Preparation method of carrier membrane, separation material and application

Abstract

The invention discloses a preparation method of a carrier membrane, a separation material and application of the separation material, and the preparation method comprises the following steps: pretreatment of a support body; preparation of intermediate layer molecular sieve crystal seeds: stirring a structure-directing agent SDA, a silicon source and deionized water to form first sol, aging the first sol, carrying out reaction synthesis, and washing and drying the first sol to obtain intermediate layer molecular sieve crystal grains; loading of intermediate layer crystal seeds: adding dried molecular sieve crystal grains into ethanol for modification to prepare 0.5-2% (w / w) ethanol crystal seed turbid liquid, sealing two ends of the dried inorganic porous carrier, immersing the inorganic porous carrier into the turbid liquid for 10-30 seconds, then taking out the inorganic porous carrier, and drying the inorganic porous carrier in a drying oven at 80-120 DEG C for 6-12 hours; preparing a secondary growth solution; and loading a ZSM-5 membrane layer. The membrane prepared by the method is high in separation efficiency, low in energy consumption, simple to operate, long in service life and low in maintenance cost, and has a wide industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve membrane material preparation and application technology, specifically relating to a method for preparing a carrier membrane, separation materials, and applications. Background Technology

[0002] Tetramethylsilane (TMS) is an important organosilicon material with wide applications in pharmaceuticals, aerospace, construction, and machinery. Ultra-high purity TMS (mass fraction > 99.99%) is often used as a precursor for chemical vapor deposition (CVD) or plasma-enhanced chemical vapor deposition (PECVD) to prepare high-quality silicon carbide thin films. In recent years, with the rapid development of the semiconductor industry, the demand for TMS, as one of the precursor products for atomic deposition (ALD) and CVD, has been increasing year by year.

[0003] Currently, the main method for obtaining high-purity TMS is through the purification of low-boiling components (usually referring to mixtures of components with low boiling points) from the organosilicon synthesis process. These components typically contain over 40% TMS, making this a highly economically valuable source. The mainstream purification processes include distillation and adsorption.

[0004] Regarding distillation, since the boiling points of the components in low-boiling-point compounds are very close (TMS has a boiling point of 299.7 K, and isopentane has a boiling point of 300.7 K), purification using only distillation requires a high theoretical plate number for the distillation column, and the prepared TMS cannot achieve very high purity. For example, in existing technologies, multi-tower distillation is used to separate the products of the direct synthesis of methylchlorosilane. In the resulting low-boiling-point fraction, tetramethylsilane and other impurities have boiling points close to each other, making it difficult to obtain high-purity products through simple distillation.

[0005] In the adsorption method, researchers have focused on adsorption to achieve the preparation of ultra-high purity TMS. The team led by Wang Yue at Soochow University, based on the slight size difference between TMS and impurity molecules, selected the zirconium-based metal-organic framework material MOF-801 with a cage structure to separate TMS from isopentane, achieving a TMS purification level of up to 99.98%. However, the high cost of MOF material preparation limits its further industrial application. In addition, some researchers have used ZSM-5 molecular sieves or a combination of ZSM-5 and 13X molecular sieves for the adsorption and purification of low-boiling substances, achieving a TMS content of over 99.99%. However, this method suffers from high adsorbent regeneration costs and complex processes, reducing the efficiency of industrial applications. For example, existing technologies using ZSM-5 molecular sieves for adsorption require periodic regeneration, which consumes a large amount of energy, and the loading, unloading, and replacement of the adsorption column also increases operational complexity.

[0006] Membrane separation, as a highly efficient separation method based on the selective sieving effect of membrane materials, is widely used in various fields such as industry, environmental protection, and energy. Compared with traditional distillation and adsorption processes, membrane separation has advantages such as higher separation efficiency and precision, lower energy consumption and operating costs, and milder conditions. Utilizing the unique molecular pore structure of ZSM-5 molecular sieves to prepare membranes has broad industrial application prospects in TMS purification. However, existing methods for preparing molecular sieve membranes often struggle to form highly oriented pore structures, resulting in less than ideal separation efficiency and flux, failing to meet the high-precision requirements of tetramethylsilane purification.

