JP2002097083A - Porous material and composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite material of a mixed conductor compact membrane and a porous material which can be manufactured easily and has good oxygen permeability in an industrial selective filtration and separation process of oxygen by an oxide ion mixed conductor and a hydrocarbon partial oxidation process. SOLUTION: The porous material of this invention consists of a porcelain component which is a mixed conductor oxide having the composition formula: AFexO(3-δ) of which A is selected from Ba, Sr and Ca, x is in the range of 0.98<=x<=1.02 and δ satisfies charge neutralized conditions. By setting the highest heat treatment temperature during the porous material manufacturing higher than the highest treatment temperature in the compact membrane manufacturing process, porosity deterioration of the porous material in the membrane manufacturing process can be prevented and a composite material with high oxygen permeability can be easily manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dense continuous membrane of an oxide ion mixed conductor and a porous membrane applied to an industrial selective permeation / separation process of oxygen or a membrane reactor for partial oxidation of hydrocarbons. The present invention relates to a composite material having a body as a main component and a porous body suitable for the composite material.

[0002]

2. Description of the Related Art In recent years, a process of thinning an ion conductive material and industrially separating or purifying a specific component using the thin film has been remarkably advanced and developed. Above all, the process of separating and purifying oxygen by selectively permeating oxygen from air and other gas mixtures is expected to be applied from small-scale oxygen pumps for medical use to large-scale gas generation and purification plants. ing. Recently, a method of isolating an oxygen mixed gas and a hydrocarbon gas with a membrane made of an ion conductive material and selectively oxidizing oxygen to partially oxidize hydrocarbons, that is, use as a so-called membrane reactor has been studied.

As an oxide ion conductive ceramic material that can be used for this purpose, an oxide ion conductor that transmits only oxygen ions and a mixed oxide ion conductor that simultaneously transmits oxygen ions and electrons or holes are known. ing.
Among them, oxide-ion mixed conductors can conduct electrons or holes by themselves, so that the charge necessary to maintain the movement of oxygen ions can be compensated without forming an external current circuit. Therefore, it is considered to be more suitable for oxygen separation applications. That is, in order to perform oxygen separation by the oxide ion mixed conductor, it is only necessary to make the oxygen potentials on both sides of the mixed conductor different, and only oxygen is supplied from the higher oxygen partial pressure side to the lower oxygen partial pressure side. Other gas components cannot permeate through the mixed conductor and pass through the mixed conductor, so that selective permeation and separation of oxygen can be performed.

By the way, in the elementary process which becomes rate-limiting when oxygen passes through the mixed conductor, diffusion in the mixed conductor is rate-limiting (diffusion-limited) as the thickness of the mixed conductor is reduced.
Thus, the oxygen exchange with the gas phase at the surface of the mixed conductor changes to a rate-determining (surface reaction-determining). Therefore, even when the mixed conductor materials having the same composition are used, as long as the surface reaction is limited, the thinner the thickness, the larger the amount of oxygen permeation can be. For this reason, it is considered more effective to actually separate oxygen than to use a mixed oxide ion conductor as a single bulk and to form and composite it as a thin film on a porous body. (Teraoka et al., Journal of the Ceramic Society of Japan, vol.97, No.4, pp467-72, 1989).
The mechanical strength of the composite material is ensured by the porous body portion, and the porous body functions as a support. The role of selectively permeating and separating oxygen from the source gas is played by the thin film portion.

[0005] In order to fulfill the role of selective separation of this gas,
A mixed conductor material having high oxygen ion conductivity needs to be formed as a dense and airtight thin film in the thin film portion. Here, the denseness means that the density of the film portion is about 94% or more of the theoretical density. Further, being airtight means that no gas leaks through the film or that it is practically negligible. In order to obtain an airtight mixed conductor thin film, it is a necessary condition that the film is dense. However, as described later, care must be taken because even if the film is dense, gas leakage may occur and the film may not be airtight.

