JP5204816B2 - Oxygen separation membrane element and manufacturing method thereof - Google Patents

Description

  The present invention relates to an oxygen separation membrane element and a manufacturing method thereof.

As oxygen ion conductors having oxygen ions (typically O ²⁻ ; also called oxide ions) conductivity, so-called perovskite type oxide ceramics and pyrochlore type oxide ceramics are known. In particular, in addition to being an oxygen ion conductor, a dense ceramic material made of a perovskite oxide that is an oxygen ion-electron mixed conductor (hereinafter simply referred to as a “mixed conductor”) that has electronic conductivity, Typically, a ceramic material formed in a film shape can continuously transmit oxygen ions from one surface to the other surface without using an external electrode or an external circuit for short-circuiting both surfaces thereof. For this reason, as an oxygen separator that selectively permeates oxygen from the oxygen-containing gas (air or the like) supplied to one surface to the other surface, it is particularly suitable in a high temperature range where the operating temperature is 800 to 1000 ° C. Can be used.

  For example, an oxygen separation material (oxygen separation membrane element) having an oxygen separation membrane composed of a mixed conductor such as a perovskite oxide on a porous support is a cryogenic separation method or a PSA (Pressure Swing Adsorption) method. It can be suitably used as an effective oxygen purification means instead of the above. Alternatively, the oxygen separation membrane element having such a configuration oxidizes hydrocarbons (methane gas or the like) supplied to the other surface by oxygen ions supplied from one surface to the other surface to synthesize liquid fuel (methanol or the like). Can be suitably used in the GTL (Gas To Liquid) technology for manufacturing the fuel cell, or in the fuel cell field. As this type of prior art, Patent Documents 1 and 2 disclose a good example of an oxygen separator (membrane element) including an oxygen separation membrane made of a perovskite oxide.

JP 2001-269555 A JP 2007-050358 A

  By the way, it is desirable that the oxygen separation membrane is formed thin so that the permeation distance of oxygen ions in the membrane is shortened. In recent years, attempts have been made to reduce the thickness of the oxygen separation membrane. However, when the oxygen separation membrane is thin, if there are a small amount of pores (defects such as pinholes and cracks) in the oxygen separation membrane, the pores tend to be through holes. For this reason, as the film thickness is reduced, it is difficult to ensure the airtightness of the oxygen separation membrane, and there is a problem that leakage (gas leakage) tends to occur.

  This invention is made | formed in view of this point, The main objective is to provide an oxygen separation membrane element provided with an oxygen separation membrane with high airtightness, and its manufacturing method.

  The production method provided by the present invention is a production method for producing an oxygen separation membrane element in which an oxygen separation membrane having oxygen ion conductivity is formed on at least a part of a surface portion of a porous support.

This manufacturing method has the general formula: Ln _{1-x A} e _x Co _{1- y My} O ₃
Here, in the formula, Ln is at least one selected from lanthanoids, Ae is one or a combination of two or more selected from the group consisting of Sr, Ca and Ba, and M is Mg, Mn, Ga, Ti. , Ni, Al, Fe, Cu, In, Sn, Zr, V, Cr, Zn, Ge, Sc and Y, or a combination of two or more, and x is 0 <x <1 Y is a real number satisfying 0 <y <1;
A raw material powder for a porous support containing a perovskite type oxide represented by a step of forming a raw material powder having an average particle size of 10 μm or more into a molded body having a predetermined shape;
At least a portion of the surface of the molded article, the general _{formula: Ln 1-x Ae x Co} 1-y M y O 3
Here, in the formula, Ln is at least one selected from lanthanoids, Ae is one or a combination of two or more selected from the group consisting of Sr, Ca and Ba, and M is Mg, Mn, Ga, Ti, Ni, Al, Fe, Cu, In, Sn, Zr, V, Cr, Zn, Ge, Sc, and a combination of two or more selected from the group consisting of Y, and x is 0 <x < A real number satisfying 1 and y is a real number satisfying 0 <y <1;
A step of providing a precursor for forming an oxygen separation membrane substantially composed of a perovskite oxide represented by:
A step of forming an oxygen separation membrane on the porous support and its surface by co-firing the molded body and the precursor in a temperature range of 1150 ° C. to 1250 ° C. for 24 hours or more;
Is included.

According to the production method of the present invention, since the molded body and the precursor are co-fired in a temperature range of 1150 ° C. to 1250 ° C. for 24 hours or more, an oxygen separation membrane is formed on the porous support and its surface portion. An oxygen separation element having excellent mechanical strength and oxygen separation performance can be produced.
If the firing temperature is too low, sintering does not saturate, which may reduce the density of the oxygen separation membrane. On the other hand, if the firing temperature is too high, cobalt (Co) is decomposed during firing, so the composition of the oxygen separation membrane may vary. Accordingly, the firing temperature is generally 1150 ° C. to 1250 ° C., preferably 1180 ° C. to 1240 ° C., particularly preferably 1180 ° C. to 1220 ° C. In addition, even if the firing temperature is in the range of 1150 ° C. to 1250 ° C. as described above, if the firing time is too short, oxygen does not sufficiently diffuse in the crystal lattice in the material, so that the density of the oxygen separation membrane is low. May decrease. Therefore, from the viewpoint of improving the density of the oxygen separation membrane, the firing time of the molded body and the precursor is appropriately 24 hours or longer (for example, 24 to 500 hours). Within such a range of firing temperature and firing time, a highly airtight oxygen separation having a relative density suitable for an oxygen separation membrane (for example, 97% or more, preferably 98% or more, particularly preferably 99% or more). A film can be obtained stably (without composition fluctuation due to Co decomposition).

