Oxygen generating agent

Abstract

To provide an oxygen generating agent capable of efficiently generating oxygen by irradiation with electromagnetic waves.SOLUTION: According to one aspect of the present invention, an oxygen generating agent is provided. This oxygen generating agent contains a composite oxide having the characteristic of releasing oxygen elements under a temperature environment of 300°C or higher and 770°C or lower upon irradiation with electromagnetic waves having a frequency of 300 MHz or higher and 20 GHz or lower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an oxygen generating agent. [Background technology]

[0002] In recent years, the concentration of carbon dioxide (CO2), a greenhouse gas, has been increasing in the atmosphere. This increase in the concentration of carbon dioxide in the atmosphere contributes to global warming. In order to prevent this global warming, it is important to reduce emissions of greenhouse gases such as carbon dioxide. Therefore, hydrogen has been attracting attention as an energy source that does not emit carbon dioxide. For this reason, technology that can produce hydrogen with high efficiency is important, and for example, a technology that uses gadolinium-doped cerium oxide to electrolyze water has been reported (see Non-Patent Document 1).

[0003] In the method described in Non-Patent Document 1, the cerium oxide is first irradiated with microwaves (electromagnetic waves) alone to remove oxygen, and then water is reduced by a reaction with the cerium oxide after the oxygen has been removed, to produce hydrogen. However, at present, research into compounds that have the property of removing oxygen when irradiated with microwaves has not progressed sufficiently. Furthermore, if a compound with such excellent properties, i.e., a compound (oxygen generator) that efficiently generates oxygen when irradiated with microwaves, can be found, it can be effectively used not only for hydrogen production but also for other reactions such as hydrocarbon synthesis and oxidation reactions. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] JM Serra, et al., "Hydrogen production via microwave-induced water splitting at low temperature", Nature Energy volume 5, pages 910-919 (2020) Summary of the Invention [Problem to be solved by the invention]

[0005] In view of the above circumstances, the present invention provides an oxygen generating agent that can efficiently generate oxygen when irradiated with electromagnetic waves. [Means for solving the problem]

[0006] According to one aspect of the present invention, there is provided an oxygen generating agent comprising a composite oxide that has the property of releasing oxygen element when irradiated with electromagnetic waves having a frequency of 300 MHz to 20 GHz in a temperature environment of 300°C to 770°C.

[0007] According to this embodiment, oxygen can be generated efficiently. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows gas chromatographic charts obtained in Example 1 and Reference Example 1. [Figure 2] 1 shows gas chromatograph charts obtained in Example 2 and Reference Example 2. [Figure 3] 1 shows gas chromatograph charts obtained in Example 3 and Reference Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0009] The oxygen generating agent of the present invention will be described in detail below based on preferred embodiments. [Oxygen generator] The oxygen generating agent of this embodiment contains a complex oxide that has the property of releasing oxygen element when irradiated with electromagnetic waves having a frequency of 300 MHz to 20 GHz in a temperature environment of 300°C to 770°C. The oxygen generating agent containing such a complex oxide quickly absorbs the irradiated electromagnetic waves, causing the crystal structure of the complex oxide to vibrate and generate distortion. As a result, the oxygen generating agent can efficiently release oxygen element and generate oxygen. The frequency of the electromagnetic waves is preferably 500 MHz or more and 10 GHz or less, and more preferably 700 MHz or more and 5 GHz or less, in which case the efficiency of desorption of oxygen element from the oxygen generating agent (composite oxide) can be sufficiently increased.

[0010] The environmental temperature at which the composite oxide exhibits its ability to release oxygen elements is preferably 400° C. or higher and 750° C. or lower, and more preferably 500° C. or higher and 700° C. or lower. In this case, the composite oxide releases oxygen elements even at a relatively low temperature, resulting in high energy efficiency. Specifically, when irradiated with electromagnetic waves, the composite oxide preferably starts to release oxygen elements at a lower temperature than when heated only in a furnace, and more specifically, the oxygen elements preferably start to release at a temperature 50° C. or more lower, more preferably 75° C. or more lower, and even more preferably 100° C. or more lower, thereby further improving the above-mentioned effects. Here, the composite oxide (oxygen generating agent) is heated by irradiation with electromagnetic waves, and this heating may be carried out by irradiation with electromagnetic waves alone, or by both irradiation with electromagnetic waves and heating in a furnace. The furnace is preferably an electric furnace, a combustion furnace, or the like.

