JP2009291740A - Hydrogen separation member and hydrogen generating apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen separation member having excellent efficiency of hydrogen purification, excellent hydrogen permeability and excellent resistance to hydrogen embrittlement, and to provide a hydrogen generating apparatus. <P>SOLUTION: The hydrogen separation member includes a hydrogen separation metal film and a metal porous material arranged adjacently on at least one side of the hydrogen separation metal film, and a catalyst for modification of a fuel is supported in pores of the metal porous material. The hydrogen separation metal film and the metal porous material are preferably adhered to each other. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a hydrogen separation member used in high-purity hydrogen production and purification equipment, and the like, and relates to a hydrogen separation member excellent in efficiency of hydrogen purification reaction, hydrogen permeability and hydrogen embrittlement resistance, and a hydrogen production apparatus using the same.

  Since hydrogen, which is a fuel for fuel cells, does not exist by nature, it is artificially produced. Currently, steam reforming reaction such as natural gas (methane) is used for the production of hydrogen. The steam reforming reaction is to obtain hydrogen using a chemical reaction such as the following formula 1.

In this method, impurity gases such as CO, CO ₂ and H ₂ O are generated simultaneously with hydrogen. In particular, CO poisons fuel cell electrodes. In order to use hydrogen obtained by fossil fuel reforming in fuel cells, hydrogen must be separated and purified from these impurity gases to achieve high purity. I must.

  As a technique for extracting only hydrogen from a mixed gas generated by a fuel reforming reaction, a purification method using a hydrogen separation metal membrane is known. The amount of hydrogen that permeates the hydrogen separation metal membrane is expressed by the following formula 2. That is, the pressure difference applied to the hydrogen separation metal membrane is large, and the thinner the hydrogen separation metal membrane is, the more hydrogen is permeated.

(Where J: hydrogen permeation flux, Φ: hydrogen permeation coefficient, P _u : membrane upstream pressure, P _d : membrane downstream pressure, L: film thickness.)

  In the fuel reforming reaction, if only hydrogen can be removed, the equilibrium shifts to the right according to Le Chatelier's law. Therefore, a higher conversion rate can be obtained, and by reducing the reaction temperature, energy loss can be suppressed and the hydrogen production cost can be reduced.

  For that purpose, a fuel reforming catalyst is supported on a porous member, a fuel gas is introduced into the porous member to obtain a mixed gas containing hydrogen, and only hydrogen in the mixed gas is obtained by a hydrogen separation member that selectively separates only hydrogen. A technique (for example, Patent Document 1) for taking out the image is known.

JP 2002-126519 A

  In general, since the strength of a hydrogen separation metal membrane decreases as it becomes thinner, there is a problem that membrane breakage tends to occur when a large pressure difference is applied. That is, the method of thinning the hydrogen separation metal membrane to increase the hydrogen separation rate is contradictory to the method of increasing the pressure difference.

  Moreover, in the above-mentioned conventional technology aiming at high efficiency of the fuel reforming reaction, ceramic is used as the hydrogen separation layer, so the hydrogen separation / purification ability is low, and sufficiently high-purity hydrogen cannot be obtained. Hydrogen cannot be directly introduced into the fuel cell. In addition, in order to compensate for this, a layer that adsorbs other than hydrogen is provided, but this causes a pressure loss, resulting in a decrease in the hydrogen separation rate, resulting in a problem that the efficiency of the hydrogen production reaction is not sufficiently increased.

  Furthermore, both the fuel reforming reaction and the hydrogen purification using the hydrogen separation metal membrane are performed in a temperature environment of about 100 to 500 ° C. For this reason, it has been necessary for the hydrogen generator to have a structure that can efficiently supply heat to the catalyst that serves as the reaction field for fuel reforming and the hydrogen separation metal membrane that serves as the hydrogen purification field.

  Therefore, the present invention solves the above problems, increases the efficiency of the hydrogen production reaction, speeds up the hydrogen separation rate, and easily obtains high-purity hydrogen, and a hydrogen production device using the same The purpose is to provide.

