Composite for hydrogen separation, module for hydrogen separation, method for separating hydrogen, method for producing hydrogen, and method for producing composite for hydrogen separation

Abstract

To provide: a composite for hydrogen separation having high hydrogen permeation selectivity; a module for hydrogen separation including the composite for hydrogen separation; a method for separating hydrogen and method for producing hydrogen using the module for hydrogen separation; and a method for producing the composite for hydrogen separation.SOLUTION: There are provided: a composite for hydrogen separation in which a metal-containing compound is supported on a surface of a boron nitride molded body; a module for hydrogen separation including the composite for hydrogen separation; a method for separating hydrogen and method for producing hydrogen using the module for hydrogen separation; and a method for producing the composite for hydrogen separation.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composite for hydrogen separation, a module for hydrogen separation, a method for separating hydrogen, a method for producing hydrogen, and a method for producing a composite for hydrogen separation. [Background technology]

[0002] Hydrogen is attracting attention as a new energy source. Various hydrogen production methods are being investigated to efficiently produce hydrogen. For example, the steam reforming reaction of methane is one of the main methods for producing large amounts of hydrogen. The steam reforming reaction of methane is expressed as follows: CH4+H2O→CO+3H2 formula 1

[0003] Because the methane steam reforming reaction is an endothermic reaction, it must be carried out at high temperatures to increase the equilibrium conversion rate, which poses a challenge in terms of energy efficiency. However, if the produced hydrogen could be selectively separated, the equilibrium could be shifted toward the product in Equation 1, improving the equilibrium conversion rate without increasing the reaction temperature (allowing the reaction to be carried out at a lower temperature).

[0004] Non-Patent Document 1 discloses a composite for hydrogen separation in which a silica membrane is supported on an alumina substrate by chemical vapor deposition. It discloses that when hydrogen and nitrogen separation tests were conducted using this composite for hydrogen separation, high hydrogen permeability and hydrogen permeation selectivity were demonstrated. Because nitrogen has a smaller molecular size than methane and carbon monoxide, it is believed that hydrogen can be produced with less energy by applying the composite for hydrogen separation described in Non-Patent Document 1 to a methane steam reforming reaction. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Mikihiro Nomura et al., 'Preparation of a stable silica membrane by a counter diffusion chemical vapor deposition method', journal of Membrane Science, 251 (2005), pp.151-158. Summary of the Invention [Problem to be solved by the invention]

[0006] To realize a hydrogen society, composites for hydrogen separation that maintain high hydrogen permeability and have even higher hydrogen permeation selectivity are required. The present invention aims to provide a hydrogen separation composite having high hydrogen permeation selectivity, a hydrogen separation module comprising the hydrogen separation composite, a hydrogen separation method and hydrogen production method using the hydrogen separation module, and a method for producing the hydrogen separation composite. [Means for solving the problem]

[0007] The present invention includes the following [1] to

[13] . [1] A composite for hydrogen separation in which a metal-containing compound is supported on the surface of a boron nitride molded body. [2] A composite for hydrogen separation according to [1], wherein the ratio of the number of metal atoms to the number of boron and nitrogen atoms on the surface of the composite for hydrogen separation, as measured by X-ray photoelectron spectroscopy, is 0.03 or more and 150 or less. [3] The composite for hydrogen separation according to [1] or [2], wherein the ratio is 0.03 or more and 30 or less. [4] The composite for hydrogen separation according to any one of [1] to [3], wherein the metal is at least one metal selected from the group consisting of silicon, aluminum, titanium, and zirconium. [5] The composite for hydrogen separation according to any one of [1] to [4], wherein the metal is silicon. [6] The composite for hydrogen separation according to any one of [1] to [5], wherein the median diameter of the pores in the boron nitride molded body is 0.01 μm or more and 10 μm or less. [7] The composite for hydrogen separation according to any one of [1] to [6], wherein the boron nitride molded body has, in X-ray diffraction measurement, a ratio of the diffraction peak intensity of the (002) plane to the diffraction peak intensity of the (100) plane of hexagonal crystal structure boron nitride of 0.1 or more and 1000 or less. [8] The composite for hydrogen separation according to any one of [1] to [7], wherein the boron nitride molded body has a pore with at least one opening. [9] A hydrogen separation module comprising the composite for hydrogen separation according to any one of [1] to [8].

[10] A method for separating hydrogen, comprising supplying a mixed gas containing hydrogen and a gas other than hydrogen to the hydrogen separation module described in [9], and separating the hydrogen from the gas other than hydrogen.

[11] A method for producing hydrogen, comprising supplying a gas not containing hydrogen to the hydrogen separation module described in [9], reacting the gas to generate a mixed gas containing hydrogen and gases other than hydrogen, and separating the hydrogen from the mixed gas.

[12] A method for producing a composite for hydrogen separation according to any one of [1] to [8], comprising pretreating a boron nitride molded body by irradiating the boron nitride molded body with ultraviolet light or plasma, and contacting the pretreated boron nitride molded body with a raw material compound containing the metal.

