JP2015016420A - Hydrogen separation body and hydrogen production apparatus using hydrogen separation body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydrogen separation body capable of establishing compatibility between high hydrogen permeability and peeling resistance and a hydrogen production apparatus using the hydrogen separation body.SOLUTION: In a hydrogen separation body (1) having a porous body (20) and a hydrogen separation layer (17) filled with a hydrogen separation metal selectively permeating only hydrogen in hydrogen-containing gases in the pores of the porous body (20), a ratio (ε/τ) of a filling rate ε being an index exhibiting the filling rate of the hydrogen separation metal in the hydrogen separation layer (17) and a flexion degree τ being an index exhibiting the degree of the permeation path length of hydrogen in a thickness direction of the hydrogen separation layer (17) is in the range of 0.2-0.6.

Description

  The present invention relates to a hydrogen separator capable of obtaining a high-purity hydrogen gas by selecting and separating the hydrogen gas from a gas to be separated (source gas) such as a hydrogen-containing gas, and a hydrogen production apparatus using the hydrogen separator About.

  Conventionally, in order to produce hydrogen to be supplied to a fuel cell, for example, a hydrogen separator that selectively extracts only hydrogen from a gas containing hydrogen such as a reformed gas obtained by steam reforming natural gas has been developed. This hydrogen separator is, for example, hydrogen made of a hydrogen permeable metal (hereinafter referred to as a hydrogen separation metal) that allows only hydrogen such as palladium (Pd) or Pd alloy to permeate on the surface of a bottomed cylindrical ceramic porous body. A permeable membrane (hereinafter referred to as a hydrogen separation layer) is formed.

  Moreover, as a method for producing this type of hydrogen separator, a technique for forming a hydrogen separation layer by filling a hydrogen separation metal in the pores of a ceramic porous body is disclosed (Patent Documents 1 to 3). 3).

JP 2006-95521 A JP 2007-301514 A JP 2005-13853 A

  However, the above-described conventional technology does not disclose a design guideline for achieving both high hydrogen permeation performance and separation resistance (of the hydrogen separation layer) in the hydrogen separator. It was unclear whether both permeation performance and peel resistance could be achieved.

In addition, when the ratio with which a hydrogen separation metal is filled into a hydrogen separation layer is high, there exists a possibility that peeling may arise in the interface with a ceramic porous part in the both sides of the thickness direction of a hydrogen separation layer.
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a hydrogen separator capable of achieving both high hydrogen permeation performance and peeling resistance and a hydrogen production apparatus using the hydrogen separator. There is.

  (1) In the present invention, as a first aspect (hydrogen separator), a porous body and a hydrogen separation metal that allows permeation by selectively selecting only hydrogen from the gas containing hydrogen in the pores of the porous body are filled. And a hydrogen permeation path in the thickness direction of the hydrogen separation layer in the hydrogen separation layer, and a filling rate ε which is an index indicating a filling ratio of the hydrogen separation metal in the hydrogen separation layer. The ratio (ε / τ) to the degree of bending τ, which is an index indicating the degree of the length, is in the range of 0.2 to 0.6.

  In the first aspect, as is apparent from the experimental examples described later, the filling rate ε, which is an index indicating the filling ratio of the hydrogen separation metal in the hydrogen separation layer, and the hydrogen permeation path in the thickness direction of the hydrogen separation layer. Since the ratio (ε / τ) to the bending degree τ, which is an index indicating the degree of length, is in the range of 0.2 to 0.6, both high hydrogen permeation performance and high peel resistance can be achieved.

  Specifically, in the first aspect, since the ratio (ε / τ) between the filling rate ε and the bending degree τ is 0.2 or more, high hydrogen permeation performance can be realized, and the filling rate ε and the bending degree τ. Since the ratio (ε / τ) to 0.6 is 0.6 or less, high peel resistance can be realized.

Here, as will be described in detail later, the filling rate ε is a value represented by “area occupied by hydrogen separation metal / total area of the cross section” in the cross section along the thickness direction of the hydrogen separation layer.
The tortuosity τ is, as will be described in detail later, “the length of a hydrogen path / hydrogen separation (which is the length of a hydrogen permeation path through the hydrogen separation metal in the thickness direction of the hydrogen separation layer). This is a value indicated by “layer thickness”.

(2) The present invention is characterized in that, as a second aspect, the thickness of the hydrogen separation layer filled with the hydrogen separation metal is in the range of 0.1 to 10 μm.
In the second aspect, since the thickness of the hydrogen separation layer is 0.1 μm or more, the purity of hydrogen to be separated (from the source gas or the like) is high. Moreover, since the thickness of the hydrogen separation layer is 10 μm or less, there is an effect that the hydrogen permeation performance is high.

