An acidic gas separation membrane, a preparation method thereof and an application thereof

Abstract

The present invention relates to the technical field of gas separation membranes, and particularly relates to an acidic gas separation membrane, a preparation method thereof, and an application thereof. The acidic gas separation membrane comprises a diazotized modified MOF material, polyethersulfone, and polyethyleneimine. The acidic gas separation membrane of the present invention has the function of separating and purifying acidic gases, such as separating and purifying H2S or HBr.

Description

Technical Field

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

[0002] Acidic gases, such as hydrogen sulfide (H2S) or hydrogen bromide, are usually toxic and corrosive gases, which are widely present in the processes of oil and gas extraction, semiconductor, transportation, and chemical production and are of great significance. 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 an urgent technical problem to be solved.

[0003] The existing acidic gas separation technologies mainly include adsorption method, cooling method, and membrane separation method, etc. However, these technologies have many deficiencies 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 acidic 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 the membrane materials. Especially when dealing with low-concentration acidic gases, the existing technologies cannot meet the requirements 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 acidic gases. Summary of the Invention

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

[0005] The present invention provides an acidic gas separation membrane, which comprises a diazotized modified MOF material, polyethersulfone, and polyethyleneimine; wherein, the diazotized modified MOF material has a cubic crystal form of the space group, and the lattice parameters of the crystal form are: ; ; the molecular formula in 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 through the following steps: (1) preparing an amino-functionalized MOF material by subjecting a zirconium salt (such as ZrCl4) and 2,4-diaminoterephthalic acid to a solvothermal reaction.

[0007] (2) Add the above amino-functionalized MOF material into a hydrochloric acid solution, and then add sodium nitrite. After a diazotization reaction, the diazotized modified MOF material is obtained.

[0008] In the present invention, preferably, the acidic gas separation membrane can be prepared through the following steps: (1) Immerse the above diazotized modified MOF material in a polysulfone ether substrate solution; then fix the wet polysulfone ether substrate and the diazotized modified MOF material on a mold.

[0009] (2) Pour a 1,3,5-benzenetricarbonyl chloride solution onto the surface of the polysulfone ether substrate in the above mold. After interfacial polymerization, a preliminary composite membrane is obtained.

[0010] (3) Immerse the above preliminary composite membrane in a polyethyleneimine solution. After a covalent grafting reaction, an acidic gas separation membrane is obtained.

[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-benzenetricarbonyl 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 membrane can be adjusted according to actual needs. Preferably, the membrane thickness of the preliminary composite membrane is 0.5 - 5 μm.

[0013] In the present invention, preferably, the acidic gas separation membrane can be activated through the following steps: Immerse the acidic gas separation membrane in a solvent (such as acetone); then dry it, preferably in a vacuum environment at 40 - 70 °C; an activated acidic gas separation membrane is obtained.

[0014] The present invention provides a preparation method of an acidic gas separation membrane, and the method is the same as the preparation method of 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 modified MOF material, and the diazotized modified MOF material is defined as above.

[0017] On the basis of not violating the common knowledge in the art, the above preferred conditions can be combined arbitrarily to obtain various preferred examples of the present invention.

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

[0019] The positive and progressive effects of the present invention are as follows: The acidic gas separation membrane of the present invention can separate and purify 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 It is a single crystal structure diagram of the diazotized modified MOF material (the position of the diazo group is disordered).

[0021] Figure 2 It is the permeation curves of H2S, HBr, and CH4 gases of the acidic gas separation membrane. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] Hereinafter, the present invention will be described in detail. Here, 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 pertains. The description of the present invention and the known functions and components of the drawings will be omitted with unnecessary details.

[0023] The hydrogen sulfide gas separation membrane provided by the present invention adopts a technical solution of compounding a modified metal-organic framework (MOF) material with a polymer. The MOF material used is an amino-functionalized MOF material as a precursor, and after further diazotized modification, a diazotized modified MOF material is obtained. The preferred materials for the polymer auxiliary materials are polyethersulfone (PES) and polyethyleneimine (PEI). Through material screening and preparation condition optimization, the gas transport performance in the membrane material can be further optimized, and a highly selective separation membrane for H2S and HBr gases can be prepared. The following describes the embodiments of the present invention in detail.

