A hollow fiber gas separation membrane and its preparation method and application

Abstract

The present invention provides a hollow fiber gas separation membrane and a preparation method and application thereof. The hollow fiber gas separation membrane is an asymmetric membrane, comprising a support layer and a separation layer loaded on the support layer, wherein the support layer is a hollow fiber microporous membrane, and the separation layer is a polydimethylsiloxane network layer having a Turing structure. The hollow fiber gas separation membrane provided by the present invention has a separation layer with a special Turing structure, which is different from the nitrogen-rich separation membrane in the prior art. Combined with the selection of membrane materials, the hollow fiber gas separation membrane of the present invention has ultra-high permeability and gas selectivity as well as gas operation stability. Moreover, the preparation process of the hollow fiber gas separation membrane of the present invention is simple, the raw materials are cheap and readily available, and the film-forming process is easy to control.

Description

Technical Field

[0001] The present invention relates to the field of membrane separation technology, and in particular to a hollow fiber gas separation membrane and a preparation method and application thereof. Background Art

[0002] Nitrogen is both a single substance and a colorless and odorless gas with high chemical stability. Nitrogen is used in oil well stimulation, injection and pressure testing and pre-ventilation replacement. In particular, the pipeline nitrogen-enriched gas replacement operation before natural gas can effectively reduce the risk of explosion. A large amount of nitrogen needs to be continuously supplied. Obviously, the air contains 78% nitrogen, and air is inexhaustible. If nitrogen is separated and enriched from the air, it will be of great value.

[0003] At present, the main technology for enriching nitrogen is hollow fiber membrane separation technology, mainly from the US Prism PA4050-N3 gas separation membrane and the Korean Air MNH-4160A gas separation membrane. However, the gas production rate of these membranes is average, and there is still room for improvement. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a hollow fiber gas separation membrane and a preparation method and application thereof.

[0005] In a first aspect, the present invention provides a hollow fiber gas separation membrane, which is an asymmetric membrane, comprising a support layer and a separation layer loaded on the support layer, wherein the support layer is a hollow fiber microporous membrane, and the separation layer is a polydimethylsiloxane network layer having a Turing structure.

[0006] In order to obtain higher gas permeability and gas selectivity, the material selection of the membrane is certainly important. In addition, the surface morphology of the membrane also plays a vital role in the performance of the membrane. The present invention has found that making the separation layer of the hollow fiber gas separation membrane into a polydimethylsiloxane network layer with a Turing structure can significantly improve the gas permeability while ensuring gas selectivity.

[0007] The polydimethylsiloxane network in the separation layer is formed by the reaction of polydimethylsiloxane and a cross-linking agent, and the molecular weight of the polydimethylsiloxane is 10,000-50,000.

[0008] The "Turing structure" mentioned in the present invention refers to a structure such as stripes, stripes, rings, spirals, or mottled spots that are spontaneously organized by two components. This concept was first proposed by British mathematician and logician Alan Turing, who explored in a paper how stable patterns that appear in biological tissues are formed. "Turing structures" are widely present in nature, such as animal stripes, plant whorls of leaf arrangements, skin patterns, etc.

[0009] Furthermore, the thickness of the support layer is 0.25-0.35 mm, and the thickness of the separation layer is 0.5-10 μm.

[0010] Furthermore, in order to achieve a good separation effect, the average pore size of the hollow fiber microporous membrane is 10 to 50 nanometers, and the air permeability is 2000 to 5000 GPU.

[0011] In some embodiments of the present invention, the hollow fiber microporous membrane is a polymer membrane, and the polymer used is selected from one or more of polysulfone, polyethersulfone, polyvinylidene fluoride or polyimide. It can be prepared by conventional methods such as wet method, dry-wet method or thermally induced phase separation method.

[0012] In a second aspect, the present invention provides a method for preparing the hollow fiber gas separation membrane.

[0013] The preparation method provided by the present invention comprises: pre-treating the support layer, then immersing it in a separation layer coating liquid, obtaining a hollow fiber gas separation membrane semi-finished product by pulling, and pre-crosslinking and thermally crosslinking the obtained semi-finished product to obtain the hollow fiber gas separation membrane;

[0014] The separation layer coating liquid comprises polydimethylsiloxane, a cross-linking agent, a solvent n-heptane and an additive, wherein the additive comprises one or more of ethanol, isopropanol and isobutanol;

[0015] The volume ratio of the polydimethylsiloxane to the cross-linking agent is (6-12): (0.5-3).

[0016] In the present invention, the composition of the separation layer coating liquid is crucial to the formation of the Turing structure and the permeability of the membrane, wherein the pretreatment is to enhance the adhesion between the substrate and the separation layer, the addition of additives helps the polydimethylsiloxane and the cross-linking agent to achieve stable cross-linking, and the volume ratio of polydimethylsiloxane to the cross-linking agent needs to be controlled within the above range.

