JP5362638B2 - Production of oxygen separation membrane material and method for measuring reduction expansion coefficient of the material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for measuring a reduction expansion rate of oxygen separation membrane material appropriately. <P>SOLUTION: A method for measuring a reduction expansion rate provided by the invention is a measuring method of a reduction expansion rate of oxygen separation membrane material and includes the steps of: determining a lattice constant in a reductive atmosphere for a measuring object material 16 by measuring x-ray diffraction in the reductive atmosphere for the material 16; determining a lattice constant under air atmosphere for the material 16 by measuring x-ray diffraction under air atmosphere for the material 16; and calculating a reduction expansion rate of the material based on the lattice constant determined in the reductive atmosphere and the lattice constant determined under the air atmosphere. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to an oxygen separation membrane material and its production, and more particularly to a method for measuring the reduction expansion coefficient of the material.

As an oxygen ion conductor having oxygen ions (typically also called O ²⁻ ; oxide ions), oxide ceramics having a so-called perovskite structure are known. In particular, in addition to being an oxygen ion conductor, a dense ceramic material composed of a perovskite oxide, which is an oxygen ion-electron mixed conductor (mixed conductor) that has electronic conductivity, typically in the form of a film The formed ceramic material can transmit oxygen ions continuously 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 a material for an oxygen separation membrane that selectively permeates oxygen from an oxygen-containing gas (for example, air) supplied to one surface to the other surface, the operating temperature is particularly high such as 800 ° C. or more and less than 1000 ° C. It can be suitably used in the region.

  For example, an oxygen separation membrane composed of a mixed conductor such as a perovskite oxide is formed on a porous substrate (porous support) and used as an oxygen separation membrane element. It can be suitably used as an effective oxygen purification means to replace the Pressure Swing Adsorption) method. In addition, the oxygen separation membrane element having such a structure is an oxidation reaction device for separating oxygen-containing gas (air) and hydrocarbon gas and selectively permeating oxygen to perform partial oxidation reaction of hydrocarbon, so-called diaphragm. It can be suitably used as a component of the reactor. That is, when an oxygen-containing gas is brought into contact with the surface on one side of the oxygen separation membrane and a hydrocarbon gas (for example, methane) is brought into contact with the surface on the other side, oxygen ions that are supplied through the oxygen separation membrane from one surface are supplied. The hydrocarbon is partially oxidized on the other side. Thus, the technique of partially oxidizing hydrocarbons using an oxygen separation membrane is suitably used in the GTL (Gas To Liquid) technique for producing a synthetic liquid fuel (such as methanol) or the fuel cell field.

As this type of prior art, Patent Documents 1 to 6 describe the use of LaSrCoFe-based oxides and LaGaO ₃ -based oxides as perovskite oxides that are mixed conductors. Patent Document 7,8, LaSrTiCoFeO ₃ based oxide as a perovskite oxide is a mixed conductor, it is described that the use of LaSrZrFeO ₃ based oxide.

Japanese Patent Laid-Open No. 11-228136 Japanese Patent Laid-Open No. 11-335164 JP 2000-251534 A JP 2000-251535 A Special Table 2000-511507 JP 2001-93325 A International Publication No. WO2003 / 040058 Pamphlet JP 2007-51036 A

  By the way, the oxygen separation membrane material used in the GTL technology and the fuel cell field has a reducing atmosphere on the side through which oxygen ions permeate, that is, the hydrocarbon gas supply side (fuel electrode side). In addition, there is a demand for durability against a reducing atmosphere (hereinafter simply referred to as “reduction durability”) in which cracks do not easily occur even when used in a high temperature range. Such reduction durability easily varies depending on the ratio of the metal elements constituting the oxygen separation membrane material and the synthesis conditions (synthesis conditions such as the firing time and the firing temperature) when the oxygen separation membrane material is synthesized. It is desirable to inspect the reduction durability of the separation membrane material in advance. Conventionally, TMA (Thermo Mechanical Analysis) is used as one of the methods for inspecting the reduction durability of the oxygen separation membrane material. In the inspection by TMA, a rod-shaped (cylindrical) test piece is prepared from the oxygen separation membrane material powder, and the reduction durability is determined from the dimensional change when the test piece is heated in a reducing atmosphere (reduction expansion coefficient, that is, (Expansion coefficient in reducing atmosphere) is quantitatively calculated.

  However, the reductive expansion coefficient obtained with the above TMA is only a macroscopic material evaluation by measuring the expansion coefficient (reduction expansion coefficient) in the reducing atmosphere of the entire test piece, and a minute expansion amount (dimensional change) generated on the order of crystal grains. ) Is not strictly measured. For this reason, the inspection by TMA cannot accurately grasp the minute reduction stress generated at the individual crystal grain level. Moreover, the dimension of the test piece used for TMA is a millimeter order of diameter 3mm x length 15mm, for example, The production of the test piece is performed by processing material powder into a rod shape. Therefore, it is necessary to produce a rod-shaped test piece having the above-mentioned size for each measurement, which requires work time and labor. Further, since the test piece after the measurement cannot be reused, the millimeter-order material having the above size is wasted, and the cost is increased accordingly. In addition, when attempting to check the reduction durability of a material during thin film manufacturing, it is necessary to sample and extract for each lot, so it is possible to confirm whether each thin film really has the required reduction durability. There wasn't.

