Method for producing gas separation membrane and gas separation membrane

Abstract

To provide a gas separation membrane which dispenses with an alumina fine particle layer and an amorphous intermediate layer between a support and a separation layer, has high permeation rate and separation factor, and has high performance, and a method for producing the same.SOLUTION: A method for producing a gas separation membrane 10 includes: a first separation layer formation step of forming a first separation layer 2 having gas separability on one surface of a substrate 1 as a support; and a substrate hole formation step of forming a plurality of holes 3 penetrating from the other surface of the substrate 1 to the one surface of the substrate 1 by etching. The plurality of holes 3 have circular or rectangular cross-sectional shapes, and have lengths around the cross section of 1 to 1,000 micrometers, and a distance between centers of the holes of 1 to 1,000 micrometers.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for producing a gas separation membrane and a gas separation membrane. [Background technology]

[0002] Gas separation membranes made of zeolite, carbon, and silica membranes with nanometer-sized pores are being put to practical use to separate specific types of gas from a gas mixture. Since molecules have different sizes, they pass through nanometer-sized pores at different speeds. Taking advantage of the ratio of these permeation speeds (separation factor), a separation membrane is formed using a support.

[0003] Although high separation factors have been achieved through research into zeolite membranes, carbon membranes, and silica membranes (e.g., Non-Patent Document 1), the trade-off between the separation factor and the permeability factor remains a challenge in designing separation membranes, and efforts have been made to improve materials and permeability mechanisms.

[0004] Here, the structure of a conventionally used gas separation membrane is shown in FIG. 7. A gas separation membrane 70 is formed in a cylindrical shape, and FIG. 7 shows an enlarged schematic structure of a cross section. A separation layer 71 having gas separation properties is made of zeolite, carbon, and silica with a thickness of about 50 nm, but the separation layer 71 alone cannot maintain its structure. For this reason, a porous base material such as alumina having a thickness of 0.1 mm to several mm is used as a support 72. For example, porous alumina has a structure with a pore diameter of about 1 micrometer, but even if a separation layer is formed on such a porous support, the separation layer cannot be formed directly above the alumina pores, and pinholes are generated. Therefore, the generation of pinholes is suppressed by sandwiching an alumina fine particle layer or an amorphous intermediate layer 73 between the separation layer 71 and the support 72. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Kanesashi, “Network structure control and permeation property evaluation of silica-based gas separation membranes”, Membrane, 41(4), 183-188(2016) Summary of the Invention [Problem to be solved by the invention]

[0006] Although molecules can permeate through the alumina fine particle layer and the amorphous intermediate layer 73, they experience a large permeation resistance compared to the porous alumina support 72. Therefore, this intermediate layer 73 is a factor that reduces the molecular permeation rate in the gas separation membrane.

[0007] The present inventors have found that by applying MEMS technology used in semiconductor manufacturing and the like, it is possible to manufacture a gas separation membrane that does not require an alumina fine particle layer or an amorphous intermediate layer.

[0008] Therefore, an object of the present invention is to provide a high-performance gas separation membrane that does not require an alumina fine particle layer or an amorphous intermediate layer between the support and the separation layer and has a high permeation rate and separation factor, and a method for producing the same. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the method for manufacturing a gas separation membrane of the present invention is characterized by including a first separation layer formation step of forming a first separation layer having gas separation properties on one side of a substrate serving as a support, and a substrate hole formation step of forming a plurality of holes that extend from the other side of the substrate to one side of the substrate by etching.

[0010] In addition, the gas separation membrane manufacturing method of the present invention is characterized in that the multiple holes have a circular or rectangular cross-sectional shape, a peripheral length of the cross section of 1 to 1,000 micrometers, and a distance between the centers of the holes of 1 to 1,000 micrometers.

[0011] Furthermore, the gas separation membrane manufacturing method of the present invention is characterized by including a second separation layer formation step of forming a second separation layer having gas separation properties different from those of the first separation layer between the first separation layer and the substrate, or forming the second separation layer within the multiple holes so as to be in contact with the first separation layer, or forming the second separation layer along the other side of the substrate and the surfaces of the multiple holes.

