JP2011016684A - Oxygen deficit perovskite-type metal oxide excellent in oxygen storage capability, exhaust gas purifying catalyst and functional ceramic containing the metal oxide, and method and apparatus using the metal oxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive and practical metal oxide which has sufficient oxygen diffusion ability and oxygen non-stoichiometric property at 500°C or less, is excellent in chemical stability in an high temperature region in the vicinity of 600°C, and has an oxygen storage capability excellent as materials for an exhaust gas purifying catalyst, an oxygen storage material, an oxygen separator, an oxygen remover, an oxygen selector, an oxygen enricher, etc.SOLUTION: The oxygen deficit perovskite-type oxide is represented by formula (1), and is excellent in an oxygen storage capability which is characterized by being operated in a low temperature region of 500°C or less. Formula (1) is expressed by (BaA)B(MnC)O, wherein A is one kind or two kinds or more of alkaline earth metals except Ba, B is one kind or two kinds or more of Y, rare earth elements and Ca, C is one kind or two kinds of Fe and Co, x is 0≤x≤1.0, y is 0≤y≤2.0, and δ is 0≤δ≤1.0.

Description

  The present invention relates to an exhaust gas purifying catalyst, an oxygen-deficient perovskite-type metal oxide having excellent oxygen storage capacity that can be used in an oxygen separation device, an oxygen removal device, an oxygen selection device, an oxygen enrichment device, etc. It is about use.

  In recent years, functional materials called oxygen storage materials have attracted attention. Oxygen storage material is a substance that absorbs and releases a large amount of oxygen reversibly and is expected to be applied to catalysts for purifying automobile exhaust gas, oxygen separators, oxygen removers, oxygen selectors, oxygen enrichers, etc. Has been.

  The oxygen storage material includes (i) high oxygen diffusivity for selectively transporting oxygen ions at high speed, and (ii) large oxygen non-stoichiometry for realizing absorption and release of a large amount of oxygen gas. Is required.

Currently, as an oxygen storage material, for example, CeO ₂ —ZrO ₂ (CZ) (see Patent Document 1), Ln ₂ O ₂ SO ₄ —Ln ₂ O ₂ S (Patent Document 2 and Non-Patent Documents 1 to 4, See). CeO ₂ —ZrO ₂ (hereinafter sometimes simply referred to as “CZ”) has already been widely put into practical use as an exhaust gas purification catalyst (see Non-Patent Documents 5 to 7).

  When nitrogen oxides (NOx), carbon monoxide (CO), and hydrocarbons (HC) in the exhaust gas burn, the oxygen storage material absorbs or releases the required amount of oxygen and is optimal for combustion. Since the concentration is realized, it is considered that the purification efficiency is improved.

  The performance of the oxygen storage material is evaluated by an index of “oxygen storage capacity” (= Oxygen Storage Capacity = OSC). OSC is a value indicating the amount of absorbed oxygen per unit material amount.

In the case of CZ, the oxygen absorption / release phenomenon is manifested by a change in the valence of cerium (Ce ³⁺ ⇔Ce ⁴⁺ ). The theoretical value of CZ OSC (oxygen storage capacity) is 2.8 wt% from the following formula.

Ce _0.5 Zr _0.5 O _1.75 +1/8 O ₂ = Ce _0.5 Zr _0.5 O ₂
However, in actuality, the OSC of CZ is about 2.2 wt% (see Non-Patent Document 7), which is not necessarily a sufficient value, so the OSC exceeds the OSC of CZ (= 2.8 wt%), In addition, an oxygen storage material that is cheaper than CZ (not including an expensive element as a constituent) is demanded.

Ln ₂ O ₂ SO ₄ -Ln ₂ O ₂ S has an extremely high OSC of 18.7 wt%, and is an oxygen storage material characterized by this point. However, (a) the operating temperature (600 ° C.-) can be lowered. However, the operation is possible only in a high temperature region, and (b) S is evaporated gradually and loses its activity, so that it has problems such as poor cycle characteristics.

  Therefore, at present, a novel oxygen storage material having a high OSC and a wide operating temperature range is expected.

In addition to the above oxides, as an oxygen storage material, Patent Document 3 _discloses A _j B _k C _m D _n O _{7 + δ} (A: one or more of trivalent rare earth elements and Ca, B: alkaline earth. One or more of similar metal elements, C, D: One or more of oxygen tetracoordinate elements, at least one of which is a transition metal element, provided that j> 0 and k> 0, respectively. M ≧ 0, n ≧ 0, j + k + m + n = 6, and 0 <δ ≦ 1.5.).