[13] The method for producing a composite for hydrogen separation according to

[12] , wherein the pretreatment is carried out by irradiating with plasma. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a hydrogen separation composite having high hydrogen permeation selectivity, a hydrogen separation module comprising the hydrogen separation composite, a hydrogen separation method and hydrogen production method using the hydrogen separation module, and a method for producing the hydrogen separation composite. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view showing a schematic configuration of a composite for hydrogen separation according to one embodiment. [Figure 2] 1 is a cross-sectional view showing a schematic configuration of a composite for hydrogen separation according to one embodiment. [Figure 3] 1 is a cross-sectional view showing a schematic configuration of a composite for hydrogen separation according to one embodiment. [Figure 4] 1 is a perspective view showing a schematic configuration of a hydrogen separation module according to one embodiment. [Figure 5] FIG. 5 is a cross-sectional view taken along line VV' in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] The meanings and definitions of terms used in this specification are as follows: A numerical range expressed by "to" means a numerical range in which the numbers before and after "to" are the lower and upper limits. In this specification, the upper and lower limits can be combined in any way. In this specification, the term "metal" also includes metalloids other than boron. The "median pore diameter" can be determined from the pore distribution of the object to be measured. Specifically, in a pore distribution graph where the vertical axis represents the cumulative pore volume per unit mass and the horizontal axis represents the logarithmic scale of pore diameter, the pore diameter when the cumulative pore volume is 50% of the total pore volume is the median pore diameter. The pore distribution can be obtained by mercury intrusion porosimetry in accordance with JIS R 1655:2003 "Method for testing pore distribution in molded fine ceramics by mercury intrusion porosimetry." The "ratio of the number of metal atoms to the number of boron and nitrogen atoms" can be obtained by measuring the object to be measured by X-ray photoelectron spectroscopy (XPS method). The "degree of orientation of boron nitride" is a value calculated by the following formula 2. Orientation degree=I (002) / I (100) formula 2 In the formula 2, I (002) is the intensity of the diffraction peak on the (002) plane of hexagonal boron nitride, and I (100)is the intensity of the diffraction peak of the (100) plane of hexagonal boron nitride. Each diffraction peak can be obtained from the XRD pattern obtained by X-ray diffraction measurement.

[0011] <Hydrogen separation composite> The composite for hydrogen separation of this embodiment is a composite for hydrogen separation in which a metal-containing compound is supported on the surface of a boron nitride compact. Hereinafter, the boron nitride compact will also be referred to as a "BN compact." It is sufficient that the metal-containing compound is supported on at least the surface of the BN compact. The metal-containing compound may be supported on the entire surface and interior of the BN compact, or the metal-containing compound may be supported only on the surface of the BN compact. Of these, it is preferable that the metal-containing compound be supported only on the surface of the BN compact.

[0012] The metal is not particularly limited, but silicon, aluminum, titanium, and zirconium are preferred, and silicon is more preferred. The metal may be of one kind or of two or more kinds.

[0013] The form of the metal-containing compound is not particularly limited, but examples include oxides, nitrides, and carbides, with oxides being preferred. The term "oxide" refers to any compound having an "-O-metal atom- bond," and the metal atom may be bonded to a monovalent saturated hydrocarbon group that may have a substituent other than the oxygen atom. The monovalent saturated hydrocarbon group will be described later. Furthermore, when the metal atom is bonded to boron nitride via an oxygen atom (boron nitride-O-metal atom-), the metal-containing compound is also defined as being supported on the surface of the boron nitride molded body.

[0014] When the composite for hydrogen separation contains two or more of the above metals, two or more metal-containing compounds may be supported on the BN compact, and the metal-containing compound may be a composite oxide containing two or more metals.

[0015] The composite for hydrogen separation may contain a non-metal-containing compound in addition to the metal-containing compound. Examples of the non-metal-containing compound include impurities that are inevitably mixed in during production. It is preferable that the composite for hydrogen separation does not contain any non-metal-containing compound other than the metal-containing compound.

[0016] The ratio of the number of metal atoms to the number of boron and nitrogen atoms on the surface of the composite for hydrogen separation, as measured by X-ray photoelectron spectroscopy, is preferably 0.03 to 150, more preferably 0.03 to 30, and even more preferably 0.03 to 1. When this ratio is equal to or greater than the lower limit, hydrogen permeation selectivity is likely to be improved. When this ratio is equal to or less than the upper limit, hydrogen permeability is likely to be improved. Hereinafter, hydrogen permeability means "permeability of hydrogen," and hydrogen permeation selectivity means "permeability of hydrogen / permeability of gases other than hydrogen (e.g., nitrogen)." The respective measurement methods will be described later.

[0017] The content of boron nitride relative to the total mass of the composite for hydrogen separation may be 60 mass % or more, 70 mass % or more, or 80 mass % or more.

[0018] The hydrogen permeability of the composite for hydrogen separation at 25°C is 0.1×10 -6 mol m -2 ·s -1 Pa -1 More than 1×10 is preferable. -6 mol m -2 ·s -1 Pa -1 More than 3×10 is preferable. -6 mol m -2 ·s -1 Pa -1 The above is even more preferable.

[0019] The ratio of the hydrogen permeability at 25°C to the nitrogen permeability at 25°C of the composite for hydrogen separation is preferably 3.4 or more, more preferably 3.7 or more, and even more preferably 5.0 or more. The hydrogen permeability and nitrogen permeability can be measured by the method described in the examples below.

