JP2005305342A - Preparation method for alumina separation membrane - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a preparation method for an alumina separation membrane which comprises α-alumina having micropores with an average pore diameter of 50 nm or less or has a main skeletal structure consisting of α-alumina. <P>SOLUTION: The alumina separation membrane comprises 80-99% aluminum component derived from α-alumina fine particles and 1-20% aluminum component derived from an α-alumina precursor substance (e.g. γ-alumina) and is prepared by preparing an unbaked substance containing the α-alumina fine particles with an average particle size of 10-200 nm and the α-alumina precursor substance and baking the unbaked substance at 900-1,200°C. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a separation membrane comprising a ceramic porous body having fine pores. More specifically, the present invention relates to a method for producing an alumina separation membrane suitable for ultrafiltration, microfiltration, gas separation, catalyst support, etc., preferably an α-alumina separation membrane having excellent heat resistance, corrosion resistance, etc. It is.

  Alumina (aluminum oxide) is a ceramic excellent in heat resistance, chemical resistance, and wear resistance, and its porous body is used for various purposes such as filters and catalyst carriers. Here, alumina has several crystal types such as α, γ, δ, η, and θ types, and physical properties such as heat resistance and corrosion resistance of alumina differ depending on the crystal types. Among these crystal types of alumina, the α type is the most thermally stable crystal type, and the corrosion resistance against acid and alkali is superior to other crystal types. Note that crystal types other than α-type, such as γ-type and θ-type, are α-type intermediate phases and are therefore called transition alumina or intermediate alumina.

  As a method for producing a separation membrane or porous body made of α-alumina, mainly, a method of sintering alumina particles (for example, see Patent Document 1), a method of firing an alumina slurry or an alumina sol (for example, Patent Document) 2) is known.

  In Patent Document 1, a molded body of aluminum hydroxide or transition alumina containing fine α-alumina powder in the range of 0.01 wt% to 40 wt% is primary in air or an inert gas atmosphere. By heating and secondary heating in the presence of a halogen gas or a halogen-containing gas, an α-alumina porous coagulated sintered body having a high porosity (50% by volume or more) and a narrow pore size distribution is obtained. Yes.

  In Patent Document 2, an aluminum oxide hydrate gel to which a seed crystal such as α-alumina is preferably added in an amount of 0.4 to 0.8% by mass is formed on a support, followed by drying and baking. As a result, an α-alumina separation membrane having an average pore diameter of 50 nm or less has been produced.

Japanese Patent Laid-Open No. 11-2470777 US Pat. No. 4,968,426

  When an alumina porous body is used as a separation membrane in ultrafiltration, microfiltration and gas separation, the membrane has a nanometer (nm) level, preferably an average pore size of 50 nm or less, and sufficient porosity. Is required. The material of the alumina separation membrane is preferably α-alumina from the viewpoint of heat resistance and corrosion resistance as described above. For example, γ-alumina, which is one form of transition alumina, is generally used as a material for porous alumina, but has problems such as low alkali resistance and water vapor resistance compared to α-alumina. . Further, γ-alumina has a problem in heat resistance because it transitions to θ-alumina, α-alumina, etc. in a high temperature region of 600 ° C. or higher. Therefore, an alumina separation membrane made of α-alumina and having pores with an average pore diameter of 50 nm or less is desired, but its production method has many problems.

  As a method for producing an α-alumina separation membrane, for example, when only α-alumina particles are sintered, the pore size of the separation membrane depends on the particle size of the raw α-alumina particles, but the average pore size is Since α-alumina particles having a particle size that is small enough to obtain a separation membrane of 50 nm or less are not obtained, the α-alumina particle sintering method has an average pore size of 50 nm or less that can be used for ultrafiltration and the like. A film cannot be obtained. Further, in order to sinter the α-alumina particles, it is necessary to set the firing temperature to a high temperature (1200 ° C. <˜1500 ° C.), which causes problems in heat resistance and cost of the heat treatment apparatus.