[0007] Therefore, in order to address the above-mentioned technical problems, it is necessary to provide a method for preparing a carrier membrane, a separation material, and its application. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a carrier membrane, a separation material, and its application.

[0009] To achieve the above objectives, a specific embodiment of the present invention provides the following technical solution:

[0010] The method for preparing the carrier membrane includes the following steps:

[0011] Support pretreatment: Inorganic porous carriers should be cleaned and dried before use;

[0012] Preparation of intermediate layer molecular sieve seed crystals: The structure-directing agent SDA, silicon source and deionized water are stirred to form a first sol and aged before being reacted and synthesized. After washing and drying, intermediate layer molecular sieve crystals are obtained.

[0013] Intermediate layer seed loading: Take dried molecular sieve crystals and disperse them in ethanol to prepare a 0.5-2% (w / w) ethanol seed suspension; seal both ends of the dried inorganic porous carrier (it can be sealed with polytetrafluoroethylene plugs, etc.), immerse it in the above suspension for 10-30 seconds, take it out, and dry it in an oven at 80-120℃ for 6-12 hours.

[0014] Secondary growth solution preparation: Mix structure-directing agent SDA, silicon source, aluminum source, strong alkali (such as sodium hydroxide, potassium hydroxide, etc.) and water, and stir and age at room temperature for 12-24 hours to obtain a stable and clear second sol;

[0015] ZSM-5 membrane loading: The inorganic porous support with intermediate molecular sieve seed crystals is immersed in the second sol and hydrothermally crystallized at 80-160℃ for 12h to form a highly b-axis oriented ZSM-5 molecular sieve membrane precursor on the surface of the intermediate molecular sieve seed crystals; the molecular sieve membrane precursor is rinsed with pure water for 0.5-1h and dried, and then calcined at 200-300℃ for 12-48h to prepare the target support membrane.

[0016] Preferably, the pretreatment of the support can be as follows: the surface of the inorganic porous carrier is polished with fine sandpaper, then ultrasonically immersed and cleaned with anhydrous ethanol for 10-30 minutes, and then dried in an oven at 80-100℃ for later use. Preferably, the inorganic porous carrier is selected from α-Al₂O₃ single-channel tubular ceramic membranes or α-Al₂O₃ multi-channel tubular ceramic membranes. Preferably, the sandpaper is 200-600 grit. Preferably, the sandpaper polishing is performed for 10-20 minutes until the surface of the support reaches a preliminary smooth matte state.

[0017] Preferably, in the preparation of the intermediate layer molecular sieve seed crystals, aging is carried out at 20-40℃ for 6-24 hours. The reaction is carried out at 100-200℃ for 6-24 hours.

[0018] In one or more embodiments of the present invention, the ethanol seed suspension is stirred at 20-50°C for 2 hours after the dispersant is heated.

[0019] In one or more embodiments of the present invention, the inorganic porous carrier is a tubular carrier with a porous structure on its sidewall, wherein the pore size of the porous structure is 0.05-0.5 μm.

[0020] In one or more embodiments of the present invention, the material of the inorganic porous carrier is selected from porous glass, silicon dioxide, alumina, silicon carbide or zirconium oxide.

[0021] In one or more embodiments of the present invention, the structure directing agent SDA is one or more combinations of tritetrapropylammonium hydroxide, tetrapropylammonium hydroxide, and hexapropylammonium bis(hydroxide).

[0022] In one or more embodiments of the present invention, the silicon source is selected from: tetraethyl orthosilicate, tetramethyl orthosilicate, sodium silicate, water glass or silicon powder; and / or, the aluminum source is selected from: alumina, aluminum sulfate, aluminum isopropoxide, sodium aluminate or boehmite.

[0023] In one or more embodiments of the present invention, the ethanol seed suspension further includes 0.01-0.1% of a dispersant, wherein the dispersant is one or more combinations of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

[0024] In one or more embodiments of the present invention, the raw materials of the first sol satisfy the following: the structure-directing agent SDA, the silicon source, and the deionized water are in the following molar ratios: n(SDA) / n(silicon source) = 0.1-0.5, and n(H2O) / n(silicon source) = 100-300.