  More preferably, the molded body and the precursor are co-fired for 50 hours to 500 hours. If the firing time is too long, not only the oxygen separation membrane but also the porous support is densified, and thus the gas (oxygen) permeability of the porous support may not be ensured. On the other hand, if the firing time is too short, the porosity of the porous support becomes too large, and the mechanical strength and durability of the porous support may be lowered. Therefore, from the viewpoint of improving gas permeability and mechanical strength of the porous support, the firing time of the molded body and the precursor is appropriately 50 hours to 500 hours, preferably 50 hours to 300 hours, Especially preferably, it is 50 hours-100 hours. Within such a firing time range, the porous material has a porosity suitable for the porous support (for example, 10% to 30%, more preferably 10% to 25%, particularly preferably 18% to 25%). A quality support can be obtained stably and easily.

  According to the production method of the present invention, the porous support and the oxygen separation membrane are formed on the surface portion by co-firing the molded body and the precursor, so that the porous support and the oxygen separation membrane are laminated. The oxygen separation element can be manufactured efficiently (with high productivity). Further, by appropriately selecting the firing temperature and firing time at that time as described above, it is possible to effectively densify only the oxygen separation membrane while maintaining an appropriate porosity of the porous support. Therefore, an optimal oxygen separation element excellent in mechanical strength and oxygen separation performance can be suitably produced.

  In one aspect of the preferred oxygen separation membrane element manufacturing method disclosed herein, the oxygen separation membrane is formed to a thickness of 10 μm to 50 μm. By having a film thickness within such a predetermined range, an oxygen separation membrane excellent in oxygen ion conductivity can be obtained. Therefore, an oxygen separation element that is particularly excellent in oxygen separation performance can be produced.

The present invention also provides an oxygen separation membrane element manufactured by any of the manufacturing methods disclosed herein. That is, an oxygen separation membrane element in which an oxygen separation membrane having oxygen ion conductivity is formed on at least a part of a surface portion of a porous support, wherein the porous support and the oxygen separation membrane have the general formula: Ln _{1-x Ae x Co 1-} y M y O 3
Here, in the formula, Ln is at least one selected from lanthanoids, Ae is one or a combination of two or more selected from the group consisting of Sr, Ca and Ba, and M is Mg, Mn, Ga, Ti, Ni, Al, Fe, Cu, In, Sn, Zr, V, Cr, Zn, Ge, Sc, and a combination of two or more selected from the group consisting of Y, and x is 0 <x < A real number satisfying 1 and y is a real number satisfying 0 <y <1;
It is substantially comprised from the complex oxide shown by these. Preferably, M in the general formula is Ni. And the relative density of the said oxygen separation membrane is 97% or more, and the porosity (For example, based on mercury intrusion method. The same is the following.) Of the said porous support body is 10%-30% (preferably 10%- 25%).

  Thus, when the oxygen separation membrane has a relative density equal to or higher than a predetermined value, there are few defects (pores) such as pinholes and cracks, and gas leakage hardly occurs. Further, when the porous support has a porosity within a predetermined range, it is possible to achieve both appropriate mechanical strength and good gas (oxygen) permeability. Therefore, according to the present invention, an optimum oxygen separation membrane element excellent in mechanical strength and oxygen separation performance can be provided.

6 is a schematic diagram schematically showing a leak test module according to Test Example 3. FIG. 6 is a cross-sectional SEM image of an oxygen separation membrane element according to Test Example 4.

  Embodiments according to the present invention will be described below. In addition, this invention is not limited to the following embodiment.

Oxygen separation membrane according to the oxygen separation membrane element of the present invention have the general formula: consist essentially _{Ln 1-x Ae x Co 1} -y M y perovskite oxide having oxygen ion conductivity represented by O ₃ ing.

  Here, Ln in the above general formula is at least one element selected from lanthanoids, and typically lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), samarium (Sm 1), or two or more thereof, particularly preferably La. Ae in the above general formula is one or more elements of strontium (Sr), calcium (Ca), and barium (Ba). Among these, Sr or Ca or two combinations of Sr and Ca are preferable, and a composition having a high content of such elements is preferable. In particular, it is preferable that Ae is Sr or that the content of Sr is high (for example, 50% or more of Sr is contained in Ae). Moreover, as M in the above general formula, magnesium (Mg), manganese (Mn), gallium (Ga), titanium (Ti), nickel (Ni), aluminum (Al), iron (Fe), copper (Cu) , Indium (In), tin (Sn), zirconium (Zr), vanadium (V), chromium (Cr), zinc (Zn), germanium (Ge), scandium (Sc), and yttrium (Y) Or two or more elements. Among these, any one of Mn, Ni, Fe, Cu or Cr, or a combination of any two of these is preferable.

  Further, “x” in the above general formula is a value indicating a ratio in which Ln (typically La) is replaced by Ae in the perovskite structure, and the possible range of x is the perovskite structure. As long as the structure can be maintained without breaking, any real number may be taken as long as it is within the range of 0 <x <1. That is, the composition ratio of La (1-x) and Ae (x) is appropriately selected according to the purpose of the present configuration, but is preferably 0.2 ≦ x ≦ 0.6, particularly preferably 0.8. 3 ≦ x ≦ 0.5.

