JP2001269555A - Double layer ceramic material and oxygen separation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a double layer ceramic material with improved oxygen permeability in order to put an oxygen separation process or a method for manufacturing an oxygen-rich air to a practical use application. SOLUTION: An oxygen exchange layer made up of a composite oxide of a cubic crystal system having a different composition from the composite oxide having an oxygen ion diffusing capability is formed on both sides or one side of the composite oxide having the oxygen ion diffusing power.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite ceramic material having a high oxygen permeation rate used for separating pure oxygen from an oxygen-containing gas or producing oxygen-enriched air, etc. It can be used for a wide range of industrial applications that require air.

[0002]

2. Description of the Related Art Pure oxygen separated from oxygen-containing gas and oxygen-enriched air with an increased oxygen concentration are used to increase thermal efficiency in factories that require particularly high temperature and high heat, such as steelmaking, glass, and cement. Manufacturing is an industrially important technology. Also, pure oxygen and oxygen-enriched air have high utility value for medical use. Pure oxygen is also required for oxidation reactions that play a role in various stages of chemical production.

[0003] Various methods are known for oxygen separation or oxygen enrichment techniques, some of which have been put into practical use, but problems still remain. For example, the adsorption / desorption method using zeolite is economically disadvantageous because the apparatus is complicated because oxygen is adsorbed and desorbed repeatedly. A method using a polymer film such as a polysiloxane, a polysiloxane-polycarbonate copolymer, or an organosiloxane cannot extract high-purity oxygen because of insufficient selectivity. Also, the raw material air is pressurized to several tens of atm, which is inefficient.

[0004] A method of oxygen separation using an oxygen ion conductive solid electrolyte such as zirconium oxide is also known.
This method utilizes the property that only oxygen ions can diffuse at a high rate in an oxygen ion conductive solid electrolyte. In this method, electrodes are provided on both sides of the solid electrolyte, and both electrodes are short-circuited by an external circuit. Oxygen gas receives electrons on one electrode surface, becomes oxygen ions, diffuses in the solid electrolyte, reaches the electrode on the other surface, and releases electrons on this electrode surface to form a circuit that becomes oxygen gas. . In the system using such an oxygen ion conductive solid electrolyte,
Since the electrode reaction occurs only at the point where the three phases of the solid electrolyte, the electrode material, and the oxygen gas are in contact, the effective area where the reaction can occur is small. In addition, there is a problem that the solid contact between the electrode and the electrolyte deteriorates with time, resulting in poor stability.

[0005] Whereas the above method uses an oxygen ion conductive solid electrolyte having no electron conductivity, the use of a mixed conductive solid electrolyte having both oxygen ion conductivity and electron conductivity allows the electrode to be formed. A method of performing oxygen separation without requiring an external circuit is known. A thin film or thin plate of mixed conductive solid electrolyte composed of oxide ceramics is kept at a high temperature of 500 ° C or more, and one side of the thin film or thin plate is brought into contact with air, and the other is depressurized, or air with increased pressure is pressed to one side. By contact, oxygen is permeated into the thin film or the thin plate and oxygen is extracted by using the difference in the partial pressure of oxygen generated on both sides of the thin film or the thin plate as a driving force.

[0006] The process of oxygen separation using the mixed conductive solid electrolyte will be described in more detail. Here, the mixed gas (source gas) containing oxygen, such as air, on the side of the solid electrolyte is referred to as “inlet”, and the side on which pure oxygen gas or oxygen-enriched air to be extracted is obtained is referred to as “outlet”. I do.
In this method, the oxygen partial pressure on the outlet side is made smaller than the oxygen partial pressure on the inlet side, and the pressure difference is the driving force for oxygen ion diffusion. However, oxygen gas cannot pass through the solid electrolyte as it is as oxygen molecules. Oxygen gas is in an oxygen ion state, and moves by diffusion through a crystal lattice of a solid electrolyte, which is an oxide, through oxygen defects (the moving speed is called an oxygen ion diffusion speed). That is, the oxygen molecules on the entry side are adsorbed on the surface of the solid electrolyte, dissociated into two oxygen atoms, and further receive negative charges to become oxygen ions. When the oxygen ions move through the solid electrolyte and reach the output side, the negative ions are released on the surface of the solid electrolyte on the output side, and are bonded again to oxygen molecules. In these steps, oxygen molecules are exchanged for oxygen ions on the entrance side or oxygen ions are exchanged for oxygen molecules on the exit side, so this is called an oxygen exchange reaction, and the reaction rate is called an oxygen exchange rate. ing.