[0011] Therefore, it is preferable that such an oxygen generating agent be used at a temperature lower than the temperature at which the oxygen element starts to desorb from the composite oxide by heating in a furnace alone while irradiating the electromagnetic waves (hereinafter also referred to as the "desorption initiation temperature"). Specifically, the temperature during use (when irradiating electromagnetic waves) may be 50°C or more lower than the desorption initiation temperature, 75°C or more lower, or 100°C or more lower. In this case, it is possible to further improve energy efficiency while maintaining a sufficiently high desorption efficiency of the oxygen element from the composite oxide. The upper limit of this temperature is not particularly limited, but is a temperature approximately 150°C lower than the desorption initiation temperature.

[0012] The dielectric loss tangent of the composite oxide is preferably 0.05 or more, more preferably 0.1 or more, even more preferably 0.15 or more, and particularly preferably 0.2 or more. In this case, the composite oxide can quickly absorb electromagnetic waves regardless of frequency. The upper limit of the dielectric loss tangent of the composite oxide is not particularly limited, but is about 0.4. Furthermore, when the dielectric loss tangent of the complex oxide is within the above range, the dielectric constant is preferably 6 or less, more preferably 5 or less, even more preferably 4 or less, particularly preferably 3 or less, and most preferably 2 or less. In this case, the electromagnetic wave absorption ability of the complex oxide is more easily improved. The lower limit of the dielectric constant of the complex oxide is not particularly limited, but is about 1.

[0013] The composite oxide preferably contains at least two elements belonging to the fourth period of the periodic table. Here, examples of elements belonging to the fourth period of the periodic table include potassium (K), calcium (Ca), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), etc. Among these, calcium (Ca), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), and copper (Cu) are preferred as elements belonging to the fourth period of the periodic table.

[0014] The composite oxide preferably contains at least two elements selected from the alkaline earth metals and transition elements. Examples of elements belonging to alkaline earth metals and transition elements include magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), silver (Ag), lanthanum (La), cerium (Ce), samarium (Sm), gadolinium (Gd), hafnium (Hf), tantalum (Ta), etc. Among these, preferred elements belonging to alkaline earth metals and transition elements are calcium (Ca), strontium (Sr), titanium (Ti), manganese (Mn), iron (Fe), cobalt (Co), and copper (Cu).

[0015] The composite oxide may have any crystal structure as long as it has a high ability to absorb electromagnetic waves, but it is preferable that the composite oxide has at least one of a perovskite-type crystal structure, a spinel-type crystal structure, and a corundum-type crystal structure. Studies by the present inventors have revealed that composite oxides having the above crystal structures have a high ability to absorb electromagnetic waves. From the above, the composite oxide is x Sr 1-x FeO3 (perovskite type), SrTi x Co 1-x O 2.8 (Perovskite and spinel types), Cu x Mn 1-x At least one of Fe2O4 (spinel type and corundum type) is preferred, and Ca 0.2 Sr 0.8 FeO3, SrTi 0.2 Co 0.8 O 2.8 , Cu 0.5 Mn 0.5It is more preferable that the composite oxide is at least one of Fe2O4. These composite oxides are preferable because they have a sufficiently high ability to release oxygen elements.

[0016] The oxygen generating agent of this embodiment may be composed of a composite oxide alone, or may contain a composite oxide and a binder that binds the composite oxide together. An example of the latter embodiment is a configuration in which fine particles of a composite oxide are bound with a binder (carrier). In this case, the shape retention of the oxygen generating agent can be further improved, and the specific surface area of ​​the oxygen generating agent can also be easily adjusted. When the oxygen generating agent contains a binder, the content of the composite oxide in the oxygen generating agent is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more. In this case, the electromagnetic wave absorption efficiency of the oxygen generating agent can be improved and the amount of oxygen generated can be increased while maintaining high shape retention of the oxygen generating agent.

