JPWO2007052497A1 - COMPOSITE SEPARATION MEMBRANE, MANUFACTURING METHOD THEREOF, AND METHOD FOR SEPARATING ORGANIC LIQUID MIXTURE USING THE COMPOSITE SEPARATION MEMBRANE - Google Patents

Abstract

An industrially usable composite separation membrane having a high separation function with excellent permeability and selectivity. More specifically, even if the thickness of the separation layer on the surface is extremely thin, cracks on the surface hardly occur. Provided are a composite separation membrane having strength that can withstand typical use, a method for producing a composite separation membrane, and a method for separating an organic liquid mixture using the composite separation membrane. An inorganic porous body is used as a support, and an intermediate layer is provided between the support and the separation layer of the composite separation membrane having a separation layer. The intermediate layer has a linear expansion coefficient larger than that of one of the support and the separation layer and smaller than the other linear expansion coefficient, and is larger than the pore diameter of either the support or the separation layer. It has a smaller pore size than the other pore size. A vapor permeation method is used to separate the organic liquid mixture.

Description

  The present invention relates to a composite separation membrane and a method for producing the same, and more particularly to a composite separation membrane having a thin surface separation layer and hardly cracked, and a method for producing the same. The present invention also relates to a method for separating an organic liquid mixture using a composite separation membrane, and more particularly to a separation method for selectively permeating a desired substance in a large amount by adjusting the pore size of a composite separation membrane having a thin surface separation layer. .

  There are various types and forms of separation membranes used for gas separation and liquid separation. The functions required for the separation membrane include permeability and selectivity, and a highly functional separation membrane that can exhibit high permeability and high selectivity is required. In addition, the ease of film formation is an important factor. Further, for industrial use, durability and heat resistance, a long service life, and low costs such as price and maintenance costs are required.

  In order to increase the permeability, it is effective to reduce the thickness of the separation membrane. However, when the thickness of the separation membrane is reduced, the strength is weakened, and there is a problem that cracks are likely to occur. If the membrane is cracked, the selectivity of the membrane is significantly reduced.

  In order to increase the strength of the film, it is necessary to select an appropriate material. For example, an inorganic porous material is known as a material having high durability and heat resistance.

  As a separation membrane using an inorganic porous material as a support, for example, Patent Document 1 discloses a method for producing an acid-resistant composite separation membrane that can selectively separate water from an aqueous solution containing an organic acid. Yes. The separation membrane described in Patent Document 1 is a separation membrane in which silica gel is supported in the pores of an inorganic porous body, and is manufactured by supporting a silica sol on a porous base material and baking it. However, the separation membrane described in Patent Document 1 has a silica layer thickness of about 10 μm, and the permeation resistance is increased. Therefore, it cannot be said that there is a problem in terms of permeability. Further, since the sol concentration at the time of membrane production is high, the silica particles become large, thereby increasing the pore diameter, so there is a problem in the selectivity of the permeating substance.

Patent Document 2 discloses a gas separation membrane in which a silica metal composite layer is laminated on a ceramic base material in which a silica zirconia layer is laminated on a porous ceramic base material. However, since the separation membrane described in Patent Document 2 is intended for separation of helium or hydrogen, the pore diameter of the separation layer is large enough to allow helium (He) or hydrogen (H ₂ ) to pass through. Very small. Therefore, the separation membrane of the present application intended to permeate water molecules and organic substances is a separation membrane having a different pore size and a completely different structure.

  Non-Patent Document 1 discloses a method of preparing a silica sol having a uniform particle size and forming a thin silica layer on an alumina support by a sol-gel method. That is, by applying alumina particles on the support surface in order to flatten the surface of the alumina support, and coating three types of silica sols having a uniform particle size on the surface in order from the largest particle size, A method for forming a thin silica layer without large irregularities on the surface is described.

Further, in Non-Patent Document 2, a silica-zirconia sol is applied by hot coating to an alumina support whose surface is flattened by applying alumina particles as in Non-Patent Document 1, so that the thickness is about It is described that a 0.5 μm silica-zirconia gel layer can be formed. In addition, it is described that a silica colloid sol having a uniform particle size can be prepared by allowing the silica sol to stand at room temperature for 1 month or more and age.
Japanese Patent No. 2808479 JP 2005-305425 A (publication date: November 4, 2005) Masashi Asaeda, Kazuto Okazaki and Atushi Nakatani. Preparation of thin porous silica membranes of non-aqueous organic solvent mixtures by pervaporation. Ceramic Transactions, 31, 411-420, 1993. Masashi Asaeda, Jianhua Yang and Yoshikazu Sakou. Porous silica-zirconia (50%) membrane for Pervaporation of iso-propyl alcohol (IPA) / water mixture. Journal of Chemical Engineering of Japan, Vol. 35, No. 4, 365-371 2002. As described above, in order to obtain a highly functional separation membrane having high permeability and selectivity, it is necessary to reduce the thickness of the membrane having a small pore diameter that inhibits permeation. However, reducing the thickness of the film causes problems such as a decrease in strength and cracking of the film. Therefore, it is necessary to develop a separation membrane that does not reduce the strength of the entire membrane even when the membrane thickness is reduced, and that does not easily cause cracks or extremely large pores on the surface of the membrane.

  The present invention has been made in view of the above-mentioned problems, and the purpose thereof is an industrially usable composite separation membrane having a high separation function with excellent permeability and selectivity, more specifically, An object of the present invention is to provide a composite separation membrane having durability and strength that can withstand industrial use even if the separation layer on the surface is extremely thin and hardly cracks on the surface.

  In order to solve the above problems, the composite separation membrane according to the present invention is a composite separation membrane having an inorganic porous body as a support and having a separation layer, comprising an intermediate layer between the support and the separation layer, The intermediate layer is characterized by having a linear expansion coefficient that is larger than the linear expansion coefficient of one of the support and the separation layer and smaller than the other linear expansion coefficient.

  By the said structure, it can be made hard to generate | occur | produce the crack of the surface at the time of separation layer baking. That is, by sandwiching a layer having a linear expansion coefficient within the range between the linear expansion coefficients of both of the support and the separation layer, the surface of the surface due to the difference between the linear expansion coefficients of the support and the separation layer is reduced. Cracks can be prevented. Further, the composite separation membrane according to the present invention has high durability at high temperatures and is excellent for industrial use under high temperature conditions due to the above configuration.

  The intermediate layer is preferably composed of a plurality of layers. By using multiple layers, the linear expansion coefficient can be adapted sequentially. That is, among the plurality of layers constituting the intermediate layer, the layer adjacent to the support has a linear expansion coefficient close to the linear expansion coefficient of the support, and the layer adjacent to the separation layer is the separation layer. It is preferable to have a linear expansion coefficient close to the linear expansion coefficient, and further, the plurality of layers constituting the intermediate layer have a linear expansion coefficient from the layer adjacent to the support toward the layer adjacent to the separation layer. More preferably, the layers are stacked stepwise in order of size.

  With the above configuration, the difference between the linear expansion coefficient of the support and the linear expansion coefficient of the separation layer is gradually filled, and surface cracks can be more effectively prevented, and high-temperature conditions during the separation of various mixtures High durability can be imparted.

  It is preferable that at least one of the plurality of layers constituting the intermediate layer is a layer containing particles having a linear expansion coefficient that is the same as or close to the linear expansion coefficient of the substance constituting the support or the separation layer. . With the above configuration, a layer having uniform pores smaller than the support is formed on the surface of the support having large and non-uniform pores, and as a result, the components of the separation layer are prevented from penetrating deep into the support. And cracking of the surface can be more effectively prevented. Further, since the particles have a linear expansion coefficient that is the same as or close to that of the substance constituting the support or the separation layer, the intermediate layer is easily adjusted to a linear expansion coefficient intermediate between the support and the separation layer. be able to.

  Moreover, it is preferable that the said particle | grains are mixed particles of the particle | grains of the substance which comprises the said support body, and the particle | grains of the substance which comprises a separated layer. By appropriately changing the ratio of these two types of particles, a layer having a desired linear expansion coefficient can be easily formed. In addition, an intermediate layer having high affinity with the support and the separation layer and excellent in sinterability can be formed.

