JP2013031830A - Porous body with separation membrane - Google Patents

Abstract

Provided is a porous body with a separation membrane having a high permeation rate as a whole of the porous body with a separation membrane even if it has a plurality of tubular passages.
A porous body with a separation membrane having a plurality of tubular passages having a separation membrane having a separation function formed on an inner wall of a through hole provided in a porous body, the length direction of the tubular passage In the cross section perpendicular to, all the tubular passages face the outer peripheral surface y of the porous body with a separation membrane.
[Selection] Figure 1

Description

  The present invention relates to a porous body with a separation membrane, and more particularly to a porous body with a separation membrane useful in techniques such as dehydration concentration of hydrous alcohol, natural gas separation, and isomer separation in a petroleum plant.

  Conventionally, a filter for separating a specific gas from a mixed gas containing various gases, a filter for removing water from hydrous alcohol, a membrane reactor carrying a catalyst, etc. have been used. The scope of application has expanded, and now these separation and concentration technologies include various combustion engines, food industry, medical equipment, partial replacement for distillation in chemical plants and oil refining plants, as well as solvent recovery and waste disposal. It is also attracting attention in the field.

  For example, a filter for separating hydrogen gas can be used for recovering hydrogen gas from off-gas generated in an oil refining plant, purge gas generated in an ammonia synthesis plant, etc. The application to the removal of carbon dioxide contained in natural gas has been studied for the purpose of preventing corrosion of pipelines. Furthermore, as a filter for separating oxygen, it is applied to medical equipment, sports equipment, and various combustion engines.

  In a conventional filter, for example, a porous body with a separation membrane in which a through-hole through which a fluid to be separated is passed is provided in a porous body made of ceramic, for example, a carbon membrane having a separation function is formed on the inner wall of the through-hole is used. As a porous body with a separation membrane, there is a tubular type having a single tubular passage inside a cylindrical porous body, or inside a cylindrical porous body in the longitudinal direction of the cylinder. A monolith type having a plurality of parallel tubular passages is known (see Patent Document 1). In particular, the monolith type can flow a larger amount of fluid to be separated than the tubular type, and the number of porous bodies with separation membranes placed on the filter can be reduced. It is possible to prevent a reduction in the operating rate of the apparatus, damage during work, and problems of poor sealing.

JP 2008-221177 A

  In the porous body with a monolith type separation membrane as shown in FIG. 9, the permeation speed of the separation component in the tubular passage located near the axis of the cylinder is lower than the permeation speed in the tubular passage on the outer peripheral side. For example, when the fluid to be separated is concentrated and removed, the removed fluid to be separated is not sufficiently concentrated and needs to be re-separated or sufficiently concentrated. In order to obtain the separated fluid, there is a problem that the flow rate of the separated fluid cannot be increased and the separation efficiency is low. This is because the separation component separated from the tubular passage in the porous body with the separation membrane faces the porous body inside surface toward the outer peripheral surface of the porous body, and is in an atmosphere in contact with the pores (pores) inside and the outer surface of the porous body. 9 is discharged from the separation membrane by moving the difference in partial pressure of the separation component as a driving force. In a monolith type porous body with a separation membrane as shown in FIG. This is because the separation component separated by the tubular passage located near the axis of the cylinder in comparison has a long moving distance inside the porous body and is not easily discharged.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a porous body with a separation membrane having a high permeation rate as a whole porous body with a separation membrane even if a plurality of tubular passages are provided. .

  The porous body with a separation membrane of the present invention is a porous body with a separation membrane comprising a plurality of tubular passages in which a separation membrane having a separation function is formed on the inner wall of a through hole provided in the porous body, In the cross section perpendicular to the length direction, all the tubular passages face the outer peripheral surface of the porous body with a separation membrane.

  Here, all the tubular passages face the outer peripheral surface of the porous body with a separation membrane means that each tubular passage has a cross section perpendicular to the length direction of the tubular passage of the porous body with a separation membrane (hereinafter, In some cases, the cross-section of the porous body with a separation membrane is simply the other of the straight lines connecting the center of each tubular passage and the outer peripheral surface of the porous body with a separation membrane, This means that there is no tubular passage.

  In the porous body with a separation membrane of the present invention, the separation component separated by the separation membrane of each tubular passage is less affected by the partial pressure of the separation component separated from the other tubular passage, and the separation membrane is attached. A high permeation rate can be obtained for the entire porous body.