[0025] In one or more embodiments of the present invention, the raw materials of the second sol satisfy the following: the structure-directing agent SDA, silicon source, aluminum source, strong alkali and water are in the following molar ratios: n(SDA) / n(silicon source) = 0.1-0.5, n(silicon source) / n(aluminum source) = 10-200, n(aluminum source) / n(strong alkali) = 1-100, n(strong alkali) / n(H2O) = 0.001-0.01.

[0026] In one or more embodiments of the present invention, in the preparation of intermediate molecular sieve seed crystals and / or ZSM-5 film loading: the structure directing agent also needs to be removed, which is carried out in an air atmosphere at a heating rate of 1-10°C / min.

[0027] In one or more embodiments of the present invention, the separated material is prepared according to the aforementioned preparation method.

[0028] In one or more embodiments of the present invention, the use of the separating material in the preparation and / or purification of tetramethylsilane is described.

[0029] Compared with existing technologies, the preparation method, separation material, and application of the carrier membrane of the present invention utilize molecular layer-by-layer assembly technology to grow a densely packed and highly b-axis oriented seed layer on the surface of an inorganic porous support, followed by the introduction of a structure-directing agent for secondary growth, thus preparing a continuous and dense ZSM-5 separation layer. This separation membrane possesses a highly uniform b-axis oriented pore structure. This straight-channel structure facilitates the accelerated diffusion and separation of impurities such as isopentane, 2-chloropropane, and trans-2-pentene, enabling efficient, low-energy-consumption, and high-throughput purification of TMS. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 This is a flowchart of a method for preparing a tetramethylsilane purification membrane according to the present invention, wherein S1 is the support pretreatment, S2 is the preparation of intermediate layer molecular sieve seed crystals, S3 is the intermediate layer seed crystal loading, S4 is the preparation of secondary growth solution, and S5 is the loading of ZSM-5 membrane layer.

[0032] Figure 2 This is a SEM micrograph of the intermediate layer molecular sieve seed crystals in one embodiment of the present invention;

[0033] Figure 3 The images show (a) a cross-section and (b) a surface SEM image of the film layer in Embodiment 1 of the present invention.

[0034] Figure 4 This is an X-ray diffraction pattern of the film layer in Embodiment 1 of the present invention. Detailed Implementation

[0035] To enable those skilled in the art to better understand the technical solutions in this disclosure, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments disclosed herein. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments in this disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this disclosure.

[0036] In low-boiling organosilicon compounds, the main impurities that are difficult to remove are isopentane, 2-chloropropane, and trans-2-pentene. Existing technologies often utilize the difference in kinetic diameter between TMS and impurity molecules for adsorption and separation (TMS: 0.64nm × 0.65nm × 0.69nm; isopentane: 0.50nm × 0.61nm × 0.78nm; 2-chloropropane: 0.5~5.4nm; trans-2-pentene: 0.48~0.53nm). ZSM-5 molecular sieve has both sinusoidal channels parallel to the ac plane (0.55nm × 0.51nm) and straight channels growing along the b-axis (0.53nm × 0.56nm). Its pore size falls precisely between the diameter of TMS and impurity molecules, making it an ideal separation membrane material. This invention, based on existing pore structures, utilizes molecular layer-by-layer assembly technology to grow a densely packed, highly b-axis oriented seed layer on the surface of an inorganic porous support. A structure-directing agent is then introduced for secondary growth, resulting in a continuous and dense ZSM-5 separation layer. This separation membrane possesses a highly uniform b-axis oriented pore structure. This straight-channel structure facilitates the accelerated diffusion and separation of impurities such as isopentane, 2-chloropropane, and trans-2-pentene, enabling efficient, low-energy-consumption, and high-throughput purification of TMS.

