Separation membrane and membrane module

Abstract

To provide a separation membrane which achieves excellent permeation characteristics even when used in a low temperature environment (lower than an ordinary temperature, i.e., -196°C to 0°C).SOLUTION: A separation membrane 10 of an embodiment separates air system components and is a lamination membrane comprising an intermediate layer 8 supported on a support layer 7, and an active separation layer 9. The intermediate layer 8 is a layer made of a hydrophobic material. The active separation layer 9 is a layer which is positioned on the intermediate layer 8 and selectively separates an arbitrary component from a mixed gas containing the air system components which are raw materials.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a separation membrane and a membrane module. [Background technology]

[0002] The three main components of air (nitrogen, oxygen, and argon) are primarily separated using adsorption, cryogenic separation, and membrane separation.

[0003] Adsorption separation utilizes physical or chemical action to separate specific components from others by incorporating them into the adsorbent's site. For example, in a nitrogen / oxygen system using molecular sieves as the adsorbent, nitrogen exhibits strong adsorption, resulting in oxygen becoming the final product. Adsorption and desorption operations require pressure or temperature swings, but both are performed above room temperature. Desorption operations, in particular, become difficult at low temperatures.

[0004] Cryogenic separation separates air-based components through distillation utilizing vapor-liquid equilibrium. Because cryogenic separation requires operation under conditions where vapor and liquid coexist, the operating temperature is near the dew point (-196°C to -100°C), resulting in extremely low temperatures. Furthermore, cryogenic separation requires multiple compression and expansion strokes to provide the energy needed to liquefy and separate the air, necessitating tray columns and packed columns for distillation. Additionally, due to the constraints of vapor-liquid equilibrium, argon / oxygen systems are difficult to separate, requiring numerous distillation steps.

[0005] Membrane separation separates mixtures using the sieving action of membrane pores. Therefore, it is not subject to the constraints of vapor-liquid equilibrium, such as specific volatility. In membrane separation, higher molecular kinetic energy is generally advantageous for the mixture to pass through the pore barrier, so it is carried out at very high temperatures (e.g., 500°C to 800°C).

[0006] Incidentally, porous silica membranes are gas separation membranes that have pores of about 0.3 nm, derived from the gaps in the amorphous silica network, through which only minute molecules such as hydrogen can permeate. Furthermore, because silica is prone to densification of its membrane pores due to the generation of silanol groups by water vapor and subsequent resintering, an intermediate layer of gas separation membranes made of silica composited with ZrO2 has been used (see Non-Patent Literature 1). The intermediate layer consisting of "SiO2-ZrO2" has a pore diameter relatively larger than that of gas molecules and has also been effective in improving water vapor resistance. [Prior art documents] [Non-patent literature]

[0007] [Non-Patent Document 1] Review Article: MEMBRANE, 36(3), 97-103 (2011) [Overview of the project] [Problems that the invention aims to solve]

[0008] In membrane separation, when separation is performed in phase (e.g., gas phase and gas phase), the mechanism relies on the difference in molecular diffusivity and has a pore size distribution. As a result, separation membranes applicable to commercial operation, such as nitrogen / oxygen systems, have not yet been obtained. Incidentally, when separating air-based components by membrane separation, it has become clear that it is desirable to operate at low temperatures when utilizing surface diffusion (inhibiting the permeation of other components by adsorbing specific components into pores or agglomerating them through a similar phenomenon).

[0009] However, conventional gas separation membranes using an intermediate layer made of "SiO2-ZrO2" could not maintain their permeability characteristics at room temperature when used in low-temperature environments (below room temperature; -196°C to 0°C).

[0010] The present invention has been made in view of the above circumstances, and aims to provide a separation membrane and a membrane module that exhibit excellent permeability characteristics even when used in a low-temperature environment (below room temperature; -196°C to 0°C). [Means for solving the problem]

[0011] To solve the above problems, the present invention has the following configuration. [1] A separation membrane for separating air-based components, The operating conditions are -196℃ to 0℃. A separation membrane having a layer made of hydrophobic material. [2] The separation membrane according to [1], wherein the hydrophobic material is an inorganic material having siloxane bonds. [3] The separation membrane according to [1] or [2], which is a laminated film of an active separation layer and an intermediate layer made of the hydrophobic material. [4] The separation membrane according to [3], wherein the active separation layer is a layer made of an inorganic material having a siloxane bond crosslinking structure. [5] A separation membrane according to any one of [1] to [4], wherein the dew point of the water contained in the gas to be separated is -50°C or lower. [6] A membrane module comprising a separation section having a separation membrane according to any one of [1] to [5] on a support layer made of a porous substrate. [7] A membrane module body in which the separation portion is located in the inner space, A raw material introduction unit for introducing raw materials containing air-based components into the main body of the membrane module, A permeable component extraction unit that extracts the component that permeates through the separation unit from the module body, The membrane module according to [6], further comprising: a non-permeable component discharge section for dischargeing components that do not permeate the separation section from the module body. [8] The membrane module according to [6] or [7], wherein the support layer is hollow and cylindrical. [Effects of the Invention]

[0012] The separation membrane and membrane module of the present invention exhibit excellent permeation characteristics even when used in a low-temperature environment (room temperature or lower; -196°C to 0°C).

