JP2009011978A - Hydrogen separator and manufacturing method of the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydrogen separator maintaining a practical hydrogen permeation velocity and having excellent durability, and to provide a manufacturing method of the same. <P>SOLUTION: The hydrogen separator includes a porous substrate, and a hydrogen-separating membrane disposed on at least one surface of the porous substrate, wherein the hydrogen-permeable membrane has a defect such that He gas leaked from the other membrane surface side when He gas is supplied on one membrane surface side at a pressure of 0.9 MPa is 0.5 ml/min or smaller per piece in average. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a hydrogen separator and a method for producing the same, and more particularly to a hydrogen separator having improved durability and a method for producing the same.

  Conventionally, as a method for obtaining only a specific gas component from a multi-component mixed gas, a membrane separation method using a gas separation membrane composed of an organic substance or an inorganic substance is known. Among the separation membranes used in the membrane separation method, examples of the hydrogen separation membrane include organic polymer membranes such as polyimide and polysulfone, and inorganic compound membranes such as palladium and palladium alloys. The palladium or palladium alloy film has heat resistance, and extremely high purity hydrogen can be obtained.

  As an apparatus having a hydrogen separation membrane capable of obtaining such a high-purity hydrogen gas, a porous support, and a hydrogen separation membrane having a film formed of a metal having hydrogen separation capability on at least one surface thereof, There is known a hydrogen separator provided with (for example, see Patent Document 1). The metal having hydrogen separation ability is also filled in the small holes opened on the surface of the porous support and closes the small holes. In the hydrogen separator disclosed in Patent Document 1, high purity hydrogen is separated by reducing defects penetrating the hydrogen separation membrane.

  However, even if the hydrogen separation membrane is formed according to the manufacturing method disclosed in Patent Document 1, if the hydrogen separator is manufactured by heat-treating the formed membrane, the hydrogen purity obtained using the hydrogen separator is low. There was a problem.

In order to solve such problems, a hydrogen separator having a thickness of 1 to 30 μm and a hydrogen separation membrane having defects of 0.010 / cm ² or less on its surface is disclosed ( For example, see Patent Document 2). However, the increase in the amount of leakage from the hydrogen separation membrane increases as the size of the defect increases. Therefore, it is difficult to maintain the hydrogen purity in long-term use only by reducing the defect density. It was.

Japanese Patent No. 3213430 JP 2006-314876 A

  The permeated hydrogen purity when using a hydrogen separator depends on the leak amount of gas other than hydrogen from defects existing in the hydrogen separation membrane, and the leak amount from the defect portion increases during use. It will drop at. The increase in the leak amount is larger as the defect size is larger, that is, as the initial leak amount is larger. In order to solve this problem, for example, it is conceivable to increase the thickness of the hydrogen separation membrane. However, this causes a problem that the hydrogen permeation rate is lowered at the same time.

  Therefore, an object of the present invention is to provide a hydrogen separator having a high durability while maintaining a practical hydrogen permeation rate and a method for producing the same.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have achieved the above-mentioned problems by the fact that defects inevitably formed in the hydrogen separation film exhibit predetermined characteristics even when the hydrogen separation film is thin. As a result, the present invention has been completed.

  That is, according to the present invention, the following hydrogen separator having improved durability and a method for producing the same are provided.

  [1] A porous support, and a hydrogen separation membrane disposed on at least one surface of the porous support, the hydrogen separation membrane at a pressure of 0.9 MPa on one membrane surface side A hydrogen separator in which the He gas leaked from the other membrane surface side when the He gas is supplied has defects of 0.5 ml / min or less on average per piece.

  [2] The hydrogen separator according to [1], wherein the porous support is made of ceramics.

  [3] The hydrogen separator according to [1] or [2], wherein the hydrogen separation membrane is a membrane made of a hydrogen permeable metal or an alloy containing a hydrogen permeable metal.

  [4] The hydrogen separator according to [3], wherein the hydrogen permeable metal is palladium.

  [5] The hydrogen separator according to any one of [1] to [4], wherein the hydrogen separation membrane has a thickness of 0.5 to 10 μm.

  [6] A method for producing a hydrogen separator, wherein a hydrogen separation membrane is formed on at least one surface of a porous support in an environment having a cleanness of 100,000 or less.

  The hydrogen separator of the present invention has an effect that a practical hydrogen permeation rate is maintained and a hydrogen separation membrane having excellent durability is provided.

  Moreover, according to the method for producing a hydrogen separator of the present invention, a hydrogen separator having a hydrogen separation membrane having excellent durability while maintaining a practical hydrogen permeation rate can be produced.

  BEST MODE FOR CARRYING OUT THE INVENTION The best mode for carrying out the present invention will be described below, but the present invention is not limited to the following embodiment, and is based on the ordinary knowledge of those skilled in the art without departing from the gist of the present invention. It should be understood that modifications and improvements as appropriate to the following embodiments also fall within the scope of the present invention.