Among the above oxides, YBaCo ₄ O _{7 + δ} has a sufficient oxygen storage capacity, operates at 400 ° C. or less, and has a large response to changes in oxygen partial pressure, and thus is an effective substance as a practical material. However, YBaCo ₄ O _{7 + δ} is not necessarily an optimum substance as an exhaust gas purification catalyst that is chemically unstable in a high temperature range and the material may be exposed to a high temperature.

  In any case, at 500 ° C. or lower, sufficient oxygen diffusivity and oxygen non-stoichiometry, and excellent chemical stability in a high temperature region near 600 ° C., an exhaust gas purification catalyst, an oxygen storage material, The appearance of an inexpensive and practical metal oxide has been awaited as it has excellent oxygen storage capacity as a material for oxygen separators, oxygen removers, oxygen selectors, oxygen enrichers, and the like.

JP 2005-119949 A JP 2008-284512 A International Patent Publication WO2007 / 004681

Yasuyuki Sakamoto et al., R & D Review of Toyota CRDL 37, 14 (2002) M. Machida et al., Chem. Commun. 662 (2004) M. Machida et al., Chem. Mater. 17, 1487 (2004) K. Ikeue et al., J. Catalysis 248, 46 (2007) M. Ozawa et al., J. Alloys and Compd. 193, 73 (1993) Y. Nagai et al., Catalysis Today 74, 225 (2002) “Cerium is interesting now” (Tea I Sea Publishing, 2005)

  In view of the above demand, the present invention has a sufficient oxygen diffusivity and oxygen non-stoichiometry at 500 ° C. or lower, and is excellent in chemical stability in a high temperature region around 600 ° C. It is an object of the present invention to provide a metal oxide that has an excellent oxygen storage ability as a material for storage materials, oxygen separation devices, oxygen removal devices, oxygen selection devices, oxygen enrichment devices, etc., and that is inexpensive and practical. Furthermore, this invention makes it a subject to provide the method and apparatus which utilize effectively the metal oxide which has the outstanding oxygen storage ability.

The inventors diligently searched for metal oxides whose oxygen storage capacity exceeds that of CeO ₂ —ZrO ₂ (CZ) and YBaCo ₄ O _{7 + δ} . As a result, it has been found that the oxygen-deficient perovskite metal oxide BaYMn ₂ O _{5 + δ} has an excellent oxygen storage capacity and operates in a low temperature range of 500 ° C. or lower.

  This invention was made | formed based on the said knowledge, and the summary is as follows.

  (1) An oxygen-deficient perovskite-type metal oxide excellent in oxygen storage capacity, which is represented by the following formula (1) and operates in a low temperature range of 500 ° C. or less.

(Ba _1−x A _x ) B (Mn _2−y C _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ba
B: One or more of Y, rare earth elements, and Ca
C: One or two of Fe and Co
x: 0 ≦ x ≦ 1.0
y: 0 ≦ y ≦ 2.0
δ: 0 ≦ δ ≦ 1.0
(2) The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity as described in (1) above, wherein A is Sr and 0 ≦ x ≦ 0.5.

  (3) The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity as described in (1) or (2) above, wherein B is Y.

  (4) The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to any one of (1) to (3), wherein B is one or more rare earth elements.

  (5) The oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of (1) to (4), wherein B is Ca.

  (6) Said C is 1 type or 2 types of Fe and Co, and said y is 0 <= y <= 1.0, Any one of said (1)-(5) characterized by the above-mentioned An oxygen-deficient perovskite metal oxide with excellent oxygen storage capacity.

  (7) An exhaust gas purifying catalyst comprising the oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to any one of (1) to (6).

  (8) A functional ceramic comprising the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of (1) to (6).

  (9) A method for storing and / or separating oxygen using the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of (1) to (6), wherein oxygen changes A method for storing and / or separating oxygen, characterized in that the amount of oxygen is stored and / or separated in a range of more than 0 and not more than 21.4% with respect to the total molar amount of oxygen in the metal oxide.

  (10) An oxidation reaction comprising the oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to any one of (1) to (6), and performing an oxidation reaction using the stored oxygen apparatus.

  (11) The oxygen-deficient perovskite metal oxide having an excellent oxygen storage capacity according to any one of the above (1) to (6) is provided, and heating is performed using warm heat generated by oxygen storage and / or separation. A heating device characterized by that.