  This invention is made | formed in view of this point, The main objective is to provide the reduction expansion coefficient measuring method which can grasp | ascertain the reduction expansion coefficient of the material for oxygen separation membrane more appropriately. Another object is to provide a method for producing an oxygen separation membrane suitably using such a method for measuring the reduction expansion coefficient.

  The measurement method provided by the present invention is a method for measuring the reduction expansion coefficient of the oxygen separation membrane material. In this measurement method, a material to be measured is subjected to X-ray diffraction measurement under a reducing atmosphere, and a lattice constant under a reducing atmosphere in the reducing atmosphere of the material is obtained. And calculating the lattice constant under the air atmosphere of the material under the air atmosphere and calculating the reduction expansion coefficient of the material based on the obtained lattice constant under the reduced atmosphere and the lattice constant under the air atmosphere. Including.

  According to the method for measuring the reduction expansion coefficient of the present invention, the reduction expansion coefficient is calculated from a small dimensional change (expansion amount) generated between crystal lattices of the oxygen separation membrane material by using X-ray diffraction. Compared to the method of calculating the reduction expansion coefficient from the expansion amount of the entire test piece), the reduction expansion coefficient can be obtained with high accuracy. Moreover, since it is not necessary to produce a rod-shaped test piece as in the prior art, the reduction expansion coefficient can be easily measured. Furthermore, since measurement can be performed non-destructively using X-rays, it is not necessary to discard the oxygen separation membrane material after measurement. For this reason, such a method of measuring the reduction expansion coefficient can be easily incorporated into the manufacturing process of the oxygen separation membrane.

  In a preferred embodiment of the measurement method disclosed herein, the material is powdered and the X-ray diffraction measurement is performed. In this case, since it is not necessary to produce a rod-shaped test piece as in the prior art, the reduction expansion coefficient can be easily measured. In a preferred embodiment of the measurement method disclosed herein, the X-ray diffraction measurement is performed with the material as a film. In this case, since it can be measured in the same form as the actual use form (thin film form), a more accurate reduction expansion coefficient can be obtained.

  In a preferred embodiment of the measurement method disclosed herein, a reducing gas atmosphere containing at least hydrogen is formed as the reducing atmosphere. In this case, a reducing atmosphere suitable for the purpose of the present invention can be easily formed.

In addition, according to the present invention, there is provided a method for producing an oxygen separation membrane including any one of the methods for measuring the reduction expansion coefficient disclosed herein.
That is, the oxygen separation membrane manufacturing method disclosed here is:
Preparing an oxygen separation membrane material and measuring the reduction expansion coefficient of the material by any of the reduction expansion coefficient measurement methods disclosed herein;
Determining whether the material is non-defective based on the measured reduction expansion rate; and
Adopting an oxygen separation membrane configured using a material that has been judged as good in the above determination,
Is included. For example, when a powdery material is prepared as the material for the oxygen separation membrane and the reduction expansion coefficient of the material is measured, the powdery material determined as good in the above determination is used (in other words, determined as defective). Including the production of oxygen separation membranes (without the use of materials made).

  According to the production method of the present invention, the reductive expansion coefficient of the oxygen separation membrane material (typically a powdery material or a material after being formed into a membrane shape) is measured by the X-ray diffraction described above, and the measurement is performed. Since it is determined whether or not the material is a non-defective product based on the reduced expansion coefficient, and only the material determined to be non-defective in the determination is adopted, a high-quality oxygen separation membrane that satisfies the desired reduction durability is efficiently obtained. Can be provided. In addition, since non-destructive inspection can be performed using X-rays, it is not necessary to perform sampling extraction for each lot as in the prior art, and it is possible to inspect all thin films. Therefore, the risk that a defective product is formed in advance can be reduced, and a highly reliable oxygen separation membrane can be efficiently manufactured.

  In a preferable aspect of the production method disclosed herein, the material is determined to be non-defective when the reduction expansion coefficient of the material is 0.50% or less in the determination. Thereby, an oxygen separation membrane excellent in reduction durability can be obtained efficiently.

  In a preferred embodiment of the production method disclosed herein, the material for the oxygen separation membrane is a material made of an oxide ceramic having a perovskite structure which is an oxygen ion conductor. Perovskite structure oxide ceramics have properties that are favorable as an oxygen separation membrane, while they tend to undergo reductive expansion when exposed to a reducing atmosphere. Therefore, when the oxygen separation membrane material is composed of perovskite structure oxide ceramics, the effect of examining the reduction expansion coefficient of the oxygen separation membrane material by applying the present invention can be exhibited particularly well.

  The present invention also provides a method for inspecting (performance evaluation) an oxygen separation membrane. In this manufacturing method, the reduction expansion coefficient of the oxygen separation membrane is measured by any of the reduction expansion coefficient measurement methods disclosed herein, and the reduction durability of the oxygen separation membrane is inspected based on the obtained reduction expansion coefficient. (Evaluate). This makes it possible to easily select a high-quality oxygen separation membrane having a desired reduction durability and to eliminate an oxygen separation membrane having a low reduction durability before use. An oxygen separation membrane can be provided efficiently.

It is a schematic diagram which shows the X-ray-diffraction measuring apparatus which concerns on one Embodiment of this invention. It is a figure which shows the X-ray-diffraction pattern of the perovskite type oxide ceramic powder which concerns on one Example. It is a fragmentary sectional view which explains typically the module for evaluation of reduction durability concerning one test example.