  Further, according to the method of Patent Document 1, an α-alumina porous aggregated sintered body having a high porosity is obtained, but a sintered body having an average pore diameter of 50 nm or less has not been obtained. In addition, the manufacturing method requires two-step heat treatment under different firing atmospheres, which is troublesome. Furthermore, since the heat treatment is performed in an atmosphere containing a corrosive halogen gas or a halogen-containing gas under one condition of the heat treatment, the heat treatment apparatus needs to have corrosion resistance against a high-heat halogen gas or the like. In addition, it is necessary to take measures to prevent gas leakage, and the equipment is naturally expensive. Furthermore, it goes without saying that it is better to avoid the use of toxic gases such as halogen gas in the manufacturing environment.

  As another method, there is a method of firing an α-alumina precursor to produce an α-alumina separation membrane. In this method, the lattice constant is changed during the transition process from α-alumina precursor to α-alumina. Since the film changes greatly, the film is liable to be damaged such as cracks. Moreover, it can be produced only in the form of a composite membrane, and the presence of a support is essential.

  For example, according to the method of Patent Document 2, an α-alumina separation membrane having an average pore diameter of 50 nm or less is obtained. However, since alumina sol such as boehmite is used as the main raw material, it is necessary to pay attention to the generation of cracks and the growth of large pores, and the method has many limitations. For example, in Patent Document 2, it is necessary to pay close attention in the heating process and gradually increase the temperature over time, and in the film forming process, the thickness of the layer is set to 5 μm or more. Then, cracks are likely to occur, and in order to make a film of 5 μm or more, the film formation, drying, and firing steps must be repeated to increase the film thickness, and in order to prevent cracks, 1 μm is required. It is described that it is preferable to stack the films. Furthermore, in the method of Patent Document 2, it can be produced only in the form of a composite membrane that requires a support, and cannot be produced in the form of a single membrane.

  Therefore, in the first aspect of the present invention, a method for producing a ceramic porous body or separation membrane having heat resistance, corrosion resistance and water vapor resistance and having fine pores in a simple process and relatively mild conditions. The purpose is to provide. Furthermore, in the second aspect of the present invention, an object is to produce a separation membrane having uniform fine pores by a simple process in a manner with less environmental burden.

  The present inventor made a pre-firing material containing α-alumina fine particles and an α-alumina precursor, and calcined the pre-firing material at a relatively low temperature, thereby forming α-alumina or α-alumina. It has been found that a microporous alumina separation membrane having a main skeleton, preferably an α-alumina separation membrane made of α-alumina and having an average pore diameter of 50 nm or less can be produced.

  In the basic configuration of the first aspect of the present invention, the aluminum component from the α-alumina fine particles is 80% to 99% and the aluminum component from the α-alumina precursor is 1% to 20% with respect to the total amount of the aluminum component. A step of preparing a pre-firing material containing α-alumina fine particles having an average particle size of 10 nm to 200 nm and an α-alumina precursor, and a separation membrane pre-firing material at 900 ° C. to 1200 ° C. Provided is a method for producing an alumina separation membrane including a step of firing.

  In the first form of the above basic configuration, there is provided a method for producing an alumina separation membrane in which a pre-firing material is fired at 1000 ° C. to 1200 ° C. for a sufficient time for the α-alumina precursor to transfer to α-alumina.

  In the second form of the basic configuration, there is provided a method for producing an alumina separation membrane in which the average particle diameter of α-alumina fine particles is 10 nm to 100 nm.

  In the third form of the basic configuration, the aluminum component in the pre-firing material is 90% to 95% aluminum component from the α-alumina fine particles, and 5% to 10% aluminum component from the α-alumina precursor. A method for producing an alumina separation membrane is provided.

  In the fourth form of the basic configuration, an α-alumina precursor is provided as a method for producing an alumina separation membrane in which γ-alumina particles are used.

  In the fifth aspect of the basic configuration, there is provided a method for producing an alumina separation membrane in which the α-alumina precursor is boehmite.

  In the sixth aspect of the basic configuration, there is provided a method for producing an alumina separation membrane in which a material before firing is formed on a porous support or porous laminate and then fired.

