JP2005177554A - Fluid separating filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fluid separating filter excellent in water resistance and improved in deterioration of permeation characteristic by reducing the influence of moisture. <P>SOLUTION: A ceramic fluid separation membrane consisting of at least one metallic component of Si, Ti and Zr and an element of group IIIa in the periodic table is formed on at least a part of the surface of a porous support. It is particularly preferable that the element of group IIIa in the periodic table is at least one of Lu, Yb, Dy, Sm, Er and Eu and the separation membrane consisting of the metallic component of Si, Ti or Zr is an amorphous material. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a plant for concentrating a specific gas in petroleum refining, a plant for concentrating a specific substance from a mixed solvent, a plant for dehydration from alcohol, a water treatment plant or desalination plant for increasing the purity of water, a factory exhaust gas, Equipment that separates specific gases such as oxygen and carbon dioxide from power plants, plants that separate specific gases such as carbon dioxide, hydrogen sulfide, and methane from oil and natural gas oil fields, food-related or medical-related separators, hydrogen The present invention relates to a fuel cell that generates electricity using gas and oxygen gas as fuel, a fluid separation filter that can be suitably used as an oxygen separation membrane and a hydrogen separation membrane in a microreactor for chemical synthesis and fuel cell use, and a method for producing the same.

  Conventionally, a porous body has been used as a catalyst carrier, an electrolytic partition, etc., including a filter for filtering and separating a specific gas from a mixed gas containing various gases. The technology for separating and concentrating specific gases using a porous material has been attracting attention in various combustion engines, food industries, medical equipment, and waste disposal. On the other hand, however, there is a problem of heat resistance because the polymer is generally made of a polymer. Therefore, recently, a filter using an inorganic film has attracted attention.

  However, when an inorganic material is used, for example, as shown in FIG. 3, the adsorption of water to the film occurs due to the presence of Si—OH groups, which deteriorates the permeation characteristics in repeated measurements and adsorbs hydrophilic substances. The phenomenon of deterioration of separation characteristics due to the occurrence of this phenomenon often occurred.

Therefore, in order to increase hydrophobicity and prevent adsorption of hydrophilic substances to the membrane, a glass porous membrane generates a siloxane bond by chemically converting Si—OH present on the surface and inside of the membrane with a silylating agent, and the membrane. It has been proposed that the concentration of the remaining silylating agent is 0.60 mg / m ² . As a result, Si—OH groups serving as water adsorption points existing in the membrane are reduced, water adsorption is suppressed, and degradation of separation characteristics is suppressed (see, for example, Patent Document 1).

In addition, in order to improve hydrophobicity, the Si—OH group is changed to the Si—O—Si group (siloxane bond) by baking at a high temperature of 600 ° C. or higher to improve water resistance (for example, Patent Documents). 2).
JP-A-8-24600 Japanese Patent Application No. 2001-36343

  However, in the filter described in Patent Document 1, the Si-OH (silanol) group of the film is siloxane-bonded by a silylating agent to improve the material, and the hydrophobicity is remarkably improved immediately after the production of the filter. Although effective, there was a problem that the transmission characteristics gradually deteriorated with the passage of time.

  In addition, the filter described in Patent Document 2 has a problem that although the initial characteristics are greatly improved by the siloxane bond produced by high-temperature baking, the transmission characteristics are deteriorated due to a change with time.

  Accordingly, an object of the present invention is to provide a fluid separation filter that is excellent in water resistance by reducing the influence of moisture and improved in deterioration of permeation characteristics.

  The fluid separation filter of the present invention is a ceramic fluid separation membrane comprising at least part of the surface of a porous support and at least one metal component Si, Ti, Zr and a group 3a element of the periodic table. Is formed.

  The Group 3a element of the periodic table is preferably at least one of Lu, Yb, Dy, Sm, Er, and Eu.

  The ceramic fluid separation membrane is preferably made of an amorphous material.

The present invention, change with time, eventually finding that caused by the SiO ₂ component from dissolving in water, by changing the coupling state by adding a metal component and a periodic group 3 element, the SiO ₂ component This is a fluid separation filter that suppresses elution into water, reduces the influence of moisture, and has excellent water resistance.

  That is, in the fluid separation filter of the present invention, the separation membrane is composed of at least one of the metal components Si, Ti, and Zr and the Group 3a element of the periodic table. By forming a bond of B (A is at least one of the metal components Si, Ti, and Zr, and B is a group 3a element of the periodic table) and having a bond state different from that of the conventional A-O-A bond film, Inductive effects can improve water reactivity and separation characteristics.

  Further, when the Group 3a element of the periodic table is composed of at least one of Lu, Yb, Dy, Sm, Er, Eu, and Ce, higher water resistance can be obtained.