[0024] Example 1: Preparation of the diazotized modified MOF material.

[0025]

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

[0027] (2) Seal the mixed solution in a 500-ml hydrothermal reaction kettle and transfer it to an oven for hydrothermal reaction at 120 °C for 24 hours.

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

[0029] (4) Wash the separated solid three times with DMF and deionized water respectively, 20 ml each time.

[0030] B: Diazotization modification of the amino-functionalized MOF material, and the specific steps are as follows: (1) Add the amino-functionalized MOF material obtained in step A into 100 mL of dilute hydrochloric acid with a concentration of 1 M.

[0031] (2) Take 0.3 g of sodium nitrite and dissolve it in 20 mL of deionized water. At 5 °C, under stirring, slowly add it to the mixed solution in step (1), and react for 3 hours. Centrifuge and wash with deionized water (three times, 20 mL each time) to obtain the diazotization-modified MOF material.

[0032] Example 2: Determination of the crystal structure of the diazotization-modified MOF material.

[0033] Taking the crystal obtained in Example 1 as an example for single-crystal structure characterization. The X-ray single-crystal diffraction data of this crystal was collected on a Bruker D8 QUEST single-crystal diffractometer. The data processing was performed using the Bruker APEX4 program. The test temperature was 298 K. The single-crystal structure is as Figure 1 shown, and it is cubic space group; the unit cell volume is 9097.0(12). Other crystal-related information is shown in Table 1:

[0034]

[0035] Example 3: Preparation method of an acidic gas separation membrane.

[0036] (1) Immerse the diazotization-modified MOF material in a DMF solution (25% mass fraction, 10 mL) of a polysulfone ether substrate for 20 seconds to fill its pores with MOF material particles.

[0037] (2) Fix the wet polysulfone ether substrate and the diazotization-modified MOF material on a mold.

[0038] (3) After the surface is dried, pour a cyclohexane solution containing 0.5% mass fraction of 1,3,5-benzenetricarbonyl chloride (TMC) onto the surface of the polysulfone ether substrate. After 10 minutes of interfacial polymerization, drain the excess solution to obtain a primary composite membrane. Finally, heat the primary composite membrane at 60 °C for 5 minutes to obtain a preliminary composite membrane, and the membrane thickness can be adjusted according to actual needs, usually between 0.5 - 5 μm.

[0039] (4) Dissolve polyethyleneimine (PEI) in deionized water to prepare a 0.5% mass fraction solution. Immerse the preliminary composite membrane in the PEI solution for covalent grafting reaction for 10 minutes. After removing the excess PEI solution, rinse the membrane surface with deionized water. After heat treatment in an oven at 60 °C for 5 minutes, an acidic gas separation membrane is obtained.

[0040] Soak the obtained composite membrane material with dry acetone, 20 mL each time for 12 hours, for a total of three times. Exchange to remove the moisture in the membrane pores. Place the membrane in a vacuum drying oven, set the temperature to 60 °C, and conduct vacuum drying for activation for 12 hours to obtain the activated acidic gas separation membrane.

[0041] Example 4: Performance test of the MOF material composite membrane.

[0042] Quantitatively analyze the gas components after permeation through a constant pressure variable volume gas permeation instrument (Sicheng, GPT-201B) and a gas chromatograph (Shimadzu, 2010 plus) to evaluate the performance of the prepared gas separation membrane. The pure gas is subjected to a permeation test experiment under the conditions of 25 °C and 101.3 kPa. The shape of the membrane sheet for testing is a circular membrane sheet with a diameter of 10.27 cm and a thickness of 3.84 μm. Argon is used as the sweep gas, and its volume flow rate is 30 mL / min. The inlet temperature is 200 °C, and the column temperature program is: initial temperature 50 °C, hold for 3 minutes, heating rate 10 °C / min, maximum temperature 150 °C, hold for 5 minutes.

[0043] The following aspects are mainly tested: (1) Gas permeability: The gas permeability of the membrane material is tested by the common gas permeation method, and the gas fluxes of hydrogen sulfide and methane gases are measured to evaluate the membrane.