  The composite separation membrane according to the present invention is a composite separation membrane having an inorganic porous body as a support and having a separation layer, and an intermediate layer is provided between the support and the separation layer. The pore size is smaller than the pore size and larger than the pore size of the separation layer.

  With the above configuration, the separation layer on the surface can be thinned. By using a plurality of layers, the pore diameter can be adapted sequentially. That is, by sandwiching a layer having a pore diameter within the range sandwiched between both pore diameters between the support and the separation layer, it is possible to prevent the components of the separation layer from penetrating to the deep part of the support, As a result, the separation layer on the surface can be formed thin and with a uniform thickness.

  The intermediate layer is preferably composed of a plurality of layers. That is, among the plurality of layers constituting the intermediate layer, the layer adjacent to the support has a pore diameter close to the pore diameter of the support, and the layer adjacent to the separation layer is the pore diameter of the separation layer. Preferably, the plurality of layers constituting the intermediate layer are stepped in the order of pore size from the layer adjacent to the support to the layer adjacent to the separation layer. It is more preferable that they are laminated.

  With the above configuration, the difference between the pore size of the support and the pore size of the separation layer is gradually filled, and the penetration of the separation layer into the lower layer can be more effectively prevented, and the separation layer can be formed thinly. it can. Furthermore, by laminating the intermediate layer stepwise in the order of the size of the pore diameter, the pores of the intermediate layer increase stepwise, and mass transfer from the separation layer is promoted.

  It is preferable that at least one of the plurality of layers constituting the intermediate layer is a layer containing particles of a substance constituting the support or the separation layer. With the above configuration, a layer having uniform pores smaller than the support is formed on the surface of the support having large and non-uniform pores, and as a result, the components of the separation layer are prevented from penetrating deep into the support. The separation layer can be formed thin.

  The particles are preferably mixed particles of the substance constituting the support and the substance constituting the separation layer. With the above configuration, an intermediate layer having high affinity with the support and the separation layer and excellent in sinterability can be formed.

  The particles of the substance constituting the support and the substance constituting the separation layer preferably have a uniform particle diameter. With the above configuration, the pore diameters of the intermediate layer become uniform, and the separation layer can be made thinner and more uniform.

  In the composite separation membrane according to the present invention, the intermediate layer preferably has a thickness of 0.1 μm or more and 5.0 μm or less. With the above configuration, the total film thickness becomes extremely thin, and the occurrence of cracks due to thermal shock during firing can be remarkably prevented. In addition, the thickness of an intermediate | middle layer means the thickness from the top part of the surface of a support body.

In the composite separation membrane according to the present invention, the main component of the support is preferably α-Al ₂ O ₃ . A support mainly composed of α-Al ₂ O ₃ is excellent in chemical stability, heat resistance, and strength. Moreover, it is cheap and easy to obtain.

  In the composite separation membrane according to the present invention, the separation layer is preferably composed of an inorganic compound. A separation membrane composed of an inorganic compound is excellent in heat resistance, acid resistance, and organic solvent resistance. Silica is preferable as the inorganic compound. Silica is rich in pores, has high acid resistance, and is easy to form.

  In the composite separation membrane according to the present invention, it is preferable that the average pore diameter of the surface of the separation layer is 3 to 10 mm. Since the surface of the separation layer has such a pore diameter, a high separation factor can be realized.

  A method for producing a composite separation membrane according to the present invention is a method for producing a composite separation membrane comprising a support made of an inorganic porous material, an intermediate layer, and a separation layer, and the particles of the substance constituting the separation layer as a main component. An intermediate layer is formed by preparing a first colloid sol in which particles of a substance constituting the support are dispersed in a colloid sol to be formed, applying the first colloid sol to the surface of the support, and baking the first colloid sol. A second colloidal sol mainly composed of particles of a substance constituting the separation layer, and the second colloidal sol is applied to the surface of the intermediate layer and baked to form the separation layer. It includes a forming step.

  With the above configuration, it is possible to form an intermediate layer containing particles composed of the main component of the substance constituting the support and colloidal particles of the substance constituting the separation layer, and forming a uniform and thin separation layer on the surface thereof. be able to.

The first colloidal sol for forming the intermediate layer is composed of a plurality of types of colloidal sol in which particles of a substance constituting the support and particles having different particle diameters are dispersed,
The particle diameters in the plurality of types of colloidal sols are substantially uniform,
First, the colloidal sol in which particles having the largest particle size are dispersed is applied and fired on the surface of the support, and then the colloidal sol in which particles having a small particle size are sequentially dispersed is applied and fired on the surface of the support. It is preferable to form the plurality of intermediate layers.

  Furthermore, the particle concentration of the substance constituting the support of the first colloid sol composed of the plurality of types of colloid sols is the highest in the colloid sol in which the particles with the largest particle size are dispersed, and the particles are sequentially arranged in the order of the particle size. It is preferable that the concentration is low.

  With the above configuration, it is possible to form a plurality of intermediate layers in which the particle diameter decreases stepwise.

  Moreover, it is preferable that the thickness of the said intermediate | middle layer is 0.1 micrometer or more and 5.0 micrometers or less. By the said structure, generation | occurrence | production of the crack by the thermal shock at the time of baking can be prevented notably. In addition, the thickness of an intermediate | middle layer means the thickness from the top part of the surface of a support body.

  The method for separating an organic liquid mixture according to the present invention is characterized by using the composite separation membrane according to the present invention or the composite separation membrane produced by the production method according to the present invention. Since these composite separation membranes have a thin separation layer and high durability at high temperatures, they are suitable for separation of an organic liquid mixture under high temperature conditions.

  The organic liquid mixture separation method according to the present invention is preferably performed by a vapor permeation method, and the vapor permeation method is preferably performed so that a liquid film is formed by vapor liquefaction on the surface of the separation layer on the supply side. . The lifetime of the membrane is increased, and high permeability and high selectivity can be obtained.

  In the method for separating an organic liquid mixture according to the present invention, it is preferable to use a composite separation membrane in which the average pore diameter of the surface of the separation layer is adjusted to 3 to 10 mm. When the average pore diameter on the surface of the separation layer is small, a high capillary pressure can be obtained, so that a high permeation flux can be expressed.

  The organic liquid mixture to be separated preferably contains carboxylic acid and water, and in particular, the carboxylic acid is preferably acetic acid. In the case of separating acetic acid and water, it is preferable to use a composite separation membrane in which the average pore diameter on the surface of the separation layer is adjusted to 4 to 6 mm.

  The organic liquid mixture to be separated preferably contains a carboxylic acid ester and methanol, and the carboxylic acid ester is preferably an acetic acid ester, and methyl acetate is particularly preferable. When separating methyl acetate and methanol, it is preferable to use a composite separation membrane in which the average pore diameter on the surface of the separation layer is adjusted to 5 to 7 cm.

  Other objects, features, and advantages of the present invention will be fully understood from the following description. The benefits of the present invention will become apparent from the following description with reference to the accompanying drawings.

It is a scanning electron micrograph of the membrane cross section of the composite separation membrane which concerns on this invention. It is a schematic diagram of the membrane cross section of the composite separation membrane which concerns on this invention.

[Composite separation membrane]
The composite separation membrane according to the present invention has an inorganic porous body as a support, has a separation layer, and has an intermediate layer between the support and the separation layer.

  The intermediate layer has a linear expansion coefficient that is larger than the linear expansion coefficient of one of the support and the separation layer and smaller than the other, or smaller than the pore diameter of the support, and the fineness of the separation layer. Any material having a pore size larger than the pore size may be used.

  In this specification, the “composite separation membrane” is intended to be a membrane having a structure in which a separation layer having a mixture separation function is formed on the surface of a support of an inorganic porous material. The composite separation membrane according to the present invention has a structure in which an intermediate layer is further provided in addition to the basic structure of the support and separation layer of the inorganic porous material.

  The support preferably has a strength that can withstand industrial use. In order to increase the permeability of the membrane, it is preferable that the support has a large pore diameter and porosity.

