JP6093985B2 - Hydrogen separation membrane treatment method and hydrogen separation method - Google Patents

Description

  The present invention relates to a method for treating a hydrogen separation membrane, and more particularly to a method for oxidizing and removing organic substances on the surface of a hydrogen separation membrane not provided with a Pd-based surface layer. The present invention also relates to this hydrogen separation membrane and a hydrogen separation method using the same.

  Hydrogen separation membranes made of metal membranes are already used in industrial hydrogen purification, etc., and are expected to be applied to the separation of hydrogen contained in reformed gases and reaction gases such as city gas, petroleum, and coal. And development is ongoing. The permeation phenomenon of hydrogen into a hydrogen separation membrane made of metal is caused by the dissociation and solid solution of hydrogen on the surface of the introduction gas side, diffusion between the hydrogen separation membranes, recombination and desorption on the surface of the permeation side. It goes through a separation process. For this reason, when hydrogen permeates selectively and there is no defect in the hydrogen permeable membrane, the hydrogen purity on the permeate side becomes ultra high purity of 9N (99.99999%) or higher. Conventionally, it has been considered that Pd having catalytic activity is necessary in the surface process of hydrogen dissociation and recombination. When a Pd-based alloy is used as the separation membrane itself or when a non-Pd-based hydrogen separation membrane is used, Pd A surface thin film layer (coating metal film) has been considered necessary. This surface layer is usually formed very thin to about several hundred nm so as not to deteriorate the hydrogen permeation performance of the base metal layer.

  As a separation membrane prepared by coating a Pd surface layer on the surface of a base membrane made of a group 5A metal having a high hydrogen permeation performance and a low raw material cost compared to a Pd-based alloy, Patent Document 1 (Japanese Patent Laid-Open No. 11-276866) A hydrogen separation membrane is described in which a surface layer made of Pd or Pd alloy is provided on both sides of a metal base membrane (Nb, Ta, V or its alloy membrane) having high hydrogen permeation performance.

  Patent Document 2 (WO2012 / 039283A1) describes a hydrogen separation membrane in which Pd or Pd alloy layers are provided on both surfaces of a V alloy membrane containing W and Mo.

  In a non-Pd-based hydrogen separation membrane in which a Pd-based surface layer is provided on the surface of the base alloy layer, if hydrogen separation is continued at 400 to 600 ° C., the components of the base alloy layer and the Pd of the surface layer diffuse to each other. The hydrogen permeation performance of the membrane gradually decreases. Moreover, Pd is expensive.

  Patent Document 3 (Japanese Patent Laid-Open No. 2013-215717) describes a hydrogen separation membrane made of a group 5A metal or an alloy thereof and having no surface layer of Pd or Pd alloy on the surface. Further, paragraph 0021 of Patent Document 3 describes that the hydrogen separation membrane is heat-treated in an air atmosphere to oxidize and remove organic substances attached to the hydrogen separation membrane.

JP-A-11-276866 WO2012 / 039283A1 JP2013-215717A

  An object of the present invention is to provide a hydrogen separation membrane having a high hydrogen permeation rate and not having a surface layer of Pd or Pd alloy, a treatment method thereof, and a hydrogen separation method using the hydrogen separation membrane.

  The method for treating a hydrogen separation membrane of the present invention comprises heating a hydrogen separation membrane made of a group 5A metal or an alloy thereof and having no surface layer of Pd or Pd alloy on the surface in an oxygen-containing gas atmosphere. In the method for treating a hydrogen separation membrane in which organic substances adhering to the surface are removed by oxidation, the nitrogen concentration in the oxygen-containing gas atmosphere is 0.5 mol% or less.

  In one embodiment of the present invention, the hydrogen separation membrane is installed in a hydrogen separator, and the heat treatment in the oxygen-containing atmosphere is performed prior to a hydrogen separation operation by the hydrogen separator.

  The hydrogen separation method of the present invention is characterized in that hydrogen is separated from a hydrogen-containing gas by a hydrogen separation membrane treated by the treatment method of the present invention.

  The hydrogen separation membrane of the present invention is a hydrogen separation membrane made of a group 5A metal or an alloy thereof and having no surface layer of Pd or Pd alloy on the surface, and is substantially free of nitrogen. is there.

  In the method for treating a hydrogen separation membrane of the present invention, an oxygen-containing atmosphere having a nitrogen concentration of 0.5 mol% or less, preferably a hydrogen separation membrane made of a group 5A metal or an alloy thereof and having no surface layer of Pd or Pd alloy on the surface, preferably Oxidizes and removes organic matter by heat treatment in an oxygen atmosphere. As described above, when the hydrogen separation membrane is processed in an oxygen-containing atmosphere with a low nitrogen concentration, the organic matter is oxidized and removed without generating nitride near the surface of the hydrogen separation membrane. Thus, it was recognized that the hydrogen separation membrane from which organic substances were oxidized and removed without formation of nitride had a higher hydrogen permeation rate than the hydrogen separation membrane from which nitride was generated.