[0037] To address the problems of insufficient purity in existing tetramethylsilane purification technologies, such as high regeneration cost and complex processes in distillation methods, and unsatisfactory separation efficiency and flux of existing membrane materials, this invention provides a method for preparing a tetramethylsilane purification membrane. The ZSM-5 molecular sieve membrane prepared by this method has a highly b-axis oriented straight-channel pore structure, enabling efficient, low-energy-consumption, and high-throughput purification of TMS. Technical Solution: To achieve the above-mentioned objectives, the specific technical solution adopted by this invention is as follows:

[0038] A method for preparing a tetramethylsilane purification membrane includes the following steps:

[0039] Step (1) Support pretreatment: The surface of the selected inorganic porous support is polished with fine sandpaper, then ultrasonically cleaned with anhydrous ethanol for 10-30 minutes, and then dried in an oven at 80-100℃ for later use. The purpose of this step is to remove impurities and rough parts from the support surface, ensuring the cleanliness and smoothness of the support surface, and providing a good foundation for subsequent seed loading and film growth.

[0040] Step (2) Preparation of intermediate layer molecular sieve seed crystals: Structure-directing agent SDA, silicon source, and deionized water are mixed at a molar ratio of n(SDA) / n(SiO2) = 0.1-0.5 and n(H2O) / n(SiO2) = 100-300. After stirring to form a sol, the mixture is aged at 20-40℃ for 6-24 hours. The aged sol is then transferred to a reactor and synthesized at 100-200℃ for 6-24 hours. After washing and drying, intermediate layer molecular sieve crystals are obtained. The structure-directing agent helps form molecular sieve seed crystals with specific structures, while the aging and synthesis steps allow the seed crystals to grow and solidify fully.

[0041] Step (3) Intermediate layer seed loading: Take a small amount of the dried molecular sieve crystals prepared in step (2) and add them to ethanol for modification to prepare a 0.5-2% (w / w) ethanol seed suspension. At the same time, add 0.01-0.1% dispersant and stir at 20-50℃ for 2 hours. Seal both ends of the dried inorganic porous support with polytetrafluoroethylene plugs to prevent the seed suspension from entering the inner surface of the tubular membrane. Then immerse it in the above suspension for 10-30 seconds and take it out. Dry it in an oven at 80-120℃ for 6-12 hours. The dispersant can make the seed crystals uniformly dispersed in the suspension. The loading process makes the seed crystals firmly attached to the surface of the support, providing uniform growth sites for subsequent membrane growth.

[0042] Step (4) Preparation of secondary growth solution: The structure-directing agent SDA, silicon source, aluminum source, sodium hydroxide, and water are prepared according to the following ratios: n(SDA) / n(TEOS) = 0.1-0.5, n(TEOS) / n(α-Al2O3) = 10-200, n(α-Al2O3) / n(NaOH) = 1-100, and n(NaOH) / n(H2O) = 0.001-0.01. The resulting sol is then stirred and aged at room temperature for 12-24 hours to obtain a stable and clear sol. The ratio of the secondary growth solution directly affects the growth quality and structure of the subsequent membrane layer. The aging step makes the sol composition more uniform and stable.

[0043] Step (5) ZSM-5 membrane loading: The inorganic porous support with intermediate molecular sieve seed crystals loaded in step (3) is immersed in the sol prepared in step (4) and hydrothermally crystallized at 80-160℃ for 12h to form a highly b-axis oriented ZSM-5 molecular sieve membrane precursor on the surface of the intermediate molecular sieve seed crystals. After rinsing the molecular sieve membrane precursor with pure water for 0.5-1h and drying it, it is calcined at 200-300℃ for 12-48h to prepare the ZSM-5 molecular sieve support membrane. Hydrothermal crystallization promotes the growth of molecular sieves on the seed crystal surface to form a continuous membrane layer, while calcination is to remove impurities such as structure-directing agents in the membrane and form a stable pore structure.