  (12) The oxygen-deficient perovskite metal oxide having an excellent oxygen storage capacity according to any one of (1) to (6) is provided, and unnecessary inert gas and oxygen gas existing in the container are removed. An oxygen removing device.

Oxygen deficiency perovskite-type metal oxide of the present invention _{(Ba 1-x A x)} B (Mn 2-y C y) O 5 + δ (A: 1 or an alkaline earth metal other than Ba or two or more, B : Y, rare earth element and one or more of Ca, C: one or two of Fe and Co, δ: 0 ≦ δ ≦ 1.0) is 500 ° C. or less and a large amount of oxygen Therefore, it is an optimum material for exhaust gas purification catalysts and functional ceramics for high-performance oxygen storage and oxygen selective membranes.

Further, the oxygen deficient perovskite type metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} of the present invention is utilized by utilizing the high-speed absorption / release characteristics of oxygen. If applied to an oxygen separator or the like, it is possible to reduce the size of the apparatus and save energy compared to the case of using a conventional oxygen absorbing / releasing material.

Furthermore, since the oxygen-deficient perovskite metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} of the present invention does not contain expensive rare metal Ce, it contains expensive rare metal Ce. It is promising as a practical material to replace CZ.

Precursor BaYMn ₂ O _{5 +} δ and X-ray diffraction pattern of (YMnO mixture of ₃ and BaMnO _3-x) (top) illustrates the BaYMn ₂ O _{5 +} δ X-ray diffraction pattern (bottom). X-ray diffraction pattern of BaYMn ₂ O _{5 + δ} (bottom X-ray diffraction pattern in FIG. 1) (top) and X of BaYMn ₂ O _{5 + δ} subjected to heat treatment (in an oxygen stream at 600 ° C. for 12 hours) It is a figure which shows a line diffraction pattern (lower). Synthesis BaYMn ₂ O _{5 +} δ X-ray diffraction pattern and O processing BaYMn ₂ O _{5 +} δ X-ray diffraction pattern (Fig. 2, reference) is a graph showing changes in relative intensities and positions of the diffraction peak at. Is a graph showing changes in the crystal structure of BaYMn ₂ O 5 ₊ δ by oxygen absorption. (A) shows the crystal structure (P4 / nmm) of the synthetic BaYMn ₂ O _{5 + δ} (δ≈0), and (b) shows the O-treated BaYMn ₂ O _{5 + δ} (δ≈1) that has absorbed oxygen. Shows the crystal structure (monoclinic P2). [Delta] in BaYMn ₂ O 5 _{+ δ} is, 0 → at 1 → 0 and changing process, which is a diagram illustrating how the relative intensity and position of the X-ray diffraction pattern is how to change. The BaYMn ₂ O _{5 + δ,} in an oxygen stream, and a diagram showing the weight change rate when given heat history at 5% H ₂ in -95% N ₂ mixed gas flow. Thermogravimetric analysis results (weight change rate) performed by alternately switching the gas atmosphere to an oxygen atmosphere and a mixed gas atmosphere of 5% H ₂ -95% N ₂ while fixing the temperature of the gas atmosphere to 500 ° C. FIG. After that, a 5% H ₂ mixed gas atmosphere of -95% N ₂ is a graph showing changes in weight change (increase) rate immediately after switching to an oxygen atmosphere. Is a diagram showing an X-ray diffraction pattern of BaYMn ₂ O 5 ₊ δ in the thermal gravimetric analysis before and after after repeated oxygen absorbing and desorbing. It is a figure which shows the one aspect | mode of the sample-synthesis experiment which implements an oxygen getter simultaneous sealed tube method.

First, regarding the method for producing the oxygen-deficient perovskite type metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} of the present invention, x = 0, y = 0, and B = Y. explain.

Y ₂ O ₃ , BaCO ₃ , and Mn ₂ O ₃ were used as starting materials, and these were mixed so that Ba: Y: Mn = 1: 1: 2. The mixed powder was calcined at 1000 ° C. for 12 hours in a nitrogen stream to prepare a precursor (mixture of YMnO ₃ and BaMnO _3-x ). The mixture was pulverized in an agate mortar, pressed, and formed into a tablet shape (about 0.1 g).

  Four compacts were put into an alumina crucible, and the alumina crucible and an alumina crucible containing an oxygen getter agent (for example, 0.4 g of FeO of equal weight) were sealed in a quartz tube, and the mixture was sealed at 1100 ° C. for 24 hours. Firing was performed (see FIG. 10). This method is hereinafter sometimes referred to as “oxygen getter simultaneous sealing method”. After firing, the quartz tube was put into ice water and quenched.