In summary, the oxygen transmission rate is determined by two factors: the diffusion rate of oxygen ions in the solid electrolyte and the oxygen exchange reaction rate of oxygen molecules / oxygen ions on the surface of the solid electrolyte. Become. Therefore, in order to obtain a high oxygen permeation rate, it is important to control those two factors. Until now, in order to put the above-described oxygen separation technique into practical use, research has been conducted to obtain a solid electrolyte having a high oxygen permeation rate. For example, La
_x Sr _ax CoO ₃ (where x is in the range of 0.1 to 0.9, particularly preferably 0.3 to 0.7) (JP-A-56-92103) and La _x Sr
_1-x Co _z Fe _1-z O ₃ (however, z = 1, x = 1.0,0.6,0.3)
(Teraoka et al., Journal of the Chemical Society of Japan 1988, (7), p1084-1089). They examined a sample in which a dense oxide ceramic obtained by hardening a composite oxide was processed into a thin plate of 0.5 to 1 mm. That is, the research here was a search for a material having a high oxygen ion diffusion rate in the solid electrolyte.

However, when actually applied as an oxygen production apparatus, it is necessary to use a thin solid electrolyte in order to obtain a sufficiently high oxygen permeation rate. The thinner the solid electrolyte, the shorter the oxygen ion diffusion distance, and the higher the oxygen permeation rate is in inverse proportion to the thickness of the solid electrolyte. However, the relationship holds when the solid electrolyte is sufficiently thick, that is, when the diffusion of oxygen ions controls the oxygen permeation rate. As the solid electrolyte becomes thinner, the oxygen exchange reaction on the surface of the solid electrolyte controls the oxygen permeation rate (surface-determined). Even if the thickness is reduced to a certain thickness or less, the oxygen permeation rate does not increase. is expected.

[0009]

[Outside 1]

[0010]

As described above, in the case of an oxygen separation apparatus using a mixed conductive solid electrolyte, it is important to overcome the surface rate control. As described above, the prior art has attempted to overcome the surface rate limitation by adding a catalyst layer made of a metal such as Ag, Pt, Pd, and PrO ₂ or a metal oxide to the inside or the surface of the solid electrolyte. However, as far as the present inventors have studied, when a cubic composite oxide ceramic is used as a solid electrolyte, Pt,
No increase in oxygen permeation rate was observed even when a metal catalyst layer such as Ag or Pd or a metal oxide layer such as PrO ₂ was added.

In the present invention, in particular, in the case where a mixed conductive solid electrolyte material is used for oxygen separation, the surface phenomena is correctly grasped, and the contribution of the surface activity in the oxygen separation process is quantitatively grasped. The purpose of the present invention is to find a surface modifying material for improving the oxygen permeability and to obtain a sufficiently high oxygen permeation rate at a level of industrial value.

[0012]

The object of the present invention is to provide (1) a cubic oxide having a composition different from that of the above-mentioned composite oxide having oxygen ion diffusing ability on both or one surface of the composite oxide having oxygen ion diffusing ability. A multi-layer ceramic material, characterized by forming an oxygen-exchange layer composed of a crystalline composite oxide,
(2) A multilayer ceramic material characterized in that the oxygen exchange layer described in (1) is a dense membrane, a porous body, or an island-shaped discontinuous membrane having an average film thickness of 30 μm or less, (3) (1) ) Or
The composite oxide having oxygen ion diffusing ability described in (2)
A multilayer ceramic material characterized by being a thin film having a thickness of 300 μm or less, wherein the oxygen-exchange layer described in (4) (1), (2) or (3) is formed of La _u Sr _bu Fe _v Co _cv O _3-w (however, 0.1 ≤ u <0.5, 0.9 <b <1.1, 0 <v <1.1
, 0.9 <c <1.1), a multilayer ceramic material comprising a cubic composite oxide represented by the formula: (5)
The composite oxide having oxygen ion diffusing ability described in (1), (2), (3) or (4) is La _{x Srax} CoO _3-y (however,
A multilayer ceramic material comprising a cubic composite oxide represented by 0 ≦ x <0.1, 0.9 <a <1.1), (6) the multilayer ceramic material is a multilayer ceramic material for oxygen separation (1) to (5), (7) an oxygen separator using any of the multilayer ceramic materials (1) to (5), (8) (1) (5) A chemical reaction device using the multilayer ceramic material according to any of (5).