  That is, since the hydrogen permeation performance is inversely proportional to the thickness (layer thickness) of the hydrogen separation layer, the layer thickness of the hydrogen separation layer is preferably as thin as possible. On the other hand, as the layer is made thinner, the portion that is not filled with the hydrogen separation metal, that is, the vacancy portion increases, and leakage due to vacancies is likely to occur. For this reason, the range of 0.1-10 micrometers is suitable as a range of the layer thickness which can make hydrogen permeability and sealing performance compatible.

(3) The present invention is characterized in that the hydrogen separator according to claim 1 or 2 is provided as a third aspect (hydrogen production apparatus).
Since the hydrogen production apparatus according to the third aspect includes the hydrogen separator described above, it has high hydrogen production capacity and high durability.

It is explanatory drawing for demonstrating the procedure for calculating | requiring a path length. It is explanatory drawing for calculating | requiring the angle when a path | route bends. It is sectional drawing which fractures | ruptures and shows the hydrogen separator of an Example along an axial direction. It is explanatory drawing which fractures | ruptures the hydrogen separator of an Example along an axial direction, expands the part (A part of FIG. 3), and shows typically. It is explanatory drawing which fractures | ruptures the hydrogen separator of an Example along an axial direction, and further expands the part further and is shown typically. It is sectional drawing which fractures | ruptures and shows the hydrogen separator in an Example along an axial direction. It is explanatory drawing which shows the formation procedure etc. of a bottomed cylindrical molded object among the manufacturing methods of the hydrogen separator of an Example. It is explanatory drawing which shows the formation procedure etc. of a hydrogen separation layer among the manufacturing methods of the hydrogen separator of an Example. It is explanatory drawing which shows the electroplating of an internal electric power feeding system among the manufacturing methods of the hydrogen separator of an Example. It is a graph which shows an experimental result.

Hereinafter, embodiments of the present invention will be described.
-The porous body comprises a porous support, an inner porous layer formed on the surface of the porous support, and an outer porous layer (protective layer) formed on the surface of the inner porous layer. A configuration is mentioned.

The hydrogen separation layer is formed, for example, on a part of the inner porous layer and a part of the protective layer adjacent thereto.
As the material of the porous body, for example, ceramic is used. Examples of the ceramic include at least one of yttria stabilized zirconia, stabilized zirconia, alumina, magnesia, ceria, and doped ceria.

  -As a material which comprises a hydrogen separation layer, the porous body and the hydrogen separation metal (filled in the pore of the porous body) are mentioned. A place where the pores are not completely filled may be vacant.

  Among these, examples of the hydrogen separation metal include Pd, PdCu alloy, PdAg alloy, and PdAu alloy. Specifically, Pd, Cu, Ag, Au, PdCu alloy, PdAg alloy, and PdAu alloy can be used. Cu, Ag, and Au are not used alone, but are alloys for use in alloying with Pd having hydrogen permeability.

The filling rate ε is a value represented by “area occupied by hydrogen separation metal / area of cross section” in the cross section along the thickness direction of the hydrogen separation layer.
Specifically, the filling rate ε can be obtained by the following method.

  A cross section of the porous body including the hydrogen separation layer, broken in the thickness direction of the hydrogen separation layer (perpendicular to the plane in which the hydrogen separation layer spreads) is observed with an electron microscope (take a SEM photograph). Adjustment is made so that the hydrogen separation layer (cross section) occupies 20% or more of the entire observation visual field in the entire range of the field of view of the electron microscope. Further, the cross section of the hydrogen separation layer and the cross section of the layer adjacent to the hydrogen separation layer on both sides in the thickness direction are adjusted and observed so as to be in the field of view (take an SEM photograph).

  At the time of SEM photography, for example, as illustrated in FIG. 1, the upper side (or the lower side) of the image is adjusted so that both end faces in the thickness direction of the hydrogen separation layer (planes on which the hydrogen separation layer spreads) are parallel to each other. Then shoot. Specifically, the upper side (or lower side) of the image is parallel to the interface (outer interface) on the protective layer side (upper side in FIG. 1) and the interface (inner side interface) on the inner porous layer side (lower side in FIG. 1). Adjust and shoot as follows.

  A strip-shaped region (measurement range) having a predetermined width (for example, 0.1 μm) is set in parallel to the hydrogen separation layer, and the hydrogen separation metal and other materials (ceramics or pores) within the measurement range. ) And the ratio. Then, the measurement range in which the ratio is 50%, for example, one end face in the thickness direction of the measurement range (for example, the upper end or the lower end in FIG. 1) is defined as the outer interface or the inner interface of the hydrogen separation layer. Therefore, the thickness of the hydrogen separation layer can be obtained from the distance between the outer interface and the inner interface.