Examples of the inorganic porous material that can be used as a support include so-called ceramics composed of α-Al ₂ O ₃ (α-alumina), mullite, γ-Al ₂ O ₃ (γ-alumina), zirconia, titania, or a composite thereof. Is mentioned. However, it is not limited to these. Of these, ceramics containing α-Al ₂ O ₃ as a main component is preferable. This is because ceramics mainly composed of α-Al ₂ O ₃ are inexpensive and easily available, and are excellent in chemical resistance, heat resistance and strength.

  Although the shape of a support body is not specifically limited, A cylindrical (tube shape) or plate-shaped support body is suitable.

  The average pore diameter of the support is preferably about 0.05 μm to 10 μm. If the pore diameter is too large, the difference from the pore diameter of the separation layer becomes too large, and the intermediate layer must be thick, and cracking of the separation layer surface tends to occur. On the other hand, if the pore diameter is too small, the permeation performance decreases. More preferably, it is 0.1-5 micrometers, and 0.5-3 micrometers is especially preferable. As used herein, “pore diameter” is defined as Kelvin's capillary condensation diameter. In the present specification, “pore diameter” is used to mean an average pore diameter.

  The separation layer may be a layer having a mixture separation function. Examples of the substance constituting the separation layer include silica, silica composite metal (silica and nickel, zirconium, chromium, titanium, tantalum, iron, or oxides thereof), zeolite, and organic polymer compounds. However, it is not limited to these. Of these, inorganic compounds such as silica, silica composite metal, and zeolite are preferable. This is because a separation membrane containing an inorganic compound is excellent in heat resistance, acid resistance, and organic solvent resistance. Among inorganic compounds, silica is preferable from the viewpoint of being rich in pores, having high acid resistance, and easy film formation.

  In one embodiment, the intermediate layer of the composite separation membrane according to the present invention is capable of forming a layer having a linear expansion coefficient that is larger than one of the support and the separation layer and smaller than the other. As long as it is chemically stable, the substance constituting the intermediate layer is not limited.

  In another embodiment, the intermediate layer of the composite separation membrane according to the present invention is an intermediate layer as long as it can form a layer having a pore size smaller than the pore size of the support and larger than the pore size of the separation layer. The substance which comprises is not limited.

  The substance constituting the intermediate layer is basically arbitrary, but the same substance as the support and the separation layer is preferable from the viewpoint of sinterability, linear expansion coefficient, and ease of adjusting the pore diameter.

  The intermediate layer is preferably formed as thin as possible. When the intermediate layer is thinner, cracking of the separation layer due to thermal shock can be suppressed during firing of the separation layer. The thickness of the intermediate layer is preferably 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less. Although a lower limit is not specifically limited, If it is 0.1 micrometer or more, the crack of the separated layer by the thermal shock at the time of baking can be suppressed.

  The composite separation membrane according to the present invention has a linear expansion coefficient that is larger than the linear expansion coefficient of one of the support and the separation layer and smaller than the other linear expansion coefficient, and smaller than the pore diameter of the support, and More preferably, an intermediate layer having a pore diameter larger than that of the separation layer is provided. That is, a composite separation membrane having an inorganic porous body as a support and having a separation layer, comprising an intermediate layer between the support and the separation layer, and the intermediate layer is formed by either one of the support and the separation layer. A composite separation membrane characterized by having a linear expansion coefficient larger than the other linear expansion coefficient and smaller than the pore diameter of the support and having a pore diameter larger than the pore diameter of the separation layer, It is preferable that

  The intermediate layer may be composed of one layer, but is preferably composed of a plurality of layers. In the case of being composed of a plurality of layers, the number of layers is not particularly limited, but it is preferably composed of 2 to 4 layers. If the number of layers is larger than this, the manufacturing process becomes complicated, which causes an increase in cost, and it is difficult to form a thin intermediate layer, which may reduce the transmission performance.

  When the intermediate layer is composed of a plurality of layers having a linear expansion coefficient larger than that of one of the support and the separation layer and smaller than the other, the layer adjacent to the support is the support. It is preferable that the linear expansion coefficient is close to the linear expansion coefficient, and the layer adjacent to the separation layer has a linear expansion coefficient close to that of the separation layer. The linear expansion coefficient of layers other than the layer adjacent to the support and the layer adjacent to the separation layer is not particularly limited, but the linear expansion coefficient is large from the layer adjacent to the support toward the layer adjacent to the separation layer. It is more preferable that the layers are laminated in order. By providing an intermediate layer that is layered step by step in the order of the linear expansion coefficient, when firing the separation membrane, surface cracks due to the difference between the linear expansion coefficient of the support and the linear expansion coefficient of the separation layer Occurrence can be prevented. Furthermore, it is possible to provide a composite separation membrane having high durability at high temperatures and suitable for industrial use under high temperature conditions.

  When the intermediate layer is composed of a plurality of layers having a pore size smaller than the pore size of the support and larger than the pore size of the separation layer, the layer adjacent to the support is narrower than the pore size of the support. The layer having a pore diameter and adjacent to the separation layer preferably has a pore diameter close to the pore diameter of the separation layer. The pore diameters of the layers other than the layer adjacent to the support and the layer adjacent to the separation layer are not particularly limited, but are stepped in the order of the pore diameter from the layer adjacent to the support toward the layer adjacent to the separation layer. It is more preferable that they are laminated. Since the pore diameter of the intermediate layer adjacent to the separation layer is reduced, the penetration into the lower layer of the separation layer can be extremely reduced, and the separation layer can be formed with a thin and uniform thickness. In addition, the plurality of intermediate layers can be made thin by laminating in order of the size of the pore diameter.

  It is preferable that at least one of the plurality of layers constituting the intermediate layer is a layer containing particles of the substance constituting the support or the separation layer, and the substance constituting the support and the substance constituting the separation layer The mixed particles are preferable. Here, the particles of the substance constituting the support only have to be composed of at least one of the components of the substance constituting the support, and the particles of the substance constituting the separation layer are the substances constituting the separation layer. What is necessary is just to consist of at least one of the components.

For example, when the main component of the support is α-Al ₂ O ₃ and the main component of the separation layer is silica, the intermediate layer is a mixed particle of α-Al ₂ O ₃ particles and silica particles (silica colloid particles). Is preferably included. By including the mixed particles, it is possible to easily adjust the linear expansion coefficient between the two by changing the mixing ratio of the two as appropriate. The effect that adjustment of the pore diameter in a sintered compact becomes easy is acquired. Furthermore, an effect is obtained that an intermediate layer having high affinity with the support and the separation layer and excellent in sinterability can be formed.

Moreover, it is preferable that the particle | grains of the substance which comprises the said support body, and the substance which comprises a separated layer each have a uniform particle diameter. That is, when one layer of a plurality of layers constituting the intermediate layer is viewed, the particles composed of the main components of the substance constituting the support contained in the layer have a uniform particle size of a certain size and are separated. It is preferable that the particles composed of the main component of the substance constituting the layer also have a uniform particle size of a certain size. As a specific example, an intermediate layer (one layer of a plurality of intermediate layers) of a composite separation membrane in which the main component of the support is α-Al ₂ O ₃ having an average pore diameter of 1 μm and the main component of the separation layer is silica is 2 μm. There are cases where mixed particles of α-Al ₂ O ₃ particles having a uniform particle diameter of the above and silica colloidal particles having a uniform particle diameter of 0.02 μm are included.

  Here, “the particle size is uniform” is intended to be the case where the abundance ratio of the particles having an average particle size of 3 times or more is 1% or less. Preferably, 70% or more of all particles are present within a range of plus or minus 20% of the average particle diameter, and more preferably 90% or more of all particles are plus or minus 5 of the average particle diameter. % Is in the range of%.

  As described above, the composite separation membrane according to the present invention provides the surface of the separation layer by providing an intermediate layer having a linear expansion coefficient that is larger than the linear expansion coefficient of one of the support and the separation layer and smaller than the other. Can prevent cracking.

  When cracks occur in the separation layer, molecules larger in size than the separation target molecules can pass through the membrane, causing a decrease in separation function. Since the composite separation membrane according to the present invention has a structure in which cracks are unlikely to occur on the surface of the separation layer, the separation function is very excellent.

  In addition, the composite separation membrane according to the present invention provides an intermediate layer having a pore size smaller than the pore size of the support and larger than the pore size of the separation layer, so that the components of the separation layer penetrate deeply into the lower layer. As a result, the separation layer can be formed very thin.