[0017] The binder is not particularly limited as long as it is a compound that is not easily denatured in response to contact with the gas to be treated (hereinafter also referred to as "treated gas") or reaction conditions, and examples thereof include inorganic materials such as oxides, nitrides, oxynitrides, and carbides, and carbon materials (graphite, graphene, etc.). Among these, oxides are preferred as binders, with oxides containing at least one of magnesium (Mg), titanium (Ti), zirconium (Zr), aluminum (Al) and silicon (Si) being more preferred, and aluminum oxide being even more preferred. These oxides are preferred because they have high thermal stability and can easily stably bind the composite oxide particles.

[0018] The shape of the oxygen generating agent is not particularly limited, but for example, granular shape is preferred. Here, granular is a concept that includes powder, particles, lumps, pellets, etc., and the shape may be any of spherical, plate-like, polygonal, crushed, columnar, needle-like, scale-like, etc. The average particle size of the oxygen generating agent is preferably 1 μm or more and 5 mm or less, more preferably 10 μm or more and 1 mm or less, and even more preferably 20 μm or more and 0.5 mm or less.

[0019] In this specification, the term "average particle size" refers to the average value of particle sizes of 200 randomly selected oxygen generating agents in one field of view observed under an electron microscope. In this case, the term "particle size" refers to the maximum distance between two points on the contour line of the oxygen generating agent. When the oxygen generating agent is columnar, the maximum distance between two points on the contour line of its end face is taken as the "particle size." In addition, when the oxygen generating agent is, for example, in a blocky form where primary particles are aggregated, the term "average particle size" refers to the average particle size of secondary particles. The BET specific surface area of ​​the oxygen generator is 1m 2 / g or more 500m 2 / g or less, and 2 / g or more 450m 2 / g or less is more preferable, and 5m 2 / g or more 400m 2 When the BET specific surface area is within the above range, the treatment efficiency of the gas to be treated can be easily improved.

[0020] [Method of manufacturing oxygen generator] Next, a method for producing the oxygen generating agent will be described. The method for producing the oxygen generating agent is not particularly limited, but examples thereof include the sol-gel method, co-precipitation method, solid phase method, and hydrothermal synthesis method. As an example, the oxygen generating agent can be produced as follows. First, salts of elements constituting the oxygen generating agent are dissolved in water to prepare an aqueous solution. Next, this aqueous solution is gelled, and then dried and fired. That is, the oxygen generating agent of this embodiment can be produced easily and reliably by the so-called sol-gel method. The aqueous solution may be prepared using acidic water prepared with, for example, citric acid, acetic acid, malic acid, tartaric acid, hydrochloric acid, nitric acid, or a mixture thereof.

[0021] Examples of the salt of an element include nitrates, sulfates, chlorides, hydroxides, carbonates, and composites thereof, among which nitrates are preferred. Furthermore, hydrates of the salt of an element may be used as needed. The gel is dried preferably at a temperature of 20° C. to 200° C., more preferably 50° C. to 150° C., for a time of preferably 0.5 to 20 hours, more preferably 1 to 15 hours. By drying in this manner, the gel can be dried uniformly.

[0022] The gel is preferably fired at a temperature of 300°C to 1200°C, more preferably 700°C to 1000°C, for a time of 1 hour to 24 hours, more preferably 1.5 hours to 20 hours. The gel is preferably converted into an oxide by firing, and can be easily converted into a composite oxide (oxygen generating agent) by firing under the above firing conditions. Furthermore, firing under the above firing conditions can also prevent excessive particle growth of the oxygen generating agent. Until the above-mentioned baking temperature is reached, the temperature is increased at a rate of 1°C / min to 20°C / min, preferably 2°C / min to 10°C / min, which promotes particle growth of the oxygen generating agent and also prevents cracking of the crystals (particles).

[0023] [How to use oxygen generator] As described above, the oxygen generating agent in a state in which oxygen element has been released by irradiation with electromagnetic waves is preferably used as a reducing agent. Such a reducing agent can be suitably used, for example, in a process for producing hydrogen by electrolyzing water, a process for producing carbon valuables by reducing carbon dioxide, etc. In the latter case, the reducing agent (oxygen generating agent) can be used, for example, in a chemical looping method. More specifically, it is preferable to carry out a reduction reaction of carbon dioxide and a reduction reaction of the reducing agent, and it is preferable to use the reducing agent so that it circulates between the reduction reaction of carbon dioxide and the reduction reaction of the reducing agent. As described above, the reduction reaction of the reducing agent is carried out by irradiating the reducing agent with electromagnetic waves.