[0044] Preferably, the inorganic porous support in steps (1), (3), and (5) is a tubular support with a pore size of 0.05-0.5 μm, and the material is porous glass, silica, alumina, silicon carbide, or zirconium oxide. These materials have good chemical stability and mechanical strength, making them suitable as membrane supports. Preferably, the structure directing agent in step (2) is one or a combination of timer-TPAOH, tetrapropylammonium hydroxide (TPAOH), and dimer-TPAOH. These structure directing agents can effectively guide the ZSM-5 molecular sieve to form a specific pore structure. Preferably, the silicon source in steps (2) and (4) is tetraethyl orthosilicate, tetramethyl orthosilicate, sodium silicate, water glass, or silicon powder. The aluminum source is alumina (α-Al2O3), aluminum sulfate (Al2(SO4)3), aluminum isopropoxide (Al(OC3H7)3), sodium aluminate (NaAlO2), or boehmite (γ-AlOOH). These silicon and aluminum sources are readily available and provide the necessary elements for the formation of molecular sieves. Preferably, the dispersant in step (3) is one or a combination of sodium dodecylbenzenesulfonate (SDBS), hexadecyltrimethylammonium bromide (CTAB), and dodecyltrimethylammonium chloride (DTAC). These dispersants can effectively improve the dispersibility of seed crystals in suspension. Preferably, the removal of the structure-directing agent in steps (2) and (5) is carried out in an air atmosphere at a heating rate of 1-10 °C / min. The removal is carried out in step (2) after the reaction is completed and in step (5) after the precursor is obtained. Such removal conditions can avoid the rapid decomposition of the structure-directing agent, which would lead to the destruction of the membrane structure. Beneficial Effects: The membrane material for tetramethylsilane purification prepared in this invention consists of three continuous structural layers: an α-Al₂O₃ tubular ceramic membrane provides strength to the substrate layer; an all-silicon intermediate layer serves as a transition layer to block macropores on the support surface, forming a continuous and uniform seed layer, while also providing growth sites for the subsequent ZSM-5 molecular sieve; the ZSM-5 molecular sieve membrane layer, as the separation functional layer, has a highly b-axis oriented straight-channel pore structure for separating TMS from impurities in low-boiling substances. The pore size of this separation membrane is mainly concentrated at approximately 0.53 nm × 0.56 nm, between the diameters of TMS and impurity molecules, exhibiting high selectivity for TMS. Furthermore, the highly b-axis oriented straight-channel pores facilitate the rapid passage of impurity molecules, resulting in high throughput and low energy consumption. Compared to existing molecular sieve adsorption purification processes, this invention offers advantages such as simple operation, long lifespan, and low maintenance costs, demonstrating promising prospects for industrial development. Compared with the prior art, the present invention has the following significant advantages: high separation efficiency: the prepared ZSM-5 molecular sieve membrane has a highly b-axis oriented straight channel pore structure with precise pore size, which can efficiently separate TMS from impurities such as isopentane, 2-chloropropane, and trans-2-pentene. The purity of TMS can reach more than 99.99%, and the impurity rejection rate is high.Low energy consumption: Membrane separation processes do not require frequent regeneration operations like adsorption methods, nor do they require high theoretical plate numbers like distillation methods, significantly reducing energy consumption. The energy consumption per ton of TMS is far lower than existing adsorption and distillation methods. Simple operation: The membrane separation process is continuous, eliminating the need for complex loading, unloading, and adsorbent replacement operations. The process is simple and easy to industrialize. Long lifespan and low maintenance costs: Molecular sieve membranes have excellent stability and durability, a long service life, low maintenance costs, and can operate stably for extended periods.

[0045] Example 1

[0046] A method for preparing a tetramethylsilane purification membrane includes the following steps:

[0047] Support pretreatment: The surface of the α-Al2O3 tubular ceramic membrane was polished with fine sandpaper, then ultrasonically soaked and cleaned with anhydrous ethanol for 30 minutes, and then dried in an oven at 80℃ for later use.

[0048] Preparation of intermediate-layer molecular sieve seed crystals: Structure-directing agent SDA (tetrapropylammonium hydroxide), silicon source (tetraethyl orthosilicate), and deionized water were stirred to form a sol at a molar ratio of n(SDA) / n(SiO2) = 0.1 and n(H2O) / n(SiO2) = 100. The sol was aged at 25°C for 12 hours. The aged sol was then transferred to a reactor and synthesized at 120°C for 12 hours. After washing and drying, intermediate-layer molecular sieve crystals were obtained. Figure 2 As shown in (a), the average grain diameter is about 0.7 μm.