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The oxygen transmission rate is determined by two factors, the diffusion rate of oxygen ions in the solid electrolyte and the oxygen exchange reaction rate of oxygen molecules / oxygen ions on the surface of the solid electrolyte. Model has been proposed, but the quantitative relationship between these factors and the oxygen transmission rate has not been clarified. The inventors made an experimental device using oxygen isotopes, and made it possible to separate and evaluate the oxygen ion diffusion rate and oxygen exchange reaction rate that could not be separated by oxygen transmission rate measurement, and furthermore, their physical properties A model was developed to derive the oxygen transmission rate from The present inventors examined the oxygen ion diffusion rate and the oxygen exchange rate of various metals and oxide materials of various compositions using the above-described experimental apparatus. As a result, when the solid electrolyte is thinned,
It was found that the rate of oxygen exchange determines the rate of oxygen transmission. That is, it became clear that the surface reaction, that is, the improvement of the oxygen exchange rate was most important in practical materials. In addition, the oxygen ion diffusion rate and oxygen exchange rate of the cubic composite oxide are generally very large, however, a material having a large oxygen ion diffusion rate does not necessarily have a large oxygen exchange rate,
Also became apparent.

As described above, in the present invention, an "oxygen exchange layer" having a function of oxygen ion diffusion inside the solid electrolyte and a function of oxygen exchange reaction on the surface of the solid electrolyte is formed. Thus, the oxygen permeation rate was improved in each stage by dividing the functions into different layers suitable for each function. As an embodiment of the present invention, for example, as shown in FIG. 1, a multilayer ceramic material having a three-layer structure in which an oxygen exchange layer (101) is formed on both sides of an oxygen ion diffusion layer (102) is exemplified. Even with a multilayer ceramic material having a two-layer structure as shown in FIG. 2 in which an oxygen exchange layer is formed on one side of the oxygen ion diffusion layer, a larger oxygen permeation rate can be obtained as compared with a case where no oxygen exchange layer is formed. A multilayer ceramic material having a three-layer structure as shown in FIG. 1 capable of improving the oxygen exchange rate on both the side and the outlet side is preferable from the viewpoint of improving the oxygen permeation rate. In the case of a multilayer ceramic material having a three-layer structure, the composition and form of the oxygen-exchange layer are made different according to the different gas-phase oxygen partial pressures on the entrance side and the exit side, so that a greater oxygen permeation can be achieved. Speed is obtained.

In the case of a dense membrane, the thickness of the oxygen exchange layer is 30 μm or less, preferably 10 μm or less, more preferably, in order to prevent oxygen ion diffusion in the oxygen exchange layer. It is desirable that it be 5 μm or less. Further, forming the composite oxide of the oxygen exchange layer into an island shape as shown in FIG. 3 or making the composite oxide porous as shown in FIG. The reaction rate is substantially increased. As a result of a detailed study by the present inventors, by forming an island or making it porous, the oxygen exchange rate is increased from the same to about 10 times as compared with the case of an oxygen exchange layer composed of a dense membrane. Let me do.

Further, by forming the inside of the oxygen exchange layer into a multilayer structure or a composite structure composed of cubic composite oxides having different compositions, it is possible to provide an effect of improving abrasion resistance and heat resistance. . Alternatively, a multilayer or a composite structure with other ceramics such as oxides, metals, nitrides, etc. other than the cubic composite oxide can also have the effect of improving abrasion resistance and heat resistance. I can do it.

The effect of improving the oxygen permeation rate by the oxygen exchange layer is particularly remarkable when the thickness of the oxygen ion diffusion layer is reduced to 300 μm or less. Normally, when the thickness of the solid electrolyte layer exceeds 300 μm, oxygen ion diffusion is more dominant (diffusion limited) in the above-described mechanism of oxygen permeation. It becomes dominant (surface limited). Therefore, the effect of the improvement is greater as the thickness of the oxygen ion diffusion layer is smaller, and has a significant meaning in practical use.

The oxygen ion diffusion layer having a thickness of 300 μm or less is
Depending on its composition, it alone has low mechanical strength and may not be able to be incorporated into an oxygen separator. Therefore, a porous ceramic that can maintain mechanical strength and does not hinder the flow of oxygen gas is used as a support,
An oxygen ion diffusion layer is formed thereon. For example, as shown in FIG. 5, an oxygen exchange layer, an oxygen ion diffusion layer, and an oxygen exchange layer are formed on a porous ceramic support in this order (hereinafter, the porous ceramic support / oxygen exchange layer / oxygen ion diffusion layer / oxygen diffusion layer). It may be a multilayer ceramic material having a four-layer structure in which different oxide ceramics are formed (illustrated as an exchange layer). In this case, three layers of oxygen exchange layer / oxygen ion diffusion layer / oxygen exchange layer are responsible for oxygen permeation.