[0024] In this case, the reduction reaction of the reducing agent is the reaction shown in the following formula (A), and the reduction reaction of carbon dioxide is the reaction shown in the following formula (B). MO x + Electromagnetic waves → O2+ MO x-1 (A) CO2+ MO x-1 → CO + MO x (B) That is, in the reduction reaction of the reducing agent, oxygen is generated by irradiation with electromagnetic waves, and in the reduction reaction of carbon dioxide, carbon dioxide is reduced to generate carbon monoxide, which is a type of carbon valuable. The reaction temperature in the reduction reaction of the reducing agent is preferably the temperature as described above (i.e., a temperature 50°C or more lower than the desorption starting temperature). The reducing agent may be heated only by irradiation with electromagnetic waves, or may be heated by both irradiation with electromagnetic waves and heating in the furnace.

[0025] The output of the electromagnetic waves is not particularly limited, but is preferably set to a value equal to the unit volume (1 cm ) of the reducing agent (oxygen generating agent). 3 ) is preferably 1 W or more and 10 kW or less, more preferably 10 W or more and 5 kW or less, and even more preferably 100 W or more and 3 kW or less. The irradiation time of the electromagnetic waves is not particularly limited, but is preferably from 10 seconds to 10 hours, more preferably from 1 minute to 5 hours, and even more preferably from 10 minutes to 2 hours. Such an irradiation time is sufficient to separate the oxygen element from the reducing agent. While the reducing agent is being irradiated with electromagnetic waves, the reaction temperature of the reducing agent may be increased continuously or stepwise. By adjusting the output of the electromagnetic waves within the above range, it is easy to stabilize the rate of increase in the reaction temperature of the reducing agent (rate of temperature increase).

[0026] On the other hand, the reaction temperature in the reduction reaction of carbon dioxide is preferably a temperature above 650° C., more preferably 700° C. or higher, even more preferably 750° C. or higher, and particularly preferably 800° C. or higher. Within this temperature range, the reduction reaction of carbon dioxide can proceed efficiently. The upper limit of the reaction temperature is preferably 1050°C, more preferably 950°C or lower, and even more preferably 850°C or lower. The oxygen generating agent can carry out the reduction reaction of carbon dioxide to carbon monoxide with high efficiency at such a reaction temperature. Furthermore, by setting the upper limit of the reaction temperature within the above range, not only can waste heat be easily utilized, but also economic efficiency can be further improved. Furthermore, by setting the reaction temperature in the reduction reaction of carbon dioxide within the above range, heating during the reduction reaction of the reducing agent (irradiation of electromagnetic waves) can be omitted or only slight heating can be required.

[0027] The concentration of carbon dioxide contained in the gas to be treated that is brought into contact with the oxygen generating agent is preferably 50% or more, more preferably 80% or more, even more preferably 85% or more, particularly preferably 90% or more, and most preferably 95% or more. This makes it possible to simplify or eliminate the operation of separating the converted carbon monoxide. Note that the concentration of carbon dioxide in the gas to be treated may be 100%. The reduction product (carbon valuable product) obtained by the reduction reaction of carbon dioxide contains carbon monoxide, but may also contain substances other than carbon monoxide, or may be a mixture of carbon monoxide and other substances, such as methane.

[0028] The reduction products (carbon monoxide, etc.) obtained by the reduction reaction of carbon dioxide are preferably further converted into organic substances, etc. by microbial fermentation, etc. Examples of microbial fermentation include anaerobic fermentation. Examples of the organic substances obtained include methanol, ethanol, acetic acid, butanol, derivatives thereof, mixtures thereof, and compounds of C5 or more such as isoprene. Furthermore, reductants such as carbon monoxide may be converted by metal oxides or the like into C1 to C20 compounds, including hydrocarbons and alcohols that are conventionally synthesized by petrochemicals. Specific compounds that can be obtained include methane, ethane, ethylene, propylene, methanol, ethanol, propanol, acetaldehyde, diethyl ether, acetic acid, butyric acid, diethyl carbonate, and butadiene.

