Organic-inorganic silica composite films, their preparation methods and applications

Abstract

This invention relates to the field of gas separation membrane preparation, and discloses an organic-inorganic silica composite membrane, its preparation method, and its application. A method for preparing an organic-inorganic silica composite membrane includes the following steps: (1) preparing an organosilicon sol using 1,6-bis(triethoxysilyl)hexane as a raw material via a sol-gel method, and then introducing palladium into the organosilicon sol to obtain a palladium / organosilicon sol; (2) coating the silicon-titanium sol onto a modified support, and then performing a first calcination to obtain a transition layer; (3) coating the palladium / organosilicon sol obtained in step (1) onto the transition layer, and then performing a second calcination to obtain a separation layer. The separation membrane provided by this invention exhibits good hydrogen permeation performance in hydrogen separation.

Description

Technical Field

[0001] This invention relates to the field of gas separation membrane preparation, specifically to an organic-inorganic silica composite membrane, its preparation method, and its application. Background Technology

[0002] SiO2 membranes exhibit excellent H2 permeation performance and selectivity due to their unique Si-O-Si network structure. However, SiO2 membranes are unstable under high-temperature water vapor, limiting their gas separation performance in water vapor environments. Introducing hydrophobic organic groups into the network structure of SiO2 membranes can improve their hydrothermal stability to some extent. Kanezashi et al. [J.Am.Chem.Soc.,2009,131(2),414-415] reported that a hybrid silicon membrane prepared with 1,2-bis(triethoxysilyl)ethane (BTESE) exhibited excellent hydrothermal stability for H2 separation. However, the BTESE membrane has low hydrogen permeability, especially at 10... -7 mol·m -2 ·s -1 ·Pa -1 Modifying the BTESE membrane with metals improved hydrogen permeability, but the improvement was limited, remaining within the range of 3-7 × 10⁻⁶. -7 mol·m -2 ·s -1 ·Pa -1 Furthermore, metals disrupt short-chain networks, leading to a decrease in selectivity, for example [Microporous and Mesoporous Materials 253(2017)55-63].

[0003] Therefore, there is an urgent need to develop a new separation membrane to improve the permeation and separation performance of hydrogen. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that the hydrogen permeation performance of existing organic-inorganic silica composite membranes in gas separation needs further improvement, and to provide an organic-inorganic silica composite membrane, its preparation method, and its application. The separation membrane provided by this invention exhibits excellent hydrogen permeation performance in hydrogen separation.

[0005] To achieve the above objectives, the first aspect of the present invention provides a method for preparing an organic-inorganic silica composite film, the method comprising the following steps:

[0006] (1) Organosilicon sol was prepared by sol-gel method using 1,6-bis(triethoxysilyl)hexane as raw material, and then palladium element was introduced into the organosilicon sol to obtain palladium / organosilicon sol.

[0007] (2) The silicon-titanium sol is coated onto the modified support, and then the first calcination is performed to obtain the transition layer;

[0008] (3) The palladium / organosilicon sol obtained in step (1) is coated on the transition layer, and then a second calcination is performed to obtain the separation layer.

[0009] Preferably, the preparation process of the modified support includes: modifying the porous support with a first alumina and a second alumina to obtain the modified support, wherein the average particle size of the first alumina is 90-200% of the average pore size of the porous support, and the average particle size of the second alumina is 5-25% of the average particle size of the first alumina.

[0010] The second aspect of the present invention provides an organic-inorganic silica composite film prepared by the preparation method described in the first aspect.

[0011] The third aspect of this invention provides an application of the organic-inorganic silica composite membrane described in the second aspect in gas separation.

[0012] The beneficial effects of the present invention through the above technical solution include:

[0013] The composite membrane prepared by the method described in this invention is applied to hydrogen separation and exhibits good hydrogen permeation performance and good hydrogen selectivity. Attached Figure Description

[0014] Figure 1 The images show the XRD patterns of the Pd / BTESH dry gel from Example 1 and the BTESH dry gel from Comparative Example 1. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The first aspect of this invention provides a method for preparing an organic-inorganic silica composite film, the method comprising the following steps:

[0017] (1) Organosilicon sol was prepared by sol-gel method using 1,6-bis(triethoxysilyl)hexane as raw material, and then palladium element was introduced into the organosilicon sol to obtain palladium / organosilicon sol.

