Ceramic composite film and separation membrane

Abstract

The present invention provides a ceramic composite film for forming a separation membrane that has excellent durability and exhibits high permeation separation performance. A ceramic composite film according to an embodiment of the present invention comprises a porous support that has an average pore diameter of 0.1-5.0 µm, and a porous composite layer that is superposed on the surface of the porous support. The porous composite layer contains α-alumina fine particles that each have a particle diameter of 50-500 nm and nanoparticles that each have a particle diameter of 1-50 nm. With respect to the porous composite layer, either one of the nanoparticles and the α-alumina fine particles forms a matrix phase, and the other one forms a dispersion layer by being dispersed in the matrix phase. The nanoparticles contain at least either zirconia or titania.

Description

Ceramic composite membranes and separation membranes

[0001] The present invention relates to a ceramic composite membrane for forming a separation membrane that is excellent in durability and exhibits high permeation and separation performance, and a separation membrane using the same.

[0002] In recent years, nanoporous separation membranes such as zeolite membranes and silica membranes are expected to be used in separation membranes, membrane reactors, chemical sensors, etc., because they are capable of separating substances at the molecular level.

[0003] For example, Patent Document 1 proposes a method for forming a separation membrane module having small separation performance such as gas separation, ultrafiltration, and microfiltration, by forming a porous layer made of sinterable α-alumina particles having a particle diameter of 0.01 to 0.3 μm with a layer thickness of 0.1 to 10 μm on the surface of a porous support made of α-alumina particles having a particle diameter of 0.1 to 5 μm, forming a separation layer having an average pore diameter of 0.1 to 10 nm on the porous layer, and impregnating part of the separation membrane components into the porous layer to provide an impregnation layer.

[0004] Patent Document 2 proposes a method for providing a separation membrane module having excellent corrosion resistance, water resistance, and water vapor resistance, and a method for producing the same, in which a first porous layer made of α-alumina particles having a particle size of 0.01 to 0.3 μm is provided on the surface of a porous support made of α-alumina particles having a particle size of 0.1 to 5 μm, with a layer thickness of 0.1 to 10 μm; a second porous layer made of any one of a titania membrane, a zirconia membrane, a titania-silica composite membrane, and a zirconia-silica composite membrane having an average particle size of 10 to 100 nm is formed on the first porous layer; and a separation layer having an average pore size of 0.1 to 10 nm is further provided on the second porous layer, and an impregnation layer is provided in which a part of the components of the second porous layer is impregnated into the first porous layer.

[0005] Separation membranes are generally composed of a support layer (a layer for maintaining mechanical strength), an intermediate layer (a layer that assists in the formation of the separation layer), and a separation layer (a layer that has a separation function). However, separation membranes formed by the above-mentioned methods often suffer from cracks in the separation layer during manufacturing and heating / cooling during use, making it difficult to form separation membranes that exhibit the durability and high permeation / separation performance required for practical use.

[0006] JP 2003-220319 A JP 2004-89838 A

[0007] An object of the present invention is to provide a ceramic composite membrane for forming a separation membrane that suppresses the occurrence of cracks in the separation layer during heating and cooling during production and use, and that has excellent durability and exhibits high permeation and separation performance.

[0008] One aspect of the present invention to achieve the above object is a ceramic composite membrane comprising: a porous support having an average pore size of 0.1 to 5.0 μm; and a porous composite layer laminated on the surface of the porous support, wherein the porous composite layer comprises α-alumina fine particles having a particle size of 50 to 500 nm and nanoparticles having a particle size of 1 to 50 nm, the porous composite layer being a dispersion layer in which either the nanoparticles or the α-alumina fine particles form a matrix phase and the other is dispersed in the matrix phase, and the nanoparticles contain at least either zirconia or titania. Another aspect of the present invention is a separation membrane in which a nanoporous layer having an average pore size of 0.3 to 50 nm is further laminated on the surface of the porous composite layer in the ceramic composite membrane.

[0009] The present invention has the effect of suppressing the occurrence of cracks in the separation layer when the separation layer is heated and cooled during production and use.