  Embodiments according to the present invention will be described below with reference to the drawings. In the following drawings, members / parts having the same action are described with the same reference numerals. In addition, this invention is not limited to the following embodiment.

  The measuring method of the reductive expansion coefficient which concerns on one Embodiment of this invention is a method of measuring the reductive expansion coefficient of the material for oxygen separation membranes. In this measurement method, X-ray diffraction (XRD) measurement is performed on a material to be measured in a reducing atmosphere, and a lattice constant in the reducing atmosphere of the material in the reducing atmosphere is obtained. Further, X-ray diffraction measurement is performed on the material to be measured in an air atmosphere, and a lattice constant under the air atmosphere of the material in the air atmosphere is obtained. Then, the reduction expansion coefficient of the oxygen separation membrane material is calculated based on the obtained lattice constant under reducing atmosphere and lattice constant under air atmosphere. According to such a measuring method, since the reduction expansion coefficient is calculated from a small dimensional change (expansion amount) generated between crystal lattices of the oxygen separation membrane material using X-ray diffraction, the conventional TMA (expansion of the entire test piece) is calculated. Compared with the method of calculating the reductive expansion coefficient from the amount), the reductive expansion coefficient can be obtained with higher accuracy.

  Hereinafter, the reduction expansion coefficient measuring method of this embodiment will be further described. FIG. 1 is a schematic diagram showing an X-ray diffraction measurement apparatus 20 according to this embodiment. In the X-ray diffraction measurement of the present embodiment, X-rays 14 irradiated from the X-ray generation source 10 are incident on the sample surface 16a of the sample 16 (oxygen separation membrane material). The sample surface 16a is a surface made of material powder. At this time, while the sample 16 is rotationally scanned with a predetermined scanning axis, the incident angle to the sample 16 is changed stepwise or continuously to irradiate the X-ray 14, and the X-ray 18 diffracted by the sample 16 is inspected. 12 Then, the angle difference (diffraction angle 2θ) between the X-ray diffraction direction and the incident direction and the diffraction X-ray intensity are measured. Such an X-ray diffraction measurement can be inspected using an X-ray diffraction measurement apparatus 20 commercially available from various measurement apparatus manufacturers. For example, Rigaku Corporation X-ray diffraction measuring device RINT-2000 can be used.

In the present embodiment, first, the X-ray diffraction measurement is performed in a reducing atmosphere for the oxygen separation membrane material to be measured. In order to obtain a reducing atmosphere during the X-ray diffraction measurement, a reducing gas such as hydrogen (H ₂ ) may be present during the X-ray diffraction measurement. For example, a reducing atmosphere such as hydrogen (H ₂ ) can be supplied into the chamber 22 of the X-ray diffraction measurement apparatus to create a reducing atmosphere. As the reducing gas, methane (CH ₄ ) gas, carbon dioxide (CO ₂ ) gas, or the like can be used in addition to hydrogen gas or a mixed gas containing hydrogen gas or ammonia gas. The reducing gas may be supplied directly into the chamber 22 or may be supplied after being diluted with an inert gas such as nitrogen (N ₂ ) or argon (Ar). Although the degree of dilution is not particularly limited, it is usually sufficient that the reducing gas concentration is 5 vol% or more, and it is preferably 5 vol% to 50 vol%, for example. When supplying the reducing gas, it is preferable to completely shut off the supply of oxygen (O ₂ ) in the chamber 22, but the oxygen partial pressure is approximately 10 ⁻¹⁰ MPa or less (for example, about 10 ⁻²⁴ MPa). It is sufficient to adjust so that

In the technique disclosed herein, it is preferable to form a reducing atmosphere in the chamber 22 close to the actual use of the oxygen separation membrane. For example, when the oxygen separation membrane is exposed to a mixed gas atmosphere of hydrogen (H ₂ ) and nitrogen (N ₂ ) during actual use, a mixed gas atmosphere of hydrogen (H ₂ ) and nitrogen (N ₂ ) is used in the chamber. Preferably, it is formed within 22. When the oxygen separation membrane is exposed to a high temperature atmosphere (for example, 800 ° C. to 1000 ° C.) during actual use, the high temperature atmosphere (for example, 800 ° C. to 1000 ° C.) is preferably formed in the chamber 22. The heating in the high temperature atmosphere may be performed by attaching a heating device (a heater or the like) 24 around the sample 16 disposed in the chamber, for example. Thus, by forming a reducing atmosphere close to that during actual use, the reduction durability during actual use of the oxygen separation membrane can be accurately grasped.

  If X-ray diffraction measurement is performed in a reducing atmosphere in this way, then X-ray diffraction measurement is performed in an air atmosphere for the oxygen separation membrane material to be measured. In order to obtain an air atmosphere during X-ray diffraction measurement, air may be present during X-ray diffraction measurement. For example, an air atmosphere can be obtained by supplying an atmospheric composition gas into the chamber 22 of the X-ray diffraction measurement apparatus. When supplying the atmospheric composition gas, the oxygen partial pressure in the chamber may be adjusted to be approximately 0.1 MPa or less (for example, about 0.02 MPa). Note that the order of performing the X-ray diffraction measurement is not limited to the above, and the X-ray diffraction measurement may be performed in a reducing atmosphere after the X-ray diffraction measurement is performed in an air atmosphere.