[0018] (2) The silicon-titanium sol is coated onto the modified support, and then the first calcination is performed to obtain the transition layer;

[0019] (3) The palladium / organosilicon sol obtained in step (1) is coated on the transition layer, and then a second calcination is performed to obtain the separation layer.

[0020] In the preparation method provided by this invention, the introduction of palladium into the organosilicon sol prepared from 1,6-bis(triethoxysilyl)hexane (BTESH) improves the hydrogen separation effect of the composite membrane. Then, a specific type of silica-titanium sol is coated onto the modified support with modified pore structure to form a transition layer, further enhancing the separation performance of the composite membrane. When the composite membrane prepared by the method of this invention is applied to hydrogen separation, it exhibits good hydrogen permeation performance and good hydrogen selectivity.

[0021] Preferably, the average pore size of the modified support is 100-300nm, for example, it can be 100nm, 120nm, 140nm, 160nm, 180nm, 200nm, 220nm, 240nm, 260nm, 280nm, 300nm, and any value within the range formed by any two of these point values.

[0022] Preferably, the average pore size of the transition layer is 1-5 nm, for example, it can be 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, and any value within the range formed by any two of these point values.

[0023] Preferably, the average pore size of the separation layer is less than 1 nm, and more preferably 0.4-0.7 nm. For example, it can be 0.25 nm, 0.3 nm, 0.35 nm, 0.4 nm, 0.45 nm, 0.5 nm, 0.55 nm, 0.6 nm, 0.65 nm, 0.7 nm, 0.75 nm, 0.8 nm, and any value within the range formed by any two of these values.

[0024] Controlling the average pore size of the modified support, transition layer, and separation layer within the aforementioned range is beneficial for preparing defect-free organic-inorganic silica composite membranes, thereby improving hydrogen permeability and selectivity.

[0025] The present invention does not impose any particular limitation on the preparation process of the organosilicon sol in step (1), and can refer to conventional methods in the art. Preferably, the sol-gel method in step (1) includes: carrying out a first reaction of 1,6-bis(triethoxysilyl)hexane solution, catalyst and water to obtain organosilicon sol.

[0026] According to the present invention, preferably, the molar ratio of 1,6-bis(triethoxysilyl)hexane:water:catalyst is 1:60-120:0.1-0.5.

[0027] According to the present invention, preferably, the mass fraction of the 1,6-bis(triethoxysilyl)hexane solution is 5-7 wt%.

[0028] The present invention offers a wide range of solvent options for the 1,6-bis(triethoxysilyl)hexane solution, which can be conventional choices in the art. Preferably, the solvent in the 1,6-bis(triethoxysilyl)hexane solution is ethanol.

[0029] According to the present invention, preferably, the conditions for the first reaction include: a temperature of 40-60°C and a time of 1-10 hours.

[0030] Preferably, the first reaction is carried out under stirring conditions.

[0031] The present invention does not impose a particular limitation on the stirring rate, but aims to achieve uniform mixing and accelerate the reaction process, and can make an appropriate selection according to the specific circumstances.

[0032] The catalyst described in this invention promotes the hydrolysis and polymerization of 1,6-bis(triethoxysilyl)hexane. This invention does not particularly limit the type of catalyst; any conventional choice in the art can be used. Preferably, the catalyst is an inorganic acid, preferably selected from at least one of hydrochloric acid, nitric acid, and sulfuric acid.