Since the equilibrium partial pressure of oxygen at 1100 ° C is 10 ^-11 atm,
6FeO + O ₂ = 2Fe ₃ O ₄
Thus, a single-phase BaYMn ₂ O _{5 + δ in} which the oxygen amount (5 + δ) is adjusted to an appropriate amount can be produced.

The formation of single phase BaYMn ₂ O _{5 + δ} was confirmed by X-ray diffraction. 1, the precursor of BaYMn ₂ O _{5 +} δ and X-ray diffraction pattern of (YMnO mixture of ₃ and BaMnO _{3-x) (upper), BaYMn 2 O 5 + δ} (δ ≒ 0, P4 / nmm, a = 5.548 Å, c = 7.655 Å) (bottom).

From X-ray diffraction pattern of BaYMn ₂ O _{5 +} δ, oxygen getter simultaneously sealed tube method, it is found that it was able to synthesize BaYMn ₂ O _{5 +} δ single phase.

The oxygen amount (5 + δ) of BaYMn ₂ O _{5 + δ} can be inferred from a known X-ray diffraction pattern and confirmed to match the δ value obtained from FIGS. 6 and 7 described later.

Next, a confirmation test for confirming that the synthesized single phase BaYMn ₂ O _{5 + δ} (hereinafter sometimes referred to as “synthetic BYMO”) is a substance having excellent oxygen storage characteristics will be described.

  In order to control the oxygen amount of the synthesized single-phase synthetic BYMO, the synthetic BYMO was subjected to heat treatment at 600 ° C. for 12 hours in an oxygen stream.

FIG. 2 shows an X-ray diffraction pattern (below) of BaYMn ₂ O _{5 + δ} (hereinafter sometimes referred to as “O-treated BYMO”) that has absorbed oxygen by heat treatment, and an X-ray diffraction pattern (of FIG. 1) of synthetic BYMO. It is shown together with (lower X-ray diffraction pattern) (upper).

  The X-ray diffraction pattern of O-treated BYMO shows the X-ray diffraction pattern when δ≈1, and monoclinic crystal P2, a = 5.522５, b = 5.517Å, c = 7.608Å, and β = Assuming a 90.33 ° unit cell, the diffraction peaks could be indexed.

  In FIG. 2, the X-ray diffraction pattern of the synthetic BYMO and the X-ray diffraction pattern of the O-treated BYMO are similar, but the relative intensity and position of the diffraction peak are changed. This change is shown in FIG. It can be seen that the relative intensity and position of the [202] diffraction beak, the [220] diffraction beak, and the ([004] + [221] + [203]) diffraction beak change.

  That is, as shown in FIG. 4, by a heat treatment in an oxygen stream, a synthetic BYMO (δ≈0) (see (a) in the figure) having a crystal structure of P4 / nmm absorbs oxygen, thereby obtaining a basic skeleton structure. Remained unchanged, and changed to O-treated BYMO (δ≈1) of monoclinic crystal P2 (see (b) in the figure).

Next, the present inventors performed a reduction heat treatment at 500 ° C. in a mixed gas stream of 5% H ₂ -95% N _{2 on} O-treated BYMO (δ≈1) that has absorbed oxygen, and obtained an X-ray diffraction pattern. It was measured.

As a result, the X-ray diffraction pattern of BaYMn ₂ O _{5 + δ} obtained by reducing the O-treated BYMO (δ≈1) is almost the same as the X-ray diffraction pattern of the synthetic BYMO (δ≈0). It was found that the treated BYMO (δ≈1) returned to the crystal structure (P4 / nmm) of the original synthetic BYMO (δ≈0) by the reduction heat treatment.

FIG. 5 shows how the relative intensity and position of the X-ray diffraction pattern changed in the process of changing _δ in BaYMn ₂ O _{5 + δ} from 0 → 1 → 0. In the drawing, the upper X-ray diffraction pattern is an X-ray diffraction pattern of synthetic BYMO (δ≈0), and the lower X-ray diffraction pattern is an X of BaYMn ₂ O _{5 + δ} (δ≈0) after reduction treatment. It is a line diffraction pattern.

In order to further investigate the oxygen absorption / release (oxygen storage) characteristics of BaYMn ₂ O _{5 + δ} , the present inventors added BaYMn ₂ O _{5 + δ} to an oxygen stream and 5% H ₂ −95% N. _The required thermal history was given in the mixed gas stream ₂ and thermogravimetric analysis was performed using a thermobalance. The result is shown in FIG. The weight change is indicated on the vertical axis as a weight change (increase or decrease) rate ΔW (%).