[0012] The gas separation membrane manufacturing method of the present invention may also include an etching stopper film formation step of forming an etching stopper film between the first separation layer and one side of the substrate, and an etching stopper film removal step of removing the etching stopper film within the multiple holes.

[0013] In order to achieve the above-mentioned object, the gas separation membrane of the present invention is a gas separation membrane comprising a substrate serving as a support and a first separation layer having gas separation properties formed on one side of the substrate, wherein the substrate has a plurality of holes formed by etching from the other side to one side of the substrate.

[0014] In addition, the gas separation membrane of the present invention is characterized in that the multiple holes have a circular or rectangular cross-sectional shape, a peripheral length of the cross section of 1 to 1,000 micrometers, and a center-to-center distance between holes of 1 to 1,000 micrometers.

[0015] Furthermore, the gas separation membrane of the present invention comprises a second separation layer having gas separation properties different from those of the first separation layer, which is formed between the first separation layer and the substrate, or within the plurality of holes so as to be in contact with the first separation layer, or along the other side of the substrate and the surfaces of the plurality of holes.

[0016] The gas separation membrane of the present invention may further comprise an etching stopper film between the first separation layer and one surface of the substrate. Effect of the Invention

[0017] The gas separation membrane and the method for producing the gas separation membrane of the present invention do not require an alumina fine particle layer or an amorphous intermediate layer between the support and the separation layer, and can have a high permeation rate and separation factor. [Brief description of the drawings]

[0018] [Figure 1] 1 is a flowchart showing a method for producing a gas separation membrane according to a first embodiment of the present invention. [Diagram 2] 5 is a flowchart showing a method for producing a gas separation membrane according to a second embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic cross-sectional view of a gas separation membrane according to a third embodiment of the present invention. [Figure 4] FIG. 1 is a schematic cross-sectional view of a gas separation membrane according to a fourth embodiment of the present invention. [Diagram 5] 4 is a flowchart showing a method for producing a gas separation membrane. [Figure 6] FIG. 11 is a schematic cross-sectional view of a gas separation membrane according to a fifth embodiment of the present invention. [Figure 7] FIG. 1 is a schematic cross-sectional view of a conventional gas separation membrane. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, the embodiments of the present invention will be described in more detail, but the present invention is not limited to the embodiments described in this specification. In addition, the same components and steps are given the same reference numerals, and duplicated explanations will be omitted.

[0020] (First embodiment) Fig. 1 is a flow chart showing a manufacturing method of a first embodiment of a gas separation membrane of the present invention. A schematic cross-sectional view of a gas separation membrane 10 of the first embodiment is shown in the bottom part of Fig. 1. The gas separation membrane 10 comprises a substrate 1 serving as a support, and a separation layer 2 (first separation layer of the present invention) having gas separating properties formed on one side (front side) of the substrate 1. Furthermore, a plurality of holes 3 are formed in the substrate 1 in a substantially vertical direction from one side (front side) to the other side (back side) of the substrate 1.

[0021] A method for producing gas separation membrane 10 will be described below with reference to Fig. 1. The method for producing gas separation membrane 10 includes, in this order, a first separation layer forming step ST1, a back surface preparation processing step ST2, and a substrate hole forming step ST3 for forming a plurality of holes 3 by etching.

[0022] The first separation layer forming step ST1 is a step of forming a separation layer 2 on the surface of a smooth substrate 1 made of silicon or quartz by a well-known method such as coating and drying, coating and baking, chemical vapor deposition, physical vapor deposition, etc. The separation layer 2 can be arbitrarily selected from zeolite, carbon, and silica.

[0023] The back surface preparation process ST2 is a process in which the substrate 1 on which the separation layer 2 has been formed in the first separation layer formation process ST1 is turned over, and a necessary preparatory lowering is performed for the substrate hole formation process ST3 described later.

[0024] The substrate hole forming step ST3 is a step of forming a plurality of holes 3 by etching using a pattern generated by lithography using MEMS technology, and is composed of steps ST3a to ST3d which will be described in detail below.