FIG. 2 shows an X-ray diffraction pattern when the oxygen separation membrane material is La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ . In FIG. 2, x1 is a diffraction pattern when exposed to 1000 ° C. in a reducing atmosphere (mixed gas atmosphere of hydrogen 5 (vol%) and nitrogen 95 (vol%)), and x2 is 1000 in an air atmosphere. It is a diffraction pattern when exposed to ℃. As shown in FIG. 2, in the diffraction pattern of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ , the (110) plane (112) in the diffraction angle range of 20 ° to 65 °. ), (202), (220), (310), and (204) planes. In any of these peaks, the peak position of the reducing atmosphere x1 is shifted to a lower angle side than the peak position of the air atmosphere x2.

The lattice constant under the reducing atmosphere in the reducing atmosphere of the material is obtained from the diffraction pattern x1 under the reducing atmosphere thus obtained. Further, the lattice constant under the air atmosphere in the air atmosphere of the material is obtained from the diffraction pattern x2 under the air atmosphere. The method for obtaining the lattice constant from the diffraction patterns x1 and x2 is not particularly limited as long as it is the same as that for calculating the lattice constant from the conventional diffraction pattern. For example, the lattice constant may be obtained by applying the Rietveld method to each diffraction pattern x1, x2. In this case, the lattice constant can be obtained accurately. Alternatively, when the crystal structure is a cubic crystal, the lattice constant is obtained from the peak position derived from the (hkl) plane of the diffraction pattern using the formula a = d × (h ² + k ² + l ² ) ^1/2. May be. Here, a: lattice constant, d = λ / (2 sin θ), λ: measurement X-ray wavelength, θ: Bragg angle (diffraction angle / 2). In this case, the lattice constant can be easily obtained.

Table 1 shows an example of lattice constants obtained by applying the Rietveld method to the diffraction patterns x1 and x2 in FIG. In this example, the crystal structure of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ is orthorhombic (space group: Pbnm62), and under a reducing atmosphere obtained from the diffraction pattern x1. The lattice constants are a ₁ = 5.6225 Å, b ₁ = 5.6074 Å, c ₁ = 7.9331 、, and the lattice constants in the air atmosphere obtained from the diffraction pattern x2 are a ₂ = 5.6070 Å, b ₂ = 5. 5907 cm, c ₂ = 7.9148 cm.

Based on the lattice constant (a ₁ , b ₁ , c ₁ ) under the reducing atmosphere and the lattice constant (a ₂ , b ₂ , c ₂ ) under the air atmosphere thus obtained, the reduction of the oxygen separation membrane material is performed. The expansion coefficient α is calculated. For example, the reduction expansion coefficient α may be calculated according to the following equation (1).

α = [(v ₁ −v ₂ ) / v ₂ ] × 100 (1)

Here, α: reduction expansion coefficient, v ₁ : crystal lattice volume under reducing atmosphere obtained from lattice constant (a ₁ , b ₁ , c ₁ ) under reducing atmosphere, v ₂ : lattice constant (a ₂ , under air atmosphere) b ₂ , c ₂ ) is the crystal lattice volume under air atmosphere. For example, when the crystal structure is orthorhombic, it is calculated from the crystal lattice volume v ₁ = a ₁ × b ₁ × c _{1 in} a reducing atmosphere, and from the crystal lattice volume v ₂ = a ₂ × b ₂ × c ₂ in an air atmosphere. Can be calculated. In the case of La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ , the crystal lattice volume v ₁ = 250.1 (Å ³ ) in a reducing atmosphere, and the crystal lattice volume v _{2 in} an air atmosphere = 248.1 (Å ³ ). Then, the reduction expansion coefficient α = 0.81 (%) can be calculated. In this way, based on the lattice constant (a ₁ , b ₁ , c ₁ ) under a reducing atmosphere and the lattice constant (a ₂ , b ₂ , c ₂ ) under an air atmosphere, the reductive expansion coefficient of the material for the oxygen separation membrane α can be calculated.

  The reduction expansion coefficient α thus obtained strictly reflects the minute expansion amount (dimensional change) generated in the order of crystal grains, so that the conventional TMA (reduction expansion from the expansion amount of the entire test piece). Compared with the method for calculating the coefficient, the reduction expansion coefficient can be obtained with higher accuracy. Moreover, since it is not necessary to produce a rod-shaped test piece as in the prior art, the reduction expansion coefficient can be easily measured. Furthermore, since measurement can be performed non-destructively using X-rays, it is not necessary to discard the oxygen separation membrane material after measurement. For this reason, such a method of measuring the reduction expansion coefficient can be easily incorporated into the manufacturing process of the oxygen separation membrane.

  Next, a method for manufacturing an oxygen separation membrane that actually includes the implementation of the above-described method for measuring the reduction expansion coefficient will be described.

As described above, the method disclosed herein uses a lattice constant (a ₁ , b ₁ , b) in a reducing atmosphere obtained by X-ray diffraction measurement in a reducing atmosphere for an oxygen separation membrane material used for an oxygen separation membrane. c ₁ ) and an inspection step of inspecting the material for the oxygen separation membrane based on the lattice constant (a ₂ , b ₂ , c ₂ ) in the air atmosphere obtained by the X-ray diffraction measurement in the air atmosphere The other conditions (method for synthesizing the oxygen separation membrane material and method for constructing the oxygen separation membrane using the oxygen separation membrane material as an element) are not particularly limited.

