A GO-based oxazole-type hybrid matrix membrane and its preparation method

Abstract

This invention provides a GO-based oxazole-type mixed matrix membrane and its preparation method, comprising the following steps: preparing 2-(4-aminophenyl)-5-aminobenzoxazole; preparing oxazole-type polyimide; preparing functionalized graphene; uniformly mixing the oxazole-type polyimide, functionalized graphene, and DMAC to obtain a casting solution; applying the casting solution to a template and drying to obtain a pre-formed membrane; and treating the pre-formed membrane at high temperature to obtain the desired mixed matrix membrane. The GO-based oxazole-type mixed matrix membrane of this invention exhibits high CO2 / CH4 selectivity. The mixed matrix membrane prepared using functionalized GO as a filler further improves CO2 separation performance. The preparation method is simple, environmentally friendly, and provides excellent CO2 separation performance, offering a certain reference for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and in particular relates to a GO-based oxazole-type mixed matrix membrane and its preparation method. Background Technology

[0002] With the rapid development of the industrial economy, the consumption of fossil fuels worldwide is increasing daily. The separation and capture of CO2 is an urgent task.

[0003] The main CO2 separation technologies include absorption, adsorption, cryogenic distillation, and membrane separation. Among these, membrane separation is becoming the dominant technology due to its advantages such as low energy consumption, small footprint, and environmental friendliness. Among various membrane materials, hybrid matrix membranes can combine the advantages of both packing material and base membrane, resulting in significantly improved CO2 permeate flux and selectivity compared to pure membranes.

[0004] Polyimide (PI) is a polymer material with an imide ring in its main chain, hailed as "one of the most promising engineering plastics of the 21st century," and sits at the top of the plastics pyramid. It possesses excellent thermal stability, chemical resistance, good mechanical properties, and hydrophobicity. Using PI as a base film allows for applications under various harsh conditions, and the base film itself exhibits good CO2 / CH4 selectivity. Graphene (GO) is a two-dimensional material with voids within its layers. Using GO as a filler, its voids provide channels for gas permeation, enhancing its CO2 permeation flux.

[0005] Currently, polyimide-based membranes exhibit excellent overall performance, but their CO2 permeation flux is relatively low. Introducing GO (Glass Oxide) as a filler can largely solve this problem. However, since GO is an inorganic material, using pure GO for doping to prepare mixed matrix membranes can lead to interfacial defects, generating excessive non-selective pores and reducing CO2 selectivity. Summary of the Invention

[0006] In view of this, the present invention aims to propose a GO-based oxazole-type mixed matrix membrane and its preparation method to solve the interface defect problem and improve separation performance.

[0007] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0008] A method for preparing a GO-based oxazole-type mixed matrix membrane includes the following steps:

[0009] S1. Preparation of 2-(4-aminophenyl)-5-aminobenzoxazole;

[0010] S2. Preparation of oxazole-type polyimide;

[0011] S3. Preparation of functionalized graphene;

[0012] S4. Mix oxazole-type polyimide, functionalized graphene and DMAC evenly to obtain casting solution. Apply casting solution to template and dry to obtain pre-formed film. Treat pre-formed film at high temperature to obtain the desired mixed matrix film.

[0013] The inventive concept of this invention lies in first synthesizing 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA), and then synthesizing an oxazole-type polyimide with hexafluorodianhydride (6FAD). The oxazole ring has a strong affinity for CO2, so the 6FDA-APBOA-type polyimide has high CO2 / CH4 selectivity. After GO is functionalized with ionic liquid, the interfacial defect problem is solved. The resulting mixed matrix membrane has excellent CO2 separation performance.

[0014] Further, the method for preparing 2-(4-aminophenyl)-5-aminobenzoxazole in step S1 includes the following steps:

[0015] S11. After cooling the p-nitrobenzoyl chloride solution, add a mixed solution of 2-amino-5-nitrophenol and an acid-binding agent to react and obtain a reaction solution;

[0016] S12. Filter the reaction solution, dry the obtained solid and dissolve it in the first solvent, add the first catalyst, heat until the reaction is complete, evaporate the solvent to obtain 2-(4-nitrophenyl)-5-nitrobenzoxazole;

[0017] S13. Dissolve 2-(4-nitrophenyl)-5-nitrobenzoxazole in ethanol, add palladium on carbon and stir until homogeneous, then purge with hydrogen until the reaction is complete. Remove the palladium on carbon and ethanol to obtain 2-(4-aminophenyl)-5-aminobenzoxazole.

