Membrane module

Abstract

To provide an oxygen separation membrane which has selectivity on oxygen of a mixed gas containing air system components even when used in a low temperature environment (lower than an ordinary temperature, i.e., -196°C to 0°C), and to provide a membrane module.SOLUTION: An oxygen separation membrane 10 selectively separates oxygen from a mixed gas containing air system components and its operation condition is -196°C to 0°C. The oxygen separation membrane 10 has a layer formed of an inorganic material having a bridge structure by a siloxane bond.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an oxygen separation membrane and a membrane module.

Background Art

[0002] [[ID=ll]] For the separation of the three main components (nitrogen, oxygen, argon) contained in air, adsorption separation, cryogenic separation, and membrane separation are mainly adopted.

[0003] Adsorption separation utilizes physical or chemical actions and separates specific components from other components by taking in specific components into the sites of the adsorbent. For example, in a nitrogen / oxygen system using molecular sieve as an adsorbent, since nitrogen exhibits strong adsorptivity, oxygen, which is the other component, becomes the product. In addition, in order to perform the adsorption operation and the desorption operation, it is necessary to swing the pressure or temperature, but both operations are performed at or above room temperature. In particular, at low temperatures, the desorption operation becomes difficult.

[0004] Cryogenic separation separates air system components by distillation using vapor-liquid equilibrium. In cryogenic separation, since it is necessary to operate under conditions where gas and liquid coexist, the operating temperature is in the vicinity of its dew point (-196°C to -100°C), and it is carried out at extremely low temperatures. In addition, in cryogenic separation, in order to impart energy for liquefying and separating air, a plurality of compression / expansion strokes are required, and a tray column and a packed column for distillation are required. Furthermore, due to the constraints of vapor-liquid equilibrium, the argon / oxygen system is difficult to separate, and many distillation steps are required.

[0005] Membrane separation separates a mixture by utilizing a sieve of membrane pores. Therefore, it is not subject to the constraints of vapor-liquid equilibrium such as relative volatility. In membrane separation, since it is generally advantageous for the mixture to pass through the inner wall of the pores when the molecular kinetic energy is high, it is carried out at a very high temperature (for example, 500°C to 800°C).

[0006] Incidentally, porous silica membranes are known to be 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 pass (see Non-Patent Document 1). [Prior art documents] [Non-patent literature]

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

[0008] However, in membrane separation, when separation is performed in phase (e.g., gas phase and gas phase), separation membranes applicable to commercial operation, such as nitrogen / oxygen systems, have not yet been obtained due to the mechanism utilizing differences in molecular diffusivity and the presence of pore size distribution. Furthermore, conventional gas separation membranes using porous silica membranes could not achieve high purity and high selectivity for oxygen in mixed gases containing air components at low temperatures (below room temperature; -196°C to 0°C).

[0009] The present invention has been made in view of the above circumstances, and aims to provide an oxygen separation membrane and membrane module that exhibit selectivity for oxygen in a mixed gas containing air components, even when used in a low-temperature environment (below room temperature; -196°C to 0°C). [Means for solving the problem]

[0010] To solve the above problems, the present invention has the following configuration. [1] An oxygen separation membrane for selectively separating oxygen from a mixed gas containing air components, The operating conditions are -196℃ to 0℃. An oxygen separation membrane having a layer made of an inorganic material having a siloxane bond crosslinking structure. [2] The oxygen permeability is at least 1 × 10⁻⁶ -8 [mol / (m 2 The oxygen separation membrane described in [1] is of the following magnitude (s·Pa): [3] The oxygen separation membrane according to [1] or [2], wherein the oxygen / argon transmittance ratio is 4 or greater. [4] An oxygen separation membrane according to any one of [1] to [3], wherein the operating pressure of the separation membrane is in the range of 0.15 to 5.043 MPa. [5] An oxygen separation membrane according to any one of [1] to [4], which is a laminated film comprising an activated separation layer made of an inorganic material and an intermediate layer made of a hydrophobic material. [6] The oxygen separation membrane according to [5], wherein the hydrophobic material is an inorganic material having siloxane bonds. [7] An oxygen separation membrane according to any one of [1] to [6], wherein the mixed gas to be separated contains at least oxygen and no water. [8] An oxygen separation membrane according to any one of [1] to [6], wherein the dew point of the water contained in the mixed gas to be separated is -50°C or lower. [9] A membrane module comprising a separation section having an oxygen separation membrane according to any one of [1] to [8] on a support layer made of a porous substrate.