[0025] First, in step ST3a, a photoresist 4 is applied and dried. Next, in step ST3b, light irradiation 6 is performed (exposure) through a photomask 5, and the photoresist 4 in the irradiated portion is removed.

[0026] Next, in step ST3c, the substrate 1 is etched with an etchant 7 (a chemical species that removes substrate material) using the photoresist 4 remaining on the back surface of the substrate 1 as a resist mask. As a result, a plurality of holes 3 are formed from the back surface to the front surface of the substrate 1.

[0027] Then, in step ST3d, ashing is performed to strip and remove the photoresist 4 remaining on the back surface of the substrate 1, thereby forming a gas separation membrane 10.

[0028] Nanoimprint lithography technology makes it possible to prepare a photomask 5 having a pattern of a periodic structure on the order of micrometers, and to regularly form a plurality of holes 3 each having a circular or rectangular cross-sectional shape, a peripheral length of the cross-section of 1 to 1000 micrometers (preferably 1 to 100 micrometers), and a center-to-center distance between holes of 1 to 1000 micrometers (preferably 1 to 100 micrometers).

[0029] Furthermore, in the etching of step ST3c, the outer periphery (cross-sectional shape and area) of the opening (back surface side of substrate 1) and the bottom (front surface side of substrate 1) of hole 3 do not need to be the same, and the bottom may be smaller than the opening.

[0030] The gas separation membrane 10 has multiple holes 3 formed in the substrate 1, and by using this in place of porous alumina, it is possible to create a separation membrane that does not require an alumina fine particle layer or an amorphous intermediate layer, and thus achieves a high permeation rate and separation factor.

[0031] (Second embodiment) Fig. 2 is a flow chart showing a method for producing a gas separation membrane according to a second embodiment of the present invention. A schematic cross-sectional view of a gas separation membrane 20 according to the second embodiment is shown in the bottom part of Fig. 2. The difference from the first embodiment is that in step ST3b, an etching stopper film 8 is formed between the separation layer 2 and the substrate 1 to ensure that the etching is terminated at the interface of the separation layer 2 on the substrate side.

[0032] A method for producing the gas separation membrane 20 will now be described with reference to FIG.

[0033] In the first separation layer formation step ST1', before forming the separation layer 2 on the substrate 1, an etching stopper film which is a thin film of silicon nitride, polysilicon, aluminum oxide, or the like is formed between the substrate 1 and the separation layer 2 (etching stopper film formation step).

[0034] In the etching of step ST3c, SF was used as the etchant 7. 6 and C. 4 F8 By using this, the hole 3 can be formed down to the etching stopper film 8.

[0035] Then, between steps ST3c and ST3d, in step ST3e, the etching stopper film 8 remaining on the isolation layer 2 side of the hole 3 is etched with hot phosphoric acid or XeF 2 For example, a process of removing the etching stopper film is added.

[0036] The gas separation membranes shown in Figs. 3 to 6 are illustrative examples in which the separation layer is not limited to one type.

[0037] (Third embodiment) 3 is a schematic cross-sectional view of a third embodiment of the gas separation membrane of the present invention. In the gas separation membrane 30 of the third embodiment, a second separation layer 9 which is permeable to molecules A and B but not permeable to molecule C is further formed between a first separation layer 2 which is permeable to molecule A but not permeable to molecules B and C and a substrate 1.

[0038] Such a two-layer structure makes it possible to separate only molecule A by filtering out molecule C from a mixture of molecules A, B, and C using the second separation layer 9 and filtering out molecule B using the first separation layer 2.

[0039] (Fourth embodiment) 4 is a schematic cross-sectional view of a fourth embodiment of the gas separation membrane of the present invention. In the gas separation membrane 40 of the fourth embodiment, the second separation layer 9 is provided in a plurality of pores 3 so as to be in contact with the first separation layer 2.

[0040] Such a gas separation membrane 40 is formed by the manufacturing method shown in the flow chart of Fig. 5. After a gas separation membrane similar to the first embodiment shown in Fig. 1 is formed, in step ST10, a second separation layer 9 is embedded in the holes 3 by a coating method. Thereafter, in step ST20, the second separation layer 9 is planarized, and in step ST30, a recess is formed by using a gas that can selectively etch the second separation layer 9. In this step ST30, the etching time is controlled so that the second separation layer 9 is not entirely removed but remains inside the multiple holes 3, thereby forming the gas separation membrane 40.