[0010] 1 is a schematic diagram (cross-sectional view) showing the structure of the ceramic composite membrane of the present invention; 2 is an example of electron microscope measurement results and energy dispersive X-ray spectroscopy (EDX) measurement results showing the structure of the ceramic composite membrane of the present invention; 3 is an example of X-ray photoelectron spectroscopy (XPS) measurement results for the ceramic composite membrane of the present invention; 4 is a graph plotting He permeability and selectivity for each example and comparative example; and 5 is a graph plotting Kelvin diameter and He permeability for each example.

[0011] Next, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these.

[0012] In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0013] The ceramic composite membrane of the present invention will be described with reference to FIG. 1 . FIG. 1 is a cross-sectional view showing the structure of the ceramic composite membrane of the present invention. The ceramic composite membrane of the present invention includes a porous support 1 (corresponding to the support layer in a typical separation membrane) having an average pore size of 0.1 to 5.0 μm, and a porous composite layer 4 (corresponding to the intermediate layer in a typical separation membrane) laminated on the surface of the porous support 1. The porous composite layer 4 includes α-alumina fine particles 2 having a particle size of 50 to 500 nm and nanoparticles 3 having a particle size of 1 to 50 nm. The porous composite layer 4 is a dispersion layer in which either the α-alumina fine particles 2 or the nanoparticles 3 serve as a matrix phase, with the other dispersed in the matrix phase. The porous composite layer 4 in FIG. 1 is a dispersion layer in which the nanoparticles 3 serve as a matrix phase, and the α-alumina fine particles 2 are dispersed in the matrix phase. In the present application, the matrix phase refers to either the α-alumina fine particles 2 or the nanoparticles 3, whichever has the larger total volume of each particle contained in the porous composite layer 4. When the total volume of the α-alumina fine particles 2 and nanoparticles 3 contained in the porous composite layer 4 is the same, either the α-alumina fine particles 2 or the nanoparticles 3 can be arbitrarily made into the matrix phase.

[0014] The nanoparticles 3 preferably contain at least either zirconia or titania, and more preferably contain zirconia, in order to achieve a more effective effect of suppressing the occurrence of cracks in the separation layer when heated and cooled during production and use.

[0015] Here, the porous support 1 is made of, for example, alumina (α-Al ２ O ３ (α-alumina), γ-Al ２ O ３ Examples of ceramic supports include those containing γ-alumina, mullite, zirconia, titania, or composites thereof, and those with an average pore diameter of 0.1 to 5.0 μm are preferred. The average pore diameter of pores of 0.1 μm or more can be calculated by the bubble point / gas permeation method. The average pore diameter of pores of less than 0.1 μm can be calculated by the nanoperm porometry method described below.

[0016] The porous support 1 is preferably a porous α-alumina support having a porosity of 25 to 55%. When the porosity of the porous support 1 is within this range, the porous support 1 can have excellent pressure resistance, heat insulation, and membrane permeability.

[0017] Furthermore, in order to provide the porous support 1 with sufficient mechanical strength, it is desirable that the particles constituting the porous support 1 are sintered and bonded to each other by firing them at 600 to 1,300°C.

[0018] The porous support 1 is generally tubular in shape, and from the viewpoint of durability and practicality, it preferably has a diameter of 1 to 2 cm, a length of 20 to 120 cm, and a thickness of 1 to 5 mm.

[0019] The porous composite layer 4 contains α-alumina fine particles having a particle diameter of 50 to 500 nm. The proportion of the α-alumina fine particles having a particle diameter of 50 to 500 nm contained in all the α-alumina fine particles in the porous composite layer 4, based on all the α-alumina fine particles in the porous composite layer 4, is preferably 50 mass% or more, more preferably 80 mass% or more, even more preferably 90 mass% or more, particularly preferably 95 mass% or more, and most preferably 100 mass%. When the particle diameter of the α-alumina fine particles is within this range, it is possible to produce a ceramic composite membrane (intermediate) or a separation membrane (final product) for forming a separation membrane that is excellent in durability and exhibits high permeation and separation performance. The particle diameter of the α-alumina fine particles is obtained by measuring the particle size distribution of the α-alumina fine particles as raw material using a particle size distribution measuring device. Furthermore, the proportion of α-alumina fine particles having a particle diameter of 50 to 500 nm contained in all the α-alumina fine particles in the porous composite layer 4 is also calculated by measuring the particle diameter distribution of the α-alumina fine particles using a particle diameter distribution measuring device.

