JP2011125818A - Method for manufacturing composite - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing composite having a thin-film metal packed layer inside a porous member. <P>SOLUTION: The method for manufacturing includes: a process of making a precursor solution containing a metal source (an ion, a fine particle, a compound) or a metal source and a gelling agent to penetrate from one side of a porous base material, then solidifying the precursor solution before the precursor solution exudes from the opposite side to obtain a pore composite (A); a process of making a solution containing a reducing agent to penetrate into the pore composite (A) from the opposite side to make metal nucleus carried in the pore composite (A); and a process of electroless-plating the pore composite (B) with the metal nucleus obtained in the preceding process. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a composite used to selectively permeate and separate hydrogen gas from a mixed gas containing hydrogen. Furthermore, this invention relates to the method of isolate | separating hydrogen gas using the said composite_body | complex.

  Hydrogen gas is an industrially important gas that is used in a great variety of ways, such as raw material gas for chemical products, processing gas for glass and electronic materials, and fuel gas for rockets and fuel cells. In recent years, attention has been attracted to new hydrogen fuel cells in the near future, and there is an urgent need to develop technology for producing high-purity hydrogen at low cost. Typical methods for hydrogen production include steam reforming of petroleum hydrocarbons such as natural gas, refinery off-gas, and naphtha, or pyrolysis of heavy oil and other feed hydrocarbons. The hydrogen-containing gas produced by these is purified and separated by a hydrogen separation membrane to produce high-purity hydrogen gas.

  As such a hydrogen separation membrane, a hydrogen separation membrane (Patent Document 1) in which a thin film containing palladium is formed on the surface of a porous support made of an inorganic material, or vanadium and palladium are contained on the surface of a metal porous body. A hydrogen separation membrane (Patent Document 2) formed by forming a thin film is known. However, the former hydrogen separation membrane must use a large amount of expensive palladium, and is not practical. In addition, the latter hydrogen separation membrane is alloyed at a high temperature, and the hydrogen permeation performance is deteriorated. For this reason, attempts have been made to reduce the thickness of the hydrogen separation membrane by CVD, electroless plating, or the like in order to reduce the amount of palladium used (Patent Documents 3 and 4). However, when the film is thinned, there are problems such as hydrogen embrittlement and spherical peeling (Non-Patent Document 1), and there is a problem that the durability of the hydrogen separation membrane decreases.

  On the other hand, as a hydrogen separation membrane that maintains sufficient durability, for example, a membrane in which a rolled palladium alloy membrane is attached to the surface of a substrate having pores is known (Patent Document 5). This hydrogen separation membrane requires a palladium alloy membrane to have a thickness of 5 μm or more in order to increase durability, and it is necessary to use a large amount of expensive palladium. It is.

In order to solve the above problems, as a hydrogen separation membrane which is thinned and has sufficient durability, a metal comprising a porous substrate, a porous material, and a metal which fills the pores and closes the pores A composite film in which a dense filler and a porous protective material are sequentially laminated has been proposed (Patent Document 6).
However, since this hydrogen separation membrane has a three-layer structure, the production is complicated, and the metal in the metal dense filler that is the intermediate layer is distributed throughout the metal dense filler. The metal in the metal dense filler is likely to deteriorate. In addition, after forming a metal layer on the porous substrate and further depositing oxide fine particles on the surface and sintering, the sintering between the metals is performed at about half the melting temperature (Kelvin temperature) of the metal. Therefore, for example, palladium cannot sinter oxide fine particles at 700 ° C. or higher. Therefore, for example, the composite cannot be formed at about 1250 ° C. at which the alumina oxide fine particles are sufficiently sintered, and it is difficult to obtain a practically sufficient strength. In order to solve such a problem, a method has been proposed in which a protective layer having fine pores is formed in advance on the surface of a porous material and then directly filled with metal by a counter diffusion method (Patent Document 7). However, this hydrogen separation membrane has a problem that the permeation rate of hydrogen is slower than the hydrogen separation membrane prepared by the conventional method.

Japanese Patent Laid-Open No. 62-121616 JP-A-5-285355 JP 2002-153740 A JP 2003-135943 A JP 2006-175379 A JP 2006-95521 A JP 2009-189934 A

S. N. Paglieri, J.A. D. Way, “Separation and Purification Methods”, 31, p. 1-169, 2002

  An object of this invention is to provide the manufacturing method of the composite_body | complex which has the metal filling layer thinned inside the porous body. Furthermore, when the composite is used for hydrogen separation, a composite that is excellent in hydrogen permeability and durability and can be manufactured at low cost because the amount of metal such as palladium can be greatly reduced.

  As a result of intensive studies to solve the above problems, the present inventors have carried out metal loading in the pores of the porous substrate. For example, when the porous substrate is plate-shaped (flat film), One of the solution containing the reducing agent and the solution containing the metal source penetrates and gels from the upper surface of the porous substrate and the other from the lower surface, thereby allowing the reducing agent or metal source to move to the substrate surface. It was found that the metal can be selectively filled into the pores of the porous substrate, thereby making it possible to extremely reduce the thickness of the metal-filled layer formed in the composite. The present invention has been completed.