  If the thickness of the layer having a small pore diameter is large, the separation membrane is disadvantageous because the permeation inhibition is increased and the permeation flux is reduced. Therefore, it can be said that a single layer is generally more advantageous than a multi-layer, but an excessively thin film has low strength and is not suitable for industrial use. In the composite separation membrane according to the present invention, the thickness of the layer having a small pore diameter that inhibits permeation is extremely thin, so that the permeation inhibition is very small, and the support layer having a large pore diameter is thick, so that sufficient strength can be obtained.

  The composite separation membrane according to the present invention is preferably applied to liquid or vapor separation. That is, a preferred embodiment of the composite separation membrane according to the present invention is a composite separation membrane for liquid separation (liquid separation membrane) or a composite separation membrane for vapor separation (vapor separation membrane). Of these, application to the vapor permeation method of an organic liquid mixture is particularly preferable. The “organic liquid mixture” and the “vapor transmission method” will be described later.

  When the composite separation membrane according to the present invention is applied to the separation of an acetic acid / water mixture or the separation of a methyl acetate / methanol mixture, the average pore diameter of the surface of the separation layer is preferably from 3 to 10 mm. More preferably, when it is applied to the separation of an acetic acid / water mixture, it is 4 to 6 mm, and when it is applied to the separation of a methyl acetate / methanol mixture, it is 5 to 7 mm. When the surface of the separation layer has such a pore diameter, a high separation factor can be realized. In the present specification, the “surface of the separation layer” means the outermost layer of the separation layer. Therefore, when the separation layer is composed of a plurality of membranes, the average pore size of the outermost layer membrane may be in the above range, and the average pore size of the inner layer is not limited to the above range.

[Method for producing composite separation membrane]
A method for producing a composite separation membrane according to the present invention is a method for producing a composite separation membrane comprising a support made of an inorganic porous material, an intermediate layer, and a separation layer, and the particles of the substance constituting the separation layer as a main component. An intermediate layer is formed by preparing a first colloid sol in which particles of a substance constituting the support are dispersed in a colloid sol to be formed, applying the first colloid sol to the surface of the support, and baking the first colloid sol. A second colloidal sol mainly composed of particles of a substance constituting the separation layer, and the second colloidal sol is applied to the surface of the intermediate layer and baked to form the separation layer. What is necessary is just to include a formation process.

In this embodiment, as an example of the composite separation membrane, the main component of the support is α-Al ₂ O ₃ , the main component of the separation layer is silica, and the intermediate layer is formed of α-Al ₂ O ₃ particles and silica colloid particles. Although the manufacturing method of the composite separation membrane which is a layer to be included will be described, the manufacturing method according to the present invention is not limited thereto, and a composite separation membrane comprising a support of different components, a separation layer and an intermediate layer is also included in this method. It can be manufactured similarly.

(1) Preparation of silica colloid sol The silica colloid sol can be prepared as follows, for example. That is, tetraethoxysilane (TEOS) is dissolved in water, a small amount of nitric acid is added as a catalyst, and the mixture is stirred for a sufficient time for hydrolysis and polycondensation reaction. Thereafter, a silica colloid sol can be prepared by adding a predetermined amount of nitric acid and a large amount of water to the solution and boiling for 5 to 15 hours. During the boiling, the total amount of solution is kept constant.

  If this silica colloid sol is prepared at a low concentration (initial TEOS concentration), a silica colloid having a smaller average particle diameter can be obtained. That is, a silica colloid sol having a desired particle diameter can be prepared by changing the preparation concentration of the silica colloid sol.

In addition, metal nitrate (eg, Ni (NO ₃ ) ₂ .6H ₂ O, Co (NO ₃ ) ₂ .6H ₂ O, Fe (NO ₃ ) ₃ .9H ₂ O, Al (NO ₃ ) _3. If 9H ₂ O or the like is added, a silica metal colloidal sol can be prepared.

  The obtained silica colloid sol is preferably allowed to stand at room temperature for at least one week. By standing at room temperature for a long time, small colloidal particles disappear and colloidal particles having a uniform particle diameter can be obtained.

  The silica colloid sol prepared as described above is suitably used in the following steps.

(2) Intermediate layer forming step In the intermediate layer forming step, first, α-Al ₂ O ₃ particles are dispersed in the silica colloid sol prepared in (1) to prepare a first colloid sol. As the silica colloid sol to be used, a silica colloid sol having the largest particle size among the silica colloid sols used for forming the separation layer or a silica colloid sol having a particle size larger than that and smaller than the pore size of the support is selected. The α-Al ₂ O ₃ particles are added to the silica colloid sol and sufficiently stirred, whereby the α-Al ₂ O ₃ particles are uniformly dispersed in the silica colloid sol.

When the intermediate layer is composed of a plurality of layers, a first colloid sol composed of a plurality of colloid sols is prepared. At this time, α-Al ₂ O ₃ particles having different particle diameters are prepared so that the particle diameters of α-Al ₂ O ₃ particles dispersed in each first colloid sol are different. For example, in the case of forming the composed intermediate layer of two layers, to prepare a small alpha-Al ₂ O ₃ particles larger alpha-Al ₂ O ₃ particles and the particle diameter of the particle size. _α-Al 2 _{O 3} particles may be obtained commercially. The particle size of the large particles is preferably smaller than the α-Al ₂ O ₃ pieces constituting the support, and the small particles are preferably larger than the particle size of the silica colloid forming the separation layer.

Concentration in colloidal sol of large α-Al ₂ O ₃ particles having a particle diameter is preferably higher than the concentration in the colloidal sol of small α-Al ₂ O ₃ particle particle diameters. When three or more intermediate layers are provided, it is preferable to prepare such that the concentration increases as the particle diameter increases, corresponding to the size of the α-Al ₂ O ₃ particles.

Furthermore, the particle diameter of the silica colloid particles of the colloidal sol is such that the particle diameter of the α-Al ₂ O ₃ particles corresponds to the particle diameter of the α-Al ₂ O ₃ particles and the content concentration of the α-Al ₂ O ₃ particles. It is preferable that the particle size of the silica colloid particles contained in the colloidal sol having a large concentration is high, and the particle size of the silica colloid particles is sequentially reduced.

Once a first colloidal sol (first colloidal sol A) in which large α-Al ₂ O ₃ particles are dispersed and a first colloidal sol (first colloidal sol B) in which small α-Al ₂ O ₃ particles are dispersed are prepared, The first colloidal sol A is applied to the support surface. The coating method is not particularly limited, and examples thereof include a method in which a cloth soaked with the first colloid sol A is brought into contact with the support surface and a method in which the first colloid sol A is sprayed.

  The applied first colloidal sol A is dried at room temperature. The excess part can be wiped off with a cloth when it is not completely dry. Thereafter, the mixture is heated and finally baked to form the first colloidal sol A layer. Firing is performed, for example, in a furnace at 400 to 550 ° C. for about 10 to 15 minutes.

  In order to more uniformly form the first colloid sol A layer on the support surface, the application and firing of the first colloid sol A may be repeated a plurality of times. In the case of repeating a plurality of times, the support after firing is cooled, the first colloidal sol A is applied again to the surface, and drying, heating and firing are performed.

  The same applies to the case where the first colloid sol B layer is subsequently formed. After cooling the support on which the first colloid sol A layer is formed, the first colloid sol B is applied, dried, heated and fired. By repeating the first colloid sol B layer a plurality of times, a more uniform layer can be obtained.

  As a result, an intermediate layer having a thickness of 5 μm or less is formed.

(3) Separation layer formation step In the separation layer formation step, first, the silica colloid sol prepared in (1) is diluted to prepare a second colloid sol. The lower limit of the concentration of the diluted silica colloid sol (second colloid sol) is preferably 0.01% by weight or more, and more preferably 0.05% by weight or more. Moreover, it is preferable to make the upper limit into 0.5 weight% or less, and it is more preferable to set it as 0.4 weight% or less. By setting the concentration of the second colloid sol within the above range, it is possible to prevent the separation layer from being cracked when the separation layer (silica colloid gel layer) is formed by firing. Therefore, since it is possible to prevent a gap from being generated in the fired separation layer, a membrane having an excellent separation function can be manufactured.