In the dense thin film portion of the composite material for oxygen separation, a mixed conductor material having high oxygen ion conductivity is required, and some ceramics having a perovskite type crystal structure, such as those disclosed in 56-92103
[La _x Sr _(1-x) ] CoO _3-α (x is 0.1
0.9, α is in the range of 0 to 0.5) or JP-A-61-21717.
[La _(1-x) Sr _x ] [Co _(1-y) Fe _y ] O
Porcelain compositions such as _(3-δ) (x ranges from 0.1 to 1.0, y ranges from 0.05 to 1.0, and δ ranges from 0.5 to 0) are known as potential candidate materials.

[0007]

DISCLOSURE OF THE INVENTION The present inventors prepared a disc-shaped sintered body with the composition of (La _0.2 Sr _0.8 ) CoO _3-α disclosed in these prior arts. By sintering, a dense sample with a relative density exceeding 94% and a thickness of 1 mm could be obtained. When the oxygen permeation rate of this sample at 750 ° C. was evaluated, it showed a performance of 0.4 cc / cm ² · min, and it was confirmed that it was promising as a dense thin film material. However, the mixed conductor material SrFeO _(3-δ) also disclosed in the prior art
Attempts were made to produce a sintered body at
At a sintering temperature of 00 ° C., a dense body having a density exceeding 94% was obtained, but many fine cracks were observed on the surface of the sintered body. The oxygen transmission rate of this sample at 750 ° C. was 0.3 cc / cm ²
-Although it was min, a large gas leak, which is considered to be derived from cracks, was also observed. Furthermore, this SrFeO
_An attempt was made to prepare a sample for _(3-δ) by changing the manufacturing conditions, but an airtight sample could not be obtained, and it was difficult to use this material as a dense thin film for oxygen separation.

On the other hand, the conditions of the material for forming the porous support of the composite material for oxygen separation include the following three conditions in the above-mentioned Teraoka article: Good adhesion; 2) not reacting with the oxide ion mixed conductor membrane, or even if it reacts, the product does not decrease the oxygen permeability; 3) the oxide ion mixed conductor membrane and the thermal expansion coefficient Almost equal. All of these conditions are indispensable for the mixed conductor film to be formed on the porous body in a sound manner.

However, it is not easy to find a material that satisfies the conditions 1) to 3) at the same time. First, in connection with the condition 3), the above-mentioned Co-containing perovskite, which is a promising candidate for an oxide ion mixed conductor film, has a problem that it has an unusually large linear thermal expansion coefficient as an oxide. For example, it is disclosed in JP-A-9-235121 (L
a _0.2 Sr _0.8 ) (Co _0.8 Fe _0.2 ) O _(3-δ) and (La _0.2 Sr _0.8 ) (Co
_0.4 Fe _0.4 Cu _0.2 ) O _(3-δ) has an average linear thermal expansion coefficient from room temperature to 800 ° C of about 26 and about 20 ppm / ° C, respectively. Even the oxide magnesia known in the art is 13.4 ppm / ° C (YS Toulo
ukian et al., Thermophysical Properties of Matter
vol. 13, IFI / Plenum).

In addition, the perovskite oxide has low coexistence with other oxide materials, and the condition 2) also greatly restricts the choice of material. For example, a typical oxide material such as alumina or zirconia is used as a porous body, and
When sintering (La _1-x Sr _x ) CoO _(3-δ) or the like as a thin film, the alkaline earth element in the perovskite is pulled out and the film is decomposed, or the porous material enters the perovskite from the porous body. There is a problem that the cation forms a solid solution and the oxygen permeation rate is greatly reduced.

In order to avoid such a problem, Teraoka et al. Proposed in the above-mentioned paper to produce a porous body with the same porcelain composition as the ion-mixed conductor film, and another literature ( Teraoka et al., The Ceramic Society of Japan
vol. 97, No. 5, pp. 533-38, 1989 ₎ , a composite in which both the porous body and the mixed conductor film are (La _0.6 Sr _0.4 ) CoO _(3-δ) is being prototyped.