[10] 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 [9] further comprises a non-permeable component discharge unit for dischargeing components that do not permeate the separation unit from the module body.

[11] The membrane module according to [9] or

[10] , wherein the support layer is hollow and cylindrical. [Effects of the Invention]

[0011] The oxygen separation membrane and membrane module of the present invention exhibit selectivity for oxygen in a mixed gas containing air components, even when used in a low-temperature environment (below room temperature; -196°C to 0°C).

Brief Description of the Drawings

[0012] [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 an oxygen separation membrane which is an embodiment to which the present invention is applied. [Figure 4] It is a schematic view showing an example of an inorganic material having a crosslinked structure of a siloxane bond, where (a) shows a structural diagram of a bridged organosilica and (b) shows a structural diagram of a side-chain organosilica, respectively. [Figure 5] It is a diagram showing the pressure difference dependence of the permeance when various gases permeate in an example of the present invention, between the primary side and the secondary side of the membrane. [Figure 6] It is a schematic view for explaining a mechanism in which a permeating component inhibits adsorption to the pore surface of an active separation layer in an example of the present invention.

Mode for Carrying Out the Invention

[0013] Hereinafter, the oxygen separation membrane of the present invention will be described in detail with reference to the drawings together with a membrane module using the same. Note that the drawings used in the following description may show, for the sake of clarity of the features, the characteristic parts enlarged for convenience, and the dimensional ratios of each component etc. are not necessarily the same as the actual ones.

[0014] 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.

[0015] <Membrane Module> First, the configuration of a membrane module which is an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view schematically showing the configuration of a membrane module which is an 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.

[0016] 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.

[0017] 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.

[0018] 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 an oxygen separation membrane 10 on the support layer 7 for separating air-based components.

[0019] The support layer 7 is a hollow cylindrical member that supports the oxygen separation membrane 10. By supporting the oxygen separation membrane 10 on the support layer 7, the mechanical strength of the separation section 3A can be increased.

[0020] The material of the support layer 7 is not particularly limited, as long as it is a porous substrate that allows oxygen to permeate from the mixed gas containing the air-based components used as raw materials. 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 oxygen 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.

[0021] 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.

[0022] 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%).

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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 oxygen separation membrane 10. Examples of the separation unit 3's shape include cylindrical and rectangular prism shapes.

[0027] 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.

[0028] The raw material to be separated is a mixed gas containing at least oxygen, one of the three major components of air (nitrogen, oxygen, and argon), and containing two or more components in total. 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.

[0029] 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 of the separation unit 3 (i.e., the oxygen separation membrane 10) from the membrane module body 2.

[0030] 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.

[0031] 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 oxygen separation membrane 10) from the space 2A inside the membrane module body 2.

[0032] The membrane module 1 of this embodiment selectively separates oxygen 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.

[0033] <Oxygen separation membrane> Next, we will describe the configuration of an oxygen separation membrane, which is one embodiment to which the present invention is applied, as an example of its application to the membrane module 1 described above. Figure 3 is an enlarged cross-sectional photograph showing an oxygen separation membrane 10, which is one embodiment to which the present invention is applied.

[0034] As shown in Figure 3, the oxygen 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.

[0035] 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.

[0036] The material constituting the intermediate layer 8 is not particularly limited, but it is preferably a 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.

[0037] 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.

[0038] 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.

[0039] 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).

[0040] [ka]

[0041] [ka]

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Examples of side-chain organosilica represented by the above general formula (2) include methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS).

[0046] Examples of carbon materials composed of carbon include carbon films.

[0047] 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.

[0048] 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.

[0049] The activated separation layer 9 is located on the intermediate layer 8 and is a layer that selectively separates oxygen from a mixed gas containing air components under low temperature and high pressure conditions. The material of the active separation layer 9 is not particularly limited, as long as it can selectively separate oxygen 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.

[0050] Examples of inorganic materials having a siloxane bond crosslinking structure include sols prepared from organoalkoxysilanes and sols prepared from tetraethoxylanes. Among these, from the viewpoint of controlling pore size, it is preferable to use a sol prepared from organoalkoxysilanes.

[0051] 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.

[0052] 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).

[0053] [ka]

[0054] [ka]

[0055] 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.

