JP2955062B2 - Hydrogen gas separation membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a hydrogen gas separation membrane for separating hydrogen in a mixed gas.

[0002]

2. Description of the Related Art A film mainly composed of palladium (referred to as a Pd film) is known as a method for separating hydrogen from a mixed gas containing hydrogen to obtain hydrogen having a high purity of 99.99% or more. {Journal of the Japan Petroleum Institute, vol. 15, No. 1, (1
972), P64｝

[0003] Conventionally, Pd or an alloy mainly composed of Pd is produced by elongating it to form a thin film, and this film has been used by being supported by a support frame. There is a limit on the lower limit of the thickness of the film obtained by the distraction method, and since this film is used by being supported by a support frame, it is necessary to provide mechanical strength enough to withstand such a supporting method, If a too thin film is used, the film is easily damaged during use.

As one means for separating a specific gas from a mixed gas by a gas diffusion method, a porous gas separation membrane having pores smaller than the mean free path of gas molecules, for example, pores of 10 to several thousand degrees is used. A separation method by Knudsen diffusion is known. For example, such a method uses a relatively large molecular ratio of hydrogen (H ₂ ) / nitrogen (N ₂ ), hydrogen /
It is effective for separating H ₂ gas in a mixed gas such as carbon monoxide (CO). Generally, an organic polymer membrane (polyimide, cellulose acetate, silicon type, etc.) is used as a gas separation membrane.

However, such an organic polymer film has a defect of poor durability such as heat resistance and chemical resistance.
Attempts have been made to use a porous gas separation membrane made of an inorganic material such as a ceramic porous body, and JP-A-59-59223 proposes a porous gas separation membrane made of such an inorganic material. And is shown as a conventional example.

[0006] As a method for solving the above problems,
A method using a hydrogen separation membrane in which a thin film containing Pd is formed on a porous support made of an inorganic material is disclosed in
21616.

[0007]

The above-mentioned conventional methods have the following problems. (1) Since the ratio of the permeability of the mixed gas in the separation method by Knudsen diffusion is theoretically equal to the square root of the reciprocal of the molecular weight of each gas, it is difficult to obtain a considerably small and high-concentration hydrogen gas.

(2) In the Pd film method, a relatively thick film having a thickness of about 60 to 100 μm must be used, the amount of expensive Pd used increases, and the permeation rate of hydrogen is low.

(3) Examples of the porous support made of an inorganic material include porous glass, porous ceramics, and porous metal. Porous glass has a very low impact strength and is easily broken. The average pore diameter of the porous ceramics is 0.1 μm or more, and the average pore diameter of the porous metal is several tens of μm or more, and the thickness of the Pd film for covering the pores is tens of μm for both. Low permeation rate of hydrogen.

[0010] In view of the above technical level, the present invention does not have the disadvantages of the conventional separation membrane, and has heat resistance and pressure resistance.
Another object of the present invention is to provide a hydrogen separation membrane having properties that are practically satisfactory in both the permeation rate and the separation coefficient.

[0011]

According to the present invention, the pore size is 10 to 10.
The average pore diameter is 1 in the pores of the inorganic porous body of 10,000 mm.
0~30Å silica gel, <br/> alumina gel or average pore diameter of the average pore diameter 15~30Å is supported on silica-alumina gel 10～20A, by further forming a thin film containing Pd on the surface thereof A hydrogen gas separation membrane characterized in that:

As the inorganic porous material, porous ceramics,
There are porous glass, porous porcelain, perforated metal filter, sintered metal wire mesh, and the like, and any of them can be used in the present invention. However, if the pore size of the inorganic porous material is large, the required amount of silica gel, alumina gel or sol, which is a precursor of silica-alumina gel, is required to be large, and cracks are likely to occur. And the pore size is reduced to 100 to 10,000.
It is preferable to use about 無機 inorganic porous material. Especially,
Foamed silica, sintered alumina, mullite and the like having a pore diameter of 1,000 mm or more are preferably used.