In other published patents and articles on oxygen separation, it is often said that any porous material may be used as long as it satisfies the above conditions 1) to 3). However, there are few examples in which a dense film of a mixed conductor is formed on a porous body to produce a composite material, and even when a composite material is prototyped as disclosed in JP-A-8-276112, The porous body has the same composition as the dense film of the mixed conductor. As described above, the porous body in the prior art had to be practically forced to have the same composition as the mixed conductor film in order to satisfy the required severe conditions.

On the other hand, in the case of a composite material in which the porous body is formed of the same material as the mixed conductor film, the range of manufacturing conditions for obtaining a composite material having excellent characteristics is narrow, and the manufacturing conditions are out of this range. In such a composite material, a problem such as a decrease in purity due to the mixing of the raw material gas with the separated oxygen or a reduction in the oxygen separation rate occurs.

As a method of improving the characteristics of a composite material by devising a manufacturing method, there is known a method of performing a treatment with an acid before firing a film, as disclosed in JP-A-3-37174. . However, this method also has a problem that an extra step of acid treatment is required, and in some cases, it is necessary to repeat acid treatment and heat treatment.

As described above, according to the prior art, it is difficult to produce a composite material having a high oxygen separation rate, or even if it can be produced, the range of the production conditions becomes extremely narrow, or extra steps are required. There were problems such as need.

The present invention has been made to solve such problems, and an object of the present invention is to provide a mixed conductor having a dense membrane and a porous support for use in oxygen separation or a diaphragm reactor. In the composite material of the body, the problem that it was difficult to produce a composite material having a high oxygen permeation rate, which was inevitable with the conventional technology in which the porous body was formed of the same material as the dense membrane, and the range of process conditions that can be produced The problem is to provide a solution to such a problem that is extremely narrow.

[0017]

Means for Solving the Problems The present inventors have found the following aspects of the invention in order to solve the above problems. (1) A porous body comprising a mixed conductive oxide represented by the following (formula 1). AFe _x O _(3-δ) (where 0.98 ≦ x ≦ 1.02, A is a combination of one or more elements selected from Ba, Sr, and Ca, and δ is a value determined to satisfy the charge neutrality condition ) ... (Equation 1)

(2) A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight and dense continuous layer of the mixed conductive oxide formed on the porous body. And a porous material portion comprising the porous material according to (1).

(3) A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight and dense continuous layer of the mixed conductive oxide formed on the porous body. Wherein the maximum heat treatment temperature of the porous body is higher than the maximum heat treatment temperature of the dense continuous layer.

(4) A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight dense continuous layer of the mixed conductive oxide formed on the porous body. Wherein the porous body portion is made of the porous body of (1) and the maximum heat treatment temperature of the porous body portion is higher than the maximum heat treatment temperature of the dense continuous layer. Characteristic composite material.

(5) The composite material according to (3) or (4), wherein the dense continuous layer is composed of a mixed conductive oxide material having a composition different from that of the porous body.