(A) (b) is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a monolith type separation membrane which is an example of this invention. It is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a monolith type separation membrane which is another example of this invention. (A) (b) is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a separation membrane which is another example of this invention, respectively. It is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a separation membrane which is another example of this invention. It is a perspective view of the porous body with a separation membrane which is another example of this invention. It is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a separation membrane which is another example of this invention. It is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a separation membrane of Example 2. FIG. (A) (b) is sectional drawing perpendicular | vertical to the length direction of a tubular channel | path of the porous body with a separation membrane of a comparative example. It is a perspective view which shows an example of the conventional porous body with a monolith type separation membrane.

  FIG. 1 is a cross-sectional view of a monolith type porous body with a separation membrane which is an example of the present invention in a direction perpendicular to the length direction of the tubular passage (hereinafter, a cross section of the porous body with separation membrane and the tubular passage). Means a cross section in a direction perpendicular to the longitudinal direction of the tubular passage). In the porous body 1 with a separation membrane shown in FIG. 1 (a), for example, a separation membrane (not shown) such as a carbon membrane having a separation function is formed on the inner wall on a cylindrical ceramic porous body 12. A plurality of (six in FIG. 1) tubular passages 11 are arranged. In addition, all the tubular passages 11 face the outer peripheral surface of the porous body with the separation membrane, that is, each tubular passage 11 has the center p of each tubular passage 11 and the outer peripheral surface y of the porous body 1 with the separation membrane. Are arranged so that there is no other tubular passage 11 on the shortest line segment x. In the tubular passage 11, an intermediate layer may be provided between the inner wall of the through hole of the porous body 12 and the separation membrane.

  By arranging the tubular passages 11 in this way, the separated components separated by the separation membrane of each tubular passage 11 are less affected by the partial pressure of the separated components separated from the other tubular passages 11, A high permeation rate can be obtained as the entire porous body 1 with a separation membrane.

  These tubular passages 11 may have different lengths of the shortest line segment x for each tubular passage like x1 and x2 shown in FIG. 2, but the lengths of x are equal in all the tubular passages 11. It is preferable to arrange | position. By disposing the tubular passages 11 in this way, the distances at which the separated separated components move from the tubular passages 11 to the outer peripheral surface of the porous body 12 become equal, and the permeation speeds from the tubular passages 11 become equal. Therefore, the separation factor of the entire porous body 1 with a separation membrane can be stably increased, and the flow rate and concentration rate of the fluid to be separated can be increased.

  In the present invention, the shape of the monolith type porous body 1 with a separation membrane is not limited to a cylindrical shape, and may be an elliptical column shape, a polygonal column shape such as a triangular column, a quadrangular column, or the like. In the case of a polygonal column shape, the corners of the polygon can be rounded as desired. Further, the cross-sectional shape of the tubular passage 11 is not limited to a circle, and may be, for example, an ellipse, a polygon such as a triangle or a quadrangle. In this case, the center of the tubular passage 11 when the cross-sectional shape is other than circular refers to the geometric gravity center position.

FIG. 3 is a cross-sectional view of a porous body with a separation membrane, which is another example of the present invention. In the porous body 3 with a separation membrane, a plurality (eight in FIG. 3) are provided in a cylindrical porous body 32 provided with a through-hole H having no separation membrane on the inner wall surface in the center of the cross section. The tubular passage 31 is arranged. Also in this case, no other tubular passage 31 exists on the shortest line segment x among the line segments connecting the center of each tubular passage 31 and the outer peripheral surface y of the porous body 3 with the separation membrane. By providing the through-hole H having no separation membrane on the inner wall surface, it is possible to reduce the partial pressure of the separation component inside the through-hole H and promote the removal of the separation component from the inner peripheral surface z. The transmission speed can be further increased.

Further, by disposing a heat source such as a rod heater inside the through hole H or passing a heating fluid, the temperature of the porous body 3 with a separation membrane due to vaporization heat at the time of separation is prevented, and the separation component A decrease in permeation rate due to condensation can also be prevented. In particular, in order to improve the heating efficiency of the porous body 3, when filling the inside of the through-hole H with a heat conductive substance or passing a heated fluid, from the point of preventing impurities from being mixed into the fluid to be separated, The inner wall of the through hole H is preferably covered with a gas-impermeable material such as glass. A separation membrane may be provided between the gas impermeable coating and the porous body 3.

