Oxygen storage material, method for manufacturing oxygen storage material, and method for adsorption and desorption of oxygen

Abstract

To provide an oxygen storage material, a method for adsorbing and desorbing oxygen, and a method for manufacturing an oxygen storage material, which can repeatedly and efficiently adsorb and release oxygen reversibly in response to temperature changes. [Solution] A single-phase Cmcm space group P'2 orthorhombic layered oxide structure is provided, and the composition is Na x Mn 1-y M y It contains O2, and element M is at least one selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, and W, and in the above composition, 0.40

Description

Technical Field

[0001] The present disclosure relates to an oxygen storage material, a method for producing the oxygen storage material, and a method for adsorbing and desorbing oxygen.

Background Art

[0002] Oxygen storage materials that retain oxygen within their structures have attracted attention. Among these, materials having oxygen storage capacity capable of storing and releasing oxygen in accordance with fluctuations in oxygen concentration and fluctuations in atmospheric temperature, for example, are expected to be useful for various applications such as recovering and storing oxygen from nitrogen oxides that are problematic in automobile exhaust gas, and producing oxygen gas by selectively adsorbing oxygen in the air.

[0003] Various oxygen storage materials that selectively adsorb and retain oxygen have been studied. For example, as an exhaust gas purification catalyst, an oxygen storage material in which a ceria-zirconia composite oxide is supported on zirconia particles has been proposed (see Patent Document 1). Furthermore, the present inventors have disclosed that a P2 orthorhombic layered bronze crystal structure in the Cmcm space group having a specific crystal structure, which is a sodium transition metal-based cathode material suitable for a rechargeable sodium battery, and has the composition Na x M y Mn 1-y O2, wherein 0.60 < x < 0.95, M is one or more elements selected from the group consisting of Cu, Zn, and Ni, and 0 < y < 0.20 (see Patent Document 2).

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problem to be Solved by the Invention

[0005] While various materials that selectively adsorb and retain oxygen have been investigated, there is a need for oxygen storage materials that efficiently perform reversible oxygen adsorption and release. However, the oxygen storage material described in Patent Document 1 is for use as a catalyst for exhaust gas purification, has a particle size on the nanoscale, is difficult to handle when used for other applications, and its initial oxygen retention capacity and oxygen re-adsorption capacity after release are not good enough to be applied to applications other than catalysts. Furthermore, it has the problem of requiring expensive metal materials and having a complex manufacturing process. Furthermore, the P2 orthorhombic layered bronze crystal structure described in Patent Document 2 is useful as a sodium transition metal-based cathode material, and the resulting rechargeable sodium battery exhibits good cycle characteristics. However, Patent Document 2 does not focus on the oxygen adsorption and release capabilities of the material.

[0006] The object of one embodiment of this disclosure is to provide an oxygen storage material and an oxygen adsorption / desorption method that can repeatedly and efficiently adsorb and release oxygen reversibly in response to temperature changes. The object of other embodiments of this disclosure is to provide a method for manufacturing an oxygen storage material that can efficiently perform reversible oxygen adsorption and release in response to temperature changes. [Means for solving the problem]

[0007] The means for solving the above problems include the following embodiments. <1> It has a single-phase Cmcm space group P'2 orthorhombic layered oxide structure, and its composition is Na x Mn 1-y M y It contains O2, and the element M is Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe , which is at least one selected from the group consisting of Co, Ni, Cu, Zn, Nb, Mo and W, wherein in said composition, 0.40<x<0.95 and 0≤y<0.20, and the amount of oxygen adsorbed / desorbed obtained from the oxygen adsorption step and the oxygen desorption step is 1.0% to 5.0% relative to the total mass of the oxygen storage material. The oxygen storage material. <2> The oxygen storage material according to <1>, wherein said M is at least one selected from the group consisting of Sc, Ti, Co, Fe and Cu. <3> The oxygen storage material according to <1> or <2>, wherein the average particle diameter is in the range of 3 μm to 12 μm. <4> When the P'2 orthorhombic layered oxide in said oxygen storage material is measured by X-ray powder diffraction using Cu-Kα radiation as an X-ray source, a diffraction peak intensity ratio R is provided between the maximum peak value at 15.5°±1.5° and the maximum peak value at 37.5°±1.5°, Said R is defined as R=I2 / I1, wherein I1 is the diffraction intensity of the maximum peak at 18.5°±1.5°, and I2 is the diffraction intensity of the maximum peak at 43.5°±1.5°, The oxygen storage material according to any one of <1> to <3>, wherein R≥0.02.