In general, the method for producing silica gel is as follows: (1) A water glass solution in which a large amount of a salt such as NaCl or Na ₂ SO ₄ is added to a water glass solution, and the acid is neutralized to obtain a white powdery silica gel. (2) SiCl ₄ is burned in a steam stream to generate SiO ₂ gas, and the SiCl ₄ combustion method for collecting the SiO ₂ gas is collected. (3) SiO ₂ is evaporated at about 1,700 ° C. There is a SiO ₂ vapor aggregation method for condensation and the like.

However, it is extremely difficult to coat the SiO ₂ particles obtained by these methods on a thin film having a thickness of about several tens of μm, and to form a porous film having a thickness of about 10 to 30 °. Therefore, in the present invention, the method of Japanese Patent Application No. 02-172639 is recommended as a method for obtaining a silica gel capable of forming a thin film without the above-mentioned problems.

That is, in the above method, it is recommended to use a precursor obtained by hydrolyzing an alkoxysilane containing, for example, an ethoxysilane group or a methoxy group, as a precursor of silica gel. Examples of such alkoxysilanes include tetraethoxysilane (ethyl silicate), tetramethoxysilane (methyl silicate), and the like.

The silica gel produced by this method has an average pore diameter of 10 to 30 °, and has a molecular diameter of 2.3 ° and has no pore resistance to H ₂ permeation. Also, since the surface of this silica gel is much smoother than a conventional porous body, even if a Pd thin film having a thickness of 1 μm or less is carried on this surface, it does not cause pinholes, and the H ₂ transmission Greatly improve speed.

As a method for producing alumina gel, there is generally the following method. (1) Method of hydrolyzing Al alkoxide Isopropoxide produced by dissolving Al in isopropyl alcohol is often used because it has a low boiling point (140.5 ° C.). As the hydrolysis method, there are a homogeneous phase hydrolysis of an alcohol solution and a heterogeneous phase hydrolysis of a benzene solution. (2) Method of hydrolyzing Al salt by adding catalyst Al ₂ (SO ₄ ) O ₃ , AlCl ₃ , A
l (NO ₃ ) O _{3 and the} like. As a catalyst, nitric acid, NH ₃
There are water, Na ₂ CO _{3 and the} like. (3) Method of hydrolyzing alkali aluminate Hydrochloric acid is added to an aqueous solution of NaAlO ₂ to perform hydrolysis.

The alumina gel varies depending on the production method.
Approximately 15-30 ° pores are formed. (Japanese Patent Application No. 59-3
4421, Japanese Patent Application No. 60-180980)

The following method is generally used for producing silica-alumina gel. As a production method, after supporting an alumina sol obtained by hydrolyzing an aluminum alkoxide or an aluminum chelate, an aqueous solution of sodium silicate is supported, followed by drying after acid treatment and gelling.
Aluminum alkoxides include aluminum isopropoxide, aluminum-2-butyrate, and the like, and aluminum chelates include aluminum tris (ethyl acetoacetate) and ethyl acetoacetate aluminum diisopropylate.

The average pore size of the silica-alumina gel produced by the above method is about 10 to 20 °. (Japanese Patent Application No. 60
No.-30546)

As a method for supporting the Pd thin film, there is the following method. (1) Liquid phase method such as plating A method of surface activation (alternately immersed in an aqueous solution of tin chloride and a solution of palladium chloride) followed by electroless plating (immersed in a solution containing a compound of palladium and a reducing agent) And electroplating after electroless plating. (2) A vapor phase method such as a vacuum deposition method, an ion plating, and a vapor phase chemical reaction method (CVD).

The hydrogen gas separation membrane having the Pd or Pd alloy thin film formed thereon as described above selectively permeates only hydrogen. That is, when a mixed gas containing hydrogen is supplied to one side of the gas separation membrane, the hydrogen gas separation membrane selectively transmits only hydrogen, and pure hydrogen flows out from the other side of the hydrogen gas separation membrane. .

The permeation rate of hydrogen increases as the temperature increases,
Also, the larger the pressure difference of hydrogen on both sides of the hydrogen gas separation membrane, the larger the difference. The preferred operating temperature range of the hydrogen gas separation membrane of the present invention is 200 to 500 ° C.