When the porous ceramics support is formed of an oxide having a high oxygen exchange rate, the porous ceramics support itself acts as an oxygen exchange layer. / Oxygen ion diffusion layer (103)
The multilayer ceramic material having a three-layer structure composed of the oxygen / oxygen exchange layer (101) also shows a large oxygen permeation rate. As the composition of the oxygen exchange layer, all composite oxides having a higher oxygen exchange rate than the composite oxide of the oxygen ion diffusion layer correspond. Composite oxide cubic Among them, as compared with metal oxides such as metal or PrO ₂ such as Pt and Pd which are conventionally reported, suitable as several orders of magnitude oxygen exchange layer has a great oxygen exchange rate ing. The present inventors reported that La _0.05 Sr _0.95 C having a thickness of 100 μm
oO _3-y composite oxide is used as an oxygen ion diffusion layer, and u
, B, v, and c are defined as 0.1 ≦ u <0.5, 0.9 <b <1.1, 0
La _u Sr changed in the range of <v <1.1, 0.9 <c <1.1
A series of samples using _bu Fe _v Co _cv O _3-w composite oxide as an oxygen exchange layer were prepared, and the oxygen permeation rate was evaluated. as a result,
The oxygen permeation rate increased significantly when u was in the range of 0.1 to 0.5. Further, in the range of 0 <v <1.1, almost no difference in the oxygen transmission rate depending on v was recognized. At this time, the value of _w in La _u Sr _bu Fe _v Co _cv O _3-w is determined by electrical neutrality, but the value of w is a composition before being subjected to oxygen separation, and is actually When used for oxygen separation, the composition may be slightly different. Most of them become oxygen deficient. Further, other components may be contained as long as the oxygen exchange rate is not impaired.

The effect of the oxygen exchange layer in the present invention is as follows.
Combination with oxygen ion diffusion layer with high ion diffusion rate
This is particularly noticeable when Recently, the present inventors have described the La_x
Sr_{a- x}CoO_3-y0.5mm thick for composite oxides
And a set of 0 ≦ x <0.1, 0.9 <a <1.1
Oxygen permeation characteristics that surpass conventional materials in the growth region
However, the ceramic material of the invention (Japanese Patent Application No. 11-221740)
Is hard to crack and easy to make into a thin film. Therefore,
La_xSr_axCoO_3-ySystem composite oxide is the oxygen ion of the present invention.
Most suitable as a material for the diffusion layer. The value of y is electrical
The value of y is used for oxygen separation.
Before use in oxygen separation
May differ slightly from this composition. Many are oxygen
It becomes a state of loss. It also impairs the oxygen ion diffusion rate.
It does not matter if other components are contained within the
I don't support it.

[0021]

[Outside 2]

In order to form an oxygen ion diffusion layer of 300 μm or less, a porous ceramic is used as a support, and a vacuum deposition method, a reactive sputtering method, a chemical vapor deposition method,
There are methods such as chemical spraying and oxidation of alloy plating.
Alternatively, a slurry in which a composite oxide powder whose composition has been adjusted in advance is dispersed with a binder is applied to a porous ceramic support and fired.

As the composition of the porous support, for example, a composite oxide having the same composition as that of the cubic composite oxide of the present invention, or an oxide containing magnesium as a main component (Japanese Patent Application No. Hei 10-284,837).
11-281544) can be used. The thickness of the porous support should be thicker for the purpose of maintaining mechanical strength,
For the purpose of not hindering gas diffusion, a thinner one is desirable.
A typical thickness for both purposes is from 0.5mm to
1.0 cm. The shape of the porous support can take various forms, such as a flat plate and a tube, depending on the application, and the oxygen ion diffusion layer formed thereon can also take various forms such as a flat membrane and a tubular membrane.

The oxygen exchange layer is also formed on the oxygen ion diffusion layer by a method such as vacuum deposition, reactive sputtering, chemical vapor deposition, chemical spraying, and oxidation of alloy plating. Alternatively, a slurry obtained by mixing the calcined raw material powder with a solvent to form a paste may be applied and fired. In particular, when an island-shaped or porous oxygen exchange layer is formed, a method using a slurry is suitable, and the form can be controlled by controlling the amount of application and the baking time.

In order to separate oxygen in a mixed gas using the multilayer ceramic material of the present invention, an airtight chamber is provided on both sides of the ceramic material, and a mixed gas containing oxygen gas is supplied to one of the chambers. The conditions of both chambers are set so that the oxygen partial pressure of the other chamber is lower than the oxygen partial pressure. For example, one chamber is set to normal pressure or a pressurized state, and the other chamber is depressurized, or one chamber is pressurized to set the other chamber to normal pressure, whereby high-purity oxygen is supplied to the low oxygen partial pressure side. Can be taken out. The temperature at which the multilayer ceramic material of the present invention is used for oxygen separation is usually from 400 to 1200 ° C, preferably from 500 to 1000 ° C.

