Monolithic base and manufacturing process

Abstract

Monolithic base comprising pores and formed from alumina particles as aggregate and an oxide phase as binder, wherein the alumina particles comprise microscopic alumina particles with a particle diameter greater than or equal to 0.5 µm and less than or equal to 5 µm and coarse alumina particles with a particle diameter greater than 5 µm, the number of microscopic alumina particles encapsulated in the oxide phase is greater than or equal to 50% of the total number of microscopic alumina particles and coarse alumina particles, and the porosity of the monolithic base is greater than or equal to 20% and less than or equal to 60%.

Description

TECHNICAL FIELD

[0001] The present invention relates to a monolithic base and a manufacturing method therefor. STATE OF THE ART

[0002] Regarding a typical monolithic structure provided with a monolithic base including a plurality of filtration cells and a separation membrane formed on an inner surface of the filtration cells, a technique for inhibiting adverse effects on strength resulting from high-temperature alkali processing by appropriately providing a thickness for the separation layer and a partition wall thickness between two filtration cells has been proposed (reference is made to Patent Document 1). Document listPatent document [Patent document 1] WO 2012 / 128218 A1 [Patent document 2] DE 39 35 471 A1 [Patent document 3] DE 43 43 121 A1 [Patent document 4] DE 10 2009 011 790 A1 SUMMARY OF THE INVENTIONTechnical Problem

[0003] According to the method disclosed in Patent Document 1, the structural strength of the monolithic base can be increased by a structural measure of increasing the partition wall thickness of the base between two filtration cells in a monolithic structure. However, it is sometimes the case that a reduction in weight and / or an increase in compactness is desired in view of an application of the monolithic structure, and in view of increasing the strength of the structure without increasing the partition wall thickness, there is a need to increase the strength of the material itself constituting the monolithic base. Other prior art is known from Patent Documents 2 to 4.

[0004] The present invention is proposed in view of the situation described above and has an object to provide a monolithic base having excellent strength and a method for producing the same. Solution to the problem

[0005] The monolithic base according to the present invention is a porous alumina body comprising pores and formed from alumina particles as an aggregate and an oxide phase as a binding material. The alumina particles include microscopic alumina particles with a particle diameter greater than or equal to 0.5 µm and less than or equal to 5 µm, and coarse alumina particles with a particle diameter greater than 5 µm. The number of microscopic alumina particles encapsulated in the oxide phase is greater than or equal to 50% of the total number of microscopic alumina particles and coarse alumina particles. Effect of the invention

[0006] The present invention makes it possible to provide a monolithic base having excellent strength and a method for producing the same. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a perspective view showing a monolithic separation membrane structure. Fig. 2 shows a plan view of a first end face of the monolithic separation membrane structure. Fig. 3 is a sectional view along AA in the Fig. 2. Fig. Figure 4 is a SEM (scanning electron microscope) cross-sectional image of a monolithic base according to Example 1. Fig. Figure 5 is a SEM cross-sectional image of a monolithic base according to Example 5. Fig. Figure 6 is a SEM cross-sectional image of a monolithic base according to Example 6. Fig. 7 is a SEM cross-sectional image of a monolithic base according to Comparative Example 1. DESCRIPTION OF EMBODIMENTS

[0007] Next, embodiments of the present invention will be described with reference to the figures. In the following description of the figures, the same or corresponding portions are denoted by the same or corresponding reference numerals. However, the figures are for illustrative purposes only, and the relationship of the respective dimensions or the like may differ from the actual dimensions. Therefore, the actual dimensions or the like should be determined by reference to the following description. Furthermore, it is understood that the ratios or relationships of dimensions used in the respective figures may be different.

[0008] In the following embodiments, the term “monolithic” represents a concept that denotes a shape including a plurality of through holes formed in the longitudinal direction and includes a honeycomb shape. Overview of the structure

[0009] The monolithic separation membrane structure 100 is suitably applied to the separation of water from a mixture of alcohol and water. As described in the Fig. 1 to Fig. 3, the monolithic separation membrane structure 100 is formed of a ceramic porous body and is provided with a monolithic base 10 having the two end surfaces 11S, 11T and an outer peripheral surface 11U. The outer shape of the monolithic base 10 is cylindrical. The monolithic base 10 includes a plurality of filtration cells 24 and a plurality of water collection cells 25. The plurality of filtration cells 24 pass from one end surface 11S to the other end surface 11T and are arranged in a row generally in the transverse direction in the Fig. 1. The plurality of water collecting cells 25 pass from one end surface 11S to the other end surface 11T and are arranged in a row generally in the transverse direction in the Fig. 1 trained.

[0010] The cross-sectional shape of the filtration cells 24 and the water collection cells 25 in the monolithic separation membrane structure 100 is circular. The filtration cells 24 are open on both end surfaces 11S, 11T. The opening of the two end surfaces 11S, 11T in the water collection cells 25 is closed with a closure member 12, 13, and a discharge channel 26 is provided so that the water collection cells 25 communicate with an outside space. Furthermore, an intermediate layer 20 and a separation membrane 30 are arranged on an inner wall surface of the filtration cells 24, which have a circular cross-sectional shape.

[0011] The monolithic separation membrane structure 100 forms two discharge channels 26 near the two end surfaces 11S, 11T for each row (hereinafter referred to as “water collection cell row”) 25L of the plurality of water collection cells 25. There are 5 water collection cell rows 25L in the monolithic separation membrane structure 100, and at each row, the discharge channel 26 connects the plurality of water collection cells 25 and is opened on an outer peripheral surface 11U of the monolithic base 10.

[0012] In the Fig. 1 to Fig. 3, the number of discharge channels 26 in the monolithic separation membrane structure 100 at both ends is 10, since 5 water collection cell rows 25L are present in the monolithic separation membrane structure 100.

