JP2003117362A - Oxygen separating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen separating apparatus having oxygen separation ability without inconvenience caused by a supporting body. SOLUTION: The oxygen separating apparatus is constituted of a self- sustained structure composed of a dense mixed conductive metal oxide which consists essentially of lanthanum, strontium, cobalt and iron, has a molar ratio expressed by the following relation, La:Sr:Co:Fe=x:(1-x):(1-y):y (where 0<x<0.15, 0<y<0.15), and has <=2% opening porosity and 150-500 μm thickness.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an oxygen separation device for separating oxygen in air or oxygen-containing mixed gas.

[0002]

2. Description of the Related Art Mixed conductive oxides are widely known as substances that selectively transport only oxygen components from an oxygen-containing mixed gas such as air. Here, the mixed conductive oxide is an oxide that conducts electrons or holes and simultaneously conducts oxygen ions (also referred to as oxide ions).

In order to industrially carry out selective oxygen transport utilizing such a mixed conductive oxide, the oxygen ion conductivity under the operating conditions needs to be about 0.1 S / cm or more, preferably. , 0.5 S / cm or more, and most preferably 1 S / cm or more. Further, it is necessary that the electronic conductivity has a value equal to or higher than those. That is, the mixed conductive oxide targeted by the present invention refers to an oxide whose electron conductivity and oxygen ion conductivity are both about 0.1 S / cm or more under operating conditions.

As a mixed conductive oxide satisfying this definition, there have long been known Japanese Patent Laid-Open Nos. 56-92103 and 6-62.
As disclosed in JP 1-21717 A, La _x
Oxides having a perovskite type crystal structure such as Sr _{1 -x} CoO _{3 -a} and La _{1 -x} Sr _x Co _{1 -y} Fe _y O ₃ -z are known.

More recently, US Pat. No. 5,356,728.
And No. 5580497,
A typical composition is Sr ₄ Fe _6-x Co _x O _z (13−δ ≦ z ≦ 1
3 + δ), and one of the main crystalline phases is a non-perovskite type (Sr ₄ Fe ₆ in the above publication) at least near room temperature.
The same layered perovskite type as the O ₁₃ compound), and has a crystal structure of 10 to 30 S / cm in the atmosphere.
An oxide having an electronic conductivity of about (800 to 950 ° C.) has been invented.

Further, an academic paper by Teraoka et al. (Journal of the Chemical Society of Japan, vol.1988, No.7, pp1084-1089, 1988, "L
a _1-x Sr _x Co _1-y Fe _y O ₃ oxygen permeation capacity of perovskite type oxide ”), as a result of changing x and y from 0 to 1.0, except for SrCoO _2.5 , x is A composition having a large y and a small y, for example, SrCo _0.8 Fe _0.2 O ₃
In that case, it is described that a good oxygen permeability can be obtained.

[0007] Teraoka et al. Further published the proceedings of the 68th conference of the Institute of Electrochemistry (1J26, pp175, April 1-3, 2001, "Sr,
“Synthesis and oxygen permeability of La—Sr—Co—Fe-based perovskite in the Co-rich composition region”), La at the A site.
Since the oxygen permeability at low temperature is improved by containing
La-Sr-Co-Fe consisting of four components, and Sr
And Co having the highest possible composition, for example La _0.1
It has been reported that good oxygen permeability can be obtained with a composition of Sr _0.9 Co _0.9 Fe _0.1 O ₃ . With this composition, SrCo which is the most preferable composition in the above literature
_It is said that it is effective in improving the oxygen permeability in a lower temperature region as compared with _0.8 Fe _0.2 O ₃ .

[0008]

The mixed conductive oxide is
It was originally invented for the purpose of separating and recovering an oxygen component from an oxygen-containing mixed gas, and has a thickness of 1 mm or less, preferably 0.5 mm in order to increase the oxygen permeation rate.
It is said that a thin film is used below.

