JP2021010909A - Oxygen permeation membrane, method for manufacturing same, and reformer - Google Patents

Abstract

To enhance durability and oxygen permeation performance of an oxygen permeation membrane.SOLUTION: An oxygen permeation membrane (10) comprises a first layer (12) which contains a complex oxide, and has oxygen ion conductivity and electron conductivity and through which oxygen is permeated from a high oxygen partial pressure side to a low oxygen partial pressure side due to an oxygen partial pressure difference between both faces of the first layer; and a second layer (13) which is formed on a first face of the first layer, has a porosity larger than that of the first layer and comprises a porous body of which a porosity is 30% or more, and which comprises a catalyst porous body (15) made of a ceramic having catalytic activity on an area of at least a part of the second layer which includes a boundary face between itself and the first layer. A catalytic metal (16) is carried on at least a part of a surface of the porous body which constitutes the second layer.SELECTED DRAWING: Figure 1

Description

The present invention relates to an oxygen permeable membrane, a method for producing the same, and a reformer.

Conventionally, as an oxygen permeable film that selectively permeates oxygen, an oxide exhibiting oxygen ion (oxide ion) conductivity (for example, gadolinium solid-soluble ceria) and an oxide exhibiting electron conductivity (for example, iron) are contained. An oxygen permeable membrane mixed with a spinel-type composite oxide is known. As one of the uses of such an oxygen permeable membrane, there is known a use of generating oxygen necessary for a reforming reaction to generate hydrogen from a reforming raw material (see, for example, Patent Document 1). In this conventional technique, oxygen is extracted from air using an oxygen permeable film, and the obtained oxygen is used to reform a reforming raw material such as a hydrocarbon fuel by a partial oxidation reaction and supply it to a fuel cell or the like. A method of obtaining hydrogen for this purpose is disclosed.

Japanese Unexamined Patent Publication No. 2005-281806 Patent No. 5233202

Thinning of the oxygen permeable membrane is being studied as one of the methods for improving the performance of the oxygen permeable membrane. When the oxygen permeable membrane having oxygen ion conductivity and electron conductivity is thinned, the resistance in the oxygen permeable membrane is reduced, so that the oxygen permeable rate is improved. However, when the thickness of the oxygen permeable membrane is set to a certain value or less, the surface exchange reaction rate on the surface of the oxygen permeable membrane is higher than the oxygen diffusion rate inside the oxygen permeable membrane (the rate at which oxygen ions permeate the oxygen permeable membrane). The oxygen permeation rate does not increase even if the film thickness is reduced. Therefore, there is a limit to improving the performance of the oxygen permeable membrane by making the oxygen permeable membrane thinner. The surface exchange reaction rate is defined as the reaction in which oxygen ions are generated from oxygen molecules on one surface of the oxygen permeable membrane as shown in the following equation (1), and the following (2) on the other surface. ) Is the rate at which the reaction in which oxygen molecules are generated from oxygen ions proceeds as shown in the equation.

(1/2) O ₂ + 2e ⁻ → O ^2- … (1)
O ^2- → (1/2) O ₂ + 2e ⁻ … (2)

As one of the methods for further improving the oxygen permeation rate, a method of providing a catalyst for promoting the surface exchange reaction on the surface of the oxygen permeation membrane is known. Conventionally, as such a catalyst, a noble metal such as platinum (Pt) and a metal such as nickel (Ni) have been used (see, for example, Patent Document 2). However, precious metals are expensive and may be difficult to adopt.

Further, when a metal other than a noble metal such as Ni is used as a catalyst, the performance of the oxygen permeable membrane may deteriorate due to repeated oxidation and reduction of the catalyst depending on the usage environment of the oxygen permeable membrane. Specific examples of the usage environment in which oxidation / reduction of the catalyst becomes a problem include the usage environment when an oxygen permeable membrane is used for the reforming reaction to generate hydrogen as described above. Here, the oxygen-containing gas is supplied to one surface side (high oxygen partial pressure side) of the oxygen permeable membrane. Further, a reforming raw material such as a hydrocarbon fuel is supplied to the other surface side (low oxygen partial pressure side), and on the other surface, oxygen permeated through the oxygen permeable membrane is used to prepare the reforming raw material. The partial oxidation reaction proceeds. Therefore, while the reforming reaction is in progress, the catalyst on the other surface of the oxygen permeable membrane exists in the state of Ni by being exposed to the reducing atmosphere, but the supply of the reforming raw material is stopped and oxygen is generated. When exposed to, Ni is oxidized to nickel oxide (NiO) and expands. Therefore, if the reforming reaction using the oxygen permeable membrane is repeatedly progressed and stopped, the catalyst on the low oxygen partial pressure side repeats expansion and contraction due to oxidation and reduction, and the catalyst is damaged, resulting in poor durability of the oxygen permeable membrane. It could be enough.

The present invention has been made to solve the above-mentioned problems, and can be realized as the following forms.

(1) According to one embodiment of the present invention, an oxygen permeable membrane is provided. This oxygen permeable film is a first layer containing a composite oxide and having oxygen ion conductivity and electron conductivity, and low oxygen from the high oxygen partial pressure side due to the oxygen partial pressure difference between both sides of the first layer. A first layer that allows oxygen to permeate to the pressure dividing side; formed on the first surface of the first layer, has a higher porosity than the first layer, and has a porosity of 30% or more. A second layer made of a porous body, which comprises a catalytic porous body made of a ceramic having catalytic activity in a region including an interface with the first layer in at least a part of the second layer. A catalyst metal is supported on at least a part of the surface of the porous body which is provided with a second layer; and constitutes the second layer.
According to this form of oxygen permeable film, by supporting the catalyst metal on the surface of at least a part of the second layer including the catalyst porous body, the amount of the catalyst metal such as a noble metal used can be suppressed, and the oxygen permeable film can be used. Oxygen permeation performance can be improved. Further, even if the oxygen permeable membrane is used in an environment where the reducing atmosphere and the oxidizing atmosphere are repeatedly switched, the deterioration of the oxygen permeable performance can be suppressed and the oxygen permeable operation can be stably continued. Here, the term "ceramic having catalytic activity" means that the ceramic portion itself in the second layer exhibits catalytic activity. Further, by setting the pore ratio of the second layer to 30% or more, the gas used for the reaction proceeding on the surface of the oxygen permeable membrane and the gas generated by the reaction proceeding on the surface of the oxygen permeable membrane (for example, oxygen permeation). Oxygen that has permeated the membrane, hydrocarbons that are used as reforming raw materials, hydrogen-containing gas that is generated by the reaction of oxygen that has permeated the oxygen permeation membrane and hydrocarbons, etc.) can be easily diffused in the second layer, and oxygen The performance of the permeable membrane can be improved.

(2) In the oxygen permeable membrane of the above form, the catalytic porous body may include an oxygen ion conductor and an electron conductor. According to this form of oxygen permeable membrane, a reaction that proceeds on the catalytic porous body (for example, a reaction in which oxygen ions become oxygen molecules, or when an oxygen permeable membrane is used in a reformer, it is modified with oxygen ions. It facilitates the transfer of electrons in the process of (reaction etc. progressing with the raw material gas), and can improve the oxygen permeation performance of the oxygen permeation membrane.

(3) In the oxygen permeable membrane of the above embodiment, the second layer is a support layer composed of a ceramic provided apart from the interface with the first layer in addition to the catalyst porous body. May be provided. According to this form of the oxygen permeable membrane, the strength of the oxygen permeable membrane can be increased, the first layer can be further thinned, and the performance of the oxygen permeable membrane can be improved.

(4) In the oxygen permeable film of the above form, the electron conductor contained in the catalytic porous body is a perovskite type composite oxide having a basic structure of ABO ₃ , and the element corresponding to A is lanthanum ( It is at least one element selected from La), strontium (Sr), calcium (Ca), and barium (Ba), and the element corresponding to B may be chromium (Cr) and nickel (Ni). Good. According to this form of oxygen permeable membrane, the effect of improving the performance of the oxygen permeable membrane can be enhanced.

(5) in an oxygen permeable membrane of the embodiment, the electron conductor contained in the catalyst porous _{body, La 1-x Sr x Cr} 1-y Ni y O 3-z (0 <x <0.4, It may be a perovskite-type composite oxide represented by 0 <y <0.20, z is arbitrary). According to this form of oxygen permeable membrane, the effect of improving the performance of the oxygen permeable membrane is enhanced, and even if the catalyst porous body is repeatedly oxidized and reduced, the catalyst porous body is caused by expansion and contraction of the catalytic porous body. The effect of suppressing damage to the body can be enhanced. In the electron conductor, when x is 0.4 or more, a heterogeneous phase having high resistance due to reaction with the oxygen ion conductor contained in the catalytic porous body during the manufacturing process and use of the oxygen permeable membrane exposed to high temperature. Is generated, and the performance of the oxygen permeable membrane tends to deteriorate. Further, when x is 0, the electron conductivity of the catalyst porous body is lowered, and the oxygen permeation performance of the oxygen permeable membrane is lowered. Further, when y is 0, the catalytic activity of the electron conductor is lowered, so that the performance of the oxygen permeable membrane is lowered. Further, when y is 0.2 or more, Ni cannot be completely dissolved in the electron conductor, and some of the Ni atoms contained in the manufacturing raw material do not form a perovskite structure and expand due to oxidation / reduction. It will form NiO particles with a higher shrinkage rate. As a result, when the catalyst porous body is repeatedly oxidized and reduced, the catalyst porous body may be damaged due to expansion and contraction of the catalyst porous body. When y is 0.2 or more, some of the Ni atoms in the raw material form NiO, so that the perovskite-type composite oxide is in a state in which B sites are partially deleted, and the catalytic activity is increased. It may decrease and the oxygen permeation performance may decrease.

(6) In the oxygen permeable membrane of the above embodiment, the element constituting the catalyst metal may be the same as the metal element constituting the electron conductor contained in the catalyst porous body. According to this form of oxygen permeable film, the oxygen permeation performance of the oxygen permeable film is further enhanced by the interaction between the metal element constituting the electron conductor contained in the catalytic porous body and the element constituting the catalyst metal. Oxygen permeation can be stably continued.

(7) In the oxygen permeable film of the above form, the electron conductor contained in the catalytic porous body is a perovskite-type composite oxide having a basic structure of ABO ₃ , and the element corresponding to A is lanthanum (La). ) And strontium (Sr), and the elements corresponding to B may be chromium (Cr) and nickel (Ni), and the catalyst metal may be nickel (Ni). According to this form of oxygen permeable membrane, the catalytic activity of Ni promotes the reaction between oxygen that has permeated the oxygen permeable membrane and the hydrocarbon that is the reforming raw material, for example, when the oxygen permeable membrane is used in the reformer. , The oxygen permeation performance of the oxygen permeation membrane can be further enhanced, and the oxygen permeation operation can be stably continued.

(8) In the oxygen permeable membrane of the above form, the porosity of the support layer may be larger than the porosity of the catalytic porous body. According to this form of oxygen permeation membrane, it is possible to suppress a decrease in oxygen permeation performance due to preventing gas (for example, a gas containing oxygen, hydrocarbons or hydrogen) from diffusing in the support.

(9) According to another embodiment of the present invention, the method for producing an oxygen permeable membrane according to any one of (1) to (8) is provided. In the method for producing the oxygen permeable film, a first precursor layer or the first layer for forming the first layer and a second precursor layer for forming the second layer are used. A step of forming a laminated precursor laminate; a step of firing the precursor laminate to obtain a fired laminate having the first layer and the second layer; the step of forming the fired laminate. A step of impregnating at least a part of the second layer with a solution containing the catalyst metal to support the catalyst metal on the surface of at least a part of the second layer;
According to the method for producing an oxygen permeable membrane of this form, a catalyst metal is applied to at least a part of the second layer by a simple operation of impregnating at least a part of the second layer with a solution containing the catalyst metal. It can be carried. Further, since the catalyst metal can be supported after the firing step, deterioration of the performance of the catalyst metal due to firing can be suppressed.