[0013] The above structure enables efficient separation of a component that has passed through the filtration cells 24 from a mixed fluid (fluid mixture or gaseous mixture) flowing into the filtration cells 24. Specifically, a permeation component that has passed through the separation membrane 30 of the inner surface of the filtration cells 24 and that has passed through the intermediate layer 20 then sequentially flows into the porous body forming the partition wall inner portion of the monolithic base 10 and is discharged from the outer partition wall 11U. However, the length of the permeation distance to be traversed in the partition wall (porous body) increases in proportion to an internal position for a filtration cell 24.In this regard, the provision of the water collection cells 25 and the discharge channels 26 enables continuous flow in the partition wall between existing filtration cells 24 and facilitates discharge with a low pressure loss through the discharge channels 26 and the water collection cells 25 into an outside space.

[0014] The monolithic separation membrane structure 100 is provided with sealing portions 14, 15 for covering the porous body of the two end surfaces 11S, 11T of the monolithic base 10 into which the mixed fluid flows, to prevent a mixed fluid from directly flowing in and discharging from the porous portion of the two end surfaces 11S, 11T of the monolithic base 10 without being separated by the separation membrane 30 formed on an inner wall surface of the predetermined filtration cells 24. Both ends of the filtration cells 24 provided with the separation membrane 30 are connected to and opened on the sealing portions 14, 15. The inner surfaces of the plurality of respective filtration cells 24 include the intermediate layer 20 and the separation membrane 30 formed sequentially. Structure for respective structures

[0015] The monolithic base 10 is formed in a cylindrical shape. The longitudinal length of the monolithic base 10 can be 100 to 2000 mm. The diameter of the monolithic base 10 can be 30 to 220 mm. The monolithic base 10 can also be an elliptical cylinder or a polygonal prism.

[0016] Although there is no specific limitation on the partition wall thickness D1 excluding the intermediate layer 20 and the separation membrane 30 of the shortest section between two adjacent filtration cells 24, it may be greater than or equal to 0.05 mm to less than or equal to 0.8 mm, and it is preferably greater than or equal to 0.05 mm to less than 0.2 mm. A structure in which the partition wall thickness D1 between two filtration cells 24 is less than 0.2 mm enables densification of the filtration cells 24 and an increase in the total surface area of ​​the separation membrane 30, thus increasing compactness and / or reducing weight.In view of increasing the total surface area of ​​the separation membrane 30, although densification of the filtration cells 24 is enabled when the partition thickness D1 is reduced, since the strength will be insufficient if the thickness is too thin and the partition structure of the monolithic base 10 may collapse during manufacture and / or use, the actual thickness may be greater than or equal to 0.05 mm. In view of increasing the total surface area while preventing the partition structure of the monolithic base 10 from collapsing, the partition thickness D1 of two filtration cells 24 is preferably greater than or equal to 0.10 mm and less than or equal to 0.18 mm. In the present embodiment, although all positions between two adjacent filtration cells 24 are formed with a uniform partition thickness D1, a plurality of types of partition thickness D1 may be provided.

[0017] As it is in the Fig. 2, when the first end surface 11S is viewed in plan view, the plurality of filtration cells 24 form a plurality of filtration cell rows 24L. The plurality of respective filtration cell rows 24L include two or more filtration cells 24 aligned along a transverse direction (example of a predetermined direction) orthogonal to the longitudinal direction. In the present embodiment, 28 filtration cell rows 24L are formed, aligning 7 to 29 filtration cells 24 in each row. However, the number of filtration cells 24 in each row or the number of filtration cell rows 24L may be appropriately varied.

[0018] Although there is no particular limitation on the partition thickness D3 excluding the intermediate layer 20 and the separation membrane 30 of the shortest section of adjacent filtration cells 24 and water collection cells 25, it may be greater than or equal to 0.05 mm to less than 0.8 mm, and it is preferably greater than or equal to 0.05 mm to less than 0.2 mm. A structure in which the partition thickness D3 is less than 0.2 mm enables an increase in the total surface area of ​​the separation membrane 30. With regard to increasing the total surface area of ​​the separation membrane 30, although a reduction in the partition thickness D3 is preferable due to the resulting densification of the filtration cells 24, since the strength will be insufficient if the thickness is too small and the partition structure of the monolithic base 10 may collapse during manufacture and / or use, the actual thickness may be greater than or equal to 0.05 mm.In view of the fact that the total surface area can be increased while preventing the collapse of the partition wall structure of the monolithic base 10, the partition wall thickness D3 is preferably greater than or equal to 0.1 mm and less than or equal to 0.18 mm. Furthermore, in the present embodiment, although all positions between adjacent filtration cells 24 and water collection cells 25 are formed with a uniform partition wall thickness D3, a plurality of types of the partition wall thickness D3 may be provided. Moreover, although not shown in the drawings, the distance between adjacent water collection cells 25 may be greater than or equal to 0.05 mm and less than 0.2 mm, and more preferably greater than or equal to 0.1 mm and less than or equal to 0.18 mm.

[0019] As it is in the Fig. As shown in FIG. 2, when the first end surface 11S is viewed in plan view, the plurality of water collection cells 25 constitute a plurality of water collection cell rows 25L. The plurality of respective water collection cell rows 25L include two or more water collection cells 25 aligned along a transverse direction (an example of a predetermined direction). In the present embodiment, five water collection cell rows 25L are arranged at mutually separate positions, and although 22 to 29 water collection cells 25 are aligned in each row, the number of water collection cells 25 included in each row or the number or position of the water collection cell rows 25L may be appropriately varied.

[0020] As it is in the Fig. 1, the discharge channels 26 include an opening 26a opened on the outer peripheral surface 11U. The opening 26a may be drilled at only one of the two end surfaces of the monolithic base 10, or it may be drilled by drilling along the longitudinal direction in addition to both end surfaces of the monolithic base 10. In view of uniform discharge of the permeation component, the opening 26a is preferably provided at least at both end surfaces. The number, shape, and position of the discharge channels 26 may be identical or may be different in all the water collection cell rows 25L.