  In the separation layer forming step, a hot coating method can be suitably used. The hot coating method is a method for coating a material to be coated by bringing a coating solution into contact with a preheated material to be coated and instantaneously evaporating the solvent of the solution. According to the hot coating method, an extremely thin film can be easily formed. The substrate to be coated in this production method, that is, the support on which the intermediate layer has been formed, may be heated in advance so that the temperature when contacting with the second colloidal sol that is the coating material is about 170 ° C. to 190 ° C.

  After coating by the hot coating method, the separation layer can be formed by baking. Firing is performed, for example, in a furnace at 400 to 550 ° C. for about 10 to 15 minutes. Moreover, in order to form a layer uniformly, you may repeat coating and baking in multiple times.

  Moreover, it is good also as a separated layer comprised from a some layer. When the separation layer is composed of a plurality of layers, each layer uses silica colloidal sols having different particle diameters, the second colloidal sol layer containing the silica colloid having the largest particle diameter is formed on the innermost side, and the particle diameters are successively increased What is necessary is just to form a layer on the outer side in that order.

  In this manner, by forming the separation layer as a plurality of layers formed in the order of the particle diameter, it is possible to further prevent a gap from being generated in the separation layer. Further, increase in permeation resistance due to particles entering the lower layer can be prevented. Furthermore, since the layer having the smallest particle diameter can be formed extremely thin, the permeability can be increased.

  For example, when forming a separation layer consisting of four layers, the average particle diameter of the silica colloid sol is 1-8 nm for the outermost layer, 5-20 nm for the second layer, It is preferable that it is 10-120 nm and a lowermost layer is 20-700 nm. More preferably, the outermost layer is 3 to 8 nm, the second layer is 8 to 12 nm, the third layer is 12 to 24 nm, and the lowermost layer is 24 to 48 nm.

  With the manufacturing method according to the present invention, the thickness of the separation layer can be 0.2 μm to 0.5 μm.

  The average pore diameter on the surface of the separation layer can be adjusted by changing the particle diameter of the silica colloid sol applied to the outermost layer. In order to form a separation layer having a desired average pore diameter, the silica colloid sol particle diameter may be selected so as to have a pore diameter when it is assumed that the silica colloid sol particles are packed most closely.

  The particle size and distribution of the silica colloid sol can be controlled by changing the acid catalyst concentration, reaction time, reaction temperature, and TEOS concentration during the preparation of the silica colloid sol. For example, when the TEOS concentration is increased, the particle size is increased, and conversely, when the TEOS concentration is decreased, the particle size is decreased. Regarding the distribution, particles having a narrow distribution range (uniform particles) can be obtained by removing excessive particles and excessive particles by filtration. The use of particles having a narrow distribution range is preferable because uniform pore diameters are easily obtained and the performance of the membrane is improved.

  When the composite separation membrane produced by the production method according to the present invention is applied to the separation of an acetic acid / water mixture or the separation of a methyl acetate / methanol mixture, the average pore diameter of the surface of the separation layer is 3 to 10 mm. It is preferable to adjust. More preferably, when it is applied to the separation of an acetic acid / water mixture, it is 4 to 6 mm, and when it is applied to the separation of a methyl acetate / methanol mixture, it is 5 to 7 mm. When the surface of the separation layer has such a pore diameter, a high separation factor can be realized.

[Method for separating organic liquid mixture]
The separation method of the organic liquid mixture according to the present invention may be any method using the composite separation membrane according to the present invention or the composite separation membrane produced by the production method according to the present invention. Since the composite separation membrane according to the present invention has high durability at high temperatures, the organic liquid mixture can be separated under high temperature conditions.

  In the present specification, the “organic liquid mixture” means a liquid in which several kinds of organic substances are mixed. A liquid in which water is mixed with an organic substance is also included in the “organic liquid mixture”. Specifically, for example, ethanol / water, acetone / water, t-butanol / water, IPA / water, t-butanol / IPA / methanol / water, acetic acid / water, methyl acetate / methanol, acetic acid / methyl acetate / methanol. / Water, THF / water, THF / cyclohexane / water, and the like.

  In the method for separating an organic liquid mixture according to the present invention, the vapor permeation method is preferably used. In the vapor permeation method, since the permeation substance is supplied by vapor, there is an advantage that concentration polarization hardly occurs on the film and the film life is prolonged.

  In the vapor permeation method, in separation using capillary pressure as the driving force for separation, a vapor film is formed on the surface of the separation layer on the supply side due to vapor liquefaction, and concentration vapor on the membrane is less likely to occur. It is more preferable to carry out under conditions where the speed is high. As a result, high permeability by the vapor permeation method can be obtained, and high selectivity comparable to the permeation vaporization method in which the liquid is allowed to permeate through the membrane and vaporized and separated.

  The liquid film is formed when the permeation component in the mixed vapor decreases on the film and the boiling point of the mixture increases, and the temperature of the supply vapor is lower than the boiling point. However, if the vapor temperature is not set within the range of the boiling point and dew point of the mixture having a reduced permeation component, the concentration of the permeation component in the liquid film will be lower, so the ability will be lower than that of the pervaporation method. As the conditions for vapor permeation, it is usually preferable to carry out in the range of +1 to 10 ° C. with respect to the saturated vapor temperature given by the composition of the organic liquid mixture. However, when the boiling point of the permeating component is higher than the boiling point of the non-permeating component and the boiling point of the mixture decreases due to a decrease in the permeating component in the mixed vapor on the membrane (for example, acetone / water mixture, methyl acetate) / Methanol mixtures, etc.) may be the saturated vapor temperature of the feed mixture.

  A higher temperature and pressure are suitable for permeation, but practically the temperature is preferably 60 to 200 ° C. and the pressure is preferably in the range of 0.1 to 2.0 MPa. In general, the pressure on the permeate side is usually about 1 to 2 Torr. However, in the present invention, the energy required for condensing the membrane permeation vapor becomes smaller when the pressure is 55 Torr or more. This is preferable because it is easy to recover.

  In the method for separating an organic liquid mixture according to the present invention, it is preferable to use a composite separation membrane in which the average pore diameter of the surface of the separation layer is adjusted to 3 to 10 mm. This is because when the average pore diameter on the surface of the separation layer is small, a high capillary pressure can be obtained, so that a high permeation flux can be expressed.

  The composition to be separated in the method for separating an organic liquid mixture according to the present invention can be applied in any range as long as it is a mixture, but is preferably applied to a region having a low relative volatility or azeotropic composition separation.

  In the method for separating an organic liquid mixture according to the present invention, it is preferable that the components of the organic liquid mixture to be separated include carboxylic acid and water. This is because, since the relative volatility of carboxylic acid and water is small, a large amount of energy is required for the separation in the evaporation method, but it is appropriate to use as a target for membrane separation not involving gas-liquid equilibrium. The carboxylic acid is not particularly limited, but is preferably acetic acid. When the permeation component is mainly water, it is preferable to use a composite separation membrane in which the average pore diameter on the surface of the separation layer is adjusted to 4 to 6 inches.

  Regarding the composition of the acetic acid / water mixture to be separated, since the relative volatility is low over almost the entire composition range, it can be said that application in all ranges is preferable. However, for practical use, it is preferable to use 0.1 to 70 wt% of water.

  The pressure and temperature are preferably a pressure exceeding 0.1 MPa and a temperature exceeding 100 ° C. In practice, if the pressure and temperature are too low, the heat of the membrane impermeate cannot be efficiently recovered, and if the pressure is too high, the amount of energy used increases, and if the temperature is too high, In the separation method according to the present invention, since the membrane performance is likely to deteriorate, the membrane separation is preferably performed at a pressure of 0.1 to 0.45 MPa and loaded with the composite separation membrane according to the present invention at 100 to 170 ° C. Supply to the device.

  The pressure on the membrane permeation side is usually about 1 to 2 Torr, but in the present invention, the energy required for condensation of the membrane permeation vapor becomes smaller when the pressure is 55 Torr or more, and the heat possessed by the membrane permeation side steam This is preferable because it is easy to recover.

  The pressure on the transmission side is preferably 55 Torr or more.