(10) According to still another embodiment of the present invention, the method for producing an oxygen permeable membrane according to (3) is provided. The method for producing the oxygen permeable film includes a step of preparing the support layer; a step of forming a catalyst porous body precursor layer for forming the catalyst porous body on the support layer; and a step of forming the catalyst porous body on the support layer. A first precursor layer for forming the first layer is formed on the catalyst porous body precursor layer or the catalyst porous body obtained from the catalyst porous body precursor layer formed in the above. And the step of forming the precursor laminate; the step of calcining the precursor laminate to obtain the calcined laminate having the support layer, the catalyst porous body, and the first layer; Of the support layer and the catalyst porous body constituting the above, a portion including at least a part of the support layer is impregnated with a solution containing the catalyst metal, and the surface of the region impregnated with the solution is covered with the above. It comprises a step of supporting a catalyst metal and;
According to the method for producing an oxygen permeable film of this form, the catalyst metal can be supported after the step of firing the oxide constituting the oxygen permeable film, so that the deterioration of the performance of the catalyst metal due to firing can be suppressed. be able to. At this time, in the first layer, the catalyst metal can be easily arranged in the vicinity of the surface on the side covered by the support layer.

(11) In the method for producing an oxygen permeable membrane of the above embodiment, the melting point of the catalyst metal may be lower than the sintering temperature at the time of firing the precursor laminate. According to the method for producing an oxygen permeable film of this form, a catalyst metal having a melting point lower than the firing temperature of the precursor laminate and having a high catalytic activity can be selected. Therefore, while ensuring freedom of selection regarding the catalyst metal, It is possible to suppress a decrease in catalytic activity due to firing.

(12) According to still another embodiment of the present invention, the oxygen permeable membrane according to any one of (1) to (8) is provided, and hydrogen is generated from the modified raw material by a partial oxidation reaction. Pawnbrokers are provided. This reformer is formed on the oxygen permeable membrane on the first surface side of the first layer, and has a reforming raw material supply path through which the reforming raw material flows; a second of the first layer. The oxygen-containing gas flow path formed on the oxygen-containing membrane on the surface side and through which the oxygen-containing gas flows; is provided, and the partial oxidation reaction using oxygen in the oxygen-containing gas that has passed through the oxygen-containing membrane proceeds. To do.
According to this type of reformer, the durability and oxygen permeation performance of the oxygen permeable membrane included in the reformer are enhanced, so that the durability and reforming efficiency of the entire reformer can be improved.

The present invention can be realized in various forms other than the above, for example, in a form such as a fuel reforming method.

It is sectional drawing which shows the schematic structure of an oxygen permeable membrane and a reformer. It is a process drawing which shows the manufacturing method of an oxygen permeable membrane. It is sectional drawing which shows the schematic structure of an oxygen permeable membrane and a reformer. It is a process drawing which shows the manufacturing method of an oxygen permeable membrane. It is explanatory drawing which shows the result of having investigated the structure of an oxygen permeable membrane and the performance of an oxygen permeable membrane. It is explanatory drawing which shows the schematic structure of the measuring apparatus.

A. First Embodiment:
(A-1) Composition of oxygen permeable membrane:
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of an oxygen permeable membrane 10 as a first embodiment of the present invention and a reformer 20 including the oxygen permeable membrane 10. First, the oxygen permeable membrane 10 will be described.

The oxygen permeable membrane 10 includes a first layer 12, a first catalyst layer 13 provided on one surface (first surface) side of the first layer 12, and the other surface of the first layer 12. It has a laminated structure including a second catalyst layer 14 provided on the (second surface) side. The first layer 12 is a gas-impermeable dense layer having both oxygen ion conductivity and electron conductivity. By providing the first layer 12, the oxygen permeable membrane 10 selectively permeates oxygen from the high oxygen partial pressure side to the low oxygen partial pressure side by using the oxygen partial pressure difference between both sides of the oxygen permeable membrane 10 as a driving force. Will be possible. In the present embodiment, the first catalyst layer 13 is arranged on the surface on the low oxygen partial pressure side of both surfaces of the first layer 12, and the second catalyst layer 14 is the surface on the high oxygen partial pressure side. It is placed on top. The oxygen permeable membrane 10 of the present embodiment is configured as a self-supporting membrane having no carrier (base material, support).

The first layer 12 is formed by a mixture of an oxide having oxygen ion conductivity (hereinafter referred to as an oxygen ion conductor) and a substance having electron conductivity (hereinafter referred to as an electron conductor). Can be done. Further, the first layer 12 may be formed of an oxide having both oxygen ion conductivity and electron conductivity (hereinafter, also referred to as a mixed conductive oxide). Alternatively, the first layer 12 may be formed by a mixture of an oxygen ion conductor and / or an electron conductor and a mixed conductive oxide.

As the oxygen ion conductor contained in the first layer 12, for example, an oxygen ion conductor selected from stabilized zirconia, partially stabilized zirconia, and a ceria-based solid solution can be used. Stabilized zirconia is zirconia stabilized by dissolving one or more dopants, which are oxides, in zirconium oxide (ZrO ₂ ). Oxides that can be used as dopants include, for example, yttrium oxide (Y ₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ), ytterbium oxide (Yb ₂ O ₃ ), calcium oxide (CaO), and magnesium oxide (MgO). Can be mentioned. From the viewpoint of improving oxygen ion conductivity and stability, the stabilized zirconia is preferably selected from Scandia-stabilized zirconia (hereinafter, also referred to as ScSZ) and yttria-stabilized zirconia (hereinafter, also referred to as YSZ). Examples of the ceria-based solid solution include cerium-based composite oxides such as gadolinium solid-dissolved ceria (GDC) and samarium solid-dissolved ceria (SDC).

Examples of the electron conductor included in the first layer 12 include an oxide electron conductor having a perovskite structure, an oxide electron conductor having a spinel-type crystal structure, and an electron conductor selected from a metal material such as a noble metal. The body can be used. As the oxide electron conductor having a perovskite structure, for example, an LSM-based oxide in which Sr is added to La sites in a LaMnO _3- based compound, or a composite oxide such as CaTIO ₃ or BaTiO ₃ can be used. Alternatively, a composite oxide represented by the following formula (3) may be used. The alkaline earth metal M in the formula (3) is preferably strontium (Sr) or calcium (Ca).

La _1-x M _x CrO _3-z ... (3)
(In the formula, M is an element selected from alkaline earth metals other than magnesium (Mg), and 0 ≦ x ≦ 0.4. In addition, z is the ratio of metal elements in the formula and the environment. It is a value indicating that the amount of oxygen atoms fluctuates depending on the temperature and atmosphere.)

The mixed conducting oxides first layer 12 comprises, for example, in LaGaO ₃ type compound, with the addition of Sr to La site, LSGF based oxide having a perovskite structure with the addition of Fe to the Ga site and, SrCoO _{Among the three} compounds, a BSCF oxide having a perovskite structure in which Ba is added to Sr sites and Fe is added to Co sites can be mentioned. Alternatively, as the mixed conductive oxide contained in the first layer 12, an oxide having a layered perovskite structure, an oxide having a fluorite-type structure, an oxide having an oxyapatite structure, an oxide having a melilite structure, or the like is used. You can also do it.

The film thickness of the first layer 12 can be, for example, 1 to 1000 μm. However, if the strength and denseness of the first layer 12 are within the permissible range, it may be less than 1 μm, and if the decrease in oxygen permeation rate due to the thickening of the first layer 12 is within the permissible range, it exceeds 1000 μm. You may. The thinner the film thickness of the first layer 12, the higher the gas permeability of the first layer 12, and the thicker the film thickness of the first layer 12, the more oxygen permeates the first layer 12. The resistance at the time may increase and the oxygen permeation rate may decrease. Further, the porosity of the first layer 12 can be 10% or less. However, if the oxygen permeation performance of the oxygen permeation membrane 10 can be ensured, the porosity of the first layer 12 may exceed 10%. The larger the porosity of the first layer 12, the less dense the first layer 12 may be. If the denseness of the first layer 12 is reduced and oxygen is present that passes through the first layer 12 in the form of oxygen molecules rather than permeating through the first layer 12 in the state of oxygen ions. The oxygen permeation performance of the oxygen permeation membrane 10 is lowered. Therefore, the film thickness and porosity of the first layer 12 may be appropriately set so that the first layer 12 is substantially impermeable to gas within a range in which the performance of the oxygen permeable membrane 10 can be sufficiently ensured. ..

The pore ratio of the first layer 12 can be measured by observing the cross section of the first layer 12 with a scanning electron microscope (SEM). Specifically, a plurality of straight lines are drawn in an SEM image obtained by magnifying the cross section of the first layer 12 by 500 times, the total length of all the straight lines drawn in the SEM image is L, and the pores of all the straight lines are formed. When the above L and L'are measured with the total length of the portions crossing the above as L', the porosity P (%) is expressed by the following equation (4).

P = L'/ L × 100 ... (4)

By ensuring a sufficient number of the plurality of straight lines, the porosity P can be measured with high accuracy. In this embodiment, two SEM images obtained by magnifying the cross section of the first layer 12 by 500 times are used for measuring the porosity. Then, 10 straight lines for each SEM image, a total of 20 straight lines are drawn, and the above L and L'are measured to calculate the porosity P.

The first catalyst layer 13 includes a catalyst porous body 15 and a catalyst metal 16 supported on the surface of the catalyst porous body 15.

The catalytic porous body 15 is formed of a ceramic having an activity of promoting the reaction of the above-mentioned formula (2) in which oxygen molecules are generated from oxygen ions. The catalyst porous body 15 is formed to have a larger porosity than the first layer 12, and has pores that communicate three-dimensionally, so that oxygen molecules generated by the reaction of the reaction (2) and modifications can be made. Hydrocarbon gas, which is a raw material for quality reaction, and hydrogen-containing gas generated by reforming reaction can flow in the pores.

The porosity of the catalyst porous body 15 is caused by hindering the diffusion of oxygen molecules generated in the reaction of equation (2), hydrocarbon gas which is a raw material of the reforming reaction, and hydrogen-containing gas generated by the reforming reaction. From the viewpoint of suppressing a decrease in oxygen permeation performance, it may be 30% or more, and more preferably 40% or more. The porosity of the catalyst porous body 15 is preferably 80% or less, and more preferably 60% or less, from the viewpoint of maintaining the structure of the catalyst porous body 15 well. The porosity of the catalyst porous body 15 (and the first catalyst layer 13) can be measured by the same method as the porosity of the first layer 12 described above.

The catalyst porous body 15 may have an activity of promoting the reaction of the formula (2) and may be stable under the conditions (temperature, atmosphere, etc.) in which the oxygen permeable membrane 10 is used. The catalyst porous body 15 further preferably has at least one of oxygen ion conductivity and electron conductivity. That is, the catalyst porous body 15 may include at least one of an oxygen ion conductor and an electron conductor. In order to make the catalyst porous body 15 a mixed conductor exhibiting both oxygen ion conductivity and electron conductivity, the catalyst porous body 15 is configured to contain both an oxygen ion conductor and an electron conductor. In addition, it may contain a mixed conductive oxide. As a result, the conductivity of the oxygen ions that have passed through the first layer 12 and the electrons generated by the reaction of the formula (2) in the catalytic porous body 15 can be improved, and the oxygen permeation performance can be improved. It is desirable that the catalytic porous body 15 further exhibits an activity of promoting a partial oxidation reaction described later.

Examples of the electron conductor having an activity of promoting the reaction of the formula (2) include a composite oxide having a perovskite structure whose basic structure is ABO ₃ , and the element corresponding to A is lanthanum (La). At least one element selected from strontium (Sr), calcium (Ca), and barium (Ba), and the element corresponding to B is preferably a composite oxide of chromium (Cr) and nickel (Ni). Can be used. Such a composite oxide is an electron conductor having an activity of promoting a partial oxidation reaction described later in addition to an activity of promoting the reaction of the formula (2). This composite oxide promotes the reaction between the oxygen that has permeated the oxygen permeation membrane and the hydrocarbon that is the reforming raw material by the catalytic activity of nickel (Ni), and further enhances the oxygen permeation performance of the oxygen permeation membrane. Can be done.