The hydrogen permeation rate is extremely high,
100 ° -140cm when 0 ° C and pressure difference 2kg / cm ²
It is about ³ / cm ² · min, which is 4 to 6 times that of a hydrogen separation membrane in which Pd is directly supported on a conventional porous substrate.

[0025]

The hydrogen gas separation membrane of the present invention has a Pd
Since the thickness of the thin film is reduced to 1/5 to 1/10, the amount of Pd carried is reduced, and the hydrogen permeation rate is also improved, so that it is possible to greatly reduce the size, and as a result, the cost can be significantly reduced. .

[0026]

【Example】

(Example 1) As an inorganic porous body of a base material, a ceramic tube manufactured by NGK Insulators, Ltd. (average pore diameter 0.5 μm, outer diameter 1
0 mm, length 250 mm), and the following treatment was performed.

(1) Preparation of Silica Sol 1 A chemical having the composition shown in Table 1 was placed in a beaker, and rapidly stirred and mixed at room temperature with a stirrer. 80 ° C. with continuous stirring
Exothermic reaction starts when preheated to (boiling state), about 20 ~
The viscosity rises rapidly in 25 minutes. 15 minutes after the start of boiling, 2
The liquids for 0 minute and 25 minutes were cooled, respectively, and 1-A, 1-B,
1-C liquid. 1-A is a slightly high viscosity liquid,
Liquid B has a higher viscosity and is a jelly-like liquid when cooled to room temperature. The 1-C liquid is in a state of being solidified by cooling at room temperature.

[Table 1]

(2) Preparation of Silica Sol 2 A drug having the composition shown in Table 1 was placed in a beaker and stirred and mixed with a stirrer at room temperature for 60 minutes to obtain silica sol 2.

(3) Method for Carrying Silica Sol (a) Carrying Silica Sol 1 Solution A tube made of an inorganic porous material was immersed in the above-mentioned silica sol 1-A solution to carry silica sol on the wall of the porous material tube.
The porous body was fired in an electric furnace set at 200 ° C. for 10 minutes. Next, the porous body was fired in an electric furnace set at 300 ° C. for 10 minutes. Next, the porous body was fired in an electric furnace set at 550 ° C. for 10 minutes. The above operations-were repeated twice. Next, the same treatment as in 1 was performed using the 1-B solution. Next, the same treatment as in 1 was performed using the 1-C solution.

(B) Carrying of two silica sol solutions Next, the same treatment as described above was carried out using two silica sol solutions.

A sample in which Pd was deposited on the surface of the ceramic tube supporting silica gel manufactured by the above method under the following conditions was manufactured. Sample 1: Only Pd was deposited Sample 2: Alloy of Pd and silver Ag (Pd: Ag = 85:
15 weight ratio)

A hydrogen permeation experiment was performed using the apparatus shown in FIG. The hydrogen gas separation membrane 1 is fixed to a stainless steel outer tube 3 with an O-ring 2, and the outside thereof is heated by an electric furnace. The temperature was measured at the center of the inner tube using a thermocouple 8.

The mixed gas of H ₂ / N ₂ = 1 (molar ratio) is continuously supplied from the supply hole 4, the bleed gas is discharged from the discharge hole 5, and 99.99% or more of the bleed gas is discharged from the lower discharge hole 6. Pure hydrogen could be obtained.

Table 2 shows the experimental results at a temperature of 500 ° C. at a mixed gas pressure of 3 kg / cm ² G and a gas flow rate of 20 Nl / min.

[Table 2]

(Example 2) (1) Al is deposited on the surface of a porous metal body obtained by randomly sintering and sintering stainless steel fibers, and then subjected to a heating / diffusion treatment in a vacuum to form a porous metal body. The diffused Al was subjected to an oxidation treatment, and a porous metal having aluminum oxide formed on the surface of the porous metal was used as a support material, and an alumina gel film was supported in the porous material. The average pore size is 1 μm.