  Here, in the present invention, α-alumina precursor refers to transition alumina and alumina sol. The transition alumina means an intermediate aluminum compound that is transformed into α-aluminum by heat treatment. That is, it means an aluminum oxide other than α-alumina such as γ-alumina and θ-alumina, and includes a precursor material of alumina such as aluminum hydroxide. Alumina sol refers to amorphous alumina or alumina hydrate called aluminum oxide hydrate, boehmite, aluminum hydroxide hydrate or the like, or a colloidal form of a precursor substance of alumina. .

  The objectives according to the first and second aspects of the present invention can be achieved by the above-described basic structure and the method for producing an alumina separation membrane of each of the first to sixth aspects. In this case, it is considered that it acts as a sintering aid such as a binder. The mechanism based on the consideration will be described in detail below.

  In the temperature range as in the basic configuration and the first embodiment, the α-alumina particles remain in a solid state, but the α-alumina precursor is considered to be in a liquid phase (molten) state. In such a state, it is considered that the α-alumina precursor in the liquid phase moves between the α-alumina particles, forms a neck portion between the particles, and binds the α-alumina particles to each other. . In addition, it is considered that the α-alumina precursor in the liquid phase fills the space (gap) between the α-alumina particles, thereby reducing the pore diameter of the created pores.

  In addition, α-alumina precursors in the liquid phase are close to α-alumina, so that α-alumina particles act like seed crystals and are easily transferred to α-alumina even at low temperatures. It is guessed. Furthermore, since the α-alumina precursor sinters the α-alumina particles, it is not necessary to heat the α-alumina particles until the α-alumina particles are in a liquid phase. It is considered that the α-alumina particles could be sintered at a relatively low temperature as in the basic configuration and the first form.

  The correctness of the consideration that the α-alumina precursor acts as a sintering aid is that α-alumina particles are used as the main raw material and α-alumina precursor as the auxiliary raw material in the basic configuration and the third embodiment. This is also supported by the fact that this is a preferable condition. Furthermore, in the above basic configuration and the second embodiment, the use of α-alumina fine particles having a small particle diameter is considered to have the effect of reducing the pore diameter of the created pores and lowering the firing temperature. It is done.

  According to the basic configuration and the first to sixth embodiments of the present invention, a separation membrane made of α-alumina excellent in heat resistance, alkali resistance, water vapor resistance, etc., or separation having α-alumina as the main skeleton A membrane can be obtained. In addition, an alumina separation membrane suitable for microfiltration, ultrafiltration, gas separation, etc., having fine pores with an average pore diameter of 2 nm to 50 nm and a porosity of at least 20% or more can be obtained.

  Moreover, according to the basic configuration and each of the first to sixth embodiments, α-alumina particles are used as the main raw material, so that the influence of change in lattice constant due to transition can be reduced, and there is no damage such as cracks. Alternatively, very few α-alumina separation membranes or alumina separation membranes having α-alumina as the main skeleton can be produced by a simple method.

  Furthermore, according to the basic configuration and the first to sixth embodiments, when only the α-alumina particles are sintered, it is usually necessary to heat at a temperature higher than 1200 ° C, but the comparison is 900 ° C to 1200 ° C. An α-alumina separation membrane can be obtained under moderate conditions. Moreover, since an alumina separation membrane can be produced in an air atmosphere and in a single firing step, it is possible to avoid complication of the process and an increase in costs such as raw material costs and equipment costs.

  Furthermore, according to the basic configuration and each of the first to sixth embodiments, it can be produced in any form of a single membrane or a composite membrane, and α-alumina separation in a form according to the purpose / use A membrane or an alumina separation membrane having α-alumina as a main skeleton can be produced.