[0033] According to the present invention, preferably, the method for introducing palladium into the organosilicon sol in step (1) includes: firstly, subjecting an acid solution containing palladium salt, an alcohol, and the organosilicon sol obtained in step (1) to a second reaction to obtain a palladium / organosilicon sol. In the palladium / organosilicon sol, the Pd particles formed can both modify the large pore size to achieve the sieving effect of N2 and C3H8, and promote H2 permeation, which is beneficial for improving the hydrothermal stability of the prepared composite membrane and enhancing hydrogen separation performance.

[0034] According to the present invention, preferably, the conditions for the second reaction include: a temperature of 40-80°C and a time of 1-10 hours.

[0035] The present invention does not impose any particular limitation on how to achieve the second reaction temperature of the present invention, and conventional methods in the art can be used. For example, a water bath method can be used.

[0036] Preferably, the second reaction is carried out under stirring conditions.

[0037] The present invention does not impose a particular limitation on the stirring rate, but aims to accelerate the reaction process, and can be appropriately selected according to specific circumstances.

[0038] According to a preferred embodiment of the present invention, preferably, the method of introducing palladium element into organosilicon sol in step (1) includes: first reacting an acid solution containing palladium salt and an alcohol for 0.5-5 hours, and then adding the organosilicon sol obtained in step (1) and reacting for 0.5-5 hours to obtain palladium / organosilicon sol.

[0039] According to the present invention, preferably, the molar ratio of palladium salt (based on elemental composition) to organosilicon sol (based on elemental composition) is 0.1-1:1, more preferably 0.1-0.8:1. This preferred embodiment facilitates the dispersion of palladium and ensures the integrity of the organosilicon network.

[0040] According to the present invention, preferably, the molar ratio of palladium salt to acid, calculated by element, is 1:0.5-4.

[0041] The present invention allows for a wide range of choices of the acid, and preferably, the acid is selected from at least one of nitric acid, hydrochloric acid and sulfuric acid.

[0042] According to the present invention, preferably, the amount of alcohol used is such that, based on the total mass of the palladium / organosilicon sol obtained in step (1), the mass content of organosilicon is 0.5-5%.

[0043] The alcohol used in this invention can reduce palladium ions in palladium salts to elemental palladium. Preferably, the alcohol is an alcohol containing at least two hydroxyl groups, and is preferably selected from at least one of ethylene glycol, glycerol, and butanediol.

[0044] According to the present invention, preferably, the preparation process of the modified support includes: modifying the porous support sequentially with a first alumina and a second alumina to obtain the modified support, wherein the average particle size of the first alumina is 90-200% of the average pore size of the porous support, and the average particle size of the second alumina is 5-25% of the average particle size of the first alumina.

[0045] Existing commercially available porous supports suffer from defects such as uneven pore structure and some large pores. However, during their research, the inventors discovered that a modified support obtained using the specific method described above effectively overcomes these defects, forming a continuous separation membrane layer and improving hydrogen separation performance.

[0046] In this invention, the average particle size of the first alumina is 90-200% of the average pore size of the porous support, preferably 90-110%.

[0047] In this invention, the average particle size of the second alumina is 5-25% of the average particle size of the first alumina, preferably 5-20%.

[0048] Controlling the average particle size of the first alumina and the second alumina within the above range is beneficial to obtaining a modified support with uniform pore distribution and an average pore size of 100-300 nm, which provides better support for the sol coating of the transition layer and is beneficial to improving the hydrogen permeability of the separation membrane.

[0049] According to the present invention, preferably, the modified support preparation process includes: coating a first alumina onto a porous support, and then performing a third calcination to obtain a solid product; coating a second alumina onto the solid product, and then performing a fourth calcination to obtain a modified support.

[0050] The present invention does not impose any particular limitation on the coating method used in the preparation of the modified support, and conventional methods in the art can be used.

[0051] To optimize the coating effect, the present invention preferably employs a method of coating in small amounts multiple times.

[0052] There is no particular limitation on the number of coatings during the solid product formation process of this invention, nor is there a particular limitation on the amount of first alumina used during the coating process, with the standard being that the surface of the obtained solid product has no exposed large pores (which can be seen through a scanning electron microscope).