Brief Description of the Drawings

[0013] [Figure 1] It is a cross-sectional view schematically showing the configuration of a membrane module which is an embodiment to which the present invention is applied. [Figure 2] It is a cross-sectional view showing an example of the configuration of a separation unit applicable to a membrane module which is an embodiment to which the present invention is applied. [Figure 3] It is an enlarged cross-sectional photograph showing a separation membrane which is an embodiment to which the present invention is applied. [Figure 4] It is a schematic diagram showing an example of an inorganic material having a crosslinked structure of a siloxane bond, where (a) shows the structural diagram of a bridged organosilica and (b) shows the structural diagram of a side-chain organosilica, respectively. [Figure 5] It is a diagram showing the temperature dependence of the permeation rates of various gases in the separation unit (separation membrane) of the example. [Figure 6] It is a diagram showing the temperature dependence of the permeation rates of various gases in the separation unit (separation membrane) of the comparative example. [Figure 7] It is a diagram showing the temperature dependence of the permeation rates of various gases in the separation unit (separation membrane) of the example.

Modes for Carrying Out the Invention

[0014] Hereinafter, the separation membrane of the present invention will be described in detail with reference to the drawings together with the membrane module using the same. In the drawings used in the following description, for the sake of easy understanding of the features, there are cases where the characteristic parts are enlarged for convenience, and the dimensional ratios of each component are not necessarily the same as the actual ones.

[0015] Also, when "~" is used to indicate a numerical range in this specification, the numerical values described before and after "~" are included as the lower limit value and the upper limit value.

[0016] <Membrane Module> First, the configuration of a membrane module, which is one embodiment of the present invention, will be described. Figure 1 is a schematic cross-sectional view showing the configuration of a membrane module, which is one embodiment to which the present invention is applied. As shown in Figure 1, the membrane module 1 of this embodiment is generally configured to include a membrane module body 2, a separation unit 3, a raw material introduction section 4, a permeable component discharge section 5, and a non-permeable component discharge section 6.

[0017] The membrane module body 2 is a cylindrical container having a sealed space 2A inside. The membrane module body 2 is provided with a raw material introduction section 4 at one end and a permeable component discharge section 5 at the other end. The membrane module body 2 is also provided with a non-permeable component discharge section 6 in the cylindrical body. Furthermore, the separation unit 3 is located in the inner space 2A of the membrane module body 2.

[0018] Figure 2 is a cross-sectional view showing an example of the configuration of a separation unit 3 applicable to a membrane module 1, which is one embodiment to which the present invention is applied. As shown in Figures 1 and 2, the separation unit 3 extends axially from the membrane module body 2 and is a hollow cylindrical member with a closed end on the raw material introduction section 4 side and an open end on the permeate component discharge section 5 side. The separation unit 3 has a separation section 3A and a support section 3B.

[0019] The separation section 3A is located near the end of the separation unit 3 on the raw material introduction section 4 side. The separation section 3A also has a separation membrane 10 on the support layer 7 for separating air-based components.

[0020] The support layer 7 is a hollow cylindrical member that supports the separation membrane 10. By supporting the separation membrane 10 on the support layer 7, the mechanical strength of the separation section 3A can be increased.

[0021] The material of the support layer 7 is not particularly limited as long as it is a porous substrate that allows air-based components, which are the raw materials, to pass through. The porous substrate may be either an inorganic porous material or an organic porous material, and it is preferable that it has sufficient strength to withstand industrial use. Furthermore, in order to increase the permeability of the separation membrane 10, it is preferable that the pore size and porosity of the porous substrate be large. The average pore size of the porous substrate is preferably about 0.05 μm to 10 μm. If the pore size is too large, the difference with the pore size of the separation membrane becomes too large, and if the pore size is too small, the permeability decreases. More preferably, it is 0.1 μm to 5 μm, and particularly preferably 0.5 μm to 3 μm.

