Organic-inorganic silicon dioxide composite film as well as preparation method and application thereof

Abstract

The invention relates to the field of preparation of gas separation membranes, and discloses an organic-inorganic silicon dioxide composite membrane as well as a preparation method and application thereof. The invention relates to a preparation method of an organic-inorganic silicon dioxide composite film, which comprises the following steps: (1) preparing organic silicon sol by using 1, 6-bis (triethoxysilyl) hexane as a raw material through a sol-gel method, and then introducing palladium element into the organic silicon sol to obtain palladium / organic silicon sol; (2) coating the modified support body with the silicon-titanium sol, and then carrying out first calcination to obtain a transition layer; and (3) coating the transition layer with the palladium / organic silicon sol obtained in the step (1), and then carrying out second calcination to obtain the separation layer. The separation membrane provided by the invention is used for hydrogen separation and shows good hydrogen permeability.

Description

Technical Field

[0001] The invention relates to the field of preparation of gas separation membranes, and in particular to an organic-inorganic silicon dioxide composite membrane and a preparation method and application thereof. Background Art

[0002] SiO2 membranes have a unique Si-O-Si network structure and exhibit excellent H2 permeability and selectivity. However, SiO2 membranes are unstable under high-temperature water vapor, which limits their gas separation in water vapor environments. The hydrothermal stability of SiO2 membranes can be improved to a certain extent by introducing hydrophobic organic groups into their network structure. Kanezashi et al. [J.Am.Chem.Soc., 2009, 131(2), 414-415] reported that hybrid silicon membranes prepared with 1,2-bis(triethoxysilyl)ethane (BTESE) exhibited excellent hydrothermal stability for H2 separation. However, the BTESE membrane has a low permeability to hydrogen and is ineffective at 10 -7 mol·m -2 ·s -1 ·Pa -1 The hydrogen permeability of BTESE membranes was improved by metal modification, but the improvement was limited and still within 3-7×10 -7 mol·m -2 ·s -1 ·Pa -1 , and metals destroy the short-chain network, resulting in 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 the present invention is to overcome the problem that the hydrogen permeability in gas separation of the existing organic-inorganic silicon dioxide composite membrane needs to be further improved, and to provide an organic-inorganic silicon dioxide composite membrane and a preparation method and application thereof. The separation membrane provided by the present invention is used in hydrogen separation and exhibits good hydrogen permeability.

[0005] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an organic-inorganic silicon dioxide composite film, the method comprising the following steps:

[0006] (1) using 1,6-bis(triethoxysilyl)hexane as a raw material to prepare an organosilicon sol by a sol-gel method, and then introducing palladium into the organosilicon sol to obtain palladium / organosilicon sol;

[0007] (2) coating the silicon-titanium sol on the modified support, and then performing a first calcination to obtain a transition layer;

[0008] (3) coating the palladium / organic silica sol obtained in step (1) on the transition layer, and then performing a second calcination to obtain a separation layer.

[0009] Preferably, the preparation process of the modified support body includes: modifying the porous support body with the first alumina and the second alumina to obtain a modified support body, wherein the average particle size of the first alumina is 90-200% of the average pore size of the porous support body, 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 silicon dioxide composite film prepared by the preparation method described in the first aspect.

[0011] 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.

[0012] Through the above technical solution, the beneficial effects of the present invention include:

[0013] The composite membrane prepared by the method of the present invention is applied to hydrogen separation and exhibits good hydrogen permeability and good hydrogen selectivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 1 is the XRD spectra of the Pd / BTESH dry gel of Example 1 and the BTESH dry gel of Comparative Example 1. DETAILED DESCRIPTION

[0015] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

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

[0017] (1) using 1,6-bis(triethoxysilyl)hexane as a raw material to prepare an organosilicon sol by a sol-gel method, and then introducing palladium into the organosilicon sol to obtain palladium / organosilicon sol;

[0018] (2) coating the silicon-titanium sol on the modified support, and then performing a first calcination to obtain a transition layer;

[0019] (3) coating the palladium / organic silica sol obtained in step (1) on the transition layer, and then performing a second calcination to obtain a separation layer.