Further, the multilayer ceramic material of the present invention comprises:
It can also be used for applications other than oxygen separation, especially for chemical reaction devices involving oxidation reactions. For example, it is used in a reactor for the partial oxidation reaction of methane, which produces a synthesis gas composed of carbon monoxide and hydrogen from methane. Conventionally, a reaction apparatus for obtaining a synthesis gas by a catalytic reaction using a mixed gas of methane and oxygen as a starting material has been used. In the reaction apparatus using the multilayer ceramic material of the present invention, for example, air (or a mixed gas containing oxygen) and methane are separately flowed through the multilayer ceramic material, and Rh or the like is applied to the ceramic surface on the side where methane is flowing. A conventional catalyst for syngas production is arranged.
By heating the multilayer ceramic, only oxygen permeates according to the same principle as described above, and subsequently reacts with methane on the ceramic surface on the methane side to generate synthesis gas. Therefore, there is a great effect that there is no need to produce oxygen in advance as in the conventional method, a synthesis gas can be obtained efficiently because no raw material gas is mixed, and a continuous reaction occurs to simplify the production apparatus. Since the multilayer ceramic material of the present invention has a higher oxygen permeation rate than conventional materials, a highly efficient reactor can be realized. In addition to the partial oxidation of methane, the present invention can be used in all kinds of reactors involving oxidation reactions, such as partial oxidation of hydrocarbons to form olefins, partial oxidation of ethane, and substitution of aromatic compounds.

[0027]

EXAMPLES The case where the multilayer ceramic material of the present invention is used particularly for oxygen separation will be specifically described with reference to Examples. (Example 1) In this example, the oxygen permeation rate in the case where an oxygen exchange layer in the form of a dense membrane is formed on both sides of an oxygen ion diffusion layer having a thickness range of 32 µm to 3.2 mm will be specifically described. At this time, when the oxygen ion diffusion layer is thin, the porous ceramic support (105) / oxygen exchange layer (101) / oxygen ion diffusion layer (102) / oxygen exchange layer (101) are formed in this order as shown in FIG. It has a four-layer structure. When the oxygen ion diffusion layer is relatively thick, an oxygen exchange layer is formed on both sides of the oxygen ion diffusion layer (102) made of a thin plate cut out of the sintered body as shown in Fig. 1.
(101) is a three-layer structure.

First, a method for producing a porous ceramic support will be described. Strontium carbonate, ferric oxide SrFeO _3-w
And weighed together with isopropyl alcohol using a ball mill. After mixing, the mixture was dried to remove isopropyl alcohol, and calcined at 900 ° C. for 12 hours. The obtained calcined powder was mixed with PVA, molded into a cylindrical disk having a diameter of 14 mm and a height of 3 mm, and then calcined at 1200 ° C. for 5 hours in the atmosphere. Further, both bottom surfaces of the cylindrical disk were polished with sandpaper to form a cylindrical disk having a thickness of 1 mm, and then ultrasonically cleaned in an ethanol solvent.

Next, a method for producing a thin oxygen ion diffusion layer on the above porous ceramic support will be described.
First, lanthanum oxide, strontium carbonate, and tetracobalt trioxide were weighed to be La _0.05 Sr _0.95 CoO _3-w and mixed with isopropyl alcohol by a ball mill.
After mixing, dry to remove isopropyl alcohol, 900
Calcination was performed at ℃ for 12 hours. Further, a solvent was prepared by mixing and stirring ethyl carbitol and ethyl cellulose, and a slurry kneaded with the above calcined powder was prepared. Further, the slurry was applied on a porous ceramics support which had been prepared in advance, and baked at 1200 ° C. for 5 hours in the air. However, in this embodiment, since the oxygen exchange layers are formed on both sides of the oxygen ion diffusion layer, the oxygen exchange layer is first formed on the porous ceramic substrate, and then the oxygen ion diffusion layer is formed. In this embodiment, the thickness of the completed oxygen ion diffusion layer was set to 32, 63, 100, and 200 μm.

A method for manufacturing an oxygen ion diffusion layer made of a sintered body will be described. First, lanthanum oxide, strontium carbonate, and tetracobalt trioxide were weighed to be La _0.05 Sr _0.95 CoO _3-w and mixed with isopropyl alcohol by a ball mill. After mixing, the mixture was dried to remove isopropyl alcohol, and calcined at 900 ° C. for 12 hours. The obtained calcined powder was formed into a cylindrical disk having a diameter of 14 mm and a height of 3.5 mm.
It was calcined in the atmosphere at 00 ° C. for 5 hours. Heating / cooling rate is 120
° C / h. After slicing the fired body to the desired thickness,
The surface was flattened with sandpaper. In this example, the oxygen permeation rate was evaluated for three types of cylindrical disk-shaped samples having a thickness of the oxygen ion diffusion layer of 0.5, 1.0, and 3.2 mm.

