Mixed matrix membrane for gas separation as well as preparation method and application of mixed matrix membrane

Abstract

The invention belongs to the field of gas separation, and relates to a mixed matrix membrane for gas separation and a preparation method and application thereof, the preparation method comprises the following steps: mixing hydroxide, water, an aluminum source, a template agent and a silicon source to obtain sol; stirring and aging the sol, performing crystallization reaction, and drying to obtain a molecular sieve; fully stirring and mixing a molecular sieve and a dispersing solvent, and performing ultrasonic treatment to obtain a molecular sieve suspension; dripping the molecular sieve suspension onto a support body, drying and calcining to obtain an oriented layered molecular sieve membrane; the preparation method comprises the following steps: taking out a mixed matrix membrane, soaking the mixed matrix membrane in a 1, 2, 4, 5-phenylenetetramine tetrahydrochloride solution, taking out the mixed matrix membrane until no obvious liquid drops exist on the surface, dropwise adding a toluene solution of terephthalaldehyde, and drying to obtain the mixed matrix membrane for gas separation. The method well solves the problem that gas permeability and selectivity are difficult to balance, and can be used for high-permeability and high-selectivity separation of hydrogen and nitrogen.

Description

Technical Field

[0001] The invention belongs to the field of gas separation and relates to a mixed matrix membrane for gas separation and a preparation method and application thereof. Background Art

[0002] Hydrogen is a secondary energy source that cannot be obtained directly. Steam reforming of fossil energy and water-gas conversion reaction are currently the main ways to produce hydrogen, but the hydrogen produced by this method contains a large amount of by-products such as N2, CO2, and H2O, so the hydrogen needs to be separated and purified.

[0003] Traditional gas separation generally uses distillation. Compared with traditional distillation separation, membrane separation is easy to operate, occupies a small area, and can reduce energy consumption by about 90%. It is an environmentally friendly and efficient alternative to traditional gas separation. Membrane materials are mainly divided into organic membranes and inorganic membranes. Organic polymers have the advantages of strong plasticity, simple preparation, diverse functions, low cost, and good selectivity. They are currently the most widely used separation membrane materials, but they have disadvantages such as heat resistance, corrosion resistance, poor mechanical strength, and low permeability. For example, the selectivity of polybenzimidazole membrane H2 / CO2 can reach 140, but the permeability to H2 is only 3.15×10 -10 mol . m -2. s -1. Pa -1 Inorganic membranes based on molecular sieve materials have uniform and clear pore structures, which facilitate the passage of gas molecules and are usually characterized by high flux and thermal stability. However, the selectivity of molecular sieve membranes is generally low. For example, the MCM-22 molecular sieve membrane obtained by single vacuum filtration has a H2 / N2 selectivity of only 2, but the H2 permeation flux exceeds 1.0×10 -6 mol . m -2. s -1. Pa -1 , and it is easy to fall off, making it difficult to prepare a continuous defect-free film.

[0004] In summary, existing membrane materials used for hydrogen / nitrogen separation currently have problems such as low hydrogen permeability and low selectivity between hydrogen and other gases. These factors have greatly restricted the development and industrial application of hydrogen separation membranes. Summary of the invention

[0005] The technical problem to be solved by the present invention is that it is difficult to balance the gas permeability and selectivity of existing gas separation membrane materials, and a new molecular sieve mixed matrix membrane for hydrogen / nitrogen separation is provided. The method has the advantage of being able to balance the gas permeability and selectivity of gas separation membrane materials.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0007] A preparation method of a mixed matrix membrane for gas separation comprises the following steps: mixing hydroxide, water, an aluminum source, a template agent and a silicon source to obtain a sol; stirring and aging the sol, performing a crystallization reaction, and drying to obtain a molecular sieve; fully stirring and mixing the molecular sieve with a dispersion solvent, and then ultrasonicating to obtain a molecular sieve suspension; dropping the molecular sieve suspension onto a support, drying, and calcining to obtain an oriented layered molecular sieve membrane; immersing the oriented layered molecular sieve membrane in a 1, 2, 4, 5-benzenetetramine tetrahydrochloride solution, taking it out until there are no obvious droplets on the surface, dropping a toluene solution of terephthalaldehyde, and drying to obtain a mixed matrix membrane for gas separation.