BaYMn ₂ O _{5 + δ} (δ≈0) was heated in an oxygen stream to 600 ° C. at a heating rate of 1 ° C./min. The substance weight began to increase from around 200 ° C. and was saturated at 390 ° C. (oxygen absorption completion temperature) (see the temperature rise line in FIG. 6). The increase in the substance weight is due to a change in the amount of oxygen (δ), that is, absorption of oxygen. The weight increase rate ΔW (%) is 3.75% (see FIG. 6).

The weight increase rate “3.75%” corresponds to δ≈0.97, which substantially coincides with ΔW (%) = 3.85% expected when δ = 1. Further, “3.75%” is a value that greatly exceeds the oxygen storage capacity (OSC) “2.8%” of CeO ₂ —ZrO ₂ .

Thereafter, BaYMn ₂ O _{5 + δ} (δ≈0.97) was cooled in an oxygen stream. The substance weight was almost constant (see the cooling line (b) in FIG. 6).

Subsequently, BaYMn ₂ O _{5 + δ} (δ≈0.97) was heated to 600 ° C. at a heating rate of 1 ° C./min in a mixed gas stream of 5% H ₂ -95% N ₂ . The substance weight began to decrease from around 200 ° C. and was saturated at 490 ° C. (oxygen release completion temperature) (see the temperature rise line in FIG. 6 (c)). During the cooling process from 600 ° C., the weight of the substance was almost constant, and the weight after cooling coincided with the weight before thermogravimetric analysis (see the cooling line (d) in FIG. 6).

The decrease in the weight of the substance is due to a change in the amount of oxygen (δ), that is, the release of oxygen, and the fact that the weight after cooling matched the weight before thermogravimetric analysis was 5% H ₂ −95% N in the reduction heat treatment in a mixed gas flow of _{2, BaYMn 2 O 5 + δ} (δ ≒ 0.97) , all the absorbed oxygen released, returns to the original _{BaYMn 2 O 5 + δ (δ} ≒ 0) It shows that.

The present inventors have confirmed that the X-ray diffraction patterns of BaYMn ₂ O _{5 + δ} match before and after thermogravimetric analysis.

BaYMn ₂ O _{5 + δ} is a substance that exhibits an oxygen absorption / release phenomenon in a low temperature range of 200 to 500 ° C.

From the above, the BaYMn ₂ O _{5 + δ,} in a practical temperature range, greatly exceeds the oxygen storage capacity of the CeO ₂ -ZrO _2, it can be seen that a substance with excellent oxygen storage capacity.

The inventors further investigated the weight change of BaYMn ₂ O _{5 + δ} , that is, the reversibility and rapidity of oxygen absorption / release. The reversibility and rapidity of oxygen absorption / release are important as functional ceramics for oxygen storage or oxygen selective membranes.

The inventors fixed the temperature of the gas atmosphere at 500 ° C., slightly exceeding the oxygen release completion temperature of 490 ° C. of BaYMn ₂ O _{5 + δ} (δ≈1). The thermogravimetric analysis was performed using a thermobalance by alternately switching to a mixed gas atmosphere of H ₂ -95% N ₂ . The result is shown in FIG.

From FIG. 7, the weight of BaYMn ₂ O _{5 + δ} (δ≈1) immediately increases in an oxygen atmosphere, and immediately decreases when the gas atmosphere is switched to a mixed gas atmosphere of 5% H ₂ -95% N _2. I understand what to do. The weight change rate ΔW (%) by switching the gas atmosphere is 3.75 to 3.80%, and ΔW (%) expected to be BaYMn ₂ O _{5 + δ} (δ = 1) = 3.85%. It almost agreed. This means that BaYMn ₂ O _{5 + δ} has excellent reversibility in the oxygen absorption / release phenomenon.

6 and 7 that BaYMn ₂ O _{5 + δ} has oxygen absorption / release (oxygen storage) characteristics. This is the knowledge forming the basis of the present invention.

Also, what should be noted in the oxygen absorption / release phenomenon of BaYMn ₂ O _{5 + δ} is that the rate of weight increase, that is, the oxygen absorption rate is extremely high.