  The area of the region (measurement region; SR) formed by the interface (for example, the left end and the right end of FIG. 1) at both ends in the width direction of the hydrogen separation layer (for example, the left and right direction in FIG. 1) and the outer interface and the inner interface, The total area. The area of the ceramic portion, the hydrogen separation metal, and the pores is calculated by image analysis. A value obtained by dividing the area occupied by the hydrogen separation metal by the total area (of the hydrogen separation layer) subjected to image analysis is defined as a filling rate ε. In addition, SA of FIG. 1 has shown the thickness (layer thickness) of the hydrogen separation layer.

The bending degree τ is a value indicated by “(path length of hydrogen through which hydrogen permeates through the hydrogen separation metal in the thickness direction of the hydrogen separation layer) / thickness of the hydrogen separation layer”.
Specifically, the bending degree τ can be obtained by the following method.

The route length is determined by the length of the route line. Further, the length of the route line can be obtained by the following method.
First, a perpendicular line is drawn in the thickness direction of the hydrogen separation layer (vertical direction in FIG. 1) with respect to the strip-shaped region (measurement range) described above. For example, a perpendicular line is drawn perpendicularly (vertical direction in the figure) to the hydrogen separation layer spreading in the horizontal direction in the figure.
Secondly, a route line is drawn from the outer interface toward the inner interface as shown by the white line in FIG. The start hole (K) is removed from the path, and the start is from the hydrogen separation metal (M) or ceramic (S). In the meantime, holes in the middle are treated as ceramic.

<When starting from hydrogen separation metal>
(A) A route line is drawn along the vertical line in the region where the hydrogen separation metal exists.
(B) When the route line drawn in (A) reaches the ceramic portion The boundary line between the ceramic portion and the hydrogen separation metal and the route line intersect at a point P. The inclination of the boundary line at the point P is obtained. An angle θ (see FIG. 2) formed by a tilt line and a perpendicular line in a direction extending to the inner interface is obtained.

(B-1) When the angle θ is larger than 50 ° When the route line is advanced from the point P (P1) along the perpendicular line, the boundary line between the ceramic portion and the hydrogen separation metal and the route line intersect at the point Q. . A virtual circle is drawn with the length of point P and point Q as the diameter. A semicircle of a virtual circle connecting the point P and the point Q becomes a route line. The length of the route line is half of the circumference of the virtual circle. From the point Q, the process returns to the rule (A).

(B-2) When the angle θ is 50 ° or less The route line is advanced from the point P (P2) along a straight line approximating the boundary line. Then, the route line is advanced to the point R where the hydrogen separation metal appears in the direction in which the angle between the straight line and the perpendicular is 0 °. At point R, it proceeds again in the direction of θ = 0 ° (downward direction in FIG. 1). From the point R, the process returns to the rule (A).

  When the route line is advanced from the point P (P3) along the straight line approximating the boundary line, when the angle formed by the straight line approximating the boundary line and the perpendicular becomes larger than 50 °, Go to the rules.

<When starting from ceramic>
Start with the rule (B-1).
And the operation according to these rules is repeated within the range of the thickness of the hydrogen separation layer. Thereby, the distance (path length) that actual hydrogen travels in the hydrogen separation metal is calculated.

  Therefore, the bending degree τ is calculated by dividing the path length by the thickness of the hydrogen separation layer. Since there are actually variations, the bending degree τ is calculated by the same operation at five or more locations on the same screen, and an average of these values is used as τ for actual calculation.

Here, when the ratio (ε / τ) of the filling rate ε and the bending degree τ is adjusted to the range of 0.2 to 0.6, the state of the porous body filled with the hydrogen separation metal is controlled. do it.
Specifically, the state of pores (pores) in the porous body can be adjusted by adjusting the particle size of the porous raw material powder, the firing temperature at the time of formation, etc. The filling state of the hydrogen separation metal to be filled (and hence the state of the structure of the hydrogen separator) can be controlled.

  Specifically, if the average particle size of the raw material powder is reduced, the particles are easily sintered, so that the sintering between the particles proceeds and the voids in the porous layer (that is, the space of the filled portion) decreases, or If the firing temperature is increased, similarly, the sintering between the particles proceeds and the voids in the porous layer are reduced, so that the ratio (ε / τ) between the filling rate ε and the bending degree τ can be reduced. On the contrary, if the average particle diameter of the raw material powder is increased or the firing temperature is decreased, the ratio (ε / τ) between the filling rate ε and the bending degree τ can be increased.