[0020] The porous composite layer 4 contains nanoparticles having a particle diameter of 1 to 50 nm. The proportion of nanoparticles having a particle diameter of 1 to 50 nm contained in all nanoparticles in the porous composite layer 4 is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and most preferably 100% by mass, based on the total nanoparticles in the porous composite layer 4. When the particle diameter of the nanoparticles is within this range, a ceramic composite membrane (intermediate) or a separation membrane (final product) can be produced that has excellent durability and exhibits high permeation and separation performance. The particle diameter of the nanoparticles is obtained by measuring the particle diameter distribution of the raw material nanoparticles using a particle diameter distribution measuring device. The proportion of nanoparticles having a particle diameter of 1 to 50 nm contained in all nanoparticles in the porous composite layer 4 is also calculated by measuring the particle diameter distribution of the nanoparticles using a particle diameter distribution measuring device, and the proportion of nanoparticles having a particle diameter of 1 to 50 nm contained in all nanoparticles.

[0021] In the porous composite layer 4, it is preferable that the α-alumina fine particles 2 are not bonded to each other by sintering, but are bonded to each other via nanoparticles 3 (for example, when the nanoparticles 3 function as a binder). The proportion of the α-alumina fine particles 2 directly bonded to each other in the porous composite layer 4 (number of α-alumina fine particles 2 directly bonded to each other / number of α-alumina fine particles 2 indirectly bonded to each other via nanoparticles × 100) is preferably 50% or less, and more preferably 20% or less, from the viewpoint of exhibiting an excellent effect of suppressing the occurrence of cracks in the separation layer during heating and cooling during production and use. The proportion of the α-alumina fine particles 2 directly bonded to each other in the porous composite layer 4 can be determined by the following procedure. (1) Cross-sectional photographs are taken using a scanning electron microscope at any 10 locations on the porous composite layer 4, and all α-alumina fine particles in the photographed images are observed to count the number of particles in which the α-alumina fine particles 2 are directly bonded to each other and the number of particles in which the α-alumina fine particles 2 are indirectly bonded to each other via nanoparticles. (2) The number of particles in which the α-alumina fine particles 2 are directly bonded to each other by the number of particles in which the α-alumina fine particles 2 are indirectly bonded to each other via nanoparticles is divided and multiplied by 100 to obtain the result.

[0022] The nanoparticles 3 preferably contain at least either zirconia or titania. Generally, when α-alumina fine particles 2 are sintered and bonded together, they are produced by repeating a firing process at 600 to 1,300°C several times. On the other hand, in the present invention, to prevent the α-alumina fine particles 2 from being sintered and directly bonded together, nanoparticles 3 are applied as a binder to the surfaces of the α-alumina fine particles 2, and the particles are heated in the range of 300 to 600°C, thereby forming a porous composite layer 4 in which the α-alumina fine particles 2 are indirectly bonded together via the nanoparticles 3, without being directly bonded together.

[0023] The thickness of the porous composite layer 4 is in the range of 0.1 to 10 μm, and preferably in the range of 0.5 to 5 μm in consideration of practical durability and membrane permeability.

[0024] Furthermore, by forming a nanoporous layer 5 (corresponding to a separation layer in a general separation membrane) having an average pore size of 0.3 to 50 nm on the porous composite layer 4, a separation membrane having excellent durability and exhibiting high permeation and separation performance can be formed, and a separation membrane (final product) can be produced. It is also possible to form layers (not shown) having various functions on the nanoporous layer 5. In this case, the ceramic composite membrane includes a porous support 1, a porous composite layer 4 laminated on the surface of the porous support 1, and a nanoporous layer 5 formed on the porous composite layer 4, and by forming a functional layer thereon, a separation membrane (final product) having functionality can be produced.