[0020] In the preparation method provided by the present invention, palladium is introduced into the organic silica sol prepared from 1,6-bis(triethoxysilyl)hexane (BTESH) as a raw material, which is beneficial to improving the hydrogen separation effect of the composite membrane; then a specific type of silicon titanium sol is coated on the modified support body after the pore structure is modified to form a transition layer, which is further beneficial to improving the separation performance of the composite membrane. The composite membrane prepared by the method of the present invention is applied to hydrogen separation, showing good hydrogen permeability and good hydrogen selectivity.

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

[0024] Controlling the average pore size of the modified support, transition layer, and separation layer within the above range is beneficial to preparing a defect-free organic-inorganic silicon dioxide composite membrane, thereby improving hydrogen permeability and selectivity.

[0025] The present invention has no particular limitation on the preparation process of the organosilicon sol in step (1), and the preparation process can be carried out according to conventional methods in the art. Preferably, the sol-gel method in step (1) comprises: subjecting a 1,6-bis(triethoxysilyl)hexane solution, a catalyst and water to a first reaction to obtain an 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 has a wide range of solvents for the 1,6-bis(triethoxysilyl)hexane solution, which can be a conventional choice 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 of the first reaction include: temperature of 40-60° C., and time of 1-10 h.

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

[0031] The present invention has no particular limitation on the stirring rate, which is based on uniform mixing and accelerating the reaction process, and can be appropriately selected according to specific circumstances.

[0032] The catalyst of the present invention can promote the hydrolysis and polymerization of 1,6-bis(triethoxysilyl)hexane. The present invention has no particular limitation on the type of the catalyst, and it can be a conventional choice in the art. Preferably, the catalyst is an inorganic acid, preferably at least one selected from hydrochloric acid, nitric acid and sulfuric acid.

[0033] According to the present invention, preferably, the method of introducing palladium into the organosilicon sol in step (1) comprises: firstly subjecting the acid solution containing palladium salt, alcohol and the organosilicon sol obtained in step (1) to a second reaction to obtain palladium / organosilicon sol. In the palladium / organosilicon sol, the formed Pd particles can not only modify the large pore size to screen N2 and C3H8 effects, but also promote H2 penetration, which is beneficial to improve the hydrothermal stability of the prepared composite membrane and improve the hydrogen separation performance.

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

[0035] The present invention has no particular limitation on how to achieve the second reaction temperature of the present invention, and the reaction can be carried out by conventional methods in the art, for example, by using a water bath.

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

[0037] The present invention has no particular limitation on the stirring rate, which is based on accelerating 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 the organic silica sol in step (1) comprises: first reacting an acid solution containing a palladium salt with an alcohol for 0.5-5h, and then adding the organic silica sol obtained in step (1) to react for 0.5-5h to obtain a palladium / organic silica sol.

[0039] According to the present invention, preferably, the molar ratio of palladium salt calculated as element to organosilicon sol calculated as silicon element is 0.1-1:1, preferably 0.1-0.8:1. This preferred embodiment is conducive to the dispersion of palladium and the integrity of the organosilicon network.

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

[0041] The present invention has a wide range of choices for the type of the acid. 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 the mass content of organosilicon in the palladium / organosilica sol obtained in step (1) is 0.5-5% based on the total mass of the palladium / organosilica sol. `

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

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

[0045] The existing commercially available porous support products have defects such as uneven pore structure and some large pores. However, the inventors found in the research process that the modified support obtained by the above specific method effectively overcomes the above defects, forms a continuous separation membrane layer, and improves the separation performance of hydrogen.

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

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

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

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

[0050] The present invention has no particular limitation on the coating method used in the preparation of the modified support, and the coating method can be carried out using conventional methods in the art.

[0051] In order to optimize the coating effect, the present invention preferably adopts a small amount and multiple times method for coating.

[0052] There is no particular limitation on the number of coating times during the formation of the solid product of the present invention, and there is no particular limitation on the amount of the first alumina used during the coating process, with the solid product having no exposed macropores on its surface (which can be seen through a scanning electron microscope) as the basis.

[0053] There is no particular limitation on the number of coating times in the process of forming the modified support of the present invention, and there is no particular limitation on the amount of the second aluminum oxide used in the coating process, as long as the average pore size of the modified support obtained is within the range of 100-300 nm.

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

[0055] Preferably, after coating the first aluminum oxide onto the porous support, before the third calcination, drying is performed at 15-40° C. In this preferred embodiment, the bubble defects formed in the transition layer due to the volatilization of the solvent in the pores of the modified support can be prevented during the formation of the transition layer.

[0056] When there are excess particles on the surface of the porous support after drying, they are wiped off and then subjected to the third calcination.