[0053] There is no particular limitation on the number of coatings during the formation of the modified support in this invention, nor is there a particular limitation on the amount of second alumina used during the coating process, as long as the average pore size of the obtained modified support is in the range of 100-300 nm.

[0054] Specifically, the modified support preparation process includes: coating a first alumina onto a porous support, then performing a third calcination, repeating the coating-third calcination process to obtain a solid product; coating a second alumina onto the solid product, then performing a fourth calcination, repeating the coating-fourth calcination process to obtain the modified support.

[0055] Preferably, after the first alumina is coated onto the porous support, it is dried at 15-40°C before the third calcination. This preferred embodiment prevents solvent evaporation from the pores of the modified support from causing bubble defects in the transition layer during its formation.

[0056] When there are excess particles on the surface of the dried porous support, wipe them off before the third calcination.

[0057] When there are no excess particles on the surface of the dried porous support, there is no need to wipe them off before proceeding to the third calcination.

[0058] Similarly, after the second alumina is coated onto the porous support, it also needs to be dried at 15-40°C before the fourth calcination. The specific process is as described above, and will not be repeated here.

[0059] According to the present invention, preferably, the conditions for the third and fourth calcinations each independently include: a temperature of 500-600°C and a time of 20-40 minutes. This preferred embodiment is beneficial for the formation of nanopores in the transition layer.

[0060] According to the present invention, preferably, the average pore diameter of the porous support is 1-2 μm.

[0061] The present invention allows for a wide range of choices for the porous support. In a preferred embodiment, the porous support can be selected from at least one of porous ceramics, porous glass, porous metals (such as porous stainless steel), porous quartz, and polymers, and more preferably porous ceramics.

[0062] The porous ceramics described in this invention can be of conventional types in the art, for example, selected from one or more of Al2O3, SiO2, BaSO4, BaO, TiO2, CuO, MgO, Mg(OH)2, LiAlO2, ZrO2, CNT, BN, SiC, Si3N4, WC, BC, AlN, Fe2O3, BaTiO3, MoS2, α-V2O5, PbTiO3, TiB2, CaSiO3, molecular sieves, clay, boehmite, and kaolin. To improve the separation performance of the separation membrane and considering cost, the porous support is preferably alumina, more preferably α-Al2O3.

[0063] The present invention does not have any particular limitation on the source of the porous support. It can be obtained commercially or made by conventional methods, as long as it meets the above-mentioned pore size requirements.

[0064] The present invention allows for a wide range of selections for the first and second alumina, such as α-Al₂O₃, γ-Al₂O₃, and θ-Al₂O₃. Preferably, the first and second alumina are α-Al₂O₃.

[0065] When the surface of a porous support is smooth, the porous support can be modified without polishing.

[0066] When the surface of the porous support is rough, preferably, the method further includes: polishing the porous support before modification to obtain a porous support with a smooth surface.

[0067] More preferably, the porous support is polished, cleaned, and dried to obtain a porous support with a smooth surface. The surface is cleaned until no sand or impurities remain.

[0068] According to a specific embodiment of the present invention, the porous support is polished and then boiled in water for 10-30 minutes, followed by ultrasonic cleaning, water rinsing, and drying.

[0069] The present invention does not particularly limit the specific methods of grinding, ultrasonic cleaning, water cleaning and drying, and can be carried out according to conventional methods.

[0070] The present invention does not have any particular limitation on the coating method used in the preparation of the transition layer in step (2), and conventional methods in the art can be used.

[0071] To optimize the coating effect, the present invention preferably employs a method of coating in small amounts multiple times.

[0072] There is no particular limitation on the number of coatings during the formation of the transition layer in this invention, nor is there a particular limitation on the amount of silicon titanium sol used during the coating process, with the average pore size of the obtained transition layer being in the range of 1-5 nm.

[0073] According to a specific embodiment of the present invention, the preparation process of the transition layer in step (2) includes: coating a silicon-titanium sol onto a modified support, and then performing a first calcination, repeating the coating-first calcination process to obtain the transition layer.