  For example, the shape (outer shape) of the oxygen separation membrane is not particularly limited. For example, a plate shape (including a flat shape, a spherical shape, etc.), a tubular shape (including an open tube with both ends open, a closed tube with one end open and the other closed), a honeycomb shape, or a combination thereof It can be set as a shape. For example, a plate-like or membrane-like material that can be suitably used for a fuel cell or GTL is an example of a particularly suitable shape. An oxygen separation membrane having a thickness of 10 mm or less, particularly 5 mm or less, and further 1 mm or less is preferable because high oxygen permeation performance is easily exhibited. By varying the oxygen partial pressure on both sides of the membrane, oxygen ions can be efficiently transmitted from one surface of the membrane to the other. The produced oxygen separation membrane is preferably dense and substantially impermeable to gas.

  The oxygen separation membrane material used in the manufacturing method disclosed herein is not particularly limited as long as it is the same as the oxygen separation membrane material used for the conventional oxygen separation membrane. In this embodiment, a composite oxide ceramic powder having a perovskite structure, which is an oxygen ion conductor, is used as a material for an oxygen separation membrane. Or you may employ | adopt the film-form material shape | molded from the said complex oxide ceramic powder.

  The oxide ceramic is not limited to a specific constituent element, but is preferably composed of an element that provides an excellent mixed conductor having both oxygen ion conductivity and electron conductivity. When the oxygen separation membrane material disclosed herein has mixed conductivity, one side of the oxygen separation membrane (the side to which the oxygen-containing gas is supplied) and the other side (oxygen ions that have passed through the oxygen separation membrane material) Oxygen ions are continuously permeated from one to the other without using an external electrode or an external circuit for short-circuiting the side that is oxidized as oxygen gas or the side that reacts with the supplied hydrocarbon gas) In addition, the oxygen ion permeation rate can be increased.

The oxide ceramics of this type, the general formula _(1): perovskite oxide having a composition represented by _{Ln 1-x A x MO 3} -δ is preferred. Here, Ln in the formula is at least one selected from lanthanoids (typically lanthanum (La)). A is one or more elements of strontium (Sr), barium (Ba), and calcium (Ca), and particularly preferably Sr. M is a metal element that can form a perovskite structure. For example, magnesium (Mg), manganese (Mn), gallium (Ga), titanium (Ti), cobalt (Co), 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).

  Further, “x” in the general formula (1) is a value indicating the ratio of Ln (typically La) replaced by A in this perovskite structure. The range that x can take is not particularly limited as long as the structure can be maintained without destroying the perovskite structure, but 0 ≦ x <1 is appropriate, and preferably 0.4 ≦ x ≦ 0.6. is there. Note that δ is a value determined so as to satisfy the charge neutrality condition. The number of oxygen atoms in the above general formula varies depending on the type of atom substituting a part of the perovskite structure, the substitution ratio, and other conditions, so that it is difficult to display accurately. For this reason, a positive number δ (0 <δ <1) not exceeding 1 is adopted as a value determined to satisfy the charge neutrality condition, and the number of oxygen atoms is displayed as 3-δ.

  As the perovskite oxide, a commercially available perovskite oxide prepared in advance with a predetermined composition can be used. Alternatively, an oxide containing a metal element constituting the perovskite oxide to be produced or a compound that can be converted into an oxide by heating (a carbonate, nitrate, sulfate, phosphate, acetate, oxalate of the metal atom) , Halides, hydroxides, oxyhalides, etc.) are blended at a blending ratio corresponding to the composition ratio of the perovskite type oxide, respectively, as a starting material (powder), and this is fired (calcined) What was obtained by doing so can also be used as a material for the oxygen separation membrane.

  Here, the oxygen separation membrane material (perovskite oxide) has a reducing atmosphere on the side through which oxygen ions permeate, so cracks occur even when used in such an atmosphere and in a high temperature range. There is a demand for reduction durability that is difficult to achieve. Such reduction durability easily varies depending on the ratio of the metal elements constituting the oxygen separation membrane material and the synthesis conditions (synthesis conditions such as the firing time and the firing temperature) when the oxygen separation membrane material is synthesized. It is desirable to inspect the reduction durability of the material in advance when manufacturing the separation membrane. However, in the inspection by the conventional TMA, it is necessary to produce a rod-shaped test piece for each inspection, which requires work time and labor. In addition, since the test piece after the inspection cannot be reused, the material on the millimeter order is wasted. Further, since sampling is performed for each lot, there is a problem that it cannot be confirmed whether each thin film has the required reduction durability.

  Therefore, in this configuration, first, reduction expansion using X-ray diffraction is performed on a ceramic material (perovskite oxide; typically formed into a powdery material or a film-like material) used for an oxygen separation membrane. The rate α is measured, and it is determined whether or not the ceramic material is a good product based on the measured reduction expansion rate α. And the oxygen separation membrane comprised using the ceramic material made into the quality goods in the determination is employ | adopted. For example, when a powdery material as the ceramic material is prepared and the reduction expansion coefficient of the material is measured, the powdery material that is determined to be non-defective in the above determination (in other words, a material that is determined to be defective) Oxygen separation membrane should be prepared.