[0029] The oxygen generating agent of the above embodiment can efficiently generate oxygen by releasing oxygen element under a relatively low temperature environment when irradiated with electromagnetic waves. Furthermore, the oxygen generating agent in an oxidized state can more efficiently convert carbon dioxide into carbon monoxide (carbon valuables) through a chemical looping reaction. Other uses of the oxygen generating agent include, for example, production of hydrogen by reduction of water, synthesis of hydrocarbons, and various oxidation reactions. Furthermore, the oxygen generated by the oxygen generating agent can be used for, for example, cultivating aerobic microorganisms, increasing the temperature of a furnace such as a gasification furnace, etc. Furthermore, it may be provided in the following aspects.

[0030] (1) An oxygen generating agent comprising a composite oxide having the property of releasing oxygen element when irradiated with electromagnetic waves having a frequency of 300 MHz or more and 20 GHz or less in a temperature environment of 300°C or more and 770°C or less.

[0031] (2) The oxygen generating agent according to (1) above, wherein the composite oxide starts to release the oxygen element when irradiated with the electromagnetic waves at a temperature lower than when heated only in a furnace.

[0032] (3) The oxygen generating agent according to (2) above, wherein the oxygen generating agent is used at a temperature lower than the temperature at which the composite oxide starts to release the oxygen element by heating in the furnace alone while being irradiated with the electromagnetic waves.

[0033] (4) The oxygen generating agent according to any one of (1) to (3) above, wherein the composite oxide has a dielectric loss tangent of 0.05 or more.

[0034] (5) The oxygen generating agent according to any one of (1) to (4) above, wherein the composite oxide contains at least two kinds of elements belonging to the fourth period of the periodic table.

[0035] (6) The oxygen generating agent according to any one of (1) to (5) above, wherein the composite oxide contains at least two elements selected from the group consisting of alkaline earth metals and transition elements.

[0036] (7) The oxygen generating agent according to any one of (1) to (6) above, wherein the composite oxide has at least one of a perovskite-type crystal structure, a spinel-type crystal structure, and a corundum-type crystal structure.

[0037] (8) In the oxygen generating agent according to any one of (1) to (7), the composite oxide is Ca x Sr 1-x FeO3, SrTi x Co 1-x O 2.8 , Cu x Mn 1-x and an oxygen generating agent, which is at least one of Fe2O4.

[0038] (9) The oxygen generating agent according to any one of (1) to (8) above, wherein the content of the composite oxide in the oxygen generating agent is 50 mass % or more.

[0039] (10) The oxygen generating agent according to any one of (1) to (9) above, wherein the oxygen generating agent from which the oxygen element has been released is used as a reducing agent.

[0040] (11) The oxygen generating agent according to (10) above, wherein the reducing agent reduces carbon dioxide to generate carbon valuables. Of course, this is not the case.

[0041] As described above, various embodiments of the present invention have been described, but these are presented as examples and do not limit the scope of the invention in any way. The novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, when handling numerical values ​​in the present invention, values ​​with digits after the significant digit are rounded off and converted to values ​​with digits of the significant digit. [Example]

[0042] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to these examples.

[0043] 1. Oxygen Generator Precursor Preparation The following compounds were prepared as precursors of the oxygen generating agent (sources of elements constituting the oxygen generating agent). Calcium nitrate tetrahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) Strontium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) Iron(III) nitrate nonahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) Titanium(IV) chloride solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., contains 16.0-17.0% titanium and 29.0-33.0% chlorine) Cobalt(II) nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) Copper(II) nitrate trihydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.0%) Manganese(II) nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 98.0%)

[0044] 2. Manufacture of oxygen generators (Sample No. 1) First, predetermined amounts of calcium nitrate tetrahydrate, strontium nitrate, and iron (III) nitrate nonahydrate were each weighed out. Next, 14.5 g of citric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) was weighed and dissolved in 5.1 mL of deionized water to obtain a citric acid aqueous solution. The precursor (nitrate) was then added to the citric acid aqueous solution at room temperature while stirring to prepare a precursor aqueous solution. The molar ratio of Ca:Sr:Fe in the precursor aqueous solution was 0.2:0.8:1. After 30 minutes had passed, 5.1 g of ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) was added to the precursor aqueous solution, and the temperature was raised to 80°C.