[0008] <5> a step of preparing at least one manganese compound selected from the group consisting of Mn(OH)2, MnOOH, Mn2O3, MnO2 and MnCO3; a step of preparing at least one sodium compound selected from NaOH and Na2CO3; a step of mixing said stoichiometric amount of the manganese compound with said sodium compound in an excess amount of 1% to 5% relative to the stoichiometry; a step of heating the obtained mixture to 1000°C or higher in an oxygen-containing atmosphere; a step of cooling the heated mixture to obtain a single-phase P'2 orthorhombic layered oxide belonging to space group Cmcm. A method for producing an oxygen storage material, comprising the step of: <6> The step of cooling the heated mixture includes at least one of the following: cooling in an oxygen-containing atmosphere at a cooling rate exceeding 50°C / min, and cooling in an oxygen-free atmosphere. <5> A method for producing an oxygen storage material as described above. <7> The process further includes a step of preparing at least one compound selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates, which contains at least one element M selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, and W. The step of mixing with the sodium compound involves mixing a stoichiometric amount of the manganese compound and a compound containing a stoichiometric amount of element M with the sodium compound in an excess of 1% to 5% relative to the stoichiometric amount. <5> or <6> A method for producing an oxygen storage material as described above.

[0009] <8> The heating step includes heating at a heating rate of 3°C / min to 8°C / min until a temperature A of 700°C to 900°C is reached, and then heating at a heating rate of 0.5°C / min to 1.5°C / min until the temperature exceeds 1000°C. <5> ~ <7> A method for producing an oxygen storage material as described in any one of the following. <9> The step of cooling the heated mixture includes cooling at a cooling rate of 100°C / min to 200°C / min. <5> ~ <8> A method for producing an oxygen storage material as described in any one of the following. <10> <1> ~ <4> A method for adsorbing and desorbing oxygen, comprising heating an oxygen storage material described in any one of the above to adsorb oxygen, and cooling it to release oxygen. [Effects of the Invention]

[0010] According to one embodiment of the present disclosure, an oxygen storage material and an oxygen adsorption / desorption method are provided that can repeatedly and efficiently adsorb and release oxygen in a reversible manner. According to other embodiments of this disclosure, a method for producing an oxygen storage material is provided that can efficiently perform reversible adsorption and release of oxygen. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a graph showing the results of measuring the amount of oxygen absorbed by heating and cooling in one embodiment of the oxygen storage material of the present disclosure having a P'2 orthorhombic layered oxide structure. [Figure 2] Figure 2 is a graph showing the XRD measurement results of the oxygen storage materials for Example 1 and Comparative Example 1. [Figure 3] Figure 3 is a graph showing the XRD measurement results of the oxygen storage materials in Example 1 and Example 2. [Figure 4] Figure 4 is a graph showing the measurement results of the particle size distribution of the oxygen storage material in Example 1. [Figure 5] Figure 5 is a graph showing the temperature change of the oxygen storage material in Example 1 under an atmospheric environment, and the amount of oxygen adsorbed and released in response to the temperature change. [Figure 6] Figure 6 is a graph showing the amount of gas adsorption and release corresponding to temperature changes when the oxygen storage material from Example 1 is subjected to an argon atmosphere as a control example, under the same conditions as the temperature change in the atmosphere in Example 1. [Figure 7] Figure 7 is a graph showing the measurement results of the particle size distribution of the oxygen storage material in Example 2. [Figure 8] Figure 8 is a graph showing the temperature change of the oxygen storage material in Example 2 under an atmospheric environment, and the amount of oxygen adsorbed and released in response to the temperature change. [Figure 9] Figure 9 is a graph showing the measured particle size distribution of the Na2 / 3MnO2 crystal of Comparative Example 1. [Figure 10] Figure 10 is a graph showing the XRD measurement results of the oxygen storage materials for Examples 3 to 10. [Modes for carrying out the invention]

[0012] Hereinafter, modes for carrying out embodiments of the present disclosure will be described in detail. However, embodiments of the present disclosure are not limited to the following embodiments. In the following embodiments, the constituent elements (including element steps and the like) are not essential unless explicitly stated. The same applies to numerical values and their ranges, which do not limit the embodiments of the present disclosure.