  For example, according to the study of the present inventor, when the reduction expansion coefficient of a ceramic material (perovskite oxide) used for manufacturing exceeds about 0.60%, the reduction of the oxygen separation membrane constructed using the ceramic material It was found that leaks are likely to occur in the durability test. That is, it is considered that an oxygen separation membrane constructed using a ceramic material having a reductive expansion rate exceeding about 0.60% is likely to break down the membrane due to stress generated in a reducing atmosphere. In this case, for example, for a ceramic material used for manufacturing, the reduction expansion coefficient α is measured using X-ray diffraction, and the ceramic material is determined to be non-defective when the measured reduction expansion coefficient is 0.50% or less. When the reductive expansion coefficient exceeds 0.50%, the ceramic material is good. And it is good to employ | adopt the oxygen separation membrane using only the ceramic material made into the quality goods in the determination.

  The method for constructing the oxygen separation membrane using the ceramic material is not particularly limited, and various conventionally known methods can be employed. As a preferred example, first, a ceramic material powder composed of the perovskite oxide is mixed with an appropriate binder, a dispersant, a plasticizer, a solvent, etc. to prepare a slurry, and a granulator such as a spray dryer is used. Granulate to a desired particle size (for example, an average particle size of 10 μm to 100 μm). Next, the obtained granulated powder is pressure-molded by using a conventionally known molding method such as uniaxial compression molding, isostatic pressing (CIP) or other press molding to form a molded body having a predetermined shape. Then, the obtained molded body is fired at an appropriate temperature, and the obtained sintered body is processed (for example, mechanically polished), so that the film thickness is, for example, 5 mm or less, preferably 1 mm or less. A thin-film oxygen separation membrane can be manufactured.

If necessary, a catalyst on the surface of an oxygen separation membrane (for example, including a thin plate-like oxygen separation material) can be attached to improve oxygen separation performance and / or oxidation reactivity with oxygen ions. For example, a structure in which a catalyst for promoting permeation of oxygen ions is attached to the surface of the oxygen separation membrane on the air feeding side (hereinafter referred to as “air side”) can be employed. As such an oxygen ion permeable catalyst, (La _x Sr _1-x ) M′O ₃ (provided that 0.1 ≦ x <1), and M ′ is one or more selected from Co, Cu, Fe, and Mn. And the like are preferably used. Such an oxygen separation membrane containing an oxygen ion promoting catalyst can be preferably used in an oxygen separation device, an oxidation reaction device (for example, a hydrocarbon partial oxidation reaction device) for oxidizing various gases to be oxidized, or the like. .

  On the other side of the oxygen separation membrane, that is, the surface of the side where the permeated oxygen ions are oxidized with the target gas (for example, a fuel gas such as methane) (hereinafter referred to as “reaction side”), an oxidation reaction is performed. It can be set as the structure which the catalyst to promote adheres. Such oxidation reaction promoting catalysts include the group consisting of Ni, Rh, Ag, Au, Bi, Mn, V, Pt, Pd, Ru, Cu, Zn, Co, Cr, Fe, In-Pr mixture and In-Sn mixture. A conventionally known oxidation catalyst and / or dehydrogenation catalyst such as a compound containing at least one metal selected from the group consisting of metal oxides and / or metal oxides can be used. Among these, a nickel catalyst or a rhodium catalyst can be preferably used.

  The method of attaching the above catalyst to the surface of the oxygen separation membrane is not particularly limited. For example, a slurry containing catalyst powder is prepared, and the slurry is applied to the surface of an oxygen separation membrane (dense sintered body) and dried to adhere (coating) the target catalyst. Thereafter, the adhered catalyst powder may be further baked to be supported on the surface of the oxygen separation membrane. It should be noted that the method for providing the oxygen ion permeation promoting catalyst or the oxidation reaction promoting catalyst itself may be any conventionally known method and does not particularly characterize the present invention, and therefore will not be described in further detail.

  According to the manufacturing method of the present embodiment, the reductive expansion coefficient of the oxygen separation membrane material is measured by X-ray diffraction, and it is determined whether or not the material is a non-defective product based on the measured reductive expansion coefficient. Since an oxygen separation membrane using a material determined to be non-defective in the determination is adopted, a high-quality oxygen separation membrane satisfying a desired reduction durability can be efficiently provided. Further, since non-destructive inspection can be performed using X-rays, it is not necessary to perform sampling extraction for each lot as in the prior art, and includes a previously manufactured membrane material (produced as an oxygen separation membrane). ) All inspections (reduction durability evaluation). Therefore, it is possible to reduce the cost by discarding only defective products and to manufacture a highly reliable oxygen separation membrane.

  EXAMPLES Examples relating to the present invention will be described below, but the present invention is not intended to be limited to those shown in the following examples.

<Measurement of reduction expansion coefficient using X-ray diffraction>
Five types of perovskite oxide ceramic powders (see Table 2 below) having different compositions were prepared as oxygen separation membrane material powders, and powder X-ray diffraction measurements were performed in a reducing atmosphere. Specifically, a sample (perovskite oxide ceramic powder) accommodated in the chamber of the X-ray diffraction measurement apparatus was heated to 1000 ° C. Under such temperature conditions, a mixed gas of hydrogen (4 vol%) and nitrogen (96 vol%) is supplied into the chamber at a flow rate of about 100 mL / min, and the oxygen partial pressure in the chamber is adjusted to 10 ⁻²⁴ MPa. did. Then, the lattice constant (a ₁ , b ₁ , c ₁ ) under a reducing atmosphere was derived by applying the Rietveld method to the obtained diffraction pattern. As the X-ray diffraction measurement conditions, Rigaku RINT2000 was used (CuKα (wavelength 0.154 nm) was used for the X-ray source), step width 0.02 ° in the range of 2θ = 20 ° to 70 °, step Time was set to 2s.