  Details of the present invention will be described below. In the method for producing an alumina separation membrane of the present invention, α-alumina particles are used as a main raw material. The α-alumina particles having an average particle diameter of 10 nm to 200 nm, preferably 10 nm to 150 nm, and more preferably 10 nm to 100 nm are used. The average particle size of the alumina particles can be selected according to the intended pore size of the alumina separation membrane. Generally, if the average particle size of α-alumina is reduced, the pore size of the produced alumina separation membrane is also reduced. Tend. In general, if the average particle diameter of α-alumina is reduced, the sintering temperature tends to be lowered. The particle size distribution of the α-alumina particles is preferably a narrow distribution centering on the average particle size. For example, in the pore size distribution curve of α-alumina particles, the half width is preferably about 3 to 4 times or less of the average particle size, and more preferably about 2 or less times the average particle size.

  In the method for producing an alumina separation membrane of the present invention, an α-alumina precursor is used as an auxiliary material. The α-alumina precursor means transition alumina particles and alumina sol.

  Transition aluminas include aluminas other than α-alumina, that is, γ-, δ-, η-, θ-, κ-, ρ- and χ-alumina, which are generally known as the crystal forms of the intermediate phase of α-alumina. , And aluminum hydroxide, a precursor material of these aluminas. The form of the transition alumina used in the present invention is preferably particulate, and the crystal form thereof is preferably γ-alumina from the viewpoint of availability. The average particle diameter of the transition alumina particles can be used if it is 200 nm or less. However, since the sinterability becomes easier as the average particle diameter becomes smaller, it is preferably 100 nm or less. The particle size distribution is preferably a narrow distribution centered on the average particle size in order to uniformly sinter at a constant temperature. For example, in the pore size distribution curve of transition alumina particles, the half width is preferably about 3 to 4 times or less of the average particle size, and more preferably about 2 or less times the average particle size.

As the alumina sol, amorphous alumina called aluminum oxide hydrate Al ₂ O ₃ · nH ₂ O, boehmite AlO (OH), aluminum hydroxide hydrate Al (OH) ₃ · nH ₂ O, etc. Or a hydrated alumina, or a colloidal material of a pre-stage material of alumina can be used. The alumina sol used in the present invention is preferably boehmite from the viewpoint of shrinkage. The average particle size of the alumina sol can be used as long as it is 200 nm or less. However, since the sinterability becomes easier as the average particle size becomes smaller, it is preferably 100 nm or less. The particle size distribution is preferably a narrow distribution centered on the average particle size in order to uniformly sinter at a constant temperature. For example, if a pore size distribution curve of an α-alumina precursor is prepared, the half width is preferably about 3 to 4 times or less of the average particle size, and more preferably about 2 or less times the average particle size.

  In comparison between transition alumina particles and alumina sol, for example, when comparing γ-alumina particles and boehmite, γ-alumina is generally cheaper and solid (powdered), so it is easier to handle, but boehmite The formability is better. In addition, when α-alumina precursor is transferred to α-alumina, the lattice is distorted, but since alumina sol is not completely skeleton formed, alumina sol is easier to transfer to α-alumina than transition alumina. . Whether to use transition alumina particles or alumina sol can be selected according to the situation such as the purpose. It is also possible to use both at the same time (mixed).

  Regarding the mixing ratio of the α-alumina particles and the α-alumina precursor in the pre-firing material, the aluminum component from the α-alumina particles is 80% to 99% with respect to the total amount of the aluminum component, and from the α-alumina precursor. The aluminum component is adjusted to 1% to 20%. Preferably, the aluminum component from the α-alumina particles is 90% to 95%, and the aluminum component from the α-alumina precursor is 5% to 10%. For example, when γ-alumina particles are used, the molecular weight of α-alumina and γ-alumina is the same, so the amount added is α-alumina relative to the total mass of α-alumina particles and γ-alumina particles. The particles are 80% to 99% by mass, and the γ-alumina particles are 1% to 20% by mass. Also, for example, when boehmite AlO (OH) is used, the total number of moles of α-alumina particles and the aluminum component of boehmite is different because α-alumina particles and boehmite have different molecular weights and different numbers of aluminum atoms in one molecule. On the other hand, the aluminum component from the α-alumina particles is 80 mol% to 99 mol%, and the aluminum component from boehmite is 1 mol% to 20 mol%.