[0021] The first closure element 12 and the second closure element 13 are arranged in all water collection cells 25. The first closure element 12 and the second closure element 13 are arranged in an opposing configuration on both end surfaces of each water collection cell 25. The first closure element 12 and the second closure element 13 can be formed from a porous material. The filling depth of the first closure element 12 and the second closure element 13 can be approximately 5 to 20 mm.

[0022] The first sealing portion 14 covers a portion of the outer peripheral surface 11U and the entire surface of the first end surface 11S. The first sealing portion 14 prevents the penetration of a mixed fluid into the first end surface 11S. The first sealing portion 14 is formed so as not to block the inflow opening of the filtration cells 24. The first sealing portion 14 covers the first closure member 12. The material constituting the first sealing portion 14 includes glass or metal, rubber, resin, or the like, with glass being preferable in view of its matching with the thermal expansion coefficient of the monolithic base 10.

[0023] The second sealing portion 15 covers a portion of the outer peripheral surface 11U and the entire surface of the second end surface 11T. The second sealing portion 15 prevents the penetration of a mixed fluid into the second end surface 11T. The second sealing portion 15 is formed so that the inflow opening of the filtration cells 24 is not blocked. The second sealing portion 15 covers the second closure member 13. The second sealing portion 15 can be formed of the same material as the first sealing portion 14. Monolithic Base 10

[0024] The monolithic base 10 is a porous alumina body including pores and is formed of alumina particles as an aggregate and an oxide phase as a binding material. 1. Aggregat

[0025] The alumina particles used as the aggregate are suitable as an aggregate of raw materials (aggregate particles) with a controlled particle diameter, which are readily available and enable the formation of a stable clay accompanied by excellent corrosion resistance. Although there is no specific limitation on the volume fraction of the aggregate to the total volume of the bonding material and the aggregate, it may be, for example, greater than or equal to 65% by volume and less than or equal to 85% by volume. The volume fraction of the aggregate is preferably greater than or equal to 70% by volume and less than or equal to 80% by volume. A structure in which the volume fraction of the aggregate is greater than or equal to 70% by volume enables a reduction in defects such as firing cracks or the like by suppressing contraction during firing (firing shrinkage).A structure in which the volume fraction of the aggregate is less than or equal to 80% by volume allows for the improvement of sufficient strength between the bonding material and the aggregate particles. The content fraction of alumina particles can be measured using the Archimedes method.

[0026] In this context, the Fig. 4 an example of a cross-sectional SEM (scanning electron microscope) image of the monolithic base 10. The SEM cross-sectional image in the Fig. Figure 4 shows the aluminum oxide particles (aggregate) light gray, the oxide phase (binding material) dark gray and the pores (holes) black.

[0027] As it is in the Fig. 4, the alumina particles include microscopic alumina particles and coarse alumina particles. In the present embodiment, "microscopic alumina particle" means an alumina particle having a particle diameter of greater than or equal to 0.5 μm and less than or equal to 5 μm. "Coarse alumina particle" means an alumina particle having a particle diameter of greater than 5 μm. The diameter of the alumina particle for each aggregate particle in the SEM cross-sectional image of the alumina porous body is assumed to have a circular configuration, and it is a diameter calculated based on this surface area. In the following description, both the microscopic alumina particles and the coarse alumina particles may be collectively referred to as alumina particles.

[0028] As it is in the Fig. 4, a part of all the microscopic alumina particles and a part of all the coarse alumina particles are encapsulated in the oxide phase. That is, the surface of each microscopic alumina particle of a part of the total microscopic alumina particles is covered by the oxide phase, and the surface of each coarse alumina particle of a part of the total coarse alumina particles is covered by the oxide phase. In the present embodiment, the terms "encapsulated in the oxide phase" and "covered by the oxide phase" with respect to the alumina particles mean that more than or equal to 50% of the surface of the alumina particles is in contact with the oxide phase. Therefore, a structure in which a part of more than 50% of the surface of an alumina particle is adjacent to a pore is a structure not covered by the oxide phase.In the SEM cross-sectional image, when the length of the contact surface in contact with an oxide relative to the length of an outer circumference of an alumina particle is greater than or equal to half, it can be determined that more than or equal to 50% of the surface of the alumina particle is in contact with the oxide phase.

[0029] The number of microscopic alumina particles encapsulated in the oxide phase is greater than or equal to 50% of the total number of microscopic alumina particles and coarse alumina particles. In this way, the strength of the monolithic base 10 can be significantly increased. Although the reason for the increase in strength as a result of the presence of a large number of microscopic alumina particles in the oxide phase is unclear, it is generally the case that cracks extend in an oxide phase with a low strength when a crack is generated as a result of applying a stress to the porous alumina body constituting the base. In this context, it can be considered that the strength is increased due to the suppression of such crack propagation in the oxide phase as a result of the presence of microscopic alumina particles in the oxide phase.It is preferable that the number of microscopic alumina particles encapsulated in the oxide phase be greater than or equal to 60% and less than or equal to 95% of the total number of microscopic alumina particles and coarse alumina particles. It should be noted that, in view of more effectively suppressing crack propagation, it is preferable that the microscopic alumina particles encapsulated in the oxide phase be formed by a larger number of microscopic alumina particles than a number of comparatively larger particles. The number of microscopic alumina particles encapsulated in the oxide phase can be obtained by counting the number in an SEM cross-sectional image of microscopic alumina particles of which more than or equal to 50% have continuous contact with the oxide phase.

