Oil-gas separation membrane as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of membrane separation, and particularly relates to an oil-gas separation membrane as well as a preparation method and application thereof. The invention relates to an oil-gas separation membrane. The separation membrane comprises a PT610 resin polymer; the separation membrane is configured to separate dissolved gases in a non-polar oil phase environment and maintain the integrity of its chemical skeletal structure in the environment. The invention also provides an application of the oil-gas separation membrane in on-line oil-gas separation or dissolved gas analysis of electric power equipment.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of membrane separation technology, and particularly relates to an oil-gas separation membrane and a preparation method and application thereof. BACKGROUND

[0002] Large oil-immersed power transformers are key equipment in power systems, and their stability and reliability of operation are directly related to the safety of the entire power grid. During long-term operation, the organic materials such as insulating oil and insulating paper inside the transformer will gradually age and decompose due to the combined effects of electricity, heat, and chemicals, producing various characteristic gases such as hydrogen, methane, ethane, ethylene, acetylene, carbon monoxide, and carbon dioxide. These gases will dissolve in the insulating oil, and changes in their composition and content can accurately reflect whether there are latent faults such as overheating and discharge inside the transformer, as well as their nature and severity. Therefore, online analysis of dissolved gases in transformer oil is the most effective and direct technical means to warn of equipment failure and ensure safe operation of the power grid. Compared with traditional offline sampling analysis, online monitoring systems can provide real-time and continuous data, which has irreplaceable important value for timely detection of early faults and prevention of accident expansion.

[0003] In order to realize online monitoring, the gas dissolved in the oil needs to be effectively separated from the oil body first, which is the premise and key for subsequent gas detection and analysis. Currently, the gas degassing method based on membrane separation technology is the mainstream technical route for oil-gas separation. Early studies mostly used microporous polymer membranes, such as porous hydrophobic materials such as polytetrafluoroethylene or polypropylene. This type of membrane material uses its micro-porous channels to form a physical interface between the oil and the detection chamber, preventing the passage of liquid oil while allowing gas molecules to permeate. However, this microporous membrane has obvious defects in practical application: on the one hand, its separation selectivity is low, and its separation ability for different gas components is limited; on the other hand, and more fatally, its microporous structure is easily infiltrated, clogged, and even contaminated by small oil droplets, impurity particles, or oil aging products in the insulating oil. This "membrane clogging" phenomenon can cause a sharp decline in gas permeation flux, seriously affecting the long-term operation stability of the system and the accuracy of the detection results.

[0004] To solve the above problems of microporous membranes, the technical development turned to dense non-porous solution-diffusion type polymer membranes, especially amorphous fluoropolymer membranes with excellent chemical inertness. This kind of membrane material relies on the process of gas molecule dissolution and diffusion in its polymer matrix to realize separation, fundamentally avoiding the problem of pore blockage, and can provide higher gas separation selectivity. Although this kind of advanced membrane material has more advantages in theory, they still face serious challenges in the harsh application environment of transformer online monitoring. Insulating oil itself is a non-polar hydrocarbon mixture, long-term and high-temperature immersion will have irreversible effects on the physical and chemical properties of the polymer membrane material, such as causing swelling and plasticization of polymer chain segments, and even causing weak degradation of chemical structure. These subtle structural changes caused by physical adsorption or penetration of oil molecules will destroy the mechanical integrity of the membrane material and change the internal free volume distribution for gas transmission, ultimately leading to the deterioration of its gas separation performance over time, which cannot meet the long-period and maintenance-free monitoring requirements of power equipment. Therefore, the existing technology still has obvious technical bottlenecks in providing an oil-gas separation membrane that can balance high-efficiency oil-gas separation performance and long-term oil immersion stability. SUMMARY

[0005] The purpose of the present application is to solve the above problems, and provide an oil-gas separation membrane, a preparation method and application thereof.