[0049] Intermediate layer seed loading: A small amount of the dried molecular sieve crystals prepared in step (2) were added to ethanol for modification, and a 0.5% (w / w) ethanol seed suspension was prepared. At the same time, 0.05% sodium dodecylbenzenesulfonate (SDBS) was added and stirred at 25°C for 2 hours for later use. The dried α-Al2O3 tubular ceramic membrane was sealed at both ends with polytetrafluoroethylene plugs, then immersed in the above suspension for 30 seconds and then removed and dried in an oven at 100°C for 12 hours.

[0050] Secondary growth solution preparation: The structure-directing agent SDA (tetrapropylammonium hydroxide), silicon source (tetraethyl orthosilicate), aluminum source (α-Al2O3), sodium hydroxide, and water were prepared according to the following ratios: n(SDA) / n(TEOS) = 0.5, n(TEOS) / n(α-Al2O3) = 20, n(α-Al2O3) / n(NaOH) = 50, and n(NaOH) / n(H2O) = 0.003. The resulting sol was stirred and aged at room temperature for 12 hours to obtain a stable and clear sol.

[0051] ZSM-5 membrane loading: The α-Al2O3 tubular ceramic membrane with intermediate molecular sieve seed crystals loaded in step (3) was immersed in the sol prepared in step (4), and hydrothermally crystallized at 150℃ for 12h to form a highly b-axis oriented ZSM-5 molecular sieve membrane on the surface of the intermediate molecular sieve seed crystals. After rinsing the molecular sieve membrane with pure water for 0.5h and drying it, it was calcined at 200℃ for 24h to obtain the ZSM-5 molecular sieve membrane, as shown below. Figure 3 As shown.

[0052] The prepared membrane (M1) was used to separate low-boiling substances (TMS 60%, isopentane 9.94%, trans-2-pentene 0.09%, 2-chloropropane 2.41%, and others 27.56%) at 40 °C. The test results are shown in Table 1.

[0053] Example 2

[0054] The operating steps are the same as in Example 1, except for step (2): n(SDA) / n(SiO2)=0.2, n(H2O) / n(SiO2)=200; after stirring to form a sol, it is aged at 25℃ for 12h; then the aged sol is transferred to a reactor and synthesized at 120℃ for 12h, and after washing and drying, intermediate layer molecular sieve crystals are obtained, such as Figure 2 As shown in (b), the average grain diameter is about 1 μm.

[0055] The prepared membrane (M2) was used to separate low-boiling substances at 40℃, and the test results are shown in Table 1.

[0056] Example 3

[0057] The operating steps are the same as in Example 1, except for step (2): n(SDA) / n(SiO2)=0.5, n(H2O) / n(SiO2)=300; after stirring to form a sol, it is aged at 25°C for 12 hours; then the aged sol is transferred to a reactor and synthesized at 120°C for 12 hours, and after washing and drying, intermediate layer molecular sieve crystals are obtained, such as Figure 2 As shown in (c), the average grain diameter is about 0.3 μm.

[0058] The prepared membrane (M3) was used to separate low-boiling substances at 40℃, and the test results are shown in Table 1.

[0059] Example 4

[0060] The operation steps are the same as in Example 1, except that step (4) is different: the secondary growth solution of ZSM-5 molecular sieve membrane is prepared in the ratio of n(SDA) / n(TEOS)=0.1, n(TEOS) / n(α-Al2O3)=50, n(α-Al2O3) / n(NaOH)=50, and n(NaOH) / n(H2O)=0.002. The resulting sol is stirred and aged at room temperature for 12 hours to obtain a stable and clear sol.

[0061] The prepared membrane (M4) was used to separate low-boiling substances at 40℃, and the test results are shown in Table 1.