As the perovskite oxide as described above, one containing Ni or Fe as M in the general formula is more preferable. Specifically, composite oxides represented by La _1-x Sr _x Co _1-y Ni _y O ₃ (LSCN oxide) and La _1-x Sr _x Co _1-y Fe _y O ₃ (LSCF oxide) are used. Can be mentioned. Here, “x” is 0 <x <1 (for example, 0.4 ≦ x ≦ 0.6). Further, the above “y” is a value indicating the ratio of Co being replaced by other metal elements such as Ni and Fe in the perovskite structure, and the range that y can take is without breaking the perovskite structure. As long as the structure can be maintained, it may be in the range of 0 <y <1. That is, the composition ratio of Co (1-y) and M (y) is appropriately selected according to the purpose of this configuration, but for example 0 <y ≦ 0.5, and preferably 0 <y ≦ 0. 2, particularly preferably 0 <y ≦ 0.1.

In the above general formula, the number of oxygen atoms is displayed as if it was 3, but the number of oxygen atoms may actually be 3 or less (typically less than 3). However, since the number of oxygen atoms varies depending on the type of atoms (for example, a part of Ae and M in the formula) substituting a part of the perovskite structure, the substitution ratio, and other conditions, it is difficult to display accurately. is there. For this reason, in the present specification, in the general formula indicating a perovskite oxide, the number of oxygen atoms is represented as 3 for convenience, but it is not intended to limit the technical scope of the invention disclosed herein. . Therefore, the number of oxygen atoms can be indicated as, for example, 3-δ (for example, the general formula is expressed as Ln _1-x Ae _x Co _{1-y My 0 3-δ} ). Here, δ is typically a positive number not exceeding 1 (0 <δ <1).

  The oxygen separation membrane according to the oxygen separation membrane element disclosed herein can be extremely dense because it is manufactured through a firing step under predetermined conditions described later. For example, the relative density is 97% or more, preferably 98% or more, more preferably 99% or more, still more preferably 99.5% or more, and particularly preferably 99.8% or more. Further, the film thickness can be appropriately selected according to the application, but it is usually preferable to set the film thickness to 50 μm or less, which is good in oxygen ion conductivity, for example, a range of 10 μm to 50 μm is appropriate. More preferably, it is the range of 10 micrometers-40 micrometers, Most preferably, it is the range of 10 micrometers-30 micrometers. As a preferable example of the oxygen separation membrane disclosed herein, the relative density of the oxygen separation membrane is 97% or more and the film thickness is in the range of 40 μm to 50 μm, and the relative density of the oxygen separation membrane is 98% or more. A film having a thickness of 30 μm to 50 μm, a relative density of the oxygen separation membrane of 99% or more and a film thickness of 20 μm to 50 μm, and a relative density of the oxygen separation membrane of 99.99 μm. Examples thereof include 5% or more and a film thickness in the range of 10 μm to 50 μm. By having both the relative density and the film thickness within such a predetermined range, an oxygen separation membrane that realizes both excellent oxygen ion conductivity and high airtightness (leakage prevention effect) at a high level. Can do.

  When the oxygen separation membrane is a thin film having a thickness of 50 μm or less as described above, the average particle size of particles (sintered particles) constituting the oxygen separation membrane is generally in the range of 5 μm to 10 μm. preferable. If it exceeds or falls below this range, the airtightness of the oxygen separation membrane may tend to decrease. As a preferred example of the oxygen separation membrane disclosed herein, the sintered particles in the oxygen separation membrane have an average particle diameter of 5 μm to 10 μm and a film thickness in the range of 10 μm to 50 μm. The average particle diameter (sintered particle diameter) of the particles is 7 μm to 10 μm, and the film thickness is in the range of 20 μm to 50 μm. By having both the average particle diameter and the film thickness of the sintered particles within such a predetermined range, an oxygen separation membrane that achieves both excellent oxygen ion conductivity and high airtightness that could not be obtained conventionally. Can be obtained more reliably.

  The relative density (%) of the oxygen separation membrane is obtained by dividing the bulk density of the oxygen separation membrane (= the mass of the oxygen separation membrane / the apparent volume of the oxygen separation membrane) by the theoretical density of the material constituting the oxygen separation membrane. It can be determined by multiplying the value by 100. Moreover, the average particle diameter of the sintered particles in the oxygen separation membrane can be easily grasped from the observation of the oxygen separation membrane by a scanning electron microscope (SEM). For example, an arbitrary straight line is drawn on the oxygen separation membrane in the SEM image, and a value obtained by dividing the length of the straight line by the number of the sintered particles included in the straight line is calculated as the average particle diameter of the sintered particles. (Line intercept method).

  Next, the porous support according to the oxygen separation membrane element disclosed herein will be described.

The porous support is composed of the same oxide as described in the oxygen separation membrane according to the oxygen separation membrane element. In other words, the general _formula: is substantially constituted from perovskite type oxide represented by _{Ln 1-x Ae x Co 1} -y M y O 3. Among these, particularly preferred ones are the same as the oxygen separation membrane, and thus detailed description thereof is omitted.

According to the oxygen separation membrane element disclosed herein, from the viewpoint of improving mechanical strength and durability, the porous support and the oxygen separation membrane are substantially composed of a perovskite oxide having the same composition. Preferably it is. Preferred perovskite oxides are La _1-x Sr _x Co _1-y Ni _y O ₃ (LSCN oxide) and La _1-x Sr _x Co _1-y Fe _y O ₃ (LSCF oxide). A composite oxide is mentioned.