Among such composite oxides, the perovskite-type composite oxide represented by the following formula (5) can be particularly preferably used. That is, an LaCrO ₃ type compound basic structure having a perovskite structure is ABO _3, with the addition of Sr to La site, it is possible to use a composite oxide in which Ni is added to Cr site.

_{La 1-x Sr x Cr 1} -y Ni y O 3-z ... (5)
(In the formula, x and y are non-zero positive values. In addition, z is a value indicating that the amount of oxygen atoms fluctuates depending on the ratio of metal elements in the formula, the environmental temperature and the atmosphere. Is.)

Here, in the above formula (5), the values of x and y indicate the degree to which the composite oxide exhibits the activity of promoting the reaction of the formula (2), and the values of x and y are different from those of other compounds in the process of producing the catalytic porous body 15. It may be appropriately set according to the degree to which a heterogeneous phase having high resistance is generated by the reaction. Specifically, in the above equation (5), the larger the value of x or y (the larger the substitution amount of La site or Cr site), the higher the catalytic activity and the higher the electron conductivity. become. However, as the amount of substitution increases, the crystal structure becomes unstable and the reactivity with other elements increases. As a result, in the firing step for producing the oxygen permeable membrane 10 and the process of using the oxygen permeable membrane 10, it has a composition different from that of the composite oxide of the above formula (5) and becomes a resistance at the time of oxygen permeation. The amount of heterogeneous phase produced can increase. Therefore, in order to suppress the formation of the heterogeneous phase and secure the oxygen permeation performance of the oxygen permeation membrane 10, for example, in the above equation (5), 0 <x <0.4, 0 <y <. It is preferably 0.2, and more preferably 0 <x <0.25 and 0 <y <0.175.

When x is 0.4 or more, the amount of highly resistant heterogeneous phase formed by the reaction of the composite oxide of the formula (5) with other compounds increases in the process of producing the catalytic porous body 15, and the oxygen permeable membrane The oxygen permeation performance of 10 tends to decrease. Further, when x is 0, the electron conductivity of the catalyst porous body 15 is lowered, and the oxygen permeation performance of the oxygen permeable membrane 10 is lowered. Further, when y is 0.2 or more, a part of Ni atoms cannot be solid-solved in the perovskite type crystal structure, and NiO particles are formed. Since the degree of expansion and contraction of NiO due to repeated redox is larger than that of a composite oxide having a perovskite-type crystal structure, when y is 0.2 or more, the catalyst porous due to repeated redox. Damage to the body 15 is likely to occur. Further, when y is 0, the catalytic activity for promoting the reaction of the formula (2) is lowered, and the oxygen permeation performance of the oxygen permeation membrane 10 is lowered.

Further, among the composite oxides of the formula (5), the perovskite-type composite oxide represented by the following formula (6) can be particularly preferably used. With such a configuration, the activity of the catalytic porous body 15 to promote the reaction of the formula (2) can be particularly enhanced. Further, with such a configuration, even if the catalyst porous body 15 is repeatedly oxidized and reduced, damage to the catalyst porous body 15 due to expansion and contraction of the catalyst porous body 15 can be suppressed.

_{La 1-x Sr x Cr 1} -y Ni y O 3-z ... (6)
(In the formula, 0 <x <0.4, 0 <y <0.20. In addition, z varies in the amount of oxygen atoms depending on the ratio of metal elements in the formula, the environmental temperature and the atmosphere. It is a value indicating that it should be done.)

Further, as another example of the electron conductor having an activity of promoting the reaction of the formula (2), for example, a composite oxide represented by the following formula (7) can be mentioned. That is, a SrTiO ₃ based compound having a perovskite structure, it is possible to use a composite oxide doped with La to Sr sites. The composite oxide of the formula (7) is an electron conductor having an activity of generating oxygen molecules from oxygen ions permeated in the first layer 12 and an activity of promoting a partial oxidation reaction described later.

Sr _1-x La _x TiO _3-z ... (7)
(In the formula, x is a non-zero positive value. In addition, z is a value indicating that the amount of oxygen atoms fluctuates depending on the ratio of metal elements in the formula, the environmental temperature and the atmosphere. .)

Here, in the above equation (7), the value of x may be appropriately set so that different phases are unlikely to be generated in the process of producing the catalyst porous body 15, and it is desirable that 0 <x <0.4.

The catalyst porous body 15 may contain, as an electron conductor, at least one oxide selected from the composite oxides of the formulas (5) to (7), and further another electron conductor. good. As the electron conductor that can be contained, a substance selected from the electron conductors described in the description of the first layer 12 can be used.

As the oxygen ion conductor contained in the catalyst porous body 15, a composite oxide selected from the oxygen ion conductors described in the description of the first layer 12 can be used.

In the first catalyst layer 13 of the present embodiment, as described above, the catalyst metal 16 is further dispersed and supported on the surface of the catalyst porous body 15 described above. The catalyst metal 16 is a metal having an activity of promoting the reaction of the above-mentioned formula (2). When the oxygen permeable membrane 10 is applied to the reformer 20 as shown in FIG. 1, it is desirable that the catalyst metal 16 further has an activity of promoting a partial oxidation reaction described later. Here, the surface of the catalyst porous body 15 includes the surface of the pores formed inside the catalyst porous body 15.

The catalyst metal 16 may have the above-mentioned catalytic activity and may be stable under the conditions (temperature, atmosphere, etc.) in which the oxygen permeable membrane 10 is used. As the catalyst metal 16, for example, nickel (Ni) can be preferably used. Alternatively, precious metals such as rhodium (Rh) and platinum (Pt), cobalt (Co), and copper (Cu) can also be used.

In particular, it is desirable that the catalyst metal 16 is a metal of the same type as the metal contained in the composite oxide that constitutes the catalytic porous body 15 and has catalytic activity. For example, when the composite oxide of the formula (5) is used as the constituent material of the catalyst porous body 15, it is desirable to use Ni as the catalyst metal 16.

In the present embodiment, the catalyst metal 16 does not have to be supported over the entire surface of the pores formed in the catalyst porous body 15, and the catalyst is formed on the pore surface in at least a part of the catalyst porous body 15. It suffices if the metal 16 is supported. The "catalytic porous body 15" in the present embodiment corresponds to the "second layer" in the [means for solving the problem].

The second catalyst layer 14 is formed of a ceramic porous body having an activity of promoting the reaction of the above-mentioned formula (1) in which oxygen ions are generated from oxygen molecules. The second catalyst layer 14 has a porosity larger than that of the first layer 12, and has pores that communicate three-dimensionally, so that oxygen molecules used in the reaction of the formula (1) can be contained. It can be distributed in the pores. The porosity of the second catalyst layer 14 can be, for example, the same as that of the catalyst porous body 15.

The second catalyst layer 14 may have an activity of promoting the reaction of the formula (1) and may be stable under the conditions (temperature, atmosphere, etc.) in which the oxygen permeable membrane 10 is used. The second catalyst layer 14 is preferably a mixed conductor, further having oxygen ion conductivity and electron conductivity. Examples of the electron conductor having an activity of promoting the reaction of the formula (1) include composite oxides such as La _0.8 Sr _0.2 MnO _3-z and La _0.8 Sr _0.2 CrO _3-z . (Z in the above formula is a value indicating that the amount of oxygen atoms fluctuates depending on the ratio of metal elements in the formula, the environmental temperature and the atmosphere). As the oxygen ion conductor contained in the second catalyst layer 14, a composite oxide selected from the oxygen ion conductors described in the description of the first layer 12 can be used.

(A-2) Method for producing oxygen permeable membrane:
FIG. 2 is a process diagram showing a method for producing the oxygen permeable membrane 10 of the present embodiment. When manufacturing the oxygen permeable membrane 10, first, the first layer 12 is made (step S100). In order to prepare the first layer 12, a raw material containing a composite oxide (an oxide selected from an oxygen ion conductor, an electron conductor, and a mixed conductive oxide) constituting the first layer 12 is used. prepare. The composite oxide constituting the first layer 12 can be formed by, for example, a solid-phase reaction method. In the solid phase reaction method, powder raw materials such as oxides, carbonates, and nitrates are weighed so that the metal elements in the powder raw materials are in a predetermined ratio according to the composition of the oxide to be produced. This is a well-known method for synthesizing a desired oxide by performing heat treatment (calcination) after mixing. The method for producing the oxide constituting the first layer 12 may be a method other than the solid phase reaction method, and various methods capable of producing a composite oxide such as a coprecipitation method, a pechini method and a sol-gel method can be used. The method can be adopted. The pechini method is a method in which a precursor is prepared by an esterification reaction of a chelate compound of a metal ion and citric acid with a polyalcohol such as ethylene glycol, and oxide particles are obtained by heat treatment.

In order to prepare the first layer 12, for example, powders of raw materials such as the above-mentioned oxides may be prepared, mixed in a state where the particle size of each of these raw material powders is sufficiently small, and fired after molding. The mixed raw material powder may be molded, for example, by press molding. The layer obtained by molding the mixed raw material powder is also referred to as a "first precursor layer". By adjusting the temperature and time when firing the first precursor layer, the desired denseness can be ensured in the first layer 12.

Further, when producing the oxygen permeable membrane 10, a first catalyst paste for forming the catalyst porous body 15 and a second catalyst paste for forming the second catalyst layer 14 are prepared. (Step S110). The composite oxide constituting the catalyst porous body 15 or the second catalyst layer 14 may be, for example, a solid phase reaction method, a coprecipitation method, a pechini method, or the same as the composite oxide constituting the first layer 12. It can be produced by the sol-gel method. The first catalyst paste and the second catalyst paste are obtained by adding other materials such as other oxides and pore-forming agents to such a composite oxide as necessary to obtain a raw material powder. It is obtained by mixing a solvent with this raw material powder. The porosity of the catalytic porous body 15 of the first catalyst layer 13 and the second catalyst layer 14 can be adjusted, for example, by adjusting the particle size and the amount of fine particles constituting the pore-forming agent.

Then, the first catalyst paste is applied onto one surface of the first layer 12 produced in step S100, and the second catalyst paste is applied onto the other surface of the first layer 12 (step S120). ). The application of each catalyst paste onto the first layer 12 can be carried out by, for example, a method selected from a screen printing method, a spray method, a dip coating method, a doctor blade method, an inkjet method and the like. In addition, in this embodiment, since the catalyst porous body 15 corresponds to the “second layer” in the [means for solving the problem], from the first catalyst paste for forming the catalyst porous body 15. The layer before firing corresponds to the "second precursor layer". The laminate obtained in step S120 in which the second precursor layer is formed on the first layer 12 corresponds to the “precursor laminate”.

Then, the precursor laminate obtained by applying the first catalyst paste and the second catalyst paste on the first layer 12 is fired to obtain a fired body (step S130). The fired body composed of the catalyst porous body 15, the first layer 12, and the second catalyst layer 14 obtained in step S130 corresponds to the “fired laminate” in [Means for Solving Problems].

Then, the catalyst metal 16 is supported on the surface of the catalyst porous body 15 of the fired body (step S140) to complete the oxygen permeable membrane 10. To support the catalyst metal 16, for example, a solution containing the catalyst metal 16 is placed on the catalyst porous body 15, and then the laminate is heated to transfer the catalyst metal 16 in the solution to the catalyst porous body 15. It can be done by baking on the surface. As the solution containing the catalyst metal 16, for example, an aqueous solution of a salt of the catalyst metal 16 can be used. The solution containing the catalyst metal 16 may be a solution other than an aqueous solution of a salt of the catalyst metal 16 as long as the catalyst metal 16 can be dispersed and supported on the surface of the catalyst porous body 15, and may be, for example, a resistate solution. ..