  The pre-firing material containing the α-alumina particles and the α-alumina precursor can be in the form of a single film or a composite film, and can be formed into a shape and size according to the purpose. FIG. 1 shows a schematic diagram of the configuration of the alumina separation membrane of the present invention. FIG. 1A shows the structure of a single membrane consisting only of the alumina separation membrane of the present invention, such as in the case of press molding, and FIG. 1B shows the support (or intermediate layer) of the alumina separation membrane of the present invention. ) The composition of the composite film formed above is shown.

  In the case of a single film, a binder is added to a mixture of α-alumina particles and α-alumina precursor and mixed to form. As the molding method, any method can be used as long as it can mold the material before firing, such as extrusion molding and press molding. The shape of the film can be formed into various shapes such as a cylindrical shape and a pellet shape, and the size is not particularly limited. Any binder can be used as long as it is usually used.

  In the case of forming a composite film, for example, in the case of slurry coating, a solvent, a dispersant, a pH adjuster, a plasticizer, a binder, etc. are added to and mixed with a mixture of α-alumina particles and α-alumina precursor. To prepare a slurry-like pre-fired material. As the solvent used here, any solvent can be used as long as it can be used for producing a porous body, such as water, or an organic solvent such as alcohol or xylene. It can select suitably according to dispersibility etc. Dispersants, pH adjusters, plasticizers, binders, and other additives can also be added as needed, such as the desired viscosity, pH, pore size, film thickness, etc., and used for the production of porous materials Any one can be used.

  As the support for coating the slurry of the material before firing, a ceramic porous body such as alumina, silica, zirconia, or a porous body formed from a mixture thereof can be used. Therefore, the support is preferably made of silica and alumina. Further, the ceramic porous body used as the support generally has a porosity of about 20% to 60%, preferably 30 to 40%, and uniform pores having an average pore diameter of about 60 nm to 1000 nm, preferably 60 nm to 200 nm. Those having the following are preferred. The shape of the support is generally preferably a hollow fiber membrane, but may be any shape such as a film shape or a sheet shape. In addition, the support can have a laminated structure having an intermediate layer.

  In the present invention, the pre-firing material can be fired at a temperature range of 800 ° C to 1400 ° C. However, considering the pore size and porosity of the resulting alumina separation membrane, or the heat resistance of the heating device, the pre-fired material of the present invention is preferably fired at a temperature of 900 ° C to 1200 ° C. The firing atmosphere can be performed in any atmosphere such as an inert gas atmosphere, an air atmosphere, or a halogen-containing gas presence atmosphere, and is not particularly limited. The firing time can be appropriately selected in consideration of the degree of transition of the α-alumina precursor to α-alumina, the pore size / porosity of the separation membrane, the burden on the separation membrane, the manufacturing cost, and the like.

  The alumina separation membrane produced according to the present invention includes an α-alumina separation membrane in which the added α-alumina precursor is obtained as an α-alumina separation membrane that is completely α-ized, It may be obtained as an alumina separation membrane having a main skeleton.

  The amount of transition alumina remaining in the alumina separation membrane of the present invention after firing is affected by various factors such as firing temperature, firing time, whether to use transition alumina or alumina sol, and the particle size of α-alumina precursor. Receive. For example, when γ-alumina particles are used as the α-alumina precursor, a completely α-ized alumina separation membrane can be obtained by heating at 1200 ° C. for 2 hours, but completely at 900 ° C. for 2 hours. It cannot be alpha. For example, when α-alumina particles having small average particle diameter and boehmite are used, the α-alumina particles can be completely α-ized by heating at 1000 ° C. for 2 hours.

  Conditions for facilitating the transfer of α-alumina precursor to α-alumina include increasing the firing temperature, increasing the firing time, reducing the particle size of α-alumina particles, transition alumina particles and alumina sol, And the use of alumina sol instead of transition alumina particles. In order to obtain a completely α-α-alumina separation membrane, the firing temperature is preferably 1000 ° C. or higher, more preferably 1100 ° C. or higher. The firing time for complete alpha conversion is not uniquely determined because it is greatly influenced by other factors. However, when firing at 900 ° C. to 1200 ° C., the firing time is at least 1 hour, preferably 2 hours or more. I need time.