  The hydrogen separator of the present invention has a porous support and a hydrogen separation membrane on at least one surface of the porous support. Hereinafter, the components of the hydrogen separator according to the present invention will be described in detail.

(I) Porous support:
The hydrogen separator of the present invention has a porous support and a hydrogen separation membrane on at least one surface of the porous support. Due to the presence of the porous support, even when the hydrogen separation membrane is made into a thin film, it is supported by the porous support and its shape is maintained, so that it is possible to prevent damage and the like.

  The porous support body of a hydrogen separator is not specifically limited, The porous support body used for a conventionally well-known hydrogen separator can be used suitably. For example, there are ceramics, metal, a composite of ceramics and metal, and the like. In the hydrogen separator of this embodiment, the porous support is preferably composed mainly of ceramics. This is because it is excellent in heat resistance and corrosion resistance, and can increase the mechanical strength of the hydrogen separator.

  The type of ceramic is not particularly limited, and any ceramic generally used as a hydrogen separator can be used. Examples include alumina, titania, silica, silica-alumina, mullite, cordierite, and zirconia. In addition, as components other than ceramics, a small amount of components inevitably contained or components that are usually added may be contained. Moreover, it is also preferable that the porous support is composed of two or more kinds of ceramics or a composite material of ceramics and metal in order to adjust, for example, the coefficient of thermal expansion.

  The porous support has a large number of small pores that are three-dimensionally continuous on the surface. The hole diameter of the small holes is preferably 0.003 to 2 μm, and more preferably 0.1 to 1 μm. If the pore diameter is less than 0.003 μm, the resistance when hydrogen passes may increase. On the other hand, when the pore diameter is more than 2 μm, when forming the hydrogen separation membrane, it is difficult to close the small holes with the hydrogen permeable metal, and the airtightness may be lowered.

  The small holes preferably have the same hole diameter. As a result, when forming the hydrogen separation membrane, it is possible to avoid the problem that small holes that are not blocked by the hydrogen permeable metal are generated and the airtightness is lowered.

(II) Hydrogen separation membrane:
The hydrogen separator of the present invention has a porous support and a hydrogen separation membrane disposed on at least one surface of the porous support. The presence of the hydrogen separation membrane makes it possible to separate the target high-purity hydrogen.

  The hydrogen separation membrane is not particularly limited as long as it selectively permeates hydrogen, and a hydrogen separation membrane composed of a metal or an alloy having a selective permeability to hydrogen is preferable. Examples of the metal or alloy having hydrogen-selective permeability include, for example, metals such as palladium (Pd), tantalum (Ta), niobium (Nb), and vanadium (V), or alloys containing these as a main component, and metal glass. Etc.

  More preferably, the hydrogen separation membrane is formed from palladium or an alloy containing palladium. Palladium has the property of allowing hydrogen to dissolve and permeate. As the alloy containing palladium, an alloy of palladium and silver or an alloy of palladium and copper is preferable. By alloying palladium and silver or copper, there is an effect that hydrogen degradation of palladium is prevented and hydrogen separation efficiency at high temperatures is improved.

  The thickness of the hydrogen separation membrane is preferably 0.5 to 10 μm, more preferably 1 to 5 μm, and particularly preferably 1 to 4 μm. If it is less than 0.5 μm, the hydrogen separation ability may be insufficient. On the other hand, if it exceeds 10 μm, the hydrogen permeability may be insufficient due to the thick film thickness.

  When a hydrogen separation membrane is formed on the surface of the porous support, inevitable defects are generated on the surface. When He gas is supplied at a pressure of 0.9 MPa to one membrane surface side of the hydrogen separation membrane, the average amount of leak of He gas generated per defect is 0.5 ml / min or less. It is preferably 2 ml / min or less, and more preferably 0.05 ml / min or less. If the leak amount of He gas generated per defect exceeds 0.5 ml / min, the rate of increase in the leak amount from the defective portion in the hydrogen separation membrane increases every time it is used. Durability may be reduced.

  Further, the smaller the amount of He gas leaked per unit area resulting from defects, the higher the permeated hydrogen purity. Specifically, the average leak amount of He gas per unit area is preferably 0.05 ml / min or less, more preferably 0.03 ml / min or less, and 0.01 ml / min or less. It is particularly preferred.