[0030] Although there is no specific limitation on the number of coarse alumina particles encapsulated in the oxide phase among the total coarse alumina particles, it may be less than or equal to 30% of the total number of microscopic alumina particles and coarse alumina particles. Unlike the microscopic alumina particles, since the coarse alumina particles primarily act as an aggregate supporting the porous alumina body forming the monolithic base, a configuration in which there is alignment with the bonding material (oxide phase) to thereby support a defined bonding surface with the adjacent microscopic alumina particles is essentially sufficient without the need for encapsulation in the oxide phase. The proportion of the oxide phase increases as the number of coarse alumina particles aligned with the oxide phase increases.Conversely, this feature becomes a cause of defects such as firing cracks as a result of increased contraction (shattering) during firing. It is preferable that the number of coarse alumina particles encapsulated in the oxide phase be less than or equal to 15% of the total number of microscopic alumina particles and coarse alumina particles. The number of coarse alumina particles encapsulated in the oxide phase can be obtained by counting the number of coarse alumina particles in a SEM cross-sectional image, of which more than or equal to 50% are continuously in contact with the oxide phase.

[0031] Although there is no difference in the 50% diameter (hereinafter referred to as “D g50") in the cumulative volume particle diameter distribution of the aluminum oxide particles constituting the base, there is no specific limitation, it may be greater than or equal to 5 µm to less than or equal to 40 µm. D g 50 is the so-called median diameter. D g 50 is preferably greater than or equal to 10 µm to less than or equal to 25 µm, and more preferably less than or equal to 20 µm.

[0032] If the 50% diameter is 10 z µm, the 10% diameter (hereinafter referred to as “D910”) in the cumulative volume particle diameter distribution of the alumina particles is preferably less than or equal to 10( z-0,2 ) µm. Furthermore, if the D g 50 than 10 z µm, the 90% diameter (hereinafter referred to as “D g 90”) in the cumulative volume particle diameter distribution of the base particles is preferably greater than or equal to 10 (z+0,2)µm. Therefore, it is preferred that the grain size distribution D g 10 ≦ 10( z-0,2 ) µm and D g 90 ≧ 10 (z+0,2) µm, meaning that there is a broad grain size distribution.

[0033] The cumulative volume particle diameter distribution of the base particles can be measured by calculating the diameter based on the surface area, assuming a circular configuration, for all base particles included in an SEM cross-sectional image with any surface. Specifically, the pores, alumina particles, and oxide phase are distinguished by using ternary value processing using image analysis of an SEM cross-sectional image in a 200 × 200 µm area. The surface area is measured with respect to each distinguished alumina particle, thereby enabling the calculation of the diameter of each alumina particle through a circularity approximation. Image analysis can be performed, for example, using application software (Image-ProPlus (trade name)) used for image analysis and manufactured by MEDIA CYBERNETICS Inc. 2. Binding material

[0034] The oxide phase used as the bonding material is a glass material comprising silicon (Si) and aluminum (Al), and at least one of an alkali metal and an alkaline earth metal. The oxide phase preferably comprises both an alkali metal and an alkaline earth metal. The alkali metal includes the use of at least one of sodium (Na), potassium (K), and lithium (Li). The oxide phase may contain an alkali metal as the alkali metal oxide. The alkaline earth metal includes the use of at least one of magnesium (Mg), calcium (Ca), strontium (Sr), and barium (Ba). The oxide phase may contain an alkaline earth metal as the alkaline earth metal oxide. The oxide phase may contain Si as SiO2. The oxide phase may contain Al as Al2O3.

[0035] The Si content ratio in the oxide phase can be greater than or equal to 50 mass% and less than or equal to 90 mass% according to SiO2 conversion. The total content ratio of the alkali metal or alkaline earth metal in the oxide phase is preferably greater than or equal to 9 mass% and less than or equal to 15 mass% according to oxide conversion. In this way, the eutectic point of the oxide phase can be lowered, the wettability with respect to the alumina particles can be improved, and penetration between alumina particles is facilitated. Therefore, the microscopic alumina particles tend to be encapsulated by the oxide phase. As a result, the strength of the monolithic base 10 is significantly increased because a large number of microscopic alumina particles can be encapsulated in the oxide phase in addition to the pronounced contraction between alumina particles.Furthermore, since the eutectic point is reduced, the firing temperature for the monolithic base 10 can be reduced and the required energy during the firing process can be reduced.

[0036] Although there is no specific restriction on the Al content in the oxide phase, it can be greater than or equal to 0.1 mass% and less than or equal to 41 mass% according to Al2O3 conversion. In order to lower the eutectic point of the oxide phase, the Al content in the oxide phase is preferably greater than or equal to 5 mass% and less than or equal to 25 mass% according to Al2O3 conversion.

[0037] The weight of the monolithic base 10 can be reduced by reducing the specific gravity of the oxide phase with a structure in which the content of Si in the oxide phase is greater than the content of Al. Although there is no specific limitation on the specific gravity of the oxide phase, it may, for example, be greater than or equal to 1 g / cm 3 and less than or equal to 3 g / cm 3and increasing the Si content allows for a reduction in its specific gravity. The specific gravity of the oxide phase can be calculated based on the content of the oxide phase and the alumina particles and measured using the Archimedes method. The content of the respective elements in the oxide phase can be measured by eluting only the oxide phase from the monolithic base 10 using a hydrofluoric acid method and quantifying the resulting solution using an inductively coupled plasma atomic emission spectrometer (ICP-AES).

[0038] Although there is no specific limitation on the content ratio of the oxide phase in the monolithic base 10, it may be greater than or equal to 15 volume % and less than or equal to 40 volume %. The content ratio of the oxide phase is preferably greater than or equal to 22 volume % from the viewpoint of increasing strength by encapsulating microscopic alumina particles and reducing the contraction of coarse alumina particles, and preferably less than or equal to 38 volume % from the viewpoint of reducing defects such as firing cracks by suppressing contraction (shattering) during firing. The content ratio of the oxide phase can be measured by quantifying it in terms of the occupied surface area of ​​the oxide phase in the SEM cross-sectional image. 3. Pores

[0039] The porosity of the monolithic base 10 is greater than or equal to 20% and less than or equal to 60%.