In addition, the degree of filling ratio ε and the ratio of bending degree τ (ε / τ) can be determined in advance by experiments based on the above-described tendency.
It is considered that the following relationship exists between the hydrogen permeation performance and the ratio (ε / τ) between the filling rate ε and the bending degree τ.

In the case where the hydrogen separation layer is a membrane made of a dense hydrogen separation metal, it is considered that the hydrogen permeation performance (here, the hydrogen permeation flow rate) is determined by the following formula (1).
J = q × (S / d) · {(P1) ^1/2 − (P2) ^1/2 } (1)
J: Hydrogen permeation flow rate [mol / m ² / sec]
q: Hydrogen permeability coefficient [mol / sec / Pa0.5]
S: Hydrogen separation layer area [m ² ]
d: Hydrogen separation layer thickness [m]
P1: Supply side pressure [Pa]
P2: Permeation side pressure [Pa]
Moreover, when the hydrogen separation metal is filled in the pores, it is considered that there is a relationship of the following formulas (2) and (3).

  In the following formula (2), the hydrogen separation layer area is the apparent area of the hydrogen separation layer (surface area of the hydrogen separation layer portion in the hydrogen separator), and the equivalent hydrogen separation layer area is the apparent area. It is a value obtained by multiplying the filling rate of the hydrogen separation metal, and represents the area actually occupied by the hydrogen separation metal in the hydrogen separation layer area.

  In the following formula (3), the measured hydrogen separation layer thickness is the measured hydrogen separation layer thickness, and the equivalent hydrogen separation layer thickness is a value obtained by multiplying the measured hydrogen separation layer thickness by the bending degree. , Represents the distance that hydrogen actually passes when passing through the hydrogen-permeable layer from the supply side to the permeation side.

S = S ′ × ε (2)
d = d ′ × τ (3)
S: equivalent hydrogen separation layer area [m ² ]
S ′: Hydrogen separation layer area [m ² ]
d: equivalent hydrogen separation layer thickness [m]
d ′: Actual hydrogen separation layer thickness [m]
ε: Filling rate
τ: Degree of bending Therefore, the following formula (4) is obtained by substituting the above formulas (2) and (3) into the above (1).

J = q × (S ′ / d ′) · (ε / τ) · {(P1) ^1/2 − (P2) ^1/2 } (4)
Therefore, it can be seen from this equation (4) that there is a correspondence between the hydrogen permeation performance and ε / τ.

  Examples of the present invention will be described below.

Here, an embodiment of a hydrogen separator that selectively separates hydrogen from a source gas and a hydrogen production apparatus including the hydrogen separator will be described.
a) First, the configuration of the hydrogen separator of this example will be described.

  As shown in FIG. 3, the hydrogen separator 1 of this embodiment is a test tube-shaped member that selectively separates hydrogen from a raw material gas (for example, a reformed gas produced by bringing natural gas and water vapor into contact with a catalyst). The distal end side (upper side in the figure) is closed, the proximal end side (lower side in the figure) is opened, and the center hole 3 is provided at the axial center.

  The hydrogen separator 1 has, as a basic structure, a test tube-shaped porous support 5 on the distal end side and a cylindrical dense support 7 on the proximal end side. The support body 5 and the dense support body 7 are arranged coaxially to constitute an integral ceramic support body 9.

The dimensions of the hydrogen separator 1 are, for example, length 300 mm × inner diameter 6 mm × outer diameter 10 mm.
Among these, the porous support 5 is made of, for example, yttria-stabilized zirconia (YSZ), and is a support made of porous ceramics having air permeability that can transmit the raw material gas.

On the other hand, the dense support 7 is a dense ceramic support made of YSZ, that is, a support having no air permeability.
As will be described later, a layered surface structure 11 is formed on the outer surface of the ceramic support 9 so as to cover most of the ceramic support 9 (excluding the base end side).

  The surface structure 11 includes an inner porous layer 13 covering the surface of the porous support 5 and the surface of the inner porous layer 13, as shown in FIG. And an outer porous layer (hereinafter referred to as a protective layer) 15 and a hydrogen separation layer 17 formed over (in part of) the inner porous layer 13 and the protective layer 15. A porous layer 19 is composed of the inner porous layer 13 and the protective layer 15, and a porous body 20 is composed of the porous support 5 and the porous layer 19. Each configuration will be described below.

The inner porous layer 13 is configured to cover the entire outer peripheral surface of the porous support 5 and the outer peripheral surface of the dense support 7 on the (porous support 5) end side.
The inner porous layer 13 is a coating layer made of YSZ and made of porous ceramics having air permeability capable of transmitting a raw material gas.

  The protective layer 15 is formed so as to cover the entire outer surface of the inner porous layer 13. Further, the proximal end side of the protective layer 15 is formed so as to be in close contact with and bonded to the outer peripheral surface on the distal end side of the dense support 7.

