Method for producing at least one of hydrogen and carbon monoxide, method for producing synthesis gas, and reaction medium

Abstract

A method for producing hydrogen and / or carbon monoxide which comprises a first step, in which an oxidized form of a compound having a perovskite structure is thermally reduced to release oxygen, and a second step, in which when the reduced form of the compound is oxidized to return to the oxidized form, a hydrogen-containing substance and / or a substance containing carbon and oxygen is reacted with the reduced form to thereby yield hydrogen and / or carbon monoxide. The oxidized form is represented by the general formula A(1-x)QxB(1-y)RyO3 (A is a rare-earth element; Q is an alkaline-earth metal element; B is a first transition element or Mg; R is Co, Ni, or Mg and differs from the B; and y is 0<y≤0.5 when R is Co, is 0.15<y≤0.3 when R is Ni, and is 0<y<0.15 when R is Mg).

Description

Technical Field

[0001] The present invention relates to a method for producing at least one of hydrogen and carbon monoxide, a method for producing synthesis gas, and a reaction medium.

Background Art

[0002] A technique for producing a liquid fuel with a high energy density by the Fischer-Tropsch reaction using synthesis gas containing hydrogen and carbon monoxide as a raw material is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding the production of hydrogen, a technique for producing hydrogen by a two-step hydrothermal decomposition cycle using solar heat is known. Also, regarding the production of carbon monoxide, a technique for producing carbon monoxide from carbon dioxide contained in exhaust gas or the like by a reverse shift reaction or the like is known. By using hydrogen and carbon monoxide produced by these techniques for the production of synthesis gas, it is possible to contribute to the realization of carbon neutrality. From such a situation, an improvement in the production efficiency of hydrogen and carbon monoxide is desired.

[0005] The present invention has been made in view of such a situation, and one of its objects is to provide a technique for improving the production efficiency of at least one of hydrogen and carbon monoxide.

Means for Solving the Problems

[0006] One aspect of the present invention is a method for producing at least one of hydrogen and carbon monoxide. This production method includes a first step of heating and reducing an oxide of a compound having a perovskite structure to release oxygen, and a second step of reacting at least one of a hydrogen-containing substance and a substance containing carbon and oxygen with the reduced form of the compound obtained in the first step when oxidizing the reduced form of the compound to return it to the oxidized form to produce at least one of hydrogen and carbon monoxide. The oxide of the compound has the general formula A (1-x) Q x B (1-y) R y O3 (A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is at least one element selected from the group consisting of first transition elements and Mg, R is Co, Ni or Mg and is different from B, x satisfies 0.1 ≦ x ≦ 0.4, when R is Co, y satisfies 0 < y ≦ 0.5, when R is Ni, y satisfies 0.15 < y ≦ 0.3, and when R is Mg, y satisfies 0 < y < 0.15).

[0007] Another aspect of the present invention is a method for producing synthesis gas. This production method includes producing both hydrogen and carbon monoxide by the production method of the above aspect to produce synthesis gas.

[0008] Another aspect of the present invention is a reaction medium. This reaction medium contains a compound having a perovskite structure. When the oxide of the compound is heated and reduced to become a reduced form and releases oxygen, and the reduced form is oxidized to return to the oxidized form, it reacts with at least one of a hydrogen-containing substance and a substance containing carbon and oxygen to produce at least one of hydrogen and carbon monoxide. The oxide of the compound has the general formula A (1-x) Q x B (1-y) R yO3 (where A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is at least one element selected from the group consisting of first transition elements and Mg, R is Co, Ni or Mg and is different from B, x satisfies 0.1 ≦ x ≦ 0.4, when R is Co, y satisfies 0 < y ≦ 0.5, when R is Ni, y satisfies 0.15 < y ≦ 0.3, and when R is Mg, y satisfies 0 < y < 0.15).

[0009] Any combination of the above components, and those obtained by converting the expressions of the present disclosure among methods, devices, systems, etc. are also valid as aspects of the present disclosure.