In fact, La _0.1 Sr _0.9 Co _0.9 Fe described in Teraoka et al.'S Proceedings of the 68th Annual Meeting of the Electrochemical Society of Japan.
_The mixed conductive oxide represented by _0.1 O ₃ is about 1 mm
Assuming that the air thickness is 1 atm on the supply side and He is used on the extraction side to make the oxygen partial pressure difference on both sides about 0.2 atm, at 900 ° C. about 2 cm ³ · cm ⁻² · min ⁻¹ In order to obtain 16 cm ³ · cm ⁻² · min ⁻¹ which has oxygen permeability but is industrially usable when used for separation and recovery of oxygen and for use as a membrane reactor, the above composition is further added. It is necessary to reduce the film thickness.

Since such a composition having a conventional perovskite structure generally has low mechanical strength and is easily cracked, it should be formed on a support at a thickness that provides an industrially applicable oxygen transport rate. I have no choice.

However, the support must be porous as it must be permeable to air or oxygen-containing gas mixtures, and to obtain a mixed conductive oxide industrially available selective oxygen transport rate. Temperature required for 700
Since the temperature is as high as about 950 ° C., there is concern about mechanical damage to the support and damage due to thermal shock. For example, typical structural materials such as alumina (Al ₂ O ₃ ) and mullite (3
Al ₂ O ₃ .2SiO ₂ ), silicon nitride (Si ₃ N ₄ ), sialon (Si-Al-O-N solid solution), cordierite (2Al
₂ O ₃ · MgO · 5SiO ₂ ), stabilized zirconia (CaO-
Even if doped ZrO ₂ or Y ₂ O ₃ -doped ZrO ₂ ) or silicon carbide (SiC) is used as a porous support, cracks or peeling may occur in the mixed conductive oxide, or the mixed conductive oxide may not be formed. This causes inconvenience such as destruction with the porous support.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an oxygen separation device having a high oxygen separation ability without causing inconvenience associated with a support.

[0013]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies on an oxygen separation device using a perovskite-type mixed conductive oxide having good oxygen permeability, and as a result, have found that the perovskite-type mixed conductive oxide having a specific component composition is used. By using a dense sintered oxide as the porous oxide, it is possible to configure the oxygen separator as a self-supporting structure that does not use a support and has a thickness that allows sufficient oxygen transmission characteristics to be obtained. I found it.

The present invention has been made on the basis of such findings, and provides the following (1) to (7).

(1) Oxidized mixed conductive metal oxide containing lanthanum, strontium, cobalt and iron as main components, the molar ratio of these component elements being represented by the following formula (1), and having an open porosity of 2% or less. It is made of objects and has a thickness of 150 to 500
An oxygen separation device comprising a self-supporting structure having a range of μm. La: Sr: Co: Fe = x: 1-x: 1-y: y (1) (where 0 <x <0.15, 0 <y <0.15)

(2) In the above (1), the operation is performed with the difference between the supply-side oxygen partial pressure on the outer side and the sampling-side oxygen partial pressure on the inner side of the self-supporting structure set to 0.5 to 3 atm. Oxygen separator.

(3) From a dense mixed conductive metal oxide containing barium, cobalt and iron as main components, the molar ratio of the component elements is represented by the following formula (2), and the open porosity is 3% or less. And an oxygen separation device comprising a self-supporting structure having a thickness of 200 to 2500 μm. Ba: Co: Fe = 1: 1-y ': y' (2) (where 0 <y '<0.25)

(4) In the above (3), the operation is performed with the difference between the oxygen partial pressure on the supply side which is the outer side of the self-supporting structure and the oxygen partial pressure on the sampling side which is the inner side being 0.1 to 3 atm. Characteristic oxygen separation device.

(5) In any one of the above (1) to (4), the self-supporting structure has a cylindrical shape with at least one end closed by a flat plate or a hemispherical shell.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail below. The oxygen separator according to the present invention contains lanthanum, strontium, cobalt and iron as main components,
A self-supporting structure in which the molar ratio of the component elements is represented by the following formula (1), is composed of a dense mixed conductive metal oxide having an open porosity of 2% or less, and has a thickness in the range of 150 to 500 μm. It is configured. La: Sr: Co: Fe = x: 1-x: 1-y: y (1) (where 0 <x <0.15, 0 <y <0.15)

Here, the self-supporting structure means a structure substantially composed of itself without using a support.

In the mixed conductive oxide, the cation is La-.
It is a mixed oxide which can be represented by the chemical formula ABO _{x, which} is composed of each component of Sr—Co—Fe. La and Sr
Is located at the site denoted by A in this chemical formula, while
Co and Fe are located at the site represented by B.