  The porous support according to the oxygen separation membrane element disclosed herein has a porosity of 10% to 30%, preferably 10% to 28%, more preferably 10% to 25. %, Particularly preferably in the range of 18% to 25%. By having such a porosity within a predetermined range, both high mechanical strength and excellent oxygen gas permeability (that is, sufficient securing of the gas contact area in the oxygen separation membrane) are satisfied and compatible. Can do. In addition, although it does not restrict | limit especially as an average pore diameter of a porous support body, about 3 micrometers-about 10 micrometers are suitable in general, Preferably it is the range of 3 micrometers-8 micrometers, Most preferably, it is the range of 5 micrometers-8 micrometers. By having such an average pore diameter within a predetermined range, both high mechanical strength and excellent oxygen gas permeability (that is, sufficient securing of the gas contact area in the oxygen separation membrane) are satisfied and compatible. be able to.

From the viewpoint of preventing densification of the porous support, the porous support and the oxygen separation membrane may be composed of perovskite oxides having different compositions. For example, in the porous support and the oxygen separation membrane substantially composed of a perovskite oxide represented by La _{1-x A} e _x Co _1-y M _y O ₃ , M in the formula is mutually Can be different. For example, the porous support is composed of a composite oxide represented by _{La 1-x Sr x Co 1} -y Ni y O 3 (LSCN oxide), wherein the oxygen separation membrane _{La 1-x} Sr x _{Co 1- y} Fe _y O ₃ may be composed of a composite oxide represented by (LSCF oxide). According to such a configuration, the mechanical strength and durability can be improved, and the effect of preventing the densification of the porous support can be achieved at the same time.

  Next, the manufacturing method of the oxygen separation membrane element according to the present invention will be described.

According to the production method of the present invention, first, a molded body for producing a porous support is formed. Raw material powder to be used has the general formula described in oxygen separation membrane element of the present _{configuration:} If the raw material powder containing a perovskite type oxide represented by _{Ln 1-x Ae x Co 1} -y M y O 3, either Available powders may be used. Commercial products may be used as they are. In particular, in order to prevent densification of the support during film baking, it is 10 μm or more, preferably 20 μm or more (for example, 20 μm to 100 μm), more preferably 40 μm or more (for example, 40 μm to 100 μm), still more preferably 50 μm or more, particularly preferably. It is preferable to have an average particle size belonging to 50 μm to 100 μm.

Alternatively, when a perovskite oxide having an average particle size not within the predetermined average particle size range is used, it can be granulated and calcined to a predetermined particle size and grown to a desired particle size. As the means, any means is not particularly limited. For example, the perovskite oxide is mixed with a predetermined amount of an additive such as a binder and a dispersant, kneaded well by a ball mill or the like, and dried to obtain an aggregate. Next, the aggregate is calcined and, if desired, pulverized to obtain a raw material powder having a desired particle size.
Alternatively, after adding a predetermined amount of a binder, a dispersion medium, a dispersant and the like to the perovskite oxide to form a slurry, the powder is dried and calcined by a spray dryer or the like to obtain a raw material powder having a desired particle size. Can be obtained.

Alternatively, those that decompose into a perovskite oxide during firing, for example, various hydroxides, carbonates, nitrates, organic acid salts, etc. are fired in the air, preferably in an oxygen atmosphere at a predetermined temperature range. . This also makes it possible to obtain a raw material powder having a predetermined particle size. Alternatively, in the case of a complex oxide represented by La _1-x Ae _x Co _1-y M _y O ₃ , compounds of La, Ae, Co, and M (typically oxides) that are the respective composition components are predetermined. The raw material powder having a predetermined particle diameter can also be obtained by mixing so as to have a ratio (molar ratio) and firing in the same manner. In addition, the raw material powder to be used can contain components other than the respective oxides as long as the performance (oxygen ion conductivity, electron conductivity, crack generation prevention property, etc.) is not significantly impaired.

  Various conventionally known forming means can be employed as means for forming the raw material powder into a molded body having a predetermined shape. For example, conventionally known molding methods such as uniaxial compression molding, isostatic pressing, and extrusion molding can be employed without any particular limitation. Alternatively, a conventionally known binder, dispersion medium, dispersant, or the like may be used for this molding, and a desired shape may be obtained by a casting method, an extrusion molding method, an injection molding method, or the like while being in a slurry or a plastic solid.

  The shape of this molded body is not particularly limited. Specifically, it includes various shapes such as a flat shape, a curved surface shape, a tubular shape (including an open tubular shape with both ends open, a closed tubular shape with one end open and one closed end), and a honeycomb shape. . The thickness of the molded body is not particularly limited. For example, in the case of a flat shape or a tubular shape, the thickness can be 0.5 mm to 50 mm, preferably 1 mm to 20 mm, more preferably 2 mm to 10 mm, and still more preferably. Is 2-5 mm. By forming to a thickness within this range, it is possible to provide a porous body support that is particularly excellent in mechanical strength and has an improved gas contact area ratio of the membrane.

Then, according to the production method of the present invention, at least a portion of the surface of the obtained porous support shaped body, the general _formula: perovskites represented by _{Ln 1-x Ae x Co 1} -y M y O 3 A precursor for forming an oxygen separation membrane substantially composed of a type oxide is added.

The precursor is a perovskite-type oxide raw material powder represented by the general formula: Ln _1-x Ae _x Co _{1- y My} O ₃ described in the oxygen separation membrane element of the present configuration, and any of the obtained powders Possible perovskite oxide raw material powders can be preferably used. Alternatively, it may be a perovskite oxide that reacts during firing, and is not necessarily produced from a perovskite oxide. Accordingly, as the precursor, various hydroxides, carbonates, nitrates, organic acid salts and the like can be used in addition to the original perovskite oxide. For _example, in the case of a composite oxide represented by _{La 1-x Ae x Co 1} -y M y O 3 is, La as the respective composition components, Ae, compound of Co and M (typically oxide) powder May be mixed and used at a predetermined ratio (molar ratio).