(6) A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight dense continuous layer of the mixed conductive oxide formed on the porous body. The method for producing a composite material, wherein the porous body portion is constituted by the porous body of (1), wherein the porous body portion is formed at 1200 ° C.
A method for producing a composite material, comprising: performing heat treatment at a maximum heat treatment temperature in the range of 1400 ° C. or less, and heat treating the dense continuous layer at a maximum heat treatment temperature that is at least 20 ° C. lower than the maximum heat treatment temperature of the porous body.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The inventor first studied the problems of the prior art in which a porous body was formed of the same material as a dense film. In the composite material, in order to form a mixed conductor film without gas leak by a sintering method or the like, the maximum heat treatment temperature at the time of forming the film is set to a temperature equal to or higher than a temperature necessary for densifying the film material, and It is necessary to form a dense film. Here, it has been found that when the film and the porous body have the same composition, the sinterability is the same, so that the porous body is also densified in the process of forming the film. Due to the decrease in the porosity of the porous body, the permeation rate of the gas in the porous body is reduced, which causes a problem of a reduction in the oxygen separation rate of the composite material. Also, if the maximum heat treatment temperature during film formation is reduced or the heat treatment time is shortened to avoid a decrease in the porosity of the porous body, the film will not be sufficiently densified and the film will adhere to the porous body. Was also insufficient, and it was found that a problem of leakage of the supply gas during the oxygen separation process occurred. Furthermore, the present inventors have paid attention to the high-temperature stability of each of the materials constituting the composite material while studying means for solving these problems. If the material used for the porous body is stable without being decomposed even when exposed to a temperature higher than the temperature required for densification of the material constituting the film, a temperature higher than the densification temperature of the film material It was found that the maximum heat treatment temperature for the production of the porous body could be set, the porosity of the porous body did not change during the dense film formation process, and a composite material having a high oxygen permeation rate could be easily obtained. In addition, the perovskite-type mixed conductor containing Co is liable to be decomposed when exposed to a temperature higher than the temperature required for densification. It was found that the densification temperature could not be too high.

On the other hand, the present inventors considered that SrFe _x O
_The perovskite-type mixed conductor in which the B site such as _(3-δ) is composed only of Fe has a densification temperature of about 1200 ° C., but is much higher than 1200 ° C., for example, 1350 ° C.
It has been found that even at a high temperature of about a certain level, problems such as decomposition do not occur and the composition is stable. Then, it was confirmed that a porous body having a sufficient porosity as a support could be produced even when the porous body was manufactured in a temperature range higher than the densification temperature.

As described above, when a dense body is made of, for example, SrFe _x O _(3-δ) , cracks are likely to occur, and a material having sufficient airtightness and mechanical strength for use as a separation membrane is obtained. While it was difficult, the porous support made of SrFe _x O _(3-δ) was found to have sufficient mechanical strength. Furthermore, these porous supports have excellent properties as described in the formula AFe _x O _{(3-δ) wherein} Sr of SrFe _x O _(3-δ) is replaced with another alkaline earth element (where 0.98 ≦ x ≦ 1.0
2, A was also confirmed in a material represented by the following formula: A is a combination of one or more elements selected from Ba, Sr, and Ca, and δ is a value determined to satisfy the charge neutrality condition. Similar porous support properties were obtained even when the porous support contained a small amount of a heterogeneous phase such as metal Ag.

On the other hand, this AFe_xO_(3-δ) Porous support
When a dense film is formed of the same material on the
If SrFe_xO_(3-δ)From the results of bulk sintered body fabrication
Forming a gas-tight and gas-leak-free film
And could not. In contrast, (La_0.2Sr_0.8) CoO_3-α
AFe with a composition that can produce an airtight bulk sintered body such as_xO_(
3-δ) When a dense membrane is formed on a porous support,
An excellent composite for oxygen separation without sleeks was obtained.

That is, in preparing a composite material for oxygen separation or a membrane reactor, the material of the porous body must satisfy the following conditions, but the porous body provided by the present invention satisfies all of these conditions. It was confirmed that: 1) Heat treatment at a higher temperature than the dense film is possible. 2) Good adhesion to oxide ion mixed conductor film. 3) It does not react with the oxide ion mixed conductor membrane, or even if it reacts, the product does not decrease the oxygen permeability. 4) The thermal expansion coefficient is almost equal to that of the oxide ion mixed conductor film.