[0041] (Fifth embodiment) 6 is a schematic cross-sectional view of a fifth embodiment of the gas separation membrane of the present invention. In the gas separation membrane 50 of the fifth embodiment, the second separation layer 9 is formed conformally along the rear surface of the substrate 1 and the surfaces of the plurality of holes 3. In other words, the second separation layer 9 is formed in the form of a thin film of uniform thickness.

[0042] Such a conformal structure can be formed by atomic layer deposition technology. For example, when forming a silica-based second separation layer 9 by atomic layer deposition technology, an organosilicon compound is supplied and adsorbed on the surface, and then the supply of the organosilicon compound is stopped and an oxidizing agent is supplied. The organosilicon compound adsorbed on the surface reacts with the oxidizing agent to become part of the thin silica film. After the reaction, the supply of the oxidizing agent is stopped and the supply of the organosilicon compound is resumed. By repeating this process, a thin film can be grown uniformly on the surface.

[0043] As the organosilicon compound, various aminosilanes and alkoxysilanes as well as the molecules used to form the first separation layer 2 can be used. As the oxidizing agent, oxygen, ozone, hydrogen peroxide, etc. can be selected.

[0044] In the gas separation membranes shown in the third to fifth embodiments, materials with different separation principles can be used for the first separation layer 2 and the second separation layer 9. For example, the first separation layer 2 can be a zeolite membrane or a silica membrane that allows for sieving based on the dynamic molecular diameter of molecules, and the second separation layer 9 can be a zirconia or palladium membrane that allows for sieving based on the chemical interaction between molecules and the membrane.

[0045] Although the present invention has been described based on the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments. The present invention can be embodied in various forms without departing from the spirit of the present invention, and for example, the following modifications are also possible.

[0046] The substrate 1 is not limited to silicon or quartz, but may be any substrate having only pores (including crystal voids, crystal grain boundaries, etc.) smaller in diameter than the coating material or constituent components (molecules or particles) of the separation layer 2, and may be sapphire, polymer, etc.

[0047] Moreover, the etching in step ST3c can be selected from methods such as dry etching, wet etching, ion milling, etc. There is also no limitation on the gas or chemical liquid used as the etchant 7.

[0048] Furthermore, the separating layer (first separating layer 2) does not have to be of a single-layer structure, and may be of a multi-layer structure.

[0049] Furthermore, although each embodiment is a flat gas separation membrane, the separation layer 2 may be supported on a tubular support (substrate) as in conventional gas separation membranes.

[0050] The gas separation membrane according to the present invention is suitable for separating gases that individually constitute air, mainly oxygen, nitrogen, argon, rare gases, hydrogen, etc., at room temperature to low temperatures, or for use as an additional unit outside or inside an air separation unit. The flow rate is not particularly limited, but it is used at a scale that processes a processing flow rate, specifically a flow rate of 1 to 2 L / min, when, for example, a silicon or quartz substrate 1 measuring 50 mm square is used.

[0051] When used in an air separation unit, the pressure can be such that the primary side of the membrane is pressurized and the secondary side is at approximately atmospheric pressure, or it is also possible to operate with the primary side of the membrane pressurized and the secondary side at a vacuum, and with the primary side of the membrane at normal pressure and the secondary side at a vacuum. In the case of pressurization, the pressure is 3 MPa or less, and most preferably 600 kPa or less. There are no particular limitations on the operating temperature, but depending on the properties of the membrane, for example in the case of membranes whose permeable components change between low and normal temperatures, it is preferable to set the operating temperature so that the components with higher partial pressures in the feed become the components that permeate the membrane. The most preferable operating temperature range is from -196°C to 300°C. EXAMPLES

[0052] As an example, an experiment was conducted to separate helium and nitrogen using a gas separation membrane 10 manufactured based on the first embodiment of the present invention, and as a comparative example, a gas separation membrane in the prior art based on Figure 7. The results of comparing the permeation rates and separation factors of helium and nitrogen are shown in Table 1.