Advantages of the Invention

[0010] According to the present invention, it is possible to improve the production efficiency of at least one of hydrogen and carbon monoxide.

Brief Description of the Drawings

[0011] [Figure 1] It is a schematic diagram of an apparatus for measuring the amount of hydrogen generated. [Figure 2] It is a schematic diagram of an apparatus for measuring the amount of carbon monoxide generated. [Figure 3] It is a diagram showing the amount of oxygen generated, the amount of carbon monoxide generated, and the carbon monoxide / oxygen ratio in each sample compound. [Figure 4] It is a diagram showing the amount of oxygen generated, the amount of carbon monoxide generated, and the carbon monoxide / oxygen ratio in each sample compound.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described with reference to the drawings based on preferred embodiments. The embodiments are illustrative and do not limit the technical scope of the present invention. Not all features and combinations thereof described in the embodiments are necessarily essential to the invention. Therefore, within the scope not departing from the inventive concept defined in the claims, many design changes such as component changes, additions, deletions, etc. are possible. New embodiments with design changes have the combined effects of the combined embodiments and the modifications. In the embodiments, regarding the content where such design changes are possible, expressions such as "in the present embodiment" and "in the present embodiment" are used for emphasis, but design changes are also allowed for the content without such expressions. Any combination of the components described in the embodiments is also valid as an aspect of the present invention. The same or equivalent components, members, and processes shown in each drawing are denoted by the same reference numerals, and duplicate explanations are omitted as appropriate. Also, the scales and shapes of each part shown in each figure are set for convenience to facilitate the explanation and are not to be construed in a limited manner unless otherwise specified. Further, when terms such as "first" and "second" are used in this specification or claims, these terms do not represent any order or importance but are for distinguishing one configuration from another. Also, in each drawing, some members that are not important for explaining the embodiments are omitted from the display.

[0013] The method for producing hydrogen by a two-stage thermal decomposition cycle is one of the promising technologies as a method for producing hydrogen at low cost. This production method generates hydrogen and oxygen through a two-stage reaction. As an example, the reaction models for each stage when decomposing water are shown below. By repeating the following reduction reaction and oxidation reaction, hydrogen can be continuously generated. [Reduction reaction] MO X → MO (X-δ) +0.5δO2 (endothermic reaction) [Oxidation reaction] MO (X-δ) +δH2O → MO X +δH2 (exothermic reaction)

[0014] Furthermore, the two-stage pyrolysis cycle for producing carbon monoxide is a promising technology for producing carbon monoxide at low cost. This method produces carbon monoxide and oxygen in two stages. As an example, the reaction models for each stage when decomposing carbon dioxide are shown below. By repeating the reduction and oxidation reactions described below, carbon monoxide can be continuously produced. [Reduction reaction] MO X → MO (X-δ) +0.5δO2 (endothermic reaction) [Oxidation reaction] MO (X-δ) +δCO2→MO X + δCO (exothermic reaction)

[0015] A key element of these technologies is a compound called the reaction medium (MO). X The inventors diligently investigated various compounds that could serve as this reaction medium and focused on a compound having a perovskite structure (perovskite-type composite oxide) as one of them. They then conceived the idea that hydrogen and carbon monoxide could be efficiently produced by using a reaction medium containing this compound, with its composition adjusted, in a two-stage thermal decomposition cycle. The reaction medium may contain impurities such as simple oxides of the constituent elements (La2O3, SrO, MnO, etc.), composite oxides having a structure other than perovskite consisting of some or all of the constituent elements (pyrochlore, La2Mn2O7, etc.), and impurities resulting from the manufacturing process (Al2O3, SiO2, etc.). Furthermore, the impurities are not limited to those mentioned above.

[0016] This embodiment includes a method for producing carbon monoxide and a method for producing hydrogen. The method for producing hydrogen according to this embodiment includes a first step of heating and reducing an oxidized compound having a perovskite structure to release oxygen, and a second step of reacting a hydrogen-containing substance with the reduced compound obtained in the first step to produce hydrogen when oxidizing the reduced compound back to an oxidized compound.

