JP6208067B2 - Method for producing composite having thin metal-filled layer inside porous substrate, and composite - Google Patents

Description

  The present invention relates to a method for producing a composite having a thin metal filling layer inside a porous substrate. The present invention also relates to a method for producing a hydrogen separation membrane, which is a composite having a thin metal-filled layer inside a porous substrate, and the hydrogen separation membrane.

  As a method for producing hydrogen gas which is an industrially important gas, a method for separating and purifying hydrogen from a mixed gas using a metal thin film as a hydrogen separation membrane has been actively studied in recent years. For example, studies have been conducted in which a metal rolled membrane (for example, Patent Documents 1 and 2) or a metal film combined with a porous substrate (for example, Patent Documents 3 to 10) is used as a hydrogen separation membrane.

  The method of using a rolled membrane as a hydrogen separation membrane (Patent Documents 1 and 2) has high durability and hydrogen separation performance of the membrane, and is capable of producing a metal film of a multi-component alloy. (I) A large amount of expensive palladium must be used, resulting in high costs. (Ii) For example, when a hydrogen-containing gas is produced by a steam reforming method, a catalyst and a rolled film used for the steam reforming method Are alloyed and the film is damaged, and (iii) the film is damaged by flying objects.

  As a method of combining the porous substrate and the metal film, for example, a method of forming a metal film on the surface of the porous substrate by electroless plating, electrolytic plating, sputtering, CVD or the like (for example, Patent Documents 3 to 7) ) However, this composite in which a metal film is formed on the surface of the porous substrate can reduce the cost of the metal film and reduce the cost, hydrogen permeation performance and hydrogen separation performance as compared with the rolled film described above. While having the advantage of being high, (I) generation of cracks due to thermal stress caused by the large difference in thermal expansion coefficient between the substrate and the metal film, (II) damage due to hydrogen embrittlement, spherical delamination, etc. Non-Patent Document 1), (III) There are problems such as film damage caused by alloying with a catalyst used for producing a hydrogen-containing gas such as a steam reforming method, and (IV) damage due to flying objects.

  In the above method for forming a metal film on the surface of the porous substrate, a method of forming a protective layer on the metal film is also being studied in order to solve the problem caused by the exposed metal film. . For example, in Patent Document 8, after a base material layer, a supported porous material layer containing a metal seed nucleus, and a porous protective material layer are sequentially formed, electroless plating is performed to form a metal film on the supported porous material layer. A method of forming a film is disclosed. However, since the method described in Patent Document 8 has a three-layer structure, it is complicated to manufacture, and since it is laminated using different materials, deterioration due to a difference in thermal expansion coefficient is likely to occur. There is a problem. Further, Patent Document 9 proposes a method in which a microporous oxide film is formed on a substrate, and a metal is directly filled in the central portion rather than both ends of the oxide film by a counter diffusion method. . However, the hydrogen separation membrane obtained by the method described in Patent Document 9 has a problem that the hydrogen permeation rate is slower than the hydrogen separation membrane obtained by the method described in Patent Documents 3 to 8 and the like.

  Further, in Patent Document 10, in the electroless plating process, after nucleating (seeding) palladium on the surface of the porous substrate, the palladium nuclei are removed to a predetermined depth on the surface with a mixed aqueous solution of hydrochloric acid and nitric acid. Then, a method of forming a protective layer by performing electroless plating is disclosed. However, in the method described in Patent Document 10, a dangerous solution (aqua regia: a mixed aqueous solution of hydrochloric acid and nitric acid) is used, making industrialization difficult, the thickness of the metal film, and the depth at which the metal film is formed. In addition, there are problems such as difficulty in controlling the uniformity of the film.

  In Patent Document 11, in the electroless plating step, when the metal nucleus is supported in the pores of the porous substrate, the pores are formed by filling the pores with a gelling agent and gelling at a predetermined position. A method is disclosed in which the position where the metal film is formed is controlled by sealing and controlling the position where the metal source and the reducing agent contact in the porous substrate. The method described in Patent Document 11 is that the obtained hydrogen separation membrane is more resistant to hydrogen embrittlement and thermal degradation than those obtained by the methods of Patent Documents 3 to 8, and the amount of metal source (palladium) used is While there are advantages such as being able to reduce, being able to suppress alloying, and being able to physically protect the metal film, (a) the process of solidifying (gelling) the gelling agent is complicated , (B) it is very difficult to gel at the desired position, (c) it is difficult to control the position of the membrane and the performance of the membrane is not stable, (d) the gel is finally Since it is removed, it becomes a waste, and (e) the metal source (palladium etc.) mixed in the gel is also discarded together. is there.

  Therefore, a method for producing a composite of a porous substrate and a metal thin film that can form a uniform metal thin film at a desired position inside the porous substrate without requiring a complicated operation has been desired. .

JP 2010-6659 A JP 2009-154040 A JP 2002-153740 A Japanese Patent Laid-Open No. 62-121616 JP-A-5-285355 Japanese Patent Laid-Open No. 2003-135943 JP 2006-175379 A JP 2006-95521 A JP 2009-189934 A Japanese Patent No. 5155343 Japanese Patent No. 5253369

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

  In view of the above situation, an object of the present invention is to provide a method for producing a composite of a porous base material and a metal thin film, which does not require complicated operations and can form a metal thin film inside the porous base material. The main issue is to do. Furthermore, when the composite is used for hydrogen separation, it is also an object to provide a composite that is excellent in hydrogen permeability and durability, and that can be manufactured at a low cost by greatly reducing the amount of metal such as palladium. To do.

  As a result of intensive studies in order to solve the above problems, the present inventors have carried out a metal support in the pores of the porous substrate. For example, when the porous substrate is tubular, After filling the solution containing metal ions in the pores in an acidic state, plug one end of the tube, fill the inside of the tube with the acidic solution, and place the reducing agent on the outside of the tube. Unexpectedly and usefully, the metal can be selectively supported in the pores at a desired depth from the surface of the porous substrate by being immersed in the solution containing As a result, the present invention was completed.

That is, the present invention relates to the following.
[1] A method for producing a composite having a thin metal-filled layer inside a porous substrate,
(1) A step of filling a pore of the porous substrate with a solution having a pH of 4 or less containing the metal ion (A),
(2) While contacting one surface of the porous substrate filled with the metal ion (A) obtained in the step (1) with a solution (H) having a pH of 4 or less, the opposite of the porous substrate A step of infiltrating the solution (C) containing the reducing agent from the surface on the side, and supporting the metal seed nucleus in the pores of the porous substrate, and (3) the metal seed nucleus obtained in the step (2) A step of electroless plating a porous substrate carrying metal with a plating solution containing metal ions (B) (wherein the metal ions (A) and the metal ions (B) are the same or different) May be)
A method for producing the composite, comprising:
[2] including a step of removing metal ions (A) adhering to the surface of the porous substrate on the side infiltrating the solution (C) before infiltrating the solution (C) in the step (2). The production method according to [1], wherein
[3] In the step (1), when the metal ions (A) are filled in the pores of the porous body, a sensitizing / activating method or a catalyzing / accelrating method is used. [1] The production method according to [2].
[4] The manufacturing method according to any one of [1] to [3], wherein the metal ion (A) is palladium ion (II).
[5] The metal species of the metal ion (B) is silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium or titanium [1] ] The manufacturing method of any one of [4].
[6] The production method according to any one of [1] to [5], wherein the metal ion (B) is palladium ion (II).
[7] 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, formic acid, The production method according to any one of [1] to [6], which is one or more selected from the group consisting of glucose and tin chloride.
[8] The position at which the thin metal filling layer is formed is controlled by controlling the concentration of the solution (H) and / or the solution (C), [1] to [7] ] The manufacturing method of any one of.
[9] A hydrogen separation membrane obtained by the production method according to any one of [1] to [8].
[10] A hydrogen separation composite membrane having a thin palladium metal layer inside a porous substrate, wherein the hydrogen selectivity is 300,000 or more.

