Preparation method of natural gas dehydration membrane, natural gas dehydration membrane and application thereof

Abstract

The application belongs to the field of membrane material preparation, and discloses a preparation method of a natural gas dehydration membrane, the natural gas dehydration membrane and application thereof. The preparation method comprises the following steps: S1, preparing a mixed solution, wherein the mixed solution comprises polyetherimide, water wheel phenol and a solvent; S2, coating the mixed solution obtained in step S1 into a film; S3, placing the film obtained in step S2 on a substrate or a cold table at-10 to-2 DEG C for 1 to 10 min; S4, placing the film obtained in step S3 at a temperature of 30 to 45 DEG C for 2 to 5 min; S5, placing the film obtained in step S4 into a coagulation solution containing 4-methyl catechol for solidification; and S6, placing the film obtained in step S5 into a pyrrole aqueous solution for immersion, thereby obtaining the natural gas dehydration membrane. The natural gas dehydration membrane prepared by the application has high water permeability and a H2O / CH4 separation coefficient, and can be used in the dehydration process before natural gas transportation.

Description

Technical Field

[0001] This invention belongs to the field of membrane material preparation, specifically relating to the preparation of a gas separation membrane material, and more specifically, to a method for preparing a natural gas dehydration membrane, the natural gas dehydration membrane, and its application. Background Technology

[0002] Natural gas hydrates have attracted widespread attention in recent years due to their advantages such as low carbon emissions, cleanliness, and abundant reserves. However, the natural gas obtained after the extraction of natural gas hydrates still contains moisture. During the natural gas transportation process, this moisture can condense into water or even freeze in pipelines, clogging them and affecting transportation efficiency.

[0003] Currently, the main methods for natural gas dehydration include absorption, adsorption, condensation, and membrane separation. Compared to other methods, membrane separation offers advantages such as high separation efficiency, less secondary pollution, and energy conservation and environmental friendliness, thus possessing significant application potential in the field of natural gas dehydration. Polymer membranes are widely used in natural gas dehydration due to their good processability and low cost, but their performance often fails to meet practical requirements. To further improve the separation coefficient of polymer membranes for H2O / CH4, the preparation of mixed-matrix membranes using nanofillers is currently the most widely used method (Fuel, 2021, 285: 119161; Journal of Applied Polymer Science, 2024: e55253). Compared to methane molecules, water molecules have a smaller kinetic diameter, and the pore structure of nanoparticles and the gaps between them and the polymer matrix can provide channels for mass transfer of water molecules in the mixed-matrix membrane, thereby improving the H2O / CH4 separation coefficient. However, the performance of mixed-matrix membranes prepared by current methods still cannot meet the needs of actual production, and the high cost of nanoparticles makes large-scale production difficult. Summary of the Invention

[0004] To address the shortcomings of the existing technology, this invention provides a method for preparing a natural gas dehydration membrane, the natural gas dehydration membrane itself, and its applications. The natural gas dehydration membrane prepared by this invention exhibits high water permeability and a high H2O / CH4 separation coefficient.

[0005] The specific technical solution is as follows:

[0006] One objective of this invention is to provide a method for preparing a natural gas dehydration membrane, characterized by comprising the following steps:

[0007] S1. Prepare a mixed solution, wherein the mixed solution contains polyetherimide, hydrophenol and a solvent;

[0008] S2. Coat the mixed solution obtained in step S1 into a film;

[0009] S3. Place the film obtained in step S2 on a substrate or cold stage at -10~-2℃ for 1~10 min;

[0010] S4. Let the membrane obtained in step S3 stand at a temperature of 30~45℃ for 2~5 min;

[0011] S5. Place the membrane obtained in step S4 into a coagulation solution containing 4-methylcatechol for curing;

[0012] S6. Immerse the membrane obtained in step S5 in a pyrrole aqueous solution to obtain a natural gas dehydration membrane.

[0013] Molecular waterwheel (Noria) refers to the Noria material. It can be prepared using the following literature: Molecular waterwheel (Noria) from a simple condensation of resorcinol and an alkanedial. Angewandte Chemie International Edition, 2006, 45: 7948-7952.

