Dehydrogenation catalyst

Abstract

We provide a technology to improve the heat resistance of dehydrogenation catalysts. The dehydrogenation catalyst is a compound represented by the general formula (A 1-x A' x )(Zr 1-y-z B y B' z )O 3-δ (wherein A is at least one element selected from alkaline earth metals, A' is at least one element of La and Y, B is at least one element of Ti and Ce, and B' is at least one element selected from Y, Sc, Yb, Al, In, and Nd, satisfying 0≦x≦0.4, 0.3≦(1-z)≦1, 0≦y, 0<(1-yz), and δ represents the amount of oxygen vacancy), and a subphase composed of at least one of three composite oxides represented by the general formulas AB'2O4, A2B'2O5, and A3B'4O9.

Description

[Technical Field]

[0001] The present disclosure relates to a catalyst for dehydrogenation reactions. [Background technology]

[0002] Various catalysts have been proposed as methane oxidative coupling catalysts for producing hydrocarbons having two or more carbon atoms, such as ethylene, from methane (for example, Patent Documents 1 and 2, and Non-Patent Document 1). Patent Document 1 discloses an alkali metal halide-supported samarium oxide catalyst as a methane oxidative coupling catalyst, and shows that such a catalyst can withstand durability tests at a temperature of 750°C. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 08-010620 [Patent Document 2] Japanese Patent Publication No. 61-282323 [Non-patent literature]

[0004] [Non-Patent Document 1] Seoyeon Lim, Jae-Wook Choi, Dong Jin Suh, Kwang Ho Song, Hyung Chul Ham, Jeong-Myeong Ha, “Combined experimental and density functional theory (DFT) studies on the catalyst design for the oxidative coupling of methane”, Journal of Catalysis, Volume 375, July 2019, Pages 478-492 Summary of the Invention [Problem to be solved by the invention]

[0005] Because the methane oxidative coupling reaction is an exothermic reaction, there is a possibility that the catalyst temperature will rise rapidly as the reaction progresses. For example, when a hydrocarbon production facility using the methane oxidative coupling reaction is converted into a plant (large-scale), the degree of catalyst temperature rise may become even greater due to the rapid progress of the exothermic reaction. Such a significant rise in catalyst temperature may lead to inconveniences such as deactivation of the methane oxidative coupling catalyst. Therefore, there is a need for further improvement in the heat resistance of methane oxidative coupling catalysts. The methane oxidative coupling reaction is a type of dehydrogenation reaction. However, dehydrogenation reactions in general, including the methane oxidative coupling reaction, are exothermic reactions and therefore there is a possibility that the catalyst temperature will rise rapidly as the reaction progresses. Therefore, the above-mentioned problem regarding the heat resistance of the catalyst is a common problem for dehydrogenation catalysts.

[0006] However, even with prior art such as Patent Documents 1 and 2 and Non-Patent Document 1, there is still room for improvement in the technology for improving the heat resistance of dehydrogenation catalysts. Also, even with prior art such as Patent Documents 1 and 2 and Non-Patent Document 1, there is still room for improvement in the technology for increasing the catalytic activity of dehydrogenation catalysts. Furthermore, even with prior art such as Patent Documents 1 and 2 and Non-Patent Document 1, there is still room for improvement in the technology for increasing the catalytic activity of dehydrogenation catalysts that promotes dehydrogenation at low temperatures. [Means for solving the problem]

[0007] The present disclosure can be realized in the following forms. (1) According to one aspect of the present disclosure, a dehydrogenation catalyst is provided. The dehydrogenation catalyst is represented by the general formula (A 1-x A' x )(Zr 1-y-z B y B' z )O 3-δThe present invention relates to a composite oxide having a main phase composed of a perovskite oxide represented by the general formula AB'2O4, AB'2O5, or AB'4O9 (wherein A is at least one element selected from alkaline earth metals, A' is at least one element selected from lanthanum (La) and yttrium (Y), B is at least one element selected from titanium (Ti) and cerium (Ce), and B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd), and where 0≦x≦0.4, 0.3≦(1-z)≦1, 0≦y, and 0<(1-yz) are satisfied, and δ represents the amount of oxygen vacancy), and a subphase composed of at least one of three composite oxides represented by the general formula AB'2O4, AB'2O5, or AB'4O9 (wherein A and B' are elements common to A and B' that constitute the perovskite oxide). According to the dehydrogenation catalyst of this embodiment, the heat resistance of the dehydrogenation catalyst can be improved.

[0008] (2) In the dehydrogenation catalyst of the above embodiment, A may be barium (Ba), B' may be scandium (Sc), and the subphase may be composed of barium scandate (at least one of three composite oxides: BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9). With such a configuration, the catalytic activity of the dehydrogenation catalyst can be further enhanced.

[0009] (3) In the dehydrogenation catalyst of the above embodiment, the subphase may be composed of Ba3Sc4O9. With this configuration, a catalyst having high catalytic activity as a dehydrogenation catalyst can be easily obtained.

[0010] (4) In the dehydrogenation catalyst of the above embodiment, the main phase is BaZr 1-z Sc z O 3-δ (where 0.1≦z≦0.7). With such a configuration, the catalytic activity as a dehydrogenation catalyst can be further enhanced.

[0011] (5) In the dehydrogenation catalyst of the above embodiment, in a powder X-ray diffraction pattern using CuKα radiation, the perovskite oxide constituting the main phase may have a first peak whose peak intensity is maximum in the diffraction angle 2θ range of 29.5-30.5°, and the composite oxide constituting the subphase may have a second peak whose peak intensity is maximum in the diffraction angle 2θ range of 30.6-31.0°, and the ratio of the intensity of the second peak to the intensity of the first peak may be 0.04 or more. With this configuration, the catalytic activity as a dehydrogenation catalyst can be further improved.

[0012] (6) In the dehydrogenation catalyst of the above embodiment, the subphase may be composed of any one of the three composite oxides. With this configuration, a catalyst with high catalytic activity as a dehydrogenation catalyst can be easily obtained.

[0013] (7) The dehydrogenation catalyst of the above embodiment may be a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane. With this configuration, the heat resistance of the methane oxidative coupling catalyst can be improved.

[0014] (8) In another embodiment of the dehydrogenation catalyst, the spectrum of the O1s orbital included in a photoelectron spectrum obtained by X-ray photoelectron spectroscopy is divided by peak separation fitting into a first curve having a first peak corresponding to a maximum value in the binding energy range of 525-530 eV and a second curve having a second peak corresponding to a maximum value in the binding energy range of 530-535 eV, and the area of ​​the convex portion including the first peak in the first curve is defined as the first peak area, and the area of ​​the convex portion including the second peak in the second curve is defined as the second peak area, whereby the ratio of the second peak area to the first peak area is greater than 1. According to this embodiment of the dehydrogenation catalyst, adsorbable oxygen species are more likely to be adsorbed onto the surface of the dehydrogenation catalyst, thereby enhancing the catalytic activity of the dehydrogenation catalyst.

[0015] (9) The dehydrogenation catalyst of the above embodiment has oxygen deficiency. With this configuration, the amount of adsorbed oxygen species on the surface of the dehydrogenation catalyst can be increased, thereby further enhancing the catalytic activity of the dehydrogenation catalyst.

[0016] (10) In the dehydrogenation catalyst of the above embodiment, the main phase of the catalyst has a perovskite structure. With this configuration, the catalytic activity of the dehydrogenation catalyst can be further improved.

[0017] (11) In the dehydrogenation catalyst of the above embodiment, the specific surface area measured by the BET method is 10 m 2 With this configuration, the amount of adsorbed oxygen species on the surface of the dehydrogenation catalyst can be increased, and therefore the catalytic activity of the dehydrogenation catalyst can be further improved.

[0018] (12) The dehydrogenation catalyst according to the above embodiment is a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane. With this configuration, the catalytic activity of the methane oxidative coupling catalyst can be increased.

[0019] (13) Furthermore, another type of dehydrogenation catalyst is a catalyst represented by the general formula (La 1-x M1 x )M2O 3-δ (wherein M1 is at least one element selected from alkaline earth metals, M2 is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and gallium (Ga), and δ represents the amount of oxygen deficiency and satisfies 0≦x≦0.6). The dehydrogenation catalyst of this form can promote the dehydrogenation reaction at low temperatures and can enhance the catalytic activity as a dehydrogenation catalyst.

[0020] (14) In the dehydrogenation catalyst of the above embodiment, M1 is strontium (Sr) or barium (Ba). With this configuration, the catalytic activity of the dehydrogenation catalyst, particularly the catalytic activity of promoting the dehydrogenation reaction at relatively low temperatures, can be further enhanced.

[0021] (15) The dehydrogenation catalyst of the above embodiment is a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane. With this configuration, the catalytic activity of the methane oxidative coupling catalyst at low temperatures can be increased.

[0022] The present disclosure may be realized in various forms other than those described above, such as a method for producing a dehydrogenation catalyst, an apparatus including a dehydrogenation catalyst, or an ethylene production apparatus including a methane oxidative coupling catalyst. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is an explanatory diagram showing a phase diagram of an oxide containing barium and scandium. [Figure 2] FIG. 1 is a first explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst. [Figure 3] FIG. 2 is a second explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst. [Figure 4] FIG. 1 shows chemical formulas for various dehydrogenation reactions that can be promoted by a dehydrogenation catalyst. [Figure 5] FIG. 1 is a first diagram illustrating the characteristics of the dehydrogenation catalyst of the first embodiment. [Figure 6] FIG. 2 is a second diagram illustrating the characteristics of the dehydrogenation catalyst of the first embodiment. [Figure 7] FIG. 2 is a diagram showing an XRD chart of the dehydrogenation catalyst of the first embodiment. [Figure 8] FIG. 2 is a diagram illustrating an XRD chart of the dehydrogenation catalyst of the first embodiment. [Figure 9] FIG. 1 is a first diagram illustrating the C2 yield of the dehydrogenation catalyst of the first embodiment. [Figure 10] FIG. 3 is a graph showing the change in C2 yield with temperature in the dehydrogenation catalyst of the first embodiment. [Figure 11] FIG. 2 is a second diagram illustrating the C2 yield of the dehydrogenation catalyst of the first embodiment. [Figure 12] FIG. 1 is a first diagram showing an SEM image of a dehydrogenation catalyst according to a first embodiment. [Figure 13] FIG. 2 is a second diagram showing an SEM image of the dehydrogenation catalyst of the first embodiment. [Figure 14] FIG. 2 is a diagram showing the specific surface area of ​​the dehydrogenation catalyst of the first embodiment. [Figure 15] FIG. 1 is a first diagram showing an XPS spectrum of a dehydrogenation catalyst according to a first embodiment. [Figure 16] FIG. 2 is a second diagram showing the XPS spectrum of the dehydrogenation catalyst of the first embodiment. [Figure 17] FIG. 3 is a third diagram illustrating the C2 yield of the dehydrogenation catalyst of the first embodiment. [Figure 18] FIG. 1 is a diagram illustrating a method for calculating an XPS ratio. [Figure 19] FIG. 4 is a fourth diagram illustrating the C2 yield of the dehydrogenation catalyst of the first embodiment. [Figure 20] FIG. 5 is a fifth diagram illustrating the C2 yield of the dehydrogenation catalyst of the first embodiment. [Figure 21] FIG. 6 is a sixth diagram illustrating the C2 yield of the dehydrogenation catalyst of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] First Embodiment [Dehydrogenation catalyst] The dehydrogenation catalyst of this embodiment is a composite oxide comprising a main phase having a perovskite-type oxide crystal structure represented by the following general formula (1), and a subphase having at least one of three composite oxides represented by the following general formulas (2a) to (2c).

[0025] (A1-x A' x )(Zr 1-y-z B y B' z )O 3-δ … (1) AB'2O4… (2a) A2B'2O5… (2b) A3B'4O9… (2c) In the formula (1), A is at least one element selected from alkaline earth metals, A' is at least one element selected from lanthanum (La) and yttrium (Y), B is at least one element selected from titanium (Ti) and cerium (Ce), and B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd). In formula (1), x, y, and z satisfy the relationships shown in formulas (3a) to (3d) below. δ represents the amount of oxygen vacancy required to achieve electrical neutrality, and is, for example, 0≦δ≦0.5.

[0026] 0≦x≦0.4 … (3a) 0.3≦(1−z)≦1 … (3b) 0≦y … (3c) 0<(1-yz) … (3d) In the above formulas (2a) to (2c), A and B' are elements common to A and B' that constitute the perovskite oxide represented by formula (1).