[0074] According to the present invention, preferably, the silicon-titanium molar ratio of the silicon-titanium sol is 1:1-10, for example, it can be 1:0.5, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, and any value within the range formed by any two of these point values.

[0075] According to the present invention, preferably, the concentration of the silicon-titanium sol is 0.5-10 wt%.

[0076] The present invention does not have any particular limitation on the source of the silicon-titanium sol. It can be obtained commercially or made by conventional methods, as long as it meets the above-mentioned characteristic parameters.

[0077] According to the present invention, preferably, the conditions for the first calcination in step (2) include: a temperature of 500-600°C and a time of 20-40 min.

[0078] The present invention does not have any particular limitation on the coating method used in the preparation of the separation layer in step (3), and conventional methods in the art can be used.

[0079] To optimize the coating effect, the present invention preferably employs a method of coating in small amounts multiple times.

[0080] There is no particular limitation on the number of coatings during the formation of the separation layer in this invention, nor is there a particular limitation on the amount of palladium / organosilicon sol used during the coating process, as long as the average pore size of the obtained separation layer is less than 1 nm.

[0081] According to a specific embodiment of the present invention, the preparation process of the separation layer in step (3) includes: coating the palladium / organosilicon sol obtained in step (1) onto the transition layer, and then performing a second calcination, repeating the coating-second calcination process to obtain the separation layer.

[0082] According to the present invention, preferably, the conditions for the second calcination in step (3) include: a temperature of 200-300°C and a time of 0.5-1h.

[0083] In this invention, the terms "first," "second," and "third" do not limit the substances and operations, but are only used to distinguish the substances introduced in different steps and the operations performed in different stages.

[0084] The second aspect of the present invention provides an organic-inorganic silica composite film prepared by the preparation method described in the first aspect.

[0085] The third aspect of the present invention provides an application of the organic-inorganic silica composite membrane described in the second aspect in gas separation, preferably in hydrogen separation.

[0086] When the composite membrane described in this invention is applied to hydrogen separation, it exhibits good hydrogen permeation performance and good hydrogen selectivity.

[0087] The present invention will be described in detail below through embodiments.

[0088] In the following embodiments,

[0089] Gas permeability = (gas flux) / (membrane area × pressure difference);

[0090] Wherein, gas flux, mol / s; membrane area, m² 2 Pressure difference, Pa;

[0091] H2 / N2 selectivity = H2 permeability / N2 permeability;

[0092] H2 / C3H8 selectivity = H2 permeability / C3H8 permeability.

[0093] Example 1

[0094] (1) The sheet ceramic support (α-Al2O3 with an average pore size of 1μm) was boiled in deionized water for 15 minutes, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 minutes. Finally, it was dried in a forced-air oven at 120℃ for 6 hours to obtain the treated support.

[0095] (2) Preparation of organosilicon sol: Dissolve BTESH in ethanol, then add water and hydrochloric acid, wherein the molar ratio of BTESH:H2O:HCl is 1:120:0.2, stir at 40℃ for 1.5h to obtain a BTESH sol with a mass fraction of 5%.

[0096] (3) Preparation of Pd / BTESH sol: Palladium chloride was dissolved in hydrochloric acid, the molar ratio of Pd / HCl was 1:2, the reducing agent was ethylene glycol, and the mixture was stirred in a water bath at 60°C for 30 min. Then, the BTESH sol obtained in step (2) was added to make the molar ratio of Pd / Si = 0.1 and the BTESH content of the obtained Pd / BTESH sol was 0.5 wt.%. The mixture was stirred in a water bath at 60°C for 1.5 h to obtain Pd / BTESH sol.

[0097] (4) Alumina with an average particle size of 1 μm is applied to the support after step (1) and then calcined at 550°C for 20 min to obtain a solid product; Alumina with an average particle size of 0.1 μm is applied to the solid product and then calcined at 550°C for 20 min to obtain a modified support with an average pore size of 100 nm.