[0031] Finally, a method of forming an oxygen exchange layer having the composition of _{La 0.3 Sr 0.7 Fe 0.8 Co 0.2} O 3-w. Lanthanum oxide, strontium carbonate, ferrous oxide, weighed trioxide four cobalt such that the _{La 0.3 Sr 0.7 Fe 0.8 Co 0.2} O 3-w, and mixed by a ball mill together with isopropyl alcohol. After mixing, dry to remove isopropyl alcohol,
Calcination was performed at 900 ° C for 12 hours. Further, a solvent was prepared by mixing and stirring ethyl carbitol and ethyl cellulose, and a slurry kneaded with the above calcined powder was prepared. Here, oxygen exchange layers were formed on both sides of the oxygen ion diffusion layer. Therefore, first, the slurry is applied on a cylindrical ceramic porous ceramic support that has been prepared in advance, and 12
It was calcined in the atmosphere at 00 ° C. for 5 hours. Next, after forming an oxygen ion diffusion layer thereon, the above slurry was further applied and baked at 1200 ° C. for 5 hours in the air. In this case, the thickness of the oxygen exchange layer was 5 μm, and the form was a dense membrane.

The oxygen permeation rate was evaluated using the apparatus shown in FIG. A 21% oxygen / 79% helium mixed gas was introduced at a rate of 40 cc / min from the oxygen-containing mixed gas inlet 1 to the high oxygen partial pressure side (entrance side). High-purity argon gas was introduced from the argon inlet 2 to the low oxygen partial pressure side (outside). The cylindrical disk-shaped sample 6 was set by a glass seal 8 and a glass side seal 9 so as to maintain airtightness on the entrance side and the exit side. The fact that the oxygen ion diffusion layer in Sample 6 was completely dense with no gas leak was confirmed by gas analysis of the discharged argon gas using the quadrupole mass spectrometer 11, and no helium gas was detected. Also, in order to distinguish between permeated oxygen and oxygen in the air entering from the middle of the gas line, 100% helium is introduced into the inlet and argon is introduced into the outlet, and the measured oxygen concentration in the argon is used as the background. deducted. Heating was performed in an electric furnace 5, and the conditions of 850 ° C., an inlet oxygen partial pressure of 0.21 atm, and an outlet oxygen partial pressure of 0.01 atm were used as standard measurement conditions. However, in the case of a cylindrical disk-shaped sample having an oxygen exchange layer / oxygen ion diffusion layer / oxygen exchange layer formed on a porous ceramic support, the three-layer membrane portion is disposed on the low oxygen partial pressure side in FIG.

Now, the above sample (the thickness of the oxygen ion exchange layer was 32, 63, 100, 200 μm, 0.5, 1.0, 3.2 mm)
FIG. 8 shows the oxygen exchange rate evaluated for each type and oxygen exchange layer (a dense membrane of 5 μm). The black circles are the measured values.
As a comparative example, the results of the oxygen permeation rate evaluated for the sample having only the oxygen ion diffusion layer without the oxygen exchange layer are shown by white circles. As can be seen from FIG. 8, in the comparative example having no oxygen exchange layer, the oxygen permeation rate began to be saturated in a sample in which the thickness of the oxygen ion diffusion layer was 1 mm or less, and almost completely saturated in a sample having a thickness of about 100 μm or less. As a result, the effect of reducing the thickness of the oxygen ion diffusion layer is lost. On the other hand, in the sample on which the oxygen exchange layer is formed, the oxygen transmission rate increases in inverse proportion to the film thickness even when the thickness of the oxygen ion diffusion layer is 1 mm or less, and the oxygen transmission rate is significantly increased by the effect of the invention. Oxygen ion diffusion layer thickness
In the case of 32 μm, the oxygen transmission rate of the sample of the present invention was about twice that of the comparative example. (Embodiment 2) In this embodiment, a dense membrane, an island-shaped discontinuous membrane, and a porous oxygen exchange layer were formed on both sides of an oxygen ion diffusion layer having a thickness of 100 μm. The transmission speed will be specifically described. This sample is a multilayer ceramic material with a four-layer structure as shown in Fig. 5 formed in the order of porous ceramic support (105) / oxygen exchange layer (101) / oxygen ion diffusion layer (102) / oxygen exchange layer (101). And
A material having no oxygen exchange layer having a two-layer structure of a porous ceramic support / oxygen ion diffusion layer was used as a comparative example.

Table 1 summarizes the layer structure of the multilayer ceramic material evaluated in this example and the oxygen transmission rate of each material. In all samples including the comparative example, the support was
mm, thickness of porous body of SrFeO _3-w composition, oxygen ion diffusion layer
This is a dense thin film having a composition of 100 μm and La _0.05 Sr _0.95 CoO _3-w . The composition of the oxygen exchange layer, a _{La 0.3 Sr 0.7 Fe 0.5 Co 0.5} O 3-w, showing the effect of changing its form.