When the substitution ratio of Sr by La in the A site is represented by x, 0 <x <0.15. When La is not present, the oxygen permeability in a low temperature range of 500 to 900 ° C. becomes low, but the overall oxygen permeability decreases as x increases. Therefore, it is within the above range to obtain high oxygen permeability. It is necessary.

When the substitution rate of Co in the B site by Fe is represented by y, 0 <y <0.15. If Fe is not present, the symmetry of the crystal structure is lowered, and the presence of Fe is essential because migration of oxide ions or oxygen defects is less likely to occur, but if y is increased to some extent or more, the overall oxygen permeability is lowered. Therefore, in order to obtain high oxygen permeability, the above composition is required.

In order to increase the oxygen permeability (selective oxygen transport rate) of the mixed conductive oxide having the above composition, not only the composition of the mixed conductive oxide, but also the oxygen permeability as a dense microstructure is required. It is extremely important to increase it. That is, it is necessary to make the La—Sr—Co—Fe mixed conductive oxide having the above composition have an open porosity of 2% or less. That is, La-Sr-Co having the above composition
If a large number of physical voids exist in the —Fe-based mixed conductive oxide, atmospheric gas passing through the voids will be mixed as impurities, and the oxygen permeability will be reduced. 2% open porosity
The following can sufficiently suppress the mixing of the impurities.

The thickness of the self-supporting structure composed of the La—Sr—Co—Fe mixed conductive oxide having the above composition is preferably as thin as possible when the oxygen permeation rate is diffusion-controlled and mixed-controlled, but is more than 150 μm. The thinner it is, the more susceptible it is to mechanical damage. On the other hand, when the thickness is more than 500 μm, a very large pressure difference is required to secure a practical level of oxygen permeation amount, and the material is easily broken. Therefore,
The thickness of the self-supporting structure made of the La-Sr-Co-Fe mixed conductive oxide having the above composition is in the range of 150 to 500 μm. In order to maintain high reliability on an industrial level, it is preferably 300 μm or more.

As described above, La _0.1 Sr _0.9 Co _0.9
Assuming that the mixed conductive oxide material of Fe _0.1 O ₃ composition has a thickness of about 1 mm, if 1 atm of air is used on the supply side and He is used on the extraction side and the oxygen partial pressure difference on both sides is about 0.2 atm. , Has an oxygen permeability of about 2 cm ³ · cm ⁻² · min ⁻¹ at 900 ° C, but the oxygen permeability of the mixed conductive oxide is
Since it is inversely proportional to the thickness as described above, if a self-supporting structure with a thickness of, for example, 500 μm can be formed,
Oxygen permeability is about 0.4cm ³ · cm ^-2 · min ^- a ^1.

An oxygen separator according to another aspect of the present invention is
Main component is barium, cobalt and iron, the molar ratio of these component elements is expressed by the following formula (2), and the open porosity is 3%.
The self-supporting structure is composed of the following dense mixed conductive metal oxides and has a thickness in the range of 200 to 2500 μm. Ba: Co: Fe = 1: 1-y ': y' (2) (where 0 <y '<0.25)

In the mixed conductive oxide, the cation is Ba-
It is a mixed oxide that can be represented by the chemical formula ABO _x that is composed of each component of Co—Fe. Ba is A in this chemical formula
, And Co and Fe are located at the site represented by B.

When the substitution rate of Fe in the B site is represented by y ', 0 <y'<0.25. If Fe is not present, the symmetry of the crystal structure is reduced, and it is important that Fe is present because the migration of oxide ions or oxygen vacancies is less likely to occur. Since it decreases, it is necessary to be within the above range in order to obtain high oxygen permeability.

As described above, in order to increase the oxygen permeability (selective oxygen transport rate) of the mixed conductive oxide, not only the composition of the mixed conductive oxide, but also the oxygen permeability as a dense microstructure. It is extremely important that the Ba-Co-Fe mixed conductive oxide of the above composition has a high open porosity of 3% or less. When the open porosity is 3% or less, the mixing of impurities can be sufficiently suppressed.