[0018] Furthermore, the first catalyst is one or more of trifluoromethanesulfonic acid, concentrated sulfuric acid, and polyphosphoric acid.

[0019] Further, the mass ratio of palladium on carbon to 2-(4-nitrophenyl)-5-nitrobenzoxazole is 0.01-0.05:1; preferably, the palladium on carbon is 5 wt%.

[0020] Furthermore, the method for preparing oxazole-type polyimide in step S2 includes the following steps:

[0021] S21. After mixing and reacting hexafluorodianhydride, 2-(4-aminophenyl)-5-aminobenzoxazole with DMAC, a dehydrating agent and a second catalyst are added, and the reaction is continued until complete to obtain a reaction solution.

[0022] S22. Add the reaction solution to a poor solvent, filter, wash and dry the precipitated solid to obtain the desired oxazole-type polyimide.

[0023] Furthermore, the unsuitable solvent is one of deionized water, methanol, ethanol, and isopropanol; preferably methanol or ethanol; more preferably ethanol.

[0024] Furthermore, the method for preparing functionalized graphene in step S3 includes the following steps:

[0025] The ionic liquid and the second solvent were mixed evenly, graphene was added, and after stirring evenly, the solvent was evaporated to obtain functionalized graphene.

[0026] Furthermore, the ionic liquid is a solution of one or both of 1,3-dimethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium methyl sulfate.

[0027] Furthermore, the solid content of the casting solution in step S4 is 5wt%-10wt%; preferably, the high-temperature treatment temperature of the pre-cast film is 180-220℃.

[0028] GO-based oxazole-type mixed matrix membranes prepared according to any of the preparation methods described above.

[0029] Compared with existing technologies, the GO-based oxazole-type mixed matrix membrane and its preparation method described in this invention have the following advantages:

[0030] The GO-based oxazole-type mixed matrix membrane described in this invention has high CO2 / CH4 selectivity. The mixed matrix membrane prepared with functionalized GO as a filler further improves the CO2 separation performance. The preparation method is simple, environmentally friendly, and has excellent CO2 separation performance, providing a certain reference for industrialization. Attached Figure Description

[0031] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0032] Figure 1 This is a schematic diagram of the synthetic route of 2-(4-aminophenyl)-5-aminobenzoxazole according to an embodiment of the present invention;

[0033] Figure 2 This is an HPLC schematic diagram of the 2-(4-nitrophenyl)-5-nitro group obtained in Example 1 of the present invention;

[0034] Figure 3 This is an HPLC schematic diagram of 2-(4-nitrophenyl)-5-amino obtained in Example 1 of the present invention;

[0035] Figure 4 This is a schematic diagram of the gas separation testing instrument for the separation membrane used in the test examples of the present invention;

[0036] Figure 5 This is a schematic diagram of the test results for a test example of the present invention. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0039] Example 1

[0040] Synthesis of 2-(4-nitrophenyl)-5-nitrobenzoxazole

[0041] 19.48 g of p-nitrobenzoyl chloride was dissolved in 50 mL of acetonitrile and cooled to 0 °C. Then, 15.41 g of 2-amino-4-nitrophenol and 6.96 g of propylene oxide were dissolved in 40 mL of acetonitrile and added dropwise to the above solution. After the addition was complete, the mixture was reacted at room temperature for 6 h. The product precipitated, filtered, and dried under vacuum at 80 °C for 5 h. The dried solid was added to 200 mL of γ-butyrolactone, along with 9.23 g of concentrated H₂SO₄. After stirring evenly, the mixture was heated to 80 °C and reacted for 12 h. The solvent was evaporated to dryness, and the product was washed with 500 mL of deionized water and dried under vacuum at 110 °C for 18 h to obtain 27.49 g of the target nitro compound, with a molar yield of 96.4% and a purity of 99.92%.