The porous material provided by the present invention is represented by the following formula (1): AF
It is composed of a mixed conductive oxide represented by e _x O _(3-δ) ,
Generally, the crystal structure is a perovskite type. The A site (site to which 12 anions coordinate) of the perovskite structure may be composed of one kind of element among Ba, Sr, and Ca, or may be used by combining plural kinds of these elements. Is also good. On the other hand, the B site of the perovskite structure (the site where six anions are coordinated) is characterized by being composed of Fe. These constituent elements may include impurity elements, but the allowable range is about 2 mol% or less. Also, limiting the range of x to 0.98 ≦ x ≦ 1.02 is
If the value of x is out of the above range, the strength of the porous body is reduced and the thermal expansion coefficient is changed.

In the porous body provided by the present invention, the porosity is preferably 20% or more and 80% or less, more preferably 40% or less.
The range is at least 60%. The range of the porosity of the porous body is determined by the conditions under which the porous body does not become a gas permeation resistance during the oxygen separation process and the conditions under which the mechanical strength of the composite material is kept healthy. The porosity of the porous body is calculated by {100-relative bulk density (%)}, and the relative bulk density is obtained by dividing the bulk density of the porous body by the theoretical density. In the case of a porous body having a simple shape such as a disk, a cylinder, or a plate, the bulk density of the porous body can be easily obtained by measuring the outer size of the porous body, obtaining the volume, and dividing the weight.

The porosity of the porous body can be changed by the amount and type of the resin mixed with the oxide raw material in the production of the porous body, the molding conditions, the maximum heat treatment temperature in the production of the porous body, and the like. . That is, the porosity of the porous body can be increased by increasing the amount of the resin to be mixed, reducing the pressure during molding, or setting the maximum heat treatment temperature of the porous body to be lower.

The thickness of the dense continuous film of the mixed conductor of the film portion formed on the porous body is preferably in the range of 10 μm or more and 1 mm or less. If the thickness of the dense membrane is made thicker than this,
There is a problem that the amount of oxygen that can be separated by the composite material is reduced. If the thickness is reduced outside this range, it becomes difficult to form a dense film without gas leak,
The strength of the membrane is reduced and the membrane is fragile, causing problems such as a decrease in gas selectivity during use of the composite material for oxygen separation.

It is one of the points of the present invention to set the maximum heat treatment temperature for producing a porous body higher than the maximum heat treatment temperature for forming a dense film. In particular,
The maximum heat treatment temperature in the production of the porous body needs to be at least 20 ° C. or more, preferably 50 ° C. or more, higher than the maximum heat treatment temperature in the production of the dense film. In addition, in order to sufficiently increase the density of the dense film and secure airtightness, the maximum heat treatment temperature for film formation is required to make the film material densification temperature, that is, the relative density of the material, for example, 94% or more. It is necessary to set it at about the firing temperature.

As a film material suitable for forming an airtight and dense continuous layer in combination with the porous material provided by the present invention, for example, [La _x A _(1-x) ] [Co _{(1-y) )} Fe _y ] _z O _3-α (A is
Ba, Sr, a combination of one or more elements selected from Ca, 0.7 ≦ x ≦ 1.0, 0 ≦ y ≦ 1.0, 0.98 ≦ z ≦ 1.0
2, α is a value determined to satisfy the charge neutrality condition), or [Ln _1-a A _a ] [Co _x Fe _y B _z B '_z' ] O _(3-δ) (Ln is Y or lanthanoid element A is a combination of one or more elements selected from A, A is a combination of one or more elements selected from Ba, Sr, and Ca, B is one or a combination selected from Nb and Ta A combination of two elements, B 'is C
u, Ni, Zn, Li, a combination of one or more elements selected from Mg, 0.8 ≦ a ≦ 1, 0 ≦ x, 0 ≦ y, 0 <z ≦
0.5, 0 ≦ z ′ ≦ 0.2, 0.98 ≦ x + y + z + z ′ ≦ 1.02, and δ is a value determined to satisfy the charge neutrality condition).

In addition to the airtight and dense film, the film portion may include a porous catalyst layer of metal or oxide formed on the surface of the film or at the interface between the film and the porous body. This porous catalyst layer is composed of oxygen and oxygen between the gas phase and the solid phase on the surface of the dense membrane.
It is effective for improving the oxygen ion exchange reaction rate. Further, in the present invention, for the purpose of reinforcing the strength of the composite, a reinforcing body may be provided in addition to the porous body and the membrane.