The operation of arranging the solution containing the catalyst metal 16 on the catalyst porous body 15 can be performed, for example, by impregnating the catalyst porous body 15 with the solution containing the catalyst metal 16. Alternatively, a solution containing the catalyst metal 16 may be applied to the surface of the catalyst porous body 15. In the case of impregnation, the solution is allowed to enter the pores of the catalyst porous body 15 by a simple operation of immersing at least a part of the catalyst porous body 15 in the solution. Can be done.

(A-3) Reformer configuration:
The reformer 20 shown in FIG. 1 includes the oxygen permeable membrane 10 described above, and reforming in which a fluid as a reforming raw material flows on one surface side (first catalyst layer 13 side) of the oxygen permeable membrane 10. The raw material flow path 22 is formed. Further, an air flow path 24 through which air as an oxygen-containing gas flows is formed on the other surface side of the oxygen permeable membrane 10. The air flow path 24 corresponds to the "oxygen-containing gas flow path" described in [Means for solving the problem], and the reforming raw material flow path 22 is described in [Means for solving the problem]. Corresponds to [modified raw material supply channel]. As described above, the oxygen permeable membrane 10 has oxygen ion permeability and has a property of specifically moving oxygen from the side where the oxygen partial pressure is high to the side where the oxygen partial pressure is low. Therefore, in the reformer 20, oxygen in the air flow path 24 permeates to the reforming raw material flow path 22 side through the oxygen permeation membrane 10. Then, on the surface of the oxygen permeable membrane 10 on the side of the modified raw material flow path 22, the partial oxidation reaction of the modified raw material proceeds by utilizing the oxygen permeated through the oxygen permeable membrane 10.

In FIG. 1, the oxygen partial pressure (PO ₂ ) on the air flow path 24 side is higher than the oxygen partial pressure (P'O ₂ ) on the reforming raw material flow path 22 side, and is between both sides of the oxygen permeable membrane 10. The state in which the oxygen partial pressure gradient is generated is conceptually shown by a broken line. In the oxygen permeable membrane 10, oxygen permeates from the high oxygen partial pressure side (air flow path 24) to the low oxygen partial pressure side (modified raw material flow path 22) by using such an oxygen partial pressure difference between both sides as a driving force. .. At this time, the oxygen molecules in the air flow path 24 are ionized on the surface of the oxygen permeation film 10 on the air flow path 24 side, and the generated oxygen ions reform the inside of the oxygen permeation film 10 having oxygen ion conductivity. It moves to the flow path 22 side. Since the oxygen permeable membrane 10 of the present embodiment has electron conductivity as well as oxygen ion conductivity, when oxygen ions move as described above, electrons move in the membrane in the opposite direction to the oxygen ions. Therefore, oxygen can be permeated without applying a voltage to the oxygen permeation membrane 10 from the outside. The electron conductivity in the oxygen permeable membrane 10 may be both electron conduction and Hall conduction, or may be either one. In the present embodiment, the term electron conductivity of the oxygen permeable membrane 10 includes the case of both electron conduction and Hall conduction, or one of them.

When oxygen is transported to the modified raw material flow path 22 side as described above, the modified raw material is subjected to a partial oxidation reaction on the modified raw material flow path 22 side (first catalyst layer 13) of the oxygen permeation membrane 10. Modification is performed. As the reforming raw material, various gas fuels or liquid fuels can be used. As the gaseous fuel, for example, hydrocarbon fuels such as methane and natural gas containing methane as a main component can be used. Further, as the liquid fuel, for example, liquid hydrocarbons, alcohols such as methanol, or ethers can be used. When the liquid fuel is used, the liquid fuel may be vaporized prior to the supply to the reforming raw material flow path 22. As an example of the partial oxidation reaction of the reforming raw material, the partial oxidation reaction of methane is shown in the following equation (8).

CH ₄ + (1/2) O ₂ → CO + 2H ₂ … (8)

As described above, the reformer 20 that produces hydrogen and carbon monoxide from a reforming raw material such as a hydrocarbon can be used, for example, to obtain hydrogen to be supplied as a fuel gas to a fuel cell. Alternatively, the obtained hydrogen and carbon monoxide may be further subjected to hydrocarbon conversion to produce a liquid hydrocarbon fuel, that is, used for GTL (Gas To Liquid) technology.

According to the method for producing the oxygen permeable membrane 10 of the present embodiment and the oxygen permeable membrane 10 configured as described above, the activity of the surface exchange reaction (reaction of the formula (2)) in the first catalyst layer 13 is determined. In addition to increasing the activity, the activity of the partial oxidation reaction of the formula (8) can be enhanced when used in the reformer 20. As a result, the oxygen permeation flow velocity density in the oxygen permeation membrane is improved, and the performance as an oxygen permeation membrane is improved.

Specifically, since the first catalyst layer 13 arranged on the low oxygen concentration side is formed by further supporting the catalyst metal 16 on the catalyst porous body 15 made of ceramic having catalytic activity, the catalyst The performance of the oxygen permeable film can be improved as compared with the case where the catalyst layer is formed only by the active ceramic. In particular, when the low oxygen concentration side (one surface side) of the oxygen permeable membrane 10 has a reducing atmosphere, as in the case of applying the oxygen permeable membrane 10 to the reformer 20, the oxygen permeable performance of the oxygen permeable membrane is improved. The effect of enhancing can be remarkably obtained.

The reason is considered as follows. That is, in a ceramic having catalytic activity, it is considered that the metal element in the composite oxide contained in the ceramic exhibits high catalytic activity on the surface of the catalyst layer under a reducing atmosphere (for example, in a hydrogen atmosphere). For example, when the catalyst porous body 15 contains the composite oxide of the formula (5), when the environment of the first catalyst layer 13 becomes a reducing atmosphere, a part of Ni atoms contained in the Cr site of the perovskite structure However, it is considered that minute Ni fine particles are formed on the surface of the composite oxide. Since such Ni fine particles are much smaller than Ni particles, which is an embodiment of a Ni catalyst composed of nickel (Ni) under a reducing atmosphere, the amount of Ni forming the Ni fine particles is very small. Can also exhibit extremely high catalytic activity. In the present embodiment, since the catalyst metal is further supported on the ceramic, an interaction acts between the supported catalyst metal and the metal element in the composite oxide, and the metal element in the composite oxide is composited. It is considered that the above-mentioned fine particles are easily formed on the surface of the oxide. As a result, it is considered that the catalytic activity of the entire catalyst layer is enhanced as compared with the case where the catalyst layer composed of only the catalyst ceramic or only the catalyst metal is provided.

Here, when the reducing power of the atmosphere is relatively weak (for example, under a modified raw material atmosphere), for example, the reaction in which Ni is reduced from the Cr site of the perovskite structure to form Ni fine particles on the surface is weakened, and the reaction is weakened in the perovskite structure. The expression of catalytic activity by the solid-dissolved Ni atom may be relatively weak. In the present embodiment, by further supporting the catalyst metal 16 on the catalyst porous body 15, the above-mentioned interaction works and the above-mentioned fine particles are easily formed on the surface of the composite oxide. It is considered that high catalytic activity can be obtained even in an atmosphere having a relatively weak reducing power as shown below.

If the elements constituting the catalyst metal 16 supported on the catalyst porous body 15 are the same as the metal elements constituting the composite oxide such as an electron conductor contained in the catalyst porous body 15, the above-mentioned mutual It is considered that the effect of strengthening the action and improving the catalytic activity (oxygen permeation performance) is further enhanced. Here, among the metal elements that can constitute the catalyst metal 16, a noble metal such as platinum (Pt) has a property of being relatively easily aggregated when it exists in the form of particles. Therefore, the metal element in the composite oxide contained in the catalyst porous body 15 and the metal element constituting the catalyst metal 16 are of the same type as each other, and by using a base metal element such as nickel (Ni). , Aggregation of catalytic metal fine particles in a reducing atmosphere can be suppressed, and the effect of suppressing performance deterioration can be enhanced.

Further, according to the present embodiment, since the catalytic porous body 15 of the first catalyst layer 13 is formed by using the composite oxide having catalytic activity, the oxygen permeable film 10 is repeatedly used to permeate oxygen. Even when the operation of switching between the reducing atmosphere and the oxidizing atmosphere is repeated on the low oxygen concentration side of the film 10, it is possible to suppress a decrease in oxygen permeation performance. For example, when the catalyst layer is composed of nickel (Ni) which is a catalyst metal, the catalyst metal is oxidized to the state of Ni when the atmosphere on the low oxygen concentration side of the oxygen permeable film 10 is switched as described above. The catalyst layer may be damaged by switching to the nickel (NiO) state and repeating expansion and contraction. On the other hand, the catalyst porous body 15 included in the first catalyst layer 13 of the present embodiment has an extremely small degree of expansion / contraction due to oxidation / reduction as compared with the catalyst metal. This is a state in which the composite oxide constituting the catalytic porous body 15 forms fine particles on the surface of, for example, a part of Ni atoms contained in the perovskite structure as described above due to oxidation and reduction. This is because it changes between the state of solid solution in the perovskite crystal structure. Further, in the present embodiment, since the catalyst metal 16 supported on the catalyst porous body 15 is dispersed and supported in the form of fine particles on the catalyst porous body 15, even if the individual fine particles expand or contract, even if the individual fine particles expand or contract. The degree of causing damage to the entire structure of the first catalyst layer 13 is extremely small. Therefore, even when the operation of switching between the reducing atmosphere and the oxidizing atmosphere is repeated, damage to the first catalyst layer 13 can be suppressed and performance deterioration can be suppressed.

Further, according to the present embodiment, since the catalyst metal 16 is supported on the catalyst porous body 15 made of ceramic to form the first catalyst layer 13, it is not necessary to form the catalyst layer using the noble metal. The cost of the oxygen permeable film 10 and the reformer 20 can be reduced. For example, even when a noble metal is used as the catalyst metal supported on the catalyst porous body 15, the amount of the noble metal dispersed and supported on the catalyst porous body 15 is extremely small, so that a catalyst layer made of the noble metal is formed. Compared with, the cost can be greatly reduced.

Further, according to the method for producing the oxygen permeable film 10 of the present embodiment, the operation of supporting the catalyst metal on the catalytic porous body 15 is performed after the step of calcining the oxide constituting the oxygen permeable film 10. .. Therefore, the oxide constituting the oxygen permeable film 10 can be fired at a temperature equal to or higher than the melting point of the catalyst metal 16, and the deterioration of the performance of the catalyst metal 16 due to firing at a high temperature can be suppressed. That is, as the catalyst metal 16, a metal having a melting point lower than the sintering temperature when firing the oxide constituting the oxygen permeable film 10 can be selected, so that the degree of freedom in selecting the catalyst metal is increased and the melting point is increased. It becomes possible to easily use a relatively low base metal such as Ni.

In the oxygen permeable membrane 10 of the present embodiment, when the composite oxide of the formula (5) is used as the electron conductor contained in the catalytic porous body 15 and having an activity of promoting the reaction of the formula (2). Since the composite oxide of the formula (5) exhibits difficulty in sintering, it is necessary to set the firing temperature at the time of production particularly high. In such a case, for example, if nickel (Ni), which is an element of the same type as the metal element constituting the composite oxide of the formula (5), is selected as the catalyst metal, the catalyst metal melts at the firing temperature, so that the firing step It is not possible to support the catalyst metal on the catalytic porous body 15 prior to the above. According to the method for producing the oxygen permeable film 10 of the present embodiment, the catalyst metal is supported on the catalyst porous body 15 by impregnating the solution containing the catalyst metal with the catalyst porous body after the firing step. I'm doing it. Therefore, despite the combination of the catalytic porous body 15 exhibiting poor sinterability and the catalyst metal having a low melting point, an oxygen permeable membrane having the above combination can be easily produced to permeate oxygen exhibiting high oxygen permeation performance. A membrane can be obtained. When a metal having a melting point higher than the firing temperature of the catalytic porous body 15 is selected as the catalyst metal, the catalyst metal can be supported on the catalytic porous body 15 prior to the firing step. ..