The thickness of the self-supporting structure made of the Ba—Co—Fe mixed conductive oxide having the above composition is preferably as thin as possible when the oxygen permeation rate is diffusion rate-controlled and mixed rate-controlled.
If it is thinner than 00 μm, it is likely to be mechanically damaged. On the other hand, if the thickness is more than 2500 μm, it becomes difficult to secure a practical level of oxygen permeation amount. Therefore, the thickness of the self-supporting structure made of the Ba—Co—Fe mixed conductive oxide having the above composition is in the range of 200 to 2500 μm.
350μ to maintain high reliability at an industrial level
It is preferably m or more.

When a mixed conductive oxide material having a composition of Co _0.9 Fe _0.1 O _x is made to have a thickness of about 1 mm, 1 at at the supply side.
m of air is about 5 cm ³ · c at 900 ° C when He is used on the extraction side and the oxygen partial pressure difference on both sides is about 0.2 atm.
Although it has an oxygen permeability of m ⁻² · min ⁻¹ , the oxygen transmission rate of the mixed conductive oxide is inversely proportional to its thickness as described above, and thus it is possible to form a self-supporting structure with a thickness of 500 μm, for example. If possible, oxygen permeability is about 10 cm ³ · c
It becomes m ^-2 · min ^-1 .

The shape of the self-supporting structure constituting the oxygen separation device is not particularly limited, but a cylinder with one end closed is preferable.
The shape of the end portion at this time may be a shape closed by a flat disc surface as shown in FIG. 1A, but since stress may concentrate on the end surface, it may break. Figure 1 shows the shape of the end
It is more preferable that the shape is a so-called test tube shape that results in the hemispherical shell shown in (b). In order to obtain such a shape, it is desirable to integrally form it, but as shown in FIGS. 2 (a) and 2 (b), even if the cylindrical portion and the end portion are manufactured separately, they can be joined together. good. As an example of the joining method, a paste containing the same material as that of the support is applied to the joining surfaces, and the members are pressure-bonded and then heat-treated.

In order for the separation of oxygen, that is, the selective oxygen transport, to proceed by such a cylindrical self-supporting structure composed of the mixed conductive oxide material having the above-mentioned composition, one of the self-supporting structures of the mixed conductive oxide is required. The oxygen partial pressure on the surface (p ₁ ) needs to be lower than that on the other side (p ₂ ), and the larger the oxygen partial pressure difference, the higher the selective oxygen transport rate. The oxygen transmission rate is proportional to the logarithm of the oxygen partial pressure ratio p ₂ / p ₁ on both surfaces. Therefore, if the oxygen partial pressure difference is multiplied by 10,
Double the oxygen transmission rate. In order to generate an oxygen partial pressure difference, generally, air is supplied to the oxygen supply side and the oxygen sampling side is degassed, but in order to obtain a sufficient amount of oxygen permeation, the pressure difference on each side is large. Therefore, the outside of the self-supporting structure is the oxygen supply side where the pressure is high, and the inside is the oxygen collection side where the pressure is low. The practical oxygen partial pressure difference is L of the above composition.
When the oxygen separator is composed of a free-standing structure made of a-Sr-Co-Fe mixed conductive oxide, 0.5 to 3a.
tm, when the oxygen separator is composed of a self-supporting structure composed of the Ba—Co—Fe mixed conductive oxide having the above composition, it is preferably 0.1 to 3 atm. The oxidation permeation rate increases as the pressure difference increases, but the mechanical strength of the above-mentioned material forming the self-supporting structure is lower than that of general structural materials. There arises a problem that various components are mixed from the supply gas side to the extraction gas side.

The method for producing the self-standing structure of the perovskite-type mixed conductive oxide as described above is not particularly limited and may be carried out according to a conventional method. As a typical example, the starting raw materials are mixed and pulverized by a wet ball mill or the like, the resulting mixed raw material is dried and then calcined, and then pulverized again by a ball mill or the like, and then formed by an appropriate method such as a doctor blade method or an extrusion molding method, A method of performing main firing can be mentioned. When powder is required for molding, the raw material crushed after calcination is further crushed and used, but in the case of the doctor blade method and extrusion molding method, it is usually used as a slurry.