  In addition, the shape of the porous body with a separation membrane in which the through-hole H which does not have a separation membrane is provided in the inner wall surface is not restricted to a cylindrical shape, For example, the porous body with a separation membrane shown in FIG.3 (b) It may be a quadrangular cylinder with rounded corners such as the body 4, other polygonal cylinders, or an elliptical cylinder, and a plurality of through holes H may be provided.

  It is preferable that the outer peripheral shape in the cross section of the porous body with a separation membrane is flat. When the outer periphery of the cross section is flat, when the outer periphery of the cross section is surrounded by a rectangular frame, the ratio of the length of the long side to the length of the short side of the rectangular frame having the smallest area is It is larger than 1. For example, in FIG. 4, the porous body 5 with a separation membrane has a plurality of (eight in FIG. 4) tubular passages 51 arranged in two rows on a rectangular porous body 52 with rounded corners. Each tubular passage 51 is arranged such that no other tubular passage 51 exists on the shortest line segment x among the line segments connecting the center p and the outer peripheral surface y of the porous body 5 with the separation membrane.

Further, like a porous body 6 with a separation membrane shown in FIG. 5, a rectangular porous body 62 with rounded corners.
A plurality (eight in FIG. 5) of tubular passages 61 may be arranged in a line. In this way, by arranging the tubular passages 61 in a row, the outer periphery in the cross section of the porous body with the separation membrane is compared with the porous body with the separation membrane of other shapes in which the same number of tubular passages having the same cross-sectional area are arranged. The ratio of the cross-sectional area can be reduced with respect to the length, and the volume of the porous body with a separation membrane can be reduced. In this case, the center of each tubular passage 61 does not necessarily need to be located on the same straight line. However, when the porous body with a separation membrane is downsized, the center of each tubular passage 61 is on the same straight line. Preferably, the outer circumference of the porous body with a separation membrane is formed along a line segment connecting the centers of the tubular passages 61 located at both ends of the row. Preferably it is. In addition, it is more preferable that the distance between the outer periphery of the porous body with the separation membrane and the line segment connecting the centers of the tubular passages 61 positioned at both ends of the row is constant.

  Further, the shape of the porous body is not limited to the rectangular shape, and for example, as shown in FIG. 6, irregularities may be provided on the outer peripheral surface of the porous body 7 with a separation membrane so as to follow the shape of the tubular passage 71.

  The manufacturing method of the porous body with a separation membrane which is an example of this invention is demonstrated.

  First, a porous body provided with predetermined through holes is prepared. Regarding the various shapes of the porous body and the arrangement of the through holes, for example, if molding is performed by extrusion molding, a desired molded body may be produced by appropriately designing a mold or the like, or a molded body or a fired body. May be processed.

  As the material for the porous body, ceramics such as alumina, mullite, cordierite, zirconia, magnesia, silicon carbide, and silicon nitride can be suitably used. The average particle diameter of the ceramic particles constituting the porous body is 1 to 100 μm, preferably 1 to 30 μm, and the average pore diameter is 0.1 to 30 μm, preferably 0.1 to 10 μm. preferable.