[0017] Furthermore, the method for producing carbon monoxide according to this embodiment includes a first step of heating and reducing the oxidized form of a compound having a perovskite structure to release oxygen, and a second step of reacting the reduced form obtained in the first step with a substance containing carbon and oxygen to produce carbon monoxide when oxidizing the reduced form back to the oxidized form.

[0018] The compound contained in the reaction medium according to this embodiment has the general formula A in its oxidized state. (1-x) Q x B (1-y) R y It has a structure represented by O3. In other words, the compound has a perovskite structure in which part of the A site ion is substituted with a Q ion and part of the B site ion is substituted with a R ion.

[0019] A is at least one element selected from the group consisting of rare earth elements. Suitable rare earth elements for A include Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. More preferably, A is La. Q is at least one element selected from the group consisting of alkaline earth metal elements. Suitable alkaline earth metal elements for Q include Ca, Sr, Ba, and Ra. More preferably, Q is Sr.

[0020] B is at least one element selected from the group consisting of first transition elements and Mg. Suitable first transition elements for B include Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. More preferably, B is Mn. R is Co, Ni, or Mg. Also, R is an element different from B.

[0021] x is in the range satisfying 0.1 ≦ x ≦ 0.4. More preferably, x is 0.3. y varies depending on the type of R. When R is Co, y is in the range satisfying 0 < y ≦ 0.5. When R is Ni, y is in the range satisfying 0.15 < y ≦ 0.3. When R is Mg, y is in the range satisfying 0 < y < 0.15. More preferably, when R is Co, y is in the range satisfying 0.05 ≦ y ≦ 0.4, and even more preferably in the range satisfying 0.05 ≦ y ≦ 0.3. When R is Ni, y is in the range satisfying 0.175 ≦ y ≦ 0.3. When R is Mg, y is in the range satisfying 0.05 ≦ y ≦ 0.125.

[0022] The oxidized form of the compound is heated and reduced to release oxygen, and becomes a reduced form represented by the general formula A (1-x) Q x B (1-y) R y O (3ーδ) This reaction is represented by the following Reaction Formula 1. [Reaction Formula 1] A (1-x) Q x B (1-y) R y O3 → A (1-x) Q x B (1-y) R y O (3-δ) +0.5δO2

[0023] The reduced form of the compound is oxidized to take in oxygen and returns to the oxidized form represented by the general formula A (1-x) Q x B (1-y) R y O3. When the reduced form returns to the oxidized form, hydrogen can be generated from the substance by reacting the substance containing hydrogen with the reduced form. This reaction is represented by the following Reaction Formula 2. [Reaction Formula 2][[ID=​​​​​​​​​​​​​​​​​​​

[0024] Furthermore, when the reduced form reverts to its oxidized form, carbon monoxide can be produced from a substance containing carbon and oxygen by reacting the reduced form with that substance. This reaction is represented by the following reaction equation 3. [Reaction Equation 3] A (1-x) Q x B (1-y) R y O (3-δ) +δCO2→ A (1-x) Q x B (1-y) R y O3 + δCO

[0025] In other words, when the reduced form of a compound reacts with a hydrogen-containing substance and undergoes oxidation, an oxidized form and hydrogen are produced. Similarly, when the reduced form of a compound reacts with a carbon- and oxygen-containing substance and undergoes oxidation, an oxidized form and carbon monoxide are produced. Water is an example of a hydrogen-containing substance used in the oxidation reaction of a reduced form. Carbon dioxide is an example of a carbon- and oxygen-containing substance used in the oxidation reaction of a reduced form.

[0026] The value δ, which indicates the amount of oxygen released in the oxidized form of the compound, is determined by the compound's composition, temperature, oxygen partial pressure, etc. The oxidized form tends to release oxygen more readily at higher temperatures and lower oxygen partial pressures. Oxygen release and uptake in the oxidized form include a first mode and a second mode.