[0098] (5) Apply silicon-titanium sol (concentration of 0.5 wt.% and silicon-titanium molar ratio of 1:1) to the modified support obtained in step (4), and then calcine at 550°C for 20 min to form a transition layer with an average pore size of 1 nm.

[0099] (6) The Pd / BTESH sol obtained in step (3) is applied to the transition layer and then calcined at 250°C for 0.5 h to obtain a separation layer with an average pore size of 0.5 nm.

[0100] An example XRD pattern of Pd / BTESH dry gel is shown below. Figure 1 Compared to BTESH dry gel, it has characteristic peaks of elemental Pd at 2θ of 40°, 46° and 68°, indicating that Pd exists in the separation layer as an element, and the BTESH network structure does not change in any other way. This shows that the presence of Pd has little impact on the BTESH network structure, which is beneficial to improving the membrane separation performance.

[0101] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0102] Example 2

[0103] (1) The sheet ceramic support (α-Al2O3 with an average pore size of 1μm) was boiled in deionized water for 15 minutes, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 minutes. Finally, it was dried in a forced-air oven at 120℃ for 6 hours to obtain the treated support.

[0104] (2) Preparation of organosilicon sol: Dissolve BTESH in ethanol, then add water and hydrochloric acid, wherein the molar ratio of BTESH:H2O:HCl is 1:120:0.5, stir at 40℃ for 1.5h to obtain a BTESH sol with a mass fraction of 7%.

[0105] (3) Preparation of Pd / BTESH sol: Palladium chloride was dissolved in hydrochloric acid, the molar ratio of Pd / HCl was 1:2, the reducing agent was ethylene glycol, and the mixture was stirred in a water bath at 60°C for 30 min. Then, the BTESH sol obtained in step (2) was added to make the molar ratio of Pd / Si = 0.5 and the BTESH content of the obtained Pd / BTESH sol was 1 wt.%. The mixture was stirred in a water bath at 60°C for 1.5 h to obtain Pd / BTESH sol.

[0106] (4) Alumina with an average particle size of 1 μm is coated onto the support after step (1) and then calcined at 550°C for 20 min to obtain a solid product; Alumina with an average particle size of 0.2 μm is coated onto the solid product and then calcined at 550°C for 20 min to obtain a modified support with an average pore size of 200 nm.

[0107] (5) Apply silicon-titanium sol (concentration of 2wt.%, silicon-titanium molar ratio of 1:3) to the modified support obtained in step (4), and then calcine at 550℃ for 20 min to form a transition layer with an average pore size of 3nm.

[0108] (6) The Pd / BTESH sol obtained in step (3) is applied to the transition layer and then calcined at 250°C for 0.5 h to obtain a separation layer with an average pore size of 0.55 nm.

[0109] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0110] Example 3

[0111] (1) The sheet ceramic support (α-Al2O3, with an average pore size of 2μm) was polished with sandpaper until the surface was smooth. It was then boiled in deionized water for 15 minutes, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 minutes. It was then cleaned with deionized water until there were no sand or impurities on the surface. Finally, it was dried in a forced-air oven at 120℃ for 6 hours to obtain the treated support.

[0112] (2) Preparation of organosilicon sol: Dissolve BTESH in ethanol, then add water and hydrochloric acid, wherein the molar ratio of BTESH:H2O:HCl is 1:60:0.5, stir at 40℃ for 2h to obtain BTESH sol with a mass fraction of 7%.

[0113] (3) Preparation of Pd / BTESH sol: Palladium chloride was dissolved in hydrochloric acid, the molar ratio of Pd / HCl was 1:3, the reducing agent was ethylene glycol, and the mixture was stirred in a water bath at 60°C for 30 min. Then, the BTESH sol obtained in step (2) was added to make the molar ratio of Pd / Si = 1, and BTESH accounted for 3 wt.% of the obtained Pd / BTESH sol. The mixture was stirred in a water bath at 60°C for 1.5 h to obtain Pd / BTESH sol.