[0020] <BN molded body> The BN molded body contains boron nitride. The content (purity) of boron nitride with respect to the total mass of the BN molded body is preferably 70% by mass or more, more preferably 97% by mass or more, and still more preferably 99% by mass or more. When the content of boron nitride is at least the above lower limit value, it is easy to maintain high hydrogen permeability of the hydrogen separation composite, and it is easy to improve hydrogen permeation selectivity. The upper limit of the content (purity) of boron nitride with respect to the total mass of the BN molded body is not particularly limited, but since inevitable impurities derived from raw materials and manufacturing processes may be mixed in, for example, it is 99.9% by mass or less. The content (purity) of boron nitride with respect to the total mass of the BN molded body can be calculated by nitrogen amount (mass%) × 1.772 when the molded body does not contain nitrides other than boron nitride. The nitrogen amount can be determined, for example, by measurement using an oxygen / nitrogen simultaneous analyzer, neutral titration method after alkali fusion, etc. When the molded body contains nitrides other than boron nitride, it can be calculated from the ratio of nitrides other than boron nitride added during raw material powder mixing, the X-ray diffraction pattern of the molded body, etc.

[0021] The median diameter of the pores of the BN molded body is preferably 0.01 to 10 μm, more preferably 0.05 to 3 μm, and still more preferably 0.1 to 1 μm. When the median diameter of the pores of the BN molded body is at least the above lower limit value, it is easy to improve hydrogen permeability. When the median diameter of the pores of the BN molded body is at most the above upper limit value, it is easy to improve hydrogen permeation selectivity.

[0022] In the X-ray diffraction measurement using CuKα rays, the ratio (orientation degree) of the intensity of the diffraction peak of the (002) plane to the intensity of the diffraction peak of the (100) plane of hexagonal boron nitride in the BN molded body is preferably 0.1 to 1000, and more preferably 7 to 700. Hexagonal boron nitride has a flaky particle shape. For example, when the BN molded body is plate-shaped, a high orientation degree means that the ratio of flaky particles oriented parallel to the plate surface is large. When the orientation degree is at least the above lower limit value, it is easy to improve the strength in the direction perpendicular to the plate surface. When the orientation degree is at most the above upper limit value, it is easy to improve hydrogen permeation selectivity while maintaining high hydrogen permeability.

[0023] The density of the BN compact is, for example, 1.00 to 2.25 g / cm 3 is preferable, and 1.20 to 2.00 g / cm 3 is more preferable. The density of the BN compact can be measured by the Archimedes method. When the density of the BN compact is at least the lower limit value, it is easy to ensure the strength of the compact. When the density of the BN compact is at most the upper limit value, it is easy to improve the hydrogen permeability.

[0024] <Method for manufacturing BN compact> The method for manufacturing the BN compact of the present embodiment has, for example, a step of molding and firing a raw material powder containing boron nitride powder having a hexagonal crystal structure to obtain a boron nitride sintered body (BN compact). In addition to the boron nitride powder having a hexagonal crystal structure, the raw material powder may contain amorphous boron nitride powder.

[0025] The raw material powder may contain a sintering aid. Examples of the sintering aid include oxides of rare earth elements such as yttria, oxides such as aluminum oxide, magnesium oxide, and calcium oxide, carbonates of alkali metals such as lithium carbonate and sodium carbonate, and boron oxide. From the viewpoint of making the purity of boron nitride in the boron nitride sintered body sufficiently high, the boron nitride sintered body may be manufactured without using a sintering aid. That is, the raw material powder may not contain a sintering aid.

[0026] The preparation of the raw material powder may be performed by dry pulverization and dry mixing, or may be performed by wet pulverization and wet mixing using a ball mill or the like. An apparatus having a high dispersing power such as a bead mill may be used. In order to improve the formability, an organic binder may be blended and granulation may be performed by a spray dryer.

[0027] The obtained raw material powder may be press-molded into a predetermined shape in advance. Mold molding (uniaxial pressure molding) may be performed using a mold, or CIP molding may be performed using a cold isostatic pressure pressing apparatus. When the bulk density of the raw material powder is high and the formability is low, mold molding may be performed before CIP molding.

[0028] The molding pressure during molding is preferably 50 MPa or more. By adjusting the molding pressure, the median diameter, density, and degree of orientation of the pores in the BN compact can be adjusted.

[0029] For example, a batch furnace or a continuous furnace can be used for the firing. Examples of batch furnaces include muffle furnaces, tubular furnaces, and atmosphere furnaces. Examples of continuous furnaces include tunnel furnaces, belt furnaces, and pusher furnaces. The firing may be carried out at normal pressure (atmospheric pressure). Alternatively, molding and firing may be carried out simultaneously, as in hot pressing.

[0030] The firing preferably includes a firing step in which the molded body (raw material powder in the case of hot pressing) is heat-treated at a heating temperature of 1900 to 2200° C. for 3 hours or more to obtain a boron nitride sintered body.

[0031] When the compact contains an organic binder, a degreasing step for decomposing and removing the organic binder may be carried out before the firing step.

[0032] The firing is preferably carried out in an inert gas atmosphere, such as argon, helium, or nitrogen.

