Acid gas separation membrane as well as preparation method and application thereof

Abstract

The invention relates to the technical field of gas separation membranes, in particular to an acid gas separation membrane as well as a preparation method and application thereof. The acid gas separation membrane comprises a diazotization modified MOF material, polyether sulfone and polyethyleneimine. The acidic gas separation membrane of the present invention has the function of separating and purifying acidic gas, such as H2S or HBr.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation membranes, and in particular to an acidic gas separation membrane, a preparation method and application thereof. Background Art

[0002] Acidic gases, such as hydrogen sulfide (H2S) or hydrogen bromide, are usually toxic and corrosive gases that are widely present in oil and natural gas extraction, semiconductors, transportation and chemical production processes. Due to their harm to human health and the environment, as well as their corrosiveness to equipment, how to efficiently and safely separate acidic gases has become a technical problem that needs to be solved urgently.

[0003] Existing acid gas separation technologies mainly include adsorption, cooling and membrane separation. However, these technologies have many shortcomings in practical applications: the adsorption method usually has problems such as limited processing capacity and difficulty in adsorbent regeneration; the cooling method has high energy consumption and poor separation effect for low-concentration acid gases. Although the traditional membrane separation method has the advantages of low energy consumption and simple operation, the existing membrane materials have disadvantages such as poor selectivity, low separation efficiency and poor stability of membrane materials. Especially when dealing with low-concentration acid gases, the existing technology cannot meet the needs of efficient separation. Therefore, there is an urgent need for a membrane material that is efficient, stable and suitable for the separation of low-concentration acid gases. Summary of the invention

[0004] In order to overcome the above-mentioned deficiencies of the prior art, the present invention provides an acidic gas separation membrane, a preparation method and its application, aiming to solve the problems of low acidic gas separation efficiency, poor selectivity, poor stability of membrane materials and the like in the prior art.

[0005] The present invention provides an acidic gas separation membrane, which comprises a diazo-modified MOF material, polyethersulfone and polyethyleneimine; wherein the diazo-modified MOF material has a cubic The crystal form of the space group, the unit cell parameters of the crystal form: ; ; The molecular formula within the unit cell volume of the crystal form is C 48 H 12 N 24 O 32 Cl 12 Zr6.

[0006] In the present invention, the diazotized modified MOF material can be prepared by the following steps: (1) preparing an amino-functionalized MOF material by solvent thermal reaction of a zirconium salt (such as ZrCl4) and 2,4-diaminoterephthalic acid.

[0007] (2) Adding the amino-functionalized MOF material to a hydrochloric acid solution, and then adding sodium nitrite to perform a diazotization reaction to obtain the diazotized modified MOF material.

[0008] In the present invention, preferably, the acidic gas separation membrane can be prepared by the following steps: (1) soaking the above-mentioned diazotized MOF material in a polysulfone ether substrate solution; and then fixing the wet polyethersulfone substrate and the diazotized MOF material on a mold.

[0009] (2) Pour the 1,3,5-benzenetricarboxylic acid chloride solution onto the surface of the polyethersulfone substrate in the above mold, and obtain a preliminary composite membrane after interfacial polymerization.

[0010] (3) The preliminary composite membrane is immersed in a polyethyleneimine solution and subjected to a covalent grafting reaction to obtain an acidic gas separation membrane.

[0011] In the present invention, preferably, in step 1, the solvent of the polysulfone ether substrate solution is DMF; in step 2, the solvent of the 1,3,5-benzenetricarboxylic acid chloride solution is cyclohexane; in step 3, the solvent of the polyethyleneimine solution is water.

[0012] In the present invention, preferably, in step 2, the preliminary composite film can be adjusted according to actual needs, and preferably, the thickness of the preliminary composite film is 0.5-5 μm.

[0013] In the present invention, preferably, the acidic gas separation membrane can be activated by the following steps: soaking the acidic gas separation membrane with a solvent (such as acetone); and then drying, preferably, drying under a vacuum environment at 40-70°C; to obtain an activated acidic gas separation membrane.

[0014] The present invention provides a method for preparing an acidic gas separation membrane, and the method is the same as the method for preparing the above-mentioned acidic gas separation membrane.

[0015] The present invention provides an application of the above acidic gas separation membrane in gas purification; preferably, the gas is H2S or HBr.

[0016] The present invention also provides a diazotized MOF material, wherein the diazotized MOF material is as defined above.

[0017] Without violating the common sense in the art, the above-mentioned preferred conditions can be arbitrarily combined to obtain the preferred embodiments of the present invention.

[0018] The reagents and raw materials used in the present invention are commercially available.

[0019] The positive and progressive effects of the present invention are that the acidic gas separation membrane of the present invention can separate and purify the functions of acidic gases, such as separating and purifying H2S or HBr; and it has excellent separation efficiency, high selectivity and high membrane stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the single crystal structure diagram of the diazotized MOF material (the diazo group has positional disorder).