[0040] When considering the pressure loss during the passage of a liquid that has penetrated the separation membrane 30 and then passes through the porous alumina body forming the monolithic base 10, it is preferable that the porosity be greater than or equal to 30%. Furthermore, in view of maintaining high strength with respect to the porous alumina body forming the monolithic base, the value is preferably less than or equal to 45%. The porosity can be measured using a mercury injection method.

[0041] Although there is no difference in the 50% diameter (hereinafter referred to as “D p 50") in the cumulative volume pore diameter distribution of the monolithic base 10, it may be greater than or equal to 1 µm to less than or equal to 10 µm. The D p50 of the pore diameter is preferably greater than or equal to 2 µm to less than or equal to 6 µm. The D p 50 of the pore diameter is the so-called median diameter.

[0042] Although there is no information available regarding the 10% diameter (hereinafter referred to as “D p 10") in the cumulative volume pore diameter distribution of the monolithic base 10, there is no special limitation when the D p 50 than 10 y µm, it is preferably less than or equal to 10 (y+0,5) µm. Although there is no difference in the 90% diameter (hereinafter referred to as “D p 90") in the cumulative volume pore diameter distribution of the monolithic base 10, there is no special limitation when the D p 50 than 10 y µm, it is preferably greater than or equal to 10 (y-0,5) µm. Therefore, it is preferred that the pore diameter of the monolithic base be 10 D p 10 ≦ 10 (y+0,5)µm and D p 90 ≧ 10 (y-0,5) µm is sufficient. This feature means that the pore diameter of 80% of the total number of pores has a pore diameter distribution that lies within the range of 10 (y±0,5) µm, meaning there is a sharp pore diameter distribution. A sharp pore diameter distribution means that there is a small number of fine pores or coarse pores relative to the D p 50. A small number is preferred because small, fine pores cannot effectively reduce the pressure loss of a liquid. On the other hand, a small number of large, coarse pores is preferred because the base pores are blocked by the penetration of an interlayer slurry into an inner portion of the base during film formation of the interlayer on the monolithic base.

[0043] The cumulative volume pore diameter distribution of the monolithic base 10 can be measured using a mercury injection method. Method for producing a monolithic separation membrane structure 100

[0044] First, an alumina powder is prepared as the basic raw material. The alumina powder is an alumina powder that contains a D g 50 from greater than or equal to 5 µm to less than or equal to 40 µm, and if the D g 50 10 7 µm, the D g 10 less than or equal to 10( z-0,2 ) µm and the D g 90 is greater than or equal to 10 (z+0,2) µm. The use of an alumina powder exhibiting this type of broad grain size distribution allows for the simultaneous provision of coarse alumina particles that form a solid base and a large number of microscopic alumina particles that increase the strength of the oxide phase.

[0045] Next, an oxide phase is prepared as the bonding material. The oxide phase contains Si and Al and at least one of an alkali metal and an alkaline earth metal. The content ratio of Si in the oxide phase can be greater than or equal to 50 mass% and less than or equal to 90 mass% according to SiO2 conversion. The total content ratio of an alkali metal or alkaline earth metal in the oxide phase is preferably greater than or equal to 9 mass% and less than or equal to 15 mass% according to oxide conversion. The content ratio of Al in the oxide phase is preferably greater than or equal to 0.1 mass% and less than or equal to 41 mass% according to Al2O3 conversion.

[0046] Next, the alumina particles and the oxide phase are weighed. The masses are calculated so that the proportion of the oxide phase relative to the total amount of the oxide phase and the alumina particles is greater than or equal to 22% by volume and less than or equal to 38% by volume. For example, if the weighing is carried out such that the volume ratio of the oxide phase to the alumina particles is 78:22, in the case where the specific gravity of the oxide phase is 1 g / cm 3 and the specific gravity of the aluminum oxide particles is 4 g / cm 3 , the weighing should be carried out in such a way that the mass ratio of the oxide phase and the aluminum oxide particles has a value of 93.4:6.6. Furthermore, for example, if the weighing is carried out in such a way that the volume ratio of the oxide phase and the aluminum oxide particles has a value of 62:38, in the case where the specific gravity of the oxide phase is 3 g / cm3 and the specific gravity of the aluminum oxide particles is 4 g / cm 3 , the weighing must be carried out such that the mass ratio of the oxide phase and the aluminum oxide particles has a value of 69:32. This means that the weighing can be carried out such that the mass of the oxide phase, based on the total mass of the oxide phase and the aluminum oxide particles, is greater than or equal to 6.6 mass% and less than or equal to 32 mass% according to an oxide conversion.

[0047] Next, a clay is prepared by adding water, a dispersant, and an organic binder, such as methylcellulose, to the weighed oxide phase and alumina particles, followed by kneading. If it is desired to increase the porosity of the monolithic base, a pore-forming agent is added.

[0048] Then, the prepared clay is extrusion-molded, for example, by means of a vacuum extruder, so that a green body for the monolithic base is obtained, which has a plurality of filtration cells 24 and a plurality of water collection cells 25.

[0049] Then, the green body for the monolithic base is fired, for example, at 900 to 1600°C to obtain a monolithic base, and a cut for the discharge channel is formed so as to connect from one position of the outer peripheral surface through the water collection cell 25 to another position. The cut for the discharge channel can be formed with a band saw or a cutting wheel device, a wire saw, or the like provided with a diamond abrasive, while a laser reference is applied to both end surfaces where the discharge channel 26 is formed. During the cutting process, friction and / or heat generation can be reduced by using a solvent such aswater or the like, since the life of the cutting tool is reduced as a result of heat generation and / or loss of diamond abrasive due to friction between the monolithic base and the cutting tool.

[0050] Next, in the resulting monolithic base, a sealing material in the form of a slurry is filled into a space reaching the discharge channel 26 from both end faces of the water collection cells formed by cutting the discharge channel, thereby obtaining a sealing material-filled monolithic base. Specifically, a film (masking) such as a polyester or the like is applied to both end faces of the monolithic base, and a hole is drilled in the film by laser irradiation or the like at the portion corresponding to the discharge channel 26.