[0027] Furthermore, in the dehydrogenation catalyst of this embodiment, the spectrum of the O1s orbital contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy is divided by peak separation fitting into a first curve having a first peak corresponding to a maximum value in the binding energy range of 525-530 eV and a second curve having a second peak corresponding to a maximum value in the binding energy range of 530-535 eV. If the area of ​​the convex portion containing the first peak in the first curve is defined as the first peak area and the area of ​​the convex portion containing the second peak in the second curve is defined as the second peak area, the ratio of the second peak area to the first peak area is greater than 1. In the spectrum of the O1s orbital contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy, the first peak area is derived from lattice oxygen species on the surface of the dehydrogenation catalyst, and the second peak area is derived from adsorbed oxygen species on the surface of the dehydrogenation catalyst. In other words, a ratio of the second peak area to the first peak area greater than 1 indicates the presence of a large amount of activated adsorbed oxygen species in the dehydrogenation catalyst. This promotes the dehydrogenation reaction. Details of the "first peak area" and the "second peak area" will be described later.

[0028] A dehydrogenation catalyst having a ratio of the second peak area to the first peak area of ​​greater than 1 preferably has oxygen deficiency. Specifically, for example, a catalyst having a composition formula of Ba(Zr 1-x Y x )O 3-δ The larger the value of x, the more likely the dehydrogenation catalyst represented by the formula (2) is to have oxygen vacancies due to charge compensation. This allows for a larger amount of activated adsorbed oxygen species on the surface of the dehydrogenation catalyst. Furthermore, a dehydrogenation catalyst in which the ratio of the second peak area to the first peak area is greater than 1 has a specific surface area of ​​10 m2 measured by the BET method. 2 / g or more, which allows the amount of activated adsorbed oxygen species to be increased on the surface of the dehydrogenation catalyst.

[0029] In the dehydrogenation catalyst of this embodiment, at least the perovskite-type oxide of formula (1) constituting the main phase has catalytic activity for dehydrogenation. Here, the "main phase" refers to a phase having a peak intensity ratio of 50% or more in a powder X-ray diffraction pattern using CuKα radiation. In addition to the main phase, the dehydrogenation catalyst of this embodiment also has a subphase composed of at least one of the three composite oxides represented by formulas (2a) to (2c), resulting in improved heat resistance of the catalyst.

[0030] [Perovskite-type oxides that make up the main phase] As described above, in the dehydrogenation catalyst of this embodiment, at least the perovskite-type oxide of formula (1) constituting the main phase has activity as a dehydrogenation catalyst. The perovskite-type oxide of formula (1) will be further described below.

[0031] The perovskite oxide of formula (1) contains at least one element selected from alkaline earth metals in the so-called A site of the perovskite structure. The alkaline earth metal is preferably an element selected from barium (Ba), calcium (Ca), and strontium (Sr). Hereinafter, the alkaline earth metal element contained in the A site will also be referred to as "element A." The perovskite oxide of formula (1) may further contain at least one element selected from lanthanum (La) and yttrium (Y) in the A site of the perovskite structure. However, lanthanum (La) and yttrium (Y) are not essential. Hereinafter, the lanthanum (La) and yttrium (Y) contained in the A site will also be referred to as "element A'." In the dehydrogenation catalyst of this embodiment, the contents of element A and element A' in formula (1) described above satisfy formula (3a).

[0032] The perovskite oxide of formula (1) also contains zirconium (Zr) at the so-called B site of the perovskite structure. This perovskite oxide may further contain at least one element selected from titanium (Ti) and cerium (Ce) at the B site. However, titanium (Ti) and cerium (Ce) are not essential. Hereinafter, the titanium (Ti) and cerium (Ce) contained at the B site will also be referred to as "element B." The perovskite oxide of formula (1) may further contain at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd) at the B site of the perovskite structure. However, at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd) is not essential. Hereinafter, at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd) contained in the B site will also be referred to as "element B'." In the perovskite oxide of formula (1), the contents of Zr, element B, and element B' satisfy formulas (3b) to (3d) in the aforementioned formula (1).

[0033] In the perovskite oxide of formula (1), it is desirable that x satisfy the following formula (3e), which can further enhance the catalytic activity as a dehydrogenation catalyst that promotes the dehydrogenation reaction. 0≦x≦0.2 … (3e)

[0034] Furthermore, the perovskite oxide of formula (1) preferably has a perovskite structure represented by the following general formula (4), which can further enhance the catalytic activity as a dehydrogenation catalyst that promotes the dehydrogenation reaction. BaZr 1-z B' z O 3-δ … (4) Here, B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), indium (In), and neodymium (Nd). In this case, when B' is scandium (Sc), that is, the perovskite oxide of formula (4) is BaZr 1-z Sc z O 3-δ (However, it is particularly desirable that z be in the range of 0.1≦z≦0.7). This can further enhance the catalytic activity as a dehydrogenation catalyst, which promotes the dehydrogenation reaction.

[0035] Furthermore, the perovskite oxide of formula (1) has catalytic activity as a dehydrogenation catalyst that promotes the dehydrogenation reaction, as well as proton conductivity and at least one of electron conductivity and hole conductivity.

[0036] [Composite oxides that make up the subphase] As described above, the dehydrogenation catalyst of this embodiment has a subphase composed of at least one of the three composite oxides represented by formulas (2a) to (2c), and as a result of having such a structure, heat resistance is improved. Specifically, even when the dehydrogenation catalyst is used under temperature conditions of, for example, 800°C or higher, it is possible to suppress a decrease in catalytic activity as a dehydrogenation catalyst that promotes dehydrogenation. It is more preferable that the subphase be composed of any one of the three composite oxides represented by formulas (2a) to (2c).

[0037] In formulas (2a) to (2c), A and B' are elements common to A and B' that constitute the perovskite oxide of formula (1) that constitutes the main phase. As described below, such a subphase composite oxide can be formed together with the perovskite oxide of formula (1) that constitutes the main phase by mixing raw material powders of the perovskite oxide of formula (1) that constitutes the main phase and firing them at a relatively high temperature of approximately 1300-1600°C during the production of a dehydrogenation catalyst. Which of the composite oxides represented by formulas (2a) to (2c) constitutes the subphase depends on the elements contained in the A site and B site of the perovskite oxide of formula (1). Which of the composite oxides constitutes the subphase can also be determined by the mixing ratio of the raw material powders of the main phase when producing a dehydrogenation catalyst.

[0038] In the dehydrogenation catalyst of this embodiment, element A in formula (1) is barium (Ba), element B' is scandium (Sc), and the subphase is preferably composed of at least one of three composite oxides, namely, barium scandate, BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9. In this case, it is particularly preferable that the subphase be composed of Ba3Sc4O9.

[0039] FIG. 1 is an explanatory diagram showing, as an example, a phase diagram of an oxide containing barium (Ba) and scandium (Sc) (source: Kovba LM, Lykova LN, Paromova MV, Kalinina TA (1981). X-ray and thermographic investigation of compounds in the BaO-Sc2O3 system. Dokl. Akad. Nauk SSSR, 260, 924-927). As shown in FIG. 1, it can be seen that three types of composite oxides containing barium (Ba) and scandium (Sc) can be formed: BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9. From the composite oxides shown in this phase diagram, it can be seen that the three types of composite oxides represented by formulas (2a) to (2c) can also be formed when an alkaline earth metal other than barium (Ba) is used as element A and an element other than scandium (Sc) is used as element B'.

[0040] In a powder X-ray diffraction pattern using CuKα radiation, when the maximum peak of the perovskite oxide constituting the main phase of the dehydrogenation catalyst of this embodiment is defined as the first peak, and the maximum peak of the composite oxide constituting the subphase is defined as the second peak, the ratio of the intensity of the second peak to the intensity of the first peak is preferably 0.02 or more, more preferably 0.03 or more, and even more preferably 0.04 or more. By ensuring the ratio of the composite oxide constituting the subphase in this way, it becomes easy to improve the heat resistance of the dehydrogenation catalyst. For example, when the perovskite oxide constituting the main phase is BaZr 1-z Sc z O 3-δ When the composite oxide constituting the subphase is Ba3Sc4O9, the powder X-ray diffraction pattern using CuKα radiation shows a first peak in the diffraction angle range 2θ = 29.5-30.5° and a second peak in the diffraction angle range 2θ = 30.6-31.0°.

[0041] The dehydrogenation catalyst of this embodiment, configured as described above, comprises a main phase having a perovskite-type oxide crystal structure represented by the aforementioned formula (1) and a subphase containing at least one of the three composite oxides represented by the aforementioned formulas (2a) to (2c). This enhances the catalytic activity of the dehydrogenation catalyst, which promotes the dehydrogenation reaction of desorbing hydrogen from a compound, and also improves the heat resistance of the dehydrogenation catalyst. In the dehydrogenation catalyst of this embodiment, the catalytic activity for promoting the dehydrogenation reaction is primarily achieved by the perovskite-type oxide constituting the main phase. By further comprising a subphase containing at least one of the three composite oxides represented by the aforementioned formulas (2a) to (2c), the dehydrogenation catalyst can suppress a decrease in its catalytic activity for promoting the dehydrogenation reaction, even when used at higher temperatures.

[0042] The dehydrogenation catalyst of this embodiment can promote various dehydrogenation reactions in which hydrogen is released from compounds. Examples of dehydrogenation reactions include the oxidative coupling of methane (OCM) reaction for producing hydrocarbons having two or more carbon atoms from methane. Also included are various reactions for producing hydrogen from various hydrocarbon compounds, including hydrocarbons and alcohols, through dehydrogenation reactions. Specific examples include a steam reforming reaction in which hydrogen is produced from the hydrocarbon compounds and steam, a partial oxidation reaction in which hydrogen is produced from the hydrocarbon compounds, and a shift reaction in which carbon monoxide produced together with hydrogen in the partial oxidation reaction and steam are used to produce carbon dioxide and hydrogen.

[0043] FIG. 2 is a first explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst. FIG. 3 is a second explanatory diagram showing an example of a reaction that proceeds on a dehydrogenation catalyst. FIGS. 2 and 3 are explanatory diagrams showing an example of a methane oxidative coupling reaction that proceeds on a methane oxidative coupling catalyst when the dehydrogenation catalyst of this embodiment is a methane oxidative coupling catalyst, as an example of a reaction including a dehydrogenation reaction. When a dehydrogenation reaction proceeds, in which hydrogen is released from a compound, the covalent bond between an atom such as carbon and a hydrogen atom that constitutes the compound is generally cleaved. The dehydrogenation catalyst of this embodiment is thought to exhibit high activity in promoting such a reaction by promoting the dehydrogenation reaction. In the methane oxidative coupling reaction, a reaction that produces methyl radicals from methane, as shown in formula (5) below, proceeds. Furthermore, reactions shown in formulas (6) and (7) below (see FIG. 2) and reactions shown in formulas (8) and (9) below (see FIG. 3) proceed, and C2 hydrocarbons such as ethylene are thought to be produced. The overall reaction that produces ethylene by the methane oxidative coupling reaction is expressed by formula (10) below.

[0044] CH4 → CH3 + H + +e - … (5) 2·CH3+1 / 2O2→ C2H4+H2O … (6) 1 / 2O2+2H + +2e - → H2O … (7) 2·CH3 → C2H6 → C2H4+2H + +2e - … (8) O2+4H + +4e - → 2H2O …(9) 2CH4+O2→ C2H4+2H2O … (10)

[0045] Here, the covalent bond between the carbon atom and the hydrogen atom in methane has a bond energy of 104 kcal / mol, making it an extremely stable bond. Therefore, in the methane oxidative coupling reaction, the reaction of producing methyl radicals by dehydrogenation from methane, which has a stable covalent bond as described above (the reaction represented by the above formula (5)), is generally considered to be the rate-determining step. The dehydrogenation catalyst of this embodiment, at least in its main phase, has high activity in promoting reactions involving the cleavage of covalent bonds in hydrogen, such as the reaction of producing methyl radicals from methane described above. Therefore, it is considered that the catalyst can widely promote dehydrogenation reactions, such as the methane oxidative coupling reaction, involving the cleavage of covalent bonds in hydrogen. Furthermore, as described above, at least the main phase of the dehydrogenation catalyst of this embodiment is a proton conductor, capable of protonating and transferring hydrogen from hydrogen-containing molecules. Therefore, it is considered that the catalyst has high activity in promoting reactions involving the cleavage of covalent bonds containing hydrogen, and can widely promote dehydrogenation reactions, such as the methane oxidative coupling reaction, involving the cleavage of covalent bonds containing hydrogen.

[0046] 2 and 3 show the location where the reaction of formula (5), which produces methyl radicals from methane, proceeds as an "oxidation site." Furthermore, FIGS. 2 and 3 show the progress of the reaction of formula (6) or (8), which produces ethylene from the methyl radicals, at this oxidation site. Also, FIGS. 2 and 3 show the location where the reaction of formula (7) or (9), which produces water using the protons and electrons generated along with the methyl radicals in formula (5), proceeds as a "reduction site." Thus, when reactions including dehydrogenation proceed in the dehydrogenation catalyst of this embodiment, the transfer of protons and electrons generally occurs. Therefore, to enhance catalytic activity, it is desirable for the dehydrogenation catalyst to have high proton conductivity and electron conductivity (including hole conductivity) in addition to high activity in promoting the reaction of formula (5), which is the rate-determining process described above. Specifically, it is desirable for the proton conductivity and proton transport number, or the electron conductivity (including hole conductivity) and electron transport number (including hole transport number) to be high. It is also desirable that the total conductivity of the dehydrogenation catalyst as a whole, which is the sum of the proton conductivity and the electron conductivity (including the hole conductivity), is higher.