[0006] In a first aspect, an oil-gas separation membrane is provided, which employs the following technical solutions:

[0007] An oil-gas separation membrane, the separation membrane comprises a PT610 resin polymer, and the structural formula is as follows:

[0008]

[0009] The separation membrane is configured to separate dissolved gas in a non-polar oil phase environment, and maintains the integrity of its chemical skeleton structure in the environment.

[0010] Further, the non-polar oil phase environment is a transformer oil environment.

[0011] Further, the dissolved gas includes carbon dioxide and / or nitrogen.

[0012] Further, the thickness of the oil-gas separation membrane is 50-150 μm.

[0013] In a second aspect, a preparation method of an oil-gas separation membrane is provided, which employs the following technical solutions:

[0014] A preparation method of an oil-gas separation membrane, comprising the following steps: dissolving a PT610 resin polymer in a perfluorinated solvent to form a casting solution; performing flow casting to form a film; and removing the solvent through heat treatment to obtain a self-supporting oil-gas separation membrane.

[0015] Further, the perfluorinated solvent is perfluorotributylamine.

[0016] Further, in the heat treatment step, the heat treatment temperature is 130-160 DEG C, and the heat treatment time is 8-16 h.

[0017] In a third aspect, the application relates to an oil-gas separation membrane, which adopts the following technical scheme:

[0018] The oil-gas separation membrane is applied to online oil-gas separation or dissolved gas analysis of power equipment.

[0019] Further, the power equipment is a transformer.

[0020] Further, the online oil-gas separation or dissolved gas analysis is used for online fault diagnosis or state monitoring of the power equipment.

[0021] The application has the following beneficial effects:

[0022] The application provides an oil-gas separation membrane, which solves the technical problems of swelling, aging and performance attenuation of the existing separation membrane in a long-term oil immersion environment compared with the prior art. The fluorine-containing high polymer membrane has strong resistance to oil product corrosion, and after being continuously immersed in non-polar transformer oil for dozens of days, the mass growth rate is less than 1%, and almost no visible swelling phenomenon occurs, which proves that the physical adsorption and absorption of the separation membrane material to non-polar oil molecules are extremely weak. Infrared spectrum analysis further proves that long-term immersion does not change the core C-F chemical skeleton structure, and does not cause any chain segment rupture or chemical degradation, ensuring the fundamental stability of the separation membrane material at the molecular level. The separation membrane material of the application maintains excellent mechanical properties in a harsh environment, and after long-term oil immersion, the separation membrane does not appear to be brittle or have a decrease in strength, and the elongation at break is even improved, showing excellent flexibility and fatigue resistance, which ensures that the separation membrane can serve for a long time without physical damage in actual working conditions. The separation membrane material solves the core pain point of the separation performance attenuation over time in the prior art, and the permeation rate and separation selectivity of the separation membrane to key fault characteristic gases such as carbon dioxide and nitrogen remain basically unchanged after long-term oil immersion, with minimal fluctuations, which proves that the free volume structure for gas transmission inside the separation membrane is not negatively changed due to oil molecule penetration, ensuring that the online monitoring system can output long-term stable, reliable and accurate gas analysis data, providing a solid technical guarantee for state evaluation and fault warning of power equipment. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 The FTIR spectrum comparison chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion.

[0024] Figure 2 The water contact angle comparison chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion.

[0025] Figure 3 The thermogravimetric curve chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion.

[0026] Figure 4 The nitrogen adsorption / desorption curve chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion.

[0027] Figure 5 The tensile curve chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion.

[0028] Figure 6 The gas permeation curve chart of the PT610 oil-gas separation membrane provided for Example 1 before and after transformer oil immersion. DETAILED DESCRIPTION

[0029] In order to make the objects, technical solutions and advantages of the present application clearer, the following will further describe the present application with reference to the accompanying drawings, and the described embodiments should not be regarded as limiting the present application. All other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0030] In the following description, "some embodiments" are related to a subset of all possible embodiments, but it can be understood that "some embodiments" can be the same subset or different subsets of all possible embodiments, and can be combined with each other without conflict. Unless otherwise defined, all technical and scientific terms used in the embodiments of the present application have the same meaning as understood by those skilled in the art to which the embodiments of the present application belong. The terms used in the embodiments of the present application are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