B. Second embodiment:
(B-1) Composition of oxygen permeable membrane:
FIG. 3 is a schematic cross-sectional view showing a schematic configuration of an oxygen permeable membrane 110 as a second embodiment of the present invention and a reformer 120 including the oxygen permeable membrane 110. In the second embodiment shown in FIG. 3, the same reference number is given to the portion common to the first embodiment shown in FIG. 1, and detailed description thereof will be omitted.

The oxygen permeable membrane 110 of the second embodiment is, in addition to the first layer 12, the first catalyst layer 13, and the second catalyst layer 14 of the oxygen permeable membrane 10 of the first embodiment, further. A support layer 17 for reinforcing the oxygen permeable membrane 110 is provided on the catalyst layer 13 of 1 on a side different from the side on which the first layer 12 is arranged.

The support layer 17 is a porous layer made of ceramic, and has pores that communicate three-dimensionally, so that it is a raw material for oxygen molecules generated in the reaction of equation (2) and a modification reaction. Hydrocarbon gas and hydrogen-containing gas generated by the reforming reaction can flow in the pores. The pore ratio of the support layer 17 is due to hindering the diffusion of oxygen molecules generated in the reaction of equation (2), hydrocarbon gas which is a raw material of the reforming reaction, and hydrogen-containing gas generated by the reforming reaction. From the viewpoint of suppressing deterioration of oxygen permeation performance, it is preferably 30% or more, and more preferably 40% or more. Further, the porosity of the support layer 17 is preferably 80% or less, more preferably 60% or less, from the viewpoint of maintaining the structure of the support layer 17 well. Further, from the viewpoint of improving the performance of the oxygen permeable film by satisfactorily diffusing the oxygen molecules generated in the reaction of the formula (2), the hydrocarbon gas which is the raw material of the reforming reaction, and the hydrogen-containing gas generated by the reforming reaction. Therefore, it is desirable that the support layer 17 has a larger pore ratio than the catalytic porous body 15. The porosity of the support layer 17 can be measured by the same method as the porosity of the first layer 12 described above.

The thickness of the support layer 17 may be appropriately set so as to suppress a decrease in oxygen permeation performance due to hindering the diffusion of oxygen molecules generated in the reaction of the formula (2), for example, 0.2 to 0.2. It can be 3 mm. In order for the support layer 17 to enhance the effect of reinforcing the oxygen permeable membrane 110, it is desirable that the thickness of the support layer 17 is thicker than that of the first layer 12. It should be noted that "the thickness of the support layer 17 is thicker than that of the first layer 12" means that the thickness of the support layer 17 and the first layer 12 is always compared at any position of the oxygen permeable membrane 110. , Indicates that the support layer 17 is thicker.

The support layer 17 can be constructed using, for example, the stabilized zirconia described in the description of the first layer 12 as an oxygen ion conductor. Further, the support layer 17 is made of oxides that do not substantially exhibit oxygen ion conductivity and electron conductivity, such as magnesium oxide (MgO), aluminum oxide (Al ₂ O ₃ ), and spinel (Mg Al ₂ O ₄ ). It may be constructed using at least one selected oxide. The support layer 17 may have both electronic conductivity and ionic conductivity, may have either one, or may not have either. From the viewpoint of improving the performance of the oxygen permeable membrane 110, it is desirable to have at least one of electron conductivity and ionic conductivity, and it is more desirable to have both.

In the oxygen permeable membrane 110 of the second embodiment, the catalyst metal 16 is supported on the support layer 17 in addition to the catalyst porous body 15 of the first catalyst layer 13. In the present embodiment, the catalytic porous body 15 and the support layer 17 correspond to the “second layer” in the [means for solving the problem].

In the second embodiment, the catalyst metal 16 is supported on the surface (the surface of the pores formed inside) of both the catalyst porous body 15 and the support layer 17 constituting the second layer. ..

(B-2) Method for producing oxygen permeable membrane:
FIG. 4 is a process diagram showing a method for manufacturing the oxygen permeable membrane 110 of the present embodiment. When manufacturing the oxygen permeable membrane 110, first, the support layer 17 is prepared (step S200). The support layer 17 can be obtained, for example, by adding a pore-forming agent or a binder to the above-mentioned oxide powder which is a material constituting the support layer 17, mixing the powder, forming a powder, and then firing the powder. it can. The support layer 17 having a desired porosity can be obtained by adjusting the particle size and amount of the fine particles constituting the pore-forming agent to be used, the pressure at the time of forming the dust, and the like. The support layer 17 after firing can be adjusted to a desired thickness by polishing if necessary.

Next, a mixed conduction paste for forming the first layer 12, a first catalyst paste for forming the catalyst porous body 15, and a second catalyst for forming the second catalyst layer 14. A paste is prepared (step S210). The mixed conduction paste is obtained by obtaining a raw material powder containing a composite oxide constituting the first layer and mixing a solvent with the mixed powder in the same manner as in step S100 of the first embodiment. The first catalyst paste and the second catalyst paste can be produced in the same manner as in step S110 of the first embodiment.

Then, the catalyst porous body 15, the first layer 12, and the second catalyst layer 14 are formed on the support layer 17 to obtain a fired body (step S220). In the present embodiment, the catalyst porous body 15 is formed by applying the first catalyst paste on the support layer 17 and firing it, and further coating the mixed conduction paste on the support layer 17 and firing the first catalyst paste. The second catalyst layer 14 is formed by forming the layer 12 and further applying the second catalyst paste on the layer and firing the layer 12. At this time, the layer obtained by applying the first catalyst paste on the support layer 17 corresponds to the "catalyst porous body precursor layer" in [Means for Solving Problems]. Further, the layer obtained by applying the mixed conduction paste on the catalyst porous body 15 corresponds to the “first precursor layer”, and the laminate composed of the catalyst porous body 15 and the first precursor layer is “1st precursor layer”. Corresponds to "precursor laminate". Further, the laminate provided with the support layer 17, the catalytic porous body 15, and the first layer 12 corresponds to the “fired laminate”.

Then, the catalyst metal 16 is supported on the surface of the support layer 17 and the catalyst porous body 15 of the fired body obtained in step S220 (step S230) to complete the oxygen permeable membrane 110. The catalyst metal 16 is supported, for example, by impregnating the support layer 17 and the catalyst porous body 15 of the fired body with a solution containing the catalyst metal 16 in the same manner as in the first embodiment. It can be done by baking after that.

According to the method for producing the oxygen permeable membrane 110 of the second embodiment and the oxygen permeable membrane 110 configured as described above, the same effect as that of the first embodiment can be obtained. Further, in the second embodiment, since the oxygen permeable membrane 110 is reinforced by having the support layer 17, the first layer 12 through which oxygen ions permeate can be made thinner to improve the oxygen permeable performance. become.

Further, according to the method for producing the oxygen permeable membrane 110 of the present embodiment, the operation of arranging the solution containing the catalyst metal on the catalyst porous body 15 is performed by impregnation. Therefore, even though the catalyst porous body 15 is covered with the first layer 12 and the support layer 17, the operation of supporting the catalyst metal on the surface of the catalyst porous body 15 constitutes the oxygen permeable film 110. This can be done after the step of calcining the oxide. As a result, the oxide constituting the oxygen permeable film 110 can be fired at a temperature equal to or higher than the melting point of the catalyst metal 16, and the deterioration of the performance of the catalyst metal 16 due to firing at a high temperature can be suppressed.

In the second embodiment, the catalyst metal 16 is supported on the surfaces of both the catalyst porous body 15 and the support layer 17, but different configurations may be used. For example, the catalyst metal 16 may be supported on only one of the catalyst porous body 15 and the support layer 17. The catalyst metal 16 may be supported on at least a part of the surface of the porous body constituting the second layer including the catalyst porous body 15 and the support layer 17, whereby the catalyst porous body 15 may be supported. It is possible to obtain the same effect of enhancing the catalytic performance of the first catalyst layer 13 provided with.

At this time, the catalytic porous body 15 may be provided in a region including an interface with the first layer 12 of at least a part of the second layer including the catalytic porous body 15 and the support layer 17. .. However, it is desirable that the catalytic porous body 15 includes a larger range of the interface between the second layer and the first layer 12, and as shown in FIG. 3, oxygen permeation in the first layer 12 It is more desirable to include the entire interface within a range that can substantially contribute to.

C. Modification example:
-Deformation example 1 (deformation of catalyst layer):
In each of the above embodiments, the catalyst layer arranged on the low oxygen concentration side of the oxygen permeable membrane has a configuration in which the catalyst metal is supported on the catalyst porous body, but a different configuration may be used. For example, the catalyst metal may be supported on the catalytic porous body in the catalyst layer on the high oxygen concentration side instead of the low oxygen concentration side or in addition to the low oxygen concentration side. Even with such a configuration, the catalytic activity can be enhanced in the catalyst layer adopting the configuration in which the catalyst metal is supported on the porous catalyst body, and the same effects as those of each embodiment can be obtained.

However, when the support layer is provided as in the second embodiment, it is desirable that the catalyst layer on the exposed side without being covered by the support layer is on the high oxygen concentration side through which an oxygen-containing gas such as air flows. .. In this way, it is possible to prevent the rate at which oxygen permeates from the oxygen-containing gas into the oxygen permeable membrane to be rate-determining due to the suppression of gas diffusion into the catalyst layer by the support layer. ..

Further, in each of the above examples, in the oxygen permeable film, the porous body having catalytic activity is also on the side different from the side provided with the catalyst layer (first catalyst layer 13) on which the catalyst metal is supported on the catalyst porous body. Although the catalyst layer made of the body (second catalyst layer 14) is provided, it may have a different configuration. For example, the reaction of the above-mentioned formula (1) or (2) sufficiently proceeds on the surface of the first layer 12 on a side different from the side provided with the catalyst layer supporting the catalyst metal on the catalyst porous body. In this case, the catalyst layer may not be provided on the different sides.

-Modification example 2 (transformation of manufacturing method):
In the first embodiment, in step S100, the first precursor layer is fired to form the first layer 12, and then the first catalyst paste is applied onto the first layer 12. On the other hand, a second precursor layer is formed by applying the first catalyst paste on the first precursor layer before firing, and the first precursor layer and the second precursor layer are fired at the same time. You may. In this case, the laminate in which the first catalyst paste is applied on the first precursor layer corresponds to the "precursor laminate" in [Means for Solving the Problem].

Further, in the second embodiment, the firing step is performed for each of the catalyst porous body 15, the first layer 12, and the second catalyst layer 14, but different configurations may be used. For example, after applying the first catalyst paste for the catalyst porous body 15, the mixed conduction paste for the first layer 12 may be further applied without firing, and then firing may be performed. Alternatively, after applying the mixed conduction paste for the first layer 12, the second catalyst paste for the second catalyst layer 14 may be applied without firing, and then firing may be performed. Even with such a configuration, by firing the catalyst porous body precursor layer to form the catalyst porous body 15 and then supporting the catalyst metal 16 on the catalyst porous body 15, the same effect as in each embodiment can be obtained. Is obtained.

By firing the plurality of layers together in this way, the manufacturing process can be simplified. However, when a plurality of unfired layers are fired together, the combination of compounds constituting adjacent layers is a combination in which the reactivity is sufficiently low in the environment of the firing process, and the oxygen permeation performance is deteriorated. It is desirable that the generation of heterogeneous phases leading to is sufficiently small. For example, when the compound constituting the second catalyst layer 14 is relatively easy to form a heterogeneous phase, the firing temperature of the first layer 12 needs to be set higher for densification. It is desirable to apply a second catalyst paste later.