[0022] Examples of porous substrates include ceramics made from alumina (α-Al2O3 (α-alumina), γ-Al2O3 (γ-alumina)), mullite, zirconia, titania, or composites thereof. Among these, ceramics mainly composed of α-alumina are preferred because they are inexpensive, readily available, and have excellent chemical resistance, heat resistance, and strength.

[0023] The shape of the support layer 7 is not particularly limited, but it is preferably cylindrical or plate-shaped. More specifically, the support layer 7 can be a porous alumina tube (average pore size: 1 μm, porosity: approximately 50%).

[0024] The support portion 3B is a hollow cylindrical member. The space inside the support portion 3B, together with the space inside the support layer 7 that constitutes the separation portion 3A, forms a flow path for the component (permeate gas) that permeates through the separation portion 3A.

[0025] The material of the support section 3B is not particularly limited, as long as it does not allow the air components of the raw material to permeate it. Examples of such materials include non-porous alumina tubes and Pyrex glass tubes. Among these, non-porous alumina tubes are preferable when considering the pressure resistance at the operating pressure (0.5 MPa) of the air separation device and its use at extremely low temperatures.

[0026] The separation unit 3 is constructed by fixing the separation section 3A and the support section 3B to each other with an intermediate material (not shown) in between. The material of the intermediate material is not particularly limited as long as it mitigates the difference in thermal expansion coefficients between the separation section (support layer 7) 3A and the support section 3B. Examples of such materials include glass frit.

[0027] The shape of the separation unit 3 is not particularly limited as long as it has a cylindrical space inside, and can be appropriately selected according to the area and application of the separation membrane 10. Examples of the separation unit 3's shape include cylindrical and rectangular prism shapes.

[0028] As shown in Figure 1, the raw material introduction section 4 is located at one end of the membrane module body 2. The raw material introduction section 4 is a gas component inlet that introduces raw materials containing air-based components into the inner space 2A of the membrane module body 2.

[0029] The raw material is a mixed gas containing at least one of the three major components of air—nitrogen, oxygen, and argon—and at least two other components overall. Examples of gas components other than air-based components include carbon dioxide, neon, hydrogen, helium, krypton, and xenon. The ratio of each component in the raw material is not particularly limited. Furthermore, since the membrane module 1 of this embodiment is used under operating conditions of -196°C to 0°C, it is preferable that the mixed gas used as the raw material does not contain components that solidify in the above temperature range, such as water and carbon dioxide. In particular, the amount of water in the mixed gas to be separated should have a dew point of -50°C or lower, preferably -70°C or lower, and more preferably -100°C or lower.

[0030] The permeate component outlet 5 is located at the other end of the membrane module body 2. The permeate component outlet 5 is a gas component outlet that discharges the components (permeate gas) that permeate through the separation section 3A (i.e., the separation membrane 10) of the separation unit 3 from the membrane module body 2.

[0031] The permeate component outlet 5 is connected in a sealed state to the open end of the separation unit 3 and is in communication with the space inside the support portion 3 that constitutes the separation unit 3. This allows the component (permeate gas) that permeates through the separation portion 3A of the separation unit 3 to be discharged from the permeate component outlet 5 to the outside of the membrane module body 2.

[0032] The non-permeable component outlet 6 is located in the body of the membrane module body 2. The non-permeable component outlet 6 is a gas component outlet that discharges components (non-permeable gases) that do not permeate the separation section 3A of the separation unit 3 (i.e., the separation membrane 10) from the space 2A inside the membrane module body 2.

[0033] The membrane module 1 of this embodiment selectively separates arbitrary components from a mixed gas containing air components under operating conditions of -196°C to 0°C. In other words, the mixed gas containing the air-based components that serve as raw materials is cooled to the above temperature range beforehand. Furthermore, it is preferable that the membrane module 1 is placed inside a constant temperature bath cooled by a refrigerant during operation and maintained at a temperature similar to that of the raw material gas. If the membrane module 1 is not in an environment cooled by a constant temperature bath or the like, it is preferable that it be insulated by insulating material or vacuum insulation provided around it.

[0034] <Separation membrane> Next, we will describe the configuration of a separation membrane, which is one embodiment to which the present invention is applied, as an example when applied to the membrane module 1 described above. Figure 3 is an enlarged cross-sectional photograph showing a separation membrane 10, which is one embodiment to which the present invention is applied.

[0035] As shown in Figure 3, the separation membrane 10 of this embodiment is a laminated membrane consisting of an intermediate layer 8 supported on a support layer 7 and an active separation layer 9.

[0036] The intermediate layer 8 is located on the support layer 7 and supports the active separation layer 9. By providing the intermediate layer 8 between the support layer 7 and the active separation layer 9, the difference in average pore diameter between adjacent layers can be reduced. In this case, the intermediate layer 8 has an average pore diameter that is smaller than the average pore diameter of the support layer 7 and larger than the average pore diameter of the active separation layer 9.