[0042] Synthesis of 2-(4-aminophenyl)-5-aminobenzoxazole

[0043] 20 g of 2-(4-nitrophenyl)-5-nitro, 0.3 g of palladium on carbon, and 150 g of ethanol were added to a 500 mL autoclave. After stirring until homogeneous, the temperature was raised to 60 °C. H2 was introduced at 1 MPa, and the reaction was maintained at this temperature for 12 h. After the reaction was complete, the palladium on carbon was removed by hot filtration, and 100 g of ethanol was recovered by vacuum distillation. The mixture was then cooled to 0 °C, resulting in the precipitation of a large amount of white crystals. After filtration, the solid was obtained and dried under vacuum at 60 °C for 8 h to yield 15.4 g of product, with a molar yield of 97.51% and a purity of 99.95%.

[0044] Example 2

[0045] Synthesis of 2-(4-nitrophenyl)-5-nitrobenzoxazole

[0046] 19.87 g of p-nitrobenzoyl chloride was dissolved in 50 mL of acetonitrile and cooled to 0 °C. Then, 15.41 g of 2-amino-4-nitrophenol and 9.49 g of pyridine were dissolved in 40 mL of acetonitrile. These were then added dropwise to the above solution. After the addition was complete, the reaction was allowed to proceed at room temperature for 7 h. The product precipitated, was filtered, washed with 200 mL of deionized water, and dried under vacuum at 100 °C for 5 h. The dried solid was added to 200 mL of dioxane, along with 21.23 g of polyphosphoric acid. After stirring thoroughly, the mixture was heated to 80 °C and reacted for 12 h. The solvent was evaporated to dryness, washed with 500 mL of deionized water, and dried under vacuum at 110 °C for 18 h to obtain 27.03 g of the target nitro compound, with a molar yield of 94.8% and a purity of 99.73%.

[0047] Synthesis of 2-(4-aminophenyl)-5-aminobenzoxazole

[0048] 20 g of 2-(4-nitrophenyl)-5-nitro, 0.25 g of palladium on carbon, and 150 g of ethanol were added to a 500 mL autoclave. After stirring until homogeneous, the temperature was raised to 60 °C. H2 at 0.8 MPa was introduced, and the reaction was maintained at this temperature for 12 h. After the reaction was complete, the palladium on carbon was removed by hot filtration, and 100 mL of ethanol was recovered by vacuum distillation. The mixture was then cooled to 0 °C, resulting in the precipitation of a large amount of white crystals. After filtration, the solid was obtained and dried under vacuum at 60 °C for 8 h to yield 15.28 g of product, with a molar yield of 96.74% and a purity of 99.85%.

[0049] Example 3

[0050] 10 g of hexafluorodianhydride was added to 30 mL of dimethylacetamide and stirred until dissolved. The mixture was then cooled to 0 °C. 5.07 g of APBOA was added to the reaction mixture, and the reaction was maintained at this temperature for 8 h. Next, 9.19 g of acetic anhydride and 2.28 g of triethylamine were added to the reaction system, and the temperature was raised to 25 °C for 6 h. The mixture was then poured into 500 mL of ethanol, resulting in the precipitation of a large amount of filamentous solid. This solid was filtered, washed again with 500 mL of ethanol for 8 h, and then vacuum dried at 130 °C for 24 h to obtain 13.53 g of oxazole-type polyimide 6FDA-APBOA.

[0051] Example 4

[0052] 9.97 g of hexafluorodianhydride was added to 30 mL of dimethylacetamide and stirred until dissolved. The mixture was then cooled to 0 °C. 5.07 g of APBOA was added to the reaction solution, and the reaction was maintained at this temperature for 8 h. Then, 2.93 g of propionic anhydride and 1.78 g of pyridine were added to the reaction system, and the temperature was raised to 25 °C for 6 h. The mixture was then poured into 500 mL of isopropanol, resulting in the precipitation of a large amount of filamentous solid. This solid was filtered, washed again with 500 mL of isopropanol for 8 h, and then vacuum dried at 130 °C for 24 h to obtain 12.98 g of oxazole-type polyimide 6FDA-APBOA.