[0027] The first mode is based on the oxygen nonstoichiometry of the oxidized material, where oxygen is released and incorporated while the perovskite structure (crystal structure) is maintained. Reaction equations 1 to 3 above correspond to the first mode reaction. On the other hand, the second mode is based on the phase transition of the oxidized material, where oxygen is released and incorporated while the perovskite structure changes. The reaction of the second mode is represented by reaction equation 4 below as an example. [Reaction Equation 4] A (1-x) Q x B (1-y) R y O3 → 0.5A 2(1-x)0.5Q 2x B (1-y) R y O4+0.5B (1-y) R y 0+0.25O2

[0028] In this embodiment, a two-stage pyrolysis cycle is achieved by the release and incorporation of oxygen in the first mode. The temperature T1 at which the first step, i.e., the reduction reaction represented by reaction formula 1, is carried out, is preferably in the range of 1000°C to 1500°C, and more preferably in the range of 1100°C to 1400°C. The temperature T2 at which the second step, i.e., the oxidation reaction represented by reaction formulas 2,3, is carried out, is preferably in the range of 700 to 1300°C (where T2 ≤ T1), and more preferably in the range of 900 to 1100°C (where T2 ≤ T1).

[0029] Hydrogen and carbon monoxide may also be produced by the release and incorporation of oxygen in the second mode. However, the reaction proceeds faster in the first mode, which does not involve a phase transition, than in the second mode, which does involve a phase transition. For this reason, by performing a two-stage pyrolysis cycle in the first mode, as in this embodiment, the production efficiency of hydrogen and carbon monoxide can be further improved.

[0030] Next, an example of a method for measuring the amount of hydrogen produced by the hydrogen production method according to the embodiment will be described. Figure 1 is a schematic diagram of a device 100 for measuring the amount of hydrogen produced. In this example, the device 100 introduces nitrogen gas flowing in from the inlet 10 into a test tube 12 filled with pure water PW. This purges the pathway within the device 100. The test tube 12 is kept at a constant temperature in a 95°C oil bath 14. The heat transfer medium in the oil bath 14 is constantly stirred by a stirrer 16.

[0031] In this embodiment, the reaction medium 18 is placed inside the infrared image furnace 20. The reaction medium 18 contains the reduced form of the compound described above. The temperature of the reaction medium 18 is adjusted to, for example, 1200°C by the thermocouple 22 provided in the infrared image furnace 20. Then, water (water vapor) that has flowed out of the test tube 12 is introduced into the infrared image furnace 20. When the water reaches the infrared image furnace 20, the reaction medium 18 is oxidized and hydrogen is generated.

[0032] The mixed gas of hydrogen and unreacted water generated in the infrared imaging furnace 20 is discharged from the infrared imaging furnace 20. The unreacted water is cooled in the water-cooled trap 24. The hydrogen is sent to a known thermal conductivity detector 26. The amount of hydrogen generated is then measured by gas chromatography analysis using the thermal conductivity detector 26. Note that the structure of the apparatus 100 and the method for measuring the amount of hydrogen generated are not limited to those described above.

[0033] Next, an example of a method for measuring the amount of carbon monoxide produced by the carbon monoxide production method according to the embodiment will be described. Figure 2 is a schematic diagram of a device 200 for measuring the amount of carbon monoxide produced. In this example, the device 200 sends carbon dioxide flowing in from the inlet 10 to the infrared image furnace 20. A reaction medium 18 is placed inside the infrared image furnace 20. The reaction medium 18 contains the reduced form of the compound described above. The temperature of the reaction medium 18 is adjusted to, for example, 1200°C by a thermocouple 22 provided in the infrared image furnace 20. When the carbon dioxide flowing in from the inlet 10 reaches the infrared image furnace 20, the reaction medium 18 is oxidized and carbon monoxide is produced.