[0047] From this viewpoint, for example, the total conductivity of the main phase of the dehydrogenation catalyst of this embodiment is 1.0 × 10 -5 The proton conductivity of the main phase is preferably 1.0×10 S / cm or more. -4 S / cm or more. The proton transport number of the main phase is preferably 0.01 or more. The sum of the electron transport number and the hole transport number of the main phase is preferably 0.01 or more. The proton transport number and the sum of the electron transport number and the hole transport number of the main phase are preferably 0.10 or more. On the other hand, if the electronic conductivity (including the hole conductivity) is excessively high, for example, in the methane oxidative coupling reaction, the peroxidation of methane, i.e., the complete oxidation reaction that produces carbon dioxide and water from methane, becomes more likely to proceed, and the reaction that produces ethylene from methane may be suppressed. Therefore, the total conductivity of the main phase of the dehydrogenation catalyst is 1.0 × 10 -1The total of the electron transport number and the hole transport number of the main phase is preferably 0.95 or less. When the perovskite oxide constituting the main phase of the dehydrogenation catalyst satisfies the above-mentioned formula (1) and formulas (3a) to (3d), it becomes easy to satisfy the above-mentioned numerical ranges.

[0048] [Other dehydrogenation reactions] FIG. 4 is an explanatory diagram showing examples of various dehydrogenation reactions that can be promoted by the dehydrogenation catalyst of this embodiment. The dehydrogenation catalyst of this embodiment can promote various reactions depending on the raw materials (reactants) used. Formulas (11) to (22) in FIG. 4 show reactions that combine reactants containing at least one of methane and methane derivatives (hereinafter also referred to as "methanes"). Such reactions are also referred to as "oxidative coupling reactions of methanes." The dehydrogenation catalyst of this embodiment, which promotes the oxidative coupling reactions of methanes, is also referred to as "oxidative coupling catalysts of methanes." In formulas (13) to (22) in FIG. 4, A and B contained in the methane derivative represent atoms or atomic groups as substituents that replace hydrogen atoms in the methane molecule, and n is an integer of 2 or greater. The methane derivative shown in FIG. 4 has one or two hydrogen atoms in the methane molecule substituted with the above-mentioned substituents. When a molecule has substituents A and B, A and B may be the same or different substituents. Examples of the substituent represented by A or B include a halogen element, a hydroxy group (-OH), and a phenyl group (-C6H5).

[0049] In Figure 4, equation (11), like equation (10), represents the reaction in which ethylene is produced from methane. Equation (12) represents the reaction in which the polymerization reaction proceeds further to produce polyethylene. Unlike equation (10), equations (11) to (22) only show the changes in methane and methane derivatives among the molecules involved in the reaction.

[0050] Equations (11) and (12) show reactions in which methane is a reactant. Equations (13) and (14) show reactions in which a methane derivative represented by BACH2 is a reactant. Equations (15) and (16) show reactions in which a methane derivative represented by ACH3 is a reactant. Equations (17) and (18) show reactions in which a methane derivative represented by ACH3 and methane are reactants. Equations (19) and (20) show reactions in which a methane derivative represented by ACH3 and a methane derivative represented by CA2H2 are reactants. Equations (21) and (22) show reactions in which a methane derivative represented by CABH2 and methane are reactants.

[0051] Furthermore, formulas (11), (13), (15), (17), (19), and (21) show reactions using reactants selected from hydrocarbons with one carbon atom (methane) and methane derivatives (hereinafter also referred to as "C1 hydrocarbons") to produce hydrocarbons with two carbon atoms (ethylene) or ethylene derivatives (hereinafter also referred to as "C2 hydrocarbons"). Formulas (12), (14), (16), (18), (20), and (22) show reactions using reactants selected from C1 hydrocarbons to produce polymers. When producing polymers, C2 hydrocarbons may be produced from C1 hydrocarbons, and then these C2 hydrocarbons may be further polymerized with each other. Alternatively, C1 hydrocarbons may be sequentially polymerized to the ends of molecules to produce polymers. Both of these reactions may occur.

[0052] To explain the reaction shown in Figure 4 more specifically, for example, in formula (14), if the substituents A and B are both fluorine atoms (F), polytetrafluoroethylene (PTFE) is obtained as the product. In formula (18), if the substituent A is a chlorine atom (Cl), polyvinyl chloride (PVC) is obtained as the product. If the substituent A is a hydroxyl group (-OH), polyvinyl alcohol (PVOH) is obtained as the product. If the substituent A is a phenyl group (-CH), polystyrene (PS) is obtained as the product. In formula (22), if the substituents A and B are both fluorine atoms (F), polyvinylidene fluoride (PVDF) is obtained as the product. If the substituents A and B are both chlorine atoms (Cl), polyvinylidene chloride (PVDC) is obtained as the product. Furthermore, in formula (22), if the substituent A is a methyl group (-CH) and the substituent B is a methoxycarbonyl group (-COOCH), polymethyl methacrylate (PMMA) is obtained as the product.

[0053] Although FIG. 4 illustrates the oxidative coupling reaction of methanes, the dehydrogenation catalyst of this embodiment can also be used to promote dehydrogenation reactions other than the oxidative coupling reaction of methanes. Examples of dehydrogenation reactions promoted by the dehydrogenation catalyst of this embodiment include a reaction of combining reactants containing at least one of an alkane and an alkane derivative (hereinafter also referred to as "alkanes"). Such a reaction, together with the oxidative coupling reaction of methanes described above, is also referred to as the "oxidative coupling reaction of alkanes." The dehydrogenation catalyst of this embodiment, which promotes the oxidative coupling reaction of alkanes, is also referred to as the "oxidative coupling catalyst of alkanes." The number of carbon atoms in alkanes, which are the reactants of the oxidative coupling reaction of alkanes promoted by the dehydrogenation catalyst of this embodiment, can be, for example, 1 to 10, preferably 1 to 5, and more preferably 1 or 2. The alkane derivative used in the oxidative coupling reaction of alkanes is one in which hydrogen atoms contained in the alkane molecule have been substituted with the substituents described above, but which has a covalent bond between the carbon atom to be dehydrogenated and the hydrogen atom.

[0054] The dehydrogenation catalyst of this embodiment can also be used to promote dehydrogenation reactions other than the oxidative coupling reaction of alkanes. Examples of other dehydrogenation reactions promoted by the dehydrogenation catalyst of this embodiment include the dehydrogenation reaction of alkanes as exemplified by formula (23) in FIG. 4 and the dehydrogenation reaction of alcohols or alcohol derivatives (hereinafter also referred to as "alcohols") as exemplified by formulas (24) and (25). In formulas (23) to (25), A and B represent hydrogen or, as in formulas (13) to (22), an atom or atomic group as a substituent replacing hydrogen. Formula (23) represents a reaction in which an alkene or an alkene derivative is produced from an alkane. Formula (24) represents a reaction in which an aldehyde is produced from an alcohol, and formula (25) represents a reaction in which a ketone is produced from an alcohol. In this way, the dehydrogenation catalyst of this embodiment can be used as a catalyst to promote various dehydrogenation reactions.

[0055] [Method of manufacturing a dehydrogenation catalyst] The dehydrogenation catalyst of this embodiment can be prepared, for example, by a solid-state reaction method. Specifically, powders of metal oxides, metal carbonates, or the like, which are raw materials for the main phase represented by formula (1), are mixed in a ball mill or the like using a solvent such as ethanol, and then the mixture is dried to remove the solvent and calcined. By calcining at a relatively high temperature of approximately 1300-1600°C, a composite oxide can be obtained that has not only the main phase represented by formula (1) but also a subphase containing at least one of the three composite oxides represented by formulas (2a) to (2c).

[0056] Various methods for producing composite oxides are known, including solid-state reaction methods, complex polymerization methods, coprecipitation methods, and sol-gel methods. Complex polymerization methods, in particular, are known to be excellent catalyst production methods because they enable the mixing of raw materials at the molecular level. However, complex polymerization methods are prone to structural changes due to heat, and calcination at high temperatures such as those described above can easily cause changes such as an increase in particle size, which can result in a decrease in catalytic performance. In contrast, solid-state reaction methods are less susceptible to structural changes due to heat, and can suppress a decrease in catalytic performance even when calcined at high temperatures such as those described above. Furthermore, when a dehydrogenation catalyst is produced by the solid-state reaction method involving calcination at high temperatures, the structure of the composite oxide is stabilized under high-temperature calcination conditions, so that when the resulting dehydrogenation catalyst is used (to proceed with the dehydrogenation reaction) at temperatures lower than the calcination temperature, deterioration such as structural changes, including volatilization of constituent elements, is suppressed. Therefore, even when the catalyst temperature rises sharply as an exothermic reaction including a dehydrogenation reaction progresses, it is possible to prevent problems such as deactivation of the dehydrogenation catalyst, thereby improving the heat resistance and durability of the dehydrogenation catalyst.

[0057] Example 1 FIG. 5 is a first diagram illustrating the characteristics of the dehydrogenation catalyst of this embodiment. FIG. 6 is a second diagram illustrating the characteristics of the dehydrogenation catalyst of this embodiment. FIGS. 5 and 6 are explanatory diagrams showing the results of examining the performance of 34 types of composite oxides, Samples A1 to A34. Here, their performance as dehydrogenation catalysts was evaluated as methane oxidative coupling catalysts. Of Samples A1 to A34, Samples A1 to A29 correspond to the main phase in the dehydrogenation catalyst of the previously described embodiment and are perovskite-type oxides satisfying the previously described formulas (1) and (3a) to (3d). Samples A30 to A34 are composite oxides that do not satisfy at least one of Formulas (1) and (3a) to (3d). These composite oxides of Samples A1 to A34 were prepared by complex polymerization. In the following explanations and drawings, the number of oxygen atoms in the formula may be abbreviated as "O3", but these notations should be interpreted as "O 3-δ " and does not mean that δ is strictly 0. The configuration, manufacturing method, evaluation method, and performance evaluation results of each sample are explained below.

[0058] [Preparation of Sample A1] The catalyst of sample A1 (BaZr 0.8 Sc 0.2 O3) was prepared by the complex polymerization method. The raw material powders used were barium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), zirconyl nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and scandium nitrate (manufactured by Alfa Aesar). These raw material powders were mixed in a solution containing the metal elements in the composition formula BaZr 0.8 Sc 0.2The raw material powder was weighed to achieve the composition ratio in O3. Then, a citric acid solution and propylene glycol were added to the raw material powder so that the ratio of metal elements:citric acid:propylene glycol was 1:3:3 (molar ratio), and the mixture was stirred and mixed at 80°C for 1 hour. This solution was then slowly heated to 300°C to obtain a polymer with each metal element dispersed therein. The resulting polymer was then carbonized by heat treatment at 400°C for 2 hours and pulverized in an agate mortar to obtain a catalyst powder precursor. The resulting catalyst powder precursor was then heat treated at a heat treatment temperature of 1200°C ("T_treat" in Figures 5 and 6) for 6 hours to obtain a powdered dehydrogenation catalyst designated as Sample A1.

[0059] It was confirmed by powder XRD analysis that the powdered methane oxidative coupling catalysts obtained for Sample A1 and Samples A2 to A34 described below had the desired composition. Specifically, this was confirmed by the results of powder XRD analysis, which showed that a perovskite structure was obtained and that no peaks were observed from the raw material powder or from simple oxides (oxides containing only one element other than oxygen) or carbonates derived from the raw material powder. Furthermore, the specific surface areas of the powdered methane oxidative coupling catalysts obtained for Sample A1 and Samples A2 to A34 described below were measured by gas adsorption, and all were found to be 5 m 2 / g~10m 2 It was confirmed that the value was within the range of / g.

[0060] [Preparation of Samples A2 to A34] Powdered dehydrogenation catalysts for Samples A2 to A34 were obtained in the same manner as Sample A1, except that the types and weighed amounts of the catalyst raw material powders were adjusted to correspond to the composition ratios of the composition formulas of Samples A2 to A34 shown in Figures 5 and 6, and the heat treatment temperature of the catalyst powder precursor was set to the temperature shown in Figures 5 and 6 ("T_treat" shown in Figures 5 and 6). To add barium, zirconium, scandium, yttrium, ytterbium, indium, neodymium, cerium, lanthanum, strontium, calcium, iron, and titanium as constituent elements, barium nitrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), zirconyl nitrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), scandium nitrate (Alfa The following nitrates were used: Aesar, yttrium nitrate (Sigma-Aldrich), ytterbium nitrate (Sigma-Aldrich), indium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), neodymium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), cerium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), lanthanum nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), strontium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), calcium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.), iron nitrate (Sigma-Aldrich), and tetra-i-propoxytitanium (High Purity Chemical Laboratory Co., Ltd.).