[0057] When there are no extra particles on the surface of the porous support after drying, the third calcination is directly performed without wiping.

[0058] Similarly, after the second alumina is coated on 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 the present invention will not be repeated here.

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

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

[0061] The porous support of the present invention has a wide range of choices. Preferably, the porous support of the present invention can be selected from at least one of porous ceramics, porous glass, porous metal (such as porous stainless steel), porous quartz and high molecular polymer, more preferably porous ceramics.

[0062] The type of porous ceramics of the present invention can be a conventional choice in the art, for example, it can be 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. In order to improve the separation performance of the separation membrane and based on cost considerations, preferably, the porous support is alumina, preferably α-Al2O3.

[0063] The present invention has no particular limitation on the source of the porous support, which can be obtained from commercial sources or prepared by conventional methods, as long as the above-mentioned pore size requirements are met.

[0064] The present invention has a wide range of selections for the types of the first aluminum oxide and the second aluminum oxide, for example, α-Al2O3, γ-Al2O3, θ-Al2O3, etc. Preferably, the first aluminum oxide and the second aluminum oxide are α-Al2O3.

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

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

[0067] Further preferably, the porous support is polished, cleaned and dried to obtain a porous support with a smooth surface. The porous support is cleaned until there is no grit or impurities on the surface.

[0068] According to a specific embodiment of the present invention, the porous support is polished and then boiled in water for 10-30 minutes, and then ultrasonically cleaned, washed with water, and dried.

[0069] The present invention has no particular limitation on the specific methods of polishing, ultrasonic cleaning, water cleaning and drying, which can be carried out according to conventional methods.

[0070] The present invention has no particular limitation on the coating method used in the preparation of the transition layer in step (2), and the coating method can be carried out using conventional methods in the art.

[0071] In order to optimize the coating effect, the present invention preferably adopts a small amount and multiple times method for coating.

[0072] There is no particular limitation on the number of coating times in the process of forming the transition layer of the present invention, and there is no particular limitation on the amount of silicon-titanium sol used in the coating process, as long as the average pore size of the obtained transition layer is within 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 the silicon-titanium sol on the modified support, then performing a first calcination, and 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 in 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 has no particular limitation on the source of the silicon-titanium sol, which can be obtained from commercial sources or prepared by conventional methods, as long as the above characteristic parameters are met.

[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 has no particular limitation on the coating method used in the process of preparing the separation layer in step (3), and the coating method can be carried out using conventional methods in the art.

[0079] In order to optimize the coating effect, the present invention preferably adopts a small amount and multiple times method for coating.

[0080] There is no particular limit on the number of coating times in the separation layer formation process of the present invention, and there is no particular limit on the amount of palladium / organic silica sol used in the coating process, as long as the average pore size of the separation layer obtained 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 / organic silica sol obtained in step (1) on the transition layer, then performing a second calcination, and repeating the coating-second calcination process to obtain the separation layer.

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

[0083] In the present invention, the "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 silicon dioxide 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 silicon dioxide composite membrane described in the second aspect in gas separation, preferably in hydrogen separation.

[0086] The composite membrane of the present invention is applied to hydrogen separation, and exhibits good hydrogen permeability and good hydrogen selectivity.

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

[0088] In the following embodiments,

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

[0090] Where, gas flux, mol / s; membrane area, m 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) A ceramic support sheet (α-Al2O3, average pore size of 1 μm) was placed in deionized water and boiled for 15 min, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 min, and then dried in a forced air oven at 120°C for 6 h to obtain a treated support.

[0095] (2) Preparation of organosilica sol: BTESH was dissolved in ethanol, and then water and hydrochloric acid were added, wherein the molar ratio of BTESH:H2O:HCl was 1:120:0.2, and the mixture was stirred at 40°C for 1.5 h 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 with a Pd / HCl molar ratio of 1:2, ethylene glycol was used as a reducing agent, 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 Pd / Si molar ratio = 0.1, and BTESH accounted for 0.5 wt.% of the obtained Pd / BTESH sol. The mixture was stirred in a water bath at 60°C for 1.5 h to obtain a Pd / BTESH sol.

[0097] (4) Alumina with an average particle size of 1 μm is rubbed onto the support body treated in 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 rubbed onto the solid product, and then calcined at 550°C for 20 min to obtain a modified support body with an average pore size of 100 nm.