[0034] The mixed gas of carbon monoxide and unreacted carbon dioxide generated in the infrared image furnace 20 is discharged from the infrared image furnace 20. A portion of the mixed gas is sent from the capillary 28 to a known mass spectrometer 30. The amount of carbon monoxide generated is then measured by the mass spectrometer 30. The structure of the apparatus 200 and the method for measuring the amount of carbon monoxide generated are not limited to those described above. For example, instead of the mass spectrometer 30, a known thermogravimetric analyzer (TGA) may be used to measure the amount of carbon monoxide generated, as in the example described later.

[0035] This embodiment also includes a method for producing synthesis gas. This method for producing synthesis gas involves producing both hydrogen and carbon monoxide using the carbon monoxide production method and hydrogen production method described above to produce synthesis gas. The resulting synthesis gas is then subjected to Fischer-Tropsch synthesis (2nH2 + nCO → -(CH2) n It can be used in hydrocarbon production processes using (- + nH2O).

[0036] Energy can be obtained by burning hydrocarbons produced by the Fischer-Tropsch synthesis. Furthermore, the carbon dioxide generated during this combustion, as well as the water obtained from the Fischer-Tropsch synthesis, can be decomposed again into carbon monoxide and hydrogen using the reaction medium 18 and reused in the Fischer-Tropsch synthesis. The heat required for the two-stage pyrolysis cycle using the reaction medium 18 can be obtained from clean energy sources such as solar heat. Therefore, this embodiment can contribute to the realization of a carbon-neutral cycle. Note that the embodiment is not limited to the production of both hydrogen and carbon monoxide, but also includes the production of only one of them.

[0037] The embodiments may be specified by the items described below. [1st item] The first step involves heating and reducing the oxidized form of a compound having a perovskite structure to release oxygen, The process includes a second step in which, when the reduced compound obtained in the first step is oxidized back to the oxidized compound, the reduced compound is reacted with a hydrogen-containing substance and at least one of a carbon- and oxygen-containing substance to produce at least one of hydrogen and carbon monoxide. The oxidized form is general formula A (1-x) Q x B (1-y) R yO3 (A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is at least one element selected from the group consisting of first transition elements and Mg, R is Co, Ni or Mg and is different from B, x satisfies 0.1 ≦ x ≦ 0.4, when R is Co, y satisfies 0 < y ≦ 0.5, when R is Ni, y satisfies 0.15 < y ≦ 0.3, and when R is Mg, y satisfies 0 < y < 0.15). A method for producing at least one of hydrogen and carbon monoxide. [Item 2] When R is Co, y satisfies 0.05 ≦ y ≦ 0.3, when R is Ni, y satisfies 0.175 ≦ y ≦ 0.3, and when R is Mg, y satisfies 0.05 ≦ y ≦ 0.125. The production method according to Item 1. [Item 3] A is La, Q is Sr, and B is Mn. The production method according to Item 1 or Item 2. [Item 4] Producing both hydrogen and carbon monoxide by the production method according to any one of Items 1 to 3 to produce synthesis gas. A method for producing synthesis gas. [Item 5] A reaction medium containing a compound having a perovskite structure, When the oxidized form of the compound is heated and reduced to become a reduced form and releases oxygen, and when the reduced form is oxidized and returns to the oxidized form, it reacts with at least one of a substance containing hydrogen and a substance containing carbon and oxygen to produce at least one of hydrogen and carbon monoxide. The oxidized form is represented by the general formula A (1-x) Q x B (1-y) R yO3 (A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is at least one element selected from the group consisting of first transition elements and Mg, R is Co, Ni or Mg and is different from B, x satisfies 0.1 ≦ x ≦ 0.4, when R is Co, y satisfies 0 < y ≦ 0.5, when R is Ni, y satisfies 0.15 < y ≦ 0.3, and when R is Mg, y satisfies 0 < y < 0.15). Reaction medium (18).

Examples

[0038] Hereinafter, examples of the present invention will be described. However, the examples are merely illustrative for preferably explaining the present invention and do not limit the present invention in any way.