[0061] [Total conductivity measurement] Each of Samples A1 to A34 was press-molded into a rectangular parallelepiped and sintered at 1600°C for 6 hours. Platinum wire was then wrapped around the sample in four places, after which platinum paste (TR-7905, manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.) was applied over the wire and baked at 1000°C for 1 hour to prepare a measurement sample. Each measurement sample was placed in a tubular electric furnace and heated while humidified hydrogen was flowing through it using a bubbler. The total conductivity ("C_total" in Figures 5 and 6) was measured at 750°C using the AC four-terminal method. The relative density of each sintered compact used for the total conductivity measurement was measured using the Archimedes method, and it was confirmed that all sintered compacts had a relative density of 96% or higher.

[0062] [Measurement of proton and electron / hole transference numbers, and calculation of proton conductivity] Each of Samples A1 to A34 was press-molded into a disk shape and sintered at 1600°C for 6 hours. Platinum paste was then screen-printed on both sides of the disk and baked at 1000°C for 1 hour to prepare a measurement sample. The transference number measurement device included two alumina tubes, one above the other, with their axes aligned. The measurement sample was sandwiched between the two alumina tubes, ensuring a gas seal between the alumina tubes and the measurement sample. The section containing the measurement sample was then placed in an electric furnace to measure the transference number. Specifically, the two alumina tubes were heated to 750°C in the electric furnace while humidified hydrogen with different concentrations or humidification levels was circulated through one space and the other, separated by the measurement sample. The proton transport number ("TN_pro" in Figures 5 and 6) and the electron / hole transport number ("TN_e / h" in Figures 5 and 6) were determined by measuring the electromotive force generated between one surface and the other surface of the measurement sample. The proton conductivity ("C_pro" in Figures 5 and 6) was calculated by multiplying the total conductivity measured as above by the proton transport number.

[0063] [Measurement of C2 yield] 0.1 g of each of Samples A1 to A34 was weighed and placed in a fixed-bed flow reactor. The reactor was heated to 750°C and a mixture of methane, oxygen, and nitrogen was introduced at a flow rate ratio of CH4:O2:N2 = 3.8:1:4 under 1 atmosphere and 45 cm 3The catalytic activity test was performed with each sample heated to 750 °C. The composition of the gases fed into and discharged from the catalytic activity test equipment was analyzed using a micro gas chromatograph (Agilent Technologies, 3000A). The C2 yield at 750 °C was calculated using the results of the composition analysis ("YC2-750" shown in Figures 5 and 6). The C2 hydrocarbons in the gas discharged from the equipment included ethylene and ethane, but the proportion of ethylene in the resulting C2 hydrocarbons was approximately 60-70% in all samples (data not shown).

[0064] As shown in Figures 5 and 6, Samples A1 to A29 exhibited higher C2 yields than Samples A30 to A34. This confirms that the perovskite oxide constituting the main phase of a dehydrogenation catalyst exhibits enhanced catalytic activity when it satisfies the aforementioned formulas (1) and (3a) to (3d). More specifically, when the A' element (at least one of lanthanum (La) and yttrium (Y)) is contained in the A site of the perovskite structure, a comparison of Samples A13 and A32 suggests that x ≤ 0.4 (formula (3a)) or x ≤ 0.2 (formula (3e)) is desirable. Furthermore, a comparison of Sample A5 with Samples A13 and A14, and a comparison of Sample A21 with Sample A25, confirms that catalytic activity tends to be enhanced, particularly when x = 0. Furthermore, for example, comparisons of Sample A5 with Sample A18 and Sample A21, Sample A1 with Sample A20 and Sample A23, and Sample A6 with Sample A19 and Sample A22 confirmed that catalytic activity tends to be enhanced by substituting barium (Ba) for the alkaline earth metal A element in formula (1). In other words, it was confirmed that the main phase of the dehydrogenation catalyst preferably has a perovskite structure represented by the general formula (4) described above.

[0065] Also, for example, from the comparison between Sample A1 to Sample A5 and Sample A30, and the comparison between Sample A5 to Sample A7 and Sample A31, it is considered desirable to set "0 ≦ z ≦ 0.7". And, for example, from the comparison between Sample A1 to Sample A4 and Sample A5, and the comparison between Sample A6, and Sample A7 and Sample A5, it was confirmed that the catalytic activity tends to increase by setting "0 < z", particularly "0.2 ≦ z".

[0066] Figure 7 is a diagram showing the XRD chart of the dehydrogenation reaction catalyst of the first embodiment. Figure 8 is a diagram explaining the XRD chart of the dehydrogenation reaction catalyst of the first embodiment. Figure 7 is a diagram showing the XRD charts of Sample A3 and Sample A35. Figure 8 is a diagram explaining the XRD chart of Sample A35 shown in Figure 7. Sample A3 and Sample A35 are represented by the same composition formula (BaZr 0.4 Sc 0.6 O3), but their production methods are different. Here, the change in the performance of the methane oxidative coupling catalyst due to the presence or absence of the secondary phase in the dehydrogenation reaction catalyst was evaluated.

[0067] [Production of Sample A35] Sample A35 (BaZr 0.4 Sc 0.6 O3) was produced by the solid phase reaction method. As the raw material powders, barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Rare Metals Chemical Industry Co., Ltd.), and scandium oxide (manufactured by Alfa Aesar) were used. These raw material powders were used such that the ratio of the metal elements was in accordance with the composition formula BaZr 0.4 Sc 0.6The powder was weighed to achieve the composition ratio of O3. Then, 5 mm diameter balls and ethanol were added and mixed using a ball mill for 15 hours. The ethanol component was then removed to obtain a solid component, which was then sieved using a 250 μm mesh sieve. Then, calcination was performed at 1300°C for 5 hours. The resulting powder was then added with 5 mm diameter balls and ethanol, ground again in a ball mill, and mixed for 15 hours. The ethanol component was then removed to obtain a solid component, which was then sieved using a 250 μm mesh sieve. Then, calcination was performed at 1300°C for 5 hours. The resulting powder was then added with 5 mm diameter balls and ethanol, ground again in a ball mill, and mixed for 15 hours. The ethanol component was then removed to obtain a solid component, which was then sieved using a 250 μm mesh sieve. Sample A35, a dehydrogenation catalyst, was obtained. Sample A3 was prepared by the complex polymerization method, as described above.

[0068] As shown in FIG. 7, the XRD chart of sample A35 shows peaks derived from subphases that are not seen in the XRD chart of sample A3. That is, sample A35 has a subphase in addition to the main phase composed of the perovskite oxide of sample A3. Specifically, as shown in FIG. 8, in the XRD chart of sample A35, the perovskite oxide (BaZr 0.4 Sc 0.6 The figure shows that the first peak, where the peak intensity of the complex oxide (Ba3Sc4O9) constituting the subphase is maximum, is present in the diffraction angle 2θ range of 29.5-30.5°, and the second peak, where the peak intensity of the complex oxide (Ba3Sc4O9) constituting the subphase is maximum, is present in the diffraction angle 2θ range of 30.6-31.0°. In other words, it can be seen that in sample A35, the subphase of Ba3Sc4O9 is mixed into the main phase of the BaZrO3-based material. The database numbers of the ICDD (International Centre for Diffraction Data) used in Figure 8 are 00-001-0890 for perovskite-type oxides and 00-031-0161 for Ba3Sc4O9. Also, Ba(Zr 1-x Sc x )O 3-δIt is known that the peak of BaZrO3 is slightly shifted to the low angle side in the XRD chart shown in Figure 8. 0.4 Sc 0.6 It was considered to be O3.

[0069] 9 is a first diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment, which shows the C2 yield at different temperatures and the peak intensity ratio obtained from the XRD chart shown in FIG. 7 for each of Sample A3 and Sample A35.

[0070] [Measurement of C2 yield] For sample A3 and sample A35, the C2 yield at 750°C ("YC2-750" in FIG. 9) and the C2 yield at 800°C ("YC2-800" in FIG. 9) were measured using the C2 yield measurement method described above. In addition, the measured C2 yields at 750°C and 800°C were used to calculate the rate of decrease in the C2 yield at 800°C relative to the C2 yield at 750°C ("ΔYC2" in FIG. 9).

[0071] [Derivation of peak intensity ratio] Samples A3 and A35 were analyzed by powder XRD to determine the peak intensity ratios of the main and subphases. A SmartLab-3kw (Rigaku Corporation) was used as the X-ray diffractometer. The measurement conditions for powder XRD were a scan range (2θ) of 10°–80°, a step width of 0.02°, and a scan rate of 20° / min. Measurements were performed using a focusing optical system. CuKα radiation was used as the X-ray source at a tube voltage of 40 kV and a tube current of 30 mA. Data analysis of the obtained powder X-ray diffraction patterns was performed using the following method. Smoothing was performed using a weighted average of seven smoothing points. Background subtraction was performed using the Sonnevelt-Visser method with a peak width threshold of 0.1 and an intensity threshold of 0.01. Kα2 subtraction was performed using an intensity ratio of 0.5. In the powder X-ray diffraction pattern using CuKα radiation obtained by the above method, a first peak, which is the maximum peak intensity of the perovskite oxide constituting the main phase, and a second peak, which is the maximum peak intensity of the composite oxide constituting the subphase, were identified, and the ratio of the intensity of the second peak to the intensity of the first peak ("R_peak intensity" shown in Figure 9) was calculated.

[0072] As shown in FIG. 9, it was confirmed that sample A35 has a higher C2 yield at 800°C than sample A3, and the rate of decrease in C2 yield at 800°C relative to the C2 yield at 750°C is very small. In other words, the main phase (BaZr in sample A35) is composed of a perovskite-type oxide having catalytic activity as a dehydrogenation catalyst. 0.4 Sc 0.6 In addition to the perovskite oxide (Ba3Sc4O3), the perovskite oxide is provided with a subphase (Ba3Sc4O9 in sample A35) composed of a complex oxide formed in the perovskite oxide during its production. This improves the heat resistance of the dehydrogenation catalyst, and it has been confirmed that the decrease in catalytic activity as a dehydrogenation catalyst is suppressed even at temperatures of, for example, 800°C.

[0073] Fig. 10 is a graph showing the temperature change of the C2 yield of the dehydrogenation catalyst of this embodiment. Fig. 10 is an explanatory diagram showing the results of measuring the C2 yield for sample A3 and sample A35 when heated at temperatures of 650°C, 700°C, 750°C, and 800°C. Of these results, Fig. 9 already shows the measurement results at 750°C and 800°C.

[0074] The complex polymerization method used to manufacture Sample A3 allows for the mixing of raw materials at the molecular level, and is therefore generally known to produce catalysts with higher catalytic activity than solid-state reaction methods. Figure 10 also shows that Sample A3 had a higher C2 yield than Sample A35 at temperatures of 700°C and 750°C. However, when the operating temperature of the dehydrogenation catalyst increased to 800°C, Sample A3's catalytic activity (C2 yield) as a dehydrogenation catalyst decreased. In contrast, Sample A35, which was produced by the solid-state reaction method and contains a subphase, showed little decline in catalytic activity even at 800°C. Thus, the dehydrogenation catalyst of Sample A35, produced by the solid-state reaction method, was confirmed to have improved heat resistance. The improved heat resistance of Sample A35 is thought to be due to the heat treatment temperature during catalyst preparation and the presence of the Ba3Sc4O9 subphase.

[0075] Fig. 11 is a second diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment. Fig. 11 is a diagram illustrating the effect of the presence of multiple phases on the performance of the catalyst. Fig. 11 shows the results of the case where the main phase is BaZr 0.4 Sc 0.6For Sample A35 (Ba3Sc4O9), Samples A36 to A38 have different zirconium and scandium ratios in the main phase, and Sample A39 (Ba3Sc4O9) was prepared by a solid-state reaction method. The graph shows the C2 yield at different temperatures ("YC2-750" and "YC2-800" in Figure 11), the rate of decrease in C2 yield at 800°C relative to the C2 yield at 750°C ("ΔYC2" in Figure 11), and the peak intensity ratio obtained from the XRD chart ("R_peak intensity" in Figure 11). The C2 yield and the peak intensity ratio obtained from the XRD chart were measured using the same method as described for Figure 9. Note that Figure 11 also shows the evaluation results for Sample A3 shown in Figure 9.

[0076] [Preparation of Samples A36 to A39] Samples A36 to A39 were prepared in a manner similar to that of Sample A35. Specifically, powdered dehydrogenation catalysts were obtained in the same manner as Sample A35, except that the types and weighed amounts of the catalyst raw material powders were adjusted to correspond to the compositional ratios of the composition formulas of Samples A36 to A39 shown in FIG. 11 and the heat treatment temperature ("T-treat") of the catalyst powder precursor was set to the temperature shown in FIG. 11. Barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and scandium oxide (manufactured by Alfa Aesar) were used as raw material powders. Samples A36 to A39 include samples that underwent heat treatments differently from Sample A35, but the number of heat treatments may be different.