That is, the present invention
[1] A method for producing a composite, wherein (1) a precursor solution containing a metal source and a gelling agent is prepared, and the precursor solution is infiltrated from one side of the porous substrate, and then from the opposite side. Before the precursor solution exudes, solidifying the precursor solution to obtain a composite (A), (2) from the opposite side where the precursor solution has penetrated the composite (A), A step of supporting a metal seed nucleus in the pores of the composite (A) by infiltrating a solution containing a reducing agent, and (3) a composite supporting the metal seed nucleus obtained in the step (2). A process for producing a composite comprising the step of subjecting the body (B) to electroless plating,
[2] A method for producing a composite, wherein (1) a precursor solution containing a reducing agent and a gelling agent is infiltrated from one side of the porous substrate, and then the precursor solution is exuded from the opposite side. Solidifying the precursor solution to obtain a composite (C); (2) impregnating the composite (C) with a solution containing a metal source from the opposite side into which the precursor solution has been impregnated. (3) Electroless plating treatment of the composite (D) supporting the metal seed nucleus obtained in the step (2). A process for producing a composite comprising the steps of:
[3] The above [1] or [3] further comprising a step of washing and / or firing the composite obtained in the step (2) before the step (3) or after the step (3). 2],
[4] The gelling agent is agarose, agar, starch, gum arabic, psyllium seed gum, pullulan, gelatin, dextrin, tragacanth, pectin, glucomannan, galactomannan, xanthan gum, tamarind seed gum, carrageenan, gellan gum, One or more selected from the group consisting of carboxyvinyl polymer, acrylic copolymer, polyacrylamide, water-soluble cellulosic polymer, polyvinylpyrrolidone, bentonite, ethylcellulose, polyethylene, propylene glycol, sodium carboxymethylcellulose, gaddy gum, arabinogalactan and curdlan The production method according to any one of [1] to [3],
[5] The reducing agent is ascorbic acid, sodium ascorbate, sodium borohydride, potassium borohydride, dimethylamine borane, trimethylamine borane, citric acid, sodium citrate, tannic acid, diborane, hydrazine, formaldehyde, glucose and chloride. The production method according to any one of the above [1] to [4], which is one or more selected from the group consisting of tin,
[6] The production method according to any one of [1] to [5], wherein the metal source is a metal ion, metal fine particles, or a compound containing a metal.
[7] The production method according to the above [6], wherein the metal is a transition metal of any of Groups 4, 5, and 8 to 11 in the periodic table.
[8] The production method of the above-mentioned [6], wherein the metal is palladium.
[9] A hydrogen separation membrane obtained by the production method according to any one of [1] to [8], and [10] a mixed gas containing hydrogen, according to [9] A hydrogen separation method characterized by contacting hydrogen separation membrane and selectively permeating hydrogen;
About.

  In the composite according to the present invention, in the metal filling layer constituting the composite, the filled metal is distributed in a narrow range in the porous base material, so that the amount of metal to be filled can be reduced. In particular, when the composite of the present invention is used specifically for hydrogen separation, the palladium (Pd) packed layer thickness can be reduced, that is, the amount of palladium used can be greatly reduced. Moreover, by filling the porous substrate with metal, the composite according to the present invention not only has excellent hydrogen permeability, but also has high resistance to peeling and damage from the surface of the substrate. It has excellent durability that hydrogen embrittlement can be remarkably mitigated by growing a metal in a substrate. Furthermore, since there is no need to laminate a protective material on the surface of the base material, the manufacturing is simple, it is possible to directly fill the metal inside any commercially available porous base material, and also for pinhole repair of inorganic films, etc. Applicable. In addition, when the metal membrane module is applied to a membrane reactor integrated with a catalyst reactor (membrane reactor), the metal is not exposed on the surface of the porous substrate, and therefore, due to physical contact with the catalyst inside the reactor. It is possible to prevent film deterioration due to film breakage or alloying. Alternatively, there is an advantage that the metal is not exposed on the surface of the porous substrate even during the movement and maintenance of the membrane module, so that it is difficult to break.

FIG. 1 shows a schematic diagram of the second embodiment of the present invention when the porous substrate is an alumina substrate and the metal source is palladium. FIG. 2 shows an example of a cross-sectional view of the composite according to the present invention. FIG. 3 shows a schematic diagram of the first embodiment of the present invention when the porous substrate is an alumina substrate, the precursor solution is palladium chloride gel, and the reducing agent is hydrazine. FIG. 4 shows an observation result of observation of the composite obtained in Example 1 with a laser microscope. FIG. 5 shows the results of observation of the composite obtained in Example 2 by laser microscope observation. The right figure is an enlarged view of the left figure. FIG. 6 shows an analysis result with an energy dispersive X-ray analyzer (EDX). FIG. 6A shows the analysis results after the primary plating, and FIG. 6B shows the analysis results after the secondary plating. FIG. 7 is a schematic diagram of a gas permeation test apparatus. FIG. 8 is a gas permeation test result (500 to 200 ° C.) of the composite of Example 1. FIG. 9 is a gas permeation test result (600 to 200 ° C.) of the composite of Example 2. FIG. 10 shows the gas permeation test results (500 ° C.) of the composite of Example 3.

  Below, the 1st aspect of this invention is demonstrated. In the method for producing a composite of the present invention, (1) after impregnating a precursor solution containing a metal source and a gelling agent from one side of a porous substrate, before the precursor solution exudes from the opposite side Solidifying the precursor solution to obtain a composite (A), (2) by infiltrating the composite (A) with a solution containing a reducing agent from the opposite side where the sol is infiltrated, A step of supporting metal seed nuclei in the pores of the composite (A), and (3) a step of electroless plating the composite (B) supporting the metal seed nuclei obtained in the step (2). , Including. Hereinafter, each step will be described.

  In step (1), a mixed solution containing a metal source and a gelling agent (hereinafter also referred to as precursor solution (A)) is infiltrated from one side of the porous substrate, and then the precursor solution is introduced from the opposite side. This is a step of obtaining the composite (A) by solidifying the precursor solution (A) before leaching. By this step, a gel layer containing a metal source and a gelling agent can be formed inside the porous substrate.

  The porous substrate is not particularly limited as long as it supports a metal-filled layer and imparts mechanical strength to the entire composite, but is preferably made of a porous ceramic or a porous metal from the viewpoint of heat resistance. The thing is mentioned and you may use a commercial item. Furthermore, what was already used as a hydrogen separation membrane can also be used as a porous substrate. This is because the composite membrane can be regenerated and used many times. The term “porous” means a material having pores and having the breathability through the communication of the pores.

  Examples of the porous ceramics include oxides, nitrides or carbides. Specifically, alumina, zirconia, titania, niobia, ceria, silica, cordierite, mullite, silicon nitride, silicon carbide, nickel oxide, oxide Examples include cobalt, iron oxide, chromium oxide, manganese oxide, zinc oxide, tungsten oxide, and molybdenum oxide. Among them, alumina, silica, zirconia, cordierite, mullite, silicon nitride, silicon carbide, and the like are preferable. Not limited to this, various porous bodies can be used. These porous ceramics may be used alone or in combination of two or more.