[0033] <Shape of composite for hydrogen separation> The shape of the composite for hydrogen separation is not particularly limited, but examples include a cylindrical shape, a prismatic shape, a pyramidal shape, a truncated pyramidal shape, a conical shape, and a truncated conical shape, with a cylindrical shape and a prismatic shape being preferred. The hydrogen separation composite preferably has a hole with at least one opening. The hole may be a through-hole with two or more openings, preferably a through-hole with two openings. Alternatively, the hole may be a through-hole with one opening, with one of the openings being sealed. When the hydrogen separation composite has a cylindrical or prismatic shape, the through-hole preferably has openings at both ends of the axial direction (height direction) of the cylindrical or prismatic shape. The through-hole may be a linear through-hole parallel to the axial direction of the cylindrical or prismatic shape, or may be a bent or curved through-hole. The shape of the through-hole is not particularly limited, but examples include a cylindrical shape, a prismatic shape, a pyramidal shape, a truncated pyramidal shape, a conical shape, and a truncated conical shape, with a cylindrical shape and a prismatic shape being preferred. The shapes of the hydrogen separation composite and the hole are preferably derived from the BN compact. That is, the hydrogen separation composite is preferably produced by supporting a metal-containing compound on a BN compact of a desired shape. Examples of methods for forming the BN compact into a desired shape include molding and processing after molding.

[0034] The volume of the composite for hydrogen separation (excluding the volume of the pores) can be appropriately set depending on the amount of gas to be separated. -4 ~40L is also acceptable, 2×10 -2 It may be up to 40L, or 2 to 40L. When the composite for hydrogen separation has through holes, the number of through holes may be one or more. When the composite for hydrogen separation has a plurality of through holes, the number of through holes is, for example, preferably 2 to 2000, more preferably 100 to 1800, and even more preferably 1000 to 1800. When the composite for hydrogen separation has a plurality of through holes, the through holes may be connected to each other by communicating holes. Furthermore, the through holes may have a monolithic structure.

[0035] The ratio of the pore volume to the volume of the composite for hydrogen separation (excluding the pore volume) is preferably 3 to 80% by volume, more preferably 5 to 60% by volume, and even more preferably 10 to 40% by volume.

[0036] 1 to 3 show examples of composites for hydrogen separation according to this embodiment, but the present invention is not limited to these.

[0037] FIG. 1 is a perspective view of a hydrogen separation composite 1 having a cylindrical shape and one through-hole parallel to the axial direction of the cylinder. The through-hole also has a cylindrical shape. FIG. 2 is a cross-sectional view of the hydrogen separation composite 1 in the axial direction of the cylinder, and FIG. 3 is a cross-sectional view of the hydrogen separation composite 1 in the planar direction of the cylinder. In the hydrogen separation composite 1 shown in FIG. 1, the metal-containing compound is supported not on the surface on the through-hole side (inner surface) but on the outer surface (external surface) of the hydrogen separation composite 1 opposite the through-hole side. In FIGS. 2 and 3, the hydrogen separation composite 1 has a metal-containing compound-supported region 11 on which the metal-containing compound is supported and a metal-containing compound-unsupported region 12 on which the metal-containing compound is not supported. In FIGS. 1 to 3, the metal-containing compound is supported on the outer surface (external surface) of the hydrogen separation composite 1 opposite the through-hole side, but the metal-containing compound may also be supported on the surface on the through-hole side (inner surface). The metal-containing compound may also be supported on both the outer and inner surfaces.

[0038] <Hydrogen separation module> The hydrogen separation module of this embodiment includes the above-described composite for hydrogen separation. Figures 4 and 5 show examples of the hydrogen separation module of this embodiment, but the present invention is not limited to these.

[0039] FIG. 4 is a perspective view of a hydrogen separation module 10. FIG. 5 is a cross-sectional view of the hydrogen separation module 10 of FIG. 4 taken along line V-V'. The hydrogen separation module 10 shown in FIGS. 4 and 5 includes a hydrogen separation composite 1 in a housing 2. One end of the hydrogen separation composite 1 is fixed by an immobilizing member 4 in the housing 2. The other end of the hydrogen separation composite 1 is sealed by a sealing member 3. Note that if the opening at the end is sealed (in the case of a hydrogen separation composite 1 having a hole with one opening, in which one opening of the above-mentioned two-opening through-hole is sealed), the sealing member 3 is not necessary. The immobilizing member 4 has a through-hole and is connected to the through-hole of the hydrogen separation composite 1. The housing 2 is connected to a mixed gas supply line 5 at one end and to a hydrogen-reduced gas discharge line 6 and a hydrogen-enriched gas discharge line 7 at the other end. In the case of the hydrogen separation module 10 shown in Figures 4 and 5, in the hydrogen separation composite 1, it is preferable that the metal-containing compound is supported on the outer surface (outer face) of the hydrogen separation composite 1, opposite to the through-hole side, as shown in Figures 1 to 3.

[0040] The number of hydrogen separation composites 1 in the hydrogen separation module 10 is preferably 2 to 300, more preferably 50 to 300, and even more preferably 100 to 300.