FIG. 8 shows a change in the weight change (increase) rate immediately after switching the mixed gas atmosphere of 5% H ₂ -95% N ₂ to the oxygen atmosphere. FIG. 8 shows that the weight increase rate reaches the saturation value in about 10 seconds immediately after switching the mixed gas atmosphere of 5% H ₂ -95% N ₂ to the oxygen atmosphere. FIG. 8 shows the temperature change of BaYMn ₂ O _{5 + δ} accompanying oxygen absorption / release. The temperature rise to 600 ° C. during oxygen absorption is due to an oxidation reaction caused by oxygen absorption. It is considered that the temperature rise to 550 ° C. during oxygen release is due to the heat of combustion of hydrogen.

The inventors measured the X-ray diffraction pattern of BaYMn ₂ O _{5 + δ} before and after thermogravimetric analysis in order to confirm whether or not phase decomposition occurred in the process of repeating oxygen absorption / release. The result is shown in FIG. In FIG. 9, the upper is an X-ray diffraction pattern of synthetic BYMO, and the lower is an X-ray diffraction pattern of BaYMn ₂ O _{5 + δ} (δ≈0) after repeating oxygen absorption / release three times. It can be seen from FIG. 9 that phase decomposition does not occur in the process of repeating oxygen absorption / release.

BaYMn ₂ O _{5 + δ} is an oxygen absorption / release phenomenon that is excellent in reversibility and rapidly expressed, and is a phenomenon that has not been known so far. BaYMn ₂ O _{5 + δ} is used for oxygen storage or oxygen selective membranes. It is shown to be useful as a practical functional ceramic.

Although the oxygen storage capacity of BaYMn ₂ O _{5 + δ} has been described above, the oxygen-deficient perovskite metal oxide of the present invention is not limited to BaYMn ₂ O _{5 + δ} . The oxygen-deficient perovskite metal oxide of the present invention is a metal oxide represented by the following formula (1).

(Ba _1−x A _x ) B (Mn _2−y C _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ba
B: One or more of Y, rare earth elements, and Ca
C: One or two of Fe and Co
x: 0 ≦ x ≦ 1.0
y: 0 ≦ y ≦ 2.0
δ: 0 ≦ δ ≦ 1.0

  Since a plurality of elements can be dissolved in the Ba site, Ba may be substituted with one or more of alkaline earth metals other than Ba. The amount of substitution can be 0 to 1.0 (total amount) by atomic ratio. The alkaline earth metal other than Ba is preferably Sr. The substitution amount x is preferably 0 to 0.5 containing a large amount of Ba that promotes the formation of the layered structure.

  A plurality of elements can be dissolved in the B site. B is one or more of Y, rare earth elements, and Ca. B is preferably Y, and the rare earth element is preferably La or Yb. Ca with a small ion radius can also enter the B site.

  A plurality of elements can be dissolved in the Mn site. Mn can be substituted with one or two of transition metals Fe and Co in the same manner as Mn. The total amount of Mn may be substituted with one or two of Fe and Co. Therefore, although the substitution amount y is 0 to 2.0 in terms of atomic ratio, 0 to 1.0 is preferable because the oxygen storage capacity improves as the amount of Mn increases.

  The oxygen amount δ is 0 to 1.0. When δ is 0, it corresponds to a composition having only a skeleton structure that does not contain excess oxygen. When δ is 1.0, this corresponds to a composition in which all oxygen deficient sites in the perovskite crystal structure are filled. Therefore, the oxygen amount δ is freely changed in the range of 0 to 1.0.

In addition to BaYMn ₂ O _{5 + δ} , preferred element combinations include BaLaMn ₂ O _{5 + δ} , BaYbMn ₂ O _{5 + δ} , Ba (Y, La) Mn ₂ O _{5 + δ} , Ba (Yb, Y, La) Mention may be made of Mn ₂ O _{5 + δ} . Also, (Ba, Sr) YMn ₂ O _{5 + δ} , Ba (Y, Ca) Mn ₂ O _{5 + δ} , (Ba, Sr) (Y, Ca) Mn ₂ O _{5 + δ} , BaY (Mn, Fe) ₂ O _{5 + δ} , BaY (Mn, Co) ₂ O _{5 + δ} , BaYFe ₂ O _{5 + δ} , and BaYCo ₂ O _{5 + δ} are also preferable element combinations.

  The oxygen absorption / release amount of the oxygen-deficient perovskite metal oxide of the present invention can be controlled usually at 0 to 1 atm. In the above metal oxide, oxygen gas at 1 atm is sufficient to make δ = 1.

  Next, examples of the present invention will be described. The conditions adopted in the examples are one example of conditions used for confirming the feasibility and effects of the present invention, and the present invention is an example of this one condition. It is not limited to. The present invention can adopt various conditions as long as the object of the present invention is achieved without departing from the gist of the present invention.