  Regarding the porous metal, from the viewpoint of its structure, a metal non-woven fabric, a metal powder sintered porous body, a metal perforated body, etc., from the viewpoint of its physical properties, metals and alloys having heat resistance and corrosion resistance, such as nickel, stainless steel, etc. Respectively. These porous metals may be used alone or in combination of two or more.

  The form of the porous substrate is not particularly limited and can be appropriately selected as necessary. Examples thereof include a tubular shape (tube shape) and a plate shape. For example, when the porous substrate is tubular, the “one side” may be the inside or the outside of the tube. The pore diameter of the pores of the porous substrate is not particularly limited as long as the object of the present invention is not impaired, but is usually 0.001 to 20 μm, preferably 0.004 to 1 μm.

  The precursor solution (A) can be obtained by preparing a solution containing a metal source and mixing and stirring the solution and the gelling agent.

  The metal source of the solution containing the metal source is not particularly limited as long as it is a metal that can be electrolessly plated. For example, a transition metal simple substance or an alloy may be used, and ions, fine particles, and compounds of these metals may be used. Either is acceptable. Examples of the transition metal include metals of Group 4, Group 5, Group 8, Group 9, Group 10, or Group 11 of the periodic table. Specific examples include silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium, and titanium. Examples of the alloy include an alloy made of palladium and a metal such as silver, copper, or nickel. These metals may be used alone or in combination of two or more. The metal is preferably a hydrogen selective permeable metal such as palladium. Examples of the solution containing a metal source include a solution in which the metal source is dissolved in an appropriate solvent. When the metal is palladium, examples thereof include palladium compounds such as palladium acetate, palladium nitrate, palladium chloride, palladium chloride acid, palladium acetylacetonate, palladium hexafluoroacetylacetonate. Examples of the solvent include water, ethanol, propanol, chloroform, hydrochloric acid and the like. The density | concentration of the solution containing a metal source is about 0.001-10M normally, Preferably it is about 0.005-0.1M.

  Examples of the gelling agent include agarose, agar, starch, gum arabic, psyllium seed gum, pullulan, gelatin, dextrin, tragacanth, pectin, glucomannan, galactomannan, xanthan gum, tamarind seed gum, carrageenan, gellan gum, carboxy Examples include vinyl polymers, acrylic copolymers, polyacrylamides, water-soluble cellulosic polymers, polyvinyl pyrrolidone, bentonite, ethyl cellulose, polyethylene, propylene glycol, sodium carboxymethyl cellulose, gaddy gum, arabinogalactan, curdlan and the like. Examples of the water-soluble cellulosic polymer include carboxyalkyl cellulose, hydroxyalkyl cellulose, alkyl cellulose, and hydroxyalkylalkyl cellulose. Examples of the bentonite include Na-bentonite and Ca-bentonite. Examples of hydroxyalkylalkylcellulose include hydroxypropylmethylcellulose.

  The gelling agent may be added to a solution containing a metal source and mixed and stirred. A suitable solvent (for example, polar solvent such as water, ethanol, propanol, N, N-dimethylformamide, dimethyl sulfoxide, ethyl acetate) In addition, a solution containing a gelling agent dissolved in a nonpolar solvent such as toluene may be mixed with a solution containing a metal source. When used as a solution containing a gelling agent, depending on the type of gelling agent, heating (for example, 100 to 200 ° C., 5 minutes to 5 minutes) under pressure (eg, 1.1 to 2 atmospheres) by an autoclave or the like as desired. 3 hours) and may be dissolved. For example, when agarose is used as a gelling agent, it is added to water to a concentration of about 0.5 to 7%, heated in an autoclave to prepare an agarose solution, and a solution containing the agarose solution and a metal source is prepared. By mixing, the precursor solution (A) can be obtained.

The viscosity of the precursor solution (A) is usually 0.5 mPa · s to 1 × 10 ⁵ mPa · s, preferably 1.0 mPa · s to 1 × 10 ⁴ mPa · s, and the pores of the porous substrate From the viewpoint that the precursor solution (A) is sufficiently permeated into the inside, 1.0 mPa · s to 1 × 10 ³ mPa · s is particularly preferable, and sol is preferable as a form. If it is less than 0.5 mPa · s, when the precursor solution (A) is infiltrated into the porous substrate, the precursor solution (A) may be solidified before the precursor solution (A) reaches the surface. If it exceeds 1 × 10 ⁵ mPa · s, the viscosity increases in the process of rapid cooling in contact with the porous substrate, and the penetration rate of the precursor solution (A) becomes extremely high. This is because it is difficult to sufficiently infiltrate the precursor solution (A) into the porous substrate. When the viscosity of the precursor solution (A) is, for example, low viscosity (1 × 10 ⁴ or less), Brookfield Digital Viscometer LVDV-I + C / P (trade name, product number: KN3312530, manufactured by Techjam Corporation), etc. Brookfield viscometer (rotary viscometer), medium viscosity, Brookfield viscometer RVDV-II + PRO for medium viscosity / KN3312541 (trade name, product number: KN3312541, manufactured by Techjam Corporation) It can be measured using a Brookfield viscometer (rotary viscometer).

  In this step, the temperature at which the precursor solution (A) penetrates into the porous substrate is not particularly limited, but is usually 4 to 100 ° C, and preferably 40 to 90 ° C. The time for allowing the precursor solution (A) to permeate into the porous substrate is particularly limited because it is appropriately selected depending on the size (diameter, pore diameter, etc.) of the porous substrate and the viscosity of the precursor solution (A). However, for example, an alumina tube having a pore diameter of 0.1 μm, a diameter of 10 mm, an inner diameter of 7 mm, and a length of 30 cm (both ends glass seal, effective length: 5 cm) is used as the porous substrate, and the precursor solution (A) When using a 5% agarose sol containing palladium (hereinafter also referred to as a palladium-containing agarose sol) and infiltrating the precursor solution (A) from the inside of the alumina tube, the precursor solution (A) is used as the alumina tube. For 5 seconds to 5 minutes. For the penetration of the precursor solution (A), the viscosity and temperature conditions of the precursor solution (A) are appropriately set so that the precursor solution (A) does not come out on the surface in a few minutes, and visually confirmed. The precursor solution (A) is solidified before leaching to the surface. In addition, when the precursor solution (A) is infiltrated into the porous base material, when the porous base material is tubular, the precursor solution (A ) May penetrate into the porous substrate. Thereby, the quantity of the precursor solution (A) to be used can be reduced.