[0041] <Hydrogen separation method, hydrogen production method> The hydrogen separation method of this embodiment is a method in which a mixed gas containing hydrogen and gases other than hydrogen is supplied to the hydrogen separation module, and hydrogen is separated from the other gases.

[0042] A hydrogen separation method will be described below with reference to Figures 4 and 5. A mixed gas containing hydrogen and gases other than hydrogen is supplied to a hydrogen separation module 10 through a mixed gas supply line 5. The mixed gas is separated into hydrogen and gases other than hydrogen by a hydrogen separation composite 1. Specifically, hydrogen permeates the hydrogen separation composite 1 and moves into the through-holes of the hydrogen separation composite 1. On the other hand, gases other than hydrogen are less likely to permeate the hydrogen separation composite 1. Gas containing a high concentration of hydrogen is discharged from a hydrogen-enriched gas discharge line 7 through the through-holes of the immobilization member 4. On the other hand, gas containing a low concentration of hydrogen is discharged from a hydrogen-reduced gas discharge line 6.

[0043] The pressure in space 8 within casing 2 is preferably pressurized, and is preferably 0.2 to 40 MPa, more preferably 1 to 40 MPa, and even more preferably 10 to 40 MPa. The pressure within the through-holes of hydrogen separation composite 1 is preferably 1 MPa or less, and more preferably 0.2 MPa or less. The pressure difference between the pressure in space 8 within casing 2 and the pressure within the through-holes of hydrogen separation composite 1 is preferably 0.1 to 40 MPa, and more preferably 1 to 40 MPa.

[0044] Although the gas other than hydrogen is not particularly limited, the effects of the present invention are particularly pronounced when the molecule has a diameter 1.1 to 3 times that of a hydrogen molecule (diameter: 0.29 nm). Examples of such gases include carbon monoxide (diameter: 0.36 nm), carbon dioxide (diameter: 0.33 nm), nitrogen (diameter: 0.36 nm), methane (diameter: 0.38 nm), toluene (diameter: 0.68 nm), and oxygen (diameter: 0.35 nm).

[0045] It is preferable that hydrogen and gases other than hydrogen are completely separated, but gases other than hydrogen may be contained in the gas containing a high concentration of hydrogen discharged from the hydrogen-enriched gas discharge line 7, and hydrogen may be contained in the gas containing a low concentration of hydrogen discharged from the hydrogen-reduced gas discharge line 6.

[0046] The supply rate of the mixed gas containing hydrogen and gases other than hydrogen supplied from the mixed gas supply line 5 can be set appropriately depending on the processing capacity of the hydrogen separation module 10. For example, the supply rate is preferably 30 to 100,000 L / hour, more preferably 30 to 50,000 L / hour, and even more preferably 30 to 30,000 L / hour.

[0047] The mixed gas supply line 5 may be connected to a hydrogen production device. That is, a hydrogen-containing gas produced in the hydrogen production device may be supplied as a mixed gas containing hydrogen and gases other than hydrogen from the mixed gas supply line 5 to the hydrogen separation module 10. Examples of hydrogen production devices include a methane steam reformer and a photocatalytic water decomposition device.

[0048] The hydrogen separation module 10 may have a hydrogen production function. In this case, hydrogen can be produced and separated in the hydrogen separation module 10. Specifically, a gas not containing hydrogen may be supplied to the hydrogen separation module 10, and the gas may be reacted to produce a mixed gas containing hydrogen and gases other than hydrogen, and the hydrogen may be separated from the mixed gas. For example, when hydrogen is produced by a steam reforming reaction of methane, the gas not containing hydrogen is methane and steam.

[0049] In the case of the hydrogen separation module 10 having a hydrogen production function, it is preferable that a hydrogen production catalyst (not shown) is contained in the hydrogen separation composite 1. For example, when hydrogen is produced by a steam reforming reaction of methane, the hydrogen production catalyst is a metal catalyst, and metals such as palladium, platinum, rhodium, nickel, etc., or oxides thereof are preferred.

[0050] 4 and 5, in the hydrogen separation composite 1, the metal-containing compound is supported on the outer surface (external face) of the hydrogen separation composite 1, opposite the through-hole side. In this case, a mixed gas containing hydrogen and gases other than hydrogen is supplied from the outer surface (external face) side opposite the through-hole side of the hydrogen separation composite 1, and hydrogen is separated by permeating the hydrogen into the through-holes of the hydrogen separation composite 1. The present invention is not limited to the above embodiment, and the metal-containing compound may be supported on the surface (inner surface) on the through-hole side of the hydrogen separation composite 1. In this case, hydrogen may be separated by supplying a mixed gas containing hydrogen and a gas other than hydrogen from the surface (inner surface) on the through-hole side of the hydrogen separation composite 1 and allowing the hydrogen to permeate to the outer surface (outer surface) of the hydrogen separation composite 1. Although a hydrogen separation module 10 of this embodiment is not shown, it is sufficient to configure the hydrogen separation module 10 so that the above embodiment can be realized, such as by connecting lines.

[0051] <Method for manufacturing composite for hydrogen separation> The method for producing a hydrogen composite of this embodiment includes a supporting step of bringing a raw material compound containing the metal into contact with a BN compact. Preferably, the method further includes a pretreatment step of irradiating the BN compact with ultraviolet light or plasma before the supporting step.

