JPH04349926A - Hydrogen gas separation membrane - Google Patents

Abstract

PURPOSE:To obtain a separation membrane having high hydrogen gas separating capacity by supporting a silica gel, an alumina gel or a silica/alumina gel in the pores of an inorg. porous body and forming a membrane containing palladium to the surfaces of the gel layers of said pores. CONSTITUTION:An inorg. porous body such as porous ceramics, porous glass porous pottery or a metallic perforated filter body is immersed in a silica gel, an alumina gel or a silica/alumina gel to support the gel in the pores of the porous body. Next, the inorg. porous body having the silica gel or the like supported thereon is dried and fired at predetermined temp. Subsequently, this fired body is subjected to surface activating treatment and an electroless plating method, a vacuum vapor deposition method, an ion plating method or a gaseous phase chemical reacting method is adapted to the fired body to form a palladium membrane to the surface of the fired body to obtain a hydrogen has separation membrane. When a hydrogen-containing gaseous mixture is brought into contact with one surface of the obtained hydrogen gas separation membrane, the separation membrane permits only hydrogen to selectively transmit and pure hydrogen flows out from the other surface of the separation membrane.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydrogen gas separation membrane for separating hydrogen from a mixed gas.

0002

2. Description of the Related Art A palladium-based membrane (referred to as a Pd membrane) is known as a method for separating hydrogen from a hydrogen-containing mixed gas and obtaining hydrogen with a purity of 99.99% or higher. {Journal of Japan Petroleum Institute, vol. 15, No. 1, (1
972), P64}

[0003] Conventionally, Pd or a Pd-based alloy was stretched to form a thin film, and this film was used while being supported by a support frame. There is a lower limit to the thickness of the membrane that can be obtained by the stretching method, and since this membrane is used while being supported by a support frame, it is necessary to provide it with sufficient mechanical strength to withstand such a support method. If a too thin membrane is used, the membrane is likely to be damaged during use.

As a means of separating a specific gas from a mixed gas by the gas diffusion method, a porous gas separation membrane having pores with a diameter smaller than the mean free path of gas molecules, for example, 10 Å to several 1,000 Å, is used. A separation method using Knudsen diffusion is known. For example, this method is effective for separating H2 gas from mixed gases such as hydrogen (H2)/nitrogen (N2), hydrogen/carbon monoxide (CO), etc., which have relatively large molecular ratios, and is generally used as a gas separation membrane using organic Polymer membranes (polyimide, cellulose acetate, silicone, etc.) are used.

However, such organic polymer films have the disadvantage of poor durability such as heat resistance and chemical resistance.
Attempts have been made to use porous gas separation membranes made of inorganic materials such as porous ceramics, and JP-A-59-59223 proposes a porous gas separation membrane made of such inorganic materials. and is shown as a conventional example.

[0006] Furthermore, 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 JP-A-62-1.
It is shown in Japanese Patent No. 21616.

[0007]

The conventional methods described above each have the following problems. (1) The ratio of permeability coefficients of mixed gases in the Knudsen diffusion separation method is theoretically equal to the square root of the reciprocal of the molecular weight of each gas, so it is quite small and difficult to obtain highly concentrated hydrogen gas.

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

(3) Examples of porous supports made of inorganic materials include porous glass, porous ceramics, and porous metals. Porous glass has very low impact strength and is easily damaged. The average pore diameter of porous ceramics is 0
．． 1 μm or more, and the average pore diameter of porous metals is several tens of μm or more, and in both cases P is used to cover the pores.
The thickness of the d film is several tens of micrometers, and the hydrogen permeation rate is low.

[0010] In view of the above-mentioned technical level, the present invention does not have the problems of conventional separation membranes, has heat resistance and pressure resistance,
The present invention also aims to provide a hydrogen separation membrane having practically satisfactory properties in terms of permeation rate and separation coefficient.

[0011]

[Means for Solving the Problems] The present invention is characterized by supporting silica gel, alumina gel, or silica/alumina gel in the pores of an inorganic porous body, and further forming a thin film containing Pd on the surface of the silica gel, alumina gel, or silica/alumina gel. This is a hydrogen gas separation membrane.

[0012] As the inorganic porous body, porous ceramics,
There are porous glass, porous porcelain, metal perforated filter bodies, metal wire mesh sintered bodies, etc., and any of them can be used in the present invention. However, when the pore size of the inorganic porous material becomes large, the amount of silica gel, alumina gel, or sol that is a precursor of silica/alumina gel is required to be supported, and cracks are likely to occur. The pore diameter is 100 to 10,000.
It is preferable to use an inorganic porous material of about . especially,
Foamed silica, sintered alumina, mullite, etc. with a pore diameter of 1,000 Å or more are preferably used.