The protective layer 15 is a coating layer made of porous ceramics made of YSZ and having air permeability that allows hydrogen gas to pass therethrough.
Since the protective layer 15 extends to the outside of the hydrogen separation layer 17 (upward in FIG. 4), contaminants (for example, Fe) that damage the hydrogen separation layer 17 from the outside adhere to the hydrogen separation layer 17. Is preventing.

  The hydrogen separation layer 17 includes an inner layer 17a on the protective layer 15 side in the inner porous layer 13, and an outer layer 17b on the inner porous layer 13 side in the protective layer 15. The hydrogen separation layer 17 is formed over the entire plane in which the porous layer 19 extends so as to cover all the gas flow paths in the thickness direction (from inside to outside) of the hydrogen separator 1 in the porous layer 19. . The thickness of the hydrogen separation layer 17 (the vertical dimension in FIG. 4) is in the range of 0.1 to 10 μm (for example, 4.0 μm).

  Specifically, as shown schematically in FIG. 5 (further expanding FIG. 4), the hydrogen separation layer 17 is formed in the inner porous layer 13 made of YSZ and the pores 21 and 23 of the protective layer 15, A hydrogen separating metal which is a hydrogen permeable metal (PdAg alloy in this embodiment) is filled. This hydrogen separation metal is a metal that separates hydrogen from the source gas by selecting and allowing only hydrogen from the source gas to permeate.

  That is, the hydrogen separation layer 17 is a ceramic portion filled with a hydrogen separation metal in the inner porous layer 13 and the protective layer 15 (that is, the porous layer 19) made of ceramic (the width range in the horizontal direction in FIG. 3). And a hydrogen separation metal filled in the pores 21 and 23.

Hereinafter, a portion made of the hydrogen separation metal filled in the pores 21 and 23 of the hydrogen separation layer 17 is referred to as a hydrogen separation metal portion 27.
In particular, in this embodiment, the filling rate ε, which is an index indicating the filling ratio of the hydrogen separation metal in the porous layer 19 (specifically, the hydrogen separation layer 17), and the hydrogen permeation path in the thickness direction of the hydrogen separation layer 17 are shown. The ratio (ε / τ) to the degree of bending τ, which is an index indicating the degree of length, is in the range of 0.2 to 0.6.

b) Next, a hydrogen production apparatus that is a hydrogen separation apparatus including the hydrogen separator 1 will be briefly described.
As this hydrogen production apparatus, for example, an apparatus described in JP 2012-7727 A can be employed.

  Specifically, as shown in FIG. 6, the hydrogen production apparatus 31 includes a hydrogen separator 1, a cylindrical mounting bracket 33 into which the open end side of the hydrogen separator 1 is inserted, and an outer peripheral surface of the hydrogen separator 1. And a cylindrical sealing layer 35 (for performing gas sealing) disposed between the inner peripheral surface of the mounting bracket 33 and a cylindrical sealing member that is fitted on the hydrogen separator 1 and presses the distal end side of the sealing layer 35. A pressing metal fitting 37 and a cylindrical fixing metal fitting 39 that is externally fitted to the pressing metal fitting 37 and screwed into the mounting metal fitting 33 are provided. In FIG. 6, the surface structure 11 is omitted.

  The mounting bracket 33 includes a distal end side tubular portion 41, a flange portion 43, and the like, and a through hole (hollow portion) 45 serving as a gas flow path is formed at the center of the shaft. The base end side end of the hydrogen separator 1 is accommodated. The fixing bracket 39 includes a pressing plate 47 and a cylindrical portion 49. The pressing metal 37 is disposed adjacent to the seal layer 35 (made of expanded graphite) in the space 50 between the mounting metal 33 and the hydrogen separator 1.

  Here, the metal fitting 51 is constituted by the mounting fitting 33, the pressing fitting 37, and the fixing fitting 39, and the hydrogen separator 1 (and hence the hydrogen production apparatus 31) is made of a stainless metal container 53 by the metal fitting 51. It is fixed and accommodated. A hydrogen separation module 55 is configured by the hydrogen production apparatus 31 accommodated in the metal container 53.

  In the hydrogen separation module 55 described above, for example, when the source gas is supplied to the outside of the hydrogen separator 1 (therefore, inside the metal container 53), the hydrogen separator 1 separates the source gas into hydrogen. The hydrogen separator 1 is taken out through the central hole 3.