  The solidification method is not particularly limited as long as the precursor solution can be gelled before leaching from the side on which the precursor solution has been permeated, and the solidifying temperature of the gelling agent is not more than room temperature. In this case, it may be dried and solidified at room temperature, or it may be solidified by cooling with ice or a known cooler up to the solidification temperature of the gelling agent or lower. The cooling temperature is not particularly limited as long as the object of the present invention is not hindered, but is preferably about 0 ° C. to 40 ° C. from the viewpoint that the gel filled in the porous substrate solidifies more uniformly. Moreover, according to the kind of gelatinizer, you may add a crosslinking agent, a polymerization initiator, etc. suitably. For example, when the gelling agent is an acrylamide, ammonium peroxide and N, N, N ′, N′-tetramethylethylenediamine (TEMED) are added to the sol in the presence of N, N′-methylenebisacrylamide as a crosslinking agent. A polyacrylamide gel is obtained by adding as a polymerization initiator and solidifying by radical polymerization. By solidifying, a composite (A) having a metal source (for example, palladium chloride or the like) in the pores of the porous substrate can be obtained.

  In the step (2), the composite (A) is impregnated with a solution containing a reducing agent from the opposite side where the precursor solution (A) is permeated, so that the inside of the pores of the composite (A) This is a step of supporting metal seed nuclei on the substrate.

  Examples of the reducing agent include ascorbic acid, sodium ascorbate, sodium borohydride, potassium borohydride, dimethylamine borane, trimethylamine borane, citric acid, sodium citrate, tannic acid, diborane, hydrazine, and aldehydes (for example, formaldehyde). , Glucose, tin chloride and the like. The reducing agent is dissolved in a suitable solvent to obtain a solution containing the reducing agent. Examples of the solvent include water, ethanol, chloroform and the like. The reducing agent is more preferably used in a solution. The concentration of the reducing agent solution is usually about 0.001 to 1M, preferably about 0.01 to 0.5M.

The permeation of the solution containing the reducing agent into the porous substrate is usually about 2 to 60 ° C., preferably about 20 to 40 ° C., usually about 30 seconds to 100 hours, preferably about 5 minutes to 48 hours. . Next, the solution is removed by washing with water, and the metal is supported in the pores of the porous substrate by drying at about 20 to 110 ° C. for about 1 to 48 hours, preferably about 8 to 16 hours. By the above operation, the metal source is reduced at the portion where the metal source in the gel and the solution containing the reducing agent are in contact to form a metal seed nucleus, and the metal seed nucleus is formed in the pores of the porous substrate. Can be obtained. In the composite obtained by the production method of the present invention, the metal does not adhere to the surface of the porous base material, and thus it is not necessary to laminate a protective material on the surface of the porous base material.

  Step (3) is a step of subjecting the composite (B) carrying the metal seed nucleus obtained in the step (2) to electroless plating. By electroless plating treatment, the metal seed nucleus can be grown, and the pores of the porous substrate can be closed with the grown metal to form a metal filled layer. The method of electroless plating treatment is not particularly limited as long as it is a commonly used method, and is the same as the method disclosed in Patent Document 6 (JP 2006-95521 A), JP 2005-248192 A, and the like. Can be done.

  In the electroless plating treatment, it is preferable to use a plating solution containing a metal ion, a complexing agent, a reducing agent, and a solvent. This metal ion is provided as a plating solution component of an appropriate metal salt, for example, acetate, chloride, nitrate, sulfate, etc., and the metal corresponding to the metal ion can be electrolessly plated as described above. Examples of the transition metal include, but are not limited to, metals of Group 4, Group 5, Group 8, Group 10, Group 11 or Group 11 of the periodic table. Among them, silver, palladium, rhodium, Examples include ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium or titanium. These metals may be used alone or in combination of two or more.

  The complexing agent is not particularly limited as long as it can stably dissolve metal ions, and examples thereof include a combination of ammonia and a chelating agent, and particularly a combination of ammonia and EDTA. In addition, NTA (nitrilotriacetic acid) and aliphatic oxyacids such as citric acid and tartaric acid can be used. As the reducing agent used in the electroless plating treatment, the above-described one can be used. Examples of the solvent used for the electroless plating treatment include water or organic solvents such as acetonitrile, benzene, and chloroform, although depending on the type of complexing agent.

  About a plating solution composition, when it contains a metal ion, a chelating agent, ammonia, and a reducing agent, each density | concentration is about 0.001-0.05M, about 0.01-0.5M, about 5-15M, 0.00. About 005-0.05M is good. When preparing a plating solution, it is preferable to add a reducing agent immediately before the electroless plating treatment.

  The temperature of the electroless plating treatment can be appropriately set, but is usually about 1 to 60 ° C, more preferably about 2 to 50 ° C. Although the electroless plating treatment time depends on the plating solution temperature and film thickness, it is usually about 1 minute to 100 hours, preferably about 1 to 72 hours. After the electroless plating treatment, the obtained composite is washed and dried by a conventional method to obtain the composite of the present invention.

  In the present invention, if necessary, before and after the step (3) or after the step (3), the obtained composite is washed and / or baked to carry unnecessary gels and metal sources. A step of removing excess residues other than the metal nuclides may be included. Although it does not specifically limit as a washing | cleaning method, For example, after immersing a composite_body | complex in water, ethanol, etc., the method of ultrasonically washing at room temperature, for example, with a warm bath (for example, about 60-90 degreeC for 1 to 5 hours). There is a method of removing unnecessary materials. Residues (excess metal source, gel, etc.) obtained by ultrasonic cleaning can be recovered and reused. Further, a baking treatment may be performed in order to completely remove the gel and the like. Although the temperature of a baking process is not specifically limited, For example, 400-900 degreeC is preferable. The time for the baking treatment is not particularly limited, but is preferably about 1 to 48 hours. The firing treatment may be performed in air or in the presence of an inert gas. The temperature rising rate during firing is not particularly limited, but is preferably about 0.1 to 1 ° C./min.