[0039] (Synthesis of sample compound) Using the improved Pechini method, a sample compound having a perovskite structure was synthesized. The sample compound has the general formula A (1-x) Q x B (1-y) R y O3, where A is La, Q is Sr, B is Mn, and the substitution ratio at the A site is 30% (i.e., x is 0.3) (La 0.7 Sr 0.3 Mn (1-y) R y O3). Also, R was Cr, Fe, Co, Ni, Cu, Mg, Al, Ga.

[0040] Furthermore, for sample compounds where R is Cr, Fe, Cu, Al, and Ga, one type was synthesized for each, with a B-site substitution ratio of 10% (i.e., y = 0.1). For sample compounds where R is Co, multiple types were synthesized with B-site substitution ratios of 5%, 10%, 15%, 17.5%, 20%, 25%, 30%, 35%, 40%, and 50% (i.e., y = 0.05, 0.1, 0.15, 0.175, 0.2, 0.25, 0.3, 0.35, 0.4, and 0.5). For sample compounds where R is Ni, multiple types were synthesized with B-site substitution ratios of 5%, 10%, 15%, 17.5%, 20%, 25%, and 30%. Furthermore, for sample compounds where R is Mg, multiple types were synthesized with B-site substitution ratios of 5%, 10%, 12.5%, and 15%.

[0041] Specifically, each sample compound was synthesized according to the following procedure. That is, each metal nitrate of La, Sr, Mn, and B-site substituted metal ions was placed in a flask and dissolved in deionized water. The amount of each metal nitrate added was adjusted to match the A-site and B-site substitution ratios described above. Ethylene glycol and citric acid were added to the resulting metal nitrate solution and heated and stirred at 80°C for 1 hour. Then, it was heated and stirred at 170°C for approximately 1 hour until a gel was formed. After the gel was formed, it was dried at 300°C in an air atmosphere for 5 hours. The resulting dried gel was then calcined at 1200°C in an air atmosphere for 8 hours. The sample compounds were obtained through the above steps. For comparison, a sample compound with a B-site substitution ratio of 0% (La) was also prepared. 0.7 Sr 0.3 We also synthesized MnO3.

[0042] (Characterization of sample compounds) To confirm the success of the synthesis of the sample compounds, XRD measurements were performed using an X-ray diffraction spectrometer D2PHASER (BRUKER). Phase identification was then performed on the XRD results using the analysis software Match!3 (Light Stone). Rietveld analysis was also performed on the XRD results. These results confirmed that all sample compounds possessed the desired perovskite structure.

[0043] (Carbon dioxide thermal decomposition cycle test) For each sample compound, a carbon dioxide pyrolysis cycle test was performed using a thermogravimetric analyzer STA2500 Regulus (Netzch). First, approximately 50 mg of the sample compound was weighed into a platinum pan and placed in the instrument along with an empty platinum pan used as a reference. Next, 100 Ncm² was applied. 3 High-purity N2 was circulated through the reaction system of the apparatus at a flow rate of / min for 1.25 hours. This purged the air in the reaction system. Subsequently, the reaction system was heated to 300°C at a heating rate of 50K / min and maintained at that temperature for 30 minutes. This removed foreign matter adsorbed onto the sample compound. After the adsorption was removed, the temperature in the reaction system was raised to 1400°C at a heating rate of 20K / min. The sample compound was then thermally reduced at 1400°C for 90 minutes.

[0044] After the thermal reduction treatment, the mixture was cooled to 1200°C at a cooling rate of 20 K / min. Subsequently, 100 Ncm² was added to the reaction system. 3 High-purity N2 is flowed at a flow rate of / min, 50 Ncm 3 G1 grade CO2 was flowed at a flow rate of / min. This changed the atmosphere in the reaction system to one with a CO2 concentration of 50%. Under this atmosphere, carbon dioxide decomposition treatment was carried out at 1200°C for 30 minutes. The cycle of the heat reduction treatment and carbon dioxide decomposition treatment described above was repeated until stable data was obtained.

