Metal organic framework glass-crystal composite membrane with high gas separation efficiency

Abstract

The invention discloses a metal organic framework glass-crystal composite film with high gas separation efficiency, which is characterized in that a bottom layer takes porous aluminum oxide as a film substrate, a first layer covers a ZIF-8 film layer, a second layer covers a ZIF-62 film layer, and mutual melting and leveling of the two film layers are realized in an argon atmosphere through a melting quenching method, so that the metal organic framework glass-crystal composite film with high gas separation efficiency is obtained. And finally, the defect-free glass-crystal composite film is obtained. The composite film obtained by matching a layer-by-layer in-situ compounding method with a melting quenching method has a certain prospect in the field of separation and purification of carbon dioxide gas in mixed gas.

Description

Technical Field

[0001] The invention relates to the technical field of membrane separation materials, and in particular to a metal organic skeleton glass-crystal composite membrane with high gas separation efficiency. Background Art

[0002] As a new type of porous solid material, the MOF material of the present invention has considerable potential in separation and purification applications. The MOF crystal film is a porous film in which a MOF crystal layer is grown on a porous carrier such as aluminum oxide or titanium dioxide. Therefore, this type of MOF film has higher flux and selectivity. However, the MOF crystal film also has many problems such as high cost, easy to produce defects, poor matrix-MOF layer bonding, poor mechanical strength, etc., which limits the further development of the MOF crystal film.

[0003] Mixed matrix membranes often have inherent compatibility issues between inorganic fillers and polymer matrix materials, which leads to defects at the filler-matrix interface, resulting in reduced membrane selectivity. Compared with MOF crystal membranes, mixed matrix membranes (MMMs) with polymer as matrix and MOF as filler have the advantages of low cost, easy processing, good mechanical strength, good selectivity and permeability. However, the obtained MMMs have inevitable phase segregation, low filler loading and partial clogging of micropores, which significantly weakens its molecular sieving effect.

[0004] Compared with the above-mentioned thin films whose main system is polycrystalline MOF, MOF glass membranes are dense, have no grain boundaries, are isotropic, and exhibit excellent separation performance. The research on this type of membrane material has certain prospects. Summary of the invention

[0005] In view of the problems existing in the prior art, the object of the present invention is to provide a metal organic framework glass-crystal composite membrane with high gas separation efficiency.

[0006] To solve the above problems, the present invention adopts the following technical solutions.

[0007] In a preferred embodiment of the present invention, a composite film composed of a circular substrate, a ZIF-8 membrane layer, and a ZIF-62 glass membrane layer is used for purifying and separating carbon dioxide in a natural gas mixture.

[0008] In a preferred embodiment of the present invention, the circular base liner is made of alumina.

[0009] In a preferred embodiment of the present invention, the base liner has a diameter of 20 mm, a thickness of 0.5 mm, and a purity of 96%.

[0010] In a preferred embodiment of the present invention, the ZIF-8 membrane layer and the ZIF-62 membrane layer are synthesized by an in-situ solvent thermal method, and the solvent is N,N-dimethylformamide (DMF).

[0011] In a preferred embodiment of the present invention, the in-situ solvent thermal reaction temperature of the ZIF-8 membrane layer is 100°C.

[0012] In a preferred embodiment of the present invention, the in-situ solvent thermal reaction temperature of the ZIF-62 membrane layer is 110°C.

[0013] In a preferred embodiment of the present invention, the ZIF-62 glass film layer is prepared by a ZIF-62 crystal film layer through a melt quenching method.

[0014] In a preferred embodiment of the present invention, the reaction temperature of the ZIF-62 glass film melt quenching is 440°C.

[0015] In a preferred embodiment of the present invention, the ZIF-8 membrane layer and the ZIF-62 glass membrane layer are synthesized by a layer-by-layer composite method and belong to a double-layer composite membrane with a typical "sandwich" structure.