[0025] The thickness of the nanoporous layer 5 is preferably 0.1 to 5 μm, more preferably 0.1 to 1 μm, from the viewpoint of permeability and durability.

[0026] Various nanoparticles of 1 to 50 nm are layered on the porous composite layer 4 by the sol-gel method, and then heated in the range of 200 to 600°C, thereby forming a nanoporous layer 5 with an average pore diameter in the range of 0.3 to 50 nm.

[0027] As the material for the nanoporous layer 5, ceramic materials such as silica, silica-zirconia, zirconia, and polymer sol can be used as raw materials. When a ceramic material is used as the raw material, the heating temperature during production is preferably in the range of 350 to 600°C. On the other hand, when the nanoporous layer 5 is made of, for example, (RO) ３ ・SiXSi・(OR) ３ When a polymer sol obtained by hydrolysis and dehydration condensation of a compound represented by the formula (I) is used as a raw material, the heating temperature during production is preferably in the range of 200 to 350°C to suppress decomposition of the organic components. In the above compound, R represents an alkyl group such as a methyl group, an ethyl group, or a propyl group, and X represents a linear saturated hydrocarbon chain or a linear unsaturated hydrocarbon chain in which one or more hydrogen atoms may be substituted. Specific examples of the above compound include bistriethoxysilylmethane (BTESM), bistriethoxysilylethane (BTESE), and bistriethoxylylacetylene (BTESA).

[0028] The ceramic composite membrane (intermediate) or separation membrane (final product) manufactured in this way can remarkably reduce the occurrence of cracks (membrane defects) during heating and cooling during manufacturing and use. As a result, the He and SF ６ It is possible to reproducibly form a separation membrane that exhibits high permeation and separation performance, such as excellent selectivity (selectivity of gas permeability).

[0029] Next, examples of the present invention will be described together with comparative examples, but the present invention is not limited to these examples.

[0030] The porous support was a cylindrical α-alumina porous support (manufactured by Iwao Porcelain Industries Co., Ltd., average pore size 1 to 3 μm, model number GP-30) with a diameter of 12 mm and a thickness of 1.5 mm, cut to a length of 40 cm. The α-alumina fine particles were high-purity alumina (manufactured by Sumitomo Chemical Co., Ltd., model number AKP-50), all of which had particle sizes in the range of 50 to 500 nm. Various zirconia, titania, silica, and silica-zirconia nanoparticles were compared and examined as nanoparticles. The particle size distributions of the α-alumina fine particles and various nanoparticles used were confirmed using a particle size distribution analyzer (manufactured by Malvern Panalytical Ltd, model number Zetasizer Nano).

[0031] First, high-purity alumina, all of whose particles had a particle size in the range of 50 to 500 nm, was applied to the surface of the α-alumina porous support, followed by application of the nanoparticles used as binders in each of the Examples and Comparative Examples, and firing at 550°C for 10 minutes. This process was repeated 2 to 6 times until the permeation of airborne particles with a particle size of 0.5 μm or greater was no longer observed in the treated porous composite layer using a particle counter (Nippon Kanomax Co., Ltd., Model No. 3889). This process can be considered to have resulted in a ceramic composite membrane free of large cracks and pinholes.