  ADVANTAGE OF THE INVENTION According to this invention, manufacture of the composite of a porous base material and a metal thin film which can form a metal thin film (thinned metal filling layer) inside a porous base material without requiring complicated operation. A method can be provided. Moreover, according to the manufacturing method of this invention, the position formed in the porous base material of the said metal thin film can be controlled. Moreover, according to the manufacturing method of this invention, the metal thin film with a uniform position and film thickness can be obtained. Furthermore, when the composite is used for hydrogen separation, it is possible to provide a composite that is excellent in hydrogen permeability and durability, and that can be manufactured at a low cost by greatly reducing the amount of metal such as palladium. And according to this invention, the hydrogen selectivity is very high, and the composite_body | complex with very high hydrogen permeability can be provided.

FIG. 1 shows a scheme of steps (1) to (3) in Example 1. 2 (a) and 2 (b) show images obtained by observing a cross section of the composite produced in Example 1 with a laser microscope. FIG. 3 shows an observation image or analysis image of a cross section of the composite produced in Example 1. 3A shows an image observed with an SEM, and FIGS. 3B and 3C show images analyzed with an energy dispersive X-ray analyzer (EDX). FIG. 4 shows an observation image of a cross section of the composite produced in Examples 2 to 4 with a laser microscope. 4A is an image of the cross section of the composite produced in Example 2, FIG. 4B is an image of the cross section of the composite produced in Example 3, and FIG. 4C is produced in Example 4. It is the image of a composite cross section. FIG. 5 shows images of cross sections of the composites produced in Examples 1, 5 and 6 observed with a laser microscope. 5A is an image of a cross section of the composite produced in Example 5, FIG. 5B is an image of a cross section of the composite produced in Example 6, and FIG. 5C is produced in Example 1. It is the image of a composite cross section. FIG. 6 shows an observation image or an analysis image of the cross section of the composite produced in Example 7. 6A shows an image observed with a laser microscope, and FIGS. 6B and 6C show images analyzed with EDX. FIG. 7 shows an observation image or an analysis image of the cross section of the composite produced in Example 8. FIG. 7A shows an image observed with a laser microscope, and FIGS. 7B and 7C show images analyzed with EDX. FIG. 8 shows an observation image or analysis image of the cross section of the composite produced in Example 9. 8A shows an image observed with a laser microscope, and FIGS. 8B and 8C show images analyzed with EDX. FIG. 9 shows an observation image or analysis image of the cross section of the composite produced in Example 10. 9A shows an image observed with a laser microscope, and FIGS. 9B and 9C show images analyzed with EDX. FIG. 10 shows images observed by a laser microscope of cross sections of the composites produced in Examples 11 and 12. 10A is an image of the cross section of the composite produced in Example 12, and FIG. 10B is an image of the cross section of the composite produced in Example 13. FIG. 11 shows images observed by a laser microscope of cross sections of the composites produced in Examples 13 and 14. 11A is an image of the cross section of the composite produced in Example 13, and FIG. 11B is an image of the cross section of the composite produced in Example 14. FIG. 12 shows an observation image of a cross section of the composite produced in Comparative Example 1 with a laser microscope. FIG. 13 is a schematic diagram of a gas permeation test apparatus in Test Example 1.

  The present invention will be described in detail below.

  One aspect of the present invention relates to a method for producing a composite having a thin metal filling layer inside a porous substrate.

  The metal species of the “thin metal-filled layer” is not particularly limited, but is preferably a metal that can be electrolessly plated. Examples of metals that can be electrolessly plated include transition metals, and the transition metals are preferably metals of Group 4, Group 5, Group 8, Group 10, Group 11 or Group 11 of the periodic table. . Among them, silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium, titanium, and the like can be given. These metals may be used alone or in combination of two or more.

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 from the viewpoint of heat resistance, it is preferably made of porous ceramics or porous metals. A commercially available product may be used. Furthermore, the used composite after using the composite of the present invention for a desired purpose (for example, hydrogen separation, etc.) can also be used as the porous substrate. In the present invention, since the composite membrane can be regenerated and used many times by using the used composite as a porous substrate, waste can be reduced.
In the present invention, the term “porous” means a material having pores and communicating with each other through 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, oxidation Cobalt, iron oxide, chromium oxide, manganese oxide, zinc oxide, tungsten oxide, molybdenum oxide, etc., or porous ceramics in which the crystal structure of these oxides, nitrides, carbides, etc. is stabilized by additives, etc. Is mentioned. Among these, alumina, silica, zirconia, cordierite, mullite, silicon nitride, silicon carbide, etc. and those whose crystal structure is stabilized by additives, etc. are preferably mentioned, but not limited to these, various porous bodies can be used. 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 used in the present invention is not particularly limited, and may be appropriately selected as desired. For example, it may be tubular (tubular or tubular), plate-shaped, or the like.
In the present invention, the “one side” of the porous substrate may be, for example, the inside or the outside of the tube when the porous substrate is tubular.
The pore diameter of the porous substrate is not particularly limited as long as the object of the present invention is not impaired, but is usually about 0.001 to about 20 μm, preferably about 0.004 to about 1 μm.

In one embodiment of the present invention, the method for producing the composite comprises:
(1) A step of filling the pores of the porous substrate with a solution having a pH of about 4 or less containing the metal ion (A) is included.

  In the present invention, the “metal ion” includes a metal atom present in a state where the charge is not zero.

  The metal species of the metal ion (A) is not particularly limited, and examples thereof include transition metals. Examples of transition metals include groups 4, 5, 8, 9, 10, and 11 of the periodic table. The metal etc. are mentioned. Among these, silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium, titanium, and the like are preferable, and palladium, platinum, and gold are more preferable. The metal species of the metal ion (A) is preferably one having catalytic activity in electroless plating, more preferably selected from palladium, copper and silver, and particularly preferably palladium.

In the step (1), the method for filling the metal ions (A) into the pores of the porous substrate is not particularly limited. For example, the porous substrate is immersed in a solution containing the metal ions (A). It may be done by. Hereinafter, in this specification, “a solution containing a metal ion (A)” is also referred to as “solution A”.
The pH of the solution A is not particularly limited, and may be any state such as acidic, neutral or alkaline, and finally the pores of the porous substrate with the metal ion (A) being about pH 4 or less. What is necessary is just to be filled in. Therefore, metal ions (A) may be filled in the pores by immersing the porous substrate in the solution A having a pH of about 4 or less, and the porous substrate is immersed in the solution A having a pH of about 4 or more. Then, after filling the metal ions (A) in the pores, the pH in the pores may be adjusted to about 4 or less by immersing the porous substrate in an acidic solution.
The concentration of the solution A may be appropriately selected as desired, and is not particularly limited. However, it is generally about 0.00001 to about 10 mol / L, preferably about 0 from the viewpoint of controlling the production efficiency and the performance of the obtained film. About 0.0005 to about 0.1 mol / L.