[0017] Furthermore, the volume usage of the solvent n-heptane is 90-95 times that of the polydimethylsiloxane.

[0018] Furthermore, the molecular weight of the polydimethylsiloxane is 10000-50000, and the cross-linking agent is tetraethyl orthosilicate.

[0019] Furthermore, the additive is added in an amount of 0.5-3wt%.

[0020] Furthermore, the pretreatment step includes: soaking the support layer in a pretreatment reagent for 1-12 hours, and then drying at 20-50° C. for standby use; the pretreatment reagent is selected from one or more of water, ethanol, n-hexane, and n-heptane.

[0021] Furthermore, the support layer is immersed in the separation layer coating liquid for 0.1-15 min, and the pulling speed is 20-50 cm / min.

[0022] Furthermore, the pre-crosslinking is to stand at room temperature for 1-24 hours; the thermal crosslinking is to heat at 60-110°C for 5 minutes to 6 hours. The room temperature refers to 20-30°C. Preferably, the thermal crosslinking temperature is 80-90°C.

[0023] In some embodiments of the present invention, the thermal cross-linking temperature is 80° C. and the thermal cross-linking time is 10 min, so that a hollow fiber gas separation membrane with a Turing structure can be prepared.

[0024] In other embodiments of the present invention, the thermal cross-linking temperature is 90° C. and the thermal cross-linking time is 5 min, so that a hollow fiber gas separation membrane with a Turing structure can be prepared.

[0025] In some embodiments of the present invention, the method for preparing the hollow fiber gas separation membrane comprises the following steps:

[0026] Step 1, soaking the support layer in a pretreatment reagent for 1-12 hours, and then drying it at 20-50° C. for standby use; the pretreatment reagent is one or more of water, ethanol, n-hexane, and n-heptane;

[0027] Step 2, dissolving polydimethylsiloxane and a cross-linking agent in a volume ratio of (6-12): (0.5-3) in n-heptane, and adding 0.5-3wt% of an additive to obtain a separation layer coating liquid; the molecular weight of the polydimethylsiloxane is 10000-50000, the cross-linking agent is tetraethyl orthosilicate, and the additive is one or more of ethanol, isopropanol, and isobutanol;

[0028] Step 3, immersing the support layer in the separation layer coating liquid for 0.1-15 min, and then obtaining a hollow fiber gas separation membrane semi-finished product by pulling at a pulling speed of 20-50 cm / min;

[0029] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 1-24 hours for pre-crosslinking, and then heat-crosslinked at 60-110° C. for 5 minutes to 6 hours.

[0030] In a third aspect, the present invention provides the use of the above hollow fiber gas separation membrane in gas separation, especially in oxygen-enriched combustion and oxygen-nitrogen separation.

[0031] The present invention provides a hollow fiber gas separation membrane and a preparation method and application thereof. The hollow fiber gas separation membrane provided by the present invention has a special Turing structure in the separation layer. Different from the nitrogen-rich separation membrane in the prior art, combined with the selection of membrane materials, the hollow fiber gas separation membrane of the present invention has ultra-high gas permeability, and the nitrogen yield of a single membrane fiber is as high as 161 mL / min. The gas production rate is nearly 30 times that of the U.S. Prism PA4050-N3 gas separation membrane and the Korean Air MNH-4160A gas separation membrane, and has extremely high gas permeability; it also has ultra-high gas selectivity, and can purify nitrogen to more than 97%, which fully meets the replacement gas standard in natural gas extraction; it also has ultra-high gas operation stability, and there is no attenuation phenomenon when running at 1.2 MPa for 1000 hours. Moreover, the preparation process of the hollow fiber gas separation membrane of the present invention is simple, the raw materials are cheap and easy to obtain, and the membrane formation process is easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 This is a hollow fiber gas separation membrane with a Turing structure in Example 1 of the present invention (where a is a microscopic image of the support layer, and b is a microscopic image of the separation layer after preparation).

[0034] Figure 2 It is a hollow fiber gas separation membrane without a Turing structure in Comparative Example 1 of the present invention (where a is a microscopic image of the support layer, and b is a microscopic image of the membrane surface after preparation). DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the field or the product instructions are used. If no manufacturer is specified for the reagents or instruments used, they are all conventional products that can be purchased through regular channels.

[0037] If not otherwise specified, in the following embodiments, the support layer is a polymer membrane selected from polysulfone, polyethersulfone, polyvinylidene fluoride or polyimide, with an average pore size of 10-50 nm and an air permeability of 2000-5000 GPU. The molecular weight of the polydimethylsiloxane used is 10000-50000.