[0044] The permeability coefficient P of gas i i (unit: Barrer) is calculated by formula (I):

[0045] Where, Q i (unit: cm³(STP) / s) is the volume flow rate, l (unit: cm) is the thickness of the membrane, Δ p i (unit: cmHg) is the transmembrane partial pressure difference, A (unit: cm²) is the effective membrane area.

[0046] The experimental results are as Figure 2 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.

[0047] (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):

[0048] The experimental results show that the selectivity factor for the methane / hydrogen sulfide gas pair is 10.10.

[0049] The test results show that the selectivity factor for the methane / hydrogen bromide gas pair is 6.68.

[0050] From the above test results, it can be seen that the membrane of the present invention has excellent selectivity for acidic gases, especially for hydrogen sulfide and hydrogen bromide.

[0051] Thus, 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 contains diazotized modified MOF material, polyethersulfone and polyethyleneimine; Among them, the diazotized modified MOF material has a cubic crystal form with a space group, and the unit cell parameters of the crystal form are: ; the molecular formula within the unit cell volume of the crystal form is ; the diazotized modified MOF material is prepared through the following steps: (1) React with 2,4-diaminoterephthalic acid through solvothermal reaction to prepare an amino-functionalized MOF material; ​ (2) Add the amino-functionalized MOF material into hydrochloric acid solution, then add sodium nitrite, and through diazotization reaction, obtain the diazotized modified MOF material; The acidic gas separation membrane is prepared through the following steps: (1) Immerse the diazotized modified MOF material in the polyethersulfone substrate solution; then fix the polyethersulfone substrate and the diazotized modified MOF material on a mold; (2) Pour the 1,3,5-benzenetricarbonyl chloride solution onto the surface of the polyethersulfone substrate in the mold, and obtain a preliminary composite membrane through interfacial polymerization; (3) Immerse the preliminary composite membrane in the polyethyleneimine solution, and through covalent grafting reaction, obtain the acidic gas separation membrane.

2. The acidic gas separation membrane according to claim 1, characterized in that, In the preparation method of the acidic gas separation membrane: In step 1, the solvent of the polyethersulfone substrate solution is DMF; in step 2, the solvent of the 1,3,5-benzenetricarbonyl chloride solution is cyclohexane; in step 3, the solvent of the polyethyleneimine solution is water.

3. The acidic gas separation membrane according to claim 2, wherein In the preparation method of the acidic gas separation membrane: In step 2, the membrane thickness of the preliminary composite membrane is 0.5 - 5 μm.

4. The acid gas separation membrane according to claim 1, wherein The acidic gas separation membrane is activated through the following steps: Immerse the acidic gas separation membrane in acetone; then dry it in a vacuum environment at 40 - 70 °C; obtain the activated acidic gas separation membrane.

5. A method for preparing an acidic gas separation membrane, characterized in that, Using the diazotized modified MOF material as described in claim 1, it includes the following steps: (1) Immerse the diazotized modified MOF material in the polyethersulfone substrate solution; then fix the polyethersulfone substrate and the diazotized modified MOF material on a mold; (2) Pour the 1,3,5-benzenetricarbonyl chloride solution onto the surface of the polyethersulfone substrate in the mold, and obtain a preliminary composite membrane through interfacial polymerization; (3) Immerse the preliminary composite membrane in the polyethyleneimine solution, and through covalent grafting reaction, obtain the acidic gas separation membrane.

6. Application of the acidic gas separation membrane as described in any one of claims 1 - 4 in gas purification.

7. The application according to claim 6, characterized in that, The gas is or HBr.

8. A diazotized modified MOF material, characterized in that, It has a cubic crystal form with a space group, and the unit cell parameters of the crystal form are: ; The molecular formula within the unit cell volume of the crystal form is ; The diazotized modified MOF material is prepared through the following steps: (1) Prepare an amino-functionalized MOF material by subjecting and 2,4-diaminoterephthalic acid to a solvothermal reaction; (2) Add the amino-functionalized MOF material into hydrochloric acid solution, then add sodium nitrite, and through diazotization reaction, obtain the diazotized modified MOF material.

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