  Furthermore, when the ceramic fluid separation membrane is made of an amorphous material, the interstitial distance can be controlled so as to have an optimum pore diameter for gas separation, and a flow rate sufficient for gas to pass through can be obtained. In addition, there is an effect of increasing selectivity.

  The fluid separation filter of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing the structure of the fluid separation filter of the present embodiment. As shown in FIG. 1, the fluid separation filter 1 includes a porous support 2, a ceramic fluid separation membrane 3 formed on at least one surface of the porous support 2 and having a large number of pores 4, Consists of.

  An intermediate layer 5 can be provided between the porous support 2 and the ceramic fluid separation membrane 3 as desired. The intermediate layer 5 is preferably set to be smaller than the pore diameter of the porous support 2 and larger than the pore diameter of the ceramic fluid separation membrane 3.

According to the present invention, be converted to conventional Si-OH group to siloxane bond was found to be converted back to Si-OH groups in the presence of water over time, eventually SiO ₂ water I found out that the cause is that it melts in.

  Therefore, according to the present invention, it is important that the separation layer in contact with the fluid of the ceramic fluid separation membrane is composed of at least one metal component Si, Ti, Zr and Group 3a element (rare earth element) of the periodic table. is there. In this way, by doping rare earth elements in the separation layer, Si, Ti, Zr alone dissolved into water is A-O-B (A is a metal component of Si, Ti, Zr). In any case, B is a periodic table group 3a element) bond, so that dissolution into water can be suppressed and water resistance can be significantly improved.

  FIG. 2 is a schematic view showing a bonded state of the ceramic fluid separation membrane. As shown in FIG. 2, when considering the Si / Er composite oxide film, the ceramic fluid separation membrane 3 is basically formed by a cyclic bond represented by —Si—O—Er—, and the pores 4 are formed. It includes a plurality of amorphous oxides. A similar cyclic bond can be produced by doping any of Lu, Dy, Sm, Yb, and Eu instead of Er, and the same effect can be obtained.

  Thus, the portion in contact with the fluid is composed of a complex oxide composed of any one of the metal components Si, Ti, Zr and the Group 3a element of the periodic table, thereby suppressing the dissolution of the metal component in water, Water resistance can be increased.

  Furthermore, it is desirable that the ceramic fluid separation membrane is made of an amorphous material. When it is amorphous, it is possible to adjust the pores 4 formed in the cyclic bond including the A—O—B bond in a wider range than the crystalline state, and the gas permeability can be increased. Can be increased.

  In addition, since the size of the pores 4 and the distribution state thereof vary depending on the type and production conditions of the Group 3a element of the periodic table, it is necessary to appropriately select and combine them to determine the pore diameter.

  The ceramic fluid separation membrane 3 is deposited on the surface of the porous support 2, but does not generate a reaction product at the interface with the porous support 2, and is layered on the surface of the porous support 2. It is desirable to form a smooth surface by coating, and the thickness of the ceramic fluid separation membrane is preferably 0.01 to 5 μm from the viewpoint of improving the separation performance.

  The porous support 2 has a pore diameter of 0.05 to 2 μm in that it can transmit a fluid such as gas and has a necessary strength as a structure and enhances the film forming property of the ceramic fluid separation membrane 3. It is desirable. Moreover, in order to improve the film formability of the ceramic fluid separation membrane 3, it is desirable that the porous support 2 has a smooth surface.

  In order to allow the mixed gas to permeate through the porous support 2 without applying a high pressure, the porous support 2 preferably has a porosity of 20% or more. In order to secure the strength and prevent the porous support from being broken when the filter 1 is assembled, and to prevent the particles constituting the porous support 2 from being shattered during the operation, the porous support 2 The porosity is desirably 30 to 50%.

  The porous support 2 can be formed of ceramics mainly composed of α-alumina or stabilized zirconia, silica-based glass (phase-separated glass), etc., but has high heat resistance, can be easily manufactured, and is low in cost. It is desirable to be made of ceramics mainly composed of α-alumina.

  In order to improve the film formability of the ceramic fluid separation membrane 3, it is desirable that the porous support 2 has a smooth surface with a surface roughness (Ra) of 0.1 to 2.0 μm.

  The porous support 2 is preferably a tubular body having an inner diameter of 1 to 5 mm and a wall thickness of 0.3 to 1 mm in terms of compactness, ease of handling, and permeation gas permeation.

  Although the ceramic fluid separation membrane 3 may be formed directly on the porous support 2 as described above, an air-permeable intermediate layer 5 is interposed between the porous support 2 and the ceramic fluid separation membrane 3. It is desirable. Thereby, since the film-forming property of the ceramic fluid separation membrane 3 on the porous support 2 is improved, the thickness of the ceramic fluid separation membrane 3 can be reduced, and the gas separation processing speed is improved.