[0114] (4) Alumina with an average particle size of 2 μm is coated onto the support after step (1) and then calcined at 550°C for 20 min to obtain a solid product; Alumina with an average particle size of 0.3 μm is coated onto the solid product and then calcined at 550°C for 20 min to obtain a modified support with an average pore size of 300 nm.

[0115] (5) Apply silicon-titanium sol (concentration of 2wt.%, silicon-titanium molar ratio of 1:5) to the modified support obtained in step (4), and then calcine at 550℃ for 40 min to form a transition layer with an average pore size of 5nm.

[0116] (6) The Pd / BTESH sol obtained in step (3) is applied to the transition layer and then calcined at 250°C for 1 hour to obtain a separation layer with an average pore size of 0.6 nm.

[0117] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0118] Comparative Example 1

[0119] The method of Example 1 was followed, except that step (3) was not performed. Instead, the organosilicon sol obtained in step (2) was directly coated onto the transition layer to obtain a separation layer with an average pore size of 0.4 nm.

[0120] XRD pattern of BTESH dry gel is shown below. Figure 1 The BTESH dry gel samples showed only dispersed broad peaks in the 2θ range of 5°-80°, without sharp diffraction peaks, indicating that the organosilicon BTESH network is an amorphous network.

[0121] Gas testing was performed on the obtained membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0122] Comparative Example 2

[0123] The method was followed as in Comparative Example 1, except that BTESH was not used as the raw material; instead, BTESE was used to prepare the organosilicon sol.

[0124] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0125] Comparative Example 3

[0126] The method of Example 1 was followed, except that BTESH was not used as a raw material, but 1,8-bis(triethoxysilyl)octane was used as a raw material to prepare the organosilicon sol.

[0127] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0128] Comparative Example 4

[0129] The method of Example 1 was followed, except that BTESH was not used as a raw material, but BTESE was used to prepare the organosilicon sol.

[0130] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0131] Comparative Example 5

[0132] The method of Example 1 was followed, except that step (4) was omitted. Instead, a commercially available ceramic support with an average particle size of 100 nm was directly used without modification of the support, and a Pd / BTESH membrane was finally prepared.

[0133] Gas testing was performed on the obtained hybrid membrane. N2, H2, and C3H8 gases were continuously introduced into the membrane module heated to 200℃, and the gauge pressure on the feed side was controlled at 200 kPa. After stabilization for 1 hour, the gas permeability and selectivity were measured. The results are shown in Table 1.

[0134] Table 1

[0135]

[0136] As can be seen from the results in Table 1, under similar H2 / N2 selectivity conditions, the composite membrane described in this invention exhibits significantly better H2 permeation performance when applied to hydrogen separation, with all values ​​exceeding 10. -6 mol·m -2 ·s -1 ·Pa -1 above.

[0137] Moreover, as can be seen from the results in Table 1, the composite membrane described in this invention exhibits significantly better H2 / C3H8 selectivity when applied to hydrogen separation.

[0138] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing an organic-inorganic silica composite film, the method comprising the following steps: (1) Organosilicon sol was prepared by sol-gel method using 1,6-bis(triethoxysilyl)hexane as raw material, and then palladium element was introduced into the organosilicon sol to obtain palladium / organosilicon sol; (2) The silicon-titanium sol is coated onto the modified support, and then subjected to a first calcination to obtain a transition layer; (3) The palladium / organosilicon sol obtained in step (1) is coated on the transition layer, and then a second calcination is performed to obtain the separation layer; The method for introducing palladium into the organosilicon sol in step (1) includes: firstly, subjecting an acid solution containing palladium salt, an alcohol, and the organosilicon sol obtained in step (1) to a second reaction to obtain a palladium / organosilicon sol; wherein the alcohol is an alcohol containing at least two hydroxyl groups; The preparation process of the modified support includes: modifying the porous support with a first alumina and a second alumina in sequence to obtain the modified support, wherein the average particle size of the first alumina is 90-200% of the average pore size of the porous support, and the average particle size of the second alumina is 5-25% of the average particle size of the first alumina.