  The inventors of the present invention have made extensive efforts to use a hydrogen separation metal membrane for the hydrogen separation layer, a metal porous body as the porous member, and a catalyst for fuel reforming to be supported in the pores of the metal porous body. Thus, the inventors have found that the above-mentioned problem can be solved by making both adjacent.

  That is, the hydrogen separating member of the present invention is a hydrogen separating metal membrane and a hydrogen separating member in which a metal porous body is adjacent to at least one surface of the hydrogen separating metal membrane. The catalyst is supported.

  According to this configuration, the hydrogen separation metal film and the metal porous body are brought into close contact with each other, whereby the hydrogen separation metal film can be reinforced and further thinning can be performed, so that the hydrogen separation rate can be improved. Further, since the fuel reforming catalyst is supported on the metal porous body, the surface area provided for the fuel reforming reaction is increased and the reaction efficiency of the fuel reforming is increased. In addition, the hydrogen separation metal membrane has a higher hydrogen separation ability than ceramic-based ones, and it is not necessary to provide an adsorption layer between the porous metal body, so the gas flows through the hydrogen separation metal membrane without causing pressure loss. Hydrogen separation can be performed well. Furthermore, since hydrogen is quickly removed from the fuel reforming reaction system, the fuel reforming reaction can be further improved in efficiency. Further, in the hydrogen production apparatus using the hydrogen separation member, since the metal porous body serves as a medium for heat transfer, a fuel reforming catalyst supported on the metal porous body, a hydrogen separation metal membrane closely attached to the metal porous body, It becomes possible to quickly supply the heat necessary for the operation.

  In the hydrogen separation member configured as described above, the hydrogen separation metal film is mainly composed of Pd, V, Nb, Ta, Zr, Ni, Ti metal films, or two or more of Pd, V, Nb, Ta, Zr, Ni, Ti. An alloy film as a component can be used. Further, a catalyst layer for promoting a reaction of dissociating hydrogen molecules into atoms or recombining hydrogen atoms with hydrogen molecules can be provided on the surface of the hydrogen separation metal film.

  As the metal porous body having the above structure, Ni or Ni-base alloy, Cu or Cu-base alloy, Al or Al-base alloy, or stainless steel can be used.

  The metal porous body preferably has a porosity of 30% to 90%. The reason for limiting the porosity is that when the porosity is less than 30%, the pressure loss is large and the hydrogen separation rate decreases, and conversely, when the porosity is more than 90%, it is sufficient for fuel reforming. This is because the amount of catalyst cannot be supported and the efficiency of the fuel reforming reaction is lowered.

  The hydrogen separation metal membrane and the metal porous body can be used while being adhered to each other. As a bonding method, welding, rolling bonding, or a brazing material suitable for the material of the hydrogen separation metal film and the metal porous body can be used.

  The hydrogen separation metal membrane preferably has a thickness of 0.1 μm to 1 mm. Since the hydrogen separation metal membrane has a hydrogen separation rate that is inversely proportional to the thickness, a sufficient hydrogen separation rate cannot be obtained when the thickness exceeds 1 mm. On the other hand, if the thickness is less than 0.1 μm, pinholes are likely to occur during the production of the film, resulting in a problem that it is difficult to obtain high-purity hydrogen. The preferred thickness is 0.3 μm or more and 500 μm or less, and more preferably 1 μm or more and 300 μm or less.

  The fuel used for the fuel reforming reaction is not particularly limited as long as it is a substance containing hydrogen. For example, fossil fuels such as gasoline, kerosene, light oil and natural gas, organic compounds such as methane, propane, dimethyl ether, methanol, ethanol, propanol, butanol, methylcyclohexane, decalin and methyldecalin, and inorganic compounds such as ammonia and hydrazine. Can be used.

  As the catalyst used in the fuel reforming reaction, an appropriate catalyst can be used according to the fuel. For example, Pt or Pt base alloy, Pd or Pd base alloy, Ni or Ni base alloy, Cu or Cu base alloy.