The method for producing the porous ceramic support and the method for producing the thin-film oxygen ion diffusion layer formed thereon were the same as those in Example 1. The oxygen exchange layer was also manufactured by applying a calcined powder slurry in the same manner as in Example 1, but depending on the amount of application and the firing temperature, a dense film, an island-shaped discontinuous film, or a porous film was formed. Was controlled to the form. In this embodiment, the thickness of the oxygen exchange layer having the form of a dense membrane is
It was 5 μm. The thickness of the porous oxygen exchange layer is 30μ
m, the porosity was 30%, and the average radius of the pores was 2 μm. In addition, the thickness of the oxygen exchange layer composed of the island-shaped discontinuous membrane is
The average radius of the island was 10 μm and the average radius of the island was 20 μm.

In this example, in all the samples on which the surface exchange layer was formed, compared with the comparative example having no oxygen exchange layer,
It was confirmed that the oxygen permeation rate increased. Of which
When the oxygen exchange layer was a porous membrane, the oxygen permeation rate was the highest, showing 6.7 times the oxygen permeation rate of the comparative example, and the effect of forming the oxygen exchange layer was high.

[0037]

[Table 1]

(Embodiment 3) In this embodiment, the thickness is 120 μm.
The respective oxygen permeation rates when porous oxygen exchange layers having various compositions are formed on both sides of the oxygen ion diffusion layer are specifically described. This sample is a multilayer ceramic material having a four-layer structure as shown in FIG. 5 formed in the order of a porous ceramic support / oxygen exchange layer / oxygen ion diffusion layer / oxygen exchange layer. A material having no oxygen exchange layer having a two-layer structure was used as a comparative example.

The multilayer ceramic material evaluated in this example
Table 2 summarizes the layer structure and the oxygen transmission rate of each material.
Was. In all samples including the comparative example, the support was
mm, SrFeO_3-wComposition porous body, thickness of oxygen ion diffusion layer
120 μm, La_0.1Ba_0.9Fe_0.1Co_{0 .9}O_3-wWith a dense thin film of composition
are doing. The oxygen exchange layer is porous and the composition is La_0.
TwoSr_0.8CoO_3-wOr La_0.4Sr_0.6CoO_3-wEach set when
The effect of changing the arrangement of the components was shown.

The method for producing the porous ceramic support, the method for producing the thin film oxygen ion diffusion layer formed thereon, and the method for producing the porous oxygen exchange layer were the same as in Examples 1 and 2. In this example, in all the samples on which the surface exchange layer was formed, compared with the comparative example having no oxygen exchange layer,
It was confirmed that the oxygen permeation rate increased. Of which
High oxygen partial pressure side La _0.2 to oxygen exchange layer of Sr _0.8 CoO _3-w, the oxygen transmission rate is the highest in the case of arranging the La _0.4 Sr _0.6 CoO _3-w to oxygen exchange layer of low oxygen partial pressure side, in the comparative example The oxygen permeation rate was 6.7 times higher, and the effect of forming an oxygen exchange layer was high. When the composition of the oxygen exchange layer was reversed, the effect of forming the oxygen exchange layer was 5.5 times that of the comparative example.

[0041]

[Table 2]

Example 4 In this example, the composition of the porous ceramic support was changed, and a multilayer ceramic material having the effect of an oxygen exchange layer on the support was studied. Table 3 summarizes the layer structure of the multilayer ceramic material evaluated in this example and the oxygen transmission rate of each material. Example 4-2
Prepared a porous ceramic support using a composite oxide having the same composition as that of the oxygen exchange layer 2 in Example 4-1. A material having no oxygen exchange layer having a two-layer structure of a porous ceramic support / oxygen ion diffusion layer was used as a comparative example.

The method for producing the porous ceramic support, the method for producing the thin film oxygen ion diffusion layer formed thereon, and the method for producing the porous oxygen exchange layer were the same as in Examples 1 and 2. In each of Examples 4-1 and 4-2, it was confirmed that the oxygen permeation rate was increased about eight times as compared with the comparative example in which the oxygen exchange layer was not formed. However, Examples 4-1 and 4-
It is considered that the oxygen transmission rate of No. 2 is almost equal, and if the composition of the porous ceramic support is selected, the porous ceramic support can have a function as an oxygen exchange layer.

[0044]

[Table 3]

[0045]

According to the present invention, a conventional oxide is formed by forming an oxygen exchange layer having a composition different from that of the composite oxide having oxygen ion diffusing ability on the surface of the composite oxide having oxygen ion diffusing ability. Compared with the multi-layer ceramic material for oxygen separation, the oxygen permeation rate has been dramatically improved, and it has become possible to separate oxygen gas from air at low cost with small equipment.
It can be used for a wide range of industrial applications that require high-purity oxygen gas and oxygen-enriched air.