[0037] The intermediate layer 8 is a layer made of hydrophobic material. Examples of hydrophobic materials include inorganic materials having siloxane bonds (-Si-O-Si-) and carbon materials composed of carbon. Among these, inorganic materials having siloxane bonds are preferred from the viewpoint of low-temperature resistance.

[0038] In this case, if a hydrophilic material is used as the intermediate layer 8, even if high-temperature firing with an inert gas is performed, some moisture that cannot be completely removed remains in the membrane pores. Therefore, at temperatures below 0°C, the moisture remaining in the membrane pores freezes, causing physical blockage and inhibiting gas permeability. In contrast, with the separation membrane 10 of this embodiment, since the intermediate layer 8 is made of a hydrophobic material, no moisture remains in the membrane pores after high-temperature firing, and even at low temperatures below 0°C, blockage due to freezing of residual moisture does not occur, and gas permeability is not inhibited.

[0039] Examples of inorganic materials containing siloxane bonds include sols prepared from organoalkoxysilanes and sols prepared from tetraethoxysilanes. Among these, from the viewpoint of controlling pore size, it is preferable to use a sol prepared from organoalkoxysilanes.

[0040] Examples of organoalkoxysilanes include one or more precursors selected from 1,2-bis(triethoxysilyl)methane (BTESM), 1,2-bis(triethoxysilyl)ethane (BTESE), 1,2-bis(triethoxysilyl)propane (BTESP), and 1,2-bis(triethoxysilyl)benzene (BTESB), and one or more sols obtained from their hydrolysates. Among these, BTESM or BTESE, which are crosslinked with at least a C3 component, preferably with a C2 or lower component, are preferred from the viewpoint of exhibiting properties similar to inorganic materials.

[0041] Examples of gel structures formed by calcining a sol prepared from organoalkoxysilane include cross-linked organosilica represented by the following general formula (1) and side-chain organosilica represented by the following general formula (2).

[0042] [ka]

[0043] [ka]

[0044] In the above general formula (1), the linking group X located between silicon atoms (Si) is an unsaturated hydrocarbon having unsaturated bonds between carbon atoms. The number of carbon atoms in the above unsaturated hydrocarbon is 1 to 6, and preferably 1 to 3. Furthermore, the aforementioned linking group X also includes structures in which some of the hydrogen atoms are replaced by elemental metal ions or compounds such as metal oxides. Examples of metal species that constitute the above-mentioned metal ions or metal oxides include Ag, Cu, Fe, Ni, Co, Al, Ti, and Zr. Note that the metal species listed here are merely examples and are not necessarily limited to these metals.

[0045] Furthermore, in the general formula (1) above, the organic group R is an unsaturated hydrocarbon having unsaturated bonds between hydrogen atoms or carbon atoms with 1 to 10 carbon atoms. The organic group R also includes structures in which some of the hydrogen atoms are replaced by elemental metal ions or compounds such as metal oxides. Examples of metal species that constitute the above-mentioned metal ions or metal oxides include Ag, Cu, Fe, Ni, Co, Al, Ti, and Zr. Note that the metal species listed here are merely examples and are not necessarily limited to these metals.

[0046] In the above general formula (2), the organic group R can be the same as that in the above general formula (1). Furthermore, in the general formula (2) above, OR' is a side chain (pendant) attached to the siloxane bond, and examples of the organic group R' include CH3 and C2H5.

[0047] Examples of side-chain organosilica represented by the above general formula (2) include methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS).

[0048] Examples of carbon materials composed of carbon include carbon films.

[0049] The average pore size of the intermediate layer 8 is not particularly limited, as long as it is smaller than the average pore size of the support layer 7 and larger than the average pore size of the active separation layer 9. It is particularly preferable that the average pore size of the intermediate layer 8 be approximately 2 nm or less. Note that if the average pore size of the intermediate layer 8 is too large, the selectivity during gas separation will decrease. Conversely, if the average pore size of the intermediate layer 8 is too small, the gas permeability will decrease.

[0050] The thickness of the intermediate layer 8 is not particularly limited, as long as it is thick enough to cover the irregularities on the upper surface of the support layer 7 and flatten the active separation layer 9. Examples of such thicknesses include 10 to 500 nm, preferably 50 to 400 nm, and more preferably 100 to 200 nm.