[0062] Example 5

[0063] The operation steps are the same as in Example 1, except that step (4) is different: the secondary growth solution of ZSM-5 molecular sieve membrane is prepared in the ratio of n(SDA) / n(TEOS)=0.2, n(TEOS) / n(α-Al2O3)=100, n(α-Al2O3) / n(NaOH)=100, and n(NaOH) / n(H2O)=0.003. The resulting sol is stirred and aged at room temperature for 12 hours to obtain a stable and clear sol.

[0064] The prepared membrane (M5) was used to separate low-boiling substances at 40℃, and the test results are shown in Table 1.

[0065] Example 6

[0066] The operation steps are the same as in Example 1, except for step (4): the secondary growth solution of ZSM-5 molecular sieve membrane is prepared in the ratio of n(SDA) / n(TEOS)=0.2, n(TEOS) / n(α-Al2O3)=200, n(α-Al2O3) / n(NaOH)=50, and n(NaOH) / n(H2O)=0.001. The resulting sol is stirred and aged at room temperature for 12 hours to obtain a stable and clear sol.

[0067] The prepared membrane (M6) was used to separate low-boiling substances at 40℃, and the test results are shown in Table 1.

[0068] Comparative Example 1

[0069] Without preparing a separation membrane, the adsorption column was directly filled with ZSM-5 molecular sieve and the low-boiling substances were adsorbed at 40℃. The test results are shown in Table 1.

[0070] Comparative Example 2

[0071] Without preparing a separation membrane, the adsorption column was directly filled with 13X molecular sieve and the low-boiling substances were adsorbed at 40℃. The test results are shown in Table 1.

[0072] Comparative Example 3

[0073] Compared with Example 1, steps (2) and (3) are omitted, while the other steps are the same. The membrane prepared is used to separate low-boiling substances at 40°C. Without the preparation and loading of intermediate seed crystals, an effective separation membrane layer cannot be formed, and there is almost no separation effect.

[0074] Comparative Example 4

[0075] Compared with Example 1, the addition of the directing agent was omitted in steps (2) and (4), while the other steps were the same. The prepared membrane was used to separate low-boiling substances at 40°C, and the test results are shown in Table 1.

[0076] Table 1 Comparison of purification results of low-boiling-point substances in Examples 1-6 and Comparative Examples 1-3

[0077]

[0078]

[0079] Note:

[0080] Membrane separation operating parameters: Membrane module dimensions: inner diameter 8mm × outer diameter 12mm × length 110mm, operating pressure difference 0.5Mpa, operating temperature 40℃;

[0081] Adsorption operation parameters: Adsorption column size: diameter 5cm × height 50cm, adsorption time 30min, adsorption temperature 40℃, regeneration: 300℃ × 2h.

[0082] Impurity abbreviations: IPT (isopentane), CP (2-chloropropane), TP (trans-2-pentene).

[0083] Depend on Figure 4As shown in Example 1, within the diffraction range of 5°–50°, excluding the characteristic peaks of the Al2O3 support, high-intensity b-axis oriented (0k0) crystal plane characteristic diffraction peaks appeared at 8.78° (020), 24.36° (040), and 45.12° (060). The calculated crystal preferential orientation value Kcpo(0k0) = 0.86. This indicates that the prepared ZSM-5 membrane is dense and b-axis oriented. The results from Examples 1-6 show that the prepared molecular sieve membranes with highly b-axis oriented characteristic pores can achieve efficient separation of TMS and impurities. The experimental variables in the membrane preparation of Examples 1-6 focused on two key points—the SDA / SiO2 molar ratio (0.1-0.5) during seed crystal synthesis and the ratio of the secondary growth solution in hydrothermal synthesis. The best results were achieved when the SDA / SiO2 ratio in Example 1 was 0.1, which conforms to the molecular sieve synthesis principle: an excessively high template agent ratio leads to an increase in lattice defects, resulting in a decrease in TMS purity. Furthermore, Comparative Example 3 omits the intermediate layer preparation step, and the subsequent ZSM-5 membrane layer is directly grown on the large-pore support, making it difficult to form a dense membrane layer with many defects, resulting in unsatisfactory purification effect for TMS. The sampled membrane layer in Comparative Example 4 lacks the structure-directing agent added in steps (2) and (4), and the prepared membrane layer does not possess high-strength b-axis orientation, resulting in relatively poor separation effect and high energy consumption. Comparing the results of Examples 1-6 with Comparative Examples 1-2, the purity of TMS prepared by membrane separation is comparable to that of adsorption, but because adsorption requires adsorbent regeneration and nitrogen purging, its energy consumption is approximately 4-5 times that of membrane separation. This indicates that the molecular sieve membrane has advantages over traditional adsorption separation methods in TMS purification, including high separation efficiency, small footprint, and low energy consumption, and has broad application prospects.