[0031] Those skilled in the art should understand that in the following description of the embodiments of the present application, the order of the serial numbers does not mean the order of execution, and some or all steps can be executed in parallel or in sequence, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0032] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0033] Those skilled in the art will understand that the numerical ranges in the embodiments of the present invention should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Each smaller range between any stated value and an intermediate value within the stated range, as well as any other stated value or an intermediate value within the stated range, is also included within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0034] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may be used in embodiments or test cases of the invention. All references to this specification are generally incorporated herein by reference to disclose and describe methods and / or materials associated with said references. In the event of any conflict with any incorporated reference, the contents of this application shall prevail.

[0035] It should be noted that all raw materials and / or reagents in the embodiments of the present invention were purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0036] Reagents and materials:

[0037] PT610 fluorinated polymer and perfluorinated solvent FC-40 were purchased from Chemours, DuPont. The transformer oil was supplied by the Yunnan Power Grid Co., Ltd. Electric Power Research Institute.

[0038] Equipment and Instruments:

[0039] Fourier transform infrared spectroscopy (FTIR) was performed using a Bruker TENSOR27 FTIR spectrometer; water contact angle (WCA) was measured using a KRUSSDSA100S contact angle measuring instrument; thermogravimetric analysis (TGA) was performed using a Mettler ToledoTGA1 thermogravimetric analyzer; tensile properties were tested using a Shenzhen Sansi Testing Instruments Co., Ltd. CMT6503 electronic universal testing machine; specific surface area was measured using a Micromeritics ASAP 2020Plus HD88 analyzer; and gas permeation was measured using a Jinan Langguang Electromechanical Technology Co., Ltd. C101B permeameter.

[0040] Example

[0041] Example 1

[0042] This Example 1 provides an oil and gas separation membrane, the separation membrane comprising a PT610 resin polymer, having the following structural formula:

[0043]

[0044] The separation membrane is configured for separating dissolved gases in a non-polar oil phase environment, and maintaining the integrity of its chemical backbone structure in the environment.

[0045] Example 1 also provides a method for preparing an oil and gas separation membrane, comprising the following steps:

[0046] 5 grams of PT610 resin polymer was dissolved in perfluorinated solvent FC-40 at a mass fraction of 1%, and magnetically stirred at 30°C for 48h to ensure complete swelling of the polymer. The resulting uniform transparent solution was cast on the surface of a glass substrate which was ultrasonically cleaned with ethanol and deionized water in sequence and dried, and placed in a ventilated environment at room temperature (30°C) for 3h to volatilize the main solvent; then together with the substrate, it was placed in an oven and heat treated at 130°C for 16h to remove the residual FC-40 and anneal the polymer matrix; after natural cooling to room temperature, the self-supported PT610 oil and gas separation membrane was peeled off from the substrate, with a thickness of about 100μm.

[0047] Example 1 also provides an application of an oil and gas separation membrane, the PT610 oil and gas separation membrane prepared in Example 1 is soaked in transformer oil, for separating dissolved gases such as carbon dioxide and / or nitrogen in a transformer oil environment.

[0048] Example 2

[0049] Example 2 provides a method for preparing an oil and gas separation membrane, comprising the following steps:

[0050] 5 grams of PT610 resin polymer was dissolved in perfluorinated solvent FC-40 at a mass fraction of 0.5%, and magnetically stirred at 30°C for 48h to ensure complete swelling of the polymer. The resulting uniform transparent solution was cast on the surface of a glass substrate which was ultrasonically cleaned with ethanol and deionized water in sequence and dried, and placed in a ventilated environment at room temperature (30°C) for 1h to volatilize the main solvent; then together with the substrate, it was placed in an oven and heat treated at 130°C for 8h to remove the residual FC-40 and anneal the polymer matrix; after natural cooling to room temperature, the self-supported PT610 oil and gas separation membrane was peeled off from the substrate, with a thickness of about 50μm.