[0051] The activated separation layer 9 is located on the intermediate layer 8 and is a layer that selectively separates desired components from the mixed gas containing the raw material, which is the air-based component. The material of the active separation layer 9 is not particularly limited, as long as it can selectively separate any component from a mixed gas containing air components. Examples of such materials include inorganic materials having a siloxane bond crosslinking structure with organoalkoxysilane as a precursor, and inorganic materials composed of metal oxides such as zirconia, titanium, and iron. Among these, it is preferable to use an inorganic material having a siloxane bond crosslinking structure with organoalkoxysilane as a precursor, from the viewpoint of controlling pore size and hydrophobicity.

[0052] Examples of inorganic materials having a siloxane bond crosslinking structure include sols prepared from organoalkoxysilanes and sols prepared from tetraethoxylanes. Among these, it is preferable to use sols prepared from organoalkoxysilanes from the viewpoint of controlling pore size. By controlling the pore size, it can also be applied to the separation of gases with high diffusion coefficients, such as helium and hydrogen, from mixed gases containing air components.

[0053] Examples of organoalkoxysilanes include one or more precursors selected from 1,2-bis(triethoxysilyl)methane (BTESM), 1,2-bis(triethoxysilyl)ethane (BTESE), 1,2-bis(triethoxysilyl)propane (BTESP), and 1,2-bis(triethoxysilyl)benzene (BTESB), and one or more sols obtained from their hydrolysates. Among these, those with three or fewer carbon atoms in the organic group R (BTESM, BTESE, BTESP) are preferred from the viewpoint of exhibiting properties similar to inorganic materials. This reflects the conventional finding that as the number of carbon atoms in the organic group R increases, it begins to exhibit the properties of organic materials.

[0054] Examples of gel structures formed by calcining a sol prepared from organoalkoxysilane include cross-linked organosilica represented by the following general formula (3) and side-chain organosilica represented by the following general formula (4).

[0055] [ka]

[0056] [ka]

[0057] In the above general formula (3), the linking group X located between silicon atoms (Si) is an unsaturated hydrocarbon having unsaturated bonds between carbon atoms. The number of carbon atoms in the above unsaturated hydrocarbon is 1 to 6, and preferably 1 to 3. Furthermore, the aforementioned linking group X also includes structures in which some of the hydrogen atoms are replaced by elemental metal ions or compounds such as metal oxides. Examples of metal species that constitute the above-mentioned metal ions or metal oxides include Ag, Cu, Fe, Ni, Co, Al, Ti, and Zr. Note that the metal species listed here are merely examples and are not necessarily limited to these metals.

[0058] Furthermore, in the general formula (3) above, the organic group R is an unsaturated hydrocarbon having an unsaturated bond between a hydrogen atom or carbon atoms with 1 to 10 carbon atoms. The organic group R also includes structures in which some of the hydrogen atoms are replaced by elemental metal ions or compounds such as metal oxides. Examples of metal species that constitute the above-mentioned metal ions or metal oxides include Ag, Cu, Fe, Ni, Co, Al, Ti, and Zr. Note that the metal species listed here are merely examples and are not necessarily limited to these metals.

[0059] In the above general formula (4), the organic group R can be the same as that in the above general formula (3). Furthermore, in the general formula (4) above, OR' is a side chain (pendant) attached to the siloxane bond, and examples of the organic group R' include CH3 and C2H5.

[0060] Examples of side-chain organosilica represented by the above general formula (4) include methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS).

[0061] Figure 4 is a schematic diagram showing an example of an inorganic material having a siloxane bond crosslinking structure, where (a) is a structural diagram of a crosslinked organosilica and (b) is a structural diagram of a side-chain organosilica. As the active separation layer 9, it is preferable to use a gel in which the siloxane bonds are substituted with linking groups X, as shown in Figure 4(a). The linking group X is not particularly limited and can be appropriately selected depending on the type of gas to be separated. Examples of linking group X include alkyl groups having 1 to 8 carbon atoms and aromatic groups such as phenyl groups.

[0062] Inorganic materials composed of metal oxides such as zirconia, cobalt, nickel, aluminum, and iron include, for example, composites of precursors such as TEOS and metal nitrates. Among these, cobalt and nickel are preferred from the viewpoint of water vapor resistance. Depending on the target of separation and the separation environment, it can also be applied to the separation of hydrocarbon gases such as hydrogen and propane / propylene from mixed gases containing air components.

[0063] The average pore size of the active separation layer 9 is preferably 1 nm or less. Within this range, oxygen can be selectively separated from a mixed gas containing air components.

[0064] Specifically, for example, if the average pore size of the active separation layer 9 is 1 nm or less, oxygen can be selectively separated from a mixed gas containing air components. When selectively separating oxygen from a mixed gas containing air components, the average pore size of the active separation layer 9 is more preferably 0.1 nm to 0.8 nm, and particularly preferably 0.2 nm to 0.6 nm.