  When the washing and / or baking treatment is performed after step (3), an electroless plating treatment may be performed under the above-described conditions as necessary for the purpose of improving the densification of the metal in the composite. It may be repeated from step (2) or may be repeated from step (1). For example, for the first time, the electroless plating process of step (3) is performed for a short time (for example, about 5 to 30 minutes), and after the washing and / or baking process, step (2) is performed again, The method of performing the electroless plating process (for example, about 1-3 hours) of a process (3) is mentioned preferably.

  The second aspect of the present invention will be described below. In the second aspect of the method for producing a composite of the present invention, (1) after impregnating a precursor solution containing a reducing agent and a gelling agent from one side of the porous substrate, the precursor solution exudes from the opposite side. Solidifying the precursor solution before obtaining a composite (C); (2) infiltrating the composite (C) with a solution containing a metal source from the opposite side into which the precursor solution has been impregnated. A step of supporting metal seed nuclei in the pores of the composite (C), (3) electroless plating of the composite (D) supporting the metal seed nuclei obtained in the step (2) A step of processing. FIG. 1 shows a schematic diagram of the production method when the porous substrate is an alumina substrate and the solution containing the metal source is palladium chloride. Hereinafter, each step will be described.

  In step (1), a mixed solution containing a reducing agent and a gelling agent (hereinafter also referred to as a precursor solution (B)) is infiltrated from one side of the porous substrate, and then the precursor solution exudes from the opposite side. This step is a step of solidifying the precursor solution (B) to obtain a composite (C) before performing. As the porous substrate, the reducing agent, and the gelling agent, the same materials as those in the first aspect described above can be used.

  The precursor solution (B) can be obtained by preparing a solution containing a reducing agent and mixing and stirring the solution and the gelling agent.

  The gelling agent may be added to a solution containing a reducing agent and mixed and stirred. A suitable solvent (for example, polar solvent such as water, ethanol, propanol, N, N-dimethylformamide, dimethyl sulfoxide, ethyl acetate) In addition, a solution containing a gelling agent dissolved in a nonpolar solvent such as toluene may be mixed with a solution containing a reducing agent. When used as a solution containing a gelling agent, depending on the type of gelling agent, heating (for example, 100 to 200 ° C., 5 minutes to 5 minutes) under pressure (eg, 1.1 to 2 atmospheres) by an autoclave or the like as desired. 3 hours) and may be dissolved. For example, when agarose is used as a gelling agent, it is added to water to a concentration of about 0.5 to 7%, heated in an autoclave to prepare an agarose solution, and a solution containing the agarose solution and a reducing agent is prepared. By mixing, a precursor solution (B) can be obtained.

The viscosity of the precursor solution (B) is not particularly limited, but is usually 0.5 mPa · s to 1 × 10 ⁵ mPa · s, preferably 1.0 mPa · s to 1 × 10 ⁴ mPa · s, and is porous. In view of sufficiently allowing the precursor solution (B) to penetrate into the pores of the base material, 1.0 mPa · s to 1 × 10 ³ mPa · s is particularly preferable, and the form is preferably sol. If it is less than 0.5 mPa · s, when the precursor solution (B) is infiltrated into the porous substrate, the precursor solution (B) may be solidified before the precursor solution (B) reaches the surface. When it exceeds 1 × 10 ⁵ mPa · s, the viscosity increases in the process of rapidly cooling in contact with the porous substrate, and the penetration rate of the precursor solution (B) is extremely high. This is because it is difficult to sufficiently infiltrate the precursor solution (B) into the porous substrate. For example, when the viscosity of the precursor solution (B) is low (1 × 10 ⁴ or less), Brookfield Digital Viscometer LVDV-I + C / P (trade name, product number: KN3312530, manufactured by Techjam Co., Ltd.), etc. Brookfield viscometer (rotary viscometer), medium viscosity, Brookfield viscometer RVDV-II + PRO for medium viscosity / KN3312541 (trade name, product number: KN3312541, manufactured by Techjam Corporation) It can be measured using a Brookfield viscometer (rotary viscometer).

  In this step, the temperature, time, and the like when the precursor solution (B) permeates into the porous substrate are not particularly limited, and those similar to those described in the first aspect can be used. The solidification method includes the same method as in the first aspect described above, and the composite (C) can be obtained by solidification.

  In the step (2), the composite (C) is impregnated with a solution containing a metal source from the opposite side where the precursor solution (B) is impregnated. This is a step of supporting metal seed nuclei on the substrate.

  As a solution containing a metal source, the same solution as in the first embodiment described above can be used. In the second embodiment, since the gelling agent is included in the precursor solution (B), the gelling agent is not included in the solution containing the metal source.

  The penetration of the solution containing the metal source into the porous substrate is usually about 2 to 60 ° C., preferably about 20 to 40 ° C., usually about 1 to 120 minutes, preferably about 10 to 40 minutes. Next, the solution is removed, and the metal is supported in the pores of the porous substrate by drying at about 20 to 110 ° C. for about 1 to 48 hours, preferably about 8 to 16 hours. By the above operation, the metal source is reduced at the portion where the reducing agent in the gel and the solution containing the metal source are in contact with each other to form a metal seed nucleus, and the metal seed nucleus is formed in the pores of the porous substrate. Can be obtained. In the composite obtained by the production method of the present invention, the metal does not adhere to the surface of the porous base material, and thus it is not necessary to laminate a protective material on the surface of the porous base material.

  Step (3) is a step of subjecting the composite (D) carrying the metal seed nucleus obtained in the step (2) to electroless plating. The electroless plating treatment can be performed in the same manner as in the first aspect described above.

  Further, as in the first aspect described above, the obtained complex is washed and / or baked before the step (3) or after the step (3) as necessary, and an unnecessary gel is obtained. And a step of removing excess residues other than the supported metal nuclide such as a metal source. Although it does not specifically limit as a washing | cleaning method, For example, after immersing a composite_body | complex in water, ethanol, etc., the method of performing ultrasonic cleaning is mentioned. Residues (excess metal source, gel, etc.) obtained by ultrasonic cleaning can be recovered and reused. Further, in order to completely remove the gel or the like, a baking treatment (for example, 400 to 900 ° C.) may be performed in the air.