In the hydrogen separation membrane of the present invention, since the Pd or Pd alloy surface layer is not provided on the surface of the group 5A metal membrane, the following effects are obtained.
(1) It is possible to reduce the production cost of the hydrogen separation membrane by reducing the amount of expensive Pd used and omitting the Pd surface layer deposition process.
(2) Since the mutual diffusion of the components of Pd and the base alloy layer does not occur, the hydrogen separation performance of the 5A group metal membrane having high hydrogen separation performance does not decrease, and the durability can be improved.
(3) Although it is necessary to reduce the thickness of the membrane in order to improve the hydrogen permeation performance, the processability is improved compared to a hydrogen separation membrane having a Pd-based surface layer, and the film is formed on a porous support that supports the membrane. Will also be easier.

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  Hereinafter, the present invention will be described in detail.

  The hydrogen separation membrane of the present invention is made of a group 5A metal or an alloy thereof and does not have a surface layer of Pd or Pd alloy on the surface.

  V, Nb, and Ta are suitable as the Group 5A metal, and the alloy may be any of Nb alloy, V alloy, Ta alloy, and the like. The alloy may be an alloy of 5A group metals, and W, Mo, Cr, Mn, Fe, Co, Ni, Ru, Rh, Pd, Re, Os, other than 5A group and other than 5A group. An alloy with at least one alloy element such as Ir, Pt, Ti, Zr, Hf, and Al may be used. The content of alloy elements other than Group 5A is preferably 30 mol% or less, particularly preferably 15 mol% or less.

  The group 5A metal or alloy film thereof can be produced by melting the group 5A metal or alloy thereof and rolling it to a thickness of preferably 1 to 600 μm, particularly preferably 50 to 200 μm. In addition, you may employ | adopt means other than rolling for thin film formation. Further, the hydrogen separation membrane of the present invention may be formed on the surface of the air-permeable support material by a film forming method such as sputtering, CVD, or plating to have a thickness of 1 to 100 μm, particularly about 1 to 20 μm. .

  The hydrogen separation membrane of the present invention is not provided with a surface layer of Pd or a Pd-based alloy on the surface. This hydrogen separation membrane is made of a group 5A metal or an alloy thereof, but a 5A group metal having a thickness of about 1000 to 1500 nm is formed on the surface of the hydrogen separation membrane by heat treatment in an oxygen-containing gas atmosphere described below. An oxide layer is formed.

  In order to oxidize and remove organic substances adhering to the surface of the hydrogen separation membrane, the hydrogen separation membrane is preferably 100 ° C. or higher, particularly preferably 200 ° C. or higher, preferably 800 ° C. or lower, particularly preferably 600 ° C. or lower. Heat treatment is performed in an oxygen-containing gas atmosphere of 5 mol% or less to oxidize and remove organic substances. The oxygen-containing gas is preferably oxygen gas, but may be oxygen-enriched air or a gas obtained by adding a rare gas such as helium to oxygen.

  In this way, by subjecting the hydrogen separation membrane to heat treatment in an oxygen-containing gas atmosphere, organic substances adhering to the surface of the hydrogen separation membrane are oxidized and removed. In the present invention, since the nitrogen concentration in the oxygen-containing gas is low or does not contain nitrogen, no or almost no nitride is generated in the hydrogen separation membrane. Presumably, the formation of nitrides in this way increases the hydrogen permeation rate of the hydrogen separation membrane.

  When said heat processing temperature is lower than 100 degreeC, there exists a possibility that the oxidation process of organic substance may become inadequate. When the heat treatment temperature is higher than 800 ° C., the thickness of the oxide layer on the surface of the hydrogen separation membrane tends to be excessively large. The contact time between the oxygen-containing gas and the hydrogen separation membrane is effective for several seconds to 10 seconds, and the longer the time, the more easily the oxide layer becomes thicker.

  As a hydrogen separation apparatus equipped with a hydrogen separation membrane, the hydrogen separation membrane is installed in a container called a housing, casing, vessel or the like, and has a primary chamber and a secondary chamber separated by a hydrogen separation membrane. The structure is not particularly limited as long as it further has heating means as required. The form of the film may be any form such as a flat film type and a cylindrical type. The hydrogen separation membrane may be superimposed on a porous support or a support plate having a groove on the surface, or may be formed on the surface of the porous body. As a porous body, any of a metal material, a ceramic material, etc. may be sufficient.