[0084] It will be apparent to those skilled in the art that this disclosure is not limited to the details of the exemplary embodiments described above, and that this disclosure can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of this disclosure is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within this disclosure. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0085] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a carrier membrane, comprising the following steps: Support pretreatment: Inorganic porous carriers should be cleaned and dried before use; Preparation of intermediate layer molecular sieve seed crystals: The structure-directing agent SDA, silicon source and deionized water are stirred to form a first sol and aged before being reacted and synthesized. After washing and drying, intermediate layer molecular sieve crystals are obtained. Intermediate layer seed loading: Take dried molecular sieve crystals and add them to ethanol for modification, prepare a 0.5-2% (w / w) ethanol seed suspension, seal both ends of the dried inorganic porous carrier, immerse it in the above suspension for 10-30s, take it out, and dry it in an oven at 80-120℃ for 6-12h. Secondary growth solution preparation: Mix structure-directing agent SDA, silicon source, aluminum source, strong alkali and water, and stir and age at room temperature for 12-24 hours to obtain a stable and clear second sol; ZSM-5 membrane loading: The inorganic porous support with intermediate molecular sieve seed crystals is immersed in the second sol and hydrothermally crystallized at 80-160℃ for 12h to form a highly b-axis oriented ZSM-5 molecular sieve membrane precursor on the surface of the intermediate molecular sieve seed crystals; the molecular sieve membrane precursor is rinsed with pure water for 0.5-1h and dried, and then calcined at 200-300℃ for 12-48h to prepare the target support membrane.

2. The preparation method according to claim 1, characterized in that, The inorganic porous carrier is a tubular carrier with a porous structure on its sidewalls, and the pore size of the porous structure is 0.05-0.5 μm.

3. The preparation method according to claim 2, characterized in that, The inorganic porous carrier is made of porous glass, silicon dioxide, alumina, silicon carbide, or zirconium oxide.

4. The preparation method according to claim 1, characterized in that, The structure-directing agent SDA is one or more combinations of tritetrapropylammonium hydroxide, tetrapropylammonium hydroxide, and hexapropylammonium dihydrogen hydroxide.

5. The preparation method according to claim 1, characterized in that, The silicon source is selected from: tetraethyl orthosilicate, tetramethyl orthosilicate, sodium silicate, water glass, or silicon powder; and / or, the aluminum source is selected from: alumina, aluminum sulfate, aluminum isopropoxide, sodium aluminate, or boehmite.

6. The preparation method according to claim 1, characterized in that, The ethanol seed suspension also includes 0.01-0.1% dispersant, which is one or more combinations of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, and dodecyltrimethylammonium chloride.

7. The preparation method according to claim 1, characterized in that, The raw materials of the first sol satisfy the following: the structure-directing agent SDA, silicon source, and deionized water are in the following molar ratios: n(SDA) / n(silicon source) = 0.1-0.5, and n(H2O) / n(silicon source) = 100-300.

8. The preparation method according to claim 1, characterized in that, The raw materials of the second sol satisfy the following: the structure-directing agent SDA, silicon source, aluminum source, strong alkali and water are in the following molar ratios: n(SDA) / n(silicon source) = 0.1-0.5, n(silicon source) / n(aluminum source) = 10-200, n(aluminum source) / n(strong alkali) = 1-100, n(strong alkali) / n(H2O) = 0.001-0.

01.

9. The separated material is prepared by the preparation method according to any one of claims 1-8.

10. The application of the separating material according to claim 9 in the preparation and / or purification of tetramethylsilane.

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