[0013] In the present disclosure, the term referring to a process includes not only a process independent of other processes, but also a process even if it cannot be clearly distinguished from other processes, as long as the object of the process is achieved. In the present disclosure, the numerical range indicated by using "~" includes the numerical values described before and after "~" as the minimum value and the maximum value, respectively. In the numerical ranges described stepwise in the present disclosure, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical ranges described in other stepwise descriptions. In addition, in the numerical ranges described in the present disclosure, the upper limit or lower limit of the numerical range may be replaced with the values shown in the examples.

[0014] <Oxygen Storage Material> In one aspect of the present disclosure, the oxygen storage material of the present disclosure has a single-phase P'2 orthorhombic layered oxide structure of Cmcm space group, and has the composition Na x Mn 1-y M y O2, wherein the element M is at least one selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo and W, in the composition, 0.40 < x < 0.95 and 0 ≤ y < 0.20, and the amount of oxygen adsorption / desorption obtained from oxygen adsorption and oxygen release is 1.0% to 5.0% based on the total mass of the oxygen storage material.

[0015] The oxygen storage material of the present disclosure has a single-phase P'2 orthorhombic layered oxide structure in the Cmcm space group. Since the oxygen storage material is a single-phase P'2 orthorhombic layered oxide with a distorted entire lattice, it absorbs oxygen accompanying a structural change occurring at a specific temperature to form a P2 hexagonal layered oxide. It is considered that this results in good oxygen storage capacity, a fast absorption rate, and enables repeated and efficient absorption and release of oxygen.

[0016] The oxygen storage material of the present disclosure has a composition of Na x Mn 1-y M y O2, and when y=0, the composition is Na x MnO2, which is an unsubstituted product that does not contain the element M. The composition of Na x MnO2 is a first embodiment of the oxygen storage material of the present disclosure, and is an embodiment that does not contain any elements other than Na and Mn. In the composition, x satisfies 0.40<x<0.95, and 0.60<x<0.90 is preferable. As Na x MnO2, examples include Na 2 / 3 MnO2, Na 3 / 4 MnO2, Na 5 / 6 MnO2, and the like. In the present disclosure, as an embodiment, attention has been focused on Na 2 / 3 MnO2 having a stable single-phase orthorhombic layered oxide structure. Conventional oxygen storage materials often essentially contain rare metals, but it has been confirmed that in the oxygen storage material of the present disclosure, a material having excellent oxygen absorption and release capacity can be obtained from Na and Zn depending on production conditions. In addition, Patent Document 2 relates to a sodium cathode material, for which doping with specific divalent metal ions is considered essential for the purpose of improving rate performance and the like. However, the oxygen storage material of the present disclosure aims to improve the performance of oxygen absorption and release, and in particular, the presence of elements other than Na and Mn is not essential, and the material may be an unsubstituted product.

[0017] The oxygen storage material of the present disclosure may further contain an element M other than Na and Mn, in addition to Na and Mn. That is, depending on the purpose, in addition to the above composition, a composition Na further comprising at least one element M selected from the group consisting of Fe, Cu, Ti, Zn, and Co x Mn 1-y M y can be O2.

[0018] A second embodiment of the oxygen storage material of the present disclosure has a composition Na x Mn 1-y M y O2, wherein in the composition, 0.40 < x < 0.95. Further, by satisfying 0 < y < 0.20, the second embodiment further includes the element M in the composition. The element M is at least one selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo and W; from the viewpoint of effects, the element M is preferably at least one selected from the group consisting of Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo and W, more preferably at least one selected from the group consisting of Sc, Ti, Co, Fe and Cu, and still more preferably Fe. The content of the element M is preferably lower than that of Mn, and an embodiment not containing the element M, that is, the first embodiment described above may be employed. From such a viewpoint, y satisfies 0 ≤ y < 0.20, preferably 0 ≤ y < 0.15, and more preferably 0 ≤ y ≤ 0.10.

[0019] Including the element M other than Na and Mn in the composition of the oxygen storage material has advantages such as reducing production cost and enabling particle size control.

[0020] In each of the above compositions, Na is located in the sodium layer of the crystal structure, Mn and M are located in the non-sodium metal layer, and x is about 2 / 3, or preferably more than 2 / 3.