[0051] Then, the end face of the monolithic base with the film applied thereto is pressed into a container filled with the sealing material (slurry) and filled by applying a pressure of, for example, 200 kg using an air cylinder or the like, thereby obtaining a sealing material-filled monolithic base. The sealing material-filled fired monolithic base is fired, for example, at 900 to 1400 °C, thereby obtaining a sealing material-filled monolithic base.

[0052] Then, an interlayer 20 as a base for the separation membrane 30 is formed on an inner wall surface of the filtration cells 24 of the sealing material-filled monolithic base. First, an interlayer slurry is prepared to form the interlayer 20 (film formation). The interlayer slurry can be prepared by adding 400 parts by mass of water to 100 parts by mass of a ceramic raw material having a desired particle diameter (e.g., an average particle diameter of 1 µm to 5 µm). Then, an inorganic membrane bonding material can be added to the interlayer slurry to increase the membrane strength after sintering. The inorganic membrane bonding material can include the use of clay, kaolin, a titanium oxide sol, a silica sol, a glass frit, or the like.The addition amount of the inorganic membrane bonding material is preferably 5 to 42 parts by mass in view of the film strength.

[0053] The interlayer slurry is applied to an inner wall surface of the filtration cells 24, and after drying, the interlayer 20 is formed by sintering, for example, at 900 to 1050°C. The interlayer 20 can be formed into a film as a plurality of separate layers, such as the interlayer 21 and the interlayer 22, by using a plurality of types of slurry in which the average particle diameter is varied. In a configuration in which the interlayer 20 is formed into a plurality of layers, the film-forming process and the firing process can be performed with respect to each interlayer, or an integrated firing process can be performed after repeating a plurality of film-forming processes.

[0054] Next, after applying a glass raw material slurry by spraying or brushing onto an end face of the resulting monolithic base with the intermediate layer attached thereto, a green body for the first and second sealing portions 14, 15 can be formed by firing at, for example, 800 to 1000°C. A glass raw material slurry can be adjusted into a glass frit by mixing an organic binder and water. Although a structure has been described in which the material for the first and second sealing portions 14 and 15 is glass, as long as the first and second sealing portions 14 and 15 allow the passage of the separation fluid discharged from the discharge channel 26 after separation from the mixed fluid that is the subject of the separation process, for example, a silicone resin or a Teflon (registered trademark) resin or the like can be used.In a structure in which the intermediate layer 20 has a multi-layer structure, a green body for the first and second sealing portions 14 and 15 may be formed during the formation of the intermediate layer 20.

[0055] Next, the separation membrane 30 is formed on an inner surface of the intermediate layer 20. In this connection, when the average pore diameter of the separation membrane 30 is less than 1 nm, and when a thinner film needs to be formed to reduce pressure loss, it is preferable to further form a base layer between the intermediate layer 20 and the separation membrane 30. For example, it is preferable that, on top of the intermediate layer 20, a titanium oxide sol is obtained by hydrolyzing titanium isopropoxide in the presence of nitric acid, diluted with water to prepare a base layer sol, and then, after the prepared base layer sol flows onto the inner wall surface of a predetermined cell of the monolithic base provided with the intermediate layer, a heat treatment is performed, for example, at 400 to 500°C to form a base layer film.The method for forming the separation membrane 30 may be an appropriate method depending on the type of the separation membrane.

[0056] The separation membrane 30 may use a known MF (microfiltration) membrane, UF (ultrafiltration) membrane, gas separation membrane, pervaporation membrane or vapor permeable membrane or the like. Specifically, the separation membrane 30 includes the use of a ceramic membrane (e.g., reference is made to Japanese Patent Application Laid-Open No. 3-267129 and Japanese Patent Application Laid-Open No. 2008-246304), a carbon monoxide separation membrane (e.g., reference is made to Japanese Patent No. 4006107), a helium separation membrane (e.g., reference is made to Japanese Patent No. 3953833), a hydrogen separation membrane (e.g., reference is made to Japanese Patent No. 3933907), a carbon membrane (e.g., reference is made to Japanese Patent Application Laid-Open No. 2003-286018), a zeolite membrane (e.g., reference is made to Japanese Patent Application Laid-Open No. 2004-66188), a silica membrane (e.g.,Reference is made to the description of PCT Published Application 2008 / 050812), an organic-inorganic hybrid silica membrane (e.g., reference is made to Japanese Patent Application Laid-Open No. 2013-203618), and p-tolyl group-containing silica (e.g., reference is made to Japanese Patent Application Laid-Open No. 2013-226541), or the like. The method for forming the separation membrane 30 may be any suitable method depending on the type of the separation membrane. Further embodiments

[0057] Although an embodiment of the present invention has been described, the present invention is not limited to the above embodiment, and various modifications are possible within a scope that does not deviate from the gist of the invention.

[0058] The monolithic separation membrane structure 100 was provided with filtration cells 24 and water collection cells 25. However, the water collection cells 25 may be omitted, and in such a configuration, the discharge channel 26 may also be omitted from the monolithic separation membrane structure 100.

[0059] Although all inner diameters of the filtration cells 24 are identical, there is no limitation in this regard. Although all inner diameters of the water collection cells 25 are identical, there is no limitation in this regard.

[0060] The respective first and second sealing portions 14, 15 are formed to cover a portion of the outer peripheral surface 11U. However, the outer peripheral surface 11U does not need to be covered. Examples

[0061] Examples of a monolithic base (porous alumina body) according to the present invention are described below. However, the present invention is not limited to the following examples. Preparation of Examples No. 1 to No. 9 and Comparative Examples 1 and 2

[0062] A monolithic base according to Examples Nos. 1 to No. 9 and Comparative Examples 1 and 2 was prepared in the manner described below.

[0063] First, the binding material and the aggregate were weighed as shown in Table 1, then a clay was prepared by adding water, a dispersant and a thickener and optionally additionally a pore former to the binding material and the aggregate which had been weighed and kneading.