[0014] The mechanism of this invention is as follows: The hydrophenol introduced into the natural gas dehydration membrane of this invention contains molecular cavities, which can improve the water vapor permeation rate and separation coefficient; the pre-placement in the low temperature plate can improve the density of the membrane skin layer and improve the separation coefficient; during the phase transformation of the membrane, 4-methylcatechol enters the membrane from the coagulation bath and subsequently reacts with pyrrole to improve the hydrophilicity and density of the membrane, thereby improving the separation coefficient and water permeability.

[0015] Furthermore, in step S1: the concentration of polyetherimide in the mixed solution is preferably 5wt%~20wt%, and the concentration of hydroquinone in the mixed solution is preferably 0.1wt%~4wt%.

[0016] Furthermore, in step S1, the solvent is preferably N-methylpyrrolidone.

[0017] Furthermore, in step S1: the mixed solution preferably also contains an additive to increase the amount of 4-methylcatechol in the membrane through hydrogen bonding and electrostatic interactions. The additive is at least one selected from triethylamine, N,N-diisopropylethylamine, pyridine, and triethylenediamine. The concentration of the additive in the mixed solution is preferably 0.05 wt% to 5 wt%.

[0018] Specifically, in step S1: it is preferable to dissolve the mixed solution under ultrasonic conditions.

[0019] Specifically, in step S2: the mixed solution is allowed to stand to degas before being coated into a film.

[0020] Specifically, after coating in step S2, the film is preferably transferred to a low-temperature substrate or a cold stage immediately.

[0021] Furthermore, in step S3: the substrate is preferably a glass plate. Preferably, the film is placed on a low-temperature glass plate.

[0022] Furthermore, in step S4: it is preferable to let it stand under conditions of humidity of 30% to 60%.

[0023] Furthermore, in step S5: the coagulation solution contains water and N-methylpyrrolidone. Specifically, the coagulation solution is a mixture of water containing 4-methylcatechol and N-methylpyrrolidone.

[0024] Furthermore, in step S5, the concentration of 4-methylcatechol in the coagulation solution is preferably 0.02wt% to 10wt%.

[0025] Specifically, in step S5, the coagulated solution is prepared by dissolving 4-methylcatechol in a mixture of water and N-methylpyrrolidone. The preferred volume ratio of water to N-methylpyrrolidone is (90~97):(3~10), more preferably 95:5. The water is preferably deionized water.

[0026] Furthermore, in step S5: it is preferable to place the membrane obtained in step S4 into a coagulation solution for curing treatment for 8~15 h.

[0027] Furthermore, in step S6: the concentration of pyrrole in the pyrrole aqueous solution is preferably 0.05wt% to 1wt%. It is preferable to use deionized water to prepare the pyrrole aqueous solution.

[0028] Furthermore, in step S6: the membrane obtained in step S5 is preferably soaked in a pyrrole aqueous solution for 18-36 h.

[0029] A second objective of this invention is to provide a natural gas dehydration membrane obtained using the above-described preparation method.

[0030] A third objective of this invention is to provide the application of the aforementioned natural gas dehydration membrane in natural gas dehydration.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] This invention improves the water vapor permeation rate and separation coefficient of the natural gas dehydration membrane by introducing hydroquinone containing molecular cavities, enhances the membrane layer density and separation coefficient through low-temperature plate pre-placement, and improves the membrane's hydrophilicity and density, separation coefficient, and water permeability through 4-methylcatechol and pyridine. The natural gas dehydration membrane prepared by this invention has high water permeability and H2O / CH4 separation coefficient, exceeding 1000; moreover, it has low raw material costs, is simple to operate, and is suitable for large-scale production, making it suitable for dehydration processes before natural gas transportation. Attached Figure Description

[0033] Figure 1 To test the separation performance of the natural gas dehydration membrane obtained in Example 1 of Example 2 for feed gases with different compositions;

[0034] Figure 2 To test the separation performance of the natural gas dehydration membrane obtained in Example 1 of Example 2 at different test temperatures. Detailed Implementation

[0035] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention. Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0036] In the specific implementation method: the molecular formula of hydroquinone is C 102 H 96 O 24 It was prepared using the method disclosed in the following reference: Molecular waterwheel (Noria) from a simple condensation of resorcino and an alkanedial. Angewandte Chemie International Edition, 2006, 45: 7948-7952.