Further, in each embodiment, the first layer 12, the catalyst porous body 15, the second catalyst layer 14, and the support layer 17 are produced by a production method involving firing, but may have different configurations. At least a part of each of the above layers may be formed by a film forming method that does not involve firing. Examples of the film forming method without firing include a PVD method such as a PLD method (pulse laser deposition method), a CVD method, a dip method, thermal spraying, and a sputtering method. It may be appropriately selected according to the constituent material of each layer. Even with such a configuration, the same effect as in each embodiment can be obtained, in which the performance of the oxygen permeable membrane is improved by supporting the catalyst metal 16 on the catalyst porous body 15 made of ceramic.

Further, when the support layer 17 is provided as in the second embodiment, instead of sequentially forming a film on the support layer 17 to obtain a laminated body, the support layer 17 is formed in the same manner as in the first embodiment. After forming the oxygen permeable film 10 having a three-layer structure that does not have the oxygen permeable film 10, a separately prepared support layer 17 may be attached onto the first catalyst layer 13 of the oxygen permeable film 10. In this case, the catalyst metal 16 may be further supported on the support layer 17. Even with such a configuration, the catalytic activity of the catalyst layer is as compared with the case where the first catalyst layer 13 is formed only by the catalyst porous body 15 or the case where the first catalyst layer 13 is formed only by the catalyst metal. The same effect can be obtained as well as increasing the durability of the oxygen permeable film.

-Modification example 3 (transformation of reformer):
The reformer of each of the above embodiments includes a single plate-shaped oxygen permeable membrane, but the reformer can be in various forms. For example, a plurality of flat oxygen permeable membranes may be laminated, and the reforming raw material flow path 22 and the air flow path 24 may be alternately provided between the laminated oxygen permeable membranes.

Alternatively, the reformer may be formed in a cylindrical shape, the outside of the cylinder may be exposed to the outside air to form an air flow path 24, and the inside of the cylinder may be used as a reforming raw material flow path 22. In this case, a flow path for supplying the reforming raw material is connected to one end of the cylinder, and a flow path for taking out hydrogen and carbon monoxide obtained in the reforming reaction is provided at the other end of the cylinder. Just connect. In such a configuration, for example, the support layer 17 is formed in a cylindrical shape, and the first catalyst layer 13, the first layer 12, and the second catalyst layer 14 are formed on the inner wall surface of the cylindrical support layer 17. It can be realized by forming in order.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to the description of these Examples.

FIG. 5 is an explanatory diagram showing the results of preparing 10 types of oxygen permeable membranes from Samples 1 to 10 and examining their performance, and the configuration of each sample. The configuration and manufacturing method of each sample and the result of evaluating the performance will be described below.

<Preparation of each sample>
[Sample 1]
Sample 1 includes a support layer 17, a first catalyst layer 13, a first layer 12, and a second catalyst layer 14, similar to the oxygen permeable membrane 110 shown in FIG.

The method for producing the support layer 17 (step S200) of Sample 1 will be described below. The support layer 17 of sample 1 is composed of calcia-stabilized zirconia (CSZ). As a material for calcia-stabilized zirconia, CSZ powder manufactured by Daiichi Rare Element Chemical Industry Co., Ltd. was used. An acrylic resin-based pore-forming material and a cellulose-based binder were added to the CSZ powder and mixed, and the powder was compacted into pellets at a molding pressure of 50 MPa. After molding, the temperature was raised to 400 ° C. at a heating rate of 2 ° C./min and degreased at 400 ° C. for 1 hour. Then, the temperature was raised to 1500 ° C. at a heating rate of 5 ° C./min, and firing was performed at 1500 ° C. for 24 hours. The surface of the obtained fired body was polished to obtain a support layer 17 having a thickness of 0.4 mm. The porosity of the support layer 17 of the sample 1 and the support layers included in the samples 2 and 4 to 10 described later was measured by the method using the formula (4) described in the first embodiment. It was 40-45%.

The method for producing the mixed conduction paste for forming the first layer 12 of Sample 1 (step S210) will be described below. The first layer 12 of Sample 1 contains Scandia-stabilized zirconia (ScSZ) as an oxygen ion conductor and La _0.8 Sr _0.2 CrO ₃ -z as an electron conductor. As ScSZ, a powder of scandium-stabilized zirconia (manufactured by Daiichi Rare Element Chemical Industry Co., Ltd., 10Sc1CeSZ) containing scandium (Sc) and cerium (Ce) was used. La _0.8 Sr _0.2 CrO _3-z was prepared by the solid phase reaction method as follows. The raw material powders include lanthanum oxide (La ₂ O ₃ , manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%), strontium carbonate (SrCO ₃ , manufactured by High Purity Chemical Laboratory, purity 99.9%), and chromium oxide (purity 99.9%). Cr ₂ O ₃ , manufactured by the Institute of High Purity Chemistry, with a purity of 99.99%) was used. These raw material powders were weighed so that the ratio of the metal elements was the composition ratio in the composition formula La _0.8 Sr _0.2 CrO _3-z . Then, using ZrO ₂ balls and a resin pot, wet mixing and pulverization of these raw material powders was carried out together with ethanol for 15 hours. Then, it is dried in hot water to remove ethanol, and the obtained mixed powder is heated to 1500 ° C. at a heating rate of 15 ° C./min and calcined at 1500 ° C. for 24 hours to obtain La, which is a calcined powder. A powder of _0.8 Sr _0.2 CrO _3-z was obtained.

Further, a dispersant and a binder were added to the calcined powder, and wet mixed pulverization was performed using ethanol under the same conditions as the wet mixed pulverization described above, and the mixture was dried to obtain a powder containing the calcined powder. .. Then, a powder containing the calcined powder so that the mixing ratio of La _0.8 Sr _0.2 CrO _{3-z in} the mixture of ScSZ and La _0.8 Sr _0.2 CrO _3-z is 30 vol%. Was mixed with ScSZ to obtain a mixed powder of ScSZ and La _0.8 Sr _0.2 CrO _3-z . Butyl carbitol as a solvent and ethyl cellulose (Etocell (registered trademark) manufactured by Nikkei Seisei Co., Ltd.) were added to the obtained mixed powder and mixed with a raker to prepare a mixed conduction paste. When the above-mentioned mixed powder is obtained, it is assumed that La _0.8 Sr _0.2 CrO _3-z is formed in the calcined powder with 100% efficiency, and the mixed amount of the powder containing the calcined powder is assumed. It was set.

The method for producing the first catalyst paste A for forming the catalyst porous body 15 of Sample 1 (step S210) will be described below. In the first catalyst layer 13 of Sample 1, the catalyst porous body 15 contains Scandia-stabilized zirconia (ScSZ) as an oxygen ion conductor, and La _0.8 Sr _0.2 Cr as a catalyst which is an electron conductor. _It contains _0.85 Ni _0.15 O _3-z . As ScSZ, ScSZ similar to ScSZ contained in the first layer 12 was used. La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z was prepared by the solid phase reaction method as follows. The raw material powders include lanthanum oxide (La ₂ O ₃ , manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%), strontium carbonate (SrCO ₃ , manufactured by High Purity Chemical Laboratory, purity 99.9%), chromium oxide (Cr). ₂ O ₃ , high-purity chemical laboratory, 99.99% pure), and nickel oxide (NiO, high-purity chemical laboratory, 99.9% pure) powder were used. These raw material powders were weighed so that the ratio of the metal elements was the composition ratio in the composition formula La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z . Then, using ZrO ₂ balls and a resin pot, wet mixing and pulverization of these raw material powders was carried out together with ethanol for 15 hours. Then, it is dried in hot water to remove ethanol, and the obtained mixed powder is heated to 1500 ° C. at a heating rate of 15 ° C./min and calcined at 1500 ° C. for 24 hours to obtain La, which is a calcined powder. A powder of _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z was obtained.

Further, a dispersant and a binder were added to the calcined powder, and wet mixed pulverization was performed using ethanol under the same conditions as the wet mixed pulverization described above, and the mixture was dried to obtain a powder containing the calcined powder. .. Then, ScSZ was added to the powder containing the calcined powder so that the mixing ratio of ScSZ in the mixture of ScSZ and La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z was 35 vol%. Mixing was performed to obtain a mixed powder of ScSZ and La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z . Acrylic resin-based pore-forming agent is added to the obtained mixed powder and mixed, and the solvents butyl carbitol and ethyl cellulose (Etocell (registered trademark) manufactured by Nikkei Seisei Co., Ltd.) are added to the raker. To prepare the first catalyst paste A.

The method for producing the second catalyst paste (step S210) for forming the second catalyst layer 14 of the sample 1 will be described below. The second catalyst layer 14 of Sample 1 contains Scandia-stabilized zirconia (ScSZ) as an oxygen ion conductor and La _0.8 Sr _0.2 MnO _3-z as a catalyst which is an electron conductor. As ScSZ, ScSZ similar to ScSZ contained in the first layer 12 was used. Lanthanum oxide (La ₂ O ₃ , manufactured by Wako Pure Chemical Industries, Ltd., purity 99.9%), strontium carbonate (SrCO ₃ , high) are used as raw material powders for producing La _0.8 Sr _0.2 MnO _3-z. purity chemical Laboratory, Ltd., purity 99.9%), and powder was used manganese oxide _(Mn 2 _{O 3} Kojundo chemical Laboratory, Ltd., purity: 99.9%). Using these raw material powders, under the same conditions as those for producing a calcined powder of La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z contained in the catalyst porous body 15. By the solid phase reaction method, a calcined powder of La _0.8 Sr _0.2 MnO _3-z was obtained. Further, using the calcined powder of La _0.8 Sr _0.2 MnO _3-z, a second catalyst paste was prepared by the same method as the method for producing the first catalyst paste A.

The process of step S220 when manufacturing the sample 1 will be described below. The first catalyst paste A is applied onto one surface of the support layer 17 obtained in step S200 by a screen printing method, dried at 120 ° C., heated to 1100 ° C. in the air, and 1100 ° C. It was held for 1 hour and fired. As a result, a layer containing ScSZ and La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z was baked onto one surface of the support layer 17 to form the catalyst porous body 15. .. The film thickness of the catalyst porous body 15 was about 50 μm. The porosity of the catalytic porous body 15 of sample 1 and the catalytic porous body of samples 2 to 8 described later was measured by the method using the formula (4) described in the first embodiment. Both were 30-40%.

Then, the mixed conduction paste is applied onto the catalyst porous body 15 formed as described above by a screen printing method, dried at 120 ° C., and then heated to 1500 ° C. in a nitrogen atmosphere to 1500 ° C. It was held for 24 hours and fired. As a result, a layer containing ScSZ and La _0.8 Sr _0.2 CrO _3-z was baked and densified on the catalyst porous body 15 to form the first layer 12. The film thickness of the first layer 12 was about 100 μm.

Then, the second catalyst layer 14 was formed on the first layer 12 formed as described above by the same method as the above-mentioned porous catalyst 15 using the second catalyst paste. As a result, a fired laminate having a support layer 17, a catalyst porous body 15, a first layer 12, and a second catalyst layer 14 was obtained. The film thickness of the second catalyst layer 14 was about 50 μm.

The process of step S230 when manufacturing the sample 1 will be described below. The first catalyst layer 13 of sample 1 includes nickel (Ni) as the catalyst metal 16. When the sample 1 was produced, nickel (II) nitrate hexahydrate was used as a material containing the catalyst metal 16. Specifically, nickel (II) nitrate hexahydrate was dissolved in pure water and adjusted to a concentration of 1 mol / L to prepare an aqueous nickel nitrate solution. The support layer 17 and the catalyst porous body 15 of the fired laminate obtained in step S220 described above are immersed in the nickel nitrate aqueous solution thus prepared, and the nickel nitrate aqueous solution is applied to the support layer 17 and the catalyst porous body. 15 was impregnated. Next, the fired laminate impregnated with the nickel nitrate aqueous solution was sufficiently dried on a hot plate heated to 100 ° C., and then held at 500 ° C. for 1 hour to bake the catalyst metal 16. Further, a membrane kept at 800 ° C. for 1 hour under a hydrogen atmosphere was used as an oxygen permeable membrane of Sample 1. The application form of the catalyst metal 16 (Ni is dispersed and supported on the pore surfaces of the support layer 17 and the catalyst porous body 15) is an electron microscope such as TEM or SEM and an element of EPMA attached thereto. Confirmed by analysis.