Example 1
(1-1) BaYMn ₂ O _{5 + δ} was synthesized by an oxygen getter simultaneous sealing method using BaCO ₃ , Y ₂ O ₃ and Mn ₂ O ₃ as raw materials. BaCO ₃ , Y ₂ O ₃ , and Mn ₂ O ₃ powders were mixed so that Ba: Y: Mn = 1: 1: 2, and the mixed powder was 1000 ° C. for 12 hours in a nitrogen stream. And calcining to prepare a precursor (mixture of YMnO ₃ and BaMnO _3-x ). The precursor was pulverized in an agate mortar and then pressed to form a tablet shape (about 0.1 g).

  As shown in FIG. 10, an alumina crucible 3a containing four compact samples 1 and an alumina crucible 3b containing 0.4 g of FeO (oxygen getter agent) 2 (equal weight to four compact samples) Quartz rods 5 were arranged at both ends as spacers and sealed in 11 mmφ quartz tubes 4 (oxygen getter simultaneous sealing method). The enclosed quartz tube 4 was heated at 1100 ° C. for 24 hours. After heating, the quartz tube was put into ice water and quenched.

It was confirmed by an X-ray diffraction method that the molded body sample taken out of the quartz tube (hereinafter referred to as “synthetic sample”) was single-phase BaYMn ₂ O _{5 + δ} (see FIG. 1). The amount of oxygen (5 + δ) was estimated as δ≈0 from a known X-ray diffraction pattern. The crystal structure was P4 / nmm, and the lattice constants were a = 5.548Å and c = 7.655Å.

(1-2) The synthesized sample was heat-treated at 600 ° C. in an oxygen stream to adjust the amount of oxygen. A sample subjected to heat treatment in an oxygen stream (hereinafter referred to as “O ₂ -treated sample”) was subjected to phase identification and structural analysis by an X-ray diffraction method.

The X-ray diffraction pattern of the O ₂ -treated sample resembles that of the synthetic sample, but the relative intensity and position of the diffraction peaks changed (see FIG. 2). The X-ray diffraction pattern of the O ₂ -treated sample coincides with the X-ray diffraction pattern of δ≈1.0, and the crystal structure is monoclinic P2, a = 5.522Å, b = 5.517Å, c = 7 It was possible to index by assuming a unit cell of .608 cm, β = 90.33 °.

(1-3) Subsequently, a reduction heat treatment was performed on an O ₂ treated sample with δ≈1.0 at 500 ° C. in a mixed gas stream of 5% H ₂ -95% N ₂ . Phase identification and structural analysis were performed by X-ray diffractometry on a sample heat treated in a mixed gas stream of 5% H ₂ -95% N ₂ (hereinafter referred to as “5% H ₂ -treated sample”). . The X-ray diffraction pattern of the 5% H ₂ -treated sample was almost the same as the X-ray diffraction pattern of the synthetic sample (see FIG. 5), and it was confirmed that δ returned to the original δ≈0.

(Example 2)
(2-1) In order to investigate the oxygen absorption / release characteristics of BaYMn ₂ O _{5 + δ} , thermogravimetric analysis was performed in an oxygen stream and in a mixed gas stream of 5% H ₂ -95% Ar. The sample of δ≈0 was heated up to 600 ° C. in an oxygen stream at 1 ° C./min.

The sample weight started to increase from around 200 ° C. and was saturated at 390 ° C. or higher. This increase in weight is thought to be due to a change in the amount of oxygen. The weight increase rate is 3.75%, and this value corresponds to the oxygen amount change Δδ = 0.97 of BaYMn ₂ O _{5 + δ} , and the expected weight increase rate is 3.85% (Δδ = 1. 0). In the subsequent cooling process in the oxygen stream, the sample weight was almost constant (see FIG. 6).

(2-2) Subsequently, the sample of δ≈1.0 was heated to 600 ° C. at 1 ° C./min in a mixed gas stream of 5% H ₂ -95% Ar. A weight decrease (a phenomenon corresponding to oxygen release) was observed from around 200 ° C., and the sample weight was saturated at 490 ° C. or higher (see FIG. 6). The sample weight after cooling from 600 ° C. completely coincided with that before thermogravimetric analysis, and it was confirmed that all absorbed oxygen was released and returned to the original sample of δ≈0. Note that the X-ray diffraction patterns before and after thermogravimetric analysis almost completely matched.

