Ceramic composite membrane and separation membrane

Abstract

To provide a ceramic composite membrane for forming a separation membrane excellent in durability and exhibiting a high permeation separation performance.SOLUTION: A ceramic composite membrane according to an aspect includes: a porous support having an average pore diameter of 0.1 to 5.0 μm; and a porous composite layer stacked on a surface of the porous support. The porous composite layer contains an α-alumina particulate having a particle size of 50 to 500 nm, and nano particle having a particle size of 1 to 50 nm. The porous composite layer is a dispersion layer in which one of the nano particle and the α-alumina particulate serves as a matrix phase and the other of them is dispersed in the matrix phase. The nano particle at least contains any of zirconia and titania.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[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. [Background technology]

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

[0003] For example, Patent Document 1 proposes a method for producing a separation membrane module having separation capabilities 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 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, or 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, with an impregnation layer being provided in which a portion of the components of the second porous layer are impregnated into the first porous layer.

[0005] Separation membranes generally consist 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 separation function). However, separation membranes formed using the above method often suffer from cracks in the separation layer during manufacturing and heating and cooling during use, making it difficult to form separation membranes that exhibit the durability and high permeation and separation performance required for practical use. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-220319 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-89838 Summary of the Invention [Problem to be solved by the invention]

[0007] The object of the present invention is to provide a ceramic composite membrane that can suppress the occurrence of cracks in the separation layer during heating and cooling during production and use, thereby forming a separation membrane that is excellent in durability and exhibits high permeation and separation performance. [Means for solving the problem]

[0008] In order to achieve the above object, one aspect of the present invention is to The ceramic composite membrane comprises 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 contains 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 of the ceramic composite membrane. [Effects of the Invention]

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

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

[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 numerical range 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 comprises a porous support 1 (corresponding to the support layer in a general 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 general separation membrane) laminated on the surface of the porous support 1. The porous composite layer 4 comprises 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 a larger total volume of the particles contained in the porous composite layer 4. Note that when the total volumes of the α-alumina fine particles 2 and the nanoparticles 3 contained in the porous composite layer 4 are the same, either the α-alumina fine particles 2 or the nanoparticles 3 can be arbitrarily used as the matrix phase.

[0014] From the viewpoint of achieving a more excellent effect of suppressing the occurrence of cracks in the separation layer during heating and cooling during production and use, it is preferable that the nanoparticles 3 contain at least either zirconia or titania, and it is more preferable that they contain zirconia.

[0015] Here, examples of the porous support 1 include ceramic supports containing alumina (α-Al2O3 (α-alumina), γ-Al2O3 (γ-alumina)), mullite, zirconia, titania, or composites thereof, and the average pore diameter is preferably 0.1 to 5.0 μm. The average pore size of pores of 0.1 μm or more can be calculated by the bubble point / gas permeation method, and that 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] In addition, in order to provide the porous support 1 with sufficient mechanical strength, it is desirable that the particles that make up the porous support 1 are fired at 600 to 1,300°C, so that the particles are sintered and bonded to each other.

[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 with a particle diameter of 50 to 500 nm. The proportion of the α-alumina fine particles with a particle diameter of 50 to 500 nm contained in 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% based on all the α-alumina fine particles in the porous composite layer 4. 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 size of the α-alumina particles is obtained by measuring the particle size distribution of the raw material α-alumina particles using a particle size distribution measuring device. The proportion of α-alumina particles with a particle size of 50 to 500 nm contained in all the α-alumina particles in the porous composite layer 4 is also measured using the particle size distribution measuring device, and the proportion of α-alumina particles with a particle size of 50 to 500 nm contained in all the α-alumina particles is calculated.

[0020] The porous composite layer 4 contains nanoparticles with a particle diameter of 1 to 50 nm. The proportion of nanoparticles with a particle diameter of 1 to 50 nm contained in all nanoparticles 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% based on all nanoparticles in the porous composite layer 4. When the particle diameter of the nanoparticles 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 size of the nanoparticles is obtained by measuring the particle size distribution of the raw material nanoparticles using a particle size distribution measuring device. The proportion of nanoparticles with a particle size of 1 to 50 nm contained in all nanoparticles in the porous composite layer 4 is also calculated by measuring the particle size distribution of the nanoparticles using the particle size distribution measuring device.