When the fired laminate is immersed in the catalyst metal solution, the extent to which the catalyst metal solution is impregnated in the porous body constituting the fired laminate can be adjusted by the immersion time. is there. When preparing the sample 1, the surface portion of the fired laminate on the support layer 17 side is immersed in the catalyst metal solution, and the immersion time is varied so that the immersion time and the range in which the catalyst metal solution is impregnated are set. The relationship was investigated in advance. Then, the time for the entire support layer 17 and the catalyst porous body 15 to impregnate the catalyst metal solution was set, and the operation of impregnating the catalyst metal solution was performed based on the set time.

[Sample 2]
When the catalyst metal 16 is supported on the oxygen permeable film of sample 2, the immersion time is set so that only the support layer 17 portion of the fired laminate obtained in step S220 is impregnated with the nickel nitrate aqueous solution. , The same as Sample 1 except that the catalyst metal 16 was supported only on the support layer 17.

[Sample 3]
The oxygen permeable membrane of Sample 3 includes a first catalyst layer 13, a first layer 12, and a second catalyst layer 14, similar to the oxygen permeable membrane 10 shown in FIG.

The method for producing the first layer 12 (step S100) of the sample 3 will be described below. The first layer 12 of sample 3 has the same composition as the first layer 12 of sample 1. Therefore, first, a mixed powder of ScSZ and La _0.8 Sr _0.2 CrO _3-z was obtained in the same manner as in the method for producing the mixed conduction paste in Sample 1. Then, the mixed powder of ScSZ and La _0.8 Sr _0.2 CrO _3-z was press-molded to obtain a disc-shaped pellet having a diameter of 20 mm. The pellets were dried at 120 ° C., heated to 1500 ° C. in a nitrogen atmosphere, and held at 1500 ° C. for 24 hours for densification. The densified pellets were ground to a thickness of 100 μmm with a surface grinding machine to form a first layer 12.

The first catalyst layer 13 and the second catalyst layer 14 of the sample 3 have the same composition as that of the sample 1. Therefore, in step S110, the same first catalyst paste A and second catalyst paste as in sample 1 were prepared as the first catalyst paste and the second catalyst paste.

In step S120, the precursor laminate A is coated on one surface of the first layer 12 and the second catalyst paste is applied on the other surface by a screen printing method. Got After drying this at 120 ° C., the temperature was raised to 1100 ° C. in the air, and the mixture was held at 1100 ° C. for 1 hour for firing. As a result, the catalyst porous body 15 and the second catalyst layer 14 were baked onto each surface of the first layer 12 (step S130). In the obtained fired body, the film thickness of each of the catalyst porous body 15 and the second catalyst layer 14 was about 50 μm.

Then, in the same manner as in step S230 of the manufacturing method of sample 1, nickel (Ni) as a catalyst metal is supported on the catalyst porous body 15 of the fired body (step S140), and the oxygen permeable membrane of sample 3 is formed. Obtained.

[Sample 4]
The oxygen permeable membrane of Sample 4 is a catalytic porous material containing gadolinium solidified ceria (GDC) as an oxygen ion conductor and Sr _0.9 La _0.1 TiO _3-z as a catalyst which is an electron conductor. The configuration is the same as that of sample 1 except that 15 is provided. That is, the oxygen permeable membrane of sample 1 except that the first catalyst paste B containing GDC and Sr _0.9 La _0.1 TiO _3-z was used in place of the first catalyst paste A. It was produced in the same manner as above.

When the first catalyst paste B was prepared, GDC powder manufactured by Shin-Etsu Chemical Co., Ltd. was used as a material for the gadolinium solid solution ceria. Further, Sr _0.9 La _0.1 TiO _3-z is the same as La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z contained in the first catalyst paste A. It was prepared by the solid phase reaction method. Strontium carbonate (SrCO ₃ , manufactured by High Purity Chemical Laboratory, purity 99.9%), lanthanum oxide (La ₂ O ₃ , Wako Pure Chemical Industries, Ltd.) are used as raw material powders for Sr _0.9 La _0.1 TiO _3-z. , 99.9% purity), and titanium oxide (TiO ₂ , Showa Denko, 99.9% purity) powder was used. The first catalyst paste B was prepared in the same manner as the first catalyst paste A, except that the raw materials used were different as described above.

[Sample 5]
The oxygen permeable membrane of Sample 5 has the same configuration as that of Sample 1 except that platinum (Pt) is used as the catalyst metal 16 instead of nickel (Ni). When preparing the oxygen permeable membrane of Sample 5, a dinitrodiammine platinum nitric acid solution (5 mmol / L) was used instead of nickel (II) nitrate hexahydrate as the solution containing the catalyst metal 16 used in step S230. .. The oxygen permeable membrane of Sample 5 was prepared in the same manner as in Sample 1 except that the solution containing the catalyst metal 16 was different.

[Sample 6]
The oxygen permeable membrane of Sample 6 was prepared in the same manner as in Sample 1 except that the step of supporting the catalyst metal 16 in step S230 was not performed. That is, in the oxygen permeable membrane of Sample 6, the catalyst metal 16 is not supported on the catalyst porous body 15.

[Sample 7]
The oxygen permeable membrane of Sample 7 was prepared in the same manner as in Sample 4 except that the step of supporting the catalyst metal 16 in step S230 was not performed. That is, in the oxygen permeable membrane of sample 7, the catalyst metal 16 is not supported on the catalyst porous body 15.

[Sample 8]
The oxygen permeable membrane of Sample 8 was prepared in the same manner as that of Sample 1 except that the composition of the first catalyst layer was different. Specifically, when preparing the first catalyst paste in step S210, NiO is used instead of La _0.8 Sr _0.2 Cr _0.85 Ni _0.15 O _3-z , and NiO and ScSz are used. When the mixed powder with was obtained, the mixing ratio of ScSZ was set to 39 vol%. Further, step S230 was not performed, and in sample 8, neither the support layer 17 nor the first catalyst layer supported the catalyst metal. As described above, NiO constituting the first catalyst layer of Sample 8 is a catalyst that becomes Ni in a reducing atmosphere.

[Sample 9]
The oxygen permeable membrane of Sample 9 was prepared in the same manner as in Sample 1 except that the first catalyst layer 13 was not provided. That is, in sample 9, the first layer 12 was formed directly on the support layer 17.

[Sample 10]
The oxygen permeable membrane of Sample 10 was prepared in the same manner as in Sample 1 except that the catalyst porous body 15 was not provided. That is, in sample 10, the first layer 12 is formed directly on the support layer 17, and only the support layer 17 is impregnated with the catalyst metal solution (nickel nitrate aqueous solution), and Ni, which is a catalyst metal, is impregnated on the support layer 17. Was carried.

<Measurement of oxygen permeation rate>
FIG. 6 is an explanatory diagram showing a schematic configuration of a measuring device 30 which is a device for measuring oxygen permeation characteristics of each sample. The measuring device 30 includes two transparent quartz tubes 31 and 32, alumina tubes 33 and 34, an electric furnace 35, and a thermocouple 36. The two transparent quartz tubes 31 and 32 are arranged one above the other, and each sample is sandwiched between them for measurement. When joining the transparent quartz tube 31 and the sample, a thin gold ring having an inner diameter of 10 mm is placed on the sample, and the transparent quartz tube 31 is pressed onto the thin film ring to raise the temperature to 1050 ° C. to soften the gold. And ensured gas sealability. Alumina tubes 33 and 34 were arranged inside the transparent quartz tubes 31 and 32. When measuring the oxygen permeation special velocity, hydrogen gas was passed through the alumina tube 33, and air was passed through the alumina tube 34. The transparent quartz tubes 31 and 32 were arranged in the electric furnace 35, and the sample sandwiched between the transparent quartz tubes 31 and 32 was arranged in the soaking portion in the electric furnace 35. Further, in the alumina tube 34, a thermocouple 36 was arranged so as to reach the vicinity of the sample in order to measure the sample temperature. When measuring the oxygen permeation characteristics, heating was performed by the electric furnace 35 so that the sample temperature was maintained at 1000 ° C. Each sample was arranged so that air was supplied to the second catalyst layer 14 side, and hydrogen gas was supplied to the first catalyst layer 13 side when the first catalyst layer 13 was provided.

In each sample arranged in the above-mentioned measuring device 30, when oxygen permeates the sample from the air side (transparent quartz tube 32 side) to the hydrogen gas side (transparent quartz tube 31 side), it permeates on the hydrogen gas side. Water (steam) is generated using the oxygen. Since it is considered that all the water vapor in the hydrogen-containing gas discharged from the measuring device 30 is derived from permeated oxygen, the water vapor concentration in the discharged hydrogen-containing gas is measured using a mirror dew point meter (manufactured by Toyo Technica). It was measured and the amount of permeated oxygen was calculated. Such a permeate oxygen amount calculated in the, on the basis of the transmission area of the sample was calculated oxygen permeation flux density j _{H2 (0 2).} At this time, the amount of hydrogen gas supplied through the alumina tube 33 and the amount of air supplied through the alumina tube 34 were set to 200 mL and 300 mL / min, respectively, using a mass flow controller.

<Repeated oxidation / reduction test>
Each sample was subjected to repeated oxidation and reduction tests to examine the stability of the catalyst layer with respect to the atmosphere. The method of repeated oxidation / reduction test will be described below. The measuring device 30 of FIG. 6 was used for the repeated oxidation / reduction test.

The oxidation-reduction cycle test was first measured oxygen permeability flux density j _H2 as described above the _{(0 2)} as an initial value. Then, after measuring the initial value of the oxygen permeation flow velocity density for each sample, the supply of the amount of hydrogen gas to each sample via the alumina tube 33 was continued for 1 hour, and the oxygen permeation flow velocity density was measured again. After that, the hydrogen supply was stopped for 1 hour, the hydrogen supply was restarted and the hydrogen supply was continued for 1 hour, the oxygen permeation flow velocity density was measured, and the hydrogen supply and stop operations were performed 5 times in total. The change in oxygen permeation characteristics was repeatedly investigated. While the hydrogen supply to the samples is stopped, each sample is exposed to air.

<Methane reforming test>
The methane reforming test was carried out using the measuring device 30 of FIG. 6 in the same manner as the oxygen permeation rate measuring test described above. However, a mixed gas of argon (Ar) and methane (10% CH ₄ ) was flowed through the alumina tube 33 as a methane-containing gas instead of hydrogen. In addition, a quadrupole mass spectrometer (OmniStar manufactured by Hakuto Co., Ltd.) was used instead of the dew point meter for the composition analysis of the gas generated by the reaction of permeated oxygen and methane. Then, the oxygen permeation flow velocity density j _CH4 (O ₂ ) was calculated from the gas composition generated by the reaction of methane and permeated oxygen.

<Evaluation result>
In Figure 7, the structure of each sample, the initial value of the oxygen permeation flux density j _{H2 (0 2),} oxygen permeation flux density j _CH4 is methane reforming test result (O _2), the oxidation-reduction cycle test The result and the comprehensive judgment result are shown. According to the results of the repeated oxidation / reduction test, as described above, when the oxygen permeation flow velocity density after repeating the hydrogen supply and stop operations 5 times is 95% or more of the initial value of the oxygen permeation flow velocity density, oxidation occurs. -It was judged that the performance related to repeated reduction was good and was marked with "○". In other cases, it was judged that the performance was insufficient and marked with "x". Overall judgment result, the oxygen permeation rate density j _CH4 (O ₂₎ is the result of the methane reforming test is equivalent to the oxygen permeability flux density initial value at which the oxygen permeation rate density j _{H2 (0 2),} and When the repeated oxidation / reduction test results were also good, it was judged as "○", and when at least one of the results was judged to be insufficient, it was judged as "x".