[0077] As shown in Figure 11, Samples A35 to A38 were prepared at a higher heat treatment temperature than Sample A3. Furthermore, subphases were also formed in Samples A35 to A38, and the XRD peak intensity ratio (R_peak intensity) was confirmed to be 0.04 or greater relative to the main phase. The subphase Ba3Sc4O9 did not exhibit a decrease in C2 yield with increasing temperature, as shown in Sample A39. On the other hand, the catalytic performance of Sample A39 was confirmed to be lower than that of Ba(Zr,Sc)O3-based materials. For Samples A35 to A38, the decrease in C2 yield at 800°C (YC2-800) relative to the C2 yield at 750°C (YC2-750) (ΔYC2) was confirmed to be within ±1.3%. This indicates that Samples A35 to A38 maintain relatively high catalytic activity while improving heat resistance.

[0078] <Example 2> Fig. 12 is a first diagram showing an SEM image of the dehydrogenation catalyst of this embodiment. Fig. 13 is a second diagram showing an SEM image of the dehydrogenation catalyst of this embodiment. Fig. 12 is an SEM image of sample B1 produced by a solid-state reaction method, and Fig. 13 is an SEM image of sample B12 produced by a complex polymerization method. Here, changes in surface shape due to the difference in production method were evaluated for each of two types of dehydrogenation catalyst samples produced by different production methods.

[0079] [Preparation of Sample B1] Sample B1 (BaZr 0.8 Y 0.2 Sample A35) was prepared by a solid phase reaction method similar to that used for sample A35. The raw material powders used were barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), and yttrium oxide (manufactured by Shin-Etsu Chemical Co., Ltd.). These raw material powders were mixed in a mixture of BaZr 0.8 Y 0.2The powder was weighed to achieve the composition ratio in O3. Then, 5 mm diameter balls and ethanol were added, and the mixture was mixed using a ball mill for 15 hours. The ethanol component was then removed, and the solid component was obtained, which was then sieved using a sieve with 250 μm openings. Then, the mixture was fired at 1300°C for 5 hours (firing step). 5 mm diameter balls and ethanol were added to the obtained powder, and the mixture was again crushed in a ball mill, and mixed for 15 hours (crushing step). Then, the ethanol component was removed, and the solid component was obtained, which was then sieved using a sieve with 250 μm openings, to obtain a dehydrogenation catalyst as Sample B1.

[0080] [Preparation of Sample B12] Sample B12 (BaZr 0.8 Y 0.2 Sample O3) was prepared by a complex polymerization method in accordance with the preparation method of sample A1. The raw material powders used were barium nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), zirconyl nitrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and yttrium nitrate (manufactured by Sigma-Aldrich). These raw material powders were mixed in a solution containing yttrium nitrate with the ratio of metal elements of the composition formula BaZr 0.8 Y 0.2 The raw material powder was weighed to have the composition ratio of metal element:citric acid:propylene glycol = 1:3:3 (molar ratio), and then citric acid aqueous solution and propylene glycol were added to the raw material powder and stirred at 80°C for 1 hour. This solution was then slowly heated to 300°C to obtain a polymer with each metal element dispersed therein. The obtained polymer was then carbonized by heat treatment at 400°C for 2 hours and pulverized in an agate mortar to obtain a catalyst powder precursor. The obtained catalyst powder precursor was then heat treated at 1200°C for 6 hours to obtain a powdered dehydrogenation catalyst designated as Sample B12.

[0081] Comparing the SEM image of sample B1 shown in Figure 12 with the SEM image of sample B12 shown in Figure 13, it is clear that they have the same composition (BaZr 0.8 Y 0.2Although the samples were made using the same process (O3), the surface shapes were found to be significantly different at the micron level. Specifically, it was confirmed that sample B1, which was made using the solid-state reaction method, had a finer surface structure than sample B12, which was made using the complex polymerization method. The solid-state reaction method used to make sample B1 includes a grinding process using a ball mill, while the complex polymerization method used to make sample B12 does not include a grinding process. This is thought to be why the surface shapes and the size of the particulate agglomerates that make up the surface shapes are different, as shown in Figures 12 and 13.

[0082] Fig. 14 is a diagram showing the specific surface area of ​​the dehydrogenation catalyst of this embodiment. Fig. 14 is a diagram illustrating the influence of the composition and production method on the specific surface area of ​​the dehydrogenation catalyst. Fig. 14 shows the results of comparing the specific surface area of ​​multiple samples B1 to B5, which have different compositions and were produced by the solid-state reaction method, with sample B12, which was produced by the complex polymerization method.

[0083] [Preparation of Samples B2 to B5] Samples B2 to B5 were prepared in a manner similar to that of Sample B1. Specifically, powdered dehydrogenation catalysts were obtained in the same manner as Sample B1, except that the types and weighed amounts of the catalyst raw material powders were adjusted to achieve the compositional ratios of Samples B2 to B5 shown in FIG. 14. Samples B3 to B5 may also be prepared by repeating a calcination process (heat treatment temperature: 1300°C, calcination time: 5 hours) and a pulverization process using a ball mill. The raw material powders used were barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), yttrium oxide (manufactured by Shin-Etsu Chemical Co., Ltd.), and scandium oxide (manufactured by Alfa Aesar).

[0084] [Measurement of specific surface area] The specific surface areas of Samples B1 to B5 and Sample B12 were measured using a specific surface area analyzer (Macsorb HM model-1208, manufactured by Mountec Co., Ltd.) by the BET flow single-point method (He:N2 = 7:3). Specifically, the particles of Samples B1 to B5 and Sample B12 were packed into sample tubes, degassed at 200°C for 60 minutes, and then cooled together with the sample tube. After cooling, the amount of gas physically adsorbed on the surfaces of the particles packed in the sample tube was measured using the change in gas concentration, and the specific surface area of ​​the particles ("Specific surface area" shown in Figure 14) was calculated.

[0085] As shown in Figure 14, a comparison of the specific surface area of ​​Sample B1 and the specific surface area of ​​Sample B12 confirmed that the change in surface shape, as shown in Figures 12 and 13, resulted in a change in the specific surface area of ​​the dehydrogenation catalyst. Specifically, it was confirmed that the specific surface area of ​​Sample B1 was more than twice the specific surface area of ​​Sample B12. This is expected to result in higher reactivity with the dehydrogenation catalyst per unit weight. In Samples B1 to B5, the specific surface area measured by the BET flow single-point method was 10 m 2 / g or more. For example, a comparison between Sample B1 and Sample B3 confirmed that the specific surface area is larger when scandium is contained in the B site than when yttrium is contained in the B site. A comparison between Sample B1 and Sample B2, or Samples B3 to B6, confirmed that the specific surface area increases as the zirconium ratio increases.

[0086] Fig. 15 is a first diagram showing the XPS spectrum of the dehydrogenation catalyst of this embodiment, which shows the spectrum of the O1s orbital included in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy for each of Sample B1 and Sample B12.

[0087] [O1s spectrum measurement] X-ray photoelectron spectroscopy (XPS) was used to obtain the O1s orbital spectrum for each of Sample B1 and Sample B12. Specifically, XPS spectra were obtained over a 100 μmφ area on the fracture surface of a compact made from particles of Sample B1 or Sample B12 using monochromated AlKα X-rays with a pass energy of 140 eV.

[0088] Two peaks were confirmed in the O1s orbital spectra of Sample B1 and Sample B12 shown in FIG. 15 . Of the two peaks appearing in the O1s orbital spectra, the peak at a binding energy of approximately 532 eV (within the region Aao shown in FIG. 15 ) is a peak derived from adsorbed oxygen species. The peak at a binding energy of approximately 528 eV (within the region Alo shown in FIG. 15 ) is a peak derived from lattice oxygen species. Comparing the areas of the convex portions containing the peaks derived from adsorbed oxygen species with the areas of the convex portions containing the peaks derived from lattice oxygen species for Sample B1 and Sample B12, it was confirmed that the area of ​​the convex portion containing the peaks derived from lattice oxygen species was larger in Sample B12 than the area of ​​the convex portion containing the peaks derived from adsorbed oxygen species, whereas the area of ​​the convex portion containing the peaks derived from adsorbed oxygen species was larger in Sample B1 than the area of ​​the convex portion containing the peaks derived from lattice oxygen species. For Sample B1, the solid-state reaction method used to prepare Sample B1 includes a ball mill grinding step, which is thought to create a surface suitable for oxygen adsorption due to mechanical force, as shown in the SEM image in Figure 12. On the other hand, for Sample B12, the complex polymerization method used to prepare Sample B12 does not include a mechanical force-applying step like the grinding step in the solid-state reaction method, and therefore does not have a surface shape similar to that of Sample B1, as shown in the SEM image in Figure 13. Thus, because the surface shapes of Sample B1 and Sample B12 differ depending on whether or not they include a grinding step, it is thought that the relationship between the amount of adsorbed oxygen species and the amount of lattice oxygen species changes. Specific comparison results for the area of ​​the convex portion containing the peak in the XPS spectrum will be discussed later.

[0089] FIG. 16 is a second diagram showing the XPS spectrum of the dehydrogenation catalyst of this embodiment. FIG. 16 shows the spectrum of the O1s orbital contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy for each of Sample B1, Sample B2, and Sample B13. Sample B1, Sample B2, and Sample B13 shown in FIG. 16 all have the composition formula Ba(Zr 1-x Y x )O 3-δ The dehydrogenation catalysts are represented by the formula: but the value of x is different (Sample B1: x=0.2, Sample B2: x=0.4, Sample B13: x=0).

[0090] [Preparation of sample B13] Sample B13 (BaZrO3) was prepared by a solid-state reaction method similar to that used for preparing Sample B1. Specifically, a powdered dehydrogenation catalyst was obtained as Sample B13 in the same manner as Sample B1, except that the type and amount of raw catalyst powder were adjusted to achieve the composition ratio of the composition formula of Sample B13. Barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.) and zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.) were used as raw material powders.

[0091] As shown in FIG. 16, the composition formula Ba(Zr 1-x Y x )O 3-δ The larger the value of x, the more likely the dehydrogenation catalyst represented by the formula (I) is to have oxygen vacancies due to charge compensation. Among the three samples shown in FIG. 16, it was confirmed that sample B2, in which x is larger than sample B1, has a larger ratio of the area of ​​the convex portion containing peaks derived from adsorbed oxygen species to the area of ​​the convex portion containing peaks derived from lattice oxygen species than sample B1, while sample B13, in which x is smaller than sample B1, has a smaller ratio of the area of ​​the convex portion containing peaks derived from adsorbed oxygen species to the area of ​​the convex portion containing peaks derived from lattice oxygen species than sample B1. In other words, it was confirmed that the larger the value of x, the greater the ratio of the area of ​​the convex portion containing peaks derived from adsorbed oxygen species to the area of ​​the convex portion containing peaks derived from lattice oxygen species tends to be. The composition formula Ba(Zr 1-x Yx )O 3-δ In the dehydrogenation catalyst represented by the formula, increasing the value of x increases the amount of oxygen vacancies, which is thought to increase the degree of coordinative unsaturation on the catalyst surface near the oxygen vacancies. This allows more oxygen to be adsorbed, which is thought to increase the amount of adsorbed oxygen species.

[0092] Fig. 17 is a third diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment. Fig. 17 is an explanatory diagram showing the relationship between the composition of the dehydrogenation catalyst and the C2 yield. Fig. 17 shows the ratio of the peak area attributable to adsorbed oxygen species to the peak area attributable to lattice oxygen species in the O1s orbital spectrum obtained by XPS measurement (hereinafter simply referred to as "XPS ratio"), and the C2 yield at 700°C for each of Samples B1 to B11 and B13 prepared by the solid-state reaction method and Sample B12 prepared by the complex polymerization method.

[0093] [Preparation of Samples B6 to B11] Samples B6 to B11 were prepared using a method similar to that used for Sample B1. Specifically, powdered dehydrogenation catalysts were obtained in the same manner as Sample B1, except that the types and weighed amounts of the catalyst raw material powders were adjusted to achieve the compositional ratios of Samples B6 to B11 shown in FIG. 17 . For Samples B6 and B7, the powdered dehydrogenation catalysts may be obtained by repeating the calcination step and the pulverization step using a ball mill. For Samples B8 to B11, the heat treatment temperature in the calcination step was changed within the range of 1300°C to 1500°C to increase the proportion of the target substance. For example, the temperature was 1400°C for Sample B10 and 1350°C for Sample B11. In this manner, the heat treatment temperature in the calcination step during sample preparation may be changed to increase the proportion of the target substance. The raw material powders used were barium carbonate (manufactured by Sakai Chemical Industry Co., Ltd.), zirconium oxide (manufactured by Daiichi Kigenso Kagaku Kogyo Co., Ltd.), scandium oxide (manufactured by Alfa Aesar), lanthanum hydroxide (manufactured by Shin-Etsu Chemical Co., Ltd.), and strontium carbonate (manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.).