  At the start of the operation of the hydrogen separator, an oxygen-containing gas having a nitrogen concentration of 0.5 mol% or less is introduced into the hydrogen separator before supplying the raw material hydrogen gas after the temperature of the hydrogen separator is increased. It is preferable to oxidize and remove the adhering organic matter.

  The operating temperature (specifically, the gas temperature on the primary side) of the hydrogen separator is usually about 300 to 700 ° C., particularly about 400 to 600 ° C., although it depends on the composition of the membrane.

  In the present invention, hydrogen gas of about 2N (99%) to 7N (99.99999%) is permeabilized to produce ultra-high purity hydrogen gas of more than 7N, particularly 9N (99.9999999%) or more. Is preferred. Such ultra-high purity hydrogen gas is suitable for use in semiconductor manufacturing processes and the like. However, the present invention is not limited to this, and can be used for the purpose of separating hydrogen from various hydrogen-containing gases.

  Hereinafter, examples and comparative examples will be described.

[Example 1]
Pure V was rolled to produce a hydrogen separation membrane having a thickness of 202 μm and a diameter of 12 mm. This hydrogen separation membrane was installed in a hydrogen permeation rate measuring apparatus, and was subjected to heat treatment according to the following procedure, and then the hydrogen permeation rate was measured.
[Heat treatment method]
(1) Heat from room temperature to 550 ° C. in 30 minutes while evacuating.
(2) Oxygen (oxygen purity 99.5%) is introduced from an oxygen gas cylinder to atmospheric pressure.
(3) Evacuate immediately.
(4) After 5 minutes, oxygen is again introduced to atmospheric pressure and then evacuated.
(5) After 5 minutes, hydrogen is introduced to 0.4 MPa.
(6) After 5 minutes, evacuate.
(7) After 5 minutes, hydrogen is introduced again to 0.4 MPa.
(8) After 5 minutes, evacuate.
Thereafter, a hydrogen permeation rate measurement test is performed under the following conditions.

  When measuring the hydrogen permeation rate, the hydrogen separation membrane was heated to 550 ° C. under vacuum as described in (8) above, at a process side pressure (Inlet pressure) of 200 kPa and a hydrogen permeation side pressure (Outlet pressure) of 100 kPa. Hydrogen gas was supplied to the process side, and the flow rate of hydrogen permeating to the hydrogen permeation side (hydrogen permeation rate) was measured. The results are shown in FIG. Moreover, the composition which analyzed the surface of the hydrogen separation membrane after this heat processing by Auger electron spectroscopy is shown in FIG.

[Comparative Example 1]
A hydrogen separation membrane made of pure V in the same manner as in Example 1 except that air was introduced instead of oxygen gas in the above steps (2) and (4) when the hydrogen separation membrane was heat-treated. After removing organic substances on the surface by oxidation, the hydrogen permeation rate was measured. The results are shown in FIG. Moreover, the composition which analyzed the surface of this hydrogen separation membrane by Auger electron spectroscopy is shown in FIG.

[Comparative Example 2]
The hydrogen permeation rate was measured without heating the hydrogen separation membrane. The results are shown in FIG. Moreover, the composition which analyzed the surface of this hydrogen separation membrane by Auger electron spectroscopy is shown in FIG.

[Discussion]
As is apparent from FIGS. 1, 3, and 4, when a hydrogen separation membrane made of a group 5A metal or an alloy thereof having no Pd-based catalyst layer is heat-treated in an oxygen gas atmosphere, heat treatment in an air atmosphere or heating Compared with the case without treatment, the hydrogen permeation rate is remarkably increased.

  As shown in FIG. 2, when heat treatment is performed in an oxygen gas atmosphere, an oxide layer having a thickness of about 1000 nm is formed on the surface of the hydrogen separation membrane, but no nitride is formed.

Claims (4)

Hydrogen separation consisting of a 5A group metal or an alloy thereof and heating a hydrogen separation membrane that does not have a surface layer of Pd or Pd alloy on the surface in an oxygen-containing gas atmosphere to oxidize and remove organic substances attached to the surface of the hydrogen separation membrane In a method for treating a membrane,
A method for treating a hydrogen separation membrane, wherein the nitrogen concentration in the oxygen-containing gas atmosphere is 0.5 mol% or less.   2. The method for treating a hydrogen separation membrane according to claim 1, wherein the oxygen-containing atmosphere is an oxygen atmosphere.   3. The hydrogen separation membrane according to claim 1 or 2, wherein the hydrogen separation membrane is installed in a hydrogen separator, and the heat treatment in the oxygen-containing atmosphere is performed prior to a hydrogen separation operation by the hydrogen separator. A method for treating a hydrogen separation membrane.   A hydrogen separation method, wherein hydrogen is separated from a hydrogen-containing gas by a hydrogen separation membrane treated by the treatment method according to any one of claims 1 to 3.

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