Generally, the method for producing silica gel is (1
) A precipitation method from a water glass solution in which a large amount of salts such as NaCl, Na2 SO4, etc. are added to the water glass solution, and the acid is further neutralized to obtain white powdery silica gel. (2) SiCl4 is burned in a stream of steam. SiO2
There is the SiCl4 combustion method (3) in which gas is generated and collected, and the SiO2 vapor condensation method in which SiO2 is evaporated at around 1,700° C. and condensed.

[0014] However, it is extremely difficult to coat the SiO2 particles obtained by these methods into a thin film of about several tens of micrometers and to make it porous with a thickness of about 10 to 30 Å. Therefore, in the present invention, the method disclosed in Japanese Patent Application No. 02-172639 is recommended as a method for obtaining silica gel that is free from the above-mentioned problems and can be formed into a thin film.

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

The average pore diameter of the silica gel produced by this method is 10 to 30 Å, which is a pore diameter that does not provide any resistance to the permeation of H2 having a molecular diameter of 2.3 Å. In addition, since the surface of this silica gel is extremely smooth compared to conventional porous materials, even if a Pd thin film with a thickness of 1 μm or less is supported on this surface, it will not cause pinholes and the H2 permeation rate will increase. greatly improve.

[0017] Generally, there are the following methods for producing alumina gel. (1) Method of hydrolyzing Al alkoxide Isopropoxide prepared by dissolving Al in isopropyl alcohol is often used because it has a low boiling point (140.5°C). Hydrolysis methods include homogeneous phase hydrolysis of alcohol solutions and heterogeneous phase hydrolysis of benzene solutions. (2) Method of hydrolyzing Al salt by adding a catalyst Al salts include Al2 (SO4)O3, AlCl3, A
l(NO3)O3, etc., and the catalysts are nitric acid, N
There are H3 water, Na2 CO3, etc. (3) Method of hydrolyzing alkali aluminate NaAl
Add hydrochloric acid to an O2 aqueous solution to hydrolyze it.

[0018] Alumina gel varies depending on the manufacturing method, but
Pores of approximately 15-30 Å are formed. (Special application 1986-3
No. 4421, patent application No. 180980/1980)

0019
] Furthermore, there are generally the following methods for producing silica/alumina gel. The manufacturing method is to support an alumina sol obtained by hydrolyzing aluminum alkoxide or aluminum chelate, then support an aqueous sodium silicate solution, and then dry and gel after acid treatment. Examples of aluminum alkoxides include aluminum isopropoxide and aluminum-2-butyrate, and examples of aluminum chelates include aluminum tris(
ethyl acetoacetate) and ethyl acetoacetate aluminum diisopropylate.

The average pore diameter of the silica-alumina gel produced by the above method is about 10 to 20 Å. (Special application 1986
-30546)

The following methods can be used to support the Pd thin film. (1) A method of electroless plating (immersion in a solution containing a palladium compound and a reducing agent) after liquid-phase surface activation treatment such as plating (immersion in an aqueous solution of tin chloride and a solution of palladium chloride alternately). and a method of electroplating after electroless plating. (2) Vapor phase methods such as vacuum evaporation, ion plating, and vapor phase chemical reaction (CVD).

The hydrogen gas separation membrane in which the Pd or Pd alloy thin film is formed 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 permeates only hydrogen, and pure hydrogen flows out from the other side of the hydrogen gas separation membrane. .

[0023] The higher the temperature, the greater the hydrogen permeation rate;
Further, the larger the pressure difference between hydrogen on both sides of the hydrogen gas separation membrane, the larger the difference becomes. The preferred operating temperature range of the hydrogen gas separation membrane of the present invention is 200 to 500°C.

[0024] Furthermore, the hydrogen permeation rate is extremely high, 40
100~140c at 0℃ and pressure difference 2kg/cm2
m3/cm2·min, which is 4 to 6 times that of conventional hydrogen separation membranes in which Pd is directly supported on a porous base material.

[0025]

[Operation] The hydrogen gas separation membrane of the present invention has a higher Pd content than the conventional method.
Since the thickness of the thin film is reduced to 1/5 to 1/10, the amount of Pd supported is reduced and the hydrogen permeation rate is also improved, making it possible to significantly downsize the product and, as a result, significantly reduce costs. .

[0026]

【Example】

(Example 1) A ceramic tube manufactured by NGK Insulators (average pore diameter 0.5 μm, outer diameter 10 m
m, length 250 mm), and the following processing was performed.

(1) Preparation of silica sol 1 Place Table 1 in the beaker.
Add the chemical composition shown in the figure below, and stir rapidly with a stirrer at room temperature.
Mixed. When preheated to 80° C. (boiling state) while stirring, an exothermic reaction starts, and the viscosity increases rapidly in about 20 to 25 minutes. The liquids are cooled 15 minutes, 20 minutes, and 25 minutes after the start of boiling, respectively, to obtain liquids 1-A, 1-B, and 1-C. 1-A is a liquid with a slightly high viscosity, and liquid 1-B has an even higher viscosity and becomes a jelly-like liquid when cooled to room temperature. 1
-C liquid The liquid is in a state of being solidified by cooling at room temperature.