[0045] The amount of oxygen and carbon monoxide produced in each cycle was calculated from the increase or decrease in the weight of each sample compound during the carbon dioxide pyrolysis cycle. The ratio of carbon monoxide production to oxygen production (CO / O2 ratio) was also calculated. Due to the oxygen non-stoichiometric properties of the sample compounds, the amount of oxygen produced in the first cycle differed significantly from that of subsequent cycles. However, the amount of oxygen produced from the second cycle onward was stable. This confirmed that the sample compounds exhibited high cycle stability.

[0046] To compare the reactivity of each sample compound, the average value of the oxygen generation amount, the average value of the carbon monoxide generation amount, and the average value of the carbon monoxide / oxygen ratio for each cycle were calculated respectively. The results are shown in Figures 3 and 4. Figures 3 and 4 are diagrams showing the oxygen generation amount, the carbon monoxide generation amount, and the carbon monoxide / oxygen ratio for each sample compound. Note that "unsubstituted" in Figure 3 indicates a sample compound in which the substitution at the B-site was not performed.

[0047] As shown in Figures 3 and 4, in the sample compounds with the B-site substituted with Co, Ni, and Mg, the tendency for the generation amounts of oxygen and carbon monoxide to increase was remarkable compared to the sample compound without B-site substitution. That is, the sample compounds with the B-site substituted with Co, Ni, and Mg showed high reactivity in both the thermal reduction treatment and the carbon dioxide decomposition treatment.

[0048] When the substitution ion was Co, when the substitution ratio was more than 0% and 50% or less (0 < y ≤ 0.5), the generation amount of carbon monoxide was larger than that in the case of no B-site substitution. Also, when the substitution ratio was 5% or more and 50% or less (0.05 ≤ y ≤ 0.5), the generation amount of carbon monoxide was larger not only than that in the case of no B-site substitution but also than that in the case where the substitution ions were Cr, Fe, Cu, Al, and Ga. Furthermore, when the substitution ratio was 15% or more and 50% or less (0.15 ≤ y ≤ 0.5), the generation amount of carbon monoxide was significantly more than about 1.5 times that in the case of no B-site substitution. Also, when the substitution ratio was 30% or more and 50% or less (0.3 ≤ y ≤ 0.5), the generation amount of carbon monoxide further increased.

[0049] When the substitution ion was Ni, when the substitution ratio was more than 15% and 30% or less (0.15 < y ≤ 0.3), the generation amount of carbon monoxide was significantly more than about 1.5 times that in the case of no B-site substitution. Also, when the substitution ratio was 17.5% or more and 30% or less (0.175 ≤ y ≤ 0.3), the generation amount of carbon monoxide further increased.

[0050] When the replacement ion is Mg, when the replacement ratio is more than 0% and less than 15% (0 < y < 0.15), the amount of carbon monoxide generated was larger than that in the case of non-replacement of the B site. Also, when the replacement ratio is 5% or more and 12.5% or less (0.05 ≤ y ≤ 0.125), the amount of carbon monoxide generated was larger not only in the case of non-replacement of the B site but also compared to the cases where the replacement ions are Cr, Fe, Cu, Al, and Ga. Furthermore, when the replacement ratio is 10% or more and 12.5% or less (0.1 ≤ y ≤ 0.125), the amount of carbon monoxide generated was significantly larger, about 1.5 times or more, compared to the case of non-replacement of the B site.

[0051] Also, when comparing the XRD patterns of the sample compounds before and after the cycle test, almost no by-products were confirmed in the sample compounds with the B site replaced by Co, Ni, and Mg. Therefore, these sample compounds were shown to stably maintain their crystal structures in the two-step thermal decomposition cycle. Also, from the time integral of the weight change of the sample compounds in the cycle test, the generation rates of oxygen and carbon monoxide were calculated. As a result, in the sample compounds with the B site replaced by Co, Ni, and Mg, the generation rates of oxygen and carbon monoxide were improved compared to the case of non-replacement of the B site. Also, in the sample compounds of Co50%, Cu10%, Mg5%, and Mg15%, a phase change was observed during the cycle test.

