). Figure 9 step 1-10.

[0093] Example 16 Separation of xylene isomers by PAP / [BMIM][PF6]

[0094] PAP / [BMIM][PF6] was weighed at 60 mg and added to a 100 mL round-bottom flask, and 60 mL of water was added. The mixture was stirred and ultrasonically dispersed for 30 min until the dispersion became a uniform black opaque liquid. A 5 mL syringe was used to extract 5 mL of the PAP / [BMIM][PF6] dispersion and inject it into a filter head (0.22 μ), and the filtrate was water and the PAP / [BMIM][PF6] filter cake remained in the filter head. A water dispersion of PX / MX / OX (1 / 1 / 1) was prepared by mixing 25 ul of PX, 25 ul of MX and 25 ul of OX with 5 ml of water and ultrasonically dispersing for 30 min. The dispersion was injected into the filter head loaded with PAP / [BMIM][PF6] prepared above through a 1 mL syringe, and the filtrate was collected. The filtrate was sampled and analyzed by gas chromatography for the ratio of xylene isomers, which was PX / MX / OX = 1 / 1.1 / 1.6 (as shown in Table 3). Figure 10

[0095] ​Example 17 PAP / [BMIM][BF4] regeneration and recycling for separating xylene isomers

[0096] The filter head for separating xylene isomers loaded with PAP / [BMIM][BF4] in Example 5 was washed with a total amount of 50 mL of deionized water, 5 mL of deionized water was sucked into the filter head by a syringe, the deionized water was pressed into the filter head, the filter head was washed, the cycle was repeated 10 times, and no xylene isomers were detected by a gas chromatograph, indicating that the washing was complete. The aqueous dispersion of PX / MX / OX (1 / 1 / 1) was injected into the above-mentioned regenerated filter head loaded with PAP / [BMIM][BF4] through a 1 mL syringe, and the filtrate was collected. The filtrate was sampled and analyzed for the ratio of xylene isomers by a gas chromatograph. The PAP / [BMIM][BF4] regeneration and PX / MX / OX (1 / 1 / 1) separation operation was repeated 5 times, and the results of the analysis of the ratio of xylene isomers in the obtained filtrate were as follows:

[0097] Table 3. The ratio of xylene isomers obtained by the recycling operation of PAP / [BMIM][BF4] regeneration and PX / MX / OX (1 / 1 / 1) separation

[0098]

[0099] The results of the above-mentioned examples of the adsorbent separating xylene isomers show that the performance of PAP / [BMIM][BF4] is better than that of PAP / [BMIM][PF6], from the difference in the saturated adsorption amount of the three xylene isomers by the two adsorbents, the PAP / [BMIM][BF4] is greater than the PAP / [BMIM][PF6], the PAP / [BMIM][BF4] has a strong effect on adsorbing xylene; from the contact angle analysis, the 68° of PAP / [BMIM][BF4] is less than the 78° of PAP / [BMIM][PF6], indicating that the diffusion of the xylene aqueous dispersion in PAP / [BMIM][BF4] is better than that in PAP / [BMIM][PF6]; from the SEM morphology analysis, the PAP / [BMIM][BF4] has better porosity than the PAP / [BMIM][PF6], therefore, compared with PAP / [BMIM][PF6], PAP / [BMIM][BF4] can more effectively amplify the difference in the molecular structure of xylene isomers by repeated adsorption-desorption, has better performance for separating xylene isomers, and can be regenerated and recycled.

[0100] The above-mentioned examples are only a preferred scheme of the present application, and are not intended to limit the present application. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present application. Therefore, any technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present application.

Claims

1. A polymer composite adsorbent, characterized in that, The adsorbent is a complex of 1-aminopyrene polymer and supporting electrolyte, wherein the supporting electrolyte is 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6]. When the supporting electrolyte is 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], the degree of polymerization of 1-aminopyrene in the 1-aminopyrene polymer is 14~130; When the supporting electrolyte is 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], the degree of polymerization of 1-aminopyrene in the 1-aminopyrene polymer is 23~2790. The synthesis method of the polymer composite adsorbent is as follows: 1-aminopyrene is added to an electrolytic cell with an anode and a cathode, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] is added as a supporting electrolyte. Electrochemical polymerization reaction is carried out in an organic solvent at a constant potential of 1.0 ~ 3.0 V to obtain a 1-aminopyrene polymer doped with supporting electrolyte.

2. A method for synthesizing a polymer composite adsorbent, characterized in that: 1-Aminopyrene was added to an electrolytic cell with an anode and a cathode, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6] was added as a supporting electrolyte. Electrochemical polymerization was carried out in an organic solvent at a constant potential of 1.0 ~ 3.0 V to obtain a 1-aminopyrene polymer doped with supporting electrolyte.

3. The synthesis method as described in claim 2, characterized in that: The electrolytic cell is a single-cell electrolytic cell.

4. The synthesis method according to claim 2, characterized in that: The anode is a graphite anode.

5. The synthesis method as described in claim 2, characterized in that: The cathode is a graphite cathode.

6. The synthesis method according to claim 2, characterized in that: The organic solvent is acetonitrile.

7. An adsorbent for separating xylene isomers prepared from the polymer composite adsorbent as described in claim 1.

8. A method for separating xylene isomers, characterized in that: The aqueous dispersion of xylene isomers was adsorbed and separated using the polymer composite adsorbent as described in claim 1.

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