  In particular, the precursor is preferably selected from the viewpoint of mechanical strength and durability so that the fired oxygen separation membrane becomes an oxide having the same composition as the porous support. On the other hand, it is preferable to have a different composition from the viewpoint of preventing densification of the porous support. The preferred combination of the porous support and the composition of the oxygen separation membrane is the same as that described in the oxygen separation membrane element of the present invention, and a detailed description thereof will be omitted.

  When powder is used as a raw material for the precursor, the average particle diameter is generally 0.5 μm to 3 μm, preferably 0.8 μm to 2.5 μm, and particularly preferably 1 μm to 2 μm. By having such an average particle diameter in a predetermined range, an oxygen separation membrane that is particularly dense and excellent in oxygen ion conductivity can be obtained.

  Various means used in any conventionally known thin film forming process can be adopted as means for applying the precursor to the molded article for the porous support. For example, a dip coating method, a spin coating method, a screen printing method, and a spray method using a slurry-like forming material in which the raw material powder and a binder such as an organic solvent are dispersed may be mentioned.

  In particular, the dip coating method can suppress the penetration of the precursor into the molded body for the porous support, and further contributes to the suppression of the destruction of the fine structure due to gas generation, capillary pressure, firing shrinkage, etc. accompanying thermal decomposition. Can do. Therefore, the dip coating method is particularly suitable for directly forming an oxygen separation membrane having substantially no defects on the surface of the porous support. Specifically, the raw material powder is dispersed in a dispersion medium such as water and / or an organic solvent, specifically polyvinyl alcohol, methylcelluloses, polyethylene glycols, propylene glycol, glycerin, and the like, and if necessary, a binder and a dispersant. Then, a plasticizer or the like is added and mixed, and well kneaded using a ball mill. The porous support is dipped (immersed) in the coating liquid (slurry) in which the obtained precursor (raw material powder) is dispersed. The dip time may be several seconds to 1 minute. About 5 to 30 seconds is preferable. As a result, the precursor for the oxygen separation membrane can be evenly laminated on the surface portion of the molded article for the porous support.

  The film thickness of the oxygen separation membrane to be formed depends on the concentration of the raw material powder in the coating liquid, the viscosity of the coating liquid by changing the type and / or concentration of the dispersant, dispersion medium, and / or plasticizer to be added, film formation, and drying cycle. It is possible to control by changing variously. As the oxygen separation membrane, the film thickness can be appropriately determined according to the use, but it is usually preferably 50 μm or less, in which oxygen ion conductivity is good, for example, 10 μm to 50 μm is suitable, and more preferably It is 10 micrometers-40 micrometers, Most preferably, they are 10 micrometers-30 micrometers.

  In addition, examples of means for forming the oxygen separation membrane include a vacuum deposition method, a chemical vapor deposition method, and a reactive sputtering method. The oxygen separation membrane may be formed only on one surface of the porous support or may be formed on both sides of the porous support depending on the application.

  Next, the compact and the precursor are simultaneously fired to simultaneously form a porous support and an oxygen separation membrane provided on the surface of the porous support. Here, the firing temperature (maximum firing temperature) for simultaneous firing of the molded body and the precursor needs to be approximately 1150 ° C. to 1250 ° C. If the firing temperature is too low, sintering does not saturate, and the density of the oxygen separation membrane may be reduced. On the other hand, if the firing temperature is too high, cobalt (Co) is decomposed during firing, so the composition of the oxygen separation membrane may vary. Therefore, the firing temperature of the molded body and the precursor is generally 1150 ° C to 1250 ° C, preferably 1180 ° C to 1240 ° C, and particularly preferably 1180 ° C to 1220 ° C.

  In addition, even if the firing temperature is in the range of 1150 ° C. to 1250 ° C. as described above, if the firing time is too short, oxygen does not sufficiently diffuse in the crystal lattice in the material, so that the density of the oxygen separation membrane is low. May decrease. Therefore, from the viewpoint of improving the density of the oxygen separation membrane, the firing time of the molded body and the precursor is suitably 24 hours or longer (for example, 24 hours to 500 hours). Within such a range of firing temperature and firing time, a highly airtight oxygen separation having a relative density suitable for an oxygen separation membrane (for example, 97% or more, preferably 98% or more, particularly preferably 99% or more). A film can be obtained stably (without composition fluctuation due to Co decomposition).

  More preferably, the firing time is approximately 50 hours to 500 hours. If the firing time is too long, not only the oxygen separation membrane but also the porous support is densified, and thus the gas (oxygen) permeability of the porous support may not be ensured. On the other hand, if the firing time is too short, the porosity of the porous support becomes too large, and the mechanical strength and durability of the porous support may be reduced. Therefore, from the viewpoint of improving gas permeability and mechanical strength of the porous support, the firing time of the molded body and the precursor is appropriately 50 hours to 500 hours, preferably 50 hours to 300 hours, More preferably, it is 50 hours-100 hours, Most preferably, it is 50 hours-75 hours. Within such a firing time range, the porous material has a porosity suitable for the porous support (for example, 10% to 30%, more preferably 10% to 25%, particularly preferably 18% to 25%). A quality support can be obtained stably and easily.