[0051] Example 2 also provides an application of an oil and gas separation membrane, the PT610 oil and gas separation membrane prepared in Example 1 is soaked in transformer oil, for separating dissolved gases such as carbon dioxide and / or nitrogen in a transformer oil environment.

[0052] Example 3

[0053] Example 3 provides a method for preparing an oil-gas separation membrane, comprising the following steps:

[0054] 5 grams of PT610 resin polymer was dissolved in perfluorinated solvent FC-40 at a mass fraction of 1.5%, and stirred magnetically at 30°C for 48 h to ensure complete swelling of the polymer. The resulting uniform transparent solution was cast on the surface of a glass substrate which had been ultrasonically cleaned with ethanol and deionized water in turn and dried, and placed in a ventilated environment at room temperature (30°C) for 2 h to volatilize the main solvent; then together with the substrate, it was placed in an oven and heat treated at 160°C for 12 h to remove the residual FC-40 and anneal the polymer matrix; after natural cooling to room temperature, the self-supporting PT610 oil-gas separation membrane was peeled off from the substrate, with a thickness of about 150 μm.

[0055] Example 3 also provides an application of an oil-gas separation membrane. The PT610 oil-gas separation membrane prepared in Example 1 was immersed in transformer oil, and used for separating dissolved gases such as carbon dioxide and / or nitrogen in a transformer oil environment.

[0056] Performance test

[0057] The self-supporting PT610 oil-gas separation membrane provided in Example 1 was subjected to the following performance tests.

[0058] I. Performance test method

[0059] (1) Fourier transform infrared spectroscopy (FTIR): The infrared absorption spectrum of the membrane sample was measured at room temperature using the attenuated total reflection (ATR) mode. The scanning wave number range was 400 cm -1 -4000 cm -1 , the spectral resolution was 4 cm -1 , and the scanning number was 64.

[0060] (2) Water contact angle (WCA): 5 μL of deionized water was added to the surface of the membrane with a microsyringe, and after the water droplet was stable within 5 s, the contact angles on the left and right sides were measured simultaneously by the tangent method provided by the instrument and the average value was taken.

[0061] (3) Thermogravimetric analysis (TGA): The membrane sample (mass 5-10 mg) was subjected to thermogravimetric test in a nitrogen atmosphere (flow rate 50 mL·min -1 ). The heating rate was set to 10°C·min -1 , and the temperature range was 30-800°C to evaluate the thermal decomposition behavior of the membrane.

[0062] (4) Specific surface area test: The specific surface area of the membrane sample was determined by nitrogen adsorption-desorption isotherm method. Before testing, the membrane sample was cut into small pieces of about 1 cm x 1 cm and pre-dried at 60°C for 12 h in a vacuum drying oven to remove the residual moisture and solvent on the surface and in the pores. Then, the sample was placed in a sample tube and degassed at 120°C for 6 h under vacuum, and then automatically cooled to liquid nitrogen temperature. During the test, the measurement points of the nitrogen adsorption-desorption isotherm were arranged in the relative pressure (P / P0) range of 0.01-0.99, a total of 30 data points, and the residence time was 10 s.

[0063] (5) Tensile property test: The test sample size was 50 mm x 5 mm x 0.1 mm, and the tensile rate was 50 mm / min -1 , and the test was carried out until the sample broke. The tensile strength, elongation at break and Young's modulus were obtained from the stress-strain curve.

[0064] (6) Gas permeation test: The permeation properties of the membrane to a single gas (such as CO2, N2) were determined by constant-volume variable-pressure method at 35°C. The membrane sample with a diameter of 50 mm was installed in a custom test chamber, first pumped to a base pressure of 5 Pa with a mechanical pump, and kept in the chamber overnight to completely remove the residual solvent; the upstream pressure change was recorded in real time during the test, and the gas permeability and ideal selectivity were calculated.