[0021] The oxygen storage material of this disclosure is a particle having the above-described crystalline structure and composition. In one embodiment, the average particle diameter of the oxygen storage material is preferably in the range of 3 μm to 12 μm, and more preferably in the range of 4 μm to 8 μm. The particle size of oxygen storage materials can be measured, for example, using a laser diffraction / scattering particle size distribution analyzer. In this disclosure, the average particle size is obtained using a volume-based particle size distribution analyzer (Partica mini LA-350) manufactured by Horiba, Ltd. The values ​​are based on measurements taken using deionized water as the dispersion medium, with the refractive index of the deionized water set to 1.30 and the refractive index of the sample set to 1.66.

[0022] The oxygen storage material of this disclosure has an oxygen adsorption and desorption amount of 1.0% to 5.0% of the total mass of the oxygen storage material, preferably 1.5% to 4.5%, and more preferably 2.2% to 3.5%. Figure 1 is a graph showing the results of measuring the amount of oxygen absorbed by heating and cooling in one embodiment of the oxygen storage material of this disclosure having a P'2 orthorhombic layered oxide structure. The absorption reaction described above is the following reaction: Na 2 / 3 MnO2 + 1 / 10*O2 ⇒ Na 2 / 3 MnO 2.2 As shown in Figure 1, the oxygen storage capacity is 3.3%, indicating that the oxygen storage capacity is higher than that of conventionally known oxygen storage materials. Furthermore, the graph shown in Figure 1 indicates that the amount of oxygen absorbed changes with heating and cooling, and from the evaluation of each example described later, it can be seen that the oxygen absorbent material of this disclosure reversibly adsorbs and releases oxygen in response to temperature changes.

[0023] The oxygen storage material of this disclosure preferably contains a high-purity single-phase Cmcm space group P'2 orthorhombic layered oxide, with as little P2 hexagonal layered oxide present as possible. The purity of the P'2 orthorhombic layered oxide can be measured by the powder X-ray diffraction method described in detail below. It is preferable that the amount of P2 hexagonal layered oxide detected by the powder X-ray diffraction method be as small as possible, and more preferably that there be no contamination at all. Note that "no contamination" includes trace amounts of contamination that do not impair the effects of this disclosure, for example, a state in which P2 hexagonal layered oxide is present as an unavoidable impurity.

[0024] One preferred embodiment of the oxygen storage material of the present disclosure is one in which, when the P'2 orthorhombic layered oxide of the oxygen storage material is measured by X-ray powder diffraction using Cu-Kα rays as the X-ray source, there is a diffraction peak intensity ratio R between the maximum peak value at 15.5°±1.5° and the maximum peak value at 37.5°±1.5°, and R≧0.02. The diffraction peak intensity ratio R is expressed as R = I2 / I1, where I1 is the diffraction intensity of the maximum peak at 18.5°±1.5° and I2 is the diffraction intensity of the maximum peak at 43.5°±1.5°. Figure 2 shows the results of measuring the oxygen storage material of Example 1 and the oxygen storage material of Comparative Example 1, described later, by X-ray powder diffraction using Cu-Kα rays as the X-ray source. The oxygen storage material of Example 1 contains P'2 orthorhombic layered oxide, so R as defined by the formula above is 0.33. On the other hand, the oxygen storage material of Comparative Example 1 does not contain P'2 orthorhombic layered oxide, but contains P2 hexagonal layered oxide, so R is 0.017, and it can be seen that it does not satisfy the preferred specification.

[0025] <Method of oxygen absorption and desorption> The oxygen adsorption / desorption method of this disclosure includes heating to adsorb oxygen and cooling to release oxygen. The oxygen storage material of this disclosure is capable of reversible oxygen adsorption and desorption, adsorbing oxygen upon heating and releasing oxygen upon cooling. Therefore, the oxygen storage agent of this disclosure can be suitably used in oxygen adsorption and desorption methods that include heating to adsorb oxygen and cooling to release oxygen.

[0026] The oxygen storage material of the present disclosure can be easily obtained by the method for producing an oxygen storage material of the present disclosure described later.