(2) Carrying of alumina gel film 5 g of aluminum isoprooxide was added to 100 g of water in water kept at 80 ° C. to hydrolyze aluminum isoprooxide. 0.6 ml of concentrated nitric acid was added thereto, kept at 80 ° C. for 24 hours, and peptized to obtain an alumina sol. The porous metal was immersed in the alumina sol for 5 minutes, dried at room temperature for 24 hours, dried at 80 ° C. for 2 hours, fired at 350 ° C. for 2 hours, and fired at 600 ° C. for 2 hours. This operation was repeated four times to support the alumina gel in the porous metal body.

Next, aluminum isoprooxide was dissolved at a weight ratio of 5 with respect to 100 of trichlene, and the porous metal filled with amylna was impregnated with this solution to volatilize trichlene, and aluminum was contained in the pores. Prooxide was deposited. Next, while reducing the pressure on one side of the porous metal, the porous metal was put into steam at 100 ° C. to hydrolyze the aluminum isoprooxide, and dried at room temperature.
It baked at 0 degreeC for 2 hours, and also baked at 600 degreeC for 1 hour.
This operation was repeated three times.

The average pore size distribution of the porous metal supporting alumina gel produced by the above operation was 16 °.

A porous metal body carrying an alumina gel film manufactured by the above method was used, and P
A sample on which d was deposited was manufactured.

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. H ₂ / N from supply hole 4
A mixed gas of ₂ = 1 (molar ratio) is continuously supplied, bleed gas is discharged from the discharge hole 5, and 9 to 9 from the lower discharge holes 6.
At least 9.99% of pure hydrogen could be obtained.

Table 3 shows the experimental results at 500 ° C. at a mixed gas pressure of 3 kg / cm ² G and a gas flow rate of 20 Nl / min.

[Table 3]

Example 3 Al was deposited on the surface of a porous metal obtained by laminating and sintering a wire mesh, and then heated and diffused in a vacuum to oxidize the aluminum diffused into the porous metal. A separation membrane was produced by treating the porous metal body with aluminum oxide formed on the surface of the porous metal body as a support, and carrying a silica gel membrane on the surface of the porous body in the same manner as in Example 1. . Wire mesh: 0.5 μm diameter Material: SUS 3
04

A porous metal material carrying a silica gel film produced by the above method is used, and Pd
Was fabricated.

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. H ₂ / N from supply hole 4
A mixed gas of ₂ = 1 (molar ratio) is continuously supplied, bleed gas is discharged from the discharge hole 5, and 9 to 9 from the lower discharge holes 6.
At least 9.99% of pure hydrogen could be obtained.

Table 4 shows the experimental results at 500 ° C. at a mixed gas pressure of 3 kg / cm ² G and a gas flow rate of 20 Nl / min.

[Table 4]

Example 4 A ceramic tube carrying a silica gel film produced by the method of Example 1 was used, and Pd was further carried on its surface by electroless plating.

The electroless plating was performed under the following conditions. 1) Reagents Tetraamminepalladium chloride (II) [Pd (NH ₃ )
₄ ] Cl ₂ · H ₂ ONH ₃ (28% aqueous solution) 2) Conditions Temperature = 50 ° C, pH = 12

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. Table 5 shows the experimental results.

[Table 5]

Example 5 The same ceramic tube manufactured by NGK Insulators, Ltd. (average pore diameter 0.5 μm, outer diameter 1
0 mm, length 250 mm), and the following treatment was performed.

(1) Preparation of Silica Sol A drug having the composition shown in Table 6 was placed in a beaker, and rapidly stirred and mixed at room temperature with a stirrer. 80 ° C with continuous stirring
When it is preheated to (boiling state), it starts boiling by hydrolysis. After boiling for 25 minutes, cool with tap water from outside the beaker. In this state, the silica sol is a slightly viscous liquid.

[Table 6]

(2) Method for Carrying Silica Sol A tube made of an inorganic porous material was immersed in the silica sol to carry the silica sol on the wall of the porous tube. The porous body was placed in an electric furnace, heated to 500 ° C. at a heating rate of 10 ° C., held for 10 minutes, fired, and then cooled to room temperature.
The above operations-were repeated four times.

(3) A sample in which Pd was vapor-deposited on the surface of a porous metal body carrying a silica gel film produced by the above method was produced.