Examples of the source gas include a mixed gas of a hydrocarbon gas such as methane and water vapor, or a mixed gas containing at least hydrogen gas.
c) Next, the manufacturing method of the hydrogen separator 1 of a present Example is demonstrated.
<First powder filling step>
In this embodiment, press molding is performed using a mold 61 as shown in FIG. A cylindrical inner hole 65 corresponding to the outer shape of the hydrogen separator 1 is formed at the axial center of the cylindrical rubber mold 63 of the mold 61, and hydrogen separation is performed at the axial center of the inner hole 65. A cylindrical (test tube shape) center pin 67 corresponding to the shape of the center hole 3 of the body 1 is provided upright. Thereby, a substantially cylindrical mold hole 69 is formed.

Then, YSZ granulated powder was filled into the mold hole 69 of the rubber mold 63 as a material for forming the dense support 7, thereby producing a cylindrical dense forming portion 71.
<Second powder filling step>
Next, as shown in FIG. 7 (b), similarly, a pore former is used as a material for forming the porous support 5 on the dense formation portion 71 in the mold hole 69 of the rubber mold 63. As above, YSZ granulated powder added with 48% by volume of organic beads was filled.
<Pressurization process>
Next, as shown in FIG. 7C, the upper mold 73 was fixed to the upper part of the rubber mold 63.

In this state, the bottomed cylindrical molded body corresponding to the shape of the hydrogen separator 1 as shown in FIG. 7 (d) is formed by pressurizing and pressing at 100 MPa from the outer peripheral side of the rubber mold 63. 79 was produced.
<Baking process>
Next, the bottomed cylindrical molded body 79 taken out from the rubber mold 63 is degreased, and then fired in the atmosphere at 1500 ° C. for 1 hour, thereby obtaining φ10 mm × length as shown in FIG. A 300 mm ceramic fired body 85 was obtained. The ceramic fired body 85 includes the dense support 7 and the porous support 5 <inner porous layer forming step>
Next, a slurry in which YSZ powder was dispersed in an organic solvent was prepared, and the slurry was adhered to the surface of the ceramic fired body 85 (that is, the surface of the porous support 5) by a dip coating method.

Then, the ceramic fired body 85 to which the slurry is attached is baked at 1150 ° C. for 2 hours in the atmosphere, and as shown in FIG. 8B (enlarged B part in FIG. 8A), The inner porous layer 13 covering the surface of the ceramic fired body 85 (that is, the surface of the porous support 5) was formed.
<Pd metal nucleation process>
Next, the porous support 5 (outside) provided with the inner porous layer 13 is immersed in an Sn ion solution, and Sn ions are placed on the surface side of the inner porous layer 13 (on the right side in FIG. 8B). It was adsorbed, washed with water, immersed in a Pd ion solution, and Pd ions were adsorbed by an exchange reaction between Sn ions and Pd ions.

Then, Pd ions were reduced by dipping in a hydrazine solution to form Pd metal nuclei (plating nuclei). That is, Pd metal nuclei were attached to the inner peripheral surface of the pores 21 of the inner porous layer 13.
<Protective layer forming step>
Next, after the above-described YSZ slurry is again dip-coated on the inner porous layer 13 to which the Pd metal nuclei are attached, baking is performed at 1500 ° C. for 2 hours in the atmosphere, as shown in FIG. Thus, the protective layer 15 was formed.

As a result, a hydrogen separation intermediate 87 in which the inner porous layer 13 and the protective layer 15 were formed on the surface of the porous support 5 was obtained.
<Electroless plating process>
Next, as shown in FIG. 8D, Pd metal nuclei attached in the pores 21 of the inner porous layer 13 are grown by an electroless plating method (chemical plating method). An electroless plating layer 91 made of Pd with a thickness of 3.0 μm was formed on the surface side of the inner porous layer 13 (the protective layer 15 side: the right side of FIG. 8D) so as to fill the portion.

In this electroless plating method, the portion of the porous support 5 covered with the inner porous layer 13 and the protective layer 15 is placed in an electroless Pd plating solution (palladium compound: concentration 2 g / L) at a bath temperature of 60 ° C. The electroless plating layer 91 was formed by performing electroless plating for 20 minutes.
<Electrolytic plating process>
Next, as shown in FIG. 8E, an electrolytic plating layer 93 was formed by electrolytic plating on the surface side (protective layer 15 side) of the electroless plating layer 91 by electrolytic plating.

Specifically, as shown in FIG. 9, a 6.0 mol / L NaCl aqueous solution (NaCl saturated aqueous solution) was introduced as an electrolyte into the center hole 3 of the hydrogen separation intermediate 87.
Further, after inserting the feeding electrode 95 into the NaCl electrolyte, the hydrogen separation intermediate 87 is placed in an electrolytic Ag plating solution (silver nitrate solution: concentration 37 g / L) at a bath temperature of 30 ° C. in which the counter electrode 97 is previously arranged. I set it. The electrolytic Ag plating solution is supplied to the outside of the protective layer 15 (the right side of the right diagram in FIG. 9).