[0065] The thickness of the active separation layer 9 is not particularly limited, as long as it is a thickness that allows for the selective separation of any component from a mixed gas containing air components. Examples of such thicknesses include 200 to 300 nm, preferably 100 to 200 nm, and more preferably 50 to 100 nm.

[0066] The separation membrane 10 of this embodiment selectively separates any component from a mixed gas containing air components under operating conditions of -196°C to 0°C. Here, "permeance," an indicator of the performance of the separation membrane, is defined as the value obtained by dividing the molar flow rate that has permeated the membrane by the outer surface area of ​​the membrane and the gas partial pressure.

[0067] For example, if a sol obtained from BTESP is used as the active separation layer 9 and a sol prepared from BTESE is used as the intermediate layer 8, the separation membrane 10 of this embodiment becomes an oxygen separation membrane that permeates oxygen from a mixed gas containing air components. In this case, the performance of the separation membrane 10 of this embodiment is such that, under operating conditions of -196°C to 0°C, the oxygen permeability is at least 1 × 10⁻¹⁰. -8 [mol / (m 2 (·s·Pa) or more, 1 × 10 -6 [mol / (m 2 It is preferable that the value is above (·s·Pa).

[0068] Furthermore, if the separation membrane 10 in this embodiment is an oxygen separation membrane, the performance of the separation membrane 10 preferably has an oxygen / argon permeability ratio of at least 4, and more preferably 10 or higher. With such performance, the separation membrane 10 of this embodiment can be used to separate oxygen and argon from a mixed gas containing oxygen and argon.

[0069] (Method for manufacturing separation membranes) The method for manufacturing the separation membrane 10 of this embodiment, as shown in Figures 2 and 3, will be described in detail. First, a porous alumina tube (average pore size: 1 μm, porosity: approximately 50%) is used as the support layer 7, and an intermediate layer 8 is formed on the surface of the support layer 7.

[0070] It is preferable to first homogenize the surface of the support layer 7 before forming the intermediate layer 8. For the material used for homogenization, it is preferable to use fine particles of the same material as the porous substrate used as the support layer 7. For example, if alumina is used as the porous substrate, it is preferable to support fine alumina particles of the same material on the surface of the porous substrate and homogenize them. The alumina nanoparticles can be supported on a porous substrate by using a sol of the same material as the material used to form the intermediate layer 8 (for example, a sol obtained from organoalkoxysilane) as a binder, dispersing the alumina nanoparticles in the binder, applying it to the surface of the porous substrate, drying, and firing. It is also preferable to homogenize the surface of the porous substrate by performing the above process multiple times, in which case it is preferable to gradually reduce the size of the alumina nanoparticles dispersed in the binder.

[0071] An intermediate layer 8 is formed on the homogenized support layer 7. The intermediate layer 8 is preferably formed by a hot coating method as follows. In the hot coating method, the porous substrate is preheated to about 170°C to 180°C, a dilute solution of a sol obtained from organoalkoxysilane is applied to the surface of the porous substrate, and the intermediate layer 8 is formed by firing. Note that the above process may be repeated multiple times to obtain an intermediate layer 8 of the desired thickness.

[0072] Next, an active separation layer 9 is formed on the surface of the intermediate layer 8. Specifically, the active separation layer 9 is formed by condensation polymerization of organoalkoxysilane using the sol-gel method. First, hydrochloric acid or nitric acid is added as an acid to an ethanol solution at 50°C with a water / silica ratio, and the mixture is stirred for about 1 hour. Then, to thin the resulting sol, it is coated onto the preheated intermediate layer and sintered. After that, it is fired at 300°C under a nitrogen atmosphere to obtain a gel in which siloxane bonds are replaced in the shaded areas (see Figure 4).

[0073] As described above, the separation membrane 10 of this embodiment and the membrane module 1 using it have an intermediate layer 8 made of a hydrophobic material, and therefore exhibit excellent permeability characteristics even when used in low-temperature environments below room temperature (-196°C to 0°C), just as they do at room temperature. Therefore, the separation membrane 10 of this embodiment, and the membrane module 1 using it, can maintain their membrane performance even at extremely low temperatures, such as when an air separation device is in operation.

[0074] It should be noted that the technical scope of the present invention is not limited to the embodiments described above, and also includes designs and the like that do not depart from the spirit of the present invention. [Examples]

[0075] The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following description.

[0076] <Example 1> A separation unit (separation membrane) with the configuration shown in Figure 2 was created under the following conditions, and the temperature dependence of the air system components in the temperature range from room temperature to -30°C was evaluated.