  When the washing and / or baking treatment is performed after step (3), an electroless plating treatment may be performed under the above-described conditions as necessary for the purpose of improving the densification of the metal in the composite. It may be repeated from step (2) or may be repeated from step (1). For example, for the first time, the electroless plating process of step (3) is performed for a short time (for example, about 5 to 30 minutes), and after the washing and / or baking process, step (2) is performed again, The method of performing the electroless plating process (for example, about 1-3 hours) of a process (3) is mentioned preferably.

  By the production method of the present invention described above, a composite is obtained in which the pores of the porous substrate are filled with metal to form a layer, and the surface of the porous substrate does not have a protective layer.

  As described above, the composite according to the present invention is filled with metal in the pores of the porous substrate, and the pores are blocked by the metal, and the metal is not the surface of the porous substrate. , Existing in layers from the surface of the substrate. A cross-sectional view of the composite is shown in FIG.

  The thickness of the metal filling layer in the composite according to the present invention is not particularly limited, but is preferably 1 to 10 μm. Since the composite obtained by the production method of the present invention has a porosity of the metal-filled layer of about 30%, it is possible to reduce the amount of filler metal (for example, palladium) used.

  Next, a hydrogen separation method when the composite produced by the production method of the present invention is used as a hydrogen separation membrane will be described. The hydrogen separation method of the present invention is characterized in that hydrogen is selectively permeated by bringing a mixed gas containing hydrogen (hereinafter referred to as hydrogen mixed gas) into contact with the composite.

  As a specific aspect of this method, a hydrogen mixed gas is placed on one side of the composite (for example, the inner side in the case of a tubular composite), and the hydrogen partial pressure on the opposite side (for example, the outer side in the case of a composite). Can be made to be equal to or lower than the hydrogen partial pressure of the hydrogen mixed gas, hydrogen can selectively permeate through the composite, and hydrogen in the hydrogen mixed gas can be separated to the opposite side. This hydrogen separation method can be suitably carried out at a temperature of usually room temperature to about 700 ° C., preferably about 300 to 600 ° C.

  The hydrogen mixed gas is not particularly limited as long as it contains hydrogen. For example, hydrogen and oxygen, nitrogen, helium, neon, argon, krypton, xenon, radon, fluorine, chlorine, bromine, one Carbon dioxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, hydrogen chloride, water (steam), methanol, ethanol, paraffinic hydrocarbons, olefinic hydrocarbons, etc. . The paraffinic hydrocarbons are also called saturated chain hydrocarbons, alkanes, or methane hydrocarbons. Examples of such paraffinic hydrocarbons include methane, ethane, propane, butane, pentane, hexane, and heptane. , Octane and the like.

  Hereinafter, the present invention will be described using examples and test examples, but the present invention is not limited to these examples. In the following examples, the porous substrate is an α-alumina tubular substrate (manufactured by NGK Co., Ltd.) having a pore diameter of 0.1 μm, a diameter of 10 mm, and an inner diameter of 7 mm (hereinafter referred to as “alumina substrate”). For short).

[Example 1]
A composite was produced as follows. A synthetic scheme of all steps is shown in FIG.
[Step (1)]
A palladium chloride sol was prepared by dispersing palladium chloride as a raw material for the seed crystal of palladium in an agarose sol as follows. The palladium chloride solution was prepared by dissolving 0.025 g of palladium chloride (Wako Pure Chemical Industries, Ltd.) in 0.025 ml of hydrochloric acid and adding deionized water to a total volume of 5 ml. To a glass bottle, 1.25 g of Agarose L (Nippon Gene Co., Ltd.) and 20 ml of deionized water were added and heated in a thermostat set at 100 ° C. for 3 hours to prepare a 5% agarose sol solution. The agarose sol solution immediately after preparation had an extremely low viscosity (about 1.0 mPa · s) as much as water. Since the obtained agarose sol solution did not start to solidify, the palladium chloride solution was added to the agarose sol solution immediately after preparation and stirred to prepare a palladium chloride sol solution as a precursor solution. The palladium chloride sol solution immediately after preparation was poured into the inner cylinder side of the alumina substrate, and the solution was immersed for about 1 minute at room temperature. Next, a plastic beaker with a capacity of 3 L was filled with water and ice to prepare an ice tub, and a glass test tube having a round bottom of φ40 × 350 mm filled with deionized water was inserted into the ice tub. By inserting the filled alumina substrate, the palladium chloride sol solution is cooled and solidified (solidification temperature of agarose: 35 ° C) before the palladium chloride sol solution exudes from the surface, and the palladium chloride gel is immobilized. I let you.

[Step (2)]
The palladium composite to the porous alumina substrate was carried out by the following procedure. A hydrazine aqueous solution was used as a reducing agent. The hydrazine aqueous solution was prepared by diluting 1 ml of hydrous hydrazine (Wako Pure Chemical Industries, Ltd.) with deionized water to make the total amount 200 ml. The alumina substrate filled with the palladium chloride gel obtained in the step (1) is immersed in a hydrazine aqueous solution at room temperature for 30 seconds, and a reducing agent is injected to reduce the palladium in the gel. Formed. After the reduction treatment, it was thoroughly washed with deionized water.

[Step (3)]
After the formation of the palladium seed nuclei, an electroless plating treatment was performed on the alumina porous substrate as follows for the purpose of improving the palladium filling rate. The plating solution used was a commercially available palladium plating solution, Paratop (trade name, reducing agent: sodium formate, Okuno Pharmaceutical Co., Ltd.) diluted to a prescribed concentration. That is, deionized water was added to 20 ml of Paratop A liquid and 20 ml of Paratop B liquid, and used as a total volume of 200 ml. The reaction was performed at a plating temperature of 50 ° C. and a plating time of 1 hour 30 minutes. After electroless plating, the composite was immersed in deionized water at 80 ° C., the plating solution was washed, and the palladium chloride gel was removed to obtain a composite.