The self-supporting structure is La-Sr-Co having the above composition.
When it is made of a —Fe-based mixed conductive oxide, for example,
As starting materials, lanthanum oxide, strontium carbonate,
Using iron oxide and cobalt oxide, crushed by a wet ball mill etc., dried, calcined at 750 to 900 ° C., crushed again by a wet ball mill and molded, and then 110
Baking is performed at 0 to 1300 ° C.

The self-supporting structure has the above composition of Ba--Co--Fe.
In the case of using a mixed type conductive oxide, for example, barium carbonate, iron oxide, or cobalt oxide is used as a starting material, crushed by a wet ball mill or the like, dried, and then 750 to 750.
It is calcined at 1000 ° C., then pulverized again by a wet ball mill, shaped, and then fired at 950 to 1200 ° C.

The above La _0.1 S obtained as described above
A mixed conductive oxide material having a composition of r _0.9 Co _0.9 Fe _0.1 O _{x was} used as a self-supporting structure having a thickness of 300 μm, 10 atm of air was supplied to one surface and He was supplied to the other surface to reduce the oxygen partial pressure difference. At 2 atm, about 16 cm ³ at 900 ° C
・ 16 cm ³・ cm ^-2・ m that can be industrially used because it can exhibit oxygen permeability of cm ^-2・ min ^-1
in ^-1 can be achieved. In addition, the above Co _0.9 F
e _0.1 O _x composition mixed conductive oxide material, thickness 300μ
As m, when 10 atm of air is supplied to one surface and He is supplied to the other surface to make the oxygen partial pressure difference about 2 atm,
About 17cm ³ · cm ^-2 · min at 900 ° C. ^- will be ^one of the oxygen permeability can be exhibited, industrially value exceeding 16cm ³ · cm ^-2 · min ^-1, which is made available is obtained.

[0040]

EXAMPLES Examples of the present invention will be described below together with comparative examples.

Example 1 As shown in Table 1, as a starting material for a self-supporting structure, La ₂ O ₃ (Wako Pure Chemical Industries, purity 99.
9%), SrCO ₃ (Kanto Kagaku, 99.9%), Co ₂ O
₃ (Kanto Chemical, purity 99.95%) and Fe ₂ O
₃ (Wako Pure Chemical Industries, 99.9%) with La: Sr: Co: Fe
Weighed so that the cation ratio was = 1: 9: 9: 1.
These raw materials were mixed and pulverized by a wet ball mill.
The calcination was performed at 950 ° C. for 10 hours in an alumina bowl to obtain a perovskite single phase. This powder was again ground by a wet ball mill. After adding 1 part by weight of PVA as a binder to 100 parts by weight of the powder in the slurry and further mixing, the viscosity was adjusted while removing air bubbles, and a coating film was formed with a doctor blade and dried. Make the thickness of the self-supporting structure about 300 μm,
The viscosity of the slurry was adjusted. Then, it was punched out as a disk having a diameter of 15 mm and used as the bottom of the self-supporting structure. In addition, the cylindrical portion of the self-supporting structure is formed by coating the above dry coating film on the short side 52 ×
It was cut out to a long side of 70 mm, and 5 mm of the short side was used as a glue margin, and toluene was sprayed thereto to swell, rolled, and the glue margin portion was pressure-bonded. These were adhered via the above slurry, dried and then fired at 1200 to 1300 ° C. to obtain an oxygen permeable self-supporting structure. The open porosity of the thus obtained self-supporting structure was determined by the underwater Archimedes method.

The oxygen permeability was measured four times at intervals of about 10 minutes after the temperature was raised to the measurement temperature in a pressure vessel equipped with a gas supply / exhaust pipe and held for about 30 minutes in a tubular furnace. air
(O ₂ : 21%, N ₂ : 79%) has a gauge pressure of about 12 atm, and He gas has a gauge pressure of 0.2 atm.
20 ml / mi from each cylinder via pressure reducing valve and flow meter
n. O ₂ , N ₂ and CO ₂ were detected with a gas chromatograph, and the oxygen permeability was determined from the O ₂ amount, the presence of cracks in the sample was determined from the N ₂ amount, and the presence of outside air was determined from the CO ₂ amount. Detected.

As shown in Table 1, the self-supporting structure had an open porosity of 1.4% and an oxygen permeability of 16.7c at 900 ° C.
It was m ³ · cm ⁻² · min ⁻¹ , which was confirmed to be at a practical level.