[0008] Further, the hydroxide is one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide; the aluminum source is one or two of sodium aluminate and aluminum hydroxide; preferably sodium aluminate; preferably sodium hydroxide; the template is one or more of hexamethyleneimine, dicyclohexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and N, N, N-trimethyladamantanammonium hydroxide; preferably hexamethyleneimine and dicyclohexylamine; the silicon source is one or more of silica gel, sodium metasilicate nonahydrate, tetraethyl orthosilicate, and white carbon black, preferably silica gel.

[0009] Furthermore, the molar ratio of hydroxide, water, aluminum source, template and silicon source is 0.1-0.2:18:0.01-0.066:0.3-1:1.

[0010] Furthermore, the stirring aging temperature is 20-40°C, the stirring aging time is 2-5 hours; the crystallization reaction temperature is 160-200°C, the crystallization reaction time is 1-7 days; and the ultrasonic time is 0.5-3 hours.

[0011] Furthermore, the dispersion solvent for preparing the molecular sieve suspension is one of water, ethyl acetate, ethanol or methanol; and the concentration of the molecular sieve suspension is 0.125-1 wt%.

[0012] Furthermore, the support body is placed on a heating table for heating, and the temperature of the heating table is 80-200°C.

[0013] Furthermore, the calcination temperature is 500-600°C, and the calcination time is 4-8 hours.

[0014] Furthermore, the layered molecular sieve membrane is immersed in the 1, 2, 4, 5-benzenetetraamine tetrahydrochloride solution for 0.5 to 3 hours.

[0015] Furthermore, the synthesized molecular sieve is one of two-dimensional six-membered ring molecular sieves such as MCM-22 and ITQ-2, preferably MCM-22.

[0016] The support is mullite or α-Al2O3 ceramic, preferably α-Al2O3 ceramic.

[0017] The present invention also provides a mixed matrix membrane for gas separation, which is prepared by the above preparation method.

[0018] The present invention also provides application of the mixed matrix membrane in hydrogen separation.

[0019] Beneficial Effects

[0020] In the present invention, the MCM-22 molecular sieve is loaded on the support by using the method of hot dripping of the molecular sieve solution, so that the orientation of the obtained MCM-22 molecular sieve membrane is much higher than that of the molecular sieve membrane prepared by the usual hydrothermal method, and thus has a higher hydrogen permeability. In addition, the method of the present invention composites the poly-p-phenylbenzimidazole membrane on the inorganic oriented MCM-22 molecular sieve layer, has a higher hydrogen permeability, balances the permeation amount and selectivity of the gas, and can be used for the separation of high permeability and high selectivity hydrogen and nitrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a scanning electron microscope (SEM) image of the surface of the oriented MCM-22 molecular sieve membrane prepared by the method of Example 1.

[0022] Figure 2 This is a scanning electron microscope (SEM) image of the cross section of the oriented MCM-22 molecular sieve membrane prepared by the method of Example 1.

[0023] Figure 3 The X-ray diffraction (XRD) patterns of the MCM-22 molecular sieve powder and the oriented MCM-22 molecular sieve membrane prepared by the method of Example 1 are shown.

[0024] Figure 4 This is a scanning electron microscope (SEM) image of the surface of the oriented MCM-22 molecular sieve mixed matrix membrane prepared by the method of Example 1. DETAILED DESCRIPTION

[0025] Example 1

[0026] A method for preparing a mixed matrix membrane for gas separation comprises the following steps:

[0027] (1) First, add water, sodium hydroxide and sodium aluminate into a beaker for 30 min. o After adding hexamethyleneimine dropwise into the beaker, stirring was continued for 30 minutes until the mixture was uniformly mixed. After adding dicyclohexylamine and stirring for 30 minutes until the mixture was uniformly mixed, silica gel (40%) was slowly added dropwise. After the mixture was stirred and aged at 30 °C for 4 hours, it was transferred to a stainless steel kettle lined with polytetrafluoroethylene and incubated at 170 °C. oC crystallizes for 3 days, after the crystallization is completed, washes with water until neutral, and obtains MCM-22 molecular sieve after drying. The molar ratio of silica gel: sodium aluminate: sodium hydroxide: hexamethyleneimine: dicyclohexylamine: water in the mixed solution is 1: 0.033: 0.1: 0.3: 0.4: 18;

[0028] (2) The MCM-22 molecular sieve prepared in (1) was diluted with water to obtain a 0.125 wt% MCM-22 molecular sieve suspension. After ultrasonic dispersion for 1 hour, 2.5 mL of the molecular sieve suspension was hot-dropped onto a support placed on a 150°C heating table. The support was an α-Al2O3 ceramic substrate with a pore size of 0.22 μm and a diameter of cm. The suspension was cooled to room temperature. o C for 6 hours to obtain a high permeability oriented layered MCM-22 molecular sieve membrane;