[0052] <Pretreatment process> The pretreatment step involves irradiating the BN compact with ultraviolet light or plasma, which changes the surface properties of the BN compact and improves the wettability of the raw material compound to the BN compact surface in the loading step described below.

[0053] In this embodiment, plasma irradiation is preferred, and atmospheric pressure plasma irradiation is more preferred. By irradiating the BN compact with plasma, the wettability of the raw material compound to the surface of the BN compact is further improved in the supporting step described below.

[0054] Atmospheric pressure plasma refers to plasma generated at normal pressure. Examples of atmospheric pressure plasma irradiation methods include remote plasma and direct plasma. Remote plasma is a method in which plasma is generated by applying a high voltage between metal electrodes facing each other across a space and a dielectric, and then a process gas is supplied into the plasma, irradiating the workpiece (BN compact) with the plasma-converted process gas. Direct plasma is a method in which the workpiece (BN compact) is placed between opposing metal electrodes with a dielectric interposed between them, and the workpiece is directly exposed to plasma. In this embodiment, it is preferable to perform atmospheric pressure plasma irradiation using remote plasma.

[0055] <Supporting process> The supporting step is a step in which a raw material compound containing a metal is brought into contact with the BN compact (including a BN compact that has been subjected to a pretreatment step).

[0056] (raw material compounds containing metals) The metal-containing raw material compound is not particularly limited, but examples thereof include metal alkoxides, metal halides, silazanes, and siloxane compounds, with metal alkoxides being preferred.

[0057] The metal alkoxide is preferably a metal alkoxide represented by the following formula 3. MR 1 a R 2 m-a In the formula 3, M is a metal atom, and R 1 is an alkoxy group, and R 2 is a monovalent saturated hydrocarbon group which may have a monovalent group having a heteroatom as a substituent, m is the valence of the metal atom of M, and a is an integer of 1 to m. For example, when M is a silicon atom, m is 4 and a is an integer of 1 to 4.

[0058] M is not particularly limited, but is preferably a silicon atom (m=4), an aluminum atom (m=3), a titanium atom (m=4), or a zirconium atom (m=4), and more preferably a silicon atom.

[0059] R 1 Examples of the alkyl group include a methoxy group, an ethoxy group, a linear or branched propoxy group, a linear or branched butoxy group, and a linear or branched pentoxy group, and methoxy and ethoxy groups are preferred due to their high reactivity.

[0060] R 2Examples of R include a linear or branched alkyl group and a cycloalkyl group. 2 The number of carbon atoms in R is preferably 1 to 20, more preferably 1 to 10, and even more preferably 1 to 6. 2 As the alkyl group, a linear or branched alkyl group is preferable, a methyl group, an ethyl group, a linear or branched propyl group, a linear or branched butyl group, or a linear or branched pentyl group is more preferable, and a methyl group, an ethyl group, or a linear or branched propyl group is even more preferable.

[0061] R 2 may have a monovalent group having a hetero atom as a substituent. The term "having a monovalent group having a hetero atom as a substituent" means that R 2 This means that at least one, preferably 1 to 10, and more preferably 1 to 6 hydrogen atoms in the monovalent saturated hydrocarbon group are substituted with the above-mentioned substituent. Examples of heteroatoms include halogen atoms and oxygen atoms, with halogen atoms being preferred and fluorine atoms being more preferred.

[0062] In one embodiment, a is preferably m-1, and in yet another embodiment, a is preferably m.

[0063] (contact conditions) The contact between the BN compact and the raw material compound may be carried out by contacting the BN compact with the gaseous raw material compound or the liquid raw material compound, with the liquid raw material compound being preferred. An example of a method for contacting the BN compact with the gaseous raw material compound is to deposit the gaseous raw material compound on the surface of the BN compact by chemical vapor deposition.

[0064] When the BN compact is brought into contact with the liquid raw material compound, a small amount of the liquid raw material compound may be added to the BN compact, or the BN compact may be immersed in a large amount of the liquid raw material compound, with the immersion of the BN compact in a large amount of the liquid raw material compound being preferred. The amount of the liquid raw material compound used per 100 parts by mass of the BN compact is preferably 3 to 1,000 parts by mass, more preferably 10 to 1,000 parts by mass, and even more preferably 100 to 1,000 parts by mass. When the BN compact is brought into contact with the liquid raw material compound, it is preferable not to use any other substance such as a solvent.

[0065] The temperature at which the BN compact is brought into contact with the liquid raw material compound can be appropriately selected taking into consideration the melting point, boiling point, etc. of the liquid raw material compound, and is preferably -20 to 100°C, more preferably 0 to 100°C, and even more preferably 15 to 100°C. The contact time between the BN compact and the liquid raw material compound is preferably 0.01 to 100 hours, more preferably 10 to 90 hours, and even more preferably 30 to 85 hours. When the contact time is equal to or greater than the lower limit, a sufficient amount of the metal-containing compound is easily supported on the BN compact.

[0066] In the case of the method of immersing the BN compact in a liquid raw material compound, it is preferable to remove the BN compact by solid-liquid separation after immersion and then carry out heating.