  The structure of the produced composite (composite film) was observed with a laser microscope (VK-8500: trade name, manufactured by Keyence Corporation). The observation result of laser microscope observation is shown in FIG. The palladium composite layer formed by the electroless plating treatment was 15 μm, and it was confirmed that the composite layer was selectively formed in the alumina substrate. This is because palladium nuclei serving as a reaction field for electroless plating are selectively disposed in advance in an alumina support.

[Example 2]
[Step (1)]
As described below, an agarose sol was prepared by dispersing tin chloride as a reducing agent in an agarose sol. The tin chloride solution was prepared by dissolving 0.05 g of tin chloride (Wako Pure Chemical Industries, Ltd.) in 0.05 ml of hydrochloric acid to make the total amount 10 ml. 0.75 g of Agarose L (Nippon Gene Co., Ltd.) and 4.0 ml of deionized water were added to a glass bottle and heated in a thermostatic bath set at 100 ° C. for 3 hours to prepare a 5% agarose sol solution. The agarose sol solution immediately after preparation had an extremely low viscosity (about 1.0 mPa · s) as much as water. Since the obtained agarose sol solution did not start to solidify, the tin chloride solution was added to the agarose sol solution immediately after preparation and stirred to prepare a reducing agent sol solution as a precursor solution. Immediately after preparation, the reducing agent sol solution is injected into the inner cylinder side of the alumina substrate, and the solution is allowed to permeate at room temperature for about 1 minute. Before the solution exudes from the surface, it is cooled in air and solidified to fix the reducing agent gel. Made it.

[Step (2)]
The palladium composite to the porous alumina substrate was carried out by the following procedure. A palladium chloride acid aqueous solution was used as a palladium source. A palladium chloride acid aqueous solution was prepared by dissolving 0.1 g of palladium (II) chloride (Wako Pure Chemical Industries, Ltd.) in 0.1 ml of hydrochloric acid to make a total amount of 1000 ml. The alumina substrate filled with the reducing agent gel obtained in the step (1) was immersed in an aqueous chloropalladium acid solution at room temperature for 10 minutes to carry palladium on the alumina substrate. After the formation of palladium seed nuclei, it was thoroughly washed with deionized water.

[Step (3)]
After the formation of the palladium seed nuclei, an electroless plating treatment was performed on the alumina porous substrate as follows for the purpose of improving the palladium filling rate. After dissolving 3.6 g of palladium chloride and 74.5 g of ethylenediaminetetraacetic acid disodium salt (Wako Pure Chemical Industries, Ltd.) in 680 ml of 28% aqueous ammonia (Wako Pure Chemical Industries, Ltd.), deionization The volume was made up to 1000 ml by adding water. Thereafter, immediately before the electroless plating treatment, 0.5 ml of hydrazine monohydrate was added to obtain an electroless plating solution. Electroless plating was performed by infiltrating the plating solution from the outside of the porous substrate (the side opposite to the surface on which the reducing agent sol solution was injected). The reaction was performed at a plating temperature of 50 ° C. and a plating time of 2 hours.

[Step (4)]
After electroless plating, the composite was immersed in deionized water at 80 ° C. for 3 hours to wash the plating solution and remove the agarose gel. For the purpose of improving the denseness of the Pd layer, the composite was sintered after the electroless plating treatment. A baking treatment was performed at 700 ° C. for 20 hours under a condition (200 ml / min) in which an inert gas (nitrogen gas) was circulated.

[Step (5)]
After the baking treatment, it was performed for the purpose of improving the densification of the Pd film. The electroless plating process described above was performed for 1 hour to densify the film.

  The structure of the produced composite (composite film) was observed with a laser microscope (VK-8500: trade name, manufactured by Keyence Corporation), and an energy dispersive X-ray analyzer (EDX, product name: Genesis-XM2, EDAX) -Japan Co., Ltd.) The observation result of laser microscope observation is shown in FIG. As a result of laser microscope observation, the palladium composite layer formed by electroless plating was 20 μm, and it was confirmed that the composite layer was selectively formed in the alumina substrate.

[Example 3]
The process up to Step (3) was performed in the same manner as in Example 1 except that the electroless plating treatment (primary plating) in Step (3) of Example 1 was 10 minutes. Next, the obtained composite was immersed in deionized water at 80 ° C. to extract the gel, and then baked for 12 hours at 850 ° C. in air to remove the remaining gel. The obtained composite was immersed in a hydrazine aqueous solution overnight to perform a reduction treatment. The hydrazine aqueous solution was prepared by diluting 1 ml of hydrous hydrazine (Wako Pure Chemical Industries, Ltd.) with deionized water to make the total amount 200 ml. After performing the reduction treatment, the secondary plating treatment was performed at 50 ° C. for 1 hour and 30 minutes. The primary plating and the secondary plating used a plating solution prepared by a paratop manufactured by Okuno Pharmaceutical Co., Ltd. under specified conditions. FIG. 6A and FIG. 6B show the results of EDX analysis of the produced film.

  From the result of FIG. 6, the Pd peak was also confirmed after the secondary plating at the position where the Pd peak was confirmed after supporting the palladium nucleus precipitation and after the primary plating. The palladium-filled layer formed by electroless plating is 8 μm, and it was confirmed that the metal can be selectively filled in the alumina substrate according to the present invention.

[Test Example 1]
A gas permeation test was performed using the palladium composite alumina membrane obtained in Example 1. A hydrogen / nitrogen (H ₂ / N ₂ = 50/50) mixed gas permeation test was performed under the following conditions under a temperature condition of 600 ° C. to 200 ° C. A schematic diagram of the gas permeation test apparatus is shown in FIG. As shown in FIG. 7, the H ₂ / N ₂ mixed gas was brought into contact with the composite obtained in the example, and the gas permeated through the composite (permeated gas) was sampled, under the following experimental conditions. Gas chromatography (GC) measurement was performed. The gas permeation test results from 500 ° C. to 200 ° C. are shown in FIG.