[0065] II. Performance test results

[0066] 1. Mass change

[0067] According to gravimetric analysis, the mass of the PT610 oil-gas membrane increased from 0.9006 g to 0.9089 g after continuous immersion in transformer oil for 45 days, and the mass change rate was less than 1% (as shown in Table 1), indicating that the membrane material hardly absorbed oil in the long-term oil phase environment. Such weak expansion is mainly due to two factors: one is that the affinity of the perfluorodioxane main chain to non-polar hydrocarbon molecules is very low, and it is difficult to form a stable adsorption layer; the other is that the tight packing structure of the polymer chain segment effectively hinders the diffusion and penetration of oil molecules on the microscale. It can be seen that the PT610 oil-gas separation membrane can maintain the stability of size and morphology in the oil environment at high temperature and high pressure, laying a foundation for long-term maintenance of excellent mechanical properties and permeation characteristics in online oil-gas separation and dissolved gas analysis applications.

[0068] Table 1 Comparison of physical properties of PT610 oil-gas separation membrane before and after immersion in transformer oil

[0069]

[0070] 2. Infrared spectrum

[0071] Figure 2 The ATR-FTIR spectral characteristics of the PT610 oil-gas separator membrane after immersion in transformer oil for 45 days are shown. First, at 1236 cm⁻¹... -1 The absorption peak of the CF stretching vibration at the point did not show significant shift or intensity decay, indicating that the PT610 polymer backbone maintained an intact covalent skeleton structure after long-term immersion in the oil phase, without chain segment breakage or skeleton modification; this is closely related to the strong and tough perfluorodioxane backbone and high thermal stability of the polymer itself.

[0072] Secondly, 2800-3000cm -1 Several weak CH stretching vibration absorption peaks appeared in the region, corresponding to methylene groups in the oil phase. These peaks gradually increased in intensity within the highly overlapping background spectrum as the immersion time increased, indicating that a small number of nonpolar hydrocarbon molecules accumulated on the membrane surface or near the surface free volume through physical adsorption. Notably, the appearance of these CH absorption peaks was not accompanied by the generation of any new polar functional group signals such as carbonyl (C=O), hydroxyl (OH), or amino (NH), further confirming that the adsorption process is mainly non-chemically bonded van der Waals interactions, rather than chemical cross-linking or degradation reactions.

[0073] The weak but reproducible adsorption peak indicates that the high free volume fraction of the PT610 oil-gas separation membrane provides a large number of micro- and nano-sized pores, allowing trace amounts of oil to temporarily reside at the interface. Simultaneously, the tight packing of polymer chains and their inert molecular framework effectively limit deep diffusion, preventing a large amount of free oil from entering the matrix. This phenomenon partially explains the reason for the membrane oil absorption rate ≤1% in the previous gravimetric analysis, and is consistent with the trace porosity found in the BET surface area and pore volume tests.

[0074] Based on the FTIR analysis above, the PT610 oil-gas separation membrane exhibits only trace amounts of physical adsorption at the surface or near-surface level in harsh oil-phase environments, while its internal chemical structure and macroscopic mechanical properties remain highly stable. This finding provides important guidance for the design of online oil-gas separation and dissolved gas detection systems, indicating that the PT610 oil-gas separation membrane can operate for extended periods without significant changes to its molecular structure, providing reliable material support for the online diagnosis and maintenance of power equipment.