In one embodiment of the present invention, when the porous substrate is immersed in the solution A and the metal ions (A) are filled in the pores, only one side of the porous substrate is immersed in the solution A. Alternatively, both sides of the porous substrate may be immersed in the solution A. For example, when the porous substrate is tubular, (i) For example, one of the ports is plugged, the inside of the tube is filled with a liquid other than the solution A, the outside of the tube is immersed in the solution A, and the tube The solution A may be filled by permeating into the pores of the porous substrate from the outer surface, or (ii) for example, one end is plugged and the outside of the tube is immersed in a liquid other than the solution A The solution A may be filled inside the tube and the solution A may be filled into the pores of the porous substrate from the inner surface of the tube, or (iii) without plugging the tube The tube may be immersed in solution A and filled by allowing solution A to penetrate into the pores from both the inner and outer surfaces of the tube. When the solution A is infiltrated only from one surface of the porous substrate as in the above (i) or (ii), the solution A does not need to be filled in the pores of the entire porous substrate. The solution A may be filled only in the pores from one side surface of the porous base material immersed in A to a certain depth.
In addition, when the porous substrate is plate-shaped, as a method of immersing only one side of the porous substrate in the solution A, for example, a plate-shaped porous substrate is used so that the container is completely partitioned into two spaces. There is a method in which one of the partitioned containers is filled with a liquid other than the solution A, and the other side is filled with the solution A.
The “liquid other than the solution A” in the present embodiment is not particularly limited, and may be water, an acidic solution, a neutral solution, an alkaline solution, or the like. The “liquid other than the solution A” may be the same as the solution (H) described later.

  In one embodiment of the present invention, the solution A may be a solution containing the metal ion (A) and is not particularly limited. However, when the metal species of the metal ion (A) is palladium, the solution A is In this case, examples of the solution A include palladium chloride (II) solution, palladium nitrate (II) solution, palladium sulfate (II) solution, palladium acetate (II). ) Solution, tetraamminepalladium (II) hydrochloride solution, diamminedinitropalladium (II) solution, bis (acetylacetonato) palladium (II) solution, trans-dichlorobis (triphenylphosphine) palladium (II) solution, etc. . You may use these individually or in combination of 2 or more types. Among these, solutions containing palladium (II) ions are palladium (II) chloride solution, palladium (II) nitrate solution, palladium (II) sulfate solution, and palladium (II) acetate from the viewpoint of ease of handling and price. Those selected from solutions are preferred.

In one embodiment of the present invention, in the step (1), although not essential, when the solution A is filled in the pores of the porous substrate, the sensitizing (generally performed by electroless plating) ( Sensitization) -activating (activation) method or catalyzing-accelrating method may be performed. Sensitizing-activating method or catalyzing-accelrating method has been well established, and in the present invention, a known method, a method known per se, or a method analogous thereto may be used.
In the step (1) of the present invention, the sensitizing / activating method or the catalyzing / accelrating method may be repeated, and when it is repeated, the number of times is not particularly limited, Usually, 2 to 10 times, preferably from 2 to 6 times from the viewpoint of production efficiency. Further, the treatment such as the sensitizing-activating method or the catalyzing-accelrating method may be performed by treating only one side of the porous substrate, or both sides may be treated. When processing only one side of the porous substrate, for example, one side of the porous substrate is immersed in a solution different from the solution used for processing (for example, a solution (H) described later), and only the opposite side is immersed. The treatment may be performed by immersing in a treatment liquid.
By performing the above treatment, the uniformity of the obtained film is preferably improved.

In a preferred embodiment of the present invention, the sensitizing-activating method is performed, for example, when the solution A is a solution containing palladium (II) ions, silver ions or copper ions, for example, tin (II) ions. (Sn ²⁺ ) is adsorbed (sensitized or sensitized) into the pores of the porous substrate, and then the inside of the pores is treated with solution A to reduce some metal ions, You may carry out by making it precipitate (activate or activate). In this embodiment, the sensitizing solution used in the above sensitizing is not particularly limited. For example, SnCl ₂ , Sn (CH ₃ COCHCOCH ₃ ) ₂ as described in International Publication WO 2010/023895 pamphlet. , A solution containing one or more Sn compounds selected from SnBr ₂ , SnI ₂ , and SnSO ₄ .
The concentration of the sensitizing solution may be appropriately selected as desired, and is not particularly limited. However, from the viewpoint of usually about 0.0001 to about 1 mol / L, production efficiency, and performance of the obtained composite, etc., 0.001 to about 0.5 mol / L.

  In another preferred embodiment of the present invention, the catalyzing-accelrating method includes, for example, immersing a porous substrate in a solution in which a protective colloid of palladium (II) protected with a tin (IV) compound is dispersed. The palladium (II) protective colloid is adsorbed in the pores of the porous substrate, and then the inside of the pores is treated with an acid solution such as hydrochloric acid to dissolve the colloidal tin compound to activate the palladium (II). (Acceleration rating) may be performed.

In one particularly preferred embodiment of the present invention, the treatment by the sensitizing-activating method may be performed, for example, by the following procedure:
<1> One side of the porous substrate is immersed in the solution (H), and the other side is immersed in a sensitizing solution containing tin (II) ions, and sensitized in the pores of the porous substrate. Infiltrate the liquid and perform the sensitization treatment;
<2> Thereafter, one side of the porous substrate immersed in the sensitizing solution is immersed in the solution A instead of the sensitizing solution, and the solution A is placed in the pores of the sensitized porous substrate. Infiltrate and activate.
The processes <1> and <2> are preferably repeated about 2 to 10 times, more preferably about 2 to 6 times. The time for immersing the porous substrate in the sensitizing solution and the solution A is not particularly limited, and the material, size, and shape of the porous substrate, the pore size of the porous substrate, and the type of treatment liquid Or, it can be appropriately selected depending on the processing temperature, etc., but each time may be usually from about 5 seconds to about 10 hours, preferably from about 10 seconds to about 5 hours, more preferably about 10 from the viewpoint of production efficiency and the like. Seconds to about 1 hour. The treatment temperature is not particularly limited, but may usually be about 5 ° C. to about 60 ° C., and is preferably about 10 ° C. to about 40 ° C., more preferably about 15 ° C. to about 35 ° C. from the viewpoint of production efficiency. is there.
In this embodiment, the solution A is not particularly limited, but preferably contains palladium (II) ions, more preferably palladium (II) chloride solution, palladium (II) nitrate solution, palladium sulfate (II). ) Solution and at least one selected from palladium (II) acetate solution. The solution (H) is not particularly limited, but is preferably an acidic solution having a pH of about 4 or less. The acidic solution having a pH of about 4 or less is not particularly limited, and examples thereof include an aqueous solution containing an acid. The acid may be an inorganic acid or an organic acid. Examples of the inorganic acid include hydrochloric acid, nitric acid, phosphoric acid, sulfuric acid, boric acid, and hydrofluoric acid. Examples of the organic acid include formic acid, acetic acid, lactic acid, citric acid, oxalic acid, succinic acid, An organic sulfonic acid etc. are mentioned, These may be used individually or in combination of 2 or more types.
Furthermore, in this embodiment, although not essential, after the treatment of <1> above, the step of immersing the porous substrate surface on the side immersed in the sensitizing solution in the solution (H), or on the surface Step <1 ′>, which is a step of pouring the solution (H), may be included. By performing this step, it is possible to remove tin (II) ions that are preferably attached to the surface of the porous substrate. Similarly, although not essential, the surface of the porous substrate immersed in the solution A is immersed in the solution (H) after the treatment <2>, or the solution (H) is immersed in the surface. The step <2 ′> for pouring may be included. By performing this step, it is possible to remove palladium (II) ions that are preferably attached to the surface of the porous substrate. By performing the above steps <1 ′> and <2 ′>, the uniformity of the obtained film is preferably improved.
The porous substrate obtained by repeating the sensitizing / activating process as described above about 2 to 10 times, preferably about 2 to 6 times, can be used in the step (2) described in detail below. .