[0098] (5) A silicon-titanium sol (concentration of 0.5 wt.%, silicon-titanium molar ratio of 1:1) was applied on the modified support obtained in step (4), and then calcined 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 rubbed on 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] The XRD pattern of Pd / BTESH xerogel is shown in Figure 1 Compared with 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 a single substance and there is no other change in the BTESH network structure, indicating that the presence of Pd has little damage to the BTESH network structure, which is beneficial to improving the membrane separation performance.

[0101] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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) A ceramic support sheet (α-Al2O3, average pore size of 1 μm) was placed in deionized water and boiled for 15 min, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 min, and then dried in a forced air oven at 120°C for 6 h to obtain a treated support.

[0104] (2) Preparation of organosilica sol: BTESH was dissolved in ethanol, and then water and hydrochloric acid were added, wherein the molar ratio of BTESH:H2O:HCl was 1:120:0.5, and the mixture was stirred at 40°C for 1.5 h 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 with a Pd / HCl molar ratio of 1:2, ethylene glycol was used as a reducing agent, 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 Pd / Si molar ratio = 0.5, and BTESH accounted for 1 wt.% of the obtained Pd / BTESH sol. The mixture was stirred in a water bath at 60°C for 1.5 h to obtain a Pd / BTESH sol.

[0106] (4) Alumina with an average particle size of 1 μm is coated on the support body treated in 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 on the solid product, and then calcined at 550°C for 20 min to obtain a modified support body with an average pore size of 200 nm.

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

[0108] (6) The Pd / BTESH sol obtained in step (3) was rubbed on 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] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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) A ceramic support sheet (α-Al2O3, average pore size of 2 μm) was polished with sandpaper until the surface was smooth, boiled in deionized water for 15 min, cooled to room temperature, and then placed in an ultrasonic cleaner for 5 min. The support sheet was cleaned with deionized water until there was no sand or gravel impurities on the surface, and then dried in a blast oven at 120°C for 6 h to obtain a treated support sheet.

[0112] (2) Preparation of organosilica sol: BTESH was dissolved in ethanol, and then water and hydrochloric acid were added, wherein the molar ratio of BTESH:H2O:HCl was 1:60:0.5, and the mixture was stirred at 40°C for 2 h to obtain a BTESH sol with a mass fraction of 7%.

[0113] (3) Preparation of Pd / BTESH sol: palladium chloride was dissolved in hydrochloric acid with a Pd / HCl molar ratio of 1:3, ethylene glycol was used as a reducing agent, 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 Pd / Si molar ratio = 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 a Pd / BTESH sol.

[0114] (4) Alumina with an average particle size of 2 μm is coated on the support body treated in 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 on the solid product, and then calcined at 550°C for 20 min to obtain a modified support body with an average pore size of 300 nm.

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

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

[0117] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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 is followed, except that step (3) is not performed, and instead the organic silica sol obtained in step (2) is directly coated on the transition layer to obtain a separation layer with an average pore size of 0.4 nm.

[0120] The XRD pattern of BTESH xerogel is shown in Figure 1 The BTESH xerogel sample only showed a dispersed broad peak in the range of 2θ 5°-80°, without a sharp diffraction peak, indicating that the network composed of the silicone BTESH was an amorphous network.

[0121] The obtained membrane was subjected to gas testing, and N2, H2, and C3H8 gases were continuously introduced into the membrane module heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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 of Comparative Example 1 was followed, except that BTESE was used as the raw material instead of BTESH to prepare the organosilicon sol.

[0124] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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 1,8-bis(triethoxysilyl)octane was used as the raw material to prepare the organosilica sol instead of BTESH.

[0127] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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 BTESE was used as the raw material instead of BTESH to prepare the organosilica sol.

[0130] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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 not performed. Instead, a commercially available ceramic support with an average particle size of 100 nm was directly used without modifying the support, and finally a Pd / BTESH membrane was prepared.

[0133] The obtained hybrid membrane was subjected to gas testing, where N2, H2, and C3H8 gases were continuously introduced into the membrane assembly heated at 200°C, and the gauge pressure on the raw material side was controlled to be 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] From the results in Table 1, it can be seen that under the condition of similar H2 / N2 selectivity, the composite membrane of the present invention has significantly better H2 permeation performance when applied to hydrogen separation, both at 10 -6 mol·m -2 ·s -1 ·Pa -1 above.