[0027] <Method for Producing Oxygen Storage Material> The method for producing an oxygen storage material of the present disclosure comprises: a step of preparing at least one manganese compound selected from the group consisting of Mn(OH)₂, MnOOH, Mn₂O₃, MnO₂, and MnCO₃; a step of preparing at least one sodium compound selected from NaOH and Na₂CO₃; a step of mixing said stoichiometric amount of the manganese compound with 1% to 5% excess of said sodium compound relative to the stoichiometric amount; a step of heating the obtained mixture to 1000°C or higher in an oxygen-containing atmosphere; and a step of cooling the heated mixture to obtain a single-phase P'2 orthorhombic layered oxide of Cmcm space group. According to said production method, the oxygen storage material has a single-phase P'2 orthorhombic layered oxide structure of Cmcm space group and has a composition Na x Mn 1-y M y O₂, wherein the element M is at least one selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo and W, and in the composition, 0.40<x<0.95 and 0≤y<0.20. The oxygen storage material of the present disclosure described above can be easily obtained. According to studies by the present inventors, it has been confirmed that P'2 orthorhombic layered oxides containing each element M can be obtained by replacing the raw materials containing the element M with FeO₂, MgO, Al₂O₃, Sc₂O₃, TiO₂, CoO, Cu₂O, and ZnO respectively.

[0028] It is preferable that the step of cooling the mixture after heating includes at least one of a step of cooling at a cooling rate exceeding 50°C / min in an oxygen-containing atmosphere and a step of cooling in an oxygen-free atmosphere, because this makes the purity of the obtained single-phase P'2 orthorhombic layered oxide of Cmcm space group higher.

[0029] According to the method for producing oxygen storage materials of this disclosure, a high-purity single-phase P'2 orthorhombic layered oxide of the Cmcm space group can be obtained. Here, high purity refers to a state in which the main component of the obtained crystal is P'2 orthorhombic layered oxide, with as little P'2 hexagonal layered oxide present as possible. The purity of the P'2 orthorhombic layered oxide can be measured by the powder X-ray diffraction method described in detail below. It is preferable that the amount of P2 hexagonal layered oxide detected by the powder X-ray diffraction method be as small as possible, and more preferably that there be no contamination at all. Note that "no contamination" includes trace amounts of contamination that do not impair the effects of this disclosure, for example, a state in which P2 hexagonal layered oxide is present as an unavoidable impurity.

[0030] Here, the oxygen storage material produced is a composition containing the element M mentioned earlier, Na x Mn 1-y M y In the case of a compound containing O2, the method for producing the oxygen storage material of the present disclosure further includes the step of preparing at least one compound selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates, which contains at least one element M selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, and W, and the step of mixing with the sodium compound is the step of mixing a stoichiometric amount of the manganese compound and a compound containing element M with the sodium compound in an excess amount of 1% to 5% relative to the stoichiometric amount.

[0031] In this case, if the oxygen storage material contains element M, it is preferable that in the step of preparing a compound containing element M, the compound containing element M is at least one compound selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates. Note that the hydroxide may be an oxyhydroxide, and the carbonate may be an oxycarbonate. The sodium compound is preferably at least one of NaOH and Na2CO3.

[0032] A more preferable combination is when the manganese compound is Mn2O3 and the sodium compound is Na2CO3. The compound containing the element M preferably includes at least one compound selected from the group consisting of Fe2O3 as an iron-containing compound, Cu2O as a copper-containing compound, and ZnO as a zinc-containing compound.

[0033] In the method for producing an oxygen storage material according to the present disclosure, the heating step is preferably characterized by heating at a heating rate of 3°C / min to 8°C / min until a temperature A of 700°C to 900°C is reached, and then heating at a heating rate of 0.5°C / min to 1.5°C / min until the temperature exceeds 1000°C after reaching temperature A, from the viewpoint of controlling the crystal structure.

[0034] Furthermore, if the cooling process is carried out in an oxygen-containing atmosphere, it is preferable to perform the cooling at a rate exceeding 50°C / min, and cooling at a rate of 100°C / min to 200°C / min is more preferable from the viewpoint of controlling the crystal structure.

[0035] According to the method for producing the oxygen storage material described above, an oxygen storage material with good oxygen absorption and release capabilities can be easily obtained. [Examples]

[0036] The embodiments of the present disclosure will now be described in detail with reference to examples, but the embodiments of the present disclosure are not limited to these examples.