[Table 1]

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

(3) Method for supporting silica sol (a) Supporting 1 liquid of silica sol (2) A tube made of an inorganic porous body was immersed in the silica sol 1-A liquid to support the silica sol on the wall of the porous body tube. ■
The porous body was fired for 10 minutes in an electric furnace set at 200°C. (2) Next, the porous body was fired for 10 minutes in an electric furnace set at 300°C. ■ Next, the porous body was
It was fired for 10 minutes in an electric furnace set at 0°C. ■ The above operations from ■ to ■ were repeated twice. (2) Next, the same treatments as (1) to (4) were carried out using liquid 1-B. ■ Next 1
The same treatments as ① to ① were carried out using -C solution.

(b) Supporting two silica sol liquids Next, using two silica sol liquids, the same treatments as in (1) to (4) above were carried out.

[0031] Using the ceramic tube supporting silica gel manufactured by the above method, a sample was manufactured in which Pd was further deposited on the surface under the following conditions. Sample 1: Vapor deposited only Pd Sample 2: Alloy of Pd and silver (Pd:Ag=85:
15 weight ratio)

A hydrogen permeation experiment was conducted using the apparatus shown in FIG. A 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 in an electric furnace. The temperature was measured using thermocouple 8 at the center of the inner tube.

A mixed gas of H2/N2 = 1 (molar ratio) is continuously supplied from the supply hole 4, bleed gas is discharged from the discharge hole 5, and 99.99% or more pure gas is discharged from the lower extraction hole 6. We were able to obtain hydrogen.

Table 2 shows the experimental results at 500° C. with 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 was vapor-deposited on the surface of a porous metal body obtained by randomly stacking and sintering stainless steel fibers, and then heated and diffused in a vacuum to form an ink inside the porous metal body. A porous metal body in which Al was diffused was subjected to oxidation treatment to generate aluminum oxide on the surface of the porous metal body, and the porous metal body was used as a support material, and an alumina gel film was supported within the porous body. The average pore diameter is 1 μm.

(2) Supporting alumina gel membrane 5 g of aluminum isoprooxide was added to 100 g of water maintained at 80° C., and the aluminum isoprooxide was hydrolyzed. Add 0.6ml of concentrated nitric acid to this and
The mixture was kept at ℃ for 24 hours and peptized to obtain an alumina sol. After immersing the porous metal in this alumina sol for 5 minutes, it was dried at room temperature for 24 hours, dried at 80°C for 2 hours, and then further dried for 3 hours.
It was fired at 50°C for 2 hours and at 600°C for 2 hours. This operation was repeated four times to support alumina gel within the porous metal body.

Next, aluminum isoprooxide is dissolved in a weight ratio of 5 parts to 100 parts of trichlene, and the porous metal filled with alumina is impregnated with this solution. Prooxide was precipitated. Next, one side of this porous metal was placed in steam at 100°C under reduced pressure to hydrolyze aluminum isoprooxide, dried at room temperature, and heated to 35°C.
It was fired at 0°C for 2 hours and then at 600°C for 1 hour. This operation was repeated three times.

The average pore distribution of the alumina gel-supported porous metal produced by the above procedure was 16 Å.

[0039] A porous metal body supporting an alumina gel film produced by the above method was used, and P was further applied to the surface of the porous metal body.
A sample was prepared by vapor-depositing d.

Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. From supply hole 4 H2 /
A mixed gas of N2 = 1 (molar ratio) was continuously supplied, bleed gas was discharged from the discharge hole 5, and 99.99% or more pure hydrogen could be obtained from the lower extraction hole 6.

Table 3 shows the experimental results at 500° C. with 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 vapor-deposited on the surface of a porous metal body obtained by laminating and sintering wire mesh, and then heated and diffused in a vacuum to diffuse Al into the porous metal body, which was then oxidized. A separation membrane was manufactured by using a metal porous body treated to generate aluminum oxide on the surface of the metal porous body as a support material and supporting a silica gel membrane on the surface of the porous body in the same manner as in Example 1. . Wire mesh: Diameter 0.5μm Material: SUS 304

[0043] A porous metal body supporting a silica gel film prepared by the above method was used, and Pd was further applied to the surface of the porous metal body.
A sample was prepared by vapor-depositing.

[0044] Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. From supply hole 4 H2 /
A mixed gas of N2 = 1 (molar ratio) was continuously supplied, bleed gas was discharged from the discharge hole 5, and 99.99% or more pure hydrogen could be obtained from the lower extraction hole 6.