[0016] Compared with the prior art, the advantages of the present invention are:

[0017] This patent realizes a metal organic framework glass-crystal composite gas separation membrane, selects ZIF-62 glass as the matrix and ZIF-8 as the filler, and synthesizes and fires the composite glass film in situ for gas separation through layer-by-layer composite method. The composite glass membrane retains some pores and has no grain boundary defects compared to MOF polycrystalline membrane, and has better gas separation efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of the structure of the present invention;

[0019] Figure 2 is the XRD pattern of the present invention;

[0020] Figure 3 is a scanning electron microscope surface topography image of the surface of the present invention;

[0021] Figure 4 It is a scanning electron microscope cross-sectional view of the surface of the present invention. DETAILED DESCRIPTION

[0022] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention; it is obvious that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments, and all other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making creative work are within the scope of protection of the present invention.

[0023] Reference Figure 1 The present invention proposes a metal organic framework glass-crystal composite membrane with high gas separation efficiency, including a porous substrate 1, a ZIF-8 membrane layer 2, and a ZIF-62 glass membrane layer 3.

[0024] The method for preparing the above metal organic framework glass-crystal composite film is as follows.

[0025] Before synthesizing the film, the porous substrate 1 was pretreated: the aluminum oxide was polished with 1200 mesh and 2000 mesh sandpaper until the surface was smooth, the surface dust was washed with deionized water, the substrate was immersed in a 6% hydrochloric acid solution in an oven at 60°C for 6 hours, ultrasonically washed with deionized water for 2 hours, and dried at 100°C for use.

[0026] The composite membrane is prepared by a solvent-thermal layer-by-layer composite method, that is, a ZIF-8 membrane layer 2 is first synthesized, then covered with a layer of ZIF-62 crystals, and then sintered into a ZIF-62 glass layer 3 in a tubular furnace under an argon atmosphere, and finally the composite glass membrane is obtained.

[0027] The ZIF-8 membrane layer 2 was prepared by an in-situ solvothermal method. The raw materials were (NO3)2·6H2O and 2-methylimidazole. DMF was selected as the solvent. The mass of the required drug and solvent was calculated based on the molar ratio of Zn:2-MIM:DMF=1:3:208. After adding 50 ml of DMF to the drug, the mixture was stirred on a magnetic stirrer for 30 minutes to mix evenly. The polytetrafluoroethylene liner was placed in a stainless steel reactor and reacted in an oven at 50°C and 100°C for 2 hours, 4 hours, and 8 hours, respectively, to obtain a crystal membrane. The taken out membrane was rinsed three times with DMF to remove residual crystals on the surface and dried in an oven at 100°C overnight.

[0028] The ZIF-62 crystal membrane was prepared by an in-situ solvothermal method. The raw materials were (NO3)2·6H2O, imidazole, and benzimidazole. DMF was selected as the solvent. The mass of the required drugs and solvent was calculated based on the molar ratio of Zn:IM:BIM:DMF=1:13.5:1.5:111. After adding 50 ml of DMF to the drugs, the mixture was stirred on a magnetic stirrer for 30 minutes to mix evenly. The pre-dried ZIF-8 membrane layer was placed in the reaction solution and the polytetrafluoroethylene liner was placed in a stainless steel reactor. The reaction was carried out in an oven at 110°C for 48 hours. The taken out membrane was rinsed three times with DMF to remove residual crystals on the surface and then dried at 100°C overnight to obtain a composite crystal membrane.

[0029] Preparation of composite glass membrane. The dried composite crystal membrane was placed in a tubular furnace and fired in an argon atmosphere. The ZIF-62 crystal was converted into glass by melt quenching. The temperature was raised from 25°C to 430°C at a heating rate of 10 k / min, and then kept at 450°C for 10 min and 15 min, then naturally cooled to room temperature and taken out to obtain a glass crystal composite membrane.