[0037] (Example 1: Na 2 / 3 Preparation of MnO2) Na2CO3 powder and Mn2O3 powder were prepared, and a mixture was created. The Na2CO3 powder and Mn2O3 powder were mixed in an amount such that the amount of Na contained in each compound was 67% to 1% in excess of Mn in molar ratio. The resulting mixture was heated in air to a maximum temperature of 1050°C. The heating rate was 5°C / min until the temperature reached 900°C, and then 1°C / min from 900°C to 1050°C. After heating, the sample is rapidly cooled to room temperature at a rate of 200°C / min and immediately transferred to an argon-filled glove box to obtain crystalline Na. 2 / 3 MnO2 was obtained. The obtained Na 2 / 3 Analysis of the MnO2 crystal using powder X-ray diffraction (XRD) revealed that it is a P'2 orthorhombic layered oxide. For the XRD measurements, a Rigaku SmartLab equipped with a high-speed one-dimensional semiconductor detector (D / teX Ultra 250) was used for powder X-ray diffraction, and measurements were performed using a Bragg-Brentano optical system. A Cu tube (CuK, 1.5418 Å) was used as the X-ray source, and a Ni filter was used to remove K-rays. Figure 3 shows the XRD measurement results for the oxygen storage material of Example 1. In Figure 3, the graph labeled Me=Mn in the lower section shows the measurement results for the oxygen storage material of Example 1.

[0038] The oxygen storage material obtained in Example 1 (Na 2 / 3 The average particle size of the MnO2 crystal was measured using the measurement method described below. Specifically, a volume-based particle size distribution was obtained using a laser diffraction / scattering particle size distribution analyzer (Particle Size Distribution: Partica mini LA-350) manufactured by Horiba, Ltd. Ion-exchanged water was used as the dispersion medium, with a refractive index of 1.30 for the ion-exchanged water and 1.66 for the sample. The measurement results of the particle size distribution are shown in Figure 4. The measurement results showed that the average particle size was 54 μm.

[0039] (Performance evaluation) The Na obtained in Example 1 2 / 3 MnO2 crystals were analyzed under atmospheric conditions using a thermogravimeter-differential thermal analyzer (TG-DTA). TG-DTA was measured using Shimadzu Corporation's DTG-60 / 60H. An alumina sample container was used to obtain crystalline Na. 2 / 3 MnO2 was measured by placing several mg to several tens of mg of the sample into a sample container. TG-GTA measurement involves heating from room temperature to 700°C and then cooling down to 300°C at a heating rate and cooling rate of 5°C / min, repeating this process five times. 2 / 3 The absorption and release of oxygen were calculated from the mass change of the MnO2 crystal. The results are shown in Table 1 and Figure 4. Table 1 shows the material composition, the mass changes after the first and fifth cycles, and the mass change rate after five cycles of heating and cooling. Figure 5 is a graph showing the temperature change of the oxygen storage material in Example 1 under an atmospheric atmosphere, and the amount of oxygen adsorbed and released in response to the temperature change. As is clear from Figure 5, the oxygen storage material in Example 1 is Na 2 / 3 It was found that the MnO2 crystal could absorb and desorb 2.6% of oxygen, and this effect was maintained even after five repetitions.

[0040] [Table 1]

[0041] (Control experiment under controlled conditions) The Na obtained in Example 1 2 / 3 TG-DTA measurements were performed on MnO2 crystals under an argon atmosphere using the measurement method described above. The heating rate and cooling rate were both 5°C / min, and the temperature was raised from room temperature to 700°C, then cooled to 300°C. This operation was repeated 5 times. 2 / 3 The absorption and emission of argon gas were calculated from the mass change of the MnO2 crystal. The results are shown in Table 1 and Figure 6. Figure 6 is a graph showing the amount of gas adsorption and release corresponding to temperature changes when the oxygen storage material from Example 1 is subjected to an argon atmosphere as a control atmosphere, under the same conditions as the temperature change in air in Example 1. As is clear from Figure 6, no gas absorption or release was observed in the measurements under the control atmosphere. From this, it can be concluded that the Na in Example 1... 2 / 3MnO2 crystals can specifically absorb and release oxygen, and this effect is maintained even after repeated testing.

[0042] (Example 2) In addition to the Na2CO3 powder and Mn2O3 powder used in Example 1, FeO2, a compound containing Fe as element M, was prepared, and a mixture of the three components was created. The Mn contained in Mn2O3 and the Fe contained in FeO2 were mixed in amounts that resulted in a molar ratio of 0.9:0.1, and the Na contained in each compound was mixed in an amount that was 67% to 1% in excess of the total molar ratio of Mn and Fe. Except for using FeO2 in addition to Na2CO3 powder and Mn2O3 powder as raw materials, the same process as in Example 1 was carried out to produce the Na of Example 2. 2 / 3 Mn 0.9 Fe 0.1 O2 crystals were obtained.