[0053] Example 5

[0054] 200 mg of the ionic liquid 1,3-dimethylimidazolium tetrafluoroborate was dissolved in 10 mL of tetrahydrofuran. 100 mg of GO was added and stirred for 3 h, followed by sonication for 3 h. The mixture was then poured into a beaker and slowly stirred at 50 °C for 1 h, during which the solution was slowly evaporated to dryness. The solid was then vacuum dried at 60 °C for 8 h, yielding 260 mg of functionalized graphene IL-GO-1.

[0055] Example 6

[0056] 200 mg of the ionic liquid methyl 1-ethyl-3-methylimidazolium sulfate was dissolved in 10 mL of dichloromethane. 100 mg of GO was added and the mixture was stirred for 3 hours, followed by sonication for 3 hours. The solution was then poured into a beaker and slowly stirred at 50 °C for 1 hour until the solid was evaporated to dryness. The solid was then vacuum dried at 60 °C for 8 hours, yielding 280 mg of functionalized graphene IL-GO-2.

[0057] Example 7

[0058] 0.5 g of oxazole-type polyimide 6FDA-APBOA was dissolved in 7 mL of DMAc, stirred for 2 h, and sonicated for 3 h to remove air bubbles. The solution was then coated onto a tetrafluoroethylene plate and placed on a heating platform at 50 °C for 8 h to fix it into a pre-formed membrane. After peeling, it was vacuum dried in a vacuum oven at 200 °C for 24 h to obtain the separation membrane, 6FDA-APBOA.

[0059] 0.5 g of oxazole-type polyimide 6FDA-APBOA was dissolved in 7 mL of DMAc. Then, 2 mg of IL-GO-1 was ground and incorporated into the casting solution. The mixture was stirred for 2 hours, sonicated for 3 hours to remove air bubbles, and then coated onto a tetrafluoroethylene plate. The plate was then placed on a heating platform at 50°C for 8 hours to fix it into a pre-formed membrane. After peeling, the membrane was vacuum-dried at 200°C for 24 hours to obtain the separation membrane, IL-GO-1 / 6FDA-APBOA.

[0060] Example 8

[0061] 0.5 g of oxazole-type polyimide 6FDA-APBOA was dissolved in 7 mL of DMAc. Then, 2 mg of IL-GO-2 was ground and incorporated into the casting solution. The mixture was stirred for 2 hours, sonicated for 3 hours to remove air bubbles, and then coated onto a tetrafluoroethylene plate. The plate was then placed on a heating platform at 50°C for 8 hours to fix it into a pre-formed membrane. After peeling, the membrane was vacuum-dried at 200°C for 24 hours to obtain the separation membrane, IL-GO-2 / 6FDA-APBOA.

[0062] Test case

[0063] The separation membranes prepared in Examples 7-8 were subjected to CO2 / CH4 gas separation performance tests. The connection structure of the gas separation performance testing equipment is as follows. Figure 4 As shown, F1-F10 are all valves. The specific experimental steps are as follows:

[0064] (1) After loading the separation membranes prepared in Examples 7-8 into the membrane cells, first turn on the vacuum pump, then turn on F3, F6, and F7, then turn on F4 and F5, and then slowly turn on F8 to simultaneously evacuate the upper and lower membrane cells. At this time, F1 and F2 are in the off state; when the vacuum degree reaches 3.0 × 10 -2 Tests can be performed when the torque is below a certain level;

[0065] (2) First, turn off F4 and F8 in sequence, then turn on F1 to fill in the test gas at a certain pressure, and repeatedly turn on F2 to replace the gas three times. After adjusting the injection pressure, turn off F3 (according to the test gas requirements), F6, F7 and vacuum pump, turn on F4 and click "start" to start data acquisition. At this time, F1 and F2 are still in the off state.

[0066] (3) After the test, turn on the vacuum pump, F3, F6 and F7, close the pressure reducing valve, open F1 and F2 to purge the gas in the sample inlet pipeline, then close F1 and F2, and then slowly open F8 to pump gas at the same time.