[0032] The ceramic composite membranes and separation membranes of each example and comparative example are described in detail below. (Example 1) A porous composite layer was formed using zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number: ZSL-13) all of which had a particle size in the range of 1 to 50 nm as the nanoparticles used as a binder (hereinafter, nanoparticles may be referred to as composite particles). Cross-sectional electron microscope images of the resulting ceramic composite membrane and porous composite layer are shown in Figures 2(A) to 2(E). A structure was confirmed in which α-alumina fine particles, all of which had a particle size in the range of 50 to 500 nm, were bonded with zirconia nanoparticles, all of which had a particle size in the range of 1 to 50 nm. The results of surface elemental analysis (XPS) of the porous composite layer are shown in Figure 3(A). The cross-sectional electron microscope image revealed that the porous composite layer had a thickness of approximately 1 to 2 μm. The results of surface elemental analysis (XPS) confirmed that the porous composite layer was composed of Al, Zr, and O elements. Subsequently, a polymer sol (particle size: 1-50 nm) obtained by hydrolysis and dehydration condensation of bistriethoxysilylethane (BTESE) was applied to the surface of the porous composite layer, followed by heating and drying at 300°C for 10 minutes to form a nanoporous layer. A cross-sectional electron microscope image of the separation membrane obtained after the nanoporous layer was formed is shown in Figure 2(F), and the results of surface elemental analysis (XPS) are shown in Figure 3(B). The cross-sectional electron microscope image revealed that the thickness of the nanoporous layer was approximately 100-200 nm. Furthermore, the results of surface elemental analysis (XPS) indicated that the membrane surface was composed of elements Si and C, and by scraping the surface by sputtering, the composition approached that of the porous composite layer, which contains large amounts of elements Zr, Al, and O. Furthermore, cross-sectional electron microscope images were taken at 10 random locations on the porous composite layer, and the α-alumina microparticles contained in the images were observed. The number of α-alumina microparticles directly bonded to each other and the number of α-alumina microparticles indirectly bonded to each other via nanoparticles were counted. The percentage of α-alumina particles directly bonded to each other in the porous composite layer was calculated from the number of α-alumina particles directly bonded to each other and the number of α-alumina particles indirectly bonded to each other via nanoparticles. As a result, the percentage of α-alumina particles directly bonded to each other in the porous composite layer was found to be 20% or less.

[0033] Example 2 A porous composite layer was formed using titania nanoparticles (manufactured by Ishihara Sangyo Kaisha, Ltd., model number: STS-21) with all particles having a particle size in the range of 1 to 50 nm as the nanoparticles used as a binder. A polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was then applied to the surface of the porous composite layer, followed by heating and drying at 300°C for 10 minutes to form a nanoporous layer. A cross-sectional electron microscope image of the separation membrane obtained after the nanoporous layer was formed is shown in Figure 2(G), energy dispersive X-ray spectroscopy images are shown in Figures 2(H) to 2(I), and the results of surface elemental analysis (XPS) are shown in Figure 3(C). A structure in which α-alumina fine particles were bonded with titania nanoparticles with particle sizes of 1 to 50 nm was confirmed. Furthermore, the nanoporous layer that forms the membrane surface was composed of the elements Si and C, and by scraping the surface by sputtering, the composition approached that of the porous composite layer, which contains large amounts of elements Ti, Al, and O. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0034] Example 3: Zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number: ZSL-13), all of whose particle diameters were in the range of 1 to 50 nm, were additionally applied to the surface of the porous composite layer formed in Example 1, and the layer was then fired at 550°C for 10 minutes in an attempt to form a nanoporous layer made of zirconia. The additional application and firing process was repeated 2 to 8 times, thereby adjusting the nanopore diameter to approximately 10 to 50 nm. The results of surface elemental analysis (XPS) of the ceramic composite membrane obtained after the nanoporous layer was formed are shown in Figure 3(D). The results of surface elemental analysis (XPS) reveal that the membrane surface is composed of Zr and O elements. Furthermore, by scraping the surface by sputtering, the Zr element density was slightly less than 30% and the Al element density was several percent up to approximately 200 minutes of sputtering time. At approximately 460 minutes of sputtering time, the Zr element density and the Al element density became equivalent. After that, the Al element density increased and the Zr element density decreased. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0035] Example 4 An attempt was made to form a nanoporous layer made of silica material by applying additional silica nanoparticles, all of whose particles had a particle size in the range of 1 to 50 nm, to the surface of the porous composite layer formed in Example 1 and baking the layer at 550°C for 10 minutes. By adjusting the number of additional application and baking steps to within a range of 2 to 12 times, the nanopore size was adjusted to within a range of approximately 1 to 10 nm. Note that the proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0036] Example 5 A BTESE polymer sol with particle diameters of 5 to 50 nm, from which small nanoparticles had been removed by aging, was additionally applied to the surface of the porous composite layer formed in Example 1, and the resulting layer was heated and dried at 300°C for 10 minutes to form a nanoporous layer. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0037] Comparative Example 1 A porous composite layer was formed using silica-zirconia nanoparticles, all of which had a particle size in the range of 1 to 50 nm, as the nanoparticles used as a binder. The silica-zirconia nanoparticles were prepared by adding TEOS and ZrTB (zirconium tetra-n-butoxide) to water, adding nitric acid as a catalyst, and heating at 100°C for 6 to 8 hours. Subsequently, a polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was applied to the surface of the porous composite layer, and the layer was heated and dried at 300°C for 10 minutes to form a nanoporous layer. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0038] (Comparative Example 2) A porous composite layer was formed using silica nanoparticles (manufactured by Nissan Chemical Industries, Ltd., model number ST-C) all of whose particle diameters were in the range of 1 to 50 nm as the nanoparticles used as a binder. Thereafter, a polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was applied to the surface of the porous composite layer, and the layer was heated and dried at 300°C for 10 minutes to form a nanoporous layer 5. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0039] (Comparative Example 3) A porous composite layer was formed using zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number: ZSL-20N) as the nanoparticles used as a binder, all of the particles having a particle size in the range of 50 to 100 nm. Then, a polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was applied to the surface of the porous composite layer, and the layer was heated and dried at 300°C for 10 minutes to form a nanoporous layer. The proportion of α-alumina fine particles directly bonded to each other in the porous composite layer was 20% or less.