In the present invention, the concentration of the solution (H) may be appropriately selected as desired and is not particularly limited. For example, the concentration is usually about 0.01 to about 10 mol / L, production efficiency and performance of the obtained composite From the viewpoint of the above, it is preferably about 0.05 to about 5 mol / L, more preferably about 0.1 to about 1.5 mol / L.
In addition, the inventors of the present invention unexpectedly, in the study of the present invention, by controlling the concentration of the solution (H), the composite having a thin metal-filled layer inside the porous substrate of the present invention. A remarkable and useful finding unique to the present invention has been obtained that the position of the body where the metal-filled layer is formed can be controlled. That is, when the concentration of the solution (H) is lowered within the above range, the distance from the surface of the porous substrate to the metal-filled layer is increased, and when the concentration of the solution (H) is raised within the above range, the porous substrate is obtained. The new knowledge that the distance from the surface to the metal filling layer becomes short was acquired. A method of controlling the position where the metal filling layer is formed by adjusting the concentration of the solution (H) is also included in one aspect of the present invention.

In one embodiment of the present invention, the method for producing the composite comprises:
(2) While bringing one surface of the porous substrate obtained in the step (1) into contact with a solution (H) having a pH of about 4 or less, a reducing agent is introduced from the surface on the opposite side of the porous substrate. A step of impregnating the containing solution (C) and supporting metal seed nuclei in the pores of the porous substrate.

  The “solution (H) having a pH of about 4 or less” used in the step (2) is not particularly limited, but may be the same as the solution (H) described above. Further, “contacting one surface of the porous substrate with the liquid” includes “immersing one side of the porous substrate in the liquid”.

  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, aldehydes (for example, formaldehyde Etc.), formic acid, glucose, tin chloride and the like. The reducing agent is dissolved in an appropriate solvent to obtain a solution (C) containing the reducing agent. Although it does not specifically limit as a solvent which dissolves a reducing agent, For example, water, ethanol, chloroform etc. are mentioned, These may be used individually or in mixture of 2 or more types.

In the present invention, the concentration of the solution (C) may be appropriately selected as desired, and is not particularly limited. For example, the concentration is usually about 0.001 to about 1 mol / L, production efficiency, performance of the obtained composite, and the like. From the viewpoint, it is preferably about 0.01 to about 0.5 mol / L.
In addition, the inventors of the present invention unexpectedly, in the study of the present invention, by controlling the concentration of the solution (C), the composite having a thin metal-filled layer inside the porous substrate of the present invention. A remarkable and useful finding unique to the present invention has been obtained that the position of the body where the metal-filled layer is formed can be controlled. That is, when the concentration of the solution (C) is lowered within the above range, the distance from the surface of the porous substrate to the metal-filled layer is increased, and when the concentration of the solution (H) is raised within the above range, the porous substrate is obtained. The new knowledge that the distance from the surface to the metal filling layer becomes short was acquired. A method of controlling the position where the metal filling layer is formed by adjusting the concentration of the solution (C) is also included in one aspect of the present invention.

In one preferred embodiment of the present invention, the step (2) may be carried out by the following procedure: one side of the porous substrate obtained by the step (1) and having pores filled with the solution A It is immersed in the solution (H), and the opposite side of the porous substrate is immersed in the solution (C).
In this embodiment, the time for immersing the porous substrate in the solution (C) is not particularly limited, and the material, size and shape of the porous substrate, the pore size of the porous substrate, and the solution (C ), Or the processing temperature, etc., but it may usually be from about 5 seconds to about 10 hours, preferably from about 10 seconds to about 5 hours, more preferably from the viewpoint of production efficiency and the like. About 10 seconds to about 1 hour. The treatment temperature is not particularly limited, but may usually be about 5 ° C. to about 60 ° C., and is preferably about 10 ° C. to about 40 ° C., more preferably about 15 ° C. to about 35 ° C. from the viewpoint of production efficiency. is there.
When the solution (C) penetrates into the pores and the pH in the pores is about 4 or more, the metal ions (A) in the solution A are reduced to form metal seed nuclei, and the porous substrate is finely divided. Metal seed nuclei can be supported in the pores.

In the composite of the porous substrate and metal seed nucleus obtained by the step (2) of the present invention, the metal seed nucleus is hardly or not attached to the surface of the porous substrate, and the metal seed nucleus is porous. From the surface of the porous substrate, preferably present uniformly in the pores at a certain depth.
Therefore, in the method for producing a composite of the present invention, the step of laminating a protective material, or the metal seed nucleus attached to the surface and the pores near the surface as described in Japanese Patent No. 5155343 is dissolved. The complicated process for forming a protective layer on the surface of a porous base material, such as the process of removing, is not required.

In another preferred embodiment of the present invention, when the step (1) includes the steps <1>, <1 ′>, <2> and <2 ′>, the step (2) is performed according to the following procedure. You may go:
The surface of the porous substrate from which palladium (II) ions have been removed with the solution (H) in the step <2 ′> is immersed in the solution (C), and the solution (C) is infiltrated into the pores. In this step, palladium (II) ions present in the pores are reduced by being brought into contact with the reducing agent and having a pH of about 4 or more, and are precipitated as palladium metal, and are deposited in the pores of the porous substrate. To form palladium nuclei. In this embodiment, the time or temperature for immersing the solution (C) and the surface of the porous substrate with the solution (C) may be the same as described above.

In one embodiment of the present invention, the method for producing the composite comprises:
(3) including a step of subjecting the porous substrate carrying the metal seed nucleus obtained in the step (2) to an electroless plating treatment with a plating solution containing a metal ion (B).
By the electroless plating treatment in the step (3), 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 (metal film).

  The method of the electroless plating treatment in the step (3) of the present invention is not particularly limited as long as it is a commonly used method, and is described in Patent Document 8 (Japanese Patent Laid-Open No. 2006-95521) and Japanese Patent Laid-Open No. 2005-248192. The method can be performed in the same manner as in the method described in Japanese Patent Publication No. Gazette.

  In one embodiment of the present invention, the plating solution preferably contains a metal ion (B), a complexing agent, a reducing agent, and a solvent. The metal ion (B) is provided as a plating solution component such as an appropriate metal salt, for example, acetate, chloride, nitrate, or sulfate.

The metal species of the metal ion (B) is not particularly limited, and examples thereof include transition metals. Examples of the transition metal include groups 4, 5, 8, 9, 10, or 11 of the periodic table. The metal etc. are mentioned. Among these, silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium, titanium, and the like are preferable, and palladium, copper, silver, platinum, and gold are more preferable.
In the present invention, the metal species of the metal ion (B) may be the same as or different from the metal ion (A), and may be appropriately selected according to the use of the resulting composite. It's okay.

  The complexing agent is not particularly limited as long as it can stably dissolve the metal ion (B), and an example thereof is preferably a combination of ammonia and a chelating agent, particularly a combination of ammonia and EDTA. In addition to EDTA, NTA (nitrilotriacetic acid), aliphatic oxyacids such as citric acid and tartaric acid, and the like can be mentioned. As the reducing agent used in the electroless plating treatment, the same one as the solution (C) described above can be used. The solvent used for the electroless plating treatment may be appropriately selected depending on the type of complexing agent, and examples thereof include water, organic solvents such as acetonitrile, benzene, and chloroform.