[0094] [XPS ratio measurement] FIG. 18 illustrates a method for calculating the XPS ratio. To calculate the XPS ratio, as shown in FIG. 18, the O1s orbital spectrum Sp1 obtained by XPS measurement is divided into a first curve Cr1 having a first peak corresponding to a maximum value in the binding energy range Ra1 of 525-530 eV, and a second curve Cr2 having a second peak corresponding to a maximum value in the binding energy range Ra2 of 530-535 eV, using peak separation fitting. A base line Ba1 is set as the base of the first curve Cr1, and the area enclosed by the first curve Cr1 and the base line Ba1 is defined as the first peak area S10 derived from lattice oxygen species. A base line Ba2 is set as the base of the second curve Cr2, and the area enclosed by the second curve Cr2 and the base line Ba2 is defined as the second peak area S10 derived from adsorbed oxygen species. Therefore, the XPS ratio is calculated as S10 / S10. In FIG. 17, the XPS ratio is indicated as "S10 / S10." The first peak area Slo corresponds to the "area of ​​the convex portion including the first peak" in the claims. The second peak area Sao corresponds to the "area of ​​the convex portion including the second peak" in the claims.

[0095] [Measurement of C2 yield] The C2 yield of each of Samples B1 to B13 was measured using a fixed-bed flow reactor, similar to the measurement of the C2 yield of Samples A1 to A34 described above. Specifically, 0.1 g of each of Samples B1 to B13 was weighed and placed in a fixed-bed flow reactor, and while heated to a predetermined temperature, a mixed gas of methane, oxygen, and nitrogen was introduced at a flow rate ratio of CH4:O2:N2 = 3.8:1:4 under 1 atmosphere and 45 cm 3 The catalytic activity test was carried out by flowing the catalyst at a rate of 1 / min. "YC2-700" shown in Figure 17 shows the results of the test carried out when each sample was heated to 700°C.

[0096] As shown in FIG. 17, it was confirmed that the C2 yield at 700°C ("YC2-700" in FIG. 17) tends to increase as the XPS ratio ("Sao / Slo" in FIG. 17) increases. In particular, it was confirmed that Samples B1 to B11, in which the XPS ratio, i.e., the ratio of the second peak area to the first peak area, is greater than 1, tend to have an even higher C2 yield at 700°C. In the dehydrogenation catalyst, the adsorbed oxygen species exist in an activated state, which increases the dehydrogenation reactivity of the dehydrogenation catalyst. A high XPS ratio, which indicates the ratio of the first peak area derived from adsorbed oxygen species to the second peak area derived from lattice oxygen species, indicates the presence of a relatively large amount of adsorbed oxygen species. Therefore, a high XPS ratio increases the dehydrogenation reactivity of the dehydrogenation catalyst.

[0097] From the results shown in Figure 17, it appears that in order to increase the XPS ratio of a dehydrogenation catalyst, two factors must be met: (a) the method for preparing the dehydrogenation catalyst must include a crushing process using a solid-state reaction method, and (b) oxygen vacancies must be introduced by element substitution. The synergistic effect of these two factors (a) and (b) can increase the XPS ratio of a dehydrogenation catalyst. Of the multiple samples shown in Figure 17, Samples B1 to B11 satisfy both factors (a) and (b). Meanwhile, Sample B12 satisfies factor (b) but not factor (a). Sample B13 satisfies factor (a) but not factor (b).

[0098] FIG. 19 is a fourth diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment. FIG. 19 is an explanatory diagram showing the relationship between the calculated XPS ratio and the C2 yield. FIG. 19 plots the numerical values ​​of the 13 types of samples B1 to B13 shown in FIG. 17 on a graph with the XPS ratio (Sao / Slo) on the horizontal axis and the C2 yield at 700°C (YC2-700) on the vertical axis. As shown in FIG. 19, it was confirmed that the C2 yield at 700°C increases when the XPS ratio is higher than 1. This is thought to be because the amount of activated adsorbed oxygen species on the surface of the dehydrogenation catalyst increases relatively, accelerating the dehydrogenation reaction.

[0099] Fig. 20 is a fifth diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment. Fig. 20 is a diagram illustrating the temperature dependence of the C2 yield of the dehydrogenation catalyst. Fig. 20 shows the C2 yield (YC2-750) at 750°C for each of Samples B4 to B7 among Samples B1 to B13 shown in Fig. 17. Samples B4 to B7 are so-called Ba(Zr,Sc)O3-based materials.

[0100] [Measurement of C2 yield] The C2 yields of Samples B4 to B7 at 750°C were measured using a fixed-bed flow reactor, similar to the measurement of the C2 yields of Samples B1 to B13 at 700°C. "YC2-750" in Figure 20 represents the results obtained when each sample was heated to 750°C.

[0101] 20, it was confirmed that the C2 yield at 750°C was higher for all of Samples B4 to B7 than at 700°C. Therefore, it was confirmed that the performance of the dehydrogenation catalysts made of perovskite-type oxides of Ba(Zr,Sc)O3-based materials, which were prepared by the solid-state reaction method, as dehydrogenation catalysts, did not deteriorate when the temperature increased from 700°C to 750°C.

[0102] According to the dehydrogenation catalyst of this embodiment configured as described above, 1-x A' x )(Zr 1-y-z B y B' z )O 3-δ and a subphase composed of at least one of three composite oxides represented by the general formulas AB'2O4, A2B'2O5, and A3B'4O9. In the main phase, A is at least one element selected from alkaline earth metals, A' is at least one element from lanthanum (La) and yttrium (Y), B is at least one element from titanium (Ti) and cerium (Ce), and B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd), satisfying the conditions 0≦x≦0.4, 0.3≦(1-z)≦1, 0≦y, and 0<(1-yz), δ represents the amount of oxygen vacancy, and A and B' in the subphase are elements common to A and B' constituting the perovskite oxide. This can improve the heat resistance of the dehydrogenation catalyst.

[0103] Furthermore, in the dehydrogenation catalyst of this embodiment, A is barium (Ba), B' is scandium (Sc), and the subphase is composed of at least one barium scandate selected from the three composite oxides BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9, thereby further improving the heat resistance of the dehydrogenation catalyst.

[0104] Furthermore, according to the dehydrogenation catalyst of this embodiment, the subphase is composed of Ba3Sc4O9, which can further improve the heat resistance of the dehydrogenation catalyst.

[0105] Furthermore, according to the dehydrogenation catalyst of this embodiment, the main phase is BaZr 1-z Sc z O 3-δ(where 0.1≦z≦0.7). This makes it possible to further enhance the catalytic activity as a dehydrogenation catalyst.

[0106] Furthermore, in the dehydrogenation catalyst of this embodiment, the ratio of the second peak intensity to the first peak intensity in the powder X-ray diffraction pattern using CuKα radiation is 0.04 or more, which further improves the heat resistance of the dehydrogenation catalyst.

[0107] Furthermore, in the dehydrogenation catalyst of this embodiment, the subphase is composed of any one of the composite oxides BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9, which can further improve the heat resistance of the dehydrogenation catalyst.

[0108] Furthermore, the dehydrogenation catalyst of this embodiment can be used as a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane, thereby improving the heat resistance of the methane oxidative coupling catalyst.

[0109] Furthermore, according to the dehydrogenation catalyst of this embodiment, in the spectrum of the O1s orbital contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy, the ratio of the second peak area to the first peak area is greater than 1. This makes it easier for adsorbable oxygen species to be adsorbed onto the surface of the dehydrogenation catalyst, thereby increasing the catalytic activity of the dehydrogenation catalyst.

[0110] Furthermore, the dehydrogenation catalyst of this embodiment has oxygen deficiencies, which can increase the amount of oxygen species adsorbed on the surface of the dehydrogenation catalyst, thereby further enhancing the catalytic activity of the dehydrogenation catalyst.

[0111] Furthermore, according to the dehydrogenation catalyst of this embodiment, the main phase of the catalyst has a perovskite structure, which can further enhance the catalytic activity of the dehydrogenation catalyst.

[0112] Furthermore, according to the dehydrogenation catalyst of this embodiment, the specific surface area measured by the BET method is 10 m 2 This makes it possible to increase the amount of adsorbed oxygen species on the surface of the dehydrogenation catalyst, thereby further enhancing the catalytic activity of the dehydrogenation catalyst.

[0113] Furthermore, the dehydrogenation catalyst of this embodiment can be used as a methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane, thereby improving the catalytic performance of the methane oxidative coupling catalyst. Second Embodiment

[0114] The dehydrogenation catalyst of the second embodiment has a different composition formula from the dehydrogenation catalyst of the first embodiment.

[0115] [Dehydrogenation catalyst] The dehydrogenation catalyst of this embodiment is a composite oxide having a perovskite-type oxide crystal structure represented by the following general formula (26). (La 1-x M1 x )M2O 3-δ … (26) In the above formula (26), M1 is at least one element selected from alkaline earth metals, M2 is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and gallium (Ga), and δ represents the amount of oxygen vacancy, and 0≦x≦0.6 is satisfied.

[0116] In the dehydrogenation catalyst of this embodiment, the perovskite oxide of formula (26) has catalytic activity as a dehydrogenation catalyst. The perovskite oxide of formula (26) contains lanthanum (La) and at least one element M1 selected from alkaline earth metals at the so-called A site of the perovskite structure. The element M1 is preferably selected from strontium (Sr) or barium (Ba). The perovskite oxide of formula (26) also contains an element M2 at the so-called B site of the perovskite structure. The element M2 includes at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and gallium (Ga).

[0117] In the perovskite oxide of formula (26), x satisfies the following formula (27): As a result, the dehydrogenation catalyst of this embodiment has relatively high catalytic activity as a dehydrogenation catalyst that promotes the dehydrogenation reaction. 0≦x≦0.6 … (27)

[0118] The dehydrogenation catalyst of this embodiment configured as described above has a perovskite-type oxide crystal structure represented by formula (26), which enhances the catalytic activity of the dehydrogenation catalyst, promoting the dehydrogenation reaction at relatively low temperatures, for example, from about 650°C to 700°C.

[0119] The dehydrogenation catalyst of this embodiment can promote various dehydrogenation reactions in which hydrogen is released from compounds. Examples of dehydrogenation reactions include the oxidative coupling of methane (OCM) reaction, which is used to produce hydrocarbons having two or more carbon atoms from methane. Therefore, the dehydrogenation catalyst of this embodiment can also be used as a methane oxidative coupling catalyst. Other examples include various reactions in which hydrogen is produced from various hydrocarbon compounds, including hydrocarbons and alcohols, through dehydrogenation. Specific examples include a steam reforming reaction in which hydrogen is produced from hydrocarbon compounds and steam, a partial oxidation reaction in which hydrogen is produced from hydrocarbon compounds, and a shift reaction in which carbon monoxide, produced together with hydrogen in a partial oxidation reaction, and steam are used to produce carbon dioxide and hydrogen.

[0120] 2 and 3 are explanatory diagrams showing an example of a methane oxidative coupling reaction that occurs on a methane oxidative coupling catalyst of the present embodiment, as an example of a reaction including a dehydrogenation reaction. When a dehydrogenation reaction in which hydrogen is released from a compound progresses, the covalent bond between the hydrogen atom and an atom such as carbon constituting the compound is generally cleaved. It is believed that the dehydrogenation catalyst of the present embodiment exhibits high activity in promoting the dehydrogenation reaction by promoting such a reaction. In the methane oxidative coupling reaction, a reaction that produces methyl radicals from methane, as shown in the following formula (5), proceeds. Furthermore, reactions shown in the following formulas (6) and (7) (see FIG. 2) and reactions shown in the following formulas (8) and (9) (see FIG. 3) proceed, which are thought to produce C2 hydrocarbons such as ethylene. The overall reaction that produces ethylene through the methane oxidative coupling reaction is expressed by the following formula (10).

[0121] CH4 → CH3 + H + +e - … (5) 2·CH3+1 / 2O2→ C2H4+H2O … (6) 1 / 2O2+2H + +2e -→ H2O … (7) 2·CH3 → C2H6 → C2H4+2H + +2e - … (8) O2+4H + +4e - → 2H2O …(9) 2CH4+O2→ C2H4+2H2O … (10)

[0122] Here, the covalent bond between the carbon atom and the hydrogen atom in methane has a bond energy of 104 kcal / mol, making it an extremely stable bond. Therefore, in the methane oxidative coupling reaction, the reaction of producing methyl radicals by dehydrogenation from methane, which has a stable covalent bond as described above (reaction (5)), is generally considered to be the rate-determining step. The dehydrogenation catalyst of this embodiment has high activity in promoting reactions involving the cleavage of covalent bonds in hydrogen, such as the reaction of producing methyl radicals from methane described above. Therefore, it is considered that it can widely promote dehydrogenation reactions, such as the methane oxidative coupling reaction, which involves the cleavage of covalent bonds in hydrogen. Furthermore, since the dehydrogenation catalyst of this embodiment is a perovskite-type oxide, it is a proton conductor and can protonate and transfer hydrogen from hydrogen-containing molecules. Therefore, it has high activity in promoting reactions involving the cleavage of covalent bonds containing hydrogen, and it is considered that it can widely promote dehydrogenation reactions, such as the methane oxidative coupling reaction, which involves the cleavage of covalent bonds containing hydrogen.