[0077] (Materials used) • Support section: Non-perforated alumina tube (length 200 mm) • Support layer: Porous alumina tube (Outer diameter: 10 mm, Length: 100 mm, Average pore size: 1 μm, Porosity: approx. 50%) • Intermediate layer: BTESE gel is supported as a hydrophobic material (thickness: 200-300 nm) • Active separation layer: Supported with BTESP polymer gel (thickness: 50-100 nm)

[0078] (Preparation ratio) ·Middle layer ···BTESE:H2O:HCl=1:240:0.1 ·Active separation layer ··BTESP:H2O:HCl=1:200:0.1

[0079] (Film forming method) After supporting a support layer (α-Al2O3) with fine particles of Al2O3 dissolved in water, the material was fired at 300°C for 15 minutes in an N2 atmosphere. This process was repeated several times. As an intermediate layer, the BTESE sol prepared according to the above ratio was applied to a preheated support layer and sintered to support it. Then, it was fired at 300°C under an N2 atmosphere. This process was repeated several times. As the active separation layer, the BTESP sol prepared according to the above ratio was coated onto a preheated support layer and sintered to support it. Then, it was fired at 300°C under an N2 atmosphere. This process was repeated several times. The fabricated separation membrane was placed inside a membrane module and fired again at 300°C.

[0080] (evaluation) Various pure gases were supplied to the prepared separation unit (separation membrane) under the following conditions, and the permeance of each gas was measured. The results are shown in Figure 5. • Gas types: Hydrogen (H2), Helium (He), Oxygen (O2), Argon (Ar), Nitrogen (N2) • Gas temperature: -30 to 200°C • Flow rate through the membrane: 1 L / min • Outer surface area of ​​the membrane: 3.14 × 10 -3 m 2 Primary pressure: 200 kPaG Secondary pressure: atmospheric pressure

[0081] Figure 5 shows the temperature dependence of the permeance when various gases permeate the separation unit (separation membrane) of Example 1. In Figure 5, the first X-axis (bottom) represents the reciprocal of the operating temperature [K] multiplied by 1000, the second X-axis (top) represents the gas temperature, and the Y-axis represents the permeance. As shown in Figure 5, the separation unit (separation membrane) of Example 1 uses a layer made of a hydrophobic material as an intermediate layer, and it was confirmed that the permeability of various gases falls on the extrapolation line at room temperature. In other words, it was confirmed that the membrane performance is maintained even at -30°C by using a hydrophobic material for the intermediate layer of the separation membrane.

[0082] <Comparative Example 1> Similar to Example 1, a separation unit (separation membrane) was prepared, and the temperature dependence of the air system components in a temperature range from room temperature to -30°C was evaluated.

[0083] (Materials used) Except for changing the intermediate layer, the procedure was the same as in Example 1. • Intermediate layer: Gel using SiO2-ZrO2 is supported (thickness: 200-300 nm)

[0084] (Film forming method) Except for the intermediate layer, the procedure was the same as in Example 1. To prepare the SiO2-ZrO2 colloidal sol, first, ethanol was added to a 500 ml flask, and the Si precursor TEOS, water, and the acid catalyst hydrochloric acid were added and stirred at room temperature for 3 hours. Next, the Zr precursor ZrTBt, water, and hydrochloric acid were added and stirred for 12 hours. After stirring, more water and hydrochloric acid were added and stirred at room temperature for 10 minutes. Then, to control the particle size, a predetermined amount of hydrochloric acid was added, and water was added up to the 500 ml mark. Finally, by boiling and stirring (200°C) for 8 hours, an SiO2-ZrO2 colloidal sol with a particle size of 20-30 nm was obtained. As an intermediate layer, the obtained SiO2-ZrO2 colloidal sol was coated onto a preheated support layer and sintered to support it. Then, it was fired at 350°C under an N2 atmosphere. This process was repeated several times.

[0085] (evaluation) The permeance of various gases was measured when they permeated the fabricated separation unit (separation membrane) under the following conditions. The results are shown in Figure 6. • Gas types: Hydrogen (H2), Helium (He), Argon (Ar), Nitrogen (N2) • Gas temperature: -30 to 200°C • Molar flow rate permeating the membrane: 1 L / min • Outer surface area of ​​the membrane: 3.14 × 10 -3 m 2 Primary pressure: 200 kPaG Secondary pressure: atmospheric pressure

[0086] Figure 6 shows the temperature dependence of the permeance when various gases permeate the separation unit (separation membrane) of Comparative Example 1. In Figure 6, the first X-axis (bottom) represents the reciprocal of the operating temperature [K] multiplied by 1000, the second X-axis (top) represents the gas temperature, and the Y-axis represents the permeance. As shown in Figure 6, the separation unit (separation membrane) of Comparative Example 1 uses a layer made of "SiO2-ZrO2" as an intermediate layer, and it was confirmed that the permeability of all gases decreased significantly at temperatures below 10°C. In other words, it was confirmed that using a hydrophilic material for the intermediate layer of the separation membrane causes it to be affected by water vapor remaining on the membrane surface or in the supplied gas, resulting in a decrease in membrane performance under low-temperature conditions.