Further, powder X-ray diffraction measurement was performed on each of the five types of perovskite oxide ceramic powders in an air atmosphere. Specifically, a sample (perovskite oxide ceramic powder) accommodated in the chamber of the X-ray diffraction measurement apparatus was heated to 1000 ° C. Under such temperature conditions, the air composition gas was supplied into the chamber at a flow rate of about 100 mL / min, and the oxygen partial pressure in the chamber was adjusted to 0.02 MPa. The lattice constant (a ₂ , b ₂ , c ₂ ) was derived under the air atmosphere by applying the Rietveld method to the obtained X-ray diffraction pattern. The five types of perovskite oxide ceramic powders used were orthorhombic and the space group was Pbnm62. As an example, an X-ray diffraction pattern in the case of using La _0.6 Sr _0.4 Ti _0.1 Fe _0.9 O _3-δ is shown in FIG. In FIG. 2, x1 is a diffraction pattern under a reducing atmosphere, and x2 is a diffraction pattern under an air atmosphere. Table 1 shows the lattice constants (a ₁ , b ₁ , c ₁ ) under the reducing atmosphere and the lattice constants (a ₂ , b ₂ , c ₂ ) under the air atmosphere derived from the diffraction patterns x 1 and x ₂ . The X-ray diffraction measurement conditions under the air atmosphere were set to the same conditions as those under the reducing atmosphere described above except that the air composition gas was introduced into the chamber.

From the obtained lattice constant (a ₁ , b ₁ , c ₁ ) under the reducing atmosphere and the lattice constant (a ₂ , b ₂ , c ₂ ) under the air atmosphere, the reduction expansion coefficient α is calculated according to the above-described equation (1). did. The results are shown in Table 2. As shown in Table 2, the reduction expansion coefficients of the five types of perovskite oxide ceramic powders used were different from each other.

<Measurement of reduction expansion coefficient using TMA>
For reference, the thermal expansion coefficient (average value between room temperature (25 ° C.) and 1000 ° C.) based on the differential expansion method (TMA) was measured for the five types of perovskite oxide ceramic powders described above. . Here, the reductive expansion coefficient by TMA is the coefficient of thermal expansion (%) in a reducing atmosphere between 25 ° C. and 1000 ° C. (in a mixed gas atmosphere of hydrogen (5 vol%) and nitrogen (95 vol%)). _red is a value obtained from the following equation, where E _air is the coefficient of thermal expansion (%) in air (atmosphere).

Reduction expansion rate (%) by TMA = [{(1 + E _red / 100) − (1 + E _air / 100)} / (1 + E _air / 100)] × 100

<Production of oxygen separation membrane>
An appropriate amount of a general binder and a solvent (water) are mixed with the perovskite oxide ceramic powder described above to prepare a slurry, which is then formed into particles having a particle size of about 50 μm using a granulator such as a spray dryer. Grained. 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 4 mm. The obtained press-molded body was fired at about 1400 ° C. in the atmosphere for 6 hours, thereby firing the above-mentioned molded body. Thus, a sintered body according to this example was obtained.

<Manufacture of modules and evaluation of reduction durability>
A reduction durability evaluation module 50 shown in FIG. 3 was produced using the disk-shaped sintered body obtained as described above. That is, the disk-shaped sintered body was mechanically polished to prepare an oxygen separation membrane (diameter 30 mm) 30 having a thickness of 0.5 mm. Next, one surface (reaction side) surface 30a of the obtained oxygen separation membrane 30 was coated with Ni oxide as an oxygen reaction promoting catalyst. Further, the other surface (air side) surface 30b was coated with LaSrCo oxide as an oxygen ion permeation promoting catalyst.

Then, as schematically shown in FIG. 3, the catalyst-attached oxygen separation membrane 30 is set so that one side 30a is on the reaction side (upper side in the figure) and the other side is on the air side (lower side in the figure). The alumina tube 32 made of alumina on the reaction (fuel) side and the alumina tube 34 made of air on the air side were disposed. The contact portion between the alumina cylindrical tubes 32 and 34 and the oxygen separation membrane 30 was sealed with a glass-based sealing member 35. The reaction side and air side alumina cylindrical tubes 32 and 34 are respectively provided with an alumina inner tube 36 for supplying fuel gas (here, CH ₄ gas) and an alumina inner tube 38 for supplying air (Air). Was installed. A heater 40 was installed outside the alumina cylindrical tubes 32 and 34.