Then, constant current electrolytic plating was performed for 2.0 minutes at a current value (current density) of 0.3 A / dm ² , and an electroplating layer 93 having a thickness of 1.0 μm as an Ag plating film was formed on the electroless plating layer 91. To form a metal part forming body 101 (which later becomes the hydrogen separation metal part 27).

  The electrolytic plating layer 93 is also formed on a part of the inner side of the protective layer 15, but as a product, the outer porous portion not filled with the plating metal substantially functions as the protective layer 15.

Further, in this electrolytic plating, electrons are supplied to the electroless plating layer 91 via the electrolytic solution supplied to the central hole 3 inside the porous support 5 (and hence the pore 103 of the porous support 5). The plating metal (here, Ag) is supplied to the outside of the electroless plating layer 91 through the electrolytic Ag plating solution supplied to the outside of the protective layer 15 (and hence the pores 23 of the protective layer 15).
<Alloying process>
After cleaning, the metal part forming body 101 was heat-treated at 750 ° C. in nitrogen to alloy Pd and Ag, thereby obtaining a hydrogen separation metal part 27 made of a PdAg alloy having a thickness of 4 μm. Thereby, a hydrogen separation layer 17 having a thickness of 4 μm was formed.

Through these steps, the hydrogen separator 1 was completed. Further, a metal joint 51 was attached to the hydrogen separator 1 to complete the hydrogen separator 31.
e) Next, the effect of the present embodiment will be described.

  In this embodiment, as is apparent from the experimental examples described later, the filling rate ε, which is an index indicating the filling ratio of the hydrogen separation metal in the porous body 20, and the hydrogen permeation path in the thickness direction of the hydrogen separation layer 17 Since the ratio (ε / τ) to the bending degree τ, which is an index indicating the degree of the length, is in the range of 0.2 to 0.6, both high hydrogen permeation performance and high peel resistance can be achieved.

In the present embodiment, since the thickness of the hydrogen separation layer 17 is 0.1 μm or more, the purity of hydrogen separated (from the raw material gas or the like) is high. Moreover, since the thickness of the hydrogen separation layer 17 is 10 μm or less, there is an effect that the hydrogen permeation performance is high.
[Experimental example]
Next, experimental examples conducted for confirming the effects of the present invention will be described.

  Samples of Examples 1 to 5 shown in Table 1 below were produced as hydrogen separators used in the experiment. Moreover, the sample of Comparative Examples 1-6 was produced as a comparative example. The manufacturing method (manufacturing conditions) is the same as that in the above-described example except for the contents shown in Table 1 below.

  Then, for these samples, the filling rate ε, the bending degree τ, the thickness d, and the hydrogen permeation performance in the hydrogen separation layer were examined by the method described above. Moreover, the presence or absence of peeling at the interface in the thickness direction of the hydrogen separation layer was examined with a magnifying glass.

The hydrogen permeation performance was measured by the following method.
Under the condition of a temperature of 550 ° C., hydrogen gas is supplied to the outside (supply side) of the hydrogen separator and permeated to the inside (permeation side), and the pressure difference between the outside and inside becomes 0.1 MPa. Then, using a wet gas meter, the permeation amount [cc] per unit area [cm ² ] and unit time [min] of hydrogen gas permeating inward was measured.

  The results are shown in Table 1 below and FIG. In addition, the vertical axis | shaft of FIG. 10 shows hydrogen permeability (Hydrogen permeability), and a horizontal axis | shaft shows ratio ((epsilon) / (tau)) of the filling rate (epsilon) and bending degree (tau).

  In Tables 2 to 5 below, calculation procedures of the degree of bending τ in Examples 1 to 3 and Comparative Example 1 are shown. In Tables 2 to 5, the straight portion path length is the length (excluding the inside of the circle) of the white line (vertical direction) of the white line in FIG. 1, and the shaded portion path length is the length of the inclined portion. The circumferential path length is the length of the semicircular part of the circle, the total path length is the total length of these three types, and the bending degree τ is the total path length. Divided by the layer thickness d.

In addition, although the layer thickness in Table 1 and the average thickness in the following Tables 2, 3, and 4 are slightly different, Table 1 is based on the rules shown in the section explaining the method for obtaining the above-described filling rate ε. It is the length in the thickness direction of the hydrogen separation layer in the cut out measurement region. The hydrogen separation layer thickness of 1 to 5 excludes the vacancies at the start as described in the section explaining the method for obtaining the path length described above. For this reason, there may be a slight difference in the layer thickness between the two, but this is a difference of about 1%, and the influence on the bending degree τ is very small and can be ignored, so there is no problem.
<Example 1>
In Example 1, the area ratio in the hydrogen separation layer by image analysis is 1.2% of holes, 47.1% of YSZ, 51.7% of PdAg, and a thickness of 4.48 μm.