2. The method according to claim 1, wherein, The modified support has an average pore size of 100-300 nm; The average pore size of the transition layer is 1-5 nm; The average pore size of the separation layer is less than 1 nm.

3. The method according to claim 2, wherein, The average pore size of the separation layer is 0.4-0.7 nm.

4. The method according to any one of claims 1-3, wherein, Step (1) of the sol-gel method includes: reacting a 1,6-bis(triethoxysilyl)hexane solution, a catalyst and water to obtain an organosilicon sol.

5. The method according to claim 4, wherein, The molar ratio of 1,6-bis(triethoxysilyl)hexane:water:catalyst is 1:60-120:0.1-0.

5.

6. The method according to claim 4, wherein, The mass fraction of the 1,6-bis(triethoxysilyl)hexane solution is 5-7 wt%.

7. The method according to claim 4, wherein, The conditions for the first reaction include: a temperature of 40-60℃ and a time of 1-10h.

8. The method according to claim 4, wherein, The catalyst is an inorganic acid.

9. The method according to claim 8, wherein, The catalyst is selected from at least one of hydrochloric acid, nitric acid, and sulfuric acid.

10. The method according to any one of claims 1-3, wherein, The conditions for the second reaction include a temperature of 40-80℃ and a time of 1-10h.

11. The method according to any one of claims 1-3, wherein, The molar ratio of palladium salt (based on elemental composition) to organosilicon sol (based on elemental composition) is 0.1-1:

1.

12. The method according to claim 11, wherein, The molar ratio of palladium salt (based on elemental composition) to organosilicon sol (based on elemental composition) is 0.1-0.8:

1.

13. The method according to any one of claims 1-3, wherein, The molar ratio of palladium salt to acid, calculated as an element, is 1:0.5-4.

14. The method according to any one of claims 1-3, wherein, The acid is selected from at least one of nitric acid, hydrochloric acid, and sulfuric acid.

15. The method according to any one of claims 1-3, wherein, The amount of alcohol used is such that, based on the total mass of the palladium / organosilicon sol obtained in step (1), the mass content of organosilicon is 0.5-5%.

16. The method according to any one of claims 1-3, wherein, The alcohol is selected from at least one of ethylene glycol, glycerol, and butanediol.

17. The method according to any one of claims 1-3, wherein, The modified support preparation process includes: coating a first alumina onto a porous support, followed by a third calcination to obtain a solid product; coating a second alumina onto the solid product, followed by a fourth calcination to obtain the modified support.

18. The method according to claim 17, wherein, The conditions for the third and fourth calcinations each independently include: a temperature of 500-600℃ and a time of 20-40 minutes.

19. The method according to any one of claims 1-3, wherein, The average particle size of the first alumina is 90-110% of the average pore size of the porous support; The average particle size of the second alumina is 5-20% of the average particle size of the first alumina.

20. The method according to any one of claims 1-3, wherein, The average pore size of the porous support is 1-2 μm.

21. The method according to any one of claims 1-3, wherein, The porous support is aluminum oxide.

22. The method according to any one of claims 1-3, wherein, The silicon-titanium molar ratio of the silicon-titanium sol is 1:1-10.

23. The method according to any one of claims 1-3, wherein, The concentration of the silicon-titanium sol is 0.5-10 wt%.

24. The method according to any one of claims 1-3, wherein, Step (2) The conditions for the first calcination include: a temperature of 500-600℃ and a time of 20-40min.

25. The method according to any one of claims 1-3, wherein, Step (3) The conditions for the second calcination include: a temperature of 200-300℃ and a time of 0.5-1h.

26. An organic-inorganic silica composite film prepared by the preparation method according to any one of claims 1-25.

27. The application of the organic-inorganic silica composite membrane of claim 26 in gas separation.

28. The application according to claim 27, wherein, Application of the organic-inorganic silica composite membrane in hydrogen separation.

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