  In addition, in order to obtain the uniform pores by decomposing and removing organic additives, for example, a binder and a dispersing agent in advance, one or more preliminary calcinations may be performed before the main calcination. The preliminary calcination can be performed at a temperature lower than the main calcination at which the organic matter can be decomposed, for example, 100 to 1000 ° C., preferably about 200 to 500 ° C. for 3 to 15 hours, preferably about 6 to 12 hours. After the preliminary firing, the main firing is performed by raising the temperature to the maximum firing temperature. Here, the rate of temperature increase is not particularly limited, but is usually 1 to 10 ° C./min, preferably 1 to 2 ° C./min. The firing atmosphere is preferably an oxidizing atmosphere or an inert gas atmosphere in which the perovskite oxide is sintered. In addition, it is desirable to raise the relative density of the calcined product to about 90% to 96% (preferably 93% to 96%, particularly preferably 93% to 95%) by the preliminary calcination in the initial stage. By performing the main firing for a long time (24 hours or more, preferably 50 hours to 500 hours) by raising the temperature from the relative density of 90% to 96% in the initial firing stage to the maximum firing temperature (1150 ° C. to 1250 ° C.) The oxygen separation membrane can be in a sufficiently dense state (for example, a relative density of 97% or more, preferably 98% or more, particularly preferably 99% or more).

  In this way, the manufacture of the oxygen separation element according to this embodiment is completed. According to the manufacturing method of the present embodiment, the porous support and the oxygen separation membrane are formed on the surface portion by co-firing the molded body and the precursor, so the porous support and the oxygen separation membrane are laminated. The produced oxygen separation element can be manufactured efficiently (with high productivity). Further, by appropriately selecting the firing temperature and firing time at that time as described above, it is possible to effectively densify only the oxygen separation membrane while maintaining an appropriate porosity of the porous support. Therefore, an optimal oxygen separation element excellent in mechanical strength and oxygen separation performance can be suitably produced.

  The obtained oxygen separation membrane element can carry a catalyst to improve oxygen separation performance and / or oxidation reactivity by oxygen ions. For example, the catalyst can be supported on the side that feeds air into the membrane (hereinafter referred to as the air side) and / or the side where the mixed gas reacts with oxygen ions that have permeated the membrane (hereinafter referred to as the reaction side). . For example, as a means for supporting the catalyst on the air side, oxygen ion permeation promoting catalyst powder, such as LaSrCo oxide powder, a dispersion medium (water and / or organic solvent, etc.), and optionally a binder, a dispersant, a plasticizer After impregnating the support or the like with a slurry or a plastic solid to which etc. are added, it is dried. Furthermore, it can be baked at 800 to 1000 ° C., for example. Alternatively, the support may be impregnated, dried, and fired with an aqueous solution, an organic compound, or the like that has a desired oxide composition, for example, a LaSrCo oxide composition after firing.

  Further, as a means for supporting the catalyst on the reaction side, a dispersion medium (water and / or organic solvent, etc.) was added to an oxidation promotion catalyst powder, for example, Ni-based oxide powder, and a binder, a dispersant, etc. were added as necessary. The slurry or plastic solid is applied or printed on the film surface and then dried. Furthermore, it can be baked at 800 to 1000 ° C., for example. The Ni-based oxide functions as a catalyst by being partially reduced or completely reduced in a reducing atmosphere such as methane gas. In the present invention, it is not limited to the catalyst loading method, and for example, it can be loaded on either the air side or the reaction side of the support. Further, any conventionally known catalyst material other than the above can be applied. The oxygen separation membrane element of the present invention can be suitably used for applications exhibiting various oxygen ion conductivity, for example, fuel cells.

  Hereinafter, although the test example regarding this invention is demonstrated, it is not intending to limit this invention to what is shown to the following test examples. In the following Test Examples 1 to 3, the main purpose was to evaluate the performance of the oxygen separation membrane provided in the oxygen separation membrane element provided by the present invention, and therefore, it was composed only of an oxygen separation membrane without a porous support. A specimen was prepared and its performance was evaluated. In Test Example 4, an oxygen separation membrane element in which a porous support and an oxygen separation membrane were laminated was produced using the production method of the present invention, and the characteristics thereof were evaluated.

<Test Example 1: Production of oxygen separation membrane composed of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ >
In this example, an oxygen separation membrane specimen composed of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ was produced. First, commercially available lanthanum oxide powder (particle size: about 2 μm), strontium carbonate powder (particle size: about 2 μm), cobalt oxide powder (particle size: about 1 μm), and nickel oxide powder (particle size: about 1 μm) are weighed at a predetermined ratio. And kneaded well using a ball mill. Thereafter, it is calcined by calcining at 1000 ° C. for 6 hours and used for an oxygen separation membrane having an average particle diameter of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ of about 1 μm. Raw material powder was obtained. The particle diameter of the (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ raw material powder was measured using a laser diffraction particle size distribution meter, and the average particle diameter was also measured. Asked.

Next, the obtained (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ raw material powder is mixed with an appropriate amount of a general binder and a solvent (water) to form a slurry. And granulated into particles having a particle size of about 50 to 100 μm using a granulator such as a spray dryer. The granulated particles were press-molded to obtain a disk-shaped press-molded body having a diameter of about 30 mm and a thickness of about 1.0 mm. The obtained press-molded body was first heated to 200 to 500 ° C. in the atmosphere and held for 10 hours to decompose and remove organic substances. Thereafter, the temperature was raised to the firing temperature shown in Table 1 in the air, and the disc was held for the firing time shown in Table 1 to obtain a disk-shaped sintered body. The obtained disc-shaped sintered body was mechanically polished to produce a total of 17 types of oxygen separation membranes (thickness 0.5 mm, diameter 24 mm) with different firing temperatures and firing times (samples 1 to 17).