[0029] (3) immersing the oriented layered MCM-22 molecular sieve membrane prepared in (2) in a 1.5 wt% 1, 2, 4, 5-benzenetetramine tetrahydrochloride (BTA) solution for 0.5 h, taking it out until there are no obvious droplets on the surface, adding a 1.0 wt% toluene solution of terephthalaldehyde (TPA), and drying to obtain an MCM-22 molecular sieve mixed matrix membrane, which is recorded as M0.125-0.5;

[0030] (4) The MCM-22 molecular sieve mixed matrix membrane prepared in step (3) was subjected to a gas separation test.

[0031] Figure 1 This is a scanning electron microscope (SEM) image of the surface of the oriented MCM-22 molecular sieve membrane prepared by the method of Example 1. The result shows that the α-Al2O3 ceramic substrate is completely covered by the flaky MCM-22 molecular sieve, and the membrane surface is continuous.

[0032] Figure 2 This is a scanning electron microscope (SEM) image of the cross section of the oriented MCM-22 molecular sieve mixed matrix membrane prepared by the method of Example 1. The thickness of the membrane layer is about 1 micron.

[0033] Figure 3 The X-ray diffraction (XRD) patterns of the MCM-22 molecular sieve powder and the oriented MCM-22 molecular sieve membrane prepared by the method of Example 1 show that an obvious (001) peak appears in the XRD spectrum, indicating that the prepared MCM-22 molecular sieve membrane has orientation.

[0034] Figure 4 This is a scanning electron microscope (SEM) image of the surface of the oriented MCM-22 molecular sieve mixed matrix membrane prepared by the method of Example 1. The results show that the surface of the MCM-22 molecular sieve membrane is completely covered by the poly(p-phenylbenzimidazole) film layer, and the surface is continuous without obvious defects.

[0035] Example 2-3

[0036] According to the method of Example 1, only the immersion time in step (3) was changed. The adjusted immersion time was 2 hours and 3 hours respectively, which were recorded as M0.125-x, where x=2.0 and 3.0.

[0037] Example 4

[0038] According to the method of Example 1, only the concentration of the suspension in step (2) was changed. The adjusted concentration of the suspension was 0.5 wt %. The sample was recorded as M0.5-0.5.

[0039] Embodiment 5-6

[0040] According to the method of Example 4, only the immersion time in step (3) was changed. The adjusted immersion time was 2 hours and 3 hours respectively, denoted as M0.5-x, where x=2.0 and 3.0.

[0041] Example 7

[0042] According to the method of Example 1, only the concentration of the suspension in step (2) was changed. The adjusted concentration of the suspension was 1.0 wt %. The sample was recorded as M1.0-0.5.

[0043] Embodiment 8-9

[0044] According to the method of Example 7, only the immersion time in step (3) was changed. The adjusted immersion time was 2 hours and 3 hours respectively, denoted as M1.0-x, where x=2.0 and 3.0.

[0045] Comparative Example 1

[0046] A method for preparing a mixed matrix membrane for gas separation comprises the following steps: (1) firstly depositing MCM-22 molecular sieve onto an α-Al2O3 ceramic substrate by an ultrasound-assisted method; (2) mixing silica sol at 50 o C for 60 hours, and then aged at room temperature for about 7 days. The aged silica sol is diluted 256 times (type A silica sol) and 128 times (type B silica sol) with ethanol, and the α-Al2O3 ceramic substrate is vertically immersed in contact with type A silica sol for 20 seconds, and then dried for 40 seconds. The α-Al2O3 ceramic substrate is vertically immersed in contact with type B silica sol for 20 seconds, and then dried for 40 seconds. This process is repeated 3 times. (3) The MCM-22 molecular sieve membrane prepared in step (2) is dried in an oven at 120°C to obtain a sample, which is recorded as MS. (4) The MCM-22 molecular sieve membrane prepared in step (3) is subjected to a gas separation test.