  The average of the leak amount of He gas generated from one defect existing on the surface of the hydrogen separation membrane is obtained as follows. First, a leak amount of He gas generated from all defects present in the hydrogen separation membrane is measured. Specifically, 0.9 MPa He gas is supplied to one side of the hydrogen separation membrane, and the amount of He gas leaking to the other side is measured. Next, the number of defects present on the surface of the hydrogen separation membrane is measured. Specifically, from the surface (one surface) side of the hydrogen separation membrane that is not disposed on the porous support, the entire membrane is immersed in water while supplying 0.3 MPa of He gas, and the other surface side It is measured by counting the bubble generation locations of the He gas leaking from. The amount of He gas leaked from one defect present on the surface of the hydrogen separation membrane is calculated by dividing the amount of He gas leak caused by the total defects present on the surface of the hydrogen separation membrane by the number of defects. can do.

  The method for producing a hydrogen separator according to the present invention comprises hydrogen separation on at least one surface of a porous support in an environment having a cleanness of 100,000 or less, preferably 10,000 or less, more preferably 1,000 or less. A film is formed. As a result, when He gas is supplied to one membrane surface side of the hydrogen separation membrane at a pressure of 0.9 MPa, the He gas leaking from the other membrane surface side is an average of 0.5 ml / min or less per defect. A hydrogen separator having a certain hydrogen separation membrane can be obtained.

  As used herein, “cleanness” refers to an index representing cleanliness in a clean room, which is defined based on the US Federal Standard Federal Standard 209D (FED-STD-209D). Specifically, it is indicated by the upper limit value of the number of particles of 0.5 μm or more existing in a space of 1 CF (1 cubic foot = about 28.3 L).

  The hydrogen separation membrane is formed by, for example, a plating method, a sputtering method, or a vacuum deposition method in a clean room having a cleanness of 100,000 or less, preferably 10,000 or less, more preferably 1,000 or less. It can be formed on the surface of a porous support. In addition, a hydrogen separation membrane composed of an alloy of palladium and silver or copper is formed on the surface of the porous support by performing heat treatment in an inert gas after laminating each metal membrane. be able to. A hydrogen separation membrane made of a palladium alloy is preferable because metal degradation can be suppressed.

  Specifically, the hydrogen separation membrane is preferably formed by a plating method in that a hydrogen permeable membrane having high hydrogen permeation performance is easily formed. Specific examples of the plating method include an electroless plating method. The electroless plating method usually includes an activation process and a plating process.

  First, the activation process will be described. After immersing one surface of the porous support in a solution containing an activated metal, the solution containing the activated metal is attached to one surface, and then washed with water. When palladium is used as the activation metal, for example, an aqueous hydrochloric acid solution of palladium chloride can be used. Next, an activated metal is deposited on one surface. As this method, for example, when palladium is used as the activation metal, it is preferable to immerse the porous support alternately in an aqueous hydrochloric acid solution of palladium chloride and an aqueous hydrochloric acid solution of tin chloride.

  Next, the plating process will be described. After attaching the activated metal to one surface, after immersing one surface side of the porous support in a solution containing palladium divalent ions, a reduction treatment is performed, and the activated metal is used as a nucleus. , Palladium is deposited. The reduction treatment is performed by immersing in a plating solution containing divalent palladium ions and a reducing agent. Specific examples of the reducing agent include hydrazine, dimethylamine borane, sodium phosphinate, sodium phosphonate, and the like.

  Thereafter, it is also preferable that the deposited palladium is further plated with silver and alloyed by heat treatment in an inert gas such as argon gas. At this time, it is preferable to perform electroplating using a layer made of chemical plating or palladium as an electrode. Moreover, it is preferable that mass ratio (palladium: silver) of palladium and silver is 90:10 to 70:30.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the examples and comparative examples, “parts” and “%” are based on mass unless otherwise specified.

[Cleanness]: Measured according to the US federal standard FEDERAL STANDARD 209D.

[He leak amount per unit area]: 0.9 MPa of He gas was supplied to the outside of the hydrogen separation membrane, and the amount of He gas leaking inside was measured and divided by the membrane area.

[He leak amount per defect]: The number of defects is determined by immersing the entire membrane in water with 0.3 MPa of He gas supplied to the inside of the membrane, and counting the locations of bubbles on the hydrogen separation membrane. And the amount of He leak was divided by the number of defects.

(Examples 1-4)
As the porous support, an α-alumina tube having a cylindrical tube shape having an outer diameter of 10 mm and a length of 100 mm and an average pore diameter of 0.1 μm on the surface was used. Palladium and silver were sequentially plated on the surface of the porous support in a clean room having a cleanness of 1,000. In addition, the ratio of palladium and silver was adjusted so that silver might be 20 parts with respect to 80 parts of palladium. This was alloyed by heat treatment at 700 ° C. for 1 hour in argon gas to produce hydrogen separators (Examples 1 to 4) having a palladium alloy as a hydrogen separation membrane. The thickness of the hydrogen separation membrane was adjusted to 2 μm. For these hydrogen separation membranes, the amount of He leak per unit area and the amount of He leak per defect were measured. The measurement results are shown in Table 1. In addition, a graph plotting the He leak amount per unit area of the hydrogen separation membrane constituting the hydrogen separator is shown in FIG. 1, and a graph plotting the He leak amount per defect is shown in FIG.