[0052] Note that there is a correlation between the carbon monoxide generation ability and the hydrogen generation ability in the perovskite-type composite oxide. Therefore, it can be said that the sample compounds shown to have a high carbon monoxide generation ability by the above cycle test also have a high hydrogen generation ability. Also, the oxygen release and uptake in the perovskite-type composite oxide mainly occur due to the valence change of the constituent ions. And although the valence of the B-site ions changes, the valence of the A-site ions does not substantially change. For this reason, it can be said that the perovskite-type composite oxides with the B site replaced by Co, Ni, and Mg have a high carbon monoxide and hydrogen generation ability regardless of the type and replacement ratio of the A-site ions.

[0053] Based on the above, it was confirmed that perovskite-type composite oxides in which B-site ions are substituted with Co, Ni, and Mg in predetermined proportions exhibit excellent carbon monoxide and hydrogen production quantities and rates, as well as high physical and chemical stability against high-temperature cyclic reactions. Therefore, reaction media containing these perovskite-type composite oxides can improve the efficiency of hydrogen and carbon monoxide production. [Industrial applicability]

[0054] The present invention can be used in a method for producing at least one of hydrogen and carbon monoxide, a method for producing synthesis gas, and a reaction medium. [Explanation of Symbols]

[0055] 10 inlets, 12 test tubes, 14 oil bath, 16 stirrer, 18 reaction medium, 20 infrared imaging furnace, 22 thermocouples, 24 water-cooled trap, 26 thermal conductivity detector, 28 capillary, 30 mass spectrometer, 100,200 instruments.

Claims

1. The first step involves heating and reducing the oxidized form of a compound having a perovskite structure to release oxygen, The process includes a second step in which, when the reduced form of the compound obtained in the first step is oxidized back to the oxidized form, the reduced form is reacted with a hydrogen-containing substance and at least one of a carbon- and oxygen-containing substance to produce at least one of hydrogen and carbon monoxide. The aforementioned oxidized material is general formula A （１－ｘ） Q ｘ B （１－ｙ） R ｙ O ３ (A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is Mn, R is Co, Ni, or Mg, x is in the range satisfying 0.1 ≤ x ≤ 0.4, when R is Co, y is in the range satisfying 0.3 ≤ y ≤ 0.5, when R is Ni, y is in the range satisfying 0.175 ≤ y ≤ 0.3, and when R is Mg, y is in the range satisfying 0.05 ≤ y ≤ 0.125) A method for producing at least one of hydrogen and carbon monoxide.

2. When R is Mg, y is in the range satisfying 0.1 ≤ y ≤ 0.

125. The manufacturing method according to claim 1.

3. A is La, and Q is Sr. The manufacturing method according to claim 1 or 2.

4. The manufacturing method described in claim 1 or 2 includes producing both hydrogen and carbon monoxide to produce synthesis gas, A method for producing synthesis gas.

5. A reaction medium comprising a compound having a perovskite structure, The oxidized form of the compound is reduced by heating to become a reduced form and release oxygen, and when the reduced form is oxidized back to the oxidized form, it reacts with a hydrogen-containing substance and at least one of a carbon and oxygen-containing substance to produce hydrogen and at least one of carbon monoxide. The oxidized body is represented by the general formula A （１－ｘ） Q ｘ B （１－ｙ） R ｙ O ３ (A is at least one element selected from the group consisting of rare earth elements, Q is at least one element selected from the group consisting of alkaline earth metal elements, B is Mn, R is Co, Ni or Mg, x satisfies 0.1 ≦ x ≦ 0.4, when R is Co, y satisfies 0.3 ≦ y ≦ 0.5, when R is Ni, y satisfies 0.175 ≦ y ≦ 0.3, and when R is Mg, y satisfies 0.05 ≦ y ≦ 0.125). Reaction medium.

Images