[0043] The obtained Na 2 / 3 Mn 0.9 Fe 0.1 Analysis of the O2 crystal in the same manner as in Example 1 confirmed that it is a P'2 orthorhombic layered oxide. The XRD measurement results for the oxygen storage material of Example 2 are shown in Figure 3. In Figure 3, the graph labeled Me=Fe in the upper section shows the measurement results for the oxygen storage material of Example 2.

[0044] The oxygen storage material obtained in Example 2 (Na 2 / 3 Mn 0.9 Fe 0.1 The average particle size of the O2 crystals was measured using the same measurement method as in Example 1. The measurement results of the particle size distribution are shown in Figure 7. The measurement results showed that the average particle size was 3.1 μm.

[0045] (Performance evaluation) The Na obtained in Example 2 2 / 3 Mn 0.9 Fe 0.1O2 crystals were subjected to TG-DTA measurements using the previously described measurement method under an atmospheric environment. The heating rate and cooling rate were both 5°C / min, and the temperature was raised from room temperature to 700°C, then cooled to 300°C. This operation was repeated 5 times. 2 / 3 Mn 0.9 Fe 0.1 The absorption and release of oxygen were calculated from the mass change of the O2 crystal. The results are shown in Table 1 and Figure 8. Figure 8 is a graph showing the temperature change of the oxygen storage material in Example 2 under an atmospheric atmosphere, and the amount of oxygen adsorbed and released in response to the temperature change. As is clear from Figure 8, the oxygen storage material in Example 2 is Na 2 / 3 Mn 0.9 Fe 0.1 It was found that the O2 crystal could absorb and desorb 2.4% of oxygen, and this effect was maintained even after five repetitions.

[0046] (Comparative Example 1) In Example 1, after heating to a maximum temperature of 1050°C, the mixture was slowly cooled to room temperature at a cooling rate of 50°C / min or less, and then immediately transferred to an argon-filled glove box to obtain the Na sample from Comparative Example 1. 2 / 3 MnO2 crystals were obtained. Comparative Example 1Na obtained 2 / 3 The average particle size of the MnO2 crystals was measured using the same measurement method as in Example 1. The measurement results of the particle size distribution are shown in Figure 9. The measurement results showed that the average particle size was 5.5 μm. Na in Comparative Example 1 2 / 3 The results of analyzing the MnO2 crystal by powder X-ray diffraction, in the same manner as in Example 1, are shown in Figure 2. The measurement results indicated that it was a P2 hexagonal layered oxide, not a P'2 orthorhombic layered oxide. Therefore, no further performance evaluation was performed.

[0047] (Examples 3 to 10) In Example 2, the starting material containing element M (FeO2) was replaced with MgO, Al2O3, Sc2O3, TiO2, CoO, NiO, Cu2O, and ZnO, respectively, and a P'2 orthorhombic layered oxide was obtained in the same manner as in Example 2.

[0048] Example 3: Raw material containing element M: MgO, obtained crystal: Na 2 / 3 Mn 0.9 Mg 0.1 O₂ crystal. Example 4: Raw material containing element M: Al₂O₃, obtained crystal: Na 2 / 3 Mn 0.9 Al 0.1 O₂ crystal. Example 5: Raw material containing element M: Sc₂O₃, obtained crystal: Na 2 / 3 Mn 0.9 Sc 0.1 O₂ crystal. Example 6: Raw material containing element M: TiO₂, obtained crystal: Na 2 / 3 Mn 0.9 Ti 0.1 O₂ crystal. Example 7: Raw material containing element M: CoO, obtained crystal: Na 2 / 3 Mn 0.9 Co 0.1 O₂ crystal. Example 8: Raw material containing element M: NiO, obtained crystal: Na 2 / 3 Mn 0.9 Ni 0.1 O₂ crystal. Example 9: Raw material containing element M: Cu₂O, obtained crystal: Na 2 / 3 Mn 0.9 Cu 0.1 O₂ crystal. Example 10: Raw material containing element M: ZnO, obtained crystal: Na 2 / 3 Mn 0.9 Zn 0.1 O₂ crystal. The above obtained crystals: Na 2 / 3 Mn 0.9 Mg 0.1 O₂ crystal (Example 3), Na 2 / 3 Mn 0.9 Al 0.1 O₂ crystal (Example 4), Na 2 / 3 Mn 0.9 Sc 0.1 O₂ crystal (Example 5), Na 2 / 3 Mn 0.9 Ti 0.1 O₂ crystal (Example 6), Na 2 / 3 Mn 0.9 Co 0.1O2 crystal (Example 7), Na 2 / 3 Mn 0.9 Ni 0.1 O2 crystal (Example 8), Na 2 / 3 Mn 0.9 Cu 0.1 O2 crystals (Example 9) and Na 2 / 3 Mn 0.9 Zn 0.1 XRD measurements were performed on the O2 crystal (Example 10) in the same manner as in Example 1, and the results confirmed that all of them were P'2 orthorhombic layered oxides.