(Example 3)
(3-1) The thermogravimetric analysis was performed while the temperature was fixed at 500 ° C. and the gas atmosphere was alternately switched between O ₂ and 5% H ₂ -95% Ar. The sample weight immediately increased in the oxygen stream and immediately decreased in the mixed gas stream of 5% H ₂ -95% Ar (see FIG. 7). The amount of weight change almost coincided with the OSC value “3.85 wt%” of BaYMn ₂ O _{5 + δ} . Moreover, this weight change has shown the outstanding reversibility with respect to gas atmosphere.

The rate of weight increase, that is, the oxygen absorption rate was extremely fast, and the sample weight was saturated in about 10 seconds after switching to oxygen gas (see FIG. 8). It can be seen that the BaYMn ₂ O _{5 + δ of the} present invention has an excellent oxygen absorption capacity.

(3-2) The X-ray diffraction pattern of the sample after thermogravimetric analysis shows almost the same X-ray diffraction pattern as that of the sample before thermogravimetric analysis, which is accompanied by phase decomposition during the oxygen absorption / release phenomenon. It was confirmed that there was no (see FIG. 9). That is, it was confirmed that the basic skeleton of BaYMn ₂ O _{5 + δ} was unchanged even after a series of procedures, and only oxygen absorption / release phenomenon occurred.

As described above, the oxygen-deficient perovskite metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} (A: one of the alkaline earth metals other than Ba or 2 or more, B: Y, rare earth elements, and one or more of Ca, C: one or two of Fe and Co, δ: 0 ≦ δ ≦ 1.0) is 500 ° C. or less Therefore, since it has a remarkable thermogravimetric change characteristic of absorbing and releasing a large amount of oxygen at a high speed, it is an optimum material as an exhaust gas purification catalyst and a functional ceramic for high performance oxygen storage and oxygen selective membrane.

Further, the oxygen deficient perovskite type metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} of the present invention is utilized by utilizing the high-speed absorption / release characteristics of oxygen. If applied to an oxygen separator or the like, it is possible to reduce the size of the apparatus and save energy compared to the case of using a conventional oxygen absorbing / releasing material.

Furthermore, since the oxygen-deficient perovskite metal oxide (Ba _1-x A _x ) B (Mn _2−y C _y ) O _{5 + δ} of the present invention does not contain expensive rare metal Ce, it contains expensive rare metal Ce. It is promising as a practical material to replace CZ. Therefore, the present invention has great industrial applicability.

1 Molded body (sample)
2 FeO (oxygen getter agent)
3a, 3b Alumina crucible 4 Quartz tube 5 Quartz rod

Claims (12)

An oxygen-deficient perovskite-type metal oxide excellent in oxygen storage capacity, which is represented by the following formula (1) and operates in a low temperature range of 500 ° C. or less.
(Ba _1−x A _x ) B (Mn _2−y C _y ) O _{5 + δ} (1)
Here, A: one or more of alkaline earth metals other than Ba
B: One or more of Y, rare earth elements, and Ca
C: One or two of Fe and Co
x: 0 ≦ x ≦ 1.0
y: 0 ≦ y ≦ 2.0
δ: 0 ≦ δ ≦ 1.0   2. The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to claim 1, wherein A is Sr and 0 ≦ x ≦ 0.5.   The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to claim 1 or 2, wherein B is Y.   The oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 3, wherein B is one or more rare earth elements.   The oxygen-deficient perovskite metal oxide having excellent oxygen storage capacity according to any one of claims 1 to 4, wherein B is Ca.   The oxygen storage capacity according to any one of claims 1 to 5, wherein the C is one or two of Fe and Co, and the y is 0 ≦ y ≦ 1.0. Excellent oxygen-deficient perovskite metal oxide.   An exhaust gas purifying catalyst comprising the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6.   A functional ceramic comprising the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6.   A method for storing and / or separating oxygen using the oxygen-deficient perovskite-type metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6, wherein the amount of oxygen change is An oxygen storage / separation method characterized by storing and / or separating oxygen in a range of more than 0 to 21.4% or less with respect to the total amount of oxygen in the metal oxide.   An oxidation reaction apparatus comprising the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6 and performing an oxidation reaction using stored oxygen.   It comprises the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6, and is heated using heat generated by storage and / or separation of oxygen, Heating device.   It comprises the oxygen-deficient perovskite metal oxide excellent in oxygen storage capacity according to any one of claims 1 to 6, and is characterized by removing unnecessary inert gas and oxygen gas present in the container. To remove oxygen.