  The material constituting the oxygen separation membrane is the bulk density of the oxygen separation membrane (= the mass of the oxygen separation membrane / the apparent volume of the oxygen separation membrane) measured by the Archimedes method for the relative density of the various oxygen separation membranes obtained above. It was calculated by multiplying the value divided by the theoretical density of 100 by 100. Various oxygen separation membranes were observed with a scanning electron microscope (SEM). And the average particle diameter (sintered particle diameter) of the particle | grains (particle | grains after sintering) which comprises an oxygen separation membrane by the line intercept method was computed. The results are shown in Table 1.

  As is clear from the results in Table 1, the oxygen separation membranes of Samples 4 and 9-15 fired at 1150 to 1250 ° C. for 24 hours or more have a high relative density after sintering of 98.8% or more, and the oxygen separation membranes. It was suitable as. In particular, by firing at 1200 to 1250 ° C. for 24 hours or more, an extremely high relative density of 99% or more was realized. In addition, the oxygen separation membranes of Samples 4, 9 to 13 and 15 fired at 1150 to 1250 ° C. for 24 to 500 hours have a sintered particle diameter in the range of 6 to 9.5 μm and are optimal for thinning to 50 μm or less. I found out. In addition, the oxygen separation membranes of Samples 16 and 17 fired at 1300 ° C. for 6 to 24 hours had a tendency to decrease the relative density after sintering as compared to Samples 4 and 9 to 13 and 15. This is presumably because Co was scattered and the composition of the oxygen separation membrane was changed because the firing temperature was too high at 1300 ° C. From this result, it is desirable to bake at 1150 to 1250 ° C. for 24 hours or more from the viewpoint of improving the density of the oxygen separation membrane.

<Test Example 2: Production of oxygen separation membrane composed of (La _0.6 , Sr _0.4 ) (Co _0.8 , Fe _0.2 ) O ₃ >
In this example, an oxygen separation membrane specimen composed of (La _0.6 , Sr _0.4 ) (Co _0.8 , Fe _0.2 ) O ₃ was prepared. Oxygen separation membranes were prepared in the same manner as in Test Example 1 except that commercially available iron oxide powder was used instead of nickel oxide powder (Samples 18 to 23). The relative density of the obtained oxygen separation membrane was calculated in the same manner as in Test Example 1. The results are shown in Table 2.

  As is clear from the results in Table 2, the oxygen separation membranes of Samples 18 to 23 fired at 1200 ° C. for 24 hours or more have a very high relative density of 97.9% or more after sintering, and are suitable as oxygen separation membranes. Met. In particular, by firing at 1200 ° C. for 50 hours or longer, an extremely high relative density of 98% or higher was realized.

<Test Example 3: Gas leak test>
N ₂ gas pressure with a differential pressure of 0.8 MPa was applied to the various oxygen separation membranes obtained in Test Examples 1 and 2, and the amount of gas leak at that time was measured. Specifically, as schematically shown in FIG. 1, alumina cylindrical tubes 32 and 34 are disposed on both surfaces of the oxygen separation membrane 30, respectively, and the boundary between the alumina cylindrical tubes 32 and 34 and the oxygen separation membrane 30. The portion was sealed with a glass-based sealing member 35. In the module 50 having such a configuration, the inside of one alumina cylindrical tube 32 is decompressed to form a vacuum atmosphere, and nitrogen (N ₂ ) gas is introduced into the other alumina cylindrical tube 34 under a pressure of 0.8 MPa. It was introduced and left in that state for 0.5 hours. During this time, the amount of N ₂ gas flowing into the alumina cylindrical tube on the decompression side 32 from the N ₂ gas supply side 34 was determined to evaluate whether or not N ₂ gas leaked through the oxygen separation membrane 30.

Tables 1 and 2 show the gas leak evaluation results. In Tables 1 and 2, the ratio of the amount of N ₂ gas flowing into the alumina cylindrical tube 32 to the total amount of N ₂ gas introduced into the alumina cylindrical tube 34 is defined as a leak rate (%), and the leak rate is 1%. The following were considered good (◯), those with a leak rate exceeding 1% to 5% or less were appropriate (Δ), and those with a leak rate exceeding 5% were considered inappropriate (×).

  As shown in Tables 1 and 2, the oxygen separation membranes of Samples 1, 2, 16, and 17 fired at a temperature lower than 1150 ° C. or higher than 1250 ° C. were insufficient in airtightness. % Or more gas leak was observed. In addition, even when firing at 1150 to 1250 ° C., gas leakage of 3% to 5% or more was observed when the firing time was less than 24 hours (Samples 3 and 5 to 8). On the other hand, gas leakage was preferably prevented for the oxygen separation membranes of Samples 4, 9-15, and 21-23 fired at 1150 to 1250 ° C. for 24 to 1000 hours.

  From the above results, according to this test example, it was possible to form an oxygen separation membrane having high airtightness by firing at a temperature of 1150 ° C. to 1250 ° C. for 24 hours to 1000 hours. Therefore, according to this configuration, a high-performance oxygen separation membrane element including an oxygen separation membrane in which gas leakage is preferably prevented can be realized.

<Test Example 4: Production of an oxygen separation membrane element composed of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ by simultaneous firing>
In this example, an oxygen separation membrane element including a porous support composed of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ and an oxygen separation membrane is manufactured by simultaneous firing. did. First, commercially available lanthanum oxide powder (particle size: about 2 μm), strontium carbonate powder (particle size: about 2 μm), cobalt oxide powder (particle size: about 1 μm), and nickel oxide powder (particle size: about 1 μm) are weighed at a predetermined ratio. And kneaded well using a ball mill. Thereafter, it is temporarily fired at 1000 ° C. for 6 hours and pulverized, and is used for a porous support having an average particle diameter of (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ of 50 μm. A raw material powder and an oxygen separation membrane raw material powder having an average particle diameter of 1 μm were obtained.