[0047] Comparative Example 2

[0048] A method for preparing a mixed matrix membrane for gas separation comprises the following steps: (1) firstly adding water, sodium hydroxide and sodium aluminate into a beaker; o C was stirred until clear and transparent to obtain solution A. Hexamethyleneimine was added dropwise to solution A and stirred for 30 minutes until the mixture was uniformly mixed to obtain solution B. Dicyclohexylamine was added to solution B and stirred for 30 minutes until the mixture was uniformly mixed to obtain solution C. Silica gel (40%) was slowly added dropwise to solution C to obtain solution D. After stirring and aging solution D for 4 hours, solution D was transferred to a stainless steel kettle lined with polytetrafluoroethylene and heated at 150 o C for 3 days. After crystallization, wash with water until neutral, and dry to obtain MCM-22 molecular sieve. The molar ratio of silica gel: sodium aluminate: sodium hydroxide: hexamethyleneimine: dicyclohexylamine: water in the mixed solution is 1: 0.028: 0.15: 0.5: 0.4: 44. (2) Anhydrous ethanol is used as a solvent to disperse the MCM-22 molecular sieve obtained in step (1) into a solution with a concentration of 5 g / L, which is recorded as solution E. The dried ceramic tube is slowly placed in solution E, immersed for 30 seconds, then slowly taken out, and then placed in 110 o C oven and dried. Repeat the impregnation process after 1 hour. (3) Place solution D and the ceramic tube obtained in step (3) into a polytetrafluoroethylene stainless steel crystallization kettle at 150 o C was crystallized for 3 days, taken out for washing, drying and calcining to obtain an MCM-22 molecular sieve membrane, which was denoted as M. (4) The MCM-22 molecular sieve membrane prepared in step (3) was subjected to a gas separation test.

[0049] Comparative Example 3

[0050] A method for preparing a mixed matrix membrane for gas separation comprises the following steps: (1) firstly, water and sodium hydroxide are stirred at room temperature until they are clear and transparent to obtain solution A. Aluminum foil is added to solution A until the mixture is uniformly mixed to obtain solution B. Silica sol is mixed with water and rapidly stirred at 60°C to obtain solution C. Solution B is added to solution C and stirred at room temperature overnight. The mixed solution is prepared in a ratio of 50 Na2O: 1 Al2O3: 5 SiO2: 1005 H2O. (2) The mixed solution is transferred to a stainless steel reactor lined with polytetrafluoroethylene, an α-Al2O3 ceramic substrate is placed vertically, and the mixture is heated at 120°C. o C for 24 hours. (3) After the crystallization is completed, wash with water until neutral, and dry to obtain a primary SOD molecular sieve membrane. (4) Repeat the above steps to obtain a secondary SOD molecular sieve membrane, and the sample is recorded as SOD. (5) The secondary SOD molecular sieve membrane prepared in step (4) is subjected to a gas separation test.

[0051] Comparative Example 4

[0052] A method for preparing a mixed matrix membrane for gas separation comprises the following steps: (1) adding 2, 3, 5, 6-tetrafluoroterephthalonitrile (2.00 g), 5, 5', 6, 6'-tetrahydroxy-3, 3', 3'-tetramethyl-1, 1'-spirodinitrile TTSBI (3.20 g), potassium carbonate (3.45 g) and N, N-2-methylpyrrolidone / toluene (15.0 / 5.00 mL) into a three-necked flask. Nitrogen is passed through the flask and reacted at 155°C for 3.5 hours to obtain a mixed solution A. The mixed solution A is poured into methanol, washed and dried to obtain PIM-1. (2) PIM-1 (2.00 g) obtained in step (1) and 200 mL of tetrahydrofuran are added into the three-necked flask and stirred at 65°C for 8 hours under a nitrogen atmosphere to obtain a mixed solution B. 20.0 mL of hydroxylamine solution was added to the mixture B at 69 °C, and the reaction was continued for 20 hours to obtain reactant C. The reactant C was poured into ethanol, filtered and dried to obtain AO-PIM. (3) γ-(2,3-epoxypropoxy)propyltrimethoxysilane (0.23 mmol) and polyetheramine M2070 (0.23 mmol) were stirred at 50 °C for 5 hours to obtain mixture D. SOD (0.23 mmol) was added to mixture D at 30 °C to obtain reactant E. The reactant E was dialyzed, rotated and dried to obtain SOD (PLs). (4) SOD (PLs) and AO-PIM were added to DMF and ultrasonically treated to obtain solution F and solution G, respectively. Then solution F and solution G were mixed and stirred continuously to obtain mixture H. Mixture H was cast to obtain AO-PIM film.

[0053] The specific example results and comparative example results are shown in the following table:

[0054]

[0055] 1 Suspension concentration; 2 Soaking time; 3 Hydrogen permeability; 4 Hydrogen / Nitrogen Selectivity.