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. H ₂ / N from supply hole 4
A mixed gas of ₂ = 1 (molar ratio) is continuously supplied, bleed gas is discharged from the extraction hole 5, and 9 to 9 from the lower extraction holes 6.
At least 9.99% of pure hydrogen could be obtained.

Table 7 shows the results of experiments at a mixed gas pressure of 3 kg / cm ² G and a gas flow rate of 20 Nl / min at 500 ° C.

[Table 7]

(Example 6) The same ceramic tube (manufactured by NGK Insulators, Ltd.) of Example 1 (average pore diameter: 0.5 μm, outer diameter: 1)
0 mm, length 250 mm), and the following treatment was performed.

(1) Preparation of Silica Sol As a raw material of the silica sol, a chemical having a composition shown in Table 8 was placed in a beaker, and rapidly stirred and mixed at room temperature with a stirrer. Start boiling by hydrolysis. After boiling for 10 minutes, cool with tap water from outside the beaker. In this state, the silica sol is a slightly viscous liquid.

[Table 8]

(2) Method for Carrying Silica Sol A tube made of an inorganic porous material was immersed in the silica sol to carry the silica sol on the wall of the porous tube. The porous body was placed in an electric furnace, heated to 500 ° C. at a heating rate of 10 ° C., held for 30 minutes, fired, and then cooled to room temperature.
The above operations-were repeated four times.

(3) A sample in which Pd was vapor-deposited on the surface of a porous metal body carrying a silica gel film produced by the above method was produced.

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. H ₂ / N from supply hole 4
A mixed gas of ₂ = 1 (molar ratio) is continuously supplied, bleed gas is discharged from the discharge hole 5, and 9 to 9 from the lower discharge holes 6.
At least 9.99% of pure hydrogen could be obtained.

Table 9 shows the experimental results at 500 ° C. at a pressure of the mixed gas of 3 kg / cm ² G and a gas flow rate of 20 Nl / min.

[Table 9]

(Example 7) The same ceramic tube (manufactured by NGK Insulators, Ltd.) as in Example 1 (average pore diameter 0.5 μm, outer diameter 1
0 mm, length 250 mm), and the following treatment was performed.

(1) Preparation of Alumina Sol A chemical having the composition shown in Table 10 was placed in a beaker and hydrolyzed at 80 ° C. for 24 hours while stirring and mixing with a stirrer.

[Table 10]

(2) Method for Carrying Silica-Alumina Gel A ceramic tube was immersed in the alumina sol for 5 minutes to carry the silica sol on the wall of the porous tube. The porous body was immersed in a 0.1 mol / l aqueous solution of sodium silicate for 1 minute. The porous body was kept in steam at 100 ° C. for 1 hour. After repeating the above operations 4 times,
It was immersed in hot water of 90 ° C. for 1 minute.

(3) Using a ceramic tube carrying a silica-alumina gel film produced by the above method,
Further, a sample in which Pd was deposited on the surface was manufactured.

Using this sample, a hydrogen permeation experiment was performed in the same manner as in Example 1. H ₂ / N from supply hole 4
A mixed gas of ₂ = 1 (molar ratio) is continuously supplied, bleed gas is discharged from the discharge hole 5, and 9 to 9 from the lower discharge holes 6.
At least 9.99% of pure hydrogen could be obtained.

Table 11 shows the experimental results at 500 ° C. at a pressure of the mixed gas of 3 kg / cm ² G and a gas flow rate of 20 Nl / min.

[Table 11]

[0067]

As described above, the hydrogen gas separation membrane of the present invention can separate hydrogen from a mixed gas with a high separation performance and a high permeation rate, and the method for producing the hydrogen separation membrane of the present invention is easy. The present invention is industrially useful.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of an experimental apparatus used to demonstrate the performance of the gas separation membrane of the present invention.

Claims (1)

(57) [Claims] 1. A pore size 10~10,000Å of the inorganic porous material having an average pore diameter of 10~30Å in pores silica gel <br/> Le, alumina gel having an average pore diameter of 15~30Å or flat
A hydrogen gas separation membrane comprising a silica-alumina gel having an average pore diameter of 10 to 20 ° and a palladium-containing thin film formed on the surface thereof.