  Regarding the plating solution composition, for example, when a metal ion (B), a chelating agent, ammonia and a reducing agent are contained, each concentration is about 0.001 to about 0.05 mol / L of the metal ion (B), and the chelating agent. Is about 0.01 to about 0.5 mol / L, ammonia is about 5 to about 15 mol / L, and the reducing agent is about 0.005 to about 0.05 mol / L. 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 may be appropriately set as desired, and is not particularly limited. For example, it is usually about 1 to about 80 ° C., more preferably about 2 to about 75 ° C. The electroless plating treatment time may be appropriately selected according to the plating solution temperature and film thickness, and is not particularly limited. For example, it is usually about 1 minute to about 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 another preferred embodiment of the present invention, when the step (1) includes the steps <1>, <1 ′>, <2> and <2 ′>, the step (3) includes, for example, In the step (2), the porous base material carrying the metal seed nucleus in the pores, the solution (H) and the solution (C) that have been immersed are separated and desired After washing the surface of the porous substrate with water or the like, the porous substrate is immersed in a plating solution. After the electroless plating treatment, the obtained composite and the plating solution may be separated, and the surface of the composite may be washed with warm water or the like as desired.
In this aspect, the composition of the plating solution, the metal ion (B), the temperature or time of the electroless plating treatment, and the like may be the same as described above.

  In one embodiment of the present invention, if desired, (4) a step of firing the composite may be included after the electroless plating treatment in the step (3). Although a calcination temperature is not specifically limited, For example, about 400 degreeC-about 1500 degreeC normally, Preferably it is about 500 degreeC-about 1400 degreeC, More preferably, it is about 500 degreeC-about 1350 degreeC. The firing time is not particularly limited, and is, for example, usually about 1 to about 72 hours, preferably about 1 to about 48 hours, and more preferably about 1 to about 40 hours. The firing may be performed in an air atmosphere or an inert gas atmosphere such as nitrogen gas. Furthermore, the rate of temperature increase during firing is not particularly limited, but is preferably about 0.1 to about 1 ° C./min. Further, the step (4) may include a step of reducing the composite after the baking treatment. By performing the reduction treatment, the performance of the obtained film is preferably improved. The reduction treatment of the composite membrane may be performed by immersing the composite in the solution (C), or may be performed by a method of reducing hydrogen while raising the temperature of the composite in a hydrogen gas stream. . Hydrogen reduction has been well established in the past, and may be carried out according to the present invention by a known method, a method known per se, or a method analogous thereto.

  In one embodiment of the present invention, after the firing treatment in the step (4), for the purpose of improving the densification of the metal layer in the obtained composite, the same electroless method as in the step (3) may be further desired. Plating treatment may be performed. In the present embodiment, when the step (3) is performed again, the step (2) may be repeated or the step (1) may be repeated. In a preferred embodiment of the present invention, the electroless plating process in the first step (3) is performed in a short time (for example, about 5 minutes to about 1 hour), followed by performing the process (4). The electroless plating process in the second step (3) may be performed for a longer time (for example, about 1 hour to about 5 hours) than the first time.

In a preferred embodiment of the present invention, a method for producing a composite having a thin metal-filled layer inside a porous substrate comprises:
(1) A step of filling the pores of the porous substrate with a solution having a pH of about 4 or less containing the metal ion (A),
(2) While contacting one surface of the porous substrate filled with the metal ion (A) obtained in the step (1) with a liquid having a pH of about 4 or less, the opposite side of the porous substrate Impregnating a solution (C) containing a reducing agent from the surface of the substrate, and supporting the metal seed nucleus in the pores of the porous substrate; and (3) the metal seed nucleus obtained in the step (2). A process of electroless plating the supported porous substrate with a plating solution containing metal ions (B);
including.
In this embodiment, the metal ion (A) and the metal ion (B) may be the same or different, and the metal species of the metal ion (A) and the metal ion (B) are the same as described above. It's okay. Further, the liquid having a pH of about 4 or less, the reducing agent, the solution (C), the plating solution, the electroless plating treatment conditions, and the like may be the same as described above.

In another preferred embodiment of the present invention, a method for producing a composite having a metal-filled layer formed into a thin film inside a porous substrate comprises:
(1) A step of filling the pores of the porous substrate with a solution having a pH of about 4 or less containing the metal ion (A),
(2) While contacting one surface of the porous substrate filled with the metal ion (A) obtained in the step (1) with a liquid having a pH of about 4 or less, the opposite side of the porous substrate Impregnating a solution (C) containing a reducing agent from the surface of the substrate, and supporting metal seed nuclei in the pores of the porous substrate;
(3) a step of electroless plating the porous substrate carrying the metal seed nucleus obtained in the step (2) with a plating solution containing a metal ion (B); and
(4) A step of firing the composite obtained in the step (3),
including.
In this embodiment, the metal ion (A) and the metal ion (B) may be the same or different, and the metal species of the metal ion (A) and the metal ion (B) are the same as described above. It's okay. Further, the liquid having a pH of about 4 or less, the reducing agent, the solution (C), the plating solution, the electroless plating treatment conditions, the firing conditions, and the like may be the same as described above.

In still another preferred embodiment of the present invention, a method for producing a composite having a metal-filled layer formed into a thin film inside a porous substrate comprises:
(1) A step of filling the pores of the porous substrate with a solution having a pH of about 4 or less containing the metal ion (A),
(2) While contacting one surface of the porous substrate filled with the metal ion (A) obtained in the step (1) with a liquid having a pH of about 4 or less, the opposite side of the porous substrate Impregnating a solution (C) containing a reducing agent from the surface of the substrate, and supporting metal seed nuclei in the pores of the porous substrate;
(3) a step of electroless plating the porous substrate carrying the metal seed nucleus obtained in the step (2) with a plating solution containing a metal ion (B);
(4) a step of firing the composite obtained in the step (3), and
(5) A step of further subjecting the composite fired in the step (4) to an electroless plating treatment,
including.
In this embodiment, the metal ion (A) and the metal ion (B) may be the same or different, and the metal species of the metal ion (A) and the metal ion (B) are the same as described above. It's okay. Further, the liquid having a pH of about 4 or less, the reducing agent, the solution (C), the plating solution, the electroless plating treatment conditions, the firing conditions, and the like may be the same as described above.
In addition, the electroless plating treatment in the step (5) is only the same treatment as the step (3), the same treatment as the steps (2) and (3), or the step (1), ( You may perform by the process similar to 2) and (3). Furthermore, the electroless plating treatment (second electroless plating treatment) in the step (5) may be performed in a longer time than the electroless plating treatment (first electroless plating treatment) in the step (3). preferable.

  By the above-described production method of the present invention, a composite having a uniform metal-filled layer formed into a thin film is preferably obtained inside the porous substrate. The surface of the composite is a layer of a porous substrate substantially not filled with a metal, and this layer functions as a protective layer for the metal-filled layer (metal film). The method does not require a special step (for example, a step of laminating a protective material separately) for forming the 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.

  The thickness of the metal-filled layer in the composite of the present invention is not particularly limited, but is usually about 1 to about 20 μm, preferably about 1 to about 18 μm, more preferably about 1 to about 15 μm. Since the composite obtained by the production method of the present invention has a porosity of the porous base material 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 embodiment 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 content on the opposite side (for example, the outer side in the case of a tubular composite). If the pressure is set 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 about 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 Mixed gas with carbon oxide, carbon dioxide, nitrogen monoxide, nitrogen dioxide, ammonia, sulfur dioxide, hydrogen sulfide, hydrogen chloride, water (steam), methanol, ethanol, toluene, paraffinic hydrocarbon or olefinic hydrocarbon Can be mentioned. 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, methylcyclohexane and the like.