[0075] 3. Water contact angle

[0076] like Figure 3As shown in Table 1, after 45 days of continuous immersion in transformer oil, the static water contact angle of PT610 oil-gas separation membrane only slightly decreased from 117.4° of the original membrane to 116.6°, and the surface hydrophobic and oleophobic properties only changed by about 0.8°. This phenomenon indicates that although oil molecules have a detectable physical adsorption on the membrane surface, the amount of such adsorption is extremely small and is limited to the outermost nanoscale free volume and a small amount of rough peak and valley regions of the membrane. First, the PT610 high molecular chain contains a perfluorodioxane structure, which has a low surface energy and excellent oil-repellent property, effectively repelling long-chain alkyl and aromatic hydrocarbon molecules in insulating oil, making it difficult for them to form a stable oil film on the membrane surface. Second, the micro-morphology of the membrane surface changes little during oil immersion, neither obvious swelling and wrinkling nor new rough structure is generated, so the surface roughness has negligible effect on the contact angle. Third, the nanoscale segment rearrangement can cause a slight micro-displacement of the small amount of adsorbed hydrocarbon molecules, but this segment loosening does not cause the main chain to break or the chemical functional group to change, so the chemical structure remains intact and no polar group or hydroxyl group is introduced, thereby not significantly increasing the surface free energy. Combined with the absence of new peaks generated by ATR-FTIR and the slight occupation of micropore volume in BET testing, it can be seen that the oil is mainly dispersed in trace amounts on the surface layer of the membrane, which is not enough to change the overall interfacial properties. Overall, after 45 days of high-temperature and high-pressure oil immersion, the PT610 oil-gas separation membrane still maintains a high contact angle of more than 110° and good water-repellent and oil-repellent performance, which not only ensures the resistance of the membrane to oil phase in the online gas extraction process, but also maximizes the reduction of oil droplets or water droplets on the membrane surface. The excellent interfacial stability provides a solid material foundation for the long-term and reliable operation of oil-gas separation membranes in online monitoring and fault diagnosis of power equipment, and also provides an important experimental and design reference for the subsequent development of high-performance oil-repellent membrane system based on fluoropolymer.

[0077] 4. Thermal stability

[0078] As Figure 4 As shown in Table 1, after 45 days of continuous immersion in transformer oil, the 5% mass loss temperature (T 5％) from 298 °C to 250 °C, the thermal stability deteriorated. This phenomenon mainly originated from the permeation plasticization effect of oil molecules in the high free volume molecular network, which reduced the required breaking energy of inter-chain interaction; in addition, trace amounts of oxidized or oligomeric hydrocarbon components in the oil phase could also catalyze the initial degradation process, thus slightly shifting the decomposition temperature. However, 250 °C was still much higher than the common operating temperature of transformer oil (≤ 100 °C), fully demonstrating that the PT610 oil-gas separation membrane still maintained excellent thermodynamic stability in the high-temperature and high-humidity oil phase environment. This result not only verified the heat-resistant advantage of the PT610 polymer skeleton, but also highlighted its application feasibility in long-term online oil-gas separation and dissolved gas monitoring. The study further showed that by controlling the free volume distribution and optimizing the molecular chain arrangement, the influence of the oil phase medium on the thermal performance of the membrane material could be maximized while ensuring high permeability, providing an important design idea for the subsequent development of fluoropolymer membranes with higher temperature resistance.

[0079] 5, specific surface area

[0080] As Figure 5 shown in Table 2, after continuous immersion in transformer oil for 45 days, the pore structure of the PT610 oil-gas separation membrane showed obvious evolution: the BET surface area decreased from the initial 373.2 m 2 / g to 295.4 m 2 / g, with a decrease of about 21%; while the average pore width calculated based on the Horvath-Kawazoe (H-K) model increased from to , with an increase of about 32%. The pore structure change mechanism was mainly caused by two aspects. First, the molecules in the transformer oil first preferentially enter and occupy the micropores (< 2 nm) in the polymer network that are most easily accessible and have the best flowability, causing a significant decrease in micropore volume and number, which is directly reflected in the decrease of BET surface area; on the other hand, the plasticizing effect and chain relaxation effect of oil molecules promote the fusion of part of the micropores or the expansion of the distance between adjacent chains, forming more mesopores and macropores, thus making the average pore size and pore volume distribution move to the large pore size interval. Since oil molecules do not penetrate deep to cause macroscopic deformation, this process mainly focuses on the rearrangement of nanoscale chain segments and the reconstruction of pore channels, so the change in the external surface area of the membrane is small.