[0038] Example 1

[0039] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer supported on the support layer, and the preparation method thereof is as follows:

[0040] Step 1, soaking the support layer (polysulfone membrane) in ethanol and n-hexane for 12 hours respectively, and then drying at 20°C for standby use; Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 6:3 in n-heptane (the volume of n-heptane is 95 times that of polydimethylsiloxane), and adding 1wt% of isobutanol to obtain a separation layer coating liquid;

[0041] Step 3, immersing the support layer in the separation layer coating liquid for 10 minutes, and then pulling it at a pulling speed of 35 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0042] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 70° C. for 80 minutes.

[0043] The hollow fiber gas separation membrane obtained in this embodiment has a Turing structure, such as Figure 1 As shown, the thickness of the support layer is 0.25 mm and the thickness of the separation layer is 1 μm.

[0044] Example 2

[0045] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer supported on the support layer, and the preparation method thereof is as follows:

[0046] Step 1, soak the support layer (polyvinylidene fluoride membrane) in ethanol and n-hexane for 12 hours respectively, and then dry it at 40°C for later use;

[0047] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 12:0.5 in n-heptane (the volume of n-heptane is 90 times that of polydimethylsiloxane), and adding 0.5 wt % of isobutyl alcohol to obtain a separation layer coating liquid;

[0048] Step 3, immersing the support layer in the separation layer coating liquid for 15 minutes, and then pulling it at a pulling speed of 50 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0049] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 80° C. for 10 minutes.

[0050] The hollow fiber gas separation membrane obtained in this example has a Turing structure, wherein the thickness of the support layer is 0.35 mm, and the thickness of the separation layer is 2.1 μm.

[0051] Example 3

[0052] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer supported on the support layer, and the preparation method thereof is as follows:

[0053] Step 1, soak the support layer (polyimide membrane) in n-heptane for 12 hours, and then dry it at 30° C. for later use;

[0054] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 6:0.5 in n-heptane (the volume of n-heptane is 90 times that of polydimethylsiloxane), and adding 2 wt % of isopropanol to obtain a separation layer coating liquid;

[0055] Step 3, immersing the support layer in the separation layer coating liquid for 0.1 min, and then pulling it at a pulling speed of 20 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0056] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 90° C. for 5 minutes.

[0057] The hollow fiber gas separation membrane obtained in this example has a Turing structure, wherein the thickness of the support layer is 0.3 mm, and the thickness of the separation layer is 3.2 μm.

[0058] Example 4

[0059] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer supported on the support layer, and the preparation method thereof is as follows:

[0060] Step 1, soak the support layer (polyethersulfone membrane) in water for 12 hours, and then dry it at 40° C. for later use;

[0061] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 12:3 in n-heptane (the volume of n-heptane is 95 times that of polydimethylsiloxane), and adding 3 wt % of ethanol to obtain a separation layer coating liquid;

[0062] Step 3, immersing the support layer in the separation layer coating liquid for 10 minutes, and then pulling it at a pulling speed of 35 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0063] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 100° C. for 5 minutes.

[0064] The hollow fiber gas separation membrane obtained in this example has a Turing structure, wherein the thickness of the support layer is 0.28 mm, and the thickness of the separation layer is 5 μm.

[0065] Example 5

[0066] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer supported on the support layer. The difference between this embodiment and embodiment 1 is that the molecular weight of the polydimethylsiloxane used is 60,000.

[0067] Example 6

[0068] This embodiment provides a hollow fiber gas separation membrane, which is composed of a support layer and a separation layer loaded on the support layer. The difference between this embodiment and Example 1 is that the average pore size of the support layer polysulfone membrane used is 100 nm and the air permeability is 10000 GPU.

[0069] Comparative Example 1

[0070] This comparative example provides a hollow fiber gas separation membrane, and its preparation method is as follows:

[0071] Step 1, soak the support layer in ethanol and n-hexane for 12 hours respectively, and then dry it at 20°C for later use;

[0072] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 30:1 in n-heptane to obtain a separation layer coating liquid;

[0073] Step 3, immersing the support layer in the separation layer coating liquid for 10 minutes, and then pulling it at a pulling speed of 35 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0074] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 70° C. for 80 minutes.

[0075] The hollow fiber gas separation membrane obtained in this comparative example does not have a Turing structure, such as Figure 2 As shown, the thickness of the support layer is 0.25 mm and the thickness of the separation layer is 0.2 microns.

[0076] Comparative Example 2

[0077] This comparative example provides a hollow fiber gas separation membrane, and its preparation method is as follows:

[0078] Step 1, soak the support layer in ethanol and n-hexane for 12 hours respectively, and then dry it at 20°C for later use;

[0079] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 1:1 in n-heptane, and adding 1 wt % of isobutyl alcohol to obtain a separation layer coating liquid;

[0080] Step 3, immersing the support layer in the separation layer coating liquid for 10 minutes, and then pulling it at a pulling speed of 35 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0081] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 70° C. for 80 minutes.