[0037] In the specific implementation method: the number-average molecular weight of polyetherimide is 25000 g / mol. Example 1

[0038] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, and triethylamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentration of polyetherimide was 5 wt%, the concentration of cyclophenol was 0.1 wt%, and the concentration of triethylamine was 0.1 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -10°C for 1 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 30% and a temperature of 45°C for 3 minutes; S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 0.02 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized water solution with a pyrrole concentration of 1 wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 2

[0039] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, and pyridine are dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentration of polyetherimide is 20 wt%, the concentration of cyclophenol is 4 wt%, and the concentration of pyridine is 0.1 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -2℃ for 10 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 60% and a temperature of 30°C for 2 minutes; S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 10 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized aqueous solution with a pyrrole concentration of 0.05wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 3

[0040] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, and triethylenediamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentration of polyetherimide was 20 wt%, the concentration of cyclophenol was 2 wt%, and the concentration of triethylenediamine was 0.1 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -5°C for 5 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 50% and a temperature of 40°C for 5 minutes. S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 6 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized water solution with a pyrrole concentration of 0.3wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 4

[0041] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, and N,N-diisopropylethylamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentration of polyetherimide was 10 wt%, the concentration of cyclophenol was 3 wt%, and the concentration of N,N-diisopropylethylamine was 0.1 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -8°C for 3 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 40% and a temperature of 45°C for 5 minutes. S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 0.1 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized aqueous solution with a pyrrole concentration of 0.5wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 5

[0042] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, and N,N-diisopropylethylamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentration of polyetherimide was 15 wt%, the concentration of cyclophenol was 0.5 wt%, and the concentration of N,N-diisopropylethylamine was 0.1 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -8°C for 3 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 40% and a temperature of 45°C for 3 minutes. S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 10 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized aqueous solution with a pyrrole concentration of 0.5wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 6

[0043] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, N,N-diisopropylethylamine, and triethylamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentrations of polyetherimide, cyclophenol, N,N-diisopropylethylamine, and triethylamine were 12 wt%, 3 wt%, 0.05 wt%, and 0.5 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -5°C for 8 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 40% and a temperature of 45°C for 3 minutes. S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 5 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized aqueous solution with a pyrrole concentration of 0.5wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Example 7

[0044] The method for preparing a natural gas dehydration membrane is as follows: S1. Polyetherimide, cyclophenol, pyridine, and N,N-diisopropylethylamine were dissolved in N-methylpyrrolidone under ultrasonic conditions to obtain a mixed solution; in the mixed solution, the concentrations of polyetherimide, cyclophenol, pyridine, and N,N-diisopropylethylamine were 15 wt%, 3 wt%, 1.5 wt%, and 3.5 wt%. S2. After the mixed solution obtained in step S1 is allowed to stand to remove bubbles, it is then coated into a film. S3. Immediately after coating, place the film obtained in step S2 on a low-temperature glass plate at -10°C for 2 min; S4. Place the membrane obtained in step S3 in an oven with a humidity of 40% and a temperature of 45°C for 3 minutes. S5. Place the membrane obtained in step S4 into the coagulation solution for 10 h and then remove it; the coagulation solution is a mixture of deionized water containing 10 wt% 4-methylcatechol and N-methylpyrrolidone (volume ratio of deionized water to N-methylpyrrolidone 95:5). S6. The membrane obtained in step S5 is immersed in a pyrrole deionized aqueous solution with a pyrrole concentration of 0.5wt% for 24 h, and then removed to obtain a natural gas dehydration membrane. Comparative Example 1

[0045] Referring to Example 2, the difference from Example 2 is that the mixed solution in step S1 does not contain hydroquinone, while the composition and concentration of other components remain unchanged.

[0046] Other technical features are the same as in Example 2. Comparative Example 2

[0047] Referring to Example 2, the difference from Example 2 is that step S3 is not performed; that is, the membrane obtained in step S2 is directly subjected to the operation of step S4.

[0048] Other technical features are the same as in Example 2. Comparative Example 3

[0049] Referring to Example 2, the difference from Example 2 is that in step S5: the coagulation liquid is a mixture of water and N-methylpyrrolidone (volume ratio 95:5) and does not contain 4-methylcatechol; the operation of step S6 is not performed.

[0050] Other technical features are the same as in Example 2.