[0081] From the perspective of gas separation applications, the stability of the microporous network directly determines the diffusion selectivity of the membrane for light gases, while the mesopore expansion helps to improve the permeation flux. The test data show that although the BET surface area decreases by more than 20%, the CO2 and N2 permeation rates of the PT610 oil-gas separation membrane change by less than 5% before and after immersion, and the CO2 / N2 ideal selectivity remains essentially unchanged. This indicates that the partial plugging of micropores has limited impact on the overall gas transmission path, and the mesopore expansion compensates for the loss of pore volume, thereby maintaining the stability of the permeation performance.

[0082] However, from the perspective of the reliability of long-term online oil-gas separation and online dissolved gas monitoring, the continuous evolution of the micropore distribution still needs attention: if the micropore network is excessively occupied or further fused, it may have a cumulative impact on the gas separation efficiency under longer immersion periods or higher temperature conditions. For this reason, subsequent research can focus on enhancing the anti-adsorption ability of the polymer matrix to micropores through molecular design or surface modification methods, or introducing a barrier thin layer on the membrane surface to delay the occupation of the micropore network by oil. In summary, the pore structure rearrangement characteristics exhibited by the PT610 oil-gas separation membrane under 45-day oil immersion conditions provide a key reference for the long-term performance optimization of high-free-volume molecular membranes in harsh oil environments.

[0083] Table 2 Comparison of BET test results of PT610 membrane before and after transformer oil immersion

[0084]

[0085] 6. Mechanical properties

[0086] As Figure 6 As shown in Table 1 and Table 2, after the PT610 oil-gas separation membrane was immersed in transformer oil for 45 days, the tensile test results revealed that its mechanical properties had undergone controllable and limited changes: the Young's modulus decreased from 1.30 GPa to 1.04 GPa, with a decrease of about 20%; at the same time, the elongation at break increased from 5.6% to 6.4%, with an increase of about 14%. This "softening-toughening" effect can be explained by the oil plasticization mechanism in the high-free-volume molecular network.

[0087] Firstly, the van der Waals forces between PT610 polymer chains and the interactions between chain segments are weakened to some extent after oil penetration, and oil molecules act as "lubricants" between chains, increasing the movement freedom of chain segments at the microscopic level, thereby reducing the overall rigidity, which is manifested as a decrease in Young's modulus. Secondly, due to the increased activity of local chain segments, when the sample is under stress, the molecular chains can slide and rearrange in a larger range, delaying the formation of stress concentration points, and ultimately improving the elongation at break of the material. This phenomenon is highly consistent with the similar softening and toughness improvement trends exhibited by fluoropolymer membranes in non-polar liquids in other studies.

[0088] This performance is of great significance for online oil-gas separation and dissolved gas monitoring applications. In online DGA systems, membrane modules must not only withstand continuous oil pressure and temperature cycles, but also resist fluid shear and sustained stress. The PT610 oil-gas separation membrane maintains sufficient rigidity to resist system pressure after immersion aging, while possessing sufficient toughness to absorb occasional impacts or vibration loads, thus ensuring long-term stable operation of the membrane module under various complex operating conditions.

[0089] In summary, this embodiment, by quantifying the plasticizing and toughness-enhancing effects of the PT610 oil-gas separation membrane, not only verifies the mechanical reliability of the material in harsh oil-phase environments, but also provides ideas for designing high free volume molecular membranes with better "soft and hard" characteristics: rigidity and toughness can be further balanced by controlling the free volume distribution, the proportion of comonomers, or surface modification, laying a theoretical and experimental foundation for the engineering application and performance optimization of oil-immersed membrane materials.

[0090] 7. Changes in gas permeability

[0091] like Figure 6 As shown in Table 3, after immersion in transformer oil for 45 days, the PT610 oil-gas separation membrane exhibited less than 5% change in CO2 and N2 permeability, and its CO2 / N2 selectivity remained almost unchanged. This indicates that the membrane material possesses excellent dimensional stability and gas separation performance stability in a long-term oil phase environment. Specifically, the slight increase in permeability stems from the limited diffusion of oil molecules through a high free volume molecular network, resulting in a slight plasticizing effect between polymer chains. This slightly enhances the mobility of chain segments and the local free volume fraction, thus mildly promoting the diffusion rate of gas molecules without significantly weakening the dissolution selectivity.