[0040] Comparative Example 4 Among the experimental examples described in Patent Documents 1 and 2, Experiment No. 17, which showed the highest selectivity among the experiments judged as good in Table 1 of Patent Document 1, where the selectivity values ​​are clearly stated, was compared with a conventional ceramic composite membrane for reference.

[0041] To evaluate the permeation and separation performance of the formed ceramic composite membrane and separation membrane, a separation membrane module was used to measure the permeation and separation performance of helium gas (He: molecular diameter 0.27 nm) and sulfur hexafluoride (SF ６ The gas permeation rate of each gas in a pure gas state was measured. The permeability P [mol / (m ２ s Pa)] was measured, and the selectivity α, which represents the separation performance, was calculated and evaluated from the permeability value using the following formula 1. (Formula 1) Selectivity α (He / SF ６ )=P(He) / P(SF ６ The measurement results are shown in Table 1 and Figure 4. The pore diameter of the nanoporous layer was 0.3 to 0.5 nm, and the SF ６ The fewer voids (membrane defects) larger than ６ ) is expected to be shown. First, even the best conventional separation membranes disclosed in the inventions described in Patent Documents 1 and 2 have a selectivity (He / SF ６ In contrast, the composite of α-alumina fine particles and zirconia nanoparticles in Example 1 showed an unexpectedly remarkable selectivity (He / SF ６) = 9,903 to 18,888. In order to confirm reproducibility, a total of four samples were produced and tested. ６ ) was also shown. In Example 2, the composite of α-alumina fine particles and titania nanoparticles showed a sufficiently significant selectivity (He / SF ６ In Comparative Example 1, the composite of α-alumina fine particles and silica-zirconia nanoparticles also showed a reasonably high selectivity (He / SF ６ ) = 1,143 to 1,391, but did not reach the performance of Examples 1 and 2. In Comparative Example 2, even the composite of α-alumina fine particles and silica nanoparticles showed a reasonable selectivity (He / SF ６ ) = 138 to 204, which was worse than the conventional product of Comparative Example 4. In Comparative Example 3, even the composite of α-alumina fine particles and zirconia nanoparticles showed a reasonable selectivity (He / SF ６ ) = 281 to 324, which was a worse result than the conventional product of Comparative Example 4. As described above, although the detailed mechanism by which the use of zirconia and titania nanoparticles provides superior effects has not yet been elucidated, it can be inferred that the combination of Examples 1 and 2 of the present invention, due to its excellent durability, suppresses the occurrence of cracks in the separation layer when heated and cooled during production and use, and forms a separation membrane that exhibits high permeation and separation performance, thereby providing superior effects.