[0067] The heating temperature in the heating step is preferably 15 to 180°C, more preferably 50 to 180°C, and even more preferably 100 to 180°C. The heating time in the heating step is preferably 0.1 to 48 hours, more preferably 0.1 to 36 hours, and even more preferably 0.1 to 24 hours. The heating atmosphere may be, for example, an air atmosphere, a nitrogen atmosphere, or a helium atmosphere. [Example]

[0068] The present invention will be explained in more detail below using examples, but the present invention is not limited to these examples.

[0069] <Measurement method> (Mean pore diameter measurement) The median pore diameter of the BN compact was measured using the method described above. The pore distribution of the BN compact was measured using a mercury intrusion apparatus (Micromeritics, AutoPore V9620). The amount of BN compact used in the measurement was 0.6 g, the measurement starting pressure was 0.5 psia, the measurement maximum pressure was 60,000 psia, and the mercury parameters were a surface tension of 484 dyne / cm and a contact angle of 130°.

[0070] (Orientation degree measurement) The degree of orientation was measured using the method described above. XRD patterns were obtained by X-ray diffraction measurement. Specifically, an XRD pattern was obtained by performing 2θ-θ scan measurement on the BN compact using an X-ray diffractometer (Malvern Panatical, Empyrean) with a parallel beam and a Cu-Kα source at a diffraction angle of 2θ = 10° to 70°. From the XRD pattern, the diffraction peak intensity of the (002) plane of hexagonal boron nitride and the diffraction peak intensity of the (100) plane of hexagonal boron nitride were identified, and the degree of orientation was calculated using Equation 2 above.

[0071] (Measurement of the ratio of silicon atoms to boron and nitrogen atoms) The ratio of the number of silicon atoms to the number of boron and nitrogen atoms was measured by the method described above. Specifically, the measurement was performed using a K-Alpha X-ray photoelectron spectrometer (manufactured by Thermo Fisher Scientific) under the following conditions: (conditions) Excitation source: Al-X-ray source with monochromator X-ray irradiation diameter: 400 μm x 200 μm Analysis surface: Surface (atmospheric pressure plasma irradiated surface) Number of analysis locations: 3 locations Use Neutralization Gun Analysis software: Avantage (Thermo Fisher Scientific, Version: 5.9925, Build: 0.6702) Quantitative Library: Scofield (Al source) Decay length (Energy correction method): KE^(ecsf) Charge correction with C1s (284.8 eV) Background processing: Shirley method Integration range: B 1s: 194-186 eV, N 1s: 403-394 eV, Si 2p: 108-99 eV Relative sensitivity coefficients: B 1s; 0.49, N 1s; 1.80, Si 2p; 0.82 Conditions other than those mentioned above: Followed the default settings in the device manual.

[0072] (Measurement of hydrogen permeability and nitrogen permeability) Hydrogen permeability and nitrogen permeability were measured by a single-component gas permeation test. A gas pipe was connected to a cylindrical hydrogen separation composite (thickness: 2 mm) via a φ7 mm O-ring, and the supply gas (hydrogen or nitrogen) was passed through the pipe. The test was held at room temperature (25°C) for 30 minutes or more. After the test, the pressure difference between the upstream (supply side) and downstream (permeation side) of the hydrogen separation composite was measured with a pressure gauge, and the permeated gas flow rate was measured with a bubble flow meter. The hydrogen or nitrogen gas permeability P was calculated using the following formula 4. P=F / (A·Δp) Equation 4 In the above formula 4, P is the gas permeability (mol m -2 ·s -1 Pa -1 ) and F is the flow rate of the permeated gas (mol s -1 ) and A is the permeation area (m 2 ) and Δp indicates the pressure difference (Pa) between the feed side and the permeation side.

[0073] [BN molded body] Hexagonal boron nitride powder and amorphous boron nitride powder were dry-mixed in a mass ratio of 60:40, and the resulting mixed powder was molded and CIP-molded at 100 MPa. The mixture was then sintered at 2050°C in a nitrogen atmosphere (atmospheric pressure) for 8 hours to obtain a BN compact ingot with a purity of over 99% by mass. The resulting BN compact ingot was processed into a cylindrical BN compact with a diameter of 10 mm and a thickness of 2 mm. The following examples and comparative examples use BN compact 1 and BN compact 2, which were cut from two different ingots. The BN compact 1 has a pore median diameter of 0.49 μm, an orientation degree of 140, and a density of 1.46 g / cm3 It was. The BN compact 2 has a pore median diameter of 0.63 μm, an orientation degree of 230, and a density of 1.51 g / cm 3 It was.

[0074] [Example 1] The BN compact 1 was immersed in tetramethoxysilane (hereinafter referred to as "TMOS," manufactured by Tokyo Chemical Industry Co., Ltd., purity over 99%) at room temperature. The immersion time in TMOS was 24 hours. The BN compact was then removed from the TMOS and heated in air at 150°C for 24 hours to obtain a composite for hydrogen separation 1. The presence or absence of plasma irradiation, the irradiation dose, the type of raw material compound, and the contact time (immersion time) are shown in Table 1 (the same applies hereinafter to Examples 2 to 7 and Comparative Example 1). Using the obtained composite for hydrogen separation 1, the ratio of the number of silicon atoms to the number of boron and nitrogen atoms, the hydrogen permeability, and the nitrogen permeability were measured. The results are shown in Table 1 (the same applies hereinafter to Examples 1 to 7 and Comparative Example 1). Note that "-" in Table 1 indicates that no measurement was performed. The "atomic ratio" in Table 1 refers to the ratio of the number of silicon atoms to the number of boron and nitrogen atoms.