Example 2 Starting material was La: Sr: C
A self-supporting structure was produced in the same manner as in Example 1 except that the cation ratio of o: Fe was 1.5: 8.5: 8.5: 1.5. The thickness of this self-supporting structure was 290 μm, and the open porosity was 0.8%. Then, the oxygen permeability was measured in the same manner as in Example 1, and as a result, as shown in Table 1, 900 ° C.
It was confirmed that the oxygen permeability was about 16 cm ³ · cm ⁻² · min ⁻¹ , which was at a practical level.

(Comparative Example 1) The starting material was La: Sr: C.
o: Fe = 2: 8: 8: 2 cation ratio
A self-supporting structure was prepared in the same manner as in Example 1 except that the above was added. table
1, the thickness of this self-supporting structure is 340 μm,
The open porosity was 1.6%. And similar to the first embodiment
As a result of measuring oxygen permeability, there is a slight difference in composition.
Even if the oxygen partial pressure difference is larger than in Examples 1 and 2,
Oxygen permeability at 00 ° C is about 9 cm³・ Cm ^-2・ Min^-1When
It was small and did not reach the practical level.

(Comparative Example 2) A self-supporting structure was prepared in the same manner as in Example 1 except that the viscosity of the slurry for forming a coating film was lowered by the doctor blade method to reduce the thickness. As shown in Table 1, in this case, the open porosity was 2.6.
%, And the thickness was as thin as 120 μm, the ceramic self-supporting structure was cracked and the oxygen permeability could not be measured even when the oxygen partial pressure difference was smaller (the supply air pressure was smaller) than in the examples. .

Comparative Example 3 A self-supporting structure was prepared in the same manner as in Example 1 except that the viscosity of the slurry for forming a coating film was increased by the doctor blade method to increase the thickness. Table 1
In this case, although the open porosity was as small as 0.2% in this case, even if the oxygen partial pressure difference was made larger than that in the example, the oxygen content at 900 ° C. was increased because the self-supporting structure had a large thickness of 1000 μm. The permeability is as small as about 4 cm ³ · cm ^-2 · min ^-1 ,
It did not reach the practical level.

Example 3 As shown in Table 2, as a starting material for the self-supporting structure, BaCO ₃ (Kanto Chemical Co., purity 99.
9%), Co ₂ O ₃ (Kanto Kagaku, purity 99.95%), and Fe ₂ O ₃ (Wako Pure Chemical Industries, 99.9%) as Ba: Co:
It was weighed so as to have a cation ratio of Fe = 10: 9: 1. These raw materials were mixed and pulverized by a wet ball mill. The calcination was performed at 900 ° C. for 10 hours in an alumina bowl to obtain a perovskite single phase. This powder was again ground by a wet ball mill. After adding 1 part by weight of PVA as a binder to 100 parts by weight of the powder in the slurry and further mixing, the viscosity was adjusted while removing air bubbles, and a coating film was formed with a doctor blade and dried. The viscosity of the slurry was adjusted so that the thickness of the self-supporting structure was about 600 μm. Then, it was punched out as a disk having a diameter of 15 mm and used as the bottom of the self-supporting structure.
In addition, the cylindrical portion of the self-supporting structure has the dry coating film on the short side
C. A long side was cut out to 70 mm, and 5 mm of the short side was used as a glue margin. Toluene was sprayed thereto to swell it, and it was rolled to press the glue margin portion. These were adhered via the slurry, dried, and then fired at 1200 to 1300 ° C. to obtain an oxygen permeable self-supporting structure. The open porosity of the thus obtained self-supporting structure was determined by the underwater Archimedes method. The measurement of oxygen permeability was performed in the same manner as in Example 1.

As shown in Table 2, the free-standing structure had an open porosity of 1.4% and an oxygen permeability of about 17 cm at 900 ° C.
^{It was 3} · cm ⁻² · min ⁻¹ , which was confirmed to be at a practical level.

Example 4 The starting material is Ba: Co: Fe.
= 10: 8: 2 except for the cation ratio
A self-supporting structure was prepared in the same manner as in Example 3. The thickness of this self-supporting structure was 540 μm, and the open porosity was 1.1%.
Then, as a result of measuring the oxygen permeability as in Example 1,
As shown in Table 2, the oxygen permeability at 900 ° C is 16.6c.
It was m ³ · cm ⁻² · min ⁻¹ , which was confirmed to be at a practical level.