[0056] From the above results, it can be seen that the MCM-22 molecular sieve membrane obtained in Comparative Example 1 has a H2 / N2 selectivity of 100, which is equivalent to the effect of Example 5 of the present invention. However, due to the multiple deposition of the sol, the preparation process is complicated compared with the method of the present invention, and the hydrogen permeability is only 2.0×10 -8 mol . m -2. s -1. Pa -1, which is 13 times lower than the hydrogen permeability of Example 5 of the present invention. The hydrogen permeability of the MCM-22 molecular sieve membrane obtained in Comparative Example 2 reached 1.09×10 -6 mol . m -2. s -1. Pa -1 , which is equivalent to the effect of Example 1 of the present invention. However, since this method is an inorganic membrane, the surface of the MCM-22 molecular sieve layer is not composited with the poly(p-phenylbenzimidazole) membrane used in the present invention, and the H2 / N2 selectivity is only 3.6, which is about 9 times lower than the H2 / N2 selectivity of Example 1 of the present invention. The hydrogen permeability of the MCM-22 molecular sieve membrane obtained in Comparative Example 3 reached 9.5×10 -6 mol . m -2. s -1. Pa -1 , which is equivalent to the effect of Example 2 of the present invention. However, since the surface of the MCM-22 molecular sieve layer in this method is not composited with the poly(p-phenylbenzimidazole) membrane used in the present invention, the H2 / N2 selectivity is only 5.46, which is about 14 times lower than the H2 / N2 selectivity of Example 1 of the present invention. Moreover, compared with the method of the present invention, the method described in Comparative Example 3 takes a long time to prepare and is complicated to operate. The AO-PIM film obtained in Comparative Example 4 has a H2 / N2 selectivity of 34.2 and a -6 mol . m -2. s -1. Pa -1 The hydrogen permeability is comparable to that of Example 1 of the present invention. However, since this method involves doping a small amount of inorganic SOD molecular sieve into the polymer, compared with the method of the present invention, the mechanical properties are poorer, and the preparation process is complex and time-consuming, and a large amount of toxic and hazardous substances, such as tetrahydrofuran, are used in the preparation process.

Claims

1. A method for preparing a mixed matrix membrane for gas separation, characterized in that: The following steps are involved: A sol is obtained by mixing hydroxide, water, an aluminum source, a template and a silicon source; the sol is stirred and aged, and then a crystallization reaction is performed, and a molecular sieve is obtained after drying; The molecular sieve and the dispersion solvent are fully stirred and mixed, and then ultrasonicated to obtain a molecular sieve suspension; the molecular sieve suspension is dropped onto a support, dried and calcined to obtain an oriented layered molecular sieve membrane; the oriented layered molecular sieve membrane is immersed in a 1, 2, 4, 5-benzenetetramine tetrahydrochloride solution, taken out until there are no obvious droplets on the surface, and then a toluene solution of terephthalaldehyde is dropped, and dried to obtain a mixed matrix membrane for gas separation.

2. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The hydroxide is one or more of sodium hydroxide, potassium hydroxide, and cesium hydroxide; the aluminum source is one or both of sodium aluminate and aluminum hydroxide; the template is one or more of hexamethyleneimine, dicyclohexylamine, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and N, N, N-trimethyladamantanammonium hydroxide; and the silicon source is one or more of silica gel, sodium metasilicate nonahydrate, tetraethyl orthosilicate, and white carbon black.

3. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The molar ratio of hydroxide, water, aluminum source, template and silicon source is 0.1-0.2:18:0.01-0.066:0.3-1:

1.

4. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The stirring aging temperature is 20-40°C, and the stirring aging time is 2-5 hours; the crystallization reaction temperature is 160-200°C, and the crystallization reaction time is 1-7 days; and the ultrasonic time is 0.5-3 hours.

5. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The dispersion solvent for preparing the molecular sieve suspension is one of water, ethyl acetate, ethanol or methanol; the concentration of the molecular sieve suspension is 0.125-1 wt%.

6. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The support is placed on a heating platform for heating, and the temperature of the heating platform is 80-200°C.

7. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The calcination temperature is 500~600 ℃, and the calcination time is 4~8 hours.

8. The method for preparing a mixed matrix membrane for gas separation according to claim 1, characterized in that: The layered molecular sieve membrane is immersed in the 1, 2, 4, 5-benzenetetraamine tetrahydrochloride solution for 0.5 to 3 hours.

9. A mixed matrix membrane for gas separation, characterized in that: Prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the mixed matrix membrane according to claim 9 in hydrogen separation.

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