  By reinforcing the hydrogen separation metal membrane with a metal porous body, the hydrogen separation metal membrane can be made thin and the pressure applied to the membrane can be increased, and as a result, high speed hydrogen separation can be achieved. Furthermore, by supporting a catalyst for fuel reforming on the metal porous body, the efficiency of the fuel reforming reaction is improved, and a high-purity hydrogen can be easily obtained at high speed by a synergistic effect with the above effect. A member could be provided. Furthermore, since the fuel reforming reaction and the hydrogen separation can be performed with a single member, the hydrogen generator utilizing the present invention can be downsized.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

(Example 1)
In the practice of the present invention, a Pd membrane (thickness 1 μm to 1 mm) as a hydrogen separation metal membrane, a SUS316 metal porous body (porosity 60%), and a commercially available Ni-based catalyst were used. First, after a Ni-based catalyst was dispersed in ethanol, this dispersion was impregnated with a metal porous body, and after drying, a heat treatment was performed at 400 ° C. × 1 h to prepare a metal porous body 2 carrying the catalyst. The Pd membrane 1 was sandwiched between the metal porous body 2 supporting the catalyst and the metal porous body 3 not supporting the catalyst to form a hydrogen separation member. A hydrogen production device shown in FIG. 1 was produced using the produced hydrogen separation member.

A pipe shown in FIG. 2 was connected to this hydrogen generator, and a fuel reforming reaction was performed. The fuel was CH ₄ , and the reaction conditions were an S / C ratio of 2.5, a reaction temperature of 500 ° C., and a reaction pressure of 0.8 MPa. Using the gas chromatograph 12 and the mass flow meter 10, the reaction efficiency of the fuel reforming reaction, the hydrogen separation rate, and the purity of the obtained hydrogen were measured. Table 1 shows the results. Here, the reaction efficiency was calculated from the concentrations of CH ₄ , CO and CO ₂ remaining after the reaction in the above formula 1. The hydrogen separation rate indicates the ratio obtained as high-purity hydrogen among the hydrogen produced by the reforming reaction. The hydrogen generator has a port for discharging only hydrogen and a port for discharging remaining impurity gas as gas discharge ports, and a hydrogen separation member is present so as to close the hydrogen discharge port. For this reason, when the hydrogen permeation speed of the hydrogen separation member is slow, the generated hydrogen is also discharged from the impurity gas outlet. That is, the high hydrogen separation rate indicates that the hydrogen permeation rate of the hydrogen separation member is sufficiently high. The yield is a product of reaction efficiency and hydrogen separation rate.

(Comparative Example 1)
A hydrogen separation member was obtained by sandwiching a Pd membrane, which is a hydrogen separation membrane, with a metal porous body (porosity 60%) made of SUS316 that does not carry a catalyst. A Ni-based catalyst was mixed with ethanol to form a slurry, which was degreased by heating at 400 ° C. × 1 h after pressure molding to form a catalyst mass. As shown in FIG. 3, the catalyst mass 6 was installed in the reaction tank 4 and the hydrogen separation member was installed in the purification tank 5 to produce a hydrogen production device. In addition, the same member as Example 1 is shown with the same number. The piping shown in FIG. 2 was connected to this hydrogen generator, and a fuel reforming reaction was performed in the same manner as in Example 1. The results are shown in Table 1. It can be seen that Example 1 significantly improves both the reaction efficiency and the hydrogen separation rate as compared with Comparative Example 1. In the case of the configuration as shown in Comparative Example 1, since the steam reforming of CH ₄ is usually performed at 800 ° C. or higher, the present invention can achieve high efficiency of the fuel reforming reaction and high speed of hydrogen separation. It was.

(Comparative Examples 2 and 3)
As the SUS316 porous metal body, those having a porosity of 25% and those having a porosity of 95% were used, and a hydrogen separation member and a hydrogen production device were produced in the same manner as in Example 1. The fuel reforming reaction was performed in the same manner as in Example 1 by connecting the pipe shown in FIG. Compared to Example 1, it can be seen that in Comparative Example 2, both the reaction efficiency and the hydrogen separation rate are reduced. In the configuration of Comparative Example 2, the pressure loss is increased due to the reduced porosity of the metal porous body. For this reason, the fuel gas supply rate is reduced and the fuel reforming reaction rate is lowered, and the flow of the generated gas is hindered and the hydrogen permeation rate is also lowered. In Comparative Example 3, the reaction efficiency is greatly reduced, but it can be seen that almost all of the hydrogen produced by the reaction can be separated. This is because, in Comparative Example 3, the porosity was too high, so that a sufficient amount of catalyst for carrying out an efficient reaction could not be supported.