(Examples 5 and 6)
A hydrogen separator (Examples 5 and 6) was manufactured by forming a hydrogen separation membrane in the same manner as in Examples 1 to 4, except that the plating operation of the hydrogen separation membrane was performed in a clean room with a clean degree of 100,000. did. For these hydrogen separation membranes, the amount of He leak per unit area and the amount of He leak per defect were measured. The measurement results are shown in Table 1. FIG. 1 shows a graph plotting the amount of He leak per unit area of the hydrogen separation membrane constituting the hydrogen separator, and FIG. 2 shows a graph plotting the amount of He leak per defect.

(Examples 7 to 10)
A hydrogen separator (Examples 7 to 10) was manufactured by forming a hydrogen separation membrane in the same manner as in Examples 1 to 4, except that the thickness of the hydrogen separation membrane was adjusted to 5 μm. For these hydrogen separation membranes, the amount of He leak per unit area and the amount of He leak per defect were measured. The measurement results are shown in Table 1. FIG. 1 shows a graph plotting the amount of He leak per unit area of the hydrogen separation membrane constituting the hydrogen separator, and FIG. 2 shows a graph plotting the amount of He leak per defect.

(Comparative Examples 1-4)
A hydrogen separator (comparative example) was formed by forming a hydrogen separation membrane in the same manner as in Examples 1 to 4, except that the plating operation of the hydrogen separation membrane was performed in a normal laboratory (equivalent to a cleanness of 1,000,000). 1-4) were produced. For this hydrogen separation membrane, the amount of He leak per unit area and the amount of He leak per defect were measured. The measurement results are shown in Table 1. In addition, a graph plotting the He leak amount per unit area of the hydrogen separation membrane constituting the hydrogen separator is shown in FIG. 1, and a graph plotting the He leak amount per defect is shown in FIG.

(An endurance test)
After sealing the both ends of each porous support body of the hydrogen separator of Example 1, Example 7, and Comparative Example 1, it set in the pressure-resistant container, and the permeation durability test of the hydrogen separation membrane was done. In the durability test, the hydrogen separation membrane was heated to 500 ° C. in an argon gas atmosphere by heating the pressure vessel, then 0.7 MPa of hydrogen was introduced into the pressure vessel and the hydrogen permeation test was performed for 1 hour. After removing hydrogen from the separated body, the operation of lowering the temperature of the hydrogen separation membrane from 500 ° C. to room temperature in an argon gas atmosphere was defined as one cycle. A durability test was repeated for 26 cycles. Every time the endurance test was performed for two cycles, the amount of He gas leaked from defects in the hydrogen separation membrane was measured. The measurement results are shown in Table 2. Moreover, the graph which plotted the amount of He gas leaks per unit area with respect to the cycle of an endurance test is shown in FIG. In addition, about the hydrogen separator of the comparative example 1, since the leak amount of He gas increased greatly in the measurement to the 16th cycle, the subsequent measurement was not performed.

(result)
From the results of this endurance test, when forming a hydrogen separation membrane on the surface of the porous support, by forming the film in a low clean environment, the amount of He leak per unit area and the He leak per defect It can be seen that the durability of the hydrogen separator is improved even when the amount is reduced and the hydrogen separation membrane is a thin film.

  Since the hydrogen separator of the present invention has a hydrogen separation membrane that maintains a practical hydrogen permeation rate and has excellent durability, it can be used repeatedly for separating high-purity hydrogen.

It is the graph which plotted the amount of He leak per unit area of the hydrogen separation membrane which constitutes a hydrogen separator.

It is the graph which plotted the amount of He leak per defect of the hydrogen separation membrane which constitutes a hydrogen separator.

It is the graph which plotted He leak amount per unit area with respect to the cycle of an endurance test.

Claims (6)

A porous support, and a hydrogen separation membrane disposed on at least one surface of the porous support,
When the hydrogen separation membrane supplies He gas at a pressure of 0.9 MPa to one membrane surface side, the He gas leaking from the other membrane surface side has an average defect of 0.5 ml / min or less per piece. Having a hydrogen separator.   The hydrogen separator according to claim 1, wherein the porous support is made of ceramics.   The hydrogen separator according to claim 1 or 2, wherein the hydrogen separation membrane is a membrane made of a hydrogen permeable metal or an alloy containing a hydrogen permeable metal.   The hydrogen separator according to claim 3, wherein the hydrogen permeable metal is palladium.   The hydrogen separator according to any one of claims 1 to 4, wherein a thickness of the hydrogen separation membrane is 0.5 to 10 µm.   A method for producing a hydrogen separator, wherein a hydrogen separation membrane is formed on at least one surface of a porous support in an environment having a cleanness of 100,000 or less.

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