According to the present invention, even when the thickness of the oxygen-permeable ceramic layer is reduced to 300 μm or less, a large oxygen transmission rate of 50 sccm / cm ² or more can be obtained. As a result, a level of performance that can be practically used can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram 1 of a layer structure of a multilayer ceramic material according to the present invention (when oxygen exchange layers are formed on both sides of an oxygen ion diffusion layer).

FIG. 2 is a conceptual diagram of a layer structure of a multilayer ceramic material according to the present invention 2 (when a dense oxygen exchange layer is formed on one side of an oxygen ion diffusion layer).

FIG. 3 is a conceptual diagram of a layer structure of a multilayer ceramic material according to the present invention (in a case where an island-shaped oxygen exchange layer is formed on one side of an oxygen ion diffusion layer).

FIG. 4 is a conceptual diagram of a layer structure of a multilayer ceramic material according to the present invention 4 (when a porous oxygen exchange layer is formed on one side of an oxygen ion diffusion layer)

FIG. 5 is a conceptual diagram of a layer structure of a multilayer ceramic material in the present invention (porous ceramic support / oxygen exchange layer /
(When it has a layer structure of oxygen ion diffusion layer / oxygen exchange layer)

FIG. 6 is a conceptual diagram of a layer structure of a multilayer ceramic material according to the present invention (in the case of having a layer structure of a porous ceramic support / oxygen ion diffusion layer / oxygen exchange layer).

FIG. 7 is a schematic diagram of an apparatus used for evaluating an oxygen permeation rate of a solid electrolyte.

FIG. 8: Dense La with a thickness of 10 μm_0.3Sr_0.7Fe_0.8Co_0.2O_3-w
La for oxygen exchange layer_0.05Sr_0.95CoO_{Three -w}Both oxygen ion diffusion layers
Oxygen Permeation Rate of Multi-Layered Ceramic Material Formed on Surface

[Explanation of symbols]

 1… oxygen-containing mixed gas inlet 2… argon gas inlet 3… outer tube 4… inner tube 5… electric furnace 6… cylindrical disk-shaped sample 7… thermocouple 8… glass seal 9… glass side seal 10… oxygen concentration meter 11 ... quadrupole mass spectrometer 101 ... oxygen exchange layer 102 ... oxygen ion diffusion layer 103 ... oxygen exchange layer (island) 104 ... oxygen exchange layer (porous) 105 ... porous ceramic support

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Toru Nagai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Corporation Technology Development Division (72) Inventor Noriko Yamada 20-1 Shintomi, Futtsu-shi, Chiba New Japan (72) Inventor Tadashi Sajika 20-1 Shintomi, Futtsu-shi, Chiba F-term (reference) in Nippon Steel Corporation Technology Development Headquarters 4D006 GA41 HA42 MA06 MA31 MC03 NA05 NA64 PB17 PB62 PC41 PC71 4G042 BA28 BA35 BB02 4G048 AA05 AB02 AB05 AC08 AD02 AE05 AE07

Claims (8)

[Claims] 1. An oxygen-exchange layer comprising a cubic composite oxide having a composition different from that of said composite oxide having oxygen ion diffusing ability on both or one surface of the composite oxide having oxygen ion diffusing ability. A multilayer ceramic material characterized by having formed thereon. 2. The oxygen-exchange layer is a dense membrane, a porous body, or an island-shaped discontinuous membrane having an average film thickness of 30 μm or less.
The multilayer ceramic material for oxygen separation according to the above. 3. A composite oxide having oxygen ion diffusing ability
3. The multilayer ceramic material according to claim 1, which is a thin film having a thickness of 300 μm or less. 4. The method according to claim 1, wherein the oxygen exchange layer is La _u Sr _bu Fe _v Co _cv O
_3-w (however, 0.1 ≤ u <0.5, 0.9 <b <1.1, 0 <v
4. The multilayer ceramic material according to claim 1, comprising a cubic composite oxide represented by <1.1, 0.9 <c <1.1). 5. The composite oxide having oxygen ion diffusing ability is La _{x Srax} CoO _3-y (where 0 ≦ x <0.1, 0.9 <
5. The multilayer ceramic material according to claim 1, comprising a cubic composite oxide represented by a <1.1). 6. The multilayer ceramic material according to claim 1, wherein the multilayer ceramic material is a multilayer ceramic material for oxygen separation. 7. An oxygen separator using the multilayer ceramic material according to any one of claims 1 to 5. 8. A chemical reaction apparatus using the multilayer ceramic material according to claim 1.