[0053] The gas separation membrane 10 used in the example employs silicon as the substrate 1 and has a thickness of 525 micrometers. The substrate 1 has a plurality of holes 3 with a circular cross section formed therein, the cross-sectional circumference of which is 4 micrometers and the distance between the centers of the holes is 2 micrometers. The separation layer 2 is formed by coating and firing zeolite to a thickness of 2 micrometers.

[0054] The comparative example has a circular (hollow fiber) shape with an outer diameter of 10 mm and an inner diameter of 6 mm, as shown in Figure 7, and uses porous alumina with an average pore diameter of 1 micrometer and a porosity of approximately 50% as support 72, zeolite as separation layer 71, and an alumina fine particle layer as intermediate layer 73 between support 72 and separation layer 71.

[0055] [Table 1]

[0056] From the results in Table 1, it was confirmed that the gas separation membrane of the present invention is a high-performance gas separation membrane having a high permeation rate and separation factor, and that this membrane does not have an alumina fine particle layer or an amorphous intermediate layer, by utilizing MEMS technology. [Explanation of symbols]

[0057] 1...substrate, 2...separation layer (first separation layer), 3...hole, 4...photoresist, 5...photomask, 6...light irradiation, 7...etchant, 8...etching stopper film, 9...second separation layer, 10, 20, 30, 40, 50...gas separation membrane, ST1, ST1'...first separation layer forming step, ST2...back surface preparation processing step, ST3...substrate hole forming step

Claims

1. a first separation layer forming step of forming a first separation layer having gas separation properties on one surface of a substrate serving as a support; and a substrate hole forming step of forming a plurality of holes that reach the one surface of the substrate by etching from the other surface of the substrate. A method for producing a gas separation membrane comprising the steps of:

2. The method for producing a gas separation membrane according to claim 1, characterized in that the plurality of holes have a circular or rectangular cross-sectional shape, a peripheral length of the cross section of 1 to 1000 micrometers, and a center-to-center distance between holes of 1 to 1000 micrometers.

3. A second separation layer having a gas separation property different from that of the first separation layer is formed between the first separation layer and the substrate. The method for producing a gas separation membrane according to claim 1 .

4. A second separation layer forming step of forming a second separation layer having a gas separation property different from that of the first separation layer in the plurality of holes so as to be in contact with the first separation layer. The method for producing a gas separation membrane according to claim 1 .

5. A second separation layer forming step of forming a second separation layer having a gas separation property different from that of the first separation layer along the other surface of the substrate and the surfaces of the plurality of holes. The method for producing a gas separation membrane according to claim 1 .

6. an etching stopper film forming step of forming an etching stopper film between the first separation layer and one surface of the substrate; an etching stopper film removing step of removing the etching stopper film in the plurality of holes; The method for producing the gas separation membrane according to any one of claims 1 to 5, comprising:

7. A substrate serving as a support; a first separation layer having gas separation properties formed on one surface of the substrate; A gas separation membrane comprising: The substrate has a plurality of holes formed by etching from one surface to the other surface of the substrate. A gas separation membrane characterized by:

8. The gas separation membrane according to claim 7, characterized in that the plurality of holes have a circular or rectangular cross-sectional shape, a peripheral length of the cross section of 1 to 1000 micrometers, and a center-to-center distance between holes of 1 to 1000 micrometers.

9. A second separation layer having a gas separation property different from that of the first separation layer is provided between the first separation layer and the substrate. The gas separation membrane according to claim 7.

10. A second separation layer having a gas separation property different from that of the first separation layer is provided in the plurality of holes so as to be in contact with the first separation layer. The gas separation membrane according to claim 7.

11. a second separation layer having a gas separation property different from that of the first separation layer, the second separation layer being formed along the other surface of the substrate and the surfaces of the plurality of holes; The gas separation membrane according to claim 7.

12. An etching stopper film is provided between the first separation layer and one surface of the substrate. The gas separation membrane according to any one of claims 7 to 11.

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