For the production of the porous body according to the present invention, a method usually used for producing a porous ceramic body can be used. As one of the methods, there is a method in which an oxide containing a necessary element is used as a raw material and is fired. As a raw material, in addition to oxides, salts such as inorganic salts such as carbonates, nitrates and sulfates, organic acid salts such as acetates and oxalates, halides such as chloride and bromide iodide, or water There is a method of using an oxide and an oxyhalide, mixing these at a predetermined ratio, and firing. In addition, among the above salts, a method of dissolving in water at a predetermined ratio and dissolving in water at a predetermined ratio and evaporating and drying, or a method of drying by freeze drying or spray drying and then firing,
After dissolving a water-soluble salt in water, an alkaline solution such as aqueous ammonia is added, and a hydroxide is precipitated and calcined, or a coprecipitation method is used. A sol-gel method of obtaining and firing a gel is also applicable.

The sintering of the porous body is generally divided into two steps: calcination and main sintering (sintering). The calcination temperature is usually in the range of 400 to 1000 ° C. for several hours to several tens of hours. The calcined powder may be molded as it is, and the main baking may be performed. Alternatively, the calcined powder may be mixed with a resin such as polyvinyl alcohol (PVA), and then molded and calcined. On the other hand, the temperature of the main firing is usually the highest heat treatment temperature in the production of the porous body, but the main firing temperature of the porous body provided by the present invention is 700 to 1450 ° C, preferably 1000 to 1350 ° C. . Further, the firing usually requires several hours or more. The atmosphere for the main firing is generally sufficient in the air, but may be fired in a controlled atmosphere if necessary. As a method of forming the porous body, calcined powder or mixed powder may be packed in a die and pressed and molded in the same manner as in the production of ordinary bulk ceramics. Or the like may be used.

On the other hand, the dense continuous film can be produced by a method usually used for producing a ceramic film.
The film may be formed by a so-called thin film formation method such as PVD or CVD such as a vacuum evaporation method, but more economically, a raw material powder or a calcined powder in a slurry state is applied on a porous body and fired. Is preferred. The temperature of this dense film firing is usually the maximum heat treatment temperature in film production, but this is to densify the film so that gas leak does not occur,
It is necessary to select conditions under which the porosity of the porous body does not significantly decrease during the firing process. Therefore, the firing temperature of the dense film is desirably about the densification temperature of the material constituting the film, and is 20 ° C. higher than the maximum heat treatment temperature of the porous body.
As described above, it is more preferable that the temperature be lower by 50 ° C. or more. It usually takes several hours to fire this dense film.

In order to selectively permeate and separate oxygen from the oxygen-containing gas mixture by the composite material formed by the above process, the oxygen potential on both surfaces of the composite material may be made different. For example, in order to separate oxygen from the atmosphere, it is only necessary to pressurize the raw material air side or reduce the pressure on the oxygen extraction side. The operating temperature of this oxygen separation is in the range of 500-1000C, preferably 650-950C.

As described above, the porous body and the composite material of the present invention can be applied to an apparatus for producing pure oxygen or oxygen-enriched air. Further, the present invention can be used for applications other than oxygen separation, particularly for a chemical reaction device involving an oxidation reaction. For example, it is used for a reactor for a 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 reactor using the mixed conductive ceramics of the present invention, for example, air (or a mixed gas containing oxygen) and methane are separately flowed through the mixed conductive ceramics, and Rh or the like is applied to the ceramic surface on the side where the methane is flowing. Is disposed. By heating the ceramic, only oxygen permeates according to the same principle as oxygen separation, and subsequently reacts with methane on the ceramic surface on the methane side to generate synthesis gas. Therefore, unlike the conventional method, there is no need to produce oxygen in advance, and since the raw material gas is not mixed, a synthesis gas can be obtained efficiently, and a large effect such as a continuous reaction and a simplified production apparatus can be obtained. is there.
In addition to the partial oxidation of methane, the present invention can be used in any reaction apparatus involving an oxidation reaction, such as partial oxidation of hydrocarbons to form olefins, partial oxidation of ethane, and substitution of aromatic compounds.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below, but they are for the purpose of illustration only, and the scope of the present invention is not limited to these contents.