[0137] Furthermore, it can be seen from the results in Table 1 that the composite membrane of the present invention has significantly better H2 / C3H8 selectivity when applied to hydrogen separation.

[0138] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing an organic-inorganic silicon dioxide composite film, the method comprising the following steps: (1) using 1,6-bis(triethoxysilyl)hexane as a raw material to prepare an organosilicon sol by a sol-gel method, and then introducing palladium into the organosilicon sol to obtain palladium / organosilicon sol; (2) coating the silicon-titanium sol on the modified support, and then performing a first calcination to obtain a transition layer; (3) coating the palladium / organic silica sol obtained in step (1) on the transition layer, and then performing a second calcination to obtain a separation layer.

2. The method according to claim 1, wherein The average pore size of the modified porous support is 100-300 nm; Preferably, the average pore size of the transition layer is 1-5 nm; Preferably, the average pore size of the separation layer is less than 1 nm, preferably 0.4-0.7 nm.

3. The method according to claim 1 or 2, wherein: The sol-gel method of step (1) comprises: subjecting a 1,6-bis(triethoxysilyl)hexane solution, a catalyst and water to a first reaction to obtain an organosilicon sol; Preferably, the molar ratio of 1,6-bis(triethoxysilyl)hexane: water: catalyst is 1: 60-120: 0.1-0.5; Preferably, the mass fraction of 1,6-bis(triethoxysilyl)hexane solution is 5-7wt%; Preferably, the conditions of the first reaction include: temperature of 40-60°C, time of 1-10h; Preferably, the catalyst is an inorganic acid, preferably at least one selected from hydrochloric acid, nitric acid and sulfuric acid.

4. The method according to claim 1 or 2, wherein: The method of introducing palladium element into the organosilicon sol in step (1) comprises: firstly subjecting an acid solution containing palladium salt, alcohol and the organosilicon sol obtained in step (1) to a second reaction to obtain palladium / organosilicon sol; Preferably, the conditions of the second reaction include: temperature of 40-80°C, time of 1-10h; Preferably, the molar ratio of palladium salt calculated as element to organosilicon sol calculated as silicon element is 0.1-1:1, preferably 0.1-0.8:1; Preferably, the molar ratio of palladium salt to acid, calculated as the element, is 1:0.5-4; Preferably, the acid is selected from at least one of nitric acid, hydrochloric acid and sulfuric acid; Preferably, the amount of alcohol used is such that in the palladium / organosilica sol obtained in step (1), the mass content of organosilicon is 0.5-5% based on the total mass of the palladium / organosilica sol; Preferably, the alcohol is an alcohol containing at least two hydroxyl groups, preferably at least one selected from ethylene glycol, glycerol and butanediol.

5. The method according to any one of claims 1 to 4, wherein: The preparation process of the modified support body comprises: modifying the porous support body with the first alumina and the second alumina in sequence to obtain the modified support body, wherein the average particle size of the first alumina is 90-200% of the average pore size of the porous support body, and the average particle size of the second alumina is 5-25% of the average particle size of the first alumina; Preferably, the modified support preparation process comprises: coating a first aluminum oxide on a porous support, and then performing a third calcination to obtain a solid product; coating a second aluminum oxide on the solid product, and then performing a fourth calcination to obtain a modified support.

6. The method according to claim 5, wherein: The conditions of the third calcination and the fourth calcination independently include: a temperature of 500-600° C. and a time of 20-40 min.

7. The method according to claim 5, wherein: The first alumina has an average particle size of 90-110% of the average pore size of the porous support; Preferably, the average particle size of the second alumina is 5-20% of the average particle size of the first alumina; Preferably, the average pore size of the porous support is 1-2 μm; Preferably, the porous support is alumina.

8. The method according to any one of claims 1 to 7, wherein: The silicon-titanium molar ratio of the silicon-titanium sol is 1:1-10; Preferably, the concentration of the silicon-titanium sol is 0.5-10wt%; Preferably, the conditions of the first calcination in step (2) include: a temperature of 500-600° C. and a time of 20-40 min; Preferably, the conditions for the second calcination in step (3) include: temperature of 200-300° C. and time of 0.5-1 h.

9. An organic-inorganic silicon dioxide composite film obtained by the preparation method according to any one of claims 1 to 8.

10. Use of the organic-inorganic silicon dioxide composite membrane according to claim 9 in gas separation, preferably in hydrogen separation.

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