[0021] Figure 2 It is the permeation curve of H2S, HBr and CH4 gas of acid gas separation membrane. DETAILED DESCRIPTION

[0022] Hereinafter, the present invention will be described in detail. Herein, unless otherwise specified, the technical and scientific terms used herein have the meanings understood by those skilled in the art to which the present invention belongs. Known functions and components that obscure the description and drawings of the present invention with unnecessary details will be omitted.

[0023] The hydrogen sulfide gas separation membrane provided by the present invention adopts a technical solution of a modified metal organic framework (MOF) material and a polymer composite, wherein the MOF material used is an amino-functionalized MOF material as a precursor, and a diazo-modified MOF material is obtained after further diazo modification, and polyethersulfone (PES) and polyethyleneimine (PEI) are preferably used as polymer auxiliary materials. After material screening and optimization of preparation conditions, the transmission performance of the gas in the membrane material can be further optimized, and a highly selective separation membrane for H2S and HBr gases can be prepared. The embodiments of the present invention are described in detail below.

[0024] Example 1: Preparation of diazotization-modified MOF materials.

[0025]

[0026] A: Amino-functionalized MOF was synthesized by hydrothermal method. The specific steps are as follows: (1) Mix 1.0 g ZrCl4, 0.74 g 2,4-diaminoterephthalic acid and 10 ml deionized water with 200 ml DMF and stir well.

[0027] (2) The mixed solution was sealed in a 500 mL hydrothermal reactor and transferred to an oven for hydrothermal reaction at 120 °C for 24 h.

[0028] (3) After the solution has cooled to room temperature, the product is separated by centrifugation.

[0029] (4) The separated solid was washed three times with DMF and then with deionized water, 20 mL each time.

[0030] B: Diazotization modification of amino-functionalized MOF materials. The specific steps are as follows: (1) Add the amino-functionalized MOF material obtained in step A to 100 ml of 1 M dilute hydrochloric acid.

[0031] (2) Dissolve 0.3 g of sodium nitrite in 20 mL of deionized water. Slowly add the mixture to the mixed solution in step 5 at 5°C with stirring and react for 3 hours. Centrifuge and wash with deionized water (three times, 20 mL each time) to obtain the diazotized MOF material.

[0032] Example 2: Determination of the crystal structure of diazotized MOF materials.

[0033] The crystal obtained in Example 1 was used as an example to characterize the single crystal structure. The X-ray single crystal diffraction data of the crystal was collected on a Bruker D8 QUEST single crystal diffractometer. The data was processed using the Bruker APEX4 program. The test temperature was 298 K. The single crystal structure is shown in FIG. Figure 1 As shown, it is a cubic Space group; unit cell volume is 9097.0(12). Other crystal related information is shown in Table 1:

[0034] Example 3: Method for preparing acidic gas separation membrane.

[0035] (1) The diazotized MOF material was immersed in a DMF solution of polysulfone ether matrix (25% mass fraction, 10 mL) for 20 seconds so that its pores were filled with MOF material particles.

[0036] (2) Fix the wet polyethersulfone substrate and the diazo-modified MOF material on the mold.

[0037] (3) After the surface is dried, a cyclohexane solution containing 0.5% by mass of 1,3,5-benzenetricarboxylic acid chloride (TMC) is poured onto the surface of the polyethersulfone substrate. After 10 minutes of interfacial polymerization, the excess solution is drained to obtain a primary composite membrane. Finally, the primary composite membrane is heated at 60°C for 5 minutes to obtain a preliminary composite membrane. The membrane thickness can be adjusted according to actual needs, usually between 0.5-5 μm.

[0038] (4) Polyethyleneimine (PEI) was dissolved in deionized water to prepare a 0.5% mass fraction solution. The preliminary composite membrane was immersed in the PEI solution for a covalent grafting reaction for 10 minutes. After removing the excess PEI solution, the membrane surface was rinsed with deionized water. After heat treatment in an oven at 60°C for 5 minutes, an acidic gas separation membrane was obtained.

[0039] (5) Soak the obtained composite membrane material in dry acetone, 20 ml each time for 12 hours, for a total of three times. Exchange and remove the moisture in the membrane pores. Place the membrane in a vacuum drying oven, set the temperature to 60°C, and vacuum dry for 12 hours to obtain an activated acid gas separation membrane.

[0040] Example 4: Performance test of MOF material composite membrane.

[0041] The gas composition after permeation was quantitatively analyzed by constant pressure variable volume gas permeameter (Saicheng, GPT-201B) and gas chromatograph (Shimadzu, 2010 plus), and the performance of the prepared gas separation membrane was evaluated. The pure gas was tested for permeation at 25°C and 101.3kPa. The shape of the membrane used for the test was a circular membrane with a diameter of 10.27 cm and a thickness of 3.84 μm. Argon was used as a sweep gas with a volume flow rate of 30 mL / min. The injection port temperature was 200°C, and the column temperature program was: initial temperature 50°C, maintained for 3 minutes, heating rate 10°C / min, maximum temperature 150°C, maintained for 5 minutes.