[0123] 2 and 3 show the location where the reaction of formula (5), which produces methyl radicals from methane, proceeds as an "oxidation site." Furthermore, FIGS. 2 and 3 show the progress of the reaction of formula (6) or (8), which produces ethylene from the methyl radicals, at this oxidation site. Also, FIGS. 2 and 3 show the location where the reaction of formula (7) or (9), which produces water using the protons and electrons generated along with the methyl radicals in formula (5), proceeds as a "reduction site." Thus, when reactions including dehydrogenation proceed in the dehydrogenation catalyst of this embodiment, the transfer of protons and electrons generally occurs. Therefore, to enhance catalytic activity, it is desirable for the dehydrogenation catalyst to have high proton conductivity and electron conductivity (including hole conductivity) in addition to high activity in promoting the reaction of formula (5), which is the rate-determining process described above. Specifically, it is desirable for the proton conductivity and proton transport number, or the electron conductivity (including hole conductivity) and electron transport number (including hole transport number) to be high. It is also desirable that the total conductivity of the dehydrogenation catalyst as a whole, which is the sum of the proton conductivity and the electron conductivity (including the hole conductivity), is higher.

[0124] [Other dehydrogenation reactions] FIG. 4 shows chemical formulas of various dehydrogenation reactions that can be promoted by the dehydrogenation catalyst of this embodiment. The dehydrogenation catalyst of this embodiment can promote various reactions depending on the raw materials (reactants) used. Formulas (11) to (22) in FIG. 4 show reactions that combine reactants containing at least one of methane and methane derivatives (hereinafter also referred to as "methanes"). Such reactions are also referred to as "oxidative coupling reactions of methanes." The dehydrogenation catalyst of this embodiment, which promotes the oxidative coupling reactions of methanes, is also referred to as "oxidative coupling catalysts of methanes." In formulas (13) to (22) in FIG. 4, A and B contained in the methane derivative represent atoms or atomic groups as substituents that replace hydrogen atoms in the methane molecule, and n is an integer of 2 or greater. The methane derivative shown in FIG. 4 has one or two hydrogen atoms in the methane molecule substituted with the above-mentioned substituents. When a molecule has substituents A and B, A and B may be the same or different substituents. Examples of the substituent represented by A or B include a halogen element, a hydroxy group (-OH), and a phenyl group (-C6H5).

[0125] In Figure 4, equation (11), like equation (10), represents the reaction in which ethylene is produced from methane. Equation (12) represents the reaction in which the polymerization reaction proceeds further to produce polyethylene. Unlike equation (10), equations (11) to (22) only show the changes in methane and methane derivatives among the molecules involved in the reaction.

[0126] Equations (11) and (12) show reactions in which methane is a reactant. Equations (13) and (14) show reactions in which a methane derivative represented by BACH2 is a reactant. Equations (15) and (16) show reactions in which a methane derivative represented by ACH3 is a reactant. Equations (17) and (18) show reactions in which a methane derivative represented by ACH3 and methane are reactants. Equations (19) and (20) show reactions in which a methane derivative represented by ACH3 and a methane derivative represented by CA2H2 are reactants. Equations (21) and (22) show reactions in which a methane derivative represented by CABH2 and methane are reactants.

[0127] Furthermore, formulas (11), (13), (15), (17), (19), and (21) show reactions using reactants selected from hydrocarbons with one carbon atom (methane) and methane derivatives (hereinafter also referred to as "C1 hydrocarbons") to produce hydrocarbons with two carbon atoms (ethylene) or ethylene derivatives (hereinafter also referred to as "C2 hydrocarbons"). Formulas (12), (14), (16), (18), (20), and (22) show reactions using reactants selected from C1 hydrocarbons to produce polymers. When producing polymers, C2 hydrocarbons may be produced from C1 hydrocarbons, and then these C2 hydrocarbons may be further polymerized with each other. Alternatively, C1 hydrocarbons may be sequentially polymerized to the ends of molecules to produce polymers. Both of these reactions may occur.

[0128] To explain the reaction shown in Figure 4 more specifically, for example, in formula (14), if the substituents A and B are both fluorine atoms (F), polytetrafluoroethylene (PTFE) is obtained as the product. In formula (18), if the substituent A is a chlorine atom (Cl), polyvinyl chloride (PVC) is obtained as the product. If the substituent A is a hydroxyl group (-OH), polyvinyl alcohol (PVOH) is obtained as the product. If the substituent A is a phenyl group (-CH), polystyrene (PS) is obtained as the product. In formula (22), if the substituents A and B are both fluorine atoms (F), polyvinylidene fluoride (PVDF) is obtained as the product. If the substituents A and B are both chlorine atoms (Cl), polyvinylidene chloride (PVDC) is obtained as the product. Furthermore, in formula (22), if the substituent A is a methyl group (-CH) and the substituent B is a methoxycarbonyl group (-COOCH), polymethyl methacrylate (PMMA) is obtained as the product.

[0129] Although FIG. 4 illustrates the oxidative coupling reaction of methanes, the dehydrogenation catalyst of this embodiment can also be used to promote dehydrogenation reactions other than the oxidative coupling reaction of methanes. Examples of dehydrogenation reactions promoted by the dehydrogenation catalyst of this embodiment include a reaction of combining reactants containing at least one of an alkane and an alkane derivative (hereinafter also referred to as "alkanes"). Such a reaction, together with the oxidative coupling reaction of methanes described above, is also referred to as the "oxidative coupling reaction of alkanes." The dehydrogenation catalyst of this embodiment, which promotes the oxidative coupling reaction of alkanes, is also referred to as the "oxidative coupling catalyst of alkanes." The number of carbon atoms in alkanes, which are the reactants of the oxidative coupling reaction of alkanes promoted by the dehydrogenation catalyst of this embodiment, can be, for example, 1 to 10, preferably 1 to 5, and more preferably 1 or 2. The alkane derivative used in the oxidative coupling reaction of alkanes is one in which hydrogen atoms contained in the alkane molecule have been substituted with the substituents described above, but which has a covalent bond between the carbon atom to be dehydrogenated and the hydrogen atom.

[0130] The dehydrogenation catalyst of this embodiment can also be used to promote dehydrogenation reactions other than the oxidative coupling reaction of alkanes. Examples of other dehydrogenation reactions promoted by the dehydrogenation catalyst of this embodiment include the dehydrogenation reaction of alkanes as exemplified by formula (23) in FIG. 4 and the dehydrogenation reaction of alcohols or alcohol derivatives (hereinafter also referred to as "alcohols") as exemplified by formulas (24) and (25). In formulas (23) to (25), A and B represent hydrogen or, as in formulas (13) to (22), an atom or atomic group as a substituent replacing hydrogen. Formula (23) represents a reaction in which an alkene or an alkene derivative is produced from an alkane. Formula (24) represents a reaction in which an aldehyde is produced from an alcohol, and formula (25) represents a reaction in which a ketone is produced from an alcohol. In this way, the dehydrogenation catalyst of this embodiment can be used as a catalyst to promote various dehydrogenation reactions.

[0131] [Method of manufacturing a dehydrogenation catalyst] The dehydrogenation catalyst of this embodiment can be prepared, for example, by a solid-state reaction method. Specifically, powders of metal oxides, metal carbonates, or the like, which are raw materials for the perovskite oxide represented by formula (26), are mixed in a ball mill or the like using a solvent such as ethanol, and then the mixture is dried to remove the solvent and calcined. By calcining at a relatively high temperature of approximately 1300-1600°C, the composite oxide represented by formula (26) can be obtained. Various methods are known for preparing composite oxides, including solid-state reaction methods, complex polymerization, coprecipitation, and sol-gel methods, and these methods can also be used to prepare the composite oxide.

[0132] FIG. 21 is a sixth diagram illustrating the C2 yield of the dehydrogenation catalyst of this embodiment. FIG. 21 is an explanatory diagram showing the results of examining the performance of 12 types of composite oxides, Samples C1 to C12, which were prepared. Among Samples C1 to C12, Samples C1 to C8 are perovskite oxides that satisfy the aforementioned conditions of formula (26), the element species at the A site, the ratio of elements at the A site, the element species at the B site, and the amount of oxygen vacancy. Samples 9 to C12 are composite oxides that do not satisfy at least one of the conditions of formula (26), the element species at the A site, the ratio of elements at the A site, the element species at the B site, and the amount of oxygen vacancy. In FIG. 21, the proportion of lanthanum at the A site in each of the perovskite oxides of Samples C1 to C12 is indicated as "P-La." Note that in the following explanation and in the figures, the number of oxygen atoms in the formula may be abbreviated as "O3," but these notations should be used interchangeably. 3-δ " and does not mean that δ is strictly 0. Below, the composition, manufacturing method, evaluation method, and performance evaluation results of each sample are explained. Here, the performance as a dehydrogenation catalyst was evaluated as a methane oxidative coupling catalyst.

[0133] [Preparation of sample C1] The catalyst of sample C1 (La 0.9 Sr 0.1 ScO3) was prepared by a solid-state reaction method. The raw material powders used were lanthanum hydroxide (manufactured by Shin-Etsu Chemical Co., Ltd.), strontium carbonate (manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), and scandium oxide (manufactured by Alfa Aesar). These raw material powders were mixed in a solution containing lanthanum hydroxide (manufactured by Shin-Etsu Chemical Co., Ltd.), strontium carbonate (manufactured by Kojundo Kagaku Kenkyusho Co., Ltd.), and scandium oxide (manufactured by Alfa Aesar). The ratio of the metal elements was calculated based on the composition formula La 0.9 Sr 0.1The powder was weighed to achieve the composition ratio in ScO3. Then, 5 mm diameter balls and ethanol were added, and the mixture was mixed for 15 hours using a ball mill. The ethanol component was then removed, and the solid component was obtained. This was then sieved using a sieve with 250 μm openings. Then, the mixture was fired at 1300°C for 5 hours. The resulting powder was again crushed using a ball mill, and the mixture was mixed for 15 hours. The ethanol component was removed, and the solid component was then sieved using a sieve with 250 μm openings, yielding a dehydrogenation catalyst as sample C1.

[0134] [Preparation of Samples C2 to C9] Powdered dehydrogenation catalysts were obtained as Samples C2 to C9 in the same manner as Sample C1, except that the type and weighed amount of catalyst raw material powder were adjusted to achieve the composition ratios of Samples C2 to C9 shown in FIG. 21. For Samples C3 and C4, the heat treatment temperature in the firing step was changed within the range of 1300°C to 1500°C so as to increase the proportion of the target substance. For example, the temperature was 1400°C for Sample C3 and 1350°C for Sample C4. In this way, the heat treatment temperature in the firing step during sample production may be changed so as to increase the proportion of the target substance. To add lanthanum, strontium, scandium, barium, aluminum, gallium, and zirconium as constituent elements to the dehydrogenation catalyst, the raw material powders used were lanthanum hydroxide (Shin-Etsu Chemical Co., Ltd.), strontium carbonate (Kojundo Scientific Research Institute Co., Ltd.), scandium oxide (Alfa Aesar), barium carbonate (Sakai Chemical Industry Co., Ltd.), aluminum oxide (Sumitomo Chemical Co., Ltd.), gallium oxide (Kishida Chemical Co., Ltd.), and zirconium oxide (Daiichi Kigenso Kagaku Kogyo Co., Ltd.).

[0135] [Preparation of sample C10] The catalyst (SrTiO3) of Sample C10 was prepared by complex polymerization. Strontium nitrate (Fujifilm Wako Pure Chemical Industries, Ltd.) and tetra-i-propoxytitanium (Kojundo Chemical Laboratory Co., Ltd.) were used as raw material powders. These raw material powders were weighed so that the ratio of metal elements corresponded to the composition ratio of the SrTiO3 composition. A citric acid solution and propylene glycol were then added to the raw material powder so that the ratio of metal elements to citric acid to propylene glycol was 1:3:3 (molar ratio), and the mixture was stirred and mixed at 80°C for 1 hour. The solution was then slowly heated to 300°C to obtain a polymer with dispersed metal elements. The resulting polymer was then carbonized by heat treatment at 400°C for 2 hours and pulverized in an agate mortar to obtain a catalyst powder precursor. The resulting catalyst powder precursor was then heat-treated at 1200°C for 6 hours to obtain a powdered dehydrogenation catalyst, designated Sample C10.