  In the method for separating an organic liquid mixture according to the present invention, it is suitable that a component of the organic liquid mixture to be separated contains a carboxylic acid ester and methanol. In an industrial process, because a carboxylic acid ester is converted into a carboxylic acid by hydrolysis due to the presence of a small amount of water, separation is possible without deterioration of the membrane by an inorganic porous membrane having excellent acid resistance. .

  The carboxylic acid ester is not particularly limited, but is preferably an acetate ester, and more preferably methyl acetate. This is because methyl acetate and methanol azeotrope and are difficult to separate by distillation, but are easy to separate by membrane separation not involving gas-liquid equilibrium. When the permeation component is mainly methanol, it is preferable to use a composite separation membrane in which the average pore diameter on the surface of the separation layer is adjusted to 5 to 7 mm.

  The pressure and temperature are preferably a pressure exceeding 0.1 MPa and a temperature exceeding 54 ° C. In practice, if the pressure and temperature are too low, the heat of the membrane impermeate cannot be efficiently recovered, and if the pressure is too high, the amount of energy used increases, and if the temperature is too high, In the separation method according to the present invention, since the membrane performance is likely to deteriorate, the membrane separation is preferably pressurized at 0.1 to 1.7 MPa and loaded with the composite separation membrane according to the present invention at 54 to 170 ° C. Supply to the device.

  Usually, the pressure on the membrane permeation side is usually about 1 to 2 Torr, but in the present invention, the energy required for condensation of the membrane permeation vapor becomes smaller when the pressure is 390 Torr or more, and the heat possessed by the membrane permeation side vapor This is preferable because it is easy to recover.

〔Example〕
EXAMPLES Hereinafter, although this invention is demonstrated concretely using an Example, this invention is not limited to this. In the following examples, “%” represents “% by weight”.

[Example 1: Production of composite separation membrane according to the present invention and measurement of pore diameter and film thickness of the separation layer]
In this example, a porous α-alumina tube (manufactured by NGK Co., Ltd., outer diameter 10 mm, length 800 mm) having an average pore diameter of about 1 μm was used as the support.

(1) Preparation of silica colloid sol The silica colloid sol was prepared as follows. That is, TEOS, water, and nitric acid (catalyst) were mixed so as to have the weight composition shown in Table 1, and then stirred at room temperature for 1 hour to perform hydrolysis and polycondensation reaction.

  Subsequently, this solution was stirred for 10 hours while boiling to prepare a silica colloid sol. The pH of the solution was 2 or less. During the boiling, the total amount of the solution was adjusted to be kept constant. The obtained silica colloid sol was allowed to stand at room temperature for 1 week, and then used for the production of the composite separation membrane of the present invention. As shown in Table 1, when the TEOS concentration was 3.0%, 2.0%, 1.5%, and 0.8%, four types of silica colloid sols 1 to 4 having different particle diameters were used. Was prepared. When the particle size distribution of the silica colloid sol of these solutions was measured by the light scattering method, the average particle size was as shown in Table 2.

(2) Formation of intermediate layer Among silica colloid sols 1 to 4 prepared as described above, uniform colloidal α-alumina particles (Sumitomo Chemical Co., Ltd.) having a particle diameter of about 2 μm were added to silica colloid sol 1 having a TEOS concentration of 3.0%. Silica colloidal sol A in which high purity alpha alumina ALS-43B) is dispersed to 10% and uniform α-alumina particles having a particle diameter of about 0.2 μm (manufactured by Sumitomo Chemical Co., Ltd., high purity alpha alumina) Silica colloidal sol B in which AKP-50) was dispersed to 5% was prepared.

  First, silica colloidal sol A in which particles having a particle diameter of about 2 μm were dispersed was applied to the surface of the support at room temperature and dried for 20 minutes. Then, after heating at 180 degreeC for 10 minutes, it baked at 500 degreeC for 20 minutes. This was cooled, the same silica colloid sol A was applied again, dried and heated under the same conditions. This operation was repeated twice.

  Next, silica colloid sol B in which particles having a particle diameter of about 0.2 μm were dispersed was applied to the surface of the layer formed as described above, and dried at room temperature for 20 minutes. Then, after heating at 180 degreeC for 10 minutes, it baked at 500 degreeC for 20 minutes. This was cooled, the same silica colloid sol B was applied again, dried and heated under the same conditions. This operation was repeated twice.

  In this example, the application and firing of each silica sol were repeated 2 to 8 times, but it is not essential to repeat a plurality of times, and the number of repetitions is not limited.

  Thus, an intermediate layer was formed on the support surface.

(3) Formation of Separation Layer and Measurement of Pore Diameter and Film Thickness Each of the four types of silica colloid sols (silica sols 1 to 4 in Table 1) prepared in (1) above was diluted 4 times, respectively. Used as.

  First, the support on which the intermediate layer obtained in the above (2) was formed was heated at 190 ° C. for 5 minutes, sprayed with diluted silica sol 1 on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. That is, the capillary condensation diameter of Kelvin was measured by the wet gas permeation method. This method is a method of measuring the pore distribution by gradually increasing the humidity of the wet gas, measuring the leakage flux of the gas at that time, and applying the theoretical formula of Kelvin's capillary condensation.

  The average pore diameter of the silica sol 1 film was 6 nm. The above heating, spraying, and firing were repeated 4 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 2 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 2 film was 3 nm. The above heating, spraying, and firing were repeated 4 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 3 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 3 film was 2 nm. The above heating, spraying, and firing were repeated 4 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 4 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 4 film was 0.5 nm. The above heating, spraying, and firing were repeated twice so as to eliminate remarkably large pores of more than 10 nm.

  It was 0.4 micrometer when the thickness of the separation layer (silica membrane) of the composite separation membrane of this invention manufactured by the above was measured with the scanning electron microscope.

  FIG. 1 shows a scanning electron micrograph of the cross section of the composite separation membrane. FIG. 1 shows that a very thin separation layer is formed, and an intermediate layer is formed between the separation layer and the support. FIG. 2 shows a schematic diagram of a cross section of the composite separation membrane. In FIG. 2, the support is a porous α-alumina tube having an average pore diameter of about 1 μm. The intermediate layer is composed of two layers. The layer on the support side contains uniform α-alumina particles and silica colloidal particles having a particle diameter of about 2 μm, and the separation layer side has a uniform particle diameter of about 0.2 μm. α-alumina particles and silica colloidal particles are included. The separation layer is composed of four layers, and the outer layer has a smaller silica colloid particle size, so that the pore size of the separation layer gradually increases toward the intermediate layer.

[Comparative Example 1: Measurement of pore diameter and film thickness of separation layer of composite separation membrane having no intermediate layer]
In this comparative example, the same support as in Example 1 (a porous α-alumina tube having an average pore diameter of about 1 μm (manufactured by NGK Co., Ltd., outer diameter: 10 mm, length: 800 mm)) and Example 1 was used. A composite separation membrane having no intermediate layer is manufactured using four types of silica colloidal sols (silica sols 1 to 4 in Table 1), and the pore diameter of each silica membrane and the thickness of the formed separation layer (silica membrane) are determined. The measurement was performed in the same manner as in Example 1.

  The support was heated at 190 ° C. for 5 minutes, diluted silica sol 1 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 1 film was 6 nm. The above heating, spraying, and firing were repeated 30 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 2 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 2 film was 3 nm. The above heating, spraying, and firing were repeated 30 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 3 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 3 film was 2 nm. The above heating, spraying, and firing were repeated 30 times so as to eliminate remarkably large pores of more than 10 nm.

  Next, the support was heated at 190 ° C. for 5 minutes, diluted silica sol 4 was sprayed on the surface, and baked at 500 ° C. for 10 minutes.

  This was cooled and the pore diameter was measured. The average pore diameter of the silica sol 4 film was 0.5 nm. The above heating, spraying, and firing were repeated 30 times so as to eliminate remarkably large pores of more than 10 nm.

  The thickness of the separation layer (silica membrane) of the composite separation membrane produced as described above was 4.0 μm.

  The results of Example 1 and Comparative Example 1 were compared and shown in Table 3.