(Comparative Example 4)
A Pd film having a thickness of 0.08 μm was produced by sputtering on one side of a porous metal body 2 carrying a catalyst produced in the same manner as in Example 1. A hydrogen separation member was prepared by adhering to the other side of the Pd membrane with a metal porous body 1 made of SUS316 not supporting a catalyst. The produced hydrogen separation member was subjected to a hydrogen production device in the same manner as in Example 1. The fuel reforming reaction was performed in the same manner as in Example 1 by connecting the pipe shown in FIG. Compared with Example 1, in Comparative Example 4, both the reaction efficiency and the hydrogen separation rate are higher than in Example 1, but it can be seen that impurity gas is present in the obtained hydrogen and the purity is low. This means that CO, CO ₂ or the like that does not permeate the hydrogen separation metal membrane is contained in the purified gas, and is a result indicating that pinholes exist in the hydrogen separation metal membrane.

(Comparative Example 5)
Using a Pd membrane with a thickness of 1.2 mm, a hydrogen separation member and a hydrogen production device were produced in the same manner as in Example 1. The fuel reforming reaction was performed in the same manner as in Example 1 by connecting the pipe shown in FIG. It can be seen that both the reaction efficiency and the hydrogen separation rate are reduced. Since the permeation rate of hydrogen through the hydrogen separation metal membrane is expressed by the above equation 2, it is considered that such a result is due to an increase in the thickness of the hydrogen separation metal membrane.

(Example 2)
An Nb alloy film (composition: Ni ₃₀ Nb ₄₀ Ti ₃₀ , thickness: 50 μm) was prepared, and a Pd layer (thickness: 0.1 μm) was provided as a catalyst on both surfaces of the film by sputtering. It was. In the same manner as in Example 1, a metal porous body 2 supporting a catalyst on one surface of the hydrogen separation metal membrane and a metal porous body 3 not supporting a catalyst on the other surface are bonded to form a hydrogen separation member, And a hydrogen generator was made.

(Comparative Example 6)
An Nb alloy film (composition: Ni ₃₀ Nb ₄₀ Ti ₃₀ , thickness: 50 μm) is prepared, and a Pd layer (thickness: 0.1 μm) is provided by sputtering on both surfaces of the film as a catalyst, thereby producing a hydrogen separation metal film did. A Ni-based catalyst mass was prepared in the same manner as in Comparative Example 1. As shown in FIG. 4, a hydrogen separation membrane and a catalyst lump were installed in the pipe to produce a hydrogen production device.

The piping shown in FIG. 2 was connected to the hydrogen generators of Example 2 and Comparative Example 6, and a fuel reforming reaction was performed. The fuel was CH ₄ , the reaction conditions were an S / C ratio of 2.5, and a reaction temperature of 500 ° C. Using the gas chromatograph 12 and the mass flow meter 10, the reaction efficiency of the fuel reforming reaction for each reaction pressure, the hydrogen separation rate, and the purity of the obtained hydrogen were measured. The results are shown in FIGS. The purity of the hydrogen obtained does not change in either Example 2 or Comparative Example 6, but it can be seen that Example 2 is superior in reaction efficiency and hydrogen separation rate. When the reaction pressure reached 0.6 MPa, cracks were observed in the hydrogen separation membrane of Comparative Example 6, but the hydrogen separation membrane of Example 2 was not cracked even when the reaction pressure was 0.9 MPa. This result shows that the hydrogen separation membrane is reinforced by the metal porous body.

(Example 3)
In order to measure the temperature distribution in the hydrogen generator, a Pd membrane (thickness: 100 μm) as a hydrogen separation metal membrane was prepared in the same manner as in Example 1, and a porous metal body made of SUS316 carrying a catalyst. And a metal porous body 3 not supporting a catalyst, a model device of a hydrogen production device as shown in FIG. 8 was produced.