[0067] The gas permeability coefficient P can be calculated by testing the curve of gas pressure change over time in the upper membrane chamber. For example... Figure 5 As shown, according to the technical solution provided by the present invention, the obtained oxazole-type polyimide (6FDA-APBOA) as the base membrane has excellent CO2 separation performance. The mixed matrix membrane prepared by using functionalized GO as filler has high CO2 permeation flux and high CO2 / CH4 selectivity.

[0068] Using 6FDA-APBOA as the base membrane, the CO2 permeation flux was 15.67 Barrer, and the CO2 / CH4 selectivity was 46.89. Compared to the base membrane, IL-GO-1 / 6FDA-APBOA showed a 68.94% increase in permeation flux and a 52.67% increase in CO2 / CH4 selectivity, while IL-GO-2 / 6FDA-APBOA showed a 57.38% increase in permeation flux and a 32.54% increase in CO2 / CH4 selectivity.

Claims

1. A method for preparing a GO-based mixed matrix membrane of oxazole type, characterized in that, The method comprises the following steps: S1, preparing 2-(4-aminophenyl)-5-aminobenzoxazole; S2, preparing oxazole type polyimide; S3, preparing functionalized graphene; S4, mixing the oxazole type polyimide, the functionalized graphene and DMAC uniformly to obtain a casting solution, applying the casting solution on a template, drying to obtain a preformed film, and high-temperature treating the preformed film to obtain a desired mixed matrix film; The method for preparing the oxazole type polyimide in step S2 comprises the following steps: S21, mixing hexafluorodianhydride, 2-(4-aminophenyl)-5-aminobenzoxazole and DMAC, adding a dehydrating agent and a second catalyst after reaction, and continuing to react until complete to obtain a reaction solution; The dehydrating agent is at least one selected from acetic anhydride and propionic anhydride, and the second catalyst is at least one selected from triethylamine and pyridine; S22, adding the reaction solution into a poor solvent, filtering, washing and drying the precipitated solid to obtain the desired oxazole type polyimide; The method for preparing the functionalized graphene in step S3 comprises the following steps: Mixing the ionic liquid and a second solvent uniformly, adding graphene, stirring uniformly, and evaporating the solvent to obtain the functionalized graphene; The second solvent is at least one selected from tetrahydrofuran and dichloromethane.

2. The production method according to claim 1, characterized by, The method for preparing 2-(4-aminophenyl)-5-aminobenzoxazole in step S1 comprises the following steps: S11, cooling the p-nitrobenzoyl chloride solution, adding a mixed solution of 2-amino-5-nitrophenol and an acid binding agent to react, and obtaining a reaction solution; S12, filtering the reaction solution, drying the obtained solid, dissolving it in a first solvent, adding a first catalyst, heating until the reaction is complete, evaporating the solvent, and obtaining 2-(4-nitrophenyl)-5-nitrobenzoxazole; S13, dissolving 2-(4-nitrophenyl)-5-nitrobenzoxazole in ethanol, adding palladium-carbon and stirring uniformly, passing hydrogen until the reaction is complete, removing the palladium-carbon and ethanol, and obtaining 2-(4-aminophenyl)-5-aminobenzoxazole.

3. The method of claim 2, wherein: The first catalyst is one or more of trifluoromethanesulfonic acid, concentrated sulfuric acid and polyphosphoric acid.

4. The method of claim 2, wherein: The mass ratio of palladium-carbon to 2-(4-nitrophenyl)-5-nitrobenzoxazole is 0.01-0.05:

1.

5. The method of claim 2, wherein: The palladium-carbon is 5wt%.

6. The method of claim 1, wherein: The poor solvent is one of deionized water, methanol, ethanol and isopropanol.

7. The method of claim 6, wherein: The poor solvent is methanol or ethanol.

8. The method of claim 7, wherein: The poor solvent is ethanol.

9. The method of claim 1, wherein, The ionic liquid is a solution of one or both of 1,3-dimethylimidazolium tetrafluoroborate and 1-ethyl-3-methylimidazolium methyl sulfate.

10. The method of claim 1, wherein, The solid content of the casting solution in step S4 is 5wt%-10wt%.

11. The method of claim 1, wherein, The high-temperature treating temperature of the preformed film in step S4 is 180-220℃.

12. The GO-based oxazole type mixed matrix film prepared by the method according to any one of claims 1-11.

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