[0042] The pore distribution of the nanoporous layers formed in Examples 3 to 5 is generally and effectively evaluated by nanoperm porometry when the membrane pore diameter is 0.5 to 50 nm. In this method, a mixture of non-condensable gas and condensable vapor is supplied to the porous membrane, and the pore diameter is evaluated based on the Kelvin equation (Equation 2 below). (Equation 2) (θ: contact angle, ν: molar volume of condensable vapor, σ: surface tension, R: gas constant, T: temperature, Ps: saturated vapor pressure at temperature T, P: partial pressure of condensable vapor under measurement conditions) The measurement principle is that condensable vapor blocks pores through capillary condensation at a relative pressure (vapor partial pressure relative to saturated vapor pressure) corresponding to the Kelvin diameter (d), which reduces the permeability of non-condensable gases. Therefore, by measuring the permeability of non-condensable gases using relative pressure as a parameter, it is possible to estimate which pore size contributes to the degree of permeation. Here, water vapor was used as the condensable vapor, and nitrogen was used as the non-condensable gas. Nitrogen gas (N ２ Measurements were carried out at a total flow rate of 5 L (STP) / min, at 25°C, and at a relative humidity range of 0 to 95.9% (Kelvin diameter 0 to 50 nm). The test membrane sample was evaluated at a length of 40 cm. In evaluating the pore size, calculations were made assuming a contact angle θ = 0, since the layer was hydrophilic. Figure 5 shows the pore distribution profiles of the nanoporous layers formed in Examples 3 to 5. By adjusting the type of nanoparticles to be applied, it was possible to obtain nanoparticles with a pore size (Kelvin diameter) in the range of 0.5 to 50 nm, with nanoparticles larger than the specified pore size. ２ The transmittance was controlled to 0.1% or less. ２ The Kelvin diameter, which indicates the transmittance, is taken as the average pore size.

[0043] The present invention can be used as a ceramic composite membrane for forming a separation membrane that is excellent in durability and exhibits high permeability and separation performance by suppressing the occurrence of cracks in the separation layer during heating and cooling during production and use. Specifically, when the nanopore layer is in the range of 0.3 to 0.5 nm, the separation membrane exhibits high permeability and separation performance for hydrogen, CO ２ It is expected that the nanoporous layer will be used as a separation membrane for small molecules such as methane, hydrocarbons, organic solvents, and water vapor. When the nanoporous layer is in the range of 5 to 50 nm, it is expected to be used in industry for separating various nanoparticles and as a substrate for various functional membranes. CROSS-REFERENCE TO RELATED APPLICATIONS

[0044] This application claims priority based on Japanese Patent Application No. 2024-85819, filed with the Japan Patent Office on May 27, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

[0045] 1: Porous support 2: α-alumina fine particles 3: Nanoparticles (1 to 50 nm) 4: Porous composite layer 5: Nanoporous layer

Claims

1. A ceramic composite membrane comprising: a porous support having an average pore size of 0.1 to 5.0 μm; and a porous composite layer laminated on the surface of the porous support; wherein the porous composite layer comprises α-alumina fine particles having a particle size of 50 to 500 nm and nanoparticles having a particle size of 1 to 50 nm; the porous composite layer is a dispersion layer in which either the nanoparticles or the α-alumina fine particles form a matrix phase, and the other is dispersed in the matrix phase; and the nanoparticles contain at least either zirconia or titania.

2. A separation membrane in which a nanoporous layer having an average pore size of 0.3 to 50 nm is further laminated on the surface of the porous composite layer of the ceramic composite membrane according to claim 1.

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