[0064] Next, a green body for the monolithic base, which has a plurality of filtration cells and a plurality of water collection cells, was formed by extrusion molding the prepared clay.

[0065] A monolithic base was prepared by firing the green body for the monolithic base for 2 hours at a firing temperature according to Table 1. Cross-sectional investigation of the monolithic base

[0066] A cross-sectional SEM image (backscattered electron micrograph, JSM-5410, manufactured by JEOL Ltd.) of the monolithic base was used to calculate the percentage of alumina microparticles encapsulated in the oxide phase relative to the total alumina particles.

[0067] Furthermore, the oxide phase content (volume %) was calculated using the SEM cross-sectional image. The oxide phase content (volume %) was calculated based on the surface area occupied by the oxide phase in the SEM cross-sectional image. The measurement results are shown in Table 1. Quantification of the respective elements in the oxide phase

[0068] The monolithic base was treated with hydrofluoric acid, and the eluted oxide phase was quantified using an inductively coupled plasma atomic emission spectrometer (ULTIMA2, manufactured by Horiba Ltd.). The resulting content of each element is shown in Table 1. Porosity and pore diameter distribution of the monolithic base

[0069] The porosity and pore diameter distribution (D p 50, D p 10, D p90) of the monolithic base in Examples 1 to 9 and Comparative Examples 1 and 2 was measured using a mercury injection method. The measurement results are shown in Table 1. Strength of the monolithic base

[0070] The 4-point strength of the monolithic base in Examples 1 to 9 and Comparative Examples 1 and 2 was measured according to JIS R 1601.

[0071] As shown in Table 1, compared to Comparative Example 1 (a prior art example), it was difficult to increase compactness and / or reduce weight because the membrane surface area of ​​the monolithic base was reduced when attempting to realize a larger membrane surface area, and the structural strength was increased by increasing the partition wall thickness. Furthermore, it was not possible to reduce the partition wall thickness because there was a tendency for the extrusion die to block when molding was performed using coarse alumina aggregate, even when the partition wall thickness was reduced using the same starting material.In contrast, Comparative Example 2 had a small partition wall thickness and formed filtration cells using a highly densified base having a large membrane surface area by using an aggregate having a small average particle diameter (D. g 50). However, the structural strength could not be maintained compared to Comparative Example 1 because the partition wall thickness is less than or equal to 1 / 5.

[0072] On the other hand, in Examples 1 to 9, the strength of the material (porous alumina body) itself constituting the monolithic base was increased because the percentage of microscopic alumina particles encapsulated in the oxide phase was greater than or equal to 50% as a result of using an aggregate powder having a broad grain size distribution. As a result, Examples 1 to 9 were able to maintain the structural strength of the monolithic base even when the partition wall thickness was reduced compared to Comparative Example 1. As shown in the Fig. 4 to Fig.6, in Examples 1 to 9, a large number of microscopic alumina particles encapsulated in the oxide phase were included, and the proportions are shown in Table 1. Although the reason for the increase in strength due to the presence of a large number of microscopic alumina particles in the oxide phase is unclear, it is considered that the strength is increased due to suppression of crack propagation in the oxide phase by these microscopic alumina particles.

[0073] Furthermore, although Table 1 shows the chemical composition in the oxide phase in Examples 1 to 6, it can be seen that adjusting the content ratio of the alkaline earth metal and / or alkali metal resulted in a reduction in the eutectic point and an increase in wettability, as well as facilitating the encapsulation of the microscopic alumina particles by the oxide phase. On the other hand, Comparative Examples 1 and 2 contained an insufficient amount of an alkaline earth metal and / or an alkali metal and therefore could not sufficiently reduce the eutectic point. Therefore, the firing temperature had to be increased, and consequently, the energy required during firing increased.

[0074] Furthermore, the content ratio of SiO2 in the oxide phase of Examples 1 to 6 was adjusted in a suitable manner, thereby enabling a reduction in the specific gravity of the oxide phase and a reduction in the weight of the monolithic base.

[0075] It should also be noted that although the oxide phase was reduced in Example 2 compared to Example 1, it can be seen that sufficient strength is imparted as long as it is within the scope of the present invention. Similarly, in Example 3, the pressure loss of the resulting porous alumina body was reduced by increasing the proportion (porosity) of pores through the use of a pore former. At the same time, although the surface area of ​​contact between alumina particles and pores is increased by the corresponding increase in pores, the proportion of alumina particles encapsulated in the oxide phase is reduced. However, sufficient strength is imparted as long as it is within the scope of the present application.The sintering properties and strength in Example 4 were further improved as a result of increasing the alkaline earth metal and / or alkali metal in the oxide phase by adding CaO. In Example 5, the microscopic alumina particles encapsulated in the oxide phase were increased, and a further increase in strength was made possible by increasing the oxide phase itself.

[0076] Furthermore, as compared with Example 1, although the number of microscopic alumina particles was reduced in Example 6, it is apparent that sufficient strength was imparted as long as it is within the range of the present application.

[0077] Furthermore, compared with Example 2, although the oxide phase was further reduced in Example 7, sufficient strength could be maintained because a reduction in the eutectic point and an increase in wettability were enabled by sufficiently adjusting the content ratio of the alkaline earth metal and / or the alkali metal, and because the ratio of the microscopic alumina particles encapsulated in the oxide phase was within the range of the present application even with a reduced amount of the oxide phase.

[0078] Furthermore, compared with Example 2, since the content ratio of the alkaline earth metal and / or the alkali metal was reduced in Example 8, the eutectic point could not be sufficiently reduced. Since the firing temperature was the same, it can be seen that sufficient strength was imparted as long as it was within the range of the present application, although the resulting wettability of the oxide phase was not increased and the proportion of microscopic alumina particles encapsulated in the oxide phase was reduced. Although there was a reduction in the content ratio of SiO2 in Example 8, it can be seen that the specific gravity of the oxide phase could be maintained at a relatively small value as long as it was within the range of the present application.