[0056] 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.

[0057] 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.

[0058] Examples of side-chain organosilica represented by the above general formula (4) include methyltriethoxysilane (MTES) and methyltrimethoxysilane (MTMS).

[0059] 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.

[0060] 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.

[0061] 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 oxygen from the 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.

[0062] The oxygen separation membrane 10 of this embodiment selectively separates oxygen 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.

[0063] For example, when 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 performance of the oxygen separation membrane 10 in this embodiment is such that, under operating conditions of -196°C to 0°C, the oxygen permeability is at least 1 × 10⁻¹⁶. -8 [mol / (m 2 (·s·Pa) or more, 1 × 10 -6 [mol / (m 2 It is preferable that the value is above (·s·Pa).

[0064] Furthermore, the performance of the oxygen separation membrane 10 in this embodiment preferably has an oxygen / argon permeability ratio of at least 4, and more preferably 10 or higher. With such performance, the oxygen separation membrane 10 of this embodiment can be used to separate oxygen and argon from a mixed gas containing oxygen and argon.

[0065] (Method for manufacturing separation membranes) The method for manufacturing the oxygen 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.

[0066] 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.

[0067] 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.

[0068] 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).

[0069] As described above, the oxygen separation membrane 10 of this embodiment and the membrane module 1 using it have an active separation layer 9 made of an inorganic material having a siloxane bond crosslinking structure, and therefore exhibit selectivity for oxygen in a mixed gas containing air components under low temperature and high pressure conditions. Furthermore, since the oxygen separation membrane 10 of this embodiment and the membrane module 1 using it have an intermediate layer 8 made of a hydrophobic material, they exhibit excellent oxygen selectivity even when used in low-temperature environments below room temperature (-196°C to 0°C), just as they do at room temperature. Therefore, the oxygen separation membrane 10 of this embodiment, and the membrane module 1 using the same, can maintain oxygen selectivity even at extremely low temperatures, such as when an air separation device is in operation.

[0070] 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]

[0071] The present invention will be specifically described below through verification tests, but the present invention is not limited to the following description.

[0072] <Verification Test> The oxygen separation membrane of the present invention was fabricated, and the dependence of the air system components on pure gas pressure at room temperature (30°C) and low temperature (-115°C) was evaluated.

[0073] (Separation unit) A separation unit (oxygen separation membrane) with the configuration shown in Figure 2 was manufactured under the following manufacturing conditions.

[0074] [Support layer] • Porous alumina tube (average pore size: 1 μm, porosity: approximately 50%)

[0075] [Middle class] • A gel using BTESE as a hydrophobic material is supported (average pore size: 10-20 nm). "Manufacturing method and conditions" • Adjust the mixture in ethanol solvent to BTESM:H2O:HCl:=1:200:0.1 (BTESE:2wt%). By stirring at 50°C for 60 minutes, a hydrolysis-condensation reaction is carried out to prepare BTESM sol. "Film forming" Two types of α-alumina particles were coated onto the surface of an α-alumina porous tube (average pore size: coarse: 1.2 μm, fine: 0.5 μm). BTESE gel was then loaded onto the tube several times using a hot coating method and fired at 300°C in a nitrogen atmosphere for 30 minutes. This process was repeated several times.

[0076] [Active separation layer] • Sol is supported using BTESM (average pore size: 0.7~1.2 nm) "Manufacturing method and conditions" • Adjust the mixture in ethanol solvent to BTESM:H2O:HCl:=1:200:0.1 (BTESM:2wt%). By stirring at 50°C for 60 minutes, a hydrolysis-condensation reaction is carried out to prepare BTESM sol. "Film forming" The BTESM gel was repeatedly loaded onto the intermediate layer using a hot coating method and then fired at 300°C in a nitrogen atmosphere for 30 minutes. This process was repeated several times.