An intermediate layer composed of ceramic particles having an average particle size smaller than that of the porous body may be provided between the inner wall of the through hole of the porous body serving as the tubular passage and the separation membrane. As the material for the intermediate layer, ceramics such as alumina, mullite, cordierite, zirconia, magnesia, silicon carbide, and silicon nitride can be suitably used. For the intermediate layer, for example, a raw material powder composed of ceramic particles having an average particle diameter of 0.01 to 10 μm, preferably 0.02 to 1 μm is appropriately weighed, and dispersed in water using a hydrophilic dispersant, for example, dip coating. It can be formed by applying to the inner wall of the through-hole of the porous body using an application means such as a method (dip coating method), drying, and then heat-treating. At this time, the ceramic particles constituting the formed intermediate layer only need to be partially bonded by the neck, and the particle size thereof is substantially equal to the particle size of the raw material powder. The thickness of the intermediate layer can be adjusted by, for example, the immersion time and the number of immersions, and can be set in the range of, for example, 5 to 1000 μm. The average pore diameter of the intermediate layer may be appropriately selected within the range of 0.01 to 3 μm, preferably 0.1 to 0.5 μm. The thickness of the intermediate layer may be any thickness that can cover the unevenness present on the inner wall of the through hole of the porous body with the intermediate layer. The thickness of the intermediate layer constitutes the inner wall of the through hole of the porous body from the viewpoint of preventing surface defects such as pinholes from remaining on the inner wall of the separation membrane formed thereon and increasing the permeation speed. 1 to 50 times the average particle size of the ceramic particles to be processed is preferable, and 2 to 20 times is more preferable. The thickness of the intermediate layer can be determined from a cross-sectional photograph of the porous body and the intermediate layer by a scanning electron microscope (SEM), and the average of the ceramic particles forming the porous body and the ceramic particles forming the intermediate layer The particle size can be calculated, for example, from the cross-sectional photograph by the intercept method. Moreover, the average pore diameter of the porous body and the intermediate layer can be determined by a mercury intrusion method. In addition, about the porous body with a separation membrane in which the separation membrane was formed, when the separation membrane is a carbon membrane, it can be removed by oxidizing the carbon component, for example, in air at 800 ° C. for about 30 minutes. The average pore diameter may be measured after removing the carbon component from the surface of the porous body with the separation membrane and the inside of the pores by heat-treating the porous body with the separation membrane under conditions. For separation membranes other than carbon membranes, as appropriate, by immersing the porous body with a separation membrane in a solvent or chemical that can remove the components of the separation membrane without affecting the ceramic particles forming the porous body, etc. After removing the separation membrane component from the surface of the porous body with the separation membrane and the inside of the pores, the average pore diameter may be measured.

  A porous body with a separation membrane can be obtained by forming a separation membrane such as a carbon membrane on the inner wall of the through hole of the porous body or an intermediate layer formed there. For example, in the case of forming a carbon membrane as a separation membrane, the separation membrane is formed by dissolving aromatic polyimide, polypropylene, polyfuryl alcohol, polyvinylidene chloride, phenol resin, etc. as a carbon membrane precursor in a solvent. A film precursor solution (sometimes simply referred to as a precursor solution) is prepared, and a carbon film precursor film is formed on the inner wall of the through hole of the porous body or an intermediate layer formed there by dip coating or the like, After drying, a carbon film is formed by heat treatment at a temperature of 550 to 1000 ° C. in a non-oxidizing atmosphere such as a nitrogen atmosphere or in a vacuum. When forming the carbon film precursor coating, helium gas is supplied at a pressure of about 1 kPa into the pores of the porous body in order to prevent the precursor solution from entering the pores of the porous body. You may carry out, pressurizing the inside of a pore. Moreover, after repeating the formation and drying of the carbon film precursor coating a plurality of times, heat treatment may be performed.

  The thickness of the separation membrane is preferably from 0.01 to 5 μm, particularly preferably from 0.1 to 3 μm, from the viewpoint of suppressing the occurrence of defects such as pinholes and increasing the permeation rate.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these Examples.

  A porous body with a separation membrane having six tubular passages shown in FIGS. 1 and 7 was produced as Example 1 and Example 2, respectively. The outer shape of the porous body of Example 1 was 90 mm in diameter and 200 mm in length, and the outer shape of the porous body in Example 2 was 30 mm × 180 mm in cross section and 200 m in length. C represents the minimum thickness of the porous body between the tubular passage and the outer peripheral surface of the porous body with the separation membrane, D represents the diameter of the tubular passage, and E represents the minimum thickness of the porous body between the adjacent tubular passages. It is shown in 1.

First, alumina powder (average particle size 0.02-0.9 μm) is mixed with water and polyvinyl alcohol (
PVA) to prepare an alumina slurry. As the porous body, a porous body having an average pore diameter of 1.1 μm composed of alumina particles having an average particle diameter of 3.0 μm was immersed in the previously prepared alumina slurry and pulled up at a constant speed. A film serving as an intermediate layer was formed on the surface and the inner wall of the through hole and dried. Thereafter, the entire porous body was heat-treated at 1100 ° C. to form an intermediate layer having an average pore diameter of 0.05 μm and a thickness of 30 μm made of alumina particles having an average particle diameter of 0.2 μm on the inner wall of the through hole. The thickness of the intermediate layer, the alumina particles constituting the porous body, and the average particle diameter of the alumina particles constituting the intermediate layer are obtained from cross-sectional photographs of the alumina porous body and the intermediate layer taken by a scanning electron microscope (SEM). The average pore diameter was determined by mercury porosimetry.