[0030] The present invention is further explained below with a specific embodiment:

[0031] After the alumina base liner was pre-treated by grinding, acid immersion, etc., the mass of the required chemicals and solvents was calculated with the molar ratio of Zn:2-MIM:DMF=1:3:208. 0.9246g of Zn(NO3)2·6H2O and 0.7656g of 2-methylimidazole were placed in a polytetrafluoroethylene liner, 50ml of DMF was added, and the chemicals were stirred on a magnetic stirrer for 30min to mix evenly. The polytetrafluoroethylene liner was placed in a stainless steel reactor and reacted in an oven at 100°C for 8 hours to obtain a crystal film. The taken out film was rinsed three times with DMF to remove residual crystals on the surface and dried in an oven at 100°C overnight. The mass of the required drugs and solvents was calculated with the molar ratio of Zn:IM:BIM:DMF=1:13.5:1.5:111. 1.7326g of Zn(NO3)2·6H2O, 5.3527g of imidazole and 1.0321g of benzimidazole were placed in a polytetrafluoroethylene liner, 50ml of DMF was added, and the drugs were stirred on a magnetic stirrer for 30min to mix evenly. The pre-dried ZIF-8 membrane layer was placed in the reaction solution. The polytetrafluoroethylene liner was placed in a stainless steel reactor and reacted in an oven at 110℃ for 48 hours. The taken out membrane was rinsed with DMF three times to remove the residual crystals on the surface, and then dried at 100℃ overnight to obtain a composite crystal membrane. The dried composite crystal membrane was placed in a tubular furnace and fired in an argon atmosphere. The ZIF-62 crystal was converted into glass by melt quenching method. The temperature was raised from 25℃ to 450℃ at a rate of 10k / min, kept for 10min, and then naturally cooled to room temperature and taken out. Test the powder XRD spectrum before and after melt quenching, refer to Figure 2 It was found that ZIF-62 crystals were transformed into glass and ZIF-8 was also transformed into amorphous state. The cross-sectional morphology of the obtained film was analyzed by scanning electron microscopy. Figure 3 , Figure 4 It was found that the composite glass membrane after melting and quenching in a tubular furnace had a smooth surface without crystalline particles, a thin and uniform thickness, and a calculated average thickness of about 39μm. The separation efficiency of the composite glass membrane for gases such as carbon dioxide was tested using a self-assembled gas separation test device. The results showed that the film had a high separation efficiency for carbon dioxide / hydrogen and carbon dioxide / methane, and was quite promising for the separation of mixed gases containing carbon dioxide.

[0032] The above is only a preferred specific implementation of the present invention; however, the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solution and its improved conception within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A metal organic framework glass-crystal composite membrane with high gas separation efficiency, characterized in that: It includes a composite film consisting of a bottom circular substrate, a MOF crystal film layer and a MOF glass film layer.

2. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The bottom circular lining is made of porous material and is in the shape of hollow fibers.

3. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The bottom circular base lining has a diameter in the range of 10-20 mm and a thickness in the range of 0.5-1 mm.

4. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The purity of the bottom circular substrate is 90%-99%.

5. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The original crystal film layer corresponding to the MOF crystal film layer and the MOF glass film layer is synthesized by a seed secondary growth method or an in-situ solvent thermal method, and the solvent is N,N-dimethylformamide.

6. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 5, characterized in that: The solvent thermal reaction temperature of the MOF crystal film layer is set in the range of 25°C-100°C.

7. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The solvent thermal reaction temperature of the original crystal film layer corresponding to the MOF glass film layer is set in the range of 100°C-150°C.

8. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The MOF glass film layer is prepared by a melt-quenching method using a corresponding original MOF crystal film layer.

9. The metal organic framework glass-crystal composite membrane with high gas separation efficiency according to claim 1, characterized in that: The MOF crystal film layer and the MOF glass film layer are synthesized through a layer-by-layer composite method.

10. A metal organic framework glass-crystal composite membrane with high gas separation efficiency according to any one of claims 1 to 9, characterized in that: The composite membrane is used for separation and purification of mixed gas containing carbon dioxide.

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