(Example 1) In this example, in order to confirm that the characteristics of the porous body provided by the present invention do not deteriorate even after film formation, a porous body was manufactured and then a dense film was formed. Further heat treatment was carried out at the same temperature as in Example 1 and the porosity before and after the treatment was compared. The raw materials for the sample were CaCO ₃ , SrCO ₃ , BaCO ₃ , Fe ₂ O ₃ ,
After weighing each required amount using Co ₃ O ₄ , ball mill mixing was performed for 24 hours together with zirconia balls using isopropyl alcohol as a dispersion medium. The obtained slurry is dried and crushed, packed in MgO square pods, and 850 ° C.
Time calcination was performed. 30% by weight of PVA was added to the obtained calcined powder, and mixed and pulverized in a ball mill for 2 hours. The obtained mixed powder was packed in a 12 mmφ die, uniaxially formed into a tablet shape, and further packed in an ice bag to perform CIP molding. The obtained molded body was degreased at 450 ° C. for 5 hours in a square pod made of MgO, and further fired at each firing temperature for 5 hours. A disk-shaped porous body having a thickness of 1 mm was cut out from the obtained sintered body, and the porosity was measured. Further, the substrate was subjected to a heat treatment at 1200 ° C. for 5 hours, and the porosity was evaluated again. This heat treatment is performed under substantially the same conditions as the formation of the dense film, and changes in the porous body during the thin film formation process can be confirmed.

Table 1 shows the composition of the sample, the firing temperature when the porous body was prepared, and the porosity after firing and after the heat treatment. A material having a porosity of less than 20% after firing and heat treatment is considered to be unsuitable as a porous body, but materials within the scope of the present invention satisfy this condition. It was confirmed that.

[0043]

[Table 1]

Example 2 In this example, a composite material was actually manufactured and its characteristics were confirmed. First, a disc-shaped porous body having a thickness of 1 mm was produced in the same manner as in Example 1. On the other hand, the same method as in Example 1 (La
₂ O ₃ ) to prepare a calcined powder, disperse this in a solvent to form a slurry, apply and dry on one side of the porous body,
The firing was performed in the atmosphere for 5 hours. This coating and baking process was repeated three times to form a dense mixed conductive ceramics thin film, thereby obtaining a composite material. The thickness of the formed thin film, assuming that the thin film is dense to theoretical density,
The change in weight of the sample before and after the formation of the thin film, the area of the thin film obtained from the sample shape, and the theoretical density were calculated. For some of the composite materials, the porosity of the porous body after the formation of the film portion was evaluated by removing the thin film portion. In the case of the composite materials within the scope of the present invention, the porosity of each of the porous bodies was 20%. % Was maintained in the range of 80% or less.

In order to evaluate the oxygen permeation rate of the obtained composite material, the sample was adhered to the tip of an Al ₂ O ₃ tube, the outside was exposed to air, and the inside was depressurized. The oxygen partial pressure on the reduced pressure side was measured, and the oxygen permeation rate was determined based on the difference from the partial pressure value when there was no oxygen permeation through the sample. The sample temperature was 750 ° C. The measured value is expressed as the volume of permeated oxygen per unit surface area per minute in the standard state, and the unit is cc / c.
m ² · min. The presence or absence of gas leakage through the sample was examined using a helium leak detector, changing the outside to a mixed gas of air and helium. As a result, no gas leak was observed in the composite material shown as an example of the present invention, and it was confirmed that the film formed on the porous body was airtight.