  In Comparative Example 1, since the silica sol was directly sprayed and fired on the support, the silica sol penetrated deeply into the pores of the support and a large number of remarkably large pores of 10 nm or more were generated. Therefore, in order to eliminate a remarkably large hole, it was necessary to repeat the spraying and baking of silica sol 30 times each. Therefore, the finally formed silica membrane (separation layer) had a thickness of 4.0 μm.

  On the other hand, since the composite separation membrane of Example 1 had an intermediate layer, the silica sol was prevented from penetrating deeply into the pores of the support, and the generation of extremely large pores of 10 nm or more was very small. Therefore, if the spraying and firing of the silica sol were repeated several times (2 to 4 times), extremely large pores could be eliminated. As a result, the finally formed silica membrane (separation layer) had a thickness of 0.4 μm, which was 1/10 that of Comparative Example 1.

  As described above, the composite separation membrane according to the present invention has a sharp pore size distribution necessary for having high permeation selectivity in the separation of the mixture, no remarkably large pores of several nanometers or more, and the separation layer membrane. It became clear that the film was very thin.

[Example 2: Examination of separation conditions of acetic acid / water mixture]
(2-1) A 90% aqueous solution of acetic acid was evaporated, pressurized to 0.21 MPa, and supplied to the composite separation membrane of the composite separation membrane of Example 1 at 141 ° C.

When the state of the film was observed with a pressure-resistant glass container, a thin liquid film was formed on the film surface, and it was confirmed that the liquid sometimes dropped on the film when observed for a long time. As a result of performing the vapor permeation method while maintaining the pressure on the permeation side at 120 torr, the permeation flux was 9 kg / m ² · hr and the separation factor was 1000. Moreover, although this separation was carried out continuously for 30 days, there was no significant decrease in permeation flux and separation factor.

  (2-2) Using the composite separation membrane of Comparative Example 1, the permeation flux and separation factor were measured under the same conditions as in (2-1) above. That is, an acetic acid 90% aqueous solution was evaporated, pressurized to 0.21 MPa, and supplied to the composite separation membrane of Comparative Example 1 at 141 ° C.

As a result of carrying out the vapor permeation method while maintaining the pressure on the permeate side at 120 torr, the permeation flux was 3 kg / m ² · hr and the separation factor was 20. These were 1/3 of the permeation flux and 1/50 of the separation factor in the composite separation membrane of Example 1.

  (2-3) Using the composite separation membrane of Example 1, the temperature flux was changed and the permeation flux and separation factor were measured. That is, an acetic acid 90% aqueous solution was evaporated, pressurized to 0.21 MPa, and supplied to the composite separation membrane of Example 1 at 150 ° C.

As a result of performing the vapor permeation method while maintaining the pressure on the permeate side at 120 torr, the permeation flux was 4 kg / m ² · hr and the separation factor was 400. When the state of the film was observed with a pressure-resistant glass container, it was observed that the film surface was always dry.

  (2-4) Using the composite separation membrane of Example 1, separation was performed by the pervaporation method instead of the vapor permeation method. That is, a 90% acetic acid aqueous solution was heated to 135 ° C. and supplied to the composite separation membrane of Example 1 in a liquid state.

As a result of performing the pervaporation method while maintaining the pressure on the permeate side at 120 torr, the permeation flux was 9 kg / m ² · hr and the separation factor was 1000. This was the same capacity as the permeation flux and separation factor in (2-1) above. However, after 30 days of testing, the permeation flux was 8 kg / m ² · hr and the separation factor was 1000.

  From the above results, it was found that the composite separation membrane of the present invention produced in Example 1 obtains a high permeation flux and separation coefficient by vapor permeation at an optimum temperature. Moreover, it was shown that vapor permeation has a longer lifetime for the composite separation membrane than liquid permeation and is suitable for industrial use.

[Example 3: Examination of pore diameter suitable for separation of methyl acetate / methanol mixture]
(3-1) In place of the silica colloid sol 4 in Example 1, a silica colloid sol having a composition of TEOS 1.2%, water 98.8%, acid catalyst: nitric acid 0.5% was used. A composite separation membrane was prepared in the same procedure as in 1. When the silica colloid sol particle size distribution of the silica colloid sol solution was measured by a light scattering method, the average particle size was 7 nm. Further, when the pore distribution of the silica colloid sol membrane (separation layer) was measured by applying the theoretical formula of Kelvin capillary condensation, the average pore diameter was 0.7 nm.

A methanol solution of 20% methyl acetate was evaporated, pressurized to 1.1 MPa, and supplied to the composite separation membrane (average pore diameter of the separation layer 0.7 nm) prepared at 141 ° C. as described above. As a result of performing the vapor permeation method while maintaining the pressure on the permeate side at 390 torr, the permeation flux was 30 kg / m ² · hr and the separation factor was 300. When the state of the film was observed with a pressure-resistant glass container, a thin liquid film was formed on the film surface, and it was confirmed that the liquid sometimes dropped on the film when observed for a long time. Moreover, although this separation was carried out continuously for 30 days, there was no significant decrease in permeation flux and separation factor.

  (3-2) The silica colloid sol 3 (TEOS 1.5%, water 98.0%, acid catalyst: nitric acid 0.5%) membrane was used as the outermost layer of the separation layer without using the silica colloid sol 4 in Example 1. A composite separation membrane as a membrane was prepared in the same procedure as in Example 1. Therefore, the average pore diameter of the composite separation membrane is 2 nm (see Example 1).

A mixed solution of methyl acetate 80% and methanol 20% was evaporated, pressurized to 1.1 MPa, and supplied to the composite separation membrane (average pore diameter of the separation layer 1 nm) prepared as described above at 141 ° C. As a result of performing the vapor permeation method while maintaining the pressure on the permeate side at 390 torr, the permeation flux was 10 kg / m ² · hr and the separation factor was 1.1.

  From the above results, it has been clarified that the composite separation membrane of the present invention has a separation layer having an appropriate pore size close to that of the permeating substance, thereby obtaining a high separation coefficient in vapor permeation.

[Reference Example 1: Measurement of film thickness of a separation layer of a film produced by the method described in Patent Document 1 (Japanese Patent No. 2808479)]
(1) Preparation of silica sol 5 Tetraethoxysilane, water and nitric acid were mixed and stirred at room temperature so as to have the weight composition shown in Table 1. While stirring was continued, the mixture was heated to 80 ° C. and boiled. After starting boiling, the liquids for 25 minutes, 20 minutes, and 15 minutes were cooled to form silica sols 5A, 5B, and 5C.

(2) Preparation of silica sol 6 TEOS, water and nitric acid were mixed at room temperature so as to have the weight composition shown in Table 3 and stirred for 60 minutes to obtain silica sol 6.

(3) Formation of Silica Film Electricity set at 200 ° C. by supporting a silica sol by immersing a ceramic tube (average pore diameter 0.5 μm, outer diameter 10 mm, length 500 mm) manufactured by NGK Co., Ltd. in silica sol 5A. Baking for 10 minutes in the furnace. Next, firing was performed for 10 minutes in an electric furnace set to 300 ° C., 10 minutes in an electric furnace set to 400 ° C., and 10 minutes in an electric furnace set to 500 ° C. The above operation was repeated twice.

  Next, the ceramic tube carrying the silica sol 5A was immersed in the silica sol 5B, and the same treatment as above was performed.

  Further, the ceramic tube carrying the silica sols 5A and 5B was immersed in the silica sol 5C, and the same treatment as above was performed.

  Finally, the ceramic tube carrying the silica sols 5A, 5B and 5C was immersed in the silica sol 6 and subjected to the same treatment as above to produce a film.

(4) Measurement of the thickness of the silica film The thickness of the silica film was measured with a scanning electron microscope and found to be 8.0 μm.

  As described above, since the separation membrane produced by the method described in Patent Document 1 uses high-concentration silica gel, the thickness of the silica membrane was 20 times that of the membrane of Example 1.

  It should be noted that the specific embodiments or examples made in the best mode for carrying out the invention are merely to clarify the technical contents of the present invention, and are limited to such specific examples. The present invention should not be interpreted in a narrow sense, and various modifications can be made within the spirit of the present invention and the following claims.

  Moreover, all the academic literatures and patent literatures described in this specification are incorporated herein by reference.