[0045] The temperature was maintained at 80°C with continuous stirring until a viscous gel was formed, after which the gel was transferred to a drying oven. The gel was dried at 120°C for 5 hours. The resulting swollen mass of organic and inorganic compounds was pulverized and heated from room temperature to 450°C at a rate of 8°C / min in an air atmosphere, then fired at 450°C for 4 hours, then further heated to 950°C at a rate of 8°C / min, and fired at 950°C for 8 hours. Finally, the fired mass was mechanically pulverized to obtain the oxygen generating agent composed solely of the target composite oxide. The obtained oxygen generating agent was granular and had an average particle size of 44.4 μm.

[0046] (Sample No. 2) An oxygen generating agent composed solely of the composite oxide was produced in the same manner as Sample No. 1, except that predetermined amounts of strontium nitrate, titanium (IV) chloride solution, and cobalt (II) nitrate hexahydrate were each measured and used. The molar ratio of Sr:Ti:Co in the aqueous precursor solution was 1:0.2:0.8. The oxygen generating agent obtained was in the form of particles, with an average particle size of 26.1 μm.

[0047] (Sample No. 3) An oxygen generating agent composed solely of a composite oxide was produced in the same manner as Sample No. 1, except that copper (II) nitrate trihydrate, manganese (II) nitrate hexahydrate, and iron (III) nitrate nonahydrate were each weighed out and used in predetermined amounts. The molar ratio of Cu:Mn:Fe in the aqueous precursor solution was 0.5:0.5:2. The obtained oxygen generating agent was in the form of particles, with an average particle size of 29.1 μm.

[0048] 3. Identification of oxygen generator The elemental composition of the oxygen generating agent (composite oxide) was analyzed and identified by ICP emission spectrometry using argon gas using a SPECTRO ARCOS manufactured by AMETEK Corporation. The measurement solution was prepared by the following method: 50 mg to 100 mg of oxygen generating agent was dissolved in 100 mL of 1% nitric acid or 1% hydrofluoric acid, and the resulting solution was further diluted 10 times.

[0049] 4. Confirmation of the crystal structure of the oxygen generator The crystal structure of each oxygen generator (complex oxide) was identified and its weight fraction was calculated using X-ray diffraction (PANalytical AERIS device, CuKα radiation, 40 kV, 15 mA) and analytical software HighScore Ver. 4.6. The crystal structure was identified by referencing the crystal structure matched with the ICDD PDF-2 database. The weight fraction of each oxygen generator (complex oxide) was calculated using a semi-quantitative function based on the RIR value. The oxygen generating agent of Sample No. 1 was composed of a perovskite phase, and the amount of the perovskite phase was approximately 100 parts by mass per 100 parts by mass of the oxygen generating agent. The oxygen generating agent of Sample No. 2 was composed of a perovskite phase and a spinel phase, and the perovskite phase accounted for 79 parts by mass relative to 100 parts by mass of the oxygen generating agent. The oxygen generating agent of Sample No. 3 was composed of a spinel phase and a corundum phase, and the spinel phase accounted for 64 parts by mass relative to 100 parts by mass of the oxygen generating agent.

[0050] 5. Measurement of dielectric loss tangent, relative dielectric constant and temperature of oxygen generating agent The dielectric loss tangent (tan δ), relative dielectric constant and temperature of the oxygen generating agent were measured as follows. The dielectric constant was measured using a 915 MHz semiconductor microwave oscillator manufactured by Ryowa Electronics and a TM010-mode cavity resonator. The measurement sample was prepared as follows: 50 mg to 150 mg of oxygen generating agent was filled into a quartz container and introduced into the cavity resonator. Electromagnetic waves were irradiated with microwaves at a power of 10 W or more, and the resonant frequency and Q value were measured. These values ​​were used to calculate the dielectric loss tangent and relative permittivity according to the relationship described in JIS C 2565:1992. The temperature of the oxygen generating agent was measured using a radiation thermometer (FLHX-TNE0090-0200S007-000) manufactured by Japan Sensor Co., Ltd. The thermal radiation emitted from the oxygen generating agent during heating was measured in the wavelength range of 1.95 μm to 2.6 μm, and the thermal radiation intensity was converted to temperature.