  The intermediate layer 5 may be any layer that does not produce a reaction product between the porous support 2 and the ceramic fluid separation membrane 3 and covers the surface of the porous support 2 in a layered manner to form a smooth surface. . For example, when α-alumina ceramics is used as the porous support 2, γ-alumina is suitable as the intermediate layer 5.

  Further, the average pore diameter of the intermediate layer 5 is smaller than the average pore diameter of the porous support 2 in terms of the gas permeation rate and the film forming property of the ceramic fluid separation membrane 3, and the ceramic fluid separation membrane. The average pore diameter is preferably larger than 3, and specifically 1 to 50 nm, particularly 1 to 15 nm.

  Next, the manufacturing method of the fluid separation filter of the present invention will be described by taking as an example the case of manufacturing a gas separation filter using silicon alkoxide as metal alkoxide and erbium alkoxide as Group 3a element of the periodic table.

  First, a porous support is prepared. In detail, those having the above-mentioned materials, porosity, and average pore diameter can be used.

  If desired, an intermediate layer can be formed on this porous support. The intermediate layer can be formed, for example, by hydrolyzing an aluminum alkoxide such as aluminum secondary butoxide to produce a boehmite sol and depositing the boehmite sol on the surface of the porous support.

  As a method for depositing boehmite sol on the surface of the porous support, a method of applying or injecting boehmite sol, or a method of impregnating the porous support in a boehmite sol solution and pulling it up is preferably used.

  Thereafter, the deposited boehmite sol is dried and gelled, and this is heat-treated in the atmosphere at 400 to 900 ° C., particularly 400 to 600 ° C., thereby forming an intermediate layer on the porous support surface. it can. When the firing temperature is lower than 400 ° C., the intermediate layer is weakly bonded to the porous support and the intermediate layer peels off. When the firing temperature is higher than 900 ° C., the sintering proceeds too much. This is because the pore diameter of the intermediate layer becomes large and a desired pore diameter cannot be obtained.

  Next, a ceramic fluid separation membrane is formed. Specifically, for example, silicon alkoxide is hydrolyzed to prepare a precursor sol. Here, as the silicon alkoxide, for example, tetraethoxysilane (TEOS) in which four ethoxy groups are bonded to the Si element is used.

  The above alkoxide is dissolved in a solvent. As the solvent, alcohols such as methanol, ethanol, propanol, butanol, 2-methoxyethanol, and 2-ethoxyethanol are preferably used. The solubility of the alkoxide, the affinity of the gel for the porous support and the drying property From the viewpoint of film-forming properties such as, lower alcohols such as methanol or ethanol are optimal.

  In addition, it is desirable to add 0.1 to 10 mol, preferably 0.2 to 5 mol of water with acid or alkali together with 1 mol of silicon alkoxide together with a solvent to hydrolyze, whereby 1 part of silicon alkoxide is hydrolyzed. The precursor sol in solution can be prepared by condensation polymerization.

  Next, erbium methoxyethoxide is used as an erbium alkoxide and added to the precursor sol. In addition, when using Lu, Yb, Dy, Sm, Eu instead of Er, similarly, ruthenium methoxy ethoxide, yttrium methoxy ethoxide, dysium methoxy ethoxide, samarium methoxy ethoxide, and iodine. Methoxyethoxide can be preferably used.

  The purpose of adding erbium alkoxide later is to have a more uniform -Si-O-Er-network by pre-hydrolyzing the less reactive alkoxide in order to uniformly react alkoxides with different reaction rates. A sol can be produced.

  After adding erbium, an appropriate amount of water is added to conduct hydrolysis and polycondensation reaction. The amount of water added is 0.5 to 100 mol, preferably 1 to 20 mol, based on 1 mol of silicon alkoxide and erbium alkoxide in total. Thereby, the separation layer sol can be prepared.

  Here, when the amount of water is set in the above range, sufficient hydrolysis can be expected, and a bond having a sufficient -Si-O-Er-network can be obtained. Cracks and peeling are unlikely to occur in the film, hydrolysis proceeds moderately, no precipitation occurs, and a stable sol can be obtained.

  Next, the above sol is deposited on the surface of the porous support or the intermediate layer, and this is dried and gelled. The deposition forming method can be performed by the same method as the intermediate layer forming method.

  And it is preferable to heat-process the porous support body which formed the gel on the surface at 200-900 degreeC in air | atmosphere atmosphere, especially 300-700 degreeC. As a result, —Si—O—Er—network bonding proceeds in the gel, and a stronger film is formed.

  Thus, an alkoxide containing a Group 3 element is added to a silicon alkoxide precursor sol, which is partially hydrolyzed and then baked to form a separation membrane on the porous support. By doing so, it is possible to realize a fluid separation filter having excellent water resistance and improved deterioration of separation characteristics.