[0042] The main tests are as follows: (1) Gas permeability: The common gas permeation method is used to test the gas permeability of the membrane material, and the hydrogen sulfide and methane gases are measured to evaluate the flux of the membrane.

[0043] Permeability coefficient P of gas i i (Unit: Barrer) Calculated by formula (I):

[0044] in, Q i (Unit: cm³(STP) / s) is the volume flow rate, l (unit: cm) is the thickness of the film, Δ p i (unit: cmHg) is the partial pressure difference across the membrane, A (Unit: cm²) is the effective membrane area.

[0045] The experimental results are as follows Figure 2 As shown, specifically, under 1 atmosphere, within 4 hours, the average permeability coefficient of hydrogen sulfide gas is 4.98 Barrer, the average permeability coefficient of hydrogen sulfide gas is 7.53 Barrer, and the permeability coefficient of methane gas is 50.29 Barrer.

[0046] (2) Selectivity: Determine the separation selectivity of the membrane for the methane / hydrogen sulfide gas pair and calculate the separation selectivity factor. The selectivity factor of the methane / hydrogen sulfide gas pair ( α i / j ) is calculated by formula (II):

[0047] The experimental results show that the selectivity factor of the methane / hydrogen sulfide gas pair is 10.10.

[0048] The test results show that the selectivity factor of the methane / hydrogen bromide gas pair is 6.68.

[0049] It can be seen from the above test results that the membrane of the present invention has excellent selectivity for acid gases, especially for hydrogen sulfide and hydrogen bromide.

[0050] It can be seen that the membrane of the present invention has broad application prospects in the separation or purification of acidic gases (such as hydrogen sulfide and hydrogen bromide).

Claims

1. An acidic gas separation membrane, characterized in that: It comprises a diazo-modified MOF material, polyethersulfone and polyethyleneimine; wherein the diazo-modified MOF material has a cubic The crystal form of the space group, the unit cell parameters of the crystal form: ; ; The molecular formula within the unit cell volume of the crystal form is C 48 H 12 N 24 O 32 Cl 12 Zr6.

2. The acidic gas separation membrane according to claim 1, characterized in that: The diazotized MOF material is prepared by the following steps: (1) preparing an amino-functionalized MOF material by solvent thermal reaction of ZrCl4 and 2,4-diaminoterephthalic acid; (2) adding the amino-functionalized MOF material to a hydrochloric acid solution, and then adding sodium nitrite to obtain the diazotized MOF material through a diazotization reaction.

3. The acidic gas separation membrane according to claim 1, characterized in that: The acidic gas separation membrane is prepared by the following steps: (1) immersing the diazotized MOF material in a polysulfone ether substrate solution; then fixing the polyethersulfone substrate and the diazotized MOF material on a mold; (2) pouring a 1,3,5-benzenetricarboxylic acid chloride solution on the surface of the polyethersulfone substrate in the mold, and obtaining a preliminary composite membrane after interfacial polymerization; (3) immersing the preliminary composite membrane in a polyethyleneimine solution, and obtaining the acidic gas separation membrane after a covalent grafting reaction.

4. The acidic gas separation membrane according to claim 3, characterized in that: In step 1, the solvent of the polysulfone ether substrate solution is DMF; in step 2, the solvent of the 1,3,5-benzenetricarboxylic acid chloride solution is cyclohexane; in step 3, the solvent of the polyethyleneimine solution is water.

5. The acidic gas separation membrane according to claim 3, characterized in that: In step 2, the thickness of the preliminary composite film is 0.5-5 μm.

6. The acidic gas separation membrane according to claim 1, characterized in that: The acidic gas separation membrane is activated by the following steps: soaking the acidic gas separation membrane in acetone; then drying it in a vacuum environment at 40-70° C.; and obtaining the activated acidic gas separation membrane.

7. A method for preparing an acidic gas separation membrane, characterized in that: The method comprises the following steps: (1) immersing a diazo-modified MOF material in a polysulfone ether substrate solution; then fixing the polyethersulfone substrate and the diazo-modified MOF material on a mold; (2) pouring a 1,3,5-benzenetricarboxylic acid chloride solution on the surface of the polyethersulfone substrate in the mold, and obtaining a preliminary composite membrane after interfacial polymerization; (3) immersing the preliminary composite membrane in a polyethyleneimine solution, and obtaining the acidic gas separation membrane after a covalent grafting reaction; wherein the diazo-modified MOF material is as defined in any one of claims 1 to 6.

8. Use of the acidic gas separation membrane according to any one of claims 1 to 6 in gas purification.

9. The use according to claim 8, characterized in that The gas is H2S or HBr.

10. A diazotized MOF material, characterized in that: It has a cubic The crystal form of the space group, the unit cell parameters of the crystal form: ; ; The molecular formula within the unit cell volume of the crystal form is C 48 H 12 N 24 O 32 Cl 12 Zr6.

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