In one preferred embodiment of the present invention, the complex obtained by the above production method usually has a hydrogen selectivity at about 600 ° C. of about 300,000 or more (nitrogen is below the detection limit). Accordingly, a composite having a thin palladium metal layer inside a porous substrate and having a hydrogen selectivity at about 600 ° C. of usually about 300,000 or more is also included in the embodiment of the present invention.
In the present invention, “hydrogen selectivity is 300,000 or more” is a value obtained by dividing the hydrogen permeability by the nitrogen permeability in a gas permeation test using the apparatus shown in FIG.
The measurement conditions for gas chromatography measurement in the gas permeation test are shown below:
Gas: Gas chromatography; GC (TCD)
Column: Porapak-N 2m, molecular Sieve 13X 2m (GL Science Co., Ltd.)
Carrier gas: Ar
Test gas: H2 / N2 = 75:25
Gas flow rate: 1000 ml / min Inlet gas pressure: 150 kPa (differential pressure 150 kPa from the permeate side).
For more detailed conditions of the gas permeation test, reference may be made to Test Example 1 described later.

  Furthermore, when the metal filling layer is silver in the composite having a thin metal filling layer inside the porous base material of the present invention, the composite can be used as an electromagnetic field shield and a sterilization coat.

  Next, the present invention will be described more specifically with reference to experimental examples and examples. However, the present invention is not limited to these examples, and many modifications are within the technical idea of the present invention. This is possible by those with ordinary knowledge in the field.

  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 synthesis scheme of the steps (1) to (3) is shown in FIG.

[Step (1)]
A palladium chloride solution used as a raw material for the seed crystal of palladium was prepared by the following procedure. 0.10 g of palladium (II) chloride (manufactured by Wako Pure Chemical Industries, Ltd., hereinafter simply referred to as “palladium chloride”) was dissolved in 12.5 μL of hydrochloric acid (manufactured by Wako Pure Chemical Industries, Ltd.) and deionized. 20 mL of water was added and stirred to dissolve palladium chloride. A palladium chloride solution was prepared by taking 5 ml of dissolved palladium chloride and adding deionized water to a total volume of 200 mL. The tin chloride solution used as the reducing agent was 0.20 g of tin (II) chloride (Wako Pure Chemical Industries, Ltd., purity 97%, hereinafter simply referred to as “tin chloride”) dissolved in 0.20 mL of hydrochloric acid. And was prepared by adding deionized water to a total volume of 200 mL. The hydrochloric acid solution was prepared by adding deionized water to 20 ml of hydrochloric acid to make a total volume of 200 mL. This is designated as hydrochloric acid solution 1 (1.2 mol / L). Separately from hydrochloric acid solution 1, hydrochloric acid solution 2 (1.2 mol / L) was prepared by adding deionized water to 2 ml of hydrochloric acid to make a total volume of 20 mL. The prepared hydrochloric acid solution 2 was poured into the inner cylinder side of the alumina substrate. The prepared palladium chloride solution, tin chloride solution, and hydrochloric acid solution 1 were put in a glass test tube having a round bottom φ40 × 350 mm, respectively, and the alumina substrate filled with hydrochloric acid solution 2 was tin chloride solution, hydrochloric acid solution 1, palladium chloride solution, hydrochloric acid. In the order of Solution 1, immersion for 1 minute each at room temperature was repeated three times.

[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 aqueous hydrazine solution was prepared by diluting 2 mL of hydrazine monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) with deionized water to a total volume of 200 mL. The alumina substrate obtained in the step (1) was immersed in an aqueous hydrazine solution at room temperature for 1 minute to reduce palladium to form palladium seed nuclei. After the reduction treatment, the hydrochloric acid solution poured into the inner cylinder side of the alumina substrate was removed, and the substrate was sufficiently 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 solution and 20 mL of Paratop B solution, and the total amount was used as 200 mL. The reaction was performed at a plating temperature of 50 ° C. and a plating time of 30 minutes.

[Step (4)]
After the electroless plating, the composite was immersed in deionized water at 50 ° C., washed with the plating solution, and then fired for 24 hours under air conditions at 1250 ° C. to perform palladium sintering. The obtained composite was immersed in a hydrazine aqueous solution overnight to perform a reduction treatment. The aqueous hydrazine solution was prepared by diluting 1 mL of hydrazine monohydrate (manufactured by Wako Pure Chemical Industries, Ltd.) with deionized water to a total volume of 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.

(result)
The structure of the composite (composite film) produced in Example 1 was observed with a laser microscope (VK-8500: trade name, manufactured by Keyence Corporation). The observation results of the laser microscope observation are shown in FIGS. 2 (a) and 2 (b). It was confirmed that the palladium composite layer formed by electroless plating was selectively formed in the alumina substrate. This is considered to be due to the fact that palladium nuclei serving as a reaction field for electroless plating are selectively arranged in advance in an alumina substrate.

  Further, FIG. 3A shows an observation image of the composite produced in Example 1 by SEM (S-5000: Hitachi high-resolution field emission scanning microscope, manufactured by Hitachi High-Technologies Corporation), FIG. 3B and FIG. 3 (c) shows an image analyzed by an energy dispersive X-ray analyzer (EDX, product name: Genesis-XM2, Edax Japan Co., Ltd.). From the result shown in FIG. 3, it was confirmed that the metal can be selectively filled in the alumina substrate according to the present invention. The thickness of the palladium composite layer formed by electroless plating was 9 μm, and the distance from the alumina substrate surface to the filling layer was 15.4 μm.

  In the present invention, the position of the palladium composite layer from the surface of the alumina substrate can be controlled by changing the concentration of hydrochloric acid in step (1) of Example 1. Details are described in Examples 2-4.

[Example 2]
Step (1) to Step 1 of Example 1 except that the hydrochloric acid solution in Step (1) is 0.3 mol / L and the amount of hydrazine monohydrate in the aqueous hydrazine solution (200 mL) in Step (2) is 70 μL. A composite (composite film) was prepared in the same manner as (3). In this example, step (4) of Example 1 was not performed.
[Example 3]
A composite (composite membrane) was produced in the same manner as in Example 2 except that the hydrochloric acid solution in step (1) was changed to 0.6 mol / L.
[Example 4]
A composite (composite membrane) was produced in the same manner as in Example 2 except that the hydrochloric acid solution in step (1) was changed to 1.2 mol / L.

(result)
The cross-sectional structure of the composite (composite film) produced in Examples 2 to 4 was observed with a laser microscope. The observation result of the laser microscope is shown in FIG. In the composite (Example 2, FIG. 4 (a)) having a hydrochloric acid solution of 0.3 mol / L, the distance from the alumina substrate surface to the palladium composite film was 73 μm. In the composite (Example 3, FIG. 4 (b)) in which the hydrochloric acid solution was 0.6 mol / L, the distance from the alumina substrate surface to the palladium composite film was 63 μm. In the composite (Example 4, FIG. 4 (c)) in which the hydrochloric acid solution was 1.2 mol / L, the distance from the alumina substrate surface to the palladium composite film was 50 μm. From the results shown in FIG. 4, it was confirmed that the composite layer can be controlled to an arbitrary position by changing the concentration of hydrochloric acid.

  In the present invention, it is possible to control the position of the palladium composite layer from the surface of the alumina substrate by changing the concentration of drazine in step (2) of Example 1. Details are described in Examples 5 and 6.

[Example 5]
A composite was produced in the same manner as in steps (1) to (3) of Example 1 except that the amount of hydrazine monohydrate in the aqueous hydrazine solution (200 mL) in step (2) was 0.2 mL. In this example, step (4) was not performed.
[Example 6]
A composite was prepared in the same manner as in Example 5 except that 1 mL of hydrazine monohydrate in the hydrazine aqueous solution in step (2) was used.