Industrial applicability

  The composite separation membrane according to the present invention includes an intermediate layer having a linear expansion coefficient that is larger than one of the support and the separation layer and smaller than the other. Therefore, the intermediate layer fills the difference in linear expansion coefficient between the support and the separation layer, and cracks and composite separation membranes that are likely to occur when firing the separation layer are heated from normal temperature to high temperature during use and from high temperature to normal temperature. There is an effect that it is possible to prevent cracks at the time of thermal shock such as cooling. Furthermore, the durability is high at high temperatures, and the effect of being excellent in industrial use under high temperature conditions is exhibited.

  Further, the composite separation membrane according to the present invention includes a homogeneous intermediate layer having a pore diameter larger than the pore diameter of one of the support and the separation layer and smaller than the other pore diameter. Therefore, there is an effect that the thickness of the separation layer can be extremely reduced without allowing the components of the separation layer to penetrate into the deep part of the support.

  In other words, the thickness of the layer with a small pore diameter that guarantees the selective permeability of the separation target can be made very thin, so that the permeation inhibition is extremely small and a high permeation flux can be obtained even in the separation system of various mixtures. A membrane can be provided.

  If the method for producing a composite separation membrane according to the present invention is used, the intermediate layer and / or the support and the separation having a linear expansion coefficient larger than that of one of the support and the separation layer and smaller than the other. An intermediate layer having a pore size larger than one of the pores and smaller than the other pore size can be formed, and a very thin separation layer can be formed thereon.

  The separation method of the organic liquid mixture according to the present invention uses the composite separation membrane according to the present invention or the composite separation membrane produced by the production method according to the present invention, and sets the pore size of the separation layer to an appropriate diameter close to that of the permeating substance. By adjusting, high permeability and selectivity can be realized in the vapor permeation method.

  As described above, the composite separation membrane according to the present invention has high permeation selectivity and excellent permeation flux. Moreover, it has the strength and heat resistance that can withstand industrial use. Therefore, it has very high utility value as a liquid separation membrane and a vapor separation membrane, and is suitable for industrial use.

Claims (33)

A composite separation membrane having an inorganic porous body as a support and having a separation layer,
An intermediate layer is provided between the support and the separation layer,
The composite separation membrane, wherein the intermediate layer has a linear expansion coefficient larger than that of one of the support and the separation layer and smaller than the other linear expansion coefficient.   The composite separation membrane according to claim 1, wherein the intermediate layer is composed of a plurality of layers.   Of the plurality of layers constituting the intermediate layer, the layer adjacent to the support has a linear expansion coefficient close to the linear expansion coefficient of the support, and the layer adjacent to the separation layer is the linear expansion of the separation layer. The composite separation membrane according to claim 2, which has a linear expansion coefficient close to the coefficient.   A plurality of layers constituting the intermediate layer are laminated stepwise from the layer adjacent to the support toward the layer adjacent to the separation layer in the order of the linear expansion coefficient. The composite separation membrane according to claim 2 or 3.   At least one of the plurality of layers constituting the intermediate layer is a layer containing particles having a linear expansion coefficient that is the same as or close to that of the substance constituting the support or the separation layer. The composite separation membrane according to any one of claims 2 to 4.   6. The composite separation membrane according to claim 5, wherein the particles are mixed particles of particles of a substance constituting the support and particles of a substance constituting a separation layer. A composite separation membrane having an inorganic porous body as a support and having a separation layer,
An intermediate layer is provided between the support and the separation layer,
The composite separation membrane, wherein the intermediate layer has a pore size smaller than the pore size of the support and larger than the pore size of the separation layer.   The composite separation membrane according to claim 7, wherein the intermediate layer is composed of a plurality of layers.   Of the plurality of layers constituting the intermediate layer, the layer adjacent to the support has a pore diameter close to the pore diameter of the support, and the layer adjacent to the separation layer is close to the pore diameter of the separation layer The composite separation membrane according to claim 8, which has a pore size.   The plurality of layers constituting the intermediate layer are laminated stepwise from the layer adjacent to the support toward the layer adjacent to the separation layer in order of the size of the pore diameter. Item 10. The composite separation membrane according to Item 8 or 9.   11. The method according to claim 8, wherein at least one of the plurality of layers constituting the intermediate layer is a layer containing particles of a substance constituting the support or the separation layer. Composite separation membrane.   12. The composite separation membrane according to claim 11, wherein the particles are mixed particles of the substance particles constituting the support and the substance particles constituting the separation layer.   13. The composite separation membrane according to claim 12, wherein the particles of the substance constituting the support and the particles of the substance constituting the separation layer each have a uniform particle diameter.   The composite separation membrane according to claim 1, wherein the intermediate layer has a thickness of 0.1 μm or more and 5.0 μm or less. The composite separation membrane according to claim 1, wherein a main component of the support is α-Al ₂ O ₃ .   The composite separation membrane according to any one of claims 1 to 13, wherein the separation layer contains an inorganic compound.   The composite separation membrane according to claim 16, wherein the inorganic compound is silica.   The composite separation membrane according to any one of claims 1 to 13, wherein an average pore diameter of the surface of the separation layer is 3 to 10 mm. A method for producing a composite separation membrane comprising a support comprising an inorganic porous material, an intermediate layer and a separation layer,
Preparing a first colloid sol in which particles of a substance constituting the support are dispersed in a colloid sol mainly composed of particles of the substance constituting the separation layer, and applying the first colloid sol to the surface of the support; An intermediate layer forming step of forming the intermediate layer by firing; and preparing a second colloid sol mainly composed of particles of the substance constituting the separation layer, and applying the second colloid sol to the surface of the intermediate layer. A method for producing a composite separation membrane, comprising a separation layer forming step of forming the separation layer by firing. The first colloidal sol for forming the intermediate layer is composed of a plurality of types of colloidal sol in which particles of a substance constituting the support and particles having different particle diameters are dispersed,
The particle diameters in the plurality of types of colloidal sols are substantially uniform,
First, the colloidal sol in which particles having the largest particle size are dispersed is applied and fired on the surface of the support, and then the colloidal sol in which particles having a small particle size are sequentially dispersed is applied and fired on the surface of the support. The method for producing a composite separation membrane according to claim 19, wherein the plurality of intermediate layers are formed.   The particle concentration of the substance constituting the support of the first colloid sol composed of the plurality of types of colloid sols is the highest in the colloid sol in which the particles with the largest particle size are dispersed, and the particle concentration increases in the order of the particle size. 21. The method of producing a composite separation membrane according to claim 20, wherein the method is lowered.   The method for producing a composite separation membrane according to any one of claims 19 to 21, wherein the thickness of the intermediate layer is 0.1 µm or more and 5.0 µm or less.   An organic liquid using the composite separation membrane according to any one of claims 1 to 18 or the composite separation membrane produced by the production method according to any one of claims 19 to 22. Method for separating the mixture.   The method for separating an organic liquid mixture according to claim 23, wherein the separation is performed by a vapor permeation method.   25. The method for separating an organic liquid mixture according to claim 24, wherein the vapor permeation method is performed such that a liquid film is formed by vapor liquefaction on the surface of the separation layer on the supply side.   The method for separating an organic liquid mixture according to any one of claims 23 to 25, wherein a composite separation membrane having an average pore diameter of 3 to 10 mm is used on the surface of the separation layer.   27. The method for separating an organic liquid mixture according to any one of claims 23 to 26, wherein the organic liquid mixture contains a carboxylic acid and water.   28. The method for separating an organic liquid mixture according to claim 27, wherein the carboxylic acid is acetic acid.   29. The method for separating an organic liquid mixture according to claim 28, wherein a composite separation membrane having an average pore diameter of 4 to 6 mm is used on the surface of the separation layer.   27. The method for separating an organic liquid mixture according to any one of claims 23 to 26, wherein the organic liquid mixture contains a carboxylic acid ester and methanol.   The method for separating an organic liquid mixture according to claim 30, wherein the carboxylic acid ester is an acetic acid ester.   32. The method for separating an organic liquid mixture according to claim 31, wherein the acetate is methyl acetate.   33. The method for separating an organic liquid mixture according to claim 32, wherein a composite separation membrane having an average pore diameter of 5 to 7 mm is used on the surface of the separation layer.