[0051] Test 1

[0052] The separation performance of the natural gas dehydration membranes obtained in each embodiment and comparative example was tested. The test conditions were as follows: At 0.1 MPa and 30°C, using a two-component gas mixture of H2O / CH4 (3.5 v% / 96.5 v%) as the feed gas, permeate was collected on the other side of the membrane to test the separation performance of the natural gas dehydration membrane. The permeability unit was GPU. The test results are shown in Table 1, including water permeability and the H2O / CH4 separation coefficient. The H2O / CH4 separation coefficient was calculated as: H2O / CH4 separation coefficient = H2O permeability / CH4 permeability.

[0053] Table 1. Natural Gas Dehydration Membrane Separation Performance

[0054]

[0055] The test results show that the H2O / CH4 separation coefficient of the present invention is high, with the H2O / CH4 separation coefficient of the natural gas dehydration membrane in each embodiment exceeding 1000, significantly higher than that of the comparative examples. Furthermore, the water permeability of the natural gas dehydration membrane in each embodiment of the present invention is also superior to that of the comparative examples. The comparison between Example 2 and Comparative Example 1 demonstrates that hydroxylamine can significantly improve water permeability and the separation coefficient. The comparison between Example 2 and Comparative Example 2 demonstrates that pretreatment with a low-temperature substrate before curing can significantly improve the membrane's separation coefficient. The comparison between Example 2 and Comparative Example 3 demonstrates that the use of 4-methylcatechol and pyrrole can significantly improve the membrane's separation coefficient and water permeability.

[0056] Test 2

[0057] The separation performance of the natural gas dehydration membrane obtained in Example 1 was tested for feed gases with different water contents. The test method was the same as in Test 1, except that the water content in the feed gases was different. The test results are shown in […]. Figure 1 .

[0058] The separation performance of the natural gas dehydration membrane obtained in Example 1 on natural gas feedstock was tested at different test temperatures. The test method was the same as in Test 1, except for the test temperature. The test results are shown below. Figure 2 .

[0059] like Figure 1 As shown, with the increase of water content in the feed gas, the permeability of water vapor gradually increases, while the H2O / CH4 separation coefficient does not change significantly and remains above 1200, indicating that the prepared natural gas dehydration membrane has high separation performance for feed gases of different compositions; Figure 2 As shown, with the increase of test temperature, the permeability of water vapor gradually increases and the H2O / CH4 separation coefficient gradually decreases, but the separation coefficients are all above 1000, indicating that the prepared natural gas dehydration membrane has excellent temperature resistance.

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a natural gas dehydration membrane, characterized in that, Includes the following steps: S1. Prepare a mixed solution, wherein the mixed solution contains polyetherimide, hydrophenol and a solvent; S2. Coat the mixed solution obtained in step S1 into a film; S3. Place the film obtained in step S2 on a substrate or cold stage at -10~-2℃ for 1~10 min; S4. Let the membrane obtained in step S3 stand at a temperature of 30~45℃ for 2~5 min; S5. Place the membrane obtained in step S4 into a coagulation solution containing 4-methylcatechol for curing; S6. Immerse the membrane obtained in step S5 in a pyrrole aqueous solution to obtain a natural gas dehydration membrane.

2. The preparation method according to claim 1, characterized in that, In step S1: the concentration of polyetherimide in the mixed solution is 5wt%~20wt%, and the concentration of hydroquinone in the mixed solution is 0.1wt%~4wt%.

3. The preparation method according to claim 1, characterized in that, In step S1: the solvent is N-methylpyrrolidone.

4. The preparation method according to claim 1, characterized in that, In step S1: the mixed solution further contains an additive, which is at least one of triethylamine, N,N-diisopropylethylamine, pyridine, and triethylenediamine.

5. The preparation method according to claim 1, characterized in that, In step S4: Let it stand under conditions of 30%~60% humidity.

6. The preparation method according to claim 1, characterized in that, In step S5: the coagulated liquid contains water and N-methylpyrrolidone.

7. The preparation method according to claim 1, characterized in that, In step S5: The concentration of 4-methylcatechol is 0.02wt% to 10wt%.

8. The preparation method according to claim 1, characterized in that, In step S6: the concentration of pyrrole in the pyrrole aqueous solution is 0.05wt%~1wt%.

9. A natural gas dehydration membrane, obtained using the preparation method described in any one of claims 1 to 8.

10. The application of the natural gas dehydration membrane as described in claim 9 in natural gas dehydration.

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