As shown in FIG. 7, in Samples 1 to 5, the oxygen permeation flow velocity density j _CH4 (O ₂ ), which is the result of the methane reforming test, is the initial value of the oxygen permeation flow velocity density j _H2 (0). It was equivalent to ₂ ). That is, the oxygen permeable membranes of Samples 1 to 5 supporting the catalyst metal 16 in the first catalyst layer 13 including the catalyst porous body 15 exhibit high oxygen permeable performance even when applied to a reformer. It was confirmed that. In addition, the oxygen permeation characteristics of Samples 1 to 5 did not deteriorate even after repeated oxidation and reduction, and were stable.

Here, the oxygen permeation rate density _j H2 _{(0 2)} and _{j CH4 (O 2),} a sample 1 that carries the catalyst metal 16 in the first catalytic layer 13, the sample 6 not carrying the catalyst metal 16 The sample 1 showed good results. In contrast, in Sample 6, the oxygen permeation rate density j _{H2 (0 2)} although a relatively high value, the value of the methane reforming oxygen with the test permeation rate density j _CH4 (O ₂₎ was greatly reduced. From this, it was confirmed that the catalyst metal 16 is supported on the first catalyst layer 13 so that a high oxygen permeation rate can be obtained even in the environment of the reformer. The results of comparing Samples 4 and 7 in which the composition of the catalyst porous body 15 was different from that of Samples 1 and 6 were also similar. Incidentally, no sample 9 of the first catalyst layer 13 (catalytic porous body 15 and the catalytic metal 16) is a very low value any of the oxygen permeation flux density _j H2 _{(0 2)} and _{j CH4 (O 2)} there were.

Oxygen permeation flux density _j H2 _{(0 2)} and _{j CH4 (O 2),} a sample 1 that carries the catalytic metal 16 on both the catalyst the porous body 15 and the support layer 17, the catalytic metal 16 only to the supporting layer 17 Comparing the supported sample 2 with that of the sample 2, the sample 1 showed a higher oxygen flow velocity density than the sample 2. From this, if the catalyst metal 16 is supported on either one of the catalyst porous body 15 and the support layer 17 in the first catalyst layer 13, it is high even in the environment of the reformer. It was confirmed that it is more desirable that the catalyst metal 16 is supported on both the catalyst porous body 15 and the support layer 17, although the oxygen permeation rate can be obtained.

Incidentally, without having catalytic porous body 15, a sample 10 for carrying the catalyst metal 16 only on the support layer 17, the oxygen permeation rate density _j H2 _{(0 2)} and _{j CH4} both very low _{(O 2)} It was a value. From this, it was confirmed that the catalyst metal 16 supported on the support layer 17, which is a porous body having substantially no catalytic activity, is not sufficient as the catalyst for the oxygen permeable membrane.

Further, the oxygen permeability flux density _j H2 _{(0 2)} and _{j CH4 (O 2),} when comparing the sample 1 and the sample 4 and sample 5, in any of the _{samples, j CH4 (O 2)} is _{j H2} ( 0 ₂₎ and showed comparable values, the sample 1 showed the highest value. From this, it was confirmed that it is desirable that the element constituting the catalyst metal 16 supported on the catalyst porous body 15 is the same as the metal element constituting the composite oxide contained in the catalyst porous body 15. ..

When the oxidation / reduction repeated tests were compared for each sample, it was judged that the performance of only sample 8 in which the porous portion constituting the catalyst layer contained the catalyst metal was insufficient. From this, it was confirmed that the durability of the oxygen permeable membrane in an environment accompanied by repeated oxidation and reduction is improved by using the catalytic porous body 15 made of ceramic having catalytic activity.

The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations within a range not deviating from the gist thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the column of the outline of the invention may be used to solve some or all of the above-mentioned problems. , It is possible to replace or combine as appropriate in order to achieve a part or all of the above-mentioned effects. Further, if the technical feature is not described as essential in the present specification, it can be appropriately deleted.

10, 110 ... Oxygen permeable film 12 ... First layer 13 ... First catalyst layer 14 ... Second catalyst layer 15 ... Catalyst porous body 16 ... Catalyst metal 17 ... Support layer 20, 120 ... Reformer 22 ... Reforming raw material flow path 24 ... Air flow path 30 ... Measuring device 31 ... Transparent quartz tube 33, 34 ... Alumina tube 35 ... Electric furnace 36 ... Thermocouple

The present invention has been made to solve the above-mentioned problems, and can be realized as the following forms.
[Form 1] An oxygen permeable film, a first layer containing a composite oxide and having oxygen ion conductivity and electron conductivity, and high oxygen due to the difference in oxygen partial pressure between both sides of the first layer. A first layer that allows oxygen to permeate from the pressure dividing side to the low oxygen partial pressure side, and a first layer formed on the first surface of the first layer, the pore ratio is larger than that of the first layer, and the pore ratio is higher. A second layer made of a porous body of 30% or more, which is represented by the following formula (i) in a region including an interface with the first layer, which is at least a part of the second layer. A second layer comprising a catalytic porous body made of ceramic having an activity of promoting the reaction is provided, and O ^2- → (1/2) O ₂ + 2e ⁻ … (i) constitutes the second layer. A catalyst metal having an activity of promoting the reaction represented by the above formula (i) is supported on at least a part of the surface of the porous body, and the catalytic porous body is an oxygen ion conductor and electron conduction. The electron conductor contained in the catalyst porous body including a body is a perovskite-type composite oxide having a basic structure of ABO ₃ , and the elements corresponding to A are lanthanum (La) and strontium (Sr). ), Calcium (Ca), and barium (Ba), and the elements corresponding to B are chromium (Cr) and nickel (Ni), which are contained in the catalytic porous body. the electron _{conductor, La 1-x Sr x Cr} 1-y Ni y O 3-z (0 <x <0.4,0 <y <0.20, z is optional) perovskite-type composite oxide represented by An oxygen permeable film characterized by being a thing.

<Evaluation result>
In Figure 5, the structure of each sample, the initial value of the oxygen permeation flux density j _{H2 (0 2),} oxygen permeation flux density j _CH4 is methane reforming test result (O _2), the oxidation-reduction cycle test The result and the comprehensive judgment result are shown. According to the results of the repeated oxidation / reduction test, as described above, when the oxygen permeation flow velocity density after repeating the hydrogen supply and stop operations 5 times is 95% or more of the initial value of the oxygen permeation flow velocity density, oxidation occurs. -It was judged that the performance related to repeated reduction was good and was marked with "○". In other cases, it was judged that the performance was insufficient and marked with "x". Overall judgment result, the oxygen permeation rate density j _CH4 (O ₂₎ is the result of the methane reforming test is equivalent to the oxygen permeability flux density initial value at which the oxygen permeation rate density j _{H2 (0 2),} and When the repeated oxidation / reduction test results were also good, it was judged as "○", and when at least one of the results was judged to be insufficient, it was judged as "x".

As shown in FIG. 5 , in Samples 1 to 5, the oxygen permeation flow velocity density j _CH4 (O ₂ ), which is the result of the methane reforming test, is the initial value of the oxygen permeation flow velocity density j _H2 (0). It was equivalent to ₂ ). That is, the oxygen permeable membranes of Samples 1 to 5 supporting the catalyst metal 16 in the first catalyst layer 13 including the catalyst porous body 15 exhibit high oxygen permeable performance even when applied to a reformer. It was confirmed that. In addition, the oxygen permeation characteristics of Samples 1 to 5 did not deteriorate even after repeated oxidation and reduction, and were stable.

Claims (12)

It is an oxygen permeable membrane
A first layer containing a composite oxide and having oxygen ion conductivity and electron conductivity, and oxygen is transferred from the high oxygen partial pressure side to the low oxygen partial pressure side by the oxygen partial pressure difference between both sides of the first layer. The first layer to be transparent and
A second layer formed on the first surface of the first layer and composed of a porous body having a porosity larger than that of the first layer and a porosity of 30% or more. A second layer comprising a catalytically porous body made of a ceramic having catalytic activity in a region of at least a part of the second layer including an interface with the first layer.
With
An oxygen permeable membrane characterized in that a catalyst metal is supported on at least a part of the surface of the porous body constituting the second layer. The oxygen permeable membrane according to claim 1.
The catalyst porous body is an oxygen permeable membrane comprising an oxygen ion conductor and an electron conductor. The oxygen permeable membrane according to claim 2.
The oxygen permeable membrane is characterized in that the second layer is further provided with a support layer made of ceramic provided apart from the interface with the first layer in addition to the catalyst porous body. The oxygen permeable membrane according to claim 2 or 3.
The electron conductor contained in the catalytic porous body is a perovskite-type composite oxide having a basic structure of ABO ₃ , and the elements corresponding to A are lanthanum (La), strontium (Sr), and calcium (Ca). ), And at least one element selected from barium (Ba), wherein the element corresponding to B is chromium (Cr) and nickel (Ni). The oxygen permeable membrane according to claim 4.
Wherein said electron conductor contained in the catalyst porous _{body, La 1-x Sr x Cr} 1-y Ni y O 3-z (0 <x <0.4,0 <y <0.20, z is an arbitrary An oxygen permeable membrane characterized by being a perovskite-type composite oxide represented by). The oxygen permeable membrane according to claim 2 or 3.
An oxygen permeable membrane characterized in that the element constituting the catalyst metal is the same as the metal element constituting the electron conductor contained in the catalyst porous body. The oxygen permeable membrane according to claim 6.
The electron conductor contained in the catalyst porous body is a perovskite-type composite oxide having a basic structure of ABO ₃ , and the elements corresponding to A are lanthanum (La) and strontium (Sr), and B contains Applicable elements are chromium (Cr) and nickel (Ni).
An oxygen permeable membrane characterized in that the catalyst metal is nickel (Ni). The oxygen permeable membrane according to claim 3.
An oxygen permeable membrane characterized in that the porosity of the support layer is larger than the porosity of the catalytic porous body. The method for producing an oxygen permeable membrane according to any one of claims 1 to 8.
A precursor laminate in which a first precursor layer for forming the first layer or the first layer and a second precursor layer for forming the second layer are laminated is formed. Process and
A step of firing the precursor laminate to obtain a fired laminate having the first layer and the second layer.
A step of impregnating at least a part of the second layer constituting the fired laminate with a solution containing the catalyst metal to support the catalyst metal on the surface of at least a part of the second layer. ,
A method for producing an oxygen permeable membrane, which comprises the above. The method for producing an oxygen permeable membrane according to claim 3.
The process of preparing the support layer and
A step of forming a catalyst porous body precursor layer for forming the catalyst porous body on the support layer, and a step of forming the catalyst porous body precursor layer.
A first precursor for forming the first layer on the catalyst porous body precursor layer formed on the support layer or the catalyst porous body obtained from the catalyst porous body precursor layer. The process of forming a layer to form a precursor laminate,
A step of calcining the precursor laminate to obtain a calcined laminate having the support layer, the catalyst porous body, and the first layer.
A region of the support layer and the catalyst porous body constituting the fired laminate, in which a portion including at least a part of the support layer is impregnated with a solution containing the catalyst metal and impregnated with the solution. The step of supporting the catalyst metal on the surface of the
A method for producing an oxygen permeable membrane, which comprises the above. The method for producing an oxygen permeable membrane according to claim 9 or 10.
A method for producing an oxygen permeable membrane, wherein the melting point of the catalyst metal is lower than the sintering temperature at the time of firing the precursor laminate. A reformer comprising the oxygen permeable membrane according to any one of claims 1 to 8 and producing hydrogen from a reforming raw material by a partial oxidation reaction.
A modified raw material supply path formed on the oxygen permeable membrane on the first surface side of the first layer and through which the modified raw material flows.
An oxygen-containing gas flow path formed on the oxygen-permeable membrane on the second surface side of the first layer and through which an oxygen-containing gas flows, and an oxygen-containing gas flow path.
With
A reformer characterized in that the partial oxidation reaction using oxygen in the oxygen-containing gas that has permeated the oxygen permeable membrane proceeds.

Images