Table 2 shows the compositions of the porous body and the dense thin film, the firing temperature of the porous body and the thin film, the thickness of the thin film, and the measured values of the oxygen transmission rate. As a result of these tests, it was confirmed that the composite materials within the scope of the present invention exhibited excellent oxygen permeation characteristics.

[0047]

[Table 2]

[0048]

According to the present invention, excellent oxygen permeation characteristics can be exhibited in a technical field such as a selective permeation / separation process of oxygen using a mixed oxide ion conductor or a membrane reactor for partial oxidation of hydrocarbons. At the same time, it is possible to obtain a composite material of a dense continuous film of a mixed ion conductor and a porous material, which is easy to produce. The technology provided by the present invention can achieve high performance and low cost of an oxygen separation device from air or a membrane reactor.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C01G 49/00 C01G 49/00 C C04B 35/495 C04B 41/85 C 35/64 35/00 J 41 / 85 35/64 C (72) Inventor Wataru Ito 20-1 Shintomi, Futtsu City Nippon Steel Corporation Technology Development Division (72) Inventor Tadashi Sachika 20-1 Shintomi Futtsu City Nippon Steel Corporation Technology F term in the Development Division (reference) 4D006 GA41 MB04 MB15 MB16 MC03X NA46 NA63 PB17 PB62 PB68 4G002 AA08 AB01 AE05 4G019 FA11 GA02 GA04 4G030 AA08 AA09 AA10 AA27 BA02 BA03 CA09 GA27 GA33 GA35

Claims (6)

[Claims] 1. The formula AFe _x O _(3-δ) (where 0.98 ≦ x ≦ 1.02, where A is Ba, Sr, C
a combination of one or more elements selected from a, and δ is a value determined to satisfy the charge neutrality condition). body. 2. A method according to claim 1, wherein the porous body has a mixed conductive porous oxide, and the film includes an airtight and dense continuous layer of the mixed conductive oxide formed on the porous body. Wherein the porous body portion has the formula AFe _x O _(3-δ) (where 0.98 ≦ x ≦ 1.02, where A is Ba, Sr, C
a is a combination of one or more elements selected from a, and δ is a value determined to satisfy the charge neutrality condition). A composite material. 3. A film portion comprising: a porous body portion having a mixed conductive porous oxide; and an airtight dense continuous layer of the mixed conductive oxide formed on the porous body portion. Wherein the maximum heat treatment temperature of the porous body is higher than the maximum heat treatment temperature of the dense continuous layer. 4. A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight and dense continuous layer of the mixed conductive oxide formed on the porous body portion. Wherein the porous body portion has the formula AFe _x O _(3-δ) (where 0.98 ≦ x ≦ 1.02, A is Ba, Sr, C
a is a combination of one or more elements selected from a, and δ is a value determined to satisfy the charge neutrality condition). And a maximum heat treatment temperature of the porous body portion is higher than a maximum heat treatment temperature of the dense continuous layer. 5. The composite material according to claim 3, wherein the dense continuous layer is made of a mixed conductive oxide material having a composition different from that of the porous body portion. 6. A porous body portion having a mixed conductive porous oxide, and a film portion including an airtight and dense continuous layer of the mixed conductive oxide formed on the porous body portion. Wherein the porous body portion has the formula AFe _x O _(3-δ) (where 0.98 ≦ x ≦ 1.02, where A is Ba, Sr, C
a is a combination of one or more elements selected from a, and δ is a value determined to satisfy the charge neutrality condition). A method for producing a composite material, wherein the porous body portion is heat-treated at a maximum heat treatment temperature in a range of 1200 ° C. to 1400 ° C., and the dense continuous layer is heated at a temperature higher than the maximum heat treatment temperature of the porous body portion by 20 ° C. A method for producing a composite material, wherein the heat treatment is performed at a maximum heat treatment temperature lower by at least ℃.