(result)
The observation result of the cross section of the composite produced in Examples 1, 5 and 6 with a laser microscope is shown in FIG. The composite (Example 5, FIG. 5 (a)) in which the hydrazine monohydrate in 200 ml of the hydrazine aqueous solution was 0.2 ml had a distance from the alumina substrate surface to the palladium composite film of 60 μm. In the composite containing 1 ml of hydrated hydrazine (Example 6, FIG. 5B), the distance from the alumina substrate surface to the palladium composite film was 30 μm. The composite containing 2 ml of hydrous hydrazine (Example 1, FIG. 5C) had a distance of 15 μm from the alumina substrate surface to the palladium composite membrane. From the results shown in FIG. 5, it was confirmed that the composite layer can be controlled to an arbitrary position by changing the concentration of hydrazine. Although the reason is not clear, it is considered that by changing the concentration of hydrazine, the neutralization point approaches the surface of the alumina substrate, and good palladium colloid is generated at the neutralization point.

  The metal that can be used in the present invention is not limited to palladium, but is effective for other metals. The manufacturing method of each composite_body | complex is demonstrated to Examples 7-9.

[Example 7]
Steps (1) and (2) were carried out in the same manner as in Example 1. After the formation of palladium seed nuclei, electroless plating of copper was performed on the alumina substrate as follows. As the plating solution, OPC-750 electrolytic copper M-A, B and C (trade name, reducing agent: formaldehyde, Okuno Pharmaceutical Co., Ltd.), which are commercially available copper plating solutions, were diluted to a prescribed concentration and used. That is, deionized water was added to 20 mL of OPC-750 electroless copper MA solution, 20 mL of OPC-750 electroless copper MB solution, and 0.4 mL of OPC-750 electroless copper MC solution, and the total amount Was used as 200 mL. The reaction was carried out at a plating temperature of room temperature and a plating time of 30 minutes.
[Example 8]
Steps (1) and (2) were carried out in the same manner as in Example 1. After the formation of palladium seed nuclei, an electroless plating treatment of palladium was performed on the alumina substrate. As the plating solution, Paratop which is a commercially available palladium plating solution was diluted to a prescribed concentration and used. The reaction was performed at a plating temperature of 50 ° C. and a plating time of 10 minutes. The alumina substrate after palladium plating was immersed in a hydrazine solution for 30 seconds. The aqueous hydrazine solution was prepared by diluting 1 mL of hydrazine monohydrate with water to 200 mL. After immersing the alumina substrate in an aqueous hydrazine solution, the alumina substrate was washed with deionized water and subjected to silver electroless plating. The plating solution is 0.972 g of silver nitrate, 0.108 g of dichlorotetraamminepalladium, 6.72 g of 2Na · EDTA, 130 mL of aqueous ammonia (28%), and 70 μL of hydrazine monohydrate in a 200 mL volumetric flask. 200 mL. The reaction was performed at a plating temperature of 50 ° C. and a plating time of 10 minutes.
[Example 9]
Steps (1) and (2) were carried out in the same manner as in Example 1. After the formation of palladium seed nuclei, platinum electroless plating was performed on the alumina substrate. The plating solution was 0.088 g of dichlorotetraammine platinum monohydrate, 0.8 mL of aqueous ammonia (28%), 0.03 mL of ethylenediamine, and 0.2 mL of hydrazine in a 200 mL volumetric flask, and water was added to make a total volume of 200 mL. did. The reaction was performed at a plating temperature of 75 ° C. and a plating time of 30 minutes.

(result)
The cross-sectional structure of the composites (composite films) prepared in Examples 7 to 9 was observed and analyzed with a laser microscope and EDX. The results are shown in FIGS.
The observation result of the composite produced in Example 7 with a laser microscope is shown in FIG. 6 (a), and the analysis result of EDX is shown in FIG. 6 (b) and FIG. 6 (c). From the results shown in FIG. 6, it was confirmed that the copper composite can be formed in the alumina substrate by the production method of the present invention.
The observation result of the composite (composite film) produced in Example 8 with a laser microscope is shown in FIG. 7A, and the analysis result of EDX is shown in FIG. 7B and FIG. 7C. From the results shown in FIG. 7, it was confirmed that a silver composite can be formed in an alumina substrate by the production method of the present invention.
The observation result of the composite (composite film) produced in Example 9 with a laser microscope is shown in FIG. 8A, and the analysis result of EDX is shown in FIG. 8B and FIG. 8C. From the results shown in FIG. 8, it was confirmed that a platinum composite can be formed in an alumina substrate by the production method of the present invention.

  The porous substrate that can be used in the present invention is not limited to the alumina substrate, but is effective for other porous substrates. A palladium composite was produced for other porous substrates as follows. Details are described in Example 10.

[Example 10]
Except for changing the alumina substrate used in Example 1 to a mullite substrate, steps (1) to (3) were performed in the same manner as in Example 1 to produce a composite (composite film). The “mullite substrate” is a tubular porous substrate (made by Nikkato Corporation) made of mullite (mixture of aluminum oxide and silicon dioxide) having a diameter of 12 mm, an inner diameter of 9 mm, and a pore diameter of 1.2 μm.
In this example, step (4) was not performed.

(result)
The structure of the composite (composite film) produced in Example 10 was observed with a laser microscope. The observation results are shown in FIG. Moreover, the analysis result of EDX is shown in FIG.9 (b) and FIG.9 (c). The distance from the surface of the mullite substrate to the palladium composite film was about 14 μm. From the results shown in FIG. 9, it was confirmed that the composite film can be selectively formed in the mullite substrate according to the manufacturing method of the present invention.

  The acidic solution that can be used in the present invention is not limited to hydrochloric acid, and other acidic solutions are also effective. Details are described in Examples 11 and 12.

[Example 11]
The steps (1) to (3) were carried out in the same manner as in Example 1 except that hydrochloric acid 1 and 2 used in Example 1 were changed to nitric acid (manufactured by Wako Pure Chemical Industries, Ltd.) 1.2 mol / L. Thus, a composite (composite film) was produced. In this example, step (4) was not performed.
[Example 12]
A composite (composite membrane) was carried out in the same manner as in Example 11 except that nitric acid (manufactured by Wako Pure Chemical Industries, Ltd.) 1.2 mol / L was changed to 0.6 mol / L of sulfuric acid (Wako Pure Chemical Industries, Ltd.). Was made.

(result)
The result of observation with a laser microscope of the cross section of the composite (composite film) produced in Examples 11 and 12 is shown in FIG. Even when nitric acid was used (Example 11, FIG. 10 (a)), it was confirmed that a palladium complex could be formed. The distance from the alumina substrate surface to the palladium composite film was 38 μm. Further, it was confirmed that a palladium complex can be formed even when sulfuric acid is used (Example 12, FIG. 10B). The distance from the alumina substrate surface to the palladium composite was 11 μm. From the results of Examples 11 and 12, it was confirmed that the acidic solution used in the production method of the present invention is not limited to hydrochloric acid, and other acidic solutions can form a composite film in the substrate.

  The reducing agent used in the present invention is not limited to hydrazine, and other reducing agents are also effective. Details are described in Examples 13 and 14.

[Example 13]
The steps (1) to (3) were carried out in the same manner as in Example 1 except that the reducing agent used in Example 1 was replaced with hydrazine aqueous solution to formaldehyde (0.2 mol / L). Composite membrane). In this example, step (4) was not performed.
[Example 14]
A composite (composite film) was prepared in the same manner as in Example 13 except that formaldehyde (0.2 mol / L) was changed to trimethylamine borane (0.02 mol / L).

(result)
The results of observation with a laser microscope of the cross section of the composite (composite film) produced in Examples 13 and 14 are shown in FIG. Even when formaldehyde was used (Example 13, FIG. 11 (a)), it was confirmed that a palladium complex could be formed. The distance from the surface of the alumina substrate was 43 μm. It was also confirmed that the formation of a palladium complex was possible even when trimethylamine borane was used (Example 14, FIG. 11B). The distance from the alumina substrate surface was 30 μm. From the results of Examples 13 and 14, it was confirmed that the reducing agent used in the production method of the present invention is not limited to hydrazine, and other reducing agents can form a composite film in the substrate.