[0082] The hollow fiber gas separation membrane obtained in this comparative example does not have a Turing structure, wherein the thickness of the support layer is 0.25 mm, and the thickness of the separation layer is 0.1 μm.

[0083] Comparative Example 3

[0084] This comparative example provides a hollow fiber gas separation membrane, and its preparation method is as follows:

[0085] Step 1, soak the support layer in ethanol and n-hexane for 12 hours respectively, and then dry it at 20°C for later use;

[0086] Step 2, dissolving polydimethylsiloxane and tetraethyl orthosilicate in a volume ratio of 6:3 in n-heptane to obtain a separation layer coating liquid; Step 3, immersing the support layer in the separation layer coating liquid for 10 minutes, and then pulling it at a pulling speed of 35 cm / min to obtain a hollow fiber gas separation membrane semi-finished product;

[0087] Step 4, the semi-finished product in step 3 is allowed to stand at room temperature for 24 hours for pre-crosslinking, and then heat-crosslinked at 70° C. for 80 minutes.

[0088] The hollow fiber gas separation membrane obtained in this comparative example does not have a Turing structure, wherein the thickness of the support layer is 0.3 mm, and the thickness of the separation layer is 0.5 μm.

[0089] Performance Testing

[0090] For comparison, two membranes that have been commercialized and used for nitrogen-rich separation were selected for testing, namely the American Prism PA4050-N3 gas separation membrane and the Korean Air MNH-4160A gas separation membrane. The above two membranes and the hollow fiber gas separation membranes of the embodiments and comparative examples of the present invention were assembled into gas separation membrane modules according to conventional methods. The module consists of 10 19 cm long membrane filaments. The temperature of the gas separation performance test is 40°C and the test pressure is 1.15MPa. Air enters from the air inlet and then exits from the air outlet to obtain high-purity nitrogen-rich gas. The results are shown in Table 1, indicating that under the same conditions, the gas selectivity of the present invention is higher than that of the other two commercial membranes, and the air permeability can even reach a gas production rate of 161mL / min. It can be seen that the hollow fiber gas separation membrane of the present invention has high permeability and selectivity.

[0091] Table 1 Gas separation performance table

[0092]

[0093] It should be noted that the endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this article.

[0094] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "specific implementations", or "some specific implementations" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A hollow fiber gas separation membrane, characterized in that: The hollow fiber gas separation membrane is an asymmetric membrane, comprising a support layer and a separation layer loaded on the support layer, the support layer is a hollow fiber microporous membrane, and the separation layer is a polydimethylsiloxane network layer with a Turing structure; The thickness of the support layer is 0.25-0.35 mm, and the thickness of the separation layer is 0.5-10 μm; The polydimethylsiloxane network in the separation layer is formed by the reaction of polydimethylsiloxane and a crosslinking agent, and the molecular weight of the polydimethylsiloxane is 10000-50000; The average pore size of the hollow fiber microporous membrane is 10 to 50 nanometers, and the air permeability is 2000 to 5000 GPU.

2. The method for preparing a hollow fiber gas separation membrane according to claim 1, characterized in that: include: After pre-treating the support layer, immersing it in a separation layer coating liquid, obtaining a hollow fiber gas separation membrane semi-finished product by pulling, and pre-crosslinking and thermally crosslinking the obtained semi-finished product to obtain the hollow fiber gas separation membrane; The separation layer coating liquid comprises polydimethylsiloxane, a cross-linking agent, a solvent n-heptane and an additive, wherein the additive comprises one or more of ethanol, isopropanol and isobutanol; The volume ratio of the polydimethylsiloxane to the cross-linking agent is (6-12): (0.5-3); The molecular weight of the polydimethylsiloxane is 10000-50000, and the cross-linking agent is tetraethyl orthosilicate.

3. The method for preparing a hollow fiber gas separation membrane according to claim 2, characterized in that: The additive is used in an amount of 0.5-3 wt%.

4. The method for preparing a hollow fiber gas separation membrane according to claim 2, characterized in that: The pre-processing step comprises: The support layer is immersed in a pretreatment reagent for 1-12 hours, and then dried at 20-50° C. for standby use; the pretreatment reagent is selected from one or more of water, ethanol, n-hexane, and n-heptane.

5. The method for preparing a hollow fiber gas separation membrane according to claim 2, characterized in that: The support layer is immersed in the separation layer coating liquid for 0.1-15 min, and the pulling speed is 20-50 cm / min.

6. The method for preparing a hollow fiber gas separation membrane according to claim 2, characterized in that: The pre-crosslinking is performed by standing at room temperature for 1-24 hours; The thermal crosslinking is performed by heating at a temperature of 60-110° C. for 5 min-6 h.

7. Use of the hollow fiber gas separation membrane according to claim 1 in separating gases.

Images