[0136] [Preparation of Samples C11 to C13] Powdered dehydrogenation catalysts were obtained as Samples C11 to C13 in the same manner as Sample C10, except that the type and weighed amounts of catalyst raw material powders were adjusted to achieve the compositional ratios of the composition formulas of Samples C11 to C13 shown in Figure 21. To add strontium, lanthanum, titanium, barium, zirconium, and yttrium to the dehydrogenation catalyst as constituent elements, strontium nitrate (manufactured by FUJIFILM Wako Pure Chemical Corporation), lanthanum nitrate (manufactured by FUJIFILM Wako Pure Chemical Corporation), tetra-i-propoxytitanium (manufactured by Kojundo Chemical Laboratory Co., Ltd.), barium nitrate (manufactured by FUJIFILM Wako Pure Chemical Corporation), zirconyl nitrate (manufactured by FUJIFILM Wako Pure Chemical Corporation), and yttrium nitrate (manufactured by Sigma-Aldrich) were used as raw material powders.

[0137] [Measurement of C2 yield] 0.1 g of each of Samples C1 to C13 was weighed and placed in a fixed-bed flow reactor. The reactor was heated to 750°C and a mixed gas of methane, oxygen, and nitrogen was introduced at a flow rate ratio of CH4:O2:N2 = 3.8:1:4 under 1 atmosphere and 45 cm3 A catalytic activity test was performed with each sample heated to 650 °C. The composition of the gases fed into the system and the gases discharged from the system was analyzed using a micro gas chromatograph (Agilent Technologies, Inc., 3000A). The results of the composition analysis were used to calculate the C2 yield at 650 °C ("YC2-650" in Figure 21).

[0138] 21, it was confirmed that, among Samples C1 to C13, Samples C1 to C8, which are composite oxides containing a relatively large proportion of lanthanum at the A site, have a higher C2 yield (YC2-650) at 650°C than Samples C9 to C13, which are composite oxides that do not contain much lanthanum at the A site. It was confirmed that composite oxides containing a large amount of lanthanum at the A site are basic oxides, and have improved catalytic activity as dehydrogenation catalysts at the relatively low temperature of 650°C.

[0139] Furthermore, among Samples C1 to C8, Samples C1 to C4 have a portion of the strontium or barium at the A site substituted with lanthanum. This increases the basicity and oxygen vacancy of Samples C1 to C4 as dehydrogenation catalysts. At high temperatures above 700°C, the movement of CO molecules, which are generated as a by-product of the methane oxidative coupling reaction, is activated. Therefore, regardless of the material, composite oxides containing strontium or barium are less susceptible to the adsorption of CO molecules. Therefore, composite oxides containing strontium or barium are useful as catalysts for the methane oxidative coupling reaction. However, at temperatures below 700°C, such as 650°C, the alkaline earth metals strontium and barium are prone to carbonate formation, which can lead to catalyst poisoning, resulting in the adsorption of CO molecules, a by-product of the methane oxidative coupling reaction, and the catalyst becoming more susceptible to deactivation. On the other hand, by replacing part of the strontium or barium in the A site with lanthanum, which is less likely to form carbonates, as in samples C1 to C4, the dehydrogenation catalyst is less likely to form carbonates than a composite oxide containing strontium or barium. This is thought to reduce the effect of adsorption of CO2 molecules at 650°C, making it less likely to be deactivated.

[0140] Furthermore, as shown in sample C11, it was revealed that the introduction of lanthanum into SrTiO3 reduces its catalytic activity as a dehydrogenation catalyst. This confirmed that the amount of lanthanum added is insufficient to improve catalytic activity without being affected by the adsorption of CO2 molecules. When the amount of lanthanum added is small, the effect of lanthanum being lower than strontium becomes dominant, resulting in a decrease in catalytic activity. Thus, a large amount of lanthanum is required to exert the effect of lanthanum being less likely to adsorb CO2 molecules.

[0141] Furthermore, when the B site is a tetravalent element, as in sample C11, the lanthanum substitution amount is thought to be insufficient. Therefore, dehydrogenation catalysts including perovskite oxides in which the B site is a trivalent element and lanthanum is introduced into the A site, such as samples C1 to C8, are superior in methane oxidative coupling reaction to dehydrogenation catalysts including perovskite oxides with a tetravalent B site, such as sample C11. Furthermore, sample C3, in which the lanthanum substitution amount at the A site is 0.6, was confirmed to exhibit excellent methane oxidative coupling reaction as a dehydrogenation catalyst. Therefore, by setting the lanthanum substitution amount at the A site to at least 0.4, a dehydrogenation catalyst can exhibit excellent methane oxidative coupling reaction.

[0142] The dehydrogenation catalyst of this embodiment configured as described above includes a perovskite oxide containing lanthanum at the A site, which can promote the dehydrogenation reaction at low temperatures and enhance the catalytic activity as a dehydrogenation catalyst.

[0143] Furthermore, according to the dehydrogenation catalyst of this embodiment, the A site contains strontium or barium in addition to lanthanum, which further enhances the catalytic activity of the dehydrogenation catalyst, particularly the catalytic activity of promoting the dehydrogenation reaction at relatively low temperatures.

[0144] Furthermore, when the dehydrogenation catalyst of this embodiment is used as a methane oxidative coupling catalyst, the catalytic activity of the methane oxidative coupling catalyst at low temperatures can be increased.

[0145] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0146] [Variation 1] In the first embodiment, a dehydrogenation catalyst having a ratio of the second peak area to the first peak area greater than 1 in the spectrum of the O1s orbital contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy is a composite oxide including a main phase having a perovskite-type oxide crystal structure represented by formula (1) and a subphase having at least one of the three composite oxides represented by formulas (2a) to (2c). However, the configuration of a dehydrogenation catalyst having a ratio of the second peak area to the first peak area greater than 1 is not limited to this.

[0147] The present disclosure is not limited to the above-described embodiments, and can be realized in various configurations without departing from the spirit thereof. For example, the technical features in the embodiments corresponding to the technical features in each aspect described in the Summary of the Invention section can be appropriately replaced or combined to solve some or all of the above-described problems or achieve some or all of the above-described effects. Furthermore, if a technical feature is not described as essential in this specification, it can be appropriately deleted.

[0148] The present disclosure can also be realized in the following forms. [Application example 1] A dehydrogenation catalyst comprising: General formula (A 1-x A' x )(Zr 1-y-z B y B' z )O 3-δa main phase composed of a perovskite-type oxide represented by the formula (wherein A is at least one element selected from alkaline earth metals, A' is at least one element from lanthanum (La) and yttrium (Y), B is at least one element from titanium (Ti) and cerium (Ce), and B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd), satisfying 0≦x≦0.4, 0.3≦(1-z)≦1, 0≦y, and 0<(1-yz), and δ represents the amount of oxygen vacancy; and a subphase composed of at least one of three composite oxides represented by the general formulas AB'2O4, A2B'2O5, and A3B'4O9 (wherein A and B' are elements common to A and B' constituting the perovskite oxide), Catalyst for dehydrogenation reactions. [Application example 2] The dehydrogenation catalyst according to Application Example 1, A is barium (Ba), B' is scandium (Sc), The subphase is characterized in that it is composed of barium scandate (at least one of three composite oxides: BaSc2O4, Ba2Sc2O5, and Ba3Sc4O9). Catalyst for dehydrogenation reactions. [Application example 3] The dehydrogenation catalyst according to Application Example 1 or Application Example 2, The subphase is composed of Ba3Sc4O9. Catalyst for dehydrogenation reactions. [Application example 4] The dehydrogenation catalyst according to any one of Application Examples 1 to 3, The main phase is BaZr 1-z Sc z O 3-δ (wherein 0.1≦z≦0.7), Catalyst for dehydrogenation reactions. [Application example 5] The dehydrogenation catalyst according to any one of Application Examples 1 to 4, In a powder X-ray diffraction pattern using CuKα radiation, the perovskite oxide constituting the main phase has a first peak whose peak intensity is maximum in a diffraction angle range of 2θ=29.5-30.5°, and the composite oxide constituting the subphase has a second peak whose peak intensity is maximum in a diffraction angle range of 2θ=30.6-31.0°, The ratio of the intensity of the second peak to the intensity of the first peak is 0.04 or more. Catalyst for dehydrogenation reactions. [Application Example 6] The dehydrogenation catalyst according to any one of Application Examples 1 to 5, The subphase is composed of any one of the three composite oxides. Catalyst for dehydrogenation reactions. [Application Example 7] The dehydrogenation catalyst according to any one of Application Examples 1 to 6, A methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane, Catalyst for dehydrogenation reactions. [Application Example 8] A dehydrogenation catalyst comprising: Regarding the O1s orbital spectrum contained in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy, By peak separation fitting process, the curve is divided into a first curve having a first peak corresponding to a maximum value in the binding energy range of 525-530 eV and a second curve having a second peak corresponding to a maximum value in the binding energy range of 530-535 eV; When the area of ​​a convex portion including the first peak in the first curve is defined as a first peak area, and the area of ​​a convex portion including the second peak in the second curve is defined as a second peak area, The ratio of the second peak area to the first peak area is greater than 1. Catalyst for dehydrogenation reactions. [Application Example 9] The dehydrogenation catalyst according to any one of Application Examples 1 to 8, characterized by having oxygen deficiencies, Catalyst for dehydrogenation reactions. [Application Example 10] The dehydrogenation catalyst according to any one of Application Examples 1 to 9, The main phase of the catalyst has a perovskite structure. Catalyst for dehydrogenation reactions. [Application Example 11] The dehydrogenation catalyst according to any one of Application Examples 1 to 10, The specific surface area measured by the BET method is 10 m 2 / g or more, Catalyst for dehydrogenation reactions. [Application Example 12] The dehydrogenation catalyst according to any one of Application Examples 1 to 11, A methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane, Catalyst for dehydrogenation reactions. [Application Example 13] A dehydrogenation catalyst comprising: General formula (La 1-x M1 x )M2O 3-δ (wherein M1 is at least one element selected from alkaline earth metals, M2 is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and gallium (Ga), and δ represents the amount of oxygen vacancy, and δ satisfies 0≦x≦0.6), Catalyst for dehydrogenation reactions. [Application Example 14] The dehydrogenation catalyst according to any one of Application Examples 1 to 13, The M1 is strontium (Sr) or barium (Ba), Catalyst for dehydrogenation reactions. [Application Example 15] The dehydrogenation catalyst according to any one of Application Examples 1 to 14, A methane oxidative coupling catalyst for producing hydrocarbons having two or more carbon atoms from methane, Catalyst for dehydrogenation reactions.

Claims

1. A catalyst for dehydrogenation reactions, The main phase is one in which the proportion of peak intensity in the powder X-ray diffraction pattern using CuKα rays is 50% or more, General formula (A 1-x1 A' x1) (Zr 1-yz B y B' z) O 3- δ 1 (where A is at least one element selected from alkaline earth metals, A' is at least one element from lanthanum (La) and yttrium (Y), B is at least one element from titanium (Ti) and cerium (Ce), B' is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and neodymium (Nd), and δ1 represents the oxygen deficiency, satisfying 0 ≤ x1 ≤ 0.4, 0.3 ≤ (1-z) ≤ 1, 0 ≤ y, 0 < (1-y-z), and 0 ≤ δ1 ≤ 0.5). or The system comprises a main phase composed of a perovskite-type oxide represented by the general formula (La 1-x2 M1 x2) M2O 3- δ2 (where M1 is at least one element selected from alkaline earth metals, M2 is at least one element selected from yttrium (Y), scandium (Sc), ytterbium (Yb), aluminum (Al), indium (In), and gallium (Ga), and δ2 represents the oxygen deficiency, satisfying 0 < x2 ≤ 0.6 and 0 ≤ δ2 ≤ 0.5), Regarding the spectrum of the O1s orbital included in the photoelectron spectrum obtained by X-ray photoelectron spectroscopy, The peak separation fitting process divides the curve into a first curve having a first peak corresponding to the maximum value of the binding energy in the range of 525-530 eV, and a second curve having a second peak corresponding to the maximum value of the binding energy in the range of 530-535 eV. If the area of ​​the convex portion including the first peak in the first curve is defined as the first peak area, and the area of ​​the convex portion including the second peak in the second curve is defined as the second peak area, The ratio of the second peak area to the first peak area is greater than 1, Catalyst for dehydrogenation reactions.

2. A catalyst for a dehydrogenation reaction according to claim 1, Characterized by having an oxygen deficiency, Catalyst for dehydrogenation reactions.

3. A dehydrogenation reaction catalyst according to claim 1 or claim 2, The specific surface area measured by the BET method is 10 m². 2 Characterized by being 1 / g or more, Catalyst for dehydrogenation reactions.

4. A catalyst for a dehydrogenation reaction according to claim 1 or claim 2, A methane oxidation coupling catalyst for producing hydrocarbons with two or more carbon atoms from methane, Catalyst for dehydrogenation reactions.

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