  Subsequently, the obtained raw material powder for porous support was mixed with a binder and a dispersant in a mortar (dry type) to obtain an aggregate having the same composition. The aggregate was press-extruded with a press extruder under a pressure of 100 MPa, and formed into a disk shape having a diameter of about 20 mm and a thickness of about 3 mm to obtain a molded body for a porous support.

Next, the raw material powder for the oxygen separation membrane is well kneaded with a binder and a dispersant using a ball mill to prepare a (La _0.5 , Sr _0.5 ) (Co _0.9 , Ni _0.1 ) O ₃ slurry. did. In the obtained slurry liquid, one side of the disk-shaped porous support molded body obtained as described above is dipped (immersed) for 20 seconds, and the slurry is evenly distributed on one surface portion of the porous support molded body. Laminated. Thereafter, the porous support molded body was pulled up from the slurry and dried at 60 ° C. for 4 hours to form a precursor for an oxygen separation membrane on one surface of the porous support molded body.

  In the atmosphere, the temperature was first raised to 200 to 500 ° C. and held for 10 hours to decompose and remove organic substances. Thereafter, the temperature was raised to the firing temperature shown in Table 3 in the air, and the molding and the precursor were co-fired by maintaining for the firing time shown in Table 3. Thereafter, it was allowed to cool to form a porous support and an oxygen separation membrane at the same time. In this way, a total of five types of oxygen separation membrane elements with different firing times were produced (samples 24-28).

  A cross-sectional SEM image of the obtained oxygen separation membrane element of Sample 26 is shown in FIG. As apparent from FIG. 2, the oxygen separation membrane had a dense structure, while the porous support had appropriate pores. The thickness of the oxygen separation membrane was measured by SEM observation, and was about 50 μm.

  The porosity and average pore diameter of the porous support provided in the various oxygen separation membrane elements obtained above were simultaneously measured using an Autopore IV apparatus manufactured by Shimadzu Corporation. The results are shown in Table 3.

  As apparent from the results in Table 3, the porous support of Sample 28 baked at 1200 ° C. for 1000 hours had a porosity of 7% and was not suitable as a porous support. On the other hand, the porous support of samples 24-27 calcined at 1200 ° C. for 24-500 hours had a porosity of 18% -28% and was suitable as a porous support. In particular, by firing at 1200 ° C. for 50 to 500 hours, it was possible to obtain a porous support that achieved both high gas permeability and mechanical strength of 18% to 25%. From this result, from the viewpoint of ensuring gas permeability and mechanical strength of the porous support, the firing time is desirably 50 to 500 hours.

  From the above results, according to this test example, it is possible to form a porous support body having both appropriate mechanical strength and good gas permeability by simultaneous firing at 1200 ° C. for 50 to 500 hours. It was. Therefore, according to this configuration, a high-performance oxygen separation membrane element excellent in mechanical strength and oxygen separation performance can be realized.

  As mentioned above, although this invention was demonstrated by suitable embodiment, such description is not a limitation matter and of course various modifications are possible.

30 Oxygen separation membrane 32, 34 Alumina cylindrical tube 35 Seal member 50 Module

Claims (4)

A method for producing an oxygen separation membrane element in which an oxygen separation membrane having oxygen ion conductivity is formed on at least a part of a surface portion of a porous support,
General _{formula: Ln 1-x Ae x Co} 1-y M y O 3
Here, in the formula, Ln is at least one selected from lanthanoids, Ae is one or a combination of two or more selected from the group consisting of Sr, Ca and Ba, and M is Mg, Mn, Ga, Ti. , Ni, Al, Fe, Cu, In, Sn, Zr, V, Cr, Zn, Ge, Sc and Y, or a combination of two or more, and x is 0 <x <1 Y is a real number satisfying 0 <y <1;
A raw material powder for a porous support containing a perovskite type oxide represented by a step of forming a raw material powder having an average particle size of 10 μm or more into a molded body having a predetermined shape;
At least a portion of the surface of the molded article, the general _{formula: Ln 1-x Ae x Co} 1-y M y O 3
Here, in the formula, Ln is at least one selected from lanthanoids, Ae is one or a combination of two or more selected from the group consisting of Sr, Ca and Ba, and M is Mg, Mn, Ga, Ti. , Ni, Al, Fe, Cu, In, Sn, Zr, V, Cr, Zn, Ge, Sc and Y, or a combination of two or more, and x is 0 <x <1 Y is a real number satisfying 0 <y <1;
A step of providing a precursor for forming an oxygen separation membrane substantially composed of a perovskite oxide represented by:
A porous support and an oxygen separation membrane provided on the surface of the porous support by co-firing the molded body and the precursor in a temperature range of 1150 ° C. to 1250 ° C. for 24 hours to 500 hours And simultaneously forming
A method for producing an oxygen separation membrane element, comprising:   The method for producing an oxygen separation membrane element according to claim 1, wherein the co-firing time is 50 hours to 500 hours.   The manufacturing method of the oxygen separation membrane element of Claim 1 or 2 which forms the said oxygen separation membrane in the film thickness of 10 micrometers-50 micrometers.   The method for producing an oxygen separation membrane element according to any one of claims 1 to 3, wherein the porous support and the oxygen separation membrane are composed of perovskite oxides having substantially the same composition.