Table 4 shows the experimental results at 500° C. with 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 supporting the silica gel film manufactured by the method of Example 1 was used, and Pd was further supported on its surface by electroless plating.

[0047] Electroless plating was carried out under the following conditions. 1) Reagent Tetraamminepalladium(II) chloride [Pd(NH3
)4]Cl2 ・H2 ONH3 (28% aqueous solution)
2) Conditions Temperature = 50°C, pH = 12

Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. The experimental results are shown in Table 5.

[Table 5]

(Example 5) The same Japanese insulator as in Example 1 (
Ceramic tube made by Co., Ltd. (average pore diameter 0.5 μm, outer diameter 10
mm, length 250 mm), and the following processing was performed.

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

[Table 6]

(2) Method for supporting silica sol (2) A tube made of an inorganic porous material was immersed in the silica sol, and the silica sol was supported on the wall of the porous tube. ■ The porous body was placed in an electric furnace and heated to 500°C at a heating rate of 10°C.
After firing by holding for 0 minutes, the temperature was lowered to room temperature. ■ The above operations from ■ to ■ were repeated four times.

(3) Using the metal porous body supporting the silica gel film manufactured by the above method, a sample was manufactured in which Pd was further deposited on the surface of the metal porous body.

Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. From supply hole 4 H2 /
A mixed gas of N2 = 1 (molar ratio) was continuously supplied, bleed gas was discharged from the extraction hole 5, and 99.99% or more pure hydrogen could be obtained from the lower extraction hole 6.

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

[Table 7]

(Example 6) The same Japanese insulator as in Example 1 (
Ceramic tube made by Co., Ltd. (average pore diameter 0.5 μm, outer diameter 10
mm, length 250 mm), and the following processing was performed.

(1) Preparation of silica sol As raw materials for silica sol, chemicals having the composition shown in Table 8 were placed in a beaker and rapidly stirred and mixed with a stirrer at room temperature. Boiling starts due to hydrolysis. After boiling for 10 minutes, cool the beaker with tap water from the outside. In this state, silica sol is a slightly viscous liquid.

[Table 8]

(2) Method for supporting silica sol (2) A tube made of an inorganic porous material was immersed in the silica sol, and the silica sol was supported on the wall of the porous tube. ■ The porous body was placed in an electric furnace and heated to 500°C at a heating rate of 10°C.
After firing by holding for 0 minutes, the temperature was lowered to room temperature. ■ The above operations from ■ to ■ were repeated four times.

(3) A sample was manufactured using the metal porous body supporting the silica gel film produced by the above method, and further having Pd deposited on its surface.

Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. From supply hole 4 H2 /
A mixed gas of N2 = 1 (molar ratio) was continuously supplied, bleed gas was discharged from the discharge hole 5, and 99.99% or more pure hydrogen could be obtained from the lower extraction hole 6.

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

[Table 9]

(Example 7) The same Japanese insulator as in Example 1 (
Ceramic tube made by Co., Ltd. (average pore diameter 0.5 μm, outer diameter 10
mm, length 250 mm), and the following processing was performed.

(1) Preparation of alumina sol Table 1 was prepared in a beaker.
A chemical having the composition shown in 0 was added and hydrolyzed at 80° C. for 24 hours while stirring and mixing with a stirrer.

[Table 10]

(2) Method for supporting silica/alumina gel■
The ceramic tube was immersed in the alumina sol for 5 minutes to support the silica sol on the porous tube wall. (2) The porous body was immersed in a 0.1 mol/l aqueous sodium silicate solution for 1 minute. ■ The porous body was immersed in water vapor at 100°C for 1 hour.
Holds time. (2) After repeating the above operations (1) to (2) four times, the sample was immersed in hot water at 90°C for 1 minute.

(3) Using the ceramic tube supporting the silica/alumina gel film manufactured by the above method,
Furthermore, a sample was fabricated with Pd deposited on its surface.

[0065] Using this sample, a hydrogen permeation experiment was conducted in the same manner as in Example 1. From supply hole 4 H2 /
A mixed gas of N2 = 1 (molar ratio) was continuously supplied, bleed gas was discharged from the discharge hole 5, and 99.99% or more pure hydrogen could be obtained from the lower extraction hole 6.

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

[Table 11]

[0067]

[Effects of the Invention] The hydrogen gas separation membrane of the present invention has high separation performance and can separate hydrogen from a mixed gas at a high permeation rate, and furthermore, the method for manufacturing the hydrogen separation membrane of the present invention is easy. , the present invention is industrially useful.

[Brief explanation of the drawing]

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

Claims (1)

[Claims] 1. A hydrogen gas separation membrane characterized by supporting silica gel, alumina gel, or silica/alumina gel in the pores of an inorganic porous body, and further forming a thin film containing palladium on the surface of the membrane.