Next, in order to form a carbon film on the intermediate layer formed on the inner wall of the through hole of the porous body, a phenol resin is dissolved in tetrahydrofuran (THF) as a carbon film precursor solution, and the concentration of the phenol is 35%. A THF solution of the resin was prepared. One of the openings of the through hole in which the intermediate layer is formed is sealed, the precursor solution is injected from the other opening and held for 1 minute, and then the precursor solution is discharged, and a phenol resin coating is formed on the intermediate layer. Formed and dried at 130 ° C. for 10 minutes. Thereafter, the opening of the sealed through-hole is opened, and the entire porous body is heat-treated at 850 ° C. for 10 minutes in a nitrogen atmosphere to form a 200 mm-long porous body with a separation membrane on which a carbon separation membrane having a thickness of 2 μm is formed. Was made.

  As a comparative example, a porous body 9 with a separation membrane having six tubular passages 91 shown in FIG. 8 was produced by the same production method as in Example 1. The outer shape of the porous body was 90 mm in diameter and 200 mm in length, as in the example, and this porous body 9 with a separation membrane has one tubular passage 91 at the center, and five outside on the outside. Tubular passages 91 are arranged uniformly, and C1, C2, E1, and E2 shown in FIG.

About the produced porous body with a separation membrane, the water / ethanol mixed solution was passed through the tubular passage, and pervaporation measurement was performed. The water / ethanol mixed solution in the tubular passage of the porous body with the separation membrane is set with the supply side (inside of the tubular passage) at atmospheric pressure and the permeation side (the outer peripheral surface side of the porous body with separation membrane) in the vacuum. The pressure difference was used as the driving force to allow permeation to the porous body side, and the separation coefficient α and permeation speed Q at that time were compared. The feed solution had a water / ethanol (EtOH) ratio of 10/90 (mass%) and a temperature of 75 ° C. The contents (mass%) of ethanol and water on the supply side and the permeation side were measured using a gas chromatograph GC-2014 (Shimadzu Corporation). The separation factor α and the transmission rate Q were calculated using the following equations.

  In the cross section of the porous body with the separation membrane, all the tubular passages face the outer peripheral surface of the porous body with the separation membrane. The porous bodies with the separation membrane in Examples 1 and 2 have the same number of tubular passages. Both the permeation rate and the separation factor were higher than those of the comparative example in which a tubular passage not facing the outer peripheral surface was present.

1-10: Porous bodies with separation membranes 11, 21, 31, 41, 51, 61, 71, 81, 91, 101: Tubular passages 12, 22, 32, 42, 52, 62, 72, 82, 92, 102: Porous body p: Center of tubular passage x, x1, x2: Line segment connecting the center of tubular passage and outer peripheral surface of porous body with separation membrane at the shortest distance y: Outer peripheral surface C of porous body with separation membrane C1, C2: Minimum thickness of the porous body between the tubular passage and the outer peripheral surface of the porous body with the separation membrane D: Diameter of the tubular passage E, E1, E2: The porous body between the adjacent tubular passages Minimum thickness H: Through-hole that has no separation membrane on the inner wall surface

Claims (6)

A porous body with a separation membrane comprising a plurality of tubular passages in which a separation membrane having a separation function is formed on the inner wall of a through hole provided in the porous body,
A porous body with a separation membrane, wherein all the tubular passages face an outer peripheral surface of the porous body with a separation membrane in a cross section perpendicular to the length direction of the tubular passage.   The porous body with a separation membrane according to claim 1, wherein an outer peripheral shape in the cross section of the porous body with the separation membrane is flat.   The porous body with a separation membrane according to claim 1 or 2, wherein the porous body with a separation membrane is provided with a through-hole that does not have a separation membrane on the inner wall surface.   The porous body with a separation membrane according to claim 3, wherein the inner wall of the through hole having no separation membrane on the inner wall surface is coated with a gas-impermeable material.   5. The porous body with a separation membrane according to claim 3, wherein a heat source is provided in a through hole that does not have a separation membrane on the inner wall surface.   In the cross section, the plurality of tubular passages are arranged in a row so that the centers of the tubular passages are located on the same straight line, and the outer periphery of the porous body with the separation membrane is located at both ends of the row. The porous body with a separation membrane according to claim 2, wherein the porous body is formed along a line segment connecting the centers of the tubular passages.

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