[0087] <Example 2> A separation unit (separation membrane) with the configuration shown in Figure 2 was created under the following conditions, and the temperature dependence of the air system components in the temperature range from room temperature to -115°C was evaluated.

[0088] (Materials used) • Support section: Non-perforated alumina tube (length 200 mm) • Support layer: Porous alumina tube (Outer diameter: 10 mm, Length: 100 mm, Average pore size: 1 μm, Porosity: approx. 50%) • Intermediate layer: BTESE gel is supported as a hydrophobic material (thickness: 200-300 nm) • Active separation layer: Supports BTESM gel (thickness: 50-100 nm)

[0089] (Preparation ratio) ·Middle layer ···BTESE:H2O:HCl=1:240:0.1 ·Active separation layer ···BTESM:H2O:HCl=1:200:0.1

[0090] (Film forming method) After supporting a support layer (α-Al2O3) with fine particles of Al2O3 dissolved in water, the material was fired at 300°C for 15 minutes in an N2 atmosphere. This process was repeated several times. As the intermediate layer, the BTESE sol prepared at the above preparation ratio was sintered and supported by applying it onto a pre-heated support layer. Then, it was fired under the condition of 300 °C in a N2 atmosphere. This was repeated several times. As the active separation layer, the BTESM sol prepared at the above preparation ratio was sintered and supported by applying it onto a pre-heated support layer. Then, it was fired under the condition of 300 °C in a N2 atmosphere. This was repeated several times. The prepared separation membrane was stored in a membrane module and fired again at 300 °C.

[0091] (Evaluation) The permeance when various gases permeated through the prepared separation unit (separation membrane) was measured under the following conditions. The results are shown in Fig. 7. · Gas species: hydrogen (H2), helium (He), oxygen (O2), argon (Ar), nitrogen (N2) · Gas temperature: -115 to 200 °C · Molar flow rate permeating through the membrane: 1 L / min · Outer surface area of the membrane: 3.14×10 -3 m 2 · Primary side pressure: 200 kPaG · Secondary side pressure: atmospheric pressure

[0092] Fig. 7 is a diagram showing the temperature dependence of the permeance when various gases permeate through the separation unit (separation membrane) of Example 1. In Fig. 7, the first X-axis (lower) shows 1000 times the reciprocal of the operating temperature [K], the second X-axis (upper) shows the gas temperature, and the Y-axis shows the permeance. As shown in Fig. 7, since the intermediate layer of the separation membrane of Example 1 is a hydrophobic material, it was confirmed that the membrane performance was maintained without the separation membrane being damaged even at -115 °C.

Explanation of symbols

[0093] 1... membrane module 2... membrane module body 2A... space 3…Separate ユニット 3A…Separation Section 3B…Support Department 4…Raw Material Inlet Section 5…Through the ingredient export section 6…Non-permeable component extraction section 7…Support Layer 8…Intermediate layer 9…Active Separation Layer 10…Separation membrane

Claims

1. A separation membrane for separating air-based components, The operating conditions are -196°C to 0°C. The separation membrane is a laminated film consisting of an active separation layer and an intermediate layer formed of a compound having siloxane bonds. A separation membrane in which the compound having the siloxane bond is a gel formed by calcining a sol prepared from an organoalkoxysilane.

2. The separation membrane according to claim 1, wherein the active separation layer is a layer formed of a compound having a siloxane bond crosslinking structure.

3. The separation membrane according to claim 1, wherein the dew point of the water contained in the gas to be separated is -50°C or lower.

4. A membrane module comprising a separation section having the separation membrane described in claim 1, on a support layer made of a porous substrate.

5. The membrane module body in which the separation part is located in the inner space, A raw material introduction unit for introducing raw materials containing air-based components into the main body of the membrane module, A permeable component extraction unit that extracts the component that permeates through the separation unit from the module body, The membrane module according to claim 4, further comprising: a non-permeable component discharge unit for dischargeing components that do not permeate the separation unit from the module body.

6. The membrane module according to claim 5, wherein the support layer is hollow and cylindrical.

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