  The above explanation is made for the case where the metal component is Si. However, even if the metal component is Ti or Zr, the same effect can be obtained, and a heat resistant stable film can be obtained. it can. The periodic table 3a is Er, but the same effect can be obtained by using Lu, Yb, Dy, Sm, Eu, and Ce.

  Α-alumina porous support having an inner diameter of 2.3 mm, a wall thickness of 0.4 mm, and a length of 250 mm, an average particle diameter of 0.2 μm, a porosity of 39%, and a surface roughness (Ra) of 0.3 μm or less The body was made.

  Further, 1 mol of aluminum secondary butoxide was added to 110 mol of water for hydrolysis, and further nitric acid was added, followed by refluxing for 16 hours to prepare a boehmite sol. Then, the tip of the porous support is plugged, impregnated in the boehmite sol solution, held for 60 seconds, taken out at a rate of 5 mm / second, and dried at room temperature for 2 hours to gel the boehmite sol. The intermediate layer made of γ-alumina on the outer surface of the α-alumina porous support is obtained by repeating the step of firing the porous support with the gel deposited thereon at 500 ° C. four times in the air. Was formed.

  On the other hand, with respect to 1 mol of metal alkoxide (A), an ethanol solution containing 1 mol of water and 0.28 mol of HCl is added and mixed to prepare a partially hydrolyzed sol, and then the periodic table 3a (B) with respect to 1 mol of silicon alkoxide. Was added as an ethanol solution at the ratio shown in Table 1.

  A mixed solution of 10 mol of water and ethanol was added to the composite alkoxide for hydrolysis, followed by stirring to prepare a separation layer sol.

  Next, the porous support having the intermediate layer formed thereon is immersed in the obtained separation layer sol solution for 30 seconds, pulled up at a speed of 5 mm / second, dried at room temperature for 1 hour, and subsequently Firing was performed for 1 hour under the conditions shown in FIG. 1, and a series of operations of dipping, drying, and firing was repeated four times to deposit an oxide film containing (A) and (B) on the γ-alumina layer. .

  The obtained filter was heated to the temperature shown in Table 1, and 200 kPa (2.0 atm) of hydrogen was allowed to flow to the outside of the tube at a rate of 100 ml / min with the inside of the tube being open to the atmosphere and 100 kPa (atmospheric pressure). The permeate flow rate was measured for the gas recovered at the permeate gas outlet, and the permeability represented by hydrogen gas permeation amount / (membrane area × differential pressure × time) was calculated.

  Further, the carbon monoxide gas permeability was obtained in the same manner as described above, and the permeability coefficient ratio α (hydrogen permeability / carbon monoxide permeability) was calculated as the selectivity. Further, in order to examine the water resistance and the change with time, the transmittance change rate was measured. That is, 5 mol% of water vapor was introduced into the supply gas to be measured, the transmittance after 3 hours was measured, and the rate of change relative to the transmittance in the dry state was calculated. The rate of change is represented by (C−D) / C × 100 (%), where C is the transmittance in the dry state and D is the transmittance after the introduction of water vapor.

The transmittance was all measured at 100 ° C. The results are shown in Table 1.

Sample No. of the present invention. In 1-6 and 8-13, the transmittance change rate was as small as 21% or less, and the temporal change in transmittance was greatly improved. In particular, Sample No. No. 2 was heat-treated at 200 to 900 ° C. using Si. 1～6,8 and _12, H 2 / CO selectivity was large and 74 above. Sample No. using Ti and Zr. 9 to 11 had a large H ₂ transmittance of 10 × 10 ⁻⁷ mol / (m ² · sec · Pa) or more in a dry state.

On the other hand, sample no. 7 showed a H ₂ transmittance of 6.43 × 10 ⁻⁷ mol / (m ² · sec · Pa) in a dry state, but the H ₂ transmittance after exposure to water vapor was 0.63 × 10 ^{− It} was drastically reduced to ⁷ mol / (m ² · sec · Pa), the transmittance change rate was as large as 90.2%, there was no water resistance, and the change with time was large.

It is a schematic sectional drawing which shows the fluid separation filter of this invention. It is a schematic diagram which shows the combined state of the ceramic fluid separation membrane which comprises the fluid separation filter of this invention. It is a schematic diagram which shows the coupling | bonding state of the ceramic fluid separation membrane which comprises the conventional fluid separation filter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fluid separation filter 2 ... Porous support body 3 ... Ceramic fluid separation membrane 4 ... Pore 5 ... Intermediate layer

Claims (3)

A ceramic fluid separation membrane composed of at least one metal component Si, Ti, Zr and a group 3a element of the periodic table is formed on at least a part of the surface of the porous support. A fluid separation filter. The fluid separation filter according to claim 1, wherein the Group 3a element of the periodic table is at least one of Lu, Yb, Dy, Sm, Er, and Eu. The fluid separation filter according to claim 1 or 2, wherein the ceramic fluid separation membrane is made of an amorphous material.

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