[0049] Figure 10 shows the XRD measurement results of the crystals obtained in Examples 3 to 10. The type of element M is indicated in each graph as Me=●. Figure 10 shows the XRD measurement results for Example 1 (crystal without element M: Me=Mn) and Example 2 (crystal containing Fe: Me=Fe).

Claims

1. It has a single-phase Cmcm space group P'2 orthorhombic layered oxide structure, and its composition is Na ｘ Mn １－ｙ M ｙ O ２ An oxygen storage material having the following characteristics: element M is at least one selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, and W; in the composition, 0.40 < x < 0.95 and 0 ≤ y < 0.20; and the amount of oxygen adsorbed and desorbed from oxygen during oxygen adsorption and oxygen release is 1.0% to 5.0% of the total mass of the oxygen storage material.

2. The oxygen storage material according to claim 1, wherein the element M is at least one selected from the group consisting of Sc, Ti, Co, Fe, and Cu.

3. The oxygen storage material according to claim 1 or claim 2, wherein the average particle size is in the range of 3 μm to 12 μm.

4. When the P'2 orthorhombic layered oxide in the oxygen storage material was measured by X-ray powder diffraction using Cu-Kα rays as the X-ray source, a diffraction peak intensity ratio R was found between the maximum peak value at 15.5°±1.5° and the maximum peak value at 37.5°±1.5°. The aforementioned R is R = I ２ / I １ And I １ This is the diffraction intensity of the maximum peak at 18.5° ± 1.5°, and I ２ This is the diffraction intensity of the maximum peak at 43.5° ± 1.5°. Furthermore, the oxygen storage material according to claim 1 or claim 2, wherein R ≥ 0.

02.

5. Mn(OH) ２ , MnOOH, Mn ２ O ３ , MnO ２ , and MnCO ３ a step of preparing at least one manganese compound selected from the group consisting of NaOH and Na ２ CO ３ A step of preparing at least one of the sodium compounds, A step of mixing a stoichiometric amount of the manganese compound with a sodium compound in an excess of 1% to 5% relative to the stoichiometric amount, The process involves heating the resulting mixture to over 1000°C in an oxygen-containing atmosphere, The process includes cooling the heated mixture to obtain a single-phase Cmcm space group P'2 orthorhombic layered oxide. A method for manufacturing oxygen storage materials.

6. The method for producing an oxygen storage material according to claim 5, wherein the step of cooling the heated mixture includes at least one of the following steps: cooling in an oxygen-containing atmosphere at a cooling rate of more than 50°C / min, and cooling in an oxygen-free atmosphere.

7. The process further includes a step of preparing at least one compound selected from the group consisting of metal oxides, metal hydroxides, and metal carbonates, which contains at least one element M selected from the group consisting of Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Nb, Mo, and W. The method for producing an oxygen storage material according to claim 5 or claim 6, wherein the step of mixing with the sodium compound involves mixing a compound containing a stoichiometric amount of the manganese compound and a stoichiometric amount of element M with the sodium compound in an excess amount of 1% to 5% relative to the stoichiometric amount.

8. The method for producing an oxygen storage material according to claim 5 or claim 6, wherein the heating step includes heating at a heating rate of 3°C / min to 8°C / min until a temperature A of 700°C to 900°C is reached, and then heating at a heating rate of 0.5°C / min to 1.5°C / min until the temperature exceeds 1000°C.

9. The method for producing an oxygen storage material according to claim 5 or claim 6, wherein the step of cooling the heated mixture includes cooling at a cooling rate of 100°C / min to 200°C / min.

10. A method for adsorbing and desorbing oxygen, comprising heating the oxygen storage material according to claim 1 or claim 2 to adsorb oxygen, and cooling it to release oxygen.

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