[0021] The porous composite layer 4 preferably contains α-alumina fine particles 2 in which 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 achieving 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 microparticles in the photographed images are observed to count the number of particles in which the α-alumina microparticles 2 are directly bonded to each other and the number of particles in which the α-alumina microparticles 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 is divided by the number of particles in which the α-alumina fine particles 2 are indirectly bonded to each other via nanoparticles, and the result is multiplied by 100 to obtain the number.

[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 with excellent durability and high permeability and separation performance can be formed, and a separation membrane (final product) can be produced. It is also possible to form various functional layers (not shown) 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 on top of them, a separation membrane (final product) with 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 heated in the range of 200 to 600°C to form a nanoporous layer 5 with an average pore diameter in the range of 0.3 to 50 nm.

[0027] The nanoporous layer 5 can be made from ceramic materials such as silica, silica-zirconia, and zirconia, or polymer sol. When using ceramic materials as raw materials, 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 from a polymer sol obtained by hydrolysis and dehydration condensation of a compound represented by (RO)3·SiXSi·(OR)3, 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 compounds, 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 compounds include bistriethoxysilylmethane (BTESM), bistriethoxysilylethane (BTESE), and bistriethoxylylacetylene (BTESA).

[0028] The ceramic composite membrane (intermediate) or separation membrane (final product) manufactured in this way can be significantly reduced in the occurrence of cracks (membrane defects) during heating and cooling during manufacturing and use. As a result, separation membranes that exhibit high permeation and separation performance, such as excellent selectivity (gas permeability selectivity) between He and SF, as described below, can be formed with good reproducibility.

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

[0030] The porous support was a cylindrical α-alumina porous support (manufactured by Iwao Porcelain Industry Co., Ltd., average pore size 1-3 μm, model number GP-30) with a diameter of 12 mm and a thickness of 1.5 mm, cut into a length of 40 cm. The α-alumina microparticles were high-purity alumina (manufactured by Sumitomo Chemical Co., Ltd., model number AKP-50), all of which had particle sizes in the range of 50-500 nm. Various zirconia, titania, silica, and silica-zirconia nanoparticles were compared for nanoparticle analysis. The particle size distributions of the α-alumina microparticles 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 the nanoparticles used as binders in each example and comparative example, and then fired 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 more 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 the respective Examples and Comparative Examples will be described in detail. Example 1 Zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number: ZSL-13), all of which had a particle size in the 1-50 nm range, were used as the binder nanoparticles (hereinafter, nanoparticles may be referred to as composite particles). A porous composite layer was formed using these nanoparticles. Cross-sectional electron microscope images of the resulting ceramic composite membrane and porous composite layer are shown in Figures 2(A)-(E). A structure was confirmed in which α-alumina microparticles, all of which had a particle size in the 50-500 nm range, were bonded together with zirconia nanoparticles, all of which had a particle size in the 1-50 nm range. The results of surface elemental analysis (XPS) of the porous composite layer are shown in Figure 3(A). The cross-sectional electron microscope image indicated that the porous composite layer was approximately 1-2 μm thick. The results of surface elemental analysis (XPS) confirmed that the porous composite layer was composed of Al, Zr, and O elements. Next, a polymer sol (particle size 1-50 nm) 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. Figure 2(F) shows a cross-sectional electron microscope image of the separation membrane obtained after the nanoporous layer was formed, and Figure 3(B) shows the results of surface elemental analysis (XPS). Cross-sectional electron microscope images showed that the thickness of the nanoporous layer was approximately 100 to 200 nm. Surface elemental analysis (XPS) showed that the surface of the film was composed of the elements Si and C, and by scraping the surface through sputtering, the composition approached that of a porous composite layer containing large amounts of the elements Zr, Al, and O. In addition, cross-sectional electron microscope images were taken at 10 random locations on the porous composite layer, and the α-alumina microparticles in the images were observed to count the number of α-alumina microparticles that were directly bonded to each other and the number of α-alumina microparticles that were indirectly bonded to each other via nanoparticles.The percentage of α-alumina microparticles that were directly bonded to each other in the porous composite layer was calculated from the obtained numbers of α-alumina microparticles that were directly bonded to each other and the number of α-alumina microparticles that were indirectly bonded to each other via nanoparticles.As a result, the percentage of α-alumina microparticles that were directly bonded to each other in the porous composite layer was found to be 20% or less.