[Example 15]
0.10 g of palladium chloride (Wako Pure Chemical Industries, Ltd.) was dissolved in 12.5 μL of hydrochloric acid, and 20 mL of deionized water was added and stirred to dissolve palladium chloride. Subsequently, a 1.2 mol / L hydrochloric acid solution was prepared. The prepared palladium chloride solution (5 mL) and hydrochloric acid solution (15 mL) were mixed to make a total of 20 mL. This mixed solution was injected into the alumina substrate. The alumina substrate filled with the mixed solution was washed with water. Thereafter, the same operations as in steps (2) and (3) of Example 1 were performed to produce a composite (composite film). In addition, when implementing a process (2) in a present Example, the hydrochloric acid solution 2 was filled inside the alumina substrate similarly to Example 1. FIG. In this example, step (4) was not performed.
(result)
Also in this example, a composite having a metal-filled layer in an alumina substrate could be produced.

[Comparative Example 1]
A tin chloride solution and a palladium chloride solution were prepared by the same method as in step (1) of Example 1. In this Comparative Example 1, unlike Example 1, the following treatment was carried out without filling the inside of the alumina substrate with the hydrochloric acid solution: both ends of the alumina substrate were plugged, and the outside of the cylinder of the alumina substrate was tin chloride. The solution, deionized water, palladium chloride, and deionized water were each immersed for 1 minute three times in this order (1 set 4 minutes x 3 times) for a total of 12 minutes. Next, water was added to a mixture of 15 ml of hydrochloric acid and 5 ml of nitric acid to prepare a mixed solution (aqua regia) with a total amount of 100 ml. The alumina substrate subjected to the treatment for 12 minutes described above was immersed in this mixed solution for 1 minute. Thereafter, reduction treatment (formation of palladium seed nuclei) and electroless plating treatment were performed by the same operations as in steps (2) and (3) of Example 1. However, unlike Example 1, in Comparative Example 1, the process was performed without filling the inside of the alumina substrate with the hydrochloric acid solution in Steps (2) and (3).

(result)
FIG. 12 shows the result of observation of the cross-sectional structure of the composite produced in Comparative Example 1 with a laser microscope. Although the formation of a film can be confirmed on the extreme surface side of the alumina substrate, the formation position of the film and the thickness of the film are not uniform.

[Test Example 1]
A gas permeation test was conducted using the palladium-composited alumina membrane (composite membrane) produced in Example 1. A hydrogen / nitrogen (H2 / N2 = 75/25 (vol / vol)) mixed gas test was performed under the following conditions under a temperature condition of 600 to 200 ° C. A schematic diagram of the gas permeation test apparatus is shown in FIG.
As shown in FIG. 13, a H2 / N2 mixed gas was brought into contact with the composite in a tubular furnace. At this time, the inlet gas pressure when feeding the mixed gas into the tubular furnace was set to 100 kPa, 150 kPa, or 200 kPa (non-permeation side (outside of the composite membrane cylinder) and permeation side (inside of the composite membrane cylinder) ) Differential pressure (ΔP) of 100 kPa, 150 kPa, or 200 kPa). Then, the gas permeated through the composite (permeate gas) is sampled, a part is sent to a flow meter to measure the flow rate of the permeate gas, and a part is sent to a gas chromatograph to satisfy the following conditions: Gas chromatography (GC) measurement was performed. The flow rate when the H2 / N2 mixed gas was fed into the tubular furnace was 1000 mL / min.
The gas permeation | transmission test result in 600 to 400 degreeC is shown to Tables 1-3.

(GC measurement conditions)
Gas analysis: Gas chromatography; GC (GL Science Co., Ltd.)
Column: Porapak-N 2m, molecular Sieve 13X 2m (GL Science Co., Ltd.)
Carrier gas: Ar
Test gas: H2 / N2 = 75:25
Detector: TCD (thermal conductivity detector)
Measurement temperature: 200-600 ° C (measured at the same temperature as the temperature of the tube furnace)
Injector temperature: 60 ℃

In Tables 1 to 3, ΔP represents a differential pressure between the in-cylinder (non-permeation side) pressure of the composite membrane and the in-cylinder (permeation side) pressure of the composite membrane. The non-permeation side pressure> the permeation side pressure.

(result)
As a result of the gas permeation test at 600 ° C., the hydrogen permeability is about 3.3 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ (when ΔP = 150 kPa), and the hydrogen selectivity (α) is The initial value was 300,000 or more (nitrogen was below the detection limit). After the temperature was lowered from 600 ° C. to 200 ° C., the hydrogen permeability when the temperature was raised again to 600 ° C. was 3.3 × 10 ⁻⁸ m ³ m ⁻² s ⁻¹ Pa ⁻¹ , The hydrogen selectivity of 000 or more was maintained. This is presumably because the film was not suddenly broken due to peeling of the palladium layer.

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

  According to the present invention, there is provided a method for producing a composite of a porous substrate and a metal thin film capable of forming a uniform metal thin film at a desired position inside the porous substrate without requiring a complicated operation. Can be provided. Moreover, according to the manufacturing method of this invention, the position formed in the porous base material of the said metal thin film can be controlled. Moreover, according to the manufacturing method of this invention, the metal thin film with a uniform position and film thickness can be obtained. Furthermore, when the composite is used for hydrogen separation, it is possible to provide a composite that is excellent in hydrogen permeability and durability, and that can be manufactured at a low cost by greatly reducing the amount of metal such as palladium. And the composite_body | complex of this invention has very high hydrogen selectivity, According to this invention, the composite_body | complex with very high hydrogen separation efficiency can be provided.

Claims (8)

A method for producing a composite having a metal-filled layer formed into a thin film inside a porous substrate,
(1) A step of filling a pore of the porous substrate with a solution having a pH of 4 or less containing the metal ion (A),
(2) While contacting one surface of the porous substrate filled with the metal ion (A) obtained in the step (1) with a solution (H) having a pH of 4 or less, the opposite of the porous substrate A step of infiltrating the solution (C) containing the reducing agent from the surface on the side, and supporting the metal seed nucleus in the pores of the porous substrate, and (3) the metal seed nucleus obtained in the step (2) A step of electroless plating a porous substrate carrying metal with a plating solution containing metal ions (B) (wherein the metal ions (A) and the metal ions (B) are the same or different) May be)
A method for producing the composite, comprising:   In the step (2), before the solution (C) is infiltrated, the method includes a step of removing the metal ions (A) adhering to the surface of the porous substrate on the side infiltrating the solution (C). The manufacturing method according to claim 1.   The sensitizing / activating method or catalyzing / accelrating method is used when the metal ions (A) are filled in the pores of the porous body in the step (1). Or the manufacturing method of 2.   The said metal ion (A) is palladium ion (II), The manufacturing method of any one of Claims 1-3 characterized by the above-mentioned.   The metal species of the metal ion (B) is silver, palladium, rhodium, ruthenium, gold, platinum, iridium, osmium, copper, nickel, cobalt, iron, vanadium or titanium. The manufacturing method of any one of these.   The said metal ion (B) is palladium ion (II), The manufacturing method of any one of Claims 1-5 characterized by the above-mentioned.   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, formic acid, glucose and chloride. The manufacturing method of any one of Claims 1-6 which is 1 or more chosen from the group which consists of tin.   The position where the thin metal filling layer is formed is controlled by controlling the concentration of the solution (H) and / or the solution (C). The production method according to item.