(Comparative Example 4) The starting material was Ba: Co: Fe.
= 10: 7: 3, except for the cation ratio
A self-supporting structure was prepared in the same manner as in Example 3. As shown in Table 2, the film thickness of this self-supporting structure was 620 μm, and the open porosity was 1.0%. Then, as a result of measuring the oxygen permeability in the same manner as in Example 1, even if the oxygen partial pressure difference was made larger than in Examples 3 and 4 due to a slight difference in composition, the oxygen permeability at 900 ° C. was 13.7 cm. ³ · cm ⁻² · min ⁻¹ ,
It did not reach the practical level.

(Comparative Example 5) A self-supporting structure was prepared in the same manner as in Example 3 except that the viscosity of the slurry for forming a coating film was reduced by the doctor blade method to reduce the thickness. In this case, as shown in Table 2, the thickness is 150 μm.
Therefore, even if the oxygen partial pressure difference was made smaller (the supply air pressure was made smaller) than in the example, the ceramic freestanding structure was cracked and the oxygen permeability could not be measured.

Comparative Example 6 A self-supporting structure was prepared in the same manner as in Example 3 except that the viscosity of the slurry for forming a coating film was increased by the doctor blade method to increase the thickness. Table 2
In this case, although the open porosity was as small as 1.1% in this case, even if the oxygen partial pressure difference was made larger than that in the example, the oxygen content at 900 ° C. was increased because the thickness of the self-supporting structure was as thick as 2900 μm. The permeability was as small as 3.3 cm ³ · cm ⁻² · min ^−1, which was below the practical level.

[0054]

[Table 1]

[0055]

[Table 2]

[0056]

As described above, according to the present invention,
Since the oxygen separator is composed of a self-supporting structure having a predetermined thickness and made of a dense mixed conductive metal oxide having a perovskite type structure having a predetermined component composition, the support is not required and the disadvantages associated with the support are eliminated. It is possible to obtain an oxygen separation device having a high oxygen separation ability without being generated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an oxygen separation device according to an embodiment of the present invention.

2 is a cross-sectional view showing a state in which the oxygen separation device of FIG. 1 is manufactured by joining.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) C01G 51/00 C01G 51/00 BF term (reference) 4D006 GA41 HA28 KE06R KE30R MA02 MA24 MA31 MB12 MC03X NA62 PB17 PB62 PC71 4G002 AA10 AE05 AF01 4G042 BA31 BB02 DA02 DB10 DB11 DD02 DE04 DE05 DE06 DE08 DE12 DE14 4G048 AA05 AB02 AC08 AD02 AE05

Claims (5)

[Claims] 1. A dense mixed conductive metal oxide containing lanthanum, strontium, cobalt and iron as main components, the molar ratio of the component elements being represented by the following formula (1) and having an open porosity of 2% or less. And has a thickness of 150 to 500 μm
The oxygen separation device is characterized by being constituted by a self-supporting structure within the range. La: Sr: Co: Fe = x: 1-x: 1-y: y (1) (where 0 <x <0.15, 0 <y <0.15) 2. The difference between the supply-side oxygen partial pressure on the outside and the sampling-side oxygen partial pressure on the inside of the self-supporting structure is 0.5 to 3 at.
The oxygen separation device according to claim 1, which is operated as m. 3. Barium, cobalt and iron as main components, the molar ratio of these component elements is represented by the following formula (2),
An oxygen separation device, characterized in that it is composed of a dense mixed conductive metal oxide having an open porosity of 3% or less and a self-supporting structure having a thickness in the range of 200 to 2500 μm. Ba: Co: Fe = 1: 1-y ': y' (2) (where 0 <y '<0.25) 4. The difference between the oxygen partial pressure on the supply side, which is the outer side of the self-supporting structure, and the oxygen partial pressure on the sampling side, which is the inner side, is 0.1 to 3.
The oxygen separation device according to claim 3, which is operated as an atm. 5. The oxygen separation device according to claim 1, wherein the self-supporting structure has a cylindrical shape in which at least one end is closed by a flat plate or a hemispherical shell.