<Example 2>
In Example 2, the area ratio in the hydrogen separation layer by image analysis is 1.5% of holes, 56.2% of YSZ, 42.3% of PdAg, and a thickness of 3.96 μm.

<Example 3>
In Example 3, the area ratio in the hydrogen separation layer by image analysis is 1.3% of pores, 64.1% of YSZ, 34.6% of PdAg, and 4.71 μm in thickness.

<Comparative Example 1>
In Comparative Example 1, the area ratio in the hydrogen separation layer by image analysis is 1.3% vacancy, 72.5% YSZ, 26.2% PdAg, and 4.92 μm in thickness.

As is clear from Table 1 and FIG. 10, in the samples (Examples 1 to 5) in which the ratio (ε / τ) between the filling rate ε and the bending degree τ is 0.2 or more, the hydrogen permeation performance is 18.7. [Cc / min / cm ² ] or higher is preferable.

The hydrogen permeation performance is preferably 15 [cc / min / cm ² ] or more, and below this value, in order to obtain a sufficient amount of hydrogen (and hence the amount of hydrogen production) when used as a hydrogen production apparatus. The required membrane area is increased (hydrogen permeation performance NG). That is, it is not preferable because the apparatus becomes large and the cost becomes high.

In addition, a sample (Examples 1 to 5) having a ratio (ε / τ) of the filling rate ε and the bending degree τ of 0.6 or less is preferable because peeling at the interface of the hydrogen separation layer is not observed.
That is, from this experiment, when the ratio (ε / τ) between the filling rate ε and the bending degree τ is in the range of 0.2 to 0.6 (Examples 1 to 5), high hydrogen permeation performance and high It can be seen that both the peel resistance can be achieved.

  On the other hand, in Comparative Examples 1 to 3, since the ratio (ε / τ) between the filling rate ε and the bending degree τ is less than 0.2, the hydrogen permeation performance is low, which is not preferable. Further, in Comparative Examples 4 to 6, the ratio (ε / τ) between the filling rate ε and the bending degree τ exceeds 0.6, and thus peeling is not preferable (peeling NG).

In addition, this invention is not limited to the said embodiment and Example at all, and it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from this invention.
(1) For example, the filling rate in the hydrogen separation metal layer may be inclined from one side to the opposite side in the layer thickness direction, and may be inclined so as to increase the filling rate in the central part. May be composed of a plurality of different layers.

  (2) In addition to the above-described internal feeding type electrolytic plating, normal electrolytic plating can be employed. In this case, one electrode is attached to the Pd metal layer or the like formed in the entire porous layer with a clip or the like so as to be conductive, and electrolytic plating can be performed as usual.

That is, electrolytic plating can be performed by supplying a plating solution between a metal layer (with one electrode attached) and the other electrode and applying a voltage between the two electrodes.
(3) Further, in the case of the internal power feeding method, the electrolytic solution may be supplied to the outside of the ceramic support, and the electrolytic plating solution may be supplied to the inside to deposit the plating metal from the inside (center hole side). .

  (4) Further, a raw material gas such as natural gas is reformed (for example, steam reforming) in the hydrogen separator of each of the above embodiments (for example, a porous support body) to obtain a hydrogen-rich reformed gas. A reforming catalyst (such as Ni) may be added.

DESCRIPTION OF SYMBOLS 1 ... Hydrogen separator 5 ... Porous support 7 ... Dense support 9 ... Ceramic support 13 ... Inner porous layer 15 ... Outer porous layer (protective layer)
17 ... Hydrogen separation layer 19 ... Porous layer 20 ... Porous body

Claims (3)

In a hydrogen separator having a porous body, and a hydrogen separation layer filled with a hydrogen separation metal that selectively allows permeation of hydrogen in a gas containing hydrogen in the pores of the porous body,
A filling rate ε, which is an index indicating the filling ratio of the hydrogen separation metal in the hydrogen separation layer, and a bending degree τ, which is an index indicating the degree of the length of the hydrogen permeation path in the thickness direction of the hydrogen separation layer; A hydrogen separator having a ratio (ε / τ) of 0.2 to 0.6.   2. The hydrogen separator according to claim 1, wherein a thickness of the hydrogen separation layer filled with the hydrogen separation metal is in a range of 0.1 to 10 μm.   A hydrogen production apparatus comprising the hydrogen separator according to claim 1.