[0092] First, the perfluorodioxane framework of PT610 exhibits extremely low affinity for nonpolar oil phases, making it difficult for large amounts of oil to penetrate the membrane's microporous network. Oil only occupies trace amounts in the micro- and nano-pores at the interface or near the surface, resulting in only slight volumetric plasticization on a macroscopic scale. Second, the high free volume distribution provides multiple efficient gas transport pathways. Even if some micropores are temporarily occupied by oil, the remaining channels can still perform the main permeation function, thus maintaining the stability of the overall permeation flux. Furthermore, local rearrangement and relaxation of polymer segments do not cause irreversible collapse of the pore network, preserving the continuity of the permeation pathways. After 45 days of oil immersion, the PT610 oil-gas separation membrane maintained stable gas separation performance, meeting the requirements of high permeability, high selectivity, and long-term reliability for online oil-gas separation and dissolved gas online monitoring.

[0093] Table 3 Comparison of gas permeation performance of PT610 membrane before and after transformer oil immersion.

[0094]

[0095] The present application first systematically evaluates the immersion behavior of PT610 membrane in transformer oil for up to 45 days, revealing that it only produces weak performance changes under harsh oil phase conditions, filling the research gap of the material in the field of online oil-gas separation; thermogravimetric test shows that the 5% decomposition temperature of the membrane decreases by about 50℃, the Young's modulus decreases by 20%, the elongation at break increases by about 13%, the water contact angle decreases by about 1°, the BET specific surface area decreases by about 20%, and only very weak C-H absorption peaks appear in ATR-FTIR, indicating that the chemical structure and surface morphology are basically intact; the permeability of carbon dioxide and nitrogen changes by ≤5% within all immersion times, fully verifying that the influence of oil penetration and surface adsorption on gas transport performance can be ignored; the results show that PT610 membrane has excellent thermodynamic, mechanical and gas separation stability, providing key basis for the long-term application of online dissolved gas analysis and oil-gas separation sensors, and providing important inspiration for the selection and design of high free volume molecular membranes in similar harsh media.

[0096] Other variations or changes can be made on the basis of the above description for a person of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all embodiments, and the obvious changes or variations derived therefrom are still within the protection scope of the inventive claims.

Claims

1. An oil-gas separation membrane, characterized in that, The separation membrane comprises a PT610 resin polymer, with the following structural formula: The separation membrane is configured to separate dissolved gases in a non-polar oil phase environment while maintaining the integrity of its chemical framework structure in the environment.

2. The oil-gas separation membrane according to claim 1, characterized in that, The non-polar oil phase environment is a transformer oil environment.

3. The oil-gas separation membrane according to claim 1, characterized in that, The dissolved gas includes carbon dioxide and / or nitrogen.

4. The oil-gas separation membrane according to claim 1, characterized in that, The thickness of the oil-gas separation membrane is 50μm-150μm.

5. A method for preparing the oil-gas separation membrane as described in claim 1, characterized in that, Includes the following steps: PT610 resin polymer is dissolved in a perfluorinated solvent to form a casting solution; the casting solution is then cast into a film; the solvent is removed by heat treatment to obtain a self-supporting oil-gas separation membrane.

6. The method according to claim 5, characterized in that, The perfluorinated solvent is perfluorotributylamine.

7. The method according to claim 5, characterized in that, In the heat treatment step, the heat treatment temperature is 130℃-160℃, and the heat treatment time is 8h-16h.

8. The application of the oil-gas separation membrane as described in claim 1 in online oil-gas separation or dissolved gas analysis of power equipment.

9. The application according to claim 8, characterized in that, The electrical equipment is a transformer.

10. The application according to claim 8, characterized in that, The online oil-gas separation or dissolved gas analysis is used for online fault diagnosis or condition monitoring of the power equipment.

Images