[0051] 6. Confirmation of oxygen generation Example 1 The oxygen generating agent of sample No. 1 was filled in a quartz sample tube with 50 mg to 150 mg, and the frequency was 915 MHz and the unit volume of the oxygen generating agent (1 cm 3 The oxygen generating agent was heated by irradiating it with electromagnetic waves of 100 W or more and 3 kW or less per 100 W for 2 hours. The output was changed within the above range to irradiate the electromagnetic waves, thereby adjusting the temperature rise rate of the oxygen generating agent to be approximately constant. Oxygen was generated from the oxygen generating agent in this manner, and the concentration was measured using a gas chromatograph (Shimadzu Corporation, "GC2014") in the temperature range of 60°C or higher and 710°C or lower. Example 2 In the same manner as in Example 1, oxygen was generated from the oxygen generating agent of Sample No. 2, and the concentration was measured in the temperature range of 200°C or higher and 850°C or lower. Example 3 In the same manner as in Example 1, oxygen was generated from the oxygen generating agent of Sample No. 3, and the concentration was measured in the temperature range of 90°C or higher and 750°C or lower.

[0052] (Reference example 1) The oxygen generating agent of Sample No. 1 was heated in an electric furnace to generate oxygen without irradiating it with electromagnetic waves, and the concentration was measured in the same manner as in Example 1 within the temperature range of 25°C to 1000°C. (Reference example 2) The oxygen generating agent of Sample No. 2 was heated in an electric furnace to generate oxygen without irradiating it with electromagnetic waves, and the concentration was measured in the same manner as in Example 1 within the range of 0°C to 1000°C. (Reference example 3) The oxygen generating agent of Sample No. 3 was heated in an electric furnace to generate oxygen without irradiating it with electromagnetic waves, and the concentration was measured in the same manner as in Example 1 within the range of 120°C to 1000°C.

[0053] These results are shown in the following Table 1. The amount of oxygen generated is shown as the amount (mmol) per 1 g of the oxygen generating agent. [Table 1]

[0054] As shown in Table 1, in the oxygen generating agents of Samples No. 1 and No. 3, when heated by irradiation with electromagnetic waves, oxygen began to desorb at a temperature significantly lower than when heated only in an electric furnace, and the amount of oxygen generated was also greater than when heated only in an electric furnace. In addition, with the oxygen generating agent of sample No. 2, the amount of oxygen generated was slightly less than when heated only in an electric furnace, but the temperature at which oxygen generation began was significantly lower due to heating by irradiation with electromagnetic waves than when heated only in an electric furnace.

Claims

1. An oxygen generator, An oxygen generating agent comprising a complex oxide having a property of releasing oxygen element in a temperature environment of 300°C or higher and 770°C or lower when irradiated with electromagnetic waves having a frequency of 300 MHz or higher and 20 GHz or lower.

2. The oxygen generating agent according to claim 1, The oxygen generating agent is such that, when irradiated with the electromagnetic waves, the composite oxide starts to release the oxygen element at a lower temperature than when heated only in a furnace.

3. The oxygen generating agent according to claim 2, The oxygen generating agent is used at a temperature lower than the temperature at which the composite oxide starts to release the oxygen element by heating in the furnace alone while being irradiated with the electromagnetic waves.

4. The oxygen generating agent according to claim 1, The oxygen generating agent, wherein the composite oxide has a dielectric loss tangent of 0.05 or more.

5. The oxygen generating agent according to claim 1, The oxygen generating agent, wherein the composite oxide contains at least two elements belonging to the fourth period of the periodic table.

6. The oxygen generating agent according to claim 1, The oxygen generating agent, wherein the composite oxide contains at least two elements selected from the group consisting of alkaline earth metals and transition elements.

7. The oxygen generating agent according to claim 1, The oxygen generating agent, wherein the composite oxide has at least one of a perovskite-type crystal structure, a spinel-type crystal structure, and a corundum-type crystal structure.

8. The oxygen generating agent according to claim 1, The composite oxide is ｘ Sr １－ｘ FeO ３ , SrTi ｘ Co １－ｘ O ２．８ , Cu ｘ Mn １－ｘ Fe ２ O ４ The oxygen generating agent is at least one of the following:

9. The oxygen generating agent according to claim 1, The oxygen generating agent has a content of the composite oxide of 50 mass % or more.

10. The oxygen generating agent according to claim 1, The oxygen generating agent in a state in which the oxygen element has been released is used as a reducing agent.

11. The oxygen generating agent according to claim 10, The reducing agent is an oxygen generating agent that reduces carbon dioxide to produce carbon values.

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