[0033] Example 2 Titania nanoparticles (Ishihara Sangyo Kaisha, Ltd., model number: STS-21), all of which had particle diameters in the 1-50 nm range, were used as binder nanoparticles to form a porous composite layer. A polymer sol obtained by hydrolysis and dehydration 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. Figure 2(G) shows a cross-sectional electron microscope image of the resulting separation membrane after nanoporous layer formation. Figures 2(H)–(I) show energy-dispersive X-ray spectroscopy images, and Figure 3(C) shows the results of surface elemental analysis (XPS). A structure in which α-alumina particles were bonded with titania nanoparticles with particle diameters in the 1-50 nm range was confirmed. Furthermore, the nanoporous layer on the membrane surface was composed of silicon and carbon elements. By removing the surface through sputtering, the composition of the porous composite layer, which contains large amounts of titanium, aluminum, and oxygen, was achieved. The proportion of α-alumina particles directly bonded to each other in the porous composite layer was 20% or less.

[0034] Example 3 We attempted to form a nanoporous layer made of zirconia by applying additional zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number ZSL-13) to the surface of the porous composite layer formed in Example 1, all of whose particles had a particle size ranging from 1 to 50 nm, and then firing the layer at 550°C for 10 minutes. By repeating this additional application and firing process two to eight times, we were able to adjust the nanopore size to approximately 10 to 50 nm. Figure 3(D) shows the results of surface elemental analysis (XPS) of the ceramic composite membrane obtained after the nanoporous layer was formed. The results of surface elemental analysis (XPS) indicate 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 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 particle diameters were 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 between 2 and 12 times, the nanopore diameter was adjusted to within the range of approximately 1 to 10 nm. Furthermore, 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 sizes 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 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) The porous composite layer was formed using silica-zirconia nanoparticles, all of which had particle sizes in the 1-50 nm range, as the binder nanoparticles. 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 6-8 hours. 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. The proportion of α-alumina particles directly bonded to each other in the porous composite layer was less than 20%.

[0038] (Comparative Example 2) A porous composite layer was formed using silica nanoparticles (Nissan Chemical Co., Ltd., model number ST-C) with particle diameters of all particles ranging from 1 to 50 nm as the nanoparticles used as the binder. A polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was then 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 particles directly bonded to each other in the porous composite layer was 20% or less.

[0039] (Comparative Example 3) Zirconia nanoparticles (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd., model number: ZSL-20N), all of which had a particle size in the range of 50 to 100 nm, were used as the nanoparticles used as binders to form a porous composite layer. A polymer sol obtained by hydrolyzing and dehydrating condensation of bistriethoxysilylethane (BTESE) was then applied to the surface of the porous composite layer, which was then heated and dried at 300°C for 10 minutes to form a nanoporous layer. The proportion of α-alumina 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, the gas permeation rates of helium gas (He: molecular diameter 0.27 nm) and sulfur hexafluoride (SF6: molecular diameter 0.55 nm) in their pure gas state at 200°C were measured using a separation membrane module. The permeability P [mol / (m 2 s Pa)] was calculated, and the selectivity α, which indicates the separation performance, was calculated from this permeability value using the following formula 1 for evaluation. (Formula 1) Selectivity α(He / SF6)=P(He) / P (SF6) The measurement results are shown in Table 1 and FIG. It is expected that the nanoporous layer will exhibit a higher selectivity α(He / SF6) if the pore diameter is 0.3 to 0.5 nm and the number of voids (membrane defects) larger than SF6 is reduced. [Table 1] First, even the best conventional separation membranes specified in the inventions described in Patent Documents 1 and 2 had a selectivity (He / SF6) of 510. In contrast, the composite of α-alumina fine particles and zirconia nanoparticles in Example 1 showed an unexpectedly remarkable selectivity (He / SF6) of 9,903 to 18,888. A total of four samples were produced and tested to confirm reproducibility, and they showed remarkably high selectivity (He / SF6) with good reproducibility. In Example 2, the composite of α-alumina fine particles and titania nanoparticles also showed a sufficiently significant selectivity (He / SF6) of 1,958 to 5,054. In Comparative Example 1, the composite of α-alumina fine particles and silica-zirconia nanoparticles also showed a reasonably high selectivity (He / SF6) of 1,143 to 1,391, but did not reach the performance of Examples 1 and 2. In Comparative Example 2, the composite of α-alumina fine particles and silica nanoparticles showed a reasonable selectivity (He / SF6) of 138 to 204, but the result was worse than that of the conventional product in Comparative Example 4. In Comparative Example 3, the composite of α-alumina fine particles and zirconia nanoparticles showed a reasonable selectivity (He / SF6) of 281 to 324, but the result was worse than that of the conventional product in Comparative Example 4. As described above, although the detailed mechanism by which the use of zirconia and titania nanoparticles results in superior effects has not yet been elucidated, it is presumed that the combination of Examples 1 and 2 of the present invention has excellent durability, which prevents cracks from occurring in the separation layer when heated and cooled during production and use, and results in the formation of a separation membrane that exhibits high permeation and separation performance, thereby exhibiting superior effects.