  When the transition alumina remains in the separation membrane after firing, the α-alumina precursor remains as transition alumina without being transferred to α-alumina, or a part thereof is transferred to α-alumina. In some cases, the α-alumina precursor does not remain in the crystal form before firing, and has been transferred to another crystal form other than the α form by firing. For example, when γ-alumina is used as the α-alumina precursor, the transition alumina after firing may remain as γ type, or may transition to θ type, which is an intermediate phase between γ type and α type. Sometimes it is. When alumina sol is used, it is not present in the form of alumina sol after firing because it is dehydrated to transition alumina when heated to several hundred degrees. Needless to say, the amount of transition alumina remaining in the alumina separation membrane is less than the amount of α-alumina precursor added.

  The average pore diameter of the alumina separation membrane obtained after firing is 2 nm to 100 nm, even when completely alphatized or when transition alumina remains, and in a preferred embodiment it is 2 nm to 50 nm. is there. Moreover, the porosity of the alumina porous body after firing is about 20% to 60%, and in a preferred embodiment, it is about 30% to 40%. Furthermore, the pore size distribution of the pores is narrow, and in the pore size distribution curve, the half width is preferably about 30 nm to 40 nm or less, more preferably 20 nm or less.

  Examples of the present invention will be described below. In the examples, the porosity and pore size distribution of the alumina separation membrane were measured and calculated using a mercury porosimeter (Autopore III, manufactured by Shimadzu Corp.). When the pore size distribution was 6 nm or less of the measurement limit of the mercury porosimeter, the pore size distribution was measured using a nitrogen adsorption method (AMS8000, manufactured by Okura Riken) and a nano palm porometer (TNF-W, manufactured by Seika Sangyo). . The nitrogen permeation flux was measured and calculated using the gas permeation test apparatus shown in FIG. The crystal phase of the alumina separation membrane after firing was identified by measuring an X-ray diffraction line (RAD-RVB, manufactured by RIGAKU). The structure of the alumina separation membrane was observed using a scanning electron microscope (SEM) (S-3200N, manufactured by Hitachi) at a magnification of 40,000. The true specific gravity was measured using a fully automatic true density measuring device (pentapycnometer, manufactured by Gandachrome). The particle size distribution of the slurry was measured using a concentrated particle size analyzer (FPAR-1000, manufactured by Otsuka Electronics).

The BET specific surface area of α-alumina particles having an average particle diameter of 27 nm used in the following examples is 35 m ² · g ⁻¹ , and the particle size distribution is shown in FIG. Moreover, the BET specific surface area of the α-alumina particles having an average particle diameter of 100 nm is 18.5 m ² · g ⁻¹ , and the particle size distribution is shown in FIG. The BET specific surface area of the γ-alumina particles having an average particle diameter of 33 nm used in the examples is 50 m ² · g ⁻¹ , and the BET specific surface area of the γ-alumina particles having an average particle diameter of 90 nm is 120 m ² · g ^−1. It is. Furthermore, the concentration of boehmite sol used in the examples is 1 mol·l ⁻¹ , the average particle size is 20 nm, and the BET specific surface area after drying and firing is 230 m ² · g ⁻¹ . 5 shows.

  The support used in the examples was an α-alumina layer having an average pore diameter of 0.7 μm and a porosity of 40% on an α-alumina substrate as an intermediate layer having an average pore diameter of 0.06 μm, a porosity of 40% and a thickness of about 100 μm. (Noritake NF membrane).