(Comparative Example 7)
A Pd membrane (thickness: 100 μm) as a hydrogen separation metal membrane was prepared in the same manner as in Example 1, and a metal porous mass 2a made of SUS316 carrying a catalyst and a metal porous mass 3a not carrying a catalyst were used. As a result, a model device of a hydrogen generator as shown in FIG. 9 was produced. The weights of the metal porous body 2a carrying the catalyst and the metal porous body 2b not carrying the catalyst were adjusted so as to be equal to the respective metal porous bodies 2 and 3 of Example 3.

  Hydrogen of 0.1 MPa was sealed in the model devices of Example 3 and Comparative Example 7. Thereafter, the model device was placed in an electric furnace and heated. After the temperature in the electric furnace reaches a predetermined temperature, the temperature in the vicinity of the porous metal body 2 and the porous metal body 2a (measurement points A and B) supporting the catalyst in the model device and the vicinity of the hydrogen separation metal membrane (measurement) The temperature at point C) was measured. The results are shown in FIG. In Comparative Example 7, the heat applied from the electric furnace is transmitted through the internal hydrogen to heat the catalyst and the hydrogen separation metal membrane, and the hydrogen separation metal membrane is heated by the heat transmitted from the outer wall of the container. On the other hand, in Example 3, in addition to the above heat conduction, both the catalyst and the hydrogen separation metal membrane are also heated by the heat transmitted from the metal porous body. Since the metal generally has a higher thermal conductivity than the gas, Example 3 can reach the target reaction temperature more quickly.

Example 4
Using a Pd membrane (thickness: 100 μm) as a hydrogen separation metal membrane, a SUS316 catalyst-supported metal porous body produced in the same manner as in Example 1, and a SUS316 metal porous body not supporting a catalyst, shown in FIG. A vessel was made.

It is a schematic diagram of the hydrogen production device using the hydrogen separation member of the present invention. It is a schematic diagram of piping for performing a fuel reforming reaction. It is a schematic diagram of the hydrogen production device of Comparative Examples 1-5. 6 is a schematic diagram of a hydrogen generator produced in Comparative Example 6. FIG. It is the figure which showed the reaction efficiency in Example 2 and Comparative Example 6 with respect to the reaction pressure. It is the figure which showed the hydrogen separation rate in Example 2 and Comparative Example 6 with respect to the reaction pressure. It is the figure which showed the purity of the hydrogen obtained in Example 2 and Comparative Example 6 with respect to the reaction pressure. 6 is a schematic diagram of a model device of a hydrogen production device produced in Example 3. FIG. 10 is a schematic diagram of a model device of a hydrogen production device produced in Comparative Example 7. FIG. It is the figure which showed the temperature in the model machine in Example 3 and Comparative Example 7 with respect to the temperature of an electric furnace. 6 is a schematic diagram of a hydrogen production device produced in Example 4. FIG.

Explanation of symbols

1: Hydrogen separation metal membrane 2: Metal porous body supporting catalyst 3: Metal porous body not supporting catalyst 4: Reaction tank 5: Purification tank 6: Catalyst lump 7: Fuel supply pump 8: Steam supply tank 9: Hydrogen production Apparatus 10: Mass flow meter 11: Four-way valve 12: Gas chromatograph 13: Thermocouple

Claims (5)

A hydrogen separation metal membrane and a hydrogen separation member having a metal porous body adjacent to at least one surface of the hydrogen separation metal membrane, and a catalyst for fuel reforming is supported in the pores of the metal porous body. A hydrogen separation member. The hydrogen separation member according to claim 1, wherein the hydrogen separation metal membrane and the metal porous body are bonded to each other. The hydrogen separation member according to claim 1, wherein the hydrogen separation metal membrane has a thickness of 0.1 μm or more and 1 mm or less. The hydrogen separation member according to any one of claims 1 to 3, wherein the porous metal body has a porosity of 30% or more and 90% or less. A hydrogen generator using the hydrogen separation member according to claim 1.