[0042] When the membrane pore diameter is 0.5 to 50 nm, the pore distribution of the nanoporous layers formed in Examples 3 to 5 can be generally and effectively evaluated by nanoperm porometry. In this method, a mixture of a non-condensable gas and a condensable vapor is supplied to the porous membrane, and the pore diameter is evaluated based on the Kelvin equation (Equation 2 below). (Formula 2) TIFF2025179036000003.tif17170 (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 vapors block pores through capillary condensation at a relative pressure (vapor partial pressure relative to saturated vapor pressure) corresponding to the Kelvin diameter (d), thereby reducing the permeability of noncondensable gases. Therefore, by measuring the permeability of noncondensable gases using relative pressure as a parameter, it is possible to estimate the contribution of each pore size to the permeability. Here, water vapor was used as the condensable vapor and nitrogen was used as the noncondensable gas. Measurements were performed at a nitrogen gas (N2) total flow rate of 5 L (STP) / min at 25°C and a relative humidity range of 0 to 95.9% (Kelvin diameter range of 0 to 50 nm). Test membrane samples were evaluated at a length of 40 cm. Because the nanoporous layers were hydrophilic, pore size was calculated assuming a contact angle θ = 0. Figure 5 shows the pore size distribution profiles of the nanoporous layers formed in Examples 3 to 5. By adjusting the type of nanoparticles applied, we were able to control the N2 permeability of pores larger than a specified diameter to 0.1% or less, with pore diameters (Kelvin diameters) ranging from 0.5 to 50 nm. Note that in the nanoperm porometry method, the Kelvin diameter showing 50% N2 permeability is defined as the average pore diameter. [Industrial Applicability]

[0043] The present invention can be used as a ceramic composite membrane to form a separation membrane that suppresses cracking in the separation layer during heating and cooling during manufacturing and use, and that has excellent durability and exhibits high permeability and separation performance. Specifically, when the nanopore layer is in the range of 0.3 to 0.5 nm, it is expected to be used as a separation membrane for small molecules such as hydrogen, CO2, methane, hydrocarbons, organic solvents, and water vapor. When the nanopore layer is in the range of 5 to 50 nm, it is expected to be used industrially for separating various nanoparticles and as a substrate for various functional membranes. [Explanation of symbols]

[0044] 1: Porous support 2: α-alumina fine particles 3: Nanoparticles (1-50 nm) 4: Porous composite layer 5: Nanoporous layer

Claims

1. A porous support having an average pore diameter of 0.1 to 5.0 μm and a porous composite layer laminated on the surface of the porous support, the porous composite layer contains α-alumina fine particles having a particle diameter of 50 to 500 nm and nanoparticles having a particle diameter of 1 to 50 nm, the porous composite layer is a dispersion layer in which either the nanoparticles or the α-alumina fine particles are present as a matrix phase, and the other is dispersed in the matrix phase; The ceramic composite film, wherein the nanoparticles contain at least either zirconia or titania.

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

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