(Experimental conditions)
Gas analysis: gas chromatography; GC (TCD)
Column: Porapak-N 2m, Molecular Sieve 13X 2m (GL Science Co., Ltd.)
Carrier gas: Ar
Test gas: H ₂ / N ₂ = 50/50
Gas flow rate: 2000 ml / min Inlet gas pressure: 50 kPa (Outlet is vacuum pump depressurized and differential pressure is 150 kPa)

(result)
As a result of the gas permeation test at 500 ° C., the hydrogen permeability P _H2 is about 3.5 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ , and the hydrogen selectivity α = P _H2 / P _N2 is 100. It showed almost stable performance during the test. Further, even when the test temperature is lowered to 200 ° C. at which hydrogen embrittlement occurs, the hydrogen selectivity is maintained at about 25 in the test time of 50 hours, and the hydrogen permeability is 1.1 × 10 ⁻⁸ m ³ m. A value of about ⁻² s ⁻¹ Pa ⁻¹ was shown. When the temperature was raised again to 500 ° C. after 100 hours from the start of the test, the hydrogen permeability of 3.5 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ equivalent to the initial state and the hydrogen selectivity of about 100 were obtained. Indicated.

[Test Example 2]
A gas permeation test was performed using the palladium composite alumina membrane obtained in Example 2. The test was carried out under the same conditions as in Test Example 1 except that the temperature was from 500 ° C to 200 ° C. The results are shown in FIG.

(result)
As a result of the gas permeation test at 500 ° C., the hydrogen permeability is about 1.8 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ , and the hydrogen selectivity is about 700 at the initial value and is almost stable during the test. Showed performance. Further, even when the test temperature is lowered to 200 ° C. where hydrogen embrittlement occurs, the hydrogen selectivity is maintained at about 80 in the test time of 70 hours, and the hydrogen permeability is 1.1 × 10 ⁻⁸ m ³ m. A value of about ⁻² s ⁻¹ Pa ⁻¹ was shown. When the temperature was raised again to 500 ° C. after 100 hours from the start of the test, the hydrogen permeability of 1.8 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ equivalent to the initial state and hydrogen selectivity of about 700 were obtained. Indicated. When the temperature was further raised to 600 ° C., hydrogen permeability of 2.7 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ and hydrogen selectivity of about 800 were exhibited.

[Test Example 3]
A gas permeation test was performed using the palladium composite alumina membrane obtained in Example 3. The test was carried out under the same conditions as in Test Example 1 except that the temperature was 500 ° C. The results are shown in FIG.

(result)
As a result of the gas permeation test at 500 ° C., the hydrogen permeability was about 2.5 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ , and the hydrogen selectivity showed an initial value of about 6000. In addition, the hydrogen selectivity of about 5000 was maintained even in a continuous test for 200 hours. This is presumably because the film was not broken rapidly due to peeling of the Pd layer.

  From the results of the above Test Examples 1 to 3, the production method of the present invention can improve the hydrogen durability and increase the performance life of the membrane when the obtained composite is used as a hydrogen separation membrane. It is possible to produce a hydrogen separation membrane having an excellent permeation rate. Further, the hydrogen separation membrane has a structure in which palladium particles are filled in an alumina substrate, and is useful in practical use such as improvement of heat resistance and protection of the membrane surface. Moreover, since the porosity estimated from the structure of the produced composite is about 20 to 30%, the amount of Pd used can be reduced.

  The composite obtained by the production method of the present invention is excellent in hydrogen permeability and durability, and is provided inexpensively and simply, and thus is useful for a hydrogen production apparatus included in a fuel cell system.

DESCRIPTION OF SYMBOLS 1 Metal filling layer 2 Porous base material 3 Composite 4 Metal nucleus 5 Gel

Claims (10)

A method for producing a composite, comprising:
(1) After preparing a precursor solution containing a metal source and a gelling agent and infiltrating the precursor solution from one side of the porous substrate, before the precursor solution exudes from the opposite side, the precursor solution Solidifying the body solution to obtain the composite (A),
(2) A metal seed nucleus is supported in the pores of the composite (A) by impregnating the composite (A) with a solution containing a reducing agent from the opposite side into which the precursor solution has been impregnated. The process of
(3) A method for producing a composite, comprising a step of electroless plating the composite (B) carrying the metal seed nucleus obtained in the step (2). A method for producing a composite, comprising:
(1) After allowing a precursor solution containing a reducing agent and a gelling agent to permeate from one side of the porous substrate, before the precursor solution exudes from the opposite side, the precursor solution is solidified to form a composite Obtaining (C),
(2) A metal seed nucleus is supported in the pores of the composite (C) by infiltrating the composite (C) with a solution containing a metal source from the opposite side into which the precursor solution has been infiltrated. Process,
(3) A method for producing a composite, comprising a step of subjecting the composite (D) carrying the metal seed nucleus obtained in the step (2) to electroless plating.   Furthermore, the manufacturing of Claim 1 or 2 including the process of wash | cleaning and / or baking the composite_body | complex obtained by the process of said (2) before the process of said (3) or after the process of (3). Method.   Gelling agents are agarose, agar, starch, gum arabic, psyllium gum, pullulan, gelatin, dextrin, tragacanth, pectin, glucomannan, galactomannan, xanthan gum, tamarind seed gum, carrageenan, gellan gum, carboxyvinyl polymer 1 or more selected from the group consisting of acrylic copolymers, polyacrylamides, water-soluble cellulosic polymers, polyvinylpyrrolidone, bentonite, ethylcellulose, polyethylene, propylene glycol, sodium carboxymethylcellulose, gaddy gum, arabinogalactan and curdlan The manufacturing method in any one of 1-3.   The reducing agent consists of ascorbic acid, sodium ascorbate, sodium borohydride, potassium borohydride, dimethylamine borane, trimethylamine borane, citric acid, sodium citrate, tannic acid, diborane, hydrazine, formaldehyde, glucose and tin chloride It is 1 or more chosen from a group, The manufacturing method in any one of Claims 1-4.   6. The method according to claim 1, wherein the metal source is a metal ion, metal fine particles, or a compound containing a metal.   The manufacturing method according to claim 6, wherein the metal is a transition metal of any of groups 4, 5, and 8 to 11 in the periodic table.   The method according to claim 6, wherein the metal is palladium.   A hydrogen separation membrane obtained by the production method according to claim 1.   A hydrogen separation method, wherein hydrogen is selectively permeated by bringing a mixed gas containing hydrogen into contact with the hydrogen separation membrane according to claim 9.