[0075] [Example 2] The surface of the BN compact 2 was irradiated with atmospheric pressure plasma under the following conditions. (conditions) Irradiation method: Remote plasma Gas: Nitrogen Nitrogen flow rate: 80 L / min Irradiation distance: 2mm The plasma-irradiated BN compact 2 was immersed in TMOS at room temperature for 24 hours. The BN compact 2 was then removed from the TMOS and heated in air at 150°C for 24 hours to obtain a composite for hydrogen separation 2.

[0076] [Example 3] A composite 3 for hydrogen separation was obtained in the same manner as in Example 2, except that the plasma irradiation dose was increased.

[0077] [Example 4] A composite for hydrogen separation 4 was obtained in the same manner as in Example 3, except that the immersion time in TMOS was 72 hours.

[0078] [Example 5] A composite for hydrogen separation 5 was obtained in the same manner as in Example 2, except that trifluoropropyltrimethoxysilane (hereinafter referred to as "TFPrTMOS", manufactured by Tokyo Chemical Industry Co., Ltd., purity over 99%) was used instead of TMOS.

[0079] [Example 6] A composite for hydrogen separation 6 was obtained in the same manner as in Example 5, except that the plasma irradiation dose was increased.

[0080] [Example 7] Composite 7 for hydrogen separation was obtained in the same manner as in Example 6, except that the immersion time in TFPrTMOS was 72 hours.

[0081] [Comparative Example 1] Using the BN compact 1, hydrogen permeability and nitrogen permeability were measured.

[0082] [Table 1]

[0083] The composites for hydrogen separation obtained in Examples 1 to 7 had higher hydrogen permeation selectivity, expressed as H2 permeability / N2 permeability, than the composite for hydrogen separation obtained in Comparative Example 1. The H2 permeabilities obtained in Examples 1 to 7 were also at a very high level. In particular, it was found that the hydrogen permeation selectivity was higher in Examples 2 to 7, which were subjected to plasma irradiation. [Industrial Applicability]

[0084] The hydrogen separation composite and hydrogen separation module of the present invention can be used in hydrogen separation devices in factories and other places, and in devices for producing hydrogen and other renewable energy. [Explanation of symbols]

[0085] 1...hydrogen separation composite, 2...casing, 3...sealing material, 4...immobilization member, 5...mixed gas supply line, 6...hydrogen-reduced gas discharge line, 7...hydrogen-enriched gas discharge line, 8...space, 10...hydrogen separation module, 11...metal-containing compound-supported region, 12...metal-containing compound-unsupported region, 13...through hole

Claims

1. A composite for hydrogen separation, comprising a boron nitride molded body and a metal-containing compound supported on the surface thereof.

2. 2. The composite for hydrogen separation according to claim 1, wherein the ratio of the number of atoms of the metal to the number of atoms of boron and nitrogen on the surface of the composite for hydrogen separation, as measured by X-ray photoelectron spectroscopy, is 0.03 or more and 150 or less.

3. 3. The composite for hydrogen separation according to claim 2, wherein the ratio is 0.03 or more and 30 or less.

4. 4. The composite for hydrogen separation according to claim 1, wherein the metal is at least one metal selected from the group consisting of silicon, aluminum, titanium, and zirconium.

5. 5. The composite for hydrogen separation according to claim 4, wherein the metal is silicon.

6. 4. The composite for hydrogen separation according to claim 1, wherein the median diameter of pores in the boron nitride molded body is 0.01 μm or more and 10 μm or less.

7. 4. The composite for hydrogen separation according to claim 1, wherein the boron nitride molded body has, in X-ray diffraction measurement, a ratio of the diffraction peak intensity of the (002) plane to the diffraction peak intensity of the (100) plane of hexagonal boron nitride of 0.1 or more and 1000 or less.

8. 4. The composite for hydrogen separation according to claim 1, wherein the boron nitride molded body has a pore with at least one opening.

9. A module for hydrogen separation comprising the composite for hydrogen separation according to claim 8.

10. A method for separating hydrogen, comprising supplying a mixed gas containing hydrogen and a gas other than hydrogen to the hydrogen separation module according to claim 9, and separating the hydrogen from the gas other than hydrogen.

11. A method for producing hydrogen, comprising: supplying a gas that does not contain hydrogen to the hydrogen separation module described in claim 9; reacting the gas to generate a mixed gas containing hydrogen and a gas other than hydrogen; and separating hydrogen from the mixed gas.

12. A method for producing the composite for hydrogen separation according to any one of claims 1 to 3, pretreating the boron nitride compact by irradiating the boron nitride compact with ultraviolet light or plasma; A method for producing a composite for hydrogen separation, comprising contacting the pretreated boron nitride molded body with a raw material compound containing the metal.

13. The method for producing a composite for hydrogen separation according to claim 12, wherein the pretreatment is carried out by irradiating with plasma.

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