Α-alumina fine particles having an average particle diameter of 27 nm and γ-alumina fine particles having an average particle diameter of 33 nm were wet-mixed at a mass ratio of 95: 5 and dried, and then a binder was added and mixed to obtain a pre-firing material. The pellets were molded into pellets having a diameter of 20 mm and a thickness of 2 mm by uniaxial pressing at a pressure of 300 kg · cm ⁻² to form a molded article having a relative density of 58%. When calcined at 1200 ° C. for 2 hours in an air atmosphere, a completely α-aluminated uniform α-alumina film having an average pore diameter of 10 nm and a porosity of 42% could be obtained. The nitrogen permeation flux was 1.5 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

Water, a dispersant, a pH adjuster, a plasticizer, and a binder were added to and mixed with α-alumina fine particles having an average particle diameter of 27 nm and boehmite sol at a mass ratio of 90:10 to prepare an alumina slurry. The prepared alumina slurry was dip coated on a support and dried. When calcined at 900 ° C. for 2 hours in an air atmosphere, a uniform alumina film having an average pore diameter of 4 nm and a porosity of 40% in which about 5% of γ-alumina remained could be obtained. The nitrogen permeation flux was 4.0 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance. FIG. 6 shows a pore size distribution diagram of the obtained separation membrane, and FIG. 7 shows a measurement result of the pore size distribution using the nano palm porometer. According to FIG. 7, it can be seen that there are no through holes having a hole diameter of 5 nm or more.

To a mixture of α-alumina fine particles having an average particle size of 27 nm and γ-alumina fine particles having an average particle size of 33 nm in a mass ratio of 95: 5, water, a dispersant, a pH adjuster, a plasticizer, and a binder are added and mixed. An alumina slurry was prepared. The prepared alumina slurry was dip coated on a support and dried. When calcination was performed at 1200 ° C. for 2 hours in an air atmosphere, a uniform α-alumina film having an average pore diameter of 8 nm and a porosity of 44% that was completely α-aluminated could be obtained. An SEM image of the produced α-alumina film is shown in FIG. 8, and a pore size distribution diagram is shown in FIG. The nitrogen permeation flux was 6.8 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

To a mixture of α-alumina fine particles having an average particle size of 100 nm and γ-alumina fine particles having an average particle size of 33 nm at a mass ratio of 80:20, water, a dispersant, a pH adjuster, a plasticizer, and a binder are added and mixed. An alumina slurry was prepared. The prepared alumina slurry was dip coated on a support and dried. When calcined at 900 ° C. for 2 hours in an air atmosphere, a uniform alumina film having an average pore diameter of 38 nm and a porosity of 37%, in which about 10% is γ-alumina, was obtained. FIG. 10 shows an SEM image of the produced alumina film, FIG. 11 shows an XRD measurement result, and FIG. 12 shows a pore size distribution diagram. The nitrogen permeation flux was 9.8 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

To a mixture of α-alumina fine particles with an average particle size of 100 nm and γ-alumina fine particles with an average particle size of 90 nm at a mass ratio of 95: 5, add and mix water, a dispersant, a pH adjuster, a plasticizer, and a binder. An alumina slurry was prepared. The particle size distribution measurement result of the alumina slurry is shown in FIG. The prepared alumina slurry was dip coated on a support and dried. When calcined at 1200 ° C. for 2 hours in an air atmosphere, a uniform α-alumina film having an average pore diameter of 45 nm and a porosity of 40% completely α-aluminated could be obtained. FIG. 14 shows an SEM image of the produced α-alumina film, FIG. 15 shows an XRD measurement result, and FIG. 16 shows a pore size distribution diagram. The nitrogen permeation flux was 1.2 × 10 ⁻⁵ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

Alumina slurry is prepared by adding and mixing xylene, dispersant, plasticizer, and binder to a mixture of α-alumina fine particles with an average particle size of 100 nm and γ-alumina fine particles with an average particle size of 33 nm at a mass ratio of 95: 5. did. The prepared alumina slurry was dip coated on a support and dried. When calcined at 1000 ° C. for 2 hours in an air atmosphere, a uniform α-alumina film having an average pore diameter of 31 nm and a porosity of 38% could be obtained. The nitrogen permeation flux was 9.1 × 10 ⁻⁵ mol · m ^{−2 ·} s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

Water, a dispersant, a pH adjuster, a plasticizer, and a binder were added to and mixed with α-alumina fine particles having an average particle diameter of 27 nm and boehmite sol at a mass ratio of 90:10 to prepare an alumina slurry. The prepared alumina slurry was dip coated on a support and dried. When baked at 1000 ° C. for 2 hours in an air atmosphere, a uniform α-alumina film having an average pore diameter of 9 nm could be obtained. The nitrogen permeation flux was 6.0 × 10 ⁻⁶ mol · m ⁻² · s ⁻¹ · Pa ⁻¹ and had sufficient gas permeation performance.