[0079] Furthermore, the firing temperature was increased because the alkaline earth metal and / or alkali metal content was further reduced in Example 9, and it is assumed that the eutectic point could not be further reduced. As a result, it can be seen that the strength was increased because the wettability was increased and the proportion of microscopic alumina particles encapsulated in the oxide phase was sufficiently maintained. However, because the SiO2 content was reduced, the specific gravity of the oxide phase was large.

[0080] Furthermore, since the pore diameter distribution in Examples 1 to 6 and 9 was the sharp pore diameter distribution shown in Table 1, as long as it was within the range of the present application, the pressure loss was effectively reduced, and when the interlayer was formed on the monolithic base, the base pores were not blocked as a result of the penetration of the interlayer slurry into the inner portion of the base. On the other hand, in Example 7, since the amount of the oxide phase was small, the fine microscopic pores formed in the gaps of the microscopic alumina particles could not be sufficiently reduced. Furthermore, in Example 7, it was not sufficiently possible to sufficiently reduce the coarse pores by reducing the effective connection ratio between the coarse alumina particles due to the fact that a similarly small amount of the oxide phase existed.Furthermore, in Example 8, since a sufficient increase in the wettability of the oxide phase was not allowed, the oxide phase did not penetrate into the spaces between the microscopic alumina particles and the fine microscopic pores could not be sufficiently reduced. DESCRIPTION OF REFERENCE SYMBOLS 100 MONOLITHIC SEPARATION MEMBRANE STRUCTURE 10 MONOLITHIC BASE 11S FIRST END FACE 11T SECOND END FACE 11U SIDE PANEL 12 FIRST CLOSING ELEMENT 13 SECOND CLOSING ELEMENT 14 FIRST SEALING SECTION 15 SECOND SEALING SECTION 20 INTERLAYER 21 FIRST INTERMEDIATE LAYER 22 SECOND INTERMEDIATE LAYER 24 Filtration Cell 25 WATER COLLECTION CELL 24L FILTRATION CELL SERIES 25L WATER COLLECTION CELL SERIES 26 DELIVERY CHANNEL 26a OPENING 30 TRENNMEMBRAN

Claims

[1] Monolithic base comprising pores and formed from alumina particles as aggregate and an oxide phase as binder, wherein the alumina particles comprise microscopic alumina particles with a particle diameter greater than or equal to 0.5 µm and less than or equal to 5 µm and coarse alumina particles with a particle diameter greater than 5 µm, the number of microscopic alumina particles encapsulated in the oxide phase is greater than or equal to 50% of the total number of microscopic alumina particles and coarse alumina particles, and the porosity of the monolithic base is greater than or equal to 20% and less than or equal to 60%. [2] A monolithic base according to claim 1, wherein the oxide phase comprises Si and Al and at least one of an alkaline earth metal and an alkali metal. [3] A monolithic base according to claim 2, wherein the content ratio of the oxide phase is greater than or equal to 22 volume% and less than or equal to 38 volume%. [4] A monolithic base according to claim 2 or claim 3, wherein the content of Si in the oxide phase according to a SiO2 conversion is greater than or equal to 50 mass% and less than or equal to 90 mass%, and the total content of an alkali metal and an alkaline earth metal in the oxide phase is greater than or equal to 9 mass% and less than or equal to 15 mass% according to an oxide conversion. [5] Monolithic base according to claim 4, wherein the specific gravity of the oxide phase is greater than or equal to 1 g / cm 3 and less than or equal to 3 g / cm 3 is. [6] A monolithic base according to any one of claim 1 to claim 5, comprising: a plurality of filtration cells each extending from a first end face to a second end face, wherein the partition wall thickness between two adjacent through holes of the plurality of filtration cells is greater than or equal to 0.05 mm to less than or equal to 0.20 mm. [7] A monolithic base according to any one of claim 1 to claim 6, wherein the porosity of the pores, measured by a mercury injection method, is greater than or equal to 30% to less than or equal to 45%. [8] Monolithic base according to one of claim 1 to claim 7, wherein D p 50 of the pores are greater than or equal to 2 µm to less than or equal to 6 µm. [9] Monolithic base according to claim 8, wherein then, if D p 50 of the pores 10 y µm is, D p 10 of the pores less than or equal to 10 (y+0,5) µm, and then, if D p 50 of the pores 10 yµm is, D p 90 of the pores greater than or equal to 10 (y-0,5) µm. [10] A method for producing a monolithic base, comprising: Forming a green body for a monolithic base having a plurality of pores, which is formed from an oxide phase raw material powder as a binder and an alumina particle powder as an aggregate, and Burning of the green body, whereby D g 50 of the alumina particle powder is greater than or equal to 5 µm to less than or equal to 40 µm, D g 10 of the alumina particle powder is less than or equal to 10 (z-0,2) µm is when D g 50 of the aluminum oxide particle powder 10 z µm, and D g 90 of the alumina particle powder is greater than or equal to 10 (z+0,2) µm is when D g 50 of the aluminum oxide particle powder 10 z µm. [11] A method for producing a monolithic base according to claim 10, wherein the oxide phase comprises Si and Al and at least one of an alkaline earth metal and an alkali metal, and the content of the oxide phase according to an oxide conversion is greater than or equal to 6.6 mass% and less than or equal to 32 mass%. [12] A method for producing a monolithic base according to claim 11, wherein the content of Si in the oxide phase according to a SiO2 conversion is greater than or equal to 50 mass% and less than or equal to 90 mass%, and the content proportion of an alkali metal and an alkaline earth metal in the oxide phase is greater than or equal to 9 mass% and less than or equal to 15 mass% according to an oxide conversion. [13] A method of manufacturing a monolithic base according to any one of claim 10 to claim 12, wherein the firing temperature in the step of firing the green body is greater than or equal to 1100 °C and less than or equal to 1400 °C.

Images