  In the module 50 constructed as described above, the inside was heated to about 1000 ° C. by the heater 40. First, a mixed gas (5% hydrogen + 95% nitrogen) was introduced from the alumina inner tube 36 on the reaction side to reduce the Ni oxide. Subsequently, pure methane gas was introduced from the alumina inner pipe 36 at a rate of 10 mL / min to 200 mL / min, and air was introduced from the air side alumina inner pipe 38 at a rate of 10 mL / min to 500 mL / min. This test was performed continuously for 3 to 10 hours. During this time, the synthesis gas released from the alumina cylindrical tube 32 on the reaction side was measured by a gas chromatograph, and the amount of nitrogen contained in the synthesis gas was measured from the composition measurement by the gas chromatograph. Then, the ratio of the amount of nitrogen contained in the entire synthesis gas was defined as a leak rate (%), and the reduction durability of the oxygen separation membrane was evaluated. Here, 3 to 10 hours has a leak rate of 1% or less, good (◯), 3 hours or less leak rate is more than 1%, and 3% or less is suitable (Δ), 3 hours or less leak rate A value exceeding 3% was regarded as inappropriate (x). The leak rate was 1% or less before the methane gas flow. In other words, this reflects the increase in the leak rate as the film breaks down due to reducing stress.

  The results are shown in the corresponding column of Table 2. As is clear from this result, it was confirmed that there was a certain correlation between the reduction expansion coefficient and reduction durability obtained in this example. Specifically, it was confirmed that the reduction durability of the membrane improves as the reduction expansion coefficient of the oxygen separation membrane material decreases. In particular, when the reduction expansion coefficient was 0.50% or less, the gas leak was 1% or less, and high reduction durability was obtained. From this result, it was confirmed that when the reduction durability of the material for oxygen separation membrane is inspected by applying the present invention, about 0.50% should be used as the threshold value for determining the quality of the material.

  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.

  For example, in the above-described example, the case where the oxygen separation membrane material is powdered and X-ray diffraction measurement is performed is illustrated, but the present invention is not limited to this. For example, the material powder may be formed into a film (typically after an oxygen separation membrane is constructed), and X-ray diffraction measurement may be performed on the membrane. In this case, since it can be measured in the same form as the actual use form (oxygen separation membrane), a more accurate reduction expansion coefficient can be obtained.

Further, the reduction expansion coefficient obtained by the present invention may be any one that can be an index for relatively evaluating the reduction durability of the oxygen separation membrane material, and various modifications are possible. For example, in the above-described example, the crystal structure of the oxygen separation membrane material (perovskite oxide ceramics) is orthorhombic, and the reduction expansion coefficient α is calculated from the volume change of the crystal lattice using the above-described equation (1). Although the case was illustrated, it is not limited to this. For example, when the oxygen separation membrane material exhibits isotropic or anisotropic reductive expansion, the reductive expansion coefficient α ′ = [(a ₁ −a ₂ ) / from the uniaxial dimension (length) change of the lattice constant. a ₂ ] × 100 may be calculated. Here, a _{1 is} the length of one side of the predetermined axis of the lattice constant under a reducing atmosphere, and a ₂ is the length of one side of the predetermined axis of the lattice constant under an air atmosphere. Even in this case, an index for relatively evaluating the reduction durability of the oxygen separation membrane material can be obtained.

  As one form of the oxygen separation membrane produced according to the present invention, this composite oxide ceramic (oxygen separation) is provided on at least one surface side of an oxygen separation membrane made of a composite oxide ceramic having a perovskite structure which is an oxygen ion conductor. It is good also as a structure provided with the porous support body which supports a film | membrane mechanically.

DESCRIPTION OF SYMBOLS 10 X-ray generation source 12 Inspection device 14 X-ray 16 Sample 16a Sample surface 18 X-ray 20 X-ray diffraction measuring device 22 Chamber 24 Heating device 26 Reducing gas 30 Oxygen separation membrane 32, 34 Alumina cylindrical tube 35 Glass-based seal member 36, 38 Alumina inner tube 40 Heater 50 Reduction durability evaluation module

Claims (7)

A method for measuring the reduction expansion coefficient of an oxygen separation membrane material,
A step of performing X-ray diffraction measurement in a reducing atmosphere for a material to be measured to obtain a lattice constant in a reducing atmosphere in the reducing atmosphere of the material;
Performing an X-ray diffraction measurement on the material in an air atmosphere to obtain a lattice constant under the air atmosphere of the material in an air atmosphere;
A reduction expansion coefficient measuring method including a step of calculating a reduction expansion coefficient of the material based on the obtained lattice constant under a reducing atmosphere and the lattice constant under an air atmosphere.   The method of measuring a reduction expansion coefficient according to claim 1, wherein the X-ray diffraction measurement is performed with the material in a powder form or a film form.   The reducing expansion coefficient measuring method according to claim 1, wherein a reducing gas atmosphere containing at least hydrogen is formed as the reducing atmosphere. A method for producing an oxygen separation membrane, comprising:
Preparing an oxygen separation membrane material and measuring the reductive expansion coefficient of the material by the method according to claim 1;
Determining whether the material is non-defective based on the measured reduction expansion rate; and
A method for manufacturing an oxygen separation membrane, comprising adopting an oxygen separation membrane configured using a material that has been determined to be good in the determination.   The manufacturing method according to claim 4, wherein in the determination, the material is determined to be non-defective when the reduction expansion coefficient of the material is 0.50% or less.   6. The manufacturing method according to claim 4, wherein the material for the oxygen separation membrane is a material made of an oxide ceramic having a perovskite structure which is an oxygen ion conductor.   A method for inspecting an oxygen separation membrane, wherein the reduction expansion coefficient of the oxygen separation membrane is measured by the method according to any one of claims 1 to 3, and the reduction of the oxygen separation membrane is performed based on the obtained reduction expansion coefficient. A method for inspecting an oxygen separation membrane, characterized by inspecting durability.

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