[0077] (evaluation) The permeance of various gases was measured when they permeated the fabricated separation unit (oxygen separation membrane) under the following conditions. The results are shown in Figure 5. • Gas types: Oxygen (O2), Argon (Ar), Nitrogen (N2) • Gas temperature: -115℃, 30℃ • Primary pressure of the membrane: 200-600 (kPa) • Secondary pressure of the membrane: atmospheric pressure • Molar flow rate through the membrane: 1 (L / min) • Outer surface area of ​​the membrane: 3.14 × 10 -3 (m 2 )

[0078] Figure 5 shows the dependence of the permeance of various gases on the pressure difference between the primary and secondary sides of the membrane when various gases permeate the fabricated separation unit (oxygen separation membrane). In Figure 5, the X axis represents the pressure difference between the primary and secondary sides of the membrane, and the Y axis represents the permeance. As shown in Figure 5, at 30°C, the permeability of all gas components was constant regardless of the pressure difference between the primary and secondary sides of the membrane. This indicates that the amount of permeation per unit thrust is constant, and that there is no change in the permeation mechanism by which gases permeate through the membrane pores at or near room temperature and atmospheric pressure.

[0079] On the other hand, at -115°C, the permeability of oxygen alone decreased with increasing pressure difference between the primary and secondary sides of the membrane. Since the reproducibility of the membrane performance after this phenomenon occurred was confirmed, it was determined that the cause was not the breakdown or change of the membrane material due to the decrease in temperature and the increase in pressure on the primary side of the membrane.

[0080] Furthermore, since pure gas was used in this verification test, interference from other components is unlikely. In other words, as shown in Figure 6, it is thought that the permeation of oxygen is inhibited because it is adsorbed onto the pore surface of the activated separation layer, or aggregates through a similar phenomenon.

[0081] Furthermore, conventional nitrogen / oxygen-based PSA (Pressure Swing Adsorption) systems primarily adsorbed nitrogen, resulting in oxygen as the final product. Consequently, in conventional PSA systems, argon, which is difficult to separate from oxygen, remained as an impurity in the product and could not be removed.

[0082] In contrast, the separation unit (oxygen separation membrane) of the present invention captures only the most diffusive oxygen within the pores of the activated separation layer, suggesting that it is possible to obtain oxygen with the argon component removed (see Figure 6). [Explanation of symbols]

[0083] 1…Membrane module 2…Membrane module body 2A…Space 3…Separation Unit 3A…Separation part 3B…Support part 4...Raw material introduction section 5...Transmission component derivation section 6...Non-transparent component derivation section 7…Support layer 8…Middle class 9…Active separation layer 10…Oxygen separation membrane

Claims

1. A membrane module comprising a separation section having an oxygen separation membrane on a support layer made of a porous substrate, The oxygen separation membrane is an oxygen separation membrane that selectively separates oxygen from a mixed gas containing air components, The separation operation conditions for the separation unit are -196°C to 0°C. The separation section comprises an active separation layer formed of a compound having a siloxane bond crosslinking structure, an intermediate layer formed of a compound having a siloxane bond, and a support layer. A membrane module characterized in that the average pore diameter of the active separation layer is smaller than the average pore diameter of the intermediate layer, and the average pore diameter of the intermediate layer is smaller than the average pore diameter of the support layer.

2. The oxygen permeability of the separation unit is at least 1 × 10 －８ [mol / (m ２ The membrane module according to claim 1, wherein the pressure is sPa or greater.

3. The membrane module according to claim 1 or 2, wherein the oxygen / argon transmittance ratio of the separation section is 4 or more.

4. The membrane module according to claim 1 or 2, used for separating the mixed gas, wherein the external pressure of the separation section is in the range of 0.15 to 5.043 MPa.

5. The membrane module according to claim 1 or 2, wherein the compound having a siloxane bond that forms the intermediate layer is a gel formed by calcining a sol prepared from an organoalkoxysilane.

6. The membrane module according to claim 5, wherein the sol prepared from the organoalkoxysilane is one or more sols obtained from one or more precursors selected from 1,2-bis(triethoxysilyl)methane, 1,2-bis(triethoxysilyl)ethane, 1,2-bis(triethoxysilyl)propane, and 1,2-bis(triethoxysilyl)benzene, and hydrolysates thereof.

7. The membrane module according to claim 1 or 2, wherein the mixed gas to be separated contains at least oxygen and no water.

8. The membrane module according to claim 1 or 2, wherein the dew point of the water contained in the mixed gas to be separated is -50°C or lower.

9. 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 permeation component discharge unit discharges the component that permeates through the separation unit from the main body of the membrane module, The membrane module according to claim 8, further comprising: a non-permeable component guide-out section for guideing out components that do not permeate the separation section from the membrane module body.

10. The membrane module according to claim 9, wherein the support layer is in the shape of a hollow cylinder.

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