  According to the method for producing an alumina separation membrane of the present invention, it has fine pores and a sharp pore size distribution suitable for solid-liquid separation, liquid degassing, gas separation, etc., has no defects such as cracks, and is severe. An alumina separation membrane comprising α-alumina that can be used under the conditions or having α-alumina as the main skeleton can be produced in a simple process and under mild conditions.

  Further, if the present invention is applied, it can be used not only for alumina but also for sintering two or more ceramic materials having different sintering temperatures.

It is the schematic which shows the structure of the alumina separation membrane produced by the manufacturing method of this invention. It is the schematic of the nitrogen gas permeation | transmission test apparatus for measuring a nitrogen permeation | transmission flow rate. FIG. 3 is a pore size distribution diagram of α-alumina particles having an average particle size of 27 nm used in Examples 1, 2, 3, and 7. 6 is a pore size distribution diagram of α-alumina particles having an average particle size of 100 nm used in Examples 4, 5 and 6. FIG. It is a particle size distribution map of the alumina sol used in Examples 2 and 7. 6 is a pore size distribution diagram of an alumina separation membrane produced in Example 2. FIG. It is a measurement result of the nano palm porometer of the alumina separation membrane produced in Example 2. FIG. 4 is an SEM image of an alumina separation membrane produced in Example 3. 6 is a pore size distribution diagram of an alumina separation membrane produced in Example 3. FIG. 4 is an SEM image of the alumina separation membrane of the present invention produced in Example 4. It is an XRD measurement result of the alumina separation membrane produced in Example 4. 6 is a pore size distribution diagram of an alumina separation membrane produced in Example 4. FIG. 10 is a measurement result of particle size distribution of an alumina slurry produced in Example 5. 6 is a SEM image of an alumina separation membrane produced in Example 5. It is an XRD measurement result of the alumina separation membrane produced in Example 5. 6 is a pore size distribution diagram of an alumina separation membrane produced in Example 5. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Alumina separation membrane 2 ... Intermediate | middle layer 3 ... Support body layer 4 ... Membrane module 5 ... Pressure gauge 6 ... Valve 7 ... Gas cylinder 8 ... Vacuum pump 9 ... Electric furnace 10 ... Soap film meter

Claims (7)

The average particle size is 10 nm to 200 nm so that the aluminum component from the α-alumina fine particles is 80% to 99% and the aluminum component from the α-alumina precursor is 1% to 20% with respect to the total amount of the aluminum component. A step of producing a pre-fired material containing the α-alumina fine particles and the α-alumina precursor, and a step of firing the pre-fired material at 900 ° C. to 1200 ° C.,
A process for producing an alumina separation membrane, comprising:   2. The alumina separation membrane according to claim 1, wherein the pre-fired material is fired at a firing temperature of 1000 ° C. to 1200 ° C. for a sufficient time for the α-alumina precursor to transfer to α-alumina. Production method.   The method for producing an alumina separation membrane according to claim 1 or 2, wherein the α-alumina fine particles have an average particle diameter of 10 nm to 100 nm.   The aluminum component in the pre-fired material is 90% to 95% aluminum component from the α-alumina fine particles, and 5% to 10% aluminum component from the α-alumina precursor. Item 4. The method for producing an alumina separation membrane according to any one of Items 1 to 3.   The method for producing an alumina separation membrane according to any one of claims 1 to 4, wherein the α-alumina precursor is γ-alumina particles.   The method for producing an alumina separation membrane according to any one of claims 1 to 4, wherein the α-alumina precursor is boehmite.   The method for producing an alumina separation membrane according to any one of claims 1 to 6, wherein the material before firing is formed on a porous support or a porous laminate and then fired.